tag:blogger.com,1999:blog-69057804898698242832024-03-06T00:41:50.156-08:00rippleripplehttp://www.blogger.com/profile/17326365690819936341noreply@blogger.comBlogger1019125tag:blogger.com,1999:blog-6905780489869824283.post-42715163132381496862011-03-22T11:34:00.000-07:002011-04-06T14:15:46.771-07:00Foreign exchange market<div dir="ltr" style="text-align: left;" trbidi="on"><div class="dablink">"Forex" redirects here. For the football club, see <a href="http://en.wikipedia.org/wiki/FC_Forex_Bra%C5%9Fov">FC Forex Braşov</a>.</div><table class="navbox" style="clear: right; float: right; margin: 0 0 1em 1em; width: 185px;"><tbody><tr> <th style="background: lightblue; font-size: larger;"><a href="http://en.wikipedia.org/wiki/Exchange_rate" title="Exchange rate">Foreign exchange</a></th> </tr><tr> <td><b>Exchange rates</b><br /><a href="http://en.wikipedia.org/wiki/Currency_band">Currency band</a><br /><a href="http://en.wikipedia.org/wiki/Exchange_rate">Exchange rate</a><br /><a href="http://en.wikipedia.org/wiki/Exchange_rate_regime">Exchange rate regime</a><br /><a href="http://en.wikipedia.org/wiki/Fixed_exchange_rate">Fixed exchange rate</a><br /><a href="http://en.wikipedia.org/wiki/Floating_exchange_rate">Floating exchange rate</a><br /><a href="http://en.wikipedia.org/wiki/Linked_exchange_rate">Linked exchange rate</a></td> </tr><tr> <td><b>Markets</b><br /><b class="selflink">Foreign exchange market</b><br /><a href="http://en.wikipedia.org/wiki/Futures_exchange">Futures exchange</a><br /><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Retail_forex" title="Retail forex">Retail forex</a></td> </tr><tr> <td><b>Products</b><br /><a href="http://en.wikipedia.org/wiki/Currency">Currency</a><br /><a href="http://en.wikipedia.org/wiki/Currency_future">Currency future</a><br /><a href="http://en.wikipedia.org/wiki/Non-deliverable_forward">Non-deliverable forward</a><br /><a href="http://en.wikipedia.org/wiki/Forex_swap">Forex swap</a><br /><a href="http://en.wikipedia.org/wiki/Currency_swap">Currency swap</a><br /><a href="http://en.wikipedia.org/wiki/Foreign_exchange_option">Foreign exchange option</a></td> </tr><tr> <td><b>Historical agreements</b><br /><a href="http://en.wikipedia.org/wiki/United_Nations_Monetary_and_Financial_Conference" title="United Nations Monetary and Financial Conference">Bretton Woods Conference</a><br /><a href="http://en.wikipedia.org/wiki/Smithsonian_Agreement">Smithsonian Agreement</a><br /><a href="http://en.wikipedia.org/wiki/Plaza_Accord">Plaza Accord</a><br /><a href="http://en.wikipedia.org/wiki/Louvre_Accord">Louvre Accord</a></td> </tr><tr> <td><b>See also</b><br /><a href="http://en.wikipedia.org/wiki/Bureau_de_change" title="Bureau de change">Bureau de change / currency exchange (office)</a><br /><a href="http://en.wikipedia.org/wiki/Safe-haven_currency">Safe-haven currency</a></td> </tr></tbody></table>The <b>foreign exchange market</b> (<b>forex</b>, <b>FX</b>, or <b>currency market</b>) is a worldwide decentralized <a href="http://en.wikipedia.org/wiki/Over-the-counter_%28finance%29" title="Over-the-counter (finance)">over-the-counter</a> financial market for the trading of currencies. Financial centers around the world function as anchors of trading between a wide range of different types of buyers and sellers around the clock, with the exception of weekends. The foreign exchange market determines the relative values of different currencies.<sup class="reference" id="cite_ref-0"><a href="http://en.wikipedia.org/wiki/Forex#cite_note-0">[1]</a></sup><br />The primary purpose of the foreign exchange is to assist international trade and investment, by allowing businesses to convert one currency to another currency. For example, it permits a US business to import British goods and pay <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Pound_Sterling" title="Pound Sterling">Pound Sterling</a>, even though the business's income is in <a class="mw-redirect" href="http://en.wikipedia.org/wiki/US_dollars" title="US dollars">US dollars</a>. It also supports speculation, and facilitates the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Carry_trade" title="Carry trade">carry trade</a>, in which investors borrow low-yielding currencies and lend (invest in) high-yielding currencies, and which (it has been claimed) may lead to loss of competitiveness in some countries.<sup class="reference" id="cite_ref-UNCTAD_1-0"><a href="http://en.wikipedia.org/wiki/Forex#cite_note-UNCTAD-1">[2]</a></sup><br />In a typical foreign exchange transaction, a party purchases a quantity of one currency by paying a quantity of another currency. The modern foreign exchange market began forming during the 1970s when countries gradually switched to <a href="http://en.wikipedia.org/wiki/Floating_exchange_rate" title="Floating exchange rate">floating exchange rates</a> from the previous <a href="http://en.wikipedia.org/wiki/Exchange_rate_regime">exchange rate regime</a>, which remained <a href="http://en.wikipedia.org/wiki/Fixed_exchange_rate" title="Fixed exchange rate">fixed</a> as per the <a href="http://en.wikipedia.org/wiki/Bretton_Woods_system">Bretton Woods system</a>.<br />The foreign exchange market is unique because of<br /><ul><li>its huge trading volume, leading to high <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Liquidity" title="Liquidity">liquidity</a>;</li><li>its geographical dispersion;</li><li>its continuous operation: 24 hours a day except weekends, i.e. trading from 20:15 <a class="mw-redirect" href="http://en.wikipedia.org/wiki/GMT" title="GMT">GMT</a> on Sunday until 22:00 GMT Friday;</li><li>the variety of factors that affect <a href="http://en.wikipedia.org/wiki/Exchange_rate" title="Exchange rate">exchange rates</a>;</li><li>the low margins of relative profit compared with other markets of fixed income; and</li><li>the use of <a href="http://en.wikipedia.org/wiki/Leverage_%28finance%29" title="Leverage (finance)">leverage</a> to enhance profit margins with respect to account size.</li></ul>As such, it has been referred to as the market closest to the ideal of <a href="http://en.wikipedia.org/wiki/Perfect_competition">perfect competition</a>, notwithstanding <a href="http://en.wikipedia.org/wiki/Currency_intervention">currency intervention</a> by <a href="http://en.wikipedia.org/wiki/Central_bank" title="Central bank">central banks</a>. According to the <a href="http://en.wikipedia.org/wiki/Bank_for_International_Settlements">Bank for International Settlements</a>,<sup class="reference" id="cite_ref-BIS_2-0"><a href="http://en.wikipedia.org/wiki/Forex#cite_note-BIS-2">[3]</a></sup> as of April 2010, average daily turnover in global foreign exchange markets is estimated at $3.98 trillion, a growth of approximately 20% over the $3.21 trillion daily volume as of April 2007. Some firms specializing on foreign exchange market had put the average daily turnover in excess of US$4 trillion.<sup class="reference" id="cite_ref-3"><a href="http://en.wikipedia.org/wiki/Forex#cite_note-3">[4]</a></sup><br />The $3.98 trillion break-down is as follows:<br /><ul><li>$1.490 trillion in <a href="http://en.wikipedia.org/wiki/Foreign_exchange_spot_trading" title="Foreign exchange spot trading">spot</a> transactions</li><li>$475 billion in <a href="http://en.wikipedia.org/wiki/Forward_contract" title="Forward contract">outright forwards</a></li><li>$1.765 trillion in <a href="http://en.wikipedia.org/wiki/Forex_swap" title="Forex swap">foreign exchange swaps</a></li><li>$43 billion currency swaps</li><li>$207 billion in options and other products</li></ul><br /><table class="toc" id="toc"><tbody><tr> <td><div id="toctitle"><h2>Contents</h2><span class="toctoggle">[<a class="internal" href="http://en.wikipedia.org/wiki/Forex#" id="togglelink">hide</a>]</span></div><ul><li class="toclevel-1 tocsection-1"><a href="http://en.wikipedia.org/wiki/Forex#Market_Size_and_liquidity"><span class="tocnumber">1</span> <span class="toctext">Market Size and liquidity</span></a></li><li class="toclevel-1 tocsection-2"><a href="http://en.wikipedia.org/wiki/Forex#Market_participants"><span class="tocnumber">2</span> <span class="toctext">Market participants</span></a> <ul><li class="toclevel-2 tocsection-3"><a href="http://en.wikipedia.org/wiki/Forex#Banks"><span class="tocnumber">2.1</span> <span class="toctext">Banks</span></a></li><li class="toclevel-2 tocsection-4"><a href="http://en.wikipedia.org/wiki/Forex#Commercial_companies"><span class="tocnumber">2.2</span> <span class="toctext">Commercial companies</span></a></li><li class="toclevel-2 tocsection-5"><a href="http://en.wikipedia.org/wiki/Forex#Central_banks"><span class="tocnumber">2.3</span> <span class="toctext">Central banks</span></a></li><li class="toclevel-2 tocsection-6"><a href="http://en.wikipedia.org/wiki/Forex#Forex_Fixing"><span class="tocnumber">2.4</span> <span class="toctext">Forex Fixing</span></a></li><li class="toclevel-2 tocsection-7"><a href="http://en.wikipedia.org/wiki/Forex#Hedge_funds_as_speculators"><span class="tocnumber">2.5</span> <span class="toctext">Hedge funds as speculators</span></a></li><li class="toclevel-2 tocsection-8"><a href="http://en.wikipedia.org/wiki/Forex#Investment_management_firms"><span class="tocnumber">2.6</span> <span class="toctext">Investment management firms</span></a></li><li class="toclevel-2 tocsection-9"><a href="http://en.wikipedia.org/wiki/Forex#Retail_foreign_exchange_traders"><span class="tocnumber">2.7</span> <span class="toctext">Retail foreign exchange traders</span></a></li><li class="toclevel-2 tocsection-10"><a href="http://en.wikipedia.org/wiki/Forex#Non-bank_foreign_exchange_companies"><span class="tocnumber">2.8</span> <span class="toctext">Non-bank foreign exchange companies</span></a></li><li class="toclevel-2 tocsection-11"><a href="http://en.wikipedia.org/wiki/Forex#Money_transfer.2Fremittance_companies"><span class="tocnumber">2.9</span> <span class="toctext">Money transfer/remittance companies</span></a></li></ul></li><li class="toclevel-1 tocsection-12"><a href="http://en.wikipedia.org/wiki/Forex#Trading_characteristics"><span class="tocnumber">3</span> <span class="toctext">Trading characteristics</span></a></li><li class="toclevel-1 tocsection-13"><a href="http://en.wikipedia.org/wiki/Forex#Determinants_of_FX_rates"><span class="tocnumber">4</span> <span class="toctext">Determinants of FX rates</span></a> <ul><li class="toclevel-2 tocsection-14"><a href="http://en.wikipedia.org/wiki/Forex#Economic_factors"><span class="tocnumber">4.1</span> <span class="toctext">Economic factors</span></a></li><li class="toclevel-2 tocsection-15"><a href="http://en.wikipedia.org/wiki/Forex#Political_conditions"><span class="tocnumber">4.2</span> <span class="toctext">Political conditions</span></a></li><li class="toclevel-2 tocsection-16"><a href="http://en.wikipedia.org/wiki/Forex#Market_psychology"><span class="tocnumber">4.3</span> <span class="toctext">Market psychology</span></a></li></ul></li><li class="toclevel-1 tocsection-17"><a href="http://en.wikipedia.org/wiki/Forex#Financial_instruments"><span class="tocnumber">5</span> <span class="toctext">Financial instruments</span></a> <ul><li class="toclevel-2 tocsection-18"><a href="http://en.wikipedia.org/wiki/Forex#Spot"><span class="tocnumber">5.1</span> <span class="toctext">Spot</span></a></li><li class="toclevel-2 tocsection-19"><a href="http://en.wikipedia.org/wiki/Forex#Forward"><span class="tocnumber">5.2</span> <span class="toctext">Forward</span></a></li><li class="toclevel-2 tocsection-20"><a href="http://en.wikipedia.org/wiki/Forex#Swap"><span class="tocnumber">5.3</span> <span class="toctext">Swap</span></a></li><li class="toclevel-2 tocsection-21"><a href="http://en.wikipedia.org/wiki/Forex#Future"><span class="tocnumber">5.4</span> <span class="toctext">Future</span></a></li><li class="toclevel-2 tocsection-22"><a href="http://en.wikipedia.org/wiki/Forex#Option"><span class="tocnumber">5.5</span> <span class="toctext">Option</span></a></li></ul></li><li class="toclevel-1 tocsection-23"><a href="http://en.wikipedia.org/wiki/Forex#Speculation"><span class="tocnumber">6</span> <span class="toctext">Speculation</span></a></li><li class="toclevel-1 tocsection-24"><a href="http://en.wikipedia.org/wiki/Forex#Risk_aversion_in_forex"><span class="tocnumber">7</span> <span class="toctext">Risk aversion in forex</span></a></li><li class="toclevel-1 tocsection-25"><a href="http://en.wikipedia.org/wiki/Forex#See_also"><span class="tocnumber">8</span> <span class="toctext">See also</span></a></li><li class="toclevel-1 tocsection-26"><a href="http://en.wikipedia.org/wiki/Forex#Notes"><span class="tocnumber">9</span> <span class="toctext">Notes</span></a></li><li class="toclevel-1 tocsection-27"><a href="http://en.wikipedia.org/wiki/Forex#References"><span class="tocnumber">10</span> <span class="toctext">References</span></a></li><li class="toclevel-1 tocsection-28"><a href="http://en.wikipedia.org/wiki/Forex#External_links"><span class="tocnumber">11</span> <span class="toctext">External links</span></a></li></ul></td> </tr></tbody></table><h2><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Foreign_exchange_market&action=edit&section=1" title="Edit section: Market Size and liquidity">edit</a>]</span> <span class="mw-headline" id="Market_Size_and_liquidity">Market Size and liquidity</span></h2><div class="thumb tright"><div class="thumbinner" style="width: 302px;"><a class="image" href="http://en.wikipedia.org/wiki/File:G_foreign_exchange_market_turnover.gif"><img alt="" class="thumbimage" height="207" src="http://upload.wikimedia.org/wikipedia/commons/thumb/a/a3/G_foreign_exchange_market_turnover.gif/300px-G_foreign_exchange_market_turnover.gif" width="300" /></a> <br /><div class="thumbcaption"><div class="magnify"><a class="internal" href="http://en.wikipedia.org/wiki/File:G_foreign_exchange_market_turnover.gif" title="Enlarge"><img alt="" height="11" src="http://bits.wikimedia.org/skins-1.17/common/images/magnify-clip.png" width="15" /></a></div>Main foreign exchange market turnover, 1988–2007, measured in billions of USD.</div></div></div>The foreign exchange market is the largest and most <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Liquidity" title="Liquidity">liquid</a> financial market in the world. Traders include large banks, <a href="http://en.wikipedia.org/wiki/Central_bank" title="Central bank">central banks</a>, <a href="http://en.wikipedia.org/wiki/Institutional_investor" title="Institutional investor">institutional investors</a>, currency <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Speculators" title="Speculators">speculators</a>, corporations, <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Governments" title="Governments">governments</a>, other <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Financial_institutions" title="Financial institutions">financial institutions</a>, and retail investors. The average daily turnover in the global foreign exchange and related markets is continuously growing. According to the 2010 Triennial Central Bank Survey, coordinated by the <a href="http://en.wikipedia.org/wiki/Bank_for_International_Settlements">Bank for International Settlements</a>, average daily turnover was <a class="mw-redirect" href="http://en.wikipedia.org/wiki/US$" title="US$">US$</a>3.98 trillion in April 2010 (vs $1.7 trillion in 1998).<sup class="reference" id="cite_ref-BIS_2-1"><a href="http://en.wikipedia.org/wiki/Forex#cite_note-BIS-2">[3]</a></sup> Of this $3.98 trillion, $1.5 trillion was spot foreign exchange transactions and $2.5 trillion was traded in outright forwards, FX swaps and other currency <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Derivative_security" title="Derivative security">derivatives</a>.<br />Trading in <a href="http://en.wikipedia.org/wiki/London">London</a> accounted for 36.7% of the total, making London by far the most important global center for foreign exchange trading. In second and third places, respectively, trading in <a href="http://en.wikipedia.org/wiki/New_York_City">New York City</a> accounted for 17.9%, and <a href="http://en.wikipedia.org/wiki/Tokyo">Tokyo</a> accounted for 6.2%.<sup class="reference" id="cite_ref-BIS_survey_4-0"><a href="http://en.wikipedia.org/wiki/Forex#cite_note-BIS_survey-4">[5]</a></sup><br />Turnover of exchange-traded foreign exchange futures and options have grown rapidly in recent years, reaching $166 billion in April 2010 (double the turnover recorded in April 2007). Exchange-traded currency derivatives represent 4% of OTC foreign exchange turnover. FX <a href="http://en.wikipedia.org/wiki/Futures_contract" title="Futures contract">futures contracts</a> were introduced in 1972 at the <a href="http://en.wikipedia.org/wiki/Chicago_Mercantile_Exchange">Chicago Mercantile Exchange</a> and are actively traded relative to most other futures contracts.<br />Most developed countries permit the trading of FX derivative products (like currency futures and options on currency futures) on their exchanges. All these developed countries already have fully convertible capital accounts. A number of emerging countries do not permit FX derivative products on their exchanges in view of controls on the capital accounts. The use of foreign exchange derivatives is growing in many emerging economies.<sup class="reference" id="cite_ref-5"><a href="http://en.wikipedia.org/wiki/Forex#cite_note-5">[6]</a></sup> Countries such as Korea, South Africa, and India have established currency futures exchanges, despite having some controls on the capital account.<br /><table align="left" class="wikitable" style="font-size: 98%; text-align: center;"><caption><b>Top 10 currency traders</b> <sup class="reference" id="cite_ref-6"><a href="http://en.wikipedia.org/wiki/Forex#cite_note-6">[7]</a></sup> <small>% of overall volume, May 2010</small></caption> <tbody><tr bgcolor="background:#eee;"> <th>Rank</th> <th>Name</th> <th>Market share</th> </tr><tr> <td>1</td> <td align="left"><span class="flagicon"><a href="http://en.wikipedia.org/wiki/Germany" title="Germany"><img alt="Germany" class="thumbborder" height="13" src="http://upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Flag_of_Germany.svg/22px-Flag_of_Germany.svg.png" width="22" /></a></span> <a href="http://en.wikipedia.org/wiki/Deutsche_Bank">Deutsche Bank</a></td> <td align="right">18.06%</td> </tr><tr> <td>2</td> <td align="left"><span class="flagicon"><a href="http://en.wikipedia.org/wiki/Switzerland" title="Switzerland"><img alt="Switzerland" class="thumbborder" height="20" src="http://upload.wikimedia.org/wikipedia/commons/thumb/f/f3/Flag_of_Switzerland.svg/20px-Flag_of_Switzerland.svg.png" width="20" /></a></span> <a class="mw-redirect" href="http://en.wikipedia.org/wiki/UBS_AG" title="UBS AG">UBS AG</a></td> <td align="right">11.30%</td> </tr><tr> <td>3</td> <td align="left"><span class="flagicon"><a href="http://en.wikipedia.org/wiki/United_Kingdom" title="United Kingdom"><img alt="United Kingdom" class="thumbborder" height="11" src="http://upload.wikimedia.org/wikipedia/commons/thumb/a/ae/Flag_of_the_United_Kingdom.svg/22px-Flag_of_the_United_Kingdom.svg.png" width="22" /></a></span> <a href="http://en.wikipedia.org/wiki/Barclays_Capital">Barclays Capital</a></td> <td align="right">11.08%</td> </tr><tr> <td>4</td> <td align="left"><span class="flagicon"><a href="http://en.wikipedia.org/wiki/United_States" title="United States"><img alt="United States" class="thumbborder" height="12" src="http://upload.wikimedia.org/wikipedia/commons/thumb/a/a4/Flag_of_the_United_States.svg/22px-Flag_of_the_United_States.svg.png" width="22" /></a></span> <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Citi" title="Citi">Citi</a></td> <td align="right">7.69%</td> </tr><tr> <td>5</td> <td align="left"><span class="flagicon"><a href="http://en.wikipedia.org/wiki/United_Kingdom" title="United Kingdom"><img alt="United Kingdom" class="thumbborder" height="11" src="http://upload.wikimedia.org/wikipedia/commons/thumb/a/ae/Flag_of_the_United_Kingdom.svg/22px-Flag_of_the_United_Kingdom.svg.png" width="22" /></a></span> <a href="http://en.wikipedia.org/wiki/Royal_Bank_of_Scotland">Royal Bank of Scotland</a></td> <td align="right">6.50%</td> </tr><tr> <td>6</td> <td align="left"><span class="flagicon"><a href="http://en.wikipedia.org/wiki/United_States" title="United States"><img alt="United States" class="thumbborder" height="12" src="http://upload.wikimedia.org/wikipedia/commons/thumb/a/a4/Flag_of_the_United_States.svg/22px-Flag_of_the_United_States.svg.png" width="22" /></a></span> <a class="mw-redirect" href="http://en.wikipedia.org/wiki/JPMorgan" title="JPMorgan">JPMorgan</a></td> <td align="right">6.35%</td> </tr><tr> <td>7</td> <td align="left"><span class="flagicon"><a href="http://en.wikipedia.org/wiki/United_Kingdom" title="United Kingdom"><img alt="United Kingdom" class="thumbborder" height="11" src="http://upload.wikimedia.org/wikipedia/commons/thumb/a/ae/Flag_of_the_United_Kingdom.svg/22px-Flag_of_the_United_Kingdom.svg.png" width="22" /></a></span> <a href="http://en.wikipedia.org/wiki/HSBC">HSBC</a></td> <td align="right">4.55%</td> </tr><tr> <td>8</td> <td align="left"><span class="flagicon"><a href="http://en.wikipedia.org/wiki/Switzerland" title="Switzerland"><img alt="Switzerland" class="thumbborder" height="20" src="http://upload.wikimedia.org/wikipedia/commons/thumb/f/f3/Flag_of_Switzerland.svg/20px-Flag_of_Switzerland.svg.png" width="20" /></a></span> <a href="http://en.wikipedia.org/wiki/Credit_Suisse">Credit Suisse</a></td> <td align="right">4.44%</td> </tr><tr> <td>9</td> <td align="left"><span class="flagicon"><a href="http://en.wikipedia.org/wiki/United_States" title="United States"><img alt="United States" class="thumbborder" height="12" src="http://upload.wikimedia.org/wikipedia/commons/thumb/a/a4/Flag_of_the_United_States.svg/22px-Flag_of_the_United_States.svg.png" width="22" /></a></span> <a href="http://en.wikipedia.org/wiki/Goldman_Sachs">Goldman Sachs</a></td> <td align="right">4.28%</td> </tr><tr> <td>10</td> <td align="left"><span class="flagicon"><a href="http://en.wikipedia.org/wiki/United_States" title="United States"><img alt="United States" class="thumbborder" height="12" src="http://upload.wikimedia.org/wikipedia/commons/thumb/a/a4/Flag_of_the_United_States.svg/22px-Flag_of_the_United_States.svg.png" width="22" /></a></span> <a href="http://en.wikipedia.org/wiki/Morgan_Stanley">Morgan Stanley</a></td> <td align="right">2.91%</td> </tr></tbody></table>Foreign exchange trading increased by 20% between April 2007 and April 2010 and has more than doubled since 2004.<sup class="reference" id="cite_ref-7"><a href="http://en.wikipedia.org/wiki/Forex#cite_note-7">[8]</a></sup> The increase in turnover is due to a number of factors: the growing importance of foreign exchange as an asset class, the increased trading activity of high-frequency traders, and the emergence of retail investors as an important market segment. The growth of electronic execution methods and the diverse selection of execution venues have lowered transaction costs, increased market liquidity, and attracted greater participation from many customer types. In particular, electronic trading via online portals has made it easier for retail traders to trade in the foreign exchange market. By 2010, retail trading is estimated to account for up to 10% of spot FX turnover, or $150 billion per day (see <a href="http://en.wikipedia.org/wiki/Retail_forex_platform" title="Retail forex platform">retail trading platforms</a>).<br />Because foreign exchange is an <a href="http://en.wikipedia.org/wiki/Over-the-counter_%28finance%29" title="Over-the-counter (finance)">OTC</a> market where brokers/dealers negotiate directly with one another, there is no central exchange or clearing house. The biggest geographic trading centre is the UK, primarily London, which according to <a href="http://en.wikipedia.org/wiki/TheCityUK">TheCityUK</a> estimates has increased its share of global turnover in traditional transactions from 34.6% in April 2007 to 36.7% in April 2010. Due to London's dominance in the market, a particular currency's quoted price is usually the London market price. For instance, when the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/IMF" title="IMF">IMF</a> calculates the value of its <a href="http://en.wikipedia.org/wiki/Special_Drawing_Rights" title="Special Drawing Rights">SDRs</a> every day, they use the London market prices at noon that day.<br /><h2><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Foreign_exchange_market&action=edit&section=2" title="Edit section: Market participants">edit</a>]</span> <span class="mw-headline" id="Market_participants">Market participants</span></h2><table class="navbox" style="clear: right; float: right; margin: 0 0 1em 1em; width: 160px;"><tbody><tr> <th style="background: lightblue; font-size: larger;"><b><a href="http://en.wikipedia.org/wiki/Financial_market" title="Financial market">Financial markets</a></b></th> </tr><tr> <td><a class="image" href="http://en.wikipedia.org/wiki/File:Bruxelles_Bourse.jpg"><img alt="Bruxelles Bourse.jpg" height="101" src="http://upload.wikimedia.org/wikipedia/commons/thumb/e/ef/Bruxelles_Bourse.jpg/135px-Bruxelles_Bourse.jpg" width="135" /></a><br /><a href="http://en.wikipedia.org/wiki/Market" title="Market">Public market</a><br /><hr /><a href="http://en.wikipedia.org/wiki/Exchange_%28organized_market%29" title="Exchange (organized market)">Exchange</a><br /><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Securities" title="Securities">Securities</a></td> </tr><tr> <th style="background: light;"><b><a href="http://en.wikipedia.org/wiki/Bond_market">Bond market</a></b></th> </tr><tr> <td><a href="http://en.wikipedia.org/wiki/Fixed_income">Fixed income</a><br /><a href="http://en.wikipedia.org/wiki/Corporate_bond">Corporate bond</a><br /><a href="http://en.wikipedia.org/wiki/Government_bond">Government bond</a><br /><a href="http://en.wikipedia.org/wiki/Municipal_bond">Municipal bond</a><br /><a href="http://en.wikipedia.org/wiki/Bond_valuation">Bond valuation</a><br /><a href="http://en.wikipedia.org/wiki/High-yield_debt">High-yield debt</a></td> </tr><tr> <th style="background: light;"><b><a href="http://en.wikipedia.org/wiki/Stock_market">Stock market</a></b></th> </tr><tr> <td><a href="http://en.wikipedia.org/wiki/Stock">Stock</a><br /><a href="http://en.wikipedia.org/wiki/Preferred_stock">Preferred stock</a><br /><a href="http://en.wikipedia.org/wiki/Common_stock">Common stock</a><br /><a href="http://en.wikipedia.org/wiki/Registered_share">Registered share</a><br /><a href="http://en.wikipedia.org/wiki/Voting_share">Voting share</a><br /><a href="http://en.wikipedia.org/wiki/Stock_exchange">Stock exchange</a></td> </tr><tr> <th style="background: light;"><b><a href="http://en.wikipedia.org/wiki/Derivatives_market">Derivatives market</a></b></th> </tr><tr> <td><a href="http://en.wikipedia.org/wiki/Securitization">Securitization</a><br /><a href="http://en.wikipedia.org/wiki/Hybrid_security">Hybrid security</a><br /><a href="http://en.wikipedia.org/wiki/Credit_derivative">Credit derivative</a><br /><a href="http://en.wikipedia.org/wiki/Futures_exchange">Futures exchange</a><br /><hr /></td> </tr><tr> <th style="background: light;"><b><a href="http://en.wikipedia.org/wiki/Over-the-counter_%28finance%29" title="Over-the-counter (finance)">OTC</a></b>, non organized</th> </tr><tr> <td><a href="http://en.wikipedia.org/wiki/Spot_market">Spot market</a><br /><a href="http://en.wikipedia.org/wiki/Forward_contract" title="Forward contract">Forwards</a><br /><a href="http://en.wikipedia.org/wiki/Swap_%28finance%29" title="Swap (finance)">Swaps</a><br /><a href="http://en.wikipedia.org/wiki/Option_%28finance%29" title="Option (finance)">Options</a></td> </tr><tr> <th style="background: light;"><b><b class="selflink">Foreign exchange</b></b></th> </tr><tr> <td><a href="http://en.wikipedia.org/wiki/Exchange_rate">Exchange rate</a><br /><a href="http://en.wikipedia.org/wiki/Currency">Currency</a><br /><hr /></td> </tr><tr> <th style="background: light;"><b>Other markets</b></th> </tr><tr> <td><a href="http://en.wikipedia.org/wiki/Money_market">Money market</a><br /><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Reinsurance_market" title="Reinsurance market">Reinsurance market</a><br /><a href="http://en.wikipedia.org/wiki/Commodity_market">Commodity market</a><br /><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Real_estate_market" title="Real estate market">Real estate market</a></td> </tr><tr> <th style="background: light;"><b><a href="http://en.wikipedia.org/wiki/Trader_%28finance%29" title="Trader (finance)">Practical trading</a></b></th> </tr><tr> <td><a href="http://en.wikipedia.org/wiki/Financial_market_participants" title="Financial market participants">Participants</a><br /><a href="http://en.wikipedia.org/wiki/Clearing_house_%28finance%29" title="Clearing house (finance)">Clearing house</a><br /><a href="http://en.wikipedia.org/wiki/Financial_regulation">Financial regulation</a></td> </tr><tr> <td><hr /><b><a href="http://en.wikipedia.org/wiki/Finance">Finance</a> series</b><br /><a href="http://en.wikipedia.org/wiki/Bank" title="Bank">Banks and banking</a><br /><a href="http://en.wikipedia.org/wiki/Corporate_finance">Corporate finance</a><br /><a href="http://en.wikipedia.org/wiki/Personal_finance">Personal finance</a><br /><a href="http://en.wikipedia.org/wiki/Public_finance">Public finance</a></td> </tr><tr> <td><span class="noprint plainlinks navbar"><span style="white-space: nowrap; word-spacing: -0.12em;"><a href="http://en.wikipedia.org/wiki/Template:Financial_markets" title="Template:Financial markets"><span title="View this template">v</span></a> <b>·</b> <a href="http://en.wikipedia.org/wiki/Template_talk:Financial_markets" title="Template talk:Financial markets"><span title="Discuss this template">d</span></a> <b>·</b> <a class="external text" href="http://en.wikipedia.org/w/index.php?title=Template:Financial_markets&action=edit" rel="nofollow"><span title="Edit this template">e</span></a></span></span></td> </tr></tbody></table>Unlike a stock market, the foreign exchange market is divided into levels of access. At the top is the <a href="http://en.wikipedia.org/wiki/Interbank_market" title="Interbank market">inter-bank market</a>, which is made up of the largest <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Commercial_banks" title="Commercial banks">commercial banks</a> and <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Investment_bank" title="Investment bank">securities dealers</a>. Within the inter-bank market, spreads, which are the difference between the bid and ask prices, are razor sharp and not known to players outside the inner circle. The difference between the bid and ask prices widens (for example from 0-1 <a href="http://en.wikipedia.org/wiki/Percentage_in_point" title="Percentage in point">pip</a> to 1-2 pips for a currencies such as the EUR) as you go down the levels of access. This is due to volume. If a trader can guarantee large numbers of transactions for large amounts, they can demand a smaller difference between the bid and ask price, which is referred to as a better spread. The levels of access that make up the foreign exchange market are determined by the size of the "line" (the amount of money with which they are trading). The <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Top-tier" title="Top-tier">top-tier</a> <a href="http://en.wikipedia.org/wiki/Interbank_market">interbank market</a> accounts for 53% of all transactions. After that there are usually smaller banks, followed by large multi-national corporations (which need to hedge risk and pay employees in different countries), large hedge funds, and even some of the retail FX <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Market_makers" title="Market makers">market makers</a>. According to Galati and Melvin, “Pension funds, insurance companies, mutual funds, and other institutional investors have played an increasingly important role in financial markets in general, and in FX markets in particular, since the early 2000s.” (2004) In addition, he notes, “Hedge funds have grown markedly over the 2001–2004 period in terms of both number and overall size”.<sup class="reference" id="cite_ref-8"><a href="http://en.wikipedia.org/wiki/Forex#cite_note-8">[9]</a></sup> <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Central_banks" title="Central banks">Central banks</a> also participate in the foreign exchange market to align currencies to their economic needs.<br /><h3><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Foreign_exchange_market&action=edit&section=3" title="Edit section: Banks">edit</a>]</span> <span class="mw-headline" id="Banks">Banks</span></h3>The interbank market caters for both the majority of commercial turnover and large amounts of speculative trading every day. A large bank may trade billions of dollars daily. Some of this trading is undertaken on behalf of customers, but much is conducted by proprietary desks, trading for the bank's own account. Until recently, foreign exchange brokers did large amounts of business, facilitating interbank trading and matching anonymous counterparts for large fees. Today, however, much of this business has moved on to more efficient electronic systems. The broker <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Squawk_box" title="Squawk box">squawk box</a> lets traders listen in on ongoing interbank trading and is heard in most <a href="http://en.wikipedia.org/wiki/Trading_room" title="Trading room">trading rooms</a>, but turnover is noticeably smaller than just a few years ago.<sup class="Template-Fact" style="white-space: nowrap;" title="This claim needs references to reliable sources from October 2010">[<i><a href="http://en.wikipedia.org/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed">citation needed</a></i>]</sup><br /><h3><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Foreign_exchange_market&action=edit&section=4" title="Edit section: Commercial companies">edit</a>]</span> <span class="mw-headline" id="Commercial_companies">Commercial companies</span></h3>An important part of this market comes from the financial activities of companies seeking foreign exchange to pay for goods or services. Commercial companies often trade fairly small amounts compared to those of banks or speculators, and their trades often have little short term impact on market rates. Nevertheless, trade flows are an important factor in the long-term direction of a currency's exchange rate. Some multinational companies can have an unpredictable impact when very large positions are covered due to exposures that are not widely known by other market participants.<br /><h3><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Foreign_exchange_market&action=edit&section=5" title="Edit section: Central banks">edit</a>]</span> <span class="mw-headline" id="Central_banks">Central banks</span></h3>National central banks play an important role in the foreign exchange markets. They try to control the <a href="http://en.wikipedia.org/wiki/Money_supply">money supply</a>, <a href="http://en.wikipedia.org/wiki/Inflation">inflation</a>, and/or <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Interest_rates" title="Interest rates">interest rates</a> and often have official or unofficial target rates for their currencies. They can use their often substantial foreign exchange reserves to stabilize the market. Nevertheless, the effectiveness of central bank "stabilizing speculation" is doubtful because central banks do not go bankrupt if they make large losses, like other traders would, and there is no convincing evidence that they do make a profit trading.<br /><h3><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Foreign_exchange_market&action=edit&section=6" title="Edit section: Forex Fixing">edit</a>]</span> <span class="mw-headline" id="Forex_Fixing">Forex Fixing</span></h3>Forex fixing is the daily monetary exchange rate fixed by the national bank of each country. The idea is that central banks use the fixing time and exchange rate to evaluate behavior of their currency. Fixing exchange rates reflects the real value of equilibrium in the forex market. Banks, dealers and online foreign exchange traders use fixing rates as a trend indicator.<br />The mere expectation or rumor of central bank <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Central_Bank#Interest_rate_interventions" title="Central Bank">intervention</a> might be enough to stabilize a currency, but aggressive intervention might be used several times each year in countries with a <a href="http://en.wikipedia.org/wiki/Managed_float_regime" title="Managed float regime">dirty float</a> currency regime. Central banks do not always achieve their objectives. The combined resources of the market can easily overwhelm any central bank.<sup class="reference" id="cite_ref-9"><a href="http://en.wikipedia.org/wiki/Forex#cite_note-9">[10]</a></sup> Several scenarios of this nature were seen in the 1992–93 <a href="http://en.wikipedia.org/wiki/European_Exchange_Rate_Mechanism" title="European Exchange Rate Mechanism">ERM</a> collapse, and in more recent times in Southeast Asia.<br /><h3><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Foreign_exchange_market&action=edit&section=7" title="Edit section: Hedge funds as speculators">edit</a>]</span> <span class="mw-headline" id="Hedge_funds_as_speculators">Hedge funds as speculators</span></h3>About 70% to 90%<sup class="Template-Fact" style="white-space: nowrap;" title="This claim needs references to reliable sources from August 2009">[<i><a href="http://en.wikipedia.org/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed">citation needed</a></i>]</sup> of the foreign exchange transactions are speculative. In other words, the person or institution that bought or sold the currency has no plan to actually take delivery of the currency in the end; rather, they were solely speculating on the movement of that particular currency. <a href="http://en.wikipedia.org/wiki/Hedge_fund" title="Hedge fund">Hedge funds</a> have gained a reputation for aggressive currency speculation since 1996. They control billions of dollars of <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Equity_investment" title="Equity investment">equity</a> and may borrow billions more, and thus may overwhelm intervention by central banks to support almost any currency, if the economic fundamentals are in the hedge funds' favor.<br /><h3><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Foreign_exchange_market&action=edit&section=8" title="Edit section: Investment management firms">edit</a>]</span> <span class="mw-headline" id="Investment_management_firms">Investment management firms</span></h3>Investment management firms (who typically manage large accounts on behalf of customers such as pension funds and endowments) use the foreign exchange market to facilitate transactions in foreign securities. For example, an investment manager bearing an international equity portfolio needs to purchase and sell several pairs of foreign currencies to pay for foreign securities purchases.<br />Some investment management firms also have more speculative specialist <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Currency_Overlay" title="Currency Overlay">currency overlay</a> operations, which manage clients' currency exposures with the aim of generating profits as well as limiting risk. Whilst the number of this type of specialist firms is quite small, many have a large value of assets under management (AUM), and hence can generate large trades.<br /><h3><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Foreign_exchange_market&action=edit&section=9" title="Edit section: Retail foreign exchange traders">edit</a>]</span> <span class="mw-headline" id="Retail_foreign_exchange_traders">Retail foreign exchange traders</span></h3>Retail traders (individuals) constitute a growing segment of this market with the advent of <a href="http://en.wikipedia.org/wiki/Retail_forex_platform" title="Retail forex platform">retail forex platforms</a>, both in size and importance. Currently, they participate indirectly through <a href="http://en.wikipedia.org/wiki/Commodity_broker" title="Commodity broker">brokers</a> or banks. Retail brokers, while largely controlled and regulated in the USA by the <a href="http://en.wikipedia.org/wiki/Commodity_Futures_Trading_Commission" title="Commodity Futures Trading Commission">CFTC</a> and <a href="http://en.wikipedia.org/wiki/National_Futures_Association" title="National Futures Association">NFA</a> have in the past been subjected to periodic <a href="http://en.wikipedia.org/wiki/Forex_scam" title="Forex scam">foreign exchange scams</a>.<sup class="reference" id="cite_ref-WSJ1_10-0"><a href="http://en.wikipedia.org/wiki/Forex#cite_note-WSJ1-10">[11]</a></sup><sup class="reference" id="cite_ref-NYTimes1_11-0"><a href="http://en.wikipedia.org/wiki/Forex#cite_note-NYTimes1-11">[12]</a></sup> To deal with the issue, the NFA and CFTC began (as of 2009) imposing stricter requirements, particularly in relation to the amount of Net Capitalization required of its members. As a result many of the smaller and perhaps questionable brokers are now gone or have moved to countries outside the US. A number of the forex brokers operate from the UK under <a href="http://en.wikipedia.org/wiki/Financial_Services_Authority" title="Financial Services Authority">FSA</a> regulations where forex trading using <a href="http://en.wikipedia.org/wiki/Margin_%28finance%29" title="Margin (finance)">margin</a> is part of the wider <a href="http://en.wikipedia.org/wiki/Over-the-counter_%28finance%29" title="Over-the-counter (finance)">over-the-counter</a> derivatives trading industry that includes <a href="http://en.wikipedia.org/wiki/CFD" title="CFD">CFDs</a> and <a href="http://en.wikipedia.org/wiki/Spread_betting#Financial_spread_betting" title="Spread betting">financial spread betting</a>.<br />There are two main types of retail FX brokers offering the opportunity for speculative currency trading: <i>brokers</i> and <i>dealers</i> or <i>market makers</i>. <i>Brokers</i> serve as an agent of the customer in the broader FX market, by seeking the best price in the market for a retail order and dealing on behalf of the retail customer. They charge a commission or mark-up in addition to the price obtained in the market. <i>Dealers</i> or <i>market makers</i>, by contrast, typically act as principal in the transaction versus the retail customer, and quote a price they are willing to deal at. The customer then has the choice whether or not to trade at that price.<br />In assessing the suitability of an FX trading service, the customer should consider the ramifications of whether the service provider is acting as principal or agent. When the service provider acts as agent, the customer is generally assured of a known cost above the best inter-dealer FX rate. When the service provider acts as principal, no commission is paid, but the price offered may not be the best available in the market—since the service provider is taking the other side of the transaction, a conflict of interest may occur.<br /><h3><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Foreign_exchange_market&action=edit&section=10" title="Edit section: Non-bank foreign exchange companies">edit</a>]</span> <span class="mw-headline" id="Non-bank_foreign_exchange_companies">Non-bank foreign exchange companies</span></h3>Non-bank <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Foreign_exchange_companies" title="Foreign exchange companies">foreign exchange companies</a> offer currency exchange and international payments to private individuals and companies. These are also known as foreign exchange brokers but are distinct in that they do not offer speculative trading but rather currency exchange with payments (i.e., there is usually a physical delivery of currency to a bank account).<br />It is estimated that in the UK, 14% of currency transfers/payments<sup class="reference" id="cite_ref-12"><a href="http://en.wikipedia.org/wiki/Forex#cite_note-12">[13]</a></sup> are made via Foreign Exchange Companies.<sup class="reference" id="cite_ref-13"><a href="http://en.wikipedia.org/wiki/Forex#cite_note-13">[14]</a></sup> These companies' selling point is usually that they will offer better exchange rates or cheaper payments than the customer's bank. These companies differ from Money Transfer/Remittance Companies in that they generally offer higher-value services.<br /><h3><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Foreign_exchange_market&action=edit&section=11" title="Edit section: Money transfer/remittance companies">edit</a>]</span> <span class="mw-headline" id="Money_transfer.2Fremittance_companies">Money transfer/remittance companies</span></h3><a href="http://en.wikipedia.org/wiki/Money_transfer" title="Money transfer">Money transfer companies</a>/remittance companies perform high-volume low-value transfers generally by economic migrants back to their home country. In 2007, the <a class="new" href="http://en.wikipedia.org/w/index.php?title=Aite_Group&action=edit&redlink=1" title="Aite Group (page does not exist)">Aite Group</a> estimated that there were $369 billion of remittances (an increase of 8% on the previous year). The four largest markets (<a href="http://en.wikipedia.org/wiki/India">India</a>, <a href="http://en.wikipedia.org/wiki/China">China</a>, <a href="http://en.wikipedia.org/wiki/Mexico">Mexico</a> and the <a href="http://en.wikipedia.org/wiki/Philippines">Philippines</a>) receive $95 billion. The largest and best known provider is <a href="http://en.wikipedia.org/wiki/Western_Union">Western Union</a> with 345,000 agents globally followed by <a href="http://en.wikipedia.org/wiki/UAE_Exchange">UAE Exchange</a><sup class="Template-Fact" style="white-space: nowrap;" title="This claim needs references to reliable sources from May 2010">[<i><a href="http://en.wikipedia.org/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed">citation needed</a></i>]</sup><br /><h2><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Foreign_exchange_market&action=edit&section=12" title="Edit section: Trading characteristics">edit</a>]</span> <span class="mw-headline" id="Trading_characteristics">Trading characteristics</span></h2><table align="right" class="wikitable" style="font-size: 98%; text-align: center;"><caption><b>Most traded currencies</b><sup class="reference" id="cite_ref-BIS_2-2"><a href="http://en.wikipedia.org/wiki/Forex#cite_note-BIS-2">[3]</a></sup> <small>Currency distribution of reported FX market turnover</small><sup class="reference" id="cite_ref-14"><a href="http://en.wikipedia.org/wiki/Forex#cite_note-14">[15]</a></sup></caption> <tbody><tr bgcolor="background:#eee;"> <th>Rank</th> <th>Currency</th> <th><a href="http://en.wikipedia.org/wiki/ISO_4217">ISO 4217</a> code<br />(Symbol)</th> <th> % daily share<br />(April 2010)</th> </tr><tr> <td><div class="center" style="margin-left: auto; margin-right: auto; width: auto;">1</div></td> <td align="left"><span class="flagicon"><a href="http://en.wikipedia.org/wiki/United_States" title="United States"><img alt="United States" class="thumbborder" height="12" src="http://upload.wikimedia.org/wikipedia/commons/thumb/a/a4/Flag_of_the_United_States.svg/22px-Flag_of_the_United_States.svg.png" width="22" /></a></span> <a href="http://en.wikipedia.org/wiki/United_States_dollar">United States dollar</a></td> <td><div class="center" style="margin-left: auto; margin-right: auto; width: auto;">USD ($)</div></td> <td align="right">84.9%</td> </tr><tr> <td><div class="center" style="margin-left: auto; margin-right: auto; width: auto;">2</div></td> <td align="left"><span class="flagicon"><a href="http://en.wikipedia.org/wiki/European_Union" title="European Union"><img alt="European Union" class="thumbborder" height="15" src="http://upload.wikimedia.org/wikipedia/commons/thumb/b/b7/Flag_of_Europe.svg/22px-Flag_of_Europe.svg.png" width="22" /></a></span> <a href="http://en.wikipedia.org/wiki/Euro">Euro</a></td> <td><div class="center" style="margin-left: auto; margin-right: auto; width: auto;">EUR (€)</div></td> <td align="right">39.1%</td> </tr><tr> <td><div class="center" style="margin-left: auto; margin-right: auto; width: auto;">3</div></td> <td align="left"><span class="flagicon"><a href="http://en.wikipedia.org/wiki/Japan" title="Japan"><img alt="Japan" class="thumbborder" height="15" src="http://upload.wikimedia.org/wikipedia/commons/thumb/9/9e/Flag_of_Japan.svg/22px-Flag_of_Japan.svg.png" width="22" /></a></span> <a href="http://en.wikipedia.org/wiki/Japanese_yen">Japanese yen</a></td> <td><div class="center" style="margin-left: auto; margin-right: auto; width: auto;">JPY (¥)</div></td> <td align="right">19.0%</td> </tr><tr> <td><div class="center" style="margin-left: auto; margin-right: auto; width: auto;">4</div></td> <td align="left"><span class="flagicon"><a href="http://en.wikipedia.org/wiki/United_Kingdom" title="United Kingdom"><img alt="United Kingdom" class="thumbborder" height="11" src="http://upload.wikimedia.org/wikipedia/commons/thumb/a/ae/Flag_of_the_United_Kingdom.svg/22px-Flag_of_the_United_Kingdom.svg.png" width="22" /></a></span> <a href="http://en.wikipedia.org/wiki/Pound_sterling">Pound sterling</a></td> <td><div class="center" style="margin-left: auto; margin-right: auto; width: auto;">GBP (£)</div></td> <td align="right">12.9%</td> </tr><tr> <td><div class="center" style="margin-left: auto; margin-right: auto; width: auto;">5</div></td> <td align="left"><span class="flagicon"><a href="http://en.wikipedia.org/wiki/Australia" title="Australia"><img alt="Australia" class="thumbborder" height="11" src="http://upload.wikimedia.org/wikipedia/commons/thumb/b/b9/Flag_of_Australia.svg/22px-Flag_of_Australia.svg.png" width="22" /></a></span> <a href="http://en.wikipedia.org/wiki/Australian_dollar">Australian dollar</a></td> <td><div class="center" style="margin-left: auto; margin-right: auto; width: auto;">AUD ($)</div></td> <td align="right">7.6%</td> </tr><tr> <td><div class="center" style="margin-left: auto; margin-right: auto; width: auto;">6</div></td> <td align="left"><span class="flagicon"><a href="http://en.wikipedia.org/wiki/Switzerland" title="Switzerland"><img alt="Switzerland" class="thumbborder" height="20" src="http://upload.wikimedia.org/wikipedia/commons/thumb/f/f3/Flag_of_Switzerland.svg/20px-Flag_of_Switzerland.svg.png" width="20" /></a></span> <a href="http://en.wikipedia.org/wiki/Swiss_franc">Swiss franc</a></td> <td><div class="center" style="margin-left: auto; margin-right: auto; width: auto;">CHF (Fr)</div></td> <td align="right">6.4%</td> </tr><tr> <td><div class="center" style="margin-left: auto; margin-right: auto; width: auto;">7</div></td> <td align="left"><span class="flagicon"><a href="http://en.wikipedia.org/wiki/Canada" title="Canada"><img alt="Canada" class="thumbborder" height="11" src="http://upload.wikimedia.org/wikipedia/commons/thumb/c/cf/Flag_of_Canada.svg/22px-Flag_of_Canada.svg.png" width="22" /></a></span> <a href="http://en.wikipedia.org/wiki/Canadian_dollar">Canadian dollar</a></td> <td><div class="center" style="margin-left: auto; margin-right: auto; width: auto;">CAD ($)</div></td> <td align="right">5.3%</td> </tr><tr> <td><div class="center" style="margin-left: auto; margin-right: auto; width: auto;">8</div></td> <td align="left"><span class="flagicon"><a href="http://en.wikipedia.org/wiki/Hong_Kong" title="Hong Kong"><img alt="Hong Kong" class="thumbborder" height="15" src="http://upload.wikimedia.org/wikipedia/commons/thumb/5/5b/Flag_of_Hong_Kong.svg/22px-Flag_of_Hong_Kong.svg.png" width="22" /></a></span> <a href="http://en.wikipedia.org/wiki/Hong_Kong_dollar">Hong Kong dollar</a></td> <td><div class="center" style="margin-left: auto; margin-right: auto; width: auto;">HKD ($)</div></td> <td align="right">2.4%</td> </tr><tr> <td><div class="center" style="margin-left: auto; margin-right: auto; width: auto;">9</div></td> <td align="left"><span class="flagicon"><a href="http://en.wikipedia.org/wiki/Sweden" title="Sweden"><img alt="Sweden" class="thumbborder" height="14" src="http://upload.wikimedia.org/wikipedia/commons/thumb/4/4c/Flag_of_Sweden.svg/22px-Flag_of_Sweden.svg.png" width="22" /></a></span> <a href="http://en.wikipedia.org/wiki/Swedish_krona">Swedish krona</a></td> <td><div class="center" style="margin-left: auto; margin-right: auto; width: auto;">SEK (kr)</div></td> <td align="right">2.2%</td> </tr><tr> <td><div class="center" style="margin-left: auto; margin-right: auto; width: auto;">10</div></td> <td align="left"><span class="flagicon"><a href="http://en.wikipedia.org/wiki/New_Zealand" title="New Zealand"><img alt="New Zealand" class="thumbborder" height="11" src="http://upload.wikimedia.org/wikipedia/commons/thumb/3/3e/Flag_of_New_Zealand.svg/22px-Flag_of_New_Zealand.svg.png" width="22" /></a></span> <a href="http://en.wikipedia.org/wiki/New_Zealand_dollar">New Zealand dollar</a></td> <td><div class="center" style="margin-left: auto; margin-right: auto; width: auto;">NZD ($)</div></td> <td align="right">1.6%</td> </tr><tr> <td align="center" colspan="3"><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Currencies_of_the_World" title="Currencies of the World">Other Currencies</a></td> <td align="right">18.6%</td> </tr><tr> <td align="right" colspan="3"><b>Total</b><sup class="reference" id="cite_ref-15"><a href="http://en.wikipedia.org/wiki/Forex#cite_note-15">[notes 1]</a></sup></td> <td align="right"><b>200%</b></td> </tr></tbody></table>There is no unified or centrally cleared market for the majority of FX trades, and there is very little cross-border regulation. Due to the <a href="http://en.wikipedia.org/wiki/Over-the-counter_%28finance%29" title="Over-the-counter (finance)">over-the-counter</a> (OTC) nature of currency markets, there are rather a number of interconnected marketplaces, where different currencies <a href="http://en.wikipedia.org/wiki/Financial_instrument" title="Financial instrument">instruments</a> are traded. This implies that there is not a <i>single</i> exchange rate but rather a number of different rates (prices), depending on what bank or market maker is trading, and where it is. In practice the rates are often very close, otherwise they could be exploited by <a href="http://en.wikipedia.org/wiki/Arbitrage" title="Arbitrage">arbitrageurs</a> instantaneously. Due to London's dominance in the market, a particular currency's quoted price is usually the London market price. A joint venture of the <a href="http://en.wikipedia.org/wiki/Chicago_Mercantile_Exchange">Chicago Mercantile Exchange</a> and <a href="http://en.wikipedia.org/wiki/Reuters">Reuters</a>, called <a href="http://en.wikipedia.org/wiki/Fxmarketspace">Fxmarketspace</a> opened in 2007 and aspired but failed to the role of a central market <a href="http://en.wikipedia.org/wiki/Clearing_%28finance%29" title="Clearing (finance)">clearing</a> mechanism.<sup class="Template-Fact" style="white-space: nowrap;" title="This claim needs references to reliable sources from June 2010">[<i><a href="http://en.wikipedia.org/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed">citation needed</a></i>]</sup><br />The main trading center is <a href="http://en.wikipedia.org/wiki/London">London</a>, but <a href="http://en.wikipedia.org/wiki/New_York">New York</a>, <a href="http://en.wikipedia.org/wiki/Tokyo">Tokyo</a>, <a href="http://en.wikipedia.org/wiki/Hong_Kong">Hong Kong</a> and <a href="http://en.wikipedia.org/wiki/Singapore">Singapore</a> are all important centers as well. Banks throughout the world participate. Currency trading happens continuously throughout the day; as the Asian trading session ends, the European session begins, followed by the North American session and then back to the Asian session, excluding weekends.<br />Fluctuations in <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Exchange_rates" title="Exchange rates">exchange rates</a> are usually caused by actual monetary flows as well as by expectations of changes in monetary flows caused by changes in <a href="http://en.wikipedia.org/wiki/Gross_domestic_product">gross domestic product</a> (GDP) growth, inflation (<a href="http://en.wikipedia.org/wiki/Purchasing_power_parity">purchasing power parity</a> theory), interest rates (<a href="http://en.wikipedia.org/wiki/Interest_rate_parity">interest rate parity</a>, <a href="http://en.wikipedia.org/wiki/Fisher_hypothesis" title="Fisher hypothesis">Domestic Fisher effect</a>, <a href="http://en.wikipedia.org/wiki/International_Fisher_effect">International Fisher effect</a>), budget and <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Trade_deficits" title="Trade deficits">trade deficits</a> or surpluses, large cross-border <a class="mw-redirect" href="http://en.wikipedia.org/wiki/M%26A" title="M&A">M&A</a> deals and other macroeconomic conditions. Major news is released publicly, often on scheduled dates, so many people have access to the same news at the same time. However, the large banks have an important advantage; they can see their customers' <a class="new" href="http://en.wikipedia.org/w/index.php?title=Order_flow&action=edit&redlink=1" title="Order flow (page does not exist)">order flow</a>.<br />Currencies are traded against one another. Each <a href="http://en.wikipedia.org/wiki/Currency_pair">currency pair</a> thus constitutes an individual trading product and is traditionally noted XXXYYY or XXX/YYY, where XXX and YYY are the <a href="http://en.wikipedia.org/wiki/ISO_4217" title="ISO 4217">ISO 4217 international three-letter code</a> of the currencies involved. The first currency (XXX) is the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Base_currency" title="Base currency">base currency</a> that is quoted relative to the second currency (YYY), called the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Counter_currency" title="Counter currency">counter currency</a> (or quote currency). For instance, the quotation <i>EURUSD (EUR/USD) 1.5465</i> is the price of the <a href="http://en.wikipedia.org/wiki/Euro">euro</a> expressed in <a class="mw-redirect" href="http://en.wikipedia.org/wiki/US_dollar" title="US dollar">US dollars</a>, meaning 1 euro = 1.5465 dollars. The market convention is to quote most exchange rates against the USD with the US dollar as the base currency (e.g. USDJPY, USDCAD, USDCHF). The exceptions are the British pound (GBP), Australian dollar (AUD), the New Zealand dollar (NZD) and the euro (EUR) where the USD is the counter currency (e.g. GBPUSD, AUDUSD, NZDUSD, EURUSD).<br />The factors affecting XXX will affect both XXXYYY and XXXZZZ. This causes positive currency <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Correlation" title="Correlation">correlation</a> between XXXYYY and XXXZZZ.<br />On the <a href="http://en.wikipedia.org/wiki/Spot_price" title="Spot price">spot</a> market, according to the 2010 Triennial Survey, the most heavily traded bilateral currency pairs were:<br /><ul><li>EURUSD: 28%</li><li>USDJPY: 14%</li><li>GBPUSD (also called <i><a href="http://en.wikipedia.org/wiki/Cable_%28foreign_exchange%29" title="Cable (foreign exchange)">cable</a></i>): 9%</li></ul>and the US currency was involved in 84.9% of transactions, followed by the euro (39.1%), the yen (19.0%), and sterling (12.9%) (see <a href="http://en.wikipedia.org/wiki/Forex#Trading_characteristics">table</a>). Volume percentages for all individual currencies should add up to 200%, as each transaction involves two currencies.<br />Trading in the euro has grown considerably since the currency's creation in January 1999, and how long the foreign exchange market will remain dollar-centered is open to debate. Until recently, trading the euro versus a non-European currency ZZZ would have usually involved two trades: EURUSD and USDZZZ. The exception to this is EURJPY, which is an established traded currency pair in the interbank spot market. As the dollar's value has eroded during 2008, interest in using the euro as reference currency for prices in commodities (such as oil), as well as a larger component of foreign reserves by banks, has increased dramatically. Transactions in the currencies of commodity-producing countries, such as AUD, NZD, CAD, have also increased.<br /><h2><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Foreign_exchange_market&action=edit&section=13" title="Edit section: Determinants of FX rates">edit</a>]</span> <span class="mw-headline" id="Determinants_of_FX_rates">Determinants of FX rates</span></h2><div class="rellink boilerplate seealso">See also: <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Exchange_rates" title="Exchange rates">exchange rates</a></div>The following theories explain the fluctuations in FX rates in a <a href="http://en.wikipedia.org/wiki/Floating_exchange_rate">floating exchange rate</a> regime (In a <a href="http://en.wikipedia.org/wiki/Fixed_exchange_rate">fixed exchange rate</a> regime, FX rates are decided by its government):<br /><dl><dd>(a) International parity conditions: <a href="http://en.wikipedia.org/wiki/Relative_Purchasing_Power_Parity">Relative Purchasing Power Parity</a>, <a href="http://en.wikipedia.org/wiki/Interest_rate_parity">interest rate parity</a>, <a href="http://en.wikipedia.org/wiki/Fisher_hypothesis" title="Fisher hypothesis">Domestic Fisher effect</a>, <a href="http://en.wikipedia.org/wiki/International_Fisher_effect">International Fisher effect</a>. Though to some extent the above theories provide logical explanation for the fluctuations in exchange rates, yet these theories falter as they are based on challengeable assumptions [e.g., free flow of goods, services and capital] which seldom hold true in the real world.</dd></dl><dl><dd>(b) Balance of payments model (see <a href="http://en.wikipedia.org/wiki/Exchange_rate">exchange rate</a>): This model, however, focuses largely on tradable goods and services, ignoring the increasing role of global capital flows. It failed to provide any explanation for continuous appreciation of dollar during 1980s and most part of 1990s in face of soaring US current account deficit.</dd></dl><dl><dd>(c) Asset market model (see <a href="http://en.wikipedia.org/wiki/Exchange_rate">exchange rate</a>): views currencies as an important asset class for constructing investment portfolios. Assets prices are influenced mostly by people’s willingness to hold the existing quantities of assets, which in turn depends on their expectations on the future worth of these assets. The asset market model of exchange rate determination states that “the exchange rate between two currencies represents the price that just balances the relative supplies of, and demand for, assets denominated in those currencies.”</dd></dl>None of the models developed so far succeed to explain FX rates levels and volatility in the longer time frames. For shorter time frames (less than a few days) <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Algo_trading" title="Algo trading">algorithm</a> can be devised to predict prices. Large and small institutions and professional individual traders have made consistent profits from it. It is understood from above models that many macroeconomic factors affect the exchange rates and in the end currency prices are a result of dual forces of demand and supply. The world's currency markets can be viewed as a huge melting pot: in a large and ever-changing mix of current events, <a href="http://en.wikipedia.org/wiki/Supply_and_demand">supply and demand</a> factors are constantly shifting, and the price of one currency in relation to another shifts accordingly. No other market encompasses (and distills) as much of what is going on in the world at any given time as foreign exchange.<br />Supply and demand for any given currency, and thus its value, are not influenced by any single element, but rather by several. These elements generally fall into three categories: <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Economic" title="Economic">economic</a> factors, <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Political" title="Political">political</a> conditions and <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Market_psychology" title="Market psychology">market psychology</a>.<br /><h3><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Foreign_exchange_market&action=edit&section=14" title="Edit section: Economic factors">edit</a>]</span> <span class="mw-headline" id="Economic_factors">Economic factors</span></h3>These include: (a)economic policy, disseminated by government agencies and <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Central_banks" title="Central banks">central banks</a>, (b)economic conditions, generally revealed through economic reports, and other <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Economic_indicators" title="Economic indicators">economic indicators</a>.<br /><ul><li>Economic policy comprises government <a href="http://en.wikipedia.org/wiki/Fiscal_policy">fiscal policy</a> (budget/spending practices) and <a href="http://en.wikipedia.org/wiki/Monetary_policy">monetary policy</a> (the means by which a government's central bank influences the supply and "cost" of money, which is reflected by the level of <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Interest_rates" title="Interest rates">interest rates</a>).</li><li>Government budget deficits or surpluses: The market usually reacts negatively to widening government <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Budget_deficit" title="Budget deficit">budget deficits</a>, and positively to narrowing budget deficits. The impact is reflected in the value of a country's currency.</li><li>Balance of trade levels and trends: The trade flow between countries illustrates the demand for goods and services, which in turn indicates demand for a country's currency to conduct trade. Surpluses and deficits in trade of goods and services reflect the competitiveness of a nation's economy. For example, <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Trade_deficits" title="Trade deficits">trade deficits</a> may have a negative impact on a nation's currency.</li><li>Inflation levels and trends: Typically a currency will lose value if there is a high level of <a href="http://en.wikipedia.org/wiki/Inflation">inflation</a> in the country or if inflation levels are perceived to be rising. This is because inflation erodes <a href="http://en.wikipedia.org/wiki/Purchasing_power">purchasing power</a>, thus demand, for that particular currency. However, a currency may sometimes strengthen when inflation rises because of expectations that the central bank will raise short-term interest rates to combat rising inflation.</li><li>Economic growth and health: Reports such as GDP, <a href="http://en.wikipedia.org/wiki/Employment">employment</a> levels, <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Retail_sales" title="Retail sales">retail sales</a>, <a href="http://en.wikipedia.org/wiki/Capacity_utilization">capacity utilization</a> and others, detail the levels of a country's <a href="http://en.wikipedia.org/wiki/Economic_growth">economic growth</a> and health. Generally, the more healthy and robust a country's economy, the better its currency will perform, and the more demand for it there will be.</li><li>Productivity of an economy: Increasing productivity in an economy should positively influence the value of its currency. Its effects are more prominent if the increase is in the traded sector <a class="external autonumber" href="http://papers.ssrn.com/sol3/papers.cfm?abstract_id=711362" rel="nofollow">[1]</a>.</li></ul><h3><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Foreign_exchange_market&action=edit&section=15" title="Edit section: Political conditions">edit</a>]</span> <span class="mw-headline" id="Political_conditions">Political conditions</span></h3>Internal, regional, and international <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Political" title="Political">political</a> conditions and events can have a profound effect on currency markets.<br />All exchange rates are susceptible to political instability and anticipations about the new ruling party. Political upheaval and instability can have a negative impact on a nation's economy. For example, destabilization of coalition governments in Pakistan and Thailand can negatively affect the value of their currencies. Similarly, in a country experiencing financial difficulties, the rise of a political faction that is perceived to be fiscally responsible can have the opposite effect. Also, events in one country in a region may spur positive/negative interest in a neighboring country and, in the process, affect its currency.<br /><h3><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Foreign_exchange_market&action=edit&section=16" title="Edit section: Market psychology">edit</a>]</span> <span class="mw-headline" id="Market_psychology">Market psychology</span></h3><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Market_psychology" title="Market psychology">Market psychology</a> and trader perceptions influence the foreign exchange market in a variety of ways:<br /><ul><li>Flights to quality: Unsettling international events can lead to a "<a class="mw-redirect" href="http://en.wikipedia.org/wiki/Flight_to_quality" title="Flight to quality">flight to quality</a>," a type of <a href="http://en.wikipedia.org/wiki/Capital_flight">capital flight</a> whereby investors move their assets to a perceived "<a href="http://en.wikipedia.org/wiki/Safe-haven_currency" title="Safe-haven currency">safe haven</a>." There will be a greater demand, thus a higher price, for currencies perceived as stronger over their relatively weaker counterparts. The <a href="http://en.wikipedia.org/wiki/United_States_dollar" title="United States dollar">U.S. dollar</a>, <a href="http://en.wikipedia.org/wiki/Swiss_franc">Swiss franc</a> and <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Gold_as_investment" title="Gold as investment">gold</a> have been traditional safe havens during times of political or economic uncertainty.<sup class="reference" id="cite_ref-16"><a href="http://en.wikipedia.org/wiki/Forex#cite_note-16">[16]</a></sup></li><li>Long-term trends: Currency markets often move in visible long-term <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Market_trends" title="Market trends">trends</a>. Although currencies do not have an annual growing season like physical commodities, <a href="http://en.wikipedia.org/wiki/Business_cycle" title="Business cycle">business cycles</a> do make themselves felt. Cycle analysis looks at longer-term price trends that may rise from economic or political trends.<sup class="reference" id="cite_ref-17"><a href="http://en.wikipedia.org/wiki/Forex#cite_note-17">[17]</a></sup></li><li>"Buy the rumor, sell the fact": This market truism can apply to many currency situations. It is the tendency for the price of a currency to reflect the impact of a particular action before it occurs and, when the anticipated event comes to pass, react in exactly the opposite direction. This may also be referred to as a market being "oversold" or "overbought".<sup class="reference" id="cite_ref-18"><a href="http://en.wikipedia.org/wiki/Forex#cite_note-18">[18]</a></sup> To buy the rumor or sell the fact can also be an example of the <a href="http://en.wikipedia.org/wiki/Cognitive_bias">cognitive bias</a> known as <a href="http://en.wikipedia.org/wiki/Anchoring">anchoring</a>, when investors focus too much on the relevance of outside events to currency prices.</li><li>Economic numbers: While <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Economic_indicators" title="Economic indicators">economic numbers</a> can certainly reflect economic policy, some reports and numbers take on a talisman-like effect: the number itself becomes important to market psychology and may have an immediate impact on short-term market moves. "What to watch" can change over time. In recent years, for example, <a href="http://en.wikipedia.org/wiki/Money_supply">money supply</a>, <a href="http://en.wikipedia.org/wiki/Employment">employment</a>, <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Trade_balance" title="Trade balance">trade balance</a> figures and <a href="http://en.wikipedia.org/wiki/Inflation">inflation</a> numbers have all taken turns in the spotlight.</li><li><a href="http://en.wikipedia.org/wiki/Technical_analysis" title="Technical analysis">Technical trading</a> considerations: As in other markets, the accumulated price movements in a currency pair such as EUR/USD can form apparent patterns that traders may attempt to use. Many traders study price charts in order to identify such patterns.<sup class="reference" id="cite_ref-19"><a href="http://en.wikipedia.org/wiki/Forex#cite_note-19">[19]</a></sup></li></ul><h2><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Foreign_exchange_market&action=edit&section=17" title="Edit section: Financial instruments">edit</a>]</span> <span class="mw-headline" id="Financial_instruments">Financial instruments</span></h2><h3><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Foreign_exchange_market&action=edit&section=18" title="Edit section: Spot">edit</a>]</span> <span class="mw-headline" id="Spot">Spot</span></h3>A <a href="http://en.wikipedia.org/wiki/Spot_price" title="Spot price">spot</a> transaction is a two-day delivery transaction (except in the case of trades between the US Dollar, Canadian Dollar, Turkish Lira, EURO and Russian Ruble, which settle the next business day), as opposed to the <a href="http://en.wikipedia.org/wiki/Futures_contract" title="Futures contract">futures contracts</a>, which are usually three months. This trade represents a “direct exchange” between two currencies, has the shortest time frame, involves cash rather than a contract; and interest is not included in the agreed-upon transaction.<br /><h3><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Foreign_exchange_market&action=edit&section=19" title="Edit section: Forward">edit</a>]</span> <span class="mw-headline" id="Forward">Forward</span></h3><div class="rellink boilerplate seealso">See also: <a href="http://en.wikipedia.org/wiki/Forward_contract">forward contract</a></div>One way to deal with the foreign exchange risk is to engage in a <a href="http://en.wikipedia.org/wiki/Forward_contract" title="Forward contract">forward</a> transaction. In this transaction, money does not actually change hands until some agreed upon future date. A buyer and seller agree on an exchange rate for any date in the future, and the transaction occurs on that date, regardless of what the market rates are then. The duration of the trade can be one day, a few days, months or years. Usually the date is decided by both parties. Then the forward contract is negotiated and agreed upon by both parties.<br /><h3><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Foreign_exchange_market&action=edit&section=20" title="Edit section: Swap">edit</a>]</span> <span class="mw-headline" id="Swap">Swap</span></h3><div class="rellink relarticle mainarticle">Main article: <a href="http://en.wikipedia.org/wiki/Forex_swap" title="Forex swap">foreign exchange swap</a></div>The most common type of forward transaction is the <a class="new" href="http://en.wikipedia.org/w/index.php?title=FX_swap&action=edit&redlink=1" title="FX swap (page does not exist)">FX swap</a>. In an FX swap, two parties exchange currencies for a certain length of time and agree to reverse the transaction at a later date. These are not standardized contracts and are not traded through an exchange.<br /><h3><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Foreign_exchange_market&action=edit&section=21" title="Edit section: Future">edit</a>]</span> <span class="mw-headline" id="Future">Future</span></h3><div class="rellink relarticle mainarticle">Main article: <a href="http://en.wikipedia.org/wiki/Currency_future">currency future</a></div>Futures are standardized and are usually traded on an exchange created for this purpose. The average contract length is roughly 3 months. Futures contracts are usually inclusive of any interest amounts.<br /><h3><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Foreign_exchange_market&action=edit&section=22" title="Edit section: Option">edit</a>]</span> <span class="mw-headline" id="Option">Option</span></h3><div class="rellink relarticle mainarticle">Main article: <a href="http://en.wikipedia.org/wiki/Foreign_exchange_option">foreign exchange option</a></div>A foreign exchange option (commonly shortened to just FX option) is a derivative where the owner has the right but not the obligation to exchange money denominated in one currency into another currency at a pre-agreed exchange rate on a specified date. The FX options market is the deepest, largest and most liquid market for options of any kind in the world..<br /><h2><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Foreign_exchange_market&action=edit&section=23" title="Edit section: Speculation">edit</a>]</span> <span class="mw-headline" id="Speculation">Speculation</span></h2>Controversy about currency <a href="http://en.wikipedia.org/wiki/Speculation" title="Speculation">speculators</a> and their effect on currency devaluations and national economies recurs regularly. Nevertheless, economists including <a href="http://en.wikipedia.org/wiki/Milton_Friedman">Milton Friedman</a> have argued that speculators ultimately are a stabilizing influence on the market and perform the important function of providing a market for <a href="http://en.wikipedia.org/wiki/Hedge_%28finance%29" title="Hedge (finance)">hedgers</a> and transferring risk from those people who don't wish to bear it, to those who do.<sup class="reference" id="cite_ref-20"><a href="http://en.wikipedia.org/wiki/Forex#cite_note-20">[20]</a></sup> Other economists such as <a href="http://en.wikipedia.org/wiki/Joseph_Stiglitz">Joseph Stiglitz</a> consider this argument to be based more on politics and a free market philosophy than on economics.<sup class="reference" id="cite_ref-21"><a href="http://en.wikipedia.org/wiki/Forex#cite_note-21">[21]</a></sup><br />Large <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Hedge_funds" title="Hedge funds">hedge funds</a> and other well capitalized "position traders" are the main professional speculators. According to some economists, individual traders could act as "noise traders" and have a more destabilizing role than larger and better informed actors.<sup class="reference" id="cite_ref-22"><a href="http://en.wikipedia.org/wiki/Forex#cite_note-22">[22]</a></sup><br />Currency speculation is considered a highly suspect activity in many countries.<sup class="noprint Inline-Template" style="white-space: nowrap;" title="The geographic scope in the vicinity of this tag is ambiguous">[<i><a href="http://en.wikipedia.org/wiki/Wikipedia:WikiProject_Countering_systemic_bias" title="Wikipedia:WikiProject Countering systemic bias">where?</a></i>]</sup> While investment in traditional financial instruments like bonds or stocks often is considered to contribute positively to economic growth by providing capital, currency speculation does not; according to this view, it is simply <a href="http://en.wikipedia.org/wiki/Gambling">gambling</a> that often interferes with economic policy. For example, in 1992, currency speculation forced the <a href="http://en.wikipedia.org/wiki/Sveriges_Riksbank" title="Sveriges Riksbank">Central Bank of Sweden</a> to raise interest rates for a few days to 500% per annum, and later to devalue the krona.<sup class="reference" id="cite_ref-23"><a href="http://en.wikipedia.org/wiki/Forex#cite_note-23">[23]</a></sup> Former Malaysian Prime Minister <a href="http://en.wikipedia.org/wiki/Mahathir_Mohamad">Mahathir Mohamad</a> is one well known proponent of this view. He blamed the devaluation of the <a href="http://en.wikipedia.org/wiki/Malaysian_ringgit">Malaysian ringgit</a> in 1997 on <a href="http://en.wikipedia.org/wiki/George_Soros">George Soros</a> and other speculators.<br /><a href="http://en.wikipedia.org/wiki/Gregory_J._Millman">Gregory J. Millman</a> reports on an opposing view, comparing speculators to "vigilantes" who simply help "enforce" international agreements and anticipate the effects of basic economic "laws" in order to profit.<sup class="reference" id="cite_ref-24"><a href="http://en.wikipedia.org/wiki/Forex#cite_note-24">[24]</a></sup><br />In this view, countries may develop unsustainable financial <a href="http://en.wikipedia.org/wiki/Economic_bubble" title="Economic bubble">bubbles</a> or otherwise mishandle their national economies, and foreign exchange speculators made the inevitable collapse happen sooner. A relatively quick collapse might even be preferable to continued economic mishandling, followed by an eventual, larger, collapse. Mahathir Mohamad and other critics of speculation are viewed as trying to deflect the blame from themselves for having caused the unsustainable economic conditions.<br /><h2><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Foreign_exchange_market&action=edit&section=24" title="Edit section: Risk aversion in forex">edit</a>]</span> <span class="mw-headline" id="Risk_aversion_in_forex">Risk aversion in forex</span></h2><div class="rellink boilerplate seealso">See also: <a href="http://en.wikipedia.org/wiki/Safe-haven_currency">Safe-haven currency</a></div><div class="thumb tright"><div class="thumbinner" style="width: 182px;"><a class="image" href="http://en.wikipedia.org/wiki/File:Equities_usd.JPG"><img alt="" class="thumbimage" height="93" src="http://upload.wikimedia.org/wikipedia/commons/thumb/1/1c/Equities_usd.JPG/180px-Equities_usd.JPG" width="180" /></a> <br /><div class="thumbcaption"><div class="magnify"><a class="internal" href="http://en.wikipedia.org/wiki/File:Equities_usd.JPG" title="Enlarge"><img alt="" height="11" src="http://bits.wikimedia.org/skins-1.17/common/images/magnify-clip.png" width="15" /></a></div>Fig.1 Chart showing MSCI World Index of Equities fell while the US Dollar Index rose.</div></div></div>Risk aversion in the forex is a kind of trading behavior exhibited by the foreign exchange market when a potentially adverse event happens which may affect market conditions. This behavior is caused when risk averse traders <a href="http://en.wikipedia.org/wiki/Liquidation" title="Liquidation">liquidate</a> their positions in risky assets and shift the funds to less risky assets due to uncertainty.<sup class="reference" id="cite_ref-25"><a href="http://en.wikipedia.org/wiki/Forex#cite_note-25">[25]</a></sup><br />In the context of the forex market, traders liquidate their positions in various currencies to take up positions in <a href="http://en.wikipedia.org/wiki/Safe-haven_currency" title="Safe-haven currency">safe-haven currencies</a>, such as the US Dollar.<sup class="reference" id="cite_ref-26"><a href="http://en.wikipedia.org/wiki/Forex#cite_note-26">[26]</a></sup> Sometimes, the choice of a safe haven currency is more of a choice based on prevailing sentiments rather than one of economic statistics. An example would be the Financial Crisis of 2008. The value of equities across world fell while the US Dollar strengthened (see Fig.1). This happened despite the strong focus of the crisis in the USA.<sup class="reference" id="cite_ref-27"><a href="http://en.wikipedia.org/wiki/Forex#cite_note-27">[27]</a></sup><br /><h2><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Foreign_exchange_market&action=edit&section=25" title="Edit section: See also">edit</a>]</span> <span class="mw-headline" id="See_also">See also</span></h2><table cellpadding="0" cellspacing="0" style="background: transparent;"><tbody><tr valign="top"> <td style="width: 15em;"><ul><li><a href="http://en.wikipedia.org/wiki/Balance_of_trade">Balance of trade</a></li><li><a href="http://en.wikipedia.org/wiki/Bretton_Woods_system">Bretton Woods system</a></li><li><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Currency_codes" title="Currency codes">Currency codes</a></li><li><a href="http://en.wikipedia.org/wiki/Currency_pair">Currency pair</a></li><li><a href="http://en.wikipedia.org/wiki/Currency_strength">Currency strength</a></li><li><a href="http://en.wikipedia.org/wiki/Foreign_currency_mortgage">Foreign currency mortgage</a></li></ul></td> <td style="width: 1.25em;"><br /></td> <td style="width: 15em;"><ul><li><a href="http://en.wikipedia.org/wiki/Foreign_exchange_controls">Foreign exchange controls</a></li><li><a href="http://en.wikipedia.org/wiki/Foreign_exchange_hedge">Foreign exchange hedge</a></li><li><a href="http://en.wikipedia.org/wiki/Foreign_exchange_reserves">Foreign exchange reserves</a></li><li><a href="http://en.wikipedia.org/wiki/Forex_scam" title="Forex scam">Foreign exchange scam</a></li><li><a href="http://en.wikipedia.org/wiki/Forex_swap" title="Forex swap">Foreign exchange swap</a></li></ul></td> <td style="width: 1.25em;"><br /></td> <td style="width: 15em;"><ul><li><a href="http://en.wikipedia.org/wiki/Money_market">Money market</a></li><li><a href="http://en.wikipedia.org/wiki/Nonfarm_payrolls">Nonfarm payrolls</a></li><li><a href="http://en.wikipedia.org/wiki/Special_Drawing_Rights">Special Drawing Rights</a></li><li><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Tobin_Tax" title="Tobin Tax">Tobin Tax</a></li><li><a href="http://en.wikipedia.org/wiki/World_currency">World currency</a></li></ul></td> <td style="width: 1.25em;"><br /><br /><br /></td> </tr></tbody></table><h2><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Foreign_exchange_market&action=edit&section=26" title="Edit section: Notes">edit</a>]</span> <span class="mw-headline" id="Notes">Notes</span></h2><div class="reflist" style="list-style-type: decimal;"><ol class="references"><li id="cite_note-15"><b><a href="http://en.wikipedia.org/wiki/Forex#cite_ref-15">^</a></b> The total sum is 200% because each currency trade always involves a <a href="http://en.wikipedia.org/wiki/Currency_pair">currency pair</a>.</li></ol></div><h2><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Foreign_exchange_market&action=edit&section=27" title="Edit section: References">edit</a>]</span> <span class="mw-headline" id="References">References</span></h2><div class="reflist references-column-count references-column-count-2" style="-moz-column-count: 2; -webkit-column-count: 2; column-count: 2; list-style-type: decimal;"><ol class="references"><li id="cite_note-0"><b><a href="http://en.wikipedia.org/wiki/Forex#cite_ref-0">^</a></b> <a class="external free" href="https://docs.google.com/fileview?id=0B_Qxj5U7eaJTZTJkODYzN2ItZjE3Yy00Y2M0LTk2ZmUtZGU0NzA3NGI4Y2Y5&hl=en&pli=1" rel="nofollow">https://docs.google.com/fileview?id=0B_Qxj5U7eaJTZTJkODYzN2ItZjE3Yy00Y2M0LTk2ZmUtZGU0NzA3NGI4Y2Y5&hl=en&pli=1</a></li><li id="cite_note-UNCTAD-1"><b><a href="http://en.wikipedia.org/wiki/Forex#cite_ref-UNCTAD_1-0">^</a></b> <a class="external text" href="http://www.igidr.ac.in/%7Emoney/mfc_10/Massimiliano_submission_40.pdf" rel="nofollow">Global imbalances and destabilizing speculation</a> (2007), UNCTAD Trade and development report 2007 (Chapter 1B).</li><li id="cite_note-BIS-2">^ <a href="http://en.wikipedia.org/wiki/Forex#cite_ref-BIS_2-0"><sup><i><b>a</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Forex#cite_ref-BIS_2-1"><sup><i><b>b</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Forex#cite_ref-BIS_2-2"><sup><i><b>c</b></i></sup></a> <a class="external text" href="http://www.bis.org/publ/rpfxf10t.htm" rel="nofollow">2010 Triennial Central Bank Survey</a>, Bank for International Settlements.</li><li id="cite_note-3"><b><a href="http://en.wikipedia.org/wiki/Forex#cite_ref-3">^</a></b> "<i><a class="external text" href="http://au.ibtimes.com/articles/110821/20110210/what-is-foreign-exchange-currency-conversion-financial-markets-forex-foreign-exchange-markets.htm" rel="nofollow">What is Foreign Exchange?</a></i>". Published by the <i><a class="external text" href="http://au.ibtimes.com/forex" rel="nofollow">International Business Times AU</a></i>. Retrieved: February 11, 2011.</li><li id="cite_note-BIS_survey-4"><b><a href="http://en.wikipedia.org/wiki/Forex#cite_ref-BIS_survey_4-0">^</a></b> <a class="external text" href="http://www.bis.org/publ/rpfx10.pdf" rel="nofollow">BIS Triennial Central Bank Survey</a>, published in September 2010.</li><li id="cite_note-5"><b><a href="http://en.wikipedia.org/wiki/Forex#cite_ref-5">^</a></b> <a class="external text" href="http://www.bis.org/publ/qtrpdf/r_qt1012f.htm" rel="nofollow">"Derivatives in emerging markets"</a>, the <a href="http://en.wikipedia.org/wiki/Bank_for_International_Settlements">Bank for International Settlements</a>, December 13, 2010</li><li id="cite_note-6"><b><a href="http://en.wikipedia.org/wiki/Forex#cite_ref-6">^</a></b> Source: Euromoney FX survey <a class="external text" href="http://www.euromoneyfix.com/Article.aspx?ArticleID=2473943" rel="nofollow">FX Poll 2010</a>: The Euromoney FX survey is the largest global poll of foreign exchange service providers.'</li><li id="cite_note-7"><b><a href="http://en.wikipedia.org/wiki/Forex#cite_ref-7">^</a></b> <a class="external text" href="http://www.bis.org/publ/qtrpdf/r_qt1012e.htm" rel="nofollow">"The $4 trillion question: what explains FX growth since the 2007 survey?</a>, the <a href="http://en.wikipedia.org/wiki/Bank_for_International_Settlements">Bank for International Settlements</a>, December 13, 2010</li><li id="cite_note-8"><b><a href="http://en.wikipedia.org/wiki/Forex#cite_ref-8">^</a></b> <span class="citation web">Gabriele Galati, Michael Melvin (December 2004). <a class="external text" href="http://www.bis.org/publ/qtrpdf/r_qt0412f.pdf" rel="nofollow">"Why has FX trading surged? Explaining the 2004 triennial survey"</a>. <a href="http://en.wikipedia.org/wiki/Bank_for_International_Settlements">Bank for International Settlements</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Why+has+FX+trading+surged%3F+Explaining+the+2004+triennial+survey&rft.atitle=&rft.aulast=Gabriele+Galati%2C+Michael+Melvin&rft.au=Gabriele+Galati%2C+Michael+Melvin&rft.date=December+2004&rft.pub=%5B%5BBank+for+International+Settlements%5D%5D&rft_id=http%3A%2F%2Fwww.bis.org%2Fpubl%2Fqtrpdf%2Fr_qt0412f.pdf&rfr_id=info:sid/en.wikipedia.org:Foreign_exchange_market"></span></li><li id="cite_note-9"><b><a href="http://en.wikipedia.org/wiki/Forex#cite_ref-9">^</a></b> <a href="http://en.wikipedia.org/wiki/Alan_Greenspan">Alan Greenspan</a>, <a class="external text" href="http://opinionjournal.com/editorial/feature.html?id=110010981" rel="nofollow"><i>The Roots of the Mortgage Crisis: Bubbles cannot be safely defused by monetary policy before the speculative fever breaks on its own.</i></a> , the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Wall_Street_Journal" title="Wall Street Journal">Wall Street Journal</a>, December 12, 2007</li><li id="cite_note-WSJ1-10"><b><a href="http://en.wikipedia.org/wiki/Forex#cite_ref-WSJ1_10-0">^</a></b> <span class="citation news">McKay, Peter A. (2005-07-26). <a class="external text" href="http://online.wsj.com/article/SB112233850336095645.html?mod=Markets-Main" rel="nofollow">"Scammers Operating on Periphery Of CFTC's Domain Lure Little Guy With Fantastic Promises of Profits"</a>. <i><a href="http://en.wikipedia.org/wiki/The_Wall_Street_Journal">The Wall Street Journal</a></i> (Dow Jones and Company)<span class="reference-accessdate">. Retrieved 2007-10-31</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Scammers+Operating+on+Periphery+Of+CFTC%27s+Domain+Lure+Little+Guy+With+Fantastic+Promises+of+Profits&rft.jtitle=%5B%5BThe+Wall+Street+Journal%5D%5D&rft.aulast=McKay&rft.aufirst=Peter+A.&rft.au=McKay%2C%26%2332%3BPeter+A.&rft.date=2005-07-26&rft.pub=Dow+Jones+and+Company&rft_id=http%3A%2F%2Fonline.wsj.com%2Farticle%2FSB112233850336095645.html%3Fmod%3DMarkets-Main&rfr_id=info:sid/en.wikipedia.org:Foreign_exchange_market"></span></li><li id="cite_note-NYTimes1-11"><b><a href="http://en.wikipedia.org/wiki/Forex#cite_ref-NYTimes1_11-0">^</a></b> <span class="citation news">Egan, Jack (2005-06-19). <a class="external text" href="http://www.nytimes.com/2005/06/19/business/yourmoney/19fore.html?_r=2&adxnnl=1&oref=slogin&adxnnlx=1191337503-g1yHfewhqPWye0XtI+Eq0A&oref=slogin" rel="nofollow">"Check the Currency Risk. Then Multiply by 100"</a>. <i><a href="http://en.wikipedia.org/wiki/The_New_York_Times">The New York Times</a></i><span class="reference-accessdate">. Retrieved 2007-10-30</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Check+the+Currency+Risk.+Then+Multiply+by+100&rft.jtitle=%5B%5BThe+New+York+Times%5D%5D&rft.aulast=Egan&rft.aufirst=Jack&rft.au=Egan%2C%26%2332%3BJack&rft.date=2005-06-19&rft_id=http%3A%2F%2Fwww.nytimes.com%2F2005%2F06%2F19%2Fbusiness%2Fyourmoney%2F19fore.html%3F_r%3D2%26adxnnl%3D1%26oref%3Dslogin%26adxnnlx%3D1191337503-g1yHfewhqPWye0XtI%2BEq0A%26oref%3Dslogin&rfr_id=info:sid/en.wikipedia.org:Foreign_exchange_market"></span></li><li id="cite_note-12"><b><a href="http://en.wikipedia.org/wiki/Forex#cite_ref-12">^</a></b> The Sunday Times (UK), 16 July 2006</li><li id="cite_note-13"><b><a href="http://en.wikipedia.org/wiki/Forex#cite_ref-13">^</a></b> The 5 largest in the UK are <a href="http://en.wikipedia.org/wiki/Travelex_Group" title="Travelex Group">Travelex</a>, <a href="http://en.wikipedia.org/wiki/Moneycorp">Moneycorp</a>, <a href="http://en.wikipedia.org/wiki/HiFX">HiFX</a>, <a href="http://en.wikipedia.org/wiki/World_First">World First</a> and <a href="http://en.wikipedia.org/wiki/Currencies_Direct">Currencies Direct</a></li><li id="cite_note-14"><b><a href="http://en.wikipedia.org/wiki/Forex#cite_ref-14">^</a></b> Reserve Currencies correct as of Friday, September 17, 2010. Australian Dollar, Canadian Dollar and Swiss Francs are rarely 5th or 6th most traded currency in the world.</li><li id="cite_note-16"><b><a href="http://en.wikipedia.org/wiki/Forex#cite_ref-16">^</a></b> <a class="external text" href="http://glossary.reuters.com/index.php/Safe_Haven_Currency" rel="nofollow">Safe haven currency</a></li><li id="cite_note-17"><b><a href="http://en.wikipedia.org/wiki/Forex#cite_ref-17">^</a></b> John J. Murphy, <i>Technical Analysis of the Financial Markets</i> (New York Institute of Finance, 1999), pp. 343–375.</li><li id="cite_note-18"><b><a href="http://en.wikipedia.org/wiki/Forex#cite_ref-18">^</a></b> <a class="external text" href="http://www.investopedia.com/terms/o/overbought.asp" rel="nofollow">Investopedia</a></li><li id="cite_note-19"><b><a href="http://en.wikipedia.org/wiki/Forex#cite_ref-19">^</a></b> Sam Y. Cross, <a class="external text" href="http://www.newyorkfed.org/education/addpub/usfxm/" rel="nofollow"><i>All About the Foreign Exchange Market in the United States</i></a>, <a href="http://en.wikipedia.org/wiki/Federal_Reserve_Bank_of_New_York">Federal Reserve Bank of New York</a> (1998), chapter 11, pp. 113–115.</li><li id="cite_note-20"><b><a href="http://en.wikipedia.org/wiki/Forex#cite_ref-20">^</a></b> Michael A. S. Guth, "<a class="external text" href="http://michaelguth.com/economist/chap1.htm" rel="nofollow">Profitable Destabilizing Speculation</a>," Chapter 1 in Michael A. S. Guth, SPECULATIVE BEHAVIOR AND THE OPERATION OF COMPETITIVE MARKETS UNDER UNCERTAINTY, Avebury Ashgate Publishing, Aldorshot, England (1994), <a class="internal mw-magiclink-isbn" href="http://en.wikipedia.org/wiki/Special:BookSources/1856289850">ISBN 1856289850</a>.</li><li id="cite_note-21"><b><a href="http://en.wikipedia.org/wiki/Forex#cite_ref-21">^</a></b> <a class="external text" href="http://www.globalpolicy.org/socecon/bwi-wto/critics/2000/whatilearned.htm" rel="nofollow">What I Learned at the World Economic Crisis</a> Joseph Stiglitz, The New Republic, April 17, 2000, reprinted at GlobalPolicy.org</li><li id="cite_note-22"><b><a href="http://en.wikipedia.org/wiki/Forex#cite_ref-22">^</a></b> Summers LH and Summers VP (1989) 'When financial markets work too well: a Cautious case for a securities transaction tax' Journal of financial services</li><li id="cite_note-23"><b><a href="http://en.wikipedia.org/wiki/Forex#cite_ref-23">^</a></b> <a class="external text" href="http://www.iht.com/articles/1992/09/17/perc.php" rel="nofollow">But Don't Rush Out to Buy Kronor: Sweden's 500% Gamble - International Herald Tribune</a></li><li id="cite_note-24"><b><a href="http://en.wikipedia.org/wiki/Forex#cite_ref-24">^</a></b> Gregory J. Millman, Around the World on a Trillion Dollars a Day, Bantam Press, New York, 1995.</li><li id="cite_note-25"><b><a href="http://en.wikipedia.org/wiki/Forex#cite_ref-25">^</a></b> <span class="citation web"><a class="external text" href="http://www.investopedia.com/terms/r/riskaverse.asp" rel="nofollow">"Risk Averse"</a>. <a href="http://en.wikipedia.org/wiki/Investopedia">Investopedia</a><span class="reference-accessdate">. Retrieved 2010-02-25</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Risk+Averse&rft.atitle=&rft.pub=%5B%5BInvestopedia%5D%5D&rft_id=http%3A%2F%2Fwww.investopedia.com%2Fterms%2Fr%2Friskaverse.asp&rfr_id=info:sid/en.wikipedia.org:Foreign_exchange_market"></span></li><li id="cite_note-26"><b><a href="http://en.wikipedia.org/wiki/Forex#cite_ref-26">^</a></b> <span class="citation news"><a class="external text" href="http://www.reuters.com/article/idUSN0515775320100205" rel="nofollow">"GLOBAL MARKETS-US stocks rebound, dollar gains on risk aversion"</a>. <a href="http://en.wikipedia.org/wiki/Reuters">Reuters</a>. 2010-02-05<span class="reference-accessdate">. Retrieved 2010-02-27</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=GLOBAL+MARKETS-US+stocks+rebound%2C+dollar+gains+on+risk+aversion&rft.atitle=&rft.date=2010-02-05&rft.pub=%5B%5BReuters%5D%5D&rft_id=http%3A%2F%2Fwww.reuters.com%2Farticle%2FidUSN0515775320100205&rfr_id=info:sid/en.wikipedia.org:Foreign_exchange_market"></span></li><li id="cite_note-27"><b><a href="http://en.wikipedia.org/wiki/Forex#cite_ref-27">^</a></b> <span class="citation news">Stewart, Heather (2008-04-09). <a class="external text" href="http://www.guardian.co.uk/business/2008/apr/09/useconomy.subprimecrisis" rel="nofollow">"IMF says US crisis is 'largest financial shock since Great Depression'"</a>. London: <a href="http://en.wikipedia.org/wiki/Guardian.co.uk">guardian.co.uk</a><span class="reference-accessdate">. Retrieved 2010-02-27</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=IMF+says+US+crisis+is+%27largest+financial+shock+since+Great+Depression%27&rft.atitle=&rft.aulast=Stewart&rft.aufirst=Heather&rft.au=Stewart%2C%26%2332%3BHeather&rft.date=2008-04-09&rft.place=London&rft.pub=%5B%5Bguardian.co.uk%5D%5D&rft_id=http%3A%2F%2Fwww.guardian.co.uk%2Fbusiness%2F2008%2Fapr%2F09%2Fuseconomy.subprimecrisis&rfr_id=info:sid/en.wikipedia.org:Foreign_exchange_market"></span></li></ol></div><h2><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Foreign_exchange_market&action=edit&section=28" title="Edit section: External links">edit</a>]</span> <span class="mw-headline" id="External_links">External links</span></h2><table class="metadata mbox-small plainlinks" style="background-color: #f9f9f9; border: 1px solid #aaa;"><tbody><tr> <td class="mbox-image"><img alt="" height="40" src="http://upload.wikimedia.org/wikipedia/commons/thumb/4/4a/Commons-logo.svg/30px-Commons-logo.svg.png" width="30" /></td> <td class="mbox-text">Wikimedia Commons has media related to: <i><b><a class="extiw" href="http://commons.wikimedia.org/wiki/Category:Foreign_exchange_market" title="commons:Category:Foreign exchange market">Foreign exchange market</a></b></i></td> </tr></tbody></table><ul><li><a class="external text" href="http://www.bis.org/publ/qtrpdf/r_qt1012h.htm" rel="nofollow">A user's guide to the Triennial Central Bank Survey of foreign exchange market activity, Bank for International Settlements</a></li><li><a class="external text" href="http://www.bankofengland.co.uk/markets/forex/fxjsc/" rel="nofollow">London Foreign Exchange Committee with links (on right) to committees in NY, Tokyo, Canada, Australia, HK, Singapore</a></li><li><a class="external text" href="http://www.federalreserve.gov/releases/h10/update/" rel="nofollow">United States Federal Reserve daily update of exchange rates</a></li><li><a class="external text" href="http://www.bankofcanada.ca/en/rates/exchform.html" rel="nofollow">Bank of Canada historical (10-year) currency converter and data download</a></li><li><a class="external text" href="http://www.cfr.statslab.cam.ac.uk/events/content/20056/mcgroarty2.pdf" rel="nofollow">Microstructure effects, bid-ask spreads and volatility in the spot foreign exchange market pre and post-EMU</a></li><li><a class="external text" href="http://stats.oecd.org/Index.aspx?QueryId=169" rel="nofollow">OECD Exchange rate statistics (monthly averages)</a></li><li><a class="external text" href="http://www.voxeu.org/index.php?q=node/4170" rel="nofollow">"Lessons for the foreign exchange market from the global financial crisis" Two experts review how global FX markets coped after Lehman's bankruptcy in Sept 2008</a></li></ul></div>ripplehttp://www.blogger.com/profile/17326365690819936341noreply@blogger.comtag:blogger.com,1999:blog-6905780489869824283.post-9828299246228389552011-03-22T11:32:00.000-07:002011-04-06T14:15:46.811-07:00Mardi Gras<div dir="ltr" style="text-align: left;" trbidi="on"><div class="dablink">This article is about the carnival. For other uses, see <a href="http://en.wikipedia.org/wiki/Mardi_Gras_%28disambiguation%29">Mardi Gras (disambiguation)</a>.</div><table cellspacing="5" class="infobox" style="width: 22em;"><tbody><tr> <th class="" colspan="2" style="background-color: lavender; font-size: 125%; font-weight: bold; text-align: center; text-align: center;">Mardi Gras<br /><small>(Also known as <a href="http://en.wikipedia.org/wiki/Shrove_Tuesday">Shrove Tuesday</a> or Fat Tuesday)</small></th> </tr><tr class=""> <td class="" colspan="2" style="text-align: center;"><a class="image" href="http://en.wikipedia.org/wiki/File:KosmicFrenchmenPurpleFaceMardiGras2009.JPG" title="Mardi Gras(Also known as Shrove Tuesday or Fat Tuesday)"><img alt="Mardi Gras(Also known as Shrove Tuesday or Fat Tuesday)" height="169" src="http://upload.wikimedia.org/wikipedia/commons/thumb/3/3d/KosmicFrenchmenPurpleFaceMardiGras2009.JPG/225px-KosmicFrenchmenPurpleFaceMardiGras2009.JPG" width="225" /></a><br />Mardi Gras celebrations in <a href="http://en.wikipedia.org/wiki/New_Orleans">New Orleans</a>, USA</td> </tr><tr class=""> <th scope="row" style="text-align: left;">Type</th> <td class="">Local, cultural, Catholic</td> </tr><tr class=""> <th scope="row" style="text-align: left;">Significance</th> <td class="">Celebration prior to fasting season of <a href="http://en.wikipedia.org/wiki/Lent">Lent</a>.</td> </tr><tr class=""> <th scope="row" style="text-align: left;">2011 date</th> <td class="">March 8</td> </tr><tr class=""> <th scope="row" style="text-align: left;">2012 date</th> <td class="">February 21</td> </tr><tr class=""> <th scope="row" style="text-align: left;">Celebrations</th> <td class="">Parades, parties</td> </tr><tr class=""> <th scope="row" style="text-align: left;">Related to</th> <td class=""><a href="http://en.wikipedia.org/wiki/Carnival">Carnival</a></td> </tr></tbody></table>The terms "<b>Mardi Gras</b>" (pronounced <span class="IPA" title="Pronunciation in the International Phonetic Alphabet (IPA)"><a href="http://en.wikipedia.org/wiki/Wikipedia:IPA_for_English" title="Wikipedia:IPA for English">/ˈmɑrdiɡrɑː/</a></span>), "<b>Mardi Gras season</b>", and "<b>Carnival season</b>",<sup class="reference" id="cite_ref-AU_0-0"><a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_note-AU-0">[1]</a></sup><sup class="reference" id="cite_ref-EN_1-0"><a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_note-EN-1">[2]</a></sup><sup class="reference" id="cite_ref-NO_2-0"><a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_note-NO-2">[3]</a></sup><sup class="reference" id="cite_ref-AL_3-0"><a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_note-AL-3">[4]</a></sup><sup class="reference" id="cite_ref-SD_4-0"><a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_note-SD-4">[5]</a></sup><sup class="reference" id="cite_ref-TX_5-0"><a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_note-TX-5">[6]</a></sup> in English, refer to events of the <a href="http://en.wikipedia.org/wiki/Carnival">Carnival</a> celebrations, beginning on or after <a href="http://en.wikipedia.org/wiki/Epiphany_%28holiday%29" title="Epiphany (holiday)">Epiphany</a> and culminating on the day before <a href="http://en.wikipedia.org/wiki/Ash_Wednesday">Ash Wednesday</a>. Mardi Gras is French for "Fat Tuesday" (in ethnic English tradition, <a href="http://en.wikipedia.org/wiki/Shrove_Tuesday">Shrove Tuesday</a>), referring to the practice of the last night of eating richer, fatty foods before the ritual fasting of the <a href="http://en.wikipedia.org/wiki/Lent" title="Lent">Lenten</a> season, which begins on <a href="http://en.wikipedia.org/wiki/Ash_Wednesday">Ash Wednesday</a>. Related popular practices are associated with celebrations before the fasting and religious obligations associated with the <a href="http://en.wikipedia.org/wiki/Penitential">penitential</a> season of <a href="http://en.wikipedia.org/wiki/Lent">Lent</a>. Popular practices include wearing masks and costumes, overturning social conventions, dancing, sports competitions, parades, etc. Similar expressions to Mardi Gras appear in other European languages sharing the Christian tradition. In English, the day is called Shrove Tuesday, associated with the religious requirement for confession before Lent begins.<br />In many areas, the term "Mardi Gras" has come to mean the whole period of activity related to the celebratory events, beyond just the single day. In some US cities, it is now called "Mardi Gras Day" or "Fat Tuesday".<sup class="reference" id="cite_ref-AU_0-1"><a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_note-AU-0">[1]</a></sup><sup class="reference" id="cite_ref-EN_1-1"><a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_note-EN-1">[2]</a></sup><sup class="reference" id="cite_ref-NO_2-1"><a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_note-NO-2">[3]</a></sup><sup class="reference" id="cite_ref-AL_3-1"><a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_note-AL-3">[4]</a></sup><sup class="reference" id="cite_ref-SD_4-1"><a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_note-SD-4">[5]</a></sup><sup class="reference" id="cite_ref-TX_5-1"><a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_note-TX-5">[6]</a></sup> The festival season varies from city to city, as some traditions consider Mardi Gras the entire period between <a href="http://en.wikipedia.org/wiki/Epiphany_%28holiday%29" title="Epiphany (holiday)">Epiphany</a> or <a href="http://en.wikipedia.org/wiki/Twelfth_Night_%28holiday%29" title="Twelfth Night (holiday)">Twelfth Night</a> and Ash Wednesday.<sup class="reference" id="cite_ref-carnivalterminology_6-0"><a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_note-carnivalterminology-6">[7]</a></sup> Others treat the final three-day period before Ash Wednesday as the Mardi Gras.<sup class="reference" id="cite_ref-7"><a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_note-7">[8]</a></sup> In <a href="http://en.wikipedia.org/wiki/Mardi_Gras_in_Mobile" title="Mardi Gras in Mobile">Mobile</a>, <a href="http://en.wikipedia.org/wiki/Alabama">Alabama</a>, Mardi Gras-associated social events begin in November, followed by <a href="http://en.wikipedia.org/wiki/Mystic_society">mystic society</a> balls on <a href="http://en.wikipedia.org/wiki/Thanksgiving">Thanksgiving</a>,<sup class="reference" id="cite_ref-carnivalterminology_6-1"><a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_note-carnivalterminology-6">[7]</a></sup><sup class="reference" id="cite_ref-MCA_8-0"><a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_note-MCA-8">[9]</a></sup> then New Year's Eve, followed by parades and balls in January and February, celebrating up to midnight before <a href="http://en.wikipedia.org/wiki/Ash_Wednesday">Ash Wednesday</a>. In earlier times parades were held on New Year's Day.<sup class="reference" id="cite_ref-carnivalterminology_6-2"><a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_note-carnivalterminology-6">[7]</a></sup> Other cities famous for Mardi Gras celebrations include <a href="http://en.wikipedia.org/wiki/Rio_de_Janeiro">Rio de Janeiro</a>, Brazil, <a href="http://en.wikipedia.org/wiki/Barranquilla">Barranquilla</a>, Colombia, <a href="http://en.wikipedia.org/wiki/Sydney">Sydney</a>, Australia, <a href="http://en.wikipedia.org/wiki/Port_of_Spain">Port of Spain</a>, Trinidad and Tobago, <a href="http://en.wikipedia.org/wiki/Quebec_City">Quebec City</a>, Canada; <a href="http://en.wikipedia.org/wiki/Mazatl%C3%A1n">Mazatlán</a>, <a href="http://en.wikipedia.org/wiki/Sinaloa">Sinaloa</a> in Mexico; and <a href="http://en.wikipedia.org/wiki/New_Orleans">New Orleans</a>, <a href="http://en.wikipedia.org/wiki/Louisiana">Louisiana</a>, United States.<br />Carnival is an important celebration in Catholic European nations. In the United Kingdom and Ireland, the week before Ash Wednesday is called "<a class="mw-redirect" href="http://en.wikipedia.org/wiki/Shrovetide" title="Shrovetide">shrovetide</a>", ending on Shrove Tuesday. It has its popular celebratory aspects as well. Pancakes are a traditional food. Pancakes and related fried breads or pastries made with sugar, fat and eggs are also traditionally consumed at this time in many parts of Latin America and the <a href="http://en.wikipedia.org/wiki/Caribbean_Carnival" title="Caribbean Carnival">Caribbean</a>.<br /><div class="thumb tright"><div class="thumbinner" style="width: 222px;"><a class="image" href="http://en.wikipedia.org/wiki/File:MardiGrasDakar.JPG"><img alt="" class="thumbimage" height="165" src="http://upload.wikimedia.org/wikipedia/commons/thumb/b/b3/MardiGrasDakar.JPG/220px-MardiGrasDakar.JPG" width="220" /></a> <br /><div class="thumbcaption"><div class="magnify"><a class="internal" href="http://en.wikipedia.org/wiki/File:MardiGrasDakar.JPG" title="Enlarge"><img alt="" height="11" src="http://bits.wikimedia.org/skins-1.17/common/images/magnify-clip.png" width="15" /></a></div>Mardi Gras in <a href="http://en.wikipedia.org/wiki/Dakar">Dakar</a>, Senegal.</div></div></div><div class="thumb tright"><div class="thumbinner" style="width: 222px;"><a class="image" href="http://en.wikipedia.org/wiki/File:Marseille-carnival-sun-and-moon.jpg"><img alt="" class="thumbimage" height="176" src="http://upload.wikimedia.org/wikipedia/commons/thumb/d/de/Marseille-carnival-sun-and-moon.jpg/220px-Marseille-carnival-sun-and-moon.jpg" width="220" /></a> <br /><div class="thumbcaption"><div class="magnify"><a class="internal" href="http://en.wikipedia.org/wiki/File:Marseille-carnival-sun-and-moon.jpg" title="Enlarge"><img alt="" height="11" src="http://bits.wikimedia.org/skins-1.17/common/images/magnify-clip.png" width="15" /></a></div>Mardi Gras in <a href="http://en.wikipedia.org/wiki/Marseille">Marseille</a>, France.</div></div></div><div class="thumb tright"><div class="thumbinner" style="width: 222px;"><a class="image" href="http://en.wikipedia.org/wiki/File:Binche_-_Les_Gilles.jpg"><img alt="" class="thumbimage" height="157" src="http://upload.wikimedia.org/wikipedia/commons/thumb/7/71/Binche_-_Les_Gilles.jpg/220px-Binche_-_Les_Gilles.jpg" width="220" /></a> <br /><div class="thumbcaption"><div class="magnify"><a class="internal" href="http://en.wikipedia.org/wiki/File:Binche_-_Les_Gilles.jpg" title="Enlarge"><img alt="" height="11" src="http://bits.wikimedia.org/skins-1.17/common/images/magnify-clip.png" width="15" /></a></div>Mardi Gras in <a href="http://en.wikipedia.org/wiki/Binche">Binche</a>, Belgium.</div></div></div><table class="toc" id="toc"><tbody><tr> <td><div id="toctitle"><h2>Contents</h2><span class="toctoggle">[<a class="internal" href="http://en.wikipedia.org/wiki/Mardi_gras#" id="togglelink">hide</a>]</span></div><ul><li class="toclevel-1 tocsection-1"><a href="http://en.wikipedia.org/wiki/Mardi_gras#Belgium"><span class="tocnumber">1</span> <span class="toctext">Belgium</span></a></li><li class="toclevel-1 tocsection-2"><a href="http://en.wikipedia.org/wiki/Mardi_gras#Germany"><span class="tocnumber">2</span> <span class="toctext">Germany</span></a></li><li class="toclevel-1 tocsection-3"><a href="http://en.wikipedia.org/wiki/Mardi_gras#Italy"><span class="tocnumber">3</span> <span class="toctext">Italy</span></a></li><li class="toclevel-1 tocsection-4"><a href="http://en.wikipedia.org/wiki/Mardi_gras#Netherlands"><span class="tocnumber">4</span> <span class="toctext">Netherlands</span></a></li><li class="toclevel-1 tocsection-5"><a href="http://en.wikipedia.org/wiki/Mardi_gras#Sweden"><span class="tocnumber">5</span> <span class="toctext">Sweden</span></a></li><li class="toclevel-1 tocsection-6"><a href="http://en.wikipedia.org/wiki/Mardi_gras#United_States"><span class="tocnumber">6</span> <span class="toctext">United States</span></a></li><li class="toclevel-1 tocsection-7"><a href="http://en.wikipedia.org/wiki/Mardi_gras#See_also"><span class="tocnumber">7</span> <span class="toctext">See also</span></a></li><li class="toclevel-1 tocsection-8"><a href="http://en.wikipedia.org/wiki/Mardi_gras#References"><span class="tocnumber">8</span> <span class="toctext">References</span></a></li><li class="toclevel-1 tocsection-9"><a href="http://en.wikipedia.org/wiki/Mardi_gras#External_links"><span class="tocnumber">9</span> <span class="toctext">External links</span></a></li></ul></td> </tr></tbody></table><h2><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Mardi_Gras&action=edit&section=1" title="Edit section: Belgium">edit</a>]</span> <span class="mw-headline" id="Belgium">Belgium</span></h2>In the Belgian city of <a href="http://en.wikipedia.org/wiki/Binche">Binche</a> the <i>Mardi Gras</i> festival is the most important day of the year and the summit of the <a href="http://en.wikipedia.org/wiki/Carnival_of_Binche">Carnival of Binche</a>. Around 1000 <i><a href="http://en.wikipedia.org/wiki/Gilles">Gilles</a></i> can be found dancing throughout the city from morning till well past dusk, whilst traditional carnival songs play. In 2003, the "Carnival of Binche" was proclaimed one of the <a href="http://en.wikipedia.org/wiki/Masterpieces_of_the_Oral_and_Intangible_Heritage_of_Humanity">Masterpieces of the Oral and Intangible Heritage of Humanity</a> by <a href="http://en.wikipedia.org/wiki/UNESCO">UNESCO</a>.<br /><h2><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Mardi_Gras&action=edit&section=2" title="Edit section: Germany">edit</a>]</span> <span class="mw-headline" id="Germany">Germany</span></h2>The celebration of Mardi Gras in Germany is called <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Karneval" title="Karneval">Karneval</a>, <a href="http://en.wikipedia.org/wiki/Fastnacht">Fastnacht</a>, or <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Fasching" title="Fasching">Fasching</a>.<sup class="reference" id="cite_ref-9"><a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_note-9">[10]</a></sup> <i>Fastnacht</i> means "Eve of the Beginning of the Fast", and is celebrated the day before Ash Wednesday.<br />The most famous parades are held in <a href="http://en.wikipedia.org/wiki/Cologne">Cologne</a>, <a href="http://en.wikipedia.org/wiki/Mainz">Mainz</a>, and <a href="http://en.wikipedia.org/wiki/D%C3%BCsseldorf">Düsseldorf</a> on the Monday before Ash Wednesday, called <i>Rosenmontag</i>.<br /><h2><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Mardi_Gras&action=edit&section=3" title="Edit section: Italy">edit</a>]</span> <span class="mw-headline" id="Italy">Italy</span></h2>Carnevale is the traditional pre-Lenten celebration in Italy. Carnevale was Mardi Gras predecessor. The French borrowed this idea and made it popular. This is a time of merry-making, masquerade processions, masked balls, parades, pageants, jugglers, magicians, stilt walkers, elegant costumes and opulent masks, singing and dancing, fireworks, and outdoor feasts in the weeks prior to Ash Wednesday. The festivities of the last days of carnevale are the most intense as they culminate on <i>Martedí Grasso</i> (Mardi Gras or Shrove Tuesday). There are traditional foods and <i>dolci</i> (sweets) distinctively associated with carnevale, including fritelle, crespelle, sfingi, castagnole, cenci, nodi, chiacchere, bugie, galani, fritole, berlingaccio, sanguinaccio and tortelli, among others.<br />In <a href="http://en.wikipedia.org/wiki/Milan">Milan</a> Mardi Gras is not the climax of Carnival, since the Carnival lasts four more days, ending on the Saturday after <a href="http://en.wikipedia.org/wiki/Ash_Wednesday">Ash Wednesday</a>, because of the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Ambrosian_rite" title="Ambrosian rite">Ambrosian rite</a>. The last day of Carnival, therefore, is the "Sabato grasso" (Shrove or Fat Saturday).<br /><h2><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Mardi_Gras&action=edit&section=4" title="Edit section: Netherlands">edit</a>]</span> <span class="mw-headline" id="Netherlands">Netherlands</span></h2>The Netherlands also has a festival similar to Mardi Gras. It's called <a href="http://en.wikipedia.org/wiki/Carnival" title="Carnival">Carnaval</a> and is similar to the Venice Carnival. The origin of the word Carnaval is 'Carne Vale' which means Goodbye to the meat in Latin. It marks the beginning of the sacred period that leads to Easter.<br />The real festival is held in the southern part of the Netherlands in the province of <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Noord-Brabant" title="Noord-Brabant">Noord-Brabant</a> and <a href="http://en.wikipedia.org/wiki/Limburg">Limburg</a>.<br /><h2><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Mardi_Gras&action=edit&section=5" title="Edit section: Sweden">edit</a>]</span> <span class="mw-headline" id="Sweden">Sweden</span></h2>In Sweden the celebration is called <a href="http://en.wikipedia.org/wiki/Fettisdagen">Fettisdagen</a>. It comes from the word "fett" (fat) and "tisdag" (Tuesday). Originally, this was the only day one should eat <a href="http://en.wikipedia.org/wiki/Semla" title="Semla">semlor</a>.<sup class="reference" id="cite_ref-semla_10-0"><a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_note-semla-10">[11]</a></sup> These are now sold in most grocery stores and bakeries preceding the holiday, and up until Easter.<br /><h2><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Mardi_Gras&action=edit&section=6" title="Edit section: United States">edit</a>]</span> <span class="mw-headline" id="United_States">United States</span></h2><div class="thumb tright"><div class="thumbinner" style="width: 222px;"><a class="image" href="http://en.wikipedia.org/wiki/File:My_favorite_costume_of_the_day_Mardi_Gras_2010.jpg"><img alt="" class="thumbimage" height="293" src="http://upload.wikimedia.org/wikipedia/commons/thumb/b/b2/My_favorite_costume_of_the_day_Mardi_Gras_2010.jpg/220px-My_favorite_costume_of_the_day_Mardi_Gras_2010.jpg" width="220" /></a> <br /><div class="thumbcaption"><div class="magnify"><a class="internal" href="http://en.wikipedia.org/wiki/File:My_favorite_costume_of_the_day_Mardi_Gras_2010.jpg" title="Enlarge"><img alt="" height="11" src="http://bits.wikimedia.org/skins-1.17/common/images/magnify-clip.png" width="15" /></a></div>Mardi Gras 2010 celebrants in the French Quarter of New Orleans, in the traditional colors of purple, green, and gold.</div></div></div><div class="rellink relarticle mainarticle">Main article: <a href="http://en.wikipedia.org/wiki/Mardi_Gras_in_the_United_States">Mardi Gras in the United States</a></div>While not observed nationally throughout the United States, a number of traditionally ethnic French cities and regions in the country have notable celebrations. Mardi Gras arrived in North America as a French Catholic tradition with the Le Moyne brothers,<sup class="reference" id="cite_ref-MGtime_11-0"><a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_note-MGtime-11">[12]</a></sup> <a href="http://en.wikipedia.org/wiki/Pierre_Le_Moyne_d%27Iberville">Pierre Le Moyne d'Iberville</a> and <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Jean-Baptiste_Le_Moyne_de_Bienville" title="Jean-Baptiste Le Moyne de Bienville">Jean-Baptiste Le Moyne de Bienville</a>, in the late 17th century, when <a class="mw-redirect" href="http://en.wikipedia.org/wiki/King_Louis_XIV" title="King Louis XIV">King Louis XIV</a> sent the pair to defend France's claim on the territory of <i><a href="http://en.wikipedia.org/wiki/Louisiana_%28New_France%29" title="Louisiana (New France)">Louisiane</a></i>, which included what are now the U.S. states of <a href="http://en.wikipedia.org/wiki/Alabama">Alabama</a>, <a href="http://en.wikipedia.org/wiki/Mississippi">Mississippi</a>, and <a href="http://en.wikipedia.org/wiki/Louisiana">Louisiana</a>.<sup class="reference" id="cite_ref-MGtime_11-1"><a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_note-MGtime-11">[12]</a></sup><br />The expedition, led by Iberville, entered the mouth of the <a href="http://en.wikipedia.org/wiki/Mississippi_River">Mississippi River</a> on the evening of March 2, 1699, <a href="http://en.wikipedia.org/wiki/Lundi_Gras">Lundi Gras</a>. They did not yet know it was the river explored and claimed for France by <a href="http://en.wikipedia.org/wiki/Ren%C3%A9-Robert_Cavelier,_Sieur_de_La_Salle">René-Robert Cavelier, Sieur de La Salle</a> in 1683. The party proceeded upstream to a place on the west bank about 60 miles downriver from where <a href="http://en.wikipedia.org/wiki/New_Orleans">New Orleans</a> is today, and made camp. This was on March 3, 1699, Mardi Gras, so in honor of this holiday, Iberville named the spot <i>Point du Mardi Gras</i> (French: "Mardi Gras Point") and called the nearby tributary Bayou Mardi Gras. <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Jean-Baptiste_Le_Moyne_de_Bienville" title="Jean-Baptiste Le Moyne de Bienville">Bienville</a> went on to found the settlement of <a href="http://en.wikipedia.org/wiki/Mobile,_Alabama">Mobile, Alabama</a> in 1702 as the first capital of French Louisiana.<sup class="reference" id="cite_ref-TLhist_12-0"><a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_note-TLhist-12">[13]</a></sup> In 1703 French settlers in Mobile began the Mardi Gras celebration tradition.<sup class="reference" id="cite_ref-MGtime_11-2"><a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_note-MGtime-11">[12]</a></sup><sup class="reference" id="cite_ref-LOCgras_13-0"><a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_note-LOCgras-13">[14]</a></sup><sup class="reference" id="cite_ref-MBAYgras_14-0"><a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_note-MBAYgras-14">[15]</a></sup> By 1720, <a href="http://en.wikipedia.org/wiki/Biloxi,_Mississippi" title="Biloxi, Mississippi">Biloxi</a> had been made capital of Louisiana. The French customs had already accompanied colonists who settled there.<sup class="reference" id="cite_ref-MGtime_11-3"><a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_note-MGtime-11">[12]</a></sup><br />In 1723, the capital of Louisiana was moved to <a href="http://en.wikipedia.org/wiki/New_Orleans">New Orleans</a>, founded in 1718.<sup class="reference" id="cite_ref-TLhist_12-1"><a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_note-TLhist-12">[13]</a></sup> The tradition has expanded to the point that it became strongly associated with the city in popular perception, and embraced by residents of New Orleans beyond those of French or Catholic heritage. Mardi Gras celebrations are part of the basis of the slogan, <i><a href="http://en.wikipedia.org/wiki/Laissez_les_bons_temps_rouler">Laissez les bons temps rouler</a></i>, (Let the good times roll) and the nickname "<a class="mw-redirect" href="http://en.wikipedia.org/wiki/Big_Easy" title="Big Easy">Big Easy</a>".<sup class="reference" id="cite_ref-MGtime_11-4"><a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_note-MGtime-11">[12]</a></sup> Mobile, Alabama, the former capital of New France, also has a long tradition of celebrating Mardi Gras. Other cities along the Gulf Coast formerly occupied and owned by the French from <a href="http://en.wikipedia.org/wiki/Pensacola,_Florida">Pensacola, Florida</a>, and its suburbs to <a href="http://en.wikipedia.org/wiki/Lafayette,_Louisiana">Lafayette, Louisiana</a>, have active Mardi Gras celebrations. In the rural <a href="http://en.wikipedia.org/wiki/Acadiana">Acadiana</a> area, many <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Cajuns" title="Cajuns">Cajuns</a> celebrate with the <i><a href="http://en.wikipedia.org/wiki/Courir_de_Mardi_Gras">Courir de Mardi Gras</a></i>, a tradition that dates to medieval celebrations in France.<sup class="reference" id="cite_ref-RURALACADIANA_15-0"><a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_note-RURALACADIANA-15">[16]</a></sup> In more recent times several other U.S. cities without a French heritage have instituted a kind of Mardi Gras celebration; for instance, the UETA Jamboozie festival is held late January in <a href="http://en.wikipedia.org/wiki/Laredo,_Texas">Laredo, Texas</a>.<br />In the last decade of the 20th century, the rise in producing commercial <a href="http://en.wikipedia.org/wiki/Videotape" title="Videotape">videotapes</a> catering to <a href="http://en.wikipedia.org/wiki/Voyeurism" title="Voyeurism">voyeurs</a> helped encourage a tradition of women baring breasts in exchange for beads and trinkets.<sup class="reference" id="cite_ref-shrum_16-0"><a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_note-shrum-16">[17]</a></sup> This is practiced only in very small fragments of where Mardi Gras is celebrated, mostly by visitors rather than locals.<br /><h2><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Mardi_Gras&action=edit&section=7" title="Edit section: See also">edit</a>]</span> <span class="mw-headline" id="See_also">See also</span></h2><ul><li><a href="http://en.wikipedia.org/wiki/Joie_de_vivre">Joie de vivre</a></li><li><a href="http://en.wikipedia.org/wiki/Carnaval_de_Ponce">Carnaval de Ponce</a></li></ul><h2><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Mardi_Gras&action=edit&section=8" title="Edit section: References">edit</a>]</span> <span class="mw-headline" id="References">References</span></h2><div class="reflist references-column-width" style="-moz-column-width: 30em; -webkit-column-width: 30em; column-width: 30em; list-style-type: decimal;"><ol class="references"><li id="cite_note-AU-0">^ <a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_ref-AU_0-0"><sup><i><b>a</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_ref-AU_0-1"><sup><i><b>b</b></i></sup></a> In Australia, Mardi Gras season: "NSW: Mardi Gras still alive and well, say organisers", encyclopedia.com, 2003, webpage: <a class="external text" href="http://www.encyclopedia.com/doc/1P1-132075596.html" rel="nofollow">ency-596</a>.</li><li id="cite_note-EN-1">^ <a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_ref-EN_1-0"><sup><i><b>a</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_ref-EN_1-1"><sup><i><b>b</b></i></sup></a> In London, Mardi Gras season: "Paul's Pastry Shop kneads a ton of dough in Picayune", Allbusiness.com, 2008, webpage: <a class="external text" href="http://www.allbusiness.com/north-america/united-states-mississippi/1014135-1.html" rel="nofollow">Allbusiness-35</a>.</li><li id="cite_note-NO-2">^ <a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_ref-NO_2-0"><sup><i><b>a</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_ref-NO_2-1"><sup><i><b>b</b></i></sup></a> In New Orleans, Mardi Gras season: "Mardi Gras in New Orleans | Metro.co.uk", Metro.co.uk, 2009, webpage: <a class="external text" href="http://www.metro.co.uk/home/article.html?in_article_id=2315&in_page_id=1" rel="nofollow">Metro.co.uk-2315</a>.</li><li id="cite_note-AL-3">^ <a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_ref-AL_3-0"><sup><i><b>a</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_ref-AL_3-1"><sup><i><b>b</b></i></sup></a> In Mobile, Mardi Gras season: "New Orleans has competition for Mardi Gras", USATODAY.com, February 2006, webpage: <a class="external text" href="http://www.usatoday.com/travel/destinations/2006-02-17-mardi-gras_x.htm" rel="nofollow">USATODAY-com-mardi</a>.</li><li id="cite_note-SD-4">^ <a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_ref-SD_4-0"><sup><i><b>a</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_ref-SD_4-1"><sup><i><b>b</b></i></sup></a> In San Diego, Mardi Gras season: "sandiego.com - Mardi Gras in San Diego: FAQ's", SanDiego.com, 2008, webpage: <a class="external text" href="http://www.sandiego.com/seasonal/mardi-gras/mardi-gras-in-san-diego:-faq%27s/" rel="nofollow">SanDiego.com-SD</a>.</li><li id="cite_note-TX-5">^ <a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_ref-TX_5-0"><sup><i><b>a</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_ref-TX_5-1"><sup><i><b>b</b></i></sup></a> In Texas, Mardi Gras season: "Let’s Celebrate: Mardi Gras 2008", Southernbyways.com, January 2008, webpage: <a class="external text" href="http://www.southernbyways.com/lets-celebrate-mardi-gras-2008/" rel="nofollow">southernbyways-com-TX</a>.</li><li id="cite_note-carnivalterminology-6">^ <a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_ref-carnivalterminology_6-0"><sup><i><b>a</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_ref-carnivalterminology_6-1"><sup><i><b>b</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_ref-carnivalterminology_6-2"><sup><i><b>c</b></i></sup></a> <span class="citation web"><a class="external text" href="http://www.mobile.org/vis_mardigras_terms.php" rel="nofollow">"Mardi Gras Terminology"</a>. <i>"Mobile Bay Convention & Visitors Bureau"</i><span class="reference-accessdate">. Retrieved November 18, 2007</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Mardi+Gras+Terminology&rft.atitle=%22Mobile+Bay+Convention+%26+Visitors+Bureau%22&rft_id=http%3A%2F%2Fwww.mobile.org%2Fvis_mardigras_terms.php&rfr_id=info:sid/en.wikipedia.org:Mardi_Gras"></span></li><li id="cite_note-7"><b><a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_ref-7">^</a></b> <span class="citation web"><a class="external text" href="http://www.crivoice.org/cylent.html" rel="nofollow">"The Season of Lent"</a>. Crivoice.org. January 7, 2010<span class="reference-accessdate">. Retrieved October 16, 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=The+Season+of+Lent&rft.atitle=&rft.date=January+7%2C+2010&rft.pub=Crivoice.org&rft_id=http%3A%2F%2Fwww.crivoice.org%2Fcylent.html&rfr_id=info:sid/en.wikipedia.org:Mardi_Gras"></span></li><li id="cite_note-MCA-8"><b><a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_ref-MCA_8-0">^</a></b> "Mobile Carnival Association, 1927", MardiGrasDigest.com, 2006, webpage: <a class="external text" href="http://www.mardigrasdigest.com/Bureau/Mobile/mobile_carnival_association.htm" rel="nofollow">mardigrasdigest-Mobile</a>.</li><li id="cite_note-9"><b><a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_ref-9">^</a></b> <a class="external autonumber" href="http://www.serve.com/shea/germusa/karneval.htm" rel="nofollow">[1]</a><sup class="noprint Inline-Template"><span style="white-space: nowrap;" title=" since October 2010">[<i><a href="http://en.wikipedia.org/wiki/Wikipedia:Link_rot" title="Wikipedia:Link rot">dead link</a></i>]</span></sup></li><li id="cite_note-semla-10"><b><a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_ref-semla_10-0">^</a></b> <span class="citation web"><a class="external text" href="http://www.sweden.se/eng/Home/Lifestyle/Traditions/Reading/Swedish-semla-more-than-just-a-bun/" rel="nofollow">"Swedish semla: more than just a bun"</a>. <i>Sweden.se</i><span class="reference-accessdate">. Retrieved February 22, 2011</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Swedish+semla%3A+more+than+just+a+bun&rft.atitle=Sweden.se&rft_id=http%3A%2F%2Fwww.sweden.se%2Feng%2FHome%2FLifestyle%2FTraditions%2FReading%2FSwedish-semla-more-than-just-a-bun%2F&rfr_id=info:sid/en.wikipedia.org:Mardi_Gras"></span></li><li id="cite_note-MGtime-11">^ <a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_ref-MGtime_11-0"><sup><i><b>a</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_ref-MGtime_11-1"><sup><i><b>b</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_ref-MGtime_11-2"><sup><i><b>c</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_ref-MGtime_11-3"><sup><i><b>d</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_ref-MGtime_11-4"><sup><i><b>e</b></i></sup></a> "New Orleans & Mardi Gras History Timeline" (event list), Mardi Gras Digest, 2005, webpage: <a class="external text" href="http://www.mardigrasdigest.com/html/mardi_gras_history__timeline.htm" rel="nofollow">MG-time</a>.</li><li id="cite_note-TLhist-12">^ <a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_ref-TLhist_12-0"><sup><i><b>a</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_ref-TLhist_12-1"><sup><i><b>b</b></i></sup></a> "Timeline 18th Century:" (events), Timelines of History, 2007, webpage: <a class="external text" href="http://timelines.ws/1700_1724.HTML" rel="nofollow">TLine-1700-1724</a>: on "1702-1711" of Mobile.</li><li id="cite_note-LOCgras-13"><b><a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_ref-LOCgras_13-0">^</a></b> "Mardi Gras in Mobile" (history), <a href="http://en.wikipedia.org/wiki/Jeff_Sessions">Jeff Sessions</a>, Senator, <a href="http://en.wikipedia.org/wiki/Library_of_Congress">Library of Congress</a>, 2006, webpage: <a class="external text" href="http://lcweb2.loc.gov/cocoon/legacies/AL/200002665.html" rel="nofollow">LibCongress-2665</a>.</li><li id="cite_note-MBAYgras-14"><b><a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_ref-MBAYgras_14-0">^</a></b> "Mardi Gras" (history), Mobile Bay Convention & Visitors Bureau, 2007, webpage: <a class="external text" href="http://www.mobile.org/ab_mardigras.php/ab_mardigras_history.php" rel="nofollow">MGmobile</a>.</li><li id="cite_note-RURALACADIANA-15"><b><a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_ref-RURALACADIANA_15-0">^</a></b> <span class="citation web"><a class="external text" href="http://web.lsue.edu/acadgate/mardmain.htm" rel="nofollow">"Mardi Gras in Rural Acadiana"</a><span class="reference-accessdate">. Retrieved February 18, 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Mardi+Gras+in+Rural+Acadiana&rft.atitle=&rft_id=http%3A%2F%2Fweb.lsue.edu%2Facadgate%2Fmardmain.htm&rfr_id=info:sid/en.wikipedia.org:Mardi_Gras"></span></li><li id="cite_note-shrum-16"><b><a href="http://en.wikipedia.org/wiki/Mardi_gras#cite_ref-shrum_16-0">^</a></b> Shrum, W. and J. Kilburn. <a class="external text" href="http://links.jstor.org/sici?sici=0037-7732%28199612%2975%3A2%3C423%3ARDAMGC%3E2.0.CO%3B2-2" rel="nofollow">"Ritual Disrobement at Mardi Gras: Ceremonial Exchange and Moral Order"</a>. <i>Social Forces</i>, Vol. 75, No. 2. (Dec., 1996), pp. 423-458.</li></ol></div><h2><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Mardi_Gras&action=edit&section=9" title="Edit section: External links">edit</a>]</span> <span class="mw-headline" id="External_links">External links</span></h2><ul><li><a class="external text" href="http://worldmusic.about.com/od/northamerican/p/CajunMardiGras.htm" rel="nofollow">Traditional Cajun Mardi Gras Celebrations</a></li><li><a class="external text" href="http://www.encyclopediaofalabama.org/face/Article.jsp?id=h-1437" rel="nofollow">Mardi Gras in Mobile, Encyclopedia of Alabama</a></li><li><a class="external text" href="http://carlnivale.theatricana.com/" rel="nofollow">Prof. Carl Nivale's Compleat Carnival Compendium and Mardi Gras Manual</a></li><li><a class="external text" href="http://www3.signonsandiego.com/photos/galleries/2009/feb/25/mardi-gras-2009/" rel="nofollow">Mardi Gras 2009 celebration photos</a></li><li><a class="external text" href="http://www.mardigrascostumepics.com/" rel="nofollow">Mardi Gras Costumer photos in New Orleans</a></li><li><a class="external text" href="http://www.guardian.co.uk/travel/gallery/2009/jan/21/mardi-gras-carnival-festivals-guide" rel="nofollow">Where to Celebrate Mardi Gras Around the World</a> - slideshow by <i><a href="http://en.wikipedia.org/wiki/The_Guardian">The Guardian</a></i></li></ul><table cellspacing="0" class="navbox"><tbody><tr> <td style="padding: 2px;"><table cellspacing="0" class="nowraplinks collapsible autocollapse" id="collapsibleTable0" style="background: transparent; color: inherit; width: 100%;"><tbody><tr> <th class="navbox-title" colspan="2" style="background: #DDD4A5;"><span class="collapseButton">[<a href="http://en.wikipedia.org/wiki/Mardi_gras#" id="collapseButton0">hide</a>]</span><span style="float: left; text-align: left; width: 6em;"><span class="noprint plainlinks navbar"><span style="white-space: nowrap; word-spacing: -0.12em;"><a 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template">e</span></a></span></span></span><span class="" style="font-size: 110%;"><a href="http://en.wikipedia.org/wiki/Public_holidays_in_the_United_States" title="Public holidays in the United States">Holidays, observances, and celebrations in the United States</a></span></th> </tr><tr style="height: 2px;"> <td><br /></td> </tr><tr> <td class="navbox-group" style="background: #CCC3D5;">Days</td> <td class="navbox-list navbox-odd" style="border-left-style: solid; border-left-width: 2px; padding: 0px; text-align: left; width: 100%;"><div style="padding: 0em 0.25em;"><span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Arbor_Day">Arbor Day</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Ash_Wednesday">Ash Wednesday</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Carl_Garner_Federal_Lands_Cleanup_Day">Carl Garner Federal Lands Cleanup Day</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/C%C3%A9sar_Ch%C3%A1vez" title="César Chávez">César Chávez Day</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Child_Health_Day">Child Health Day</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Christmas_Eve">Christmas Eve</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Christmas" title="Christmas">Christmas Day</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Cinco_de_Mayo">Cinco de Mayo</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Columbus_Day">Columbus Day</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Confederate_Memorial_Day">Confederate Memorial Day</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Constitution_Day_%28United_States%29" title="Constitution Day (United States)">Constitution Day</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Courir_de_Mardi_Gras">Courir de Mardi Gras</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Earth_Day">Earth Day</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Easter_Monday">Easter Monday</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Easter" title="Easter">Easter Sunday</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Father%27s_Day">Father's Day</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Festivus">Festivus</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Flag_Day_%28United_States%29" title="Flag Day (United States)">Flag Day</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Four_Chaplains" title="Four Chaplains">Four Chaplains Day</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Free_Comic_Book_Day">Free Comic Book Day</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Gold_Star_Mothers_Club" title="Gold Star Mothers Club">Gold Star Mothers Day</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Good_Friday">Good Friday</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Groundhog_Day">Groundhog Day</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Halloween">Halloween</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Independence_Day_%28United_States%29" title="Independence Day (United States)">Independence Day</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Jefferson%27s_Birthday">Jefferson's Birthday</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Juneteenth">Juneteenth</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Labor_Day">Labor Day</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Lee%E2%80%93Jackson_Day">Lee–Jackson Day</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Leif_Erikson_Day">Leif Erikson Day</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Lincoln%27s_Birthday">Lincoln's Birthday</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Lyndon_Baines_Johnson_Day">Lyndon Baines Johnson Day</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Mardi_Gras_in_the_United_States" title="Mardi Gras in the United States">Mardi Gras</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Martin_Luther_King,_Jr._Day">Martin Luther King, Jr. Day</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/May_Day">May Day</a> (<a href="http://en.wikipedia.org/wiki/Law_Day,_U.S.A." title="Law Day, U.S.A.">Law Day</a> / <a href="http://en.wikipedia.org/wiki/Loyalty_Day">Loyalty Day</a>) •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Memorial_Day">Memorial Day</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Mother%27s_Day_%28U.S.%29" title="Mother's Day (U.S.)">Mother's Day</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/National_Aviation_Day">National Aviation Day</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/National_Day_of_Prayer">National Day of Prayer</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/National_Defense_Transportation_Day">National Defense Transportation Day</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/National_Freedom_Day">National Freedom Day</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/National_Grandparents_Day">National Grandparents Day</a> •</span> <span style="white-space: nowrap;">National Korean War Veterans Armistice Day •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/United_States_National_Maritime_Day" title="United States National Maritime Day">National Maritime Day</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/National_Pearl_Harbor_Remembrance_Day" title="National Pearl Harbor Remembrance Day">Pearl Harbor Remembrance Day</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/New_Year%27s_Day">New Year's Day</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/New_Year%27s_Eve">New Year's Eve</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Palm_Sunday">Palm Sunday</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Pan_American_Aviation_Day">Pan American Aviation Day</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Parents%27_Day">Parents' Day</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Patriot_Day">Patriot Day</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Patriots%27_Day">Patriots' Day</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Peace_Officers_Memorial_Day">Peace Officers Memorial Day</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Ronald_Reagan_Day">Ronald Reagan Day</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Robert_E._Lee_Day">Robert E. Lee Day</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Rosh_Hashanah">Rosh Hashanah</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Saint_Joseph%27s_Day">Saint Joseph's Day</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Saint_Patrick%27s_Day">Saint Patrick's Day</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Stephen_Foster_Memorial_Day">Stephen Foster Memorial Day</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Susan_B._Anthony_Day">Susan B. Anthony Day</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Thanksgiving_%28United_States%29" title="Thanksgiving (United States)">Thanksgiving</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Truman_Day">Truman Day</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Valentine%27s_Day">Valentine's Day</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Veterans_Day">Veterans Day</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Walpurgis_Night">Walpurgis Night</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Washington%27s_Birthday">Washington's Birthday</a> (Presidents Day) •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/White_Cane_Safety_Day">White Cane Safety Day</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Women%27s_Equality_Day">Women's Equality Day</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Wright_Brothers_Day">Wright Brothers Day</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Yom_Kippur">Yom Kippur</a></span></div></td> </tr><tr style="height: 2px;"> <td><br /></td> </tr><tr> <td class="navbox-group" style="background: #CCC3D5;">Weeks<br /><small>(or multiple weeks)</small></td> <td class="navbox-list navbox-even" style="border-left-style: solid; border-left-width: 2px; padding: 0px; text-align: left; width: 100%;"><div style="padding: 0em 0.25em;"><span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Chinese_New_Year">Chinese New Year</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Constitution_Week">Constitution Week</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Days_of_Remembrance_of_the_Victims_of_the_Holocaust">Days of Remembrance of the Victims of the Holocaust</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Hanukkah">Hanukkah</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Honor_America_Days">Honor America Days</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Kwanzaa">Kwanzaa</a> •</span> <span style="white-space: nowrap;">National Flag Week •</span> <span style="white-space: nowrap;">National Forest Products Week •</span> <span style="white-space: nowrap;">National Friendship Week •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/National_Poison_Prevention_Week">National Poison Prevention Week</a> •</span> <span style="white-space: nowrap;">National Safe Boating Week •</span> <span style="white-space: nowrap;">National School Lunch Week •</span> <span style="white-space: nowrap;">National Transportation Week •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Passover">Passover</a> •</span> <span style="white-space: nowrap;">Police Week •</span> <span style="white-space: nowrap;">Save Your Vision Week</span></div></td> </tr><tr style="height: 2px;"> <td><br /></td> </tr><tr> <td class="navbox-group" style="background: #CCC3D5;">Months</td> <td class="navbox-list navbox-odd" style="border-left-style: solid; border-left-width: 2px; padding: 0px; text-align: left; width: 100%;"><div style="padding: 0em 0.25em;"><span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/American_Heart_Month">American Heart Month</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Asian_Pacific_American_Heritage_Month">Asian Pacific American Heritage Month</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Black_History_Month">Black History Month</a> •</span> <span style="white-space: nowrap;">Cancer Control Month •</span> <span style="white-space: nowrap;">Child Abuse Prevention Month •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Confederate_History_Month">Confederate History Month</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Gay_and_Lesbian_Pride_Month">Gay and Lesbian Pride Month</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Jewish_American_Heritage_Month">Jewish American Heritage Month</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/National_Breast_Cancer_Awareness_Month">National Breast Cancer Awareness Month</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/National_Disability_Employment_Awareness_Month">National Disability Employment Awareness Month</a> •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/National_Hispanic_Heritage_Month">National Hispanic Heritage Month</a> •</span> <span style="white-space: nowrap;">National Nutrition Month •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Ramadan">Ramadan</a> •</span> <span style="white-space: nowrap;">Steelmark Month •</span> <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Women%27s_History_Month">Women's History Month</a></span></div></td> </tr></tbody></table></td> </tr></tbody></table><div id="mw-normal-catlinks"><a href="http://en.wikipedia.org/wiki/Special:Categories" title="Special:Categories">Categories</a>: <span dir="ltr"><a href="http://en.wikipedia.org/wiki/Category:Mardi_Gras" title="Category:Mardi Gras">Mardi Gras</a></span> | <span dir="ltr"><a href="http://en.wikipedia.org/wiki/Category:American_folklore" title="Category:American folklore">American folklore</a></span> | <span dir="ltr"><a href="http://en.wikipedia.org/wiki/Category:February_observances" title="Category:February observances">February observances</a></span> | <span dir="ltr"><a href="http://en.wikipedia.org/wiki/Category:French_loanwords" title="Category:French loanwords">French loanwords</a></span> | <span dir="ltr"><a href="http://en.wikipedia.org/wiki/Category:French_words_and_phrases" title="Category:French words and phrases">French words and phrases</a></span> | <span dir="ltr"><a href="http://en.wikipedia.org/wiki/Category:March_observances" title="Category:March observances">March observances</a></span> | <span dir="ltr"><a href="http://en.wikipedia.org/wiki/Category:Music_festivals_in_the_United_States" title="Category:Music festivals in the United States">Music festivals in the United States</a></span> | <span dir="ltr"><a href="http://en.wikipedia.org/wiki/Category:Religious_festivals" title="Category:Religious festivals">Religious festivals</a></span></div></div>ripplehttp://www.blogger.com/profile/17326365690819936341noreply@blogger.comtag:blogger.com,1999:blog-6905780489869824283.post-5611146048590097952011-03-22T11:27:00.000-07:002011-04-06T14:15:46.853-07:00Energy<div dir="ltr" style="text-align: left;" trbidi="on"><div class="dablink">This article is about the scalar physical quantity. For other uses, see <a href="http://en.wikipedia.org/wiki/Energy_%28disambiguation%29">Energy (disambiguation)</a>.</div><div class="thumb tright"><div class="thumbinner" style="width: 302px;"><a class="image" href="http://en.wikipedia.org/wiki/File:Lightning_over_Oradea_Romania_zoom.jpg"><img alt="" class="thumbimage" height="197" src="http://upload.wikimedia.org/wikipedia/commons/thumb/2/23/Lightning_over_Oradea_Romania_zoom.jpg/300px-Lightning_over_Oradea_Romania_zoom.jpg" width="300" /></a> <br /><div class="thumbcaption"><div class="magnify"><a class="internal" href="http://en.wikipedia.org/wiki/File:Lightning_over_Oradea_Romania_zoom.jpg" title="Enlarge"><img alt="" height="11" src="http://bits.wikimedia.org/skins-1.17/common/images/magnify-clip.png" width="15" /></a></div><a href="http://en.wikipedia.org/wiki/Lightning">Lightning</a> is the electric breakdown of air by strong electric fields, which produce a force on charges. When these charges move through a distance, a flow of energy occurs. The electric <a href="http://en.wikipedia.org/wiki/Potential_energy">potential energy</a> in the atmosphere then is transformed into thermal energy, light, and sound, which are other forms of energy.</div></div></div>In <a href="http://en.wikipedia.org/wiki/Physics">physics</a>, <b>energy</b> (<a href="http://en.wikipedia.org/wiki/Ancient_Greek">Ancient Greek</a>: <span lang="grc">ἐνέργεια</span> <span lang="grc-Latn"><i><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Energeia" title="Energeia">energeia</a></i></span> "activity, operation"<sup class="reference" id="cite_ref-0"><a href="http://en.wikipedia.org/wiki/Energy#cite_note-0">[1]</a></sup>) is a quantity that is often understood as the ability a <a href="http://en.wikipedia.org/wiki/Physical_system">physical system</a> has to do <a href="http://en.wikipedia.org/wiki/Work_%28physics%29" title="Work (physics)">work</a> on other physical systems.<sup class="reference" id="cite_ref-1"><a href="http://en.wikipedia.org/wiki/Energy#cite_note-1">[2]</a></sup><sup class="reference" id="cite_ref-2"><a href="http://en.wikipedia.org/wiki/Energy#cite_note-2">[3]</a></sup> Since work is defined as a <a href="http://en.wikipedia.org/wiki/Force">force</a> acting through a distance (a length of space), energy is always equivalent to the ability to exert pulls or pushes against the basic forces of nature, along a path of a certain length.<br />The total energy contained in an object is identified with its <a href="http://en.wikipedia.org/wiki/Mass">mass</a>, and energy (like mass), cannot be created or destroyed. When <a href="http://en.wikipedia.org/wiki/Matter">matter</a> (ordinary material particles) is changed into energy (such as energy of motion, or into radiation), the <b>mass</b> of the system does not change through the transformation process. However, there may be mechanistic limits as to how much of the matter in an object may be changed into other types of energy and thus into <a href="http://en.wikipedia.org/wiki/Work_%28thermodynamics%29" title="Work (thermodynamics)">work</a>, on other systems. Energy, like mass, is a <a href="http://en.wikipedia.org/wiki/Scalar_%28physics%29" title="Scalar (physics)">scalar</a> physical quantity. In the <a href="http://en.wikipedia.org/wiki/International_System_of_Units">International System of Units</a> (SI), energy is measured in <a href="http://en.wikipedia.org/wiki/Joule" title="Joule">joules</a>, but in many fields other units, such as <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Kilowatt-hour" title="Kilowatt-hour">kilowatt-hours</a> and <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Kilocalorie" title="Kilocalorie">kilocalories</a>, are customary. All of these units translate to units of work, which is always defined in terms of forces and the distances that the forces act through.<br />A system can transfer energy to another system by simply transferring matter to it (since matter is equivalent to energy, in accordance with its mass). However, when energy is transferred by means other than matter-transfer, the transfer produces changes in the second system, as a result of work done on it. This work manifests itself as the effect of force(s) applied through distances within the target system. For example, a system can emit energy to another by transferring (radiating) <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Electromagnetic_energy" title="Electromagnetic energy">electromagnetic energy</a>, but this creates forces upon the particles that absorb the radiation. Similarly, a system may transfer energy to another by physically impacting it, but that case the energy of motion in an object, called <a href="http://en.wikipedia.org/wiki/Kinetic_energy">kinetic energy</a>, results in forces acting over distances (new energy) to appear in another object that is struck. Transfer of <a href="http://en.wikipedia.org/wiki/Thermal_energy">thermal energy</a> by <a href="http://en.wikipedia.org/wiki/Heat">heat</a> occurs by both of these mechanisms: heat can be transferred by electromagnetic radiation, or by physical contact in which direct particle-particle impacts transfer kinetic energy.<br />Energy may be stored in systems without being present as matter, or as kinetic or electromagnetic energy. Stored energy is created whenever a particle has been moved through a field it interacts with (requiring a force to do so), but the energy to accomplish this is stored as a new position of the particles in the field—a configuration that must be "held" or fixed by a different type of force (otherwise, the new configuration would resolve itself by the field pushing or pulling the particle back toward its previous position). This type of energy "stored" by force-fields and particles that have been forced into a new physical configuration in the field by doing work on them by another system, is referred to as <a href="http://en.wikipedia.org/wiki/Potential_energy">potential energy</a>. A simple example of potential energy is the work needed to lift an object in a gravity field, up to a support. Each of the basic forces of nature is associated with a different type of potential energy, and all types of potential energy (like all other types of energy) appears as system <a href="http://en.wikipedia.org/wiki/Mass">mass</a>, whenever present. For example, a compressed spring will be slightly more massive than before it was compressed. Likewise, whenever energy is transferred between systems by any mechanism, an associated mass is transferred with it.<br />Any form of energy may be <a href="http://en.wikipedia.org/wiki/Energy_transformation" title="Energy transformation">transformed</a> into another form. For example, all types of potential energy are converted into kinetic energy when the objects are given freedom to move to different position (as for example, when an object falls off a support). When energy is in a form other than thermal energy, it may be transformed with good or even perfect efficiency, to any other type of energy, including <a href="http://en.wikipedia.org/wiki/Electricity">electricity</a> or production of new particles of matter. With thermal energy, however, there are often limits to the efficiency of the conversion to other forms of energy, as described by the <a href="http://en.wikipedia.org/wiki/Second_law_of_thermodynamics">second law of thermodynamics</a>.<br />In all such <a href="http://en.wikipedia.org/wiki/Energy_transformation">energy transformation</a> processes, the total energy remains the same, and a transfer of energy from one system to another, results in a loss to compensate for any gain. This principle, the <a href="http://en.wikipedia.org/wiki/Conservation_of_energy">conservation of energy</a>, was first postulated in the early 19th century, and applies to any <a href="http://en.wikipedia.org/wiki/Isolated_system">isolated system</a>. According to <a href="http://en.wikipedia.org/wiki/Noether%27s_theorem">Noether's theorem</a>, the conservation of energy is a consequence of the fact that the laws of physics do not change over time.<sup class="reference" id="cite_ref-jphysics_3-0"><a href="http://en.wikipedia.org/wiki/Energy#cite_note-jphysics-3">[4]</a></sup><br />Although the total energy of a system does not change with time, its value may depend on the <a href="http://en.wikipedia.org/wiki/Frame_of_reference">frame of reference</a>. For example, a seated passenger in a moving airplane has zero kinetic energy relative to the airplane, but non-zero kinetic energy (and higher total energy) relative to the <a href="http://en.wikipedia.org/wiki/Earth">Earth</a>.<br /><div class="toclimit-2"><table class="toc" id="toc"><tbody><tr> <td><div id="toctitle"><h2>Contents</h2><span class="toctoggle">[<a class="internal" href="http://en.wikipedia.org/wiki/Energy#" id="togglelink">hide</a>]</span></div><ul><li class="toclevel-1 tocsection-1"><a href="http://en.wikipedia.org/wiki/Energy#History"><span class="tocnumber">1</span> <span class="toctext">History</span></a></li><li class="toclevel-1 tocsection-2"><a href="http://en.wikipedia.org/wiki/Energy#Energy_in_various_contexts"><span class="tocnumber">2</span> <span class="toctext">Energy in various contexts</span></a></li><li class="toclevel-1 tocsection-3"><a href="http://en.wikipedia.org/wiki/Energy#Conservation_of_energy"><span class="tocnumber">3</span> <span class="toctext">Conservation of energy</span></a></li><li class="toclevel-1 tocsection-4"><a href="http://en.wikipedia.org/wiki/Energy#Applications_of_the_concept_of_energy"><span class="tocnumber">4</span> <span class="toctext">Applications of the concept of energy</span></a> </li><li class="toclevel-1 tocsection-18"><a href="http://en.wikipedia.org/wiki/Energy#Measurement"><span class="tocnumber">5</span> <span class="toctext">Measurement</span></a> </li><li class="toclevel-1 tocsection-22"><a href="http://en.wikipedia.org/wiki/Energy#Forms_of_energy"><span class="tocnumber">6</span> <span class="toctext">Forms of energy</span></a> </li><li class="toclevel-1 tocsection-37"><a href="http://en.wikipedia.org/wiki/Energy#Transformations_of_energy"><span class="tocnumber">7</span> <span class="toctext">Transformations of energy</span></a></li><li class="toclevel-1 tocsection-38"><a href="http://en.wikipedia.org/wiki/Energy#See_also"><span class="tocnumber">8</span> <span class="toctext">See also</span></a></li><li class="toclevel-1 tocsection-39"><a href="http://en.wikipedia.org/wiki/Energy#Notes_and_references"><span class="tocnumber">9</span> <span class="toctext">Notes and references</span></a></li><li class="toclevel-1 tocsection-40"><a href="http://en.wikipedia.org/wiki/Energy#Further_reading"><span class="tocnumber">10</span> <span class="toctext">Further reading</span></a></li><li class="toclevel-1 tocsection-41"><a href="http://en.wikipedia.org/wiki/Energy#External_links"><span class="tocnumber">11</span> <span class="toctext">External links</span></a></li></ul></td> </tr></tbody></table></div><h2><span class="mw-headline" id="History">History</span></h2><div class="rellink relarticle mainarticle">Main articles: <a href="http://en.wikipedia.org/wiki/History_of_energy">History of energy</a> and <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Timeline_of_thermodynamics,_statistical_mechanics,_and_random_processes" title="Timeline of thermodynamics, statistical mechanics, and random processes">timeline of thermodynamics, statistical mechanics, and random processes</a></div>The word <i>energy</i> derives from the Greek <span lang="grc">ἐνέργεια</span> <i><span lang="grc-Latn"><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Energeia" title="Energeia">energeia</a></span></i>, which possibly appears for the first time in the work of <a href="http://en.wikipedia.org/wiki/Aristotle">Aristotle</a> in the 4th century BC.<br />The concept of energy emerged out of the idea of <i><a href="http://en.wikipedia.org/wiki/Vis_viva">vis viva</a></i> (living force), which <a href="http://en.wikipedia.org/wiki/Gottfried_Leibniz">Gottfried Leibniz</a> defined as the product of the mass of an object and its velocity squared; he believed that total <i>vis viva</i> was conserved. To account for slowing due to friction, Leibniz theorized that thermal energy consisted of the random motion of the constituent parts of matter, a view shared by <a href="http://en.wikipedia.org/wiki/Isaac_Newton">Isaac Newton</a>, although it would be more than a century until this was generally accepted. In 1807, <a href="http://en.wikipedia.org/wiki/Thomas_Young_%28scientist%29" title="Thomas Young (scientist)">Thomas Young</a> was possibly the first to use the term "energy" instead of <i>vis viva</i>, in its modern sense.<sup class="reference" id="cite_ref-4"><a href="http://en.wikipedia.org/wiki/Energy#cite_note-4">[5]</a></sup> <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Gustave-Gaspard_Coriolis" title="Gustave-Gaspard Coriolis">Gustave-Gaspard Coriolis</a> described "<a href="http://en.wikipedia.org/wiki/Kinetic_energy">kinetic energy</a>" in 1829 in its modern sense, and in 1853, <a href="http://en.wikipedia.org/wiki/William_John_Macquorn_Rankine" title="William John Macquorn Rankine">William Rankine</a> coined the term "<a href="http://en.wikipedia.org/wiki/Potential_energy">potential energy</a>". It was argued for some years whether energy was a substance (the <a href="http://en.wikipedia.org/wiki/Caloric_theory" title="Caloric theory">caloric</a>) or merely a physical quantity, such as <a href="http://en.wikipedia.org/wiki/Momentum">momentum</a>.<br />William Thomson (<a class="mw-redirect" href="http://en.wikipedia.org/wiki/Lord_Kelvin" title="Lord Kelvin">Lord Kelvin</a>) amalgamated all of these laws into the laws of <a href="http://en.wikipedia.org/wiki/Thermodynamics">thermodynamics</a>, which aided in the rapid development of explanations of chemical processes by <a href="http://en.wikipedia.org/wiki/Rudolf_Clausius">Rudolf Clausius</a>, <a href="http://en.wikipedia.org/wiki/Josiah_Willard_Gibbs">Josiah Willard Gibbs</a>, and <a href="http://en.wikipedia.org/wiki/Walther_Nernst">Walther Nernst</a>. It also led to a mathematical formulation of the concept of <a href="http://en.wikipedia.org/wiki/Entropy">entropy</a> by Clausius and to the introduction of laws of <a href="http://en.wikipedia.org/wiki/Radiant_energy">radiant energy</a> by <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Jo%C5%BEef_Stefan" title="Jožef Stefan">Jožef Stefan</a>.<br />During a 1961 lecture<sup class="reference" id="cite_ref-RPF1_5-0"><a href="http://en.wikipedia.org/wiki/Energy#cite_note-RPF1-5">[6]</a></sup> for undergraduate students at the <a href="http://en.wikipedia.org/wiki/California_Institute_of_Technology">California Institute of Technology</a>, <a href="http://en.wikipedia.org/wiki/Richard_Feynman">Richard Feynman</a>, a celebrated physics teacher and <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Nobel_Laureate" title="Nobel Laureate">Nobel Laureate</a>, said this about the concept of energy:<br /><blockquote class="templatequote"><div>There is a fact, or if you wish, a <i>law</i>, governing all natural phenomena that are known to date. There is no known exception to this law—it is exact so far as we know. The law is called the <i><a href="http://en.wikipedia.org/wiki/Conservation_of_energy">conservation of energy</a></i>. It states that there is a certain quantity, which we call energy, that does not change in manifold changes which nature undergoes. That is a most abstract idea, because it is a mathematical principle; it says that there is a numerical quantity which does not change when something happens. It is not a description of a mechanism, or anything concrete; it is just a strange fact that we can calculate some number and when we finish watching nature go through her tricks and calculate the number again, it is the same.</div><div class="templatequotecite">—<i><a href="http://en.wikipedia.org/wiki/The_Feynman_Lectures_on_Physics">The Feynman Lectures on Physics</a></i></div></blockquote>Since 1918 it has been known that the law of <a href="http://en.wikipedia.org/wiki/Conservation_of_energy">conservation of energy</a> is the direct mathematical consequence of the <a href="http://en.wikipedia.org/wiki/Translational_symmetry">translational symmetry</a> of the quantity <a href="http://en.wikipedia.org/wiki/Conjugate_variables" title="Conjugate variables">conjugate</a> to energy, namely <a href="http://en.wikipedia.org/wiki/Time">time</a>. That is, energy is conserved because the laws of physics do not distinguish between different instants of time (see <a href="http://en.wikipedia.org/wiki/Noether%27s_theorem">Noether's theorem</a>).<br /><h2><span class="mw-headline" id="Energy_in_various_contexts">Energy in various contexts</span></h2>The concept of energy and its <a href="http://en.wikipedia.org/wiki/Energy_transformation" title="Energy transformation">transformations</a> is useful in explaining and predicting most natural phenomena. The <i>direction</i> of transformations in energy (what kind of energy is transformed to what other kind) is often described by <a href="http://en.wikipedia.org/wiki/Entropy">entropy</a> (equal energy spread among all available <a href="http://en.wikipedia.org/wiki/Degrees_of_freedom_%28physics_and_chemistry%29" title="Degrees of freedom (physics and chemistry)">degrees of freedom</a>) considerations, as in practice all energy transformations are permitted on a small scale, but certain larger transformations are not permitted because it is statistically unlikely that energy or matter will randomly move into more concentrated forms or smaller spaces.<br />The <a href="http://en.wikipedia.org/wiki/Concept">concept</a> of energy is widespread in all sciences.<br /><ul><li>In the context of <a href="http://en.wikipedia.org/wiki/Chemistry#Energy">chemistry</a>, energy is an attribute of a substance as a consequence of its atomic, molecular or aggregate structure. Since a chemical transformation is accompanied by a change in one or more of these kinds of structure, it is invariably accompanied by an increase or decrease of energy of the substances involved. Some energy is transferred between the surroundings and the reactants of the reaction in the form of heat or light; thus the products of a reaction may have more or less energy than the reactants. A reaction is said to be <a href="http://en.wikipedia.org/wiki/Exergonic">exergonic</a> if the final state is lower on the energy scale than the initial state; in the case of <a href="http://en.wikipedia.org/wiki/Endergonic">endergonic</a> reactions the situation is the reverse. Chemical reactions are invariably not possible unless the reactants surmount an energy barrier known as the <a href="http://en.wikipedia.org/wiki/Activation_energy">activation energy</a>. The <i>speed</i> of a chemical reaction (at given temperature <i>T</i>) is related to the activation energy <i>E</i>, by the Boltzmann's population factor e<sup>−<i>E</i>/<i>kT</i></sup> – that is the probability of molecule to have energy greater than or equal to <i>E</i> at the given temperature <i>T</i>. This exponential dependence of a reaction rate on temperature is known as the <a href="http://en.wikipedia.org/wiki/Arrhenius_equation">Arrhenius equation</a>.The activation energy necessary for a chemical reaction can be in the form of thermal energy.</li><li><span id="Biology"></span>In <a href="http://en.wikipedia.org/wiki/Biology#Energy">biology</a>, energy is an attribute of all biological systems from the biosphere to the smallest living <a href="http://en.wikipedia.org/wiki/Organism">organism</a>. Within an organism it is responsible for growth and development of a biological <a href="http://en.wikipedia.org/wiki/Cell_%28biology%29" title="Cell (biology)">cell</a> or an <a href="http://en.wikipedia.org/wiki/Organelle">organelle</a> of a biological <a href="http://en.wikipedia.org/wiki/Organism">organism</a>. Energy is thus often said to be stored by <a href="http://en.wikipedia.org/wiki/Cell_%28biology%29" title="Cell (biology)">cells</a> in the structures of molecules of substances such as <a href="http://en.wikipedia.org/wiki/Carbohydrate" title="Carbohydrate">carbohydrates</a> (including sugars), <a href="http://en.wikipedia.org/wiki/Lipid" title="Lipid">lipids</a>, and <a href="http://en.wikipedia.org/wiki/Protein" title="Protein">proteins</a>, which release energy when reacted with <a href="http://en.wikipedia.org/wiki/Oxygen">oxygen</a> in <a href="http://en.wikipedia.org/wiki/Respiration_%28physiology%29" title="Respiration (physiology)">respiration</a>. In human terms, the <a href="http://en.wikipedia.org/wiki/Human_equivalent">human equivalent</a> (H-e) (Human energy conversion) indicates, for a given amount of energy expenditure, the relative quantity of energy needed for human <a href="http://en.wikipedia.org/wiki/Metabolism">metabolism</a>, assuming an average human energy expenditure of 12,500kJ per day and a <a href="http://en.wikipedia.org/wiki/Basal_metabolic_rate">basal metabolic rate</a> of 80 watts. For example, if our bodies run (on average) at 80 watts, then a light bulb running at 100 watts is running at 1.25 human equivalents (100 ÷ 80) i.e. 1.25 H-e. For a difficult task of only a few seconds' duration, a person can put out thousands of watts, many times the 746 watts in one official horsepower. For tasks lasting a few minutes, a fit human can generate perhaps 1,000 watts. For an activity that must be sustained for an hour, output drops to around 300; for an activity kept up all day, 150 watts is about the maximum.<sup class="reference" id="cite_ref-6"><a href="http://en.wikipedia.org/wiki/Energy#cite_note-6">[7]</a></sup> The human equivalent assists understanding of energy flows in physical and biological systems by expressing energy units in human terms: it provides a “feel” for the use of a given amount of energy<sup class="reference" id="cite_ref-7"><a href="http://en.wikipedia.org/wiki/Energy#cite_note-7">[8]</a></sup></li><li>In <a href="http://en.wikipedia.org/wiki/Earth_science#earth.27s_energy" title="Earth science">geology</a>, <a href="http://en.wikipedia.org/wiki/Continental_drift">continental drift</a>, <a href="http://en.wikipedia.org/wiki/Mountain" title="Mountain">mountain ranges</a>, <a href="http://en.wikipedia.org/wiki/Volcano" title="Volcano">volcanoes</a>, and <a href="http://en.wikipedia.org/wiki/Earthquake" title="Earthquake">earthquakes</a> are phenomena that can be explained in terms of energy transformations in the Earth's interior.,<sup class="reference" id="cite_ref-8"><a href="http://en.wikipedia.org/wiki/Energy#cite_note-8">[9]</a></sup> while <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Metereology" title="Metereology">meteorological</a> phenomena like <a href="http://en.wikipedia.org/wiki/Wind">wind</a>, <a href="http://en.wikipedia.org/wiki/Rain">rain</a>, <a href="http://en.wikipedia.org/wiki/Hail">hail</a>, <a href="http://en.wikipedia.org/wiki/Snow">snow</a>, <a href="http://en.wikipedia.org/wiki/Lightning">lightning</a>, <a href="http://en.wikipedia.org/wiki/Tornado" title="Tornado">tornadoes</a> and <a href="http://en.wikipedia.org/wiki/Tropical_cyclone" title="Tropical cyclone">hurricanes</a>, are all a result of energy transformations brought about by <a href="http://en.wikipedia.org/wiki/Solar_energy">solar energy</a> on the <a href="http://en.wikipedia.org/wiki/Atmosphere">atmosphere</a> of the planet Earth.</li><li>In <a href="http://en.wikipedia.org/wiki/Physical_cosmology#Energy_of_the_cosmos" title="Physical cosmology">cosmology and astronomy</a> the phenomena of <a href="http://en.wikipedia.org/wiki/Star" title="Star">stars</a>, <a href="http://en.wikipedia.org/wiki/Nova">nova</a>, <a href="http://en.wikipedia.org/wiki/Supernova">supernova</a>, <a href="http://en.wikipedia.org/wiki/Quasar" title="Quasar">quasars</a> and <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Gamma_ray_burst" title="Gamma ray burst">gamma ray bursts</a> are the universe's highest-output energy transformations of matter. All <a class="extiw" href="http://en.wiktionary.org/wiki/stellar" title="wikt:stellar">stellar</a> phenomena (including solar activity) are driven by various kinds of energy transformations. Energy in such transformations is either from gravitational collapse of matter (usually molecular hydrogen) into various classes of astronomical objects (stars, black holes, etc.), or from nuclear fusion (of lighter elements, primarily hydrogen).</li></ul>Energy transformations in the universe over time are characterized by various kinds of potential energy that has been available since the <a href="http://en.wikipedia.org/wiki/Big_Bang">Big Bang</a>, later being "released" (transformed to more active types of energy such as kinetic or radiant energy), when a triggering mechanism is available.<br />Familiar examples of such processes include nuclear decay, in which energy is released that was originally "stored" in heavy isotopes (such as <a href="http://en.wikipedia.org/wiki/Uranium">uranium</a> and <a href="http://en.wikipedia.org/wiki/Thorium">thorium</a>), by <a href="http://en.wikipedia.org/wiki/Nucleosynthesis">nucleosynthesis</a>, a process ultimately using the gravitational potential energy released from the <a href="http://en.wikipedia.org/wiki/Gravitational_collapse">gravitational collapse</a> of <a href="http://en.wikipedia.org/wiki/Supernova" title="Supernova">supernovae</a>, to store energy in the creation of these heavy elements before they were incorporated into the solar system and the Earth. This energy is triggered and released in nuclear <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Fission_bomb" title="Fission bomb">fission bombs</a>. In a slower process, <b><a href="http://en.wikipedia.org/wiki/Radioactive_decay">radioactive decay</a></b> of these atoms in the core of the Earth releases heat. This thermal energy drives <a href="http://en.wikipedia.org/wiki/Plate_tectonics">plate tectonics</a> and may lift mountains, via <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Orogenesis" title="Orogenesis">orogenesis</a>. This slow lifting represents a kind of gravitational potential energy storage of the thermal energy, which may be later released to active kinetic energy in landslides, after a triggering event. Earthquakes also release stored elastic potential energy in rocks, a store that has been produced ultimately from the same radioactive heat sources. Thus, according to present understanding, familiar events such as landslides and earthquakes release energy that has been stored as potential energy in the Earth's gravitational field or elastic strain (mechanical potential energy) in rocks. Prior to this, they represent release of energy that has been stored in heavy atoms since the collapse of long-destroyed supernova stars created these atoms.<br />In another similar chain of transformations beginning at the dawn of the universe, <b><a href="http://en.wikipedia.org/wiki/Nuclear_fusion">nuclear fusion</a></b> of hydrogen in the Sun also releases another store of potential energy which was created at the time of the <a href="http://en.wikipedia.org/wiki/Big_Bang">Big Bang</a>. At that time, according to theory, space expanded and the universe cooled too rapidly for hydrogen to completely fuse into heavier elements. This meant that hydrogen represents a store of potential energy that can be released by <a href="http://en.wikipedia.org/wiki/Nuclear_fusion" title="Nuclear fusion">fusion</a>. Such a fusion process is triggered by heat and pressure generated from gravitational collapse of hydrogen clouds when they produce stars, and some of the fusion energy is then transformed into sunlight. Such sunlight from our Sun may again be stored as gravitational potential energy after it strikes the Earth, as (for example) water evaporates from oceans and is deposited upon mountains (where, after being released at a hydroelectric dam, it can be used to drive turbines or generators to produce electricity). Sunlight also drives many weather phenomena, save those generated by volcanic events. An example of a solar-mediated weather event is a hurricane, which occurs when large unstable areas of warm ocean, heated over months, give up some of their thermal energy suddenly to power a few days of violent air movement. Sunlight is also captured by plants as <i>chemical potential energy</i> in <a href="http://en.wikipedia.org/wiki/Photosynthesis">photosynthesis</a>, when carbon dioxide and water (two low-energy compounds) are converted into the high-energy compounds carbohydrates, lipids, and proteins. Plants also release oxygen during photosynthesis, which is utilized by living organisms as an <a href="http://en.wikipedia.org/wiki/Electron_acceptor">electron acceptor</a>, to release the energy of carbohydrates, lipids, and proteins. Release of the energy stored during photosynthesis as heat or light may be triggered suddenly by a spark, in a forest fire, or it may be made available more slowly for animal or human metabolism, when these molecules are ingested, and <a href="http://en.wikipedia.org/wiki/Catabolism">catabolism</a> is triggered by <a href="http://en.wikipedia.org/wiki/Enzyme">enzyme</a> action.<br />Through all of these transformation chains, potential energy stored at the time of the Big Bang is later released by intermediate events, sometimes being stored in a number of ways over time between releases, as more active energy. In all these events, one kind of energy is converted to other types of energy, including heat.<br /><h2><span class="mw-headline" id="Conservation_of_energy">Conservation of energy</span></h2><div class="rellink relarticle mainarticle">Main article: <a href="http://en.wikipedia.org/wiki/Conservation_of_energy">Conservation of energy</a></div>Energy is subject to the <b>law of conservation of energy</b>. According to this law, energy can neither be created (produced) nor destroyed by itself. It can only be transformed.<br />Most kinds of energy (with gravitational energy being a notable exception)<sup class="reference" id="cite_ref-9"><a href="http://en.wikipedia.org/wiki/Energy#cite_note-9">[10]</a></sup> are also subject to strict local conservation laws, as well. In this case, energy can only be exchanged between adjacent regions of space, and all observers agree as to the volumetric density of energy in any given space. There is also a global law of conservation of energy, stating that the total energy of the universe cannot change; this is a corollary of the local law, but not vice versa.<sup class="reference" id="cite_ref-RPF1_5-1"><a href="http://en.wikipedia.org/wiki/Energy#cite_note-RPF1-5">[6]</a></sup><sup class="reference" id="cite_ref-thermo-laws_10-0"><a href="http://en.wikipedia.org/wiki/Energy#cite_note-thermo-laws-10">[11]</a></sup> <a href="http://en.wikipedia.org/wiki/Conservation_of_energy">Conservation of energy</a> is the mathematical consequence of <a href="http://en.wikipedia.org/wiki/Translational_symmetry">translational symmetry</a> of <a href="http://en.wikipedia.org/wiki/Time">time</a> (that is, the indistinguishability of time intervals taken at different time)<sup class="reference" id="cite_ref-11"><a href="http://en.wikipedia.org/wiki/Energy#cite_note-11">[12]</a></sup> - see <a href="http://en.wikipedia.org/wiki/Noether%27s_theorem">Noether's theorem</a>.<br />According to <a href="http://en.wikipedia.org/wiki/Energy_conservation">energy conservation</a> law the total inflow of energy into a system must equal the total outflow of energy from the system, plus the change in the energy contained within the system.<br />This law is a fundamental principle of physics. It follows from the <a href="http://en.wikipedia.org/wiki/Translational_symmetry">translational symmetry</a> of <a href="http://en.wikipedia.org/wiki/Time">time</a>, a property of most phenomena below the cosmic scale that makes them independent of their locations on the time coordinate. Put differently, yesterday, today, and tomorrow are physically indistinguishable.<br />This is because energy is the quantity which is <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Canonical_conjugate" title="Canonical conjugate">canonical conjugate</a> to time. This mathematical entanglement of energy and time also results in the uncertainty principle - it is impossible to define the exact amount of energy during any definite time interval. The uncertainty principle should not be confused with energy conservation - rather it provides mathematical limits to which energy can in principle be defined and measured.<br />In <a href="http://en.wikipedia.org/wiki/Quantum_mechanics">quantum mechanics</a> energy is expressed using the Hamiltonian <a href="http://en.wikipedia.org/wiki/Operator_%28physics%29" title="Operator (physics)">operator</a>. On any time scales, the uncertainty in the energy is by<br /><dl><dd><img alt="\Delta E \Delta t \ge \frac { \hbar } {2 } " class="tex" src="http://upload.wikimedia.org/math/f/f/a/ffaddda8eccc1fde70b14602f09b3fe7.png" /></dd></dl>which is similar in form to the Heisenberg <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Heisenberg_Uncertainty_Principle" title="Heisenberg Uncertainty Principle">uncertainty principle</a> (but not really mathematically equivalent thereto, since <i>H</i> and <i>t</i> are not dynamically conjugate variables, neither in classical nor in quantum mechanics).<br />In <a href="http://en.wikipedia.org/wiki/Particle_physics">particle physics</a>, this inequality permits a qualitative understanding of <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Virtual_particles" title="Virtual particles">virtual particles</a> which carry <a href="http://en.wikipedia.org/wiki/Momentum">momentum</a>, exchange by which and with real particles, is responsible for the creation of all known <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Fundamental_forces" title="Fundamental forces">fundamental forces</a> (more accurately known as <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Fundamental_interactions" title="Fundamental interactions">fundamental interactions</a>). <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Virtual_photons" title="Virtual photons">Virtual photons</a> (which are simply lowest quantum mechanical <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Energy_state" title="Energy state">energy state</a> of <a href="http://en.wikipedia.org/wiki/Photon" title="Photon">photons</a>) are also responsible for electrostatic interaction between <a href="http://en.wikipedia.org/wiki/Electric_charge" title="Electric charge">electric charges</a> (which results in <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Coulomb_law" title="Coulomb law">Coulomb law</a>), for <a href="http://en.wikipedia.org/wiki/Spontaneous_fission" title="Spontaneous fission">spontaneous</a> radiative decay of exited atomic and nuclear states, for the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Casimir_force" title="Casimir force">Casimir force</a>, for <a href="http://en.wikipedia.org/wiki/Van_der_Waals_force" title="Van der Waals force">van der Waals bond forces</a> and some other observable phenomena.<br /><h2><span class="mw-headline" id="Applications_of_the_concept_of_energy">Applications of the concept of energy</span></h2>Energy is subject to a strict <a href="http://en.wikipedia.org/wiki/Conservation_law" title="Conservation law">global conservation law</a>; that is, whenever one measures (or calculates) the total energy of a system of particles whose interactions do not depend explicitly on time, it is found that the total energy of the system always remains constant.<sup class="reference" id="cite_ref-12"><a href="http://en.wikipedia.org/wiki/Energy#cite_note-12">[13]</a></sup><br /><ul><li>The total energy of a <a href="http://en.wikipedia.org/wiki/System">system</a> can be subdivided and classified in various ways. For example, it is sometimes convenient to distinguish <a href="http://en.wikipedia.org/wiki/Potential_energy">potential energy</a> (which is a function of coordinates only) from <a href="http://en.wikipedia.org/wiki/Kinetic_energy">kinetic energy</a> (which is a function of coordinate time <a href="http://en.wikipedia.org/wiki/Derivative" title="Derivative">derivatives</a> only). It may also be convenient to distinguish gravitational energy, electric energy, thermal energy, and other forms. These classifications overlap; for instance, thermal energy usually consists partly of kinetic and partly of potential energy.</li><li>The <i>transfer</i> of energy can take various forms; familiar examples include work, heat flow, and advection, as discussed <a href="http://en.wikipedia.org/wiki/Energy#Energy_transfer">below</a>.</li><li>The word "energy" is also used outside of physics in many ways, which can lead to ambiguity and inconsistency. The vernacular terminology is not consistent with <a href="http://en.wikipedia.org/wiki/Technical_terminology">technical terminology</a>. For example, while energy is always conserved (in the sense that the total energy does not change despite energy transformations), energy can be converted into a form, e.g., thermal energy, that cannot be utilized to perform work. When one talks about "conserving energy by driving less," one talks about conserving fossil fuels and preventing useful energy from being lost as heat. This usage of "conserve" differs from that of the law of conservation of energy.<sup class="reference" id="cite_ref-thermo-laws_10-1"><a href="http://en.wikipedia.org/wiki/Energy#cite_note-thermo-laws-10">[11]</a></sup></li></ul>In <a href="http://en.wikipedia.org/wiki/Classical_physics">classical physics</a> energy is considered a scalar quantity, the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Canonical_conjugate" title="Canonical conjugate">canonical conjugate</a> to <a href="http://en.wikipedia.org/wiki/Time">time</a>. In <a href="http://en.wikipedia.org/wiki/Special_relativity">special relativity</a> energy is also a scalar (although not a <a href="http://en.wikipedia.org/wiki/Lorentz_scalar">Lorentz scalar</a> but a time component of the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Energy-momentum" title="Energy-momentum">energy-momentum</a> <a class="mw-redirect" href="http://en.wikipedia.org/wiki/4-vector" title="4-vector">4-vector</a>).<sup class="reference" id="cite_ref-MTW_13-0"><a href="http://en.wikipedia.org/wiki/Energy#cite_note-MTW-13">[14]</a></sup> In other words, energy is invariant with respect to rotations of <a href="http://en.wikipedia.org/wiki/Space">space</a>, but not invariant with respect to rotations of <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Space-time" title="Space-time">space-time</a> (= <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Lorentz_boost" title="Lorentz boost">boosts</a>).<br /><h3><span class="mw-headline" id="Energy_transfer">Energy transfer</span></h3>Because energy is strictly conserved and is also locally conserved (wherever it can be defined), it is important to remember that by the definition of energy the transfer of energy between the "system" and adjacent regions is work. A familiar example is <i><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Mechanical_work" title="Mechanical work">mechanical work</a></i>. In simple cases this is written as the following equation:<br /><dl><dd><table style="background: none; border-collapse: collapse; border: none; margin: 0;"><tbody><tr> <td nowrap="nowrap" style="border: none; padding: 0.08em; vertical-align: middle;"><div style="margin: 0;"><span class="texhtml">Δ<i>E</i> = <i>W</i></span></div></td> <td style="border: none; padding: 0.08em; vertical-align: middle; width: 99%;"><table style="background: none; border-collapse: collapse; border: none; margin: 0; width: 99%;"><tbody><tr> <td rowspan="2" style="border: none; padding: 0.08em;"><div style="font-size: 4pt; margin: 0;"><br /></div></td> <td style="border: none; padding: 0.08em; width: 100%;"><div style="font-size: 1pt; margin: 0;"><br /></div></td> <td rowspan="2" style="border: none; padding: 0.08em;"><div style="font-size: 4pt; margin: 0;"><br /></div></td> </tr><tr> <td style="border-bottom: none; border-left: none; border-right: none; border-top: 0px none #e5e5e5; padding: 0.08em;"><div style="font-size: 1pt; margin: 0;"><br /></div></td> </tr></tbody></table></td> <td nowrap="nowrap" style="border: none; padding: 0.08em; vertical-align: middle;"><div style="margin: 0pt;"><b>(<cite id="math_1"></cite><span class="reference plainlinksneverexpand"><cite id="math_1"><a href="http://en.wikipedia.org/wiki/Energy#equation_1">1</a></cite><b><cite id="math_1"></cite>)</b></span></b></div></td> </tr></tbody></table></dd></dl>if there are no other energy-transfer processes involved. Here <span class="texhtml"><i>E</i></span> is the amount of energy transferred, and <span class="texhtml"><i>W</i></span> represents the work done on the system.<br />More generally, the energy transfer can be split into two categories:<br /><dl><dd><table style="background: none; border-collapse: collapse; border: none; margin: 0;"><tbody><tr> <td nowrap="nowrap" style="border: none; padding: 0.08em; vertical-align: middle;"><div style="margin: 0;"><span class="texhtml">Δ<i>E</i> = <i>W</i> + <i>Q</i></span></div></td> <td style="border: none; padding: 0.08em; vertical-align: middle; width: 99%;"><table style="background: none; border-collapse: collapse; border: none; margin: 0; width: 99%;"><tbody><tr> <td rowspan="2" style="border: none; padding: 0.08em;"><div style="font-size: 4pt; margin: 0;"><br /></div></td> <td style="border: none; padding: 0.08em; width: 100%;"><div style="font-size: 1pt; margin: 0;"><br /></div></td> <td rowspan="2" style="border: none; padding: 0.08em;"><div style="font-size: 4pt; margin: 0;"><br /></div></td> </tr><tr> <td style="border-bottom: none; border-left: none; border-right: none; border-top: 0px none #e5e5e5; padding: 0.08em;"><div style="font-size: 1pt; margin: 0;"><br /></div></td> </tr></tbody></table></td> <td nowrap="nowrap" style="border: none; padding: 0.08em; vertical-align: middle;"><div style="margin: 0pt;"><b>(<cite id="math_2"></cite><span class="reference plainlinksneverexpand"><cite id="math_2"><a href="http://en.wikipedia.org/wiki/Energy#equation_2">2</a></cite><b><cite id="math_2"></cite>)</b></span></b></div></td> </tr></tbody></table></dd></dl>where <span class="texhtml"><i>Q</i></span> represents the heat flow into the system.<br />There are other ways in which an open system can gain or lose energy. In chemical systems, energy can be added to a system by means of adding substances with different chemical potentials, which potentials are then extracted (both of these process are illustrated by fueling an auto, a system which gains in energy thereby, without addition of either work or heat). Winding a clock would be adding energy to a mechanical system. These terms may be added to the above equation, or they can generally be subsumed into a quantity called "energy addition term <span class="texhtml"><i>E</i></span>" which refers to <i>any</i> type of energy carried over the surface of a control volume or system volume. Examples may be seen above, and many others can be imagined (for example, the kinetic energy of a stream of particles entering a system, or energy from a laser beam adds to system energy, without either being either work-done or heat-added, in the classic senses).<br /><dl><dd><table style="background: none; border-collapse: collapse; border: none; margin: 0;"><tbody><tr> <td nowrap="nowrap" style="border: none; padding: 0.08em; vertical-align: middle;"><div style="margin: 0;"><span class="texhtml">Δ<i>E</i> = <i>W</i> + <i>Q</i> + <i>E</i></span></div></td> <td style="border: none; padding: 0.08em; vertical-align: middle; width: 99%;"><table style="background: none; border-collapse: collapse; border: none; margin: 0; width: 99%;"><tbody><tr> <td rowspan="2" style="border: none; padding: 0.08em;"><div style="font-size: 4pt; margin: 0;"><br /></div></td> <td style="border: none; padding: 0.08em; width: 100%;"><div style="font-size: 1pt; margin: 0;"><br /></div></td> <td rowspan="2" style="border: none; padding: 0.08em;"><div style="font-size: 4pt; margin: 0;"><br /></div></td> </tr><tr> <td style="border-bottom: none; border-left: none; border-right: none; border-top: 0px none #e5e5e5; padding: 0.08em;"><div style="font-size: 1pt; margin: 0;"><br /></div></td> </tr></tbody></table></td> <td nowrap="nowrap" style="border: none; padding: 0.08em; vertical-align: middle;"><div style="margin: 0pt;"><b>(<cite id="math_3"></cite><span class="reference plainlinksneverexpand"><cite id="math_3"><a href="http://en.wikipedia.org/wiki/Energy#equation_3">3</a></cite><b><cite id="math_3"></cite>)</b></span></b></div></td> </tr></tbody></table></dd></dl>Where E in this general equation represents other additional advected energy terms not covered by work done on a system, or heat added to it.<br />Energy is also transferred from potential energy (<span class="texhtml"><i>E</i><sub><i>p</i></sub></span>) to kinetic energy (<span class="texhtml"><i>E</i><sub><i>k</i></sub></span>) and then back to potential energy constantly. This is referred to as conservation of energy. In this closed system, energy cannot be created or destroyed; therefore, the initial energy and the final energy will be equal to each other. This can be demonstrated by the following:<br /><dl><dd><table style="background: none; border-collapse: collapse; border: none; margin: 0;"><tbody><tr> <td nowrap="nowrap" style="border: none; padding: 0.08em; vertical-align: middle;"><div style="margin: 0;"><span class="texhtml"><i>E</i><sub><i>p</i><i>i</i></sub> + <i>E</i><sub><i>k</i><i>i</i></sub> = <i>E</i><sub><i>p</i><i>F</i></sub> + <i>E</i><sub><i>k</i><i>F</i></sub></span></div></td> <td style="border: none; padding: 0.08em; vertical-align: middle; width: 99%;"><table style="background: none; border-collapse: collapse; border: none; margin: 0; width: 99%;"><tbody><tr> <td rowspan="2" style="border: none; padding: 0.08em;"><div style="font-size: 4pt; margin: 0;"><br /></div></td> <td style="border: none; padding: 0.08em; width: 100%;"><div style="font-size: 1pt; margin: 0;"><br /></div></td> <td rowspan="2" style="border: none; padding: 0.08em;"><div style="font-size: 4pt; margin: 0;"><br /></div></td> </tr><tr> <td style="border-bottom: none; border-left: none; border-right: none; border-top: 0px none #e5e5e5; padding: 0.08em;"><div style="font-size: 1pt; margin: 0;"><br /></div></td> </tr></tbody></table></td> <td nowrap="nowrap" style="border: none; padding: 0.08em; vertical-align: middle;"><div style="margin: 0pt;"><b>(<cite id="math_4"></cite><span class="reference plainlinksneverexpand"><cite id="math_4"><a href="http://en.wikipedia.org/wiki/Energy#equation_4">4</a></cite><b><cite id="math_4"></cite>)</b></span></b></div></td> </tr></tbody></table></dd></dl>The equation can then be simplified further since <span class="texhtml"><i>E</i><sub><i>p</i></sub> = <i>m</i><i>g</i><i>h</i></span> (mass times acceleration due to gravity times the height) and <img alt="E_k = \frac{1}{2} mv^2" class="tex" src="http://upload.wikimedia.org/math/a/3/8/a38c32f3f00f593c1dc17692bc224c0f.png" /> (half mass times velocity squared). Then the total amount of energy can be found by adding <span class="texhtml"><i>E</i><sub><i>p</i></sub> + <i>E</i><sub><i>k</i></sub> = <i>E</i><sub><i>t</i><i>o</i><i>t</i><i>a</i><i>l</i></sub></span>.<br /><h3><span class="mw-headline" id="Energy_and_the_laws_of_motion">Energy and the laws of motion</span></h3>In <a href="http://en.wikipedia.org/wiki/Classical_mechanics">classical mechanics</a>, energy is a conceptually and mathematically useful property, as it is a <a href="http://en.wikipedia.org/wiki/Conservation_of_energy" title="Conservation of energy">conserved quantity</a>. Several formulations of mechanics have been developed using energy as a core concept.<br /><h4><span class="mw-headline" id="The_Hamiltonian">The Hamiltonian</span></h4>The total energy of a system is sometimes called the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Hamilton%27s_equations" title="Hamilton's equations">Hamiltonian</a>, after <a href="http://en.wikipedia.org/wiki/William_Rowan_Hamilton">William Rowan Hamilton</a>. The classical equations of motion can be written in terms of the Hamiltonian, even for highly complex or abstract systems. These classical equations have remarkably direct analogs in nonrelativistic quantum mechanics.<sup class="reference" id="cite_ref-14"><a href="http://en.wikipedia.org/wiki/Energy#cite_note-14">[15]</a></sup><br /><h4><span class="mw-headline" id="The_Lagrangian">The Lagrangian</span></h4>Another energy-related concept is called the <a href="http://en.wikipedia.org/wiki/Lagrangian">Lagrangian</a>, after <a href="http://en.wikipedia.org/wiki/Joseph_Louis_Lagrange">Joseph Louis Lagrange</a>. This is even more fundamental than the Hamiltonian, and can be used to derive the equations of motion. It was invented in the context of <a href="http://en.wikipedia.org/wiki/Classical_mechanics">classical mechanics</a>, but is generally useful in modern physics. The Lagrangian is defined as the kinetic energy <i>minus</i> the potential energy.<br />Usually, the Lagrange formalism is mathematically more convenient than the Hamiltonian for non-conservative systems (such as systems with friction).<br /><h3><span class="mw-headline" id="Energy_and_thermodynamics">Energy and thermodynamics</span></h3><h4><span class="mw-headline" id="Internal_energy">Internal energy</span></h4><a href="http://en.wikipedia.org/wiki/Internal_energy">Internal energy</a> is the sum of all microscopic forms of energy of a system. It is the energy needed to create the system. It is related to the potential energy, e.g., molecular structure, crystal structure, and other geometric aspects, as well as the motion of the particles, in form of kinetic energy. Thermodynamics is chiefly concerned with changes in internal energy and not its absolute value, which is impossible to determine with thermodynamics alone.<sup class="reference" id="cite_ref-klotz_15-0"><a href="http://en.wikipedia.org/wiki/Energy#cite_note-klotz-15">[16]</a></sup><br /><h4><span class="mw-headline" id="The_laws_of_thermodynamics">The laws of thermodynamics</span></h4>According to the <a href="http://en.wikipedia.org/wiki/Second_law_of_thermodynamics">second law of thermodynamics</a>, work can be totally converted into <a href="http://en.wikipedia.org/wiki/Heat">heat</a>, but not vice versa. This is a mathematical consequence of <a href="http://en.wikipedia.org/wiki/Statistical_mechanics">statistical mechanics</a>. The <a href="http://en.wikipedia.org/wiki/First_law_of_thermodynamics">first law of thermodynamics</a> simply asserts that energy is conserved,<sup class="reference" id="cite_ref-KK_16-0"><a href="http://en.wikipedia.org/wiki/Energy#cite_note-KK-16">[17]</a></sup> and that heat is included as a form of energy transfer. A commonly used corollary of the first law is that for a "system" subject only to <a href="http://en.wikipedia.org/wiki/Pressure">pressure</a> forces and heat transfer (e.g., a cylinder-full of gas), the differential change in energy of the system (with a <i>gain</i> in energy signified by a positive quantity) is given as the following equation:<br /><dl><dd><img alt="\mathrm{d}E = T\mathrm{d}S - P\mathrm{d}V\," class="tex" src="http://upload.wikimedia.org/math/d/2/f/d2fbdc6df4546def0c18d4c7de9be488.png" />,</dd></dl>where the first term on the right is the heat transfer into the system, defined in terms of <a href="http://en.wikipedia.org/wiki/Temperature">temperature</a> <i>T</i> and <a href="http://en.wikipedia.org/wiki/Entropy">entropy</a> <i>S</i> (in which entropy increases and the change d<i>S</i> is positive when the system is heated), and the last term on the right hand side is identified as "work" done on the system, where pressure is <i>P</i> and volume <i>V</i> (the negative sign results since compression of the system requires work to be done on it and so the volume change, d<i>V</i>, is negative when work is done on the system). Although this equation is the standard textbook example of energy conservation in classical thermodynamics, it is highly specific, ignoring all chemical, electric, nuclear, and gravitational forces, effects such as <a href="http://en.wikipedia.org/wiki/Advection">advection</a> of any form of energy other than heat, and because it contains a term that depends on temperature. The most general statement of the first law (i.e., conservation of energy) is valid even in situations in which temperature is undefinable.<br />Energy is sometimes expressed as the following equation:<br /><dl><dd><img alt="\mathrm{d}E=\delta Q+\delta W\," class="tex" src="http://upload.wikimedia.org/math/b/2/8/b28392162e19a3be03fd22d8c65424f2.png" />,</dd></dl>which is unsatisfactory<sup class="reference" id="cite_ref-thermo-laws_10-2"><a href="http://en.wikipedia.org/wiki/Energy#cite_note-thermo-laws-10">[11]</a></sup> because there cannot exist any thermodynamic state functions <i>W</i> or <i>Q</i> that are meaningful on the right hand side of this equation, except perhaps in trivial cases.<br /><h3><span class="mw-headline" id="Equipartition_of_energy">Equipartition of energy</span></h3>The energy of a mechanical <a href="http://en.wikipedia.org/wiki/Harmonic_oscillator">harmonic oscillator</a> (a mass on a spring) is alternatively <a href="http://en.wikipedia.org/wiki/Kinetic_energy" title="Kinetic energy">kinetic</a> and <a href="http://en.wikipedia.org/wiki/Potential">potential</a>. At two points in the oscillation <a href="http://en.wikipedia.org/wiki/Frequency" title="Frequency">cycle</a> it is entirely kinetic, and alternatively at two other points it is entirely potential. Over the whole cycle, or over many cycles, net energy is thus equally split between kinetic and potential. This is called <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Equipartition_principle" title="Equipartition principle">equipartition principle</a>; total energy of a system with many degrees of freedom is equally split among all available degrees of freedom.<br />This principle is vitally important to understanding the behavior of a quantity closely related to energy, called <a href="http://en.wikipedia.org/wiki/Entropy">entropy</a>. Entropy is a measure of evenness of a <a href="http://en.wikipedia.org/wiki/Distribution_%28mathematics%29" title="Distribution (mathematics)">distribution</a> of energy between parts of a system. When an isolated system is given more degrees of freedom (i.e., given new available <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Energy_state" title="Energy state">energy states</a> that are the same as existing states), then total energy spreads over <b>all</b> available degrees equally without distinction between "new" and "old" degrees. This mathematical result is called the <a href="http://en.wikipedia.org/wiki/Second_law_of_thermodynamics">second law of thermodynamics</a>.<br /><h3><span class="mw-headline" id="Oscillators.2C_phonons.2C_and_photons">Oscillators, phonons, and photons</span></h3><table class="metadata plainlinks ambox ambox-content"><tbody><tr> <td class="mbox-image"><div style="width: 52px;"><img alt="" height="40" src="http://upload.wikimedia.org/wikipedia/en/f/f4/Ambox_content.png" width="40" /></div></td> <td class="mbox-text">This section <b>may contain <a href="http://en.wikipedia.org/wiki/Wikipedia:No_original_research" title="Wikipedia:No original research">original research</a></b>. Please <a class="external text" href="http://en.wikipedia.org/w/index.php?title=Energy&action=edit" rel="nofollow">improve it</a> by <a href="http://en.wikipedia.org/wiki/Wikipedia:Verifiability" title="Wikipedia:Verifiability">verifying</a> the claims made and adding <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Wikipedia:References" title="Wikipedia:References">references</a>. Statements consisting only of original research may be removed. More details may be available on the <a href="http://en.wikipedia.org/wiki/Talk:Energy" title="Talk:Energy">talk page</a>. <small><i>(August 2009)</i></small></td> </tr></tbody></table>In an ensemble (connected collection) of unsynchronized <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Oscillator" title="Oscillator">oscillators</a>, the average energy is spread equally between kinetic and potential types.<br />In a solid, <a href="http://en.wikipedia.org/wiki/Thermal_energy">thermal energy</a> (often referred to loosely as heat content) can be accurately described by an ensemble of thermal <a href="http://en.wikipedia.org/wiki/Phonon" title="Phonon">phonons</a> that act as mechanical oscillators. In this model, thermal energy is equally kinetic and potential.<br />In an <a href="http://en.wikipedia.org/wiki/Ideal_gas">ideal gas</a>, the interaction potential between particles is essentially the <a href="http://en.wikipedia.org/wiki/Dirac_delta_function" title="Dirac delta function">delta function</a> which stores no energy: thus, all of the thermal energy is kinetic.<br />Because an electric oscillator (<a href="http://en.wikipedia.org/wiki/LC_circuit">LC circuit</a>) is analogous to a mechanical oscillator, its energy must be, on average, equally kinetic and potential. It is entirely arbitrary whether the magnetic energy is considered kinetic and whether the electric energy is considered potential, or vice versa. That is, either the <a href="http://en.wikipedia.org/wiki/Inductor">inductor</a> is analogous to the mass while the <a href="http://en.wikipedia.org/wiki/Capacitor">capacitor</a> is analogous to the spring, or vice versa.<br />1. By extension of the previous line of thought, in <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Free_space" title="Free space">free space</a> the electromagnetic field can be considered an ensemble of oscillators, meaning that <a href="http://en.wikipedia.org/wiki/Radiant_energy" title="Radiant energy">radiation energy</a> can be considered equally potential and kinetic. This model is useful, for example, when the electromagnetic <a href="http://en.wikipedia.org/wiki/Lagrangian">Lagrangian</a> is of primary interest and is interpreted in terms of potential and kinetic energy.<br />2. On the other hand, in the key equation <span class="texhtml"><i>m</i><sup>2</sup><i>c</i><sup>4</sup> = <i>E</i><sup>2</sup> − <i>p</i><sup>2</sup><i>c</i><sup>2</sup></span>, the contribution <span class="texhtml"><i>m</i><i>c</i><sup>2</sup></span> is called the rest energy, and all other contributions to the energy are called kinetic energy. For a particle that has mass, this implies that the kinetic energy is <span class="texhtml">0.5<i>p</i><sup>2</sup> / <i>m</i></span> at speeds much smaller than <i>c</i>, as can be proved by writing <span class="texhtml"><i>E</i> = <i>m</i><i>c</i><sup>2</sup></span> √<span class="texhtml">(1 + <i>p</i><sup>2</sup><i>m</i> <sup>− 2</sup><i>c</i> <sup>− 2</sup>)</span> and expanding the square root to lowest order. By this line of reasoning, the energy of a photon is entirely kinetic, because the photon is massless and has no rest energy. This expression is useful, for example, when the energy-versus-momentum relationship is of primary interest.<br />The two analyses are entirely consistent. The electric and magnetic degrees of freedom in item 1 are <i>transverse</i> to the direction of motion, while the speed in item 2 is <i>along</i> the direction of motion. For non-relativistic particles these two notions of potential versus kinetic energy are numerically equal, so the ambiguity is harmless, but not so for relativistic particles.<br /><h3><span class="mw-headline" id="Work_and_virtual_work">Work and virtual work</span></h3><div class="rellink relarticle mainarticle">Main articles: <a href="http://en.wikipedia.org/wiki/Mechanics">Mechanics</a>, <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Mechanical_work" title="Mechanical work">Mechanical work</a>, <a href="http://en.wikipedia.org/wiki/Thermodynamics">Thermodynamics</a>, and <a href="http://en.wikipedia.org/wiki/Quantum_mechanics">Quantum mechanics</a></div>Work, a form of energy, is force times distance.<br /><dl><dd><img alt=" W = \int_C \mathbf{F} \cdot \mathrm{d} \mathbf{s}" class="tex" src="http://upload.wikimedia.org/math/c/f/c/cfc3b91d97dabc27dd8054f1c8b3cc52.png" /></dd></dl>This says that the work (<span class="texhtml"><i>W</i></span>) is equal to the <a href="http://en.wikipedia.org/wiki/Line_integral">line integral</a> of the <a href="http://en.wikipedia.org/wiki/Force">force</a> <b>F</b> along a path <i>C</i>; for details see the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Mechanical_work" title="Mechanical work">mechanical work</a> article.<br />Work and thus energy is <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Frame_dependent" title="Frame dependent">frame dependent</a>. For example, consider a ball being hit by a bat. In the center-of-mass reference frame, the bat does no work on the ball. But, in the reference frame of the person swinging the bat, considerable work is done on the ball.<br /><h3><span class="mw-headline" id="Quantum_mechanics">Quantum mechanics</span></h3><div class="rellink relarticle mainarticle">Main article: <a href="http://en.wikipedia.org/wiki/Energy_operator">Energy operator</a></div>In quantum mechanics energy is defined in terms of the <a href="http://en.wikipedia.org/wiki/Hamiltonian_%28quantum_mechanics%29" title="Hamiltonian (quantum mechanics)">energy operator</a> as a time derivative of the <a href="http://en.wikipedia.org/wiki/Wave_function">wave function</a>. The <a href="http://en.wikipedia.org/wiki/Schr%C3%B6dinger_equation">Schrödinger equation</a> equates the energy operator to the full energy of a particle or a system. In results can be considered as a definition of measurement of energy in quantum mechanics. The Schrödinger equation describes the space- and time-dependence of slow changing (non-relativistic) <a href="http://en.wikipedia.org/wiki/Wave_function">wave function</a> of quantum systems. The solution of this equation for bound system is discrete (a set of permitted states, each characterized by an <a href="http://en.wikipedia.org/wiki/Energy_level">energy level</a>) which results in the concept of <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Quanta" title="Quanta">quanta</a>. In the solution of the Schrödinger equation for any oscillator (vibrator) and for electromagnetic waves in a vacuum, the resulting energy states are related to the frequency by the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Planck" title="Planck">Planck</a> equation <span class="texhtml"><i>E</i> = <i>h</i>ν</span> (where <span class="texhtml"><i>h</i></span> is the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Planck%27s_constant" title="Planck's constant">Planck's constant</a> and <span class="texhtml">ν</span> the frequency). In the case of electromagnetic wave these energy states are called quanta of <a href="http://en.wikipedia.org/wiki/Light">light</a> or <a href="http://en.wikipedia.org/wiki/Photon" title="Photon">photons</a>.<br /><h3><span class="mw-headline" id="Relativity">Relativity</span></h3>When calculating kinetic energy (<a class="mw-redirect" href="http://en.wikipedia.org/wiki/Mechanical_work" title="Mechanical work">work</a> to accelerate a <a href="http://en.wikipedia.org/wiki/Mass">mass</a> from zero <a href="http://en.wikipedia.org/wiki/Speed">speed</a> to some finite speed) relativistically - using <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Lorentz_transformations" title="Lorentz transformations">Lorentz transformations</a> instead of <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Newtonian_mechanics" title="Newtonian mechanics">Newtonian mechanics</a>, Einstein discovered an unexpected by-product of these calculations to be an energy term which does not vanish at zero speed. He called it <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Rest_mass_energy" title="Rest mass energy">rest mass energy</a> - energy which every mass must possess even when being at rest. The amount of energy is directly proportional to the mass of body:<br /><dl><dd><span class="texhtml"><i>E</i> = <i>m</i><i>c</i><sup>2</sup></span>,</dd></dl>where<br /><dl><dd><i>m</i> is the mass,</dd><dd><i>c</i> is the <a href="http://en.wikipedia.org/wiki/Speed_of_light">speed of light</a> in vacuum,</dd><dd><i>E</i> is the rest mass energy.</dd></dl>For example, consider <a href="http://en.wikipedia.org/wiki/Electron">electron</a>-<a href="http://en.wikipedia.org/wiki/Positron">positron</a> annihilation, in which the rest mass of individual particles is destroyed, but the inertia equivalent of the system of the two particles (its <a href="http://en.wikipedia.org/wiki/Invariant_mass">invariant mass</a>) remains (since all energy is associated with mass), and this inertia and invariant mass is carried off by photons which individually are massless, but as a system retain their mass. This is a reversible process - the inverse process is called <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Pair_creation" title="Pair creation">pair creation</a> - in which the rest mass of particles is created from energy of two (or more) annihilating photons. In this system the <a href="http://en.wikipedia.org/wiki/Matter">matter</a> (electrons and positrons) is destroyed and changed to non-matter energy (the photons). However, the total system mass and energy do not change during this interaction.<br />In general relativity, the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Stress-energy_tensor" title="Stress-energy tensor">stress-energy tensor</a> serves as the source term for the gravitational field, in rough analogy to the way mass serves as the source term in the non-relativistic Newtonian approximation.<sup class="reference" id="cite_ref-MTW_13-1"><a href="http://en.wikipedia.org/wiki/Energy#cite_note-MTW-13">[14]</a></sup><br />It is not uncommon to hear that energy is "equivalent" to mass. It would be more accurate to state that every energy has an inertia and gravity equivalent, and because mass is a form of energy, then mass too has inertia and gravity associated with it.<br /><h3><span class="mw-headline" id="Energy_and_life">Energy and life</span></h3><div class="rellink relarticle mainarticle">Main article: <a href="http://en.wikipedia.org/wiki/Bioenergetics">Bioenergetics</a></div><div class="thumb tright"><div class="thumbinner" style="width: 222px;"><a class="image" href="http://en.wikipedia.org/wiki/File:Energy_and_life.png"><img alt="" class="thumbimage" height="163" src="http://upload.wikimedia.org/wikipedia/commons/thumb/d/d1/Energy_and_life.png/220px-Energy_and_life.png" width="220" /></a> <br /><div class="thumbcaption"><div class="magnify"><a class="internal" href="http://en.wikipedia.org/wiki/File:Energy_and_life.png" title="Enlarge"><img alt="" height="11" src="http://bits.wikimedia.org/skins-1.17/common/images/magnify-clip.png" width="15" /></a></div>Basic overview of <a href="http://en.wikipedia.org/wiki/Bioenergetics" title="Bioenergetics">energy and human life</a>.</div></div></div>Any living organism relies on an external source of energy—radiation from the Sun in the case of green plants; chemical energy in some form in the case of animals—to be able to grow and reproduce. The daily 1500–2000 <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Kilocalorie" title="Kilocalorie">Calories</a> (6–8 MJ) recommended for a human adult are taken as a combination of oxygen and food molecules, the latter mostly carbohydrates and fats, of which <a href="http://en.wikipedia.org/wiki/Glucose">glucose</a> (C<sub>6</sub>H<sub>12</sub>O<sub>6</sub>) and <a href="http://en.wikipedia.org/wiki/Stearin">stearin</a> (C<sub>57</sub>H<sub>110</sub>O<sub>6</sub>) are convenient examples. The food molecules are oxidised to <a href="http://en.wikipedia.org/wiki/Carbon_dioxide">carbon dioxide</a> and <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Water_%28molecule%29" title="Water (molecule)">water</a> in the <a href="http://en.wikipedia.org/wiki/Mitochondrion" title="Mitochondrion">mitochondria</a><br /><dl><dd><dl><dd>C<sub>6</sub>H<sub>12</sub>O<sub>6</sub> + 6O<sub>2</sub> → 6CO<sub>2</sub> + 6H<sub>2</sub>O</dd><dd>C<sub>57</sub>H<sub>110</sub>O<sub>6</sub> + 81.5O<sub>2</sub> → 57CO<sub>2</sub> + 55H<sub>2</sub>O</dd></dl></dd></dl>and some of the energy is used to convert <a href="http://en.wikipedia.org/wiki/Adenosine_diphosphate" title="Adenosine diphosphate">ADP</a> into <a href="http://en.wikipedia.org/wiki/Adenosine_triphosphate" title="Adenosine triphosphate">ATP</a><br /><dl><dd><dl><dd>ADP + HPO<sub>4</sub><sup>2−</sup> → ATP + H<sub>2</sub>O</dd></dl></dd></dl>The rest of the chemical energy in the carbohydrate or fat is converted into heat: the ATP is used as a sort of "energy currency", and some of the chemical energy it contains when split and reacted with water, is used for other <a href="http://en.wikipedia.org/wiki/Metabolism">metabolism</a> (at each stage of a <a href="http://en.wikipedia.org/wiki/Metabolic_pathway">metabolic pathway</a>, some chemical energy is converted into heat). Only a tiny fraction of the original chemical energy is used for work:<sup class="reference" id="cite_ref-17"><a href="http://en.wikipedia.org/wiki/Energy#cite_note-17">[18]</a></sup><br /><dl><dd>gain in kinetic energy of a sprinter during a 100 m race: 4 kJ</dd><dd>gain in gravitational potential energy of a 150 kg weight lifted through 2 metres: 3kJ</dd><dd>Daily food intake of a normal adult: 6–8 MJ</dd></dl>It would appear that living organisms are remarkably <a href="http://en.wikipedia.org/wiki/Energy_conversion_efficiency" title="Energy conversion efficiency">inefficient (in the physical sense)</a> in their use of the energy they receive (chemical energy or radiation), and it is true that most real <a href="http://en.wikipedia.org/wiki/Machine" title="Machine">machines</a> manage higher efficiencies. In growing organisms the energy that is converted to heat serves a vital purpose, as it allows the organism tissue to be highly ordered with regard to the molecules it is built from. The <a href="http://en.wikipedia.org/wiki/Second_law_of_thermodynamics">second law of thermodynamics</a> states that energy (and matter) tends to become more evenly spread out across the universe: to concentrate energy (or matter) in one specific place, it is necessary to spread out a greater amount of energy (as heat) across the remainder of the universe ("the surroundings").<sup class="reference" id="cite_ref-18"><a href="http://en.wikipedia.org/wiki/Energy#cite_note-18">[19]</a></sup> Simpler organisms can achieve higher energy efficiencies than more complex ones, but the complex organisms can occupy <a href="http://en.wikipedia.org/wiki/Ecological_niche" title="Ecological niche">ecological niches</a> that are not available to their simpler brethren. The conversion of a portion of the chemical energy to heat at each step in a metabolic pathway is the physical reason behind the pyramid of biomass observed in <a href="http://en.wikipedia.org/wiki/Ecology">ecology</a>: to take just the first step in the <a href="http://en.wikipedia.org/wiki/Food_chain">food chain</a>, of the estimated 124.7 Pg/a of carbon that is <a href="http://en.wikipedia.org/wiki/Carbon_fixation" title="Carbon fixation">fixed</a> by <a href="http://en.wikipedia.org/wiki/Photosynthesis">photosynthesis</a>, 64.3 Pg/a (52%) are used for the metabolism of green plants,<sup class="reference" id="cite_ref-19"><a href="http://en.wikipedia.org/wiki/Energy#cite_note-19">[20]</a></sup> i.e. reconverted into carbon dioxide and heat.<br /><h2><span class="mw-headline" id="Measurement">Measurement</span></h2><div class="thumb tright"><div class="thumbinner" style="width: 222px;"><a class="image" href="http://en.wikipedia.org/wiki/File:X-ray_microcalorimeter_diagram.jpg"><img alt="" class="thumbimage" height="128" src="http://upload.wikimedia.org/wikipedia/commons/thumb/d/d2/X-ray_microcalorimeter_diagram.jpg/220px-X-ray_microcalorimeter_diagram.jpg" width="220" /></a> <br /><div class="thumbcaption"><div class="magnify"><a class="internal" href="http://en.wikipedia.org/wiki/File:X-ray_microcalorimeter_diagram.jpg" title="Enlarge"><img alt="" height="11" src="http://bits.wikimedia.org/skins-1.17/common/images/magnify-clip.png" width="15" /></a></div>A <a href="http://en.wikipedia.org/wiki/Schematic" title="Schematic">schematic diagram</a> of a <a href="http://en.wikipedia.org/wiki/Calorimeter">Calorimeter</a> - An instrument used by physicists to measure energy</div></div></div>Because energy is defined as the ability to do work on objects, there is no absolute measure of energy. Only the transition of a system from one state into another can be defined and thus energy is measured in relative terms. The choice of a baseline or zero point is often arbitrary and can be made in whatever way is most convenient for a problem.<br /><h3><span class="mw-headline" id="Methods">Methods</span></h3>The methods for the <a href="http://en.wikipedia.org/wiki/Measurement">measurement</a> of energy often deploy methods for the measurement of still more fundamental concepts of science, namely <a href="http://en.wikipedia.org/wiki/Mass">mass</a>, <a href="http://en.wikipedia.org/wiki/Distance">distance</a>, <a href="http://en.wikipedia.org/wiki/Radiation">radiation</a>, <a href="http://en.wikipedia.org/wiki/Temperature">temperature</a>, <a href="http://en.wikipedia.org/wiki/Time">time</a>, <a href="http://en.wikipedia.org/wiki/Electric_charge">electric charge</a> and <a href="http://en.wikipedia.org/wiki/Electric_current">electric current</a>.<br />Conventionally the technique most often employed is <a href="http://en.wikipedia.org/wiki/Calorimetry">calorimetry</a>, a <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Thermodynamic" title="Thermodynamic">thermodynamic</a> technique that relies on the measurement of temperature using a <a href="http://en.wikipedia.org/wiki/Thermometer">thermometer</a> or of intensity of radiation using a <a href="http://en.wikipedia.org/wiki/Bolometer">bolometer</a>.<br /><h3><span class="mw-headline" id="Units">Units</span></h3><div class="rellink relarticle mainarticle">Main article: <a href="http://en.wikipedia.org/wiki/Units_of_energy">Units of energy</a></div>Throughout the history of science, energy has been expressed in several different units such as <a href="http://en.wikipedia.org/wiki/Erg" title="Erg">ergs</a> and <a href="http://en.wikipedia.org/wiki/Calorie" title="Calorie">calories</a>. At present, the accepted unit of measurement for energy is the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/SI" title="SI">SI</a> unit of energy, the <a href="http://en.wikipedia.org/wiki/Joule">joule</a>. In addition to the joule, other units of energy include the <a href="http://en.wikipedia.org/wiki/Kilowatt_hour">kilowatt hour</a> (kWh) and the <a href="http://en.wikipedia.org/wiki/British_thermal_unit">British thermal unit</a> (Btu). These are both larger units of energy. One kWh is equivalent to exactly 3.6 million joules, and one Btu is equivalent to about 1055 joules.<sup class="reference" id="cite_ref-20"><a href="http://en.wikipedia.org/wiki/Energy#cite_note-20">[21]</a></sup><br /><h3><span class="mw-headline" id="Energy_density">Energy density</span></h3><div class="rellink relarticle mainarticle">Main article: <a href="http://en.wikipedia.org/wiki/Energy_density">Energy density</a></div><b>Energy density</b> is a term used for the amount of useful energy stored in a given system or region of space per unit volume.<br />For <a href="http://en.wikipedia.org/wiki/Fuel" title="Fuel">fuels</a>, the energy per unit volume is sometimes a useful parameter. In a few applications, comparing, for example, the effectiveness of <a href="http://en.wikipedia.org/wiki/Hydrogen_fuel">hydrogen fuel</a> to <a href="http://en.wikipedia.org/wiki/Gasoline">gasoline</a> it turns out that hydrogen has a higher <a href="http://en.wikipedia.org/wiki/Specific_energy">specific energy</a> than does gasoline, but, even in liquid form, a much lower energy <i>density</i>.<br /><h2><span class="mw-headline" id="Forms_of_energy">Forms of energy</span></h2><div class="thumb tright"><div class="thumbinner" style="width: 222px;"><a class="image" href="http://en.wikipedia.org/wiki/File:Hot_metalwork.jpg"><img alt="" class="thumbimage" height="160" src="http://upload.wikimedia.org/wikipedia/commons/thumb/a/a9/Hot_metalwork.jpg/220px-Hot_metalwork.jpg" width="220" /></a> <br /><div class="thumbcaption"><div class="magnify"><a class="internal" href="http://en.wikipedia.org/wiki/File:Hot_metalwork.jpg" title="Enlarge"><img alt="" height="11" src="http://bits.wikimedia.org/skins-1.17/common/images/magnify-clip.png" width="15" /></a></div><a href="http://en.wikipedia.org/wiki/Heat">Heat</a>, a form of energy, is partly <a href="http://en.wikipedia.org/wiki/Potential_energy">potential energy</a> and partly <a href="http://en.wikipedia.org/wiki/Kinetic_energy">kinetic energy</a>.</div></div></div>In the context of <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Physical_science" title="Physical science">physical sciences</a>, several forms of energy have been defined. These include:<br /><table><tbody><tr> <td><ul><li><a href="http://en.wikipedia.org/wiki/Thermal_energy">Thermal energy</a>, thermal energy in transit is called <a href="http://en.wikipedia.org/wiki/Heat">heat</a></li><li><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Chemical_energy#Chemical_energy" title="Chemical energy">Chemical energy</a></li><li><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Electrical_energy" title="Electrical energy">Electrical energy</a></li><li><a href="http://en.wikipedia.org/wiki/Radiant_energy">Radiant energy</a>, the energy of <a href="http://en.wikipedia.org/wiki/Electromagnetic_radiation">electromagnetic radiation</a></li><li><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Nuclear_energy" title="Nuclear energy">Nuclear energy</a></li></ul></td> <td><ul><li><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Energy_%28physics%29#Magnetic_energy" title="Energy (physics)">Magnetic energy</a></li><li><a href="http://en.wikipedia.org/wiki/Elastic_energy">Elastic energy</a></li><li><a href="http://en.wikipedia.org/wiki/Sound" title="Sound">Sound energy</a></li><li><a href="http://en.wikipedia.org/wiki/Mechanical_energy">Mechanical energy</a></li><li><a href="http://en.wikipedia.org/wiki/Luminous_energy">Luminous energy</a></li></ul></td> <td><br /></td> </tr></tbody></table>These energies may be divided into two main groups; <a href="http://en.wikipedia.org/wiki/Kinetic_energy">kinetic energy</a> and <a href="http://en.wikipedia.org/wiki/Potential_energy">potential energy</a>. Other familiar types of energy are a varying mix of both potential and kinetic energy. Energy may be <a href="http://en.wikipedia.org/wiki/Energy_transformation" title="Energy transformation">transformed</a> between these forms.<br />The above list of the known possible forms of energy is not necessarily complete. Whenever physical scientists discover that a certain phenomenon appears to violate the <a href="http://en.wikipedia.org/wiki/Conservation_of_energy" title="Conservation of energy">law of energy conservation</a>, new forms may be added, as is the case with <a href="http://en.wikipedia.org/wiki/Dark_energy">dark energy</a>, a hypothetical form of energy that permeates all of space and tends to increase the rate of expansion of the universe.<br /><a href="http://en.wikipedia.org/wiki/Classical_mechanics">Classical mechanics</a> distinguishes between <a href="http://en.wikipedia.org/wiki/Potential_energy">potential energy</a>, which is a function of the position of an object, and <a href="http://en.wikipedia.org/wiki/Kinetic_energy">kinetic energy</a>, which is a function of its <a href="http://en.wikipedia.org/wiki/Motion_%28physics%29" title="Motion (physics)">movement</a>. Both position and movement are relative to a <a href="http://en.wikipedia.org/wiki/Frame_of_reference">frame of reference</a>, which must be specified: this is often (and originally) an arbitrary fixed point on the surface of the Earth, the <i>terrestrial</i> frame of reference. It has been attempted to categorize <i>all</i> forms of energy as either kinetic or potential: this is not incorrect, but neither is it clear that it is a real simplification, as Feynman points out:<br /><blockquote class="toccolours" style="display: table; float: none; padding: 10px 15px 10px 15px;">These notions of potential and kinetic energy depend on a notion of length scale. For example, one can speak of <i>macroscopic</i> potential and kinetic energy, which do not include thermal potential and kinetic energy. Also what is called chemical potential energy (below) is a macroscopic notion, and closer examination shows that it is really the sum of the potential <i>and kinetic</i> energy on the atomic and subatomic scale. Similar remarks apply to nuclear "potential" energy and most other forms of energy. This dependence on length scale is non-problematic if the various length scales are decoupled, as is often the case ... but confusion can arise when different length scales are coupled, for instance when friction converts macroscopic work into microscopic thermal energy.</blockquote><table class="wikitable" style="float: right; margin: 10px; width: 150px;"><caption>Examples of the interconversion of energy</caption> <tbody><tr> <th colspan="2">Mechanical energy is converted</th> </tr><tr> <th>into</th> <th>by</th> </tr><tr> <td><b><a href="http://en.wikipedia.org/wiki/Mechanical_energy">Mechanical energy</a></b></td> <td><a href="http://en.wikipedia.org/wiki/Lever">Lever</a></td> </tr><tr> <td><b><a href="http://en.wikipedia.org/wiki/Thermal_energy">Thermal energy</a></b></td> <td><a href="http://en.wikipedia.org/wiki/Brake" title="Brake">Brakes</a></td> </tr><tr> <td><b><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Electric_energy" title="Electric energy">Electric energy</a></b></td> <td><a href="http://en.wikipedia.org/wiki/Dynamo">Dynamo</a></td> </tr><tr> <td><b><a href="http://en.wikipedia.org/wiki/Electromagnetic_radiation">Electromagnetic radiation</a></b></td> <td><a href="http://en.wikipedia.org/wiki/Synchrotron">Synchrotron</a></td> </tr><tr> <td><b><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Chemical_energy" title="Chemical energy">Chemical energy</a></b></td> <td><a href="http://en.wikipedia.org/wiki/Match" title="Match">Matches</a></td> </tr><tr> <td><b><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Nuclear_energy" title="Nuclear energy">Nuclear energy</a></b></td> <td><a href="http://en.wikipedia.org/wiki/Particle_accelerator">Particle accelerator</a></td> </tr></tbody></table><h3><span class="mw-headline" id="Mechanical_energy">Mechanical energy</span></h3>Mechanical energy manifest in many forms,but can be broadly classified into elastic potential energy and kinetic energy. The term potential energy is a very general term, because it exists in all force fields, such as gravitation, electrostatic and magnetic fields. Potential energy refers to the energy any object gets due to its position in a force field.<br /><div class="rellink relarticle mainarticle">Main article: <a href="http://en.wikipedia.org/wiki/Potential_energy">Potential energy</a></div>Potential energy, symbols <i>E</i><sub>p</sub>, <i>V</i> or <i>Φ</i>, is defined as the work done <i>against a given force</i> (= work of <i>given force</i> with minus sign) in changing the position of an object with respect to a reference position (often taken to be infinite separation). If <b>F</b> is the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Force_%28physics%29" title="Force (physics)">force</a> and <b>s</b> is the <a href="http://en.wikipedia.org/wiki/Displacement_%28vector%29" title="Displacement (vector)">displacement</a>,<br /><dl><dd><dl><dd><img alt="E_{\rm p} = -\int \mathbf{F}\cdot{\rm d}\mathbf{s}" class="tex" src="http://upload.wikimedia.org/math/2/b/a/2baae4b0cf4cdabcaafab46188f44cc6.png" /></dd></dl></dd></dl>with the dot representing the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Scalar_product" title="Scalar product">scalar product</a> of the two <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Vector_%28geometric%29" title="Vector (geometric)">vectors</a>.<br />The name "potential" energy originally signified the idea that the energy could readily be transferred as work—at least in an idealized system (reversible process, see below). This is not completely true for any real system, but is often a reasonable first approximation in classical mechanics.<br />The general equation above can be simplified in a number of common cases, notably when dealing with <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Gravity" title="Gravity">gravity</a> or with elastic forces.<br /><h4><span class="mw-headline" id="Elastic_potential_energy">Elastic potential energy</span></h4><div class="thumb tright"><div class="thumbinner" style="width: 222px;"><a class="image" href="http://en.wikipedia.org/wiki/File:Bouncing_ball_strobe_edit.jpg"><img alt="" class="thumbimage" height="142" src="http://upload.wikimedia.org/wikipedia/commons/thumb/3/3c/Bouncing_ball_strobe_edit.jpg/220px-Bouncing_ball_strobe_edit.jpg" width="220" /></a> <br /><div class="thumbcaption"><div class="magnify"><a class="internal" href="http://en.wikipedia.org/wiki/File:Bouncing_ball_strobe_edit.jpg" title="Enlarge"><img alt="" height="11" src="http://bits.wikimedia.org/skins-1.17/common/images/magnify-clip.png" width="15" /></a></div>As a ball falls freely under the influence of <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Gravity" title="Gravity">gravity</a>, it accelerates downward, its initial <a href="http://en.wikipedia.org/wiki/Potential_energy">potential energy</a> converting into <a href="http://en.wikipedia.org/wiki/Kinetic_energy">kinetic energy</a>. On impact with a hard surface the ball deforms, converting the kinetic energy into <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Elastic_potential_energy" title="Elastic potential energy">elastic potential energy</a>. As the ball springs back, the energy converts back firstly to kinetic energy and then as the ball re-gains height into potential energy. Energy conversion to heat due to <a href="http://en.wikipedia.org/wiki/Elasticity_%28physics%29" title="Elasticity (physics)">inelastic</a> <a href="http://en.wikipedia.org/wiki/Deformation_%28mechanics%29" title="Deformation (mechanics)">deformation</a> and <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Air_resistance" title="Air resistance">air resistance</a> cause each successive bounce to be lower than the last.</div></div></div><div class="rellink relarticle mainarticle">Main article: <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Elastic_potential_energy" title="Elastic potential energy">Elastic potential energy</a></div>Elastic potential energy is defined as a work needed to compress (or expand) a spring. The force, <b>F</b>, in a <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Spring_%28mechanics%29" title="Spring (mechanics)">spring</a> or any other system which obeys <a href="http://en.wikipedia.org/wiki/Hooke%27s_law">Hooke's law</a> is proportional to the extension or compression, <b>x</b>,<br /><dl><dd><dl><dd><span class="texhtml"><i>F</i> = − <i>k</i><i>x</i></span></dd></dl></dd></dl>where <i>k</i> is the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Force_constant" title="Force constant">force constant</a> of the particular spring (or system). In this case, the calculated work becomes<br /><dl><dd><dl><dd><img alt="E_{\rm p,e} = {1\over 2}kx^2" class="tex" src="http://upload.wikimedia.org/math/6/9/3/693f4a3d15a1ae0e1785ab105a85461c.png" /></dd></dl></dd></dl>only when <i>k</i> is constant. Hooke's law is a good approximation for behaviour of <a href="http://en.wikipedia.org/wiki/Chemical_bond" title="Chemical bond">chemical bonds</a> under normal conditions, i.e. when they are not being broken or formed.<br /><h4><span class="mw-headline" id="Kinetic_energy">Kinetic energy</span></h4><div class="rellink relarticle mainarticle">Main article: <a href="http://en.wikipedia.org/wiki/Kinetic_energy">Kinetic energy</a></div>Kinetic energy, symbols <i>E</i><sub>k</sub>, <i>T</i> or <i>K</i>, is the work required to accelerate an object to a given speed. Indeed, calculating this work one easily obtains the following:<br /><dl><dd><dl><dd><img alt="E_{\rm k} = \int \mathbf{F} \cdot d \mathbf{x} = \int \mathbf{v} \cdot d \mathbf{p}= {1\over 2}mv^2" class="tex" src="http://upload.wikimedia.org/math/0/7/e/07e1face7fd37ed238c925b718199e9b.png" /></dd></dl></dd></dl>At speeds approaching the <a href="http://en.wikipedia.org/wiki/Speed_of_light">speed of light</a>, <i>c</i>, this work must be calculated using <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Lorentz_transformations" title="Lorentz transformations">Lorentz transformations</a>, which results in the following:<br /><dl><dd><dl><dd><img alt=" E_{\rm k} = m c^2\left(\frac{1}{\sqrt{1 - (v/c)^2}} - 1\right) " class="tex" src="http://upload.wikimedia.org/math/e/8/a/e8aed09c2f00a9337f240b859ce11f25.png" /></dd></dl></dd></dl>Here the two terms on the right hand side are identified with the total energy and the rest energy of the object, respectively. This equation reduces to the one above it, at small (compared to <b>c</b>) speed. The kinetic energy is zero at v=0, so that at rest, the total energy is the rest energy. Thus, a resting mass has the amount of total energy equal to:<br /><dl><dd><dl><dd><span class="texhtml"><i>E</i><sub>rest</sub> = <i>m</i><i>c</i><sup>2</sup></span></dd></dl></dd></dl>This energy is thus called <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Rest_mass_energy" title="Rest mass energy">rest mass energy</a>.<br /><h4><span class="mw-headline" id="Surface_energy">Surface energy</span></h4>If there is any kind of tension in a surface, such as a stretched sheet of rubber or material interfaces, it is possible to define <b>surface energy</b>. In particular, any meeting of dissimilar materials that don't mix will result in some kind of <a href="http://en.wikipedia.org/wiki/Surface_tension">surface tension</a>, if there is freedom for the surfaces to move then, as seen in <a href="http://en.wikipedia.org/wiki/Capillary_surface" title="Capillary surface">capillary surfaces</a> for example, the minimum energy will as usual be sought.<br />A <a href="http://en.wikipedia.org/wiki/Minimal_surface">minimal surface</a>, for example, represents the smallest possible energy that a surface can have if its energy is proportional to the area of the surface. For this reason, (open) soap films of small size are minimal surfaces (small size reduces gravity effects, and openness prevents pressure from building up. Note that a bubble is a minimum energy surface but not a <a href="http://en.wikipedia.org/wiki/Minimal_surface">minimal surface</a> by definition).<br /><h4><span class="mw-headline" id="Sound_energy">Sound energy</span></h4>Sound is a form of mechanical vibration which propagates through any mechanical medium. It is closely related to the ability of the human ear to perceive sound. The wide outer area of the ear is maximized to collect sound vibrations. It is amplified and passed through the outer ear, striking the eardrum, which transmits sounds into the inner ear. Auditory nerves fire according to the particular vibrations of the sound waves in the inner ear, which designate such things as the pitch and volume of the sound. The ear is set up in an optimal way to interpret sound energy in the form of vibrations.<br /><h3><span class="mw-headline" id="Gravitational_energy">Gravitational energy</span></h3><div class="rellink relarticle mainarticle">Main article: <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Gravitational_potential_energy" title="Gravitational potential energy">Gravitational potential energy</a></div>The <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Gravitational_force" title="Gravitational force">gravitational force</a> near the Earth's surface varies very little with the height, <i>h</i>, and is equal to the <a href="http://en.wikipedia.org/wiki/Mass">mass</a>, <i>m</i>, multiplied by the <a href="http://en.wikipedia.org/wiki/Gravitational_acceleration">gravitational acceleration</a>, <i>g</i> = 9.81 m/s². In these cases, the gravitational potential energy is given by<br /><dl><dd><dl><dd><span class="texhtml"><i>E</i><sub>p,g</sub> = <i>m</i><i>g</i><i>h</i></span></dd></dl></dd></dl>A more general expression for the potential energy due to <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Newtonian_gravitation" title="Newtonian gravitation">Newtonian gravitation</a> between two bodies of masses <i>m</i><sub>1</sub> and <i>m</i><sub>2</sub>, useful in <a href="http://en.wikipedia.org/wiki/Astronomy">astronomy</a>, is<br /><dl><dd><dl><dd><img alt="E_{\rm p,g} = -G{{m_1m_2}\over{r}}" class="tex" src="http://upload.wikimedia.org/math/2/a/8/2a8510f5370617937f1def5a87da8fd6.png" />,</dd></dl></dd></dl>where <i>r</i> is the separation between the two bodies and <i>G</i> is the <a href="http://en.wikipedia.org/wiki/Gravitational_constant">gravitational constant</a>, 6.6742(10)×10<sup>−11</sup> m<sup>3</sup>kg<sup>−1</sup>s<sup>−2</sup>.<sup class="reference" id="cite_ref-CODATA_21-0"><a href="http://en.wikipedia.org/wiki/Energy#cite_note-CODATA-21">[22]</a></sup> In this case, the reference point is the infinite separation of the two bodies.<br /><h3><span class="mw-headline" id="Thermal_energy">Thermal energy</span></h3><table class="wikitable" style="float: right; margin: 10px; width: 150px;"><caption>Examples of the interconversion of energy</caption> <tbody><tr> <th colspan="2">Thermal energy is converted</th> </tr><tr> <th>into</th> <th>by</th> </tr><tr> <td><b><a href="http://en.wikipedia.org/wiki/Mechanical_energy">Mechanical energy</a></b></td> <td><a href="http://en.wikipedia.org/wiki/Steam_turbine">Steam turbine</a></td> </tr><tr> <td><b><a href="http://en.wikipedia.org/wiki/Thermal_energy">Thermal energy</a></b></td> <td><a href="http://en.wikipedia.org/wiki/Heat_exchanger">Heat exchanger</a></td> </tr><tr> <td><b><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Electric_energy" title="Electric energy">Electric energy</a></b></td> <td><a href="http://en.wikipedia.org/wiki/Thermocouple">Thermocouple</a></td> </tr><tr> <td><b><a href="http://en.wikipedia.org/wiki/Electromagnetic_radiation">Electromagnetic radiation</a></b></td> <td><a href="http://en.wikipedia.org/wiki/Black_body" title="Black body">Hot objects</a></td> </tr><tr> <td><b><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Chemical_energy" title="Chemical energy">Chemical energy</a></b></td> <td><a href="http://en.wikipedia.org/wiki/Blast_furnace">Blast furnace</a></td> </tr><tr> <td><b><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Nuclear_energy" title="Nuclear energy">Nuclear energy</a></b></td> <td><a href="http://en.wikipedia.org/wiki/Supernova">Supernova</a></td> </tr></tbody></table><div class="rellink relarticle mainarticle">Main article: <a href="http://en.wikipedia.org/wiki/Thermal_energy">Thermal energy</a></div>Thermal energy (of some media - gas, plasma, solid, etc.) is the energy associated with the microscopical random motion of particles constituting the media. For example, in case of monoatomic gas it is just a kinetic energy of motion of atoms of gas as measured in the reference frame of the center of mass of gas. In case of molecules in the gas rotational and vibrational energy is involved. In the case of liquids and solids there is also potential energy (of interaction of atoms) involved, and so on.<br />A heat is defined as a transfer (flow) of thermal energy across certain boundary (for example, from a hot body to cold via the area of their contact. A practical definition for small transfers of heat is<br /><dl><dd><dl><dd><img alt="\Delta q = \int C_{\rm v}{\rm d}T" class="tex" src="http://upload.wikimedia.org/math/0/9/1/0918c0885f3aefdc281b54a1c68c51aa.png" /></dd></dl></dd></dl>where <i>C</i><sub>v</sub> is the <a href="http://en.wikipedia.org/wiki/Heat_capacity">heat capacity</a> of the system. This definition will fail if the system undergoes a <a href="http://en.wikipedia.org/wiki/Phase_transition">phase transition</a>—e.g. if ice is melting to water—as in these cases the system can absorb heat without increasing its temperature. In more complex systems, it is preferable to use the concept of <a href="http://en.wikipedia.org/wiki/Internal_energy">internal energy</a> rather than that of thermal energy (see <a href="http://en.wikipedia.org/wiki/Energy#Chemical_energy"><i>Chemical energy</i> below</a>).<br />Despite the theoretical problems, the above definition is useful in the experimental measurement of energy changes. In a wide variety of situations, it is possible to use the energy released by a system to raise the temperature of another object, e.g. a bath of water. It is also possible to measure the amount of <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Electric_energy" title="Electric energy">electric energy</a> required to raise the temperature of the object by the same amount. The <a href="http://en.wikipedia.org/wiki/Calorie">calorie</a> was originally defined as the amount of energy required to raise the temperature of one gram of water by 1 °C (approximately 4.1855 J, although the definition later changed), and the <a href="http://en.wikipedia.org/wiki/British_thermal_unit">British thermal unit</a> was defined as the energy required to heat one <a href="http://en.wikipedia.org/wiki/Pound_%28mass%29" title="Pound (mass)">pound</a> of water by 1 <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Degree_Fahrenheit" title="Degree Fahrenheit">°F</a> (later fixed as 1055.06 J).<br /><h3><span class="mw-headline" id="Electric_energy">Electric energy</span></h3><div class="rellink relarticle mainarticle">Main articles: <a href="http://en.wikipedia.org/wiki/Electromagnetism">Electromagnetism</a> and <a href="http://en.wikipedia.org/wiki/Electricity">Electricity</a></div><table class="wikitable" style="float: right; margin: 10px; width: 150px;"><caption>Examples of the interconversion of energy</caption> <tbody><tr> <th colspan="2">Electric energy is converted</th> </tr><tr> <th>into</th> <th>by</th> </tr><tr> <td><b><a href="http://en.wikipedia.org/wiki/Mechanical_energy">Mechanical energy</a></b></td> <td><a href="http://en.wikipedia.org/wiki/Electric_motor">Electric motor</a></td> </tr><tr> <td><b><a href="http://en.wikipedia.org/wiki/Thermal_energy">Thermal energy</a></b></td> <td><a href="http://en.wikipedia.org/wiki/Resistor">Resistor</a></td> </tr><tr> <td><b><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Electric_energy" title="Electric energy">Electric energy</a></b></td> <td><a href="http://en.wikipedia.org/wiki/Transformer">Transformer</a></td> </tr><tr> <td><b><a href="http://en.wikipedia.org/wiki/Electromagnetic_radiation">Electromagnetic radiation</a></b></td> <td><a href="http://en.wikipedia.org/wiki/Light-emitting_diode">Light-emitting diode</a></td> </tr><tr> <td><b><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Chemical_energy" title="Chemical energy">Chemical energy</a></b></td> <td><a href="http://en.wikipedia.org/wiki/Electrolysis">Electrolysis</a></td> </tr><tr> <td><b><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Nuclear_energy" title="Nuclear energy">Nuclear energy</a></b></td> <td><a href="http://en.wikipedia.org/wiki/Synchrotron">Synchrotron</a></td> </tr></tbody></table><h4><span class="mw-headline" id="Electrostatic_energy">Electrostatic energy</span></h4>The <a href="http://en.wikipedia.org/wiki/Electric_potential_energy">electric potential energy</a> of given configuration of charges is defined as the <a href="http://en.wikipedia.org/wiki/Work_%28thermodynamics%29" title="Work (thermodynamics)">work</a> which must be done against the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Coulomb_force" title="Coulomb force">Coulomb force</a> to rearrange charges from infinite separation to this configuration (or the work done by the Coulomb force separating the charges from this configuration to infinity). For two point-like charges <i>Q</i><sub>1</sub> and <i>Q</i><sub>2</sub> at a distance <i>r</i> this work, and hence electric potential energy is equal to:<br /><dl><dd><dl><dd><img alt="E_{\rm p,e} = {1\over {4\pi\epsilon_0}}{{Q_1Q_2}\over{r}}" class="tex" src="http://upload.wikimedia.org/math/c/2/f/c2fa711a4ffc1e2b149258416015009b.png" /></dd></dl></dd></dl>where ε<sub>0</sub> is the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Electric_constant" title="Electric constant">electric constant</a> of a vacuum, 10<sup>7</sup>/4π<i>c</i><sub>0</sub>² or 8.854188…×10<sup>−12</sup> F/m.<sup class="reference" id="cite_ref-CODATA_21-1"><a href="http://en.wikipedia.org/wiki/Energy#cite_note-CODATA-21">[22]</a></sup> If the charge is accumulated in a <a href="http://en.wikipedia.org/wiki/Capacitor">capacitor</a> (of <a href="http://en.wikipedia.org/wiki/Capacitance">capacitance</a> <i>C</i>), the reference configuration is usually selected not to be infinite separation of charges, but vice versa - charges at an extremely close proximity to each other (so there is zero net charge on each plate of a capacitor). The justification for this choice is purely practical - it is easier to measure both voltage difference and magnitude of charges on a capacitor plates not versus infinite separation of charges but rather versus discharged capacitor where charges return to close proximity to each other (electrons and ions recombine making the plates neutral). In this case the work and thus the electric potential energy becomes<br /><dl><dd><dl><dd><img alt="E_{\rm p,e} = {{Q^2}\over{2C}}" class="tex" src="http://upload.wikimedia.org/math/b/b/1/bb132e97188049590ce9024f32b2018d.png" /></dd></dl></dd></dl><h4><span class="mw-headline" id="Electric_energy_2">Electric energy</span></h4>If an <a href="http://en.wikipedia.org/wiki/Electric_current">electric current</a> passes through a <a href="http://en.wikipedia.org/wiki/Resistor">resistor</a>, electric energy is converted to heat; if the current passes through an electric appliance, some of the electric energy will be converted into other forms of energy (although some will always be lost as heat). The amount of electric energy due to an electric current can be expressed in a number of different ways:<br /><dl><dd><dl><dd><img alt="E = UQ = UIt = Pt = {{U^2}{t}\over{R}} = {I^2}Rt " class="tex" src="http://upload.wikimedia.org/math/2/d/2/2d2b280cd71c14b05db1b67cb916baa0.png" /></dd></dl></dd></dl>where <i>U</i> is the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Electric_potential_difference" title="Electric potential difference">electric potential difference</a> (in <a href="http://en.wikipedia.org/wiki/Volt" title="Volt">volts</a>), <i>Q</i> is the charge (in <a href="http://en.wikipedia.org/wiki/Coulomb" title="Coulomb">coulombs</a>), <i>I</i> is the current (in <a href="http://en.wikipedia.org/wiki/Ampere" title="Ampere">amperes</a>), <i>t</i> is the time for which the current flows (in seconds), <i>P</i> is the <a href="http://en.wikipedia.org/wiki/Power_%28physics%29" title="Power (physics)">power</a> (in <a href="http://en.wikipedia.org/wiki/Watt" title="Watt">watts</a>) and <i>R</i> is the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Electric_resistance" title="Electric resistance">electric resistance</a> (in <a href="http://en.wikipedia.org/wiki/Ohm" title="Ohm">ohms</a>). The last of these expressions is important in the practical measurement of energy, as potential difference, resistance and time can all be measured with considerable accuracy.<br /><h4><span class="mw-headline" id="Magnetic_energy">Magnetic energy</span></h4>There is no fundamental difference between magnetic energy and electric energy: the two phenomena are related by <a href="http://en.wikipedia.org/wiki/Maxwell%27s_equations">Maxwell's equations</a>. The potential energy of a <a href="http://en.wikipedia.org/wiki/Magnet">magnet</a> of <a href="http://en.wikipedia.org/wiki/Magnetic_moment">magnetic moment</a> <b>m</b> in a <a href="http://en.wikipedia.org/wiki/Magnetic_field">magnetic field</a> <b>B</b> is defined as the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Mechanical_work" title="Mechanical work">work</a> of magnetic force (actually of magnetic <a href="http://en.wikipedia.org/wiki/Torque">torque</a>) on re-alignment of the vector of the magnetic dipole moment, and is equal:<br /><dl><dd><dl><dd><img alt="E_{\rm p,m} = -m\cdot B" class="tex" src="http://upload.wikimedia.org/math/d/1/e/d1e3e79378214765681b5df326c257d1.png" /></dd></dl></dd></dl>while the energy stored in an <a href="http://en.wikipedia.org/wiki/Inductor">inductor</a> (of <a href="http://en.wikipedia.org/wiki/Inductance">inductance</a> <i>L</i>) when current <i>I</i> is passing via it is<br /><dl><dd><dl><dd><img alt="E_{\rm p,m} = {1\over 2}LI^2" class="tex" src="http://upload.wikimedia.org/math/1/0/a/10ab29f62ab364fae8a2598a177a70b7.png" />.</dd></dl></dd></dl>This second expression forms the basis for <a href="http://en.wikipedia.org/wiki/Superconducting_magnetic_energy_storage">superconducting magnetic energy storage</a>.<br /><h4><span class="mw-headline" id="Electromagnetic_Energy">Electromagnetic Energy</span></h4><table class="wikitable" style="float: right; margin: 10px; width: 150px;"><caption>Examples of the interconversion of energy</caption> <tbody><tr> <th colspan="2">Electromagnetic radiation is converted</th> </tr><tr> <th>into</th> <th>by</th> </tr><tr> <td><b><a href="http://en.wikipedia.org/wiki/Mechanical_energy">Mechanical energy</a></b></td> <td><a href="http://en.wikipedia.org/wiki/Solar_sail">Solar sail</a></td> </tr><tr> <td><b><a href="http://en.wikipedia.org/wiki/Thermal_energy">Thermal energy</a></b></td> <td><a href="http://en.wikipedia.org/wiki/Solar_collector">Solar collector</a></td> </tr><tr> <td><b><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Electric_energy" title="Electric energy">Electric energy</a></b></td> <td><a href="http://en.wikipedia.org/wiki/Solar_cell">Solar cell</a></td> </tr><tr> <td><b><a href="http://en.wikipedia.org/wiki/Electromagnetic_radiation">Electromagnetic radiation</a></b></td> <td><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Non-linear_optics" title="Non-linear optics">Non-linear optics</a></td> </tr><tr> <td><b><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Chemical_energy" title="Chemical energy">Chemical energy</a></b></td> <td><a href="http://en.wikipedia.org/wiki/Photosynthesis">Photosynthesis</a></td> </tr><tr> <td><b><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Nuclear_energy" title="Nuclear energy">Nuclear energy</a></b></td> <td><a href="http://en.wikipedia.org/wiki/M%C3%B6ssbauer_spectroscopy">Mössbauer spectroscopy</a></td> </tr></tbody></table>Calculating <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Mechanical_work" title="Mechanical work">work</a> needed to create an electric or magnetic field in unit volume (say, in a capacitor or an inductor) results in the electric and magnetic fields <a href="http://en.wikipedia.org/wiki/Energy_density" title="Energy density">energy densities</a>:<br /><dl><dd><dl><dd><img alt=" u_e=\frac{\epsilon_0}{2} E^2 " class="tex" src="http://upload.wikimedia.org/math/c/c/2/cc27e82861c0c33a091fe85a97a55d88.png" /></dd></dl></dd></dl>and<br /><dl><dd><dl><dd><img alt=" u_m=\frac{1}{2\mu_0} B^2 " class="tex" src="http://upload.wikimedia.org/math/0/e/c/0ec2b15cbc96483d88952167b7b29d75.png" />,</dd></dl></dd></dl>in SI units.<br />Electromagnetic radiation, such as <a href="http://en.wikipedia.org/wiki/Microwave" title="Microwave">microwaves</a>, <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Visible_light" title="Visible light">visible light</a> or <a href="http://en.wikipedia.org/wiki/Gamma_ray" title="Gamma ray">gamma rays</a>, represents a flow of electromagnetic energy. Applying the above expressions to magnetic and electric components of electromagnetic field both the volumetric density and the flow of energy in e/m field can be calculated. The resulting <a href="http://en.wikipedia.org/wiki/Poynting_vector">Poynting vector</a>, which is expressed as<br /><dl><dd><dl><dd><img alt="\mathbf{S} = \frac{1}{\mu} \mathbf{E} \times \mathbf{B}," class="tex" src="http://upload.wikimedia.org/math/4/6/d/46dcbca182f979c5671947a8a043baca.png" /></dd></dl></dd></dl>in SI units, gives the density of the flow of energy and its direction.<br />The energy of electromagnetic radiation is quantized (has discrete <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Energy_levels" title="Energy levels">energy levels</a>). The spacing between these levels is equal to<br /><dl><dd><dl><dd><span class="texhtml"><i>E</i> = <i>h</i>ν</span></dd></dl></dd></dl>where <i>h</i> is the <a href="http://en.wikipedia.org/wiki/Planck_constant">Planck constant</a>, 6.6260693(11)×10<sup>−34</sup> Js,<sup class="reference" id="cite_ref-CODATA_21-2"><a href="http://en.wikipedia.org/wiki/Energy#cite_note-CODATA-21">[22]</a></sup> and <i>ν</i> is the <a href="http://en.wikipedia.org/wiki/Frequency">frequency</a> of the radiation. This quantity of electromagnetic energy is usually called a photon. The photons which make up visible light have energies of 270–520 yJ, equivalent to 160–310 kJ/mol, the strength of weaker <a href="http://en.wikipedia.org/wiki/Chemical_bond" title="Chemical bond">chemical bonds</a>.<br /><h3><span class="mw-headline" id="Chemical_energy">Chemical energy</span></h3><div class="rellink relarticle mainarticle">Main article: <a href="http://en.wikipedia.org/wiki/Chemical_thermodynamics">Chemical thermodynamics</a></div><table class="wikitable" style="float: right; margin: 10px; width: 150px;"><caption>Examples of the interconversion of energy</caption> <tbody><tr> <th colspan="2">Chemical energy is converted</th> </tr><tr> <th>into</th> <th>by</th> </tr><tr> <td><b><a href="http://en.wikipedia.org/wiki/Mechanical_energy">Mechanical energy</a></b></td> <td><a href="http://en.wikipedia.org/wiki/Muscle">Muscle</a></td> </tr><tr> <td><b><a href="http://en.wikipedia.org/wiki/Thermal_energy">Thermal energy</a></b></td> <td><a href="http://en.wikipedia.org/wiki/Fire">Fire</a></td> </tr><tr> <td><b><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Electric_energy" title="Electric energy">Electric energy</a></b></td> <td><a href="http://en.wikipedia.org/wiki/Fuel_cell">Fuel cell</a></td> </tr><tr> <td><b><a href="http://en.wikipedia.org/wiki/Electromagnetic_radiation">Electromagnetic radiation</a></b></td> <td><a href="http://en.wikipedia.org/wiki/Glowworm" title="Glowworm">Glowworms</a></td> </tr><tr> <td><b><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Chemical_energy" title="Chemical energy">Chemical energy</a></b></td> <td><a href="http://en.wikipedia.org/wiki/Chemical_reaction">Chemical reaction</a></td> </tr></tbody></table><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Chemical_energy" title="Chemical energy">Chemical energy</a> is the energy due to associations of atoms in molecules and various other kinds of aggregates of <a href="http://en.wikipedia.org/wiki/Matter">matter</a>. It may be defined as a work done by electric forces during re-arrangement of mutual positions of electric charges, electrons and protons, in the process of aggregation. So, basically it is electrostatic potential energy of electric charges. If the chemical energy of a system decreases during a chemical reaction, the difference is transferred to the surroundings in some form (often <a href="http://en.wikipedia.org/wiki/Heat">heat</a> or <a href="http://en.wikipedia.org/wiki/Light">light</a>); on the other hand if the chemical energy of a system increases as a result of a <a href="http://en.wikipedia.org/wiki/Chemical_reaction">chemical reaction</a> - the difference then is supplied by the surroundings (usually again in form of <a href="http://en.wikipedia.org/wiki/Heat">heat</a> or <a href="http://en.wikipedia.org/wiki/Light">light</a>). For example,<br /><dl><dd>when two <a href="http://en.wikipedia.org/wiki/Hydrogen">hydrogen</a> atoms react to form a dihydrogen molecule, the chemical energy <i>decreases</i> by 724 zJ (the <a href="http://en.wikipedia.org/wiki/Bond_energy">bond energy</a> of the H–H bond);</dd><dd>when the electron is completely removed from a hydrogen atom, forming a hydrogen ion (in the gas phase), the chemical energy <i>increases</i> by 2.18 aJ (the <a href="http://en.wikipedia.org/wiki/Ionization_energy">ionization energy</a> of hydrogen).</dd></dl>It is common to quote the changes in chemical energy for one <a href="http://en.wikipedia.org/wiki/Mole_%28unit%29" title="Mole (unit)">mole</a> of the substance in question: typical values for the change in molar chemical energy during a chemical reaction range from tens to hundreds of kilojoules per mole.<br />The chemical energy as defined above is also referred to by <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Chemists" title="Chemists">chemists</a> as the <a href="http://en.wikipedia.org/wiki/Internal_energy">internal energy</a>, <b>U</b>: technically, this is measured by keeping the <a href="http://en.wikipedia.org/wiki/Volume">volume</a> of the system constant. Most practical chemistry is performed at constant pressure and, if the volume changes during the reaction (e.g. a gas is given off), a correction must be applied to take account of the work done by or on the atmosphere to obtain the <a href="http://en.wikipedia.org/wiki/Enthalpy">enthalpy</a>, <b>H</b>:<br /><dl><dd><dl><dd>Δ<b>H</b> = Δ<b>U</b> + <b>P</b>Δ<b>V</b></dd></dl></dd></dl>A second correction, for the change in <a href="http://en.wikipedia.org/wiki/Entropy">entropy</a>, <b>S</b>, must also be performed to determine whether a chemical reaction will take place or not, giving the <a href="http://en.wikipedia.org/wiki/Gibbs_free_energy">Gibbs free energy</a>, <b>G</b>:<br /><dl><dd><dl><dd>Δ<b>G</b> = Δ<b>H</b> − <b>T</b>Δ<b>S</b></dd></dl></dd></dl>These corrections are sometimes negligible, but often not (especially in reactions involving gases).<br />Since the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Industrial_revolution" title="Industrial revolution">industrial revolution</a>, the <a href="http://en.wikipedia.org/wiki/Combustion" title="Combustion">burning</a> of <a href="http://en.wikipedia.org/wiki/Coal">coal</a>, <a href="http://en.wikipedia.org/wiki/Petroleum" title="Petroleum">oil</a>, <a href="http://en.wikipedia.org/wiki/Natural_gas">natural gas</a> or products derived from them has been a socially significant transformation of chemical energy into other forms of energy. the energy "consumption" (one should really speak of "energy transformation") of a society or country is often quoted in reference to the average energy released by the <a href="http://en.wikipedia.org/wiki/Combustion">combustion</a> of these <a href="http://en.wikipedia.org/wiki/Fossil_fuel" title="Fossil fuel">fossil fuels</a>:<br /><dl><dd>1 tonne of coal equivalent (TCE) = 29.3076 GJ = 8,141 <a href="http://en.wikipedia.org/wiki/Kilowatt_hour">kilowatt hour</a></dd><dd>1 <a href="http://en.wikipedia.org/wiki/Tonne_of_oil_equivalent">tonne of oil equivalent</a> (TOE) = 41.868 GJ = 11,630 <a href="http://en.wikipedia.org/wiki/Kilowatt_hour">kilowatt hour</a></dd></dl>On the same basis, a tank-full of <a href="http://en.wikipedia.org/wiki/Gasoline">gasoline</a> (45 litres, 12 gallons) is equivalent to about 1.6 GJ of chemical energy. Another chemically based unit of measurement for energy is the "tonne of <a href="http://en.wikipedia.org/wiki/Trinitrotoluene" title="Trinitrotoluene">TNT</a>", taken as 4.184 GJ. Hence, burning a tonne of oil releases about ten times as much energy as the explosion of one tonne of TNT: fortunately, the energy is usually released in a slower, more controlled manner.<br />Simple examples of storage of chemical energy are batteries and food. When food is digested and metabolized (often with oxygen), chemical energy is released, which can in turn be transformed into heat, or by muscles into kinetic energy.<br /><h3><span class="mw-headline" id="Nuclear_energy">Nuclear energy</span></h3><div class="rellink relarticle mainarticle">Main article: <a href="http://en.wikipedia.org/wiki/Nuclear_binding_energy">Nuclear binding energy</a></div><table class="wikitable" style="float: right; margin: 10px; width: 150px;"><caption>Examples of the interconversion of energy</caption> <tbody><tr> <th colspan="2">Nuclear binding energy is converted</th> </tr><tr> <th>into</th> <th>by</th> </tr><tr> <td><b><a href="http://en.wikipedia.org/wiki/Mechanical_energy">Mechanical energy</a></b></td> <td><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Alpha_radiation" title="Alpha radiation">Alpha radiation</a></td> </tr><tr> <td><b><a href="http://en.wikipedia.org/wiki/Thermal_energy">Thermal energy</a></b></td> <td><a href="http://en.wikipedia.org/wiki/Sun">Sun</a></td> </tr><tr> <td><b><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Electrical_energy" title="Electrical energy">Electrical energy</a></b></td> <td><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Beta_radiation" title="Beta radiation">Beta radiation</a></td> </tr><tr> <td><b><a href="http://en.wikipedia.org/wiki/Electromagnetic_radiation">Electromagnetic radiation</a></b></td> <td><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Gamma_radiation" title="Gamma radiation">Gamma radiation</a></td> </tr><tr> <td><b><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Chemical_energy" title="Chemical energy">Chemical energy</a></b></td> <td><a href="http://en.wikipedia.org/wiki/Radioactive_decay">Radioactive decay</a></td> </tr><tr> <td><b><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Nuclear_energy" title="Nuclear energy">Nuclear energy</a></b></td> <td><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Nuclear_isomerism" title="Nuclear isomerism">Nuclear isomerism</a></td> </tr></tbody></table><b><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Nuclear_Energy" title="Nuclear Energy">Nuclear potential energy</a></b>, along with <a href="http://en.wikipedia.org/wiki/Electric_potential_energy">electric potential energy</a>, provides the energy released from <a href="http://en.wikipedia.org/wiki/Nuclear_fission">nuclear fission</a> and <a href="http://en.wikipedia.org/wiki/Nuclear_fusion">nuclear fusion</a> processes. The result of both these processes are nuclei in which the more-optimal size of the nucleus allows the <a href="http://en.wikipedia.org/wiki/Nuclear_force">nuclear force</a> (which is opposed by the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Electromagnetic_force" title="Electromagnetic force">electromagnetic force</a>) to bind nuclear particles more tightly together than before the reaction.<br />The <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Weak_nuclear_force" title="Weak nuclear force">Weak nuclear force</a> (different from the strong force) provides the potential energy for certain kinds of radioactive decay, such as <a href="http://en.wikipedia.org/wiki/Beta_decay">beta decay</a>.<br />The energy released in nuclear processes is so large that the relativistic change in mass (after the energy has been removed) can be as much as several parts per thousand.<br />Nuclear particles (<a href="http://en.wikipedia.org/wiki/Nucleon" title="Nucleon">nucleons</a>) like protons and neutrons are <i>not</i> destroyed (law of conservation of <a href="http://en.wikipedia.org/wiki/Baryon_number">baryon number</a>) in fission and fusion processes. A few lighter particles may be created or destroyed (example: beta minus and beta plus decay, or electron capture decay), but these minor processes are not important to the immediate energy release in fission and fusion. Rather, fission and fusion release energy when collections of baryons become more tightly bound, and it is the energy associated with a fraction of the mass of the nucleons (but not the whole particles) which appears as the heat and electromagnetic radiation generated by nuclear reactions. This heat and radiation retains the "missing" mass, but the mass is missing only because it escapes in the form of heat or light, which retain the mass and conduct it out of the system where it is not measured.<br />The energy from the <a href="http://en.wikipedia.org/wiki/Sun">Sun</a>, also called <a href="http://en.wikipedia.org/wiki/Solar_energy">solar energy</a>, is an example of this form of energy conversion. In the <a href="http://en.wikipedia.org/wiki/Sun">Sun</a>, the process of hydrogen fusion converts about 4 million metric tons of solar "matter" per second into light, which is radiated into space, but during this process, although protons change into neutrons, the number of total protons-plus-neutrons does not change. In this system, the radiated light itself (as a system) retains the "missing" mass, which represents 4 million tons per second of electromagnetic radiation, moving into space. Each of the helium nuclei which are formed in the process are less massive than the four protons from they were formed, but (to a good approximation), no particles are destroyed in the process of turning the Sun's nuclear potential energy into light. Instead, the four nucleons in a helium nucleus in the Sun have an average mass that is less than the protons which formed them, and this mass difference (4 million tons/second) is the mass that moves off as sunlight.<sup class="Template-Fact" style="white-space: nowrap;" title="This claim needs references to reliable sources from March 2011">[<i><a href="http://en.wikipedia.org/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed">citation needed</a></i>]</sup><br /><h2><span class="mw-headline" id="Transformations_of_energy">Transformations of energy</span></h2><div class="rellink relarticle mainarticle">Main article: <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Energy_conversion" title="Energy conversion">Energy conversion</a></div>One form of energy can often be readily transformed into another with the help of a device- for instance, a battery, from <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Chemical_energy" title="Chemical energy">chemical energy</a> to <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Electric_energy" title="Electric energy">electric energy</a>; a <a href="http://en.wikipedia.org/wiki/Dam">dam</a>: <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Gravitational_potential_energy" title="Gravitational potential energy">gravitational potential energy</a> to <a href="http://en.wikipedia.org/wiki/Kinetic_energy">kinetic energy</a> of moving <a href="http://en.wikipedia.org/wiki/Water">water</a> (and the blades of a <a href="http://en.wikipedia.org/wiki/Turbine">turbine</a>) and ultimately to <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Electric_energy" title="Electric energy">electric energy</a> through an <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Electric_generator" title="Electric generator">electric generator</a>. Similarly, in the case of a <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Chemical_explosive" title="Chemical explosive">chemical explosion</a>, <a href="http://en.wikipedia.org/wiki/Chemical_potential">chemical potential</a> energy is transformed to <a href="http://en.wikipedia.org/wiki/Kinetic_energy">kinetic energy</a> and <a href="http://en.wikipedia.org/wiki/Thermal_energy">thermal energy</a> in a very short time. Yet another example is that of a <a href="http://en.wikipedia.org/wiki/Pendulum">pendulum</a>. At its highest points the <a href="http://en.wikipedia.org/wiki/Kinetic_energy">kinetic energy</a> is zero and the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Gravitational_potential_energy" title="Gravitational potential energy">gravitational potential energy</a> is at maximum. At its lowest point the <a href="http://en.wikipedia.org/wiki/Kinetic_energy">kinetic energy</a> is at maximum and is equal to the decrease of <a href="http://en.wikipedia.org/wiki/Potential_energy">potential energy</a>. If one (unrealistically) assumes that there is no <a href="http://en.wikipedia.org/wiki/Friction">friction</a>, the conversion of energy between these processes is perfect, and the <a href="http://en.wikipedia.org/wiki/Pendulum">pendulum</a> will continue swinging forever.<br />Energy gives rise to weight when it is trapped in a system with zero momentum, where it can be weighed. It is also equivalent to mass, and this mass is always associated with it. Mass is also equivalent to a certain amount of energy, and likewise always appears associated with it, as described in <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Mass-energy_equivalence" title="Mass-energy equivalence">mass-energy equivalence</a>. The formula <i>E</i> = <i>mc</i>², derived by <a href="http://en.wikipedia.org/wiki/Albert_Einstein">Albert Einstein</a> (1905) quantifies the relationship between rest-mass and rest-energy within the concept of special relativity. In different theoretical frameworks, similar formulas were derived by <a href="http://en.wikipedia.org/wiki/J._J._Thomson">J. J. Thomson</a> (1881), <a href="http://en.wikipedia.org/wiki/Henri_Poincar%C3%A9">Henri Poincaré</a> (1900), <a href="http://en.wikipedia.org/wiki/Friedrich_Hasen%C3%B6hrl">Friedrich Hasenöhrl</a> (1904) and others (see <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Mass-energy_equivalence#History" title="Mass-energy equivalence">Mass-energy equivalence#History</a> for further information).<br /><a href="http://en.wikipedia.org/wiki/Matter">Matter</a> may be destroyed and converted to energy (and vice versa), but mass cannot ever be destroyed; rather, mass remains a constant for both the matter and the energy, during any process when they are converted into each other. However, since <span class="texhtml"><i>c</i><sup>2</sup></span> is extremely large relative to ordinary human scales, the conversion of ordinary amount of <a href="http://en.wikipedia.org/wiki/Matter">matter</a> (for example, 1 kg) to other forms of energy (such as heat, light, and other radiation) can liberate tremendous amounts of energy (~<span class="texhtml">9<i>x</i>10<sup>16</sup></span> joules = 21 megatons of TNT), as can be seen in nuclear reactors and nuclear weapons. Conversely, the mass equivalent of a unit of energy is minuscule, which is why a loss of energy (loss of mass) from most systems is difficult to measure by weight, unless the energy loss is very large. Examples of energy transformation into matter (i.e., kinetic energy into particles with rest mass) are found in high-energy <a href="http://en.wikipedia.org/wiki/Nuclear_physics">nuclear physics</a>.<br />Transformation of energy into useful work is a core topic of thermodynamics. In nature, transformations of energy can be fundamentally classed into two kinds: those that are thermodynamically <a href="http://en.wikipedia.org/wiki/Reversible_process_%28thermodynamics%29" title="Reversible process (thermodynamics)">reversible</a>, and those that are thermodynamically <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Irreversibility" title="Irreversibility">irreversible</a>. A <a href="http://en.wikipedia.org/wiki/Reversible_process_%28thermodynamics%29" title="Reversible process (thermodynamics)">reversible process in thermodynamics</a> is one in which no energy is dissipated (spread) into empty energy states available in a volume, from which it cannot be recovered into more concentrated forms (fewer quantum states), without degradation of even more energy. A reversible process is one in which this sort of dissipation does not happen. For example, conversion of energy from one type of potential field to another, is reversible, as in the pendulum system described above. In processes where heat is generated, quantum states of lower energy, present as possible exitations in fields between atoms, act as a reservoir for part of the energy, from which it cannot be recovered, in order to be converted with 100% efficiency into other forms of energy. In this case, the energy must partly stay as heat, and cannot be completely recovered as usable energy, except at the price of an increase in some other kind of heat-like increase in disorder in quantum states, in the universe (such as an expansion of matter, or a randomization in a crystal).<br />As the universe evolves in time, more and more of its energy becomes trapped in irreversible states (i.e., as heat or other kinds of increases in disorder). This has been referred to as the inevitable thermodynamic <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Heat_death" title="Heat death">heat death</a> of the universe. In this <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Heat_death" title="Heat death">heat death</a> the energy of the universe does not change, but the fraction of energy which is available to do produce work through a <a href="http://en.wikipedia.org/wiki/Heat_engine">heat engine</a>, or be transformed to other usable forms of energy (through the use of generators attached to heat engines), grows less and less.<br /><h2><span class="mw-headline" id="See_also">See also</span></h2><div class="noprint tright portal" style="border: solid #aaa 1px; margin: 0.5em 0 0.5em 0.5em;"><table style="background: #f9f9f9; font-size: 85%; line-height: 110%; max-width: 175px;"><tbody><tr> <td style="text-align: center;"><a class="image" href="http://en.wikipedia.org/wiki/File:Crystal_energy.svg"><img alt="" height="28" src="http://upload.wikimedia.org/wikipedia/commons/thumb/1/14/Crystal_energy.svg/29px-Crystal_energy.svg.png" width="29" /></a></td> <td style="padding: 0 0.2em; vertical-align: middle;"><i><b><a href="http://en.wikipedia.org/wiki/Portal:Energy" title="Portal:Energy">Energy portal</a></b></i></td> </tr><tr valign="middle"> <td style="text-align: center;"><a class="image" href="http://en.wikipedia.org/wiki/File:Stylised_Lithium_Atom.svg"><img alt="" height="28" src="http://upload.wikimedia.org/wikipedia/commons/thumb/e/e1/Stylised_Lithium_Atom.svg/25px-Stylised_Lithium_Atom.svg.png" width="25" /></a></td> <td style="padding: 0 0.2em; vertical-align: middle;"><i><b><a href="http://en.wikipedia.org/wiki/Portal:Physics" title="Portal:Physics">Physics portal</a></b></i></td> </tr></tbody></table></div><div style="-moz-column-width: 30em; -webkit-column-width: 30em; column-width: 30em;"><table class="metadata mbox-small" style="background-color: #f9f9f9; border: 1px solid #aaa;"><tbody><tr> <td class="mbox-image"><a href="http://en.wikipedia.org/wiki/Wikipedia:Books" title="Wikipedia:Books"><img alt="" height="30" src="http://upload.wikimedia.org/wikipedia/commons/thumb/a/a8/Office-book.svg/30px-Office-book.svg.png" width="30" /></a></td> <td class="mbox-text"><i><b><a href="http://en.wikipedia.org/wiki/Book:Energy" title="Book:Energy">Book: Energy</a></b></i></td> </tr><tr> <td class="mbox-text" colspan="2"><small><a href="http://en.wikipedia.org/wiki/Wikipedia:Books" title="Wikipedia:Books">Wikipedia Books</a> are collections of articles that can be downloaded or ordered in print.</small></td> </tr></tbody></table><ul><li><a href="http://en.wikipedia.org/wiki/Index_of_energy_articles">Index of energy articles</a></li><li><a href="http://en.wikipedia.org/wiki/Outline_of_energy">Outline of energy</a></li></ul></div><h2><span class="mw-headline" id="Notes_and_references">Notes and references</span></h2><div class="reflist references-column-width" style="-moz-column-width: 30em; -webkit-column-width: 30em; column-width: 30em; list-style-type: decimal;"><ol class="references"><li id="cite_note-0"><b><a href="http://en.wikipedia.org/wiki/Energy#cite_ref-0">^</a></b> <span class="citation web">Harper, Douglas. <a class="external text" href="http://www.etymonline.com/index.php?term=energy" rel="nofollow">"Energy"</a>. <i>Online Etymology Dictionary</i><span class="reference-accessdate">. Retrieved May 1, 2007</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Energy&rft.atitle=Online+Etymology+Dictionary&rft.aulast=Harper&rft.aufirst=Douglas&rft.au=Harper%2C%26%2332%3BDouglas&rft_id=http%3A%2F%2Fwww.etymonline.com%2Findex.php%3Fterm%3Denergy&rfr_id=info:sid/en.wikipedia.org:Energy"></span></li><li id="cite_note-1"><b><a href="http://en.wikipedia.org/wiki/Energy#cite_ref-1">^</a></b> <span class="citation web"><a class="external text" href="http://faculty.clintoncc.suny.edu/faculty/michael.gregory/files/bio%20101/bio%20101%20lectures/chemistry/chemistr.htm" rel="nofollow">"Retrieved on 2010-Dec-05"</a>. Faculty.clintoncc.suny.edu<span class="reference-accessdate">. Retrieved 2010-12-12</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Retrieved+on+2010-Dec-05&rft.atitle=&rft.pub=Faculty.clintoncc.suny.edu&rft_id=http%3A%2F%2Ffaculty.clintoncc.suny.edu%2Ffaculty%2Fmichael.gregory%2Ffiles%2Fbio%2520101%2Fbio%2520101%2520lectures%2Fchemistry%2Fchemistr.htm&rfr_id=info:sid/en.wikipedia.org:Energy"></span></li><li id="cite_note-2"><b><a href="http://en.wikipedia.org/wiki/Energy#cite_ref-2">^</a></b> <span class="citation web"><a class="external text" href="http://www.geo.cornell.edu/geology/classes/Chapters/Chapter02.pdf" rel="nofollow">"Retrieved on 2010-Dec-05"</a> (PDF)<span class="reference-accessdate">. Retrieved 2010-12-12</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Retrieved+on+2010-Dec-05&rft.atitle=&rft_id=http%3A%2F%2Fwww.geo.cornell.edu%2Fgeology%2Fclasses%2FChapters%2FChapter02.pdf&rfr_id=info:sid/en.wikipedia.org:Energy"></span></li><li id="cite_note-jphysics-3"><b><a href="http://en.wikipedia.org/wiki/Energy#cite_ref-jphysics_3-0">^</a></b> <span class="citation book">Lofts, G; O'Keeffe D; et al. (2004). "11 — Mechanical Interactions". <i>Jacaranda Physics 1</i> (2 ed.). Milton, Queensland, Australia: John Willey & Sons Australia Ltd.. p. 286. <a href="http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="http://en.wikipedia.org/wiki/Special:BookSources/0701637773" title="Special:BookSources/0701637773">0701637773</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=11+%E2%80%94+Mechanical+Interactions&rft.atitle=Jacaranda+Physics+1&rft.aulast=Lofts&rft.aufirst=G&rft.au=Lofts%2C%26%2332%3BG&rft.date=2004&rft.pages=p.%26nbsp%3B286&rft.edition=2&rft.place=Milton%2C+Queensland%2C+Australia&rft.pub=John+Willey+%26+Sons+Australia+Ltd.&rft.isbn=0701637773&rfr_id=info:sid/en.wikipedia.org:Energy"></span></li><li id="cite_note-4"><b><a href="http://en.wikipedia.org/wiki/Energy#cite_ref-4">^</a></b> <span class="citation book">Smith, Crosbie (1998). <i>The Science of Energy - a Cultural History of Energy Physics in Victorian Britain</i>. The University of Chicago Press. <a href="http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="http://en.wikipedia.org/wiki/Special:BookSources/0-226-76420-6" title="Special:BookSources/0-226-76420-6">0-226-76420-6</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Science+of+Energy+-+a+Cultural+History+of+Energy+Physics+in+Victorian+Britain&rft.aulast=Smith&rft.aufirst=Crosbie&rft.au=Smith%2C%26%2332%3BCrosbie&rft.date=1998&rft.pub=The+University+of+Chicago+Press&rft.isbn=0-226-76420-6&rfr_id=info:sid/en.wikipedia.org:Energy"></span></li><li id="cite_note-RPF1-5">^ <a href="http://en.wikipedia.org/wiki/Energy#cite_ref-RPF1_5-0"><sup><i><b>a</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Energy#cite_ref-RPF1_5-1"><sup><i><b>b</b></i></sup></a> <span class="citation book">Feynman, Richard (1964). <i>The Feynman Lectures on Physics; Volume 1</i>. U.S.A: Addison Wesley. <a href="http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="http://en.wikipedia.org/wiki/Special:BookSources/0-201-02115-3" title="Special:BookSources/0-201-02115-3">0-201-02115-3</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Feynman+Lectures+on+Physics%3B+Volume+1&rft.aulast=Feynman&rft.aufirst=Richard&rft.au=Feynman%2C%26%2332%3BRichard&rft.date=1964&rft.place=U.S.A&rft.pub=Addison+Wesley&rft.isbn=0-201-02115-3&rfr_id=info:sid/en.wikipedia.org:Energy"></span></li><li id="cite_note-6"><b><a href="http://en.wikipedia.org/wiki/Energy#cite_ref-6">^</a></b> <span class="citation web"><a class="external text" href="http://www.uic.edu/aa/college/gallery400/notions/human%20energy.htm" rel="nofollow">"Retrieved on May-29-09"</a>. Uic.edu<span class="reference-accessdate">. Retrieved 2010-12-12</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Retrieved+on+May-29-09&rft.atitle=&rft.pub=Uic.edu&rft_id=http%3A%2F%2Fwww.uic.edu%2Faa%2Fcollege%2Fgallery400%2Fnotions%2Fhuman%2520energy.htm&rfr_id=info:sid/en.wikipedia.org:Energy"></span></li><li id="cite_note-7"><b><a href="http://en.wikipedia.org/wiki/Energy#cite_ref-7">^</a></b> Bicycle calculator - speed, weight, wattage etc. <a class="external autonumber" href="http://bikecalculator.com/" rel="nofollow">[1]</a>.</li><li id="cite_note-8"><b><a href="http://en.wikipedia.org/wiki/Energy#cite_ref-8">^</a></b> <span class="citation web"><a class="external text" href="http://okfirst.ocs.ou.edu/train/meteorology/EnergyBudget.html" rel="nofollow">"Earth's Energy Budget"</a>. Okfirst.ocs.ou.edu<span class="reference-accessdate">. Retrieved 2010-12-12</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Earth%27s+Energy+Budget&rft.atitle=&rft.pub=Okfirst.ocs.ou.edu&rft_id=http%3A%2F%2Fokfirst.ocs.ou.edu%2Ftrain%2Fmeteorology%2FEnergyBudget.html&rfr_id=info:sid/en.wikipedia.org:Energy"></span></li><li id="cite_note-9"><b><a href="http://en.wikipedia.org/wiki/Energy#cite_ref-9">^</a></b> <span class="citation web"><a class="external text" href="http://www.physics.ucla.edu/%7Ecwp/articles/noether.asg/noether.html" rel="nofollow">"E. Noether's Discovery of the Deep Connection Between Symmetries and Conservation Laws"</a>. Physics.ucla.edu. 1918-07-16<span class="reference-accessdate">. Retrieved 2010-12-12</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=E.+Noether%27s+Discovery+of+the+Deep+Connection+Between+Symmetries+and+Conservation+Laws&rft.atitle=&rft.date=1918-07-16&rft.pub=Physics.ucla.edu&rft_id=http%3A%2F%2Fwww.physics.ucla.edu%2F%7Ecwp%2Farticles%2Fnoether.asg%2Fnoether.html&rfr_id=info:sid/en.wikipedia.org:Energy"></span></li><li id="cite_note-thermo-laws-10">^ <a href="http://en.wikipedia.org/wiki/Energy#cite_ref-thermo-laws_10-0"><sup><i><b>a</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Energy#cite_ref-thermo-laws_10-1"><sup><i><b>b</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Energy#cite_ref-thermo-laws_10-2"><sup><i><b>c</b></i></sup></a> <a class="external text" href="http://www.av8n.com/physics/thermo-laws.htm" rel="nofollow"><i>The Laws of Thermodynamics</i></a> including careful definitions of energy, free energy, et cetera.</li><li id="cite_note-11"><b><a href="http://en.wikipedia.org/wiki/Energy#cite_ref-11">^</a></b> <span class="citation web"><a class="external text" href="http://ptolemy.eecs.berkeley.edu/eecs20/week9/timeinvariance.html" rel="nofollow">"Time Invariance"</a>. Ptolemy.eecs.berkeley.edu<span class="reference-accessdate">. Retrieved 2010-12-12</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Time+Invariance&rft.atitle=&rft.pub=Ptolemy.eecs.berkeley.edu&rft_id=http%3A%2F%2Fptolemy.eecs.berkeley.edu%2Feecs20%2Fweek9%2Ftimeinvariance.html&rfr_id=info:sid/en.wikipedia.org:Energy"></span></li><li id="cite_note-12"><b><a href="http://en.wikipedia.org/wiki/Energy#cite_ref-12">^</a></b> Berkeley Physics Course Volume 1. Charles Kittel, Walter D Knight and Malvin A Ruderman</li><li id="cite_note-MTW-13">^ <a href="http://en.wikipedia.org/wiki/Energy#cite_ref-MTW_13-0"><sup><i><b>a</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Energy#cite_ref-MTW_13-1"><sup><i><b>b</b></i></sup></a> <span class="citation book">Misner, Thorne, Wheeler (1973). <i>Gravitation</i>. San Francisco: W. H. Freeman. <a href="http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="http://en.wikipedia.org/wiki/Special:BookSources/0716703440" title="Special:BookSources/0716703440">0716703440</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Gravitation&rft.aulast=Misner%2C+Thorne%2C+Wheeler&rft.au=Misner%2C+Thorne%2C+Wheeler&rft.date=1973&rft.place=San+Francisco&rft.pub=W.+H.+Freeman&rft.isbn=0716703440&rfr_id=info:sid/en.wikipedia.org:Energy"></span></li><li id="cite_note-14"><b><a href="http://en.wikipedia.org/wiki/Energy#cite_ref-14">^</a></b> <a class="external text" href="http://www.sustech.edu/OCWExternal/Akamai/18/18.013a/textbook/HTML/chapter16/section03.html" rel="nofollow">The Hamiltonian</a> MIT OpenCourseWare website 18.013A Chapter 16.3 Accessed February 2007</li><li id="cite_note-klotz-15"><b><a href="http://en.wikipedia.org/wiki/Energy#cite_ref-klotz_15-0">^</a></b> I. Klotz, R. Rosenberg, <i>Chemical Thermodynamics - Basic Concepts and Methods</i>, 7th ed., Wiley (2008), p.39</li><li id="cite_note-KK-16"><b><a href="http://en.wikipedia.org/wiki/Energy#cite_ref-KK_16-0">^</a></b> <span class="citation book">Kittel and Kroemer (1980). <i>Thermal Physics</i>. New York: W. H. Freeman. <a href="http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="http://en.wikipedia.org/wiki/Special:BookSources/0-7167-1088-9" title="Special:BookSources/0-7167-1088-9">0-7167-1088-9</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Thermal+Physics&rft.aulast=Kittel+and+Kroemer&rft.au=Kittel+and+Kroemer&rft.date=1980&rft.place=New+York&rft.pub=W.+H.+Freeman&rft.isbn=0-7167-1088-9&rfr_id=info:sid/en.wikipedia.org:Energy"></span></li><li id="cite_note-17"><b><a href="http://en.wikipedia.org/wiki/Energy#cite_ref-17">^</a></b> These examples are solely for illustration, as it is not the energy available for work which limits the performance of the athlete but the <a href="http://en.wikipedia.org/wiki/Power_%28physics%29" title="Power (physics)">power</a> output of the sprinter and the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Force_%28physics%29" title="Force (physics)">force</a> of the weightlifter. A worker stacking shelves in a supermarket does more work (in the physical sense) than either of the athletes, but does it more slowly.</li><li id="cite_note-18"><b><a href="http://en.wikipedia.org/wiki/Energy#cite_ref-18">^</a></b> <a href="http://en.wikipedia.org/wiki/Crystal" title="Crystal">Crystals</a> are another example of highly ordered systems that exist in nature: in this case too, the order is associated with the transfer of a large amount of heat (known as the <a href="http://en.wikipedia.org/wiki/Lattice_energy">lattice energy</a>) to the surroundings.</li><li id="cite_note-19"><b><a href="http://en.wikipedia.org/wiki/Energy#cite_ref-19">^</a></b> Ito, Akihito; Oikawa, Takehisa (2004). "<a class="external text" href="http://www.terrapub.co.jp/e-library/kawahata/pdf/343.pdf" rel="nofollow">Global Mapping of Terrestrial Primary Productivity and Light-Use Efficiency with a Process-Based Model.</a>" in Shiyomi, M. et al. (Eds.) <i>Global Environmental Change in the Ocean and on Land.</i> pp. 343–58.</li><li id="cite_note-20"><b><a href="http://en.wikipedia.org/wiki/Energy#cite_ref-20">^</a></b> Ristinen, Robert A., and Kraushaar, Jack J. Energy and the Environment. New York: John Wiley & Sons, Inc., 2006.</li><li id="cite_note-CODATA-21">^ <a href="http://en.wikipedia.org/wiki/Energy#cite_ref-CODATA_21-0"><sup><i><b>a</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Energy#cite_ref-CODATA_21-1"><sup><i><b>b</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Energy#cite_ref-CODATA_21-2"><sup><i><b>c</b></i></sup></a> <span class="citation Journal">Mohr, Peter J.; Taylor, Barry N.; Newell, David B. (2008). <a class="external text" href="http://physics.nist.gov/cuu/Constants/codata.pdf" rel="nofollow">"CODATA Recommended Values of the Fundamental Physical Constants: 2006"</a>. <i><a href="http://en.wikipedia.org/wiki/Reviews_of_Modern_Physics" title="Reviews of Modern Physics">Rev. Mod. Phys.</a></i> <b>80</b>: 633–730. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.1103%2FRevModPhys.80.633" rel="nofollow">10.1103/RevModPhys.80.633</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=CODATA+Recommended+Values+of+the+Fundamental+Physical+Constants%3A+2006&rft.jtitle=%5B%5BReviews+of+Modern+Physics%7CRev.+Mod.+Phys.%5D%5D&rft.aulast=Mohr&rft.aufirst=Peter+J.&rft.au=Mohr%2C%26%2332%3BPeter+J.&rft.date=2008&rft.volume=80&rft.pages=633%E2%80%93730&rft_id=info:doi/10.1103%2FRevModPhys.80.633&rft_id=http%3A%2F%2Fphysics.nist.gov%2Fcuu%2FConstants%2Fcodata.pdf&rfr_id=info:sid/en.wikipedia.org:Energy"></span></li></ol></div><h2><span class="mw-headline" id="Further_reading">Further reading</span></h2><div class="refbegin"><ul><li><span class="citation book">Alekseev, G. N. (1986). <i>Energy and Entropy</i>. Moscow: Mir Publishers.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Energy+and+Entropy&rft.aulast=Alekseev&rft.aufirst=G.+N.&rft.au=Alekseev%2C%26%2332%3BG.+N.&rft.date=1986&rft.place=Moscow&rft.pub=Mir+Publishers&rfr_id=info:sid/en.wikipedia.org:Energy"></span></li><li><span class="citation book">Crowell, Benjamin (2007) [2003]. <a class="external text" href="http://www.lightandmatter.com/html_books/2cl/ch01/ch01.html#Section1.2" rel="nofollow"><i>Conservation Laws</i></a>. Light and matter series of introductory physics textbooks. <b>2.2</b>. Fullerton, CA: Light and Matter. <a href="http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="http://en.wikipedia.org/wiki/Special:BookSources/0970467028" title="Special:BookSources/0970467028">0970467028</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Conservation+Laws&rft.aulast=Crowell&rft.aufirst=Benjamin&rft.au=Crowell%2C%26%2332%3BBenjamin&rft.date=2007&rft.series=Light+and+matter+series+of+introductory+physics+textbooks&rft.volume=2.2&rft.place=Fullerton%2C+CA&rft.pub=Light+and+Matter&rft.isbn=0970467028&rft_id=http%3A%2F%2Fwww.lightandmatter.com%2Fhtml_books%2F2cl%2Fch01%2Fch01.html%23Section1.2&rfr_id=info:sid/en.wikipedia.org:Energy"></span></li><li><span class="citation web">Ross, John S. (23 April 2002). <a class="external text" href="http://www.physnet.org/modules/pdf_modules/m20.pdf" rel="nofollow">"Work, Power, Kinetic Energy"</a>. <i>Project PHYSNET</i>. Michigan State University.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Work%2C+Power%2C+Kinetic+Energy&rft.atitle=Project+PHYSNET&rft.aulast=Ross&rft.aufirst=John+S.&rft.au=Ross%2C%26%2332%3BJohn+S.&rft.date=23+April+2002&rft.pub=Michigan+State+University&rft_id=http%3A%2F%2Fwww.physnet.org%2Fmodules%2Fpdf_modules%2Fm20.pdf&rfr_id=info:sid/en.wikipedia.org:Energy"></span></li><li><span class="citation book">Smil, Vaclav (2008). <i>Energy in nature and society: general energetics of complex systems</i>. Cambridge, USA: <a href="http://en.wikipedia.org/wiki/MIT_Press">MIT Press</a>. <a href="http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="http://en.wikipedia.org/wiki/Special:BookSources/0-262-19565-8" title="Special:BookSources/0-262-19565-8">0-262-19565-8</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Energy+in+nature+and+society%3A+general+energetics+of+complex+systems&rft.aulast=Smil%2C+Vaclav&rft.au=Smil%2C+Vaclav&rft.date=2008&rft.place=Cambridge%2C+USA&rft.pub=%5B%5BMIT+Press%5D%5D&rft.isbn=0-262-19565-8&rfr_id=info:sid/en.wikipedia.org:Energy"></span></li><li><span class="citation book">Walding, Richard, Rapkins, Greg, Rossiter, Glenn (1999-11-01). <i>New Century Senior Physics</i>. Melbourne, Australia: <a href="http://en.wikipedia.org/wiki/Oxford_University_Press">Oxford University Press</a>. <a href="http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="http://en.wikipedia.org/wiki/Special:BookSources/0-19-551084-4" title="Special:BookSources/0-19-551084-4">0-19-551084-4</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=New+Century+Senior+Physics&rft.aulast=Walding%2C+Richard%2C%26nbsp%3B+Rapkins%2C+Greg%2C%26nbsp%3B+Rossiter%2C+Glenn&rft.au=Walding%2C+Richard%2C%26nbsp%3B+Rapkins%2C+Greg%2C%26nbsp%3B+Rossiter%2C+Glenn&rft.date=1999-11-01&rft.place=Melbourne%2C+Australia&rft.pub=%5B%5BOxford+University+Press%5D%5D&rft.isbn=0-19-551084-4&rfr_id=info:sid/en.wikipedia.org:Energy"></span></li></ul></div><h2><span class="mw-headline" id="External_links">External links</span></h2><table class="metadata plainlinks mbox-small" style="background-color: #f9f9f9; border: 1px solid #aaa;"><tbody><tr> <td colspan="2" style="margin: auto; text-align: center;">Find more about <b>Energy</b> on Wikipedia's <a href="http://en.wikipedia.org/wiki/Wikipedia:Wikimedia_sister_projects" title="Wikipedia:Wikimedia sister projects">sister projects</a>:</td> </tr><tr> <td><a href="http://en.wiktionary.org/wiki/Special:Search/Energy" title="Search Wiktionary"><img alt="" height="25" src="http://upload.wikimedia.org/wikipedia/commons/thumb/f/f8/Wiktionary-logo-en.svg/23px-Wiktionary-logo-en.svg.png" width="23" /></a></td> <td><a class="extiw" href="http://en.wiktionary.org/wiki/Special:Search/Energy" title="wikt:Special:Search/Energy">Definitions</a> from Wiktionary</td> </tr><tr> <td><a href="http://commons.wikimedia.org/wiki/Special:Search/Energy" title="Search Commons"><img alt="" height="24" src="http://upload.wikimedia.org/wikipedia/commons/thumb/4/4a/Commons-logo.svg/18px-Commons-logo.svg.png" width="18" /></a></td> <td><a class="extiw" href="http://commons.wikimedia.org/wiki/Special:Search/Energy" title="commons:Special:Search/Energy">Images and media</a> from Commons</td> </tr><tr> <td><a href="http://en.wikiversity.org/wiki/Special:Search/Energy" title="Search Wikiversity"><img alt="" height="23" src="http://upload.wikimedia.org/wikipedia/commons/thumb/1/1b/Wikiversity-logo-en.svg/25px-Wikiversity-logo-en.svg.png" width="25" /></a></td> <td><a class="extiw" href="http://en.wikiversity.org/wiki/Special:Search/Energy" title="v:Special:Search/Energy">Learning resources</a> from Wikiversity</td> </tr><tr> <td><a href="http://en.wikinews.org/wiki/Special:Search/Energy" title="Search Wikinews"><img alt="" height="14" src="http://upload.wikimedia.org/wikipedia/commons/thumb/2/24/Wikinews-logo.svg/25px-Wikinews-logo.svg.png" width="25" /></a></td> <td><a class="extiw" href="http://en.wikinews.org/wiki/Special:Search/Energy" title="n:Special:Search/Energy">News stories</a> from Wikinews</td> </tr><tr> <td><a href="http://en.wikiquote.org/wiki/Special:Search/Energy" title="Search Wikiquote"><img alt="" height="25" src="http://upload.wikimedia.org/wikipedia/commons/thumb/f/fa/Wikiquote-logo.svg/21px-Wikiquote-logo.svg.png" width="21" /></a></td> <td><a class="extiw" href="http://en.wikiquote.org/wiki/Special:Search/Energy" title="q:Special:Search/Energy">Quotations</a> from Wikiquote</td> </tr><tr> <td><a href="http://en.wikisource.org/wiki/Special:Search/Energy" title="Search Wikisource"><img alt="" height="25" src="http://upload.wikimedia.org/wikipedia/commons/thumb/4/4c/Wikisource-logo.svg/24px-Wikisource-logo.svg.png" width="24" /></a></td> <td><a class="extiw" href="http://en.wikisource.org/wiki/Special:Search/Energy" title="s:Special:Search/Energy">Source texts</a> from Wikisource</td> </tr><tr> <td><a href="http://en.wikibooks.org/wiki/Special:Search/Energy" title="Search Wikibooks"><img alt="" height="25" src="http://upload.wikimedia.org/wikipedia/commons/thumb/f/fa/Wikibooks-logo.svg/25px-Wikibooks-logo.svg.png" width="25" /></a></td> <td><a class="extiw" href="http://en.wikibooks.org/wiki/Special:Search/Energy" title="b:Special:Search/Energy">Textbooks</a> from Wikibooks</td> </tr></tbody></table><ul><li><a class="external text" href="http://www.dmoz.org/Science/Technology/Energy/" rel="nofollow">Energy</a> at the <a href="http://en.wikipedia.org/wiki/Open_Directory_Project">Open Directory Project</a></li></ul></div>ripplehttp://www.blogger.com/profile/17326365690819936341noreply@blogger.comtag:blogger.com,1999:blog-6905780489869824283.post-85606891382774314922011-03-22T11:25:00.000-07:002011-04-06T14:15:46.875-07:00Mathematics<div dir="ltr" style="text-align: left;" trbidi="on"><br /><div class="dablink">"Maths" and "Math" redirect here. For other uses of "Mathematics" or "Math", see <a href="http://en.wikipedia.org/wiki/Mathematics_%28disambiguation%29">Mathematics (disambiguation)</a> and <a href="http://en.wikipedia.org/wiki/Math_%28disambiguation%29">Math (disambiguation)</a>.</div><div class="metadata topicon" id="protected-icon" style="display: none; right: 55px;"><a href="http://en.wikipedia.org/wiki/Wikipedia:Protection_policy#semi" title="This article is semi-protected."><img alt="Page semi-protected" height="20" src="http://upload.wikimedia.org/wikipedia/commons/thumb/f/fc/Padlock-silver.svg/20px-Padlock-silver.svg.png" width="20" /></a></div><div class="thumb tright"> <div class="thumbinner" style="width: 222px;"><a class="image" href="http://en.wikipedia.org/wiki/File:Euclid.jpg"><img alt="" class="thumbimage" height="184" src="http://upload.wikimedia.org/wikipedia/commons/thumb/2/21/Euclid.jpg/220px-Euclid.jpg" width="220" /></a> <div class="thumbcaption"> <div class="magnify"><a class="internal" href="http://en.wikipedia.org/wiki/File:Euclid.jpg" title="Enlarge"><img alt="" height="11" src="http://bits.wikimedia.org/skins-1.17/common/images/magnify-clip.png" width="15" /></a></div><a href="http://en.wikipedia.org/wiki/Euclid">Euclid</a>, Greek mathematician, 3rd century BC, as imagined by <a href="http://en.wikipedia.org/wiki/Raphael">Raphael</a> in this detail from <i><a href="http://en.wikipedia.org/wiki/The_School_of_Athens">The School of Athens</a></i>.<sup class="reference" id="cite_ref-0"><a href="http://en.wikipedia.org/wiki/Mathematics#cite_note-0"><span>[</span>1<span>]</span></a></sup></div></div></div><b>Mathematics</b> is the study of <a href="http://en.wikipedia.org/wiki/Quantity">quantity</a>, <a href="http://en.wikipedia.org/wiki/Structure">structure</a>, <a href="http://en.wikipedia.org/wiki/Space">space</a>, and <a href="http://en.wikipedia.org/wiki/Calculus" title="Calculus">change</a>. <a href="http://en.wikipedia.org/wiki/Mathematician" title="Mathematician">Mathematicians</a> seek out <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Patterns" title="Patterns">patterns</a>,<sup class="reference" id="cite_ref-1"><a href="http://en.wikipedia.org/wiki/Mathematics#cite_note-1"><span>[</span>2<span>]</span></a></sup><sup class="reference" id="cite_ref-2"><a href="http://en.wikipedia.org/wiki/Mathematics#cite_note-2"><span>[</span>3<span>]</span></a></sup> formulate new <a href="http://en.wikipedia.org/wiki/Conjecture" title="Conjecture">conjectures</a>, and establish <a href="http://en.wikipedia.org/wiki/Truth">truth</a> by <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Mathematical_rigour" title="Mathematical rigour">rigorous</a> <a href="http://en.wikipedia.org/wiki/Deductive_reasoning" title="Deductive reasoning">deduction</a> from appropriately chosen <a href="http://en.wikipedia.org/wiki/Axiom" title="Axiom">axioms</a> and <a href="http://en.wikipedia.org/wiki/Definition" title="Definition">definitions</a>.<sup class="reference" id="cite_ref-3"><a href="http://en.wikipedia.org/wiki/Mathematics#cite_note-3"><span>[</span>4<span>]</span></a></sup><br />Through the use of <a href="http://en.wikipedia.org/wiki/Abstraction_%28mathematics%29" title="Abstraction (mathematics)">abstraction</a> and <a href="http://en.wikipedia.org/wiki/Logic" title="Logic">logical</a> <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Reasoning" title="Reasoning">reasoning</a>, mathematics evolved from <a href="http://en.wikipedia.org/wiki/Counting">counting</a>, <a href="http://en.wikipedia.org/wiki/Calculation">calculation</a>, <a href="http://en.wikipedia.org/wiki/Measurement">measurement</a>, and the systematic study of the <a href="http://en.wikipedia.org/wiki/Shape" title="Shape">shapes</a> and <a href="http://en.wikipedia.org/wiki/Motion_%28physics%29" title="Motion (physics)">motions</a> of physical objects. Practical mathematics has been a human activity for as far back as <a class="mw-redirect" href="http://en.wikipedia.org/wiki/History_of_Mathematics" title="History of Mathematics">written records</a> exist. <a href="http://en.wikipedia.org/wiki/Logic" title="Logic">Rigorous arguments</a> first appeared in <a href="http://en.wikipedia.org/wiki/Greek_mathematics">Greek mathematics</a>, most notably in <i><a href="http://en.wikipedia.org/wiki/Euclid%27s_Elements">Euclid's Elements</a></i>. Mathematics continued to develop, for example in China in 300 BC, in India in AD 100, and in the <a href="http://en.wikipedia.org/wiki/Muslim_world">Muslim world</a> in AD 800, until the <a href="http://en.wikipedia.org/wiki/Renaissance">Renaissance</a>, when mathematical innovations interacting with new <a href="http://en.wikipedia.org/wiki/Timeline_of_scientific_discoveries" title="Timeline of scientific discoveries">scientific discoveries</a> led to a rapid increase in the rate of mathematical discovery that continues to the present day.<sup class="reference" id="cite_ref-4"><a href="http://en.wikipedia.org/wiki/Mathematics#cite_note-4"><span>[</span>5<span>]</span></a></sup><br />There is debate over whether mathematical objects such as <a href="http://en.wikipedia.org/wiki/Number" title="Number">numbers</a> and points exist naturally or are human creations. The mathematician <a href="http://en.wikipedia.org/wiki/Benjamin_Peirce">Benjamin Peirce</a> called mathematics "the science that draws necessary conclusions".<sup class="reference" id="cite_ref-5"><a href="http://en.wikipedia.org/wiki/Mathematics#cite_note-5"><span>[</span>6<span>]</span></a></sup> <a href="http://en.wikipedia.org/wiki/Albert_Einstein">Albert Einstein</a>, on the other hand, stated that "as far as the laws of mathematics refer to reality, they are not certain; and as far as they are certain, they do not refer to reality."<sup class="reference" id="cite_ref-certain_6-0"><a href="http://en.wikipedia.org/wiki/Mathematics#cite_note-certain-6"><span>[</span>7<span>]</span></a></sup><br />Mathematics is used throughout the world as an essential tool in many fields, including <a href="http://en.wikipedia.org/wiki/Natural_science">natural science</a>, <a href="http://en.wikipedia.org/wiki/Engineering">engineering</a>, <a href="http://en.wikipedia.org/wiki/Medicine">medicine</a>, and the <a href="http://en.wikipedia.org/wiki/Social_sciences">social sciences</a>. <a href="http://en.wikipedia.org/wiki/Applied_mathematics">Applied mathematics</a>, the branch of mathematics concerned with application of mathematical knowledge to other fields, inspires and makes use of new mathematical discoveries and sometimes leads to the development of entirely new mathematical disciplines, such as <a href="http://en.wikipedia.org/wiki/Statistics">statistics</a> and <a href="http://en.wikipedia.org/wiki/Game_theory">game theory</a>. Mathematicians also engage in <a href="http://en.wikipedia.org/wiki/Pure_mathematics">pure mathematics</a>, or mathematics for its own sake, without having any application in mind, although practical applications for what began as pure mathematics are often discovered.<sup class="reference" id="cite_ref-7"><a href="http://en.wikipedia.org/wiki/Mathematics#cite_note-7"><span>[</span>8<span>]</span></a></sup><br /><table class="toc" id="toc"><tbody><tr> <td> <div id="toctitle"> <h2>Contents</h2><span class="toctoggle">[<a class="internal" href="http://en.wikipedia.org/wiki/Mathematics#" id="togglelink">hide</a>]</span></div><ul><li class="toclevel-1 tocsection-1"><a href="http://en.wikipedia.org/wiki/Mathematics#Etymology"><span class="tocnumber">1</span> <span class="toctext">Etymology</span></a></li><li class="toclevel-1 tocsection-2"><a href="http://en.wikipedia.org/wiki/Mathematics#History"><span class="tocnumber">2</span> <span class="toctext">History</span></a></li><li class="toclevel-1 tocsection-3"><a href="http://en.wikipedia.org/wiki/Mathematics#Inspiration.2C_pure_and_applied_mathematics.2C_and_aesthetics"><span class="tocnumber">3</span> <span class="toctext">Inspiration, pure and applied mathematics, and aesthetics</span></a></li><li class="toclevel-1 tocsection-4"><a href="http://en.wikipedia.org/wiki/Mathematics#Notation.2C_language.2C_and_rigor"><span class="tocnumber">4</span> <span class="toctext">Notation, language, and rigor</span></a></li><li class="toclevel-1 tocsection-5"><a href="http://en.wikipedia.org/wiki/Mathematics#Mathematics_as_science"><span class="tocnumber">5</span> <span class="toctext">Mathematics as science</span></a></li><li class="toclevel-1 tocsection-6"><a href="http://en.wikipedia.org/wiki/Mathematics#Fields_of_mathematics"><span class="tocnumber">6</span> <span class="toctext">Fields of mathematics</span></a> <ul><li class="toclevel-2 tocsection-7"><a href="http://en.wikipedia.org/wiki/Mathematics#Foundations_and_philosophy"><span class="tocnumber">6.1</span> <span class="toctext">Foundations and philosophy</span></a></li><li class="toclevel-2 tocsection-8"><a href="http://en.wikipedia.org/wiki/Mathematics#Pure_mathematics"><span class="tocnumber">6.2</span> <span class="toctext">Pure mathematics</span></a> <ul><li class="toclevel-3 tocsection-9"><a href="http://en.wikipedia.org/wiki/Mathematics#Quantity"><span class="tocnumber">6.2.1</span> <span class="toctext">Quantity</span></a></li><li class="toclevel-3 tocsection-10"><a href="http://en.wikipedia.org/wiki/Mathematics#Structure"><span class="tocnumber">6.2.2</span> <span class="toctext">Structure</span></a></li><li class="toclevel-3 tocsection-11"><a href="http://en.wikipedia.org/wiki/Mathematics#Space"><span class="tocnumber">6.2.3</span> <span class="toctext">Space</span></a></li><li class="toclevel-3 tocsection-12"><a href="http://en.wikipedia.org/wiki/Mathematics#Change"><span class="tocnumber">6.2.4</span> <span class="toctext">Change</span></a></li></ul></li><li class="toclevel-2 tocsection-13"><a href="http://en.wikipedia.org/wiki/Mathematics#Applied_mathematics"><span class="tocnumber">6.3</span> <span class="toctext">Applied mathematics</span></a></li></ul></li><li class="toclevel-1 tocsection-14"><a href="http://en.wikipedia.org/wiki/Mathematics#Mathematics_as_profession"><span class="tocnumber">7</span> <span class="toctext">Mathematics as profession</span></a></li><li class="toclevel-1 tocsection-15"><a href="http://en.wikipedia.org/wiki/Mathematics#See_also"><span class="tocnumber">8</span> <span class="toctext">See also</span></a></li><li class="toclevel-1 tocsection-16"><a href="http://en.wikipedia.org/wiki/Mathematics#Notes"><span class="tocnumber">9</span> <span class="toctext">Notes</span></a></li><li class="toclevel-1 tocsection-17"><a href="http://en.wikipedia.org/wiki/Mathematics#References"><span class="tocnumber">10</span> <span class="toctext">References</span></a></li><li class="toclevel-1 tocsection-18"><a href="http://en.wikipedia.org/wiki/Mathematics#External_links"><span class="tocnumber">11</span> <span class="toctext">External links</span></a></li></ul></td> </tr></tbody></table><h2><span class="mw-headline" id="Etymology">Etymology</span></h2>The word "mathematics" comes from the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Ancient_Greek_language" title="Ancient Greek language">Greek</a> μάθημα (<i>máthēma</i>), which means <i>learning</i>, <i>study</i>, <i>science</i>, and additionally came to have the narrower and more technical meaning "mathematical study", even in Classical times.<sup class="reference" id="cite_ref-8"><a href="http://en.wikipedia.org/wiki/Mathematics#cite_note-8"><span>[</span>9<span>]</span></a></sup> Its adjective is <span lang="el">μαθηματικός</span> (<i>mathēmatikós</i>), <i>related to learning</i>, or <i>studious</i>, which likewise further came to mean <i>mathematical</i>. In particular, <span lang="grc">μαθηματικὴ τέχνη</span> (<i>mathēmatikḗ tékhnē</i>), <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Latin_language" title="Latin language">Latin</a>: <span lang="la"><i>ars mathematica</i></span>, meant <i>the mathematical art</i>.<br />The apparent plural form in English, like the French plural form <span lang="fr"><i>les mathématiques</i></span> (and the less commonly used singular derivative <span lang="fr"><i>la mathématique</i></span>), goes back to the Latin neuter plural <span lang="la"><i>mathematica</i></span> (<a href="http://en.wikipedia.org/wiki/Cicero">Cicero</a>), based on the Greek plural <span lang="el">τα μαθηματικά (<i>ta mathēmatiká</i>)</span>, used by <a href="http://en.wikipedia.org/wiki/Aristotle">Aristotle</a>, and meaning roughly "all things mathematical"; although it is plausible that English borrowed only the adjective <i>mathematic(al)</i> and formed the noun <i>mathematics</i> anew, after the pattern of <a href="http://en.wikipedia.org/wiki/Physics">physics</a> and <a href="http://en.wikipedia.org/wiki/Metaphysics">metaphysics</a>, which were inherited from the Greek.<sup class="reference" id="cite_ref-9"><a href="http://en.wikipedia.org/wiki/Mathematics#cite_note-9"><span>[</span>10<span>]</span></a></sup> In English, the noun <i>mathematics</i> takes singular verb forms. It is often shortened to <i>maths</i> or, in English-speaking North America, <i>math</i>.<br /><h2><span class="mw-headline" id="History">History</span></h2><div class="rellink relarticle mainarticle">Main article: <a href="http://en.wikipedia.org/wiki/History_of_mathematics">History of mathematics</a></div><div class="thumb tleft"> <div class="thumbinner" style="width: 172px;"><a class="image" href="http://en.wikipedia.org/wiki/File:Kapitolinischer_Pythagoras_adjusted.jpg"><img alt="" class="thumbimage" height="227" src="http://upload.wikimedia.org/wikipedia/commons/thumb/1/1a/Kapitolinischer_Pythagoras_adjusted.jpg/170px-Kapitolinischer_Pythagoras_adjusted.jpg" width="170" /></a> <div class="thumbcaption"> <div class="magnify"><a class="internal" href="http://en.wikipedia.org/wiki/File:Kapitolinischer_Pythagoras_adjusted.jpg" title="Enlarge"><img alt="" height="11" src="http://bits.wikimedia.org/skins-1.17/common/images/magnify-clip.png" width="15" /></a></div>Greek mathematician <a href="http://en.wikipedia.org/wiki/Pythagoras">Pythagoras</a> (c.570-c.495 BC), commonly credited with discovering the <a href="http://en.wikipedia.org/wiki/Pythagorean_theorem">Pythagorean theorem</a>.</div></div></div>The evolution of mathematics might be seen as an ever-increasing series of <a href="http://en.wikipedia.org/wiki/Abstraction_%28mathematics%29" title="Abstraction (mathematics)">abstractions</a>, or alternatively an expansion of <a href="http://en.wikipedia.org/wiki/Subject_matter">subject matter</a>. The first abstraction, which is shared by many animals,<sup class="reference" id="cite_ref-10"><a href="http://en.wikipedia.org/wiki/Mathematics#cite_note-10"><span>[</span>11<span>]</span></a></sup> was probably that of <a href="http://en.wikipedia.org/wiki/Number" title="Number">numbers</a>: the realization that a collection of two apples and a collection of two oranges (for example) have something in common, namely quantity of their members.<br />In addition to recognizing how to <a href="http://en.wikipedia.org/wiki/Counting" title="Counting">count</a> <i>physical</i> objects, <a href="http://en.wikipedia.org/wiki/Prehistory" title="Prehistory">prehistoric</a> peoples also recognized how to count <i>abstract</i> quantities, like time – days, <a href="http://en.wikipedia.org/wiki/Season" title="Season">seasons</a>, years.<sup class="reference" id="cite_ref-11"><a href="http://en.wikipedia.org/wiki/Mathematics#cite_note-11"><span>[</span>12<span>]</span></a></sup> <a href="http://en.wikipedia.org/wiki/Elementary_arithmetic">Elementary arithmetic</a> (<a href="http://en.wikipedia.org/wiki/Addition">addition</a>, <a href="http://en.wikipedia.org/wiki/Subtraction">subtraction</a>, <a href="http://en.wikipedia.org/wiki/Multiplication">multiplication</a> and <a href="http://en.wikipedia.org/wiki/Division_%28mathematics%29" title="Division (mathematics)">division</a>) naturally followed.<br />Since numeracy pre-dated <a href="http://en.wikipedia.org/wiki/Writing">writing</a>, further steps were needed for recording numbers such as <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Tally_sticks" title="Tally sticks">tallies</a> or the knotted strings called <a href="http://en.wikipedia.org/wiki/Quipu">quipu</a> used by the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Inca" title="Inca">Inca</a> to store numerical data.<sup class="Template-Fact" style="white-space: nowrap;" title="This claim needs references to reliable sources from August 2009">[<i><a href="http://en.wikipedia.org/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed">citation needed</a></i>]</sup> <a href="http://en.wikipedia.org/wiki/Numeral_system" title="Numeral system">Numeral systems</a> have been many and diverse, with the first known written numerals created by <a href="http://en.wikipedia.org/wiki/Ancient_Egypt" title="Ancient Egypt">Egyptians</a> in <a href="http://en.wikipedia.org/wiki/Middle_Kingdom_of_Egypt" title="Middle Kingdom of Egypt">Middle Kingdom</a> texts such as the <a href="http://en.wikipedia.org/wiki/Rhind_Mathematical_Papyrus">Rhind Mathematical Papyrus</a>.<sup class="Template-Fact" style="white-space: nowrap;" title="This claim needs references to reliable sources from August 2009">[<i><a href="http://en.wikipedia.org/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed">citation needed</a></i>]</sup><br /><div class="thumb tright"> <div class="thumbinner" style="width: 222px;"><a class="image" href="http://en.wikipedia.org/wiki/File:Maya.svg"><img alt="" class="thumbimage" height="254" src="http://upload.wikimedia.org/wikipedia/commons/thumb/1/1b/Maya.svg/220px-Maya.svg.png" width="220" /></a> <div class="thumbcaption"> <div class="magnify"><a class="internal" href="http://en.wikipedia.org/wiki/File:Maya.svg" title="Enlarge"><img alt="" height="11" src="http://bits.wikimedia.org/skins-1.17/common/images/magnify-clip.png" width="15" /></a></div><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Mayan_numerals" title="Mayan numerals">Mayan numerals</a></div></div></div>The earliest uses of mathematics were in <a href="http://en.wikipedia.org/wiki/Trade" title="Trade">trading</a>, <a href="http://en.wikipedia.org/wiki/Land_measurement">land measurement</a>, <a href="http://en.wikipedia.org/wiki/Painting">painting</a> and <a href="http://en.wikipedia.org/wiki/Weaving">weaving</a> patterns and the recording of time. More complex mathematics did not appear until around 3000 BC, when the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Babylonian" title="Babylonian">Babylonians</a> and Egyptians began using arithmetic, algebra and geometry for <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Taxation" title="Taxation">taxation</a> and other financial calculations, for building and construction, and for <a href="http://en.wikipedia.org/wiki/Astronomy">astronomy</a>.<sup class="reference" id="cite_ref-12"><a href="http://en.wikipedia.org/wiki/Mathematics#cite_note-12"><span>[</span>13<span>]</span></a></sup> The systematic study of mathematics in its own right began with the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Ancient_Greeks" title="Ancient Greeks">Ancient Greeks</a> between 600 and 300 BC.<sup class="reference" id="cite_ref-13"><a href="http://en.wikipedia.org/wiki/Mathematics#cite_note-13"><span>[</span>14<span>]</span></a></sup><br />Mathematics has since been greatly extended, and there has been a fruitful interaction between mathematics and <a href="http://en.wikipedia.org/wiki/Science">science</a>, to the benefit of both. Mathematical discoveries continue to be made today. According to Mikhail B. Sevryuk, in the January 2006 issue of the <i><a href="http://en.wikipedia.org/wiki/Bulletin_of_the_American_Mathematical_Society">Bulletin of the American Mathematical Society</a></i>, "The number of papers and books included in the <a href="http://en.wikipedia.org/wiki/Mathematical_Reviews">Mathematical Reviews</a> database since 1940 (the first year of operation of MR) is now more than 1.9 million, and more than 75 thousand items are added to the database each year. The overwhelming majority of works in this ocean contain new mathematical <a href="http://en.wikipedia.org/wiki/Theorem" title="Theorem">theorems</a> and their <a href="http://en.wikipedia.org/wiki/Mathematical_proof" title="Mathematical proof">proofs</a>."<sup class="reference" id="cite_ref-14"><a href="http://en.wikipedia.org/wiki/Mathematics#cite_note-14"><span>[</span>15<span>]</span></a></sup><br /><h2><span class="mw-headline" id="Inspiration.2C_pure_and_applied_mathematics.2C_and_aesthetics">Inspiration, pure and applied mathematics, and aesthetics</span></h2><div class="rellink relarticle mainarticle">Main article: <a href="http://en.wikipedia.org/wiki/Mathematical_beauty">Mathematical beauty</a></div><div class="thumb tleft"> <div class="thumbinner" style="width: 222px;"><a class="image" href="http://en.wikipedia.org/wiki/File:GodfreyKneller-IsaacNewton-1689.jpg"><img alt="" class="thumbimage" height="302" src="http://upload.wikimedia.org/wikipedia/commons/thumb/3/39/GodfreyKneller-IsaacNewton-1689.jpg/220px-GodfreyKneller-IsaacNewton-1689.jpg" width="220" /></a> <div class="thumbcaption"> <div class="magnify"><a class="internal" href="http://en.wikipedia.org/wiki/File:GodfreyKneller-IsaacNewton-1689.jpg" title="Enlarge"><img alt="" height="11" src="http://bits.wikimedia.org/skins-1.17/common/images/magnify-clip.png" width="15" /></a></div>Sir <a href="http://en.wikipedia.org/wiki/Isaac_Newton">Isaac Newton</a> (1643-1727), an <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Inventor" title="Inventor">inventor</a> of <a href="http://en.wikipedia.org/wiki/Calculus" title="Calculus">infinitesimal calculus</a>.</div></div></div>Mathematics arises from many different kinds of problems. At first these were found in <a href="http://en.wikipedia.org/wiki/Commerce">commerce</a>, <a href="http://en.wikipedia.org/wiki/Land_measurement">land measurement</a>, <a href="http://en.wikipedia.org/wiki/Architecture">architecture</a> and later <a href="http://en.wikipedia.org/wiki/Astronomy">astronomy</a>; nowadays, all sciences suggest problems studied by mathematicians, and many problems arise within mathematics itself. For example, the <a href="http://en.wikipedia.org/wiki/Physicist">physicist</a> <a href="http://en.wikipedia.org/wiki/Richard_Feynman">Richard Feynman</a> invented the <a href="http://en.wikipedia.org/wiki/Path_integral_formulation">path integral formulation</a> of <a href="http://en.wikipedia.org/wiki/Quantum_mechanics">quantum mechanics</a> using a combination of mathematical reasoning and physical insight, and today's <a href="http://en.wikipedia.org/wiki/String_theory">string theory</a>, a still-developing scientific theory which attempts to unify the four <a href="http://en.wikipedia.org/wiki/Fundamental_interaction" title="Fundamental interaction">fundamental forces of nature</a>, continues to inspire new mathematics.<sup class="reference" id="cite_ref-15"><a href="http://en.wikipedia.org/wiki/Mathematics#cite_note-15"><span>[</span>16<span>]</span></a></sup> Some mathematics is only relevant in the area that inspired it, and is applied to solve further problems in that area. But often mathematics inspired by one area proves useful in many areas, and joins the general stock of mathematical concepts. A distinction is often made between <a href="http://en.wikipedia.org/wiki/Pure_mathematics">pure mathematics</a> and <a href="http://en.wikipedia.org/wiki/Applied_mathematics">applied mathematics</a>. However pure mathematics topics often turn out to have applications, e.g. <a href="http://en.wikipedia.org/wiki/Number_theory">number theory</a> in <a href="http://en.wikipedia.org/wiki/Cryptography">cryptography</a>. This remarkable fact that even the "purest" mathematics often turns out to have practical applications is what <a href="http://en.wikipedia.org/wiki/Eugene_Wigner">Eugene Wigner</a> has called "<a href="http://en.wikipedia.org/wiki/The_Unreasonable_Effectiveness_of_Mathematics_in_the_Natural_Sciences" title="The Unreasonable Effectiveness of Mathematics in the Natural Sciences">the unreasonable effectiveness of mathematics</a>".<sup class="reference" id="cite_ref-16"><a href="http://en.wikipedia.org/wiki/Mathematics#cite_note-16"><span>[</span>17<span>]</span></a></sup> As in most areas of study, the explosion of knowledge in the scientific age has led to specialization: there are now hundreds of specialized areas in mathematics and the latest <a href="http://en.wikipedia.org/wiki/Mathematics_Subject_Classification">Mathematics Subject Classification</a> runs to 46 pages.<sup class="reference" id="cite_ref-17"><a href="http://en.wikipedia.org/wiki/Mathematics#cite_note-17"><span>[</span>18<span>]</span></a></sup> Several areas of applied mathematics have merged with related traditions outside of mathematics and become disciplines in their own right, including <a href="http://en.wikipedia.org/wiki/Statistics">statistics</a>, <a href="http://en.wikipedia.org/wiki/Operations_research">operations research</a>, and <a href="http://en.wikipedia.org/wiki/Computer_science">computer science</a>.<br />For those who are mathematically inclined, there is often a definite aesthetic aspect to much of mathematics. Many mathematicians talk about the <i>elegance</i> of mathematics, its intrinsic <a href="http://en.wikipedia.org/wiki/Aesthetics">aesthetics</a> and inner <a href="http://en.wikipedia.org/wiki/Beauty">beauty</a>. <a href="http://en.wikipedia.org/wiki/Simplicity">Simplicity</a> and generality are valued. There is beauty in a simple and elegant <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Proof_%28mathematics%29" title="Proof (mathematics)">proof</a>, such as <a href="http://en.wikipedia.org/wiki/Euclid">Euclid</a>'s proof that there are infinitely many <a href="http://en.wikipedia.org/wiki/Prime_number" title="Prime number">prime numbers</a>, and in an elegant <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Numerical_method" title="Numerical method">numerical method</a> that speeds calculation, such as the <a href="http://en.wikipedia.org/wiki/Fast_Fourier_transform">fast Fourier transform</a>. <a href="http://en.wikipedia.org/wiki/G._H._Hardy">G. H. Hardy</a> in <i><a href="http://en.wikipedia.org/wiki/A_Mathematician%27s_Apology">A Mathematician's Apology</a></i> expressed the belief that these aesthetic considerations are, in themselves, sufficient to justify the study of pure mathematics. He identified criteria such as significance, unexpectedness, inevitability, and economy as factors that contribute to a mathematical aesthetic.<sup class="reference" id="cite_ref-18"><a href="http://en.wikipedia.org/wiki/Mathematics#cite_note-18"><span>[</span>19<span>]</span></a></sup> Mathematicians often strive to find proofs of theorems that are particularly elegant, a quest <a href="http://en.wikipedia.org/wiki/Paul_Erd%C5%91s">Paul Erdős</a> often referred to as finding proofs from "The Book" in which God had written down his favorite proofs.<sup class="reference" id="cite_ref-19"><a href="http://en.wikipedia.org/wiki/Mathematics#cite_note-19"><span>[</span>20<span>]</span></a></sup><sup class="reference" id="cite_ref-20"><a href="http://en.wikipedia.org/wiki/Mathematics#cite_note-20"><span>[</span>21<span>]</span></a></sup> The popularity of <a href="http://en.wikipedia.org/wiki/Recreational_mathematics">recreational mathematics</a> is another sign of the pleasure many find in solving mathematical questions.<br /><h2><span class="mw-headline" id="Notation.2C_language.2C_and_rigor">Notation, language, and rigor</span></h2><div class="rellink relarticle mainarticle">Main article: <a href="http://en.wikipedia.org/wiki/Mathematical_notation">Mathematical notation</a></div><div class="thumb tright"> <div class="thumbinner" style="width: 172px;"><a class="image" href="http://en.wikipedia.org/wiki/File:Leonhard_Euler_2.jpg"><img alt="" class="thumbimage" height="212" src="http://upload.wikimedia.org/wikipedia/commons/thumb/6/60/Leonhard_Euler_2.jpg/170px-Leonhard_Euler_2.jpg" width="170" /></a> <div class="thumbcaption"> <div class="magnify"><a class="internal" href="http://en.wikipedia.org/wiki/File:Leonhard_Euler_2.jpg" title="Enlarge"><img alt="" height="11" src="http://bits.wikimedia.org/skins-1.17/common/images/magnify-clip.png" width="15" /></a></div><a href="http://en.wikipedia.org/wiki/Leonhard_Euler">Leonhard Euler</a>, who created and popularized much of the mathematical notation used today</div></div></div>Most of the mathematical notation in use today was not invented until the 16th century.<sup class="reference" id="cite_ref-21"><a href="http://en.wikipedia.org/wiki/Mathematics#cite_note-21"><span>[</span>22<span>]</span></a></sup> Before that, mathematics was written out in words, a painstaking process that limited mathematical discovery.<sup class="reference" id="cite_ref-22"><a href="http://en.wikipedia.org/wiki/Mathematics#cite_note-22"><span>[</span>23<span>]</span></a></sup> <a href="http://en.wikipedia.org/wiki/Leonhard_Euler" title="Leonhard Euler">Euler</a> (1707–1783) was responsible for many of the notations in use today. Modern notation makes mathematics much easier for the professional, but beginners often find it daunting. It is extremely compressed: a few symbols contain a great deal of information. Like <a href="http://en.wikipedia.org/wiki/Musical_notation">musical notation</a>, modern mathematical notation has a strict syntax (which to a limited extent varies from author to author and from discipline to discipline) and encodes information that would be difficult to write in any other way.<br />Mathematical <a href="http://en.wikipedia.org/wiki/Language">language</a> can be difficult to understand for beginners. Words such as <i>or</i> and <i>only</i> have more precise meanings than in everyday speech. Moreover, words such as <i><a href="http://en.wikipedia.org/wiki/Open_set" title="Open set">open</a></i> and <i><a href="http://en.wikipedia.org/wiki/Field_%28mathematics%29" title="Field (mathematics)">field</a></i> have been given specialized mathematical meanings. <a href="http://en.wikipedia.org/wiki/Mathematical_jargon">Mathematical jargon</a> includes technical terms such as <i><a href="http://en.wikipedia.org/wiki/Homeomorphism">homeomorphism</a></i> and <i><a href="http://en.wikipedia.org/wiki/Integral" title="Integral">integrable</a></i>. But there is a reason for special notation and technical jargon: mathematics requires more precision than everyday speech. Mathematicians refer to this precision of language and logic as "rigor".<br /><a href="http://en.wikipedia.org/wiki/Mathematical_proof">Mathematical proof</a> is fundamentally a matter of <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Rigor" title="Rigor">rigor</a>. Mathematicians want their theorems to follow from axioms by means of systematic reasoning. This is to avoid mistaken "<a href="http://en.wikipedia.org/wiki/Theorem" title="Theorem">theorems</a>", based on fallible intuitions, of which many instances have occurred in the history of the subject.<sup class="reference" id="cite_ref-23"><a href="http://en.wikipedia.org/wiki/Mathematics#cite_note-23"><span>[</span>24<span>]</span></a></sup> The level of rigor expected in mathematics has varied over time: the Greeks expected detailed arguments, but at the time of <a href="http://en.wikipedia.org/wiki/Isaac_Newton">Isaac Newton</a> the methods employed were less rigorous. Problems inherent in the definitions used by Newton would lead to a resurgence of careful analysis and formal proof in the 19th century. Misunderstanding the rigor is a cause for some of the common misconceptions of mathematics. Today, mathematicians continue to argue among themselves about <a href="http://en.wikipedia.org/wiki/Computer-assisted_proof" title="Computer-assisted proof">computer-assisted proofs</a>. Since large computations are hard to verify, such proofs may not be sufficiently rigorous.<sup class="reference" id="cite_ref-24"><a href="http://en.wikipedia.org/wiki/Mathematics#cite_note-24"><span>[</span>25<span>]</span></a></sup><br /><a href="http://en.wikipedia.org/wiki/Axiom" title="Axiom">Axioms</a> in traditional thought were "self-evident truths", but that conception is problematic. At a formal level, an axiom is just a string of symbols, which has an intrinsic meaning only in the context of all derivable formulas of an <a href="http://en.wikipedia.org/wiki/Axiomatic_system">axiomatic system</a>. It was the goal of <a href="http://en.wikipedia.org/wiki/Hilbert%27s_program">Hilbert's program</a> to put all of mathematics on a firm axiomatic basis, but according to <a class="mw-redirect" href="http://en.wikipedia.org/wiki/G%C3%B6del%27s_incompleteness_theorem" title="Gödel's incompleteness theorem">Gödel's incompleteness theorem</a> every (sufficiently powerful) axiomatic system has <a href="http://en.wikipedia.org/wiki/Independence_%28mathematical_logic%29" title="Independence (mathematical logic)">undecidable</a> formulas; and so a final <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Axiomatization" title="Axiomatization">axiomatization</a> of mathematics is impossible. Nonetheless mathematics is often imagined to be (as far as its formal content) nothing but <a href="http://en.wikipedia.org/wiki/Set_theory">set theory</a> in some axiomatization, in the sense that every mathematical statement or proof could be cast into formulas within set theory.<sup class="reference" id="cite_ref-25"><a href="http://en.wikipedia.org/wiki/Mathematics#cite_note-25"><span>[</span>26<span>]</span></a></sup><br /><h2><span class="mw-headline" id="Mathematics_as_science">Mathematics as science</span></h2><div class="thumb tleft"> <div class="thumbinner" style="width: 172px;"><a class="image" href="http://en.wikipedia.org/wiki/File:Carl_Friedrich_Gauss.jpg"><img alt="" class="thumbimage" height="218" src="http://upload.wikimedia.org/wikipedia/commons/thumb/9/9b/Carl_Friedrich_Gauss.jpg/170px-Carl_Friedrich_Gauss.jpg" width="170" /></a> <div class="thumbcaption"> <div class="magnify"><a class="internal" href="http://en.wikipedia.org/wiki/File:Carl_Friedrich_Gauss.jpg" title="Enlarge"><img alt="" height="11" src="http://bits.wikimedia.org/skins-1.17/common/images/magnify-clip.png" width="15" /></a></div><a href="http://en.wikipedia.org/wiki/Carl_Friedrich_Gauss">Carl Friedrich Gauss</a>, himself known as the "prince of mathematicians",<sup class="reference" id="cite_ref-26"><a href="http://en.wikipedia.org/wiki/Mathematics#cite_note-26"><span>[</span>27<span>]</span></a></sup> referred to mathematics as "the Queen of the Sciences".</div></div></div>Carl Friedrich Gauss referred to mathematics as "the Queen of the Sciences".<sup class="reference" id="cite_ref-27"><a href="http://en.wikipedia.org/wiki/Mathematics#cite_note-27"><span>[</span>28<span>]</span></a></sup> In the original Latin <i>Regina Scientiarum</i>, as well as in <a href="http://en.wikipedia.org/wiki/German_language" title="German language">German</a> <i>Königin der Wissenschaften</i>, the word corresponding to <i>science</i> means (field of) knowledge. Indeed, this is also the original meaning in English, and there is no doubt that mathematics is in this sense a science. The specialization restricting the meaning to <i>natural</i> science is of later date. If one considers <a href="http://en.wikipedia.org/wiki/Science">science</a> to be strictly about the physical world, then mathematics, or at least <a href="http://en.wikipedia.org/wiki/Pure_mathematics">pure mathematics</a>, is not a science. <a href="http://en.wikipedia.org/wiki/Albert_Einstein">Albert Einstein</a> stated that <i>"as far as the laws of mathematics refer to reality, they are not certain; and as far as they are certain, they do not refer to reality.</i>"<sup class="reference" id="cite_ref-certain_6-1"><a href="http://en.wikipedia.org/wiki/Mathematics#cite_note-certain-6"><span>[</span>7<span>]</span></a></sup><br />Many philosophers believe that mathematics is not experimentally <a href="http://en.wikipedia.org/wiki/Falsifiability" title="Falsifiability">falsifiable</a>, and thus not a science according to the definition of <a href="http://en.wikipedia.org/wiki/Karl_Popper">Karl Popper</a>.<sup class="reference" id="cite_ref-28"><a href="http://en.wikipedia.org/wiki/Mathematics#cite_note-28"><span>[</span>29<span>]</span></a></sup> However, in the 1930s <a href="http://en.wikipedia.org/wiki/G%C3%B6del%27s_incompleteness_theorems">Gödel's incompleteness theorems</a> convinced many mathematicians<sup class="noprint Inline-Template" style="white-space: nowrap;" title="The material in the vicinity of this tag may use weasel words or too-vague attribution. from January 2011">[<i><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Wikipedia:Avoid_weasel_words" title="Wikipedia:Avoid weasel words">who?</a></i>]</sup> that mathematics cannot be reduced to logic alone, and Karl Popper concluded that "most mathematical theories are, like those of <a href="http://en.wikipedia.org/wiki/Physics">physics</a> and <a href="http://en.wikipedia.org/wiki/Biology">biology</a>, <a href="http://en.wikipedia.org/wiki/Hypothesis" title="Hypothesis">hypothetico</a>-<a class="mw-redirect" href="http://en.wikipedia.org/wiki/Deductive" title="Deductive">deductive</a>: pure mathematics therefore turns out to be much closer to the natural sciences whose hypotheses are conjectures, than it seemed even recently."<sup class="reference" id="cite_ref-29"><a href="http://en.wikipedia.org/wiki/Mathematics#cite_note-29"><span>[</span>30<span>]</span></a></sup> Other thinkers, notably <a href="http://en.wikipedia.org/wiki/Imre_Lakatos">Imre Lakatos</a>, have applied a version of <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Falsificationism" title="Falsificationism">falsificationism</a> to mathematics itself.<br />An alternative view is that certain scientific fields (such as <a href="http://en.wikipedia.org/wiki/Theoretical_physics">theoretical physics</a>) are mathematics with axioms that are intended to correspond to reality. In fact, the theoretical physicist, <a class="mw-redirect" href="http://en.wikipedia.org/wiki/J._M._Ziman" title="J. M. Ziman">J. M. Ziman</a>, proposed that science is <i>public knowledge</i> and thus includes mathematics.<sup class="reference" id="cite_ref-30"><a href="http://en.wikipedia.org/wiki/Mathematics#cite_note-30"><span>[</span>31<span>]</span></a></sup> In any case, mathematics shares much in common with many fields in the physical sciences, notably the <a href="http://en.wikipedia.org/wiki/Deductive_reasoning" title="Deductive reasoning">exploration of the logical consequences</a> of assumptions. <a href="http://en.wikipedia.org/wiki/Intuition_%28knowledge%29" title="Intuition (knowledge)">Intuition</a> and <a href="http://en.wikipedia.org/wiki/Experiment" title="Experiment">experimentation</a> also play a role in the formulation of <a href="http://en.wikipedia.org/wiki/Conjecture" title="Conjecture">conjectures</a> in both mathematics and the (other) sciences. <a href="http://en.wikipedia.org/wiki/Experimental_mathematics">Experimental mathematics</a> continues to grow in importance within mathematics, and computation and simulation are playing an increasing role in both the sciences and mathematics, weakening the objection that mathematics does not use the <a href="http://en.wikipedia.org/wiki/Scientific_method">scientific method</a>.<sup class="Template-Fact" style="white-space: nowrap;" title="This claim needs references to reliable sources from August 2009">[<i><a href="http://en.wikipedia.org/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed">citation needed</a></i>]</sup> In his 2002 book <i><a href="http://en.wikipedia.org/wiki/A_New_Kind_of_Science">A New Kind of Science</a></i>, <a href="http://en.wikipedia.org/wiki/Stephen_Wolfram">Stephen Wolfram</a> argues that computational mathematics deserves to be explored empirically as a scientific field in its own right.<br />The opinions of mathematicians on this matter are varied. Many mathematicians<sup class="noprint Inline-Template" style="white-space: nowrap;" title="The material in the vicinity of this tag may use weasel words or too-vague attribution. from August 2009">[<i><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Wikipedia:Avoid_weasel_words" title="Wikipedia:Avoid weasel words">who?</a></i>]</sup> feel that to call their area a science is to downplay the importance of its aesthetic side, and its history in the traditional seven <a href="http://en.wikipedia.org/wiki/Liberal_arts">liberal arts</a>; others<sup class="noprint Inline-Template" style="white-space: nowrap;" title="The material in the vicinity of this tag may use weasel words or too-vague attribution. from August 2009">[<i><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Wikipedia:Avoid_weasel_words" title="Wikipedia:Avoid weasel words">who?</a></i>]</sup> feel that to ignore its connection to the sciences is to turn a blind eye to the fact that the interface between mathematics and its applications in science and <a href="http://en.wikipedia.org/wiki/Engineering">engineering</a> has driven much development in mathematics. One way this difference of viewpoint plays out is in the philosophical debate as to whether mathematics is <i>created</i> (as in art) or <i>discovered</i> (as in science). It is common to see <a href="http://en.wikipedia.org/wiki/University" title="University">universities</a> divided into sections that include a division of <i>Science and Mathematics</i>, indicating that the fields are seen as being allied but that they do not coincide. In practice, mathematicians are typically grouped with scientists at the gross level but separated at finer levels. This is one of many issues considered in the <a href="http://en.wikipedia.org/wiki/Philosophy_of_mathematics">philosophy of mathematics</a>.<sup class="Template-Fact" style="white-space: nowrap;" title="This claim needs references to reliable sources from August 2009">[<i><a href="http://en.wikipedia.org/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed">citation needed</a></i>]</sup><br /><h2><span class="mw-headline" id="Fields_of_mathematics">Fields of mathematics</span></h2><div class="thumb tright"> <div class="thumbinner" style="width: 222px;"><a class="image" href="http://en.wikipedia.org/wiki/File:Abacus_6.png"><img alt="" class="thumbimage" height="129" src="http://upload.wikimedia.org/wikipedia/commons/thumb/a/af/Abacus_6.png/220px-Abacus_6.png" width="220" /></a> <div class="thumbcaption"> <div class="magnify"><a class="internal" href="http://en.wikipedia.org/wiki/File:Abacus_6.png" title="Enlarge"><img alt="" height="11" src="http://bits.wikimedia.org/skins-1.17/common/images/magnify-clip.png" width="15" /></a></div>An <a href="http://en.wikipedia.org/wiki/Abacus">abacus</a>, a simple calculating tool used since ancient times.</div></div></div>Mathematics can, broadly speaking, be subdivided into the study of quantity, structure, space, and change (i.e. <a href="http://en.wikipedia.org/wiki/Arithmetic">arithmetic</a>, <a href="http://en.wikipedia.org/wiki/Algebra">algebra</a>, <a href="http://en.wikipedia.org/wiki/Geometry">geometry</a>, and <a href="http://en.wikipedia.org/wiki/Mathematical_analysis" title="Mathematical analysis">analysis</a>).<sup class="Template-Fact" style="white-space: nowrap;" title="This claim needs references to reliable sources from October 2010">[<i><a href="http://en.wikipedia.org/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed">citation needed</a></i>]</sup> In addition to these main concerns, there are also subdivisions dedicated to exploring links from the heart of mathematics to other fields: to <a href="http://en.wikipedia.org/wiki/Mathematical_logic" title="Mathematical logic">logic</a>, to <a href="http://en.wikipedia.org/wiki/Set_theory">set theory</a> (<a href="http://en.wikipedia.org/wiki/Foundations_of_mathematics" title="Foundations of mathematics">foundations</a>), to the empirical mathematics of the various sciences (<a href="http://en.wikipedia.org/wiki/Applied_mathematics">applied mathematics</a>), and more recently to the rigorous study of <a href="http://en.wikipedia.org/wiki/Uncertainty">uncertainty</a>.<br /><h3><span class="mw-headline" id="Foundations_and_philosophy">Foundations and philosophy</span></h3>In order to clarify the <a href="http://en.wikipedia.org/wiki/Foundations_of_mathematics">foundations of mathematics</a>, the fields of <a href="http://en.wikipedia.org/wiki/Mathematical_logic">mathematical logic</a> and <a href="http://en.wikipedia.org/wiki/Set_theory">set theory</a> were developed. Mathematical logic includes the mathematical study of <a href="http://en.wikipedia.org/wiki/Logic">logic</a> and the applications of formal logic to other areas of mathematics; set theory is the branch of mathematics that studies <a href="http://en.wikipedia.org/wiki/Set_%28mathematics%29" title="Set (mathematics)">sets</a> or collections of objects. <a href="http://en.wikipedia.org/wiki/Category_theory">Category theory</a>, which deals in an abstract way with <a href="http://en.wikipedia.org/wiki/Mathematical_structure" title="Mathematical structure">mathematical structures</a> and relationships between them, is still in development. The phrase "crisis of foundations" describes the search for a rigorous foundation for mathematics that took place from approximately 1900 to 1930.<sup class="reference" id="cite_ref-31"><a href="http://en.wikipedia.org/wiki/Mathematics#cite_note-31"><span>[</span>32<span>]</span></a></sup> Some disagreement about the foundations of mathematics continues to the present day. The crisis of foundations was stimulated by a number of controversies at the time, including the <a href="http://en.wikipedia.org/wiki/Controversy_over_Cantor%27s_theory" title="Controversy over Cantor's theory">controversy over Cantor's set theory</a> and the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Brouwer-Hilbert_controversy" title="Brouwer-Hilbert controversy">Brouwer-Hilbert controversy</a>.<br />Mathematical logic is concerned with setting mathematics within a rigorous <a href="http://en.wikipedia.org/wiki/Axiom" title="Axiom">axiomatic</a> framework, and studying the implications of such a framework. As such, it is home to <a href="http://en.wikipedia.org/wiki/G%C3%B6del%27s_incompleteness_theorems">Gödel's incompleteness theorems</a> which (informally) imply that any <a href="http://en.wikipedia.org/wiki/Formal_system">formal system</a> that contains basic arithmetic, if <i>sound</i> (meaning that all theorems that can be proven are true), is necessarily <i>incomplete</i> (meaning that there are true theorems which cannot be proved <i>in that system</i>). Whatever finite collection of number-theoretical axioms is taken as a foundation, Gödel showed how to construct a formal statement that is a true number-theoretical fact, but which does not follow from those axioms. Therefore no formal system is a complete axiomatization of full number theory. Modern logic is divided into <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Recursion_theory" title="Recursion theory">recursion theory</a>, <a href="http://en.wikipedia.org/wiki/Model_theory">model theory</a>, and <a href="http://en.wikipedia.org/wiki/Proof_theory">proof theory</a>, and is closely linked to <a href="http://en.wikipedia.org/wiki/Theoretical_computer_science" title="Theoretical computer science">theoretical</a> <a href="http://en.wikipedia.org/wiki/Computer_science">computer science</a>.<sup class="Template-Fact" style="white-space: nowrap;" title="This claim needs references to reliable sources from March 2011">[<i><a href="http://en.wikipedia.org/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed">citation needed</a></i>]</sup><br /><a href="http://en.wikipedia.org/wiki/Theoretical_computer_science">Theoretical computer science</a> includes <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Computability_theory_%28computation%29" title="Computability theory (computation)">computability theory</a>, <a href="http://en.wikipedia.org/wiki/Computational_complexity_theory">computational complexity theory</a>, and <a href="http://en.wikipedia.org/wiki/Information_theory">information theory</a>. Computability theory examines the limitations of various theoretical models of the computer, including the most well known model – the <a href="http://en.wikipedia.org/wiki/Turing_machine">Turing machine</a>. Complexity theory is the study of tractability by computer; some problems, although theoretically solvable by computer, are so expensive in terms of time or space that solving them is likely to remain practically unfeasible, even with rapid advance of computer hardware. A famous problem is the "<a class="mw-redirect" href="http://en.wikipedia.org/wiki/P_%3D_NP_problem" title="P = NP problem">P=NP?</a>" problem, one of the <a href="http://en.wikipedia.org/wiki/Millennium_Prize_Problems">Millennium Prize Problems</a>.<sup class="reference" id="cite_ref-32"><a href="http://en.wikipedia.org/wiki/Mathematics#cite_note-32"><span>[</span>33<span>]</span></a></sup> Finally, information theory is concerned with the amount of data that can be stored on a given medium, and hence deals with concepts such as <a href="http://en.wikipedia.org/wiki/Data_compression" title="Data compression">compression</a> and <a href="http://en.wikipedia.org/wiki/Entropy_%28information_theory%29" title="Entropy (information theory)">entropy</a>.<br /><dl><dd> <table cellspacing="15" style="border: 1px solid #ddd; margin: auto; text-align: center;"><tbody><tr> <td><img alt=" p \Rightarrow q \," class="tex" src="http://upload.wikimedia.org/math/a/6/4/a644166cefb23015623cb1670becf7b2.png" /></td> <td><a class="image" href="http://en.wikipedia.org/wiki/File:Venn_A_intersect_B.svg"><img alt="Venn A intersect B.svg" height="91" src="http://upload.wikimedia.org/wikipedia/commons/thumb/6/6d/Venn_A_intersect_B.svg/128px-Venn_A_intersect_B.svg.png" width="128" /></a></td> <td><a class="image" href="http://en.wikipedia.org/wiki/File:Commutative_diagram_for_morphism.svg"><img alt="Commutative diagram for morphism.svg" height="96" src="http://upload.wikimedia.org/wikipedia/commons/thumb/e/ef/Commutative_diagram_for_morphism.svg/96px-Commutative_diagram_for_morphism.svg.png" width="96" /></a></td> <td><a class="image" href="http://en.wikipedia.org/wiki/File:DFAexample.svg"><img alt="DFAexample.svg" height="57" src="http://upload.wikimedia.org/wikipedia/commons/thumb/9/9d/DFAexample.svg/96px-DFAexample.svg.png" width="96" /></a></td> </tr><tr> <td><a href="http://en.wikipedia.org/wiki/Mathematical_logic">Mathematical logic</a></td> <td><a href="http://en.wikipedia.org/wiki/Set_theory">Set theory</a></td> <td><a href="http://en.wikipedia.org/wiki/Category_theory">Category theory</a></td> <td><a href="http://en.wikipedia.org/wiki/Theory_of_computation">Theory of computation</a></td> </tr></tbody></table></dd></dl><h3><span class="mw-headline" id="Pure_mathematics">Pure mathematics</span></h3><h4><span class="mw-headline" id="Quantity">Quantity</span></h4>The study of quantity starts with <a href="http://en.wikipedia.org/wiki/Number" title="Number">numbers</a>, first the familiar <a href="http://en.wikipedia.org/wiki/Natural_number" title="Natural number">natural numbers</a> and <a href="http://en.wikipedia.org/wiki/Integer" title="Integer">integers</a> ("whole numbers") and arithmetical operations on them, which are characterized in <a href="http://en.wikipedia.org/wiki/Arithmetic">arithmetic</a>. The deeper properties of integers are studied in <a href="http://en.wikipedia.org/wiki/Number_theory">number theory</a>, from which come such popular results as <a href="http://en.wikipedia.org/wiki/Fermat%27s_Last_Theorem">Fermat's Last Theorem</a>. The <a href="http://en.wikipedia.org/wiki/Twin_prime">twin prime</a> conjecture and <a href="http://en.wikipedia.org/wiki/Goldbach%27s_conjecture">Goldbach's conjecture</a> are two unsolved problems in number theory.<br />As the number system is further developed, the integers are recognized as a <a href="http://en.wikipedia.org/wiki/Subset">subset</a> of the <a href="http://en.wikipedia.org/wiki/Rational_number" title="Rational number">rational numbers</a> ("<a href="http://en.wikipedia.org/wiki/Fraction_%28mathematics%29" title="Fraction (mathematics)">fractions</a>"). These, in turn, are contained within the <a href="http://en.wikipedia.org/wiki/Real_number" title="Real number">real numbers</a>, which are used to represent <a href="http://en.wikipedia.org/wiki/Continuous_function" title="Continuous function">continuous</a> quantities. Real numbers are generalized to <a href="http://en.wikipedia.org/wiki/Complex_number" title="Complex number">complex numbers</a>. These are the first steps of a hierarchy of numbers that goes on to include <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Quarternion" title="Quarternion">quarternions</a> and <a href="http://en.wikipedia.org/wiki/Octonion" title="Octonion">octonions</a>. Consideration of the natural numbers also leads to the <a href="http://en.wikipedia.org/wiki/Transfinite_number" title="Transfinite number">transfinite numbers</a>, which formalize the concept of "<a href="http://en.wikipedia.org/wiki/Infinity">infinity</a>". Another area of study is size, which leads to the <a href="http://en.wikipedia.org/wiki/Cardinal_number" title="Cardinal number">cardinal numbers</a> and then to another conception of infinity: the <a href="http://en.wikipedia.org/wiki/Aleph_number" title="Aleph number">aleph numbers</a>, which allow meaningful comparison of the size of infinitely large sets.<br /><dl><dd> <table cellspacing="20" style="border: 1px solid #ddd; margin: auto; text-align: center;"><tbody><tr> <td><img alt="1, 2, 3\,...\!" class="tex" src="http://upload.wikimedia.org/math/b/0/7/b07947c404d2ce48330ed6aaa8ad9002.png" /></td> <td><img alt="...-2, -1, 0, 1, 2\,...\!" class="tex" src="http://upload.wikimedia.org/math/b/e/f/befaa134771dce5348c45e460f748448.png" /></td> <td><img alt=" -2, \frac{2}{3}, 1.21\,\!" class="tex" src="http://upload.wikimedia.org/math/9/b/6/9b6892bffb24f4e8eb088036e5f7efff.png" /></td> <td><img alt="-e, \sqrt{2}, 3, \pi\,\!" class="tex" src="http://upload.wikimedia.org/math/9/d/6/9d6f418bda5bf70193627a3ee78805f4.png" /></td> <td><img alt="2, i, -2+3i, 2e^{i\frac{4\pi}{3}}\,\!" class="tex" src="http://upload.wikimedia.org/math/7/5/9/759cf14c729639e5c1152dad2c4843e7.png" /></td> </tr><tr> <td><a href="http://en.wikipedia.org/wiki/Natural_number" title="Natural number">Natural numbers</a></td> <td><a href="http://en.wikipedia.org/wiki/Integer" title="Integer">Integers</a></td> <td><a href="http://en.wikipedia.org/wiki/Rational_number" title="Rational number">Rational numbers</a></td> <td><a href="http://en.wikipedia.org/wiki/Real_number" title="Real number">Real numbers</a></td> <td><a href="http://en.wikipedia.org/wiki/Complex_number" title="Complex number">Complex numbers</a></td> </tr></tbody></table></dd></dl><h4><span class="mw-headline" id="Structure">Structure</span></h4>Many mathematical objects, such as <a href="http://en.wikipedia.org/wiki/Set_%28mathematics%29" title="Set (mathematics)">sets</a> of numbers and <a href="http://en.wikipedia.org/wiki/Function_%28mathematics%29" title="Function (mathematics)">functions</a>, exhibit internal structure as a consequence of <a href="http://en.wikipedia.org/wiki/Operation_%28mathematics%29" title="Operation (mathematics)">operations</a> or <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Relation_%28mathematics%29" title="Relation (mathematics)">relations</a> that are defined on the set. Mathematics then studies properties of those sets that can be expressed in terms of that structure; for instance <a href="http://en.wikipedia.org/wiki/Number_theory">number theory</a> studies properties of the set of <a href="http://en.wikipedia.org/wiki/Integer" title="Integer">integers</a> that can be expressed in terms of <a href="http://en.wikipedia.org/wiki/Arithmetic">arithmetic</a> operations. Moreover, it frequently happens that different such structured sets (or <a href="http://en.wikipedia.org/wiki/Mathematical_structure" title="Mathematical structure">structures</a>) exhibit similar properties, which makes it possible, by a further step of <a href="http://en.wikipedia.org/wiki/Abstraction">abstraction</a>, to state <a href="http://en.wikipedia.org/wiki/Axiom" title="Axiom">axioms</a> for a class of structures, and then study at once the whole class of structures satisfying these axioms. Thus one can study <a href="http://en.wikipedia.org/wiki/Group_%28mathematics%29" title="Group (mathematics)">groups</a>, <a href="http://en.wikipedia.org/wiki/Ring_%28mathematics%29" title="Ring (mathematics)">rings</a>, <a href="http://en.wikipedia.org/wiki/Field_%28mathematics%29" title="Field (mathematics)">fields</a> and other abstract systems; together such studies (for structures defined by algebraic operations) constitute the domain of <a href="http://en.wikipedia.org/wiki/Abstract_algebra">abstract algebra</a>. By its great generality, abstract algebra can often be applied to seemingly unrelated problems; for instance a number of ancient problems concerning <a href="http://en.wikipedia.org/wiki/Compass_and_straightedge_constructions">compass and straightedge constructions</a> were finally solved using <a href="http://en.wikipedia.org/wiki/Galois_theory">Galois theory</a>, which involves field theory and group theory. Another example of an algebraic theory is <a href="http://en.wikipedia.org/wiki/Linear_algebra">linear algebra</a>, which is the general study of <a href="http://en.wikipedia.org/wiki/Vector_space" title="Vector space">vector spaces</a>, whose elements called <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Vector_%28geometric%29" title="Vector (geometric)">vectors</a> have both quantity and direction, and can be used to model (relations between) points in space. This is one example of the phenomenon that the originally unrelated areas of <a href="http://en.wikipedia.org/wiki/Geometry">geometry</a> and <a href="http://en.wikipedia.org/wiki/Algebra">algebra</a> have very strong interactions in modern mathematics. <a href="http://en.wikipedia.org/wiki/Combinatorics">Combinatorics</a> studies ways of enumerating the number of objects that fit a given structure.<br /><dl><dd> <table cellspacing="15" style="border: 1px solid #ddd; margin: auto; text-align: center;"><tbody><tr> <td><img alt="\begin{matrix} (1,2,3) & (1,3,2) \\ (2,1,3) & (2,3,1) \\ (3,1,2) & (3,2,1) \end{matrix}" class="tex" src="http://upload.wikimedia.org/math/b/c/a/bca5b51d15b30266dc37decb94175dc2.png" /></td> <td><a class="image" href="http://en.wikipedia.org/wiki/File:Elliptic_curve_simple.svg"><img alt="Elliptic curve simple.svg" height="107" src="http://upload.wikimedia.org/wikipedia/commons/thumb/d/da/Elliptic_curve_simple.svg/96px-Elliptic_curve_simple.svg.png" width="96" /></a></td> <td><a class="image" href="http://en.wikipedia.org/wiki/File:Rubik%27s_cube.svg"><img alt="Rubik's cube.svg" height="100" src="http://upload.wikimedia.org/wikipedia/commons/thumb/a/a6/Rubik%27s_cube.svg/96px-Rubik%27s_cube.svg.png" width="96" /></a></td> <td><a class="image" href="http://en.wikipedia.org/wiki/File:Group_diagdram_D6.svg"><img alt="Group diagdram D6.svg" height="96" src="http://upload.wikimedia.org/wikipedia/commons/thumb/0/0e/Group_diagdram_D6.svg/96px-Group_diagdram_D6.svg.png" width="96" /></a></td> <td><a class="image" href="http://en.wikipedia.org/wiki/File:Lattice_of_the_divisibility_of_60.svg"><img alt="Lattice of the divisibility of 60.svg" height="77" src="http://upload.wikimedia.org/wikipedia/commons/thumb/5/51/Lattice_of_the_divisibility_of_60.svg/96px-Lattice_of_the_divisibility_of_60.svg.png" width="96" /></a></td> </tr><tr> <td><a href="http://en.wikipedia.org/wiki/Combinatorics">Combinatorics</a></td> <td><a href="http://en.wikipedia.org/wiki/Number_theory">Number theory</a></td> <td><a href="http://en.wikipedia.org/wiki/Group_theory">Group theory</a></td> <td><a href="http://en.wikipedia.org/wiki/Graph_theory">Graph theory</a></td> <td><a href="http://en.wikipedia.org/wiki/Order_theory">Order theory</a></td> </tr></tbody></table></dd></dl><h4><span class="mw-headline" id="Space">Space</span></h4>The study of space originates with <a href="http://en.wikipedia.org/wiki/Geometry">geometry</a> – in particular, <a href="http://en.wikipedia.org/wiki/Euclidean_geometry">Euclidean geometry</a>. <a href="http://en.wikipedia.org/wiki/Trigonometry">Trigonometry</a> is the branch of mathematics that deals with relationships between the sides and the angles of triangles and with the trigonometric functions; it combines space and numbers, and encompasses the well-known <a href="http://en.wikipedia.org/wiki/Pythagorean_theorem">Pythagorean theorem</a>. The modern study of space generalizes these ideas to include higher-dimensional geometry, <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Non-euclidean_geometry" title="Non-euclidean geometry">non-Euclidean geometries</a> (which play a central role in <a href="http://en.wikipedia.org/wiki/General_relativity">general relativity</a>) and <a href="http://en.wikipedia.org/wiki/Topology">topology</a>. Quantity and space both play a role in <a href="http://en.wikipedia.org/wiki/Analytic_geometry">analytic geometry</a>, <a href="http://en.wikipedia.org/wiki/Differential_geometry">differential geometry</a>, and <a href="http://en.wikipedia.org/wiki/Algebraic_geometry">algebraic geometry</a>. Within differential geometry are the concepts of <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Fiber_bundles" title="Fiber bundles">fiber bundles</a> and calculus on <a href="http://en.wikipedia.org/wiki/Manifold" title="Manifold">manifolds</a>, in particular, <a href="http://en.wikipedia.org/wiki/Vector_calculus" title="Vector calculus">vector</a> and <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Tensor_calculus" title="Tensor calculus">tensor calculus</a>. Within algebraic geometry is the description of geometric objects as solution sets of <a href="http://en.wikipedia.org/wiki/Polynomial">polynomial</a> equations, combining the concepts of quantity and space, and also the study of <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Topological_groups" title="Topological groups">topological groups</a>, which combine structure and space. <a href="http://en.wikipedia.org/wiki/Lie_group" title="Lie group">Lie groups</a> are used to study space, structure, and change. <a href="http://en.wikipedia.org/wiki/Topology">Topology</a> in all its many ramifications may have been the greatest growth area in 20th century mathematics; it includes <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Point-set_topology" title="Point-set topology">point-set topology</a>, <a href="http://en.wikipedia.org/wiki/Set-theoretic_topology">set-theoretic topology</a>, <a href="http://en.wikipedia.org/wiki/Algebraic_topology">algebraic topology</a> and <a href="http://en.wikipedia.org/wiki/Differential_topology">differential topology</a>. In particular, instances of modern day topology are <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Metrizability_theory" title="Metrizability theory">metrizability theory</a>, <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Axiomatic_set_theory" title="Axiomatic set theory">axiomatic set theory</a>, <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Homotopy_theory" title="Homotopy theory">homotopy theory</a>, and <a href="http://en.wikipedia.org/wiki/Morse_theory">Morse theory</a>. Topology also includes the now solved <a href="http://en.wikipedia.org/wiki/Poincar%C3%A9_conjecture">Poincaré conjecture</a> and the controversial <a href="http://en.wikipedia.org/wiki/Four_color_theorem">four color theorem</a>, whose only proof, by computer, has never been verified by a human.<br /><dl><dd> <table cellspacing="15" style="border: 1px solid #ddd; margin: auto; text-align: center;"><tbody><tr> <td><a class="image" href="http://en.wikipedia.org/wiki/File:Illustration_to_Euclid%27s_proof_of_the_Pythagorean_theorem.svg"><img alt="Illustration to Euclid's proof of the Pythagorean theorem.svg" height="104" src="http://upload.wikimedia.org/wikipedia/commons/thumb/2/26/Illustration_to_Euclid%27s_proof_of_the_Pythagorean_theorem.svg/96px-Illustration_to_Euclid%27s_proof_of_the_Pythagorean_theorem.svg.png" width="96" /></a></td> <td><a class="image" href="http://en.wikipedia.org/wiki/File:Sine_cosine_plot.svg"><img alt="Sine cosine plot.svg" height="64" src="http://upload.wikimedia.org/wikipedia/commons/thumb/3/38/Sine_cosine_plot.svg/96px-Sine_cosine_plot.svg.png" width="96" /></a></td> <td><a class="image" href="http://en.wikipedia.org/wiki/File:Hyperbolic_triangle.svg"><img alt="Hyperbolic triangle.svg" height="64" src="http://upload.wikimedia.org/wikipedia/commons/thumb/8/89/Hyperbolic_triangle.svg/96px-Hyperbolic_triangle.svg.png" width="96" /></a></td> <td><a class="image" href="http://en.wikipedia.org/wiki/File:Torus.png"><img alt="Torus.png" height="61" src="http://upload.wikimedia.org/wikipedia/commons/thumb/1/17/Torus.png/96px-Torus.png" width="96" /></a></td> <td><a class="image" href="http://en.wikipedia.org/wiki/File:Mandel_zoom_07_satellite.jpg"><img alt="Mandel zoom 07 satellite.jpg" height="72" src="http://upload.wikimedia.org/wikipedia/commons/thumb/b/b3/Mandel_zoom_07_satellite.jpg/96px-Mandel_zoom_07_satellite.jpg" width="96" /></a></td> <td><a class="image" href="http://en.wikipedia.org/wiki/File:Measure_illustration.png"><img alt="Measure illustration.png" height="115" src="http://upload.wikimedia.org/wikipedia/commons/thumb/a/a6/Measure_illustration.png/70px-Measure_illustration.png" width="70" /></a></td> </tr><tr> <td><a href="http://en.wikipedia.org/wiki/Geometry">Geometry</a></td> <td><a href="http://en.wikipedia.org/wiki/Trigonometry">Trigonometry</a></td> <td><a href="http://en.wikipedia.org/wiki/Differential_geometry">Differential geometry</a></td> <td><a href="http://en.wikipedia.org/wiki/Topology">Topology</a></td> <td><a href="http://en.wikipedia.org/wiki/Fractal" title="Fractal">Fractal geometry</a></td> <td><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Measure_theory" title="Measure theory">Measure theory</a></td> </tr></tbody></table></dd></dl><h4><span class="mw-headline" id="Change">Change</span></h4>Understanding and describing change is a common theme in the <a href="http://en.wikipedia.org/wiki/Natural_science" title="Natural science">natural sciences</a>, and <a href="http://en.wikipedia.org/wiki/Calculus">calculus</a> was developed as a powerful tool to investigate it. <a href="http://en.wikipedia.org/wiki/Function_%28mathematics%29" title="Function (mathematics)">Functions</a> arise here, as a central concept describing a changing quantity. The rigorous study of <a href="http://en.wikipedia.org/wiki/Real_number" title="Real number">real numbers</a> and functions of a real variable is known as <a href="http://en.wikipedia.org/wiki/Real_analysis">real analysis</a>, with <a href="http://en.wikipedia.org/wiki/Complex_analysis">complex analysis</a> the equivalent field for the <a href="http://en.wikipedia.org/wiki/Complex_number" title="Complex number">complex numbers</a>. <a href="http://en.wikipedia.org/wiki/Functional_analysis">Functional analysis</a> focuses attention on (typically infinite-dimensional) <a href="http://en.wikipedia.org/wiki/Space#Mathematics" title="Space">spaces</a> of functions. One of many applications of functional analysis is <a href="http://en.wikipedia.org/wiki/Quantum_mechanics">quantum mechanics</a>. Many problems lead naturally to relationships between a quantity and its rate of change, and these are studied as <a href="http://en.wikipedia.org/wiki/Differential_equation" title="Differential equation">differential equations</a>. Many phenomena in nature can be described by <a href="http://en.wikipedia.org/wiki/Dynamical_system" title="Dynamical system">dynamical systems</a>; <a href="http://en.wikipedia.org/wiki/Chaos_theory">chaos theory</a> makes precise the ways in which many of these systems exhibit unpredictable yet still <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Deterministic_system_%28mathematics%29" title="Deterministic system (mathematics)">deterministic</a> behavior.<br /><table cellspacing="20" style="border: 1px solid #ddd; margin: auto; text-align: center;"><tbody><tr> <td><a class="image" href="http://en.wikipedia.org/wiki/File:Integral_as_region_under_curve.svg"><img alt="Integral as region under curve.svg" height="84" src="http://upload.wikimedia.org/wikipedia/commons/thumb/f/f2/Integral_as_region_under_curve.svg/96px-Integral_as_region_under_curve.svg.png" width="96" /></a></td> <td><a class="image" href="http://en.wikipedia.org/wiki/File:Vector_field.svg"><img alt="Vector field.svg" height="96" src="http://upload.wikimedia.org/wikipedia/commons/thumb/c/c2/Vector_field.svg/96px-Vector_field.svg.png" width="96" /></a></td> <td><a class="image" href="http://en.wikipedia.org/wiki/File:Airflow-Obstructed-Duct.png"><img alt="Airflow-Obstructed-Duct.png" height="69" src="http://upload.wikimedia.org/wikipedia/commons/thumb/1/17/Airflow-Obstructed-Duct.png/96px-Airflow-Obstructed-Duct.png" width="96" /></a></td> <td><a class="image" href="http://en.wikipedia.org/wiki/File:Limitcycle.jpg"><img alt="Limitcycle.jpg" height="72" src="http://upload.wikimedia.org/wikipedia/commons/thumb/a/a1/Limitcycle.jpg/96px-Limitcycle.jpg" width="96" /></a></td> <td><a class="image" href="http://en.wikipedia.org/wiki/File:Lorenz_attractor.svg"><img alt="Lorenz attractor.svg" height="96" src="http://upload.wikimedia.org/wikipedia/commons/thumb/f/f4/Lorenz_attractor.svg/96px-Lorenz_attractor.svg.png" width="96" /></a></td> <td><a class="image" href="http://en.wikipedia.org/wiki/File:Princ_Argument_C1.svg"><img alt="Princ Argument C1.svg" height="76" src="http://upload.wikimedia.org/wikipedia/commons/thumb/7/7a/Princ_Argument_C1.svg/96px-Princ_Argument_C1.svg.png" width="96" /></a></td> </tr><tr> <td><a href="http://en.wikipedia.org/wiki/Calculus">Calculus</a></td> <td><a href="http://en.wikipedia.org/wiki/Vector_calculus">Vector calculus</a></td> <td><a href="http://en.wikipedia.org/wiki/Differential_equation" title="Differential equation">Differential equations</a></td> <td><a href="http://en.wikipedia.org/wiki/Dynamical_system" title="Dynamical system">Dynamical systems</a></td> <td><a href="http://en.wikipedia.org/wiki/Chaos_theory">Chaos theory</a></td> <td><a href="http://en.wikipedia.org/wiki/Complex_analysis">Complex analysis</a></td> </tr></tbody></table><h3><span class="mw-headline" id="Applied_mathematics">Applied mathematics</span></h3><a href="http://en.wikipedia.org/wiki/Applied_mathematics">Applied mathematics</a> considers the use of abstract mathematical tools in solving concrete problems in the <a href="http://en.wikipedia.org/wiki/Science" title="Science">sciences</a>, <a href="http://en.wikipedia.org/wiki/Business">business</a>, and other areas.<br />Applied mathematics has significant overlap with the discipline of <a href="http://en.wikipedia.org/wiki/Statistics">statistics</a>, whose theory is formulated mathematically, especially with <a href="http://en.wikipedia.org/wiki/Probability_theory">probability theory</a>. Statisticians (working as part of a research project) "create data that makes sense" with <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Random_sampling" title="Random sampling">random sampling</a> and with randomized <a href="http://en.wikipedia.org/wiki/Design_of_experiments" title="Design of experiments">experiments</a>; the design of a statistical sample or experiment specifies the analysis of the data (before the data be available). When reconsidering data from experiments and samples or when analyzing data from <a href="http://en.wikipedia.org/wiki/Observational_study" title="Observational study">observational studies</a>, statisticians "make sense of the data" using the art of <a href="http://en.wikipedia.org/wiki/Statistical_model" title="Statistical model">modelling</a> and the theory of <a href="http://en.wikipedia.org/wiki/Statistical_inference" title="Statistical inference">inference</a> – with <a href="http://en.wikipedia.org/wiki/Model_selection">model selection</a> and <a href="http://en.wikipedia.org/wiki/Estimation">estimation</a>; the estimated models and consequential <a href="http://en.wikipedia.org/wiki/Scientific_method#Predictions_from_the_hypothesis" title="Scientific method">predictions</a> should be <a href="http://en.wikipedia.org/wiki/Statistical_hypothesis_testing" title="Statistical hypothesis testing">tested</a> on <a href="http://en.wikipedia.org/wiki/Scientific_method#Evaluation_and_improvement" title="Scientific method">new data</a>.<sup class="reference" id="cite_ref-33"><a href="http://en.wikipedia.org/wiki/Mathematics#cite_note-33"><span>[</span>34<span>]</span></a></sup><br /><a href="http://en.wikipedia.org/wiki/Computational_mathematics">Computational mathematics</a> proposes and studies methods for solving <a href="http://en.wikipedia.org/wiki/Mathematical_problem" title="Mathematical problem">mathematical problems</a> that are typically too large for human numerical capacity. <a href="http://en.wikipedia.org/wiki/Numerical_analysis">Numerical analysis</a> studies methods for problems in <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Analysis_%28mathematics%29" title="Analysis (mathematics)">analysis</a> using ideas of <a href="http://en.wikipedia.org/wiki/Functional_analysis">functional analysis</a> and techniques of <a href="http://en.wikipedia.org/wiki/Approximation_theory">approximation theory</a>; numerical analysis includes the study of <a href="http://en.wikipedia.org/wiki/Approximation">approximation</a> and <a href="http://en.wikipedia.org/wiki/Discretization">discretization</a> broadly with special concern for <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Rounding_error" title="Rounding error">rounding errors</a>. Other areas of computational mathematics include <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Computer_algebra" title="Computer algebra">computer algebra</a> and <a href="http://en.wikipedia.org/wiki/Symbolic_computation">symbolic computation</a>.<br /><table cellspacing="20" style="border: 1px solid #ddd; margin: 0 auto; text-align: center;"><tbody><tr> <td><a class="image" href="http://en.wikipedia.org/wiki/File:Gravitation_space_source.png"><img alt="Gravitation space source.png" height="64" src="http://upload.wikimedia.org/wikipedia/commons/thumb/2/26/Gravitation_space_source.png/96px-Gravitation_space_source.png" width="96" /></a></td> <td><a class="image" href="http://en.wikipedia.org/wiki/File:BernoullisLawDerivationDiagram.svg"><img alt="BernoullisLawDerivationDiagram.svg" height="45" src="http://upload.wikimedia.org/wikipedia/commons/thumb/2/20/BernoullisLawDerivationDiagram.svg/96px-BernoullisLawDerivationDiagram.svg.png" width="96" /></a></td> <td><a class="image" href="http://en.wikipedia.org/wiki/File:Composite_trapezoidal_rule_illustration_small.svg"><img alt="Composite trapezoidal rule illustration small.svg" height="64" src="http://upload.wikimedia.org/wikipedia/commons/thumb/d/dd/Composite_trapezoidal_rule_illustration_small.svg/96px-Composite_trapezoidal_rule_illustration_small.svg.png" width="96" /></a></td> <td><a class="image" href="http://en.wikipedia.org/wiki/File:Maximum_boxed.png"><img alt="Maximum boxed.png" height="91" src="http://upload.wikimedia.org/wikipedia/commons/thumb/1/1a/Maximum_boxed.png/96px-Maximum_boxed.png" width="96" /></a></td> <td><a class="image" href="http://en.wikipedia.org/wiki/File:Two_red_dice_01.svg"><img alt="Two red dice 01.svg" height="62" src="http://upload.wikimedia.org/wikipedia/commons/thumb/3/36/Two_red_dice_01.svg/96px-Two_red_dice_01.svg.png" width="96" /></a></td> <td><a class="image" href="http://en.wikipedia.org/wiki/File:Oldfaithful3.png"><img alt="Oldfaithful3.png" height="96" src="http://upload.wikimedia.org/wikipedia/commons/thumb/0/0f/Oldfaithful3.png/96px-Oldfaithful3.png" width="96" /></a></td> <td><a class="image" href="http://en.wikipedia.org/wiki/File:Caesar3.svg"><img alt="Caesar3.svg" height="40" src="http://upload.wikimedia.org/wikipedia/commons/thumb/2/2b/Caesar3.svg/96px-Caesar3.svg.png" width="96" /></a></td> </tr><tr> <td><a href="http://en.wikipedia.org/wiki/Mathematical_physics">Mathematical physics</a></td> <td><a href="http://en.wikipedia.org/wiki/Fluid_dynamics">Fluid dynamics</a></td> <td><a href="http://en.wikipedia.org/wiki/Numerical_analysis">Numerical analysis</a></td> <td><a href="http://en.wikipedia.org/wiki/Optimization_%28mathematics%29" title="Optimization (mathematics)">Optimization</a></td> <td><a href="http://en.wikipedia.org/wiki/Probability_theory">Probability theory</a></td> <td><a href="http://en.wikipedia.org/wiki/Statistics">Statistics</a></td> <td><a href="http://en.wikipedia.org/wiki/Cryptography">Cryptography</a></td> </tr><tr> <td><a class="image" href="http://en.wikipedia.org/wiki/File:Market_Data_Index_NYA_on_20050726_202628_UTC.png"><img alt="Market Data Index NYA on 20050726 202628 UTC.png" height="64" src="http://upload.wikimedia.org/wikipedia/commons/thumb/4/46/Market_Data_Index_NYA_on_20050726_202628_UTC.png/96px-Market_Data_Index_NYA_on_20050726_202628_UTC.png" width="96" /></a></td> <td><a class="image" href="http://en.wikipedia.org/wiki/File:Arbitrary-gametree-solved.svg"><img alt="Arbitrary-gametree-solved.svg" height="65" src="http://upload.wikimedia.org/wikipedia/commons/thumb/d/d7/Arbitrary-gametree-solved.svg/96px-Arbitrary-gametree-solved.svg.png" width="96" /></a></td> <td><a class="image" href="http://en.wikipedia.org/wiki/File:Signal_transduction_v1.png"><img alt="Signal transduction v1.png" height="70" src="http://upload.wikimedia.org/wikipedia/commons/thumb/2/29/Signal_transduction_v1.png/96px-Signal_transduction_v1.png" width="96" /></a></td> <td><a class="image" href="http://en.wikipedia.org/wiki/File:Ch4-structure.png"><img alt="Ch4-structure.png" height="99" src="http://upload.wikimedia.org/wikipedia/commons/thumb/5/55/Ch4-structure.png/96px-Ch4-structure.png" width="96" /></a></td> <td><a class="image" href="http://en.wikipedia.org/wiki/File:GDP_PPP_Per_Capita_IMF_2008.png"><img alt="GDP PPP Per Capita IMF 2008.png" height="44" src="http://upload.wikimedia.org/wikipedia/commons/thumb/f/fa/GDP_PPP_Per_Capita_IMF_2008.png/96px-GDP_PPP_Per_Capita_IMF_2008.png" width="96" /></a></td> <td><a class="image" href="http://en.wikipedia.org/wiki/File:Simple_feedback_control_loop2.png"><img alt="Simple feedback control loop2.png" height="33" src="http://upload.wikimedia.org/wikipedia/commons/thumb/4/45/Simple_feedback_control_loop2.png/96px-Simple_feedback_control_loop2.png" width="96" /></a></td> </tr><tr> <td><a href="http://en.wikipedia.org/wiki/Mathematical_finance">Mathematical finance</a></td> <td><a href="http://en.wikipedia.org/wiki/Game_theory">Game theory</a></td> <td><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Mathematical_biology" title="Mathematical biology">Mathematical biology</a></td> <td><a href="http://en.wikipedia.org/wiki/Mathematical_chemistry">Mathematical chemistry</a></td> <td><a href="http://en.wikipedia.org/wiki/Mathematical_economics">Mathematical economics</a></td> <td><a href="http://en.wikipedia.org/wiki/Control_theory">Control theory</a></td> </tr></tbody></table><h2><span class="mw-headline" id="Mathematics_as_profession">Mathematics as profession</span></h2>The best-known award in mathematics is the <span style="white-space: nowrap;"><a href="http://en.wikipedia.org/wiki/Fields_Medal">Fields Medal</a></span>,<sup class="reference" id="cite_ref-34"><a href="http://en.wikipedia.org/wiki/Mathematics#cite_note-34"><span>[</span>35<span>]</span></a></sup><sup class="reference" id="cite_ref-35"><a href="http://en.wikipedia.org/wiki/Mathematics#cite_note-35"><span>[</span>36<span>]</span></a></sup> established in 1936 and now awarded every 4 years. It is often considered the equivalent of science's <a href="http://en.wikipedia.org/wiki/Nobel_Prize" title="Nobel Prize">Nobel Prizes</a>. The <a href="http://en.wikipedia.org/wiki/Wolf_Prize_in_Mathematics">Wolf Prize in Mathematics</a>, instituted in 1978, recognizes lifetime achievement, and another major international award, the <a href="http://en.wikipedia.org/wiki/Abel_Prize">Abel Prize</a>, was introduced in 2003. The <a href="http://en.wikipedia.org/wiki/Chern_Medal">Chern Medal</a> was introduced in 2010 to recognize lifetime achievement. These are awarded for a particular body of work, which may be innovation, or resolution of an outstanding problem in an established field.<br />A famous list of 23 <a href="http://en.wikipedia.org/wiki/Open_problem" title="Open problem">open problems</a>, called "<a href="http://en.wikipedia.org/wiki/Hilbert%27s_problems">Hilbert's problems</a>", was compiled in 1900 by German mathematician <a href="http://en.wikipedia.org/wiki/David_Hilbert">David Hilbert</a>. This list achieved great celebrity among mathematicians, and at least nine of the problems have now been solved. A new list of seven important problems, titled the "<a href="http://en.wikipedia.org/wiki/Millennium_Prize_Problems">Millennium Prize Problems</a>", was published in 2000. Solution of each of these problems carries a $1 million reward, and only one (the <a href="http://en.wikipedia.org/wiki/Riemann_hypothesis">Riemann hypothesis</a>) is duplicated in Hilbert's problems.<br /><br /><h2><span class="mw-headline" id="See_also">See also</span></h2><div class="noprint tright portal" style="border: solid #aaa 1px; margin: 0.5em 0 0.5em 0.5em;"> <table style="background: #f9f9f9; font-size: 85%; line-height: 110%; max-width: 175px;"><tbody><tr> <td><a class="image" href="http://en.wikipedia.org/wiki/File:Nuvola_apps_edu_mathematics_blue-p.svg"><img alt="Nuvola apps edu mathematics blue-p.svg" height="28" src="http://upload.wikimedia.org/wikipedia/commons/thumb/3/3e/Nuvola_apps_edu_mathematics_blue-p.svg/28px-Nuvola_apps_edu_mathematics_blue-p.svg.png" width="28" /></a></td> <td style="padding: 0 0.2em;"><i><b><a href="http://en.wikipedia.org/wiki/Portal:Mathematics" title="Portal:Mathematics">Mathematics portal</a></b></i></td> </tr></tbody></table></div><table class="metadata mbox-small" style="background-color: #f9f9f9; border: 1px solid #aaa;"><tbody><tr> <td class="mbox-image"><a href="http://en.wikipedia.org/wiki/Wikipedia:Books" title="Wikipedia:Books"><img alt="" height="30" src="http://upload.wikimedia.org/wikipedia/commons/thumb/a/a8/Office-book.svg/30px-Office-book.svg.png" width="30" /></a></td> <td class="mbox-text"><i><b><a href="http://en.wikipedia.org/wiki/Book:Mathematics" title="Book:Mathematics">Book: Mathematics</a></b></i></td> </tr><tr> <td class="mbox-text" colspan="2"><small><a href="http://en.wikipedia.org/wiki/Wikipedia:Books" title="Wikipedia:Books">Wikipedia Books</a> are collections of articles that can be downloaded or ordered in print.</small></td> </tr></tbody></table><div class="rellink relarticle mainarticle">Main article: <a href="http://en.wikipedia.org/wiki/Lists_of_mathematics_topics">Lists of mathematics topics</a></div><div style="-moz-column-count: 2; -webkit-column-count: 2; column-count: 2;"> <ul><li><a href="http://en.wikipedia.org/wiki/Definitions_of_mathematics">Definitions of mathematics</a></li><li><a href="http://en.wikipedia.org/wiki/Dyscalculia">Dyscalculia</a></li><li><a href="http://en.wikipedia.org/wiki/Iatromathematicians">Iatromathematicians</a></li><li><a href="http://en.wikipedia.org/wiki/List_of_mathematics_competitions">List of mathematics competitions</a></li><li><a href="http://en.wikipedia.org/wiki/Mathematical_anxiety">Mathematical anxiety</a></li><li><a href="http://en.wikipedia.org/wiki/Mathematical_game">Mathematical game</a></li><li><a href="http://en.wikipedia.org/wiki/Mathematical_model">Mathematical model</a></li><li><a href="http://en.wikipedia.org/wiki/Mathematics_and_art">Mathematics and art</a></li><li><a href="http://en.wikipedia.org/wiki/Mathematics_education">Mathematics education</a></li><li><a href="http://en.wikipedia.org/wiki/Pseudomathematics">Pseudomathematics</a></li></ul></div><h2><span class="mw-headline" id="Notes">Notes</span></h2><div class="reflist references-column-count references-column-count-2" style="-moz-column-count: 2; -webkit-column-count: 2; column-count: 2; list-style-type: decimal;"> <ol class="references"><li id="cite_note-0"><b><a href="http://en.wikipedia.org/wiki/Mathematics#cite_ref-0">^</a></b> No likeness or description of Euclid's physical appearance made during his lifetime survived antiquity. Therefore, Euclid's depiction in works of art depends on the artist's imagination (<i>see <a href="http://en.wikipedia.org/wiki/Euclid">Euclid</a></i>).</li><li id="cite_note-1"><b><a href="http://en.wikipedia.org/wiki/Mathematics#cite_ref-1">^</a></b> <a href="http://en.wikipedia.org/wiki/Lynn_Steen" title="Lynn Steen">Steen, L.A.</a> (April 29, 1988). <i>The Science of Patterns</i> <a href="http://en.wikipedia.org/wiki/Science_%28journal%29" title="Science (journal)">Science</a>, 240: 611–616. and summarized at <a class="external text" href="http://www.ascd.org/publications/curriculum-handbook/409/chapters/The-Future-of-Mathematics-Education.aspx" rel="nofollow">Association for Supervision and Curriculum Development</a>, ascd.org</li><li id="cite_note-2"><b><a href="http://en.wikipedia.org/wiki/Mathematics#cite_ref-2">^</a></b> <a href="http://en.wikipedia.org/wiki/Keith_Devlin" title="Keith Devlin">Devlin, Keith</a>, <i>Mathematics: The Science of Patterns: The Search for Order in Life, Mind and the Universe</i> (Scientific American Paperback Library) 1996, <a class="internal mw-magiclink-isbn" href="http://en.wikipedia.org/wiki/Special:BookSources/9780716750475">ISBN 978-0-7167-5047-5</a></li><li id="cite_note-3"><b><a href="http://en.wikipedia.org/wiki/Mathematics#cite_ref-3">^</a></b> Jourdain.</li><li id="cite_note-4"><b><a href="http://en.wikipedia.org/wiki/Mathematics#cite_ref-4">^</a></b> Eves</li><li id="cite_note-5"><b><a href="http://en.wikipedia.org/wiki/Mathematics#cite_ref-5">^</a></b> Peirce, p. 97.</li><li id="cite_note-certain-6">^ <a href="http://en.wikipedia.org/wiki/Mathematics#cite_ref-certain_6-0"><sup><i><b>a</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Mathematics#cite_ref-certain_6-1"><sup><i><b>b</b></i></sup></a> Einstein, p. 28. The quote is Einstein's answer to the question: "how can it be that mathematics, being after all a product of human thought which is independent of experience, is so admirably appropriate to the objects of reality?" He, too, is concerned with <i><a href="http://en.wikipedia.org/wiki/The_Unreasonable_Effectiveness_of_Mathematics_in_the_Natural_Sciences">The Unreasonable Effectiveness of Mathematics in the Natural Sciences</a></i>.</li><li id="cite_note-7"><b><a href="http://en.wikipedia.org/wiki/Mathematics#cite_ref-7">^</a></b> Peterson</li><li id="cite_note-8"><b><a href="http://en.wikipedia.org/wiki/Mathematics#cite_ref-8">^</a></b> Both senses can be found in Plato. Liddell and Scott, <i>s.voce</i>μαθηματικός</li><li id="cite_note-9"><b><a href="http://en.wikipedia.org/wiki/Mathematics#cite_ref-9">^</a></b> <i><a href="http://en.wikipedia.org/wiki/The_Oxford_Dictionary_of_English_Etymology">The Oxford Dictionary of English Etymology</a></i>, <i><a href="http://en.wikipedia.org/wiki/Oxford_English_Dictionary">Oxford English Dictionary</a></i>, <i>sub</i> "mathematics", "mathematic", "mathematics"</li><li id="cite_note-10"><b><a href="http://en.wikipedia.org/wiki/Mathematics#cite_ref-10">^</a></b> <span class="citation Journal">S. Dehaene; G. Dehaene-Lambertz; L. Cohen (Aug 1998). "Abstract representations of numbers in the animal and human brain". <i>Trends in Neuroscience</i> <b>21</b> (8): 355–361. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.1016%2FS0166-2236%2898%2901263-6" rel="nofollow">10.1016/S0166-2236(98)01263-6</a>. <a class="mw-redirect" href="http://en.wikipedia.org/wiki/PubMed_Identifier" title="PubMed Identifier">PMID</a> <a class="external text" href="http://www.ncbi.nlm.nih.gov/pubmed/9720604" rel="nofollow">9720604</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Abstract+representations+of+numbers+in+the+animal+and+human+brain&rft.jtitle=Trends+in+Neuroscience&rft.aulast=S.+Dehaene&rft.au=S.+Dehaene&rft.au=G.+Dehaene-Lambertz&rft.au=L.+Cohen&rft.date=Aug+1998&rft.volume=21&rft.issue=8&rft.pages=355%E2%80%93361&rft_id=info:doi/10.1016%2FS0166-2236%2898%2901263-6&rft_id=info:pmid/9720604&rfr_id=info:sid/en.wikipedia.org:Mathematics"></span></li><li id="cite_note-11"><b><a href="http://en.wikipedia.org/wiki/Mathematics#cite_ref-11">^</a></b> See, for example, Raymond L. Wilder, <i>Evolution of Mathematical Concepts; an Elementary Study</i>, <i>passim</i></li><li id="cite_note-12"><b><a href="http://en.wikipedia.org/wiki/Mathematics#cite_ref-12">^</a></b> Kline 1990, Chapter 1.</li><li id="cite_note-13"><b><a href="http://en.wikipedia.org/wiki/Mathematics#cite_ref-13">^</a></b> "<i><a class="external text" href="http://books.google.com/books?id=drnY3Vjix3kC&pg=PA1&dq&hl=en#v=onepage&q=&f=false" rel="nofollow">A History of Greek Mathematics: From Thales to Euclid</a></i>". Thomas Little Heath (1981). <a class="internal mw-magiclink-isbn" href="http://en.wikipedia.org/wiki/Special:BookSources/0486240738">ISBN 0-486-24073-8</a></li><li id="cite_note-14"><b><a href="http://en.wikipedia.org/wiki/Mathematics#cite_ref-14">^</a></b> Sevryuk</li><li id="cite_note-15"><b><a href="http://en.wikipedia.org/wiki/Mathematics#cite_ref-15">^</a></b> <span class="citation book">Johnson, Gerald W.; Lapidus, Michel L. (2002). <i>The Feynman Integral and Feynman's Operational Calculus</i>. <a href="http://en.wikipedia.org/wiki/Oxford_University_Press">Oxford University Press</a>. <a href="http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="http://en.wikipedia.org/wiki/Special:BookSources/0821824139" title="Special:BookSources/0821824139">0821824139</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Feynman+Integral+and+Feynman%27s+Operational+Calculus&rft.aulast=Johnson%2C+Gerald+W.%3B+Lapidus%2C+Michel+L.&rft.au=Johnson%2C+Gerald+W.%3B+Lapidus%2C+Michel+L.&rft.date=2002&rft.pub=%5B%5BOxford+University+Press%5D%5D&rft.isbn=0821824139&rfr_id=info:sid/en.wikipedia.org:Mathematics"></span></li><li id="cite_note-16"><b><a href="http://en.wikipedia.org/wiki/Mathematics#cite_ref-16">^</a></b> <span class="citation Journal">Wigner, Eugene (1960). <a class="external text" href="http://www.dartmouth.edu/%7Ematc/MathDrama/reading/Wigner.html" rel="nofollow">"The Unreasonable Effectiveness of Mathematics in the Natural Sciences"</a>. <i><a href="http://en.wikipedia.org/wiki/Communications_on_Pure_and_Applied_Mathematics">Communications on Pure and Applied Mathematics</a></i> <b>13</b> (1): 1–14.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=The+Unreasonable+Effectiveness+of+Mathematics+in+the+Natural+Sciences&rft.jtitle=%5B%5BCommunications+on+Pure+and+Applied+Mathematics%5D%5D&rft.aulast=Wigner&rft.aufirst=Eugene&rft.au=Wigner%2C%26%2332%3BEugene&rft.date=1960&rft.volume=13&rft.issue=1&rft.pages=1%E2%80%9314&rft_id=http%3A%2F%2Fwww.dartmouth.edu%2F%7Ematc%2FMathDrama%2Freading%2FWigner.html&rfr_id=info:sid/en.wikipedia.org:Mathematics"></span></li><li id="cite_note-17"><b><a href="http://en.wikipedia.org/wiki/Mathematics#cite_ref-17">^</a></b> <span class="citation web"><a class="external text" href="http://www.ams.org/mathscinet/msc/pdfs/classification2010.pdf" rel="nofollow">"Mathematics Subject Classification 2010"</a> (PDF)<span class="reference-accessdate">. Retrieved 2010-11-09</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Mathematics+Subject+Classification+2010&rft.atitle=&rft_id=http%3A%2F%2Fwww.ams.org%2Fmathscinet%2Fmsc%2Fpdfs%2Fclassification2010.pdf&rfr_id=info:sid/en.wikipedia.org:Mathematics"></span></li><li id="cite_note-18"><b><a href="http://en.wikipedia.org/wiki/Mathematics#cite_ref-18">^</a></b> <span class="citation book">Hardy, G. H. (1940). <i>A Mathematician's Apology</i>. Cambridge University Press. <a href="http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="http://en.wikipedia.org/wiki/Special:BookSources/0521427061" title="Special:BookSources/0521427061">0521427061</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=A+Mathematician%27s+Apology&rft.aulast=Hardy%2C+G.+H.&rft.au=Hardy%2C+G.+H.&rft.date=1940&rft.pub=Cambridge+University+Press&rft.isbn=0521427061&rfr_id=info:sid/en.wikipedia.org:Mathematics"></span></li><li id="cite_note-19"><b><a href="http://en.wikipedia.org/wiki/Mathematics#cite_ref-19">^</a></b> <span class="citation book">Gold, Bonnie; Simons, Rogers A. (2008). <i>Proof and Other Dilemmas: Mathematics and Philosophy</i>. MAA.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Proof+and+Other+Dilemmas%3A+Mathematics+and+Philosophy&rft.aulast=Gold%2C+Bonnie%3B+Simons%2C+Rogers+A.&rft.au=Gold%2C+Bonnie%3B+Simons%2C+Rogers+A.&rft.date=2008&rft.pub=MAA&rfr_id=info:sid/en.wikipedia.org:Mathematics"></span></li><li id="cite_note-20"><b><a href="http://en.wikipedia.org/wiki/Mathematics#cite_ref-20">^</a></b> <span class="citation book">Aigner, Martin; Ziegler, Gunter M. (2001). <i>Proofs from the Book</i>. Springer. <a href="http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="http://en.wikipedia.org/wiki/Special:BookSources/3540404600" title="Special:BookSources/3540404600">3540404600</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Proofs+from+the+Book&rft.aulast=Aigner%2C+Martin%3B+Ziegler%2C+Gunter+M.&rft.au=Aigner%2C+Martin%3B+Ziegler%2C+Gunter+M.&rft.date=2001&rft.pub=Springer&rft.isbn=3540404600&rfr_id=info:sid/en.wikipedia.org:Mathematics"></span></li><li id="cite_note-21"><b><a href="http://en.wikipedia.org/wiki/Mathematics#cite_ref-21">^</a></b> <a class="external text" href="http://jeff560.tripod.com/mathsym.html" rel="nofollow">Earliest Uses of Various Mathematical Symbols</a> (Contains many further references).</li><li id="cite_note-22"><b><a href="http://en.wikipedia.org/wiki/Mathematics#cite_ref-22">^</a></b> Kline, p. 140, on <a href="http://en.wikipedia.org/wiki/Diophantus">Diophantus</a>; p.261, on <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Franciscus_Vieta" title="Franciscus Vieta">Vieta</a>.</li><li id="cite_note-23"><b><a href="http://en.wikipedia.org/wiki/Mathematics#cite_ref-23">^</a></b> See <i><a class="mw-redirect" href="http://en.wikipedia.org/wiki/False_proof" title="False proof">false proof</a></i> for simple examples of what can go wrong in a formal proof. The <a class="mw-redirect" href="http://en.wikipedia.org/wiki/History_of_the_four_color_theorem" title="History of the four color theorem">history of the Four Color Theorem</a> contains examples of false proofs accidentally accepted by other mathematicians at the time.</li><li id="cite_note-24"><b><a href="http://en.wikipedia.org/wiki/Mathematics#cite_ref-24">^</a></b> Ivars Peterson, <i>The Mathematical Tourist</i>, Freeman, 1988, <a class="internal mw-magiclink-isbn" href="http://en.wikipedia.org/wiki/Special:BookSources/0716719533">ISBN 0-7167-1953-3</a>. p. 4 "A few complain that the computer program can't be verified properly", (in reference to the Haken-Apple proof of the Four Color Theorem).</li><li id="cite_note-25"><b><a href="http://en.wikipedia.org/wiki/Mathematics#cite_ref-25">^</a></b> Patrick Suppes, <i>Axiomatic Set Theory</i>, Dover, 1972, <a class="internal mw-magiclink-isbn" href="http://en.wikipedia.org/wiki/Special:BookSources/0486616304">ISBN 0-486-61630-4</a>. p. 1, "Among the many branches of modern mathematics set theory occupies a unique place: with a few rare exceptions the entities which are studied and analyzed in mathematics may be regarded as certain particular sets or classes of objects."</li><li id="cite_note-26"><b><a href="http://en.wikipedia.org/wiki/Mathematics#cite_ref-26">^</a></b> <span class="citation book">Zeidler, Eberhard (2004). <i>Oxford User's Guide to Mathematics</i>. Oxford, UK: Oxford University Press. p. 1188. <a href="http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="http://en.wikipedia.org/wiki/Special:BookSources/0198507631" title="Special:BookSources/0198507631">0198507631</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Oxford+User%27s+Guide+to+Mathematics&rft.aulast=Zeidler&rft.aufirst=Eberhard&rft.au=Zeidler%2C%26%2332%3BEberhard&rft.date=2004&rft.pages=p.%26nbsp%3B1188&rft.place=Oxford%2C+UK&rft.pub=Oxford+University+Press&rft.isbn=0198507631&rfr_id=info:sid/en.wikipedia.org:Mathematics"></span></li><li id="cite_note-27"><b><a href="http://en.wikipedia.org/wiki/Mathematics#cite_ref-27">^</a></b> Waltershausen</li><li id="cite_note-28"><b><a href="http://en.wikipedia.org/wiki/Mathematics#cite_ref-28">^</a></b> <span class="citation book">Shasha, Dennis Elliot; Lazere, Cathy A. (1998). <i>Out of Their Minds: The Lives and Discoveries of 15 Great Computer Scientists</i>. Springer. p. 228.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Out+of+Their+Minds%3A+The+Lives+and+Discoveries+of+15+Great+Computer+Scientists&rft.aulast=Shasha%2C+Dennis+Elliot%3B+Lazere%2C+Cathy+A.&rft.au=Shasha%2C+Dennis+Elliot%3B+Lazere%2C+Cathy+A.&rft.date=1998&rft.pages=p.%26nbsp%3B228&rft.pub=Springer&rfr_id=info:sid/en.wikipedia.org:Mathematics"></span></li><li id="cite_note-29"><b><a href="http://en.wikipedia.org/wiki/Mathematics#cite_ref-29">^</a></b> Popper 1995, p. 56</li><li id="cite_note-30"><b><a href="http://en.wikipedia.org/wiki/Mathematics#cite_ref-30">^</a></b> Ziman</li><li id="cite_note-31"><b><a href="http://en.wikipedia.org/wiki/Mathematics#cite_ref-31">^</a></b> Luke Howard Hodgkin & Luke Hodgkin, <i>A History of Mathematics</i>, Oxford University Press, 2005.</li><li id="cite_note-32"><b><a href="http://en.wikipedia.org/wiki/Mathematics#cite_ref-32">^</a></b> <a class="external text" href="http://www.claymath.org/millennium/P_vs_NP/" rel="nofollow">Clay Mathematics Institute</a>, P=NP, claymath.org</li><li id="cite_note-33"><b><a href="http://en.wikipedia.org/wiki/Mathematics#cite_ref-33">^</a></b> Like other mathematical sciences such as <a href="http://en.wikipedia.org/wiki/Physics">physics</a> and <a href="http://en.wikipedia.org/wiki/Computer_science">computer science</a>, statistics is an autonomous discipline rather than a branch of applied mathematics. Like research physicists and computer scientists, research statisticians are mathematical scientists. Many statisticians have a degree in mathematics, and some statisticians are also mathematicians.</li><li id="cite_note-34"><b><a href="http://en.wikipedia.org/wiki/Mathematics#cite_ref-34">^</a></b> "<i>The Fields Medal is now indisputably the best known and most influential award in mathematics.</i>" Monastyrsky</li><li id="cite_note-35"><b><a href="http://en.wikipedia.org/wiki/Mathematics#cite_ref-35">^</a></b> Riehm</li></ol></div><h2><span class="mw-headline" id="References">References</span></h2><div class="refbegin references-column-count references-column-count-2" style="-moz-column-count: 2; -webkit-column-count: 2; column-count: 2;"> <ul><li>Benson, Donald C., <i>The Moment of Proof: Mathematical Epiphanies</i>, <a href="http://en.wikipedia.org/wiki/Oxford_University_Press">Oxford University Press</a>, USA; New Ed edition (December 14, 2000). <a class="internal mw-magiclink-isbn" href="http://en.wikipedia.org/wiki/Special:BookSources/0195139194">ISBN 0-19-513919-4</a>.</li><li><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Carl_B._Boyer" title="Carl B. Boyer">Boyer, Carl B.</a>, <i>A History of Mathematics</i>, Wiley; 2 edition (March 6, 1991). <a class="internal mw-magiclink-isbn" href="http://en.wikipedia.org/wiki/Special:BookSources/0471543977">ISBN 0-471-54397-7</a>. — A concise history of mathematics from the Concept of Number to contemporary Mathematics.</li><li>Courant, R. and H. Robbins, <i>What Is Mathematics? : An Elementary Approach to Ideas and Methods</i>, Oxford University Press, USA; 2 edition (July 18, 1996). <a class="internal mw-magiclink-isbn" href="http://en.wikipedia.org/wiki/Special:BookSources/0195105192">ISBN 0-19-510519-2</a>.</li><li><a href="http://en.wikipedia.org/wiki/Philip_J._Davis" title="Philip J. Davis">Davis, Philip J.</a> and <a href="http://en.wikipedia.org/wiki/Reuben_Hersh" title="Reuben Hersh">Hersh, Reuben</a>, <i><a href="http://en.wikipedia.org/wiki/The_Mathematical_Experience">The Mathematical Experience</a></i>. Mariner Books; Reprint edition (January 14, 1999). <a class="internal mw-magiclink-isbn" href="http://en.wikipedia.org/wiki/Special:BookSources/0395929687">ISBN 0-395-92968-7</a>. — A gentle introduction to the world of mathematics.</li><li><span class="citation Journal"><a href="http://en.wikipedia.org/wiki/Albert_Einstein" title="Albert Einstein">Einstein, Albert</a> (1923). <i>Sidelights on Relativity (Geometry and Experience)</i>. P. Dutton., Co.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Sidelights+on+Relativity+%28Geometry+and+Experience%29&rft.aulast=Einstein&rft.aufirst=Albert&rft.au=Einstein%2C%26%2332%3BAlbert&rft.date=1923&rft.pub=P.+Dutton.%2C+Co&rfr_id=info:sid/en.wikipedia.org:Mathematics"></span></li><li>Eves, Howard, <i>An Introduction to the History of Mathematics</i>, Sixth Edition, Saunders, 1990, <a class="internal mw-magiclink-isbn" href="http://en.wikipedia.org/wiki/Special:BookSources/0030295580">ISBN 0-03-029558-0</a>.</li><li><a href="http://en.wikipedia.org/wiki/Jan_Gullberg" title="Jan Gullberg">Gullberg, Jan</a>, <i>Mathematics — From the Birth of Numbers</i>. <a href="http://en.wikipedia.org/wiki/W._W._Norton_%26_Company">W. W. Norton & Company</a>; 1st edition (October 1997). <a class="internal mw-magiclink-isbn" href="http://en.wikipedia.org/wiki/Special:BookSources/039304002X">ISBN 0-393-04002-X</a>. — An encyclopedic overview of mathematics presented in clear, simple language.</li><li>Hazewinkel, Michiel (ed.), <i><a href="http://en.wikipedia.org/wiki/Encyclopaedia_of_Mathematics">Encyclopaedia of Mathematics</a></i>. <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Kluwer_Academic_Publishers" title="Kluwer Academic Publishers">Kluwer Academic Publishers</a> 2000. — A translated and expanded version of a Soviet mathematics encyclopedia, in ten (expensive) volumes, the most complete and authoritative work available. Also in paperback and on CD-ROM, and <a class="external text" href="http://eom.springer.de/default.htm" rel="nofollow">online</a>.</li><li>Jourdain, Philip E. B., <i>The Nature of Mathematics</i>, in <i>The World of Mathematics</i>, James R. Newman, editor, <a href="http://en.wikipedia.org/wiki/Dover_Publications">Dover Publications</a>, 2003, <a class="internal mw-magiclink-isbn" href="http://en.wikipedia.org/wiki/Special:BookSources/0486432688">ISBN 0-486-43268-8</a>.</li><li><a href="http://en.wikipedia.org/wiki/Morris_Kline" title="Morris Kline">Kline, Morris</a>, <i>Mathematical Thought from Ancient to Modern Times</i>, Oxford University Press, USA; Paperback edition (March 1, 1990). <a class="internal mw-magiclink-isbn" href="http://en.wikipedia.org/wiki/Special:BookSources/0195061357">ISBN 0-19-506135-7</a>.</li><li><span class="citation Journal">Monastyrsky, Michael (2001) (PDF). <a class="external text" href="http://www.fields.utoronto.ca/aboutus/FieldsMedal_Monastyrsky.pdf" rel="nofollow"><i>Some Trends in Modern Mathematics and the Fields Medal</i></a>. Canadian Mathematical Society<span class="reference-accessdate">. Retrieved 2006-07-28</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Some+Trends+in+Modern+Mathematics+and+the+Fields+Medal&rft.aulast=Monastyrsky%2C+Michael&rft.au=Monastyrsky%2C+Michael&rft.date=2001&rft.pub=Canadian+Mathematical+Society&rft_id=http%3A%2F%2Fwww.fields.utoronto.ca%2Faboutus%2FFieldsMedal_Monastyrsky.pdf&rfr_id=info:sid/en.wikipedia.org:Mathematics"></span></li><li><a href="http://en.wikipedia.org/wiki/Oxford_English_Dictionary">Oxford English Dictionary</a>, second edition, ed. John Simpson and Edmund Weiner, <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Clarendon_Press" title="Clarendon Press">Clarendon Press</a>, 1989, <a class="internal mw-magiclink-isbn" href="http://en.wikipedia.org/wiki/Special:BookSources/0198611862">ISBN 0-19-861186-2</a>.</li><li><i><a href="http://en.wikipedia.org/wiki/The_Oxford_Dictionary_of_English_Etymology">The Oxford Dictionary of English Etymology</a></i>, 1983 reprint. <a class="internal mw-magiclink-isbn" href="http://en.wikipedia.org/wiki/Special:BookSources/0198611129">ISBN 0-19-861112-9</a>.</li><li>Pappas, Theoni, <i>The Joy Of Mathematics</i>, Wide World Publishing; Revised edition (June 1989). <a class="internal mw-magiclink-isbn" href="http://en.wikipedia.org/wiki/Special:BookSources/0933174659">ISBN 0-933174-65-9</a>.</li><li><span class="citation Journal">Peirce, Benjamin (1882). <a class="external text" href="http://books.google.com/?id=De0GAAAAYAAJ&pg=PA1&dq=Peirce+Benjamin+Linear+Associative+Algebra+&q=" rel="nofollow">"Linear Associative Algebra"</a>. <i>American Journal of Mathematics</i> (Vol. 4, No. 1/4. (1881).</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Linear+Associative+Algebra&rft.jtitle=American+Journal+of+Mathematics&rft.aulast=Peirce&rft.aufirst=Benjamin&rft.au=Peirce%2C%26%2332%3BBenjamin&rft.date=1882&rft.issue=Vol.+4%2C+No.+1%2F4.+%281881&rft_id=http%3A%2F%2Fbooks.google.com%2F%3Fid%3DDe0GAAAAYAAJ%26pg%3DPA1%26dq%3DPeirce%2BBenjamin%2BLinear%2BAssociative%2BAlgebra%2B%26q%3D&rfr_id=info:sid/en.wikipedia.org:Mathematics"></span>.</li><li>Peterson, Ivars, <i>Mathematical Tourist, New and Updated Snapshots of Modern Mathematics</i>, Owl Books, 2001, <a class="internal mw-magiclink-isbn" href="http://en.wikipedia.org/wiki/Special:BookSources/0805071598">ISBN 0-8050-7159-8</a>.</li><li><span class="citation book"><a href="http://en.wikipedia.org/wiki/John_Allen_Paulos" title="John Allen Paulos">Paulos, John Allen</a> (1996). <i>A Mathematician Reads the Newspaper</i>. Anchor. <a href="http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="http://en.wikipedia.org/wiki/Special:BookSources/0-385-48254-X" title="Special:BookSources/0-385-48254-X">0-385-48254-X</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=A+Mathematician+Reads+the+Newspaper&rft.aulast=Paulos&rft.aufirst=John+Allen&rft.au=Paulos%2C%26%2332%3BJohn+Allen&rft.date=1996&rft.pub=Anchor&rft.isbn=0-385-48254-X&rfr_id=info:sid/en.wikipedia.org:Mathematics"></span></li><li><span class="citation book"><a href="http://en.wikipedia.org/wiki/Karl_Popper" title="Karl Popper">Popper, Karl R.</a> (1995). "On knowledge". <i>In Search of a Better World: Lectures and Essays from Thirty Years</i>. Routledge. <a href="http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="http://en.wikipedia.org/wiki/Special:BookSources/0-415-13548-6" title="Special:BookSources/0-415-13548-6">0-415-13548-6</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=On+knowledge&rft.atitle=In+Search+of+a+Better+World%3A+Lectures+and+Essays+from+Thirty+Years&rft.aulast=Popper&rft.aufirst=Karl+R.&rft.au=Popper%2C%26%2332%3BKarl+R.&rft.date=1995&rft.pub=Routledge&rft.isbn=0-415-13548-6&rfr_id=info:sid/en.wikipedia.org:Mathematics"></span></li><li><span class="citation Journal">Riehm, Carl (August 2002). <a class="external text" href="http://www.ams.org/notices/200207/comm-riehm.pdf" rel="nofollow">"The Early History of the Fields Medal"</a> (PDF). <i>Notices of the AMS</i> (AMS) <b>49</b> (7): 778–782.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=The+Early+History+of+the+Fields+Medal&rft.jtitle=Notices+of+the+AMS&rft.aulast=Riehm&rft.aufirst=Carl&rft.au=Riehm%2C%26%2332%3BCarl&rft.date=August+2002&rft.volume=49&rft.issue=7&rft.pages=778%E2%80%93782&rft.pub=AMS&rft_id=http%3A%2F%2Fwww.ams.org%2Fnotices%2F200207%2Fcomm-riehm.pdf&rfr_id=info:sid/en.wikipedia.org:Mathematics"></span></li><li><span class="citation Journal"><a class="new" href="http://en.wikipedia.org/w/index.php?title=Mikhail_B._Sevryuk&action=edit&redlink=1" title="Mikhail B. Sevryuk (page does not exist)">Sevryuk, Mikhail B.</a> (January 2006). <a class="external text" href="http://www.ams.org/bull/2006-43-01/S0273-0979-05-01069-4/S0273-0979-05-01069-4.pdf" rel="nofollow">"Book Reviews"</a> (PDF). <i><a href="http://en.wikipedia.org/wiki/Bulletin_of_the_American_Mathematical_Society">Bulletin of the American Mathematical Society</a></i> <b>43</b> (1): 101–109. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.1090%2FS0273-0979-05-01069-4" rel="nofollow">10.1090/S0273-0979-05-01069-4</a><span class="reference-accessdate">. Retrieved 2006-06-24</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Book+Reviews&rft.jtitle=%5B%5BBulletin+of+the+American+Mathematical+Society%5D%5D&rft.aulast=Sevryuk&rft.aufirst=Mikhail+B.&rft.au=Sevryuk%2C%26%2332%3BMikhail+B.&rft.date=January+2006&rft.volume=43&rft.issue=1&rft.pages=101%E2%80%93109&rft_id=info:doi/10.1090%2FS0273-0979-05-01069-4&rft_id=http%3A%2F%2Fwww.ams.org%2Fbull%2F2006-43-01%2FS0273-0979-05-01069-4%2FS0273-0979-05-01069-4.pdf&rfr_id=info:sid/en.wikipedia.org:Mathematics"></span></li><li><span class="citation book"><a href="http://en.wikipedia.org/wiki/Wolfgang_Sartorius_von_Waltershausen" title="Wolfgang Sartorius von Waltershausen">Waltershausen, Wolfgang Sartorius von</a> (1856, repr. 1965). <a class="external text" href="http://www.amazon.de/Gauss-Ged%e4chtnis-Wolfgang-Sartorius-Waltershausen/dp/3253017028" rel="nofollow"><i>Gauss zum Gedächtniss</i></a>. Sändig Reprint Verlag H. R. Wohlwend. <a href="http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="http://en.wikipedia.org/wiki/Special:BookSources/3-253-01702-8" title="Special:BookSources/3-253-01702-8">3-253-01702-8</a>. <a href="http://en.wikipedia.org/wiki/International_Standard_Serial_Number" title="International Standard Serial Number">ISSN</a> <a class="external text" href="http://www.worldcat.org/issn/ASIN:" rel="nofollow">B0000BN5SQ ASIN: B0000BN5SQ</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Gauss+zum+Ged%C3%A4chtniss&rft.aulast=Waltershausen&rft.aufirst=Wolfgang+Sartorius+von&rft.au=Waltershausen%2C%26%2332%3BWolfgang+Sartorius+von&rft.date=1856%2C+repr.+1965&rft.pub=S%C3%A4ndig+Reprint+Verlag+H.+R.+Wohlwend&rft.isbn=3-253-01702-8&rft.issn=ASIN%3A+B0000BN5SQ&rft_id=http%3A%2F%2Fwww.amazon.de%2FGauss-Ged%25e4chtnis-Wolfgang-Sartorius-Waltershausen%2Fdp%2F3253017028&rfr_id=info:sid/en.wikipedia.org:Mathematics"></span></li><li><span class="citation Journal">Ziman, J.M., F.R.S. (1968). <a class="external text" href="http://info.med.yale.edu/therarad/summers/ziman.htm" rel="nofollow"><i>Public Knowledge:An essay concerning the social dimension of science</i></a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Public+Knowledge%3AAn+essay+concerning+the+social+dimension+of+science&rft.aulast=Ziman%2C+J.M.%2C+F.R.S.&rft.au=Ziman%2C+J.M.%2C+F.R.S.&rft.date=1968&rft_id=http%3A%2F%2Finfo.med.yale.edu%2Ftherarad%2Fsummers%2Fziman.htm&rfr_id=info:sid/en.wikipedia.org:Mathematics"></span></li></ul></div><h2><span class="mw-headline" id="External_links">External links</span></h2><table class="metadata plainlinks mbox-small" style="background-color: #f9f9f9; border: 1px solid #aaa;"><tbody><tr> <td colspan="2" style="margin: auto; text-align: center;">Find more about <b>Mathematics</b> on Wikipedia's <a href="http://en.wikipedia.org/wiki/Wikipedia:Wikimedia_sister_projects" title="Wikipedia:Wikimedia sister projects">sister projects</a>:</td> </tr><tr> <td><a href="http://en.wiktionary.org/wiki/Special:Search/Mathematics" title="Search Wiktionary"><img alt="" height="25" src="http://upload.wikimedia.org/wikipedia/commons/thumb/f/f8/Wiktionary-logo-en.svg/23px-Wiktionary-logo-en.svg.png" width="23" /></a></td> <td><a class="extiw" href="http://en.wiktionary.org/wiki/Special:Search/Mathematics" title="wikt:Special:Search/Mathematics">Definitions</a> from Wiktionary</td> </tr><tr> <td><a href="http://commons.wikimedia.org/wiki/Special:Search/Mathematics" title="Search Commons"><img alt="" height="24" src="http://upload.wikimedia.org/wikipedia/commons/thumb/4/4a/Commons-logo.svg/18px-Commons-logo.svg.png" width="18" /></a></td> <td><a class="extiw" href="http://commons.wikimedia.org/wiki/Special:Search/Mathematics" title="commons:Special:Search/Mathematics">Images and media</a> from Commons</td> </tr><tr> <td><a href="http://en.wikiversity.org/wiki/Special:Search/Mathematics" title="Search Wikiversity"><img alt="" height="23" src="http://upload.wikimedia.org/wikipedia/commons/thumb/1/1b/Wikiversity-logo-en.svg/25px-Wikiversity-logo-en.svg.png" width="25" /></a></td> <td><a class="extiw" href="http://en.wikiversity.org/wiki/Special:Search/Mathematics" title="v:Special:Search/Mathematics">Learning resources</a> from Wikiversity</td> </tr><tr> <td><a href="http://en.wikinews.org/wiki/Special:Search/Mathematics" title="Search Wikinews"><img alt="" height="14" src="http://upload.wikimedia.org/wikipedia/commons/thumb/2/24/Wikinews-logo.svg/25px-Wikinews-logo.svg.png" width="25" /></a></td> <td><a class="extiw" href="http://en.wikinews.org/wiki/Special:Search/Mathematics" title="n:Special:Search/Mathematics">News stories</a> from Wikinews</td> </tr><tr> <td><a href="http://en.wikiquote.org/wiki/Special:Search/Mathematics" title="Search Wikiquote"><img alt="" height="25" src="http://upload.wikimedia.org/wikipedia/commons/thumb/f/fa/Wikiquote-logo.svg/21px-Wikiquote-logo.svg.png" width="21" /></a></td> <td><a class="extiw" href="http://en.wikiquote.org/wiki/Special:Search/Mathematics" title="q:Special:Search/Mathematics">Quotations</a> from Wikiquote</td> </tr><tr> <td><a href="http://en.wikisource.org/wiki/Special:Search/Mathematics" title="Search Wikisource"><img alt="" height="25" src="http://upload.wikimedia.org/wikipedia/commons/thumb/4/4c/Wikisource-logo.svg/24px-Wikisource-logo.svg.png" width="24" /></a></td> <td><a class="extiw" href="http://en.wikisource.org/wiki/Special:Search/Mathematics" title="s:Special:Search/Mathematics">Source texts</a> from Wikisource</td> </tr><tr> <td><a href="http://en.wikibooks.org/wiki/Special:Search/Mathematics" title="Search Wikibooks"><img alt="" height="25" src="http://upload.wikimedia.org/wikipedia/commons/thumb/f/fa/Wikibooks-logo.svg/25px-Wikibooks-logo.svg.png" width="25" /></a></td> <td><a class="extiw" href="http://en.wikibooks.org/wiki/Special:Search/Mathematics" title="b:Special:Search/Mathematics">Textbooks</a> from Wikibooks</td> </tr></tbody></table><div class="infobox sisterproject"> <div style="float: left;"> <div class="floatnone"><a class="image" href="http://en.wikipedia.org/wiki/File:Wikiversity-logo-en.svg" title="Wikiversity"><img alt="Wikiversity" height="45" src="http://upload.wikimedia.org/wikipedia/commons/thumb/1/1b/Wikiversity-logo-en.svg/50px-Wikiversity-logo-en.svg.png" width="50" /></a></div></div><div style="margin-left: 60px;">At <a href="http://en.wikipedia.org/wiki/Wikiversity">Wikiversity</a> you can learn more and teach others about <b>Mathematics</b> at: <div style="margin-left: 10px;"><a class="extiw" href="http://en.wikiversity.org/wiki/School:Mathematics" title="v:School:Mathematics">The School of Mathematics</a></div></div></div><div class="refbegin"> <ul><li><a class="external text" href="http://www.bbc.co.uk/programmes/p00545hk" rel="nofollow">Mathematics</a> on <a href="http://en.wikipedia.org/wiki/In_Our_Time_%28BBC_Radio_4%29" title="In Our Time (BBC Radio 4)">In Our Time</a> at the <a href="http://en.wikipedia.org/wiki/BBC">BBC</a>. (<a class="external text" href="http://www.bbc.co.uk/iplayer/console/p00545hk/In_Our_Time_Mathematics" rel="nofollow">listen now</a>)</li><li><a class="external text" href="http://freebookcentre.net/SpecialCat/Free-Mathematics-Books-Download.html" rel="nofollow">Free Mathematics books</a> Free Mathematics books collection.</li><li><a href="http://en.wikipedia.org/wiki/Encyclopaedia_of_Mathematics">Encyclopaedia of Mathematics</a> online encyclopaedia from <a class="external text" href="http://eom.springer.de/" rel="nofollow">Springer</a>, Graduate-level reference work with over 8,000 entries, illuminating nearly 50,000 notions in mathematics.</li><li><a class="external text" href="http://hyperphysics.phy-astr.gsu.edu/Hbase/hmat.html" rel="nofollow">HyperMath site at Georgia State University</a></li><li><a class="external text" href="http://www.freescience.info/mathematics.php" rel="nofollow">FreeScience Library</a> The mathematics section of FreeScience library</li><li>Rusin, Dave: <i><a class="external text" href="http://www.math-atlas.org/" rel="nofollow">The Mathematical Atlas</a></i>. A guided tour through the various branches of modern mathematics. (Can also be found at <a class="external text" href="http://www.math.niu.edu/%7Erusin/known-math/index/index.html" rel="nofollow">NIU.edu</a>.)</li><li>Polyanin, Andrei: <i><a class="external text" href="http://eqworld.ipmnet.ru/" rel="nofollow">EqWorld: The World of Mathematical Equations</a></i>. An online resource focusing on algebraic, ordinary differential, partial differential (<a href="http://en.wikipedia.org/wiki/Mathematical_physics">mathematical physics</a>), integral, and other mathematical equations.</li><li>Cain, George: <a class="external text" href="http://www.math.gatech.edu/%7Ecain/textbooks/onlinebooks.html" rel="nofollow">Online Mathematics Textbooks</a> available free online.</li><li><a class="external text" href="http://www.tricki.org/" rel="nofollow">Tricki</a>, Wiki-style site that is intended to develop into a large store of useful mathematical problem-solving techniques.</li><li><a class="external text" href="http://math.chapman.edu/cgi-bin/structures?HomePage" rel="nofollow">Mathematical Structures</a>, list information about classes of mathematical structures.</li><li><a class="external text" href="http://www-history.mcs.st-and.ac.uk/%7Ehistory/" rel="nofollow">Mathematician Biographies</a>. The <a href="http://en.wikipedia.org/wiki/MacTutor_History_of_Mathematics_archive">MacTutor History of Mathematics archive</a> Extensive history and quotes from all famous mathematicians.</li><li><i><a class="external text" href="http://metamath.org/" rel="nofollow">Metamath</a></i>. A site and a language, that formalize mathematics from its foundations.</li><li><a class="external text" href="http://www.nrich.maths.org/public/index.php" rel="nofollow">Nrich</a>, a prize-winning site for students from age five from <a href="http://en.wikipedia.org/wiki/University_of_Cambridge" title="University of Cambridge">Cambridge University</a></li><li><a class="external text" href="http://garden.irmacs.sfu.ca/" rel="nofollow">Open Problem Garden</a>, a <a href="http://en.wikipedia.org/wiki/Wiki">wiki</a> of open problems in mathematics</li><li><i><a class="external text" href="http://planetmath.org/" rel="nofollow">Planet Math</a></i>. An online mathematics encyclopedia under construction, focusing on modern mathematics. Uses the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/CC_BY_SA" title="CC BY SA">Attribution-ShareAlike</a> license, allowing article exchange with Wikipedia. Uses <a href="http://en.wikipedia.org/wiki/TeX">TeX</a> markup.</li><li><a class="external text" href="http://www-math.mit.edu/daimp" rel="nofollow">Some mathematics applets, at MIT</a></li><li>Weisstein, Eric et al.: <i><a class="external text" href="http://www.mathworld.com/" rel="nofollow">MathWorld: World of Mathematics</a></i>. An online encyclopedia of mathematics.</li><li>Patrick Jones' <a class="external text" href="http://www.youtube.com/user/patrickJMT" rel="nofollow">Video Tutorials</a> on Mathematics</li><li><a class="external text" href="http://en.citizendium.org/wiki/Theory_%28mathematics%29" rel="nofollow">Citizendium: Theory (mathematics)</a>.</li></ul></div></div>ripplehttp://www.blogger.com/profile/17326365690819936341noreply@blogger.comtag:blogger.com,1999:blog-6905780489869824283.post-2431685250789282492011-03-22T11:22:00.000-07:002011-04-06T14:15:46.891-07:00Moon<div dir="ltr" style="text-align: left;" trbidi="on"><div id="siteNotice"><div id="localNotice"></div></div><br /><div class="metadata topicon" id="protected-icon" style="display: none; right: 55px;"><a href="http://en.wikipedia.org/wiki/Wikipedia:Protection_policy#semi" title="This article is semi-protected."><img alt="Page semi-protected" height="20" src="http://upload.wikimedia.org/wikipedia/commons/thumb/f/fc/Padlock-silver.svg/20px-Padlock-silver.svg.png" width="20" /></a></div><div class="metadata topicon" id="featured-star" style="display: none; right: 10px;"><a href="http://en.wikipedia.org/wiki/Wikipedia:Featured_articles" title="This is a featured article. Click here for more information."><img alt="Featured article" height="13" src="http://upload.wikimedia.org/wikipedia/commons/thumb/e/e7/Cscr-featured.svg/14px-Cscr-featured.svg.png" width="14" /></a></div><div class="dablink">This article is about Earth's Moon. For moons in general, see <a href="http://en.wikipedia.org/wiki/Natural_satellite">Natural satellite</a>. For other uses, see <a href="http://en.wikipedia.org/wiki/Moon_%28disambiguation%29">Moon (disambiguation)</a>.</div><table cellspacing="2" class="infobox vcard" style="font-size: 90%; text-align: left; width: 20em;"><caption><span class="fn org" style="font-size: 120%;"><b>Moon</b></span> <a class="image" href="http://en.wikipedia.org/wiki/File:Moon_symbol_decrescent.svg" title="Moon symbol"><img alt="Moon symbol" height="25" src="http://upload.wikimedia.org/wikipedia/commons/thumb/c/c6/Moon_symbol_decrescent.svg/25px-Moon_symbol_decrescent.svg.png" width="25" /></a></caption> <tbody><tr> <td colspan="2" style="line-height: 1.2em; text-align: center;"><a class="image" href="http://en.wikipedia.org/wiki/File:Full_Moon_Luc_Viatour.jpg" title="Moon just past full"><img alt="Moon just past full, in the darkness of the night sky. It is patterned with a mix of light-tone regions and darker, irregular blotches, and scattered with varying sizes of impact craters, circles surrounded by out-thrown rays of bright ejecta." height="283" src="http://upload.wikimedia.org/wikipedia/commons/thumb/d/dd/Full_Moon_Luc_Viatour.jpg/280px-Full_Moon_Luc_Viatour.jpg" width="280" /></a> <br /><div style="font-size: 95%; padding-top: 0.25em;">A moon just past <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Full_Moon" title="Full Moon">full</a> as seen from <a href="http://en.wikipedia.org/wiki/Earth">Earth</a>'s northern hemisphere</div></td> </tr><tr> <th colspan="2" style="padding-top: 0.75em; text-align: center;"><div style="background: #dddddd;">Designations</div></th> </tr><tr> <th style="line-height: 1.1em;"><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Adjectivals_and_demonyms_for_astronomical_bodies" title="Adjectivals and demonyms for astronomical bodies">Adjective</a></th> <td style="line-height: 1.2em;"><a class="extiw" href="http://en.wiktionary.org/wiki/lunar" title="wikt:lunar">lunar</a></td> </tr><tr> <th colspan="2" style="padding-top: 0.75em; text-align: center;"><div style="background: #dddddd;"><a href="http://en.wikipedia.org/wiki/Orbit" title="Orbit">Orbital characteristics</a></div></th> </tr><tr> <th style="line-height: 1.1em;"><a href="http://en.wikipedia.org/wiki/Apsis" title="Apsis">Perigee</a></th> <td style="line-height: 1.2em;">363,104 km (0.0024 <a href="http://en.wikipedia.org/wiki/Astronomical_unit" title="Astronomical unit">AU</a>)</td> </tr><tr> <th style="line-height: 1.1em;"><a href="http://en.wikipedia.org/wiki/Apsis" title="Apsis">Apogee</a></th> <td style="line-height: 1.2em;">405,696 km (0.0027 AU)</td> </tr><tr> <th style="line-height: 1.1em;"><a href="http://en.wikipedia.org/wiki/Semi-major_axis">Semi-major axis</a></th> <td style="line-height: 1.2em;">384,399 km (<span style="white-space: nowrap;">0.002<span style="margin-left: 0.25em;">5</span>7 AU</span>)<sup class="reference" id="cite_ref-W06_0-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-W06-0">[1]</a></sup></td> </tr><tr> <th style="line-height: 1.1em;"><a href="http://en.wikipedia.org/wiki/Orbital_eccentricity" title="Orbital eccentricity">Eccentricity</a></th> <td style="line-height: 1.2em;"><span style="white-space: nowrap;">0.0549</span><sup class="reference" id="cite_ref-W06_0-1"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-W06-0">[1]</a></sup></td> </tr><tr> <th style="line-height: 1.1em;"><a href="http://en.wikipedia.org/wiki/Orbital_period">Orbital period</a></th> <td style="line-height: 1.2em;"><span style="white-space: nowrap;">27.321<span style="margin-left: 0.25em;">5</span>82 <a href="http://en.wikipedia.org/wiki/Day" title="Day">d</a></span> <span style="white-space: nowrap;">(27 d 7 h 43.1 min<sup class="reference" id="cite_ref-W06_0-2"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-W06-0">[1]</a></sup>)</span></td> </tr><tr> <th style="line-height: 1.1em;"><a href="http://en.wikipedia.org/wiki/Orbital_period" title="Orbital period">Synodic period</a></th> <td style="line-height: 1.2em;"><span style="white-space: nowrap;">29.530<span style="margin-left: 0.25em;">5</span>89 d</span> <span style="white-space: nowrap;">(29 d 12 h 44 min 2.9 s)</span></td> </tr><tr> <th style="line-height: 1.1em;"><a href="http://en.wikipedia.org/wiki/Orbital_speed" title="Orbital speed">Average orbital speed</a></th> <td style="line-height: 1.2em; vertical-align: middle;">1.022 <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Kilometre_per_second" title="Kilometre per second">km/s</a></td> </tr><tr> <th style="line-height: 1.1em;"><a href="http://en.wikipedia.org/wiki/Inclination">Inclination</a></th> <td style="line-height: 1.2em;">5.145° to the <a href="http://en.wikipedia.org/wiki/Ecliptic">ecliptic</a><sup class="reference" id="cite_ref-W06_0-3"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-W06-0">[1]</a></sup><br />(between 18.29° and 28.58° to Earth's <a href="http://en.wikipedia.org/wiki/Equator">equator</a>)</td> </tr><tr> <th style="line-height: 1.1em;"><a href="http://en.wikipedia.org/wiki/Longitude_of_the_ascending_node" title="Longitude of the ascending node">Longitude of ascending node</a></th> <td style="line-height: 1.2em; vertical-align: middle;">regressing by one <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Orbital_revolution" title="Orbital revolution">revolution</a> in 18.6 years</td> </tr><tr> <th style="line-height: 1.1em;"><a href="http://en.wikipedia.org/wiki/Argument_of_periapsis" title="Argument of periapsis">Argument of perigee</a></th> <td style="line-height: 1.2em; vertical-align: middle;">progressing by one revolution in 8.85 years</td> </tr><tr> <th style="line-height: 1.1em;"><a href="http://en.wikipedia.org/wiki/Natural_satellite" title="Natural satellite">Satellite of</a></th> <td style="line-height: 1.2em;"><a href="http://en.wikipedia.org/wiki/Earth">Earth</a></td> </tr><tr> <th colspan="2" style="padding-top: 0.75em; text-align: center;"><div style="background: #dddddd;">Physical characteristics</div></th> </tr><tr> <th style="line-height: 1.1em;">Mean radius</th> <td style="line-height: 1.2em;"><span style="white-space: nowrap;">1,737.10 km </span> <span style="white-space: nowrap;">(0.273 Earths)</span><sup class="reference" id="cite_ref-W06_0-4"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-W06-0">[1]</a></sup><sup class="reference" id="cite_ref-NSSDC_1-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-NSSDC-1">[2]</a></sup></td> </tr><tr> <th style="line-height: 1.1em;"><a href="http://en.wikipedia.org/wiki/Equator" title="Equator">Equatorial</a> radius</th> <td style="line-height: 1.2em;">1,738.14 km (0.273 Earths)<sup class="reference" id="cite_ref-NSSDC_1-1"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-NSSDC-1">[2]</a></sup></td> </tr><tr> <th style="line-height: 1.1em;"><a href="http://en.wikipedia.org/wiki/Geographical_pole" title="Geographical pole">Polar</a> radius</th> <td style="line-height: 1.2em;"><span style="white-space: nowrap;">1,735.97 km </span> <span style="white-space: nowrap;">(0.273 Earths)</span><sup class="reference" id="cite_ref-NSSDC_1-2"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-NSSDC-1">[2]</a></sup></td> </tr><tr> <th style="line-height: 1.1em;"><a href="http://en.wikipedia.org/wiki/Flattening">Flattening</a></th> <td style="line-height: 1.2em;"><span style="white-space: nowrap;">0.001<span style="margin-left: 0.25em;">2</span>5</span></td> </tr><tr> <th style="line-height: 1.1em;">Circumference</th> <td style="line-height: 1.2em;"><span style="white-space: nowrap;">10,921 km</span> (<a href="http://en.wikipedia.org/wiki/Equator" title="Equator">equatorial</a>)</td> </tr><tr> <th style="line-height: 1.1em;"><a href="http://en.wikipedia.org/wiki/Spheroid#Surface_area" title="Spheroid">Surface area</a></th> <td style="line-height: 1.2em;"><span style="white-space: nowrap;">3.793 × 10<sup>7</sup> km<sup>2</sup> </span> <span style="white-space: nowrap;">(0.074 Earths)</span></td> </tr><tr> <th style="line-height: 1.1em;"><a href="http://en.wikipedia.org/wiki/Volume">Volume</a></th> <td style="line-height: 1.2em;"><span style="white-space: nowrap;">2.1958 × 10<sup>10</sup> <a href="http://en.wikipedia.org/wiki/1_E%2B9_m%C2%B3" title="1 E+9 m³">km<sup>3</sup></a> </span> <span style="white-space: nowrap;">(0.020 Earths)</span></td> </tr><tr> <th style="line-height: 1.1em;"><a href="http://en.wikipedia.org/wiki/Mass">Mass</a></th> <td style="line-height: 1.2em;"><span style="white-space: nowrap;">7.3477 × 10<sup>22</sup> kg </span> <span style="white-space: nowrap;">(0.0123 Earths<sup class="reference" id="cite_ref-W06_0-5"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-W06-0">[1]</a></sup>)</span></td> </tr><tr> <th style="line-height: 1.1em;">Mean <a href="http://en.wikipedia.org/wiki/Density">density</a></th> <td style="line-height: 1.2em;"><span style="white-space: nowrap;">3.3464 <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Gram_per_cubic_centimeter" title="Gram per cubic centimeter">g/cm<sup>3</sup></a><sup class="reference" id="cite_ref-W06_0-6"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-W06-0">[1]</a></sup></span></td> </tr><tr> <th style="line-height: 1.1em;"><a href="http://en.wikipedia.org/wiki/Surface_gravity" title="Surface gravity">Equatorial surface gravity</a></th> <td style="line-height: 1.2em; vertical-align: middle;"><span style="white-space: nowrap;">1.622 <a href="http://en.wikipedia.org/wiki/Metre_per_second_squared" title="Metre per second squared">m/s<sup>2</sup></a></span> <span style="white-space: nowrap;">(0.165 4 <a href="http://en.wikipedia.org/wiki/G-force" title="G-force">g</a>)</span></td> </tr><tr> <th style="line-height: 1.1em;"><a href="http://en.wikipedia.org/wiki/Escape_velocity">Escape velocity</a></th> <td style="line-height: 1.2em; vertical-align: middle;"><span style="white-space: nowrap;">2.38 k<a href="http://en.wikipedia.org/wiki/Metre_per_second" title="Metre per second">m/s</a></span></td> </tr><tr> <th style="line-height: 1.1em;"><a href="http://en.wikipedia.org/wiki/Rotation_period" title="Rotation period">Sidereal rotation<br />period</a></th> <td style="line-height: 1.2em; vertical-align: middle;"><span style="white-space: nowrap;">27.321582 <a href="http://en.wikipedia.org/wiki/Day" title="Day">d</a></span> (<a href="http://en.wikipedia.org/wiki/Synchronous_rotation" title="Synchronous rotation">synchronous</a>)</td> </tr><tr> <th style="line-height: 1.1em;">Equatorial rotation velocity</th> <td style="line-height: 1.2em; vertical-align: middle;"><span style="white-space: nowrap;">4.627 m/s</span></td> </tr><tr> <th style="line-height: 1.1em;"><a href="http://en.wikipedia.org/wiki/Axial_tilt">Axial tilt</a></th> <td style="line-height: 1.2em;">1.5424° (to <a href="http://en.wikipedia.org/wiki/Ecliptic">ecliptic</a>)<br />6.687° (to <a href="http://en.wikipedia.org/wiki/Orbital_plane_%28astronomy%29" title="Orbital plane (astronomy)">orbit plane</a>)</td> </tr><tr> <th style="line-height: 1.1em;"><a href="http://en.wikipedia.org/wiki/Albedo">Albedo</a></th> <td style="line-height: 1.2em;">0.136<sup class="reference" id="cite_ref-Saari_2-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-Saari-2">[3]</a></sup></td> </tr><tr> <th style="line-height: 1.1em;">Surface <a href="http://en.wikipedia.org/wiki/Temperature" title="Temperature">temp.</a><br /><span style="white-space: nowrap;"> </span>equator<br /><span style="white-space: nowrap;"> </span>85°N<span style="position: relative; top: 0.3em;"><sup class="reference" id="cite_ref-Vasavada1999_5-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-Vasavada1999-5">[4]</a></sup></span></th> <td><table border="0" cellpadding="0" cellspacing="0" style="background: #f9f9f9; width: 100%;"><tbody><tr> <th style="line-height: 1.1em; padding-right: 0.25em; text-align: left; width: 31%;">min</th> <th style="line-height: 1.1em; padding-right: 0.25em; text-align: left; width: 38%;">mean</th> <th style="line-height: 1.1em; padding-right: 0.25em; text-align: left; width: 31%;">max</th> </tr><tr> <td style="line-height: 1.1em;">100 <a href="http://en.wikipedia.org/wiki/Kelvin" title="Kelvin">K</a></td> <td style="line-height: 1.1em;">220 K</td> <td style="line-height: 1.1em;">390 K</td> </tr><tr> <td style="line-height: 1.1em;">70 K</td> <td style="line-height: 1.1em;">130 K</td> <td style="line-height: 1.1em;">230 K</td> </tr></tbody></table></td> </tr><tr> <th style="line-height: 1.1em;"><a href="http://en.wikipedia.org/wiki/Apparent_magnitude">Apparent magnitude</a></th> <td style="line-height: 1.2em; vertical-align: middle;">−2.5 to −12.9<sup class="reference" id="cite_ref-maxval_3-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-maxval-3">[nb 1]</a></sup><br />−12.74 (mean <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Full_Moon" title="Full Moon">full Moon</a>)<sup class="reference" id="cite_ref-NSSDC_1-3"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-NSSDC-1">[2]</a></sup></td> </tr><tr> <th style="line-height: 1.1em;"><a href="http://en.wikipedia.org/wiki/Angular_diameter">Angular diameter</a></th> <td style="line-height: 1.2em; vertical-align: middle;">29.3 to 34.1 <a href="http://en.wikipedia.org/wiki/Minute_of_arc" title="Minute of arc">arcminutes</a><sup class="reference" id="cite_ref-NSSDC_1-4"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-NSSDC-1">[2]</a></sup><sup class="reference" id="cite_ref-angular_size_4-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-angular_size-4">[nb 2]</a></sup></td> </tr><tr> <th colspan="2" style="padding-top: 0.75em; text-align: center;"><div style="background: #dddddd;">Atmosphere<sup class="reference" id="cite_ref-L06_6-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-L06-6">[5]</a></sup><sup class="reference" id="cite_ref-pressure_explanation_7-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-pressure_explanation-7">[nb 3]</a></sup></div></th> </tr><tr> <th style="line-height: 1.1em;">Surface <a href="http://en.wikipedia.org/wiki/Atmospheric_pressure" title="Atmospheric pressure">pressure</a></th> <td style="line-height: 1.2em;">10<sup>−7</sup> <a href="http://en.wikipedia.org/wiki/Pascal_%28unit%29" title="Pascal (unit)">Pa</a> (day)<br />10<sup>−10</sup> Pa (night)</td> </tr><tr> <th style="line-height: 1.1em;">Composition</th> <td style="line-height: 1.2em;"><a href="http://en.wikipedia.org/wiki/Argon" title="Argon">Ar</a>, <a href="http://en.wikipedia.org/wiki/Helium" title="Helium">He</a>, <a href="http://en.wikipedia.org/wiki/Sodium" title="Sodium">Na</a>, <a href="http://en.wikipedia.org/wiki/Potassium" title="Potassium">K</a>, <a href="http://en.wikipedia.org/wiki/Hydrogen" title="Hydrogen">H</a>, <a href="http://en.wikipedia.org/wiki/Radon" title="Radon">Rn</a></td> </tr><tr> <td colspan="2"></td> </tr></tbody></table>The <b>Moon</b> is <a href="http://en.wikipedia.org/wiki/Earth">Earth</a>'s only <a href="http://en.wikipedia.org/wiki/Natural_satellite">natural satellite</a><sup class="reference" id="cite_ref-8"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-8">[nb 4]</a></sup><sup class="reference" id="cite_ref-Morais2002_9-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-Morais2002-9">[6]</a></sup> and the <a href="http://en.wikipedia.org/wiki/List_of_natural_satellites" title="List of natural satellites">fifth largest</a> satellite in the <a href="http://en.wikipedia.org/wiki/Solar_System">Solar System</a>. It is the largest natural satellite of a planet in the Solar System relative to the size of its <a href="http://en.wikipedia.org/wiki/Primary_%28astronomy%29" title="Primary (astronomy)">primary</a> (though <a href="http://en.wikipedia.org/wiki/Charon_%28moon%29" title="Charon (moon)">Charon</a>, which orbits <a href="http://en.wikipedia.org/wiki/Dwarf_planet">dwarf planet</a> <a href="http://en.wikipedia.org/wiki/Pluto">Pluto</a>, is proportionally larger), a quarter the diameter of Earth and <span class="frac"><sup>1</sup>⁄<sub>81</sub></span> its mass. The Moon is the second densest satellite after <a href="http://en.wikipedia.org/wiki/Io_%28moon%29" title="Io (moon)">Io</a>. It is in <a href="http://en.wikipedia.org/wiki/Synchronous_rotation">synchronous rotation</a> with Earth, always showing the same face; the <a href="http://en.wikipedia.org/wiki/Near_side_of_the_Moon" title="Near side of the Moon">near side</a> is marked with dark volcanic <a href="http://en.wikipedia.org/wiki/Lunar_mare" title="Lunar mare">maria</a> among the bright ancient crustal highlands and prominent <a href="http://en.wikipedia.org/wiki/Impact_crater" title="Impact crater">impact craters</a>. It is the brightest object in the sky after the <a href="http://en.wikipedia.org/wiki/Sun">Sun</a>, although its surface is actually very dark, with a similar reflectance to coal. Its prominence in the sky and its regular cycle of <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Lunar_phases" title="Lunar phases">phases</a> have since ancient times made the Moon an important cultural influence on <a href="http://en.wikipedia.org/wiki/Moon#Name_and_etymology" title="Moon">language</a>, <a href="http://en.wikipedia.org/wiki/Lunar_calendar" title="Lunar calendar">calendars</a>, <a href="http://en.wikipedia.org/wiki/Moon_in_fiction" title="Moon in fiction">art</a> and <a href="http://en.wikipedia.org/wiki/Lunar_deity" title="Lunar deity">mythology</a>.<sup class="noprint Inline-Template" style="white-space: nowrap;" title="The text in the vicinity of this tag needs clarification or removal of jargon from March 2011">[<i><a href="http://en.wikipedia.org/wiki/Wikipedia:Please_clarify" title="Wikipedia:Please clarify">clarification needed</a></i>]</sup> The Moon's gravitational influence produces the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Ocean_tides" title="Ocean tides">ocean tides</a> and the <a href="http://en.wikipedia.org/wiki/Tidal_acceleration" title="Tidal acceleration">minute lengthening</a> of the day. The Moon's current orbital distance, about thirty times the diameter of the Earth, causes it to appear almost the same size in the sky as the Sun, allowing it to cover the Sun nearly precisely in total <a href="http://en.wikipedia.org/wiki/Solar_eclipse" title="Solar eclipse">solar eclipses</a>.<br />The Moon is the only <a href="http://en.wikipedia.org/wiki/Astronomical_object" title="Astronomical object">celestial body</a> on which <a href="http://en.wikipedia.org/wiki/Moon_landing" title="Moon landing">humans have landed</a>. While the <a href="http://en.wikipedia.org/wiki/Soviet_Union">Soviet Union</a>'s <a href="http://en.wikipedia.org/wiki/Luna_programme">Luna programme</a> was the first to reach the Moon with unmanned <a href="http://en.wikipedia.org/wiki/Spacecraft">spacecraft</a> in 1959, the United States' <a href="http://en.wikipedia.org/wiki/NASA">NASA</a> <a href="http://en.wikipedia.org/wiki/Apollo_program">Apollo program</a> achieved the only manned missions to date, beginning with the first manned lunar orbiting mission by <a href="http://en.wikipedia.org/wiki/Apollo_8">Apollo 8</a> in 1968, and six manned lunar landings between 1969 and 1972—the first being <a href="http://en.wikipedia.org/wiki/Apollo_11">Apollo 11</a> in 1969. These missions returned over 380 kg (840 lb) of <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Moon_rocks" title="Moon rocks">lunar rocks</a>, which have been used to develop a detailed geological understanding of the Moon's origins (it is thought to have formed some 4.5 billion years ago in <a href="http://en.wikipedia.org/wiki/Giant_impact_hypothesis" title="Giant impact hypothesis">a giant impact</a> event involving Earth), the formation of <a href="http://en.wikipedia.org/wiki/Internal_structure_of_the_Moon" title="Internal structure of the Moon">its internal structure</a>, and <a href="http://en.wikipedia.org/wiki/Geology_of_the_Moon" title="Geology of the Moon">its subsequent history</a>.<br />After the <a href="http://en.wikipedia.org/wiki/Apollo_17">Apollo 17</a> mission in 1972, the Moon has been visited only by unmanned spacecraft, notably by <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Soviet" title="Soviet">Soviet</a> <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Lunokhod" title="Lunokhod">Lunokhod</a> <a href="http://en.wikipedia.org/wiki/Rover_%28space_exploration%29" title="Rover (space exploration)">rovers</a>. Since 2004, Japan, China, India, the United States, and the <a href="http://en.wikipedia.org/wiki/European_Space_Agency">European Space Agency</a> have each sent lunar orbiters. These spacecraft have contributed to confirming the discovery of <a href="http://en.wikipedia.org/wiki/Lunar_water" title="Lunar water">lunar water ice</a> in permanently shadowed craters at the poles and bound into the lunar <a href="http://en.wikipedia.org/wiki/Regolith">regolith</a>. Future manned missions to the Moon are planned but not yet underway; the Moon remains, under the <a href="http://en.wikipedia.org/wiki/Outer_Space_Treaty">Outer Space Treaty</a>, free to all nations to explore for peaceful purposes.<br /><table class="toc" id="toc"><tbody><tr> <td><div id="toctitle"><h2>Contents</h2><span class="toctoggle">[<a class="internal" href="http://en.wikipedia.org/wiki/Moon#" id="togglelink">hide</a>]</span></div><ul><li class="toclevel-1 tocsection-1"><a href="http://en.wikipedia.org/wiki/Moon#Name_and_etymology"><span class="tocnumber">1</span> <span class="toctext">Name and etymology</span></a></li><li class="toclevel-1 tocsection-2"><a href="http://en.wikipedia.org/wiki/Moon#Formation"><span class="tocnumber">2</span> <span class="toctext">Formation</span></a></li><li class="toclevel-1 tocsection-3"><a href="http://en.wikipedia.org/wiki/Moon#Physical_characteristics"><span class="tocnumber">3</span> <span class="toctext">Physical characteristics</span></a> <ul><li class="toclevel-2 tocsection-4"><a href="http://en.wikipedia.org/wiki/Moon#Internal_structure"><span class="tocnumber">3.1</span> <span class="toctext">Internal structure</span></a></li><li class="toclevel-2 tocsection-5"><a href="http://en.wikipedia.org/wiki/Moon#Surface_geology"><span class="tocnumber">3.2</span> <span class="toctext">Surface geology</span></a> <ul><li class="toclevel-3 tocsection-6"><a href="http://en.wikipedia.org/wiki/Moon#Volcanic_features"><span class="tocnumber">3.2.1</span> <span class="toctext">Volcanic features</span></a></li><li class="toclevel-3 tocsection-7"><a href="http://en.wikipedia.org/wiki/Moon#Impact_craters"><span class="tocnumber">3.2.2</span> <span class="toctext">Impact craters</span></a></li><li class="toclevel-3 tocsection-8"><a href="http://en.wikipedia.org/wiki/Moon#Presence_of_water"><span class="tocnumber">3.2.3</span> <span class="toctext">Presence of water</span></a></li></ul></li><li class="toclevel-2 tocsection-9"><a href="http://en.wikipedia.org/wiki/Moon#Gravity_and_magnetic_fields"><span class="tocnumber">3.3</span> <span class="toctext">Gravity and magnetic fields</span></a></li><li class="toclevel-2 tocsection-10"><a href="http://en.wikipedia.org/wiki/Moon#Atmosphere"><span class="tocnumber">3.4</span> <span class="toctext">Atmosphere</span></a></li><li class="toclevel-2 tocsection-11"><a href="http://en.wikipedia.org/wiki/Moon#Seasons"><span class="tocnumber">3.5</span> <span class="toctext">Seasons</span></a></li></ul></li><li class="toclevel-1 tocsection-12"><a href="http://en.wikipedia.org/wiki/Moon#Relationship_to_Earth"><span class="tocnumber">4</span> <span class="toctext">Relationship to Earth</span></a> <ul><li class="toclevel-2 tocsection-13"><a href="http://en.wikipedia.org/wiki/Moon#Orbit"><span class="tocnumber">4.1</span> <span class="toctext">Orbit</span></a></li><li class="toclevel-2 tocsection-14"><a href="http://en.wikipedia.org/wiki/Moon#Relative_size"><span class="tocnumber">4.2</span> <span class="toctext">Relative size</span></a></li><li class="toclevel-2 tocsection-15"><a href="http://en.wikipedia.org/wiki/Moon#Appearance_from_Earth"><span class="tocnumber">4.3</span> <span class="toctext">Appearance from Earth</span></a></li><li class="toclevel-2 tocsection-16"><a href="http://en.wikipedia.org/wiki/Moon#Tidal_effects"><span class="tocnumber">4.4</span> <span class="toctext">Tidal effects</span></a></li><li class="toclevel-2 tocsection-17"><a href="http://en.wikipedia.org/wiki/Moon#Eclipses"><span class="tocnumber">4.5</span> <span class="toctext">Eclipses</span></a></li></ul></li><li class="toclevel-1 tocsection-18"><a href="http://en.wikipedia.org/wiki/Moon#Study_and_exploration"><span class="tocnumber">5</span> <span class="toctext">Study and exploration</span></a> <ul><li class="toclevel-2 tocsection-19"><a href="http://en.wikipedia.org/wiki/Moon#Early_studies"><span class="tocnumber">5.1</span> <span class="toctext">Early studies</span></a></li><li class="toclevel-2 tocsection-20"><a href="http://en.wikipedia.org/wiki/Moon#First_direct_exploration:_1959.E2.80.931976"><span class="tocnumber">5.2</span> <span class="toctext">First direct exploration: 1959–1976</span></a> <ul><li class="toclevel-3 tocsection-21"><a href="http://en.wikipedia.org/wiki/Moon#Soviet_missions"><span class="tocnumber">5.2.1</span> <span class="toctext">Soviet missions</span></a></li><li class="toclevel-3 tocsection-22"><a href="http://en.wikipedia.org/wiki/Moon#United_States_missions"><span class="tocnumber">5.2.2</span> <span class="toctext">United States missions</span></a></li></ul></li><li class="toclevel-2 tocsection-23"><a href="http://en.wikipedia.org/wiki/Moon#Current_era:_1990.E2.80.93present"><span class="tocnumber">5.3</span> <span class="toctext">Current era: 1990–present</span></a></li></ul></li><li class="toclevel-1 tocsection-24"><a href="http://en.wikipedia.org/wiki/Moon#Legal_status"><span class="tocnumber">6</span> <span class="toctext">Legal status</span></a></li><li class="toclevel-1 tocsection-25"><a href="http://en.wikipedia.org/wiki/Moon#In_culture"><span class="tocnumber">7</span> <span class="toctext">In culture</span></a></li><li class="toclevel-1 tocsection-26"><a href="http://en.wikipedia.org/wiki/Moon#References"><span class="tocnumber">8</span> <span class="toctext">References</span></a></li><li class="toclevel-1 tocsection-27"><a href="http://en.wikipedia.org/wiki/Moon#Further_reading"><span class="tocnumber">9</span> <span class="toctext">Further reading</span></a></li><li class="toclevel-1 tocsection-28"><a href="http://en.wikipedia.org/wiki/Moon#External_links"><span class="tocnumber">10</span> <span class="toctext">External links</span></a></li></ul></td> </tr></tbody></table><h2><span class="mw-headline" id="Name_and_etymology">Name and etymology</span></h2>The English <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Proper_name" title="Proper name">proper name</a> for Earth's natural satellite is "the Moon".<sup class="reference" id="cite_ref-10"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-10">[7]</a></sup><sup class="reference" id="cite_ref-PN-FAQ_11-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-PN-FAQ-11">[8]</a></sup> The noun <i>moon</i> derives from <i>moone</i> (around 1380), which developed from <i>mone</i> (1135), which derives from <a href="http://en.wikipedia.org/wiki/Old_English">Old English</a> <i>mōna</i> (dating from before 725), which, like all <a href="http://en.wikipedia.org/wiki/Germanic_languages" title="Germanic languages">Germanic language</a> cognates, ultimately stems from <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Proto-Germanic" title="Proto-Germanic">Proto-Germanic</a> <i>*mǣnōn</i>.<sup class="reference" id="cite_ref-barnhart1995_12-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-barnhart1995-12">[9]</a></sup><br />The principal modern English adjective pertaining to the Moon is <i>lunar</i>, derived from the Latin <i>Luna</i>. Another less common adjective is <i>selenic</i>, derived from the Ancient Greek <i>Selene</i> (<span lang="el"><i>Σελήνη</i></span>), from which the prefix "seleno-" (as in <i>selenography</i>) is derived.<sup class="reference" id="cite_ref-oed_13-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-oed-13">[10]</a></sup><br /><h2><span class="mw-headline" id="Formation">Formation</span></h2><div class="rellink relarticle mainarticle">Main article: <a href="http://en.wikipedia.org/wiki/Giant_impact_hypothesis">Giant impact hypothesis</a></div>Several mechanisms have been proposed for the Moon's formation <span style="white-space: nowrap;">4.527 ± 0.010 billion</span> years ago,<sup class="reference" id="cite_ref-age_14-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-age-14">[nb 5]</a></sup> some 30–50 million years after the origin of the Solar System.<sup class="reference" id="cite_ref-15"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-15">[11]</a></sup> These include the fission of the Moon from the Earth's crust through <a href="http://en.wikipedia.org/wiki/Centrifugal_force" title="Centrifugal force">centrifugal forces</a>,<sup class="reference" id="cite_ref-Binder_16-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-Binder-16">[12]</a></sup> which would require too great an initial spin of the Earth,<sup class="reference" id="cite_ref-BotM_17-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-BotM-17">[13]</a></sup> the gravitational capture of a pre-formed Moon,<sup class="reference" id="cite_ref-Mitler_18-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-Mitler-18">[14]</a></sup> which would require an unfeasibly extended <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Earth%27s_atmosphere" title="Earth's atmosphere">atmosphere of the Earth</a> to <a href="http://en.wikipedia.org/wiki/Dissipation" title="Dissipation">dissipate</a> the energy of the passing Moon,<sup class="reference" id="cite_ref-BotM_17-1"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-BotM-17">[13]</a></sup> and the co-formation of the Earth and the Moon together in the primordial <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Accretion_disk" title="Accretion disk">accretion disk</a>, which does not explain the depletion of metallic iron in the Moon.<sup class="reference" id="cite_ref-BotM_17-2"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-BotM-17">[13]</a></sup> These hypotheses also cannot account for the high <a href="http://en.wikipedia.org/wiki/Angular_momentum">angular momentum</a> of the Earth–Moon system.<sup class="reference" id="cite_ref-19"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-19">[15]</a></sup><br />The prevailing hypothesis today is that the Earth–Moon system formed as a result of a <a href="http://en.wikipedia.org/wiki/Giant_impact_hypothesis" title="Giant impact hypothesis">giant impact</a>: a <a href="http://en.wikipedia.org/wiki/Mars">Mars</a>-sized body hit the nearly formed <a href="http://en.wikipedia.org/wiki/History_of_the_Earth" title="History of the Earth">proto-Earth</a>, blasting material into orbit around the proto-Earth, which accreted to form the Moon.<sup class="reference" id="cite_ref-taylor1998_20-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-taylor1998-20">[16]</a></sup> Giant impacts are thought to have been common in the early Solar System. Computer simulations modelling a giant impact are consistent with measurements of the angular momentum of the Earth–Moon system, and the small size of the lunar core; they also show that most of the Moon came from the impactor, not from the proto-Earth.<sup class="reference" id="cite_ref-21"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-21">[17]</a></sup> However, <a href="http://en.wikipedia.org/wiki/Meteorite" title="Meteorite">meteorites</a> show that other inner Solar System bodies such as <a href="http://en.wikipedia.org/wiki/Mars">Mars</a> and <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Vesta_%28asteroid%29" title="Vesta (asteroid)">Vesta</a> have very different oxygen and tungsten <a href="http://en.wikipedia.org/wiki/Isotope" title="Isotope">isotopic</a> compositions to the Earth, while the Earth and Moon have near-identical isotopic compositions. Post-impact mixing of the vaporized material between the forming Earth and Moon could have equalized their isotopic compositions,<sup class="reference" id="cite_ref-Pahlevan2007_22-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-Pahlevan2007-22">[18]</a></sup> although this is debated.<sup class="reference" id="cite_ref-23"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-23">[19]</a></sup><br />The large amount of energy released in the giant impact event and the subsequent reaccretion of material in Earth orbit would have melted the outer shell of the Earth, forming a magma ocean.<sup class="reference" id="cite_ref-Warren1985_24-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-Warren1985-24">[20]</a></sup><sup class="reference" id="cite_ref-25"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-25">[21]</a></sup> The newly formed Moon would also have had its own <a href="http://en.wikipedia.org/wiki/Lunar_magma_ocean">lunar magma ocean</a>; estimates for its depth range from about 500 km to the entire radius of the Moon.<sup class="reference" id="cite_ref-Warren1985_24-1"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-Warren1985-24">[20]</a></sup><br />An <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Exoplanet" title="Exoplanet">exoplanetary</a> system has been discovered in which two planets share the same orbit. Such co-orbital planets are thought to be the origin of the impact that produced the Earth-Moon system because models suggest the collision was low-speed<sup class="reference" id="cite_ref-26"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-26">[22]</a></sup><br /><h2><span class="mw-headline" id="Physical_characteristics">Physical characteristics</span></h2><h3><span class="mw-headline" id="Internal_structure">Internal structure</span></h3><div class="rellink relarticle mainarticle">Main article: <a href="http://en.wikipedia.org/wiki/Internal_structure_of_the_Moon">Internal structure of the Moon</a></div><div class="thumb tright"><div class="thumbinner" style="width: 292px;"><a class="image" href="http://en.wikipedia.org/wiki/File:Main_lunar_core.jpg"><img alt="" class="thumbimage" height="289" src="http://upload.wikimedia.org/wikipedia/en/thumb/1/14/Main_lunar_core.jpg/290px-Main_lunar_core.jpg" width="290" /></a> <br /><div class="thumbcaption"><div class="magnify"><a class="internal" href="http://en.wikipedia.org/wiki/File:Main_lunar_core.jpg" title="Enlarge"><img alt="" height="11" src="http://bits.wikimedia.org/skins-1.17/common/images/magnify-clip.png" width="15" /></a></div>Internal structure of the moon</div></div></div><table class="wikitable" style="clear: right; float: right; margin-left: 2em; text-align: center;"><caption>Chemical composition of the lunar surface regolith (derived from crustal rocks)<sup class="reference" id="cite_ref-27"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-27">[23]</a></sup></caption> <tbody><tr> <th rowspan="2">Compound</th> <th rowspan="2">Formula</th> <th colspan="2">Composition (wt %)</th> </tr><tr> <th style="font-size: smaller;">Maria</th> <th style="font-size: smaller;">Highlands</th> </tr><tr> <td style="text-align: left;"><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Silica" title="Silica">silica</a></td> <td>SiO<sub>2</sub></td> <td>45.4%</td> <td>45.5%</td> </tr><tr> <td style="text-align: left;"><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Alumina" title="Alumina">alumina</a></td> <td>Al<sub>2</sub>O<sub>3</sub></td> <td>14.9%</td> <td>24.0%</td> </tr><tr> <td style="text-align: left;"><a href="http://en.wikipedia.org/wiki/Calcium_oxide" title="Calcium oxide">lime</a></td> <td>CaO</td> <td>11.8%</td> <td>15.9%</td> </tr><tr> <td style="text-align: left;"><a href="http://en.wikipedia.org/wiki/Iron%28II%29_oxide">iron(II) oxide</a></td> <td>FeO</td> <td>14.1%</td> <td>5.9%</td> </tr><tr> <td style="text-align: left;"><a href="http://en.wikipedia.org/wiki/Magnesium_oxide" title="Magnesium oxide">magnesia</a></td> <td>MgO</td> <td>9.2%</td> <td>7.5%</td> </tr><tr> <td style="text-align: left;"><a href="http://en.wikipedia.org/wiki/Titanium_dioxide">titanium dioxide</a></td> <td>TiO<sub>2</sub></td> <td>3.9%</td> <td>0.6%</td> </tr><tr> <td style="text-align: left;"><a href="http://en.wikipedia.org/wiki/Sodium_oxide">sodium oxide</a></td> <td>Na<sub>2</sub>O</td> <td>0.6%</td> <td>0.6%</td> </tr><tr> <th colspan="2">Total</th> <th>99.9%</th> <th>100.0%</th> </tr></tbody></table>The Moon is a <a href="http://en.wikipedia.org/wiki/Planetary_differentiation" title="Planetary differentiation">differentiated</a> body: it has a <a href="http://en.wikipedia.org/wiki/Geochemistry" title="Geochemistry">geochemically</a> distinct <a href="http://en.wikipedia.org/wiki/Crust_%28geology%29" title="Crust (geology)">crust</a>, <a href="http://en.wikipedia.org/wiki/Mantle_%28geology%29" title="Mantle (geology)">mantle</a>, and <a href="http://en.wikipedia.org/wiki/Planetary_core" title="Planetary core">core</a>. The moon has a solid iron-rich inner core with a radius of 240 kilometers and a fluid outer core primarily made of liquid iron with a radius of roughly 300 kilometers. Around the core is a partially molten boundary layer with a radius of about 500 kilometers.<sup class="reference" id="cite_ref-28"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-28">[24]</a></sup> This structure is thought to have developed through the <a href="http://en.wikipedia.org/wiki/Fractional_crystallization_%28geology%29" title="Fractional crystallization (geology)">fractional crystallization</a> of a global <a href="http://en.wikipedia.org/wiki/Lunar_magma_ocean" title="Lunar magma ocean">magma ocean</a> shortly after the Moon's formation 4.5 billion years ago.<sup class="reference" id="cite_ref-29"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-29">[25]</a></sup> Crystallization of this magma ocean would have created a <a href="http://en.wikipedia.org/wiki/Mafic">mafic</a> mantle from the <a href="http://en.wikipedia.org/wiki/Precipitation_%28chemistry%29" title="Precipitation (chemistry)">precipitation</a> and sinking of the minerals <a href="http://en.wikipedia.org/wiki/Olivine">olivine</a>, <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Clinopyroxene" title="Clinopyroxene">clinopyroxene</a>, and <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Orthopyroxene" title="Orthopyroxene">orthopyroxene</a>; after about three-quarters of the magma ocean had crystallised, lower-density <a href="http://en.wikipedia.org/wiki/Plagioclase">plagioclase</a> minerals could form and float into a crust on top.<sup class="reference" id="cite_ref-S06_30-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-S06-30">[26]</a></sup> The final liquids to crystallise would have been initially sandwiched between the crust and mantle, with a high abundance of <a href="http://en.wikipedia.org/wiki/Compatibility_%28geochemistry%29" title="Compatibility (geochemistry)">incompatible</a> and heat-producing elements.<sup class="reference" id="cite_ref-W06_0-7"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-W06-0">[1]</a></sup> Consistent with this, geochemical mapping from orbit shows the crust is mostly <a href="http://en.wikipedia.org/wiki/Anorthosite">anorthosite</a>,<sup class="reference" id="cite_ref-L06_6-1"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-L06-6">[5]</a></sup> and <a href="http://en.wikipedia.org/wiki/Moon_rock">moon rock</a> samples of the flood lavas erupted on the surface from partial melting in the mantle confirm the mafic mantle composition, which is more iron rich than that of Earth.<sup class="reference" id="cite_ref-W06_0-8"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-W06-0">[1]</a></sup> Geophysical techniques suggest that the crust is on average ~50 km thick.<sup class="reference" id="cite_ref-W06_0-9"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-W06-0">[1]</a></sup><br />The Moon is the second densest satellite in the Solar System after <a href="http://en.wikipedia.org/wiki/Io_%28moon%29" title="Io (moon)">Io</a>.<sup class="reference" id="cite_ref-Schubert2004_31-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-Schubert2004-31">[27]</a></sup> However, the inner core of the Moon is small, with a radius of about 350 km or less;<sup class="reference" id="cite_ref-W06_0-10"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-W06-0">[1]</a></sup> this is only ~20% the size of the Moon, in contrast to the ~50% of most other <a href="http://en.wikipedia.org/wiki/Terrestrial_planet" title="Terrestrial planet">terrestrial bodies</a>. Its composition is not well constrained, but it is probably metallic iron alloyed with a small amount of <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Sulphur" title="Sulphur">sulphur</a> and <a href="http://en.wikipedia.org/wiki/Nickel">nickel</a>; analyses of the Moon's time-variable rotation indicate that it is at least partly molten.<sup class="reference" id="cite_ref-32"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-32">[28]</a></sup><br /><h3><span class="mw-headline" id="Surface_geology">Surface geology</span></h3><div class="rellink relarticle mainarticle">Main articles: <a href="http://en.wikipedia.org/wiki/Geology_of_the_Moon">Geology of the Moon</a> and <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Moon_rocks" title="Moon rocks">Moon rocks</a></div><div class="rellink boilerplate seealso">See also: <a href="http://en.wikipedia.org/wiki/Topography_of_the_Moon">Topography of the Moon</a> and <a href="http://en.wikipedia.org/wiki/List_of_features_on_the_Moon">List of features on the Moon</a></div><div class="thumb tright" style="width: 356px;"><div class="thumbinner"><div style="float: left; margin: 1px; width: 172px;"><div class="thumbimage"><a class="image" href="http://en.wikipedia.org/wiki/File:Moon_PIA00302.jpg" title="Near side of the Moon"><img alt="The dark irregular mare lava plains are prominent in the fully illuminated disk. A single bright star of ejecta, with rays stretching a third of the way across the disk, emblazons the lower centre: this is the crater Tycho." height="170" src="http://upload.wikimedia.org/wikipedia/commons/thumb/7/73/Moon_PIA00302.jpg/170px-Moon_PIA00302.jpg" width="170" /></a></div><div class="thumbcaption" style="clear: left;"><a href="http://en.wikipedia.org/wiki/Near_side_of_the_Moon">Near side of the Moon</a></div></div><div style="float: left; margin: 1px; width: 172px;"><div class="thumbimage"><a class="image" href="http://en.wikipedia.org/wiki/File:Moon_PIA00304.jpg" title="Far side of the Moon. Note the lack of dark maria.[29]"><img alt="This full disk is nearly featureless, a uniform grey surface with no dark mare. There are many bright overlapping dots of impact craters." height="170" src="http://upload.wikimedia.org/wikipedia/commons/thumb/2/2a/Moon_PIA00304.jpg/170px-Moon_PIA00304.jpg" width="170" /></a></div><div class="thumbcaption" style="clear: left;"><a href="http://en.wikipedia.org/wiki/Far_side_of_the_Moon">Far side of the Moon</a>. Note the lack of dark <a href="http://en.wikipedia.org/wiki/Lunar_mare" title="Lunar mare">maria</a>.<sup class="reference" id="cite_ref-33"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-33">[29]</a></sup></div></div></div></div><div class="thumb tright"><div class="thumbinner" style="width: 347px;"><a class="image" href="http://en.wikipedia.org/wiki/File:MoonTopoLOLA.png"><img alt="" class="thumbimage" height="238" src="http://upload.wikimedia.org/wikipedia/commons/thumb/b/b0/MoonTopoLOLA.png/345px-MoonTopoLOLA.png" width="345" /></a> <br /><div class="thumbcaption"><div class="magnify"><a class="internal" href="http://en.wikipedia.org/wiki/File:MoonTopoLOLA.png" title="Enlarge"><img alt="" height="11" src="http://bits.wikimedia.org/skins-1.17/common/images/magnify-clip.png" width="15" /></a></div>Topography of the Moon.</div></div></div>The <a href="http://en.wikipedia.org/wiki/Topography">topography</a> of the Moon has been measured with <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Laser_altimetry" title="Laser altimetry">laser altimetry</a> and <a href="http://en.wikipedia.org/wiki/Stereoscopy" title="Stereoscopy">stereo image analysis</a>.<sup class="reference" id="cite_ref-34"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-34">[30]</a></sup> The most visible topographic feature is the giant far side <a href="http://en.wikipedia.org/wiki/South_Pole_%E2%80%93_Aitken_basin">South Pole – Aitken basin</a>, some 2,240 km in diameter, the largest crater on the Moon and the largest known crater in the Solar System.<sup class="reference" id="cite_ref-Spudis1994_35-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-Spudis1994-35">[31]</a></sup><sup class="reference" id="cite_ref-36"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-36">[32]</a></sup> At 13 km deep, its floor is the lowest elevation on the Moon.<sup class="reference" id="cite_ref-Spudis1994_35-1"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-Spudis1994-35">[31]</a></sup><sup class="reference" id="cite_ref-37"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-37">[33]</a></sup> The highest elevations are found just to its north-east, and it has been suggested that this area might have been thickened by the oblique formation impact of South Pole – Aitken.<sup class="reference" id="cite_ref-38"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-38">[34]</a></sup> Other large impact basins, such as <a href="http://en.wikipedia.org/wiki/Mare_Imbrium" title="Mare Imbrium">Imbrium</a>, <a href="http://en.wikipedia.org/wiki/Mare_Serenitatis" title="Mare Serenitatis">Serenitatis</a>, <a href="http://en.wikipedia.org/wiki/Mare_Crisium" title="Mare Crisium">Crisium</a>, <a href="http://en.wikipedia.org/wiki/Mare_Smythii" title="Mare Smythii">Smythii</a>, and <a href="http://en.wikipedia.org/wiki/Mare_Orientale" title="Mare Orientale">Orientale</a>, also possess regionally low elevations and elevated rims.<sup class="reference" id="cite_ref-Spudis1994_35-2"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-Spudis1994-35">[31]</a></sup> The lunar far side is on average about 1.9 km higher than the near side.<sup class="reference" id="cite_ref-W06_0-11"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-W06-0">[1]</a></sup><br /><h4><span class="mw-headline" id="Volcanic_features">Volcanic features</span></h4><div class="rellink relarticle mainarticle">Main article: <a href="http://en.wikipedia.org/wiki/Lunar_mare">Lunar mare</a></div>The dark and relatively featureless lunar plains which can clearly be seen with the naked eye are called <i><a href="http://en.wikipedia.org/wiki/Lunar_mare" title="Lunar mare">maria</a></i> (<a class="mw-redirect" href="http://en.wikipedia.org/wiki/Latin_language" title="Latin language">Latin</a> for "seas"; singular <i>mare</i>), since they were believed by ancient astronomers to be filled with water.<sup class="reference" id="cite_ref-39"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-39">[35]</a></sup> They are now known to be vast solidified pools of ancient <a href="http://en.wikipedia.org/wiki/Basalt" title="Basalt">basaltic</a> lava. While similar to terrestrial basalts, the mare basalts have much higher abundances of iron and are completely lacking in minerals altered by water.<sup class="reference" id="cite_ref-40"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-40">[36]</a></sup><sup class="reference" id="cite_ref-41"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-41">[37]</a></sup> The majority of these lavas erupted or flowed into the depressions associated with <a href="http://en.wikipedia.org/wiki/Impact_crater" title="Impact crater">impact basins</a>. Several <a href="http://en.wikipedia.org/wiki/Geologic_province" title="Geologic province">geologic provinces</a> containing <a href="http://en.wikipedia.org/wiki/Shield_volcano" title="Shield volcano">shield volcanoes</a> and volcanic <a href="http://en.wikipedia.org/wiki/Lunar_dome" title="Lunar dome">domes</a> are found within the near side maria.<sup class="reference" id="cite_ref-42"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-42">[38]</a></sup><br />Maria are found almost exclusively on the near side of the Moon, covering 31% of the surface on the near side,<sup class="reference" id="cite_ref-worldbook_43-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-worldbook-43">[39]</a></sup> compared with a few scattered patches on the far side covering only 2%.<sup class="reference" id="cite_ref-44"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-44">[40]</a></sup> This is thought to be due to a <a href="http://en.wikipedia.org/wiki/KREEP" title="KREEP">concentration of heat-producing elements</a> under the crust on the near side, seen on geochemical maps obtained by <i><a href="http://en.wikipedia.org/wiki/Lunar_Prospector">Lunar Prospector</a>'</i>s gamma-ray spectrometer, which would have caused the underlying mantle to heat up, partially melt, rise to the surface and erupt.<sup class="reference" id="cite_ref-S06_30-1"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-S06-30">[26]</a></sup><sup class="reference" id="cite_ref-45"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-45">[41]</a></sup><sup class="reference" id="cite_ref-46"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-46">[42]</a></sup> Most of the Moon's <a href="http://en.wikipedia.org/wiki/Lunar_mare" title="Lunar mare">mare basalts</a> erupted during the Imbrian period, 3.0–3.5 billion years ago, although some radiometrically dated samples are as old as 4.2 billion years,<sup class="reference" id="cite_ref-Papike_47-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-Papike-47">[43]</a></sup> and the youngest eruptions, dated by <a href="http://en.wikipedia.org/wiki/Crater_counting">crater counting</a>, appear to have been only 1.2 billion years ago.<sup class="reference" id="cite_ref-Hiesinger_48-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-Hiesinger-48">[44]</a></sup><br />The lighter-coloured regions of the Moon are called <i>terrae</i>, or more commonly <i>highlands</i>, since they are higher than most maria. They have been radiometrically dated as forming 4.4 billion years ago, and may represent <a href="http://en.wikipedia.org/wiki/Plagioclase">plagioclase</a> <a href="http://en.wikipedia.org/wiki/Cumulate_rock" title="Cumulate rock">cumulates</a> of the <a href="http://en.wikipedia.org/wiki/Lunar_magma_ocean">lunar magma ocean</a>.<sup class="reference" id="cite_ref-Papike_47-1"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-Papike-47">[43]</a></sup><sup class="reference" id="cite_ref-Hiesinger_48-1"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-Hiesinger-48">[44]</a></sup> In contrast to the Earth, no major lunar mountains are believed to have formed as a result of tectonic events.<sup class="reference" id="cite_ref-49"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-49">[45]</a></sup><br /><h4><span class="mw-headline" id="Impact_craters">Impact craters</span></h4><div class="rellink boilerplate seealso">See also: <a href="http://en.wikipedia.org/wiki/List_of_craters_on_the_Moon">List of craters on the Moon</a></div>The other major geologic process that has affected the Moon's surface is <a href="http://en.wikipedia.org/wiki/Impact_crater" title="Impact crater">impact cratering</a>,<sup class="reference" id="cite_ref-50"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-50">[46]</a></sup> with craters formed when asteroids and comets collide with the lunar surface. There are estimated to be roughly 300,000 craters wider than 1 km on the Moon's near side alone.<sup class="reference" id="cite_ref-51"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-51">[47]</a></sup> Some of these are <a href="http://en.wikipedia.org/wiki/Selenography#Mapping_and_naming_the_Moon" title="Selenography">named</a> for scholars, scientists, artists and explorers.<sup class="reference" id="cite_ref-gazetteer_52-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-gazetteer-52">[48]</a></sup> The <a href="http://en.wikipedia.org/wiki/Lunar_geologic_timescale">lunar geologic timescale</a> is based on the most prominent impact events, including <a href="http://en.wikipedia.org/wiki/Nectarian" title="Nectarian">Nectaris</a>, <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Lower_Imbrian" title="Lower Imbrian">Imbrium</a>, and <a href="http://en.wikipedia.org/wiki/Mare_Orientale" title="Mare Orientale">Orientale</a>, structures characterized by multiple rings of uplifted material, typically hundreds to thousands of kilometres in diameter and associated with a broad apron of ejecta deposits that form a regional <a href="http://en.wikipedia.org/wiki/Stratigraphy" title="Stratigraphy">stratigraphic horizon</a>.<sup class="reference" id="cite_ref-geologic_53-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-geologic-53">[49]</a></sup> The lack of an atmosphere, weather and recent geological processes mean that many of these craters are well-preserved. While only a few multi-ring basins have been definitively dated, they are useful for assigning relative ages. Since impact craters accumulate at a nearly constant rate, counting the number of craters per unit area can be used to estimate the age of the surface.<sup class="reference" id="cite_ref-geologic_53-1"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-geologic-53">[49]</a></sup> The radiometric ages of impact-melted rocks collected during the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Apollo_missions" title="Apollo missions">Apollo missions</a> cluster between 3.8 and 4.1 billion years old: this has been used to propose a <a href="http://en.wikipedia.org/wiki/Late_Heavy_Bombardment">Late Heavy Bombardment</a> of impacts.<sup class="reference" id="cite_ref-54"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-54">[50]</a></sup><br />Blanketed on top of the Moon's crust is a highly <a href="http://en.wikipedia.org/wiki/Comminution" title="Comminution">comminuted</a> (broken into ever smaller particles) and <a href="http://en.wikipedia.org/wiki/Impact_gardening" title="Impact gardening">impact gardened</a> surface layer called <a href="http://en.wikipedia.org/wiki/Regolith">regolith</a>, formed by impact processes. The finer regolith, the <a href="http://en.wikipedia.org/wiki/Lunar_soil">lunar soil</a> of <a href="http://en.wikipedia.org/wiki/Silicon_dioxide">silicon dioxide</a> glass, has a texture like snow and smell like spent <a href="http://en.wikipedia.org/wiki/Gunpowder">gunpowder</a>.<sup class="reference" id="cite_ref-55"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-55">[51]</a></sup> The regolith of older surfaces is generally thicker than for younger surfaces: it varies in thickness from 10–20 m in the highlands and 3–5 m in the maria.<sup class="reference" id="cite_ref-56"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-56">[52]</a></sup> Beneath the finely comminuted regolith layer is the <i>megaregolith</i>, a layer of highly fractured bedrock many kilometres thick.<sup class="reference" id="cite_ref-57"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-57">[53]</a></sup><br /><ul class="gallery"><li class="gallerybox" style="width: 155px;"> <div style="width: 155px;"><div class="thumb" style="height: 150px; width: 150px;"><div style="margin: 16px auto;"><a class="image" href="http://en.wikipedia.org/wiki/File:Moon-craters.jpg"><img alt="" height="117" src="http://upload.wikimedia.org/wikipedia/commons/thumb/d/d4/Moon-craters.jpg/120px-Moon-craters.jpg" width="120" /></a></div></div><div class="gallerytext">Lunar crater <a href="http://en.wikipedia.org/wiki/Daedalus_%28crater%29" title="Daedalus (crater)">Daedalus</a> on the Moon's far side</div></div></li><li class="gallerybox" style="width: 155px;"> <div style="width: 155px;"><div class="thumb" style="height: 150px; width: 150px;"><div style="margin: 15px auto;"><a class="image" href="http://en.wikipedia.org/wiki/File:Moon_nearside_LRO.jpg"><img alt="" height="120" src="http://upload.wikimedia.org/wikipedia/en/thumb/c/c9/Moon_nearside_LRO.jpg/120px-Moon_nearside_LRO.jpg" width="120" /></a></div></div><div class="gallerytext">Detailed view from <a href="http://en.wikipedia.org/wiki/Lunar_Reconnaissance_Orbiter" title="Lunar Reconnaissance Orbiter">LRO</a></div></div></li><li class="gallerybox" style="width: 155px;"> <div style="width: 155px;"><div class="thumb" style="height: 150px; width: 150px;"><div style="margin: 41px auto;"><div id="ogg_player_1"><div><a class="image" href="http://en.wikipedia.org/wiki/File:Electrified_Lunar_Polar_Craters.OGG" title="Electrified Lunar Polar Craters.OGG"><img alt="Electrified Lunar Polar Craters.OGG" height="68" src="http://upload.wikimedia.org/wikipedia/commons/thumb/9/97/Electrified_Lunar_Polar_Craters.OGG/mid-Electrified_Lunar_Polar_Craters.OGG.jpg" width="120" /></a></div></div></div></div><div class="gallerytext"><small>Research from NASA's Lunar Science Institute indicates that the <a href="http://en.wikipedia.org/wiki/Solar_wind">solar wind</a> may be charging certain craters at the lunar poles to hundreds of volts.</small></div></div></li></ul><h4><span class="mw-headline" id="Presence_of_water">Presence of water</span></h4><div class="rellink relarticle mainarticle">Main article: <a href="http://en.wikipedia.org/wiki/Lunar_water">Lunar water</a></div><div class="thumb tright"><div class="thumbinner" style="width: 222px;"><a class="image" href="http://en.wikipedia.org/wiki/File:Moon_South_Pole.jpg"><img alt="Twenty degrees of latitude of the Moon's disk, completely covered in the overlapping circles of craters. The illumination angles are from all directions, keeping almost all the crater floors in sunlight, but a set of merged crater floors right at the south pole are completely shadowed." class="thumbimage" height="220" src="http://upload.wikimedia.org/wikipedia/commons/thumb/9/90/Moon_South_Pole.jpg/220px-Moon_South_Pole.jpg" width="220" /></a> <br /><div class="thumbcaption"><div class="magnify"><a class="internal" href="http://en.wikipedia.org/wiki/File:Moon_South_Pole.jpg" title="Enlarge"><img alt="" height="11" src="http://bits.wikimedia.org/skins-1.17/common/images/magnify-clip.png" width="15" /></a></div>Mosaic image of the lunar south pole as taken by <i><a href="http://en.wikipedia.org/wiki/Clementine_%28spacecraft%29" title="Clementine (spacecraft)">Clementine</a></i>: note permanent polar shadow.</div></div></div>Liquid water cannot persist on the lunar surface. When exposed to solar radiation, water quickly decomposes through a process known as <a href="http://en.wikipedia.org/wiki/Photodissociation">photodissociation</a> and is lost to space. However since the 1960s, scientists have hypothesized that water ice may be deposited by impacting <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Comets" title="Comets">comets</a> or possibly produced by the reaction of oxygen-rich lunar rocks, and hydrogen from <a href="http://en.wikipedia.org/wiki/Solar_wind">solar wind</a>, leaving traces of water which could possibly survive in cold, permanently shadowed craters at either pole on the Moon.<sup class="reference" id="cite_ref-Margot1999_58-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-Margot1999-58">[54]</a></sup><sup class="reference" id="cite_ref-59"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-59">[55]</a></sup> Computer simulations suggest that up to 14,000 km<sup>2</sup> of the surface may be in permanent shadow.<sup class="reference" id="cite_ref-M03_60-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-M03-60">[56]</a></sup> The presence of usable quantities of water on the Moon is an important factor in rendering <a href="http://en.wikipedia.org/wiki/Colonization_of_the_Moon" title="Colonization of the Moon">lunar habitation</a> as a cost-effective plan; the alternative of transporting water from Earth would be prohibitively expensive.<sup class="reference" id="cite_ref-seedhouse2009_61-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-seedhouse2009-61">[57]</a></sup><br />In years since, signatures of water have been found to exist on the lunar surface.<sup class="reference" id="cite_ref-moonwater_18032010_62-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-moonwater_18032010-62">[58]</a></sup> In 1994, the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Clementine_mission#Bistatic_Radar_Experiment" title="Clementine mission">bistatic radar experiment</a> located on the <i><a href="http://en.wikipedia.org/wiki/Clementine_%28spacecraft%29" title="Clementine (spacecraft)">Clementine</a></i> spacecraft, indicated the existence of small, frozen pockets of water close to the surface. However, later radar observations by <a href="http://en.wikipedia.org/wiki/Arecibo_Observatory" title="Arecibo Observatory">Arecibo</a>, suggest these findings may rather be rocks ejected from young impact craters.<sup class="reference" id="cite_ref-63"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-63">[59]</a></sup> In 1998, the <a href="http://en.wikipedia.org/wiki/Lunar_Prospector#Neutron_Spectrometer_.28NS.29" title="Lunar Prospector">neutron spectrometer</a> located on the <i>Lunar Prospector</i> spacecraft, indicated that high concentrations of hydrogen are present in the first meter of depth in the regolith near the polar regions.<sup class="reference" id="cite_ref-Feldman1998_64-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-Feldman1998-64">[60]</a></sup> In 2008, an analysis of volcanic lava beads, brought back to Earth aboard Apollo 15, showed small amounts of water to exist in the interior of the beads .<sup class="reference" id="cite_ref-Saal2008_65-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-Saal2008-65">[61]</a></sup><br />The 2008, <i><a href="http://en.wikipedia.org/wiki/Chandrayaan-1">Chandrayaan-1</a></i> spacecraft has since confirmed the existence of surface water ice, using the on-board <a href="http://en.wikipedia.org/wiki/Moon_Mineralogy_Mapper">Moon Mineralogy Mapper</a>. The spectrometer observed absorption lines common to <a href="http://en.wikipedia.org/wiki/Hydroxyl">hydroxyl</a>, in reflected sunlight, providing evidence of large quantities of water ice, on the lunar surface. The spacecraft showed that concentrations may possibly be as high as 1,000 <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Parts_per_million" title="Parts per million">ppm</a>.<sup class="reference" id="cite_ref-Pieters2009_66-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-Pieters2009-66">[62]</a></sup> In 2009, <i><a href="http://en.wikipedia.org/wiki/LCROSS">LCROSS</a></i> sent a 2300 kg impactor into a permanently shadowed polar crater, and detected at least 100 kg of water in a plume of ejected material.<sup class="reference" id="cite_ref-Planetary_67-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-Planetary-67">[63]</a></sup><sup class="reference" id="cite_ref-Colaprete_68-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-Colaprete-68">[64]</a></sup> Another examination of the LCROSS data showed the amount of detected water, to be closer to 155-kilograms (± 12 kg).<sup class="reference" id="cite_ref-Colaprete2010_69-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-Colaprete2010-69">[65]</a></sup><br /><h3><span class="mw-headline" id="Gravity_and_magnetic_fields">Gravity and magnetic fields</span></h3><div class="rellink relarticle mainarticle">Main articles: <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Gravity_of_the_Moon" title="Gravity of the Moon">Gravity of the Moon</a> and <a href="http://en.wikipedia.org/wiki/Magnetic_field_of_the_Moon">Magnetic field of the Moon</a></div>The gravitational field of the Moon has been measured through tracking the <a href="http://en.wikipedia.org/wiki/Doppler_effect" title="Doppler effect">Doppler shift</a> of radio signals emitted by orbiting spacecraft. The main lunar gravity features are <a href="http://en.wikipedia.org/wiki/Mass_concentration_%28astronomy%29" title="Mass concentration (astronomy)">mascons</a>, large positive gravitational anomalies associated with some of the giant <a href="http://en.wikipedia.org/wiki/Impact_crater" title="Impact crater">impact basins</a>, partly caused by the dense mare basaltic lava flows that fill these basins.<sup class="reference" id="cite_ref-70"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-70">[66]</a></sup> These anomalies greatly influence the orbit of spacecraft about the Moon. There are some puzzles: lava flows by themselves cannot explain all of the gravitational signature, and some mascons exist that are not linked to mare volcanism.<sup class="reference" id="cite_ref-71"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-71">[67]</a></sup><br />The Moon has an external <a href="http://en.wikipedia.org/wiki/Magnetic_field">magnetic field</a> of the order of one to a hundred <a href="http://en.wikipedia.org/wiki/Tesla_%28unit%29" title="Tesla (unit)">nanoteslas</a>, less than one-hundredth that of the <a href="http://en.wikipedia.org/wiki/Earth%27s_magnetic_field" title="Earth's magnetic field">Earth</a>. It does not currently have a global <a href="http://en.wikipedia.org/wiki/Dipole" title="Dipole">dipolar</a> magnetic field, as would be generated by a liquid metal core <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Geodynamo" title="Geodynamo">geodynamo</a>, and only has crustal magnetization, probably acquired early in lunar history when a geodynamo was still operating.<sup class="reference" id="cite_ref-GB2009_72-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-GB2009-72">[68]</a></sup><sup class="reference" id="cite_ref-73"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-73">[69]</a></sup> Alternatively, some of the remnant magnetization may be from transient magnetic fields generated during large impact events, through the expansion of an impact-generated plasma cloud in the presence of an ambient magnetic field—this is supported by the apparent location of the largest crustal magnetizations near the <a href="http://en.wikipedia.org/wiki/Antipodes">antipodes</a> of the giant impact basins.<sup class="reference" id="cite_ref-74"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-74">[70]</a></sup><br /><h3><span class="mw-headline" id="Atmosphere">Atmosphere</span></h3><div class="rellink relarticle mainarticle">Main article: <a href="http://en.wikipedia.org/wiki/Atmosphere_of_the_Moon">Atmosphere of the Moon</a></div>The Moon has an atmosphere so tenuous as to be nearly <a href="http://en.wikipedia.org/wiki/Vacuum">vacuum</a>, with a total mass of less than 10 metric tons.<sup class="reference" id="cite_ref-75"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-75">[71]</a></sup> The surface pressure of this small mass is around 3 × 10<sup>−15</sup> <a href="http://en.wikipedia.org/wiki/Atmosphere_%28unit%29" title="Atmosphere (unit)">atm</a> (0.3 <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Nanopascal" title="Nanopascal">nPa</a>); it varies with the lunar day. Its sources include <a href="http://en.wikipedia.org/wiki/Outgassing">outgassing</a> and <a href="http://en.wikipedia.org/wiki/Sputtering">sputtering</a>, the release of atoms from the bombardment of lunar soil by <a href="http://en.wikipedia.org/wiki/Solar_wind">solar wind</a> ions.<sup class="reference" id="cite_ref-L06_6-2"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-L06-6">[5]</a></sup><sup class="reference" id="cite_ref-76"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-76">[72]</a></sup> Elements that have been detected include <a href="http://en.wikipedia.org/wiki/Sodium">sodium</a> and <a href="http://en.wikipedia.org/wiki/Potassium">potassium</a>, produced by sputtering, which are also found in the atmospheres of <a href="http://en.wikipedia.org/wiki/Mercury_%28planet%29" title="Mercury (planet)">Mercury</a> and <a href="http://en.wikipedia.org/wiki/Io_%28moon%29" title="Io (moon)">Io</a>; <a href="http://en.wikipedia.org/wiki/Helium-4">helium-4</a> from the solar wind; and <a href="http://en.wikipedia.org/wiki/Argon" title="Argon">argon-40</a>, <a href="http://en.wikipedia.org/wiki/Radon" title="Radon">radon-222</a>, and <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Polonium-210" title="Polonium-210">polonium-210</a>, outgassed after their creation by <a href="http://en.wikipedia.org/wiki/Radioactive_decay">radioactive decay</a> within the crust and mantle.<sup class="reference" id="cite_ref-Stern1999_77-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-Stern1999-77">[73]</a></sup><sup class="reference" id="cite_ref-78"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-78">[74]</a></sup> The absence of such neutral species (atoms or molecules) as <a href="http://en.wikipedia.org/wiki/Oxygen">oxygen</a>, <a href="http://en.wikipedia.org/wiki/Nitrogen">nitrogen</a>, <a href="http://en.wikipedia.org/wiki/Carbon">carbon</a>, <a href="http://en.wikipedia.org/wiki/Hydrogen">hydrogen</a> and <a href="http://en.wikipedia.org/wiki/Magnesium">magnesium</a>, which are present in the <a href="http://en.wikipedia.org/wiki/Regolith">regolith</a>, is not understood.<sup class="reference" id="cite_ref-Stern1999_77-1"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-Stern1999-77">[73]</a></sup> Water vapour has been detected by <i><a href="http://en.wikipedia.org/wiki/Chandrayaan-1">Chandrayaan-1</a></i> and found to vary with latitude, with a maximum at ~60–70 degrees; it is possibly generated from the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Sublimation_%28chemistry%29" title="Sublimation (chemistry)">sublimation</a> of water ice in the regolith.<sup class="reference" id="cite_ref-Sridharan2010_79-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-Sridharan2010-79">[75]</a></sup> These gases can either return into the regolith due to the Moon's gravity, or be lost to space: either through solar radiation pressure, or if they are ionised, by being swept away by the solar wind's magnetic field.<sup class="reference" id="cite_ref-Stern1999_77-2"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-Stern1999-77">[73]</a></sup><br /><h3><span class="mw-headline" id="Seasons">Seasons</span></h3>The Moon's axial tilt is only 1.54°, much less than the 23.44° of the Earth. Because of this, the Moon's solar illumination varies much less with season, and topographical details play a crucial role in seasonal effects.<sup class="reference" id="cite_ref-bbc_80-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-bbc-80">[76]</a></sup> From images taken by <i><a href="http://en.wikipedia.org/wiki/Clementine_%28spacecraft%29" title="Clementine (spacecraft)">Clementine</a></i> in 1994, it appears that four mountainous regions on the rim of <a href="http://en.wikipedia.org/wiki/Peary_%28crater%29" title="Peary (crater)">Peary crater</a> at the Moon's north pole remain illuminated for the entire lunar day, creating <a href="http://en.wikipedia.org/wiki/Peak_of_Eternal_Light" title="Peak of Eternal Light">peaks of eternal light</a>. No such regions exist at the south pole. Similarly, there are places that remain in permanent shadow at the bottoms of many polar craters,<sup class="reference" id="cite_ref-M03_60-1"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-M03-60">[56]</a></sup> and these dark craters are extremely cold: <i><a href="http://en.wikipedia.org/wiki/Lunar_Reconnaissance_Orbiter">Lunar Reconnaissance Orbiter</a></i> measured the lowest summer temperatures in craters at the southern pole at 35 K (−238 °C),<sup class="reference" id="cite_ref-81"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-81">[77]</a></sup> and just 26 K close to the winter solstice in north polar <a href="http://en.wikipedia.org/wiki/Hermite_%28crater%29" title="Hermite (crater)">Hermite Crater</a>. This is the coldest temperature in the Solar System ever measured by a spacecraft, colder even than the surface of <a href="http://en.wikipedia.org/wiki/Pluto">Pluto</a>.<sup class="reference" id="cite_ref-bbc_80-1"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-bbc-80">[76]</a></sup><br /><h2><span class="mw-headline" id="Relationship_to_Earth">Relationship to Earth<span id="Orbit_and_relationship_to_Earth"></span></span></h2><div class="thumb tright"><div class="thumbinner" style="width: 352px;"><a class="image" href="http://en.wikipedia.org/wiki/File:Earth-Moon.PNG"><img alt="The Earth has a pronounced axial tilt; the Moon's orbit is not perpendicular to Earth's axis, but lies close to the Earth's orbital plane." class="thumbimage" height="222" src="http://upload.wikimedia.org/wikipedia/commons/thumb/4/43/Earth-Moon.PNG/350px-Earth-Moon.PNG" width="350" /></a> <br /><div class="thumbcaption"><div class="magnify"><a class="internal" href="http://en.wikipedia.org/wiki/File:Earth-Moon.PNG" title="Enlarge"><img alt="" height="11" src="http://bits.wikimedia.org/skins-1.17/common/images/magnify-clip.png" width="15" /></a></div>Schematic of the Earth-Moon system (without a consistent scale)</div></div></div><h3><span class="mw-headline" id="Orbit">Orbit</span></h3><div class="rellink relarticle mainarticle">Main articles: <a href="http://en.wikipedia.org/wiki/Orbit_of_the_Moon">Orbit of the Moon</a> and <a href="http://en.wikipedia.org/wiki/Lunar_theory">Lunar theory</a></div>The Moon makes a complete orbit around the Earth with respect to the fixed stars about once every 27.3 days<sup class="reference" id="cite_ref-orbpd_82-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-orbpd-82">[nb 6]</a></sup> (its <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Sidereal_period" title="Sidereal period">sidereal period</a>). However, since the Earth is moving in its orbit about the Sun at the same time, it takes slightly longer for the Moon to show the same <a href="http://en.wikipedia.org/wiki/Lunar_phase" title="Lunar phase">phase</a> to Earth, which is about 29.5 days<sup class="reference" id="cite_ref-synpd_83-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-synpd-83">[nb 7]</a></sup> (its <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Synodic_period" title="Synodic period">synodic period</a>).<sup class="reference" id="cite_ref-worldbook_43-1"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-worldbook-43">[39]</a></sup> Unlike most satellites of other planets, the Moon orbits nearer the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Ecliptic_plane" title="Ecliptic plane">ecliptic plane</a> than to the planet's <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Equatorial_plane" title="Equatorial plane">equatorial plane</a>. The Moon's orbit is subtly <a href="http://en.wikipedia.org/wiki/Perturbation_%28astronomy%29" title="Perturbation (astronomy)">perturbed</a> by the Sun and Earth in many small, complex and interacting ways. For example, the plane of the Moon's orbital motion <a href="http://en.wikipedia.org/wiki/Precession" title="Precession">gradually rotates</a>, which affects other aspects of lunar motion. These follow-on effects are mathematically described by <a href="http://en.wikipedia.org/wiki/Cassini%27s_Laws">Cassini's laws</a>.<sup class="reference" id="cite_ref-Beletskii2_84-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-Beletskii2-84">[78]</a></sup><br /><h3><span class="mw-headline" id="Relative_size">Relative size</span></h3><div class="thumb tright"><div class="thumbinner" style="width: 282px;"><a class="image" href="http://en.wikipedia.org/wiki/File:EarthAndMoon.jpg"><img alt="The dark shadowed disk of the Moon moves across the face of the quarter-phase Earth, covering only a small part of the cloud-swirled semicircle." class="thumbimage" height="210" src="http://upload.wikimedia.org/wikipedia/en/thumb/3/37/EarthAndMoon.jpg/280px-EarthAndMoon.jpg" width="280" /></a> <br /><div class="thumbcaption"><div class="magnify"><a class="internal" href="http://en.wikipedia.org/wiki/File:EarthAndMoon.jpg" title="Enlarge"><img alt="" height="11" src="http://bits.wikimedia.org/skins-1.17/common/images/magnify-clip.png" width="15" /></a></div>Comparative sizes of the Earth and the Moon, as imaged at separation of <span style="white-space: nowrap;">50 million km</span><sup class="reference" id="cite_ref-85"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-85">[79]</a></sup></div></div></div>The Moon is exceptionally large relative to the Earth: a quarter the diameter of the planet and 1/81 its mass.<sup class="reference" id="cite_ref-worldbook_43-2"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-worldbook-43">[39]</a></sup> It is the largest moon orbiting a <a href="http://en.wikipedia.org/wiki/Planet">planet</a> in the solar system relative to the size of its planet (although <a href="http://en.wikipedia.org/wiki/Charon_%28moon%29" title="Charon (moon)">Charon</a> is larger relative to the <a href="http://en.wikipedia.org/wiki/Dwarf_planet">dwarf planet</a> <a href="http://en.wikipedia.org/wiki/Pluto">Pluto</a>, at slightly more than 1/9 (11.6%) of Pluto's mass.)<sup class="reference" id="cite_ref-86"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-86">[80]</a></sup><br />However, the Earth and Moon are still considered a planet–satellite system, rather than a double-planet system, as their <a href="http://en.wikipedia.org/wiki/Center_of_mass#Barycenter_in_astrophysics_and_astronomy" title="Center of mass">barycentre</a>, the common centre of mass, is located 1,700 km (about a quarter of the Earth's radius) beneath the surface of the Earth.<sup class="reference" id="cite_ref-87"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-87">[81]</a></sup><br /><h3><span class="mw-headline" id="Appearance_from_Earth">Appearance from Earth<span id="Observation"></span><span id="Appearance_from_Earth"></span></span></h3><div class="rellink boilerplate seealso">See also: <a href="http://en.wikipedia.org/wiki/Lunar_phase">Lunar phase</a>, <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Earthshine" title="Earthshine">Earthshine</a>, and <a href="http://en.wikipedia.org/wiki/Observing_the_Moon">Observing the Moon</a></div>The Moon is in <a href="http://en.wikipedia.org/wiki/Synchronous_rotation">synchronous rotation</a>: it rotates about its axis in about the same time it takes to <a href="http://en.wikipedia.org/wiki/Orbit">orbit</a> the Earth. This results in it nearly always keeping the same face turned towards the Earth. The Moon used to rotate at a faster rate, but early in its history, its rotation slowed and became <a href="http://en.wikipedia.org/wiki/Tidal_locking" title="Tidal locking">tidally locked</a> in this orientation as a result of <a href="http://en.wikipedia.org/wiki/Friction" title="Friction">frictional</a> effects associated with <a href="http://en.wikipedia.org/wiki/Tidal_force" title="Tidal force">tidal</a> deformations caused by the Earth.<sup class="reference" id="cite_ref-88"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-88">[82]</a></sup> The side of the Moon that faces Earth is called the <a href="http://en.wikipedia.org/wiki/Near_side_of_the_Moon" title="Near side of the Moon">near side</a>, and the opposite side the <a href="http://en.wikipedia.org/wiki/Far_side_of_the_Moon" title="Far side of the Moon">far side</a>. The far side is often called the "dark side," but in fact, it is illuminated as often as the near side: once per lunar day, during the new Moon phase we observe on Earth when the near side is dark.<sup class="reference" id="cite_ref-89"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-89">[83]</a></sup><br />The Moon has an exceptionally low <a href="http://en.wikipedia.org/wiki/Albedo">albedo</a>, giving it a similar reflectance to <a href="http://en.wikipedia.org/wiki/Coal">coal</a>. Despite this, it is the second brightest object in the sky after the <a href="http://en.wikipedia.org/wiki/Sun">Sun</a>.<sup class="reference" id="cite_ref-worldbook_43-3"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-worldbook-43">[39]</a></sup><sup class="reference" id="cite_ref-brightness_90-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-brightness-90">[nb 8]</a></sup> This is partly due to the brightness enhancement of the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Opposition_effect" title="Opposition effect">opposition effect</a>; at quarter phase, the Moon is only one-tenth as bright, rather than half as bright, as at full Moon.<sup class="reference" id="cite_ref-Moon_91-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-Moon-91">[84]</a></sup> Additionally, <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Colour_constancy" title="Colour constancy">colour constancy</a> in the <a href="http://en.wikipedia.org/wiki/Visual_system">visual system</a> recalibrates the relations between the colours of an object and its surroundings, and since the surrounding sky is comparatively dark, the sunlit Moon is perceived as a bright object. The edges of the full Moon seem as bright as the centre, with no <a href="http://en.wikipedia.org/wiki/Limb_darkening">limb darkening</a>, due to the <a href="http://en.wikipedia.org/wiki/Lambert%27s_cosine_law#Lambertian_scatterers" title="Lambert's cosine law">reflective properties</a> of <a href="http://en.wikipedia.org/wiki/Lunar_soil">lunar soil</a>, which reflects more light back towards the Sun than in other directions. The Moon does appear larger when close to the horizon, but this is a purely psychological effect, known as the <a href="http://en.wikipedia.org/wiki/Moon_illusion">Moon illusion</a>, first described in the 7th century BC.<sup class="reference" id="cite_ref-92"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-92">[85]</a></sup> The full Moon subtends an arc of about 0.52° (on average) in the sky.<br /><div class="thumb tnone" style="margin-left: auto; margin-right: auto; max-width: 808px; width: 99%;"><div class="thumbinner"><div class="overflowbugx" style="overflow: auto;"><a class="image" href="http://en.wikipedia.org/wiki/File:Moon_phases_en.jpg" title="The monthly changes of angle between the direction of illumination by the Sun and viewing from Earth, and the phases of the Moon that result"><img alt="" height="320" src="http://upload.wikimedia.org/wikipedia/commons/thumb/4/46/Moon_phases_en.jpg/800px-Moon_phases_en.jpg" width="800" /></a></div><div class="thumbcaption"><div class="magnify"><a href="http://en.wikipedia.org/wiki/File:Moon_phases_en.jpg" title="Enlarge"><img alt="" height="11" src="http://upload.wikimedia.org/wikipedia/commons/6/6b/Magnify-clip.png" width="15" /></a></div>The monthly changes of angle between the direction of illumination by the Sun and viewing from Earth, and the phases of the Moon that result</div></div></div>The highest <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Altitude_%28astronomy%29" title="Altitude (astronomy)">altitude</a> of the Moon in the sky varies: while it has nearly the same limit as the Sun, it alters with the lunar phase and with the <a href="http://en.wikipedia.org/wiki/Season">season</a> of the year, with the full Moon highest during winter. The 18.6-year <a href="http://en.wikipedia.org/wiki/Lunar_node" title="Lunar node">nodes cycle</a> also has an influence: when the <a href="http://en.wikipedia.org/wiki/Orbital_node" title="Orbital node">ascending node</a> of the lunar orbit is in the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Vernal_equinox" title="Vernal equinox">vernal equinox</a>, the lunar <a href="http://en.wikipedia.org/wiki/Declination">declination</a> can go as far as 28° each month. This means the Moon can go overhead at latitudes up to 28° from the equator, instead of only 18°. The orientation of the Moon's crescent also depends on the latitude of the observation site: close to the equator, an observer can see a smile-shaped crescent Moon.<sup class="reference" id="cite_ref-93"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-93">[86]</a></sup><br />The distance between the moon and the Earth varies from around 221,000 miles (356,000 km) at its <a href="http://en.wikipedia.org/wiki/Apsis" title="Apsis">perigree</a> (closest), and 252,000 miles (406,000 km) at apogee (farthest). A perigee while the moon is also at full phase occurs around once every 18 years, and on 19 March 2011, it was closer to the earth while at full phase than it has been since 1993.<sup class="reference" id="cite_ref-94"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-94">[87]</a></sup> Reported as a "<a href="http://en.wikipedia.org/wiki/Supermoon" title="Supermoon">super moon</a>", this closest point coincides within an hour of a <a href="http://en.wikipedia.org/wiki/Full_moon">full moon</a>, and it thus appeared 30 percent brighter, and 14 percent larger than when at its greatest distance.<sup class="reference" id="cite_ref-95"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-95">[88]</a></sup><sup class="reference" id="cite_ref-96"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-96">[89]</a></sup><sup class="reference" id="cite_ref-97"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-97">[90]</a></sup><br />There has been historical controversy over whether features on the Moon's surface change over time. Today, many of these claims are thought to be illusory, resulting from observation under different lighting conditions, poor <a href="http://en.wikipedia.org/wiki/Astronomical_seeing">astronomical seeing</a>, or inadequate drawings. However, <a href="http://en.wikipedia.org/wiki/Outgassing">outgassing</a> does occasionally occur, and could be responsible for a minor percentage of the reported <a href="http://en.wikipedia.org/wiki/Transient_lunar_phenomenon" title="Transient lunar phenomenon">lunar transient phenomena</a>. Recently, it has been suggested that a roughly 3 km diameter region of the lunar surface was modified by a gas release event about a million years ago.<sup class="reference" id="cite_ref-98"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-98">[91]</a></sup><sup class="reference" id="cite_ref-99"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-99">[92]</a></sup> The Moon's appearance, like that of the Sun, can be affected by Earth's atmosphere: common effects are a 22° <a href="http://en.wikipedia.org/wiki/Halo_%28optical_phenomenon%29" title="Halo (optical phenomenon)">halo ring</a> formed when the Moon's light is refracted through the ice crystals of high <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Cirrostratus" title="Cirrostratus">cirrostratus</a> cloud, and smaller <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Corona_%28meteorology%29" title="Corona (meteorology)">coronal rings</a> when the Moon is seen through thin clouds.<sup class="reference" id="cite_ref-100"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-100">[93]</a></sup><br /><h3><span class="mw-headline" id="Tidal_effects">Tidal effects</span></h3><div class="rellink relarticle mainarticle">Main articles: <a href="http://en.wikipedia.org/wiki/Tidal_force">Tidal force</a>, <a href="http://en.wikipedia.org/wiki/Tidal_acceleration">Tidal acceleration</a>, <a href="http://en.wikipedia.org/wiki/Tide">Tide</a>, and <a href="http://en.wikipedia.org/wiki/Theory_of_tides">Theory of tides</a></div>The tides on the Earth are mostly generated by the gradient in intensity of the Moon's gravitational pull from one side of the Earth to the other, the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Tidal_forces" title="Tidal forces">tidal forces</a>. This forms two tidal bulges on the Earth, which are most clearly seen in elevated sea level as <a href="http://en.wikipedia.org/wiki/Tide" title="Tide">ocean tides</a>.<sup class="reference" id="cite_ref-Lambeck1977_101-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-Lambeck1977-101">[94]</a></sup> Since the Earth spins about 27 times faster than the Moon moves around it, the bulges are dragged along with the Earth's surface faster than the Moon moves, rotating around the Earth once a day as it spins on its axis.<sup class="reference" id="cite_ref-Lambeck1977_101-1"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-Lambeck1977-101">[94]</a></sup> The ocean tides are magnified by other effects: frictional coupling of water to Earth's rotation through the ocean floors, the <a href="http://en.wikipedia.org/wiki/Inertia">inertia</a> of water's movement, ocean basins that get shallower near land, and oscillations between different ocean basins.<sup class="reference" id="cite_ref-102"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-102">[95]</a></sup> The gravitational attraction of the Sun on the Earth's oceans is almost half that of the Moon, and their gravitational interplay is responsible for <a href="http://en.wikipedia.org/wiki/Tide#Range_variation:_springs_and_neaps" title="Tide">spring and neap tides</a>.<sup class="reference" id="cite_ref-Lambeck1977_101-2"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-Lambeck1977-101">[94]</a></sup><br /><div class="thumb tright"><div class="thumbinner" style="width: 222px;"><a class="image" href="http://en.wikipedia.org/wiki/File:Lunar_libration_with_phase_Oct_2007_450px.gif"><img alt="Over one lunar month more than half of the Moon's surface can be seen from the surface of the Earth." class="thumbimage" height="220" src="http://upload.wikimedia.org/wikipedia/commons/thumb/b/ba/Lunar_libration_with_phase_Oct_2007_450px.gif/220px-Lunar_libration_with_phase_Oct_2007_450px.gif" width="220" /></a> <br /><div class="thumbcaption"><div class="magnify"><a class="internal" href="http://en.wikipedia.org/wiki/File:Lunar_libration_with_phase_Oct_2007_450px.gif" title="Enlarge"><img alt="" height="11" src="http://bits.wikimedia.org/skins-1.17/common/images/magnify-clip.png" width="15" /></a></div>The <a href="http://en.wikipedia.org/wiki/Libration">libration</a> of the Moon over a single lunar month.</div></div></div>Gravitational coupling between the Moon and the bulge nearest the Moon acts as a <a href="http://en.wikipedia.org/wiki/Torque">torque</a> on the Earth's rotation, draining <a href="http://en.wikipedia.org/wiki/Angular_momentum">angular momentum</a> and rotational <a href="http://en.wikipedia.org/wiki/Kinetic_energy">kinetic energy</a> from the Earth's spin.<sup class="reference" id="cite_ref-Lambeck1977_101-3"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-Lambeck1977-101">[94]</a></sup><sup class="reference" id="cite_ref-touma1994_103-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-touma1994-103">[96]</a></sup> In turn, angular momentum is added to the Moon's orbit, accelerating it, which lifts the Moon into a higher orbit with a longer period. As a result, the distance between the Earth and Moon is <a href="http://en.wikipedia.org/wiki/Tidal_acceleration" title="Tidal acceleration">increasing</a>, and the Earth's spin slowing down.<sup class="reference" id="cite_ref-touma1994_103-1"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-touma1994-103">[96]</a></sup> Measurements from <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Lunar_laser_ranging_experiment" title="Lunar laser ranging experiment">lunar ranging experiments</a> with laser reflectors left during the Apollo missions have found that the Moon's distance to the Earth increases by 38 mm per year<sup class="reference" id="cite_ref-104"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-104">[97]</a></sup> (though this is only 0.10 <a href="http://en.wikipedia.org/wiki/Parts-per_notation" title="Parts-per notation">ppb</a>/year of the radius of the Moon's orbit). <a href="http://en.wikipedia.org/wiki/Atomic_clock" title="Atomic clock">Atomic clocks</a> also show that the Earth's day lengthens by about 15 <a href="http://en.wikipedia.org/wiki/Microsecond" title="Microsecond">microseconds</a> every year,<sup class="reference" id="cite_ref-105"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-105">[98]</a></sup> slowly increasing the rate at which <a href="http://en.wikipedia.org/wiki/Coordinated_Universal_Time" title="Coordinated Universal Time">UTC</a> is adjusted by <a href="http://en.wikipedia.org/wiki/Leap_second" title="Leap second">leap seconds</a>. This tidal drag will continue until the spin of the Earth has slowed to match the orbital period of the Moon; however, long before this could happen, the Sun will have become a <a href="http://en.wikipedia.org/wiki/Red_giant#The_Sun_as_a_red_giant">red giant</a>, engulfing the Earth.<sup class="reference" id="cite_ref-106"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-106">[99]</a></sup><sup class="reference" id="cite_ref-107"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-107">[100]</a></sup><br />The lunar surface also experiences tides of amplitude ~10 cm over 27 days, with two components: a fixed one due to the Earth, as they are in <a href="http://en.wikipedia.org/wiki/Synchronous_rotation">synchronous rotation</a>, and a varying component from the Sun.<sup class="reference" id="cite_ref-touma1994_103-2"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-touma1994-103">[96]</a></sup> The Earth-induced component arises from <a href="http://en.wikipedia.org/wiki/Libration">libration</a>, a result of the Moon's orbital eccentricity; if the Moon's orbit were perfectly circular, there would only be solar tides.<sup class="reference" id="cite_ref-touma1994_103-3"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-touma1994-103">[96]</a></sup> Libration also changes the angle from which the Moon is seen, allowing about 59% of its surface to be seen from the Earth (but only half at any instant).<sup class="reference" id="cite_ref-worldbook_43-4"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-worldbook-43">[39]</a></sup> The cumulative effects of stress built up by these tidal forces produces <i>moonquakes</i>. Moonquakes are much less common and weaker than earthquakes, although they can last for up to an hour – a significantly longer time than terrestrial earthquakes – because of the absence of water to damp out the seismic vibrations. The existence of moonquakes was an unexpected discovery from <a href="http://en.wikipedia.org/wiki/Seismometer" title="Seismometer">seismometers</a> placed on the Moon by <a href="http://en.wikipedia.org/wiki/Apollo_program" title="Apollo program">Apollo</a> <a href="http://en.wikipedia.org/wiki/Astronaut" title="Astronaut">astronauts</a> from 1969 through 1972.<sup class="reference" id="cite_ref-108"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-108">[101]</a></sup><br /><h3><span class="mw-headline" id="Eclipses">Eclipses</span></h3><div class="rellink relarticle mainarticle">Main articles: <a href="http://en.wikipedia.org/wiki/Solar_eclipse">Solar eclipse</a>, <a href="http://en.wikipedia.org/wiki/Lunar_eclipse">Lunar eclipse</a>, and <a href="http://en.wikipedia.org/wiki/Eclipse_cycle">Eclipse cycle</a></div><div class="thumb tright" style="width: 316px;"><div class="thumbinner"><div style="float: left; margin: 1px; width: 152px;"><div class="thumbimage"><a class="image" href="http://en.wikipedia.org/wiki/File:Solar_eclips_1999_4_NR.jpg" title="The 1999 solar eclipse"><img alt="The fiercely bright disk of the Sun is completely obscured by the exact fit of the disk of the dark, non-illuminated Moon, leaving only the radial, fuzzy, glowing coronal filaments of the Sun around the edge." height="148" src="http://upload.wikimedia.org/wikipedia/commons/thumb/3/3c/Solar_eclips_1999_4_NR.jpg/150px-Solar_eclips_1999_4_NR.jpg" width="150" /></a></div><div class="thumbcaption" style="clear: left;">The 1999 solar eclipse</div></div><div style="float: left; margin: 1px; width: 152px;"><div class="thumbimage"><a class="image" href="http://en.wikipedia.org/wiki/File:STEREO-B_solar_eclipse.jpg" title="The Moon passing in front of the Sun, from the STEREO-B spacecraft.[102]"><img alt="The bright disk of the Sun, showing many coronal filaments, flares and grainy patches in the wavelength of this image, is partly obscured by a small dark disk: here, the Moon covers less than a fifteenth of the Sun." height="150" src="http://upload.wikimedia.org/wikipedia/commons/thumb/a/ae/STEREO-B_solar_eclipse.jpg/150px-STEREO-B_solar_eclipse.jpg" width="150" /></a></div><div class="thumbcaption" style="clear: left;">The Moon passing in front of the Sun, from the <a href="http://en.wikipedia.org/wiki/STEREO">STEREO</a>-B spacecraft.<sup class="reference" id="cite_ref-109"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-109">[102]</a></sup></div></div><div class="thumbcaption" style="background: transparent; clear: left; text-align: left;">From the Earth, the Moon and Sun appear the same size. From a satellite in an Earth-trailing orbit, the Moon may appear smaller than the Sun.</div></div></div>Eclipses can only occur when the Sun, Earth, and Moon are all in a straight line. <a href="http://en.wikipedia.org/wiki/Solar_eclipse" title="Solar eclipse">Solar eclipses</a> occur near a <a class="mw-redirect" href="http://en.wikipedia.org/wiki/New_Moon" title="New Moon">new Moon</a>, when the Moon is between the Sun and Earth. In contrast, <a href="http://en.wikipedia.org/wiki/Lunar_eclipse" title="Lunar eclipse">lunar eclipses</a> occur near a <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Full_Moon" title="Full Moon">full Moon</a>, when the Earth is between the Sun and Moon. The angular diameters of the Moon and the Sun as seen from Earth overlap in their variation, so that both <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Total_eclipse" title="Total eclipse">total</a> and <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Annular_eclipse" title="Annular eclipse">annular</a> solar eclipses are possible.<sup class="reference" id="cite_ref-110"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-110">[103]</a></sup> In a total eclipse, the Moon completely covers the disc of the Sun and the solar <a href="http://en.wikipedia.org/wiki/Corona">corona</a> becomes visible to the <a href="http://en.wikipedia.org/wiki/Naked_eye">naked eye</a>. Since the distance between the Moon and the Earth is very slowly increasing over time,<sup class="reference" id="cite_ref-Lambeck1977_101-4"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-Lambeck1977-101">[94]</a></sup> the angular diameter of the Moon is decreasing. This means that hundreds of millions of years ago the Moon would always completely cover the Sun on solar eclipses, and no annular eclipses were possible. Likewise, about 600 million years from now (if the angular diameter of the Sun does not change), the Moon will no longer cover the Sun completely, and only annular eclipses will occur.<sup class="reference" id="cite_ref-eclipse_111-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-eclipse-111">[104]</a></sup><br />Because the Moon's orbit around the Earth is inclined by about 5° to the <a href="http://en.wikipedia.org/wiki/Ecliptic" title="Ecliptic">orbit of the Earth around the Sun</a>, eclipses do not occur at every full and new Moon. For an eclipse to occur, the Moon must be near the intersection of the two orbital planes.<sup class="reference" id="cite_ref-eclipse_111-1"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-eclipse-111">[104]</a></sup> The periodicity and recurrence of eclipses of the Sun by the Moon, and of the Moon by the Earth, is described by the <a href="http://en.wikipedia.org/wiki/Saros_cycle">saros cycle</a>, which has a period of approximately 18 years.<sup class="reference" id="cite_ref-112"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-112">[105]</a></sup><br />As the Moon is continuously blocking our view of a half-degree-wide circular area of the sky,<sup class="reference" id="cite_ref-area_113-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-area-113">[nb 9]</a></sup><sup class="reference" id="cite_ref-114"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-114">[106]</a></sup> the related phenomenon of <a href="http://en.wikipedia.org/wiki/Occultation">occultation</a> occurs when a bright star or planet passes behind the Moon and is occulted: hidden from view. In this way, a solar eclipse is an occultation of the Sun. Because the Moon is comparatively close to the Earth, occultations of individual stars are not visible everywhere on the planet, nor at the same time. Because of the <a href="http://en.wikipedia.org/wiki/Precession">precession</a> of the lunar orbit, each year different stars are occulted.<sup class="reference" id="cite_ref-115"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-115">[107]</a></sup><br /><h2><span class="mw-headline" id="Study_and_exploration">Study and exploration<span id="Study_and_exploration"></span><span id="Exploration"></span></span></h2><div class="rellink boilerplate seealso">See also: <a href="http://en.wikipedia.org/wiki/Robotic_exploration_of_the_Moon">Robotic exploration of the Moon</a>, <a href="http://en.wikipedia.org/wiki/List_of_current_and_future_lunar_missions">List of current and future lunar missions</a>, <a href="http://en.wikipedia.org/wiki/Colonization_of_the_Moon">Colonization of the Moon</a>, and <a href="http://en.wikipedia.org/wiki/List_of_man-made_objects_on_the_Moon">List of man-made objects on the Moon</a></div><div class="thumb tright"><div class="thumbinner" style="width: 222px;"><a class="image" href="http://en.wikipedia.org/wiki/File:Moon_by_Johannes_hevelius_1645.PNG"><img alt="On an open folio page is a carefully drawn disk of the full Moon. In the upper corners of the page are waving banners held aloft by pairs of winged cherubs. In the lower left page corner a cherub assists another to measure distances with a pair of compasses; in the lower right corner a cherub views the main map through a handheld telescope, while another, kneeling, peers at the map from over a low cloth-draped table." class="thumbimage" height="198" src="http://upload.wikimedia.org/wikipedia/commons/thumb/0/03/Moon_by_Johannes_hevelius_1645.PNG/220px-Moon_by_Johannes_hevelius_1645.PNG" width="220" /></a> <br /><div class="thumbcaption"><div class="magnify"><a class="internal" href="http://en.wikipedia.org/wiki/File:Moon_by_Johannes_hevelius_1645.PNG" title="Enlarge"><img alt="" height="11" src="http://bits.wikimedia.org/skins-1.17/common/images/magnify-clip.png" width="15" /></a></div>Map of the Moon by <a href="http://en.wikipedia.org/wiki/Johannes_Hevelius">Johannes Hevelius</a> from his Selenographia (1647), the first map to include the <a href="http://en.wikipedia.org/wiki/Libration">libration</a> zones.</div></div></div><h3><span class="mw-headline" id="Early_studies">Early studies</span></h3><div class="rellink relarticle mainarticle">Main articles: <a href="http://en.wikipedia.org/wiki/Exploration_of_the_Moon#Early_history" title="Exploration of the Moon">Exploration of the Moon: Early history</a>, <a href="http://en.wikipedia.org/wiki/Selenography">Selenography</a>, and <a href="http://en.wikipedia.org/wiki/Lunar_theory">Lunar theory</a></div>Understanding of the Moon's cycles was an early development of astronomy: by the <span style="white-space: nowrap;">5th century BC</span>, <a href="http://en.wikipedia.org/wiki/Babylonian_astronomy" title="Babylonian astronomy">Babylonian astronomers</a> had recorded the 18-year <a href="http://en.wikipedia.org/wiki/Saros_cycle">Saros cycle</a> of <a href="http://en.wikipedia.org/wiki/Lunar_eclipse" title="Lunar eclipse">lunar eclipses</a>,<sup class="reference" id="cite_ref-116"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-116">[108]</a></sup> and <a href="http://en.wikipedia.org/wiki/Indian_astronomy" title="Indian astronomy">Indian astronomers</a> had described the Moon’s monthly elongation.<sup class="reference" id="cite_ref-Sarma-Ast-Ind_117-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-Sarma-Ast-Ind-117">[109]</a></sup> The <a href="http://en.wikipedia.org/wiki/Chinese_astronomy" title="Chinese astronomy">Chinese astronomer</a> <a href="http://en.wikipedia.org/wiki/Shi_Shen">Shi Shen</a> <span style="white-space: nowrap;">(fl. 4th century BC)</span> gave instructions for predicting solar and lunar eclipses.<sup class="reference" id="cite_ref-needham411_118-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-needham411-118">[110]</a></sup> Later, the physical form of the Moon and the cause of <a href="http://en.wikipedia.org/wiki/Moonlight">moonlight</a> became understood. The <a href="http://en.wikipedia.org/wiki/Ancient_Greece" title="Ancient Greece">ancient Greek</a> philosopher <a href="http://en.wikipedia.org/wiki/Anaxagoras">Anaxagoras</a> <span style="white-space: nowrap;">(d. 428 BC)</span> reasoned that the Sun and Moon were both giant spherical rocks, and that the latter reflected the light of the former.<sup class="reference" id="cite_ref-119"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-119">[111]</a></sup><sup class="reference" id="cite_ref-Needham227_120-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-Needham227-120">[112]</a></sup> Although the Chinese of the <a href="http://en.wikipedia.org/wiki/Han_Dynasty">Han Dynasty</a> believed the Moon to be energy equated to <i><a href="http://en.wikipedia.org/wiki/Qi">qi</a></i>, their 'radiating influence' theory also recognized that the light of the Moon was merely a reflection of the Sun, and <a href="http://en.wikipedia.org/wiki/Jing_Fang">Jing Fang</a> (78–37 BC) noted the sphericity of the Moon.<sup class="reference" id="cite_ref-Needham413-4_121-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-Needham413-4-121">[113]</a></sup> In 499 AD, the Indian astronomer <a href="http://en.wikipedia.org/wiki/Aryabhata">Aryabhata</a> mentioned in his <i><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Aryabhatiya" title="Aryabhatiya">Aryabhatiya</a></i> that reflected sunlight is the cause of the shining of the Moon.<sup class="reference" id="cite_ref-122"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-122">[114]</a></sup> The astronomer and physicist <a href="http://en.wikipedia.org/wiki/Alhazen">Alhazen</a> (965–1039) found that <a href="http://en.wikipedia.org/wiki/Sunlight">sunlight</a> was not reflected from the Moon like a mirror, but that light was emitted from every part of the Moon's sunlit surface in all directions.<sup class="reference" id="cite_ref-123"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-123">[115]</a></sup> <a href="http://en.wikipedia.org/wiki/Shen_Kuo">Shen Kuo</a> (1031–1095) of the <a href="http://en.wikipedia.org/wiki/Song_Dynasty">Song Dynasty</a> created an allegory equating the waxing and waning of the Moon to a round ball of reflective silver that, when doused with white powder and viewed from the side, would appear to be a crescent.<sup class="reference" id="cite_ref-Needham415-6_124-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-Needham415-6-124">[116]</a></sup><br />In <a href="http://en.wikipedia.org/wiki/Aristotle" title="Aristotle">Aristotle's</a> (384–322 BC) <a href="http://en.wikipedia.org/wiki/On_the_Heavens" title="On the Heavens">description of the universe</a>, the Moon marked the boundary between the spheres of the mutable elements (earth, water, air and fire), and the imperishable stars of <a href="http://en.wikipedia.org/wiki/Aether_%28classical_element%29" title="Aether (classical element)">aether</a>, an <a href="http://en.wikipedia.org/wiki/Aristotelian_physics" title="Aristotelian physics">influential philosophy</a> that would dominate for centuries.<sup class="reference" id="cite_ref-125"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-125">[117]</a></sup> However, in the <span style="white-space: nowrap;">2nd century BC</span>, <a href="http://en.wikipedia.org/wiki/Seleucus_of_Seleucia">Seleucus of Seleucia</a> correctly theorized that <a href="http://en.wikipedia.org/wiki/Tide" title="Tide">tides</a> were due to the attraction of the Moon, and that their height depends on the Moon's position relative to the <a href="http://en.wikipedia.org/wiki/Sun">Sun</a>.<sup class="reference" id="cite_ref-126"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-126">[118]</a></sup> In the same century, <a href="http://en.wikipedia.org/wiki/Aristarchus_of_Samos" title="Aristarchus of Samos">Aristarchus</a> <a href="http://en.wikipedia.org/wiki/Aristarchus_On_the_Sizes_and_Distances" title="Aristarchus On the Sizes and Distances">computed the size and distance</a> of the Moon from Earth, obtaining a value of about twenty times the <a href="http://en.wikipedia.org/wiki/Earth_radius">Earth radius</a> for the distance. These figures were greatly improved by <a href="http://en.wikipedia.org/wiki/Ptolemy">Ptolemy</a> (90–168 AD): his values of a mean distance of 59 times the Earth's radius and a diameter of 0.292 Earth diameters were close to the correct values of about 60 and 0.273 respectively.<sup class="reference" id="cite_ref-127"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-127">[119]</a></sup> <a href="http://en.wikipedia.org/wiki/Archimedes">Archimedes</a> (287–212 BC) invented a planetarium calculating motions of the Moon and the known planets.<sup class="reference" id="cite_ref-128"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-128">[120]</a></sup><br />During the <a href="http://en.wikipedia.org/wiki/Middle_Ages">Middle Ages</a>, before the invention of the telescope, the Moon was increasingly recognised as a sphere, though many believed that it was "perfectly smooth".<sup class="reference" id="cite_ref-129"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-129">[121]</a></sup> In 1609, <a href="http://en.wikipedia.org/wiki/Galileo_Galilei">Galileo Galilei</a> drew one of the first telescopic drawings of the Moon in his book <span lang="la"><i><a href="http://en.wikipedia.org/wiki/Sidereus_Nuncius">Sidereus Nuncius</a></i></span> and noted that it was not smooth but had mountains and craters. Telescopic mapping of the Moon followed: later in the 17th century, the efforts of <a href="http://en.wikipedia.org/wiki/Giovanni_Battista_Riccioli">Giovanni Battista Riccioli</a> and <a href="http://en.wikipedia.org/wiki/Francesco_Maria_Grimaldi">Francesco Maria Grimaldi</a> led to the system of naming of lunar features in use today. The more exact 1834-6 <span lang="la"><i>Mappa Selenographica</i></span> of <a href="http://en.wikipedia.org/wiki/Wilhelm_Beer">Wilhelm Beer</a> and <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Johann_Heinrich_M%C3%A4dler" title="Johann Heinrich Mädler">Johann Heinrich Mädler</a>, and their associated 1837 book <span lang="de"><i>Der Mond</i></span>, the first <a href="http://en.wikipedia.org/wiki/Trigonometry" title="Trigonometry">trigonometrically</a> accurate study of lunar features, included the heights of more than a thousand mountains, and introduced the study of the Moon at accuracies possible in earthly geography.<sup class="reference" id="cite_ref-130"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-130">[122]</a></sup> Lunar craters, first noted by Galileo, were thought to be <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Volcanic" title="Volcanic">volcanic</a> until the 1870s proposal of <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Richard_Proctor" title="Richard Proctor">Richard Proctor</a> that they were formed by collisions.<sup class="reference" id="cite_ref-worldbook_43-5"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-worldbook-43">[39]</a></sup> This view gained support in 1892 from the experimentation of geologist <a href="http://en.wikipedia.org/wiki/Grove_Karl_Gilbert">Grove Karl Gilbert</a>, and from comparative studies from 1920 to the 1940s,<sup class="reference" id="cite_ref-Hall1977_131-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-Hall1977-131">[123]</a></sup> leading to the development of <a href="http://en.wikipedia.org/wiki/Lunar_geologic_timescale" title="Lunar geologic timescale">lunar stratigraphy</a>, which by the 1950s was becoming a new and growing branch of <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Astrogeology" title="Astrogeology">astrogeology</a>.<sup class="reference" id="cite_ref-worldbook_43-6"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-worldbook-43">[39]</a></sup><br /><h3><span class="mw-headline" id="First_direct_exploration:_1959.E2.80.931976">First direct exploration: 1959–1976</span></h3><h4><span class="mw-headline" id="Soviet_missions">Soviet missions</span></h4><div class="rellink relarticle mainarticle">Main articles: <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Luna_program" title="Luna program">Luna program</a> and <a href="http://en.wikipedia.org/wiki/Lunokhod_programme">Lunokhod programme</a></div><div class="thumb tright"><div class="thumbinner" style="width: 222px;"><a class="image" href="http://en.wikipedia.org/wiki/File:Lunokhod_hires.jpg"><img alt="" class="thumbimage" height="178" src="http://upload.wikimedia.org/wikipedia/en/thumb/5/5c/Lunokhod_hires.jpg/220px-Lunokhod_hires.jpg" width="220" /></a> <br /><div class="thumbcaption"><div class="magnify"><a class="internal" href="http://en.wikipedia.org/wiki/File:Lunokhod_hires.jpg" title="Enlarge"><img alt="" height="11" src="http://bits.wikimedia.org/skins-1.17/common/images/magnify-clip.png" width="15" /></a></div><a href="http://en.wikipedia.org/wiki/Lunokhod_1">Lunokhod 1</a> (lit. <i>moonwalker</i>), the first successful <a href="http://en.wikipedia.org/wiki/Rover_%28space_exploration%29" title="Rover (space exploration)">space rover</a>.</div></div></div>The <a href="http://en.wikipedia.org/wiki/Cold_War">Cold War</a>-inspired <a href="http://en.wikipedia.org/wiki/Space_Race">Space Race</a> between the Soviet Union and the U.S. led to an acceleration of interest in <a href="http://en.wikipedia.org/wiki/Exploration_of_the_Moon">exploration of the Moon</a>. Once launchers had the necessary capabilities, these nations sent unmanned probes on both flyby and impact/lander missions. Spacecraft from the Soviet Union's <a href="http://en.wikipedia.org/wiki/Luna_programme" title="Luna programme"><i>Luna</i> program</a> were the first to accomplish a number of goals: following three unnamed, failed missions in 1958,<sup class="reference" id="cite_ref-132"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-132">[124]</a></sup> the first man-made object to escape Earth's gravity and pass near the Moon was <i><a href="http://en.wikipedia.org/wiki/Luna_1">Luna 1</a></i>; the first man-made object to impact the lunar surface was <i><a href="http://en.wikipedia.org/wiki/Luna_2">Luna 2</a></i>, and the first photographs of the normally occluded far side of the Moon were made by <i><a href="http://en.wikipedia.org/wiki/Luna_3">Luna 3</a></i>, all in 1959.<br />The first spacecraft to perform a successful lunar <a href="http://en.wikipedia.org/wiki/Lander_%28spacecraft%29" title="Lander (spacecraft)">soft landing</a> was <i><a href="http://en.wikipedia.org/wiki/Luna_9">Luna 9</a></i> and the first unmanned vehicle to orbit the Moon was <i><a href="http://en.wikipedia.org/wiki/Luna_10">Luna 10</a></i>, both in 1966.<sup class="reference" id="cite_ref-worldbook_43-7"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-worldbook-43">[39]</a></sup> <a href="http://en.wikipedia.org/wiki/Moon_rock" title="Moon rock">Rock and soil samples</a> were brought back to Earth by three <i>Luna</i> <a href="http://en.wikipedia.org/wiki/Sample_return_mission" title="Sample return mission">sample return missions</a> (<i><a href="http://en.wikipedia.org/wiki/Luna_16">Luna 16</a></i>, <i><a href="http://en.wikipedia.org/wiki/Luna_20" title="Luna 20">20</a></i>, and <i><a href="http://en.wikipedia.org/wiki/Luna_24" title="Luna 24">24</a></i>), which returned 0.3 kg total.<sup class="reference" id="cite_ref-133"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-133">[125]</a></sup> Two pioneering robotic spacecrafts of <a href="http://en.wikipedia.org/wiki/Rover_%28space_exploration%29" title="Rover (space exploration)">rover</a> type landed on the Moon in 1970 and 1973 as a part of Soviet <a href="http://en.wikipedia.org/wiki/Lunokhod_programme">Lunokhod programme</a>.<br /><h4><span class="mw-headline" id="United_States_missions">United States missions</span></h4><div class="rellink relarticle mainarticle">Main articles: <a href="http://en.wikipedia.org/wiki/Apollo_program">Apollo program</a> and <a href="http://en.wikipedia.org/wiki/Moon_landing">Moon landing</a></div><div class="thumb tright"><div class="thumbinner" style="width: 222px;"><a class="image" href="http://en.wikipedia.org/wiki/File:NASA-Apollo8-Dec24-Earthrise.jpg"><img alt="The small blue-white semicircle of the Earth, almost glowing with colour in the blackness of space, rising over the limb of the desolate, cratered surface of the Moon." class="thumbimage" height="220" src="http://upload.wikimedia.org/wikipedia/commons/thumb/a/a8/NASA-Apollo8-Dec24-Earthrise.jpg/220px-NASA-Apollo8-Dec24-Earthrise.jpg" width="220" /></a> <br /><div class="thumbcaption"><div class="magnify"><a class="internal" href="http://en.wikipedia.org/wiki/File:NASA-Apollo8-Dec24-Earthrise.jpg" title="Enlarge"><img alt="" height="11" src="http://bits.wikimedia.org/skins-1.17/common/images/magnify-clip.png" width="15" /></a></div><a href="http://en.wikipedia.org/wiki/Earth">Earth</a> as viewed from the Moon during the <a href="http://en.wikipedia.org/wiki/Apollo_8">Apollo 8</a> mission, <a href="http://en.wikipedia.org/wiki/Christmas_Eve">Christmas Eve</a>, 1968. Africa is at the sunset terminator, both Americas are under cloud, and Antarctica is at the left end of the terminator.</div></div></div><div class="thumb tright"><div class="thumbinner" style="width: 222px;"><a class="image" href="http://en.wikipedia.org/wiki/File:Aldrin_Apollo_11_original.jpg"><img alt="An astronaut in an American Apollo-program spacesuit, standing on the flat, heavily footprinted landing area, with the utterly black sky of space above the horizon." class="thumbimage" height="222" src="http://upload.wikimedia.org/wikipedia/commons/thumb/9/98/Aldrin_Apollo_11_original.jpg/220px-Aldrin_Apollo_11_original.jpg" width="220" /></a> <br /><div class="thumbcaption"><div class="magnify"><a class="internal" href="http://en.wikipedia.org/wiki/File:Aldrin_Apollo_11_original.jpg" title="Enlarge"><img alt="" height="11" src="http://bits.wikimedia.org/skins-1.17/common/images/magnify-clip.png" width="15" /></a></div><a href="http://en.wikipedia.org/wiki/Astronaut">Astronaut</a> <a href="http://en.wikipedia.org/wiki/Buzz_Aldrin">Buzz Aldrin</a> photographed by <a href="http://en.wikipedia.org/wiki/Neil_Armstrong">Neil Armstrong</a> during the <a href="http://en.wikipedia.org/wiki/Apollo_11" title="Apollo 11">first Moon landing</a> on 20 July 1969</div></div></div>American lunar exploration began with robotic missions aimed at developing understanding of the lunar surface for an eventual manned landing: the <a href="http://en.wikipedia.org/wiki/Jet_Propulsion_Laboratory">Jet Propulsion Laboratory</a>'s <a href="http://en.wikipedia.org/wiki/Surveyor_Program" title="Surveyor Program"><i>Surveyor</i> program</a> landed <a href="http://en.wikipedia.org/wiki/Surveyor_1" title="Surveyor 1">its first spacecraft</a> four months after <i>Luna 9</i>. <a href="http://en.wikipedia.org/wiki/NASA">NASA</a>'s manned <a href="http://en.wikipedia.org/wiki/Apollo_program">Apollo program</a> was developed in parallel; after a series of unmanned and manned tests of the Apollo spacecraft in Earth orbit, and spurred on by a potential <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Soviet_moonshot" title="Soviet moonshot">Soviet lunar flight</a>, in 1968 <a href="http://en.wikipedia.org/wiki/Apollo_8">Apollo 8</a> made the first crewed mission to lunar orbit. The subsequent landing of the first humans on the Moon in 1969 is seen by many as the culmination of the Space Race.<sup class="reference" id="cite_ref-CNN_134-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-CNN-134">[126]</a></sup> <a href="http://en.wikipedia.org/wiki/Neil_Armstrong">Neil Armstrong</a> became the first person to walk on the Moon as the commander of the American mission <a href="http://en.wikipedia.org/wiki/Apollo_11">Apollo 11</a> by first setting foot on the Moon at 02:56 UTC on 21 July 1969.<sup class="reference" id="cite_ref-135"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-135">[127]</a></sup> The Apollo missions 11 to 17 (except <a href="http://en.wikipedia.org/wiki/Apollo_13">Apollo 13</a>, which aborted its planned lunar landing) returned 382 kg of lunar rock and soil in 2,196 separate samples.<sup class="reference" id="cite_ref-136"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-136">[128]</a></sup> The American <a href="http://en.wikipedia.org/wiki/Moon_landing">Moon landing</a> and return was enabled by considerable technological advances in the early 1960s, in domains such as <a href="http://en.wikipedia.org/wiki/Ablation">ablation</a> chemistry, <a href="http://en.wikipedia.org/wiki/Software_engineering">software engineering</a> and <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Atmospheric_re-entry" title="Atmospheric re-entry">atmospheric re-entry</a> technology, and by highly competent management of the enormous technical undertaking.<sup class="reference" id="cite_ref-137"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-137">[129]</a></sup><sup class="reference" id="cite_ref-138"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-138">[130]</a></sup><br />Scientific instrument packages were installed on the lunar surface during all the Apollo missions. Long-lived <a href="http://en.wikipedia.org/wiki/Apollo_Lunar_Surface_Experiments_Package" title="Apollo Lunar Surface Experiments Package">instrument stations</a>, including heat flow probes, <a href="http://en.wikipedia.org/wiki/Seismometer" title="Seismometer">seismometers</a>, and <a href="http://en.wikipedia.org/wiki/Magnetometer" title="Magnetometer">magnetometers</a>, were installed at the <a href="http://en.wikipedia.org/wiki/Apollo_12">Apollo 12</a>, <a href="http://en.wikipedia.org/wiki/Apollo_14" title="Apollo 14">14</a>, <a href="http://en.wikipedia.org/wiki/Apollo_15" title="Apollo 15">15</a>, <a href="http://en.wikipedia.org/wiki/Apollo_16" title="Apollo 16">16</a>, and <a href="http://en.wikipedia.org/wiki/Apollo_17" title="Apollo 17">17</a> landing sites. Direct transmission of data to Earth concluded in late 1977 due to budgetary considerations,<sup class="reference" id="cite_ref-139"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-139">[131]</a></sup><sup class="reference" id="cite_ref-140"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-140">[132]</a></sup> but as the stations' <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Lunar_laser_ranging_experiment" title="Lunar laser ranging experiment">lunar laser ranging</a> corner-cube retroreflector arrays are passive instruments, they are still being used. Ranging to the stations is routinely performed from earth-based stations with an accuracy of a few centimetres, and data from this experiment are being used to place constraints on the size of the lunar core.<sup class="reference" id="cite_ref-141"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-141">[133]</a></sup><br /><h3><span class="mw-headline" id="Current_era:_1990.E2.80.93present">Current era: 1990–present</span></h3>Post-Apollo and <i>Luna</i>, many more countries have become involved in direct exploration of the Moon. In 1990, Japan became the third country to place a spacecraft into lunar orbit with its <i><a href="http://en.wikipedia.org/wiki/Hiten">Hiten</a></i> spacecraft. The spacecraft released a smaller probe, <i>Hagoromo</i>, in lunar orbit, but the transmitter failed, preventing further scientific use of the mission.<sup class="reference" id="cite_ref-142"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-142">[134]</a></sup> In 1994, the U.S. sent the joint Defense Department/NASA spacecraft <i><a href="http://en.wikipedia.org/wiki/Clementine_%28spacecraft%29" title="Clementine (spacecraft)">Clementine</a></i> to lunar orbit. This mission obtained the first near-global topographic map of the Moon, and the first global <a href="http://en.wikipedia.org/wiki/Multi-spectral_image" title="Multi-spectral image">multispectral</a> images of the lunar surface.<sup class="reference" id="cite_ref-143"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-143">[135]</a></sup> This was followed in 1998 by the <i><a href="http://en.wikipedia.org/wiki/Lunar_Prospector">Lunar Prospector</a></i> mission, whose instruments indicated the presence of excess hydrogen at the lunar poles, which is likely to have been caused by the presence of water ice in the upper few meters of the regolith within permanently shadowed craters.<sup class="reference" id="cite_ref-144"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-144">[136]</a></sup><br />The European spacecraft <i><a href="http://en.wikipedia.org/wiki/SMART-1">SMART-1</a></i>, the second <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Ion_propulsion" title="Ion propulsion">ion-propelled</a> spacecraft, was in lunar orbit from 15 November 2004 until its lunar impact on 3 September 2006, and made the first detailed survey of chemical elements on the lunar surface.<sup class="reference" id="cite_ref-145"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-145">[137]</a></sup> China has expressed <a href="http://en.wikipedia.org/wiki/Chinese_Lunar_Exploration_Program" title="Chinese Lunar Exploration Program">ambitious plans</a> for exploring the Moon, and successfully orbited its first spacecraft, <i><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Chang%27e-1" title="Chang'e-1">Chang'e-1</a></i>, from 5 November 2007 until its controlled lunar impact on 1 March 2008.<sup class="reference" id="cite_ref-xinhua_20090301_146-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-xinhua_20090301-146">[138]</a></sup> In its sixteen-month mission, it obtained a full image map of the Moon. Between 4 October 2007 and 10 June 2009, the <a href="http://en.wikipedia.org/wiki/Japan_Aerospace_Exploration_Agency">Japan Aerospace Exploration Agency</a>'s <i><a href="http://en.wikipedia.org/wiki/SELENE" title="SELENE">Kaguya</a> (Selene)</i> mission, a lunar orbiter fitted with a <a href="http://en.wikipedia.org/wiki/High-definition_video" title="High-definition video">high-definition video camera</a>, and two small radio-transmitter satellites, obtained lunar geophysics data and took the first high-definition movies from beyond Earth orbit.<sup class="reference" id="cite_ref-147"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-147">[139]</a></sup><sup class="reference" id="cite_ref-148"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-148">[140]</a></sup> India's first lunar mission, <i><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Chandrayaan" title="Chandrayaan">Chandrayaan I</a></i>, orbited from 8 November 2008 until loss of contact on 27 August 2009, creating a high resolution chemical, mineralogical and photo-geological map of the lunar surface, and confirming the presence of water molecules in lunar soil.<sup class="reference" id="cite_ref-149"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-149">[141]</a></sup> The <a href="http://en.wikipedia.org/wiki/Indian_Space_Research_Organisation">Indian Space Research Organisation</a> plans to launch <i><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Chandrayaan_II" title="Chandrayaan II">Chandrayaan II</a></i> in 2013, which is slated to include a Russian robotic lunar rover.<sup class="reference" id="cite_ref-150"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-150">[142]</a></sup><sup class="reference" id="cite_ref-151"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-151">[143]</a></sup> The U.S. co-launched the <i><a href="http://en.wikipedia.org/wiki/Lunar_Reconnaissance_Orbiter">Lunar Reconnaissance Orbiter</a></i> (LRO) and the <i><a href="http://en.wikipedia.org/wiki/LCROSS">LCROSS</a></i> impactor and follow-up observation orbiter on 18 June 2009; <i>LCROSS</i> completed its mission by making a planned and widely observed impact in the crater <a href="http://en.wikipedia.org/wiki/Cabeus_%28crater%29" title="Cabeus (crater)">Cabeus</a> on 9 October 2009,<sup class="reference" id="cite_ref-152"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-152">[144]</a></sup> while <i>LRO</i> is currently in operation, obtaining precise lunar <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Altimetry" title="Altimetry">altimetry</a> and high-resolution imagery.<br />Other upcoming lunar missions include Russia's <i><a href="http://en.wikipedia.org/wiki/Luna-Glob">Luna-Glob</a></i>: an unmanned lander, set of seismometers, and an orbiter based on its Martian <i><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Phobos-Grunt" title="Phobos-Grunt">Phobos-Grunt</a></i> mission, which is slated to launch in 2012.<sup class="reference" id="cite_ref-153"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-153">[145]</a></sup><sup class="reference" id="cite_ref-154"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-154">[146]</a></sup> Privately funded lunar exploration has been promoted by the <a href="http://en.wikipedia.org/wiki/Google_Lunar_X_Prize">Google Lunar X Prize</a>, announced 13 September 2007, which offers US$20 million to anyone who can land a robotic rover on the Moon and meet other specified criteria.<sup class="reference" id="cite_ref-155"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-155">[147]</a></sup><br />NASA began to <a href="http://en.wikipedia.org/wiki/Vision_for_Space_Exploration" title="Vision for Space Exploration">plan to resume manned missions</a> following the call by U.S. President <a href="http://en.wikipedia.org/wiki/George_W._Bush">George W. Bush</a> on 14 January 2004 for a mission to the Moon by 2020.<sup class="reference" id="cite_ref-156"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-156">[148]</a></sup> The <a href="http://en.wikipedia.org/wiki/Constellation_program">Constellation program</a> was funded and construction and testing begun on a <a href="http://en.wikipedia.org/wiki/Orion_%28spacecraft%29" title="Orion (spacecraft)">manned spacecraft</a> and <a href="http://en.wikipedia.org/wiki/Aries_%28rocket%29" title="Aries (rocket)">launch vehicle</a>,<sup class="reference" id="cite_ref-157"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-157">[149]</a></sup> and design studies for a lunar base.<sup class="reference" id="cite_ref-158"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-158">[150]</a></sup> However, that program has been placed in jeopardy by the proposed 2011 budget, which will cancel Constellation in favour of NASA pursuing space technology and heavy-lift rocketry research.<sup class="reference" id="cite_ref-159"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-159">[151]</a></sup> <a href="http://en.wikipedia.org/wiki/India">India</a> has also expressed its hope to send a manned mission to the Moon by 2020.<sup class="reference" id="cite_ref-160"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-160">[152]</a></sup><br /><h2><span class="mw-headline" id="Legal_status">Legal status</span></h2><div class="rellink relarticle mainarticle">Main article: <a href="http://en.wikipedia.org/wiki/Space_law">Space law</a></div>Although <i><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Luna_program" title="Luna program">Luna</a></i> landers scattered pennants of the <a href="http://en.wikipedia.org/wiki/Soviet_Union">Soviet Union</a> on the Moon, and <a class="mw-redirect" href="http://en.wikipedia.org/wiki/U.S._flag" title="U.S. flag">U.S. flags</a> were symbolically planted at their landing sites by the <a href="http://en.wikipedia.org/wiki/List_of_Apollo_astronauts" title="List of Apollo astronauts">Apollo astronauts</a>, no nation currently claims ownership of any part of the Moon's surface.<sup class="reference" id="cite_ref-unoosa_q6_161-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-unoosa_q6-161">[153]</a></sup> Russia and the U.S. are party to the 1967 <a href="http://en.wikipedia.org/wiki/Outer_Space_Treaty">Outer Space Treaty</a>,<sup class="reference" id="cite_ref-unoosa_q4_162-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-unoosa_q4-162">[154]</a></sup> which defines the Moon and all outer space as the "province of all mankind".<sup class="reference" id="cite_ref-unoosa_q6_161-1"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-unoosa_q6-161">[153]</a></sup> This treaty also restricts the use of the Moon to peaceful purposes, explicitly banning military installations and <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Weapons_of_mass_destruction" title="Weapons of mass destruction">weapons of mass destruction</a>.<sup class="reference" id="cite_ref-unoosa_q5_163-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-unoosa_q5-163">[155]</a></sup> The 1979 <a href="http://en.wikipedia.org/wiki/Moon_Treaty" title="Moon Treaty">Moon Agreement</a> was created to restrict the exploitation of the Moon's resources by any single nation, but it has not been signed by any of the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Space-faring_nations" title="Space-faring nations">space-faring nations</a>.<sup class="reference" id="cite_ref-unoosa_moon_164-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-unoosa_moon-164">[156]</a></sup> While several individuals have made <a href="http://en.wikipedia.org/wiki/Extraterrestrial_real_estate" title="Extraterrestrial real estate">claims to the Moon</a> in whole or in part, none of these are considered credible.<sup class="reference" id="cite_ref-unoosa_q7_165-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-unoosa_q7-165">[157]</a></sup><sup class="reference" id="cite_ref-iisl_2004_166-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-iisl_2004-166">[158]</a></sup><sup class="reference" id="cite_ref-iisl_2009_167-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-iisl_2009-167">[159]</a></sup><br /><h2><span class="mw-headline" id="In_culture">In culture</span></h2><div class="rellink boilerplate seealso">See also: <a href="http://en.wikipedia.org/wiki/Moon_in_fiction">Moon in fiction</a>, <a href="http://en.wikipedia.org/wiki/Lunar_calendar">Lunar calendar</a>, <a href="http://en.wikipedia.org/wiki/Metonic_cycle">Metonic cycle</a>, <a href="http://en.wikipedia.org/wiki/Lunar_deity">Lunar deity</a>, <a href="http://en.wikipedia.org/wiki/Lunar_effect">Lunar effect</a>, and <a href="http://en.wikipedia.org/wiki/Blue_moon">Blue moon</a></div><div class="thumb tright"><div class="thumbinner" style="width: 222px;"><a class="image" href="http://en.wikipedia.org/wiki/File:M%C3%A1ni_and_S%C3%B3l_by_Lorenz_Fr%C3%B8lich.jpg"><img alt="" class="thumbimage" height="243" src="http://upload.wikimedia.org/wikipedia/commons/thumb/a/ae/M%C3%A1ni_and_S%C3%B3l_by_Lorenz_Fr%C3%B8lich.jpg/220px-M%C3%A1ni_and_S%C3%B3l_by_Lorenz_Fr%C3%B8lich.jpg" width="220" /></a> <br /><div class="thumbcaption"><div class="magnify"><a class="internal" href="http://en.wikipedia.org/wiki/File:M%C3%A1ni_and_S%C3%B3l_by_Lorenz_Fr%C3%B8lich.jpg" title="Enlarge"><img alt="" height="11" src="http://bits.wikimedia.org/skins-1.17/common/images/magnify-clip.png" width="15" /></a></div>The gods <a href="http://en.wikipedia.org/wiki/M%C3%A1ni">Máni</a> (left) and <a class="mw-redirect" href="http://en.wikipedia.org/wiki/S%C3%B3l_%28Sun%29" title="Sól (Sun)">Sól</a> (right), the personified Moon and Sun in <a href="http://en.wikipedia.org/wiki/Norse_mythology">Norse mythology</a>, as depicted in an illustration by <a href="http://en.wikipedia.org/wiki/Lorenz_Fr%C3%B8lich">Lorenz Frølich</a> (1895)</div></div></div>The Moon's regular phases make it a very convenient timepiece, and the periods of its waxing and waning form the basis of many of the oldest calendars. <a href="http://en.wikipedia.org/wiki/Tally_stick" title="Tally stick">Tally sticks</a>, notched bones dating as far back as 20–30,000 years ago, are believed by some to mark the phases of the Moon.<sup class="reference" id="cite_ref-Marshack_168-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-Marshack-168">[160]</a></sup><sup class="reference" id="cite_ref-169"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-169">[161]</a></sup><sup class="reference" id="cite_ref-170"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-170">[162]</a></sup> The ~30-day month is an approximation of the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Lunar_cycle" title="Lunar cycle">lunar cycle</a>. The English noun <i><a href="http://en.wikipedia.org/wiki/Month">month</a></i> and its cognates in other Germanic languages stem from Proto-Germanic <i>*mǣnṓth-</i>, which is connected to the above mentioned Proto-Germanic <i>*mǣnōn</i>, indicating the usage of a <a href="http://en.wikipedia.org/wiki/Lunar_calendar">lunar calendar</a> among the <a href="http://en.wikipedia.org/wiki/Germanic_peoples">Germanic peoples</a> (<a href="http://en.wikipedia.org/wiki/Germanic_calendar">Germanic calendar</a>) prior to the adoption of a <a href="http://en.wikipedia.org/wiki/Solar_calendar">solar calendar</a>.<sup class="reference" id="cite_ref-barnhart-and-germania_171-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-barnhart-and-germania-171">[163]</a></sup> The same <a href="http://en.wikipedia.org/wiki/Proto-Indo-European_language" title="Proto-Indo-European language">Indo-European root</a> as <i>moon</i> led, via <a href="http://en.wikipedia.org/wiki/Latin">Latin</a>, to <i>measure</i> and <i>menstrual</i>, words which echo the Moon's importance to many ancient cultures in measuring time (see <a href="http://en.wikipedia.org/wiki/Latin">Latin</a> <span lang="la"><i>mensis</i></span> and <a href="http://en.wikipedia.org/wiki/Ancient_Greek">Ancient Greek</a> <span lang="el"><i>μήνας</i></span> (<i>mēnas</i>), meaning "month").<sup class="reference" id="cite_ref-172"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-172">[164]</a></sup><sup class="reference" id="cite_ref-173"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-173">[165]</a></sup><br /><div class="thumb tleft"><div class="thumbinner" style="width: 302px;"><a class="image" href="http://en.wikipedia.org/wiki/File:Moonstar.jpg"><img alt="" class="thumbimage" height="202" src="http://upload.wikimedia.org/wikipedia/commons/thumb/2/28/Moonstar.jpg/300px-Moonstar.jpg" width="300" /></a> <br /><div class="thumbcaption"><div class="magnify"><a class="internal" href="http://en.wikipedia.org/wiki/File:Moonstar.jpg" title="Enlarge"><img alt="" height="11" src="http://bits.wikimedia.org/skins-1.17/common/images/magnify-clip.png" width="15" /></a></div>A crescent Moon and a star are a common symbol of <a href="http://en.wikipedia.org/wiki/Muslim">Muslim</a> people, appearing in numerous flags including those of <a href="http://en.wikipedia.org/wiki/Flag_of_Turkey" title="Flag of Turkey">Turkey</a> and <a href="http://en.wikipedia.org/wiki/Flag_of_Pakistan" title="Flag of Pakistan">Pakistan</a>.</div></div></div>The Moon has been the subject of many works of art and literature and the inspiration for countless others. It is a motif in the visual arts, the performing arts, poetry, prose and music. A 5,000-year-old rock carving at <a href="http://en.wikipedia.org/wiki/Knowth">Knowth</a>, Ireland, may represent the Moon, which would be the earliest depiction discovered.<sup class="reference" id="cite_ref-spacetoday_174-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-spacetoday-174">[166]</a></sup> The contrast between the brighter highlands and darker maria create the patterns seen by different cultures as the <a href="http://en.wikipedia.org/wiki/Man_in_the_Moon">Man in the Moon</a>, the <a href="http://en.wikipedia.org/wiki/Moon_rabbit" title="Moon rabbit">rabbit</a> and the buffalo, among others. In many prehistoric and ancient cultures, the Moon was personified as <a href="http://en.wikipedia.org/wiki/Lunar_deity" title="Lunar deity">a deity</a> or other <a href="http://en.wikipedia.org/wiki/Supernatural">supernatural</a> phenomenon, and <a href="http://en.wikipedia.org/wiki/Moon_%28astrology%29" title="Moon (astrology)">astrological views</a> of the Moon continue to be propagated today.<br />The Moon has a long association with insanity and irrationality; the words <i>lunacy</i> and <i>loony</i> are derived from the Latin name for the Moon, <i>Luna</i>. Philosophers such as <a href="http://en.wikipedia.org/wiki/Aristotle">Aristotle</a> and <a href="http://en.wikipedia.org/wiki/Pliny_the_Elder">Pliny the Elder</a> argued that the full Moon induced insanity in susceptible individuals, believing that the brain, which is mostly water, must be affected by the Moon and its power over the tides, but the Moon's gravity is too slight to affect any single person.<sup class="reference" id="cite_ref-sciam_175-0"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-sciam-175">[167]</a></sup> Even today, people insist that admissions to psychiatric hospitals, traffic accidents, homicides or suicides increase during a full Moon, although there is no scientific evidence to support such claims.<sup class="reference" id="cite_ref-sciam_175-1"><a href="http://en.wikipedia.org/wiki/Moon#cite_note-sciam-175">[167]</a></sup><br /><h2><span class="mw-headline" id="References">References</span></h2><dl><dt>Notes</dt></dl><div class="reflist" style="list-style-type: decimal;"><ol class="references"><li id="cite_note-maxval-3"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-maxval_3-0">^</a></b> The <i>maximum value</i> is given based on scaling of the brightness from the value of −12.74 given for an equator to Moon-centre distance of 378 000 km in the NASA factsheet reference to the minimum Earth-Moon distance given there, after the latter is corrected for the Earth's equatorial radius of 6 378 km, giving 350 600 km. The <i>minimum value</i> (for a distant <a class="mw-redirect" href="http://en.wikipedia.org/wiki/New_Moon" title="New Moon">new Moon</a>) is based on a similar scaling using the maximum Earth-Moon distance of 407 000 km (given in the factsheet) and by calculating the brightness of the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Earthshine" title="Earthshine">earthshine</a> onto such a new Moon. The brightness of the earthshine is <span style="white-space: nowrap;">[ Earth <a href="http://en.wikipedia.org/wiki/Albedo">albedo</a> ×</span> <span style="white-space: nowrap;">(<a href="http://en.wikipedia.org/wiki/Earth_radius">Earth radius</a> /</span> Radius of <a href="http://en.wikipedia.org/wiki/Orbit_of_the_Moon" title="Orbit of the Moon">Moon's orbit</a>)<sup>2</sup> ] relative to the direct solar illumination that occurs for a full Moon. (<span style="white-space: nowrap;">Earth albedo = 0.367</span>; <span style="white-space: nowrap;">Earth radius = (polar</span> radius × equatorial <span style="white-space: nowrap;">radius)<sup>½</sup> = 6 367 km</span>.)</li><li id="cite_note-angular_size-4"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-angular_size_4-0">^</a></b> The range of angular size values given are based on simple scaling of the following values given in the fact sheet reference: at an Earth-equator to Moon-centre distance of 378 000 km, the <a href="http://en.wikipedia.org/wiki/Angular_diameter" title="Angular diameter">angular size</a> is 1896 <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Arcsecond" title="Arcsecond">arcseconds</a>. The same fact sheet gives extreme Earth-Moon distances of 407 000 km and 357 000 km. For the maximum angular size, the minimum distance has to be corrected for the Earth's equatorial radius of 6 378 km, giving 350 600 km.</li><li id="cite_note-pressure_explanation-7"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-pressure_explanation_7-0">^</a></b> Lucey <i>et al.</i> (2006) give <span style="white-space: nowrap;">10<sup>7</sup> particles <a href="http://en.wikipedia.org/wiki/Cubic_centimetre" title="Cubic centimetre">cm<sup>−3</sup></a></span> by day and <span style="white-space: nowrap;">10<sup>5</sup> particles cm<sup>−3</sup></span> by night. Along with equatorial surface temperatures of 390 <a href="http://en.wikipedia.org/wiki/Kelvin" title="Kelvin">K</a> by day and 100 K by night, the <a href="http://en.wikipedia.org/wiki/Ideal_gas_law">ideal gas law</a> yields the pressures given in the infobox (rounded to the nearest <a href="http://en.wikipedia.org/wiki/Order_of_magnitude">order of magnitude</a>; 10<sup>−7</sup> <a href="http://en.wikipedia.org/wiki/Pascal_%28unit%29" title="Pascal (unit)">Pa</a> by day and 10<sup>−10</sup> Pa by night.</li><li id="cite_note-8"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-8">^</a></b> There are a number of <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Near-Earth_asteroid" title="Near-Earth asteroid">near-Earth asteroids</a> including <a href="http://en.wikipedia.org/wiki/3753_Cruithne">3753 Cruithne</a> that are <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Co-orbital" title="Co-orbital">co-orbital</a> with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term (Morais et al, 2002). These are <a href="http://en.wikipedia.org/wiki/Quasi-satellite" title="Quasi-satellite">quasi-satellites</a> and not true moons. For more information, see <a href="http://en.wikipedia.org/wiki/Other_moons_of_Earth">Other moons of Earth</a>.</li><li id="cite_note-age-14"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-age_14-0">^</a></b> This age is calculated from isotope dating of lunar rocks.</li><li id="cite_note-orbpd-82"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-orbpd_82-0">^</a></b> More accurately, the Moon's mean sidereal period (fixed star to fixed star) is 27.321661 days <span style="white-space: nowrap;">(27d 07h 43m 11.5s)</span>, and its mean tropical orbital period (from equinox to equinox) is 27.321582 days <span style="white-space: nowrap;">(27d 07h 43m 04.7s)</span> (<i>Explanatory Supplement to the Astronomical Ephemeris</i>, 1961, at p.107).</li><li id="cite_note-synpd-83"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-synpd_83-0">^</a></b> More accurately, the Moon's mean synodic period (between mean solar conjunctions) is 29.530589 days <span style="white-space: nowrap;">(29d 12h 44m 02.9s)</span> (<i>Explanatory Supplement to the Astronomical Ephemeris</i>, 1961, at p.107).</li><li id="cite_note-brightness-90"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-brightness_90-0">^</a></b> The Sun's <a href="http://en.wikipedia.org/wiki/Apparent_magnitude">apparent magnitude</a> is −26.7, and the full Moon's apparent magnitude is −12.7.</li><li id="cite_note-area-113"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-area_113-0">^</a></b> On average, the Moon covers an area of <span style="white-space: nowrap;">0.21078 square degrees</span> on the night sky.</li></ol></div><dl><dt>Footnotes</dt></dl><div class="reflist references-column-width" style="-moz-column-width: 30em; -webkit-column-width: 30em; column-width: 30em; list-style-type: decimal;"><ol class="references"><li id="cite_note-W06-0">^ <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-W06_0-0"><sup><i><b>a</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-W06_0-1"><sup><i><b>b</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-W06_0-2"><sup><i><b>c</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-W06_0-3"><sup><i><b>d</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-W06_0-4"><sup><i><b>e</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-W06_0-5"><sup><i><b>f</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-W06_0-6"><sup><i><b>g</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-W06_0-7"><sup><i><b>h</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-W06_0-8"><sup><i><b>i</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-W06_0-9"><sup><i><b>j</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-W06_0-10"><sup><i><b>k</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-W06_0-11"><sup><i><b>l</b></i></sup></a> <span class="citation Journal">Wieczorek, M.; <i>et al.</i> (2006). "The constitution and structure of the lunar interior". <i>Reviews in Mineralogy and Geochemistry</i> <b>60</b> (1): 221–364. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.2138%2Frmg.2006.60.3" rel="nofollow">10.2138/rmg.2006.60.3</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=The+constitution+and+structure+of+the+lunar+interior&rft.jtitle=Reviews+in+Mineralogy+and+Geochemistry&rft.aulast=Wieczorek&rft.aufirst=M.&rft.au=Wieczorek%2C%26%2332%3BM.&rft.date=2006&rft.volume=60&rft.issue=1&rft.pages=221%E2%80%93364&rft_id=info:doi/10.2138%2Frmg.2006.60.3&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-NSSDC-1">^ <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-NSSDC_1-0"><sup><i><b>a</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-NSSDC_1-1"><sup><i><b>b</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-NSSDC_1-2"><sup><i><b>c</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-NSSDC_1-3"><sup><i><b>d</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-NSSDC_1-4"><sup><i><b>e</b></i></sup></a> <span class="citation web">Williams, Dr. David R. (2 February 2006). <a class="external text" href="http://nssdc.gsfc.nasa.gov/planetary/factsheet/moonfact.html" rel="nofollow">"Moon Fact Sheet"</a>. <a href="http://en.wikipedia.org/wiki/NASA">NASA</a> (National Space Science Data Center)<span class="reference-accessdate">. Retrieved 31 December 2008</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Moon+Fact+Sheet&rft.atitle=&rft.aulast=Williams&rft.aufirst=Dr.+David+R.&rft.au=Williams%2C%26%2332%3BDr.+David+R.&rft.date=2+February+2006&rft.pub=%5B%5BNASA%5D%5D+%28National+Space+Science+Data+Center%29&rft_id=http%3A%2F%2Fnssdc.gsfc.nasa.gov%2Fplanetary%2Ffactsheet%2Fmoonfact.html&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-Saari-2"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-Saari_2-0">^</a></b> <span class="citation Journal">Matthews, Grant (2008). "Celestial body irradiance determination from an underfilled satellite radiometer: application to albedo and thermal emission measurements of the Moon using CERES". <i>Applied Optics</i> <b>47</b> (27): 4981–93. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.1364%2FAO.47.004981" rel="nofollow">10.1364/AO.47.004981</a>. <a class="mw-redirect" href="http://en.wikipedia.org/wiki/PubMed_Identifier" title="PubMed Identifier">PMID</a> <a class="external text" href="http://www.ncbi.nlm.nih.gov/pubmed/18806861" rel="nofollow">18806861</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Celestial+body+irradiance+determination+from+an+underfilled+satellite+radiometer%3A+application+to+albedo+and+thermal+emission+measurements+of+the+Moon+using+CERES&rft.jtitle=Applied+Optics&rft.aulast=Matthews&rft.aufirst=Grant&rft.au=Matthews%2C%26%2332%3BGrant&rft.date=2008&rft.volume=47&rft.issue=27&rft.pages=4981%E2%80%9393&rft_id=info:doi/10.1364%2FAO.47.004981&rft_id=info:pmid/18806861&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-Vasavada1999-5"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-Vasavada1999_5-0">^</a></b> <span class="citation Journal">A.R. Vasavada, D.A. Paige, and S.E. Wood (1999). "Near-Surface Temperatures on Mercury and the Moon and the Stability of Polar Ice Deposits". <i>Icarus</i> <b>141</b> (2): 179. <a href="http://en.wikipedia.org/wiki/Bibcode">Bibcode</a> <a class="external text" href="http://adsabs.harvard.edu/abs/1999Icar..141..179V" rel="nofollow">1999Icar..141..179V</a>. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.1006%2Ficar.1999.6175" rel="nofollow">10.1006/icar.1999.6175</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Near-Surface+Temperatures+on+Mercury+and+the+Moon+and+the+Stability+of+Polar+Ice+Deposits&rft.jtitle=Icarus&rft.aulast=A.R.+Vasavada%2C+D.A.+Paige%2C+and+S.E.+Wood&rft.au=A.R.+Vasavada%2C+D.A.+Paige%2C+and+S.E.+Wood&rft.date=1999&rft.volume=141&rft.issue=2&rft.pages=179&rft_id=info:bibcode/1999Icar..141..179V&rft_id=info:doi/10.1006%2Ficar.1999.6175&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-L06-6">^ <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-L06_6-0"><sup><i><b>a</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-L06_6-1"><sup><i><b>b</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-L06_6-2"><sup><i><b>c</b></i></sup></a> <span class="citation Journal">Lucey, P.; <i>et al.</i> (2006). "Understanding the lunar surface and space-Moon interactions". <i>Reviews in Mineralogy and Geochemistry</i> <b>60</b> (1): 83–219. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.2138%2Frmg.2006.60.2" rel="nofollow">10.2138/rmg.2006.60.2</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Understanding+the+lunar+surface+and+space-Moon+interactions&rft.jtitle=Reviews+in+Mineralogy+and+Geochemistry&rft.aulast=Lucey&rft.aufirst=P.&rft.au=Lucey%2C%26%2332%3BP.&rft.date=2006&rft.volume=60&rft.issue=1&rft.pages=83%E2%80%93219&rft_id=info:doi/10.2138%2Frmg.2006.60.2&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-Morais2002-9"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-Morais2002_9-0">^</a></b> <span class="citation Journal">Morais, M.H.M.; Morbidelli, A. (2002). "The Population of Near-Earth Asteroids in Coorbital Motion with the Earth". <i>Icarus</i> <b>160</b> (1): 1–9. <a href="http://en.wikipedia.org/wiki/Bibcode">Bibcode</a> <a class="external text" href="http://adsabs.harvard.edu/abs/2002Icar..160....1M" rel="nofollow">2002Icar..160....1M</a>. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.1006%2Ficar.2002.6937" rel="nofollow">10.1006/icar.2002.6937</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=The+Population+of+Near-Earth+Asteroids+in+Coorbital+Motion+with+the+Earth&rft.jtitle=Icarus&rft.aulast=Morais&rft.aufirst=M.H.M.&rft.au=Morais%2C%26%2332%3BM.H.M.&rft.date=2002&rft.volume=160&rft.issue=1&rft.pages=1%E2%80%939&rft_id=info:bibcode/2002Icar..160....1M&rft_id=info:doi/10.1006%2Ficar.2002.6937&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-10"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-10">^</a></b> <span class="citation web"><a class="external text" href="http://www.iau.org/public_press/themes/naming/#spelling" rel="nofollow">"Naming Astronomical Objects: Spelling of Names"</a>. <a href="http://en.wikipedia.org/wiki/International_Astronomical_Union">International Astronomical Union</a><span class="reference-accessdate">. Retrieved 29 March 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Naming+Astronomical+Objects%3A+Spelling+of+Names&rft.atitle=&rft.pub=%5B%5BInternational+Astronomical+Union%5D%5D&rft_id=http%3A%2F%2Fwww.iau.org%2Fpublic_press%2Fthemes%2Fnaming%2F%23spelling&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-PN-FAQ-11"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-PN-FAQ_11-0">^</a></b> <span class="citation web"><a class="external text" href="http://planetarynames.wr.usgs.gov/nomenFAQ.html" rel="nofollow">"Gazetteer of Planetary Nomenclature: Planetary Nomenclature FAQ"</a>. USGS Astrogeology Research Program<span class="reference-accessdate">. Retrieved 29 March 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Gazetteer+of+Planetary+Nomenclature%3A+Planetary+Nomenclature+FAQ&rft.atitle=&rft.pub=USGS+Astrogeology+Research+Program&rft_id=http%3A%2F%2Fplanetarynames.wr.usgs.gov%2FnomenFAQ.html&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-barnhart1995-12"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-barnhart1995_12-0">^</a></b> <span class="citation book">Barnhart, Robert K. (1995). <i>The Barnhart Concise Dictionary of Etymology</i>. USA: Harper Collins. p. 487. <a href="http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="http://en.wikipedia.org/wiki/Special:BookSources/0-06-270084-7" title="Special:BookSources/0-06-270084-7">0-06-270084-7</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Barnhart+Concise+Dictionary+of+Etymology&rft.aulast=Barnhart&rft.aufirst=Robert+K.&rft.au=Barnhart%2C%26%2332%3BRobert+K.&rft.date=1995&rft.pages=p.%26nbsp%3B487&rft.place=USA&rft.pub=Harper+Collins&rft.isbn=0-06-270084-7&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-oed-13"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-oed_13-0">^</a></b> <span class="citation web"><a class="external text" href="http://dictionary.oed.com/cgi/entry/50136796?single=1&query_type=word&queryword=lunar&first=1&max_to_show=10" rel="nofollow">"Oxford English Dictionary: lunar, a. and n."</a>. <i>Oxford English Dictionary: Second Edition 1989</i>. Oxford University Press<span class="reference-accessdate">. Retrieved 23 March 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Oxford+English+Dictionary%3A+lunar%2C+a.+and+n.&rft.atitle=Oxford+English+Dictionary%3A+Second+Edition+1989&rft.pub=Oxford+University+Press&rft_id=http%3A%2F%2Fdictionary.oed.com%2Fcgi%2Fentry%2F50136796%3Fsingle%3D1%26query_type%3Dword%26queryword%3Dlunar%26first%3D1%26max_to_show%3D10&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-15"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-15">^</a></b> <span class="citation Journal">Kleine, T.; Palme, H.; Mezger, K.; Halliday, A.N. (2005). "Hf–W Chronometry of Lunar Metals and the Age and Early Differentiation of the Moon". <i><a href="http://en.wikipedia.org/wiki/Science_%28journal%29" title="Science (journal)">Science</a></i> <b>310</b> (5754): 1671–1674. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.1126%2Fscience.1118842" rel="nofollow">10.1126/science.1118842</a>. <a class="mw-redirect" href="http://en.wikipedia.org/wiki/PubMed_Identifier" title="PubMed Identifier">PMID</a> <a class="external text" href="http://www.ncbi.nlm.nih.gov/pubmed/16308422" rel="nofollow">16308422</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Hf%E2%80%93W+Chronometry+of+Lunar+Metals+and+the+Age+and+Early+Differentiation+of+the+Moon&rft.jtitle=%5B%5BScience+%28journal%29%7CScience%5D%5D&rft.aulast=Kleine&rft.aufirst=T.&rft.au=Kleine%2C%26%2332%3BT.&rft.date=2005&rft.volume=310&rft.issue=5754&rft.pages=1671%E2%80%931674&rft_id=info:doi/10.1126%2Fscience.1118842&rft_id=info:pmid/16308422&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-Binder-16"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-Binder_16-0">^</a></b> <span class="citation Journal">Binder, A.B. (1974). "On the origin of the Moon by rotational fission". <i>The Moon</i> <b>11</b> (2): 53–76. <a href="http://en.wikipedia.org/wiki/Bibcode">Bibcode</a> <a class="external text" href="http://adsabs.harvard.edu/abs/1974Moon...11...53B" rel="nofollow">1974Moon...11...53B</a>. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.1007%2FBF01877794" rel="nofollow">10.1007/BF01877794</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=On+the+origin+of+the+Moon+by+rotational+fission&rft.jtitle=The+Moon&rft.aulast=Binder&rft.aufirst=A.B.&rft.au=Binder%2C%26%2332%3BA.B.&rft.date=1974&rft.volume=11&rft.issue=2&rft.pages=53%E2%80%9376&rft_id=info:bibcode/1974Moon...11...53B&rft_id=info:doi/10.1007%2FBF01877794&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-BotM-17">^ <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-BotM_17-0"><sup><i><b>a</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-BotM_17-1"><sup><i><b>b</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-BotM_17-2"><sup><i><b>c</b></i></sup></a> <span class="citation book">Stroud, Rick (2009). <i>The Book of the Moon</i>. Walken and Company. pp. 24–27. <a href="http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="http://en.wikipedia.org/wiki/Special:BookSources/0-8027-1734-9" title="Special:BookSources/0-8027-1734-9">0-8027-1734-9</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Book+of+the+Moon&rft.aulast=Stroud&rft.aufirst=Rick&rft.au=Stroud%2C%26%2332%3BRick&rft.date=2009&rft.pages=pp.%26nbsp%3B24%E2%80%9327&rft.pub=Walken+and+Company&rft.isbn=0-8027-1734-9&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-Mitler-18"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-Mitler_18-0">^</a></b> <span class="citation Journal">Mitler, H.E. (1975). "Formation of an iron-poor moon by partial capture, or: Yet another exotic theory of lunar origin". <i><a href="http://en.wikipedia.org/wiki/Icarus_%28journal%29" title="Icarus (journal)">Icarus</a></i> <b>24</b> (2): 256–268. <a href="http://en.wikipedia.org/wiki/Bibcode">Bibcode</a> <a class="external text" href="http://adsabs.harvard.edu/abs/1975Icar...24..256M" rel="nofollow">1975Icar...24..256M</a>. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.1016%2F0019-1035%2875%2990102-5" rel="nofollow">10.1016/0019-1035(75)90102-5</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Formation+of+an+iron-poor+moon+by+partial+capture%2C+or%3A+Yet+another+exotic+theory+of+lunar+origin&rft.jtitle=%5B%5BIcarus+%28journal%29%7CIcarus%5D%5D&rft.aulast=Mitler&rft.aufirst=H.E.&rft.au=Mitler%2C%26%2332%3BH.E.&rft.date=1975&rft.volume=24&rft.issue=2&rft.pages=256%E2%80%93268&rft_id=info:bibcode/1975Icar...24..256M&rft_id=info:doi/10.1016%2F0019-1035%2875%2990102-5&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-19"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-19">^</a></b> <span class="citation Journal">Stevenson, D.J. (1987). "Origin of the moon–The collision hypothesis". <i>Annual Review of Earth and Planetary Sciences</i> <b>15</b> (1): 271–315. <a href="http://en.wikipedia.org/wiki/Bibcode">Bibcode</a> <a class="external text" href="http://adsabs.harvard.edu/abs/1987AREPS..15..271S" rel="nofollow">1987AREPS..15..271S</a>. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.1146%2Fannurev.ea.15.050187.001415" rel="nofollow">10.1146/annurev.ea.15.050187.001415</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Origin+of+the+moon%E2%80%93The+collision+hypothesis&rft.jtitle=Annual+Review+of+Earth+and+Planetary+Sciences&rft.aulast=Stevenson&rft.aufirst=D.J.&rft.au=Stevenson%2C%26%2332%3BD.J.&rft.date=1987&rft.volume=15&rft.issue=1&rft.pages=271%E2%80%93315&rft_id=info:bibcode/1987AREPS..15..271S&rft_id=info:doi/10.1146%2Fannurev.ea.15.050187.001415&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-taylor1998-20"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-taylor1998_20-0">^</a></b> <span class="citation web">Taylor, G. Jeffrey (31 December 1998). <a class="external text" href="http://www.psrd.hawaii.edu/Dec98/OriginEarthMoon.html" rel="nofollow">"Origin of the Earth and Moon"</a>. Planetary Science Research Discoveries<span class="reference-accessdate">. Retrieved 7 April 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Origin+of+the+Earth+and+Moon&rft.atitle=&rft.aulast=Taylor&rft.aufirst=G.+Jeffrey&rft.au=Taylor%2C%26%2332%3BG.+Jeffrey&rft.date=31+December+1998&rft.pub=Planetary+Science+Research+Discoveries&rft_id=http%3A%2F%2Fwww.psrd.hawaii.edu%2FDec98%2FOriginEarthMoon.html&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-21"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-21">^</a></b> <span class="citation Journal">Canup, R.; Asphaug, E. (2001). "Origin of the Moon in a giant impact near the end of the Earth's formation". <i>Nature</i> <b>412</b> (6848): 708–712. <a href="http://en.wikipedia.org/wiki/Bibcode">Bibcode</a> <a class="external text" href="http://adsabs.harvard.edu/abs/2001Natur.412..708C" rel="nofollow">2001Natur.412..708C</a>. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.1038%2F35089010" rel="nofollow">10.1038/35089010</a>. <a class="mw-redirect" href="http://en.wikipedia.org/wiki/PubMed_Identifier" title="PubMed Identifier">PMID</a> <a class="external text" href="http://www.ncbi.nlm.nih.gov/pubmed/11507633" rel="nofollow">11507633</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Origin+of+the+Moon+in+a+giant+impact+near+the+end+of+the+Earth%27s+formation&rft.jtitle=Nature&rft.aulast=Canup&rft.aufirst=R.&rft.au=Canup%2C%26%2332%3BR.&rft.date=2001&rft.volume=412&rft.issue=6848&rft.pages=708%E2%80%93712&rft_id=info:bibcode/2001Natur.412..708C&rft_id=info:doi/10.1038%2F35089010&rft_id=info:pmid/11507633&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-Pahlevan2007-22"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-Pahlevan2007_22-0">^</a></b> <span class="citation Journal">Pahlevan, Kaveh; Stevenson, David J. (2007). "Equilibration in the aftermath of the lunar-forming giant impact". <i>Earth and Planetary Science Letters</i> <b>262</b> (3–4): 438–449. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.1016%2Fj.epsl.2007.07.055" rel="nofollow">10.1016/j.epsl.2007.07.055</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Equilibration+in+the+aftermath+of+the+lunar-forming+giant+impact&rft.jtitle=Earth+and+Planetary+Science+Letters&rft.aulast=Pahlevan&rft.aufirst=Kaveh&rft.au=Pahlevan%2C%26%2332%3BKaveh&rft.date=2007&rft.volume=262&rft.issue=3%E2%80%934&rft.pages=438%E2%80%93449&rft_id=info:doi/10.1016%2Fj.epsl.2007.07.055&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-23"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-23">^</a></b> <span class="citation Journal">Nield, Ted (2009). <a class="external text" href="http://www.geolsoc.org.uk/gsl/geoscientist/geonews/page6072.html" rel="nofollow">"Moonwalk (summary of meeting at Meteoritical Society's 72nd Annual Meeting, Nancy, France)"</a>. <i>Geoscientist</i> <b>19</b>: 8.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Moonwalk+%28summary+of+meeting+at+Meteoritical+Society%27s+72nd+Annual+Meeting%2C+Nancy%2C+France%29&rft.jtitle=Geoscientist&rft.aulast=Nield&rft.aufirst=Ted&rft.au=Nield%2C%26%2332%3BTed&rft.date=2009&rft.volume=19&rft.pages=8&rft_id=http%3A%2F%2Fwww.geolsoc.org.uk%2Fgsl%2Fgeoscientist%2Fgeonews%2Fpage6072.html&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-Warren1985-24">^ <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-Warren1985_24-0"><sup><i><b>a</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-Warren1985_24-1"><sup><i><b>b</b></i></sup></a> <span class="citation Journal">Warren, P. H. (1985). "The magma ocean concept and lunar evolution". <i>Annual review of earth and planetary sciences.</i> <b>13</b> (1): 201–240. <a href="http://en.wikipedia.org/wiki/Bibcode">Bibcode</a> <a class="external text" href="http://adsabs.harvard.edu/abs/1985AREPS..13..201W" rel="nofollow">1985AREPS..13..201W</a>. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.1146%2Fannurev.ea.13.050185.001221" rel="nofollow">10.1146/annurev.ea.13.050185.001221</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=The+magma+ocean+concept+and+lunar+evolution&rft.jtitle=Annual+review+of+earth+and+planetary+sciences.&rft.aulast=Warren&rft.aufirst=P.+H.&rft.au=Warren%2C%26%2332%3BP.+H.&rft.date=1985&rft.volume=13&rft.issue=1&rft.pages=201%E2%80%93240&rft_id=info:bibcode/1985AREPS..13..201W&rft_id=info:doi/10.1146%2Fannurev.ea.13.050185.001221&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-25"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-25">^</a></b> <span class="citation Journal">Tonks, W. Brian; Melosh, H. Jay (1993). "Magma ocean formation due to giant impacts". <i>Journal of Geophysical Research</i> <b>98</b> (E3): 5319–5333. <a href="http://en.wikipedia.org/wiki/Bibcode">Bibcode</a> <a class="external text" href="http://adsabs.harvard.edu/abs/1993JGR....98.5319T" rel="nofollow">1993JGR....98.5319T</a>. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.1029%2F92JE02726" rel="nofollow">10.1029/92JE02726</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Magma+ocean+formation+due+to+giant+impacts&rft.jtitle=Journal+of+Geophysical+Research&rft.aulast=Tonks&rft.aufirst=W.+Brian&rft.au=Tonks%2C%26%2332%3BW.+Brian&rft.date=1993&rft.volume=98&rft.issue=E3&rft.pages=5319%E2%80%935333&rft_id=info:bibcode/1993JGR....98.5319T&rft_id=info:doi/10.1029%2F92JE02726&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-26"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-26">^</a></b> <a class="external text" href="http://www.newscientist.com/article/dn20160-two-planets-found-sharing-one-orbit.html" rel="nofollow">Two planets found sharing one orbit</a>, New Scientist, 24 February 2011</li><li id="cite_note-27"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-27">^</a></b> <span class="citation book">Taylor, Stuart Ross (1975). <a class="external text" href="http://articles.adsabs.harvard.edu//full/1975lspa.book.....T/0000064.000.html" rel="nofollow"><i>Lunar science: A post-Apollo view</i></a>. New York, Pergamon Press, Inc.. p. 64.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Lunar+science%3A+A+post-Apollo+view&rft.aulast=Taylor%2C+Stuart+Ross&rft.au=Taylor%2C+Stuart+Ross&rft.date=1975&rft.pages=p.%26nbsp%3B64&rft.pub=New+York%2C+Pergamon+Press%2C+Inc.&rft_id=http%3A%2F%2Farticles.adsabs.harvard.edu%2F%2Ffull%2F1975lspa.book.....T%2F0000064.000.html&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-28"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-28">^</a></b> <span class="citation web"><a class="external text" href="http://www.nasa.gov/topics/moonmars/features/lunar_core.html" rel="nofollow">"NASA Research Team Reveals Moon Has Earth-Like Core"</a>. NASA. 01.06.11.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=NASA+Research+Team+Reveals+Moon+Has+Earth-Like+Core&rft.atitle=&rft.date=01.06.11&rft.pub=NASA&rft_id=http%3A%2F%2Fwww.nasa.gov%2Ftopics%2Fmoonmars%2Ffeatures%2Flunar_core.html&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-29"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-29">^</a></b> <span class="citation Journal">Nemchin, A.; Timms, N.; Pidgeon, R.; Geisler, T.; Reddy, S.; Meyer, C. (2009). "Timing of crystallization of the lunar magma ocean constrained by the oldest zircon". <i>Nature Geoscience</i> <b>2</b> (2): 133–136. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.1038%2Fngeo417" rel="nofollow">10.1038/ngeo417</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Timing+of+crystallization+of+the+lunar+magma+ocean+constrained+by+the+oldest+zircon&rft.jtitle=Nature+Geoscience&rft.aulast=Nemchin&rft.aufirst=A.&rft.au=Nemchin%2C%26%2332%3BA.&rft.au=Timms%2C%26%2332%3BN.&rft.au=Pidgeon%2C%26%2332%3BR.&rft.au=Geisler%2C%26%2332%3BT.&rft.au=Reddy%2C%26%2332%3BS.&rft.au=Meyer%2C%26%2332%3BC.&rft.date=2009&rft.volume=2&rft.issue=2&rft.pages=133%E2%80%93136&rft_id=info:doi/10.1038%2Fngeo417&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-S06-30">^ <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-S06_30-0"><sup><i><b>a</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-S06_30-1"><sup><i><b>b</b></i></sup></a> <span class="citation Journal">Shearer, C.; <i>et al.</i> (2006). "Thermal and magmatic evolution of the Moon". <i>Reviews in Mineralogy and Geochemistry</i> <b>60</b> (1): 365–518. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.2138%2Frmg.2006.60.4" rel="nofollow">10.2138/rmg.2006.60.4</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Thermal+and+magmatic+evolution+of+the+Moon&rft.jtitle=Reviews+in+Mineralogy+and+Geochemistry&rft.aulast=Shearer&rft.aufirst=C.&rft.au=Shearer%2C%26%2332%3BC.&rft.date=2006&rft.volume=60&rft.issue=1&rft.pages=365%E2%80%93518&rft_id=info:doi/10.2138%2Frmg.2006.60.4&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-Schubert2004-31"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-Schubert2004_31-0">^</a></b> <span class="citation book">Schubert, J. <i>et al.</i> (2004). "Interior composition, structure, and dynamics of the Galilean satellites.". In F. Bagenal <i>et al.</i>. <i>Jupiter: The Planet, Satellites, and Magnetosphere</i>. Cambridge University Press. pp. 281–306. <a href="http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="http://en.wikipedia.org/wiki/Special:BookSources/978-0-521-81808-7" title="Special:BookSources/978-0-521-81808-7">978-0-521-81808-7</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Interior+composition%2C+structure%2C+and+dynamics+of+the+Galilean+satellites.&rft.atitle=Jupiter%3A+The+Planet%2C+Satellites%2C+and+Magnetosphere&rft.aulast=Schubert&rft.aufirst=J.+%27%27et+al.%27%27&rft.au=Schubert%2C%26%2332%3BJ.+%27%27et+al.%27%27&rft.date=2004&rft.pages=pp.%26nbsp%3B281%E2%80%93306&rft.pub=Cambridge+University+Press&rft.isbn=978-0-521-81808-7&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-32"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-32">^</a></b> <span class="citation Journal">Williams, J.G.; Turyshev, S.G.; Boggs, D.H.; Ratcliff, J.T. (2006). "Lunar laser ranging science: Gravitational physics and lunar interior and geodesy". <i>Advances in Space Research</i> <b>37</b> (1): 6771. <a href="http://en.wikipedia.org/wiki/Bibcode">Bibcode</a> <a class="external text" href="http://adsabs.harvard.edu/abs/1987AREPS..15..271S" rel="nofollow">1987AREPS..15..271S</a>. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.1016%2Fj.asr.2005.05.013" rel="nofollow">10.1016/j.asr.2005.05.013</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Lunar+laser+ranging+science%3A+Gravitational+physics+and+lunar+interior+and+geodesy&rft.jtitle=Advances+in+Space+Research&rft.aulast=Williams&rft.aufirst=J.G.&rft.au=Williams%2C%26%2332%3BJ.G.&rft.date=2006&rft.volume=37&rft.issue=1&rft.pages=6771&rft_id=info:bibcode/1987AREPS..15..271S&rft_id=info:doi/10.1016%2Fj.asr.2005.05.013&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-33"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-33">^</a></b> <span class="citation web"><a class="external text" href="http://www.esa.int/esaSC/SEMDWNWALPE_index_0.html" rel="nofollow">"Landscapes from the ancient and eroded lunar far side"</a>. esa<span class="reference-accessdate">. Retrieved 15 February 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Landscapes+from+the+ancient+and+eroded+lunar+far+side&rft.atitle=&rft.pub=esa&rft_id=http%3A%2F%2Fwww.esa.int%2FesaSC%2FSEMDWNWALPE_index_0.html&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-34"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-34">^</a></b> <span class="citation Journal">Spudis, Paul D.; Cook, A.; Robinson, M.; Bussey, B.; Fessler, B. (01/1998). "Topography of the South Polar Region from Clementine Stereo Imaging". <i>Workshop on New Views of the Moon: Integrated Remotely Sensed, Geophysical, and Sample Datasets</i>: 69. <a href="http://en.wikipedia.org/wiki/Bibcode">Bibcode</a> <a class="external text" href="http://adsabs.harvard.edu/abs/1998nvmi.conf...69S" rel="nofollow">1998nvmi.conf...69S</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Topography+of+the+South+Polar+Region+from+Clementine+Stereo+Imaging&rft.jtitle=Workshop+on+New+Views+of+the+Moon%3A+Integrated+Remotely+Sensed%2C+Geophysical%2C+and+Sample+Datasets&rft.aulast=Spudis%2C+Paul+D.%3B+Cook%2C+A.%3B+Robinson%2C+M.%3B+Bussey%2C+B.%3B+Fessler%2C+B.&rft.au=Spudis%2C+Paul+D.%3B+Cook%2C+A.%3B+Robinson%2C+M.%3B+Bussey%2C+B.%3B+Fessler%2C+B.&rft.date=01%2F1998&rft.pages=69&rft_id=info:bibcode/1998nvmi.conf...69S&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-Spudis1994-35">^ <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-Spudis1994_35-0"><sup><i><b>a</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-Spudis1994_35-1"><sup><i><b>b</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-Spudis1994_35-2"><sup><i><b>c</b></i></sup></a> <span class="citation Journal">Spudis, Paul D.; Reisse, Robert A.; Gillis, Jeffrey J. (1994). "Ancient Multiring Basins on the Moon Revealed by Clementine Laser Altimetry". <i>Science</i> <b>266</b> (5192): 1848–1851. <a href="http://en.wikipedia.org/wiki/Bibcode">Bibcode</a> <a class="external text" href="http://adsabs.harvard.edu/abs/1994Sci...266.1848S" rel="nofollow">1994Sci...266.1848S</a>. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.1126%2Fscience.266.5192.1848" rel="nofollow">10.1126/science.266.5192.1848</a>. <a class="mw-redirect" href="http://en.wikipedia.org/wiki/PubMed_Identifier" title="PubMed Identifier">PMID</a> <a class="external text" href="http://www.ncbi.nlm.nih.gov/pubmed/17737079" rel="nofollow">17737079</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Ancient+Multiring+Basins+on+the+Moon+Revealed+by+Clementine+Laser+Altimetry&rft.jtitle=Science&rft.aulast=Spudis&rft.aufirst=Paul+D.&rft.au=Spudis%2C%26%2332%3BPaul+D.&rft.date=1994&rft.volume=266&rft.issue=5192&rft.pages=1848%E2%80%931851&rft_id=info:bibcode/1994Sci...266.1848S&rft_id=info:doi/10.1126%2Fscience.266.5192.1848&rft_id=info:pmid/17737079&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-36"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-36">^</a></b> <span class="citation Journal">Pieters, C.M.; Tompkins, S.; Head, J.W.; Hess, P.C. (1997). <a class="external text" href="http://www.agu.org/pubs/crossref/1997/97GL01718.shtml" rel="nofollow">"Mineralogy of the Mafic Anomaly in the South Pole‐Aitken Basin: Implications for excavation of the lunar mantle"</a>. <i>Geophysical Research Letters</i> <b>24</b> (15): 1903–1906. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.1029%2F97GL01718" rel="nofollow">10.1029/97GL01718</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Mineralogy+of+the+Mafic+Anomaly+in+the+South+Pole%E2%80%90Aitken+Basin%3A+Implications+for+excavation+of+the+lunar+mantle&rft.jtitle=Geophysical+Research+Letters&rft.aulast=Pieters&rft.aufirst=C.M.&rft.au=Pieters%2C%26%2332%3BC.M.&rft.au=Tompkins%2C%26%2332%3BS.&rft.au=Head%2C%26%2332%3BJ.W.&rft.au=Hess%2C%26%2332%3BP.C.&rft.date=1997&rft.volume=24&rft.issue=15&rft.pages=1903%E2%80%931906&rft_id=info:doi/10.1029%2F97GL01718&rft_id=http%3A%2F%2Fwww.agu.org%2Fpubs%2Fcrossref%2F1997%2F97GL01718.shtml&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-37"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-37">^</a></b> <span class="citation web">Taylor, G.J. (17 July 1998). <a class="external text" href="http://www.psrd.hawaii.edu/July98/spa.html" rel="nofollow">"The Biggest Hole in the Solar System"</a>. Planetary Science Research Discoveries, Hawai'i Institute of Geophysics and Planetology<span class="reference-accessdate">. Retrieved 12 April 2007</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=The+Biggest+Hole+in+the+Solar+System&rft.atitle=&rft.aulast=Taylor&rft.aufirst=G.J.&rft.au=Taylor%2C%26%2332%3BG.J.&rft.date=17+July+1998&rft.pub=Planetary+Science+Research+Discoveries%2C+Hawai%27i+Institute+of+Geophysics+and+Planetology&rft_id=http%3A%2F%2Fwww.psrd.hawaii.edu%2FJuly98%2Fspa.html&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-38"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-38">^</a></b> <span class="citation Journal">Schultz, P. H. (03/1997). "Forming the south-pole Aitken basin – The extreme games". <i>Conference Paper, 28th Annual Lunar and Planetary Science Conference</i> <b>28</b>: 1259. <a href="http://en.wikipedia.org/wiki/Bibcode">Bibcode</a> <a class="external text" href="http://adsabs.harvard.edu/abs/1997LPI....28.1259S" rel="nofollow">1997LPI....28.1259S</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Forming+the+south-pole+Aitken+basin+%E2%80%93+The+extreme+games&rft.jtitle=Conference+Paper%2C+28th+Annual+Lunar+and+Planetary+Science+Conference&rft.aulast=Schultz&rft.aufirst=P.+H.&rft.au=Schultz%2C%26%2332%3BP.+H.&rft.date=03%2F1997&rft.volume=28&rft.pages=1259&rft_id=info:bibcode/1997LPI....28.1259S&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-39"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-39">^</a></b> <span class="citation book">Wlasuk, Peter (2000). <a class="external text" href="http://books.google.com/?id=TWtLIOlPwS4C&pg=PT30" rel="nofollow"><i>Observing the Moon</i></a>. Springer. p. 19. <a href="http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="http://en.wikipedia.org/wiki/Special:BookSources/1-85233-193-3" title="Special:BookSources/1-85233-193-3">1-85233-193-3</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Observing+the+Moon&rft.aulast=Wlasuk%2C+Peter&rft.au=Wlasuk%2C+Peter&rft.date=2000&rft.pages=p.%26nbsp%3B19&rft.pub=Springer&rft.isbn=1-85233-193-3&rft_id=http%3A%2F%2Fbooks.google.com%2F%3Fid%3DTWtLIOlPwS4C%26pg%3DPT30&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-40"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-40">^</a></b> <span class="citation web">Norman, M. (21 April 2004). <a class="external text" href="http://www.psrd.hawaii.edu/April04/lunarAnorthosites.html" rel="nofollow">"The Oldest Moon Rocks"</a>. Planetary Science Research Discoveries<span class="reference-accessdate">. Retrieved 12 April 2007</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=The+Oldest+Moon+Rocks&rft.atitle=&rft.aulast=Norman&rft.aufirst=M.&rft.au=Norman%2C%26%2332%3BM.&rft.date=21+April+2004&rft.pub=Planetary+Science+Research+Discoveries&rft_id=http%3A%2F%2Fwww.psrd.hawaii.edu%2FApril04%2FlunarAnorthosites.html&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-41"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-41">^</a></b> <span class="citation book">Varricchio, L. (2006). <i>Inconstant Moon</i>. Xlibris Books. <a href="http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="http://en.wikipedia.org/wiki/Special:BookSources/1-59926-393-9" title="Special:BookSources/1-59926-393-9">1-59926-393-9</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Inconstant+Moon&rft.aulast=Varricchio&rft.aufirst=L.&rft.au=Varricchio%2C%26%2332%3BL.&rft.date=2006&rft.pub=Xlibris+Books&rft.isbn=1-59926-393-9&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-42"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-42">^</a></b> <span class="citation Journal">Head, L.W.J.W. (2003). <a class="external text" href="http://www.agu.org/pubs/crossref/2003/2002JE001909.shtml" rel="nofollow">"Lunar Gruithuisen and Mairan domes: Rheology and mode of emplacement"</a>. <i>Journal of Geophysical Research</i> <b>108</b> (E2): 5012. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.1029%2F2002JE001909" rel="nofollow">10.1029/2002JE001909</a><span class="reference-accessdate">. Retrieved 12 April 2007</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Lunar+Gruithuisen+and+Mairan+domes%3A+Rheology+and+mode+of+emplacement&rft.jtitle=Journal+of+Geophysical+Research&rft.aulast=Head&rft.aufirst=L.W.J.W.&rft.au=Head%2C%26%2332%3BL.W.J.W.&rft.date=2003&rft.volume=108&rft.issue=E2&rft.pages=5012&rft_id=info:doi/10.1029%2F2002JE001909&rft_id=http%3A%2F%2Fwww.agu.org%2Fpubs%2Fcrossref%2F2003%2F2002JE001909.shtml&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-worldbook-43">^ <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-worldbook_43-0"><sup><i><b>a</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-worldbook_43-1"><sup><i><b>b</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-worldbook_43-2"><sup><i><b>c</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-worldbook_43-3"><sup><i><b>d</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-worldbook_43-4"><sup><i><b>e</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-worldbook_43-5"><sup><i><b>f</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-worldbook_43-6"><sup><i><b>g</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-worldbook_43-7"><sup><i><b>h</b></i></sup></a> <span class="citation web">Spudis, P.D. (2004). <a class="external text" href="http://www.nasa.gov/worldbook/moon_worldbook.html" rel="nofollow">"Moon"</a>. World Book Online Reference Center, <a href="http://en.wikipedia.org/wiki/NASA">NASA</a><span class="reference-accessdate">. Retrieved 12 April 2007</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Moon&rft.atitle=&rft.aulast=Spudis&rft.aufirst=P.D.&rft.au=Spudis%2C%26%2332%3BP.D.&rft.date=2004&rft.pub=World+Book+Online+Reference+Center%2C+%5B%5BNASA%5D%5D&rft_id=http%3A%2F%2Fwww.nasa.gov%2Fworldbook%2Fmoon_worldbook.html&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-44"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-44">^</a></b> <span class="citation Journal">Gillis, J.J.; Spudis, P.D. (1996). "The Composition and Geologic Setting of Lunar Far Side Maria". <i>Lunar and Planetary Science</i> <b>27</b>: 413–404. <a href="http://en.wikipedia.org/wiki/Bibcode">Bibcode</a> <a class="external text" href="http://adsabs.harvard.edu/abs/1996LPI....27..413G" rel="nofollow">1996LPI....27..413G</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=The+Composition+and+Geologic+Setting+of+Lunar+Far+Side+Maria&rft.jtitle=Lunar+and+Planetary+Science&rft.aulast=Gillis&rft.aufirst=J.J.&rft.au=Gillis%2C%26%2332%3BJ.J.&rft.date=1996&rft.volume=27&rft.pages=413%E2%80%93404&rft_id=info:bibcode/1996LPI....27..413G&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-45"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-45">^</a></b> <span class="citation Journal">Lawrence, D. J. <i>et al.</i> (11 August 1998). <a class="external text" href="http://www.sciencemag.org/cgi/content/full/281/5382/1484" rel="nofollow">"Global Elemental Maps of the Moon: The Lunar Prospector Gamma-Ray Spectrometer"</a>. <i><a href="http://en.wikipedia.org/wiki/Science_%28journal%29" title="Science (journal)">Science</a></i> (HighWire Press) <b>281</b> (5382): 1484–1489. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.1126%2Fscience.281.5382.1484" rel="nofollow">10.1126/science.281.5382.1484</a>. <a href="http://en.wikipedia.org/wiki/International_Standard_Serial_Number" title="International Standard Serial Number">ISSN</a> <a class="external text" href="http://www.worldcat.org/issn/1095-9203" rel="nofollow">1095-9203</a>. <a class="mw-redirect" href="http://en.wikipedia.org/wiki/PubMed_Identifier" title="PubMed Identifier">PMID</a> <a class="external text" href="http://www.ncbi.nlm.nih.gov/pubmed/9727970" rel="nofollow">9727970</a><span class="reference-accessdate">. Retrieved 29 August 2009</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Global+Elemental+Maps+of+the+Moon%3A+The+Lunar+Prospector+Gamma-Ray+Spectrometer&rft.jtitle=%5B%5BScience+%28journal%29%7CScience%5D%5D&rft.aulast=Lawrence%2C+D.+J.+%27%27et+al.%27%27&rft.au=Lawrence%2C+D.+J.+%27%27et+al.%27%27&rft.date=11+August+1998&rft.volume=281&rft.issue=5382&rft.pages=1484%E2%80%931489&rft.pub=HighWire+Press&rft_id=info:doi/10.1126%2Fscience.281.5382.1484&rft.issn=1095-9203&rft_id=info:pmid/9727970&rft_id=http%3A%2F%2Fwww.sciencemag.org%2Fcgi%2Fcontent%2Ffull%2F281%2F5382%2F1484&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-46"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-46">^</a></b> <span class="citation web">Taylor, G.J. (31 August 2000). <a class="external text" href="http://www.psrd.hawaii.edu/Aug00/newMoon.html" rel="nofollow">"A New Moon for the Twenty-First Century"</a>. Planetary Science Research Discoveries, Hawai'i Institute of Geophysics and Planetology<span class="reference-accessdate">. Retrieved 12 April 2007</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=A+New+Moon+for+the+Twenty-First+Century&rft.atitle=&rft.aulast=Taylor&rft.aufirst=G.J.&rft.au=Taylor%2C%26%2332%3BG.J.&rft.date=31+August+2000&rft.pub=Planetary+Science+Research+Discoveries%2C+Hawai%27i+Institute+of+Geophysics+and+Planetology&rft_id=http%3A%2F%2Fwww.psrd.hawaii.edu%2FAug00%2FnewMoon.html&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-Papike-47">^ <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-Papike_47-0"><sup><i><b>a</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-Papike_47-1"><sup><i><b>b</b></i></sup></a> <span class="citation Journal">Papike, J.; Ryder, G.; Shearer, C. (1998). "Lunar Samples". <i>Reviews in Mineralogy and Geochemistry</i> <b>36</b>: 5.1–5.234.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Lunar+Samples&rft.jtitle=Reviews+in+Mineralogy+and+Geochemistry&rft.aulast=Papike&rft.aufirst=J.&rft.au=Papike%2C%26%2332%3BJ.&rft.date=1998&rft.volume=36&rft.pages=5.1%E2%80%935.234&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-Hiesinger-48">^ <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-Hiesinger_48-0"><sup><i><b>a</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-Hiesinger_48-1"><sup><i><b>b</b></i></sup></a> <span class="citation Journal">Hiesinger, H.; Head, J.W.; Wolf, U.; Jaumanm, R.; Neukum, G. (2003). "Ages and stratigraphy of mare basalts in Oceanus Procellarum, Mare Numbium, Mare Cognitum, and Mare Insularum". <i>J. Geophys. Res.</i> <b>108</b> (E7): 1029. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.1029%2F2002JE001985" rel="nofollow">10.1029/2002JE001985</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Ages+and+stratigraphy+of+mare+basalts+in+Oceanus+Procellarum%2C+Mare+Numbium%2C+Mare+Cognitum%2C+and+Mare+Insularum&rft.jtitle=J.+Geophys.+Res.&rft.aulast=Hiesinger&rft.aufirst=H.&rft.au=Hiesinger%2C%26%2332%3BH.&rft.date=2003&rft.volume=108&rft.issue=E7&rft.pages=1029&rft_id=info:doi/10.1029%2F2002JE001985&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-49"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-49">^</a></b> <span class="citation web">Munsell, K. (4 December 2006). <a class="external text" href="http://sse.jpl.nasa.gov/educ/themes/display.cfm?Item=mountains" rel="nofollow">"Majestic Mountains"</a>. <i>Solar System Exploration</i>. NASA<span class="reference-accessdate">. Retrieved 12 April 2007</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Majestic+Mountains&rft.atitle=Solar+System+Exploration&rft.aulast=Munsell&rft.aufirst=K.&rft.au=Munsell%2C%26%2332%3BK.&rft.date=4+December+2006&rft.pub=NASA&rft_id=http%3A%2F%2Fsse.jpl.nasa.gov%2Feduc%2Fthemes%2Fdisplay.cfm%3FItem%3Dmountains&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-50"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-50">^</a></b> <span class="citation book">Melosh, H. J. (1989). <i>Impact cratering: A geologic process</i>. Oxford Univ. Press. <a href="http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="http://en.wikipedia.org/wiki/Special:BookSources/0-19-504284-0" title="Special:BookSources/0-19-504284-0">0-19-504284-0</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Impact+cratering%3A+A+geologic+process&rft.aulast=Melosh&rft.aufirst=H.+J.&rft.au=Melosh%2C%26%2332%3BH.+J.&rft.date=1989&rft.pub=Oxford+Univ.+Press&rft.isbn=0-19-504284-0&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-51"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-51">^</a></b> <span class="citation web"><a class="external text" href="http://planck.esa.int/science-e/www/object/index.cfm?fobjectid=31412" rel="nofollow">"Moon Facts"</a>. <i>SMART-1</i>. European Space Agency. 2010<span class="reference-accessdate">. Retrieved 12 May 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Moon+Facts&rft.atitle=SMART-1&rft.date=2010&rft.pub=European+Space+Agency&rft_id=http%3A%2F%2Fplanck.esa.int%2Fscience-e%2Fwww%2Fobject%2Findex.cfm%3Ffobjectid%3D31412&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-gazetteer-52"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-gazetteer_52-0">^</a></b> <span class="citation web"><a class="external text" href="http://planetarynames.wr.usgs.gov/append6.html#Moon" rel="nofollow">"Gazetteer of Planetary Nomenclature: Categories for Naming Features on Planets and Satellites"</a>. U.S. Geological Survey<span class="reference-accessdate">. Retrieved 8 April 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Gazetteer+of+Planetary+Nomenclature%3A+Categories+for+Naming+Features+on+Planets+and+Satellites&rft.atitle=&rft.pub=U.S.+Geological+Survey&rft_id=http%3A%2F%2Fplanetarynames.wr.usgs.gov%2Fappend6.html%23Moon&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-geologic-53">^ <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-geologic_53-0"><sup><i><b>a</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-geologic_53-1"><sup><i><b>b</b></i></sup></a> <span class="citation Journal">Wilhelms, Don (1987). <a class="external text" href="http://ser.sese.asu.edu/GHM/ghm_07txt.pdf" rel="nofollow">"Relative Ages"</a>. <i>Geologic History of the Moon</i>. U.S. Geological Survey.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Relative+Ages&rft.atitle=Geologic+History+of+the+Moon&rft.aulast=Wilhelms&rft.aufirst=Don&rft.au=Wilhelms%2C%26%2332%3BDon&rft.date=1987&rft.pub=U.S.+Geological+Survey&rft_id=http%3A%2F%2Fser.sese.asu.edu%2FGHM%2Fghm_07txt.pdf&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-54"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-54">^</a></b> <span class="citation Journal">Hartmann, William K.; Quantin, Cathy; Mangold, Nicolas (2007). "Possible long-term decline in impact rates: 2. Lunar impact-melt data regarding impact history". <i>Icarus</i> <b>186</b> (1): 11–23. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.1016%2Fj.icarus.2006.09.009" rel="nofollow">10.1016/j.icarus.2006.09.009</a></span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Possible+long-term+decline+in+impact+rates%3A+2.+Lunar+impact-melt+data+regarding+impact+history&rft.jtitle=Icarus&rft.aulast=Hartmann&rft.aufirst=William+K.&rft.au=Hartmann%2C%26%2332%3BWilliam+K.&rft.au=Quantin%2C%26%2332%3BCathy&rft.au=Mangold%2C%26%2332%3BNicolas&rft.date=2007&rft.volume=186&rft.issue=1&rft.pages=11%E2%80%9323&rft_id=info:doi/10.1016%2Fj.icarus.2006.09.009&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-55"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-55">^</a></b> <span class="citation web"><a class="external text" href="http://science.nasa.gov/headlines/y2006/30jan_smellofmoondust.htm" rel="nofollow">"The Smell of Moondust"</a>. NASA. 30 January 2006<span class="reference-accessdate">. Retrieved 15 March 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=The+Smell+of+Moondust&rft.atitle=&rft.date=30+January+2006&rft.pub=NASA&rft_id=http%3A%2F%2Fscience.nasa.gov%2Fheadlines%2Fy2006%2F30jan_smellofmoondust.htm&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-56"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-56">^</a></b> <span class="citation book">Heiken, G.; Vaniman, D.; French, B. (eds.) (1991). <i>Lunar Sourcebook, a user's guide to the Moon</i>. New York: Cambridge University Press. pp. 736. <a href="http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="http://en.wikipedia.org/wiki/Special:BookSources/0-521-33444-6" title="Special:BookSources/0-521-33444-6">0-521-33444-6</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Lunar+Sourcebook%2C+a+user%27s+guide+to+the+Moon&rft.aulast=Heiken&rft.aufirst=G.&rft.au=Heiken%2C%26%2332%3BG.&rft.date=1991&rft.pages=pp.%26nbsp%3B736&rft.place=New+York&rft.pub=Cambridge+University+Press&rft.isbn=0-521-33444-6&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-57"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-57">^</a></b> <span class="citation Journal">Rasmussen, K.L.; Warren, P.H. (1985). "Megaregolith thickness, heat flow, and the bulk composition of the Moon". <i>Nature</i> <b>313</b> (5998): 121–124. <a href="http://en.wikipedia.org/wiki/Bibcode">Bibcode</a> <a class="external text" href="http://adsabs.harvard.edu/abs/1985Natur.313..121R" rel="nofollow">1985Natur.313..121R</a>. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.1038%2F313121a0" rel="nofollow">10.1038/313121a0</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Megaregolith+thickness%2C+heat+flow%2C+and+the+bulk+composition+of+the+Moon&rft.jtitle=Nature&rft.aulast=Rasmussen&rft.aufirst=K.L.&rft.au=Rasmussen%2C%26%2332%3BK.L.&rft.date=1985&rft.volume=313&rft.issue=5998&rft.pages=121%E2%80%93124&rft_id=info:bibcode/1985Natur.313..121R&rft_id=info:doi/10.1038%2F313121a0&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-Margot1999-58"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-Margot1999_58-0">^</a></b> <span class="citation Journal">Margot, J. L.; Campbell, D. B.; Jurgens, R. F.; Slade, M. A. (4 June 1999). "Topography of the Lunar Poles from Radar Interferometry: A Survey of Cold Trap Locations". <i>Science</i> <b>284</b> (5420): 1658–1660. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.1126%2Fscience.284.5420.1658" rel="nofollow">10.1126/science.284.5420.1658</a>. <a class="mw-redirect" href="http://en.wikipedia.org/wiki/PubMed_Identifier" title="PubMed Identifier">PMID</a> <a class="external text" href="http://www.ncbi.nlm.nih.gov/pubmed/10356393" rel="nofollow">10356393</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Topography+of+the+Lunar+Poles+from+Radar+Interferometry%3A+A+Survey+of+Cold+Trap+Locations&rft.jtitle=Science&rft.aulast=Margot%2C+J.+L.%3B+Campbell%2C+D.+B.%3B+Jurgens%2C+R.+F.%3B+Slade%2C+M.+A.&rft.au=Margot%2C+J.+L.%3B+Campbell%2C+D.+B.%3B+Jurgens%2C+R.+F.%3B+Slade%2C+M.+A.&rft.date=4+June+1999&rft.volume=284&rft.issue=5420&rft.pages=1658%E2%80%931660&rft_id=info:doi/10.1126%2Fscience.284.5420.1658&rft_id=info:pmid/10356393&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-59"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-59">^</a></b> <span class="citation Journal">Ward, William R. (1 August 1975). "Past Orientation of the Lunar Spin Axis". <i>Science</i> <b>189</b> (4200): 377–379. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.1126%2Fscience.189.4200.377" rel="nofollow">10.1126/science.189.4200.377</a>. <a class="mw-redirect" href="http://en.wikipedia.org/wiki/PubMed_Identifier" title="PubMed Identifier">PMID</a> <a class="external text" href="http://www.ncbi.nlm.nih.gov/pubmed/17840827" rel="nofollow">17840827</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Past+Orientation+of+the+Lunar+Spin+Axis&rft.jtitle=Science&rft.aulast=Ward&rft.aufirst=William+R.&rft.au=Ward%2C%26%2332%3BWilliam+R.&rft.date=1+August+1975&rft.volume=189&rft.issue=4200&rft.pages=377%E2%80%93379&rft_id=info:doi/10.1126%2Fscience.189.4200.377&rft_id=info:pmid/17840827&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-M03-60">^ <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-M03_60-0"><sup><i><b>a</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-M03_60-1"><sup><i><b>b</b></i></sup></a> <span class="citation web">Martel, L.M.V. (4 June 2003). <a class="external text" href="http://www.psrd.hawaii.edu/June03/lunarShadows.html" rel="nofollow">"The Moon's Dark, Icy Poles"</a>. Planetary Science Research Discoveries, Hawai'i Institute of Geophysics and Planetology<span class="reference-accessdate">. Retrieved 12 April 2007</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=The+Moon%27s+Dark%2C+Icy+Poles&rft.atitle=&rft.aulast=Martel&rft.aufirst=L.M.V.&rft.au=Martel%2C%26%2332%3BL.M.V.&rft.date=4+June+2003&rft.pub=Planetary+Science+Research+Discoveries%2C+Hawai%27i+Institute+of+Geophysics+and+Planetology&rft_id=http%3A%2F%2Fwww.psrd.hawaii.edu%2FJune03%2FlunarShadows.html&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-seedhouse2009-61"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-seedhouse2009_61-0">^</a></b> <span class="citation book">Seedhouse, Erik (2009). <a class="external text" href="http://books.google.com/?id=ZJm_i3GS4r4C&pg=PA136" rel="nofollow"><i>Lunar Outpost: The Challenges of Establishing a Human Settlement on the Moon</i></a>. Springer-Praxis Books in Space Exploration. Germany: Springer Praxis. p. 136. <a href="http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="http://en.wikipedia.org/wiki/Special:BookSources/0-387-09746-5" title="Special:BookSources/0-387-09746-5">0-387-09746-5</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Lunar+Outpost%3A+The+Challenges+of+Establishing+a+Human+Settlement+on+the+Moon&rft.aulast=Seedhouse&rft.aufirst=Erik&rft.au=Seedhouse%2C%26%2332%3BErik&rft.date=2009&rft.series=Springer-Praxis+Books+in+Space+Exploration&rft.pages=p.%26nbsp%3B136&rft.place=Germany&rft.pub=Springer+Praxis&rft.isbn=0-387-09746-5&rft_id=http%3A%2F%2Fbooks.google.com%2F%3Fid%3DZJm_i3GS4r4C%26pg%3DPA136&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-moonwater_18032010-62"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-moonwater_18032010_62-0">^</a></b> <span class="citation web">Coulter, Dauna (18 March 2010). <a class="external text" href="http://science.nasa.gov/headlines/y2010/18mar_moonwater.htm?list940097" rel="nofollow">"The Multiplying Mystery of Moonwater"</a>. Science@NASA<span class="reference-accessdate">. Retrieved 28 March 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=The+Multiplying+Mystery+of+Moonwater&rft.atitle=&rft.aulast=Coulter&rft.aufirst=Dauna&rft.au=Coulter%2C%26%2332%3BDauna&rft.date=18+March+2010&rft.pub=Science%40NASA&rft_id=http%3A%2F%2Fscience.nasa.gov%2Fheadlines%2Fy2010%2F18mar_moonwater.htm%3Flist940097&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-63"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-63">^</a></b> <span class="citation web">Spudis, P. (6 November 2006). <a class="external text" href="http://www.thespacereview.com/article/740/1" rel="nofollow">"Ice on the Moon"</a>. The Space Review<span class="reference-accessdate">. Retrieved 12 April 2007</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Ice+on+the+Moon&rft.atitle=&rft.aulast=Spudis&rft.aufirst=P.&rft.au=Spudis%2C%26%2332%3BP.&rft.date=6+November+2006&rft.pub=The+Space+Review&rft_id=http%3A%2F%2Fwww.thespacereview.com%2Farticle%2F740%2F1&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-Feldman1998-64"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-Feldman1998_64-0">^</a></b> <span class="citation Journal">Feldman, W. C.; S. Maurice, A. B. Binder, B. L. Barraclough, R. C. Elphic, D. J. Lawrence (1998). "Fluxes of Fast and Epithermal Neutrons from Lunar Prospector: Evidence for Water Ice at the Lunar Poles". <i>Science</i> <b>281</b> (5382): 1496–1500. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.1126%2Fscience.281.5382.1496" rel="nofollow">10.1126/science.281.5382.1496</a>. <a class="mw-redirect" href="http://en.wikipedia.org/wiki/PubMed_Identifier" title="PubMed Identifier">PMID</a> <a class="external text" href="http://www.ncbi.nlm.nih.gov/pubmed/9727973" rel="nofollow">9727973</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Fluxes+of+Fast+and+Epithermal+Neutrons+from+Lunar+Prospector%3A+Evidence+for+Water+Ice+at+the+Lunar+Poles&rft.jtitle=Science&rft.aulast=Feldman&rft.aufirst=W.+C.&rft.au=Feldman%2C%26%2332%3BW.+C.&rft.date=1998&rft.volume=281&rft.issue=5382&rft.pages=1496%E2%80%931500&rft_id=info:doi/10.1126%2Fscience.281.5382.1496&rft_id=info:pmid/9727973&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-Saal2008-65"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-Saal2008_65-0">^</a></b> <span class="citation Journal">Saal, Alberto E.; Hauri, Erik H.; Cascio, Mauro L.; van Orman, James A.; Rutherford, Malcolm C.; Cooper, Reid F. (2008). "Volatile content of lunar volcanic glasses and the presence of water in the Moon's interior". <i>Nature</i> <b>454</b> (7201): 192–195. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.1038%2Fnature07047" rel="nofollow">10.1038/nature07047</a>. <a class="mw-redirect" href="http://en.wikipedia.org/wiki/PubMed_Identifier" title="PubMed Identifier">PMID</a> <a class="external text" href="http://www.ncbi.nlm.nih.gov/pubmed/18615079" rel="nofollow">18615079</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Volatile+content+of+lunar+volcanic+glasses+and+the+presence+of+water+in+the+Moon%27s+interior&rft.jtitle=Nature&rft.aulast=Saal&rft.aufirst=Alberto+E.&rft.au=Saal%2C%26%2332%3BAlberto+E.&rft.date=2008&rft.volume=454&rft.issue=7201&rft.pages=192%E2%80%93195&rft_id=info:doi/10.1038%2Fnature07047&rft_id=info:pmid/18615079&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-Pieters2009-66"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-Pieters2009_66-0">^</a></b> <span class="citation Journal">Pieters, C. M.; Goswami, J. N.; Clark, R. N.; Annadurai, M.; Boardman, J.; Buratti, B.; Combe, J.-P.; Dyar, M. D.; Green, R.; Head, J. W.; Hibbitts, C.; Hicks, M.; Isaacson, P.; Klima, R.; Kramer, G.; Kumar, S.; Livo, E.; Lundeen, S.; Malaret, E.; McCord, T.; Mustard, J.; Nettles, J.; Petro, N.; Runyon, C.; Staid, M.; Sunshine, J.; Taylor, L. A.; Tompkins, S.; Varanasi, P. (2009). "Character and Spatial Distribution of OH/H2O on the Surface of the Moon Seen by M3 on Chandrayaan-1". <i>Science</i> <b>326</b> (5952): 568–72. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.1126%2Fscience.1178658" rel="nofollow">10.1126/science.1178658</a>. <a class="mw-redirect" href="http://en.wikipedia.org/wiki/PubMed_Identifier" title="PubMed Identifier">PMID</a> <a class="external text" href="http://www.ncbi.nlm.nih.gov/pubmed/19779151" rel="nofollow">19779151</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Character+and+Spatial+Distribution+of+OH%2FH2O+on+the+Surface+of+the+Moon+Seen+by+M3+on+Chandrayaan-1&rft.jtitle=Science&rft.aulast=Pieters&rft.aufirst=C.+M.&rft.au=Pieters%2C%26%2332%3BC.+M.&rft.date=2009&rft.volume=326&rft.issue=5952&rft.pages=568%E2%80%9372&rft_id=info:doi/10.1126%2Fscience.1178658&rft_id=info:pmid/19779151&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-Planetary-67"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-Planetary_67-0">^</a></b> <span class="citation web">Lakdawalla, Emily (13 November 2009). <a class="external text" href="http://planetary.org/news/2009/1113_LCROSS_Lunar_Impactor_Mission_Yes_We.html" rel="nofollow">"LCROSS Lunar Impactor Mission: "Yes, We Found Water!""</a>. The Planetary Society<span class="reference-accessdate">. Retrieved 13 April 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=LCROSS+Lunar+Impactor+Mission%3A+%22Yes%2C+We+Found+Water%21%22&rft.atitle=&rft.aulast=Lakdawalla&rft.aufirst=Emily&rft.au=Lakdawalla%2C%26%2332%3BEmily&rft.date=13+November+2009&rft.pub=The+Planetary+Society&rft_id=http%3A%2F%2Fplanetary.org%2Fnews%2F2009%2F1113_LCROSS_Lunar_Impactor_Mission_Yes_We.html&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-Colaprete-68"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-Colaprete_68-0">^</a></b> <span class="citation Journal">Colaprete, A.; Ennico, K.; Wooden, D.; Shirley, M.; Heldmann, J.; Marshall, W.; Sollitt, L.; Asphaug, E.; Korycansky, D.; Schultz, P.; Hermalyn, B.; Galal, K.; Bart, G. D.; Goldstein, D.; Summy, D. (March 1–5, 2010). "Water and More: An Overview of LCROSS Impact Results". <i>41st Lunar and Planetary Science Conference</i> <b>41</b> (1533): 2335. <a href="http://en.wikipedia.org/wiki/Bibcode">Bibcode</a> <a class="external text" href="http://adsabs.harvard.edu/abs/2010LPI....41.2335C" rel="nofollow">2010LPI....41.2335C</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Water+and+More%3A+An+Overview+of+LCROSS+Impact+Results&rft.jtitle=41st+Lunar+and+Planetary+Science+Conference&rft.aulast=Colaprete&rft.aufirst=A.&rft.au=Colaprete%2C%26%2332%3BA.&rft.date=March+1%E2%80%935%2C+2010&rft.volume=41&rft.issue=1533&rft.pages=2335&rft_id=info:bibcode/2010LPI....41.2335C&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-Colaprete2010-69"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-Colaprete2010_69-0">^</a></b> <span class="citation Journal">Colaprete, A.; Schultz, P.; Heldmann, J.; Wooden, D.; Shirley, M.; Ennico, K.; Hermalyn, B.; Marshall, W; Ricco, A.; Elphic, R. C.; Goldstein, D.; Summy, D.; Bart, G. D.; Asphaug, E.; Korycansky, D.; Landis, D.; Sollitt, L. (22 October 2010). "Detection of Water in the LCROSS Ejecta Plume". <i>Science</i> <b>330</b> (6003): 463–468. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.1126%2Fscience.1186986" rel="nofollow">10.1126/science.1186986</a>. <a class="mw-redirect" href="http://en.wikipedia.org/wiki/PubMed_Identifier" title="PubMed Identifier">PMID</a> <a class="external text" href="http://www.ncbi.nlm.nih.gov/pubmed/20966242" rel="nofollow">20966242</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Detection+of+Water+in+the+LCROSS+Ejecta+Plume&rft.jtitle=Science&rft.aulast=Colaprete%2C+A.%3B+Schultz%2C+P.%3B+Heldmann%2C+J.%3B+Wooden%2C+D.%3B+Shirley%2C+M.%3B+Ennico%2C+K.%3B+Hermalyn%2C+B.%3B+Marshall%2C+W%3B+Ricco%2C+A.%3B+Elphic%2C+R.+C.%3B+Goldstein%2C+D.%3B+Summy%2C+D.%3B+Bart%2C+G.+D.%3B+Asphaug%2C+E.%3B+Korycansky%2C+D.%3B+Landis%2C+D.%3B+Sollitt%2C+L.&rft.au=Colaprete%2C+A.%3B+Schultz%2C+P.%3B+Heldmann%2C+J.%3B+Wooden%2C+D.%3B+Shirley%2C+M.%3B+Ennico%2C+K.%3B+Hermalyn%2C+B.%3B+Marshall%2C+W%3B+Ricco%2C+A.%3B+Elphic%2C+R.+C.%3B+Goldstein%2C+D.%3B+Summy%2C+D.%3B+Bart%2C+G.+D.%3B+Asphaug%2C+E.%3B+Korycansky%2C+D.%3B+Landis%2C+D.%3B+Sollitt%2C+L.&rft.date=22+October+2010&rft.volume=330&rft.issue=6003&rft.pages=463%E2%80%93468&rft_id=info:doi/10.1126%2Fscience.1186986&rft_id=info:pmid/20966242&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-70"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-70">^</a></b> <span class="citation Journal">Muller, P.; Sjogren, W. (1968). "Mascons: lunar mass concentrations". <i>Science</i> <b>161</b> (3842): 680–684. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.1126%2Fscience.161.3842.680" rel="nofollow">10.1126/science.161.3842.680</a>. <a class="mw-redirect" href="http://en.wikipedia.org/wiki/PubMed_Identifier" title="PubMed Identifier">PMID</a> <a class="external text" href="http://www.ncbi.nlm.nih.gov/pubmed/17801458" rel="nofollow">17801458</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Mascons%3A+lunar+mass+concentrations&rft.jtitle=Science&rft.aulast=Muller&rft.aufirst=P.&rft.au=Muller%2C%26%2332%3BP.&rft.date=1968&rft.volume=161&rft.issue=3842&rft.pages=680%E2%80%93684&rft_id=info:doi/10.1126%2Fscience.161.3842.680&rft_id=info:pmid/17801458&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-71"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-71">^</a></b> <span class="citation Journal">Konopliv, A.; Asmar, S.; Carranza, E.; Sjogren, W.; Yuan, D. (2001). "Recent gravity models as a result of the Lunar Prospector mission". <i>Icarus</i> <b>50</b> (1): 1–18. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.1006%2Ficar.2000.6573" rel="nofollow">10.1006/icar.2000.6573</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Recent+gravity+models+as+a+result+of+the+Lunar+Prospector+mission&rft.jtitle=Icarus&rft.aulast=Konopliv&rft.aufirst=A.&rft.au=Konopliv%2C%26%2332%3BA.&rft.date=2001&rft.volume=50&rft.issue=1&rft.pages=1%E2%80%9318&rft_id=info:doi/10.1006%2Ficar.2000.6573&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-GB2009-72"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-GB2009_72-0">^</a></b> <span class="citation Journal">Garrick-Bethell, Ian; Weiss, iBenjamin P.; Shuster, David L.; Buz, Jennifer (2009). "Early Lunar Magnetism". <i>Science</i> <b>323</b> (5912): 356–359. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.1126%2Fscience.1166804" rel="nofollow">10.1126/science.1166804</a>. <a class="mw-redirect" href="http://en.wikipedia.org/wiki/PubMed_Identifier" title="PubMed Identifier">PMID</a> <a class="external text" href="http://www.ncbi.nlm.nih.gov/pubmed/19150839" rel="nofollow">19150839</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Early+Lunar+Magnetism&rft.jtitle=Science&rft.aulast=Garrick-Bethell&rft.aufirst=Ian&rft.au=Garrick-Bethell%2C%26%2332%3BIan&rft.au=Weiss%2C%26%2332%3BiBenjamin+P.&rft.au=Shuster%2C%26%2332%3BDavid+L.&rft.au=Buz%2C%26%2332%3BJennifer&rft.date=2009&rft.volume=323&rft.issue=5912&rft.pages=356%E2%80%93359&rft_id=info:doi/10.1126%2Fscience.1166804&rft_id=info:pmid/19150839&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-73"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-73">^</a></b> <span class="citation web"><a class="external text" href="http://lunar.arc.nasa.gov/results/magelres.htm" rel="nofollow">"Magnetometer / Electron Reflectometer Results"</a>. Lunar Prospector (NASA). 2001<span class="reference-accessdate">. Retrieved 17 March 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Magnetometer+%2F+Electron+Reflectometer+Results&rft.atitle=&rft.date=2001&rft.pub=Lunar+Prospector+%28NASA%29&rft_id=http%3A%2F%2Flunar.arc.nasa.gov%2Fresults%2Fmagelres.htm&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-74"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-74">^</a></b> <span class="citation Journal">Hood, L.L.; Huang, Z. (1991). "Formation of magnetic anomalies antipodal to lunar impact basins: Two-dimensional model calculations". <i>J. Geophys. Res.</i> <b>96</b> (B6): 9837–9846. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.1029%2F91JB00308" rel="nofollow">10.1029/91JB00308</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Formation+of+magnetic+anomalies+antipodal+to+lunar+impact+basins%3A+Two-dimensional+model+calculations&rft.jtitle=J.+Geophys.+Res.&rft.aulast=Hood&rft.aufirst=L.L.&rft.au=Hood%2C%26%2332%3BL.L.&rft.date=1991&rft.volume=96&rft.issue=B6&rft.pages=9837%E2%80%939846&rft_id=info:doi/10.1029%2F91JB00308&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-75"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-75">^</a></b> <span class="citation book">Globus, Ruth (1977). <a class="external text" href="http://settlement.arc.nasa.gov/75SummerStudy/5appendJ.html" rel="nofollow">"Chapter 5, Appendix J: Impact Upon Lunar Atmosphere"</a>. In Richard D. Johnson & Charles Holbrow. <i>Space Settlements: A Design Study</i>. NASA<span class="reference-accessdate">. Retrieved 17 March 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Chapter+5%2C+Appendix+J%3A+Impact+Upon+Lunar+Atmosphere&rft.atitle=Space+Settlements%3A+A+Design+Study&rft.aulast=Globus&rft.aufirst=Ruth&rft.au=Globus%2C%26%2332%3BRuth&rft.date=1977&rft.pub=NASA&rft_id=http%3A%2F%2Fsettlement.arc.nasa.gov%2F75SummerStudy%2F5appendJ.html&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-76"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-76">^</a></b> <span class="citation Journal">Crotts, Arlin P.S. (2008) (PDF). <a class="external text" href="http://www.astro.columbia.edu/%7Earlin/TLP/paper1.pdf" rel="nofollow"><i>Lunar Outgassing, Transient Phenomena and The Return to The Moon, I: Existing Data.</i></a>. Department of Astronomy, Columbia University<span class="reference-accessdate">. Retrieved 29 September 2009</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Lunar+Outgassing%2C+Transient+Phenomena+and+The+Return+to+The+Moon%2C+I%3A+Existing+Data.&rft.aulast=Crotts&rft.aufirst=Arlin+P.S.&rft.au=Crotts%2C%26%2332%3BArlin+P.S.&rft.date=2008&rft.pub=Department+of+Astronomy%2C+Columbia+University&rft_id=http%3A%2F%2Fwww.astro.columbia.edu%2F%7Earlin%2FTLP%2Fpaper1.pdf&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-Stern1999-77">^ <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-Stern1999_77-0"><sup><i><b>a</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-Stern1999_77-1"><sup><i><b>b</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-Stern1999_77-2"><sup><i><b>c</b></i></sup></a> <span class="citation Journal">Stern, S.A. (1999). "The Lunar atmosphere: History, status, current problems, and context". <i>Rev. Geophys.</i> <b>37</b> (4): 453–491. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.1029%2F1999RG900005" rel="nofollow">10.1029/1999RG900005</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=The+Lunar+atmosphere%3A+History%2C+status%2C+current+problems%2C+and+context&rft.jtitle=Rev.+Geophys.&rft.aulast=Stern&rft.aufirst=S.A.&rft.au=Stern%2C%26%2332%3BS.A.&rft.date=1999&rft.volume=37&rft.issue=4&rft.pages=453%E2%80%93491&rft_id=info:doi/10.1029%2F1999RG900005&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-78"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-78">^</a></b> <span class="citation Journal">Lawson, S.; Feldman, W.; Lawrence, D.; Moore, K.; Elphic, R.; Belian, R. (2005). "Recent outgassing from the lunar surface: the Lunar Prospector alpha particle spectrometer". <i>J. Geophys. Res.</i> <b>110</b> (E9): 1029. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.1029%2F2005JE002433" rel="nofollow">10.1029/2005JE002433</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Recent+outgassing+from+the+lunar+surface%3A+the+Lunar+Prospector+alpha+particle+spectrometer&rft.jtitle=J.+Geophys.+Res.&rft.aulast=Lawson&rft.aufirst=S.&rft.au=Lawson%2C%26%2332%3BS.&rft.date=2005&rft.volume=110&rft.issue=E9&rft.pages=1029&rft_id=info:doi/10.1029%2F2005JE002433&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-Sridharan2010-79"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-Sridharan2010_79-0">^</a></b> <span class="citation Journal">Sridharan, R.; S.M. Ahmed, Tirtha Pratim Dasa, P. Sreelathaa, P. Pradeepkumara, Neha Naika, and Gogulapati Supriya (2010). "‘Direct’ evidence for water (H2O) in the sunlit lunar ambience from CHACE on MIP of Chandrayaan I". <i>Planetary and Space Science</i> <b>58</b> (6): 947. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.1016%2Fj.pss.2010.02.013" rel="nofollow">10.1016/j.pss.2010.02.013</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=%E2%80%98Direct%E2%80%99+evidence+for+water+%28H2O%29+in+the+sunlit+lunar+ambience+from+CHACE+on+MIP+of+Chandrayaan+I&rft.jtitle=Planetary+and+Space+Science&rft.aulast=Sridharan&rft.aufirst=R.&rft.au=Sridharan%2C%26%2332%3BR.&rft.date=2010&rft.volume=58&rft.issue=6&rft.pages=947&rft_id=info:doi/10.1016%2Fj.pss.2010.02.013&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-bbc-80">^ <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-bbc_80-0"><sup><i><b>a</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-bbc_80-1"><sup><i><b>b</b></i></sup></a> <span class="citation news">Jonathan Amos (16 December 2009). <a class="external text" href="http://news.bbc.co.uk/1/hi/8416749.stm" rel="nofollow">"'Coldest place' found on the Moon"</a>. BBC News<span class="reference-accessdate">. Retrieved 20 March 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=%27Coldest+place%27+found+on+the+Moon&rft.atitle=&rft.aulast=Jonathan+Amos&rft.au=Jonathan+Amos&rft.date=16+December+2009&rft.pub=BBC+News&rft_id=http%3A%2F%2Fnews.bbc.co.uk%2F1%2Fhi%2F8416749.stm&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-81"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-81">^</a></b> <span class="citation web"><a class="external text" href="http://www.diviner.ucla.edu/blog/?p=123" rel="nofollow">"Diviner News"</a>. UCLA. 17 September 2009<span class="reference-accessdate">. Retrieved 17 March 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Diviner+News&rft.atitle=&rft.date=17+September+2009&rft.pub=UCLA&rft_id=http%3A%2F%2Fwww.diviner.ucla.edu%2Fblog%2F%3Fp%3D123&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-Beletskii2-84"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-Beletskii2_84-0">^</a></b> <span class="citation book">V V Belet︠s︡kiĭ (2001). <a class="external text" href="http://books.google.com/?id=byWZusmVSecC&pg=PA183&dq=%22Cassini%27s+laws%22" rel="nofollow"><i>Essays on the Motion of Celestial Bodies</i></a>. Birkhäuser. p. 183. <a href="http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="http://en.wikipedia.org/wiki/Special:BookSources/3-7643-5866-1" title="Special:BookSources/3-7643-5866-1">3-7643-5866-1</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Essays+on+the+Motion+of+Celestial+Bodies&rft.aulast=V+V+Belet%EF%B8%A0s%EF%B8%A1ki%C4%AD&rft.au=V+V+Belet%EF%B8%A0s%EF%B8%A1ki%C4%AD&rft.date=2001&rft.pages=p.%26nbsp%3B183&rft.pub=Birkh%C3%A4user&rft.isbn=3-7643-5866-1&rft_id=http%3A%2F%2Fbooks.google.com%2F%3Fid%3DbyWZusmVSecC%26pg%3DPA183%26dq%3D%2522Cassini%2527s%2Blaws%2522&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-85"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-85">^</a></b> <a class="external text" href="http://antwrp.gsfc.nasa.gov/apod/ap080903.html" rel="nofollow"><i>Astronomy Picture of the Day</i></a>, 2008 September 3</li><li id="cite_note-86"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-86">^</a></b> <span class="citation web"><a class="external text" href="http://www.planetary.org/explore/topics/pluto/" rel="nofollow">"Space Topics: Pluto and Charon"</a>. The Planetary Society<span class="reference-accessdate">. Retrieved 6 April 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Space+Topics%3A+Pluto+and+Charon&rft.atitle=&rft.pub=The+Planetary+Society&rft_id=http%3A%2F%2Fwww.planetary.org%2Fexplore%2Ftopics%2Fpluto%2F&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-87"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-87">^</a></b> <span class="citation web"><a class="external text" href="http://www.iau.org/public_press/news/release/iau0601/q_answers/" rel="nofollow">"Planet Definition Questions & Answers Sheet"</a>. International Astronomical Union. 2006<span class="reference-accessdate">. Retrieved 24 March 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Planet+Definition+Questions+%26+Answers+Sheet&rft.atitle=&rft.date=2006&rft.pub=International+Astronomical+Union&rft_id=http%3A%2F%2Fwww.iau.org%2Fpublic_press%2Fnews%2Frelease%2Fiau0601%2Fq_answers%2F&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-88"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-88">^</a></b> <span class="citation Journal">Alexander, M. E. (1973). "The Weak Friction Approximation and Tidal Evolution in Close Binary Systems". <i>Astrophysics and Space Science</i> <b>23</b> (2): 459–508. <a href="http://en.wikipedia.org/wiki/Bibcode">Bibcode</a> <a class="external text" href="http://adsabs.harvard.edu/abs/1973Ap&SS..23..459A" rel="nofollow">1973Ap&SS..23..459A</a>. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.1007%2FBF00645172" rel="nofollow">10.1007/BF00645172</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=The+Weak+Friction+Approximation+and+Tidal+Evolution+in+Close+Binary+Systems&rft.jtitle=Astrophysics+and+Space+Science&rft.aulast=Alexander&rft.aufirst=M.+E.&rft.au=Alexander%2C%26%2332%3BM.+E.&rft.date=1973&rft.volume=23&rft.issue=2&rft.pages=459%E2%80%93508&rft_id=info:bibcode/1973Ap%26SS..23..459A&rft_id=info:doi/10.1007%2FBF00645172&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-89"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-89">^</a></b> <span class="citation web"><a href="http://en.wikipedia.org/wiki/Phil_Plait">Phil Plait</a>. <a class="external text" href="http://www.badastronomy.com/bad/misc/dark_side.html" rel="nofollow">"Dark Side of the Moon"</a>. Bad Astronomy:Misconceptions<span class="reference-accessdate">. Retrieved 15 February 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Dark+Side+of+the+Moon&rft.atitle=&rft.aulast=%5B%5BPhil+Plait%5D%5D&rft.au=%5B%5BPhil+Plait%5D%5D&rft.pub=Bad+Astronomy%3AMisconceptions&rft_id=http%3A%2F%2Fwww.badastronomy.com%2Fbad%2Fmisc%2Fdark_side.html&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-Moon-91"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-Moon_91-0">^</a></b> <span class="citation web">Luciuk, Mike. <a class="external text" href="http://www.asterism.org/tutorials/tut26-1.htm" rel="nofollow">"How Bright is the Moon?"</a>. Amateur Astronomers, Inc.<span class="reference-accessdate">. Retrieved 16 March 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=How+Bright+is+the+Moon%3F&rft.atitle=&rft.aulast=Luciuk%2C+Mike&rft.au=Luciuk%2C+Mike&rft.pub=Amateur+Astronomers%2C+Inc.&rft_id=http%3A%2F%2Fwww.asterism.org%2Ftutorials%2Ftut26-1.htm&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-92"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-92">^</a></b> <span class="citation book">Hershenson, Maurice (1989). <i>The Moon illusion</i>. Routledge. pp. 5. <a href="http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="http://en.wikipedia.org/wiki/Special:BookSources/978-0-8058-0121-7" title="Special:BookSources/978-0-8058-0121-7">978-0-8058-0121-7</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Moon+illusion&rft.aulast=Hershenson&rft.aufirst=Maurice&rft.au=Hershenson%2C%26%2332%3BMaurice&rft.date=1989&rft.pages=pp.%26nbsp%3B5&rft.pub=Routledge&rft.isbn=978-0-8058-0121-7&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-93"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-93">^</a></b> <span class="citation web">Spekkens, K. (18 October 2002). <a class="external text" href="http://curious.astro.cornell.edu/question.php?number=393" rel="nofollow">"Is the Moon seen as a crescent (and not a "boat") all over the world?"</a>. Curious About Astronomy<span class="reference-accessdate">. Retrieved 16 March 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Is+the+Moon+seen+as+a+crescent+%28and+not+a+%22boat%22%29+all+over+the+world%3F&rft.atitle=&rft.aulast=Spekkens&rft.aufirst=K.&rft.au=Spekkens%2C%26%2332%3BK.&rft.date=18+October+2002&rft.pub=Curious+About+Astronomy&rft_id=http%3A%2F%2Fcurious.astro.cornell.edu%2Fquestion.php%3Fnumber%3D393&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-94"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-94">^</a></b> <span class="citation web"><a class="external text" href="http://www.pe.com/localnews/stories/PE_News_Local_D_moon19.23a6364.html" rel="nofollow">"Full moon tonight is as close as it gets"</a>. The Press Enterprise. 18 March 2011<span class="reference-accessdate">. Retrieved 19 March 2011</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Full+moon+tonight+is+as+close+as+it+gets&rft.atitle=&rft.date=18+March+2011&rft.pub=The+Press+Enterprise&rft_id=http%3A%2F%2Fwww.pe.com%2Flocalnews%2Fstories%2FPE_News_Local_D_moon19.23a6364.html&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-95"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-95">^</a></b> <span class="citation web">Dr. Tony Phillips (16 March 2011). <a class="external text" href="http://science.nasa.gov/science-news/science-at-nasa/2011/16mar_supermoon/" rel="nofollow">"Super Full Moon"</a>. NASA<span class="reference-accessdate">. Retrieved 2011-03-19</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Super+Full+Moon&rft.atitle=&rft.aulast=Dr.+Tony+Phillips&rft.au=Dr.+Tony+Phillips&rft.date=16+March+2011&rft.pub=NASA&rft_id=http%3A%2F%2Fscience.nasa.gov%2Fscience-news%2Fscience-at-nasa%2F2011%2F16mar_supermoon%2F&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-96"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-96">^</a></b> <span class="citation web">Richard K. De Atley (18 March 2011). <a class="external text" href="http://www.pe.com/localnews/stories/PE_News_Local_D_moon19.23a6364.html" rel="nofollow">"Full moon tonight is as close as it gets"</a>. The Press-Enterprise<span class="reference-accessdate">. Retrieved 2011-03-19</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Full+moon+tonight+is+as+close+as+it+gets&rft.atitle=&rft.aulast=Richard+K.+De+Atley&rft.au=Richard+K.+De+Atley&rft.date=18+March+2011&rft.pub=The+Press-Enterprise&rft_id=http%3A%2F%2Fwww.pe.com%2Flocalnews%2Fstories%2FPE_News_Local_D_moon19.23a6364.html&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-97"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-97">^</a></b> <span class="citation web"><a class="external text" href="http://www.guardian.co.uk/science/2011/mar/19/super-moon-closest-point-years" rel="nofollow">"'Super moon' to reach closest point for almost 20 years"</a>. The Guardian. 19 March 2011<span class="reference-accessdate">. Retrieved 19 March 2011</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=%27Super+moon%27+to+reach+closest+point+for+almost+20+years&rft.atitle=&rft.date=19+March+2011&rft.pub=The+Guardian&rft_id=http%3A%2F%2Fwww.guardian.co.uk%2Fscience%2F2011%2Fmar%2F19%2Fsuper-moon-closest-point-years&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-98"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-98">^</a></b> <span class="citation web">Taylor, G.J. (8 November 2006). <a class="external text" href="http://www.psrd.hawaii.edu/Nov06/MoonGas.html" rel="nofollow">"Recent Gas Escape from the Moon"</a>. Planetary Science Research Discoveries, Hawai'i Institute of Geophysics and Planetology<span class="reference-accessdate">. Retrieved 4 April 2007</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Recent+Gas+Escape+from+the+Moon&rft.atitle=&rft.aulast=Taylor&rft.aufirst=G.J.&rft.au=Taylor%2C%26%2332%3BG.J.&rft.date=8+November+2006&rft.pub=Planetary+Science+Research+Discoveries%2C+Hawai%27i+Institute+of+Geophysics+and+Planetology&rft_id=http%3A%2F%2Fwww.psrd.hawaii.edu%2FNov06%2FMoonGas.html&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-99"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-99">^</a></b> <span class="citation Journal">Schultz, P.H.; Staid, M.I.; Pieters, C.M. (2006). "Lunar activity from recent gas release". <i>Nature</i> <b>444</b> (7116): 184–186. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.1038%2Fnature05303" rel="nofollow">10.1038/nature05303</a>. <a class="mw-redirect" href="http://en.wikipedia.org/wiki/PubMed_Identifier" title="PubMed Identifier">PMID</a> <a class="external text" href="http://www.ncbi.nlm.nih.gov/pubmed/17093445" rel="nofollow">17093445</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Lunar+activity+from+recent+gas+release&rft.jtitle=Nature&rft.aulast=Schultz&rft.aufirst=P.H.&rft.au=Schultz%2C%26%2332%3BP.H.&rft.date=2006&rft.volume=444&rft.issue=7116&rft.pages=184%E2%80%93186&rft_id=info:doi/10.1038%2Fnature05303&rft_id=info:pmid/17093445&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-100"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-100">^</a></b> <span class="citation web"><a class="external text" href="http://ww2010.atmos.uiuc.edu/%28Gh%29/guides/mtr/opt/ice/halo/22.rxml" rel="nofollow">"22 Degree Halo: a ring of light 22 degrees from the sun or moon"</a>. Department of Atmospheric Sciences at the University of Illinois at Urbana-Champaign.<span class="reference-accessdate">. Retrieved 13 April 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=22+Degree+Halo%3A+a+ring+of+light+22+degrees+from+the+sun+or+moon&rft.atitle=&rft.pub=Department+of+Atmospheric+Sciences+at+the+University+of+Illinois+at+Urbana-Champaign.&rft_id=http%3A%2F%2Fww2010.atmos.uiuc.edu%2F%2528Gh%2529%2Fguides%2Fmtr%2Fopt%2Fice%2Fhalo%2F22.rxml&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-Lambeck1977-101">^ <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-Lambeck1977_101-0"><sup><i><b>a</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-Lambeck1977_101-1"><sup><i><b>b</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-Lambeck1977_101-2"><sup><i><b>c</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-Lambeck1977_101-3"><sup><i><b>d</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-Lambeck1977_101-4"><sup><i><b>e</b></i></sup></a> <span class="citation Journal">Lambeck, K. (1977). "Tidal Dissipation in the Oceans: Astronomical, Geophysical and Oceanographic Consequences". <i>Philosophical Transactions for the Royal Society of London. Series A, Mathematical and Physical Sciences</i> <b>287</b> (1347): 545–594. <a href="http://en.wikipedia.org/wiki/Bibcode">Bibcode</a> <a class="external text" href="http://adsabs.harvard.edu/abs/1977RSPTA.287..545L" rel="nofollow">1977RSPTA.287..545L</a>. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.1098%2Frsta.1977.0159" rel="nofollow">10.1098/rsta.1977.0159</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Tidal+Dissipation+in+the+Oceans%3A+Astronomical%2C+Geophysical+and+Oceanographic+Consequences&rft.jtitle=Philosophical+Transactions+for+the+Royal+Society+of+London.+Series+A%2C+Mathematical+and+Physical+Sciences&rft.aulast=Lambeck&rft.aufirst=K.&rft.au=Lambeck%2C%26%2332%3BK.&rft.date=1977&rft.volume=287&rft.issue=1347&rft.pages=545%E2%80%93594&rft_id=info:bibcode/1977RSPTA.287..545L&rft_id=info:doi/10.1098%2Frsta.1977.0159&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-102"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-102">^</a></b> <span class="citation Journal">Le Provost, C.; Bennett, A. F.; Cartwright, D. E. (1995). "Ocean Tides for and from TOPEX/POSEIDON". <i>Science</i> <b>267</b> (5198): 639–42. <a href="http://en.wikipedia.org/wiki/Bibcode">Bibcode</a> <a class="external text" href="http://adsabs.harvard.edu/abs/1995Sci...267..639L" rel="nofollow">1995Sci...267..639L</a>. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.1126%2Fscience.267.5198.639" rel="nofollow">10.1126/science.267.5198.639</a>. <a class="mw-redirect" href="http://en.wikipedia.org/wiki/PubMed_Identifier" title="PubMed Identifier">PMID</a> <a class="external text" href="http://www.ncbi.nlm.nih.gov/pubmed/17745840" rel="nofollow">17745840</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Ocean+Tides+for+and+from+TOPEX%2FPOSEIDON&rft.jtitle=Science&rft.aulast=Le+Provost&rft.aufirst=C.&rft.au=Le+Provost%2C%26%2332%3BC.&rft.date=1995&rft.volume=267&rft.issue=5198&rft.pages=639%E2%80%9342&rft_id=info:bibcode/1995Sci...267..639L&rft_id=info:doi/10.1126%2Fscience.267.5198.639&rft_id=info:pmid/17745840&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-touma1994-103">^ <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-touma1994_103-0"><sup><i><b>a</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-touma1994_103-1"><sup><i><b>b</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-touma1994_103-2"><sup><i><b>c</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-touma1994_103-3"><sup><i><b>d</b></i></sup></a> <span class="citation Journal">Touma, Jihad; Wisdom, Jack (1994). "Evolution of the Earth-Moon system". <i>The Astronomical Journal</i> <b>108</b> (5): 1943–1961. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.1086%2F117209" rel="nofollow">10.1086/117209</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Evolution+of+the+Earth-Moon+system&rft.jtitle=The+Astronomical+Journal&rft.aulast=Touma&rft.aufirst=Jihad&rft.au=Touma%2C%26%2332%3BJihad&rft.date=1994&rft.volume=108&rft.issue=5&rft.pages=1943%E2%80%931961&rft_id=info:doi/10.1086%2F117209&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-104"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-104">^</a></b> <span class="citation Journal">Chapront, J.; Chapront-Touzé, M.; Francou, G. (2002). "A new determination of lunar orbital parameters, precession constant and tidal acceleration from LLR measurements". <i>Astronomy and Astrophysics</i> <b>387</b> (2): 700–709. <a href="http://en.wikipedia.org/wiki/Bibcode">Bibcode</a> <a class="external text" href="http://adsabs.harvard.edu/abs/2002A&A...387..700C" rel="nofollow">2002A&A...387..700C</a>. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.1051%2F0004-6361%3A20020420" rel="nofollow">10.1051/0004-6361:20020420</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=A+new+determination+of+lunar+orbital+parameters%2C+precession+constant+and+tidal+acceleration+from+LLR+measurements&rft.jtitle=Astronomy+and+Astrophysics&rft.aulast=Chapront&rft.aufirst=J.&rft.au=Chapront%2C%26%2332%3BJ.&rft.date=2002&rft.volume=387&rft.issue=2&rft.pages=700%E2%80%93709&rft_id=info:bibcode/2002A%26A...387..700C&rft_id=info:doi/10.1051%2F0004-6361%3A20020420&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-105"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-105">^</a></b> <span class="citation web">Ray, R. (15 May 2001). <a class="external text" href="http://bowie.gsfc.nasa.gov/ggfc/tides/intro.html" rel="nofollow">"Ocean Tides and the Earth's Rotation"</a>. IERS Special Bureau for Tides<span class="reference-accessdate">. Retrieved 17 March 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Ocean+Tides+and+the+Earth%27s+Rotation&rft.atitle=&rft.aulast=Ray&rft.aufirst=R.&rft.au=Ray%2C%26%2332%3BR.&rft.date=15+May+2001&rft.pub=IERS+Special+Bureau+for+Tides&rft_id=http%3A%2F%2Fbowie.gsfc.nasa.gov%2Fggfc%2Ftides%2Fintro.html&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-106"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-106">^</a></b> <span class="citation book">Murray, C.D. and Dermott, S.F. (1999). <i>Solar System Dynamics</i>. Cambridge University Press. p. 184. <a href="http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="http://en.wikipedia.org/wiki/Special:BookSources/0-521-57295-9" title="Special:BookSources/0-521-57295-9">0-521-57295-9</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Solar+System+Dynamics&rft.aulast=Murray%2C+C.D.+and+Dermott%2C+S.F.&rft.au=Murray%2C+C.D.+and+Dermott%2C+S.F.&rft.date=1999&rft.pages=p.%26nbsp%3B184&rft.pub=Cambridge+University+Press&rft.isbn=0-521-57295-9&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-107"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-107">^</a></b> <span class="citation book"><a href="http://en.wikipedia.org/wiki/Terence_Dickinson" title="Terence Dickinson">Dickinson, Terence</a> (1993). <i>From the Big Bang to Planet X</i>. Camden East, Ontario: <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Camden_House" title="Camden House">Camden House</a>. pp. 79–81. <a href="http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="http://en.wikipedia.org/wiki/Special:BookSources/0-921820-71-2" title="Special:BookSources/0-921820-71-2">0-921820-71-2</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=From+the+Big+Bang+to+Planet+X&rft.aulast=Dickinson&rft.aufirst=Terence&rft.au=Dickinson%2C%26%2332%3BTerence&rft.date=1993&rft.pages=pp.%26nbsp%3B79%E2%80%9381&rft.place=Camden+East%2C+Ontario&rft.pub=%5B%5BCamden+House%5D%5D&rft.isbn=0-921820-71-2&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-108"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-108">^</a></b> <span class="citation Journal">Latham; Ewing, Maurice; Dorman, James; Lammlein, David; Press, Frank; Toksőz, Naft; Sutton, George; Duennebier, Fred et al. (1972). <a class="external text" href="http://www.springerlink.com/content/jt12323560565365/" rel="nofollow">"Moonquakes and lunar tectonism"</a>. <i>Earth, Moon, and Planets</i> <b>4</b> (3–4): 373–382. <a href="http://en.wikipedia.org/wiki/Bibcode">Bibcode</a> <a class="external text" href="http://adsabs.harvard.edu/abs/1972Moon....4..373L" rel="nofollow">1972Moon....4..373L</a>. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.1007%2FBF00562004" rel="nofollow">10.1007/BF00562004</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Moonquakes+and+lunar+tectonism&rft.jtitle=Earth%2C+Moon%2C+and+Planets&rft.aulast=Latham&rft.au=Latham&rft.au=Ewing%2C%26%2332%3BMaurice&rft.au=Dorman%2C%26%2332%3BJames&rft.au=Lammlein%2C%26%2332%3BDavid&rft.au=Press%2C%26%2332%3BFrank&rft.au=Toks%C5%91z%2C%26%2332%3BNaft&rft.au=Sutton%2C%26%2332%3BGeorge&rft.au=Duennebier%2C%26%2332%3BFred&rft.au=Nakamura%2C%26%2332%3BYosio&rft.date=1972&rft.volume=4&rft.issue=3%E2%80%934&rft.pages=373%E2%80%93382&rft_id=info:bibcode/1972Moon....4..373L&rft_id=info:doi/10.1007%2FBF00562004&rft_id=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fjt12323560565365%2F&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-109"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-109">^</a></b> <span class="citation web">Phillips, Tony (12 March 2007). <a class="external text" href="http://science.nasa.gov/headlines/y2007/12mar_stereoeclipse.htm" rel="nofollow">"Stereo Eclipse"</a>. <i><a class="external text" href="http://science.nasa.gov/" rel="nofollow">Science@NASA</a></i><span class="reference-accessdate">. Retrieved 17 March 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Stereo+Eclipse&rft.atitle=%5Bhttp%3A%2F%2Fscience.nasa.gov%2F+Science%40NASA%5D&rft.aulast=Phillips%2C+Tony&rft.au=Phillips%2C+Tony&rft.date=12+March+2007&rft_id=http%3A%2F%2Fscience.nasa.gov%2Fheadlines%2Fy2007%2F12mar_stereoeclipse.htm&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-110"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-110">^</a></b> <span class="citation web">Espenak, F. (2000). <a class="external text" href="http://www.mreclipse.com/Special/SEprimer.html" rel="nofollow">"Solar Eclipses for Beginners"</a>. MrEclipse<span class="reference-accessdate">. Retrieved 17 March 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Solar+Eclipses+for+Beginners&rft.atitle=&rft.aulast=Espenak&rft.aufirst=F.&rft.au=Espenak%2C%26%2332%3BF.&rft.date=2000&rft.pub=MrEclipse&rft_id=http%3A%2F%2Fwww.mreclipse.com%2FSpecial%2FSEprimer.html&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-eclipse-111">^ <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-eclipse_111-0"><sup><i><b>a</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-eclipse_111-1"><sup><i><b>b</b></i></sup></a> <span class="citation web">Thieman, J.; Keating, S. (2 May 2006). <a class="external text" href="http://eclipse99.nasa.gov/pages/faq.html" rel="nofollow">"Eclipse 99, Frequently Asked Questions"</a>. NASA<span class="reference-accessdate">. Retrieved 12 April 2007</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Eclipse+99%2C+Frequently+Asked+Questions&rft.atitle=&rft.aulast=Thieman&rft.aufirst=J.&rft.au=Thieman%2C%26%2332%3BJ.&rft.date=2+May+2006&rft.pub=NASA&rft_id=http%3A%2F%2Feclipse99.nasa.gov%2Fpages%2Ffaq.html&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-112"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-112">^</a></b> <span class="citation web">Espenak, F.. <a class="external text" href="http://sunearth.gsfc.nasa.gov/eclipse/SEsaros/SEsaros.html" rel="nofollow">"Saros Cycle"</a>. NASA<span class="reference-accessdate">. Retrieved 17 March 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Saros+Cycle&rft.atitle=&rft.aulast=Espenak&rft.aufirst=F.&rft.au=Espenak%2C%26%2332%3BF.&rft.pub=NASA&rft_id=http%3A%2F%2Fsunearth.gsfc.nasa.gov%2Feclipse%2FSEsaros%2FSEsaros.html&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-114"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-114">^</a></b> <span class="citation Journal">Guthrie, D.V. (1947). <a class="external text" href="http://adsabs.harvard.edu/abs/1947PA.....55..200" rel="nofollow">"The Square Degree as a Unit of Celestial Area"</a>. <i>Popular Astronomy</i> <b>55</b>: 200–203.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=The+Square+Degree+as+a+Unit+of+Celestial+Area&rft.jtitle=Popular+Astronomy&rft.aulast=Guthrie%2C+D.V.&rft.au=Guthrie%2C+D.V.&rft.date=1947&rft.volume=55&rft.pages=200%E2%80%93203&rft_id=http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F1947PA.....55..200&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-115"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-115">^</a></b> <span class="citation web"><a class="external text" href="http://occsec.wellington.net.nz/total/totoccs.htm" rel="nofollow">"Total Lunar Occultations"</a>. Royal Astronomical Society of New Zealand<span class="reference-accessdate">. Retrieved 17 March 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Total+Lunar+Occultations&rft.atitle=&rft.pub=Royal+Astronomical+Society+of+New+Zealand&rft_id=http%3A%2F%2Foccsec.wellington.net.nz%2Ftotal%2Ftotoccs.htm&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-116"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-116">^</a></b> <span class="citation Journal">Aaboe, A.; Britton, J. P.; Henderson,, J. A.; <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Otto_Neugebauer" title="Otto Neugebauer">Neugebauer, Otto</a>; Sachs, A. J. (1991). "Saros Cycle Dates and Related Babylonian Astronomical Texts". <i>Transactions of the American Philosophical Society</i> (<a href="http://en.wikipedia.org/wiki/American_Philosophical_Society">American Philosophical Society</a>) <b>81</b> (6): 1–75. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.2307%2F1006543" rel="nofollow">10.2307/1006543</a>. <a href="http://en.wikipedia.org/wiki/JSTOR">JSTOR</a> <a class="external text" href="http://www.jstor.org/stable/1006543" rel="nofollow">1006543</a>. "One comprises what we have called "Saros Cycle Texts," which give the months of eclipse possibilities arranged in consistent cycles of 223 months (or 18 years)."</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Saros+Cycle+Dates+and+Related+Babylonian+Astronomical+Texts&rft.jtitle=Transactions+of+the+American+Philosophical+Society&rft.aulast=Aaboe&rft.aufirst=A.&rft.au=Aaboe%2C%26%2332%3BA.&rft.au=Britton%2C%26%2332%3BJ.+P.&rft.au=Henderson%2C%2C%26%2332%3BJ.+A.&rft.au=Neugebauer%2C%26%2332%3BOtto&rft.au=Sachs%2C%26%2332%3BA.+J.&rft.date=1991&rft.volume=81&rft.issue=6&rft.pages=1%E2%80%9375&rft.pub=%5B%5BAmerican+Philosophical+Society%5D%5D&rft_id=info:doi/10.2307%2F1006543&rft.jstor=1006543&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-Sarma-Ast-Ind-117"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-Sarma-Ast-Ind_117-0">^</a></b> <span class="citation book"><a href="http://en.wikipedia.org/wiki/K._V._Sarma" title="K. V. Sarma">Sarma, K. V.</a> (2008). "Astronomy in India". In Helaine Selin. <i>Encyclopaedia of the History of Science, Technology, and Medicine in Non-Western Cultures</i> (2 ed.). <a href="http://en.wikipedia.org/wiki/Springer_Science%2BBusiness_Media" title="Springer Science+Business Media">Springer</a>. pp. 317–321. <a href="http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="http://en.wikipedia.org/wiki/Special:BookSources/978-1-4020-4559-2" title="Special:BookSources/978-1-4020-4559-2">978-1-4020-4559-2</a></span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Astronomy+in+India&rft.atitle=Encyclopaedia+of+the+History+of+Science%2C+Technology%2C+and+Medicine+in+Non-Western+Cultures&rft.aulast=Sarma&rft.aufirst=K.+V.&rft.au=Sarma%2C%26%2332%3BK.+V.&rft.date=2008&rft.pages=pp.%26nbsp%3B317%E2%80%93321&rft.edition=2&rft.pub=%5B%5BSpringer+Science%2BBusiness+Media%7CSpringer%5D%5D&rft.isbn=978-1-4020-4559-2&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-needham411-118"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-needham411_118-0">^</a></b> <a href="http://en.wikipedia.org/wiki/Moon#CITEREFNeedham1986">Needham 1986</a>, p. 411</li><li id="cite_note-119"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-119">^</a></b> <span class="citation web">O'Connor, J.J.; Robertson, E.F. (February 1999). <a class="external text" href="http://www-history.mcs.st-andrews.ac.uk/Biographies/Anaxagoras.html" rel="nofollow">"Anaxagoras of Clazomenae"</a>. University of St Andrews<span class="reference-accessdate">. Retrieved 12 April 2007</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Anaxagoras+of+Clazomenae&rft.atitle=&rft.aulast=O%27Connor&rft.aufirst=J.J.&rft.au=O%27Connor%2C%26%2332%3BJ.J.&rft.date=February+1999&rft.pub=University+of+St+Andrews&rft_id=http%3A%2F%2Fwww-history.mcs.st-andrews.ac.uk%2FBiographies%2FAnaxagoras.html&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-Needham227-120"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-Needham227_120-0">^</a></b> <a href="http://en.wikipedia.org/wiki/Moon#CITEREFNeedham1986">Needham 1986</a>, p. 227</li><li id="cite_note-Needham413-4-121"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-Needham413-4_121-0">^</a></b> <a href="http://en.wikipedia.org/wiki/Moon#CITEREFNeedham1986">Needham 1986</a>, p. 413–414</li><li id="cite_note-122"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-122">^</a></b> <span class="citation web">Robertson, E. F. (November 2000). <a class="external text" href="http://www-history.mcs.st-andrews.ac.uk/Biographies/Aryabhata_I.html" rel="nofollow">"Aryabhata the Elder"</a>. Scotland: School of Mathematics and Statistics, University of St Andrews<span class="reference-accessdate">. Retrieved 15 April 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Aryabhata+the+Elder&rft.atitle=&rft.aulast=Robertson&rft.aufirst=E.+F.&rft.au=Robertson%2C%26%2332%3BE.+F.&rft.date=November+2000&rft.place=Scotland&rft.pub=School+of+Mathematics+and+Statistics%2C+University+of+St+Andrews&rft_id=http%3A%2F%2Fwww-history.mcs.st-andrews.ac.uk%2FBiographies%2FAryabhata_I.html&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-123"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-123">^</a></b> <span class="citation book">A. I. Sabra (2008). "Ibn Al-Haytham, Abū ʿAlī Al-Ḥasan Ibn Al-Ḥasan". <i>Dictionary of Scientific Biography</i>. Detroit: Charles Scribner's Sons. pp. 189–210, at 195.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Ibn+Al-Haytham%2C+Ab%C5%AB+%CA%BFAl%C4%AB+Al-%E1%B8%A4asan+Ibn+Al-%E1%B8%A4asan&rft.atitle=Dictionary+of+Scientific+Biography&rft.aulast=A.+I.+Sabra&rft.au=A.+I.+Sabra&rft.date=2008&rft.pages=pp.%26nbsp%3B189%E2%80%93210%2C+at+195&rft.place=Detroit&rft.pub=Charles+Scribner%27s+Sons&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-Needham415-6-124"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-Needham415-6_124-0">^</a></b> <a href="http://en.wikipedia.org/wiki/Moon#CITEREFNeedham1986">Needham 1986</a>, p. 415–416</li><li id="cite_note-125"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-125">^</a></b> <span class="citation book"><a href="http://en.wikipedia.org/wiki/C._S._Lewis" title="C. S. Lewis">Lewis, C. S.</a> (1964). <i>The Discarded Image</i>. Cambridge: Cambridge University Press. p. 108. <a href="http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="http://en.wikipedia.org/wiki/Special:BookSources/0-521047735-2" title="Special:BookSources/0-521047735-2">0-521047735-2</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Discarded+Image&rft.aulast=Lewis&rft.aufirst=C.+S.&rft.au=Lewis%2C%26%2332%3BC.+S.&rft.date=1964&rft.pages=p.%26nbsp%3B108&rft.place=Cambridge&rft.pub=Cambridge+University+Press&rft.isbn=0-521047735-2&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-126"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-126">^</a></b> <span class="citation Journal"><a href="http://en.wikipedia.org/wiki/Bartel_Leendert_van_der_Waerden" title="Bartel Leendert van der Waerden">van der Waerden, Bartel Leendert</a> (1987). "The Heliocentric System in Greek, Persian and Hindu Astronomy". <i>Annals of the New York Academy of Sciences</i> <b>500</b>: 1–569. <a class="mw-redirect" href="http://en.wikipedia.org/wiki/PubMed_Identifier" title="PubMed Identifier">PMID</a> <a class="external text" href="http://www.ncbi.nlm.nih.gov/pubmed/3296915" rel="nofollow">3296915</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=The+Heliocentric+System+in+Greek%2C+Persian+and+Hindu+Astronomy&rft.jtitle=Annals+of+the+New+York+Academy+of+Sciences&rft.aulast=van+der+Waerden&rft.aufirst=Bartel+Leendert&rft.au=van+der+Waerden%2C%26%2332%3BBartel+Leendert&rft.date=1987&rft.volume=500&rft.pages=1%E2%80%93569&rft_id=info:pmid/3296915&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-127"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-127">^</a></b> <span class="citation book">Evans, James (1998). <i>The History and Practice of Ancient Astronomy</i>. Oxford & New York: Oxford University Press. pp. 71, 386. <a href="http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="http://en.wikipedia.org/wiki/Special:BookSources/978-0-19-509539-5" title="Special:BookSources/978-0-19-509539-5">978-0-19-509539-5</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+History+and+Practice+of+Ancient+Astronomy&rft.aulast=Evans&rft.aufirst=James&rft.au=Evans%2C%26%2332%3BJames&rft.date=1998&rft.pages=pp.%26nbsp%3B71%2C+386&rft.place=Oxford+%26+New+York&rft.pub=Oxford+University+Press&rft.isbn=978-0-19-509539-5&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-128"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-128">^</a></b> <span class="citation news"><a class="external text" href="http://www.nytimes.com/2008/07/31/science/31computer.html?hp" rel="nofollow">"Discovering How Greeks Computed in 100 B.C."</a>. <i>The New York Times</i>. 31 July 2008<span class="reference-accessdate">. Retrieved 27 March 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Discovering+How+Greeks+Computed+in+100+B.C.&rft.jtitle=The+New+York+Times&rft.date=31+July+2008&rft_id=http%3A%2F%2Fwww.nytimes.com%2F2008%2F07%2F31%2Fscience%2F31computer.html%3Fhp&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-129"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-129">^</a></b> <span class="citation web">Van Helden, A. (1995). <a class="external text" href="http://galileo.rice.edu/sci/observations/moon.html" rel="nofollow">"The Moon"</a>. Galileo Project<span class="reference-accessdate">. Retrieved 12 April 2007</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=The+Moon&rft.atitle=&rft.aulast=Van+Helden&rft.aufirst=A.&rft.au=Van+Helden%2C%26%2332%3BA.&rft.date=1995&rft.pub=Galileo+Project&rft_id=http%3A%2F%2Fgalileo.rice.edu%2Fsci%2Fobservations%2Fmoon.html&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-130"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-130">^</a></b> <span class="citation Journal">Consolmagno, Guy J. (1996). <a class="external text" href="http://www.jstor.org/stable/1576348?seq=2" rel="nofollow">"Astronomy, Science Fiction and Popular Culture: 1277 to 2001 (And beyond)"</a>. <i>Leonardo</i> (The MIT Press) <b>29</b> (2): 128.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Astronomy%2C+Science+Fiction+and+Popular+Culture%3A+1277+to+2001+%28And+beyond%29&rft.jtitle=Leonardo&rft.aulast=Consolmagno&rft.aufirst=Guy+J.&rft.au=Consolmagno%2C%26%2332%3BGuy+J.&rft.date=1996&rft.volume=29&rft.issue=2&rft.pages=128&rft.pub=The+MIT+Press&rft_id=http%3A%2F%2Fwww.jstor.org%2Fstable%2F1576348%3Fseq%3D2&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-Hall1977-131"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-Hall1977_131-0">^</a></b> <span class="citation web">Hall, R. Cargill (1977). <a class="external text" href="http://history.nasa.gov/SP-4210/pages/App_A.htm" rel="nofollow">"Appendix A: LUNAR THEORY BEFORE 1964"</a>. <i>NASA History Series. LUNAR IMPACT: A History of Project Ranger.</i>. Washington, D.C.: Scientific and Technical Information Office, NATIONAL AERONAUTICS AND SPACE ADMINISTRATION<span class="reference-accessdate">. Retrieved 13 April 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Appendix+A%3A+LUNAR+THEORY+BEFORE+1964&rft.atitle=NASA+History+Series.+LUNAR+IMPACT%3A+A+History+of+Project+Ranger.&rft.aulast=Hall&rft.aufirst=R.+Cargill&rft.au=Hall%2C%26%2332%3BR.+Cargill&rft.date=1977&rft.place=Washington%2C+D.C.&rft.pub=Scientific+and+Technical+Information+Office%2C+NATIONAL+AERONAUTICS+AND+SPACE+ADMINISTRATION&rft_id=http%3A%2F%2Fhistory.nasa.gov%2FSP-4210%2Fpages%2FApp_A.htm&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-132"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-132">^</a></b> <span class="citation web">Zak, Anatoly (2009). <a class="external text" href="http://www.russianspaceweb.com/spacecraft_planetary_lunar.html" rel="nofollow">"Russia's unmanned missions toward the Moon"</a><span class="reference-accessdate">. Retrieved 20 April 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Russia%27s+unmanned+missions+toward+the+Moon&rft.atitle=&rft.aulast=Zak&rft.aufirst=Anatoly&rft.au=Zak%2C%26%2332%3BAnatoly&rft.date=2009&rft_id=http%3A%2F%2Fwww.russianspaceweb.com%2Fspacecraft_planetary_lunar.html&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-133"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-133">^</a></b> <span class="citation web"><a class="external text" href="http://curator.jsc.nasa.gov/lunar/index.cfm" rel="nofollow">"Rocks and Soils from the Moon"</a>. NASA<span class="reference-accessdate">. Retrieved 6 April 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Rocks+and+Soils+from+the+Moon&rft.atitle=&rft.pub=NASA&rft_id=http%3A%2F%2Fcurator.jsc.nasa.gov%2Flunar%2Findex.cfm&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-CNN-134"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-CNN_134-0">^</a></b> <span class="citation news">Coren, M (26 July 2004). <a class="external text" href="http://edition.cnn.com/2004/TECH/space/07/16/moon.landing/index.html" rel="nofollow">"'Giant leap' opens world of possibility"</a>. CNN<span class="reference-accessdate">. Retrieved 16 March 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=%27Giant+leap%27+opens+world+of+possibility&rft.atitle=&rft.aulast=Coren&rft.aufirst=M&rft.au=Coren%2C%26%2332%3BM&rft.date=26+July+2004&rft.pub=CNN&rft_id=http%3A%2F%2Fedition.cnn.com%2F2004%2FTECH%2Fspace%2F07%2F16%2Fmoon.landing%2Findex.html&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-135"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-135">^</a></b> <span class="citation web"><a class="external text" href="http://history.nasa.gov/ap11ann/ap11events.html" rel="nofollow">"Record of Lunar Events, 24 July 1969"</a>. <i>Apollo 11 30th anniversary</i>. NASA.<span class="reference-accessdate">. Retrieved 13 April 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Record+of+Lunar+Events%2C+24+July+1969&rft.atitle=Apollo+11+30th+anniversary&rft.pub=NASA.&rft_id=http%3A%2F%2Fhistory.nasa.gov%2Fap11ann%2Fap11events.html&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-136"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-136">^</a></b> <span class="citation web">Martel, Linda M. V. (21 December 2009). <a class="external text" href="http://www.psrd.hawaii.edu/Dec09/PSRD-Apollo-lunar-samples.pdf" rel="nofollow">"Celebrated Moon Rocks --- Overview and status of the Apollo lunar collection: A unique, but limited, resource of extraterrestrial material."</a>. Planetary Science and Research Discoveries<span class="reference-accessdate">. Retrieved 6 April 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Celebrated+Moon+Rocks+---+Overview+and+status+of+the+Apollo+lunar+collection%3A+A+unique%2C+but+limited%2C+resource+of+extraterrestrial+material.&rft.atitle=&rft.aulast=Martel&rft.aufirst=Linda+M.+V.&rft.au=Martel%2C%26%2332%3BLinda+M.+V.&rft.date=21+December+2009&rft.pub=Planetary+Science+and+Research+Discoveries&rft_id=http%3A%2F%2Fwww.psrd.hawaii.edu%2FDec09%2FPSRD-Apollo-lunar-samples.pdf&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-137"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-137">^</a></b> <span class="citation web">Launius, Roger D. (July 1999). <a class="external text" href="http://history.nasa.gov/ap11ann/legacy.htm" rel="nofollow">"The Legacy of Project Apollo"</a>. NASA History Office<span class="reference-accessdate">. Retrieved 13 April 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=The+Legacy+of+Project+Apollo&rft.atitle=&rft.aulast=Launius&rft.aufirst=Roger+D.&rft.au=Launius%2C%26%2332%3BRoger+D.&rft.date=July+1999&rft.pub=NASA+History+Office&rft_id=http%3A%2F%2Fhistory.nasa.gov%2Fap11ann%2Flegacy.htm&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-138"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-138">^</a></b> <span class="citation book"><i>SP-287 What Made Apollo a Success? A series of eight articles reprinted by permission from the March 1970 issue of Astronautics & Aeronautics, a publicaion of the American Institute of Aeronautics and Astronautics.</i>. Washington, D.C.: Scientific and Technical Information Office, National Aeronautics and Space Administration. 1971.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=SP-287+What+Made+Apollo+a+Success%3F+A+series+of+eight+articles+reprinted+by+permission+from+the+March+1970+issue+of+Astronautics+%26+Aeronautics%2C+a+publicaion+of+the+American+Institute+of+Aeronautics+and+Astronautics.&rft.date=1971&rft.place=Washington%2C+D.C.&rft.pub=Scientific+and+Technical+Information+Office%2C+National+Aeronautics+and+Space+Administration&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-139"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-139">^</a></b> <span class="citation press release"><a class="external text" href="http://www.nasa.gov/centers/johnson/pdf/83129main_1977.pdf" rel="nofollow">"NASA news release 77-47 page 242"</a> (PDF). Press release. 1 September 1977<span class="reference-accessdate">. Retrieved 16 March 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=NASA+news+release+77-47+page+242&rft.atitle=&rft.date=1+September+1977&rft.series=Press+release&rft_id=http%3A%2F%2Fwww.nasa.gov%2Fcenters%2Fjohnson%2Fpdf%2F83129main_1977.pdf&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-140"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-140">^</a></b> <span class="citation news">Appleton, James; Radley, Charles; Deans, John; Harvey, Simon; Burt, Paul; Haxell, Michael; Adams, Roy; Spooner N.; Brieske, Wayne (1977). <a class="external text" href="http://web.archive.org/web/20071210143103/http://www.ast.cam.ac.uk/%7Eipswich/Miscellaneous/Archived_spaceflight_news.htm" rel="nofollow">"OASI Newsletters Archive"</a>. NASA Turns A Deaf Ear To The Moon. Archived from <a class="external text" href="http://www.ast.cam.ac.uk/%7Eipswich/Miscellaneous/Archived_spaceflight_news.htm" rel="nofollow">the original</a> on December 10, 2007<span class="reference-accessdate">. Retrieved 29 August 2007</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=OASI+Newsletters+Archive&rft.atitle=&rft.aulast=Appleton&rft.aufirst=James&rft.au=Appleton%2C%26%2332%3BJames&rft.date=1977&rft.place=NASA+Turns+A+Deaf+Ear+To+The+Moon&rft_id=http%3A%2F%2Fweb.archive.org%2Fweb%2F20071210143103%2Fhttp%3A%2F%2Fwww.ast.cam.ac.uk%2F%7Eipswich%2FMiscellaneous%2FArchived_spaceflight_news.htm&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-141"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-141">^</a></b> <span class="citation Journal">Dickey, J.; <i>et al.</i> (1994). "Lunar laser ranging: a continuing legacy of the Apollo program". <i>Science</i> <b>265</b> (5171): 482–490. <a href="http://en.wikipedia.org/wiki/Bibcode">Bibcode</a> <a class="external text" href="http://adsabs.harvard.edu/abs/1994Sci...265..482D" rel="nofollow">1994Sci...265..482D</a>. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.1126%2Fscience.265.5171.482" rel="nofollow">10.1126/science.265.5171.482</a>. <a class="mw-redirect" href="http://en.wikipedia.org/wiki/PubMed_Identifier" title="PubMed Identifier">PMID</a> <a class="external text" href="http://www.ncbi.nlm.nih.gov/pubmed/17781305" rel="nofollow">17781305</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Lunar+laser+ranging%3A+a+continuing+legacy+of+the+Apollo+program&rft.jtitle=Science&rft.aulast=Dickey&rft.aufirst=J.&rft.au=Dickey%2C%26%2332%3BJ.&rft.date=1994&rft.volume=265&rft.issue=5171&rft.pages=482%E2%80%93490&rft_id=info:bibcode/1994Sci...265..482D&rft_id=info:doi/10.1126%2Fscience.265.5171.482&rft_id=info:pmid/17781305&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-142"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-142">^</a></b> <span class="citation web"><a class="external text" href="http://solarsystem.nasa.gov/missions/profile.cfm?MCode=Hiten&Display=ReadMore" rel="nofollow">"Hiten-Hagomoro"</a>. NASA<span class="reference-accessdate">. Retrieved 29 March 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Hiten-Hagomoro&rft.atitle=&rft.pub=NASA&rft_id=http%3A%2F%2Fsolarsystem.nasa.gov%2Fmissions%2Fprofile.cfm%3FMCode%3DHiten%26Display%3DReadMore&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-143"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-143">^</a></b> <span class="citation web"><a class="external text" href="http://nssdc.gsfc.nasa.gov/planetary/cleminfo.html" rel="nofollow">"Clementine information"</a>. NASA. 1994<span class="reference-accessdate">. Retrieved 29 March 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Clementine+information&rft.atitle=&rft.date=1994&rft.pub=NASA&rft_id=http%3A%2F%2Fnssdc.gsfc.nasa.gov%2Fplanetary%2Fcleminfo.html&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-144"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-144">^</a></b> <span class="citation web"><a class="external text" href="http://lunar.arc.nasa.gov/results/neutron.htm" rel="nofollow">"Lunar Prospector: Neutron Spectrometer"</a>. NASA. 2001<span class="reference-accessdate">. Retrieved 29 March 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Lunar+Prospector%3A+Neutron+Spectrometer&rft.atitle=&rft.date=2001&rft.pub=NASA&rft_id=http%3A%2F%2Flunar.arc.nasa.gov%2Fresults%2Fneutron.htm&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-145"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-145">^</a></b> <span class="citation web"><a class="external text" href="http://www.esa.int/SPECIALS/SMART-1/SEMSDE1A6BD_0.html" rel="nofollow">"SMART-1 factsheet"</a>. European Space Agency. 26 February 2007<span class="reference-accessdate">. Retrieved 29 March 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=SMART-1+factsheet&rft.atitle=&rft.date=26+February+2007&rft.pub=European+Space+Agency&rft_id=http%3A%2F%2Fwww.esa.int%2FSPECIALS%2FSMART-1%2FSEMSDE1A6BD_0.html&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-xinhua_20090301-146"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-xinhua_20090301_146-0">^</a></b> <span class="citation news"><a class="external text" href="http://www.chinadaily.com.cn/china/2009-03/01/content_7523687.htm" rel="nofollow">"China's first lunar probe ends mission"</a>. Xinhua. 1 March 2009<span class="reference-accessdate">. Retrieved 29 March 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=China%27s+first+lunar+probe+ends+mission&rft.atitle=&rft.date=1+March+2009&rft.pub=Xinhua&rft_id=http%3A%2F%2Fwww.chinadaily.com.cn%2Fchina%2F2009-03%2F01%2Fcontent_7523687.htm&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-147"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-147">^</a></b> <span class="citation web"><a class="external text" href="http://www.selene.jaxa.jp/en/profile/index.htm" rel="nofollow">"KAGUYA Mission Profile"</a>. JAXA<span class="reference-accessdate">. Retrieved 13 April 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=KAGUYA+Mission+Profile&rft.atitle=&rft.pub=JAXA&rft_id=http%3A%2F%2Fwww.selene.jaxa.jp%2Fen%2Fprofile%2Findex.htm&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-148"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-148">^</a></b> <span class="citation web"><a class="external text" href="http://www.jaxa.jp/press/2007/11/20071107_kaguya_e.html" rel="nofollow">"KAGUYA (SELENE) World’s First Image Taking of the Moon by HDTV"</a>. Japan Aerospace Exploration Agency (JAXA) and NHK (Japan Broadcasting Corporation). 7 November 2007<span class="reference-accessdate">. Retrieved 13 April 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=KAGUYA+%28SELENE%29+World%E2%80%99s+First+Image+Taking+of+the+Moon+by+HDTV&rft.atitle=&rft.date=7+November+2007&rft.pub=Japan+Aerospace+Exploration+Agency+%28JAXA%29+and+NHK+%28Japan+Broadcasting+Corporation%29&rft_id=http%3A%2F%2Fwww.jaxa.jp%2Fpress%2F2007%2F11%2F20071107_kaguya_e.html&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-149"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-149">^</a></b> <span class="citation web"><a class="external text" href="http://www.isro.org/Chandrayaan/htmls/mission_sequence.htm" rel="nofollow">"Mission Sequence"</a>. Indian Space Research Organisation. 17 November 2008<span class="reference-accessdate">. Retrieved 13 April 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Mission+Sequence&rft.atitle=&rft.date=17+November+2008&rft.pub=Indian+Space+Research+Organisation&rft_id=http%3A%2F%2Fwww.isro.org%2FChandrayaan%2Fhtmls%2Fmission_sequence.htm&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-150"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-150">^</a></b> <span class="citation web"><a class="external text" href="http://www.isro.org/scripts/futureprogramme.aspx#Space" rel="nofollow">"Indian Space Research Organisation: Future Program"</a>. Indian Space Research Organisation<span class="reference-accessdate">. Retrieved 13 April 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Indian+Space+Research+Organisation%3A+Future+Program&rft.atitle=&rft.pub=Indian+Space+Research+Organisation&rft_id=http%3A%2F%2Fwww.isro.org%2Fscripts%2Ffutureprogramme.aspx%23Space&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-151"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-151">^</a></b> <span class="citation web"><a class="external text" href="http://web.archive.org/web/20071217203828/http://isro.org/pressrelease/Nov14_2007.htm" rel="nofollow">"India and Russia Sign an Agreement on Chandrayaan-2"</a>. Indian Space Research Organisation. 14 November 2007. Archived from <a class="external text" href="http://isro.org/pressrelease/Nov14_2007.htm" rel="nofollow">the original</a> on 17 December 2007<span class="reference-accessdate">. Retrieved 13 April 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=India+and+Russia+Sign+an+Agreement+on+Chandrayaan-2&rft.atitle=&rft.date=14+November+2007&rft.pub=Indian+Space+Research+Organisation&rft_id=http%3A%2F%2Fweb.archive.org%2Fweb%2F20071217203828%2Fhttp%3A%2F%2Fisro.org%2Fpressrelease%2FNov14_2007.htm&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-152"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-152">^</a></b> <span class="citation web"><a class="external text" href="http://lcross.arc.nasa.gov/observation.htm" rel="nofollow">"Lunar CRater Observation and Sensing Satellite (LCROSS): Strategy & Astronomer Observation Campaign"</a>. NASA. October 2009<span class="reference-accessdate">. Retrieved 13 April 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Lunar+CRater+Observation+and+Sensing+Satellite+%28LCROSS%29%3A+Strategy+%26+Astronomer+Observation+Campaign&rft.atitle=&rft.date=October+2009&rft.pub=NASA&rft_id=http%3A%2F%2Flcross.arc.nasa.gov%2Fobservation.htm&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-153"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-153">^</a></b> <span class="citation web">Covault, C. (4 June 2006). <a class="external text" href="http://www.aviationnow.com/avnow/news/channel_awst_story.jsp?id=news/aw060506p2.xml" rel="nofollow">"Russia Plans Ambitious Robotic Lunar Mission"</a>. Aviation Week<span class="reference-accessdate">. Retrieved 12 April 2007</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Russia+Plans+Ambitious+Robotic+Lunar+Mission&rft.atitle=&rft.aulast=Covault&rft.aufirst=C.&rft.au=Covault%2C%26%2332%3BC.&rft.date=4+June+2006&rft.pub=Aviation+Week&rft_id=http%3A%2F%2Fwww.aviationnow.com%2Favnow%2Fnews%2Fchannel_awst_story.jsp%3Fid%3Dnews%2Faw060506p2.xml&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-154"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-154">^</a></b> <span class="citation web"><a class="external text" href="http://rt.com/Top_News/2009-02-25/Russia_to_send_mission_to_Mars_this_year__Moon_in_three_years_.html" rel="nofollow">"Russia to send mission to Mars this year, Moon in three years"</a>. "TV-Novosti". 25 February 2009<span class="reference-accessdate">. Retrieved 13 April 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Russia+to+send+mission+to+Mars+this+year%2C+Moon+in+three+years&rft.atitle=&rft.date=25+February+2009&rft.pub=%22TV-Novosti%22&rft_id=http%3A%2F%2Frt.com%2FTop_News%2F2009-02-25%2FRussia_to_send_mission_to_Mars_this_year__Moon_in_three_years_.html&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-155"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-155">^</a></b> <span class="citation web"><a class="external text" href="http://www.googlelunarxprize.org/lunar/about-the-prize" rel="nofollow">"About the Google Lunar X Prize"</a>. X-Prize Foundation. 2010<span class="reference-accessdate">. Retrieved 24 March 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=About+the+Google+Lunar+X+Prize&rft.atitle=&rft.date=2010&rft.pub=X-Prize+Foundation&rft_id=http%3A%2F%2Fwww.googlelunarxprize.org%2Flunar%2Fabout-the-prize&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-156"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-156">^</a></b> <span class="citation press release">NASA (14 December 2004). <a class="external text" href="http://www.nasa.gov/missions/solarsystem/bush_vision.html" rel="nofollow">"President Bush Offers New Vision For NASA"</a>. Press release<span class="reference-accessdate">. Retrieved 12 April 2007</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=President+Bush+Offers+New+Vision+For+NASA&rft.atitle=&rft.aulast=NASA&rft.au=NASA&rft.date=14+December+2004&rft.series=Press+release&rft_id=http%3A%2F%2Fwww.nasa.gov%2Fmissions%2Fsolarsystem%2Fbush_vision.html&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-157"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-157">^</a></b> <span class="citation web"><a class="external text" href="http://www.nasa.gov/mission_pages/constellation/main/index.html" rel="nofollow">"Constellation"</a>. NASA<span class="reference-accessdate">. Retrieved 13 April 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Constellation&rft.atitle=&rft.pub=NASA&rft_id=http%3A%2F%2Fwww.nasa.gov%2Fmission_pages%2Fconstellation%2Fmain%2Findex.html&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-158"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-158">^</a></b> <span class="citation press release">NASA (4 December 2006). <a class="external text" href="http://www.nasa.gov/home/hqnews/2006/dec/HQ_06361_ESMD_Lunar_Architecture.html" rel="nofollow">"NASA Unveils Global Exploration Strategy and Lunar Architecture"</a>. Press release<span class="reference-accessdate">. Retrieved 12 April 2007</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=NASA+Unveils+Global+Exploration+Strategy+and+Lunar+Architecture&rft.atitle=&rft.aulast=NASA&rft.au=NASA&rft.date=4+December+2006&rft.series=Press+release&rft_id=http%3A%2F%2Fwww.nasa.gov%2Fhome%2Fhqnews%2F2006%2Fdec%2FHQ_06361_ESMD_Lunar_Architecture.html&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-159"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-159">^</a></b> <span class="citation web"><a class="external text" href="http://www.nasa.gov/pdf/420990main_FY_201_%20Budget_Overview_1_Feb_2010.pdf" rel="nofollow">"Budget Information: FY 2011 Budget Overview"</a>. NASA<span class="reference-accessdate">. Retrieved 13 April 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Budget+Information%3A+FY+2011+Budget+Overview&rft.atitle=&rft.pub=NASA&rft_id=http%3A%2F%2Fwww.nasa.gov%2Fpdf%2F420990main_FY_201_%2520Budget_Overview_1_Feb_2010.pdf&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-160"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-160">^</a></b> <span class="citation web"><a class="external text" href="http://www.space.com/news/061110_india_mannedspace.html" rel="nofollow">"India's Space Agency Proposes Manned Spaceflight Program"</a>. SPACE.com. 10 November 2006<span class="reference-accessdate">. Retrieved 23 October 2008</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=India%27s+Space+Agency+Proposes+Manned+Spaceflight+Program&rft.atitle=&rft.date=10+November+2006&rft.pub=SPACE.com&rft_id=http%3A%2F%2Fwww.space.com%2Fnews%2F061110_india_mannedspace.html&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-unoosa_q6-161">^ <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-unoosa_q6_161-0"><sup><i><b>a</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-unoosa_q6_161-1"><sup><i><b>b</b></i></sup></a> <span class="citation web"><a class="external text" href="http://www.unoosa.org/oosa/en/FAQ/splawfaq.html#Q6" rel="nofollow">"Can any State claim a part of outer space as its own?"</a>. United Nations Office for Outer Space Affairs<span class="reference-accessdate">. Retrieved 28 March 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Can+any+State+claim+a+part+of+outer+space+as+its+own%3F&rft.atitle=&rft.pub=United+Nations+Office+for+Outer+Space+Affairs&rft_id=http%3A%2F%2Fwww.unoosa.org%2Foosa%2Fen%2FFAQ%2Fsplawfaq.html%23Q6&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-unoosa_q4-162"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-unoosa_q4_162-0">^</a></b> <span class="citation web"><a class="external text" href="http://www.unoosa.org/oosa/en/FAQ/splawfaq.html#Q4" rel="nofollow">"How many States have signed and ratified the five international treaties governing outer space?"</a>. United Nations Office for Outer Space Affairs. 1 January 2006<span class="reference-accessdate">. Retrieved 28 March 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=How+many+States+have+signed+and+ratified+the+five+international+treaties+governing+outer+space%3F&rft.atitle=&rft.date=1+January+2006&rft.pub=United+Nations+Office+for+Outer+Space+Affairs&rft_id=http%3A%2F%2Fwww.unoosa.org%2Foosa%2Fen%2FFAQ%2Fsplawfaq.html%23Q4&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-unoosa_q5-163"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-unoosa_q5_163-0">^</a></b> <span class="citation web"><a class="external text" href="http://www.unoosa.org/oosa/en/FAQ/splawfaq.html#Q5" rel="nofollow">"Do the five international treaties regulate military activities in outer space?"</a>. United Nations Office for Outer Space Affairs<span class="reference-accessdate">. Retrieved 28 March 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Do+the+five+international+treaties+regulate+military+activities+in+outer+space%3F&rft.atitle=&rft.pub=United+Nations+Office+for+Outer+Space+Affairs&rft_id=http%3A%2F%2Fwww.unoosa.org%2Foosa%2Fen%2FFAQ%2Fsplawfaq.html%23Q5&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-unoosa_moon-164"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-unoosa_moon_164-0">^</a></b> <span class="citation web"><a class="external text" href="http://www.unoosa.org/oosa/en/SpaceLaw/moon.html" rel="nofollow">"Agreement Governing the Activities of States on the Moon and Other Celestial Bodies"</a>. United Nations Office for Outer Space Affairs<span class="reference-accessdate">. Retrieved 28 March 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Agreement+Governing+the+Activities+of+States+on+the+Moon+and+Other+Celestial+Bodies&rft.atitle=&rft.pub=United+Nations+Office+for+Outer+Space+Affairs&rft_id=http%3A%2F%2Fwww.unoosa.org%2Foosa%2Fen%2FSpaceLaw%2Fmoon.html&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-unoosa_q7-165"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-unoosa_q7_165-0">^</a></b> <span class="citation web"><a class="external text" href="http://www.unoosa.org/oosa/en/FAQ/splawfaq.html#Q7" rel="nofollow">"The treaties control space-related activities of States. What about non-governmental entities active in outer space, like companies and even individuals?"</a>. United Nations Office for Outer Space Affairs<span class="reference-accessdate">. Retrieved 28 March 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=The+treaties+control+space-related+activities+of+States.+What+about+non-governmental+entities+active+in+outer+space%2C+like+companies+and+even+individuals%3F&rft.atitle=&rft.pub=United+Nations+Office+for+Outer+Space+Affairs&rft_id=http%3A%2F%2Fwww.unoosa.org%2Foosa%2Fen%2FFAQ%2Fsplawfaq.html%23Q7&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-iisl_2004-166"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-iisl_2004_166-0">^</a></b> <span class="citation web"><a class="external text" href="http://www.iislweb.org/docs/IISL_Outer_Space_Treaty_Statement.pdf" rel="nofollow">"Statement by the Board of Directors of the IISL On Claims to Property Rights Regarding The Moon and Other Celestial Bodies (2004)"</a>. International Institute of Space Law. 2004<span class="reference-accessdate">. Retrieved 28 March 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Statement+by+the+Board+of+Directors+of+the+IISL+On+Claims+to+Property+Rights+Regarding+The+Moon+and+Other+Celestial+Bodies+%282004%29&rft.atitle=&rft.date=2004&rft.pub=International+Institute+of+Space+Law&rft_id=http%3A%2F%2Fwww.iislweb.org%2Fdocs%2FIISL_Outer_Space_Treaty_Statement.pdf&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-iisl_2009-167"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-iisl_2009_167-0">^</a></b> <span class="citation web"><a class="external text" href="http://www.iislweb.org/docs/Statement%20BoD.pdf" rel="nofollow">"Further Statement by the Board of Directors of the IISL On Claims to Lunar Property Rights (2009)"</a>. International Institute of Space Law. 22 March 2009<span class="reference-accessdate">. Retrieved 28 March 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Further+Statement+by+the+Board+of+Directors+of+the+IISL+On+Claims+to+Lunar+Property+Rights+%282009%29&rft.atitle=&rft.date=22+March+2009&rft.pub=International+Institute+of+Space+Law&rft_id=http%3A%2F%2Fwww.iislweb.org%2Fdocs%2FStatement%2520BoD.pdf&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-Marshack-168"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-Marshack_168-0">^</a></b> Marshack, Alexander (1991): <i>The Roots of Civilization</i>, Colonial Hill, Mount Kisco, NY.</li><li id="cite_note-169"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-169">^</a></b> Brooks, A.S. and Smith, C.C. (1987): "Ishango revisited: new age determinations and cultural interpretations", <i>The African Archaeological Review</i>, 5 : 65–78.</li><li id="cite_note-170"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-170">^</a></b> <span class="citation book">Duncan, David Ewing (1998). <i>The Calendar</i>. Fourth Estate Ltd.. pp. 10–11. <a href="http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="http://en.wikipedia.org/wiki/Special:BookSources/978-1-85702-721-1" title="Special:BookSources/978-1-85702-721-1">978-1-85702-721-1</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Calendar&rft.aulast=Duncan&rft.aufirst=David+Ewing&rft.au=Duncan%2C%26%2332%3BDavid+Ewing&rft.date=1998&rft.pages=pp.%26nbsp%3B10%E2%80%9311&rft.pub=Fourth+Estate+Ltd.&rft.isbn=978-1-85702-721-1&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-barnhart-and-germania-171"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-barnhart-and-germania_171-0">^</a></b> For etymology, see <span class="citation book">Barnhart, Robert K. (1995). <i>The Barnhart Concise Dictionary of Etymology</i>. Harper Collins. p. 487. <a href="http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="http://en.wikipedia.org/wiki/Special:BookSources/0-06-270084-7" title="Special:BookSources/0-06-270084-7">0-06-270084-7</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Barnhart+Concise+Dictionary+of+Etymology&rft.aulast=Barnhart&rft.aufirst=Robert+K.&rft.au=Barnhart%2C%26%2332%3BRobert+K.&rft.date=1995&rft.pages=p.%26nbsp%3B487&rft.pub=Harper+Collins&rft.isbn=0-06-270084-7&rfr_id=info:sid/en.wikipedia.org:Moon"></span> For the lunar calendar of the Germanic peoples, see <span class="citation book">Birley, A. R. (Trans.) (1999). Agricola and Germany. Oxford World's Classics. USA: Oxford. p. 108. <a href="http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="http://en.wikipedia.org/wiki/Special:BookSources/978-0-19-283300-6" title="Special:BookSources/978-0-19-283300-6">978-0-19-283300-6</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=%27%27Agricola+and+Germany%27%27&rft.aulast=Birley&rft.aufirst=A.+R.+%28Trans.%29&rft.au=Birley%2C%26%2332%3BA.+R.+%28Trans.%29&rft.date=1999&rft.series=Oxford+World%27s+Classics&rft.pages=p.%26nbsp%3B108&rft.place=USA&rft.pub=Oxford&rft.isbn=978-0-19-283300-6&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-172"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-172">^</a></b> <span class="citation book">Smith, William George (1849). <a class="external text" href="http://books.google.com/?id=PJ0YAAAAIAAJ&dq=Dictionary%20of%20Greek%20and%20Roman%20Biography%20and%20Mythology&pg=PA768#v=onepage&q=" rel="nofollow"><i>Dictionary of Greek and Roman Biography and Mythology: Oarses-Zygia</i></a>. <b>3</b>. J. Walton. p. 768<span class="reference-accessdate">. Retrieved 29 March 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Dictionary+of+Greek+and+Roman+Biography+and+Mythology%3A+Oarses-Zygia&rft.aulast=Smith%2C+William+George&rft.au=Smith%2C+William+George&rft.date=1849&rft.volume=3&rft.pages=p.%26nbsp%3B768&rft.pub=J.+Walton&rft_id=http%3A%2F%2Fbooks.google.com%2F%3Fid%3DPJ0YAAAAIAAJ%26dq%3DDictionary%2520of%2520Greek%2520and%2520Roman%2520Biography%2520and%2520Mythology%26pg%3DPA768%23v%3Donepage%26q%3D&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-173"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-173">^</a></b> <span class="citation book">Estienne, Henri (1846). <a class="external text" href="http://books.google.com/?id=0qQ_AAAAcAAJ&dq=%CE%BC%CE%AE%CE%BD%CE%B1%CF%82%20%CE%BC%CE%AE%CE%BD%CE%B7&pg=RA1-PA581#v=onepage&q=" rel="nofollow"><i>Thesaurus graecae linguae</i></a>. <b>5</b>. Didot. p. 1001<span class="reference-accessdate">. Retrieved 29 March 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Thesaurus+graecae+linguae&rft.aulast=Estienne%2C+Henri&rft.au=Estienne%2C+Henri&rft.date=1846&rft.volume=5&rft.pages=p.%26nbsp%3B1001&rft.pub=Didot&rft_id=http%3A%2F%2Fbooks.google.com%2F%3Fid%3D0qQ_AAAAcAAJ%26dq%3D%25CE%25BC%25CE%25AE%25CE%25BD%25CE%25B1%25CF%2582%2520%25CE%25BC%25CE%25AE%25CE%25BD%25CE%25B7%26pg%3DRA1-PA581%23v%3Donepage%26q%3D&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-spacetoday-174"><b><a href="http://en.wikipedia.org/wiki/Moon#cite_ref-spacetoday_174-0">^</a></b> <span class="citation web"><a class="external text" href="http://www.spacetoday.org/SolSys/Earth/OldStarCharts.html" rel="nofollow">"Carved and Drawn Prehistoric Maps of the Cosmos"</a>. Space Today Online. 2006<span class="reference-accessdate">. Retrieved 12 April 2007</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Carved+and+Drawn+Prehistoric+Maps+of+the+Cosmos&rft.atitle=&rft.date=2006&rft.pub=Space+Today+Online&rft_id=http%3A%2F%2Fwww.spacetoday.org%2FSolSys%2FEarth%2FOldStarCharts.html&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li id="cite_note-sciam-175">^ <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-sciam_175-0"><sup><i><b>a</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Moon#cite_ref-sciam_175-1"><sup><i><b>b</b></i></sup></a> <span class="citation web">Lilienfeld, Scott O.; Arkowitz, Hal (2009). <a class="external text" href="http://www.scientificamerican.com/article.cfm?id=lunacy-and-the-full-moon" rel="nofollow">"Lunacy and the Full Moon"</a>. Scientific American<span class="reference-accessdate">. Retrieved 13 April 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Lunacy+and+the+Full+Moon&rft.atitle=&rft.aulast=Lilienfeld&rft.aufirst=Scott+O.&rft.au=Lilienfeld%2C%26%2332%3BScott+O.&rft.au=Arkowitz%2C%26%2332%3BHal&rft.date=2009&rft.pub=Scientific+American&rft_id=http%3A%2F%2Fwww.scientificamerican.com%2Farticle.cfm%3Fid%3Dlunacy-and-the-full-moon&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li></ol></div><dl><dt>Bibliography</dt></dl><div class="refbegin"><span id="CITEREFNeedham1986"></span><span class="citation book">Needham, Joseph (1986). <i>Science and Civilization in China</i>. <b>3, Mathematics and the Sciences of the Heavens and Earth</b>. Taipei: Caves Books. <a href="http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="http://en.wikipedia.org/wiki/Special:BookSources/0-521-05801-5" title="Special:BookSources/0-521-05801-5">0-521-05801-5</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Science+and+Civilization+in+China&rft.aulast=Needham&rft.aufirst=Joseph&rft.au=Needham%2C%26%2332%3BJoseph&rft.date=1986&rft.volume=3%2C+Mathematics+and+the+Sciences+of+the+Heavens+and+Earth&rft.place=Taipei&rft.pub=Caves+Books&rft.isbn=0-521-05801-5&rfr_id=info:sid/en.wikipedia.org:Moon"></span></div><h2><span class="mw-headline" id="Further_reading">Further reading</span></h2><div class="references-small"><ul><li><span class="citation book">Bussey, B.; <a href="http://en.wikipedia.org/wiki/Paul_Spudis" title="Paul Spudis">Spudis, P.D.</a> (2004). <i>The Clementine Atlas of the Moon</i>. Cambridge University Press. <a href="http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="http://en.wikipedia.org/wiki/Special:BookSources/0-521-81528-2" title="Special:BookSources/0-521-81528-2">0-521-81528-2</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Clementine+Atlas+of+the+Moon&rft.aulast=Bussey&rft.aufirst=B.&rft.au=Bussey%2C%26%2332%3BB.&rft.date=2004&rft.pub=Cambridge+University+Press&rft.isbn=0-521-81528-2&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li><span class="citation Journal">Jolliff, B.; Wieczorek, M.; Shearer, C.; Neal, C. (eds.) (2006). <a class="external text" href="http://www.minsocam.org/msa/RIM/Rim60.html" rel="nofollow">"New views of the Moon"</a>. <i>Rev. Mineral. Geochem.</i> (Chantilly, Virginia: Min. Soc. Amer.) <b>60</b> (1): 721. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.2138%2Frmg.2006.60.0" rel="nofollow">10.2138/rmg.2006.60.0</a>. <a href="http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="http://en.wikipedia.org/wiki/Special:BookSources/0939950723" title="Special:BookSources/0939950723">0939950723</a><span class="reference-accessdate">. Retrieved 12 April 2007</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=New+views+of+the+Moon&rft.jtitle=Rev.+Mineral.+Geochem.&rft.aulast=Jolliff&rft.aufirst=B.&rft.au=Jolliff%2C%26%2332%3BB.&rft.date=2006&rft.volume=60&rft.issue=1&rft.pages=721&rft.place=Chantilly%2C+Virginia&rft.pub=Min.+Soc.+Amer.&rft_id=info:doi/10.2138%2Frmg.2006.60.0&rft.isbn=0939950723&rft_id=http%3A%2F%2Fwww.minsocam.org%2Fmsa%2FRIM%2FRim60.html&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li><span class="citation book">Mackenzie, Dana (2003). <i>The Big Splat, or How Our Moon Came to Be</i>. Hoboken, New Jersey: John Wiley & Sons, Inc. <a href="http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="http://en.wikipedia.org/wiki/Special:BookSources/0-471-15057-6" title="Special:BookSources/0-471-15057-6">0-471-15057-6</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Big+Splat%2C+or+How+Our+Moon+Came+to+Be&rft.aulast=Mackenzie&rft.aufirst=Dana&rft.au=Mackenzie%2C%26%2332%3BDana&rft.date=2003&rft.place=Hoboken%2C+New+Jersey&rft.pub=John+Wiley+%26+Sons%2C+Inc&rft.isbn=0-471-15057-6&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li><span class="citation book"><a href="http://en.wikipedia.org/wiki/Patrick_Moore" title="Patrick Moore">Moore, P.</a> (2001). <i>On the Moon</i>. Tucson, Arizona: Sterling Publishing Co.. <a href="http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="http://en.wikipedia.org/wiki/Special:BookSources/0-304-35469-4" title="Special:BookSources/0-304-35469-4">0-304-35469-4</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=On+the+Moon&rft.aulast=%5B%5BPatrick+Moore%7CMoore%2C+P.%5D%5D&rft.au=%5B%5BPatrick+Moore%7CMoore%2C+P.%5D%5D&rft.date=2001&rft.place=Tucson%2C+Arizona&rft.pub=Sterling+Publishing+Co.&rft.isbn=0-304-35469-4&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li><span class="citation book">Spudis, P.D. (1996). <i>The Once and Future Moon</i>. Smithsonian Institution Press. <a href="http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="http://en.wikipedia.org/wiki/Special:BookSources/1-56098-634-4" title="Special:BookSources/1-56098-634-4">1-56098-634-4</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Once+and+Future+Moon&rft.aulast=Spudis&rft.aufirst=P.D.&rft.au=Spudis%2C%26%2332%3BP.D.&rft.date=1996&rft.pub=Smithsonian+Institution+Press&rft.isbn=1-56098-634-4&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li><span class="citation book">Taylor, S.R. (1992). <i>Solar system evolution</i>. Cambridge Univ. Press. pp. 307. <a href="http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="http://en.wikipedia.org/wiki/Special:BookSources/0-521-37212-7" title="Special:BookSources/0-521-37212-7">0-521-37212-7</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Solar+system+evolution&rft.aulast=Taylor&rft.aufirst=S.R.&rft.au=Taylor%2C%26%2332%3BS.R.&rft.date=1992&rft.pages=pp.%26nbsp%3B307&rft.pub=Cambridge+Univ.+Press&rft.isbn=0-521-37212-7&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li><span class="citation Journal">Wilhelms, D.E. (1987). <a class="external text" href="http://ser.sese.asu.edu/GHM/" rel="nofollow">"Geologic History of the Moon"</a>. <i>U.S. Geological Survey Professional paper</i> <b>1348</b><span class="reference-accessdate">. Retrieved 12 April 2007</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Geologic+History+of+the+Moon&rft.jtitle=U.S.+Geological+Survey+Professional+paper&rft.aulast=Wilhelms&rft.aufirst=D.E.&rft.au=Wilhelms%2C%26%2332%3BD.E.&rft.date=1987&rft.volume=1348&rft_id=http%3A%2F%2Fser.sese.asu.edu%2FGHM%2F&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li><span class="citation book">Wilhelms, D.E. (1993). <a class="external text" href="http://www.lpi.usra.edu/publications/books/rockyMoon/" rel="nofollow"><i>To a Rocky Moon: A Geologist's History of Lunar Exploration</i></a>. Tucson, Arizona: University of Arizona Press. <a href="http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="http://en.wikipedia.org/wiki/Special:BookSources/0-8165-1065-2" title="Special:BookSources/0-8165-1065-2">0-8165-1065-2</a><span class="reference-accessdate">. Retrieved 10 March 2009</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=To+a+Rocky+Moon%3A+A+Geologist%27s+History+of+Lunar+Exploration&rft.aulast=Wilhelms&rft.aufirst=D.E.&rft.au=Wilhelms%2C%26%2332%3BD.E.&rft.date=1993&rft.place=Tucson%2C+Arizona&rft.pub=University+of+Arizona+Press&rft.isbn=0-8165-1065-2&rft_id=http%3A%2F%2Fwww.lpi.usra.edu%2Fpublications%2Fbooks%2FrockyMoon%2F&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li></ul></div><h2><span class="mw-headline" id="External_links">External links</span></h2><table class="metadata plainlinks mbox-small" style="background-color: #f9f9f9; border: 1px solid #aaa;"><tbody><tr> <td colspan="2" style="margin: auto; text-align: center;">Find more about <b>Moon</b> on Wikipedia's <a href="http://en.wikipedia.org/wiki/Wikipedia:Wikimedia_sister_projects" title="Wikipedia:Wikimedia sister projects">sister projects</a>:</td> </tr><tr> <td><a href="http://en.wiktionary.org/wiki/Special:Search/Moon" title="Search Wiktionary"><img alt="" height="25" src="http://upload.wikimedia.org/wikipedia/commons/thumb/f/f8/Wiktionary-logo-en.svg/23px-Wiktionary-logo-en.svg.png" width="23" /></a></td> <td><a class="extiw" href="http://en.wiktionary.org/wiki/Special:Search/Moon" title="wikt:Special:Search/Moon">Definitions</a> from Wiktionary</td> </tr><tr> <td><a href="http://commons.wikimedia.org/wiki/Special:Search/Moon" title="Search Commons"><img alt="" height="24" src="http://upload.wikimedia.org/wikipedia/commons/thumb/4/4a/Commons-logo.svg/18px-Commons-logo.svg.png" width="18" /></a></td> <td><a class="extiw" href="http://commons.wikimedia.org/wiki/Special:Search/Moon" title="commons:Special:Search/Moon">Images and media</a> from Commons</td> </tr><tr> <td><a href="http://en.wikiversity.org/wiki/Special:Search/Moon" title="Search Wikiversity"><img alt="" height="23" src="http://upload.wikimedia.org/wikipedia/commons/thumb/1/1b/Wikiversity-logo-en.svg/25px-Wikiversity-logo-en.svg.png" width="25" /></a></td> <td><a class="extiw" href="http://en.wikiversity.org/wiki/Special:Search/Moon" title="v:Special:Search/Moon">Learning resources</a> from Wikiversity</td> </tr><tr> <td><a href="http://en.wikinews.org/wiki/Special:Search/Moon" title="Search Wikinews"><img alt="" height="14" src="http://upload.wikimedia.org/wikipedia/commons/thumb/2/24/Wikinews-logo.svg/25px-Wikinews-logo.svg.png" width="25" /></a></td> <td><a class="extiw" href="http://en.wikinews.org/wiki/Special:Search/Moon" title="n:Special:Search/Moon">News stories</a> from Wikinews</td> </tr><tr> <td><a href="http://en.wikiquote.org/wiki/Special:Search/Moon" title="Search Wikiquote"><img alt="" height="25" src="http://upload.wikimedia.org/wikipedia/commons/thumb/f/fa/Wikiquote-logo.svg/21px-Wikiquote-logo.svg.png" width="21" /></a></td> <td><a class="extiw" href="http://en.wikiquote.org/wiki/Special:Search/Moon" title="q:Special:Search/Moon">Quotations</a> from Wikiquote</td> </tr><tr> <td><a href="http://en.wikisource.org/wiki/Special:Search/Moon" title="Search Wikisource"><img alt="" height="25" src="http://upload.wikimedia.org/wikipedia/commons/thumb/4/4c/Wikisource-logo.svg/24px-Wikisource-logo.svg.png" width="24" /></a></td> <td><a class="extiw" href="http://en.wikisource.org/wiki/Special:Search/Moon" title="s:Special:Search/Moon">Source texts</a> from Wikisource</td> </tr><tr> <td><a href="http://en.wikibooks.org/wiki/Special:Search/Moon" title="Search Wikibooks"><img alt="" height="25" src="http://upload.wikimedia.org/wikipedia/commons/thumb/f/fa/Wikibooks-logo.svg/25px-Wikibooks-logo.svg.png" width="25" /></a></td> <td><a class="extiw" href="http://en.wikibooks.org/wiki/Special:Search/Moon" title="b:Special:Search/Moon">Textbooks</a> from Wikibooks</td> </tr></tbody></table><div class="noprint tright portal" style="border: solid #aaa 1px; margin: 0.5em 0 0.5em 0.5em;"><table style="background: #f9f9f9; font-size: 85%; line-height: 110%; max-width: 175px;"><tbody><tr> <td><a class="image" href="http://en.wikipedia.org/wiki/File:Solar_system.jpg"><img alt="Solar system.jpg" height="27" src="http://upload.wikimedia.org/wikipedia/commons/thumb/8/83/Solar_system.jpg/22px-Solar_system.jpg" width="22" /></a></td> <td style="padding: 0 0.2em;"><i><b><a href="http://en.wikipedia.org/wiki/Portal:Solar_System" title="Portal:Solar System">Solar System portal</a></b></i></td> </tr></tbody></table></div><dl><dt>Further reading</dt></dl><ul><li><span class="citation web"><a class="external text" href="http://www.lpi.usra.edu/expmoon/" rel="nofollow">"Exploring the Moon"</a>. Lunar and Planetary Institute<span class="reference-accessdate">. Retrieved 12 April 2007</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Exploring+the+Moon&rft.atitle=&rft.pub=Lunar+and+Planetary+Institute&rft_id=http%3A%2F%2Fwww.lpi.usra.edu%2Fexpmoon%2F&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li><span class="citation web"><a class="external text" href="http://www.psrd.hawaii.edu/Archive/Archive-Moon.html" rel="nofollow">"Moon Articles"</a>. Planetary Science Research Discoveries.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Moon+Articles&rft.atitle=&rft.pub=Planetary+Science+Research+Discoveries&rft_id=http%3A%2F%2Fwww.psrd.hawaii.edu%2FArchive%2FArchive-Moon.html&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li><span class="citation web">Jones, E.M. (2006). <a class="external text" href="http://www.hq.nasa.gov/office/pao/History/alsj/" rel="nofollow">"Apollo Lunar Surface Journal"</a>. NASA<span class="reference-accessdate">. Retrieved 12 April 2007</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Apollo+Lunar+Surface+Journal&rft.atitle=&rft.aulast=Jones&rft.aufirst=E.M.&rft.au=Jones%2C%26%2332%3BE.M.&rft.date=2006&rft.pub=NASA&rft_id=http%3A%2F%2Fwww.hq.nasa.gov%2Foffice%2Fpao%2FHistory%2Falsj%2F&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li><span class="citation web">Teague, K. (2006). <a class="external text" href="http://www.apolloarchive.com/apollo_archive.html" rel="nofollow">"The Project Apollo Archive"</a><span class="reference-accessdate">. Retrieved 12 April 2007</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=The+Project+Apollo+Archive&rft.atitle=&rft.aulast=Teague&rft.aufirst=K.&rft.au=Teague%2C%26%2332%3BK.&rft.date=2006&rft_id=http%3A%2F%2Fwww.apolloarchive.com%2Fapollo_archive.html&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li><span class="citation web">Cain, Fraser. <a class="external text" href="http://www.astronomycast.com/astronomy/episode-17-where-does-the-moon-come-from/" rel="nofollow">"Where does the Moon Come From?"</a>. Universe Today<span class="reference-accessdate">. Retrieved 1 April 2008</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Where+does+the+Moon+Come+From%3F&rft.atitle=&rft.aulast=Cain&rft.aufirst=Fraser&rft.au=Cain%2C%26%2332%3BFraser&rft.pub=Universe+Today&rft_id=http%3A%2F%2Fwww.astronomycast.com%2Fastronomy%2Fepisode-17-where-does-the-moon-come-from%2F&rfr_id=info:sid/en.wikipedia.org:Moon"></span> (podcast and transcript)</li><li><a class="external text" href="http://www.bbc.co.uk/worldservice/specials/948_discovery_2008/page4.shtml" rel="nofollow">The Moon</a> BBC World Service, Discovery 2008</li></ul><dl><dt>Cartographic resources</dt></dl><ul><li><span class="citation web"><a class="external text" href="http://www.lpi.usra.edu/resources/lunar_atlases/" rel="nofollow">"Lunar Atlases"</a>. Lunar and Planetary Institute<span class="reference-accessdate">. Retrieved 12 April 2007</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Lunar+Atlases&rft.atitle=&rft.pub=Lunar+and+Planetary+Institute&rft_id=http%3A%2F%2Fwww.lpi.usra.edu%2Fresources%2Flunar_atlases%2F&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li><a class="external text" href="http://planetarynames.wr.usgs.gov/jsp/FeatureTypes2.jsp?system=Earth&body=Moon&systemID=3&bodyID=11" rel="nofollow">Gazetteer of Planetary Nomenclature (USGS)</a> List of feature names.</li><li><span class="citation web"><a class="external text" href="http://www.cmf.nrl.navy.mil/clementine/clib/" rel="nofollow">"Clementine Lunar Image Browser"</a>. U.S. Navy. 15 October 2003<span class="reference-accessdate">. Retrieved 12 April 2007</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Clementine+Lunar+Image+Browser&rft.atitle=&rft.date=15+October+2003&rft.pub=U.S.+Navy&rft_id=http%3A%2F%2Fwww.cmf.nrl.navy.mil%2Fclementine%2Fclib%2F&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li>3d zoomable globes: <span class="citation web"><a class="external text" href="http://moon.google.com/" rel="nofollow">"Google Moon"</a>. Google. 2007<span class="reference-accessdate">. Retrieved 12 April 2007</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Google+Moon&rft.atitle=&rft.date=2007&rft.pub=Google&rft_id=http%3A%2F%2Fmoon.google.com&rfr_id=info:sid/en.wikipedia.org:Moon"></span>, <span class="citation web"><a class="external text" href="http://www.worldwindcentral.com/wiki/Moon" rel="nofollow">"Moon"</a>. <i>World Wind Central</i>. NASA. 2007<span class="reference-accessdate">. Retrieved 12 April 2007</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Moon&rft.atitle=World+Wind+Central&rft.date=2007&rft.pub=NASA&rft_id=http%3A%2F%2Fwww.worldwindcentral.com%2Fwiki%2FMoon&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li><span class="citation web">Aeschliman, R. <a class="external text" href="http://ralphaeschliman.com/id26.htm" rel="nofollow">"Lunar Maps"</a>. <i>Planetary Cartography and Graphics</i><span class="reference-accessdate">. Retrieved 12 April 2007</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Lunar+Maps&rft.atitle=Planetary+Cartography+and+Graphics&rft.aulast=Aeschliman&rft.aufirst=R&rft.au=Aeschliman%2C%26%2332%3BR&rft_id=http%3A%2F%2Fralphaeschliman.com%2Fid26.htm&rfr_id=info:sid/en.wikipedia.org:Moon"></span> Maps and panoramas at Apollo landing sites</li><li><a class="external text" href="http://wms.selene.jaxa.jp/index_e.html" rel="nofollow">Japan Aerospace Exploration Agency (JAXA)</a> <a href="http://en.wikipedia.org/wiki/Selene" title="Selene">Kaguya (Selene)</a> images</li></ul><dl><dt>Observation tools</dt></dl><ul><li><span class="citation web"><a class="external text" href="http://sunearth.gsfc.nasa.gov/eclipse/SKYCAL/SKYCAL.html" rel="nofollow">"NASA's SKYCAL—Sky Events Calendar"</a>. NASA Eclipse Home Page<span class="reference-accessdate">. Retrieved 27 August 2007</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=NASA%27s+SKYCAL%E2%80%94Sky+Events+Calendar&rft.atitle=&rft.pub=NASA+Eclipse+Home+Page&rft_id=http%3A%2F%2Fsunearth.gsfc.nasa.gov%2Feclipse%2FSKYCAL%2FSKYCAL.html&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li><span class="citation web"><a class="external text" href="http://www.timeanddate.com/worldclock/moonrise.html" rel="nofollow">"Find moonrise, moonset and moonphase for a location"</a>. 2008<span class="reference-accessdate">. Retrieved 18 February 2008</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Find+moonrise%2C+moonset+and+moonphase+for+a+location&rft.atitle=&rft.date=2008&rft_id=http%3A%2F%2Fwww.timeanddate.com%2Fworldclock%2Fmoonrise.html&rfr_id=info:sid/en.wikipedia.org:Moon"></span></li><li><span class="citation web"><a class="external text" href="http://www.crescentmoonwatch.org/nextnewmoon.htm" rel="nofollow">"HMNAO's Moon Watch"</a>. 2005<span class="reference-accessdate">. Retrieved 24 May 2009</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=HMNAO%27s+Moon+Watch&rft.atitle=&rft.date=2005&rft_id=http%3A%2F%2Fwww.crescentmoonwatch.org%2Fnextnewmoon.htm&rfr_id=info:sid/en.wikipedia.org:Moon"></span> See when the next new crescent moon is visible for any location.</li></ul></div>ripplehttp://www.blogger.com/profile/17326365690819936341noreply@blogger.comtag:blogger.com,1999:blog-6905780489869824283.post-42994533248865557232011-03-22T11:16:00.000-07:002011-04-06T14:15:46.930-07:00Bank<div dir="ltr" style="text-align: left;" trbidi="on"><table class="metadata plainlinks ambox ambox-content"><tbody><tr><td class="mbox-image"><div style="width: 52px;"><img alt="" height="40" src="http://upload.wikimedia.org/wikipedia/en/f/f4/Ambox_content.png" width="40" /></div></td> <td class="mbox-text"> <div> <div style="text-align: left;"><b>This article has multiple issues.</b> Please help <b><a class="external text" href="http://en.wikipedia.org/w/index.php?title=Bank&action=edit" rel="nofollow">improve it</a></b> or discuss these issues on the <b><a href="http://en.wikipedia.org/wiki/Talk:Bank" title="Talk:Bank">talk page</a></b>.</div><ul><li>It needs <b>additional <a href="http://en.wikipedia.org/wiki/Wikipedia:Citing_sources" title="Wikipedia:Citing sources">references or sources</a> for <a href="http://en.wikipedia.org/wiki/Wikipedia:Verifiability" title="Wikipedia:Verifiability">verification</a>.</b> <small>Tagged since July 2008.</small></li><li>It may require general <b><a href="http://en.wikipedia.org/wiki/Wikipedia:Cleanup" title="Wikipedia:Cleanup">cleanup</a></b> to meet Wikipedia's <a href="http://en.wikipedia.org/wiki/Wikipedia:Manual_of_Style" title="Wikipedia:Manual of Style">quality standards</a>. <small>Tagged since June 2010.</small></li></ul></div></td> </tr></tbody></table><table class="toccolours" style="float: right; font-size: 90%; margin: 0 0 1em 1em; text-align: center;"><tbody><tr> <td colspan="2" style="font-size: larger;"><b><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Banking" title="Banking">Banking</a></b></td> </tr><tr> <td> <b>Types of banks</b><br /><a href="http://en.wikipedia.org/wiki/Central_bank">Central bank</a><br /><a href="http://en.wikipedia.org/wiki/Advising_bank">Advising bank</a><br /><a href="http://en.wikipedia.org/wiki/Commercial_bank">Commercial bank</a><br /><a href="http://en.wikipedia.org/wiki/Community_development_bank">Community development bank</a><br /><a href="http://en.wikipedia.org/wiki/Credit_union">Credit union</a><br /><a href="http://en.wikipedia.org/wiki/Custodian_bank">Custodian bank</a><br /><a href="http://en.wikipedia.org/wiki/Depository_bank">Depository bank</a><br /><a href="http://en.wikipedia.org/wiki/Export_credit_agency">Export credit agency</a><br /><a href="http://en.wikipedia.org/wiki/German_public_bank">German public bank</a><br /><a href="http://en.wikipedia.org/wiki/Investment_banking" title="Investment banking">Investment bank</a><br /><a href="http://en.wikipedia.org/wiki/Industrial_loan_company" title="Industrial loan company">Industrial bank</a><br /><a href="http://en.wikipedia.org/wiki/Islamic_banking">Islamic banking</a><br /><a href="http://en.wikipedia.org/wiki/Merchant_bank">Merchant bank</a><br /><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Mutual_bank" title="Mutual bank">Mutual bank</a><br /><a href="http://en.wikipedia.org/wiki/Mutual_savings_bank">Mutual savings bank</a><br /><a href="http://en.wikipedia.org/wiki/National_bank">National bank</a><br /><a href="http://en.wikipedia.org/wiki/Offshore_bank">Offshore bank</a><br /><a href="http://en.wikipedia.org/wiki/Private_bank">Private bank</a><br /><a href="http://en.wikipedia.org/wiki/Savings_and_loan_association">Savings and loan association</a><br /><a href="http://en.wikipedia.org/wiki/Savings_bank">Savings bank</a><br /><a href="http://en.wikipedia.org/wiki/Banking_in_Switzerland" title="Banking in Switzerland">Swiss bank</a><br /></td> </tr><tr> <td> <b><a href="http://en.wikipedia.org/wiki/Deposit_account" title="Deposit account">Deposit accounts</a></b><br /><a href="http://en.wikipedia.org/wiki/Savings_account">Savings account</a><br /><a href="http://en.wikipedia.org/wiki/Transactional_account">Transactional account</a><br /><a href="http://en.wikipedia.org/wiki/Money_market_account">Money market account</a><br /><a href="http://en.wikipedia.org/wiki/Time_deposit">Time deposit</a><br /></td> </tr><tr> <td> <a href="http://en.wikipedia.org/wiki/ATM_card">ATM card</a><br /><a href="http://en.wikipedia.org/wiki/Debit_card">Debit card</a><br /><a href="http://en.wikipedia.org/wiki/Credit_card">Credit card</a><br /></td> </tr><tr> <td> <b><a href="http://en.wikipedia.org/wiki/Electronic_funds_transfer">Electronic funds transfer</a></b><br /><a href="http://en.wikipedia.org/wiki/Automated_Clearing_House">Automated Clearing House</a><br /><a href="http://en.wikipedia.org/wiki/Electronic_bill_payment">Electronic bill payment</a><br /><a href="http://en.wikipedia.org/wiki/Giro">Giro</a><br /><a href="http://en.wikipedia.org/wiki/Wire_transfer">Wire transfer</a><br /></td> </tr><tr> <td> <b>Banking terms</b><br /><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Anonymous_banking" title="Anonymous banking">Anonymous banking</a><br /><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Automatic_teller_machine" title="Automatic teller machine">Automatic teller machine</a><br /><a href="http://en.wikipedia.org/wiki/Loan">Loan</a><br /><a href="http://en.wikipedia.org/wiki/Money_creation">Money creation</a><br /><a href="http://en.wikipedia.org/wiki/Substitute_check">Substitute check</a><br /></td> </tr><tr> <td> <b><a class="mw-redirect" href="http://en.wikipedia.org/wiki/List_of_banks" title="List of banks">List of banks</a></b><br /></td> </tr><tr> <td> <hr /> <b><a href="http://en.wikipedia.org/wiki/Finance">Finance</a> series</b><br /><a href="http://en.wikipedia.org/wiki/Financial_market">Financial market</a><br /><a href="http://en.wikipedia.org/wiki/Financial_market_participants">Financial market participants</a><br /><a href="http://en.wikipedia.org/wiki/Corporate_finance">Corporate finance</a><br /><a href="http://en.wikipedia.org/wiki/Personal_finance">Personal finance</a><br /><a href="http://en.wikipedia.org/wiki/Public_finance">Public finance</a><br /><strong class="selflink">Banks and Banking</strong><br /><a href="http://en.wikipedia.org/wiki/Financial_regulation">Financial regulation</a><br /></td> </tr><tr> <td><span class="noprint plainlinks navbar"><span style="white-space: nowrap; word-spacing: -.12em;"><a href="http://en.wikipedia.org/wiki/Template:Banking" title="Template:Banking"><span title="View this template">v</span></a> <span><b>·</b></span> <a href="http://en.wikipedia.org/wiki/Template_talk:Banking" title="Template talk:Banking"><span title="Discuss this template">d</span></a> <span><b>·</b></span> <a class="external text" href="http://en.wikipedia.org/w/index.php?title=Template:Banking&action=edit" rel="nofollow"><span title="Edit this template">e</span></a></span></span></td> </tr></tbody></table><table cellpadding="0" cellspacing="5" class="vertical-navbox nowraplinks" style="background: #f9f9f9; border-spacing: 0.4em 0; border: 1px solid #aaa; clear: right; color: black; float: right; font-size: 88%; line-height: 1.4em; margin: 0 0 1.0em 1.0em; padding: 0.2em; text-align: center; width: 16em;"><tbody><tr> <th class="" style="font-size: 145%; font-weight: bold; line-height: 1.15em; padding: 0.2em 0.4em 0.2em;"><a href="http://en.wikipedia.org/wiki/Finance">Finance</a></th> </tr><tr> <td style="padding-bottom: 0.2em; padding-top: 0.2em;"> <div class="NavFrame collapsed" id="NavFrame1" style="border: none; padding: 0;"> <div align="left" class="NavHead" style="background: transparent; font-size: 105%;"><a href="http://en.wikipedia.org/wiki/Financial_market" title="Financial market">Financial markets</a><a class="NavToggle" href="" id="NavToggle1">[show]</a></div></div></td> </tr><tr> <td style="padding-bottom: 0.2em;"> <div class="NavFrame collapsed" id="NavFrame2" style="border: none; padding: 0;"> <div align="left" class="NavHead" style="background: transparent; font-size: 105%;"><a href="http://en.wikipedia.org/wiki/Financial_instrument" title="Financial instrument">Financial instruments</a><a class="NavToggle" href="" id="NavToggle2">[show]</a></div></div></td> </tr><tr> <td style="padding-bottom: 0.2em;"> <div class="NavFrame collapsed" id="NavFrame3" style="border: none; padding: 0;"> <div align="left" class="NavHead" style="background: transparent; font-size: 105%;"><a href="http://en.wikipedia.org/wiki/Corporate_finance">Corporate finance</a><a class="NavToggle" href="" id="NavToggle3">[show]</a></div></div></td> </tr><tr> <td style="padding-bottom: 0.2em;"> <div class="NavFrame collapsed" id="NavFrame4" style="border: none; padding: 0;"> <div align="left" class="NavHead" style="background: transparent; font-size: 105%;"><a href="http://en.wikipedia.org/wiki/Personal_finance">Personal finance</a><a class="NavToggle" href="" id="NavToggle4">[show]</a></div></div></td> </tr><tr> <td style="padding-bottom: 0.2em;"> <div class="NavFrame collapsed" id="NavFrame5" style="border: none; padding: 0;"> <div align="left" class="NavHead" style="background: transparent; font-size: 105%;"><a href="http://en.wikipedia.org/wiki/Public_finance">Public finance</a><a class="NavToggle" href="" id="NavToggle5">[show]</a></div></div></td> </tr><tr> <td style="padding-bottom: 0.2em;"> <div class="NavFrame collapsed" id="NavFrame6" style="border: none; padding: 0;"> <div align="left" class="NavHead" style="background: transparent; font-size: 105%;"><strong class="selflink">Banks and banking</strong><a class="NavToggle" href="" id="NavToggle6">[show]</a></div></div></td> </tr><tr> <td style="padding-bottom: 0.2em;"> <div class="NavFrame collapsed" id="NavFrame7" style="border: none; padding: 0;"> <div align="left" class="NavHead" style="background: transparent; font-size: 105%;"><a href="http://en.wikipedia.org/wiki/Financial_regulation">Financial regulation</a><a class="NavToggle" href="" id="NavToggle7">[show]</a></div></div></td> </tr><tr> <td style="padding-bottom: 0.2em;"> <div class="NavFrame collapsed" id="NavFrame8" style="border: none; padding: 0;"> <div align="left" class="NavHead" style="background: transparent; font-size: 105%;"><a href="http://en.wikipedia.org/wiki/International_standard" title="International standard">Standards</a><a class="NavToggle" href="" id="NavToggle8">[show]</a></div></div></td> </tr><tr> <td style="padding-bottom: 0.2em;"> <div class="NavFrame collapsed" id="NavFrame9" style="border: none; padding: 0;"> <div align="left" class="NavHead" style="background: transparent; font-size: 105%;"><a href="http://en.wikipedia.org/wiki/Economic_history">Economic history</a><a class="NavToggle" href="" id="NavToggle9">[show]</a></div></div></td> </tr><tr> <td style="padding-top: 0.6em; text-align: right;"><span class="noprint plainlinks navbar"><span style="white-space: nowrap; word-spacing: -.12em;"><a href="http://en.wikipedia.org/wiki/Template:Finance_sidebar" title="Template:Finance sidebar"><span title="View this template">v</span></a> <span><b>·</b></span> <a href="http://en.wikipedia.org/wiki/Template_talk:Finance_sidebar" title="Template talk:Finance sidebar"><span title="Discuss this template">d</span></a> <span><b>·</b></span> <a class="external text" href="http://en.wikipedia.org/w/index.php?title=Template:Finance_sidebar&action=edit" rel="nofollow"><span title="Edit this template">e</span></a></span></span></td> </tr></tbody></table><table class="navbox" style="clear: right; float: right; margin: 0 0 1em 1em; width: 170px;"><tbody><tr> <th style="background: #cce; font-size: larger;"><b><a href="http://en.wikipedia.org/wiki/Personal_finance">Personal finance</a></b></th> </tr><tr> <td><a class="image" href="http://en.wikipedia.org/wiki/File:Smartcard2.png"><img alt="Smartcard2.png" height="89" src="http://upload.wikimedia.org/wikipedia/commons/thumb/7/70/Smartcard2.png/140px-Smartcard2.png" width="140" /></a> <hr /></td> </tr><tr> <th style="background: #f0f0ff;"><b><a href="http://en.wikipedia.org/wiki/Credit_%28finance%29" title="Credit (finance)">Credit</a></b> and <b><a href="http://en.wikipedia.org/wiki/Debt">debt</a></b><br /><a href="http://en.wikipedia.org/wiki/Pawnbroker">Pawnbroker</a><br /><a href="http://en.wikipedia.org/wiki/Student_loan">Student loan</a><br /></th> </tr><tr> <th style="background: #f0f0ff;"><b><a href="http://en.wikipedia.org/wiki/Employment_contract">Employment contract</a></b></th> </tr><tr> <td> <a href="http://en.wikipedia.org/wiki/Salary">Salary</a><br /><a href="http://en.wikipedia.org/wiki/Wage">Wage</a><br /><a href="http://en.wikipedia.org/wiki/Employee_stock_option">Employee stock option</a><br /><a href="http://en.wikipedia.org/wiki/Employee_benefit">Employee benefit</a><br /><a href="http://en.wikipedia.org/wiki/Deferred_compensation">Deferred compensation</a><br /><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Direct_deposit_%28disambiguation%29" title="Direct deposit (disambiguation)">Direct deposit</a><br /></td> </tr><tr> <th style="background: #f0f0ff;"><b><a href="http://en.wikipedia.org/wiki/Retirement">Retirement</a></b></th> </tr><tr> <td> <a href="http://en.wikipedia.org/wiki/Pension">Pension</a><br /><a href="http://en.wikipedia.org/wiki/Defined_benefit_pension_plan" title="Defined benefit pension plan">Defined benefit</a><br /><a href="http://en.wikipedia.org/wiki/Defined_contribution_plan" title="Defined contribution plan">Defined contribution</a><br /><a href="http://en.wikipedia.org/wiki/Social_security">Social security</a><br /><a href="http://en.wikipedia.org/wiki/Business_plan">Business plan</a><br /><a href="http://en.wikipedia.org/wiki/Corporate_action">Corporate action</a><br /></td> </tr><tr> <th style="background: #f0f0ff;"><b><a href="http://en.wikipedia.org/wiki/Personal_budget">Personal budget</a></b></th> </tr><tr> <td> <a href="http://en.wikipedia.org/wiki/Financial_planner">Financial planner</a><br /><a href="http://en.wikipedia.org/wiki/Financial_adviser">Financial adviser</a><br /><a href="http://en.wikipedia.org/wiki/Financial_independence">Financial independence</a><br /><a href="http://en.wikipedia.org/wiki/Estate_planning">Estate planning</a><br /></td> </tr><tr> <th style="background: #f0f0ff;"><b>See also</b></th> </tr><tr> <td> <strong class="selflink">Banks</strong> and <a href="http://en.wikipedia.org/wiki/Credit_union" title="Credit union">credit unions</a><br /><a href="http://en.wikipedia.org/wiki/Cooperative" title="Cooperative">Cooperatives</a><br /><hr /></td> </tr><tr> <td><br /></td> </tr><tr> <td align="right"><small><a class="external text" href="http://en.wikipedia.org/w/wiki.phtml?title=Template:Personal_finance&action=edit" rel="nofollow">edit this box</a></small></td> </tr></tbody></table>A <b>bank</b> is a <a href="http://en.wikipedia.org/wiki/Financial_intermediary">financial intermediary</a> and appears in several related basic forms:<br /><ul><li>a <a href="http://en.wikipedia.org/wiki/Central_bank">central bank</a> issues money on behalf of a government, and regulates the <a href="http://en.wikipedia.org/wiki/Money_supply">money supply</a></li><li>a <a href="http://en.wikipedia.org/wiki/Commercial_bank">commercial bank</a> accepts <a href="http://en.wikipedia.org/wiki/Deposit_account" title="Deposit account">deposits</a> and channels those deposits into <a href="http://en.wikipedia.org/wiki/Loan" title="Loan">lending</a> activities, either directly or through <a href="http://en.wikipedia.org/wiki/Capital_market" title="Capital market">capital markets</a>. A bank connects customers with capital deficits to customers with <a href="http://en.wikipedia.org/wiki/Capital_surplus" title="Capital surplus">capital surpluses</a> on the world's open <a href="http://en.wikipedia.org/wiki/Financial_market" title="Financial market">financial markets</a>.</li><li>a <a href="http://en.wikipedia.org/wiki/Savings_bank">savings bank</a>, also known as a <a href="http://en.wikipedia.org/wiki/Building_society">building society</a> in Britain is only allowed to borrow and save from members of a financial <a href="http://en.wikipedia.org/wiki/Cooperative">cooperative</a></li></ul>Banks often start as <a href="http://en.wikipedia.org/wiki/Microcredit">microcredit</a> or <a href="http://en.wikipedia.org/wiki/Christmas_club" title="Christmas club">savings clubs</a> which become formalized, first as <a href="http://en.wikipedia.org/wiki/Credit_union" title="Credit union">credit unions</a> and later savings banks which transform themselves from cooperatives to <a href="http://en.wikipedia.org/wiki/Limited_liability">limited liability</a> companies. A fuller description of these forms appears below.<br />Banking is generally a <a href="http://en.wikipedia.org/wiki/Bank_regulation" title="Bank regulation">highly regulated</a> industry, and government restrictions on financial activities by banks have varied over time and location. The current set of global bank capital standards are called <a href="http://en.wikipedia.org/wiki/Basel_II">Basel II</a>. In some countries such as <a href="http://en.wikipedia.org/wiki/Germany">Germany</a>, banks have historically owned major stakes in industrial corporations while in other countries such as the <a href="http://en.wikipedia.org/wiki/United_States">United States</a> banks are prohibited from owning non-financial companies. In <a href="http://en.wikipedia.org/wiki/Japan">Japan</a>, banks are usually the nexus of a cross-share holding entity known as the <a href="http://en.wikipedia.org/wiki/Keiretsu">keiretsu</a>. In Iceland banks had very light regulation prior to the <a href="http://en.wikipedia.org/wiki/2008%E2%80%932010_Icelandic_financial_crisis" title="2008–2010 Icelandic financial crisis">2008 collapse</a>.<br />The oldest bank still in existence is <a href="http://en.wikipedia.org/wiki/Monte_dei_Paschi_di_Siena">Monte dei Paschi di Siena</a>, headquartered in <a href="http://en.wikipedia.org/wiki/Siena">Siena</a>, <a href="http://en.wikipedia.org/wiki/Italy">Italy</a>, and has been operating continuously since 1472.<sup class="reference" id="cite_ref-boland1_0-0"><a href="http://en.wikipedia.org/wiki/Bank#cite_note-boland1-0"><span>[</span>1<span>]</span></a></sup><br /><table class="toc" id="toc"><tbody><tr> <td> <div id="toctitle"> <h2>Contents</h2><span class="toctoggle">[<a class="internal" href="http://en.wikipedia.org/wiki/Bank#" id="togglelink">hide</a>]</span></div><ul><li class="toclevel-1 tocsection-1"><a href="http://en.wikipedia.org/wiki/Bank#History"><span class="tocnumber">1</span> <span class="toctext">History</span></a> <ul><li class="toclevel-2 tocsection-2"><a href="http://en.wikipedia.org/wiki/Bank#Origin_of_the_word"><span class="tocnumber">1.1</span> <span class="toctext">Origin of the word</span></a></li></ul></li><li class="toclevel-1 tocsection-3"><a href="http://en.wikipedia.org/wiki/Bank#Definition"><span class="tocnumber">2</span> <span class="toctext">Definition</span></a></li><li class="toclevel-1 tocsection-4"><a href="http://en.wikipedia.org/wiki/Bank#Banking"><span class="tocnumber">3</span> <span class="toctext">Banking</span></a> <ul><li class="toclevel-2 tocsection-5"><a href="http://en.wikipedia.org/wiki/Bank#Standard_activities"><span class="tocnumber">3.1</span> <span class="toctext">Standard activities</span></a></li><li class="toclevel-2 tocsection-6"><a href="http://en.wikipedia.org/wiki/Bank#Channels"><span class="tocnumber">3.2</span> <span class="toctext">Channels</span></a></li><li class="toclevel-2 tocsection-7"><a href="http://en.wikipedia.org/wiki/Bank#Business_model"><span class="tocnumber">3.3</span> <span class="toctext">Business model</span></a></li><li class="toclevel-2 tocsection-8"><a href="http://en.wikipedia.org/wiki/Bank#Products"><span class="tocnumber">3.4</span> <span class="toctext">Products</span></a> <ul><li class="toclevel-3 tocsection-9"><a href="http://en.wikipedia.org/wiki/Bank#Retail"><span class="tocnumber">3.4.1</span> <span class="toctext">Retail</span></a></li><li class="toclevel-3 tocsection-10"><a href="http://en.wikipedia.org/wiki/Bank#Wholesale"><span class="tocnumber">3.4.2</span> <span class="toctext">Wholesale</span></a></li></ul></li></ul></li><li class="toclevel-1 tocsection-11"><a href="http://en.wikipedia.org/wiki/Bank#Risk_and_capital"><span class="tocnumber">4</span> <span class="toctext">Risk and capital</span></a></li><li class="toclevel-1 tocsection-12"><a href="http://en.wikipedia.org/wiki/Bank#Banks_in_the_economy"><span class="tocnumber">5</span> <span class="toctext">Banks in the economy</span></a> <ul><li class="toclevel-2 tocsection-13"><a href="http://en.wikipedia.org/wiki/Bank#Economic_functions"><span class="tocnumber">5.1</span> <span class="toctext">Economic functions</span></a></li><li class="toclevel-2 tocsection-14"><a href="http://en.wikipedia.org/wiki/Bank#Bank_crisis"><span class="tocnumber">5.2</span> <span class="toctext">Bank crisis</span></a></li><li class="toclevel-2 tocsection-15"><a href="http://en.wikipedia.org/wiki/Bank#Size_of_global_banking_industry"><span class="tocnumber">5.3</span> <span class="toctext">Size of global banking industry</span></a></li></ul></li><li class="toclevel-1 tocsection-16"><a href="http://en.wikipedia.org/wiki/Bank#Regulation"><span class="tocnumber">6</span> <span class="toctext">Regulation</span></a></li><li class="toclevel-1 tocsection-17"><a href="http://en.wikipedia.org/wiki/Bank#Types_of_banks"><span class="tocnumber">7</span> <span class="toctext">Types of banks</span></a> <ul><li class="toclevel-2 tocsection-18"><a href="http://en.wikipedia.org/wiki/Bank#Types_of_retail_banks"><span class="tocnumber">7.1</span> <span class="toctext">Types of retail banks</span></a></li><li class="toclevel-2 tocsection-19"><a href="http://en.wikipedia.org/wiki/Bank#Types_of_investment_banks"><span class="tocnumber">7.2</span> <span class="toctext">Types of investment banks</span></a></li><li class="toclevel-2 tocsection-20"><a href="http://en.wikipedia.org/wiki/Bank#Both_combined"><span class="tocnumber">7.3</span> <span class="toctext">Both combined</span></a></li><li class="toclevel-2 tocsection-21"><a href="http://en.wikipedia.org/wiki/Bank#Other_types_of_banks"><span class="tocnumber">7.4</span> <span class="toctext">Other types of banks</span></a></li></ul></li><li class="toclevel-1 tocsection-22"><a href="http://en.wikipedia.org/wiki/Bank#Challenges_within_the_banking_industry"><span class="tocnumber">8</span> <span class="toctext">Challenges within the banking industry</span></a> <ul><li class="toclevel-2 tocsection-23"><a href="http://en.wikipedia.org/wiki/Bank#United_States"><span class="tocnumber">8.1</span> <span class="toctext">United States</span></a></li><li class="toclevel-2 tocsection-24"><a href="http://en.wikipedia.org/wiki/Bank#Competition_for_loanable_funds"><span class="tocnumber">8.2</span> <span class="toctext">Competition for loanable funds</span></a></li></ul></li><li class="toclevel-1 tocsection-25"><a href="http://en.wikipedia.org/wiki/Bank#Accounting_for_bank_accounts"><span class="tocnumber">9</span> <span class="toctext">Accounting for bank accounts</span></a> <ul><li class="toclevel-2 tocsection-26"><a href="http://en.wikipedia.org/wiki/Bank#Brokered_deposits"><span class="tocnumber">9.1</span> <span class="toctext">Brokered deposits</span></a></li></ul></li><li class="toclevel-1 tocsection-27"><a href="http://en.wikipedia.org/wiki/Bank#Banking_by_country"><span class="tocnumber">10</span> <span class="toctext">Banking by country</span></a></li><li class="toclevel-1 tocsection-28"><a href="http://en.wikipedia.org/wiki/Bank#See_also"><span class="tocnumber">11</span> <span class="toctext">See also</span></a></li><li class="toclevel-1 tocsection-29"><a href="http://en.wikipedia.org/wiki/Bank#References"><span class="tocnumber">12</span> <span class="toctext">References</span></a></li><li class="toclevel-1 tocsection-30"><a href="http://en.wikipedia.org/wiki/Bank#External_links"><span class="tocnumber">13</span> <span class="toctext">External links</span></a></li></ul></td> </tr></tbody></table><h2><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Bank&action=edit&section=1" title="Edit section: History">edit</a>]</span> <span class="mw-headline" id="History">History</span></h2><div class="rellink relarticle mainarticle">Main article: <a href="http://en.wikipedia.org/wiki/History_of_banking">History of banking</a></div>Banking in the modern sense of the word can be traced to medieval and early <a href="http://en.wikipedia.org/wiki/Renaissance">Renaissance</a> <a href="http://en.wikipedia.org/wiki/Italy">Italy</a>, to the rich cities in the north like <a href="http://en.wikipedia.org/wiki/Florence">Florence</a>, <a href="http://en.wikipedia.org/wiki/Venice">Venice</a> and <a href="http://en.wikipedia.org/wiki/Genoa">Genoa</a>. The <a href="http://en.wikipedia.org/wiki/Bardi_family" title="Bardi family">Bardi</a> and <a href="http://en.wikipedia.org/wiki/Peruzzi">Peruzzi</a> families dominated banking in 14th century Florence, establishing branches in many other parts of <a href="http://en.wikipedia.org/wiki/Europe">Europe</a>.<sup class="reference" id="cite_ref-1"><a href="http://en.wikipedia.org/wiki/Bank#cite_note-1"><span>[</span>2<span>]</span></a></sup> Perhaps the most famous Italian bank was the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Medici" title="Medici">Medici</a> bank, set up by Giovanni Medici in 1397.<sup class="reference" id="cite_ref-2"><a href="http://en.wikipedia.org/wiki/Bank#cite_note-2"><span>[</span>3<span>]</span></a></sup> The earliest known state deposit bank, <i><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Bank_of_Saint_George_%28Genoa%29" title="Bank of Saint George (Genoa)">Banco di San Giorgio</a></i> (Bank of St. George), was founded in 1407 at <a href="http://en.wikipedia.org/wiki/Genoa">Genoa</a>, <a href="http://en.wikipedia.org/wiki/Italy">Italy</a>.<sup class="reference" id="cite_ref-3"><a href="http://en.wikipedia.org/wiki/Bank#cite_note-3"><span>[</span>4<span>]</span></a></sup><br />Banks can be traced back to ancient times even before money when <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Temples" title="Temples">temples</a> were used to store commodities. During the 3rd century AD, banks in <a href="http://en.wikipedia.org/wiki/Iran" title="Iran">Persia</a> and other territories in the Persian <a href="http://en.wikipedia.org/wiki/Sassanid_Empire">Sassanid Empire</a> issued <a href="http://en.wikipedia.org/wiki/Letter_of_credit" title="Letter of credit">letters of credit</a> known as <i>Ṣakks</i>.<sup class="Template-Fact" style="white-space: nowrap;" title="This claim needs references to reliable sources from August 2010">[<i><a href="http://en.wikipedia.org/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed">citation needed</a></i>]</sup> <a href="http://en.wikipedia.org/wiki/Islamic_economics_in_the_world" title="Islamic economics in the world">Muslim traders</a> are known to have used the <a href="http://en.wikipedia.org/wiki/Cheque">cheque</a> or <i><a class="extiw" href="http://en.wiktionary.org/wiki/%E1%B9%A3akk" title="wikt:ṣakk">ṣakk</a></i> system since the time of <a href="http://en.wikipedia.org/wiki/Harun_al-Rashid">Harun al-Rashid</a> (9th century) of the <a href="http://en.wikipedia.org/wiki/Abbasid_Caliphate">Abbasid Caliphate</a>. In the 9th century, a Muslim businessman could cash an early form of the cheque in <a href="http://en.wikipedia.org/wiki/China">China</a> drawn on sources in <a href="http://en.wikipedia.org/wiki/Baghdad">Baghdad</a>,<sup class="reference" id="cite_ref-Vallely_4-0"><a href="http://en.wikipedia.org/wiki/Bank#cite_note-Vallely-4"><span>[</span>5<span>]</span></a></sup><sup class="noprint Inline-Template" style="white-space: nowrap;" title="The material in the vicinity of this tag needs to be fact-checked with the cited source(s) from June 2010">[<i><a href="http://en.wikipedia.org/wiki/Wikipedia:Verifiability" title="Wikipedia:Verifiability">verification needed</a></i>]</sup> a tradition that was significantly strengthened in the 13th and 14th centuries, during the <a href="http://en.wikipedia.org/wiki/Mongol_Empire">Mongol Empire</a>.<sup class="Template-Fact" style="white-space: nowrap;" title="This claim needs references to reliable sources from May 2010">[<i><a href="http://en.wikipedia.org/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed">citation needed</a></i>]</sup> Fragments found in the <a href="http://en.wikipedia.org/wiki/Cairo_Geniza">Cairo Geniza</a> indicate that in the 12th century cheques remarkably similar to our own were in use, only smaller to save costs on the paper. They contain a sum to be paid and then the order "May so and so pay the bearer such and such an amount". The date and name of the issuer are also apparent.<br /><h3><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Bank&action=edit&section=2" title="Edit section: Origin of the word">edit</a>]</span> <span class="mw-headline" id="Origin_of_the_word">Origin of the word</span></h3>The word <i>bank</i> was borrowed in <a href="http://en.wikipedia.org/wiki/Middle_English">Middle English</a> from <a href="http://en.wikipedia.org/wiki/Middle_French">Middle French</a> <i>banque</i>, from Old <a href="http://en.wikipedia.org/wiki/Italian_language" title="Italian language">Italian</a> <i>banca</i>, from <a href="http://en.wikipedia.org/wiki/Old_High_German">Old High German</a> <i>banc, bank</i> "bench, counter". Benches were used as desks or exchange counters during the <a href="http://en.wikipedia.org/wiki/Renaissance">Renaissance</a> by <a href="http://en.wikipedia.org/wiki/Florence" title="Florence">Florentine</a> bankers, who used to make their transactions atop desks covered by green tablecloths.<sup class="reference" id="cite_ref-5"><a href="http://en.wikipedia.org/wiki/Bank#cite_note-5"><span>[</span>6<span>]</span></a></sup><br />The earliest evidence of money-changing activity is depicted on a silver Greek drachm coin from ancient Hellenic colony Trapezus on the Black Sea, modern <a href="http://en.wikipedia.org/wiki/Trabzon">Trabzon</a>, c. 350–325 BC, presented in the <a href="http://en.wikipedia.org/wiki/British_Museum">British Museum</a> in London. The coin shows a banker's table (<i>trapeza</i>) laden with coins, a pun on the name of the city. In fact, even today in <a href="http://en.wikipedia.org/wiki/Modern_Greek">Modern Greek</a> the word Trapeza (<i>Τράπεζα</i>) means both a table and a bank.<br /><h2><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Bank&action=edit&section=3" title="Edit section: Definition">edit</a>]</span> <span class="mw-headline" id="Definition">Definition</span></h2>The definition of a bank varies from country to country. See the relevant country page (below) for more information.<br />Under <a class="mw-redirect" href="http://en.wikipedia.org/wiki/English_common_law" title="English common law">English common law</a>, a banker is defined as a person who carries on the business of banking, which is specified as:<sup class="reference" id="cite_ref-6"><a href="http://en.wikipedia.org/wiki/Bank#cite_note-6"><span>[</span>7<span>]</span></a></sup><br /><ul><li>conducting current accounts for his customers</li><li>paying cheques drawn on him, and</li><li>collecting cheques for his customers.</li></ul><div class="thumb tright"> <div class="thumbinner" style="width: 302px;"><a class="image" href="http://en.wikipedia.org/wiki/File:Banco_de_Venezuela,_Coro.JPG"><img alt="" class="thumbimage" height="169" src="http://upload.wikimedia.org/wikipedia/commons/thumb/1/14/Banco_de_Venezuela%2C_Coro.JPG/300px-Banco_de_Venezuela%2C_Coro.JPG" width="300" /></a> <div class="thumbcaption"> <div class="magnify"><a class="internal" href="http://en.wikipedia.org/wiki/File:Banco_de_Venezuela,_Coro.JPG" title="Enlarge"><img alt="" height="11" src="http://bits.wikimedia.org/skins-1.17/common/images/magnify-clip.png" width="15" /></a></div><a href="http://en.wikipedia.org/wiki/Banco_de_Venezuela">Banco de Venezuela</a> in <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Coro,_Venezuela" title="Coro, Venezuela">Coro</a>.</div></div></div>In most common law jurisdictions there is a Bills of Exchange Act that codifies the law in relation to <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Negotiable_instruments" title="Negotiable instruments">negotiable instruments</a>, including <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Cheques" title="Cheques">cheques</a>, and this Act contains a statutory definition of the term <i>banker</i>: <i>banker</i> includes a body of persons, whether incorporated or not, who carry on the business of banking' (Section 2, Interpretation). Although this definition seems circular, it is actually functional, because it ensures that the legal basis for bank transactions such as <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Cheques" title="Cheques">cheques</a> does not depend on how the bank is organised or regulated.<br />The business of banking is in many <a class="mw-redirect" href="http://en.wikipedia.org/wiki/English_common_law" title="English common law">English common law</a> countries not defined by statute but by common law, the definition above. In other English common law jurisdictions there are statutory definitions of the <i>business of banking</i> or <i>banking business</i>. When looking at these definitions it is important to keep in mind that they are defining the business of banking for the purposes of the legislation, and not necessarily in general. In particular, most of the definitions are from legislation that has the purposes of entry regulating and supervising banks rather than regulating the actual business of banking. However, in many cases the statutory definition closely mirrors the common law one. Examples of statutory definitions:<br /><ul><li>"banking business" means the business of receiving money on current or deposit account, paying and collecting cheques drawn by or paid in by customers, the making of advances to customers, and includes such other business as the Authority may prescribe for the purposes of this Act; (Banking Act (Singapore), Section 2, Interpretation).</li></ul><ul><li>"banking business" means the business of either or both of the following:</li></ul><ol><li>receiving from the general public money on current, deposit, savings or other similar account repayable on demand or within less than [3 months] ... or with a period of call or notice of less than that period;</li><li>paying or collecting cheques drawn by or paid in by customers<sup class="reference" id="cite_ref-7"><a href="http://en.wikipedia.org/wiki/Bank#cite_note-7"><span>[</span>8<span>]</span></a></sup></li></ol>Since the advent of <a href="http://en.wikipedia.org/wiki/EFTPOS">EFTPOS</a> (Electronic Funds Transfer at Point Of Sale), direct credit, <a href="http://en.wikipedia.org/wiki/Direct_debit">direct debit</a> and <a href="http://en.wikipedia.org/wiki/Online_banking" title="Online banking">internet banking</a>, the cheque has lost its primacy in most banking systems as a payment instrument. This has led legal theorists to suggest that the cheque based definition should be broadened to include financial institutions that conduct current accounts for customers and enable customers to pay and be paid by third parties, even if they do not pay and collect cheques.<sup class="reference" id="cite_ref-8"><a href="http://en.wikipedia.org/wiki/Bank#cite_note-8"><span>[</span>9<span>]</span></a></sup><br /><h2><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Bank&action=edit&section=4" title="Edit section: Banking">edit</a>]</span> <span class="mw-headline" id="Banking">Banking</span></h2><h3><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Bank&action=edit&section=5" title="Edit section: Standard activities">edit</a>]</span> <span class="mw-headline" id="Standard_activities">Standard activities</span></h3><div class="thumb tright"> <div class="thumbinner" style="width: 252px;"><a class="image" href="http://en.wikipedia.org/wiki/File:WinonaSavingsBankVault.JPG"><img alt="" class="thumbimage" height="156" src="http://upload.wikimedia.org/wikipedia/commons/thumb/8/87/WinonaSavingsBankVault.JPG/250px-WinonaSavingsBankVault.JPG" width="250" /></a> <div class="thumbcaption"> <div class="magnify"><a class="internal" href="http://en.wikipedia.org/wiki/File:WinonaSavingsBankVault.JPG" title="Enlarge"><img alt="" height="11" src="http://bits.wikimedia.org/skins-1.17/common/images/magnify-clip.png" width="15" /></a></div>Large door to an old <a href="http://en.wikipedia.org/wiki/Bank_vault">bank vault</a>.</div></div></div>Banks act as payment agents by conducting <a href="http://en.wikipedia.org/wiki/Transactional_account" title="Transactional account">checking or current accounts</a> for customers, paying <a href="http://en.wikipedia.org/wiki/Cheque" title="Cheque">cheques</a> drawn by customers on the bank, and collecting cheques deposited to customers' current accounts. Banks also enable customer payments via other payment methods such as <a href="http://en.wikipedia.org/wiki/Telegraphic_transfer">telegraphic transfer</a>, <a href="http://en.wikipedia.org/wiki/EFTPOS">EFTPOS</a>, and <a href="http://en.wikipedia.org/wiki/Automated_teller_machine" title="Automated teller machine">ATM</a>.<br />Banks borrow money by accepting funds deposited on current accounts, by accepting term deposits, and by issuing debt securities such as <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Banknotes" title="Banknotes">banknotes</a> and <a href="http://en.wikipedia.org/wiki/Bond_%28finance%29" title="Bond (finance)">bonds</a>. Banks lend money by making advances to customers on current accounts, by making <a href="http://en.wikipedia.org/wiki/Installment_loan" title="Installment loan">installment loans</a>, and by investing in marketable debt securities and other forms of money lending.<br />Banks provide almost all payment services, and a bank account is considered indispensable by most businesses, individuals and governments. Non-banks that provide payment services such as remittance companies are not normally considered an adequate substitute for having a bank account.<br />Banks borrow most funds from households and non-financial businesses, and lend most funds to households and non-financial businesses, but non-bank lenders provide a significant and in many cases adequate substitute for bank loans, and money market funds, cash management trusts and other non-bank financial institutions in many cases provide an adequate substitute to banks for lending savings too.<sup class="noprint Inline-Template" style="white-space: nowrap;" title="The text in the vicinity of this tag needs clarification or removal of jargon from March 2009">[<i><a href="http://en.wikipedia.org/wiki/Wikipedia:Please_clarify" title="Wikipedia:Please clarify">clarification needed</a></i>]</sup><br /><h3><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Bank&action=edit&section=6" title="Edit section: Channels">edit</a>]</span> <span class="mw-headline" id="Channels">Channels</span></h3>Banks offer many different channels to access their banking and other services:<br /><ul><li><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Automatic_teller_machine" title="Automatic teller machine">ATM</a> is a machine that dispenses cash and sometimes takes deposits without the need for a human <a href="http://en.wikipedia.org/wiki/Bank_teller">bank teller</a>. Some ATMs provide additional services.</li><li>A <a href="http://en.wikipedia.org/wiki/Branch_%28banking%29" title="Branch (banking)">branch</a> is a retail location</li><li><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Call_center" title="Call center">Call center</a></li><li><a href="http://en.wikipedia.org/wiki/Mail">Mail</a>: most banks accept check deposits via mail and use mail to communicate to their customers, e.g. by sending out statements</li><li><a href="http://en.wikipedia.org/wiki/Mobile_banking">Mobile banking</a> is a method of using one's mobile phone to conduct banking transactions</li><li><a href="http://en.wikipedia.org/wiki/Online_banking">Online banking</a> is a term used for performing transactions, payments etc. over the Internet</li><li><a href="http://en.wikipedia.org/wiki/Customer_relationship_management" title="Customer relationship management">Relationship Managers</a>, mostly for private banking or business banking, often visiting customers at their homes or businesses</li><li><a href="http://en.wikipedia.org/wiki/Telephone_banking">Telephone banking</a> is a service which allows its customers to perform transactions over the telephone without speaking to a human</li><li><b><a href="http://en.wikipedia.org/wiki/Video_banking">Video banking</a></b> is a term used for performing banking transactions or professional banking consultations via a remote video and audio connection. Video banking can be performed via purpose built banking transaction machines (similar to an Automated teller machine), or via a <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Videoconference" title="Videoconference">videoconference</a> enabled bank branch.</li></ul><h3><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Bank&action=edit&section=7" title="Edit section: Business model">edit</a>]</span> <span class="mw-headline" id="Business_model">Business model</span></h3>A bank can generate revenue in a variety of different ways including interest, transaction fees and financial advice. The main method is via charging <a href="http://en.wikipedia.org/wiki/Interest">interest</a> on the capital it lends out to customers<sup class="Template-Fact" style="white-space: nowrap;" title="This claim needs references to reliable sources from January 2011">[<i><a href="http://en.wikipedia.org/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed">citation needed</a></i>]</sup>. The bank profits from the differential between the level of interest it pays for deposits and other sources of funds, and the level of interest it charges in its lending activities.<br />This difference is referred to as the <i>spread</i> between the cost of funds and the loan interest rate. Historically, profitability from lending activities has been cyclical and dependent on the needs and strengths of loan customers and the stage of the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Economic_cycle" title="Economic cycle">economic cycle</a>. Fees and financial advice constitute a more stable revenue stream and banks have therefore placed more emphasis on these revenue lines to smooth their financial performance.<br />In the past 20 years American banks have taken many measures to ensure that they remain profitable while responding to increasingly changing market conditions. First, this includes the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Gramm-Leach-Bliley_Act" title="Gramm-Leach-Bliley Act">Gramm-Leach-Bliley Act</a>, which allows banks again to merge with investment and insurance houses. Merging banking, investment, and insurance functions allows traditional banks to respond to increasing consumer demands for "one-stop shopping" by enabling cross-selling of products (which, the banks hope, will also increase profitability).<br />Second, they have expanded the use of <a href="http://en.wikipedia.org/wiki/Risk-based_pricing">risk-based pricing</a> from business lending to consumer lending, which means charging higher interest rates to those customers that are considered to be a higher credit risk and thus increased chance of <a href="http://en.wikipedia.org/wiki/Default_%28finance%29" title="Default (finance)">default</a> on loans. This helps to offset the losses from bad loans, lowers the price of loans to those who have better credit histories, and offers credit products to high risk customers who would otherwise be denied credit.<br />Third, they have sought to increase the methods of payment processing available to the general public and business clients. These products include <a href="http://en.wikipedia.org/wiki/Debit_card" title="Debit card">debit cards</a>, prepaid cards, <a href="http://en.wikipedia.org/wiki/Smart_card" title="Smart card">smart cards</a>, and <a href="http://en.wikipedia.org/wiki/Credit_card" title="Credit card">credit cards</a>. They make it easier for consumers to conveniently make transactions and smooth their consumption over time (in some countries with underdeveloped financial systems, it is still common to deal strictly in cash, including carrying suitcases filled with cash to purchase a home).<br />However, with convenience of easy credit, there is also increased risk that consumers will mismanage their financial resources and accumulate excessive debt. Banks make money from card products through <a href="http://en.wikipedia.org/wiki/Interest">interest</a> payments and fees charged to consumers and <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Transaction_fee" title="Transaction fee">transaction fees</a> to companies that accept the cards. This helps in making profit and facilitates economic development as a whole<sup class="Template-Fact" style="white-space: nowrap;" title="This claim needs references to reliable sources from January 2011">[<i><a href="http://en.wikipedia.org/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed">citation needed</a></i>]</sup>.<br /><h3><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Bank&action=edit&section=8" title="Edit section: Products">edit</a>]</span> <span class="mw-headline" id="Products">Products</span></h3><div class="thumb tright"> <div class="thumbinner" style="width: 222px;"><a class="image" href="http://en.wikipedia.org/wiki/File:Halifax_bank,_Commercial_Street,_Leeds_%2827th_May_2010%29.jpg"><img alt="" class="thumbimage" height="165" src="http://upload.wikimedia.org/wikipedia/commons/thumb/5/55/Halifax_bank%2C_Commercial_Street%2C_Leeds_%2827th_May_2010%29.jpg/220px-Halifax_bank%2C_Commercial_Street%2C_Leeds_%2827th_May_2010%29.jpg" width="220" /></a> <div class="thumbcaption"> <div class="magnify"><a class="internal" href="http://en.wikipedia.org/wiki/File:Halifax_bank,_Commercial_Street,_Leeds_%2827th_May_2010%29.jpg" title="Enlarge"><img alt="" height="11" src="http://bits.wikimedia.org/skins-1.17/common/images/magnify-clip.png" width="15" /></a></div>A former <a href="http://en.wikipedia.org/wiki/Building_society">building society</a>, now a modern retail bank in <a href="http://en.wikipedia.org/wiki/Leeds">Leeds</a>, <a href="http://en.wikipedia.org/wiki/West_Yorkshire">West Yorkshire</a>.</div></div></div><div class="thumb tright"> <div class="thumbinner" style="width: 222px;"><a class="image" href="http://en.wikipedia.org/wiki/File:NatWest_Castle_Street.jpg"><img alt="" class="thumbimage" height="165" src="http://upload.wikimedia.org/wikipedia/commons/thumb/3/3e/NatWest_Castle_Street.jpg/220px-NatWest_Castle_Street.jpg" width="220" /></a> <div class="thumbcaption"> <div class="magnify"><a class="internal" href="http://en.wikipedia.org/wiki/File:NatWest_Castle_Street.jpg" title="Enlarge"><img alt="" height="11" src="http://bits.wikimedia.org/skins-1.17/common/images/magnify-clip.png" width="15" /></a></div>An interior of a branch of <a href="http://en.wikipedia.org/wiki/National_Westminster_Bank">National Westminster Bank</a> on Castle Street, <a href="http://en.wikipedia.org/wiki/Liverpool">Liverpool</a></div></div></div><h4><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Bank&action=edit&section=9" title="Edit section: Retail">edit</a>]</span> <span class="mw-headline" id="Retail">Retail</span></h4><ul><li><a class="new" href="http://en.wikipedia.org/w/index.php?title=Business_loan&action=edit&redlink=1" title="Business loan (page does not exist)">Business loan</a></li><li><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Checking_account" title="Checking account">Cheque account</a></li><li><a href="http://en.wikipedia.org/wiki/Credit_card">Credit card</a></li><li><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Home_loan" title="Home loan">Home loan</a></li><li><a class="new" href="http://en.wikipedia.org/w/index.php?title=Insurance_advisor&action=edit&redlink=1" title="Insurance advisor (page does not exist)">Insurance advisor</a></li><li><a href="http://en.wikipedia.org/wiki/Mutual_fund">Mutual fund</a></li><li><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Personal_loan" title="Personal loan">Personal loan</a></li><li><a href="http://en.wikipedia.org/wiki/Savings_account">Savings account</a></li></ul><h4><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Bank&action=edit&section=10" title="Edit section: Wholesale">edit</a>]</span> <span class="mw-headline" id="Wholesale">Wholesale</span></h4><ul><li><a class="new" href="http://en.wikipedia.org/w/index.php?title=Capital_raising&action=edit&redlink=1" title="Capital raising (page does not exist)">Capital raising</a> (<a href="http://en.wikipedia.org/wiki/Equity_%28finance%29" title="Equity (finance)">Equity</a> / <a href="http://en.wikipedia.org/wiki/Debt">Debt</a> / <a href="http://en.wikipedia.org/wiki/Hybrid_security" title="Hybrid security">Hybrids</a>)</li><li><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Mezzanine_finance" title="Mezzanine finance">Mezzanine finance</a></li><li><a href="http://en.wikipedia.org/wiki/Project_finance">Project finance</a></li><li><a href="http://en.wikipedia.org/wiki/Revolving_credit">Revolving credit</a></li><li><a href="http://en.wikipedia.org/wiki/Risk_management">Risk management</a> (<a href="http://en.wikipedia.org/wiki/Foreign_exchange_market" title="Foreign exchange market">FX</a>, <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Interest_rates" title="Interest rates">interest rates</a>, <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Commodities" title="Commodities">commodities</a>, <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Derivatives" title="Derivatives">derivatives</a>)</li><li><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Term_loan" title="Term loan">Term loan</a></li></ul><h2><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Bank&action=edit&section=11" title="Edit section: Risk and capital">edit</a>]</span> <span class="mw-headline" id="Risk_and_capital">Risk and capital</span></h2>Banks face a number of <a href="http://en.wikipedia.org/wiki/Financial_risk" title="Financial risk">risks</a> in order to conduct their business, and how well these risks are managed and understood is a key driver behind profitability, and how much <a href="http://en.wikipedia.org/wiki/Capital_requirement" title="Capital requirement">capital</a> a bank is required to hold. Some of the main risks faced by banks include:<br /><ul><li><a href="http://en.wikipedia.org/wiki/Credit_risk">Credit risk</a>: risk of loss<sup class="Template-Fact" style="white-space: nowrap;" title="This claim needs references to reliable sources from November 2010">[<i><a href="http://en.wikipedia.org/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed">citation needed</a></i>]</sup> arising from a borrower who does not make payments as promised.</li><li><a href="http://en.wikipedia.org/wiki/Liquidity_risk">Liquidity risk</a>: risk that a given security or asset cannot be traded quickly enough in the market to prevent a loss (or make the required profit).</li><li><a href="http://en.wikipedia.org/wiki/Market_risk">Market risk</a>: risk that the value of a portfolio, either an investment portfolio or a trading portfolio, will decrease due to the change in value of the market risk factors.</li><li><a href="http://en.wikipedia.org/wiki/Operational_risk">Operational risk</a>: risk arising from execution of a company's business functions.</li></ul>The <a href="http://en.wikipedia.org/wiki/Capital_requirement">capital requirement</a> is a <a href="http://en.wikipedia.org/wiki/Bank_regulation">bank regulation</a>, which sets a framework on how banks and depository institutions must handle their capital. The categorization of assets and capital is highly standardized so that it can be risk weighted (see <a href="http://en.wikipedia.org/wiki/Risk-weighted_asset">risk-weighted asset</a>).<br /><h2><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Bank&action=edit&section=12" title="Edit section: Banks in the economy">edit</a>]</span> <span class="mw-headline" id="Banks_in_the_economy">Banks in the economy</span></h2><div class="rellink boilerplate seealso">See also: <a href="http://en.wikipedia.org/wiki/Financial_system">Financial system</a></div><h3><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Bank&action=edit&section=13" title="Edit section: Economic functions">edit</a>]</span> <span class="mw-headline" id="Economic_functions">Economic functions</span></h3>The economic functions of banks include:<br /><ol><li>Issue of money, in the form of <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Banknotes" title="Banknotes">banknotes</a> and current accounts subject to <a href="http://en.wikipedia.org/wiki/Cheque">cheque</a> or payment at the customer's order. These claims on banks can act as money because they are negotiable or repayable on demand, and hence valued at par. They are effectively transferable by mere delivery, in the case of <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Banknotes" title="Banknotes">banknotes</a>, or by drawing a cheque that the payee may bank or cash.</li><li>Netting and settlement of payments – banks act as both collection and paying agents for customers, participating in interbank clearing and settlement systems to collect, present, be presented with, and pay payment instruments. This enables banks to economise on reserves held for settlement of payments, since inward and outward payments offset each other. It also enables the offsetting of payment flows between geographical areas, reducing the cost of settlement between them.</li><li>Credit intermediation – banks borrow and lend back-to-back on their own account as middle men.</li><li>Credit quality improvement – banks lend money to ordinary commercial and personal borrowers (ordinary credit quality), but are high quality borrowers. The improvement comes from diversification of the bank's assets and capital which provides a buffer to absorb losses without defaulting on its obligations. However, banknotes and deposits are generally unsecured; if the bank gets into difficulty and pledges assets as security, to raise the funding it needs to continue to operate, this puts the note holders and depositors in an economically subordinated position.</li><li><a href="http://en.wikipedia.org/wiki/Asset_liability_mismatch" title="Asset liability mismatch">Maturity transformation</a> – banks borrow more on demand debt and short term debt, but provide more long term loans. In other words, they borrow short and lend long. With a stronger credit quality than most other borrowers, banks can do this by aggregating issues (e.g. accepting deposits and issuing banknotes) and redemptions (e.g. withdrawals and redemptions of banknotes), maintaining reserves of cash, investing in marketable securities that can be readily converted to cash if needed, and raising replacement funding as needed from various sources (e.g. wholesale cash markets and securities markets).</li></ol><h3><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Bank&action=edit&section=14" title="Edit section: Bank crisis">edit</a>]</span> <span class="mw-headline" id="Bank_crisis">Bank crisis</span></h3>Banks are susceptible to many forms of risk which have triggered occasional systemic crises. These include <a href="http://en.wikipedia.org/wiki/Liquidity_risk">liquidity risk</a> (where many depositors may request withdrawals in excess of available funds), <a href="http://en.wikipedia.org/wiki/Credit_risk">credit risk</a> (the chance that those who owe money to the bank will not repay it), and <a href="http://en.wikipedia.org/wiki/Interest_rate_risk">interest rate risk</a> (the possibility that the bank will become unprofitable, if rising interest rates force it to pay relatively more on its deposits than it receives on its loans).<br />Banking crises have developed many times throughout history, when one or more risks have materialized for a banking sector as a whole. Prominent examples include the <a href="http://en.wikipedia.org/wiki/Bank_run">bank run</a> that occurred during the <a href="http://en.wikipedia.org/wiki/Great_Depression">Great Depression</a>, the U.S. <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Savings_and_Loan_crisis" title="Savings and Loan crisis">Savings and Loan crisis</a> in the 1980s and early 1990s, the <a href="http://en.wikipedia.org/wiki/Japan" title="Japan">Japanese</a> banking crisis during the 1990s, and the <a href="http://en.wikipedia.org/wiki/Subprime_mortgage_crisis">subprime mortgage crisis</a> in the 2000s.<br /><h3><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Bank&action=edit&section=15" title="Edit section: Size of global banking industry">edit</a>]</span> <span class="mw-headline" id="Size_of_global_banking_industry">Size of global banking industry</span></h3>Assets of the largest 1,000 banks in the world grew by 6.8% in the 2008/2009 financial year to a record $96.4 trillion while profits declined by 85% to $115bn. Growth in assets in adverse market conditions was largely a result of recapitalisation. EU banks held the largest share of the total, 56% in 2008/2009, down from 61% in the previous year. Asian banks' share increased from 12% to 14% during the year, while the share of US banks increased from 11% to 13%. Fee revenue generated by global investment banking totalled $66.3bn in 2009, up 12% on the previous year.<sup class="reference" id="cite_ref-ifsl_9-0"><a href="http://en.wikipedia.org/wiki/Bank#cite_note-ifsl-9"><span>[</span>10<span>]</span></a></sup><br />The United States has the most banks in the world in terms of institutions (7,085 at the end of 2008) and possibly branches (82,000).<sup class="Template-Fact" style="white-space: nowrap;" title="This claim needs references to reliable sources from November 2009">[<i><a href="http://en.wikipedia.org/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed">citation needed</a></i>]</sup> This is an indicator of the geography and regulatory structure of the USA, resulting in a large number of small to medium-sized institutions in its banking system. As of Nov 2009, China's top 4 banks have in excess of 67,000 branches (<a class="mw-redirect" href="http://en.wikipedia.org/wiki/ICBC" title="ICBC">ICBC</a>:18000+, <a href="http://en.wikipedia.org/wiki/BOC">BOC</a>:12000+, <a href="http://en.wikipedia.org/wiki/CCB">CCB</a>:13000+, <a href="http://en.wikipedia.org/wiki/Agricultural_Bank_of_China" title="Agricultural Bank of China">ABC</a>:24000+) with an additional 140 smaller banks with an undetermined number of branches. Japan had 129 banks and 12,000 branches. In 2004, Germany, France, and Italy each had more than 30,000 branches—more than double the 15,000 branches in the UK.<sup class="reference" id="cite_ref-ifsl_9-1"><a href="http://en.wikipedia.org/wiki/Bank#cite_note-ifsl-9"><span>[</span>10<span>]</span></a></sup><br /><h2><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Bank&action=edit&section=16" title="Edit section: Regulation">edit</a>]</span> <span class="mw-headline" id="Regulation">Regulation</span></h2><div class="rellink relarticle mainarticle">Main article: <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Banking_regulation" title="Banking regulation">Banking regulation</a></div><div class="rellink boilerplate seealso">See also: <a href="http://en.wikipedia.org/wiki/Basel_II">Basel II</a></div>Currently in most jurisdictions commercial banks are regulated by government entities and require a special bank licence to operate.<br />Usually the definition of the business of banking for the purposes of regulation is extended to include acceptance of deposits, even if they are not repayable to the customer's order—although money lending, by itself, is generally not included in the definition.<br />Unlike most other regulated industries, the regulator is typically also a participant in the market, being either a publicly or privately governed central bank. Central banks also typically have a monopoly on the business of issuing <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Banknotes" title="Banknotes">banknotes</a>. However, in some countries this is not the case. In the UK, for example, the <a href="http://en.wikipedia.org/wiki/Financial_Services_Authority">Financial Services Authority</a> licences banks, and some commercial banks (such as the <a href="http://en.wikipedia.org/wiki/Bank_of_Scotland">Bank of Scotland</a>) issue their own <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Banknotes" title="Banknotes">banknotes</a> in addition to those issued by the <a href="http://en.wikipedia.org/wiki/Bank_of_England">Bank of England</a>, the UK government's central bank.<br />Banking law is based on a contractual analysis of the relationship between the <i>bank</i> (defined above) and the <i>customer</i>—defined as any entity for which the bank agrees to conduct an account.<br />The law implies rights and obligations into this relationship as follows:<br /><ol><li>The bank account balance is the financial position between the bank and the customer: when the account is in credit, the bank owes the balance to the customer; when the account is overdrawn, the customer owes the balance to the bank.</li><li>The bank agrees to pay the customer's cheques up to the amount standing to the credit of the customer's account, plus any agreed overdraft limit.</li><li>The bank may not pay from the customer's account without a mandate from the customer, e.g. a cheque drawn by the customer.</li><li>The bank agrees to promptly collect the cheques deposited to the customer's account as the customer's agent, and to credit the proceeds to the customer's account.</li><li>The bank has a right to combine the customer's accounts, since each account is just an aspect of the same credit relationship.</li><li>The bank has a <a href="http://en.wikipedia.org/wiki/Lien">lien</a> on cheques deposited to the customer's account, to the extent that the customer is indebted to the bank.</li><li>The bank must not disclose details of transactions through the customer's account—unless the customer consents, there is a public duty to disclose, the bank's interests require it, or the law demands it.</li><li>The bank must not close a customer's account without reasonable notice, since cheques are outstanding in the ordinary course of business for several days.</li></ol>These implied contractual terms may be modified by express agreement between the customer and the bank. The statutes and regulations in force within a particular jurisdiction may also modify the above terms and/or create new rights, obligations or limitations relevant to the bank-customer relationship.<br />Some types of financial institution, such as <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Building_Society" title="Building Society">building societies</a> and <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Credit_unions" title="Credit unions">credit unions</a>, may be partly or wholly exempt from bank licence requirements, and therefore regulated under separate rules.<br />The requirements for the issue of a bank licence vary between jurisdictions but typically include:<br /><ol><li>Minimum capital</li><li>Minimum capital ratio</li><li>'Fit and Proper' requirements for the bank's controllers, owners, directors, or senior officers</li><li>Approval of the bank's business plan as being sufficiently prudent and plausible.</li></ol><h2><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Bank&action=edit&section=17" title="Edit section: Types of banks">edit</a>]</span> <span class="mw-headline" id="Types_of_banks">Types of banks</span></h2>Banks' activities can be divided into <a href="http://en.wikipedia.org/wiki/Retail_banking">retail banking</a>, dealing directly with individuals and small businesses; <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Business_banking" title="Business banking">business banking</a>, providing services to mid-market business; corporate banking, directed at large business entities; <a href="http://en.wikipedia.org/wiki/Private_banking">private banking</a>, providing wealth management services to <a href="http://en.wikipedia.org/wiki/High_net_worth_individual" title="High net worth individual">high net worth individuals</a> and families; and <a href="http://en.wikipedia.org/wiki/Investment_banking">investment banking</a>, relating to activities on the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Financial_markets" title="Financial markets">financial markets</a>. Most banks are profit-making, private enterprises. However, some are owned by government, or are <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Non-profit_organization" title="Non-profit organization">non-profit organizations</a>.<br /><h3><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Bank&action=edit&section=18" title="Edit section: Types of retail banks">edit</a>]</span> <span class="mw-headline" id="Types_of_retail_banks">Types of retail banks</span></h3><div class="thumb tright"> <div class="thumbinner" style="width: 222px;"><a class="image" href="http://en.wikipedia.org/wiki/File:NatBankRep.jpg"><img alt="" class="thumbimage" height="167" src="http://upload.wikimedia.org/wikipedia/en/thumb/4/43/NatBankRep.jpg/220px-NatBankRep.jpg" width="220" /></a> <div class="thumbcaption"> <div class="magnify"><a class="internal" href="http://en.wikipedia.org/wiki/File:NatBankRep.jpg" title="Enlarge"><img alt="" height="11" src="http://bits.wikimedia.org/skins-1.17/common/images/magnify-clip.png" width="15" /></a></div>National Bank of the Republic, <a href="http://en.wikipedia.org/wiki/Salt_Lake_City">Salt Lake City</a> 1908</div></div></div><div class="thumb tright"> <div class="thumbinner" style="width: 202px;"><a class="image" href="http://en.wikipedia.org/wiki/File:ATM_AL_RAJHI_BANK.JPG"><img alt="" class="thumbimage" height="150" src="http://upload.wikimedia.org/wikipedia/commons/thumb/d/da/ATM_AL_RAJHI_BANK.JPG/200px-ATM_AL_RAJHI_BANK.JPG" width="200" /></a> <div class="thumbcaption"> <div class="magnify"><a class="internal" href="http://en.wikipedia.org/wiki/File:ATM_AL_RAJHI_BANK.JPG" title="Enlarge"><img alt="" height="11" src="http://bits.wikimedia.org/skins-1.17/common/images/magnify-clip.png" width="15" /></a></div><a href="http://en.wikipedia.org/wiki/Automated_teller_machine" title="Automated teller machine">ATM</a> <a href="http://en.wikipedia.org/wiki/Al-Rajhi_Bank">Al-Rajhi Bank</a></div></div></div><div class="thumb tright"> <div class="thumbinner" style="width: 222px;"><a class="image" href="http://en.wikipedia.org/wiki/File:NatCuBank.jpg"><img alt="" class="thumbimage" height="257" src="http://upload.wikimedia.org/wikipedia/en/thumb/4/44/NatCuBank.jpg/220px-NatCuBank.jpg" width="220" /></a> <div class="thumbcaption"> <div class="magnify"><a class="internal" href="http://en.wikipedia.org/wiki/File:NatCuBank.jpg" title="Enlarge"><img alt="" height="11" src="http://bits.wikimedia.org/skins-1.17/common/images/magnify-clip.png" width="15" /></a></div>National Copper Bank, <a href="http://en.wikipedia.org/wiki/Salt_Lake_City">Salt Lake City</a> 1911</div></div></div><ul><li><a href="http://en.wikipedia.org/wiki/Commercial_bank">Commercial bank</a>: the term used for a normal bank to distinguish it from an investment bank. After the <a href="http://en.wikipedia.org/wiki/Great_Depression">Great Depression</a>, the U.S. Congress required that banks only engage in banking activities, whereas investment banks were limited to <a href="http://en.wikipedia.org/wiki/Capital_market">capital market</a> activities. Since the two no longer have to be under separate ownership, some use the term "commercial bank" to refer to a bank or a division of a bank that mostly deals with deposits and loans from corporations or large businesses.</li><li><a href="http://en.wikipedia.org/wiki/Community_banks">Community banks</a>: locally operated financial institutions that empower employees to make local decisions to serve their customers and the partners.</li><li><a href="http://en.wikipedia.org/wiki/Community_development_bank" title="Community development bank">Community development banks</a>: regulated banks that provide financial services and credit to under-served markets or populations.</li><li><a href="http://en.wikipedia.org/wiki/Credit_union" title="Credit union">Credit unions</a>: not-for-profit <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Cooperatives" title="Cooperatives">cooperatives</a> owned by the depositors and often offering rates more favorable than for-profit banks. Typically, membership is restricted to employees of a particular company, residents of a defined neighborhood, members of a certain labor union or religious organizations, and their immediate families.</li><li><a href="http://en.wikipedia.org/wiki/Postal_savings_system" title="Postal savings system">Postal savings banks</a>: savings banks associated with national postal systems.</li><li><a href="http://en.wikipedia.org/wiki/Private_banking" title="Private banking">Private banks</a>: banks that manage the assets of high net worth individuals. Historically a minimum of USD 1 million was required to open an account, however, over the last years many private banks have lowered their entry hurdles to USD 250,000 for private investors.<sup class="Template-Fact" style="white-space: nowrap;" title="This claim needs references to reliable sources from August 2010">[<i><a href="http://en.wikipedia.org/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed">citation needed</a></i>]</sup></li><li><a href="http://en.wikipedia.org/wiki/Offshore_bank" title="Offshore bank">Offshore banks</a>: banks located in jurisdictions with low taxation and regulation. Many offshore banks are essentially private banks.</li><li><a href="http://en.wikipedia.org/wiki/Savings_bank">Savings bank</a>: in Europe, savings banks took their roots in the 19th or sometimes even in the 18th century. Their original objective was to provide easily accessible savings products to all strata of the population. In some countries, savings banks were created on public initiative; in others, socially committed individuals created foundations to put in place the necessary infrastructure. Nowadays, European savings banks have kept their focus on retail banking: payments, savings products, credits and insurances for individuals or small and medium-sized enterprises. Apart from this retail focus, they also differ from commercial banks by their broadly decentralised distribution network, providing local and regional outreach—and by their socially responsible approach to business and society.</li><li><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Building_societies" title="Building societies">Building societies</a> and <a href="http://en.wikipedia.org/wiki/Landesbank" title="Landesbank">Landesbanks</a>: institutions that conduct retail banking.</li><li><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Ethical_bank" title="Ethical bank">Ethical banks</a>: banks that prioritize the transparency of all operations and make only what they consider to be socially-responsible investments.</li><li>A <a href="http://en.wikipedia.org/wiki/Direct_bank" title="Direct bank">Direct or Internet-Only bank</a> is a banking operation without any physical bank branches, conceived and implemented wholly with networked computers.</li></ul><h3><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Bank&action=edit&section=19" title="Edit section: Types of investment banks">edit</a>]</span> <span class="mw-headline" id="Types_of_investment_banks">Types of investment banks</span></h3><ul><li><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Investment_bank" title="Investment bank">Investment banks</a> "<a class="mw-redirect" href="http://en.wikipedia.org/wiki/Underwrite" title="Underwrite">underwrite</a>" (guarantee the sale of) stock and bond issues, trade for their own accounts, make markets, and advise corporations on <a href="http://en.wikipedia.org/wiki/Capital_market">capital market</a> activities such as mergers and acquisitions.</li><li><a href="http://en.wikipedia.org/wiki/Merchant_bank" title="Merchant bank">Merchant banks</a> were traditionally banks which engaged in <a href="http://en.wikipedia.org/wiki/Trade_finance">trade finance</a>. The modern definition, however, refers to banks which provide capital to firms in the form of shares rather than loans. Unlike <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Venture_capital_firm" title="Venture capital firm">venture capital firms</a>, they tend not to invest in new companies.</li></ul><h3><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Bank&action=edit&section=20" title="Edit section: Both combined">edit</a>]</span> <span class="mw-headline" id="Both_combined">Both combined</span></h3><ul><li><a href="http://en.wikipedia.org/wiki/Universal_bank" title="Universal bank">Universal banks</a>, more commonly known as <a href="http://en.wikipedia.org/wiki/Financial_services">financial services</a> companies, engage in several of these activities. These big banks are very diversified groups that, among other services, also distribute insurance— hence the term <a href="http://en.wikipedia.org/wiki/Bancassurance">bancassurance</a>, a <a href="http://en.wikipedia.org/wiki/Portmanteau" title="Portmanteau">portmanteau word</a> combining "banque or bank" and "assurance", signifying that both banking and insurance are provided by the same corporate entity.</li></ul><h3><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Bank&action=edit&section=21" title="Edit section: Other types of banks">edit</a>]</span> <span class="mw-headline" id="Other_types_of_banks">Other types of banks</span></h3><ul><li><a href="http://en.wikipedia.org/wiki/Central_bank" title="Central bank">Central banks</a> are normally government-owned and charged with quasi-regulatory responsibilities, such as supervising commercial banks, or controlling the cash <a href="http://en.wikipedia.org/wiki/Interest_rate">interest rate</a>. They generally provide liquidity to the banking system and act as the <a href="http://en.wikipedia.org/wiki/Lender_of_last_resort">lender of last resort</a> in event of a crisis.</li><li><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Islamic_bank" title="Islamic bank">Islamic banks</a> adhere to the concepts of <a href="http://en.wikipedia.org/wiki/Sharia" title="Sharia">Islamic law</a>. This form of banking revolves around several well-established principles based on Islamic canons. All banking activities must avoid interest, a concept that is forbidden in Islam. Instead, the bank earns profit (<a href="http://en.wikipedia.org/wiki/Markup_%28business%29" title="Markup (business)">markup</a>) and fees on the financing facilities that it extends to customers.</li></ul><h2><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Bank&action=edit&section=22" title="Edit section: Challenges within the banking industry">edit</a>]</span> <span class="mw-headline" id="Challenges_within_the_banking_industry">Challenges within the banking industry</span></h2><table class="metadata plainlinks ambox ambox-content"><tbody><tr> <td class="mbox-image"> <div style="width: 52px;"><img alt="Globe icon." height="40" src="http://upload.wikimedia.org/wikipedia/commons/thumb/b/bd/Ambox_globe_content.svg/48px-Ambox_globe_content.svg.png" width="48" /></div></td> <td class="mbox-text">The examples and perspective in this section <b>may not represent a <a href="http://en.wikipedia.org/wiki/Wikipedia:WikiProject_Countering_systemic_bias" title="Wikipedia:WikiProject Countering systemic bias">worldwide view</a> of the subject</b>. Please <a class="external text" href="http://en.wikipedia.org/w/index.php?title=Bank&action=edit" rel="nofollow">improve this article</a> and discuss the issue on the <a href="http://en.wikipedia.org/wiki/Talk:Bank" title="Talk:Bank">talk page</a>. <small><i>(September 2009)</i></small></td> </tr></tbody></table><table class="metadata plainlinks ambox ambox-content"><tbody><tr> <td class="mbox-image"> <div style="width: 52px;"><img alt="" height="39" src="http://upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/50px-Question_book-new.svg.png" width="50" /></div></td> <td class="mbox-text">This section <b>does not <a href="http://en.wikipedia.org/wiki/Wikipedia:Citing_sources" title="Wikipedia:Citing sources">cite</a> any <a href="http://en.wikipedia.org/wiki/Wikipedia:Verifiability" title="Wikipedia:Verifiability">references or sources</a></b>.<br /><small>Please help <a class="external text" href="http://en.wikipedia.org/w/index.php?title=Bank&action=edit" rel="nofollow">improve this article</a> by adding citations to <a href="http://en.wikipedia.org/wiki/Wikipedia:Identifying_reliable_sources" title="Wikipedia:Identifying reliable sources">reliable sources</a>. Unsourced material may be <a href="http://en.wikipedia.org/wiki/Template:Citation_needed" title="Template:Citation needed">challenged</a> and <a href="http://en.wikipedia.org/wiki/Wikipedia:Verifiability#Burden_of_evidence" title="Wikipedia:Verifiability">removed</a>. <i>(September 2008)</i></small></td> </tr></tbody></table><h3><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Bank&action=edit&section=23" title="Edit section: United States">edit</a>]</span> <span class="mw-headline" id="United_States">United States</span></h3><div class="rellink relarticle mainarticle">Main article: <a href="http://en.wikipedia.org/wiki/Banking_in_the_United_States">Banking in the United States</a></div>In the United States, the banking industry is a highly regulated industry with detailed and focused regulators. All banks with FDIC-insured deposits have the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/FDIC" title="FDIC">FDIC</a> as a regulator; however, for examinations,<sup class="noprint Inline-Template" style="white-space: nowrap;" title="The text in the vicinity of this tag needs clarification or removal of jargon from September 2008">[<i><a href="http://en.wikipedia.org/wiki/Wikipedia:Please_clarify" title="Wikipedia:Please clarify">clarification needed</a></i>]</sup> the <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Federal_Reserve" title="Federal Reserve">Federal Reserve</a> is the primary federal regulator for Fed-member state banks; the <a href="http://en.wikipedia.org/wiki/Office_of_the_Comptroller_of_the_Currency">Office of the Comptroller of the Currency</a> (“OCC”) is the primary federal regulator for national banks; and the <a href="http://en.wikipedia.org/wiki/Office_of_Thrift_Supervision">Office of Thrift Supervision</a>, or OTS, is the primary federal regulator for <a href="http://en.wikipedia.org/wiki/Thrift" title="Thrift">thrifts</a>. State non-member banks are examined by the state agencies as well as the FDIC. National banks have one primary regulator—the OCC. Qualified Intermediaries & Exchange Accommodators are regulated by MAIC.<br />Each regulatory agency has their own set of rules and regulations to which banks and thrifts must adhere.<br />The <a href="http://en.wikipedia.org/wiki/Federal_Financial_Institutions_Examination_Council">Federal Financial Institutions Examination Council</a> (FFIEC) was established in 1979 as a formal interagency body empowered to prescribe uniform principles, standards, and report forms for the federal examination of financial institutions. Although the FFIEC has resulted in a greater degree of regulatory consistency between the agencies, the rules and regulations are constantly changing.<br />In addition to changing regulations, changes in the industry have led to consolidations within the Federal Reserve, FDIC, OTS, MAIC and OCC. Offices have been closed, supervisory regions have been merged, staff levels have been reduced and budgets have been cut. The remaining regulators face an increased burden with increased workload and more banks per regulator. While banks struggle to keep up with the changes in the regulatory environment, regulators struggle to manage their workload and effectively regulate their banks. The impact of these changes is that banks are receiving less hands-on assessment by the regulators, less time spent with each institution, and the potential for more problems slipping through the cracks, potentially resulting in an overall increase in bank failures across the United States.<br />The changing economic environment has a significant impact on banks and thrifts as they struggle to effectively manage their interest rate spread in the face of low rates on loans, rate competition for deposits and the general market changes, industry trends and economic fluctuations. It has been a challenge for banks to effectively set their growth strategies with the recent economic market. A rising interest rate environment may seem to help financial institutions, but the effect of the changes on consumers and businesses is not predictable and the challenge remains for banks to grow and effectively manage the spread to generate a return to their shareholders.<br />The management of the banks’ asset portfolios also remains a challenge in today’s economic environment. Loans are a bank’s primary asset category and when loan quality becomes suspect, the foundation of a bank is shaken to the core. While always an issue for banks, declining <a href="http://en.wikipedia.org/wiki/Asset_quality">asset quality</a> has become a big problem for financial institutions. There are several reasons for this, one of which is the lax attitude some banks have adopted because of the years of “good times.” The potential for this is exacerbated by the reduction in the regulatory oversight of banks and in some cases depth of management. Problems are more likely to go undetected, resulting in a significant impact on the bank when they are recognized. In addition, banks, like any business, struggle to cut costs and have consequently eliminated certain expenses, such as adequate employee training programs.<br />Banks also face a host of other challenges such as aging ownership groups. Across the country, many banks’ management teams and board of directors are aging. Banks also face ongoing pressure by shareholders, both public and private, to achieve earnings and growth projections. Regulators place added pressure on banks to manage the various categories of risk. Banking is also an extremely competitive industry. Competing in the financial services industry has become tougher with the entrance of such players as insurance agencies, credit unions, check cashing services, credit card companies, etc.<br />As a reaction, banks have developed their activities in <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Financial_instruments" title="Financial instruments">financial instruments</a>, through <a href="http://en.wikipedia.org/wiki/Financial_market">financial market</a> operations such as <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Brokerage" title="Brokerage">brokerage</a> and MAIC trust & Securities Clearing services <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Trading_%28finance%29" title="Trading (finance)">trading</a> and become big players in such activities.<br /><h3><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Bank&action=edit&section=24" title="Edit section: Competition for loanable funds">edit</a>]</span> <span class="mw-headline" id="Competition_for_loanable_funds">Competition for loanable funds</span></h3>To be able to provide homebuyers and builders with the funds needed, banks must compete for deposits. The phenomenon of <a href="http://en.wikipedia.org/wiki/Disintermediation">disintermediation</a> had to dollars moving from savings accounts and into direct market instruments such as <a class="mw-redirect" href="http://en.wikipedia.org/wiki/U.S._Treasury" title="U.S. Treasury">U.S. Treasury</a> obligations, agency securities, and corporate debt. One of the greatest factors in recent years in the movement of deposits was the tremendous growth of money market funds whose higher interest rates attracted consumer deposits.<sup class="reference" id="cite_ref-multiple3_10-0"><a href="http://en.wikipedia.org/wiki/Bank#cite_note-multiple3-10"><span>[</span>11<span>]</span></a></sup><br />To compete for deposits, US savings institutions offer many different types of plans<sup class="reference" id="cite_ref-multiple3_10-1"><a href="http://en.wikipedia.org/wiki/Bank#cite_note-multiple3-10"><span>[</span>11<span>]</span></a></sup>:<br /><ul><li><a href="http://en.wikipedia.org/wiki/Passbook">Passbook</a> or ordinary <a href="http://en.wikipedia.org/wiki/Deposit_account" title="Deposit account">deposit accounts</a> — permit any amount to be added to or withdrawn from the account at any time.</li><li>NOW and Super NOW accounts — function like checking accounts but earn interest. A minimum balance may be required on Super NOW accounts.</li><li><a href="http://en.wikipedia.org/wiki/Money_market_account" title="Money market account">Money market accounts</a> — carry a monthly limit of preauthorized transfers to other accounts or persons and may require a minimum or average balance.</li><li>Certificate accounts — subject to loss of some or all interest on withdrawals before maturity.</li><li>Notice accounts — the equivalent of certificate accounts with an indefinite term. Savers agree to notify the institution a specified time before withdrawal.</li><li><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Individual_retirement_account" title="Individual retirement account">Individual retirement accounts</a> (IRAs) and <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Keogh_plan" title="Keogh plan">Keogh plans</a> — a form of retirement savings in which the funds deposited and interest earned are exempt from income tax until after withdrawal.</li><li><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Checking_account" title="Checking account">Checking accounts</a> — offered by some institutions under definite restrictions.</li><li>Club accounts and other <a href="http://en.wikipedia.org/wiki/Savings_account" title="Savings account">savings accounts</a> — designed to help people save regularly to meet certain goals.</li></ul><h2><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Bank&action=edit&section=25" title="Edit section: Accounting for bank accounts">edit</a>]</span> <span class="mw-headline" id="Accounting_for_bank_accounts">Accounting for bank accounts</span></h2><div class="thumb tright"> <div class="thumbinner" style="width: 222px;"><a class="image" href="http://en.wikipedia.org/wiki/File:BBTLexington.jpg"><img alt="" class="thumbimage" height="128" src="http://upload.wikimedia.org/wikipedia/commons/thumb/b/bc/BBTLexington.jpg/220px-BBTLexington.jpg" width="220" /></a> <div class="thumbcaption"> <div class="magnify"><a class="internal" href="http://en.wikipedia.org/wiki/File:BBTLexington.jpg" title="Enlarge"><img alt="" height="11" src="http://bits.wikimedia.org/skins-1.17/common/images/magnify-clip.png" width="15" /></a></div>Suburban bank branch</div></div></div>Bank statements are accounting records produced by banks under the various accounting standards of the world. Under <a class="mw-redirect" href="http://en.wikipedia.org/wiki/GAAP" title="GAAP">GAAP</a> and <a class="new" href="http://en.wikipedia.org/w/index.php?title=MAIC&action=edit&redlink=1" title="MAIC (page does not exist)">MAIC</a> there are two kinds of accounts: debit and credit. Credit accounts are Revenue, Equity and Liabilities. Debit Accounts are Assets and Expenses. This means you credit a <i>credit account</i> to increase its balance, and you debit a <i>credit account</i> to decrease its balance.<sup class="reference" id="cite_ref-11"><a href="http://en.wikipedia.org/wiki/Bank#cite_note-11"><span>[</span>12<span>]</span></a></sup><br />This also means you credit your savings account every time you deposit money into it (and the account is normally in credit), while you debit your credit card account every time you spend money from it (and the account is normally in debit).<br />However, if you read your bank statement, it will say the opposite—that you credit your account when you deposit money, and you debit it when you withdraw funds. If you have cash in your account, you have a positive (or credit) balance; if you are overdrawn, you have a negative (or deficit) balance.<br />Where bank transactions, balances, credits and debits are discussed below, they are done so from the viewpoint of the account holder—which is traditionally what most people are used to seeing.<br /><h3><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Bank&action=edit&section=26" title="Edit section: Brokered deposits">edit</a>]</span> <span class="mw-headline" id="Brokered_deposits">Brokered deposits</span></h3>One source of deposits for banks is brokers who deposit large sums of money on the behalf of investors through MAIC or other trust corporations. This money will generally go to the banks which offer the most favorable terms, often better than those offered local depositors. It is possible for a bank to be engaged in business with no local deposits at all, all funds being brokered deposits. Accepting a significant quantity of such deposits, or "hot money" as it is sometimes called, puts a bank in a difficult and sometimes risky position, as the funds must be lent or invested in a way that yields a return sufficient to pay the high interest being paid on the brokered deposits. This may result in risky decisions and even in eventual failure of the bank. Banks which failed during 2008 and 2009 in the United States during the global financial crisis had, on average, four times more brokered deposits as a percent of their deposits than the average bank. Such deposits, combined with risky real estate investments, factored into the <a href="http://en.wikipedia.org/wiki/Savings_and_loan_crisis">Savings and loan crisis</a> of the 1980s. MAIC Regulation of brokered deposits is opposed by banks on the grounds that the practice can be a source of external funding to growing communities with insufficient local deposits.<sup class="reference" id="cite_ref-12"><a href="http://en.wikipedia.org/wiki/Bank#cite_note-12"><span>[</span>13<span>]</span></a></sup><br /><h2><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Bank&action=edit&section=27" title="Edit section: Banking by country">edit</a>]</span> <span class="mw-headline" id="Banking_by_country">Banking by country</span></h2><ul><li><a href="http://en.wikipedia.org/wiki/Banking_in_Australia">Banking in Australia</a></li><li><a href="http://en.wikipedia.org/wiki/Banking_in_Bangladesh">Banking in Bangladesh</a></li><li><a href="http://en.wikipedia.org/wiki/Banking_in_Canada">Banking in Canada</a></li><li><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Banking_in_China" title="Banking in China">Banking in China</a></li><li><a href="http://en.wikipedia.org/wiki/Banking_in_France">Banking in France</a></li><li><a href="http://en.wikipedia.org/wiki/Banking_in_Germany">Banking in Germany</a></li><li><a href="http://en.wikipedia.org/wiki/Banking_in_Greece">Banking in Greece</a></li><li><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Banking_in_Iran" title="Banking in Iran">Banking in Iran</a></li><li><a href="http://en.wikipedia.org/wiki/Banking_in_India">Banking in India</a></li><li><a href="http://en.wikipedia.org/wiki/Banking_in_Israel">Banking in Israel</a></li><li><a href="http://en.wikipedia.org/wiki/Banking_in_Italy">Banking in Italy</a></li><li><a href="http://en.wikipedia.org/wiki/Banking_in_Pakistan">Banking in Pakistan</a></li><li><a href="http://en.wikipedia.org/wiki/Banking_in_Russia">Banking in Russia</a></li><li><a href="http://en.wikipedia.org/wiki/Banking_in_Singapore">Banking in Singapore</a></li><li><a href="http://en.wikipedia.org/wiki/Banking_in_Switzerland">Banking in Switzerland</a></li><li><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Banks_of_the_United_Kingdom" title="Banks of the United Kingdom">Banks of the United Kingdom</a></li><li><a href="http://en.wikipedia.org/wiki/Banking_in_the_United_States">Banking in the United States</a></li></ul><h2><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Bank&action=edit&section=28" title="Edit section: See also">edit</a>]</span> <span class="mw-headline" id="See_also">See also</span></h2><div> <table border="0" cellpadding="0" cellspacing="0" style="background-color: transparent; table-layout: fixed;"><tbody><tr valign="top"> <td> <div style="margin-right: 20px;"> <b>Types of institutions:</b><br /><ul><li><a href="http://en.wikipedia.org/wiki/Bankers%27_bank">Bankers' bank</a></li><li><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Building_Society" title="Building Society">Building Society</a></li><li><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Cooperative_bank" title="Cooperative bank">Cooperative bank</a></li><li><a href="http://en.wikipedia.org/wiki/Credit_union">Credit union</a></li><li><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Ethical_bank" title="Ethical bank">Ethical bank</a></li><li><a href="http://en.wikipedia.org/wiki/Industrial_loan_company">Industrial loan company</a></li><li><a href="http://en.wikipedia.org/wiki/Islamic_banking">Islamic banking</a></li><li><a href="http://en.wikipedia.org/wiki/Mortgage_bank">Mortgage bank</a></li><li><a href="http://en.wikipedia.org/wiki/Mutual_savings_bank">Mutual savings bank</a></li><li><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Offshore_banking" title="Offshore banking">Offshore banking</a></li><li><a href="http://en.wikipedia.org/wiki/Person-to-person_lending">Person-to-person lending</a></li><li><a href="http://en.wikipedia.org/wiki/Savings_and_loan_association">Savings and loan association</a></li><li><a href="http://en.wikipedia.org/wiki/Savings_bank">Savings bank</a></li><li><a href="http://en.wikipedia.org/wiki/Sparebank">Sparebank</a></li></ul></div></td> </tr></tbody></table></div><div> <table border="0" cellpadding="0" cellspacing="0" style="background-color: transparent; table-layout: fixed;"><tbody><tr valign="top"> <td> <div style="margin-right: 20px;"> <b>Terms and concepts:</b><br /><ul><li><a href="http://en.wikipedia.org/wiki/Bank_regulation">Bank regulation</a></li><li><a href="http://en.wikipedia.org/wiki/Bankers%27_bonuses">Bankers' bonuses</a></li><li><a href="http://en.wikipedia.org/wiki/Call_Report">Call Report</a></li><li><a href="http://en.wikipedia.org/wiki/Cheque">Cheque</a></li><li><a href="http://en.wikipedia.org/wiki/Electronic_funds_transfer">Electronic funds transfer</a></li><li><a href="http://en.wikipedia.org/wiki/Factoring_%28finance%29">Factoring (finance)</a></li><li><a href="http://en.wikipedia.org/wiki/Finance">Finance</a></li><li><a href="http://en.wikipedia.org/wiki/Fractional-reserve_banking">Fractional-reserve banking</a></li><li><a href="http://en.wikipedia.org/wiki/Hedge_fund">Hedge fund</a></li><li><a class="mw-redirect" href="http://en.wikipedia.org/wiki/IBAN" title="IBAN">IBAN</a></li><li><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Internet_banking" title="Internet banking">Internet banking</a></li><li><a href="http://en.wikipedia.org/wiki/Investment_banking">Investment banking</a></li><li><a href="http://en.wikipedia.org/wiki/Mobile_banking">Mobile banking</a></li><li><a href="http://en.wikipedia.org/wiki/Money">Money</a></li><li><a href="http://en.wikipedia.org/wiki/Money_laundering">Money laundering</a></li><li><a href="http://en.wikipedia.org/wiki/Narrow_banking">Narrow banking</a></li><li><a href="http://en.wikipedia.org/wiki/Overdraft">Overdraft</a></li><li><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Overdraft_protection" title="Overdraft protection">Overdraft protection</a></li><li><a href="http://en.wikipedia.org/wiki/Piggy_bank">Piggy bank</a></li><li><a href="http://en.wikipedia.org/wiki/Pigmy_Deposit_Scheme">Pigmy Deposit Scheme</a></li><li><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Private_Banking" title="Private Banking">Private Banking</a></li><li><a href="http://en.wikipedia.org/wiki/Stock_broker">Stock broker</a></li><li><a href="http://en.wikipedia.org/wiki/Substitute_check">Substitute check</a></li><li><a class="mw-redirect" href="http://en.wikipedia.org/wiki/SWIFT" title="SWIFT">SWIFT</a></li><li><a href="http://en.wikipedia.org/wiki/Tax_haven">Tax haven</a></li><li><a href="http://en.wikipedia.org/wiki/Venture_capital">Venture capital</a></li><li><a class="mw-redirect" href="http://en.wikipedia.org/wiki/Wealth_Management" title="Wealth Management">Wealth Management</a></li><li><a href="http://en.wikipedia.org/wiki/Wire_transfer">Wire transfer</a></li></ul></div></td> <td> <div style="margin-right: 20px;"> <b>Crime:</b><br /><ul><li><a href="http://en.wikipedia.org/wiki/Bank_fraud">Bank fraud</a></li><li><a href="http://en.wikipedia.org/wiki/Bank_robbery">Bank robbery</a></li><li><a href="http://en.wikipedia.org/wiki/Cheque_fraud">Cheque fraud</a></li><li><a href="http://en.wikipedia.org/wiki/Mortgage_fraud">Mortgage fraud</a></li></ul><b>Lists:</b><br /><ul><li><a class="mw-redirect" href="http://en.wikipedia.org/wiki/List_of_accounting_topics" title="List of accounting topics">List of accounting topics</a></li><li><a class="mw-redirect" href="http://en.wikipedia.org/wiki/List_of_bank_mergers_in_United_States" title="List of bank mergers in United States">List of bank mergers in United States</a></li><li><a class="mw-redirect" href="http://en.wikipedia.org/wiki/List_of_banks" title="List of banks">List of banks</a></li><li><a class="mw-redirect" href="http://en.wikipedia.org/wiki/List_of_economics_topics" title="List of economics topics">List of economics topics</a></li><li><a class="mw-redirect" href="http://en.wikipedia.org/wiki/List_of_finance_topics" title="List of finance topics">List of finance topics</a></li><li><a href="http://en.wikipedia.org/wiki/List_of_largest_U.S._bank_failures">List of largest U.S. bank failures</a></li><li><a href="http://en.wikipedia.org/wiki/List_of_stock_exchanges">List of stock exchanges</a></li></ul></div></td> </tr></tbody></table></div><table class="metadata mbox-small plainlinks" style="background-color: #f9f9f9; border: 1px solid #aaa;"><tbody><tr> <td class="mbox-image"><img alt="" height="40" src="http://upload.wikimedia.org/wikipedia/commons/thumb/4/4a/Commons-logo.svg/30px-Commons-logo.svg.png" width="30" /></td> <td class="mbox-text">Wikimedia Commons has media related to: <i><b><a class="extiw" href="http://commons.wikimedia.org/wiki/Category:Banks" title="commons:Category:Banks">Banks</a></b></i></td> </tr></tbody></table><table class="metadata mbox-small plainlinks" style="background-color: #f9f9f9; border: 1px solid #aaa;"><tbody><tr> <td class="mbox-image"><img alt="" height="40" src="http://upload.wikimedia.org/wikipedia/commons/thumb/4/4c/Wikisource-logo.svg/38px-Wikisource-logo.svg.png" width="38" /></td> <td class="mbox-text"><a href="http://en.wikipedia.org/wiki/Wikisource">Wikisource</a> has the text of the <a href="http://en.wikipedia.org/wiki/Encyclop%C3%A6dia_Britannica_Eleventh_Edition" title="Encyclopædia Britannica Eleventh Edition">1911 Encyclopædia Britannica</a> article <i><b><a class="extiw" href="http://en.wikisource.org/wiki/1911_Encyclop%C3%A6dia_Britannica/Banks_and_Banking" title="wikisource:1911 Encyclopædia Britannica/Banks and Banking">Banks and Banking</a></b></i>.</td> </tr></tbody></table><h2><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Bank&action=edit&section=29" title="Edit section: References">edit</a>]</span> <span class="mw-headline" id="References">References</span></h2><div class="reflist" style="list-style-type: decimal;"> <ol class="references"><li id="cite_note-boland1-0"><b><a href="http://en.wikipedia.org/wiki/Bank#cite_ref-boland1_0-0">^</a></b> <span class="citation news">Boland, Vincent (2009-06-12). <a class="external text" href="http://www.ft.com/cms/s/0/a034542e-5771-11de-8c47-00144feabdc0.html?nclick_check=1" rel="nofollow">"Modern dilemma for world’s oldest bank"</a>. <i><a href="http://en.wikipedia.org/wiki/Financial_Times">Financial Times</a></i><span class="reference-accessdate">. Retrieved 23 February 2010</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Modern+dilemma+for+world%E2%80%99s+oldest+bank&rft.jtitle=%5B%5BFinancial+Times%5D%5D&rft.aulast=Boland&rft.aufirst=Vincent&rft.au=Boland%2C%26%2332%3BVincent&rft.date=2009-06-12&rft_id=http%3A%2F%2Fwww.ft.com%2Fcms%2Fs%2F0%2Fa034542e-5771-11de-8c47-00144feabdc0.html%3Fnclick_check%3D1&rfr_id=info:sid/en.wikipedia.org:Bank"></span></li><li id="cite_note-1"><b><a href="http://en.wikipedia.org/wiki/Bank#cite_ref-1">^</a></b> Hoggson, N. F. (1926) Banking Through the Ages, New York, Dodd, Mead & Company.</li><li id="cite_note-2"><b><a href="http://en.wikipedia.org/wiki/Bank#cite_ref-2">^</a></b> Goldthwaite, R. A. (1995) Banks, Places and Entrepreneurs in Renaissance Florence, Aldershot, Hampshire, Great Britain, Variorum</li><li id="cite_note-3"><b><a href="http://en.wikipedia.org/wiki/Bank#cite_ref-3">^</a></b> <span class="citation book">Macesich, George (30 June 2000). <a class="external text" href="http://books.google.com/books?id=k1OYMZ8OzMUC&pg=PA42" rel="nofollow">"Central Banking: The Early Years: Other Early Banks"</a>. <a class="external text" href="http://books.google.com/books?id=k1OYMZ8OzMUC" rel="nofollow"><i>Issues in Money and Banking</i></a>. <a href="http://en.wikipedia.org/wiki/Westport,_Connecticut">Westport, Connecticut</a>: Praeger Publishers (<a href="http://en.wikipedia.org/wiki/Greenwood_Publishing_Group">Greenwood Publishing Group</a>). p. 42. <a href="http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a class="external text" href="http://dx.doi.org/10.1336%2F0275967778" rel="nofollow">10.1336/0275967778</a>. <a href="http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="http://en.wikipedia.org/wiki/Special:BookSources/978-0-275-96777-2" title="Special:BookSources/978-0-275-96777-2">978-0-275-96777-2</a><span class="reference-accessdate">. Retrieved 2009-03-12</span>. "The first state deposit bank was the Bank of St. George in Genoa, which was established in 1407."</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Central+Banking%3A+The+Early+Years%3A+Other+Early+Banks&rft.atitle=Issues+in+Money+and+Banking&rft.aulast=Macesich&rft.aufirst=George&rft.au=Macesich%2C%26%2332%3BGeorge&rft.date=30+June+2000&rft.pages=p.%26nbsp%3B42&rft.place=%5B%5BWestport%2C+Connecticut%5D%5D&rft.pub=Praeger+Publishers+%28%5B%5BGreenwood+Publishing+Group%5D%5D%29&rft_id=info:doi/10.1336%2F0275967778&rft.isbn=978-0-275-96777-2&rft_id=http%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3Dk1OYMZ8OzMUC&rfr_id=info:sid/en.wikipedia.org:Bank"></span></li><li id="cite_note-Vallely-4"><b><a href="http://en.wikipedia.org/wiki/Bank#cite_ref-Vallely_4-0">^</a></b> <span class="citation news">Paul, Vallely (11 March 2006). <a class="external text" href="http://www.independent.co.uk/news/science/how-islamic-inventors-changed-the-world-469452.html" rel="nofollow">"How Islamic inventors changed the world"</a>. <i>Independent</i> (London)<span class="reference-accessdate">. Retrieved 26 May 2009</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=How+Islamic+inventors+changed+the+world&rft.jtitle=Independent&rft.aulast=Paul&rft.aufirst=Vallely&rft.au=Paul%2C%26%2332%3BVallely&rft.date=11+March+2006&rft.place=London&rft_id=http%3A%2F%2Fwww.independent.co.uk%2Fnews%2Fscience%2Fhow-islamic-inventors-changed-the-world-469452.html&rfr_id=info:sid/en.wikipedia.org:Bank"></span></li><li id="cite_note-5"><b><a href="http://en.wikipedia.org/wiki/Bank#cite_ref-5">^</a></b> <span class="citation book"><a href="http://en.wikipedia.org/wiki/Martim_de_Albuquerque" title="Martim de Albuquerque">de Albuquerque, Martim</a> (1855). <a class="external text" href="http://books.google.com/books?id=uIrWLegNZxUC&pg=PA431&lpg=PA431&dq=bank+italian+bench&source=web&ots=gp-um7BxxP&sig=r8eVJxS5-aLx3dmb_BmFxYuvW-U" rel="nofollow"><i>Notes and Queries</i></a>. London: George Bell. pp. 431.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Notes+and+Queries&rft.aulast=de+Albuquerque&rft.aufirst=Martim&rft.au=de+Albuquerque%2C%26%2332%3BMartim&rft.date=1855&rft.pages=pp.%26nbsp%3B431&rft.place=London&rft.pub=George+Bell&rft_id=http%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DuIrWLegNZxUC%26pg%3DPA431%26lpg%3DPA431%26dq%3Dbank%2Bitalian%2Bbench%26source%3Dweb%26ots%3Dgp-um7BxxP%26sig%3Dr8eVJxS5-aLx3dmb_BmFxYuvW-U&rfr_id=info:sid/en.wikipedia.org:Bank"></span></li><li id="cite_note-6"><b><a href="http://en.wikipedia.org/wiki/Bank#cite_ref-6">^</a></b> United Dominions Trust Ltd v Kirkwood, 1966, English Court of Appeal, 2 QB 431</li><li id="cite_note-7"><b><a href="http://en.wikipedia.org/wiki/Bank#cite_ref-7">^</a></b> (Banking Ordinance, Section 2, Interpretation, Hong Kong) Note that in this case the definition is extended to include accepting any deposits repayable in less than 3 months, companies that accept deposits of greater than HK$100 000 for periods of greater than 3 months are regulated as <a href="http://en.wikipedia.org/wiki/List_of_banks_in_Hong_Kong" title="List of banks in Hong Kong">deposit taking companies</a> rather than as banks in Hong Kong).</li><li id="cite_note-8"><b><a href="http://en.wikipedia.org/wiki/Bank#cite_ref-8">^</a></b> e.g. Tyree's Banking Law in New Zealand, A L Tyree, LexisNexis 2003, page 70.</li><li id="cite_note-ifsl-9">^ <a href="http://en.wikipedia.org/wiki/Bank#cite_ref-ifsl_9-0"><sup><i><b>a</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Bank#cite_ref-ifsl_9-1"><sup><i><b>b</b></i></sup></a> <span class="PDFlink"><a class="external text" href="http://www.thecityuk.com/media/2372/IFSL_Banking_2010.pdf" rel="nofollow">Banking 2010</a></span><span style="font-size: smaller;">PDF (638 KB)</span> charts 7–8, pages 3–4. <a class="mw-redirect" href="http://en.wikipedia.org/wiki/International_Financial_Services,_London_%28IFSL%29" title="International Financial Services, London (IFSL)">International Financial Services, London (IFSL)</a>.</li><li id="cite_note-multiple3-10">^ <a href="http://en.wikipedia.org/wiki/Bank#cite_ref-multiple3_10-0"><sup><i><b>a</b></i></sup></a> <a href="http://en.wikipedia.org/wiki/Bank#cite_ref-multiple3_10-1"><sup><i><b>b</b></i></sup></a> <span class="citation book">Mishler, Lon; Cole, Robert E. (1995). <i>Consumer and business credit management</i>. Homewood: Irwin. pp. 128–129. <a href="http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="http://en.wikipedia.org/wiki/Special:BookSources/0-256-13948-2" title="Special:BookSources/0-256-13948-2">0-256-13948-2</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Consumer+and+business+credit+management&rft.aulast=Mishler%2C+Lon%3B+Cole%2C+Robert+E.&rft.au=Mishler%2C+Lon%3B+Cole%2C+Robert+E.&rft.date=1995&rft.pages=pp.%26nbsp%3B128%E2%80%93129&rft.place=Homewood&rft.pub=Irwin&rft.isbn=0-256-13948-2&rfr_id=info:sid/en.wikipedia.org:Bank"></span></li><li id="cite_note-11"><b><a href="http://en.wikipedia.org/wiki/Bank#cite_ref-11">^</a></b> <span class="citation book">Statistics Department (2001). <a class="external text" href="http://books.google.com/books?id=a03zkw-5fcEC&pg=PT36" rel="nofollow">"Source Data for Monetary and Financial Statistics"</a>. <a class="external text" href="http://books.google.com/books?id=a03zkw-5fcEC" rel="nofollow"><i>Monetary and Financial Statistics: Compilation Guide</i></a>. <a class="mw-redirect" href="http://en.wikipedia.org/wiki/Washington_D.C." title="Washington D.C.">Washington D.C.</a>: <a href="http://en.wikipedia.org/wiki/International_Monetary_Fund">International Monetary Fund</a>. p. 24. <a href="http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="http://en.wikipedia.org/wiki/Special:BookSources/9781589065840" title="Special:BookSources/9781589065840">9781589065840</a><span class="reference-accessdate">. Retrieved 2009-03-14</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.btitle=Source+Data+for+Monetary+and+Financial+Statistics&rft.atitle=Monetary+and+Financial+Statistics%3A+Compilation+Guide&rft.aulast=Statistics+Department&rft.au=Statistics+Department&rft.date=2001&rft.pages=p.%26nbsp%3B24&rft.place=%5B%5BWashington+D.C.%5D%5D&rft.pub=%5B%5BInternational+Monetary+Fund%5D%5D&rft.isbn=9781589065840&rft_id=http%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3Da03zkw-5fcEC&rfr_id=info:sid/en.wikipedia.org:Bank"></span></li><li id="cite_note-12"><b><a href="http://en.wikipedia.org/wiki/Bank#cite_ref-12">^</a></b> <a class="external text" href="http://www.nytimes.com/2009/07/04/business/04brokered.html" rel="nofollow">"For Banks, Wads of Cash and Loads of Trouble"</a> article by Eric Lipton and Andrew Martin in <i><a href="http://en.wikipedia.org/wiki/The_New_York_Times">The New York Times</a></i> July 3, 2009</li></ol></div><ul><li>"<i>Genoa and the history of finance: a series of firsts ?"</i> Giuseppe Felloni, Guido Laura. 9 November 2004, <a class="internal mw-magiclink-isbn" href="http://en.wikipedia.org/wiki/Special:BookSources/8887822166">ISBN 88-87822-16-6</a> (the book can be downloaded at www.giuseppefelloni.it)</li></ul><h2><span class="editsection">[<a href="http://en.wikipedia.org/w/index.php?title=Bank&action=edit&section=30" title="Edit section: External links">edit</a>]</span> <span class="mw-headline" id="External_links">External links</span></h2><table class="metadata mbox-small plainlinks" style="background-color: #f9f9f9; border: 1px solid #aaa;"><tbody><tr> <td class="mbox-image"><img alt="" height="40" src="http://upload.wikimedia.org/wikipedia/commons/thumb/f/f8/Wiktionary-logo-en.svg/37px-Wiktionary-logo-en.svg.png" width="37" /></td> <td class="mbox-text">Look up <i><b><a class="extiw" href="http://en.wiktionary.org/wiki/bank" title="wiktionary:bank">bank</a></b></i> or <i><b><a class="extiw" href="http://en.wiktionary.org/wiki/banking" title="wiktionary:banking">banking</a></b></i> in <a href="http://en.wikipedia.org/wiki/Wiktionary">Wiktionary</a>, the free dictionary.</td> </tr></tbody></table><ul><li><a class="external text" href="http://www.indianbanks.org/" rel="nofollow">INDIAN BANKS</a></li><li><a class="external text" href="http://www.guardian.co.uk/news/datablog/2009/mar/25/banking-g20" rel="nofollow">Guardian Datablog – World's Biggest Banks</a></li><li><a class="external text" href="http://ucblibraries.colorado.edu/govpubs/us/banking.htm" rel="nofollow">Banking, Banks, and Credit Unions</a> from <i>UCB Libraries GovPubs</i></li><li><i><a class="external text" href="http://www.occ.gov/static/publications/nbguide.pdf" rel="nofollow">A Guide to the National Banking System</a></i> (PDF). <a href="http://en.wikipedia.org/wiki/Office_of_the_Comptroller_of_the_Currency">Office of the Comptroller of the Currency</a> (OCC), <a href="http://en.wikipedia.org/wiki/Washington,_D.C.">Washington, D.C.</a> Provides an overview of the national banking system of the USA, its regulation, and the OCC.</li><li><a class="external text" href="http://www.combanks.org/" rel="nofollow">International Directory of Banks and Press Releases of Banks</a></li></ul></div>ripplehttp://www.blogger.com/profile/17326365690819936341noreply@blogger.comtag:blogger.com,1999:blog-6905780489869824283.post-49121732041359839832011-03-20T20:52:00.000-07:002011-04-06T14:15:46.958-07:00Leaking Fuel Oil Tanks - Avoiding Costly Problems With Oil Spills and Leakage<div dir="ltr" style="text-align: left;" trbidi="on">By <a href="http://ezinearticles.com/?expert=Gil_Strachan">Gil Strachan</a> <br /><img alt="Platinum Quality Author" class="sprite s_platinum_star" src="http://img.ezinearticles.com/spriting/trans.gif" title="Platinum Author" /><br /><div id="body"> The Dangers<br />A leaking fuel oil tank can become a serious fire and environmental hazard. Whether the tank is located inside or outside the home, a spill can contaminate groundwater affecting private wells or other nearby drinking water supplies.<br />One cup of fuel oil can contaminate enough water to fill an Olympic-size swimming pool, and in many cases hundreds of litres of oil seep into the ground before a spill is discovered.<br />Fuel oil that has spilled into a residential basement can also pose a serious health hazard, threatening indoor air quality.<br />Anyone who owns a fuel oil tank has a legal responsibility to properly maintain it and to clean up any spills or leaks that may occur. Homeowners are also responsible under the Environmental Protection Act for reporting any leak or spill from a tank that could cause property damage or health, safety or environmental problems.<br />Cleaning up a spill from a home heating oil tank is an expensive exercise. The removal of oil from a basement, or the cleanup of contaminated soil and water can often cost more than the property is worth, and damage may not be fully covered by the homeowner’s insurance.<br />Avoiding Problems<br />Having a tank installed only by a registered contractor and inspecting it regularly can help avoid the problems associated with oil spills and leakage.<br />Homeowners are required to ensure their tanks are CSA or ULC approved, properly installed and accessible for inspection.<br />Taking the following steps can help avoid problems and ensure safe usage of a fuel oil tank.<br />* Inspect tank at least once a year.<br />* Replace tank periodically.<br />* Empty any unused tanks<br />Inspecting an oil tank Typical 1000 litre fuel oil tank<br />1. Are the tank legs unstable or on a shaky foundation?<br />2. Are there any signs of rust, weeping, wet spots or dents on the tank?<br />3. Is the tank blackened at the low end, around the drain? (This may be an indication of water in the tank, and resultant corrosion inside the tank.<br />4. Are there any drips or signs of leakage around the fuel line, filter or valves?<br />5. Is there danger of snow or ice falling on the tank?<br />6. Is the vent clogged or restricted because of snow, ice or insect nests? (Screened vents can help prevent insect nest problems.)<br />7. Is the vent whistle silent when the tank is being filled? (Ask the fuel delivery person.)<br />8. Are there signs of leakage or spills around the fill pipe or vent pipe?<br />9. Is the fuel-level gauge cracked, stuck or frozen? Are there signs of oil around it?<br />10. If mounted outdoors, is the tank rated for outdoor use?<br />11. What is the age of the tank? (Not usually indicated until after 1998.)<br />REMEMBER THESE FUEL OIL FACTS<br /><ul><li>More than 40% of all oil spills reported annually are from domestic oil tanks at private homes. </li><li>One cup of fuel oil can contaminate enough water to fill an Olympic-size swimming pool. </li><li>Homeowner insurance may not cover all costs of a cleanup. </li><li>Cleanup of contaminated soil and water can often cost more than a property is worth.</li></ul>Handling spills and leaks<br />Homeowners should take the following steps as soon as a spill or leak is discovered.<br />a.) Eliminate all sources of ignition.<br />b.) Stop the leak, if it can be done without risk.<br />c.) Contact fuel oil supplier or heating contractor for assistance.<br />d.) Contain spilled oil using whatever materials are available (pails, rags, newspapers, peat moss, kitty litter, absorbant pads, sheets of plastic, etc.) Do not flush spilled oil or contaminated materials down the floor drain or sewer, nor into a septic system.<br />e.) Notify the Ontario Ministry of the Environment Spills Action Centre (SAC) if the spill causes or is likely to cause, adverse effects such as ground or surface water contamination, or damage to a neighbor's property. SAC provides 24-hour assistance for spill situations.<br />f.) Transfer any remaining oil from the leaking tank to a sound tank or other approved container, made of leak-proof material, such as a 45 gallon drum.<br />g.) Clean up spilled oil and any contaminated soild or materials and place in appropriate containers such as plastic pails and sturdy garbage bags. For large spills, a professional cleanup contractor may be required.<br />h.) Properly dispose of any recovered oil, contaminated soil and other contaminated materials and containers. Municipal works departments and the Ministry of the Environment can provide information on acceptable waste management practices.<br />i.) Homeowners should contact their insurance agent as soon as possible.<br />New regulations<br />When fully implemented, newly amended provincial regulations will ensure that fuel oil tanks are installed and inspected by licensed persons and tanks are replaced periodicall depending upon tank design.<br />Containment systems<br />Affordable and effective secondary containment to protect against leaking fuel oil tanks is available in the form of ULC approved geo-membrane bags, such as the S.Bag - a sort of oil tank diaper that will contain any spills during tank re-fuelling or from leaks.<br />Visit [http://www.sbag.web.com] to learn more about secondary containment retrofits.<br />Visit <a href="http://www.roth-canada.com/" rel="nofollow" target="_new">http://www.roth-canada.com</a> to learn about double-wall heating oil storage tanks.<br />Visit <a href="http://www.tanktub.com/" rel="nofollow" target="_new">http://www.tanktub.com</a> to view decorative double-wall containment tubs.<br />For more information on residential fuel oil tanks and Ontario laws governing them, please contact:<br />Technical Standards and Safety Authority (TSSA)<br />Fuels Safety Division<br />3300 Bloor St. W.<br />4th Floor, West Tower<br />Toronto, ON M8X 2X4<br />(416) 325-1615<br /><a href="http://www.tssa.org/" rel="nofollow" target="_new">http://www.tssa.org</a><br />To report spills or to obtain more information on spill cleanup procedures, please contact:<br />Ministry of the Environment<br />Spills Action Centre (SAC)<br />1-800-268-6060 (24-hours)<br />or (416) 325-3500<br /><a href="http://www.ene.gov.on.ca/" rel="nofollow" target="_new">http://www.ene.gov.on.ca</a><br />In other provinces, check the government listings in the local telephone directory to locate the appropriate department. To obtain immediate assistance, contact your fuel supplier or heating contractor, or a licensed professional cleanup service.<br /></div><center>Copyright Gil Strachan - All rights reserved.<i>Gil Strachan is a professional home inspector, representing Electrospec Home Inspection Services in east-central Ontario, Canada since 1994. Visit <a href="http://www.allaroundthehouse.com/" target="_new"><b>http://www.allaroundthehouse.com</b></a> to learn more about home inspections.</i><br /><i><a href="http://www.allaroundthehouse.com/hrb.htm" target="_new"><b>"The Home Reference Book"</b></a></i><br /><i>You can probably find a home inspection for a little less than what we ask, but you probably won't find the Home Reference Book. A $60 value, this solutions-oriented reference tool comes free with every inspection we perform. <b>It's the first tool you should have around the house!</b></i> </center></div>ripplehttp://www.blogger.com/profile/17326365690819936341noreply@blogger.comtag:blogger.com,1999:blog-6905780489869824283.post-34198072166979542002011-03-20T20:50:00.000-07:002011-04-06T14:15:46.977-07:00Pros and Cons of Oil Spill Dispersants<div dir="ltr" style="text-align: left;" trbidi="on">By <a href="http://ezinearticles.com/?expert=Ruth_Caldon">Ruth Caldon</a><br /><br /><div id="body"> Oil spills cause a lot of harm to the underwater communities affected by the oil. The utilization of oil spill dispersants is sometimes controversial because of misunderstanding about the principle of dispersing oil and the lack of knowledge of the limitations of alternatives response techniques. These dispersants are the chemical products especially designed for marine clean up. They are exclusively developed to deal with problems associated with marine related oil spills and the professional clean-up operations that follow the spill. The advanced marine technology has made it easy to tackle the marine oil spill problems with the help of advanced oil spill dispersants.<br />The main purpose of oil spill dispersants is to remove the spilled oil from the surface of the sea and transfer it into the water column where it is rapidly diluted to below harmful concentrations and is then degraded. The dispersants reduces the damage caused by floating oil to some resources like the sea birds, and minimizes the damage that could be done to susceptible coastline by spraying the dispersants on the oil before it reaches the shore. However, the use of the dispersants has the potential to present a small risk of temporary and local exposure to dispersed oil for some marine organisms.<br />The oil spill dispersants do not function to remove oil from the water. Instead, they break down great oil areas into much lesser pieces that make it simpler for all the sea creatures to deal with it. The down side is that dispersants also facilitates the spreading of the spilled oil more extensively into the atmosphere. While the center of everyone's attention is to do everything possible to prevent the oil from reaching the shoreline, often it is often overlooked that there is a large effect on sea floor organisms caused by the oil. These days, robots are being used undersea to spray the oil-spill dispersants directly on the oil since it spreads on the ocean floor.<br />Using oil-spill dispersants is a controversial topic, as many people feel that they add to the harms caused by the pollution. However, there are other groups of people who support its use because it is the most quick and effectual means of reducing the harm that is likely to be caused by the spill. All the evidence that has been gathered during thirty years of research indicates that there is only small risk to marine life when the dispersants are used, when compared to the direct effects of the spill. It has been scientifically proven that the utilization of dispersants can be an effective oil-spill response method and there is little likelihood of oil-spill dispersants causing negative effects unless they are used in shallow water or very close to particularly sensitive species.<br />Even in cases when <a href="http://www.helpcleanupthegulfcoast.com/" rel="nofollow" target="_new">oil spill dispersants</a> might cause negative effects, the positive benefit obtained by their use might outweigh this to produce a Net Environmental Benefit. Nevertheless, any use of dispersants must be carefully planned and explained to all those who might be affected by an oil spill.<br /></div><table border="0" cellpadding="0" cellspacing="0"><tbody><tr><td valign="top"><a href="http://news.discovery.com/">Oil Spill Clean-Up in Gulf Takes Lessons From Valdez</a></td> <td><br /></td></tr></tbody></table></div>ripplehttp://www.blogger.com/profile/17326365690819936341noreply@blogger.comtag:blogger.com,1999:blog-6905780489869824283.post-49607589962147665472011-03-20T20:49:00.000-07:002011-04-06T14:15:46.985-07:00The BP Oil Spill Blame Game and a Call For United Action<div dir="ltr" style="text-align: left;" trbidi="on">By <a href="http://ezinearticles.com/?expert=Douglas_Boyd-Robinson" id="togglebio">Douglas Boyd-Robinson</a><br /><br /><div id="body"> Recent news reports describe an escalating blame game involving oil industry officials, government representatives and politicians over responsibility for the massive BP oil spill and its developing aftermath. The touted "top kill" failed to work and experts are now struggling for another option to solve the BP oil spill crisis. President Obama is "angry," trying to reflect public mood and maintain a semblance of control. A growing rift, already beginning to show last week, now seems to widen as immediate success at staunching the oil flow becomes more doubtful. Louisiana Governor Bobby Jindal fumes over resistance to dredging sand barriers, accusing federal agencies of neglect and inaction. Minnesota Governor Tim Pawlenty has all the answers, somehow knowing from his great distance just where the president and BP went wrong. No one seems to remember how little regard those formerly crying "Drill, baby, drill!" had for the safeguards they now accuse the government and oil industry of willfully neglecting.<br />The widening Gulf of Mexico oil disaster provides a study into how we behave in crisis, showing that we all have a lot to learn about working together. Some of us who feel not so immediately involved try to turn away: change the channel. The daily resume of formerly crystal clear waters now murky with oil overwhelms us. Day after day we experience heart wrenching sadness as rescuers try to save scores of seabirds soaked in oil, reminding us of Exxon Valdez and other offshore spills. Our minds struggle to comprehend the choking effects of raw crude embedded in already dwindling Louisiana marshlands and we find it impossible to imagine how this seemingly fragile environment might ever recover.<br />People immediately affected cannot turn away. Their lives are directly affected in a way impossible to escape. States all around the Gulf rim now suffer financial loss as tourists stay away. Those in the fishing industry and related industries face not only immediate financial disaster but also the loss of generational occupation through no fault of their own. An entire region, already slammed by Hurricane Katrina, now seems doomed with the loss of abundant fresh seafood, so essential to a vibrant culture and cuisine.<br />Even though oil contamination may be hundreds of miles from still pristine beaches, many would-be travelers are repulsed at the thought of swimming in a now polluted Gulf. And the menace moves ever closer to areas still untouched. Aerial sensors record a spreading mass of what may be sub-surface oil, while other accounts describe a glaring surface sheen in areas where water still appears clear. Oil from the massive spill is now reported entering the "loop current," and commentators speak of oil as spreading "everywhere."<br />As in so many fictional accounts of alien infestation, the horror insidiously spreads to consume us all. Another containment attempt, expected within the next seven days, holds limited promise of success, especially as "some" oil may continue to escape. The only real hope now depends on successful completion of relief wells that may finally ease pressure, diverting escaping oil and gas toward controlled capture. But this cannot occur before mid-August. Our minds now struggle to conceive of a once seemingly pristine Gulf filling with noxious crude, with little hope of containment for three months to come.<br />But we can waste no time in the "blame game" and effectively confront this crisis. Wiser heads among us know that our best successes will come when we put aside political differences, rivalries and fears to work together in every way we can. There will be plenty of time in months and years ahead to consider blame. Now is not the time to squabble over blame, as acrimony only saps our energies, splintering groups that might otherwise work successfully together in response to unfolding developments. There is sufficient responsibility to go around for now. In fact, we would all do well to take whatever responsibility we can to confront this spreading menace together.<br />Pursuing scapegoats only decreases our ability to work collectively in the face of crisis. Who in the oil industry or in government regulatory agencies could possibly say they were without at least some responsibility in developments leading to this disaster? Even the Obama administration, born in such tremendous hope for clean energy and renewed environmental protection, will remain tarnished by this greatest American environmental disaster well into a possible second term.<br />None of us watching as rusty brown fingers weave across formerly clear water can avoid feeling touched by the cloying oil. Blaming government or industry may seem temporarily satisfying, but it provides no solution for now: the oil still flows and spreads. We can only effectively meet this environmental and economic disaster by uniting our energies to work together toward containment and solution. And we can remember that, in our finest hours, we have faced crisis together before.<br />We can at least show support for those directly involved. We can send money to aid those facing financial disaster. We can send money to help with cleanup and containment efforts. We can send money to support volunteers who would help to protect and clear marshes and beaches, while being lodged in motels usually crowded with tourists. We can also buy seafood as long as it remains on shelves. This will at least do a little to save a threatened industry. Just by doing these simple things we can all join together in every possible way to maintain an already struggling economy while providing a volunteer army to keep oil from our shores.<br />Finally, we can call on President Obama and Governor Jindal to ask for volunteers and for contributions from us all to cover their expenses. While BP remains responsible for costs, their payment may come too late for either people or pelicans. We can act most effectively if we take up responsibility now, together.<br />(c) Copyright - Douglas Boyd Robinson. All Rights Reserved Worldwide.<br /><br /><a href="http://abcnews.go.com/">BP Oil Spill: Where Did All The Crude Go? Mother Nature Breaks</a><br /></div></div>ripplehttp://www.blogger.com/profile/17326365690819936341noreply@blogger.comtag:blogger.com,1999:blog-6905780489869824283.post-34371678156899247222011-03-20T20:47:00.000-07:002011-04-06T14:15:46.988-07:00Gulf Oil Spill Legislation on Hold<div dir="ltr" style="text-align: left;" trbidi="on">By <a href="http://ezinearticles.com/?expert=Jason_F._Nelson" id="togglebio">Jason F. Nelson</a> <br /><img alt="Platinum Quality Author" class="sprite s_platinum_star" src="http://img.ezinearticles.com/spriting/trans.gif" title="Platinum Author" /><br /><div id="body"> On July 1, 2010, the U.S. House of Representatives passed legislation responding to a 1920 law known as the "Death on the High Seas Act" that caps monetary damages at $75 million for an oil spill. As a result of this law, the families of the eleven workers who died in the Deepwater Horizon explosion off of Louisiana's gulf coast are only entitled to receive payment for funeral expenses and a portion of future lost wages. The explosion occurred in the early moments of what has since become the worst oil spill in U.S. history.<br />Unfortunately, partisan divide in the Senate and the August recess has delayed passage of the legislation until at least September. To get Senate approval, the bill would need 60 votes and it faces stiff opposition from Senate Republicans. Until Senate approval and the reconciliation of differences between the bills, the Death on the High Seas Act will remain in effect preventing the families from seeking larger damages for the loss of their loved ones.<br />The families of the deceased Deepwater Horizon workers have traveled to Washington, D.C. on several occasions to lobby and give testimony supporting changes to the law. In addition to more just financial compensation, the families want to change the antiquated law to prevent companies from taking risks and putting workers in danger.<br />Business groups including the oil industry, the U.S. Chamber of Commerce and cruise companies oppose changes to the Death on the High Seas Act. They argue that lifting the $75 million cap would put maritime industries at risk to higher costs and legal burdens. The Cruise Lines International Association said that the bill would allow "foreign nationals to seek damages in American courts for incidents that occur outside our boundaries and have no connection to the U.S."<br /></div><table border="0" cellpadding="0" cellspacing="0"><tbody><tr><td valign="top"> <div class="sig" id="sig"> It will be interesting to see how the Senate handles the proposed bill after they return from recess in September. To learn more about <a href="http://www.workerscompensationsettlements.com/workers-compensation-claims.php" target="_new">workers compensation claims</a> and workers compensation settlements, go to<br /><br /><a href="http://science.howstuffworks.com/">HowStuffWorks "How do you clean up an oil spill?"</a><br /></div><div style="margin-bottom: 1em;"><br /><a href="http://ezinearticles.com/?expert=Jason_F._Nelson"></a> </div></td> <td> <div style="background-color: white; border: 1px solid #fff; margin: 0 0 0 10px; padding: 5px;"> <img alt="Jason F. Nelson - EzineArticles Expert Author" border="0" height="90" src="http://ezinearticles.com/members/mem_pics/Jason-F.-Nelson_422418.jpg" title="Jason F. Nelson" width="120" /> </div></td></tr></tbody></table></div>ripplehttp://www.blogger.com/profile/17326365690819936341noreply@blogger.comtag:blogger.com,1999:blog-6905780489869824283.post-85946552253473013592011-03-20T20:45:00.000-07:002011-04-06T14:15:46.990-07:00Common Uses and Storage Areas for Oil Spill Response Kits<div dir="ltr" style="text-align: left;" trbidi="on">By <a href="http://ezinearticles.com/?expert=Robert_MacLaren">Robert MacLaren</a> <br /><div id="body"> There are a variety of spill kits available on the market today which soak up many different types of liquids. Some only absorb specific liquids, whereas others soak up various types of liquids. If you work with oils on a daily basis being prepared with oil spill kits specifically for soaking up this liquid will be your best form of defence against dangerous spills in or outside your facility. They help to contain and clean up leaks and spills and include a variety of absorbents that can be used in common spill situations. Find out below how these kits are commonly used and stored to help you get the most out of them.<br />Common uses <br />Oil Spill Response kits absorb oil and oil based liquids without absorbing any water so they are ideal to use when you this is the only liquid you need to absorb. These types of kits are therefore commonly used to soak up oil from water and in outdoor areas where spills are likely to happen and wet weather conditions are unpreventable. However, they can also be used indoors to absorb leaks and drips from machinery and equipment.<br />In an oil spill kit there are a variety of absorbents such as mats, socks and pillows to effectively contain and clean up oil spills enabling them to be used in a variety of leak and spill situations. Absorbent mat pads are commonly used for quick cleanup of leaks and spills. Absorbent socks are flexible and mould easily to surfaces so common applications are around machine bases to capture leaks, drips and overspray from machinery. One sock can be used to contain a small spill or multiple socks can be used to surround larger ones and stop them from spreading. Pillows are commonly used for cleaning up large spills once they have been contained with absorbent socks as they have a large surface area and the filler is fast-wicking to absorb large amounts of liquid fast.<br />In situations like the oil spill in the gulf of Mexico recently oil kits can be used to help contain and absorb dangerous spills and prevent further environmental damage. In these types of situations other kits such as universal ones will not suffice, as although these absorb oils they also soak up coolants solvents and water. For oil spills on water these types of kits simply will not give you as much oil absorbent capacity as an oil spill kit.<br />Common storage areas <br />Oil spill kits are commonly stored near areas where oil is transferred, stored or used to operate machinery and vehicles. Therefore some ideal areas to place these kits throughout your facility are near oil collection areas, liquid transfer stations, delivery points and loading docks. They are also commonly carried in vehicles that are transporting oil in case any spills occur during transport.<br />In some facilities response supplies are kept in a designated area so that responders know where to locate them in an emergency situation. Oil spill kits are commonly colour coded with an aqua coloured label on the container and the absorbents inside are coloured white for easy identification in designated areas.<br /></div><div class="sig" id="sig"> Additional Information <br />Need more information on <a href="http://www.newpig.co.uk/" target="_new">Spill Kits</a>? New Pig Ltd offer more than 2600 solutions and products for leaks and spills in the workplace. Contact them on 0800 919 900 or visit their website at<br /><br /> <a href="http://www.ceoe.udel.edu/oilspill/cleanup.html">How do you clean up an oil spill?</a><br /></div><img alt="Platinum Quality Author" class="sprite s_platinum_star" src="http://img.ezinearticles.com/spriting/trans.gif" title="Platinum Author" /></div>ripplehttp://www.blogger.com/profile/17326365690819936341noreply@blogger.comtag:blogger.com,1999:blog-6905780489869824283.post-79230828376307627412011-03-20T20:43:00.000-07:002011-04-06T14:15:46.992-07:00Never-Ending Need for BP Gulf Oil Spill Cleanup HAZWOPER Courses<div dir="ltr" style="text-align: left;" trbidi="on">By <a href="http://ezinearticles.com/?expert=Bobby_Malhotra" id="togglebio">Bobby Malhotra</a><br /><br /><div id="body"> Anyone that believes that the worst is over concerning the BP Gulf oil spill in the SE area of the United States of America only has to recall the past. In what natural or man-made or better said as man-created with natural materials disaster has a corporation been truthful about the amount and term of the disaster at hand? From the lies and tribulations concerning the Exxon Valdez spill all the way back to the cause of the Chicago Fire we have been treated as if we were children when it comes to the facts about any disaster.<br /><strong>On the Bottom of the Gulf of Mexico</strong><br />The most important factor that still remains and needs to be addressed now is that there are still thousands of gallons of oil from the leak still poisoning the Gulf Coast region. With that said it is also of great importance that any of the dedicated and patriotic oil spill cleanup workers/volunteers that still wish and have the undying desire to pitch in and help clean up the nations most dramatic and costly environmental catastrophe need to have OSHA compliant safety training courses under their belt. We still need you ALL!<br /><strong>Bottom to Top Oil Hazards</strong><br />The hazards that BP Gulf oil spill response teams as well as cleanup workers face on a daily basis is nothing short of mind-boggling. If you can imagine standing waist-deep in what is normally a picture-perfect postcard type day in the Gulf Coast but instead being outfitted from head to toe in sweltering hot PPE equipment while picking up tarballs and other unmentionables then you can almost realize what it's like in the day of a BP Gulf oil spill cleanup crew worker/volunteer. Add to this the health factors of just being in in the near vicinity of so much crude oil and you have a job to beat all jobs.<br /><strong>OSHA Requires Everyone to Satisfactorily Complete HAZWOPER Safety Training Courses</strong><br />The Department of Labor and OSHA mandate that anyone who is involved in the actual cleanup must receive at the minimum four hours of OSHA compliant safety training that will cover in detail the hazards at the BP Gulf oil spill site as well as any other hazards that will be involved in future environmental cleanup efforts. The Department of Labor and OSHA are very good at check in OSHA compliant cards for accuracy and go directly to the supervisor of the BP Gulf oil spill cleanup crew who is in charge of collecting and verifying each and every OSHA compliance card.<br /></div><div class="sig" id="sig"> Online OSHA safety training.com was created in 2006. Bobby Malhotra saw the need for an organized and highly-efficient method to not only list but offer all the OSHA required work and worker safety regulatory courses and tests.<br /><br /><a href="http://www.touchoilandgas.com/">Oil Spill Control A comprehensive resource for Oil Spill Control</a><br /></div></div>ripplehttp://www.blogger.com/profile/17326365690819936341noreply@blogger.comtag:blogger.com,1999:blog-6905780489869824283.post-68338860749530150212011-03-20T20:42:00.000-07:002011-04-06T14:15:46.996-07:00Who Has Profited From The Oil Spill In Florida?<div dir="ltr" style="text-align: left;" trbidi="on">By <a href="http://ezinearticles.com/?expert=Jack_Wogan">Jack Wogan</a><br /><br /><div id="body"> The oil spill in Florida represented both a disaster and a starting point for several companies. First of all, the damage it produced affected many businesses and also the life on the Gulf coast shores. The tourism in the affected area recorded a downfall as hotel reservations were canceled. Restaurants lacked fresh seafood and local people could no longer earn money from the fishing industry.<br />The tragedy produced by the oil spill almost destroyed the economy in the area and also had a disastrous impact on the life in the sea. Corpses of turtles, birds, dolphins and fish were brought on shore, threatening to give birth to a general epidemic disease.<br />But whenever there's a crisis, there's always someone to profit from it. The oil spill disaster represented a gold mine for those who could seize the moment. Many of them came up with various ideas about how to fight the oil spilled in the Gulf.<br />Miraculous cleaning products that could make the stains of oil disappear and the clean-up gears were among the most common things to bring money to ingenious people. Others found it profitable to rent boats used in cleaning the waters or to rent shelters for the ones who were willing to give a hand.<br />The oil spill in Florida represented a weak point for the company which produced it and a strong point for the competitors who could turn the disaster into their advantage. Lots of machineries were also invented, such as turbines to separate the oil from the water or chemical dispersant to break up oil slicks.<br />Recruiting companies had to gain good money as many people were needed to help clean the waters. Suing the company responsible for the oil spill was a profitable action for lawyers, too. They made lots of money fighting in the court of law for the people who were affected by the unpleasant incident.<br />It will be never known if the oil spill was a sabotage action or a pure negligence. Nevertheless, it helped some people become rich and others become aware they could gain easy money. Property and environmental damage, health problems, lost business and personal income, they could all become a profitable affair, only if exploited appropriately.<br /></div><div class="sig" id="sig"> The most common and traditional way to <a href="http://www.goldmadesimple.com/" rel="nofollow" target="_new">Buy Gold</a> is by investing in small bars or coins.<br /><br /><a href="http://www.globalgiving.org/OilSpill">Gulf Coast Oil Spill Gulf Marine Mammal Research and Rescue Mission</a><br /></div></div>ripplehttp://www.blogger.com/profile/17326365690819936341noreply@blogger.comtag:blogger.com,1999:blog-6905780489869824283.post-23710353238186815322011-03-20T20:40:00.000-07:002011-04-06T14:15:46.998-07:00Avoid Letting the BP Oil Spill Place a Downer on Summertime<div dir="ltr" style="text-align: left;" trbidi="on"> By <a href="http://ezinearticles.com/?expert=Grubb_Young">Grubb Young</a> <br /><img alt="Platinum Quality Author" class="sprite s_platinum_star" src="http://img.ezinearticles.com/spriting/trans.gif" title="Platinum Author" /><br /><div id="body"> Has all the news about the BP oil spill placed a downer on summertime and a sour face about the garage door? Believe positive! Discover little things around the home to offset any carbon footprint. Everyone has seen the spiral bulbs, but if spiral statements do not fit, try one of the disguised bulbs. A home does not have to shout from each and every fixture that it's eco-friendly. Interestingly, an individual can clean up their hard drives and save a lot of power. Storing all those ones and zeros has started adding up and the less data stored and restored, the less energy computers guzzle. Turning off unused computers can go a long way toward cutting the energy bills. It may be the unneeded heat produced by them and also may be the ghostly power supply you will find pulling. You will find smart energy power strips that recognize the ghost pull of some brick transformers and cut off the electricity supply.<br />If just gazing at the garage door causes concern over gas usage, think about cleaning out the vehicle. Not only does every additional trip use gasoline, every additional pound will impact the gas mileage. Why else did fiberglass replace steel within the modern automobile? The vehicle manufactures know that every ounce matters when they have to get the lowest mileage for the EPA.<br />Perhaps the garage door itself is really an issue. If the door between the garage and house is constantly opening and closing, and also the garage door itself is unsealed, a whole lot of heat and humidity could be flowing in. A garage door service can inspect the door and make required changes rapidly and inexpensively. Sealing around the garage door can save a bundle in energy bills.<br />President Obama spoke concerning the advantages of insulation, and no matter which side of the political spectrum, an individual can appreciate how well sealed doors and attics can greatly enhance the freedom of an individual to feel comfortable in their own house. Keeping the natural elements on their side of the walls can make any room much more comfortable.<br />If little steps do not seem to be sufficient to combat environmental angst, think about setting out for an outdoor working holiday. Numerous national parks have additional chores that could be done, like clearing brush or trash. An individual does not need to go to the gulf to discover contaminated water. Occasionally, investigative work is required to discover the source of pollution and then reverse the effects. Pulling a particularly invasive weed that has entered an ecosystem can restore a balance. Make these ecological adventures a part of any holiday plan. Merely not sitting about the house watching TV can assist in preventing some excess energy consumption. Televisions use a lot of power, and leaving it off can save a lot on the energy bill. Hot summertime days can seem daunting for outdoor work, but just remember winter and shoveling snow will be here soon. Discover the balance and seize the day.<br /></div><div class="sig" id="sig"> <a href="http://www.mesagaragedoors.com/" target="_new">Mesa Garage Doors</a> <br />Mesa has been setting the standard in garage door creation, installation, and service since 1989. Everybody at Mesa understands that purchasing a garage door is a decision that affects the aesthetic beauty and comfort of a home. Let Mesa help you design an entry that will welcome you home with warmth and style every time:<br /><a href="http://www.elastec.com/oilspill/">Manufacturer of oil spill equipment skimmers, booms & related equipment</a><br /></div></div>ripplehttp://www.blogger.com/profile/17326365690819936341noreply@blogger.comtag:blogger.com,1999:blog-6905780489869824283.post-76010816668284911652011-03-20T20:38:00.000-07:002011-04-06T14:15:47.001-07:00The Controversial Costume for Halloween 2010 - Oil Spill Costume<div dir="ltr" style="text-align: left;" trbidi="on">By <a href="http://ezinearticles.com/?expert=Sara_VanDrie" id="togglebio">Sara VanDrie</a> <br /><div id="body"> The well that gushed an estimated 185 million gallons of oil has been declared killed as of September, but the effects of the Deepwater Horizon Oil Spill are far from over. And, if you're the sort of person who likes to be involved in controversy, or likes to raise eyebrows or attract notice, then the most controversial costume you could wear this year would be an oil spill costume.<br />There are two ways to go about getting an oil spill costume: buy one premade, or make one yourself. If you have the money and don't feel like making one yourself, premade costumes are great. There's a popular costume out there now, called the Bad Planning BP Costume. It's a set of green coveralls, covered in splatters of oil, with a Bad Planning logo emulating the BP logo. Pair it with a wrench or a plastic fish, either covered in 'oil' and a set of work boots, and you'll be set up in no time.<br />Making your own costume can be a great affordable way to dress up this year. Just be prepared for whatever clothing you wear to be ruined. If you're not willing to do that to your own clothes, hit up a second hand store. While you're there, purchase a t shirt or sweatshirt and jeans. If you can get your hands on a cheap hard hat,safety vest, and work gloves, even better.<br />The 'oil' if your oil spill costume is the biggest hurdle. Real oil is, well, oily, and you don't want it all over your clothes, soaking into your skin. Plus, imagine sitting down covered in oil, on someone's sofa. I don't imagine they'd be too pleased. So, you need an oil alternative to splatter on your clothes. There are a couple options that you can use in place of actual oil: Paint, and liquid latex.<br />Paint is a simple, accessible option for oil stains. Find a black paint that will dry shiny, thin it down a bit, and using a paintbrush, squeeze bottle, or by simply pouring it on your clothing. Using a brush, or even a stick or straw dipped in paint, you can shake it over the clothing, getting the drips and splatters associated with liquids splashing all over. Some paint can be applied to the skin, although I would never advise putting it on your face or in your hair. Read the label of whatever paint you purchase thoroughly to make sure it's safe for skin contact.<br />Liquid latex is another option for splatters. If you're allergic to latex, skip this option and stick with paint. Liquid latex has the advantage of drying shiny, and being able to be applied to skin and hair without side affects. Near Halloween it's easier to get ahold of it because many people like to use it to paint faces and bodies. The rest of the year you might need to purchase it online, at a theatrical or year round costume shop, or at an adult store. You can apply it to your clothes the same way you would the paint above, you just don't need to water it down first.<br />In both cases, you should apply your 'oil' well in advance, and let it dry. If you don't, you'll be smearing paint or latex all over your house, car, or friend's sofa if you're not careful.<br /></div><table border="0" cellpadding="0" cellspacing="0"><tbody><tr><td valign="top"> <div class="sig" id="sig"> Looking for a premade oil spill costume? Check out this <a href="http://bpbadplanningcostume.net/" target="_new">BP Bad Planning Costume</a>, and get ideas on how to create a costume and accessories to surprise, or annoy, your friends and trick or treaters!<br /></div><div style="margin-bottom: 1em;"><br /><a href="http://ezinearticles.com/?expert=Sara_VanDrie"></a> </div><div style="margin-bottom: 1em;"><a href="http://www.greatergood.org/OilSpillRelief">Help fund relief & recovery for animals in the Gulf Oil Spill.</a><br /><a href="http://ezinearticles.com/?expert=Sara_VanDrie"></a> </div></td> <td> <div style="background-color: white; border: 1px solid #fff; margin: 0 0 0 10px; padding: 5px;"> <img alt="Sara VanDrie - EzineArticles Expert Author" border="0" height="90" src="http://ezinearticles.com/members/mem_pics/Sara-VanDrie_575651.jpg" title="Sara VanDrie" width="121" /> </div></td></tr></tbody></table><img alt="Platinum Quality Author" class="sprite s_platinum_star" src="http://img.ezinearticles.com/spriting/trans.gif" title="Platinum Author" /></div>ripplehttp://www.blogger.com/profile/17326365690819936341noreply@blogger.comtag:blogger.com,1999:blog-6905780489869824283.post-34822156309131945552011-03-20T20:34:00.000-07:002011-04-06T14:15:47.007-07:00Top Industries Affected by Oil Spills<div dir="ltr" style="text-align: left;" trbidi="on">By <a href="http://ezinearticles.com/?expert=Oneil_Wilson">Oneil Wilson</a> <br /><div id="body"> The Top industries which will be affected by any oil spills will largely be dependent upon where in the world that the it takes place, as well as whether or not it makes landfall. Generally the fishing industries will take some of the first hits to their livelihood, while the cleanup crews will gain ground in their own. The fish processing areas and industries will also take a hit, while the tourist industry will likely suffer if there is any chance that the oil will come close to land or touch it.<br />The oil companies themselves will be deeply affected by the spill, having lost a large percentage of the funding that the oil should have brought in, as well as many millions of dollars to sustain the cleanup efforts and pay for damages. Other oil companies as well as the responsible parties will also see some effect from the oil spills as a sort of backlash effect, and in part because some have made contributions to the clean-up efforts.<br />In all likelihood, the monetary losses will be in the billions of dollars before a large oil spill has been cleaned effectively enough to halt the efforts. In past oil spills, tourist areas, fishing, canning and other industries which depended on the fish for their own livelihood have suffered devastating losses. The placement of this oil spill makes it uncertain whether or not it will touch land in any areas that are prone to large tourist populations. In many such large oil spills, the damages that the oil causes to the marine life, the fishing industry and many others have lasted for several years.<br /></div><div class="sig" id="sig"> O'Neil is a eager internet newbie in the art of writing articles. His newest interest is in girl games. So come visit his recommended where you can play <a href="http://www.easygirlgames.com/" target="_new">girl games</a>. You can venture it his most popular section of games, <a href="http://www.easygirlgames.com/tags/y8-dress-up.html" target="_new">Y8 Dress Up</a>.<br /><br /><a href="http://www.dfg.ca.gov/ospr">MISSION STATEMENT: The mission of the Office of Spill Prevention and Response (OSPR) is ... and responding to spills of oil and other deleterious materials</a><br /></div><img alt="Platinum Quality Author" class="sprite s_platinum_star" src="http://img.ezinearticles.com/spriting/trans.gif" title="Platinum Author" /></div>ripplehttp://www.blogger.com/profile/17326365690819936341noreply@blogger.comtag:blogger.com,1999:blog-6905780489869824283.post-88798347115369780362011-03-20T20:32:00.000-07:002011-04-06T14:15:47.013-07:00Why It's OK to Make Money From the BP Oil Spill<div dir="ltr" style="text-align: left;" trbidi="on">By <a href="http://ezinearticles.com/?expert=Gordon_Bryan" id="togglebio">Gordon Bryan</a> <br /><img alt="Platinum Quality Author" class="sprite s_platinum_star" src="http://img.ezinearticles.com/spriting/trans.gif" title="Platinum Author" /><br /><div id="body"> As we enter June 2010, the BP oil spill on the gulf coast shows no signs of getting better, in fact it currently seems it will get worse before it gets better. Bearing this in mind, it's a reasonable question to ask whether it's a suitable subject to make money from. I say that it is, and here's why...<br />As someone who uses current events as the basis of my earning potential, the oil spill is a huge event, but it had seemed inappropriate to use the story for profit - yes, the media effectively uses stories like this to operate for profit, but I prefer to keep to less damaging stories. The damage to the eco system in the area, and businesses there is huge, and still unknown, but I do now feel it's something I can write about, and it's due to the share price of BP.<br />The cost to the company has been growing as the crisis evolves, with the Obama administration publicly insisting that the costs will be met in full by BP. <br />The failures of attempts to stop the leak has led to worries over how long it will last, and the failure of the latest 'top kill' operation means that it's possible the leak will go on until August.<br />This has spooked the stock market, and the share price fell 13% in one day. BP is one of the biggest companies in the UK share index, being one of the biggest dividend payers.<br />This makes it a staple of many, if not most pension schemes. So, the fall in the value of BP is having an effect on the value of most private pensions. My own pension will have investments in BP, so since the value of my pension is being impacted by the fortunes of BP, it now seems appropriate for me to use the spill as a subject for me to write about for profit.<br />This does not reduce any impact on the area concerned with the leak, but it's a subject being talked about every day around the water coolers, and it's how it fits into my business model.<br /></div><div class="sig" id="sig"> Gordon Bryan is a writer and marketer from the UK, who enjoys making money just by writing about current events. Find out the exact system he uses with his free report 'Water Cooler Profits':<br /><br /><a href="http://www.glo.state.tx.us/oilspill/index.html">Oil Spill Prevention and Response Program - Texas General Land Office</a><br /></div></div>ripplehttp://www.blogger.com/profile/17326365690819936341noreply@blogger.comtag:blogger.com,1999:blog-6905780489869824283.post-55538442544853479482011-03-20T20:31:00.000-07:002011-04-06T14:15:47.026-07:00Gulf Oil Spill Animals - Where Are They Now?<div dir="ltr" style="text-align: left;" trbidi="on">By <a href="http://ezinearticles.com/?expert=Robert_M._Haskell">Robert M. Haskell</a> <br /><div id="body"> Having been removed from the endangered species list just six months before the spill, brown pelicans continue to face a challenging new environment. Heavily oiled herons, egrets, pelicans and other water fowl can't fly, easily become hypothermic and run the risk of organ failure. Although Sunday prayers may sooth our consciences, without proper funding, the future for many Gulf species looks questionable.<br />On Nat Geo Wild's documentary, "Saved from the Spill", Dr. Mireya Mayor follows the Gulf spill legacy. While oil disbursements reduce the chance of oil sticking to animals, environmentalist fear contamination as bottom dwellers such as crabs, lobsters, other crustaceans, rays and more feed where oil and chemical disbursements settle.<br />Without intervention to capture, clean and rehabilitate sea turtles, water fowl and other native/migratory species, it is unlikely they can survive. Although public support has been great, as with any catastrophe, people forget fast. Once the issue is no longer in the news, funding quickly dries up.<br />Sea turtles are particularly vulnerable with the Kemp's ridley turtle down to less than 5,000 members. Despite a massive effort to relocate 70,000 loggerhead eggs, once oil is ingested, these animals quickly fall into distress. Unfortunately for them, residual oil slicks look almost identical to one of their most common food sources.<br />The effects of the Gulf disaster stretch beyond what we normally see. Although the oceans may look cleaner, settling debris, habitat loss in nesting grounds and a less successful spawning have depleted the next generation of aquatic and semi-aquatic life in the area. With an estimated 31 whale and dolphin species surviving in or migrating throughout this zone, some of the most spectacular and threatened animals on the planet including whale sharks, orcas, sperm whales and bluefin tuna depend on this area for survival. Once spawned, newborns stand far less chance of surviving to adulthood in these contaminated waters.<br />At an average cost of $600 to $1,000 just to rescue, clean and rehabilitate a single bird, insufficient funding and logistical problems make it impossible to save every distressed animal. In some cases, it is simply not practical to capture, clean and nurse an animal back to health. Trying to rescue distressed birds in nesting grounds can disrupt fledglings, contaminate other bird nests and possibly even cause some nests to be abandoned completely.<br />In a race against time, the U.S. Fish and Wildlife Service, NOAA, state and local authorities, concerned volunteers and privately sponsored groups continue to do what they can. But they need help. While some may use the excuse that they are "just animals", what goes around comes around and that includes what ends up on our plates, vitamins we intake, shampoos, cosmetics and most of all, the collective consciences that supposedly make us better as humans.<br /></div><div class="sig" id="sig"> Robert Haskell is a contributing author and manager of consumer affairs for <a href="http://www.officesalesusa.com/" target="_new">http://www.officesalesusa.com</a> which offers a great selection of Earth-friendly products that are safer for the environment including <a href="http://www.officesalesusa.com/Biodegradable.php" target="_new">biodegradable trash bags</a>, corn starch utensils, recycled products and more.<br /><br /><a href="http://www.exxonmobil.com/Australia.../PA/energy_spillprev.aspx">Oil spill prevention. ExxonMobil takes a proactive approach to avoid contamination of the environment. Whether unloading diesel from supply vessels</a><br /></div><img alt="Platinum Quality Author" class="sprite s_platinum_star" src="http://img.ezinearticles.com/spriting/trans.gif" title="Platinum Author" /></div>ripplehttp://www.blogger.com/profile/17326365690819936341noreply@blogger.comtag:blogger.com,1999:blog-6905780489869824283.post-19506696827874196072011-03-20T20:29:00.000-07:002011-04-06T14:15:47.029-07:00The Best Oil Spill Absorbents<div dir="ltr" style="text-align: left;" trbidi="on">By <a href="http://ezinearticles.com/?expert=John_F_Smith" id="togglebio">John F Smith</a> <br /><img alt="Platinum Quality Author" class="sprite s_platinum_star" src="http://img.ezinearticles.com/spriting/trans.gif" title="Platinum Author" /><br /><div id="body"> Working in factories would mean that you work with a lot of heavy machinery. This usually equates to a lot of oil spills and leaks as these machines require a lot of maintenance to work smoothly everyday. This is why you will need an effective oil spill absorbent to prevent spills from causing accidents or creating a lot of mess. One such product line that would cater to your needs is the Spilfyter absorbents as they have universal products that can effectively absorb spills of any type and oil-only products that are made for absorbing oil and hydrocarbons only.<br />Going back to factories that usually need to clean oil and lubricant spills, the Spilfyter products have several products that can help prevent and clean such messes with great efficiency. Oil-only absorbent pads and rolls can be used to prevent leaks from spreading by placing them on the bases of heavy machines or leaky containers. They can also double up as rags to clean spills incurred during normal working procedures. Another product that can be used to prevent leaks from spreading is the oil-only socks. Using socks is useful for larger scale leaks due to its increased absorbing capacity. Aside from this, it can also be placed firmly attached to machines and containers due to its elastic nature. It acts as a barrier to prevent leaks from escaping, while also absorbing oil that it comes in contact with. Absorbent granules can be used to absorb stray spills as well while their absorbent drum tops can be used to ensure clean drums even with leaky faucets.<br />So if you usually encounter any type of oil spills of leaks in your workplace, look for the Spilfyter product that will best help you in preventing or cleaning up the mess. This way, can spend less time and effort in cleaning while ensuring a cleaner and safer workplace for the workers.<br /></div><div class="sig" id="sig"> For more information on using <a href="http://www.thejanitorialsupply.com/s/oil-spill-absorbent.html" target="_new">oil spill absorbent</a>, go to <a href="http://www.thejanitorialsupply.com/" target="_new">TheJanitorialSupply.com</a>. TheJanitorialSupply is the one-stop shop for industrial and home-use cleaning and janitorial supplies.<br /><br /><a href="http://www.guardian.co.uk/environment/2010/aug/06/oil-spill-prevention">If new oil wells are to be sunk at huge depths under the sea, it should be a requirement that a second bore, or relief well,</a><br /><br /><br /></div></div>ripplehttp://www.blogger.com/profile/17326365690819936341noreply@blogger.comtag:blogger.com,1999:blog-6905780489869824283.post-58124376049860906692011-03-20T20:27:00.000-07:002011-04-06T14:15:47.033-07:00Learn From the Oil Spill Disaster<div dir="ltr" style="text-align: left;" trbidi="on">By <a href="http://ezinearticles.com/?expert=Davis_Goss" id="togglebio">Davis Goss</a><br /><div id="body">The BP oil spill in the Gulf of Mexico is a classic example of what can happen when over confident people think they can take shortcuts when dealing with natural laws and principles. Had engineers respected the irrevocable nature of these laws and principles the present catastrophe would not have happened.<br />This universe and all it contains is infinite. It is self controlled and self maintained in perpetuity by irrevocable natural laws and principles. Webster defines these natural laws and principles as: "The creative and controlling forces of the universe."<br />With uncompromising effort adhered to the implementation of these laws and principles, conclusions are inevitable and predictable. Similarly, to compromise these laws and principles will assure failure.<br />Because BP engineers and management have not succeeded in stopping the oil leak tells me that, either through conscious intent or through ignorance, they have not adhered one or more of these laws. This is tantamount to implementing efforts to stop the sunrise. Natural laws and principles will not be denied!<br />Dr. Einstein and other thinkers throughout history have reminded us, "You cannot solve a problem from within the same consciousness that created it." BP doesn't need more of the technological "expertise" that caused the problem, they need to reject their "expertise" and be responsive to new IDEAS.<br />There is a creative process that will meet any need, solve any problem and meet any goal or objective. There is virtually no adverse situation or circumstance that cannot be resolved by the proper application of natural laws and principles; "the creative and controlling forces of the universe." (Webster)<br />In all recorded history nothing was ever accomplished, no need was ever met and no problem was ever solved that didn't begin with an IDEA. Ideas do not originate in a finite world of technology and limitation. Ideas are infinite and already available in the one and only, all inclusive Consciousness; YOUR consciousness. We can access this infinite Consciousness by opening our thought to a listening attitude. This is providing the necessary mental environment in which the right idea can reveal itself to you.<br />Perhaps we can all learn a lesson from a company that had a vat of liquid filled with a lot of loose material suspended in it on the first floor of their building. They needed to transfer just the liquid into a vat on the second floor.<br />No problem. All they had to do was to pump it up, right? Wrong! The solid debris fouled up the pump. Pump experts were consulted and new pumps were installed with similar clogging results. It was then decided that what they needed was a better filtering system to remove the debris before it got to the pumps. Various filter designs were tested but they, too, became clogged. The company's management was convinced they had a serious filter/pump problem that was not only insurmountable but costly.<br />The solution to their "impossible" situation lay, not in addressing it as a filter/pump problem, but in looking away from it and seeing it as a need to transfer clean liquid from point A to point B. What they really needed was to reject the usual engineering approach (that didn't work!) and find a new IDEA that would. They needed a new creative approach.<br />"Creativity" is defined by Webster as, "The ability to be productive through imaginative skills". (notice he makes no reference to technology or skilled training, just the imagination) and "productive", "to establish results, benefits and profits."<br />A new, unorthodox system was developed and implemented that involve neither pumps nor filters. A conveyor belt affixed with sponges was cycled through the lower vat, absorbing just the liquid, and conveyed to the second floor where the clean liquid was simply wrung out. "Mickey Mouse" simple? Yes! But the objective was achieved!<br />Two axioms come into play:<br />1. The longer a person (technician) works in a given field the less likely he will come up with a creative idea. Familiarity can thwart expansive thinking.<br />2. History proves that the greatest creative contributions are made through a mind not too fully packed with existing knowledge or the awareness of past failure. New ideas usually come from sources outside the organization.<br />There are lots of ways to plug up a pipe. To date, all the "obvious" technological approaches have failed. As in the case of our pump / filter scenario, the solution will come through innovation, defined by Webster as " the introduction of something new; a new idea or method."<br />There are thousands of people with ideas on how to solve the problem (myself included). It has been my experience that trying to get an objective evaluation of any new idea is tantamount to pushing a rope.<br />Traditionally, organization is the enemy of innovation and tends to retreat into an "N. I. H. (Not Invented Here) mode" to defend themselves against anything that might challenge their technological mindset.<br />Be alert to not make the same mistake BP made. When confronted with a problem, personal, professional, corporate or national, look away from it, resist the temptation to force a solution with the puny human intellect and its "knee jerk" reaction to what it appears to be. With a LISTENING attitude, lift your consciousness to embrace the fact that the solution already exists and is ready and willing to reveal itself to you. Problems are negative and cannot exist without there being a positive answer or solution to be negative about. Knowing this, the right ideas and / or the proper procedures will become apparent.<br />I am not a trained engineer or technician, but for more than 50 years as a creative consultant this approach has allowed me to resolve complex technical problems through innovation that have not yielded through mainstream technology.<br />When all else fails, INNOVATE!</div><div class="sig" id="sig">Over the past 50+ years working as a creative consultant, with focus on problem solving, Davis Goss has developed, tested and proven a singularly unique approach to resolving "impossible" problems to the benefit of a widely diverse client base.<br />The logical continuity of these natural laws and principles are explained in detail in his book, "The Science of LIVING BETTER FOREVER" available in print form from Amazon or in an expanded E-book version through his website <a href="http://www.livingbetterforever.com/" target="_new">http://www.livingbetterforever.com</a></div><br /><br /><a href="http://www.alyeska-pipe.com/.../OilSpillPreventionAndResponse.html">Oil Spill Prevention and Response</a> </div>ripplehttp://www.blogger.com/profile/17326365690819936341noreply@blogger.comtag:blogger.com,1999:blog-6905780489869824283.post-2655046935129519612011-03-20T20:24:00.000-07:002011-04-06T14:15:47.035-07:00Miami Tourism: Plain Sailing or Troubled Water Since the BP Oil Spill?<div dir="ltr" style="text-align: left;" trbidi="on">By <a href="http://ezinearticles.com/?expert=Mike_Leverency">Mike Leverency</a><br /><br /><div id="body"> Miami beach is one of the most recognisable locations in the world, after the BP Oil Spill will the beach be a white heaven or a black hell? Here's a quick timeline of the oil spill to put some of it into perspective:<br />20th April: The Oil Rig, Deep Water Horizon reports an explosion and fire, eleven people are missing and 17 injured<br />22nd April: The Deep water Horizon sinks in 5,000ft of water. There are reports of a five mile ling oil slick<br />25th April: The underwater well is leaking at 1,000 barrels of oil a day.<br />28th April: The Coastguard announces that the flow of oil is at 5,000 barrels per day, five times larger than first estimated. Controlled burns begin.<br />29th April: President Obama gives his first public speech about the spill, pledging that he will spare no resource to stop the spill.<br />1st May: The coastguard announce that the spill will affect the coast.<br />13th May: A researcher from Purdue University puts the amount of oil leaking at 70,000 barrels per day.<br />15th June: President Obama says that the Oil Spill is the worst environmental disaster America has ever faced<br />19th September: BP finally stops the ruptured well from leaking.<br />It's been a tragic summer for the Gulf of Mexico, with the President saying that the Oil Spill is the worst environmental disaster in U.S history.<br />As you can see from the timeline above, the Oil Spill did hit the coast of the US, and our TV screens were filled with reports of tar and oil balls washing up onto the shores. The big question is whether this disaster is going to affect tourism? We know that it affected the fishing trade as the fishing boats were banned from the spill sight. It has also had some lasting environmental damage, with a species of seahorse almost going extinct as a result.<br />After the spill had stopped the reports of the little black tar balls disappeared from our TV's but the question still remains that whether this disaster will affect tourism to one of America's tourism hotspots.<br />We have already seen political representative's promoting Florida's and Alabama's beaches. Barrack Obama was photographed swimming with his daughter, and more recently Governor Charlie Crist has been photographed promoting Miami's South Beach.<br />Tourism figures are looking healthy, but only time will tell. The Tourism board can do nothing apart from parade officials along beaches to try and transmit a positive image. It is hard to tell which way the tourists will swing on this one, keep an eye out because there may be very <a href="http://www.travelspec.com/en/flights/United-States/Miami-flights" rel="nofollow" target="_new">cheap flights to Miami</a> in the coming months.<br />But Florida isn't just about the beaches, there are plenty of activities and things to see and do around the Gulf. By all accounts the beach is fine, but, if the beaches aren't fine, will that affect Tourism in a negative way? Or will tourists just avoid the beach?<br /></div><div class="sig" id="sig"> I'm Mike, I want to educate, help and inspire people to think about travel.<br /><a href="http://www.epa.gov/oilspill">Oil Spills | Emergency Management | US EPA</a><br /></div></div>ripplehttp://www.blogger.com/profile/17326365690819936341noreply@blogger.comtag:blogger.com,1999:blog-6905780489869824283.post-13434285664235020562011-03-20T20:22:00.000-07:002011-04-06T14:15:47.037-07:00Oil Spill Equipment - Protecting the Environment by Containing Oil Spills Effectively<div dir="ltr" style="text-align: left;" trbidi="on">By <a href="http://ezinearticles.com/?expert=Travis_Zdrazil" id="togglebio">Travis Zdrazil</a> <br /><div id="body"> Oil spills pose a great threat to the environment. That's especially true if a spill occurs in a body of water. Read on to find out how the spills can be contained to minimize the damage.<br />When prevention has failed and a spill has happened, it's time to bring out the oil spill equipment. And there are a number of options.<br />The first task is to contain the damage. Oil can spread very quickly, and so the key is to keep it confined to a small or controllable area. This way, it can be removed by absorbents later.<br />They key tools for containing oil spills are Containment Booms of various types, specifically non-absorbent booms.<br />Why various types? Depending on where the spill occurred, the conditions will vary, and not every containment boom is suited to every type of watery environment.<br /><strong>For calm and protected waters</strong><br />The most popular oil containment boom is the EconoMax, a non-absorbent boom that is especially suited to calm and protected waters. You can use it to contain oil and debris in marinas, harbors, and on inland waterways. It is very compact and light in weight, which means that it floats on water. The fact that it is also quite inexpensive no doubt contributes to its popularity.<br />It's closed cell foam panels can be folded, which makes it easy to transport. In fact, you can keep it handy in boats, trucks, or even cars so that it's handy when there's a spill.<br /><strong>For smaller waterways and shallow areas</strong><br />If you want something for smaller waterways, including roadside ditches, shallow ater areas, and small streams and canals, you may want to opt for the Super Swamp Containment Boom, which is very lightweight and can be transported and deployed even more easily.<br /><strong>For rougher waters, including shorelines</strong><br />On the other hand, you may have to deal with rougher water, which calls for more heavy duty oil spill equipment. One that fits the bill is a marine grade, heavy duty oil containment boom, for example the Simplex Oil Boom.<br />It is perfectly suited to protect shorelines and coasts from oil spills. While it has high buoyancy and is also light in weight, it has a much sturdier construction. It is also designed in a way that allows it to be moved easily in order to let boats pass.<br />With its handles and anchor points as well as its heavy duty connectors, it can withstand even rough waters.<br />And those are just a few of the possibilities. When it comes to protecting the environment from spilled oil, there's oil spill equipment available to meet the challenge, no matter what the exact nature of the body of water.<br /></div><div class="sig" id="sig"> Want to know more about <a href="http://www.absorbentsonline.com/spill-containment-boom/containment-boom-oil-containment-booms.htm" target="_new">oil spill equipment</a>? Get valuable tips and the latest news about absorbents and other environmental safety products on Travis Zdrazil's <a href="http://www.safetymaintenancenews.com/" target="_new">Safety Maintenance News</a> blog and get his free newsletter too. Travis is an expert on environmental safety products and has supplied businesses with products to aid in meeting EPA and OSHA requirements for more than 10 years.<br />You may publish this article, but must keep the resource box ©2009 PCI Products Company. All rights reserved.<br /><br /><a href="http://www.oilspillinfo.org/">More than 99.997 percent of oil delivered by tankers to the U.S. over the last decade reached its destination without incident. Spill Prevention Response</a><br /></div><img alt="Platinum Quality Author" class="sprite s_platinum_star" src="http://img.ezinearticles.com/spriting/trans.gif" title="Platinum Author" /></div>ripplehttp://www.blogger.com/profile/17326365690819936341noreply@blogger.comtag:blogger.com,1999:blog-6905780489869824283.post-82937892152566176662011-03-20T20:16:00.000-07:002011-04-06T14:15:47.040-07:00Cleaning Up Oil Spills and Other Other Hydrocarbon Liquid Spills With Eco-Friendly Absorbent Pads<div dir="ltr" style="text-align: left;" trbidi="on">By <a href="http://ezinearticles.com/?expert=Thomas_Bourne">Thomas Bourne</a><br /><br /><div id="body">For years, the options were limited to clay-based adsorbents that do little more than pool the liquids but don't really absorb the spill. These products are heavy, non-renewable, and pose certain health risks. In recent years, oil and other liquid absorbent pads have entered the market making it easier to clean up spills, but with varying degrees of effectiveness and cost-efficiency. There are numerous products out there but to make a fair comparison, you should look carefully at the following factors:<br />1. Price to Absorbency Ratio <br />2. Durability of Product <br />3. Material Size Flexibility<br />Simply put, you're better off spending a bit more for a highly absorbent roll or set of oil spill pads that you can keep around for a while and have on hand in case a spill occurs. Also, if the pads don't absorb much relative to their size, then you'll have to use a lot of material even for the most minor spill and that will end up costing you more. Finding the right balance of price, absorbency and flexible pad sizes should be key factors in your decision making.<br />But there's one more very important factor that should enter your decision making: How environmentally friendly are the oil absorbent pads and products that you are using. In this day and age of greater environmental controls, regulations and restrictions, the more eco-friendly you can make your operation, the better off you'll be. Using eco-friendly oil absorbent pads is an "easy" and "cost-effective" way to get more value for your buck.<br />Eco-friendly oil-only and universal absorbent pads are becoming easier to find. A growing number of environmentally friendly oil absorbent and other hydrocarbon liquid absorbent pads are available with various ranges of price and absorbency. These eco-friendly oil products should be made from renewable sources and/or waste products. Some of these products are also recyclable which gives them added value. We tend to equate, environmentally friendly with less effective or cost-efficient, however, when it comes to cleaning up oil spills with eco-friendly pads this is no longer the case. Oftentimes, the environmentally friendly oil absorbent product options have much higher price/absorbency ratios than competing non-renewable versions and are available in various options that can absorb different types of liquids such as oil, gasoline, paint, hydraulic fluid and the like. Look for products that have been proven in the market and that clearly demonstrate their effectiveness and commitment to environmental responsibility.<br />To learn more search the web for eco-friendly oil absorbent pad options or talk to your oil and gas products distributor or oil spill cleanup professional about eco-friendly oil spill options to get better oil spill and general spill clean up results with an environmentally-friendly checkmark on top.</div><div class="sig" id="sig">Thomas Bourne, CEO, Terrenew LLC. Terrenew, in affiliation with Cornell University, manufactures and sells OilMaster Eco-Friendly Oil Absorbent Products are available in Granular Oil Absorbent and Oil Absorbent Pad versions. To learn more, please visit <a href="http://www.terrenew.com/" target="_new">http://www.terrenew.com</a><br /><br /><a href="http://www.foxnews.com/us/.../coast-guard-investigating-reports-oil-spill-gulf/">The U.S. Coast Guard is investigating reports of a potentially massive oil sheen about 20 miles north of the site of last April's Deepwater </a> </div></div>ripplehttp://www.blogger.com/profile/17326365690819936341noreply@blogger.comtag:blogger.com,1999:blog-6905780489869824283.post-77952506839647585162011-03-20T20:14:00.000-07:002011-04-06T14:15:47.054-07:00Is the Oil Spill Disaster Judgment From God?<div dir="ltr" style="text-align: left;" trbidi="on">By <a href="http://ezinearticles.com/?expert=P_Maillet" id="togglebio">P Maillet</a> <br /><img alt="Platinum Quality Author" class="sprite s_platinum_star" src="http://img.ezinearticles.com/spriting/trans.gif" title="Platinum Author" /><br /><div id="body"> For years I have spoken and written about the Arab-Israeli conflict and have tried to make clear the basis for it, that it is the "everlasting hatred" of Ishmael against the descendants of Isaac. That is, of course, true. But I came to see that it's far more than that.<br />The true basis for the conflict is the hatred of Satan for God. And until people understand this, they will not be able to understand what's really going on in the world and in the Middle East.<br />Satan knows the "signs of the times" as well as we do, he knows the Scriptures. And he knows that the re-establishment of the nation of Israel after having been desolate for 2,000 years, signals the approaching end of his career. For those who understand this it will be obvious, as he does everything in his power to destroy Israel in order to prevent or delay the coming of the Messiah, because it is written that it is the Messiah of Israel who will bring Satan's career to an end. Satan's master-plan was perpetrated in the Holocaust. His intent was to destroy all the Jews. He managed to destroy 6 million of them, and was enraged when that very effort was what brought in the rebirth of Israel shortly afterwards. His hatred knows no bounds and the world will see that hatred manifested in all that he will do, especially against Israel, as this story comes to its conclusion.<br />* * Don't ever lose sight of this one thing: it is the opposition of Satan against God which is the basis for all the hatred against Israel. This is a story that started in Genesis, and is reaching its culmination in our days, right before our eyes. If you truly understand this, it will make you rethink everything you know about these days. * *<br />I've said for years that in order for "the Antichrist" to take over, America has to go down. And for years I wondered how that would or could happen. I never suspected that America would become so corrupt that it would invoke the wrath of God upon her. It's still hard to believe that the America we knew and loved as young people has become so reprobate. The bottom line as far as America goes: using as a pretext the total twisting and misapplication of the first amendment to our Constitution, the American people have kicked God out of every public place, and God is not going to stay in a place where he is rejected and where he is insulted daily. And when God leaves, America will find out what the ramifications are. I don't know if "natural" disasters will destroy this country, or whether it might be nuclear, chemical, and/or biological attacks. Maybe all the above. All we know is that America is not referred to in the "last days" passages which identify the nations who WILL be involved. The greatest nation that has EVER been on the earth not even mentioned? That says it all. America won't be here, at least not as a super-power. Consider this too: if all the Christians were removed, the restraining power of the believers would no longer be an obstacle to the spread of evil, and evil would take over totally and quickly.<br />There are a lot of things working together to create the one-world global government which the Scriptures tell us will be headed by "the Antichrist." In times past, we wondered how a global government could possibly come into being, because the ideologies of the countries of the world differ so much. But it seems clear that disasters, plus the failing monetary systems, are going to be powerful players in the rise of global government. Just days ago, president Obama was speaking at West Point and he used the buzz-words "new world order." It's this "new world order," spoken of for centuries, that will progress into the global government over which the Antichrist will rule. The Antichrist will be empowered by Satan himself and will persuade the world with supernatural signs and wonders, leading them to believe HE is the Messiah.<br /><u>America-Israel</u><br />Take note that as US pressure upon Israel creates a great threat to her borders, we have had noticeable threats to OUR borders. "The powers that be" in America are allowing foreigners to come into this country and use up our resources, creating a great strain on our financial and also our health systems. It makes absolutely no sense whatsoever that this country is willing to allow foreigners to break our immigration laws and saturate our resources, getting free health care, free housing, free education, etc, etc, etc. There is no explanation in the natural for something as insane as this. It has to be the hand of God. As the United States government has caused Israel to be stressed to the max with its "Palestinian" population creating havoc within and around its borders, so there are foreigners now creating havoc within OUR borders. So clear you can hardly miss it, yet the eyes of our officials have been blinded.<br /><u>Israel becoming isolated</u><br />Zephaniah 2:1 calls her the "nation not desired." And it's obvious that most of the world, including the UN, is against Israel. Until this administration, America was the one and only major nation in the world who stood with Israel. Note, too, that America has been the most blessed nation on the earth. But there's been a change, a change you can feel everywhere. And this change has brought Israel into isolation. Just remember that God is ultimately in control. He is going to bring Israel to the point where they have NO ONE to turn to and the entire world is against them. But that's where Israel needs to be, because when there's no way out, they will finally realize that only God can save them. Israel is stubborn. They have to get to a point of helplessness. So yes, Satan is enacting this, but in doing so he's moving them right into the isolation they need to be in, where they will finally cry out to their God.<br /><u>Oil</u><br />There are principles or laws that God has established which are as sure as the "laws" of nature. Throw a ball up, you can be sure it will come down. Oppose Israel, and you can be sure judgment will come upon you. Notice the context in which the oil spill disaster hit America: Obama is bowing before the Muslim nations. Why? There are several reasons but one is the oil wealth of those nations. So as America rejects Israel and bows to the oil-rich Muslim nations, America is harshly judged with an unprecedented oil disaster. Not only that, but it happens just when Israel discovers a very, very large resource of oil and natural gas right off the coast of Haifa, deposits so huge that they will make Israel non-dependent on anyone else for energy resources. Incredible coincidence? Of course not. It's the ongoing story in which all the factors are moving into place just before the great Tribulation comes upon the world.<br />I don't write so much on these subjects anymore, because I find that believers already know these things, and as for unbelievers - they do not "see" no matter how clear you make it. I have the sense that it's too late. People's minds are made up and it's too late to change them. When Jesus walked this earth, he got to the point where he stated that he would no longer speak to the people except through parables that they wouldn't understand, and it was basically for the same reason: by that point, people had made up their minds. He expounded and clarified things to his disciples, but no longer to the people. <em>(Matthew 13:10-16)</em><br />Yes, people have made up their minds already. I used to quote Joel 3:14, "Multitudes, multitudes in the valley of decision..." But I suspect the time has come or is near when it's too late, they've made their decisions.<br />So: <br />"He who is unjust, let him be unjust still; he who is filthy, let him be filthy still; he who is righteous, let him be righteous still; he who is holy, let him be holy still." <em>(Revelation 22:11)</em><br /></div><div class="sig" id="sig"> Having several blogs now, the following is the link to the Home Page from which all the other blogs can be accessed. <a href="http://pmailletblogs.blogspot.com/" target="_new">http://pmailletblogs.blogspot.com/</a><br /></div></div>ripplehttp://www.blogger.com/profile/17326365690819936341noreply@blogger.comtag:blogger.com,1999:blog-6905780489869824283.post-83391667621274564022011-03-20T19:59:00.000-07:002011-04-06T14:15:47.062-07:00End of Days - Was Gulf Oil Spill a Message From God?<div dir="ltr" style="text-align: left;" trbidi="on">By <a href="http://ezinearticles.com/?expert=Jer_Bosky">Jer Bosky</a> <br /><img alt="Platinum Quality Author" class="sprite s_platinum_star" src="http://img.ezinearticles.com/spriting/trans.gif" title="Platinum Author" /><br /><div id="body"> Some people believe we have entered the End of Days and that the disasters we are witnessing, both natural and man-made, are the work of God.<br />Most often it is Bible believers who speak using this terminology, but increasingly you also hear well-known non-believers express the same idea.<br />Recently, media mogul Ted Turner spoke out with his opinion on the BP oil rig explosion and the ensuing oil leak, the biggest in history. Turner told a CNN interviewer that the disaster in the Gulf of Mexico could be God's work, saying, "He's sending us a message."<br />The comment came in the course of an interview on energy policy in the United States. Turner elaborated that even though is "not a real religious person" he does wonder if God is telling us that we shouldn't be doing offshore drilling. He also brought in the West Virginia coal mine disaster, in which 29 miners were killed, as another sign that someone may be displeased with us.<br />It is common for preachers such as Pat Robertson to quickly blame disasters on the wrath of God. Robertson himself, for instance, stirred up a storm when he said the calamitous earthquake in Haiti was the result of that country making a pact with the devil during the revolt against the French two centuries ago.<br />It is much less common to hear someone such as Ted Turner bring God into a discussion of the latest news events. The fact that this is happening now could be another sign we really are in the End of Days.<br />Messages from God or not, many signs are pointing to something momentous on the horizon. The world is due for some big changes, particularly as they relate to the prophetic year of 2012. And 2012 is not far off. Will you be ready for it?<br /></div><div class="sig" id="sig"> <strong>Want to learn more about what's coming for 2012?</strong><br />Don't believe everything you hear about 2012 and what it will mean to you personally -- but don't dismiss it all, either. The truth is out there and can be known. See the <a href="http://www.2012alarm.com/" target="_new">2012 Predictions</a> site at <a href="http://www.2012alarm.com/" target="_new">http://www.2012alarm.com</a>.<br /></div></div>ripplehttp://www.blogger.com/profile/17326365690819936341noreply@blogger.com