Editing Moon (section)

===Rotation===
[[File:Tidal locking of the Moon with the Earth.gif|thumb|Comparison between the Moon on the left, rotating tidally locked (correct), and with the Moon on the right, without rotation (incorrect)]]
The [[synchronous rotation|tidally locked synchronous rotation]] of the Moon as it orbits the Earth results in it always keeping nearly the same face turned towards the planet. The side of the Moon that faces Earth is called the [[near side]], and the opposite the [[far side of the Moon|far side]]. The far side is often inaccurately called the "dark side", but it is in fact illuminated as often as the near side: once every 29.5 Earth days. During [[dark moon]] to [[new moon]], the near side is dark.<ref>{{cite web |title=Dark Side of the Moon |author=Phil Plait |publisher=[[Bad Astronomy]]: Misconceptions |url=http://www.badastronomy.com/bad/misc/dark_side.html |access-date=February 15, 2010 |url-status=live |archive-url=https://web.archive.org/web/20100412192834/http://www.badastronomy.com/bad/misc/dark_side.html |archive-date=April 12, 2010 |author-link=Phil Plait}}</ref>

The Moon originally rotated at a faster rate, but early in its history its rotation slowed and became [[tidally locked]] in this orientation as a result of [[friction]]al effects associated with [[tidal force|tidal]] deformations caused by Earth.<ref>{{cite journal |last=Alexander |first=M.E. |title=The Weak Friction Approximation and Tidal Evolution in Close Binary Systems |journal=[[Astrophysics and Space Science]] |date=1973 |volume=23 |issue=2 |pages=459–508 |bibcode=1973Ap&SS..23..459A |doi=10.1007/BF00645172 |s2cid=122918899}}</ref> With time, the energy of rotation of the Moon on its axis was dissipated as heat, until there was no rotation of the Moon relative to Earth. In 2016, planetary scientists using data collected on the 1998–99 NASA ''[[Lunar Prospector]]'' mission found two hydrogen-rich areas (most likely former water ice) on opposite sides of the Moon. It is speculated that these patches were the poles of the Moon billions of years ago before it was tidally locked to Earth.<ref>{{cite news |title=Moon used to spin 'on different axis' |url=https://www.bbc.com/news/science-environment-35883576 |access-date=March 23, 2016 |url-status=live |archive-url=https://web.archive.org/web/20160323203442/http://www.bbc.com/news/science-environment-35883576 |archive-date=March 23, 2016 |work=BBC News |date=March 23, 2016}}</ref>