Moon, The

   The natural satellite which orbits the Earth. It has a diameter of about 3,480 kilometers (2,160 miles), which is more than one quarter the size of the Earth, with a volume equal to about one fiftieth of the Earths. Since the density of the Moon is only three fifths that of the Earth, the Moon's gravitational pull is one sixth of Earths. From New Moon to New Moon takes 29 1/2 days. The Moon reflects 7% of the light that hits its surface, this is about the same reflectivity as coal dust. The surface temperature ranges from -173° C - 127° C (-279° F - 261° F). The Moon is about 4,600,000,000 years old, and has about 3,000,000,000,000 craters with a diameter over 1 meter (3.32 feet). Water ice has been found on the Moon's south polar region, possible left there by a comet impact about 3,600,000,000 years ago. The patch of ice is about 7.6 meters (25 feet) thick, and about 183 meters (200 yards) across. See Waxing, Waning, New Moon, Quarter Moon, Regolith and Mascons.