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The mass of the Moon is about 1/80 that of the Earth, and its diameter is
about 1/4 that of the Earth. The orbit
of the Moon is very nearly circular (eccentricity ~ 0.05) with a mean
separation from the Earth of about 384,000 km, which is about 60 Earth radii.
The plane of the orbit is tilted about 5 degrees with respect to the ecliptic
plane. The Apollo missions to the Moon left devices that can reflect laser light
sent to the moon from the Earth. By timing the roundtrip of such light, it is
possible to determine the distance to the Moon at any particular time with an
uncertainty of only a few centimeters (!).
Since the synodic rotational period of the Moon is 29.5 days, Lunar day and
Lunar night are each about 15 Earth days long. During the Lunar night the
temperature drops to around -113 degrees Celsius, while during the Lunar day the
temperature reaches 100 degrees Celsius. The temperature changes are very rapid
since there is no atmosphere or surface water to store heat.
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