ETYM Old Eng. mone, as. môna.
1. Any natural satellite of a planet.
2. Any object resembling a moon.
3. The natural satellite of the Earth.
Natural satellite of Earth, 3,476 km/2,160 mi in diameter, with a mass 0.012 (approximately one-eightieth) that of Earth.
Its surface gravity is only 0.16 (one-sixth) that of Earth. Its average distance from Earth is 384,400 km/238,855 mi, and it orbits in a west-to-east direction every 27.32 days (the sidereal month). It spins on its axis with one side permanently turned toward Earth. The Moon has no atmosphere or water.
Phases.
The Moon is illuminated by sunlight, and goes through a cycle of phases of shadow, waxing from new (dark) via first quarter (half Moon) to full, and waning back again to new every 29.53 days (the synodic month, also known as a lunation). On its sunlit side, temperatures reach 110şC/230şF, but during the two-week lunar night the surface temperature drops to -170şC/-274şF.
Origins.
The origin of the Moon is still open to debate. Scientists suggest the following theories: that it split from the Earth; that it was a separate body captured by Earth's gravity; that it formed in orbit around Earth; or that it was formed from debris thrown off when a body the size of Mars struck Earth. Future exploration of the Moon may detect water permafrost, which could be located at the permanently shadowed lunar poles.
Research.
The far side of the Moon was first photographed from the Soviet Lunik 3 Oct 1959. Much of our information about the Moon has been derived from this and other photographs and measurements taken by us and Soviet Moon probes, from geological samples brought back by us Apollo astronauts and by Soviet Luna probes, and from experiments set up by the us astronauts 1969–72. nasa announced 1995 it will be sending a new probe to the Moon in 1997. The Lunar Prospector will search for surface ice, and monitor escaping gas as a measure of tectonic activity.
Composition.
The Moon’s composition is rocky, with a surface heavily scarred by meteorite impacts that have formed craters up to 240 km/150 mi across. Seismic observations indicate that the Moon’s surface extends downward for tens of kilometers; below this crust is a solid mantle about 1,100 km thick, and below that a silicate core, part of which may be molten. Rocks brought back by astronauts show the Moon is 4.6 billion years old, the same age as Earth. It is made up of the same chemical elements as Earth, but in different proportions, and differs from Earth in that most of the Moon’s surface features were formed within the first billion years of its history when it was hit repeatedly by meteorites. The youngest craters are surrounded by bright rays of ejected rock. The largest scars have been filled by dark lava to produce the lowland plains called seas, or maria (plural of mare). These dark patches form the so-called “man-in-the-Moon” pattern.
The us lunar probe Clementine discovered an enormous crater on the far side of the Moon 1994. The South Pole-Aitken crater is 2,500 km across and 13 km deep, making it the largest crater in the Solar System discovered so far.
In astronomy, any natural satellite that orbits a planet. Mercury and Venus are the only planets in the Solar System that do not have moons.

(1920-) Korean industrialist and founder of the Unification Church (Moonies) 1954. From 1973 he launched a major mission in the US and elsewhere. The church has been criticized for its manipulative methods of recruiting and keeping members. He was convicted of tax fraud in the US 1982.
Moon has allegedly been associated with extreme right-wing organizations, arms manufacture, and the Korean Central Intelligence Agency.

1. To be idle in a listless or dreamy way; SYN. moon around, moon on.
2. To expose one's buttocks to