The moon's radius is 1737.4 km. Surface gravity is about 1/6 that of Earth's. The moon orbits the Earth once every 29.53 days (this of course played havoc on the Ancient Egyptians who had to add days to the calender to make up for the difference between the lunar months and the Earth's orbit around the sun). During the lunar month, the moon will go through a whole cycle of phases from new moon to full moon and back. The moon is at an average distance of 384,467 km from the Earth. Gravitational forces between the Earth and moon account for the tides of the oceans.

The moon has no atmosphere, therefore, no wind or water to cause erosion. Craters caused by impacts from meteors have remained on the moon since they were formed. On Earth, wind and rain and volcanic activity have erased most all of the impact craters created here during the Earth's formation.

The first spacecraft from Earth to reach the moon was the Soviet Luna 1 craft which performed a flyby to within 5995 km of the moon on January 4, 1959.

The first spacecraft from Earth to land on the moon was the Soviet Luna 2 which made a crash landing on September 14, 1959.

Luna 3 returned the first photos of the far side of the moon on October 7, 1959 from a distance of 63,500 km from the moon.

On February 3, 1966, Luna 9 became the first spacecraft from Earth to make a successful soft landing on the lunar surface. Luna 9 landed in Ocean Procellarum and sent back to Earth the first ever photos taken on the lunar surface.

In January of 1994, the unmanned Clemintine spacecraft mapped most of the lunar surface in different resolutions and wavelengths. Lunar Prospector carried out an investigation of the lunar poles in low polar orbit. Lunar Prospector then crash landed on the surface on July 31, 1999 in hopes of confirming the existance of water in the lunar poles, but results of the impact did not produce any observable signiture of water.

Clemintine and Lunar Prospector did return valuable data about the moon. The crust is highly enriched in aluminum on a global basis, thus supporting the theory of its origin by early global melting (the magma ocean). The South Pole-Aitken Basin on the far side of the moon is the largest and deepest impact basin known in the solar system at 2600 km in diameter and over 12 km deep. The moon shows many areas of excess subsurface mass that cause the gravity field of the moon to be 'lumpy', requiring constant adjustments for orbiting spacecraft. Areas near the poles are in permanent darkness and some may be in permanent sunlight. The data from these missions is still being analyzed and is sure to yield more information and probably raise more questions about the moon.