The Moon is Earth's largest natural satellite, and we usually see it in the night sky. Some other planets also have moons or natural satellites.
Our moon is about a quarter the size of the Earth. Because it is far away it looks small, about half a degree wide. The gravity on the moon is one-sixth of the Earth's gravity. It means that something will be six times lighter on the Moon than on Earth. The Moon is a rocky and dusty place. The Moon moves slowly away from the earth at a rate of 3.8cm per year, due to the effect of tidal dissipation.
see also: Wikipedia 
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