Earth's moon

The Moon is Earth's only natural satellite, and the fifth largest moon in the Solar System. The average centre-to-centre distance from the Earth to the Moon is 384,403 km which is about thirty times the diameter of the Earth. The Moon has a diameter of 3,474 km —slightly more than a quarter that of the Earth and a little bit smaller than the length across the United States. This means that the volume of the Moon is close to 1/50th that of Earth. The gravitational pull at its surface is about 1/6th of Earth's. The Moon makes a complete orbit around the Earth every 27.3 days, and the periodic variations in the geometry of the Earth–Moon–Sun system are responsible for the lunar phases that repeat every 29.5 days.
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