moon

A large body (natural satellite) that orbits around a planet. The Moon is a natural satellite of the Earth. Unlike the Earth, the Moon has no atmosphere or water. The Moon is much smaller than the Earth, barely a quarter of the size, with a diameter of 3476 kilometres. Its surface gravity is only about one‐sixth that of the Earth. The Moon orbits in a west–east direction, about 385 000 kilometres from the Earth, and each orbit takes 27.32 days (a sidereal month) to complete. It also spins on its axis, with one face permanently turned towards the Earth. On Earth the tides (cyclic rise and fall of sea level) are caused by the gravitational pull of the Moon and Sun, so the movements of the Moon affect the oceans which cover two‐thirds of the Earth's surface. The Moon might also be implicated in global climate change, because recent research has shown that the Moon affects temperatures on Earth through the influence of the alignment of Earth, Moon, and Sun on the tides.