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The Moon (Latin: Luna) 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 (238,863 mi) which is about 30 times the diameter of the Earth.

The Moon has a diameter of 3,474 km (2159 mi)^[1]—slightly more than a quarter that of the Earth. This means that the volume of the Moon is close to 1/50^th that of Earth. The gravitational pull at its surface is about 1/6^th 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.

The Moon is the only celestial body to which humans have travelled and upon which humans have landed. The first artificial object to escape Earth's gravity and pass near the Moon was the Soviet Union's Luna 1, the first artificial object to impact the lunar surface was Luna 2, and the first photographs of the normally occluded far side of the Moon were made by Luna 3, all in 1959. The first spacecraft to perform a successful lunar soft landing was Luna 9, and the first unmanned vehicle to orbit the Moon was Luna 10, both in 1966.^[1] The United States (U.S.) Apollo program achieved the only manned missions to date, resulting in six landings between 1969 and 1972. Human exploration of the Moon ceased with the conclusion of the Apollo program, although, as of 2007, several countries have announced plans to send either people or robotic spacecraft to the Moon.