Moon : Earth's only planet, the neighbor

The average distance from the Earth to the Moon is 384,399 km, which is about 30 times the diameter of the Earth. The Moon is about one-third the size of the Earth and has a diameter of 3,474 km. It is the fifth largest moon in the Solar System behind Ganymede, Titan, Callisto and Io. The Moon makes one complete orbit about 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 gravitational attraction of the Moon is responsible for the tides on Earth.

The Moon is the only celestial body on which human beings have orbited and landed. The first man-made object to escape Earth's gravity and pass near the Moon was the Soviet Union's Luna 1, the first man-made 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. The United States' Apollo program achieved the first (and only) manned missions to the Moon, culminating in 6 landings between 1969 and 1972.