Portal:Outer space/Selected article/14

The Moon is Earth's only permanent 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 kilometres (238,857 miles). The gravitational pull at its surface is about a sixth 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 gravitational, centripetal forces generated by the rotation of the Moon and Earth around a common axis, the barycentre, are largely responsible for the tides on Earth. The Moon is the only celestial body that humans have traveled to and landed on. 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 U.S. Apollo program has achieved the first (and 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 2024, several countries have announced plans to send either people or robotic spacecraft to the Moon.