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 kilometres (238,857 mi), which is about 30 times the diameter of the Earth. The Moon has a diameter of 3,474 kilometres (2,159 mi)[1]—slightly more than a quarter that of the Earth. 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.

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.

Earth’s ocean tides are initiated by the tidal force of Moon’s gravity and are magnified by a host of effects in Earth’s oceans. The gravitational tidal force arises because the side of Earth facing the Moon (nearest it) is attracted more strongly by the Moon’s gravity than is the center of the Earth and—even less so—the Earth’s far side. The gravitational tide stretches the Earth’s oceans into an ellipse—with the Earth in the center. The effect takes the form of two bulges—elevated sea level—relative to the Earth: one nearest the Moon and one farthest from it. Since these two bulges rotate around the Earth once a day as it spins on its axis, ocean water is continuously rushing towards the ever-moving bulges. The effects of the two bulges and the massive ocean currents chasing them are magnified by an interplay of other effects; namely frictional coupling of water to Earth’s rotation through the ocean floors, inertia of water’s movement, ocean basins that get shallower near land, and oscillations between different ocean basins. The magnifying effect is a bit like water sloshing high up the sloped end of a bathtub after a relatively small disturbance of one’s body in the deep part of the tub.

http://en.wikipedia.org/wiki/Moon

http://www.nineplanets.org/luna.html

http://www.enchantedlearning.com/subjects/astronomy/moon/

http://news.nationalgeographic.com/news/2004/07/0714_040714_moonfacts.html