The Moon is the second brightest object in our sky after the Sun and is Earth's only natural satellite. The moon orbits only 384 400 kilometres away from Earth and has a diameter of 3476 kilometres and weighs only 7.35e22 kilograms.

It takes a month for the Moon to orbit around the Earth and as the angle between the Earth, Moon and Sun changes, we see different phases of the Moon. The time between new moons in 29.5 days- or to be 709 hours is slightly different from the Moon's orbital period since the Earth also a significant distance in its orbit around the Sun.

Some information is known about the composition of the Moon. The Moon's crust is approximately 68 kilometres thick, although this varies with a range from 0-107 kilometres. Below this are the mantle and a small core. The core has a radius of about 340 kilometres and this makes up 2% of the Moon's mass.

Unlike the planets, the Moon has no atmosphere, but evidence from a probe called Clementine proposes that there might be water ice in some deep craters near the Moon's south pole, an area which is permanently shaded. The probe, Lunar Prospector confirmed this theory and also discovered ice at the north pole as well. The Moon also has no global magnetic field. But as some of it's surface rocks exhibit remanent magnetism, which means that there may once have been a global magnetic field previously in the Moon's history.