No concrete evidence explains why there is a moon. The best hypothesis presented is the Giant Impactor hypothesis: It suggests that around 4.45 billion years ago, while the Earth was still forming, a large object hit the... More »

A moon is a natural satellite consisting of solid material that naturally orbits a planet or dwarf planet. Although the Earth has just one moon, there are other planets that have more, and some that even have none. Moons... More »

There are varying theories on how the moon was created. Some scientists believe that it was created when a Mars-sized planet named Theia crashed into the Earth during the early years of the formation of the solar system. More » Science Astronomy Our Moon

There is evidence that the moon is seismically active, which means it can experience the moon version of an earthquake. During the 1969 and 1972 moon landings, astronauts placed seismometers on the moon in order to allow... More » Science Astronomy Our Moon

Shadows can cross the moon either from right to left or from left to right, depending on the source of the shadow. Shadows caused by the moon's phases pass from right to left relative to an earthbound observer. The shado... More »

A moon schedule is available at, or The moon goes through eight different phases every 29.5 days. The modern calendar month is based on the moon's orbit through the eight phases... More » Science Astronomy Our Moon

The moon orbits the Earth at approximately 2,288 miles per hour and completes one full orbit every 27.322 days. Additionally, the moon takes approximately 27 days to complete one full rotation on its own axis, called its... More »