Moon explained to kids

The Moon is an astronomical body that orbits Earth, being Earth's only permanent natural satellite. The Moon is the fifth-largest natural satellite in the Solar System, and the largest among planetary satellites relative to the size of the planet that it orbits (its primary). The Moon is after Jupiter's satellite Io the second-densest satellite in the Solar System among those whose densities are known. The Moon is thought to have formed not long after Earth. The most widely accepted explanation is that the Moon formed from the debris left over after a giant impact between Earth and a Mars-sized body called Theia. The Moon has a visibly uneven surface, with large dark patches (maria, Latin for "seas") on a brighter background; however, in total it reflects about as much sunlight as fresh snow. Its prominence in the sky and its regular cycle of phases have, since ancient times, made the Moon an important cultural influence on language, calendars, art, and mythology. The Moon's gravitational influence produces the ocean tides, body tides, and the slight lengthening of the day. The Moon's average orbital distance is 384,402 km (238,856 mi), or 1.28 light-seconds. This is about thirty times the diameter of Earth. The Moon's apparent size in the sky is the same as that of the Sun, since the star is about 400 times the lunar distance and diameter. Therefore, the Moon covers the Sun nearly perfectly during a total solar eclipse. The Moon orbits Earth in about 27.3 days. Its orbit is slightly elliptical, so one side (near Earth) is slightly closer than the other (farther from Earth). The "near" side of the Moon is marked by dark volcanic maria that fill impact basins that were created by ancient collisions with other astronomical objects. The far side of the Moon, in contrast, is heavily cratered and has very few maria. There is evidence that the Moon was formed about 4.51 billion years ago, not long after Earth. The most widely accepted explanation is that the Moon formed from the debris left over after a giant impact between Earth and a Mars-sized body called Theia. The Moon has a diameter of 3,474 km (2,159 mi) and a mass of 7.35e22 kg, about 1/81 of Earth's mass. The Moon is denser than Earth, but not as much as expected given its small size, with a bulk composition resembling that of the Earth's mantle. The Moon is the second-densest satellite in the Solar System after Jupiter's satellite Io.