The Moon is the Earth's only natural satellite, or orbiting body. Most astronomers believe that the Moon was formed about 4.51 billion years ago—about 30 million years after the Earth—as the result of a massive impact between the Earth and a planet-sized asteroid, known as Theia.
|Mass||7.300 × 1022 kg||5.972 × 1024 kg|
|Volume||21,970,000,000 km3||1,083,000,000,000 km3|
|Average Orbital Speed||3,679 kph||107,200 kph|
Because the Moon itself rotates as it orbits Earth, only 60% of its surface is ever visible from the Earth. That is why there is a dark side of the moon. In fact, however, the far side of the moon is illuminated by the Sun just as much as the near side!
As of 2019, more than 200 moons have been discovered (Jupiter has 67 known moons and Saturn 62).
The tallest is Mons Huygens, which, at about 4,700 m tall, is about half the height of Mt. Everest (8,848 m).
It takes about 1.255 seconds for moonlight to reach Earth. That means that when we look at the moon, we're really seeing what the moon looked like over a second ago!