The larger moons of the Solar System. Earth's moon is the fifth biggest – it's about 3500 km (2200 mi) in diameter.

Earth is the only Solar System planet with just one moon.
The Moon is around 384,400 km (240,250 mi) away from us. Most astronomers think the Moon is made of material thrown out from a young Earth and from the Mars-sized object that collided with it about 4.5 billion years ago.

The Moon shines, but it's not hot like the Sun.
The Moon is a rocky body like the Earth. It shines when it reflects sunlight. We can also see planets when they reflect sunlight. If you were on the Moon facing the Earth, you could see Earth shining.

The Moon orbits the Earth.
In the time it takes the Moon to orbit the Earth, it turns once on its axis. This keeps the same side always facing us. Apollo astronauts are the only people ever to see the far side of the Moon, though we can see pictures of it taken by orbiters.

There is day and night on the Moon.
We can't see the Moon's far side from Earth, but it still gets its share of sunlight. Each side faces the Sun in turn. A lunar day has about 14 Earth days of sunlight and 14 Earth days of darkness.

The Moon seems to change shape during a month – we call the shapes phases.
We see different parts of the sunlit half of the Moon as it orbits. Since we can only see part of the Moon, it looks as if it's changing shape. The Moon takes 29.5 days to go through all the phases and back to the start.

The Moon has no atmosphere.
Without an atmosphere to act like a blanket, temperatures are extreme. Daytime can easily be 120°C (250 °F), while nighttime temperatures drop to -170°C (-280°F). There are even places on the Moon that are much colder than that. The floor of Hermite Crater near the North Pole is -250°C (-410°F) – colder than Pluto.

The Moon doesn't have liquid water.
There's some water on the Moon, but you couldn't swim in it. The water is all frozen, and most of the Moon is drier than Earth's deserts.

We see light and dark areas on the Moon.
Many people think the dark patches make a face ("the man in the moon"). Others see a rabbit, a toad or perhaps a woman's profile. These dark patches are made of dark rock. Long ago large asteroids hit the Moon and made big shallow craters. Later, lava filled them and hardened into a dark rock. The light-colored rocks of the highlands surround them.

The Moon doesn't have weather.
This means the surface of the Moon is very old. On Earth, wind and rain and moving water change the surface. Neil Armstrong's famous footprint is probably still on the Moon after more than fifty years. It wouldn't have lasted long on Earth.

The Moon's gravity is weaker than the Earth's.
The Moon is smaller than the Earth and less dense. (Density is how much matter there is in a cube of a given size.) If you weigh 80 lbs (36 kg) on Earth, on the Moon you would only weigh about 13 lbs (6 kg).

The Moon is the only heavenly body that humans have visited.
Most astronauts don't go very far into space, but twelve Apollo astronauts have walked on the Moon. The first man on the Moon, Neil Armstrong, died on August 25, 2012.