What is the Moon?

The Moon is the Earth’s only satellite, and it has been orbiting our planet for at least 4,000 million years. It is a rocky sphere about 3,476 km in diameter, which is about one-quarter the size of the Earth.

Scientists believe that the Moon formed when another planet about the size of Mars collided with the Earth. The collision splashed a huge mass of molten (liquid) rock into space. This molten rock quickly formed into a sphere, and the Moon rapidly cooled into its solid form. The Moon’s surface is heavily pitted by collisions with debris such as asteroids. 

 

 

 

What is a lunar eclipse?

The Earth casts a long shadow into space, and when this shadow passes over the Moon it causes an eclipse.

A lunar eclipse can only happen during a full Moon, when the Sun is directly behind the Earth. It happens only occasionally, because the orbit of the Moon is slightly tilted and so the shadow usually misses it. Lunar eclipses can last for over one hour, but they do not completely black out the shadowed part of the Moon. Some sunlight always filters through, making the shadow look a reddish-brown colour.