Why does the Moon change shape?

The Moon is a large ball of rock that doesn't change shape - it just looks as through it does. The shape we see in the sky today depends on how much of the Moon's face is lit up. Sometimes we observe a thin crescent, and at other times we see half or three quarters of the Moon, and then a fully lit face - a Full Moon.

How the Moon was formed?

  

1. A Mars-sized asteroid collides into Earth at a speed of 20 km per sec (12 miles per sec).
2. Smashed asteroid pieces and material gouged out of Earth's rocky mantle form a ring around Earth.
3. Over several million years, the pieces of orbiting material bump into each other and join together.
4. They form one large body - the Moon. About a quarter the size of Earth, it slowly moves out to its present orbit.