Why does the Moon change shape?

The Moon isn’t really changing its shape. It is always round. As the Moon moves around Earth, we only see the parts of the Moon that are lit by the Sun. The Sun’s light bounces, or reflects, off the Moon.

During each month, the Moon seems to change from a tiny sliver to a large bright ball. These shapes are the phases of the Moon. When there is a Full Moon, the Sun lights up the entire side of the Moon that faces Earth. When there is a New Moon, the unlit side of the Moon faces Earth. During a New Moon, you cannot see the Moon.