A description of why the shape of the Moon appears to change when seen from the Earth. The half of the Moon facing the Sun gets illuminated and the other half is in darkness. When the dark side of the Moon is facing Earth we cannot see it. This is called a new moon. As the Moon continues to orbit Earth we can see more and more of the lit side. At various stages in its orbit it is called a crescent moon, a quarter moon and a gibbous moon. It is called a full moon when we can see all of its sunlit side.

First broadcast:
12 October 2007

Students could use ping-pong balls painted or coloured half black, and ask them to recreate the demonstration they observed on the clip, noticing how the proportion of white of the ping-pong ball increases as it orbits them. Students could record the changing shape of the moon in diagrammatic form. A moon diary, recorded over a month, would be a useful way of consolidating their learning.