Some nights, the Moon looks like a bright circle. On other nights, it looks like a thin smile in the sky. Does it really change shape?

No. The Moon stays round. What changes is the part of its bright side that we can see from Earth.

The Moon does not make its own light. The Sun shines on it. As the Moon travels around Earth, we see different amounts of the side lit by the Sun.

These changes happen in a regular pattern. After about one month, the Moon looks nearly the same again.

A brother and sister decide to watch the Moon every evening. They draw its shape in a notebook. At first, it is a thin curve. Later, it becomes bigger and brighter.

Their drawings help them see something important: the Moon has not changed size. Only the way it looks from Earth has changed.

The Moon looks different on different nights. Sometimes it looks round. Sometimes we see only a little part. The Moon is still the same. We see light from the Sun on it.