Have you ever noticed that the moon looks different every time you look up at the night sky?

What do you think is causing the appearance to change?

Is the moon changing shape?

Is it moving closer, then further away?

Actually, the moon itself is not changing at all. The appearance of the moon each night is caused by the moon's orbit around the Earth.

The moon makes a complete circle, or revolution, around the Earth approximately every 28 days.

Over the course of that 28 day period, the moon's appearance gradually changes.

This is known as the 'lunar cycle.'

At all times during the lunar cycle, half of the moon's surface is lit up by the sun while the other half is dark.

The part of the moon that we can see from Earth is called the 'visible face' of the moon.

The amount of illumination on the visible face of the moon is called the moon's 'phase.'

Our lunar cycle consists of 8 major named phases of the moon.