Phases of the Moon

If you look at the Moon every night for a month, you'll notice it changes shape.

You will see it as a full moon.

full moon

A full moon becomes a waning gibbous...

waning gibbous

Then a last quarter...

last quarter

Before shrinking to a waning crescent.

waning crescent

It then disappears altogether, known as a new moon...

new moon

Before becoming a full moon once again.

The changing shapes of the Moon are called phases.

phases

A complete cycle of phases is known as a lunar month.

lunar month
complete cycle of phases

Have you ever wondered what causes these phases of the Moon?

Phases of the Moon

Actually, the Moon does not change shape...

The different phases are caused by the Moon's orbit around planet Earth.

The Moon takes around 28 days to orbit the Earth.

The Moon takes 28 days to orbit Earth.

As the Moon orbits the Earth, light from the Sun is reflected by the Moon's surface.

This allows us to see the Moon.

When the Earth is directly between the Sun and the Moon, we see a full moon.

This is because the side of the Moon reflecting sunlight is facing us.

When we see a last quarter moon, the Moon is further on in its orbit, and we see less of its reflected light.

When the Moon moves between the Sun and the Earth, we see no Moon at all, as the side reflecting the Sun is facing away from the Earth.

This is a new moon.

So, even though it looks like the Moon is changing shape over the course of a month, it is not.

The changing phases are caused by the Moon's orbit around Earth.

phases of the Moon
lunar month