Phases of the Moon

Phases of the moon

Sometimes the moon looks like a circle, sometimes it looks like a crescent, and sometimes you can’t see it at all. What’s going on?

The moon never actually changes shape: it’s always a sphere, like a ball or an orange. But it looks different at different times because of the relationship between the moon, the sun, and the earth.

We live on the earth. The moon travels around the earth, and the earth travels around the sun.

We see the sun shining during the day, and we see the moon shining at night. But the sun doesn’t turn off at night—it’s always shining. We just can’t see it because our part of the earth has turned away from it. And the moon doesn’t shine by itself; it’s just reflecting light from the sun.

phases of the moon

What does all this mean?

It means that the moon, the sun, and the earth are always in different positions compared to each other. And depending on these positions, different parts of the moon are lit by the sun, and this makes it look different.

This is a little hard to picture, so here’s an activity that makes it easier to understand.

moon experiment

You need:

  • An orange
  • A flashlight
  • A dark room
  • A helper

Imagine that you are the earth. The orange is the moon, and the flashlight is the sun.

Stand in the dark room and hold the orange up in front of your face. Ask your helper to walk around the room with the flashlight, pointing it at the orange. As they move, the orange will be lit in different ways.

moon experiment full moon

When the flashlight is behind you, the orange appears fully lit,  as long as it’s not in your own shadow! This is called a full moon.




new moonWhen the flashlight is in front of you, the orange appears fully in shadow, like this is called a new moon.




half moonWhen the flashlight is halfway in between, the orange appears half in shadow, this is called a half moon.




crescent moonWhen the flashlight is almost but not quite in front of you, the orange appears, this is called a crescent moon.




Just like the moon, the orange is always the same shape, but it looks different depending on the angle of the light.

When you’re finished, eat the orange! Vitamin C is good for you.

All these changes in shape are called the phases of the moon. The moon goes through all of these phases about once per month, and then it starts over again. In fact, the word “month” comes from the word “moon”.

What does the moon look like tonight? Where does that mean the sun is?

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Grant Harding is a puppeteer with a degree in biology and a passion for education and the environment. Follow Grant on Twitter, or check out his website.


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