Day and Night: Why the Sky Changes

The bright Sun

Look outside in the morning. The sky is bright. There is light everywhere. Where does all that light come from?

The light comes from the Sun. The Sun is a giant ball of hot, glowing gas, far, far away in space. It is so bright that it lights up the whole sky for us. We call this time day.

The Sun is like a big light for the whole world. It helps us see. It keeps us warm. Plants need it to grow. We could not live without the Sun!

Then it gets dark

Now think about the evening. Slowly, the sky turns orange, then pink, then dark blue. Soon it is dark. The stars come out. This is night.

At night the Sun is gone from your sky. It feels cooler. We go to sleep. But where did the Sun go? Did someone turn it off?

No! Here is the big secret: the Sun never turns off. It is always shining. So why does it get dark?

The Earth spins

Our Earth is a huge round ball in space. And the Earth is always spinning. It turns round and round, slowly, like a very slow spinning top.

You cannot feel it, but right now you are spinning with the Earth!

Hold up a ball. Shine a torch on it. One side of the ball is bright. The other side is dark. The torch can only light up the side facing it.

The Earth is just like that ball. The Sun can only light up the side of Earth facing it.

• When your part of Earth faces the Sun → it is day. Bright!
• When your part of Earth turns away from the Sun → it is night. Dark!

The Earth keeps spinning, so day turns into night, and night turns back into day. Round and round, every single day.

The Sun only looks like it moves

In the morning the Sun is low. At lunchtime it is high. In the evening it is low again, and then it goes down. It looks like the Sun is sliding across the sky.

But the Sun is not moving across the sky. The Sun stays still. It is you who is moving, because the Earth is spinning! The Sun only looks like it moves. Tricky, isn't it?

Try it yourself: make day and night

You can be the Earth and a grown-up can hold a torch as the Sun.

You will need: a torch and a small sticker.

1. Ask a grown-up to stand still and shine the torch at you. The torch is the Sun.
2. Put a sticker on your tummy. The sticker is your house.
3. Stand facing the torch. Your sticker is bright. It is day for your house!
4. Now slowly spin yourself all the way around.
5. Watch the sticker. When it faces the torch → day. When it turns away → night. You made day and night!

Stay safe: never shine a torch straight into your eyes, and spin slowly so you do not get dizzy.

What we learned

The Sun is always shining. The Earth spins like a slow top. When our side faces the Sun, it is day. When our side turns away, it is night. That is why the sky changes from bright to dark and back again, every day.

Want to learn more about light? Find out how light makes shapes on the ground in Light and Shadows.