What colour is the sky?

If somebody asked you to tell them what colour the sky is, you’d probably say blue. Most people do. But is the sky really blue? If the sky was blue, it should stay blue all the time, but the sky turns different colours at sunrise and sunset. So what colour is the sky?

It’s actually clear!

Our planet is surrounded by the atmosphere: a layer of gases that keep the air we breathe inside and helps protect us from harmful radiation from space. The atmosphere is a little like a bubble. If you think of a soap bubble, it’s clear but you can sometimes see colours on the surface.

The reason whe can see colours is because white light is acutally made up of seven different colours. We can see this if we break apart the light using a prism. A soap bubble acts a little like a prism, breaking up white light and scattering the different colours. Whatever colours reach our eyes are the colours that we see.

The sky looks blue because when the sun is overhead, the atmosphere scatters more blue light than any other colour, so the colour that reaches our eyes is blue! But at sunset, the light has to travel farther to reach our eyes. The blue light gets scattered so much that is disappears, and the colours that now reach us are reds, oranges, and pinks. And after the sun sets, there’s no more light to scatter, so we can see straight though the clear atmosphere to the stars in space!