Why is the sky blue?

Have you ever looked up on a sunny day and wondered why the sky is such a lovely blue? Let’s find out!

Sunlight is sneaky

The light from the Sun looks white, but it is really all the colours of the rainbow hiding together — red, orange, yellow, green, blue, and purple. When sunlight zooms down to Earth, it bumps into tiny, tiny bits of air.

The blue light bounces best

When sunlight hits the air, the colours get scattered, like a ball bouncing around a room. The blue light is small and wiggly, so it bounces the most. It scatters all across the sky in every direction.

So when you look up, blue light is coming at your eyes from everywhere. That is why the whole sky looks blue!

Why are sunsets orange?

In the evening, the Sun is low and its light has to travel through much more air to reach you. By then, most of the blue has bounced away, and the reds and oranges get their turn to shine. That is why sunsets are full of warm colours.

Wonder fact: On the Moon there is no air to bounce the light, so the sky there is always black — even in the daytime!