Why is the sky blue?

Question

Ask Eartha · Accepted Answer

Sunlight looks white, but it's actually made of every colour mixed together. When it hits our air, blue light bounces around the most and spreads all over the sky. That's why you see blue everywhere you look up. Red light doesn't scatter as much, so it stays out of the way. Clever sky! Sunlight looks white, but it's really a mix of every colour of the rainbow travelling together in tiny waves. Some colours have short, wiggly waves, and some have long, lazy waves. When sunlight zooms into our sky, it smashes into tiny bits of air. Blue light has short waves, so it bounces off in every direction, again and again, like a bouncy ball in a small room. Red and orange light have longer waves, so they mostly zoom straight through without bouncing around as much. Because blue light scatters so much more, it fills the whole sky and reaches your eyes from every direction. This scattering trick is named after a scientist called Lord Rayleigh, so scientists call it Rayleigh scattering. It's the same reason sunsets turn red, just the opposite trick happening at a different angle.

Why is the sky blue?

The longer story

Try this at home: make your own scattering

Words to know

For grown-ups: what is my child learning here?

Why is the sky blue?

The longer story

Try this at home: make your own scattering

Words to know

For grown-ups: what is my child learning here?

More questions kids ask