Why is the sky blue?

Sunlight looks white, but it is really made of many colours mixed together — red, orange, yellow, green, blue, indigo and violet.

When sunlight enters the air around the Earth, it bumps into tiny bits of gas and dust. Blue light is scattered — spread around — much more than red light, because blue light travels in shorter waves.

So when you look up, blue light comes to your eyes from every part of the sky. That is why the sky looks blue in the daytime.

At sunset, the light travels through more air. Most of the blue is scattered away before it reaches you, and the red and orange are left. That is why sunsets are orange and red.