Explainer studio

Sunlight is white. So why is the sky blue?

Sunlight looks white. So why does the whole sky turn blue?

White light is every colour at once

White light is really every colour mixed together, each with its own wavelength.

Not all colours travel the same way

Red light has long waves that pass straight through air. Blue light has short waves that bounce off air molecules.

This is Rayleigh scattering

It's called Rayleigh scattering. Blue light gets scattered across the sky, so it reaches your eyes from every direction.

Then why isn't the sky violet?

Violet scatters even more, but the sun makes less of it and our eyes barely notice it.

Sunsets flip the effect

At sunset, light crosses much more air. The blue scatters away, and the reds are what's left.

The sky is blue because blue light scatters the most.

So the sky is blue because blue light scatters the most.