Why is the sky blue and red-orange in the evening?

Imagine light as a colorful rainbow made of many little parts, which together look white. These colors travel like tiny waves through the air.

Sometimes you can see a rainbow in the sky – it shows that light is made of different colors.

White light from the sun contains the colors: red, orange, yellow, green, blue, and violet.

When light hits something – like tiny particles in the air – it gets sent out in all directions. This is called scattering.

Imagine you shine a flashlight through fog: The light spreads out in the fog and becomes visible everywhere, not just where you point it.

It’s the same with sunlight in our air. Especially blue light waves are scattered more than red ones.

Because blue light is scattered more strongly, many more blue light particles reach our eyes from all directions in the sky. The other colors don't reach us as often.

That's why the sky appears blue during the day. The blue comes from the fact that these light waves are directed towards us the most.

 

When the sun is low, for example in the evening, sunlight has to travel a much longer path through the air to reach us.

Most of the blue and green light gets scattered away and is lost along the long path.

Mainly the red and orange light waves remain, which make it all the way to our eyes. That’s why the sky often looks red, orange, or pink.

Imagine you have a flashlight in the dark and it’s foggy. The light from the flashlight gets scattered by the fog. You see the light shining everywhere in the fog, not just at the target point of the flashlight.

It’s the same with the sun and the air in the sky. Our air is much clearer than fog, but many tiny particles (like dust or water droplets) scatter the light – especially blue light. That's why our sky looks blue!

This table helps you remember it quickly!