Why is the sunset orange?

The answer, for parents

Short answer: At sunset, light travels through more air, so the blue scatters away and orange and red light reaches us.

Sunlight looks white. But it is a mix of all the colours of the rainbow. A rainbow appears when sunlight is split into its colours. The Earth is wrapped in air, called the atmosphere. The air bounces sunlight in all directions. This is called scattering. Blue light scatters the most, so the daytime sky looks blue.

At sunset, the Sun is low. Its light must travel through much more air to reach you. Most of the blue light is scattered away on the way. Mostly orange and red light is left. Dust, smoke and haze can scatter even more light. So sunsets can look extra red when the air is hazy. Look back at the haze lesson!

In the lesson, your child puts this cause-and-effect chain in order: Sunlight is a mix of colours → Air scatters blue light the most → At sunset, light travels through more air → Most of the blue is scattered away → Orange and red light reaches our eyes.

What if the Earth had no air? There would be no blue sky. The sky would look black, even in the daytime. And there would be no orange sunsets.

Is the sunrise orange too? Yes. At sunrise the Sun is low too. Its light also travels through lots of air. Morning skies can be orange or pink.