Question: why does the sky change colours as it gets nearer to night

Dervil Cody answered on 15 Nov 2016:

Great question Laura, I’ll try to answer it! The light from the Sun, like all white light, is made up of a range of different colours – Red, Orange, Yellow, Green, Blue, Indigo, Violet (ROYGBIV). You’ve probably done an experiment in class where you use a prism to split light up into the different colours, like a rainbow effect? This is kind of similar.

As light particles pass through the atmosphere, they bounce or scatter off the molecules of oxygen and nitrogen. The part of the light that is blue is scattered to a greater extent, and so the sky appears blue during the day when the Sun is directly overhead.

As the day turns into the evening, the sky starts to turn orangey/red. This is because the Sun has moved towards the West and is no longer directly overhead, so the light particles have to travel a greater distance, and so they bounce off a greater number of air molecules. As a result of this, orange and red light is scattered more, and so the sky appears red! The more molecules in the air, the redder the sky will be. So if there is more pollution in the air, the sunset will be redder.

I hope that answers your question!