Question: why is the sky blue ?

Ceri-Wyn Thomas answered on 23 Jun 2010:

The sky is blue because the particles and molecules in our atmosphere scatter the sun’s light. This is known as Raleigh scattering and the light bounces off these molecules in all different directions. Longer wavelengths of visible light aren’t affected as much, so red and orange wavelengths pass through- but the shorter wavelengths towards the blue end of the spectrum bounce off all of the molecules in our atmosphere and we see that reflected blue light everywhere we look. When you look at the horizon the sky is usually much paler and that’s because the blue light has to pass through more atmosphere to reach your eyes and gets scattered more.