• Question: why is the sky blue

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      Asked by Rhiii<3 to Richard on 16 Mar 2016. This question was also asked by !!.
      • Photo: Richard Friend

        Richard Friend answered on 16 Mar 2016:

        Haha, yeah! Love this question. It’s all about light scattering as it hits the atmosphere. The light from the sun is made up of lots of different wavelengths, and the gases in the atmosphere affect these differently. Blue light is scattered much more than red light – this means that light which wouldn’t normally hit your eyes gets scattered by the atmosphere into your eyes, and as the light which is scattered the most is blue, the sky appears blue.

        For the same reasons the sunset appears red when the sun is closer to the horizon, as the light is travelling through much more of the atmosphere, so more of the blue light is scattered away, leaving the red light going straight to your eyes. Also – the sun from space appears to be white, and it’s only because of light scattering that it appears yellow from Earth.

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    • Photo: Stuart

      Stuart commented on :

      And the process is known as Rayleigh scattering! It’s a similar principle to diffraction, which is what happens when X-rays shine on a crystal – it’s used to work out where all the atom positions in the crystal are. You can see diffraction with visible light by looking at a distant bright light through a finely-woven fabric like an umbrella. You should see the dot of light broken up into a symmetrical pattern.