• Question: Why is the sky blue?

    Asked by naadine to Charlie, Eoin, Jemma, Julian, Steve on 21 Mar 2011.
    • Photo: Julian Rayner

      Julian Rayner answered on 17 Mar 2011:

      Because the atmosphere scatters the light from the sun. Light is a mixture of many colours (hence rainbows). Red and yellow have longer wavelengths, which pass through the atmosphere. Blue has a smaller wavelength, so gets scattered more – making the sky seem blue.

    • Photo: Charlie Ryan

      Charlie Ryan answered on 17 Mar 2011:

      hello naadine great question and also quite a tricky one. I think, but i might be wrong, that it was einstein who first managed to work out why!! so it must be tricky!
      When light from the sun enters the atmosphere it hits air particles – mostly nitrogen and oxygen because that is what the atmosphere is mostly made from. These particles scatter the light in all sorts of directions, effectively bouncing the light waves round the sky. But they are better at scattering light of certain wavelengths and it just so happens that it is the wavelength of blue light that they best scatter it. so the blues light bounces around more (gets scattered) and makes the sky seem blue.
      I think that’s right!

    • Photo: Stephen Moss

      Stephen Moss answered on 17 Mar 2011:

      Hi Naadine

      I think it was Einstein who was came up with a solution to this question, and it was something to do with the scattering of light by molecules. If I was a physicist I’d be able to give you a better answer.

    • Photo: Eoin Lettice

      Eoin Lettice answered on 17 Mar 2011:

      Hi naadine,
      Sunlight (white light) is made up of all the colours in the rainbow. Most of those colours come right through the atmosphere fine, but lots of the blue light is scattered by gas molecules in the sky, so that when we look up, everything looks blue.
      One of the first scientist to ever answer this question was an Irishman called John Tyndall. You can read more about him here: http://url.ie/a9bw

      Eoin

    • Photo: Jemma Ransom

      Jemma Ransom answered on 21 Mar 2011:

      I think it’s something to do with the way the Earth’s atmosphere scatters (or refracts) sunlight – but you would have to confirm that with a physicist!

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