• Question: why actually is the sky blue,if it is something to do with light?

    Asked by to Mark, Matthew, Mike, Paul, Sabina on 13 Mar 2014. This question was also asked by .
    • Photo: Paul Coxon

      Paul Coxon answered on 13 Mar 2014:

      Hi thebiggerinfinity, you’re right it is to do with light 🙂

      The sky is blue due to a process known as Rutherford Scattering.

      Light from the sun is white – ie a mixture of all the colours in the optical spectrum. Blue light has a short wavelength, red light has longer wavelengths.

      When the light from the sun passes through the atmosphere it interacts with the tiny molecules in the air and is scattered in all directions. Blue light, with its smaller wavelength is scattered much more than the red part of the spectrum. This is why when we look at the sky, we see the effects of scattering. Blue light dominates and so the sky appears blue.

    • Photo: Mike Lee

      Mike Lee answered on 13 Mar 2014:

      Imagine the sky is loads of tiny mirrors that only reflect blue light. When the sunshines, only the blue light from the sun is reflected by the sky. The tiny mirrors are too small to see and they actually reflect light in all directions.

    • Photo: Mark Jackson

      Mark Jackson answered on 17 Mar 2014:

      Yup! Sunlight is made up of all the colors of the rainbow: red, orange, yellow, green, blue, and violet. The gas molecules in the atmosphere interact with the sunlight before the light reaches our eyes.

      The gas molecules in the atmosphere scatter the higher-energy (high frequency) blue portion of the sunlight more than they scatter the lower-energy red portion of the sunlight (this is called Rayleigh scattering, named for the physicist Lord John Rayleigh). The Sun appears reddish-yellow and the sky surrounding the Sun is colored by the scattered blue waves.

      When the Sun is lower in the horizon (near sunrise or sunset), the sunlight must travel through a greater thickness of atmosphere than it does when it is overhead, and even more light is scattered (not just blue, but also green, yellow, and orange) before the light reaches your eyes. This makes the sun look much redder.

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