• Question: Why are clouds white?

    Asked by cookieland to Ed, Sam, Steve on 22 Jun 2011.
    • Photo: Sam Tazzyman

      Sam Tazzyman answered on 22 Jun 2011:

      They are made from water vapour, like steam, which is white. But I don’t know *why* water vapour is white, except that it must reflect all wavelengths of light equally well. Anyone else?

    • Photo: Ed Morrison

      Ed Morrison answered on 22 Jun 2011:

      I guess it’s because they scatter light so that it all mixes together, producing white. But ultimately everything has to be some colour. There’s no particular reason in many cases.

    • Photo: Steven Daly

      Steven Daly answered on 22 Jun 2011:

      It is for a similar reason to why the sky is blue, and why the sunset is red. For clouds it comes down to the fact that the water droplets and ice crystals that make clouds are much bigger than the wavelength of all the visible colours. This means that it scatters all light equally well, and that makes them white.

      Things like chemicals, blood, books, etc. get their colour from depending on what colours the object will absorb and what colours will make it to your eyes. So for example red things absorb blue light best.

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