• Question: What is your favourite phenomena to do with light in the Earth's or another planet's atmosphere (e.g. aurorae, circumzenithal arcs etc.)? Can you explain how and why it happens?

    Asked by strangeness to Arttu, Ceri, James_M, Monica, Philip on 20 Jun 2011.
    • Photo: James M Monk

      James M Monk answered on 20 Jun 2011:

      A moonbow is a pretty cool phenomenon. It happens when the moon is very bright, usually in the spray of a waterfall. There is a famous one at Yosemite Falls in California – sadly I did not see it when I was there, but I found some pictures here:http://www.txstate.edu/news/news_releases/news_archive/2007/04/Moonbow041207.html

      The explanation is the same as a normal rainbow – the white moon light is twice internally reflected in the drops of water. Since blue light slows down more than red light in water, the blue light is bent through a greater angle than the red, thus separating the colours.

    • Photo: Arttu Rajantie

      Arttu Rajantie answered on 20 Jun 2011:

      I think nothing beats the good old sunset.

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