Double rainbow

In his work Meteorologica (III.2, 371b33-372a3), Aristote wrote:

Not more than two rainbows occur at the same time. Of two such simultaneous rainbows each is three-coloured, the colours being the same in each and equal in number, but (i) dimmer in the outer bow and (ii) placed in the reverse order.

On 31 August 2010 Zagreb saw some drammatic weather, including heavy nimbostratus clouds which started to tear apart on the western horizon at the sunset. Here are two photographs I made from the window of my study, facing east, which verify Aristotle’s points (i) and(ii). I became aware of these two facts only after reading the quoted passage.

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2 Responses to Double rainbow

  1. Great blog. It’s a shame, professor, that you don’t get that much response to your posts. As for double rainbow, I’ve read that this happens because the light enters the sphere of a raindrop from two different angles. One set of raindrops will deflect the light at 42° and the other at 51°. It is also interesting that if a person watches the two rainbows from a great height (like from a travelling airplane), he or she would see the two bows in reverse order. The one that seems dimmer to us from the ground would have the colour and brightness of the primary rainbow, and viceversa.

  2. Vita Žiborski says:

    Have you ever seen a circular rainbow? extraordinary experience, I sow it recently above Zagreb descending with the plane just before entering the clouds. I wonder how and when scientists got aware that every rainbow is a circular one?

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