What causes a halo around the sun? © Getty Images

What causes a halo around the sun?

It’s not often that refraction starts rumours, but when it does they get around.

Asked by: Bilge Sutcliffe, Newquay

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The appearance of a huge, perfectly circular halo round the sun in Mexico earlier this year sparked rumours of the impending end of the world. In reality, it was the product of sunlight being refracted through hexagonal ice crystals high in the atmosphere. Water droplets can do the same, producing a smaller but more colourful halo.


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