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
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.
Subscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun science facts.
Authors
Robert is a science writer and visiting professor of science at Aston University. He likes maths, West End musicals and hamsters.
