The past few weeks have been thoroughly depressing in the South East, with a succession of grey skies. But Tuesday was gloriously sunny and ended with a stunning sunset with an intense orange colour, framed by a dark bank of clouds. The scene was so surreal it seemed almost like a scene from a movie and it served as a reminder that the Earth’s atmosphere can do wonderful tricks with sunlight.
As sunlight travels through the Earth’s atmosphere it is refracted by gases and tiny particles of dust and this creates blue-coloured skies. At sunset, the light has to pass through more atmosphere — up to 40 times as much air compared to midday — and bounces the sunlight around so much that the blue colours are lost completely, leaving behind yellows, oranges and reds. The amounts of moisture, dust and pollution in the air are all factors that produce different coloured sunsets.
Last week a very strange sight was seen over China, two suns appeared almost side by side in the sky, one slightly fuzzy and orange, the other crisper and more yellow. A video of the phenomenon can be seen at http://bit.ly/h1b40I
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This extremely rare spectacle was not sun dogs, in which images of the suns appear much further away from the real sun, created by ice crystals in high cirrus clouds. The double suns seen in China were very different and may have been a type of mirage.
One clue comes from a report on June 14, 1956, made by the crew of a ship in the North Atlantic: “Shortly before sunset. twin suns were observed side by side, quite clearly separated. This phenomenon persisted for two minutes, after which the image gradually elongated in the direction of the true sun, eventually merging with it.”
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In this incident, it appears that an unusually dense patch of atmosphere appearing in front of the sun may have bent the sunlight like a glass prism, creating an extra image of the sun before merging with it.