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a Studiolab production.


food design course at TUDelft
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Posted in May 2011

Lights in the sky

Being a nerd is all about seeing things in a different light. And about absorbing vast amounts of knowledge about all sorts of things, and being able to apply it (or at least regurgitate it) when it is necessary. Or also when it is not necessary at all, but you just think it is neat. In this spirit, I once read through the Atmospheric Optics site to satisfy my curiosity about some strange colored spot I had seen in the sky.

It turns out that, of course, there are people that do whole PhDs on this type of thing. Without further ado, here is one photograph.


This was taken in Brussels, shooting directly towards the sun with a fisheye lens. I am holding the lens cap in front of the sun in order to reduce light ghosts and flares. If you look in the upper portion of the picture, close to the flue on the left, you can discern something like a rainbow. A bit lower, right above the sun, there is another slight spray of color like a smiling mouth. These are not artifices from the lens: they were visible then and there. To help you see them, I have increased contrast and saturation along a top to bottom gradient.





In the enhanced picture, you can see the upper arc, the lower upturned arc (very weak) and two curious spots of color on either side of the sun. The one on the right appears just behind that irritating tree, the one on the left is barely visible. I have added outlines to the pictures, so you know what I am talking about.



OK, but what are these things? you are asking yourself. They are optical atmospheric phenomena produced by the interaction of sunrays and tiny ice crystals in the high atmosphere – contrast that with the rainbow, that is produced by interaction with tiny drops of water. The ice cristals can take on various shapes and orientation, giving rise to various phenomena. The best place to see them is not Bruxelles, but rather the South Pole. You can find more detailed information at the Atmospheric Optics website.

My best identification is as follows; the lower two twin splotches of light are sundogs also known as parhelia (always at 22 degrees from the sun!), a useful word for casual conversation. The weak one in the center  is an upper tangent arc, and the big one on top looks to me like part of a supralateral arc. From this information, you can deduce many cheerful facts about the state of the high atmosphere over Bruxelles. 


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