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  • Writer's pictureGethin Thomas

Crepuscular Rays

Originally published on Photoblog by Gethin Thomas NOVEMBER. 18, 2020

[105-365] 18th. November 2020- A few years back I was in a photography club and we would have photo meets, sometimes in the evening. One such evening I discovered the word crepuscular. I had never heard it before but I just thought it was a brilliant word, a word that is just enjoyable to say especially if you roll the r a little. Several members of the club had science backgrounds and a few of us were also in the Understanding Science Group too.

On this evening we saw these distinctive rays of sunlight that filter through cloud which I also witnessed today at dusk, I had seen them before but had no idea what they were called or what caused them. They are more commonly seen just after sunset as you need something to act as a broken barrier to split the light into separate rays. A mountain range on the horizon after sunset will also do the trick.

Crepuscular- Resembling or relating to twilight. Mid 17th century: from Latin crepusculum ‘twilight.

What is fascinating though is knowing that although they seem to fan out into a classic Art Deco sun with rays motif, the rays from the sun are parallel when they reach Earth, and that they only appear to fan out like this due to perspective, in exactly the same way that railway tracks disappearing into the distance appear to converge. We know that railway tracks are always parallel and that trains do not actually get smaller as they get further away and the tracks do not converge, but for some reason we have trouble visualising exactly that when it comes to sunrays.

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