Raios crepusculares nos Céus do Brasil [Anticrepuscular Ray]

Balance

Senior Member.
No idea what title I should use so stole the FB one. There appears to be two opposing sunets? just...Wow.



 
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Anti-crepuscular ray:
http://en.wikipedia.org/wiki/Anticrepuscular_rays

Anticrepuscular rays are similar to crepuscular rays, but seen opposite the sun in the sky. Anticrepuscular rays are near-parallel, but appear to converge at the antisolar point because of linear perspective.[1] Anticrepuscular rays are most frequently visible near sunrise or sunset. Crepuscular rays are usually much brighter than anticrepuscular rays. This is because for crepuscular rays, seen on the same side of the sky as the sun, the atmospheric light scattering and making them visible is taking place at small angles (see Mie theory).

Although anticrepuscular rays appear to converge onto a point opposite the sun, the convergence is actually an illusion. The rays are in fact (almost) parallel, and the apparent convergence is to the vanishing point at infinity.[2]
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In the example in the OP, there's basically a gap in the clouds that is letting in one ray of the setting sun that goes all the way across the sky. A lucky arrangement of clouds and timing.
 
More commonly, the ray is a shadow. Here you can see the shadow cast by a cloud on the horizon:


But imagine that scene with a long line of clouds blocking all the sun, and a single gap where the cloud is. You'd get an inverted image, with a golden ray of light instead of a shadow. And if you are lucky enough it will go all the way across the sky, and you will get the anti-crepuscular ray.
 
I can understand (and most probably have seen) crepuscular rays but the anti ones scrambles my brain as they converge opposite the source
 
I can understand (and most probably have seen) crepuscular rays but the anti ones scrambles my brain as they converge opposite the source

Stand on some train tracks. Look one way - the track converge in the distance. Turn around, look the other way, they converge . Same thing.

While the rays look like they are diverging from a point light source, the sun is 93 million miles away, so the rays are parallel in the sky.

Something like this which seems to have diverging rays:


is actually parallel rays.

http://earthobservatory.nasa.gov/IOTD/view.php?id=76261
 
Ah, I get it now. The fact they "seem" brighter as they narrow, giving the impression the source is opposite the sun is also explained. I think that's where my thoughts stalled.
 
Ah, I get it now. The fact they "seem" brighter as they narrow, giving the impression the source is opposite the sun is also explained. I think that's where my thoughts stalled.

And I think in this instance the ray hits some clouds way in the distance, creating a bright spot that looks a bit like a sun. Again the parallel nature of the sun's rays is what creates the illusion.
 
It's also interesting to note that the moon is also responsible for crepuscular rays.
upload_2014-6-10_15-4-51.jpeg
Explanation: What's happening over that castle? While waiting for the Moon to rise last month in Thurso, Scotland, amateur astrophotographer Stewart Watt took a three minute exposure of the background stars. The above image was the surprising result. Patchy clouds in front of the rising moon created crepuscular rays streaming across the night sky in spectacular fashion. In the foreground is a stone tower from Thurso Castle, a 12th century fortress augmented in the 17th century. Above thecrepuscular moon rays are stars, many from the constellation of the Lion (Leo). Visible to the right of the tower is the planet Saturn.
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