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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Mick West

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

Mick West

Administrator
Staff member
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.
 

Balance

Senior Member.
I can understand (and most probably have seen) crepuscular rays but the anti ones scrambles my brain as they converge opposite the source
 

Mick West

Administrator
Staff member
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
 

Balance

Senior Member.
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.
 

Mick West

Administrator
Staff member
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.
 

Jason

Senior Member
It's also interesting to note that the moon is also responsible for crepuscular rays.
upload_2014-6-10_15-4-51.jpeg
 
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