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Strange Earth Science PoD

Posted: Mon Oct 03, 2011 8:59 pm
by JohnD
The EarthPoD for toady 3rd Oct 2011 shows a green flash.
But the cloud scape around the Sun is strange, making it look as if the Sun is popping up through the clouds.

http://epod.usra.edu/blog/

Explanations for this illusion?

JOhn

Re: Strange Earth Science PoD

Posted: Tue Oct 04, 2011 5:04 am
by geckzilla
The atmosphere grows thicker and thicker toward the bottom of the sun until the light is dimmed enough that it can no longer penetrate the clouds. The gradient from thinner at the top to thicker at the bottom creates the illusion. /layman's understanding

Re: Strange Earth Science PoD

Posted: Tue Oct 04, 2011 6:27 am
by JohnD
Thanks, geckzilla, but if I may explain the appearance that puzzles me?

There is a clear line of cloud that delimits the lower visible edge of the Sun. But the horizon is, apparnetly, also a line of cloud, and that is higher up the Sun, making it appear that the Sun is in front of the horizon!. The hulking mass of cloud to the right also appear to be further away than the sun, perhpas because dark objects always recede.

ThIs is clearly an aillusion, but a remarkable one. Any one else see it?
John

Re: Strange Earth Science PoD

Posted: Wed Oct 05, 2011 3:35 am
by geckzilla
Oh, I definitely see what you mean. Once, there was an APOD with a similar illusion which showed the moon and also Jupiter and its moons... All behind clouds. Check it out: http://apod.nasa.gov/apod/image/0907/lu ... 4_riou.jpg

Somehow that photo still baffles me.