Silly solar question?...

Chadford

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From time to time you may take a snapshot like this...

mryee1.jpg


...(sorry If i'm being really thick) but why does the sun appear as a point source
just above the clouds (i.e. way too close)?

:confused:

Must be a cloud reflection thing???
 
you need filter caps and the like if you are taking shots like that I would think, as the sun is just too damn bright even behind clouds
 
51328y.jpg


Perhaps creationism will endow us with all the knowledge we need?

:)
 
It's not the sun which is a point source, it's a small break in the clouds. Possibly even the one which can be seen in the picture.
 
Possibly because the setting sun is roughly at the same level as the camera and the cloud bank, giving the impression of a close point source (through the breaks in the cloud).
 
I had to read the OP a couple of times to grasp the problem.

If I sight down a long straight road, the parallel edges still sweep outwards and past each side of my field of view and behind me, even though they don't geometrically converge. Now put a head-light at the end of the road, and imagine light rays illuminating the edges.
 
I had to read the OP a couple of times to grasp the problem.

If I sight down a long straight road, the parallel edges still sweep outwards and past each side of my field of view and behind me, even though they don't geometrically converge. Now put a head-light at the end of the road, and imagine light rays illuminating the edges.

Good theory, but I don't think that's it, the angles are too sharp for that.

If it is the sun reflecting off a cloud then why are the beams seemingly coming from one point rather than reflecting all over the place?

:)
 
After a bit more thought, I think I was wrong. It would be a bit of a coincidence if it were a simple pinhole effect through the clouds, and it doesn't look right anyway.

What we're seeing is sunlight reflected off dust particles in the air. I think what happens is that only rays which strike the particles at a certain angle are reflected to the eye. Assuming all the particles are roughly the same size and shape, then we'd only see those particular rays, which would line up like in the picture.

It's similar to how a rainbow works with water droplets.

It's only a guess, mind you.
 
Gaps in the cloud let beams of light through. Mist/dust/drops in the line of the beams scatter light in the direction of the viewer. The beams radiate from the sun. The viewer can not see the component of the beam which is in the direction he is looking, only that which is orthogonal.

Or...imagine the moon on the horizon,and a laser shining from it to a building, say, ten miles to your left.

What would you see?.....nothing. But if there was dust in the atmosphere along the path of the beam, then light would be scattered towards you and you'd see the beam. That beam would start somewhere in the vicinity of the moon and then you would see it apparently sweep around the horizon to the building. i.e. it'd appear to radiate sideways from the moon.
 
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Gaps in the cloud let beams of light through. Mist/dust/drops in the line of the beams scatter light in the direction of the viewer. The beams radiate from the sun. The viewer can not see the component of the beam which is in the direction he is looking, only that which is orthogonal.

Or...imagine the moon on the horizon,and a laser shining from it to a building, say, ten miles to your left.

What would you see?.....nothing. But if there was dust in the atmosphere along the path of the beam, then light would be scattered towards you and you'd see the beam. That beam would start somewhere in the vicinity of the moon and then you would see it apparently sweep around the horizon to the building. i.e. it'd appear to radiate sideways from the moon.
That effect only works with a tight beam, like a laser or car headlights in fog, and all viewers see the same thing from all angles. It won't work with the Sun or Moon.

What worries Chadford (I think?), and it's a good question, is that the Sun is not a point source, so why do the rays seem to emanate from one; and sunlight is not unidirectional, it radiates at all angles. As I say, I think it's preferential scattering, like a rainbow.
 
The sun isn't a point source, but it's only 1/2 degree wide. The edges of shadows are pretty clearly defined after all!

Okay - let's try another way: imagine looking down a long tube, with spaced parallel lines drawn up the inside from far end to near end. If you lose depth perception then it will look like a circle radiating lines out radially, like spokes.
 

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