Why do rays of light from the Sun appear to be angled?

[Hobart]

When the sun's rays break through a cloud there appears a radiating pattern but if one drew a line through these rays they would meet much closer than the distance to the sun. How come?

 

[jbriggs444]

When the sun's rays break through a cloud there appears a radiating pattern but if one drew a line through these rays they would meet much closer than the distance to the sun. How come?

You are imputing an angle that is not there. The rays, if extended, would meet at the sun. There are no good distance cues to make it clear that those rays are nearly parallel to your line of sight rather than at right angles to it.

 

[mfb]

Parallel straight lines, seen from an angle, appear to come together at a fixed point in the sky - in this case the fixed point is the Sun. Where else would you expect the rays to point to? You don't see their distance easily, but the rays are mainly pointing away from you as you look upwards.

 

[sophiecentaur]

The rays, if extended, would meet at the sun.

That simple statement would apply if the Sun were a simple point source. But every shadow from the sun has a fuzzy edge (penumbra) due to the finite size of the source. This gives a +_0.5° spread (= 1° total) which is visible and probably exaggerated / foreshortened by the viewing angle of the sunbeams.

 

[DrGreg]

Perspective!

 

[anorlunda]

When the sun's rays break through a cloud there appears a radiating pattern but if one drew a line through these rays they would meet much closer than the distance to the sun. How come?

Do you mean this?

 

[sophiecentaur]

Do you mean this?
View attachment 223121

The way light beams appear is not intuitive and accounts for one of the groundless arguments that the Moon Landing Photos were faked.

 

[Shadow89]

When the sun's rays break through a cloud there appears a radiating pattern but if one drew a line through these rays they would meet much closer than the distance to the sun. How come?

I noticed that too. My personal theory: These "beams" (actually light bounced off of moisture/dust in the air) have already been reflected one or more times before you see them. Thus, the beams may seem to radiate from Area A (brightly lit, top of the clouds) through Area B (Shadow zone beneath the clouds).

I remember watching an oil-painting tutorial with a professional painter who dicussed this, and how to use it to set the scene in an environment painting, but I can't find the video now, unfortunately.

 

[sophiecentaur]

I noticed that too. My personal theory: These "beams" (actually light bounced off of moisture/dust in the air) have already been reflected one or more times before you see them. Thus, the beams may seem to radiate from Area A (brightly lit, top of the clouds) through Area B (Shadow zone beneath the clouds).

Yep. I could believe that, too. The 'tunnel' between clouds can be very bright due to scattering.

 

[mfb]

I noticed that too. My personal theory: These "beams" (actually light bounced off of moisture/dust in the air) have already been reflected one or more times before you see them. Thus, the beams may seem to radiate from Area A (brightly lit, top of the clouds) through Area B (Shadow zone beneath the clouds).

What you see with your eyes is light scattered in the air, obviously, but the regions you see are straight lines directly from the Sun.

 

[russ_watters]

I noticed that too. My personal theory: These "beams" (actually light bounced off of moisture/dust in the air) have already been reflected one or more times before you see them. Thus, the beams may seem to radiate from Area A (brightly lit, top of the clouds) through Area B (Shadow zone beneath the clouds).

Ok, but you realize based on the other explanations that this is wrong, right? Those rays are in fact nearly parallel. They are not bounced around, creating a new source.

What you see with your eyes is light scattered in the air...

I'm not sure what you mean by that, but it sounds pretty wrong; air (the atmosphere) is pretty transparent. There is minimal scattering.

[edit] Softened my adjectives. The scattering is quite a bit more than I realized: just a few percent for red, but 20% for violet.
http://www.skyandtelescope.com/astronomy-resources/transparency-and-atmospheric-extinction/

 

[sophiecentaur]

; air (the atmosphere) is pretty transparent. There is minimal scattering.

If that were totally the case, you wouldn't see sunbeams 'side on'.

 

[CWatters]

Try a picture where the sun is visible. They seem to converge on the sun to me..

https://goo.gl/images/VhEbVA

If you are asking why aren't they nearly parallel it's due to perspective as already mentioned. Railway lines are parallel but seem to converge due to perspective.

 

[russ_watters]

If that were totally the case, you wouldn't see sunbeams 'side on'.

What tiny fraction of a percent would that be, and what is your threshold for "minimal"?

 

[pikpobedy]

The sun is extremely far as such the rays are parallel when they arrive on Earth and as such the wave front is planar,
The hole in the clouds acts as a gross point source that the rays emanate from.

As for the parallax cited by others... not really from the sun.
Parallax from the opening in the cloud... yes.

 

[jbriggs444]

As for the parallax cited by others... not really from the sun.
Parallax from the opening in the cloud... yes.

In every picture I can find, the beams converge on the position of the sun, not on some hypothetical single hole in the clouds.

 

[pikpobedy]

You know the sun is 150 million kilometers distant.

 

[jbriggs444]

You know the sun is 150 million kilometers distant.

Yes. And the holes (plural) through which its beams peek are not.

 

[CWatters]

Shadows also converge on the sun. No "hole" required.

http://www.raysoflightministry.com

 

[CWatters]

You can make the same rays or shadow converge or diverge simply by looking at them from different direction...

 

[Keith_McClary]

You can make the same rays or shadow converge or diverge simply by looking at them from different direction...

You can sometimes see the rays converging to the anti-solar point. (The Sun is at your back when looking at a rainbow.)

 

[A.T.]

The sun is extremely far as such the rays are parallel when they arrive on earth

Yes

The hole in the clouds acts as a gross point source that the rays emanate from.

No. The rays visible in the pictures are still parallel in 3D, just not in the 2D projection of the picture.

 

[klimatos]

As to the question of how much on the incoming sunlight is diffused (molecular and particulate scattering of photons), the most reliable recent breakdown appears to be 23% absorbed by the atmosphere, 30% diffused by the atmosphere, and the remaining 47% transmitted by the atmosphere to the surface of the earth.
[K. E. Trenberth, J. T. Fasullo, and J. Kiehl; “Earth’s Global Energy Budget”; Journal of the American Meteorological Society, March 2009.]

 

[Keith_McClary]

Sunbeams viewed from an airplane look almost parallel.
https://www.flickr.com/photos/stuckincustoms/20154632802/in/photostream/
They should look parallel when viewed from space. Has this ever been photographed?

 

[mfb]

Of course

 

[OmCheeto]

...
They should look parallel when viewed from space. Has this ever been photographed?

From directly above they would, but not at an angle.

original and my attempt to doodle lines that follow the shadows​

 

[sophiecentaur]

From directly above they would, but not at an angle.

View attachment 223780
original and my attempt to doodle lines that follow the shadows​

1. What sort of lens was used for that picture? Wide angle, no doubt.
2. The picture was taken from only 400miles above and the Earth's curvature could account for the apparent different angles of shadows. Remember all the hoohaah about the shadows in pictures taken on the Moon and the suggestions that they had to be faked? The effect of the appearance of shadows is not intuitive.
The lines you sketched would pass through the anti solar point which is 150Mkm away and not just to one side of Earth.

 

[DaveC426913]

Sunbeams viewed from an airplane look almost parallel.
https://www.flickr.com/photos/stuckincustoms/20154632802/in/photostream/
They should look parallel when viewed from space. Has this ever been photographed?

To be clear, the degree to which they look parallel has nothing to do with what altitude you view them from - be it the ground, an airplane or the ISS.

It is entirely due to your viewing angle being normal (90 degrees) to the rays.

From the ground, at sunset, if you were to look at the zenith, you would see parallel rays.
From an airplane, if you were to look at the rays 90 degrees to their emanation, they would look parallel.
From an airplane, if you were to look at rays immediately around the sun, they would be just as divergent as seen from the ground.
And likewise from the ISS.

Fun fact:
Those rays in the left column are called crepuscular rays.
Those rays in the right column are called anti-crepuscular rays.

 

[OmCheeto]

1. What sort of lens was used for that picture? Wide angle, no doubt.

I think it was just a standard lens.
If you'll note, the solar panels are straight.

With a wide angle lens, straight objects aligned with the periphery will curve:

2. The picture was taken from only 400miles above and the Earth's curvature could account for the apparent different angles of shadows. Remember all the hoohaah about the shadows in pictures taken on the Moon and the suggestions that they had to be faked? The effect of the appearance of shadows is not intuitive.
The lines you sketched would pass through the anti solar point which is 150Mkm away and not just to one side of Earth.

I don't think the curvature of the Earth has much effect in my first image.
I modeled the image of a view from the ISS, flattening what was visible, and came up with this:

Looks very similar, in my imagination.

 

[sophiecentaur]

Looks very similar, in my imagination.

How about for larger angles? I wasn't sure what your modelling was showing. This sort of geometry is hard to visualise. (Hence the Apollo misconceptions)

Wide angle lenses don't always give curved lines and some are terrible. The panels in the cloud shots are tapered, implying a fairly wide angle lens. But the taper goes the other way compared with the shadows so you can probably ignore my comment. (Situation normal.)

 

[OmCheeto]

How about for larger angles?

I was afraid you would ask that.
Unfortunately, I didn't set up my original simulation for such a task, and it would have taken me another 3 hours to add larger angles, so I scratched my head, and came up with a faster solution: Google Earth Pro and their "grid" lines.

Looking west (latitude lines are parallel) from the height of the ISS:

It looks as though the Earth's curvature throws things off a bit more than I suspected, but not too much.

And from a geosynchronous orbit height:

The lines are "visually" quite linear.

I wasn't sure what your modelling was showing. This sort of geometry is hard to visualise. (Hence the Apollo misconceptions)

"hard to visualize"? I'd say; "Impossible".

Though, I did find one video that shows it quite well:

Wide angle lenses don't always give curved lines and some are terrible. The panels in the cloud shots are tapered, implying a fairly wide angle lens. But the taper goes the other way compared with the shadows so you can probably ignore my comment. (Situation normal.)

Along with finishing an on-line Linear Algebra course last week, I went back and studied lens/lense "stuff" yesterday. All I can say is; "Ehr mehr gerd! Maths is Hard!"

 

[Mister T]

When the sun's rays break through a cloud there appears a radiating pattern

God's rays!

I read an article some 10 years ago or so that explained this. The same explanation is given here:

Of course

Let me expand a bit on this comment:

You are imputing an angle that is not there. The rays, if extended, would meet at the sun. There are no good distance cues to make it clear that those rays are nearly parallel to your line of sight rather than at right angles to it.

Note that when you expose your eyes to a bright source, such as a bare light bulb, you can then see an after-image of that source when you blink your eyes. Practice this until you see it happen for yourself. (Some people who wear contact lenses may not be able to see this phenomenon.)

When you are able to see this after-image clearly by blinking, do so when staring a near-by wall. Now do the same thing for a far-away wall, that is, blink to see the same after-image while staring at a wall that is much further away. This is a fascinating demonstration! The after-image is much larger when the wall is farther away.

The reason is the same as the reason why the moon looks bigger when it's near the horizon.

The theory is that we learn as children that things that are further away appear smaller. Mom's face looks huge when she comes into rub noses with us, but when she's on the other side of the room it looks smaller. So in our minds we learn to compensate. We artificially inflate the sizes of things that are far away to make up for the fact that they subtend a smaller angle. When we look at a moon that is high above the horizon we have no clues as to how far away it is. But when the moon is low and near the horizon we can see it next to other things like trees. There we know it's further away than the trees so we inflate, in our minds, it's size.

The same reasoning applies to God's rays. The distance between any adjacent pair of rays is very nearly the same, that is, the rays are parallel. But in our minds we artificially inflate that distance for portions of the rays that are further away from us.

 

[sophiecentaur]

blink to see the same after-image while staring at a wall that is much further away.

You can rely on your brain to let you down when you need it most.

 

[DaveC426913]

Note that when you expose your eyes to a bright source, such as a bare light bulb, you can then see an after-image of that source when you blink your eyes. Practice this until you see it happen for yourself. (Some people who wear contact lenses may not be able to see this phenomenon.)

When you are able to see this after-image clearly by blinking, do so when staring a near-by wall. Now do the same thing for a far-away wall, that is, blink to see the same after-image while staring at a wall that is much further away. This is a fascinating demonstration! The after-image is much larger when the wall is farther away.

The reason is the same as the reason why the moon looks bigger when it's near the horizon.

I've known about the Moon size thing for a long time, and have often struggled to explain it to people. I've never heard it demonstrated so eloquently using a light bulb afterimage! Thanks!

 

[dAVID wINTERS]

This convergence perception is NOT, repeat NOT, due to mere parallax converging on the sun. L

Anybody who understands celestial navigation knows that the first unshakable tenant is that celestial bodies viewed from Earth at any particular moment display NO PARALLAX. NONE. Not even a smidgen. They are simply too far away. Without that understood, celestial navigation would be impossible.
That is what makes the apparent parallax of sun rays through clouds such an interesting paradox.