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I got into a discussion regarding the light from the Sun that reaches the Earth and whether it maintains the same path from the moment it was emitted to the point it is processed by our eyes. My thoughts were that each photon reaching the surface of the Earth must have undergone some refraction/reflection while passing through the Earths atmosphere, so while the apparent path of any individual photon can be traced on a straight line directly back to the Sun, the chances of this occurring are slim and from this and one of the answers from this, it would appear some bending does occur, so it is near impossible to have a photon reach our eyes that has maintained a straight path from the Sun since being emitted.

The question here is: if light travels in a parallel path, what then explains the phenomenon where a break in cloud cover produces two rays of light that seemingly converge at a point (Sun).

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My thoughts were that the sheer size of the Sun and the amount of light being emitted would create such an illusion of the divergence in light beams, but then I am unable to reconcile that with the beams not maintaining their actual path. Any explanation or pointers would be appreciated.

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  • The effect is like looking at an object under-water from above. There is clearly a refraction occuring, but you don't see the object diverge, or blurr, though the position or size that you see in your eye is not the true position or size of the object. – philip_0008 Jun 16 '16 at 03:58
  • Yeah, that seems about right, but what explanation can be given for divergent rays that might break through cloud cover that seems to imply that the light rays from the sun are not parallel? – driftavalii Jun 16 '16 at 04:45
  • Does it look like this? – philip_0008 Jun 16 '16 at 05:08
  • yes, that would describe it, but considering cases where the different beams of light could be a lot further apart but still seem to converge. – driftavalii Jun 16 '16 at 05:49
  • Thanks for that link, almost answered my questions, I would appreciate a little further clarification. My understanding was that perspective as applied to lines on earth are in large part a result of the earth's curvature and how our eyes work, in explaining the seeming convergence of the sun rays, which would be applicable, eyes or horizon, I would guess just the eyes since standing at say the equator with the sun overhead, the curvature of the earth shouldn't contribute any perspective effects right? – driftavalii Jun 17 '16 at 00:41
  • I am not an expert in this, but according to QED doesn't the photon travel infinite paths that either average out (or highest probability path) is the direct one (ie. each photon is actually a "photon field")? – Jack R. Woods Jun 17 '16 at 02:06
  • Above comment aside, I think you are right about the light coming in through the atmosphere being somewhat like light coming through water from the bottom of a swimming pool. Isn't this why the sun seems larger when near the horizon? – Jack R. Woods Jun 17 '16 at 02:10
  • Yes, I assume "all" the light undergoes some alteration right? I believe so but would like confirmation or pointers that say otherwise. – driftavalii Jun 17 '16 at 02:32

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