You can often not see a mountain that is just a few dozen miles away, yet you are trying to convince us that we should be capable of seeing infinitly through the atmoplane.
Yes, you often can't see a mountain that is some distance away because it is below the horizon.
We can see stars quite close to the horizon, even though they would have to go through just as much atmoplane as the sun light would.
But that is another big issue with the sun, the angles are all wrong.
If you can not see infinitely through the atmoplane, then at some point, the sun would not be visible. Why does this concept confuse you roundies?
Only if the sun gets infinitely far away or reaches some threshhold distance.
But the big issue is with how it disappears. If this was the case, it would shrink to a point or go blurry and the light would fade until we couldn't see it. Instead we see it clearly disappear from the bottom up.
Perhaps you are under the impression that light only ever travels in straight lines?
No, it will also curve towards things which have mass, and it can be refracted by the atmosphere.
But both of these things would make it appear higher, not lower.