IF the density of the atmosphere decreases with height (surely not that difficult to prove) and IF light refracts through those different densities (harder to prove, I think) then doesn’t that mean that, on a flat earth, light would not refract for anything on your (sorry, a, assuming the earth’s flat) horizontal. The density of the atmosphere across a horizontal is the same and therefore would not refract.
The point being you should be able to sight anything on a horizontal at any distance and whatever it is you’ve sighted should be EXACTLY the same height (above mean sea level) as you were when you sighted it. Every single time.
I can’t quite get my head around how things should look with that kind of refraction either. I initially think things would look weird(er than they do) but I doubt that’s actually the case.
There’s also the interesting part of how do you determine your height above sea level? Like ... Read even more