Why Does the Horizon Appear Flat
If the Ground (Or Water) Surface Is Colder Than the Air Above It, a Cold, Dense Layer of Air Forms Close to the Surface, Causing Light to Be Refracted Downward...
Why Does The Horizon Appear Flat?
If the ground (or water) surface is colder than the air above it, a cold, dense layer of air forms close to the surface, causing light to be refracted downward as it travels, and therefore, to some extent, to go around the curvature of the Earth.
Is the horizon line always straight?
Horizon lines are always straight across the horizontal span of a scene and not the jagged rocks of our mountain example. Your horizon line, in this case, is likely going to be that part of the scene where the base of the mountain meets the foreground.