Atmospherics

People assume that if the earth was truly flat,  they SHOULD be able to see Mount Everest from anywhere they are.

An observer looking from point A to point B will have to take atmospherics into account.  Rain, fog, sleet, snow, haze, smog, dust, and debris will prevent you from looking forever across a flat plane.  Some days you can’t see 1 mile in the distance due to fog.

Try looking underwater at a lake.  You can’t see too far.  If you poured that same water into a clear glass you would see right through it.  The atmosphere is the same.  It appears clear but is actually full of moisture and debris.

Then you have to factor in perspective.  Mt. Everest would become too small to see as you travel away.