Is not this, was speaking about human eye anatomy, is limited so no matter how much you go in height, the horizon line is compressed and never drops, is physics, so you can't see more unless you use a camera zoom, and of course since i do not believe there is any curvature you can see much more beyond it as the video show. Would have preferred the author avoid to spread fake news and propaganda in a comic or create something explainable with magic since is fantasy.
The Strait of Gibraltar is 14.2 km in width, according to what you said
you cant see the Rock from Morocco.
The higher we go the longer we can see, of course object
sizes matter but that not what you said, you made the statment we can only see 5km and then everything beyond needs some kind of magnification.
I would point out the Moon but flat earthers dont believe on its existence so I will use another example, Mount Everest that have a elevation of 8,849 m meaning nobody could see the peak unless they were halfway into the mountain ... I am not going to post the many images were we can clearly see the peak to keep this clean.
Also in case anyone is wondering human eyesight is
infinite due to how our eyes work (they capture light) so its really just a question of the size of the objects (as well brightness), we cannot see mount Everest in Paris because not only of the earth curvature but because it would be so distant that it wouldnt appear in our sight being too small.
The reason why they couldnt see the island
at the sea level is because it was hidden by the horizon because its relative flat, with elevation they could because of perspective as well the horizon line being moved further back. Its the same as looking at a sheet of paper looking at it strait and then move the eyes up.
