Here are two simple ways for FE to prove if the FE beliefs of this"horizon" and "sinking ship" are true. This should settle the question once and for all. But I doubt FE would accept the results anyway..
Go down to the sea shore on a clear, calm day with no unusual atmospheric conditions . You don't even have to go to sea aboard a ship, but you can perform the same experiments aboard a ship, or you can do both. Take a telescope, binoculars and/or a camera with a zoom lens or telescope lens for photographic evidence. But then again , there is the problem that FE does not accept photographs as evidence. Please accept my word if you can that there are days that the sea and sky are perfectly clear with no fog, atmospheric conditions or mirages to interfere with these eperiments.
(1) The horizon
Looking out to sea from the ship or the shore. If all you see in the distance is a blur which fades away at some indefinite distance that should prove the FE statement that there is no horizon to be observed if the earth is flat. Remember, this is on a clear, calm day.....no fog, etc. .
(2) The "sinking ship"
Again looking out to sea from the ship or the shore. Observe a large ship such a container ship, large cruise ship or a large aircraft carrier. When the ship passes out of view if you can restore the ship in its entirety this should prove the FE statement that the earth is flat. It would seem that if you had the proper equipment such as telescopic or zoom lenses, filters and film to eliminate any atmospheric or haze conditions (again you will have to take my word for it that they do exist) the ship would never disappear from view as you increased the magnifying power of the camera, binoculars or telescope, much less ever disappear from view..
These experiments should be performed at low levels of height above the sea.
PS - Perhaps I have erred in using the term "Atmospheric" instead of the FE term of "Atmoplanic" in the above.
Please present the results of these experiments. I have performed them many times myself, but the results of these experiments should come from a FE as evidence and prove of the FE statement that they deal with their belief that the earth is flat from these and other FE beliefs.