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Chris 249 said..
One thing I wonder about flat earthers is how come they have not been to sea. For a start, when you're sailing at sea you can clearly see the effect of the curved surface by the way objects can be seen near the horizon; you can see the top of a lighthouse or the upperworks of a ship long before you can see the lower sections of them, and that is only explainable by the curvature of the earth.
But the other thing is that long distance sailing navigators follow "Great Circle" routes, which deviate from the theoretical straight line (as seen on a conventional map) so the vessel follows a shorter distance. For decades, ocean racing yachties have been sailing such routes and comparing logs afterwards, and then publishing the results. They have also often had to report their positions by radio at regular intervals.
If the earth was flat, then boats that went south on the Cape Town to Auckland leg of the Round the World race, for example, would be sailing almost twice as far as the boat that went "straight" according to the flat-earth map. The boats that went south would obviously show far more miles covered on their logs and would finish well behind. But of course, in reality, that doesn't happen. Not only that, the compass courses are of course very different.
So if the flat earthers were right, just about every RTW sailing yachtie would have to be in on some giant conspiracy. The "authorities" would have to have gotten to every single navigator and skipper and most of the crews, from every country, and doctored every log and every race result. And that's not even taking into account fishermen, commercial seamen and the Chinese and Russian navies.
Obviously the flat earth idea is silly, but it's sometimes interesting to consider just how silly it is.
You obviously have no idea how stupid they are. No point arguing with them.