A common claim flat-Earthers make about ships sailing over the horizon is that they're just disappearing from view due to perspective, often they "prove" that by zooming in on a ship that seemed to have disappeared and bringing it back into view. That's forgetting that, with how many factors that can make distant objects harder to see, the ships can simply not be over the horizon yet. So I'm annoyed to then also see a flat-Earther using those same factors as their excuse for why things over the horizon aren't visible.