With binoculars you can follow the contrails of an airplane to the horizon in clear weather. This is about 50 to 60 minutes. The distance of the plane is then about 800 km. According to the Earth Curve Calculator, the plane should be 50 kilometers below the horizon. Explanation?

Episcoop;-)

Ha, nice suggestion! I myself think that it is not ... Could it be that the "earth" is much larger than the known earth so that the curvature is also much less? I don't think the theory of the flat earth is plausible, but it is a huge earth ... so outside the south pole edge ...