Although there are many trolls on the internet who pretend to believe that the earth is flat, there are undoubtedly many people who legitimately hold that belief. Here is a list of things that people who believe in a flat earth cannot explain using a flat earth model. Each item on this list is independently verifiable (since flat earthers believe the conspiracy theory that photographs of the earth from space are faked) and any flat earth believer can directly observe each item on the list.
1) How does a Foucault pendulum work?
2) Why do flights from Buenos Aires, Argentina, to Sydney, Australia fly over the coast of Antarctica?
3) How can there be two celestial poles?
4) Why is the South Pole in constant sunlight for six months of the year?
5) How do GPS devices and satellite television receivers work?
6) Why can someone standing on the beach in Chicago not see the city of Gary, Indiana, but a person standing in the observatory of Willis Tower can see it easily?
7) How did the crow’s nest of old sailing ships help sailors see further?
8) Why does the earth have a magnetic field?
9) Why does the moon appear upside-down in Australia compared to how it appears in the United Kingdom?
10) Why does the sun disappear below the horizon?
11) How can a lunar eclipse always project a round shadow onto the moon?
12) Why do sailing ships in the distance have only their sails visible?
13) Many flat-earth models state that the moon is small and close to earth. If that is so, then why is only one side of the moon ever visible from earth?
14) From where does the Coriolis force originate?
15) Why do stars rotate counterclockwise in the sky in the northern hemisphere but rotate clockwise in the southern hemisphere?
Great questions. I’d love to hear flat-earth explanations!
Number 11 dates to Aristotle.