The Greeks had already figured that all that out, and anybody with basic trigonometry knowledge, and I mean absolutely basic, can repeat the experiments.

As for gravity, I mentioned Galileo, i.e., someone from the 16th century precisely for the same reason. It's direct observation that can be replicated with the most rudimentary materials.

Now, of course if you are a BELIEVER in a flat Earth, that's a different story and of course no amount of direct evidence will ever convince you otherwise.