I thought it was interesting when I learned how long humans have known the Earth is round. In relatively modern (non-prehistoric) history, Eratosthenes measured the circumference of the Earth as 25,000 miles, which is basically correct. He did this in 230 B.C. He also used the fact that the sun is really far away, so the rays coming from it could be treated as parallel.
Another test you can do is to stand at about sea level and observe a ship. Then travel away from the ship on the ground and it will slowly go over the horizon. Then keep moving away but go up a mountain, and it will reappear. The simplicity of this experiment suggests people have known the Earth is round for as long as they could reason well enough to come up with this experiment.
Of course, maybe the Earth is rounded on top but flat on the bottom, like a Nilla(tm) wafer? You could argue this wasn't known for sure until Magellan circumnavigated the globe in 1524.
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I thought it was interesting when I learned how long humans have known the Earth is round. In relatively modern (non-prehistoric) history, Eratosthenes measured the circumference of the Earth as 25,000 miles, which is basically correct. He did this in 230 B.C. He also used the fact that the sun is really far away, so the rays coming from it could be treated as parallel.
Another test you can do is to stand at about sea level and observe a ship. Then travel away from the ship on the ground and it will slowly go over the horizon. Then keep moving away but go up a mountain, and it will reappear. The simplicity of this experiment suggests people have known the Earth is round for as long as they could reason well enough to come up with this experiment.
Of course, maybe the Earth is rounded on top but flat on the bottom, like a Nilla(tm) wafer? You could argue this wasn't known for sure until Magellan circumnavigated the globe in 1524.