>>16707747 (OP)Like the majority of humans in the past, I make sure to stare at the night sky semi-regularly.
I observe that the stars appear to rotate on an axis. If I only had knowledge of my approximate location in a 200 sq mile radius, perhaps I could be persuaded that the sky merely "does that."
But with knowledge of how the sky appears on the equator and in the southern hemisphere (the entirely different sets of stars as well as a different Southern Polestar), I conclude that the Earth is spherical. There is no other way to explain how the night sky looks at disparate locations on the Earth.