system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: If people used to think the earth was flat, what did they think was on the bottom side?
gpt
The "Flat Earth" thing is one of those insults that dumb people think makes them sound smart or science-y. Most scholars, and this goes back before Christ, knew that the Earth was round or at least spherical. 

This Myth came out of the anti religous establishment back in the 1800's. Anti Christians have seized on it and use it as Strawman to attack people who don't support their own beliefs.

It would be very difficult to ascertain what ancient people thought was on the underside of the "flat earth" since most did not believe the earth was flat or did not even consider the shape of the earth anyway.