I was discussing this a few days ago. It is more subtle and interesting than that. As far as we can tell, Every society that sails is aware the earth is curved, so they knew the earth was not flat probably as far back as awareness of surroundings goes. By the 6thBC it was not simply a matter of "knowing the earth was round" it had been measured. But there is an easily overlooked quirk in this. They knew for certain the earth was not flat. But they essentially just assumed it was spherical because it was a common shape. As an interesting thought experiment can you propose an experiment which you as an individual could carry out (ie not relying on satellite images etc) whereby you could demonstrate the earth was round rather than any other curved shape like a grape or dimpled like a golfball or a conic section. It is obvious because of mountaons that the earth is not a mathematical sphere so we also have to decide when we call 'more or less round' just 'round'.





And then we can talk about elections.