The easiest way to determine the earth is not round is to simply view the data. From there, later one comes to the realization that the most reasonable model in lieu of this is that the earth is flat.
This is incorrect. Most people view the data as seeing that the earth is round.
I haven't yet seen a single post that says why the earth can't be round. All I have seen is lol theories, that talk about how gravity is impossible and how a round Earth would violate the laws of motion. Oh yeah, lets not forget that because in some abstract mathematical constructs, that addition changes so that 1+1=1, that means the earth can't be round, or that because birds don't take the great circle, the earth can't be round