We are arguing about whether the Earth is convex round or flat , but we haven't even ruled out all the possibilities! Do we even have enough proof to rule out the Earth being concave!? It sounds completely absurd , but so does the other side's belief. Could it be possible for the Earth to be concave? Could there be alternate theories that explain everything for a concave Earth , just like there are for Flat Earth/Round Earth? (I am saying both to not offend others) Could a concave Earth even exist , or is there no way for it to exist? We need to rule out a concave Earth before confirming which one is the definite truth.