And the moon is made of green cheese

It appears there are still those who believe the earth is flat.  Hard to believe now we have pictures from satellites showing a very round earth.  But you don't have to go into space to prove it - the ancient Greeks realised that simply observing approaching ships as they appeared over the horizon - top of the mast first - could only be explained if the ship was travelling uphill relative to the observer. And as this phenomenon was observable irrespective of where the observer was and which direction he was facing, the only possible explanation was that the earth was a sphere.