I believe that a greek philosopher named Eratosthenes did the dual stick experiment ( not sure when ).
He planted two sticks, one in cyene, one in Alexandria. The difference in shadows was taken to mean that the earth is round.
FE theorists claim that this claim can be explained with a flat earth, in that the sun is only a few thousand miles above the earth. This is a little of topic, but why do FE theorists keep using miles and feet. This isn't very scientific.
And this is another indicator of the americans in the society.