The earth is round!

-You see further the higher you are off the ground
-Images from space show that the earth is round, including other planets
-Fly on a plane in one direction... there is no end, you will just go around and around.
-Put a stick in the ground, the shadow that it forms will move over time
-Stand by the ocean horizon, approaching ships dont just appear out of the horizon, but rather emerge from beneath the sea