
How to prove flat Earth.
On the flat Earth, lines of latitude for concentric circle. Let's define "west" as facing north then turning 90^(o) counterclockwise. Both globe and flat Earth would agree that if you are doing this then you are facing due west. Do this in Brisbane, Australia and travel in a straight line. I did not say travel west because while that is the same thing on a globe Earth, on a flat Earth as soon as you start moving you would no longer be facing west as you travel. If the Earth is a globe, you will travel across the whole of Australia while on a flat Earth you would hit water somewhere near Adelaide.
So the proof is go to Brisbane, turn west and start walking in a straight line and see where you end up.