[DarkTree]

I am trying to think of a way to prove without a doubt that the earth is not flat. I thought about sending them into space, and having them look through a window at the round earth suspended in the black. But then I almost know what they would say; the window is somehow distorting the true appearance of the earth. If it doesn't conform to their view, they will create reasons as to why. There are so many similar examples of people rejecting new information/evidence within our world now.

[lgas]

Don't be so hasty, I think sending them into space would be a good start.

[BlackFly]

Measure your shadow at solar noon, fly south and measure your shadow at solar noon there. (Solar noon may differ from 1200.)

Essentially, just repeat this ancient experiment: http://www.juliantrubin.com/bigten/eratosthenes.html

[tzs]

That only works if the people you are trying to convince believe that the Sun is far enough away for its rays to be essentially parallel at the two measuring locations.

Do flat Earth believers believe in a sufficiently large solar system for that to be true?