Here's a link to a nice little historical video about flat-earthers of the 1800s and attempts to rationally, scientifically demonstrate that the Earth was a globe. Part of this episode involved Alfred Russel Wallace, he of natural selection fame (or not, if you've never heard of him), and an simple, but elegant demonstration of the Earth's curvature. Using a straight, "flat" canal, Wallace put poles on bridges each measured to a precise height above the water. Then backing off to the next bridge, he set up a telescope at the same height, leveled it, and observed the poles. Although all were the same height above the water, the top of each successively more distant pole was below the top of the previous pole, as predicted, and the only conclusion that could be reached is that the "flat" canal was on a curved surface. Of course it's the only conclusion a rational person could reach, and Wallace's demonstration settled nothing and led to Wallace's severe harrassment by his adversary. The video concludes that there is nothing to be gained by debating or trying to reason or demonstrate science to people dedicated to creationism either. It's a nice video.
HT to Aron Ra.
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