In Ian Stewart’s book, *Professor Stewart’s Casbook of Mathematical Mysteries*, he writes about an easy way one might prove that the earth is not flat. His “easy” proof can be done by booking some flights and timing them… or, simply looking up actual flights from certain cities to other cities. If it is much much shorter for a certain flight from A to D while A to B to C to D in a nearly straight line is much longer, it’s effectively a proof you can go around the world without falling off…