Perhaps you’ve heard of these absurd creationist challenges: Kent Hovind challenge of $250,000 for scientific evidence of evolution; Joseph Mastropaolo’s challenge of $10,000 to “prove evolution”; Ray Comfort’s challenge of $10,000 to show him a transitional fossil. They all sound like easy money, but don’t try: they’ve loaded the dice in every case.
Dana Hunter gives a 19th century example I did not know about before. Alfred Russel Wallace accepted a bet to show the curvature of the earth by a flat-earther, and he did it, too, with a simple and clever observation. You’d think he’d be wallowing in the cash — £500 — that he’d won, but you don’t know denialists. They never change.