Everyone had a pretty good idea that the Earth was round, but the size was somewhat up for debate. Columbus did some bad math and came up with a really badly un

Everyone had a pretty good idea that the Earth was round, but the size was somewhat up for debate. Columbus did some bad math and came up with a really badly underestimated size and thought he had a clever way to the indies. If he hadn't run into a whole other continent unknown to him, he'd have perished long before he made it all the way around the Earth. The part I find most bizarre I think is that we still call Native Americans "Indians" to this day based on his now half-millennia old mistake.