2. Christopher Colombus’s contemporaries thought the world was flat

The popular myth told to children is that Columbus had trouble raising funds for his trip west because his contemporaries believed the world was flat, and that he would sale off the edge. That’s ludicrous. The real reason he had trouble was because he was a moron on a suicide mission that just happened to hit land. We’ve known the Earth was round since Ancient Greece, and have had a pretty good estimate of its size since about then. Every sailor in the world knew it, just from sailing out far enough that the curvature of the Earth was visible. Columbus stupidly believed that the Earth was much smaller than it actually was, and that by sailing west from Europe he could circle the globe and hit India, thus saving the long overground treck. His numbers were completely wrong, and if he hadn’t lucked into landing on another continent, his entire fleet would have died.