When Columbus landed on San Salvador on October 13, he had discovered what was to Europeans a brave new world. The Vikings may have been first, but they didn’t introduce the Norweigan rat, smallpox, and gunpowder to the Americas, nor did their adventures bring back quantities of silver sufficient to eventually destroy the economy of their home country, so they don’t count. Columbus’ discovery, such as it was, was epoch-making and its results so intertwined in Europe’s subsequent history that science fiction writers and bar trivia fiends could argue about counterfactuals for years; it was, however, no scientific revolution. The contemporary Flat Earth Society is sadly self-aware and Fortean, throwing the question of how serious their predecessors were into severe doubt. But the joke begins earlier; the idea that the educated citizens of 1492, whose world contained not only the printing press but also the rifle, the slotted screw, and reasonably accurate clocks, didn’t know the world was round is simply slander. It was first invented by a Frenchmen, Antoine-Jean Letronne, as part of his attack on the religion in the nineteenth century. He wanted to depict the citizens of pre-Columbian Europe as ignorant yokels kept in chains by a science-hating Catholic Church. A few church fathers in the early middle ages argued for the flat earth, but the whole idea was tied to the question of whether Jesus had redeemed the people walking upside down in the antipodes. Philosophers argued about whether the idea of the antipodes was holy, heretical, or simply silly, but by and large — from late antiquity’s Augustine to the Venerable Bede to Thomas Aquinas, the most important Christian scholar of the Middle Ages — they accepted the idea of the spherical earth.

Stripped of the combative trappings, however, the role of scientific radical was one with real myth-making potential. And so Washington Irving, not content with simply making up the traditions of modern Christmas celebrations, repeated Letronne’s claims in his The Life and Voyages of Christopher Columbus, and from that point on it has been a staple of junior high-school history textbooks. But it wasn’t true; any well-educated nobleman of the time knew that the world was round from their Aristotle. Columbus, of good family but "defective" education, knew it too; the novelty in his voyage came not from his believe in a spherical planet but from his theory about the earth’s size, which he clung to in the face of all received wisdom, experimental evidence, and common sense. Columbus was a visionary. Columbus was inspired. Columbus was a crank.

He may simply have been tricked by the maps he was looking at. Conveying a three-dimensional space in two dimensions is hard; great circles seem somehow wrong as the shortest distance between two cities, and an entire field of mathematics has grown out of the fact that lines on the sphere aren’t quite like lines on the plane. There are a vast array of maps which attempt to depict the globe, accurately preserving some features at the expense of others; at least one even managed to become controversial after its popularizer accused other projections of ethnocentricism. But Columbus seized upon the theorists (until Magellan circumnavigated the globe, there were no scientists engaged in practical studies of the earth’s size) who agreed with him, ignoring such cutting edge thinkers as Eratosthenes of Cyrene, who calculated a reasonably accurate value for earth’s diameter. Eratosthenes’ work was based on observations of shadows cast by a pole at noon on the summer solstice; he died in 194 BC.

Historians can argue about how big Eratosthenes’ stadia were, but the calculations could be recreated if Columbus had cared to. He didn’t; he used bad estimates about the earth’s size, threw in a guess by Marco Polo about Japan’s distance from China, and stirred in two drops of pure, naked greed. A western passage to India on Columbus’ small earth would have been almost the same distance as travelling east and considerably quicker with no Africa (or imaginary Atlantean continent) in the way. The name "Columbus" would have rung through history as the greatest explorer of all time. And it happened anyway; Columbus never quite admitted that he was wrong; the term "Indians" persists to this day, and he died believing that he had made his way to India and Malaysia. He and his crew would have quietly died on their trip, costing Queen Isabel three perfectly good caravels, had San Salvador and the eastern edge of North America not simply happened to be where Columbus insisted India was. Some people assert that Columbus earned credibility through balancing an egg on its end, but they haven’t thought the anecdote through; sometimes you can balance an egg through an insightful hack, sometimes you can do it through clever design, but sometimes it’s just a steady hand and pure, dumb luck.