Long before the fifteenth century, every educated European, including Roman Catholic prelates, knew the earth was round.2 Sphere was the title of the most popular medieval textbook on astronomy, written early in the thirteenth century. The opposition Columbus encountered was not about the shape of the earth, but about the fact that he was wildly wrong about the circumference of the globe. He estimated it was about 2,800 miles from the Canary Islands to Japan. In reality it is about 14,000 miles. His opponents knew how far it was and opposed his voyage on grounds that Columbus and his men would
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