What do you think of this fact?
The story goes like this: medieval people thought the Earth was a disc, and Columbus sailed off to prove them wrong. Nice drama. Almost none of it holds up.
The Middle Ages knew it was a ball
Educated people in the Middle Ages knew the Earth was a sphere. Medievalists.net lists the Venerable Bede, and later Roger Bacon and Thomas Aquinas in the thirteenth century, among those who described a round Earth. The ninth-century astronomer Ahmad al-Farghani noted that ships sink slowly below the horizon instead of vanishing all at once. Even the orb in royal regalia reflected the idea of a spherical world.
The ancient Greeks had worked it out long before. James Hannam writes that Eratosthenes estimated the Earth’s circumference at about 23,000 miles. The true value is about 24,900 miles.
What Columbus actually got wrong
Columbus’s critics did not fear he would fall off the edge. They thought his numbers were off. According to Hannam, the dispute was about the size of the world, not its shape: the committee in Salamanca believed Columbus had underestimated the distance to the East Indies. Ripley’s says he calculated the Earth’s circumference as 25 percent smaller than it really is.
The critics were right. According to Ripley’s, his first voyage proved it. Columbus never reached Asia on that trip; he landed on San Salvador.
Bonus fact: Even in Irving’s own story, the learned critics at Salamanca accepted that the Earth was round. As Darin Hayton points out, their objection was that it was so big that crossing the Atlantic would take three years.
Where the myth comes from
The flat-Earth version owes a lot to the American writer Washington Irving. In 1828 he published a book on the life and voyages of Christopher Columbus. Medievalists.net calls it a novel rather than a historical account, despite its title. Hayton describes how Irving dramatized the real meeting in Salamanca, painting Columbus’s opponents as driven by “monastic bigotry” and attacking him with quotes from the Bible. Later writers kept the story going, Hannam notes, among them Andrew Dickson White in a book from 1896.
So the people who pictured a flat medieval world weren’t medieval at all. They were reading 19th-century books.