One of the myths perpetuated by William Manchester in his atrocious book A World Lit Only By Fire is that even in Columbus’s time, and certainly throughout the Middle Ages, people actually believed the world was flat. Nonsense, said University of Wisconsin-Madison professor and historian of science David Lindberg, in an interview for Christian History magazine. (I’ll add that Lindberg is co-editor of the Cambridge History of Science, so he knows his apples.) The full interview can be found here, but this is the pertinent section:
What other myths about science and Christianity are commonly accepted today?
One obvious one maintains that before Columbus, Europeans believed nearly unanimously in a flat earth—a belief allegedly drawn from certain biblical statements and enforced by the medieval church.
This myth seems to have had an eighteenth-century origin, elaborated and popularized by Washington Irving, who flagrantly fabricated evidence for it in his four-volume history of Columbus. The myth was then picked up by White and others.
The truth is that it’s almost impossible to find an educated person after Aristotle (d. 322 B.C.) who doubts that the earth is a sphere. In the Middle Ages, you couldn’t emerge from any kind of education, cathedral school or university, without being perfectly clear about the earth’s sphericity and even its approximate circumference.