People in the Middle Ages believed the Earth was flat.

The flat-earth Middle Ages is one of the most durable myths in the history of science, deployed for more than a century in arguments about religious obscurantism and the triumph of Enlightenment reason. In schools, it served as a convenient contrast to the heroic Columbus narrative: the brave empiricist versus credulous medievals terrified of sailing off the edge of the world. The story had obvious uses, which is why it persisted despite being demonstrably false.

Medieval European scholars knew the Earth was round. The knowledge was not esoteric or contested. It was standard curriculum. The ancient Greeks had established Earth's sphericity by the fifth century BCE, and Eratosthenes calculated its circumference with remarkable accuracy around 240 BCE using shadow angles at different latitudes. This knowledge never disappeared. It was preserved through the works of Pliny, Ptolemy, and other classical authorities whose texts remained in circulation throughout the Middle Ages.

Roger Bacon discussed the spherical Earth in his thirteenth-century Opus Majus, treating it as settled fact rather than hypothesis. Thomas Aquinas referenced it without controversy. Dante's Divine Comedy, written in the early fourteenth century, is built on a cosmology with a spherical Earth at its center, hell burrowing toward the core and heaven rising in concentric spheres above. Church scholars from Isidore of Seville in the seventh century to Albertus Magnus in the thirteenth accepted sphericity as obvious. The Catholic Church, so often cast as the villain of flat-earth histories, never taught that the Earth was flat. Medieval mapmakers often depicted the world as a circular disk for symbolic or artistic purposes, with Jerusalem at the center, but this was theological diagram, not geographic claim. Educated Europeans understood the difference.

The myth was largely invented in the nineteenth century. Washington Irving's 1828 biography of Columbus dramatized a fictional confrontation between the visionary navigator and flat-earth clerics at the Spanish court of Salamanca. Irving was writing entertaining historical fiction, not scholarship, but the scene proved irresistible. It fit perfectly into an emerging narrative about science versus superstition that served ideological needs in the Victorian era.

John William Draper's History of the Conflict Between Religion and Science (1874) and Andrew Dickson White's A History of the Warfare of Science with Theology in Christendom (1896) formalized this narrative into what became known as the conflict thesis: the idea that science and religion have been locked in perpetual combat, with religion consistently on the wrong side. These works were enormously influential in shaping popular history and public education. The flat-earth medievals became a standard example, taught to generations of schoolchildren as evidence of what happens when religious dogma suppresses inquiry.

The historian Jeffrey Burton Russell documented this invention rigorously in Inventing the Flat Earth (1991). He traced the myth's origins and found that virtually every medieval scholar who commented on the subject affirmed the spherical Earth. The flat-earth Middle Ages was a nineteenth-century projection, not a historical description. It was a polemical tool, crafted for battles over Darwinian evolution and the authority of the church in an age of science.

Why does the myth survive? Because it is useful. It tells a simple story about ignorance and enlightenment that flatters the present. It allows us to imagine a clear break between the benighted past and the rational present, a comforting fiction that places us on the winning side of history. It gives the false impression that human progress has been a steady march from religious superstition toward scientific reason, when the actual history is considerably messier and more interesting. The medieval scholars who knew the Earth was round, who preserved and built upon classical learning, who reconciled faith and reason in ways we still struggle to understand, disappear in this telling. What remains is a cartoon, vivid and memorable and wrong.