Recently I spoke in Denver on myths about science and religion. I did not realize that a few weeks prior the same city had hosted the Flat Earth International Conference. Many of the 650 people who attended the wacky flat-earth event told a reporter something notable. They said they had “been kicked out of churches, or lost jobs with churches, or suffered broken relationships with family members” because of their belief in a flat earth. Ignorance has consequences.

Celebrity astrophysicist Neil deGrasse Tyson is a smart man. However, he is relatively ignorant about the early history of his own scientific discipline. Back in 2016, he responded to rapper B.o.B., a flat-earth promoter, with a tweet. Tyson wrote, “Duude — to be clear: Being five centuries regressed in your reasoning doesn’t mean we all can’t still like your music.” Tyson follower Andy Teal responded: “Five centuries? I believe the knowledge of Earth’s shape goes back a bit farther than that.” Tyson tweeted back: “Yes. Ancient Greece inferred from Earth’s shadow during Lunar Eclipses. But it was lost to the Dark Ages.”

Dark Ages?

People stopped believing in a spherical earth during the Middle Ages? Not really. Medieval intellectuals had many reasons for grasping that the earth is round. Those reasons included the curved shadow of the earth projected on the moon during a lunar eclipse. To deny medieval belief in a round earth is to be guilty of what I call the flat myth. This is the most enduring component of the larger myth of the “Dark Ages.” The allegedly anti-science “Christian Dark Ages” never happened, as I show in my book Unbelievable: 7 Myths About the History and Future of Science and Religion.

Tyson is obviously right about how ridiculous contemporary flat-earth belief is. Some “believers” such as Shaquille O’Neal and Kyrie Irving of NBA fame have said they were only joking. And who can tell what the small number of people behind today’s flat-earth societies actually think? If most of them are joking, it would come as little surprise.

But the fact is that Tyson, one of the world’s most influential voices for science, is spreading misinformation about medieval views.

Tyson’s false ideas have a history. They trace back to writers in the 1800s. For example, the 19th-century chemist-historian John William Draper claimed that medieval Christians believed “the Scriptures contain the sum of all knowledge.” They therefore “discouraged any investigation of Nature,” including the study of the earth’s shape. Supposedly this ignorance continued until the time of Columbus.

Consider the 1,200 American college students I have taught astronomy over the past quarter century. The vast majority learned something false from their precollege teachers. They were told that Europeans in the Middle Ages were ignorant of the earth’s roundness until Christopher Columbus proved it in 1492. Only some of my students had previously detected the typical anti-Christian slant to the story. After I did my job they all understood how this fake history perpetuates the myth of warfare between science and Christianity.

Medieval Round-Earth Arguments

Imagine the year is 1300. You are a student at the University of Salamanca, Spain’s oldest university. In class you have studied Aristotle’s argument for a spherical earth based on the changing positions of the stars as one travels north or south. This was standard in the medieval curriculum. You wish to demonstrate it for yourself. How will you do this?

First you note that the apparently motionless North Star is located about 40 degrees above your horizon in Salamanca. Then you travel to the southernmost point of Europe. There you find that this star appears only about 35 degrees above the horizon. Why the change of angle?

Almost every medieval university student learned a simple explanation: the earth is round. This and other reasonable arguments combined to present a very strong case.

Back Around to Today

Here’s a surprise. My students have typically been less able to defend the earth’s roundness by such scientific arguments than the average medieval student. Upon completing my astronomy course, they finally caught up to the Middle Ages!

Most students today accept the roundness of earth as a mere fact. They are unable to reason from observations to this conclusion. This is not an isolated observation, unfortunately. Science today is, more often than not, taught this way: as something to be accepted, not necessarily understood. That’s a loss for students. Things were, in this respect, brighter in the so-called Dark Ages.

Michael N. Keas is Lecturer in the History and Philosophy of Science at Biola University and a Fellow of Discovery Institute’s Center for Science & Culture. His new book is Unbelievable: 7 Myths About the History and Future of Science and Religion.