Ideas

Ideas | Courtney Humphries

What does it take to believe the world is flat?

brendan lynch/globe staff

The Internet has helped a host of new conspiracy theories gain traction, but it’s also helped revive a much older one: the belief that the earth is flat. Boston Celtics player Kyrie Irving, for instance, has promoted that theory with oblique comments that caught fire on social media. While not fully endorsing it, and even occasionally seeming to disavow it, the point guard has embraced flat-earthism just enough to demand more “research” about it.

Historically, belief in a flat earth was much less common than we assume. Even Aristotle knew that the earth is spherical. So how does it persist today? How do today’s flat earthers rationalize a plainly disproven view?

brendan lynch/globe staff

The modern idea began with a 19th century writer, Samuel Rowbotham, who promoted a flat earth in a book called “Zetetic Astronomy.” A showman, he perfected the use of pseudoscience in debates. Flat-earth societies later formed in the 20th century only to languish as the Space Age dawned.

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But they seem to have taken off more recently. Pete Svarrior, a 24-year-old computer science PhD student who’s a longstanding member of the Flat Earth Society, says, “in the past, the means of communication weren’t effective enough to allow relatively small groups to connect and grow,” but that “the modern information era has allowed us to spread information so quickly.”

That information capitalizes on the fact that most of us perceive the world as flat in our day-to-day lives. “It’s trusting nobody but yourself and your observations,” Svarrior says. Flat-earth ideas “boil down to people wanting to experience things for themselves rather than taking anybody’s word for it.”

But believing in a flat earth also means ignoring the abundant evidence of the planet’s roundness that’s confirmed by telescopes, space vessels, satellites, airplanes, radio signals, seismic activity, and simple observations. So modern flat-earthism means believing in a vast conspiracy devoted to hiding the true nature of the earth.

It’s not surprising, then, that flat earthers don’t even trust each other. Eric Dubay, a founder of the Flat Earth Research Society, has accused other groups of being government conspirators trying to make the flat-earth movement look bad. But more substantive disagreements also plague the movement, Svarrior admits. Some groups are religious, while others tend to an atheistic view, and they disagree on how a flat earth operates. “We’re trying to do the best to come together,” he says.

In the end, though, much of the appeal of flat-earth ideas doesn’t come from offering a coherent model of the universe. Instead, flat-earthers often focus on small-scale experiments that “prove” the Earth is flat, and offer alternative explanations for phenomena that rely on a round Earth, like time zones, GPS, and the simple “sinking ship” effect (when a ship disappears on the horizon hull-first because of the earth’s curvature).

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Like climate-change denial and anti-vaccination activism, flat-earthism depends more on the personalities and motives of its adherents than on any scientific facts. It’s an elaborate exercise in confirmation bias — a willful refusal to accept collective knowledge about how things really work. Today’s flat-earthers are skeptical of science, yet they’re convinced that government is organized, powerful, and competent enough to execute a planetary conspiracy.

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The leading vision of how a flat earth operates

• Some groups propose the Earth is an infinite plane, but most flat-earth models show the planet as a disc with the North Pole at the center. Antarctica is a wall of ice around the outside.

• What about gravity? Many flat earthers say that objects fall to the earth because the planet is moving upward through space, accelerating at a pace of 9.8 meters per second squared, propelled by a force called dark energy or “aetheric wind.” There’s some debate about whether this ever-accelerating Earth will eventually reach the speed of light.

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Because a compass always points to the North Pole, traveling east or west takes you in circles around the disc — not in a straight line.

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• Some groups believe the sky is a glass dome over the earth. Others believe the sun and moon are spheres 32 miles wide circling 3,000 miles above the Earth. By this account, the sun isn’t a giant luminous body but a spotlight that only shines on one part of the earth at a time, giving us day and night. Seasons are created by the sun narrowing and widening the circle, shining more on what we call the northern and southern hemispheres. Differences in the altitude of the sun and moon create the moon’s phases.

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Courtney Humphries is a freelance journalist in Boston.