In case you were lucky enough to miss the recent hysterical Twitter rants and potshot headlines: There are people alive today who legitimately believe the Earth is flat.

Flat-Earthers’ general theory is that the Earth is disc-shaped, with the Arctic at the center and Antarctic ice (guarded by NASA) around the edges, containing the oceans. If you roamed too far, you would fall off the edge.

You’d be forgiven if your first reaction is: What the fuck, people? This sort of thing was disproven literally thousands of years ago. How does such an improbable and unsupported theory have any traction?

It helps that a few believers happen to be social media heavyweights. Rapper B.o.B unleashed a bizarre string of tweets at the end of January. Astronomer Neil deGrasse Tyson’s response diss-track propelled the flat-Earth truther message even further. And B.o.B is far from the only high(ish)-profile believer. It’s possible that B.o.B got the idea from reality TV star Tila Tequila, who went on a Twitter dissertation of her own earlier in the month.

It would be easy to dismiss flat-Earthers as desperate for attention and/or lunatics, except for the fact that so many believers are sane and capable of rational thought.

Among the most baffling facts of the flat Earth theory is that it’s a modern invention. Since the time of Ancient Greeks, educated people around the planet have understood the world is a sphere.

No, Columbus didn’t set out to prove the world is round, in defiance of religious elite — that, too, is a myth.

People today have access to more information than ever, and yet this weird belief is having a moment in 2016. What gives?

Psychologists have some ideas about what makes humans so prone to the sort of thinking errors that lead to these sorts of unsubstantiated beliefs. A feeling of being out of control is the main thread that ties conspiracy theorists together.

University of Miami political scientists Joseph Uscinski and Joseph Parent present the evidence for this in their 2014 book, American Conspiracy Theories. In lab settings, subjects induced to feel anxious and out of control (say, by having them remember times when they felt powerless) are more likely to latch onto the idea that big, conspiratorial forces are behind terrible events.

Believing that a powerful hand is playing puppet-master is more comforting, the theory goes, than submitting to the idea that random, awful events are a fact of life, and that they may be landing on you in disproportionate heaps.

People are also inclined to conspiracy depending on their mood, but their general worldview is an even more important predictor. If you believe one conspiracy, you’re likely to believe several.

Why? Some people are prone to particular errors in thinking, or as philosopher Linda Zagzebski calls them, intellectual vices. Conspiracy theorists are guilty of a sort of gullibility, and also a sort of close-mindedness, argues philosophy professor Quassim Cassam. Because they are close-minded, it is almost impossible to argue with them. Use evidence to call them out for their errant beliefs, and they’ll counter that you’re gullible and close-minded. Stalemate.

“It feels good to be the wise old goat in a flock of sheep,” as The New York Times puts it.

The flat Earth theory begins with a sort of logic — the Earth must be flat because it appears to be so. The extension of this belief must be that every image of the curvature of the horizon, every view of Earth from space is doctored in a deep and vast conspiracy.

And the wealth of information accessible to anyone with a smartphone, or a damn book? It turns out, in most cases, to do a disservice to the truth. Thanks to confirmation bias, if you expose flat-Earthers to evidence that undermines their position, they’re likely to dig in their heels even further.

Search “ship rising over horizon” on YouTube (say, in an effort to sway a misguided friend) and you get mostly videos from flat-Earthers exposing the “truth” of the round Earth “myth.”

The intractability of a believer’s logic can be astonishing and infuriating. Researchers have yet to find a formula for how to dissuade a conspiracy theorist.

For a lot of flat-Earthers, the truth is that their beliefs are probably too entrenched to ever be changed. The only solace is that, though anti-intellectual, the flat-Earth theory is relatively benign as conspiracies go. It’s still among the strangest ideas that a weird pocket of the internet is willing to defend to the edges of the Earth.

Photos via NASA/Denis Steele