On the last Sunday afternoon in March, Mike Hughes, a sixty-two-year-old limousine driver from Apple Valley, California, successfully launched himself above the Mojave Desert in a homemade steam-powered rocket. He’d been trying for years, in one way or another. In 2002, Hughes set a Guinness World Record for the longest ramp jump—a hundred and three feet—in a limo, a stretch Lincoln Town Car. In 2014, he allegedly flew thirteen hundred and seventy-four feet in a garage-built rocket and was injured when it crashed. He planned to try again in 2016, but his Kickstarter campaign, which aimed to raise a hundred and fifty thousand dollars, netted just two supporters and three hundred and ten dollars. Further attempts were scrubbed—mechanical problems, logistical hurdles, hassles from the U.S. Bureau of Land Management. Finally, a couple of months ago, he made good. Stuff was leaking, bolts needed tightening, but at around three o’clock, and with no countdown, Hughes blasted off from a portable ramp—attached to a motorhome he’d bought through Craigslist—soared to nearly nineteen hundred feet, and, after a minute or so, parachuted less than gently back to Earth.

For all of that, Hughes might have attracted little media attention were it not for his outspoken belief that the world is flat. “Do I believe the Earth is shaped like a Frisbee? I believe it is,” he told the Associated Press. “Do I know for sure? No. That’s why I want to go up in space.”

Hughes converted fairly recently. In 2017, he called in to the Infinite Plane Society, a live-stream YouTube channel that discusses Earth’s flatness and other matters, to announce his beliefs and ambitions and ask for the community’s endorsement. Soon afterward, The Daily Plane, a flat-Earth information site (“News, Media and Science in a post-Globe Reality”), sponsored a GoFundMe campaign that raised more than seventy-five hundred dollars on Hughes’s behalf, enabling him to make the Mojave jump with the words “Research Flat Earth” emblazoned on his rocket.

To be clear, Hughes did not expect his flight to demonstrate Earth’s flatness to him; nineteen hundred feet up, or even a mile, is too low of a vantage point. And he doesn’t like that the mainstream media has portrayed things otherwise. This flight was just practice. His flat-Earth mission will come sometime in the future, when he will launch a rocket from a balloon (a “rockoon”) and go perhaps seventy miles up, where the splendor of our disk will be evident beyond dispute.

If you are only just waking up to the twenty-first century, you should know that, according to a growing number of people, much of what you’ve been taught about our planet is a lie: Earth really is flat. We know this because dozens, if not hundreds, of YouTube videos describe the coverup. We’ve listened to podcasts—Flat Earth Conspiracy, The Flat Earth Podcast—that parse the minutiae of various flat-Earth models, and the very wonkiness of the discussion indicates that the over-all theory is as sound and valid as any other scientific theory. We know because on a clear, cool day it is sometimes possible, from southwestern Michigan, to see the Chicago skyline, more than fifty miles away—an impossibility were Earth actually curved. We know because, last February, Kyrie Irving, the Boston Celtics point guard, told us so. “The Earth is flat,” he said. “It’s right in front of our faces. I’m telling you, it’s right in front of our faces. They lie to us.” We know because, last November, a year and a day after Donald Trump was elected President, more than five hundred people from across this flat Earth paid as much as two hundred and forty-nine dollars each to attend the first-ever Flat Earth Conference, in a suburb of Raleigh, North Carolina.

“Look around you,” Darryle Marble, the first featured speaker on the first morning of the conference, told the audience. “You’ll notice there’s not a single tinfoil hat.” He added, “We are normal people that have an abnormal perspective.”

The unsettling thing about spending two days at a convention of people who believe that Earth is flat isn’t the possibility that you, too, might come to accept their world view, although I did worry a little about that. Rather, it’s the very real likelihood that, after sitting through hours of presentations on “scientism,” lightning angels, and NASA’s many conspiracies—the moon-landing hoax, the International Fake Station, so-called satellites—and in chatting with I.T. specialists, cops, college students, and fashionably dressed families with young children, all of them unfailingly earnest and lovely, you will come to actually understand why a growing number of people are dead certain that Earth is flat. Because that truth is unnerving.

The November conference was held in a darkened ballroom of an Embassy Suites near the Raleigh airport. Dozens of rows of chairs had been set out and nearly all were filled. To my right, a young couple with a stroller listened intently; a man in front of me wore a T-shirt with the words “They Lied” across the back. Onstage, Marble recounted his awakening. Marble is African-American and was one of a handful of people of color in the room. He had enlisted in the Army and gone to Iraq after 9/11; when he returned home, to Arkansas, he “got into this whole conspiracy situation,” he said.

For two years, Marble and his girlfriend drank in YouTube. “We went from one thing to another to another—Sandy Hook, 9/11, false flags,” he said. “We got into the Bilderberg, Rothschilds, Illuminati. All these general things that one ends up looking into when you go on here, because you look at one video and then another suggestion pops up along the same lines.” Finally, he had to step away. “You come to a place where you start to feel that reality is just kind of scary,” he said. “You’ll find out that nothing, ultimately, is what it seems to be. I hit my low point, where everything was just terrifying.”

Marble found the light in his YouTube sidebar. While looking for videos related to “Under the Dome,” a TV sci-fi drama, he came across “Under the Dome,” a two-hour film, which takes the form of a documentary, by Mark K. Sargent, one of the leading flat-Earth proselytizers. The flat-Earth movement had burbled along in relative darkness until February of 2015, when Sargent uploaded “Flat Earth Clues,” a series of well-produced videos that, the Enclosed World site notes, “delves into the possibility of our human civilization actually being inside a ‘Truman Show’-like enclosed system, and how it’s been hidden from the public.” (Access to those videos and more is available on Sargent’s personal Web site, for ten dollars a month.) It announced itself as “a Reader’s Digest version” of the flat-Earth theory; Marble watched it over and over, all weekend.

“Each thing started to make that much more sense,” he said. “I was already primed to receive the whole flat-Earth idea, because we had already come to the conclusion that we were being deceived about so many other things. So of course they would lie to us about this.”

If we can agree on anything anymore, it’s that we live in a post-truth era. Facts are no longer correct or incorrect; everything is potentially true unless it’s disagreeable, in which case it’s fake. Recently, Lesley Stahl, of “60 Minutes,” revealed that, in an interview after the 2016 election, Donald Trump told her that the reason he maligns the press is “to discredit you all and demean you all so that when you write negative stories about me no one will believe you.” Or, as George Costanza put it, coming from the opposite direction, “It’s not a lie if you believe it.”