The belief that the Earth is flat has been described as the ultimate conspiracy theory. According to the Flat Earth Society's leadership, its ranks have grown by 200 people (mostly Americans and Britons) per year since 2009. Judging by the exhaustive effort flat-earthers have invested in fleshing out the theory on their website, as well as the staunch defenses of their views they offer in media interviews and on Twitter, it would seem that these people genuinely believe the Earth is flat.

But in the 21st century, can they be serious? And if so, how is this psychologically possible?

Through a flat-earther's eyes

First, a brief tour of the worldview of a flat-earther: While writing off buckets of concrete evidence that Earth is spherical, they readily accept a laundry list of propositions that some would call ludicrous. The leading flat-earther theory holds that Earth is a disc with the Arctic Circle in the center and Antarctica, a 150-foot-tall wall of ice, around the rim. NASA employees, they say, guard this ice wall to prevent people from climbing over and falling off the disc. (In keeping with their skepticism of NASA, known flat-earther conspiracy theorist Nathan Thompson recently approached a man he said was a NASA employee in a Starbucks in mid-May 2017. In a YouTube video of the exchange, Thompson, founder of the Official Flat Earth and Globe Discussion page, shouted that he had proof the Earth is flat — apparently saying an astronaut drowning was that proof — and that NASA is "lying.")