Still, most adherents demonstrate plenty of anti-scientific tendencies. It's hard to find a flat Earther who doesn't believe most other conspiracies under the sun; a flat-Earth conference is invariably also a gathering of anti-vaxxers, 9/11 truthers and Illuminati subscribers, to name a few.
It's that hyper-skeptical mindset that helps flat earthers answer the big questions -- like who's hiding the true shape of the planet from us?
"The ruling elite, from the royal family to the Rockefellers, the Rothschilds ... all of those groups that run the world, they're in on it," says Weiss.
But "once you get into flat earth, the other (conspiracy theories) get knocked down into another tier," says Mark Sargent, a filmmaker and stalwart of the movement who was featured in the 2018 Netflix documentary "Behind the Curve."
"Everybody here, they've got their top 20 conspiracies -- and you could walk around door to door and those top 20 would differ from person to person. But everybody's number one is always flat Earth," he tells CNN.
It helps that the group has a mutual target. "Most of our ire is pointed towards NASA. That's our bread and butter," Sargent says of the agency flat Earthers believe is ultimately behind the conspiracy.
But why, and how, could people believe a conspiracy theory so out of this universe?
"People, in essence, are just trying to understand the world," says Daniel Jolley, a senior lecturer in the psychology of conspiracy theories at the UK's Northumbria University. "And they're looking at the world in a gaze where they're biased in their thinking."
"They may have distrust towards powerful people or groups, which could be the government or NASA, and when they look towards evidence that makes sense to them ... this world view (is) endorsed," he says. "It's difficult to break out of that mindset."
Scientists have also noted that a social motive draws people to conspiracy theories -- the desire to "maintain a positive view of the self and the groups we belong to," as social psychologist Karen Douglas of the University of Kent says.
And few groups have as strong a community as flat Earthers.
"This (conference) is an outlet for a lot of people that might otherwise get ostracized by friends and family and co-workers. When they come here, they know it's absolutely a safe space," Sargent says of this week's event.
But perhaps the most important driver is an underlying need for power and control. "People want to feel safe and secure in the world," Douglas says. And power comes from knowledge -- no matter how questionable it may be.
"When you find out the Earth is flat ... then you become empowered," Weiss says.
That feeling helps believers to understand the world better, as they see it. "You feel like you've got a better handle on life and the universe. It's now more manageable," adds Sargent.