People not so sure the Earth is round have come from around the globe to Denver this week to discuss their beliefs at the Flat Earth International Conference, hosted at the Crowne Plaza Denver Airport Convention Center.
The two-day conference began on Thursday and ends Friday.
Self-described "flat-earthers" believe the Earth's shape has not been proven using the scientific method.
"Scientifically when you go and try to prove the curvature, or the movement, of the Earth - you can't do it," said Robbie Davidson, the founder and organizer of the conference. "There's not one experiment, from Earth, to prove Earth as what we've been taught."
Davidson said he used to believe Earth is round until 2015, when he came across a video making fun of the Flat Earth movement.
"I just started looking into it and, as a Christian, I started looking at the Bible," he said. "Well, why does the Bible say this? So, for me, it was just looking into the evidence."
Flat-earthers also believe, despite evidence to the contrary, that the Earth doesn't rotate. They say everything in the sky moves under a dome or firmament.
"I take a biblical mindset the fact that the firmament divided the waters from the waters, so that the sun, moon, and stars are inside the firmament - so it placed the sun, moon, and stars in the firmament on day four, after the Earth - so how do you have the Earth created first and then the sun, moon and stars?" Davidson questioned.
Dr. Robert Sungenis, the author of a book called "Flat Earth Flat Wrong" said he believes flat-earthers are misinterpreting scientific data.
"So the movement of the flat-earthers is more or less spawned by this, 'let's fill in the gaps about what we don't know based on what they see.' And we see that the Earth is flat and we can do experiments show you that the Earth is flat," Sungenis said. "And when it comes to satellites, they would say we don't believe that satellites exist. We don't believe that you can send a rocket beyond the dome of the Earth."
Sungenis is a theologian who also has seminary training and majored in physics at his alma mater.
His book also addresses the biblical take on the flat earth movement.
"There are a few different verses in the Bible, maybe a dozen or so, that are not very clear about what the shape of the Earth is, it's more or less ambiguous," he said. "So you really have to get deep into the original languages of the Bible, and I know both Hebrew and Greek because I'm a graduate of the seminary many years ago. Many of these people here are not well-versed in biblical languages or biblical exegesis, so they'll read a passage in the Bible that says there is four corners of the Earth and they'll automatically believe the Earth is square with four corners and that's the depth that they'll go into it."
Sungenis was part of a debate at the Flat Earth International Conference Thursday night. He argued his take on why the Earth is round against Rob Skiba, a documentary filmmaker and author, who believes the earth is flat.
"So he thinks I'm totally wrong, I think he's totally wrong about the Bible," Sungenis said jokingly. The two are good friends.
Both the flat Earth crowd and the scientists Thursday said they encourage people not to blindly listen to them, but to do their own research.
This is what they said when asked what they hoped attendees got out of the conference, and the debate.
"To think, to not just absorb what somebody is so enthusiastic about, even though he may sound scientific, even though he may sound biblical, there is another side to the story," Sungenis said. "Even if they are not convinced at my argument at least they now know the other side of the story - they can think for themselves and walk out of here seeing the world in a different way."
"The one thing I will say is don't believe anything we say blindly; go out and do your own research that's what I would like you to take away," Davidson said. "Even with my own children, I want them to understand both models and believe it for their investigation, I don't want them to believe it because dad believes it."
Davidson also said he wanted to make sure the flat-earthers at the conference aren't confused with the Flat Earth Society, which believes the Earth is more of a pancake shape that has an edge.
"We think it's ridiculous too. The two things we all agree on is the Earth isn't moving at all; it's stationary, everything in the sky moves, and also that we are not a spinning ball flying through space," Davidson said. "That's one thing we all unify under."