Colorado pastor Will Duffy’s obsession with the flat-Earth conspiracy theory began with a longtime friend’s post on Facebook.

A quick direct message led to a months-long debate between Duffy and his friend, who held the archaic and false belief that our planet is a flat disc.

Three years later, after immersing himself in the conspiracy online, Duffy thought he could end the debate for everyone by traveling to Antarctica to livestream 24 straight hours of sunlight.

The phenomenon occurs because the Earth’s Southern Hemisphere is tilted toward the sun as the planet rotates around it, and Antarctica is at its closest point to the sun on the rotation. Flat-Earth believers do not believe this happens.

Duffy launched a YouTube channel called “The Final Experiment” to promote the trip, then invited flat-Earthers and well-known “globers” — people who understand the Earth is round — to accompany him this past December on a four-day stay on the continent.

“I decided that is it. That will solve this once and for all,” Duffy said in an interview this month. “We need to go to Antarctica. I need to take a flat-Earther or two with me and see the 24-hour sun and then this whole thing is over. So that began the journey of ‘The Final Experiment.’ “

Now, the 41-year-old pastor of a Wheat Ridge church is at center of a global firestorm among flat-Earthers, who are flooding social media with ideas on how to debunk “The Final Experiment” by picking apart camera angles, shadows and footprints. One Alabama pastor is even preaching that Satan was involved in the deception.

“The flat Earth community is imploding,” Duffy said. “They cannot decide what to believe. They’ve all come up with their own conspiracies.”

A debunked fallacy

The idea that Earth is a flat disc was proven wrong by scientists centuries ago, with ancient Greeks getting credit for the discovery that the planet is, in fact, a sphere. Science has backed their discovery for generations.

Skeptics about Earth’s shape have always existed, but YouTube and social media sites have made it easier to spread that conspiracy.

People from all over the world tune into videos and group chats to discuss it. In 2018, hundreds gathered in Denver for the Flat Earth International Conference. Duffy’s YouTube channel has 21,000 subscribers, and some days his videos attract more than twice that many views.

Since digging into the flat-Earth world, Duffy has learned how passionate — and sometimes aggressive — its believers can be.

He has been accused of stealing money from his church, Agape Kingdom Fellowship, to fund the expedition.

And bad investment advice from his time as a financial adviser has come back to haunt him as the flat-Earth crowd digs into the background of a pastor.

‘At that point the debate’s over’

Duffy found four flat-Earth believers and four globers to travel with him.

The trip cost about $35,000 per person, although Duffy’s expenses were covered by the expedition company because he brought eight people with him.

The group first traveled to Chile before catching a flight on Dec. 14 to Antarctica’s Union Glacier Base Camp.

There, they set up cameras and satellite communication so they could record pictures and videos and conduct livestream broadcasts to their followers.

“We interacted with over 4,000 people that were watching,” Duffy said. “We don’t know if that’s ever been done in history. It was midnight in Antarctica and the sun was still up. And so I showed everybody the sun was still up. It’s midnight, so at that point the debate’s over.”

But it’s not over for thousands of people who watched.

The group left Antarctica on Dec. 17 ahead of an incoming storm. Since then, debate has raged online as people try dissect how Duffy and his team might have faked the 24-hour sun.

One Alabama pastor even preached a sermon titled “The Final Experiment Debunked,” and suggested Satan accompanied Duffy to Antarctica then created a fireball in the sky to light up the night.

“You don’t think Satan would go, ‘OK boys, y’all head on down there to Antarctica. I’ll be there on this day. I’ll clear the weather up for you, and I’ll be the angelic light in the sky?’ ” Dean Olde said during his Dec. 30 sermon.

Stepping away from flat Earth

But one person who is changing his mind is Jaren Campanella, a well-known flat-Earth believer who has produced YouTube videos under the name Jarenism for almost 10 years and who traveled with Duffy to Antarctica.

Campanella told The Post he is going to “step away” from the flat-Earth community.

He said the flat-Earth map that he used, called the azimuthal equidistant map, would not be legitimate if a 24-hour sun existed. Once he saw it with his own eyes, he realized his theory no longer worked.

“Even if I don’t feel like I’m on a sphere, even if i don’t feel like I’m upside down, even if i don’t feel like I’m flying through space, the flat Earth doesn’t work for me,” Campanella said. “I couldn’t go on once I knew it was not the case. There’s not a part of me that could on and do another show.”