The experiment has reportedly been a favorite of flat-Earthers since 1836, when Samuel Birley Rowbotham first did it on the Old Bedford River.
Editor's note: This article was originally published on February 4, 2022. It has since been updated.
A clip that resurfaced on Reddit has brought renewed attention to the 2018 documentary "Behind the Curve," which focuses on "the growing, worldwide community of theorists who defend the belief that the Earth is flat while living in a society who vehemently rejects it." Shared to the r/facepalm community, the video clip shows a scene from the very end of the documentary where a Flat-Earther named Jeran Campanella performs an experiment to prove that the Earth is actually a flat plane and not a spheroid. Unfortunately for him, the experiment inevitably proves that the Earth is, in fact, not flat.
In the clip, Campanella—who is part of a YouTube channel called Globe Busters—sets up an experiment involving a camera, two boards with holes at a height of 5.18 meters (17 feet) above water level and another person holding a torch. The camera is aimed in such a manner that its viewfinder is centered on the holes in the boards, which are set up in a straight line but at increasingly further distances. Meanwhile, Campanella's friend with the flashlight stands at a distance further beyond the boards.
Here's what Campanella sets out to prove through the experiment: If the earth actually is flat, no matter how the flashlight is, the camera should be able to perfectly record its light without any occlusion, when it's held at the same height and aligned with the holes. On the other hand, if the earth is round, the planet's curvature comes into play. So the second, more distant hole, would slightly cover the light unless the person with the flashlight positioned the light above his head (7 meters/23 feet above the water level). Needless to say, since the Earth is round, the light doesn't appear on camera when everything is positioned in a way meant to prove the planet's flatness.
A perplexed Campanella radioed his friend to confirm that the light is held 17 feet above sea level and when told that it is, asks him to lift the light above his head. Look and behold, the light shines through. "Interesting. That's interesting," Campanella says of the result. According to Insider, this particular experiment has been a staple of flat-Earthers since 1836, when Samuel Birley Rowbotham first did it on the Old Bedford River. "Time and time again, it has revealed the curvature of the Earth," the publication states.
In addition to hearing from multiple big names in the flat-Earth community, "Behind the Curve" also features expert commentary from an astrophysicist, a psychologist, a psychiatry professor and a number of physics experts. Speaking to Entertainment Weekly, director Daniel J. Clark revealed how he approached his subjects with empathy and humanity rather than trying to disprove their beliefs. "I think the first step is to not be condescending and not to talk down and not belittle people whose beliefs, in most people's eyes, are wrong, because that doesn't change much. Shaming someone doesn't change the way they feel about something. In fact, it probably just reinforces it and they become more entrenched in their belief," he said.
"So approaching it from the angle of, 'I see where you're coming from, now here's where I'm coming from,' is better. I think it's probably idealistic because some people aren't to listen necessarily. And this isn't just Flat Earthers, this is everybody. So if you come at it from a more understanding and empathetic angle, I think you have a better chance of at least having them understand where you're coming from," Clark added. Physicist Spiros Michalakis makes a similar point in the film. "The problem I see is actually not from the side of the conspiracy theorists, it is actually from our side. From the side of science. Very often it's difficult not to look down [on the flat-earthers]," he says, according to Digital Spy. "The worst case scenario is you just completely push these individuals to the fringe of society. And then society has just lost them."