I have ranty feelings about that.
Sometimes, to have images both striking and calming, I watch the video feed from the International Space Station looking at Earth as the ISS orbits. Flat Earthers have to believe that this is either faked or, somehow, distorted. Wide-angle lenses to "cause" curvature to the Earth, I'm guessing, never mind that those would distort any equipment or, say, astronauts on EVAs that went in front of those cameras.
Meanwhile, there's an image that shows up all over the Web, supposedly a quote from the Flat Earth Society, saying that the society has members "all around the globe." I saw that again this morning — I see it a lot — and imagined a Flat Earther huffing about people who laugh at that and going "Duh, we mean that metaphorically. It's an idiom." Idiots can use idioms.
It's simple: the world would not work if it were flat. Anything orbiting the disc-Earth would fly off and away. Gravity at different parts of the world would be wildly variable, as the Earth would be far, far thinner than the 7,917.5 miles from the surface to the center. (Wait: would gravity on a flat disc-Earth pull at an angle? Instead of straight down towards the core? I NEVER THOUGHT OF IT THAT WAY...)
I've heard some details of some flat-Earth theories. "The atmosphere stays and doesn't fly away from Earth because there's a giant wall the governments don't talk about! It encircles the world in the deep reaches of Antartica! And it's guarded!" Guarded. By guards. Guards guarding a wall that would have to be tens of thousands of miles long.
Flat-Eartherism (I don't know if that's the accepted term, and I don't care) is, incredibly, even more nonsensical than most conspiracy theories. Lots of conspiracy theories try at least to impose a storytelling logic on reality; Flat Eartherism can't even do that. And as almost all conspiracy theories do, it collapses when you think of how many, many people would need to keep a secret, well, secret. Every astronomer, passenger jet pilot, astronaut, operator of a geosynchronous satellite, operator of that satellite literally one million miles away from Earth with a camera pointed at Earth's sunlit side, ISS Mission Control employee, that guy who parachuted from over 127,000 feet, and more would have to be lying to us. At least.
(I can have fun with conspiracy theories. I do believe the one that says the layout of the hotel in the Stanley Kubrick version of The Shining was designed to be impossible, to mess with audience's perceptions. But that's, for me, a rare exception. And note that it's about A FILM, NOT REAL LIFE.)
Let's approach this another way. A lot of people my age and older were taught that Christopher Columbus sailed west partly to prove the Earth was round, but no, that was already accepted. Had been for centuries. Over 200 years before Christ was born, a Greek scientist in Egypt calculated the circumference of the Earth and was 10% off — a huge discrepancy by our standards, but incredibly good for that era. A scientist from India, working in the Sixth Century A.D., calculated it and was only 1% off. Christopher Columbus, amazingly and kind of maddeningly, used estimates and assumptions that led him to underestimate the Earth's circumference by 25%. That's why he thought his trip was doable. Had the Americas NOT been there, and had there been nothing but ocean and mmmmmaybe isolated islands from Europe to Japan, Columbus and his crew would have run out of supplies and starved and died.
But speaking of Columbus, I remember a comment writer Ken Jennings once made: "There might be more flat earth believers on Facebook today than there ever were in Renaissance Europe." With the increase in both the human population and the ability to share information, whether correct or wrong, this could very well be true. And it makes my head hurt.
It may be pointless to argue with Flat Earthers. They're not likely to listen. So many debaters don't truly want to argue, but to exhaust the people who disagree with them, by what-abouting and sealioning and dismissing. And meanwhile, a man who believes in the Flat Earth theory succeeded in launching himself in a rocket earlier this year and getting less than half a mile off the ground. Less than half a mile. 1,875 feet. That's not even as high as the Burj Khalifa in Dubai is tall. Um, at least the guy didn't kill himself in that rocket, but HE ALSO DIDN'T PROVE ANYTHING.
Yes, I sometimes think how otherwise intelligent people say, and believe, "I see a flat Earth so it's all a flat Earth."