Flat-earthers are a special breed of stubborn. They are steadfast in their belief that the Earth is flat. Some believe the Earth is a disk or the bottom of a dome. And many, no matter how much evidence to the contrary that they are presented with, refuse to believe otherwise.
Some flat-earthers are able to be swayed by science, though. One Reddit user asked people who used to believe the Earth was flat to explain what changed their mind. The answers are varied, but they all point to an ultimate willingness to recognize the truth.
TrungusMcTungus is not a flat-earther, but they met someone in the Navy who joined specifically because he wanted to prove the Earth was flat while at sea. He charted the ship's speed, location, etc. obsessively to make comprehensive maps of its path.
"Ultimately, he realized that the path the ship was taking would be impossible if the Earth was flat, based on the distance they were traveling vs. their speed," they wrote. He realized he couldn't see the land they were aiming for because the horizon curved, and that's when he finally realized the Earth is spherical.
I_literally_can_not claims they weren't exactly a flat-earther but fell for lots of conspiracies concerning the Earth's shape and makeup when they were younger. What finally convinced them that the Earth is a non-hollow sphere?
They saw a video of an experiment where "one group flew a helicopter far out over the ocean and another group watched it with a powerful telescope as it slowly lowered to the horizon." Eventually, the helicopter disappeared behind the horizon even though it was still the same distance from the ground. From that moment, they were convinced.
The travel conundrum is also what convinced spacedandy1baby that the Earth is a globe. They write that the flat Earth map "really falls apart" when you consider that, if the Earth were flat, it shouldn't take as long as it does to travel to the North Pole, for example. Without that curve, it'd be a fraction of the distance away from, say, the equator, than it actually is. Only a curve can explain that.
It really is the horizon that transforms most people. Hasslesass explains that their roommate and friend got deep into the flat-earth conspiracy, but then they did an experiment with lasers, where they went to opposite sides of a large inlet bay.
The friend shined a laser and slowly lowered it to try to hit them, but it always disappeared before it got to him, proving that the Earth is curved. And that's what finally made him accept that the Earth is not flat.
SW_Shadow's experience was different. They grew up in an evangelical Christian household and was brought up to believe the Earth was flat (among a bunch of other conspiracy theories). But since their mom was a "lazy, delusional narcissist" who didn't actually homeschool them, TV became their "only teaching resource" when they were about 12 years old. They learned real science from the Discovery Channel and other educational TV channels and didn't look back.
For seaotter_toebeans' husband, it was more about flat-earthers themselves that made him change his mind. They wrote that he "got trapped in a YouTube black hole of flat-earth videos for a while." But the thing that changed his mind was that "he discovered the majority of flat-earthers are Trumpers with extreme political views." His flat-earth views ended as abruptly as they started.
Some flat-earthers seem so set in their beliefs and so unwilling to accept scientific evidence to the contrary that they will probably never change their minds. But if a person is open to truth and facts and science, it is possible for them to see the light...and the curve of the Earth.