"the amount of energy needed to refute bullshit is an order of magnitude bigger than to produce it." https://statmodeling.stat.columbia.edu/2019/01/28/bullshit-a...

The trivial way is a phone call to a friend in a different time zone. It's dark there; it's not dark here. It's just past dawn here; the sun is at the highest a few time zones east. More phone calls to more places and it's pretty quickly apparent that the angle to the sun is exactly what you'd expect from a sphere and not from a disk.

Not that it matters. Flerfers have had decades coming up with increasingly elaborate and absurd cosmologies. They don't understand them, but that's what science looks like to them as well, so they figure it's your word against theirs. And since their word is the Bible, they win.

If they were genuinely curious, there are a million ways to show the roundness of the earth. But there are zero ways to demonstrate it to a person who is fundamentally incurious and doesn't want to know.

Why do you need to prove them wrong? Have they given you doubt the world is round?

https://physics.stackexchange.com/questions/26427/what-is-th...

https://en.wikipedia.org/wiki/Hitchens%27s_razor "What can be asserted without evidence can also be dismissed without evidence." Let them bring evidence of Earth's flatness.

Don't waste your time?

Just go find different people to talk to

Meet them at night, point to the moon, walk away without saying a word.

Out of curiosity, what religion was that?

> Ran into a few religious people who suggest the earth is a firmament

The firmament is the sky, not the ground.

Ignore their idiocy. Such folks cannot be convinced by mere facts.

Did they, by any chance, mention elephants and a big turtle too?

Ask them to take you to the edge of the Earth and show you where you can jump off. /s

You don't. You respect their mind. Simple. Make love not war of any kind.