I’ve never met a flat earther, and probably this post will never be read by one. I turn 44 this year and when I was growing up this wasn’t something anyone believed. For a long time I thought it was a meme, and honestly I still wonder. Until I actually meet someone who makes the case I think I’ll be unsure.

My hunch is the flat earth idea is actually more of a thought experiment than anything. It asks, “How do you, personally, really know though?“. It’s an exercise in skepticism. And from that perspective, the replies people actually give to the theory frustrate me. So here’s my backseat quarterbacking put to paper. If a genuine flat earther ever reads this, hey, drop me a line.

Okay, so, the general question is “How do you personally really know though?”, right? So let’s start small. I don’t know where you live, but would you say you know how far away the next town is? Like, how many miles? It’s pretty hard for the government to be lying to you about that, because you see it every day. You know roughly how much gas your car uses, even if the signs were all wrong. And the people in the next town, they all know how far away the next town over is too, because they’re just like you. Some of them are driving those distances every day. This applies out across the whole country you’re living in. There’s no patch of it that doesn’t have people driving around in it, and you really can’t lie to those people about how far they’re driving. If you don’t trust databases like Google Maps, you can put paper maps if you want, and add it all up yourself. You can buy the same ones they’re using locally, that have to agree with what all the people who live there experience.

Okay, so let’s assume for now that the distances on the map of your country are right. Well, the same really applies everywhere. Every country has ordinary people living in it, and the government can’t be lying to them about the distances they see every day, and you can get the same maps they use and check whether the distances are what the globe says they are.

I know that you don’t have to have all the answers on something to be skeptical. Like, it’s okay to say “that can’t be right” even if you can’t come back with a theory that’s exactly right either. So if you think the world isn’t round, okay, maybe you don’t know exactly how the true map is shaped. But still, look at the options for the best guess of how a flat earth map could be shaped. The one I see the most (the azimuthal projection) would have the distances mostly add up for around US, Canada, Europe, Russia. But in order to do that the shape of Australia is way off — it’s 2.5 times as wide on the azimuthal projection as it really is. And well, I do personally know that’s not right. I haven’t driven all the way across Australia, but I know lots of people who have, and I’ve made lots of shorter trips where the distance already would be way off. You can conclude I’m part of the conspiracy, but then the conspiracy has to include every ordinary Australian — and many of them are skeptical about a lot of the things you are.

You can drive east/west almost all the way around the world — through Europe and Russia, then a short ferry over to Alaska, then all the way across Canada. You can also start almost at the north pole in Canada and head south, through the US, through Mexico, and through central America. You can’t drive down into Colombia, but you can get a ferry, and then you can drive all the way down to the tip of Patagonia, which isn’t that far from Antarctica. And once you’re in South America you can drive east/west and check those distances too. If you do that you’ll see with your own eyes that the distances are all what they are on the globe map.

Now look, you’re not going to do that drive, and I haven’t done it either. But almost the whole way down you’ll be passing ordinary people who live there, who know how far away the next town is just like you do where you live. You can’t have a conspiracy where everyone’s in on it, because then where even is the lie? Is it a conspiracy just against you specifically? So even without doing the drive you know the distances are right. How can you make a flat map where that’s true, and also where you can travel around Europe, through Russia, and end up within sight of Alaska?

If we disagree about the shape of the earth (globe vs flat), we disagree about the shape of the map, which means we disagree about how far away things are from each other. But the thing about big distances is, they’re made up of lots of little distances. And ordinary people know all those distances, they verify them with their own eyes every day. So how could the big distances be wrong? And if they’re not wrong, how could the earth be flat?