So, I've done a fair bit of research into this whole flat earth theory stuff, and I can accept that someone could reasonably believe everything they say if you'd be willing to acknowledge the existence of a conspiracy large and powerful enough. Okay sure, gravity's not real, the Sun is actually only thousands of miles away and only 32 miles wide, the south pole is actually a wall, everyone's working to cover it up etc etc. I mean, I consider it to be off-the-deep-end nuts, but I'll acknowledge whatever limited validity it has in their worldview.

But here's what I don't get, and if anyone could help shine light on how this could possibly make sense to a flat earther: the Moon. I'm not even going to go so high level as lunar phases or even "what light is reflecting off the moon to allow us to see it?" But just... look at the moon. It always looks the same way. We're always looking at the same side of the moon, the moon always has the same distinct features visible, it's completely recognizable.

Basically, we've established that every full moon looks the same as every other full moon, in perpetuity. That is... until you go to the southern hemisphere, where it appears upside-down. In the entire southern hemisphere, it appears upside-down.

If the flat earth theory were true, and the southern hemisphere were actually the furthest "rings" away from the center of the earth (the north pole), then why is the moon upside down once you get far enough away from the "center" of the flat-earth? How can you take a plane trip during the night from Florida to Brazil, and by the end of the trip you'll see a different orientation? And yet, going from Brazil to Singapore, on roughly the same "latitude" despite being at completely opposite ends of the plate, you see the same orientation (upside-down)?

If anyone could help me understand how this is even possibly reconcilable to a flat earther, that'd be much appreciated. I definitely can't understand it. Otherwise, feel free to use this argument against any flat earthers you meet. I'd be curious to know what sort of mental gymnastics they'd jump through to explain it.