America’s flat-Earth movement appears to be growing – Daily chart

However, flat Earthers aren't "wrong" in the same way that Newton was, they don't simply have an alternative model of reality which is useful in its own peculiar way. Newtonian mechanics and Einstein don't contradict each other, and one doesn't override the other. Flat Earthism, meanwhile, is like the crackpot who denies all this newfangled quantum timespace relativity mumbo jumbo and refuses to believe in anything but Newton, because Newton is simple and obvious. It doesn't refine and augment existing knowledge, it denies its validity altogether.

Thinking of the earth as being flat at human scale is simple and obvious. Thinking of the earth in its entirety as being flat is simple and obvious and wrong in ways that even the ancients could figure out. There's no domain in which that's useful.

The goal is to determine if a Round Earth model is a more useful model than a Square or Disk Earth model.

I've demonstrated it empirically to my own satisfaction.

I've seen the Southern Cross right at the horizon from the Florida Keys, but not visible father north. I've seen that the North Star rises higher in the sky as I've gone north. And in summer I've seen that the daytime is much longer in Michigan than Florida, and how the sunlight in the evening goes through the windows of the north side of buildings, which it doesn't really do in Miami.

I've driven across the US and seen that the sun rises a couple of hours later in the West than the East.

I've been below the Equator, and seen Orion cross the sky upside down, while the Southern Cross and the Magellanic Clouds were high in the sky. I also got confused when driving because it turns out my sense of direction was based on the expectation that the Sun should be in the south at midday, not in the north.

I was once at about 55 degrees north latitude, in early December, and the sun was low in the sky at noon. By measuring the shadow length I calculated the latitude to within a couple of degrees. (This calculation does require knowing the axial tilt, which I have not independently measured.)

These are all consistent with a Round Earth model, and not at all consistent with any description of a Flat Earth model that I've come across.

Now of course it's possible to say that I've not measured the radius of the Earth to sufficient precision, or demonstrated that the diameter between the poles is shorter than the equatorial bulge.

But that's changing the goalposts. I did not have to appeal to any authorities to confirm that the round earth model is a much better fit to my observations than a flat earth one.

Why are you not able to make similar empirical tests? If you are able to carry them out, why are they not enough for you?

The TV series "Ring of Truth" from the 1980s tried to address the question of how you can test things out for yourself. One of the things they did, in such a way that you could reproduce their work, was to drive along a long north-south road and measure the elevation change in a star. From this they could estimate the size of the Earth. They call it the "Van of Eratosthenes." You can see it at https://www.youtube.com/watch?v=yRY2SkMTafc .

Again, there's no reason to trust what the said. Rather, you can use it to reproduce their methods yourself, which is the sort of empirical test you asked about.

It's quite possible to both demonstrate that the Earth is round and get an accurate first-order approximation of its size with tools available 2,000+ years ago.

We know this is possible with certainty because it was actually done 2,000+ years ago, by Eratosthenes.

The notion that the earth is flat is absurd to all but the ignorant.

There’s a reason why skeptics target things like round vs. flat earth — it’s a variant of “the big lie” approach used by oppressive political regimes. As humans, we dig into and push back against nuanced arguments. But when you challenge fundamental things, people who are actively ignorant and charismatic have an easier time convincing people about nonsense.

A similar example is the UFO phenomenon of the 80s and 90s, where the military planted or encouraged wacky stories to divert attention from aircraft and cruise missile testing.