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Three things that I rarely see mentioned in discussions of this topic: 1. Flat and round are not a dichotomy. Flat is just the limiting case of round as the

by lisper 4y ago

Three things that I rarely see mentioned in discussions of this topic: 1. Flat and round are not a dichotomy. Flat is just the limiting case of round as the radius approaches infinity. 2. Carl Sagan got it wrong in Cosmos when describing the reasoning used by Aristarchus. It is not enough to observe different shadows in different locations. To show the earth is round you also have to show that the sun is very far away. Aristarchus actually had some evidence for that, but his estimate of the distance to the sun was off by a factor of 20. In any case, Aristarchus obviously did get it right, but his argument at the time was not the slam-dunk that Sagan makes it out to be. 3. There is a slam-dunk argument that the earth cannot be flat: time zones. Flat-earthers explain time zones by saying that the sun shines its light in a sort of cone pattern, but this cannot account for the fact that the sun sets below the horizon at different times in different places. On a flat earth, if the sun goes below the horizon, that has to happen at the same time for all observers.

Karellen 4y ago
> Flat is just the limiting case of round as the radius approaches infinity. Reminds me a lot of Asimov's "The Relativity of Wrong": > Nowadays, of course, we are taught that the flat-Earth theory is wrong; that it is all wrong, terribly wrong, absolutely. But it isn't. The curvature of the Earth is nearly 0 per mile, so that although the flat-Earth theory is wrong, it happens to be nearly right. That's why the theory lasted so long. [...] > The curvature of such a sphere is about 0.000126 per mile, a quantity very close to 0 per mile as you can see, and one not easily measured by the techniques at the disposal of the ancients. The tiny difference between 0 and 0.000126 accounts for the fact that it took so long to pass from the flat Earth to the spherical Earth. [...] > To put it another way, on a flat surface, curvature is 0 per mile everywhere. On Earth's spherical surface, curvature is 0.000126 per mile everywhere (or 8 inches per mile). On Earth's oblate spheroidical surface, the curvature varies from 7.973 inches to the mile to 8.027 inches to the mile. > The correction in going from spherical to oblate spheroidal is much smaller than going from flat to spherical. Therefore, although the notion of the Earth as sphere is wrong, strictly speaking, it is not as wrong as the notion of the Earth as flat. -- Isaac Asimov, 1986 https://hermiene.net/essays-trans/relativity_of_wrong.html https://hermiene.net/essays-trans/relativity_of_wrong.html
retrac 4y ago
You can see the curvature of the planet on a very clear day from certain high points. And while you may wonder at first if it's an optical illusion, there's less doubt if you watch a ship head off to horizon: the hull disappears before the mast does.
prng2021 4y ago
Cool, I never considered timezones but that's a great point. I don't find the first point about infinite radius to be relevant to this debate though. It's a true statement, but what flat earthers are talking about is whether the earth is flat in all directions or a curvature can measured and observed by humans, not abstract concepts of infinities.
- lisper 4y ago
  Time zones by themselves are not enough. You have to combine that with the fact that the sun sets below the horizon. And it’s not a question of abstract infinities. How would you experimentally distinguish between a flat earth and a round one with a radius of (say) one light year?

by lisper 4y ago

Karellen 4y ago

> Flat is just the limiting case of round as the radius approaches infinity. Reminds me a lot of Asimov's "The Relativity of Wrong": > Nowadays, of course, we are taught that the flat-Earth theory is wrong; that it is all wrong, terribly wrong, absolutely. But it isn't. The curvature of the Earth is nearly 0 per mile, so that although the flat-Earth theory is wrong, it happens to be nearly right. That's why the theory lasted so long. [...] > The curvature of such a sphere is about 0.000126 per mile, a quantity very close to 0 per mile as you can see, and one not easily measured by the techniques at the disposal of the ancients. The tiny difference between 0 and 0.000126 accounts for the fact that it took so long to pass from the flat Earth to the spherical Earth. [...] > To put it another way, on a flat surface, curvature is 0 per mile everywhere. On Earth's spherical surface, curvature is 0.000126 per mile everywhere (or 8 inches per mile). On Earth's oblate spheroidical surface, the curvature varies from 7.973 inches to the mile to 8.027 inches to the mile. > The correction in going from spherical to oblate spheroidal is much smaller than going from flat to spherical. Therefore, although the notion of the Earth as sphere is wrong, strictly speaking, it is not as wrong as the notion of the Earth as flat. -- Isaac Asimov, 1986 https://hermiene.net/essays-trans/relativity_of_wrong.html https://hermiene.net/essays-trans/relativity_of_wrong.html

retrac 4y ago

You can see the curvature of the planet on a very clear day from certain high points. And while you may wonder at first if it's an optical illusion, there's less doubt if you watch a ship head off to horizon: the hull disappears before the mast does.

prng2021 4y ago

Cool, I never considered timezones but that's a great point. I don't find the first point about infinite radius to be relevant to this debate though. It's a true statement, but what flat earthers are talking about is whether the earth is flat in all directions or a curvature can measured and observed by humans, not abstract concepts of infinities.

lisper 4y ago
Time zones by themselves are not enough. You have to combine that with the fact that the sun sets below the horizon. And it’s not a question of abstract infinities. How would you experimentally distinguish between a flat earth and a round one with a radius of (say) one light year?