As for one, at least, if the Ancient Greeks and Egyptians knew the world was spherical (as they did, and had an approximate measure of its dimension), this could be easily predicted and might make part of whatever speculative discussion they had that was the equivalence of HN or general interested internerdery here.

The second is harder to find an excuse for.

(O/T) Of interest to me is something I learned from HN - https://en.wikipedia.org/wiki/Cape_Bojador - a large rocky shoal off the North Western African coast that scuppered many attempts at sailing around that area. It was, somewhat naively, the first thing in my long life that made me really appreciate how challenging old sea faring would have been.

Eratosthenes calculated the diameter of the Earth pretty well in 00240 BCE. Aristotle claimed it was round around 00350 BCE, and might have had a correct value, but uncertainty about units of measurement means his error could have been as large as a factor of 2, and the roundness of the earth was still a matter of debate at the time.

Herodotus died around 00425 BCE and probably wrote closer to 00435 BCE.

They were all "ancient Greeks" (and Eratosthenes lived in Egypt, so I guess he was an "ancient Egyptian" too) but that doesn't mean they were contemporary. Imagine someone in the year 04542 CE writing, "If the ancient Terrans knew about nuclear energy (as they did, and had unreliable and inefficient fission power plants and nuclear weapons), then Lincoln could have easily used atomic bombs in the US Civil War!" The timespan from Lincoln to Hiroshima was 80 years, from Herodotus to Aristotle about 100 years, and from Herodotus to Eratosthenes about 200 years. And those were very eventful centuries, much like our own.

Yes, and there is a large chasm between discovery and information that is widely known and accepted among the population. For instance, many Europeans went with Ptolemy's less accurate calculation (made hundreds of years after Eratosthenes's) until the 16th century.

> there is a large chasm between discovery and information that is widely known and accepted among the population

There are even more extreme examples of this. The Moscow Papyrus is from 01850 BCE, and it explains how to calculate the area of a hemisphere from its diameter and how to calculate the volume of a truncated pyramid, so this information had already been discovered 3870 years ago—perhaps for many centuries.

Yet what fraction of people today know it? Try asking your taxi driver next time you're on vacation in Perú or the Philippines. Heck, I don't know the pyramid-volume thing myself! I'd have to work it out by integrating a quadratic.

(I recall that studying the calculus as a kid was a bit of a transition for me, because for the first time I came face to face with the realization that most adults' intellectual development was arrested around the year 01583 for some reason. It wasn't that they took a long time to grasp differentiation, or that they had some weird irrational belief at odds with reality, but that they just stopped learning and never grasped differentiation in the decades and decades they lived, converting themselves into intellectual dwarfs. I was still young enough to imagine that somehow I would avoid this...)

There is finite space in your brain. If you don't use it regularly it isn't odd to not retain it.

The phenomenon I'm talking about is not that people learned how to differentiate functions in college, then forgot, though that certainly does happen. I'm talking about people who never learned to differentiate at all, or never learned linear algebra, or never learned group theory, or never learned complexity theory. And not because they were busily learning something else and just hadn't gotten to group theory yet, but because at some point they just stopped learning things.

I'm not convinced of this finite-space theory. I mean, yes, in a physical sense, there's clearly finite space in your skull. But even the synaptic connections outnumber the bits in the textbooks for a B.A. by about four orders of magnitude, and the potential neural DNA methylation sites outnumber synaptic connections by another six orders of magnitude. So I don't think this intellectual stunting is accounted for by space limitations.

True, and surely some did—not just in the Mediterranean but in Perú and in Punt, and not just 2500 years ago but even a quarter million years ago—but, despite the whole lunar-eclipse thing, nobody had a really compelling argument until Eratosthenes precisely measured its curvature.

That is, though the wise could imagine a spherical Earth for as long as they have had fruit, they could just as easily imagine a non-spherical Earth. More easily, I think, because, I mean, look around you, it looks flat. It wasn't until Eratosthenes that the wise lost the ability to believe that the Earth was flat.

There’s this guy, Randall Carlson, who claims the great pyramid of Cheops is a scaled version of the northern hemisphere. If true, I guess it would mean the Egyptians knew the earth was round.

https://sacredgeometryinternational.com/the-great-pyramid-de...

“Sacred geometry”?

Beware this type of thing. It’s an introduction to madness.

Some of these pyramid folks claim that they were built as signposts for alien landing strips. And it gets more and more nuts from there.

That article is mostly just a hard to read description of latitude, longitude and meridians. Didn't actually see anywhere that the point was made.

It’s hard to read because it’s a video transcript of a Joe Rogan interview. In the actual interview his explanation becomes more clear imo.

_If_ they thought that was a scale model of half of earth, they must have thought the earth has the shape of an octahedron (possibly a slightly deformed one), not that of a sphere.