There’s another thread about the myth that Columbus proved the world was round. It’s typically brought up that by that time everyone knew the world was round.
When was ‘that time’? I’m not talking about highly educated people or those with windows that looked out at oft-mentioned ship masts, but the common, everyday person. If you walked through a handful of 15th century villages and asked if the world was flat or round, would most people have picked round?
Also, when did the concept of rounded edges translate to the concept of a sphere? While I understand how the ship-mast thing and other observations translate to a curved horizon, how/when was the leap made to the Earth curving all the way to the other side? That is, if I stand on a gentle hill I’ll get the same visual effects. If I put a large non-rigid disk on a pedestal, I’ll see a curved surface—of an ostensibly flat object. When did it become ‘known’ that with enough wind, food, and balls you could sail west and end up in the east?
The ancient Greeks knew that the earth is round. I think it was Aristotle who remarked that the earth casts a round shadow on the moon during a lunar eclipse. This was confirmed by astronomers in the third century BC. Don’t know whether the average Greek would have agreed.
It’s going to vary form place to place. In China and Japan *everyone *thought the wold was flat until the 14th century. In Europe, by the 14th Century at the latest people write of the world as a globe without any explanation, even when addressing soldiers and craftsmen. So it’s safe to assume that by that time the round Earth was the prevailing view. Exactly when that view became standard, we don’t know. Since the fact was known to Clergy men since the fall of Rome, and since they were the main educators, it’s possible that people in Europe have accepted that the world was a globe for thousands of years. There’s certainly little evidence that they thought otherwise.
For most of history, most educated people knew that the world was round. Most common people were for most of history much more concerned with where their next meal was coming from to bother with the shape of the world.
Without cite, my guess is that wave of the discovery voyages in the 16th century, the production of globes and general education (Schooling) was the breakthrough.
You could ask the same question for most of what we consider basic knowledge today, though, for similar reasons: Algebra was not considered necessary to people not involved with trade or banks (which themselves started in the 13th century), so most people wouldn’t know that 2+2=4.
Even today, how many of the poor people in 3rd world countries who can’T afford education would know that the world is round? They probably haven’t heard of anything beyond their village and county.
When I was a schoolboy way back in the 20th century, we were taught that the mighty Christopher Columbus proved the Earth was round.
But, we also were taught that George Washington cut down his father’s apple tree.
Truly, anyone who is lucky enough to live on a coastline and witness a ship leave over the horizon could watch as the hull disappeared before the mast.
That, in of itself, would provide evidence that the Earth was (and is) spherical.
Funky. I heard it was a cherry tree.
The second paragraph is a bit I have a hard time wrapping my head around (heh). A flat surface with curved/sloped edges seems much more intuitive than a world that goes around to the other side. A flat Earth that bulges in the centre (where the land was) and slopes off at the edges fits a lot closer than one that wraps around.
Only, the world had been represented as a globe on religious imagery for thereabouts of a thousand years, if not longer. The globe used in coronations (and used in any statue of a saint king) represented the world. How many people realized it represented the world in a literal as well as symbolic sense, that I don’t know.
That’s not algebra, it’s arithmetic and everybody knew it. They may not know how to write it (although for centuries learning one’s numbers was more widespread than learning one’s letters), but they sure did know it.
Definitely not Anaximander, who explicitly held that the Earth was flat, as did his successor, Anaximines. They were arounfd in teh mid 6th century BC I don’t think it is known for certain who first realized that the Earth is a sphere, and spread the idea, but Aristotle (and Plato before him), writing in the later 4th century seems to take it pretty much for granted, so it was somewhere in between. I have seen the discovery attributed to both Parmenides and Pythagorus, but given that Pythagorus, even by Aristotle’s time, was a semi-mythical figure, the founder of a religious movement, who tended to be given the credit for all sorts of unlikely things (he did not discover Pythagorus’ Theorem, either), Parmenides seems the much better bet. The claim that it was Parmenides seems to have originated with Aristotle’s leading pupil and immediate successor, Theophrastus, who wrote the first systematic history of philosophy, which is generally regarded as having been pretty reliable by the standards of the time. (Unfortunately, only fragments of Theophrastus’ work survived into modern, or even medieval times, but much of what is said about the early history of philosophy by writers in later Greek and Roman classical times probably derives ultimately from Theophrastus.)
Incidentally, the Ancient astronomer who is said to have belied in in a heliocentic universe is Aristarchus, who was a generation or so after Aristotle’s time (and who also takes the spherical Earth for granted). We do not know why he advocated heliocentrism (if he really did, the evidence is not that strong), but we can be pretty confident that that he did not have good empirical reasons for it. (Heck, even Copernicus did not have good empirical reasons!)
As for the OP’s question, I should imagine that common knowledge of the Earth’s sphericity would coincide with the spread of education for the lower classes of society, so, I guess, the 19th century.
But that doesn’t really preclude it from being perceived as a flat, round circle rather than a sphere that’s rotating.
ETA: nitpicky annoyance - “round” is not the appropriate word to use in this discussion, since circles are round. The OP is asking about when people knew that the Earth was (roughly) spherical.
If the world were a disk, then sometimes (usually, in fact) the shadow would be elliptical, not circular. For it to always be circular, a sphere is by far the simplest explanation.
And by some accounts, Pythagoras’ view might also have been considered heliocentric, but it’s debatable. He wrote of the world orbiting a “central fire”, but this was probably metaphysical, and the central fire probably did not refer to the Sun.
Oh, and Aristarchus did actually have observational evidence, albeit weak, for heliocentrism. He was the first to measure the distance to the Sun, and hence its size, found that it was larger than the Earth, and argued that it made more sense for the smaller object to orbit the larger one. His method for measuring the distance was not very good (no fault of his; he did the best that could be done with the technology available to him) and so his experimental error on the distance measurement was huge, but he did at least do well enough to correctly confirm that the Sun is larger than the Earth.
No, it wouldn’t. Not in a geocentric model where the sun and moon rotate around the Earth on fixed axes perpendicular to the plane of the disk. The shadow cast would always be circular.
Correction to my above post: not axes perpendicular to the plane of the disk, but rotating around an axis which goes straight through the center of the disk, along the same plane as it.
Anyone on the ship would see the harbour town’s buildings disappear before a tower or church steeple, and if he then climbed to the top of the mast quickly enough (if he could, even thousands of years ago), he would see the buildings again.
In any event, having come from the town, he’d know it wasn’t about to fall off the edge of the Earth. And when the ship returned, it was obvious it hadn’t, either.
But that works without the need for the overall shape of things to be spherical. Standing at the top of a hill and watching a giraffe parade will have the same effect. Watch long enough and you’ll see their feet, legs, and absurd necks slowly disappear off the edge. Even if you’ve never been to the other side of the hill you don’t (intuitively) expect the giraffes to come to an edge and tumble down past all the turtles. You just assume the hill keeps going down or maybe levels out at some point.
That the Earth is curvy I’ll give to seafarers and a couple of their friends. That the sailors, well aware that the Earth was curved, also thought it kept curving around on itself is what I’m curious about.
Only if the eclipses happened at midnight. If you had a lunar eclipse right at moonrise or moonset in such a model, the shadow would be a line, and somewhere between a line and a circle (i.e., an ellipse) for an eclipse at any other time.