What about the differences in the night sky? As your latitude changes, stars appear and disappear on the horizons. This should have been noticed as soon as travel over significant distances was practical. The astrolabe and armillary sphere, both ancient inventions, depend on a round Earth to work. An armillary sphere even has a ball in the center to represent the Earth.
An Atlas is depicted with a globe on his back, although I understand it’s not meant to represent the Earth.
Nitpicky indeed! Do you think anyone in this thread is actually confused about it? Anyway, the ancient Greeks (from probably about Parmenides on) knew that the Earth was spherical. (They did not think it was rotating, however.) The shadow on the Moon was not their only evidence. There was also the thing about ships disappearing below the horizon, for one.
Anaximander actually did think the world was round, but not spherical (he said “shaped like a drum,” i.e. a cylindrical disc), but this was probably just a WAG, and had nothing to do with the evidence of shadows (or ships). That was cottoned to later (probably by Parmenides, as I said).
We actually do not know of a single word that Pythagorus wrote, or even if he wrote anything at all (probably he did not). In fact, we know almost nothing about him as an individual. What we do know is that there were quite large numbers of Greeks in the 5th and 4th centuries BC who were known as Pythagoreans, and who were thought (and probably thought themselves) to be followers of Pythagorus. The views of the Pythagoreans, however, seem to have been quite diverse. For one thing, some of them were intensely interested im mathematics, and is probably amongst this group that “Pythagorus’ Theorem” was proved, and the irrationality of root 2 was discovered. However, other Pythagoreans seem to have had no special interest in mathematics. The claim that there is a “central fire” at the heart of the universe probably stemmed from the Pythagorean movement (not necessarily Pythagorus himself), but, as you say, its meaning is obscure. It probably originated with the “Pythagorean” Philolaus, but his astronomical system was thoroughly wacky, and does not seem have been much in contact with the empirical facts at all (even as then known). It has a moving Earth, but it ain’t heliocentrism!
The consensus of scholarship today is that we know very little for certain about what the Pythagoreans believed, and almost nothing certain about Pythagorus himself. Most of the earlier scholarship on the subject (and I mean more than about a couple of decades old) is now thought to be highly unreliable, having fallen for all sorts of myths and legends that accumulated around his name from quite soon after his time, and continued to accumulate throughout much of antiquity. This means, of course, that most modern secondary sources are not to be trusted, and even most texts from antiquity are unreliable on the subject. Sources relatively close to his time, notably Aristotle, are presumably more reliable, but, in fact, there is not that much information on the subject in Aristotle, and Aristotle himself may not have had a very good grasp of what the Pythagoreans believed. Pythagorus was already a quasi-mythical figure by then. Most of the other ancient sources we have are from much later, when even more myth and confusion has accumulated.
Good summary accounts of the recent scholarly consensus on Pythagorus and the Pythagoreans can be found in the Stanford Encyclopedia of Philosophy. Most other stuff you will find online, and in most books (and what you might have learned in college, unless you were in a fairly recent class, taught by a specialist), should not be trusted.
Yes, he did this, but, the thing is, we do have the work where he describes his measurements of the distance to the Sun (actually, the relative distances of the Sun and Moon), and there is no hint of heliocentrism in it. The heliocentrism was, allegedly, in another work that is now lost. If Aristarchus really was a heliocentrist, most likely it was not for any empirical reasons but because he was influenced by Philolaus’ gobbledegook about the “central fire”.
As you say, the Sun being bigger than the Earth is very weak empirical support for heliocentrism. In fact, I am not sure it is any support at all in the absence of even a qualitative conception of gravity, which the ancients did not have. It may seem intuitive to you, post-Newton, that the smaller (and thereby presumably lighter) body would be orbiting the larger, rather than vice-versa, but it is by no means obvious that that would have been intuitive in ancient times.
In fact, Aristotle also believed (though I do not think it is known on what grounds) that the Sun is several times larger than the Earth, and it never in the slightest tempted him, or any of the very many people who would have read about it in his writings in the centuries between him and Copernicus, to consider heliocentrism as an option.
Anyway, this vid proves Bugs Bunny discovered America.
Seafarers and a couple of their friends would probably cover most ancient Greeks. Their economy was heavily dependent on maritime trade. There was also a lot of fishing.
And, of course, they would have found that this curving down below the horizon worked wherever you were, and in whichever direction you were facing, on all of the many coastlines of the Greek Mediterranean world. The only reasonable explanation is that the Earth is curved all over, in all directions.
Anyway, I am not sure what you are arguing for. We have the texts to prove that they did believe it to be a sphere, and by Aristotle’s time the idea was not controversial.
I am having trouble with the idea that at the time of the Renaissance everybody believed in a spherical earth. Maybe Aristotle did, but western Europe went through the dark ages losing knowledge. Are we to throw out all the history of Columbus educating Ferdinand and Isabella? The ancient pictures of him holding the globe in court? Couldn’t he have just started with his business plan of the cost of provisioning the ships and trading goods for a long voyage to the riches of India China on the far side of the Alantic?
Gravity doesn’t actually have anything to do with it; you’ll get the same effect with any sort of interaction. Compare, for instance, an athlete spinning a throwing-hammer around him: The smaller hammer goes around the larger athlete, mostly not vice-versa.
Not arguing per se. No, wait. I think I am. I’m arguing that the sailors/mast thing is wholly unpersuasive. It demonstrates a curved surface, but does nothing to suggest that the curve continues around to the other side of the world. That it’s a very large curved surface is unpersuasive as well.
The argument strikes me as having been made up to justify fracturing the Columbus myth–replacing one myth with another.
Also note I’m not saying that we just discovered the spherical shape of the world last Tuesday. I get that Aristotle and a host of others had come to the correct conclusion. My initial post is about when that went from a super-minority of the population to relatively common knowledge. Clearly by the time circumnavigation was becoming commonplace the concept was becoming widespread. Is that when? Before? Did it take years/decades/centuries to trickle into leaflets, stories and other literature?
Columbus wasn’t educating Ferdinand and Isabella on the shape of the Earth, but the size of it. He (incorrectly) calculated a much smaller size than was was the commonly believed (and much closer to correct) size.
While there was a loss of education in the middle ages, the idea of a spherical Earth never went away. In the 8th century the venerable Bede wrote the basic primer on calculating Easter, “De Temporum Ratione.” It was widely reproduced and became required reading for priests throughout the Carolingian empire. It it he described the Earth as “… not merely circular like a shield [or] spread out like a wheel, but resembl[ing] more a ball,” and “… the roundness of the Earth, for not without reason is it called ‘the orb of the world’ on the pages of Holy Scripture and of ordinary literature. It is, in fact, set like a sphere in the middle of the whole universe.”
So the idea survived into the so called Dark Ages. Five centuries later, the greatest western scholar of his day Thomas Aquinas discusses it as a known fact,
“The physicist proves the earth to be round by one means, the astronomer by another: for the latter proves this by means of mathematics, e.g. by the shapes of eclipses, or something of the sort; while the former proves it by means of physics, e.g. by the movement of heavy bodies towards the center, and so forth.” So it was still around and known to be true by scholars, with known testable and reproducible means. It is hard to imagine that Ferdinand and Isabella didn’t know that a spherical earth was the standard model of the day.
I’m not sure there is a good answer to this. What we have of course, prior to the invention of the press in the 15th century, is mostly scholarly texts. We don’t have the opinions of the common man, at least not until it started to become fairly common to be literate. By that time a round Earth had obviously entered into education enough that if you could read, you probably knew the Earth was round.
It has been a long, long time since I did my medieval literature classes. There are some books from the time period that do present a flat-earth model. But the authors are clearly aware of the spherical model and are arguing against it. I can’t recall anything that presents the view of the common person.
You know that because you know (post Galileo and Newton) physics. They did not. They had no reason to think that the experience of things like hammer throwing was likely to be relevant to the large-scale structure of the universe. In principle the ancients could have had Newtonian mechanics.
The relevant evidence was all available (unlike the relevant evidence for heliocentrism), but they didn’t, not because they were dumb or bigoted, but because they did not know what they were supposed to be looking for. Scientific advances like that take centuries of hard conceptual work. Being clever is not enough. Heck, even in the 17th century it took about three generations to put heliocentrism on a firm footing, and they had to thoroughly rejig the laws of physics in order to do so. Even at the start of that, though, Copernicus could not have come up with what he did (and would not have been motivated to) if he had not had the sophisticated astronomical system of Ptolemy to react against and cannibalize for concepts an mathematical techniques. Aristachus had nothing like that to build on.
In the Roman era, educated people knew what philosophers thought about such things, and all the philosophers, by then, knew that the Earth was a sphere.
In the middle ages, they did lose a lot of the ancient knowledge, but the one thing they didn’t lose, or not for very long, was the knowledge of Aristotle. Aristotle was not esoteric then. His works were the first thing you would read after the Bible. There was not much else to read. Being educated largely amounted to knowing your Aristotle backwards and forwards.
Uneducated people are a different matter of course. As I said before, knowledge of the sphericity of the Earth probably did not become common knowledge until most of the population as a whole started getting some education, probably in the 19th century. But that does not mean that the uneducated before that had a firm opinion that the Earth is flat. If they happened to wonder about it they would probably ask an educated person, and defer to their superior learning.
And no-one is saying that the knowledge came just from ships disappearing over the horizon. On the contrary, the evidence suggests that the main clue was the shadow of the Earth on the Moon. Put those together, and perhaps add in other things like being able to see different stars at different latitudes, and you build up a strong case.
I’m not convinced that the shape of the Earth was ever likely to have been a conversational topic for the average field hand in 900AD.
I doubt they believed the world was flat, specifically. It’s far more likely that the question of what shape the world is never actually came up. The bible, so far as I know, does not say anything about the world being flat or any other shape. So why would some inland peasant have any particular opinion about it? They were generally going to be too busy getting on with the business of life to indulge in much cosmic speculation.
Did a little checking of my concordance. It is for the RSV. It does not list orb or sphere. I didn’t take time to check all the references to earth. It does seem the Bible has little to say about the form of the earth. One of the few references, ‘‘the 4 corners of the earth’’ suggest to me a flat, square earth. That would hardly clash with what a typical peasant saw with his own eyes. Of course, the Bible is not about the earth, but would have had a big influence on many in the middle ages.
Of course the educated and the common man had no more confidence in each other then than now. Why would an educated person waste precious ink and paper recording the views of peasants?
The way to look at this question is not to examine scientific works or navagation, but rather to look at common turns of phrase.
For example, we know that people in England would have, in general, thought the world spherical at least as early as 1599 because of the famous “Globe” theatre - there would be no point in naming it the “Globe” if people did not make the connection between Globe = the whole Earth.
Look then to early uses of terms of that sort.
Of course the version of the Bible you would need to look at to see what the medieval scholars were reading is the Latin Vulgate. In one of those odd happy coincidences there is a word that is used frequently in reference to the Earth, “orbem.” In classic Latin this was translated as a ring or a circle. By the early middle ages, it had also picked up the meanings of globe or orb (which in English is obviously derived from orbem), and just as importantly it had also picked up the meaning of world or earth.
So you have passages like this all over the place:
1 Samuel 2:8
teneat Domini enim sunt cardines terrae et posuit super eos orbem
Which the NIV translates as:
For the foundations of the earth are the LORD’s; on them he has set the world.
Here is another example:
1 Chronicles 16:30
commoveatur a facie illius omnis terra ipse enim fundavit orbem inmobilem
Tremble before him, all the earth! The world is firmly established; it cannot be moved.
For a reader like Bede, the word orbem did mean world, but it also meant globe. The idea that the world was an orb was implicit in the definition of the word. So for Bede the passages would have read something more like:
For the foundations of the earth are the LORD’s; on them he has set the globe.
and
Tremble before him, all the earth! The globe is firmly established; it cannot be moved.
So we have the happy coincidence that a shift in the meaning of a word preserved knowledge of the shape of the Earth because the word orbem was used to translate the Greek words for world and circle (at least in phrases like circles of the earth), even when the original meaning actually was quite different.
I believe that Fata Morgana would distort the image badly enough and/or often enough that a ship sailing over the horizon would not reliably prove that the earth is curved.
I think that the earth’s curvature was proven and measured in ancient times by digging vertical wells at different latitudes and comparing the angle of the sun’s rays at noon. At least this was how I remember it. They could have just used vertical poles and had the same results.
Well, you are mistaken. Fata morgana are rare phenomona that depend on very specific atmospheric conditions.
This may be a garbled memory of hearing about how Eratosthenes actually measured the circumference of the Earth. That came long after it was known to be a sphere, however. If you had bothered to read the rest of the thread you would know that the Earth was most likely originally proved to be sphere through observing the shape of its shadow cast on the Moon during a lunar eclipse.