There seems to be almost a consensus that the medieval belief on flat earth is a myth. Wikipedia even has a whole article dedicated to this subject, and the general argument is that the "flat earth myth" was constructed by 19th century scholars who wished ill on the Church.

However, I recently came across this book "The House of Wisdom: How the Arabs Transformed Western Civilization". In chapter two, the author Jonathan Lyons claims that most medieval scholars indeed did believe earth to be flat. He bases this on the fact that a 6th century scholar, Isidore of Seville, made a mistake when translating ancient Greek texts to Latin, which lead to a hugely popular medieval encyclopedia claiming that the Earth was actually flat. Lyons proposes that while another author of the same era, a British monk named Beda, did indeed study the original texts of Plinius and did discover that the earth was round, his work was not as widespread as Isidores and thus the "Flat Earth" became a consensus among the scholars of the Middle Ages, even though some retained knowledge of the spherical form of Earth.

Since most internet sources on medieval flat earth theory do not even mention Etymologiae, yet it does seem to have been an influential work, it is left unclear whether most medieval scholars in Europe believed Earth to be round or flat. Which one is it?

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    Beda was hugely influential. Pretty much all medieval chronicles use him as a source in one way or another, so claiming that his work "was not as widespread" sounds fishy. Also, even if six centuries later, Dante Alighieri unambiguously stated that the Earth was round in his Comedy, and he certainly was claiming to be reporting a consensus opinion. Commented May 17, 2018 at 9:05
  • 14
    The "scholars believed in a flat earth* idea is trivially wrong, as the earth is obviously round to anyone who does a bit of observation. Ships appear and disappear at the horizon from the bottom up, for example, and if the world were flat, there could be no twilight; day would transition to night, and night to day, instantaneously. Just off the top of my head, these two examples both easily show that the world is round, with essentially no room for controversy. There's little to nothing to suggest scholars have ever taken a flat-earth model seriously. Commented May 17, 2018 at 13:12
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    @jamesqf That is not only blatantly false as all the answers demonstrate, but ironically probably also the same mentality that gave rise to flat earth myth in the first place.
    – Semaphore
    Commented May 17, 2018 at 19:34
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    @jamesqf - The Bible absolutely does not claim that the earth is flat. To the contrary: "It is he that sitteth upon the circle of the earth, and the inhabitants thereof are as grasshoppers; that stretcheth out the heavens as a curtain, and spreadeth them out as a tent to dwell in:" - Isaiah 40:22 (KJV) For the record, they also don't teach a geocentric model of the universe.
    – Truth
    Commented May 17, 2018 at 20:49
  • 12
    Please do not use the terms round vs flat. circles and spheres are both round. Spherical vs flat or spherical vs circular are best
    – Scott
    Commented May 18, 2018 at 0:33

10 Answers 10


Lyon's theory is rather flawed.

First of all, the Etymologiae was written in the 7th century. Just because one paragraph from one chapter in the book might possibly be construed as implying a flat earth, does not mean serious scholars for the next 1,000 years all believe the earth to be flat. Without direct evidence of medieval scholars calling the Earth flat, one cannot possibly extrapolate a single book's alleged errors to an entire continent.

The existence of Newton's extremely influential work does not prove 21st century physicists 400 years later are unaware of relativity.

Secondly, it's not clear that Etymologiae actually says the Earth is flat, mistranslation or otherwise. This is what it says:

Orbis a rotunditate circuli dictus, quia sicut rota est; unde brevis etiam rotella orbiculus appellatur. Vndique enim Oceanus circumfluens eius in circulo ambit fines. Divisus est autem trifarie: e quibus una pars Asia, altera Europa, tertia Africa nuncupatur.

The globe (orbis) derives its name from the roundness of the circle, because it resembles a wheel; hence a small wheel is called a ‘small disk’ (orbiculus).1 Indeed, the Ocean that flows around it on all sides encompasses its furthest reaches in a circle. It is divided into three parts, one of which is called Asia, the second Europe, the third Africa.

Barney, Stephen A., et al. The Etymologies of Isidore of Seville. Cambridge University Press, 2006.

Textually, this is ambiguous at most, so the the other argument from proponents of the flat earth myth is the accompanying illustration:

enter image description here
Page from the Etymologiae. Source: Wikipedia

This argument is however easily dismissed. Pick up any atlas or world map today - modern detail and projection are vastly superior, but it's still flat! This is merely the inevitable result of attempting to represent a 3D globe on a 2D surface. It does not mean either mapmaker or the reader actually think the Earth is flat.

Finally, Isidore of Seville left more than just the Etymologiae. In fact, according to the late Italian professor Umberto Eco:

Isidore of Seville (who was surely not a model of scientific precision) calculates at a certain point that the equator was eighty thousand stadii in length.

Eco, Umberto. Serendipities: Language and Lunacy. Columbia University Press, 1998.

This is not particularly accurate, though not that bad considering Christopher Columbus's later example. However, the mere fact that he tried calculate the equator proves that not even Isidore thought the Earth was flat.

Last but not the least, we know for a fact that it is the consensus of medieval scholars that the Earth is indeed spherical.

If we examine the work of even early-medieval writers, particularly in Europe, we find that with few exceptions they held a spherical-earth theory . . . From the seventh to the fourteenth century, every important medieval thinker concerned about the natural world stated more or less explicitly that the world was a globe, and many of them incorporated Ptolemy's astronomy and Aristotle's physics in ttheir work.

Numbers, Ronald L., and Kostas Kampourakis, eds. Newton's Apple and other Myths about Science. Harvard University Press, 2015.

For example, in the 5th century Augustine of Hippo wrote of the antipodes in his hugely influential The City of God that:

[A]lthough it be supposed or scientifically demonstrated that the world is of a round and spherical form, yet it does not follow that the other side of the earth is bare of water; nor even, though it be bare, does it immediately follow that it is peopled.

Schaff, Philip. NPNF1-02. St. Augustine's City of God and Christian Doctrine. CCEL, 1890.

Notice how St Augustine has no qualms with the Earth being "scientifically demonstrated" to be spherical. All of his arguments in this chapter were merely that the other side of the sphere was not populated.

In any case, St Augustine was more explicit in the lesser known The Literal Meaning of Genesis:

Although water still covered all the earth, there was nothing to prevent the massive watery sphere from having day on one side by the presence of light, and on the other side, night by the absence of light. Thus, in the evening, darkness would pass to that side from which light would be turning to the other.

Genesi Ad Litteram. Paulist Press, 1982.

  • 11
    Well-written and thorough argument. It all seems to point out to the fact that at the time of writing Etymologiae, Isidore either knew Earth was round or he was not sure, but at a later date he most likely was aware of the spherical nature of the planet. His original encyclopedia might have given the wrong impression to few of the early scholars, but this possible misintrepertation was relatively small-scale and didn't last long.
    – A. McMount
    Commented May 17, 2018 at 10:25
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    @A.McMount It's also worth noting that the Etymologiae is an encyclopedic compendium of classical knowledge, so while it was indeed super influential as a standard reference source or a textbook for students, it wasn't an authoritative scientific treatise. So I wouldn't necessarily expect more learned scholars to be misled by it - there were numerous other sources affirming a spherical earth at the time, e.g. Augustine.
    – Semaphore
    Commented May 17, 2018 at 12:40
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    A belief that all of the earth's land is concentrated on one half of the Earth would allow the "days" and "nights" of Genesis to be a global phenomenon, since there would be times when no land would be illuminated by daylight. With modern timekeeping and communication, it's possible to determine that for much of the year, the Sun doesn't fully set on the west coast of Europe before it starts to rise in the easternmost parts of Asia, but I don't think anyone could have proven that before the invention of the chronometer.
    – supercat
    Commented May 17, 2018 at 21:48
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    Regarding Isidore, you can see also T and O map : "The T-O map represents the physical world as first described by the 7th-century scholar Isidore of Seville in his Etymologiae (chapter 14, de terra et partibus).Although Isidore taught in the Etymologiae that the Earth was "round", his meaning was ambiguous and some writers think he referred to a disc-shaped Earth. However, other writings by Isidore make it clear that he considered the Earth to be globular." 1/2 Commented May 18, 2018 at 13:34
  • 3
    The ref is to Wesley Stevens, The Figure of the Earth in Isidore's 'De natura rerum', Isis (1980). Commented May 18, 2018 at 13:37

Thomas Aquinas wrote a number of works in the 13th century, some of which were introductory (at least to medieval students - less so to today's students, who are not familiar with scholastic terminology). Most of these would have been read by many, if not most, scholars during their Trivium studies.

One of these works, well-known to this day, is the Summa Theologica.

In the very first Quaestio, specifically in Iª q. 1 a. 1 ad 2, Thomas discusses the different ways of arriving at truth. As an example (!), he notes that astronomers (astrologus in medieval nomenclature) and natural philosophers demonstrate that the earth is round (rotundus) by mathematical arguments and by recourse to matter itself.

Ad secundum dicendum quod diversa ratio cognoscibilis diversitatem scientiarum inducit. Eandem enim conclusionem demonstrat astrologus et naturalis, puta quod terra est rotunda, sed astrologus per medium mathematicum, idest a materia abstractum; naturalis autem per medium circa materiam consideratum.

Here is a translation:

Sciences are differentiated according to the various means through which knowledge is obtained. For the astronomer and the physicist both may prove the same conclusion: that the earth, for instance, is round: the astronomer by means of mathematics (i.e. abstracting from matter), but the physicist by means of matter itself.

Thus, the roundness of the earth was apparently accepted generally enough that it did not require further demonstration or argument but could be used as a throwaway example to illustrate a more fundamental issue.

Edit: Ctrl-C takes issue with rotundus possibly meaning "round" rather than "spherical". Fair enough. Happily, Thomas Aquinas also wrote the Summa Contra Gentiles, and in lib. 2 cap. 38 n. 9, again as an illustration that requires no further argument, says:

... sicut simul dum sol est in puncto orientis, illuminat nostrum hemisphaerium.

It does not get much more (hemi-)spherical than hemisphaerium.

  • 6
    Nice answer. I love the quote too -- about sciences coming to the same conclusion through various lines of evidence. This is a fairly clear demonstration that it was generally accepted in the 13th century. Can we go much further back with as clear evidence that the round earth was scientific consensus?
    – Eff
    Commented May 17, 2018 at 13:18
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    @Eff: I'd be interested in something farther back, too. Unfortunately, I'm not a historian, just a random dude with a strange fascination with scholastic theology. Commented May 17, 2018 at 13:32
  • 6
    It's nit-picking, but I think the word "round" is unsatisfactory here. "Spherical" would be awesome. "Round" can be related to a disc.
    – Ctrl-C
    Commented May 18, 2018 at 13:37
  • 1
    @Morgen : The real big thing would be running into a Flat Earther not out of touch with reality.
    – Evargalo
    Commented May 23, 2018 at 15:37
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    @Ctrl-C: sorry it took me three years to answer your comment, but my going though Aquinas is slow. I added a similar quote from the Summa Contra Gentiles where Aquinas talks about nostrum hemisphaerium. Commented Dec 8, 2021 at 21:30

Well, it isn't exactly true that medieval scholars understood the world to be round. They were much, much more subtle in their thinking that that. You see, it was quite clear that the world couldn't be precisely round, and much of their thinking went into improving that model.

To see why the medieval view was much more subtle than authors like Lyon even seem to imagine, you have to understand that the roundness of the Earth was intimately tied to the medieval understanding of the workings of gravity. Of course, in this era no one was close to anticipating anything like Newtonian gravitation. Indeed, they would have considered ridiculous the idea that two bodies could act on each other without some physical connection. (Note: Newton's theory was not broadly accepted as a physical model for decades after publication for the same reason. Newton barely even tried to explain how gravity actually worked. Newton's math, of course, was accepted and celebrated, but scientists struggled for years to come up with a mechanism that allowed for what appeared to be "action at a distance".)

Instead of Newtonian gravity, the Aristotelian thought common in the Middle Ages held that objects rose or fell according to their elements in a kind of sorting process, all things tending to the center of the universe (that is, Earth). Objects made of Earth had the strongest affinity for the center, followed by water, then air, then fire. Thus the Universe is more-or-less a set of concentric spheres, with Earth at the center, surrounded by Water, then Air, then Fire. And every substance naturally seeks it's proper level. This model is quite sensible - most of our everyday observations of rocks, water, bubbles and such seem to confirm it, and what few counterexamples exist can be explained away more-or-less convincingly.

(You might notice that Copernicus' solar-centric model contradicts this model, and Copernicus failed to provide even a cursory explanation of how his system could work. Putting a fiery body at the center of the system quite literally turns the universe upside-down. Copernicus' math may have been excellent, but lacking a theory of gravity, his physics were absurd.)

So medieval scholars not only understood the world to be round, they had a fully developed physical theory of gravity which demanded that the world was round. Lyon could not have been more wrong - the roundness of the Earth was central to the entire understanding of how the Universe worked. But scholars knew that there was a problem with this entire worldview - indeed, the problem was right beneath their feet.

The riddle they struggled with was simple: how can there be dry land? The general expectation was that there were similar (if not exactly the same) amounts of earth, air, fire and water in the universe. But if there were similar amounts of earth and water, and the earth was (almost) entirely closer to the center than the water, then the water layer should be very thick and there should be not a bit of dry land poking above this layer. Scholars provided many different theories to explain this, all of which required some deviation from the simplistic statement that the world was round. They considered the possibility that the water-sphere had a different center than the earth-sphere, that the earth-sphere was egg-shaped, and other alternatives. The one explanation that seems to have completely eluded them is that there isn't nearly as much water as earth, and that the water just forms a thin shell on the surface. This theory quietly became universal within a few decades of Columbus' discoveries, almost without debate.

In sum, medieval scholars weren't all ignorant rubes that thought the world was round. They knew the world was much more complicated than that!

  • 3
    Copernicus' math wasn't that good, either, as he had circular orbits and it was already well known that circular orbits could not reproduce the observed motions in the sky.
    – Mark Olson
    Commented May 17, 2018 at 15:32
  • 1
    Well, yes and no. It required some very good math to get as far as he got, and in that era Copernicus was probably more admired for that than for his conclusion.
    – pokep
    Commented May 17, 2018 at 18:04
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    This is the best answer I have seen. Thank you!
    – user
    Commented May 18, 2018 at 0:22
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    Well, taking earth/water/air/fire sorting physics, I would suggest that you would come to the conclusion that earth tends towards the centre of the universe because you already have evidence that the world is a sphere. Lacking that, it would be just as natural (if not more so) to believe that earth tends towards the bottom of the universe, which leads to the conclusion that the world must be flat. I'm not saying you're incorrect about what medieval scholars actually believed, but I think this conception of physics doesn't necessarily demand that the world be round.
    – Ben
    Commented May 21, 2018 at 9:01
  • 3
    @Ben The concept of the "center" of the universe makes much more sense that the "bottom" of the universe. The latter would require some hypothesis as to what the bottom is made up of, and what holds it up, and whether there is anything under it. Commented May 21, 2018 at 18:23

You can see De sphaera mundi by the astronomer Johannes de Sacrobosco (c. 1195 – c. 1256) :

"it was one of the most influential works of pre-Copernican astronomy in Europe. Though principally about the universe, De sphaera contains a clear description of the Earth as a sphere which agrees with widespread opinion in Europe during the higher Middle Ages, in contrast to statements of some 19th- and 20th-century historians that medieval scholars thought the Earth was flat."

See the English translation :

THE EARTH A SPHERE. -- That the earth, too, is round is shown thus. The signs and stars do not rise and set the same for all men everywhere but rise and set sooner for those in the east than for those in the west; and of this there is no other cause than the bulge of the earth. Moreover, celestial phenomena evidence that they rise sooner for Orientals than for westerners. For one and the same eclipse of the moon which appears to us in the first hour of the night appears to Orientals about the third hour of the night, which proves that they had night and sunset before we did, of which setting the bulge of the earth is the cause.

For its success, see here :

Johannes de Sacrobosco's 13th century Tractatus de Sphaera was one of the most popular astronomical books of all times. Before the invention of the press, it was widely used in manuscript form. In the 15th century, shortly after the development of printing, it was one of the first scientific books to be published, in 1472. Afterwards, it underwent successive editions – more than 200, up to the 17th century.


Middle Ages lasted from the 5th to the 15th century.

Some dates :

The turning point was the contact with the Islamic civilization of Al-Andalus that under the Caliphate of Córdoba from 929 to 1031 became one of the leading cultural and economic centres throughout the Mediterranean Basin, Europe, and the Islamic world.

The rediscovery of Ancient Greek science and philosophy started in Wetern Europe with transaltions from Arabic : the Italian Gerard of Cremona (c.1114 – 1187) went to Toledo (no later than 1144), in the Caliphate of Cordoba, to learn Arabic.

Gerard of Cremona's Latin translation of the Arabic version of Ptolemy’s Almagest made c.1175 was the most widely known in Western Europe before the Renaissance.

In total, Gerard of Cremona translated 87 books from the Arabic language, including such originally Greek works as Archimedes' On the Measurement of the Circle, Aristotle's On the Heavens, and Euclid's Elements of Geometry.


Medieval Scholars were much more sophisticated than they are usually given credit for.

Knowledge of the shape of the Earth were never really "lost". Apart from their own observations, there were also classical works that supported this view. During late antiquity, Boethius had access to Ptolemy, even if it later was forgotten and had to be reintroduced to Western Europe. Two other works, however, Pliny's Natural history and Platon's Timaeus were available throughout the period. There are a few examples of scholars that suggested other shapes, but they were exceptions, not the rule.

Some examples

Adam of Bremen (second half of eleventh century) is known as a historian, and an important source of Nordic history, but in his Gesta Hammaburgensis Ecclesiae Pontificum he also wrote on the midnight sun:

[In the north], you can during summer, at the solstice, see the sun above the horizon for fourteen days in a row, and during winter it disappears in the corresponding manner for as many days. This is strange and bewildering for the savage peoples, as they do not know that the shifting length of the days is a consequence of the higher or lower orbit of the Sun. From the spherical shape of the Earth, it follows necessarily, that when the Sun closes in, brings daylight, but as it removes itself leaves night. When it rises during the solstice, it prolongs the days and shortens the nights for those who lives in the north, but when it sets during the winter solstice, it does the same for those in the south.

It appears that he got this from Bede's The reckoning of time, but it does show that the knowledge was well spread.

Vincent of Beauvais (c. 1184/1194 – c. 1264) correctly described what would happen if an object was dropped in a hole through the entire world.

Nicole Oresme (c. 1320–1325 – 1382) correctly argued that there were no way of knowing if it was the Earth that rotated, or the celestial sphere; if the air and water moved with the Earth, there would be no physical sensation. He did in the end say that he believed in a stationary Earth, but that seems more a matter of tradition.


I translated the passage from Adam from the Swedish of Emanuel Svenberg's translation.

Vincent of Beauvais I found mentioned in C.S. Lewis The Discarded Image.

Nicole Oresme is quoted at length in Károly Simonyi's A cultural history of physics. It also contains a useful introduction to what classical works were available to medieval scholars.

  • "... Nicole Oresme ... correctly argued that there were no way of knowing if it was the Earth that rotated ..." - not really correctly - you can measure centrifugal and coriolis forces.
    – Edheldil
    Commented May 18, 2018 at 15:23
  • True. It would have been more better of me to say that he correctly dismissed priorly presented arguments against Earth moving, so that at that time, there were no way of distinguishing whether Earth was rotating, or the celestial spheres.
    – andejons
    Commented May 18, 2018 at 15:39

I have a tiny bit of evidence of another type to add about medieval belief in a spherical Earth.

A globus cruciger is a globe or orb topped by a cross, and part of the regalia of Christian monarchs.

In ancient times gods and monarchs were depicted with orbs that symbolized the spherical Earth and/or the spherical heavens believed to surround the Earth.

After Constantine I converted to Christianity the Christian emperors began to be depicted holding globes with crosses on top to symbolize that Christianity would someday rule the world.



I once read that for an imperial coronation in the 11th century, possibly that of Conrad II or Henry III, a hollow imperial orb was filled with dirt from the different realms ruled by the emperor, thus showing that in that specific case the orb was definitely believed to represent the spherical Earth and not the spherical heavens.

I believe that I read that in a book by Edward Francis Twining, Baron Twining, either A History of the Crown Jewels of Europe (1960) or European Regalia (1967).


In God's Philosophers: How the Medieval World Laid the Foundations of Modern Science, James Hannam states that:

The myth that a flat earth was part of Christian doctrine in the Middle Ages appears to have originated with Sir Francis Bacon (1561–1626), who wrongly claimed that geographers had been put on trial for impiety after asserting the contrary. There were a few authentic flat-earthers in late antiquity, but none among the scholars of the Middle Ages proper.

Even scholars from the very early medieval period believed the earth to be a sphere. Much has been said on western scholars in other answers (although John Philoponus, died circa. 570 AD, is also worth a mention), but it is also worth looking at India and Aryabhata (476 to 550 AD). This mathematician and astronomer's work influenced Persian and Arabian scholars and he calculated the circumference of the earth with only a very small error:

Modern estimates suggest that Aryabhata’s computation was 39,968km (24,835 miles), just off the currently accepted value of 40,074km by an incredible 0.27%.

This diagram explains how he probably did it. In his commentary GolapAda, Boogola or Gola, Aryabhata

applied plane trigonometry to spherical geometry by projecting points and lines on the surface of a sphere onto appropriate planes. Topics include prediction of solar and lunar eclipses and an explicit statement that the apparent westward motion of the stars is due to the spherical Earth’s rotation about its axis. Aryabhata also correctly ascribed the luminosity of the Moon and planets to reflected sunlight.

According to the article Spherical Shape of Earth as described by Aryabhata I, he wrote that

The globe of the Earth stands...in space at the centre of the circular frame of the asterisms...surrounded by the orbits (of the planets); it is made up of water, earth, fire and air and is spherical...

  • A nitpick and a suggestion: a circle is flat and round; how about "spherical"? A much stronger evidence than a scholar's opinion might be found in spherical objects representing the earth from that time, like the Globus Cruciger. Commented May 17, 2018 at 9:44
  • Lars Bosteen This is all true, but your answer deals with how this myth was constructed at a later era, instead of the actual beliefs of the scholars of medieval period. After early middle ages it seems to have been well-established that the Earth was spherical, but there seems to be some mystery over 6th to 8th century beliefs.
    – A. McMount
    Commented May 17, 2018 at 9:56

Gerbert d'Aurilla (c.946 – 1003) reintroduced the concept of a spherical earth to Western Europe. He taught and promoted the use of armillary spheres. Granted his version had the earth as the center of the "universe" as opposed to the sun. (And of course the sun is the center of the solar system and not the center of the universe.)

Gerbert later became pope (Sylvester II) and further promoted the armillary sphere.

We can say that as of the turn of the millennium (1000 AD) it was understood, in educated circles, that the earth was a sphere.

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    If he "reintroduced" a spherical Earth, then idea would need to have been lost. Given the Earth was round in Bede's De temporum ratione (The Reckoning of Time) in 725, widely used to calculate Easter in Britain and France and Germany, I have my doubts
    – Henry
    Commented May 17, 2018 at 17:47
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    That's a very good point. I too question the concept of "reintroduced". I suppose that it's a position I've not examined carefully enough. I agree with Marc Bloch's three-pronged invasion thesis which states that Western Europe's economic and academic progress collapsed under the weight of the invasions, Thus ... reintroduced may not be the best term. Perhaps repopularised would be better. But, as you said, this information would have had to have been lost. Was it? Perhaps as Gerbert was greatly praised for the armillary sphere and the abacus. And we know there were abacus' in Roman times.
    – Mayo
    Commented May 17, 2018 at 18:07

In classical philosophy I read that around 350 BC, Aristotle declared that the Earth was a sphere and about a century later Aristarchus and Eratosthenes measured the size of the Earth. Although much of the ancient Greek's writings were destroyed by the Church during the dark ages Aristotle's work was preserved.

  • 10
    That should really be "much of the Ancient Greeks' writing was preserved by the Church during the Dark Ages". Commented May 18, 2018 at 12:52
  • 1
    In a less well-known treatise "the sand reckoner" Archimedes pictures a universe where the sun is in the centre, the distance between the earth and the sun is huge., the diameter of the sun is larger than the earth and the ratio between sun diameter and earth orbit, is equal to earth orbit and the stars. This is remarkably qualitatively correct, but it was merely to fill the cosmos with grains of sand in order to prove that mathematics is able to express that number. Because the cosmos was a side trail, it gives an insight about how archimedes pictured the cosmos. Commented May 18, 2018 at 15:52
  • Not only is this answer implied in the opening question, it also doesn't necessarily mean that Medieval scholars knew of Eratosthenes or believed him.
    – cmw
    Commented Feb 23 at 2:33

People knew the Earth was round since the Greeks, around 200 BC. In 240 BC, Eratosthenes, thou even as far back as 500 BC. Eratosthenes measured the angle of a shadow cast by a stick he had planted in the ground, at exact noon on the summer solstice in Alexandria, Egypt. Unlike other region called Syene, he measure that cast NO shadow; he made an angle of about 7.2 degrees, or about 1/50 of a complete circle. Using the distance of Syene and Alexandria, he could get 50x and calculate the circumference of the Earth.

  • 1
    Sources would improve this
    – MCW
    Commented Dec 9, 2021 at 10:32
  • Not only is this answer implied in the opening question, it also doesn't necessarily mean that Medieval scholars knew of Eratosthenes or believed him.
    – cmw
    Commented Feb 23 at 2:33

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