Thursday, 21 July 2016

Ancient flat-earthers

‘In the fourteenth century, most people believed the world was flat.
‘It makes you think.’
-- Victoria University of Wellington TV ad campaign, ca. 2005
...or rather: a decade ago, many people believed that people in the fourteenth century believed that the world was flat.

In 2016 it’s fairly widely known that there was no such belief in the flat earth. Not at that time, anyway. The myth even has its own Wikipedia page, ‘Myth of the flat earth’. The whole idea of mediaeval flat-earthism was more or less invented out of thin air in the 19th century. I still occasionally encounter someone who assumes it’s true, but I get the impression it’s less universal than it once was.

The cylindrical earth envisioned by Anaximander, early 6th cent. BCE
(Illustration by Léon Benett: C. Flammarion, Histoire du ciel, Paris, 1872, p. 289)

The myth’s underlying assumption is that, once upon a time, Eratosthenes estimated the circumference of the earth, but at some point, the knowledge that the earth is (very nearly) spherical somehow vanished. 19th century proponents of the myth often blame this on Catholics. And -- still according to the myth -- knowledge of the earth’s spherical shape was reinvented by Columbus in 1492.

To be clear, Europeans throughout the whole mediaeval period were well aware that we all live on a ball, not a pancake; and Columbus wasn’t out to prove the earth was round, he was trying to reach the East Indies, believing it was a journey of no more than 5000 km. (In fact it’s over 22,000 km, or would be if the Americas weren’t in the way; Columbus’ estimate of the east-west width of Eurasia was around 40% too high, and he accepted Ptolemy’s lower figure for the earth’s circumference, which was 28% too low). The idea that Columbus was fighting against entrenched flat-earthism was fabricated by Washington Irving in his History of the Life and Voyages of Christopher Columbus (1828; especially book 2, chapter 4). Irving believed that opposition to Columbus was based on ‘monkish bigotry and false learning’ (p. 10-11). Throughout the 19th century, anti-Catholic sentiment continued to fuel the Columbus myth: another key moment was Draper’s History of the conflict between religion and science (1875). Jeffrey Burton Russell’s book Inventing the flat earth: Columbus and modern historians (1991) tells a detailed story of how the Columbus myth came about.

To be fair, Washington Irving doesn’t deserve 100% of the blame for the myth -- maybe only 90%. Long before he came along, Copernicus and Kepler had both cherry-picked ancient flat-earthist testimony as a strawman for their own arguments.

For make no mistake: genuine flat-earthers did exist. Flat-earthism has probably never been anything other than a fringe belief, in any place and time where an awareness of the earth’s curvature has been known at all (with one possible exception, as we shall see below). But there has to have been a first time that the earth’s curvature was discovered; and even after discovery, dissenting voices have existed.

A scene from a debunking of flat-earthism. Modern flat-earthers have made screeds of ‘proofs’ of the earth’s flatness, but it is relatively uncommon to see a simulation like this of a ‘realistic’ flat earth, which pretty much instantly dispels the myth.
(source: YouTube)

Before Aristotle

In the Greek world, the turning-point between flat-earthism and round-earthism seems to be ca. 400 BCE. Prior to 400 BCE we have no evidence of anyone knowing or believing that the earth is round; after 400 BCE we see scarcely any more flat-earthers, and round-earthers pop up very quickly.

Early Greek myth didn’t have a single, coherent cosmology. The earliest texts that give us any idea at all of a cosmology are the mythical poems of Homer and Hesiod, in the first part of the 7th century BCE. Hesiod is vague and inconsistent, however: he doesn’t give a consistent portrayal of a well-defined universe. There’s more consistency in Homer, and Homer is much better known, which tends to give the impression that his version was standard; but that isn’t necessarily the case. In Homer, the cosmos comes broadly speaking in four layers, with ground-level at the middle.

A very approximate sketch of Homeric cosmology

Modern discussions sometimes portray the earth in Homeric cosmology as a disc. All we’re actually told is that it’s flat: that doesn’t automatically imply circular. The descriptions of Achilles’ and Heracles’ shields in the Iliad (ca. 670-650 BCE) and the Shield (ca. 600 BCE?) have them portraying a symbolic world surrounded by the mythical river Ocean running in a circle around the earth, but the shields were circular, so that’s not exactly surprising.

We get indications of a flat disc, or at least a circular object, in the 6th and 5th centuries BCE, with Anaximander (early 500s) and Herodotus (ca. 420s). Herodotus tells us that early map-makers were in the habit of making the Ocean circular (4.36.2): he condemns the practice, believing the shape of the Eurasian-African landmass to be more irregular. Anaximander is credited as the very first map-maker, and he envisaged the earth as a cylinder (see the illustration at the start of this post):
ὑπάρχειν δέ φησι τῶι μὲν σχήματι τὴν γῆν κυλινδροειδῆ, ἔχειν δὲ τοσοῦτον βάθος ὅσον ἂν εἴη τρίτον πρὸς τὸ πλάτος.
And he says that the earth is cylindrical in shape, and has a depth that is however much a third of its width is.
τὴν δὲ γῆν εἶναι μετέωρον ὑπὸ μηδενὸς κρατουμένην, μένουσαν δὲ διὰ τὴν ὁμοίαν πάντων ἀπόστασιν. τὸ δὲ σχῆμα αὐτῆς γυρόν, στρογγύλον, κίονι λίθωι παραπλήσιον: τῶν δὲ ἐπιπέδων ὧι μὲν ἐπιβεβήκαμεν, ὃ δὲ ἀντίθετον ὑπάρχει.
(And he says) that the earth is suspended in the sky, not held up by anything, staying in place because of its equal separation from all things. And that its shape is curved, round, similar to a stone column; and we walk on one of its faces, but it has an opposite (face).
(Anaximander frs. 12.A.10, A.11 ed. Diels-Kranz; similarly A.21, A.25, B.5)
(I have encountered some people who have been misled about Anaximander by Isaac Asimov: in an educational children’s book (1972), he misinterpreted the first of these fragments as suggesting that we live on the curved side of the cylinder. Actually the ‘stone column’ refers to column segments like these. The second fragment above, and Herodotus’ criticism of map-makers, both make it clear that Anaximander envisaged the cylinder as lying flat.)

It would be nice if we had more information about what early natural philosophers thought. Some testimony does exist, though. Two isolated, and very late, references attribute round-earthism to Pythagoras and Thales: Pythagoras, Diog. L. 8.48; Thales, Aëtius Plac. 3.10. But there’s essentially no doubt that these are both untrue. The Pythagoras passage also ascribes round-earthism to Hesiod and Anaximander, and we know both of these are false; and the source, Diogenes Laertius, isn’t very reliable as a rule. And in Thales’ case, a much earlier source tells us that he taught the earth floats in water like a piece of wood (Aristotle On the sky 294a28-b1 = fr. 11.A.14 ed. Diels-Kranz; see further Couprie 2011: 63-7).

Besides, in 6th-5th-century BCE thinkers we see an overwhelming consensus that the earth was flat. If Pythagoras or Thales were round-earthers, it would have been a very exceptional thing, so we’d expect a well-informed writer like Aristotle to highlight it. Here’s a selection of what pre-Socratic thinkers did believe about the shape of the world (fragment numbers follow the standard edition of Diels and Kranz 1952):
  • Anaximenes (500s BCE): the earth is πλατεῖαν μάλα ‘very flat’ (fr. 13.A.6; also A.7§4, which adds that sun, moon, and other astronomical bodies are all flat; also A.20), and suspended in space by air pressure underneath (A.20).
  • Anaxagoras (ca. 460-430): the earth is πλατείας ‘flat’ (frs. 59.A.1§8, A.42§3, A.47, A.87); as in Anaximenes, it is suspended by air pressure (13.A.20).
  • Archelaus (ca. 450): the earth is not perfectly flat but κύκλῳ μὲν οὖσαν ὑψηλήν, μέσον δὲ κοίλην ‘high in a ring, and concave in the middle’; he uses this to explain different times of sunrise and sunset in different parts of the world (fr. 60.A.4§4).
  • Empedocles (mid-400s): the earth is κυκλοτερής ‘circular’ (i.e. disc-shaped; fr. 31.A.56; also A.50, which discusses the earth’s horizontal expanse).
  • Leucippus (400s): the earth is τυμπανῶδες or τυμπανοειδῆ ‘drum-shaped’ (frs. 67.A.1§30, A.26), but tilts downwards to the south, resulting in colder climates in the north (A.1§33).
  • Diogenes of Apollonia (ca. 440-430): the earth is στρογγύλην, ἠρεισμένην ἐν τῷ μέσῳ ‘circular, supported in the middle’ (fr. 64.A.1; στρογγύλος can also mean ‘spherical’, but in context it must refer to a flat circle).
  • Democritus (second half of 400s): as in Archelaus, the earth is δισκοειδῆ μὲν τῷ πλάτει, κοίλην δὲ τῷ μέσῳ ’disc-shaped in its surface, but concave in the middle’ (fr. 68.A.94); it is not a perfect disc, however, but προμήκης ... ἡμιόλιον το μῆκος τοῦ πλάτους ἔχουσα ‘elongated, oblong along the length of its surface’ (B.15§2); as in Leucippus, the earth tilts downwards to the south (A.1§33); as in Anaximenes and Anaxagoras, it is suspended in space by air pressure underneath (13.A.20).
Early Greek cosmology could get pretty wild. It’s just as well we don’t have to go into the cosmology that we see in Parmenides and in Plato’s Timaeus just now, or we’d really go bananas. However, in the midst of all this speculation some useful ideas did pop up. Notably Anaximander and Archelaus: though they were flat-earthers, they did lay an important piece of conceptual groundwork for the principle of round-earth gravity, in which all things fall towards the centre of the earth. As we saw above, Anaximander’s earth was stable in the centre of the cosmos because of its ‘equal separation from all things’; Archelaus’ earth was at the centre because all things gravitate towards the centre (fr. 60.A.4§2). In both cases the earth requires no physical supports. Both of these are counter-arguments to the Pythagorean picture of the cosmos, which has the earth attached to one of the celestial spheres moving around the central fire. If Anaximander’s and Archelaus’ ideas of the suspended earth hadn’t existed, it might have been a lot harder for round-earthism to take off.

For take off it did. We don’t know who came up with the idea first. Dirk Couprie (2011: 169) suspects Oenopides (mid-400s BCE), who is credited as the discoverer of the ecliptic. The ecliptic is the plane of the earth’s orbit, at an angle to the equator, so one might wonder if Oenopides also realised that it implied a spherical earth. We can’t be sure.

Whoever it was, the earth’s sphericity was well known enough by the early 300s BCE that Plato could take knowledge of it for granted (Phaedo 108e-109a). By the mid-to-late 300s we find Aristotle (On the sky 296b-297b) explicitly discussing empirical evidence for the spherical shape of the earth; how gravity impels all objects towards the centre of the earth; and an (inaccurate) estimate for its circumference. Perhaps most famously, in the mid-200s Eratosthenes comes up with the first roughly accurate and empirical determination of the earth’s circumference.

Aristotle’s evidence for the earth’s sphericity
(source:, adapted)

From Aristotle onwards the earth’s shape was common knowledge.

Aristotle to the 4th century CE

Flat-earthers didn’t vanish altogether -- Epicurus, who lived into the 200s BCE, was a flat-earther, and plenty of later Epicureans subscribed to his teachings -- but they were a minority. Roman thinkers like Cicero and Pliny spend time discussing the spherical earth and Aristotelean gravity; the round earth is fundamental to the work of astronomers like Hipparchus; and its shape was considered very carefully in Eratosthenes’ Geography, Strabo’s Geography (2.5.1-11), and Ptolemy’s Geographica.

All three of these writers discuss the problem of how to project a spherical surface onto a flat map. Strabo, the least technical of the three, is relatively dismissive: as far as he’s concerned, make the map big enough and the inaccuracies won’t matter (2.5.10). But for Eratosthenes and Ptolemy it was a serious problem. (Even today people still argue over which flat projection is best.) Ptolemy devotes most of the first book of the Geographica to an extended theoretical discussion of the ‘right’ projection; the rest of his atlas is a catalogue of place-names and topographical details, using a very modern-looking system of latitude and longitude. For Eratosthenes and Strabo things were somewhat simpler, in that they only needed to worry about a smaller portion of the earth as known to them. Eratosthenes regarded the known world, or oikoumenē, as a quadrilateral on the curved surface of the earth (Eratosthenes Geography fr 30 ed. Roller = Strabo 2.5.5-6; similarly Erat. frs. 31, 32, 33, 34). According to Strabo, the resulting non-Euclidean shape was called a sphondylos (‘whorl’), and the land within this region was the shape of a chlamys (‘cloak’) draped over the sphere.

Eratosthenes’ sphondylos ‘whorl’: the quadrilateral of the known world (oikoumenē). The edges of the quadrilateral are lines of latitude and longitude.

Incidentally, Ptolemy is the person responsible for the modern convention of putting north at the top of a map. This practice isn’t self-evident, and it wasn’t a universal standard in Ptolemy’s time: Cleomedes (somewhere between 2nd and 4th century CE) arranges west at the top, and north to the right. Ptolemy, in the prologue to Geographica book 2, observes that he has the most detailed geographical data for the north-west of the Eurasian landmass, so he decides to put that material in the first place that people will look -- at the top left of his map. In the Renaissance, 15th century western cartographers revived Ptolemy’s convention, so that it has become the modern standard. (If Greek had been written right-to-left in Ptolemy’s time, our maps today would have west at the top ...)

Crates of Mallos, a Greek scholar living in Rome in the 2nd century BCE, is sometimes credited as creating the first ever globe map. He certainly discussed the nature of the globe, as reported by Strabo 2.5.10: but Strabo doesn’t refer to a physical globe, only to a Kratēteion, ‘Crates’ (interpretation)’. Anything else would be very surprising anyway: Crates wasn’t a natural philosopher, but a very bookish literary critic. Strabo was probably thinking of Crates writing about the geography in the Homeric Odyssey, and Crates’ bizarre argument that Homer must have known the earth was spherical (Crates frs. 37 and 54 ed. Broggiato).

Even poets took the round earth for granted. Here’s a passage from the opening of Ovid’s epic the Metamorphoses, describing the primordial state of the universe (Met. 1.5-13) --
Before the sea and earth, and the sky which touches all things,
the form of nature was one throughout the entire universe:
they called it Chaos. ...
... and [as yet] the earth did not hang in the air flowing around it,
poised by its own weights ...
‘Poised by its own weights’ refers to the Aristotelean teaching on gravity: all bodies are attracted to the centre of the earth, so the earth’s weight is balanced around the centre.

Late antiquity and the mediaeval period

In the history of the Latin west we know of vanishingly few flat-earthers prior to the emergence of modern flat-earthism in the Victorian period. The only one who is at all well known is Lactantius, a rhetorician and Christian apologist of the late 200s/early 300s CE. His mockery of round-earthism (Divine institutes 3.24) is routinely cited as exemplary of the backwardness of Christian thought. It was Copernicus who began the tradition of targetting him -- though unlike later writers, Copernicus doesn’t pick on Lactantius’ religion (De revolutionibus ivb).

But Lactantius is almost unique. Nearly all other figures in the Latin world who had anything to say on the subject -- Augustine, Macrobius, Boethius, Isidore, Bede, Thomas Aquinas, Dante (all Christians, you’ll notice) -- were round-earthers. Augustine, City of God 16.9, is sometimes cited as belonging to the flat-earth camp, but the only doubt he expresses is over the assumption that there must necessarily be a landmass at the antipodes, or that if there is one that it is necessarily inhabited. (By luck he was quite right: the point on the earth’s surface opposite his hometown, Hippo in modern Algeria, is underwater in the southern Pacific, over 1100 km east of Auckland, New Zealand -- and indeed there were no humans in New Zealand in Augustine’s lifetime.)

Bede is an especially striking exemplar of western learning on the subject: his treatise On the measuring of time is precisely about the astronomical basis for the calendar, and he talks at length about the spatial relationships between the sun, moon, stars, and the spherical earth: for example (De ratione temporum §32),
causa autem inaequalitatis eorundem dierum terrae rotunditas est: neque enim frustra et in scripturae divinae, et in communium literarum paginis orbis terrae vocatur. est enim re vera orbis idem in medio totius mundi positus, non in latitudinis solum gyro, quasi instar scuti rotundus, sed instar potius pilae undique versum aequali rotunditate persimilis: ...
The cause of the inequality of days is the roundness of the earth. It is not for nothing that it is called ‘the orb of the earth’ in the pages of both divine scripture and general literature. For in fact the orb is positioned in the centre of the entire cosmos, not just in a wide circle in the likeness of a shield, but rather in the likeness of a ball which is identical in equal roundness on every side ...
Notice that this passage doesn’t just show an awareness of the earth’s shape, but also of the angle of the ecliptic and its importance to the seasons. See also Bede’s De natura rerum, at sections §46 (‘We refer to the orb of the earth not because its shape is that of a perfect orb, given the great difference between mountains and plains, but because ... [its overall shape] makes a figure of a perfect orb’) and §5-§10.

The Greek-speaking world is much less tidy. There, we do find a cluster of genuine flat-earthers, and a pronounced absence of round-earthers -- to the point where it looks very much as if some parts of the early Byzantine world were, after all, predominantly flat-earthers.

In the decades before and after emperor Theodosius I, who waged a campaign of radical dehellenisation in the 380s and 390s CE, we find many figures espousing flat-earthism on the basis of biblical passages -- Ephrem of Syria, John Chrysostom, Diodorus of Tarsus, Severian of Gabala, and Theodore of Mopsuestia, and perhaps several others who are less clear-cut. Most of these figures came from Syria and learned from each other: John Chrysostom studied under Diodorus, Severian knew Ephrem’s work and had a troubled relationship with both Chrysostom and Diodorus. Johannes Zellinger has written of them as representing a ‘Syrian-Antiochene school’ of biblical literalism (Zellinger 1916: 75). Was flat-earthism confined to Syria, though? John Chrysostom, Diodorus, and Severian taught and preached in Constantinople too.

Full references:
Later Byzantines were less concerned with literalism. John Philoponus (6th cent.) admits, in his On the creation of the world, that it’s impossible to write about the Genesis creation story in physical or astronomical terms without contradiction (De opificio mundi 1.2). And Photius, the 9th century scholar and patriarch who is our source for Diodorus of Tarsus, is doubtful about Diodorus’ theories (Myr. 210b.4: ‘there is no compelling proof of this’).

But flat-earthism lived on beyond the 4th and 5th centuries. The most notorious piece of Byzantine flat-earthism comes from Philoponus’ time. In the 6th century we find a work called Christian topography by Cosmas, an Alexandrian monk (nicknamed Indikopleustes, ‘sailor to India’, because he embarked on a voyage there once, though he didn’t reach his destination). Cosmas again adopts a radically literalist reading of some biblical passages, but goes into far more detail than any of the Syrians. Topography book 2 (text; translation) gives a description of the shape and size of the world that is totally uncontaminated by anything non-biblical. Led by Genesis 1, Cosmas takes Hebrews 9:1-14 to be saying that the universe has the same form as the tabernacle described in Exodus 25-26, and that the earth has the same form as the ark of the covenant -- that is to say: flat, with four walls, and a lid on top. (Yes, really. Here are a couple more discussions of Cosmas that go into more detail: 1, 2.)

Cosmas’ conception of the earthly world (source: Zellinger 1916: 81)

So even though none of the details invented by Washington Irving are real, the flat earth myth isn’t all imaginary. There were flat-earthers in antiquity and in the early mediaeval period. And some flat-earthers did take their beliefs from literalist interpretations of biblical passages. But, once round-earthism initially took off, they were never a majority -- with the possible exception of 4th-5th century Syria (and Constantinople?).

‘But yeah but yeah but that was only educated people. Uneducated people still believed the earth was flat, right?’

That kind of anti-scepticism -- the insistence that people in times past must have been stupid -- is worthy of the History Channel. Ultimately what we have to go on is what the evidence tells us. And the evidence suggests that flat-earthism was a tightly confined phenomenon, at least until the Victorian era. We have essentially no evidence of flat-earthism in the Latin west; and the evidence that we do have from the Greek east comes to us from only one period of religious extremism.


  • Asimov, I. 1972. How did we find out the earth is round? New York: Walker & Co.
  • Broggiato, M. 2001. Cratete di Mallo. I frammenti. La Spezia: Agorà Edizioni.
  • Couprie, D. 2011. Heaven and earth in ancient Greek cosmology: from Thales to Heraclides Ponticus. New York: Springer.
  • Diels, H.; Kranz, W. 1952. Die Fragmente der Vorsokratiker, 3 vols., 6th ed. Berlin: Weidmann.
  • Roller, D. W. 2010. Eratosthenes’ Geography. Princeton: Princeton University Press.
  • Zellinger, J. 1916. Die Genesishomilien des Bischofs Severian von Gabala. Münster: Aschendorffsche Buchhandlung.


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