Repeat after me! – They knew it was round, damn it!

Last week saw various reports about a rare stolen copy of a Columbus letter that had turned up in the Library of Congress and has now been restored to its Italian owners; a comparatively happy end to one of a series of recent stories about the theft of precious books and documents from archives and libraries. Unfortunately the report on the website of NPR (that’s National Public Radio a non-commercial public American educational radio network) opened with the following paragraph:

The heist of a major historical document apparently went undiscovered for more than 20 years. Now, a stolen letter from Christopher Columbus spreading the news that the world isn’t flat has been returned from the U.S. to Italy.

As some readers might already have guessed the second sentence, specifically the phrase spreading the news that the world isn’t flat, had me screaming and banging my head against the wall to relieve the pain. This is just horrendously wrong in several different ways.

Posthumous portrait of Christopher Columbus by Sebastiano del Piombo, 1519. There are no known authentic portraits of Columbus. Source: Wikimedia Commons

Posthumous portrait of Christopher Columbus by Sebastiano del Piombo, 1519. There are no known authentic portraits of Columbus.
Source: Wikimedia Commons

On his first voyage Columbus set sail from Spain in September 1492 and after approximately a month of sailing westward he landed on a set of previous unknown islands, unknown to the Europeans that is. This voyage proves or disproves absolutely nothing about the shape of the earth. To even contemplate a voyage proving the earth to be spherical and not flat we would have to fast forward thirty years to the return to Spain of the one ship and eighteen men from Ferdinand Magellan’s disastrous circumnavigation in 1522; just for the record Magellan was not one of the eighteen survivors, so to call him the first man to circumnavigate the world, as many people do, is simply false. Some flat-earthers could, and probably do/did, argue that Magellan’s fleet just sailed round in a circle on a flat disc and not around a spherical earth so even that is not a totally convincing proof (even if the objection is somewhat iffy).

Let us return to the good Cristoforo. One could argue that he set sail westward to reach the Spice Islands, instead of heading to the east, as was normal because he believed the earth to be a sphere and also believed that that sphere was small enough that the route west to the Spice Islands was shorter and thus quicker than the route east (A belief, as it turns out, that was based on faulty calculation, of which more later). Having reached what he erroneously believed to be the Spice Islands, leading to the equally erroneous name, the West Indies, he believed that he had proved the world to be spherical. There is however a fundamental flaw in this argument. Columbus did not sail westward because he believed the earth to be a sphere; he did so because he, like almost every other educated European, knew that it was a sphere, knowledge that had been part of the European cultural heritage for the best part of two thousand years.

This should in the meantime be well known, but for those, like the NPR reporter(s), who have been sitting at the back and not paying attention let us pass review over those two thousand years.

We have no direct records but latter authors tell us that the Pythagoreans in the sixth century BCE already accepted that the earth was spherical. Their reasons for doing so are unknown but it was possible in analogy to the celestial sphere of the so-called fixed stars. If you look up into the heavens on a clear dark night the sky appears to take the form of an inverted bowl or hemisphere. By the latest in the fourth century BCE, Aristotle, who would go on to have a massive influence on European intellectual history, knew that the earth was spherical and he offers up a series of empirical proofs for this claim. For example he wrote, “there are stars seen in Egypt and […] Cyprus which are not seen in the northerly regions.” Since this could only happen on a curved surface, he too believed Earth was a sphere “of no great size, for otherwise the effect of so slight a change of place would not be quickly apparent.” (De caelo, 298a2–10). He also pointed out that the shadow of the earth on the moon during a lunar eclipse is circular. Following Aristotle all Greek schools of philosophy accepted that the earth was spherical and following them the Romans. There was no doubt in the classical world that the earth was a sphere. Ptolemaeus, the most influential Greek astronomer, brought a series of arguments and proofs for the spherical form of the earth in his Syntaxis Mathematiké (Almagest) in the second century CE. Most notably that as ships approach over the horizon one sees the top of the mast before one sees the hull.

A lot of this specific knowledge got temporarily lost within Europe in the Early Middle Ages but still almost nobody who was educated doubted that the earth was a sphere. With the rise of the Islamic empire the astronomers writing in Arabic adopted the views of Aristotle and Ptolemaeus including the spherical form of the earth.

Back in the third century BCE the astronomer mathematician Eratosthenes from Alexandria determined the size of the sphere using the angle of the sun’s shadow and a bit of basic trigonometry. He achieved a fairly accurate result, its accuracy depends on which Stadia (an ancient measure of length) you think he used; we don’t know for certain. Other geographers and astronomers also determined the size of the earth’s sphere; all arriving at reasonable ball park figures. Ptolemaeus, in his Geōgraphikḕ (Geography) also determined that the known land area the oikoumenè, Europe, Africa and Asia, stretched over 180° of the earth’s surface from east to west.

In the High Middle Ages, Europe regained this knowledge, largely via the Islamic Empire through Spain and Sicily. The standard European university astronomy text Johannes de Sacrobosco’s De sphaera mundi, written in the twelfth century CE, contained all the standard Greek arguments for a spherical earth including the lunar eclipse shadow, ship breasting the horizon and the change in visible asterism travelling from south to north. There existed no doubt amongst the educated in the Middle Ages that the earth was a sphere.

Picture from a 1550 edition of De sphaera, showing the earth to be a sphere. Source: Wikimedia Commons

Picture from a 1550 edition of De sphaera, showing the earth to be a sphere.
Source: Wikimedia Commons

When Columbus started making his plans at the end of the fifteenth century he knew that the world was a sphere, as did all of the people he tried to get to back his scheme. The only disputed point was how big the earth’s sphere was, how long the central landmass, Europe, Africa and Asia, was and thus how far the Spice Islands were if one sailed west from Europe. It was here that Columbus made some fundamental calculating errors. The Arabic astronomer al-Farghānī gave 5623 Arabic miles (being 111.8 km) as the length of one degree of longitude, whereas Ptolemaeus gave 6023 Roman miles (being 89.7 km). Columbus took al-Farghānī’s figure but multiplied it with the length of a Italian mile (much shorter than the Arabic one) to determine the circumference of the earth thus arriving at a figure that was far too small: approx. 25,255 km instead of al-Farghānī’s very accurate figure of 40,248 km. Ptolemaeus’ estimate of the spread of the main landmass was 180°, whereas it is in fact only about 130°. Columbus however took the even more inaccurate estimate of Marius from Tyre of 225°. The sum of these error meant that Columbus thought he only had about 3,700 km from the Canary Islands to Japan instead of the real 19,600 km! Having convinced his sponsors of the correctness of his calculations he set sail. If America had not been in the way Columbus and his entire crew would have stared starved to death on the open ocean.

So where does the myth of the flat earth come from? There were a few European scholars in antiquity and the early Middle Ages who, against the evidence, still argued that the earth was flat. However none of them enjoyed much support. One of the ironies of history is that Copernicus probably drew attention to the most famous of them, the third century cleric Lucius Caecilius Firmianus Lactantius, by mentioning him in his De revolutionibus. The real myth of the medieval flat earth begins first in the eighteenth and nineteenth centuries and has two principal sources. Probably the most influential of these was the American author Washington Irving who in his fictional biography of Columbus claimed that Columbus had to fight against the Church’s belief that the world was flat in order to get permission and backing for his voyage, a complete fabrication. This falsehood was supported by the nineteenth centuries false interpretation of the medieval T and O Mappa Mundi.

The Hereford Mappa Mundi, about 1300, Hereford Cathedral, England. Source: Wikimedia Commons

The Hereford Mappa Mundi, about 1300, Hereford Cathedral, England.
Source: Wikimedia Commons

These medieval world maps were in the form of a circle, the O, with the three known continents, Europe, Africa and Asia, displayed in the form of a T with east at the top. These maps were interpreted in the nineteenth century as indicating that the medieval cartographers believed the earth to be a flat disc. This is not without irony as they were circular in order to indicate that the world in a sphere. The myth of the flat medieval world was taken up by two figures well known to readers of this blog John William Draper (1811–1882) and Andrew Dickson White (1832–1918) in their widespread myth of the eternal war between religion and science. Science believing in a spherical earth whereas the reactionary Church believed in a flat one.

That Europe in the Middle Ages believed in a flat earth is a total myth that just doesn’t seem to want to die. The next time somebody tells you that the medieval Church thought the world was flat, or that Columbus was a revolutionary for believing in a spherical earth or any other version of this nonsense, do me a favour, take a large, heavy, flat, round, metal object, such as a frying pan, and beat them around the head with it.




Filed under History of Astronomy, History of Cartography, Myths of Science

27 responses to “Repeat after me! – They knew it was round, damn it!

  1. It wasn’t news to any educated person in 1492 that the world was, more or less, a sphere; but David Wooton points out in his recent Invention of Science that the more or less part mattered. According to him, Columbus thought that he was sailing uphill as he left the Azores because he thought that though the inhabited world was half of a sphere, the other half bulged out. He took the notion of the high sea literally. More generally, there was a philosophical and religious problem with a perfectly spherical world because in the dominant Aristotelian cosmology with its doctrine of natural place land that rose above the waters was an anomaly and, anyhow, the Book of Genesis portrayed the existence of continents as something that had been decreed by a special act of God—it was, in effect, miraculous. Wooton runs through various explanations, including the idea that the waters have been displaced from their original position or that the earth is no longer a sphere but has been elongated. None of these ideas ruled out getting to East by sailing West, but the controversy implies that the shape of the Earth was hardly a settled issue in Columbus’ day. (Of course there would be different argument about the shape of the Earth later on.) Well, nothing in intellectual history stays simple if you look at carefully.

  2. Dante explicitly showed the world to be round. But you last request reminded me of something from the works of the great philosopher Bugs Bunny:

  3. I’m always amazed by how the partisans of “scientific rationality” etc. continue to repeat the dumbest of factual errors about the history of science.

  4. Nice to see one of my Quora answers on the subject being given in the first comment in an attempt at educating the writer of the article. But then I read some of the idiocy in the rest of the comments and now I’m depressed.

  5. Its NPR… They drag out the noble science vs. repressive church meme about once a month. The only time the church isn’t a target of ridicule on NPR is when Pope what’s-his-name has disparaging things to say about capitalism or Trump or whatever, which makes for a nice break from the usual civil rights navel gazing or recent tends in urban foraging.

  6. If America had not been in the way Columbus and his entire crew would have stared to death on the open ocean.

    What an image: gazing at the featureless sea until insanity and finally death sets in… Somehow even the typos in this blog are touched with poetry.

    Oh yes, the spice islands: I’ve always found it charming that the great voyages of exploration were motivated primarily by the demand for the wherewithal for spicy food. (For much more on this, see Out of the East by Paul Freedman.)

  7. Augustus

    Good article, but it’s “starved to death,” not “stared to death.”

  8. Clive Raymond

    It is true that Magellan did not make it around on his famous voyage, but my understanding is that he had been out to the East Indies and back earlier in his life; meaning that effectively, starting in the East Indies, he went all the way round.

  9. “Back in the third century BCE the astronomer mathematician Eratosthenes from Alexandria determined the size of the sphere using the angle of the sun’s shadow and a bit of basic trigonometry.”

    True. However, this assumes that the Earth is spherical. Chinese astronomers used a similar argument to calculate the distance to the Sun, assuming that the Earth is flat. If it is not really far away, then moving along a flat Earth will cause the angle of the Sun above the horizon to change. I learned this from Carlo Rovelli’s book on Anaximander. Of course, he was not the first to know this, but I am surprised that I had never run across the argument before.

  10. “medieval T and O Mappa Mundi”

    Have you read “The Fourth Part of the World”?

  11. I can thoroughly recommend Jerry Brotton’s book “A History of the World in Twelve Maps”. This book also includes examples of Chinese and Korean maps, which redresses the usual exclusion of non-European cartographers.

  12. Sili

    Ludvig Holberg made fun of ‘simple peasants’ believing the world to be flat in 1722 (Erasmus Montanus), so the idea must have been “out there” even then.

    • Here the emphasis is on ‘simple peasants’. Throughout my post I refer to ‘educated’ people for a reason. You can equally well find uneducated people, ‘simple peasants’, in the nineteenth century who still believe in a geocentric cosmos, simply because they have never learnt any better.

    • There are “simple peasants” (ie the rapper BoB and internet ‘personality’ Tina Tequila) who think so today as well. But the idea that the earth was round was known well beyond the learned and seems to have been common knowledge according to most evidence.

      The popular fourteenth century collection of travellers’ tales The Travels of Sir John Mandeville includes a story of a man who unwittingly returns to his homeland from the west by sailing into the east:

      “‘I have often thought of a story I have heard, when I was young, of a worthy man of our country who went once upon a time to see the world. He passed India and many isles beyond India, where there are more than five thousand isles, and travelled so far by land and sea, girdling the globe, that he found an isle where he heard his own language being spoken…He marveled greatly, for he did not understand how this could be. But I conjecture that he had travelled so far over land and sea, circumnavigating the earth, that he had come to his own borders; if he had gone a bit further, he would have come to his own district.”

      The author doesn’t bother to explain how this would work and assumes his audience understood the earth to be a sphere.

      Similarly we have multiple passing references to the shape of the earth in a variety of vernacular works intended for an unlearned audience which use the same similes – rond comme une pomme (round like an apple) or rund cume pelote (round like a ball). Romances, which were written in part to be read to illiterate audiences, include references to the earth sitting like a yolk within the egg of the heavens. Both the Old French Roman d’Eneas and Le Couronement de Louis have references to people circumnavigating the earth. The Roman de Thebes includes a description of a map in the tent of a king divided into the five zones of Greek geography – a division that only makes sense with a spherical world. In the Alexandre de Paris Darius is depicted sending Alexander a present of a ball implying he’s a child, whereas Alexander declares it a sign that he would conquer the world, implying the audience understood that the earth was ball-shaped. The same poem ends with Alexander’s tomb being topped by a statue of him holding up an apple, symbolising his dominance of the whole world.

      This image would have been familiar to medieval audiences, since royal regalia often included the orb, representing the king’s earthly authority. Any medieval English peasant who ever looked at a penny would find on it an image of the king on his throne, holding the sceptre and the orb (or rather the globus cruciger, an orb topped with the cross).

      Finally the Old Norse King’s Mirror not only depicts the earth as a sphere but explains in detail how it can be night on one side and day on the other using a thought experiment with a candle and an apple.

      All this indicates that the idea of a spherical earth was widely accepted.

      • Jeb

        I would recommend reading ‘Ireland and the Antipodes: The Heterodoxy of Virgil of Salzburg’ by John Carey.

        Its more related to the real controversy of the period the existence of the antipodes but its interesting in regard to the relationship between elite and popular culture here.

        Antipodes and the idea of spherical earth are related and placing the subjects together also helps to balance the relationship between elite and popular culture.

  13. C M Graney

    There was a bit of a to-do in the US in January when a prominent rapper starting claiming the Earth is flat, especially after Neil deGrasse Tyson weighed in on the subject.

    • Tim O'Neill

      And the the mighty STEM Lord Tyson showed he knows about as much about history as B.o.B. knows about science with his gloriously ignorant reply:

      ““Being five centuries regressed in your reasoning doesn’t mean we all can’t still like your music.”

      And when someone tweeted noting the error, the great expert-on-everything doubled down on his error, responding:

      “Yes. Ancient Greece – inferred from Earth’s shadow during Lunar Eclipses. But it was lost to the Dark Ages>”

      Oh dear …

      • This is not the first time and it almost certainly won’t be the last the NdGT has shown himself to be an arrogant ignorant fool when it comes to the history of science

  14. Pingback: Whewell’s Gazette: Year 2, Vol. #42 | Whewell's Ghost

  15. You’ve gotten among the finest online websites

  16. Pingback: The Earth was definitely not flat in the Middle Ages | The Renaissance Mathematicus

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