Flat Earth
Flat Earth is a conception of our planet as a plane or disk, and for most of human history it was simply how the world worked. Ancient Egyptians pictured a circular landmass floating in the ocean. The Norse placed a world-encircling sea around their flat Earth, with a serpent called Jormungandr coiled in the water. Mesopotamian scribes described three layered earths in cuneiform texts. Across cultures that had no contact with each other, independent minds looked at the horizon and reached the same conclusion.
And then something changed. In ancient Greece, a competing idea caught hold. Philosophers began arguing, on physical grounds, that the Earth was a sphere. By around 330 BC, Aristotle had assembled observational evidence strong enough to make the case formally. Eratosthenes calculated the Earth's circumference around 240 BC. Ptolemy derived maps from a globe by the 2nd century AD.
Yet the flat-Earth idea never fully disappeared. It survived into the Christian theological debates of late antiquity. It persisted in Chinese scholarship until Jesuit missionaries arrived in the 17th century. And in the 21st century, after centuries of settled science, it returned as a conspiracy theory spreading through social media.
How did a demonstrably false model of the world manage to outlast so much evidence against it? That question turns out to cut through ancient cosmology, medieval myth-making, and the psychology of modern distrust.
Homer's description of the shield of Achilles in the 8th century BC placed a circular Earth at the center of an encircling sea called Oceanus. That image was not simply a poet's flourish. It appears in Hesiod, in Stasinus of Cyprus, Mimnermus, Aeschylus, and Apollonius Rhodius. Quintus Smyrnaeus was still echoing it in his Posthomerica in the 4th century AD, centuries after Greek philosophy had moved on.
Among the pre-Socratic philosophers, the flat model attracted serious thinkers. Thales, working around 550 BC, reportedly believed the Earth floated in water like a log. Anaximenes of Miletus held that "the Earth is flat and rides on air; in the same way the Sun and the Moon and the other heavenly bodies, which are all fiery, ride the air because of their flatness." Anaximander imagined something different but equally strange: a short cylinder with a flat circular top, hanging in equilibrium because it was equidistant from all things.
By the 5th century BC, some philosophers were noticing problems with the flat model. Anaxagoras, around 450 BC, believed the Earth was flat but his pupil Archelaus added that it was depressed in the middle like a saucer. That modification was meant to explain why the Sun rises and sets at different times for observers at different locations. The model was straining under the weight of the facts it could not explain.
The Norse tradition offers one of the most elaborate flat-Earth systems. The Gylfaginning describes the creation of an impassable sea placed in a ring around the Earth, formed from the blood of a primordial figure. The text is direct: "And Jafnharr said: Of the blood, which ran and welled forth freely out of his wounds, they made the sea, when they had formed and made firm the Earth together, and laid the sea in a ring round about her." Yet the same Norse tradition eventually produced the Konungs skuggsia, which uses the example of an apple held near a candle to explain why different parts of the Earth receive different amounts of heat. That text argues, with practical clarity, that the Earth is round like a ball.
The English sinologist Cullen documented what he called a fact so surprising it deserves serious examination: Chinese astronomers, "many of them brilliant men by any standards, continued to think in flat-Earth terms until the seventeenth century." This was not ignorance. It was a cosmological commitment built into the structure of Chinese thought.
Zhang Heng, the astronomer who lived from 78 to 139 AD, used the image of a hen's egg to describe the cosmos. The heavens were the shell, round like a crossbow bullet. But Zhang himself wrote that "Heaven takes its body from the Yang, so it is round and in motion. Earth takes its body from the Yin, so it is flat and quiescent." The egg was not an argument for a spherical Earth; it was an argument about relative position.
Joseph Needham, the historian of Chinese science, suggested that some passages pointed toward awareness of Earth's sphericity. Scholars who investigated those passages found otherwise. The 13th-century scholar Li Ye, who worried that a square Earth would interfere with the movements of the round heavens, did not argue for a spherical Earth. He argued for rounding off its edges to make it circular rather than square. The 4th-century scholar Yu Xi went further, suggesting the Earth could be either square or round, but this remained a minority speculation.
In the 2nd century BC, Chinese astronomers used a method similar to Eratosthenes' measurement of the Earth's circumference, but inverted it. The Huainanzi records how they assumed a flat Earth and used shadow measurements at different latitudes to calculate the height of the Sun above the surface, arriving at a distance of around 100,000 li. They had the right method and the wrong premise.
When Matteo Ricci arrived as an early Jesuit missionary, he recorded in 1595 that the Ming-dynasty Chinese said: "The Earth is flat and square, and the sky is a round canopy; they did not succeed in conceiving the possibility of the antipodes." Within a few decades, however, Ricci collaborated with Chinese cartographers and the translator Li Zhizao to publish the Kunyu Wanguo Quantu in 1602, the first Chinese world map based on European discoveries. By 1648, the treatise Gezhicao by Xiong Mingyu explicitly stated that the Earth was spherical and could be circumnavigated.
Pythagoras in the 6th century BC and Parmenides in the 5th century BC put the spherical Earth into Greek philosophical discourse, and the idea spread quickly in that world. Around 330 BC, Aristotle argued for it on both physical and observational grounds and cited an estimate of the Earth's circumference. Around 240 BC, Eratosthenes calculated that circumference using shadow measurements at different latitudes. By the 2nd century AD, Ptolemy had built on a spherical model to develop the system of latitude, longitude, and climes, composing the Almagest in Greek; the text was not translated into Latin until the 11th century, reaching the Latin West through Arabic translations.
During the early period of the Christian Church, the spherical view was broadly held. Until the mid-fourth century AD, virtually all Christian authors accepted a round Earth. Athenagoras, writing around 175 AD, described the Earth as spherical. Arnobius, writing around 305 AD, explained roundness in terms of a solid sphere with no beginning or end: "In the first place, indeed, the world itself is neither right nor left. It has neither upper nor lower regions, nor front nor back. For whatever is round and bounded on every side by the circumference of a solid sphere, has no beginning or end."
The dissenting voices were a minority. Lactantius, writing between 304 and 313 AD as an advisor to the Emperor Constantine, ridiculed the spherical model and mocked the idea of antipodes. Chrysostom, Archbishop of Constantinople and one of the four Great Church Fathers of the Eastern Church, argued from scripture that the Earth floats on water beneath the firmament. Cosmas Indicopleustes, an Alexandrian monk writing in 547 AD, described the Earth as a rectangle 400 days' journey long by 200 wide, enclosed by four massive walls supporting the firmament; he dismissed the spherical theory as "pagan."
Those dissenters were influential but not representative. By the High and Late Middle Ages, spherical Earth was the standard position in European universities. John of Sacrobosco's textbook On the Sphere of the World made the case in terms students encountered routinely. Thomas Aquinas, writing between roughly 1225 and 1274, used the spherical Earth as an example of a fact demonstrable by two different sciences simultaneously.
In the 17th century, a story began circulating that medieval Europeans had generally believed the Earth was flat. That story was false, and it was invented for specific polemical purposes. Protestant writers used it to argue against Catholic teachings, presenting the Church as the enemy of geographic common sense.
The myth gained wider currency in the 19th century through several prominent advocates. Washington Irving maintained that Christopher Columbus had to overcome the opposition of churchmen who believed in a flat Earth before he could gain sponsorship for his voyage. John William Draper and Andrew Dickson White deployed the myth as a major element in their argument that science and religion had been in perpetual conflict throughout history.
Subsequent historical research dismantled the claim. Studies of medieval science demonstrated that scholars who were actually read by Christopher Columbus held that the Earth was spherical. St Vergilius of Salzburg, who lived from around 700 to 784, was reported to Pope Zachary for teaching objectionable cosmological ideas, and Pope Zachary's reply from 748 expressed concern about belief in "another world and other men existing beneath the Earth." That language suggests the controversy was about the antipodes, not about the shape of the Earth itself. Vergilius was later appointed Bishop of Salzburg and canonised in the 13th century.
A concrete material record reinforces the point. The globus cruciger, an orb surmounted by a cross used as royal regalia, is documented from the time of the Emperor Theodosius II in 423 AD. Emperor Henry II, who died in 1024, received an imperial orb described by a contemporary chronicler as shaped like a golden apple, representing the Earth with its roundness. Rulers across medieval Europe were literally holding a sphere in their coronation ceremonies.
The first known cartographical globe is the Erdapfel, made by Martin Behaim in 1492. But the concept it expressed had been present in European intellectual life for centuries before that.
Samuel Rowbotham, an English writer, published a pamphlet called Zetetic Astronomy in 1849 and launched what became a modern flat-Earth movement. Lady Elizabeth Blount established the Universal Zetetic Society in 1893, which published journals. In 1956, Samuel Shenton set up the International Flat Earth Research Society in Dover, England, explicitly as a descendant of Blount's organization.
The Internet era accelerated the revival. YouTube, Facebook, and Twitter lowered the barriers for spreading disinformation and connecting people who held minority beliefs. Since the 2010s, flat-Earth belief has grown both through formal organizations and through unaffiliated individuals.
A 2018 study reported on by Scientific American asked 18- to 24-year-old Americans whether they had always believed the world is round. Only 82% agreed with that statement. However, firm conviction in a flat Earth remains rare: less than 2% of all age groups hold that belief with certainty.
People who do commit to the flat-Earth position face an unusual cognitive challenge. They must account for why governments, airlines, schools, scientists, surveyors, and media organizations all operate on the assumption of a spherical Earth. The tension between personal belief and the behaviour of every major institution pushes adherents toward conspiracy thinking. Believers also tend to distrust observations they have not made themselves, and researchers have noted that they frequently distrust and accuse each other of working for the conspiracies they claim to oppose.
The National Center for Science Education maintains a resource specifically aimed at helping teachers counter misinformation about the shape of the Earth, alongside other contested scientific topics.
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Common questions
When did ancient Greek philosophers first argue that the Earth was spherical?
Pythagoras in the 6th century BC and Parmenides in the 5th century BC were among the first Greek philosophers to argue for a spherical Earth. Around 330 BC, Aristotle provided strong empirical evidence for the position. Eratosthenes calculated the Earth's circumference around 240 BC.
Did medieval Europeans believe in a flat Earth?
No. The idea that medieval Europeans generally believed in a flat Earth is a historical myth created in the 17th century by Protestant writers arguing against Catholic teachings. Studies of medieval science show that most scholars of the Middle Ages, including those read by Christopher Columbus, held that the Earth was spherical. The spherical Earth was standard in medieval university textbooks.
Who started the modern flat Earth movement?
Samuel Rowbotham, an English writer, founded the modern flat-Earth movement with his 1849 pamphlet Zetetic Astronomy. Lady Elizabeth Blount built on his work by establishing the Universal Zetetic Society in 1893. In 1956, Samuel Shenton set up the International Flat Earth Research Society in Dover, England, as a direct descendant of that organisation.
Why did ancient Chinese scholars believe in a flat Earth for so long?
Ancient Chinese cosmology held that Heaven was round and in motion while the Earth was flat and quiescent, a distinction rooted in the concepts of Yang and Yin. This belief persisted virtually unchanged until Jesuit missionaries introduced European astronomy in the 17th century. As late as 1595, the early Jesuit missionary Matteo Ricci recorded Ming-dynasty Chinese saying the Earth was flat and square.
How common is flat Earth belief today?
Firm belief in a flat Earth is rare, with less than 2% acceptance across all age groups according to research. A 2018 study reported on by Scientific American found that only 82% of 18- to 24-year-old Americans said they had always believed the world is round. Flat-Earth belief has grown since the 2010s, driven partly by social media platforms.
What did early Christian writers believe about the shape of the Earth?
Until the mid-fourth century AD, virtually all Christian authors held that the Earth was round. Athenagoras described a spherical Earth around 175 AD, and Arnobius gave a similar account around 305 AD. Dissenting voices such as Lactantius and Cosmas Indicopleustes existed but were a minority, and by the High Middle Ages the spherical Earth was universally accepted among scholastic authors.
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