Antiquity

Belief in a flat Earth is found in humankind's oldest writings. In early Mesopotamian thought, the world was portrayed as a flat disk floating in the ocean, and this forms the premise for early Greek maps like those of Anaximander and Hecataeus.

By classical times an alternative idea, that Earth was spherical, had appeared. This was espoused by Pythagoras apparently on aesthetic grounds, as he also held all other celestial bodies to be spherical. Aristotle provided observational evidence for the spherical Earth:

1) Ships actually recede over the horizon, disappearing hull-first. In a flat-earth model, they should simply get smaller and smaller until no longer visible, assuming that light travels in a straight line.

2) Travelers going south see southern constellations rise higher above the horizon. This is only possible if their "straight up" direction is at an angle to northerners' "straight up". Thus Earth's surface cannot be flat.

3) The border of the shadow of Earth on the Moon during the partial phase of a lunar eclipse is always circular, no matter how high the Moon is over the horizon. Only a sphere casts a circular shadow in every direction, whereas a circular disk casts an elliptical shadow in most directions.

The Earth's circumference was measured around 240 BC by Eratosthenes. Eratosthenes knew that in Syene (now Aswan), in Egypt, the Sun was directly overhead at the summer solstice. He used geometry to come up with a circumference of 252,000 stades, which, depending on the length of the stadion unit, is within 2% and 20% of the actual circumference, 40,008 kilometres. Note that Eratosthenes could only measure the circumference of the Earth by assuming that the distance to the Sun is so great that the rays of sunlight are essentially parallel. A similar measurement, reported in a Chinese mathematical treatise the Zhoubi suanjing (1st c. BC), was used to measure the distance to the Sun by assuming that the Earth was flat.[2]

During this period Earth was generally thought of as divided into climes, with frigid climes at the poles and a deadly torrid clime at the equator. Beyond the torrid clime were the antipodes (people living on the opposite side of a spherical Earth, so called because their feet would be turned towards the opposite direction).

Lucretius was opposed to the concept of a spherical Earth, because he considered the idea of antipodes absurd. But by the 1st century, Pliny the Elder was in a position to claim that everyone agrees on the spherical shape of Earth (Natural History, 2.64), although there continued to be disputes regarding the nature of the antipodes, and how it is possible to keep the ocean in a curved shape. Interestingly, Pliny as an "intermediate" theory considers also the possibility of an imperfect sphere, "shaped like a pinecone". (Natural History, 2.65)

The Early Church

There is evidence that the spherical Earth was accepted by many Christians. For example, Emperor Theodosius II of the Byzantine Empire placed the globus cruciger (which depicts Earth as round) on his coins.

However, the antipodes (thought to be separated from the Mediterranean world by the uncrossable torrid clime) were difficult to reconcile with the Christian view of a unified human race descended from one couple and redeemed by a single Christ. Consequently, some of the Church Fathers questioned their existence and even the roundness of Earth. Saint Augustine (354-430) wrote:

"Those who affirm [a belief in antipodes] do not claim to possess any actual information; they merely conjecture that, since the Earth is suspended within the concavity of the heavens, and there is as much room on the one side of it as on the other, therefore the part which is beneath cannot be void of human inhabitants. They fail to notice that, even should it be believed or demonstrated that the world is round or spherical in form, it does not follow that the part of the Earth opposite to us is not completely covered with water, or that any conjectured dry land there should be inhabited by men. For ????ure, which confirms the truth of its historical statements by the accomplishment of its prophecies, teaches not falsehood; and it is too absurd to say that some men might have set sail from this side and, traversing the immense expanse of ocean, have propagated there a race of human beings descended from that one first man." (De Civitate Dei, 16.9)

Augustine denied that the antipodes were inhabited by men, not the idea of a round Earth. However, the phrase "even should it be believed or demonstrated that the world is round" (Latin: etiamsi figura conglobata et rotunda mundus esse credatur sive aliqua ratione monstretur) suggests that he was skeptical of the claims of the philosophers that the Earth was round, and perhaps that others were as well.

A few authors directly opposed the round Earth:

- Cosmas Indicopleustes' world picture - flat earth in a Tabernacle.Lactantius (245–325) called it "folly" because people on a sphere would fall down;
- Saint Cyril of Jerusalem (315–386) saw Earth as a firmament floating on water (though in his case, the relevant quote is found in the course of a sermon to the newly baptized, and it is unclear whether he was speaking poetically or in a physical sense);
- Saint John Chrysostom (344–408) saw a spherical Earth as contradictory to ????ure;
- Diodorus of Tarsus (d. 394) also argued for a flat Earth;
Severian, Bishop of Gabala, (d. 408);
- The Egyptian monk Cosmas Indicopleustes (547) in his Topographia Christiana, where the Covenant Ark was meant to represent the whole universe, argued on theological grounds that the Earth was flat, a parallelogram enclosed by four oceans.
- At least one early Christian writer, Basil of Caesarea (329–379), believed the matter to be theologically irrelevant. (Hexaemeron 9:1)

Different historians have maintained that these advocates of the flat Earth were either influential (a view typified by Andrew Dickson White) or relatively unimportant (typified by Jeffrey Russell) in the later Middle Ages. The scarcity of references to their beliefs in later medi???? writings convinces most of today's historians that their influence was slight.

The Middle Ages

Early Middle Ages

Europe's view of the shape of the Earth in Late Antiquity and the Early Middle Ages is best expressed by the writings of early Christian scholars:

Macrobius (c. 360 - post 422), in his commentary on Cicero's Somnium Scipionis, described the Earth as spherical, and of insignificant size in comparison to the remainder of the cosmos.[3] Many early medi???? manu????s of Macrobius include zonal maps showing the Ptolemaic climates derived from the concept of a spherical Earth and a diagram showing the Earth (labeled as globus terrae, the sphere of the Earth) at the center of the hierarchically ordered planetary spheres.[4]

Boethius (c. 480-524), who also wrote a theological treatise On the Trinity, repeated this model of the Earth as an insignificant point in the center of a spherical cosmos in his influential, and widely translated, Consolation of Philosophy.[5]

Bishop Isidore of Seville (560 – 636) taught in his widely read encyclopedia, the Etymologies, that the Earth was round. His meaning was ambiguous and some writers think he referred to a disc-shaped Earth; his other writings make it clear, however, that he considered the Earth to be globular.[6] He also admitted the possibility of people dwelling at the antipodes, considering them as legendary[7] and noting that there was no evidence for their existence.[8] Isidore's analogy continued to be used by authors clearly favouring a spherical Earth, e.g. the 9th century bishop Rabanus Maurus who compared the habitable part of the northern hemisphere (Aristotle's northern temperate clime) with a wheel, imagined as a slice of the whole sphere.

The monk Bede (c.672 – 735) wrote in his influential treatise on computus, The Reckoning of Time, that the Earth was round, explaining the unequal length of daylight from "the roundness of the Earth, for not without reason is it called 'the orb of the world' on the pages of Holy ????ure and of ordinary literature. It is, in fact, set like a sphere in the middle of the whole universe." (De temporum ratione, 32). The large number of surviving manu????s of The Reckoning of Time, copied to meet the Carolingian requirement that all priests should study the computus, indicates that many, if not most, priests were exposed to the idea of the sphericity of the Earth.[9] Abbot Ælfric of Eynsham paraphrased Bede into Old English, saying "Now the Earth's roundness and the Sun's orbit constitute the obstacle to the day's being equally long in every land."[10]

Bishop Vergilius of Salzburg (c.700 – 784) is sometimes cited as having been persecuted for teaching "a perverse and sinful doctrine ... against God and his own soul" regarding the sphericity of the earth. Pope Zachary decided that "if it shall be clearly established that he professes belief in another world and other people existing beneath the earth, or in [another] sun and moon there, thou art to hold a council, and deprive him of his sacerdotal rank, and expel him from the church."[11] The issue involved was not the sphericity of the Earth itself, but whether people living in the antipodes were not descended from Adam and hence were not in need of redemption. Vergilius succeeded in freeing himself from that charge; he later became a bishop and was canonised in the thirteenth century.[12]

A recent study of medi???? concepts of the sphericity of the Earth noted that "since the eighth century, no cosmographer worthy of note has called into question the sphericity of the Earth."[13] Of course it was probably not the few noted intellectuals who defined public opinion. It is difficult to tell what the wider population may have thought of the shape of the Earth – if they considered the question at all. It may have been as irrelevant to them as the Heisenberg uncertainty principle is to most of our contemporaries. The symbolism of the orb (Globus cruciger), used in imperial regalia from the 5th century onwards has sometimes been interpreted as showing mainstream support for the concept of a spherical world; others maintain that the orb does not represent a spherical Earth at all, but a spherical cosmos, with two hemispherical domes, the upper representing heaven and the lower representing hell.

Later Middle Ages

By the 11th century, Europe had learned of Islamic astronomy, and abundant records suggest that any doubts that Europeans had had in earlier times were generally eliminated. Lectures in the medi???? universities commonly advanced evidence in favor of the idea that the Earth was a sphere.[14] A few examples: the most important and widely taught theologian of the Middle Ages, Thomas Aquinas (1225–1274), believed in a spherical Earth. Hermannus Contractus (1013–1054) is among the earliest Christian scholars to estimate the circumference of Earth with Eratosthenes' method. In addition, Dante's Divine Comedy portrays Earth as a sphere.

The Elucidarium of Honorius Augustodunensis (c. 1120), an important manual for the instruction of lesser clergy which was translated into Middle English, Old French, Middle High German, Old Russian, Middle Dutch, Old Norse, Icelandic, Spanish, and several Italian dialects, explicitly refers to a spherical Earth. This supports the contention that the spherical shape of the Earth was common knowledge outside scholarly circles. Likewise, the fact that Bertold von Regensburg (mid-13th century) used the spherical Earth as a sermon illustration shows that he could assume this knowledge among his congregation. The sermon was held in the vernacular (i.e. German as opposed to Latin), and thus was not intended for a learned audience.

However, as late as 1400s, the Spanish theologian Tostatus disputed the existence of any inhabitants at the antipodes[15].

Modern times

Flammarion's caption translates to "A medi???? missionary tells that he has found the point where heaven and Earth meet..."During the 19th century, the Romantic conception of a European "Dark Age" gave much more prominence to the Flat Earth model than it ever possessed historically. The widely circulated woodcut of a man poking his head through the firmament of a flat Earth to view the mechanics of the spheres, ????uted in the style of the 16th century cannot be traced to an earlier source than Camille Flammarion's L'Atmosphère: Météorologie Populaire (Paris, 1888, p. 163) [11]. The woodcut illustrates the statement in the text that a medi???? missionary claimed that "he reached the horizon where the Earth and the heavens met", an anecdote that may be traced back to Voltaire, but not to any known medi???? source. In its original form, the woodcut included a decorative border that places it in the 19th century; in later publications, some claiming that the woodcut did, in fact, date to the 16th century, the border was removed. Flammarion, according to anecdotal evidence, had commissioned the woodcut himself. In any case, no source of the image earlier than Flammarion's book is known.

Russell, a professor of history at Santa Barbara who has written widely on media???? religion, heresy and witchcraft, explored the issue in Inventing the Flat Earth: Columbus and Modern Historians. Russell claims that the Flat Earth theory is a fable used to impugn pre-modern civilisation, especially that of the Middle Ages in Europe. Today essentially all professional media????ists agree with Russell that the "media???? flat Earth" is a nineteenth-century fabrication, and that the few verifiable "flat earthers" were the exception.

From a European perspective, Portuguese exploration of Africa and Asia in the 15th century removed any serious doubts, and Ferdinand Magellan's circumnavigation any remaining ones.

Modern people who do not accept the spherical Earth and base this opinion on ????ure do not represent a continuing school of Biblical exegesis. Some Christians following what they saw as a literal interpretation of ????ure tried to revive Flat Earth thinking in the 19th century. In 1898 during his solo circumnavigation of the world Joshua Slocum encounted such a group in the Transvaal Republic. President Kruger berated him, telling him "you don't mean around the world; it is impossible! You mean in the world!"[16]

The last known group, the Flat Earth Society, kept the concept alive and at one time claimed a few thousand followers. The society declined in the 1990s following a fire at its headquarters in California and vanished from public visibility after the death of its last president, Charles K. Johnson, in 2001.[17]