The notion of a Flat Earth refers to the idea that the inhabited surface of the Earth is flat, rather than curved.
It is commonly assumed that people from early antiquity generally believed the world was flat, but by the time of Pliny the Elder (1st century) its spherical shape was generally acknowledged. At that time Ptolemy derived his maps from a curved globe and developed the system of latitude and longitude. His writings remained the basis of European astronomy throughout the Middle Ages. The common misconception that people before the age of exploration believed that the earth was flat entered the popular imagination after Washington Irving's publication of The Life and Voyages of Christopher Columbus in 1828.
A few early Christian writers questioned and even opposed Earth's sphericity on theological grounds. With the astrolabe, Arab astronomy reached Europe in the 11th century, and by the 1100s at the latest, the geocentric model had supplanted it in the minds of the learned people of Europe. This did not settle, however, the question of whether the antipodes were inhabitable, or even reachable.
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 alternate 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 physical evidence for the spherical Earth:
* 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.
* 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 the Earth's surface cannot be flat.
* 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, a circular disk casts an elliptical shadow in most directions.
The Earth's circumference was estimated around 240 BC by Eratosthenes. Eratosthenes knew that in Syrene (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.
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, executed in the style of the 16th century cannot be traced to an earlier source than Camille Flammarion's L'Atmosphere: Météorologie Populaire. The woodcut illustrates the statement in the text that a medieval 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 medieval 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 mediaeval 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 myth used to impugn pre-modern civilisation, especially that of the Middle Ages in Europe. Today essentially all professional mediaevalists agree with Russell that the "mediaeval flat earth" is a nineteenth-century fabrication, and that the few verifiable "flat earthers" were the exception.
As of the beginning of the 21st Century, there remain populations within rural cultures which, unexposed to technological civilisation, consider the world to be flat. With no long-distance communication requirements or other technological endeavours, their beliefs appear to suffice.
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article " flat Earth".