In ancient times, people believed that the world was flat.
The shape of the world was a subject that fascinated a great variety of ancient cultures. It is true that the earliest cultures for which we have records on this topic, such as the Babylonians and the Egyptians, do seem to describe the world as flat. Yet, as trade became more widespread and with it came an appreciation for, and study of, geography and astronomy, the notion of a flat disc-like earth quickly came into question. Even then, a spherical globe was not the first solution offered.
In the late seventh to early sixth century BC, the Ionian geometer Thales hypothesised that the earth was a disk that floated on the ocean: so round, but still flat. His younger associate Anaximander theorised that it was a cylinder – like a column floating upright in the centre of the universe.
It is not known who was the first to suggest that the earth could have been spherical in shape, but it is often associated with the Pythagorean school. By the time that Plato was writing in the fourth century BC, the debate was well known but a philosophical consensus may well have been forming (Phaedo, 108d-e):
“However, there is nothing to prevent my telling what I believe the form of the earth to be, and the regions in it.”
“Well,” said Simmias, “that will be enough.”
“I am convinced, then,” said he, “that in the first place, if the earth is round and in the middle of the heavens, it needs neither the air.”
Plato has Socrates offer a definitive answer to the question, but it was perhaps Aristotle who was the first to really attempt to prove it. It is a topic he discusses in great detail in book II of his work On the Heavens, engaging with the various arguments that preceded him, using philopshical arguments and observations of the natural world (On the Heavens, 2.14):
How else would eclipses of the moon show segments shaped as we see them? As it is, the shapes which the moon itself each month shows are of every kind straight, gibbous, and concave-but in eclipses the outline is always curved: and, since it is the interposition of the earth that makes the eclipse, the form of this line will be caused by the form of the earth’s surface, which is therefore spherical. Again, our observations of the stars make it evident, not only that the earth is circular, but also that it is a circle of no great size.
His conclusion is characteristically strong in tone: “Its shape must necessarily be spherical” (On the Heavens, 2.14).
This idea – that the world was spherical – became pervasive in the Hellenistic period. The work of Aristarchus of Samos, the first known scholar to argue that the earth revolved around the sun instead of the other way around, assumes that the earth was round. The great mathmetician Eratosthenes must have believed that the world was a sphere, because he offerred a calculation for its circumference. By the Roman Imperial period, it was an accepted model, with authors such as Pliny the Elder and the geographer Strabo, agreeing the world was indeed spherical.
We are told that scholars in ancient India also believed that the earth was spherical. While we do not have technical texts dealing with the subject, the Greek writerMegasthenes (fourth to third century BC) wrote that the people of India had some similar views to the Greeks (fr. 41 = Strabo, Geography, 15.1.59):
[T]hey say that world had a beginning, and is liable to destruction, and is in shape spherical.
So, to say that people in ancient times believed the world was flat is predominantly false. It was one early theory, but as people began to ask more questions of the world around them it quickly came under scrutiny. By the end of the fourth century BC, the idea of a spherical world was more common place than any other answer – and Aristotle’s work, in particular, would strongly influence scholastic views on this question right through ancient and medieval Europe.
- Lesley B. Cormack, “That before Columbus, geographers and other educated people thought the Earth was flat”, in: Ronald L. Numbers and Kostas Kampourakis (eds), Newton’s Apple and Other Myths about Science (2015).
- Dirk L. Couprie, When the Earth Was Flat: Studies in Ancient Greek and Chinese Cosmology (2018).
- Christine Garwood, Flat Earth: The History of an Infamous Idea (2007).
- David A. White, Myth and Metaphysics in Plato’s Phaedo (1989).