When Did People First Realize That the Earth Is Not Flat?
Greek scholars had decided by 350 BC that the Earth must be round. But the earlier belief that it was flat persisted in other countries for many centuries afterwards. Even as late as the time of Christopher Columbus, at the end of the 15th Century, a fear of falling off the edge of the Earth existed among seamen.
One theory held by early man was that the sky was a kind of shield which came down to meet the Earth on all sides, forming a boxed-in universe. It was the Greeks who hit on the idea that it was a circular slab. A Hindu myth suggested that the slab was supported by four pillars which rested on four elephants, which stood on a gigantic turtle, which, perhaps swam in a huge ocean.
The Greek philospher, Anaximander of Miletus (611-546 BC) thought man might be living on the surface of a cylinder, which was curved from north to south. He was the first, as far as is known, to suggest any shape for the Earth other than flat.
Pythagoras in the 6th-century BC and Parmenides in the 5th-century stated that the Earth is spherical, the spherical view spread rapidly in the Greek world. Around 330 BC, Aristotle maintained on the basis of physical theory and observational evidence that the Earth was spherical, and reported on an estimate on the circumference.
The Earth’s circumference was first determined around 240 BC by Eratosthenes. By the second century AD, Ptolemy had derived his maps from a globe and developed the system of latitude, longitude, and climes. His Almagest was written in Greek and only translated into Latin in the 11th century from Arabic translations.
In the 2nd century BC, Crates of Mallus devised a terrestrial sphere that divided the Earth into four continents, separated by great rivers or oceans, with people presumed living in each of the four regions. Opposite the oikumene, the inhabited world, were the antipodes, considered unreachable both because of an intervening torrid zone (equator) and the ocean. This took a strong hold on the medieval mind.
Lucretius (1st century BC) opposed the concept of a spherical Earth, because he considered that an infinite universe had no center towards which heavy bodies would tend. Thus, he thought the idea of animals walking around topsy-turvy under the Earth was absurd. By the 1st century AD, Pliny the Elder was in a position to claim that everyone agreed on the spherical shape of Earth, though disputes continued regarding the nature of the antipodes, and how it is possible to keep the ocean in a curved shape. Pliny also considered the possibility of an imperfect sphere “shaped like a pinecone”.
In late antiquity such widely read encyclopedists as Macrobius and Martianus Capella (both 5th century AD) discussed the circumference of the sphere of the Earth, its central position in the universe, the difference of the seasons in northern and southern hemispheres, and many other geographical details. In his commentary on Cicero’s Dream of Scipio, Macrobius described the Earth as a globe of insignificant size in comparison to the remainder of the cosmos.