Spherical Earth - History - Antiquity - Classical Greece

Classical Greece

Though the earliest evidence of a spherical Earth comes from ancient Greek sources, there is no account of how the sphericity of the Earth was discovered. A plausible explanation is that it was "the experience of travellers that suggested such an explanation for the variation in the observable altitude and the change in the area of circumpolar stars, a change that was quite drastic between Greek settlements" around the eastern Mediterranean Sea, particularly those between the Nile Delta and the Crimea.

According to Diogenes Laertius, " was the first who called the earth round; though Theophrastus attributes this to Parmenides, and Zeno to Hesiod."

Pythagoras

Early Greek philosophers alluded to a spherical Earth, though with some ambiguity. Pythagoras (6th century BC) was among those said to have originated the idea, but this may reflect the ancient Greek practice of ascribing every discovery to one or another of their ancient wise men. Some idea of the sphericity of the Earth seems to have been known to both Parmenides and Empedocles in the 5th century BC, and although the idea cannot reliably be ascribed to Pythagoras, it may, nevertheless have been formulated in the Pythagorean school in the 5th century BC. After the 5th century BC, no Greek writer of repute thought the world was anything but round.

Herodotus

In The Histories, written 431–425 BC, Herodotus cast doubt on a report of the sun observed shining from the north. The phenomenon was allegedly observed during a circumnavigation of Africa undertaken by Phoenicians under Necho II c. 610–595 BC (The Histories, 4.42) who claimed to have had the sun on their right when circumnavigating in a clockwise direction. To modern historians, however, these details confirm the truth of the Phoenicians’ report.

Plato

Plato (427–347 BC) travelled to southern Italy to study Pythagorean mathematics. When he returned to Athens and established his school, Plato also taught his students that Earth was a sphere though he offered no justifications. If man could soar high above the clouds, Earth would resemble "one of those balls which have leather coverings in twelve pieces, and is decked with various colours, of which the colours used by painters on earth are in a manner samples." In Timaeus, his one work that was available throughout the Middle Ages in Latin, we read that the Creator "made the world in the form of a globe, round as from a lathe, having its extremes in every direction equidistant from the centre, the most perfect and the most like itself of all figures", though the word "world" normally refers to the universe.

Aristotle

Aristotle (384–322 BC) was Plato's prize student and "the mind of the school." Aristotle observed "there are stars seen in Egypt and Cyprus which are not seen in the northerly regions." Since this could only happen on a curved surface, he too believed Earth was a sphere "of no great size, for otherwise the effect of so slight a change of place would not be quickly apparent." (De caelo, 298a2–10)

Aristotle provided physical and observational arguments supporting the idea of a spherical Earth:

• Every portion of the Earth tends toward the center until by compression and convergence they form a sphere. (De caelo, 297a9–21)
• Travelers going south see southern constellations rise higher above the horizon; and
• The shadow of Earth on the Moon during a lunar eclipse is round. (De caelo, 297b31–298a10).

The concepts of symmetry, equilibrium and cyclic repetition permeated Aristotle's work. In his Meteorology he divided the world into five climatic zones: two temperate areas separated by a torrid zone near the equator, and two cold inhospitable regions, "one near our upper or northern pole and the other near the ... southern pole," both impenetrable and girdled with ice (Meteorologica, 362a31–35). Although no humans could survive in the frigid zones, inhabitants in the southern temperate regions could exist.