Heraclides Ponticus (387 - 312 BCE), also known as Heraklides, was a Greek philosopher who lived and died at Heraclea, now Eregli, Turkey. He has frequently been hailed as the originator of the heliocentric theory. Though this is now generally doubted, he did anticipate the thinking of later astronomers.

Heraclides' father was Euthyphron, a wealthy nobleman who sent him to study at the Academy in Athens under its founder Plato and under his successor Speusippus, though he also studied with Aristotle. According to the Suda, Plato, on his departure for Sicily in 360 BCE, left his pupils in the charge of Heraclides. Speusippus, before his death in 339 BCE, had chosen Xenocrates as his successor but Xenocrates narrowly triumphed in an ensuing election against Heraclides and Menedemus.

Many stories abound that suggest he may have been a rather vain and pompous man and the target of much ridicule. However, Heraclides seems to have been a versatile and prolific writer on philosophy, mathematics, music, grammar, physics, history and rhetoric, notwithstanding doubts about attribution of many of the works.

His major distinction is that he realised, as the result of observation, that Venus and Mercury orbit the Sun as satellites. Some writers have seen this as evidence that he originated the heliocentric theory prior to Aristarchus of Samos and Nicolaus Copernicus. However, it is now generally believed that he was proposing an essentially geocentric model in which those planets orbit the Sun but the Sun, in turn, orbits the Earth along with the Moon, a theory later revived by Tycho Brahe. He was also the first to put forward the theory that the Earth rotates on its axis once a day.

References

• O. Neugebauer, (1969) The Exact Sciences in Antiquity ISBN 0486223329
• O. Neugebauer (1975) A History of Ancient Mathematical Astronomy
• O. Voss (1896) De Heraclidis Pontici vitaet scriptis