Heraclides Ponticus (Greek: Ἡρακλείδης ὁ Ποντικός; c. 390-c. 310 BC), also known as Herakleides and Heraklides of Pontus, was a Greek philosopher and astronomer who lived and died at Heraclea Pontica, now Karadeniz Ereğli, Turkey. He is best remembered for proposing that the earth rotates on its axis, from east to west, once every 24 hours. He is also frequently hailed as the originator of the heliocentric theory, although this is doubted.
Heraclides' father was Euthyphron, a wealthy nobleman who sent him to study at the Platonic Academy in Athens under its founder Plato and under his successor Speusippus. He reportedly also attended the schools of the Pythagoreans, where he would have come in contact with Aristotle. According to the Suda, Plato, on his departure for Sicily in 361/360 BC, left his pupils in the charge of Heraclides. Heraclides was also nearly elected to succeed Speusippus as head of the academy in 339/338 BC, but narrowly lost to Xenocrates.
Like the Pythagoreans Hicetas and Ecphantus, Heraclides proposed that the apparent daily motion of the stars was created by the rotation of the Earth on its axis once a day. This view contradicted the accepted Aristotelian model of the universe, which said that the earth was fixed and that the stars and planets in their respective spheres might also be fixed.
Although some historians have proposed that Heraclides taught that Venus and Mercury revolve around the Sun, a detailed investigation of the sources has shown that "nowhere in the ancient literature mentioning Heraclides of Pontus is there a clear reference for his support for any kind of heliocentrical planetary position."
A punning on his name, dubbing him Heraclides "Pompicus," suggests he may have been a rather vain and pompous man and the target of much ridicule. According to Diogenes Laertius, he forged plays under the name of Thespis, and according to the same author, this time drawing from a different source, Dionysius the Deserter composed plays and forged them under the name of Sophocles. Heraclides was deceived by this easily and cited from them as the words of Aeschylus and Sophocles. 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. It appears that he composed various works in dialogue form.
Heraclides also seems to have had an interest in the occult. In particular he focused on explaining trances, visions and prophecies in terms of the retribution of the gods, and reincarnation.
A quote of Heraclides, of particular significance to historians, is his statement that fourth century Rome was a Greek city.
Surnamed Pontĭcus. A Greek philosopher, born at Heraclea in Pontus about B.C. 380. He came early to Athens, where he became a disciple of Plato and Aristotle, and had made a reputation by about B.C. 340. He was the author of some sixty works on a great variety of subjects-philosophy, mathematics, music, grammar, poetry, political and literary history, and geography. He was a learned and interesting writer, but somewhat deficient in critical power. There are a few fragments of his works remaining, besides an extract from a book on constitutions which bears his name, edited by Köler (Halle, 1804), Coraes (Paris, 1805), and Müller. See Deswert, De Heraclide Pontico (Louvain, 1830), and F. W. Schmidt, De Heraclidae Pontici etc. Dialogis Deperditis (Breslau, 1867).