Heracleides Ponticus

Philospher and astronomer; b. c. 390 BC (Heraclea Pontica, Bithynia), d. after 322 BC (Athens)

Heracleides was a student of Plato. He must have been an outstanding student, since it is reported that Plato occasionally left him in charge of the Academy during his absence.

Heracleides realized that the apparent motion of Mercury and Venus is due to the fact that they revolve around the Sun. He may have realized the same for other planets, although no clear evidence is available to support this. He was the first Greek astronomer to suggest that the Earth rotates around its axis:

"The stars of Hermes and Aphrodite make their retrograde motions and retardations about the rays of the Sun, forming by their courses a wreath or crown with the Sun at its centre."

The idea fell into disrepute amongst astronomers until Tycho Brahe proposed the same model 1800 years later.

Among other scientific concepts Heracleides promoted a form of atomism (the principle that matter is made up of small particles). Only few fragments of his writings remain. They indicate that he had an interest in musicology and also studied psychic phenomena such as trances, cosmological visions and prophecies. He attempted to find a scientific proof for the existence of gods. Reincarnation was also one if his interests.

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