Born c.190 BCE in Nicæa in Bithynia (in modern-day Turkey), he died on the Greek island of Rhodes c.120 BCE. An influential scientist of the Hellenistic period, perhaps the greatest astronomer of antiquity, he developed geometry, trigonometry and arithmetic; his accurate measurements of the Sun and Moon led to a precise calculation of the length of the year and a method of predicting eclipses which was unsurpassed in ancient times. His remarkable star catalogue, based on Chaldean tables, was employed by Ptolemy, some 300 years later. His most famous discovery was the precession of the equinoxes, although the phenomenon was known much earlier to initiates, as evidenced by the orientation of the pyramids and other early indicators.