Eudoxus of Cnidus

Eudoxus of Cnidus , 408?-355? BC, Greek astronomer, mathematician, and physician. From the accounts of various ancient writers, he appears to have studied with Plato in Athens, spent some time in Heliopolis, Egypt, founded a school in Cyzicus, and spent his later years in Cnidus, where he had an observatory. It is claimed that he calculated the length of the solar year, indicating a calendar reform like that made later by Julius Caesar, and that he was the discoverer of some parts of geometry included in the work of Euclid. He was the first Greek astronomer to explain the movements of the planets in a scientific manner. His system involved a number of concentric spheres supporting the planets in their paths. Some scientists still held this belief at the time of Copernicus.

Eudoxusof Cnidus (c.400–c.350bc)Greekmathematician and astronomer, born in modern Turkey. He developed a model of planetary motion in which the Sun, Moon, and planets were carried around the Earth on a series of 27 Earth-centred spheres, with axes at different angles and rotating at different speeds. This theory of ‘heavenly spheres’, as modified first by Callippus and ultimately by Ptolemy, remained the orthodox view of the Universe for two thousand years. Eudoxus is also reputed to have introduced the constellation system from Egypt.