Page "Ancient Greece" Paragraph 63

The Greeks developed astronomy, which they treated as a branch of mathematics, to a highly sophisticated level.

The first geometrical, three-dimensional models to explain the apparent motion of the planets were developed in the 4th century BC by Eudoxus of Cnidus and Callippus of Cyzicus.

Their younger contemporary Heraclides Ponticus proposed that the Earth rotates around its axis.

In the 3rd century BC Aristarchus of Samos was the first to suggest a heliocentric system, although only fragmentary descriptions of his idea survive.

Eratosthenes, using the angles of shadows created at widely separated regions, estimated the circumference of the Earth with great accuracy.

In the 2nd century BC Hipparchus of Nicea made a number of contributions, including the first measurement of precession and the compilation of the first star catalog in which he proposed the modern system of apparent magnitudes.