Greek mathematician and astronomer. He devised the first system to account for the motions of celestial bodies, believing them to be carried around the Earth on sets of spheres. Work attributed to Eudoxus includes methods to calculate the area of a circle and to derive the volume of a pyramid or a cone.
Probably Eudoxus regarded the celestial spheres as a mathematical device for ease of computation rather than as physically real, but the idea was taken up by Aristotle and became entrenched in astronomical thought until the time of Tycho Brahe.
In mathematics Eudoxus' early success was in the removal of many of the limitations imposed by Pythagoras on the theory of proportion. Eudoxus also established a test for the equality of two ratios.
The model of planetary motion was published in a book called On Rates. Further astronomical observations were included in two other works, The Mirror and Phaenomena, providing the basis of the constellation system still in use today. In a series of geographical books with the overall title of A Tour of the Earth, Eudoxus described the political, historical, and religious customs of the countries of the E Mediterranean.