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Eudoxus_of_Cnidus (c.408 - c.355 BC) was one of the greatest Greek mathematicians. He was also an astronomer, philosopher and legislator.

His main contributions to mathematics were:
  •     the theory of proportions, which resolved the crisis in Greek mathematics caused by the discovery of irrational numbers;
  •     the method_of_exhaustion, which was a precursor (by 2000 years) of the integral calculus.
He may also have been responsible for the development of the axiomatic_method, the foundation of modern mathematics.

His work in astronomy has stood the test of time less well. He developed a model of the universe  which sought to explain the motions of the sun, the moon and the planets by fixing them to a system of 27 (or according to some authorities, 55) concentric spheres. These rotated on assorted axes at various speeds with the earth at the centre. Even with all this ingenuity he was unable to explain the motions of Venus and Mars nor the variation in brightness of the moon. His scheme was a magnificent attempt to explain observed phenomena, but wrong.

More long lasting in their influence were his prose works Phaenomena (Φαινόμενα) and Entropon (Ἔντροπον) about the constellations. These formed the basis of Aratus's poem Phaenomena, through which the names of the constellations have come down to us. We still use them for the signs of the Zodiac. Eudoxus did not invent these, but carried them over from an earlier civilisation, most probably the Babylonians of c. 2500 BC.

Eudoxus (Εὔδοξος) is Greek for "of good repute".

Cnidus, latitude 36º41'N, longitude 27º22'E, was a city on the Western tip of the Datça_peninsula in what is now Turkey. It is close to the Greek islands of Kos and Rhodes and the city of Halicarnassus, where King Mausolus's tomb, the Mausoleum, was one of the seven wonders of the ancient world.