"The apparent motions of the planets, until they have been very profoundly analyzed, appear to be irregular and complicated, and not at all such as a Pythagorean Creator would have chosen. It was obvious to every Greek that the heavens ought to exemplify mathematical beauty, which would only be the case if the planets moved in circles. This would be especially evident to Plato, owing to his emphasis on the good. The problem thus arose: is there any hypothesis which would reduce the apparent disorderliness of planetary motions to order and beauty and simplicity? If there is, the idea of the good will justify us in asserting this hypothesis. Aristarchus of Samos found such a hypothesis: that all the planets, including the earth, go round the sun in circles. This view was rejected for two thousand years, partly on the authority of Aristotle, who attributes a rather similar hypothesis to "the Pythagoreans" (De Coelo, 293 a). It was revived by Copernicus, and its success might seem to justify Plato's aesthetic bias in astronomy. Unfortunately, however, Kepler discovered that the planets move in ellipses, not in circles, with the sun at a focus, not at the center; then Newton discovered that they do not move even in exact elipses. And so the geometrical simplicity sought by Plato, and apparently found by Aristarchus of Samos, proved in the end illusory."