From heliocentrism to epicycles: A commentary on pre-Ptolemaic astronomy

Abstract

If one wants to translate the heliocentric picture of planets moving uniformly on circular orbits about the sun to the perspective of a terrestrial observer, using classical (ancient) geometric means only, one is naturally led to the investigation of epicyclic constructions. The announcement of the heliocentric hypothesis by Aristarchos of Samos and the invention of the method of epicycles happened during the 3rd and 2nd centuries BC. The latter developed into the central tool of Hellenistic and Ptolemaic astronomy. In the present literature on the history of astronomy the parallel rise of the heliocentric view and the methods of epicycles is usually considered as a pure contingency. Here I explain why I do not find this view convincing.