In this book, Daniel Graham argues against the prevalent belief that the Presocratic philosophers did not produce any empirical science and that the first major Greek science, astronomy, did not develop until at least the time of Plato. Instead, Graham proposes that the advances made by Presocratic philosophers in the study of astronomy deserve to be considered as scientific contributions. Whereas philosophers of the sixth century BC treated astronomical phenomena as ephemeral events continuous with weather processes, those of the fifth century treated heavenly bodies as independent stony masses whirled in a cosmic vortex. Two historic events help to date and account for the change: a solar eclipse in 478 BC and a meteoroid that fell to earth around 466. Both events influenced Anaxagoras, who transformed insights from Parmenides into explanations of lunar and solar eclipses, meteors, and rainbows. Virtually all philosophers came to accept Anaxagoras' theory of lunar light and eclipses.