Mechanical astronomy: A route to the ancient discovery of epicycles and eccentrics

Abstract

The ancient Greek art of sphairopofia was devoted to the building of models of the universe such as celestial globes and annillary spheres. But it also included the construction of geared mechanisms that replicated the motions of the Sun, Moon, and planets, such as the famous orrery that Cicero attributed to Archimedes or the spectacular Antikythera mechanism, found in an ancient shipwreck of about 60 BC. Was sphairopoi"ia merely an imitative art, in which the modelers followed the precepts of the theoretical astronomers? Or could theoretical astronomy also learn something from the art of mechanics? In this paper, we examine the relation of astronomy to mechanics in the ancient Greek world, and argue that we should imagine astronomy and mechanics in conversation with one another, rather than in a simple, one-way transmission of influence.