The circle and its spatial realization as a sphere are the most venerable images of perfection in numerous eastern and western civilizations. In the Christian Middle Ages their ultimate theological expression was the paradoxical definition of God as an infinite circle or sphere whose center is everywhere and whose circumference is nowhere. In poetry as well, from Dante's Divine Comedy to Milton's Paradise Lost the circle served as an archetype of perfection; circular motion was a recurrent image of divine harmony; and the sphere, rotating, was conceived of as the most perfect three-dimensional shape, combining change and changelessness.1 The cosmos itself was a perfect sphere, encompassing within itself concentric transparent spheres, each revolving at its own speed about the earth at the center. This cosmic circular motion,