Volume 16

Visions of the Milky Way in the West: The Greco-Roman and Medieval Periods

Lynda Harris

Abstract

Before the new Greek cosmological system was developed, many ancient cultures had pictured the Milky Way as a vertical axis or tree, which was seen as a route leading into the heavens of a layered universe. This model began to change from about the sixth century BC, when the image of a spherical earth and geocentric universe became increasingly widespread among the educated people of Greece. The new model, standardised by Ptolemy during the second century AD, visualised a universe comprised of eight concentric crystalline spheres surrounding a fixed earth. By the Middle Ages, the Ptolemaic system had become the established picture of the cosmos in Europe and the Islamic world. Losing its old vertical image, the Milky Way was now pictured as a circular band surrounding the spherical earth. Now known as the Milky Circle, it kept something of its earlier religious significance in the pagan world. In Rome it was visualised as a post-mortem place of purification, located below the sphere of the moon. With the establishment of traditional Christianity, the Milky Way’s position became unclear. It had always been a scientific puzzle to thinkers trying to analyse its substance and define its place in the Ptolemaic universe, and its true nature remained unresolved. In one of its most intriguing identities, originated by the thirteenth century astrologer Michael Scot, it migrated to the sphere of the fixed stars where it became a mysterious, living constellation, known as the Daemon Meridianus.