Orateur
Description
Since antiquity astronomers have known that the ecliptic longitude of the fixed stars slowly changes. The stars were considered to be fixed on one sphere, traditionally called the Eighth Sphere. That its slow and apparently intricate motion was still discussed in the fifteenth and sixteenth centuries is attested by various surviving documents. These include an astonishing variety of media: written treatises, numerical tables, diagrams, and two- and three-dimensional mathematical instruments. Although the context of production of these sources is hard to reconstruct, their sheer variety offers a notion of the intermedial space of the debate on the Eighth Sphere. It allows surmising that the debate involved circles beyond students and scholars and encompassed conversations among humanists, instrument makers, publishers, and princes with their courtiers. Recent research has clarified the meaning of a complex brass armillary sphere by connecting it with J. Werner’s 1522 treatise about an alternative theory of trepidation. It appeared that those ideas, although dismissed by N. Copernicus, echoed during their time crossing the boundary between the medium of text and instrument. To uncover further strands of the Eighth-Sphere discussion, an armillary from 1575, preserved in Brussels, will be in the focus of this paper. This is one of a series of lavish brass spheres made at the Louvain workshop of G. Arsenius, and shows troubling, hitherto inexplicable details. It exposes the perplexities that arise when the historian confronts an astronomical topic that permeates various media and demands an intermedial study.
