M.
Samuel Gessner
(Centro Interuniversitário de História das Ciências e da Tecnologia, Universidade de Lisboa)
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:...
