Editing Celestial spheres (section)

{{Short description|Elements of some cosmological models}}
{{distinguish|Celestial sphere}}
{{redirect|Heavenly spheres|the album by the Studio de musique ancienne de Montréal|Heavenly Spheres}}
{{Use dmy dates|date=June 2020}}

[[File:Ptolemaicsystem-small.png|upright=1.3|thumb|Geocentric celestial spheres; [[Petrus Apianus|Peter Apian's]] ''Cosmographia'' (Antwerp, 1539)]]

The '''celestial spheres''', or '''celestial orbs''', were the fundamental entities of the [[cosmology|cosmological]] models developed by [[Plato]], [[Eudoxus of Cnidus|Eudoxus]], [[Aristotle]], [[Ptolemy]], [[Copernicus]], and others. In these celestial models, the [[diurnal motion|apparent motions]] of the [[fixed stars]] and [[classical planet|planets]] are accounted for by treating them as embedded in rotating spheres made of an aetherial, transparent fifth element ([[aether (classical element)|quintessence]]), like gems set in orbs. Since it was believed that the fixed stars did not change their positions relative to one another, it was argued that they must be on the surface of a single starry sphere.<ref>Grant, ''Planets, Stars, and Orbs'', p. 440.</ref>