Editing Celestial spheres (section)

===Renaissance===

[[Image:ThomasDiggesmap.JPG|upright=1.2|thumb|Thomas Digges' 1576 Copernican heliocentric model of the celestial orbs]]

Early in the sixteenth century [[Nicolaus Copernicus]] drastically reformed the model of astronomy by displacing the Earth from its central place in favour of the Sun, yet he called his great work ''[[De revolutionibus orbium coelestium]]'' (''On the Revolutions of the Celestial Spheres''). Although Copernicus does not treat the physical nature of the spheres in detail, his few allusions make it clear that, like many of his predecessors, he accepted non-solid celestial spheres.<ref>Nicholas Jardine, "The Significance of the Copernican Orbs", ''Journal for the History of Astronomy,'' 13 (1982): 168–94, pp.&nbsp;177–78.</ref> Copernicus rejected the ninth and tenth spheres, placed the orb of the Moon around the Earth, and moved the Sun from its orb to the center of the [[universe]]. The planetary orbs circled the center of the universe in the following order: Mercury, Venus, the great orb containing the Earth and the orb of the Moon, then the orbs of Mars, Jupiter, and Saturn. Finally he retained the eighth sphere of the [[star]]s, which he held to be stationary.<ref>Hilderich von Varel ([[:de:Edo Hildericus|Edo Hildericus]]), ''Propositiones Cosmographicae de Globi Terreni Dimensione,'' (Frankfurt a. d. Oder, 1576), quoted in Peter Barker and Bernard R. Goldstein, "Realism and Instrumentalism in Sixteenth Century Astronomy: A Reappraisal", ''Perspectives on Science'' 6.3 (1998): 232–58, pp.&nbsp;242–23.</ref>

The English almanac maker, [[Thomas Digges]], delineated the spheres of the new cosmological system in his ''Perfit Description of the Caelestiall Orbes …'' (1576). Here he arranged the "orbes" in the new Copernican order, expanding one sphere to carry "the globe of mortalitye", the Earth, the [[Classical element#Classical elements in Greece|four classical elements]], and the Moon, and expanding the sphere of stars infinitely to encompass all the stars and also to serve as "the court of the Great God, the habitacle of the elect, and of the coelestiall angelles."<ref>Koyre, ''From the Closed World'', pp.&nbsp;28–30.</ref>

[[Image:Kepler Celestial Spheres.jpg|thumb|left|Johannes Kepler's diagram of the celestial spheres, and of the spaces between them, following the opinion of Copernicus (''Mysterium Cosmographicum'', 2nd ed., 1621)]]
In the sixteenth century, a number of philosophers, theologians, and astronomers—among them [[Franciscus Patricius|Francesco Patrizi]], Andrea Cisalpino, [[Petrus Ramus|Peter Ramus]], [[Robert Bellarmine]], [[Giordano Bruno]], [[Jerónimo Muñoz]], [[Michael Neander]], Jean Pena, and [[Christoph Rothmann]]—abandoned the concept of celestial spheres.<ref>Michael A. Granada, "Did Tycho Eliminate the Celestial Spheres before 1586?", ''Journal for the History of Astronomy,'' 37 (2006): 126–45, pp.&nbsp;127–29.</ref> Rothmann argued from observations of the [[comet]] of 1585 that the lack of observed [[parallax]] indicated that the comet was beyond Saturn, while the absence of observed refraction indicated the celestial region was of the same material as air, hence there were no planetary spheres.<ref>Bernard R. Goldstein and Peter Barker, "The Role of Rothmann in the Dissolution of the Celestial Spheres", ''The British Journal for the History of Science'', 28 (1995): 385–403, pp.&nbsp;390–91.</ref>

[[Tycho Brahe]]'s investigations of a series of comets from 1577 to 1585, aided by Rothmann's discussion of the comet of 1585 and [[Michael Maestlin]]'s tabulated distances of the comet of 1577, which passed through the planetary orbs, led Tycho to conclude<ref>Michael A. Granada, "Did Tycho Eliminate the Celestial Spheres before 1586?", ''Journal for the History of Astronomy,'' 37 (2006): 126–45, pp.&nbsp;132–38.</ref> that "the structure of the heavens was very fluid and simple." Tycho opposed his view to that of "very many modern philosophers" who divided the heavens into "various orbs made of hard and impervious matter." Edward Grant found relatively few believers in hard celestial spheres before Copernicus and concluded that the idea first became common sometime between the publication of Copernicus's ''De revolutionibus'' in 1542 and Tycho Brahe's publication of his cometary research in 1588.<ref>Grant, "Celestial Orbs," pp.&nbsp;185–86.</ref><ref>Grant, ''Planets, Stars, and Orbs,'' pp.&nbsp;345–48.</ref>

In his early ''Mysterium Cosmographicum'', [[Johannes Kepler]] considered the distances of the planets and the consequent gaps required between the planetary spheres implied by the Copernican system, which had been noted by his former teacher, Michael Maestlin.<ref>Grasshoff, "Michael Maestlin's Mystery".</ref> Kepler's Platonic cosmology filled the large gaps with the five [[Platonic solid|Platonic polyhedra]], which accounted for the spheres' measured astronomical distance.<ref>Field, ''Kepler's geometric cosmology''.</ref>{{Page needed|date=February 2020}} In Kepler's mature celestial physics, the spheres were regarded as the purely geometric spatial regions containing each planetary orbit rather than as the rotating physical orbs of the earlier Aristotelian celestial physics. The eccentricity of each planet's orbit thereby defined the [[radius|radii]] of the inner and outer limits of its celestial sphere and thus its thickness. In [[Celestial mechanics#Johannes Kepler|Kepler's celestial mechanics]], the cause of planetary motion became the rotating Sun, itself rotated by its own motive soul.<ref>Johannes Kepler, ''Epitome of Copernican Astronomy'', vol. 1, book 4.2.3, pp.&nbsp;514–15 (1630).</ref> However, an immobile stellar sphere was a lasting remnant of physical celestial spheres in Kepler's cosmology.