Editing Celestial sphere (section)

==History==
{{main|Cosmic pluralism}}
{{see|History of astronomy}}
The ancient Greeks assumed the literal truth of stars attached to a celestial sphere, revolving about the Earth in one day, and a fixed Earth.<ref>
{{cite book
| last          = Seares
| first         = Frederick H.
| title         = Practical Astronomy for Engineers
| url           = https://archive.org/details/ost-engineering-practicalastrono00searuoft
| quote         = practical astronomy.
| date          = 1909
| publisher     = [[E.W. Stephens Publishing Company]], Columbia, MO
| bibcode = 1909pafe.book.....S
}}, art. 2, p. 5, at Google books.</ref> 
The [[Eudoxus of Cnidus#Eudoxan planetary models|Eudoxan planetary model]], on which the Aristotelian and [[Ptolemy|Ptolemaic]] models were based, was the first geometric explanation for the "wandering" of the [[classical planets]].<ref>{{cite web |first=Henry |last=Mendell |url=http://www.calstatela.edu/faculty/hmendel/Ancient%20Mathematics/Eudoxus/Astronomy/EudoxusHomocentricSpheres.htm |title=Eudoxus of Cnidus: Astronomy and Homocentric Spheres |series=Vignettes of Ancient Mathematics |date=16 September 2009 |url-status=dead |archive-url=https://web.archive.org/web/20110516145329/http://www.calstatela.edu/faculty/hmendel/Ancient%20Mathematics/Eudoxus/Astronomy/EudoxusHomocentricSpheres.htm |archive-date=16 May 2011 }}</ref> The outermost of these [[Celestial spheres|"crystal spheres"]] was thought to carry the [[fixed stars]]. Eudoxus used 27 concentric spherical solids to answer [[Plato|Plato's]] challenge: "By the assumption of what uniform and orderly motions can the apparent motions of the planets be accounted for?"<ref>{{cite book |last=Lloyd |first=Geoffrey Ernest Richard |date=1970 |title=Early Greek Science: Thales to Aristotle |isbn=978-0-393-00583-7 |location=New York, NY |publisher=[[W. W. Norton & Co.]] |page=84 |url=https://books.google.com/books?id=Mym7xTLfNfIC }}</ref>
[[Anaxagoras]] in the mid 5th century BC was the first known philosopher to suggest that the stars were "fiery stones" too far away for their heat to be felt. Similar ideas were expressed by [[Aristarchus of Samos]]. However, they did not enter mainstream European and Islamic astronomy of the late ancient and medieval period.
Copernican [[heliocentrism]] did away with the planetary spheres, but it did not necessarily preclude the existence of a sphere for the fixed stars. The first astronomer of the European Renaissance to suggest that the stars were distant suns was [[Giordano Bruno]] in his ''De l'infinito universo et mondi'' (1584). This idea was among the charges, albeit not in a prominent position, brought against him by the Inquisition.
The idea became mainstream in the later 17th century, especially following the publication of ''[[Conversations on the Plurality of Worlds]]'' by [[Bernard Le Bovier de Fontenelle]] (1686), and by the early 18th century it was the default working assumptions in stellar astronomy.