Celestial spheres

celestial sphereplanetary spherescelestialthe universespherespherescelestial orbsconcentric heavensheavenly sphereHeavenly Spheres
The celestial spheres, or celestial orbs, were the fundamental entities of the cosmological models developed by Plato, Eudoxus, Aristotle, Ptolemy, Copernicus, and others.wikipedia
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Orbit

orbitsorbital motionplanetary motion
In modern thought, the orbits of the planets are viewed as the paths of those planets through mostly empty space.
Historically, the apparent motions of the planets were described by European and Arabic philosophers using the idea of celestial spheres.

Fixed stars

fixed starfixedstars
In these celestial models, the apparent motions of the fixed stars and planets are accounted for by treating them as embedded in rotating spheres made of an aetherial, transparent fifth element (quintessence), like jewels set in orbs.
In Ancient Greek astronomy, the fixed stars were believed to exist on a giant celestial sphere, or firmament, that revolves daily around Earth.

Aristotle

AristotelianAristotelesAristote
The celestial spheres, or celestial orbs, were the fundamental entities of the cosmological models developed by Plato, Eudoxus, Aristotle, Ptolemy, Copernicus, and others.
Aristotle's scheme added the heavenly Aether, the divine substance of the heavenly spheres, stars and planets.

Scientific Revolution

scientificscientific revolutionsscience
Mainstream belief in the theory of celestial spheres did not survive the Scientific Revolution.

Concentric spheres

concentricastronomical globehomocentric spheres
Instead of bands, Plato's student Eudoxus developed a planetary model using concentric spheres for all the planets, with three spheres each for his models of the Moon and the Sun and four each for the models of the other five planets, thus making 26 spheres in all.
The cosmological model of concentric or homocentric spheres, developed by Eudoxus, Callippus, and Aristotle, employed celestial spheres all centered on the Earth.

Cosmology

cosmologistcosmologicalcosmologies
The celestial spheres, or celestial orbs, were the fundamental entities of the cosmological models developed by Plato, Eudoxus, Aristotle, Ptolemy, Copernicus, and others.

Sphere of fire

All these wheel rims had originally been formed out of an original sphere of fire wholly encompassing the Earth, which had disintegrated into many individual rings.
The Middle Ages broadly inherited the concept of the four elements of earth, water, air and fire arranged in concentric spheres about the earth as centre: as the purest of the four elements, fire - and the sphere of fire - stood highest in the ascending sequence of the scala naturae, and closest to the superlunary world of the aether.

Anaximander

Anaximander of MiletusAnaximandrosἈναξίμανδρος
In Greek antiquity the ideas of celestial spheres and rings first appeared in the cosmology of Anaximander in the early 6th century BC.
Furthermore, according to Diogenes Laertius (II, 2), he built a celestial sphere.

Unmoved mover

first causeprime moverPrimum movens
Each of these concentric spheres is moved by its own god—an unchanging divine unmoved mover, and who moves its sphere simply by virtue of being loved by it. The outermost moving sphere, which moved with the daily motion affecting all subordinate spheres, was moved by an unmoved mover, the Prime Mover, who was identified with God.
Aristotle adopted the geometrical model of Eudoxus of Cnidus, to provide a general explanation of the apparent wandering of the classical planets arising from uniform circular motions of celestial spheres.

Aether (classical element)

aetheretherquintessence
In these celestial models, the apparent motions of the fixed stars and planets are accounted for by treating them as embedded in rotating spheres made of an aetherial, transparent fifth element (quintessence), like jewels set in orbs.

Universe

physical worldThe Universeuniverses
The nested sphere model's distances to the Sun and planets differ significantly from modern measurements of the distances, and the size of the universe is now known to be inconceivably large and continuously expanding.
According to Aristotle's physical interpretation of the model, celestial spheres eternally rotate with uniform motion around a stationary Earth.

Almagest

cataloghis book on astronomyMagna Syntaxis
In his Almagest, the astronomer Ptolemy (fl.
Ptolemy assigned the following order to the planetary spheres, beginning with the innermost:

Empyrean

Empyrean Heavenempyrean fireheavenly sphere
Christian and Muslim philosophers modified Ptolemy's system to include an unmoved outermost region, the empyrean heaven, which came to be identified as the dwelling place of God and all the elect.
In ancient cosmologies, the Empyrean Heaven, or simply the Empyrean, was the place in the highest heaven, which was supposed to be occupied by the element of fire (or aether in Aristotle's natural philosophy).

Nicolaus Copernicus

CopernicusCopernicanNicholas Copernicus
The celestial spheres, or celestial orbs, were the fundamental entities of the cosmological models developed by Plato, Eudoxus, Aristotle, Ptolemy, Copernicus, and others.
Nicolaus Copernicus (Mikołaj Kopernik; Nikolaus Kopernikus; Niklas Koppernigk; 19 February 1473 – 24 May 1543) was a Renaissance-era polymath who formulated a model of the universe that placed the Sun rather than Earth at the center of the universe, in all likelihood independently of Aristarchus of Samos, who had formulated such a model some eighteen centuries earlier.

Classical planet

classical planetsplanetsnaked eye planets
In these celestial models, the apparent motions of the fixed stars and planets are accounted for by treating them as embedded in rotating spheres made of an aetherial, transparent fifth element (quintessence), like jewels set in orbs.

Primum Mobile

dodecatemorymovedoutermost moving sphere
The outermost moving sphere, which moved with the daily motion affecting all subordinate spheres, was moved by an unmoved mover, the Prime Mover, who was identified with God.
In classical, medieval, and Renaissance astronomy, the Primum Mobile (or "first moved") was the outermost moving sphere in the geocentric model of the universe.

Tycho Brahe

BraheTychoTyge Brahe
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 that "the structure of the heavens was very fluid and simple."
Using similar measurements, he showed that comets were also not atmospheric phenomena, as previously thought, and must pass through the supposedly immutable celestial spheres.

Cosmological argument

Prime Movercosmologicalfirst cause
The outermost moving sphere, which moved with the daily motion affecting all subordinate spheres, was moved by an unmoved mover, the Prime Mover, who was identified with God.
From an "aspiration or desire", the celestial spheres, imitate that purely intellectual activity as best they can, by uniform circular motion.

Johannes Kepler

KeplerDioptriceJohan Kepler
In Johannes Kepler's early Mysterium cosmographicum, he 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.
He found that each of the five Platonic solids could be inscribed and circumscribed by spherical orbs; nesting these solids, each encased in a sphere, within one another would produce six layers, corresponding to the six known planets—Mercury, Venus, Earth, Mars, Jupiter, and Saturn.

Firmament

star designvault of heavenWelkin
Medieval Christians identified the sphere of stars with the Biblical firmament and sometimes posited an invisible layer of water above the firmament, to accord with Genesis.
The Greeks and Stoics adopted a model of celestial spheres after the discovery of the spherical Earth in the 4th to 3rd centuries BCE.

Paradiso (Dante)

ParadisoParadiseDante's ''Paradiso
Near the beginning of the fourteenth century Dante, in the Paradiso of his Divine Comedy, described God as a light at the center of the cosmos.
After ascending through the sphere of fire believed to exist in the earth's upper atmosphere (Canto I), Beatrice guides Dante through the nine celestial spheres of Heaven, to the Empyrean, which is the abode of God.

Somnium Scipionis

Dream of ScipioCicero's Dream of ScipioCicero's eponymous classical text
In Cicero's Dream of Scipio, the elder Scipio Africanus describes an ascent through the celestial spheres, compared to which the Earth and the Roman Empire dwindle into insignificance.
Then, Scipio Aemilianus sees that the universe is made up of nine celestial spheres.

Nicole Oresme

OresmeNicholas OresmeNicolas d'Oresme
Later in the century, the illuminator of Nicole Oresme's Le livre du Ciel et du Monde, a translation of and commentary on Aristotle's De caelo produced for Oresme's patron, King Charles V, employed the same motif.
From astronomical considerations, he maintained that if the Earth were moving and not the celestial spheres, all the movements that we see in the heavens that are computed by the astronomers would appear exactly the same as if the spheres were rotating around the Earth.

Giordano Bruno

BrunoBruno, GiordanoBruno's cosmology
In the course of the sixteenth century, a number of philosophers, theologians, and astronomers—among them Francesco Patrizi, Andrea Cisalpino, Peter Ramus, Robert Bellarmine, Giordano Bruno, Jerónimo Muñoz, Michael Neander, Jean Pena, and Christoph Rothmann—abandoned the concept of celestial spheres.
The ultimate limit of the universe was the primum mobile, whose diurnal rotation was conferred upon it by a transcendental God, not part of the universe (although, as the kingdom of heaven, adjacent to it ), a motionless prime mover and first cause.

Divine Comedy

The Divine ComedyInfernoDivina Commedia
Near the beginning of the fourteenth century Dante, in the Paradiso of his Divine Comedy, described God as a light at the center of the cosmos.
After an initial ascension, Beatrice guides Dante through the nine celestial spheres of Heaven.