Celestial spheres

Celestial spheres, elements of some cosmological models.

Celestial spheres image

The celestial spheres, or celestial orbs, were the fundamental entities of the cosmological models developed by Plato, Eudoxus, Aristotle, Ptolemy, Copernicus, and others. 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. 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.In modern thought, the orbits of the planets are viewed as the paths of those planets through mostly empty space. Ancient and medieval thinkers, however, considered the celestial orbs to be thick spheres of rarefied matter nested one within the other, each one in complete contact with the sphere above it and the sphere below. When scholars applied Ptolemy's epicycles, they presumed that each planetary sphere was exactly thick enough to accommodate them.

Celestial sphere
6 months ago

Celestial sphere ... In astronomy and navigation, the celestial sphere is an abstract sphere that has an arbitrarily large radius and is concentric to Earth. All objects in...

Aristotelian physics
5 months ago

Aristotelian physics ... the cosmos into concentric spheres, with the Earth at the centre and celestial spheres around it. The terrestrial sphere was made of four elements, namely...

Celestial pole
6 months ago

Celestial pole ... south celestial poles are the two imaginary points in the sky where the Earth's axis of rotation, indefinitely extended, intersects the celestial sphere. The...

De revolutionibus orbium coelestium
6 months ago

De revolutionibus orbium coelestium ... (listen (help·info); English translation: On the Revolutions of the Heavenly Spheres) is the seminal work on the heliocentric theory of the astronomer Nicolaus...

Armillary sphere
6 months ago

Armillary sphere ... armillary sphere (variations are known as spherical astrolabe, armilla, or armil) is a model of objects in the sky (on the celestial sphere), consisting...

Unmoved mover
5 months ago

Unmoved mover ... classical planets arising from uniform circular motions of celestial spheres. While the number of spheres in the model itself was subject to change (47 or 55)...

Astral plane
6 months ago

Astral plane ... esoteric philosophies and mystery religions. It is the world of the celestial spheres, crossed by the soul in its astral body on the way to being born and...

Southern celestial hemisphere
5 months ago

Southern celestial hemisphere ... southern celestial hemisphere, also called the Southern Sky, is the southern half of the celestial sphere; that is, it lies south of the celestial equator...

Atlas (mythology)
6 months ago

Atlas (mythology) ... Earth on his shoulders, but Classical art shows Atlas holding the celestial spheres, not the terrestrial globe; the solidity of the marble globe borne...

Celestial coordinate system
6 months ago

Celestial coordinate system ... In astronomy, a celestial coordinate system (or celestial reference system) is a system for specifying positions of satellites, planets, stars, galaxies...

Zenith
6 months ago
The Celestial Sphere
5 months ago
Celestial
5 months ago
Northern celestial hemisphere
5 months ago
Globe
6 months ago
Christian angelology
6 months ago
Musica universalis
6 months ago
Celestial equator
6 months ago
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