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Visualization of a 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 the sky can be conceived as being projected upon the inner surface of the celestial sphere, which may be centered on Earth or the observer.
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 ...
The celestial sphere is conventionally divided into designated areas called constellations. Usually, the term sky informally refers to a perspective from the Earth's surface; however, the meaning and usage can vary.
Coordinate systems in astronomy can specify an object's relative position in three-dimensional space or plot merely by its direction on a celestial sphere, if the object's distance is unknown or trivial. Spherical coordinates, projected on the celestial sphere, are analogous to the geographic coordinate system used on the surface of Earth.
Thomas Aquinas (c. 1225 –1274), following Avicenna, interpreted Aristotle to mean that there were two immaterial substances responsible for the motion of each celestial sphere, a soul that was an integral part of its sphere, and an intelligence that was separate from its sphere. The soul shares the motion of its sphere and causes the sphere ...
The Quran and Hadith frequently mention the existence of seven samāwāt (سماوات), the plural of samāʾ (سماء), meaning 'heaven, sky, celestial sphere', and cognate with Hebrew shamāyim (שמים). Some of the verses in the Quran mentioning the samaawat [21] are Q41:12, Q65:12 and Q71:15.
The zenith (UK: / ˈ z ɛ n ɪ θ /, US: / ˈ z iː n ɪ θ /) [1] [2] is the imaginary point on the celestial sphere directly "above" a particular location. "Above" means in the vertical direction opposite to the gravity direction at that location . The zenith is the "highest" point on the celestial sphere.
The 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. This arbitrary sphere, on which seemingly fixed stars form constellations , appears to rotate westward around a polar axis as the Earth rotates .