User:Ignis centralis/Celestial sphere

Greek History on Celestial spheres
Celestial Spheres (or celestial orbs) were envisioned to be perfect and divine entities initially from Greek astronomers such as Aristotle (384 B.C to 322 B.C). The Greek philosopher, Aristotle, composed a set of principles called Aristotelian physics that outlined the natural order and structure of the world. With Aristotle's adoption of Eudoxus' theory, Aristotle had described celestial bodies within the Celestial sphere to be filled with pureness, perfect and quintessence (the fifth element that was known to be divine and purity according to Aristotle). Significantly, Aristotle deemed the Sun, Moon, planets and the fixed stars to be perfectly concentric spheres that is divided into two regions; the sublunary region, and the superlunary region Aristotle had asserted that these bodies (in the superlunary region) are perfect and cannot be corrupted by any of the four elements; fire, water, air, and earth. Corruptible elements were only contained in the sublunary region and incorruptible elements were in the superlunary region of Aristotle's geocentric model. Aristotle had the notion the behavior of celestial orbs must move in celestial motion (a perfect circular motion) that goes on for eternity. He also argued that the behavior and property follows strictly to a principle of natural place where the quintessence element only moves freely of divine will while other elements; fire, air, water and earth are corruptible to change and imperfection. . Aristotle's key concepts rely on the nature of the five elements distinguishing the Earth and the Heavens in the astronomical reality with applying Eudoxus' model to define the spheres to be physically real.

Numerous discoveries from Aristotle and Eudoxus (approximately 395 B.C. to 337 B.C.) have sparked differences in both of their models and sharing similar properties simultaneously. Aristotle and Eudoxus claimed two different counts of spheres in the heavens. According to Eudoxus, there were only 27 spheres in the heavens while there are 55 spheres in Aristotle's model. Eudoxus attempts to mathematically construct his model from a treatise known as On the velocities (translated from Greek to English) and asserted the shape of the hippopede or lemniscate to be associated with the planetary retrogression. Aristotle emphasized the speed of the celestial orbs are unchanging like the heavens while Eudoxus emphasizes that the orbs are in a perfect geometrical shape. Eudoxus 's spheres would produce undesirable motions to the lower region of the planets while Aristotle introduced unrollers between each set of active spheres to counteract the motions of the outer set, or else the outer motions will be transferred to the outer planets.

Aside from Aristotle and Eudoxus, Empedocles gives an explanation that the motion of the heavens, moving about it a divine (relatively high) speed that puts Earth in a stationary position due to the circular motion preventing the downward movement from natural causes. Aristotle criticized Empedocles' case as he argued that all heavy objects go towards Earth and not the whirl itself coming to Earth. He ridiculed and claimed the Empedocles' statement to be extremely absurd. Anything that defies the motion of natural place and the unchanging heavens (including the celestial spheres would be immediately be criticized from Aristotle).