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A brief history of the Ptolemaic System.

Ptolemaic System
In his Dialogue Concerning the Two Chief World Systems, Ptolemaic and Copernican of 1632, Galileo attacked the world system based on the cosmology of Aristotle (384-322 BCE)and the technical astronomy of Ptolemy (ca. 150 CE).

In his books On the Heavens , and Physics , Aristotle put forward his notion of an ordered universe or cosmos. It was governed by the concept ofplace , as opposed to space, and was divided into two distinct parts, the earthly or sublunary region, and the heavens. Theformer was the abode of change and corruption, where things came into being, grew, matured, decayed, and died; the latter was theregion of perfection, where there was no change. In the sublunary region, substances were made up of the four elements,earth, water, air, and fire. Earth was the heaviest, and its natural place was the center of the cosmos; for that reason theEarth was situated in the center of the cosmos. The natural places of water, air, and fire, were concentric spherical shellsaround the sphere of earth. Things were not arranged perfectly, and therefore areas of land protruded above the water. Objectssought the natural place of the element that predominated in them. Thus stones, in which earth predominated, move down to thecenter of the cosmos, and fire moves straight up. Natural motions were, then, radial, either down or up. The four elementsdiffered from each other only in their qualities. Thus, earth was cold and dry while air was warm and moist. Changing one orboth of its qualities, transmuted one element into another. Such transmutations were going on constantly, adding to the constantchange in this sublunary region.

Ptolemy

The heavens, on the other hand, were made up of an entirely different substance, the aether

The traditional English spelling, aether, is used here to distinguish Aristotle's heavenly substance from the modernchemical substance, ether.
or quintessence (fifth element), an immutable substance. Heavenly bodies were part of spherical shells of aether. Thesespherical shells fit tightly around each other, without any spaces between them, in the following order: Moon, Mercury,Venus, Sun, Mars, Jupiter, Saturn, fixed stars. Each spherical shell (hereafter, simply, sphere) had its particular rotation,that accounted for the motion of the heavenly body contained in it. Outside the sphere of the fixed stars, there was the primemover (himself unmoved), who imparted motion from the outside inward. All motions in the cosmos came ultimately from thisprime mover. The natural motions of heavenly bodies and their spheres was perfectly circular, that is, circular and neitherspeeding up nor slowing down.

It is to be noted about this universe that everything had its natural place, a privileged location for bodies with aparticular makeup, and that the laws of nature were not the same in the heavenly and the earthly regions. Further, there were noempty places or vacua anywhere. Finally, it was finite: beyond the sphere of the fixed stars and the prime mover, there wasnothing, not even space. The cosmos encompassed all existence.

Christian Aristotelian Cosmos. From Peter Apian, Cosmographia

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Source:  OpenStax, Solar system. OpenStax CNX. Jun 29, 2007 Download for free at http://cnx.org/content/col10432/1.1
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