The Development of Geocentric Model of the Earth - Essay Example

In Greek cosmology and cosmogony, historians agree that Ancient Greeks believed that the world began either with the world itself or with some form of primordial chaos that provides all the things that comprise the earth The Greek model for the production of the world is agricultural or architectural. Ancient Greek literature provides a great deal about elements, seeds, raw materials, and geometrical shapes. If the gods are involved in the process of creation at all, they are like farmers who plant seeds and then amuse themselves elsewhere while the seeds sprout on their own. Or else they are like the mind as it seeks mastery over the moving parts of its own body; or like a craftsman who does the best he can with whatever raw materials are available.
The most influential thinker who had the most convincing notions of cosmology before Copernicus was Aristotle (384-322 B.C.). Aristotelian assumptions about the place, space, matter, motion, and time served as the foundation for the Ptolemaic system, which dominated in the West for more than a thousand years. The plainness and unstrained authoritativeness of Aristotle's style may give us a glimpse into the sources, both rhetorical and philosophical, of his authority (Ross, 1930).
Proposing the geocentric model of the universe, Aristotle focused his study on the earth's position, shape, and rest or motion as the center of the universe. His discussion by no means operates in a philosophical vacuum but accounts briefly for other views in competition with his own. The line of argument is instructive for any who have imbibed the old cliché, according to which geocentric cosmology is “said to locate the earth in the place of greatest importance in the universe.”

In Aristotle’s geocentric model of the universe, each planet was attached to a transparent sphere of its own, and all spheres were turning around the earth. But, since this did not account for the irregularities of their motions, such as standing occasionally still and going backward for a while: their "stations" and "retrogressions" assigned to each planet were not one, but several spheres. The planet was attached to a point on the equator of a sphere, which rotates around its axis (Ferris, 1988).
As to earth's position, there is some difference of opinion: among Greeks. Most people, who regard the whole heaven as finite, say it lies at the center. But the Italian philosophers known as Pythagoreans take the contrary view. At the center, they say, is fire, and the earth is one of the stars, creating night and day by its circular motion about the center. There are many others who would agree that it is wrong to give the earth the central position, looking for confirmation rather to theory than to the facts of observation. Their view is that the most precious place befits the most precious thing. But fire, they say, is more precious than earth and the limit than the intermediate, and the circumference and the center are limits. Reasoning on this basis they take the view that it is not earth that lies at the center of the sphere, but rather fire.
In the second century AD, the Egyptian astronomer Claudius Ptolemy extended and refined Aristotle's geocentric model of the Universe. Although Ptolemy removed the aesthetically satisfying symmetry that had commended it to Aristotelians and Platonists alike, it more or less explained the observed planetary motions and was upheld as the greatest guide to the heavens until the Renaissance. However, because of its ungainliness, which disqualified it as a model of Platonic reality, it was regarded as no more than a useful mathematical fiction. Nevertheless, in the spirit of empirical induction, Ptolemy believed that his model reflected what actually existed, and he maintained that if the solution was inelegant, so was the problem (Ferris, 1988).
Ptolemy developed the most sophisticated geocentric ancient astronomical model and tried to show how it could be given a physical realization. He also argued for relatively sophisticated astrology, one immune to the more obvious skeptical counter-arguments. Read More