Saving the Appearances

Strict Aristotelian cosmology follows that all bodies are made of the four elements: earth, water, air, and fire. These four exist in the terrestrial realm and the stars exist in the celestial realm. A fifth element, aether, exists there and that is what heavenly bodies are composed of. Aristotle provided the basics of the physics that would be proven about the universe without any qualitative information. For Aristotle, the universe is not infinite in size and could be measured. Besides the up-down, back-forward, and left-right movement, there is an eternal time frame that moves in circular motion swiftly encompassing the bodies of the fundamental elements and the objects they compose. Hipparchus used two motion orbit to calculate the precession periods caused by the sidereal and solar year. He used the basis of Aristotle’s proof that the universe is a circle and can be measured using geometry with the understanding that the circumference would be twenty- four hours, the earth’s orbit. On the other hand, Ptolemy preferred the simple single model. Ptolemy was able to create models of the planets based on these descriptions of the physical universe. His calculations took into consideration that there did not exist any vacuums between the spheres so all measurements were consecutive. He enlarged Aristotle’s ideas and made the correction that the equant, the circle proposed to surround the earth, is off-center. It still would have the constant speed and angular motion that it was believed to have. The use of Aristotle’s cosmology lies in its common-sense appeal that wasn’t proven wrong for over a thousand years.

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