Aristotle :: essays research papers

To the modern reader, Aristotles views on astronomy, as presented in Metaphysics, Physics, De Caelo (On the Heavens) and Simplicius Commentary, will virtually likely seem very bizarre, as they are based more on a priori philosophical speculation than empirical observation. Although Aristotle acknowledged the importance of "scientific" astronomy - the study of the positions, distances and motions of the stars - he nevertheless treated astronomy in the abstract, linking it to his overall philosophical world picture. As a result, the modern distinction between physics and metaphysics is not present in Aristotle, and in order to full appreciate him we must try to abandon this pre-conception. Aristotle argued that the universe is spherical and finite. Spherical, because that is the most perfect shape finite, because it has a center, viz. the center of the earth, and a body with a center cannot be infinite. He believed that the earth, too, is a sphere. It is relatively small com pared to the stars, and in contrast to the celestial bodies, always at rest. For one of his proofs of this latter point, he referred to an through empirical observation testable fact if the earth were in motion, an observer on it would see the fixed stars as moving, just as he now observes the planets as moving, that is from a stationary earth. However, since this is not the case, the earth must be at rest. To prove that the earth is a sphere, he produced the argument that all earthly substances move towards the center, and thus would last have to form a sphere. He also used evidence based on observation. If the earth were not spherical, lunar eclipses would not show segments with a curved outline. Furthermore, when one travels northward or southward, one does not see the same stars at night, nor do they occupy the same positions in the sky. (De Caelo, Book II, chapter 14) That the celestial bodies must also be spherical in shape, can be determined by observation. In the case of t he stars, Aristotle argued that they would have to be spherical, as this shape, which is the most perfect, allows them to retain their positions. (De Caelo, Book II, chapter 11) By Aristotles time, Empedocles view that there are four basic elements - earth, air, fire and water - had been generally accepted. Aristotle, however, in addition to this, postulated a ordinal element called aether, which he believed to be the main constituent of the celestial bodies.