What was Aristotle's view of the universe?

Answer 1

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 compared 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 empirically 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 eventually 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. That the celestial bodies must also be spherical in shape, can be determined by observation. In the case of the stars, Aristotle argued that they would have to be spherical, as this shape, which is the most perfect, allows them to retain their positions.

Aristotle, like Eudoxus and Callippus before him, believed that each planet followed the path laid out by a certain number of spheres. Callippus had postulated 33 spheres in all, 4 each for Saturn and Jupiter, 5 each for Mars, Venus, Mercury, the sun and the moon. The problem with this model, however, was that, according to Aristotle, it did not explain how the motion of the outer spheres was to be prevented from interfering with the motion of the inner spheres. Aristotle therefore attempted a mechanical explanation, and postulated 22 counteracting spheres, which would set things in balance. It is generally held that Aristotle's addition of these counteracting spheres complicated rather than cleared up the problem of planetary motion.

Answer 2

Aristotle believed in a geocentric view of the universe, with the Earth at the center and celestial bodies moving in perfect circular orbits around it. He thought the universe was finite and spherical, with a series of concentric spheres surrounding the Earth containing the sun, moon, planets, and stars.