Beginning of Essay
To the modern reader, 's views on astronomy, as presented in Metaphysics, Physics, De Caelo (On the Heavens) and Simplicius' Commentary, will most likely seem very bizarre, as they are based more on a priori philosophical speculation than empirical observation. Al ....

Middle of Essay
.... 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 sout ....