1. The motions of the Solar-System bodies were reproduced by the motions of compounded celestial spheres. They turned at constant rates (i.e., uniformly) on offset axes. If you adjusted the rates and axes just right, you qualitatively made the planets, Sun, and Moon in model match the actual angular motions seen in the sky. In fact, the even qualitatively, yours truly thinks Aristotelian cosmology did NOT match the actual motions.

    Note that every point on a celestial sphere executed a uniform circular motion. The motions of the Heavens were made up of compounded uniform circular motions was a principle of Aristotelian cosmology and later epicycle models.

  2. The outermost of the celestial spheres was the celestial sphere of the stars which rotated around the Earth once per day.

  3. Aristotle also postulated a radical distinction between Earth and Heavens. The Heavens were a realm of eternal cyclic motions of perfect bodies.

  4. The celestial spheres and all matter from the Moon's sphere outward were made of the 5th element, aether or quintessence.

  5. The celestial spheres were real, solid objects in Aristotelian cosmology. But they were invisible, and hence have sometimes been called the crystalline spheres.

  6. It's sometimes said that Aristotle used 47 celestial spheres and sometimes 55 celestial spheres. He is just unclear on this point. But 55 seems to be the right number. See Celestial Spheres: Antiquity for NO explanation. See John North 1994, The Norton History of Astronomy and Cosmology, p. 83. for some clarification---but some extra confusion too.

  7. The celestial spheres were kept in motion by unmoved movers or prime movers. Aristotle managed to be ambiguous as to whether there was a single unmoved mover or as many unmoved movers as celestial spheres (see Wikipedia: Unmoved mover: The number of movers).

  8. The outermost celestial sphere was the celestial sphere of the stars on which the stars were pasted.

    Beyond the celestial sphere of the stars was nothing, NOT even empty space---which is something that many people, even dyed-in-the-wool Aristotelians, had a hard time buying.

    So Aristotle thought the universe was a finite sphere. It was also eternal. He had arguments for these theories, but there NOT worth knowing.

  9. As a kinematic description of the celestial motion, Aristotelian cosmology was only very roughly qualitatively valid. It's hopeless to try to make it quantitatively predictive for the writing of ephemerides (tables of predictions of the motions of astronomical objects). Maybe someone tried to make it quantatively predictive, but they couldn't get very far.

  10. Aristotle considered the unmoved movers to be Gods (non-anthropomorphic gods). In later monotheistic versions of Aristotelian cosmology, the unmoved movers were interpreted as angels.

  11. In later Greco-Roman antiquity and then in western Eurasia up until circa year 1600, Aristotelian cosmology become a philosophical dogma for Aristotelians.

    They contended that Aristotelian cosmology was physically correct, but that the actual motions of the Heavens were too complicated to be explained by it. So you needed the Ptolemaic system or the like as calculational devices.

    This is an unhappy compromise in our modern view, but Aristotelians were happy enough with it. Importantly, Nicolaus Copernicus (1473--1543) was NOT happy with the compromise.

  12. Yours truly believes that Aristotelian cosmology was always a pretty bad scientific theory in any time period. It's long vogue is probably partially accidental and partially due to the great authority that Aristotelianism in toto acquired: Aristotelian cosmology was accepted as just part of the package.

  13. Remarkably, Aristotelian cosmology has a similarity to our modern concept of the observable universe.

    The observable universe is geocentric: it's a really big sphere centered on us.

    Beyond the observable universe is NOT nothing: it's probably much like the observable universe for a long way, but probably NOT to infinity. But we are phyiscally detached from that "beyond" and cannot observe it though we can understand it theoretically.

    So Aristotle was right---a little bit.