Medieval Geocentric Cosmology

Write a schematic overview of the Aristotelian-Ptolomaic medieval worldview, starting from the innermost layer of the earth onwards up to the highest aethereal realm

The Aristotelian-Ptolemaic medieval worldview represents an integration of the philosophies of Aristotle and the astronomical theories of Claudius Ptolemy. This geocentric model was prevalent throughout much of the Middle Ages, and it explained both the structure of the universe and the metaphysical principles that governed it. Here is a schematic overview, from the innermost layer of the Earth to the highest ethereal realm:

1. Sublunary Sphere - This is the realm of Earth and includes everything under the moon. It is composed of the four classical elements, and it is where change and corruption occur.

   • Earth: The innermost layer is the Earth itself, at the center of the universe. It is made of the element earth, which is cold and dry.
   • Water: Surrounding the earth is the water, the cold and wet element.
   • Air: Above water is the air, which is hot and wet.
   • Fire: The outermost layer of the sublunary sphere is fire, which is hot and dry.

2. Celestial Spheres - Beyond the sublunary sphere, the celestial realm is where the heavenly bodies reside, and it is made of aether, a divine and incorruptible substance. These spheres move in perfect, eternal circles.

   • The Sphere of the Moon: The first celestial sphere, housing the Moon.
   • The Sphere of Mercury: The second celestial sphere, where Mercury resides.
   • The Sphere of Venus: The third celestial sphere, containing Venus.
   • The Sphere of the Sun: The fourth celestial sphere, home to the Sun.
   • The Sphere of Mars: The fifth celestial sphere, housing Mars.
   • The Sphere of Jupiter: The sixth celestial sphere, where Jupiter resides.
   • The Sphere of Saturn: The seventh celestial sphere, containing Saturn.

3. Spheres of the Fixed Stars - Beyond the spheres of the planets are the spheres of fixed stars.

   • The Firmament: The eighth sphere, containing the fixed stars.
   • The Crystalline Sphere (or Primum Mobile): This ninth sphere imparts motion to the others, governing their movements.

4. The Empyrean - The outermost boundary of the universe, beyond the physical and often identified with the divine. In some interpretations, it is the dwelling place of God and the blessed, a realm of pure light, or pure actuality.

The Aristotelian-Ptolemaic model provided a unified understanding of the cosmos, incorporating the physics, metaphysics, and cosmology of its time. Though eventually supplanted by the heliocentric model of Copernicus and refined by Kepler and Galileo, the geocentric model remains an important symbol of the medieval worldview.