Aristotle of Athens

384 to 322 BC


The world is made of four elements.
Each has its natural place.


Aristotle's astronomical model is mostly borrowed from Eudoxus.

The earth is at the center of the universe.

Outside the earth are concentric transparent spheres
These are made of "quinta essentia."
They carry the moon, sun and planets.
They rotate at different speeds about different axes -- 55 different motions in total.


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Davison E. Soper, Institute of Theoretical Science, University of Oregon, Eugene OR 97403 USA soper@bovine.uoregon.edu