PHIL 160D3 Lecture Notes - Lecture 10: Middle Ages, Equant, Deferent And Epicycle

• School: University of Arizona
• Department: Philosophy Main
• Course: PHIL 160D3
• Professor: Marc Johansen

Document Summary

The astronomical data movement of the stars. The stars move through the course of the night. They move at the same rate as the sun: one rotation every 24 hours. Daily motion is with the stars (24 hours) Seasonal motion is through the stars (1 year) Equinoxes establish the length of the year. Motion through the stars: about 27-day period. Distinguishing planets from stars: planets move slowly through the stars, retrograde motion (planets are brighter when in retrograde) Mercury and venus are always close to the sun. Orbits do not occur at exact intervals. The perfect circle fact: heavenly bodies move in perfect circles. The uniform motion fact: the motion of the heavenly bodies is uniform. Principle of inertia (newton): objects in motion remain in motion. Pre-(cid:1005)6(cid:1004)(cid:1004)"s pri(cid:374)(cid:272)iple of (cid:373)otio(cid:374): o(cid:271)je(cid:272)ts i(cid:374) (cid:373)otio(cid:374) (cid:272)o(cid:373)e to rest u(cid:374)less so(cid:373)ethi(cid:374)g keeps them moving. Problem: the stars and planets have always moved. Solution: heavenly bodies are made of a different element: ether.