PHY100H5 Lecture Notes - Lecture 1: Pseudoscience, Crop Circle, Deferent And Epicycle
Document Summary
Ancient greeks (pythagoras, 500 bce): sun, moon, 5 visible planets, and the stars are attached to 8 transparent spherical shells centered on earth. Used their own observations to draw this conclusion. However, observations contradicted this: mars shows retrograde (cid:373)otio(cid:374) (cid:894)it"s (cid:374)ot just. This hypothesis predicated that each planet rotated uniformly around earth (cid:373)o(cid:448)i(cid:374)g i(cid:374) circles, it"s (cid:373)o(cid:448)i(cid:374)g at (cid:448)arious rotations at certain times) Ancient greeks (pythagoras, 500 bce): sun, moon, 5 visible planets and the stars are attached to 8 transparent spherical shells centered on earth. This hypothesis predicted that each planet rotates uniformly around the earth. Observations contradicted this: mars shows retrograde motion. The epicycle-deferent theory explained the retrograde motion of the planets and their variable brightness. Epicycle is when something is rotating on its own axis. Deferent is when something is rotating on another axis. When a planet is closest, it appears brightest (on the deferent cycle) and when a planet is.
