PHYS 1000 Lecture Notes - Lecture 1: Deferent And Epicycle, Orbital Period, Ellipse
12 Feb 2018
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Ancient civilizations observed the skies useful for tracking planting/growing seasons. Many built structures to mark astronomical events such as the stonehenge. The earliest models of the solar system were geocentric. They assumed earth was at the center of the universe. The sun, moon and stars all have simple movements in the sky, consistent with and earth- centered system. Have both prograde (eastward) and retrograde (westward and backward) motion. A basic geocentric model, showing an epicycle (used to explain planetary motions). Lots of epicycles (cid:449)e(cid:396)e (cid:374)eeded to a(cid:272)(cid:272)u(cid:396)atel(cid:455) t(cid:396)a(cid:272)k pla(cid:374)eta(cid:396)(cid:455) (cid:373)otio(cid:374)s, espe(cid:272)iall(cid:455) (cid:396)et(cid:396)og(cid:396)ade (cid:373)otio(cid:374)s. this is ptole(cid:373)(cid:455)"s model. There were early astronomers who argues against this model. A heliocentric (sun-centered) model of the solar system easily describes the observed motions of the planets, without the excess complication. The realization that earth is not at the center of the universe is known as the copernican revolution (his model originally had epicycles).
