ASTRO 1 Lecture 30: 30
Document Summary
Retrograde motion: ancient greeks thought other planets moved around part, because of retrograde motion (the loop in the trail of the planets), they said planets moved in circles wishing the circle. Copernican revolution: copernicus came up with heliocentric model of solar system(sun at center, because earth is moving faster than mars, as earth passes mars it looks like retrograde motion. Kepler"s laws of planetary motion: kepler"s rst law. The orbit of a planet about the sun is an ellipse with the sun at one focus: kepler"s second law. A line joining a planet and the sun sweeps out equal areas in equal intervals of time: the closer a plant goes to the sun, the faster its angular speed is. Kepler"s third law: p^3 = a^3 for each of the planets. Signi cance of kepler"s laws: could describe motion of planets more accurately than any scheme before, simpler than bicycles, helped justify heliocentricity.
