CAS AS 101 Lecture Notes - Lecture 3: Ellipse, Science Daily, Orbital Period

• School: Boston University
• Department: Astronomy
• Course: CAS AS 101
• Professor: Catherine Espaillat

Document Summary

Earth is the center of the universe. The most sophisticated geocentric model was that of ptolemy the ptolemaic model. Sufficiently accurate to remain in use for 1,500 years. Explained retrograde motion as the planets actually going backwards in space. Each planet moved on a small circle whose center moved around earth on a larger circle. Copernicus proposed the sun-centered model in 1543. Incorrect because it used perfect circles for the orbitals. Tycho composed the most accurate naked eye measurements ever made of planetary positions. Still couldn"t detect stellar paralla(cid:454) and thought earth (cid:449)as still the center of the uni(cid:448)erse but acknowledged that other planets orbit the sun. Kepler"s first la(cid:449) the orbit of each planet around the sun is an ellipse with the sun at one focus. Kepler"s second la(cid:449) as a planet moves around its orbit, it sweeps out equal areas in equal times.