ASTR 101 1st edition Lecture 7 Outline of Last Lecture I Ancient Greek science II Copernican revolution Outline of Current Lecture I Key people involved in Copernican revolution II Earth centered model Current Lecture chapter 3 continued I II 3 key people involved in Copernican revolution a Tycho there is a supernova named after him b Kepler a student of Tycho c Galileo the Earth isn t stationary but is moving around the Sun just like all the other planets Earth centered model a Although Brahe compiled much data he didn t detect parallex He thought the Earth wasn t moving but maybe the other planets were Kelper was able to detect parallex Kepler knew that the Sun was in one of the focuses and he realized that the orbits were imperfect circles He broke the symmetry b Keplers 3 laws i The orbit of each planet around the Sun is an ellipse with the Sun at one focus A circle is a special kind of ellipse with the two foci on the same spot ii If the planet is further away from the Sun it will move slower closer to the Sun a planet will move faster iii P2 a3 p orbital period a average distance from the Sun in AU p 1 year 2 a 1 AU 3 It takes longer for more distant planets to orbit the Sun Orbital period is proportional to the size of the orbit and the speed of motion of the planet will be slower c Objections i Galileo s experiment showed that an object in motion stays in motion unless some other force is applied newton s first law of motion Venus orbits the Sun and not the Earth These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute ii Tycho discovered a supernova And Galileo used a telescope to observe the sky He found sunspots it s imperfect And he also found that the moon is not perfect