PHY 102 1nd Edition Lecture 4 Outline of Last Lecture I Blue Book 1 1 2 4 II The Age of Measurement continued III Mallard IV Blue Book 1 2 2 4 Outline of Current Lecture I Copernican Revolution II Two competing theories III Brahe IV Kepler V Blue Book 2 2 1 Current Lecture I Copernican Revolution a 1800 years after Aristarchus his idea of heliocentrism was revived by Nicolaus Copernicus i Afraid to publish his theory because earth wasn t at the center of the universe b Copernicus finding the geocentric model too complicated placed the sun at the center with planets and earth moving around it on circles with uniform motion c Complicated or not the geocentric model is the only alternative if the heliocentric model cannot explain all the phenomena that the geocentric model can 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 III IV V i Indeed heliocentric model explains all the phenomena that the geocentric model does With the re invention of the heliocentric model there were two competing theories of the cosmos geocentric and heliocentric a Which one is correct i Which one agreed with observation 1 BOTH until New and very precise observations were made by Tycho Brahe a Proved geocentric and heliocentric theories wrong i Choose the better theory and improve on it Johannes Kepler a Through a very careful and painstaking mathematical analysis of Mars Kepler found the key to a successful correction to the heliocentric model b Kepler s laws of planetary motion three laws that govern the motion of planets around the sun i First Law 1 Each planet moves on an ellipse with the sun at on of its foci ii Second Law 1 The planet sweeps equal areas in equal time intervals 2 Planet moves faster when closer to the sun iii Third Law 1 T2 ka3 or T1 T2 2 a1 a2 3 a Where T is period and a is the semi major axis b T measured in seconds c a measured in meters Blue Book 2 2 1
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