Intro to Planetary Motion.notebook 1 November 13, 2011 Jan 46:51 PM Chapter 7 Gravitation Objectives Relate Kepler's laws of planetary motion to the law of universal gravitation. Calculate orbital speeds and periods Solve orbital motion problems Relate weightlessness to objects in free fall Describe gravitational fields Describe views on gravitation Jan 46:56 PM Activity Follow instructions on page 171 of your textbook. Each of you has a clean sheet of paper, a ruler, and protractor. What shape do you get for the orbital path of Mercury? Jan 47:08 PM Orbital Positions of Planets and Comet Churyumon Gerasimenko Jan 47:10 PM Historical Perspective Ancient Times Planets and Sun believed to revolve around Earth Followed theories of Ptolemy (c. 100 AD) Copernicus (1473 1543) Believed objects revolved around the Sun. Orbits were circular Jan 47:21 PM Tycho Brahe (1546 1601) Believed that the Sun and Moon orbited Earth with everything else orbiting the Sun. Died (murdered?) without proving his theory which was later disproven by his student (killer?), Johannes Kepler. Jan 47:34 PM Johannes Kepler (1571 1630) Assistant to Tycho Brahe Disagreed with Brahe about the orbits of planets Believed Copernicus' heliocentric model Used Brahe's measurements to relate the laws of motion to the planets.