PHYS 183 Lecture Notes - Ellipse, Astronomical Unit
12 Apr 2014
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Document Summary
1 st law: the planets move in ellipse (not circles) The planets move in elliptical orbits with the sun at one focus. The sun-planet distance varies during its orbits but this is not the source of the seasons. A departure from insistence on perfect spheres. 2 nd law: planets sweep out equal areas in equal time. Near perihelion: in any particular amount of time (such as 30 days), a planet sweeps out an area that is short but wide. Near aphelion: in the same amount of time, a planet sweeps out an area that is long but narrow. Planets move faster when closer to the sun, and slower when farther away. 3 rd law: the more distance a planet is from the sun, the slower it moves in its orbits. P^2= a^2 - does indeed hold true, for simplicity, the graph shown only the planets known in kepler"s time.
