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Next: The Universal Law of Gravitation Up: Kepler Previous: Empiricism

Kepler's Laws of Planetary Motion

1.
ELLIPTICAL ORBITS: The orbits of the planets are10.6 ellipses10.7 with the Sun at one of the foci.
 
2.
CONSTANT AREAL VELOCITY: The area swept out per unit time by a line joining the Sun to the planet in question is constant throughout the orbit.10.8
 
3.
SCALING OF PERIODS: The square of the period  T  of the orbit is proportional to the cube of the length of the semimajor axis (or, in the case of a circular orbit, the radius  r) of the orbit:

\begin{displaymath}T^2 \propto r^3 \end{displaymath}



Jess H. Brewer
1998-10-08