| Johannes Kepler, born 1618, summarised the motions of planets and satellites
of our solar system in three laws
1. Planets and orbiting bodies move in elliptical paths with the sun being at one focus 2. The area swept out in a given time by the radius vector is always constant 3. For orbiting satellites (or planets) of any system, the ration (radius of orbit) ³ / (period) ² is constant for all satellites of that system. Newton's laws confirm this: F = GMm/r ² = m4p ²r / T² r³ / T² = GM / 4p ² This constant depends upon the central mass, and therefore can be used to calculate the speeds of periods of any orbiting satellite of a system. |