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Using observational data, Johannes Kepler (1571 - 1630) formed three laws
of planetary motion. These were later proven by Isaac Newton, through
the concept of gravitational force. Keplers first law stated that
each planetís orbit is an ellipse with the sun at one focus. In fact,
this is the case for all orbital motion about its center of mass: it travels
in one plane in the shape of an ellipse.
Now, this may sound too simple; and in fact, that is true. This motion
only considers the mutual force between the orbiting body (satellite) and
the planet it is orbiting. The attractive forces of all the other
planets, starts, asteroids, etc., acting on their system are assumed to
be very small in comparison to their mutal attraction. There are
some other effects and perturbations that exist as well, but all things
considered, this basic description of orbital motion has been shown to
be quite accurate in most cases. |
