Original Form of Kepler's Laws for Planetary Motion

This is a Java applet illustrating Kepler's original laws for the motion of a planet around a massive sun so that the effect of the center of mass may be neglected. Applet Controls: The slider bar at the bottom controls the eccentricity of the orbits. The left 3 controls at the top toggle on and off lines joining the planet to the foci of its elliptical orbit, the orbit, and information of the orbit (location of the foci and the length of the semimajor axis 'a' and the semiminor axis 'b'). The right 3 controls at the top allow the mass 'M', the semimajor axis 'a', and the speed of the animation to be set. The motion may be toggled on and off by clicking anywhere in the applet display.

The scale is indicated by the legend in the lower right of the display. The applet is set up to scale the distances always to a fixed amount so changing 'a' does not change the locations of the planet, but it changes the distance scale indicated by the legend in the lower right.

Data Display: The data displayed in the upper left of the main window correspond to the eccentricity 'e' of the orbit, the semimajor axis 'a', the mass of the sun 'M', the period, the elapsed time, and the separation of the planet and sun 'R'. All times are in Earth years, all distances in A.U., and all masses in solar units.