Kepler's Laws (orbits)

planets orbit the sun in ellipses with the sun at one
focus.
simulator
 sample calculation

the line between the sun (primary) and a planet (secondary)
sweeps out equal areas in equal times
(the law of areas).
simulator
 sample calculation

the ratio of the cube of the semimajor axis to the square
of the orbital period is a constant (the
harmonic law).
simulator
 sample calculation