Kepler's Laws of Planetary Motion in Physics

Kepler found these rules by staring at tables of observations, long before anyone could explain why they held. A planet sweeps out equal areas in equal times, which is really a statement that its angular momentum never changes. Its period squared is proportional to the cube of its orbit size, which is really a statement about the balance between gravity and the acceleration needed to keep turning. Every orbit is bound with a negative total energy, and the closer that energy sits to zero the wider the orbit becomes. The blocks give the period law in each direction, the areal law, and the energy bookkeeping that governs satellites.