For 10 points, name this law, which states that the square of the orbital period of a planet is proportional to the cube of the semi-major axis of that orbit.
Newton "corrected" this law by squaring both sides of one form of it, and this law is used to compute the Gaussian gravitational constant. Joseph Privat de Molieres proved one case of it by showing that if the normal force and centripetal force are proportional, then one over r squared is proportional to v squared over r, and since v is proportional to r over t, r cubed is proportional to t squared. For 10 points, name this law, which states that the square of the orbital period of a planet is proportional to the cube of the semi-major axis of that orbit.
Newton "corrected" this law by squaring both sides of one form of it, and this law is used to compute the Gaussian gravitational constant.
{Kepler's Third} Law [or {harmonic} law]