Law
Hubble's Law
The recessional velocity of a galaxy is directly proportional to its proper distance from the observer: .
Astrophysics
Field: Astrophysics
Sequence of Expressions
The orbit of a planet is an ellipse with the Sun at one of the two foci.
A line segment joining a planet and the Sun sweeps out equal areas during equal intervals of time.
The square of the orbital period of a planet is directly proportional to the cube of the semi-major axis of its orbit: .