Explanation

Kepler's law explains the motions of planets in the solar system.

Kepler's Laws of Planetary Motion

They describe how:

(1) planets move in elliptical orbits with the Sun as a focus

(2) a planet covers the same area of space in the same amount of time no matter where it is in its orbit

(3) a planet's orbital period is proportional to the size of its orbit (its semi-major axis).