# Kepler's Laws of Planetary Motion/Historical Note

Kepler derived his three laws of planetary motion in the early $1600$s from a concentrated study over the course of $20$ years of the colossal wealth of observational data which had been made previously by Tycho Brahe of the behavior of the planets of the solar system, and in particular Mars.
The third appears some ten years later in his Harmonices Mundi of $1619$.