Johannes Kepler was famous for his discovery of the three laws of planetary motion. These laws describe how planets move around the sun:

1. Law of Orbits: Planets orbit the sun in elliptical paths, not circular ones.

2. Law of Areas: A line connecting a planet to the sun sweeps out equal areas in equal times.

3. Law of Periods: The square of a planet's orbital period is proportional to the cube of its average distance from the sun.

These laws were groundbreaking because they challenged the long-held belief in a geocentric universe (earth-centered) and provided a more accurate model for understanding planetary motion.