While earlier astronomers like Copernicus had proposed a heliocentric model, Kepler was the one who:
* Discovered that planets' orbits are elliptical, not circular. He made this discovery by meticulously analyzing the observations of Tycho Brahe, who had spent years painstakingly charting the positions of the planets.
* Formulated his three laws of planetary motion, which mathematically described the elliptical orbits of planets, their speed, and their relationship to the Sun.
So, while Copernicus laid the groundwork for a heliocentric system, it was Kepler who truly revolutionized our understanding of the solar system by establishing the elliptical orbits of planets.
