What is the main difference between Kepler's system and Copernicus system?

Answer 1

The main difference between Kepler's system and Copernicus' system lies in their approach to planetary motion. Copernicus proposed a heliocentric model, where the Sun is at the center of the solar system, while Kepler's model focused on the elliptical orbits of planets around the Sun. Copernicus' system laid the groundwork for a sun-centered model, while Kepler's laws of planetary motion provided a more accurate description of the paths planets take as they orbit the Sun.

Answer 2

Copernicus's theory has the Sun at the centre but uses a model of circles and epicycles in the same way that the ancient Ptolemaic one used.

Kepler continued to use the idea of having the Sun at the centre but, with the help of Tycho Brahe's new accurate observations, Kepler discovered that elliptical orbits allowed a better fit to the observed positions.

Tycho instructed Kepler to work on the orbit of Mars, which was a real piece of luck because Mars's orbit is more elliptical than the other planets' orbits (except Mercury). This led Kepler to the idea of the ellipse, which is the model used today.