After the victory of the heliocentric theory, a new prejudice had to be defeated.

Both Copernicus and Galileo assumed that the orbits of the planets had to be circular, because circles are "perfect" shapes.

Kepler was able to defeat this prejudice of "circular perfection" by using the data he obtained from his own observations and those of his master, Tycho Brahe, the last defender of the geocentric theory.