The correct answer is: discovering elliptical orbits.
Elliptical orbits were discovered by Johanes Kepler (1571-1630).
In 1609 he published Astroma Nova which demonstrated that the Aristotelian cosmography of perfect forms and unknowable causes was wrong. He demonstrated that the Earth orbits the Sun.
Galileo was a famous astronomer and physicist, he created a powerful telescope that allowed him to discover that the Earth revolves around the Sun. In 1610 he discovered four moons orbiting Jupiter.
