The scientist who first stated that the paths of planets are ellipses, not circles, was Johannes Kepler.

He developed his three laws of planetary motion, which are still used today, based on the meticulous observations of Tycho Brahe.

Here's a breakdown:

* Tycho Brahe was a Danish astronomer who made incredibly precise observations of the planets, particularly Mars.

* Kepler analyzed Brahe's data and realized that the orbits of planets, including Mars, were not perfect circles but rather ellipses, with the sun at one focus of the ellipse.

This discovery was a major breakthrough in astronomy and challenged the long-held belief that the planets moved in perfect circles around the Earth.