The person who proposed that planets orbit the Sun in elliptical paths, moving fastest when closest to the Sun, was Johannes Kepler.

He developed three laws of planetary motion, and his first law states precisely this:

* Kepler's First Law: Planets move in elliptical orbits with the Sun at one focus of the ellipse.

This means that the orbits are not perfect circles, but slightly oval-shaped. As a planet moves closer to the Sun, its speed increases, and it slows down as it moves farther away.