2nd Law: Law of Equal Areas
A line from the planet to the sun sweeps out equal areas in equal amounts of time.
With elliptical orbits a planet is sometimes closer to the sun than it is at other times. The point at which it is closest is called perihelion. The point at which a planet is farthest is called aphelion. Kepler's second law basically says that the planets speed is not constant – moving slowest at aphelion and fastest at perihelion. The law allows an astronomer to calculate the orbital speed of a planet at any point