Kepler's laws of planetary motion describe how planets move around the Sun. The first law, known as the law of ellipses, states that planets travel in elliptical orbits with the Sun at one focus. This means that the distance between a planet and the Sun changes as the planet moves along its orbit. The second law, or the law of equal areas, indicates that a line drawn from a planet to the Sun sweeps out equal areas in equal times. This means that planets move faster when they are closer to the Sun and slower when they are farther away. The third law relates the time a planet takes to orbit the Sun to its average distance from the Sun.