The scientist known for his work on the laws of planetary motion is Johannes Kepler. In the early 17th century, Kepler formulated three fundamental laws that describe the motion of planets around the sun. These laws include: 1) the law of orbits (planets move in elliptical orbits), 2) the law of areas (a line segment between a planet and the sun sweeps out equal areas over equal times), and 3) the law of harmonies (the square of the orbital period of a planet is proportional to the cube of the semi-major axis of its orbit). His work laid essential groundwork for modern astronomy.