Kepler’s Law of Planetary Motion

• Ellipse


  A shape with two focus points (foci) that lie on the major or longest axis, spaced equally on each side of the center
• Kepler's First Law


  • All planets revolve around the Sun in elliptical orbits, with the Sun at one of the foci
• Kepler's Second Law


  The radius vector (line from Sun to planet) sweeps out equal areas in equal intervals of time
• Semi-major axis


  Half the distance of the major axis of an elliptical orbit
• Kepler's Third Law


  • The square of the time period of revolution of a planet is directly proportional to the cube of its semi-major axis
• Johannes Kepler was born prematurely, was a feeble child with weak vision, and at age 6 was sent to school but soon taken out to earn money for the family by working as a waiter in a hotel