KEPLER'S LAWS OF PLANETARY MOTION

In 1543 Nicolaus Copernicus stated that all planets move around the sun in circular orbits with the sun at the center. But Johannes Kepler (1571-1630) discarded this theory and proposed the elliptical orbits for the planetary motion. he formulated three laws known as Kepler's law of planetary motion.




1)  KEPLER'S FIRST LAW (LAW OF ELLIPTICAL ORBIT)

       Every planet revolves round the sun in elliptical orbits, with the sun at one of the foci.     




2)   KEPLER'S SECOND  LAW ( LAW OD EQUAL AREA)

       The line joining the sun and the planet sweeps out equal areas in equal intervals of time.  i.e., the areal velocity swept by the radius vector of ellipse is a constant.




3)   KEPLER'S THIRD LAW ( HARMONIC LAW)

      The square of the time period of the revolution of planet around the sun is directly proportional to the cube of the mean distance between the sun and planet.