Johannes Kepler

• Johannes kepler


  • A german astronomer, mathematician, astrology, natural philosopher, and music writer
  • He discovered the laws of planetary motion describing how planets orbit the sun
• The law of ellipses


  "Planets move in elliptical orbits, with the sun at one focus of the ellipse"

  • Planets travel in an ellipse rather than in perfect circle
  • An ellipse has two foci, and the sun is located at one focus while the other is empty
  • Eccentricity determines the shape of an orbit - 0 is perfect circle, closer to 1 is more elongated
• The law of equal areas


  " A planet sweeps out equal areas in equal time intervals as it moves around the sun"

  • When a planet is closer to the sun (perihelion) it moves faster
  • When a planet is farther from the sun (aphelion) it moves slower
  • However the area swept out by the line connecting the planet to the sun is always equal over the same time period
• The law of harmonies


  "The square of a planet's orbital period (T³) is proportional to the cube of its average distance from the sun (R³)"

  • The farther a planet is from the sun the longer it takes to complete an orbit
  • Planets that are closer to the sun orbit faster, while planets farther away orbit slower
  • This relationship applies to all objects orbiting the sun, including moons around planets