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Retrograde motion HTML5


Mars's trajectory seems to go backward periodically. This is called a retrogradation (or retrograde motion). Because the Earth orbits 1.88 times faster than Mars, the relative motion of both explains this phenomenon.
The animation is not drawn to scale, for either sizes or distances.

Click on to stop the motion.

Learning goals

  • To understand the retrograde motion of mars.
  • To understand why the distance between Earth and Mars varies periodically.