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In support of all the students who are displaced from school due to the Corona virus. Access to physics zone and chemistry zone lessons are now available free of charge. This will be maintained at least through August 1st 2020. Learn and be well.

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Physics Zone Lesson: Earth-Moon Orbit

A misconception in the relationship between the Earth and the Moon is that the Moon revolves around the Earth.  This is not quite right.  The Moon and the Earth actually move around or orbit their common center of mass which is called the barycenter.  As you can see in the animation below, the barycenter,shown as the red dot, is located about 1/4 of the way to the center of the Earth (~1,700Km below the surface).  The barycenter is the center of mass for the Earth-Moon system. 

Please obtain the shockwave plug-in from www.shockwave.com

By now you may have guessed that the idea of the Earth revolving around the Sun isn't quite right either.  The Sun-Earth system has a center of mass which is not in the very center of the Sun.  It is beneath the surface of the Sun but not at its center  So the Earth and the Sun actually orbit the barycenter.