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Kepler's third law, the law of periods, relates the time required for a planet to make one complete trip around the Sun to its mean distance from the Sun. "For any planet, the square of its period of revolution is directly proportional to the cube of its mean distance from the Sun." Applied to Earth satellites, Kepler's third law explains that the farther a satellite is from the Earth, the longer it will take to complete and orbit, the greater the distance it will travel to complete an orbit, and the slower its average speed will be.

Video shows artist concept of planets orbiting the Sun. It then shows a satellite orbiting the Earth, followed by two satellites orbiting the Earth. This shows that the satellite with the larger orbit covers more distance and travels slower.


A service of the High Energy Astrophysics Science Archive Research Center (HEASARC), Dr. Alan Smale (Director), within the Astrophysics Science Division (ASD) at NASA/GSFC

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