Motion and Its Causes

Force and Newton’s Laws of Motion

What does Kepler’s Third Law tell us about the motion of satellites around Earth?

Kepler’s Third Law relates the period of a satellite to its distance to the center of Earth. The table below shows the mean radius of the orbit, the altitude above Earth’s surface, and the period for some typical satellites.

Weather satellites have polar orbits so that the view of their cameras sweeps across the entire surface of Earth many times each day. The moon’s orbit is aligned with Earth’s orbit around the sun, not Earth’s equator.

Kepler’s Third Law holds for satellites about other planets and for planets revolving around the sun, but you need either Newton’s laws or Einstein’s relativity theory to explain these results.


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