Rotating frame of reference

When a system is in constant, periodic motion, with superimposed episodic, nonperiodic behavior, it is sometimes mathematically convenient to treat the system in a rotating frame of reference, which removes the constant motion. The varying motions are then generally appear to be much simpler. Consider, as an example, the rotation of the earth. We know that it is constantly moving, yet, for the most part, we mentally disregard this fact, and view the behavior of objects around us as if we were truly stationary. In other words, we observe the world from within a rotating frame.