Resonance explains why a swaying bridge collapses with a high wind, and how a wine glass shatters with a higher octave. The medium disturbances of nature. With an analysis of simple harmonic motion and a stroke of genius, Newton extended mechanics to the propagation of sound. An old momentum with a new twist. Kepler's second law of planetary motion, which is rooted here in a much deeper principle, imagined a line from the sun to a planet that sweeps out equal areas in equal times.
Angular momentum is a twist on momentum - the cross product of the radius vector and momentum.
A force with a twist is torque. When no torque acts on a system, the angular momentum of the system is conserved. Why a spinning top doesn't topple. When a torque acts on a spinning object, the angular momentum changes, but the objects only processes. The object may be a child's toy, or a part of a navigation system, or Earth itself.