Angular Momentum in Physics

Angular momentum is the quantity that keeps order when a body is spinning or moving sideways past a point. Unlike momentum it depends on where you stand, which is why the same motion can carry angular momentum about one origin and none about another. What makes it powerful is that it is conserved whenever no external torque acts, and that single fact explains a skater speeding up with arms pulled in, a collapsing star spinning faster as it shrinks, and a bicycle wheel staying upright when you lean it over. The blocks give the vector product it is built from, its particle and rigid body forms, the torque that changes it, and the slow circle a gyroscope traces.