Research overview: the cat righting reflex and zero-angular-momentum rotation

A falling cat can turn to land feet-down without any external push, a feat that puzzled physicists for over a century. This overview explains the modern understanding: the cat rotates its front and back halves in sequence while tucking and extending limbs to change each half moment of inertia, so the body reorients even though total angular momentum stays zero. Early stroboscopic photography revealed the bend-and-twist motion, and later mechanical models formalised it as a problem in non-holonomic control, related to how a falling cat resembles a coupled pair of rotors. Why it matters: the reflex is a textbook example of how shape change alone can produce reorientation, with influence reaching into spacecraft attitude control, robotics, and the study of vestibular and proprioceptive coordination.