Seven quirky sprinklers upend Feynman and Mach on reverse sprayers
New York University researchers tested seven deliberately odd “silly” sprinkler designs to pit Mach’s angular-momentum idea against Feynman’s suction-based theory. Across all designs, rotation depended on the sprinkler’s central hub where the arms meet, not on how water carried momentum inside the arms or on nozzle geometry. The results debunk both classical explanations and suggest a unified view: the hub’s dynamics govern the spin. This insight could inform engineering designs that convert fluid flow into rotation, with potential applications for turbines and energy-harvesting devices.
