Sprinkler Spin Mystery Resolved: Central Momentum Drives the Motion
Physicists tested seven deliberately odd 'silly' sprinklers to settle a long‑standing question about reverse sprinklers. The experiments debunk both Mach’s angular‑momentum balance idea and Feynman’s pressure/suction theory, showing that rotation is governed by momentum flux at the central hub where the arms meet. The results imply the reverse sprinkler behaves like an inside‑out version of a forward sprinkler, with researchers planning simulations and potential energy‑harvesting applications.