The Backyard “Silly Sprinkler” That Cracked One of Physics’ Biggest Puzzles

Researchers tested custom sprinkler shapes, including looping backyard-style designs, and confirmed that reverse sprinklers do rotate.

The results support a momentum-flux explanation for Feynman’s Sprinkler Problem, extending earlier work beyond simple S-shaped arms.

The study helps settle a long-running physics question about how flowing fluids transfer force and angular momentum.

The findings may also inform engineering applications such as turbines and other energy-conversion systems.