Researchers at New York University’s Courant Institute built custom "silly" sprinklers to test the long‑debated reverse sprinkler problem. Their experiments, published in the Proceedings of the National Academy of Sciences, confirm the 2024 momentum flux theory—the idea Perkins‑like water jets inside the sprinkler generate a torque that drives the device in reverse. The team used ultra‑low‑friction rotary bearings, controlled flow rates, dyes, and high‑speed video to map the fluid‑flow patterns.

They found the reverse sprinkler rotates about 50 times slower than a forward one but follows similar mechanisms. The results contradict earlier Mach and Feynman hypotheses and show that arm shape can be tuned to control jet flow and torque. Co‑author Brennan Sprinkle of the Colorado School of Mines said the work "provides a firmer understanding of how components respond to fluid flows—knowledge that can guide future engineering and technological advances for devices, such as turbines, that convert these flows into energy.".