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Scientists Confirm Counter-Clockwise Sprinkler Rotation, Solving Feynman Puzzle

7/15/2026

Summary

Story summary

Leif Ristroph and Brennan Sprinkle solved Feynman's Sprinkler Problem, confirming sprinklers rotate counter-clockwise.
The July 13, 2026 Proceedings of the National Academy of Sciences (PNAS) used laser imaging to show jets colliding, creating pressure that slows reverse rotation fifty times slower than forward models.
The results back theory, refute Mach and Feynman ideas, may guide turbine, tidal-energy and irrigation pump design, and were funded by NSF grants DMS-2407787 and DMS-2407788.

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Story summary

Leif Ristroph and Brennan Sprinkle solved Feynman's Sprinkler Problem, confirming sprinklers rotate counter-clockwise.
The July 13, 2026 Proceedings of the National Academy of Sciences (PNAS) used laser imaging to show jets colliding, creating pressure that slows reverse rotation fifty times slower than forward models.
The results back theory, refute Mach and Feynman ideas, may guide turbine, tidal-energy and irrigation pump design, and were funded by NSF grants DMS-2407787 and DMS-2407788.