For 141 years, physicists like Richard Feynman have puzzled over a question of fluid flow: how would a sprinkler rotate if it were underwater, sucking in the stuff instead of spewing it? Now, a team ...

For decades scientists have been trying to solve Feynman's Sprinkler Problem: How does a sprinkler running in reverse—in which the water flows into the device rather than out of it—work? Through a ...