How does a 'reverse sprinkler' work? Researchers solve decades-old physics puzzle

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 series of experiments, a team of mathematicians has figured out how flowing fluids exert forces and move structures, thereby revealing the answer to this long-standing mystery.