Each summer, lawns are marked by a familiar addition: “silly sprinklers,” whose loops and spirals spew water in creative ways. While seemingly frivolous in their construction, a team of mathematicians from Colorado School of Mines and New York University has used their design to address a long-standing mystery surrounding the laws of physics. 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...