A closer look

Richard Feynman famously nearly blew up a Princeton lab trying to figure out if an S-shaped lawn sprinkler spins in reverse when sucking water in, rather than spraying it out. Physics intuition screams yes, assuming basic action and reaction. Reality says mostly no. When sucking water in, the internal flow dynamics almost perfectly cancel out the external forces, leaving the sprinkler twitching uselessly. Nature absolutely hates elegant math.