Objects hitting water can move air at the speed of sound
A stone hitting a pond can produce a tiny supersonic splash, a new study has found.
Researchers studying the shape of an air cavity made when an object hits a liquid noticed a similarity to the shape of the nozzles that are in supersonic jet engines. Sure enough, air escaping from the cavity can reach supersonic speeds, the team reports in a paper published online January 11 in Physical Review Letters.
After an object such as a stone hits a flat liquid surface, it carves a tube of air through the liquid in its wake, Stephan Gekle of