When you’re a Jet,
You … stay … a … Jet!

Why Dropping a Stone Makes a Jet

The splash of a solid object into water–be it a coin or an Olympic high diver–is capped off by a thin jet of fluid shooting straight up from the surface. The detailed explanation of this seemingly simple event has proved elusive. Now researchers publishing in the 23 January Physical Review Letters think they have a more complete explanation than their predecessors. Using a combination of theory, simulation, and experiment, they studied the collapse of the air cavity trailing the submerged object, concluding that it ejects water like toothpaste squeezed rapidly from its tube.

Phys. Rev. Lett. 102, 034502
(issue of 23 January 2009)