But at lower air pressure, a liquid droplet does not splash at all

In stop-action photographs taken half a century ago, Harold Edgerton, the M.I.T. professor who invented the electronic flash, famously captured the balletic disintegration of a milk drop, splashing upward in the shape of a tiny crown.

But at lower air pressure, a liquid droplet does not splash at all as it hits a flat glass surface, physicists at the University of Chicago discovered. Instead, the droplet of alcohol about one-eighth of an inch wide just flattens and flows away.

"You still need something else to kind of lift this thing up," said one of the researchers, Lei Xu, a graduate student.

Air friction creates a splash, above, by slowing the liquid as it tries to flatten out, distorting its flow and breaking it apart, the Chicago physicists said.

The findings, which could help improve inkjet printing and internal combustion engines, were reported last month at a meeting of the American Physical Society in Los Angeles.

Source: The New York Times