Scientists Levitate Water Droplets, Figure Out What Drives 'Magical' Behavior

[Judi Lynn]

By Rafi Letzter, Staff Writer | November 16, 2017 11:34am ET

Even as physicists use big, expensive experiments to uncover huge gravitational waves and tiny hadrons, they can still answer questions about the thoroughly mundane. For example — Why do droplets of cold milk bounce on the surface of hot coffee before sinking? Why do teensy spheres of water skitter across the surface of a pool in the rain?

A team of researchers at the Massachusetts Institute of Technology (MIT) has for the first time observed and described the forces that cause drops of liquid to levitate above the surface of larger reservoirs. [Liquid Sculptures: Dazzling Photographs of Falling Water]

. . .

When a raindrop crashes into the surface of a puddle, the researchers found, twin engines kick in. The collision causes tiny currents to spin around inside the droplet as well as below the surface of the puddle. If you could peer into the droplet, you'd see water rushing downward along the edges inside the drop and then climbing back up toward the center, the new research found.

That spinning motion inside the droplet, invisible under most circumstances, creates enough force to tug on the air surrounding the droplet. The air forms into a thin, fast stream of wind that flows under the drop, holding it a hair's width above the surface, according to the new findings.

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[Xipe Totec]

1. In Soviet Russia, water walks on you! nt