Video: ‘tractor beam’ created in water.
Physicists at The Australian National University have created a tractor beam on water, providing a radical new technique that could confine oil spills, manipulate floating objects or explain rips at the beach.
Using a ping-pong ball in a wave tank, the group worked out the size and frequency of the waves required to move the ball in whichever direction they want.
Advanced particle tracking tools, developed by team members Dr Nicolas Francois and Dr Hua Xia, revealed that the waves generate currents on the surface of the water.
“We found that above a certain height, these complex three-dimensional waves generate flow patterns on the surface of the water,” Professor Shats said. “The tractor beam is just one of the patterns, they can be inward flows, outward flows or vortices.”
The team also experimented with different shaped plungers to generate different swirling flow patterns.
As yet no mathematical theory can explain these experiments, Dr Punzmann said.
“It’s one of the great unresolved problems, yet anyone in the bathtub can reproduce it. We were very surprised no one had described it before.”