Australian scientists have created a water-based “tractor beam” – a wave generator that is able to manipulate floating objects. However, researchers say no mathematical model exists so far to explain this complex phenomenon.
Researchers at the Australian National University in Canberra have demonstrated the ability of simple wave generators to control things adrift in the water – and even move them against the direction of the waves.
In the research, published in Nature magazine, scientists claim that their discovery “would find a broad range of applications,” from new solutions to oil spills or ways to rescue malfunctioning ships to a better understanding of dangerous rip tides that drag swimmers into the water even when waves are heading towards the shore.
The tractor beam barrows its name from science fiction, where it is successfully used to manipulate any object from a distance and move it towards an alien or future-human spacecraft.
To illustrate the principle of the technique, the team generated three-dimensional waves in a water tank, and found the very frequency and size of the waves necessary to keep a ping-pong ball floating in the tank, then moved the ball in whatever direction they wanted.
“We found that above a certain height, these complex three-dimensional waves generate flow patterns on the surface of the water,” said physicist Michael Shats, the paper's senior author, said. “The tractor beam is just one of the patterns, they can be inward flows, outward flows or vortices.”
However, as simple the process seems to be, there are no mathematical theories to back what works in practice. “It's one of the great unresolved problems, yet anyone in the bathtub can reproduce it,” said Horst Punzmann, the physicist who led the project. “We were very surprised no one had described it before.”