A group of physicists from the Australian National University have created a "tractor beam" on water that lets them manipulate floating objects.
They used wave generators and a ping pong ball in a wave tank, calculating the size and the frequency of waves needed to move the ball in any direction, even against the direction of the wave.
"We have figured out a way of creating waves that can force a floating object to move against the direction of the wave," said Dr. Horst Punzmann from the Research School of Physics and Engineering, who led the project.
The tractor beam is just one of the patterns, though. They can be inward flows, outward flows or vortices, according to the professor Michael Shats, who led the research group.
The findings could hold significant implications, as the same principle could be used for collecting oil spills.
The manipulation technique is still new, so it is difficult to fully understand the mathematics behind the discovery, according to researchers.
"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," Punzmann said.