Physicists at Australian National University have done something pretty cool using solely a tank of water and a small wave generator — they've made a simple tractor beam that can pull a ping pong ball (or any floating object) across the water's surface.
The underlying idea, which they described in an article published Sunday in Nature Physics, is straightforward. The research team, led by Michael Shats, calculated that by generating small waves of particular frequencies, they could create surface currents moving in any sort of direction — either toward the wave source (creating the tractor beam), or away from it (pushing the ping pong ball away), or even in a circle.
The idea is so straightforward, the physicists say, that they're surprised no one has figured it out before. They also note that the principles could potentially be used for a number of different applications, like corralling floating garbage or confining oil spills.
Here's the full video put out by the university on the research: