Ultrasound machine pulls on a target that is large enough to see
Tractor beams have hit the big time. A newly constructed device generates a beam of concentrated sound that, for the first time, exerts a continuous, perceptible tug on objects large enough to see. The researchers didn’t actually reel in an object, but they demonstrated that an ultrasound tractor beam could do the job.
Using a tractor beam to haul a damaged spaceship may look simple on Star Trek, but nature makes it very difficult to pull objects from a distance. Waves of light or sound fired at an object tend to bounce off its surface like raindrops on an umbrella, collectively exerting a subtle nudge called radiation pressure that pushes the object away.