Tractor beams are a staple in science fiction. The hero inevitably gets stuck on the enemy’s beam, escapes a tractor beam, or uses a tractor beam to escape. And now science has caught up. The BBC writes that researchers at St. Andrews have been able to move things with a tractor beam:
Usually when microscopic objects are hit by a beam of light, they are forced along the direction of the beam by the light photons. That radiation force was first identified by the German astronomer Johannes Kepler in 1619 when he observed that tails of comets always point away from the Sun.
Dr Cizmar’s team’s technique allows for that force to be reversed which he said some people might find counter-intuitive.
Of course, this tractor beam can only move microscopic particles. But the applications are pretty big, Cizmar told the BBC. “The practical applications could be very great, very exciting. The tractor beam is very selective in the properties of the particles it acts on, so you could pick up specific particles in a mixture,” he said.
This isn’t the first time when science has talked about tractor beams. In 2011, NASA created a $100,000 reward for anyone who could further the tractor beam idea. Three ideas emerged, the BBC wrote at the time:
One is an adaptation of a well-known effect called “optical tweezers” in which objects can be trapped in the focus of one or two laser beams. However, this version of the approach would require an atmosphere in which to operate.
The other two methods rely on specially shaped laser beams – instead of a beam whose intensity peaks at its centre and tails off gradually, the team is investigating two alternatives: solenoid beams and Bessel beams.
A few months ago, researchers from Hong Kong and China announced further progress on the beam. They wrote in a paper, “A photon carries a momentum of, so one may anticipate light to “push” on any object standing in its path via the scattering force.”
Here’s a video explaining some of the breakthroughs.
So the step might be incremental, but it’s still one step closer to a real tractor beam. Which can only be a good thing.
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