An Advance in Tractor-Beam Technology
The term “tractor beam” is thought to have made its first appearance in “Spacehounds of IPC,” a sci-fi novel by Edward E. Smith published in 1947. Smith, whose work has been cited as an influence by the likes of Arthur C. Clarke, George Lucas, and J. Michael Straczynski, the creator of the show “Babylon 5,” worked as the chief chemist for a Michigan flour mill (his specialty was doughnut mixes). His best-known works, the Lensman and Skylark series, are full of imagined technologies that, like the tractor beam, were far beyond the reaches of contemporary science but nevertheless based on seemingly sound principles.
Scientists first began working on making tractor beams a reality in the nineteen-nineties, after the Russian ceramics engineer Eugene Podkletnov reported that certain small objects, when placed above a superconducting disk supported on a rotating magnetic field, lost up to two per cent of their weight. His experiment—the results of which were met with widespread, albeit somewhat knee-jerk, skepticism in the physics community—seemed to indicate that it was possible to neutralize the force of gravity, at least in part. Further experiments followed; in 2001, Podkletnov and the Italian physicist Giovanni Modanese built what they called an impulse gravity generator, a device that emitted a beam of focussed radiation in a “short repulsive force.”
Until recently, no one had managed to move anything bigger than a particle. (There was brief excitement earlier this year, when researchers from Australia and Spain successfully moved a plastic sphere fifty nanometres across—around a thousand times thinner than a human hair—by splitting a beam of light in two and using it to press in on the sphere from each side, like a pair of tweezers.) Even NASA has tried to get in on the action, although their vision seems somewhat lacking when compared with the many tractor-beam scenarios already laid out in science fiction: the team of scientists tasked with the job are supposed to come up with more efficient ways of clearing “orbital debris,” i.e., space garbage. (And they don’t look happy about it.)
Now scientists from the University of Dundee, in Scotland, have created something with a bit more muscle. While most of the documented experiments with tractor-beam technology so far have involved light waves, the team from Dundee used sound waves to manipulate a half-inch triangular prism made of metal and rubber, successfully pulling the target toward the source of the acoustic beam. Half an inch may not sound like much, but it’s a vast improvement on fifty nanometres. The experiment was part of a larger project across four U.K. universities—Bristol, Southampton, Glasgow, and Dundee—and took nine months to complete. The results have been published in Physical Review Letters.
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http://www.newyorker.com/tech/elements/scottish-tractor-beam
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