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SALT LAKE CITY — On Halloween 2011, a group of NASA scientists won funding to develop a working tractor beam. Now, scientists at New York University have accomplished the feat, although science is a long way from realizing the tractor beams of Star Trek fame.
Scientists at Singapore's Agency for Science, Technology and Research used a Bessel beam last year that allowed for the backward movement of particles. A Bessel beam puts out light in concentric rings, allowing it to pull on particles inside the beam instead of push them away.
The problem was the beam used temperature to pull on the particles, meaning it could never be used in space — something NASA absolutely wanted.
Scientists at New York University have solved the problem, though, on a micro scale. Researchers David Ruffner and David Grier placed two of the Bessel beams side by side, overlapping them. This created a pattern of light and dark regions along the beam, allowing particles to bounce backwards along the bright spots in a type of domino effect.
The technique was able to work because the beams' photons do not spread out or scatter when obstructed by the moving particles — instead, they reform on the other side of the particles, keeping the motion intact.
Ruffner and Grier emphasized that the objects the beam was moving were microscopic: silica spheres, or grains of sand, that were suspended in water. But the microscopic tractor beam is a big advancement toward NASA's ultimate goal of using a tractor beam to gather particles from space for study.
