It is a good start that demonstrates theory is correct. It will be a long time before we get one or get one that can be used in practical situations. Yet this is a step up from simple imagination.
The tractor beam has been a staple of science ficton from the beginning. However else can you move objects in space without engaging massive hardware?
Now we wait a long time.
Reversible tractor beam can repel and attract objects
http://www.gizmag.com/reversible-tractor-beam/34327/
Dr Vladlen Shvedov (left) and Dr Cyril Hnatovsky (right) with a
magnified projection of the 'hollow' laser beam (Photo: Stuart Hay, ANU)
We're still a far cry from Star Trek's ship-towing and
repelling technology, but laser physicists at the Australian National
University (ANU) have built a tractor beam that can repel and attract
objects. The beam moved spherical glass shells one fifth of a millimeter
in diameter across a distance of up to 20 centimeters (7.87 in), which
is around 100 times further than previous experiments at this scale,
using only a single hollow laser beam that's bright around the edges and
dark in its center.
The ANU researchers previously developed a similar device that moves
very small particles over long distances using an optical vortex that
created something called photophoretic force, which pushes the particle
into a dark hollow in the center of the beam as the momentum of the
photons drives it forward.
This new technique builds on the previous study, with energy from the
laser heating the surrounding air particles to create hotspots on one
side of the glass shell's surface. The heat drives air particles away,
causing the tiny shell to recoil – thus propelling it in the opposite
direction. And by altering the polarization of the laser beam on the
fly, switching for instance from axial (shaped like a star) to azimuthal
(like a ring), the researchers can cause the shell to change direction
or stop.
The beam could have broad applications in the real-world, the
researchers believe, as a means of controlling or sampling atmospheric
pollution, and it could be scaled up to work over several meters. "Our
lab just was not big enough to show it," explained co-author Dr Vladlen
Shvedov.
It may not sound like much, but this is a big step forward in the
quest to develop optical tractor beams like those from science fiction.
Long-distance optical tractor beams were previously restricted only to
theory – a concept that in essence sees particles, the environment, or
an object's electromagnetic field manipulated by "negative forces" from lasers or Bessel beams.
"Demonstration of a large-scale laser beam like this is a kind of
Holy Grail for laser physicists," said co-author Wieslaw Krolikowski.
Now that the concept's been proven, the agonizing (and possibly futile)
wait for something truly large scale, like the Starship Enterprise
towing another ship to safety or the portal-creating, cube-moving
Aperture Science Handheld Portal Device used in the game Portal, begins.
A paper describing research appeared in the journal Nature Photonics.
Source: Australian National University
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