David Grier showing off his lab, where he and his team have developed real-life tractor beams.
(Image courtesy of NYU.)
If the term “tractor beam” sounds familiar to you, it’s probably because of Star Trek–the crew of the Enterprise used tractor beams to move huge objects like spaceships and asteroids. While Grier and his team haven’t quite achieved the Star Trek version, their tractor beam concept is essentially the same.
“It’s like science fiction being made real,” said Grier.
Making Science Fiction a Reality
Now that we’ve got Star Trek out of the way, let’s talk about what we’re really dealing with here. Grier explains that a tractor beam is nothing more than a wave, before going on to illustrate how a tractor beam isn’t as strange as it first sounds.
“A lot of people would be familiar with the idea that a wave can push,” said Grier. “If you’ve gone to the beach, waves exert force, they push you downstream. What we’ve discovered is that it’s possible to structure a wave so that now the wave doesn’t just push; the wave can actually grab an object, hold onto it or even pull it.”
Here’s how it works: you start with a special kind of wave structure and shine a light wave that has this structure on an object. The object will scatter the wave’s momentum density downstream into the direction of wave propagation. By the law of conservation of momentum, this downstream scattering causes a retrograde force to arise and push the object upstream , toward the source of the light.
The main crux of the matter is the wave structure required for this downstream scattering to be possible. The structure that Grier and his team propose is called a solenoid beam, the wavefronts of which are characterized by an independent helical pitch.
“When we were first making tractor beams in the lab, at first all we could do is move really tiny things very, very small distances, just over a micrometer,” said Grier. “We’re not lifting up an entire battle cruiser and hauling it across space, but then, once you’ve got to centimeters and then to meters, the next step really is kilometers. And that’s what we’re working toward now.”
As the tractor beam technology improves, it can be applied a number of applications besides hauling battle cruisers across space. Along with potential medical opportunities explored by separate researchers , tractor beams could find use in environmental science. And yes, there are space applications as well.
“If you have tractor beams, if you’re able to sample stuff remotely from a safe distance, you could image looking at smoke stack fumes, see what particles are contributing to pollution,” said Grier. “In space exploration this could be a very big deal. So we’re actually collaborating with NASA’s Goddard Space Center down in Maryland to create really long range tractor beams for space exploration.”
We’ll have to wait and see, but it looks like the 23 rd century may just come early.
For more Star Trek—style technology, find out why the NYU Holodeck received National Science Foundation funding .