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Scientists turn light into a tractor beam


January 28, 2013

A team led by the University of St. Andrews has turned a laser into a tractor beam that wo...

A team led by the University of St. Andrews has turned a laser into a tractor beam that works on the microscopic level

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Tractor beams are one of those things that seem on the far edge of what’s possible. The idea of a beam of energy streaming out that pulls things in is counter-intuitive, but scientists have been developing things that work like tractor beams since the 1960s and light manipulation has been tried since the 1970s.

In recent years, several ways of imitating the fictional tractor beam have been investigated, including optical vortices, optical tweezers, Bessel beams and optical pipelines. Developed in association with the Institute of Scientific Instruments (ISI) in the Czech Republic, the St. Andrews team claims that its tractor beam is different in that it’s the first time that a light beam has been made to draw objects toward the light source.

Though the tractor beam only works under very specific conditions on a microscopic scale, it involves a principle that’s been known for centuries, since Johannes Kepler first deduced that it was the pressure of light that pushed comet tails outward from the sun. This light pressure has already been harnessed for solar sails and attitude controls for satellites, but the St. Andrews team has found a way to turn this pressure into a negative force.

Schematic of the tractor beam experiment

This negative force is produced in a laboratory set up by a mixture of very specific properties of light and the object being moved. In the St. Andrews experiment, a Gaussian beam (a light beam where the profile is described by a Gaussian mathematical formula) is generated by a VERDI V5 laser. This beam is directed through a lens and then passes through a suspension of dielectric spheres set between two coverslips.

The bottom slip is a half-silvered reflecting mirror that reflects part of the beam back to the source. The incoming and reflecting beams interfere with one another and produce a standing wave. Based on the properties of the spheres and their location, the standing wave shapes in such a way that the light force pushes the spheres back toward the laser source.

Putting it simply, the standing wave at a particular spot near the light source interacts with spheres of a particular size and mass in such a way that the light waves push in the wrong direction. It’s a bit like a dinghy moored at a pier where the current is moving away from the pier, but produces eddies that push the dinghy back into the pier.

The team sees a number of applications for the tractor beam in biomedical photonics and other disciplines, such as the simple and inexpensive optical sorting of macromolecules, organelles or cells.

The findings of the team were published in Nature Photonics.

Source: University of St. Andrews

About the Author

Soooo still a push not pull. Cool idea though. Perhaps the laser can be aimed at particular planets to reflect back into the beam and create a standing wave. Booya tractor beam!

28th January, 2013 @ 07:37 am PST

Thank you scientists! We can "attract" an object with laser if you put a mirror behind it. We kind of knew that already... put a mirror behind the object and then push it from behind with lasers.

28th January, 2013 @ 08:57 am PST

That's Star Trek. Star Wars did not have tractor beams or for that matter shields or transporters.

Evan Pearce
28th January, 2013 @ 08:53 pm PST


I'm sure when Han Solo, while in the Millenium Falcon, was chasing/being chased by that TIE Fighter, he said: What's that Planet?, or something like that.

When they realized it was the Death Star is was too late and guess what, they were caught in it's Tractor Beam.

And in case you meant Star Trek, they have a tractor beam too.

Am I wrong?

Seth Kazzim
29th January, 2013 @ 03:38 am PST

Seth, you are correct, the Death Star in Star Wars did indeed have a tractor beam. In any case, I fail to see why anyone would cull out one movie from the author's list when the discussion was regarding Science Fiction movies as a genre. I like the article, because it shows where science is moving, I posted this article on my Facebook page because I find it intriguing to imagine a future where these technologies exist as everyday work items and our great great great grand children will look back and wonder how we ever made do without them :)

John A Vonesh
29th January, 2013 @ 09:02 am PST

In Star Wars Episode V: The Empire Strikes Back; The Rebel base on Ice Planet Hoth is protected from imperial bombardment by a force field (shield).

29th January, 2013 @ 04:19 pm PST

can one upscale this, wow, awesome.

If done on Microscale how bout Megascale

Stephen N Russell
29th January, 2013 @ 05:37 pm PST

This Sort of Tractor beam isn’t too practical for large objects. The Keshe Foundation has developed a practical tractor beam, as well as antigravity and free energy technology using a different Physics that posits that magnetic fields are the basic building blocks of matter and force. They gave their technology to Iran 3 years ago and they have developed antigravity and tractor beams which Keshe claims is how the Iranians were able to bring down the U.S. stealth drone. Now the Keshe foundation is sharing their technology with any country that wants it.

Herbert Dorsey
29th January, 2013 @ 05:44 pm PST

How about a tractor beam that worked by intead of the beam actually trying to do the work you alter the target to become attractive to the source - in effect the target then pull itself towards the source. Just what can you alter to suddenly make it attractive - the simplest I can think of is a simple ionising beam - to create a charge

10th June, 2013 @ 09:17 am PDT

That Star Wars had no tractor beams or shields? My God which versions of Star Wars did that guy see? And I think that he has not played any Star Wars ship games for that matter either cause if he had he would have known how wrong he was. What it did not have was transporter beams as in Star Trek but shields and tractor beams where all over.

Yes, the Death Star had a tractor beam and even the Star Destroyers had them too. It was the smaller fighter ships or transports that didn't have them.

And as for shields even many small fighters particularly those of the Rebel Alliance had them like the X-Wings, the Y-Wings and the A-Wings had them too. The Tie Fighters and the Tie Interceptors did not have shields cause the Empire relied on their sheer large numbers to mount an effective offensive.

Darth Vader's Tie Fighter had shields too because it was a special prototype piloted by Anakin and also an hyperdrive unit unlike the Tie Interceptors or Tie Fighters that didn't have them and that is why you hear Ben Kenobi mention in the first movie that the Tie Fighter was a short range ship.

In the Star Destroyers you can easily recognize the shield generators. They are the two geodesic "spheres" at the top of the bridge structure and also the large dome at their bottom.

The thing is that in Star Wars you don't get to see the effect of the shields the way they are very graphically portrayed in Star Trek. In Star Trek when a weapon or an object strikes a ship's shield you get to see a slight somewhat translucent part of the shield momentarily but in Star Wars they remain invisible.

Now, the fact that they remain invisible doesn't mean that they are not there. Also the fact that the ships have them doesn't mean that the ship is indestructible of course as you obviously saw in the movies, it is just that it takes longer and it takes more hits to destroy or damage a ship with them so the Rebel X-Wings where much harder to destroy than a Tie Fighter, it was just that the Tie Fighters where far more numerous so the Rebels where able to withstand them longer for every ship they had because of the shields.

In the movies you may not see this portrayed that well cause they have to shorten the battle scenes to fit them in a more convenient movie format and for special effects costs reasons but let's say that for every X-Wing ship destroyed there were usually many, many Tie Fighters turned into space dust.

In addition you don't hear the shields mentioned in Star Wars movies in the same way that you hear them being mentioned in Star Trek shows and movies. In Star Wars you hear mentioning of the shields but somewhat less than in Star Trek. In Star Trek they give you a low down of the status of a ship's shield moment by moment in terms of how much percent of the shields remain due to the audience hearing the characters mentioning this often like: "45% of the shields remaining captain" or something of the sort.

They play with this a helluva lot on the Star Trek dialogue but in Star Wars you hear it less often, here and there you hear something like "We lost the forward deflector shields" and in Star Trek the characters tell you little by little how much of the shields of a ship remain and then how much of the ship's hull structural integrity remain after that.

David Guzman
14th June, 2013 @ 11:26 am PDT
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