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Australian Physicists Build Reversible Tractor Beam
An anonymous reader writes: Physicists at Australian National University have developed a tiny tractor beam that improves in several ways upon previous attempts. First, it operates on scales which, while still tiny, are higher than in earlier experiments. The beam can move particles up to 200 microns in diameter, and it can do so over a distance of 20 cm. "Unlike previous techniques, which used photon momentum to impart motion, the ANU tractor beam relies on the energy of the laser heating up the particles and the air around them (abstract). The ANU team demonstrated the effect on gold-coated hollow glass particles. The particles are trapped in the dark center of the beam. Energy from the laser hits the particle and travels across its surface, where it is absorbed creating hotspots on the surface. Air particles colliding with the hotspots heat up and shoot away from the surface, which causes the particle to recoil, in the opposite direction. To manipulate the particle, the team move the position of the hotspot by carefully controlling the polarization of the laser beam."
There is still a long way to go before we can use it to move a Ferenghi vessel or to fight off the Borg. We ought to make this a national priority. If you think the Ebola thing is scary, the Borg makes viruses look like sheer child's play.
All the better to keep the ugly sheelas away with eh? Chuck another shrimp on the barbee skip!!!
...the ANU tractor beam relies on the energy of the laser heating up the particles and the air around them.
Oh, boy. It cooks you as it moves you.
Sounds like a great formula for a space rotisserie.
Despite the politicians in my country doing their best to ruin science and scientific research, it's nice to read how developments like this are still possible.
"Unlike previous techniques, which used photon momentum to impart motion, the ANU tractor beam relies on the energy of the laser heating up the particles and the air around them
Need I say more?
If they could find high end energy like the ship, this could be practical at full scale and portable. Then again the military uses lasers to down missiles I'm not sure how they generate the power for that, considering they are mobile weapons. Or the US is full of itself and doesn't have enough power to use the lasers effectively, more or less a scare tactic to other countries.
Which makes me curios, since slashdotters seem to be in all type of things, is this an actual weapon that one witnessed in action for themselves?
Is this like the Coriolis effect? Will it work in the correct direction in the hemisphere that matters?
Lets learn to speak the language, shall we?
Tractor's pull. A tractor beam would pull. This pushes. It can't pull. This means its not a reversible tractor beam, which would mean it can pull and be reversed to push ... it can only push.
Its a pusher beam, and it only works in a fluid, on objects with tiny amounts of mass that can stand to be roasted into oblivion in order to move them less than distance of a reasonable sized dictionary.
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Australian Physicists Build Reversible Tractor Beam
No they didn't. Not even remotely.
the ANU tractor beam relies on the energy of the laser heating up the particles and the air around them
Australian Physicists Build Reversible Tractor Beam
No they didn't. Not even remotely.
the ANU tractor beam relies on the energy of the laser heating up the particles and the air around them
Exactly. If I built a system that deployed a wheeled robot controlled by RF signals to drive over to something and push it toward me, that would be as much of a "tractor beam" as this is.
It is a beam that can push and pull certain types of particles... that meets the vague definition of a tractor beam quite well. And if you were to argue otherwise, "not even remotely" would still be inappropriate.
To manipulate the particle, the team move the position of the hotspot by carefully controlling the polarization of the laser beam."
And you all thought that the Star Trek writers were just spouting nonsense...
Slashdot still doesnâ(TM)t support Unicode after it was added to the HTML standard in 1997.
Australian Physicists Build Reversible Tractor Beam
No they didn't. Not even remotely.
the ANU tractor beam relies on the energy of the laser heating up the particles and the air around them
Exactly. If I built a system that deployed a wheeled robot controlled by RF signals to drive over to something and push it toward me, that would be as much of a "tractor beam" as this is.
If you did it without the robot and only used the rf beam in some way sure. This may not be a true tractor beam but at least it is a beam and it does tract. So your remote controlled fetchbot is just that. Did they say in Star Trek "use the tractor beam" to which some red shirt gets in a shuttle to get whatever they wanted?
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....you know why? There is no atmosphere!
So if this thing relies on Air molecules, how will it work, in space that is?
No. In my example the beam controls the effector function, which in this case is a pusher bot. In the Australians' case, the effector function the beam controls is superheated air.
Did they say in Star Trek "use the tractor beam" to which some red shirt gets in a shuttle to get whatever they wanted?
No. My case is reductio ad absurdum to illustrate why the Australians have NOT created any sort of tractor beam. If theirs is a tractor beam then so is mine, and I am saying that neither example is.
Well it might be able to move a whole chicken, but it can surely move fried chicken.
It's called a Repulsor Beam, you nimwits.
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The beam here isn't just about control, but directly causes the effect that moves the particles. A robot could still move things without a control beam, with near trivial changes in principle. To cause similar heating of the air in this case without a beam would require a fundamental change in methodogy (e.g. a small rocket engine, which is attaching something to the particles unlike this process).
Otherwise you could argue tractor beams are impossible. More traditional ones that use photon pressure are just using the beams to control the emission of light form the particles... which could be duplicated by attaching a light source to the particle.
Okay then, my pusher robot is powered by wireless power transmission from my beam and to a rectenna on the pushed bot. Now my beam is directly causing the effect as much as the Australians' beam is. The fact that their approach is constrained to requiring specific beads and an atmosphere is NOT a supporting argument (I.e. "my approach requires these precise artificial setup constraints, therefore it MUST be more of a tractor beam than the pusher not" isn't a valid argument).
Your move.
You're still acting like attaching a mechanism to something is still analogous to something that direct causes an effect. The point wasn't that an alternative could require a beam, but that a very similar alternative to your approach doesn't require a beam. You're also still not addressing that you're approach makes pretty much anything impossible to labeled a tractor beam, including the more traditional methods. Making up a definition for a term that is impossible to use is pointless, which might be why you're not the one defining such things in the literature.
" This may not be a true tractor beam "
Considering the microwave thruster seems to violate the laws of physics you might want to think about that some more.
Nope. You're missing the fact that this is a completely contrived experiment that requires a special beads and the action of the atmosphere. It does NOT cause a direct effect... the effector is the superheated gas. It couldn't work in a vacuum.
Electromagnets are a far better example of a tractor beam than this thing, which is a simple contrivance no different in concept than a pusher bot. Oh look: now I defined something I consider more consistent with the definition of a tractor beam while maintaining that this stupid "Australian tractor beam" is nothing more than a contrivance. A laser boiling some water in a pool and causing a rubber duck to bob around would meet your absurd criteria for a "tractor beam".
The same pulp science fiction era that introduced the term "tractor beam" in the first place also gave us "pressor beam". Both terms have been in continuous use in literature for about 50 years, maybe much longer. It's appalling that any person who claims familiarity with nerd culture, much less membership in the geek tribe, would not know this.
A tractor beam *grabs* its target, holding it in place or even drawing it towards the beam origin.
A pressor beam *pushes* its target, although the target may attempt to "roll off" the point of pressure.
These would be strong technical terms, if idiots with no familiarity with the relevant literature would stop insisting on dominating the conversation.
But anyway you're right. This thing barely qualifies as a pressor beam, and it's nonsensical to call it a "reversible tractor beam".
It does NOT cause a direct effect... the effector is the superheated gas. It couldn't work in a vacuum.
Just like how a winch and crane doesn't lift or move anything, it is only adds tension to rope, which is the really effector...
It couldn't work in a vacuum.
The same setup should work in a vacuum, just less effectively. It doesn't take much photon pressure to move small objects around (as seen by other types of tractor beams), selective heating can cause a net force from radiated heat (an effect that is significant with asteroids), and most materials will out gas to some degree when heated in a vacuum.
Electromagnets are a far better example of a tractor beam than this thing
Because they aren't material specific...
A laser boiling some water in a pool and causing a rubber duck to bob around would meet your absurd criteria for a "tractor beam".
If it could controllably pull something closer and not just cause it to wander around, it seems quite suitable as a tractor beam. And there are some projects looking into using water waves to consistently move objects closer or further with minimal effort...
We'll have a Moore's Law type thing for tractor beams soon? :)
Considering the Beam is limited to 20cm right now, my money is on grappling hooks...
Then again, if looking for space battle damage, firing an actual Tractor at the target might be more effective.
Kinda like this?
https://what-if.xkcd.com/13/
"This flow of material effectively turns the entire surface of the Moon into a rocket engine—and a surprisingly efficient one, too. Using lasers to blast off surface material like this is called laser ablation, and it turns out to be a promising method for spacecraft propulsion."
Okay, so you admit that water waves are consistent with your definition of a tractor beam. I think we're done here.