SciFi Question of the Day: Is there any scientific reason that suggests it would be easier to build a tractor beam that pulls instead of pushes, or vice-versa?
Dave Mac I would think emiting a force to repel would be easyer than grabing something and pulling it. The reason is because not all objects are made from the same material.
Bill Nevin I always thought of tractor beams like magnets on the same frequency…so my answer to your question is simply yes
Iain Penman if the physics works as I expect it would, a “tractor” beam would pull both objects together, with the mass of the objects contributing to which one was moved further (relatively). In a push effect, the same rules would apply, but the effects would be less predictable, as the “source” of the beam would be moved backwards as well. since these beams are always displayed as projecting forwards (in every sci-fi show i can recall) i guess the propulsion system would be used to stop the source machine from moving away, so the subject of the beam is moved further?
Dale Thelander A beam that pulls is a tractor beam. A beam that pushes is a repulsor beam. They would work on two dissimilar principles.
Douglas S Caprette Of the four known natural forces two only pull, one only pushes and one goes both ways.
Dan Bressler What Douglas said – tho I will point out that the strong and weak nuclear forces would be unlikely candidates for an application like this. You could argue for a gravity-based pull only beam, or assume EM, which would be either/or.
Eric Schmitt with a tractor beam, you get to wear overalls and a straw hat.
AmyBeth Fredricksen …and the cool tan that goes with it!
Dale Thelander We’ve gone from science fiction to Kenny Chesney videos.
AmyBeth Fredricksen Some Kenny Chesney videos ARE SciFi…
Douglas S Caprette Well I’m not a big fan of fan-wank, but according to popular opinion the Star Trek Warp Drive works by distorting space. The only thing we know that distorts space is mass. So if the tractor beam is based on similar technology that would suggest that it should pull, rather then push, or such, rather than blow.
Dale Thelander Don’t you mean “suck?”
Dan Bressler Science doesn’t suck! http://www.cafepress.com/mf/24587551/science-doesnt-suck_tshirt
Ask a chemistry or physics teacher – science doesn’t suck, it just creates a vacuum.
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Darren Landrum I remember an episode of Star Trek: TNG that depended on getting the tractor beam to push instead of pull. Unfortunately, it was another one of those “boy wonder Wesley saves the day” episodes. And it’s sad that I say that, because Wil Wheaton has turned out to be a pretty cool guy.
Eoghann Irving Hmm. I guess it might depend what method is being used to create this tractor beam. If it was something similar to magnetism then of course there is direction and that would be a factor when designing the beam.
But on a purely physical level it takes the same amount of energy either way.
Darren Landrum … But now let me try to actually answer your question instead of leave dumb comments.
There are two principles I can think of off the top of my head you could use to make a tractor beam: a large magnet, or some way of creating a gravity field.
The large magnet method is going to depend on the target to be towed being ferromagnetic, and will therefore always be attractive. The gravity method kinda has the same problem: it’s always going to be attractive.
There’s new observations of the cosmos showing the existence of “dark energy”, which is a repulsive force permeating the universe, kind-of an opposite of gravity. However, a “dark matter” beam would likely have to be a separate device from a “gravity tractor” beam, unless you could somehow conflate the two ideas, like using some kind of “negative matter”, which is a real idea in physics, but only theoretically.
Mince Walsh Tractor beams are now a reality using some pretty interesting laser technology although so far they can only move a few molecules. At first they could only push but recently they have come up with a method to pull also. To get beyond moving only a few molecules, a few new breakthrus will need to be performed. But push is definitely easier than pull.
Samuel Falvo II +Darren Landrum. Magnetic fields can also repel if you move them fast enough. Modern maglev trains work on exactly this principle. Moreover, they work better with non-ferrous metals, like copper, aluminum, zinc, etc.
The idea is to create a moving b-field with sufficient intensity that the induced electrical eddy currents create an equal but opposite polarity b-field, thus repelling the object.
Of course, there has to be sufficient metal content in the object for this to work.
Thus, I feel, especially since we have far more non-ferrous metals than we do ferrous, it’s way easier to build a repulsor than it is an attractor.
Darren Landrum Ah, taking advantage of back-EMF to do something useful. I can see how that works.
Mince Walsh +Samuel Falvo II If the object you want to push or pull is conductive but not magnetic then yes, a lenz magnet can be used to push it. However, depending upon how much push you use, the object is going to get VERY hot. Lenz magnets only push non-magnetic objects with two sets of magnets 90 degrees orientation and alternating current also 90 degrees out of phase. They generate eddy currents in the object and push it. It uses a great deal of power and pushing with any reasonable amount of force would heat the object enough to cook anything inside to well done.
Samuel Falvo II Youtube videos show that a simple rotating B-field, roughly 25MPH, is sufficient to levitate the rotating magnet off a fixed copper plate, without excessive heat. The faster the rotation, the greater the repulsion. (In other words, both speed of rotation and B-field intensity determine repulsion.) You don’t need to invest a huge amount of power or set up complicated 90-degree phasing. All you need is low ohmic loss metals. In the event that you have higher ohmic losses, then of course, more power will be required. But, c’est la vie. If you’re a metal object, and headed straight for my starship with shields down, I don’t care, you’re going to be moved out of my way. 😉
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Kevin Murray If we’re limiting the implementation of a ‘tractor beam’ to a literal beam of some form of energy used to move something, making it ‘pull’ a target would most likely be getting into the ‘hard light’ trope. Basically, the beam would need to ‘grab’ onto the target and draw it back to the source- this would require some substance to the beam as it would need to handle the forces involved in pulling the target, like a piece of rope.
On the other hand, an energy beam used to push would not have the same constraints. Think of lasers; they are able to ‘cut.’ Interaction between our hypothetical beam and the target could theoretically produce a significant enough impulse to cause the target to move. Compare it to bullets- they certainly apply kinetic energy to the target, but a bullet can’t “pull” back towards the gun.
Now, if we move away from the literal beam of energy interpretation, something like gravity manipulation could, if possible, draw your target closer to you.
Ultimately though, one has to wonder about the usage scenario for it- surely a series of cables with grappling hooks could accomplish most things you would want to use a ‘pulling’ tractor beam for. Certainly there is an issue with cables being of limited length, but keeping any kind of beam cohesive enough to function becomes increasingly difficult as distance increases as well- and this would apply to gravity manipulation as well, given that the force of gravity decreases sharply with distance…
Francisco Esteban Well, i think a ray is always a ejection of energy or particles, so, in that way, push will be easier than pull.
Riley E. The closest thing to a tractor “beam” i could think of is ionizing a target with a UV laser (without melting it (maybe with a pulsed high power laser with a spinning mirror to sweep over the whole body, like a laser printer))
This wouldn’t be really useful for anything that had its own propulsion system, without generating dangerous amounts of static electricity, or vaporizing the target. You could use it to slowly clump together some near-by asteroids and rubble, maybe.
For attraction you could just use something like a shaped, pulsed magnetic field generated by a superconductor.
As for repulsion, I’d just go for the low tech approach of firing a rocket or impulse thruster.
Micha Fire a tractor beam actually just holds something in place –
or moving the whole combined field of tractor and tracted
Winchell Chung Science fiction writer E. E. “Doc” Smith invented the concept in the early 1930’s. Only he had “attractor” beams that pulled an object toward the projector, and “pressor” beams (or repulsors) that pushed objects away from the projector.
If you focused both an attractor and a pressor beam on an object, you would hold it rigidly in place relative to the projectors.
Winchell Chung Real world scientists have managed to make laser beams operated like tractor beams on a microscopic scale http://physics.nyu.edu/grierlab/conveyor7c/
Sheila Miguez I immediately thought of push, given solar wind. But then I remembered optical tweezers. http://en.wikipedia.org/wiki/Optical_tweezers
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Lorena Lombardo Crap, no idea. Any engineers around? xD
Mark Means Maybe the pulling effect is based, in part, on gravity and they used that naturally occurring effect as a model?
AmyBeth Inverness Who needs a real engineer? I’ll settle for someone with plausible-sounding BS. 🙂
With negative mass, somewhat according to physics laws, you could in fact create a push (repulsive) tractor beam, of course this is PURELY THEORETICAL. Since so far, It is not possible to create negative mass. A hypothetical idea could maybe be that using a black hole with its corresponding ‘out’ hole at the end of a worm hole, you could use that back door and its pushing force that is a result of the pull from the opening of the said black hole.
Then, by creating 2 tractor beams, one with the pull end and the other with the push end, you have the two sides of the worm hole and they would ‘power up’ those tractor beams.
Of course the fact that repulsive gravity does not exist is the main issue. So for it be a scientifically based sci-fi, hence good sci-fi (says someone on my back :P), there would only be pull tractor beam.
sigh hope this is good 🙂 I have to admit, my husband googled all of the info necessary for this answer. When I asked him about the sci fi question he really got it going to answer me basing it in real scientific research.
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Vishwas Shrikhande nice question, will try to find the answer
Peter Edenist There was an article on tractor beams in New Scientist. I Should reference that.
Half-Life Stand back, my main man is a physicist and from experience I can tell you that a weapon such as the zero-point energy field manipulator or ” http://en.wikipedia.org/wiki/Gravity_gun ” has a lot more trouble pulling things compared to pushing them away. The ZPEFM generates an intense gravitational well by calling massive particles into existence from the vacuum. Secret technology developed by Eli Vance allows it to precisely direct these gravitational fields into a narrow cone which allows the user to escape its influence as long as he doesn’t point it at himself. Now gravity’s intensity follows an inverse-square law so the further you get from the well the less pull you experience, get too far and the ZPEFM will not be able to pull you toward its well. Pushing is done by “reversing the well” which is done through the use of exotic matter which has negative or so called anti gravity. This process is much more energy intensive so I would guess that pulling things will be easier than pushing them. 😉
On a serious note; optical tweezers are all the rage among the kids these days and these work with them fancy photons and make use of the electromagnetic fields to impart momentum on whatever it is that you want to move and thus work over much greater distance as they are dependant on the amount of energy you can pump into your laser. Remarkably these can pull just as well as they can push but so far only work on really tiny scales. http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-18-7-6988
Peter Edenist +Half-Life has it 🙂
Abrak Jamson It’s easy to push objects (throw things at it until it moves). We have that technology now, although doing so with photons would vaporize it long before it moved very far. We’re also quite short on power; we’d need a few suns worth.
Anyway, it’s harder to pull them. Aside from the optical tweezers mentioned above, we don’t know how to do this.
Joshwa Pohlmann super magnet with light effects
I would love to hear what you think! Even if you are reading this post a year or more after publishing, I hope you will leave a comment with your own ideas on this topic.