Tractor Beam Created Using Water Waves 71
KentuckyFC writes The idea that light waves can push a physical object is far from new. But a much more recent idea is that a laser beam can also pull objects like a tractor beam. Now a team of Australian physicists has used a similar idea to create a tractor beam with water waves that pulls floating objects rather than pushes them. Their technique is to use an elongated block vibrating on the surface of water to create a train of regular plane waves. When the amplitude of these waves is small, they gradually push the surface of the water along, creating a flow that pushes floating objects with it. However, when the amplitude increases, the waves become non-linear and begin to interact with each other in a complex way. This sets up a flow of water on the surface in the opposite direction to the movement of the waves. The result is that floating objects--ping pong balls in the experiment--are pulled towards the vibrating block, like a tractor beam.
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That's no pool...
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You don't compress space, you bend it.
And, no, I don't actually know what that means either. :-P
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Gravity bends space, although always in the same basic way. (I think)
So lets imagine there may be some other way of bending space...
Re:Won't work (Score:5, Funny)
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Bite my shiny metal ass.
Re:Won't work (Score:4, Funny)
Gravity bends space, although always in the same basic way. (I think)
So lets imagine there may be some other way of bending space...
What?!?! Next you are going to tell me that gravity can somehow draw one object towards another. Preposterous!
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Gravity bends space, although always in the same basic way. (I think)
So lets imagine there may be some other way of bending space...
You don't bend it, you fold it.
Of course, you need a supply of the spice melange, first.
Re: Won't work (Score:2)
There is. Acceleration. Accelerate hard enough and all sorts of strange things happen in your wake, the trivial example being Unruh radiation.
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Lame (Score:1)
No beam. Less space than a Nomad. Lame.
How did they discover this? (Score:2)
If the backwards flow of water is a result of a complex system of causal interactions, they couldn't have come to the conclusion that this would work based on what they already knew. So how did they discover it? Was it an accident? If not, can one of them look into the future? This is a pretty awesome result if it didn't depend on coincidence.
Re:How did they discover this? (Score:4, Insightful)
This is a pretty awesome result if it didn't depend on coincidence.
That's why I don't use penicillin.
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Have you ever taken a bath and noticed that there's a dead spider or something in the tub? You definitely don't want to touch the dead spider, but you do want to transport it down to the far end of the bath. So you try creating some waves. Somehow, the effect of the waves is to bring the spider closer to you, instead of moving it further away. Then, if you're a physicist, you say, "That's odd...."
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they couldn't have come to the conclusion that this would work based on what they already knew.
They had some good expectation for something like this to work because similar systems were built using light, it was just a matter of getting similar setups with messier water waves. The paper covers a piece of the thought process and once could see that the principles it is built on could be thought out before hand, although sometimes just building something is easier when dealing with something that might be borderline (e.g. exactly what size vorticies are produced and in what quantity, etc., although d
I see immediate practical applications. (Score:5, Insightful)
Large scale: cleaning up oil spills.
Small scale: Device for more effectively scooping up dirt and dropped leaves from a swimming pool.
Re:I see immediate practical applications. (Score:5, Funny)
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Immediate use: Cleaning up spilled ping pong balls on still water.
Finally an experiment that cleans up after itself :)
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Until someone discovers that the high freq waves kill plankton, make dolphins deaf and do one or more of the other thousand horrible things that could go wrong.
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As pushing is trivial, and both of your applications can be achieved by pushing, they were already covered before this discovery.
Suction Better (Score:2)
Re:Suction Better (Score:5, Insightful)
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Maybe auto-docking boats in a busy marina-of-the-future.
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They already have autopilots for boats..
Perhaps an automatic rescue system that pulls people who fall in back to safety at the marinas? Or maybe in a pool where children may find their way where they aren't supposed to be.
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Sucking has rather short range unless you collect a lot of water, which in turn means high energy needs. I don't know what the energy demands of a wave-sucker would be, or some form of hybrid device, but there may potentially be a saving. It could also be done using fewer moving parts, as the oscillatory motion of a wave-maker is achievable with just a magnet and a coil. You'd want to pump it at the natural resonant frequency for maximum efficiency.
I'm imagining this as an improved skimmer, using the waves
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More like, large scale: nuclear submarine wrestling matches.
agree (Score:2)
Re:agree (Score:5, Funny)
Yeah, with a video, you have a reliable proof for every theory [youtube.com].
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... but I admit, it would be impressive to have a video actually showing the pull effect.
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Just play a video of the push effect in reverse!
MIT (Score:1)
Bet this started out as a thought experiment on how to get chicks to stand close to them.
If we could only do this with space-time (Score:2)
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It's like putting too much air into a balloon!
Freakin sharks.. (Score:2)
..with TRACTOR beams!!
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Walls (Score:1)
If you can repeat it from arbitrary points and arbitrary distances then you start to have something useful.
If you can repeat it with other wave sources then it gets more useful.
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Re: Walls (Score:1)
The light stuff works totally differently (Score:4, Informative)
FWIW, this paper [arxiv.org] talks about doing this with light (in the context of micro-manipulation). Doesn't look like we will be using this for any star-ship sized objects in the near future...
The basic idea is that you use a light with a specific profile to stimulate the object you want to attract in a way that causes a scattering field such that there is a net force backward to the emitter (it only works if the amount of net forward momentum of the light is relatively small compared to the scattering).
The water stuff referenced by this article works on a completely different principle, though as described here [arxiv.org].
They are similar in that they originate with a wave generator, also hitting the target at a glancing angle is a way to achieve the necessary conditions and both provide a net attractive force (aka tractor beam), but the physics is totally different.
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Would an electrostatic force be possible in the vacuum of space?
Tractor Beam Created Using Water Waves (Score:1)
Should work in other fluids too, like air. (Score:2)
She's gone from suck, to blow!