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Australia Technology Science

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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Tractor Beam Created Using Water Waves

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  • No beam. Less space than a Nomad. Lame.

  • 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.

    • by MightyYar ( 622222 ) on Monday July 07, 2014 @03:51PM (#47402247)

      This is a pretty awesome result if it didn't depend on coincidence.

      That's why I don't use penicillin.

    • by Anonymous Coward

      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...."

    • by Anonymous Coward

      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

  • by SuricouRaven ( 1897204 ) on Monday July 07, 2014 @03:21PM (#47402013)

    Large scale: cleaning up oil spills.
    Small scale: Device for more effectively scooping up dirt and dropped leaves from a swimming pool.

    • Immediate use: Cleaning up spilled ping pong balls on still water.
    • by Anonymous Coward

      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.

    • As pushing is trivial, and both of your applications can be achieved by pushing, they were already covered before this discovery.

      • Pushing is nowhere near as effective in cleanup operations which is why vacuum cleaners suck instead of blow (and very early victorian models did). Suction concentrates the particles in a fixed location whereas blowing scatters them.
    • by pr0t0 ( 216378 )

      Maybe auto-docking boats in a busy marina-of-the-future.

      • 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.

    • More like, large scale: nuclear submarine wrestling matches.

  • by Anonymous Coward

    Bet this started out as a thought experiment on how to get chicks to stand close to them.

  • Anti-gravity! But how does one perturb space-time? We can't even detect gravitational waves much less create them. I don't think we will solve this one overnight
  • ..with TRACTOR beams!!

  • by dkman ( 863999 )
    Does it only happen when I have 3 walls that the waves can bounce off of? Because that would not work in an open water setting, only in enclosed settings. It makes me think of pool (billiards) where you could make a ball come toward you by hitting the que off two walls then into the back of the target ball.

    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.
    • Well, the solution to this would be to have multiple wave generators, would it not? Or, your singular generator could be housed in a reflector that creates the required interactions?
  • by slew ( 2918 ) on Monday July 07, 2014 @06:15PM (#47403397)

    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.

    • When you say that a relatively large scattered field (as compared to the relative momentum of the light beam used) attracts objects - how does a 'scattered field' cause this attraction? I guess I'm trying to determine how a scattered field of light would cause momentum towards the emitter...

      Would an electrostatic force be possible in the vacuum of space?
  • OK - so reversing polarity DIDN'T work - - - NOW go to MAX POWER (Wil Wheaton's last words . . .)
  • She's gone from suck, to blow!

May all your PUSHes be POPped.