Slashdot is powered by your submissions, so send in your scoop

 


Forgot your password?
Close
typodupeerror
×
Science

Physicists Devise Magnetic Shield 90

Posted by samzenpus from the leave-your-emp-gun-at-home dept.
sciencehabit writes "The sneaky science of 'cloaking' just keeps getting richer. Physicists and engineers had already demonstrated rudimentary invisibility cloaks that can hide objects from light, sound, and water waves. Now, they've devised an 'antimagnet' cloak that can shield an object from a constant magnetic field without disturbing that field. If realized, such a cloak could have medical applications, researchers say."
This discussion has been archived. No new comments can be posted.

Physicists Devise Magnetic Shield More

Physicists Devise Magnetic Shield

Comments Filter:

  • Metal Detectors? (Score:3)

    by cheater512 ( 783349 ) <nick@nickstallman.net> on Thursday September 22, 2011 @06:26PM (#37486094) Homepage

    Would this not cause a security nightmare?

    • Well, it says constant magnetic field. That's pretty hard to generate, since lots of things cause magnetic fields to fluctuate (including body movement of a metal object).

      • Re:Metal Detectors? (Score:5, Informative)

        by icebike ( 68054 ) on Thursday September 22, 2011 @06:36PM (#37486178)

        Well, it says constant magnetic field. That's pretty hard to generate, since lots of things cause magnetic fields to fluctuate (including body movement of a metal object).

        TLDR version of TFA:

        The hypothetical device would work as a magnetic cloak by creating a space that is protected from an external magnetic field while at the same time causing no telltale distortion of the field. Alternatively, it could also be used to conceal a magnetic object and prevent its magnetic field from extending out into space—

        So, yeah, if made portable enough it would be a security problem. But don't hold your breath.

        • So we should expect to walk through the hyper x-ray scanner 9000 naked in the next few months just as a precaution to such evil devices then
          • This is shielding against *magnetic* detection, i.e. conventional metal detectors, not your favorite neighborhood X-ray body scanners.
          • Not necessarily naked. And I get patent-dibs on the horizontally polarized transparent plastic coveralls with "Fly Clear" stencilled on the front. And on the vertically polarized sunglasses everybody will have to wear to preserve modesty, unless they tip their head sideways to get a peek at that absolutely gorgeous stacked blonde. Although, given the fat tattooed lady in between with a bit of paper stuck between the cheeks, most of us will probably opt to keep our heads straight up...:-)

            rgb

        • The Microwave shielding material is like a foil. I think it is feasible this is already in use by those secretive black-hat folks.

        • Sounds more like something to help hide submarines from MADs [wikipedia.org].

    • Was the TSA thinking ahead? (Score:1)

      by Anonymous Coward
      Perhaps this is the justification for restricting liquids on airplanes: presumably a liquid is required to cool the conductor to make it a superconductor.

      • Re: (Score:1)

        by izomiac ( 815208 )
        Encase the superconductive shielding in aerogel or a similarly effective insulator, and use high-temperature superconductors. You should be able to get enough time out of that arrangement to make it past security, plus it's now thermally shielded (not cloaked).

        But I doubt that's technically a problem. You see, the TSA categorizes substances by their phase of matter at room temperature. That's why they won't allow normal ice but dry ice is OK. Liquid nitrogen, helium, or hydrogen should be OK then, as

        • Wow. An electromagnetic shield to get "something" by TSA scanners? I'm pretty sure I could just hire a baggage handler to put "something" on board, without ever seeing a scanner. If money doesn't work, threatening his loved ones would.

          Yeah, that was evil, and I went there. Other people would, too.

          • Re: (Score:1)

            by izomiac ( 815208 )
            It's a security theater. But obviously it's no fun to devise clever methods of evading security when your opponent in the cat-and-mouse-game is worse than Garfield.

            • Wait, is the TSA the cat, or the mouse? Because we haven't seen all that much cleverness on either side of the game in a while. I mean seriously, shoe-bomb that doesn't work, followed by underwear bomb that doesn't work? the only thing remotely clever was the pepto-bismol-as-xray-shield, which would have worked except for the TSA gets slightly curious when things show opaque on an xray of your carry-on.

              Referring to TSA-vs-the enemy as a "cat-and-mouse-game" is insulting to both cats, and mice.

      • I think it is pretty obvious the TSA wasn't thinking.

        Just to humor the idea, though, I'm pretty sure compressed gas and cryogenic liquids were already not allowed. Although someone did try to use pepto-bismol to hide stuff from the xray machine.

    • Re: (Score:3)

      by ceoyoyo ( 59147 )

      Sure! The metal detector would be useless. You might want to search the guy walking through with a big bundle venting white vapour though.

    • Re: (Score:2)

      by jamesh ( 87723 )

      Would this not cause a security nightmare?

      Agreed. Metal detectors are useless. Cavity searches for all!

  • Kind of disappointing (Score:3)

    by theguyfromsaturn ( 802938 ) on Thursday September 22, 2011 @06:35PM (#37486170)

    From reading the headline I was almost expecting a shield a la Star Trek. All we would have left would be to find a way to make the Alcubierre warp drive something more than a theoretical possibility and I'd be donning Vulcan ears. Oh, well, I guess the waiting is not almost over yet.

    • Re: (Score:3, Insightful)

      by Commontwist ( 2452418 )

      Hey, if it, or some variation of it, could help shield a spacecraft from the Van Allen belts I'd call it a win.

      • The Van Allen belt is not problematic because of the magnet, it is the particles caught in the magnetic field that are the problem. They are flying around in circles, stuck forever (well, until they interact or decay). Dampening the field in one area would just make them fly straight for a bit, but they would be just as harmful as they were when they were flying in curly cues.

      • For that matter, if it could be scaled down small enough, it could really help isolate spacecraft components from EMI interference by other spacecraft components.
    • Agreed. The headline should have read "Physicists Devise Magnetic Cloak". It would still have been cool.
  • Now the problem with raising the magnetic field strength to get higher resolution is the the distortion of the field. Most of this distortion can be avoided just by shielding everything except what you are going to image in this magnetic shield.

    • MRI suites are already shielded.

      And no, you can not shield the specific volume (inside the magnet) to be imaged.

    • Re: (Score:2)

      by ceoyoyo ( 59147 )

      The problem is homogeneity of the field. And no, this won't help. To get a homogenous, strong magnetic field over a reasonably sized volume (head size, for example) requires a big magnet with a lot of coils. Thus, expensive. "Distortion" has nothing to do with it.

      • I'd rather say that SQUIDs should profit from this technique. http://en.wikipedia.org/wiki/SQUID [wikipedia.org]

        • Re: (Score:2)

          by ceoyoyo ( 59147 )

          Why is that? Why would you want to put your magnetometer into a device that cloaks it from external detection?

          If you mean screening out external fields to make a quieter environment, you can do that just fine using existing shielding techniques.

      • I was thinking it could be used in conjunction with MRIs, but in a different way...

        Could this shielding be used on devices that are too sensitive to allow MRIs (like pacemakers) so that the recipient of the device would be allowed to obtain MRIs?

        • Re: (Score:3)

          by ceoyoyo ( 59147 )

          Personally, I'd prefer not to have a pacemaker with a large, cryogenically cooled shield around it. Walking around with a liquid nitrogen can and hoses going into my chest would seriously cramp my lifestyle.

          I'm not even sure it would work properly - most of the danger to metallic implants, particularly sensitive electronic ones, in an MRI is from RF signals, not the magnetic field.

  • Think of the Quackery (Score:5, Insightful)

    by ZombieBraintrust ( 1685608 ) on Thursday September 22, 2011 @06:42PM (#37486228)
    Forget the actual medical applications. The applications for pseudo medicine are just as good. There are already a ton of people sleeping on magnetic mats. They would eat this up. Maybe even literally.

    • Re: (Score:2)

      by icebike ( 68054 )

      Forget the actual medical applications. The applications for pseudo medicine are just as good. There are already a ton of people sleeping on magnetic mats. They would eat this up. Maybe even literally.

      My kingdom for a mod point!!!

    • Forget both medical and pseudo medical. If you can shield something from a magnetic field, you can create a perpetual motion machine. Two magnets pull towards each other, generating energy, one gets shielded, move them away from each other, repeat.

      The possibility of a magnetic shield seems to break some thermodynamic laws, unless I am misunderstanding something.

      • Re: (Score:2)

        by bronney ( 638318 )

        what is "move them away from each other"?

      • Re: (Score:3)

        by Sabriel ( 134364 )

        The possibility of a magnetic shield seems to break some thermodynamic laws, unless I am misunderstanding something.

        The laws of conservation indicate the energy input to separate the two fields will meet or exceed the energy output from trying to pull perpetual motion shenanigans.

        And after RTFA, it's a materials-based cloak; you can't simply toggle it on/off, and moving the materials generates energy transfers which obey the conservation laws. :)

        When you consider the way the cosmos is set up, building an

      • As you obviously don't know much about thermodynamics, you likely can not judge if one is broken, or?

        After all: magnetic fields have nothing to do with thermodynamics (the word thermo comes from temperature and means HEAT). Thermodynamics applies to heat related physics ...

    • Re: (Score:2)

      by ceoyoyo ( 59147 )

      There are no actual medical applications. Somehow I think a patient will object to being opened up, their implant surrounded by a large, layered device containing liquid nitrogen or helium, then scanned. It would be easier just to remove the implant, scan, then put it back.

    • Re: (Score:2)

      by dougmc ( 70836 )

      Forget the actual medical applications. The applications for pseudo medicine are just as good. There are already a ton of people sleeping on magnetic mats. They would eat this up. Maybe even literally.

      I'm not so sure ...

      I mean, I certainly do believe that some people feel that magnetic fields (even static ones like the one created by the Earth) are making them sick -- but the technology to stop this in a room has been around for decades -- it's called a thick magnetic metal (iron, steel) box. If you've got a large budget and it needs to be as perfect as possible -- make it out of mu-metal [wikipedia.org]. Usually this is used for scientific and other work where reducing the magnetic field as much as possible really ma

    • Re: (Score:2)

      by CODiNE ( 27417 )

      Oh the other hand, maybe it'll let us make the time machine from Primer.

      hehehe

  • Better headline (Score:4, Informative)

    by pz ( 113803 ) on Thursday September 22, 2011 @07:07PM (#37486408) Journal

    A better headline would be, Physicists Come up with Idea to Build Perfect Magnetic Shield. As the article states, the device itself is hypothetical no proof of concept has been built.

    • Re: (Score:2)

      by Ihmhi ( 1206036 )

      A better headline would be, Physicists Come up with Idea to Build Perfect Magnetic Shield. As the article states, the device itself is hypothetical no proof of concept has been built.

      I'd say "Come up with idea" and "Devise" are pretty much the same thing.

  • ...or am I the only one around who remembers that totally cheesy, yet elementary schoolkid riveting, post-apocalyptic edutainment show "Tomes and Talismans"

  • This is news how? (Score:3, Informative)

    by Cosgrach ( 1737088 ) on Thursday September 22, 2011 @07:28PM (#37486574) Homepage

    Okaaaaaay. I hate to break it to you guys, but passive and active magnetic shielding has been around for a long time now. This is simply a new spin on old tech, adapting it and slightly enhancing it.

    Shielding an object from external fields is not difficult provided you have money to spend. Hospitals do it all the time for their MRI suites. The shielding may be either passive (LOTS of steel plates in the floor, walls and ceiling), or actively by installing 3-axis helmholtz coils in the walls, floor and ceiling. The coils are then driven by a set of very large and fast amplifiers. The amplifiers are driven by correction signal from a computer that has at least one 3-axis magnetometer. Obviously, the active solution is better as it can correct for things like elevators, automobiles and other things that influence the local magnetic field. The passive shielding is only good is the external field does not change.

    I remember one such shielding job in San Francisco that gave trouble because of the volume of *WATER* flow in the city water main running under the MRI suite. Yes, even water can affect magnetic fields. Passive shielding would not work, so the site had to switch to the more expensive active shielding.

    I also have had trouble calibrating magnetic instrumentation because of cars in the car park moving around. I'd have to wait for a window where there was no activity outside the building. I'm talking about smallish cars more than 50' away, and large trucks could change the fields from more than 100' away...

    • Re:This is news how? (Score:5, Informative)

      by robot256 ( 1635039 ) on Thursday September 22, 2011 @08:18PM (#37486974)
      Everything you said is true, but all those methods of shielding an enclosed space can be detected from outside the space by the resulting warp in the fields around it. The researchers in this article propose a method of layering materials so that the warping of the field is contained within the shield itself, rendering its presence undetectable. This is a significant advance over conventional shielding, but it has yet to be proven feasible.
    • Imagine having to anneal a Mumetal can the size of a MRI room?

    • Re: (Score:2)

      by mikael ( 484 )

      Certain water meters operated by actually measuring the distortion of the base level magnetic field due to the presence of ions in the water (metals from minerals, leeched elements from the pipes along with hydrogen and oxygen).
      The water meter was simply a ring of copper put around the pipe. Any changes in the flow of water created a fluctuation in the magnetic field, which in turn creates a current in the coil.

      Normally, these were intended for small pipes, but I guess it scales up for large pipes.

      Nimrod ai

  • Immediate Military Applications (Score:1)

    by Anonymous Coward

    Two I can think of:

    • Minesweeper ships - they don't want to trigger a mine's magnetic sensors, and are usually constructed entirely of wood and fiberglass.
    • Submarines - Don't want to be detected by mines or anti-submarine aircraft

    Carriers and other high-value ships are probably too big to use this. I'm not sure if their escorts would want this as much.

    Any more?

    • Warships are usually degaussed before a deployment and it can be and has been used in ships as large as a battleship. Carriers might be carrying electromagnetic coils as they did in WW2

      http://en.wikipedia.org/wiki/Deperming [wikipedia.org]
      http://en.wikipedia.org/wiki/Degaussing [wikipedia.org]

    • Re:Immediate Military Applications (Score:4, Interesting)

      by izomiac ( 815208 ) on Thursday September 22, 2011 @10:38PM (#37487800) Homepage
      Landmines. Right now, they use a bare minimum of metal to evade metal detectors, so everything is mechanical. This would allow a processor and such to be in the mine so you could have it not detonate on friendlies, and deactivate itself/start beeping after a couple years. Heck, you could even have the mines networked so the whole field detonates simultaneously when it detects large number of troops are half-way across. I'm not sure if it's in the best interest of humanity to revisit this technology, but at least some of their tactical and humanitarian problems can be addressed.

  • Can someone link me that story? Must have missed it. How do you shield something from water waves?

  • What a great material to wrap around my credit cards when they're in my eel-skin wallet.

    The eel skin has its electric field left over from its life shocking the s*** out of the fish it eats, which of course translates after death into a magnetic field that wipes the magstripe info from my credit card.

    With a layer of this between them, I wouldn't have to worry about that.

    And for that matter, this kind of shielding would probably wreck havoc on communications to the RFID chips on the "smart pay cards" like Sp

  • I can't believe that all of you missed the one obvious military application: concealment of nuclear submarines.

    Presently nuclear subs are detectable by planes (like the P3 etc. [wikipedia.org]) via use of magnetometers.

    A sub, being a very large metal object, interferes with the Earth magnetosphere (which is for the purpose of detection a constant magnetic field) and thus can be detected an "anomaly" in the magnetic field, far above their actual location deep underwater.

    This is one major weakness of modern subs that make

Slashdot Top Deals

A consultant is a person who borrows your watch, tells you what time it is, pockets the watch, and sends you a bill for it.

Close