Physicists Devise Magnetic Shield 90
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."
Metal Detectors? (Score:3)
Would this not cause a security nightmare?
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Re:Metal Detectors? (Score:5, Informative)
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.
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Invisible Submarines (Score:2)
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rgb
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The Microwave shielding material is like a foil. I think it is feasible this is already in use by those secretive black-hat folks.
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Was the TSA thinking ahead? (Score:1)
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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
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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.
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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.
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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.
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Sure! The metal detector would be useless. You might want to search the guy walking through with a big bundle venting white vapour though.
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Would this not cause a security nightmare?
Agreed. Metal detectors are useless. Cavity searches for all!
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my dentist says I have no cavities.
Kind of disappointing (Score:3)
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.
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Hey, if it, or some variation of it, could help shield a spacecraft from the Van Allen belts I'd call it a win.
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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.
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No, the 747 from 1969 is the 747-100, almost all are retired.
Most 747s you see now are 747-200s and -400s, from the 1980s through production today.
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A lot of smart folk who want to make money have gone into investment banking instead.
Also many smart people who want to make cool stuff are not doing it in aerospace. There are many other fields.
MRI can be much better with this (Score:1)
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MRI suites are already shielded.
And no, you can not shield the specific volume (inside the magnet) to be imaged.
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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.
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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.
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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?
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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)
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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!!!
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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.
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what is "move them away from each other"?
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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
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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 ...
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And why is one again down modding me? Especially why is it rated "troll"?
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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.
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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
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Oh the other hand, maybe it'll let us make the time machine from Primer.
hehehe
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It would have to be 100% efficient to even attempt that. Otherwise you'd lose energy in the conversion process and as a result end up with less energy than you had, rather than more.
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Also, you have to take into account the energy to make the shield.
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Nonsense. If the explanation as summarized is accurate you could use a permanent magnet. Let it attract an iron object on a string wound around a generator. As the object is attracted, the generator produces electricity. Normally, you have to EXPEND just as much energy to pry the object away from the magnet again. But if instead you introduce this "magic shield" between the magnet and the object just before they touch, you can pull the object away again for almost no energy expenditure. Rinse, lather,
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You forget one thing in your example: /. summary) a machine like the one you describe is no perpetuum mobile. The laws of energy conversion are still hold up.
the object you pull has to be placed back at its starting position. That costs exact the same amount of energy you have earnt before. So even with a magnetic shield device (I strongly suggest you read the article instead fo the
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According to the laws of thermodynamics, the power to create the shield would be the same or more than the power you could gain there. Makes sense, really.
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magnets don't have sides.
What do you mean by "shield one side"?
If you physically cut the magnet in half, you just have two magnets. If you left the magnet intact you wouldn't be able to shield it from itself. Unless maybe you had an infinite length shielding device spanning the whole universe...
hmmm...
trolled weren't I now?
Better headline (Score:4, Informative)
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.
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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.
Wipers had this back in the 80's... (Score:2)
...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)
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)
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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)
Two I can think of:
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?
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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)
WATER waves? (Score:2)
Can someone link me that story? Must have missed it. How do you shield something from water waves?
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Setup a standing wave of equal intensity but with (exact) opposite phase. (I think.)
New material for wallets! (Score:2)
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
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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.
MythBusters disagree [wikipedia.org]
Nuclear subs (Score:2)
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