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Building an 'Invisibility Cloak' With Electromagnetic Fields

Posted by Soulskill on from the easier-than-building-them-with-corn-fields dept.

Nerval's Lobster writes "University of Toronto researchers have demonstrated an invisibility cloak that hides objects within an electromagnetic field, rather than swaddling it in meta-materials as other approaches require. Instead of covering an object completely in an opaque cloak that then mimics the appearance of empty air, the technique developed by university engineering Prof. George Eleftheriades and Ph.D. candidate Michael Selvanayagam makes objects invisible using the ability of electromagnetic fields to redirect or scatter waves of energy. The approach is similar to that of 'stealth' aircraft whose skin is made of material that absorbs the energy from radar systems and deflects the rest away from the radar detectors that sent them. Rather than scattering radio waves passively due to the shape of its exterior, however, the Toronto pair's 'cloak' deflects energy using an electromagnetic field projected by antennas that surround the object being hidden. Most of the proposals in a long list of 'invisibility cloaks' announced during the past few years actually conceal objects by covering them with an opaque blanket, which becomes 'invisible' by displaying an image of what the space it occupies would look like if neither the cloak nor the object it concealed were present. An invisibility cloak concealing an adolescent wizard hiding in a corner, for example, would display an image of the walls behind it in an effort to fool observers into thinking there was no young wizard present to block their view of the empty corner. 'We've taken an electrical engineering approach, but that's what we are excited about,' Eleftheriades said in a public announcement of the paper's publication. (The full text is available as a free PDF here.)"

9 of 71 comments (clear)

  1. Error, Error. by girlintraining · · Score: 4, Interesting

    Invisibility cloaks like this only work within a certain range of EM frequencies. Outside of that range, it won't work; in fact it may even amplify the signal and make it more obvious whatever is being cloaked. And there are some thing no amount of cloak can deal with. You can alter the optical properties of a thing, but if it's out-gassing several thousand degree plumes... you cannot mask the infra red signature of that. These new meta materials may help in communications, but I highly doubt they will ever be able to make large human-sized physical objects disappear to any current multi-sensor technology.

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    1. Re:Error, Error. by i+kan+reed · · Score: 3, Insightful

      Sure, pragmatic constraints affect every design. But if you're worried about being spotted by cosmic rays, that's a lot better than being worried about being spotted by guards or radar.

    2. Re:Error, Error. by nospam007 · · Score: 3, Insightful

      "Invisibility cloaks like this only work within a certain range of EM frequencies. "

      Just like a concrete or brick wall. It works only within a certain range of EM frequencies.
      With the right viewing system, you can see right through.

    3. Re:Error, Error. by girlintraining · · Score: 3, Interesting

      Sure, pragmatic constraints affect every design. But if you're worried about being spotted by cosmic rays, that's a lot better than being worried about being spotted by guards or radar.

      I'd be more worried about dying of cancer, honestly. And metamaterials do offer the promise of light-weight shielding against radioactivity in space -- as has been pointed out, they do operate over certain ranges of frequencies. I'm just tired of people calling them 'invisibility cloaks', when all they're doing is reflecting emissions at certain frequencies in a novel fashion. There are a great many useful applications for this... but "invisibility cloak" doesn't make the list. Sorry. That's bad science.

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  2. Just as I thought! by DontBlameCanada · · Score: 4, Insightful

    Canada is harbouring dissident Romulan scientists brought here by James T. Kirk (Canadian William Shatner).

  3. I wish they'd stop calling it that. by Lumpio- · · Score: 4, Insightful

    I think it's only justified to call something an "invisibility cloak" when it does what people actually expect an invisibility cloak to do, that is, make things actually not visible. How about calling it a "stealth cloak" because that's what I imagine most people would associate with being invisible to a radar, as opposed to the naked eye.

  4. We have been here before it went horribly wrong by ralphaostrander · · Score: 3, Funny

    http://en.wikipedia.org/wiki/Philadelphia_Experiment

  5. Re:Just destructive interference? by Mr+D+from+63 · · Score: 5, Funny

    I don't see how this could work for radar or light.

    Of course you can't see it working. Thats the point.

  6. Invisibility Cloak, yeah right by Rotag_FU · · Score: 3, Insightful

    And I thought it was just the mayor smoking crack, apparently the whole town is now. :)