• Question: Do you believe it will be possible to make a "invisibility" cloak by reflecting photons around an object? (The algorithm on this website detecting for similar questions is so annoying)

    Asked by heisenberg to Adam, Chris, Eleanor, Jessamyn, Sinead on 18 Nov 2013.
    • Photo: Christian Wirtz

      Christian Wirtz answered on 18 Nov 2013:

      Hi Heisenberg,

      there are some really cool things we can do with light by manipulating photons but I’m not sure if we’ll ever be able to make a Harry Potter style invisibility cloak. By combining materials with different refractive indices (that is, the amount by which they bend light) and giving these materials specific shapes (like lenses with different curvatures) we can certainly direct light around objects already. It is very hard to achieve that from every viewing angle though and I severely doubt you’ll ever hide a ship or plane or even car (sorry James Bond) that way.
      Hiding a moving object simply by manipulating the light will be almost impossible as the shapes of the materials will be extremely important. A single moving part will of course alter the shape (even if it’s just spinning wheels) which will likely result in a breakdown of your invisibility. A cloak that is wrapped around your shoulders would move so much and keep changing its pattern that it would attract more attention than without it.

      But is that the end to invisibility? No! A much easier way would be using cleverly placed cameras and flexible electronic screens. The first flexible electronic screens are slowly being developed and once those are properly on the market it will only be a matter of time before someone makes a cloak out of such material. With adequate computing power and a few small high-resolution cameras it should be well within our possibilities to make the cloak look (almost) invisible. I doubt it will ever be perfect but at least from a medium and long distance away it should fool any observer.

    • Photo: Eleanor Holmes

      Eleanor Holmes answered on 18 Nov 2013:

      Well Chris has sewn this one up. He’s quite right. Any light bending trickery we could imbue into a cloak would be More noticeable as soon as whatever is under the cloak moved. Have you ever seen a shimmer in the corner of your eye? Our peripheral vision is very good at detecting motion so even if we didn’t know where to look, as soon as Harry moves we would catch him!

      Something that was envisioned in another book (The Hitchhiker’s Guide To The Galaxy Trilogy) is an interesting way of hiding something from view. It’s to project a “Somebody Else’s Problem” field and everyone will just ignore whatever is behind it because, well, it’s somebody else’s problem. Move on!

      I love this idea because it’s so silly, and yet we see it working every day! People can ignore crying children, piles of washing, wars. Not My problem. Now, obviously we don’t have the technology to do this. It would involve a contained field that can manipulate brain waves. But, perhaps the take-away message is to make our secrets look so uninteresting and difficult to deal with that people just walk on by. Psychology over technology!

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