How To Cloak Objects At a Distance 136
KentuckyFC writes "All invisibility cloaks to date work by hiding an object embedded inside them. Now a group of physicists have worked out how to remotely cloak objects that sit outside a cloaking material. The trick is to make the cloaking material with optical properties that are exactly complementary to the space outside them. Complementary means that the material reverses the effect the space has on a plane wave of light passing through it. To an observer this space would appear to vanish. The scientists say that to cloak an object sitting outside the cloaking material, first measure its optical properties and then embed a "complementary image" of the object within the cloak. So a plane wave is first distorted by the object but then restored to a plane by the complementary image of the object within the cloak (abstract). An observer sees nothing. This method has another benefit. Objects hidden in conventional cloaks are blinded because no light enters the cloaked region. But objects that are remotely cloaked like this should still be able to see their surroundings."
Re:How to not be seen at a distance, low-tech styl (Score:4, Interesting)
Re:If you give it some thought (Score:3, Interesting)
The key point (Score:4, Interesting)
... in your argument is "against another sophisticated military".
However this is rarely the case. Nowadays most engagements the US Military is involved in are against people with little more than 25-50 year old weapons. The problem the US Military has is the on the ground war against these kinds of insurgents - this tech. would be invaluable against them, you could approach a camp on foot without fear of being seen.
Re:Big-ass photo... (Score:3, Interesting)
Well, no, actually they take a photo of the subject, make a sort of translucent negative, and put it in front of the object and make the object disappear from view. Slightly more ingenious because the background can change.
Not sure how they handle the "light behind the 'cloaked object' isn't shining through it" scenario. Presumably you could bend the light around the object and back into it's orignal path - but that's the 'embedded cloaking device' as far as I can tell.
Re:I can do this (Score:3, Interesting)
no, because then you're behind/inside the cloak and your visibility in the cloaked direction is zero. you're not unbending the light with a complementary image. if the light source is behind you, you'd just look like a jackass holding up a bed sheet.
the method proposed in the article is to hide objects outside (hence, "How to Cloak Objects At a Distance") of a cloak using a complementary material. no materials have yet been developed to do this.
it doesn't even necessarily have to be a physical material. if you can use lasers or an EM field to bend(or unbend) light back to its original state, then you can simulate a virtual complementary material. you'd still need to determine the optical properties of the object that you want to cloak to create the complementary image, but you could theoretically create a mobile/non-stationary cloaking device this way.
Re:How to not be seen at a distance, low-tech styl (Score:2, Interesting)
Well, if they're hiding in the sandstorm BEFORE the attack, sure.
But during? You'll be hard pressed to find a radio wave length that'll cut through what is essentially a huge but very fluffy stone and NOT cut through humans (tiny bit of water in the middle). Infrared will be blurred out. Radar will too.
What kind of advances have the military conjured into being that'll see through a sandstorm and tell you what's inside it (outside of lots and lots and lots of sand)?