New invisibility cloak allows object to 'see' out through the cloak
March 13, 2009 By Miranda Marquit(PhysOrg.com) -- "Many groups have been working devices that make objects invisible," Che Ting Chan tells PhysOrg.com. “Most of these devices, however, encompass the object to be cloaked.” Chan, a scientist at The Hong Kong University of Science and Technology, believes that it is possible to create a cloaking device that would be able to render an object invisible without encompassing it.
“With the devices that encompass the object,” Chan continues, “the cloaked subject is ‘blind’. It can’t ‘see’ out through the cloak. We can’t see the object, but the object can’t see us, either. We wanted to create a conceptual design that would let the object ‘see’ out through the cloak while hiding it from sight.” Along with Yun Lai, Huanyang Chen and Zhao-Qing Zhang, Chan believes that this could be accomplished. Their ideas are published in Physical Review Letters: “Complementary Media Invisibility Cloak that Cloaks Objects at a Distance Outside the Cloaking Shell.”
Right now, such a device exists only theory. “We haven’t built the device,” Chan says, “but we have shown mathematically how it could work. It is a very specific description of the materials needed. If you have the time and resources, we think it could be done.” He points out that it might have interesting possibilities in a number of fields where invisibility might be desirable.
Theoretically, a device such as Chan suggests, would work through complementary media. “Our strategy is to put the cloaking device and the object to be cloak next to each other. The cloaking device is a kind of anti-object. The way the light is gathered and scattered by the two objects - the cloaking device and the object it is making invisible - would cancel each other out.” Chan continues by explaining that the cloaking device would become invisible as well. “Both must be invisible in order for this to be effective, and I think we have shown in theory how this could work.”
Chan admits that 100 percent invisibility is only available for one wavelength, however. “Right now, the usefulness, especially for military applications, is limited,” he says. “You can only make the object invisible in one wavelength, so if I made it invisible for the visible spectrum, all someone would have to do is use radar to detect the object. A lot of work would need to be done to make a cloaking device that worked for more wavelengths.” He pauses, before adding, “It might be possible to make the object almost invisible for broader wavelengths, but that would also take a lot of work. And you still wouldn’t have 100 percent visibility.”
The Hong Kong team, although interested in rendering objects invisible, is working on another ambitious project. “We have shown that we can cause invisibility in objects, and allow them to ‘see’ out of the cloak,” he says. “We are now working on how to transform how an object looks. Invisibility was just the first step in this. By understanding how complementary media invisibility might work, we can also look at how it might be possible to transform the look of an object into something else. Perhaps make an apple look like a banana.”
Science is beginning to sound more like magic by the day.
More information: Yun Lai, Huanyang Chen, Zhao-Qing Zhang, and C. T. Chan, “Complementary Media Invisibility Cloak that Cloaks Objects at a Distance Outside the Cloaking Shell.” Physical Review Letters (2009). Available online: http://link.aps.org/doi/10.1103/PhysRevLett.102.093901 .
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" ...continues by explaining that the cloaking device would become invisible as well. Both must be invisible in order for this to be effective .."
Self evident really, else I could just toss a sheet over myself and say "hey, i'm invisible".
Is there any actual information in this article?
EG: How to see out but not see in?
Ladislaus
Like perhaps wild-life watching? But animals use their ears and nose more than their black-and-white eyes.
Surprise birthday parties? Ok, but I hardly think that outweighs:
Militaries seeking Global domination (There were two world-wars and a cold-war last century, not to mention countless "minor" wars).
Assassinations (and the inherent destabilization that occurs afterwards).
Spying (from CIA to stalkers and peeping-toms).
Burgalry.
And though sci-fi tantalizing, in reality we're not evading aliens. It's only ourselves that we're using this stuff on.
Ok, some more realistic benefits:
You can have some privacy, say when you want to walk in a park without saying hi to all your friends, or when you want to pick your nose or such.
The walls of your house can turn invisible and let in sunlight... now that's passive heating!
Light-bending applications in general are productive, but I don't see as much benefit for "invisibility", per se, itself.
A 'Harry Potter' style cloak would have to be banned if invented..
I guess it would be nice to factories / wind turbines etc invisible.
I could just imagine a plane flying into a wind turbine...
How about controlling heat transfer in electronics? A cloaking tube around the processor would keep heat from affecting nearby components (a fan would carry the heat away) or a tube around a heat sensitive component would insulate it.
Cloaking in Optical computers would allow light pathways to flow around other components in the same way that Fiber Optics would allow.
And how about the warmest blanket on Earth? That cloak might make you invisible, but it would also reflect back most of your body heat when you are cold and reflect most of the heat off of you in a desert or out in space in direct sunlight.
Maybe even a cloak designed to pass deadly radiation from the Sun around a spacecraft...might be lighter than other types of sheilding.
A long tube-cloak would insulate superconducting wires to allow loss-less power transfer (maybe from those Solar farms out in the desert to the cities.)
A cloaked speed trap for policemen! No, wait, nevermind.