Bringing sight to the invisible


March 17, 2009

Harry Potter and his cloak of invisibility - which you can't see obviously

Harry Potter and his cloak of invisibility - which you can't see obviously

March 18, 2009 Invisibility has been a staple of science fiction, (and my own personal fantasies), for decades and in recent years we’ve watched as fiction edges ever closer to reality through the use of metamaterials. The problem with most of the devices currently being researched however, is that since they totally encompass the object being rendered invisible, they are also rendered blind as well, which kind of defeats the purpose. After all what’s the point of being invisible if you can’t actually see around the girl’s locker room. But a team from Hong Kong’s University of Science and Technology believes they have come up with an answer to this problem and that it is indeed possible to create a cloaking device that would be able to render an object invisible without encompassing it.

Currently such a device only exists in theory – which is to say not at all – but the team consisting of Che Ting Chan, Yun Lai, Huanyang Chen and Zhao-Qing Zhang have published their ideas in Physical Review Letters: “Complementary Media Invisibility Cloak that Cloaks Objects at a Distance Outside the Cloaking Shell,” that details how such a device could be made reality. As Che Ting Chan tells, “We haven’t built the device, 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.”

So for anyone with the time, resources and inclination how would such a device work – theoretically? Well, theoretically, the device would rely on complementary media. As Chan explains, “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 points out that the cloaking device would also be rendered invisible – in theory. Chan admits that the theory would only provide complete invisibility for one wavelength – even if an object was made invisible for the visible spectrum, it would still be visible on radar - which limits its military usefulness somewhat.

Since the ideas are only theories, who knows if or when we’ll see, (or won’t see), a real world demonstration of such invisibility technology. But the team aren’t solely concerned with making objects invisible, they say that is just the first step at understanding how to use complementary media to transform how and object looks. Anyone who has seen me first thing in the morning would understand what truly worthy research this is.

Darren Quick

About the Author
Darren Quick Darren's love of technology started in primary school with a Nintendo Game & Watch Donkey Kong (still functioning) and a Commodore VIC 20 computer (not still functioning). In high school he upgraded to a 286 PC, and he's been following Moore's law ever since. This love of technology continued through a number of university courses and crappy jobs until 2008, when his interests found a home at Gizmag. All articles by Darren Quick
1 Comment

Consider a setup with three objects. One is the object to be hidden. Two is the "anti-object" (as described in the article) with respect to the group of objects one and three, cloaking them in green light. Three is the "anti-object" with respect to the group of objects one and two, cloaking in infrared. Presto---you now have invisibility in two wavelengths. The principle could be extended to a greater number of wavelengths, and objects two and three need not actually be separate---considered together, they are the cloak. If this sounds too good to be true, it probably is. There must be a catch somewhere.

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