Permanent Human Settlement of the Earth, Space and Ocean Frontiers

Friday, May 12, 2006




Cloak of Invisibility

Ralph Buttigieg
Sydney, NSW
Australia
Invisibility is one of those great science fiction story devices and comic book super powers. H.G. Wells wrote the Invisible Man and every decade or so Hollywood does a TV show based on it. Star Trek had a “cloakng device” to hide starships. Harry Potter and Lord of the Rings both had invisibility cloaks .
Believe or not, a cloaking device may be possible. Two British mathematicians Nicolae Nicorovici and Graeme Milton have recently published a paper in a Royal Society journal outlining how it can be done. Apparently you can place an object next to a superlens and due to a process called "anomalous localised resonance" it would disappear.

The phenomenon is analogous to a tuning fork (which rings with a single sound frequency) being placed next to a wine glass. The wine glass will start to ring with the same frequency; it resonates.

The cloaking effect would exploit a resonance with light waves rather than sound waves.

The concept is at such a primitive stage that scientists are talking only at the moment of being able to cloak particles of dust - not spaceships.

In this example, an illuminated speck of dust would scatter light at frequencies that induce a strong, finely tuned resonance in a cloaking material placed very close by.

The resonance effectively cancels out the light bouncing off the speck of dust, rendering the dust particle invisible.

Remember only the maths has been done, no one has built a cloaking device yet. For me, its a case of I'll believe it when I don't see it.

What about something more personal, like Harry Potter's invisibility cloak? Well, a couple of years ago Susumu Tachi, professor of engineering at the University of Tokyo developed a crude prototype. A camera behind the wearer projects computer processed images on a jacket with the results shown above. This effect is called optical camouflage but its very early days yet. The effect is lost in bright light or if seen from the back or edge on. There should be ways around this see a real invisibility cloak one day.

The big problem all these methods have is they can't hide waste heat. Thermal imaging systems are still going to pick up optically camouflaged soldiers and spacebourne sensors cloaked spaceships. Even with todays technology passive sensors could pick up the Shuttle's main engines firing at Pluto. Like it or not we will take our wars into space with us. Expect the problems of stealth in space to be a major headache for future military planners.

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