Maybe years watching Star Trek reruns was not a total waste of
Now you see it, now you don't: cloaking device is not just
Ian Sample, science correspondent
Wednesday May 3, 2006
It's been the curse of the USS Enterprise and the Klingons' favoured
weapon. But back on Earth, mathematicians claim to have worked out how
to make a cloaking device to render objects invisible.
An outline for the device is described in a scientific paper published
today in which the authors reveal how objects placed close to a
material called a superlens appear to vanish.
Even in the world of science fiction, the technology is not perfect,
and nor is the device proposed by Graeme Milton at Utah University and
Nicolae-Alexandru Nicorovici at Sydney University of Technology.
According to their calculations, the device would only work at certain
frequencies of light, and only if the object is within close range of
The cloaking device relies on recently discovered materials used to
make superlenses that make light behave in a highly unusual way.
Instead of having a positive refractive index - the property which
makes light bend as it passes through a prism or water - the materials
have a negative refractive index, which effectively makes light travel
backwards. It's light, but not as we know it.
Prof Milton's team calculated that when certain objects are placed
next to superlenses, the light bouncing off them is essentially erased
by light reflecting off the superlens, making the object
The calculations show that while the device could be used to obscure
almost any shape of object, it only works over a short range of
wavelengths, so if used to hide objects from human vision, they might
only partially disappear.
Sir John Pendry, a theoretical physicist at Imperial College London
who invented superlenses, said: "Effectively, they are making a
piece of space seem to disappear, at least as far as light is
The research appears in the journal Proceedings of the Royal Society
Prof Pendry said the technology has great potential for hiding objects
from radar or cloaking electronic instruments so they can be used in
strong electromagnetic fields, such as those produced by hospital MRI
brain scanners. "The secret is having the cloak itself be
invisible and if you can do that cheaply and efficiently and it
doesn't need to be metres thick, it would be extremely valuable for
stealth. Even if you could cloak a single frequency, it would be very
useful. The military is extremely interested in this."
So far the researchers have only worked through the mathematics to
prove that the device is plausible. The practicalities of making one
have yet to be solved.