Physicists at The University of Texas at Dallas built an invisibility cloak they can use to hide things by superheating a sheet of carbon nanotubes, which changes in appearance from a transparent sheet of incredibly expensive plastic into what looks like a heat-shimmer mirage in the desert, but is as convenient and portable as a sheet of superheated carbon nanotubes.
You can see the video below, or read all the details of the process and principles at Nanotechnology, which is published by the Institute of Physics, a professional association for physicists and invisibility cloak makers.
The mirage effect is an optical illusion that happens when light waves bend, as they do while passing from cool air high above the ground to hotter air just above it.
Because human brains prefer that light would always behave the way they expect it to, we don't interpret the image as reality bending. Instead, our optical-processing centers pick the image it already understands that most closely resembles what we see in the bent light – usually water -- and just decides that's what it is.
Our brains do this because our eyes and the portion of our brains that drives them evolved from the simple ability to detect light into sophisticated image processors during millions of years of evolution in hundreds of thousands of species that progressed from the sea to the land and, ultimately, to the asphalt, without ever learning how to look at bent light or superheated carbon nanotubes the right way.
Carbon nanotubes, btw, are long single molecules of carbon wrapped in a clear material that keeps each strand of carbon in place and insulates it from the air. The atomic bonds holding each strand of carbon to another hold together so tightly that a sheet of them only one nanotube (one molecule) thick is stronger than steel would be if you could slice it that thin, but has the density of air.
The heat-shimmer-mirage invisibility effect is created by running a current through a stack of sheets carefully arranged so the carbon nanotubes line up neatly. Under current the sheets heat up and cool down so quickly the effect appears and disappears as quickly as turning out a light.
The weird thing – weirder even than the IOP referring to carbon nanotube sheets as CNTs, as if carbon nanotubery were common enough for routine TLA-ification – is that the invisibility effect works better under water than in the air, because the water helps the heat dissipate more quickly.
While the invisibility thing is cool, it's not really invisibility except to people stumbling through the desert dying of thirst or stumbling for other reasons that would cause them not to question the appearance of a desert heat mirage right where something valuable – an enemy tank or adolescent wizard, say – would most likely be found.
In addition to the proto-invisibility, according to The University of Texas at Dallas research team leader Ali Aliev, the experiment probes the behavior of carbon nanotubes in ways that will make it easier to develop them into thermoacoustic projectors for loud speakers and for sonar devices that produce sound by electrically stimulating nanotubes rather than by having sailors yell into huge loudspeakers, as they do now.
Which is kind of a disappointing way to use even a bad invisibility cloak, if you ask me. But covert creeping around castles at night is not everyone's idea of fun. Not even when there are millions to be made from the merchandising rights.
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