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If you're not into science, or the realms of science fiction, this may not be the diary for you. But seeing as we have a new Star Trek film in cinemas, and the Doctor Who universe is set to release Torchwood: Children Of Earth this summer, I thought this would be appropriate.

First: the invisibility cloak. I knew that scientists were working on this. The idea is pretty simple: if you can have your front display what your back can see (and vice-versa), you appear see-through.


Here's how it looks using a projector.


If you could do that with tiny cameras embedded in your clothing, you could end up with armor just like the Predator. Or you could just steer the light around you, using something called metamaterials, and look like a Romulan or Klingon ship. More about metamaterials later.

Well, here's where things get to be weird. Scientists in Hong Kong think they can manipulate this effect to make something look like anything else. Details below the fold...

OK, I'd better explain metamaterials. better yet, I'll let Wikipedia do it:

2005, Andrea Alů and Nader Engheta at the University of Pennsylvania issued a research paper which claimed that plasmons could be used to cancel out visible light or radiation coming from an object. This 'plasmonic cover' would work by suppressing light scattering by resonating with illuminated light, which could render objects "nearly invisible to an observer." The plasmonic screen would have to be tuned to the object being hidden, and would only suppress a specific wavelength - an object made invisible in red light would still be visible in multiwavelength daylight.

A concept for a cloaking device was proposed by two mathematicians in one of the UK's Royal Society journals. Shortly afterwards, blueprints for building a cloaking device were put forward in the journal Science by researchers in the US and UK. However, "Scientists not involved in the work said the plans appear feasible but that they would require more-advanced substances than currently exist".

In October 2006, a US-British team of scientists created a metamaterial which rendered an object invisible to microwave radiation. Since light is just another form of electromagnetic radiation, this was considered the first step toward a cloaking device for visible light, although more advanced nanoengineering techniques would be needed due to visible light's short wavelengths.

On 2 April 2007, two Purdue University engineers announced a theoretical design for an optical cloaking device based on the 2006 British concept. The design deploys an array of tiny needles projecting from a central spoke that would render an object within the cloak invisible in a wavelength of 632.8 nanometers.

Duke University and Imperial College London are currently researching this use of metamaterials and have managed to cloak an object in the microwave spectrum using special concentric rings; the microwaves were barely affected by the presence of the cloaked object.

Screw the Klingons and the first Khitomer Accord, we're making our own cloaks. But Star Trek didn't really hit upon what else these cloaks can do. Here's the Doctor Who part.

Invisibility cloaks work by steering light around a region of space, making any object inside that region invisible. In effect, an invisibility cloak creates the illusion of free space. This is possible because of a new generation of artificial materials called metamaterials that can, in principle at least, steer light in any way imaginable. Indeed, various teams have built real invisibility cloaks that hide objects from view in both the microwave and optical bands.

Now Che Chan and pals from the Hong Kong University of Science and Technology say that metamaterials could be used for an even more exotic effect: for cloaks that create the illusion that a different object is present.

The illusion is a two-step process, and to see how it works, imagine making a mouse look like an elephant. The first step involves an idea that these guys came up with about six months ago in which they described a way of cloaking objects at a distance.

The trick is to create a material in which the permittivity and permeability are complementary to the values in a nearby region of space containing the mouse we want to hide. "Complementary" means that the material cancels out the effect that the mouse has on a plane lightwave passing through. So a plane wave would be bent by the mouse but then bent back into a plane as it passes through the complementary material, making the mouse disappear.

The second step is to then distort this plane wave in the way that an elephant would. This means creating transformational material that distorts a plane lightwave in the same way as an elephant. So anybody looking at this mouse would instead see an elephant.

You could, for example, make your time-and-relative-space-dimension machine blend into the local surroundings. Make it look like part of a building. Or make it look like a tree in a field.


Or make it look like a police call box. Things might not work as planned if you want your TARDIS to look like a tree but the chameleon circuit is stuck on "1950's London police call box", of course.

These are truly incredible times we're living in.

Originally posted to ShawnGBR on Thu May 14, 2009 at 05:54 AM PDT.

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