Last week we heard that researchers from Imperial college London, have published a study dealing with newly engineered metamaterials. These materials allow for light hitting them to be sped up or slowed down. Doing this, creates a zone with effectively no light, rendering that zone, and everything in it, hidden from sight, or invisible. The press release can be found here.

Our vision sensors, or eyes if you like, seem to work by collecting light rays from the environment. Waves of light hit objects, bounce off those objects and get picked up by the eye. The light then enters the eye through the cornea, passes through the pupil, and hits the retina. The picture there is received upside down, and it's up to the brain to take over and flip it around, do some filtering, put it all into context and perspective, and hopefully not pull too many tricks on us, as it often does..

Basically one could argue that it makes no difference how accurate your vision sensors are, as it still all depends on the programming and functionality of the brain, to interpret the data and make sense of it. But that's totally off topic.

Anyway, the researchers found a way to continuously manipulate the refractive index of these new metamaterials. The refractive index of a material, is the speed at which light passes through it. To date, scientists believe that the speed of light in a vacuum denoted by c, is constant (299,792,458m/s) and is the cosmic speed limit. The speed of light as it passes through different materials depends on many factors. You can read more about that here.

What's so cool about these new metamaterials is that they are engineered to have constantly changing refractive indices, meaning that the speed with which light passes through them, is variable.

The team had this brilliant idea, to take the front end of a light wave hitting the metamaterial and cause it to speed up, and take the back end of that same light wave and cause it to slow down.

By doing so, they'd be creating an area in the middle where no light is present, and hence, nothing to bounce back and hit our vision sensors telling us that something is there. That would make us entirely unaware of the existence of anything in that middle light gap, or of the gap itself. I love this concept!

This is different from past cloaking device concepts, which used other methods to bend light waves around objects. In which case, rather than hitting the object, the light is simply diverted on a curved path bypassing it entirely.

The new concept would be great to use if you wanted to do something, and have others remain oblivious to your actions.

The press release gives the example of breaking into a safe. All you'd have to do is speed up the light in front of you, slow down the light behind you, and do your lock picking inside that gap. Once you were done with your pillaging, you'd simply return the safe to its original configuration, and get out of there.

To any outside observer, it would seem that the safe is fine, and undisturbed. It'd be kind of like looking at old buffered data, rather than getting real time information.

With the cloak gone, the light waves would return to their normal velocity, and the observer would seamlessly transition back to viewing things in 'real time'.

Of course there would be that problem of you having to work in the dark.. seeing as there would be no light waves around.

The light bending concept wouldn't restrict you to the dark, but it also wouldn't help you pull off this type of job. The bending trick could conceal you, and the safe too if you'd want to pull the cloak over it, but then, it'd be pretty obvious that the safe had gone missing..

Another thing I liked about this new concept, is that they mentioned they could do this same thing, this time gap, buffered data trick with sound waves as well. So you wouldn't hear anything going on in the gap. Actually I think that would be a really cool invention, tons of applications for temporary cones of silence.

As far as actually making these things, we've got a ways to go. For the time being the researchers are working on a slimmed down version of the new concept, that will only open a light gap for a few nanoseconds. The gap will be about 30cm long, and will only work if the observer is located directly ahead of oncoming light.

The bending cloaks so far have been made to conceal only certain wavelengths of light, also on small scales.

But it's a start!

This all really shows how easily manipulated we are.. bend some light here, open a small gap there, show us old data.. and we are none the wiser. Something to think about..

For more information, here are a couple of cool posts on the topic -
Space–time cloak could hide events on Nature News
How to cloak a crime in a beam of light on NewScientist

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