Invisibility

Have you ever heard of the magical Invisibility Cloak from Harry Potter. I know, it is very much fiction, hence the magic part. But, what if we could render a three-dimensional object invisible using something other than magic?  Well, that is exactly what the U.S. Department of Energy at the Berkeley Laboratory have done, with the creation of a thin cloak which when placed on a object will mould to it and leave it impossible to detect with visible light (the stuff we use to see!). You see instead of magic scientists are using physics to create Invisibility Cloaks. However, on the downside, unlike Harry's Cloak, the one designed by scientists is so small that it could maybe shield a couple of your cells, not your entire body. 

The cloak is made of little building blocks of gold Nano antennas and is about 80 nanometers thick. The principal is light reflection, wherein the light is reflected in a way that makes the object appear invisible. The metamaterials that make up the cloak (also called a skin) can bend the light, altering it's behaviour.  *Metamaterials are very organized structures and really exceed normal everyday materials. They are commonly made with a conductor (aka: a metal).

So, other than being microscopic the cloak has other downfalls, like if the observer moves the illusion is gone and the object can be seen. Plus, to actually work on such a bigger scale (like to hide a person from view) the skin would be huge, like four times the person's actual size.

Now, lets talk physics. As mentioned above we see visible light, the light is reflected off an object detected by our eyes and sent to the brain via electrical impulses which makes an image. The frequency of the light is how colour is determined, without the light frequency, we would live in a colourless world.  So, it is easy to make the conclusion that for something to be invisible we need to prevent the light from reaching our eyes. This means there are really only two options, bend the light around the observer (us) or reflect the light preventing it from reaching the observers eyes. In modern times we have a less high tech method and it is camouflage, which if done well enough means that the object is able to blend into the surrounding so that it is impossible to point out. But, camouflage is unable to render something 'invisible', all it can do it make it fit into it's surroundings. 

Lets go back to the special metamaterials which with measurements and some spectacular physics can actually produce a negative index of refraction. The idea is that the metamaterial bends the light waves around itself and the thing it is concealing, which means that no distortions of the electromagnetic waves from the metamateria are detectable by any observer. This principle is not new, there are cloaking devices for different ranges of the electromagnetic spectrum. Metamaterials can conceal and reveal, for instance they can act as lenses, showing us things that are smaller than was thought could possibly be seen, which again goes back to the negative refraction, a unique property of the metamaterial.

Want more history, or even just some cool information on cloaking devices this short video is for you!

Websites Consulted:

http://newscenter.lbl.gov/2015/09/17/making-3d-objects-disappear/

http://www.sciencealert.com/watch-nano-sized-invisibility-cloak-can-make-small-objects-disappear

http://www.physicscentral.com/explore/action/cloaking.cfm

http://discovermagazine.com/2009/apr/10-metamaterial-revolution-new-science-making-anything-disappear
https://www.youtube.com/watch?v=qcTOPFMEEkM