Close your eyes, just close your eyes. And you cannot be seen any longer. That’s what children believe: “I can’t see you, you can’t see me.” Some really encouraging mantra for the disco dancefloor, too. Anyways, the xeric reason all the kiddie-winks joyfully happen to be über-convinced of being *nana nana naaanaaa* invisible is that they are lacking some specific cognitive ability called object permanence. Touché!
So there must be other ways of becoming invisible during one’s lifetime, which is to say hiding your eyes behind the palms of your hands is no more a solution than getting stuck between you-don’t-know-where whilst your body moulders away six feet under.
Speaking of other dimensions physically isn’t quite clear yet what it means. So I won’t follow that path. Way easier is grabbing some 3D hologram-machines, that are quite interesting, but are facing one problem: you can see the machine. Just convince yourself here:
Quite not a 3D hologram-hyper-machine, just some moindre machinerie.
So, what else do we have left? Just to dismiss the idea of, i. e., invisibility cloaks as physicists did many years, in claiming that the idea if invisibility violates the laws of optics as well as the known properties of matter won’t allow invisibility? The answer is: No! There is a road. This roads runs via the strangest of strangeness: metamaterials. This stuff is soooo exciting. Even optic textbooks have to be revised and rewritten because of them. But… not too fast. Let’s follow Michiu Kaku’s footsteps in his Physics of the Impossible’s 2nd chapter “Invisibility” (pp. 16-33).
Let’s start with the coryphaesus Newton. His main course of action was to translate, i. e., the quiet or uproarious movement of ocean waves into the language of differential equations.
The second hero worthy to be mentioned is Faraday in discovering that electric fields transform into magnetic fields and vice versa.
Last but not least Master Maxwell comes into play. Taking on Newton’s line of action he put Faraday’s force fields into precise differential equations. Then he asked himself what would happen if those electric and magnetic fields would constantly transform into one another. Thus he found electromagnetic fields… propagate similar to ocean waves.
Having reached such heights it now was easy for him to calculate the speed with which the electromagnetic field propagates. And what a surprise: it conforms to the speed of light! Which is to say: “light itself … is an electromagnetic disturbance” (p. 19).
Finally, we are able to say, that the whole electromagnetic spectrum (radar, TV, infrared light, visible light, infrared light, X-rays, microwaves, gamma rays) “is nothing but Maxwell waves, which in turn are vibrating Faraday force fields” (p. 19). — Well, apart from our eyes, what else do we need to see? Correct, light. So here lies the key to invisibility.
Now let’s add another building block. Stuff consists of atoms being arranged in a specific structure. So there’s plenty of space, i. e. for light to slip through. As it is with us human beings light also is a victim of finitude. When driving its wavering course it looses speed. Not enough it even gets lost on its straight path and takes another route. It gets bended. The ability of stuff to do this to light is called “index of refraction”. In order to get to know some numerical knowledge of the index you have to divide the speed of light by its speed inside a medium. Air’s index, i. e., is 1.0003, diamond’s: 2,4.
Metamaterial. O, thou art crazy stuff!
Metamaterials “are created by embedding tiny implants [i. e., tiny electrical circuits] within a substance [i. e., copper] that force electromagnetic waves to bend in unorthodox ways”, so says Kaku (p. 21). Further there he states: “Metamaterials are so bizarre and preposterous that they were once thought to be impossible to construct.”
Now let’s pick up again the already mentioned “index of refraction”. Stuff’s ability to thwart light and change its course. We have seen that the index in stuff is always greater than 1,0, which now isn’t the case with metamaterials. Their index is negative, which means it’s 0,x. What now happens is, that light will pass around these objects like a torrent around a rock. That is the whole idea of invisibility: light floating around objects. Experiments with microwaves were successful as well as experiments in nanotechnology (1 nanometre is equal to one billionth of a metre). So here, in this dimension, scientists have proven: invisibility. We got it! But, unfortunately scientists are far from transferring experiments from these micro universes to our large scale world of naked-eye-visbility.
For further information, explantion and application have a look at this BBC’s 3’00 short documentation.
Did you hear: there is some beneficial use of it apart from military interests or magnum evility…
Invisibility?! Ha!, there is more: Phantasmagoria.
Oh you Chinese people winkling more bizarre phenomena out from metamaterials! — The goal of a Chinese research team is the following… and now listen carefully: to invent a “coat” that makes you both invisible as well as creating a phantom of you – in one and the same moment. What they managed is to create a twin-phantom of a plate.
Convince yourself here.