The Invisibility Man Wins Prestigious Scientific Award

As a self-confessed and hopeless geek, I am, of course, obsessed with the incomparable Sir Isaac Newton. If you have visited this blog before you may have read about Isaac Newton and the Cat Flap, a tongue-in-cheek but nonetheless respectful homage to the great man. I was therefore extremely interested to hear about the recent award of the Institute of Physics’ prestigious Newton medal to Professor Sir John Pendry.   This award is made annually for outstanding contributions to physics, and Sir John has won it for  pioneering  the concept of the 'invisibility cloak' and developing a new class of 'metamaterials'.

The human race has always been fascinated by the idea of invisibility, and our literature  is full of it. Probably the first and most interesting instance occurred in 1897 in HG Wells' science fiction novella (or, as Wells styles it, ‘grotesque romance’) The Invisible Man.  In this story Griffin, the anti-hero, stumbles upon an invisibility formula during his time as a medical student, and uses his invisibility to commit crimes.

Other famous invisibility plot devices occur in Star Trek, in which the Starship Enterprise protects itself from attack by means of a ‘cloaking device’ using technology stolen by Captain Kirk from a Romulan ship, and Harry Potter, where the ‘invisibility cloak’ is a magical garment which renders the wearer invisible. For all those of you who would not classify Star Trek and Harry Potter as literature, I can only apologise for mentioning them in the same breath as the great HG Wells, who is another one of my personal heroes.

In the 21st Century real scientific knowledge is starting to catch up with the predictions of science fiction. How close is current scientific knowledge to achieving true invisibility?   In HG Wells' story, invisibility was achieved chemically, with the use of 'special pigments'. Nevertheless his ideas are uncannily similar to Sir John Pendrys’s metamaterial discoveries. In chapter 19 of The Invisible Man, CERTAIN FIRST PRINCIPLES, Wells offers this scientific explanation:

 But consider, visibility depends on the action of the visible bodies on light. Either a body absorbs light, or it reflects or refracts it, or does all these things. If it neither reflects nor refracts nor absorbs light, it cannot of itself be visible. You see an opaque red box, for instance, because the colour absorbs some of the light and reflects the rest, all the red part of the light, to you. If it did not absorb any particular part of the light, but reflected it all, then it would be a shining white box. Silver! A diamond box would neither absorb much of the light nor reflect much from the general surface, but just here and there where the surfaces were favourable the light would be reflected and refracted, so that you would get a brilliant appearance of flashing reflections and translucencies—a sort of skeleton of light. A glass box would not be so brilliant, nor so clearly visible, as a diamond box, because there would be less refraction and reflection. See that? From certain points of view you would see quite clearly through it. Some kinds of glass would be more visible than others, a box of flint glass would be brighter than a box of ordinary window glass. A box of very thin common glass would be hard to see in a bad light, because it would absorb hardly any light and refract and reflect very little. And if you put a sheet of common white glass in water, still more if you put it in some denser liquid than water, it would vanish almost altogether, because light passing from water to glass is only slightly refracted or reflected or indeed affected in any way. It is almost as invisible as a jet of coal gas or hydrogen is in air. And for precisely the same reason!

Compare this with Sir John’s proposal for creating an ‘invisibility cloak’ by using metamaterials.  These are substances defined not by their chemical constitution, but by their internal structures on the smallest scale, which allow them to guide light around objects and render them invisible to the human eye. Altering the nano-scale structure of a metamaterial causes directional changes in its electromagnetic waves.  Light waves flow around objects covered in metamaterial and – hey presto – they are invisible!

I must admit that I am only a geek with no real scientific credentials, and I apologise for the inadequacy of my technical explanation. For a fuller explanation of the properties of metamaterials, why not have a look at Professor Pendry’s website? http://www.cmth.ph.ic.ac.uk/photonics/Newphotonics/

More about the Newton Medal   

This year's Newton award will be presented at a ceremony in London on November 15.  Professor Pendry will give the Institute's Newton Lecture in October. Previous winners of the Newton medal include Martin Rees, Leo Kadanoff, Edward Witten, Alan Guth and Anton Zeilinger.

From the website of the Institute of Physics:

http://www.iop.org/about/awards/newton/page_60376.html