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The play of light

Vivid images of butterflies decorate the long wall of your meticulously neat office.   Your wife picks up the frames in charity shops and you improve the sometimes quite bad pictures they contain by covering them with your photographs, taken when out and about around the South Downs.  I recall immediately of course the lepidopterist and genius writer, Nabokov.

The brilliant blue ones are the Adonis.  They have a symbiotic relationship with ants who feed the pupae and in return benefit from the emission of a scent they find appealing.  You recently learnt that the pupae talks to the ants when it needs to be fed and we wonder what this sounds like. 

The blue colour is generated in a specific way by Bragg diffraction; only blue light comes back due to the layered structure of the wings.  

You are responsive to things with visual impact and people in general are affected strongly by the signal received through the eye.  I ask you how you think of light.  You don’t tell me about some abstract mathematical idea, you say the play of light is everything:  on the leaves of trees or you think of waking in the morning and seeing the sun on red brick.

And my eyes are drawn to the immaculate still life on your shelf. 

Beneath the imagos, two perfect apples, the larger, pale green, the other reddish lean in and answer each other.   Adjacent, you have arranged a mysterious picture of Don Quixote, a gift from a physicist who rendered this in micrometres and gave you a scaled up version at around 10cm.  It is Picasso’s drawing, nodding to his precursor, the admired Daumier.  In the rear ground, against the wall you have situated a cream plastic plate-like object, maybe 30cm diameter.  I’ve never seen a lens like it, completely opaque to visible light but great for focusing the lower energy light of microwaves.  It’s made of meta material. 

Imperial is the World’s centre for meta materials.  ‘Meta’, you say is an overly grand name (not yours) implying a material that is not even a material.  Such lenses are so much lighter and less space consuming than polythene ones, so they are used in radar systems for planes and cars.  From the side, this one seems to be shot through with regularly spaced metal coils.

In spite of your love of the impactful image, with a certain irony I reflect, you are known for trying to make things disappear with your research into the invisible cloak that diverts light around the object it seeks to hide.  I looked at your web-site last night and the ‘invisible cloak’ web-page was empty....is it a physicist’s joke I ask?  You smile and say; no, just lack of time.

You love to find out how things work.  You were a child in the fifties, so you wondered about bombs and built crystal sets.  You started out in physics at Cambridge and you remember the excitement at the ‘ding, ding, ding’ of suspected alien voices, the first discovered pulsars.  You are a theorist interested in experiment and theory.  Theoretical physics without experiment is mere maths.  A long time ago you theorised that thermal conductivity is quantised.  (I am still wondering what on earth that must mean).  You told me of your delight when twenty years later a researcher in California demonstrated, right out of the blue that you are right.  The poor experimentalists have one foot tied to the ground and must work long term; you, in contrast, like to cover a broad area. 

Success in research is an accident; the pebble on the beach may be a diamond.  And you say you’ve been lucky. 

Physics is a high priesthood, not a popular pursuit which suffers from being ‘behind the machine tool’.   But you have discovered a talent for popular communication and find it worthwhile. 

You work with classical optics.  Light is the most pure and clean way to investigate physical phenomena: There is no mass and no charge to interact with things.  The equations are very precise and you know precisely what light will do.  Electrons on the other hand are a mess, they interact.  For example, friction is a complete mess.  How does it happen?  God knows.

You tell me about this elegant thought experiment, the simplest process by which you can create entropy.  Two separated pristine glass blocks slide past each other in a vacuum.  There are always quantum fluctuations even in a vacuum and the images created in the blocks by these ghosts cause a frictional force which pulls back and two beautiful pieces of light are emitted, each inexplicably correlated with the other by the phenomenon that is entanglement.

And you share with me what you believe will be the next breakthrough in physics.  It won’t be the well known suspects favoured by the media: the mass giving Higgs field or the unification of gravity with the quantum.

It will be a return to the fundamentals, an answer to ‘what do we mean by quantum mechanics?’  Take those beautiful entangled pieces of light; the information that choreographs them is de-localised. We cannot say where it is physically.  The new physics will tell us. 

John Pendry is a theoretical physicist known for his research into metamaterials and his theory of a ‘perfect lens’ – a lens with unlimited resolution. Recently he and colleagues at Duke university created the first practical "Invisibility Cloak". He is chair in theoretical solid state physics at Imperial College.  He has a fascination with butterflies and photographing them.