Here are some of my first conversations when I came to Imperial College.  They are with people doing all sorts of different research, some working on vast international projects, others in small groups or partnerships; some are PhD students, beginning their careers and others are seasoned experts.

They are written up mostly in the form of an essay attempting to capture the essence and narrative of the discussion and find a resonance. These writings are shown with the permission of the physicist.


Conversation with Nature - II

In response to the emailed question:

Oh Nature!, 

I wonder what you are and what language you speak? 

 - From your friend and admirer. 

One theoretical physicist wrote:
Oh Admirer!
I wonder at your hubris, marvel at your simplicity.
The vanishingly small part of me you perceive already captures all possible languages comprehensible to you. The contingencies upon which your particular perception of me was formed will always limit your understanding of me. And yet you persist, and I am proud of you for that.
 - Nature



Conversation with Nature I

In response to my question: "Oh Nature! I wonder what you are and what language you speak?", mathematician and physicist, Henrik Jeldtoft Jensen sent this letter on behalf of Nature, illustrated with his watercolour painting:

A water colour painted in 1991. It is called a "Detail of Nature" (En natur detalje in Danish). When I painted it I was standing under a big tree and following the shadows cast on the paper by the leaves and branches.

"Of course in reality this is a bit self-indulgent; namely nature conversing with itself. You are part of nature. Are there any entities in the universe which are not part of nature? Aren’t your thoughts or mind waves simply a special example of the dynamics of nature. 

What is nature? The totality of space and time and matter and fields and energies constituting the universe. If our contemplation about nature isn't part of nature what is it then? Are the dynamics of the energy carrying the thought about and the mathematical description of a quantum particle less part of nature than the particle?

Maybe the human mind's contemplation is at one level parallel to waves rolling up against the beach or branches swinging in the wind. At least one common aspect is that matter and energy is in dynamical upheaval. Maybe the main difference is the coordination and imprint. When the mind is contemplating, it involves the part of nature consisting of zillions of neurons that manage to represent and extract patterns of generality. These consist in relationships of some generality between nature’s constituents. Relations or patterns (say the relation between the distance travelled by the descending apple since it was released) are the branch of mind dynamics called mathematics.  Hence one of nature’s dialects is math.

But, as often pointed out by nature herself by use of the vehicle consisting of the minds of, say Zen Buddhists: contemplation and descriptions are parables, never identical to the specific motion and excitations they describe.

Nevertheless, when the part of me called humans muse about myself, we tend to use the language called math. 

What am I? To the part of me called humans, I will in the end always remain restricted to the totality of what dynamical patterns (often known as mind) can be manifested in the part of me called brain."  


Explaining the Blackett Sculpture

Located high above our heads over the Blackett laboratory entrance is a large relief sculpture that often goes unnoticed. The sculpture was installed in 1958 when the building was opened.  The content is a colourful assortment of the state of physics knowledge at the time: nine images and four blocks of densely packed equations and scientific data - some expressed in ways that would not be familiar to contemporary physicists.
There seems to be very little information about the work in the college archives, except to say that the sculpture in Irish limestone is by John Skeaping who was Professor of Sculpture at the RCA at the time and most known for his images of horses.
Various conversations in recent months have decoded the work.  I have had the great pleasure of talking with Tom Kibble and Norman Barford who were present in the department when the sculpture was installed. Others have also helped - Andrew Jaffe, Chris Phillips, Steve Rose, Lady Anne Thorne.  We are left with one outstanding point which is the identification of the spectral lines -  we wonder if they are too stylised to recognise.
Our results are recorded below against sections of the original design.  We deal with the nine images first and then the texts. Thank you to everyone who helped, with particular thanks to Tom and Norman.
a. Laminar fluid flow around a smooth object.
b. Spectral lines – various series.  Not identified. 
c. Bubble chamber picture. The reaction was probably the production of neutral particles: Lambda-0 and a K0 particle, so do not show up as visible tracks, but decay into pairs of charged particles (possibly with an extra neutral one), so they show up as V shapes, pointing back towards the initial scattering vertex.  
a. Magnetic or electric dipole aligned with the horizontal axis, showing connecting field and crossing equipotential lines. 
b. Screw dislocation possibly related to semiconductors. Maybe silicon carbide. 
a. Alpha particles in a helium filled cloud chamber.  The forking tracks are scattering of the alphas and helium nuclei which have the same mass.  Probably based on pictures taken by Blackett.
b. A crystal lattice, possibly GaAs.
c. Larmor precession - symbolic representation of the effect of a magnetic field on an electronic orbit.
The densely packed characters in the carving are separated by a colon every time the subject changes.  The same format is used in the descriptions.
a. There are two different decays on each line -- not only the decays of the mesons but also those of the strange baryons: Lambda0, Sigma+, Sigma- and Xi-.  (These are the commoner decay modes; there are others.)
b. Masses of proton, electron and neutron in electron masses.
c. Here again there are two decays in each line, all of them decays of the strange mesons (kaons), K+/- and the two varieties of K0. 
d. The masses (in terms of electron masses) of mu+/-, pi0, pi+/- and K+/-.
e. The masses of Lambda0, Sigma+, Sigma- and Xi- (in terms of electron masses).
a. Newton’s law of gravitation: Saha Boltzman equation: Ratio of the gravitational and electromagnetic forces between an electron and proton: Kepler’s period of an object moving elliptically about the sun with semi major axis ‘a’:   Energy and momentum of relativistic particle.
b. Newton’s Gravitational Constant: Diffraction: Intensity of Rutherford Scattering at angle theta: Ideal Gas Law: Entropy applying to the statistical mechanics of any system (carved on Boltzman’s burial stone).
c. Energy of relativistic particle of mass mo: Relationship between specific heat at constant pressure and that at constant volume where g is the Gibbs free energy (old fashioned notation): Bose Einstein (-) and Fermi Dirac (+) statistics: Curie’s law for magnetic susceptibility at low temperatures: General equation to show how a classical path minimises action.
a. Maxwell’s laws of electricity and magnetism.
b. Calculation of the electromotive force (v) in a circuit: The force on a charged particle in a magnetic field.
c. This is a relation between two solutions, φ and ψ of the Schrödinger equation.  The second equality, between volume and surface integrals is what is sometimes called Green's second theorem.  ds is an element of surface area, and dτ an element of volume.  The volume integral is over some volume V and the surface integral over its bounding surface. dn is a spatial derivative in the normal direction.
d. All relate to electromagnetism: D is the electric displacement vector: B is the magnetic field: Continuity equation for energy conservation. Energy dissipation is allowed for and represented by the last term E.j. 
a. Schrodinger equation: Commutation relation between p and q: De Broglie: Mass of electron: Energy of a photon:  A peculiar way of writing the Dirac Equation - β is the Dirac matrices 
b. 1s wave function in a hydrogen like atom of Bohr radius a0:  Speed of Light: Bohr’s relation for the frequency of light emitted by hydrogen: Fine Structure Constant:  Compton Scattering. 
c. Heisenberg’s Uncertainty Principle: Black body radiation: Fusion of deuterium and tritium to make Helium and energy release: Planck’s constant: The Born Rule. 

Brains thinking about brains

‘Nature in the form of man begins to recognise itself’

-          Victor Weisskopf

Not strictly a conversation....this short essay tells the story of my experiences of a seminar called ‘How the Brain Works’ - Insights from complexity and self organisation’ at Imperial College on 21st September 2011.  With thanks to Henrik Jenssen who cast his eyes over these notes.

The human brain looking back at itself - is how I thought of this seminar of mathematicians, neuroscientists and physicists on a humid mid September afternoon. 

Each presenting scientist arrived with his kit bag of mathematical tools borrowed from other areas of science and maths to investigate and model what’s actually going on in the brain. This is part of the process - each brings his own approach, favouring this hammer or that wrench and maybe over time, after blunting and forcing one tool too many will refine his apparatus by some degree or create new ones. 

The mathematicians began by looking at extreme oxygen highs or lows in the resting brain and observing brain waves, though we could only guess at what these oxygen levels signified.  A neuroscientist used information theory and the idea of ‘surprise’ which is the difference between what we experience and what we expect.  He proposed that we always try to minimise surprise, by changing our predictions or our sensations and that the brain is a Bayesian machine.  Another neuroscientist saw the brain as a network.  Cutting across anatomical structures and binning a lot of information along the way, he mapped out and analysed these networks.  He proposed that the brain optimises resource efficiency and minimises time and said more intelligent individuals seemed to have shorter pathways and I wondered about mine.....  The only brain fully mapped in this way so far is the worm.  Lastly, a computer scientist introduced another mathematical metaphor - coupled Kuramoto Oscillators and talked about how they tend to synchronise.  However, if the topology is right and under certain circumstances, and if they phase lag each other by a particular amount then they can partition into different oscillating states.  These systems have the potential to model some aspects of the rest state of the human brain and may be compatible with the wave idea the mathematicians observed at the start. There had been some success mapping these oscillator models to pigeon brains.

Brains looking at brains - it was fascinating, a marvellous phenomenon in itself.   And all these people spoke slightly different languages according to experience and discipline, with sometimes subtle sounding differences carrying vastly different meanings and I wondered what each brain took away with him or her.

I reflected on my brain and the experiences and processing it had been working on throughout the day: travelling in on my bike through busy west London, enervated by motorists on phones and the volume of traffic, choosing what to have for lunch, trying to figure out a chart of the energy contribution density of all the photons in the universe with an astrophysicist over lunch, and making the little drawings of delegates when it lost the thread of the argument in this meeting.  Sitting in the hot room, at some point, each of us probably reflected on the complex and emotional experiences of our own brains, suspecting how incredibly far these theories need to go before we begin to understand ourselves, and wondering about the question of what may be missing from our approach.  More generally, I considered our physical laws and wondered if nature felt this same unease about our theories about her.

The human brain is pint sized and has tripled in volume over the last 7 million years (maybe due to better food....).  It is 100 billion neurons – the processing centres – or grey matter.  And 1014 synapses – myelin insulated axons or white matter.  Plus Cerebro spinal fluid. 

For brain waves, please visit:

Seminar convener: Robin Carhart-Harris 

Seminar presenters: Henrik Jeldtoft Jensen, Kim Christensen, Karl Friston, Ed Bullmore, Murray Shanahan, Roseli Wedemann

Image: impressions of delegates 


Watching clouds

How many marvellous places are there in London, where no one goes, except the inquisitive?

Try the little room on the top of the physics building, twelve floors up and arrived at through a narrow black spiral staircase.  What happened, did everyone just evacuate one day?  If they did, they left in a hurry, leaving notebooks, computers and equipment.  There are power cables from the scientist’s disused experiment on the roof coming through an open window, so the wind whistles around this space of forgotten contents.

We circulate around the octagon in brilliant sunlight, looking at the views and the dust covered stuff.  I try an old fashioned rotary dial phone on the wall, wondering if a voice from the past will answer.   Then we pick the best view of the clouds, arrange the chairs and put our feet on the windowsill.  It is a particularly spectacular day above our heads, and everyone else is busy.

The view is glittering and ever changing. Today it’s mostly the whitest cumulus clouds.  The scientist says they tend to be about 1km above the ground, so we estimate their distance from us and then size.  And writing this back home, I’m calculating - if they are one kilometre long and half a kilometre deep and high and the scientist said that water makes up one millionth of the volume, this cloud weighs a quarter of a million kilograms or 200 cars.

Above the cumulus, are cirrus clouds at around 8 km, classic horse tails of ice crystals.  Planes are threading through, leaving little in the way of con trails, the air is so dry and we guess it’s not cold enough.  

We watch the weather move in from the west and wonder if the day will be transformed.

The scientist tells me that his experiment - on the roof above our heads, measured carbon dioxide flux.  The point was to figure out how to get good measurements of the general flux for comparison with computer models.... and sheer curiosity.  One day in ten, the wind comes from the east and the measurements picked up exhaust from the college power station in the engineering building.  We just make out the heat haze exiting the chimney. 

We talk about hurricanes, tornadoes, making clouds in bottles at home and the importance of introducing smoke for the vapour to condense on to, the stratosphere, the influences on the air flows across the earth: the coriolis force (the spinning of the earth) and the drag from her surface.

Who needs to photograph or film or paint these immaculate clouds?  Just looking is enough.

We must have watched for over an hour. 

Then we get up and examine the anemometers, which someone seems to have made from ping pong balls and calibrated; we spin them round on their little axes; and look at the hand drawn graphs. 

We take a last walk around the small room and return reluctantly to earth.

Nathan Sparks is in the last two weeks of his PhD researching carbon dioxide fluxes.  He also travels around the country teaching children about weather from a 7m long trailer as part of the OPAL project.



There is little we know for certain

.....even in maths...... 1+1= 2 is hard to prove

Our way of seeing the world through projection of numbers and models is so far removed from nature

Nature doesn’t think like us

She remains a mystery

Though we keep working - pulling back the carpet, then the lino, start scratching off the layers of paint and peeling varnish all the time suspecting that we may never reach the transparent window onto the universe

There are always multiple ways of seeing the problem – each model brings a different perspective

How do they all link?

Via ‘phdoodling’, (a new word with a silent p h) maybe over a lifetime a humble level of understanding can be mapped out on a wall at home or set free in the air in a network of information

Is there a different road?  A more eastern one that starts within....concentrating on the gap between the in and ex-hale to create an infinite abundance of time.....evaporating from our physical selves to unlock some secrets of nature even though we are caught within the experiment

By travelling both roads, can we feel the pulse of the universe?

Can we share the richness of multiple ways of seeing?  What starting point or foot hold can we offer?

Can we express the ‘exhilarance’ (another new word) that comes from the pleasure of finding things out?


Inspired by a philosophical conversation with a particular experimental physicist on a particular day, though it reflects sentiments expressed by others I have spoken to.

Image: Amongst my first experimental ipad drawings.  The reflection in the glass table is a nod to nabokov's, 'Bend Sinister'.  The imagined aperture to another world or course of events is used extensively via mirrors, puddles....


Short story

They were sitting in the middle of the physics common room with its mismatching furniture: red carpet, pale orange curtains, walls of magnolia and wood panelling, various muddy coloured chairs from the seventies, and some dodgy art on the walls ranging from an impressionist print through to something by someone in the department.

The guy was from somewhere up north and worked on inertial confinement fusion and the artist woman had just stepped through the sliding aluminium patio doors from the roof top.  It was a day or two after the August riots - cloudy, cool and blustery, threatening rain and she had been the only one out there, except for the little astrophysicist who went out for a smoke.

After collecting tea at the hatch from the jovial serving lady, they had settled around a low table.  Sounded like the guy had thought about becoming a writer and was still thinking about it.  He said he’d been bad at maths, though had become a theoretical physicist which surprised his maths teachers, particularly the string theory work.  But, maths at school isn’t maths he said.  Still it’s funny how things turn out.

They talked about H P Lovecraft, Martin Amis, Roald Dahl....good short story writers and she offered Capote.  The northerner said a twist in the tale is always good. 

The physicist said he was working on modelling what was going on in the thumb nail sized deuterium tritium target when it got blasted with laser beams to bring about a fusion ‘burn’ reaction.  Piles of physicists before had done this, but for some reason never got round to including the strong (nuclear) force.  When she raised her eyebrows disbelievingly, he looked up, ‘there is inertia in physics’ he shrugged.  Anyway, this is what he was doing, though he was getting sick and tired of the computer coding.

He started drawing out his designs for a cloud chamber.  This was his relief from the fusion calculations – to build something that reveals the tracks of the ionising particles that are everywhere around us – mostly from the heavens, though he might introduce a radioactive source borrowed from a smoke detector to liven things up.  Their curved backs arched over the scribbles and for a while they talked about design in some detail.  She said it might be cool to amplify the beautiful particle tracks by projecting them up on the side of the building for the passersby and the roaring traffic of South Kensington.

For a moment her mind wandered and she asked herself if the particles were really making tracks.  With the little drops of condensation, humans just thought of them like that.  She wondered what the particles were really doing.  Still they are beautiful and as the scientist said, strong magnetic fields will make them curve one way or the other according to charge.

They went back to talking about nuclear fusion.  It’s better to take energy directly from the sun the physicist said, much better than recreating fusion on earth and handing out these sophisticated technologies that release the full force of nature around the world.

The physicist said he was going north later in the summer to give a talk and he described experiments that would reveal the electrical intensity of nature to people.  The first thought experiment carefully interleaved the pages of two telephone directories.  It would take a crazy two ton force to separate them.  He said it was electromagnetism. 

In a lull, she referred back to some previous conversation they’d had:  something he’d said about seeing things in different ways.  He kind of anticipated what she was saying and said there are quantitative and qualitative ways of looking at things.  There was recognition in her face.

They wondered about people who couldn’t figure things out quantitatively......she said a scientist friend had berated her, saying it’s no good trying to explain what string theory is, it’s not even useful to explain the path of a falling stone, best to get people calculating how long they spend travelling, cooking or sleeping each year.....get them to see how numbers can overlay and reveal things about life.   They both thought there was a lesson for the politicians.

Sounded like the physicist had a load of theologian friends from college who thought he was just fiddling around with his physics, keeping busy.   When they knew the truth and had a direct line to the mind of God. 

People came and went and they must have talked for over an hour. 

Eventually they gathered up their pens and notebooks and chucked the plastic cups in the bin.  They walked out through the hallway and stopped out in the stairwell.  She held on to her glasses and they both held on to and leaned over the wooden railing to peer up and down the vertiginous drop marvelling about the space and height.  He wanted a Foucault pendulum and she thought it would be interesting to have strings that people could pluck running from top to bottom, anything that would make them stop and take in the space - the whole cavity as a musical instrument.  All those patterns, all those simple harmonic oscillators she said.  And he laughed and said they are everywhere in physics and solvable.  She took her hand away from the banister and went up the stairs, he carried on down and she continued to say something to him.

Arthur Turrell is working on his PhD, theoretically modelling the burn in an inertial confinement fusion reaction.  He is also a scientific journalist with a passion for outreach and science communication.  He plays tennis badly, but enthusiastically and reviews popular science books for correctness before printing.  He enjoys reading and hopes to do a degree in literature one day. 


1. Plasma ball.

2. The Liouville equation for a probability distribution function, describing the interaction of N particles via some potential. It is the equation of (kinetic) plasma physics, but it has to be truncated and hacked away at before it gives anything useful away.

3. The graph shows how different species in the burn phase of inertial confinement fusion equilibrate their temperatures over time, and how fantastically more energetic the fusion produced alpha particles (helium nuclei) are; this is because mass is converted into energy during the fusion process (according to a rather famous equation E = mc2) partly goes to them in the form of kinetic energy. Incredibly, they only receive 20% of the fusion energy, the remaining 80% going to neutrons which are not shown on the graph.



Source: Nasa, the sun on the date of this entry.....a quiet day.

Since the Chinese 2000 years ago who observed our roaring sun protected from blindness by the dust of their deserts, we’ve been recording the black spots on her surface.  Then Galileo Galilei, Christoph Scheiner and other renaissance astronomers came along with their telescopes   

Sunspots occur usually in pairs though they may become fragmentary and difficult to count, so these days we use surface area as the measure. 

The sun and her cycles!  She rotates every 27 days.  

Then there is the grand sinusoidal variation of her magnetic field over 22 years, which like twisted elastic, goes only so far then snaps back.  The poles flip from one cycle to the next and this magnetic field is manufactured by the solar dynamo, a mechanism that converts some of the energy from the gas flows into magnetism.

Then due to the grand cycle, there is the 11 year cycle of intensity.  The sun’s gaze oscillates a tiny amount, up to one tenth of one percent.  And these cycles vary in size from one to the other. 

The phenomena resulting directly from these oscillations you postulate are the sunspots.  And counter to my expectations, the more dark spots the more brightness.  At rare quiet times there may be no sunspot groups and when the sun is at her most industrious there may be as many as 10 or more.    Here is the largest sunspot recorded by SOHO ( Solar and Heliospheric Observatory):

At the beginning of each 11 year cycle the spots occur away from the equator and then closer to it as the cycle progresses, giving a beautiful recurring butterfly pattern in the data.

Source: Nasa

From records of sunspots and additional information from isotopes gathered in sources including coral, tree rings and ice cores, we calculate the intensities of our ancestors' sunshine, going back some 10,000 years or so.  We carefully build computer models that input sometimes idiosyncratic histories recognisable by the personalities of those who made the measurements.  And if we are fortunate and clever we may use our computer calculations to tentatively look forward. 

Streaming across the eight minute gap, from sun to earth, the light is encoded with spectral messages about what constitutes our sun’s fire, how the masses on her surface are moving - their magnetism and velocity. 

Currently there are problems with the data; confusingly our multiple sets of measuring instruments give different answers. 

For a moment, we peer up from the difficulties and wonder what the sun is doing today.

Yvonne Unruh is currently trying to answer the question ‘how much does the sun vary over the last three cycles?’, so that she can look for correlations with sun spot activity.  She also has an allotment, listens to ‘Late Junction’ and finds the playful works of sculptor Jean Tinguely interesting.


The shape of the electron and questions of existence

Image: The Pier 10, by Piet Mondrian

We’re eating sandwiches on the green, on the sunny day before the rain.

When I ask you, you say we imagine the electron to be a point particle surrounded by all the virtual particle pairs there are.  Ceaselessly coming and going.  And when I ask if this is an imaginary mathematical device, you insist this is really the case, as much as the tree on the other side of the green is there.

We laugh that when we both tell our friends about your experiment and the latest result that the electron is round, they laugh.  They raise their eyebrows and say of course what else would it be?  What have you been wasting your time doing? 

We all expect beautiful symmetry; a little cloud defined by a single number, but contrarily, actually need asymmetry to explain why we’re here.*

We imagine that nearly 14 billion years ago, our universe began symmetrically, with as much matter as anti-matter.  This would cancel out in spectacular annihilation, leaving no matter, no earth, no you or me, just light. 

So, to solve this problem, amongst other conditions, we think that the shape of this scintillating crowd needs to be an egg.  Though at the moment your experiment of staggering accuracy (a hairs breadth versus the span of our galaxy) stubbornly continues to say it is round.  You will keep looking with greater accuracy and you satisfyingly know how you’re going to do this. 

But, if you don’t find the egg, we will need to find the asymmetry somewhere else.

Mike Tarbutt is an experimentalist working in a small team to measure the shape of the electron.  

See some of my drawings of the team in discussion here


*The logic of symmetry and why the electron must be egg shaped for us to be here

We need CP symmetry violation to explain why we are here - to give a little more matter than anti-matter, this is a condition of our universe and our existence.

We know that we have CPT symmetry; this appears to be a law of Nature.   It is always preserved as far as we can tell: a change in charge, a mirror image reflection and a reversal in time, will always leave our world unchanged.

For these two statements to be true, T symmetry must be violated.  We should always be able to tell the difference between a system running forward and one running backwards.

An egg-shaped electron proves that T-symmetry is violated

Therefore, the electron should be an egg shape or it wouldn’t be here for us to see and we in turn (comprising electrons and other things) would not be here to see it. 

Further note:  we find that nature has a preference for one handedness (or chirality) over another and this is evidenced in the weak interaction.  It is a profound question whether this is related to chirality found in molecules.


Beautiful experiment


When I think of your economic and elegant experiment, I see two tiny pale clouds, glowing against grainy blackness – colder than anywhere else in our universe. 

When you say ‘go’, they free fall, side by side, 1mm, only a small distance for us, but vast for the atoms.  And when you shine light across these falling clouds we see the stripes, the beautiful and brilliant dashes of an interference pattern.  Here, we are seeing the very heart of quantum mechanics - the interference of the wave functions.

Beneath the twelve floors of the physics department, in the vivid yellow corridored basement, you share your space with the air conditioning and electrical ducts.  Like any optics lab, there is a table that looks like a bomb’s gone off – beam splitters, lenses, lasers everywhere.  It may look like a bomb has exploded, but each item is carefully arranged and this has taken years.  You and Ben love to hate the set up, for sure you would both set it up differently now...there has been so much learning. 

On an adjoining table, shrouded in black cloth is the small metal chamber where the cold rubidium clouds are made and dropped.

Central to this is the little atom chip for holding and controlling the tiny clouds:  An inch square, its gold surface glinting as you turn it around in your hand.  We look closely and examine the fine lines etched on its surface.  You run currents through the wires which create magnetic fields that hold the cold atoms in a potential well.  Turn another switch and gently the well divides the little clutch of atoms into two and holds them at slightly different potentials. 

You show me the very first atom chip.  Considering this beautiful artefact is like going back in time from a silicon chip to a valve – I like its physicality – the clarity of the mechanism spells out its workings.  A taught gold wire stretched across a gorgeous one inch gold disk.

Rubidium has a single outer electron, so behaves similarly to our simplest atom hydrogen, that’s why you use it.  And you cool it to a remarkable 200 nano Kelvins (0.0000002K).  There is nowhere in our universe this cold except for places like this, made by us.  And you do this cooling using lasers and then evaporation.  This brings all the atoms into the same state, so they are correlated to produce a beautiful, single resulting pattern. 

Just like dropping two stones into a pond, when you switch off the golden atom chip to release the two cold rubidium clouds, the waves they comprise interact and make a new pattern....the wondrous interference stripes we see. * And, we are lead again to ask the question...what it is about the universe that means we can observe these patterns across such vastly different things?

You are revealing our mathematical understanding of nature in this elegant experiment.

These little lines can even give us a measure of our weakest force - gravity, as the cloud infinitesimally closest to earth is affected infinitesimally more by gravity and this in turn remarkably affects the interference pattern.   Though much greater accuracy can be achieved you say, smiling, with the classic ball and string pendulum of our schooldays.  The gravity measurement however helps you gauge accuracy.

Possibly one day, this experiment will help us discover other extremely small dimensions.

There is much more careful work to do.  

*[Explanation: OK reader - this is going to be tricky to explain, it is quantum mechanics, but stay with me.....and consider a single atom.  What we can say about its likely location in space is governed by the square of a wavy probability distribution we call the wave function.  This is different to the large scale world you and I know where with fair accuracy we can say where things are for sure....where your cup is on the table, your car in the street.  In the world of the very small we just have probabilities for the location of say an atom.  Remember in our experiment –  we aren’t considering just a single atom – it is a cloud of them all indistinguishable, and when we shine a light on them to take a look they take up positions somewhere within the form of the square of the wavy probability function, some occupy one part of the probability distribution and others elsewhere.  When the two little clouds are overlapped, these waves of atoms produce the interference pattern.]  

Image: interference fringes

Video: Cooling of rubidium atoms to 0.2 micro kelvins and below.  The process begins with a tiny amount of atoms - ~20 million and this number is reduced to around 20,000 after cooling.  The last flash shows the atoms being loaded into the atom chip.

Joe Cotter and Ben Yuen who are experimentalists working on the interference of Bose Einstein Condensates.  They work within the laboratory of Ed Hinds.


Physics and life

At junior school in South West Spain, you remember being captivated by the planets when they had been re-scaled closer to the size of human heads and the space between them calibrated to a more domestic size.  Stephen Hawking inspired you again at the age of fourteen and other reasons for going in to physics include the additional benefits of helping future generations and the challenge.

Using quantum effects we can answer new problems and solve others faster and you look at different candidates for making quantum computers. *

But, you say, quantum physics won’t explain the world; “it is so much less rich” - you look up and cast your gaze out through the cafe window towards the sunny day - “than our day to day experience”.  When you do science you play a reductionist game and you shed this when you leave the office.

It seems like a an apt metaphor when several times you put your glasses on and take them off while we talk.

You know some artists, they seem chaotic and see this chaos as part of being creative.  So much creativity comes from careful and logical thought.  And it’s funny when you say; being the sort of person who is late is not necessarily helpful.  Logic can give a richer experience and a key to greater creativity.

Through careful analysis we abstract ideas about the world and figure out that these patterns apply elsewhere in surprising places.  We arrive at ideas beyond imagining, beyond what the chaotic mind could probably create.

Though all of our understanding is still possibly limited by the human mind.

You say that maybe physicists are more open-minded than most people.  We are comfortable with not understanding.  Nature is something that brings us peace.  Not understanding gives security, much more than understanding.  Every day you deal with trying to understand and you find peace in a humanistic way.  These are prevalent characteristics of physicists.

This helps in your life.  Problems demand routines.  You think around them and try different things.  Moving with the current instead of against it, applying a little force, small and clever corrections as you would in physics. 

We go for lunch and sit on the grass near a tree, you opt for the sun and I settle in the shadow.

Human relations shape physics.  People choose carefully who they work with according to respect, trust and liking them.  I mention the relations I observe between supervisors and the supervised, a kind of tough love and you say yes it is tender relationship. 

You are interested in scientist’s lives.  Sensitivity and creativity in science can come together and we talk about Ehrenfrest and the persecuted Turing.

The beauty and aesthetic in formulae demands sensitivity.  In this way physics is like art.

You saw some artwork recently that is pared down, one line, one colour with subtle articulation.

And you say, physics is valuable and seriously about the world.  It is not X Factor.

David Herrera Martí is working on his PhD in Quantum Information 

*There are options for physical implementation (quantum optics, superconductors, ion traps...the most promising) and options for theoretical models which can be combined (adiabatic, topological and measurement based).  



Quiet drama



You are a particle physicist who’s recently joined the Large Hadron Collider project in Geneva.   Protons – miniscule constituents of the atom are smashed into each other at huge energies to see what will happen. 

There’s a scary sense of entering a vast human system.....the first email you received was sent to 3,900 people.

What are you trying to do?  You’re looking for the famed and much reported Higgs particle.  Which is most likely to be seen in the accelerator as the decay of two photons and the energy of these need to be measured as accurately as possible so you can figure out that the Higgs caused them, remembering Einstein’s mass is energy, energy is mass.  Your focus is accurate measurement.

And the accelerator is running at half energy, smashing protons together a stunning 7 days a week, 24 hours a day.  This is enough to produce Higgs particles, but when full capacity is reached the likelihood increases.  Data just pours off continuously, is sorted and then visualised by computer programmes and summarised.  My mind’s eye leaps beyond the earth’s atmosphere to an isolated viewpoint in outer space to register this human activity: the re-enactment of the beginning and a new stone circle.

Everything that happens is predicted by the Standard Model , our anzatz, a kind of periodic table which lists all the particles we have ever found, the mathematics of how they collide and the forces between them and probabilities.  In fact you say, the whole world agrees with the Standard Model.....except one particle hasn’t been seen.   It is so incredibly important to find this particle. 

I furrow my eyebrows and ask the obvious question.  The Higgs gives us mass.   Everything in principle should be mass-less like photons travelling at the speed of light, but the Higgs slows things down.  It is everywhere, it pervades everything.  It is a uniform field everywhere that isn’t visible.  And of course I incredulously wonder out loud why we can’t detect this thing that is everywhere.  Well we need to put a lot of energy in to have the particle affects.  At big bang – Higgs particles would be whizzing around everywhere.  Not like now in our cool and complex universe. 

There is a very big question of why different particles have the masses they do.  We have the electron - e, the muon at 200 times the mass of e and the tau at 3,500 times e.   Interpret the question differently - why does the Higgs field slow down some things much more than others? You say it would be incredibly exciting if we fail to find Higgs – we may finally find what the numbers are.  There are 12 masses in the Standard Model and we don’t know how they came about.

‘It’s a quite fantastical business’, but at the end of a day as a scientist you’re busy soldering a wire on....And when I comment on how surreal this particle world seems you laugh and say, yes you still have to pay the mortgage and change nappies at the same time as trying to determine the fabric of the universe and why we exist in it.  And you do these experiments and the particles are really there.

And you show me some beautiful diagrams of particle tracks.  An electron and positron bounce off each other when they don’t collide head on; the faster they curve, you can tell the momentum and you read these like they are writing.

You got into physics when your dad got Scientific American and you read an article on particle physics and discovered you could get paid to do it.

I flick through your file of particle tracks and calculations and am struck as always by the beauty of Feynman diagrams.  You say how amazingly clever they are, a huge calculation and each one can be summarised into a diagram.  And I say, don’t you find the process weird adding up all the pathways something can happen.  Yes it’s nutty.....and circumstances are included where things run backwards in time and no one can intuit it.  Though you don’t worry about the weirdness on a day to day basis – the calculations give the right answers.  It is typical Feynman – beautiful physical visualisation.

I ask you what you’d like to tell people.  Tell people about our curiosity, we are wondering how the world works at a fundamental level.  It is like staring at the stars. 

When I ask you how much we know, you say the more you learn the more you realise you don’t know.  You never quite know what will happen.  Quantum Mechanics and Relativity hit and everything exploded.  In the next 2-3years we may find something that blows open the whole field we make a dozen Higgs all acting in different way and we start again. 

The Large Hadron Collider is asking open questions, operating at energies close to those at a fraction of a second after the start of the universe. 

It is an incredible human drama that in some ways is very quiet.


Paul Dauncey is a particle physicist.  He specialises in developing particle detectors to hopefully show the Standard Model is wrong. He also runs.

Image: simulated Higgs decays


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 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.


A new way of thinking



A kind of manifesto, discussed by two phycisist-artist women from different parts of the world, in the pub, on a rainy day in London

We want people to know that we physicists are looking for patterns.  We understand nature weaves with the longest threads.  We see an APPLE and know what binds it to the table keeps our earth CIRCLING THE SUN.  We see SUNLIGHT haloing dust motes and know that it is the same as RADIO.  We know that the SPEED OF LIGHT in a vacuum is a constant and from that and the invariance of the laws of physics deduce that SPACE AND TIME are one.

We are for wonder, the wonderful and the soulful. 

We are women who arrive from America and drink warm beer in London and talk about physics in pubs, eating pie and chips.

We are women who cycle five miles there in the sun and five miles back in the rain knowing each journey is as good and beautiful.

We aspire to make generous art and resurrect the figure. 

We reject nihilism.

We end relativism here and know that one of our greatest achievements is science which is primary as a way of understanding the world.  

We end cool conceptualism, and strike a new beginning for immersion in materials, working from original impulse and the heart.

Paint your walls yellow.

Be amongst friends and cats.  Be a cat.  They are independent and not what they seem.  Love old dogs in pubs, having dog days.

Enjoy the English rain ending a sunny day, seen through the open door.

We recognise our story and embrace the power of narrative.

We end dogma and scared conservatism.  We revel in the beauty and genius of evolution our most likely cause.

Let the gay pride march go on; we will be the security.

Read Borges, Capote and Bukowski.

We experience and talk about reality in a myriad ways.  We know it is rich and multi-faceted. 

We are thankful for National Public Radio.

We want to animate the wave function, break down boundaries and create a new way of thinking.

Writing on the window is a metaphor for our experiencing the world through physics.

Sit at any table, don’t reserve it.

Learn your craft.

Make better pictures of the world, communicate it better.

Celebrate the single atom emitting light.

Bring together a new meeting of minds, people who understand the world through analysis and feeling.

The electron is nearly round.

‘Nature in the form of man begins to recognise itself’.

Listen to your parents, but follow your heart.

Being outnumbered and surrounded will make us stronger

Don’t be proud to be ignorant.  Celebrate ‘what we can know although we are fallible’. 

Wear bright lipstick and colourful clothes.

Wear red shoes.

Live in a big house with your friends.

Do art, do physics, wonder and love the world.


Ana Jofre is an artist and physicist at the University of North Carolina in Charlotte, USA.  Ana's web-site


A kind of resonance

Haunting and evocative, I remember the music in your lecture.  One day, by chance, I am a stranger appearing in your office and I ask.  You reach for a pile of CDs.  With the music you can lose yourself in physics; forget the room; be in the moment; fill the black board.  In my charcoal drawings you recognise I’ve connected with something.  The equations look right with their slight scrawliness.  And this is the opposite of powerpoint, the deadly killer of feeling.  A feeling connection with what you’re doing.  You stop asking questions when the mind and spirit come together.   Maybe this is a kind of progress.  And there is colour and sound in mathematics.  And doing physics is about creating a kind of resonance.  Going home on the bus after a painting class and looking at the still life you made, you had an overwhelming sense of being in colour and form.  We don’t know how things connect.  Knowing the fundamentals won’t tell us.  “Sophisticated primitiveness” is an apt expression.  And some say the elements of colour, sound, symbol and number make us and appear in our dreams.  We wonder about time......even in Schrodinger’s equation is a classical guy with a stop-watch.  There are questions of interpretation.  That the whole world is described by wave functions is the only consistent view.  Our limitation. Our hard wired brains. The fascination of the human voice. A responsibility to awe. 

Jonathan Halliwell is a theoretical physicist who is interested in the emergence of classical behaviour from quantum theory and the nature of time in quantum theory. He is also interested in quantum cosmology, the application of ideas from quantum theory to models of the very early universe.