I said (broken down into 140 character chunks):

One definition of “nothing” is “vacuum”, by which physicists mean “lowest energy state”. That exists. But in quantum mechanics it’s not really empty. It is permeated by quantum fields (e.g. the photon field) and it fluctuates. Particles pop in and out of brief existence, even in the lowest energy state of space-time. And in fact the field of the Higgs boson doesn’t even fluctuate around the value of zero, but around 246 GeV. So I guess really to have “nothing” means no physical laws, no time, no space. In that sense not sure what it means to say such a thing “exists”. You can speak about it, but surely it’s the opposite of “existence”?

Hmm. Anyone got a better answer?

In fact, the boson part of “Higgs boson” is arguably more important the “Higgs” part, and is named after Satyendra Nath Bose, the Indian physicist, who worked out that bit of quantum mechanics. There have even been complaints that “boson” should be capitalised. The laws that govern bosons are called Bose-Einstein statistics, but no one knows who the other guy was.

A few days later Tom Kibble responded to the initial Sunday Times story here (which also appeared as a letter in the Times).

Interestingly the wastepaper bin and the chair don’t change.

Today I went to St.Asaph business park, to visit OpTIC Technium. This is in some sense an outpost of UCL Physics and Astronomy, in that UCL Prof David Walker leads parts of it and we have PhD students and postdocs there. They do optics, as the name suggests. The picture is one of their big polishing machines, making an octagonal mirror with a radius of curvature of 84m and with a 200 micron asphericity. If I remember the numbers correctly.

You can’t really get the scale from my rubbish snap, but the thing is more than a metre across. It’s high tech precision optical engineering. They are prototyping primary mirrors for the European Southern Observatory’s planned Extremely Large Telescope, a really important project for the future of astronomy. They also work on several industrial and non-astronomy applications of the same technology. It’s an impressive high technology cluster of skills and I’m really glad UCL (along with Glyndwr, who are much more local!) is involved.

Having gone by Virgin trains (Rhyl) and also having been to Manchester and back by the same means, a couple of things struck me.

On the way back I joined a meeting in CERN via video conference on the WiFi. We do bang on about the world wide web being invented at CERN, so I won’t mention that again, but maybe less well know is that WiFi owes quite a bit to astronomy. Radio, not optical, but it seemed appropriate on a trip to visit the industrial application edge of the subject.

Less appropriate were the names of the trains. On the Manchester trip my wife caught “Virgin Dream”. But it broke, so she had to move to “Virgin Knight” (sic, with a “K”). Then the train after, which I had to get, was called “Virgin Invader”. WTF? A little scary. Perhaps deliberately so. But then, who’s afraid of “Virgin Earwolf”?

Anyhow, enough of this. Football approaches.

Quarks are what dragged me into this mess. I’ve done about 50 hours work in the last 4 days and have run out of clean cutlery. My fridge contains only an empty tub of hummus and an out-of-date bottle of chilli sauce. I last saw my daughter on Tuesday, scrabbling around in the forest all covered in dandelion feathers, looking for edible foliage.

I found about quarks when I was an undergraduate at UCL, in the first term of my first year, when a wonderful lecturer called Andrew Fisher gave us a course called modern physics. He was (*is*, I’m sure) one of those unusual lecturers who tells you things you remember years later, as opposed to seconds.

I found a book in the science library that gave me what I craved: a table of the quarks and all of their properties: charge, mass.. then weird stuff. Some of them had distinctly worrying quantum numbers. Strangeness? Yeah, right. But it was still there when I woke up in the morning. Some quarks had strangeness. Obviously I had to look into this further.

It turned out that the quantum `number’ strangeness is exactly what it sounds. Some people were taking data from some very primitive cave-man style detector, and they found that some particles were behaving strangely. Being a physicist, okay, being a particularly `special’, creative, brilliant person (Murray Gell-Mann) this strange behavior was assigned a measure. Strangeness, of course.

The strange behavior turned out to be down to the strange quark.

So, I’m starting out with the strange quark because there was no real concept of quarkness before that. We knew that the proton had structure through all sorts of wonderful experiments which are now known as deep inelastic scattering, or DIS for short. The deep means that we are firing things at the proton that go deep, further than its ‘surface’ which is actually nothing more than a spherical(ish) force field. The ‘inelastic’ means that it doesn’t just bounce. Inelastic means that something has to break up.

The first DIS experiments told us that there was something going on inside the proton, it wasn’t smooth or solid all the way through. If you could get something (an electron) through the force-field that gave it a kind of surface, then you could clearly see that there was something inside. The electron would bounce of the innards of the proton in all sorts of directions, and when we measured these very carefully and added them all up, or integrated over them all (same thing) we thought that there almost certainly isn’t a ‘hard center’ to this thing. It is made of parts (three parts in the case of the proton), but it doesn’t have a center.

We had the parton model: partons were the things that lived inside protons and neutrons, which in turn lived inside atoms.

But that was it really, for a while. And its no wonder, when we think of the absolutely unimaginable mind-power that was required to take the next step.

Murray Gell-Mann having a little think, as potrayed by Toya Walker

Murray Gell-Mann (his name should be pronounced Gell. Mann. Not Gellman, or Jellmann. He is a keen linguist and this is apparently important to him.) constructed a space in his mind that was not our usual way of doing this, which if we are honest consists mainly of measuring up a part of our living room with our eyes and wondering if that lovely old chesterfield in the skip down the road would fit, then going to get the tape measure. He decided that one direction (say width) would be strangeness and depth would be another thing he constructed, called isospin, and height would be good old simple charge. When he put the all the newly discovered particles on this 3-D graph where you and I would put our sofa and it probably wouldn’t quite fit, they not only fit but fell into a sort of pattern. Well now that all sounds a bit hippy, because I’ve explained it all in a rather vague way and we all know we can make patterns appear meaningful when they are not.

But he really did have something. He looked and listened, and he noticed that these three things: strangeness, isospin and charge, seemed to be able to classify this new world they he was observing pretty well. If there were three of these quarks (up, down and strange), then he could explain all of the new particles’ properties by combining them in various ways. It took a while for anyone to be convinced, of course. Murray was at CERN watching a talk on recent discoveries when he realized that the latest particle filled a hole in his diagram that made it very unlikely that there was a better way of explaining these proton-innards than his way.

He called it the quark model. Quark should be pronounced “kwork” not “kwark”. He named it after a line in a book by James Joyce called Finnigan’s wake. “Three quarks for muster Mark”. I know, Mark should be rhyme with quark, but Murray felt it was kwork, and in fact if you are from that part of the country where you pronounce mister muster then you probably pronounce kwark kwork too.

So there we have it: the first three quarks: up, down and strange. There are in fact six quarks now, but the others are much more exciting and deserve heir own stories. All of matter is made of the first two and electrons. Every single atom in the Universe has nothing in it other than some combination of up quark, down quark and electron. The strange ones inhabit particles that only exists transiently, before decaying to something stable that contains only normal up and down quarks.

So I will leave you with that: strangeness is not conserved.

The picture for this post was provided by the magnificent Toya Walker.

The link for deep inelastic scattering takes you to the wikipedia page. I don’t agree with the second sentence on this page regarding the reality of quarks, but the www isn’t exactly awash with explanations of DIS that won’t make most people want to die, so wikipedia will have to do.

In 1900, shortly after the electron and radioactivity were discovered, Lord Kelvin famously remarked:

“There is nothing new to be discovered in physics. All that remains is more and more precise measurement”

He would be proved horribly wrong. The discovery of the nucleus and then its constituents, the proton and neutron, revolutionised our view of what the world was made of. Our understanding of the world changed from the classical to the quantum and up to 1933 quantum mechanics went from success to success in describing experimental observations. This culminated in the Dirac equation, which predicted the existence of anti-matter, confirmed shortly afterwards by the discovery of the anti-electron (the positron). However, the physicists’ smugness was short-lived. Behind the scenes, all was not well. Quantum Mechanics was struggling to provide an explanation for particles that were raining down on earth from the cosmos at a rate of 10,000 per minute per m2. A veritable who’s-who of physics luminaries were trying to understand the nature of these “cosmic-ray” particles. Since at that time the only known particles were electrons, protons, neutrons, photons and (yet to be directly detected) neutrinos. It was assumed that these cosmic-ray particles arriving at the earth were electrons.

The problem with this (wrong) assumption was that the “electrons” raining down on the earth seemed to come in two varieties –1. those which were easily absorbed by blocks of lead and which created a secondary shower of electrons, positrons and photons when they interacted with the lead and 2. those that penetrated the lead blocks with aplomb.

At first, quantum mechanics had no explanation for why electrons should behave in either of these ways, but gradually the theory was modified (notably by Bethe, Carlson, Heitler and Oppenheimer). They found a way to describe type 1 (the “electron” that showered in lead) but, alas, they had no such luck finding an explanation for the type 2 penetrating particles. Theoretical physicists (having enjoyed so much success up to then) were in despair. Oppenheimer, always a bloke for adding a bit of gravitas to the situation and who generally preferred his glass half empty, wrote to his brother in 1934:

Oppenheimer: nicotine fuelled Quantum Mechanics.

“As you undoubtedly know, theoretical physics – what with the haunting ghosts of neutrinos, the Copenhagen conviction, against all evidence, that cosmic rays are protons, Born’s absolutely unquantizable field theory, the divergence difficulties with the positron and the utter impossibility of making a rigorous calculation at all – is in a hell of a way”

Quickly, the idea that the penetrating particles were protons was dismissed and the physics community was faced with a stark choice: a new particle or the acceptance that quantum mechanics was hopelessly flawed. For a time (now conveniently overlooked) they fudged the issue and started to speak sotto voce about the possibility of “red and green electrons” – one type being absorbed and the other penetrating.

Thankfully, the inspired development of new experimental techniques by teams in Europe and the USA meant the experimental observations of the penetrating particles became more precise. These experimental innovations (combined with new breakthroughs in the theory) allowed an interpretation that led to the inescapable truth: the penetrating particles were something like an electron, but significantly heavier.

The particle was originally given the name the “mesotron”. As is often the case in science, there was not a “Eureka moment” of discovery, but a gradual dawning of a new paradigm through the work of many people, both theoretical and experimental. Anderson got the credit (having already bagged a Nobel Prize for observing the positron, it was probably an easier sell..) but there was a considerable dramatis personae – Bethe, Heitler, Rossi, Neddermeyer, Street, Stevenson, Carlson and Oppenheimer – without whose contributions the “mesotron” would not have been discovered. The “mesotron” was quickly renamed the muon, and it became clear that the muon wasn’t a red or green electron, since if it were just a heavy or a more energetic electron it should decay to an electron and a photon, and this was not observed. The muon appeared to be its own distinct particle and so the muon (after the electron) was the second fundamental particle (i.e. one that doesn’t seem to be made of other particles) to be discovered. Its discovery thus heralded the start of particle physics as a subject.

Muons - I felt nowt

There are several hundred muons going through your head every second. Fortunately, their low energies (and high mass) mean they are harmless. These muons originate from the collisions of cosmic-rays (primarily protons spewed out by stars) with the atoms in our upper atmosphere. After their discovery it was observed that the number of these muons decreased as you got closer to the earth and the natural (and correct) conclusion was that they were not stable particles like the electron but a bit fly-by-night (and day), and they decayed to other more familiar particles (electrons and neutrinos) in about 2 millionths of a second. At this point it was known what the mass of the electron was and neutrinos were assumed massless, so by looking at the trajectory and energy of the electron from the muon decay (or measuring the time it took for the muon to decay) it became clear the the muon was a bit of a porker. It weighed in at about 200 times the mass of the electron.

The muon is not a great impresario and has a rather restricted repertoire best suited perhaps for a fleeting appearance on X-factor. In the last 75 years we have observed it do only two things: interact and produce a neutrino or decay and produce an electron and two neutrinos. But, we believe the muon will have the last laugh and is more than a two-trick pony. The muon has something up its sleeve which will help us understand physics at energy scales well beyond the LHC. Pertinently, we believe that it will reveal a new type of fundamental interaction (in addition to the ones we know (the electromagnetic, gravitational and weak and strong nuclear interactions) that can help explain one of the longest standing problems in physics: how was the majority of the anti-matter created in The Big Bang hoovered-up (or presumably Dysoned-up these days) at the start of the Universe, in the time it takes to make a cup of tea?

We are planning to produce a beam of muons of unparalleled intensity to observe this new type of interaction (which I’ll describe in the future). Indeed, after a bit of a slack period, this is an exciting time to be a muon and their penetrating and magnetic properties are being exploited for a range of applications beyond particle physics. They were used in the 1960s to X-ray the pyramids to search for hidden chambers and recent advances in charged particle detectors have opened up the possibility to utilize cosmic-ray muons to precisely image very large volumes (sea containers, cargo vehicles, train stations, etc.) to detect bombs, fissile material or things that go bang in the night.  Muons are being used to study the properties of new compound materials that have the potential to provide novel semiconductors for the electronics industry or room-temperature superconductors with a diversity of applications from levitated trains (could be tricky on The Northern Line) to lossless power transmission. Recently a beam of muons produced at the UK ISIS facility was used to observe the phenomena of “magnetricity” in “spin-ice” which is potentially the first step towards a magnetic version of electronics.

So stay tuned, the muon is a plodder but its 15 minutes of fame is nigh.