Category Archives: Institute of Physics

Institute of Physics Spring Weekend

This weekend I was at the annual spring meeting of the Institute of Physics in Ireland in Wexford. I always enjoy these weekends – more relaxing than a technical conference and a great way of keeping in touch with physicists from all over Ireland. As ever, there were good seminars, a physics pub quiz and discussions of science and philosophy over breakfast, lunch and dinner (not to mention a 32-strong Wexford choir who gave superb after-dinner entertainment). At the same time, there was a serious side to the weekend with committee meetings, the Annual General Meeting and a highly competitive poster competition for postgraduates.

The theme of the seminars on Saturday was ‘Physics for Life’ and it mainly concerned advances in medicine/ biology that have resulted from research in fundamental areas of physics such as atomic and molecular physics (Bob McCullough of Queen’s University Belfast), solar physics (Louise Harra of University College London), nano-photonics (Brian MCraith of DCU) and molecule manipulation using ‘optical tweezers’ (Martin Hegner from Trinity). I won’t attempt to describe each talk, but you can find abstracts of the talks here.

My favourite was a general talk on causality in complex systems by world-famous cosmologist George Ellis: ‘Top-down action in the hierarchy of complexity’. This was a fascinating overview of the subject of causation, focusing on the influence of feedback from top-down processes on bottom-up causes. There were lots of great examples and the speaker was fully convincing in his conclusion that ‘no complex system can have a single cause’. I couldn’t help thinking how true this is of climate change. Some media pundits describe global warming phenomenon in terms that too simple; by citing man-made CO2 as the only factor in climate, they give great ammunition to climate skeptics who point to other factors. (The point is that while CO2 is not the only factor in global climate, it is now clear that the man-made increase in CO2 is a significant driver of warming.)

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Top-down causality: George Ellis

Sunday saw a new IoP initiative – instead of more seminars, four well-known physicists were given the ‘This is your Life’ treatment in sequence. It was a great success, with the legendary Tony Scott of UCD interviewing Ronan Mc Nulty (on the LHCb experiment), Sile McCormaic (on her path to the world of cold atoms) and Ray Bates (reknowned Irish climatologist who was one of the first in the area of climate modelling).

Best of all, the very first interviewee was Dame Jocelyn Bell-Burnell, the Belfast-born astrophysicist famed for her discovery of radio pulsars. (She is also President of the Institute of Physics). Professor Bell gave a fascinating overview of her life in physics, from failing the 11-plus exam to Cambridge. Of particular interest was her description of the postgraduate work leading up to the famous discovery: the long build of the radio-telescope from raw materials, perservering to the end as team members drifted off, the discovery of an unknown source, convincing her supervisor she was onto something, the disappearance of the source and the stress of a possible mistake and lost thesis, the re-appearance of the source, the classification of the first pulsars….terrific stuff.

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Tony Scott interviewing Jocelyn Bell-Burnell

Professor Bell’s story was reminiscent of the discovery of the microwave background by Penzias and Wilson (see post here), but with one big difference. Bell was a highly trained astrophysicist, who understood clearly that she might have discovered an important phenomenon. For this reason, it is still highly controversial that, while her supervisor Antony Hewish was awarded the Nobel prize for this work, she was not. Was it because she was still a postgraduate? Because she was a woman? Perhaps we will never know. Apparently, there was a very good BBC documentary on the story a few months ago – I misssed it but I’ll try and track it down.

As always, the most humbling part of the weekend was the postgraduate posters. The level of research made one feel seriously inadequate. You can find the results of the competition on the IoP website; choosing the winners must have been very difficult. I particularly enjoyed two posters from UCD on the LHCb experiment (an indirect measurement of luminosity using muon production rates, and the measurement the cross-section of Z boson -muon decay). Even there, Ronan had to explain to me how antiquarks arise in proton-proton collision; must revise my quark physics!

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Poster session at the meeting

All in all, a super weekend, courtesy of the Institute of Physics. Now it’s back to earth and those corrections…

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The human physics laboratory

Another great lecture at WIT this week was a public lecture on the physics of the human body. (The lecture was presented as the annual Tyndall lecture of the Institute of Physics and also as part of Engineering Week at WIT by CALMAST, see post below).

The lecture was given by Dr Kevin McGuigan, Senior Lecturer in physics at the Royal College of Surgeons of Ireland. Kevin is well-known for his successful research into the solar disinfection of drinking water, but he clearly has a second talent as a natural communicator of science.

The theme of the talk was that if you consider almost any important principle in physics, you will find a great example of its application in the human body. There were dozens of intriuging examples of this, here are just a few:

– Discussing friction, Kevin described the role of saliva in overcoming friction in indigestion. The students weren’t particularly interested until he gave a superb demonstration of the effect by getting two hapless volunteers to stuff themselves quickly with cream crackers without water!

– On Newton’s second law, the speaker explained the concept of impulse, showing clips of the effect on the neck/head of the driver of a car brought to rest from high speed, or struck from behind. He then explained the importance of both the crumple zone and air bags.

– A quick overview of the physics of rotational motion in liquids led to a discussion of the role of fluid in the ear. Kevin then gave a demonstration of the role of this liquid in balance by rotating a hapless volunteer in a chair 10 times!

The human laboratory: IoP Tyndall lecture

The speaker also discussed Bernouille’s equation, discussing what happens during an aneurysm as example. However, I suspect the students enjoyed another example of Bernouille’s equation most – ‘The physics of farts’. Here Kevin gave each member of the audience two sheets of paper and got them to observe what happens when you place them close to the mouth and blow (it behaves like a shutter opening and closing due to the difference in air pressure on the sides of each sheet). He then explained this as the same process that happens as  boys (only boys?)  attempt to release compressed air from their posteriors without making a sound, usually with a resulting brmmmmmpt!!

Another fine example was a demonstration of how sweat cools the body, using the latent heat of vapourization.

All in all, this was a super example of an outreach lecture that got a fantastic reception from a packed auditorium of students and schoolkids. I had to leave early, but I found myself frantically taking note of examples for next year’s 1st science class!

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LHCb, UCD physics and the last symmetry

This weekend I was back at my Alma Mater, the UCD school of physics, for a conference for physics teachers organised by the Institute of Physics.

I arrived late and sneaked into the back row of Theatre E of the UCD science block, just as I used to all those years ago. Such a strange feeling to be back in that same seat in that same lecture hall (one difference is that the grounds of the college are beautiful now). The feeling increased when I was joined by two of my former professors, the best teachers I ever had; Alex Montwill (who taught courses in formal quantum theory and high energy physics) and Ann Breslin (special relativity and experimental high-energy physics). Alex was Ireland’s foremost experimental particle physicist for many years, but is probably best remembered for a well-known series of public lectures on modern physics on national radio.

There were some very nice talks, including one on the discovery of The Antikythera Mechanism by Mike Edmunds of Cardiff University and one on the work of the UCD high-energy astrophysics group by John Quinn. However, I was mainly there to hear Ronan McNulty, the leader of the new experimental particle physics group at UCD (UCD has always been strong in fundamental areas of physics such as astrophysics and particle physics). Ronan’s group has been involved with the DØ experiment at the Tevatron, the L3 experiment at LEP and now with the LHCb detector at the LHC (they got some nice attention recently when they were one of the few groups able to report some preliminary measurements from the September switch-on). The work of the group is very important not just because of its fundamental nature, but because it is the only group in the Republic of Ireland that has an official involvement with the LHC (thanks to our non-membership of CERN, see post below). I’m sure Alex and Ann are very proud to see this large and very successful experimental particle physics group at UCD as they themselves had a successful particle physics group at UCD many years ago, measuring particle tracks in emulsions sent over from CERN (I did my final-year project with their research group, estimating the mass of the muon from pion decay tracks).

Ronan gave a superb talk, ranging from a basic introducton to particle physics up to the search for asymmetry in matter/antimatter decay and their contribution to the VELO detector of the LHCb experiment – all within the paltry 20 minutes he was allotted on the program. You can find the slides from the talk here. At question time, I asked him his view of the likelihood of seeing supersymmetry at the LHC: like many experimentalists, he seemed pretty sceptical, pointing out that there has been absolutely no hint of supersymmetric particles up until now.

At lunchtime, we all had a great chat, ranging from supersymmetry to ‘progressive’ ideas in university administration, to Ireland’s continued non-membership of CERN. It’s always great to catch up with the people who taught you and to hear their perspective on things as an adult. I particularly enjoy talking to Alex and Ann as they are among the very few people who understand Lochlainn’s work in gauge symmetry and the impact it had at the time. Re CERN, it seems negotiations on the issue are continuing…

In other news, although they are now officially retired, Alex and Ann have just written a book (real academics don’t do retirement): Let there be lightis due to be published by Imperial next month. I got a sneak preview and it looks superb, as you might expect of the culmination of a lifetime’s reflection on physics by two highly respected physicists. The book is pitched at a level somewhere between undergraduate and the layman and is an introduction to pretty much all of modern physics from the perspective of the study of the nature of light – from optics to wave theory, from wave/particle duality to light quanta, from electromagnetism and light to special relativity, etc. The book will be officially launched at UCD next month, so I’ll discuss it in detail then.

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Postscript

Supersymmetry has been in my mind all day today, sparked by a comment Ronan made yesterday. He mentioned that as he understands it, one of the reasons mathematicians are keen on SUSY is that it’s the last remaining symmetry under the Poincare symmetry group. I think that’s right and in fact I once heard Julius Wess comment that he sometimes wished he had used the term ‘ultimate gauge symmetry’ in the original paper (he made the comment at a Memorial Syposium two years ago). Sadly, Julius, one of the last of the supersymmetry pioneers, passed away himself last year.

Julis Wess of the Wess-Zumino model of supersymmetry.

All day I’ve been thinking thatThe Last Symmetry would be a great title for a popular book on particle physics, if supersymmetric particles do turn up – possibly a better title than The Story of Atoms . Either way, I didn’t do too much work on my imaginary book over the summer, must get back to it. On the subject of language, I also wonder about the term super-matter…I’ve never heard the term but it’s a nice word and immediately hints at an analogy with antimatter (if SUSY does exist, it must involve a broken symmetry, just like matter/antimatter decay).

As to whether SUSY really exists, a philosophical point has also been on my mind – as far as I know, there is no path to a unified field theory of the interactions without some sort of symmetry betweenfermions (leptons and quarks, the constituents of matter) and bosons (the force carriers). In the 1960s, the unification program ran into a formidable mathematical wall with the emergence of a series of no-go theorems (McGlynn, O’Raifeartaigh, Coleman and Mandula) that showed that the strong interaction could not be incorporated into a single scheme with the other interactions using the methods that had been so successful in electro-weak theory. Mathematicians were hugely relieved when SUSY, a radical new symmetry between the two most fundamental classes of particles, suggested a possible way around the problem and even hinted at the inclusion of gravity. Without some form of SUSY, it’s not clear whether unification can happen, and without unification, the picture of a single ‘superforce’ in the early universe condensing out into the fundamental interactions we see today can’t happen – a major blow for cosmology as well as for particle physics. So I like to think that either we will see SUSY sometime, or if we don’t, we haven’t got our predictions right because we simply haven’t developed the right model of supersymmetry breaking yet…

Also, there is one famous mathematical clue. When theoreticians plot the magnitude of the coupling constants of the three strongest fundamental interactions as a function of energy, they converge – but not to a single point. That is, unless SUSY is included in the calculation – in which case they converge very nicely. Hmm…

PPS: . Last week was the hundreth anniversary of Minkowski space-time. I completely forgot about this, but Stefan and Bee have a great post on it on Backreaction

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