Tag Archives: public lecture

Freeman Dyson and the Dublin Institute for Advanced Studies

On Monday, I attended the Statutory Lecture of the School of Theoretical Physics of the Dublin Institute for Advanced Studies (DIAS). This is an outreach lecture presented annually by DIAS and this year the lecture took place at University College Dublin. Better known abroad than at home, the Institute has a long and distinguished history of world-class research in fundamental areas of physics (see here), so it was entirely appropriate that the statutory lecture was given by Freeman Dyson, renowned physicist and Professor of Physics at the famous Institute for Advanced Study at Princeton, the college on which DIAS is modeled.

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Freeman Dyson at the DIAS lecture on Monday night  

The title of Freeman’s lecture was  “Are Brains Analog or Digital?” and the abstract is below:

We know that creatures like us have two separate systems for processing information, the genome and the brain. We know that the genome is digital, and we can accurately transcribe our genomes onto digital machines. We cannot transcribe our brains, and the processing of information in our brains is still a great mystery. I will be talking about real brains and real people, asking a question that will have practical consequences when we are able to answer it. I am not able to answer it now. All I can do is to examine the evidence and explain why I consider it probable that the answer will be that brains are analog.

I won’t give more details as Professor Dyson will publish his paper on the subject quite soon. Suffice it to say that tickets for the lecture sold out days in advance and there was quite a buzz on the night. Freeman held the audience spellbound, reading from his paper without the benefit of a single slide.  One could gauge the interest generated from the huge number and variety of questions afterwards. That said, I couldn’t help noticing that the Irish media took no interest whatsoever in the occasion – one wonders if a world-famous  musician or celebrity chef would be similarly ignored.

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Professor Dyson with staff from the School of Theoretical Physics at DIAS: Werner Nahm (Senior Professor and Director ), Arthur Jaffe (Professor of Mathematics at Harvard and Chairman of the board), Freeman Dyson, Vincent Cunnane (Chair of DIAS Council) and Cecil Keaveney (Registrar)

After the lecture, some of us retired to a nearby hotel where Professor Dyson and his wife regaled us with stories from his long and interesting career. Freeman was a close colleague of my late father and was instrumental in bringing Lochlainn and the rest of our family to the Institute for Advanced Study at Princeton many years ago (after this, Lochlainn returned to Ireland to take up a position at DIAS). So it was great to encounter Professor Dyson once again, this time as an adult! Not to mention that Freeman has fascinating and original views on a wide range of topics; from space travel to climate science, he remains a truly deep and original thinker.

Update

The day after the lecture, staff and friends of the Dublin Institute for Advanced Studies were treated to a private recital by the well-known Irish pianist Hugh Tinney. The connection is that Hugh’s late mother, Professor Sheila Tinney, was an accomplished mathematician who spent time at Princeton IAS and studied with Professor Dyson (Hugh himself studied maths at Trinity College Dublin before deciding on a career in music and was in the audience for Freeman’s lecture).

It was an extraordinary occasion. Hugh played beautifully and each piece was prefaced with a short discussion of the interface of mind, memory and music. The intimate setting made for one of the most exciting concerts I have experienced, far more fun than a formal venue such as the National Concert Hall. It didn’t hurt that the programme included three of my all-time favourite works, Beethoven’s ‘Moonlight’ Sonata,  Schubert’s G major Impromptu and *that* Nocturne by John Field (no.5 in B flat). The recital also had a special significance for me as it took place in the Organ Room of the Royal Irish Academy of Music, a venue I spent a great deal of time in as a young music student.

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Each piece was prefaced by a discussion of the role of mind in music

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Hugh Tinney presenting his latest CD to Professor Dyson

After the recital, we retired to dinner in a nearby restaurant. As you can imagine, one subject of conversation was the mysterious connection between maths and music. I have heard one explanation for this strange phenomenon: “People who are good at maths are good at most things!”

P.S. A video of Freeman’s lecture is now available on the DIAS website.

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The God particle at Trinity College

On Monday evening, I gave a public lecture on the Higgs boson at Trinity College Dublin. The talk was organised by Astronomy Ireland and I think it was quite a success; 200 tickets were sold and quite a few people had to be turned away.

In the Joly lecture theatre at Trinity College Dublin

How to explain the basics of particle physics to a public audience? As always, I presented the material as a short history of discovery: from the atom to the nucleus,  from protons and neutrons to Gell-mann’s quarks. I also included some theory on the fundamental interactions, right up to the Standard Model,  electro-weak unification and the role of the Higgs field in electro-weak symmetry breaking. Not for the first time, I came away with the impression that the Standard Model isn’t as intimidating for the uninitiated as you might expect. As for physics beyond the Standard Model, the audience seemed to take the hypothesis of grand unification in their stride, and the connection between particle experiments and the early universe struck a chord, as always.

The results  It was a pleasure to present the fantastic results of the ATLAS and CMS teams, first announced at CERN last July. Giving such talks is a lot easier now that the data are publicly available in two beautiful papers on the ArXiv here and here. I gave an overview of the main findings in the context of previous experiments at CERN and at the Tevatron,  and I think the audience got a feel for the historic importance of the result. Certainly, there were plenty of questions afterwards, which continued in the pub afterwards.

The famous bumps ( excess decay events) seen by both ATLAS and CMS at around 125 GeV in the di-photon decay channel

Combined signal (all decay channels) for both ATLAS and CMS

So what about that title? Yes, I did agree to the title ‘The God particle at last’? I am aware that most physicists have a major problem with the moniker; it is sensationalist, inaccurate and incurs a completely gratuitous connection with religion. (Some religious folk consider it blasphemous,  while others misunderstand the term as evidence for their beliefs).

A poster for the talk; naughty

All of this is true, yet I must admit I’ve got to like the nickname; it is catchy and just mysterious enough to cause one to think. I imagine a tired lawyer catching sight of the poster as she walks home after work;  ‘God particle’ might cause a moment of reflection, where ‘Higgs boson’ will not. At least the former expression contains the word ‘particle’, giving the reader some chance to guess the subject. Of course the ‘God’ part is hubris, but is hubris so bad if it gets people thinking about science? Also, I disagree with commentators who insist that the Higgs is ‘no more important than any other particle’. Since all massive particles are thought to interact with the Higgs field, finding the particle associated with that quantum field is of great importance.

So is it found?  CERN Director General Rolf Heuer stated in Dublin, “As far as the layman is concerned with have it. As far as the physicist is concerned, we have to characterize it”. Such characterization has been going on since July. Without question, a new particle of integer spin (boson) and mass 125 +- 0.5 GeV has been discovered. So far, the branching ratios (the ratio of various decay channels to lighter particles) match the prediction of a Standard Model Higgs boson very well. So it looks and smells like a Higgs, and we are all getting used to the idea of the Higgs field as reality rather than hypothesis. (That said, there is still the possibility of spin 1 or 2 for the new particle, but this is not very likely).

All in all, a very enjoyable evening. The slides and poster I used for the talk are available here.  No doubt, some Trinity professors may have been none too pleased to see ‘God particle’ posters in the Hamilton building. Me, I’ve decided I can live with the name if that’s what it takes to get the public excited about particle physics…

Update

Some bloke called Zephyr is upset and accuses me of misleading the public (comments). His point is that I refer to the Higgs as a particle, instead of a quantum field. There is a valid point here; what were once thought of as elementary ‘particles’ of matter are now considered to be manifestations of quantum fields. However, in the business of communicating physics to the public, each physicist must find their own balance between what is accurate and what is comprehensible. My own experience is that people grasp the idea of the Standard Model reasonably well if it’s told as a story of particle discovery (phenomenology). A small amount on quantum theory is ok, but too much soon leaves ‘em bewildered. For this reason, I much prefer books like Particle physics: A Very Brief Introduction by Frank Close to books like Higgs: The Invention and Discovery of a Particle  (Jim Baggot)

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The Royal College of Surgeons and the Institute of Physics

I attended a very enjoyable blacktie dinner at the posh Royal College of Surgeons in Dublin on Friday. The occasion was the annual meeting of the Institute of Physics in Ireland, the Irish branch of the umbrella group for physics in the UK in Ireland. I always enjoy these occasions, it’s a great way to catch up with colleagues from schools and colleges around the country. This year was no exception and the evening also featured a very enjoyable pre-dinner lecture by Nobel laureate Bill Phillips.

The Royal College of Surgeons on Stephen’s Green in Dublin

In previous years, the IoP meeting stretched over a weekend but we decided to try a single-day meeting this year. Events included an overview of current research in the different colleges, the Rosse poster competition for postgraduate students, and a ‘physicist in the chair’ interview with Bill Phillips. The meeting went on all day but I only caught the dinner and talk due to teaching commitments.

Bill’s lecture was very entertaining. Entitled ‘Time, Einstein and the coolest stuff in the universe’, he gave a simple overview of the hows and whys of laser cooling (the cooling of atoms to extremely low temperature in order to study them in slow motion). From a description of the Heisenberg Uncertainty Principle to Bose -Einstein condensates, the talk was clearly accessible to students yet worked well with a roomful of professionals. I have often noticed this before; people love being told what they already know (and we are all on the lookout for tips in science communication). My only complaint was that the lights were too bright during the during the lecture and too dim during the meal, wrong way round!

Cool atoms: a Bose-Einstein condensate

At dinner, my nearest neighbour turned out to be a climate skeptic. I was intrigued as one rarely encounters skeptics of the theory of man-made global warming amongst professional physicists nowadays. However, I didn’t hear any new arguments, merely a discussion of our ignorance of the role of cloud formation in weather. (A valid point, but hardly a reason to disregard the well-established correlation between greenhouse gas emissions and temperature rise). Indeed, my neighbour seemed unaware of the excellent research being done in this area by several physicists in his own department.

After dinner, a few of us retired to a nearby hotel bar to catch up on the latest in physics, not least, the breaking news of the resignation of the head of the OPERA neutrino experiment. All in all, an interesting night out for a nerdy physicist..

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Neutrino lecture at University College Cork

I gave another talk on the OPERA ‘faster-than-light’ neutrino experiment on Wednesday evening at University College Cork (UCC). I was booked months ago to give the talk as part of the UCC Public Lecture Series and it’s always a pleasure to visit the beautiful campus at UCC.

University College Cork – the nicest campus in Ireland?

Of course, I was concerned the topic might be a bit of damp squib. As everyone in physics knows, a technical fault associated with the OPERA experiment was recently uncovered. Specifically, a connector cable for GPS clock synchronisation was found to be faulty. Between this and other problems, the ‘faster-than-light’ result has been withdrawn (see here for details).

The neutrino detector at Gran Sasso

In fact, the lecture was great fun. We got a good turnout and I made a point of using exactly the same slides I used when the OPERA result was first announced (see here for details). I thought the parts of the talk where I explained the grounds for scepticism from the viewpoint of both special and general relativity (theory and experiment) looked well in retrospect, though I tried hard not to say We told you so. In conclusion, I introduced a few new slides where I discussed what lessons could be learnt from the incident e.g.

1. If your result is in conflict with well-known theory, check, check and check again before you publish (anywhere).

2. If your result is in conflict with decades of experiments, check even more carefully.

3. Never underestimate the media appetite for  ‘Einstein wrong’  stories. Everyone has heard of Einstein and everyone has heard of the speed of light –  this story was always going to be huge.

4. ‘Einstein not wrong after all’ is not such a great media story. In consequence, many members of the public will never get to hear of the correction. Bear this in mind before you go public with a result that may later have to be corrected.

Check your cables – all of them!

The slides I used for the UCC talk are here and I will upload the video in a day or two.

Update

This just in: a group working on an extremely similar neutrino experiment at Gran Sasso have announced the observation of neutrinos obeying the speed limit, as normal. This pretty much refutes the OPERA result completely. See here for details.

Update II

April 3: The head of the OPERA collaboration has resigned over the weekend, see here for details

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Peter Watkins and Z bosons at Trinity College Dublin

last night, I attended a terrific lecture on recent developments at CERN’s Large Hadron Collider, hosted by Astronomy Ireland at Trinity College Dublin. The lecture was presented by Professor Peter Watkins, a former leader of the particle physics group at University of Birmingham and a member of the ATLAS collaboration at the LHC. Professor Watkins was a member of one of the experimental teams that discovered the Z boson at the LEP at CERN in 1983. He is also very well-known for his work in bringing particle physics to the public and is the author of ‘The story of the W and Z, one of my favourite books on particle physics.

I try to go to as many of these public lectures as I can, in order to see how others present physics to the public. In this case, the lecture was superb, very easy to understand yet at quite a high level. It was loosely divided into five sections;

- an introduction to the building blocks of matter

-  a description of what the LHC is looking for

- a description of experimental setup of the LHC and the ATLAS detector

- a description of the methods of searching for particles

- a discussion of recent discoveries at the LHC

The first section gave a brief introduction to the standard model of particle physics. However, rather than present the audience with a list of quarks and leptons, Peter described our view of ordinary matter in terms of up and down quarks, electrons and neutrinos. Only after this did he mention the higher generations, an approach that worked really well. On the next slide, he gave a description of the fundamental forces, explaining along the way how electricity and magnetism were unified into the unified framework of electromagnetism many years ago, and how the latter interaction was more recently unified with the weak force to form the electroweak interaction. There followed a very nice discussion of the force-carrying particles, and the subsequent search for the W and Z bosons. This section finished with an overview of the role of the Higgs field in determining the mass of the particles – about as succinct an introduction to particle physics as I’ve seen!

The second section of the talk described what the LHC will search for; from the Higgs boson to supersymmetric particles, from investigations of the slight asymmetry in matter and antimatter decay to candidates for dark matter. Professor Watkins was also careful to explain that the LHC may yield great surprises, from missing energy that might constitute evidence of hidden dimensions to possible hints of new forces.

An experimental overview of the LHC and the ATLAS detector was presented in the third part of the talk. The technical challenges of LHC operation were clearly laid out, from the need for ultra-low temperatures to the problem of establishing an ultra-high vacuum on this scale, from issues with beam focusing to problems with superconducting magnets. This section included a great overview of the ATLAS detector, with each component described carefully.

The ATLAS detector, not the LHC as many newspapers seem to think

The fourth section of the talk was most unusual, where Peter gave a clear description of how the existence of elusive particles is inferred from those beautiful patterns on computer monitors.  Starting with E2 = p2c2 + m2c4, he gave a few examples where measurements of momentum and energy in the detector lead to an estimate of the mass of the parent particle. This section included a great description of the search for the Higgs via the ZZ and photon-photon decay channels.

In the last part of the talk, the speaker gave a clear description of recent work at the LHC. Touching briefly on the initial accident of 2008, he explained how ATLAS and CMS have gradually been closing the window on mass ranges for the Higgs (including earlier data from LEP). He had a nice surprise for many in the audience when he mentioned that ATLAS has already discovered its first new particle – a new state of the chi-b particle . The lecture finished with a discussion of the famous ‘bump’ in the ATLAS data at 126 GeV announced two weeks ago, and the possible significance of the discovery.

Hints of a higgs in the ATLAS measurements ? (Dec 2011)

I found this a superb lecture overall. The speaker outlined difficult concepts extremely clearly and gave a great description of how concepts emerge, rather than presenting ‘facts’ as fixed dogma. The audience certainly thought so too and there were dozens of questions afterwards. As always with Astronomy Ireland lectures, the discussion continued in the pub across the road. At one point, Peter explained that part of the current excitement is due to where the bump is; if the 126 GeV result stands, this relatively low mass for the Higgs may be compatible with extensions to the standard model such as supersymmetry….a good time to be a particle physicist!

Update

Rumours are circulating that the CMS bump has not disappeared on further analysis, but is converging on the ATLAS result, exciting times

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Faster than light and the public misunderstanding of science

Yesterday evening, I gave a public lecture in Dublin on the Gran Sasso neutrino experiment, hosted by the Irish Skeptics Society. The event formed part of Maths Week Ireland, an initiative co-ordinated by CALMAST, the science outreach group at our college. We had a great audience turnout and I enjoyed the Q&A afterwards immensely. Below is the abstract and you can find the slides for the talk here.

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In September 2011, a group of scientists announced that they had detected subatomic particles travelling at speeds greater than the speed of light in vacuum. The finding is in conflict with Einstein’s theory of relativity and has been met with great skepticism by mathematicians and physicists around the world. This lecture will examine the grounds for that skepticism and consider the role of skepticism in general in science and mathematics

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       The Gran Sasso experiment

I suspect I was invited to speak because of a letter I had published on the subject in The Irish Times (below). Although the Gran Sasso experiment has certainly raised awareness of physics, I think the way the media are portraying this experiment as an  ‘Einstein wrong’ story is most unfortunate. It is far too soon to reach that conclusion and the overall effect is to make science seem very uncertain. It is more Public Misunderstanding of Science than PUS, in my view.

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Sir, – Margaret Moore (September 29th) asks what word will be used to describe a speed faster than the speed of light. The technical term is superluminal speed. However, much of the media coverage of recent experiments at Gran Sasso has been very misleading. Almost all professional physicists (including the experimenters) consider the Gran Sasso result a curious anomaly almost certainly due to some unknown error in measurement, for several reasons:

1. Light is carried by particles of zero mass and it follows that there are fundamental theoretical reasons for supposing that the speed of light in vacuum represents a natural speed limit for particles of non-zero mass.

2. Thousands of experiments have verified that the tiniest particles of matter can be accelerated up to speeds close to, but not equal to, this limiting speed.

3. The recent Gran Sasso experiment involves measurements of time and distance of unprecedented precision, yet it was not designed for this specific purpose; thus there are many potential sources of systematic error.

It’s true that science sometimes progresses by upsetting the status quo, but scientists are a sceptical lot and extraordinary claims require extraordinary evidence! –Yours, etc,

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Does it matter how the experiment has been portrayed in the media? I think it does. A few years from now, journalists will be say ‘ but didn’t you guys think in 2011 that Einstein was wrong’? In fact, there has already been one editorial in the Wall St Journal urging inaction on climate change, on the basis that science is never certain, given the neutrino result (see point 5 of this article ). Exactly the wrong conclusion to draw…

Update

I see my lecture got a short review in today’s Irish Times. It’s not a bad overview, considering the writer wasn’t at the lecture. The last sentence doesn’t make sense, however – I suspect she meant supernovae instead of black holes!

Udate II

Just caught  BBC program on the experiment (Marcus du Sautoy). Superb, superb program. Nothing like the players themselves for conveying the concepts of science..

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‘Black Holes, the Hadron Collider and the God Particle’

We got a massive turnout on Monday evening for a public lecture I gave on the Large Hadron Collider at Trinity College Dublin. I was invited to give the talk by Astronomy Ireland and it was a great time to give it as there is still plenty of interest in the Collider because of the black hole ‘controversy’, and because last week saw the first offical conference on results from the LHC. Indeed, there has been very little media attention given to the fact that, in the space of a few months,  all four detectors at the LHC have been busily rediscovering the elementary particles of the Standard Model that took so many years to first detect, from pions, muons and kaons right up to W and Z bosons.

A lot of physicists might have a problem with the populist title ‘Black holes, the Hadron Collider and the God particle'; however the title was worked out with Astronomy Ireland, an organisation that knows a thing or two about attracting a wide audience! Also, I think controversies such as the black hole controversy are best tackled head on i.e. by describing early on in the talk what a black hole is and why one doesn’t expect to create one at the LHC  (in particle physics, one gets only a minute amount of mass  from a very large amount of energy since  m = E/c2 ). I also touched on micro-black holes and Hawking radiation; overall I had the distinct feeling the audience enjoyed this part of the talk no end!

As for the term ‘God particle’, I happen to be one of the few physicists who likes this name for the Higgs boson. Yes, it was probably originally ‘that goddamn particle’ due to its elusiveness,  but I think ‘God particle’ neatly gets across the importance of the particle; after all it is the interaction of the other particles with the Higgs field that is thought to determine their mass, according to the Standard Model.

I divided the talk into three parts; first, an overview of the LHC – how, what, why etc. Then I devoted the central part to a brief history of particle physics, from the discovery of the nucleus to protons and neutrons, from the hypothesis of quarks to the electroweak interaction and the Standard Model. In the third part, I described extensions to the SM such as supersymmetry and Grand Unified Theory and went over our expectations of the LHC experiments, from the possible detection of the Higgs boson to supersymmetric particles, from candidates for dark matter to the search for assymetries in matter/antimatter decay at LHCb.

The LHCb experiment is of particular interest to an Irish audience, as a group at University College Dublin are heavily involved, despite Ireland’s non-membership of CERN.

Finally, I can never resist showing a couple of slides on the basics; not only do experiments at accelerators give us information on the elemental structre of matter and the interaction of the fundamental forces, they also give us supporting evidence for our underlying theories of modern physics, from the observed mass-increase of particles (predicted by special relativity) to the detection of antiparticles (predicted by quantum theory). You can see the full set of slides for the talk here and a video is available here.

All in all, there was a great atmosphere at the talk and I really enjoyed the occasion. There were plenty of questions afterwards, from queries on black holes to the prospect of detecting extra dimensions. I was also asked about a recent study of the cosmic microwave background (CMB) that may cast doubt on the hypothesis of dark matter (based on a revision of measurements of perturbations in the  CMB). I haven’t studied this report yet, but I gave the answer that I always give in public fora: let’s see if other groups replicate the findings before pay too much attention. After all, the postulate of dark matter comes not primarily from measurements of the CMB, but from thousands of measurements of the movement of stars, galaxies, galaxy-clusters and halos. That said, it’s certainly an interesting paper…

Update

I really enjoy giving such talks on particle physics, there are so many fascinating subjects to cover; special relativity, quantum theory, quarks, the fundamental interactions, symmetry breaking, antimatter, dark matter etc. Yet while there are quite a few excellent books for the public on cosmology, there are remarkably few on particles physics… might be fun to try to put one together one day.

Update II

Apparently, U.S. newspapers are full of stories on the discovery of the God particle at the Tevatron. It seems these stories are based on an unpublished paper (see discussion on Not Even Wrong) – I wouldn’t pay too much attention just yet.

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