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

It’s always nice to have a science article published in a national broadsheet, and I thought it was worth revisiting the OPERA experiment before the end of 2011. I enjoyed writing the article and colleagues tell me the question and answer format worked well.

But what about that title? And the opening line? (see print edition). Both were super-imposed by the sub-editor and I find them quite poor. This keeps happening; I take time and effort to write science pieces for the public as clearly as I can, and a professional writer comes along and superimposes something quite sloppy. It’s a pity because nine out of ten cats will read no further than the title and opening sentence.

If the article and headline were submitted as student work, this would be my verdict:

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The headline used for this article breaks almost every rule of science writing

1. The English is poor  – it is not clear what a ‘relativity questioning experiment’ is

2. ‘Verdict out’ is also not clear – ‘jury out’ would be better, but is still clumsy

3. The title is also intimidating – never use a word like relativity in a headline if you can avoid it.

As a result of points 1-3, the title does not clearly describe the content of the article – hence few readers will read further.

The writer should consider alternate titles such as ‘Faster than light?’ or  ‘Was Einstein wrong?’

These titles are both clear and succinct. Most importantly, they draw in the reader in, rather than drive her away

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Update

There is also a major problem with the opening sentence; luckily, it is only in the print edition

I’m frequently asked if WIT is a let down after Harvard, but I must say I enjoyed this semester no end. I taught maths (to 1st science), physics (to 1st engineering) and my ‘concepts in cosmology’ course to our physics students. I’m writing a book based on the latter so it was fun summarizing a chapter each week and presenting it in class as bullet points. After each lecture, I found myself rushing back to the office to rewrite a paragraph or re-jig an explanation – very satisfying!

Motivated students

Then there was the neutrino experiment; a superb opportunity for public lectures on relativity. Like almost all physicists, I expect this result is an anomaly because neutrinos are known to have a finite rest mass. I really enjoy explaining this in outreach lectures so long may the anomaly survive! The Trinity lecture was very satisfying, we got a great crowd including some very eminent physicists.

Now I have four weeks to work quietly on the book, uninterrupted by classes – what a job!

Update

Meanwhile, rumours continue to circulate in the media about a possible sighting of the Higgs boson. I haven’t heard anything in physics circles so I’m betting it’s a false alarm based on a misunderstanding of the purpose of next week’s roundup meeting at CERN (see here for more on the rumours). Still, I’ll be keeping an eye on the news on Tuesday!

There was a real buzz in the air at Saturday’s lecture, thanks to the latest results from OPERA. As you probably know, the team announced on Friday that the superluminal result has passed its first major test: a repeat experiment using a much shorter proton pulse. This time they used pulses only 3 nanoseconds long, separated by by gaps ten time larger. This is vastly shorter than before (10 microseconds) and obviates the statistical approach used for matching transmitted and received pulses used in the original experiment. Like most physicists, I am still pretty certain the result will eventually turn out to be an anomaly, but I certainly hope it survives for another few months! See here for the new OPERA paper.

The lecture was hosted by Astronomy Ireland,a very interested audience that always turn out in droves. The theatre was jammers, quite a few audience members had to stand throughout. As always, I particularly enjoyed the questions and answers afterwards. It’s also fun to be come home; as a postgraduate student, I spent many long years in the magnetic resonance lab next door!

David Moore of Astronomy Ireland presents me with something (?)

Afterwards, some of us all legged it over to another Trinity lecture theatre, to hear the annual statutory lecture of the School of Theoretical Physics of the Dublin Institute for Advanced Studies. This year, the speaker was well-known string theorist Cumrun Vafa from Harvard. Titled ‘Geometric Physics’, the lecture was an excellent introduction to string theory today.

String theorist Cumrun Vafa from Harvard

And after all that, there was a reception to celebrate the fact that Werner Nahm, the director of the DIAS School, was recently made a fellow of the Royal Society. What a weekend

Update

On Sunday, Werner gave a fascinating talk on ancient astronomy at the Dublin Institute of Advanced Studies. After the seminar, many of us remained in the fading light in that famous seminar room, discussing the neutrino result and other experiments at CERN. As so often, I was struck by the depth and detail of knowledge the theorists had of particle experiments. I also enjoyed the way the discussion wandered into German for a while, then seamlessly back to English – only at DIAS!

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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

       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..

William Rowan Hamilton made a great many other contributions to mathematics and physics. For example, his formulation of a mathematical operator for the energy of a body – the Hamiltonian -  is a vital tool in quantum mechanics, the mathematical description of the quantum world. Open any modern textbook on quantum physics and you will encounter the word ‘Hamiltionian’ on almost every page.

As regards quaternions, we know exactly when Hamilton had his Eureka moment. According to his own writing, inspiration struck on the 16th october in 1843,  as he was walking with his wife from Dunsink Observatory in County Dublin (where he was Astronomer Royal) along the Royal Canal towards the city centre, in order to attend a meeting of the Royal Irish Academy, of which he was President.  He was so pleased with the breakthrough that he used his penknife to carve the new equation onto Broom bridge as they passed. The carving no longer exists but the bridge does, and the occasion is celebrated with a plaque. Every year, mathematicians and friends of mathematics congregate at Dunsink Observatory at 3pm and re-enact Hamilton’s famous walk along the canal to the bridge.

William Rowan Hamilton; the plaque displays the famous equation i² = j² = k² = ijk = -1

This year, October 16th fell on a Sunday, so mathematicians and the general public arrived from far and near. The day started in Dunsink Observatory, with a brief description of Hamilton’s life and work by Fiacre O Cairbre, event organiser and lecturer in mathematics at NUI Maynooth. There followed a lovely walk along the canal in perfect weather conditions, all the way to Broom bridge to view the plaque. The outing finished with a short description of Hamilton’s breakthrough by another Maynooth mathematician, Anthony O’ Farrell, and a chorus of ‘Happy birthday, quaternions’ by all present. I think it’s great to remember our scientific heros like this;  it’s curious that even our very best scientists and mathematicians receive far less public attention that writers and musicians.

Dunsink Observatory and Broom Bridge on the Royal Canal

Each year, the Hamilton Walk is soon followed by a prestigious lecture on mathematics presented by the Royal Irish Academy and The Irish Times. Previous speakers have included Andrew Wiles, Steven Weinberg, Murray Gellman and Lisa Randall. This year, renowned string theorist Ed Witten will give a talk on quantum knots, see here.

The Hamilton walk  is one of the core activies of Maths Week Ireland, an initiative to raise awareness of maths in Ireland with events and lectures all around the country. Co-ordinated by CALMAST, a science outreach group at Waterford Institute of Technology, Maths Week has grown larger every year – you can find the program of events here. I will give a talk in Dublin on Wednesday evening, on relativity and the recent ‘faster than the speed of light’ experiment, see here .

Tyndall’s most important contribution was his experimental demonstration of the greenhouse effect. He was the first to show that certain gases – notably carbon dioxide and water vapour – absorb radiation of infra-red wavelength, thus trapping heat reflected from the earth. This discovery forms the bedrock of the modern climate science. Today’s phenomenon of global warming (measured as an increase in global temperature, glacier-melt and sea level rise over the last few decades) has been attributed to an increased concentration of greenhouse gases in the atmosphere caused by the burning of fossil fuels.

The 2011 Tyndall climate conference was sponsored by the EPA and the Royal Irish Academy

The conference celebrated the 150^th anniversary of the publication of Tyndall’s landmark paper On the Absorption and Radiation of Heat by Gases and Vapours and took place in Dublin castle, a superb venue in the heart of Dublin’s vibrant city center (and the seat of British rule in Ireland only a century ago). Day one was an overview of Tyndall’s life and work, with a keynote lecture by eminent climatologist Richard Sommerville. The next two days featured slightly more technical talks on climate science. You can find the conference program and book of abstracts here.

I caught several excellent talks on Friday, including a talk on climate sensitivity and feedback mechanisms by John Mitchell of the UK Hadley Centre, and a talk on tipping points and their predictability by Peter Ditlevensen of the Center for Ice and Climate at the Niels Bohr Institute in Copenhagen. Another talk, by George Moore of the University of Toronto, suggested that we may already have passed such a tipping point. The lecture  ’20 years of IPCC projections’ by Ulrich Cubasch of the Free University of Berlin, demonstrated how well IPCC projections have stood the test of time. This is a point often overlooked in discussions of climate science in the media. The public are wary of theoretical models, and climate scientists sometimes forget to point out that we have had twenty years to test predictions – so far, the projections have turned out to be all too accurate.

Possibly the most advanced talk of the day was by Professor Ray Bates of the Meteorology and Climate Centre at University College Dublin, a former professor of meteorology at the Neils Bohr Institute. In his talk, Ray presented a new global climate model, contrasting it with the recent model of Dick Lindzen. The Lindzen model is quite controversial as it suggests that conventional climate models overestimate the contribution of an enhanced greenhouse effect on climate. In good scientific fashion, Ray outlined the basic physics underpinning the two models, steering clear of polemics and concentrating on the science. You can Ray’s paper on his, and other, models here .

All in all, a great conference, I was sorry to miss the first two days. One of the aspects the increased teaching workload in the Institute of Technology sector is that there is almost no time left over for conferences – someone’s idea of increased productivity.

Update

Richard Sommerville did a very nice interview on the Pat Kenny show, a flagship radio show on RTE radio 1. Pat raised almost every point favoured by climate skeptics, while Richard provided clear and cogent answers to each. Well worth a listen, you can download a podcast here.

In the OPERA experiment, a beam of neutrinos travels underground from CERN travel to Gran Sasso in Italy

The OPERA paper has been posted on the ArXiv here. Most physicists (including the participants) are calling the result an ‘anomaly’ and expect to find a hidden error, for two reasons

1. Thousands and thousands of experiments on elementary particles suggest that the speed of light represents a natural speed limit for material bodies, no matter how much energy you whack them with

2. There are deep mathematical reasons for believing that the speed of light in vacuum represents an absolute limit, from arguments of symmetry to the principle of least action. Basically, all sorts of mathematics suggests that the speed of photons- massless particles -  is the highest speed achievable. In addition, the principle underlies a great deal of observed physics, far beyond the remit of relativity.

So what is going on?

Science is a skeptical activity and scientists are slow to throw out a successful theory at the first sign of trouble -especially a theory as successful and as central as special relativity. Most scientists adopt a ‘wait and see’ approach when an experiment like this is reported.

For example, we know a great deal more about relativity than we do about neutrinos. It is only a few years since it was discovered that neutrinos have mass, and the phenomenon of neutrino oscillation – the transformation of one type of neutrino to another – is still not well understood. So it is possible that this experiment is an artefact of some unknown neutrino process.

A more prosaic possibility is that there is a systematic error in the extremely precise time/distance measurements necessary for the experiment. For example, the time of flight of the neutrinos is measured using a sophisticated version of GPS – perhaps there is a hitherto undetected error lurking in this method that is affecting the measurement. A few years ago, it was discovered that the moon has an effect on the curvature of the LHC tunnel, as does the TGV arriving at Geneva – these effects only show up because of the unprecedented precision involved in the experiments.

Finally, it is always possible that this result may turn out to be a real effect. In this case, we could be looking at some exciting new physics; not a violation of relativity, but the first evidence of hidden dimensions. String theorists have long mooted the possibility that the three familiar three dimensions of space may be accompanied by other dimensions, tiny ones that are curled up so that they are undetectable at normal energies. In principle, a particle that takes a shortcut through such a dimension could arrive early! This may sound like a rather fantastic explanation, but it is possible that an experiment at the unprecedented energy and precision of OPERA could see this effect for the first time. Certainly, it would not contradict any previous theory or experiment.

So an exciting wait, but my money is on a systematic error in the measurement of distance or time

Technical note

I keep hearing in the media that ‘relativity forbids travelling at speeds faster than the speed of light in vacuum.’ Actually, it doesn’t, as Einstein was fond of pointing out. Special relativity suggests that it is impossible for  body to be accelerated from subluminal to superluminal speed. Thus particles that travel faster than light are possible in principle so long as they always travel at that speed (known as tachyons). However, such behaviour has implications for time (it would run backwards) and for causality, and is therefore thought unlikely. Also, no such particles have been observed  in five decades of experimentation in particle physics .

Last weekend, I was quoted (well misquoted) in The Irish Times, making the last point above; you can read it here, it’s quite a good article.

Update

If it is a systematic error, what could it be?  Looking at the paper, my own guess is that it is significant that the group do not measure the time-of-flight of individual neutrinos, but massive bunches of the particles. Essentially they measure the beginning and end of a bunch, and apply statistics to get the mean time. A messy enough procedure, considering the accuracy required..

Update II

I have a letter on the experiment in The Irish Times today, you can read it here

It’s nice to be back home too – no more going around in silly shorts, suncream and shades. Back at Waterford Institute of Technology in the southeast of Ireland, we are already in the second week of teaching term. The bad news is that thanks to the recession, teaching loads have been increased (increased productivity!) leaving almost no time at all for frivolous activities such as research. On the other hand, there is much discussion of the college being upgraded to full university status, mainly because the government thinks that an upgrade ay help attract industry to a region badly hit by the recession. So after all the valiant efforts of WIT researchers, it seems an upgrade may occur for political reasons…

How does the college seem after Harvard? Colleagues keep asking me this. Yes, I miss the beautiful Harvard campus, the incredible libraries and the superb seminars. However, the main day-to-day difference is one of organization. There seems to be a problem of chaotic timetabling in WIT for the first few weeks of every semester, at least in my department. It’s very stressful and leaves no time over for prep or research. I’ve never understood why this happens every year, as our staff and courses change relatively little. One reason might be that lecturers are left to decide who teaches what amongst themselves, pitting Alice against Bob. Give me a didactic Head of Department any day…

Waterford Institute of Technology

On the other hand, it’s great to be in a job with an influx of Hopeful Young People every year. I always think that academics are v lucky in this regard, it doesn’t really matter which college you are in. Another change is that I am moving to a smaller, quieter office yipee. There is a special place in hell reserved for managers who believe that academics work well in large open-plan offices. With students coming to the door and phones continually ringing, it’s impossible to get any work done between classes. Hopefully I’ll have some quiet evenings in my nice new office….

Update; here it is in full

[I’m fast approaching the end of my year as a research fellow at Harvard – what an experience! ‘So what was it like?’, a great many colleagues in Ireland have asked. Actually, Harvard reminded me very much of Trinity College Dublin, where I did my PhD – but on a larger-than-life scale.

First, the main Harvard campus is not unlike Trinity. Although the architecture dates from a different period, the campus consists of one large quadrangle, with other quadrangles branching off. All of these beautiful quads boast fine old buildings that serve as lecture halls, libraries, dining halls and student housing. This centralization gives Harvard a great ‘lived-in’ feeling; in this respect, it is resembles a large version of Trinity, in contrast with the dispersed, collegiate system of Oxford and Cambridge.

However, Harvard is situated in the quiet district of Cambridge, Boston, not Dublin city centre. As a result, it has been able to situate its growing graduate schools in the immediate area surrounding the main campus, unlike Trinity. Indeed, much of the area between the main campus and the Charles river is filled with Harvard buildings, from graduate schools in business, law and government to student housing; the whole area is now known as Harvard Square.

What about the academic side of things? Apart from a high number of staff who are stars in their field, it doesn’t feel all that different from other universities. What strikes one most is the sheer diversity of scholarship. Consider science; as well as world-renowned departments in mathematics and physics, Harvard also boasts a famous centre for astronomy and accompanying observatory. As well as prestigious departments in traditional disciplines such as chemistry, biology and the medical sciences, Harvard has a huge History of Science department and accompanying museum. Not many universities can boast these, or Harvard’s well-known programs in Science, Technology and Society.

Academic standards are sky high, as you might imagine. Although I have my doubts about some university ranking systems, there is no denying Harvard comes in at no.1 or 2 in almost every poll. So while TCD comes in at the top of the Irish rankings, Harvard comes in at the top of the world! For my money, this is not just a question of its ability to attract the very best because of its prestige and massive endowment (and yes, they do buy in top professors). It is also the close proximity of MIT and other Boston colleges that makes for a highly competitive, interactive academic environment, at least in the sciences. This is quite a unique situation; there is a daily level of intervarsity interaction that is far beyond that of Oxford and Cambridge, or Trinity and UCD say. Most physics seminars I attended had an even mix of MIT/Harvard personnel, irrespective of where the seminar took place. Indeed, regularly trotting off to MIT was a great treat; it’s a beautiful college where any scientist feels instantly at home, not to mention the awe-inspiring number of spin-off companies ringed around the college. Indeed, MIT’s success at innovation currently far surpasses that of Harvard. Of the ‘Nobel possibles’ I was made aware of (quite a few of those over here), at least as many were MIT. So there’s not much complacency amongst the Harvard scientists. Given the relatively small size of Dublin, it’s a pity this sort of daily interaction between the colleges doesn’t happen much.

What about undergraduate life at Harvard? Here, there is a huge difference with Trinity, and indeed between the American system and the situation in Ireland and Europe. Undergraduate fees at Harvard are in the region of 40-50 thousand dollars per annum, with few scholarships. This is true of a great many of the top colleges in the US and it has major implications for society. May we never go down this road, however bad the funding situation gets. You can also see how corporate jobs that cover kids’ health insurance and college fees have an urgent appeal.

As regards tuition, class sizes can be large (> 50), but there is a huge diversity of modules offered. Students typically have 2 plenary lectures per week, with smaller sectionals run by teaching assistants. There is great emphasis on continuous assessment, with corrections done by teaching assistants rather than the Prof (nice!). Sitting in on some classes, I couldn’t help noticing that a great many students spend precious class-time fooling around on the web, so I think I will ban internet connections in my lectures when I return home.

At postgraduate level, the financial situation is very different. While competition to get into the Harvard postgraduate program is intense, once accepted, the stipends for postgraduates are quite generous. I found the difference between the undergraduate and postgraduate populations quite noticeable; while the general student population is mainly made up of well-heeled young Americans, the postgraduate population seemed to be comprised mainly of Europeans and Asians. I had plenty of time to observe this in one my favourite venues, the Harvard Graduate School of Arts and Sciences. With its own building, dining hall, library and common room, this was a great place to meet scholars of all nationalities and a wide variety of disciplines. A great idea for any college! But isn’t it interesting that the research output of the great Ivy League colleges may rest on students who have in fact been trained in European and Asian universities? We should remember this before we adopt every fashionable trend in U.S. undergraduate education.

I’ve decided to stay in Boston for the summer, writing up my research before returning to WIT in September. I’ll certainly miss Harvard, MIT, and Cambridge, I don’t think I’ve ever been in such a vibrant academic environment. More generally, Cambridge Boston is a great place for a European; a liberal, highly-educated bastion of American society, blessedly free from the right wing ideology so increasing pervasive in the US. Back at home, it’s nice to think that the Irish IoTs may someday play MIT to our universities, but I think we have some way to go. More pragmatically, I find it a great drawback being too far from Dublin/Cork to interact with university colleagues on a daily basis…]