I’m a day late posting this, but I only thought of it this morning. It’s a fine performance by the New York Philharmonic conducted by Leonard Bernstein of “The Fourth of July”, the third movement of his “Holidays Symphony” by the great Charles Ives. The video even shows the score so you can play along at home! As Ives himself famously said:
Follow @telescoperStand up and take your dissonance like a man!
A former colleague recently contacted me with a request to join my “network” on LinkedIn. That was quite hard to do as (at least until this morning) I was not on LinkedIn. That reminded me of a talk at INAM2019 a couple of years ago about the Astronomical Society of Ireland which was about to be re-launched with a new website. One of the main reasons for doing this is that Ireland recently joined the European Southern Observatory and in order to capitalize on its involvement it is important to persuade the Irish government to invest in the resources needed (especially postdocs, etc) to do as much science as possible using ESO facilities. The idea was to improve the lobbying power for astronomy in Ireland. One of the suggestions made yesterday was that astronomers in Ireland should join LinkedIn in order to raise their profile individually and collectively.
I was not on LinkedIn at the time and didn’t get around to joining it mainly because I’ve always thought it was more for businessy types than academics. Anyway, in the light of recent events I decided it couldn’t do any harm to bite the bullet and set up a LinkedIn profile, which you can find here. It’s really a rather basic profile but I think I’ve set it up so that posts from here will be posted to LinkedIn too, so if you’re on it yourself you might want to add me. Or not. It’s up to you!
P.S. The only thing I have put under “Awards and Honours” is Winner of Beard of Ireland 2020.
Follow @telescoperI was planning to be on leave now; I intended to make up for the fact that I didn’t get a summer holiday last year by taking most of July off. Unfortunately that was not to be and I have to stay at work for at least another week to participate in an interview panel. I may still get a couple of weeks after that but if I do it will be taken up with organizing the move of the rest of my belongings from Cardiff to Maynooth, rather than being an actual holiday.
Over the last few days, in an exhausted and demoralized state, I have been looking back over the best part of two years I have been Head of the Department of Theoretical Physics at Maynooth University – most of which has coincided with the Covid-19 pandemic. Frankly, I have found the burden of administration on top of the heavy teaching load required of me to be unmanageable. Because we are a very small Department teaching a full degree course, all of us have to teach many more modules than is reasonable for for staff who are expected to do research as well. I had to teach five modules* last academic year; that would have been bad enough even without having to do everything online and without the additional and frequently onerous duties associated with the Head of Department. There is no prospect of that burden decreasing for the foreseeable future.
I was appointed as Head of Department for three years, but last week I asked the University to let me step down from my role as Head of Department of Theoretical Physics from the end of September 2021, a year early. I’ll carry on as a Professor, hopefully with some time to do research, although my teaching duties will undoubtedly remain heavy.
At least now, if I do get some holiday this summer I’ll be spared some of the dread of what I’ll have to return to afterwards…
*For those who are wondering, two of those modules are 36 lectures (3 per week for a 12-week semester), two are 24 lectures (two per week for a semester) and one is computer-based (1 lecture + a 2hr lab session per week for a semester). That load is about average for full-time staff in the Department; if I did less someone else would have to do more.
UPDATE: 6th July. The University has agreed to my request. “Freedom Day” for me is October 1st 2021.
Follow @telescoperOne topic on this blog seems to be as perennial as the weeds in my garden: the so-called Hubble Tension. I just saw a review paper by Wendy Freedman, one of the acknowedged experts in this area, on arXiv here. I have abstracted the abstract here:
You can find the PDF here.
What’s particularly interesting about this discussion is that stellar distance indicators have typically produced higher values than the 69.8 ± 0.6 (stat) ± 1.6 (sys) km s-1 Mpc-1 quoted here, which is consistent with the lower value favoured by Planck. See the above graphic discussed here. So perhaps there’s no tension at all. Maybe.
Anyway, here’s that poll again! I wonder if this paper might change the voting.
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Today (1st July) is Canada Day so here is something by Canada’s finest, the great Leonard Cohen.
We miss you, Leonard.
This is the faith from which we start:
Men shall know commonwealth again
From bitter searching of the heart
We rise to play a greater part
Yesterday the Chair of the National Public Health Emergency Team (NPHET), who also happens to be the President of Maynooth University, Professor Philip Nolan published a lengthy but interesting Twitter thread (which you can find unrolled here). In these tweets he explained the reason behind NPHET’s recommendation to pause the process of relaxing Covid-19 restrictions, postponing the next phase which was due to begin on 5th July with indoor dining.
The basic reason for this is obvious. When restrictions were lifted last summer the reproduction number increased to a value in the range 1.4 to 1.6 but the infection rate was then just a handful per day (on July 1st 2020 the number of new cases reported was 6). Now the figures are orders of magnitude higher (yesterday saw 452 new cases). A period of exponential growth starting from such a high base would be catastrophic. It was bad enough last year starting from much lower levels and the Delta variant currently in circulation is more transmissable. Vaccination obviously helps, but only about 40% of the Irish population is fully immunized.
Incidentally the target earlier this year was that 82% of the adult population should have received one jab. We are missing detailed numbers because of the recent ransomware attack on the HSE system, but it is clear that number has been missed by a considerable margin. The correct figure is more like 67%. Moreover, one dose does not provide adequate protection against the Delta variant so we’re really not in a good position this summer. In fact I think there’s a strong possibility that we’ll be starting the 2021/22 academic year in worse shape than we did last year.
In general think the Government’s decision was entirely reasonable, though it obviously didn’t go down well with the hospitality sector and others. What does not seem reasonable to me is the suggestion that restaurants should be open for indoor dining only for people who are fully vaccinated. This would not only be very difficult to police, but also ignores the fact that the vast majority of people serving food in such environments would not be vaccinated and are therefore at high risk.
As things stand, I think it highly unlikely that campuses will be open in September. Rapidly growing pockets of Delta variant have already been seeded in Ireland (and elsewhere in Europe). It seems much more likely to me that September will see us yet again in a hard lockdown with all teaching online.
But the main reason for writing this post is that the thread I mentioned above includes a link to a paper on the arXiv (by Gleeson et al.) that describes the model used to describe the pandemic here in Ireland. Here is the abstract:
We describe the population-based SEIR (susceptible, exposed, infected, removed) model developed by the Irish Epidemiological Modelling Advisory Group (IEMAG), which advises the Irish government on COVID-19 responses. The model assumes a time-varying effective contact rate (equivalently, a time-varying reproduction number) to model the effect of non-pharmaceutical interventions. A crucial technical challenge in applying such models is their accurate calibration to observed data, e.g., to the daily number of confirmed new cases, as the past history of the disease strongly affects predictions of future scenarios. We demonstrate an approach based on inversion of the SEIR equations in conjunction with statistical modelling and spline-fitting of the data, to produce a robust methodology for calibration of a wide class of models of this type.
You can download a PDF of the paper here.
This model is a more complicated variation of the standard compartment-based models described here. Here’s a schematic of the structure:
This model that makes a number of simplifying assumptions but it does capture the main features of the growth of the pandemic reasonably well.
Coincidentally I set a Computational Physics project this year that involved developing a Python code that does numerical solutions of this model. It’s not physics of course, but the network of equations is similar to what you mind find in physical systems – it’s basically just a set of coupled ODEs- and I thought it would be interesting because it was topical. The main point is that if you study Theoretical Physics you can apply the knowledge and skills you obtain in a huge range of fields and disciplines. Developing the model does of course require domain-specific epidemiological knowledge but the general task of modelling complex time-evolving systems is definitely something physicists should be adept at doing. Transferable skills is the name of the game!
P.S. It came as no surprise to learn that the first author of the modelling paper, Prof. James Gleeson of the University of Limerick, has an MSc in Mathematical Physics.
Follow @telescoperAnd now the moment you’ve all been waiting for. Here is a recording of the Invited Colloquium at the International School Daniel Chalonge – Hector de Vega I gave via Zoom on 23rd June 2021, introduced by Prof. Norma Sanchez.
In the talk I give a general review of the current state of cosmology, discussing the standard model of cosmology and some of the possible ways in which it might be revised or extended. It’s not a very technical talk but does assume some knowledge of cosmology. I hope a general audience will get something out of it.
I’m sorry if the recording is a bit choppy but that’s an occupational hazard with Zoom recordings and rather limited broadband!
This is an edited version of the session which in total lasted well over three hours including lengthy discussions and a trip down memory lane at the end. I cut out the introduction but kept a few of the questions and answers at the end, so it’s still rather long despite the rather brutal edits.
A video of the full event can be found here (1.6GB) and a PDF file of the slides can be found here. The slides are also available to be viewed here.
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Today is 28th June which means that it’s the anniversary – the 52nd anniversary to be precise – of the Stonewall Riots.
I was only 6 in 1969 so wasn’t aware of this event at the time but it (and Pride Month generally) always reminds me of how far we’ve come, though many LGBT+ people still face hostility and discrimination. Nowadays though my own celebration of Pride is very subdued as it tends to makes me feel old and irrelevant as well as worried that we might be headed back right to the bigotry and intolerance of the past. The rights we have won could so easily be taken away. Although I am no longer young, I find I have become very protective towards younger LGBT+ people. I don’t want anyone to have to put up with the crap that I did when I was their age.
Despite these reservations I do find some of the manifestations of Pride quite pleasing. An Post have issued special stamps this year, as you can see above.
I haven’t bought any because I haven’t got any letters to send but I think it’s nice. 18 year old me in the middle of his A-level exams in 1981 could not have imagined such a gesture from a public body. Bród is the Irish word for Pride.
I watched the 2014 film Pride on TV the other day. I’d seen it before but enjoyed the second viewing a lot, although it did make me feel a bit ashamed that I didn’t get involved in the events of 1984 at all. I was too much of a coward.
Anyway just to change tack I thought I’d mention that the “An” in “An Post” is a definite article, which is a bit confusing to English speakers for whom “an” is a form of the indefinite article. There are no indefinite articles in Irish.
Other European languages (including Latin) don’t have any articles at all. Russian doesn’t either. It’s always fun writing a paper with Russian collaborators because articles are so alien to them. It’s not so easy to explain when to use the definite or indefinite article or no article at all to someone used to a language in which articles don’t exist.
I have been struck by the number of people upset by the latest analysis of SARS-Cov-2 “variants of concern” byPublic Health England. In particular it is in the report that over 40% of those dying from the so-called Delta Variant have had both vaccine jabs. I even saw some comments on social media from people saying that this proves that the vaccines are useless against this variant and as a consequence they weren’t going to bother getting their second jab.
This is dangerous nonsense and I think it stems – as much dangerous nonsense does – from a misunderstanding of basic probability which comes up in a number of situations, including the Prosecutor’s Fallacy. I’ll try to clarify it here with a bit of probability theory. The same logic as the following applies if you specify serious illness or mortality, but I’ll keep it simple by just talking about contracting Covid-19. When I write about probabilities you can think of these as proportions within the population so I’ll use the terms probability and proportion interchangeably in the following.
Denote by P[C|V] the conditional probability that a fully vaccinated person becomes ill from Covid-19. That is considerably smaller than P[C| not V] (by a factor of ten or so given the efficacy of the vaccines). Vaccines do not however deliver perfect immunity so P[C|V]≠0.
Let P[V|C] be the conditional probability of a person with Covid-19 having been fully vaccinated. Or, if you prefer, the proportion of people with Covid-19 who are fully vaccinated..
Now the first thing to point out is that these conditional probability are emphatically not equal. The probability of a female person being pregnant is not the same as the probability of a pregnant person being female.
We can find the relationship between P[C|V] and P[V|C] using the joint probability P[V,C]=P[V,C] of a person having been fully vaccinated and contracting Covid-19. This can be decomposed in two ways: P[V,C]=P[V]P[C|V]=P[C]P[V|C]=P[V,C], where P[V] is the proportion of people fully vaccinated and P[C] is the proportion of people who have contracted Covid-19. This gives P[V|C]=P[V]P[C|V]/P[C].
This result is nothing more than the famous Bayes Theorem.
Now P[C] is difficult to know exactly because of variable testing rates and other selection effects but is presumably quite small. The total number of positive tests since the pandemic began in the UK is about 5M which is less than 10% of the population. The proportion of the population fully vaccinated on the other hand is known to be about 50% in the UK. We can be pretty sure therefore that P[V]»P[C]. This in turn means that P[V|C]»P[C|V].
In words this means that there is nothing to be surprised about in the fact that the proportion of people being infected with Covid-19 is significantly larger than the probability of a vaccinated person catching Covid-19. It is expected that the majority of people catching Covid-19 in the current phase of the pandemic will have been fully vaccinated.
(As a commenter below points out, in the limit when everyone has been vaccinated 100% of the people who catch Covid-19 will have been vaccinated. The point is that the number of people getting ill and dying will be lower than in an unvaccinated population.)
The proportion of those dying of Covid-19 who have been fully vaccinated will also be high, a point also made here.
It’s difficult to be quantitatively accurate here because there are other factors involved in the risk of becoming ill with Covid-19, chiefly age. The reason this poses a problem is that in my countries vaccinations have been given preferentially to those deemed to be at high risk. Younger people are at relatively low risk of serious illness or death from Covid-19 whether or not they are vaccinated compared to older people, but the latter are also more likely to have been vaccinated. To factor this into the calculation above requires an additional piece of conditioning information. We could express this crudely in terms of a binary condition High Risk (H) or Low Risk (L) and construct P(V|L,H) etc but I don’t have the time or information to do this.
So please don’t be taken in by this fallacy. Vaccines do work. Get your second jab (or your first if you haven’t done it yet). It might save your life.
