Archive for October, 2021

Hallowe’en – Charles Ives

Posted in Music with tags , , on October 31, 2021 by telescoper

I posted about this fascinating piece by Charles Ives ten years ago today, when I was still in Cardiff, but the link on that post to the actual music has died so I’m posting it again today.

If you like you can read my first ever Hallowe’en post from 2008 here.

Newton’s Fractal

Posted in mathematics with tags , , on October 30, 2021 by telescoper

Here’s another thing I bookmarked recently and then forgot about. It’s about a fractal structure that arises when using Newton’s Method (aka the Newton-Raphson Method) to find the roots of a real-valued function. I hope I remember this when I’m teaching root-finding in Computational Physics next term!

Citation Metrics and “Judging People’s Careers”

Posted in Bad Statistics, The Universe and Stuff with tags , , , , on October 29, 2021 by telescoper

There’s a paper on the arXiv by John Kormendy entitled Metrics of research impact in astronomy: Predicting later impact from metrics measured 10-15 years after the PhD. The abstract is as follows.

This paper calibrates how metrics derivable from the SAO/NASA Astrophysics Data System can be used to estimate the future impact of astronomy research careers and thereby to inform decisions on resource allocation such as job hires and tenure decisions. Three metrics are used, citations of refereed papers, citations of all publications normalized by the numbers of co-authors, and citations of all first-author papers. Each is individually calibrated as an impact predictor in the book Kormendy (2020), “Metrics of Research Impact in Astronomy” (Publ Astron Soc Pac, San Francisco). How this is done is reviewed in the first half of this paper. Then, I show that averaging results from three metrics produces more accurate predictions. Average prediction machines are constructed for different cohorts of 1990-2007 PhDs and used to postdict 2017 impact from metrics measured 10, 12, and 15 years after the PhD. The time span over which prediction is made ranges from 0 years for 2007 PhDs to 17 years for 1990 PhDs using metrics measured 10 years after the PhD. Calibration is based on perceived 2017 impact as voted by 22 experienced astronomers for 510 faculty members at 17 highly-ranked university astronomy departments world-wide. Prediction machinery reproduces voted impact estimates with an RMS uncertainty of 1/8 of the dynamic range for people in the study sample. The aim of this work is to lend some of the rigor that is normally used in scientific research to the difficult and subjective job of judging people’s careers.

This paper has understandably generated a considerable reaction on social media especially from early career researchers dismayed at how senior astronomers apparently think they should be judged. Presumably “judging people’s careers” means deciding whether or not they should get tenure (or equivalent) although the phrase is not a pleasant one to use.

My own opinion is that while citations and other bibliometric indicators do contain some information, they are extremely difficult to apply in the modern era in which so many high-impact results are generated by large international teams. Note also the extreme selectivity of this exercise: just 22 “experienced astronomers” provide the :calibration” which is for faculty in just 17 “highly-ranked” university astronomy departments. No possibility of any bias there, obviously. Subjectivity doesn’t turn into objectivity just because you make it quantitative.

If you’re interested here are the names of the 22:

Note that the author of the paper is himself on the list. I find that deeply inappropriate.

Anyway, the overall level of statistical gibberish in this paper is such that I am amazed it has been accepted for publication, but then it is in the Proceedings of the National Academy of Sciences, a journal that has form when it comes to dodgy statistics. If I understand correctly, PNAS has a route that allows “senior” authors to publish papers without passing through peer review. That’s the only explanation I can think of for this.

As a rejoinder I’d like to mention this paper by Adler et al. from 12 years ago, which has the following abstract:

This is a report about the use and misuse of citation data in the assessment of scientific research. The idea that research assessment must be done using “simple and objective” methods is increasingly prevalent today. The “simple and objective” methods are broadly interpreted as bibliometrics, that is, citation data and the statistics derived from them. There is a belief that citation statistics are inherently more accurate because they substitute simple numbers for complex judgments, and hence overcome the possible subjectivity of peer review. But this belief is unfounded.

O brave new world that has such metrics in it.

Update: John Kormendy has now withdrawn the paper; you can see his statement here.

Hope Springs Eternal…

Posted in Finance, Politics on October 28, 2021 by telescoper

… in the “Office for Budget Responsibility

A decade of ludicrously over-optimistic forecasts.

“Man never is but always to be blest.”

Still no Primordial Gravitational Waves…

Posted in Astrohype, Bad Statistics, The Universe and Stuff with tags , , , , , , on October 27, 2021 by telescoper

During March 2014 this blog received the most traffic it has ever had (reaching almost 10,000 hits per day at one point). The reason for that was the announcement of the “discovery” of primordial gravitational waves by the BICEP2 experiment. Despite all the hype at the time I wasn’t convinced. This is what I said in an interview with Physics World:

It seems to me though that there’s a significant possibility of some of the polarization signal in E and B [modes] not being cosmological. This is a very interesting result, but I’d prefer to reserve judgement until it is confirmed by other experiments. If it is genuine, then the spectrum is a bit strange and may indicate something added to the normal inflationary recipe.

I also blogged about this several times, e.g. here. It turns out I was right to be unconvinced as the signal detected by BICEP2 was dominated by polarized foreground emission. The story is summarized by these two news stories just a few months apart:

Anyway, the search for primordial gravitational waves continues. The latest publication on this topic came out earlier this month in Physical Review Letters and you can also find it on the arXiv here. The last sentence of the abstract is:

These are the strongest constraints to date on primordial gravitational waves.

In other words, seven years on from the claimed “discovery” there is still no evidence for anything but polarized dust emission…

A Time to Confer

Posted in Biographical, Education, Maynooth on October 27, 2021 by telescoper

Booklet Cover

This morning I braved the inclement weather to attend a Conferring Ceremony at Maynooth University. This was the first Conferring Ceremony to be held in person since for about two years and the first ever featuring the new President of Maynooth University, Prof. Eeva Leinonen, presiding.

There were only four students from Theoretical Physics graduating this morning, and two of them graduated in absentia but I did get to see two students get their Master of Science by Research awards. If you’re interested their theses are available online here and here.

I wouldn’t say the ceremony went off without any hitches. There were quite a few late arrivals among the graduands. I think the bad weather elsewhere in Ireland caused some delays which led to some people being late for the ceremony (which was due to start at 10am, but didn’t get going until about 10.30). Then there were some last minute changes of order which led to one or two students initially getting the wrong scroll. I remember how nerve-wracking it was when that sort of reshuffling happened when I was involved in similar ceremonies at Sussex. It’s bad enough stressing over the correct pronunciation of the names! Anyway I was glad that these days all I have to do is sit there.

The last conferring ceremony I attended in person was on October 31st 2019. It was while I was en route to give a talk at DIAS that evening after the ceremony that I heard that my Mam had passed away. So much has happened between then and now that it is hard to accept that was only two years ago…

Back to Exams

Posted in Education, Maynooth on October 26, 2021 by telescoper

After a welcome break for yesterday’s traditional Hallowe’en Bank Holiday it’s time today to embark on the tradition of the Writing of the First Semester Examinations. I have to come up with four papers (two main exams for January and two repeat exams for next August) by next week, complete with solutions. I always find it very difficult writing examinations, perhaps for the same reason that I find devising clues for crosswords much harder than solving the puzzles. In this world there are setters and solvers and I definitely count myself among the latter.

Anyway, it has been decided that the exams in January will be of the traditional type, sat in person in an Examination Hall, as opposed to the online version we have been using since May 2020. I feel I should point out that was the plan this time last year too, but it didn’t work out that way in the end because of climbing Covid-19 cases. I wouldn’t rule out an abrupt volte-face this year either. The situation is not looking good at all. In fact it looks very much like last year…

I think the “open-book” style of our online examinations had much to recommend it, with an emphasis on problem solving. The one flaw is that we can’t really do anything about collusion when students are sitting remotely and can exchange messages with each other in the absence of an invigilator. I never saw any evidence of significant collusion in the exams I graded, but there’s no denying it was a possibility that we couldn’t negate.

Interestingly, the student representatives present at our Department Meeting a couple of weeks ago indicated that their discussions with other students came out heavily in favour of on-campus examinations. As a result only one of our examinations – for an advanced postgraduate module with very few students taking it – will be of the online “open-book” style. The rest, including my own, will be written and marked on paper. That’s the plan, anyway…

I don’t know how to teach…

Posted in Education, Maynooth with tags , , , , , on October 25, 2021 by telescoper

Making use of this Bank Holiday Monday morning to tidy up some things on my computer I realized I had bookmarked this short clip of Richard Feynman answering a question about teaching. I clearly intended to blog about it at some point but forgot to do so, so I’m correcting that now.

Feynman was of course a renowned lecturer both for university students and for public audiences. I think one of the things that made him so successful is that he liked talking about his subject and liked being the centre of attention; people who like neither of those things are unlikely to make good lecturers!

But the thing that really struck me about what he says in this clip is near the beginning where he says he thinks the way to approach teaching is “be chaotic” to “use every possible way of doing it”. Now some of us are occasionally chaotic by accident, but I think there is a great deal of truth in what he says. I also agree with him when he says “I really don’t know how to do it..” I don’t either

If you start from the premise that every student is different, and will consequently learn in a different way, then you have to accept that there is no one unique style of teaching that will suit everyone. It makes sense therefore to try different kinds of things: worked examples, derivations, historical asides, question-and-answer sessions, and so on. And we shouldn’t rely exclusively on lectures: there must be a range of activities: problems classes, tutorials, supplementary reading, etc. With a bit of luck the majority of your class will find something that stimulates and/or enlightens them.

The point about using every possible method at your disposal has become especially relevant now that we have had about 18 months’ experience of online teaching. I feel very strongly that we should make recordings of lectures routinely available to all students, not as a replacement for the “live” experience but to add to the set of resources a student can draw on. The same goes for other things which came into regular use doing our online period, such as printed lecture notes (again, not as a replacement for a student’s own notes but as a supplement).

I think it also helps to acknowledge that what you can actually achieve in a lecture is very limited: you shouldn’t be simply trying to “deliver” material for later regurgitation. You should be pointing out the particularly interesting aspects, explaining why they are particularly interesting, and what things students should follow up in private study where in textbooks and on the net they will find yet more different ways of approaching the subject.

After over thirty years of teaching have come to the conclusion that the main purpose of university education is to convince students that their brain is more than simply a memory device, i.e. that it can also be used for figuring things out. I’m not saying that a good memory is worthless. It can be extremely useful and memory skills are important. I’m just saying that the brain can do other things too. Likewise, examinations should not be simple memory tests. Sadly school education systems seem to be focussed on coaching students passing exams by rote learning.

We see particular evidence of this in physics, with many students afraid to even attempt to solve problems they haven’t seen before. One infers that they passed exams by simply memorizing answers to questions very similar to those on the paper. Our job is to remove that fear, not by pretending that physics is easy, but by giving students the confidence to start believing that they can do things that they previously thought were too difficult. In other words, university education is often about undoing some of the limitations imposed on students by their school education.

Back to lecturing, there are some obvious basics which lecturers need to do in order to teach competently, including being prepared, talking sufficiently loudly, writing clearly (if relevant), and so on. And of course turning up at the right theatre at the right time. But there are also those things that turn mere competence into excellence. Of course there are many ways to lecture, and you have to put your own personality into what you do, but the main tips I’d pass on to make your lectures really popular can be boiled down into the Three Es. I add that these are things that struck me while watching others lecture, rather than me claiming to be brilliant myself (which I know I’m not). Anyway, here we go:

Enthusiasm. The single most obvious response on student questionnaires about lecturing refers to enthusiasm. My take on this is that we’re all professional physicists, earning our keep by doing physics. If we can’t be enthusiastic about it then it’s clearly unreasonable to expect the students to get fired up. So convey the excitement of the subject! I don’t mean by descending into vacuous gee-whizz stuff, but by explaining how interesting things are when you look at them properly as a physicist, mathematics and all.

Engagement. This one cuts both ways. First it is essential to look at your audience, ask questions, and make them feel that they are part of a shared experience not just listening to a monologue. The latter might be fine for a public lecture, but if a teaching session is to be successful as a pedagogical exercise it can’t be passive. And if you ask a question of the audience, make your body language tell them that it’s not just rhetorical: if you don’t look like you want an answer, you won’t get one. More importantly, try to cultivate an atmosphere wherein the students feel they can contribute. You know you’ve succeeded in this when students point out mistakes you have made. On the other hand, you can’t take this too far. The lecturer is the person who is supposed to know the stuff so fundamentally there’s no symmetry between you and the audience. You have to be authoritative, though that doesn’t mean you have to behave like a pompous schoolmaster. Know your subject, explain it well and you’ll earn respect without needing to bluster.

Entertainment. As I said above, lecturing is very limited as a way of teaching physics. That is not to say that lectures don’t have a role, which I think is to highlight key concepts and demonstrate their applicability;  the rest, the details, the nuts and bolts are best done by problem-based learning. I therefore think it does no harm at all if you make your lectures fairly light on detail and (with reason) enjoyable as pieces of entertainment. By all means introduce the odd joke, refer to surprising examples, amusing analogies, and so on.  As long as you don’t overdo it, you’ll find that a bit of light relief will keep the attention levels up. A key element of this is spontaneity. A lecture should appear as if it develops naturally, in an almost improvised fashion. Of course your spontaneity will probably have to  be very carefully rehearsed, but the sense of a live performance always adds value. A lecture should be a happening, not just a presentation. Lecture demonstrations also play this role, although they seem to be deployed less frequently  nowadays than in the past. Being a showman doesn’t come naturally to everyone, and the audience will know if you’re forcing it so don’t act unnaturally, but at the very least try to move about. Believe me, watching a lecturer drone on for an hour while rooted to the spot is a very tedious experience (especially on a video recording). You’d be surprised how much difference it makes if you can convey at least the impression of being alive.

On this last point, I’ll offer a few quotes from a physicist who definitely knew a thing or two about lecturing, Michael Faraday. First, his opinion was that the lecturer should not be

…glued to the table or screwed to the floor. He must by all means appear as a body distinct and separate from the things around, and must have some motion apart from that which they possess.

Conventional wisdom nowadays suggests that one should take breaks in lectures to stop students losing concentration. I’m not sure I agree with this, actually. It’s certainly the case that attention will flag if you persist with a dreary monotone for an hour, but  I think a lecture can have a natural dynamic to it which keeps the students interested by variation rather than interruption. Faraday also thought this.

A flame should be lighted at the commencement and kept alive with unremitting splendour to the end…I very much disapprove of breaks in the lecture.

Finally, here is one of my all-time  favourite physics quotes, Faraday’s take on the need for lectures to be entertaining:

..for though to all true philosophers science and nature will have charms innumerable in every dress, yet I am sorry to say that the generality of mankind cannot accompany us one short hour unless the path is strewn with flowers.

R.I.P. Bernard Haitink (1929-2021)

Posted in Music with tags , , on October 24, 2021 by telescoper

Renowned conductor Bernard Haitink passed away on 21st October at the age of 92. It’s hard to pick one piece to commemorate such a distinguished career in music so I’m not going to try to be objective. Some time ago I bought the complete set of Mahler Symphonies performed by the Royal Concertgebouw Orchestra in 1966 with Haitink at the helm and I think their performance of Mahler Symphony No. 3 is up there with the very best.

It’s interesting that as recently as 2018, another performance of Mahler 3 directed by Haitink won the BBC Recording of the Year. There is also a complete live performance from 1983 on Youtube which I was tempted to post here but the whole Symphony is about 100 minutes long so I decided instead to just post an excerpt which, fortunately, someone has already put on Youtube.

Here’s just one movement – the sixth and last – from that epic work. This movement is marked langsam which basically means “slow” but I think many conductors take this movement too slowly. Haitink for me judges the pace perfectly. There’s an overwhelming sense of catharsis at the climax of this movement.

R.I.P. Bernard Haitink (1929-2021)

Bank Holiday Break

Posted in Biographical, Maynooth on October 23, 2021 by telescoper

So here we are then, five weeks of teaching over, we have reached the mid-term break. I actually thought it was quite unusual to reach study week after 5/12 of the Semester rather than half, but it seems it happened as recently as two years ago. The pandemic has played havoc with my powers of recollection as well as other things. Anyway, this Monday (25th October) is a Bank Holiday in Ireland. The last Monday of October (Lá Saoire i mí Dheireadh Fómhair), or the Halloween Holiday (Lá Saoire Oíche Shamhna), is always a national holiday here, although Halloween itself isn’t until next Sunday.

I’ve got a big backlog of work things to do, but I can’t face it right now so I’m going to take the long weekend off and use Tuesday to Friday to try to tackle the to-do list (apart from Wednesday, when I have to attend a Conferring Ceremony).

In the meantime I will be doing nothing more strenuous than a bit of gentle gardening, including clearing away the leaves and tackling the last bit of ivy threatening to invade my house.

On the subject of gardening, I’ve noticed that I’ve got a fine crop of toadstools on the back lawn. I don’t know enough about fungi to know whether they are toxic, edible or even hallucinogenic, though I think if they were edible the birds would have a go at them. Any experts who can identify the type shown please feel free to let me know!

It’s always puzzled me how many people thing that there must be something wrong with their garden if there are toadstools in it. As far as I’m concerned they are part of the natural ecosystem so I just let them grow. I find them quite fascinating. They only live a few weeks so will disappear in due course without any intervention from me.