Archive for Physics

“And” Time Draws Nigh

Posted in History, Poetry, The Universe and Stuff with tags , , , , , , , on November 30, 2020 by telescoper

It’s November 30th 2020, which means we have just three teaching weeks to go until the end of term. I am currently teaching two modules: Mechanics 1 and Special Relativity for first-year students and  Vector Calculus and Fourier Series for second years. We’re now getting to the “and” bit in both modules.

I didn’t want to present the two topics mentioned in the title of the second year module as completely disconnected, so I decided to link them with a lecture in which I use the divergence theorem of vector calculus to derive the heat equation, the solution of which led Joseph Fourier to devise his series in Mémoire sur la propagation de la chaleur dans les corps solides (1807), a truly remarkable work for its time that inspired so many subsequent developments.

That gives me an excuse to repost the following “remarkable” poem about Fourier by William Rowan Hamilton:

In the first-year module I will be spending most of this week talking about potentials and forces before starting special relativity next week, at the proper time.

Anyway the other time that is drawing nigh is the loosening of Ireland’s current Level 5 Covid-19 restrictions which were imposed about six weeks ago though,  judging by the crowds drinking in Courthouse Square on Saturday night, a lot of folks have thrown the rules out the window already.

I think it’s a dangerous time. The daily cases are still hovering around the 250-300 mark and will undoubtedly start climbing even before Christmas itself:The chances of us getting back to anything normality during the early part of next year are exceedingly slim.

Lecture Streaming

Posted in Education, Maynooth with tags , , , on October 7, 2020 by telescoper

When we were told, at the start of this term, to move all our teaching online my initial intention was to record most of the lectures in my office for the students to watch at their leisure rather than streaming them live.
The system we’re using, Panopto, allows for both webcast (i.e. live streaming) and pre-recorded (offline) videos. I thought that only very few students would want to watch the broadcast version. I have however changed my mind about this and am now streaming all my lectures (as well as recording them for later viewing). It also meant that I could record the lectures in advance at my without being constrained by the timetable.

Last week my office wasn’t usable for recording videos because of noise from building work so I had to find somewhere else to record the videos so I decided to go to the lecture theatre at the scheduled time primarily because I knew the room would be available at that time. When I started the first lecture I thought I might as well webcast it as well, thinking only a few students would tune in. In fact, out of my class of 45 or so second-year students, about 39 were online while I did the lecture. Since then I’ve done all the lectures live and plan to do so until further notice.

A handful of students even turn up in person to the lectures. I see no problem with this. The restrictions are designed to minimize as far as possible the number of students coming to campus, but if they are here anyway because of labs (which can’t be done virtually) then why shouldn’t they come to the lectures? (Provided, of course, that they follow the public health guidance, wear masks, wash their hands, practice social distancing, etc). I find their presence very helpful, actually. Talking to an audience is far easier than talking only to a camera. You do have to remember to look at the camera though!

It is possible to edit the webcast recording before sharing it with the students. That way you can get rid of all the mistakes, hesitations and other defective bits. Starting with a 50 minute lecture that usually means you end up with about 10 minutes of good material.

Having settled on this approach I was dismayed on Monday to find the Panopto system wasn’t working in either webcast or offline recording mode. I assumed at first that I was doing something wrong but it turns out it was a major outage affecting all of Europe that went on all day. Twitter was full of comments from academics complaining about! Panopto uses cloud storage with very little being held locally so when the connectivity fails the user is helpless. I did the lecture by Teams instead, but had lost some time faffing around trying to get Panopto to work.

Yesterday morning Panopto was back working and my office was quiet so I reran the lecture using the blackboard in my office and recorded it as an offline video. That way the students now have the lecture in the right space on the Moodle page. After that I did two more lectures as webcasts using Moodle – Tuesday is a busy teaching day this term – and everything worked fine.

I think there are two morals to be drawn from this. The first is not to assume that you know what students will find useful. The second is wherever possible to have a backup plan. Putting all your eggs in the basket marked Panopto is risky.

Challenges Past and Future

Posted in Covid-19, Education, Maynooth with tags , , , , , , on June 19, 2020 by telescoper

Yesterday afternoon we held our Departmental Examination Board in Theoretical Physics (via Microsoft Teams*) which all went remarkably well in the circumstances.

The most challenging thing to happen yesterday afternoon was that a bloke came to cut back the bushes outside my office with a very large and noisy hedge trimmer. I thought I was going to have to contend with that all afternoon but it seems he had done most of it the day before and only came back yesterday to finish off. He left before the Exam Board started.

The next stage of our Exams process is for all the Departmental results to be collated for those students on joint programmes before the final University Board takes place about ten days from now. After that students will get their results.

That doesn’t quite finish examination matters for 2019/20 however because some students will need to take repeat examinations in August. These will be a week later than usual as a knock-on effect of the extra week we were given to mark and correct the May exams. We anticipate that at least some of the repeats will be the traditional `in person’ on campus style, but some may be online timed assessments like the ones we held in May. That depends a bit on how the Covid-19 pandemic pans out in Ireland over the next few weeks (and of course how many students actually take repeats, as social distancing generates a capacity issue for the examination halls).

At the moment we are optimistic because the number of new cases of Covid-19 is low and stable. That coulld change, of course, if the virus starts to spread again so we have to have contingency plans.

Even more uncertain is what will happen in September, although I have been very annoyed by some reports in the media that seem to have been actively trying to put students off coming to University next academic year on the grounds that there won’t be any lectures. We certainly plan to offer as much face-to-face teaching as possible and I think other third-level institutions in Ireland will do likewise. There will of course have to be a backup if there is another lockdown, which may mean switching back to remote teaching at relatively short notice, but at least we’ve done that once already so know much better now what works and what doesn’t. Nevertheless I would encourage all potential students not to believe everything they read in the media nor be deterred from attending university by rumours from sources who don’t know what they are talking about.

Earlier this week I was starting to think about how we might build the required flexibility into our teaching for next year and two main things struck me.

The first is that while we have more-or-less been forced into making various kinds of video material available to students, this is something that I feel we should have been doing already. I’ve long felt that the more types of teaching we incorporate and the wider range of learning materials we provide the better the chance that students find something that works for them. Even if we do have a full programme of lectures next year, it is my intention to continue to provide, e.g., recorded video explainers as well because they might augment the battery of resources available to the student.

Some time ago I had to make some policies about `reasonable adjustments’ for some disabled students learning physics. In the course of providing extra resources for this small group I suddenly thought that it would be far better, and far more inclusive, simply to make these resources available to everyone. Likewise, we’ve been forced to adjust to providing material remotely but we should be thinking about how to keep the best things about what we’ve done over the last few months and embedding them in the curriculum for the (hopefully Coronavirus-free) future and not regard them all as temporary special measures.

The other thing that struck me is in the same vein, but a little more speculative. Over the last many years I have noticed that students use printed textbooks less and less for learning. Part of that may be because we in a digital age and they prefer to use online resources. The switch to remote learning has however revealed that there are some students who are disadvantaged by not having a good internet connection. I just wonder whether this might lead to a resurgence in the use of textbooks. I’ll certainly be making a strong recommendation to the new first-year students in Theoretical Physics that they should get hold of the recommended text, which I have previously regarded as an optional extra.

*At one point I got muddled up between Teams and Zoom and called it Tombs. It was a grave error, but it can only be a matter of time before Microsoft Tombs actually arrives…

How to Solve Physics Problems

Posted in Cute Problems, Education, Maynooth, The Universe and Stuff, YouTube with tags , , on May 14, 2020 by telescoper

Since the examination period here at Maynooth University begins tomorrow I thought I would use the opportunity provided by my brand new YouTube channel to present a video version of a post I did a few years ago about how to solve Physics problems. These are intended for the type of problems students might encounter at high school or undergraduate level either in examinations or in homework. I’ve tried to keep the advice as general as possible though so hopefully students in other fields might find this useful too.

A Memorial to Reverend Professor Callan

Posted in History with tags , , , , , on April 14, 2020 by telescoper

I chose a different route for today’s post-prandial exercise around Maynooth University’s South Campus, and thus came across this attractive little tree-lined path:

At the other end lies the historic cemetery of Maynooth College where, among many other things, I found this memorial:

This gives me an excuse to rehash an old one about the person whose memorial it is.

Father Nicholas Joseph Callan (or, more formally, The Reverend Professor Nicholas Joseph Callan) was born in County Louth in 1799 went to the seminary of St Patrick’s College, Maynooth, in 1816 on order to train as a priest. During his time as a seminarian Callan studied ‘Natural Philosophy’ and became interested in experiments involving electricity. In 1823 Callan was ordained as a priest, and went to Rome in 1826 to obtain his doctorate in Divinity. At the time Italy was a centre for research into electricity and here Callan became familiar with the work of the Italian physicist Alessandro Volta who had developed the world’s first battery. Callan returned to Maynooth where he was made chair of Natural Philosophy, a post he would hold until his death in 1864.

Callan is most famous for inventing the induction coil (in 1836). By connecting two copper wire coils to a battery and electromagnet and then interrupting the current he was able to generate much larger voltages than could be obtained from batteries alone. His 1837 version that used a clock mechanism to interrupt the current 20 times a second is estimated to have produced 60,000 volts – the largest artificially generated charge at that time. It is said that his induction coil could produce sparks 15″ long, which must have been fun to watch.

Callan’s biggest induction coil, unfinished at the time of his death, can be found in the National Science Museum of Ireland (which is in Maynooth). This was one of the largest in the world at the time. The iron core is 109 cm long. The secondary windings are 53 cm in diameter and consist of about 50 km of iron wire insulated with beeswax. They were made in three separate rings separated by air gaps, so wires carrying large voltage differences would not lie adjacent to each other, reducing the risk of the insulation breaking down. At the left end is a vibrating mercury ‘contact breaker’ in the primary circuit, actuated by the magnetic field in the primary, which interrupted the primary current to generate potentials of over 200,000 volts.

Sadly Callan’s work was forgotten for quite a period after his death – experimental electromagnetism was not a priority for St Patrick’s College at this time – for which reason the invention of the induction coil has often been attributed to Heinrich Ruhmkorff who made his first device (independently) about 15 years after Callan. More recently, however, Callan’s achievements have been more widely recognized and in 2000 the Irish government issued a stamp in his honour.

The Callan Building

Nicholas Callan was laid to rest in the College Cemetery at Maynooth in 1864. The Callan Building (above) on the North Campus of the present-day Maynooth University is named in his honour, as of course is Callan Hall, on the South Campus.

P.S. The first interment in the Cemetery took place in 1817, 200 years before I started work in Maynooth.

R.I.P. Margaret Burbidge (1919-2020)

Posted in History, The Universe and Stuff with tags , , , , , on April 6, 2020 by telescoper

I just heard via Twitter that Margaret Burbidge has passed away at the age of 100. I send my condolences to her friends, colleagues and family.

Margaret Burbidge will perhaps be best remembered as the first author anniversary of the classic work of Burbidge, Burbidge, Fowler and Hoyle in 1957 (a paper usually referred to as B2FH after the initials of its authors). It’s such an important contribution, in fact, that it has its own wikipedia page.

One of the interesting astronomical things I’ve acquired over the years is a preprint of the B2FH paper. Younger readers will probably not realize that preprints were not always produced in the electronic form they are today. We all used to make large numbers of these and post them at great expense to (potentially) interested colleagues before publication in order to get comments. In the age of the internet people don’t really bother to make hard copies of preprints for distribution any more.

Anyway, here’s a snap of it.

Sadly all of the authors have now passed away Margaret Burbidge did much more than that paper, of course. She made important contributions over a wide range of topics in astrophysics and will be greatly missed.

Rest in peace, Margaret Burbidge (1919-2020)

R.I.P. Phil Anderson (1923-2020)

Posted in Uncategorized with tags , , on March 30, 2020 by telescoper

I heard this morning via a friend who knew him personally of the death, yesterday at the age of 96, of condensed matter physicist and Nobel Laureate Professor Philip Warren Anderson. He will perhaps be best remembered known for Anderson Localization but he worked on a huge range of topics in physics and his influence was felt across many branches of science (including astrophysics). It’s too early for obituaries to have been published yet but I will add links when they become available.

Update: here is the New York Times obituary.

R.I.P. Philip W Anderson (1923-2020).

From the Inventor of the H-index

Posted in Biographical, The Universe and Stuff with tags , , , , on March 5, 2020 by telescoper

My third-year students are busily engaged with a Computational Physics class test so I thought I’d occupy myself for a few minutes by sharing an interesting little paper that appeared on the arXiv a few weeks ago. The paper is by Jorge Hirsch, the inventor of the (in)famous H-index.

Here is the abstract:

A magnetic field H is expelled from the interior of a metal becoming superconducting. Everybody thinks the phenomenon is perfectly well understood, particularly scientists with the highest H-index think that. I don’t. I will explain why I believe that without Holes, conceptualized by Heisenberg in 1931 fifty years after Hall had first detected them in some metals, neither magnetic field expulsion nor anything else about superconductivity can be understood. I have been a Heretic in the field of superconductivity for over 30 years, and believe that Hans’ little story about the emperor perfectly captures the essence of the situation. Here is (a highly condensed version of) the wHole story.

You will see that, despite the liberal sprinkling of letters H, the paper isn’t ostensibly about the H-index, but it does contain some interesting comments thereon, including:

I proposed the H-index hoping it would be an objective measure of scientific achievement. By and large, I think this is believed to be the case. But I have now come to believe that it can also fail spectacularly and have severe unintended negative consequences. I can understand how the sorcerer’s apprentice must have felt.

I think the opinion of a scientist about the value of the H-index roughly speaking divides according to whether a said scientist has a big one or a small one. Those lucky enough to have a high H-index probably think it is fine, while those who have a low value can probably find a reason why it is flawed. My own H-index (42 according to Google Scholar) is mediocre, which I reckon is a fair reflection of my status.

A Problem of Snooker

Posted in Cute Problems, The Universe and Stuff with tags , , , on February 25, 2020 by telescoper

I came across the following question in a first-year physics examination from Cambridge (Part 1A Natural Sciences) and, since I have posted anything in the Cute Problems folder for a while I thought I would share it here:

Answers through the comments box please! And please show your working!

P.S. The preamble does not say whether you can also assume irrelevant formulae without proof…

 

The Reverend Professor Callan

Posted in Biographical, History, Maynooth, The Universe and Stuff with tags , , , , , on February 5, 2020 by telescoper

I’ve had a busy day doing various things that took me to various places on the Maynooth University campus, culminating in my first visit to the Department of Mathematics and Statistics (which is based in Logic House) to give a colloquium. On my travels I passed this sign, which I hadn’t noticed before:

Since I’ve been too busy to write a post today I thought I’d rehash an old one about the person named in the plaque, which is above Callan Hall (on the South Campus)

Father Nicholas Callan (or, more formally, The Reverend Professor Nicholas Joseph Callan) was born in County Louth in 1799 went to the seminary of St Patrick’s College, Maynooth, in 1816 to train as a priest. During his time as a seminarian Callan studied ‘Natural Philosophy’ and became interested in experiments involving electricity. In 1823 Callan was ordained as a priest, and went to Rome in 1826 to obtain his doctorate in Divinity. At the time Italy was a centre for research into electricity and here Callan became familiar with the work of the Italian physicist Alessandro Volta who had developed the world’s first battery. Callan returned to Maynooth where he was made chair of Natural Philosophy, a post he would hold until his death in 1864.

Callan is most famous for inventing the induction coil (in 1836). By connecting two copper wire coils to a battery and electromagnet and then interrupting the current he was able to generate much larger voltages than could be obtained from batteries alone. His 1837 version that used a clock mechanism to interrupt the current 20 times a second is estimated to have produced 60,000 volts – the largest artificially generated charge at that time. It is said that his induction coil could produce sparks 15″ long, which must have been fun to watch.

Callan’s biggest induction coil, unfinished at the time of his death, can be found in the National Science Museum of Ireland (which is in Maynooth). This was one of the largest in the world at the time. The iron core is 109 cm long. The secondary windings are 53 cm in diameter and consist of about 50 km of iron wire insulated with beeswax. They were made in three separate rings separated by air gaps, so wires carrying large voltage differences would not lie adjacent to each other, reducing the risk of the insulation breaking down. At the left end is a vibrating mercury ‘contact breaker’ in the primary circuit, actuated by the magnetic field in the primary, which interrupted the primary current to generate potentials of over 200,000 volts.

Sadly Callan’s work was forgotten for quite a period after his death – experimental electromagnetism was not a priority for St Patrick’s College at this time – for which reason the invention of the induction coil has often been attributed to Heinrich Ruhmkorff who made his first device (independently) about 15 years after Callan. More recently, however, Callan’s achievements have been more widely recognized and in 2000 the Irish government issued a stamp in his honour.

The Callan Building

Nicholas Callan was laid to rest in the College Cemetery at Maynooth in 1864. The Callan Building (above) on the North Campus of the present-day Maynooth University is named in his honour, as of course is Callan Hall which I mentioned at the start.