Archive for Physics

Father Callan and the Induction Coil

Posted in History, Maynooth, The Universe and Stuff with tags , , , , , on July 9, 2019 by telescoper

Historically speaking, Maynooth is more strongly associated with theology than with science but I thought I’d mention here one famous pioneering physicist, who happened also to be a Roman Catholic priest, who spent his working life in these parts.

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.

Advertisements

Physics Lectureship in Maynooth!

Posted in Maynooth with tags , , , , , on June 18, 2019 by telescoper

Every now and then I have the opportunity to use the medium of this blog to draw the attention of my vast readership (both of them) to employment opportunities. Today is another such occasion, so I am happy to point out that my colleagues in the Department of Experimental Physics are advertising a lectureship. For full details, see here, but I draw your attention in particular to this paragraph:

The Department of Experimental Physics is seeking candidates with the potential to build on the research strengths of the Department in the areas of either terahertz optics or atmospheric physics. The Department is especially interested in candidates with research experience that could broaden the scope of current research activity. This could include for example terahertz applications in space, imaging, remote sensing and communications or applications of atmospheric physics related to monitoring and modelling climate change. It would be an advantage if the candidate’s research involved international collaboration with the potential for interdisciplinary initiatives with other University institutes and departments.

The deadline for applications is Sunday 28 July 2019 at 11.30pm.

Is there a role for rote learning?

Posted in Education, Maynooth with tags , , , , , , , on May 7, 2019 by telescoper

So here we are, then, back to work here in Maynooth for the last week of teaching. Or, to be precise, the last four days – yesterday was a Bank Holiday. With university and school examinations looming, it is no surprise to find an article griping about the Irish Leaving Certificate examinations and the fact that teachers seem to encourage students to approach them by by rote learning. This is something I’ve complained about before in the context of British A-levels and indeed the system of university examinations.

Over my lifetime the ratio of assessment to education has risen sharply, with the undeniable result that academic standards have fallen – especially in my own discipline of physics. The modular system encourages students to think of modules as little bit-sized bits of education to be consumed and then forgotten. Instead of learning to rely on their brains to solve problems, students tend to approach learning by memorizing chunks of their notes and regurgitating them in the exam. I find it very sad when students ask me what derivations they should memorize to prepare for examinations because that seems to imply that they think their brain is no more than a memory device. It has become very clear to me over the years that school education in the UK does not do enough to encourage students to develop their all-round intellectual potential, which means that very few have confidence in their ability to do anything other than remember things. It seems the same malaise affects the Irish system too.

On the other hand, there’s no question in my mind that a good memory is undoubtedly an extremely important asset in its own right. I went to a traditional Grammar school that I feel provided me with a very good education in which rote learning played a significant part. Learning vocabulary and grammar was an essential part of their approach to foreign languages, for example. How can one learn Latin without knowing the correct declensions for nouns and conjugations for verbs? But although these basic elements are necessary, they are not sufficient. You need other aspects of your mental capacity to comprehend, translate or compose meaningful pieces of text. I’m sure this applies to many other subjects. No doubt a good memory is a great benefit to a budding lawyer, for example,  but the ability to reason logically must surely be necessary too.

The same considerations apply to STEM disciplines. It is important to have a basic knowledge of the essential elements of mathematics and physics as a grounding, but you also need to develop the skill to apply these in unusual settings. I also think it’s simplistic to think of memory and creative intelligence as entirely separate things. I seems to me that the latter feeds off the former in a very complex way. A good memory does give you rapid access to information, which means you can do many things more quickly than if you had to keep looking stuff up, but I think there’s a lot more to it than that. Our memories are an essential part of the overall functioning of our brain, which is not  compartmentalized in  a simple way.  For example, one aspect of problem-solving skill relies on the ability to see hidden connections; the brain’s own filing system plays a key role in this.

Recognizing the importance of memory is not to say that rote learning is necessarily the best way to develop the relevant skills. My own powers of recall are not great – and are certainly not improving with age – but I find I can remember things much better if I find them interesting and/or if I can see the point of remembering them. Remembering things because they’re memorably is far easier than remembering because you need to remember them to pass an examination!

But while rote learning has a role, it should not be all there is and my worry is that the teaching-to-the-test approach is diminishing the ability of educators to develop other aspects of intelligence. There has to be a better way to encourage the development of the creative imagination, especially in the context of problem-solving. Future generations are going to have to face many extremely serious problems in the very near future, and they won’t be able to solve them simply by remembering the past.

More Order-of-Magnitude Physics

Posted in Cute Problems with tags , , , on April 25, 2019 by telescoper

A very busy day today so I thought I’d just do a quick post to give you a chance to test your brains with some more order-of-magnitude physics problems. I like using these in classes because they get people thinking about the physics behind problems without getting too bogged down in or turned off by complicated mathematics. If there’s any information missing that you need to solve the problem, make an order-of-magnitude estimate!

Give  order of magnitude answers to the following questions:

  1. What is the maximum distance at which it could be possible for a car’s headlights to be resolved by the human eye?
  2. How much would a pendulum clock gain or lose (say which) in a week if moved from a warm room into a cold basement?
  3. What area would be needed for a terrestrial solar power station capable of producing 1GW of power?
  4. What mass of cold water could be brought to the boil using the energy dissipated when a motor car is brought to rest from 100 km/h?
  5. How many visible photons are emitted by a 100W light bulb during its lifetime?

There’s no prize involved, but feel free to post answers through the comments box. It would be helpful if you explained a  bit about how you arrived at your answer!

In Praise of Omnibus Science

Posted in Education, Maynooth with tags , , , on April 16, 2019 by telescoper

I’m taking a few days off at the moment so this morning I had a bit of time to catch up on various things. One news item I stumbled across points out that first-choice applications to study at Maynooth University are the highest ever. Within the overall increase of about 7% there is a growth of 17% in Science subjects, which is very good news for the Department of Theoretical Physics as well as the other Departments in the Faculty of Science and Engineering.

Anyway, this spurred me to comment on what I think is one of the strengths of Maynooth University: the Omnibus Science programme.

Currently, most students doing Science subjects here enter on the Omnibus programme, a four-year science course that involves doing four subjects in the first year, but becoming increasingly specialised thereafter. That’s not unlike the Natural Sciences course I did at Cambridge, except that students at Maynooth can do both Theoretical Physics and Experimental Physics in the first year as separate choices. Other possibilities include Chemistry, Computer Science, Biology, etc.

In Year 1 students do four subjects (one of which is Mathematics). That is narrowed down to three in Year 2 and two in Year 3. In their final year, students can stick with two subjects for a Joint Honours degree, or specialise in one, for Single Honours.

I like this programme because it does not force the students to choose a specialism before they have had a taste of the subject, and that it is flexible enough to accommodate Joint Honours qualifications in, e.g., Theoretical Physics and Mathematics. It also allows us to enrol students onto Physics degrees who have not done Physics as part of the Leaving Certificate.

I think it’s a strength that students take such a broad first year rather than locking themselves into one discipline from the start. Part of the reason is that I went to do my own degree at Cambridge expecting to end up specialising in Chemistry, but enjoyed the physics far more, eventually specialising in Theoretical Physics. I’m sure there were others who went the other way too!

One problem with the Omnibus Science programme is that the range of possible final qualifications is perhaps not as clearly advertised as it could be, so some clearer signposting would do no harm.

Machine Learning in the Physical Sciences

Posted in The Universe and Stuff with tags , , , , , on March 29, 2019 by telescoper

If, like me, you feel a bit left behind by goings-on in the field of Machine Learning and how it impacts on physics then there’s now a very comprehensive review by Carleo et al on the arXiv.

Here is a picture from the paper, which I have included so that this post has a picture in it:

The abstract reads:

Machine learning encompasses a broad range of algorithms and modeling tools used for a vast array of data processing tasks, which has entered most scientific disciplines in recent years. We review in a selective way the recent research on the interface between machine learning and physical sciences.This includes conceptual developments in machine learning (ML) motivated by physical insights, applications of machine learning techniques to several domains in physics, and cross-fertilization between the two fields. After giving basic notion of machine learning methods and principles, we describe examples of how statistical physics is used to understand methods in ML. We then move to describe applications of ML methods in particle physics and cosmology, quantum many body physics, quantum computing, and chemical and material physics. We also highlight research and development into novel computing architectures aimed at accelerating ML. In each of the sections we describe recent successes as well as domain-specific methodology and challenges.

The next step after Machine Learning will of course be Machine Teaching…

R. I. P. Wolfgang Rindler (1924-2019)

Posted in Books, Talks and Reviews, Education, The Universe and Stuff with tags , , , , on March 5, 2019 by telescoper

A recent comment on this blog drew my attention to the sad news of the death, at the age of 94, of Wolfgang Rindler. He passed away almost a month ago, in fact, but I have only just heard. My condolences to his family, friends and colleagues.

Wolfgang Rindler was a physicist who specialized in relativity theory and especially its implications for cosmology. Among other things he is attributed with the first use of the phrase `Event Horizon‘ as well as elucidating the nature of horizons in general relativity, both in the context of black holes and in cosmology. I never met him personally but to me, and I think to many other people, Wolfgang Rindler will be familiar through his textbooks on relativity theory. I have two in my collection:

I bought the one on the right on recommendation when I was an undergraduate over thirty years ago and the other (shorter) one I acquired second-hand some years later. Both are still very widely used in undergraduate courses.
I found the first one then (as I do now) rather idiosyncratic in approach and notation but full of deep insights and extremely effective from a pedagogical point of view. I still recommend it to students, to balance more conventional modern texts which tend to be far more conventional. It’s no easy thing to write textbooks and Wolfgang Rindler deserves high praise for having devoted so much of his time, and considerable talent, into writing ones whose impact has been so widespread and lasted so long.

Rest in peace, Wolfgang Rindler (18th May 1924 – 8th February 2019).