Archive for Physics

Happy 100th Birthday, Margaret Burbidge!

Posted in The Universe and Stuff with tags , , , , , on August 12, 2019 by telescoper

I was reminded by Twitter just now that today is the 100th birthday of Margaret Burbidge, who was born on August 12th 1919. Happy Birthday Margaret!

 

This anniversary of her birth gives me an excuse to mention 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.

It’s a hefty piece of work, and an important piece of astronomical history. One thing I’ve never done, however, is check whether the preprint differs significantly from the published version..

 

Old-School Physics

Posted in Education, History, The Universe and Stuff with tags , , , on July 27, 2019 by telescoper

The recent circulation to his staff of daft (and in some cases erroneous) rules to be used when writing documents has led to much hilarity on the media we call social. Among the obvious errors are that the correct abbreviation for `Member of Parliament’ is `MP’ not ‘M.P.’ and that `full stop’ is actually two words (not `fullstop’). On top of those his insistence that civil servants use Imperial units for everything actually may be unlawful as the official system of units for the United Kingdom is the metric system.

The latter exhortation has caused a particular outcry among people under the age of about 50 (who have never been taught Imperial units), and especially scientists (who understand the obvious superiority of the SI system).

Anyway, all this reminded me that many years ago when at Cardiff there came into my possession a book of very old school and university physics examinations, which are of interest because I’ve been posting slightly less ancient examples in recent weeks. These examinations were set by the University College of South Wales and Monmouthshire, which was founded in 1883,  an institution which eventually became Cardiff University. I find them absolutely fascinating.

The papers are rather fragile, as is the book containing them, so I daren’t risk trying to scan them systematically in case flattening them out causes damage. Here instead are a few random examples that I photographed on my desk, in the manner of an old-fashioned secret agent. Sorry they’re not all that clear, but you can see them blown up if you click on them.

The collection is fairly complete, covering most of classical physics, at all examination levels from university entry to final Honours. Of course there are no questions on relativity or quantum physics appear (which had yet to be invented) but other than that – and the units! – they’re not too different from what you might find in the examinations for the early stages of contemporary physics programmes.

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.

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.