Archive for Physics

Bristol and Back

Posted in Biographical, The Universe and Stuff with tags , , on January 17, 2011 by telescoper

I almost did the unthinkable today by not posting anything on my blog. It’s been such a busy day that I wasn’t able to post at lunchtime, chiefly because I didn’t have a lunch break.  I don’t want to let the side down, so I decided to put something up, but the following “quick” post will have to do for today.

After an interminable meeting (zzzz...) of the Board of Studies this morning in the School of Physics & Astronomy at Cardiff, where I work, I had to rush back to the office, grab my things and dash off to the station to catch a train to the fine city of Bristol, where I was giving a colloquium in the School of Physics at the University of Bristol. I got there just in time for a quick slurp of tea before heading off to do my bit. I hope the talk was OK, but that’s not really for me to judge.

After the colloquium I got the chance to relax over a pint of beer, chat to staff and students and was then whisked off for a splendid curry. One of the folks that looked after me was Professor Mark Birkinshaw, who taught a course I took when I was an undergraduate at Cambridge; he seemed quite chuffed when I told him I still had the notes! And if Anton is reading this, he asked me to pass on his good wishes to you too! Thence it was back by train in the rain to Cardiff.

I think that’s all I have the energy to write. In fact, this is the first time ever I’ve used the “Quick Post” feature on WordPress, a streamlined interface limited to shorter items without graphics and other complicated extras which I don’t usually use because my typical posts don’t count as “quick” on account of the fact that I usually keep on writing long after I’ve made the points I was going to make and have run out of useful things to say, the excessive verbosity of the resulting articles giving me a bad name in the blogosphere, which, notwithstanding its more problematic aspects, does seem to me at least to have the virtue of encouraging a more concise form of communication than is to be found in other contexts while at the same time … [continued, page 94]


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Einstein and the Eclipse

Posted in Biographical, The Universe and Stuff with tags , , , , , , , on January 4, 2011 by telescoper

Following on from my previous post, I thought you might be interested in this. It’s the last programme in a series called Six Experiments that Changed the World which was presented by the late Ken Campbell. It was made for Channel 4 and first broadcast in 2000. It’s in two parts. If you watch the second one, you might see someone you recognize…


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Spare me the Passive Voice!

Posted in Education with tags , , , , , on December 16, 2010 by telescoper

I’ve felt a mini-rant brewing for a few days now, as I’ve been reading through some of the interim reports my project students have written. I usually quite enjoy reading these, in fact. They’re not too long and I’m usually pretty impressed with how the students have set about the sometimes tricky things I’ve asked them to do. One pair, for example, is reanalysing the measurements made at the 1919 Eclipse expedition that I blogged about here, which is not only interesting from a historical point of view but which also poses an interesting challenge for budding data analysts.

So it’s not the fact that I have to read these things that annoys me, but the strange way students write them, i.e. almost entirely in the passive voice, e.g. “The experiment was calibrated using a phlogiston normalisation widget…”.

I accept that people disagree about whether the passive voice is good style or not. Some journals actively encourage the passive voice while others go the opposite way entirely . I’m not completely opposed to it, in fact, but I think it’s only useful either when the recipient of the action described in the sentence is more important than the agent, or when the agent is unknown or irrelevant. There’s nothing wrong with “My car has been stolen” (passive voice) since you would not be expected to know who stole it. On the other hand “My Hamster has been eaten by Freddy Starr” would not make a very good headline.

The point is that the construction of a statement in the passive voice in English is essentially periphrastic in that it almost inevitably involves some form of circumlocution – either using more words than necessary to express the meaning or being deliberately evasive by introducing ambiguity. Both of these failings should be avoided in scientific writing.

Apparently our laboratory instructors tell students to write their reports in the passive voice as a matter of course. I think this is just wrong. In a laboratory report the student should describe what he or she did. Saying what “was done” often leaves the statement open to the interpretation that somebody else did it. The whole point of a laboratory report is surely for the students to describe their own actions. “We calibrated the experiment..” is definitely to be preferred to the form I gave above.

Sometimes it is appropriate to use the passive voice because it is the correct grammatical construction in the circumstances. Sometimes also the text just seems to work better that way too. But having to read an entire document written in the passive voice drives me to distraction. It’s clumsy and dull.

In scientific papers, things are a little bit different but I still think using the active voice makes them easier to read and less likely to be ambiguous. In the introduction to a journal paper it’s quite acceptable to discuss the background to your work in the passive voice, e.g. “it is now generally accepted that…” but when describing what you and your co-authors have done it’s much better to use the active voice. “We observed ABC1234 using the Unfeasibly Large Telescope..” is, to my mind, much better than “Observations of ABC1234 were made using..”.

Reading back over this post I notice that I have jumped fairly freely between active and passive voice, thus demonstrating that I don’t have a dogmatic objection to its use. What I’m arguing is that it shouldn’t be the default, that’s all.

My guess is that a majority of experimental scientists won’t agree with this opinion, but a majority of astronomers and theoreticians will.

This guess will now be tested using a poll…


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Take a note from me…

Posted in Education with tags , , , , on December 14, 2010 by telescoper

Having just given a lecture on probability and statistics to our first-year postgraduate students I thought I’d indulge in a bit of reflective practice (as the jargon goes) and make a few quick comments on teaching to see if I can generate some reaction. Part of the reason for doing this is that while I was munching my coffee and drinking my toast this morning – I’m never very coordinated first thing – I noticed an interesting post by a student on a blog  that somehow wound up referring some traffic to one of my old posts about lecture notes.

I won’t repeat the entire content of my earlier discussion, but one of the main points I made was about how inefficient many students are at taking notes during lectures, so much so that the effort of copying things onto paper must surely prevent them absorbing the intellectual content of the lecture.

I dealt with this problem when I was an undergraduate by learning to write very quickly without looking at the paper as I did so. That way I didn’t waste time moving my head to and fro between paper and screen or blackboard. Of course, the notes I produced using this method weren’t exactly aesthetically pleasing, but my handwriting is awful at the best of times so that didn’t make much difference to me. I always wrote my notes up more neatly after the lecture anyway. But the great advantage was that I could write down everything in real time without this interfering with my ability to listen to what the lecturer was saying.

An alternative to this approach is to learn shorthand, or invent your own form of abbreviated language. This approach is, however, unlikely to help you take down mathematical equations quickly…

My experience nowadays is that students aren’t used to taking notes like this, so they struggle to cope with the old-fashioned chalk-and-talk style of teaching that some lecturers still prefer. That’s probably because they get much less practice at school than my generation. Most of my school education was done via the blackboard..

Nowadays,  most lecturers use more “modern” methods than this. Many lecture using powerpoint, and often they give copies of the slides to students. Others give out complete sets of printed notes before, during, or after lectures. That’s all very well, I think, but what are the students supposed to be doing during the lecture if you do that? Listen, of course, but if there is to be a long-term benefit they should take notes too.

Even if I hand out copies of slides or other notes, I always encourage my students to make their own independent set of notes, as complete as possible. I don’t mean copying down what they see on the screen and what they may have on paper already, but trying to write down what I say as I say it. I don’t think many take that advice, which means much of the spoken illustrations and explanations I give don’t find their way into any long term record of the lecture.

And if the lecturer just reads out the printed notes, adding nothing by way of illustration or explanation, then the audience is bound to get bored very quickly.

My argument, then, is that regardless of what technology the lecturer uses, whether he/she gives out printed notes or not, then if the students can’t take notes accurately and efficiently then lecturing is a complete waste of time.

I like lecturing, because I like talking about physics and astronomy, but as I’ve got older I’ve become less convinced that lectures play a useful role in actually teaching anything. I think we should use lectures more sparingly, relying more on problem-based learning to instil proper understanding. When we do give lectures, they should focus much more on stimulating interest by being entertaining and thought-provoking. They should not be for the routine transmission of information, which is far too often the default.

Next year we’ll rolling out a new set of courses here in the School of Physics & Astronomy at Cardiff University. The express intent of this is to pare down the amount of material lectured to create more space for other types of activity, especially more exercise classes for problem-based learning. The only way to really learn physics is by doing it.

I’m not saying we should scrap lectures altogether. At the very least they have the advantage of giving the students a shared experience, which is good for networking and building a group identity. Some students probably get a lot out of lectures anyway, perhaps more than I did when I was their age. But different people benefit from different styles of teaching, so we need to move away from lecturing as the default option.

I don’t think I ever learned very much about physics from lectures, but I’m nevertheless glad I learned out how to take notes the way I did because I find it useful in all kinds of situations. Note-taking is a transferable skill, but it’s also a dying art.


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Ways of Thinking

Posted in Biographical, The Universe and Stuff with tags , , on November 25, 2010 by telescoper

I’m putting one more Richard Feynman clip up. This one struck me as particularly interesting, because it touches on a question I’ve often asked myself: what goes on in your head when do you mathematical calculations? I think I agree with Feynman’s suggestion that different people think in very different ways about the same kind of calculation or other activity.

There’s no doubt in my mind that I’ve become slower and slower at doing mathematics as I’ve got older, and probably less accurate too. I think that’s partly just age – and perhaps the cumulative effect of too much wine! – but it’s partly because I have so many other things to think about these days that it’s hard to spend long hours without interruption thinking about the same problem the way I could when I was a student or a postdoc.

In any case, although much of my research is mathematical, I’ve never really thought of myself as being in any sense a mathematical person. Many of my colleagues have much better technical skills in that regard than I’ve ever had. I was never particularly good at maths at school either. I was sufficiently competent at maths to do physics, of course, but I was much better at other things at that age. My best subject at O-level was Latin, for example, which possibly indicates that my brain prefers to work verbally (or perhaps symbolically) rather than, as no doubt many others’ do, geometrically or in some other abstract way.

Another strange thing is the role of vision in doing mathematics. I can’t do maths at all without writing things down on paper. I have to be able to see the equations to think about solving them. Amongst other things this makes it difficult when you’re working things out on a blackboard (or whiteboard); you have to write symbols so large that your field of view can’t take in a whole equation. I often have to step back up one of the aisles to get a good look at what I’m doing like that. Other physicists – notably Stephen Hawking – obviously manage without writing things down at all. I find it impossible to imagine having that ability.

But I endorse what Richard Feynman says at the beginning of the clip. It’s really all about being interested in the questions, which gives you the motivation to acquire the skills needed to find the answers. I think of it as being like music. If you’re drawn into the world of music, even if you’re talented you have to practice long for long hours before you can really play an instrument. Few can reach the level of Feynman (or a concert pianist) of course – I’m certainly not among either of those categories! – but I think physics is at least as much perspiration as inspiration.

In contrast to many of my colleagues I’m utterly hopeless at chess – and other games that require very sophisticated pattern-reading skills – but good at crosswords and word-puzzles. Maybe I’m in the wrong job?


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The Inconceivable Nature of Nature

Posted in The Universe and Stuff with tags , , on November 19, 2010 by telescoper

I had a couple of requests to post yet another Feynman clip. This one – about electromagnetic waves and swimming pools – is one that I vividly remember watching on BBC when it was first broadcast donkeys’ years ago. I think it’s totally wonderful.


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Through the Looking Glass

Posted in The Universe and Stuff with tags , , , on November 15, 2010 by telescoper

I’m afraid I’m too busy again for a proper post, so I’ll resort once again to the supply of wonderful Richard Feynman clips on Youtube. Here’s a particularly nice one, about the mysterious matter of mirrors. I might use this later on this year when I talk about parity to my particle physics class!


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Uncertainty

Posted in The Universe and Stuff with tags , on November 7, 2010 by telescoper

At the risk of turning this blog into a Feynman-fest – although I don’t think that would be such a bad thing, as a matter of fact – I couldn’t resist posting this little clip as a follow up to my previous one. In it he talks about a subject that has been a recurring motif on this blog – the importance of knowing when not to be certain.


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The Feynman Reaction

Posted in The Universe and Stuff with tags , , on November 5, 2010 by telescoper

I came across this clip of the great physicist Richard Feynman sort-of explaining magnetism, but was taken aback by some of the comments posted on Youtube in reaction to it. Some people appear to have found his response extremely arrogant, while others think he was just being honest (and trying his very best not to be patronising). I know what I think, but doubt if everyone agrees with my reaction.

I know the readership of this blog isn’t a fair sample, but I’d be very interested to see the general opinion on his comments. So please study the clip and complete the poll at the bottom.


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After Reading a Child’s Guide to Modern Physics

Posted in Poetry, The Universe and Stuff with tags , on October 26, 2010 by telescoper

This, written by W.H. Auden, is probably one of the most famous poems written about physics. A quick google about showed me that Cosmic Variance already featured it, along with a bit of an explanation of some of the scientific references contained within it. What I’m not sure whether what that article says about Auden’s own father was a physicist is correct. I always thought he was a medical doctor…

 

If all a top physicist knows
About the Truth be true,
Then, for all the so-and-so’s,
Futility and grime,
Our common world contains,
We have a better time
Than the Greater Nebulae do,
Or the atoms in our brains.

Marriage is rarely bliss
But, surely it would be worse
As particles to pelt
At thousands of miles per sec
About a universe
Wherein a lover’s kiss
Would either not be felt
Or break the loved one’s neck.

Though the face at which I stare
While shaving it be cruel
For, year after year, it repels
An ageing suitor, it has,
Thank God, sufficient mass
To be altogether there,
Not an indeterminate gruel
Which is partly somewhere else.

Our eyes prefer to suppose
That a habitable place
Has a geocentric view,
That architects enclose
A quiet Euclidean space:
Exploded myths – but who
Could feel at home astraddle
An ever expanding saddle?

This passion of our kind
For the process of finding out
Is a fact one can hardly doubt,
But I would rejoice in it more
If I knew more clearly what
We wanted the knowledge for,
Felt certain still that the mind
Is free to know or not.

It has chosen once, it seems,
And whether our concern
For magnitude’s extremes
Really become a creature
Who comes in a median size,
Or politicizing Nature
Be altogether wise,
Is something we shall learn

You can hear a recording, made in 1965, of the poet himself reading this poem here.


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