Author Archive

The VHC that wasn’t….

Posted in Crosswords with tags , , , on October 9, 2011 by telescoper

I was delighted to see, when I turned to the Azed Crossword in last week’s Observer, my name  among the list of those awarded a VHC (“Very Highly Commended”) for Azed No. 2049. A VHC is a sort of consolation prize for clues judged by Azed to be not quite good enough to win one of the three main prizes. Although I enjoy solving the puzzles I know I’m not very good at setting my own clues. I therefore find the monthly competition exercises me considerably and am usually more than happy to get a VHC! Also, these score points in the annual league table in which I did pretty well last year, finishing in joint 15th place – my highest every position

However, my delight turned to frustration when I found out that my name and the clue I submitted (for the word PARTY-POOPER) did not appear on the corresponding Azed Slip, a monthly report on the entries for the competition crossword. I’ve therefore not been credited with a VHC in the league table to go with the one I got the previous month in Azed No. 2045. Worse still, I didn’t keep a copy of the clue I submitted and now, over a month later on, I can’t remember what it was. I imagine Azed throws away the original entries so he probably doesn’t have it either.

It may be that my name was put in the Observer list by accident and the Azed slip is actually correct. The other possibility is that Azed forwarded the correct list to the newspaper but inadvertently skipped my name when compiling the slip. I did try emailing about this, but haven’t had a reply so I suppose I’ll have to give up on it. It doesn’t matter very much in the great cosmic scheme of things, so I suppose I shouldn’t be bitter…

A Sonnet in Autumn

Posted in Poetry with tags , , on October 8, 2011 by telescoper

What lips my lips have kissed, and where, and why,
I have forgotten, and what arms have lain
Under my head till morning; but the rain
Is full of ghosts tonight, that tap and sigh
Upon the glass and listen for reply,
And in my heart there stirs a quiet pain
For unremembered lads that not again
Will turn to me at midnight with a cry.

Thus in winter stands the lonely tree,
Nor knows what birds have vanished one by one,
Yet knows its boughs more silent than before:
I cannot say what loves have come and gone,
I only know that summer sang in me
A little while, that in me sings no more.

Sonnet No. XLIII by Edna St. Vincent Millay (1892-1950)

Honeysuckle Rose

Posted in Jazz with tags , , , on October 8, 2011 by telescoper

I’m in a vegetative mood today and the old energy levels aren’t high enough to post anything demanding, so I thought I’d put up a piece of music for your entertainment and edification. This was recorded in Paris, on April 28th 1937 and it revolves around a lengthy  tenor saxophone solo by the great Coleman Hawkins. Inspired by his sojourn in Europe, Hawkins returned to New York to record probably the most famous tenor solo ever, on the classic ballad Body and Soul, but this shows a side to his playing that was more familiar to swing era jazz fans. Listen to the drive that he injects into this performance combined with that “heavy” tenor tone, and you’ll understand why he was regarded as the pre-eminent tenor soloist of the 30s.

Other members of the band include Benny Carter who plays the alto solo near the end and who obviously did the arrangement for the four saxophones – nobody else in jazz history has ever managed to get such a biting sound out of small saxophone section as Benny Carter. And if that weren’t enough there’s a bonus in the unmistakeable form of  Django Reinhardt‘s guitar. Enjoy!

Astronomy (and Particle Physics) Look-alikes, No. 64

Posted in Astronomy Lookalikes with tags , , on October 7, 2011 by telescoper

Not related in any way to rumours which probably don’t exist and which even if they did I’d have to deny for legal reasons let me just mention that John Womersley of the Science and Technology Facilities Council reminds me quite a lot of Christopher Biggins:

Biggins

Womersley

The Invaders

Posted in Poetry with tags , , on October 7, 2011 by telescoper

Coming by night, furtively, one by one
They infiltrate according to the Plan,
Their orders memorized and their disguise
Impenetrable. With the rising sun
Our citizens welcome them. Nobody can
Think that such charming creatures might be spies.

So feeble, so helpless, no one could suspect
They come to make this commonwealth their prey;
So few, they pose no threat; their cohort grows
So imperceptibly that we neglect
To notice how it musters day by day
And, unalarmed, we watch as they impose

Themselves, make friends in all directions, take
Impressions of all keys. They gain access
To all our secrets; learn to speak our tongue
Like natives; profit by each false move we make;
Work on our weaknesses; observe and guess
The sources of power and study them to be strong.

And when it happens, there will be no fuss,
No streets running with blood, no barricade.
We shall simply wake one morning to discover,
As those who ruled this city before us
Found by each door a headstone and a spade,
That a new generation has taken over.

by A. D. Hope (1907-2000).

Bayes in the Dock

Posted in Bad Statistics with tags , , , , on October 6, 2011 by telescoper

A few days ago John Peacock sent me a link to an interesting story about the use of Bayes’ theorem in legal proceedings and I’ve been meaning to post about it but haven’t had the time. I get the distinct feeling that John, who is of the frequentist persuasion,  feels a certain amount of delight that the beastly Bayesians have got their comeuppance at last.

The story in question concerns an erroneous argument given during a trial about the significance of a match found between a footprint found at a crime scene and footwear belonging to a suspect.  The judge took exception to the fact that the figures being used were not known sufficiently accurately to make a reliable assessment, and thus decided that Bayes’ theorem shouldn’t be used in court unless the data involved in its application were “firm”.

If you read the Guardian article you will see that there’s a lot of reaction from the legal establishment and statisticians about this, focussing on the forensic use of probabilistic reasoning. This all reminds me of the tragedy of the Sally Clark case and what a disgrace it is that nothing has been done since then to improve the misrepresentation of statistical arguments in trials. Some of my Bayesian colleagues have expressed dismay at the judge’s opinion, which no doubt pleases Professor Peacock no end.

My reaction to this affair is more muted than you would probably expect. First thing to say is that this is really not an issue relating to the Bayesian versus frequentist debate at all. It’s about a straightforward application of Bayes’ theorem which, as its name suggests, is a theorem; actually it’s just a straightforward consequence of the sum and product laws of the calculus of probabilities. No-one, not even the most die-hard frequentist, would argue that Bayes’ theorem is false. What happened in this case is that an “expert” applied Bayes’ theorem to unreliable data and by so doing obtained misleading results. The  issue is not Bayes’ theorem per se, but the application of it to inaccurate data. Garbage in, garbage out. There’s no place for garbage in the courtroom, so in my opinion the judge was quite right to throw this particular argument out.

But while I’m on the subject of using Bayesian logic in the courts, let me add a few wider comments. First, I think that Bayesian reasoning provides a rigorous mathematical foundation for the process of assessing quantitatively the extent to which evidence supports a given theory or interpretation. As such it describes accurately how scientific investigations proceed by updating probabilities in the light of new data. It also describes how a criminal investigation works too.

What Bayesian inference is not good at is achieving closure in the form of a definite verdict. There are two sides to this. One is that the maxim “innocent until proven guilty” cannot be incorporated in Bayesian reasoning. If one assigns a zero prior probability of guilt then no amount of evidence will be able to change this into a non-zero posterior probability; the required burden is infinite. On the other hand, there is the problem that the jury must decide guilt in a criminal trial “beyond reasonable doubt”. But how much doubt is reasonable, exactly? And will a jury understand a probabilistic argument anyway?

In pure science we never really need to achieve this kind of closure, collapsing the broad range of probability into a simple “true” or “false”, because this is a process of continual investigation. It’s a reasonable inference, for example, based on Supernovae and other observations that the Universe is accelerating. But is it proven that this is so? I’d say “no”,  and don’t think my doubts are at all unreasonable…

So what I’d say is that while statistical arguments are extremely important for investigating crimes – narrowing down the field of suspects, assessing the reliability of evidence, establishing lines of inquiry, and so on – I don’t think they should ever play a central role once the case has been brought to court unless there’s much clearer guidance given to juries on how to use it and stricter monitoring of so-called “expert” witnesses.

I’m sure various readers will wish to express diverse opinions on this case so, as usual, please feel free to contribute through the box below!

The Three Es for Lecturing

Posted in Education with tags , , , , on October 5, 2011 by telescoper

Yet another very busy day looms in front of me. I’m off to the smoky bigness of London for an examiners’ meeting at Queen Mary this afternoon, but before that I have to squeeze in my first tutorial of the year, with a group of fresh-faced freshers. Actually I don’t know if they’re fresh faced or not because I haven’t met them yet. I had my first teaching encounter with the first years yesterday morning during an exercise class on mechanics, which I enjoyed despite some teething troubles with the facilities in the room we were using. I was very happy with the way the students chipped freely in with answers whenever I asked questions, which is a good sign.

A while ago I attended a session on teaching for our new lecturers. Actually I didn’t attend most of it, I just dropped in at the end to deliver a few tips I’ve picked up from observing other lecturers. Here in Cardiff we have “peer observation” of lectures in which one member of teaching staff sits in on a lecture by another, followed by a feedback and discussion session. While I was at Nottingham it was a different system; two nominated staff members (myself and another Professor) sat in on  lectures by each of the other staff. It was a lot of work, but gave me the chance to see quite a lot of different approaches to teaching and was consequently very interesting.

Anyway, over the years it became obvious that 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 lecturers 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 schoolmaster. Know your subject, explain it well and you’ll earn respect without needing to bluster.

Entertainment. To be absolutely honest, I think lectures  are a  fairly useless as a way of teaching physics. That is not to say that they 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 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. 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.

Well, that’s all I have time for, but please offer your own tips through the comments box if you feel so motivated!

Dark Energy’s Day

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

Following hard on the heels of the announcement of a Nobel Prize for cosmology earlier this morning, the European Space Agency has this afternoon officially announced the two candidates which have been chosen for its next M-class missions from a shortlist of three.

One of the successful candidates, EUCLID, is directly relevant to the topic covered by the Nobel Prize announced this morning. “Euclid will address key questions relevant to fundamental physics and cosmology, namely the nature of the mysterious dark energy and dark matter. Astronomers are now convinced that these substances dominate ordinary matter. Euclid would map the distribution of galaxies to reveal the underlying ‘dark’ architecture of the Universe.”

Now that it’s definitely been selected, I hope to devote time in due course for a longer post about EUCLID’s capabilities and intentions, but in the meantime I’ll just say that it’s been a very good day for Dark Energy.

P.S. The other successful candidate is called Solar Orbiter. Commiserations to advocates of the third mission on the shortlist of three, PLATO. Close, but no cigar…

Another Nobel Prize for Cosmology!

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

Just time in between teaching and meetings for a quick post on today’s announcement that the 2011 Nobel Prize for Physics has gone to Saul Perlmutter, Brian P. Schmidt and Adam G. Riess “for the discovery of the accelerating expansion of the Universe through observations of distant supernovae.”

I’ve taken the liberty of copying the following text from the press release on the Nobel Foundation website

In 1998, cosmology was shaken at its foundations as two research teams presented their findings. Headed by Saul Perlmutter, one of the teams had set to work in 1988. Brian Schmidt headed another team, launched at the end of 1994, where Adam Riess was to play a crucial role.

The research teams raced to map the Universe by locating the most distant supernovae. More sophisticated telescopes on the ground and in space, as well as more powerful computers and new digital imaging sensors (CCD, Nobel Prize in Physics in 2009), opened the possibility in the 1990s to add more pieces to the cosmological puzzle.

The teams used a particular kind of supernova, called type Ia supernova. It is an explosion of an old compact star that is as heavy as the Sun but as small as the Earth. A single such supernova can emit as much light as a whole galaxy. All in all, the two research teams found over 50 distant supernovae whose light was weaker than expected – this was a sign that the expansion of the Universe was accelerating. The potential pitfalls had been numerous, and the scientists found reassurance in the fact that both groups had reached the same astonishing conclusion.

For almost a century, the Universe has been known to be expanding as a consequence of the Big Bang about 14 billion years ago. However, the discovery that this expansion is accelerating is astounding. If the expansion will continue to speed up the Universe will end in ice.

The acceleration is thought to be driven by dark energy, but what that dark energy is remains an enigma – perhaps the greatest in physics today. What is known is that dark energy constitutes about three quarters of the Universe. Therefore the findings of the 2011 Nobel Laureates in Physics have helped to unveil a Universe that to a large extent is unknown to science. And everything is possible again.

I’m definitely among the skeptics when it comes to the standard interpretation of the supernova measurements, and more recent complementary data, in terms of dark energy. However this doesn’t diminish in any way my delight that these three scientists have been rewarded for their sterling observational efforts. The two groups involved in the Supernova Cosmology Project on the one hand, and the High Z Supernova Search, on the other, are both supreme examples of excellence in observational astronomy, taking on and overcoming what were previously thought to be insurmountable observational challenges. This award has been in the air for a few years now, and I’m delighted for all three scientists that their time has come at last. To my mind their discovery is all the more exciting because nobody really knows precisely what it is that they have discovered!

I know that Brian Schmidt is an occasional reader and commenter on this blog. I suspect he might be a little busy right now with the rest of the world’s media right to read this, let alone comment on here, but that won’t stop me congratulating him and the other winners on their achievement. I’m sure they’ll enjoy their visit to Stockholm!

Meanwhile the rest of us can bask in their reflected glory. There’s also been a huge amount of press interest in this announcement which has kept my phone ringing this morning. It’s only been five years since a Nobel Prize in physics went to cosmology, which says something for how exciting a field this is to work in!

UPDATE: There’s an interesting collection of quotes and reactions on the Guardian website, updated live.

UPDATE on the UPDATE: Yours truly gets a quote on the Nature News article about this!

Galaxies con Alma

Posted in The Universe and Stuff with tags , , , , on October 3, 2011 by telescoper

It’s back to School with a vengeance today, so not much time for the blog. However, I couldn’t resist mentioning the fact that the European Southern Observatory’s Atacama Large Millimetre Array, known to its friends as ALMA, has at last opened its eyes. Or at least some of them. ALMA in fact is an interferometer which eventually will comprise 66 dishes,   working together to with baselines as long 16km to synthesize a single huge aperture. The preliminary results that have just been released were obtained using just 16 dishes so they only offer a taste of what the full ALMA will do when it’s completed in 2013.

ALMA works in the millimetre wave region of the spectrum, operating at wavelengths between 0.3 and 9.6 mm. The overlap with the  wavelength range probed by the Herschel Space Observatory together with its much higher resolution than Herschel, which is a single telescope of only 3.5m diameter, makes the two very complementary: Herschel is good for surveying large parts of the sky, because it has a large field of view, whereas ALMA can do high-resolution follow-up of selected regions.

Anyway, here is ALMA’s view of the Antennae Galaxies (left) shown next to an optical image taken with the Very Large Telescope (VLT).

The system consists of two galaxies so close together that they interact strongly with each other via enormous tidal forces, hence the disturbed structure. The coloured regions in the ALMA image show radiation emanating from carbon monoxide present in huge clouds both in and between the galaxies. Altogether these clouds contain several billion solar masses worth of gas which has never been viewed before.