Author Archive

Time Present and Time Past

Posted in Poetry with tags , , on June 6, 2011 by telescoper

Up early this morning to set off for the airport. No time for a proper post until I get to Copenhagen so I thought I’d just put this up, as it popped into my mind after I’d written yesterday’s item. I’m a bit reluctant to post a bit of a poem, rather than a whole one, but here goes.  This is the opening passage from Burnt Norton, the first of the Four Quartets by T.S. Eliot. If you haven’t read the whole thing, you should.

Time present and time past
Are both perhaps present in time future,
And time future contained in time past.
If all time is eternally present
All time is unredeemable.
What might have been is an abstraction
Remaining a perpetual possibility
Only in a world of speculation.
What might have been and what has been
Point to one end, which is always present.
Footfalls echo in the memory
Down the passage which we did not take
Towards the door we never opened
Into the rose-garden.

From Time to Time

Posted in Biographical, The Universe and Stuff with tags , , on June 5, 2011 by telescoper

It having been my birthday yesterday, and very nice it was too, thank you for asking, I’m filled this morning with thoughts about the passage of time. It’s strange how working in education imposes a cycle on your life: admissions, teaching, exams, graduation ceremonies, summer recess, and so on. The main thing that breaks this pattern of recurrence is when students finish their finals and leave for the big wide world. Since I moved to Cardiff in 2007, the 4th year students who have just finished their examinations are the first cohort that I’ve seen through their whole degree programme at Cardiff University, and it will be great to see them all get their degrees next month in St David’s Hall, but it will be yet another reminder of the passage of the years.

Not that I’m one to get depressed about such things. I’ve taken surprisingly well to middle age and gracefully (?) surrendered the things of youth some time ago. However, time is such a mysterious thing it’s hard not to think about its passing every now and then.

This time last year I was in Copenhagen for a small cosmology workshop. There’ll be a repeat performance next week too, so I’ll be off to Denmark for a few days. In fact I bought my ticket some time ago, but realised only on Friday that it was next week, and not the week after, so have had to rearrange a few things rather hastily. The advancing years have obviously addled my brain.

Anyway, all this talk about time and cycles gives me some sort of excuse to post the following video from the ESO Very Large Telescope in Chile. The photography is wonderful. Pity about the music, though. Spoils it a bit if you ask me…

June

Posted in Poetry with tags , on June 4, 2011 by telescoper

Now summer is in flower and natures hum
Is never silent round her sultry bloom
Insects as small as dust are never done
Wi’ glittering dance and reeling in the sun
And green wood fly and blossom haunting bee
Are never weary of their melody
Round field hedge now flowers in full glory twine
Large bindweed bells wild hop and streakd woodbine
That lift athirst their slender throated flowers
Agape for dew falls and for honey showers
These round each bush in sweet disorder run
And spread their wild hues to the sultry sun.

by John Clare (1793-1864).

Whippin’ that Jelly

Posted in Jazz with tags , , on June 3, 2011 by telescoper

Summer has most definitely arrived. It’s a gorgeous day and most of the students have finished most of their examinations, so I’m sure will be taking a well-deserved break and enjoying the sunshine. It’s also Friday, and time, I think, for a little frivolity.

I’m indebted to young Miss Liggins for drawing my attention to this old record via Facebook. It’s by a relatively obscure swing band called the State Street Swingers, which was based in Chicago during the mid-1930s. From a technical point of view the musicians weren’t anything like as proficient as the leading bands of the Swing Era, especially in the horn section, so they usually tried to make up for their relatively limited abilities by playing for laughs behind various vocalists. It doesn’t say who it is on Youtube, but the singer sounds to me like Washboard Sam. He made a lot of records with other bands for the Vocalion label, which is what this one came out on, so that’s at least consistent with my hypothesis.

The State Street Swingers only ever recorded 14 tracks, most of them involving euphemistically raunchy titles, like this one, Whippin’ that Jelly. It may not be the most sophisticated music, but I hope it at least brings a smile to your face, as it does to mine every time I listen to it!

D+E+F+W=$500000

Posted in The Universe and Stuff with tags , , , , , , , on June 2, 2011 by telescoper

Just a quickie this fine summer morning to pass on the news – for those of you who haven’t heard yet – that this year’s Gruber Prize for Cosmology has been awarded to Marc Davis (Berkeley, USA), George Efstathiou (Cambridge, UK), Carlos Frenk (Durham, UK) and Simon White (Garching, Germany). This prestigious award is given for their pioneering work on the Cold Dark Matter model of structure formation, which included some of the first large-scale N-body computer simulations. The “Gang of Four” produced a number of papers during the 1980s that established the idea that galaxies form by hierarchical clustering from small initial fluctuations in a matter distribution dominated by massive collisionless non-baryonic particles, the most famous of their papers being pretty universally referred to as DEFW.

In fact, if you’ll forgive me going on a trip down memory lane, that paper, published in 1985, was one of the first papers I read when I started my research degree the same year at Sussex. It was back in the days when everyone seemed to use a VAX for big computing jobs and the simulations presented in that paper involved a mere 323 = 32768 particles. You could probably run that kind of simulation on a mobile phone these days!

This early work on Cold Dark Matter wasn’t the final word, of course. Subsequent observational evidence for an accelerating Universe resulting in our standard cosmological model being modifiel to include an additional (large) component of dark energy in addition to dark matter. Nevertheless, the core ideas presented by DEFW established the basic foundations of structure formation upon which the current standard model is built.

Incidentally, you can read an interesting account of the discovery of the accelerating universe here; a cosmologist by the name of “George F. Stathew” plays a prominent role in that piece and it’s curious I’ve never heard of him before now.

Each of the four winners gets a share of the $500000 Gruber Prize, i.e. in “normalized” terms, they get $125000 each. Why is it so controversial to suggest dividing citation counts the same way? The DEFW paper has about 1500 citations according to ADS, so I think it’s quite reasonable to award the authors 370-odd each towards their respective h-indices. That’s still a pretty good result by any bibliometric standard!

The four also get a Gold Medal each to wear at parties, although by my previous logic they should have to share one between them. Perhaps George might consider donating his to Arsenal Football Club, as their trophy cabinet is looking rather empty these days?

None of the winners are Australian undergraduates, so this award probably won’t be considered newsworthy by the mass media. Believe it or not, however, the Gruber Prize is held in even higher regard by cosmologists than the Templeton Prize, so I’d like to take this opportunity to congratulate them myself for their thoroughly well-deserved honour!

A Paradox of Galileo

Posted in Cute Problems with tags , , , on June 1, 2011 by telescoper

Going by the popularity of the little physics problem I posted last week, I thought some of you might be interested in this little conundrum which dates back to the 17th Century (to Galileo Galilei, in fact). It’s not a problem to which there’s a snappy answer, so no poll this time, but I think it’s quite a good one to think about – and please try to resist the temptation to google it!

The above figure shows a large circular wheel, which rolls from left to right, without slipping, on a flat surface, along a straight line from P to Q, making exactly one revolution as it does so. The distance PQ is thus equal to the circumference of the wheel.

Now, consider the small circle, firmly fixed to the larger circle with the two centres coincident. The small circle also makes one complete revolution as the wheel rolls, and  it travels from R to S. Similarly, therefore, the distance RS must be the circumference of the small circle.

Since RS is clearly equal to PQ it follows that the circumferences of the large wheel and the small circle must be equal!

Since the radii of the large and  small circles are different,  this conclusion is clearly false so what’s wrong with the argument?

Turandot

Posted in Opera with tags , , on May 31, 2011 by telescoper

On the way to the Wales Millennium Centre in Cardiff Bay this evening it struck me that it was quite fitting to be going to see Welsh National Opera‘s production of Turandot so soon after Friday’s concert. After all this was Giacomo Puccini‘s last Opera and it was incomplete at the time of the composer’s death in 1924. It’s a work most famous for the rousing tenor aria Nessun Dorma from Act III , which was made even more famous when, sung by the great Pavarotti, it became the theme tune for the Italia 90 World Cup. But there’s also the gorgeous Signore Ascolta in Act I and, even better, the dramatic fulcrum of the Opera, and one of the greatest Puccini’s arias of all, the climactic In Questia Reggia. Puccini undoubtedly had a great gift for writing memorable songs but there’s much more to him than that, as this opera proves. Turandot is a particularly dark and troubling story, with music to match the drama at every stage, and it contains some extremely interesting “modern” ideas alongside the classic showpiece numbers.

The story is set in China (“in legendary times”). Princess Turandot (definitely pronounced “-dot” rather than “-doh”) is a tyrannical ruler who challenges potential suitors to solve three riddles. The penalty for failure is death; no resits allowed. The Opera begins with the Prince of Persia being led to his doom. You know the sort of thing – girl meets boy, boy falls in love with girl, girl beheads boy, etc. Calaf, Prince of the Tartars, arrives with his elderly father Timur and faithful servant Liu. Crazy fool that he is, he decides to have a go at the riddles. Three sinister ministers, Ping Pang and Pong, prepare the trial, letting on as they do so just how many others have died in the attempt to woo Turandot. Calaf, of course, succeeds, but Turandot doesn’t want to go along with her side of the bargain. Calaf sets his own riddle – Turandot simply has to guess his name by dawn and he’ll give up his suit and let Turandot execute him too. She tries everything she can think of to identify the mystery contestant, including keeping the entire population of Peking up all night and torturing Liu to the point where she kills herself rather than risk giving away her master’s name. Liu loves Calaf herself, you see, so naturally she dies for her beloved’s sake. That’s what women do, in Opera. Moved by Liu’s sacrifice, Turandot feels the power of love and agrees to marry Calaf. And they all live happily ever after. Apart from Liu, of course, who’s dead.

That’s one of the thing’s that’s so problematic about this Opera for me. If Calaf is meant to be so noble and courageous, so why does he fall for Turandot who, at least at the beginning, is cruel beyond belief? And if he’s such a good egg why does he let the innocent Liu die just so he can get his leg over? This isn’t the only Puccini opera in which the romance has a dark undertone and in which the hero isn’t all that heroic when you look hard enough at him. Calaf isn’t quite as bad as the ghastly Pinkerton in Madame Butterfly, but I still think he’s basically a prat.

This production is a revival of one first performed in 1994. The setting spans a number of epochs, ancient Chinese costumes mingling with 20th century dress, and the minimal set periodically hung with mugshots of slain suitors evoking the “disappeared” in a South American dictatorship. Turandot’s dress and hairstyle in Act II made her look a lot like a cross between Ymelda Marcos and Eva Peron. In the crowd scenes, the chorus writhe with stylised anguish of an almost masochistic nature, as if their oppression by the brutal regime has become a sort of fetish for them.

Star of the show was dramatic soprano Anna Shafajinskaia as Turandot. With a name like an Icelandic volcano and a voice of exceptional power to match, she sent shivers down my spine on several occasions, especially in Act II. Gwyn Hughes Jones was a fine Calaf. Rebecca Evans being unfortunately indisposed, Liu was played by Michelle Walton. She started very hesitantly, and I wasn’t at all impressed with her rendition of Signore Ascolta; what she sang was quite nice, but it was only a vague approximation to what Puccini wrote. She did settle down as the performance went on, however, and was much more impressive in Act III. The rest of the cast were good and, as always, the Chorus of Welsh National Opera were superb throughout.

It’s difficult to explain to people who don’t “get” Opera how it can possibly work. People don’t actually sing to each other in real life, after all. All I can say is that, when it’s good, you somehow just fall into it and it takes on its own dramatic logic. That doesn’t always happen, of course, but for me it certainly happens sufficiently frequently to make it worthwhile. This one took a while to get going, and I didn’t really start to get involved until Act II, but thereafter I was gripped.

I should also say that it was very nearly a full house. Not bad for a Tuesday night!

Never Say Never …

Posted in Cricket with tags , , , , on May 30, 2011 by telescoper

It was tipping down with rain this morning so I wrote off the prospect of there being any result in the First Test between England and Sri Lanka at Cardiff which I’ve blogged about once already. However, the weather steadily improved and play eventually got started at about 3pm. England, resuming on 491 for 5, batted on for a couple of overs to allow Ian Bell to get his century then – perhaps surprisingly – declared on 496-5, with a lead of 96 on the first innings. An unusually adventurous decision by Strauss to declare so early, in fact. Nevertheless, a draw looked a virtual certainty to me (and most sports writers) so I wasn’t paying much attention to the cricket at first, deciding instead to get on with some other stuff at home.

When I checked the score around 4 o’clock I discovered Sri Lanka had lost a couple of early wickets and had gone in for tea at 33-2. It being free to get in for the last session and the weather now being very sunny, I finally decided to go and watch the final stages. A draw still seemed the likeliest outcome – Sri Lanka only had to bat out time for 35 overs or so. However, we don’t get much Test cricket in Cardiff and the last match here had an exciting finish, so I walked to the ground just after tea. There couldn’t have been more than a few hundred spectators in the ground, but what we saw turned out to be a demonstration of what Test cricket is all about.

I had hardly got to my seat when Tremlett produced a beauty that found the edge of M. Jayawardene’s bat and was caught at slip. Sri Lanka 33-3. A few minutes later Samaraweera played an inexplicable slash at spinner Graham Swann and dragged the ball onto his stumps; 36-4. Swann then disposed of Sangakkara and Maharoof, and Tremlett took the wicket of P. Jayawardene, all with the score on 43. Sri Lanka’s batting, so solid in the first innings was now in pieces on the floor. In came Herath with the air of a man wishing to commit suicide. Eventually he succeeded, playing an agricultural swipe at a delivery from Swann; he missed and the ball hit him on the back leg, plumb in front of the wicket. At 52-8 Sri Lanka looked doomed. Perera decided to take the attack to England. He played some good shots, as well as some lucky ones, and was fortunate to be dropped when two fielders ran into each other. Nevertheless, he and Mendis steadied the Sri Lankan ship for a while. I on the other hand was literally shaking with excitement and anticipation, hoping that I was about to witness a spectacular finale.

The score quickly moved onto 82 and it looked like Sri Lanka might at least have a chance of making England bat again. Then Broad replaced Tremlett, Perera tried to flick him away and Ian Bell took a superb reaction catch at short leg. 82-9. Last man Lakmal departed without troubling the scorers just three balls later, caught at 3rd slip by Alastair Cook. England had won by an innings and 14 runs. Amazing.

It had all been so exciting I hadn’t even had time to think about going for a beer. I think I’ll have one while I watch the highlights on TV.

There really is nothing like Test cricket, you know…

Missing Mass Hysteria

Posted in Astrohype, The Universe and Stuff with tags , , , on May 30, 2011 by telescoper

It’s usually very satisfying to see science get covered in the popular media. Even if the story gets a little simplified or, more likely, garbled, press coverage often succeeds in getting at least a bit of the truth across. My own field of astrophysics has more popular appeal than many other branches of physics, but can nevertheless involve complex theoretical ideas and difficult observations that can be difficult to disseminate in a form suitable for public consumption. For the most part, the press do a good job for astronomy but occasionally news stories emerge that are simply ridiculous.

Take this one, for example, which begins:

A Monash student has made a breakthrough in the field of astrophysics, discovering what has until now been described as the Universe’s ‘missing mass’. Amelia Fraser-McKelvie, working within a team at the Monash School of Physics, conducted a targeted X-ray search for the matter and within just three months found it – or at least some of it.

What makes the discovery all the more noteworthy is the fact that Ms Fraser-McKelvie is not a career researcher, or even studying at a postgraduate level. She is a 22-year-old undergraduate Aerospace Engineering/Science student who pinpointed the missing mass during a summer scholarship, working with two astrophysicists at the School of Physics, Dr Kevin Pimbblet and Dr Jasmina Lazendic-Galloway.

On the face of it, this sounds an extremely interesting story not only because it apparently involves a major scientific breakthrough, but also because the result was achieved by an undergraduate student working on a summer programme. Unfortunately, however, a little digging reveals that there is much less to it than meets the eye. I know of many astronomers around the world who think the Press Office at Monash University is guilty of shameless exaggeration in the press release that initiated this bubble. This sort of deliberately misleading distortion is very bad for science, as it almost inevitably ends up splattered in unrecognisable form all over the media, especially the downmarket end.

Here is the abstract of the actual paper which this story is supposed to be about:

Most of the baryons in the Universe are thought to be contained within filaments of galaxies, but as yet, no single study has published the observed properties of a large sample of known filaments to determine typical physical characteristics such as temperature and electron density. This paper presents a comprehensive large-scale search conducted for X-ray emission from a population of 41 bona fide filaments of galaxies to determine their X-ray flux and electron density. The sample is generated from Pimbblet et al.’s (2004) filament catalogue, which is in turn sourced from the 2 degree Field Galaxy Redshift Survey (2dFGRS). Since the filaments are expected to be very faint and of very low density, we used stacked ROSAT All-Sky Survey data. We detect a net surface brightness from our sample of filaments of (1.6 +/- 0.1) x 10^{-14} erg cm^{-2} s^{-1} arcmin^{-2} in the 0.9-1.3 keV energy band for 1 keV plasma, which implies an electron density of n_{e} = (4.7 +/- 0.2) x 10^{-4} h_{100}^{1/2} cm^{-3}. Finally, we examine if a filament’s membership to a supercluster leads to an enhanced electron density as reported by Kull & Bohringer (1999). We suggest it remains unclear if supercluster membership causes such an enhancement.

You won’t find anything in there about finding the “missing mass” of the Universe, nor will you find it anywhere else in the paper, because they haven’t. The “targeted X-ray search” involved stacking old ROSAT observations of filaments that were discovered and catalogued in previous papers; this study merely matched them to existing X-ray data. ROSAT ceased operations in 1999. The results do give some evidence for a higher electron density than previously thought in some of the filaments, so it’s a fairly interesting “incremental” paper, not by any stretch of the imagination revolutionary.

I’ve got nothing against Amelia Fraser-McKelvie, who seems to have done some solid scientific work during her summer internship, and who may not have played any role in spinnng the shameless press release that led to this story getting into the world’s media. However, the more senior scientists involved in this work should not have let the story come out in this form.

Guest Post – Bayesian Book Review

Posted in Bad Statistics, Books, Talks and Reviews with tags , , , on May 30, 2011 by telescoper

My regular commenter Anton circulated this book review by email yesterday and it stimulated quite a lot of reaction. I haven’t read the book myself, but I thought it would be fun to post his review on here to see whether it provokes similar responses. You can find the book on Amazon here (UK) or here ( USA). If you’re not completely au fait with Bayesian probability and the controversy around it, you might try reading one of my earlier posts about it, e.g. this one. I hope I can persuade some of the email commenters to upload their contributions through the box below!

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The Theory That Would Not Die: How Bayes’ Rule Cracked the Enigma Code, Hunted Down Russian Submarines, and Emerged Triumphant from Two Centuries of Controversy

by Sharon Bertsch Mcgrayne

I found reading this book, which is a history of Bayes’ theorem written for the layman, to be deeply frustrating. The author does not really understand what probability IS – which is the key to all cogent writing on the subject. She never mentions the sum and product rules, or that Bayes’ theorem is an easy consequence of them. She notes, correctly, that Bayesian methods or something equivalent to them have been rediscovered advantageously again and again in an amazing variety of practical applications, and says that this is because they are pragmatically better than frequentist sampling theory – ie, she never asks the question: Why do they work better and what deeper rationale explains this? RT Cox is not mentioned. Ed Jaynes is mentioned only in passing as someone whose Bayesian fervour supposedly put people off.

The author is correct that computer applications have catalysed the Bayesian revolution, but in the pages on image processing and other general inverse problems (p218-21) she manages to miss the key work through the 1980s of Steve Gull and John Skilling, and you will not find “Maximum entropy” in the index. She does get the key role of Markov Chain Monte Carlo methods in computer implementation of Bayesian methods, however. But I can’t find Dave Mackay either, who deserves to be in the relevant section about modern applications.

On the other hand, as a historian of Bayesianism from Bayes himself to about 1960, she is full of superb anecdotes and information about
people who are to us merely names on the top of papers, or whose personalities are mentioned tantalisingly briefly in Jaynes’ writing.
For this material alone I recommend the book to Bayesians of our sort and am glad that I bought it.