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Who put the Bang in Big Bang?

Posted in The Universe and Stuff with tags , , , , , on December 29, 2008 by telescoper

Back from the frozen North, having had a very nice time over Christmas, I thought it was time to reactivate my blog and to redress the rather shameful lack of science on what is supposed to be a science blog. Rather than writing a brand new post, though, I’m going to cheat like a TV Chef by sticking up something that I did earlier. I’ve  had the following piece floating around on my laptop for a while so I thought I’d rehash it and post it on here. It is based on an article that was published in a heavily revised and shortened form in New Scientist in 2007, where it attracted some splenetic responses despite there not being anything particular controversial in it! It’s not particularly topical, but there you go. The television is full of repeats these days too.

Around twenty-five years ago a young physicist came up with what seemed at first to be an absurd idea: that, for a brief moment in the very distant past, just after the Big Bang, something weird happened to gravity that made it push rather than pull.  During this time the Universe went through an ultra-short episode of ultra-fast expansion. The physicist in question, Alan Guth, couldn’t prove that this “inflation” had happened nor could he suggest a compelling physical reason why it should, but the idea seemed nevertheless to solve several major problems in cosmology.

Twenty five years later on, Guth is a professor at MIT and inflation is now well established as an essential component of the standard model of cosmology. But should it be? After all, we still don’t know what caused it and there is little direct evidence that it actually took place. Data from probes of the cosmic microwave background seem to be consistent with the idea that inflation happened, but how confident can we be that it is really a part of the Universe’s history?

According to the Big Bang theory, the Universe was born in a dense fireball which has been expanding and cooling for about 14 billion years. The basic elements of this theory have been in place for over eighty years, but it is only in the last decade or so that a detailed model has been constructed which fits most of the available observations with reasonable precision. The problem is that the Big Bang model is seriously incomplete. The fact that we do not understand the nature of the dark matter and dark energy that appears to fill the Universe is a serious shortcoming. Even worse, we have no way at all of describing the very beginning of the Universe, which appears in the equations used by cosmologists as a “singularity”- a point of infinite density that defies any sensible theoretical calculation. We have no way to define a priori the initial conditions that determine the subsequent evolution of the Big Bang, so we have to try to infer from observations, rather than deduce by theory, the parameters that govern it.

The establishment of the new standard model (known in the trade as the “concordance” cosmology) is now allowing astrophysicists to turn back the clock in order to understand the very early stages of the Universe’s history and hopefully to understand the answer to the ultimate question of what happened at the Big Bang itself and thus answer the question “How did the Universe Begin?”

Paradoxically, it is observations on the largest scales accessible to technology that provide the best clues about the earliest stages of cosmic evolution. In effect, the Universe acts like a microscope: primordial structures smaller than atoms are blown up to astronomical scales by the expansion of the Universe. This also allows particle physicists to use cosmological observations to probe structures too small to be resolved in laboratory experiments.

Our ability to reconstruct the history of our Universe, or at least to attempt this feat, depends on the fact that light travels with a finite speed. The further away we see a light source, the further back in time its light was emitted. We can now observe light from stars in distant galaxies emitted when the Universe was less than one-sixth of its current size. In fact we can see even further back than this using microwave radiation rather than optical light. Our Universe is bathed in a faint glow of microwaves produced when it was about one-thousandth of its current size and had a temperature of thousands of degrees, rather than the chilly three degrees above absolute zero that characterizes the present-day Universe. The existence of this cosmic background radiation is one of the key pieces of evidence in favour of the Big Bang model; it was first detected in 1964 by Arno Penzias and Robert Wilson who subsequently won the Nobel Prize for their discovery.

The process by which the standard cosmological model was assembled has been a gradual one, but it culminated with recent results from the Wilkinson Microwave Anisotropy Probe (WMAP). For several years this satellite has been mapping the properties of the cosmic microwave background and how it varies across the sky. Small variations in the temperature of the sky result from sound waves excited in the hot plasma of the primordial fireball. These have characteristic properties that allow us to probe the early Universe in much the same way that solar astronomers use observations of the surface of the Sun to understand its inner structure,  a technique known as helioseismology. The detection of the primaeval sound waves is one of the triumphs of modern cosmology, not least because their amplitude tells us precisely how loud the Big Bang really was.

The pattern of fluctuations in the cosmic radiation also allows us to probe one of the exciting predictions of Einstein’s general theory of relativity: that space should be curved by the presence of matter or energy. Measurements from WMAP reveal that our Universe is very special: it has very little curvature, and so has a very finely balanced energy budget: the positive energy of the expansion almost exactly cancels the negative energy relating of gravitational attraction. The Universe is (very nearly) flat.

The observed geometry of the Universe provides a strong piece of evidence that there is an mysterious and overwhelming preponderance of dark stuff in our Universe. We can’t see this dark matter and dark energy directly, but we know it must be there because we know the overall budget is balanced. If only economics were as simple as physics.

Computer Simulation of the Cosmic Web

The concordance cosmology has been constructed not only from observations of the cosmic microwave background, but also using hints supplied by observations of distant supernovae and by the so-called “cosmic web” – the pattern seen in the large-scale distribution of galaxies which appears to match the properties calculated from computer simulations like the one shown above, courtesy of Volker Springel. The picture that has emerged to account for these disparate clues is consistent with the idea that the Universe is dominated by a blend of dark energy and dark matter, and in which the early stages of cosmic evolution involved an episode of accelerated expansion called inflation.

A quarter of a century ago, our understanding of the state of the Universe was much less precise than today’s concordance cosmology. In those days it was a domain in which theoretical speculation dominated over measurement and observation. Available technology simply wasn’t up to the task of performing large-scale galaxy surveys or detecting slight ripples in the cosmic microwave background. The lack of stringent experimental constraints made cosmology a theorists’ paradise in which many imaginative and esoteric ideas blossomed. Not all of these survived to be included in the concordance model, but inflation proved to be one of the hardiest (and indeed most beautiful) flowers in the cosmological garden.

Although some of the concepts involved had been formulated in the 1970s by Alexei Starobinsky, it was Alan Guth who in 1981 produced the paper in which the inflationary Universe picture first crystallized. At this time cosmologists didn’t know that the Universe was as flat as we now think it to be, but it was still a puzzle to understand why it was even anywhere near flat. There was no particular reason why the Universe should not be extremely curved. After all, the great theoretical breakthrough of Einstein’s general theory of relativity was the realization that space could be curved. Wasn’t it a bit strange that after all the effort needed to establish the connection between energy and curvature, our Universe decided to be flat? Of all the possible initial conditions for the Universe, isn’t this very improbable? As well as being nearly flat, our Universe is also astonishingly smooth. Although it contains galaxies that cluster into immense chains over a hundred million light years long, on scales of billions of light years it is almost featureless. This also seems surprising. Why is the celestial tablecloth so immaculately ironed?

Guth grappled with these questions and realized that they could be resolved rather elegantly if only the force of gravity could be persuaded to change its sign for a very short time just after the Big Bang. If gravity could push rather than pull, then the expansion of the Universe could speed up rather than slow down. Then the Universe could inflate by an enormous factor (1060 or more) in next to no time and, even if it were initially curved and wrinkled, all memory of this messy starting configuration would be lost. Our present-day Universe would be very flat and very smooth no matter how it had started out.

But how could this bizarre period of anti-gravity be realized? Guth hit upon a simple physical mechanism by which inflation might just work in practice. It relied on the fact that in the extreme conditions pertaining just after the Big Bang, matter does not behave according to the classical laws describing gases and liquids but instead must be described by quantum field theory. The simplest type of quantum field is called a scalar field; such objects are associated with particles that have no spin. Modern particle theory involves many scalar fields which are not observed in low-energy interactions, but which may well dominate affairs at the extreme energies of the primordial fireball.

Classical fluids can undergo what is called a phase transition if they are heated or cooled. Water for example, exists in the form of steam at high temperature but it condenses into a liquid as it cools. A similar thing happens with scalar fields: their configuration is expected to change as the Universe expands and cools. Phase transitions do not happen instantaneously, however, and sometimes the substance involved gets trapped in an uncomfortable state in between where it was and where it wants to be. Guth realized that if a scalar field got stuck in such a “false” state, energy – in a form known as vacuum energy – could become available to drive the Universe into accelerated expansion.We don’t know which scalar field of the many that may exist theoretically is responsible for generating inflation, but whatever it is, it is now dubbed the inflaton.

This mechanism is an echo of a much earlier idea introduced to the world of cosmology by Albert Einstein in 1916. He didn’t use the term vacuum energy; he called it a cosmological constant. He also didn’t imagine that it arose from quantum fields but considered it to be a modification of the law of gravity. Nevertheless, Einstein’s cosmological constant idea was incorporated by Willem de Sitter into a theoretical model of an accelerating Universe. This is essentially the same mathematics that is used in modern inflationary cosmology.  The connection between scalar fields and the cosmological constant may also eventually explain why our Universe seems to be accelerating now, but that would require a scalar field with a much lower effective energy scale than that required to drive inflation. Perhaps dark energy is some kind of shadow of the inflaton

Guth wasn’t the sole creator of inflation. Andy Albrecht and Paul Steinhardt, Andrei Linde, Alexei Starobinsky, and many others, produced different and, in some cases, more compelling variations on the basic theme. It was almost as if it was an idea whose time had come. Suddenly inflation was an indispensable part of cosmological theory. Literally hundreds of versions of it appeared in the leading scientific journals: old inflation, new inflation, chaotic inflation, extended inflation, and so on. Out of this activity came the realization that a phase transition as such wasn’t really necessary, all that mattered was that the field should find itself in a configuration where the vacuum energy dominated. It was also realized that other theories not involving scalar fields could behave as if they did. Modified gravity theories or theories with extra space-time dimensions provide ways of mimicking scalar fields with rather different physics. And if inflation could work with one scalar field, why not have inflation with two or more? The only problem was that there wasn’t a shred of evidence that inflation had actually happened.

This episode provides a fascinating glimpse into the historical and sociological development of cosmology in the eighties and nineties. Inflation is undoubtedly a beautiful idea. But the problems it solves were theoretical problems, not observational ones. For example, the apparent fine-tuning of the flatness of the Universe can be traced back to the absence of a theory of initial conditions for the Universe. Inflation turns an initially curved universe into a flat one, but the fact that the Universe appears to be flat doesn’t prove that inflation happened. There are initial conditions that lead to present-day flatness even without the intervention of an inflationary epoch. One might argue that these are special and therefore “improbable”, and consequently that it is more probable that inflation happened than that it didn’t. But on the other hand, without a proper theory of the initial conditions, how can we say which are more probable? Based on this kind of argument alone, we would probably never really know whether we live in an inflationary Universe or not.

But there is another thread in the story of inflation that makes it much more compelling as a scientific theory because it makes direct contact with observations. Although it was not the original motivation for the idea, Guth and others realized very early on that if a scalar field were responsible for inflation then it should be governed by the usual rules governing quantum fields. One of the things that quantum physics tells us is that nothing evolves entirely smoothly. Heisenberg’s famous Uncertainty Principle imposes a degree of unpredictability of the behaviour of the inflaton. The most important ramification of this is that although inflation smooths away any primordial wrinkles in the fabric of space-time, in the process it lays down others of its own. The inflationary wrinkles are really ripples, and are caused by wave-like fluctuations in the density of matter travelling through the Universe like sound waves travelling through air. Without these fluctuations the cosmos would be smooth and featureless, containing no variations in density or pressure and therefore no sound waves. Even if it began in a fireball, such a Universe would be silent. Inflation puts the Bang in Big Bang.

The acoustic oscillations generated by inflation have a broad spectrum (they comprise oscillations with a wide range of wavelengths), they are of small amplitude (about one hundred thousandth of the background); they are spatially random and have Gaussian statistics (like waves on the surface of the sea; this is the most disordered state); they are adiabatic (matter and radiation fluctuate together) and they are formed coherently.  This last point is perhaps the most important. Because inflation happens so rapidly all of the acoustic “modes” are excited at the same time. Hitting a metal pipe with a hammer generates a wide range of sound frequencies, but all the different modes of the start their oscillations at the same time. The result is not just random noise but something moderately tuneful. The Big Bang wasn’t exactly melodic, but there is a discernible relic of the coherent nature of the sound waves in the pattern of cosmic microwave temperature fluctuations seen by WMAP. The acoustic peaks seen in the WMAP angular spectrum  provide compelling evidence that whatever generated the pattern did so coherently.
 

There are very few alternative theories on the table that are capable of reproducing the WMAP results. Some interesting possibilities have emerged recently from string theory. Since this theory requires more space-time dimensions than the four we are used to, something has to be done with the extra ones we don’t observe. They could be wrapped up so small we can’t perceive them. Or, as is assumed in braneworld cosmologies our four-dimensional universe exists as a subspace (called a “brane”) embedded within a larger dimensional space; we don’t see the extra dimensions because we are confined on the subspace. These ideas may one day lead to a viable alternative to inflationary orthodoxy. But it is early days and not all the calculations needed to establish this theory have yet been done. In any case, not every cosmologist feels the urge to make cosmology consistent with string theory, which has even less evidence in favour of it than inflation. Some of the wilder outpourings of string-inspired cosmology seem to me to be the physics equivalent of nausea-induced vomiting.

So did inflation really happen? Does WMAP prove it? Will we ever know?

It is difficult to talk sensibly about scientific proof of phenomena that are so far removed from everyday experience. At what level can we prove anything in astronomy, even on the relatively small scale of the Solar System? We all accept that the Earth goes around the Sun, but do we really even know for sure that the Universe is expanding? I would say that the latter hypothesis has survived so many tests and is consistent with so many other aspects of cosmology that it has become, for pragmatic reasons, an indispensable part our world view. I would hesitate, though, to say that it was proven beyond all reasonable doubt. The same goes for inflation. It is a beautiful idea that fits snugly within the standard cosmological and binds many parts of it together. But that doesn’t necessarily make it true. Many theories are beautiful, but that is not sufficient to prove them right. When generating theoretical ideas scientists should be fearlessly radical, but when it comes to interpreting evidence we should all be unflinchingly conservative. WMAP has also provided a tantalizing glimpse into the future of cosmology, and yet more stringent tests of the standard framework that currently underpins it. Primordial fluctuations produce not only a pattern of temperature variations over the sky, but also a corresponding pattern of polarization. This is fiendishly difficult to measure, partly because it is such a weak signal (only a few percent of the temperature signal) and partly because the primordial microwaves are heavily polluted by polarized radiation from our own Galaxy. Although WMAP achieved the detection of this polarization, the published map is heavily corrupted by foregrounds.

Future generations of experiments, such as the Planck Surveyor (due for launch in 2009), will have to grapple with the thorny issue of foreground subtraction if substantial progress is to be made. But there is a crucial target that justifies these endeavours. Inflation does not just produce acoustic waves, it also generates different modes of fluctuation, called gravitational waves, that involve twisting deformations of space-time. Inflationary models connect the properties of acoustic and gravitational fluctuations so if the latter can be detected the implications for the theory are profound. Gravitational waves produce very particular form of polarization pattern (called the B-mode) which can’t be generated by acoustic waves so this seems a promising way to test inflation. Unfortunately the B-mode signal is very weak and the experience of WMAP suggests it might be swamped by foregrounds. But it is definitely worth a go, because it would add considerably to the evidence in favour of inflation as an element of physical reality

Besides providing strong evidence for the concordance cosmology, the WMAP satellite has also furnished some tantalizing evidence that there may be something missing. Not all the properties of the microwave sky seem consistent with the model. For example, the temperature pattern should be structureless, mirroring the random Gaussian fluctuations of the primordial density perturbations. In reality the data contains tentative evidence of strange alignments, such as the so-called “Axis of Evil” discovered by Kate Land and Joao Magueijo. These anomalies could be systematic errors in the data, or perhaps residual problems with the foreground that have to be subtracted, but they could also indicate the presence of things that can’t be described within the standard model. Cosmology is now a mature and (perhaps) respectable science: the coming together of theory and observation in the standard concordance model is a great advance in our understanding of the Universe and how it works. But it should be remembered that there are still many gaps in our knowledge. We don’t know the form of the dark matter. We don’t have any real understanding of dark energy.  We don’t know for sure if inflation happened and we are certainly a long way from being able to identify the inflaton. In a way we are as confused as we ever were about how the Universe began. But now, perhaps, we are confused on a higher level and for better reasons…

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Christmas Closure

Posted in Uncategorized with tags , , on December 23, 2008 by telescoper

Dear Readers (and Associate Professors),

I’m shortly going to be climbing aboard the Deadwood Stage (with some other faggots) in order to spend Christmas with my friends in the  North.

That means that I’ll be offline for a few days but as soon as I’ve sobered up I’ll be back with more of the random drivel that this blog is famous for.

In the meantime, I’d just like you wish anyone who reads this a very Merry Christmas and a Happy New Year or, failing that, a felicitous non-denominational yuletide.

Set ’em up, Joe!

Peter

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Silver Linings

Posted in Science Politics, The Universe and Stuff with tags on December 19, 2008 by telescoper

They say that bad news sells newspapers, so I shouldn’t be surprised with the large number of hits my previous post and the one before that about the Research Assessment Exercise has generated.

However, I heard some news today which has at least provided a bit of a silver lining and put me in a better mood for the Christmas break. My recent application for a grant to the Science and Technology Facilities Council to fund research over the next three years into departures from the concordance cosmological model has actually been selected.

Owing to a budgetary crisis, STFC grants rounds have been very competitive in recent years so I’m quite relieved to have been successful in the present dire financial context. Obviously, somebody out there seems to like what I do. Being a theorist I’m also quite cheap, which probably helped. Or maybe it was just an administrative error…

Anyway, thanks to this grant I will be able to employ a postdoctoral research assistant and spend a bit more of my time on research. It also helps fund a bit of infrastructure within the department. Overall it amounts to about £350K which sounds a lot, but is actually quite small by the standards of particle physics and astronomy grants. STFC isn’t actually Tesco but every little helps.

All I have to do now is convince a potential postdoc to come and work with me in the 35th 22nd best Physics department in the country. What could be simpler?

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The Authorized Version

Posted in Science Politics with tags , on December 18, 2008 by telescoper

Following on from my previous post about the 2008 Research Assessment Exercise, I’ve been told that Cardiff University’s preferred measure of research activity is not the simple grade point average that I computed there, but an index of research power which is the average multiplied by the number of staff submitted.

Partly out of interest and partly so as not to incur the wrath of the University Thought Police I recalculated the list sorted by the official measure. So here is the authorized version, as sanctioned by the powers that be:

1. University of Cambridge 402.6
2. University of Oxford 371.3
3. Imperial College London 348.7
4. University College London 277.8
5. University of Manchester 215.3
6. University of Durham 191.1
7. University of Edinburgh 169.4
8. University of Warwick 132.6
9. University of Nottingham 126.7
10. University of Glasgow 125.8
11. Queen’s University Belfast 125.0
12. University of Bristol 121.9
13. University of Southampton 120.0
14. University of Birmingham 117.7
15. University of Leicester 114.8
16. University of St Andrews 91.8
17. University of Liverpool 91.7
18. University of Leeds 90.5
19. Queen Mary, University of London 87.5
20. University of Sheffield 86.6
21. Lancaster University 76.6
22. Cardiff University 75.9
23. University of Exeter 75.6
24. University of Strathclyde 74.4
25. University of Hertfordshire 72.8
26. Royal Holloway, University of London 71.3
27. University of Surrey 69.4
28. University of York 67.6
29. University of Bath 57.6
30. University of Sussex 54.0
31. Swansea University 52.9
32. Heriot-Watt University 51.7
33. University of Central Lancashire 51.1
34. Loughborough University 41.9
35. King’s College London 41.8
36. Liverpool John Moores University 39.6
37. Aberystwyth University 35.7
38. Keele University 22.5
39. Armagh Observatory 16.9
40. University of the West of Scotland 6.7
41. University of Kent 6.6
42. University of Brighton 2.3

Well, it’s actually quite surprising how much things change. I don’t think it means very much, but 22nd certainly sounds much better than 35th.

But, being a Newcastle United supporter, I’ve never been a great fan of league tables.

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Res Judicata

Posted in Science Politics with tags , , , , on December 18, 2008 by telescoper

Today is the day people working in British Universities have waited for in a mixture of hope and apprehension for several years. The results of the 2008 Research Assessment Exercise (RAE) were published at 0.01am GMT today (18th December).

I had a look just after midnight and the webserver crashed, but only for a few minutes and I soon got back in and found the bad news. The relevant one for me as an astrophysicist is the table for Unit of Assessment 19 which is Physics & Astronomy. Results are given as a list of numbers, consisting of the number of staff entered (not necessarily an integer, for accounting reasons) followed by the percentage of work judged by the panel to be in each of four categories explained in the following excerpt from the RAE website

The quality profiles displayed on this website are the results of the 2008 Research Assessment Exercise (RAE2008), the sixth assessment in this current format of the quality of research conducted in UK Higher Education Institutions (HEIs). The UK funding bodies for England, Northern Ireland, Scotland and Wales will use the RAE2008 results to distribute funding for research from 2009-10.

The results follow an expert review process conducted by assessment panels throughout 2008. Research in all subjects was assessed against agreed quality standards within a common framework that recognised appropriate variations between subjects in terms of both the research submitted and the assessment criteria.

Submissions were made in a standard form that included both quantitative and descriptive elements. Full details of the contents of, and arrangements for making, submissions were published in ‘Guidance on submissions‘ (RAE 03/2005).

The RAE quality profiles present in blocks of 5% the proportion of each submission judged by the panels to have met each of the quality levels defined below. Work that fell below national quality or was not recognised as research was unclassified.

4* Quality that is world-leading in terms of originality, significance and rigour.
3* Quality that is internationally excellent in terms of originality, significance and rigour but which nonetheless falls short of the highest standards of excellence.
2* Quality that is recognised internationally in terms of originality, significance and rigour.
1* Quality that is recognised nationally in terms of originality, significance and rigour.
Unclassified Quality that falls below the standard of nationally recognised work. Or work which does not meet the published definition of research for the purposes of this assessment.

The ‘international’ criterion equates to a level of excellence that it was reasonable to expect for the UOA, even though there may be no current examples of such a level in the UK or elsewhere. It should be noted that ‘national’ and ‘international’ refer to standards, not to the nature or geographical scope of particular subjects.

For my own department, the School of Physics & Astronomy, at Cardiff University, I found the following

Cardiff University (32.30) 5 45 30 20

which means that we entered 32.30 people, but only 5% of the work was judged to be at the top level (4*), 45% at 3*, 30% at 2* and 20% at 1*. On their own these figures don’t mean very much but one can do a quick comparison with the rest of the table to see that for us this is an enormous disappointment. We have a much lower fraction of 4* than the majority of departments, and also a significantly higher fraction of 1*. These findings are very worrying.

If I were working an English University with these results I would be very concerned about their financial implications, but it’s a bit more complicated with us being here in Wales. The numbers given in the table are translated into money by the funding councils and Wales has its own one of these (HEFCW, different from the English HEFCE). There are many fewer physics departments in Wales and we’re not competing with the bigger English ones for funding. We don’t yet know how much our research funds will be cut. It might not be as bad as if we were in England, but it’s clearly not good. We won’t know how much dosh will be involved until March 2009. t’s not just a matter of funding, it’s also the national and international perception of the department in the physics community.

I can see there will be a post mortem to find out what went wrong, as most of us were confident of a much better outcome. Perhaps the format of the RAE (focussing on research papers as the measure of output) is not favourable to a department with so many instrument builders in it?

But with the economy in deep recession making further cuts in research funding likely in the future, and our major external funder (STFC) already struggling to make ends meet, this poor showing in the RAE this has cast a gloomy shadow over Christmas.

Of course many places did much better, including my old department at Nottingham which has

University of Nottingham (44.45) 25 40 30 5

which can be interestingly compared with Cambridge, who have

University of Cambridge (141.25) 25 40 30 5

You can see that apart from the different numbers of staff the profile is exactly the same. I’m sure their publicity machine will pick up on this so I won’t be the last to mention it! Well done, Nottingham!

It will be interesting to see what the newspapers make of the new RAE results. They are significantly more complicated than previous versions which just gave a single number. The scope for flexibility in generating league tables is clearly greatly enhanced by this complexity so we can bet the hacks will have a field day. I thought I’d get a headstart by doing a straightforward ranking using a simple weighted average using 4=4*, 3=3*, etc and then sorting them by the average thus obtained:

1. Lancaster University 2.9
2. University of Bath 2.85
3. University of Cambridge 2.85
4. University of Nottingham 2.85
5. University of St Andrews 2.85
6. University of Edinburgh 2.8
7. University of Durham 2.75
8. Imperial College London 2.75
9. University of Sheffield 2.75
10. University College London 2.75
11. University of Glasgow 2.75
12. University of Birmingham 2.7
13. University of Exeter 2.7
14. University of Sussex 2.7
15. University of Bristol 2.65
16. University of Liverpool 2.65
17. University of Oxford 2.65
18. University of Southampton 2.65
19. Heriot-Watt University 2.65
20. University of Hertfordshire 2.6
21. University of Manchester 2.6
22. University of Warwick 2.6
23. University of York 2.6
24. King’s College London 2.55
25. University of Leeds 2.55
26. University of Leicester 2.55
27. Royal Holloway, University of London 2.55
28. University of Surrey 2.55
29. Swansea University 2.55
30. Queen Mary, University of London 2.5
31. Queen’s University Belfast 2.5
32. Loughborough University 2.45
33. Liverpool John Moores University 2.4
34. University of Strathclyde 2.35
35. Cardiff University 2.35
36. University of Brighton 2.3
37. University of Central Lancashire 2.3
38. Keele University 2.25
39. Armagh Observatory 2.25
40. University of Kent 2.2
41. Aberystwyth University 1.95
42. University of the West of Scotland 1.8

So you can see we are languishing at 35th place out of 42.

This is supposed to be the last RAE and we don’t know what is going to replace it. I don’t at all object to the principle that research funding should be peer-assessed but this particular exercise was enormously expensive in the effort spent at Universities preparing for it, not to mention the ridiculous burden placed on the panel of having to read all those papers.

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Crucial Verbalism

Posted in Crosswords, Literature with tags , , , , , on December 13, 2008 by telescoper

It’s a cold and rainy day and I’m lacking the inspiration to do anything energetic before making dinner, so I thought I’d pick something to blog about. Looking back over the past three months or so, I realise I’ve at least mentioned most things that I’m interested in, at least those that I’m willing to write about on here. But there is one other thing I haven’t covered yet and which I spend a lot of my spare time doing (especially during seminars) and that is solving cryptic crossword puzzles. In fact I simply can’t put a crossword down until I’ve solved all the clues, behaviour which I admit is bordering on the pathological. Still, I think of it as a kind of mental jogging, forcing your brain to work in unaccustomed ways is probably good for its fitness for other more useful things.

I can’t remember when I first started doing these, or even how I learned to do them. But then people can learn languages simply by picking them up as they go along so that’s probably how I learned to do crosswords.

If you’ve never done one of these puzzles before, you probably won’t understand the clues at all even if you know the answer and I can’t possibly explain them in a single post. In a nutshell, however, they involve clues that usually give two routes to the word to be entered in the crossword grid. One is a definition of the solution word and the other is a subsidiary cryptic allusion to it. Usually the main problem to be solved involves the identification of the primary definition and secondary cryptic part, which are usually heavily disguised.

The secondary clue can be of many different types. The most straightforward just exploits multiple meanings. For example, take

Fleeces, things often ordered by men of rank [6]

The answer to this is RIFLES which is defined by “fleeces” in one sense, but “men of rank” (soldiers) also order their arms hence giving a different meaning. Other types include puns, riddles, anagrams, hidden words, and so on. Many of these involve an operative word or phrase instructing the solver to do something with the letters in the clue, e.g.

Port’s apt to make you steer it erratically [7]

has the solution TRIESTE, which is an anagram of STEER+IT, port being the definition.

Most compilers agree however that the very best type of clue is of the style known as “&lit” (short for “and literally what it says”). Such clues are very difficult to construct and really beautiful when they work because both the definition and cryptic parts comprise the same words read in different ways. Here’s a simple example

The ultimate of turpitide in Lent [5]

which is FEAST. Here we have “e” as the last letter of turpitude in “fast” (lent) giving “feast” but a feast is exactly what the clue says too. Nice.

Some clues involve more than one element of this type and some defy further explanation altogether, but I hope this at least gives you a clue as to what is involved.

Cryptic crosswords like the ones you find in British newspapers were definitely invented in the United Kingdom, although the crossword itself was probably born in the USA. The first great compiler of the cryptic type used the pseudonym Torquemada in the Observer. During the 1930s such puzzles became increasingly popular with many newspapers, including famously The Times, developing their own distinctive style. People tend to assume that The Times crossword is the most difficult, but I’m not sure. I don’t actually buy that paper but whenever I’ve found one lying around I’ve never found the crossword particularly hard or, more importantly, particularly interesting.

As a Guardian reader, I have to say I enjoy their crosswords best, primarily because each day brings a different setter each of which has a different style to the others. Unlike some other newspapers they are not anonymous, but identified by a weird and wonderful collection of pseudonyms (Janus, Rufus, Shed, Logodaedalus, Gordius, Chifonie, Paul, Quantum, Brummie, etc). The best of them is the great Araucaria (whose name comes from the Monkey-Puzzle tree) and who is revered by crossword fans the length and breadth of the country for the brilliance of his clues. Araucaria is such a witty compiler that his clues often have you laughing out loud when you see how they fall into place. He is, in fact, a retired clergyman called John Graham who has been setting clues for the Guardian and other newspapers and magazines for over forty years. In fact, the Financial Times has a compiler called Cinephile who is the same person. (CINEPHILE is an an anagram of CHILE PINE, which is another word for the Monkey-Puzzle tree).

As it happens, today’s Guardian prize crossword was by Araucaria and, as usual, it was fun although it wasn’t as difficult as many of his. He followed a common tactic of connecting several clues together but as soon as you realise that

Writers’ relation to 10, maybe [6]

is BRONTE (note the position of the apostrophe indicating several writers with the same name, cryptic part is “bro” for relation and an anagram of “ten”) then the various references to the Brontes were straightforward. The only really difficult other clue is

Picture rhyme for MC in MND [10]

the answer to which is ILLUSTRATE (MND is Midsummer Night’s Dream, which explains the rhyme reference to PHILOSTRATE, a character in that play).

I also like to do the bi-weekly crossword set by Cyclops in Private Eye which has clues which are not only clever but also laced with a liberal helping of lavatorial humour and topical commentary which is right up my street. Many of the answers (“lights” in crossword parlance) are quite rude, such as

Local energy source of stress for Bush [5]

which is PUBES (“pub” from “local”+ E for energy +S for “source of stress”; Bush is the definition).

On Saturdays the Guardian crossword involves a prize so I religiously send my completed grid in the post. There are many hundreds of correct entries per week so it’s quite unlikely to win – the winner is drawn “at random” from all the correct entries. I’ve won the prize nine times over the years, an average of once every two years or so, with the result that I now have more dictionaries than I know what to do with. I don’t actually think a dictionary is a very good prize for a crossword puzzle, as surely every solver has one already! A few years ago The Guardian used to offer fancy fountain pens and watches, which are more like it. I also won a digital radio from the Financial Times puzzle, but I’ve got out of the habit of doing that one nowadays. The same is true for Salamanca in the New Statesman, which I won a couple of times years ago but have stopped doing since I lost interest in the rest of the magazine. I send off the answers to the Eye crossword every time but have never won it yet. That one has a cash prize of £100.

Anyway, Torquemada, who I mentioned above, was eventually followed as the Observer’s crossword compiler by the great Ximenes (real name D.S. Macnutt) who wrote a brilliant book called the Art of the Crossword which I heartily recommend if you want to learn more about the subject.

One of the nice stories in his book concerns the fact that crossword puzzles of the cryptic type were actually used to select recruits for British Intelligence during the Second World War, but this had a flip side. In late May 1944 the chief crossword setter for the Daily Telegraph was paid a visit by some heavies from MI5. It turned out that in a recent puzzle he had used (quite innocently and by sheer coincidence) the words MULBERRY, PLUTO, NEPTUNE and OVERLORD all of which were highly confidential code words to be used for the forthcoming D-Day invasion…

The current Observer crossword setter is the estimable Azed (real name Jonathan Crowther) who follows in the footsteps of his predecessor Ximenes. On balance I think this is consistently the best crossword I have ever done, although it is often a source of total frustration because it is quite convoluted and idiosyncratic. It is a bit different from other puzzles because it doesn’t involve any black squares like you would find in the standard `Everyman’ type of grid. This makes a very dense and intricate task for the solver, but does have the advantage that clues intersect more frequently than in the usual type. The problem with solving Azed is usually getting started as the clues are quite difficult and the words often very obscure. The one concession is that all answers are usually in the Chambers dictionary, and if they aren’t the compiler gives another hint. I’ve been tackling Azed for so long now that the Chambers has become in my mind a much more definitive dictionary than the OED. I also have several copies at home in different rooms, and one in my office at work.

Solving the Azed puzzle is hard enough, but for the special competition puzzles every four weeks one also has to supply a clue of one’s own. The winners of this competition are selected by Azed himself and there is an archive on the web of successful clues. As well as the winner of each competition, there is an annual prizewinner who produces the most good clues over the set of 13 competitions each year, and a roll of honour of all contributed clues that are deemed worthy. I’ve gradually clawed my way up this league table from 118th in 2006-7 to 46th in 2007-8 and, after four of the thirteen rounds this year, I’m currently in 28th place. I have to admit though that I am envious of the talents of many of the other competitors who routinely produce brilliant clues that even my best ones can’t compete with. For the same reasons that I don’t really enjoy setting examination questions, I don’t really like writing clues as much as solving them. My position in the roll of honour belies the fact that I’ve never produced a single clue that has won any of the individual competitions. I’m always the bridesmaid. You can find some of my more successful clues on the archive here.

Among those who have done exceedingly well in this competition over the years are the novelist Colin Dexter (in the form of N.C. Dexter) and a chap called C.J. Morse who is in fact the man that provided the name Dexter used for the crossword-loving chief Inspector in his famous detective novels. In turns out that C.J. Morse recently had his eightieth birthday and, as a special present, last Sunday’s Azed puzzle included some of his competition clues, which are real crackers. I won’t repeat them here though as you can find them all on the archive. However, solvers were invited to submit a clue to the word MORSE for the purposes of the competition, so at least I can tell you what my attempt was. Here we go:

His signal art no astronomer can comprehend [5]

By way of explanation, anagram of “astronomer” can give “morse” plus “art no”; comprehend is used in the slightly unusual sense of “comprise”; signal in the sense of “remarkable” plus reference to Morse system of signals. In the context of this puzzle, to celebrate the skills of Mr Morse, I also think this overall qualifies as an “&lit”.

I doubt if it competes with the best of the entries but I’m still quite proud of it.

10 Comments »

Misplaced Confidence

Posted in Bad Statistics, The Universe and Stuff with tags , , , on December 10, 2008 by telescoper

From time to time I’ve been posting items about the improper use of statistics. My colleague Ant Whitworth just showed me an astronomical example drawn from his own field of star formation and found in a recent paper by Matthew Bate from the University of Exeter.

The paper is a lengthy and complicated one involving the use of extensive numerical calculations to figure out the effect of radiative feedback on the process of star formation. The theoretical side of this subject is fiendishly difficult, to the extent that it is difficult to make any progress with pencil-and-paper techinques, and Matthew is one of the leading experts in the use of computational methods to tackle problems in this area.

One of the main issues Matthew was investigating was whether radiative feedback had any effect on the initial mass function of the stars in his calculations. The key results are shown in the picture below (Figure 8 from the paper) in terms of cumulative distributions of the star masses in various different situations.

untitled

The question that arises from such data is whether these empirical distributions differ significantly from each other or whether they are consistent with the variations that would naturally arise in different samples drawn from the same distribution. The most interesting ones are the two distributions to the right of the plot that appear to lie almost on top of each other.

Because the samples are very small (only 13 and 15 objects respectively) one can’t reasonably test for goodness-of-fit using the standard chi-squared test because of discreteness effects and because not much is known about the error distribution. To do the statistics, therefore, Matthew uses a popular non-parametric method called the Kolmogorov-Smirnov test which uses the maximum deviation D between the two distributions as a figure of merit to decide whether they match. If D is very large then it is not probable that it can have arisen from the same distribution. If it is smaller then it might have. As for what happens if it is very small then you’ll have to wait a bit.

This is an example of a standard (frequentist) hypothesis test in which the null hypothesis is that the empirical distributions are calculated from independent samples drawn from the same underlying form. The probability of a value of D arising as large as the measured one can be calculated assuming the null is true and is then the significance level of the test. If there’s only a 1% chance of it being as large as the measured value then the significance level is 1%.

So far, so good.

But then, in describing the results of the K-S test the paper states

A Kolmogorov-Smirnov (K-S) test on the …. distributions gives a 99.97% probability that the two IMFs were drawn from the same underlying distribution (i.e. they are statistically indistinguishable).

Agh! No it doesn’t! What it gives is a probability of 99.97% that the chance deviation between the two distributions is expected to be larger than that actually measured. In other words, the two distributions are surprisingly close to each other. But the significance level merely specifies the probability that you would reject the null-hypothesis if it were correct. It says nothing at all about the probability that the null hypothesis is correct. To make that sort of statement you would need to specify an alternative distribution, calculate the distribution of D based on it, and hence determine the statistical power of the test. Without specifying an alternative hypothesis all you can say is that you have failed to reject the null hypothesis.

Or better still, if you have an alternative hypothesis you can forget about power and significance and instead work out the relative probability of the two hypotheses using a proper Bayesian approach.

You might also reasonably ask why might D be so very small? If you find an improbably low value of chi-squared then it usually means either that somebody has cheated or that the data are not independent (which is assumed for the basis of the test). Qualitatively the same thing happens with a KS test.

In fact these two distributions can’t be thought of as independent samples anyway as they are computed from the same initial conditions but with various knobs turned on or off to include different physics. They are not “samples” drawn from the same population but slightly different versions of the same sample. The probability emerging from the KS machinery is therefore meaningless anyway in this context.

So a correct statement of the result would be that the deviation between the two computed distributions is much smaller than one would expect to arise from two independent samples of the same size drawn from the same population.

That’s a much less dramatic statement than is contained in the paper, but has the advantage of not being bollocks.

3 Comments »

Operation Skyphoto

Posted in The Universe and Stuff with tags , on December 9, 2008 by telescoper

Katherine Blundell from Oxford just contacted me with a request that I post the following message. I’m more than happy to oblige.

Dear All,

There is a one-off opportunity to buy vintage prints of the original photographic plates of the Palomar All-Sky Survey. Although no longer useful for science (they fell into disuse two decades ago because of modern data digitization) they make rather handsome objets d’art when suitably mounted and framed.

These prints are for sale to raise money for Alexander Thatte’s treatment for leukemia – Alexander is the 5-year old son of two of our colleagues.

The mounted/framed photographs could make very nice Christmas presents. For a small additional payment we can deliver them to you already tastefully gift-wrapped.

A very limited number of photographs have kindly been signed by Jocelyn Bell Burnell – please email us if you wish to request one of these.

Please see http://www.physics.ox.ac.uk/skyphoto for an order form and further details. Please feel free to forward this email to anyone whom you think might be interested in purchasing a piece of astronomical history, and helping a child in need.

Best wishes,

Katherine & the Astro Grads

I can’t think of a better Christmas gift for an astronomer.

Go on. You know you want to.

If you leave it too late to buy your presents you might end up buying something really naff. Like a paperweight.

Look, I’ve even made it easier for you. Just click the link here.

So now there’s no excuse. Do it. Buy one. Now.

1 Comment »

Una Grande Vociaccia

Posted in Music, Opera with tags , , , , , , , on December 7, 2008 by telescoper

I missed an important anniversary this week. Had she still been alive, December 2nd 2008 would have been the 85th birthday of the most renowned opera singer of her time, Maria Callas.

She was born in 1923 in New York city of Greek parents who had moved there the previous year, and christened Maria Anna Sofia Cecilia Kalogeropoulou. Disenchanted with her deteriorating marriage, her mother abandoned her husband and took Maria and her sister back to Athens in 1937. Maria enrolled at the National Conservatoire of Greece the same year after winning a scholarship with the quality of her voice, which

was warm, lyrical, intense; it swirled and flared like a flame and filled the air with melodious reverberations.

At this age, Maria was a rather plump young lady with a rather deep voice. Initially, she aspired to be a contralto but at the Conservatoire she was encouraged instead to become a dramatic soprano. Accordingly, she underwent special training to raise her natural pitch (or tessitura) and learned how to control her remarkable voice more accurately so she could sing in a sufficiently disciplined fashion that she could take on the dazzling coloratura passages that she would perform in later years with such success. She also worked on her chest tones to broaden the scope of her voice in the mezzo region. Although she became more technically refined as a singer during this period, there were some things that didn’t change. One was the sheer power of her voice, which is something that we tend to notice less in these days of microphones and studio recordings. People who heard her sing live confess to being shocked at the sheer scale of sound she could deliver without amplification. Perhaps more tellingly, she eschewed many of the devices sopranos tended to use to control the highest notes, usually involving some alteration of the throat to produce accuracy at the expense of a thinner and more constricted tone. When Callas went for a high note, she always did so in a full-throated manner. This often produced a piercing sound that could be intensely dramatic, even to the extent of almost knocking you out of your seat, but it was a very risky approach for a live performance. Audiences simply weren’t used to hearing a coloratura sing with such volume and in such a whole-hearted way. It wasn’t always pretty, but it was certainly remarkable and often very moving. It was this aspect of her voice that led her friend Tito Gobbi (who sang with her in Tosca) to call it una grande vociaccia, which I translate in my schoolboy Italian as meaning something like “a big ugly voice”. That isn’t meant to be as disparaging as it sounds (Gobbi was a great admirer of Callas’ singing).

Having listened to lots of recordings of Maria Callas I have to admit that they are certainly not all good. Sometimes the voice didn’t come off at all. Unkindly, one colleague said that she “sang with her ovaries”. When she talked about her own noice, Callas herself often referred to it as if it were some independent creature over which she had very little control. Anyway, whatever the reason, when she was bad she was definitely bad. But I adopt the philosophy that one should judge artists (and scientists, for that matter) by their best work rather than their worst, and when Callas was good she was simply phenomenal, like a sublime and irresistible force of nature. That’s why they called her La Divina.

Although her talent was very raw in the beginning there was no question that she always had a voice of exceptional power and dramatic intensity. When she started singing professionally she immediately attracted lavish praise from the critics not just for her voice but also for her acting. As a young soprano she sang in an astonishing variety of operas, including Wagner‘s Tristan und Isolde and Die Walküre, neither of which one would now associate with Callas.

It was in the late 194os that Callas began to take an interest in the type of opera that would really make her name. Bel canto opera was rather unfashionable at that time, probably because audiences preferred the grittier and more realistic verismo style. Virtually single-handed, Callas resurrected the bel canto canon by injecting a true sense of drama into works which had previously just been seen as vehicles for the singers to demonstrate their art. Callas brought an entirely new dimension to the great operas by Bellini (Norma, I Puritani, La Somnambula…) and Donizetti (Lucia di Lammermoor, Anna Bolena), although she was sufficiently versatile to also perform brilliantly in the verismo syle of Verdi and Puccini as well as lesser known composers such as Giordano (Andrea Chenier). Recordings of many of these performances are available, but it is sad that this glorious period of her singing career happened just a bit before high quality equipment was available so the true glory of her voice isn’t always evident.

In 1953, Callas decided that she wanted to change her appearance, perhaps so she would look more appropriate for the parts she was playing on stage. At the time she weighed almost 200lbs. In order to lose weight as quickly as possible, she followed the barbarous but highly effective expedient of swallowing a tapeworm. She lost 80lbs in a matter of months. The dramatic loss of weight changed her body and her face, emphasizing her high angular cheekbones and giving her a striking look very well suited to the opera stage. But it also affected her voice somewhat, especially at the upper end where she seems to have found it more difficult to avoid the dreaded “wobble” which was one of the alleged imperfections that critics tended to dwell upon.

Callas also had very poor eyesight which required her to wear very thick spectacles in order to see at all, a thing she refused to do onstage with the result that she was virtually blind during performances. In fact, during a performance of Tosca at Covent Garden she leant too far over a candle and her hair caught fire. Improvising magnificently, Tito Gobbi, as the loathsome Scarpia, extinguished the fire by throwing water at her before the audience had noticed. Although they weren’t much use for seeing with, her eyes were a great asset for her acting, in turns flashing like a demon then shining like an angel.

After her weight loss, Callas was suddenly no longer just a wonderful singer but also a strikingly beautiful woman. Her career took a back seat as she started to revel in the glamorous lifestyle that opened up in front of her. Her voice deteriorated and she performed rather less frequently. Eventually she embarked on a love affair with Aristotle Onassis, a notorious serial collector of trophy women. She hoped to marry him but he abandoned her to marry Jackie Kennedy, widow of John F. Kennedy.

She never really recovered from the failure of this affair, retired from singing and lived out the last years of her life as a virtual recluse in her apartment in Paris. She died in 1977.

I had heard a lot about Maria Callas when I was younger, but the recordings that I listened to (generally from the 1960s) were really not very good as her voice was undoubtedly much diminished by then. I just assumed that, as is the case with many artists, the legend of Callas was all mere hype. Then, about fifteen years ago, I was listening to BBC Radio 3 and they played the final scenes of the great 1954 recording of Norma with Callas in the title role, conducted by Tullio Serafin. I was completely overwhelmed by it and tears flowed freely from my eyes. I’ve always had a tendency to blub when I hear really beautiful music, but as I’ve got older I’ve learned not to be embarrassed by it. At least I don’t cry at football matches.

In England, Callas is probably best remembered for her performances in Tosca in Covent Garden. I have recordings of her in that role and they are really wonderful. But there are many fine recordings of Tosca by other singers, some of which are almost as good. In the case of Norma, though, there isn’t any other performance that comes within a mile of the Callas version. Or if there is, I’ve yet to hear it.

Now I know that there are some people, even opera lovers, who just don’t get Callas at all (just look at the comment boards on Youtube). I grant that she wasn’t always the most accurate singer, and I don’t think you could say her voice had a purely classical beauty. But even if you don’t like her voice you have to admit that she revitalized the opera stage and brought a new public into the theatres. I can’t imagine what the state of opera would be now, if there hadn’t been a Callas and you can’t argue that she is now an iconic figure. What I admire most about her is that, like it or loath it, her voice is instantly recognisable. In this sense, she always puts me in mind of a kind of operatic version of Billie Holliday. She’s a far cry from the many bland mediocrities that pass themselves off as opera singers nowadays.

I’m going to end with the obligatory clips from Youtube. There’s a lot of Callas on there, not all of it good. I’ve chosen a couple of items, although neither of them has a proper video. The first was performed live in 1955 in front of the notoriously difficult audience at La Scala in Milan and recorded from a radio broadcast so that the sound quality is quite poor. A studio recording of this aria, from Andrea Chenier, features most movingly in the film Philadelphia. This live version, however, is notable for a number of reasons. One is that you get some idea of the power of the Callas voice in the way she pushes aside the entire orchestra and is even able to cut through the distortions introduced by the rather primitive recording technology. The second thing is that she sings it so beautifully, with such feeling, lovely phrasing, and so much colour and vitality. Listen to the way the texture of her voice matches perfectly her changing emotions as she tells her story. The shattering, climactic high C that occurs near the end is a perfect example of what I was saying above. She stabs this note out like her life depended on it. It sends shivers down my spine and clearly had the same effect on the audience. The thunderous applause that follows the end of this aria is quite frightening in its intensity, but gives a good idea how much her public adored her. If you can put up with the lo-fi recording, this is certainly a better performance than the studio version.

The final piece has to be from Norma. I think Bellini is a wonderful composer of opera, but he doesn’t make life easy for the singers. There’s never any doubling of the vocal line by the orchestra so the singer is very exposed. This doesn’t bother Maria Callas. This is the famous aria Casta Diva, which has become a kind of signature tune for her and it’s one of the pieces that she always seemed to perform beautifully. It might be a bit hackneyed but I love it and, after all, it’s my blog. There’s also a nice compilation of pictures.

I’d be interested to hear what the general opinion of Callas is based on a sample of the two or three people who read my blog, so please feel free to add your comments!

16 Comments »

Pluralia Tantum

Posted in Literature, Pedantry with tags , , , on December 5, 2008 by telescoper

Meanwhile, over on the e-astronomer, Andy Lawrence recently posted an item about the lamentable tendency of astronomers to abuse the English language. The focus of his venom was “extincted”, a word used by many astro-types as an adjective to describe the state of affairs when light from a source (e.g. a quasar) has suffered “extinction” by intervening matter. “Extinction” is formed from the verb “extinguish” in the same way that “distinction” is formed from “distinguish”. Nobody would describe a professor as “distincted” (certainly not if it is Andy Lawrence) so, clearly, “extincted” is inappropriate. Actually if you really want to nit-pick you could object to “extinction” being applied to an object such as a  quasar, when it isn’t actually the object that is suffering from it but the light it has emitted.

But as a gripe, this is fair enough I’d say. Andy went on to encourage his legions of adoring readers to contribute their own pet hates, preferably with an astronomical orientation. My contribution was “decimate” which  means “to remove the tenth part” or “to reduce by ten percent”, from the Roman practice of punishing disobedient legions by killing every tenth man, but is often regrettably now used to mean “annihilate” or “obliterate”. You might think this hasn’t got much to do with astronomy but, sadly, it does. Indeed, a press release from STFC discussing the recent ten percent cuts to its grants budget states that consequent reduction in PDRAS

..will not cause the decimation of physics departments as has been speculated in media reports.

I would expect a civil servant to have done a bit better, so presumably this was written by an astronomer too. At any rate, it is precisely wrong.

You might argue that things like this don’t matter.  Language evolves,  and if modern usage deviates from its previous meanings then we should just let it change. I fully accept the dynamic nature of language and do not by any means object to all such changes. Society changes and so must the words we use. But if a change is (a) a result of sloppiness and (b) results in the loss of a very good use to be replaced by a bad one, then I think educated people should stand their ground and fight it. If we don’t do that language doesn’t just change, it decays.

Most of us practising scientists have to spend a lot of our time writing scientific papers, departmental memos, grant applications and even books. I think many astronomers see this activity as a chore, take no pleasure from it, and invest the minimum care on it. I was fortunate to have a really excellent writer, John Barrow, as my thesis supervisor and he convinced me that it was worth making the effort to write the best prose I could whatever the context. Not only does this attitude eliminate the ambiguity which is the bane of scientific writing. Taking pains over style and grammar also allows one to feel the pleasure of craftsmanship for its own sake. With John’s guidance and encouragement, I learned to enjoy writing through the satisfaction experienced by finding neat forms of words or nice turns of phrase. You never really feel good about what you do if you scrape through at the miminum acceptable level. Try to make the effort and you will be more fulfilled and the long hours of slog you spend putting together a complicated paper will at least be enlivened by a genuine sense of delight when things fall neatly into place, and a warm glow of achievement when you read it back and it sounds not just acceptable but actually good.

But I digress.

One of the other contributors to Andy’s list of examples of bad grammar was a chap called Norman Gray who objected to astronomers’ use of the word “data” as a plural noun, as in “the data indicate” rather than “the data indicates”. I was taken aback by this because I was expecting the opposite objection.

He has a lengthy rant about this on his own blog so I won’t repeat his arguments in detail here, merely a synopsis. The word “data” is formed from the latin plural of the word “datum” (itself formed from the past participle of the latin verb “dare”, meaning “to give”) hence meaning “things given” or words to that effect. The usage of “data” that we use now (to refer to measurements or quantitative information) seems not to have been present in roman or mediaeval times so Norman argues that it is a deliberate archaism to treat it as a latin plural now. He also argues that “data” in modern usage is a “mass noun” so should on that grounds also be treated as singular.

For those of you who aren’t up with such things, English nouns can be of two forms: “count” and “non-count” (or “mass”). Count nouns are those that can be enumerated and therefore have both plural and singular forms:  one eye, two eyes, etc. Non-count nouns (which is a better term than “mass nouns”) are those which describe something which is not enumerable, such as “furniture” or “cutlery”. Such things can’t be counted and they don’t have a different singular and plural forms. You can have two chairs (count noun) but can’t have two furnitures (non-count noun).

Count and non-count nouns require different grammatical treatment. You can ask “how much furniture do you have?” but not how many. The answer to a “how much” question usually requires a unit or measure word (e.g. “a vanload of furniture”) but the answer to a “how many” question would be just a number. Next time you are in a supermarket queue where it says “ten items or less” you will appreciate that it the sign is grammatically incorrect. “Item” is most definitely a count noun, so the correct form should be “ten items or fewer”..

Anyway, Norman Gray asserts that (a) “data” is a non-count noun and that (b) it should therefore be singular. Forms such as “the data are..” are out (“a vile anacoluthon”) and “the data is…” is in.

So is he right?

Not really.  Unkind though it may be to dismantle a carefully constructed obsession, I think his arguments have quite a few problems with them.

For a start, it seems clear to me that there are (at least) two distinct uses of the word data. One is clearly of non-count type. This is the use of “data” to describe an undifferentiated unspecified or unlimited quantity of information such as that stored on a computer disk. Of such stuff you might well ask “how much data do you have?” and the answer would be in some units (e.g. Gbytes). This clearly identifies it as a mass noun.

But there is another meaning, which is that ascribed to specified pieces of information either given (as per the original latin) or obtained from a measurement. Such things are precisely defined, enumerable and clearly therefore of count-noun form. Indeed one such entity could reasonably be called a datum and the plural would be data. This usage applies when the context defines the relevant quantum of information so no unit is required. This is the usage that arises in most scientific papers, as opposed to software manuals. “In Figure 1, the data are plotted…” is correct. Although it sounds clumsy you could well ask in such a situation “how many data do you have?” (meaning how many measurements do you have) and the answer would just be a number. Archaism? No. It’s just right.

To labour the point still further,  here are another two sentences that show the different uses:

“If I had less data my disk would have more free space on it.” (Non-count)

“If I had fewer data I would not be able to obtain an astrometric solution.” (Count).

Contrary to Norman’s claims, it is not unusual for the same words (if they’re nouns) to have both count and non-count forms in different contexts. I give the example of “whisky” as in “my glass is full of whisky” (non-count) versus “two whiskies, please, barman”. His objection to this was that in the second case a whisky is an artefact of a metonymic shift which takes the word “whisky” to refer to the glass containing it.

Metonymy involves using a word related to a thing rather than the word for thing itself, as in “I have hungry mouths to feed”; it’s not really the mouths that are fed, but the people the mouths belong to. In fact there’s a bit of this going on when people talk about sources being “extincted” rather than their light.

This invalidates the example because, Norman alleges, the resulting meaning is different. This objection is a bit silly because the whole point is that the two forms should have different meanings, otherwise why have them? In any case the  example  simply involves me asking for two well-defined quantities of whisky. I’m not convinced of the relevance of metonymy here. What I care about is the whisky, not what it comes in, and when I drink the whisky I don’t drink the glass anyway. Metonymy would apply if I talked about drinking a couple of glasses. Consider “I drank two whiskies, one after the other” versus “I drank two glasses one after the other”. In both cases what has actually been drunk?

There are countless other examples (pun intended). “Fire” can be a mass noun “fire is dangerous”) but also a count noun (“the firemen were fighting three fires simultaneously”). Another nice one  is “hair” which is non-count when it is on someone’s head (“my hair is going grey”) but count when  they, in the plural, are being split.

Interestingly, though, the  non-count forms of these nouns are all singular. Indeed, many non-count nouns exist only in the singular: such nouns are called singularia tantum. Examples include “dust” and “wealth”. So,  if we accept that “data” can be a non-count noun, does that mean that it should necessarily be treated as singular when it does take on that role?

An example that might be taken to support this view could be “statistics” (the field thereof) which is a non-count noun. Although it appears to be derived from a plural, you would certainly say “statistics is a hard subject”  rather than “statistics are a hard subject”.  On the other hand “statistics” can refer to a set, each element of which is a statistic (i.e. a number), thus giving another example of a noun that can be of either count or non-count form; you might reasonably say “the statistics are impressive” in the count case.  The non-count form “statistics” is a better  example of metonymy than the example above, as it refers to the study of the (count) statistics rather than to the things themselves.

In fact there are also mass nouns, described as pluralia tantum, which exist only in the plural. A (not entirely accurate) list is given here. Examples include scissors and pants, for which the normal measure  is a “pair”. Although these are technically non-count nouns (in the sense that you can’t have one scissor, etc) they don’t shed much light on the example in front of us. Perhaps more pertinent is the word “clothes” which is of non-count type but which is certainly plural. You can’t have one “clothe” (or any other number for that matter) but you would definitely say “your clothes are dirty”.

A more subtle example with relevance to the latin root of “data” is “media” which can refer to broadcast media (non-count) or plural of medium (count).  “The media are out to get me”  seems a correct construction to me, so the non-count form of this noun is a plurale tantum (singular of pluralia tantum).

So,  just because a word may be a non-count noun, it doesn’t necessarily have to be singular.

To summarise,  my argument is that (a) it is not correct to assert “data” is a mass noun. It may or may not be, depending on the context. If it is acting as a count noun (which I contend is the case in most science writing) then it is definitely plural. Furthermore, even in cases where it is clearly a mass noun, and especially if you reject the alternative meaning as a count noun, then  it is still by no means obvious that it must be treated as singular (because of the existence of the plurale tantum). In fact I would go a bit further and argue that you can only justify the singular non-count form at all if you accept that there is a count alternative. To be honest, though, I think I prefer the singular interpretation in the non-count case, as in “statistics”. It just sounds better.

If anyone has managed to read all the way through this exercise in pedantry I’d be interested to see any comments on my analysis of data.

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