Archive for November, 2008

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Nooks and Corners

Posted in Bute Park with tags , on November 30, 2008 by telescoper

bute-park-storyAs a subscriber to the esteemed organ Private Eye, I was delighted to see that the November 28th 2008 issue carried this article about Cardiff City Council’s disgraceful plans for Bute Park, and the bewildering behaviour of the Welsh Heritage Lottery Fund in supporting the proposal to increase the traffic of articulated lorries through it.

I understand there is to be a public meeting to discuss this on Friday December 12th, but the organizers are having some difficulty finding a representative of the Council who is willing to defend their conduct. I can’t say I’m surprised, but I also hope that it is not too late to persuade the Council to abandon their ridiculous scheme.

I have complained before about precisely the attitude noted in the Eye, namely that the Council sees its Parks mainly as venues for promotional events and other commercialised ventures, whereas I think a Park is best kept as a Park so people can enjoy a bit of Mother Nature in the middle of the City.

As it happens I walked  through Bute Park this afternoon on my way back from Cardiff Bay where I had been paying the deposit and ordering wine for a forthcoming Christmas celebration in one of the restaurants down there. It wasn’t too cold (considering it is the last day of November) primarily because there was very little wind so I walked there and back from my house, doing a little shopping on the way.

The Council gardeners have been hard at work preparing the borders and plots for the winter so these look pretty bare at the moment. The brown fallen leaves blend with the green of the lawns to produce a variegated groundscape which is very beautiful. Enough colour remains amongst the trees because of the presence of evergreens of various types thoughtfully planted amongst the deciduous trees.  On a bright day like this the lack of leaves on other trees really opens up the sightlines in the park so one gets a wonderful sense of space. The landscaping isn’t all that obvious when the woods are thick with greenery, but at this time of year through the minimal foliage the gentle undulations created by Capability Brown can be clearly seen. The Park is more spartan than in the summer, though not at all less enjoyable.

I love to see how Nature marks the passage of time like this. I would hate to live somewhere where the sun shines everyday and where the seasons offer no variety. With winter coming on there’s a sense of battening down the hatches and preparing for the tough times that might lie ahead, but also a reminder that eventually the cycle will begin again in the spring.  There’s a sense of peace that comes from being attuned to this reality that is deeply therapeutic and which, in modern life, especially in cities, is an increasingly rare experience. Please, Council, don’t take this away from Cardiff!

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Mumbai Memories

Posted in Biographical with tags , , , on November 29, 2008 by telescoper

Like many of you I’ve been following the events in Mumbai over the last few days with a mixture of shock and horror. It’s terrible to see the levels of cruelty and inhumanity that people can descend to. I doubt if we’ll ever really know what this murderous gang thought they were going to achieve when they set out on their killing spree on Wednesday evening. I’d be surprised if any of them could actually articulate their reasons for being involved, any more than a typical British soldier could explain, if asked, what they thought they were achieving by their presence in Iraq.

It’s a matter of great shame that we have become relatively hardened to the news of deaths abroad. Practically every day we hear of killings of occupying troops, insurgents, or non-combatants in Iraq or Afghanistan but we pay them little attention now. The death toll in Mumbai is now at least 195, but this is just a tiny fraction of the number of lives lost around the globe. What hits us hardest in the west is when we can no longer keep such events at a safe distance in our minds but when they strike on familiar territory, such as was the case in the London bombings. Only then do we see the horror close-up and personal. But we shouldn’t forget that in small towns we’ve never heard of all around the world many others are crying too, and probably for just as little reason.

I suppose it was inevitable that the events in Mumbai would send me wandering down memory lane. I have actually been there twice but both visits were long ago when the city was still called Bombay. I was supposed to go to India this summer too, but complications involved in moving house meant that I couldn’t go. However, I did once eat in the Cafe Leopold that the terrorists attacked in such cowardly fashion on Wednesday and I have waited for a train in the old Bombay Victoria station (now Chhatrapati Shivaji Terminus). We shouldn’t need to rely on such connections to shake off the numbness that we feel when hearing about atrocities in other places, but that’s what it’s like to be a complacent westerner.

My first trip to India was in early 1994 and I passed through Bombay on my way to and from Pune. My flight from London to Bombay arrived at about three o’clock in the morning and I was greeted outside the immigration area by a young man holding a sign with my name on it who had my train tickets from Bombay to Pune. The train didn’t leave until 6.30am so he asked me what I wanted to do until then. I said I thought I would just go to the station if it was open and wait there. He looked surprised, but said that, yes, the station was open all night. He then offered me a lift in his car as he was heading home and would be going roughly in that direction.

When we got to Bombay Victoria I realised why he had been surprised. I had assumed the station would be fairly empty and I might be able to sleep on a bench or something. When I walked into the concourse it was jam-packed with people sleeping all over the floor. I wandered in sheepishly, the only westerner to be seen, and started to look for what platform my train would be leaving from. Immediately I was surrounded by beggars – women with small babies, cripples, people with gruesome scabs and sores – all pushing me around and pleading for money. Then a teenage boy tried to lift my walkman from my pocket and I started to feel not just uncomfortable but scared.

Pretty soon, though, an official from the State Railways saw my predicament and came to my rescue. Delivering numerous clips around ears he speedily liberated me from my oppressors, took me to into a small kiosk situated on the platform, and offered me a cup of tea. It had far too much sugar in it, but I drank it anyway. He asked me where I was going, and I told him. He was initially suspicious, I think, because the primary place westerners tended to visit in Pune those days was the Ashram run by Bhagwan Shree Rasjneesh where his disciplines were encouraged to participate in unrestricted sexual activities. When I told my friend from the railways that I actually going to visit IUCAA, which at that time was run by the famous Professor Narlikar, he beamed with relief. I think he wasn’t unique amongst Indians who thought that Rasjneesh was a fraud and his disciples gullible idiots.

It turned out that the train I was to take to Pune was actually already in the station but was being cleaned. Since they cleaned the first class compartments first, I was allowed to get on the train early, about 4.30, and immediately nodded off. I only woke up when the train pulled out of the station and started on its journey up towards the Deccan plateau.

I enjoyed the journey enormously, partly because the train was slow enough to allow me to take in all the sights, and partly because I was sharing a compartment with a very friendly Indian couple (a professor of engineering and his wife). They had done the customary thing in such cases which is to consult the list of passenger names posted on the platform before the train left the station. When I woke up, they greeted me by name and introduced themselves. It was a refreshing change from London, where it is apparently forbidden to talk to strangers on a train.

I stayed about a month in Pune working with a colleague, Varun Sahni, on a lengthy article for Physics Reports. When that was over I had been invited to visit the Tata Institute for Fundamental Research in Bombay for a few days on my way home, so I got the train back to Victoria. Arriving on time, I left the train to be confronted by a crowd of small boys who tried to convince me that there were no taxis but that they would arrange one for me for a price of 200 rupees. That was way over the odds for a taxi so I laughed and said no thanks.

Proceeding out of the station to the taxi rank, I realised that they had been telling the truth. All the taxis in Bombay were on strike that day. I started to panic. How am I going to get to TIFR? Then I remembered that I was to have asked the taxi driver for “Navy Nagar Bus Stop”, which is right next to the guest house I was supposed to stay in. This is actually not far from the scenes of terrorist atrocities, but nearer the southern end of the Colaba peninsula, marked with an A on the map

I thought that if there’s a bus stop there must be a bus. I found a policeman and asked him where the buses went from. He gave me very clear directions and told me I needed the Number 11. I found the stop without much difficulty, but then there was a hitch. The buses themselves were red double-decker Routemaster types just like those you could find in London. Unfortunately, though, the numbers were written in Marathi script which I couldn’t read. Only when a bus went past did I see that the arabic numerals “11” were written on the back. A few minutes later I was joined at the bus stop by an Indian guy so I asked him if he could tell me the numbers of the buses as they came into view. He asked me where I was going, so I told him and it turned out he was going there too. Sorted.

On the bus I sat with my luggage around me and the front of the lower saloon facing backwards. All the locals peered at me like I was an exhibit in a museum, but most of them smiled. A couple of stops into the journey an old man got on wearing a scruffy coat. He looked rather poorly and had some sort of skin condition. He sat facing me and started scratching himself through his coat. I started to feel quite uncomfortable because this performance went on for some time. Then he started to unbutton his coat as if he was going to take it off. It was then that I realised the cause of his discomfort as a chicken poked its head out.

The bus was quite slow and the journey quite long so, when I finally got to the TIFR guest house, it was quite late. When I found the building, I was pleased to see my host, a physicist called TP Singh, in the lobby talking on the phone. He had his back towards me and was in the middle of a heated conversation, so I waited until he had finished before introducing myself. After a few minutes he put the phone down and turned around, so I offered my handshake and said hello.

He had a look of complete confusion on his face which gradually gave way to relief. Peter! He shouted. How did you get here? I got the bus, was my answer. It turned out he had found out in the afternoon (when I had already left Pune) that there would be no taxis so he had sent the TIFR car and driver to meet me at the station. I hadn’t seen the driver amongst the crowds and wasn’t expecting to be met anyway. In those days I didn’t have a mobile phone so there was no way of warning me about it. After scouring the station, the driver had returned to TIFR and reported that I was missing. When I had arrived at the guest house, my host had actually been on the phone to the local police in order to report me lost.

It was during this short visit of three days or so before flying back to London that I behaved as a tourist although I was guided around by students and staff from TIFR so I wasn’t herded around like a sheep. I visited the Gateway to India (right next to the Taj Mahal Hotel, scene of one of the recent terrorist outrages), ate at the Cafe Leopold, and took a boat to Elephanta Island.

Mumbai (as it is now) is an enormous city in which extreme wealth and abject poverty can be found in close proximity and where religious tensions are never far away. Riots are fairly commonplace and there are powerful grievances between the different social groups and claims of police corruption. The sheer scale of the place means that no casual visitor can hope to understand what the place is really like. But my visit there left me with an impression of a city full of energy and determination in which there is much kindness to be found below its rather scary surface.

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Gamma Plus

Posted in The Universe and Stuff with tags , on November 26, 2008 by telescoper

I’m a bit slow to blog about this but better late than never. The topic is the satellite formerly known as GLAST (which was an acronym: Gamma-ray Large Area Space Telescope) and which is now called Fermi (which isn’t an acronym, but a late and great physicist). I’ve got nothing against the change of name but I rather enjoyed seeing GLAST in titles of papers and conference talks, particularly in combination with the complementary ground-based facility HESS (another acronym: High Energy Stereoscopic System, situated in Namibia). “Astronomy with Hess and Glast” always sounded to me it should be like Astronomy with Sturm und Drang, or something like that. Astronomy with Hess and Fermi just doesn’t sound as exciting.

Anyway, Fermi was launched in June 2008 and by August had completed a quick scan of the whole sky in gamma rays with energies from 20 MeV up to 300 GeV. The main result of this quick look is that the telescope seems to work and that most of things you would expect are actually there in the gamma-ray sky, as you can see in this picture (courtesy of NASA/Fermi):

fermi0827081

As expected, the Galactic Plane shows up quite brightly in gamma rays because of the collisions between dust particles and high-energy cosmic rays. There are also a couple of supernova remnants nearby and one nearby active galaxy 3C454.3 outside our galaxy. It’s too early to say how many other sources Fermi will identify but it’s certainly a very promising start.

Actually things are looking up elsewhere in the high-energy astrophysics world too, as reported on cosmic variance recently, with a number of tantalising indications of immense potential interest discussed there. One of the exciting possibilities is that gamma ray observations might offer the chance to detect the annihilation of dark matter particles through collisions in our own Galaxy. Such collisions could chuck out gamma rays energies relating to the (unknown) mass of the dark matter particles.

For myself, I wonder if there might be any hint that the low-level fuzz in the Fermi map might give us about the apparent lopsidedness and other anomalies in the Cosmic Microwave background?

elongated

Hmm. Watch this space

PS. I hope my remarks about the name won’t set Enrico Fermi spinning in his grave. Or perhaps only half-spinning. (Geddit?)

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Popularisation or Propaganda?

Posted in Science Politics, The Universe and Stuff with tags , , , on November 25, 2008 by telescoper

I was just reading a piece by Jim Al-Khalili in today’s Guardian online science section. Jim is Professor of Physics and of Public Engagement in Science at the University of Surrey. His piece seems to have been inspired by the new appointment of Marcus du Sautoy to a similar position at Oxford University recently vacated by Richard Dawkins. His message is essentially that scientists should not only be more active in popularising science but also do more to “defend our rational, secular society against the rising tide of irrationalism”.

The legitimate interface between science and society has many levels to it. One aspect is the simple need to explain what science tells us about the world in order that people can play an informed part in our increasingly technological society. Another is that there needs to be encouragement for (especially young) people to study science seriously and to make it their career in order to maintain the supply of scientists for the future. And then there is the issue of the wider cultural implications of science, its impact on other belief-systems (such as religions) other forms of endeavour (such as art and literature) and even for government.

I think virtually all scientists would agree with the need for engagement in at least the first two of these. In fact, I’m sure most scientists would love to have the chance to explain their work to a lay audience, but not all subjects are as accessible or inspirational as, say, astronomy. Unfortunately also, not all scientists are very good at this sort of thing. Some might even be counterproductive if inflicted on the public in this way. So it seems relatively natural that some people have had more success than others, and have thus become identified as “science communicators”. Although some scientists are a bit snobby about those who write popular books and give popular talks, most of us agree that this kind of work is vital.

Vital, yes, but there are dangers. The number of scientists involved in this sort of work is probably more limited than it should be owing to the laziness of the popular media, who generally can’t be bothered to look outside London and the South-East for friendly scientists. The broadsheet newspapers employ very few qualified specialists among their staff even on the science pages so it’s a battle to get meaningful scientific content into print in the mass media. Much that does appear is slavishly regurgitated from one of the press agencies who are kept well fed by the public relations experts employed by research laboratories and other science institutes.

These factors mean that what comes out in the media can be a distorted representation of the real scientific process. Head of research groups and laboratories are engaged in the increasingly difficult business of securing enough money to continue their work in these uncertain financial times. Producing lots of glossy press releases seems to be one way of raising the profile and gaining the attention of funding bodies. Most scientists do this with care, but sometimes the results are ludicrously exaggerated or simply wrong. Some of the claims circulating around the time the Large Hadron Collider was switched on definitely fell into one or more of those categories. I realise that there’s a difficult balance to be struck between simplicity and accuracy, and that errors can result from overenthusiasm rather than anything more sinister, but even so we should tread carefully if we want the public to engage with what science really is.

Most worryingly is the perceived need to demonstrate black-and-white certainty over issues which are considerably more complicated than that. This is another situation where science popularisation becomes science propaganda. I’m not sure whether the public actually wants its scientists to make pronouncements as if they were infallible oracles, but the media definitely do. Scientists sometimes become cast in the role of priests, which is dangerous, especially when a result is later shown to be false. Then the public don’t just lose faith with one particular scientist, but with the whole of science.

Science is not about certainty. What it is a method for dealing rationally with uncertainty. It is a pragmatic system primarily intended for making testable inferences about the world using measurable, quantitative data. Scientists look their most arrogant and dogmatic when they try to push science beyond the (relatively limited) boundaries of its applicability and to ride roughshod over alternative ways of dealing with wider issues including, yes, religion.

I don’t have any religious beliefs that anyone other than me would recognize as such. I am also a scientist. But I don’t see any reason why being a scientist or not being a scientist should have any implications for my (lack of) religious faith. God (whatever that means) is, by construction, orthogonal to science. I’m not at all opposed to scientists talking about their religion or their atheism in the public domain, but I don’t see why their opinions are of any more interest than anyone else’s in these matters.

This brings us to the third of Jim’s suggestions: that more scientists should follow Richard Dawkins’ lead and be champions of atheism in the public domain. As a matter of fact, I agree with some of Dawkins’ agenda, such as his argument for the separation of church and state, although I don’t feel his heavy-handed use of the vitriol in The God Delusion achieved anything particularly positive (except for his bank balance, perhaps). But I don’t think it’s right to assume that all scientists should follow his example. Their beliefs are their business. I don’t think we will be much better off if we simply replace one set of priests with another.

So there you have my plea for scientists to accept that science will never have all the answers. There will always be “aspects of human experience that, even in an age of astonishing scientific advance, remain beyond the reach of scientific explanation”.

Can I have the Templeton Prize now please?

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Beethoven and Borge

Posted in Music with tags , on November 25, 2008 by telescoper

I still don’t seem able to shake off this cursed cold that I’ve had for nearly a week. I resorted to finding some of my favourite clips on youtube to cheer myself up. Actually these are so funny I think I’m quite likely to have a relapse. If there’s anyone else out there in the blogosphere who’s feeling a bit under the weather, I thought I’d share a couple of uplifting cultural moments with you.

The first is by the brilliantly talented musician and comedian Dudley Moore, who performs this hysterically funny parody of a Beethoven Piano Sonata. Dudley Moore was best known as a comedian and actor but music was his first love, and he was a wonderful pianist who could play lovely jazz as well as classical pieces. His only fault was probably that he never really acquired a style of his own. Playing Jazz, he usually sounded like Errol Garner and on the classical side he was much disposed to affectionate piss-takes like this. I particularly love the drawn-out ending which seems to take up about half the track! I wonder what old Ludwig Von would have thought of this? I suspect he would have loved it. Don’t believe everything you hear about Germans having no sense of humour.

The second is by the Danish comedian (yes, there are such things), Victor Borge. Playing half of Liszt’s Hungarian Rhapsody. It says on Youtube that it’s No. 2 but I think it’s great.

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Fine and Mellow

Posted in Jazz, Music with tags , on November 23, 2008 by telescoper

I’ve been off sick for the last few days with a nasty bug, but at least it’s given me the chance to listen to quite a lot of music. Yesterday, I was playing some of the classic recordings made in the 1930s by singer Billie Holiday and saxophonist Lester Young. I’ve had these for ages but for some reason haven’t listened to them for a while. Coming back to them after a long break just strengthened my belief that they are amongst the greatest recordings ever made in music of any kind.

Billie Holiday was born in Baltimore in 1915. After a grim and traumatic childhood she dabbled with prostitution and then ended up as a night club singer where she was spotted by talent scout John Hammond who arranged for her to make recordings with Benny Goodman‘s Orchestra in 1933. Most people don’t realise this but, by 1935, this band was a pop sensation on exactly the same scale as, say, the Beatles were to achieve three decades later.

In her early recording career, Billie wasn’t so well known so she was given relatively unpromising songs to sing. With her unique sense of phrasing, and a willingness to take outrageous liberties with both melody and rhythm, she turned out to be brilliant at turning this base metal into gold; some he was undoubtedly the best singer of a bad song there has ever been. If you ever get the chance to hear her versions of When you’re smiling or Back in your own Backyard you can marvel at how she manages to say everything about life and death using only the slenderest of lyrics.

Also featuring on both of these classic tracks was the tenor saxophonist Lester Young. Nicknamed “The President”, or “Prez” for short, he was one of the greatest of all Jazz musicians. He had a sublime gift for melodic improvisations, coupled to unrivalled sense of sheer swing as befits a mainstay of Count Basie‘s magnificently propulsive big band of the late 1930s. The sound of Lester Young at full throttle with the Basie Band riffing away behind him must have been truly magnificent to hear live and is thrilling enough on record.

Although he wasn’t at all averse to a bit of rabble rousing, and loved to see people dancing as he played, Lester Young’s solos on the Billie Holiday recordings mentioned above showed the delicate side of his nature. People often say is that the reason the two of them worked so well together musically was that they had similar sense of phrasing. I don’t agree with that at all. Billie Holiday’s vocal style sound to be more like a feminine version of Louis Armstrong’s, derived from a trumpeter’s mannerisms rather than those of a saxophonist.

Lester Young and Billie Holiday became very close friends during this period, although there is no sign that they had any form of sexual relationship. Rumours have circulated that Lester Young was gay, although I don’t think there’s any evidence to back them up. It is true that he had a rather eccentric and perhaps effeminate demeanour, but it seems that’s just the way he was. During the war, Lester Young was conscripted into the US Army and this had a dreadful effect on him personally and on his career, not least because he wasn’t allowed to play his saxophone at all. The strict discipline and macho posturing of the army affected this gentle and introverted man very badly and drove him to a nervous breakdown. He was eventually discharged from the army and, although he started playing again, his career never regained the heights it had reached in the 1930s. He had frequent bouts of ill health owing to alcoholism and drug abuse and his recordings from the late forties and fifties are of uneven quality.

Billie Holiday’s career was also in decline during the 1940s, after she became addicted to heroin, and she was imprisoned on drugs charges in 1947. Cigarettes, booze and hard drugs ravaged her voice and, although she made a number of classic records in the 1950s, her vocal style was sometimes mannered and self-conscious. I definitely prefer the earlier recordings which show her at her most original. That said, there was one song from George Gershwin‘s Porgy and Bess that invariably inspired her to an intensely moving performance, including this sensational recording made just five months before her death in 1959.

But the reason for putting this all on my blog was that playing through these old records I remembered when I used to listen to Humphrey Lyttelton‘s Jazz programme on the radio. He once admitted on the air that there was a TV recording involving Billie Holiday and Lester Young that he couldn’t watch without bursting into tears. The programme “Sounds of Jazz” was made by CBS Television in the United States in 1957 and features a vast array of great musicians, including Miles Davis and Thelonious Monk. But this excerpt is the bit that always got Humph going, and I don’t wonder why.

Lester and Billie had at one time been very close indeed, but had become estranged for some reason, and hadn’t recorded together for the best part of twenty years before this. Time had exacted its toll on both of them. Prez, in fact, was very ill during this broadcase and he looks it. Barely able to stand or hold the horn, when he plays he still manages to deliver a moving and poignant solo. The camera cuts to Billie’s reaction, full of tenderness and empathy and the emotional effect is overwhelming. So intense is that moment that you tend to forget the other magnificent players on this track (including Coleman Hawkins, the other leading saxophonist of the 1930s whose style was very different, but whom Lester Young deeply admired). As Nat Hentoff later recalled

Lester got up, and he played the purest blues I have ever heard, and [he and Holiday] were looking at each other, their eyes were sort of interlocked, and she was sort of nodding and half–smiling. It was as if they were both remembering what had been — whatever that was. And in the control room we were all crying. When the show was over, they went their separate ways.

Lester Young died in March 1959, a little over a year after this performance. In a taxi returning home from his funeral, Billie told a friend that she thought she would be the next. She died in July the same year.

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What about magnetic fields?

Posted in The Universe and Stuff with tags , , on November 20, 2008 by telescoper

If you’re stuck for a question to ask at the end of an astronomy seminar and don’t want to reveal the fact that you were asleep for most of it, there are some general questions that you can nearly always ask regardless of the topic of the talk without appearing foolish. A few years ago, “how would the presence of dust affect your conclusions?” was quite a good one, but the danger these days is that with the development of far-infrared and submillimetre instrumentation and the proliferation of people using it, this could actually have been the topic of the talk you just dozed through. However, no technological advances have threatened the viability of another old stalwart: “What about magnetic fields?”.

These thoughts came into my mind when I was listening to an excellent talk by Richard Ellis at the Royal Astronomical Society last Friday about the current state of play in the (very complicated) field of galaxy formation. I hasten to add that nobody there was sleeping. Well, not many.

In theory, galaxies condense out of the Big Bang as lumps of dark matter. Seeded by primordial density fluctuations and amplified by the action of gravity these are supposed to grow in a hierarchical, bottom-up fashion with little blobs forming first and then merging into larger objects. The physics of this process is relatively simple (at least if the dark matter is cold) as it involves only gravity.

But, by definition, the dark matter can’t be seen. At least not directly, though its presence can be inferred indirectly by dynamical measurements and gravitational lensing. What astronomers generally see is starlight, although it often arrives at the telescope in an unfamiliar part of the spectrum owing to the redshifting effect of the expansion of the Universe. The stars in galaxies sit inside the blobs of dark matter, which are usually called “haloes” although blobs is a better name. In art the whole purpose of a halo is that you can see it.

How stars form is a very complicated question to answer even when you’re asking about nearby stellar nurseries like the Orion Nebula. The basic idea is that a gas cloud cools and contracts, radiating away energy until it gets sufficiently hot that nuclear burning switches on and pressure is generated that can oppose further collapse. The early stages of this processs, though, involve very many imponderables. Star formation doesn’t just involve gravity but lots of other processes, including additional volumes of Landau & Lifshitz, such as hydrodynamics, radiative transfer and, yes, magnetic fields. Naively, despite the complicated physics, it might still be imagined that stars form in the little blobs of dark matter first and then gradually get incorporated in larger objects.

Unfortunately, as Richard Ellis pointed out, this naive picture doesn’t seem to work. Deep surveys of galaxies suggest that the most massive galaxies formed their stars quite early in the Big Bang and have been relatively quiescent since then, while smaller objects contain younger stars. In other words, pretty much the opposite of what one might have thought. This phenomenon (known appropriately in the time of the Credit Crunch as “downsizing”) suggests that something inhibits star formation early on in all but the largest of the largest haloes. It could be that powerful feedback from activity in the nuclear regions associated with a central black hole might do this, or it could be something a little less exotic such as stellar winds. Or it could be that the whole scheme is wrong in a more fundamental way. I personally wouldn’t go so far as to throw out the whole framework, as it has scored many successes, but it is definitely an open question what is going on.

Then I was reminded by a posting on the arxiv about an interesting paper that appeared in Nature last month by Art Wolfe and collaborators which revealed the presence of an enormously strong magnetic field in a galaxy at the relatively high redshift of 0.692. Actually it’s about 84 microGauss. OK, so this is just one object but the magnetic field in it is remarkably strong. It could be a freak occurence resulting from some kind of shock or bubble, but it does seem to fit in a pattern in which young galaxies generally seem to have much higher magnetic fields than previously expected. Obviously we need to know how many more such magnetic monsters are lurking out there.

So why are these results so surprising? Didn’t we already know galaxies have magnetic fields in them?

Well, yes we did. The Milky Way has a magnetic field with a strength of about 10 microGauss, much lower than that discovered by Wolfe et al. But the point is that if we understand them properly, galactic magnetic fields are supposed to be have been much lower in the past than they are now. The standard theoretical picture is that a (tiny) initial seed field is amplified by a kind of dynamo operating by virtue of the strong differential rotation in disk galaxies. This makes the field grow exponentially with time so that only a few rotations of the galaxy are needed to make a large field out of a small one. Eventually this dynamo probably quenches when the field has an energy density comparable to the gas in the galaxy (which is roughly the situation we find in our own Galaxy).

Hopefully you now see the problem. If the field is being wound up quickly then younger galaxies (those whose light comes to us from a long way away) should have much smaller magnetic fields than nearby ones. But they don’t seem to behave in this way. A few years ago, I wrote a paper about a model in which the galactic fields weren’t produced by a dynamo but were primordial in origin and large from the start. I might dust it off and look it again…

The mystery of the origin of galactic magnetic fields remains unsolved largely because, although we know magnetism exists, it is notoriously difficult to understand its behaviour when it is coupled to all the other messy things we have to deal with in astrophysics. It’s a kind of polar opposite of dark matter, which we don’t know (for sure) exists but which only acts through gravity so its behaviour is easier to model. This is the main reason why cosmological theorists prefer to think about dark matter rather than magnetic fields. I’d hazard a guess that this is one problem that won’t be resolved soon either. Things are complicated enough already!

It is also worth considering the possibility that magnetic fields might play a role in moderating the processes by which gas turns into stars within protogalaxies. At the very least, a magnetic field generates stresses that influence the onset of collapse. Although it is by no means obvious that they provide the required missing link between dark matter haloes and stars, we now have less excuse for continuing to ignore them.

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On First Looking into Chapman’s Homer

Posted in Poetry, The Universe and Stuff with tags , , on November 19, 2008 by telescoper

As a present to those who appear disgruntled by my comments about exoplanets here and there, this is from John Keats:

 

Much have I travell’d in the realms of gold,
    And many goodly states and kingdoms seen;
    Round many western islands have I been
Which bards in fealty to Apollo hold.
Oft of one wide expanse had I been told
    That deep-brow’d Homer ruled as his demesne;
    Yet did I never breathe its pure serene
Till I heard Chapman speak out loud and bold:
Then felt I like some watcher of the skies
    When a new planet swims into his ken;
Or like stout Cortez when with eagle eyes
    He star’d at the Pacific–and all his men
Look’d at each other with a wild surmise–
    Silent, upon a peak in Darien.
 

This famous sonnet was written in October 1816 and is considered the highlight of Keats’s first volume of poetry. It was originally a gift for his friend, Charles Cowden Clarke. The two men had spent an evening reading George Chapman’s superb 17th century translation of the Iliad and Odyssey.

Please note lines 9 and 10. I’m sure they capture the excitement of discovery although Keats probably wasn’t using the correct IAU nomenclature. I’m not sure about the bit about being “silent” either.

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Science and Stamp Collecting

Posted in Books, Talks and Reviews, The Universe and Stuff with tags , , on November 18, 2008 by telescoper

Musing over the comments posted on my (slightly ironic) blog item about exoplanetary ennui, I remembered a piece I wrote for the Times Literary Supplement last summer so I dusted it off, chopped it up, and updated it for presentation here because it expands a bit on the earlier contribution.

If the Sun were the size of a golf ball, then the Earth would be a speck of dust a few metres from it and the nearest star would be hundreds of kilometres away. And this is what it is like in the relatively crowded environment of the Milky Way. The unimaginable scale of our Universe means that astronomy has never really become an experimental science, but has largely remained an observational one, having more in common with, say, archaeology than chemistry or other laboratory-based disciplines. Consequently, even though it is perhaps the oldest science, it is also in some respects the least mature. The absence of the traditional interplay between theory and experiment, the inability to perform repeated experiments under slightly different conditions, and the sheer difficulty of measuring anything at all have stunted its development compared to younger fields. For this reason, one often finds in astronomy certain tendencies that other subjects have largely grown out of, such as an unhealthy mania for classification and nomenclature.

Taxonomy has its place within the scientific method: modern chemistry owes much to Dmitri Mendeleev‘s periodic table; botany could not have progressed without Linnaeus; and the theory of evolution was founded on Charles Darwin‘s painstaking studies on the Galapagos Islands. But arranging things in groups and giving them names does not in itself constitute scientific progress, no matter how systematically it is done. The great experimental physicist Ernest (Lord) Rutherford dismissed this kind of activity as not science but “stamp collecting”.

This brings us to the grand debate that took place in Prague in the summer of 2006 under the auspices of the International Astronomical Union. One of the problems before the IAU’s 26th General Assembly was what to do about the fact that recent investigations have revealed the presence of a number of objects orbiting the Sun that are ostensibly at least as worthy of the name “planet” as Pluto, which in our current textbooks is the ninth one out. Obviously, which objects should be called planets depends on how you define what a planet is. The solar system contains objects of all shapes and sizes, from tiny asteroids to immense gas giants such as Jupiter and Saturn. Where should one draw the line? The original proposal was to increase the number of planets to twelve by admitting some lowly new members to the club, but in the end the IAU decided to demote Pluto to the status of a “dwarf” planet thus restricting the number of true planets to eight. This was a controversial decision, at least in the United States, because the vital vote was taken on the last day of the meeting when most of the US delegates had to take flights home. Pluto was discovered by an American, Clyde Tombaugh, in 1930, so the decision deprived the nation of its only planet-discoverer.

The “no” decision hinged on the adoption of three criteria: that the object be round, i.e. have a shape determined by internal gravitational forces; that it should have cleared its own orbit of debris; and that it should be orbiting our own star, the Sun. None of these has any special scientific value; the resulting decision was therefore pretty arbitrary. Moreover, deep-space observations have led to the discovery of literally hundreds of planetlike objects orbiting other stars. These exoplanets offer much greater prospects for scientific progress into the general theory of planet formation than the few objects that happen to have formed in our particular vicinity, so why are they excluded from the definition? In any case, what have we learned scientifically from the new nomenclature? Pluto is still the same object that it was before August 2006, and astronomers still don’t understand what one can infer from its own particular properties about the general process of planet formation.

So is Pluto a planet?

Who cares? In this case there really is nothing in a name. When I was asked this question on the telephone by a reporter I gave precisely that answer and he was shocked. I’m sure he thought that all that astronomers do is look at things and give them names. There are some that do that, of course, but most of us prefer doing proper science.

In the field of exoplanet research we are seeing real signs of maturity, although current studies are still firmly rooted in the “discovery” and “classificatuion” stage. Witness last weeks press interest in the first directly imaged exoplanets. I am well aware of the immense potential that those pictures have for stimulating interest in science, but there is still a long way to go before this field reaches its prime. That probably makes it an excellent area for young scientists to work in. But ultimately this youthful exuberance should give way to something a bit more serious, which is to go beyond what these discoveries are in themselves and ask what deeper questions they might answer.

One can see many other parallels in the history of astronomy, such as the discovery of quasars in the late 1950s. The first few of these must have generated a huge amount of excitement because they were not at all understood. Within a few years hundreds had been detected by radio observations but their nature remained unknown. The subsequent identification of redshifted hydrogen emission lines in the spectra of these objects led to them eventually being identified as very distant extragalactic sources of immense intrinsic power. By the 1980s quasars were identified as a particular type of active galaxy and placed within a general classification scheme that also involved blazars, Seyfert galaxies, and so on. Nowadays we have samples of tens of thousands of quasar spectra and the interest evolves around how the activity in their nucleus relates to the process of galaxy formation in an expanding Universe and how we can use these objects to map out the large-scale distribution of matter. To an outsider these tasks may seem less glamorous that the early days of quasar research, but that’s what science is like.

At the extreme end of the distance scale of astronomical investigation lies my own field of cosmology, the scientific study of the Universe as a whole. The scale of the solar system is challenging enough, but the cosmos is really big. Until recently, cosmology was so lacking in reliable observational input that it was thought of as a flaky offshoot of astronomy, more a branch of metaphysics than a proper scientific discipline, a paradise for theoreticians whose wildest speculations stood no chance of ever being tested with real measurements. Over the past twenty years or so, however, staggering advances in astronomical instrumentation have allowed astronomers to probe the darkest depths of space, capturing light that has travelled for almost 14 billion years on its way towards us. Theories are now so tightly constrained by these observations that there is very little room for manoeuvre. From this interplay between conjecture and refutation has emerged a cosmological framework that accounts, at least in a broad-brush sense, for how the Universe is constructed and how it is evolving.

There are some important gaps, including some puzzling anomalies, and the precise nature of many of its constituents is yet to be understood, but the establishment of the “concordance model” is a sign that cosmology really has come of age.

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The Facebook of the Future

Posted in Uncategorized on November 17, 2008 by telescoper

If you’re not on facebook this won’t make any sense!

But thanks to Ed Gomez for sending it.

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