Andrew Jaffe: Leaves on the Line

Reformat

2013-04-16T23:19:48Z

Another technical note: I’ve just reformatted the whole blog. Let me know if there are any problems (or if you just think it’s ugly).

Infrastructure problems

2013-04-10T17:33:30Z

Just a quick note that the blog has been having some issues with its infrastructure: pointers to individual entries seem to be broken.

I’m on the case — apologies if you can’t get to anything you’re looking for.

Update: fixed, I think. Let me know if there are any further problems. (The blog should be a bit faster, too, as I’ve moved over to statically publishing all the pages. Don’t worry if you don’t know what that means.)

TimeWave — Quest for the Grail: An International Adventure Game

2013-04-09T22:27:22Z

About a year ago, I wrote about TimeWave a festival of art, science and technology coming this May to London, with tendrils snaking out to New York and LA.

As part of the festival, we’re organising Quest for the Grail: An International Adventure Game, later this month: from noon to 5pm in London and right afterwards, noon to 5pm in Manhattan, New York.

The London teams will “hunt for objects in Clerkenwell hotspots…from the Order of St. John to Blackfriars Bridge to the International Magic Shop. You may be looking for a charm against the Plague, a tombstone or a silver goblet. Your team may be asked to invent something - the holiest of drinks.” The game continues with New York teams searching in “Manhattan hotspots…from Clinton Castle to the tombstones of Trinity Church to the Grand Lodge of the Masons. You may be looking for a marker of a headless ghost who haunts Wall Street, a symbol of George Washington or a troll in the East Village”, aided by London players and puppetmasters overseeing the games.

Unfortunately, I’m in sunny California recovering from my winter (and many years) of Planck work, but if you’re in either city and would like to play, you can join as an individual, a half-team of five, or a full team of ten players. There’s more information on the site, or you can contact the organisers directly at grail@timewavefestival.com.

Planck 2013: the PR

2013-03-22T16:04:19Z

Yesterday’s release of the Planck papers and data wasn’t just aimed at the scientific community, of course. We wanted to let the rest of the world know about our results. The main press conference was at ESA HQ in Paris, and there was a smaller event here in London run by the UKSA, which I participated in as part of a panel of eight Planck scientists.

The reporters tried to keep us honest, asking us to keep simplifying our explanations so that they — and their readers — could understand them. We struggled with describing how our measurements of the typical size of spots in our map of the CMB eventually led us to a measurement of the age of the Universe (which I tried to do in my previous post). This was hard not only because the reasoning is subtle, but also because, frankly, it’s not something we care that much about: it’s a model-dependent parameter, something we don’t measure directly, and doesn’t have much of a cosmological consequence. (I ended up on the phone with the BBC’s Pallab Ghosh at about 8pm trying to work out whether the age has changed by 50 or 80 million years, a number that means more to him and his viewers than to me and my colleagues.)

There are pieces by the reporters who asked excellent questions at the press conference, at The Guardian, The Economist and The Financial Times, as well as one behind the (London) Times paywall by Hannah Devlin who was probably most rigorous in her requests for us to simplify our explanations. I’ll also point to NPR’s coverage, mostly since it is one of the few outlets to explicitly mention the topology of the Universe which was one of the areas of Planck science I worked on myself.

Aside from the press conference itself, the media were fairly clamouring for the chance to talk about Planck. Most of the major outlets in the UK and around Europe covered the Planck results. Even in the US, we made it onto the front page of the New York Times. Rather than summarise all of the results, I’ll just self-aggrandizingly point to the places where I appeared: a text-based preview from the BBC, and a short quote on video taken after the press conference, as well as one on ITV. I’m most proud of my appearance with Tom Clarke on Channel 4 News — we spent about an hour planning and discussing the results, edited down to a few minutes including my head floating in front of some green-screen astrophysics animations.

Now that the day is over, you can look at the results for yourself at the BBC’s nice interactive version, or at the lovely Planck Chromoscope created by Cardiff University’s Dr Chris North, who donated a huge amount of his time and effort to helping us make yesterday a success. I should also thank our funders over at the UK Space Agency, STFC and (indirectly) ESA — Planck is big science, and these sorts of results don’t come cheap. I hope you agree that they’ve been worth it.

Planck 2013: the science

2013-03-22T14:52:15Z

If you’re the kind of person who reads this blog, then you won’t have missed yesterday’s announcement of the first Planck cosmology results.

The most important is our picture of the cosmic microwave background itself:

But it takes a lot of work to go from the data coming off the Planck satellite to this picture. First, we have to make nine different maps, one at each of the frequencies in which Planck observes, from 30 GHz (with a wavelength of 1 cm) up to 850 GHz (0.350 mm) — note that the colour scales here are the same:

At low and high frequencies, these are dominated by the emission of our own galaxy, and there is at least some contamination over the whole range, so it takes hard work to separate the primordial CMB signal from the dirty (but interesting) astrophysics along the way. In fact, it’s sufficiently challenging that the team uses four different methods, each with different assumptions, to do so, and the results agree remarkably well.

In fact, we don’t use the above CMB image directly to do the main cosmological science. Instead, we build a Bayesian model of the data, combining our understanding of the foreground astrophysics and the cosmology, and marginalise over the astrophysical parameters in order to extract as much cosmological information as we can. (The formalism is described in the Planck likelihood paper, and the main results of the analysis are in the Planck cosmological parameters paper.)

The main tool for this is the power spectrum, a plot which shows us how the different hot and cold spots on our CMB map are distributed: In this plot, the left-hand side (low ℓ) corresponds to large angles on the sky and high ℓ to small angles. Planck’s results are remarkable for covering this whole range from ℓ=2 to ℓ=2500: the previous CMB satellite, WMAP, had a high-quality spectrum out to ℓ=750 or so; ground- and balloon-based experiments like SPT and ACT filled in some of the high-ℓ regime.

It’s worth marvelling at this for a moment, a triumph of modern cosmological theory and observation: our theoretical models fit our data from scales of 180° down to 0.1°, each of those bumps and wiggles a further sign of how well we understand the contents, history and evolution of the Universe. Our high-quality data has refined our knowledge of the cosmological parameters that describe the universe, decreasing the error bars by a factor of several on the six parameters that describe the simplest ΛCDM universe. Moreover, and maybe remarkably, the data don’t seem to require any additional parameters beyond those six: for example, despite previous evidence to the contrary, the Universe doesn’t need any additional neutrinos.

The quantity most well-measured by Planck is related to the typical size of spots in the CMB map; it’s about a degree, with an error of less than one part in 1,000. This quantity has changed a bit (by about the width of the error bar) since the previous WMAP results. This, in turn, causes us to revise our estimates of quantities like the expansion rate of the Universe (the Hubble constant), which has gone down, in fact by enough that it’s interestingly different from its best measurements using local (non-CMB) data, from more or less direct observations of galaxies moving away from us. Both methods have disadvantages: for the CMB, it’s a very indirect measurement, requiring imposing a model upon the directly measured spot size (known more technically as the “acoustic scale” since it comes from sound waves in the early Universe). For observations of local galaxies, it requires building up the famous cosmic distance ladder, calibrating our understanding of the distances to further and further objects, few of which we truly understand from first principles. So perhaps this discrepancy is due to messy and difficult astrophysics, or perhaps to interesting cosmological evolution.

This change in the expansion rate is also indirectly responsible for the results that have made the most headlines: it changes our best estimate of the age of the Universe (slower expansion means an older Universe) and of the relative amounts of its constituents (since the expansion rate is related to the geometry of the Universe, which, because of Einstein’s General Relativity, tells us the amount of matter).

But the cosmological parameters measured in this way are just Planck’s headlines: there is plenty more science. We’ve gone beyond the power spectrum above to put limits upon so-called non-Gaussianities which are signatures of the detailed way in which the seeds of large-scale structure in the Universe was initially laid down. We’ve observed clusters of galaxies which give us yet more insight into cosmology (and which seem to show an intriguing tension with some of the cosmological parameters). We’ve measured the deflection of light by gravitational lensing. And in work that I helped lead, we’ve used the CMB maps to put limits on some of the ways in which our simplest models of the Universe could be wrong, possibly having an interesting topology or rotation on the largest scales.

But because we’ve scrutinised our data so carefully, we have found some peculiarities which don’t quite fit the models. From the days of COBE and WMAP, there has been evidence that the largest angular scales in the map, a few degrees and larger, have some “anomalies” — some of the patterns show strange alignments, some show unexpected variation between two different hemispheres of the sky, and there are some areas of the sky that are larger and colder than is expected to occur in our theories. Individually, any of these might be a statistical fluke (and collectively they may still be) but perhaps they are giving us evidence of something exciting going on in the early Universe. Or perhaps, to use a bad analogy, the CMB map is like the Zapruder film: if you scrutinise anything carefully enough, you’ll find things that look a conspiracy, but turn out to have an innocent explanation.

I’ve mentioned eight different Planck papers so far, but in fact we’ve released 28 (and there will be a few more to come over the coming months, and many in the future). There’s an overall introduction to the Planck Mission, and papers on the data processing, observations of relatively nearby galaxies, and plenty more cosmology. The papers have been submitted to the journal A&A, they’re available on the ArXiV, and you can find a list of them at the ESA site.

Even more important for my cosmology colleagues, we’ve released the Planck data, as well, along with the necessary code and other information necessary to understand it: you can get it from the Planck Legacy Archive. I’m sure we’ve only just begun to get exciting and fun science out of the data from Planck. And this is only the beginning of Planck’s data: just the first 15 months of observations, and just the intensity of the CMB: in the coming years we’ll be analysing (and releasing) more than one more year of data, and starting to dig into Planck’s observations of the polarized sky.

Breaking the silence (updated)

2013-03-05T22:12:25Z

My apologies for being far too busy to post. I’ll be much louder in couple of weeks once we release the Planck data — on March 21. Until then, I have to shut up and follow the Planck rules.

OK, back to editing. (I’ll try to update this post with any advance information as it becomes available.)

Update (on timing, not content): the main Planck press conference will be held on the morning of 21 March at 10am CET at ESA HQ in Paris. There will be a simultaneous UK event (9am GMT) held at the Royal Astronomical Society in London, where the Paris event will be streamed, followed by a local Q&A session. (There will also be a more technical afternoon session in Paris.)

Probably more important for my astrophysics colleagues: the Planck papers will be posted on the ESA website at noon on the 21st, after the press event, and will appear on the ArXiV the following day, 22 March. Be sure to set aside some time next weekend!

Not-quite hacked

2013-02-03T18:46:10Z

This week, the New York Times, The Wall Street Journal and Twitter, along with several other news organizations, have all announced that they were attacked by (most likely) Chinese hackers.

I am not quite happy to join their ranks: for the last few months, the traffic on this blog has been vastly dominated by attempts to get into the various back-end scripts that run this site, either by direct password hacks or just denial-of-service attacks. In fact, I only noticed it because the hackers exceeded my bandwidth allowance by a factor of a few (and costing me a few hundred bucks in over-usage charged by my host in the process, unfortunately).

I’ve since attempted to block the attacks by denying access to the IP addresses which have been the most active (mostly from domains that look like 163data.com.cn, for what it’s worth). So, my apologies if any of this results in any problems for anyone else trying to access the blog.

Quantum SOLE

2013-01-29T23:39:13Z

A couple of weeks I received the Student On-Line Evaluation (SOLE) results for my Quantum Mechanics course.

There were only two specific questions, rating each of the following from “Very Good” through “Poor” (there’s a “no response” off to the right, as well):

The structure and delivery of the teaching sessions
The content of this module

The numerical results (at right) were pretty good. Note that 114 students — about half — responded.

The rest of the results are free-form comments. With such a big class it’s very difficult to find a style of teaching that suits everyone. Hence, the comments showed a split between the students who enjoyed the very mathematical approach of the course and those who wanted more physical examples from the beginning (not that easy in the context of an axiomatic approach to quantum mechanics — but there are a few simple system like quantum dots that exhibit some of the properties of the simplest systems we study in class; it’s clear that these should be highlighted more than I have). Similarly, some students wanted a more step-by-step approach to the mathematics, whereas others would prefer just a sketch of the proofs on the board (“put the algebra in the notes and let students work through it”).

But one set of comments especially hit home. Here’s a good example:

Frankly, I think that Prof. Jaffe has the potential to be an outstanding lecturer, one which he wastes by not being properly prepared. Just showing up to lectures and writing down on the board what was in (the previous lecturer’s) notes without thinking much about it in advance results in time spent staring at notes and board which could otherwise have been used to face the audience and explain what it is we’re doing. Maybe that sounded harsh, but he really is very good and could be outstanding if he put a little more into preparing for lectures and didn’t stick to his notes quite so much… If you actually perform the calculations, and think about the various steps yourself, then it all happens in a way, and at a pace, which suits us as students and allows us to follow.

(OK, I picked one that made an effort to heap on some praise along with the criticism.) I have to admit that this point, repeated by several students, seemed right on, for at least some of the lectures. I did always make an effort to go over the notes in detail beforehand. But these were notes indeed written by the previous lecturer, and this gives a few problems. Yes, I probably wasn’t always careful enough to go over the details of the mathematics beforehand. So sometimes I did spend too much effort trying to puzzle out exactly what I wanted to say (some students also complained about the occasional mistakes I made on the board, perhaps related to this). But sometimes the problem is more subtle: I might not always want to explain the concepts in the same way as the previous lecturer — and sometimes I might only realise this when actually doing the explaining! Either of these can happen in any lecture, but the combination of teaching this course for the first time, and doing so from someone else’s notes, certainly made it worse.

Next year, things will at least be different: I’ll be teaching for the second time, and so have some idea of the pitfalls from this past year. Moreover, our department is making some significant changes to the overall structure of the curriculum, phasing out our system of tutorials and so-called classworks for a series of three medium-sized (20 student) group sessions each week. This is happening alongside some specific changes to the quantum mechanics curriculum, with more material in the first year (happening already). My course will be shortened by a full five lectures, but I suspect that this combination of changes will give me a bit more breathing room, as well as a few different ways to make sure the material gets said in different ways, appropriate for different students.

Further criticism, comments, ideas, etc., are always welcome.

EBEX launched!

2012-12-29T02:11:20Z

My colleagues, friends and collaborators on the EBEX project are in Antarctica this (Northern) winter preparing the telescope for launch. And today, they did it:

EBEX Launch movie

Just beautiful. (The video is from Asad Aboobaker, whose blog EBEX in Flight is documenting the mission from the field.)

EBEX is a next-generation CMB telescope, with hundreds of detectors measuring temperature and polarisation, which we hope will allow us to see the effects of an early epoch of cosmic inflation through the background of gravitational radiation that it produces. But right now, we are just hoping that EBEX catches some good winds in the Antarctic Polar Vortex and comes back around the continent after about two weeks of observing from 120,000 feet.

Quantum debrief

2012-12-21T21:55:36Z

A week ago, I finished my first time teaching our second-year course in quantum mechanics. After a bit of a taster in the first year, the class concentrates on the famous Schrödinger equation, which describes the properties of a particle under the influence of an external force. The simplest version of the equation is just This relates the so-called wave function, ψ, to what we know about the external forces governing its motion, encoded in the Hamiltonian operator, Ĥ. The wave function gives the probability (technically, the probability amplitude) for getting a particular result for any measurement: its position, its velocity, its energy, etc. (See also this excellent public work by our department’s artist-in-residence.)

Over the course of the term, the class builds up the machinery to predict the properties of the hydrogen atom, which is the canonical real-world system for which we need quantum mechanics to make predictions. This is certainly a sensible endpoint for the 30 lectures.

But it did somehow seem like a very old-fashioned way to teach the course. Even back in the 1980s when I first took a university quantum mechanics class, we learned things in a way more closely related to the way quantum mechanics is used by practicing physicists: the mathematical details of Hilbert spaces, path integrals, and Dirac Notation.

Today, an up-to-date quantum course would likely start from the perspective of quantum information, distilling quantum mechanics down to its simplest constituents: qbits, systems with just two possible states (instead of the infinite possibilities usually described by the wave function). The interactions become less important, superseded by the information carried by those states.

Really, it should be thought of as a full year-long course, and indeed much of the good stuff comes in the second term when the students take “Applications of Quantum Mechanics” in which they study those atoms in greater depth, learn about fermions and bosons and ultimately understand the structure of the periodic table of elements. Later on, they can take courses in the mathematical foundations of quantum mechanics, and, yes, on quantum information, quantum field theory and on the application of quantum physics to much bigger objects in “solid-state physics”.

Despite these structural questions, I was pretty pleased with the course overall: the entire two-hundred-plus students take it at the beginning of their second year, thirty lectures, ten ungraded problem sheets and seven in-class problems called “classworks”. Still to come: a short test right after New Year’s and the final exam in June. Because it was my first time giving these lectures, and because it’s such an integral part of our teaching, I stuck to to the same notes and problems as my recent predecessors (so many, many thanks to my colleagues Paul Dauncey and Danny Segal).

Once the students got over my funny foreign accent, bad board handwriting, and worse jokes, I think I was able to get across both the mathematics, the physical principles and, eventually, the underlying weirdness, of quantum physics. I kept to the standard Copenhagen Interpretation of quantum physics, in which we think of the aforementioned wavefunction as a real, physical thing, which evolves under that Schrödinger equation — except when we decide to make a measurement, at which point it undergoes what we call collapse, randomly and seemingly against causality: this was Einstein’s “spooky action at a distance” which seemed to indicate nature playing dice with our Universe, in contrast to the purely deterministic physics of Newton and Einstein’s own relativity. No one is satisfied with Copenhagen, although a more coherent replacement has yet to be found (I won’t enumerate the possibilities here, except to say that I find the proliferating multiverse of Everett’s Many-Worlds interpretation ontologically extravagant, and Chris Fuchs’ Quantum Bayesianism compelling but incomplete).

I am looking forward to getting this year’s SOLE results to find out for sure, but I think the students learned something, or at least enjoyed trying to, although the applause at the end of each lecture seemed somewhat tinged with British irony.

Science as metaphor

2012-12-18T10:30:16Z

In further pop-culture crossover news, I was pleased to see this paragraph in John Keane’s review of Alan Ryan’s “On Politics” in this weekend’s Financial Times:

Ryan sees this period [the 1940s] as the point of triumph of liberal democracy against its Fascist and Stalinist opponents. Closer attention shows this decade was instead a moment of what physicists call dark energy: the universe of meaning of democracy underwent a dramatic expansion, in defiance of the cosmic gravity of contemporary events. The ideal of monitory democracy was born.

Not a bad metaphor. Nice to see that the author, a professor of Politics from Sydney, is paying attention to the stuff that really matters.

SDSS 1416+13B

2012-12-12T21:25:00Z

It’s not that often that I can find a reason to write about both astrophysics and music — my obsessions, vocations and avocations — at the same time. But the recent release of Scott Walker’s (certainly weird, possibly wonderful) new record Bish Bosch has given me just such an excuse: Track 4 is a 21-minute opus of sorts, entitled “SDSS1416+13B (Zercon, A Flagpole Sitter)”. The title seems a random collection of letters, numbers and words, but that’s not what it is: SDSS1416+13B is the (very slightly mangled) identification of an object in the Sloan Digital Sky Survey (SDSS) catalog — 1416+13B means that it is located at Right Ascension 14^h16^m and Declination 13° (actually, its full name is SDSS J141624.08+134826.7 which gives the location more precisely) and “B” denotes that it’s actually the second of two objects (the other one is unsurprisingly called “A”).

In fact it’s a pretty interesting object: it was actually discovered not by SDSS alone, but by cross-matching with another survey, the UK Infrared Deep Sky Survey (UKIDSS) and looking at the images by eye. It turns out that the two components are a binary system made up of two brown dwarfs — objects that aren’t massive enough to burn hydrogen via nuclear fusion, but are more massive than even the heaviest planets, often big enough to form at the centre of their own stellar systems, and heavy enough have some nuclear reactions in their core. In fact, the UKIDSS survey has been one of the best ways to find such comparatively cool objects; my colleagues Daniel Mortlock and Steve Warren found one of the coolest known brown dwarfs in UKIDSS in 2007, using techniques very similar to those they also used to find the most distant quasar yet known, recounted by Daniel in a guest-post here. Like that object, SDSS1416+13B is one of the coolest such objects ever found.

What does all this have to do with Scott Walker? I have no idea. Since he started singing as a member of the Walker Brothers in the 60s — and even more so since his 70s solo records, Walker has been known for his classical-sounding baritone, though with his mannered, massive vibrato, he always sounds a bit like a rocker’s caricature of a classical singer. I’ve always thought it was more force of personality than actual skill that drew people — especially here in the UK — to him.

His latest, Bish Bosch, the third in a purported trilogy of records he’s made since resurfacing in the mid-1990s, veers between mannered art-songs and rock’n’roll, silences punctuated with electric guitars, fart-sounds and trumpets.

The song “SDSS1416” itself is an (I assume intentionally funny?) screed, alternating sophomoric insults (my favourite is “don’t go to a mind reader, go to a palmist; I know you’ve got a palm”) with recitations of Roman numerals and, finally, the only link to observations of a brown dwarf I can find, “Infrared, infrared/ I could drop/ into the darkness.” Your guess is as good as mine. It’s compelling, but I can’t tell if that’s as an epic or a train wreck.

Prizes and Books, As Yet Unread and Unwritten

2012-11-29T23:26:24Z

Over the last couple of months, I’ve managed invites to a few swish literary shindigs.

For no literary reason at all (I’m the proud godparent of someone who works for the prize’s sponsors), I was able to make my way into this year’s ceremony for the Man Booker Prize, held in the rather splendid Guildhall in the City of London. (That’s the hall at right, being addressed I think by the chairman of the Booker Prize Committee, Sir Peter Stothard).

This year’s winner was Hilary Mantel for Bring Up the Bodies, the second volume in her fictionalisation of the life of Thomas Cromwell. I admit I haven’t read that, nor its also-prizewinning predecessor Wolf Hall (nor in fact any of the rest of this year’s crop). And I was sort of hoping to hear Will Self give a speech or, better, a rant.

The ice sculptures at the center of even our low-rent table on the outskirts was evidence of the luxury of the event, as was the remnant of my outfit (why else wear a bow tie unless you can flaunt the louche look at the end of the evening? Although alas the picture wasn’t taken on my ride home in an appropriate chauffeured limo, nor even a black cab, but the Central Line on the London Underground…).

Slightly closer to my usual bailiwick, earlier this week I went to see the award of this year’s Royal Society Winton Prize for Science Books, organised by Britain’s Royal Society, and sponsored by Winton Capital:

Those are shortlisted authors Steven Pinker, Brian Greene, host/comedian (and former Cambridge physics PhD student) Ben Miller, James Gleick, Lone Frank and Joshua Foer. Again, I’m behind on this year’s selections, and enjoyed all of the authors’ readings — though I found Foer’s bit from his Moonwalking with Einstein especially compelling. But Gleick’s The Information triumphed (and his previous books, from Chaos to his biography of Richard Feynman, have shown him to be an excellent writer and communicator, so I am sure it was well-deserved).

After the award, standing around the Royal Society’s digs, swigging the obligatory (and appreciated) champagne, we realised something strange about this year’s shortlist: no British authors. One Dane (Lone Frank) and five Americans (the fifth, Nathan Wolfe, couldn’t make it).

This has re-inspired me to go to the next level up from these monthly posts (and more frequent tweets) and think about writing that book that they say we all have in us. Let’s try a little crowdsourcing: what book should I write?

Traversant la Manche

2012-10-21T21:58:37Z

Until now, I have been forced to resist the clamour brewing among both members of my extensive readership (hi, dad!) to post a bit more often: my excuse is that, in the little over a month between early September and mid-October, I have travelled back and forth from Paris to London five times, spent a weekend in the USA, started teaching a new course, and ran a half marathon.

Ten one-way trips in six weeks is too many; the Eurostar makes it about as pleasant as it could possibly be: 2 1/4 hours from central London to central Paris by train (a flight from Heathrow to de Gaulle is faster, but the airports are less convenient and much more stressful). Most of my time in Paris was for Planck Satellite meetings, mostly devoted to the first major release of Planck data and papers next year — of course, by The Planck rules, I can’t talk about what happened. At least I have no more trips to Paris until early December (and only four or so hours a week of Planck telecons).

But in addition to three Planck meetings, I also helped out in my minor role as a member of the Scientific Organizing Committee of the Big Bang, Big Data, Big Computing meeting at the APC, which was an excellent gathering of cosmologists with computer scientists and statisticians, all doing our best to talk over the fences of jargon and habit that often keep the different fields from having productive conversations. One of my favourite talks was the technical but entertaining From mean Euler characteristics to the Gaussian kinematic formula by Robert Adler, whose work in statistics more than thirty years ago taught many in cosmology how to treat the functions that we use to describe the distribution of density and temperature in the Universe as random fields; he discussed more recent updates to that early work for much more general circumstances, the cosmological repercussions of which have yet to be digested. Another highlight was from Imperial’s own Professor David Hand, Opportunities and Challenges in Modelling and Anomaly Detection, discussing how to pull small and possibly weird (“anomalous”) signals from large amounts of data— he didn’t highlight many specific instances in cosmology, but rather gave examples with other sorts of big data, such as the distribution of prices of credit card purchases (with some particularly good anecdotes culled from gas/petrol station data).

Finally, in addition to those many days of meetings — and yes, the occasional good Parisian meal — there were a couple of instances of the most satisfying of my professional duties: two examinations for newly-minted PhDs from the Institut d’Astrophysiques de Paris and the Laboratoire Astroparticule et Cosmologie — félicitations aux Docteurs Errard et Ducout.

Harmony in the Universe

2012-10-21T21:57:40Z

Cosmology fans in and around London: Please come here my colleague Jean–Philippe Uzan, visiting us from Paris, who will talk about “ Harmony in the Universe: between science and music” this coming Thursday, 25 October 2012 in the Huxley Building here at Imperial College. It’s free, but please contact us at astro-outreach@imperial.ac.uk if you’re going to come.

Cage 100

2012-09-05T11:25:35Z

Today (September 5), John Cage would have been 100 years old. A few weeks ago, I went to the John Cage Centenary Celebration at the BBC Proms. Cage is probably best know for 4′33″, his infamous 1952 piece consisting of four minutes and thirty-three seconds of silence (originally in three movements — although he eventually decided to make the structure of the piece even less prescribed). That wasn’t performed the night I was at the proms, but a few evenings before by the London Sinfonietta, so I listened on the radio, and tried to use the opportunity to attend to the sounds around me: the movements of my neighbours, the cycling of my refrigerator, the cars on the road. (Allan Kozinn, who wrote Cage’s NY Times obituary 20 years ago, writes about an impromptu performance he conducted on an A-Train Subway car.)

Last year, some friends gave me an excellent birthday present: the score to 4′33″ in Cage’s proportional notation: 1 page = 7 inches = 56 seconds”: spare and beautiful on paper, reminding us that Cage was a visual artist as well as a composer:

The highlight of the Prom dedicated to Cage was “Branches”, for amplified cactuses and plants. This sounds like a joke, and like much of Cage’s work, it is indeed intentionally playful, and probably as much performance art as music. The players were scattered around the Albert Hall, on stage, in the central pit, in boxes among the audience, and their succulents, leaves and water bowls were set with high-gain microphones, and arranged by consultation with the I Ching, one of Cage’s favourite ways of introducing randomness into his works. The result was beautiful, and silly, and I’ll never look at a spiny cactus the same way again.

Robyn Schulkowsky leads John Cage’s Branches for amplified cactuses and plants at the BBC Proms. ©BBC/Chris Christodoulou

So now, any classical concert that doesn’t feature a smattering of plant life will feel somewhat staid, but nonetheless I am headed back tonight for John Adams’ opera “Nixon in China”. I’ve managed to see a couple of his other operas, The Death of Klinghoffer and Doctor Atomic, over the last few years, and this was his first. This semi-staged version will be conducted by Adams himself — what it lacks in sets and costumes will perhaps be made up for in other sorts of excitement. But probably not in plants.

This sporting life

2012-08-14T21:16:38Z

[Warning, this post will be largely about sport(s), a subject I am even less qualified than usual to discuss, and so is mostly an excuse to brag about my having seen the fastest man in the world live — along with 80,000 other spectators, and post some of the pictures I was lucky enough to take.]

I’ve been in Britain for more than a decade, but this summer I managed to rediscover my North American roots in the form of Baseball, courtesy of ESPN America, which shows a game or two every evening (often on delay from the previous night). Baseball is the ideal relaxed television sport — it doesn’t require rapt attention, and most of the action fits well into a single screen. Moreover, it’s well-suited to British summers, as the nightly broadcast of the BBC Proms makes an excellent soundtrack.

But a few weeks ago I was in the Bay Area, visiting Julian Borrill and my other colleagues at Lawrence Berkeley Lab’s Computational Cosmology Center, and we took a night off to visit the stadium formerly known as the Oakland Coliseum to watch the hometown Oakland A’s take on the Toronto Blue Jays (having lived in both the Bay Area and Toronto, this was an excellent matchup). We got to see the A’s new pitching phenom, Dan Strailey, just called up from the minors: he had the win until Toronto scored three runs to tie at the top of the 9th inning, forcing both teams and thousands of spectators to endure a long, cold night of extra innings. But the A’s dug it out in the end, finishing up after 15 innings. We were down near the field, close enough to heckle the players — and some of our seat mates were quite vociferous in their taunts.

Since coming back, like the rest of the world, I’ve managed to spend the last few weeks mildly obsessed with the Olympics. But for me, “coming back” was back to London, and so I got to see some part of the games. We here have spent much of the last seven years getting more and more cynical, expecting chaotic and clogged travel, fascist security, and generally no fun. By now, we all know that isn’t what happened. Instead, we got Michael Phelps, world records, Mo Farah’s smile, and a great Great British (not English, not Welsh, not Scottish, not Northern Irish) team that even made a foreigner like me feel a bit proud to live here (of course, I have the advantage of also being American so could spread my support around). The BBC coverage concentrated on the British team, of course, but had the hometown advantage of live action, unlike the ridiculously delayed NBC coverage (but Bob Costas is a better anchor than Gary Lineker).

I got very lucky indeed in the ticket lottery and made it over to the Olympic Stadium to see David Rudisha’s 800m world record and Usain Bolt’s blazing 200m win, not to mention the decathlon (no longer quite as valorised as in the days of Bruce Jenner) and the silly-looking but incredibly difficult triple jump.

I also ambled over to a couple of free events, the men’s 10K Swim in the murky Serpentine, across the road from Imperial in Hyde Park, and the perhaps slightly less gruelling marathon, finishing off the games on Sunday. (More olympic pictures here.)

And it’s not over. This weekend I’m off to Lord’s Cricket Ground to see England against South Africa in a test, those many-day long matches that make a 15-inning baseball game seem short. Next come the Paralympic Games, and then, in October, finally, I may get to participate, and not just watch: if I recover from my injuries I’ll be running in the Royal Parks Half Marathon and Run to the Beat — a full marathon spread out over 3 weeks — in October. Wish me — and my achilles tendon — luck.

Higgs vs Religion on the Radio: no contest

2012-07-04T20:20:33Z

The Higgs day continues (and I’m not even a particle physicist).

At about 5pm, just as I was dialling into one of my several-times-a-week Planck teleconferences, I had an email from Tim at the BBC, who works with the World Service “World Have Your Say” show, coming on at 6pm. Would I be able to come up with a one-minute analogy for the Higgs Boson? I came up with two (neither original). The first is that the Higgs field acts like treacle or molasses, inhibiting the motion of particles — and it’s exactly a resistance to motion that is the manifestation of inertia, and hence mass. The more fanciful analogy, due to UCL’s David Miller, is that it behaves like a roomful of partygoers when someone famous walks into the room. We peons throng to the celebrity, slowing her down (it was Margaret Thatcher in the original version); a less famous celebrity is impeded somewhat less, and even the partygoers themselves — analogous to the Higgs particles — can’t move freely. Hence, all particles have a mass.

Unfortunately, both of these had been discussed by UCL’s Professor John Butterworth (who blogs for the Guardian and whose excellent explanations made him ubiquitous in today’s media blitz), the IOP’s Caitlin Watson, and journalist (and cosmology consultant?!) Marcus Chown even before I came on. I was prepared to give up the chance for media glory, or possibly talk about the related concept of spontaneous symmetry breaking and the infamous “Mexican Hat potential”. But at just after 6, they rang back and asked if I could join the programme in progress. What I hadn’t quite realised was that the title for the show was “Is there room for Higgs Boson & Religion?”.

I suppose this stems from Leon Lederman’s book, The God Particle. The story that has been told in recent years is that Lederman wanted to call it “The Goddamn Particle” and that his American publishers wouldn’t let that pass — but I always thought that version a little too pat, both getting Lederman off the hook for an ill-conceived name, and tweaking American religious sensitivities.

But whatever the source, the host wanted to use today’s news to try to pound on the usual science-vs-religion drum, inviting listener comments on the topic along with a discussion between the scientists and a series of religious figures. Luckily, none of us really wanted to use this occasion to disagree: the spiritual types wanted to see science as a celebration of the (god-created, god-given) natural world, and we scientists didn’t want to claim more for science than its ability to answer the practical questions about the real world that it has the tools to address. Of course, I felt the need to say, many religious people and perhaps entire religions make supernatural claims about the world. And those, so far, have turned out to be false.

I would have preferred to talk about spontaneous symmetry breaking, but if you want to hear about science and religion, download the podcast.

Expat playlist

2012-07-04T18:04:55Z

I am in England for Independence Day this year, having just spent last weekend back in the USA. Here’s a taste of the view from my ancestral (i.e., my parents’) home:

So I’ll eat a burger in celebration, and listen to some appropriately-themed music from my playlist (in order of release):

Van Morrison, Almost Independence Day
Bruce Springsteen, 4th of July, Asbury Park (Sandy)
Bruce Springsteen (again), Independence Day
X, 4th of July
Galaxie 500, Fourth of July
Elliot Smith, Independence Day

Although there are mentions of the great American traditions of democracy, fireworks, and hot dogs, these songs dwell rather more on heartbreak and loss. Any other suggestions?

Fundamental Scalar found?

2012-07-04T11:18:34Z

I am just back from STFC’s media event covering what did, in the end, turn out to be the discovery of a particle that appears to be the long-predicted Higgs boson, the last component in the Standard Model of Particle Physics to be discovered, and in many ways its linchpin.

Via a mechanism known as spontaneous symmetry breaking (first applied to so-called gauge theories of particle physics in a set of 1964 papers by Higgs himself, Imperial’s Tom Kibble with Guralnik and Hagen, as well as Brout and Englert) the Higgs couples to all of the other particles in the standard model, and gives them mass.

Suffice to say that the results so far, from the LHC experiments, ATLAS and CMS, are consistent with a Higgs with a mass of 125 GeV, interacting with other particles more or less as predicted (although only the couplings to photons and the Z boson have been strongly confirmed by the current measurements). The details have implications for any physics beyond the standard model, in particular for supersymmetry — the measurements already put tight constraints on the simplest such models. (The New York Times has a comprehensive overview, including a mention of the cosmological implications of the result; Sean Carroll has an expectedly excellent discussion of Higgs physics; Peter Coles quotes and comments on the CERN press release, and like him I will avoid mentioning the confusing frequentist statistics underlying today’s results. I’m sure a search will turn up dozens of more blogs and news articles.)

But for cosmologists, one of the most exciting things about the Higgs is that it seems to exist at all. The Higgs is a boson, which means that you can pack many of them into a single state, and therefore can be thought of as a field pervading all of space — photons, which make up the electromagnetic field, are also bosons. (This is in contrast to fermions, which cannot be brought into the same state and are thus more usefully thought of as individual particles of matter.) An even more precise categorisation of particles is via their spin: bosons can take on integer values (0, 1, 2, …) , and fermions half-integer values (1/2, 3/2, …). The known bosons, like the photons, have spin 1 and are known as vector particles. The Higgs, however, has spin 0, and is called a scalar.

Scalar fields are ubiquitous in cosmology: if they are roughly constant across space they act like a vacuum energy or cosmological constant, their (negative) pressure making the Universe accelerate in its expansion. They are therefore thought to be responsible for an early period of inflation, and possibly also for the recent domination of the Universe by dark energy. However, there have been longstanding questions about whether fundamental scalar particles can exist in quantum theories. The data are still consistent with alternative models (for example, the Higgs could be a tightly-bound pair of fermions). But if confirmed, the existence of the Higgs as a scalar particle encourages us cosmologists to continue our occasionally wild speculations on the properties of scalar fields, making the Universe accelerate at early times and again today.

Future Science Bloggers Wanted

2012-07-01T10:44:52Z

Attention Imperial Postgraduates*: I’ll be helping lead a course in Science Blogging this Friday, 6 July 2012 at Imperial, along with a couple of fellow (science) bloggers: biophysicist Professor Stephen Curry and biostatistician (and actual graduate student!) Erika Cule, both of whom write at Occam’s Typewriter, an excellent grassroots network of scientist bloggers.

Imperial students should still be able to sign up — if you’re taking the course (or even if you’re not), leave a comment if you’ve got any ideas for what we should discuss.

*Language note: In the US, anyone with a university degree is called a “college graduate” and a student pursuing a Masters’ or Doctoral degree is called a “graduate student”; here in the UK, they are just plain “graduates” and “postgraduates”, respectively. (And I won’t even discuss the inconsistent use of “college” here in the UK, which also encompasses advanced high schools.)

50,000,000 Elvis Fans Can't Be Wrong

2012-06-18T22:57:52Z

I wandered across Prince Consort Road from my office in the Blackett Laboratory a few weeks ago — to the Royal Albert Hall and Elvis Costello’s Spectacular Singing Songbook tour.

Elvis has settled into a comfortable phase of his career; he hasn’t quite managed a late-period resurgence — his last true masterpiece was probably Blood & Chocolate from 1988, although he’s had great songs on most of his records throughout the 90s and 2000s. Instead, he’s something of an elder (middle-aged?) statesman, showman and even teacher.

And his show seems to acknowledge this, leaning heavily on songs from the 70s and 80s. The stage is organised around a great carnival wheel, with song titles and themes around the rim; a series of audience members is brought on stage to take a spin. We heard songs on “girls” (“This Year’s Girl”, “Spooky Girlfriend”, “Party Girl”), “time” (“Strict Time”, “Man Out Of Time”, “Out Of Time”) as well as a medley from “Get Happy” and plenty of songs from a more traditional setlist. It occasionally seemed something of a greatest-hits show — I might have liked to hear a few more songs from King of America and Imperial Bedroom, two of his great 80s records which didn’t spawn many radio hits, but the pairing of the latter’s “Beyond Belief” with a cover of Prince’s “Purple Rain” was an inspired reminder of Elvis’ great taste (and musical chops).

Elvis even let his angry not-so-young man persona out for a brief foray into politics, including a not at all apologetic rebranding of his anti-Thatcher rant “Tramp the Dirt Down” (now aimed at all the subsequent PMs as well) along with “Shipbuilding” and “Pills and Soap”. But for the most part his persona was a mix of carnival barker, crooner and storyteller.

That night we were also privileged to hear special guest and west London resident Nick Lowe, producer of many of Elvis’ great early records, and writer of his early hit, “Peace, Love and Understanding”, with which the pair magnificently closed the show.

Over the last year or so I’ve also seen shows from a couple of other ageing singer/songwriters: Paul Simon and Bob Dylan. Simon’s career has had a similar trajectory to Elvis’: not much to match the 80s heights of Graceland and its excellent if less lauded followup, Rhythm of the Saints (although Elvis Costello himself praises Simon’s latest, So Beautiful or So What). And Dylan is, well, Dylan, dragging his neverending tour to London last winter. The set was made up about equally of songs from the 60s and more recent stuff, with several from the 2006 Modern Times. And while Paul Simon and Elvis Costello were mostly faithful to the original conceptions of their own songs, Dylan continues to take pride (which some of his more staid fans might find perverse) in tearing up and turning inside out his whole back catalog, changing the rhythm, the melody, sometimes even the lyrics, until sometimes the shock of recognition doesn’t occur until the song is over (and sometimes not until you go read the setlist).

But each of these shows was an education, in rock ‘n’ roll and in doing your best to not age too gracefully while still singing, or just listening to, it.

Causerie - The Creation: On Cosmogony and Cosmology

2012-05-30T21:45:15Z

A quick alert to any friends or followers in or near Rotterdam this weekend: I’ll be participating in a series of dialogs supporting The Humans, a piece of theatrical performance art sponsored by and shown at the Witte de With Center for Contemporary Art. The production, which will encompass a series of symposia with the process of writing and design, culminating in the play itself to be staged next Spring. It has arisen from the correspondence between artist Alexandre Singh and Defne Ayas, the new director of the Witte de With:

Set before the Earth’s beginning in a proto-world populated by spirits, gods, artisans and men of clay and plaster, The Humans — with ‘creation’ as its central theme — is modelled after the ancient Greek plays of Aristophanes. Whilst the theatrical references are ancient, the satire is utterly modern: religion, morality and human hubris are all mocked with an irreverent and biting tone.

Beyond this rather ambitious setup, I don’t know much about it. But this weekend I hope to learn more: Saturday, I’ll be on stage, talking with Singh about cosmology, in the first of a series of “Causeries”, this one with the daunting title “The Creation: On Cosmogony and Cosmology” — the other participants are philosophers and historians, and I’m looking forward to seeing whether there is a common thread through the different discussions, and how (or if) they reflect back on the eventual play itself.

Bad memory. Bad law?

2012-05-12T16:10:58Z

(Warning: this post is pretty far outside of my usual bailiwick…)

I was reading today’s Guardian and came across Zoe Williams’ sketch (in UK newspapers, this is a short, often humorous, descriptive piece, usually about an event like a parliamentary debate or court proceedings), “Rebekah Brooks lays bare the secret of her success”, recounting the appearance of former News International CEO Rebekah Brooks at the Leveson Inquiry into “phone hacking” and the too-cozy relationship between the media and politicians.

The sketch was mostly remarkable for what it couldn’t say. Williams writes

But ultimately, this is a ridiculous person. You couldn’t live a life with this bad a memory. Never mind that you’d never be able to do a demanding job, you wouldn’t be able to pass your GCSEs.

And that makes the whole business grating to watch. “I can’t remember” is the defence of a person who wasn’t really concentrating, whose mind was somewhere else.

And this makes the whole business grating to read. I don’t think this is only an indulgence in some old-fashioned British circumlocution: Williams really means “I think Rebekah Brooks was lying”. But I assume she can’t write that, because that would be accusing Brooks of the crime of lying under oath, and Brooks would be free to sue for libel — and under UK libel law, the burden of proof is on the defendant to prove the statement true, impossible in this case. (I am not a lawyer, but this is my understanding.)

This is just one of the minor repercussions of the current state of UK libel law, which the government may be overhauling soon — it was discussed in last week’s Queen’s Speech (another amusing tradition in which the Monarch reads a speech written by the government recounting its plans for the next parliamentary session). Simon Singh, a science writer who was sued for liable by the [redacted] of the chiropractic industry, writes that the proposal still doesn’t go far enough, especially in its lack of distinction between individuals and corporations. (Americans may think this sounds familiar from a different context.)

SOLE Survivor

2012-05-04T21:33:00Z

This week I received the results of the “Student On-Line Evaluations” for my cosmology course. As I wrote a few weeks ago, I thought that this, my fourth and final year teaching the course, had gone pretty well, and I was happy to see that the evaluations bore this out: 80% of the responses were “good” or “very good”, the remainder “satisfactory” (and no “poor” or “very poor”, I’m happy to say). I was disappointed that only 23 student (fewer than half of the total) registered their opinion on subjects like “The structure and delivery of the lectures” and “the interest and enthusiasm generated by the lecturer”.

The weakest spot was “The explanation of concepts given by the lecturer” with 5 for satisfactory, 11 for good and 7 for very good — I suppose this reflects the actual difficulty of some of the material. In the second half of the course I need to draw more heavily on concepts from particle physics and thermodynamics that undergraduate students may not have encountered before, concepts that are necessary in order to understand how the Universe evolved from its hot, dense and simple early state to today’s wonderfully complex mix of radiation, gas, galaxies, dark matter and dark energy. Without several days to devote to the nuclear physics of big-bang nucleosynthesis, or the even longer necessary to really explain the quantum field theory in curved space-time that would be necessary to get a quantitative understanding of the density perturbations produced by an early epoch of cosmic inflation, the best I can do is give a taste of these ideas.

And I really appreciated comments such as “Work with other lecturers to show them how it’s done”. So thanks to all of my students — and good luck on the exam in early June.

Spring Break?

2012-04-15T22:02:08Z

Somehow I’ve managed to forget my usual end-of-term post-mortem of the year’s lecturing. I think perhaps I’m only now recovering from 11 weeks of lectures, lab supervision, tutoring alongside a very busy time analysing Planck satellite data.

But a few weeks ago term ended, and I finished teaching my undergraduate cosmology course at Imperial, 27 lectures covering 14 billion years of physics. It was my fourth time teaching the class (I’ve talked about my experiences in previous years here, here, and here), but this will be the last time during this run. Our department doesn’t let us teach a course more than three or four years in a row, and I think that’s a wise policy. I think I’ve arrived at some very good ways of explaining concepts such as the curvature of space-time itself, and difficulties with our models like the 122-or-so-order-of-magnitude cosmological constant problem, but I also noticed that I wasn’t quite as excited as in previous years, working up from the experimentation of my first time through in 2009, putting it all on a firmer foundation — and writing up the lecture notes — in 2010, and refined over the last two years. This year’s teaching evaluations should come through soon, so I’ll have some feedback, and there are still about six weeks until the students’ understanding — and my explanations — are tested in the exam.

Next year, I’ve got the frankly daunting responsibility of teaching second-year quantum mechanics: 30 lectures, lots of problem sheets, in-class problems to work through, and of course the mindbending weirdness of the subject itself. I’d love to teach them Dirac’s very useful notation which unifies the physical concept of quantum states with the mathematical ideas of vectors, matrices and operators — and which is used by all actual practitioners from advanced undergraduates through working physicists. But I’m told that students find this an extra challenge rather than a simplification. Comments from teachers and students of quantum mechanics are welcome.

The Sensual Universe: Touch

2012-04-11T21:30:34Z

Imperial Astrophysics is sponsoring a new series of public lectures, “The Sensual Universe: Astrophysics for the Five Senses”.

The first will concentrate on touch: The Impact of Sex In Space, presented by Dr Saralyn Mark (and unlike most of us around with a “Dr” in front of our names, Dr Mark really is an MD). Despite the name, it should be completely Safe For Work, and will happen next Tuesday, 17 April 2012 at 18:30, in Blackett Laboratory Lecture Theatre 1 here at Imperial. Attendance is free but registration is essential: email astro-outreach@imperial.ac.uk or call 020 7594 7531 stating the number of required tickets.

The next one will be given by our own Dr Subu Mohanty, on taste: Beer in Space, on 23 May 2012.

TimeWave

2012-04-04T16:55:00Z

I’ve recently become involved in TimeWave, a theatre, art and technology festival to be inaugurated up in Manchester this coming November 19-24.

It has been set up by the excellent lonyla (London-NY-LA) artists’ network founded by J. Dakota Powell, another American transplanted to London, taking advantage of the connections that we rootless cosmopolitans have gathered over years of transatlantic and intercontinental living and travel. How do we tell stories to each other across such vast distances in space and in culture?

TimeWave itself will try to realise these long-distance links. One event, multiple locations, multiple points of view, even within a single piece:

Each day of the festival will consist of a two-hour event, knitting together 8 to 10 short pieces from playwrights, poets, composers and transmedia creators to form a kaleidoscopic tapestry. Over a five-day run, the programme will resemble a prism shifting every few minutes to reveal a unique voice, style or viewpoint.

In some pieces, we will use telepresence. For example, American actors will be live-streamed on to a projection screen to interact with British actors on stage. Or audiences in Hong Kong can discuss what they’ve seen with audiences in Manchester, sharing thoughts and ideas.

The festival has already got the support of an amazing group of writers, filmmakers and directors, including Neil LaBute and David Henry Hwang.

So, please come see the festival up in Manchester this Autumn. But before then, if you can, please consider donating to the cause and help make TimeWave happen.

ER

2012-03-25T21:53:38Z

I’ve been lucky that almost everything I know about hospitals comes from fiction. But last week, having done something unpleasant to my Achilles tendon running, my local doctor sent me over to the local A&E (“accident and emergency”, the UK equivalent of the ER) to see if they could fix me up.

Having been healthy and not particularly accident-prone, this was the first time since age 6 or so that I’ve been to the hospital for myself, although I’ve accompanied or visited a few friends and loved ones over the years. Britain’s NHS is, of course, a remarkable institution: universal health care with outcomes that are overall as good as the much more expensive American system. But that very size means that patients don’t always get exactly the treatment they might like.

Before heading to the doctor that morning, a few minutes online indicated that I probably had something like insertional Achilles tendinitis, a pretty common complaint especially amongst runners. My GP couldn’t help much, but got much the same information from the computer on her desk, and decided that it required more work — possibly a cast — than she could handle there.

So after hobbling over to Charing Cross hospital, relatively nearby in London (and nowhere near Charing Cross), I was told to sit and wait, possibly for about two hours — and I was a lucky one, having come with a doctor’s note enabling me to skip the triage step and get directly on the list. So a couple of hours later, I finally made it in to see someone, a very nice nurse practitioner. I was surprised, however, when he looked at my heal and said that he had never seen anything like that before. He waved a nearby doctor into the examination room, but the latter clearly just wanted to go home after a long shift, and didn’t have much to add beyond the frankly strange suggestion of a “foreign body”. The pair were about to send me in for an x-ray when another nurse practitioner walked by, looked down, and said, “oh, that’s bursitis”, an inflammation of the bursa, the sac of fluid which keeps the joint between the tendon and the bone lubricated. This seemed altogether more plausible (although a condition I tend to associate with my now-101-year-old grandmother). And, fortunately or otherwise, the suggested treatment was just ice, anti-inflammatory painkillers, and rest. To facilitate the latter, I got a new pair of accessories, pictured at right (taken at my local, hoping that alcohol was not contraindicated).

As a not-terribly-old, not-terribly-infirm, male, I am used to deferring to pretty much everyone except teenagers for positions on lines (queues) and seats on public transport. So the crutches work a weird psycho-physical magic on me and the people around: lots more saying “sorry”, getting up or moving out of the way for me. I don’t like it.

Things are, happily, looking up. I can walk only a bit asymmetrically and without too much pain (and without the crutches for the last day or so). Let’s hope I’m running again before my next half-marathon.

ICIC

2012-03-25T10:54:50Z

Among the many other things I haven’t had time to blog about, this term we opened the new Imperial Centre for Inference and Cosmology, the culmination of several years of expansion in the Imperial Astrophysics group. In mid-March we had our in-house grand opening, with a ribbon-cutting by the group’s most famous alumnus.

Statistics and astronomy have a long history together, largely growing from the desire to predict the locations of planets and other heavenly bodies based on inexact measurements. In relatively modern times, that goes back at least to Legendre and Gauss who more or less independently came up with the least-squares method of combining observations, which can be thought of as based on the latter’s eponymous Gaussian distribution.

Our group had already had a much shorter but still significant history in what has come to be called “astrostatistics”, having been involved with large astronomical surveys such as UKIDSS and IPHAS and the many allowed by the infrared satellite telescope Herschel (and its predecessors ISO, IRAS and Spitzer). Along with my own work on the CMB and other applications of statistics to cosmology, the other “founding members” of ICIC include: my colleague Roberto Trotta who has made important forays into the rigorous application of principled Bayesian statistics to problems cosmology and particle physics; Jonathan Pritchard who studies the distribution of matter in the evolving Universe and what that can teach about its constituents and that evolution; and Daniel Mortlock, who has written about some of his work looking for rare and unusual objects elsewhere on this blog. We are lucky to have the initial membership of the group supplemented by Alan Heavens, who will be joining us over the summer and has a long history of working to understand the distribution of matter in the Universe throughout its history. This group will be joined by several members of the Statistics section of the Mathematics Department, in particular David van Dyk, David Hand and Axel Gandy.

One of the fun parts of starting up the new centre has been the opportunity to design our new suite of glass-walled offices. Once we made sure that there would be room for a couple of sofas and a coffee machine for the Astrophysics group to share, we needed something to allow a little privacy. For the main corridor, we settled on this:

The left side is from the Hubble Ultra-Deep field (in negative), a picture about 3 arc minutes on a side (about the size of a dime or 5p coin held at arm’s length), the deepest — most distant — optical image of the Universe yet taken. The right side is our Milky Way galaxy as reconstructed by the 2MASS survey.

The final wall is a bit different:

The middle panels show part of papers by each of those founding members of the group, flanked on the left and right side with the posthumously published paper by the Rev. Thomas Bayes who gave his name to the field of Bayesian Probability.

Of course, there has been some controversy about how we should actually refer to the place. Reading out the letters gives the amusing “I see, I see”, and IC² (“I-C-squared”) has a nice feel and a bit of built-in mathematics, although it does sound a bit like the outcome of a late-90s corporate branding exercise (and the pedants in the group noted that technically it would then be the incorrect I×C×C unless we cluttered it with parentheses).

We’re hoping that the group will keep growing, and we look forward to applying our tools and ideas to more and more astronomical data over the coming years. One of the most important ways to do that, of course, will be through collaboration: if you’re an astronomer with lots of data, or a statistician with lots of ideas, or, like many of us, somewhere in between, please get in touch and come for a visit.

Unfortunately we don’t yet have a webpage for the Centre..

On 'Jaffe'

2012-02-26T09:27:52Z

Despite the last decade and a half or more of the internet, I’ve never bothered to actually work out the meaning and history of my surname, “Jaffe”. Somehow I always thought it was connected to the town of Jaffa, near Tel Aviv. But in fact, 30 seconds of searching turns up information that the name comes from the Hebrew yafeh (יפה, meaning “beautiful”) and dates at least from Rabbi Mordecai Jaffe in 16th-century Prague. I was also happy to discover that, with at least half a millennium behind us, there are plenty of interesting Jaffes in history and today (although I had to be careful not to be waylaid by the possibility that we’re actually Irish…).

Of course there are a lot of physicists: Arthur and Robert, as well as several astronomers who don’t quite rate a wikipedia page (yet!): Walter, Daniel and Tess (who is one of my collaborators on Planck). But also actors — Sam, Nicole and Marielle, composers — David and Stephen, and even athletes — Peter and Scott. And there really is an Irish connection: Sir Otto, once the Lord Mayor of Belfast, born in Hamburg, lived and worked in New York as well as Ireland.

Roman Juszkiewicz

2012-01-28T16:00:20Z

I was saddened to receive a message that my friend and colleague, Roman Juszkiewicz, died earlier today.

Roman was a Polish cosmologist who began his career in the Russian school, working with Ya. Zeldovich, probably the most eminent Soviet cosmologist and astrophysicist of the 20th Century. Roman himself went on to work in Paris, Berkeley, Geneva, Princeton, and of course back in Poland in both Warsaw and more recently in Zielona Gora, always doing his best to find friends and collaborators in places worth a visit.

He specialised in trying to understand the growth of structures in the universe. I was lucky enough to work with him on a series of papers over the last decade and a half, mostly examining how the motions of galaxies respond to the distribution of matter, and how we can use that to measure the total density of matter. Most recently, in one of Roman’s very last papers, we tried to clear up some confusion about the relationships amongst different ways of measuring and describing the clustering of the matter and of the galaxies that we directly observe.

As much as I will remember and miss Roman as a collaborator, I and most of his friends will surely miss him even more as a companion: Roman liked to enjoy his friends’ company as much over food and wine as over a good scientific discussion. Ideally, of course, we managed both at the same time, often well into the night and leaving many empty bottles and plates behind.

Tonight, I will try to leave at least a couple of empty glasses behind in Roman’s memory and honour.

Constellations

2012-01-19T14:26:18Z

Many plays about science suffer from trying to do too much, telling a story while teaching science, but Nick Payne’s two-hander “Constellations”, now on at the Royal Court Theatre in London, has science and a scientist at its center, adding to the drama, not distracting us with jargon or science fictional twists.

“Constellations” is the story of Roland and Marianne, a beekeeper and a cosmologist. Without giving away too many spoilers, I’ll say that the play tells us the story of their relationship, as it might play out in the myriad possible universes of the multiverse, each one subtly different from the rest (while of course there would be vastly many more that are not subtly, but radically, different — but a play about empty, boring Universes would be less compelling). In one, Marianne tells Roland “I sit in front of the computer all day and analyse data from the Cosmic Microwave Background” which readers will know is pretty much exactly what I do. In others, she is still an astrophysicist, sometimes more theoretical, sometimes more observational (or she is the same, just choosing to highlight different parts of her work to impress Roland or drive him away). Sometimes we see their relationship end, sometimes continue, sometimes restart, as the play pushes forward in time and between the universes. And we return, repeatedly, to one particular version of their story, towards a climax in the future of one or more of the Universes, which puts the comedy of many of the situations into tragic relief.

Playwright Nick Payne needs one of his characters to be a scientist, able to describe the underlying ideas, but manages to avoid too much heavy-handed exposition, limiting the explicit discussion of cosmology to flirty conversations early on in their relationship (I don’t know about my peers, but I find cosmology very good for flirting, at least with the right people). Sally Hawkins’ Marianne and Rafe Spall’s Roland are improbably attractive but manage to get across at least some of the neediness and nerdiness of someone burrowed so deeply into both the technical problems and the broad themes of something like cosmology or beekeeping, making us care about them and their fate (or fates?).

Thanks to my Sussex University colleagues Andrew Liddle and Kathy Romer, who both acted as consultants for the play, for inviting me along to see this excellent production.

I think I'm a Bayesian. Am I wrong?

2012-01-16T21:43:07Z

Continuing my recent, seemingly interminable, series of too-technical posts on probability theory… To understand this one you’ll need to remember Bayes’ Theorem, and the resulting need for a Bayesian statistician to come up with an appropriate prior distribution to describe her state of knowledge in the absence of the experimental data she is considering, updated to the posterior distribution after considering that data. I should perhaps follow the guide of blogging-hero Paul Krugman and explicitly label posts like this as “wonkish”.

(If instead you’d prefer something a little more tutorial, I can recommend the excellent recent post from my colleague Ted Bunn, discussing hypothesis testing, stopping rules, and cheating at coin flips.)

Deborah Mayo has begun her own series of posts discussing some of the articles in a recent special volume of the excellently-named journal, “Rationality, Markets and Morals” on the topic Statistical Science and Philosophy of Science.

She has started with a discussion Stephen Senn’s “You May Believe You are a Bayesian But You Are Probably Wrong”: she excerpts the article here and then gives her own deconstruction in the sequel.

Senn’s article begins with a survey of the different philosophical schools of statistics: not just frequentist versus Bayesian (for which he also uses the somewhat old-fashioned names of “direct” versus “inverse” probability), but also how the practitioners choose to apply the probabilities that they calculate: either directly in terms of inferences about the world versus using those probabilities to make decisions in order to give a further meaning to the probability.

Having cleaved the statistical world in four, Senn makes a clever rhetorical move. In a wonderfully multilevelled backhanded compliment, he writes

If any one of the four systems had a claim to our attention then I find de Finetti’s subjective Bayes theory extremely beautiful and seductive (even though I must confess to also having some perhaps irrational dislike of it). The only problem with it is that it seems impossible to apply.

He discusses why it is essentially impossible to perform completely coherent ground-up analyses within the Bayesian formalism:

This difficulty is usually described as being the difficulty of assigning subjective probabilities but, in fact, it is not just difficult because it is subjective: it is difficult because it is very hard to be sufficiently imaginative and because life is short.

And, later on:

The … test is that whereas the arrival of new data will, of course, require you to update your prior distribution to being a posterior distribution, no conceivable possible constellation of results can cause you to wish to change your prior distribution. If it does, you had the wrong prior distribution and this prior distribution would therefore have been wrong even for cases that did not leave you wishing to change it. This means, for example, that model checking is not allowed.

I think that these criticisms mis-state the practice of Bayesian statistics, at least by the scientists I know (mostly cosmologists and astronomers). We do not treat statistics as a grand system of inference (or decision) starting from single, primitive state of knowledge which we use to reason all the way through to new theoretical paradigms. The caricature of Bayesianism starts with a wide open space of possible theories, and we add data, narrowing our beliefs to accord with our data, using the resulting posterior as the prior for the next set of data to come across our desk.

Rather, most of us take a vaguely Jaynesian view, after the cranky Edwin Jaynes, as espoused in his forty years of papers and his polemical book Probability Theory: The Logic of Science — all probabilities are conditional upon information (although he would likely have been much more hard-core). Contra Senn’s suggestions, the individual doesn’t need to continually adjust her subjective probabilities until she achieves an overall coherence in her views. She just needs to present (or summarise in a talk or paper) a coherent set of probabilities based on given background information (perhaps even more than one set). As long as she carefully states the background information (and the resulting prior), the posterior is a completely coherent inference from it.

In this view, probability doesn’t tell us how to do science, just analyse data in the presence of known hypotheses. We are under no obligation to pursue a grand plan, listing all possible hypotheses from the outset. Indeed we are free to do ‘exploratory data analysis’ using (even) not-at-all-Bayesian techniques to help suggest new hypotheses. This is a point of view espoused most forcefully by Andrew Gelman (author of another paper in the special volume of RMM).

Of course this does not solve all formal or philosophical problems with the Bayesian paradigm. In particular, as I’ve discussed a few times recently, it doesn’t solve what seems to me the most knotty problem of hypothesis testing in the presence of what one would like to be ‘wide open’ prior information.

Planck Warms Up

2012-01-16T15:13:26Z

Nearly two-and-a-half years after its launch, the end of ESA’s Planck mission has begun. (In fact, the BBC scooped the rest of the Planck collaboration itself with a story last week; you can read the UK take at the excellent Cardiff-led public Planck site.)

Planck’s High-Frequency Instrument (HFI) instrument must be cooled to 0.1 degrees above absolute zero, maintained at this temperature by a series of refrigerators — which had been making Planck the coldest known object in space, colder than the 2.7 degrees to which the cosmic microwave background itself warms even the most regions of intergalactic space. The final cooler in the chain relies on a tank of the Helium-3 isotope, which has finally run out, within days of its predicted lifetime — and giving Planck more than twice as much time observing the Universe as its nominal 14-month mission.

The Low-Frequency Instrument (LFI) doesn’t require such cold temperatures, although in fact they do use one of the earlier stages in the chain, the UK-built 4-degree cooler, as a reference against which it compares its measurements. LFI will, therefore, continue its measurements for the next half-year or so.

But our work, of course, goes on: we will continue to process and analyse Planck’s data, refining our maps of the sky, and get down to the real work of extracting a full sky’s worth of astrophysics and cosmology from our data. The first, preliminary, release of Planck data happened just one year ago, and yet more new Planck science will be presented at a conference in Bologna in a few months. The most exciting and important work will be getting cosmology from Planck data, which we expect to first present in early 2013, and likely in further iterations beyond that.

Steve Rawlings

2012-01-16T15:05:12Z

The astronomy community in the UK and beyond suffered a terrible blow last week with the passing of Steve Rawlings, Professor of Astrophysics at Oxford. I spent quite a lot of time in Oxford a few years ago, and was lucky to get to know Steve a bit. He had spent the last several years working on the Square Kilometre Array, the massive next-generation radio telescope being developed in the UK and internationally.

The detailed circumstances of his death aren’t yet known, and I hope that they remain irrelevant except for their tragic untimeliness. Much more important is that we remember his contributions and his friendship. My condolences to his wife, his family and his friends in Oxford and throughout the world.

Me, the BBC, and Stephen Hawking

2012-01-08T19:37:37Z

I made it back onto the BBC today, this time to discuss Stephen Hawking on his 70th birthday (most of the people more qualified than me are actually at a meeting in his honour in Cambridge). (Actually, my very first appearance on the BBC, which generated one of my very first blog posts, was to talk about Hawking’s bet with Preskill and Thorne about the fate of information supposedly lost into a black hole — Hawking had originally claimed that a black hole destroys any information that fell into it, which would be a violation of the tenets of quantum mechanics, but has since, somewhat controversially, conceded.)

I have been lucky enough to meet Stephen, and was even invited to a dinner party at his house, where I got to see him posing with his Presidential Medal of Freedom, awarded by Barack Obama in 2009. So I was especially disappointed to subsequently hear that he was too ill to actually attend his conference in Cambridge. I wish him a very Happy Birthday and a speedy recovery.

It’s not hard to talk about Hawking: he’s been involved with some truly exciting breakthroughs in theoretical physics over the last few decades, perhaps most importantly for teasing out the relationship between the properties of black holes and the laws of thermodynamics. This seemingly formal analogy was realized to be much more than that with Hawking’s discovery that black holes are not, in fact, “black” — rather, they glow at a temperature inversely proportional to the mass of the black hole, emitting what has come to be called Hawking Radiation.

These are very significant discoveries, teaching us something crucial about the connections between the three great theories of physics, quantum mechanics, gravity and thermodynamics. But it’s safe to say that no one yet fully understands exactly what those relationships are.

And of course Hawking’s nonscientific accomplishments are well-known and justly valorised. He has lived with — triumphed over — ALS for far longer than any of his doctors had predicted. He has written one of the best-selling popular science books of all time, A Brief History of Time. And, needless to say, he’s done some amazing scientific work, just some of which I’ve mentioned above.

There have been very many very brilliant physicists through the centuries. So it would certainly be premature, if not churlish, to take the long view and ask where Hawking would sit in the pantheon of physicists from Archimedes through Newton, Einstein and beyond. Indeed, as my friend and colleague Peter Coles has just written, Hawking’s peers have so far decided that the time is not yet ripe to elevate him to the top of the table. (Peter has also written a short book on the subject, picking apart some of the interactions between scientists, the media and the wider public.)

The Controversy about Hypothesis Testing

2011-12-20T03:46:48Z

I spent a quick couple of days last week at the The Controversy about Hypothesis Testing meeting in Madrid.

The topic of the meeting was indeed the question of “hypothesis testing”, which I addressed in a post a few months ago: how do you choose between conflicting interpretations of data? The canonical version of this question was the test of Einstein’s theory of relativity in the early 20th Century — did the observations of the advance of the perihelion of Mercury (and eventually of the gravitational lensing of starlight by the sun) match the predictions of Einstein’s theory better than Newton’s? And of course there are cases in which even more than a scientific theory is riding on the outcome: is a given treatment effective? I won’t rehash here my opinions on the subject, except to say that I think there really is a controversy: the purported Bayesian solution runs into problems in realistic cases of hypotheses about which we would like to claim some sort of “ignorance” (always a dangerous word in Bayesian circles), while the orthodox frequentist way of looking at the problem is certainly ad hoc and possibly incoherent, but nonetheless seems to work in many cases.

Sometimes, the technical worries don’t apply, and the Bayesian formalism provides the ideal solution. For example, my colleague Daniel Mortlock has applied the model-comparison formalism to deciding whether objects in his UKIDSS survey data are more likely to be distant quasars or nearby and less interesting objects. (He discussed his method here a few months ago.)

In between thoughts about hypothesis testing, I experienced the cultural differences between the statistics community and us astrophysicists and cosmologists, of which I was the only example at the meeting: a typical statistics talk just presents pages of text and equations with the occasional poorly-labeled graph thrown in. My talks tend to be a bit heavier on the presentation aspects, perhaps inevitably so given the sometimes beautiful pictures that package our data.

On the other hand, it was clear that the statisticians take their Q&A sessions very seriously, prodded in this case by the word “controversy” in the conference’s title. In his opening keynote, Jose Bernardo up from Valencia for the meeting discussed his work as a so-called “Objective Bayesian”, prompting a question from the mathematically-oriented philosopher Deborah Mayo. Mayo is an arch-frequentist (and blogger) who prefers to describe her particular version as “Error Statistics”, concerned (if I understand correctly after our wine-fuelled discussion at the conference dinner) with the use of probability and statistics to criticise the errors we make in our methods, in contrast with the Bayesian view of probability as a description of our possible knowledge of the world. These two points of view are sufficiently far apart that Bernardo countered one of the questions with the almost-rude but definitely entertaining riposte “You are bloody inconsistent — you are not mathematicians.” That was probably the most explicit almost-personal attack of the meeting, but there were similar exchanges. Not mine, though: my talk was a little more didactic than most, as I knew that I had to justify the science as well as the statistics that lurks behind any analysis of data.

So I spent much of my talk discussing the basics of modern cosmology, and applying my preferred Bayesian techniques in at least one big-picture case where the method works: choosing amongst the simple set of models that seem to describe the Universe, at least from those that obey General Relativity and the Cosmological Principle, in which we do not occupy a privileged position and which, given our observations, are therefore homogeneous and isotropic on the largest scales. Given those constraints, all we need to specify (or measure) are the amounts of the various constituents in the universe: the total amount of matter and of dark energy. The sum of these, in turn, determines the overall geometry of the universe. In the appropriate units, if the total is one, the universe is flat; if it’s larger, the universe is closed, shaped like a three-dimensional sphere; if smaller, it’s a three-dimensional hyperboloid or saddle. What we find when we make the measurement is that the amount of matter is about 0.282±0.02, and of dark energy about 0.723±0.02. Of course, these add up to just greater than one; model-selection (or hypothesis testing in other forms) allows us to say that the data nonetheless give us reason to prefer the flat Universe despite the small discrepancy.

After the meeting, I had a couple of hours free, so I went across Madrid to the Reina Sofia, to stand amongst the Picassos and Serras. And I was lucky enough to have my hotel room above a different museum:

Bluffing about Mars

2011-11-27T11:27:09Z

Saturday afternoon I received a call from a news producer at the BBC — could I come talk about the Mars Science Laboratory, launched earlier that day?

This was a tough question, publicity-monger though I am: I don’t actually know anything about Mars. I suppose to people outside of the very broad field of “astronomy”, studying the planets in the solar system is not very different from studying the Cosmic Microwave Background. After all, in both cases we use telescopes and satellites. But actually, the study of planets is much closer to geology (and, with increasing interest in the possibilities of life on those planets, to biology) than astronomy per se.

Nonetheless, I did actually know a little about the Mars Science Laboratory and its Curiosity rover: when I was visiting the Jet Propulsion Laboratory earlier this year (to work on the CMB), our group took a quick field trip across the lab to the shop where the satellite was being assembled. Everything else I admit that I learned from wikipedia and NASA PR materials in the two hours before the interview.

One of the difficulties in getting to the surface of Mars arises from its tenuous atmosphere: parachutes aren’t a very efficient braking system. Instead, the igloo-shaped structure above and below is part of the “Sky Crane”, an amazing contraption that will hover and lower the rover gently down to the Martian surface. The Curiosity rover itself is possibly the most sophisticated robot we’ve ever put on another planet: about the size of a Mini, it will scoot around the neighbourhood of the landing site, performing experiments and sending the results back to the human race. My favourite instrument is the ChemCam, which will use “laser induced breakdown spectroscopy” to analyse rocks on the Martian surface. This is the very science-fictiony idea of shooting a high-energy laser beam at a rock, high enough to vaporise it, and then take a careful spectroscopic picture of that vapour, which scientists will decode and use to figure out the rock’s constituent elements. (Of course if there were any real Martians, they might not take kindly to our shooting laser beams at their rocks, in which case we may need to figure out a defense against the Illudium Q-36 Explosive Space Modulator.)

Martians are, of course, one of the most important parts of MSL’s mission and the broader international program of exploring Mars. NASA is very careful to point out, however, that the point of the current mission is not to find life per se, but to help determine Mars’ habitability: could Mars now support life, or could it have in the past? The actual hunt for life will have to wait for a future mission.

Urban Sputnik, Live at Imperial

2011-11-04T21:52:28Z

Urban Sputnik, our collaboration with Vanessa Harden and Dominic Southgate of Gammaroot Design is currently on display at Imperial College in the main entrance of the Norman Foster-designed business school, located on Exhibition Road in London, just up the street from the Science Museum, the V&A Museum and the Natural History Museum. I’ve discussed the pieces that will be on display before, and if you’re anywhere near South Kensington in London over the next few days, please come and see them.

If that piques your interest, you can hear more from us directly: on Tuesday evening, November 8, we’ll be hosting a short presentation — with drinks and snacks — talking about the creation of the pieces and the science behind them.

A Big Day for Dark Energy

2011-10-04T16:24:50Z

For the second time this decade, the Nobel Prize in Physics has been awarded for cosmology, to Saul Perlmutter, Adam Riess and Brian Schmidt. They are among the leaders of the teams that used the properties of supernovae — exploding stars — to measure the rate of expansion of the Universe over time. In so doing, they found that the expansion has been speeding up for the last few billion years. This is difficult to accommodate in a Universe with matter that experiences gravity in the attractive way to which we are accustomed; instead it seems to require that the Universe today be dominated by an exotic form of matter given the purposely uninformative name “Dark Energy”. This is exemplified by Cosmological Constant, a term Einstein originally included in his equation of General Relativity but abandoned when it did not fit the available data — Einstein’s motivation was not to have an accelerating Universe, but a static one, with the attraction exactly balanced by the acceleration. In the late 1990s, those two groups began to see evidence of acceleration on larger scales than Einstein envisaged, evidence that has only got better over time (especially, I should say, when combined with evidence from the Cosmic Microwave Background on the flat overall geometry of the Universe).

I was impressed to see the Guardian liveblogging the announcement of the Nobel Prize in Physics, something that usually happens for Apple product announcements and high-profile sporting events. In the blog, Martin Rees makes the excellent point that, like much physics nowadays, these discoveries were made by teams of people, with excellent leadership by the prizewinners, absolutely, but that there should be a mechanism to recognise the full scope of highly expert scientists involved. (Indeed, the Gruber Cosmology prize, which was awarded for the same research in 2007, officially recognises “Saul Perlmutter & the Supernova Cosmology Project” and “Brian Schmidt & the High-z Supernova Search Team”.)

The big problem with Dark Energy isn’t the observations, however, but the underlying theory — there is no good particle physics model which allows a cosmological constant anything like we see today. The simplest ideas say that it is just zero, and the next simplest give something that is about 10 to the power 122 or so too large.

Luckily, cosmologists and astrophysicists have ideas to solidify the supernova results and hopefully get a handle on the underlying nature of whatever is causing the acceleration, by mapping the expansion of the Universe in space and time in even more detail. There are a plethora of ground-based telescopes making observations already, but the next step will be to go to space. And it turns out that there is another reason why this is a great day for scientists studying Dark Energy: we have just had word that ESA has decided that one of its next M-class (“M” for “medium”) will be Euclid, a satellite explicitly designed to measure the properties of the accelerating Universe.

Passion for Light

2011-09-26T21:37:33Z

It’s been a busy few weeks, and that seems like a good excuse for my lack of posts. Since coming back from Scotland, I’ve been to:

Paris, for our bi-monthly Planck Core Team meetings, discussing of the state of the data from the satellite, and of our ongoing processing of it;
Cambridge, for yet more Planck, this time to discuss the papers that we as collaboration will be writing over the next couple of years; and
Varenna, on Lake Como in northern Italy, for the Passion for Light meeting, sponsored by SIF (the Italian Physical Society) and EPS (the European Physical Society). The meeting was at least in part to introduce the effort to sponsor an International Year of Light in 2015, supported by the UN and international scientific organizations. My remit was “Light from the Universe”, which I took as an excuse to talk about (yes), Planck and the Cosmic Microwave Background. That makes sense because of what is revealed in this plot, a version of which I showed:

This figure (made after an excellent one which will be in an upcoming paper by Dole and Bethermin) shows the intensity of the “background light” integrated over all sources in the Universe. The horizontal axis gives the frequency of electromagnetic radiation — from the radio at the far left, to the Cosmic Microwave Background (CMB), the Cosmic Infrared Background (CIB), optical light in the middle, and on to ultraviolet, x-ray and gamma-ray light. The height of each curve is proportional to the intensity of the background, the amount of energy falling on a square meter of area per second coming from a particular direction on the sky (for aficionados of the mathematical details, we actually plot the quantity νI_ν to take account of the logarithmic axis, so that the area under the curve gives a rough estimate of the total intensity) which is itself also proportional to the total energy density of that background, averaged over the whole Universe.

Here on earth, we are dominated by the sun (or, indoors, by artificial illumination), but a planet is a very unusual place: most of the Universe is empty space, not particularly near a star. What this plot shows is that most of the background — most of the light in the Universe — isn’t from stars or other astronomical objects at all. Rather, it’s the Cosmic Microwave Background, the CMB, light from the early Universe, generated before there were any distinct objects at all, visible today as a so-called black body with temperature 2.73 degrees Kelvin. It also shows us that there is roughly the same amount of energy in infrared light (the CIB) as in the optical. This light doesn’t come directly from stars, but is re-processed as visible starlight is absorbed by interstellar dust which heats up and in turn glows in the infrared. That is one of the reasons why Planck’s sister-satellite Herschel, an infrared observatory, is so important: it reveals the fate of roughly half of the starlight ever produced. So we see that outside of the optical and ultraviolet, stars do not dominate the light of the Universe. The x-ray background comes from both very hot gas, heated by falling into clusters of galaxies on large scales, or by supernovae within galaxies, along with the very energetic collisions between particles that happen in the environments around black holes as matter falls in. We believe that the gamma ray background also come from accretion onto supermassive black holes at the centres of galaxies. But my talk centred on the yellow swathe of the CMB, although the only Planck data released so far are the relatively small contaminants from other sources in the same range of frequencies.

Other speakers in Varenna discussed microscopy, precision clocks, particle physics, the wave-particle duality, and the generation of very high-energy particles of light in the laboratory. But my favourite was a talk by Alessandro Farini, a Florentine “psychophysicist” who studies our perception of art. He showed the detailed (and extremely unphysical) use of light in art by even such supposedly realistic painters as Caravaggio, as well as using a series of optical illusions to show how our perceptions, which we think of as a simple recording of our surroundings, involve a huge amount of processing and interpretation before we are consciously aware of it. (As an aside, I was amused to see his collection of photographs with CMB Nobel Laureate George Smoot.)

And having found myself on the shores of Lake Como I took advantage of my good fortune:

(Many more pictures here.)

OK, this post has gone on long enough. I’ll have to find another opportunity to discuss speedy neutrinos, crashing satellites (and my latest appearance on the BBC World News to talk about the latter), not to mention our weeklong workshop at Imperial discussing the technical topic of photometric redshifts, and the 13.1 miles I ran last weekend.

I ramble

2011-09-04T21:07:07Z

I’ve spent the last few days in the northern half of Great Britain. Wednesday, I was an external examiner for a (successful!) PhD exam at the Durham University. Thursday, I was at the University of Glasgow in service to the other end of the PhD experience in the UK, giving a one-hour lecture on the Cosmic Microwave Background at the STFC summer school for incoming students.

But after the summer school I woke up early for the Caledonian Sleeper up to Fort William in the Western Highlands. I rode through some of the UK’s most spectacular landscape, hills and lochs in the morning fog:

Once I got to Fort William (a typically characterless UK town, unfortunately), I hit the trail, walking along the last few miles of the West Highland Way, taking in some detours to the Cow Hill Summit and the iron-age Dun Deardail Fort. The local hills, including Ben Nevis, the highest peak in Britain, were nestled in low-slung cloud all day:

Along the way, I spotted flora and fauna

and the occasional designed object:
I thought this might be a not terribly well-hidden bird hide, but in fact it’s Outlandia, a treehouse artist’s studio suspended midway up a hillside forest. And I could feel the stress and cares (of my admittedly pretty easy life as an academic in a prestigious institution) fall away, mindful not of telecons, teaching and reports, but of just putting one foot in front of the other, and staring at those hills and lochs. Legend has it Macbeth lived on an island in this one:

More photos of my wandering, staggering, walking and ambling here.

And as an added bonus, here are the Mekons, with their own take on walking in the British countryside:

(Cockermouth is a town in Cumbria near the Lake District, although this was apparently filmed in Wales, Scotland and Leeds. And this being from the Mekons, it’s as much about armageddon and the Rolling Stones as walking in the countryside.)

STFC and UKSA

2011-09-04T08:28:37Z

Funding for space missions in the UK was split from the Science and Technology Facilities Council to the the UK Space Agency earlier this year. Very roughly, UKSA will fund the missions themselves all the way through to the processing of data, while STFC will fund the science that comes from analysing the data.

To try to be a little more specific, the agencies have put out a press release on this so-called “dual key” approach: “Who does what? — Arrangements for sharing responsibility for the science programme between the STFC and the UK Space Agency.” The executive summary is:

UKSA

ESA subscriptions

Mission-specific instruments

Operation of UK instruments (Post-launch support)

Aurora integrated national programme

STFC:

Early R&D for space science (non-mission specific)

Studentships/fellowships

Scientific exploitation of missions

This still leaves many of the details of the split unanswered, or at least fuzzy: How do we ensure that government supports the two agencies adequately and jointly? How do we ensure that STFC supports science exploitation from missions that UKSA funds, so that the UK gets the full return on its investment? How do we define the split between “data analysis” and “science exploitation”?

Here at Imperial, we work on both sides of that divide for both Planck and Herschel: we are the home to data analysis centres for both missions, and want to take advantage of the resulting science opportunities. Indeed, as we take the Planck mission ahead towards its first cosmology results at the end of next year, we are already seeing some of these tensions played out, in both the decision-making process of each agency separately as well as in the overall level of funding available in these austere times.

Watch Me Move

2011-08-21T08:40:06Z

I took a bit of time out from the astrophysics this week to head over to the Barbican for the “Watch Me Move” exhibition: more than a hundred years of film and video animation. From an 1880s hand-coloured “Pierrot” and Winsor McCay’s 1911 animated version of his newspaper comic Little Nemo, to Toy Story and superheroes, most of the works took advantage of the medium to depict an unreality reflecting, but not bound by, the same laws as our everyday world.

The highlight was an amazing late-1970s soviet-era film, “Tale of Tales”, beautiful and tragic, a half-hour exploration of memory, childhood, even war. It’s made its way to YouTube in four parts. Here’s the first:

And here are links to Part I, Part II, Part III and Part IV. Please take the time to watch.

There was Ballet Mécanique, a visually gorgeous kaleidoscopic film from Fernand Léger which mirrored his painting, showing its inspirations in the modern mechanical and optical world. And the Warner Brothers cartoon stable was well-represented by Chuck Jones’ metafictional “Duck Amuck”, with a benighted Daffy tortured through the fourth wall by a malicious animator (who of course turns out to be Bugs Bunny).

I had just recently seen another amazing bit of animation, the fifteen-minute history of the Universe (made in collaboration with quite a few of my astrophysicist colleagues) embedded within Terrence Malick’s ambitious and beautiful Tree of Life, meditating, like the “Tale of Tales”, on life and death, the weight of history, the reverberations of loss.

All of this brought to mind a much sillier, dimly-remembered, old cartoon, a black and white Felix the Cat journeying to the stars. A quick search turned up “Astronomeous”, a wonderful bit of pop-surrealism from 1928:

(There are quite a few different versions; this seems the cleanest. There is even one with a Pink Floyd soundtrack…)

One chance in 3.5 million

2011-08-04T22:46:27Z

Yes, more on statistics.

In a recent NY Times article, science reporter Dennis Overbye discusses recent talks from Fermilab and CERN scientists which may hint at the discovery of the much-anticipated Higgs Boson. The executive summary is: it hasn’t been found yet.

But in the course of the article, Overbye points out that

To qualify as a discovery, some bump in the data has to have less than one chance in 3.5 million of being an unlucky fluctuation in the background noise.

That particular number is the so-called “five sigma” level from the Gaussian distribution. Normally, I would use this as an opportunity to discuss exactly what probability means in this context — is it a Bayesian “degree of belief” or a frequentist “p-value”, but for this discussion that distinction doesn’t matter: the important point is that one in 3.5 million is a very small chance indeed. [For the aficionados, the number is the probability that x > μ + 5 σ when x is described by a Gaussian distribution of mean μ and variance σ².]

Why are we physicists so conservative? Are we just being very careful not to get it wrong, especially when making such a potentially important — Nobel-worthy! — discovery? Even for less ground-breaking results, the limit is often taken to be three sigma, which is about one chance in 750. This is a lot less conservative, but still pretty improbable: I’d happily bet a reasonable amount on a sporting event if I really thought I had 749 chances out of 750 of winning. However, there’s a maxim among scientists: half of all three sigma results are wrong. This may be an exaggeration, but certainly nobody believes “one in 750” is a good description of the probability (nor one in 3.5 million for five sigma results). How could this be? Fifty percent — one in two — is several hundred times more likely than 1/750.

There are several explanations, and any or all of them may be true for a particular result. First, people often underestimate their errors. More specifically, scientists often only include errors for which they can construct a distribution function — so-called statistical or random errors. But the systematic errors, which are, roughly speaking, every other way that the experimental results could be wrong, are usually not accounted for, and of course any “unknown systematics” are ignored by definition, and usually not discovered until well after the fact.

The controversy surrounding the purported measurements of the variation of the fine-structure constant that I discussed last week lies almost entirely in the different groups’ ability to incorporate a good model for the systematic errors in their very precise spectral measurements.

And then of course there are the even-less quantifiable biases that alter what results get published and how we interpret them. Chief among these may be publication or reporting bias: scientists and journals are more likely to publish, or even discuss, exciting new results than supposedly boring confirmations of the old paradigm. If there were a few hundred unpublished three-sigma unexciting confirmations for every published groundbreaking result, we would expect many of those to be statistical flukes. Some of these may be related to the so-called “decline effect” that Jonah Lehrer wrote about in the New Yorker recently: new results seem to get less statistically significant over time as more measurements are made. Finally, as my recent interlocutor, Andrew Gelman, points out “classical statistical methods that work reasonably well when studying moderate or large effects… fall apart in the presence of small effects.”

(In fact, Overbye discussed the large number of “false detections” in astronomy and physics in another Times article almost exactly a year ago.)

Unfortunately all of this can make it very difficult to interpret — and trust — statistical statements in the scientific literature, although we in the supposedly hard sciences have it a little easier as we can often at least enumerate the possible problems even if we can’t always come up with a good statistical model to describe our ignorance in detail.

Astrophysics, Clocks and Fundamental Constants

2011-07-26T09:33:12Z

I spent last week at the Physizkentrum Bad Honnef on the Rhine, near Cologne, at conference with the name and wide-ranging remit “Astrophysics, Clocks and Fundamental Constants”. We were all there to talk about the ideas and technologies that relate those disparate fields: Can we measure what we think of as the fundamental constants of the universe (for example, the speed of light, c, or Newton’s constant of gravitation, G)? Here on Earth, this becomes the discipline of metrology, the science of measuring things. Traditionally, we would do this by comparing lengths to some standard meter stick, or masses to a standard kilogram. In fact, there is a kilogram in a vault outside of Paris, against which all others are meant to be compared, but which seems to be drifting away from the other standard kilograms elsewhere!

So the more modern way is to define our units of measure in terms of well-understood physical systems. As of 1967, the second has been defined as “the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom”.

Although the metrologists worldwide aren’t quite there yet, the eventual goal is to define all units this way, or by defining the physical constants to have specific numerical values. For example, the speed of light is defined to be c=299,792,458 meters per second. When combined with the definition of the second in terms of caesium atoms, this, in turn, defines the meter. We can then cascade our way to the kilogram, the ampere, and the other fundamental units by suitable combinations of physical systems and defined constants. In fact, the latest revision of the constants was released last week. When this is all done, in a few years, this will make up the “New SI” system of units.

The meeting was full of careful, painstaking physicists who are trying to make these measurements to a precision of a few parts in 100 million or better, including some synchronising atomic clocks which reminded me of my very first work at an observatory doing laser-lunar-ranging to measure the distance to the moon and laser-satellite-ranging as an alternate way to synchronise clocks. In some contrast, I talked about cosmology, where we are happy to refer to measurements of the density of the Universe to 1% as “precision cosmology”.

However, there is an exciting middle ground in a few areas of astrophysics. Millisecond pulsars, spinning neutron stars which I wrote about in my recent reminiscence of Don Backer, are clocks nearly as good as the best yet built in a laboratory on earth.

There was also a series of talks about attempts to measure the variation of these so-called constants over cosmological distances and times, a variation not present in most of our theories, but not logically impossible. There was a group representing a contingent at the University of New South Wales who have consistently, with very careful measurements of quasar absorption lines, found changes in the fine structure constant (α≃1/137), most recently and very unexpectedly varying across the sky. I admit that I am nearly certain that this result will turn out to be incorrect. But, as the chair of a session at last week’s meeting, I did my best to encourage a robust dialogue between the UNSW group and their interlocutors who claim to have found no such variation. Needless to say, no one’s mind was changed, but I think the rest of us understand the disagreement at least a little bit better. And I admit that I am dissatisfied with both sides’ explanations — the disagreements come down to the understanding and treatment of so-called “systematic errors”, the often-unavoidable errors that creep into these complicated measurements due to inaccuracies of calibration, and of the way the instrument is built. After listening to a few hours of discussion, my meagre understanding is that the Aussies may be slightly too cavalier in their treatment, but the other group seems far too conservative, essentially defining their result as contaminated and therefore unsuitable for any sort of further statistical treatment. I look forward to the next generation of experiments so that we can reduce these errors so that we can get or refute the extraordinary evidence required for these extraordinary claims.

Finally, on an unrelated note, here’s one of my favorite rooms from my visit to Köln’s Museum Ludwig of Modern Art: (Not as spectacular as Gerhard Richter’s stained glass in the Cathedral, but easier to photograph.)

Remembering Don Backer

2011-07-25T16:57:15Z

Today is the one-year anniversary of the death of Professor Don Backer, an astronomer at the University of California, Berkeley. I was a friend, colleague and collaborator of Don, and I never had the chance to appropriately memorialize him on that sad day a year ago.

Don was a great radio astronomer who understood both the technical details of the equipment that he used, as well as the new science enabled by that technology. He was best known for having discovered the first millisecond pulsar — a neutron star more massive than the sun and only tens of miles across, spinning at over 1000 revolutions per second.

Millisecond pulsars are exquisite clocks, comparable to the best that can be built on earth. We can use that to not only measure the properties of the pulsar itself, but also to monitor the spacetime in between the pulsar and the earth. That’s how I got to work with Don: he was interested in using pulsar timing to measure gravitational waves from the collisions of supermassive black holes at the centers of galaxies throughout the Universe, as their host galaxies merge and grow over time. We calculated the expected signal from those sources and made some predictions for how they might be detected by future pulsar observations.

Today at Imperial, on this sad anniversary, we had a talk from Professor Andrea Lommen from Franklin and Marshall College, one of Don’s former students, who has dedicated her recent career to the detection of gravitational radiation using a Pulsar Timing Array. That this field, based on Don’s original discovery as well his subsequent ideas, has grown to a world-wide effort, is testament to his energy and excellence as a science.

In addition to that energy and excellence, I remember Don as a patient mentor when I was a postdoc looking for a permanent job, as good at listening and asking questions as explaining to a naive theorist those many experimental details that he understood better than anyone. This questioning on small and large scales led him into new fields and new questions; over the last few years he became interested in the PAPER experiment, observing 21 cm radiation which can trace the evolution of gas in the Universe over billions of years.

As scientists we continue to miss his contributions to these and other fields, and as his friends we just miss him.

Urban Sputnik

2011-07-22T09:34:17Z

Urban Sputnik is a new interactive cosmology exhibit currently showing at the Royal Institution. It was created by Vanessa Harden and Dominic Southgate of Gammaroot Design collaborating with some Imperial Astrophysicists: me, Dave Clements and Roberto Trotta. Unlike my other recent foray into the science/art overlap, this one is a bit more didactic (that is, scientifically accurate!)

We’ve designed five different exhibits, and, supported by an award from the STFC, Vanessa and Dominic have made two of them. One tries to show how the shape of the Universe can seem flat up close, but curved due to the mass and energy on the largest scales. Another shows how the expansion of the Universe results in a redshift — light from further away loses energy, changing its wavelength and frequency.

The pieces are on display at the Royal Institution through 29 July, and there’s a closing event on Thursday 28 July where we’ll talk about the exhibit and both the science and design principles behind it (the event is free, but tickets are recommended to be sure you get a seat!).

Kind of Bayesian

2011-07-15T17:23:19Z

[Apologies — this is long, technical, and there are too few examples. I am putting it out for commentary more than anything else…]

In some recent articles and blog posts (including one in response to astronomer David Hogg), Columbia University statistician Andrew Gelman has outlined the philosophical position that he and some of his colleagues and co-authors hold. While starting from a resolutely Bayesian perspective on using statistical methods to measure the parameters of a model, he and they depart from the usual story when evaluating models and comparing them to one another. Rather than using the techniques of Bayesian model comparison, they eschew them in preference to a set of techniques they describe as ‘model checking’. Let me apologize in advance if I misconstrue or caricature their views in any way in the following.

In the formalism of model comparison, the statistician or scientist needs to fully specify her model: what are the numbers needed to describe the model, how does the data depend upon them (the likelihood), as well as a reasonable guess for what those numbers night be in the absence of data (the prior). Given these ingredients, one can first combine them to form the posterior distribution to estimate the parameters but then go beyond this to actually determine the probability of the fully-specified model itself.

The first part of the method, estimating the parameters, is usually robust to the choice of a prior distribution for the parameters. In many cases, one can throw the possibilities wide open (an approximation to some sort of ‘complete ignorance’) and get a meaningful measurement of the parameters. In mathematical language, we take the limit of the posterior distribution as we make the prior distribution arbitrarily wide, and this limit often exists.

The problem, noticed by most statisticians and scientists who try to apply these methods is that the next step, comparing models, is almost always sensitive to the details of the choice of prior: as the prior distribution gets wider and wider, the probability for the model gets lower and lower without limit; a model with an infinitely wide prior has zero probability compared to one with a finite width.

In some situations, where we do not wish to model some sort of ignorance, this is fine. But in others, even if we know it is unreasonable to accept an arbitrarily large value for some parameter, we really cannot reasonably choose between, say, an upper limit of 10¹⁰⁰ and 10⁵⁰, which may have vastly different consequences.

The other problem with model comparison is that, as the name says, it involves comparing models: it is impossible to merely reject a model tout court. But there are certainly cases when we would be wise to do so: the data have a noticeable, significant curve, but our model is a straight line. Or, more realistically (but also much more unusually in the history of science): we know about the advance of the perihelion of Mercury, but Einstein hasn’t yet come along to invent General Relativity; or Planck has written down the black body law but quantum mechanics hasn’t yet been formulated.

These observations lead Gelman and company to reject Bayesian model comparison entirely in favor of what they call ‘model checking’. Having made inferences about the parameters of a model, you next create simulated data from the posterior distribution and compare those simulations to the actual data. This latter step is done using some of the techniques of orthodox ‘frequentist’ methods: choosing a statistic, calculating p-values, and worrying about whether your observation is unusual because it lies in the tail of a distribution.

Having suggested these techniques, they go on to advocate a broader philosophical position on the use of probability in science: it is ‘hypothetico-deductive’, rather than ‘inductive’; Popperian rather than Kuhnian. (For another, even more critical, view of Kuhn’s philosophy of science, I recommend filmmaker Errol Morris’ excellent series of blog posts in the New York Times recounting his time as a graduate student in philosophy with Kuhn.)

At this point, I am sympathetic with their position, but worried about the details. A p-value is well-determined, but remains a kind of meaningless number: the probability of finding the value of your statistic as measured or worse. But you didn’t get a worse value, so it’s not clear why this number is meaningful. On the other hand, it is clearly an indication of something: if it is unlikely to have got a worse value then your data must, in some perhaps ill-determined sense, be itself unlikely. Indeed I think it is worries like this that lead them very often to prefer purely graphical methods — the simulations ‘don’t look like’ the data.

The fact is, however, these methods work. They draw attention to data that do not fit the model and, with well-chosen statistics or graphs, lead the scientist to understand what might be wrong with the model. So perhaps we can get away without mathematically meaningful probabilities as long as we are “just” using them to guide our intuition rather than make precise statements about truth or falsehood.

Having suggested these techniques, they go on to make a rather strange leap: deciding amongst any discrete set of parameters falls into the category of model comparison, against their rules. I’m not sure this restriction is necessary: if the posterior distribution for the discrete parameters makes sense, I don’t see why we should reject the inferences made from it.

In these articles they also discuss what it means for a model to be true or false, and what implications that has for the meaning of probability. As they argue, all models are in fact known to be false, certainly in the social sciences that most concerns Gelman, and for the most part in the physical sciences as well, in the sense that they are not completely true in every detail. Newton was wrong, because Einstein was more right, and Einstein is most likely wrong because there is likely to be an even better theory of quantum gravity. Hence, they say, the subjective view of probability is wrong, since no scientist really believes in the truth of the model she is checking. I agree, but I think this is a caricature of the subjective view of probability: it misconstrues the meaning of ‘subjectivity’. If I had to use probabilities only to reflect what I truly believe, I wouldn’t be able to do science, since the only thing that I am sure about my belief system is that it is incoherent:

Do I contradict myself?
Very well then I contradict myself,
(I am large, I contain multitudes.)
— Walt Whitman, Song of Myself

Subjective probability, at least the way it is actually used by practicing scientists, is a sort of “as-if” subjectivity — how would an agent reason if her beliefs were reflected in a certain set of probability distributions? This is why when I discuss probability I try to make the pedantic point that all probabilities are conditional, at least on some background prior information or context. So we shouldn’t really ever write a probability that statement “A” is true as P(A), but rather as P(A|I) for some background information, “I”. If I change the background information to “J”, it shouldn’t surprise me that P(A|I)≠P(A|J). The whole point of doing science is to reason from assumptions and data; it is perfectly plausible for an actual scientist to restrict the context to a choice between two alternatives that she knows to be false. This view of probability owes a lot to Ed Jaynes (as also elucidated by Keith van Horn and others) and would probably be held by most working scientists if you made them elucidate their views in a consistent way.

Still, these philosophical points do not take away from Gelman’s more practical ones, which to me seem distinct from those loftier questions and from each other: first, that the formalism of model comparison is often too sensitive to prior information; second, that we should be able to do some sort of alternative-free model checking in order to falsify a model even if we don’t have any well-motivated substitute. Indeed, I suspect that most scientists, even hardcore Bayesians, work this way even if they (we) don’t always admit it.

Guest post: finding the most distant quasar

2011-07-12T19:53:39Z

A couple of weeks ago, a few of my astrophysics colleagues here at Imperial found the most distant quasar yet discovered, the innocuous red spot in the centre of this image:

One of them, Daniel Mortlock, has offered to explain a bit more:

Surely there’s just no way that something which happened 13 billion years ago — and tens of billions of light years away — could ever be reported as “news”? And yet that’s just what happened last week when world-renowned media outlets like the BBC, Time and, er, Irish Weather Online reported the discovery of the highly luminous quasar ULAS J1120+0641 in the early Universe. (Here is a longer list of links to discussions of the quasar in the media: although at least this discovery was generally included under the science heading — the Hawai’i Herald Tribune some how reported it as “local news”, which shows the sort of broad outlook not normally associated with the most insular of the United States.) The incongruity of the timescales involved became particular clear to me when I, as one of the team of astronomers who made this discovery, fielded phonecalls from journalists who, on the one hand, seemed quite at home with the notion of the light we’ve seen from this quasar having made its leisurely way to us for most of the history of the Universe, and then on the other hand were quite relaxed about a 6pm deadline to file a story on something they hadn’t even heard of a few hours earlier. The idea that this story might go from nothing to being in print in less than a day also made a striking contrast with the rather protracted process by which we made this discovery.

The story of the discovery of ULAS J1120+0641 starts with the United Kingdom InfraRed Telescope (UKIRT), and a meeting of British astronomers a decade ago to decide how best to use it. The consensus was to perform the UKIRT Infrared Deep Sky Survey (UKIDSS), the largest ever survey of the night sky at infrared wavelengths (i.e., between 1 micron and 3 microns), in part to provide a companion to the highly successful Sloan Digital Sky Survey (SDSS) that had recently been made at the optical wavelengths visible to the human eye. Of particular interest was the fact that the SDSS had discovered quasars — the bright cores of galaxies in which gas falling onto a super-massive black hole heats up so much it outshines all the stars in the host galaxy — so distant that they are seen as they were when the Universe was just a billion years old. Even though quasars are much rarer than ordinary galaxies, they are so much brighter that detailed measurements can be made of them, and so they are very effective probes of the early Universe. However there was a limit to how far back SDSS could search as no light emitted earlier than 900 million years after the Big Bang reaches us at optical wavelengths due to a combination of absorption by hydrogen atoms present at those early times and the expansion of the Universe stretching the unabsorbed light to infrared wavelengths. This is where UKIRT comes in — whereas distant sources like ULAS J1120+0641 are invisible to optical surveys, they can be detected using infrared surveys like UKIDSS. So, starting in 2005, UKIDSS got underway, with the eventual aim of looking at about 10% of the sky that had already been mapped at shorter wavelengths by SDSS. Given the number of slightly less distant quasars SDSS had found, we expected UKIDSS to include two or three record-breaking quasars; however it would also catalogue tens of millions of other astronomical objects (stars in our Galaxy, along with other galaxies), so actually finding the target quasars was not going to be easy.

Our basic search methodology was to identify any source that was clearly detected by UKIDSS but completely absent in the SDSS catalogues. In an ideal world this would have immediately given us our record-breaking quasars, but instead we still had a list of ten thousand candidates, all of which had the desired properties. Sadly it wasn’t a bumper crop of quasars — rather it was a result of observational noise, and most of these objects were cool stars which are faint enough at optical wavelengths that, in some cases, the imperfect measurement process meant they weren’t detected by SDSS, and hence entered our candidate list. (A comparable number of such stars would also be measured as brighter in SDSS than they actually are; however it is only the objects which are scattered faintward that caused trouble for us.) A second observation on an optical telescope would suffice to reject any of these candidates, but taking ten thousand such measurements is completely impractical. Instead, we used Bayesian statistics to extract as much information from the original SDSS and UKDISS measurements as possible. By making models of the cool star and quasar populations, and knowing the precision of the SDSS and UKIDSS observations we could work out the probability that any candidate was in fact a target quasar. Taking this approach turned out to be far more effective than we’d hoped — almost all the apparently quasar-like candidates had probabilities of less than 0.01 (i.e., they were only a 1% chance to be a quasar) and so could be discarded from consideration without going near a telescope.

For the remaining 200-odd candidates we did make follow-up observations, on UKIRT, the Liverpool Telescope (LT) or the New Technology Telescope (NTT) and in fewer than ten cases were the initial SDSS and UKIDSS measurements verified. By this stage we were almost certain that we had a distant quasar, although in most cases it was sufficiently bright at optical wavelengths that we knew it wasn’t a record-breaker. However ULAS J1120+0641, identified in late 2010, remained defiantly black when looked at by the LT, and so for the first time in five years we really thought we might have struck gold. To be completely sure we used the Gemini North telescope to obtain a spectrum — essentially splitting up the light into different wavelengths, just as happens to sunlight when it passes through water droplets to form a rainbow. The observation was made on Saturday, November 2010 and we got the spectrum e-mailed to us the next day and confirmed that we’d finally got what we were looking for: the most distant quasar ever found.

We obtained more precise spectra covering a wider range of wavelengths using Gemini (again) and the Very Large Telescope, the results of which are shown here:

The black curve shows the spectrum of ULAS J1120+0641; the green curve shows the average spectrum of a number of more nearby quasars (but redshifted to longer wavelengths to account for the cosmological expansion). The two are almost identical, with the obvious exception of the cut-off at 1 micron of ULAS J1120+0641 which comes about due to the absorption by hydrogen in front of the quasar. We had all the data needed to make this plot by the end of January, but it still took another five months for the results to be published in the June 30 edition of Nature — rather longer than the 24-hour turn-around of the journalists who eventually reported on this work. But if we’d given up on the search after four years — or if the Science and Technology Funding Council had withdrawn funding for UKIRT, as seemed likely at one point — then we never would have made this discovery. It was a long time coming but for me — and hopefully for astronomy — it was worth the wait.

Sepia Astronomers

2011-06-30T12:51:32Z

When cleaning out an office here in the Astrophysics Group in the Physics Department at Imperial College, we came across this photo: The background is the Mark I telescope at Jodrell Bank, and the man in the middle with the notebook has been identified as either Fred Hoyle or Francis Graham-Smith (which is more likely now that I look at it — thanks, Peter!). Do my astronomy colleagues (or anyone else) have any more information?

Distant objects and nearby music

2011-06-29T22:55:40Z

Normally, I would be writing about the discovery of the most distant quasar by Imperial Astronomers using the UKIDSS survey (using excellent Bayesian methods), but Andy and Peter have beaten me to it. To make up for it, I’ll try to get one of the authors of the paper to discuss it here themselves, soon. (In the meantime, some other links, from STFC, ESO, Gemini, …)

But I’ve got a good excuse: I was out (with one of those authors, as it happens) seeing Paul Simon play at the Hammersmith Apollo:

Like my parents, Paul Simon grew up in the outer boroughs of New York City, a young teenager at the birth of rock’n’roll, and his music, no matter how many worldwide influences he brings in, always reminds me of home.

He played “The Sound Of Silence” (solo), most of his 70s hits from “Kodachrome” and “Mother and Child Reunion” to the soft rock of “Slip Slidin’ Away”, and covers of “Mystery Train” and “Here Comes the Sun”. But much of the evening was devoted to what is still his masterpiece, Graceland. (We were a little disappointed that the space-oriented backing video for “The Boy in the Bubble” included images neither of the Cosmic Microwave Background nor the new most distant quasar….)

Copenhagen

2011-06-08T22:49:18Z

Like my friend and colleague Peter Coles, I am just returned from the fine wine-soaked dinner for the workshop “Cosmology and Astroparticle physics from the LHC to PLANCK” held at the Niels Bohr Institute in Copenhagen. It is an honor to visit the place where so many discoveries of 20th Century physics were made, and an even greater honor to be able to speak in the same auditorium as many of the best physicists of the last hundred years. (You can see the conference photo here; apparently, the trumpet is just the latest in a long series.)

I talked about the most recent results from the Planck Satellite, gave an overview of the state of the art of (pre-Planck) measurements of the Cosmic Microwave Background, and found myself in what feels like the unlikely role as a mouthpiece for a large (and therefore conservative) community, basically putting forward the standard model of cosmology: a hot big bang with dark matter, dark energy, and inflation — a model that requires not one, not two, but (at least) three separate additions to particles and fields that we know from terrestrial observations: one to make up the bulk of the mass of today’s Universe, another to make the Universe accelerate in its expansion today, and another to make it accelerate at early times. It would sound absurd if it weren’t so well supported by observations.

Mekonathon

2011-05-29T14:37:35Z

As I’ve said repeatedly, the Mekons are my favorite rock ’n’ roll band. Their music has sustained me since about 1990, after I first saw them at Chicago’s Cabaret Metro, already more than a decade into their careers. By then, they had already gone beyond their punk roots, invented alt.country avant la lettre, and skewered capitalism on Mekons Rock and Roll. But despite all the complications, they love that rock and roll, and they’ve put on several of the best shows I’ve heard, starting with that gig in Chicago, which had become a sort of hometown for this widely scattered British band. I had only heard a few songs before that night, but I was immediately converted, not just by vocalist Sally Timms in her silver lamé dress, one of the sexiest performers I had ever seen, but by the lot of them, fronted by Jon Langford and Tom Greenhalgh, serious enough about their chosen music to know not to take it too seriously. Now in their 50s, they are all magnetic, still sexy as hell, even when they’re more-or-less knowingly fucking around, drinking too much, and still not taking anything too seriously.

So I couldn’t miss their latest UK visit, two gigs last weekend in London. With the blinders of any true fan, I admit I don’t understand why the Mekons aren’t a lot more rich and famous, and I was a little disheartened to find the clubs they played, The Lexington in Kings X, and the Windmill in Brixton, are basically pubs with stages. They packed the places, largely with mid-50s blokes in flannel shirts and short hair, who were maybe more interested in reprises of the 70s material than the (inarguably better) stuff from the 80s, 90s and 00s — with their first album of the new decade due later in the year — but I don’t quite get why they shouldn’t be playing and filling bigger clubs.

The gigs (yes, I went to both) surveyed their nearly three and a half decades, from punk to country to whatever hybrid they’re up to now, wielding their guitars — not to mention accordion, fiddle and mandolin — to tell what usually end up as stories of political or emotional betrayal, unrequited love for a better world. They played their gorgeous cover of John Anderson’s Wild and Blue, Sally taking some time for singing off from the shouting she seems to sometimes prefer; considered the modern history of London in Thee Olde Trip to Jerusalem; and lamented the ongoing death of rock ’n’ roll in Memphis, Egypt. Saturday, with multi-instrumentalist (and occasional cohort of John Lydon) Lu Edmonds off for the night, they devoted their encore to a reworking of their punk phase, albeit without putting down the accordion and fiddle.

Friday was tighter, less silly, probably less drunk — and was partially filmed for the still-planned Mekons movie — but I’m happy to put up with the Mekons however they come, put a few quid into their pockets so that they keep getting together every few years and give us a new record and a few gigs.

Bonus: A shambles of an encore from the Zurich leg of the tour, featuring Toronto’s Sadies and the Mekons performing “Memphis, Egypt” and “Where Were You?”. If you don’t already love the Mekons, this won’t convert you, but if you do, it may remind you why, and will certainly put a smile on your face. (Via Back to the World)

More from the Spherical Cows

2011-05-08T11:30:36Z

In a very different way of translating scientific ideas into other forms and media, my friend, colleague and collaborator Lloyd Knox is back with a new series of short video documentaries under the auspices of his Spherical Cow Company. After a hiatus of a few months, they set themselves a challenge of producing three videos in three days.

The first video discusses the idea that the structure we see in the Universe today — galaxies, clusters of galaxies and the three-dimensional patterns that they form — was seeded by microscopic fluctuations traceable to the innate randomness of quantum mechanics, regions of slightly higher or lower density than average. These fluctuations were originally tiny both in size — much smaller than the scale of an atom, and in amplitude — the difference between the fluctuation and the average may have been only one part in a septillion (which is 1 followed by 24 zeros). A short early period of cosmological inflation caused the fluctuations to expand to macroscopic size, and 14 billion years of gravity caused them to grow, attracting more and more matter. But don’t take my word for it — go watch Lloyd’s video.

In the next two days, Lloyd moved the discussion closer to home. First, perhaps inspired by a sunny day in California, he talks about powering the sun, or more precisely, the initial spark to the sun’s burning provided by gravity as it was formed. Finally, on Friday, Lloyd talks about neutrinos, a by-product of the sun’s nuclear burning, which gives us a way of looking directly into the center of the sun — a very difficult way, since we can only detect a tiny fraction of all of the neutrinos streaming out towards us.

(The Company’s site also has an excellent discussion between Lloyd and one his readers about some of the subtle points of the Cosmic Microwave Background radiation that both Lloyd and I have spent much of our careers thinking about.)

Senses working overtime

2011-05-08T09:20:29Z

I listened over the weekend to a story on the podcast of the radio show Studio 360 about Wanda Diaz-Merced, a blind astronomer. She is working hard at “sonification” — representing astronomical data in sound rather than in graphs. Of course, this works best for certain kinds of data — I gather from the piece that she has specialized in x-ray time series — and this seems to be the basis of her research as a graduate student at Harvard’s Smithsonian Astrophysical Observatory.

I was bowled over by the passion and energy evident in the interview. I spend all of my days reading papers, staring at screens or pages of equations and graphs; were I to lose my sight I can’t conceive of how I would be able to go on as an astrophysicist. I hope that Ms Diaz-Merced finds all of the support she needs in our field — and great data to which to apply her techniques.

Beyond Entropy and Ourselves

2011-05-04T21:35:32Z

Last summer, I helped make a (fake) time machine, an exercise in “creative misinterpretation” (in the words of my architect partner, Shin Egashira). This was part of the Beyond Entropy project organized by the Architecture Association — we showed it then in Venice but now Londoners will get a chance to see the work in the AA’s own gallery, opening Friday, 6 May. There will also be a series of events to mark the exhibit, including a night discussing time travel (and, um, shamanism) with Shin and photographer Goswin Schwendinger on May 20.

Update: New Scientist and Nature have reviews of the show.

Also, in a nice bit of synchronicity, the Royal Society is hosting the great Beyond Ourselves exhibition, featuring works by artists including Geraldine Cox, Imperial College Physics’ artist-in-residence. You have to book ahead, but it’s well worth the trip to see her and her colleagues’ fantastic explorations of scientists at work.

Submission

2011-05-04T20:40:17Z

Today, our Astrophysics Group at Imperial College submitted our first application for a new STFC “Consolidated Grant”.

These are intended to cover all of the astrophysics being done in the department for three years at a time, combining aspects of former so-called “standard” and “rolling” grants, both of which it replaces. (If you don’t know what those are, you probably don’t care.) It remains to be seen whether this new system ends up with the best or the worst of the two old ones, and whether it brings the promised economies of scale resulting from fewer, larger grants.

For us, at least, it’s more work for the first few years: we will complete our consolidation with the rest of our department in another application in only one year’s time.

We — the whole community — are worried by the changeover to a new system (and not only because we fear change). This happens now that the funding situation has stabilized after a few years of decline — down to a level about half of its 2006 maximum. Worse, a higher than average number of groups are applying this year. Will this be met with a proportionally higher allocation of funds? Or will groups just have to try again (as we are in a year)? John Womersley, Director of STFC Science Programmes answered some of these questions at the National Astronomy Meeting a few weeks ago, but the answers were, perhaps understandably, equivocal.

This was my first chance to be the Principal Investigator on a large grant proposal in the UK. All the usual problems with organizing a team of academic scientists apply: we’re bad at managing (at least, I am), we are bad at being managed, it’s like herding cats, etc. Still, we pulled together just in time, with the more-than-able help of various administrators who put up with our delays and last-minute changes.

And now, we wait…

Spacetacular!

2011-04-07T18:26:17Z

What are blogs for, if not self-publicity? In that vein, I’ll be appearing at the Spacetacular! night on April 12, in honor of Yuri’s night: the 50th anniversary of Yuri Gagarin’s first-ever manned space flight.

The evening is organized by Londonist editor Matt Brown along with comedian and presenter Helen Keen, hosting a line-up of comedians and scientists. I promise not to be funny so you can tell which I am — I’ll be talking for ten minutes or so about my adventures in space (well, working on a big space-based project, the Planck Surveyor Satellite).

We scientists often, and correctly, make the point that manned space flight has almost nothing to do with science. But I certainly wouldn’t be the scientist I am if it weren’t a morning long ago in Hooks Lane Nursery School watching one of those early moon launches, thinking I wanted to have something, anything, to do with that. So let us know if you want to come celebrate [the Facebook event link is currently broken, but this one is still up.] this amazing human achievement with comedy and science (and spacey costumes) at the Camden Head Pub in London next week.

End of Term

2011-03-30T20:46:36Z

I’ve just finished another term, in fact the heaviest teaching load I’ve ever had at once: a twenty-six hour lecture course, three hours a week as one of several computer lab “demonstrators”, and another four hours or so per week in first-year student tutorials.

For those from outside of the Imperial system: our tutorials are small group meetings during which we go over a selection of the problem sheets handed out during the week in the lecture courses; here, like most of the UK, these are not explicitly marked, but instead the students get the solutions a week or so after they are handed out. The tutorial session is one of the few chances for any sort of discussion or feedback.

The tutorials can be fun and even challenging (but I’m glad I get to see the answers before the students). It is heartening to see the students trying — sometimes struggling — to really understand the problems. However, the fourth hour in a week going over the same problems can get repetitive; there aren’t that many different questions the students ask.

On the other hand, lab demonstrating doesn’t offer much intellectual at all. I have mostly supervised computer labs, which involves standing around while the students work their way through a “script”, writing programs and (we hope) learning about programming. I admit that I don’t think this is a particularly efficient use of my time: although considerable overall high-level organization is needed, the labs themselves could be (and indeed are, partially) monitored by graduate students. Unfortunately, they don’t get more than beer money for their trouble — and postdocs don’t get paid at all.

The best part of undergraduate teaching for me, though, is lecturing. When it goes well, it can be a remarkably effective way of communicating. Of course, it doesn’t always go well. Sometimes I’m not as well-prepared as I would like, or sometimes I don’t even understand the material as well as I need to. Sometimes the students don’t have the background that I thought they did. And sometimes the material is just hard, too hard to really get the first time through. Even problem sheets and studying for exams isn’t always enough: I certainly admit that I didn’t really understand much of the material that I now use every day until I was in graduate school, applying it in the course of my research. And some stuff I didn’t understand until I had to teach it (which implies that there is plenty of physics that I still don’t understand, so still much more to learn).

This term’s Cosmology course felt pretty good: after three years not only do I understand the material, but also I understand something about how to explain it to not-yet-expert upper-level physics students. The downside of this is that my explanations get a bit longer every year, so it gets harder and harder to squeeze in the most exciting material which inevitably has to come at the end, building on the foundation of the rest of the course.

This year, the Physics Department has an artist-in-residence, Geraldine Cox. Among her many other cool projects, she has been lurking in the back of our lecture theatres, sketching furiously. Many thanks to her for these pictures of me at the blackboard, in one of my favorite striped shirts:

(The graph on the upper left is labeled “Do we live in a special time?” — We seem to live at a time labeled by the vertical line, just as the Universe is transitioning from being mostly made of “matter” — the middle of the three plateaus in the graph — to mostly something very like Einstein’s cosmological constant, or the so-called “Dark Energy” — the rightmost plateau, which may go on infinitely far to the right. So we might have expected to find ourselves near a plateau rather than a one of the few times in between. This is an anthropic argument, and must be treated with care.)

As always, I welcome feedback, anonymous or otherwise, from any of my students on this course or any other. (When I asked for some comments a few weeks into the term, the most amusing came from the student who praised my voice and asked if I was a singer — which doesn’t jibe with the other, less positive, comments on my American accent….)

Finally, today was one of the high points of post-graduate teaching: one of my students, Jude Bowyer, passed his PhD viva with his thesis, Local Methods for the Cosmic Microwave Background. Well done to the soon-to-be Dr. Bowyer!

EBEX in Flight

2011-03-29T07:18:40Z

Many of my colleagues in the EBEX experiment have just lit out for the west. Specifically, the team is heading off to Palestine (pronounced “Palesteen”), Texas, to get the telescope and instrument ready for its big Antarctic long-duration balloon flight at the end of the year, when we hope to gather our first real scientific data and observe the temperature and polarization of the cosmic microwave background (CMB) radiation. Unlike the Planck Satellite, which has a few dozen detectors changed little from those that flew on MAXIMA and BOOMEReNG in the 1990s, EBEX can use more modern technology, and will fly with thousands of detectors, allowing us to achieve far greater sensitivity to the smallest variations in the CMB.

Asad, one of the EBEX postdocs, involved in the experiment for several years, will be writing on the EBEX in Flight blog about the experiences down in Texas and, we hope, the future path of the team and telescope down to Antarctica. Follow along as the team drives across the country (at least twice), assembles and tests the instrument, breaks and fixes things, sleeps too little, works too hard, and, we hope, builds the most sensitive CMB experiment yet deployed. (And of course, eats cheeseburgers.)

And if you want a change from cosmology, you can instead follow along with another friend, Marc, who is trying to see if he can come to grips with writing on an iPad in the supposedly post-PC world, over at typelesswriter.

Industrial Action?

2011-03-23T21:43:33Z

This week is the 100th anniversary of one of the most important events in the Labor movement (at least back in the US): the Triangle Shirtwaist Factory fire, a disaster in which the garment factory’s sweatshop conditions led to the death of almost 150 workers, mostly Jewish immigrant women, locked by their bosses into their lower-Manhattan factory while the fire raged. This tragedy had remarkably swift and positive repercussions, spurring the growth of the once-powerful International Ladies’ Garment Workers’ Union and resulting in a new regime of labor laws actually intended to help workers and not their employers. (The New York Times is commemorating the fire on one of their blogs.)

So I am saddened and a little guilty that I will not be participating in the labor action being called for this week by my own union. The University and College Union represents academics in UK higher education institutions. In this precarious time for Universities, especially here in England, I am glad, in principle, that there is a union representing academics, a group of people who certainly aren’t in it for the money, and deserve at least a modicum of recompense, job security, and respect.

In principle. In practice the UCU has spent much of the last decade or so in the news not fighting for workers’ rights but because of the stance of some of its more radical (but sadly misguided) members toward Israel than for trying to improve the condition of its own workers.

Now, however, they’re trying to take on an issue that will certainly impact all of us (academics): pensions, which our employers contend have to dwindle in the light of supposed economic realities. I suspect and fear that, in the long run, the employers may actually be right, given the ageing and long-lived population, as is well known. But I also suspect that they are not negotiating with everything appropriate on the table. Hence, an impasse, and one that if not resolved will certainly harm all of us: academics, administrators and, not least, students. During this last week of our term, with only two hours of lectures left in my course, I would have preferred “action short of a strike” that would have enabled me to fulfil my teaching duties and my responsibilities toward my (blameless) students. Although, yes, I appreciate that the whole point of a strike is to cause harm, and show how indispensable we workers are, but this relies on generating sympathy for the workers, and anger directed at the employers. But with the rather woeful PR job by the UCU, I doubt many of our students would have known why their lecturers aren’t around.

NAM 2011 — On the Lookout for Cosmologists

2011-03-21T22:31:45Z

(Apologies to the non-cosmologists and non-Brits who won’t find much of interest in the following.)

This year’s UK National Astronomy Meeting will be held 17-21 April, in Llandudno, North Wales. In the usual way of British “seaside resorts” (scare quotes are certainly appropriate for that phrase) Llandudno sticks frighteningly out into the Irish Sea but, you never know, it might actually seem like Springtime when we gather there.

In any event, there is a lot of astronomy going on in the UK, so NAM is a pretty big meeting, with significant communities working on everything from our solar system out to intergalactic space and the Universe as a whole. To help cover those large scales, I’m organizing a series of sessions on Cosmology, and there are still some open slots for any UK scientists. I would especially love to have lots of input from students and young postdocs looking to show off their work.

The deadline for the submission of abstracts is this Friday — please join us in Wales next month!

100 Years

2011-03-14T12:38:23Z

I have just had the honor of celebrating the 100th Birthday of Dora Jaffe, my grandmother, born March 14, 1911 (a date she shares with Albert Einstein!), in Shepetivka, Ukraine (then part of Russia). Her father, Leib (Lewis) Greenberg, emigrated just before the war, stranding her and her mother until they could make it across Europe and the Atlantic to New York City. Speaking only Yiddish, a summer playing in the Bronx taught her enough English to start school in the Fall, and she’s been a proud American ever since.

So I know it was a pleasure for her to receive this (redacted) envelope and its contents: In fact, when I showed it to her, a good democrat and liberal for longer than I’ve known her — her father had been a union organizer in the Ukrainian orchards before emigrating — she said that it was a special honor for her to receive it from the first black President of the United States.

She spent much of the intervening century with her husband Aaron Jaffe, my grandfather, and we recently unearthed this fantastic picture of their young life in New York together:

Now, she’s the matriarch of our family, still sharp as a proverbial tack. Twenty-six of us, from the seven cousins of my generation on up, gathered this afternoon on Long Island, New York, coming in from London, Denver, and less exotic locations like New Jersey and Brooklyn to spend the day celebrating her life, telling stories, and eating. And, of course, kvetching and gossiping like any good family.

Happy Birthday, Dora!

Tacos and Power Spectra in LA

2011-02-22T22:22:20Z

One of the perks (perqs?) of academia is that occasionally I get an excuse to escape the damp grey of London Winters. The Planck Satellite is an international collaboration and, although largely backed by the European Space Agency, it has a large contribution from US scientists, who built the CMB detectors for Planck’s HFI instrument, as well as being significantly involved in the analysis of Planck data. Much of this work is centred at NASA’s famous Jet Propulsion Lab in Pasadena, and I was happy to rearrange my schedule to allow a February trip to sunny Southern California (I hope my undergraduate students enjoyed the two guest lectures during my absence).

Visiting California, I was compelled to take advantage of the local culture, which mostly seemed to involve meals. I ate as much Mexican food as I could manage, from fantastic $1.25 tacos from the El Taquito Mexicano Truck to somewhat higher-end fare at Tinga in LA proper. And I finally got to taste bánh mì, French-influenced Vietnamese sandwiches (which have arrived in London but I somehow haven’t tried them here yet). And I got to take in the view from the heights of Griffith Park:
as well as down at street level:
And even better, I got to share these meals and views with old and new friends.

Of course I was mainly in LA to do science, but even at JPL we managed to escape our windowless meeting room and check out the clean-room where NASA is assembling the Mars Science Lab:

The white pod-like structure is the spacecraft itself, which will parachute into Mars’ atmosphere in a few years, and from it will descend the circular “sky crane” currently parked behind it which will itself deploy the car-sized Curiosity Rover to do the real work of Martian geology, chemistry, climatology and (who knows?) biology.

But my own work was for the semi-annual meeting of the Planck CTP working group (I’ve never been sure if it was intentional, but the name always seemed to me a sort of science pun, obliquely referring to the famous “CPT” symmetry of fundamental physics). In Planck, “CTP” refers to C_ℓ from Temperature and Polarization: the calculation of the famous CMB power spectrum which contains much of the cosmological information in the maps that Planck will produce. The spectrum allows us to compress the millions of pixels in a map of the CMB sky, such as this one from the WMAP experiment (the colors give the temperature or intensity of the radiation, the lines its polarization), into just a few thousand numbers we can plot on a graph.

OK, this is not a publishable figure. Instead, it marks the tenth anniversary of the first CTP working group telecon in February 2001 (somewhat before I was involved in the group, actually). But given that we won’t be publishing Planck cosmology data for another couple of years, sugary spectra will have to do instead of the real ones in the meantime.

The work of the CTP group is exactly concerned with finding the best algorithms for translating CMB maps into these power spectra. They must take into account the complicated noise in the map, coming from our imperfect instruments which observe the sky with finite resolution — that is, a telescope which smooths the sky at a scale from about half down to one-tenth of a degree — and with a limited sensitivity — every measurement has a little bit of unavoidable noise added to it. Moreover, in between the CMB, produced 400,000 years after the Big Bang, and Planck’s instruments, observing today, is the entire rest of the Universe, which contains matter that both absorbs and emits (glows) in the microwaves which Planck observes. So in practice we need to simultaneously deal with all of these effects when reducing our maps down to power spectra. This is a surprisingly difficult problem: the naive, brute-force (Bayesian), solution requires a number of computer operations which scales like the cube of the number of pixels in the CMB map; at Planck’s resolution this is as many as 100 million pixels, and there still are no supercomputers capable of doing the septillion (10²⁴) operations in a reasonable time. If we smooth the map, we can still solve the full problem, but on small scales, we need to come up with useful approximations which take advantage of what we know about the data, usually taking advantage of the very large number of points that contribute, and the so-called asymptotic theorems which say, roughly, that we can learn about the right answer by doing lots of simulations, which are much less computationally expensive.

At the required levels of both accuracy and precision, the results depend on all of the details of the data processing and the algorithm: How do you account for the telescope’s optics and the pixelization of the sky? How do you model the noise in the map? How do you remove those pixels contaminated by astrophysical emission or absorption? All of this is compounded by the necessary (friendly) scientific competition: it is the responsibility of the CTP group to make recommendations for how Planck will actually produce its power spectra for the community and, naturally, each of us wants our own algorithm or computer program to be used — to win. So these meetings are as much about politics as science, but we can hope that the outcome is that all the codes are raised to an appropriate level and we can make the decisions on non-scientific grounds (ease of use, flexibility, speed, etc.) that will produce the high-quality scientific results for which we designed and built Planck — and have worked on it for the last decade or more.

Les autres choses (scientifique)

2011-02-22T17:23:09Z

I’ve been meaning to give a shout-out to my colleagues on the ADAMIS team at the APC (AstroParticule et Cosmologie) Lab at the Université Paris 7 for a while: in addition to doing lots of great work on Planck, EBEX, PolarBear and other important CMB and cosmology experiments, they’ve also been running a group blog since the Autumn, Paper(s) of the Week et les autres choses (scientifique) which dissects some of the more interesting work to come out of the cosmology community. In particular, one of my favorite collaborators has written an extremely astute analysis of what, exactly, we on the Planck team released in our lengthy series of papers last month (which I have already discussed in a somewhat more boosterish fashion).

Don Kirshner, R.I.P.

2011-01-18T22:40:18Z

Rock’n’roll impresario Don Kirshner, “the man with the golden ear”, but better known to members of my family as “Cousin Donny”, has died at 76. He was a fixture of American adolescence from the 50s through the 70s (when rock’n’roll was mostly about adolescence).

He achieved his remarkable success behind the scenes of the music industry: producer, promoter, music publisher, manager and even occasional songwriter. He started out at the famous Brill Building, working with the songwriting duos Mann & Weil and Goffin & King and with artists like Neil Sedaka, Bobby Darin and Neil Diamond (not to mention 70s anthem-rockers Kansas). But he was best known for his work with (and some would say control of) two of rock’s most famous fake bands, The Monkees and The Archies.

In the 1970s, he tentatively stepped in front of the microphone as the host of Don Kirshner’s Rock Concert, which brought live performances of everyone from KISS and the Allman Brothers to the New York Dolls and the Sex Pistols.

His deadpan delivery was (lovingly?) mocked by Paul Shaffer on Saturday Night Live, which is likely better remembered (and better syndicated) than the Rock Concert show itself. It was, probably not coincidentally, cancelled within a couple years of the launch of MTV (which, you may recall, used to play music videos).

My condolences to his wife and children, my slightly-more-distant cousins, who I hope will eventually be as heartened as I am by the many happy reminiscences that have started showing up at the New York Times obituary and elsewhere.

Update: I’m happy to see that David Segal’s 1994 article about Don Kirshner has appeared on longreads.com.

Normal-ish

2011-01-15T10:46:19Z

Ok, the blog is back up. Disasters averted and the design is a little less ragged than before, but I’m not sure of the details.

I want to test that I can still post, and this seems a good opportunity to solicit comments to help me refine my aesthetic sensibilities. Are the sidebars over on the right too busy? Are the fonts legible? Does everything work?

Oops!

2011-01-11T14:46:01Z

I’ve recently “upgraded” my software which seems to be playing havoc with the format of the blog. The blog is visible, and in many ways nicer than before, but I’ve lost all of my lovely formatting… I hope we’ll be back to normal soon.

In any event, you can probably ignore this and read my post about Planck’s new results instead!

Planck: First results

2011-01-11T14:42:11Z

The Satellite now known as the Planck Surveyor was first conceived in the mid-1990s, in the wake of the results from NASA’s COBE Satellite, the first to detect primordial anisotropies in the Cosmic Microwave Background (CMB), light from about 400,000 years after the big bang. (I am a relative latecomer to the project, having only joined in about 2000.)

After all this time, we on the team are very excited to produce our very first scientific results. These take the form of a catalog of sources detected by Planck, along with 25 papers discussing the catalog as well as the more diffuse pattern of radiation on the sky.

Planck is the very first instrument to observe the whole sky with light in nine bands with wavelengths from about 1/3 of a millimeter up to one centimeter, an unprecedented range. In fact this first release of data and papers discusses Planck as a tool for astrophysics — as a telescope observing distant galaxies and clusters of galaxies as well as our own Galaxy, the Milky Way. All of these glow in Planck’s bands (indeed they dominate over the CMB in most of them), and with our high-sensitivity all-sky maps we have the opportunity to do astronomy with Planck, the best microwave telescope ever made. Indeed, to get to this point, we actually have to separate out the CMB from the other sources of emission and, somewhat perversely, actively remove that from the data we are presenting.

Over the last year, then, we on the Planck team have written about 25 papers to support this science; a few of them are about the mission as a whole, the instruments on board Planck, and the data processing pipelines that we have written to produce our data. Then there are a few papers discussing the data we are making available, the Early Release Compact Source Catalog and the various subsets discussing separately objects within our own Milky Way Galaxy as well as more distant galaxies and clusters of galaxies. The remaining papers give our first attempts at analyzing the data and extracting the best science possible.

Most of the highlights in the current papers provide confirmation of things that astronomers have suspected, thanks to Planck’s high sensitivity and wide coverage. It has long been surmised that most stars in the Universe are formed in locations shrouded by dust, and hence not visible to optical telescopes. Rather, the birth of stars heats the dust to temperatures much lower than that of stars, but much higher than the cold dust far from star-forming regions. This warm dust radiates in Planck’s bands, seen at lower and lower frequencies for more and more distant galaxies (due to the redshift of light from these faraway objects). For the first time, Planck has observed this Cosmic Infrared Background (CIB) at frequencies that may correspond to galaxies forming when the Universe was less than 15% of its current age, less than 2 billion years after the big bang. Here is a picture of the CIB at various places around the sky, specifically chosen to be as free as possible of other sources of emission:

Another exciting result has to do with the properties of that dust in our own Milky Way Galaxies. This so-called cosmic dust is known to be made of very tiny grains, from small agglomerations of a few molecules up to those a few tens of micrometers across. Ever since the mid-1990s, there has been some evidence that this dust emits radiation at millimeter wavelengths that the simplest models could not account for. One idea, actually first proposed in the 1950s, is that some of the dust grains are oblong, and receive enough of a kick from their environment that they spin at very high rates, emitting radiation at a frequency related to that rotation. Planck’s observations seem to confirm this prediction quantitatively, seeing its effects in our galaxy. This image of the Rho Ophiuchus molecular cloud shows that the spinning dust emission at 30 GHz traces the same structures as the thermal emission at 857 GHz:

In addition, Planck has found more than twenty new clusters of galaxies, has mapped the dust in gas in the Milky Way in three dimensions, and uncovered cold gas in nearby galaxies. And this is just the beginning of what Planck is capable of. We have not yet begun to discuss the cosmological implications, nor Planck’s abilities to measure not just the intensity of light, but also its polarization.

Of course the most important thing we have learned so far is how hard it is to work in a team of 400 or so scientists, whom — myself included — like neither managing nor being managed (and are likewise not particularly skilled at either). I’ve been involved in a small way in the editing process, shepherding just a few of those 25 papers to completion, paying attention to the language and presentation as much as the science. Given the difficulties, I am relatively happy with the results — the papers can be downloaded directly from ESA, and will be available on the ArXiV on 12 January 2011, and will eventually be published in the journal Astronomy and Astrophysics. It will be very interesting to see how we manage this in two years when we may have as many as a hundred or so papers at once. Stay tuned.

Marking Time: Longplayer

2011-01-01T18:01:03Z

Yesterday, I went to visit Longplayer, Jem Finer’s thousand-year composition, for the eleventh anniversary of its first note, played on New Years Day, 1999. Longplayer is currently controlled (performed?) from Trinity Buoy Wharf in London’s simultaneously desolate and overbuilt Docklands, covered in newly built flats and offices, with hardly a human in sight.

Jem started out as a rock’n’roller, but has expanded into broader realms of visual and sonic art, as much interested in the logistics of producing sounds as the sounds themselves; I first got to know him in his role as the artist-in-residence in Oxford’s Astrophysics group where he drew maps, played music, and built — and lived in — a beautiful plywood-and-chicken-wire radio telescope.

Longplayer will take 1000 years to play, but music technology won’t be stable for that long a period (not to mention the sociology-political systems needed to arrange transmissions). Some of these questions have also been taken up by the Long Now Foundation, with which Longplayer has become affiliated. Jem has addressed some of these questions head-on over the last year with a series of Longplayer Live performances at London’s Roundhouse, and in San Francisco, as well as upcoming performances in LA, Tasmania and Porto. Although the main composition is streamed electronically, the live versions are performed on Tibetan singing bowls (which you can sponsor if you want to support the project). Jem has also transmuted the work into “Shortplayer” which uses the same algorithm and notation but is played on more conventional instruments.

Longplayer is stationed in a gorgeous lighthouse on the Thames. As you approach, it resonates with its extended, changing melody.

For the occasion, Jem provided drinks, bagels, and the opportunity to take in the view … …and the music (this is apparently just a temporary amplifier as they recover from a power failure earlier in the year)… (More pictures of Longplayer, Trinity Buoy Wharf, and environs here.)

Of course, the New Year is well-matched to the sort of long-term contemplation that Longplayer encourages. In the US and the rest of the so-called “New World”, the very idea of a thousand years is almost absurdly long — the imprint of humankind on the American continents was radically different in the year that the people there wouldn’t have called 1011. Here in Europe, not to mention Asia, much has changed technologically and politically since then, but the broad outlines of our presence would have been recognisable. But even here, the longest-lasting institutions, such as the Church, have undergone reformations and counter-reformations, sponsored states and wars between states, and certainly couldn’t be trusted to preserve a work of art for its own sake, despite the many things that have happily made their way down to us in 2011. Knowledge, of course, has proven easier to transmit than the works themselves; we can only hope that this remains true in the digital age and the rolling obsolescence of new technologies.

Longplayer is open to the public every weekend (aside from the celebratory drinks and bagels, I assume). And of course you can follow Longplayer on Twitter and, most importantly, listen to the stream anytime, anywhere.

Bayes in the World II: Million Pound Drop

2010-12-17T09:56:02Z

Embarrassing update: as pointed out by Vladimir Nesov in the comments, all of my quantitative points below are incorrect. To maximize expected winnings, you should bet on whichever alternative you judge to be most likely. If you have a so-called logarithmic utility function — which already has the property of growing faster for small amounts than large — you should bet proportional to your odds on each answer. In fact, it’s exactly arguments like these that lead many to conclude that the logarithmic utility function is in some sense “correct”. So, in order to be led to betting more on the low-probability choices, one needs a utiltity that changes even faster for small amounts and slower for large amounts. But I disagree that this is “implausible” — if I think that is the best strategy to use, I should adjust my utility function, not change my strategy to match one that has been externally imposed. Just like probabilities, utility functions encode our preferences. Of course, I should endeavor to be consistent, to always use the same utility function, at least in the same circumstances, taking into account what economists call “externalities”.

Anyway, all of this goes to show that I shouldn’t write long, technical posts after the office Christmas party….

The original post follows, mistakes included.

An even more unlikely place to find Bayesian inspiration was Channel 4’s otherwise insipid game show, “The Million Pound Drop”. In the version I saw, B-list celebs start out with a million pounds (sterling), and are asked a series of multiple-choice questions. For each one, they can bet any fraction of their remaining money on any set of answers; any money bet on wrong answers is lost (we’ll ignore the one caveat, that the contestants must wager no money on at least one answer, which means there’s always the chance that they will lose the entire stake).

Is there a best strategy for this game? Obviously, the overall goal is to maximize the actual winnings at the end of the series of questions. In the simplest example, let’s say a question is “What year did England last win the football world cup?” with possible answers “1912”, “1949”, “1966”, and “never”. In this case (assuming you know the answer), the only sensible course is to bet everything on “1966”.

Now, let’s say that the question is “When did the Chicago Bulls last win an NBA title?” with possible answers, “1953”, “1997”, “1998”, “2009”. The contestants, being fans of Michael Jordan, know that it’s either 1997 or 1998, but aren’t sure which — it’s a complete toss-up between the two. Again in this case, the strategy is clear: bet the same amount on each of the two — the expected winning is half of your stake no matter what. (The answer is 1998.)

But now let’s make it a bit more complicated: the question is “Who was the last American to win a gold medal in Olympic Decathlon?” with answers “Bruce Jenner”, “Brian Clay”, “Jim Thorpe”, and “Jess Owens”. Well, I remember that Jenner won in the 70s, and that Thorpe and Owens predate that by decades, so the only possibilities are Jenner and Clay, whom I’ve never heard of. So I’m pretty sure the answer is Jenner, but I’m by no means certain: let’s say that I’m 99:1 in favor of Jenner over Clay.

In order to maximize my expected winnings, I should bet 99 times as much on Jenner as Clay. But there’s a problem here: if it’s Clay, I end up with only one percent of my initial stake, and that one percent — which I have to go on and play more rounds with — is almost too small to be useful. This means that I don’t really want to maximize my expected winnings, but rather something that economists and statisticians call the “utility function”, or conversely, to minimize the loss function, functions which describes how useful some amount of winnings are to me: a thousand dollars is more than a thousand times useful than one dollar, but a million dollars is less than twice as useful as half a million dollars, at least in this context.

So in this case, a small amount of winnings is less useful than one might naively expect, and the utility function should reflect that by growing faster for small amounts and slower for larger amounts — I should perhaps bet ten percent on Clay. If it’s Jenner, I still get 90% of my stake, but if it’s Clay, I end up with a more-useful 10%. (The answer is Clay, by the way.)

This is the branch of statistics and mathematics called decision theory: how we go from probabilities to actions. It comes into play when we don’t want to just report probabilities, but actually act on them: whether to actually prescribe a drug, perform a surgical procedure, or build a sea-wall against a possible flood. In each of these cases, in addition to knowing the efficacy of the action, we need to understand its utility: if a flood is 1% likely over the next century and would cost one million pounds, but would save one billion in property damage and 100 lives if the flood occurred, we need to compare spending a million now versus saving a billion later (taking the “nonlinear” effects above into account) and complicate that with the loss from even more tragic possibilities. One hundred fewer deaths has the same utility as some amount of money saved, but I am glad I’m not on the panel that has to make that assignment. It is important to point out, however, that whatever decision is made, by whatever means, it is equivalent to some particularly set of utilities, so we may as well be explicit about it.

Happily, these sorts of questions tend to arise less in the physical sciences where probabilistic results are allowed, although the same considerations arise at a higher level: when making funding decisions…

Bayes in the World I: Wikileaks

2010-12-16T17:29:40Z

I've come across a couple bits of popular/political culture that give me the opportunity to discuss one of my favorite topics: the uses and abuses of probability theory.

The first is piece by Nate Silver of the New York Times' FiveThirtyEight blog, dedicated to trying to crunch the political numbers of polls and other data in as transparent a manner as possible. Usually, Silver relies on a relentlessly frequentist take on probability: he runs lots of simulations letting the inputs vary according to the poll results (correctly taking into account the "margin of error" and more than occasionally using other information to re-weight the results of different polls. Nonetheless, these techniques give a good summary of the results at any given time -- and have been far and away the best discussion of the numerical minutiae of electioneering for both the 2008 and 2010 US elections.

But yesterday, Silver wrote a column: A Bayesian Take on Julian Assange which tackles the question of Assange's guilt in the sexual-assault offense with which he has been charged. Bayes' theorem, you will probably recall if you've been reading this blog, states that the probability of some statement ("Assange is innocent of sexual assault, despite the charges against him") is the product of the probability that he would be charged if he were innocent (the "likelihood") times the probability of his innnocence in the absence of knowledge about the charge (the "prior"):

P(innocent|charged, context) ∝ P(innocent | context) × P(charged|innocent, context)

where P(A|B) means the probability of A given B, and the "∝" means that I've left off an overall number that you can mulitply by. The most important thing I've left in here is the "context": all of these probabilities depend upon the entire context in which you consider the problem.

To figure out these probabilities, there are no simulations we can perform -- we can't run a big social-science model of Swedish law-enforcement, possibly in contact with, say, American diplomats, and make small changes and see what happens. We just need to assign probabilities to these statements.

But even to do that requires considerable thought, and important decisions about the context in which we want to make these assignments. For Silver, the important context is that there is evidence that other governments, particularly the US, may have an ulterior motive for wanting to not just prosecute, but persecute Assange. Hence, the probability of his being unjustly accused [P(charged|innocent, context)] is larger than it would be for, say, an arbitrary Australian citizen traveling in Britain. Usually, Bayesian probability is accused of needing a subjective prior, but in this case the context affects and adds a subjective aspect to the likelihood.

Some of the commenters on the site make a different point: given that Assange is, at least in some sense, a known criminal (he has leaked secret documents, which is likely against the law), he is more likely to commit other criminal acts. This time, the likelihood is not affected, but the prior: the commenter believes that Assange is less likely to be innocent irrespective of the information about the charge.

Next: game shows.

Beautiful Evidence

2010-12-14T23:04:50Z

One excuse for not blogging over the last month was a couple of weeks spent in North America, first in and around New York and New Jersey, visiting my family, and then a stop in Montreal for the annual collaboration meeting for the EBEX CMB balloon project, which we expect to launch on its science mission from Antarctica in about a year (alas I will be most likely minding the fort back here in Britain rather than joining my adventurous colleagues in the frozen South).

But while in New York I got to attend my first proper art auction, one with a very scientific bent — Beautiful Evidence: The Library of Edward Tufte. Tufte is something of an “info-guru”; in a series of gorgeously produced books, he has talked about techniques for translating numbers and words into graphics. Although he’s got an over-strong aversion to computer graphics (and especially to powerpoint), much of his advice is right-on (and rarely heeded).

In the course of selling his books and giving regular, well-attended courses (and, latterly, working for the President), I expect that Tufte (who started out as a Professor of Statistics at Yale) must have amassed a reasonable nest egg, ploughed back into books, pamphlets, artwork and posters. The 127 or so lots cover everything from science and mathematics to dance and fine art.

I was most interested in the scientific books and manuscripts, and the wonderful thing about auctions is that you can play with — sorry, I mean inspect — the items on offer. I couldn’t resist:

That’s me, holding Christian Huygens’ Cosmotheoros from 1698. Amazingly, it was one of the few items not to make its reserve price, under $1000 — I could afford it that with only a little credit. But the most expensive item was an original of Galileo’s Sidereal Messenger, from which has sprung all of astronomy, most of physics, much of science, and indeed a lot of the society in which we live. Given that, $662,000 doesn’t seem unreasonable.

In between those two extremes was another item I was lucky enough to hold: A third edition of Isaac Newton’s Philosophiae Naturalis Principia Mathematica, which went for $16,250. This is the final edition printed during Newton’s lifetime, albeit with edits by one Henry Pemberton, which became “the basis for all subsequent editions” (and was notable for having lost all references to Newton’s rival in the creation of the calculus, Leibnitz). Like Galileo’s, it is one of the founding texts of modern science. But scientific progress, all that “standing on the shoulders of giants” has the slightly strange effect that such books are often mentioned, but rarely read. It is easier to learn Newton’s laws from a twenty-first century textbook (not to mention wikipedia) than from the original sources. Unlike many other such books, the Principia remains almost entirely mathematically and factually correct, but written in such a style — using geometry and pictures instead of equations, not to mention being in Latin — that even modern physicists find it hard to follow. Partially to ameliorate this (and partially to prove that he was the one of the few people who could manage the task), the great astrophsysicist S. Chandrasekhar decided, in the early 1990s, to produce an edition of “Newton’s Principia for the Common Reader”, translating Newton’s geometry into modern equations. (Needless to say, the book makes impressive demands upon the supposed “common reader”.) We could all do worse than to spend some time trying to get into Newton’s head (or Chandra’s).

Good Cause #2: Revenge of the Mekons

2010-11-08T22:20:40Z

The Mekons are the greatest rock’n’roll band in the world. They started in the 70s as a punk band from Leeds but by the mid-1980s had picked up fiddles and mandolins to go with their loud guitars, and learned to love Hank Williams and Gram Parsons as much as they’ve sadly learned to hate the injustices meted about by the systems and people that run everything. Their “Mekons Rock’n’Roll” was a simultaneous eulogy and elegy to their loud and debauched chosen musical form, “capitalism’s favorite boychild” as they themselves described it. The followup, “Curse of the Mekons” is probably the best record made about the end of the cold war, lamenting not only their cursed bad luck, but refusing to see it even a defeat for socialism which they reasonably point out can’t “really be dead when it hasn’t even happened”. A decade later, they also probably made the best (if possibly unselfconscious) record about 9/11 and its aftermath, “Out of Our Heads”.

If all of this makes them sound dour and serious, they’re not. Or at least, they know enough to seize the day, to turn their amps up and party while they watch the decay of the world around them. Over the years, they’ve dispersed to Chicago, New York, San Francisco, London and England’s West Country — and still get together every once in a while to record, tour and generally raise hell without, as far as I can tell, increasing their income too much. And in the process, they’ve probably been responsible for two or three of the best rock’n’roll shows I’ve ever been to, in North America and in the UK.

To honor (or praise, or bury) their career, filmmaker Joe Angio has shot the footage for a documentary “Revenge of the Mekons”. But they’ve run out of money for editing, and have enlisted the internet to help: Kickstarter is a brilliant site which enables groups to find (financial) supporters from around the world (and reward them in kind). You can support the film — the project is more than halfway toward their $20,000 goal. Depending on the amount of the pledge, you can get various prizes, including records and artwork by members of the band as well as books signed by some of the Mekons’ more famous fans (including rock critic Greil Marcus, novelist Jonathan Franzen, and writer Luc Sante), not to mention your name in the credits of a film. So, keep the corpse of rock’n’roll limping along — donate what you can.

Good Cause #1: Imperial Students Power the Developing World

2010-11-08T22:04:36Z

I try not to ask too much of my readers, but this post and the next are about a couple of worthwhile causes I’ve come across of late.

The first project is the BBC World Challenge competition, supporting “social entrepreneurs”, grassroots projects making an impact in the developing world. One of the twelve finalists, e.quinox, is an initiative founded by students from Imperial College. Along with students at the Kigali Institute of Technology, the team is developing solar-powered devices for rural electrification, “Electric Kiosks”, three of which have already been deployed in Rwanda.

Please vote for the team — the only one led by students — and support this fantastic project.

Astrostatistics at the Royal Astronomical Society

2010-11-08T16:46:59Z

This week I’m co-organizing a meeting at the Royal Astronomical Society in London, “Novel methods for the exploitation of large astronomical and cosmological data sets”. It’s an unwieldy title, but we’ll be discussing the implication of the huge flood of astronomical data for cosmology and astrophysics. How do we deal with the sheer volume — terabytes and petabytes of data for coming experiments (for example, the Large Scale Synoptic Telescope, one of the most important ground-based telescopes slated for the coming decade, will produce 20TB per night)? Human beings can only ever look at minuscule fractions of that, so we need computers to do much of the heavy lifting.

So we’ll hear from both astronomers and statisticians about the science and algorithms we’ll need to cope. Paolo Padovani will discuss the worldwide effort to create a virtual observatory — a set of standards (and actual code running on actual servers) which allows uniform access to a wide variety of astronomical data. We’ll also hear from Imperial’s Professor David Hand, President of the Royal Statistical Society and Ben Wandelt of the Insitut d’Astrophysique de Paris about new methods for distilling signals from noisy data, and David van Dyk from UC Irvine about comparing complicated computer models with data. Finally, Alberto Vecchio from Birmingham will discuss one of the next frontiers, the challenges of doing astronomy not with light, but with gravitational radiation, which will allow us to peer closer than ever at neutron stars, black holes, supernovae, and others of the most exotic and exciting objects in the history of the Universe.

The meeting is intended for professional astronomers, but open to all (there is a fee if you’re not a Fellow of the RAS).

Light and Gravity

2010-10-27T22:17:19Z

Yesterday, we at Imperial hosted the latest instalment of the London Cosmology Discussion Meetings (LCDM, which is a cosmology in-joke, of course), with about 40 participants — most of them students — from Imperial, QMUL and UCL. We heard talks about observing clusters of galaxies, different theories of gravity, and the observational repercussions of cosmic inflation. One excellent talk by UCL’s Chris Sabiu, drew my attention to an amazing 1941 paper by Erik Holmberg, “On the Clustering Tendencies among the Nebulae. II. a Study of Encounters Between Laboratory Models of Stellar Systems by a New Integration Procedure.”

This paper is one of the earliest attempts at a gravitational n-body simulation, calculating the motion of a pair of very simplified galaxies, each with only 37 “stars”. But Holmberg realized that to calculate the net force on any one of the stars requires knowing the force from each of the 73 other stars, and that he had to do this for each of the stars, therefore scaling overall like the square of the total number (more than 5000 pairs, taking symmetry into account), and that he would have to do this whole calculation at each step of time. This would be too much work with the pencil and paper available at the time for doing computations (the first digital computer simulations weren’t done until the early 1960s).

The important words in the title are “Laboratory Models” — Instead of calculation, Holmberg found an analogy with another physical system: light, whose intensity obeys an inverse-square law just like the gravitational force. Moreover, both the intensity and the gravitational force add up (we say “superpose” in physics). So by replacing his gravitating stars with shining light bulbs, and putting a light-meter at the location of each one, he could replace the 5000 calculations with 74 meter-readings.

With this setup, Holmberg was able to do genuinely new science, understanding the impact of tidal forces on galaxy interactions (tidal forces vary across a single object and the difference causes it to stretch, just as the tides raised by the Moon distort the shape of the Earth’s oceans).

This is a wonderful example of an “analog computer”, and just a brilliant concept, taking something that everyone who has ever studied physics has noticed — the similarity between gravitational force and intensity — and putting it to work. Current n-body simulation codes have managed to improve upon the naive expectation of scaling like the square of the number of particles in the simulation, but actually not quite as well as Holmberg’s version which scales linearly with the number, since he lets light’s properties do much of the work for him. I don’t know many scientists who have had such a creative idea in their whole careers.

Science is Vital

2010-10-02T10:03:39Z

I don’t suppose that there are many readers of this blog who are not aware of the Science Is Vital campaign for the support of UK science, but just in case: in response to the likelihood of continuing cuts to the UK science budget as spun by business secretary Vince Cable, we in the science community have begun to realize that the radio interviews and opinion pieces in more and less likely outlets may not be enough. Needless to say, blogs like this one (or even much more visible ones) tend to preach to the converted. Prompted in part by Evan Harris’ talk at Science Online 2010, many scientists and supporters of science realized that we need to talk directly to the people who actually hold the purse strings: Government and Parliament.

In particular, biologist, blogger, musician and novelist Jenny Rohn idly suggested doing something about it. As occasionally happens online, this struck a nerve, and Jenny very quickly found herself organizing something of a movement: Science Is Vital. Right now, the campaign is organizing four main activities:

The campaign has already received explicit support from The Wellcome Trust, Cancer Research UK, Nature, and many more organizations, as well as eminent scientists (and the occasional celebrity). But this isn’t and shouldn’t be restricted to scientists: we’re not doing this to protect our livelihoods (alright, we’re not only doing it to protect our livelihoods), but because, well, science is, in fact, vital to the health of the nation — that’s why so many other countries, faced with similar financial problems, are planning to increase research spending. An excellent post in the Guardian’s Data Blog details the streams for science funding in the UK and compares the level to Japan, the US and Germany. Britain is already the most cost-effective scientific nation by some measures; there is no real fat to be cut.

Nonetheless, here it seems more and more likely that we’ll have to deal with cuts of something like 15 percent to the overall science budget, and exactly how that plays out in the face of considerable fixed costs such as subscriptions to CERN and the European Space Agency is unknown (William Cullerne Bown at Research Fortnight has run the numbers for a variety of scenarios for enacting a nightmarish 30% cut. They are all miserable.) No matter what the level, one unintended consequence is likely: instead of the Government’s stated ambition of getting rid of the worst of British science (not that there is very much sub-par science being done here already), the Guardian article about the brain drain that may (will?) follow drastic cuts to science funding is already showing that the cuts may have an even worse effect, driving the best scientists out of Britain.

(Worse still, let’s not forget that this year’s yet-to-be proposed cuts are just the latest in an ongoing shrinking of the physical sciences budget, in particular, over the last few years, ever since the formation of the ill-starred STFC form the former PPARC and CCLRC councils, which began life with an £80 million budget shortfall.)

So, please, if you support science in the UK, sign the petition, attend the rally (unfortunately, I’ll be out of the country), and write your MP. For what it’s worth, here’s the letter I wrote to mine, Andy Slaughter (Labour, Hammersmith, London):

Dear Mr Slaughter,

I am one of your constituents, and am also a Professor of Physics at Imperial College.

You are probably aware that science funding has been under severe pressure for the last several years, first under the previous Labour government, and now, along with so much else, under the Coalition.

Science is crucial to the economic and social future of the UK. It would be devastating for the UK to give up its position as almost certainly the second most powerful country in the world, after only the USA, in higher education and scientific research. Even today (again, after several years of cuts to grants in the physical sciences), the vast majority (over 90%) of research funding goes to world-class scientists, as judged by the latest Research Assessment Exercise. It is impossible to cut this without reducing the amount of excellent research produced in the UK. Moreover, threats of such cuts are already making scientists consider their options — most other countries are increasing, rather than decreasing, their science budgets not despite but because of the economic downturn and growing deficits.

The evidence is clear that investing in research brings a range of economic and social benefits, and that severe cuts at the very moment that our competitor nations are investing more could jeopardize the future of UK science.

Hence, I am sure that you will take the opportunity in the coming weeks to

sign EDM 767 – Science is Vital;

join me in signing the Science is Vital petition; and

attend a lobby in Parliament on 12 October (15.30, Committee Room 10).

The Science is Vital coalition, along with the Campaign for Science and Engineering, are calling upon the Government to set out a supportive strategy, including public investment goals above or at least in step with economic growth. Without such investment and commitment the UK risks its international reputation, its market share of high-tech manufacturing and services, the ability to respond to urgent and long-term national scientific challenges, and the economic recovery.
I look forward to hearing from you. Do not hesitate to contact me if you would like to discuss these matters.

Yours sincerely,

Andrew Jaffe

Epistemology and Ontology Among Friends

2010-09-30T08:03:45Z

A week or so ago, I had an extended “conversation” on Twitter with two very old friends, Erik Davis and Ted Friedman. Erik’s a writer, specializing in “modern esoterica” which ranges from psychedelia and Led Zeppelin to Philip K Dick and Cthulu. Like me, Ted’s an academic, but he’s Professor of Communication at Georgia State University, who works on movies, digital culture, and is writing a book on Marx, Buddhism and pop culture. We all worked together on a college music ‘zine, back when those required paper and glue to put together (at least we had laser printers). And both Erik and Ted were trained in the lit-crit practice of 80s academia. They’re both damn smart, but their outlook on the way the world works and how we interpret it differs from mine, trained by what’s by now many years as a scientist.

So I thought it might be thought-provoking to present and annotate our discussion.

(It wasn’t completely trivial to recreate a linear narrative from the Twitter stream. For those of you unfamiliar with the conventions of Twitter, “@” is used to direct a message to a particular user, but everything is out in the open. Because of the infamous 140-character limit, I’ve occasionally combined successive messages (“tweets”) into a single statement. Also, I’ve changed the usernames for Ted, Erik and me to save space and make things a bit more legible; those limits, along with the slight time delays, and the distractions over the more than an hour that this lasted means that it doesn’t exactly follow a linear narrative. Finally, I’ve also put in some links to some of the articles and books mentioned.)

Ted:@Erik Exactly! The virus metaphor is too Darwinian/Freudian/scientistic/empiricist. Reflects Dawkins’ own vulgar Darwinism.

Andrew:@Ted (and @Erik) “Vulgar” darwinism?

I entered the conversation late, but I was amused by the description of Dawkins’ ideas as “vulgar” Darwinism (which Erik takes the opportunity to joke about).

Erik:RT @Andrew: @Ted “Vulgar” darwinism? I love it when Darwinism wears pink hot pants and swears like a sailor!
Ted:@Erik Magic’s a much more accurate metaphor for how culture works: Mysteriously. Unpredictably. Irrationally.

Ted:@Andrew See Gould’s critiques of Dawkins in The New York Review of Books. He’s primarily slamming evolutionary biology as Social Darwinism. But he’s also critiquing Dawkins for not accepting Gould’s concepts like spandrels and punctuated equilibrium.
Erik:@Ted Perhaps too quick to say that magic is irrational though. Emergent perhaps. Metaphorical. Unbound. But not methinks irrational.

This is when I started to get interested, but worried — I’m all for using “magic” as a metaphor, but nothing more.

Ted:@Andrew And Dawkins’s Darwinian fundamentalism is of a piece with his fundamentalist atheism. Compare to Karen Armstrong, Terry Eagleton.

And this really annoyed me: it’s wrong to use “fundamentalism” in this way (even though the application of the term to Darwin and Dawkins comes from Gould’s essay.) Armstrong and Eagleton’s recent work has attempted to be a more nuanced view of the ongoing science/religion debate, but in fact I find them to be well-written and well-thought-out sociology, but entirely miss the point that religion really does make claims about what happens in the real world, and that those claims, when tested, almost inevitably end up wrong. If you remove those claims, most believers wouldn’t recognize what is left as religion.

Ted:@Erik Good point. Depends what counts as rationality. Magic is the domain of the unconscious rather than consciousness.
Andrew:@Ted Nonetheless Dawkins is correct on both counts… (Armstrong and Eagleton are better writers, but still wrong.)
Ted:@Erik In Campbellian terms, magic is part of the Special World. As Alan Moore says, “it’s all true as long as you understand that it’s all going on in your mind.” Although that’s too cut-and-dried to explain synchronicity and action at a distance.

I couldn’t actually find that Alan Moore quote, but it sounds like something he would say. This is where I thought we would get agreement — magic is a way of interpreting the world. But it quickly became clear they wanted a more real magic than I am willing to grant, given what I know about the way the Universe works.

Erik:@Ted I would say more that magic (as a practice) is the interface between consciousness and the unconscious, a mode of mediation.
Erik:@Ted agreed. the “weird shit” still exceeds the mind-only theory. thank gods!
Andrew:@Erik @Ted Hmmm, I am all for weird shit — but all in the mind. To me, that’s the amazing power of the sub- and un-conscious.
Ted:@Erik And then there’s the stuff I really don’t have a handle on, like Rupert Sheldrake’s theories, remote viewing, and entheogens.
Ted:@Erik I like the idea that vulgar Marxism was when Engels pimped Karl out for a hot night on the town.
Ted:@Andrew Don’t you encounter tons of weird shit in your day job? Isn’t the challenge in making a TOE thinking outside the box (or collider)?
Ted:@Erik Great book on this subject: Alva Noe’s Out of Our Heads. Dismantles cognitivism via phenomenology.
Erik:@Ted Looks good! I am pleased that the embedded-enactionist consciousness folks are on the rise agin the neural mechanists.
Andrew:@Ted Of course there’s natural weird shit, too. But no need to explain, say, synchronicity, as anything more than pattern-matching. Yes, I am a (boring? pedantic?) arch-rationalist…
Erik:@Andrew I am not trying to dismantle realism (good luck) but I’m talking shit thats weirder than that. And, ya know, shit happens!
Ted:@Andrew Maybe. But pattern-matching is how we make meaning. Synchronicity resonates for the same reason as great art. The sublime. Numinous.
Ted:@Erik I like that! It lives in the limnal spaces, like the edge of the forest, the Star Wars cantina, the frontier.

I do so love that my friends have moved from Jungian synchronicity and highbrow religious studies to the Star Wars cantina in just few 140-character messages.

Ted:@Andrew Disagree. Dawkins and Armstrong are speaking at cross-purposes. Armstrong argues God is a metaphor. Dawkins says “just a metaphor.”
Ted:@Andrew To Armstrong, a world without God is a world missing a very useful word to describe a big part of what it means to be human.
Ted:@Andrew And Dawkins’s and Hitchens’s impoverished hermeneutics demonstrates how much their scientism has cost them - and all of us.
Andrew:@Ted “But pattern-matching is how we make meaning.” My point exactly — complete agreement!
Ted:@Andrew Armstrong and Jung see the disenchantment of the universe as both a given and a challenge. #fsfmedia
Ted:@Andrew My favorite response to Dawkins and Hitchens: Stephen Batchelor’s Confessions of a Buddhist Atheist. He’s a zen existentialist.
Andrew:@Ted Disagree that Dawkins’ & Hitchens’ hermeneutics are impoverished: all meaning comes from us. What could be better?
Erik:Synchro in the house: just as I was about to transcribe the word “happy” from a PKD ms [Philip K Dick manuscript]. I pressed a weird key combo and got a smiley face.
Ted:@Andrew I’m judging by excerpts, interviews and reviews, I admit. What I read suggested Dawkins is uninformed in the history of theology.
Andrew:@Ted He is better-informed on theology than 99.9% of believers.
Ted:@Andrew Meaning Dawkins found it unnecessary to study the discourse of his opponent, rather than attempt to understand, engage, synthesize. That speaks to a empiricist, technocratic arrogance, and ultimately a lack of skepticism towards one own’s assumptions.
Erik:@Andrew Dawkins may know as much theology as believers (ie, not much), but he don’t know shit about religion as a social/antho phenomenon.

Ted:@Andrew But Batchelor isn’t a believer. Armstrong and Eagleton have come to be, but remain curious and skeptical.
Andrew:@Ted I don’t disagree re: Dawkins’ tactics, but I’m all for “empiricist arrogance”. It beats “truthiness” any day.
Ted:@Andrew Harold Bloom is an atheist, but his book on American Religions is more sophisticated and sympathetic than most believers’ texts.

This is why these discussions often flounder: we can’t quite decide if we’re talking about ontology — what the world is made of, epistemology — how we interpret the world, or sociology — how is it that these systems of interpreting the world came to be (I hesitate to use the word “evolve”)

Ted:@Andrew There isn’t only a believer/nonbeliever split. There’s also a fundamentalist (believer or atheist)/skeptic (openminded) split. Skepticism is too useful a word to cede to Skeptical Inquirer and Penn & Teller. Skeptics question orthodoxy. Fringe-science weirdos with real scientific chops, like Rupert Sheldrake and Charles Tartt, are skeptics too.

Actually, the line between “skeptic” and “crackpot” is pretty well-marked…

Andrew:@Ted Category error: Dawkins &c not fundamentalist in same sense as religious types. Skepticism is part of method.

…as is the line between fundamentalists and proponents of well-tested scientific theories.

Ted:@Andrew Disagree. Empiricist arrogance leads to orthodoxy, incuriosity, and silencing skeptics. Synchronicity is more than truthy.
Andrew:@Ted I’ll let you call yourself a skeptic if you never call me a fundamentalist.
Ted:@Andrew Sorry, didn’t mean you! Dawkins just pisses me off.
Andrew:@Ted No offense taken — he annoys me, sometimes, too. But (I am steadfast on this) he is right on the facts!
Andrew:@Ted @Erik This is a fab conversation but it’s late here… I’m sure there’s more to discuss later if you want to keep it up.
Ted:Scientists: any opnion on this new book by a philosopher and a cognitivist, What Darwin Got Wrong? See this for an Overview @Andrew

Ted:@Andrew Oops - I’m late for lunch myself. Catch you all later!

So by the end, we inevitably agreed to disagree, waylaid by the need for food and drink. I do think the world is weird as hell, but that’s because all of the meaning that there is comes from our incredibly puny but incredibly powerful minds, and plenty of the weirdness comes out of those very minds. But all together, the world is still and only “a vast mosaic of local matters of particular fact, just one little thing then another” (as the philosopher David Lewis had it, following Hume). We may see patterns and want to call it magic, or synchronicity. But eventually we tame those patterns and relate them to one another and get to make a rigorous system out of it.

Needless to say, this is my gloss — Ted and Erik may well disagree. In recompense, let me do my best to pimp my friends: you should buy Ted’s book, Electric Dreams, and at least one of Erik’s too.

Consider a Spherical Cow (Company)

2010-09-29T14:26:35Z

One of my old friends from graduate school, and a colleague to the present day, Lloyd Knox — whom you may remember from such cosmology hits as the Dark Energy Song — has started an initiative to create “short documentary videos to demonstrate the explanatory power of simple physical models and to help us understand and aesthetically appreciate the natural world”. It’s called The Spherical Cow company — the name comes from the traditional physicists’ trick of idealizing and simplifying any problem he or she gets, sometimes out of all recognition — but usually, when done well, keeping enough of the salient features.

The first video does just that, giving a simple description of the formation of the Cosmic Microwave Background, in the form of a conversation between Lloyd and his son, Teddy — with interpolations for animations and narration. Even with those occasional animations, the whole thing is pleasingly low-fi, but well-explained and charming (especially so for me, as I know the protagonists). I look forward to the next videos in the series, and I’ll certainly be recommending them to students of all ages.

“Public Service Review”?

2010-09-19T10:59:30Z

A few months ago, I received a call from someone at the “Public Service Review”, supposedly a glossy magazine distributed to UK policymakers and influencers of various stripes. The gentleman on the line said that he was looking for someone to write an article for his magazine giving an example of what sort of space-related research was going on at a prominent UK institution, to appear opposite an opinion piece written by Martin Rees, president of the Royal Society.

This seemed harmless enough, although it wasn’t completely clear what I (or the Physics Department, or Imperial College) would get out of it. But I figured I could probably knock something out fairly quickly. However, he told me there was a catch: it would cost me £6000 to publish the article. And he had just ducked out of his editorial meeting in order to find someone to agree to writing the article that very afternoon. Needless to say, in this economic climate, I didn’t have an account with an unused £6000 in it, especially for something of dubious benefit. (On the other hand, astrophysicists regularly publish in journals with substantial page charges.) It occurred to me that this could be a scam, although the website itself seems legitimate (although no one I spoke to knew anything about it).

I had completely forgotten about this until this week, when another colleague in our group at Imperial told me had received the same phone call, from the same organization, with the same details: article to appear opposite Lord Rees’; short deadline; large fee.

So, this is beginning to sound fishy. Has anyone else had any similar dealings with this organization?

Update: It has come to my attention that one of the comments below was made under a false name, in particular the name of someone who actually works for the publication in question, so I have removed the name, and will possibly likely the comment unless the original write comes forward with more and truthful information (which I will not publish without permission). I have also been informed of the possibility that some other of the comments below may come from direct competitors of the publication. These, too, may be removed in the absence of further confirming information.

Update II: In the further interest of hearing both sides of the discussion, I would like to point out the two comments from staff at the organization giving further information as well as explicit testimonials in their favor.

Arvo Pärt at 75

2010-09-11T18:35:42Z

Today, among other less auspicious anniversaries, is one very worth celebrating: Arvo Pärt’s 75th Birthday.

The Estonian “holy minimalist” composer has been featured at the BBC Proms this summer, including performance of his first new symphony since the early 1970s, his take on the St John Passion, and my favorite, the short, mesmerising Cantus in Memoriam Benjamin Britten.

You can find short clips on the BBC site, but here’s a video to go along with the original recorded version, from the Tabula Rasa record (isn’t it weird that I can legally embed this, but not the music alone?):

And if you’re in London in two weeks (I’ll be around, but running — hint, hint), and fancy a bit of musicology, you can attend a two-day conference on Pärt, “Soundtrack of an Age”. In the meantime, I’m off to Lecce to teach in a cosmology summer school. Two hours of lecturing and a week in Puglia — no complaints. For now, happy birthday, Arvo.

Science: Commercially Useful or Theoretically Outstanding?

2010-09-08T22:44:20Z

Today was the next drip in the ongoing water torture that is the upshot of the government’s funding cuts on UK science: BIS Minister Vince Cable gave the coalition government’s first major speech on science. Rumors have been flying around of cuts of 20-30%, and we have been searching for any hints of the Government’s science strategy in advance of the comprehensive spending review next month. The two biggest questions have been the overall magnitude of the coming cuts, and how the remaining money would be allocated. Would “economic impact” trump scientific excellence, favoring subjects (irrespective of quality) that can be monetized in the short term over so-called blue-skies research?

Cable indeed highlighted the importance of impact, and eventually boiled down the government’s strategy to funding research that is either “commercially useful” or “theoretically outstanding”. In so doing, he mentioned that 54% of UK science researchers were rated “world class” in the last RAE, and, by implication, that the remaining 46% is in danger. Hearing this, any scientist who has ever evaluated grants for funding councils like STFC would be puzzled: over the last few years we can’t even afford to fund all of the excellent proposals, much less any that aren’t obviously world-class. Indeed: even leaving aside the clear discrepancies between fields in the ratings, what isn’t mentioned in the speech is that this 46% receives less than 10% of all research funding (from 2% to 7% depending on what gets counted as “research funding”). William Cullerne Bown speculates that Cable therefore meant we are in for a 2%-7% cut, which would be seen in the current climate as a huge victory for science (although may only be a precursor to further cuts, in any event). I am not so sure; if he is looking to make large savings in the BIS portfolio this is a good sound-bite to excuse swingeing science cuts. But I, along with almost everyone else, wait and hope.

Jenny Rohn suggests we do more than wait: that we march on Parliament. She has set up a Facebook page to organize the campaign, “Science is Vital”, putting into practice the ideas espoused by Evan Harris at last week’s Science Online 2010 conference and in the aftermath of today’s speech. As long as we can control the message, this can be effective — but we can’t be seen as merely defending our own turf or, what could be worse, as white-coated boffins waving our test tubes at MPs. This isn’t funny, and science needs to be seen, correctly, as vital to the health of the nation.

(For more information and viewpoints on the speech, see posts by Kieron Flanagan, dellybean, Roger Highfield, Evan Harris, The Times Higher, and Peter Coles.)

B/E at the Biennale

2010-08-30T23:34:14Z

As a scientist, I am used to my work being read by my peers, and I’ve made it into the occasional magazine or newspaper article, and even the odd TV and radio slot. But last week I travelled to Venice’s Architecture Biennale for the culmination of the first phase of the Architectural Association’s Beyond Entropy art/science project (which I’ve described before). I took a vaporetto to the island of San Giorgio, and next to one of Venice’s more spectacular Palladian churches, I saw the Beyond Entropy banner hanging over the entrance:
(I took these pictures, but there are many much more professional ones taken by the AA’s Valerie Bennett.)

Before arriving, I didn’t know what to expect from the project: small-scale, low-key, amateurish? In this setting, it was clearly big and serious. And inside this lovely building were these, the prototypes for our time machine:

Last year I traveled to South America to witness the launch of our several-hundred million-Euro Planck satellite, surely a big and serious project. But the sight of my own work — our texts, flywheels and gyroscopes — sitting on a plywood plinth, plausibly described as something at least related to the very different creative process of art, was nearly as disconcerting (despite the lack of highly explosive rocket fuel).

I’ll leave any assessment of the overall quality to others, although it became obvious that these pieces really are prototypes for what could become more finished works, but we have a long way to go. Nonetheless, let me explicitly thank my collaborators, Shin Egashira (whom I will also congratulate on his wedding which gave him an excellent reason to not show up in Venice) and Scrap Marshall, a student at the Architectural Association who joined us toward the end of the project and did an enormous amount of practical and creative work getting our pieces together. From speaking to members of some of the other groups, we were lucky to all be based in London, and to eventually come to see our project in similar ways, albeit from different directions; some of the more widely-dispersed groups had to deal with significantly greater practical problems, and the interpersonal ones those ended up causing.

That first day was dedicated to the AA’s visiting school, and the next day was the centrepiece: a marathon symposium of more than thirty talks, dedicated to the themes of “entropy” and “energy”. Remarkably, none of our projects addressed the ecological, societal and political aspects of these topics, while many of the speakers attacked them directly, from Richard Burdett and Reinier de Graaf’s complementary discussions of the bleak picture for energy and climate if we keep to “business as usual” in our habits of consumption and production, to Italian Green Party politician Grazia Francescato’s hopeful discussion of “Green Jobs and Green Economy”. There were a few talks on science per se, from Angelo Merlina’s brief introduction to the LHC at CERN (of which a third talked about cosmology, and a third was pre-recorded), to one of my favourites, biophysicist Tania Saxl’s description of the amazing mechanism behind the motion of rotating bacterial flagella. There was also an inexplicable prerecorded description of “parallel worlds” in film from de Gruyter and Thys, a performance from the Arazzi Laptop ensemble, and contributions from Serpentine Gallery curator Hans-Ulrik Obrist (which was interesting but mostly about himself) and Charles Jencks. Jencks tackled the overlap between science, art and architecture head-on, each as a different metaphorical system for describing and interacting with the world. This culminates in his Scottish Garden of Cosmic Speculation, a hugely symbolic landscape replete with double helixes and grassy knolls in the form of black hole spacetime diagrams (I admit I’ve also found these supposed metaphors a bit too, well, literal for my taste — with insufficient information to be effective teaching tools, but too didactic to be truly beautiful.) I think the most important thing I learned was that, in their own way, the architects are just as nerdy as us scientists, but just better looking dressed.

Also, there was plenty of fine food and free-flowing sparkling wine (which meant that I probably missed about half of the presentations).

Finally, I would like to thank everyone from the AA who made the project happen (and will continue to do so, if further funding is forthcoming): Artemis Doupa, Sylvie Taher, Esther McLaughlin, Aram Mooradian and most especially the ever-enthusiastic project director, Stefano Rabolli Pansera. Thanks also to the AA visiting students, and all of the other participants, especially Ariel Schlesinger and Wilfredo Prieto for giving me a glimpse of the Architecture Biennale through artists’ eyes.

The next decade

2010-08-15T22:05:40Z

Every ten years or so, the US astronomy community, under the auspices of the National Academy of Sciences, produces a road map for the next decade’s research in astronomy. The 2010 version, chaired by Roger Blandford, was just released, and astronomer/bloggers have already weighed in: Steinn Sigurðsson and Julianne Dalcanton (in two separate posts on the ground- and space-based recommendations), along with the UK’s Andy Lawrence and Peter Coles have already dissected the report, but I’ll repeat the headlines: the Large-Scale Synoptic Telescope (LSST) is the top ground-based project, and WFIRST is the top-rated satellite — essentially the JDEM mission, rebranded as a broader infrared telescope with major science goals in both the study of dark energy and the hunt for extraterrestrial planets. The biggest surprise comes down the satellite list: the LISA interferometric gravitational-wave telescope is placed above the IXO x-ray satellite, which is only recommended for technology development (albeit at the not inconsiderable level of $180M). Alongside these large missions there is a recommendation for an expanded role for “explorer missions” in the tradition of WMAP, Swift and GALEX.

The big question on this side of the Atlantic is what impact these recommendations (and that is all that they are — NASA, NSF and DOE still make the real decisions) will have on ESA and the various national agencies. The EU astro community has a broadly similar initiative, Astronet, but the political and funding situation is sufficiently different that no one expects it to have as concentrated an impact on European astronomy as the decadal report has in the US. Moreover, both NASA and ESA have stated — I’m not sure how officially — that any future missions are likely to be shared on an 80/20 basis, rather than a more equal 50/50 model that has been discussed for both LISA and IXO.

If this is the case, then perhaps the US is ceding x-rays to the European astronomy community, but claiming the lead for space-based gravitational radiation and infrared astronomy, which raises the question of the place of the EUCLID dark energy mission in the ESA program. Indeed, the next ESA decisions for EUCLID, IXO and LISA are all expected in the coming months, and the level of NASA/ESA cooperation will likely be crucial to the outcome.

Swedish Statistics

2010-08-14T10:56:58Z

[Apologies to those of you who may have seen an inadvertantly-published unfinished version of this post]

I’ve just returned from a week at the Annual meeting of the Institute for Mathematical Statistics in Gothenburg, Sweden. It’s always instructive to go to meetings outside of one’s specialty, outside of the proverbial comfort zone. I’ve been in my own field long enough that I’m used to feeling like one of the popular kids, knowing and being known by most of my fellow cosmologists — it’s a good corrective to an overinflated sense of self-worth to be somewhere where nobody knows your name. Having said that, I was bit disappointed in the turnout for our session, “Statistics, Physics and Astrophysics”. Mathematical statistics is a highly specialized field, but with five or more parallel sessions going on at once, most attendees could find something interesting. However, even cross-cutting sessions of supposedly general interest — our talks were by physicists, not statisticians — didn’t have the opportunity to get a wide audience.

The meeting itself, outside of that session, was very much of mathematical statistics, more about lemmas and proofs than practical data analysis. Of course these theoretical underpinnings are crucial to the eventual practical work, although it’s always disheartening to see the mathematicians idealise a problem all out of recognition. For example, the mathematicians routinely assume that the errors on a measurement are independent and identically distributed (“iid” for short) but in practice this is rarely true in the data that we gather. (I should use this as an opportunity to mention my favourite statistics terms of art: homoscedastic and heteroscedastic, describing, respectively, identical and varying distributions.)

But there were more than a couple of interesting talks and sessions, mostly concentrating upon two of the most exciting — and newsworthy — intersections between statistical problems and the real world: finance and climate. How do we compare complicated, badly-sampled, real-world economic or climate data to complicated models which don’t pretend to capture the full range of phenomena? In what sense are the predictions inherently statistical and in what sense are they deterministic? “Probability”, said de Finetti, the famous Bayesian statistician “does not exist”, by which he meant that probabilities are statements about our knowledge of the world, not statements about the world. The world does, however, give sequences of values (stock prices, temperatures, etc.) which we can test our judgements against. This, in the financial realm, was the discussion of Hans Föllmer’s Medallion Prize Lecture, which veered into the more abstract realm of stochastic integration, Martingales and Itō calculus along the way.

Another pleasure was the session chaired by Robert Adler. Adler is the author of a book called The Geometry of Random Fields, a book which has had a significant effect upon cosmology from the 1980s through today. A “random field” is something that you could measure over some regime of space and time, but for which your theory doesn’t determine its actual value, but only its statistical properties, such as its average and the way the value at different points are related to one another. The best example in cosmology is the CMB itself — none of our theories predict the temperature at any particular place, but the theories that have survived our tests make predictions about the mean value and about the product of temperatures at any two points — this is called the correlation function, and a random field in which only the mean and correlation function can be specified is called a Gaussian random field, after the Gaussian distribution that is the mathematical version of this description. Indeed, Adler uses the CMB as one of the examples on his academic home page. But there are many more application besides: the session featured talks on brain imaging and on Google’s use random fields to analyze data about the way people look at their web pages

Gothenburg itself was nice in that Scandinavian way: nice, but not terribly exciting, full of healthy, attractive people who seem pleased with their lot in life. The week of our meeting overlapped with two other important events in the town. The other big meeting in town was the World Library and Information Congress — you can only imagine the party atmosphere in a town filled with both statisticians and librarians! But adding to that, Gothenburg was hosting its summer kulturkalas festival of culture — the streets were filled with musicians and other performers to distract us from the mathematics.

Run for the trees

2010-08-04T13:34:49Z

Last year, I ran for cats and dogs. This year, it’s a different half-marathon, Run to the Beat on September 26 (“London’s Music Half-Marathon”), with a less conveniently located course in East London, and I’ve shifted Kingdoms in my charitable support: I will run for “Trees for Cities”, “an independent charity working to improve the environment in urban areas by involving local people in community tree planting, training and landscaping projects”, in London, throughout the UK, and internationally. So if you like trees, and would like to keep me on the road for 13 miles, please give!

BPol++

2010-08-02T20:34:42Z

I spent part of this week in Paris (apparently at the same time as a large number of other London-based scientists who were here for other things) discussing whether the European CMB community should rally and respond to ESA’s latest call for proposals for a mission to be launched in the next open slot—which isn’t until around 2022.

As successful as Planck seems to be, and as fun as it is working with the data, I suspect that no one on the Planck team thinks that a 400-scientist, dispersed, international team coming from a dozen countries each with its own politics and funding priorities, is the most efficient way to run such a project. But we’re stuck with it—no single European country can afford the better part of a billion Euros it will cost. Particle physics has been in this mode for the better part of fifty years, and arguably since the Manhattan Project, but it’s a new way of doing things — involving new career structures, new ways of evaluating research, new ways of planning, and a new concentration upon management — that we astrophysicists have to develop to answer our particular kinds of scientific questions.

But a longer discussion of “big science” is for another time. The next CMB satellite will probably be big, but the coming ESA call is officially for an “M-class” (for “medium”) mission, with a meagre (sic) 600 million euro cap. What will the astrophysical and cosmological community get for all this cash? How will it improve upon Planck?

Well, Planck has been designed to mine the cosmic microwave background for all of the temperature information available, the brightness of the microwave sky in all directions, down to around a few arcminutes at which scale it becomes smooth. But light from the CMB also carries information about the polarisation of light, essentially two more numbers we can measure at every point. Planck will measure some of this polarisation data, but we know that there will be much more to learn. We expect that this as-yet unmeasured polarisation can answer questions about fundamental physics that affects the early universe and describes its content and evolution. What are the details of the early period of inflation that gave the observable Universe its large-scale properties and seeded the formation of structures in it—and did it happen at all? What are the properties of the ubiquitous and light neutrino particles whose presence would have had a small but crucial effect on the evolution of structure?

The importance of these questions is driving us toward a fairly ambitious proposal for the next CMB mission. It will have a resolution comparable to that of Planck, but with many hundreds of individual detectors, compared to Plank’s many dozens—giving us over an order of magnitude increase in sensitivity to polarisation on the sky. Actually, even getting to this point took a good day or two of discussion. Should we instead make a cheaper, more focused proposal that would concentrate only on the question oaf inflation and in particular upon the background of gravitational radiation — observable as so-called “B-modes” in polarisation — that some theories predict? The problem with this proposal is that it is possible, or even likely, that it will produce what is known as a “null result”—that is, it won’t see anything at all. Moreover, a current generation of ground- and balloon-based CMB experiments, including EBEX and Polarbear, which I am lucky enough to be part of, are in progress, and should have results within the next few years, possibly scooping any too-narrowly designed future satellite.

So we will be broadening our case beyond these B-modes, and therefore making our design more ambitious, in order to make these further fundamental measurements. And, like Planck, we will be opening a new window on the sky for astrophysicists of all stripes, giving measurements of magnetic fields, the shapes of dust grains, and likely many more things we haven’t yet though of.

One minor upshot of all this is that our original name, the rather dull “B-Pol”, is no longer appropriate. Any ideas?

Talking and blogging to ourselves

2010-07-21T22:33:09Z

(Warning, scattershot blogging echo-chamber post follows.)

Last week I went to the Science Blogging Talkfest sponsored by the Biochemical Society and led by Alice Bell from Imperial’s excellent Science Communication program.

Partially because the event was mostly attended by science bloggers themselves, there was a bit of a preaching-to-the-converted sense to the proceedings. (I tried to engage in some good-natured tweaking, pointing out that probably the greatest influence of [supposedly] science blogging has been in absurdly dragged-out climategate saga, but I couldn’t get a rise out of the audience.) But it was heartening to see just how mainstream science blogging has become.

“Only” five years ago (scare-quotes denoting an eternity of internet-time), the academic-blogosphere chattered on about an anonymous article in the Chronicle of Higher Education which contended that bloggers were essentially unsuitable to be hired as faculty members, and a couple of years after that several of my colleagues felt the need to seriously restrict their blogging while searching for permanent positions. I was heartened to see that the question of whether blogging could actually hurt someone’s career seems to be less worrying. Although Petra Boynton said that one of her previous departments were less than enthusiastic about it, most of the panelists have found that, with an increased in impact and communication in general, blogging has taken its position as an effective way to engage with the public.

One of the more novel (to me) things going on at this meeting was the Twitter backchannel: the organizers projected a running stream of tweets marked with the #talkfest tag. It was a decent mix of jokes and apposite comments, especially including erstwhile MP Dr Evan Harris’ provocative comments about whether scientists should be forced to do public engagement at all. It’s certainly good that blogging and communication don’t hurt your career — but should they be requirements for scientific advancement? Not all scientists’ talents lie in that direction, and we shouldn’t expect them to. There was also a twitter discussion of the gender makeup of the panel, which was dishearteningly 1/6 female despite an audience of at least 50% women.

When science blogging started out as its own sub-genre in the middle of the decade, no one was quite sure what it would be for. Would it be used within science as an online lab notebook, or as a substitute or adjunct to papers? That doesn’t seem to have panned out — even in the post-’net open world, the structure of science encourages secrecy, at least until the work can be packaged into what are still more or less old-fashioned papers in what are still more or less old-fashioned journals (albeit with the important twist of pre-publication posting on the arXiv in many fields). Within collaborations, however, wikis, rather than blogs, have become ubiquitous as an easy way to communicate amongst scientists who are already expert — the easy ability to add small chunks of information is exactly what is needed. (Within the Planck Satellite collaboration, we actually use a wiki as a sort of blog — we keep a reverse-chronological list of “posts” discussing our latest results.)

Instead, blogs seem to be used almost exclusively as a window into the life, methods and results of scientists, directed at a knowledgeable but lay public. Indeed, it was suggested at the talkfest that someone could make a very useful living textbook from the scattered blog posts on a given subject. I’m not so sure — one of the advantages of a proper textbook is a single voice and, more prosaically, a single notation starting from scratch— but it’s probably worth trying if someone’s got the wherewithal to do the bit-work involved.

It was especially nice to meet several of my fellow Imperial College bloggers, including biophysicist Stephen Curry (whose own post on the Talkfest also has a list of other reactions to it), whom I was somewhat embarrassed to discover actually works in the same building as I do. As always at these sorts of events, much of the amusement was during the inevitable pub visit afterwards and especially the pre-panel milling about — thanks to the organizers for the excellent combination of cupcakes and beer.

Counterculture RIPs

2010-07-12T22:11:19Z

Two crucial figures from outside the mainstream of American culture have died.

Tuli Kupferberg (1923-2010) has been hanging around, writing about and stirring up trouble in New York’s Greenwich Village since the 1950s as a writer, poet, occasional political activist and rock ‘n’ roller. First in the late 60s and early 70s and occasionally thereafter, he was one of the Fugs (named after the faux-expletive from Mailer’s The Naked and the Dead) singing both the poems of William Blake as well as “Slum Goddess of the Lower East Side”. Since then, he kept writing, occasionally reformed the Fugs with his partner Ed Sanders, but had suffered a series of strokes in the last year from which he never fully recovered.

Harvey Pekar (1939-2010) was a bit better known. For the last few decades, he had been writing a series of autobiographical comics, “American Splendor”, illustrated by some of the best comics artists of the last few decades, from R. Crumb and Alan Moore to Gilbert Hernandez, Chester Brown and Joe Sacco.They chronicled his life in Cleveland, Ohio, from the tedium of his day job as a hospital clerk, a bout with cancer (in the excellent graphic novel “Our Cancer Year”), and his occasional run-ins with fame — in the 80s, he was occasional guest on David Letterman’s late-night talk show (until he famously decided to use his slot to lambaste GE, the owner of the NBC television network), and in this decade was memorably played by Paul Giamatti in a movie, also called “American Splendor”, based on the comics. Only a couple of weeks ago, I discovered The Pekar Project, devoted to getting and keeping his newest works online. He was always surly, too high-maintenance for his own good, dependably dissatisfied with whatever his life threw at him. And will nonetheless be missed.

The Planck Sky Previewed

2010-07-07T21:16:50Z

The Planck Satellite was launched in May 2009, and started regular operations late last summer. This spring, we achieved an important milestone: the satellite has observed the whole sky.

To celebrate, the Planck team have released an image of the full sky. The telescope has detectors which can see the sky with 9 bands at wavelengths ranging from 0.3 millimeters up to nearly a centimeter, out of which we have made this false-color image. The center of the picture is toward the center of the Galaxy, with the rest of the sphere unwrapped into an ellipse so that we can put it onto a computer screen (so the left and right edges are really both the same points).

At the longest and shortest wavelengths, our view is dominated by matter in our own Milky Way galaxy — this is the purple-blue cloud, mostly so-called galactic “cirrus” gas and dust, largely concentrated in a thin band running through the center which is the disk of our galaxy viewed from within.

In addition to this so-called diffuse emission, we can also see individual, bright blue-white objects. Some of these are within our galaxy, but many are themselves whole distant galaxies viewed from many thousands or millions of light years distance. Here’s a version of the picture with some objects highlighted:

Even though Planck is largely a cosmology mission, we expect these galactic and extragalactic data to be invaluable to astrophysicists of all stripes. Buried in these pictures we hope to find information on the structure and formation of galaxies, on the evolution of very faint magnetic fields, and on the evolution of the most massive objects in the Universe, clusters of galaxies.

But there is plenty of cosmology to be done: we see the Cosmic Microwave Background (CMB) in the red and yellow splotches at the top and bottom — out of the galactic plane. We on the Planck team will be spending much of the next two years separating the galactic and extragalactic “foreground” emission from the CMB, and characterizing its properties in as much detail as we can. Stay tuned.

I admit that I was somewhat taken aback by the level of interest in these pictures: we haven’t released any data to the community, or written any papers. Indeed, we’ve really said nothing at all about science. Yet we’ve made it onto the front page of the Independent and even the Financial Times, and yours truly was quoted on the BBC’s website. I hope this is just a precursor to the excitement we’ll generate when we can actually talk about science, first early next year when we release a catalog of sources on the sky for the community to observe with other telescopes, and then in a couple of years time when we will finally drop the real CMB cosmology results.

Anonymous Comments

2010-06-29T20:14:00Z

We get most of the official feedback on our teaching through a mechanism called SOLE — Student On-Line Evaluations — which asks a bunch of questions on the typical “Very Poor” … “Very Good” scale. I’ve written about my results before — they are useful, and there is even some space for ad-hoc comments, but the questionnaire format is a bit antiseptic.

On some occasions, however, students make an extra effort to let you know how they feel. Last year, I received an anonymous paper letter in the old-fashioned snail-mail post from a student in my cosmology course which said, among other statements, that I should “show appropriate humility and shame by not teaching any undergraduate courses at all this coming year.” Well, that year has come and gone, and I was not absolved of teaching responsibilities, so I soldiered on.

Today, I received another anonymous letter, from a most assuredly different student, who said that this year’s cosmology course “is without a doubt the most interesting undergraduate course I have taken at Imperial.” This would have left me ecstatic, except that this otherwise well-intentioned and obviously smart student managed to put the envelope in the mailbox with insufficient postage, which meant that I had to trudge across to the local mail facility and pay the missing 10p, along with a full £1 fee/fine! (If the author of the letter happens to read this, please consider a donation of £1.10 plus appropriate interest to the charity of your choice!).

It would be self-serving of me to make too much of this, beyond noting that, although I did make some significant changes in this year’s course, these letters more likely indicate the very different reactions that a given course can engender, rather than a vast improvement in my teaching.

My apologies to both students if they would have preferred I not quote them on-line, but such is the price of anonymity.

Training Scientists: What's the Point?

2010-06-28T22:29:37Z

My colleagues and I spend what is probably an inordinate amount of time complaining about the occasional lapses of the basic skills of our students, their inability to take notes, their obsession with marks and what’s going to be on the exams. Because, like everyone else, we like to complain.

But pretty often I get the chance to see them at their best. In the Physics department at Imperial, we interview students who are on the boundaries between final “degree classifications”, the British system of awarding degrees as First Class, 2.1, 2.2, etc. Last week, I was on the panel for this year’s cohort. And it was a pleasure to sit in front of a few of our students and watch them, in real time, thinking like physicists. Of course this means making the occasional mistake, but it also means that delicious “aha!” moment when they figure something out and (this is the best part) they know that they have, whether it’s finding a sign error in their derivation of the motion of a pendulum, or a thought experiment explaining why Einstein’s relativity makes sense.

For the interviews, I was paired with one of our external examiners, UCL particle physicist and fellow-blogger Jon Butterworth. On the same day as our interview, the Guardian published Simon Jenkins’ latest in a series of risible anti-science screeds, and Jon decided to take him to task neither with reasoned argumentation nor with a counter-polemic, but with parody. As with many great ideas on the internet, this one got picked up and built upon, so that the Guardian, to its credit, eventually gave Jon his own space to reply. Jenkins likely thinks we’re producing too many scientists (Imperial only trains scientists, doctors, and engineers, after all!) but I hope that Jon was pleased with the ones he saw.

So my congratulations to this year’s graduating students, and the best of luck to them whatever they go on to do. Pace Jenkins, the world needs more well-trained scientists like them, not fewer.

Pop Culture Notes

2010-06-08T22:20:18Z

I’ve just finished marking this year’s Cosmology exams — I’m quite pleased with the outcome. But that’s meant that I’ve rewarded myself with some happily lowbrow (meant as a descriptive, not normative, term) entertainment:

I finally got around to the finale of Lost. Watching it, I was disappointed with the purgatorial explanation for this season’s “flash-sideways”; I would have preferred a less faux-spiritual device. But on reflection, considered purely as a fictional device for letting the creators illuminate their characters — seeing them act, react and interact in new situations — it worked (and, yes, jerked the odd tear on the way).
I bought an iPad. This will undoubtedly engender both jealousy and derision, so no one will be happy. It is a pretty, erm, magical piece of hardware. Somewhere between a toy and an appliance for now, but not yet a work necessity, like my laptop, nor a real-life one, as I admit my iPhone has become. But I could see it encroaching on the role of both of those, especially as I become less wary of taking it out — and as it becomes more powerful.
Although I missed some of the episodes along the way, I’ve been enjoying the BBC’s Luther. The melodrama was a bit much, but Idris Elba was fun to watch in the Columbo/Holmes/McNulty title roll, and Ruth Wilson was embarrassingly compelling as his gorgeous and psychopathic astrophysicist (!) nemesis-cum-sidecick. But even more exciting were the weird pop culture references that kept cropping up. There was Johnny Rotten’s “ever get the feeling you’ve been cheated?”, and Faulkner’s “the past isn’t dead; it’s not even past” within a few minutes of each other in episode two. And last week we found London’s DCIs calling New York City Detective Munch (Richard Belzer’s character from Homicide, various versions of Law and Order, and a few other series along the way). What have I missed?
And of course there’s Hitch’s acknowledgement that galaxy formation may be a harder problem than the existence of god (about which I am considerably more than 95% against) or the invasion of Iraq (on which I am somewhat more equivocal, I admit).

Monsters from the Id

2010-05-25T22:40:11Z

I’ve volunteered at the last minute to appear on a panel following a screening of Monsters from the Id, a documentary about 50s Sci-Fi movies and, apparently, their influence on science itself.

The filmmaker is Homer Hickam, an engineer and novelist, author of Rocket Boys, the “novelized” memoir of his rocket-obsessed post-Sputnik childhood in the West Virginia mining country. (I haven’t read it or seen the movie, October Sky, based on it, although it’s been recommended to me several times.)

So if you’re in London and pre-cgi special effects, giant irradiated insects, aliens with ray-guns and the over-arching fear of destruction raining down from above were a big part of your childhood (or maybe your parents’), come along to the Barbican on May 26th.

Building a time machine in the Dorset woods

2010-05-07T21:50:40Z

A few weeks ago I wrote about my visit to Geneva as part of the Beyond Entropy art/architecture/science collaboration sponsored by the Architecture Association. We continued our work last weekend in the Dorset woods visiting the AA’s Hooke Park site, a 350-acre forest with a bit more space for workshops than their Bedford Square buildings in central London.

Our group’s brief was to explore the concept of “mechanical energy” and we took as our starting point “How To Build A Time Machine”, by the French pre-absurdist Alfred Jarry (who I remember first encountering as the inspiration behind the name of Cleveland proto-punks Pere Ubu and as an occasional character in Zippy the Pinhead). Like Wells’ Time Machine from the same period, Jarry envisions time as a fourth dimension, and equips a massive cube with giant flywheels. Conservation of angular momentum (real physics) keeps the machine from moving in space, and also in time (that’s the absurdity).

We started by playing with some store-bought gyroscopes, trying to fix them to the faces of a cube, but soon realized that it was difficult to connect the edges of the cube to the axes of the spinning disks, although we did make this lovely machine out of small electric motors, rotors from tape decks, and machined metal disks (where by “we” I must admit that my mechanical prowess doesn’t quite rate much beyond kibbitzing on my part).

But we wanted something more substantial, and more symmetric. The design breakthrough, and my only major contribution, came with the realization that we could join the axes of the flywheels and the corners of the faces of cube with a triangle — a simpler and more stable shape than the cube itself. Shin Egashira, the architectural side of our triangular collaboration, took this forward to an actual design. We cut it from thick plywood with a magnificent CNC machine…

…which we then put together to make this:

The flywheels spin on bearings, and can actually generate quite a bit of angular momentum. We couldn’t yet work out an efficient way to get and keep all three wheels spinning at once, but the whole mechanism is stable (and well-built!) enough to spin around rather amazingly on the ground:

Next, the work of our collaboration and the others in the Beyond Entropy “cluster” will be presented at the Festival dell’energia in Lecce, and then this summer in Venice for the Architecture Biennale. Sadly, we weren’t able to travel in time any faster (or slower) than the usual one second per second, so these events are approaching fast.

Sympathy for the Music Industry

2010-05-07T20:41:33Z

A couple of my friends have got into a bit of a spat on the internet. Megan McArdle, a writer for the Atlantic Monthly, wrote “The Freeloaders”, arguing that file sharing, as practiced by today’s 20-something young adults, is destroying the music industry.

Marc Weidenbaum, who writes the wonderful disquiet blog, first first answered in prose. Marc argues, mostly correctly I think, that Megan’s argument conflates the major-label recording industry with the music industry as a whole. Despite the illegality (and let’s not be coy about it, there is plenty of theft involved), the more general ethos of free culture has spawned plenty of great art that flourishes outside of the stranglehold of that same recording industry.

He then realized a better rejoinder would be in the great tradition of answer records: he invited some musicians to comment, musically, on the article (and its accompanying illustration): the result is Despite The Downturn, freely available (free as in beer and as in freedom), mostly electronica, an amazing turnaround of just a couple of days from thought to expression. So at least something good has come out of this disagreement.

Herschel Papers (and a few words about Planck)

2010-05-06T19:19:22Z

Results from the first major science papers from the Herschel Satellite were released this week at a conference in Holland. Launched almost a year ago on the same rocket as Planck, Herschel is an infrared and sub-millimeter telescope, which lets it see not only the stars that generate the visible light we see with our eyes and ordinary cameras, but also the gas and dust that absorb and re-radiate that light. That gas and dust carries information about both the birth and death of stars: the detritus of exploding stars pollutes the interstellar medium, which eventually condenses out to form new generations of stars. On larger scales, Herschel’s observations let us trace the evolution of entire galaxies, the most important tracers of large-scale structure, formed from seeds laid down somehow in the first instants of the Universe (and, bringing it all back to cosmology, which are viewed by Planck in a much earlier form).

My Imperial colleagues and Herschel scientists Dave Clements and Brian O’Halloran discuss the results in much more detail over on the Herschel mission blog, or you can keep more up to date on twitter. But I’ll just steal some of their bandwidth and show some pretty pictures.

Most of the dots in this picture are one of those distant galaxies, lit up in the infrared due to its once and future stars:

Image courtesy ESA/ATLAS Consortium

Closer to home, this is selection of star-forming regions, turbulent filaments of gas and dust:

Image courtesy ESA/Hi-GAL Consortium

Not coincidentally, Imperial’s Michael Rowan-Robinson, who has been doing infrared astronomy for several decades, appeared on BBC radio 4’s wonderful In Our Time this morning to discuss “The Cool Universe”: covering a century or so of infrared astronomy in forty-five minutes.

We on Planck won’t be coming out with any papers for quite a while. However, many members of the team gathered in Orsay, outside of Paris, this week, to discuss the progress of the observations (and our analyses) and, crucially, to start talking in more detail about the actual papers that we’ll be writing over the next few years. More generally, Planck is doing pretty well. It came out first in NASA’s latest round of evaluations (which is a significant achievement for a mission primarily run by ESA), and which we hope will also give further impetus to keep funds flowing in the UK. This is especially important as the length of the Planck mission is likely to be almost doubled, allowing us to extract even more science than we originally hoped.

I can’t say much more, except that we’ve got a lot of — very exciting — work ahead of us.