The last and arguably highest-tech detector elements are, this week, being installed into the giant CMS experiment at CERN: the pixel detectors. After these detectors are installed, there remains only the beam conditions monitor, a small device, and then the experiment can be buttoned up in anticipation of the first circulating proton beams, hopefully in August. Nearly the entire LHC machine is cold - superconducting cold - and so at long last it seems that we may soon see the first data. Rumor has it that there can be first protons circulating by August 9 (a week from Saturday!) but I bet it will take a bit longer. There will be a many-week shakedown process before “ramping” the beams to high energy. This year, if all goes well, it it foreseen to ramp to 10 TeV total collision energy; the design energy is 14 TeV and that will happen next year. (A TeV is a trillion electron volts, an energy equivalent to about a thousand proton masses.)

The pixel detectors are the innermost devices in CMS, and are the first to record the passage of high energy charged particles which emerge from the proton-proton collisions. The central driving idea of these devices is to record tiny three-dimensional space points along charge particle paths, allowing us to measure to within 10 microns (10 millionths of a meter; a human hair is 50 microns in diameter) the trajectory of the charged particles, and thereby infer where in space they may have emanated from.

This is particularly important information. The LHC machine has many “bunches” of protons in each counter-rotating beam, and each bunch is spread out over a length of around 8 cm. Every time bunches collide (and that will eventually be every 25 nanoseconds) we will get many proton-proton collisions. In all likelihood only one of these will be of interest for later analysis; we need to identify which particles come from that collision. The pixel detectors will help us pinpoint that location in space.

But perhaps of even more importance is to know when some of the particles appear to come from somewhere other than the “primary vertex” where the collision actually happened. The presence of these “secondary vertices” tell us that some particle travelled a distance and then decayed. In the case of a high energy bottom (b) quark, it can travel several millimeters or even centimeters and then decay into several charged particles. The presence of a b quark “jet” is often a good indicator of whether there were top (t) quarks, the heaviest of them all, produced in the event. There is a ton of physics, including searches for new physics beyond the Standard Model, that relies on these abilities of the experiment.

If we could strip away all the support frames, cooling, electronics, etc. from the pixel detectors, leaving only the detectors themselves, they would have an arrangement sort of like the diagram at right.

As you can see, there is a central “barrel” portion, and two “forward disks”. The detectors themselves are rectangular, and, as the name implies, segmented into very small pixels about a tenth of a millimeter in size. That’s a lot larger than the pixel size in your digital camera. But this detector can take 40 million pictures a second, keeping the interesting ones and discarding the vast majority.

The heart of the pixel detector is the readout chip, a silicon microchip specifically designed and fabricated for this detector, in this experiment. The effort to develop the readout chip was led by Roland Horisberger of the Paul Sherer Institut in Villigen, Switzerland. Each chip has over 4000 input channels arranged in a grid; each channel is bump-bonded to a sensor channel. The sensors are also very thin silicon wafers with one surface segmented into pixels. Each pixel channel can sense when a certain minimum amount of charge has been deposited by a passing charged particle, digitizes and time-stamps it, and sends it out onto the readout bus when a trigger signal matching the time stamp is received. All the thousands of readout chips in the detector do this in parallel, ultimately sending the torrent of data out on optical fibers to data acquisition electronics modules in the service cavern adjacent to the main detector cavern.

The PSI group built the central barrel portion of the CMS pixel detector, and the forward disks, which are somewhat more complicated mechanically, were built by a consortium of US universities and Fermilab. The forward disk detectors were assembled at Fermilab and then transported to CERN for final assembly, testing, and now installation.

My own involvement in the project has been varied, but most recently focused on getting the detectors to CERN last year, and then working with engineers at Fermilab and UC Davis to design and build the fixtures and procedures to get the forward detector installed.

A postdoc in the Davis group, Ricardo Vasquez Sierra, and I hand-carried the assembled half-disks aboard commercial aircraft from Chicago to Zurich to Geneva in four separate trips last year. These incredibly delicate devices were housed in special acrylic cases so as to facilitate security inspection. (We had made special arrangements with the TSA in Chicago…Zurich was more dificult.) The acrylic cases were in turn carried inside foam-lined hard shell cases. Needless to say, we carried each one, valued at about $500k, very carefully. People thought we were crazy - there is a certain history in our field of detectors arriving damaged when shipped - but we made it there with no problems at all. My biggest fear, I think, was some idiot tearing through the terminal and hitting one of our detectors with a luggage cart.

Meanwhile we needed to design a system to perform a sort of ship-in-a-bottle feat with the forward detectors. The detectors are deep inside the CMS tracker, the central bore of which is about seven meters long. The detector half-disks are mounted on two-meter-long carbon fiber service cylinders which also support the cables and tubes feeding power and cooling to the detector, plus some of the electronics. The two service cylinders sit vertically and slide into their final position along grooves in carbon fiber beds on the top and bottom of the bore. So as to have no uninstrumented regions in the vertical plane, at the end of travel the grooves are curved so as to make the half disks mesh. Thus, the two half cylinders need to be pushed in simultaneously with millimeter precision. Later the detectors need to be removed, at which point they will have become radioactive from exposure to the intense radiation environment in the center of the CMS detector. So the system had to be simple, easy and fast to use, so as to minimize radiation exposure to personnel.

Here is a remarkable photo of one of the forward pixel half cylinders half way into position. Note the converging tracks in which the half cylinder feet ride and the vertical beam pipe support that the detector has to clear on the way into position.

I have always been mechanically minded and enjoy problems like this. It was not the most sexy part of the pixel project, but an essential piece of making the whole thing work. We did a test of the inserttion a year ago when the tracker was still in a surface building at CERN. From the lessons we learned from a that test we built the final system for installation and tested it in May, before the beam pipe installation was completed.

So, just a few hours ago the CMS pixel detector was successfully installed. I was unable to be there, due to the recent birth of my son Ian. (Gotta have your priorities straight…) My able colleagues filled in seamlessly for me. Soon, though, the LHC and the ATLAS and CMS experiments will be up and running, and this great human adventure into inner space will commence.

Too much science on this blog, it’s getting stuffy around here. How about a poem from John Ashbery?

You can’t say it that way any more.
Bothered about beauty you have to
Come out into the open, into a clearing,
And rest. Certainly whatever funny happens to you
Is OK. To demand more than this would be strange
Of you, you who have so many lovers,
People who look up to you and are willing
To do things for you, but you think
It’s not right, that if they really knew you …
So much for self-analysis. Now,
About what to put in your poem-painting:
Flowers are always nice, particularly delphinium.
Names of boys you once knew and their sleds,
Skyrockets are good—do they still exist?
There are a lot of other things of the same quality
As those I’ve mentioned. Now one must
Find a few important words, and a lot of low-keyed,
Dull-sounding ones. She approached me
About buying her desk. Suddenly the street was
Bananas and the clangor of Japanese instruments.
Humdrum testaments were scattered around. His head
Locked into mine. We were a seesaw. Something
Ought to be written about how this affects
You when you write poetry:
The extreme austerity of an almost empty mind
Colliding with the lush, Rousseau-like foliage of its desire to communicate
Something between breaths, if only for the sake
Of others and their desire to understand you and desert you
For other centers of communication, so that understanding
May begin, and in doing so be undone.

If you would like to understand him (and then perhaps desert him for other centers of communication), Slate explains How to Read John Ashbery. Or you could just listen to him directly:

I had just stepped out of the shower yesterday (getting a bit of a late start, yes) when the building began to shake. We’re on the ninth floor of a twelve-story building in downtown Los Angeles, so it was quite exciting there for a while — the ground shook for maybe twenty seconds, the cat scampered under the bed, and an item or two had to be rescued from imminent spillage off of bookshelves. (Our cat has her own blog, so it usually takes quite a shock to drag her away from the internets.)

But a minor earthquake overall, just 5.4 on the Richter scale. No significant damage, even closer to the center (we were about 30 miles away). The interesting thing is that within seconds after the event you could hop to the US Geological Survey page to find a map of all the world’s recent earthquakes, and then home in on this one. Obviously most of the information is computer generated, although the main page for the earthquake does reassure you that “This event has been reviewed by a seismologist.”

So you can check out the Shake Map, of course:

We’re right on top of the dot labeled “Los Angeles.” But you can also find Google maps, travel times for the shocks,

and of course — waveforms!

Earthquakes are so much better with science. The only downside is that I spent the immediate aftermath looking for the kitty rather than drying my hair, so I went through the rest of the day with the dreaded “earthquake hair.”

In my last post, I discussed the puzzle posed for cosmologists and particle physicists by the observation of the baryon asymmetry of the universe (BAU) - the fact that the universe is composed almost entirely of matter, with a negligible amount of antimatter. In this post I’ll to go into a little more detail about one popular idea about how the BAU might be generated. Although I’ll be a little more technical here than usual, if people are interested in even more detail, they could read this review article, or this one.

The precise question that concerns us is; as the universe cooled from early times, at which one would expect equal amounts of matter and antimatter, to today, what processes, both particle physics and cosmological, were responsible for the generation of the BAU? In 1967, Andrei Sakharov established that any scenario for achieving this must satisfy the following three criteria;

• Violation of the baryon number (B) symmetry
• Violation of the discrete symmetries C (charge conjugation) and CP (the composition of parity and C)
• A departure from thermal equilibrium.

Continue reading ‘Matter v Antimatter II: Electroweak Baryogenesis’

I suspect the LHC must be close to ready — they’re coming out with rap videos now.

Via Adam at US/LHC Blogs, although the video was posted by writer/rapper Katherine McAlpine, formerly of Physics Buzz.

Lenny Susskind has a new book out: The Black Hole War: My Battle with Stephen Hawking to Make the World Safe for Quantum Mechanics. At first I was horrified by the title, but upon further reflection it’s grown on me quite a bit.

Some of you may know Susskind as a famous particle theorist, one of the early pioneers of string theory. Others may know his previous book: The Cosmic Landscape: String Theory and the Illusion of Intelligent Design. (Others may never have heard of him, although I’m sure Lenny doesn’t want to hear that.) I had mixed feelings about the first book; for one thing, I thought it was a mistake to put “Intelligent Design” there in the title, even if it were to be dubbed an “Illusion.” So when the Wall Street Journal asked me to review it, I was a little hesitant; I have enormous respect for Susskind as a physicist, but if I ended up not liking the book I would have to be honest about it. Still, I hadn’t ever written anything for the WSJ, and how often does one get the chance to stomp about in the corridors of capitalism like that?

The good news is that I liked the book a great deal, as the review shows. I won’t reprint the thing here, as you are all well-trained when it comes to clicking on links. But let me mention just a few words about information conservation and loss, which is the theme of the book. (See Backreaction for another account.)

It’s all really Isaac Newton’s fault, although people like Galileo and Laplace deserve some of the credit. The idea is straightforward: evolution through time, as described by the laws of physics, is simply a matter of re-arranging a fixed amount of information in different ways. The information itself is neither created nor destroyed. Put another way: to specify the state of the world requires a certain amount of data, for example the positions and velocities of each and every particle. According to classical mechanics, from that data (the “information”) and the laws of physics, we can reliably predict the precise state of the universe at every moment in the future — and retrodict the prior states of the universe at every moment in the past. Put yet another way, here is Thomasina Coverley in Tom Stoppard’s Arcadia:

If you could stop every atom in its position and direction, and if your mind could comprehend all the actions thus suspended, then if you were really, really good at algebra you could write the formula for all the future; and although nobody can be so clever as to do it, the formula must exist just as if one could.

This is the Clockwork Universe, and it is far from an obvious idea. Pre-Newton, in fact, it would have seemed crazy. In Aristotelian mechanics, if a moving object is not subject to a continuous impulse, it will eventually come to rest. So if we find an object at rest, we have no way of knowing whether until recently it was moving, or whether it’s been sitting there for a long time; that information is lost. Many different pasts could lead to precisely the same present; whereas, if information is conserved, each possible past leads to exactly one specific state of affairs at the present. The conservation of information — which also goes by the name of “determinism” — is a profound underpinning of the modern way we think about the universe.

Determinism came under a bit of stress in the early 20th century when quantum mechanics burst upon the scene. In QM, sadly, we can’t predict the future with precision, even if we know the current state to arbitrary accuracy. The process of making a measurement seems to be irreducibly unpredictable; we can predict the probability of getting a particular answer, but there will always be uncertainty if we try to make certain measurements. Nevertheless, when we are not making a measurement, information is perfectly conserved in quantum mechanics: Schrodinger’s Equation allows us to predict the future quantum state from the past with absolute fidelity. This makes many of us suspicious that this whole “collapse of the wave function” that leads to an apparent loss of determinism is really just an illusion, or an approximation to some more complete dynamics — that kind of thinking leads you directly to the Many Worlds Interpretation of quantum mechanics. (For more, tune into my Bloggingheads dialogue with David Albert this upcoming Saturday.)

In any event, aside from the measurement problem, quantum mechanics makes a firm prediction that information is conserved. Which is why it came as a shock when Stephen Hawking said that black holes could destroy information. Hawking, of course, had famously shown that black holes give off radiation, and if you wait long enough they will eventually evaporate away entirely. Few people (who are not trying to make money off of scaremongering about the LHC) doubt this story. But Hawking’s calculation, at first glance (and second), implies that the outgoing radiation into which the black hole evaporates is truly random, within the constraints of being a blackbody spectrum. Information is seemingly lost, in other words — there is no apparent way to determine what went into the black hole from what comes out.

This led to one of those intellectual scuffles between “the general relativists” (who tended to be sympathetic to the idea that information is indeed lost) and “the particle physicists” (who were reluctant to give up on the standard rules of quantum mechanics, and figured that Hawking’s calculation must somehow be incomplete). At the heart of the matter was locality — information can’t be in two places at once, and it has to travel from place to place no faster than the speed of light. A set of reasonable-looking arguments had established that, in order for information to escape in Hawking radiation, it would have to be encoded in the radiation while it was still inside the black hole, which seemed to be cheating. But if you press hard on this idea, you have to admit that the very idea of “locality” presumes that there is something called “location,” or more specifically that there is a classical spacetime on which fields are propagating. Which is a pretty good approximation, but deep down we’re eventually going to have to appeal to some sort of quantum gravity, and it’s likely that locality is just an approximation. The thing is, most everyone figured that this approximation would be extremely good when we were talking about huge astrophysical black holes, enormously larger than the Planck length where quantum gravity was supposed to kick in.

But apparently, no. Quantum gravity is more subtle than you might think, at least where black holes are concerned, and locality breaks down in tricky ways. Susskind himself played a central role in formulating two ideas that were crucial to the story — Black Hole Complementarity and the Holographic Principle. Which maybe I’ll write about some day, but at the moment it’s getting late. For a full account, buy the book.

Right now, the balance has tilted quite strongly in favor of the preservation of information; score one for the particle physicists. The best evidence on their side (keeping in mind that all of the “evidence” is in the form of theoretical arguments, not experimental data) comes from Maldacena’s discovery of duality between (certain kinds of) gravitational and non-gravitational theories, the AdS/CFT correspondence. According to Maldacena, we can have a perfect equivalence between two very different-looking theories, one with gravity and one without. In the theory without gravity, there is no question that information is conserved, and therefore (the argument goes) it must also be conserved when there is gravity. Just take whatever kind of system you care about, whether it’s an evaporating black hole or something else, translate it into the non-gravitational theory, find out what it evolves into, and then translate back, with no loss of information at any step. Long story short, we still don’t really know how the information gets out, but there is a good argument that it definitely does for certain kinds of black holes, so it seems a little perverse to doubt that we’ll eventually figure out how it works for all kinds of black holes. Not an airtight argument, but at least Hawking buys it; his concession speech was reported on an old blog of mine, lo these several years ago.

I find it extremely amusing that when Radovan Karadzic, Serbian war criminal and fugitive from justice, wanted to disguise himself with an assumed identity in a suburb of Belgrade, he chose such an interesting occupation for his alter ego — purveyor of New-Age quantum nonsense.

No one knew quite how to react when it emerged that he had been selling “human quantum energy” diviners on the internet from a flat in surburban Belgrade, speaking at conferences for alternative health and maintaining an intimate friendship with a rather good-looking younger woman.

And this wasn’t just some cover story to fall back on when strangers inquired about what he did for a living; apparently, Karadzic really went all-out. (Including a website. Every international fugitive needs a website!)

He threw himself into the role. His articles in Healthy Life, a Serbian alternative medicine magazine, show a man who was fluent in new age thinking. “It is widely believed our senses and mind can recognise only 1% of whatever exists around us. Three per cent we understand with our hearts. All that remains is shrouded in secrecy, out of the reach of our five senses; however, it is within our reach in the extra-sensory manner,” he wrote in one article.

I love the quantification. Three percent we understand with our hearts! Hopefully, improved experimental precision will enable us to pin the correct figure down to the nearest tenth of a percent.

But he was devout, you have to had him that.

He was also interested in healing through the optimal use of ‘vital energy’, a quasi-mystical, non-physical dimension of the body, similar to the Chinese notion of ‘Qi’ and the Indian concept of the ‘chakra’ centres of energy in the body. “He was very religious,” said a woman who works at the magazine and knew him. “He had his hair in a plait in order to be able to receive different energies. He was a very nice man.”

At least, when he wasn’t ordering the Srebrenica massacre. That wasn’t really very nice.

As it seems to by symmetry week here at CV, I thought I’d touch upon something related to one of the many events that happened during a recent vortex of unbloggability (i.e., when everything that I wanted to write about would only be publishable on a pseudonymous blog).

Astronomer Fritz Zwicky frequently employed the term “spherical bastard” to describe a group of rival astronomers, since in Zwicky’s view, they were bastards any way you looked at them. While Zwicky had no patience for this group, I would argue that fully-symmetric bastards are the easiest of assholes to deal with. No one is surprised when a known, calibrated asshole acts up. We all just adjust the gain on our emotional response and carry on. I’ve been quite fond of many assholes through the years, and when I look back, the one trait they shared was that while they may have been ornery, they were at least predictable.

In contrast, I cannot abide asymmetric assholes. These are the people who stroke those who are of use to them, and claw those they deem inferior. They ignore you before you win a fancy fellowship, but suddenly talk to you when you do. They flatter established faculty, but don’t hesitate to sabotage the same professor’s students.

Let me warn you, o asymmetric asshole — people talk to each other. That person you’re actively trying to sabotage? They have mentors. Who are sometimes the people whose behinds you’re trying to kiss.

You may think you’re getting away with it. But trust me. You’re not. Or at least not for long.

I’m in the middle of a couple of posts about the matter-antimatter asymmetry of the universe and have found that I keep referring to things I posted back on my old blog a long time ago. This became so frequent that I’ve decided to post a slightly edited version of these here, and in my next post, as preludes to some newer material that I’m getting to.

Antimatter is just like ordinary matter in every way, except that every quantity you can think of (apart from mass and spin), is reversed. As an example, the electron is a particle with a specific mass and carrying a specific amount of negative electric charge. The antiparticle of the electron is a positron, which has the identical mass to an electron, but precisely the opposite charge. The thing about particles and their antiparticles is that, if one puts them together, the net value of any quantity (called a quantum number by physicists) carried by the pair of them is zero. Therefore, a particle and an antiparticle together are merely mass which, thanks to Einstein’s E=mc², can be converted entirely into energy. As a result of this, when matter and antimatter come together, they annihilate, producing energy in the form of light (photons).

We know so much about antimatter for two reasons. The first is that it is a natural part of quantum field theories, which we use to describe matter, and which are among the best-tested theories in all of science. The second is that we can make and investigate antimatter in large amounts. For example, the purpose of the Fermi National Accelerator Laboratory near Chicago is to make vast numbers of antiprotons to study how they annihilate with protons.

Antimatter is important in cosmology because of the extreme temperatures and densities of the early universe. One consequence of such an extreme environment is that there is so much energy around that any kind of matter (including antimatter) can be created. Therefore, in the early universe, one expects there to have been equal amounts of both matter and antimatter and then, as the universe cooled, for these particles to find each other, annihilate, and leave our present universe with very little matter around (and an equally small amount of antimatter).

This is clearly at odds with what we observe in the universe, where we have relatively large amounts of matter and essentially no evidence of primordial antimatter. In fact, this asymmetry between matter and antimatter can be made quantitative (for baryons such as protons and neutrons) through observations of the abundances of light elements in the universe (Big Bang Nucleosynthesis - BBN) and also from the pattern of anisotropies in the cosmic microwave background radiation (CMB). Thus, there is clear quantitative evidence that the universe is composed of matter, with negligible antimatter.

This all constitutes a puzzle for cosmologists. How did the universe evolve from early times, in which there were equal numbers of baryons and antibaryons, to the present universe, in which there is a precisely measured baryon asymmetry of the universe (BAU)?

Potential solutions to this puzzle provide a wonderful example of the interplay between particle physics and cosmology. A beautiful feature of many theories beyond the standard model of particle physics is that, when considered in the context of the expanding universe, they automatically contain such a dynamical mechanism that can, in principle, explain the origin of the BAU. The generation of the BAU through one of these mechanisms is what is known as baryogenesis. This isn’t enough of course; we don’t yet know which, if any, of these theories might be the right one. However, upcoming experiments, such as those at the Large Hadron Collider (LHC), provide the exciting possibility of either ruling out some of them or providing significant evidence for one of them.

Over the course of my next few posts I’ll try to explain how some of these mechanisms work, and how they illustrate the particle-cosmology connection.

Fred Adams wonders whether we could still have stars if the constants of nature were very different. Answer: very possibly! It’s in arxiv:0807.3697:

Motivated by the possible existence of other universes, with possible variations in the laws of physics, this paper explores the parameter space of fundamental constants that allows for the existence of stars. To make this problem tractable, we develop a semi-analytical stellar structure model that allows for physical understanding of these stars with unconventional parameters, as well as a means to survey the relevant parameter space. In this work, the most important quantities that determine stellar properties — and are allowed to vary — are the gravitational constant $G$, the fine structure constant $\alpha$, and a composite parameter $C$ that determines nuclear reaction rates. Working within this model, we delineate the portion of parameter space that allows for the existence of stars. Our main finding is that a sizable fraction of the parameter space (roughly one fourth) provides the values necessary for stellar objects to operate through sustained nuclear fusion. As a result, the set of parameters necessary to support stars are not particularly rare. In addition, we briefly consider the possibility that unconventional stars (e.g., black holes, dark matter stars) play the role filled by stars in our universe and constrain the allowed parameter space.

I’ve never thought that our knowledge of what constituted “intelligent life” was anywhere near good enough to start making statements about the conditions under which it could form, apart from fairly weak stuff like “life probably can’t exist if the universe only lasts for a Planck time.” So when anthropic arguments start to hinge on thinking that fractional changes in the mass of this or that nucleus would result in a universe with no observers, it seems more prudent to admit that we just don’t know. But putting any anthropic considerations aside, it’s still interesting to ask what the universe would look like if the constants of nature were completely different. How robust are the starry skies?

Physicists love spontaneous symmetry breaking. It’s a great way to reconcile the messiness of reality with our belief in simple and beautiful underlying mechanisms. We posit that the true fundamental dynamics of the world has some symmetry — X can be exchanged with Y, and all relevant processes are unchanged — but the actual state of the world does not respect that symmetry, which leaves it hidden (or “nonlinearly realized,” if you want to sound all sciencey). Deep down, a (left-handed) electron is completely interchangeable with an electron neutrino; but in the world as we find it, this symmetry is broken, and we end up with an electron that is charged and massive, a neutrino that is neutral and nearly massless. The Higgs boson that the Large Hadron Collider is looking for would be the telltale sign of the mechanism behind this symmetry breaking.

For reasons which escape me, this concept has not been borrowed (as far as I can tell) by social scientists and pundits more generally.^* Which is too bad, as it explains a great deal. For example, appealing to the concept of spontaneous symmetry breaking would have been really helpful to Whoopi Goldberg on The View recently, as she patiently tried to explain to a distraught Elisabeth Hasselbeck why it’s just not the same when black people use the word “nigger” as when white people do. (From Sociological Images, via The Edge of the American West.)

Which is not to say that it’s always okay, or that there is no thoughtful critique of the re-appropriation of derogatory language by targeted groups, etc. Just that “If it’s wrong when white people say it, it should be wrong when black people say it too! It’s just not fair!” is far too simple-minded to carry any weight.

Let’s imagine that, in our view of a happy future utopia, all races find themselves in situations of perfect equality of opportunity and dignity. Everyone enters society with equal status, and people are judged not by the color of their skin but by the content of their character. (The “symmetric vacuum.”) In such a world, arguments like “If you can do it, why shouldn’t I be able to?” would be perfectly legitimate. But even if we want that to be the world — even if we believe that the grand unified theory of social ethics involves a symmetry of rights and obligations under the interchange of various racial categories — it’s not the world in which we live. In the real world, different races don’t go through life with the same masses and charges (if you will). There really are such things as discrimination, legacies of poverty and exclusion, and so on. We can argue about the best way to deal with those features of reality, but pretending that they don’t exist isn’t a very useful strategy.

As Whoopi explains, many blacks have chosen to re-appropriate the n-word as part of a conscious strategy of fighting back against a power dynamic that uses language to keep them at the bottom. Again, one can argue about the effectiveness of that strategy, and the circumstances under which it is appropriate, and whether Jesse Jackson should really have used that term in referring to Barack Obama. But it doesn’t follow that “if it’s fair for you, it should be fair for me.” Here is a guy who sadly doesn’t get it; a white high-school teacher who is genuinely puzzled about why he got in trouble for calling one of his black students “nigga.”

I was contemplating writing this post for a long time, with the relevant symmetry being men/women and the social milieu being the scientific community. Too many physicists reason along the following lines: “Men and women should be treated equally. Therefore, any time we privilege one over the other, as in making a special effort to encourage women in science, we are making a mistake.” That would be a reasonable argument, if the symmetry weren’t dramatically broken by the state in which we find ourselves. Which happily is not a stable vacuum! (Note that the underlying assumption is not that different genders or races are necessarily equivalent when it comes to innate abilities; that is largely beside the point, and obsession about those questions gets to be a little creepy. But they should certainly have equal opportunities — and right now, they don’t.) Treating one group differently than the other isn’t what we ultimately want to be doing — it’s not part of the happy utopia — but it might be the best response to the current state of unequal treatment overall.

But Whoopi’s little teaching moment was too good to pass up. If the discussion of race and gender in the rest of the MSM rose to that level of sophistication, we’d all be better off.

———-

^*I’ve been searching for an excuse to mention Kieran Healy’s Standard Model of Sociophysics. I’m not sure if this is it, but I’ll take it.

Everyone is amused by Wordle these days. Plug in (or link to) some text, and it makes quite a nice word cloud, customizable in all sorts of ways. At least Abbas had the modesty to try Hamlet, rather than one of his own pieces.

I’m not so modest; this is my Scientific American article.

The standard lore is that most scientists are essentially self-aware robots, thinking their rigid rightleft brain thoughts from morning to night, taking short breaks to practice mentally rotating 3-D objects. In reality, most of the scientists I know also have a long suit in one or more of the arts as well. Many are excellent musicians, artists, or writers. Even more are voracious readers, or at least, as voracious as their schedule allows.

With all the parenting and sciencing going on, the only time I really have to read is right before bed. This window allows me a bit of peace and quiet, while simultaneously serving to divert my rather obsessive brain from the pressing issues which dominate the rest of my waking thoughts. Finding the right book, however, is a problem. Non-fiction tends to work well, but fiction is a bit trickier, as if the book is too compelling, I run the risk of staying up till 3am.

Over the past decade, I’ve been on a steady diet of victorian literature (Trollop, Hardy, etc). I’ve read and enjoyed Henry James, but man alive, the latest of his is killing me. As I now learn, late-period James is a very different animal than early-period James. I’m reading “The Wings of the Dove”, and find that, in spite of being a native speaker of english and well-read in James’ contemporaries, I simply cannot understand what he writes some fraction of the time.

For example, dust off your sentence diagramming skills and see what you can make of this, which starts and ends well, but in the middle veers off into I know not where:

The difficulty with Densher was that he looked vague without looking weak — idle without looking empty. It was the accident, possibly, of his long legs, which were apt to stretch themselves, of his straight hair and his well-shaped head, never, the latter, neatly smooth, and apt, into the bargain, at the time of quite other calls upon it, to throw itself suddenly back and, supported behind by his uplifted arms and interlocked hands, place him for unconscionable periods in communion with the ceiling, the treetops, the sky.

It’s actually perfect pre-bed reading, as after about 4 pages I’m exhausted. However, at 545 pages, I may not get to read another book before Christmas.

One of the important features of the universe around us is that, on sufficiently large scales, it looks pretty much the same in every direction — “isotropy,” in cosmology lingo. There is no preferred direction to space, in which the universe would look different than in the perpendicular directions. The most compelling evidence for large-scale isotropy comes from the Cosmic Microwave Background (CMB), the leftover radiation from the Big Bang. It’s not perfectly isotropic, of course — there are tiny fluctuations in temperature, which are pretty important; they arise from fluctuations in the density, which grow under the influence of gravity into the galaxies and clusters we see today. Here they are, as measured by the WMAP satellite.

Nevertheless, there is a subtle way for the universe to break isotropy and have a preferred direction: if the tiny observed perturbations somehow have a different character in one direction than in others. The problem is, there are a lot of ways this could happen, and there is a huge amount of data involved with a map of the entire CMB sky. A tiny effect could be lurking there, and be hard to see; or we could see a hint of it, and it would be hard to be sure it wasn’t just a statistical fluke.

In fact, at least three such instances of apparent large-scale anisotropies have been claimed. One is the “axis of evil” — if you look at only the temperature fluctuations on the very largest scales, they seem to be concentrated in a certain plane on the sky. Another is the giant cold spot (or “non-Gaussianity,” if you want to sound like an expert) — the Southern hemisphere seems to have a suspiciously coherent blob of slightly lower than average CMB temperature. And then there is the lopsided universe — the total size of the fluctuations on one half of the sky seems to be slightly larger than on the other half.

All of these purported anomalies in the data, while interesting, are very far from being definitive. Although most people seem to agree that they are features of the data from WMAP, it’s hard to tell whether they are all just statistical flukes, or subtle imperfections in the satellite itself, or contamination by foregrounds (like our own galaxy), or real features of the universe.

Now we seem to have another such anomaly, in which the temperature fluctuations in the CMB aren’t distributed perfectly isotropically across the sky. It comes by way of a new paper by Nicolaas Groeneboom and Hans Kristian Eriksen:

Bayesian analysis of sparse anisotropic universe models and application to the 5-yr WMAP data

Sexy title, eh? Here is the upshot: Groeneboom and Eriksen looked for what experts would call a “quadrupole pattern of statistical anisotropy.” Similar to the lopsided universe effect, where the fluctuations seem to be larger on one side of the sky than the other, this is an “elongated universe” effect — fluctuations are larger along one axis (in both directions) as compared to the perpendicular plane. Here is a representation of the kind of effect we are talking about — not easy to make out, but the fluctuations are supposed to be a bit stronger near the red dots than in the strip in between them.

It’s not a very large signal — “3.8 sigma,” in the jargon of the trade, where 3 sigma basically means “begin to take seriously,” but you might want to get as high as 5 sigma before you say “there definitely seems to be something there.” However, the WMAP data come in different frequencies (V-band and W-band), and the effect seems to be there in both bands. Furthermore, you can look for the effect separately at large angular scales and at small angular scales, and you find it in both cases (with somewhat lower statistical significance, as you might expect). So it’s far from being a gold-plated discovery, but it doesn’t seem to be a complete fluke, either.

Remember, looking for any specific effect is quite a project — there is a lot of data, and the analysis involves manipulating huge matrices, and you have to worry about foregrounds and instrumental effects. So why were these nice folks looking for a power asymmetry along a preferred axis in the sky? Well, you might recall my paper with Lotty Ackerman and Mark Wise, described in the “Anatomy of a Paper” series of blog posts (I, II, III). We were interested in whether the (hypothetical) period of inflation in the early universe might have been anisotropic — expanding just a bit faster in one direction than in the others — and if so, how it would show up in the CMB. What we found was that the natural expectation was a power asymmetry along the preferred axis, and gave a bunch of formulas by which observers could actually look for the effect. That is what Nicolaas and Hans Kristian did, with every expectation that they would establish an upper limit on the size of our predicted effect, which we had labelled g_*. But instead, they found it! The data are saying that

So naturally, Lotty and Mark and I are brushing up on our Swedish in preparation for our upcoming invitations to Stockholm. Okay, not quite. In fact, it’s useful to be very clear about this, given the lessons that were (one hopes) learned in John’s series of posts about Higgs hunting. Namely: small, provocative “signals” such as this happen all the time. It would be completely irresponsible just to take every one of them at face value as telling you something profound about the universe. And the more surprising the result — and this one would be pretty darned surprising — the more skeptical and cautious we have every right to be.

So what are we supposed to think? Certainly not that these guys are just jokers that don’t know how to analyze CMB data; the truth couldn’t be more different. But analyzing data like this is really hard, and other groups will doubtless jump in and do their own analyses, as it should be. It’s certainly possible that there is a small systematic effect in WMAP — “correlated noise” — rather than in the universe. The authors have considered this, of course, and it doesn’t seem to fit the finding very comfortably, but it’s a possibility. The very good news is that the kind of correlated noise one would expect from WMAP (given the pattern it used to scan across the sky) is completely different from that the we would worry about from the upcoming Planck mission, scheduled to launch next year.

Or, of course, we could be learning something deep about the universe. Maybe even that inflation was anisotropic, as Lotty and Mark and I contemplated. Or, perhaps more plausibly, there is some single real effect in the universe that is conspiring to give us all of the tantalizing hints contained in the various anomalies listed above. We don’t know yet. That’s what makes it fun.

Holy crap our blog is three years old.