We’re just about to run out of poetry month! Here’s Annie Finch, to close things out until next year.

Sir, I am not a bird of prey:
a Lady does not seize the day.
I trust that brief Time will unfold
our youth, before he makes us old.
How could we two write lines of rhyme
were we not fond of numbered Time
and grateful to the vast and sweet
trials his days will make us meet?
The Grave’s not just the body’s curse;
no skeleton can pen a verse!
So while this numbered World we see,
let’s sweeten Time with poetry,
and Time, in turn, may sweeten Love
and give us time our love to prove.
You’ve praised my eyes, forehead, breast:
you’ve all our lives to praise the rest.

In response to Andrew Marvell, of course. Both poems are pretty good, so I’m reluctant to take sides. Except: Annie Finch has a blog! Does Andrew Marvell have a blog? Not to my knowledge, no. So Finch wins this round.

I’m on record as predicting that we’ll understand what happened at the Big Bang within fifty years. Not just the “Big Bang model” — the paradigm of a nearly-homogeneous universe expanding from an early hot, dense, state, which has been established beyond reasonable doubt — but the Bang itself, that moment at the very beginning. So now is as good a time as any to contemplate what we already think we do and do not understand. (Also, I’ll be talking about it Saturday night on Coast to Coast AM, so it’s good practice.)

There is something of a paradox in the way that cosmologists traditionally talk about the Big Bang. They will go to great effort to explain how the Bang was the beginning of space and time, that there is no “before” or “outside,” and that the universe was (conceivably) infinitely big the very moment it came into existence, so that the pasts of distant points in our current universe are strictly non-overlapping. All of which, of course, is pure moonshine. When they choose to be more careful, these cosmologists might say “Of course we don’t know for sure, but…” Which is true, but it’s stronger than that: the truth is, we have no good reasons to believe that those statements are actually true, and some pretty good reasons to doubt them.

I’m not saying anything avant-garde here. Just pointing out that all of these traditional statements about the Big Bang are made within the framework of classical general relativity, and we know that this framework isn’t right. Classical GR convincingly predicts the existence of singularities, and our universe seems to satisfy the appropriate conditions to imply that there is a singularity in our past. But singularities are just signs that the theory is breaking down, and has to be replaced by something better. The obvious choice for “something better” is a sensible theory of quantum gravity; but even if novel classical effects kick in to get rid of the purported singularity, we know that something must be going on other than the straightforward GR story.

There are two tacks you can take here. You can be specific, by offering a particular model of what might replace the purported singularity. Or you can be general, trying to reason via broad principles to argue about what kinds of scenarios might ultimately make sense.

Many scenarios have been put forward among the “specific” category. We have of course the “quantum cosmology” program, that tries to write down a wavefunction of the universe; the classic example is the paper by Hartle and Hawking. There have been many others, including recent investigations within loop quantum gravity. Although this program has led to some intriguing results, the silent majority or physicists seems to believe that there are too many unanswered questions about quantum gravity to take seriously any sort of head-on assault on this problem. There are conceptual puzzles: at what point does spacetime make the transition from quantum to classical? And there are technical issues: do we really think we can accurately model the universe with only a handful of degrees of freedom, crossing our fingers and hoping that unknown ultraviolet effects don’t completely change the picture? It’s certainly worth pursuing, but very few people (who are not zero-gravity tourists) think that we already understand the basic features of the wavefunction of the universe.

At a slightly less ambitious level (although still pretty darn ambitious, as things go), we have attempts to “smooth out” the singularity in some semi-classical way. Aguirre and Gratton have presented a proof by construction that such a universe is conceivable; essentially, they demonstrate how to take an inflating spacetime, cut it near the beginning, and glue it to an identical spacetime that is expanding the opposite direction of time. This can either be thought of as a universe in which the arrow of time reverses at some special midpoint, or (by identifying events on opposite sides of the cut) as a one-way spacetime with no beginning boundary. In a similar spirit, Gott and Li suggest that the universe could “create itself,” springing to life out of an endless loop of closed timelike curves. More colorfully, “an inflationary universe gives rise to baby universes, one of which turns out to be itself.”

And of course, you know that there are going to be ideas based on string theory. For a long time Veneziano and collaborators have been studying what they dub the pre-Big-Bang scenario. This takes advantage of the scale-factor duality of the stringy cosmological field equations: for every cosmological solution with a certain scale factor, there is another one with the inverse scale factor, where certain fields are evolving in the opposite direction. Taken literally, this means that very early times, when the scale factor is nominally small, are equivalent to very late times, when the scale factor is large! I’m skeptical that this duality survives to low-energy physics, but the early universe is at high energy, so maybe that’s irrelevant. A related set of ideas have been advanced by Steinhardt, Turok, and collaborators, first as the ekpyrotic scenario and later as the cyclic universe scenario. Both take advantage of branes and extra dimensions to try to follow cosmological evolution right through the purported Big Bang singularity; in the ekpyrotic case, there is a unique turnaround point, whereas in the cyclic case there are an infinite number of bounces stretching endlessly into the past and the future.

Personally, I think that the looming flaw in all of these ideas is that they take the homogeneity and isotropy of our universe too seriously. Our observable patch of space is pretty uniform on large scales, it’s true. But to simply extrapolate that smoothness infinitely far beyond what we can observe is completely unwarranted by the data. It might be true, but it might equally well be hopelessly parochial. We should certainly entertain the possibility that our observable patch is dramatically unrepresentative of the entire universe, and see where that leads us.

Continue reading ‘How Did the Universe Start?’

Extremely early this morning, I returned from a visit to the Perimeter Institute, the theoretical physics center in Waterloo, Canada, founded by Mike Lazaridis, Co-CEO of Research In Motion (RIM) - makers of your Blackberry. I had spent the last day at PI, delivering the institute colloquium yesterday afternoon, with a talk titled “Challenges of Explaining Cosmic Acceleration through Modified Gravity”.

Perimeter is a wonderful place, with an increasing number of researchers devoted to physics issues of “foundational” importance. These topics include Quantum Gravity (with members working on causal sets, loop quantum gravity and string theory); Quantum Information Theory, Cosmology, Quantum Foundations and Particle Theory. These people are housed in a beautiful new building that, as well as being aesthetically pleasing (to me, at least), is also a tremendous intellectual playground, with collaborative spaces around every corner, equipped with espresso machines.

Arriving in Waterloo the night before, I graded exams over dinner and a couple of beers before getting an early night so that I could get into PI reasonably early in the morning. This gave me plenty of time to get administrative details out of the way, settle into my office, and then meet up with postdocs Claudia de Rham, Andrew Tolley and Mark Wyman for coffee and a lengthy physics chat. We talked about what each of us was up to and then spent some time discussing the ghost states and strong coupling regimes of various modified gravity models. These are interesting questions, to do with some of the pathological problems that often arise when General Relativity is altered to try to explain cosmic acceleration.

My host, Cliff Burgess, grabbed me for lunch at noon, and we spent an hour or so talking about string theory, quantum gravity, the sociology of these fields, and generally chatting about life at PI. This gave me a half hour to look over my talk before the colloquium at 2pm.

Colloquium at the Perimeter Institute is a lively event. Certainly the faculty, at least, are happy to press and probe with many questions. My talk consisted of a broad introduction to the problem of cosmic acceleration, followed by an outline of the general issues presented by modifying gravity to account for this phenomenon. I used some specific examples to show how solar system constraints constrain certain models, and the appearance of ghost states renders other ones unworkable. I also talked about how we may exploit some loopholes in these constraints to arrive at viable modified gravity models. In the last part of the colloquium, I moved on to the question of the types of observations that might help distinguish modified gravity models from dark energy, or a cosmological constant, as competing explanations for cosmic acceleration - discussing comparisons between, for example, Cosmic Microwave Background measurements and large scale structure observations.

Even with the many great questions, I managed to finish roughly on time, tired, but having had a thoroughly enjoyable time during the talk. I always find speaking to an audience exhausting, and this was no exception. But here Perimeter’s ubiquitous espresso came in particularly useful. With the drug fresh in my system, Cliff and I spend a half hour in his office talking about the approaches he and his collaborators have to dark Energy in some string inspired models, before I met up with Lee Smolin to talk about approaches to related questions arising from loop quantum gravity.

Later in the afternoon I got together with my former colleague and friend Rafael Sorkin. Rafael is a remarkable guy - an experienced relativist with unique ideas about the right way to construct a quantum theory of gravity from causal sets. Some questions about my talk, an update on his progress in teasing out the physics of causal sets, and a sketch of Rafael’s other interests in the foundations of quantum theory took me all way up to when I had to leave and meet up with my hosts in the Black Hole Bistro (yes - really).

There my visit wound up with dinner, where I got to spend time with, among others, someone I’ve known for a long time - and even wrote a paper with once - the theoretical physicist Slava Mukhanov. Slava is visiting PI for a few months - he’s currently giving a cosmology mini-course there - and as well as being an accomplished physicists, is a hilarious storyteller - which made dinner wonderful fun.

I had spent an extremely long and full day at PI, punctuated with fascinating meeting after fascinating meeting. My drive home passed quickly partly because I found myself mulling over a number of the ideas people had mentioned to me during the day. This is one of the great things about traveling as an academic - the exposure to different ideas in an informal context (not like reading papers) in which you can get lots of insight and instant feedback to your questions. Nice to be home though!

You know what’s a really big problem? The Farm Bill. The quintennial piece of legislation that steers billions of dollars into subsidies for farmers who mass-produce the raw materials of which junk food is made. Yeah, I know, not exactly a hot topic, nor our normal fare. But Michael Pollan in the Times lays out a devastating indictment of the current system, which encourages our economy to overproduce food that is incredibly bad for us, while busting the federal budget, ruining the environment, and hurting small farmers and developing countries to boot. (Via Marginal Revolution.)

Here is the basic econo-physics of the situation:

As a rule, processed foods are more “energy dense” than fresh foods: they contain less water and fiber but more added fat and sugar, which makes them both less filling and more fattening. These particular calories also happen to be the least healthful ones in the marketplace, which is why we call the foods that contain them “junk.” Drewnowski concluded that the rules of the food game in America are organized in such a way that if you are eating on a budget, the most rational economic strategy is to eat badly — and get fat.

This perverse state of affairs is not, as you might think, the inevitable result of the free market. Compared with a bunch of carrots, a package of Twinkies, to take one iconic processed foodlike substance as an example, is a highly complicated, high-tech piece of manufacture, involving no fewer than 39 ingredients, many themselves elaborately manufactured, as well as the packaging and a hefty marketing budget. So how can the supermarket possibly sell a pair of these synthetic cream-filled pseudocakes for less than a bunch of roots?

For the answer, you need look no farther than the farm bill. This resolutely unglamorous and head-hurtingly complicated piece of legislation, which comes around roughly every five years and is about to do so again, sets the rules for the American food system — indeed, to a considerable extent, for the world’s food system. Among other things, it determines which crops will be subsidized and which will not, and in the case of the carrot and the Twinkie, the farm bill as currently written offers a lot more support to the cake than to the root. Like most processed foods, the Twinkie is basically a clever arrangement of carbohydrates and fats teased out of corn, soybeans and wheat — three of the five commodity crops that the farm bill supports, to the tune of some $25 billion a year. (Rice and cotton are the others.) For the last several decades — indeed, for about as long as the American waistline has been ballooning — U.S. agricultural policy has been designed in such a way as to promote the overproduction of these five commodities, especially corn and soy.

I remember the moment it first dawned on me that Coke was significantly less expensive than orange juice. But making soda is a complicated chemical process, while oranges literally grow on trees! Of course, once you master that process, mass-producing the chemicals is fairly straightforward, while growing oranges requires a certain amount of patience. At the time I didn’t really appreciate the other aspect of the puzzle: we pay people to grow corn, which is turned into high-fructose corn syrup, which sweetens all of the processed food we find on our supermarket shelves.

Now, there does seem to be an obvious point missing in the article: the popularity of Twinkies over carrots cannot be put down solely to the greater density of calories per dollar. A lot of people like how Twinkies taste, deep-fried or not. But that doesn’t mean we should be actively subsidizing their production.

Pollan strikes an optimistic note at the end of his piece, suggesting that the importance of the Farm Bill may finally be percolating up to the national consciousness. (At least until the next time that a celebrity with fake boobs dies of a drug overdose.) It’s long been considered political suicide to even suggest messing with farm subsidies, especially with the Iowa caucuses playing such a large role in Presidential primaries. We’ll see if next year is any different.

As we approach the final exam season, and my thoughts turn to grading the hopefully logically thought-out musings of my students, here’s a little test for your enjoyment, courtesy of ebonmusings. I’ll just provide you with a teaser:

3) You are a product tester and frequently bring your work home. Yesterday, while dressed in a flame resistant suit (up to 3,000 degrees) and carrying the latest model fire extinguisher, you discover your neighbor’s house is on fire. As the flames quickly spread, you stand and watch your neighbor’s new baby burn to death. Which of the following best describes your behavior?

A. All-powerful
B. All-knowing
C. All-loving
D. Mysterious

(Thanks Ms. Chris!)

Gravitational waves were born from the mind of Einstein in 1918. He noticed that his brand-spanking-new field equations for the general theory of relativity had a simple wave solution in the weak field regime. These solutions represent propagating waves in the fabric of spacetime, traveling at the speed of light. In another fit of creative nomenclature these were dubbed “gravitational waves”. For a ring of particles floating in space, a passing gravitational-wave will cause them to oscillate (image at right stolen from the Wikipedia entry). For an introduction to the theory behind gravitational waves, I highly recommend chapter 7 of a certain textbook. (Sean, I get a kickback, right?)

Sadly, gravitational waves have had a fairly rough childhood. First came the doubters. There was much debate within the community as to whether gravitational waves truly existed. It might sounds strange that, given an equation describing their existence, gravitational-waves could nonetheless be questioned by large numbers of physicists. However, general relativity can be tricky, and it’s not always straightforward to understand what it’s trying to tell us. In this particular case, the question was whether or not gravitational waves were a gauge artifact. It can sometimes get confusing as to whether an effect is truly physical, or is just a byproduct of the coordinate system one has chosen. For example, look at the latitute/longitude coordinate system on the Earth. This system gets weird at the poles, where suddenly the longitude is no longer well defined (there are an infinite number of valid longitudinal coordinates for the same point). The North and South poles are somehow special, and if all you had were the coordinates, you might be afraid to take a walk there. Who knows what lurks at the singularities?! Needless to say, the problem is with the coordinates, and not with the poles themselves. (Although nowadays you might be afraid to head to the North Pole because you might end up under water. But don’t worry, Bush has it under control.)

Another example of the trickiness of coordinates, drawn from general relativity, is the black hole. In the canonical Schwarschild coordinates describing a black hole, it looks like terrible things (e.g., singularities) happen at the event horizon [or Schwarschild radius, which represents the ’surface’] of the black hole. But these are a problem with the coordinates. In truth, nothing particularly weird happens as you cross the surface of a black hole (besides gravitational lensing causing the sky to appear bent and warped). This can be seen by writing the exact same spacetime in different coordinates (e.g., Kruskal coordinates), where everything becomes well behaved (except for the singularity itself). No big deal crossing the event horizon (though all hell breaks loose as you approach the singularity). A similar confusion resided in the nature of gravitational waves. There were ways to rewrite the coordinate systems such that the waves appeared to disappear. Sir Arthur Eddington supposedly quipped that gravitational waves travel at “the speed of thought” (referring to a subset of waves which indeed are coordinate artifacts). In addition, many of the early calculations were done in the linearized, weak-field regime, where simplifying assumptions are made regarding the strength of gravity. Calculating the presence of waves in the full-blown theory is not nearly as straightforward. In Einstein’s original work he presented the “quadrupole formula”, which describes the energy loss due to gravitational-wave emission from a binary system, and which is actively used to this day. But the weak-field assumptions neglect self-gravity, which could be important in a binary system. Roughly 20 years after his initial proposal of gravitational waves, Einstein submitted a paper to the Physical Review with the title “Do Gravitational Waves Exist?”, with the answer “No”. (There’s a general rule that all paper titles in the form of a question have a negative answer.) The father disavowed his own children. We all make mistakes. (In this case, the referee rejected the paper. Einstein took great offense, and never again submitted to Physical Review. The referee was right. Einstein was wrong.) It took another 40 years or so for the community to develop a full understanding of how gravitational-waves fit into general relativity. They are now considered an essential component of the theory. A very interesting discussion of this history can be found in a paper by Daniel Kennefick.

One way to think about the necessary existence of gravitational-waves is through the following thought experiment. Imagine that you are on one side of a room, and that on the other side is a very massive object (e.g., a plutonium bowling ball). The lights are off in the room, but fortunately you are carrying a very sensitive gravitometer, so that you notice the force of gravity due to the massive ball: your gravitometer points right at the bowling ball. Now let us assume that Mark sneaks in, and gives the ball a good (preferably relativistic) kick. Since the ball has moved, the gravitational field should register the change. Newton tells us that the gravitometer would instantly adjust. But from relativity we know that nothing travels faster than the speed of light (including information), and therefore we need ’something’ to go from the accelerating bowling ball to our gravitometer, to tell it that the bowling ball has indeed moved. This is a gravitational wave! It carries with it the information about the accelerating mass, rushing out at the speed of light to announce the motion of the bowling ball to the entire Universe. Also notice that, were the bowling ball to suddenly contract, but remain spherical and conserve mass, then the gravitometer wouldn’t register a change. From this, we conclude that spherically symmetric variations don’t emit gravitational waves. As with most hand-wavy arguments, there are some important details being glossed over here (e.g., near vs far-field effects; Scott and Eanna have a nice review). But it makes a compelling case that something akin to gravitational waves must exist for general relativity to be self-consistent.

In a following post I’ll discuss the next sordid chapter in the history of gravitational waves.

It’s going to be Poetry Month all month long! But really, aren’t all months Poetry Month? Especially when time for substantive blogging is hard to come by?

Today we dip back a few millenia, to offer an excerpt from Virgil’s Aeneid, in the Robert Fagles translation. The backstory is that Aeneas has fled from the fall of Troy, charged by Jupiter with traveling to Italy and founding a new city (Rome). Along the way his party is diverted to Carthage by winds whipped up by the wind god Aeolus. (Who was in turn urged on by Juno, Jupiter’s wife, who was piqued at Aeneas because his mother, Venus, was judged to be better-looking than Juno by Aeneas’s countryman Paris. Gods have rarely risen above the standards of their humans.)

So anyway, in Carthage Aeneas is smitten by the widowed queen Dido, and they become lovers. Eventually Jupiter becomes impatient with this lollygagging, and urges Aeneas on his way. Dido, heartbroken, kills herself in her grief. Once in Italy, Aeneas does what any great epic hero would do, and takes a detour to the Underworld. There he comes across the shade of Dido, and appeals to her.

      “Tragic Dido,
so, was the story true that came my way?
I heard that you were dead. . .
you took the final measure with a sword.
Oh, dear god, was it I who caused your death?
I swear by the stars, by the Powers on high, whatever
faith one swears by here in the depths of earth,
I left your shores, my Queen, against my will. Yes,
the will of the gods, that drives me through the shadows now,
these moldering places so forlorn, this deep unfathomed night–
their decrees have forced me on. Nor did I ever dream
my leaving could have brought you so much grief.
Stay a moment. Don’t withdraw from my sight.
Running away — from whom? This is the last word
that Fate allows me to say to you. The last.”

Aeneas, with such appeals, with welling tears,
tried to soothe her rage, her wild fiery glance.
But she, her eyes fixed on the ground, turned away,
her features no more moved by his pleas as he walked on
than if she were sent in stony flint or Parian marble rock.

A great article in the New York Review (subscription required) by Hayden Pelliccia unpacks the layers of meaning behind the simple line “I left your shores, my Queen, against my will.” Although to us the scene is poignant, the emotional center of the entire poem, that particular line is an echo of a comic line in a poem of Catullus that would have been well known to Virgil — “I left your head, my Queen, against my will,” spoken by a shorn lock of the hair of Queen Berenice, cousin of the Egyptian king Ptolemy. So is the scene tragic, or secretly facetious? The answer is ambiguous, but involves an intricate digression into Roman politics and the loves of Cleopatra. That’s why every month is Poetry Month.

At Crooked Timber, Ingrid Robeyns passes along an email she received from an undergraduate student she doesn’t know. It’s a list of seven essay-type questions about the work and impact of economist Amartya Sen, along the lines of “How has Sen’s thought changed traditional development?” (Tyler Cowen, playing the straight man, actually answers the questions.)

A long discussion follows: What is the duty of professors, when it comes to answering questions from students? Heated arguments from different sides, largely for good reasons, and largely talking past each other. Students are complaining that they come to school to wrestle with great and challenging ideas, work hard and become passionate about what they’re being exposed to, only to find that professors are too busy to talk to them outside of class. Professors are shaking their heads in sympathy with the original post, amazed that a student who wasn’t even in a class with someone would feel justified in essentially asking them to do their homework for them.

So where is the line exactly to be drawn? I don’t know, but it’s a really good question, to which we give very little systematic attention, preferring instead to let every professor work things out according to their own preferences. Professors hold a privileged role in our culture; in return for years of hard work and devotion to an esoteric academic pursuit, society gives them jobs with lifetime tenure (ultimately, one hopes) and no heavy lifting, thinking about ideas at the edge of our understanding. In return, they are asked to assist in the production and dissemination of knowledge — doing original research, teaching students, and talking to the wider public. But what is an appropriate portfolio of these very different activities?

At the extremes, it’s not so hard. If a professor is teaching a class, there should be some time set aside for real-time interaction with the students outside of class. Traditionally these are “office hours” (a concept which, in my experience, undergraduates love and then completely forget about when they go to grad school). And at the other end, professors shouldn’t be expected to do students’ work for them. (I once got an email from a colleague, who was forwarding an inquiry from a student that he thought I’d know the answer to. Indeed I did know the answer, because I had just given that problem on a take-home exam that the student was supposed to be doing. More or less the definition of “busted.”)

But in between the extremes it’s harder, and there are few firm guidelines. And the invention of email has lowered a great deal of barriers, for better and for worse. What emails should we answer, and in how much detail? You don’t want to be a jerk, but you do want to get work done.

Crucially important is the relationship between the emailer and the recipient. In the original example, the fact that it was an unknown student was extremely relevant; if the student had been taking a class with the professor in which they were talking about Amartya Sen, there would have been some context to evaluate whether a straightforward answer should be given, or simply some pointers about where to look. But equally important is the form of the questions. In this case, they were so vague and essay-like that there was almost no simple answer that could have been of any use; the temptation to respond with a map to the library or instructions on how to use the internet must have been overwhelming. A good rule of thumb is: the less time it would take to respond, the more likely it is that a response will be forthcoming. And if it’s pretty clear that the original emailer has done next to no work themselves, they shouldn’t get their hopes up.

I get a lot of email, as well as occasional phone calls and regular mail. And I’m happy to admit, I don’t answer all of them. If they are technical questions about general relativity (about which I’ve written a book, don’t forget), I generally do not answer, but rather point to some promising resource — exactly because I’ve written that book, and if I answered all the questions about GR that I get I would do nothing else. If they are inquiries from students or sincerely interested people on the street about the state of physics or cosmology or whatever, I try to respond with short but substantive answers. If, as is often the case, they are from crackpots who say “I dare you to refute my theory!”, I generally don’t take the dare. (An exception is a letter I recently received from a state prison in New York. The writer is not a crackpot himself, but is stuck in prison with another guy who is convinced that special relativity is internally inconsistent, and he would like to know how to respond. In that case, I’ll definitely answer.)

The answering-email issue is just part of the much larger question of how much time professors should devote to students. The paradox is that what often draws students to a university — the place’s academic reputation, which rests on the research accomplishments of the faculty — can be an obstacle to fruitful interactions once they get there. Imagine how many physics students came to Caltech because of Richard Feynman. Undoubtedly they could have had some interesting interactions with him while they were here. But undergraduates would have found that he taught graduate seminars almost exclusively, while graduates would have found that he almost never took on any Ph.D. students. Too much worry and responsibility — he wouldn’t feel right giving a student a problem that he hadn’t already solved himself. While to me this seems like a scandalous abdication of duty (where would he have been if John Wheeler and others at Princeton had felt the same way?), the motivation is perfectly understandable.

What this calculation leaves out, of course, is that it can be extremely rewarding to advise students, or more generally to help people to understand things. But that sometimes gets lost amidst the feelings of being burdened and distracted from what we’re “really” here for.

Advising graduate students is a terrifying prospect, if you take it seriously; you’re wielding an extraordinary amount of influence over a young person’s life. Answering questions by email is a much smaller burden. But multiplied by dozens or hundreds of examples, and you can quickly get swamped. I suspect that most of us try to be reasonable, but walking the line between having individual chats with every interested person in the world and actually producing the research that made us experts in the first place is a delicate operation.

I know that you’ve all booked your tickets for Chicago in August, for the big YearlyKos shindig. True, it’s not exactly like going to a physics conference; the halls will be filled with candidates trying to drum up votes, and people who use words like “netroots” unironically. But if last year’s event was any indication, there should be all sorts of fun people there, even if it’s harder to find poker tables in Chicago than in Vegas. (You have to go to the riverboats in Gary.)

Like last year, the inimitable DarkSyde is making sure that science is well-represented, including a high-powered Science Panel. Last year the role of “bearded ScienceBlogger battling against creationism” was played by PZ Myers; this year it will be played by Ed Brayton. The role of “clean-shaven 4-star general who will talk about cosmology and the anthropic principle” was played last year by Wesley Clark; this year it will be me, except for the 4-star general part. The role of Chris Mooney will continue to be played by Chris Mooney. I’m honored to be participating, even if the commenters at Daily Kos are wishing it was my fiancee instead.

I hope any readers who are at the event will give a shout. It will be fun to return to the old haunts, go down to 75th Street to listen to Vonski, maybe indulge at Alinea if we save our pennies. And we all know that the weather in Chicago in August is invariably pleasant and charming, so there’s really no exuse.

Among the many fascinating blog posts you would get from me if I didn’t have a day job is one on “Why Everyone Loves to Hate on Particle Physicists.” I would not be in favor of the hating, but I would examine it as a sociological phenomenon. But now we have an explicit example, provided by respected astrophysicist Simon White, who has put a paper on the arXiv (apparently destined to appear in Nature, if it hasn’t already) entitled Fundamentalist physics: why Dark Energy is bad for Astronomy. Here’s the abstract:

Astronomers carry out observations to explore the diverse processes and objects which populate our Universe. High-energy physicists carry out experiments to approach the Fundamental Theory underlying space, time and matter. Dark Energy is a unique link between them, reflecting deep aspects of the Fundamental Theory, yet apparently accessible only through astronomical observation. Large sections of the two communities have therefore converged in support of astronomical projects to constrain Dark Energy. In this essay I argue that this convergence can be damaging for astronomy. The two communities have different methodologies and different scientific cultures. By uncritically adopting the values of an alien system, astronomers risk undermining the foundations of their own current success and endangering the future vitality of their field. Dark Energy is undeniably an interesting problem to attack through astronomical observation, but it is one of many and not necessarily the one where significant progress is most likely to follow a major investment of resources.

Simon contrasts the way that astronomers like to work — “observatory”-style instruments, aimed at addressing many problems and used by a large number of small groups — with the favored mode of particle physicists — dedicated experiments, controlled by large groups, aimed largely at a single purpose. He holds up the Hubble Space Telescope as a very successful example of the former philosophy, and WMAP as an (also quite successful) example of the latter. HST does all sorts of things, and many of its greatest contributions weren’t even imagined when it was first built; WMAP was aimed like a laser beam on a single target (the cosmic microwave background), and when it’s done everything it can on that observation it will gracefully expire.

His real worry is that the emergence of dark energy as a deep problem introduces the danger that the particle-physics way of doing things will take over astronomy. On the one hand, trying to understand the nature of the dark energy is undoubtedly interesting and important, and might only be addressable via astronomical observations; on the other, there is some danger that we devote too much of our resources to a small number of monstrous collaborations that are all tackling that one problem, to the ultimate detriment of the agile and creative nature of traditional astronomy.

I kind of agree, actually. More specifically, this is one of those cases where I disagree with all of the background philosophizing, but am sympathetic to the ultimate conclusions. (In contrast to the framing discussion, where I’m sympathetic to the philosophizing but disagree when it comes down to specific recommendations.) Dark energy is extremely interesting, and any little bit of info we can get about it is useful; on the other hand, there is a fairly narrow set of things that we can do to get info about it, and concentrating on doing those things to the detriment of the rest of astronomy would be a bad thing. Happily, astronomy is one of those nice fields in which it’s hard to learn about one thing without learning about something else; in particular, as the dark energy task force has recognized, the actual things that can be usefully observed in an attempt to get at dark energy will inevitably teach us many interesting things about galaxies, clusters, and large-scale structure.

Still, it’s worthwhile not going overboard. More than one working astronomer has grumbled that the way to get funding these days is to insert “dark energy” randomly into each paragraph of one’s proposal. (Not that such grumblings make it true; scientists applying for funding love to grumble.) But the backstory of “particle physics” vs. “astrophysics” (or “every other kind of physics”) is a misleading one. It’s not primarily a matter of cultures or sociology; it’s a matter of the science questions we are trying to address. There is something about particle physics that is different from most other kinds of science — you need to spend a lot of money on big, expensive, long-term experiments to get detailed information about the questions you are trying to ask. The LHC is an expensive machine. But if you choose to spend half as much money on building an accelerator, you won’t get half the results — you’ll get nothing. It might be that the results are not worth the cost; I disagree, but that’s a worthwhile debate to have. But if you decide that this kind of science is worth doing for what it costs, then big collaborations and expensive machines are the only way to get it done. (Not, obviously, the only way to get information about particle physics; that can come from all sorts of clever smaller-scale experiments. But if you want the kind of detailed information necessary to figure out the structure of what is really going on at high energies, big accelerators are the way to go.)

The issue for astrophysicists is not whether they want to continue to be small-scale and nimble and charming vs. giving into the particle-physics Borg. It’s what kind of questions are interesting, and how best to get at them. There is plenty of room out there for world-class astronomy of the quirky small-science type. But there’s also an increasing need for big targeted projects to answer otherwise intractable questions. Having a passionate debate about how to balance our portfolio is a good thing; casting aspersions on the sociological tendencies of our colleagues isn’t really relevant to the discussion.

Update: Rob Knop chimes in.

From comments: Here’s video/audio for the talk at KITP that Simon White gave last summer, on which this paper is based. (Thanks to John Edge.)