I would like to embed a video!

No particular reason, really.

The best talk I heard at the International Congress of Logic Methodology and Philosophy of Science in Beijing was, somewhat to my surprise, the Presidential Address by Adolf Grünbaum. I wasn’t expecting much, as the genre of Presidential Addresses by Octogenarian Philosophers is not one noted for its moments of soaring rhetoric. I recognized Grünbaum’s name as a philosopher of science, but didn’t really know anything about his work. Had I known that he has recently been specializing in critiques of theism from a scientific viewpoint (with titles like “The Poverty of Theistic Cosmology“), I might have been more optimistic.

Grünbaum addressed a famous and simple question: “Why is there something rather than nothing?” He called it the Primordial Existential Question, or PEQ for short. (Philosophers are up there with NASA officials when it comes to a weakness for acronyms.) Stated in that form, the question can be traced at least back to Leibniz in his 1697 essay “On the Ultimate Origin of Things,” although it’s been recently championed by Oxford philosopher Richard Swinburne.

The correct answer to this question is stated right off the bat in the Stanford Encyclopedia of Philosophy: “Well, why not?” But we have to dress it up to make it a bit more philosophical. First, we would only even consider this an interesting question if there were some reasonable argument in favor of nothingness over existence. As Grünbaum traces it out, Leibniz’s original claim was that nothingness was “spontaneous,” whereas an existing universe required a bit of work to achieve. Swinburne has sharpened this a bit, claiming that nothingness is uniquely “natural,” because it is necessarily simpler than any particular universe. Both of them use this sort of logic to undergird an argument for the existence of God: if nothingness is somehow more natural or likely than existence, and yet here we are, it must be because God willed it to be so.

I can’t do justice to Grünbaum’s takedown of this position, which was quite careful and well-informed. But the basic idea is straightforward enough. When we talk about things being “natural” or “spontaneous,” we do so on the basis of our experience in this world. This experience equips us with a certain notion of natural — theories are naturally if they are simple and not finely-tuned, configurations are natural if they aren’t inexplicably low-entropy.

But our experience with the world in which we actually live tells us nothing whatsoever about whether certain possible universes are “natural” or not. In particular, nothing in science, logic, or philosophy provides any evidence for the claim that simple universes are “preferred” (whatever that could possibly mean). We only have experience with one universe; there is no ensemble from which it is chosen, on which we could define a measure to quantify degrees of probability. Who is to say whether a universe described by the non-perturbative completion of superstring theory is likelier or less likely than, for example, a universe described by a Rule 110 cellular automaton?

It’s easy to get tricked into thinking that simplicity is somehow preferable. After all, Occam’s Razor exhorts us to stick to simple explanations. But that’s a way to compare different explanations that equivalently account for the same sets of facts; comparing different sets of possible underlying rules for the universe is a different kettle of fish entirely. And, to be honest, it’s true that most working physicists have a hope (or a prejudice) that the principles underlying our universe are in fact pretty simple. But that’s simply an expression of our selfish desire, not a philosophical precondition on the space of possible universes. When it comes to the actual universe, ultimately we’ll just have to take what we get.

Finally, we physicists sometimes muddy the waters by talking about “multiple universes” or “the multiverse.” These days, the vast majority of such mentions refer not to actual other universes, but to different parts of our universe, causally inaccessible from ours and perhaps governed by different low-energy laws of physics (but the same deep-down ones). In that case there may actually be an ensemble of local regions, and perhaps even some sensibly-defined measure on them. But they’re all part of one big happy universe. Comparing the single multiverse in which we live to a universe with completely different deep-down laws of physics, or with different values for such basic attributes as “existence,” is something on which string theory and cosmology are utterly silent.

Ultimately, the problem is that the question — “Why is there something rather than nothing?” — doesn’t make any sense. What kind of answer could possibly count as satisfying? What could a claim like “The most natural universe is one that doesn’t exist” possibly mean? As often happens, we are led astray by imagining that we can apply the kinds of language we use in talking about contingent pieces of the world around us to the universe as a whole. It makes sense to ask why this blog exists, rather than some other blog; but there is no external vantage point from which we can compare the relatively likelihood of different modes of existence for the universe.

So the universe exists, and we know of no good reason to be surprised by that fact. I will hereby admit that, when I was a kid (maybe about ten or twelve years old? don’t remember precisely) I actually used to worry about the Primordial Existential Question. That was when I had first started reading about physics and cosmology, and knew enough about the Big Bang to contemplate how amazing it was that we knew anything about the early universe. But then I would eventually hit upon the question of “What if they universe didn’t exist at all?”, and I would get legitimately frightened. (Some kids are scared by clowns, some by existential questions.) So in one sense, my entire career as a physical cosmologist has just been one giant defense mechanism.

I know it seems obvious, but two of today’s news stories brought home the absurdity of how people are judged.

On the one hand we have a Republican (who would have guessed?) Senator who is accused of soliciting sex in an airport men’s bathroom.

On the other is this priceless story about legislating against the wearing of too baggy clothes.

What is striking is that I don’t think the first should be news except that the Senator in question consistently votes against gay rights and gay marriage. His fellow Senators seem concerned with the actual behavior, which I think is irrelevant, and unconcerned with his hypocrisy, which I think is abhorrent.

But the individuals involved in the second story seem to ignore completely the behavior of the persons wearing the dangerously low-riding jeans. Even those defending these loose-legged louts seem to miss the point:

“The focus should be on cleaning up the social conditions that the sagging pants comes out of,”

No, the focus should be on how they behave, not on what they wear.

Being a good citizen is about how you behave to others - what rights you support or try to deny them, or how you treat them - not about how you choose to meet sexual partners or about how you dress.

First in a prospective series of my own versions of the best arguments for conclusions I don’t personally share. I’m supposed to stick to statements that I believe are true, even if I don’t think they warrant the conclusion. The idea is to probe presuppositions, put our ideas to the test, and of course to implicitly diss the less-good arguments for things we don’t believe. And who knows, maybe we’ll come up with arguments that are so great we’ll change our minds! (By slipping into the royal “we” I’m encouraging others to play along.) So here we go: the best argument I can think of for why research on string theory is a waste of time.

Traditionally, the greatest progress in physics has come through an intense interaction between theory and experiment. We have learned new things when experiments were good enough to bring us data that didn’t fit into the models of the time, but our theoretical understanding was also sufficiently developed that we had the tools to formulate useful hypotheses. While we know that classical general relativity and quantum mechanics are fundamentally incompatible and must someday be reconciled, straightforward dimensional analysis suggests that detailed experimental information about the workings of such a reconciliation (as opposed to true-but-vague statements like “gravity exists” or “spacetime is four-dimensional on large scales”) won’t be available at energies below the Planck scale, which is hopelessly out of reach at the current time.

A defensible response to this lack of detailed experimental input would be to place the problem of quantizing gravity on the back burner while we think about other things. And this was indeed the strategy pursued by the overwhelming majority of theoretical physicists, up until the 80’s. Two things caused a change: the drying-up of the river of experimental surprises that had previously kept particle theory vibrant and unpredictable, and the appearance of string theory as a miraculously promising theory of quantum gravity. Even though the Planck scale was still just as inaccessible, string theory was so good that it became reasonable to hope that we could figure it all out just by using brainpower, even without Planckian accelerators.

But it hasn’t worked out that way. Gadflies point to the landscape of low-energy manifestations of string theory as the nail in the coffin for any hopes to uniquely predict new particle physics from string theory. But that is only a subset of the more significant challenge, and understanding particle physics beyond the Standard Model was never the primary motivation of most string theorists anyway — it was quantizing gravity.

The real problem is that string theory isn’t a theory. It’s just part of a theory, and we don’t know what that theory is, although sometimes we call it M-theory. As Aaron explains in a very nice post, the thing we understand is “perturbative” string theory, which is a fancy way of saying “the part of M-theory where small perturbations around empty space act like weakly-interacting strings.” We’ve known all along that colorful stories about loops of string propagating through spacetime only captured part of the story, but we’re beginning to catch on to how difficult it will be to capture the whole thing. The Second String Revolution in the 90’s taught us a great deal about M-theory, but it’s hard to know whether we should be more impressed with what we’ve been able to learn even without experimental input, or more daunted by the task of finishing the job.

Within our current understanding of string theory, there is not a single experiment we can even imagine doing (much less actually, realistically hope to do) that would falsify string theory. We can’t make a single unambiguous prediction, even in principle. I used to think that string theory predicted certain “stringy” behavior of scattering cross-sections at energies near the Planck scale; but that’s not right, only perturbative string theory predicts such a thing. “String theory” is part of a larger structure that we don’t understand nearly well enough to make contact with the real world as yet, and it’s completely possible that another century or two of hard thinking won’t get us to that goal. It made sense to be optimistic in the 80’s that there was enough rigidity and uniqueness in the theory that we would be led more or less directly to contact with observation; but that’s not what has happened.

The best reason to think that research on string theory is largely a waste of time is because it’s just too hard.

Pretty convincing, eh? But I don’t buy it, even though I think I’ve adhered to my self-imposed rule that I believe every individual sentence above. It might turn out to be the case that another century or two of hard thinking won’t get us any closer to connecting string theory with the real world, but I don’t see any reason to be that pessimistic. The thing that’s really hard to get across at a popular level is that the theory really is rigid and unique, deep down; it’s the connections between “deep down” and the world around us that are the hard part. Count me as one of those who is more impressed with what we have learned than daunted by what we haven’t; if I were to bet, I would say that more thinking will continue to lead to more breakthroughs, and ultimately a version of M-theory that can rightly be called “realistic.”

In the meantime, the advent of sexy new data from the LHC and elsewhere will draw a certain fraction of brainpower away from string theory and into phenomenology, but there will be plenty left over. The field as a whole will fitfully establish a portfolio of different approaches, as it usually does. And there will undoubtedly be surprises around the corner.

Our semester started yesterday, and so, as you might imagine, the last week or so has been taken up with prepping for my class and trying to finish up some papers that will inevitably get less time in the coming weeks. I’m particularly looking forward to class this semester, since I’m teaching the introductory graduate General Relativity class. For my money, G.R. is the one of the most beautiful subjects to teach or study (I’m also quite fond of graduate mathematical methods) and I’m anticipating a lot of fun as well as quite a lot of work, since the class is pretty large this year (about 12 people for now, with three or four of them auditing).

I don’t usually follow a text in my classes, preferring to give the students a range of reference material and then to try to present a relatively self-contained course on the subject matter. This class will be no exception, although since some guy recently wrote a new book that closely follows the way I’m used to thinking about G.R., I will follow that far more than I usually follow any single text.

Another thing that has been taking up some time in the frantic last week or so is the upcoming third season of Café Scientifique Syracuse. When we started this two years ago there were four organizers. Two of these have recently left the area, and so my remaining co-founder, geologist Scott Samson, and I have been busily recruiting some new organizational blood from Syracuse’s science departments. We’ve also changed the venue - moving to a place I particularly like - a cocktail and wine bar called Ohm Lounge.

The first meeting of the Fall takes place in a week, on Tuesday September 4th, and my colleague Mark Bowick - string theorist turned soft condensed matter theorist is presenting, with a talk titled “Soft and Squishy Matter at Science’s Cutting Edge”. Mark gives great talks like this, with no slides (as Café Scientifique was originally envisioned) but plenty of hands-on demonstrations of the physics he’s describing.

Well, back to work. I don’t teach tomorrow, so should have some time for research, although there’s another first in the afternoon - the first faculty meeting of the semester!

The LA Times has a front-page article, apparently free of irony, that laments the glacial rate of progress on constructing a world-class subway system for the city, and imagines wistfully how much easier it would be if only we lived in a one-party communist state. In particular, they look at the progress that Shanghai has made in building its own subway, and pout about all of those nefarious restrictions that Americans have to put up with because we give actual citizens a say in the process.

“If the government wants to do something, even if the conditions are not ready for it, it will be done,” said Zheng Shiling, an influential Chinese architect who teaches at Tongji University in Shanghai.

At the risk of only slight oversimplification, the system works like this: Planners draw subway lines on a map. Party officials approve them. Construction begins. If anything is in the way, it is moved. If they need to, Chinese planners “just move 10,000 people out of the way,” said Lee Schipper, a transport planner who has worked with several Chinese cities in his role as director of research for EMBARQ, a Washington-based transportation think tank. “They don’t have hearings.”

Schipper recalled consulting with one Chinese metropolis whose ancient city wall stood in the way of a transportation project.

“One of the members of the People’s Committee said, ‘Oh, I know how we’ll solve the problem. We’ll move the historic wall.’ ” It was, he said, as if a planner in Washington proposed moving the Potomac River to make way for construction.

One searches the article in vain for the part where they say “Of course we live in a democracy, and some people think that there are certain benefits to that kind of system, even if the government does have to ask permission before tearing down historic sites,” but the moment never comes. Instead, we are treated to stirring stories of the plucky citizens of Shanghai, who don’t raise a peep when construction displaces them from their homes — no, indeed, they are happy to be displaced, as it gives them a chance at a new life! (It might be that voices of complaint are not heard because they are actually silenced, but that smudges up the narrative.)

As a dweller in downtown LA, where a better subway system would be a life-altering good and the lamentations of fragile newcomers who are shocked at the presence of construction noise in a booming high-density urban core form a constant background chorus, I deeply sympathize with frustration at the demands the democratic process force onto city planning. But I’ll tolerate the delays if it means that, if the Mayor wants to tear down our apartments, he at least has to hold a hearing first.

People sometimes argue back and forth about whether religious belief is a good thing, because it induces believers to be moral or charitable. In a big-picture sense, I think arguments of this form completely miss the point; beliefs should be judged on whether they are correct or incorrect, not on whether they cause people to do good or bad things. (If the belief is not correct, but it makes people do something good, can we say they’ve been tricked into acting that way?) Certainly, nobody is going to convince me to believe something if they admit that it’s false, but it would be good for me to believe — recommendations of that sort are usually aimed at other people, not the one handing them out. Besides which, as a matter of historical record it’s pretty clear that religion has led people to do some really good things and also led people to do some really bad things, and trying to weigh the effects on some imaginary scales seems just hopeless. Or at least, an interesting and possibly never-ending source of discussion for sociologists and historians of religion, but fortunately orthogonal to questions of the truth or falsity of religious claims.

Still, I confess to being a bit amused by the news that, in the last years of her life, Mother Teresa didn’t believe in God. (Via Cynical-C.) Letters that she wrote have now been released as part of a book project, and they are shot through with serious doubts.

Shortly after beginning work in Calcutta’s slums, the spirit left Mother Teresa.

“Where is my faith?” she wrote. “Even deep down… there is nothing but emptiness and darkness… If there be God — please forgive me.”

Eight years later, she was still looking to reclaim her lost faith.

“Such deep longing for God… Repulsed, empty, no faith, no love, no zeal,” she said.

As her fame increased, her faith refused to return. Her smile, she said, was a mask.

“What do I labor for?” she asked in one letter. “If there be no God, there can be no soul. If there be no soul then, Jesus, You also are not true.”

I’m not someone who has strong feelings about Mother Teresa either way, and it seems sad that her doubts put her in such apparent torment. (To the extent that these letters paint a reliable picture at all, of course.) And, in the department of “things that are perfectly obvious but must nevertheless be said explicitly because it’s the internet,” this is only one individual case, from which no grand conclusions should be drawn. Except the obvious: motivations for altruistic and charitable behavior can be very complicated. We should keep them separate from our attempts to understand how the universe works.

Have you ever heard someone arguing in favor of a position with which you disagree, but their arguments are so bad that you can’t help but think “Man, I could do a better job arguing for their side than they are, and I don’t even agree with them!” I thought it might be interesting to do exactly that — consider some interesting issues, and come up with my own versions of what the people who I think are wrong should be saying.

The rules would be: (1) The claims would be somewhat judgmental, rather than straightforwardly empirical. I’m not going to waste my time arguing that the universe is not expanding, or anything like that. (2) I have to stick to making individual statements that I really do believe, even if I don’t think they are sufficient to support the ultimate conclusion. I reserve the right to come up with more rules as I think of them.

Here are some possible claims to be considered:

1. God exists.
2. The Iraq war was a good idea.
3. Women scientists shouldn’t complain about discrimination.
4. Research on string theory is a waste of time.
5. Talking about the multiverse is intrinsically non-scientific.
6. We shouldn’t worry about global climate change.

Any other suggestions? I’m sure there are lots of things I don’t believe, but could come up with better arguments for than I usually hear. It’ll be like being on the debate team again.

Over at Uncertain Principles, Chad Orzel is on vacation and has handed the keys to the blog over to Aaron Bergman and Nathan (last name mysterious), specialists in string theory and atomic physics, respectively. Good luck to them as they experience what the blogosphere is like from the other side.

Aaron has begun to talk a little about the multiverse — here, here. He has thereby earned grumpy mutterings, rolled eyes, and “help” from some sensible physicists, some crackpots, some curmudgeons, his guest co-blogger, and even himself. I don’t quite understand what all the angst is about. (Actually I do understand, of course; this is one of those times when you adopt a rhetorical stance of pretending not to understand some alternative position in order to emphasize how unimpeachably correct your own position is.)

People are very welcome to disagree with the presuppositions or conclusions of anthropic reasoning; that’s just how science goes, and is perfectly healthy. But in addition to the substantive disagreements, there’s a widespread urge to express dismay that it’s even being talked about all the time. Now, that urge can’t be sensibly directed toward the actual research being done, because on that score multiverse-type stuff is a tiny percentage of all the work that goes on. Peek at any day’s worth of abstracts on hep-th, hep-ph, gr-qc, or astro-ph; you might find something anthropic here or there if you’re lucky, but it’s a tiny minority. This stuff is not dominating science, or physics, or theoretical physics, or high-energy theory, or even string theory.

No, the complaint is that considerations of parts of the universe that we can’t possibly see tend to receive an inordinate amount of attention in public discussions — on blogs, in books, in magazines and newspapers. Which is completely true, as a factual statement. At the risk of revealing a trade secret: the public discussion of different avenues of scientific research does not faithfully reflect the amount of research effort being put into those questions. Eek! I’d be willing to bet that it has always been like that. And yet, science marches on.

You may ask why something like the multiverse exerts such an outsized pull on the public imagination. So let me break it down for you here: it’s fun. People like talking about other universes, and whether we could be living in a simulation, and what happened before the Big Bang. For one thing, anyone can dive in; you don’t need to be an expert on twistor space, or two-loop counterterms, or BRST invariance in order to pontificate about the conditions under which life could exist if the laws of physics were very different. (Comments from people who are more informed and thoughtful about the subject will generally be more useful, but anyone can say something.) For another, it’s just cool to contemplate these way-out possibilities. The lure of crazy ideas is what draws a lot of people to science in the first place.

And that’s … okay, as Stuart Smalley would remind us. It would be very bad indeed if unmoored philosophizing about other universes became the dominant paradigm in science, or any subset thereof, but there’s zero danger of that. Really. But there’s no reason why people can’t have fun contemplating some of the more provocative and accessible ideas out there. On this very blog we will occasionally write lengthy discourses on some piece of technical work related to observations — and not get anywhere near the number of comments that a two-minute toss-off about the anthropic principle gets. And yet, science has not ground to a halt. I think the enterprise is sufficiently healthy to survive a few more posts about the multiverse.

Female Science Professor talks about the frustrations associated with making sure your class has a decent room and all that fun stuff, especially when it’s a small interdisciplinary freshman seminar. The irony, of course, is that an off-the-beaten path course on a topic that the professor is really passionate about is much more likely to end up being the Best Class Ever for the enrolled students than any of the inevitable required courses, but they will always get the short end of the stick when it comes to scheduling and logistics.

But it got me thinking about the concept of the Best Class Ever. What is it that makes a college course especially memorable, years down the line? After at least fifteen seconds of quality rumination over my own experiences, two common features stand out. First, the professor was absolutely enthusiastic about the material; they weren’t just punching a clock, they were truly into it. Second, a very delicate balance was struck, in which the material was ultimately understandable (and interesting, it goes without saying), but also extremely challenging. The best classes were those in which you learned an incredible amount, but only after really sweating for it. Other than that, my favorite classes didn’t really have much in common; they were a remarkably heterogeneous group.

My favorite undergrad class, and also my favorite non-science class (among many strong contenders), was probably “Contemporary Political Images,” taught by philosopher-turned-social-theorist Jack Doody. We covered a lot of political and social theory — Marx, Rawls, Habermas, Leo Strauss, Alasdair MacIntyre, that kind of thing. It was a small seminar, and an indispensable ingredient of the class’s awesomeness was the talent and enthusiasm of the other students. Every week we were wrestling with Big Ideas about Virtue and The Good, and some of the best conversations were over breakfast in the dining hall before class. And years later, when Clarence Thomas mumbled something about Natural Law at his confirmation hearings, we all knew exactly what was going through his mind.

My favorite class in grad school, and also my favorite science class (without quite as many strong contenders) was probably Nick Warner’s general relativity course at MIT. I was a grad student at the liberal-arts college up the river, but Ted Pyne and I happily hopped on the Red Line twice a week to attend this course, given the sorry state of Harvard’s GR offerings at the time. This was a big lecture course, with detailed hand-written notes handed out beforehand, and there wasn’t too much in-class discussion — Nick talked awfully fast, and it’s not easy to stop that much momentum once it gets built up. (But there was a weekly recitation where we could ask whatever crazy questions popped into our heads.) Every week we were pushed to the limit, and loved it. We must have loved it, as Ted and I taught our own seminar to our fellow grad students the next year, and I went on to teach the course as a postdoc, and then as a professor, and write up my own notes, which eventually made it into a book. In the foreword of which, Nick gets a hearty acknowledgment.

So what were your best college classes ever? Feel free to provide supporting evidence and anecdotes, and reason inductively from there to a comprehensive theory of class awesomeness.

(I won’t reveal the best class ever from a teacher’s perspective — like children, they’re all my favorites.)