Not Even Wrong

I haven’t posted anything new here in a while, with the holidays and trying to get over a bad cold keeping me otherwise occupied. Partly because of this the comments section has been to some degree taken over by people who want to discuss things I have no interest in. I’ll try and put up something new soon (comments on Penrose’s new book), but I did want to make some remarks about the problem of crackpotism in theoretical physics, something which is especially a problem for open forums on the internet like the comment section here.

When I first started studying particle physics during the 1970s, it was pretty clear to me how to tell the difference between serious people and crackpots. The Standard Model had just recently been formulated and it had started to accumulate an impressive amount of experimental evidence in its favor. So, at least in particle theory, serious people were doing one of a small number of things. The more phenomenologically inclined were analyzing the new experimental results to see if they further validated the Standard Model, or suggesting new experiments that would test different parts of the model. More mathematically inclined sorts were trying to understand the rich structure of the model, trying to get a better grasp of its aspects that were still poorly understood. People inclined to speculation were working on ambitious extensions of the model, hoping to find something compelling that would both explain some of the model’s parameters and make new, testable predictions.

So, to my mind, crackpots were those claiming to have new ideas about particle physics, but refusing to really engage in some way with the Standard Model quantum field theory. There were plenty of them around, including S-matrix die-hards like Fritjof Capra, those who wanted to go on about what happened before the big bang and how that explained all properties of particles, and a wide variety of people with their own private TOE that completely ignored the Standard Model. All you had to do was learn to ignore such people.

During the last 20 years, distinguishing crackpots has become a lot tougher, and it has gotten much more difficult recently. Famous professors from the best research institutions in the world go on about the properties of the universe being determined by colliding branes, or by an anthropically determined point in a multiverse, or any number of similar ideas. The dominant idea in the whole field makes nothing like what would normally be considered a testable scientific prediction, and those pursuing it don’t seem too bothered by the increasing evidence that this situation will never change. Personally I haven’t much changed my criterion for crackpotism in particle physics: if someone is not engaging in a deep way with the Standard Model and/or the kind of mathematical structures it involves, they’re probably a crackpot.

When I first wrote a critical article about string theory and made it public about four years ago, I got quite a lot of reaction. Almost all of it was gratifyingly positive, but I ended up hearing from quite a few people who were convinced that since I didn’t like string theory, surely I would like their alternative. These alternatives spanned a wide range, from very serious work to complete crackpotism, including all shades of in-between. The one thing that caused me to worry that there might be something wrong with my criticisms of string theory was the nature of a small number of my supporters. Some of these people still write to me regularly, and my e-mail is full of crazier things than what appears in the comments on the weblog. It’s embarassing to get cc’d on an e-mail to a long list of very prominent physicists by someone who is quoting my criticisms of string theory to back up their own even sillier ideas.

I’ve gotten very good at hitting the delete key or, in extreme cases, using procmail to automatically filter this stuff out of my inbox. I suggest similar tactics in reading the comment section here. The first line of defense against people who you think are not making any sense is just to ignore them. Do not give in to the temptation to point out to them that they are not making sense, because all this will accomplish is to clutter things up as they respond to your response to them.

I’m not about to start just deleting comments that I think are of a crackpot nature, partly because it is now hard to set up a clear criterion for what is crackpotism (should I delete Lenny Susskind’s comments if he decides to write in some day?). But to the extent that the volume of off-topic comments starts to overwhelm those that are interesting and related to the postings, I will have to take some sort of action. If you are posting large numbers of comments, mostly far off the topic at hand, please stop doing it now. If you are responding to such off-topic comments, please stop doing that too, don’t encourage them!

Now for some comic relief:

A new issue of the Notices of the AMS is out. It contains an entertaining article entitled Foolproof: A Sampling of Mathematical Folk Humor with many examples of mathematical humor. Physicists also put in an appearance.

There’s an interview with Andy Strominger in the Calcutta newspaper The Telegraph. Strominger was presumably in India for the string theory conference there this past week.

The thing I found interesting about the interview was how skeptical the interviewer was, repeatedly asking about whether string theory might not be wrong. Perhaps at least some members of the media are starting to get a clue.

I was wondering why there were lots and lots of hits on this weblog today coming from Google searches for “first evidence for string theory”. It looks like the answer is this lead article from the latest New Scientist magazine. I don’t have access right now to the full article, but it’s clearly based on the usual cosmic string hype. After all, according to the author, string theory “is our best hope of understanding how the universe works”, so anytime astronomers see something unusual, what else could it be but a string?

Update: I finally got ahold of a copy of the full article. It is based on two separate anomalies seen by astronomers. The first is called “CSL-1”, which was first reported nearly two years ago. It appears to be two nearly identical galaxies right next to each other, but the authors of a paper about it would like to believe there is some inter-galactic cosmic string producing two images of a single galaxy via gravitational lensing. Even if you believe this, there’s no evidence this is a fundamental superstring, even Joe Polchinski doesn’t think so (see Lubos Motl’s excited posting about “astronomers prove string theory”).

The second observation actually has nothing to do with the first (despite what the opening sentences of the story suggest). It’s of a quasar called Q0957+561A,B that really is a gravitationally lensed object. One thing I don’t understand is that in the case of CSL-1, the fact that there are only two images is taken as evidence that a string is doing the lensing (and claims are made that lensing by point like objects only produces odd numbers of images), whereas for Q0957+561A,B there are only two images, but an intervening galaxy, not a string, is what is doing the lensing. For the quasar pair, some changes in brightness by about 4% have been observed, so it has been suggested this is due to a nearby cosmic string (inside our galaxy, within 10,000 light years) which is moving around in our line of sight with the quasar pair.

I’d be curious to hear what professional astronomers think of this. To me it looks like just more string theory hype, and I now suspect that for the indefinite future, whenever an astronomer somewhere, somehow sees something anomalous, we’re going to be subjected to claims that “strings have been observed!!”.

Tom Banks has a new preprint out, entitled Landskepticism: or Why Effective Potentials Don’t Count String Models. In it he argues against the idea that one can use effective potentials to study the supposed “Landscape” of different vacuum states of superstring theory. His preprint, like most of the literature in the field, is kind of a bizarre document which doesn’t even look like a conventional theoretical physics paper. In the course of twenty pages he only really manages to write down one equation (and it’s just the Schrodinger equation).

One of his claims is that it doesn’t make any sense to think of what is going on as one string theory Hamiltonian with a huge number of possible vacuum states. Instead one has to think of a huge number of possible string theory Hamiltonians, one for each asymptotic background. So I guess that’s it for the “uniqueness of string theory”.

He gets kind of vehement: “the concept of an effective potential on moduli space as a tool for finding string models of gravity, is a snare and a delusion, fostered by wishful thinking, and without regard to the actual evidence in front of us.” Sounds kind of like things I say… He footnotes this “Perhaps some over the top rhetoric is in order”.

On a different topic, he claims that the Weinberg “prediction” of the cosmological constant doesn’t hold water, since if you allow both the cosmological constant and other parameters to vary, then typical values of the cosmological constant allowing galaxy formation will be orders of magnitude larger than the observed value.

I shouldn’t give the impression that Banks is opposed to string theory. Like everyone else, he doesn’t even mention the possibility that it might be wrong. He has his own ideas about holography and cosmological breaking of supersymmetry, which he alludes to at the end.

His paper is based on a talk he gave at a String Vacuum Workshop in Munich three weeks ago. Kind of scary to see how many theorists are now working on this nonsense. At first I was worried to see my old friend and fellow Princeton student Costas Bachas’s name on the list of participants. Costas always seemed to me one of the more sensible theorists around, even if he did work a lot on string theory. Then I noticed that he wasn’t giving a talk, just leading a discussion on the topic “Does the ‘String Vacuum Project’ make sense?” Wonder what their conclusion was.

Update: For Lubos Motl’s take on this paper (Banks was his advisor), and the news that Nima Arkani-Hamed has gone over to the dark side, go here.

The winners of this year’s Nobel Prize in Physics gave their Nobel lectures in Stockholm on Wednesday. The lectures of David Gross and Frank Wilczek are available on-line, for some reason that of David Politzer isn’t, at least not yet.

Over at Sean Carroll’s Preposterous Universe there’s a first-hand report about the lectures from Thomas Larsson (who often comments here). It’s in the comment section of this post. One interesting detail from Politzer’s talk was that Coleman had originally assigned the beta-function calculation to Erick Weinberg (who is now my colleague at Columbia over in the physics department), but Erick already had enough material for his thesis and wanted to move on.

Update: Politzer’s lecture is now available at his web-site.

This morning’s New York Times has a long and prominently placed article about the 20th anniversary of the “First Superstring Revolution”. The Times has a long history of producing overhyped uncritical articles about string theory, for a classic example, see “Physicists Finally Find a Way to Test Superstring Theory”. This one does allow some critical voices to be heard, including Lawrence Krauss, who is quoted as describing string theory as a “colossal failure” (which is different than a miserable failure)

Krauss is also quoted as saying “We bemoan the fact that Einstein spent the last 30 years of his life on a fruitless quest, but we think it’s fine if a thousand theorists spend 30 years of their prime on the same quest.”

Witten is quoted extensively, but he doesn’t sound very optimistic these days, saying “It’s plausible that we will someday understand string theory”, and making the rather weird statement that string theory is “so vast, so rich you could say almost anything about it” (for instance that it is a colossal failure?). He also seems to have given up on the idea that there is some fundamental new symmetry underlying string theory, instead putting his hopes on the existence of some new principle for constructing space and time.

The article also says that few theorists will give up on string theory when supersymmetry is not found at the LHC, with Witten interpreting this not as evidence that string theory is wrong, just that unfortunately it will be harder to get experimental evidence for it than he had hoped. String theorists in general seem to have trouble getting their minds around the idea that it is even possible the theory is wrong. Jeff Harvey does admit that sometimes he wakes up thinking “What am I doing spending my whole career on something that can’t be tested experimentally?”, but the question of “What am I doing spending my whole career on a colossal failure?” doesn’t seem to keep him awake nights.

The article ends by quoting an exchange between Steve Shenker and my colleague Brian Greene. Shenker quotes Churchill, describing the state of research into string theory as “perhaps it is the end of the beginning”. Brian seems to be one of the few string theorists around willing to actually consider the idea that the theory might be wrong, arguing that if string theory is wrong, it would be good to know this soon so physics can move on.