We had the world on a string
Tim Cavanaugh | October 5, 2006, 7:23pm
I'm madder than a quark that's been mistaken for a lepton by the strong force! What's got my neutrinos in a bind? The backlash against string theory, that's what. Not that I have any attachment to this theoretical hocus pocus, but I'm going to be pretty steamed if what was supposedly the dominant physical theory of the last two decades turns out to be as short-lived as a 12-minute neutron. Over the years I've read at least a dozen articles hatin' on string theory and lamenting that you can't have a career in physics unless you subscribe to it. And I've read exactly zero articles claiming that string theory is just jake. Maybe that's just selection bias on my part, but I'm beginning to think this is one of these so-popular-nobody-likes-it things, like the way serial music supposedly dominates all musical composition.
With the double publication of Peter Woit's Not Even Wrong: The Failure of String Theory and the Search for Unity in Physical Law and Lee Smolin's The Trouble with Physics: The Rise of String Theory, the Fall of a Science, and What Comes Next, we seem to have reached a turning point for the theory of vibrating strings harmonizing the g-forces of the universe (or is it g-strings harmonizing the vibrators of the multiverse?). But this is a backlash that's been bulding up strong force for some time. Slate, a regular anti-string theory clearinghouse, has been covering the problems with the theory for years. Case Western Physics chairman Lawrence M. Krauss has been talking smack about string theory, and he can expand for half-hours about what a mathematically ingenious dead end it is.
What does it all mean? I never understood the concept in the first place, and passages like this one from Jim Holt's recent string-cutting don't inspire confidence:
At the latest count, the number of string theories is estimated to be something like one followed by five hundred zeros. "Why not just take this situation as a reductio ad absurdum?" Smolin asks. But some string theorists are unabashed: each member of this vast ensemble of alternative theories, they observe, describes a different possible universe, one with its own "local weather" and history. What if all these possible universes actually exist? Perhaps every one of them bubbled into being just as our universe did. (Physicists who believe in such a "multiverse" sometimes picture it as a cosmic champagne glass frothing with universe-bubbles.) Most of these universes will not be biofriendly, but a few will have precisely the right conditions for the emergence of intelligent life-forms like us. The fact that our universe appears to be fine-tuned to engender life is not a matter of luck. Rather, it is a consequence of the "anthropic principle": if our universe weren't the way it is, we wouldn't be here to observe it. Partisans of the anthropic principle say that it can be used to weed out all the versions of string theory that are incompatible with our existence, and so rescue string theory from the problem of non-uniqueness.
Copernicus may have dislodged man from the center of the universe, but the anthropic principle seems to restore him to that privileged position. Many physicists despise it; one has depicted it as a "virus" infecting the minds of his fellow-theorists.
I'm opposed to anything that increases man's importance in the universe, but there's one aspect of string theory that I'll be sorry to lose: the many universes. This one obviously sucks, but it was always nice to think there might be a better model out there (up there? over there? in there?) somewhere. What I'll regret most is that one of these egghead ideas will die out before I ever had a clue what it was about, undoubtedly to be replaced by another egghead theory I can't figure out. Hey, you knucklehead experimental physicists! Do some explaining. Is string theory out? Was it ever in? Does it matter?
thoreau | October 5, 2006, 9:19pm | #
I would think that the truth or falsity of string theory has zero effect for non-grant-grubbing non-physicists.
String theory is irrelevant even for 99% of grant-grubbing physicists.
String theory is an effort to reconcile quantum mechanics and general relativity. Quantum mechanics works astoundingly well at making testable predictions concerning all sorts of microscopic phenomena. And general relativity works pretty well at describing gravitational phenomena on very large scales.
The motivation for string theory is that the theories make contradictory predictions for gravitational phenomena on very, very, very short length scales. So there's a contradiction between two theories that both seem to work. Naturally, some physicists want to sort out that contradiction.
The problem is that the contradictions come about under circumstances that are way, way, way, WAY beyond what experiments can probe for now (and for the foreseeable future).
Most physicists don't give a crap about string theory. I spend my days on optics and biophysics. I have friends who spend their time on colloids, fluid dynamics, quantum computation, semiconductor materials, and lots of other things that you can actually study in, like, real experiments.
Yet somehow everybody acts as though string theory is THE frontier of physics. First, it's not even really physics, since it isn't amenable to experimental tests. And even if it was somehow testable, it would be only one of many frontiers.
Some of the critics, like Lee Smolin, are just as guilty of exaggerating the importance of string theory. The reality is that if the string theorists all quit and did something else the rest of us could go about our careers quite nicely. There are plenty of other people who are perfectly capable of teaching quantum field theory and general relativity, and we could all use the extra office space.
Also, keep in mind that many of the critics (like Lee Smolin) are working on other theories of quantum gravity that are just as difficult to test. Now, I'll admit that Lee Smolin strives mightily to make his theories testable, which is more than can be said for a lot of the quantum gravity people. And a few of the quantum gravity people are awful even by the standards of quantum gravity (e.g. the people who talk about the "landscape" of possible theories and suggest that we abandon falsifiability).
Still, at the end of the day, quantum gravity is irrelevant to the rest of physics.
Now, I should back-pedal a bit: A little bit of experimental work has been done on quantum gravity. People have studied neutrons falling in gravitational fields, and verified that their wavelengths decrease as they speed up, as predicted by quantum mechanics. (They do this with interference of waves.) They have studied neutrons bouncing above a surface in a gravitational field, and verified that the energies and frequencies of the bouncing motion are exactly what quantum mechanics predicts.
However, these experiments, while very, very cool (the measurements are quite delicate and hence impressive), don't have any real bearing on string theory. These experiments probe length scales of millimeters or longer, typically. Quantum mechanics and general relativity (which reduces to Newton's theory of gravity under the conditions of these experiments) are quite compatible on these scales. You have to get down to the scale of the Planck length (10^-35 meters, or less than a millionth of a billionth of a billionth of the radius of a hydrogen atom) for string theory to matter.
Anon | October 6, 2006, 1:06am | #
Pro Liberatate:
"String theory lacks elegance, despite what its proponents say. My gut tells me that if and when string theory becomes useful (i.e., can be tested by experiment), it'll also get much simpler."
Let me just say that I have never, ever, understood these arguments from elegance. I mean, I appreciate stories about Einstein and Maxwell's equations as much as the next guy, but theoretical particle physics is just damn ugly. The Standard Model - which is the undisputed theory all of these guys are trying to extend -- is the one of the hackiest things in physics. But it works. It works
really well. When theories are new most people think they're ugly -- then a generation down the line we start teaching undergraduates the theory and suddenly all sorts of simple models and elegant arguments emerge. Consider where quantum mechanics stood in the academic curriculum in 1900 versus 2000.
thoreau:
"String theory is irrelevant even for 99% of grant-grubbing physicists."
and later
"Most physicists don't give a crap about string theory. I spend my days on optics and biophysics. I have friends who spend their time on colloids, fluid dynamics, quantum computation, semiconductor materials, and lots of other things that you can actually study in, like, real experiments."
No offense, thoreau, but my guess would be that 99% of physicists also don't give a crap about biophysics. The fact is, given the breadth of physics specialties these days, it is very easy to find a rich vein of research and work it for a whole career -- which is fine. But your statement really has to do with specialization, not with string theory
per se. It's equivalent to an art history major suggesting that 99% of art historians don't give a crap about Japanese prints or Canadian art. That doesn't mean Hokusai or the Group of Seven aren't worthy of study.
I should be clear -- I, too, am a working scientist and, without a doubt, string theory has absolutely no significance for anything I'm doing. But so what? As you noted, "[s]tring theory is an effort to reconcile quantum mechanics and general relativity." You know what? That sounds like physics to me. Now I'm certainly not going to claim it is necessarily good physics, but it is an attempt to resolve a knotty fundamental problem in theoretical physics, not a massive scientific Sokal hoax.
And I don't mind that sometimes you have a theory that can't (currently) be tested experimentally, any more than I mind experimental results that can't (yet) be explained theoretically. Theory and experiment area rarely in perfect sync. My prior reading of Woit is that he feels string theory is pretty much divorced from experiment at this point, which is why he has suggested it should just turn itself into a branch of mathematics -- an interesting branch, too. But then I read reviews of his book like Aaron Bergman's (to be found at:http://golem.ph.utexas.edu/string/archives/000898.html) and I think that at least some string theorists
are working with an eye towards experimental results. But such a reconciliation takes time.
And that is why, in the end, this is all about institutional resources. Woit and Smolin feel that string theory has run its course, and
funding and
jobs need to be opened up to other theories. They feel it is monopolizing resources and driving graduate research to a degree out of proportion with its merits. I will note that Sean Carroll makes a nicely libertarian response to that argument at:http://cosmicvariance.com/2006/06/19/the-string-theory-backlash/. Namely, maybe a whole bunch of people are working on string theory
because it is actually a promising theory. I mean, knowing something about academic politics, I'm willing to believe that academic fiefdoms certainly exist, but taken to its limit Woit and Smolin's arguments could begin to look like Vast String Conspiracy. What is interesting to me is that the physics subcommunity we're talking about is so small that such a conspiracy is not implausible -- particularly because of the arxiv oriented publishing habits of the string theorists, of which I heartily disapprove -- but still, are theoretical physics grad students really being
brainwashed into pursuing string theory? I have yet to hear from any physics grad student who felt peer pressured into pursuing string theory as opposed to (say) loop quantum gravity.
It seems to me that Woit and Smolin are physicists who have written polemics, when what is required to make a convincing argument about the string theory monopoly (if it exists) is an institutional history written by historian of science or, even better, a sociologist. I'm not even sure how one would parse the numbers to determine whether string theorists are receiving more than their "fair share" of funding, but again, this is exactly the type of debate libertarian types would like to leave to the marketplace of ideas.
With all that said, polemics are fun, and they are a valid way to shake things up in a community. But it is strange to have all these string theory books out there -- and selling relatively well. And this leads me to my final observation. First you suggest that:
"Most physicists don't give a crap about string theory."
only to follow a moment later with
"Yet somehow everybody acts as though string theory is THE frontier of physics."
Who is this "
everybody" you refer to? It's surely not physicists, according to you. It's just ordinary folks. And if they're interested in string theory, more power to them. If the debate if overblown maybe people will learn that and start spending their time reading about biophysics instead; in the same vein I hope one day people will realize that Foley-gate was less important than the detainee act. But people's understanding of science is always going to be partial, and it is always going to be oriented towards cool things, even if those things are not representative of the field as a whole -- a really large number of physicists don't work on anything involving the words/prefixes "string", "quantum",
or "nano", for example. While I am always willing to correct people's skewed views of physics whenever the issue comes up, I don't feel the need to lecture people on what's "really" important. Which is why I do not understand why people who have no personal or professional stake in theoretical particle physics get so worked up over string theory.
Apologies if my arguments goes incoherent. I'm all high on cold medicine at the moment.
Anon
Stevo Darkly | October 6, 2006, 4:49am | #
Warren:
Another theory I never liked, Birds evolved from dinosaurs. I know that ten years ago there was an active backlash to this one. Has it become official dogma? Are there still respectable dissenters?
There is no body with the power to make it "official dogma" but it now appears to be the overwhelming consensus among paleontologists, especially those who are experts in dinosaurs.
The case has been increasingly bolstered by recent discoveries from China especially, of fossils that have both dinosaurlike and birdlike features (often including feathers) to such a degree that it is difficult to definitely classify them as one and not the other.
In fact, there is now a theory that the family (I use this term loosely) of dinosaurs that includes
Velociraptor (famous from
Jurassic Park, although the movie got the shape of the head wrong and depict the animal as two to four times bigger than the real
Velociraptor ever got) are actually flightless birds.
The reason for this is that
Velociraptor and its closest relatives have several anatomical features that make them more like modern birds than the first recognized bird,
Archaeopteryx -- even though
Archaeopteryx lived earlier in time than
Velociraptor.
Also, several of the more-birdlike features possessed by
Velociraptor and its relatives seem to be related to flying ability.
No one is suggesting that
Velociraptor could fly itself, but rather that a flying descendent of
Archaeopteryx, more birdlike but still retaining its teeth and foreclaws, lost its ability to fly and gave rise to the
Velociraptor.
One of the most vociferous and vocal opponents of the "birds are dinosaurs" theory is Alan Feduccia. He is an ornithologist, not a paleontologist -- knows lots about birds, maybe not so much about dinosaurs.
Lots of paleontologists and lay students of paleontology hang out at the Dinosaur Mailing List of the Cleveland Museum of Natural History ( dml.cmnh.org ) and they periodically criticize Feduccia's reasoning and research. I'm not a pro in the field, but they've convinced me.
Anon | October 6, 2006, 8:52am | #
Warren said:
"Also, I think you are missing one of the more important aspects of string hate. It's not just that it's untestable, it's that it doesn't look like science. It looks like philosophy dressed up as science. But of course the history of science makes that a feature. What are the great triumphs of theory if not ideas deemed heresy by the establishment on first publication?"
First of all, the Bergman link above suggests testability is not out of the question. So does the Carroll link, if you follow it a little deeper. I know Woit would disagree, and I, like you, am not in a position to thoroughly analyze the competing claims.
Second of all, you think string theory looks like the history of science? Based on reading what? String theory is one of the most equation-heavy scientific fields I know. I think you are confusing the popularizations (by Greene, for example) with the actual theory. In addition, there does seem to be a great deal of parallel discussion in the field (parallel to the equation generation) about what the equations might mean and how they might be interpreted. That's not necessarily a bad thing. Quantum mechanics went through this same thing at a more drawn out pace, and it is no worse a theory for it.
"I'm nowhere near educated enough judge the merits of string theory, but I'm throwing in with the naysayers. There's something about the smug of the proponents that rubs me wrong."
See, here's what I was getting at earlier. Just because someone is smug doesn't mean they're wrong. In fact, my guess is that thoreau would agree with me that a sad fact of graduate school existence is the realization that utter jackasses can still be capable scientists. It's a sobering discovery. If you're lucky it precedes choosing your advisor.
Full disclosure: While poking around a few string theory links yesterday, I discovered that an old high school friend is now an up-and-coming string theorists. He's one of the nicest guys I know. Do I get to believe the theory now?
Anon
