The Sciences

Discover Dialogue: Mathematician Peter Woit

"No one has a plausible idea about how string theory can explain anything."

By Susan KruglinskiFeb 20, 2006 6:00 AM


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Peter Woit is a lecturer in Columbia University's mathematics department. He launched a blog, called Not Even Wrong, two years ago to contest the underpinnings of string theory. It was a hit and has become a lively forum for bickering scientists.

You have a Ph.D. in physics. Why did you end up in a math department? W:

Well, one reason actually had to do with string theory. After I received my Ph.D. in theoretical physics, it became clear that if you wanted to keep working in theoretical physics, especially in the mathematical end of theoretical physics, you would pretty much have to do string theory. And I really wasn't very interested in that, so I thought the math department would be a better idea.

What year was this? W:

I got my Ph.D. in '84, which is right around the time the string theory fad started. One effect of it was if you were doing something else involving mathematics and physics, people just don't want to hear about it, they were just not interested. If you started looking for a job, you found out that nobody really wants what you're doing.

Why are you so interested in the problems with string theory? W:

In the mid-eighties, my reaction to it was it didn't seem that promising to me and there were all these other smart people doing it. I thought, within a couple of years either it will get somewhere, in which case they'll all want to work on it, or it won't go anywhere and they'll give up. It seemed like a perfectly reasonable thing for people to be doing. And as the years went on—and we're now 21 years past this—it became more and more disturbing that this had taken on a very different character than just a few years of people working on a very speculative idea. It had reached this kind of critical mass and totally had taken over the field. I think much of it has really gotten to the point where it's not even a legitimate science anymore.

How is it not a legitimate science? W:

At this point they really don't even have a plausible idea about how to ever make a prediction out of this, or how to use this in order to really explain anything about the world. So there's an ongoing discussion now almost at the level of philosophy of science: Is this even a science? I think I am not the only one who thinks this has gone past the point where it's not even really a science anymore.

And yet they are clearly working with math, which is scientific. How do you describe what they are doing? W:

The science writer John Horgan has a nice line about this. He calls it science fiction in mathematical form. They are certainly using mathematics, and they are building models and writing down equations for them, but the models they are working with just aren't connected to the real world. There isn't even any plausible way you could imagine that they are going to be able to connect that to the real world and to use these models to explain some experiment we are seeing.

Even string theorists admit that it is not really a theory. What is it? W:

The best way to say it is what people have now is really an approximation to a theory. The kinds of equations that they have now are the kinds of equations you would get in an approximation scheme to some underlying theory, but nobody knows what the underlying theory is.

What about the positive things that have come out of string theory? W:

It has had a very good effect on mathematics. It's gone through several different stages. In the mid-eighties, it went through something called conformal field theory, and some truly great mathematics was done because of that. And more recently there has been a lot of work in what's called topological string theory and this has led to a lot of fantastic mathematics recently, and a bit earlier on there was something called mirror symmetry which give you a completely new information about higher dimensional spaces. So from the point of view of mathematics, it's been a big success. Also, over the last ten years, there has been some very interesting work using string theory to understand the theory of the strong interactions.

So if string theory is so useful, what are your issues? W:

I think what most bothers me about it, the problem with it, is the way it has driven out other sorts of research. The way in which it has been pursued has made it virtually impossible to work on other things in the field.

Why is string theory such a phenomenon? W:

One of the big factors is that the field is a victim of its own success. The standard model, which was in place by around 1973, has been absurdly successful. There are literally zero experimental results that disagree with this model. Normally, one thing that has kept physics from becoming overly speculative or going off into the wrong direction is that sooner or later an experimentalist comes along and shows you that that was the wrong direction. That just hasn't happened.

Another aspect has to do with Edward Witten, who is the most amazing figure in the field. He legitimately is an incredible genius. And throughout the early eighties he was doing stuff that was ten times more interesting than anyone else in the field. No one had ever seen anyone like him. He got interested in this in 1984, and he was pushing the idea very strongly. So I think it was a combination of by far the most influential person in the field pushing the idea very strongly, combined with the fact that there weren't any other good ideas around, and there wasn't anything from experiments telling us which way to go. By now you have several generations of physicists—this has been going on for more than 20 years—who have spent their whole career doing this. People don't like to give up on something they have their lives invested in and try something else. It's not human nature.

Doesn't string theory fit a physics need? W:

Certainly the reason people originally got interested in it was that it held out hopes of unifying the standard model in particle physics and general relativity, the theory of gravitation. And I think there are still some people who believe in that promise. The other thing to say about string theory is that nobody really quite knows what it is. It's still a very mysterious business. It really is more of a set of hopes that some things that people already understand are an approximation of some deeper theory, although nobody knows what it is.

Why is your blog called Not Even Wrong? W:

It's a famous quote from Wolfgang Pauli, a well-known physicist from the earlier part of the century. I certainly wasn't the first one to use it or the first one even to apply it to string theory. Pauli supposedly was asked about some paper, and he just described it as, "That paper is not even wrong." Meaning that it is just so undefined that you can't even tell if it is wrong or not. It's appropriate for string theory. It's so ill-formulated that you really can't tell whether it's wrong or not. Sometimes people use it as a term of abuse, as in, "That's so stupid, it's not even wrong." But it also has an implication that something is not well-defined enough that you can even decide whether it is wrong or not.

What inspired you to start a blog? W:

Since I'm responsible for the computer system in the department, I'd played a little bit with the software. I thought, I've got a lot of things I want to say and this may be a good forum with which to do this. So I guess it was about a year and a half ago that I started it. I was immediately surprised at how much attention it started getting.

Had you felt you were not getting much reaction for earlier articles on this subject? W:

I wrote something and initially tried to get Physics Today to publish it, but they wouldn't, and then I put it up on a physics web archive, and I got quite an amazing reaction to it. I probably heard from at least 50 to 100 physicists who said, "We've always thought this. It's great that someone is saying this." And I heard from only 2 or 3 people who said, "You don't know what you're talking about." So there was a huge positive reaction.

How many hits do you get on your blog? W:

Very quickly it was a few hundred, and then a thousand, then a couple thousand, and now its up to about 5,000 per day.

Do you know of people who have changed their mind about what they were pursuing in physics because of your blog? W:

People have told me that my blog has had an effect on students who were trying to decide whether to go into string theory or not.

Brian Greene, one of the most prominent advocates of string theory, is in your department. How has your high profile as an anti-string theorist affected your relationship? W:

We get along fine. He's a very reasonable guy. We disagree about string theory to some extent, but unlike a lot of other string theorists, Brian is certainly someone who is willing to publicly admit that string theory is something that may very well be wrong.

Have you influenced each other at all? W:

The few times I ever thought there was something to string theory was after hearing Brian talk. He's certainly a very convincing speaker. I haven't talked to him much about it, so I have no idea whether I've succeeded in making him more skeptical about the prospects of string theory or not.

This is not something you sit down and talk about? W:

No, we haven't discussed it very much at all.

It seems people's attitude toward string theory has changed recently. Is that true? W:

I think definitely up until last year or so it was very rare to see anything skeptical about string theory. I think within the last year this idea has really gotten out there, has become much more commonplace, that there quite possibly is a problem with all of this.

Any idea why the climate has changed? W:

Well, one thing is, in string theory itself, things are really not going well. Regularly, every year or two, there would be some new idea they would come out with, so the field was kind of bubbling along. I think what's happened in the last two or three years, there really haven't been any new ideas to try. The other problem is that there's been a split within the string theory community. There are some who have basically decided that whatever this theory is, it has infinitely complex possible solutions [known as the string theory landscape]. As for the dream that there's going to be one solution of string theory and it's going to be the real world, I think a lot of them have given up on that. So they're trying to pursue this idea that string theory really is an infinitely complex thing. I think a lot of other string theorists are well aware that if you go down that road you really can't predict anything and you're in danger of leaving what is normal science.

Do you think there was a backlash because string theory was pushed into the public spotlight too early or too hard? W:

I think it was certainly oversold. I think if you talk to most string theorists, they actually see themselves as suffering from this overselling of the theory. They're actually not happy that they have to contend with that.

Can you compare this time in physics to another time in physics? Is this an exciting time? W:

I'm afraid I don't think it is an exciting time. It's a very difficult and challenging time. I think it really is an unparalleled situation in the history of physics. There is this new accelerator that will come online in Geneva at CERN, the LHC, Large Hadron Collider. And there are a lot of good reasons to believe that that accelerator will finally have enough energy to start to get some interesting data. And so I think what's going on among theorists is people are just kind of waiting and hanging in there for a couple of years and hoping that this will really finally return the field to a much healthier state, where there will be new experimental results coming in which will start telling us what direction to go in. So I think when you do hear people saying that this is an exciting time, often what they are referring to is that it's exciting that two or three years from now we're going to finally start getting some new data which will turn things around.

How do you respond to critics who say you are unqualified to discuss string theory? W:

I have a PhD from Princeton in particle theory and have been thinking about this subject for twenty years. The only criticism of what I've been doing over the years that I would actually agree with is that I should have spent less time thinking about string theory and complaining about it and learning about it just to criticize it, instead of devoting time to more positive things that I should be pursuing.

To you, in a perfect world, what would today's field of physics be like? How would you imagine it would be functioning at its best capacity? W:

Broadly, I think what the field needs is for people to acknowledge that this particular speculative idea doesn't really work and there aren't any obvious good ideas out there. I think it would actually be healthier for theoretical physics these days to take a look at how mathematicians operate, because mathematics has always been a less faddish subject. In mathematics there is much more of a culture where people spread out and devote their lives to thinking hard about something that interests them. There has always been much more of a culture in physics that you want to work on something where you can get results and produce a paper a few months from now. And when the problems are very hard and no one knows what to do, I think people need to be willing to dig in and spend years thinking about something different than what other people are thinking. And there really isn't the kind of institutional support within the physics community for this kind of behavior, whereas there is in mathematics. I think it would be a lot healthier if physicists would acknowledge that they are in a different situation than we've been in historically because of this lack of experiment, and under the circumstances people do need to behave differently.

Is part of it that, often, mathematicians are not searching for a larger meaning? Do you think that because physicists are looking for larger meaning, it's throwing off their objectivity? W:

The thing that keeps mathematicians honest is the notion of mathematical rigor and mathematical proof. Mathematicians have this very strong culture where everything you say has to be very precise and you have to be able to rigorously prove it. Whereas physicists have never worried too much about that because even if you are doing something that is logically a bit inconsistent, it doesn't really matter because it is all going to get sorted out by the experiment in the end. I think physicists need to spend a lot more time being clear about exactly what's working and what isn't. We have to think about what really is beautiful -- what really is a powerful, beautiful new idea and what isn't.

Do you think physicists have lost the idea of what is beautiful and powerful because they have gotten carried away? W:

I see what's happening in the field is that they are getting backed into a corner. They've got this underlying speculative idea that they don't want to give up on. If an idea doesn't work, you can always make it try to work by making it more complicated, so a lot of what is going on is that they're being forced into more complicated and more ugly things, to the extent that some of them are even trying to make a virtue of this. They're saying, well, the world really is this incredibly complicated, ugly, Rube Goldberg kind of place. That's just the way it is.

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