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Thread-Bare Theories

String-theory critic calls for balance in physics research

6 min read

Physics has a special place among the sciences. The revolution in physics during the early part of the 20th century defined subsequent decades by spawning both the transistor and the atomic bomb. And physics has always been viewed as the hardest of all sciences, a domain of mathematically rigorous theories coupled with unambiguous experiments. But now, physicist Lee Smolin argues in his new book, physics is in danger of losing its way.

Smolin, based in Toronto, says in The Trouble With Physics: The Rise of String Theory, the Fall of a Science, and What Comes Next that part of the problem is it is now almost impossible to conduct an experiment that cannot be accounted for within the framework of the Standard Model of particle physics. That model has reigned supreme for 30 years despite its incompatibility with that other great bastion of ­modern ­physics: general relativity. As a result, physicists have been starved of new ­experimental data that could clearly point the way to a fundamental theory that ­reconciles quantum mechanics and general relativity. In that experimental vacuum has risen string theory, which postulates that matter is not composed of pointlike particles but rather of structures consisting of 11-dimensional strings and membranes.

The other reason physics is in danger is sociological, and Smolin says this part of the problem facing physics should act as a warning to researchers in every field of science and engineering—that individuals and departments can make what appear to be reasonable decisions about whom to hire and what research to pursue, but ultimately those decisions can unbalance or distort a field as a whole.

Stephen Cass,IEEE Spectrum senior associate editor, talked with Smolin about the challenges facing physics.

Is there a crisis in physics?

The crisis is not in physics overall but in that part of physics whose goal is to deepen our understanding of the laws of nature. Since the middle 1970s, there has been no definitive progress, no match between a new experimental result and a new theoretical prediction. That’s worrying.

Many physicists say we have made great progress due to string theory. What’s wrong with string theory?

One of the things that’s wrong is the impression that you have been getting. The real situation is that there are several competing approaches to the problem of unifying quantum mechanics and general relativity to create a theory of quantum gravity. But string theory came to dominate the perception of the public and the American scientific academy. There are compelling reasons for interest in string theory, but there are also compelling reasons for interest in other approaches. Science would be stronger were there not an overemphasis on one approach.

On top of that, there has been overclaiming and overpromising on the part of some advocates of string theory. First of all, there was a hope, which was advocated very strongly, that string theory would lead to unique predictions about the universe. If true, that would have been a powerful reason for choosing it over the competing approaches, but it was just simply not true, and we knew from 1986 that it was not true.

String theory is not a theory in the sense that Newtonian mechanics or quantum mechanics is. It’s not defined by the statement of two or three principles that are expressed in the basic equations of the theory—which are then solved to yield examples and predictions. Instead, there are several approximation procedures and approximate arguments that describe an infinite number of cases, which are all conjectured to be solutions of a fundamental theory that has never been written down.

If string theory doesn’t have the normal characteristics of a theory, does it run the risk of undermining what it means for something to be a scientific theory?

It need not, but it has, because of the poor judgment by some advocates of string theory with regard to the question of whether the theory generates any predictions that might be tested. Once it became undeniable that string theory comes in an infinite number of different versions, which all give different predictions, some people, like Leonard Susskind and Steven Weinberg, unfortunately began to argue that, on the basis of other reasons—the mathematical beauty of the theory, et cetera—the theory was so compelling that we should consider this a situation where the rules of science should be modified.

Now, let me say that, for example, Brian Greene [author of The Elegant Universe , the best-selling 2003 book on string theory] urged me to emphasize that these people are a minority of string theorists. He believes the majority of string theorists agree with me that a scientific theory must make falsifiable predictions and that if string theory ultimately fails to do so, it will fail to be a scientific theory. But I don’t think this is a time for other renowned scientists to be calling for a weakening of the distinction between science and nonscience.

Is there a danger that string theory will become detached from reality, that it will become a so-called pathological science?

I think that ”pathological science” may be too strong, but there are things that worry me. It’s not ideal science. Identifying a field of science with one untested theory is a problem. It’s a problem when individual researchers define themselves by saying, ”I am a string theorist” or ”My research group is a string-theory group.” A large number of people are professionally, intellectually, and emotionally overcommitted to one conjecture or hypothesis in a way that I think is unhealthy for science.

How did this state of affairs arise?

American universities expanded very quickly between World War II and the mid-1970s. During this time, there was not much pressure on young people to find positions. A great diversity of people and research styles came in to the academic world that could be comfortably supported. This generation made American science dominant in the world. Then the expansion stopped, and the academic world became very competitive.

But we didn’t think about how to optimize academic science in the face of scarce resources. We failed to discuss how to make sure we diversified investment in risky areas and how to make sure that certain kinds of people who don’t quite fit the mold of a normal scientist, but who still turn out to be necessary for science, are included. I mean the kind of people who just go around and wander between fields, talk to everybody, and ask really good, provocative questions.

Instead, problem solving within a narrowly defined domain became codified as what a professional scientist is. Academic science hasn’t done what people have done in, for example, high-tech business, which is to think about how to optimize investments with what are now sparse and scarce resources, such as university positions and research funding. What happens now is that a university department has one appointment to make at a time, maybe once every five to 10 years.

If a department has a group of three or four people doing x, whether x is string theory or superconductivity research, and a faculty appointment comes up, that group tends to hire in the area that they know. This is because they believe in what they are doing, and secondly, they and their friends and colleagues have students who need positions in this competitive environment.

How can we encourage more diversity in appointments?

The department or university as a whole, as well as funding agencies like the U.S. National Science Foundation, are going to have to get involved and counter the tendency of research groups to replicate themselves. Another thing is the role of diverse funding sources. One can look to the United Kingdom, where there are multiple ways that an academic can be supported. For example, the Royal Society there makes 10-year appointments for gifted young people. This makes it possible for a university to hire that person into a permanent position, with the understanding that if the person lives up to their promise, the university will support them thereafter. As a result, the universities have supported the careers of some remarkable mavericks who in the American system would have had trouble getting started.

There is also a big role for independent foundations and philanthropy. For example, I work at the Perimeter Institute for Theoretical Physics [in Waterloo, Ont., Canada], which was founded by Mike Lazaridis [the man behind the ultra­successful BlackBerry], and which advocates that there are different approaches to quantum gravity. The point is that Mike Lazaridis chose a way to take $100 million and do much more science than he would have done had he just donated that $100 million to 15 universities.

What has been the reaction to your book from the physics community?

Mixed! I do get a lot of very positive feedback—a lot from people outside the string community saying, ”Thank you for saying this,” ”Somebody finally has to say this,” ”This is long overdue,” et cetera. From some string theorists, I also hear complimentary things, even from some people who say that their ­scientific judgment disagrees with me, but they agree about the sociological issues, the way that I have framed the question. I know that a number of people in the string-theory community are very unhappy about the book.

Some string theorists have approached it in a very professional way and communicated with me in blogs, private e-mail, and conversations. We discuss it, and it’s fine. Nothing has changed my overall conclusion so far, but I’m open-minded. A small number of people have been nasty, both in things that they’ve written and things that they’ve said to journalists and other people. I think that that’s unfortunate, because it doesn’t contribute to science; you’re not going to solve problems by calling me names. There is an irony here in that I’m actually very conflict-adverse in person. I lose some sleep when I hear that somebody whom I respect a great deal is very unhappy or angry with the book. I like to think that if they sat down and read it carefully, they wouldn’t be angry, although I can’t promise that.

I hope it’s clear that the things I’ve been talking about—changes in funding practices and so on—are not aimed at string theory in particular but are addressing general issues and would be healthy and helpful for science overall.

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