The Trouble With Physics: The Rise of String Theory, The Fall of a Science, and What Comes Next

by Lee Smolin

  When I was young the job market was good. It was important to be at a major university but you could still prosper at a smaller one. I am distressed by the coercive effect of today’s job market. Young mathematicians should have the freedom of choice we had when we were young.5

  The French mathematician Alain Connes has similar criticisms:

  The constant pressure [in the U.S. system] for producing reduces the “time unit” of most young people there. Beginners have little choice but to find an adviser [who] is sociologically well implanted (so that at a later stage he or she will be able to write the relevant recommendation letters and get a position for the student) and then write a technical thesis showing that they have good muscles, and all this in a limited amount of time which prevents them from learning stuff that requires several years of hard work. We badly need good technicians, of course, but it is only a fraction of what generates progress in research. . . . From my point of view the actual system in the U.S. really discourages people who are truly original thinkers, which often goes with a slow maturation at the technical level. Also the way the young people get their position on the market creates “feudalities,” namely a few fields well implanted in key universities which reproduce themselves leaving no room for new fields. . . . The result is that there are very few subjects which are emphasized and keep producing students and of course this does not create the right conditions for new fields to emerge.6

  In recent decades, the business world has learned that hierarchy is too costly and has moved to give young people more power and scope. There are now young bankers, software engineers, and the like still in their late twenties who are leading big projects. Every once in a while, you will encounter a lucky academic scientist in the same situation, but it’s rare. Many scientists are pushing thirty-five before they emerge from the enforced infancy of a postdoctoral position.

  The leaders of hi-tech companies know that if you want to hire the best young engineers, you need young managers. The same holds for other creative fields, such as the music business. I’m sure that some jazz musicians and old rock ’n’ roll guys appreciate hip-hop and techno, but the music industry does not let sixty-year-old former stars choose which young musicians get signed to recording contracts. Innovation in music proceeds at such a hectic, vibrant pace because young musicians can find ways to connect to audiences and other musicians quickly, in clubs and on the radio, without having to ask the permission of established artists with their own agendas.

  It is interesting to note that the quantum-mechanics revolution was made by a virtually orphaned generation of scientists. Many members of the generation above them had been slaughtered in World War I. There simply weren’t many senior scientists around to tell them they were crazy. Today, for graduate students and postdocs to survive, they have to do things that people near retirement can understand. Doing science this way is like driving with the emergency brake on.

  Science requires a balance between rebellion and respect, so there will always be arguments between radicals and conservatives. But there is no balance in the current academic world. More than at any time in the history of science, the cards are stacked against the revolutionary. Such people are simply not tolerated in the research universities. Little wonder, then, that even when the science clearly calls for one, we can’t seem to pull off a revolution.

  20

  What We Can Do for Science

  I HAVE ATTEMPTED in this book to explain why the list of the five big problems in physics is exactly the same as it was thirty years ago. To tell this story, I have had to focus on string theory, but I want to reiterate that my aim is not to demonize it. String theory is a powerful, well-motivated idea and deserves much of the work that has been devoted to it. If it has so far failed, the principal reason is that its intrinsic flaws are closely tied to its strengths—and, of course, the story is unfinished, since string theory may well turn out to be part of the truth. The real question is not why we have expended so much energy on string theory but why we haven’t expended nearly enough on alternative approaches.

  When I faced the choice of working on the foundations of quantum mechanics and sabotaging my career or working on a topic related to particle physics so that I might have one, there was a scientific argument bolstering that economic decision. It was obvious that in the previous decades much more progress had been made in particle physics than in plumbing the foundations of quantum theory. A new graduate student today is in a very different situation. The tables have turned. The previous decades have seen little progress in particle theory but a lot in the field of foundations, spurred on by the work in quantum computing.

  It has become clear by now that we cannot resolve the five big problems unless we think hard about the foundations of our understanding of space, time, and the quantum. Nor can we succeed if we treat decades-old research programs, like string theory and loop quantum gravity, as if they were established paradigms. We need young scientists with the courage, imagination, and conceptual depth to forge new directions. How do we identify and support such people, instead of discouraging them, as we do now?

  I must emphasize again that I do not believe that any individual physicists are to blame for the stasis that has overtaken theoretical physics. Many of the string theorists I know are very good scientists. They have done very good work. I’m not arguing that they should have done better, only that it’s remarkable that a large number of the best among us have not been able to succeed, given what seemed at the beginning to be such a good idea.

  What we are dealing with is a sociological phenomenon in the world of academic science. I do think that the ethics of science have been to some degree corrupted by the kind of groupthink explored in chapter 16, but not solely by the string theory community. For one thing, it is the academic community writ large that makes the rules. In a court of law, a good lawyer will do anything within the law to advance the cause of his clients. We should expect that the leaders of a scientific field will likewise do everything within the unwritten rules of academia to advance their research program. If the result is the premature takeover of a field by an aggressively promoted set of ideas that achieves its dominance by promising more than it delivers, this cannot be blamed only on its leaders, who are simply doing their jobs based on their understanding of how science works. It can and should be blamed on all of us academic scientists, who collectively make the rules and evaluate the claims made by our colleagues.

  It is perhaps a lot to ask that all of us in a field check every result before accepting it as established fact. We can and do leave that to experts in subfields. But it is our responsibility to at least keep track of the claims and the evidence. As much as any of my colleagues, I have been at fault for accepting widely held beliefs about string theory despite their having no support in the scientific literature.

  The right question to ask, then, is: What has happened to the traditional constraints of scientific ethics? As we have seen, there is a problem with the structure of academic science, as manifested in such practices as peer review and the tenure system. This is partly responsible for the dominance of string theory, but equally at fault is the confusion of normal science with revolutionary science. String theory began as an attempt to do revolutionary science, yet it is treated as if it were another research program within normal science.

  A few chapters back, I suggested that there are two kinds of theoretical physicists, the master craftspeople who power normal science and the visionaries, the seers, who can see through unjustified but universally held assumptions and ask new questions. It should be abundantly clear by now that to make a revolution in science, we need more of the latter. But, as we have seen, these people have been marginalized if not excluded outright from the academy, and they are no longer considered, as they once were, a part of mainstream theoretical physics. If our generation of theorists has failed to make a revolution, it is because we have organized the academy in such a way that we have few revolutionaries, and most of
us don’t listen to the few we have.

  I have concluded that we must do two things. We must recognize and fight the symptoms of groupthink, and we must open the doors to a wide range of independent thinkers, being sure to make room for the peculiar characters needed to make a revolution. A great deal rests on how we treat the next generation. To keep science healthy, young scientists should be hired and promoted based only on their ability, creativity, and independence, without regard to whether they contribute to string theory or any other established research program. People who invent and develop their own research programs should even be given priority, so that they can have the intellectual freedom to work on the approach they judge the most promising. The governance of science is always a matter of making choices. To prevent overinvestment in speculative directions that may turn out to be dead ends, physics departments should ensure that rival research programs and different points of view toward unsolved problems are represented on their faculties—not only because most of the time we cannot predict which views will be right but because the friendly rivalry between smart people working in close proximity is often a source of new ideas and directions.

  An openly critical and candid attitude should be encouraged. People should be penalized for doing superficial work that ignores hard problems and rewarded for attacking the long-standing open conjectures, even if progress takes many years. More room could be made for people who think deeply and carefully about the foundational issues raised by attempts to unify our understanding of space and time with quantum theory.

  Many of the sociological problems we’ve discussed have to do with the tendency of scientists—indeed, all human beings—to form tribes. To combat this tribal tendency, string theorists could de-emphasize boundaries between string theory and other approaches. They could stop categorizing theorists by whether or not they display loyalty to this or that conjecture. People who work on alternatives to string theory, or who are critical of string theory, should be invited to speak at string theory conferences, to the benefit of all. Research groups should seek out postdocs, students, and visitors who pursue rival approaches. Students should also be encouraged to learn about and work on competing approaches to unsolved problems, so that they are equipped to choose for themselves the most promising directions as their careers advance.

  We physicists need to confront the crisis facing us. A scientific theory that makes no predictions and therefore is not subject to experiment can never fail, but such a theory can never succeed either, as long as science stands for knowledge gained from rational argument borne out by evidence. There needs to be an honest evaluation of the wisdom of sticking to a research program that has failed after decades to find grounding in either experimental results or precise mathematical formulation. String theorists need to face the possibility that they will turn out to have been wrong and others right.

  Finally, there are many steps that organizations supporting science can take to keep science healthy. Funding agencies and foundations should enable scientists at every level to explore and develop viable proposals to solve the deep and difficult problems. A research program should not be allowed to become institutionally dominant before it has gathered convincing scientific proof. Until it does, alternative approaches should be encouraged, so that the progress of science is not stalled by overinvestment in a wrong direction. When there is a recalcitrant but key problem, there should be a limit on the proportion of support given to any one research program that aims to solve it—say, a third of total funding.

  Some of these proposals represent major reforms. But when it comes to theoretical physics, we are not talking about much money at all. Suppose that an agency or foundation decided to fully support all the visionaries who ignore the mainstream and follow their own ambitious programs to solve the problems of quantum gravity and quantum theory. We are talking about perhaps two dozen theorists. Supporting them fully would take a tiny fraction of any large nation’s budget for physics. But judging from what such people have contributed in the past, it’s likely that several will do something important enough to make this the best overall investment in the field.

  Indeed, even small foundations can help, by searching out independent-minded seers with PhDs in theoretical physics or mathematics who are working on their own approach to a fundamental problem—people, that is, doing something so unconventional that there’s a good chance they will never be able to have an academic career. Someone like Julian Barbour, Antony Valentini, Alexander Grothendieck—or Einstein, for that matter. Give them five years of support, extendable to a second or even third five-year term if they are getting anywhere at all.

  Sound risky? The Royal Society in the United Kingdom has a program like this. It has been responsible for jump-starting the careers of several scientists who are now important in their field and who would probably never have gotten that sort of support in the United States.

  How would you choose those people worthy of support? Simple. Ask some who already do science this way. Just to be sure, find at least one accomplished person in the candidate’s field who is deeply excited about what the candidate is trying to do. To be really sure, find at least one professor who thinks the candidate is a terrible scientist and bound to fail.

  It may seem strange to be discussing academic politics in a book for the general public, but you, the public, individually and collectively, are our patrons. If the science you pay for is not getting done, it is up to you to hold our feet to the fire and make us do our job.

  So I have some final words for different audiences.

  To the educated public: Be critical. Don’t believe most of what you hear. When a scientist claims to have done something important, ask to see the evidence. Evaluate it as strictly as you would an investment. Give it as much scrutiny as a house you would buy or a school you would send your children to.

  To those who make decisions about what science gets done—that is, to department heads, search committees, deans, officers of foundations, and funding agencies: Only people at your level can implement recommendations like the ones just listed. Why not consider them? These are proposals that should be discussed in places like the offices of the National Science Foundation, the National Academy of Sciences, and their counterparts around the world. This is not just a problem for theoretical physics. If a highly disciplined subject like physics is vulnerable to the symptoms of groupthink, what may be happening in other, less rigorous areas?

  To my fellow theoretical physicists: The problems discussed in this book are the responsibility of all of us. We constitute a scientific elite only because the larger society we are part of cares deeply about the truth. If string theory is wrong but continues to dominate our field, the consequences could be severe—for us personally as well as for our profession. It’s up to us to open the doors and allow the alternatives in, and generally raise the standards of argument.

  To put it more bluntly: If you are someone whose first reaction when challenged on your scientific beliefs is “What does X think?” or “How can you say that? Everybody good knows that . . .,” then you are in danger of no longer being a scientist. You are paid good money to do your job, and that means you have a responsibility to make a careful and independent evaluation of everything you and your colleagues believe. If you cannot give a precise defense of your beliefs and commitments, consistent with the evidence, if you let other people do your thinking for you (even if they are senior and powerful), then you are not living up to your ethical obligations as a member of a scientific community. Your doctorate is a license for you to hold your own views and make your own judgments. But it is more than that; it obliges you to think critically and independently about everything in your domain of competence.

  This is harsh. But here are even harsher words for those of us working on fundamental problems who are not string theorists. Our job is supposed to be to find the wrong assumptions, ask the new questions, find the new answers, and lead revolutions. It’s easy to see where string theory
is probably wrong, but criticizing string theory is not the job. The job is to invent the theory that’s right.

  I’ll be harshest on myself. I fully expect some readers to come back at me with “If you’re so smart, why haven’t you done any better than the string theorists?” And they’d be right. Because in the end, this book is a form of procrastination. Of course, I hope by writing it to make the way easier for those who will follow. But my craft is theoretical physics and my real job is to finish the revolution Einstein started. I haven’t done that job.

  So what am I going to do myself? I’m going to try to take advantage of the good fortune that life has shown me. To begin with, I’m going to dig out my old paper, “On the Relationship Between Quantum and Thermal Fluctuations,” and read it. Then I’m going to turn off the phone and the BlackBerry, put on some Bebel Gilberto, Esthero, and Ron Sexsmith, turn the volume way up, erase the blackboard, get out some good chalk, open a new notebook, take out my favorite pen, sit down, and start thinking.

  Notes

  Introduction

  1. Mark Wise, “Modifications to the Properties of the Higgs Boson,” Seminar talk, Mar. 23, 2006. Available at http://streamer.perimeterinstitute.ca:81/mediasite/.

  2. Brian Greene, The Fabric of the Cosmos: Space, Time, and the Texture of Reality (New York: Alfred A. Knopf, 2005), p. 376.

  3. Gerard ’t Hooft, In Search of the Ultimate Building Blocks (Cambridge: Cambridge University Press, 1996), p. 163.

  4. Quoted in New Scientist, “Nobel Laureate Admits String Theory Is in Trouble,” Dec. 10, 2005. This raised something of a controversy, so Gross clarified his remarks at the opening of the 23rd Jerusalem Winter School in Theoretical Physics (full text available at www.as.huji.ac.il/schools/phys23/media.shtml):