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

by Lee Smolin

  Here’s a description of groupthink excerpted from an Oregon State University Web site dealing with communication:

  Groupthink members see themselves as part of an in-group working against an outgroup opposed to their goals. You can tell if a group suffers from groupthink if it:

  overestimates its invulnerability or high moral stance,

  collectively rationalizes the decisions it makes,

  demonizes or stereotypes outgroups and their leaders,

  has a culture of uniformity where individuals censor themselves and others so that the facade of group unanimity is maintained, and

  contains members who take it upon themselves to protect the group leader by keeping information, theirs or other group members’, from the leader.20

  This does not match up one-to-one with my characterization of the culture of string theory, but it’s close enough to be worrying.

  Of course, string theorists will not have any trouble answering this critique. They can point to many historical examples showing that the progress of science depends on the establishment of tight consensus among a community of experts. The views of outsiders must be disregarded because outsiders are not skilled enough in the tools of the trade to evaluate evidence and pass judgment. It follows that the scientific community must have mechanisms for the establishment and enforcement of consensus. What may seem like groupthink to an outsider is in fact rationality, displayed according to tightly constrained rules.

  They can also counter the charge that they let the consensus of their research community substitute for the critical thinking of individuals. According to one prominent sociologist of science I’ve discussed this with, the fact that key conjectures are believed without being proved is not unusual.21 No scientist can directly confirm more than a small fraction of the experimental results, calculations, and proofs that form the foundations of their beliefs about their subject; few have the skills, and in contemporary science no one has the time. Thus, when you join a scientific community, you must trust your colleagues to tell the truth about the results in their domains of expertise. This can lead to a conjecture being accepted as a fact, but it happens as often in research programs that are ultimately successful as it does in those that fail. Contemporary science just cannot be done without a community of people who trust what members tell them. Thus, while episodes like this are to be regretted and should be corrected when found, they are not by themselves indications of a doomed research program or a pathological sociology.

  Finally, senior string theorists can argue that they deserve their credentials and with those comes the right to direct research as they see fit. After all, the practice of science is based on hunches, and this is their hunch. Would someone have them waste their time working on something they don’t believe in? And should they hire people who work on theories other than the one they believe has the best chance of success?

  But how does one respond to this defense? If science is based on consensus among a community of experts, then what you have in string theory is a community of experts who are in remarkable agreement about the ultimate correctness of the theory they study. Is there any rational ground to stand on—any way to mount an intelligent and useful dissent? We need to do much more than throw around terms like “groupthink.” We must have a theory of what science is and how it works, one that clearly demonstrates why it is bad for science when a particular community comes to dominate a field before its theory has passed the usual tests of proof. This is the task to which we now turn.

  17

  What Is Science?

  TO REVERSE THE TROUBLING trends in physics, we must first understand what science is—what moves it forward and what holds it back. And to do this, we must define science as something more than the sum of what scientists do. The aim of this chapter is to propose such a definition.

  When I entered graduate school at Harvard in 1976, I was a naïve student from a small college. I was in awe of Einstein, Bohr, Heisenberg, and Schrödinger and how they had changed physics through the force of their radical thinking. I dreamed, as young people do, of being one of them. I now found myself at the center of particle physics, surrounded by the leaders in the field—people like Sidney Coleman, Sheldon Glashow, and Steven Weinberg. These people were incredibly smart, but they were nothing like my heroes. In lectures, I never heard them talk about the nature of space and time or issues in the foundations of quantum mechanics. Neither did I meet many students with these interests.

  This led me to a personal crisis. I was certainly not as well prepared as students from the great universities, but I had done research as an undergraduate, which most of my peers had not, and I knew I was a quick study. So I was confident that I could do the work. But I also had a very particular idea of what a great theoretical physicist should be. The great theoretical physicists I was rubbing shoulders with at Harvard were rather different from that. The atmosphere was not philosophical; it was harsh and aggressive, dominated by people who were brash, cocky, confident, and in some cases insulting to people who disagreed with them.

  During this time, I made friends with a young philosopher of science named Amelia Rechel-Cohn. Through her, I came to know people who, like me, were interested in the deep philosophical and foundational issues in physics. But this only made matters worse. They were nicer than the theoretical physicists, but they seemed happy just to analyze precise logical issues in the foundations of special relativity or ordinary quantum physics. I had little patience for such talk; I wanted to invent theories, not criticize them, and I was sure that—as unreflective as the originators of the standard model seemed—they knew the things I needed to know if I was to get anywhere.

  Just as I started to think seriously about quitting, Amelia gave me a book by the philosopher Paul Feyerabend. It was called Against Method and it spoke to me—but what it had to say was not very encouraging. It was a blow to my naïveté and self-absorption.

  What Feyerabend’s book said to me was: Look, kid, stop dreaming! Science is not philosophers sitting in clouds. It is a human activity, as complex and problematic as any other. There is no single method to science and no single criterion for who is a good scientist. Good science is whatever works at a particular moment of history to advance our knowledge. And don’t bother me with how to define progress—define it any way you like and this is still true.

  From Feyerabend, I learned that progress sometimes requires deep philosophical thinking, but most often it does not. It is mostly furthered by opportunistic people who cut corners, exaggerating what they know and have accomplished. Galileo was one of these; many of his arguments were wrong, and his opponents—the well-educated, philosophically reflective Jesuit astronomers of the time—easily punched holes in his thinking. Nevertheless, he was right and they were wrong.

  What I also learned from Feyerabend is that no a priori argument can tell us what will work in all circumstances. What works to advance science at one moment will be wrong at another. And I learned one more thing from his stories of Galileo: You have to fight for what you believe.

  Feyerabend’s message was a none too timely wake-up call. If I wanted to do good science, I had to recognize that the people I was lucky enough to be studying with were indeed the great scientists of the day. Like all great scientists, they had succeeded because their ideas were right and they had fought for them. If your ideas are right and you fight for them, you’ll accomplish something. Don’t waste time feeling sorry for yourself or waxing nostalgic about Einstein and Bohr. No one but you can develop your ideas, and no one but you will fight for them.

  I took a long walk and decided to stay in science. I soon found I could do real research by applying the methods used by particle physicists to the problem of quantum gravity. If this meant leaving aside, for a time, the foundational issues, it was nevertheless wonderful to be able to invent new formulations and do some calculations within them.

  To thank him for saving my career, I sent a copy of my PhD thesis to Feyera
bend. In reply, he sent me his new book, Science in a Free Society (1979), with a note inviting me to look him up if I was ever in Berkeley. A few months later, I happened to be in California for a particle-physics conference and tried to track him down, but it was quite a project. He kept no office hours at the university and, indeed, no office. The Philosophy Department secretary laughed when I asked for him and advised me to try him at home. There he was in the phone book, on Miller Avenue in the Berkeley hills. I summoned up my courage, dialed, and politely asked for Professor Paul Feyerabend. Whoever was on the other end shouted “Professor Paul Feyerabend! That’s the other Paul Feyerabend. You can find him at the university” and hung up. So I dropped in on one of his classes, and found him happy to talk afterward, if only briefly. But in the few minutes he gave me, he offered an invaluable piece of advice. “Yes, the academic world is screwed up, and there’s nothing you can do about it. But don’t worry about that. Just do what you want. If you know what you want to do and advocate for it, no one will put any energy into stopping you.”

  Six months later, he wrote me a second note, which reached me in Santa Barbara, where I had just accepted a position as a postdoc at the Institute for Theoretical Physics. He mentioned that he was talking with a talented physics undergraduate who, like me, had philosophical interests. Would I like to meet him and advise him on how to proceed? What I really wanted was another chance to talk to Feyerabend, so I went up to Berkeley again and met the two of them on the steps of the philosophy building (as close, apparently, as he ever got to his colleagues.) Feyerabend treated us to lunch at Chez Panisse, then took us up to his house (which turned out to be on Miller Avenue, in the Berkeley hills) so the student and I could talk while he watched his favorite soap opera. On the way, I shared the backseat of Feyerabend’s little sports car with the inflatable raft he kept there in case an 8-point earthquake came while he was on the Bay Bridge.

  The first topic Feyerabend brought up was renormalization, the method for dealing with infinities in quantum field theory. I was surprised to find that he knew quite a lot of contemporary physics. He wasn’t antiscience, as some of my professors at Harvard had intimated he would be. It was clear that he loved physics, and he was more conversant with the technicalities than most philosophers I had met. His reputation as hostile to science had undoubtedly arisen because he considered the question of why science worked as unanswered. Was it because science has a method? So do witch doctors.

  Perhaps the difference, I ventured, is that science uses math. And so does astrology, he responded, and he would have explained the details of the various computational systems used by astrologers, if we had let him. Neither one of us knew what to say when he argued that Johannes Kepler, one of the greatest physicists who ever lived, had made several contributions to the technical refinement of astrology, and Newton had spent more time on alchemy than on physics. Did we think we were better scientists than Kepler or Newton?

  Feyerabend was convinced that science is a human activity, carried out by opportunistic people who follow no general logic or method and who do whatever it takes to increase knowledge (however you define it). So his big question was: How does science work, and why does it work so well? Even though he countered all of my own explanations, I sensed that he passionately pursued the question not because he was antiscience but because he cared about it.

  As the day progressed, Feyerabend told us his story. He had been a physics prodigy as a teenager in Vienna, but his studies were curtailed when he was drafted to fight in World War II. He was wounded on the Russian front and later ended up in Berlin, where he found work after the war as an actor. After a time, he tired of the theater world and returned to the study of physics in Vienna. He joined the philosophy club, where he discovered that he could win on any side of a philosophical debate simply by using the skills he had learned in the acting profession. This made him wonder whether academic success had any rational basis. One day, the students succeeded in inviting Ludwig Wittgenstein to come to their club. Feyerabend was so impressed that he decided to switch to philosophy. He spoke with Wittgenstein, who invited him to come to Cambridge to study with him. But by the time Feyerabend got to England, Wittgenstein was dead, so someone suggested he talk with Karl Popper, another Viennese expatriate, who was teaching at the London School of Economics. So he moved to London and began his life in philosophy by writing papers attacking Popper’s work.

  After a few years, he was offered a teaching job. He asked a friend how he could possibly teach, given how little he knew. The friend told him to write down what he thought he knew. It filled a single piece of paper. The friend then told him to make the first sentence the subject of the first lecture, the second sentence the subject of the second lecture, and so on. So the physics student turned soldier turned actor became a philosophy professor.1

  Feyerabend drove us back down to the Berkeley campus. Before leaving us, he gave us a last piece of advice. “Just do what you want to do and don’t pay any attention to anything else. Never in my career have I spent five minutes doing something I didn’t want to be doing.”

  And this is more or less what I have done. Until now. Now I feel we have to talk not just about scientific ideas but also about the scientific process. There is no choice. We have a responsibility to the generations that follow to think about why we have been so much less successful than our teachers.

  Since my visit with Feyerabend, who died in 1994 at the age of seventy, I have mentored several talented young people through crises very similar to my own. But I cannot tell them what I told my younger self—that the dominant style was so dramatically successful that it must be respected and accommodated. Now I have to agree with my younger colleagues that the dominant style is not succeeding.

  First and foremost, the style of doing science that I learned at Harvard has not led to more progress. It succeeded in establishing the standard model but failed to go beyond it. After thirty years, we must ask whether that style has, for the time being, outlived its usefulness. Perhaps this is a moment that requires the more reflective, risky, and philosophical style of Einstein and his friends.

  The problem is far wider than string theory; it involves the values and attitudes fostered by the physics community as a whole. Put simply, the physics community is structured in such a way that large research programs that promote themselves aggressively have an advantage over smaller programs that make more cautious claims. Therefore, young academic scientists have the best chance of succeeding if they impress older scientists with technically sweet solutions to long-standing problems posed by dominant research programs. To do the opposite—to think deeply and independently and try to formulate one’s own ideas—is a poor strategy for success.

  Physics thus finds itself unable to solve its key problems. It is time to reverse course—to encourage small, risky new research programs and discourage the entrenched approaches. We ought to be giving the advantage to the Einsteins—people who think for themselves and ignore the established ideas of powerful senior scientists.

  But to convince the skeptics, we have to answer Feyerabend’s question about how science works.

  There seem to be two conflicting views of science. One is science as the domain of the rebel, the individual who comes up with grand new ideas and works hard over a lifetime to prove them true. This is the myth of Galileo, and we see it played out today in the efforts of a few greatly admired scientists, like the mathematical physicist Roger Penrose, the complexity theorist Stuart Kauffman, and the biologist Lynn Margulis. Then there is the view of science as a conservative, consensual community that tolerates little deviation from orthodox thinking and channels creative energy into furthering well-defined research programs.

  In some sense, both views are true. Science requires both the rebel and the conservative. This seems at first paradoxical. How has an enterprise flourished for centuries that requires the conservative and the rebel to coexist? The trick seems to be to bring the rebel and conservative into
lifelong and uncomfortable proximity, within the community and, to some extent, within each individual as well. But how is this accomplished?

  Science is a democracy, in that every scientist has a voice, but it is nothing like majority rule. Still, whereas individual judgment is prized, consensus plays a crucial role. Indeed, what ground can I stand on when the majority of my profession embraces a research program I cannot accept even though accepting it would be to my benefit? The answer is that democracy is much more than rule by the majority. There is a system of ideals and ethics that transcends majority rule.

  Thus, if we are to argue that science is more than sociology, more than academic politics, we must have a notion of what science is that is consistent with, but more than, the idea of a self-governing community of human beings. To argue that a particular form of organization, a particular behavior, is good or bad for science, we must have a basis for making value judgments that goes beyond what is popular. We must have a basis for disagreeing with the majority without being labeled a crank.

  Let us start by breaking Feyerabend’s question down into a few simpler questions. We can say that science progresses when scientists reach consensus on a question. What are the mechanisms that govern how this happens? Before a consensus is reached, there is often controversy. What is the role of disagreement in preparing the way for scientific progress?

  To answer these questions, we should go back to the views of earlier philosophers. In the 1920s and 1930s, a philosophical movement grew up in Vienna called logical positivism. The logical positivists proposed that assertions become knowledge when they are verified by observations of the world, and they claimed that scientific knowledge is the sum of these verified propositions. Science progresses when scientists make assertions that have verifiable content, which are then verified. Their motive was to rid philosophy of metaphysics, which had filled huge books with statements that made no contact with reality. In this they partly succeeded, but their modest characterization of science did not last. There were many problems, one of which was that there is no ironclad correspondence between what is observed and what is stated. Assumptions and biases creep into the descriptions of the simplest observations. It is not practical, perhaps not even possible, to break what scientists say or write into little atoms, each of which corresponds to an observation stripped of theorizing.