The Trouble with Physics


These are excerpts from Lee Smolin¡¦s book ¡¥The Trouble with Physics¡¦. Although I have picked out a few key sections here (hopefully they make sense by themselves) the entire book is great and very relevant to TOK ¡K I thoroughly recommend you checking out the whole thing. You should be aware, however, that Smolin appears to be an outsider in the scientific community who does not share the generally accepted view that String Theory is the correct scientific explanation of the universe and this may have influenced his perspective at points.



Scientific Revolutions:

Sometimes it is rational not to throw a good theory away when it predicts things that haven¡¦t been seen. Sometimes the hypotheses you are forced to invent turn out to be right. By inventing such ad hoc hypotheses, you can not only keep an idea plausible but also sometimes predict new phenomena. But at some point you begin to stretch credulity. Exactly when you pass the point where a once good idea becomes not worth the trouble is at first a matter of judgment. There certainly have been cases in which well-trained, smart people disagreed. But eventually a point is reached where there is such a preponderance of evidence that no rational, fair-minded person will think the idea plausible.


One way to assess whether you¡¦ve reached that point is to look at uniqueness. During a scientific revolution several proposals are often on the table at any given time, threatening to take science in incompatible directions. This is normal, and in the midst of the revolution there does not need to be a rational reason to choose one over the others. At such times, even very smart people who choose between competing views too soon will often be wrong.


But one proposal may end up explaining far more than the others, and it is usually the simplest. At this point, when a single proposal is vastly superior to others in terms of generation of new insights, agreement with experiment, explanatory power and simplicity, it take on an appearance of uniqueness. We say it has the ring of the truth. (pp.26 ¡V 27)


Good Unifications:

[Good unifications demonstrate] that beauty can be misleading. Simple observations from the data are often more important. Another lesson is that correct unifications have consequences for phenomena unsuspected at the time a unification is invented, as n the case of the application of Kepler¡¦s laws to Jupiter¡¦s moons. Correct unifications also raise questions that may seem absurd at the time but lead to further unifications, as in Kepler¡¦s postulation of a force from the sun to the planets.


Most important, we see a real revolution often requires that several new proposals for unification come together to support one another. In the Newtonian revolution, there were several proposed unifications that triumphed at once: the unification of the earth with the planets, the unification of the sun with the stars, the unification of rest and uniform motion, and the unification of the gravitational force on Earth with the force by which the sun influences a planet¡¦s motions. Singly, none of these ideas could have survived; together, they trounced their rivals. The result was a revolution that transformed every aspect of our understanding of nature.


In the history of physics, there is one unification that serves more than any other as a model of what physicists have been trying to do for the past thirty years. This is the unification of electricity and magnetism achieved by James Clerk Maxwell in the 1860s ¡K (pp.30 ¡V 31)


Science as Art:

What makes theoretical physics as much an art as a science is that the best theorists have a sixth sense about what results can be ignored. Thus, the early 1960s, Sheldon Glashow, then a post-doc at the Niels Bohr Institute, suggested that the weak force was indeed described by a gauge theory. If this range problem could be solved, the weak force could then be unified with electromagnetism. But the overall problem would still have to be faced: how could you unify forces that manifest themselves as differently as electromagnetism and the strong and weak nuclear forces? (p.58)


The Impact of Accidents on Science:

By now almost everyone who thinks seriously about quantum gravity agrees with Bronstein, but it has taken about seventy years. One reason is that even such brilliant minds as Bronstein and Solomon could not escape the insanity of their time. A year after Bronstein wrote the paper I just quoted he was arrested by the NKVD, and he was executed by firing squad on February 18 1838. Solomon became a member of the French Resistance and was killed by the Germans on My 23, 1942. Their ideas were lost to history. I have worked on the problem of quantum gravity all my life and I have learned of them only while finishing this book. (pp.85 ¡V 86)


How Science Feels ¡V Intuition & Emotion:

For me (and others, I¡¦m sure), the merging of supersymmetry with a theory of space and time raised profound questions. I had learned general relativity from reading Einstein, and if I understood anything, it was how that theory merged gravity with the geometry of space and time. That idea was in my bones. Now I was being told that another deep aspect of nature was also unified with space and time ¡V the fact that there are fermions and bosons. My friends told me this, and the equations said the same thing. But neither friends nor equations told me what it meant I was missing the idea, the conception of the thing. Something in my understanding of space and time, of gravity, and of what it meant to be a fermion or boson, should deepen as a result of this unification. It should not just be math ¡V my very conception of nature should change. But it didn¡¦t ¡K (pp.94 - 95)


The Reality of Scientific Revolutions:

Thomas Kuhn, in his famous book The Structure of Scientific Revolutions, gave us a new way of thinking about events in the history of science that we think of as revolutions. According to Kuhn, a scientific revolution is preceded by the piling up of experimental anomalies. As a result, people begin to question the established theory. A few invent alternative theories. The revolution culminates in experimental results that favour one of the new alternatives over the old established theory. It is possible to take issue with Kuhn¡¦s description of science, and I will do so in the closing section of this book. But since it describes what happens in some cases, it serves as a useful point of comparison.


The events of 1984 did not follow Kuhn¡¦s structure. There never was an established theory addressing the problems that string theory addresses. There were no experimental anomalies; the standard model of particle physics and general relativity together sufficed to explain the results of all the experiments done until that time. Even so, how could one not call this a revolution? All of a sudden we had a good candidate for a final theory that could explain the universe and our place in it.


For four or five years after the superstring revolution of 1984, there was a lot of progress, and interest in string theory grew rapidly. It was the hottest game in town. Those who went into it dived in with ambition and pride. There were a lot of new technical tools to learn so to work in string theory required an investment of a few months to a year, which for a theoretical physicist is a long time. Those who did it looked down on those who wouldn¡¦t, or (the suggestion was always there) couldn¡¦t. Very quickly there developed an almost cult-like atmosphere. You were either a string theorist or you were not. A few of us tried to keep a commonsense approach Here is an interesting idea; I¡¦ll work on it some, but I¡¦ll also pursue other directions. It was hard to make that stick, because those who jumped in weren¡¦t much interesting in talking with those of us who did not declare ourselves part of the new wave.


As befits a new field, immediately there were academic conferences on string theory. These had an air of triumphant celebration. There was a sense that the one true theory had been discovered. Nothing else was important or worth thinking about. Seminars devoted to string theory sprang up at many of the major universities and research institutes. At Harvard, the string theory seminar was called the Postmodern Physics seminar.


The appellation was not meant ironically. One thing that was seldom discussed in string theory seminars and conferences was how to test the theory experimentally. While a few people did worry about this, there were others who thought it wasn¡¦t necessary. The feeling was that there could be only on consistent theory that unified all of physics and since string theory appeared to do that, it had to be right. No more reliance on experiment to check our theories. Mathematics was now sufficient to explore the laws of nature. We had entered the period of postmodern physics ¡K


The unfortunate result was that the split between believers and sceptics deepened. Each side become more entrenched, and each seemed to have good justification for its position. And it would have stayed like this for a long time, had certain dramatic developments not occurred that radically altered our appreciation of string theory. (pp.115 ¡V 116)


Just Holding On:

Philosophers and historians of science, among them Imre Lakatos, Paul Feyerabend, and Thomas Kuhn, have argued that one experimental anomaly is rarely enough to kill a theory. If a theory is believed deeply enough, by a large enough group of experts, they will go to ever more extreme measures to save it. This is not always bad for science, and occasionally it can be very good. Sometimes the theory¡¦s defenders succeed, and when they do, great and unexpected discoveries can be made. But sometimes they fail, and then lots of time and energy is wasted as theorists dig themselves deeper and deeper into a hole. The story of string theory in the last few years is one that Lakatos or Feyerabend would have understood well, for it is the story of a large group of experts doing what they can to save a cherished theory in the face of data that seem to contradict it. (p.154)



One point that string theorists are passionate about is that the theory is beautiful, or ¡¥elegant.¡¦ This is something of an aesthetic judgment that people may disagree about, so I¡¦m not sure how it should be evaluated In any case, it has no role in an objective assessment of the accomplishments of the theory. As we saw in Part I, lots of beautiful theories have turned out to have nothing to do with nature.


More generally, the fact that a physical theory inspires developments in mathematics cannot be used as an argument for the truth of the theory as a physical theory. Wrong theories have inspired many developments in mathematics. Ptolemy¡¦s theory of the epicycles might well have inspired developments in trigonometry and number theory, but that does not make it right. Newtonian physics inspired the development of major parts of mathematics, and it continues to do so, but that did not save Newtonian physics when it disagreed with experiment. There are many examples of theories based on beautiful mathematics that never had any successes and were never believed, Kepler¡¦s first theory of the planetary orbits being the signal example. So the fact that some beautiful mathematical conjectures are inspired by a physics research programme cannot save a theory that has no clearly articulated core principles and makes no physical predictions.


Hiding in Plain Sight:

Sometimes the key things are right in front of us, there for the seeing. Hiding in plains sight from [the Ancient Philosophers] were easily perceivable facts we now take for granted, like the principle of inertia or the constant acceleration of falling objects. Galileo¡¦s observations of motion on Earth did not use the telescope or the mechanical clock. As far as I know, they could have been made in Heraclitus¡¦ time ¡K he had only to ask the right questions.


So, while we bemoan how hard it is to test the ideas behind string theory, we ought to wonder what might be hiding in plain sight around us. In the history of science, there have been many instances of discoveries that surprised scientists because they were not anticipated by theory. Are there observations to day that we theorists have not asked for, that now theory invites ¡V observations that could move physics in an interesting direction? Is there a chance that such observations have already been made but ignored because, if confirmed, they would be inconvenient for our theorizing? (pp. 203 ¡V 204)


Is Science Ever Right?

If nothing else, our experiments should certainly test the fundamental principles of physics. There is a great tendency to think that these principles, once discovered, are eternal, yet history tells a different story. Almost every principle once proclaimed has been superseded. No matter how useful they are or how good an approximation they give to phenomena, sooner or later most principles fail, as experiment probes the natural world more accurately. (p.218)


Trusting Your Instincts:

When the ancients declared the circle the most perfect shape, they meant that it was the most symmetric: each point on the orbit is the same as any other. The principles that are hardest to give up are those that appeal to our need for symmetry and elevate an observed symmetry to a necessity. Modern physics is based on a collection of symmetries, which are believed to enshrine the most basic principles. No less than the ancients, many modern theorists believe instinctively that the fundamental theory must be the most symmetric possible law. Should we trust this instinct, or should we listen to the lesson of history, which tells us that (as in the example of the planetary orbits) nature becomes less rather than more symmetric the closer we look? (p.218)


How Science Really Works:

[There are] seven unusual aspects of the string theory community:

1.       Tremendous self-confidence, leading to a sense of entitlement and of belong to an elite community of experts,

2.       An unusually monolithic community, with a strong sense of consensus, whether driven by the evidence or not, and an unusual uniformity of views on open questions. These views seem related to the existence of a hierarchical structure in which the ideas of a few leaders dictate the viewpoint, strategy, and direction of the field.

3.       In some cases, a sense of identification with the group, akin to identification with a religious faith or political platform.

4.       A strong sense of the boundary between the group and other experts.

5.       A disregard for and disinterest in the ideas, opinions, and work of experts who are not part of the group, and a preference for talking only with other members of the community.

6.       A tendency to interpret evidence optimistically, to believe exaggerated or incorrect statements of results, and to disregard the possibility that the theory might be wrong. This is coupled with a tendency to believe results are true because they are ¡§widely believed¡¨, even if one has not checked [or even seen] the proof oneself.

7.       A lack of appreciation for the extent to which a research programme out to involve risk.

Of course, not all string theorists can be described this way, but few observers, inside or outside the string theory community, will disagree that some or all of these attitudes characterise that community.


I want to be clear that I am not criticising the behaviour of specific individuals. Many string theorists are personally open-minded and self-critical, and if asked, they will say that they deplore these characteristics of their community.


I must also be clear that I am as much at fault as my colleagues in string theory. For many years, I believed that basic conjectures [that I had not tested myself or seen a proof of] were proven. This is largely why I invested years of work in string theory. More than just my own work was affected for among the community of people who work on quantum gravity, I was the strongest advocate for taking string theory seriously. Yet I did not take the time to check the literature, so I, too, was willing to let the leaders of the string theory community do my critical thinking for me. And during the years I worked on string theory, I cared very much what the leaders of the community thought of my work. Just like an adolescent, I wanted to be accepted by those who were the most influential in my little circle. If I didn¡¦t actually take their advice and devote my life to the theory, it¡¦s only because I have a stubborn streak that usually wins out in these situations. For me, this is not an issue of ¡¥us¡¦ versus ¡¥them¡¦, or a struggle between two communities for dominance. These are vey personal problems which I have been contending with internally for as long as I have been a scientist. (pp. 284-285)


Against Method:

[The philosopher of science Paul Feyerabend wrote a book called ¡¥Against Method¡¦ in which he said something like] 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 ¡V define it any way you like and this is still true.


Feyerabend also attached the whole idea that method is the key to scientific progress, by showing that at critical junctures scientists will make progress by breaking the rules. Moreover, her argued ¡V convincingly in my view ¡V that science would grind to a halt were the ¡¥method¡¦s¡¦ rules always followed. The science historian Thomas Kuhn made another attack on the notion of ¡¥a scientific method¡¦ when he argued that scientists follow different methods at different times. But he was less radical than Feyerabend ; he tried to set out two methods, that of ¡¥normal science¡¦ and that of scientific revolutions. (pp. 296 ¡V 297)


The Importance of Disagreement:

Controversy is essential for the progress of science. [I believe that] when we are forced to reach a consensus, by the evidence, we should do so. But [I also believe] that until the evidence forces consensus we should encourage a wide diversity of viewpoints. This is good for science ¡V a point that Feyerabend made often, and I believe correctly. Science proceeds fastest when there are competing theories. The older, naïve view is that theories are put forward one at a time and tested against the data. This fails to take into account the extent to which the theoretical ideas we have influence which experiments we do and how we interpret them. If only one theory is contemplated at a time, we are likely to get stuck in an intellectual trap created by that theory. The only way out is if different theories compete to explain the same evidence.


Feyerabend argued that even in cases where there is a widely accepted theory that agrees with all the evidence, it is still necessary to invent competing theories in order for science to progress. This is because experiments that contradict the established view are most likely to be suggested by a competing theory and perhaps would even have been conceived were there not a competing theory.


Therefore, Feyerabend insisted that scientists should never agree, unless they are forced to. When scientists come to agreement too soon, before they are compelled to by the evidence, science is in danger. We then have to ask what influenced them to come to the premature conclusion. As they are only human, the answer to this will likely be the same factors that cause people to agree about all sorts of things that don¡¦t rely on evidence, from religious beliefs to fashion to trends in popular culture. (pp. 304 ¡V 305)


Not So Neutral After All:

In the academic world, with few exceptions, the people who evaluate you are older than you are, and more powerful. This is true all the way up the ladder, from your first college course to the applications you make for grants when you¡¦re¡¦ professor. I do not want to disparage the hard work done by so many in the service of [hiring other scientists]. Most do it sincerely. But there are big problems with it, and they are relevant to the state of physics today.


An unintended by-product of [the hiring system] is that it can easily become a mechanism for older scientists to enforce direction on younger scientists. This is so obvious that I¡¦m surprised at how rarely it is discussed. The system is set up so that we older scientists can reward those we judge worthy with good careers and punish those we judge unworthy with banishment from the community of science. This might be fine If there were clear standards and a clear methodology to ensure our objectivity, but, at least in the part of the academy where I work, there is neither.


As we have discussed in detail, different kinds of scientists contribute to theoretical physics and they all have different strengths and weaknesses. There is, however, little acknowledgement of this; instead, we speak simply about who is ¡¥good¡¦ and who is ¡¥not good¡¦ ¡V that is [we base our recruitment decisions] on the simplistic and obviously faulty assumption that scientists can be ranked on a ladder.


Here¡¦s a basic rule for predicting the kind of junior scientist that senior scientists will recommend: does the junior scientists remind them of themselves? If you see a younger version of yourself in X, then X must be really good. I know I am guilty of this, and I say so frankly. If you want to hire more people like me, I am great at picking them out. If you want to make fine distinctions among people very different from me, who are good at things I am not so good at or don¡¦t value, don¡¦t trust my judgements. (pp. 333 ¡V 334)




Smolin, L. ¡¥The Trouble with Physics, Mariner Books, 2006, Print.