Tal Cohen's Bookshelf: A Collection of Personal Opinions about Books
The Trouble with Physics / Lee Smolin
Reviewed by Tal Cohen Monday, 18 May 2009
The trouble with The Trouble with Physics is that it is, in fact, two books for the price of one. Each of these “sub-books” presents a different issue. The two issues are not in conflict, and they are certainly related, but each deserves its own discussion.

The first issue, presented in the first three parts of the book, is the trouble with string theory, and why Smolin -- a theoretical physicist -- believes it to be utterly wrong. The second issue, presented in the fourth and last part of the book, is that string theory research seems to be smothering other kinds of research in physics, especially in theoretical physics. And while I think it is the second issue that bothers Smolin the most, it seems like most reviewers focused on the first, and more technical, issue.

The book begins with an overview and history of physical research up to and including the rise of string theory. This part is a bit too long, but generally well-written. (Hurray for Smolin for not bothering the readers with needless explanations about each technical term -- he actually assumes the reader is an educated person, which is a refreshing approach). At times, it is very exciting; for example, it is easy to share the writer's thrill when the SU(5) theory is outlined, and share his disappointment when its failure under experiment is described. Smolin actually makes the reader enthusiastic about string theory, when it is first presented.

And then we journey with the author from enthusiasm to disappointment as we delve into string theory's development over time. Apparently, string theory is not “background independent”, which implies that it is incompatible with general relativity. Yet according to Smolin, string theory's main limitation is the lack of predictive power. The theory makes no predictions, and thus cannot be falsified; in fact, it encompasses an astronomical number of theories, and each experiment can be explained by some variant from this vast landscape. String theorists, when presented with this criticism, ended up labeling those who demand falsifiability “Popperazzi”, after philosopher of science Karl Popper.

Next, Smolin presents some alternatives to string theory, approaches preferred by “heretics” like himself. He naturally focuses on those theories that he himself was involved in, such as loop quantum gravity and doubly-special relativity (DSR). While he naturally believes that these theories hold the key to the true description of the physical universe (and string theory is wrong), Smolin admits that he could be mistaken: the “right” theory could be string theory, or it could be some other theory, possibly one that nobody thought of yet. What he laments is that the converse does not seem to be true: string theorists seem to him unable to conceive the possibility that string theory is simply wrong. This is the focus of the last part of the book, which presents the second, and more important, issue that Smolin is trying to press.

And thus, Part IV of The Trouble with Physics is -- as noted above -- a book in its own right, one that might have found a wider audience if it was detached from the first three parts. It is more about sociology than about physics: the sociology of the community of theoretical physicists. And when physical research makes many strides forward, and Parts I to III will be hopelessly outdated, Part IV of the book will still remain relevant.

When studying the sociology of the community, Smolin accuses string theorists of groupthink. This groupthink, he claims, prevents them from even admitting the possibility that their favorite theory is wrong. They're even accused of having a “messianic tendency”; for some (mostly younger) members of the community, string theory had become a religion, with figures like Ed Witten in the role of prophets. To the believers, those who suggest that string theory is wrong are heretics.

(From the book) At a recent string theory conference, an editor from Cambridge University Press confided to me that a string theorist had told him he would never consider publishing with the press because it had put out a book on loop quantum gravity. This kind of things is not as rare as it should be.

The fact that no experiment can prove string theory wrong certainly doesn't help. What makes this a major issue is that nowadays (according to Smolin), one has to focus on string theory if one wishes to have an academic career in the field, which oppresses any possibility of real innovation outside of strings. ''[Science] can break down, and I believe it is doing so now,” Smolin laments; and ''[W]e must have a basis for disagreeing with the majority without being labeled a crank.”

At times, Smolin's claims sound like whining. But the accusations he makes are serious, and must be taken seriously. I'm not sure about his suggested solutions, though. For example, Smolin accuses the physics community with “blatant prejudice” against women and blacks. “Anyone who has served, as I have, on decades of hiring committees and hasn't seen naked prejudice in action is either blind to it or dishonest,” he states (p. 336). He believes affirmative action is the right solution for this prejudice, which could be true; but then he moves on to suggest using affirmative action to help hire “people who just think differently,” an idea which I personally find somewhat pathetic.

So, what comes next? How can the physics community heal itself, and pull itself out of the hole it has dug? A string theorist could claim there's nothing to heal, and Smolin is merely lamenting the unpopularity of his own pet theories. But I disagree; this reader, at least, was convinced by Smolin's argument that there really is a trouble with physics. We'll probably have to look for a solution elsewhere, but acknowledging the problem is an important first step.

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Related Reading
Another complaint about string theory's deadlock, by virtue of not being falsifiable, appears in Peter Woit's Not Even Wrong: The Failure of String Theory and the Search for Unity in Physical Law. (I have not yet read this book.)

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Eran Belinsky writes:
Sounds very Thomas Khun-ish to me. A reigning paradigm has taken over and rejects other paradigms, in an almost religious manner. Why are you (and Smolin) surprised then?

One thing I didn't understand: does Smolin claim that no experiment can *ever* be conceived that will refute String theory, or that no refuting experiment has been conceived so far?

As for philosophy of science and ''popperazi'': unlike what a lot of people think, it has progressed after Popper and refutability, even up to Popper's student Paul Feyerabend claim that in science ''anything goes''.
[390] Posted on Wednesday, 20 May 2009 at 16:23 GMT [Reply to this] [Permalink]

Tal Cohen writes in reply to Eran Belinsky:
Yes, Smolin discusses Khun's theory in this respect, and claims the situation is a bit more complicated here. With normal ''paradigm takeovers'', once refuting evidence begins to appear, the ''old guard'' first tries to fix the paradigm as much as possible, but eventually a better theory appears, which explains the results better, and sometimes even explains results which the old paradigm simply cannot explain -- at which point we have a paradigm shift. But here, string theory (ST) is not facing any refuting evidence; in fact, at the moment it seems like refuting evidence simply cannot exist.

Which brings me to your second question: at the moment, it seems like, indeed, no experiment can ever be conceived that will refute ST. That's because ST is in fact a vast landscape of theories (each with different values to various variables); none of these theories, if I understood Smolin correctly, was ever actually written down, and perhaps none can be. And, if ST is ''real'', only one of the immeasurable number of theories applies to ''our'' universe. Which one? We don't know.

So, if some future experiment does refute some version of ST, it never refutes ST in general, because ''believers'' can always claim that it simply shows that some other variant of ST is the real one.

The converse of this problem is that ST can't be used to make predictions; we don't know which version of ST is the right one, so we can't use it to predict any experimental outcomes.

The landscape of variants is so vast that it clearly violates basic scientific ideals (Occam's Razor comes to mind). Smolin finds it shocking that ST believers pick the Anthropic Solution to this problem, i.e., claiming that the universe is the way it is is because, of the huge number of potential universes, this is the one in which conscious life could evolve.
[391] Posted on Wednesday, 20 May 2009 at 16:46 GMT [Reply to this] [Permalink]

Archer Krantz writes in reply to Tal Cohen:
What are the major challenges against the anthropic principle? Is there a publication you can point to? I'd like to look into it since on the surface the principle seems reasonable. Is the argument against it simply an argument against the multiverse explanation of quantum physics?
[429] Posted on Monday, 19 October 2009 at 17:14 GMT [Reply to this] [Permalink]

Tal Cohen writes in reply to Archer Krantz:
In a way, it is indeed mostly an argument against the multiverse theory. I recommend you read Smolin directly for his detailed arguments (I don't have the book at hand so I can't provide any reference he cites.)
[430] Posted on Monday, 19 October 2009 at 21:47 GMT [Reply to this] [Permalink]

elijah writes:
Related book - Gina says
Related to this book is a very interesting and amusing book written by mathematician Gil Kalai which relates to the subject of physical theories and scientific debates:
[715] Posted on Thursday, 13 October 2011 at 10:04 GMT [Reply to this] [Permalink]

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