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Stringing Along
A Review by Doug Brown

From the title, one might expect Lee Smolin to be some cranky science writer, or even some sort of anti-science Luddite. However, Smolin is the real deal. He got his doctorate in physics at Harvard, spent some time teaching at Yale, spent more time studying at the Princeton Institute for Advanced Study (the place Einstein spent his last twenty years), is one of the founders of a model called "loop quantum gravity," and he has worked on string theory. Folks in the physics community should give him a listen, and more broadly people interested in science will likely find this an interesting book.

The first half of The Trouble with Physics covers (as the subtitle says) the rise of string theory. It has been through several incarnations, each one shot down before someone modified it and started it back up. The trouble alluded to in the title is that there is no experimental evidence to support string theory. Well, actually, that's only part of the trouble. Another part is there actually isn't a string theory; there's a bunch of separate theories, each of which isn't a theory itself. What I mean is, all we have now are approximations that suggest there might be an actual theory called string theory (a.k.a. "M-Theory"), but we're too stupid to figure out the math. None of the approximations agree with each other. One of them includes gravity (it has 25 dimensions), most of the others don't (they mostly have 10 spatial dimensions). Different models (there are hundreds of thousands) can be tuned to describe different aspects of our world, but no single model does it all, and none of them predict that the world should be the way it is.

In short, from the standards that used to be applied to science, string theory is a mess. It makes no testable predictions, there is no evidence it is right, and it isn't even in a form yet where one could begin testing it anyway. So what does it have going for it? In the adjective of a popular book title, it is elegant. Well, elegant if you think heinously complicated mathematics that don't actually describe the known universe is elegant, that is. Sure, one form of it includes gravity, and that's pretty darn cool. But as Smolin details, time and time again models that seemed to unify physics have turned out to be wrong. Elegance contains no scientific weight. What else does string theory have? Boosters. It has a tight-knit group of very vocal supporters, all of whom are convinced string theory is the right answer, and all other paths of inquiry are a waste of time.

This state of affairs is the heart of The Trouble with Physics. Science is about diversity of ideas and questioning of assumptions. Smolin doesn't see this happening with string theory supporters. To hear them tell it, most of the problems are solved; it's just a matter of refining the math and finding the Holy Grail of M-Theory. However, Smolin finds that many of the claims of string theorists are just that: claims. No one has yet proven the theory is finite (it's a big deal, but complicated to explain -- by which I mean I don't really understand it), but string theorists talk about it as if the proof had already been done. No one is insisting on experimental verification, precision of mathematics, or predictive ability at all. Put simply, few of string theory's followers seem to be following the rules of science.

The rest of physics isn't in a whole lot better shape. The second half of the book begins with a review of what other theoretical physics models have been up to. The answer is: not much. Since the establishment of quantum mechanics and the standard model, there have been no major advances in theoretical physics. Lots of folks have made contributions to existing models, but nothing that has changed our view of the universe has come down the pipe. Smolin lists five major questions in physics that have been sitting unanswered for the past thirty years, and even string theory only addresses one or two of them. This is another major part of The Trouble with Physics: a de-emphasis on the big issues. In physics, doing science has become more about polishing what's known already than finding out brand new things.

So what is science? That is the topic of the last section of the book, and is why all folks who are interested in science should give this book a look. Smolin examines the pros and cons of Popperian logic, peer review, and the concept of falsification. Another problem with physics is discussed here, which is that people are discouraged from questioning the basic assumptions of what is known. If anybody wants to examine whether quantum mechanics is correct or not, they have to do it on their own time. You can't get a job (or a grant) doing it. This is the case even though some famous folks like Roger Penrose doubt that quantum mechanics is correct.

If you've read Brian Greene's The Elegant Universe and want a non-string booster summary of the field, this is the book. It is worth emphasizing that Smolin is not stating that string theory is wrong; after all, he has contributed to it himself. He is simply asking that the rules of science be applied to it more than they have. Before reading The Trouble with Physics, I had really high hopes for the Large Hadron Collider (LHC) at CERN finally proving or disproving supersymmetry, which string theory rests on. There's a particle supersymmetry calls for called the Higgs boson, which folks hope the LHC will find. However, the models that include the Higgs boson don't bother to say how heavy it is; you can tune the variables to make it however heavy you want. So if the folks at CERN don't find the Higgs particle, the string folks will just re-tune their equations to make it a really heavy particle, and say, "Well, we don't have the technology to test it yet." As Smolin points out, that's more self-fulfilling circularity than science. And that's The Trouble with Physics.