This book is not a critique of string theory, and it is not a condemnation of string theorists. He makes this clear at several points throughout the book, but the amount of time he spends criticizing string theory has led some people to believe that this book is an "anti" book to balance the spate of "pro" string theory books. In reality, this is a book about science and the nature of science. This is clear in the acknowledgments, where Smolin describes how he originally wanted to write a book on the relationship of democracy and science and settled on applying this thesis in a particular situation- that of string theory. The book is absolutely fascinating the whole way through. Along the way, one gets lessons in physics without the advanced mathematics- but one can feel Smolin's passion for both. Quantum theory and the nature of quantum theory is explained well, and the underlying principles which appear to contradict relativity are illumined clearly.
What really makes this book, though, is Smolin's own deep understanding of scientific reasoning, both in its strengths and weaknesses. Smolin reveals to us a world far more open than we had ever imagined- he describes a great variety of solutions to the problem of quantum gravity, including his own personal favorite, quantum loop gravity. He describes the way that science changed in between Einstein and the present. In the early days of 20th century physics, the great physicists- Einstein, Bohr, Heisenberg- also had astute philosophical minds, and their trade was deep reflection on the underlying nature of reality. Physics served that greater project. After this period, however, physics entered into a more pragmatic stage, where the emphasis lay in ensuring that the equations worked out. Smolin makes clear that he is not criticizing this mode- indeed, he says that such pragmatism is needed in some periods. It produced the extremely successful standard model of particle physics. But we have now moved past such a need. For issues like quantum gravity, we need philosophical minds like Einstein and Bohr to fundamentally consider the nature of reality.
In the midst of all this, Smolin describes the rise of string theory- a potentially promising unification of the forces and particles which sees all of them as manifestations of vibrating strings. The problem with string theory is that what it does predict- supersymmetry, eleven dimensions, and so on- have no evidence. The other problem is that besides this, it doesn't make predictions. There are so many solutions to the equations of string theory that one can adjust the freely varying constants to save the theory from falsification. Smolin points to earlier theories in physics which suffered the same problems- most interestingly, the Kaluza-Klein model of electromagnetism, a mathematically beautiful theory which posited that just as gravitation described the four dimensions of spacetime, electromagnetism described a curled up fifth dimension. The difficulty with these concepts is that relativity is background independent. Instead of moving against a fixed spatial background, gravity describes the warps and curves of the space itself. The Kaluza-Klein model and string theory is background dependent- that is, in trying to reconcile relativity with quantum theory, it fails to integrate the most fundamental insight of the former.
Smolin argues that the funding going to string theory is taking away from other creative thinkers, and in exploring why, he refers to the philosopher of science Paul Feyerabend, who argued in "Against Method" that there wasn't a fixed scientific method. Instead, he proposed that science develops through "scientific anarchy" where different scientists pursue their hunches for different reasons. Smolin uses this to encourage reform of the tenure and peer-review system, which has benefits, but which is presently discouraging innovation. If one needs to be cited as much as possible in order to acquire tenure, then one won't work in a new, upstart project with only a few people working with you- because others who are uninterested won't cite you. Smolin is one of the few scientists who has a real, and not merely nominal, respect for philosophy and the philosophy of science. This is very refreshing.
One point was rather odd, however, and led me to roll my eyes several times. In various places throughout the book, Smolin will take a shot at intelligent design, using it as an example of "bad science." He doesn't critique it, but merely mentions it in passing. But the critique that Smolin levels at the scientific industry is exactly that which proponents of ID have leveled. Everything he said could be quoted verbatim by them. And shouldn't Feyerabend's principle of scientific anarchy allow proponents of ID to develop their research program in peace? This is the logical conclusion of everything that Smolin has argued, and the ritual denunciation of ID was irritating.
Regardless, this is a wonderful book, and I commend it to anybody who wants to understand physics, or science itself, more deeply.
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