Lee Smolin’s “The Trouble with Physics”

I have enjoyed this book greatly. The cover (two shoes with shoe-strings tied, together) is mean but very funny. Smolin’s simplifications of string theories convey more information than other books I have read in many years. I have learned more about string theory here than from any of several recent books on the subject — for instance that most string theories must postulate that the curled up dimensions are of constant size.

I agree with Smolin on almost all points but I find his skepticism of the Anthropic principle strained. He seems implicitly to rank ‘doing science’ above ‘being right’ when he says that believing the anthropic principle precludes doing physics. Well first of all it precludes at most doing theoretical particle physics, or only substantially decreases its priority. I was persuaded of the anthropic principle by Barrow & Tipler’s book by that name, which, I recall, did not mention string theory.

Nonetheless for the reasons that Smolin gives I agree that we should invest less in String Theory and more in other varieties of unification possibilities.

On page 216 he speaks of constants of nature changing. He notes some properties of atoms that are unit free numbers, and that they might change. I am very skeptical for the same reason people have given, somewhat humorously, for why electrons all weigh the same: there is only one of them. This is the necessary perspective when we see an electron and positron annihilate each other. (A positron is an electron traveling backwards in time.) That would be impossible if they were different from each other. If old electrons differ from new ones they must be segregated and this is impossible. If these pure numbers can depend on time, surely they can depend on space. Otherwise we must chip away at the foundations of even special relativity.

On page 243 he tells briefly of Causal Set Theory and its bare bones foundation. I would be surprised and delighted if there were another path from set theory (even with a “causes” relation) to anything like the reals. The reals are logical but already too heavy, perhaps, for physics. I have never seen anything simpler than the real line that seemed like it could model what space seems to provide.

Chris Hibbert’s review of the book is very interesting.