The Trouble With Physics: The Rise of String Theory, The Fall of a Science, and What Comes Next
To qualify my review a little better, before I read this book I read:
Black Holes and Baby Universes (Stephen Hawking)
The Universe in a Nutshell (Hawking)
The Grand Design (Hawking)
The Hidden Reality (Brian Greene)
The Fabric of the Cosmos (Greene)
The Elegant Universe (Greene)
Lee Smolin's style is similar to Greene's in that he describes a chronological history of the development of string theory and gives simple analogies to explain complex topics. But his analogies are simple and more brief. Of the above, I'd recommend Greene's work and then try Smolin. If you have to pick one, pick Smolin's work.
I felt fairly well-versed in string theory and its importance to modern physics. While Greene points out some of the controversial, philosophical nature of string theory both he and Hawking purport that a theory need not create falsifiable propositions in order to be a "theory." This has always been problematic for me. Smolin, who is a respected physicist himself, opens this book by asking physics has not made any progress in 25 years. Nobel prizes require verification by experiment, which is not possible with most of string theory. His concern is that string theory is being held up as truth and that physicists suspend the definition of "science." The dictionary definition of "theory" is changing in statements about it. Fewer universities are funding positions to research alternative possibilities, it's become near impossible to get a chair or your research published if it's not pushing string theory. Smolin has purportedly tried to be a bridge between the string theorists and the ever-shrinking non-stringers, but points out through various articles, blogs, message boards, and others how vitriolic the string theorists can be. String theorists seem to always look for verification from "thought leaders" and any criticism is met with hostility. Smolin points out that even Einstein was wrong about things, this is the way science works-- no one should be above inquiry.
One problem with ST is that the various theories that have spun off of it are built on more assumptions and not proof. In fact, one key assumption that string theorists held from 1984-2001--that the finiteness of the theory had been proven long ago-- was discovered by Smolin and others to be false. He contacted the physicist most often cited by researchers as having proved the point, and he admitted he'd done no such thing. That level of blind devotion is a bit concerting. Theorists are a little like economists (which I am) who fit a curve. They invent models with a large number of constants, and then tweak those constants to fit any new discoveries. This is hugely problematic as various theories are predicting things found not to hold in the rest of physics.
What use is a theory that spins off an infinite number of possible theories? It's been two decades and string theory has yet to produce any hypotheses that are testable, with current technology (In The Universe in a Nutshell Hawking writes that you need a particle collider larger than the size of the universe to prove some aspects of string theory, and that's fine with him).
Physicists have bent the rules in order to stick with ST, why don't they demand the old rules for the rest of science?
Smolin writes that they probably should have stopped when they got above 4 dimensions necessary for string theory-- instead of the 10 required. The extra six curled-up dimensions seem to be a way of "fitting the curve," so to speak. So-called "M-theory," which Greene holds up as reality, actually has no precise equations. It's very vague and imprecise and fits no definition of the word "theory."
Smolin explains the importance of the hadron collider, he wrote the book before it was finished. The first thing the collider had to show was the Higgs-Boson or else all of physics would be "in deep trouble." He lists other things that the collider would need to show and explains them well. Super-symmetry itself, hopefully to be proven by the collider, does not require string theory, there are other alternatives (which author has worked on).
He explains the evolution of string theory as the grand unifying theory and its requirements:
Requires that special relatively hold
Requires 10 dimensions "like a car with the features you want but extras you'd rather not have."
- 6 are curled up.
- Calabi-Yau shapes
Richard Feynman himself was skeptical and many physicists jumped ship at various points above. But as string theory evolved, became cult-like-- you were in or out. Researchers speak of its "elegance" and "beauty," and its supposed symmetry, which was never proven, was held up as one of its most important aspects. Smolin has serious "issues" with new string theory pushing a brane universe (he doesn't even mention the latest idea, that we're on a hologram, or Brian Greene's assertion that we're probably all just in a simulated multiverse on someone's computer).
Smolin works in quantum gravity, and points out that if dark matter or dark energy exist then string theory has problems. He takes issue with some of the original research in the 1970s on the inflationary multiverse, which Hawking and Greene basically hold up as true, because the original researcher imagined distributing the cosmological constant randomly across all possible universes while holding all else constant-- where he should have distributed all characteristics, otherwise the prediction of the constant will be even farther off. Indeed as I write this (2015), recent evidence cited to support cosmic inflation appears to be caused by cosmic dust. The media doesn't seem to cover events if they are un-discovered so much as they hype them when they are, as in this case. I found Smolin's discussion of quantum gravity fascinating. When the media reports on evidence found for dark matter they don't point out that it bodes trouble for the string theory and inflation for which they'd recently also run stories.
Smolin points out that NASA Pioneer 10 and 11 vessels travelling through space have not traveled in a trajectory that was predicted by laws of physics. However, the craft showed unanticipated acceleration, confirmed by multiple measurements. See the wikipedia on the Pioneer anomaly. This measurement confirmed by multiple instruments. Scientists had tried to control for other variables, but had no luck as of Smolin's writing in determining what is amiss. This is important because it may have something to do with quantum gravity. (According to wikipedia, scientists were confident they'd determined the source of the acceleration by 2012.)
Could there be dark matter or dark energy? Is the speed of light always constant? Again, observed data suggest that it might not be and if general relativity does not hold, every string theory falls apart. Smolin contends in a chapter on the "sociology" of the field that theorists have "groupthink," and look to thought leaders for approval. They have not abandoned their quest in the face of evidence and criticism and Smolin finds the trend toward quasi-philosophical thinking quite disturbing.
Smolin writes that quantum gravity seems to be regaining momentum. It creates falsifiable propositions and is potentially a unifying theory itself. Even so, he closes the book with a look at pioneers who have braved poverty, isolation, and losing their prestige to do their own research outside the paradigm. Some have ended up contributing greatly to the field of physics, but the free-thinkers seem to be a dying breed under the pressure of modern academia.
I should note that Smolin is no intelligent design theorist, he rejects what he sees as a false dichotomy put forth by Hawking and Susskind that one either has to believe in God or string theory. He argues that if and when string theory is finally discarded, physicists will still examine other alternatives to explain where the universe came from. In the beginning of the book, he argues about evolution with probably the worst example of supposed Christian apologists I've ever seen, such that I doubt whether they really existed (people who believed dinosaurs are all still alive hiding in African caves). He enjoys philosophy and knows enough not to engage in philosophical debate, except in showing the illogic nature of the string theorists.
I give this book 4.5 stars out of 5. I found Smolin to be concise and engaging, he comes across as a peace maker. Some of the complaining about modern academia sounds a bit like whining, but it's universal across all fields so it's not unique to Smolin. I highly recommend this book and would like to read Smolin's other works.