The Trouble With Physics

A couple of weeks ago I was sent a review copy and probably the only copy of The Trouble with Physics by Lee Smolin, in China. For those who don't know, this is one of two books recently released which some members of the media and blogosphere have picked up on and claimed as some sort of death knell for string theory. Peter Woit's book I can't comment on but having read the hype and occasional bitter comment about Smolin's book I was pleasantly surprised by the content.

Firstly, it's a well written account which is clearly a personal viewpoint on a controversial issue. The fact that Smolin makes it clear throughout that these are his views is an important one. He also points out that his aim isn't to stop all research into string theory but to allow more ideas which aren't string theory into the picture. Clearly there's a bias in everything which is said but that's because Smolin is a human being and will be affected by his personal experiences as well as his belief in what is real science. As has been stated many times all over the blogosphere and should be noted immediately is that string theorists will stop working on the theory when one of them, or someone else comes up with a promising alternative. Smolin's point is that the current socio-political structure of science is not conducive to such alternatives.

The book starts with a history of unification in physics showing that every revolution has been due to taking two, seemingly unrelated ideas and showing that they are really one. He follows this with a list of some of the remaining questions which we may need to answer in order to 'understand' the universe. This is a preemptive list which, having explained string theory in a concise but clear way, he goes on to explain how he feels that string theory has failed on most of these points. His problems with string theory are clear and although I agree with some of his comments, many I'm not convinced about. Unsurprisingly, as a physicist working in the domain of background independent theories, the fact that string theory is currently a background dependent formulation doesn't get his vote of confidence. So, here's a physicist who doesn't agree with string theory (in its current form) - big deal thus far!

One of his concerns is that the theory hasn't been "solved" yet. Indeed it has been stated many times by people both inside and outside string theory that we don't really know what string theory is yet. His point is that we've been working on this for over 20 years and we don't seem to have answered many of the fundamental questions which are quickly raised.

My personal feelings on this subject are that any truly fundamental theory which contains both QM and GR (or something like them as Smolin would like to believe) is going to be far more mathematically rich than theories which have been developed previously. The idea of understanding the structure of highly curved space-times requires us to go beyond what we can conceive by several orders of magnitude. Such a vast increase in complexity, even if it does come in the form of an 'elegant' theory is surely something which will also take us much longer to understand. If we come to the point where string theory is no longer progressing I can see this as a much stronger criticism but since the second superstring revolution there has been major progress in many areas.

KKLT type approaches and the landscape usher in a new kind of science whereby the theory may in many ways be far less predictive than previously thought (predictive in terms of the constants of the standard model), however, Smolin argues that this work has its origins in simplifications and unknown assumptions. If this is the case then surely this is a prime area to be studied in more detail in order to really understand what the landscape means. Secondly the idea that if the landscape is truly a result of string theory then just because we don't like it we should throw it, and the rest of string theory away seems ludicrous.

At this year's Strings conference there were talks on brane-induced inflation (KKLMMT) which offered falsifiable predictions. This will not falsify string theory if the signatures aren't found but if they are then it's certainly compelling evidence. You can read my former posts on the talks from the string theory conference as to what other progress has been made in the last year.

I think that it's also important to note that the claims that string theorists aren't concerned with experimental particle physics (something which Smolin admits is a generalisation) should be contrasted with the fact that a call was made at this years conference for people to get involved more and more in the LHC. This order from the more senior ranks is an encouraging sign which I hope will make more string theorists aware of what is going on in the wider community. At TASI 2005 a significant number of lectures were dedicated to collider physics, the supersymmetric standard model and calculations of multigluon amplitudes from twistor theory.

So, Smolin criticises string theory though I don't feel that he rubbishes it - he claims that he doesn't think everyone should stop string theory and start something new. I think that it's vital for people to raise questions about a topic which has such a proud community. From my perspective, string theory is an exciting, promising theory but it's healthy to be accountable. I think that currently it has a strong argument for many people to be researching it.

He talks in detail about this community and talks about its structure and politics, and the fact that very often directions of research are dictated strongly from the top and that people who want to work in other areas may find it harder to get positions at the end of it.He also points out the two of the greatest steps forward in the last ten years have come form two young researchers, Bousso and Maldacena. I don't know what sort of pressure was laid on them to work in particular directions but clearly there is room in the community for exceptional people to make breakthroughs. As I'm somewhat detached from the bulk of the community of which he speaks, I don't know how much dictation there really is from these 'higher authorities'. Having spoken to many young US researchers at TASI, they all seemed to have ideas and directions of their own.

He speaks briefly about the concept of groupthink, though he quickly acknowledges that this is a simplification. Any social commentary is going to be up for criticism simply because such self-examination will have biases due to very many factors. I feel that with all of Smolin's book, as long as one acknowledges that this is the view of one man, be it a man who has been on both the inside and outside of the community, and not a sudden realisation of the particle physics community that it has completely failed itself, that this book has some interesting messages. Whether or not you believe Smolin's particular ideas about quantum gravity, evolving universes or the foundations of quantum mechanics, my own opinion is that it is clearly vital to have some new and perhaps radical ideas thrown around, and not just by the 'outcasts' who come up with them. Unless the community accepts and rationally discusses the views of outsiders and alternative insiders the chances of breakthroughs from surprising directions will surely be less likely. The contrast in the book between craftsmen and seers is a nice one and the handwaving budget estimates whereby a larger percentage of more unusual ideas are allowed on the table is a low risk, high yield exercise.

From my own point of view as one who straddles the boarders of the string theory landscape and QCD phenomenology I feel somewhat distanced from the core of the community (also because of my geographical location). The subject I work on is one that seems to be progressing year on year and for this reason I don't feel any hesitation in continuing this line of work. I feel I can make genuine steps towards a goal that is easily stated.

Just as Smolin intimates, there are more foundational questions which I would love to delve into and play with but the current pressure to publish papers in areas in which you will be noticed and the competition for the next position simply doesn't allow the time or freedom to do this.

This is a book written by a scientist about a subject from which he appears to have been excluded, initially by himself and then the community (by some but not all). This makes an unbiased view of the current climate difficult but I think that Smolin has done a good job given the pressures. This doesn't mean that I agree with everything he says but there are bits in the book which are genuinely inspiring. I doubt that this book will change the politics of peer review or even the decision of a recent graduate to go into string theory or not, but I think that an opinionated view of the current situation must be a healthy thing for the community (not just of string theorists) to take into account. If the string theorists can't take criticism then there is clearly something deeply worrying. There is a flip-side to this argument which says that the string theorists have answered these questions before and this is just another embittered outsider trying to rock the boat. Being outside the US means that I just don't know the answer to this question but my feeling is that within this book are a number of important issues which should be addressed.

Don't take my word for it, have a read but for those outside the scientific community I think that it is important to take into account the personal situation from which Smolin argues. All in all a worthwhile read.