Strings Agonistes

Strings are king in many of the most prominent US Physics departments, but somewhat uneasy lies the head that wears the crown. The rumblings of discontent have reached the pages of The Wall Street Journal in the form of a story by Sharon Begley that relies heavily on quotes from Peter Woit of Not Even Wrong.

A letter of rejoinder from MIT string theoriest Barton Zwiebach has been posted by Lubos Motl on his blog The Reference Frame, quoted in it's entirety below:

Dear Editor:

As a string theorist and an enthusiastic daily reader of the Journal I was baffled by the gloomy assessment in "Has String Theory Tied Up Better Ideas in the Field of Physics?", of Friday June 23, 2006. In this column, science reporter Sharon Begley presents the viewpoint of those who regret the twenty-year old dominance of String Theory in the marketplace of ideas in High-Energy Physics.

The "Not Even Wrong" epithet is hurled, suggesting that string theory is a sloppy and speculative work that cannot even be judged. To the contrary, string theory is an extraordinarily precise and rigorous framework where facts can be proven beyond doubt and computations give unequivocal answers. As every theory in science, it is speculative until confirmed by experiment -- hardly a reason to single it out. The cited naysayers correctly state that string theory has a myriad solutions, each describing possible universes. From this they conclude that making predictions, or disproving the theory, is impossible. Not really. All that is needed to confirm string theory is finding one solution that describes our universe. All that is needed to rule out string theory is showing that no solution describes our universe. An answer must exist.

Rather than speculate on the ideas that might have developed in the absence of string theory, we can celebrate the remarkable insights that have emerged from it. It has explained, for example, why black holes have entropy and temperature. It has also demonstrated a surprising fact: theories of strong nuclear forces are equivalent to theories of gravity. Over the last two months, several new papers use string theory to describe the motion of quarks in the plasma created by the Relativistic Heavy Ion Collider at Brookhaven! Not bad for a theory whose critics say is pie in the sky.

As in other collective endeavors, there is a bandwagon effect and many people rushed to string theory at the early start. There have been market corrections and a healthy equilibrium exists where string theory and other good ideas are explored and compete for attention. In this competitive environment, string theory continues to hold its own and to excite physicists with its possibilities.

Barton Zwiebach

Barton Zwiebach has written A First Course in String Theory, a book that I consider to be one of the greatest physics textbooks ever. That said, I find his letter unconvincing and somewhat disingenuous. Peter Woit has a detailed deconstruction of the letter's distortions here.

Begley did say the phrase "not even wrong" meant "sloppy and speculative" but Peter has explicitly disavowed this and I don't think that's what Pauli (the originator) meant either. Peter says it just means incapable of being tested, so Zwiebach has a point there.

I just want to add two points of criticism. Zwiebach claims: ...

string theory is an extraordinarily precise and rigorous framework where facts can be proven beyond doubt and computations give unequivocal answers.

Facts, in ordinary usage and in my dictionary, are true statements about reality. Mathematical theorems don't count. Neither do unconfirmed speculations. No doubt string theory computations do give some unequivocal answers - unfortunately, the answers given are either things we already know or don't currently have the capability to test. Peter has much more to say in related veins.

Second, Zweibach defends the landscape:

The cited naysayers correctly state that string theory has a myriad solutions, each describing possible universes. From this they conclude that making predictions, or disproving the theory, is impossible. Not really. All that is needed to confirm string theory is finding one solution that describes our universe. All that is needed to rule out string theory is showing that no solution describes our universe. An answer must exist.

This is almost beyond pathetic. The same defense could be made for Intelligent Design, Ptolamaic Epicycles, and Phlogiston. A scientific theory without any predictive power is just, just, Not Even Wrong.

If string theorists are going to defend their science, they need to be thinking about how it can make contact with experiment. The ideas of people like Lisa Randall and Nima Arkani-Hamed are much more relevant to this than appeals to the dream that somewhere, among the 10^500 compactifications in the landscape, there might be a universe (or a trillion universes) that look a lot like the one we live in.