## Thursday, June 29, 2006 ... //

### Barton Zwiebach: a letter to the editor

By Prof. Barton Zwiebach, MIT

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
Professor of Physics
Massachusetts Institute of Technology
Cambridge, MA 02139

Prof. Zwiebach is the author of the famous textbook "A first course in string theory" based on his award-winning MIT undergraduate course, and a world's leader in string field theory.