Back in 1996 John Horgan’s The End of Science appeared, which included material from a fascinating 1991 interview of Edward Witten. I had mixed feelings when reading this. On the one hand, Horgan was doing something truly remarkable, challenging Witten in a way that no one else dared. This was 7 years after the “First Superstring Revolution”, and it was starting to become clear that string theory was not working out as hoped. No journalist other than Horgan though was talking about this, or willing to confront someone of Witten’s stature with difficult questions. Pretty much every other story in the press stuck to the simple narrative that Witten was a genius, and superstring theory a great success. On the other hand, Horgan did use his author’s freedom to edit and frame the interview to make Witten look bad (today he admits the Witten profile was “pretty snarky”), so he was landing some low blows, against a rather gracious opponent.
This year Witten won the Kyoto Prize, and I was shocked to hear that Horgan was the person chosen to interview him. Witten rarely gives interviews and I would have thought that Horgan would be the last person in the world he’d agree to an interview with, given his past experience. The interview is now available here.
This time around Horgan avoids the snark, and asks some straightforward questions about whether Witten’s views have changed since 1991, and what he now thinks about string theory, the multiverse, anthropics, etc. I have to admit that I find Witten’s answers depressing, in contrast to Witten’s advisor David Gross’s current take on these issues (discussed here). About anthropics, Witten’s “I don’t like it, but may be the way to go” contrasts with Gross’s “cop-out”, and his insistence on string theory as the way forward contrasts to Gross’s emphasis on the fertility of quantum field theory.
Back in 1996, after the appearance of Horgan’s book, Gross and Witten wrote in to the Wall Street Journal (reproduced here) to argue that Horgan was wrong, since string theory would be tested by finding SUSY at the Tevatron, or, failing that, definitely at the LHC. We all know how well that has worked out, and Gross seems to have learned a lesson from this. Witten on the other hand has moved on to even more dubious testability claims (e.g. that the string theory landscape can be tested by “seeing a signature of a prior phase transition in the CMB”). From the 1996 claim that vindication would come “in the next decade”, he now is talking about “200 years from now”. His one point of close agreement with Gross is that both agree that not knowing what string theory is when time-dependent effects are large is a big problem, one that has seen no progress.
By a couple years from now, the idea of making progress in our lifetime by seeing SUSY at the LHC, then going on to use this to learn about string theory should be finally finished off. Already Gross seems to have evolved from the 1991 point of view to a more promising one, perhaps Witten at some point will start to do the same.
Update: The AMS has something similar, a Mathematical Moment with Witten. Pretty much everything said about string theory is exactly the same as thirty years ago, only change is that the story used to be that string theory would get some vindication at the LHC, now it’s:
The verification of superstring theory is probably a long way off, but could be found here on Earth, using particle accelerators (possibly much more powerful than those of today)
consistent with the “200 years” estimate from the Horgan interview.
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