Last time I visited New York was this summer and I had the pleasure of lunch with my old advisor. He thinks that string theory is a dead end, and I have to agree with him. Physics is entering a new era. My advisor would cringe at the company his opinion keeps, but Robert Laughlin A Different Universe (which I discussed here) agrees. Laughlin sees the the future of physics in emergence (as opposed to the reductionism of which string theory is a grand culmination).
A couple of items have surfaced that similarly question the future path of physics. First, John Horgan, in his review of Lee Smolin's book The Trouble With Physics: The Rise of String Theory, the Fall of a Science, and What Comes Next, writes about how the great promise string theory showed in 1990's has been achieved only frustration:
Smolin pleads with his colleagues to explore alternative theories of everything, including twistor space theory, an invention of British physicist Roger Penrose; doubly special relativity, proposed by Portuguese theorist Joäo Magueijo; and loop quantum gravity theory, to which Smolin has contributed. Acknowledging that "no idea yet has that absolute ring of truth," Smolin also calls for "a radical rethinking of our basic ideas about space, time and the quantum world."
Horgan disagrees with Smolin and thinks that money, not a new mindset, is the key to the future of physics:
Although I admire the authority and passion of Smolin's diagnosis, I disagree with his prescription. What physics desperately needs is not new ideas but hard experimental data that can test ideas or inspire new ones. But these data are costly. [etc. etc.]
Secondly, Burton Richter, former director of SLAC, writes the "Reference Frame" piece in the current Physics Today:
Richter bemoans string theory as more akin to theology than science (and he uses theology in the most pejorative sense). He especially laments Leonard Susskind's "Cosmic Landscape" of unlimited universes that sample the parameter space of all cosmic constants (review forthcoming). Richter, like Horgan, sees experiment as the ultimate way to salvation.
My prognosis for today's physics is even more dire: we are due for a larger shift than Smolin hopes for, an even more radical break than Laughlin heralds: reductionism has played itself out, but it's not emergence per se that will rule. Instead physics will have to go back to its conceptual roots to a rediscover nature as an organizing principle, of matter as possessing inherent purposes. As I've written before, teleology compliments other modes of explanation.
The shift in mindset with be tectonic. The reigning paradigm has made progress by ignoring purpose in nature, thereby blinding itself to the major component of the natural order that it seeks to describe. The program has been a great success: we've certainly managed to circumscribe the physical world of ordinary experience... and much beyond ordinary experience. But the overwhelming mathematicization of this description keeps it from being hinged on the ordinary human experience that forms the basis of human meaning.
The new physics will open man's second eye and discover a whole new dimension to the world. Experiment will necessarily play a role, but the new mindset will lead in new, more quotidian directions (directions that will be much less costly than multi-billion-dollar particle accelerators). We might actually have to open our eyes to the world around us.
The revolution will not happen overnight. The programs of renewal for which Horgan, Smolin, and Richter hope may first come and go. It may be decades before the new physics can stand on its own.
But it is coming.
Burton Richter, "Theory in particle physics: Theological speculation versus practical knowledge," Physics Today (October 2006), 8.