Since the 1980s, string theory has emerged as the leading candidate for achieving every physicist’s dream: reconciling general relativity with quantum mechanics and thereby finding a tidy explanation for all of nature’s forces — a so-called Theory of Everything. One problem: String theory has yet to be verified.
Two new books have cast a hot, critical light on the validity of string theory. Lee Smolin and Peter Woit both argue that string theorists have never generated any empirical evidence verified by expeimentation. Furthermore, Smolin and Woit lament that the dominance of string theory in physics departments has led to intellectual stagnation, stifling progress in other research areas. Not surprisingly, string-theory advocates have been busy rebutting this tide of anti-string sentiment.
THE CRITICS
Lee Smolin, founding member, Perimeter Institute for Theoretical Physics: “Because string theory is such a high-risk venture — unsupported by experiment, though very generously supported by the academic and scientific communities — there are only two ways the story can end. If string theory turns out to be right, string theorists will turn out to be the greatest heroes in the history of science. On the basis of a handful of clues — none of which has an unambiguous reading — they will have discovered that reality is far more vast than previously imagined. ... On the other hand, if string theorists are wrong, they can’t be just a little wrong. If the new dimensions and symmetries do not exist, then we will count string theorists among science’s greatest failures, like those who continued to work on Ptolemaic epicycles while Kepler and Galileo forged ahead. Theirs will be a cautionary tale of how not to do science, how not to let theoretical conjecture get so far beyond the limits of what can rationally be argued that one starts engaging in fantasy.” (The Trouble With Physics: The Rise of String Theory, the Fall of a Science, and What Comes Next)
Peter Woit, lecturer in mathematics, Columbia University: “The failure of the superstring-theory program must be recognized and lessons learned from this failure before there can be much hope of moving forward. As long as the leadership of the particle-theory community refuses to face up to what has happened and continues to train young theorists to work on a failed project, there is little likelihood of new ideas finding fertile ground in which to grow. Without a dramatic change in the way theorists choose what topics to address, they will continue to be as unproductive as they have been for two decades, waiting for some new experimental result finally to arrive.” (Not Even Wrong: The Failure of String Theory and the Search for Unity in Physical Law)
REACTIONS
Tom Siegfried, science writer: “If the final form of string theory does not yet exist, it’s strange to claim in advance that it can make no predictions. And why the 20-year time limit? Science must be testable in principle, but that is not necessarily the same thing as testable in practice, given current technological limitations. Smolin contends that previous great theories have been rapidly supported by favorable evidence, but evidence is not the same thing as the definitive proof he seems to demand from string theory. It is not uncommon for decades to go by before theories in physics are decisively confirmed. In some cases, such as the atomic theory, it has taken centuries.” (The New York Times Book Review)
Gregg Easterbrook, visiting fellow, the Brookings Institution: “The ordering of scientific notions is: conjecture, hypothesis, theory. Pope John Paul II chose his words carefully when in 1996 he called evolution ‘more than a hypothesis.’ Yet the very sorts of elite-institution academics who snigger at creationists for revealing their ignorance of scientific terminology by calling evolution ‘just a theory’ nonetheless uniformly say ‘string theory.’ Since what they’re talking about is strictly a thought experiment (just try proving there are no other dimensions), from now on, ‘string conjecture,’ please.” (Slate)
Sean Carroll, senior research associate in physics, California Institute of Technology: “The reason why string theory is so popular in physics departments is because, in the considered judgment of a large number of smart people, it is the most promising route to quantizing gravity and moving physics beyond the Standard Model. ... When you get right down to it, people like string theory for intellectual reasons, not socio-psycho-political ones. It’s not a Vast String Theory Conspiracy, funded by shadowy billionaires who funnel money through Princeton and Santa Barbara to brainwash naïve onlookers into believing the hype. It’s trained experts who think that this is the best way to go, based on the results they have seen thus far.” (Cosmic Variance)
Jim Holt, science writer: “‘How strange it would be if the final theory were to be discovered in our own lifetimes!’ Steven Weinberg wrote some years ago, adding that such a discovery would mark the sharpest discontinuity in intellectual history since the beginning of modern science, in the 17th century. Of course, it is possible that a final theory will never be found, that neither string theory nor any of the alternatives mentioned by Smolin and Woit will come to anything. Perhaps the most fundamental truth about nature is simply beyond the human intellect, the way that quantum mechanics is beyond the intellect of a dog. Or perhaps, as Karl Popper believed, there will prove to be no end to the succession of deeper and deeper theories. And, even if a final theory is found, it will leave the questions about nature that most concern us — how the brain gives rise to consciousness, how we are constituted by our genes — untouched. Theoretical physics will be finished, but the rest of science will hardly notice.” (The New Yorker)
SOURCES CITED IN THIS COLUMN
Cosmic Variance
The New York Times Book Review
The New Yorker
Not Even Wrong: The Failure of String Theory and the Search for Unity in Physical Law, by Peter Woit (Basic Books)
Slate
The Trouble With Physics: The Rise of String Theory, the Fall of a Science, and What Comes Next, by Lee Smolin (Houghton Miflin)
http://chronicle.com Section: The Chronicle Review Volume 53, Issue 8, Page B4