Physics World has published a unprecedentedly long (and mostly accessible to laypersons) article on the history, controversies and conclusions of string theory, focusing on recent debates over whether the high-profile “theory of everything” has any real-world relevance.
The conclusion? It’s really, really complicated and weird, but string theorists may be approaching the point where their abstract mathematic models could gain some experimental confirmation.
This has been an increasingly sore point in a physics world caught in a bitter rhetorical war between anti- and pro-string theorists. The nearly 40-year-old thread of abstract reasoning has resulted in visions of a universe made up of 10 or 11 dimensions, populated by multidimensional but tiny strings and “branes” (think membranes, but in two, three, or more dimensions) – but virtually none of this can be tested.
Critics have often applied a epithet coined by quantum physicist Wolfgang Pauli, calling string theory’s vision of the universe “not even wrong” – ie, it can’t pass a fundamental proviso of traditional science, calling for theories to be testable. The Physics World piece underlines just how eagerly string theorists are waiting for the Large Hadron Collider (LHC) particle accelerator in Switzerland to start operations. That facility has an outside chance of finding evidence that could be interpreted as confirming string theory predictions – tiny black holes, energy disappearing into higher dimensions, or, more likely, a menagerie of predicted particles that today remain entirely theoretical.
The piece, and its accompanying editorial has immediately and scornfully been dubbed an “advertising supplement” by Columbia physicist Peter Woit, whose “Not Even Wrong,” blog and book criticizes string theory’s claims:
I don’t know how to characterize this kind of claim that string theory is as predictive as other scientific theories, just not able to get accuracy to 10 decimal places, as anything other than out-and-out dishonesty. If someone could come up with a legitimate, distinctive, testable prediction of string theory that gave even the correct order of magnitude for some experimental result, that would be a huge breakthrough.
The magazine’s article and accompanying editorial do in fact give wide latitude to string theorists’ claims, while perhaps downplaying the fact that few think that any hard experimental confirmation from LHC is genuinely likely. But the editorial does say string proponents need to do a better job of responding to concerns like Woit’s, and most of all “need to do much more to explain their field’s genuine links to experiment.”
Researchers need to bridge a rather more gaping chasm between experiment and theory before they can verify that nature’s fundamental layer really is a cacophony of vibrating strings. Most theorists seem prepared to wait for a definitive answer as to whether string theory is a viable physical theory. “There is a story”, says Weinberg, “that when Chou En-Lai [the Chinese premier] was asked what he thought about the French Revolution, he replied that ‘It’s too soon to tell.’ I feel that way about string theory.”