The Trouble With String Theory
It's claptrap, a new book argues.
The leading universities are dominated by hooded monks who speak in impenetrable mumbo-jumbo; insist on the existence of fantastic mystical forces, yet can produce no evidence of these forces; and enforce a rigid guild structure of beliefs in order to maintain their positions and status. The Middle Ages? No, the current situation in university physics departments. I just invented the part about the hoods.
The upper rungs of the particle-physics faculties at Princeton, Stanford, and elsewhere in the academy are today heavy with advocates of "string theory," a proposed explanation for the existence of the universe. String theory seeks to explain why, at the very minute scale, matter appears to be constructed from vibrating nothing. Smash up subatomic particles into smaller units such as quarks, and the quarks don't appear to have content—puzzling, to say the least. String theory says that these seemingly amorphous infinitesimal aspects of matter are made from other dimensions, compressed to a smallness that strains imagination. In various versions, the theory also seeks to explain how the Big Bang could have been possible, to reconcile the extremely tiny realm of quantum mechanics with the cosmic kingdom of general relativity, and to answer whether the expansion of our universe will stop or continue forever.
Important stuff! But string theory works only if you assume the existence of other dimensions—nine, 11, or 25 of them, depending on your flavor of string thinking—and there's not one shred of evidence other dimensions exist. This may render string theory highfalutin nonsense that has hijacked academic physics. Such is the thesis of The Trouble With Physics, a compelling new book by Lee Smolin, among the leading physicists of the day. Smolin's is the most important book about cosmology since Steven Weinberg's 1977 volume The First Three Minutes. If you worry that even in the 21st century, intellectual fads have as much to do with university politics and careerism as with the search for abstract truth, The Trouble With Physics is a book you absolutely must read. "String theory now has such a dominant position in the academy that it is practically career suicide for young theoretical physicists not to join the field," Smolin writes. Yet since string theory became ascendant about three decades ago, "there has not been a single genuine breakthrough in understanding of elementary particle physics." Not only is string theory rife with malarkey about imperceptible dimensions, Smolin fears, it may be holding back legitimate science.
Who is Smolin? A former physics instructor at Yale and Penn State, he now works at this new Canadian think tank, established with seed money from the entrepreneur behind the BlackBerry. About 15 years ago, Smolin's name became among the most talked-about in science, for an idea that's a cosmic version of Darwin. Modern physics is troubled by the anthropocentric character of the universe. For instance, had gravity been only a teensy bit stronger or weaker, planets and stars could not have formed. So, does the fortuitous value of gravity for planets and stars show that a higher power is manipulating physical law? Some theorists have responded to this quandary by supposing that our 60-billion-galaxy universe is but a slice of a far larger "multiverse" with a cornucopia of different realities, each operating under its own physics. By chance one section of the multiverse got physical laws that favor us, and chance was all that was involved. Smolin countered with his theory of cosmic natural selection. The theory goes like this: Black holes cause Big Bangs. Any universe whose physical laws do not result in black holes thus will hit a cosmic dead end and fail to "reproduce." The set of physical laws that result in stars and planets also results in black holes, allowing universes like ours to copy themselves. Over eons, the firmament would become dominated by universes possessing the kind of laws we observe, because universes with such laws "reproduce." Therefore it is not weird that our cosmos has stars and planets; it is exactly what we should expect.
The physics establishment reacted adversely to Smolin's cosmic natural selection because the idea implies direction: Over time, existence progresses toward a condition more to the liking of beings such as us. In recent decades it has become essential at the top of academia to posit utter meaninglessness to all aspects of physics. Multiverse thinking is as meaningless as it gets—thousands or billions of universes uninhabitable and pointless, ours just a random-chance variation signifying nothing. Smolin's idea is full of problems, including the lack of any evidence that black holes cause Big Bangs. But Smolin could hardly have failed to note that he was heckled for speculating about conditions for which there is no evidence while the entire edifice of string theory rests atop no evidence. The Trouble With Physics is his rejoinder.
String theory became a media obsession about 20 years ago, with one of its proponents a cover boy of a New York Times Magazine article proclaiming string theorists were super-ultra geniuses cracking the ultimate riddles of creation. Smolin's book suggests that this caused string theorists to believe their media hype and to speak of their concepts as if they were proven. For example, they talk of "branes" (short for membranes) of limited dimensions passing through realms of multitudinous dimensions and describe branes as actual physical regions. Yet after decades of attempts, no experiment has detected any hint of additional dimensions, branes, or other core elements of string theory. Meanwhile string theory failed to predict the biggest astrophysical discovery in decades, the 1998 finding that cosmic expansion is accelerating, apparently owing to powerful "dark energy" that nobody can explain. After dark energy was discovered, string theorists simply revised their equations to predict it. That's not science, The Trouble With Physics contends.
Maybe string theory eventually will prove out; maybe the apparent vibrating nothing on which we are based is but a slice of some far grander reality. But string theory seems to contain significant helpings of blather designed to intimidate nonscientists from questioning the budgets of physics departments and tax-funded particle accelerator labs. And consider this. Today if a professor at Princeton claims there are 11 unobservable dimensions about which he can speak with great confidence despite an utter lack of supporting evidence, that professor is praised for incredible sophistication. If another person in the same place asserted there exists one unobservable dimension, the plane of the spirit, he would be hooted down as a superstitious crank.
Really, string theory isn't a theory at all. Creationists who oppose the teaching of Darwin have taken to deriding natural selection as "just a theory," and Darwin's defenders have rightly replied that in science, "theory" does not mean idle speculation. Rather, it is an honored term for an idea that has been elaborately analyzed, has not been falsified, and has made testable predictions that have later proven to be true. 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.
Smolin concludes The Trouble With Physics with a sense of urgency. The first two-thirds of the 20th century produced fundamental breakthroughs in physics—relativity, quantum mechanics, the Standard Model of the interior forces of the atom. The final third was nowhere near as productive, while researchers repeatedly got hit over the head by the unexpected, such as dark energy. It is imperative, Smolin thinks, to stop talking sci-fi claptrap about alternate universes and get back to figuring out why our own physical world is as we observe. Perhaps Smolin is right that pure-physics breakthroughs are an imperative. Or perhaps stumbling around in the dark will be the physicist's lot for generations to come—my guess is that we know the first 1 percent of what there is to be known, and it may be centuries before we learn such things as why matter exists. If we ever know.
Gregg Easterbrook is a fellow at the Brookings Institution. His most recent book is The Progress Paradox: How Life Gets Better While People Feel Worse.
Photograph of a ball of string on Slate's home page by Ryan McVay/Photodisc Blue.