The Trouble With Physics
The Rise of String Theory, the Fall of a Science,
and What Comes Next
Houghton Mifflin: 392 pp., $26
IN physics, truth and beauty often walk hand in hand. Physicists describe theories as “ugly” or “beautiful,” talk about ideas that “smell” or “feel” right. Often, aesthetic judgments lead to discoveries: as in Einstein’s theory of gravity and Paul A.M. Dirac’s discovery of antimatter. Aesthetics, French physicist Henri Poincare said, is a “delicate sieve” that sorts the true from the misleading. Or as Dirac famously put it: “It is more important to have beauty in one’s equations than to have them fit experiment.”
To mathematician Peter Woit and physicist Lee Smolin, however, the search for beauty is ruining physics. Their ire is directed at “string theory,” a magnet for physicists because it is so, well, beautiful, and has such great promise for solving what may be the central mystery of the universe -- the incompatibility between the two grand laws that describe everything we know.
Quantum theory -- which explains the subatomic world with exquisite precision -- reveals that at close range, matter, energy and motion are a choppy mosaic of jittery bits. Think pointillist painter Georges Seurat on a triple espresso. Einstein’s theory of gravity, which describes the large-scale cosmos with exquisite precision, tells us that space and time are woven into a smooth, seamless surface that warps under the influence of massive objects -- a universe painted by Salvador Dali. Where the two realms meet, the quantum jitters shatter the glassy surface of space-time like a child cannonballing into a pool.
String theory is the first approach that seems to bring the two together naturally, and such unification of opposites, like electricity and magnetism, has driven physics for more than a century. Simply put, string theory does this by replacing point-like particles with tiny strings of some fundamental stuff vibrating in 10-dimensional space -- their harmonies creating everything from quarks to galaxies. The loops of string don’t let anything get small enough to let quantum fidgeting rip space and time apart.
String theory has its troubles, which the authors analyze in great and sometimes lucid detail: It appears to be untestable because the strings are too small to be seen, and recent research suggests that the theory may have an infinite number of solutions, so it can’t make predictions. And string theory is so ill-defined that even ardent supporters admit they don’t know what, exactly, it is. This is why Woit calls the theory, and his new book, “not even wrong,” a play on a put-down by the late physicist Wolfgang Pauli.
These issues are well worth addressing, which makes it all the more disappointing that Woit, and Smolin in “The Trouble With Physics,” write mostly about how string theory has ruined their careers -- and physics as well. It has “choked off” investigation of “equally promising approaches,” Smolin says. It is a “cult” in which “believers don’t care about evidence.” Physicists who don’t work in string theory are rejected and shunned. “The ability to do mathematically clever work ... [is] valued over the possession of original ideas,” he complains. As for beauty, he writes that “elegance” is irrelevant, and “more sober minds” should insist on “a connection to reality.”
Although Smolin’s book is fairer and far more readable, both suffer from an overflow of jargon. And their language is telling: String theory is described as a “fad,” “fashion” or “trend,” its culture as “brash, aggressive, and competitive.” String theorists “swagger.” References to Smolin’s kind of physics, on the contrary, are accompanied by words such as “deep” and “thoughtful.”
Smolin is a respected physicist, having earned a PhD at Harvard University and written several delightful popular books, including “The Life of the Cosmos” and “Three Roads to Quantum Gravity.” He helped found the Perimeter Institute in Waterloo, Canada, as well as a perhaps promising theory called “quantum loop gravity.” He’s also a former string theorist, so his book is well-informed.
Woit is a different story. As a postdoctoral fellow at State University of New York at Stony Brook, he couldn’t find another position because, he says, he wasn’t working on string theory. Woit then moved to Harvard, where the physics department “let me use a desk as an unpaid visitor.” He’s now a math lecturer at Columbia University.
The authors are right to say that physicists can get cliquish; that some of them swagger; that they frequently fool themselves and that science has become too risk-averse. On the other hand, dozens of astrophysicists, cosmologists, relativists and people who study fundamental particles and interactions in ways not related to string theory do quite nicely; some even dip into theory now and then. In fact, many highly esteemed physicists who formerly disdained string theory (Nobel laureates Steven Weinberg and Murray Gell-Mann among them) have become fans.
So it’s hard to believe, as both authors charge, that physicists have been led like sheep to pursue a “failed theory,” mostly by Edward Witten, now at the Institute for Advanced Study in Princeton and generally acknowledged genius -- and also a nice guy. (In addition to his multiple prizes in physics, Witten also won the Fields Medal -- the “Nobel Prize” of mathematics.)
True, Witten is highly influential. But it’s hard to imagine him ruining an entire generation of physicists. They are not, in general, followers; getting them to agree on anything is like herding cats. They love nothing better than to prove each other wrong.
The claim that string theory can’t be tested is serious; experiment is the ultimate arbiter of truth. But it’s impossible to know what is ultimately testable. When the ghostly neutrino popped up in one of Pauli’s equations, the physicist admitted he’d done “a terrible thing. I have postulated a particle that cannot be detected.” Then in 1956, traces of neutrinos were seen in the wash of radiation spewing from newly commissioned nuclear reactors.
As for Woit’s claim that string theory has “absolutely zero connection with experiment,” experiments already planned for a new European particle accelerator will look for the existence of extra dimensions and extra families of particles -- both predicted by string theory. In fact, many statements about string theory in these books are plain wrong. To say, as Smolin does, that string theorists are not trying to figure out how space and time came into being will surprise the dozens who do just that. To say, as Woit does, that fundamental mysteries about neutrinos are being ignored will come as news to the dozens of physicists who’ve been working on these problems for years.
So what good, ultimately, is beauty? As the late physicist Victor Weisskopf said, “What’s beautiful in science is that same thing that’s beautiful in Beethoven. There’s a fog of events, and suddenly you see a connection.”
Neither Woit nor Smolin sees the beauty in string theory. But perhaps they haven’t spent enough time in the fog. Theories often seem impenetrable at the time they are being discovered -- and clear and simple (and beautiful) only in retrospect. One of the strangest charges against Witten is that he’s often openly muddled. Asked his opinion about a recent turn in string theory, he answered: “I just don’t have anything incisive to say. I hope we will learn more.” Smolin interprets this as Witten being “stumped.” Perhaps it’s a sign that he’s thinking.
In the end, Smolin admits that he hasn’t managed to do much better than string theorists, and his book is “a form of procrastination.” One hopes he will soon dive back into the fog and start making connections.