Greene may be treated as a kind of New Age, scientific guru by the public, but scientists disagree about the significance of his scholarly work. Each time Greene is featured or reviewed on television or in a magazine, one of string theory's aged, cranky critics is trotted out to offer harsh assessments. (These seem to have had no impact on the public's fascination.) In the NOVA special, Nobel laureate Sheldon Glashow drove home the obvious but downplayed fact that string theory has not been—and may never be—experimentally verified, and that it may be more philosophy than physics. More recently, in the New York Review of Books, Freeman Dyson, an octogenarian and self-proclaimed "old conservative, out of touch with the new ideas," suggested that string theory may simply be one of history's "fashionable" ideas, the kind that flourish briefly, then forever fade away. Glashow and Dyson raise important points. But in the eyes of a captivated public, such reservations appear to be little more than theoretical technicalities.
First, a quick bit of background: String theory—and superstring/M theory, a variant—both propose a scheme that encompasses two major and previously incompatible scientific frameworks, general relativity and quantum mechanics. General relativity describes gravity in terms of the curvature of space-time by matter/energy and successfully quantifies the very large. Quantum mechanics, on the other hand, explains the behavior of atoms and subatomic particles, characterizing the very small. String theory seeks to unify the mathematics of these colliding theories by positing that all matter and all fundamental forces can be described in terms of the vibrations of tiny, one-dimensional strings. (Mathematically, the theory also requires the existence of multiple, extra dimensions, said to be "curled-up" and as such beyond the realm of our sensory experience.) Greene likens the wiggling strands of string theory to the strings of musical instruments. In his telling, not only do different patterns of vibration produce different particles, but the whole universe is "akin to a string symphony vibrating matter into existence."
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Greene will go to nearly any metaphorical lengths to elucidate complex physics. To guide his readers through key concepts, he concocts elaborate scenarios often characterized by cute and slightly corny imagery. (Indeed, his writing is characterized by the rhetoric of self-help literature.) At one point, for instance, he asks us to imagine we've had a bad day—our favorite team lost, our birthday was forgotten, the "last chunk of Velveeta" was eaten by someone else—and tells us to imagine that we then take a boat out on a lake, where "beautiful moonlight reflections dance" on the water's surface. In his eagerness to prod our imaginations—and to make the science non-threatening—Greene indulges in a pandering sort of lyricism. Compared even to other pop-star scientists eager to draw a broad audience, like Stephen Jay Gould and Richard Feynman before him, he seems to work unusually hard to keep the general reader reading.
True, Greene's technical explanations are often effective. Yet the strain of romanticism that emerges—and ultimately becomes inextricable from the discussion of string theory—necessarily raises questions. Greene plays fast and loose with terms like beauty and elegance, using them in a semiclassical, semiromantic sense, with little distinction between equations and the "reality" they may represent.
In Greene's view, an equation that funnels vast complexity into a simple, logical formulation is elegant; a universe that conforms to such an equation is elegant and therefore beautiful as well. In essence, he follows in the tradition of Einstein, who famously said, "Make everything as simple as possible, but no simpler." Greene himself is even more explicit: "The tantalizing discomfort of perplexity is what inspires otherwise ordinary men and women to extraordinary feats of ingenuity and creativity; nothing quite focuses the mind like dissonant details awaiting harmonious resolution." Greene treats scientific work as a kind of poetic quest, and beauty as crucial evidence of truth. As he makes the case for string theory, we can almost hear Keats in the background whispering "beauty is truth, truth beauty."
This approach is not risk-free. Although many features of the physical world do conform to simple equations, there is no guarantee that the unknown will be "elegant" as well. That is to say, research may be prejudiced by aesthetic considerations, and as a result, we may miss out on truths that turn out to be messy and inelegant. Some, including Glashow, worry that many talented young physicists are drawn to the hip realm of string theory and pay virtually no attention to experimental work: "What we do is not of any direct interest to them," Glashow told NOVA. (Dyson goes so far as to say that quantum mechanics and relativity need not be reconciled at all, though he is clearly in the minority here; most physicists would agree that some theory capable of bridging general relativity and quantum mechanics would eventually be needed for a full understanding of black holes, for instance, or of the Big Bang.)
Greene's unifying impulse also informs his reading of history in ways that would not please a historian of science. His tale is an end-oriented one, a story of increasing progress, synthesis, and unity: "The explanatory arrow seems to be converging on a powerful, yet-to-be discovered framework that would unify all of nature's forces and all of matter within a single theory capable of describing all physical phenomena." Is this where physics has been headed all along? Or are string theorists indulging in a bit of "hubris," as Glashow and other critics contend? Greene's work is seductive in part because it puts forth the notion that we occupy a special place in the history of ideas; we are on the verge of an ultimate discovery, an idea to end all ideas. This is a dazzling vision—but it is also, statistically speaking, unlikely.
One alternative, usefully laid out by Dyson in the NYRB, is that the history of contemporary physics is propelled by cycles of revolutionary and conservative thinkers—"those who build grand castles in the air and those who prefer to lay one brick at a time on solid ground." In Dyson's schema, revolutionaries like Werner Heisenberg, Erwin Schrodinger, and Einstein were succeeded by conservatives like Richard Feynman and Dyson himself, who work out crucial details without overturning frameworks wholesale. Nicely implicit in Dyson's formulation is the idea that there is no end to science; there are moments of revolutionary change, but the process side steps, back steps, and repeats—and will continue to do so.
So what does it say about the cross-talk between science and popular culture that Brian Greene is a celebrity and Freeman Dyson is not? First, the particular state of physics today allows for the expansiveness and wonder championed by Greene: String theory has not been proved right, but it hasn't been proved wrong, either. In fact, given its unprovability, it might be "permanently safe" (Glashow again) from meaningful refutation. Thus it serves as a perfect canvas on which idealism, optimism, and romanticism can be easily projected. Greene himself confides that scientific research has made him "feel a closer connection to the cosmos; I've found that you can come to know the universe not only by resolving its mysteries, but also by immersing yourself within them." It's easy to see, then, why those inclined toward New Age thinking, or who search for spiritual significance in the material world, would find Greene highly attractive; Deepak Chopra would love Brian Greene (though the reverse is probably not true). The very qualities that make fellow scientists skeptical—the obsession with elegance, the quasi-spiritual shtick—are precisely what dazzle a public hungry for meaning.
Amanda Schaffer is a science writer living in Brooklyn, New York
The Fabric of the CosmosAs it happens, I'm about two thirds of the way through this book (one of my sons gave it to me for Father's Day).
I've just gotten to the M-theory part, so I don't have any comments about that as yet, but I was surprised by his description of what he calls the "Higgs Ocean." This is similar to the old idea of the "aether," but doesn't serve as a medium for light waves -- rather, it seems to embody the concept of inertia by resisting acceleration.
In short, he says that whenever something accelerates, the Higgs Ocean (or Higgs Field) resists that acceleration, and the resistance is proportional to the mass of that being accelerated. It doesn't resist constant motion, and it doesn't resist massless particles.
I can't remember ever seeing this particular concept before. Have you? Anyone?