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Brain Worlds

Photo by Markus Schreiber/AP

STEPHEN Hawking’s voice drifts through the air, eerily familiar. These are the synthesized vocal cords that attempted to explain to Homer Simpson the nature of space and time, that joshed on the Star Trek holodeck with Newton and Einstein. Along with the latter’s shock of hair, Hawking’s computerized tones have come to symbolize the ideal of Genius writ large. Yet the source of these sounds seems impossibly small and fragile in the flesh. Bunched in his wheelchair at the front of the room, Hawking is a man in miniature, his doll-like body in hapless contrast to the gargantuan brain it supports.

At the world’s first “string cosmology” conference, held recently at UC Santa Barbara, Hawking was expounding on his latest ideas about the creation of the universe. It’s a subject he famously catapulted to the center stage of physics with his proof that space and time must have begun with a singularity, a cosmic-scale version of a black hole. That work was the subject of his Ph.D. thesis, and it built upon Einstein’s theory of relativity to demonstrate that any viable universe had to have been born from a single, infinitely intense point — a kind of cosmological seed. Hawking had come to Santa Barbara to revise himself, presenting to an audience of fellow physicists a new model of cosmic genesis which, as he explained, describes “a universe that expands, contracts, bounces and expands again.”

Up close Hawking looks like an imp, an escapee from Lord of the Rings. His delicate features are preternaturally enhanced by four decades of living with Lou Gehrig’s disease. Since I first interviewed him 18 years ago, he has visibly shrunk, but at this point it is a medical miracle he is alive at all. It’s his eyes that demand your attention, as if the life force withdrawn from his body has concentrated in his orbs. They don’t just twinkle, they radiate light. Though he can barely move anymore and must now be attended by a small army of nurses, when he nods assent to a question, one senses the power of a still-extraordinary mind at work. This combination of gymnastic intelligence and immobile body creates a profound sense of otherness — Hawking is as close to an alien among us as Mr. Spock, and every bit as enigmatic.

While he still believes in an original beginning, Hawking suggests that since this cosmic birth our universe might have had many lives. Think of a balloon that’s inflated, deflated, then inflated again. According to his new model, our particular space and time will eventually end, but the universal whole will continue, carrying into its next life a residue of its past repetitions.

The impetus for Hawking’s revision is the revolution that has electrified the world of theoretical physics: string theory. Using the mathematical putty of this theory, physicists are playing gods, bringing forth from the pluripotent sea of their equations an explosion of universes. At UCSB, string theorists served up visions that contained not just one universe but multiple, expanding and infinitely extending arrays of universes. There were “pocket universes,” “toy universes” and “baby universes” budding like spores off parent universes — a dizzying plethora of possibility in which almost any world that might be imagined was deemed to be happening “somewhere.”

To its proponents string theory holds out the hope that this may be the longed-for “theory of everything.” To others, it seems a theory of nothing. It is not even science, they argue. For as its greatest exponents acknowledge, there is not a shred of evidence to support any of its conclusions so far. Speaking on Nova the other night, Nobel Prize–winning particle physicist Sheldon Glashow expressed his feelings in scathing terms. “Let me put it bluntly,” he said, “there are physicists and there are string theorists.” For Glashow, physics is about experiment, and without experimental verification string theory has no validity. Not since the Middle Ages has speculation so exceeded the reach of observation. “Is this a theory of physics,” Glashow asked, “or philosophy?”

WHATEVER string theory’s epistemological status, it’s hot. Glashow was part of a Nova string theory special, PBS’s most expensive science project ever, a $3.5 million, three-part epic titled The Elegant Universe. The series is based on the 1999 best-selling book of the same name by Columbia University physicist Brian Greene, and PBS honchos are clearly hoping it will be the next Cosmos, with Greene the next Carl Sagan. “If string theory is right,” Greene enthused giddily at the start of the show, “we may be living in a universe where reality meets science fiction.”

Certainly the producers seemed determined to distract us with all the techniques of sci-fi cinema — there were more things flying at the screen than in a Star Wars battle. Like Luke Skywalker, Greene seemed to be continually dodging projectiles. He took the task in stride, for he had evidently been schooled in The Crocodile Hunter style of presentation. I half expected him to wrestle one especially annoying graphic to the ground. Things whirled and whizzed and flashed; lights pulsed, objects popped in and out of existence.

Not that science shouldn’t be spectacular. It’s just that in the blitz of special effects it was often hard to keep track of the ideas. It was a relief whenever they cut to one of the physicists talking about his work. Especially good was Nobel laureate Stephen Weinberg, whose insights into why physicists care about this stuff helped to remind us that science — even string theory — remains a deeply human pursuit, driven by psychological needs and desires that all too often resist rational reduction.

 

STRING theorists are excited, Weinberg noted, because their equations suggest a path by which physics might be unified. For most of the past century, physics has portrayed a disturbingly schizophrenic vision. On the large scale, it describes the universe using Einstein’s theory of general relativity, but on the subatomic scale it reverts to the wildly “other” perspective of quantum mechanics. General relativity tells us how space and time behave on the celestial, or cosmological, scale and ultimately gives us a picture of the universe as a whole. It has made predictions tested to more than 40 decimal places of accuracy, yet at the subatomic level it breaks down. Here, quantum laws prevail and everything is ruled by laws of chance.

At the cosmological level, things flow; in the subatomic realm they jitter. Physicists like to use musical analogies, and we might say that if general relativity describes a Strauss waltz, quantum theory gives us a speed-metal riff. Practically speaking this duality has little effect, but aesthetically it’s profoundly unsatisfying. Physicists cannot bear the bifurcation within their world picture; they yearn for unity. At the Santa Barbara conference, David Berman, a young English physicist from Hawking’s department at Cambridge University, took the musical theme further. In music, he told me, “You can have two voices that sound discordant, then a third comes in and resolves them into a harmonic whole.” Physicists are searching for this resolving voice, and in string theory they believe they might have found their answer.

Certainly, the universe has no trouble reconciling itself. The schizophrenia is not in nature but in our mathematical models. It is not the world that is fractured, but our understanding of it.

ON THE DAY following Hawking’s talk, UCSB hosted another intellectual superstar, Jacques Derrida, at 73 the bad pensioner of French philosophy. Derrida had been invited to speak at a conference on religion, and his theme was living together, a subject he addressed through the prism of his experience as a Jewish child growing up in prewar Algeria. I had gone along to his sold-out lecture for entirely separate reasons beyond my interest in string theory, but it turned out there were uncanny resonances between the two events. The organizing motif of Derrida’s talk, the idea to which he returned again and again (his singularity, as it were), was the notion of the ensemble, or collection. Here, of course, he meant ensembles of people — ethnic groups, religious communities, nation-states, local neighborhoods, families and so on. But Derrida also wanted to alert us to the French use of the word, its adverb sense, ensemble, as in “vivre ensemble — living together.”

For Derrida the two senses of this one word were necessarily entwined. Unity, he said, is an illusion. Ensembles are never homogeneous; differences between members and parts of the whole will always exist. Not just small differences, but radical dissimilarity. “Otherness,” Derrida insisted, is the norm, and we must learn to live with it. Even within ourselves there is fragmentation. In Derrida’s terms we are all multiple beings, ensembles within. Accordingly, the demand for oneness is a pathology we must renounce, for only by accepting the radical “otherness” of others can we live in harmony with them. As he put it, “Living together contests the closure of the ensemble.”

From a Derridian perspective, physicists’ demand for a harmonic whole takes on the cast of an unhealthy obsession. Insistence upon closure is the very ideal he rejects.

 

STRING THEORY closes the chasm between relativity and quantum mechanics by smoothing out the jitters of the subatomic realm, replacing point particles with microscopic loops, or “strings.” According to the mathematical basis of this theory, everything in our universe is made up of tiny vibrating loops of some fundamental stringy stuff. Don’t even ask what this might be — there is no answer. Just accept the notion that at its most basic level the world is made of minute rubber bands.

But in order to get this theoretical unity, you have to be willing to take on board a radical extension of the universe beyond all bounds of human experience. According to string theory, these microscopic loops require their own dimensions of space. In most currently popular versions, strings vibrate in six dimensions, though in some versions it is seven. All of these are additional dimensions tacked on to the three dimensions of space and the one of time we normally encounter. It is this aspect of string theory that its detractors so dislike. Where are these dimensions?, they demand. What are they? How come we don’t see them?

This last question, at least, has an answer. We don’t see the extra dimensions because they are too tiny to observe with any current technology. On Nova, Brian Greene gave us an analogy: If an atom was as big as our solar system, a string would be the size of a large shrub. To detect something that small, you’d need a particle accelerator the size of a galaxy.

Strings aren’t the only things the theory predicts. The other revelation has been a class of objects called “branes,” short for membranes. Over dinner at the Santa Barbara conference, Joseph Polchinski, from UCSB’s hosting Kavli Institute for Theoretical Physics, offered some illumination. Where strings exist at the subatomic level, branes are the structures the theory generates on the cosmological scale. Strings are tiny, branes are huge. If strings are like spaghetti, branes would be vast sheets of lasagna. Our universe, according to the theory, is a brane, a cosmic-scale incarnation of the same fundamental stringy substance. “You can ask what branes are made of,” Polchinski said, “but they’re not made of anything. They’re just the stuff the theory describes.”

While strings suggest a subatomic space that has yet to be detected, branes conform to some of our usual spatial conceptions. The brane of our universe is said to have the accepted dimensions of space and time. Yet it is seen as just one potential part of a much larger five-dimensional realm known as “the bulk.” Within the bulk, Polchinski told me, there may well be other branes. Here “the universe” becomes not just our brane but the total set of branes within the bulk-space.

String theory does not stop there. In Hawking’s version, an individual brane can be continually reborn. Other versions allow the possibility of branes that spawn from prior branes or infinitely foaming seas of branes, like a vast cosmological head of beer. In Santa Barbara, Leonard Susskind, one of the pioneers of string theory, presented an alarmingly fecund vision in which there were hundreds of “dimensions” of potential universes, with new ones coming into being all the time. Spaces upon spaces upon spaces, a multiplication of possibilities that defy the very notion of limit.

Although some physicists have objected to the almost organic proliferation that string theory allows, Derrida, I think, would be pleased by this explosion of ideas, which supports in the totality of its weirdness the fundamental theme of his talk.

 

With his impeccable tailoring and leonine presence, the most controversial philosopher of our time would command attention even if he wasn’t supported by the buttress of fame. Derrida told us that the “commandment” to live together imposes upon us demands “beyond law and nature.” Law, he said, is never sufficient to dictate our actions, which operate in a wider realm of possibility than the statutes of any legal system. Derrida urged us to embrace this “excess,” to live and love in a broader field of potential. And that is what I like so much about the new string cosmologies. Despite physicists’ desire for oneness, in the end their equations also have multiplied the possibilities, giving us a vast domain of potential in which the “natural laws” here on Earth are just one set among many. It is as if nature itself resists efforts to press it into a single mode, joining Derrida on the path of radical multiplicity. Whether we can prove the existence of these alternate worlds seems of little consequence.

In string theory we have discovered a language which may well be more lyrical than empirical, but which, in that very quality, enables us to contemplate a wild excess of other options. Derrida and Hawking — the physicist and the philosopher — would, I believe, have embraced one another.


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