MIND OVER MATTER

Stephen Hawking has overcome a crippling disease to become the supernova of world physics. Unable to write, or even to speak clearly he is leaping beyond relativity beyond quantum mechanics, beyond the big bang; to the “dance of geometry" that created the universe

TIMOTHY FERRIS

Stephen Hawking’s ankles, each as thin as the throat of a Little League bat, emerged from heavy brown shoes the tops of which were scuffed but the soles unblemished. His slender legs were skewed and immobile. His right hand rested in his lap, motionless as a glove; the left gripped the control stick of his electric wheelchair. His dress was that of a man who is dressed by others, the knot of the tie standing well away from the drawn throat, the suit coat hovering an inch above the shoulders.

His hair, autumn brown shot with gray, fell over his eyes as he struggled to raise his head. Three dozen scientists who had gathered in a conference room at the University of California at Santa Barbara watched in silence. His lips drawn back in a grimace, Hawking spoke, his words slurred in a guttural rasp that sounded like an automobile engine refusing to start on a cold morning. Only one man in the room could understand him—Nick Warner, a young physicist acting as his former teacher’s interpreter, who was standing at the blackboard with a piece of chalk in his hand. Warner grinned and repeated Hawking’s instructions: “Please draw a four-dimensional sphere.”

The audience laughed. Some mathematicians claim that they can imagine what a four-dimensional sphere looks like, but nobody claims to be able to draw one.

Hawking’s blue-gray eyes glittered from within the dark cusp of the body slumped in the wheelchair. With Warner translating and chalking equations on the blackboard, Hawking explained how to “work on a four-sphere,” his tone as matter-of-fact as that of a mountain climber discussing a promising route up the north face of Eiger. Soon he interrupted himself: “I’m falling out of my chair,” he said, laughing. Warner reached under his arms and hoisted the frail body back into place.

Hawking has amyotrophic lateral sclerosis—Lou Gehrig’s disease—a progressive deterioration of the central nervous system that ultimately kills its victims through pneumonia or suffocation. The illness struck while he was still a student, but it has not prevented Hawking, now forty-two, from emerging as one of the world’s finest theoretical physicists, and as a man of ineffable charm and wit.

Hawking’s story promises—or threatens—to make him a celebrity. His mild cetacean smile has graced the cover of The New York Times Magazine, and he is pursued by television producers and reporters who troop to Cambridge University, where Hawking holds Isaac Newton’s old post as Lucasian Professor of Mathematics, to hear him speak unintelligible words on unfamiliar subjects. The publicity, however, has tended to concentrate on who Hawking is rather than what he does. Granted, theoretical physics is by nature intellectually challenging—were it not, it would scarcely be worth doing—but it is also what Hawking cares about. By offering up a Hawking sans physics, the press threatens to turn him into an adult version of a muscular-dystrophy poster child, an afflicted soul who smiles sweetly and demonstrates great courage without being expected to have anything much to say.

A rather different portrait emerges if we watch the man at work. Viewed by the lights of his scientific research, Hawking turns out to be something of a dragon slayer, the veteran of victorious sallies against one of the most daunting monsters known to physics—the singularity.

A singularity may be thought of as a dimensionless point, a knot in space, or a bottomless well in time. It resembles the Aleph in Jorge Luis Borges’s story of that name, which Borges describes as the point from which “my eyes had seen that secret and conjectured object whose name is common to all men but which no man has looked upon—the unimaginable universe.” A strange idea. Stranger still, singularities may actually exist. The extremely dense star wrecks called black holes, first imagined by theoretical physicists and later detected by astronomers, contain singularities. So, it seems, did the primordial explosion in which the universe is thought to have been bom.

Black holes are believed to be created by the death of stars. When a star several times as massive as the sun exhausts its nuclear fuel, it can collapse, settling down into a ball so dense that nothing, not even light, can escape the crush of its gravitational field. Viewed in terms of general relativity, which portrays gravitation as the curvature of space, a black hole contains a singularity—a sinkhole of infinitely curved space where trajectories converge and relativity itself founders.

The prospect that black-hole singularities exist could be glimpsed in the gravitational theories of both Newton and Einstein, but seemed too preposterous to be credible. Then, in 1967, dense collapsed stars called neutron stars were discovered. The theories that predicted the existence of neutron stars also predicted that giant stars could collapse right through the neutron-star stage to become black holes; scientists were obliged, however reluctantly, to entertain the possibility that black holes are real. A star of sufficient mass to make a black hole dies somewhere in our galaxy every thirty years or so, and inasmuch as the galaxy is some 15 billion years old, it ought by now to have peppered itself with black holes. Astronomers searching for black holes have located objects that appear to fill the bill. At some of the candidate locations, interstellar gas is being swallowed up by a small, invisible object of hefty mass. At others, stars are found wildly orbiting an object that, though it is several times more massive than the sun, emits no light.

The riddle of the singularity lurks in the gardens of genesis as well. The universe is expanding; run the rate of expansion backward in time and you will find that, some 20 billion years ago, all the stuff of the far-flung galaxies must have been mashed together. The gravitational force that pertained at such incredible densities, during the first moments after creation, would have been so intense that existing theories of physics cannot deal with it. Because the curvature of space in a singularity is infinite, general relativity, Einstein’s otherwise impeccable account of gravitation, breaks down. “Smoke starts to pour out of the computer,’’ write Charles Misner, Kip Thome, and John Archibald Wheeler in their classic textbook, Gravitation. “Einstein’s equation says, ‘This is the end,’ and physics says, ‘There is no end.’ ”

The prospect that the entire universe sprang from a singularity, where the known laws of physics apparently fail, confronted science with the galling prospect that it could explain almost nothing about the origin of everything. Not surprisingly, singularities became something of a scientific scandal, ridiculed or ignored or swept under the rug. This was the dragon Hawking went hunting at age twenty-one.

Rather than ignoring the singularity problem, Hawking seized upon it. In papers written while he was still a graduate student at Cambridge and further developed in collaboration with mathematician Roger Penrose, he demonstrated that general relativity, combined with a few reasonable assumptions about the nature of the cosmos, not only permitted but mandated that the universe began as a singularity. “There is a singularity in our past,’’ Hawking wrote.

Some scientists found this view so objectionable that they suggested altering the equations of relativity rather than accept the reality of singularities. But, as the young Hawking wrote, “the real test of a physical theory is not whether its predicted results are aesthetically attractive but whether they agree with observation,’’ and the observational evidence is consistent with the hypothesis that a singularity ruled at the moment of genesis. If, for instance, the universe really did originate as a burst of monumentally powerful energy—the “big bang,’’ in cosmological argot—residual energy from that explosion still ought to be around, though stretched out during the subsequent 20 billion years of the expansion of the universe. Just such residual radiation was detected, in 1965, by two American radio astronomers, Amo Penzias and Robert Wilson, who stumbled across it and were rewarded with a Nobel Prize. Known as cosmic background radiation, it has the temperature and spectrum predicted by the big-bang theory, and, as the theory demands, it permeates the observable universe. The observations of Penzias and Wilson and the theories of Hawking and Penrose concurred that the cosmos must have begun in the singularity of a big bang.

Hawking then turned his attention to black holes. They are forbidding objects for study. Try to explore a black hole and it will tear you into subatomic particles and keep the particles. Feed in a measuring tape and it will gobble up the tape forever. Try to take a flash photograph of a black hole and the hole will eat the light, adding fresh photons to its hoard of matter and energy and further tightening its gravitational hegemony in the process. Infinitely greedy, black holes give up nothing.

Or so Hawking, like most physicists, believed. But one small point in the scientific literature bothered him. Jacob Bekenstein, then a graduate student at Princeton University, had shown that, according to the laws of thermodynamics, a black hole ought to emit heat. Hawking thought this impossible— “Neither Bekenstein nor I believed that a black hole actually did emit particles”—so he set out to learn where Bekenstein had gone wrong.

Hawking began exploring the possibility that a rotating black hole might mimic heat radiation, by stirring up gravitational waves that could simulate the emission of particles. While visiting Moscow in 1973, he talked with two leading Soviet physicists, Yakov Zel’dovich and Alexander Starobinsky. They shared his notion that black holes might seem to emit particles without actually doing so, but Hawking was unconvinced by the mathematics of their argument. “I didn’t like the way they derived their result,” Hawking recalls, “so I set out to do it properly.”

Back in Cambridge, Hawking thought at length about just what happens at the “event horizon”—the precipice surrounding a black hole, the lip of the waterfall where curved space falls off to infinity. He drew on both general relativity, the science normally applied to the universe on the very large scale, and quantum mechanics, the science of the very small. He found that, on the steep slopes of curved space, particles can behave in surprising ways. Instead of being doomed to fall into a black hole, particles can in some cases be squirted back out into surrounding space, escaping the black hole’s clutches. “To my horror,” Hawking recalls, “the black hole seemed to be emitting particles.”

He had discovered what is known today as “Hawking radiation,” a property by which black holes, rather than being sealed off from the rest of the universe forever, can radiate energy. Singularities had begun to look a little less absolute.

(continued on page 102)

MIND OVER MATTER

(continued from page 59)

Hawking soon saw that his discovery had a remarkable consequence: If particles can be ejected from black holes, then their departure must reduce the mass of the black hole, loosening the gravitational bonds that hold it together. Unless fed fresh matter, the black hole will dwindle to the point that it can no longer muster the gravitational force required to keep itself locked up in a singularity. It will explode, regurgitating energy into our universe. Singularities, Hawking had discovered, don’t necessarily last forever. The dragon is mortal.

Hawking accepted this curious conclusion even though it was the opposite of what he had set out to prove. This sort of thing often happens in science. A new theory, like an original work of art, may at first look ugly, insofar as it challenges our preconceptions. The creative scientist is put in the position of Picasso, who once told Gertrude Stein, “When you make a thing, it is so complicated making it that it is bound to be ugly, but those that do it after you don’t have to worry about making it and they can make it pretty.”

“One always has a certain reluctance to give up a point of view that one has invested in,” Hawking recalls of his discovery, “but this was an occasion when one had to do it. It all fitted together so perfectly that it just had to be right. Nature wouldn’t have set up something that elegant if it were wrong.”

By the time Hawking’s paper on black-hole mortality was published, in 1976, his disease had progressed to the point that he was permanently confined to a wheelchair. He continued to lecture at scientific seminars, but fewer and fewer in the audience could understand his increasingly indistinct speech. The very fact that he had scored a coup in studying black holes suggested a ghastly metaphor—that Hawking the braver of singularities was disappearing from this world, as inexorably as the dwindling light of a collapsing star.

The onset of the disease discouraged Hawking—“I thought I was going to die very soon, so there wasn’t much point working at my Ph.D.”—but he has since come to speak of it almost exclusively in positive terms. “My illness made me a lot happier,” he said recently. “It made me realize that life really was worth living.”

Some of his colleagues conjecture that his condition may have helped Hawking get down to work, perhaps by visiting upon him what Alice James, dying of cancer, called the “delicious consciousness” that one will not live forever. But while Hawking concedes that he was “bored and drank too much” as a student, “the real turning point,” he says, was his engagement to Jane Wilde. “If I was going to get married, I had to get a job. And that meant I would have to make progress at my research. It was at about that point that things began to fall into shape, and I actually began to understand what I was working on.” Eighteen years of married life on borrowed time have brought Jane and Stephen three children: Robert, sixteen, Lucy, thirteen, and Timothy, five. The progress of the disease seems at last to have slowed, thanks perhaps to a gluten-free, no-sugar diet of Hawking’s devising, and Hawking has managed to overcome the isolation that the disease threatened to impose.

For years he doggedly persisted in lecturing, even though his speech had deteriorated to the point that, as Nick Warner recalls, “he was understood by only perhaps thirty-five people in an audience of seven hundred.” He tried to bridge the gap by supplementing his words with viewgraphs—words and drawings pn transparent plastic sheets, projected on a screen—but, he notes, “one mustn’t put more than two sentences on a viewgraph, otherwise people won’t take it in, and you can’t have more than two dozen viewgraphs. This means you can’t convey more than forty-eight sentences—only a bare outline.” Then, in Moscow in 1981, Hawking was asked to give a seminar for which he had not prepared. Lacking viewgraphs, he tried speaking through Warner, who repeated his words to the audience. It worked. Hawking today lives an increasingly public life, and he says that constant interaction with his student interpreters helps to promote a free flow of ideas and criticism, unimpaired by the aura of remote grandeur that otherwise tends to settle around a scientist of his stature. “Once a student has helped me in the bathroom,” he says, “he isn’t likely to feel overawed.”

Today Hawking pursues the highpressure schedule of an intellectual superstar, flying from city to city at a pace that exhausts aides half his age, sightseeing from the Alps to Death Valley, eating ravenously at exotic restaurants, writing papers at a prodigious rate, and giving frequent talks, not always on science. Accepting an award sponsored by an American defense contractor, he lectured the company’s executives on the folly of building more nuclear weapons. “We have the equivalent of four tons of high explosives for every person on earth,” he says of the arms race. “It takes half a pound of explosives to kill one person, so we have 16,000 times as much as we need. We must understand that we are not in conflict with the Soviets, that both sides have a strong interest in the stability of the other side. We ought to recognize that fact and cooperate, rather than arm ourselves against each other. ’ ’

A strain of fierceness runs through Hawking’s personality, surfacing in spates of impatience or anger. If he feels his time is being wasted he may spin his wheelchair on the spot and speed out of the room, and he retaliates against people he dislikes by running over their toes. “His great regret,” says Warner, “is that he’s not yet run over Margaret Thatcher.”

“The dominant impression I have of Stephen,” says James Hartle, of the University of California at Santa Barbara, one of Hawking’s collaborators, “is one of enormous will to do whatever he chooses to do, whether it’s to lead a normal life or to solve problems in physics. A tactic he employs is to behave as closely as possible to normal, no matter what the cost.”

Hawking has been lauded for doing superlative physics despite being unable to pick up a book or a telephone or to write so much as E=mc2. “Hawking’s feats of memory are said to be akin to Mozart composing an entire symphony in his head,” read one magazine profile. But to do science at Hawking’s level is inherently so difficult that complimenting him on his memory is rather like General Thomas Farrell’s having remarked to the nuclear physicist who was at the detonation of the first atom bomb that he was to be congratulated for being able to count backward from ten to one. And, in any case, many physicists have good memories. Hawking dazzled students at a 1983 Caltech seminar by dictating a forty-term version of the Wheeler-DeWitt equation from memory, but Nobel laureate Murray Gell-Mann promptly interrupted to point out that Hawking had omitted a term from the equation, and Gell-Mann was working from memory too, and without Hawking’s preparation in the subject at hand. Nor have physical handicaps defeated every thinker they have afflicted. Montaigne suffered from kidney stones, Einstein from recurrent heart trouble. One of Hawking’s fellow speakers at a conference last summer was a mathematician who delivered a brilliant and high-spirited discourse, scrawling equations freehand on clear viewgraphs as he went along, and only when he was led from the podium did the audience realize that the man was blind.

The interesting thing is not so much that Hawking has triumphed over a debilitating illness, but how he has triumphed. Deprived of the ability to write, he has had to improvise ways of doing physics that obviate the need for regular recourse to paper and pencil, blackboard, or electronic computer. “The trouble is that I can’t write the equations down,’’ he says. “I can’t really handle long equations in my head; one loses track of terms. So I try to avoid problems with lots of equations, and try to think of a geometrical way of approaching them.’’ The result is a bold, incisive research style that helps Hawking’s colleagues see problems in a fresh light. Hawking “gets right to the heart of a problem and reduces it to the essence,’’ says his student Chris Hull. “He has tremendous insight,” says his friend and fellow black-hole theorist Kip Thome of Caltech. “He finds ways to avoid doing cumbersome mathematics, and it’s an inspiration to see how he does it. ’ ’

In his most recent work, Hawking has turned anew to the singularity of the big bang—the throat of the lily from which the cosmos bloomed.

The question of reconstructing the origin of the universe is an Everest in theoretical physics, its slopes dotted by squads of young researchers and by the bleached bones of their elders. The work consists of creating theories or hypotheses that plausibly recount what went on in the first moments following the beginning of the expansion of the universe. One puts in what physics is known, adds reasonable guesses as to the unknown, and tries to get the equations to produce a universe that resembles the one we live in. The differences between the early and the contemporary universe are profound. In the furious heat of the big bang, the structures of matter and energy, even of space and time, must have been transformed in milliseconds as the universe expanded and cooled. Physical laws themselves may have evolved, making of the early universe an unfamiliar game the rules of which changed with each passing moment.

Theoretical work on the physics of the very early universe suggests that three of the four known forces of nature—electromagnetism and the “weak” and “strong” nuclear forces— may well have evolved from a single sort of force (called the electronuclear, or grand unified, force) which ruled the infant universe. Gravitation, however, remains unaccounted for by the new unified theories, and its role in early cosmic evolution is not well understood. The problem is that while the other three forces have been interpreted in terms of quantum theory, which works well when it comes to investigating minuscule events like the interactions of subatomic particles, there is as yet no quantum theory of gravity. Asked what he would most like to accomplish in life, Hawking will smile slyly and reply, “Quantize gravity.”

But to bring off what John Wheeler calls “the fiery marriage” of quantum physics and general relativity will be extremely difficult, owing in part to the fact that the two schools look at nature in fundamentally different ways. Relativity depicts the universe as a continuum governed by strict laws of cause and effect. Quantum physics sees nature as composed of discrete units—the quanta—the behavior of which can be predicted only in terms of probabilities. To the quantum physicist, nature resembles a color television picture, looking continuous from a distance, but, when examined more closely, resolving itself into a jumble of jiggling quanta. The uncertainty principle reveals that the behavior of the quanta cannot be predicted with exactitude. Most of the electrons fired against the back of the television screen go where they are aimed, which is why the TV works, but one cannot predict with assurance that any one electron will hit the screen at the spot where it was aimed; the outcome can be predicted only in terms of statistical probabilities.

The philosophical gulf dividing quantum theory and relativity takes on immediate practical significance in the study of die early evolution of the universe, where chance events transpiring on the subatomic scale could have had consequences that appear today in the structure of whole clusters of galaxies. Finding a theory that bridges the gulf will call for creative imagination as well as logical rigor. As Hawking himself puts it, “There’s no logical, deductive procedure for inventing the ultimate theory. One has to make a leap in the dark.”

At a conference on general relativity in Padua, Italy, last summer, Hawking gave what he considers to have been one of the most important talks of his career. In a tour de force that combined elements of quantum physics and relativity, he proposed that he had derived the wave function of the universe.

The wave function is a means by which predictions can be made in quantum physics. To forecast where a particle will be at a given moment in the future, the physicist calculates a wave of probability, its apex representing the point at which the particle is most likely to turn up. In collaboration with James Hartle, Hawking applied this tool not to particles but to geometries. In his formulation, the wave function represents the probability that the universe might be constructed upon one of a whole class of geometric structures.

Speaking through an interpreter and with the aid of diagrams, Hawking explained his new theory to a hushed audience of four hundred in the old vaulted hall where Galileo used to lecture when he was teaching at Padua by day and stargazing by night. Darkness ruled the enormous room, broken only by a few shafts of morning sunlight streaming through a high east window.

“The universe today is accurately described by classical general relativity,” Hawking began. “However, classical relativity predicts that there will be a singularity in the past, and near that singularity, the curvature [of space] will be very high, classical relativity will break down, and quantum effects will have to be taken into account. In order to understand the initial conditions of the universe, we have to turn to quantum mechanics, and the quantum state of the universe will determine the initial conditions for the classical universe. So today I want to make a proposal for the quantum state of the universe.

Plotted on graphs where time is but a coordinate, the universe according to Hawking stood still, a frozen Niagara. Its only dance was a dance of geometry, the invisible structure on which cosmological space and time are built. The wave function took the form of a helix, like the banisters of a spiral staircase. Hawking’s universe oscillates, expanding up the wave-function helix for billions of years, then collapsing down the helix and into the maelstrom of another big-bang singularity.

Nobody knows whether the real universe is destined eventually to stop expanding and then collapse—the universe is so closely balanced that observational evidence has not yet been sufficient to forecast its fate—but aside from the question of whether classical oscillating-universe theories fit reality, they suffer from an aesthetic problem: When an oscillating universe crushes itself into the singularity of a new big bang, it obliterates all coherent traces of its former history, ruling out the possibility of our learning whether there was a universe prior to the big bang. In such models, knowledge about the ultimate nature of genesis therefore remains forever out of reach.

Quantum approaches like that of Hawking and Hartle offer a way around—or through—this seemingly impenetrable barrier. Viewed in quantum terms, space appears to be foamlike, full of loopholes through which might leak information about the universe as it was prior to the big bang. As Hartle writes, “The evolution of the universe through a singularity can thus be followed quantum mechanically when it cannot be so followed classically.” The wave function might be able to penetrate through the singularity and bounce back into our world, bearing evidence about genesis like pollen on a bee.

The audience reacted with uncertainty to Hawking’s daring talk. Subrahmanyan Chandrasekhar, who would win a Nobel Prize a few months later for his pioneering work on theories of black holes, called the talk “an extremely important piece of work.” Said Kip Thome, “You were either witnessing a great moment in the history of physics or one more small, iterative step. We can’t know which for several years yet.”

“I suppose it is quite a big claim,” Hawking said that evening as he relaxed in a Spartan hotel room in Padua while a nurse tied a bib around his neck and fed him a cup of tea. “Some people would say that the boundary conditions aren’t part of physics—that they belong to metaphysics or religion. You can say, of course, that God could have started off the universe in any way He wanted. But in that case He could have made it evolve in any way He wanted. Yet the universe evolves according to certain laws of nature, so it seems reasonable to suppose that there are laws governing the initial conditions as well.”

Physicists and cosmologists today tend to think of the universe as being not only out there, but right here too; the particles from which are built the atoms of our blood and bones were, after all, part of the big bang, and can be consulted for clues about their history. Hawking shares this unified view of the cosmos, and sometimes talks as if there were no gap between mind and nature at large. One afternoon at Caltech we were discussing Schrodinger’s cat, a thought experiment devised by the physicist Erwin Schrodinger to demonstrate what he saw as the absurdity of a prevailing interpretation of quantum physics. The cat is sealed in a box with a gun pointing at it. The gun will fire if a small sample of radioactive material in the box emits a particle. Quantum physics teaches that it is impossible to predict, except in terms of probabilities, whether the radioactive material will emit a particle during any given interval. If, say, the chance of the particle’s being emitted and thereby killing the cat is 50 percent, one can think of the experiment as having generated two wave functions, each of equal magnitude. Until the box is opened, there are, in effect, two cats, one dead and one alive.

“When I hear of Schrodinger’s cat, I reach for my revolver,” Hawking said, paraphrasing Hermann Goring’s response to the word “culture.”

“Well, don’t shoot the cat,” I said. “That would spoil the experiment. The cat would have been killed, but not by a quantum effect.”

“It wouldn’t spoil the experiment,” Hawking replied with a smile, “because I myself am a quantum effect.”