Stephen Hawking (11 page)

“Of course it doesn't diverge,” Hoyle said.

“It does,” came Hawking's defiant reply.

Hoyle paused and surveyed the room for a moment. The audience was absolutely silent. “How do you know?” he snapped.

“Because I worked it out,” Hawking said slowly.

An embarrassed laugh passed through the room. This was the last thing Hoyle wanted to hear. He was furious with the
young upstart. But any enmity between the two men was short-lived—Hawking had demonstrated himself to be too good a physicist for that. But Hoyle considered Hawking's action to be unethical and told him so. In return, Hawking and others pointed out that Hoyle had been unethical in announcing results that had not been verified. The only innocent party, who no doubt had to bear the full brunt of Hoyle's anger, was the middleman, Narlikar.

Although Hoyle was every bit Hawking's intellectual equal, on this occasion the younger man turned out to be absolutely correct: the quantity Hoyle had been talking about did indeed diverge, which meant that the latest component of his theory was wrong. Hawking wrote a paper summarizing the mathematical findings that had led him to realize this. It was well received by his peers and established him as a promising young researcher. While still trying to sort out his own Ph.D. work with Sciama, Hawking was already beginning to make a name for himself within the rarefied atmosphere of cosmological research.

During his first two years at Cambridge, the effects of the ALS rapidly worsened. He was beginning to experience enormous difficulty in walking and was compelled to use a stick in order to move just a few feet. His friends helped him as best they could, but most of the time he shunned any assistance. Using walls and objects as well as sticks, he would manage, painfully slowly, to traverse rooms and open areas. There were many occasions when these supports were not enough. Sciama remembered clearly, as do his colleagues, that on some days Hawking would turn up at the office with a bandage around his head, having fallen heavily and received a nasty bump.

His speech was also becoming seriously affected by the disease. Instead of being merely slurred, his speaking voice was now rapidly becoming unintelligible, and even close colleagues were experiencing some difficulty in understanding what he was saying. Nothing slowed him down, however; in fact, he was just hitting his stride. Work was progressing faster and more positively than it had ever done in his entire career, and this serves to illustrate his attitude to his illness. Crazy as it may seem, ALS is simply not that important to him. Of course he has had to suffer the humiliations and obstructions facing all those in our society who are not able-bodied, and naturally he has had to adapt to his condition and to live under exceptional circumstances. But the disease has not touched the essence of his being, his mind, and so has not affected his work.

More than anyone else, Hawking himself would wish to underplay his disability and to concentrate on his scientific achievements, for that is really what is important to him. Those working with him, and the many physicists around the world who hold him in the highest regard, do not view Hawking as anything other than one of them. The fact that he cannot now speak and is immobile without the technology at his fingertips is quite irrelevant. To them he is friend, colleague, and, above all, great scientist.

Having come to terms with ALS and found someone in Jane Wilde with whom he could share his life on a purely personal level, he began to blossom. The couple became engaged, and the frequency of weekend visits increased. It was obvious to everyone that they were sublimely happy and immensely important to each other. Jane recalls, “I wanted to find some purpose to my existence, and I suppose I found
it in the idea of looking after him. But we were in love.”
⁹
On another occasion, she said, “I decided what I was going to do, so I did. He was very, very determined, very ambitious. Much the same as now. He already had the beginnings of the condition when I first knew him, so I've never known a fit, able-bodied Stephen.”
¹⁰

For Hawking, his engagement to Jane was probably the most important thing that had ever happened to him: it changed his life, gave him something to live for, and made him determined to live. Without the help that Jane gave him, he almost certainly would not have been able to carry on, nor would he have had the will to do so.

From this point on, his work went from strength to strength, and Sciama began to believe that Hawking might, after all, manage to bring together the disparate strands of his Ph.D. research. It was still touch and go, but another chance encounter was just around the corner.

Sciama's research group became very interested in the work of a young applied mathematician, Roger Penrose, who was then based at Birkbeck College in London. The son of an eminent geneticist, Penrose had studied at University College in London and had gone on to Cambridge in the early fifties. After research in the United States, he had begun in the early sixties to develop ideas of singularity theory that interfaced perfectly with the ideas then emerging from the DAMTP.

The group from Cambridge began to attend talks at King's College in London, where the great mathematician and
co-creator of the steady state theory, Hermann Bondi, was professor of applied mathematics. King's acted as a suitable meeting point for Penrose (who traveled across London), those from Cambridge, and a small group of physicists and mathematicians from the college itself. Sciama took Carter, Ellis, Rees, and Hawking to the meetings with the idea that the discussions might spark applications to their own work. However, there were times when Hawking almost failed to make it to London.

Brandon Carter remembers one particular occasion when the group arrived late at the railway station and the train was already drawing in. They all ran for it, forgetting about Stephen, who was struggling along with his sticks. It was only after they had installed themselves in the carriage that they were aware he was not with them. Carter recalls looking out of the window, seeing a pathetic figure struggling toward them along the platform, and realizing that Stephen might not make it before the train pulled away. Knowing how Hawking was fiercely against being treated differently from others, they did not like to help him too much. However, on this occasion Carter and one of the others jumped out to help him along the platform and onto the train.

It would have been an odd twist of fate indeed if Hawking had not made it to at least one of those London meetings, because it was through them that his whole career took another positive turn. Over the course of the talks at King's, Roger Penrose had introduced his colleagues to the idea of a spacetime singularity at the center of a black hole, and naturally the group from Cambridge was tremendously excited by this.

One night, on the way back to Cambridge, they were all seated together in a second-class compartment and had begun to discuss what had been said at the meeting that evening. Feeling disinclined to talk for a moment, Hawking peered through the window, watching the darkened fields stream past and the juxtaposition of his friends reflected in the glass. His colleagues were arguing over one of the finer mathematical points in Penrose's discussion. Suddenly, an idea struck him, and he looked away from the window. Turning to Sciama sitting across from him, he said, “I wonder what would happen if you applied Roger's singularity theory to the entire Universe.” It was that single idea that saved Hawking's Ph.D. and set him on the road to science superstardom.

Penrose published his ideas in January 1965, by which time Hawking was already setting to work on the flash of inspiration that had struck him on the way home from London to Cambridge that night after the talk. Applying singularity theory to the Universe was by no means an easy problem, and within months Sciama was beginning to realize that his young Ph.D. student was doing something truly exceptional. For Hawking, this was the first time he had really applied himself to anything. As he says:

I . . . started working hard for the first time in my life. To my surprise, I found I liked it. Maybe it is not really fair to call it work. Someone once said, “Scientists and prostitutes get paid for doing what they enjoy.”
¹¹

When he was satisfied with the mathematics behind the ideas, he began to write up his doctoral thesis. In many
respects, it ended up as a pretty messy effort because he had been in something of a wilderness for much of the first half of his time at Cambridge. The problems he and Sciama had experienced in finding him suitable research projects had left a number of holes and unanswered questions in the thesis. However, it had one saving grace—his application of singularity theory during his third year.

The final chapter of Hawking's thesis was a brilliant piece of work and made all the difference to the awarding of the Ph.D. The work was judged by an internal examiner, Dennis Sciama, and an expert external referee. As well as being passed or failed, a Ph.D. can be deferred, which means that the student has to resubmit the thesis at a later date, usually after another year. Thanks to his final chapter, Hawking was saved this humiliation and the examiners awarded him the degree. From then on, the twenty-three-year-old physicist could call himself Dr. Stephen Hawking.

5

FROM BLACK HOLES TO THE BIG BANG

I
n the early 1960s, astronomers already knew that any star which contains more than about three times as much matter as our Sun ought to end its life by collapsing inward to form what is now known as a black hole. More than twenty years previously, researchers had used Einstein's equations of general relativity to calculate that
such an object would bend spacetime completely around upon itself, cutting the central mass off from the rest of the Universe. Light rays passing near such an object would be deflected so much that even photons would orbit around the central “star” in closed loops and could never escape into the Universe outside. Obviously, since it could emit no light, such an object would be black, which is why the American relativist John Archibald Wheeler dubbed them “black holes” in 1969.

But although it was well known that the general theory made this prediction, at the time Hawking was completing his undergraduate studies and moving on to research, no one took the notion of black holes seriously. The reason is that there are very many known stars that have more than three times the mass of our Sun. They do not collapse because nuclear reactions going on inside the stars make them hot. The heat creates an outward pressure that holds the star up against the pull of gravity. Astronomers knew that when such stars run out of nuclear “fuel,” they explode, blasting away their outer layers into space. As recently as fifty years ago, astronomers assumed that such an explosion would always blow away so much matter that the core left behind would have less than three times the mass of our Sun—or, perhaps, that some as-yet undiscovered pressure would come into play as the remnant of star stuff began to shrink.

This prejudice was reinforced by the fact that astronomers had indeed discovered many old, dead stars. These stellar cinders all had a bit less than the mass of our Sun, but that mass was compressed into a volume only about as big as that of the Earth. Such planet-sized stars are known as white dwarfs. They are held up against the inward pull of gravity by the pressure of the electrons associated with the atoms of which they are made, acting like a kind of electron gas. A white dwarf is so
dense that each cubic centimeter of the star contains a million grams of material. Before 1967, these were the densest known objects in the Universe.

But although astronomers did not seriously believe that anything denser than a white dwarf could exist, a few mathematicians enjoyed playing with Einstein's equations to work out what would happen to matter if it were squeezed to still greater densities. The equations said that if three times as much matter as our Sun contains were squeezed until it occupied a spherical region with a radius of just under 9 kilometers, spacetime in its vicinity would be so distorted that not even light could escape. Because nothing can travel faster than light, this meant that nothing at all could ever escape from such an object, which the mathematicians sometimes referred to as a collapsar (from “collapsed star”). It would have become the ultimate bottomless pit into which anything could fall but from which nothing could ever emerge. And the density inside the collapsar would be greater than the density of the nucleus of an atom; this, theorists of the time thought, was clearly impossible.

In fact, they did consider (but not too seriously) the possibility of stars as dense as the nucleus of an atom. By the 1930s, physicists knew that the nucleus of an atom is made of closely packed particles called protons and neutrons. The protons each carry one unit of positive charge; the neutrons, as their name suggests, are electrically neutral, but each has about the same mass as a proton. In everyday atoms, like the ones this book is made of, each nucleus is surrounded by a cloud of electrons. Each electron carries one unit of negative charge, and there is the same number of electrons as protons, so the atom as a whole is electrically neutral.