by John Gribbin
Mitton recalls that, by the time of their first meeting in 1972, Hawking’s speech had deteriorated considerably. It was essential to concentrate hard on what he was saying in order to understand him. Mitton found that he always had to face Hawking and watch what he was saying as well as listen intently; even then, it was not easy. The best way to communicate, Mitton found, was to ask questions that required only negative or affirmative answers. So instead of asking, “When would you like to go to lunch, Stephen?,” it was far easier to say, “We are going to lunch at 12:30. Is that all right?” Fischer Dilke, who wrote and directed one of the first television documentaries about Hawking, disagrees. He says that Hawking hates nothing more than being asked such questions, because it is a sign to him that the person he is talking to is not treating him in a normal way. It obliges him to answer only “Yes” or “No,” and he would, quite naturally, like to be engaged in a standard conversation.
In retrospect, the seventies may be viewed as something of a gray decade. After the optimism and hope of the sixties, the West, with the possible exception of West Germany, was thrown into recession; only in Japan did a combination of postwar determination, a flair for the commercial application of Western technology, and sheer hard work set the pattern for industrial growth. Britain’s economy nearly foundered, hammered by a series of disastrous strikes and political turmoil. The decade began with a Labor government, which lasted until June of 1970 when Edward Heath narrowly beat Harold Wilson in a surprise victory, and ended with a new style of Tory government in the shape of the country’s first female prime minister, Margaret Thatcher.
In April 1970, the world held its breath as the drama of Apollo 13 was enacted hundreds of thousands of miles out in space, and the crippled spaceship limped home to safety. In September, high drama of a different kind was played out in the Jordanian desert when Middle Eastern terrorists blew up three jet airliners. The world lost a charismatic and influential figure in the shape of Hawking’s schoolboy hero, Bertrand Russell, who died at the age of ninety-seven. And it was in that year that Stephen Hawking began to turn his attention toward the exotic astronomical objects recently dubbed “black holes” and once again found himself in collaboration with the mathematician Roger Penrose.
It is often the case with scientific discovery that a crucial step forward comes through inspiration at an unexpected moment, and Hawking is fond of recalling the story of when his first black hole breakthrough came to him. Soon after the birth of his second child, Lucy, in November 1970, he was thinking about black holes as he got ready for bed one night. As he says:
My disability makes this rather a slow process, so I had plenty of time. Suddenly, I realized that many of the techniques that Penrose and I had developed to prove singularities could be applied to black holes.2
At that time, notions of what a black hole was really like were pretty hazy, and both Penrose and Hawking had been trying to come up with some way of stating which points in spacetime were inside a black hole and which were outside. It was just as he was about to get into bed one night that an obvious solution struck him. The answer to the problem was actually one that he claims Penrose had originally suggested but had not applied to the situation they were studying. The science is described in the next chapter; suffice it to say that the resolution was so exciting that Hawking got very little sleep that night. Early the next morning, he was on the phone to Penrose.
For the next two years (as we describe more fully in Chapter 9), the pair of them developed their ideas about the physics of black holes. As they worked, they came to see that the way they had originally perceived black-hole physics was not as clear-cut as it ought to be. To properly get to grips with it required them to dust away the mental cobwebs of dimly remembered physical concepts they had not thought about since undergraduate days. In particular, Hawking was gaining a renewed interest in a field called thermodynamics, developed by Lord Kelvin and others in the nineteenth century.
No one would have imagined that thermodynamics had any relevance to black holes at all. As Dennis Overbye has put it, “It was as if he had popped the hood on a Ferrari and found an antique steam engine chugging away inside.”3 It was ridiculous—thermodynamics was used to study gases under pressure, heat transfer, and the efficiency of steam engines, not such exotic objects as black holes. Little did Hawking realize at the time that thermodynamics was to have a huge influence on the future of black-hole theory and would shortly lead him into his second major scientific confrontation with another physicist.
By early 1973, Hawking and Penrose were beginning to use thermodynamics as an analogy for what was happening in a black hole. Scientists often do this: an everyday model helps them to understand situations as bizarre as those found in a singularity. However, a young researcher named Jacob Bekenstein, working at Princeton University, was taking things a lot further. He was not content to use thermodynamics as an analogy, but instead was applying its precepts literally. And he was coming up with some very interesting results.
When Hawking discovered Bekenstein’s work, he was incensed. He had been using thermodynamics as nothing more than a model for what was going on and believed it totally ridiculous to take it further and actually apply it to black holes. Together with his old friend from Cambridge, Brandon Carter, and the American relativist James Bardeen, he published a paper in the scientific journal Communications in Mathematical Physics that attempted to disclaim the suggestion. The argument raged in the scientific press and across the Atlantic for many months. Hawking was becoming more and more irritated by what he saw as Bekenstein’s absurd notions. In reply to a paper that Bekenstein published, Hawking, Carter, and Bardeen responded with their own, titled “The Four Laws of Black Hole Mechanics.” Both papers were later shown to be incomplete.
Most physicists sided with Hawking and his coauthors, but Bekenstein was not put off by the massed ranks of the scientific community ranged against him. Years later, he said of the confrontation:
In those days in 1973 when I was often told that I was headed the wrong way, I drew some comfort from Wheeler’s opinion that “black hole thermodynamics is crazy, perhaps crazy enough to work.”4
Hawking continued to think that Bekenstein’s notion was simply crazy—at least for a while. What brought about the change was a series of events that would lead him to a far more important conclusion about black holes and propel him to the forefront of theoretical physics. But that was half a year away, and in the intervening period the arguments continued.
Meanwhile, Hawking was finding the mathematics of the work increasingly difficult to deal with. The equations for interpreting the physics of black holes are amazingly complex, and by this stage of his illness he could use neither paper and pen nor a typewriter. Instead, he was forced to develop techniques for keeping such information in his mind and ways of manipulating equations without being able to write them down. Such a feat has been described by one of Hawking’s friends and collaborators, Werner Israel:
[The] achievement is as though Mozart had composed and carried an entire symphony in his head—anyone who saw the lines of complex mathematics covering the blackboard like musical staves at a recent seminar would have appreciated the comparison.5
Hawking has the great advantage of possessing a superb memory. In his book Beyond the Black Hole: Stephen Hawking’s Universe, John Boslough recounts an incident that demonstrates Hawking’s ability to retain detailed information in his head:
One of Hawking’s students told me that, while driving him to London for a physics conference once, Hawking remembered the page number of a minor error he had read in a book years before.6
Another anecdote describes how a secretary who worked for Hawking was amazed when he had once recalled, twenty-four hours later, a tiny mistake he had made while dictating—from memory—forty pages of equations. Hawking is not unique in having this talent. In 1983, he dazzled students at a Caltech (California Institute of Technology) seminar when he dictated a forty-term vers
ion of an important equation from memory. As his assistant finished writing the last term, his colleague, Nobel laureate Murray Gell-Mann, who happened to be sitting in on the talk, stood up and declared that Hawking had omitted a term. Gell-Mann was also working from memory.
Despite his disabilities, by the early 1970s Hawking was beginning to travel extensively. His status as a physicist had grown with his work in collaboration with Penrose, and he was frequently invited to deliver talks and address seminars around the world. At the same time as his scientific reputation was building, Hawking’s image as a determined fighter, who would go to any extreme to be treated as a normal human being, was spreading far beyond Cambridge.
One of his oldest and closest friends, the late David Schramm, of the University of Chicago, had a wealth of anecdotes about Stephen’s exploits. His favorite recollection from the early seventies concerns the occasion when he first became aware of Stephen’s huge potential for enjoying himself. After a conference in New York, Schramm took the Hawkings to a party thrown by a friend in Greenwich Village. Stephen really enjoyed himself, dancing with Jane, spinning his wheelchair around the room, and generally having a great time.
Schramm is also happy to dub his friend an incorrigible flirt and to describe his eyes as tremendously expressive. Women, Schramm claims, were always very interested in Stephen long before his international fame brought him wide attention. Indeed, David Schramm’s wife, Judy, was tremendously taken by him when they first met and found his ability to convey his personality by facial expression extremely attractive.
Hawking’s interest in dancing has never diminished, and the annual college parties at Caius would not have been the same without his joining in with the other fellows and their partners on the dance floor. Nowadays, in his elevated position as professor and head of the DAMTP, he is still to be seen at Christmas discos organized by the students, dancing the night away. His energy, both at work and at play, has become a legend. As David Schramm said, Stephen is a real party animal.
Between trips abroad and working on black holes with Roger Penrose, Hawking was collaborating with George Ellis on a book eventually to be called The Large Scale Structure of Spacetime. The idea for the book had arisen back in 1965, when Hawking was still working toward the completion of his Ph.D. Ellis remembers that the two of them had drawn up a list of future plans, which included “getting married” and “writing a cosmology book together.” Because both of them were busy with other projects and domestic changes, work on the manuscript went very slowly. Ellis spent some time in Hamburg and then in Boston, and the two of them began to see each other less frequently. Through Dennis Sciama, they managed to secure a contract with Cambridge University Press, which was just starting a series of high-level research monographs aimed at professional physicists.
It took six years to finish the manuscript. They divided up the various topics between them and worked independently, meeting when they could to go through each other’s contributions and make changes where appropriate. Ellis did all the typing; when Hawking could no longer write, he dictated his material to Ellis, who wrote it up for him. George Ellis was one of Hawking’s close associates who could understand his speech, but even he found it difficult at times. He soon discovered that it was much easier to follow what Hawking was saying in discussions about scientific matters, when the conversation consisted largely of familiar technical terms. It was in everyday conversations, which could be about almost anything, that the going got tough.
Because The Large Scale Structure of Spacetime took so long to write, events overtook it in a number of areas. In particular, Hawking’s own work on black holes (with which Ellis was not directly involved) had progressed faster than they could amend the text. The book dealt purely with classical theories of cosmology, but by the time of its publication in 1973, Hawking had made great strides in the quantum interpretation of black-hole physics, and it was not until it went into a second edition that they were able to update the text. The book caused quite a stir in academic circles and did a great deal for the general prestige of the series. Indeed, Hawking is now considered by Cambridge University Press to be the most distinguished author in its catalog.
The book is incredibly complex, completely unreadable except by experts working in the field of cosmology. Hawking and Ellis had no intention of writing a popular book, and their manuscript fit the requirements perfectly. However, a favorite story in the science department at Cambridge University Press recounts an occasion when an associate of Hawking’s ventured his opinion of this first publication. Hawking and Simon Mitton were returning to Cambridge from a meeting at the Royal Astronomical Society in London and happened to be sharing a railway carriage with the radio astronomer John Shakeshaft. As they pulled out of the station, Shakeshaft, who was sitting in the seat opposite Hawking, leaned forward and said, “Well, I got a copy of your book, Steve.”
“Oh, did you enjoy it?” asked Hawking.
“Well,” Shakeshaft replied, “I thought I might make it to page 10, but I only got as far as page 4, and I’ve given up, I’m afraid!” Despite the complexity of the book, the latest sales figures show that, since its publication, it has notched up 3,500 copies in hardback and over 20,000 in paperback—one of the best-selling research monographs ever published by Cambridge University Press.
Simon Mitton, who left the Institute of Astronomy in 1977, is now the science director at Cambridge University Press. He has suggested that the book has sold to a large number of undergraduates who bought it because it looks good on their bookshelves but have probably never gotten beyond the second page of tightly packed equations. The Large Scale Structure of Spacetime and other, later, technical books of Hawking’s showed a definite upturn in their sales curves upon the publication, many years later, of A Brief History of Time. After that, the original coauthor’s name, “S. W. Hawking,” printed on the jacket was hurriedly changed to “Stephen Hawking,” and the sales figures took another climb.
In the world of black-hole research, work was moving forward at a startling pace, and Hawking was in the vanguard. It was becoming more and more clear to him that the purely classical interpretation of black holes was deficient. In September 1973 he visited Moscow. The head of the Institute for Physical Problems of the USSR Academy of Sciences in Moscow was a fiery little man with a bald head and boundless energy named Yakov Boris Zel’dovich. He and his team had been working on black holes, in particular on the way in which they interacted with light. Hawking returned to Cambridge convinced that they were on to something but were going about things the wrong way. As he said many years later, “I didn’t like the way they derived their result, so I set out to do it properly.”7
What he then decided to attempt was quite revolutionary. As we saw in Chapter 2, the two great pillars of twentieth-century physics are quantum mechanics and relativity, but they are at opposite ends of the spectrum as far as physics is concerned. They speak a different language, and nobody had managed to reconcile the two theories. But this was exactly what Hawking had set his sights on. It seemed to be the only way forward if he were to explain the behavior of black holes thrown up by the contradictory ideas of Bekenstein on the one hand and of himself and Penrose on the other.
Sorting out the problem was easier said than done. Working on the equations in his head was difficult enough, but after months of intense work Hawking kept coming up with completely nonsensical results. According to the equations, black holes appeared to be emitting radiation. He, and everyone else at the time, believed this to be impossible. He was still convinced that he was really on to something but took the conscious decision not to discuss the problem with anyone until he had settled the matter one way or another.
Christmas 1973 came and he was still in as much of a mess with the mathematics as he had ever been. He decided to rework the equations. He knew that he had cut corners with some of the derivations and believed that these shortcuts may have held the key to the problem. During the Christmas vacation, h
e spent lonely weeks running and rerunning the equations through his mind, forcing himself to use ever more complex processes to eradicate the annoying anomalies. Finally, in January 1974 he took the plunge and confided in Dennis Sciama, who was organizing a conference at the time. To Hawking’s surprise, Sciama was very excited by the idea and, with Hawking’s permission, set about spreading the word.
A few days later, it was Hawking’s thirty-second birthday, and his family arranged a dinner party to celebrate. Soon after the meal was served, the phone rang. It was Roger Penrose calling from London—he had heard the story propagated by Sciama and wanted to know all about it. The discussion went on and on. The food grew cold, and the other guests waited patiently for Hawking to return to the table. Forty-five minutes later, with the meal ruined, he hung up. Penrose was tremendously excited and wanted to discuss it further.
Going against all current ideas about black holes, by the power of mathematical reasoning, Hawking had been forced to the unarguable conclusion that not only did tiny black holes emit radiation, but under certain conditions they could actually explode. By late January, one of his colleagues and friends from postgraduate days, Martin Rees, was convinced that Hawking had made a great discovery. Inspired by his latest discussion with Stephen, he bumped into Dennis Sciama in a corridor at the Institute of Astronomy. “Have you heard?” he said, excitedly. “Stephen’s changed everything!”