Stephen Hawking, His Life and Work

by Kitty Ferguson

  The ‘holographic principle’, then, is the idea that information is in some sense stored on the boundary of a system instead of inside it. Think of the holographic image on a credit card, where a three-dimensional image is stored on the two-dimensional surface of the card. Susskind elaborated on that idea to compare a black hole with a giant cosmic projector that takes a three-dimensional person and turns her into a two-dimensional surface on the event horizon. The bottom line was that all that information, stretched out on the edge of the black hole, is not destroyed. It is all there. Not lost.

  A very interesting suggestion about how this all happens came from string theory, in which, you will recall, particles do not look like points but rather like tiny loops of vibrating string. The way a loop of string vibrates determines which type of particle it is. First, think of a single string falling into a black hole. You are watching it from a spaceship at a distance. As it approaches the event horizon, its vibration appears to slow down. The string spreads, ending up with whatever information it carries smeared over the entire event horizon. As each string spreads out, it overlaps others, resulting in a dense tangle. Since everything is made of strings, everything that falls towards a black hole is smeared out like that. The resulting giant tangle of strings covering the surface of the black hole is able to hold the entire enormous amount of information that fell when the black hole formed and afterwards. Here, then, at the horizon, is everything that ‘fell into the black hole’. As far as the observer at a distance is concerned, it didn’t fall into the hole at all. It stopped at the horizon and was later radiated back into space.

  Susskind visited Cambridge in 1994 and looked upon it as a golden opportunity to talk with Hawking and convince him that horizon complementarity could solve the information paradox. Unfortunately Hawking was ill at the time and they were unable to connect. Finally, Hawking attended a lecture that Susskind delivered about black hole complementarity. Susskind remembers the occasion: ‘This was the last chance for a confrontation with Stephen. The lecture room was full to capacity. Stephen arrived just as I was starting and sat in the back. Normally, he sits up front near the blackboard. He was not alone; his nurse and another assistant were in attendance, just in case he needed medical attention. It was obvious that he was having trouble, and about half way through the seminar, he left. That was it.’29 Susskind’s ideas would wait until early in the twenty-first century for someone to give them a rigorous mathematical treatment.

  15

  ‘I think we have a good chance of avoiding both Armageddon and a new Dark Age’

  IN THE SPRING of 1995, seven years after it first appeared, A Brief History of Time finally went into paperback. Normally this would happen for a book about a year after its initial publication, but because the hardcover continued to sell at such a phenomenal rate, Bantam had repeatedly put off that decision. An interviewer told Hawking that with 600,000 copies sold in the UK, more than 8 million worldwide, and more than 235 weeks on the Times bestseller list, it was difficult to imagine there were still people who had waited seven years to learn the secrets of the universe, just so they could buy his book in paperback and save £8.1 Hawking disagreed: ‘It has sold one copy for every 750 men, women and children in the world, so there are 749 to go.’ ‘Hawking logic!’ chimed in his nurse.2

  Stephen and Jane Hawking finalized their divorce that spring. In July, Stephen made the first public announcement of his engagement and upcoming marriage to Elaine at the Aspen Music Festival in Colorado, at a concert to benefit the Festival and Music School and the Aspen Center for Physics.3

  Hawking’s short, joyful speech introduced a performance of Richard Wagner’s Siegfried Idyll. Unlike most of Wagner’s compositions, this is intimate chamber music and requires only a small ensemble of musicians. It has a romantic history. Wagner composed it to be played at his villa, on the staircase outside the bedroom of his wife Cosima as a surprise on Christmas morning 1870, her birthday. The couple had married the summer before. The Idyll was an inspired choice for Hawking’s engagement announcement. It combines gentle tenderness and passion in a way that is almost unique in the literature. Elaine fondled Stephen’s shoulder lovingly as he exited the stage and the music began. The physicist David Schramm, chairman of the board of the Aspen Center for Physics, commented: ‘There is a warmth – a caring expression in Stephen’s eyes when he looks at Elaine. There is a very special relationship between them.’4 Two months later, on 16 September 1995, Stephen and Elaine were married in a ceremony in a Cambridge registry office, followed by a church blessing and a celebration. None of his three children or her two boys were present. Hawking had a statement programmed and ready in his computer: ‘It’s wonderful – I have married the woman I love.’5

  The press reaction at the time of their marriage was not kind, questioning Elaine’s motives for marrying this extremely wealthy man who was probably not going to live very long. Interviewers must have hoped that Elaine’s former husband, David Mason, would provide some snide quotation, but he came to Elaine’s defence. All Elaine really wanted, he said, was someone who needed her.6 Elaine apparently needed Hawking too, for he replied to a question about his reasons for marrying Elaine that ‘It’s time I helped someone else. All my adult life people have been helping me.’7 After his wedding, Hawking consistently declined to answer press questions – and those from curious audiences – about his marriage. ‘I would rather not go into details of my private life’ was his standard reply.8 Amidst the concerned rumours and the less well-meaning gossip that would surface about Stephen’s and Elaine’s life together, there would be one consistent theme expressed by those who know him best. The bottom line was ‘He loves Elaine.’

  Jane Hawking was in Seattle visiting her son Robert when the engagement announcement was made. When she got back to Cambridge, she began to reconsider an earlier decision not to write her memoirs as Hawking’s wife. She had tried in vain to find a publisher for a book she was writing about ‘Le Moulin’, a home that she bought and restored in France. That book offered invaluable advice and practical information for others who might contemplate doing the same. Publishers, however, wanted a book about her personal life with Hawking, not about Le Moulin. One unscrupulous agent tricked her into signing a contract that promised a ‘tell-all’ later, if the publisher agreed to take the book she was writing now. Jane had waited out the term of that contract and then, in 1994, self-published At Home in France.

  In the summer and autumn of 1995, with everything changed, Stephen married to Elaine, and Jonathan and herself living openly together in Cambridge with Jane’s son Timothy, it seemed to her that the time had come to tell the entire ‘Hawking story’ from her own much less up-beat point of view. A letter came from an editor at Macmillan Publishers, asking whether she would consider writing an autobiography. This time, Jane said yes.9

  Tea and a Lecture

  When I visited Hawking for tea in the DAMTP in the spring of 1996, his book with Roger Penrose, The Nature of Space and Time, had recently appeared. One particular statement in the book had annoyed some critics.10 Hawking had re-emphasized something he’d been saying for at least a decade, that a theory in physics ‘is just a mathematical model and it is meaningless to ask whether it corresponds to reality. All that one can ask is whether its predictions agree with observation.’11 The rest of us may be curious, but Hawking was insisting, and would continue to insist, that it is meaningless to discuss such questions as whether wormholes really exist.

  Over tea, I pursued those ideas a little further with him: all right, granted, it is pointless to ask whether this theory corresponds to reality. But, is there, actually, an answer to that question? Is there reality, inaccessible to us perhaps, but solid reality, all the same? To say there is none at all, on any level, is to take a very postmodern view of things. Hawking’s reply was interesting: ‘We never have a model-independent view of reality. But that does not mean there is no model-independent reality. If I didn’t think there is, I could
not continue to do science.’12 In The Nature of Space and Time, a collection of six lectures that Hawking and Penrose had delivered at the Newton Institute in Cambridge in 1994, giving insights into the two men’s differing philosophical and scientific points of view, Hawking commented: ‘I think Penrose is a Platonist at heart but he must answer for himself.’13 Hawking’s comment to me would certainly make him a Platonist too.14

  We had our tea in the common room surrounded as usual by the bustling herd of students and physicists, their dress still casual to the point of scruffy, their language still a mixture of English and mathematics, conversations ranging across the span and history of the universe, equations scribbled on the surfaces of the low tables. In this company, it occurred to me, Hawking has never been treated as anyone extraordinary, though his colleagues and students are willing to outwait the long pauses while he composes his sentences, and consider what he says worth the wait. Because of his lack of body language and vocal nuance, the synthesized voice conveys only one mood: infinite, thoughtful patience, lending an oracular air to his statements. His humour, whether he intends it that way or not, comes across as dry wit.

  Tea was cut short that afternoon because Hawking was scheduled to give a public lecture. The tickets had all been distributed through the university weeks ago. Someone suggested that I come along with his graduate and postdoctoral students, who would be admitted without tickets. It was a particularly kind suggestion, since I was at least twenty-five years older than any of them – the lecturer’s age, not theirs.

  The lecture was a media event: sound trucks outside the building, cables snaking in, spotlights focused on the stage and the audience. The lecture hall was modern and large, though not nearly so capacious as others around the world that Hawking appearances routinely packed to the rafters. About 500 people sat on long, curved, desklike benches, others crowded into the balconies above us. There was a hush as Hawking rolled on to the platform. Something about that calm, ordinary, inexorable progress to centre stage gave it the aura of a visitation from another dimension. He had pre-programmed the lecture into his computer. An assistant worked a slide projector. Even when the lecture and slides included formulas and diagrams that few could follow, Hawking commanded rapt attention.

  At that time, Hawking was also busy with another television project, to be aired the next year. Stephen Hawking’s Universe and a companion book to go with it was a six-part collaboration between the BBC and Public Television in America. This time he got his way when he insisted the series stick to science.

  Jane and Jonathan Hellyer Jones were married in July 1997. Earlier that year, in March, Lucy had told the family that she and her fiancé, Alex Mackenzie Smith, a member of the United Nations Peace Corps in Bosnia, were expecting a child. They planned to live together in London, and were married later that spring. They named Hawking’s first grandchild William, which is of course Stephen’s middle name.15

  Censorship on a Cosmic Level

  It was time to concede another bet. The background of this one began in 1970, when Hawking was first thinking about the light rays at the event horizon of a black hole and what would happen if they approached each other, collided, and fell into the black hole. The question was, could a black hole ever end up with no horizon, with the singularity left ‘naked’, exposed to view? Roger Penrose had proposed a ‘cosmic censorship conjecture’ – that a singularity would always be clothed inside a horizon. The discussion had gone on through the years, and Hawking had bet Kip Thorne and John Preskill (also of Caltech) that Penrose was right. The loser would reward the winner or winners with ‘clothing to cover the winner’s nakedness, to be embroidered with a suitable concessionary message’. Since 1991, when the bet was made and signed, Demetrios Christodoulou of Princeton, using computer simulations by Matthew Choptuik at the University of Texas, had done some theoretical calculations which suggested that a singularity without an event horizon might be created under very unlikely special circumstances such as a collapsing black hole. The situation was about as likely as balancing a pencil upright on its sharpened tip, said Choptuik, but it was theoretically not impossible.

  Hawking conceded the bet at a public lecture in California in 1997. The message in the ‘embroidery’ on the T-shirts he gave Thorne and Preskill indicated that although a naked singularity could happen, it probably wouldn’t – or shouldn’t! The cartoon image showed a shapely woman barely concealing her nakedness behind a towel with the words ‘Nature Abhors a Naked Singularity’. When Christodoulou redid his calculations, he found that Hawking’s concession had probably been premature, so a new wager was made. This time it was clearly spelled out that the singularity would have to happen without any unlikely special conditions and the loser’s message on the garment would have to be unambiguously concessionary. Preskill had meanwhile made the remark that we do know of one naked singularity, the Big Bang.16

  Hawking made a particularly memorable journey in 1997. He, with Kip Thorne and several of their colleagues, visited Antarctica. Photographs show him bundled up in his wheelchair against a background of ice and snow. He didn’t actually get to the South Pole, however, and he’s never been to the North Pole, which means he can’t say he has personally observed that there are no boundaries there.

  Speeding Up!

  In January 1998, at a meeting of the American Astronomical Society, a young astronomer named Saul Perlmutter made an announcement that rivalled in significance Hubble’s discovery that the universe is expanding: the expansion of the universe is speeding up! Cosmologists’ jaws dropped. The media soon got the news out that something stunning had turned up, something that ran completely counter to all expectations. In the afterword to the new 2010 edition of his book with Roger Penrose, The Nature of Space and Time, Hawking exclaimed about the excitement and importance of this startling development.

  Two teams of astronomers made the discovery independently: Perlmutter and his Supernova Cosmology Project of the Lawrence Berkeley National Laboratory in California had been studying supernovae to find out whether the expansion of the universe was slowing down. They had discovered quite the opposite. It was difficult to believe they were not mistaken, but in March another research group, this one led by Brian Schmidt of the Mount Stromlo and Siding Spring Observatory in Australia, reported similar findings.

  Inflation theory was predicting a flat universe, while this new data seemed to be hinting that we might instead have an open universe (Friedmann’s second model, see Figure 6.1); but another implication of the discovery wasn’t so bad for inflation theory. What Perlmutter had found could be taken as the first strong observational evidence that there is a repulsive force operating in the universe, that the type of antigravity acceleration which inflation theory had suggested really does exist. The universe is getting an antigravity boost from somewhere.

  Were we seeing evidence of the cosmological constant Einstein had put into his equations of general relativity when he didn’t believe what they were implying? He had, of course, taken it out again. Now Perlmutter suggested that there is, after all, a small positive cosmological constant, and Hawking and many others agreed that was the simplest explanation.17 But there was some unease with this conclusion. Things might not be quite that simple. Perhaps there is a more exotic antigravity stress in the universe. There was talk of a mysterious ‘quintessence’ (named after a fifth element suggested by Aristotle).

  ‘Dark energy’ entered the physics vocabulary to describe the mysterious energy source. And energy, we know from Einstein’s most familiar equation, has an equivalence with matter. One suggestion was that, added to ordinary matter and ‘dark matter’ (whose makeup is still mysterious but whose presence is well confirmed), dark energy might actually produce precisely the flat universe that inflation theory was predicting. In the afterword to the 2010 edition of The Nature of Space and Time, Hawking suggested that the presence of enough of this energy might even produce the positive curvature necessary for the closed universe consistent
with the original no-boundary proposal.18 However, in 1998, Hawking was beginning to think he might take another look at that proposal in the light of this unexpected discovery.

  Nearing the millennium

  In 1998, President Bill Clinton announced the Millennium Evening series – eight lectures and cultural showcases to be hosted by the White House and carried live over the internet – and invited Hawking to be one of the lecturers. His lecture ‘Imagination and Change: Science in the Next Millennium’, was the second event in the series, on 6 March. He used the opportunity to warn about what he saw as serious dangers – overpopulation and unchecked energy consumption. Hawking thought there was a possibility that we will destroy all life on Earth or ‘descend into a state of brutalism and barbarity’. He also expressed his grave doubts that any laws or bans would stop all attempts to redesign human DNA in the next millennium. No matter that most people would approve a legal ban on human genetic engineering, that would not prevent someone somewhere from doing it. Perhaps because he didn’t want to leave his listeners completely devastated, he ended in a more upbeat mood: ‘I’m an optimist, I think we have a good chance of avoiding both Armageddon and a new Dark Age.’19

  America seemed to bring out both a darker and a more light-hearted side of Hawking. Back in California again in 1999, he flew from Monterey, where he was staying, to Los Angeles to do the voice of himself in an episode of The Simpsons. This assignment was of truly vital importance to him, as witness the fact that when his wheelchair broke down two days before the flight, his graduate assistant Chris Burgoyne worked for a straight thirty-six hours to repair it in time. If Hawking couldn’t rescue the entire human race from Armageddon, he could at least get to Los Angeles in time to ‘Save Lisa’s Brain’. The line best remembered from the episode was Hawking telling Homer that Homer’s theory of a doughnut-shaped universe was ‘interesting’ and that ‘I may have to steal it.’ Hawking asked the producers whether it might be possible to create an ‘action figure’ of him. That went on the market and became a bestseller in toy stores. Hawking (again doing the voice-over) also came to the rescue of the whole universe in an episode of Dilbert in which a machine accidentally created a black hole. Dogbert kidnapped Hawking in order to get him to repair spacetime. Needless to say, Dr Hawking cured the universe. Hawking went in for repairs himself that year. Surgery to reroute his larynx to prevent food falling into his lungs made eating a less hazardous and more enjoyable activity.