Stephen Hawking, His Life and Work

by Kitty Ferguson

  The Oxford visit was to deliver the third lecture in a series honouring his old mentor, Dennis Sciama. In Oviedo, Spain, he helped to celebrate the twenty-fifth anniversary of the Prince of Asturias awards, which are major global awards for scientific, technical, cultural, social and humanitarian work done at an international level.

  All this travel and activity would seem enough to exhaust the fittest of men. For Hawking, even after passing his sixtieth birthday, it was apparently exhilarating, and, despite all the moving about, Hawking’s work as a popular author continued. October 2005 saw the publication of another version of his first bestseller, this one titled A Briefer History of Time and co-authored with physicist Leonard Mlodinow. It was indeed briefer, beautifully illustrated and simpler, and brought the physics up to date. Also that year he began work compiling a collection of historical mathematical works with short biographies of important mathematicians, to be published in 2006. It would be titled God Created the Integers.

  Here and there, as Hawking lectured and met the media, he went on making provocative comments that had little or nothing to do with cosmology. His low opinion of politicians was increasingly evident. At an antiwar rally in Trafalgar Square in November 2004, he called the USA invasion of Iraq in March 2003 a ‘warcrime’.6 In 2005, when George W. Bush suggested returning astronauts to the moon, Hawking commented that ‘sending politicians would be much cheaper, because you don’t have to bring them back’.7 He admonished those who opposed stem cell research: ‘The fact that the cells may come from embryos is not an objection because the embryos are going to die anyway. It is morally equivalent to taking a heart transplant from a victim of a car accident.’8

  In May 2005 he lightened up – The Simpsons again. This time, an episode titled ‘Don’t Fear the Roofer’ had the ‘Hawking’ character announcing that he was now a Springfield resident. He had purchased the pizza parlor. He tried to get his computer to say the company motto but his computer got stuck and kept saying ‘pizza pizza’. ‘Hawking’ had to hit his computer to make it behave, something he cannot do in real life. Later in the story, ‘Hawking’ saved Homer’s sanity (if that is not an oxymoron) by explaining that it was a tear in spacetime and a little black hole, resulting in gravitational lensing, that caused Homer to be the only one able to see one of the other characters in Builder’s Barn. Hawking also made a television appearance that year in the docudrama Alien Planet, as an expert consultant.

  On 22 August 2005, the long-awaited paper that Hawking had been promising would lay out clearly and in detail his solution to the information paradox finally went to Physical Review, who published it in their 18 October edition. The paper was only three and a half pages long, with only three equations. Hawking utilized Feynman’s sums-over-histories, applying them, as he had before, to the universe. In developing his no-boundary proposal with James Hartle, Hawking had studied different histories the universe could have had, and calculated which were more probable than others. Now he was likewise asking his readers to imagine all alternative histories of universes. Some would have black holes and some would not. Information would be lost in those histories with black holes, but not in those without black holes. His solution depended on the fact that the universe histories where black holes exist would be cancelled out by those where they do not, the upshot being that information wouldn’t disappear because there would be no black holes for it to become trapped in in the first place. If you waited long enough, only those histories without black holes would be significant. Information, in the end, would be preserved.

  Given Hawking’s two explanations, and an earlier firm rejection of the idea that the information would be returned via Hawking radiation, it is a surprise to find that not long after he published this paper, in one of the children’s books he wrote with his daughter Lucy – George’s Secret Key to the Universe9 – with Christophe Galfard’s name also on the title page, he used a completely different solution to the problem, a solution that did involve Hawking radiation. It is also intriguing to discover that his top-down approach, which we will discuss a little later, is not easy to reconcile with his 2005 solution. Many of Hawking’s colleagues remained unconvinced, wondering why he preferred his solution to Leonard Susskind’s and Maldacena’s. Perhaps the reason was that, having introduced the problem in the first place, he felt that he should be the one to solve it.

  Hawking and Galfard explained the delay of the paper on the grounds of Hawking’s increasing difficulty with his hand-held clicker device. In that regard, 2005 was a dispiriting year. The speed at which he could communicate had been slowing down since 2000 until finally his hands were too weak to use the clicker. He exchanged it for a switching device attached to his glasses, developed by Words+ (the Infrared/Sound/Touch (IST) switch). The low-power infrared beam can be controlled by the blink of an eye or by moving a cheek muscle. As of 2011, Hawking controls his with his cheek muscle.

  The 2005 travel schedule did not end as planned. His schedule may have read Seattle, but he didn’t get there. He was to travel to Seattle from Oakland, California, but while he was being taken off his respirator in the morning shortly before departing from Oakland, something went wrong and Hawking ‘basically flat-lined. They had to resuscitate him, and that panicked a few people. But he’s been there before.’10 Hawking stayed in Oakland and delivered the Seattle address by live telecast.

  Undaunted by that glitch, Hawking in 2006 scheduled travel to France, Spain, China and Israel. It was not his first time in Israel. He and Jane had been there to accept the Wolf Prize in 1988. But this time he refused to accept the invitation unless he could spend part of his visit with and lecture to Palestinians. That was arranged. In Israel he added a new quip to his long list, commenting that the lack of anonymity when travelling was a down side to celebrity and worse for him than for others: ‘It is not enough for me to wear dark sunglasses and a wig. The wheelchair gives me away.’11

  The prestigious Copley Medal that he received from the Royal Society in November had travelled even further than its recipient. The Royal Society arranged for British astronaut Piers Sellers to fly it into space before presenting it to Hawking.

  Hawking’s marriage to Elaine ended in divorce in the summer of 2006. Hawking refrained from comment and his personal assistant, Judith Croasdell, brushed off reporters clamouring for a statement with the words ‘He is far too busy. This is just a distraction which is really annoying. We don’t have any time for any of this … We have no interest in any of the gossip that is going on.’12

  While observations by WMAP continued and theorists looked forward to results that would help them understand inflation theory and settle other questions, they didn’t stop in their tracks to wait. There were new models of inflation that went beyond the familiar four dimensions of our universe. In 2000, Hawking had mentioned the possible role of p-branes in inflation. Alan Guth, the founding father of inflation theory, was also studying the possibility of inflation in ‘brane world’ models. Natalia Shuhmaher and Robert Brandenberger of McGill University in Montreal came up with a model in 2006 in which it was a hot gas of branes that drove inflation. Their model had all the spatial dimensions starting out extremely compact, with the extra dimensions beyond our familiar three tucked together in what is called an ‘orbifold’. In the very early universe, the brane gas expanded and its energy density decreased until the three familiar spatial dimensions experienced an inflationary period.13

  Hawking stayed on in the large, comfortable house that he and his second wife had built together. For the first time since the beginning of his first marriage, he was living on his own, though of course still with nurses in attendance. He had resumed close contact with Jane and their children and grandchildren, relationships that had suffered over the past decade and a half, especially during the unpleasant period of the abuse issues when he had declined to honour their concerns. All seemed to have chosen to put behind them that difficult-to-understand chapter in their lives.

  Fat and Lea
n Years at the Trough

  Although string theorist Brian Greene would tell a Cambridge lecture audience in 2011 that string theorists were ‘happy as pigs in shit’, it had not always been like that. In the years leading up to his remark, beginning in the previous century, the pigsty had not always looked so appealing. As early as 1986, it had become clear to string theorists that the number of different ways the extra dimensions could curl up was distressingly enormous,14 and this was considered a serious shortcoming of string theory. However, that same year Andrei Linde cheered up his fellow theorists by insisting, in his first paper about eternal inflation, that this multiplicity of types of compactification (curling up) ‘should be considered not as a difficulty but as a virtue of these theories, since it increases the probability of the existence of mini-universes in which life of our type may appear.’15

  A happy moment came in 1997 when Maldacena, then at Harvard, introduced an idea known as ADS–CFTfn1 duality that suggested a link between conventional quantum field theory and a certain type of string theory. Recall that dualities are situations where two very different theories (sometimes seemingly contradictory) both accurately describe the same thing. Maldacena’s idea was an unproved conjecture, but it promised eventually to provide a genuine mathematic basis for string theory, and for that reason it had a strong influence on string theory’s subsequent development. ‘ADS–CFT correspondence’ also had significant implications for the relationship between string theory and brane worlds,16 and Hawking thought the idea had something to offer with regard to the information paradox, weighing in on the side of no loss of information.17

  Then, another downer. In 2000, Joe Polchinski at the University of California-Santa Barbara and Raphael Bousso at the University of California-Berkeley found that the basic equations of string theory had a truly astronomical number of different possible solutions, each representing a different way to describe a universe. It was a while before anyone could figure out whether any of these solutions were stable, but that was settled in 2003. There are (very roughly) 10500 of them. The problem this huge number presented was that string theory could never be proved right or wrong. Almost any experimental result would be consistent with it. As you will recall from Chapter 2, this is not good news for a theory.

  Again it was Andrei Linde who saved the day by pointing out that this was not such terrible news after all. Eternal inflation theory was, in fact, predicting just such a situation.

  Let’s take a look first at the curling problem … or non-problem.

  Curling Becomes an Olympic Event

  When a new universe emerges, not all the space dimensions predicted by string theory inflate. Some remain invisible but play an important role in deciding what form the new universe takes. Theorists were finding that they are not just curled up willy-nilly. Precisely how they are curled determines the apparent laws of nature in that particular universe.

  In the late 1980s and early 1990s, when Hawking had been thinking about wormholes and baby universes, he had speculated that the masses of particles and other fundamental numbers in nature might not be fundamental to the totality of universes, but different for different universes. They might be ‘quantum variables’ – numbers fixed at random at the moment of creation in each universe. A throw of the dice, with no way to know from a theory how the dice would fall.

  In M-theory, it was no longer a dice throw. As Hawking and Mlodinow would put it in The Grand Design, ‘the exact shape of the internal space determines both the values of physical constants, such as the charge of the electron, and the nature of the interactions between elementary particles’.18 In other words, the fundamental laws of M-theory permit different laws of nature in different universes, in the way that the Constitution of the USA permits different local laws in the different states. What the local laws of nature are in a universe is determined by the way the extra dimensions are curled up.

  Linde and his colleagues calculated the different ways the extra dimensions could curl up, each way leading to a unique universe.19 The number is enormous beyond imagining. Curling had indeed become an Olympic sport. The prosaic word ‘multiverse’ fails dismally as the name for all this. It’s too bad John Wheeler isn’t still around to give it a better one.

  Top Down

  Earlier in the decade, Hawking and Turok had left the pea instanton lying on a shelf and each headed off in a different direction. Turok began to favour ‘cyclic’ models where the universe expands from a big bang, eventually contracts again to a big crunch, and then reemerges in another big bang, in a cycle that keeps repeating itself.

  Hawking was more interested in models of eternal inflation. The fact that there are perhaps infinite possibilities for types of universes in this model makes it difficult, some would argue impossible, to calculate the likelihood of one kind of universe over another. Undeterred by this sticky mathematical problem, Hawking was determined to try, and in doing so he was going to utilize something that was still controversial among some of his colleagues, the anthropic principle.

  The controversy over the use of the anthropic principle, which had come to a head when Hawking and Turok introduced their pea instanton theory, had not died away. However, Hawking’s old friend Martin J. Rees and Mario Livio had given the anthropic principle and its use added respectability when they wrote in a paper in 2005 that ‘“anthropic reasoning” not only has a role in valid speculative scientific discourse, but may in fact have predictive power for sorting out allowable cosmological scenarios’. Although ‘such arguments raise the blood pressure of many scientists … it can indeed be one of many tools in the cosmological toolkit’.20 Hawking was preparing to treat it as a powerful tool.

  In February 2006, he and Thomas Hertog collaborated on a paper reporting on work in which they combined the string landscape of multiple universes with the initial conditions of the no-boundary proposal. Their suggestion was that we picture the early universe as a superposition of all possible ways it could have existed in the string theory landscape – as you might, if you were about to draw a card from an unusually large deck, visualize all the possibilities of your draw at once. Each possibility produces a different future. We are faced with a universe that has many, many possible beginnings and many, many possible histories. As Hawking quipped in a lecture at Caltech that year, ‘There will be a history in which the moon is made of blue cheese, but the amplitude for that is low, which is bad news for mice.’21

  Hawking and Hertog confined themselves to a model with a simple landscape that permitted several different inflationary histories for the universe. Should you place yourself at ‘the beginning’ and start calculating the probabilities of those universes emerging? No. In Hawking’s ‘top-down’ approach you start with the present, observing the universe as it currently exists, and then work backwards and decide how likely it is that each initial state would allow for the later existence of the populated universe we know. In this way, the present state of the universe ‘selects’ the past.

  Hawking and Hertog studied the observational consequences of the no-boundary initial conditions and came up with a scheme to test their theory. If this is a valid way of working, there will be subtle differences in the CMBR and the gravity wave spectra from what these would be like if standard inflation theory is correct. Future technology, Hawking thought, might be able to discover these subtleties.22

  Hawking delivered his 2006 lecture at Caltech controlling his computer with his cheek muscle. Titled ‘The Origins of the Universe’, it included some of the new thinking he and Hertog had been doing. Hawking would describe their top-down approach more fully later in his book The Grand Design.

  Secret Keys and Cosmic Adventures

  When Lucy Hawking’s novel Jaded had appeared in the spring of 2004, and she’d begun a second one, The Accidental Marathon, she’d talked with many interviewers about her books. Lucy was not terribly surprised but somewhat annoyed that questions about her and her writing inevitably drifted into questions about her father.


  Lucy’s life had taken a difficult turn. Her marriage had been shortlived, and soon after the separation her son William had been diagnosed with autism. ‘I actually felt as if my heart was breaking into tiny pieces,’ she said.23 Her mother Jane had insisted she persevere in finding the most effective treatment possible. William, as a result, had done remarkably well. He was very proud of his grandfather, not so much because of his physics accomplishments, but because ‘grandad has wheels’. And Hawking returned the compliment. His office was full of William’s pictures, and he even included one photo in The Universe in a Nutshell.

  Lucy’s response when the interviewers proved more interested in her father than in her was a practical one. She decided, if you can’t beat ’em, join ’em. She would collaborate on a book with him.

  In June 2006, Lucy accompanied her father on a trip to Hong Kong and Beijing, where the welcome was even more riotous than usual. When they appeared from their plane, police had to form a body chain to make a human corridor, holding back the crowds, so that they could reach the lift and get away to their hotel. Even with all that effort to protect him, Hawking came near to being pushed over. He was unflappable. He wanted to be photographed with this ‘rugby scrum’ of excited students, but the front-page newspaper photos captured only him and the rather desperate-looking policemen, until things settled down enough for a picture with a well-behaved group of small school children, unfurling a welcoming banner larger than they were. Two physics undergraduates from the Hong Kong University of Science and Technology, where Hawking was scheduled to lecture, had the honour of presenting him with flowers. Paul Chu Ching-wu, the university’s president, commented, ‘He’s one of the most famous scientists ever. If you could say that Isaac Newton changed the world, then Stephen Hawking has changed the universe.’24