Slowing down?
Hawking made yet another excursion into popular culture in the spring of 2003 when he agreed to take part in a routine on Late Night with Conan O’Brien. Comedian Jim Carrey led off the sketch by discussing cosmology. A mobile phone rang. The caller was Stephen Hawking telling Carrey not to bother: ‘Their pea brains cannot possibly grasp the concept.’ Having said that, he quickly excused himself. He couldn’t stay on the phone because he was watching Carrey’s film Dumb and Dumber, stunned by the ‘pure genius of it’. Hawking’s travel schedule that year had him criss-crossing the world, from a month at the Mitchell Institute for Fundamental Physics at Texas A&M to a meeting on cosmic inflation at the University of California-Davis, to Sweden to receive the Oskar Klein Medal from the Royal Swedish Academy of Sciences and to attend a Nobel Symposium on String Theory and Cosmology, back to America for a two-month visit at Caltech and the University of California-Santa Barbara, then over to Case Western Reserve University in Cleveland.
Unease among his physics colleagues that Stephen Hawking was slowing down seemed unfounded, given such a schedule, but they also feared he might be no longer at the height of his intellectual powers. In a poll taken among physicists at the end of the millennium asking who were the most influential physicists, Hawking’s name was not anywhere near the top. His use of the little ‘clicker’ that responded to his faint hand pressure – the only way he could communicate with colleagues – was becoming more and more difficult and slow. One way to get around this frustrating situation was to solicit the help of a research student. This time Hawking chose a young man named Christophe Galfard. The procedure would be for Hawking to consider a problem and suggest possible approaches to Galfard, who would then concentrate on the mathematical details to find out whether Hawking’s insights were correct and whether they led anywhere.
Galfard recalls that it took a while for him to get up to steam. Hawking’s ideas were coming much more rapidly than he could deal with them. In words that are encouraging to anyone like myself who has read Hawking’s papers and laboured to understand them, Galfard has described his chagrin as each sentence seemed to take about six months to decipher. He was lagging behind a half year and catching up was tough going.32
In the interest of moving things forward more rapidly, Galfard took a liberty that others had seldom taken – finishing sentences for Hawking when his intention was clear and he was struggling to select the words. In the past Hawking had often gone right ahead and completed the sentence, ignoring this second-guessing even when it was correct, but he allowed Galfard to expedite matters. Galfard also used Hawking’s ability to indicate ‘yes’ and ‘no’ with a small movement of his face, rather than wait for him to find the word on his screen. You wonder, seeing video clips of the two of them together, how Galfard avoided getting a bad crick in his neck as he bobbed back and forth between peering straight ahead at the computer screen and dipping forward to see Hawking’s face.
Galfard had his work cut out for him. In 2003, a young Argentinian physicist named Juan Martin Maldacena, at the Institute for Advanced Studies in Princeton, finally gave Leonard Susskind’s ideas for solving the information paradox a rigorous mathematical treatment that seemed to settle the issue in Susskind’s favour.33 At a conference in Santa Barbara, after-dinner speaker Jeff Harvey, instead of giving the expected talk, introduced a victory song. ‘The Maldacena’ was set to the music of a Latin dance that was popular in the mid-1990s, the ‘Macarena’. Each short verse ended with ‘Ehhh! Maldacena!’34 The audience enthusiastically joined in the singing and dancing, celebrating the rescue of physics from the ogre of the information paradox. Susskind declared the war over. It should have come to an end much earlier, he insisted, but Hawking ‘was like one of those unfortunate soldiers who wander in the jungle for years, not knowing that the hostilities have ended’.35 Although a consensus was indeed growing that Hawking was wrong, Kip Thorne stuck with him. Hawking did not change his mind. Not yet.
He asked Galfard to study Maldacena’s paper about the information paradox. Hawking had decided nothing would do but a frontal attack on this piece that was convincing people he was wrong. It was not an easy assignment. After messing with it for a year and a half, Galfard still found it difficult to decide whether information was or was not lost in black holes.
On 1 December 2003, Hawking was rushed to the hospital with pneumonia. On life support for several weeks, while others feared he was probably on his deathbed, he didn’t waste the time. He spent it thinking about black holes, intent on finding a fresh approach to the information paradox. Recovery was slow, but after his discharge in the late winter of 2004 he and Galfard began again in earnest discussing the ideas those bedridden months had produced. After many gruellingly long days and late nights, including weekends when the work seemed never to stop,36 Hawking finally felt he was ready to emerge from the quiet refuge of his office and do battle.
The Dublin Conference
That spring of 2004, Hawking gave a seminar in Cambridge to introduce some of his new ideas in a preliminary, sketchy fashion, and he let it be known that he wished to address his physics colleagues at a major conference. There was just such an event coming up in July in Dublin, the 17th International Conference on General Relativity and Gravitation. Hawking contacted the Chair of the Scientific Committee of the conference, Curt Cutner, requesting a slot on the programme with the words ‘I have solved the black hole information problem and I want to talk about it.’37 It was a big favour to request, for Hawking’s paper was a late entry – participants had been asked to submit a title and abstract by 19 March, when he was barely out of the hospital. Also he would not be releasing a preprint of the paper. Nevertheless, his stature in the field won him an hour-long slot on the conference schedule.
The media and fan frenzy his appearance generated showed that Hawking’s superstar celebrity status had not waned. A public relations firm responsible for controlling access to the auditorium charged a reported £4,000, and it earned its fee as reporters and Hawking aficionados stormed the doors. Those fortunate enough to sport press badges soon lined the aisles inside, setting up their cameras and recording paraphernalia.
There was less excitement among Hawking’s colleagues, rightfully in the hall as conference participants, as they wondered what to expect. Bursts of camera flashes followed Hawking as he made his smooth, stately, frozen progress along the aisle to the foot of a ramp that led to the stage of the grand concert hall of the Royal Dublin Society. Some believed he was about to deliver a defiant statement that would reiterate what he had been saying for more than twenty years, that information is lost in black holes. Others thought this fading genius would quietly concede the issue. Kip Thorne, who had continued through the years to agree with Hawking about the loss of information in black holes, John Preskill, who had not, Petros Florides, who chaired the conference, and Christophe Galfard were waiting on stage, facing an array of TV cameras ready to record the event. It was not a normal day at a physics conference.
Only Galfard and Thorne knew that Hawking was about to make one of his famous about-faces, but not in the way anyone was expecting. He was not going to concede to Susskind and Maldacena. Yes, the idea he had stubbornly stuck with for more than twenty years was wrong. But Susskind and Maldacena hadn’t solved the problem. Hawking would do that himself. He had thought of another way to get round the information paradox.
The session began with an introduction by Petros Florides who quipped that while it is well known that no information can travel faster than the speed of light, this law seemed not to hold when it came to the speed at which the news of an upcoming Hawking appearance travels around the world.
It had become Hawking’s custom to introduce his lectures with the question, in his calm, mechanical voice, ‘Can you hear me?’ Presumably if you couldn’t, you wouldn’t answer, so there was usually either an agreeable murmur or a cheer in reply. After that trademark beginning, he began by laying out the problem a
nd tracing the history of the information paradox all the way back to the mid-1960s, when it was discovered that all information about a body collapsing to form a black hole was lost from the outside region except for three things: mass, angular momentum and electric charge. John Wheeler called this discovery ‘black holes have no hair’, and it has been ever since known as the ‘no hair theorem’.
None of this presented a problem for information conservation. A classical black hole would last for ever preserving the information inside it, inaccessible, but there. Still part of the universe. The problem had emerged when Hawking discovered that quantum effects would cause a black hole to radiate at a steady rate – the famous Hawking radiation. That radiation carries no information about what made the black hole or what has fallen in. Still no problem until you realize that in this process the black hole would eventually evaporate away and disappear entirely. Then what would happen to all that information locked inside? It seemed the only way the information could avoid being lost would be if the Hawking radiation had subtle differences in it that would reflect what had fallen in. No one had found any way for such differences to be produced, though many physicists believed one must exist. Hawking’s calculations, however, showed that the radiation was exactly thermal, random and featureless.38
In case anyone was wondering whether a baby universe branching off a black hole might solve the information loss problem, Hawking brought them up to date:
There is no baby universe branching off inside a black hole, as I once thought. The information remains firmly in our universe. I’m sorry to disappoint science fiction fans, but if information is preserved, there is no possibility of using black holes to travel to other universes. If you jump into a black hole, your mass energy will be returned to our universe, but in a mangled form, which contains the information about what you were like, but in an unrecognizable state.39
Some in the audience must have pricked up their ears at that. Was Hawking about to say that Hawking radiation could after all be the vehicle of escape and that, as in the description earlier about restoring a burned book, it might at least in principle be possible to recover from that radiation the information hidden in a black hole?
Hawking’s new solution to the problem had to do with something else, the possibility that a black hole could have more than one geometry (topology) at the same time. Information would not be trapped because a true event horizon would not form.
Christophe Galfard remembers that Hawking’s talk seemed to leave most of his physics audience ‘largely bemused’. There were whispers of ‘big on claims, short on mathematics … not really all that convincing … mostly smoke and mirrors’. Kip Thorne commented: ‘This looks to me on the face of it to be a lovely argument, but I haven’t yet seen all the details.’40 He said he would have to take some time with Hawking’s paper before he could say whether or not Hawking was right. Roger Penrose was not convinced: ‘It seems to me that the indication that the information is lost is very powerful, and that is what Stephen originally thought. In Dublin he publicly retracted. In my view he was completely wrong to retract. He should have stuck to his guns.’41 Hawking, though he expressed intentions of trying to support his idea with a mathematical proof, was convinced enough of his conclusions to concede a bet that he and Kip Thorne had made with John Preskill of Caltech. The bet read as follows:
Whereas Stephen Hawking and Kip Thorne firmly believe that information swallowed by a black hole is for ever hidden from the outside universe, and can never be revealed even as the black hole evaporates and completely disappears,
And whereas John Preskill firmly believes that a mechanism for the information to be released by the evaporating black hole must and will be found in the correct theory of quantum gravity,
Therefore Preskill offers, and Hawking/Thorne accept, a wager that:
When an initial pure quantum state undergoes gravitational collapse to form a black hole, the final state at the end of black hole evaporation will always be a pure quantum state.
The loser(s) will reward the winner(s) with an encyclopedia of the winner’s choice, from which information can be recovered at will.
The document had been signed by all three men, Stephen Hawking’s signature being his thumbprint, and dated 6 February 1997, Pasadena, California.
Hawking ended his talk saying, ‘I will give John Preskill the encyclopedia he has requested. John is all-American, so naturally he wants an encyclopedia of baseball. I had great difficulty in finding one over here, so I offered him an encyclopedia of cricket, as an alternative, but John wouldn’t be persuaded of the superiority of cricket. Fortunately, my assistant, Andrew Dunn, persuaded the publishers Sportclassic Books to fly a copy of “Total Baseball: The Ultimate Baseball Encyclopedia” to Dublin. I will give John the encyclopedia now. If Kip agrees to concede the bet later, he can pay me back.’ Thorne was not convinced that Hawking, or anyone else, had solved the problem of the information paradox. The encyclopedia was brought on stage, and John Preskill held it over his head as though he were holding the men’s tennis championship trophy at Wimbledon.
Hawking later commented on the occasion in a lecture he gave at Caltech the following January, in 2005: ‘The [information loss] paradox had been argued for thirty years without much progress until I found what I think was its resolution. Information is not lost, but it is not returned in a useful way. It is like burning an encyclopedia. Information is not lost, but it is very hard to read. I gave John Preskill a baseball encyclopedia. Maybe I should have just given him the ashes.’42
Hawking had promised to provide his colleagues with a fuller explanation. It would take the form of a paper published in October 2005.
fn1 WMAP was the result of a partnership between the Goddard Space Flight Center and Princeton University.
18
‘Grandad has wheels’
THE BBC DEBUTED the Television film Hawking in April 2004, when Hawking had recently emerged from hospital and was preparing to do battle on the information paradox issue. This was not a full biography but a moving dramatization of two crucial years in Hawking’s life when he learned he had ALS, met Jane Wilde, and worked on singularity theorems for his thesis. A 2002 documentary, Stephen Hawking: Profile, was re-aired with the film. There were an estimated 4 million viewers.
Hawking helped with the final script, and Benedict Cumberbatch, who played young Stephen Hawking, took the trouble to study carefully the early stages of ALS. Jane, on whose autobiography the film was partially based, watched the video at first in bits and could find little to fault. ‘[Cumberbatch] was uncanny. He worked so hard in researching the exact progression of motor neurone disease. It brought back that period so very strongly. I think the young lady playing me, however, was much more feisty than ever I was. I was always extremely determined but I was also quite timid. So in that sense many of the things that appear in the film are not quite historically accurate.’ However, Jane felt that the film was true to the spirit of those years. ‘I can remember vividly the euphoric sense we had about us, that we were doing something exceptional … that, despite it all, everything was going to be possible.’1
At about the same time the film was aired, the disturbing reports and statements having to do with abuse were finally locked away in the Cambridge police files.
Hawking was not doing any less well in popularity polls. In a 2004 survey of role models that polled five hundred sixteen- to eighteen-year-old English boys, he came in second to rugby star Jonny Wilkinson, edged out again by a sports celebrity, as he had been in Japan. But Hawking was not slowing down as a world traveller and lecturer. His diary in 2005 read: January: Caltech and the University of California-Santa Barbara; February: Washington, DC, and Oxford; March: Spain; June: Hong Kong; October: Germany; November: California again and then Seattle, Washington.
During the January visit to Caltech, Hawking suggested that this time he give a lecture solely for undergraduates. The subject would be his life in physics. The title
borrowed the famous Star Trek split infinitive: ‘To Boldly Go’.
The trip to Washington, DC, in February, with his wife Elaine, was for the purpose of receiving the James Smithson Bicentennial Medal. The Smithsonian Institution arranged, with help from Jim Hartle, to present a retrospective of Hawking’s life: ‘Stephen Hawking’s Alternate Universe’. Hartle introduced his old friend in glowing terms: ‘Stephen Hawking’s work has been characterized by great mathematical precision and extraordinary physical inventiveness. He is almost always surprising.’2 Hartle quoted Hawking’s words about the career path he had followed: ‘You might think I had a grand premeditated design to address the outstanding problems concerning the origin and evolution of the universe. But it was not really like that. I did not have a master plan. Rather I followed my nose and did whatever looked interesting and possible at the time.’3
Hawking returned on this occasion to the possibility of extraterrestrial intelligent life, and his lecture was introduced by music that was clearly meant to resemble the sound track of Star Wars. ‘By intelligent life, I don’t mean only the DNA-based humanoid life like you see on Star Trek,’ he said, ‘which all is remarkably like ourselves. The range of possible life forms in the universe is much wider and includes electronic systems like computers.’4 He criticized the Star Trek image of alien civilizations as too static. Even though the suggestion was that their science and technology are more advanced than ours at present, some of the alien beings are pictured as having attained a stable state near perfection, with no further progress or evolution expected. ‘I don’t believe the Star Trek picture. We will never reach a final steady state, the end of development. Instead we shall continue to change at an ever-increasing rate.’5
Stephen Hawking, His Life and Work Page 29
