Confined to a wheelchair, unable to speak, communicating with the world only through a computer and voice synthesiser, Stephen Hawking has an easily identifiable, and totally misleading, public image. He controls the computer, his link with the outside world, with just two fingers. This is an apposite indication of Hawking’s attitude, down the years, towards authority in general and scientific icons in particular. He knows his own mind, doesn’t suffer fools gladly and has never been afraid to take issue with other scientists when certain, as he generally is, that he is right. Rather more rarely, he has also been quick to acknowledge his error when it turns out that he was wrong after all. And he has a bewildering ability to change his mind completely on a scientific issue in the light of new evidence.
Hawking shares some of these characteristics with the famous dissident astrophysicist Fred Hoyle, who was one of his boyhood heroes and whose presence in Cambridge was a major reason why Hawking decided to go there to work for his PhD. So it is ironic that Hawking was first noticed by the scientific community outside Cambridge in a confrontation with Hoyle at the Royal Society.
It was during the mid-1960s. Hawking was a research student, still wet behind the ears by scientific standards. Hoyle was an established scientist, a professor with an impressive reputation and a string of scientific successes to his name, presenting the latest cosmological ideas that he had been working on with Jayant Narlikar. At the end of the talk, Hawking, who had discussed the work with Narlikar previously, pointed out that there was a fatal flaw in the calculations. ‘How do you know?’ asked Hoyle. ‘Because I worked it out,’ came back the defiant reply. And he was right. In Hawking’s world, even boyhood heroes are not to be tolerated if they get things wrong.
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Some of the myths that have built up around Hawking are true. He did indeed work, on average, for only an hour or so a day when studying (if that is the right word) for his first degree, in Oxford. When, like lesser mortals, he panicked at the approach of Finals and made a special effort, he upped this to as much as three hours a day. The result was that, after the written papers, he was on the borderline between receiving a first-class degree or a second, and was called for an oral examination. At the end of this, he was asked about his future plans. He told the examiners that he intended to go into research, and had been offered a place at Cambridge should he gain a First. ‘If you award me a First,’ he said, ‘I will go to Cambridge. If I receive a Second, I shall stay in Oxford, so I expect you will give me a First.’ They did.
Once in Cambridge, however, Hawking struggled. Despite the famous run-in with Hoyle at the Royal Society, he found the transition to original work difficult, and suffered from the lack of advanced mathematical education. Indeed, he still describes himself as a physicist whose mathematical education stopped at A level. It was also around this time that his illness, variously known as motor neuron disease, amyotrophic lateral sclerosis, or Lou Gehrig’s Disease, was diagnosed.
This was a powerful disincentive to taking work seriously: 80 per cent of sufferers die within five years of diagnosis, and half of the rest within a further five years. But after months of depression and listening to Wagner, Hawking noticed that his condition was not deteriorating noticeably by the minute. He decided that there might be some point in finishing his PhD after all; and his will to live was fired by two lucky breaks.
First, he fell in love, and eventually married Jane Wilde in 1965, the year he was awarded that PhD. And second, an idea came to Hawking after hearing the mathematician Roger Penrose, then at Birkbeck College in London, describe his investigations of black holes. This provided the inspiration for the key piece of work in Hawking’s thesis, marking it out as something special and motivating him to take work, and life, more seriously. Black holes are those extraordinary objects, predicted by the equations of Einstein’s theory of general relativity, which are so dense that their gravity will not allow light to escape.
Penrose had been investigating whether a singularity, a point of infinite density where the laws of physics break down, must inevitably occur inside a black hole. Hawking’s first great scientific insight was to realise that the equations describing the collapse of a black hole to a singularity could be turned around to describe the expansion of our Universe out of a singularity. He showed that, mathematically speaking, the Universe is a time-reversed black hole.
The insight was one thing; proving it was another. It was hard work. Hawking still recalls the novelty of the experience. ‘I started working hard for the first time in my life. To my surprise, I found I liked it.’
The best way of understanding how Hawking’s mind works, his stubbornness, irreverence for authority and capacity for bewildering about-faces comes from the piece of work for which he is best known, the discovery, in his own words, that ‘black holes ain’t black’. In the early 1970s, as a result of his work with Penrose, Hawking was beginning to understand how black holes behave, and what goes on at the surface of one as it evolves, perhaps by swallowing matter or by merging with another black hole. The surface of a black hole is the boundary at which the escape velocity equals the speed of light – the so-called Schwarzchild horizon. One key property, which Hawking discovered, is that the surface area of a black hole can never decrease. This led Hawking, in a stroke of inspiration, to draw an analogy with the thermodynamic property known as entropy, a measure of disorder, which also can never decrease.
But he was quite specific in pointing out that this was only intended as an analogy. Although equations borrowed from thermodynamics turned out to be useful in describing properties of black holes, he stressed that it would be quite wrong to say that the surface area of a black hole is actually a measure of entropy. Apart from anything else, that would mean that a black hole had a temperature, defined in terms of its surface area, and anything that has a temperature must radiate energy, and therefore could not be a black hole.
In California, a research student called Jacob Bekenstein was not so sure that this was a problem. In a series of publications, he suggested that the surface area of a black hole was, indeed, a measure of entropy, and that black holes did have temperatures related to their surface areas. Hawking, furious at the way this upstart had picked up his ball and run off with it, hit back with articles attacking Bekenstein’s interpretation of the equations.
Late in 1973, however, Hawking visited Moscow, where he learned of work by the Russian theorist Yakov Zel’dovich and his colleagues on the way black holes interact with light. The work was interesting, but Hawking felt that the Moscow team had taken a wrong turning somewhere. Returning home, he set out to resolve the problem, by bringing in ideas from quantum physics. He found that the correct equations insisted that black holes must be emitting radiation – that they had a temperature, just as Bekenstein had said. Once he was convinced, in January 1974, Hawking made a complete about-turn. In February, he announced to a startled audience at the Rutherford Appleton Laboratory, near Oxford, that black holes could emit radiation, essentially by converting some of their gravitational energy into particles that ‘boiled off’ from the surface, and would even explode when they were small enough.
It took a couple of years for his colleagues to be persuaded, and in 1974 Hawking had to argue just as fiercely in favour of black holes having temperatures as he had previously argued against the idea. But now this discovery is regarded as one of the great achievements not just of Hawking’s career but of the past 50 years of physics. ‘Hawking radiation’, as it is now known (which must be more than a little irritating for Bekenstein), is a phenomenon that involves not only the general theory of relativity (describing the gravity of the black hole), and quantum theory (describing the conversion of gravitational energy into particles), but also thermodynamics (giving the temperature of the black hole).
The Eric Morecombe of physics
Combining general relativity and quantum mechanics, the two great triumphs of 20th-century physics, in one package was impressive enough. But adding thermodynamics, the great 19th-century theory that describes the workings of steam engines, into the mix was something else. The physics community was amazed; it was like opening the bonnet of a shiny new car and discovering that it was powered by the engine from Stephenson’s Rocket.
Hawking’s stubbornness and disregard for others is also revealed by the way he drives his electrically powered wheelchair – the one form of expression, apart from the famous boyish grin, open to him. If he thinks anybody is wasting his time, he will simply spin on his wheels and whisk from the room (and if he thinks you are a real idiot, he will go for your toes on the way). His idea of road safety is to drive flat out from a side street into a busy road, leaving the drivers of any approaching cars the job of avoiding him – an almost fatal habit when he was actually struck by a car and flung from his wheelchair early in 1991. Fortunately, he suffered only minor injuries but made the news on American television as a result.
But these ‘boy racer’ antics also reveal Hawking’s irreverent, almost childish, sense of fun. An often quoted anecdote comes from George Efstathiou of the University of Oxford, who recalls how a couple of years ago he was escorting Hawking on the way to give a lecture at the University. Their route was to be via a two-person lift, from the reception area of the building. When Hawking spotted the lift with its doors open, he hurled his machine forward at full speed, while Efstathiou, watching his guest speaker heading for the narrow gap, realised that it was too small for the wheelchair.
By the time he caught up, the chair had twisted sideways into the lift, and the doors had closed on the wheels, the most famous paralysed physics professor in the world on the inside, unable to punch the ‘open’ button.
While Efstathiou eventually succeeded in forcing the doors open wide enough to reach in with one hand and prod the relevant button, Hawking calmly programmed his chair to reverse its high-speed entrance into the lift. As the doors opened, he hurled out backwards, unscathed and grinning.
As a means of self-expression, the chair also manoeuvres to surprisingly good effect around the dance floor. Hawking is a party animal, happy to gate-crash somebody else’s party if he doesn’t have one of his own. At a major scientific meeting in Brighton in December 1990, astronomers trying to discuss deep mysteries of the Universe were put out of their stride one day by the sound checks from the road crew setting up equipment for a Status Quo concert in the hall next door. A couple of Hawking’s students went over to ask the roadies if there was any chance of getting tickets for the gig, long since officially sold out. ‘No chance,’ they were told. ‘Pity,’ one replied. ‘Stephen Hawking really wanted to see Quo.’ Within five minutes, a handful of tickets was dug up and Hawking and his students duly got to see the band.
Although there is no expression in Hawking’s computer-synthesised voice, which sounds much like the voice generated by any ordinary personal computer, the way he puts words together, in formal lectures and in conversation, expresses his mischievous sense of humour to perfection. Considering that, apart from a few stock words and phrases, every sentence has to be laboriously picked out by moving an icon around a menu on the screen of the computer, Hawking’s timing and skill with one-liners puts him in the same league as Eric Morecombe or Bob Hope.
Lectures, of course, are pre-programmed by Hawking himself, and stored on disc, ready to be played back to the audience. They always contain the kinds of (usually punning) jokes that scientists are so fond of. After the talk, Hawking, like other speakers, is prepared to answer questions. The only difference is that unless the answer is a simple ‘yes’ or ‘no’, it may take him up to 10 minutes to set up the response on the computer. ‘During this time,’ he says, ‘please talk among yourselves, read newspapers, relax.’ Sometimes, after a wait of several minutes, the answer is still simply ‘yes’ or ‘no’, a ploy which never fails to raise laughter. Occasionally, after a wait of five minutes or so, Hawking may ask the questioner to repeat the question. In cold print, it sounds silly; in the flesh, it generally brings the house down, even if you have seen the routine before.
I’ve known Stephen Hawking, as an acquaintance, for nearly a quarter of a century, and for a short period I worked in the same Institute of Astronomy as Hawking, in Cambridge. Because of the enormous difficulties involved in any kind of two-way communication, it is impossible for anyone who doesn’t spend many hours a day with Hawking to ever get to know him at all well. But I know that he is a stubborn, egotistical, brilliant scientist who has no patience with second-rate intellects, never hesitates to tell someone if he thinks their theories are wrong, but is open-minded enough to be capable of persuasion that his own ideas might, on occasion, need modifying. Suggestions that he is the ‘new Einstein’ (or ‘new Newton’) are ludicrously over the top; but he could reasonably be described as the ‘new Hoyle’, an achievement which probably would have been beyond the wildest dreams of the student who went to Cambridge in the 1960s to study cosmology because that was where Hoyle worked.
Hawking is also a friendly, funny and warm human being, too often cut off from even the amount of routine contact with other people that he is physically capable of by the escort of minders required by his fame and nurses required by his illness. He loves his children, has always been kind to dumb animals, and has a deep loathing for the political works of Margaret Thatcher. What more could you ask of any man?
Further Reading Michael White and John Gribbin, Stephen Hawking: A life in science (Viking, 1992).
