Stephen Hawking is now 50 years old, and has lived 25 years longer than he once expected to live. As a scientist he long ago earned the respect of his colleagues; more recently, with the astonishing success of his book A Brief History of Time, he has become a widely recognised public figure. Immobile for decades, he is now unable to communicate except by means of an electronic voice-synthesiser connected to a word-processor. He suffers from what is variously known as motor neurone disease, amyotrophic lateral sclerosis (ALS), or Lou Gehrig’s disease, but despite his confinement has moved into the vanguard of theoretical physics. He is one of a handful of people whose work may form the foundation of a ‘theory of everything’, a description of nature so fundamental yet so all-encompassing that it would be able to account for all the phenomena of the natural world.
Scientists who know Hawking and work with him tend to protest that once one gets past the obvious disabilities, he is a scientist like any other, with theories and ideas and opinions; Hawking himself has said that for someone with his disease, theoretical physics is a singularly fitting profession, requiring cogitation first and foremost. On the other hand, as Michael White and John Gribbin intimate, Hawking seems to have been a listless student and a rather charmless young man before ALS struck, obviously intelligent but lacking any passion to use his intelligence in one direction rather than another. Thus arises the idea that it was Hawking’s disease, and his fight against it, that gave him some intellectual mettle. According to schoolfriends, there were doubts that he would ever come to very much, and Hawking’s father, a specialist in tropical diseases, tried to steer his son towards medicine, unclear that the young man’s preference for theoretical physics and mathematics was realistic in terms either of his abilities or of the kinds of job it would lead to.
It has become a piece of scientific folklore that Albert Einstein was a poor student at school and only began to prosper once he got away from the confines of formal education to his job in the Zurich patent office, where he hatched his most brilliant ideas. Einstein’s early lack of prowess has been considerably exaggerated, but scientists seem to be fond of the romantic version of his life nevertheless, perhaps out of a suppressed need to rebel against the strictures of the formal scientific education they all endured. But generally speaking, exceptional ability in science, as in music, tends to be recognisable early on, and despite White and Gribbin’s recounting of the half-remembered doubts of a few childhood companions, it is clear that Hawking was an exceptional student. He did unusually well in his Oxford entrance exams, and continued to do unusually well as an undergraduate, excelling, in Oxbridge fashion, without great apparent effort or enthusiasm. He seems to have been directionless and more than a little vain, but he was unarguably clever.
Still, the number of clever Oxbridge students who go on to greatness is exceeded by the number that don’t. Hawking, as he finished his undergraduate career and moved to Cambridge to start a PhD under the cosmologist Dennis Sciama, struggled to find a research topic. At the same time, ALS struck. He began to have some difficulty with speech, and found himself stumbling and dropping things. It was a few months into his postgraduate life that the diagnosis was made, and at first things got rapidly worse. ALS is a wasting disease that causes nerve and spinal tissues to degenerate, leading in most cases to death through paralysis and respiratory failure, and Hawking expected to live only a couple of years.
His condition stabilised, however; he found a subject for research, and he got married. These three events, coincidental or not, mark the beginning of Hawking’s career as a scientist. He had no guarantee of any great longevity, but the threat of imminent death receded, and with enormous help from Jane Hawking his day-to-day life became stable enough to enable him to devote himself to theoretical physics. At this point, White and Gribbin, who so far have had an unusual story to tell, largely revert to the standard second half of a scientific biography: Hawking is married and has children, but his life is generally uneventful and forms a grey backdrop to a tale of intellectual growth. In a way, this narrative pattern is hard to resist. Scientific biographers who wish to describe the achievements of their subjects must necessarily spend a lot of time explaining to the reader what sort of science is involved, and with Hawking, whose recent efforts have been directed at forging a link between quantum mechanics and general relativity, the two great innovations of 20th-century physics, a lot of explaining is needed.
White and Gribbin have adopted the ungainly solution of interposing in the narrative a number of chapters exclusively taken up with scientific matters. Having spent the first chapter taking Hawking to Oxford, they insert a second chapter which might have been transplanted from another book entirely: it offers a quick but reasonably intelligible survey of what physicists have been doing since the beginning of the century, and ends by lurching back towards the story of Stephen Hawking with a device of the ‘little did he know ...’ variety. In this case, Hawking ‘would hardly have suspected that over the next thirty years he would play a key role in bringing the two theories together’. Who knows: maybe the young Hawking did have an inkling of what he was capable of.
For his graduate work and for several years flat that, Hawking was occupied with elaborately mathematical work on general relativity, the theory by which Albert Einstein replaced Newton’s idea of a gravitational force with an unexpected picture of curved space. Massive bodies fall together not through mutual attraction, as Newton perceived it, but in the same way that a couple on an old mattress find themselves rolling to the centre of the bed: an observer unaware of the properties of mattresses might suppose some sort of force was holding them together.
Among the implications of general relativity is the fact that the universe is expanding, and if it has been expanding for some time it must perforce have been more condensed in the past. Continuing this backwards extrapolation, one comes irresistibly to the idea that some fifteen billion years ago, the whole universe was essentially a mathematical point, of infinite density and infinitesimal extent. This is the Big Bang theory of the origin of the universe, and although its general principles are held true by all but a few mavericks, the notion of a truly point-like moment of creation – a singularity, in the lingo – has seemed unattractive to quite a few physicists, and there have been numerous attempts to construct cosmological models which conform to the demands of general relativity but which do not contain the initial singularity. Hawking, with the mathematician Roger Penrose, proved that all such attempts are futile. No matter how fancy the model, they demonstrated, the rules of general relativity dictate that a singularity always exists.
Naturally enough, the proof that a singularity must exist led Hawking, along with many others, to wonder what sort of physics would pertain in these scarcely imaginable conditions. The one let-out from the singularity theorem of Hawking and Penrose was that it does not take account of quantum mechanics. A mathematical point of infinite density and zero dimension may be mandated by general relativity, but is forbidden by quantum mechanics – in particular, by Heisenberg’s uncertainty principle. No physical body (which, one hopes, includes the universe) can be located in space except to some limited accuracy: a mathematical point cannot be a physical reality.
This is the starting-point for the second half of Hawking’s career, and it has led to the kind of thinking which A Brief History of Time attempts to illuminate. The contradiction between general relativity, which deals in physical masses idealised as points moving along lines, and quantum mechanics, which includes the fuzziness inherent in the uncertainty principle and deals with probabilities rather than certainties, is the great conundrum of modern physics. Perhaps it is the last great conundrum of physics. Into the quantum mechanics fold have been incorporated the electromagnetic and nuclear forces which hold the familiar world together, and now only gravity, in its modern guise of relativity, stands apart. Once the two are united (in what physicists have taken to calling a ‘theory of everything’) there will be no discord in fundamental physics, and no problems left to solve.
Whether this glorious unity will come to pass is a matter for conjecture. Physicists have thought they were close before, only to find that the solution to what was to have been the last problem in physics caused an upset somewhere else. In 1974, when he assumed the Lucasian Chair of Mathematics at Cambridge, Hawking delivered a lecture entitled ‘Is the end of theoretical physics in sight?’ and at the time put his money on something called N = 8 supergravity as the imminent theory of everything. But supergravity didn’t work out, and nowadays the talk is of superstrings – heterotic superstrings, no less, and living in ten-dimensional space.
The efforts of theoretical physicists to force quantum mechanics and general relativity to live together in harmony have so far produced a lot of theorising but little in the way of substantial results. A notable and surprising exception was Hawking’s 1973 argument that black holes are not quite black after all. A black hole, according to general relativity, is an object so massive and dense that nothing, not even light, can escape its gravitational pull. But here again, quantum mechanical considerations complicate this simple assertion. Particles are to be thought of, not as points, but as entities occupying a fuzzily-defined volume of space, and while a point mass can be said with certainty to be either inside or outside a black hole, a quantum mechanical particle has only some probability of being in one part of space or another. In effect, a particle which is ‘inside’ a black hole, and therefore hidden from our view, has some small chance of spontaneously appearing ‘outside’. A black hole is not perfectly black because particles leak slowly from it. This discovery (a theoretical discovery, since no one has ever seen a black hole directly, let alone one that is evaporating in this way) is what made Hawking a name among physicists in general. The cosmic singularity theorems were masterful but esoteric. The work on black holes, on the other hand, represented the uncovering of a qualitatively new physical phenomenon, contained neither in quantum mechanics nor in general relativity on its own, but emerging only from an ingenious combination of the two. If the singularity theorem was the work of a clever mathematical physicist, black hole evaporation required the touch of genius. This is where one begins to hear talk of Hawking as ‘the next Einstein’, But nobody describes Einstein as the second Newton.
In recent years Hawking has been trying to make some sense of the contradictions between general relativity and quantum mechanics in the case of the initial cosmic singularity – the big bang. He sets out his gathered thoughts on this problem in the later chapters of A Brief History of Time, but at present what he has to say is conjecture and guesswork. Other physicists are trying to attack the same problems from different angles, but their collective progress is like the early days of the Channel Tunnel: it will be a long time before the different digging parties meet in the middle. There is still no theory of everything.
There is plenty of speculation on what a theory of everything might look like, however, and on the domain it would rule. The growing sense among physicists that they will soon be able to explain where the universe came from has inevitably taken them into deep waters. Until now, the Big Bang model has meant a universe that is currently large and expanding, which in the past was smaller, denser and hotter, but whose first moment, the Big Bang itself, was mysterious. There was still room for a prime mover, or the hand of God. But Hawking and others, who think that the appropriate union of quantum mechanics with these cosmological models will turn the Big Bang itself into a mere physical event, perceive in their anticipated theory of everything the concomitant banishment of God. If everything in the physical world is indeed explained, and nothing is arbitrary, there can be no room for the supernatural.
On these topics, Hawking becomes evasive, as do White and Gribbin. Apart from the total neglect of the role of religion as an ethical system (physicists are too often inclined to think that God’s only purpose is to wind up the clockwork and then stand aside), it is not at all clear how comprehensive a theory of everything would have to be to leave no toehold for religion. Even if all the laws of physics are found and neatly linked together, and even if these laws dictate that the universe must have the shape and appearance we see it to have, one can still ask why these laws and not some other set of laws are the ones that actually govern the world. On this point physicists tend to argue vaguely that the correct laws will be self-evident by their simplicity or mathematical elegance, but one can then ask who decided that the laws of physics ought to be beautiful as well as correct: God, or the physicists?
What Hawking really thinks of all this is left for the reader to guess at. White and Gribbin have not been able to interview their subject or his wife, from whom he has recently separated, but the reports they quote indicate that these issues have something to do with the break-up of the marriage. Jane Hawking evidently found religion a great support in the years of looking after her husband. Recently she complained that her role had been ‘to tell him that he’s not God’. In this and in other matters where less attractive aspects of Hawking’s character might show up, White and Gribbin are a little shy. Early on, when he was working at the Institute of Astronomy in Cambridge, we are told that the staff there (not the scientists) found him difficult and demanding. White and Gribbin say he doesn’t suffer fools gladly, and ‘perhaps he simply didn’t get on with the secretaries at the Institute of Astronomy.’ They counter the concern that he might not be the right person to comment on theological matters with an old, blustery stand-by: ‘Why should Hawking be any less competent to talk about God than the next person – or the next pontiff, come to that?’