Stephen Hawking

by John Gribbin

  Hawking wanted to remove the edge in time, as well as the edge in space, to produce a model of the Universe that has no boundaries at all. He found that, without having to go into the detail of calculating every trajectory of every particle through spacetime, the general rules of the sum-over-histories approach as applied to families of curved spacetimes said that a certain kind of curvature is much more likely than any other if the no-boundary condition applies.

  Hawking stresses that this no-boundary condition is, as yet, just a guess about the nature of the Universe, but it is a guess that leads to a powerful image of reality. This is the cosmological equivalent of saying that the path integral approach tells us that an electron can follow only certain orbits around a nucleus; the Universe has only a limited number of life cycles to choose from, and they all look much the same.

  The best way to picture these models is by an extension of the idea of the Universe being represented by the surface of a balloon. In the old picture, this surface represents space, and the evolution of the Universe from bang to crunch is represented by imagining the balloon being first inflated and then deflated. In the new picture, however, the spherical surface represents both space and time, and it stays the same size—much more like the surface of the Earth than the surface of an expanding balloon. So where does the observed expansion of the Universe come into this model?

  Now, says Hawking, we have to imagine the Big Bang as corresponding to a point on the surface of the sphere, at the North Pole. A tiny circle drawn around that point (a line of latitude) corresponds to the size of the space occupied by the Universe. As time passes, we have to imagine lines of latitude being drawn farther and farther away from the North Pole, getting bigger (showing that the Universe expands) all the way to the equator. From the equator down to the South Pole, the lines of latitude get smaller once again, corresponding to the Universe shrinking back to nothing at all as time passes.

  We still have an image of the Universe being born in a super-dense state, evolving, and shrinking back into a superdense state, but there is no longer a discontinuity in time, just as there is no edge of the world at the North Pole. At the North Pole, there is no direction north, and every direction points south. But this is simply due to the geometry of the curved surface of the Earth. In the same way, at the Big Bang there was no past, and all times lay in the future. And this is simply due to the geometry of curved spacetime. The whole package of space and time, matter and energy, is completely self-contained.

  A rather nice way to understand what is going on is to imagine that you are standing a little way from the North Pole and start to walk due north. Even though you keep walking in a straight line, you will soon find that you are walking due south. In the same way, if you had a working time machine and started traveling backward in time from some moment just after the Big Bang, you would soon find that you were traveling forward in time, even though you had not altered the controls of the time machine. You just cannot get back to a time before the Big Bang (strictly speaking, before the Planck time) because there simply is no “before.”

  In A Brief History of Time, Hawking spelled out the implications for religion. He leaves his colleagues in no doubt that he is, at the very least, an agnostic and finds strong support for this belief in his cosmological studies:

  So long as the universe had a beginning, we could suppose it had a creator. But if the universe is really completely self-contained, having no boundary or edge, it would have neither beginning nor end: it would simply be. What place, then, for a creator?1

  But even without a creator there were still problems to be solved. Already, in 1981, the attention of Hawking and other theorists was focusing on the next question—how did a tiny seed of a Universe get blown up to the enormous size that we see today?

  The puzzle of how the Universe has gotten to be as big as it is today had itself loomed larger and larger during the 1970s. When everybody thought the Big Bang theory was just a model to play with, they didn’t worry too much about the details of how it might work. But as evidence built up that this model provides a very good description of the real Universe, it became increasingly important to explain exactly what makes the model, and the Universe, tick.

  There were two problems that cosmologists were simply unable to answer in the 1970s. First, why is the Universe so uniform—why does it look the same (on average) in all directions of space, and why, in particular, is the temperature of the microwave background exactly the same in all directions? Secondly, the Universe seems to be delicately balanced on the dividing line between being closed, like a black hole, and open, so that it will expand forever. In terms of the curvature of space, the Universe is remarkably flat. Why is this?

  On the basis of general relativity alone, there seems to be no reason why it could not have been, for example, much more tightly curved, in which case the Universe would have expanded only a little way out of the Big Bang before re-collapsing, and there would have been insufficient time for stars, planets, and people to evolve. Cosmologists suspected that the smoothness and flatness of the Universe were telling us something fundamental about the nature of the Big Bang, but nobody could see just what that might be until a young researcher at Cornell University, Alan Guth, came up with a new idea.

  Guth’s proposal goes by the name “inflation” and stems from quantum physics. He suggested that in the first split second after the beginning, the vacuum of the Universe existed in a highly energetic state, as allowed by the quantum rules, but unstable. The high-energy state is analogous to a container of water cooled, very slowly and carefully, to below 0°C. Such supercooling is possible if the water is cooled very carefully, but the result is unstable. At a slight disturbance, the water will freeze into ice, and as it does so it gives up energy (exactly the same amount of energy that is needed to melt an ice cube, at 0°C, is released when the same amount of water freezes).

  This is where the ice analogy breaks down slightly, for when the Universe cooled from the excited vacuum state to the stable vacuum that we know today, so much energy was released that it became super-hot, not icy, and for a time it expanded super-fast. In a tiny fraction of a second, a region of space far smaller than a proton (but packed full of energy) must have been inflated, according to this theory, into a volume about the size of a grapefruit. At that point the inflation was exhausted, and the grapefruit-sized fireball began the steady expansion associated with the standard model of the Big Bang, growing over the next 14 billion years to become the entire visible Universe.

  According to inflation theory, the Universe is so uniform because it has grown out of a seed so small that there was literally no room inside it for irregularities. And the equations also tell us that the inflation process flattened space. The best analogy for how this works is with the wrinkly surface of a prune, which is very far from flat. When you soak the prune in water, it swells up, expanding so that the surface stretches and the wrinkles are smoothed out. Imagine starting out with a prune smaller than a proton and expanding it to the size of a grapefruit, and you can see why space is so very flat today.

  The inflationary model has been extensively developed since Guth made the original proposal in 1980. Hawking has been involved in filling in details of this work throughout the 1980s, but the main developments have come from a Soviet researcher, Andrei Linde. Some of Linde’s early contributions were duplicated independently by Paul Steinhardt and Andreas Albrecht, from the University of Pennsylvania. As we shall see in Chapter 15, the early versions of inflation were overtaken in the 1980s by new insights that provide a spectacular new image of the origin and evolution of not just the Universe but a multiplicity of universes. Hawking played a part in this work, too. From now on, honors and awards would be heaped upon the man to whom the modest recognition offered by the Gravity Research Foundation had been “very welcome” just a short time before.

  12

  SCIENCE CELEBRITY

  In 1978, Hawking was awarded one the most prestigious prizes
in physics, the Albert Einstein Award given by the Lewis and Rose Strauss Memorial Fund, which announced the winner at a gala event in Washington. The citation claimed that Hawking’s work could lead to a unified field theory, “much sought after by scientists,”1 as one Cambridge newspaper put it. The Albert Einstein Award is considered to be the prestigious equivalent of a Nobel Prize and was undoubtedly the most important award Hawking had received up to that time. Journalists began to talk about the possibility of the thirty-six-year-old physicist being next in line for the greatest academic honor of all—an invitation to the Royal Academy of Sciences in Stockholm.

  However, there are two reasons why Hawking is unlikely ever to receive a Nobel Prize. First, a cursory glance at the list of winners since the first prizes in 1901 shows very few astronomers. The reason for this, according to one story, is that the chemist Alfred Nobel, who created the awards, decreed that astronomers should be ineligible. Rumor has it that their exclusion was because his wife had an affair with an astronomer, and he subsequently felt only hatred for the whole profession. Despite this, Martin Ryle and Antony Hewish shared the 1974 Nobel Prize for Physics for their work in radio astrophysics, and Subrahmanyan Chandrasekhar won it in 1983 for his theoretical studies on the origin and evolution of stars. These were awarded a good seventy years after the founder’s death, so perhaps the academy now views astronomers with greater sympathy.

  There is, however, a more important reason for Hawking’s absence from the list of winners. One of the academy’s rules states that a candidate may be considered for a prize only if his/her discovery can be supported by verifiable experimental or observational evidence. Hawking’s work is, of course, unproved. Although the mathematics of his theories is considered beautiful and elegant, science is still unable even to prove the existence of black holes, let alone verify Hawking Radiation or any of his other theoretical proposals.

  A year after receiving the Albert Einstein Award, Hawking’s second book was published by Cambridge University Press: a collection of sixteen articles to commemorate the centenary of Albert Einstein’s birth on March 14, 1879. Hawking co-edited the book, entitled General Relativity: An Einstein Centenary Survey, with his colleague Werner Israel. When Simon Mitton presented it to a sales conference in January 1979, the sales team, whose job it was to take books out on the road and convince retailers of their merit, was unusually enthusiastic. One of the sales staff said to Mitton, “That man Hawking—he’s amazing, you know. We’ll have no trouble selling this. All the quality bookshops will take it, no problem.” He was right. It was snapped up and sold exceptionally well in hardback and even better when later issued as a paperback. Hawking’s fame was spreading.

  This was also the year that Stephen Hawking finally got his own office at the DAMTP—it came with his appointment as Lucasian Professor. Hawking is well aware of his place in the history of science. He is fascinated by the fact that he was born on the three-hundredth anniversary of Galileo’s death on January 8, 1642. That year, Isaac Newton was born in Woolsthorpe, a little village in Lincolnshire, and it was Isaac Newton who was appointed Lucasian Professor at Cambridge in 1669, three hundred and ten years before Hawking.

  Albert Einstein considered Galileo the greatest of all scientists, and Hawking has claimed that he was, in his approach, the first twentieth-century scientist:

  He was the first scientist to actually start using his eyes, both figuratively and physically. And, in a sense, he was responsible for the age of science we now enjoy.2

  Galileo’s work led directly to Newton’s work and the establishment of classical physics. The work of Einstein, who was born one hundred years before Hawking received the Lucasian chair, turned “large-scale” physics on its head. Subsequently, many have seen Hawking as the physicist most likely to succeed in the enormous task of unifying the two supporting pillars of physics, quantum mechanics and relativity. Small wonder Hawking has a strong sense of science history.

  At his inauguration as Lucasian Professor, Hawking delivered a memorable lecture titled “Is the End in Sight for Theoretical Physics?,” in which he suggested that a Grand Unified Theory describing the fundamental laws of the Universe could be achieved by the end of the century.

  It was a stirring and inspiring idea. The audience knew as they streamed out of the hall that, if anyone could make that dream come true, it would be the waif-like figure who had earlier sat on the stage before them, crumpled in his motorized wheelchair, delivering powerful statements with his typical confidence.

  The appointment as Lucasian Professor of Mathematics at Cambridge University was one of the highlights of Hawking’s career. To be professor at one of the oldest and most respected universities in the world is a huge achievement in itself, but to have accomplished such a feat by the age of thirty-seven is remarkable. Newton was Hawking’s junior by ten years when he gained the chair, but in the seventeenth century there were far fewer academics and very little competition for such positions. Newton did also happen to be the youngest ever to be appointed Lucasian Professor at Cambridge.

  Easter 1979 saw the birth of Stephen and Jane’s third child, a boy they christened Timothy. It was a happy time for the Hawking family. Against all odds, they had overcome tremendous hurdles to achieve great success. Jane had completed her Ph.D. and was finding a degree of intellectual satisfaction in her teaching job; Professor Hawking was receiving the esteem of his colleagues and growing popular acclaim as the “new Einstein.” Now there was another Hawking at West Road.

  In the larger world outside the cloistered environs of Cambridge academia, the ever-shifting kaleidoscope of life was shaken yet again. Shortly before Timothy Hawking’s birth, scientists at the Jet Propulsion Laboratory in Pasadena were surprised to discover, via the deep-space probe Voyager 1, that Jupiter had rings like its celestial neighbor, Saturn. Before the year was out, Margaret Thatcher had begun her eleven-year run as Britain’s first female prime minister; the Queen’s cousin, Lord Mountbatten of Burma, was murdered by the IRA; and American embassy staff and marines were taken hostage in Tehran. Also that year, the Queen’s art adviser, Cambridge man Anthony Blunt, was exposed as the “fourth man.” Russia invaded Afghanistan, Mother Teresa of Calcutta was awarded the Nobel Peace Prize, and John Cleese continued to delight TV audiences by “not mentioning the war.” One of the year’s biggest films was Apocalypse Now.

  At the turn of the decade, Hawking could look back satisfied with his achievements over the past ten years. The symptoms of ALS had leveled off. His speech was practically unintelligible to all but his close colleagues and family, and he was confined to his motorized wheelchair, but he continued to work and to travel as intensively as he had ever done. His freedom from mundane chores and responsibilities was paying dividends scientifically.

  As of 1980, the system of taking in graduate students to help around the house was replaced by community and private nursing. Jane had help looking after Stephen for a couple of hours in the morning and evening. They could just afford to flesh out the meager assistance provided by the National Health Service by dipping into monies Hawking had received from the growing number of awards and prizes coming his way and the increased salary from his new appointment.

  Stephen and Jane began to cultivate a reputation as socialites and popular hosts on the Cambridge academic scene. Don Page has described Jane as “a great professional asset to her husband as a hostess.”3 Dr. Berman, Hawking’s tutor at Oxford, has said of her, “[Jane is] a remarkable woman. She sees that he does everything that a healthy person would do. They go everywhere and do everything.”4

  The Hawkings were soon at the center of the social in-crowd at Cambridge. Being Lucasian Professor gave Stephen a huge measure of prestige, both in academic circles and in the broader view of the international intelligentsia. Dinner parties and social gatherings on West Road and at the DAMTP were frequent events, and guests often included visiting academics as well as members of the university hierarchy. Their interest in classical musi
c was well catered for in Cambridge, and the couple was often to be seen at concerts in the city. They enjoyed going to the theater and the cinema and dining out, both at home in Cambridge and on visits abroad.

  Stephen’s obvious handicaps would sometimes cause embarrassment to those who did not know him in restaurants and at various functions to which the couple were frequently invited. Casual onlookers, unaware of the fact that they were in the presence of one of the world’s greatest scientists, could be forgiven for thinking that the withered figure slumped in his wheelchair—trying to speak but succeeding only in producing an incomprehensible noise, having to be fed, his head, insufficiently supported by atrophied neck muscles, rolling forward, chin on chest—was a hopelessly crippled and pathetically disabled man, perhaps mentally as well as physically handicapped. Nothing could have been further from the truth. On the subject of his disability, Hawking told an interviewer at the time:

  I think I’m happier now than I was before I started. Before the illness set in I was very bored with life. I drank a fair amount, I guess, didn’t do any work. It was really a rather pointless existence. When one’s expectations are reduced to zero, one really appreciates everything that one does have.5

  On another occasion, he said, “If you are disabled physically, you cannot afford to be disabled psychologically.”6 Jane echoed this view, with a typically forthright and optimistic approach to life. “We try to make the most of every moment,”7 she told one interviewer.

  A Sunday Times journalist once asked him whether he ever got depressed because of his disability. “Not normally,” he replied. “I have managed to do what I wanted to do despite it, and that gives me a feeling of achievement.”8

  Another asked what was his biggest regret about contracting his illness. “Not being able to play physically with my children,” he said.9