SCIAMA INTRODUCED me to the so-called Wheeler-Feynman electrodynamics. This theory said that electricity and magnetism were time symmetric. However, when one switched on a lamp, it was the influence of all the other matter in the universe that caused light waves to travel outward from the lamp, rather than come in from infinity and end on the lamp. For Wheeler-Feynman electrodynamics to work, it was necessary that all the light traveling out from the lamp should be absorbed by other matter in the universe. This would happen in a steady-state universe, in which the density of matter would remain constant, but not in a Big Bang universe, where the density would go down as the universe expanded. It was claimed that this was another proof, if proof were still needed, that we live in a steady-state universe.
This was supposed to explain the arrow of time, the reason disorder increases and why we remember the past but not the future. There was a conference on Wheeler-Feynman electrodynamics and the arrow of time at Cornell University in 1963. Feynman was so disgusted by the nonsense put forth about the arrow of time that he refused to let his name appear in the proceedings. He was referred to only as Mr. X, but everyone knew who that was.
I found that Hoyle and Narlikar had already worked out Wheeler-Feynman electrodynamics in expanding universes and then gone on to formulate a time-symmetric new theory of gravity. Hoyle unveiled the theory at a meeting of the Royal Society in 1964. I was at the lecture, and in the question period I said that the influence of all the matter in a steady-state universe would make his masses infinite. Hoyle asked why I said that, and I replied that I had calculated it. Everyone thought I meant that I had done it in my head during the lecture, but in fact I had been sharing an office with Narlikar and had seen a draft of the paper ahead of time, which had allowed me to do the calculations before the meeting.
Hoyle was furious. He was trying to set up his own institute, and threatened to join the brain drain to America if he didn’t get the money. He thought I had been put up to it to sabotage his plans. However, he got his institute, and later gave me a job, so he apparently didn’t harbor a grudge against me.
IN MY last year at Oxford I noticed that I was getting increasingly clumsy. I went to the doctor after falling down some stairs, but all he said was “Lay off the beer.”
I became even more clumsy after moving to Cambridge. At Christmas, when I went skating on the lake at St. Albans, I fell over and couldn’t get up. My mother noticed these problems and took me to the family doctor. He referred me to a specialist, and shortly after my twenty-first birthday I went into the hospital for testing. I was in for two weeks, during which I had a wide variety of tests. They took a muscle sample from my arm, stuck electrodes into me, and then injected some radio-opaque fluid into my spine and with X-rays watched it go up and down as they tilted the bed. After all that, they didn’t tell me what I had, except that it was not multiple sclerosis and that I was an atypical case. I gathered, however, that they expected it to continue to get worse and that there was nothing they could do except give me vitamins, though I could see they didn’t expect them to have much effect. I didn’t ask for more details at that time, because they obviously had nothing good to tell me.
The realization that I had an incurable disease that was likely to kill me in a few years was a bit of a shock. How could something like this happen to me? However, while I was in the hospital, I had seen a boy I vaguely knew die of leukemia in the bed opposite me, and it had not been a pretty sight. Clearly there were people who were worse off than me—at least my condition didn’t make me feel sick. Whenever I feel inclined to be sorry for myself, I remember that boy.
NOT KNOWING what was going to happen to me or how rapidly the disease would progress, I was at a loose end. The doctors told me to go back to Cambridge and carry on with the research I had just started in general relativity and cosmology. But I was not making progress because I didn’t have much mathematical background—and anyway, it was hard to focus when I might not live long enough to finish my PhD. I felt somewhat of a tragic character.
I took to listening to Wagner, but reports in magazine articles that I also drank heavily at that time are an exaggeration. Once one article said it, other articles copied it because it made a good story, and eventually everyone believed that anything that had appeared in print so many times must be true.
My dreams at that time, however, were rather disturbed. Before my condition was diagnosed, I had been very bored with life. There had not seemed to be anything worth doing. But shortly after I came out of the hospital, I dreamed that I was going to be executed. I suddenly realized that there were a lot of worthwhile things I could do if I was reprieved. Another dream I had several times was that I would sacrifice my life to save others. After all, if I was going to die anyway, I might as well do some good.
BUT I didn’t die. In fact, although there was a cloud hanging over my future, I found to my surprise that I was enjoying life. What really made the difference was that I got engaged to a girl called Jane Wilde, whom I had met about the time I was diagnosed with ALS. This gave me something to live for.
Punting on the Cam with Jane (illustration credit 4.1)
If we were to get married, I had to get a job, and to get a job I had to finish my PhD. I therefore started working for the first time in my life. To my surprise, I found I liked it. Maybe it is not fair to call it work, though. Someone once said that scientists and prostitutes get paid for doing what they enjoy.
To support myself during my studies, I applied for a research fellowship at Gonville and Caius College, a college within the University of Cambridge. Because my increasing clumsiness made it difficult to write or type, I was hoping that Jane would type my application. But when she came to visit me in Cambridge, she had her arm in plaster, having broken it. I must admit that I was less sympathetic than I should have been. It was her left arm, however, so she was able to write out the application as I dictated it, and I got someone else to type it.
In my application I had to give the names of two people who could provide references about my work. My supervisor suggested I should ask Hermann Bondi to be one of them. Bondi was then a professor of mathematics at King’s College, London, and an expert on general relativity. I had met him a couple of times, and he had submitted one of my papers for publication in the journal Proceedings of the Royal Society. After a lecture he gave in Cambridge, I asked him about providing a reference, and he looked at me in a vague way and said yes, he would. Obviously he didn’t remember me, for when the college wrote to him for a reference, he replied that he had not heard of me. Nowadays there are so many people applying for college research fellowships that if one of the candidate’s referees says he does not know him, that is the end of his chances. But those were quieter times. The college wrote to tell me of my referee’s embarrassing reply, and my supervisor got on to Bondi and refreshed his memory. Bondi then wrote me a reference that was probably far better than I deserved. I got a research fellowship and have been a fellow of Caius College ever since.
The fellowship meant Jane and I could get married, which we did in July 1965. We spent a week’s honeymoon in Suffolk, which was all I could afford. We then went to a summer school in general relativity at Cornell University.
That was a mistake. We stayed in a dormitory that was full of couples with noisy small children, and it put quite a strain on our marriage. In other respects, however, the summer school was very useful for me because I met many of the leading people in the field.
When we were first married, Jane was still an undergraduate at Westfield College in London. So she had to go up to London from Cambridge during the week to complete her degree. The disease was causing increasing muscle weakness, which meant that it was becoming harder to walk, and so we had to find a centrally located place where I could manage on my own. I asked the college for help but was told by the bursar that it was not college policy to help fellows with housing. We therefore put our name down to rent one of a group of new flats that was being built in th
e marketplace, a convenient location. (Years later, I discovered that those flats were actually owned by the college, but they didn’t tell me that.) When we returned to Cambridge from the summer in America, however, we found that the flats were not ready.
My wedding to Jane (illustration credit 4.2)
As a great concession, the bursar offered us a room in a hostel for graduate students. He said, “We normally charge twelve shillings and sixpence a night for this room. However, as there will be two of you in the room, we will charge twenty-five shillings.” We stayed there only three nights before we found a small house about one hundred yards from my university department. It belonged to another college, which had let it to one of its fellows. He had recently moved out to a house in the suburbs, and he sublet the house to us for the remaining three months on his lease.
During those three months, we found another house in the same road standing empty. A neighbor summoned the owner from Dorset and told her it was a scandal that her house should be vacant when young people were looking for accommodation, so she rented the house to us. After we had lived there for a few years, we wanted to buy it and fix it up, so we asked my college for a mortgage. The college did a survey and decided it was not a good risk, so in the end we got a mortgage elsewhere, and my parents gave us the money to renovate.
THE SITUATION in Caius College was at that time reminiscent of something out of the novels of C. P. Snow. There had been a bitter division in the fellowship ever since the so-called Peasants’ Revolt, in which a number of the more junior fellows had banded together to vote senior fellows out of office. There were two camps: on one side was the party of the master and bursar, and on the other side was a more progressive party that wanted to spend more of the college’s considerable wealth on academic purposes. The progressive party took advantage of a meeting of the college council at which the master and bursar were absent to elect six research fellows, including me.
At my first college meeting there were elections to the college council. The other new research fellows had been briefed on whom to vote for, but I was a complete innocent and voted for candidates of both parties. The progressive party won a majority on the college council, and Master Sir Nevill Mott (who later won a Nobel Prize for work in condensed-matter physics) resigned in anger. However, the next master, Joseph Needham (author of a multivolume history of science in China), healed the wound, and the college has been relatively peaceful ever since.
OUR FIRST child, Robert, was born after we had been married about two years. Shortly after his birth we took him to a scientific meeting in Seattle. That again was a mistake. I was not able to help much with the baby because of my increasing disability, and Jane had to cope largely on her own and got very tired. Her tiredness was compounded by further traveling we did in the United States after Seattle. Robert now lives in Seattle with his wife, Katrina, and their children, George and Rose, so obviously the experience didn’t scar him.
With my first child, Robert (illustration credit 4.3)
Jane and Robert (illustration credit 4.4)
Our second child, Lucy, was born about three years later in an old workhouse that was then being used as a maternity hospital. During the pregnancy we had to move out to a thatched cottage owned by friends while our own house was being extended. We moved back only a few days before the birth.
5
GRAVITATIONAL WAVES
IN 1969 JOSEPH WEBER REPORTED THE OBSERVATION of bursts of gravitational waves, using detectors that consisted of two aluminum bars suspended in a vacuum. When a gravitational wave came along, it would stretch things in one direction (perpendicular to the direction of travel of the wave) and compress things in the other direction (perpendicular to the wave). This would make the bars oscillate at their resonant frequency—1,660 cycles per second—and these oscillations would be detected by crystals strapped to the bars. I visited Weber near Princeton in early 1970 and inspected his equipment. With my untrained eye I could see nothing wrong, but the results that Weber was claiming were truly remarkable. The only possible sources of bursts of gravitational waves powerful enough to excite Weber’s bars would be the collapse of a massive star to form a black hole, or the collision and merger of two black holes. These sources would have to be nearby—within our galaxy. Previous estimates of such events had been about one per century, but Weber was claiming to see one or two bursts per day. This would have meant the galaxy was losing mass at a rate that could not have been continuous over the lifetime of the galaxy—or there would be no galaxy left now.
When I returned to England, I decided that Weber’s amazing claims needed independent verification. I wrote a paper with my student Gary Gibbons on the theory of the detection of bursts of gravitational waves, in which we suggested a more sensitive detector design. When it seemed that no one was about to build such a detector, Gary and I took the audacious step, for theorists, of applying to the Science Research Council for a grant to build two detectors. (One needs to observe coincidences between at least two detectors because of spurious signals from noise and earth vibrations.) Gary scoured warsurplus dumps for decompression chambers to use as vacuums and I looked for suitable sites.
Eventually we had a meeting with other groups interested in verifying Weber’s claims at the Science Research Council on the thirteenth floor of a tower block in London. (The Science Research Council couldn’t admit to superstition. They got it cheap.) As there were other groups pursuing the project, Gary and I withdrew our application. That was a narrow escape! My increasing disability would have made me hopeless as an experimenter. And it is very difficult to make a mark for oneself in an experimental subject. One is often only part of a large team, doing an experiment that takes years. On the other hand, a theorist can have an idea in a single afternoon, or, in my case, while getting into bed, and write a paper on one’s own or with one or two colleagues to make one’s name.
Gravitational wave detectors have become much more sensitive since the 1970s. The current detectors employ laser ranging to compare the lengths of two arms at right angles. The U.S. has two of these LIGO detectors. Although they are ten million times more sensitive than Weber’s, they have not so far made a reliable detection of gravitational waves. I’m very glad I remained a theorist.
6
THE BIG BANG
THE BIG QUESTION IN COSMOLOGY IN THE EARLY 1960s was whether the universe had a beginning. Many scientists were instinctively opposed to the idea, and thus to the Big Bang theory, because they felt that a point of creation would be a place where science broke down. One would have to appeal to religion and the hand of God to determine how the universe started off.
Two alternative scenarios were therefore put forward. One was the steady-state theory, in which, as the universe expanded, new matter was continually created to keep the density constant on average. The steady-state theory never had a very strong theoretical basis, because it required a negative energy field to create the matter. This would have made it unstable and prone to runaway production of matter and negative energy. But it had the great merit of making definite predictions that could be tested by observations.
By 1963 the steady-state theory was already in trouble. Martin Ryle’s radio astronomy group at the Cavendish Laboratory did a survey of faint radio sources and found that the sources were distributed fairly uniformly across the sky. This indicated that they were probably outside our galaxy, because otherwise they would be concentrated along the Milky Way. But the graph of the number of sources against source strength did not agree with the prediction of the steady-state theory. There were too many faint sources, indicating that the density of sources had been higher in the distant past.
Hoyle and his supporters put forward increasingly contrived explanations of the observations, but the final nail in the coffin of the steady-state theory came in 1965 with the discovery of a faint background of microwave radiation. (This is like the microwaves in a microwave oven but at a much lower temperature, only 2.7 kelvin, a sma
ll amount above absolute zero.) The radiation could not be accounted for in the steady-state theory, though Hoyle and Narlikar tried desperately. It was just as well I hadn’t been a student of Hoyle’s, because I would have had to defend the steady-state theory.
The microwave background indicated that the universe had had a hot, dense stage in the past. But it didn’t prove that this stage was the beginning of the universe. One might imagine that the universe had had a previous contracting phase and that it had bounced from contraction to expansion, at a high but finite density. Whether that was in fact the case was clearly a fundamental question, and it was just what I needed to complete my PhD thesis.
Gravity pulls matter together, but rotation throws it apart. So my first question was whether rotation could cause the universe to bounce. Together with George Ellis, I was able to show that the answer was no if the universe was spatially homogeneous—that is, if it was the same at each point of space. However, two Russians, Evgeny Lifshitz and Isaak Khalatnikov, claimed to have proved that a general contraction without exact symmetry would always lead to a bounce, with the density remaining finite. This result was very convenient for Marxist-Leninist dialectical materialism because it avoided awkward questions about the creation of the universe. It therefore became an article of faith for Soviet scientists.
Lifshitz and Khalatnikov were members of the old school in general relativity—that is, they wrote down a massive system of equations and tried to guess a solution. But it wasn’t clear that the solution they found was the most general one. Roger Penrose introduced a new approach, which didn’t require solving Einstein’s field equations explicitly, just certain general properties, such as that energy is positive and gravity is attractive. Penrose gave a seminar on the subject at King’s College, London, in January 1965. I wasn’t at the seminar, but I heard about it from Brandon Carter, with whom I shared an office in Cambridge’s new Department of Applied Mathematics and Theoretical Physics (DAMTP) premises in Silver Street.