Playboy Classic: Stephen Hawking

Looking back at our

conversation with the

intellectual successor

to Albert Einstein about

how our universe

really began

How (lid all this—we. this Kartli. this universe—happen? That's not an easy question, hut it's the one Stephen Hawking lias dedicated his life to answering. The theoretical physi­cist, who is perhaps the world's most influ­ential living scientist, has received almost every major science prize, and in 2009 President Ohama awarded him the Presi­dential Medal of Freedom. Many call him the intellectual successor to Albert Kin-stein, and he was the subject of our April 1990 I'layboy Interview.

Currently director of research at the Center for Theoretical Cosmology at the University ol Cambridge. Hawking broke ground with his theories about the basic laws that explain the cosmos. Some of his most important theo­rems picked up where Kinslein's left off. He is responsible for much of what's known about black holes and the birth of our universe.

Hawking isn't known only for his ivory-tower research but also for books he au­thored that explain physics to nonscientists. They're some of the biggest-selling science books in history; his seminal .4 HrieJ History of Time sold more than 10 million copies. The Apm1 Yorker called it a book of "sunny brilliance." It was followed by The Universe in a Nutshell, A Briefer History of Time anil his latest number one best-seller. The Grand Design, in which Hawking describes the na­ture of reality and what has been called "the theory of everything."

Hawking's accomplishments would be remarkable under any circumstances, but they're even more extraordinary because, nearly 50 years ago. he was diagnosed with AIJS, or Ixm Gehrig's disease, a devastating and often fatal illness. As the disease pro­gressed, Hawking's physical abilities dimin­ished. First he couldn't walk. Soon he couldn't speak. In spite ol this, he continued his re­search and writing—and he was able to grant interviews like this one. "speaking" by way ol a computer he controlled with the lew lingers he was capable of moving. His synthesized voice has become famous. Hawking has "spoken" on a Pink Floyd song and on episodes of Slur Trek: The Next Generation and The Simpsons.

Hawking, who is now 70, has been mar­ried twice and has three children: he still lives in Oxford, which is where. 22 veal's ago. our interviewer. Morgan Strong, met him. At the lime. Strong wrote that the scien­tist "looked terribly Irail and small: He could not have weighed more than 100 pounds." Nonetheless, over several days, for several hours a day, working in his home, office and a faculty dining room at Oxford. Hawking patiently answered Strong's questions.

Excerpted from the April 1990 issue

PLAYBOY: Can you tell us a little about your early life, before the secrets of the universe caught your interest? HAWKING: I was born on January 8, 1942—.500 years to the day after the death of Galileo. (continued on page 145)

HAWKING

(continued from page 89) PLAYBOY: You had a rather conventional childhood.

HAWKING: Yes. I went to a public school— what Americans call a private school—Saint Albans. I was never more than halfway up the class at school.

PLAYBOY: There's hope for us all. You really were just an average student? HAWKING: [Smiles] When I was 12, one of my friends bet another friend a bag of sweets that I would never amount to any­thing. I don't know if the bet was ever set­tled and, if so, which way it was decided. PLAYBOY: After Saint Albans, you went on to university to study physics. HAWKING: Well, my father was a doctor and wanted me to study medicine at his old college, University College, Oxford. I wanted to study mathematics, more mathematics and physics. But my father thought there would not be any jobs in mathematics, apart from teaching. He therefore made me do chemistry, physics and only a small amount of mathematics. I duly went to University College in 1959 to do physics, which was the subject that interested me, since physics governs the laws of the universe.

PLAYBOY: Had you made up your mind early on about what you wanted to do? HAWKING: Yes. From the age of 12 I had wanted to be a scientist. And cosmology seemed the most fundamental science. PLAYBOY: In your last year at Oxford, you were diagnosed as having ALS, also known as Lou Gehrig's disease, which is supposed to be fatal within a very short time. It must have transformed you. HAWKING: Yes. When you are faced with the possibility of an early death, it makes you realize that life is worth living and that there are lots of things you want to do. PLAYBOY: According to newspaper inter­views, and a recent 20/20 segment by Hugh Downs on ABC-TV, when you got your diagnosis, you went on a drinking binge for a few years.

HAWKING: It's a good story, but it's not true. PLAYBOY: What did happen? HAWKING: The realization that I had an in­curable disease that was likely to kill me in a few years was a bit of a shock. Why should it happen to me? Why should I be cut off like this? But while I was in the hospital, I saw a boy die of leukemia in the bed op­posite me. It was not a pretty sight. Clearly, there were people worse off than I. When­ever I feel inclined to be sorry for myself, I remember that boy.

PLAYBOY: And you didn't go off on the long binge, as reported?

HAWKING: I took to listening to Wagner, but the reports that I drank heavily are an exaggeration. The trouble is, once one article said it, others copied it, be­cause it made a good story. Anything that has appeared in print so many times has to be true.

PLAYBOY: Still, it's astonishing that you had so mild a reaction [to your diagno­sis]. Most people might have given up— or erone on that binee.

HAWKING: My dreams were disturbed for a while. 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 if I were reprieved, there were a lot of worthwhile things I could do. Another dream I had several times was that I would sacrifice my life to save others. After all, if I were going to die anyway, it might do some good. PLAYBOY: Doesn't this terrible disease make you angry?

HAWKING: Yes. I'm a normal human being with normal needs and emotions. PLAYBOY: You got married and started a family shortly after you were diagnosed. HAWKING: Yes, I got engaged to Jane Wilde, whom I had met just about the time my condition was diagnosed. That engagement changed my life. It gave me something to live for. But it also meant I had to get a job if we were to be mar­ried. Eventually, I applied for a research fellowship in theoretical physics at Caius College, Cambridge. And, to my great surprise, I got a fellowship and we were married a few months later. PLAYBOY: How did your disease affect your lifestyle?

HAWKING: When we were married, Jane was still an undergraduate at Westfield College in London, so she had to go up to London during the week. This meant that we had to find a place that was central, where I could manage on my own, because by then, I could not walk far. After several years, we were given the ground-floor flat in this house, which is owned by the college. This suits me very well, because it has large rooms and wide doors. It is sufficiently central so that I can get to my university department, or the college, in my electric wheelchair. It is also nice for our children, because it is surrounded by garden, which is looked after by the college gardeners. PLAYBOY: Wasn't it extremely difficult rais­ing your three children? HAWKING: Yes. Up to 1974, I was able to feed myself and get in and out of bed. Jane managed to help me, and to bring up two of our children, without outside help. But things were getting more difficult, so we took to having one of my research students live with us to help. In 1980, we changed to a system of community and private nurses, who would come in for an hour or two in the morning and the evening. PLAYBOY: You have 24-hour nursing care now. HAWKING: Yes. I caught pneumonia in 1985. I had to have a tracheotomy. After that, I had to have 24-hour nursing care. PLAYBOY: Is it the operation that prevents you from speaking?

HAWKING: Yes. Before the operation, my speech was slurred, so that only a few people who knew me well could understand me. But at least I could communicate. I wrote scientific letters by dictating to a secretary, and I gave lectures through an interpreter, who repeated my words more clearly.

But after the operation, I could commu­nicate only by spelling words out letter by letter, raising my eyebrows when someone pointed to the correct letter on a card. It is

very difficult to carry on a conversation like that, let alone write a scientific paper. PLAYBOY: And now you have the computer. HAWKING: Walt Woltosz, a software expert in California, heard of my plight. He sent me a computer program he had written called Equalizer. This allowed me to select words from a series of menus on the screen by pressing a switch in my hand. When I have built up what I want to say, I can send it to a speech synthesizer. PLAYBOY: Why did you choose theoretical physics for your research? HAWKING: Because of my disease. I chose my field because I knew I had ALS. Cos­mology, unlike many other disciplines, does not require lecturing. It was a fortu­nate choice, because it was one of the few areas in which my speech disability was not a serious handicap. I was also fortunate that when I started my research, in 1962, general relativity and cosmology were underdeveloped fields, with little compe­tition, so my disease would not be a seri­ous impediment. There were lots of excit­ing discoveries to be made, and not many people to make them. Nowadays, there is much more competition, [smiles] PLAYBOY: Did you experience difficulty at the beginning?

HAWKING: I was not making much prog­ress with my research, because I didn't have much mathematical background. But gradually, I began to understand what I was doing.

PLAYBOY: Let's see if we can understand some of it. To begin with, you use only one fundamental equation in your book A Brief History of Time, which forms the basis of your work. Can you define it for us? HAWKING: The equation, E=mc2, ex­pressed the fact that energy and mass are really the same thing. E is for energy and m is for mass. The speed of light, c, is in the equation just to make the units the same on both sides. However, you can use units in which c equals one. This equation is im­portant because it shows that matter can be transformed into energy and vice versa. In fact, it seems that in the early stages of the universe, all matter was made out of energy. PLAYBOY: Energy that was then trans­formed to mass—or the solid bodies that make up the universe. HAWKING: Yes. The energy was borrowed from the gravitational force of the uni­verse, which had compressed everything to infinite density before it was released in the big bang. The total net energy of the universe is zero. Thus, the whole universe is for nothing. Who says there is no such thing as a free lunch? [smiles] PLAYBOY: How does the total energy of the universe equal zero?

HAWKING: It takes energy to create matter. But the matter in the universe is attracting all other matter in the universe. This at­traction gives the matter a negative energy that is exactly equal to the energy required to create the matter. Thus, the total energy of the universe is zero. PLAYBOY: So once matter is created, the en­ergy exists in the matter, which is spread out across the universe. Where did the en­ergy that was needed for the big bang to occur come from?

HAWKING: The energy needed to create the big bang came from the universe it created. PLAYBOY: In the equation, time is also im­portant. Why?

HAWKING: Before Einstein, time was thought of as completely separate from space. People believed that there was what was called absolute time. That is, each event could be given a unique value of time. However, experiments showed that this could not be the case. And Einstein showed that the experiments could be ex­plained if one said that time was not sepa­rate from space but was combined with it in something called space-time. PLAYBOY: According to Einstein, that means the time of an observed event in space is dependent on the position of the observer. So it becomes another measurement, like width and height.

HAWKING: Yes. Later, Einstein was able to show that gravity could be explained if space-time were not flat but curved. This idea of space-time has completely trans­formed the way we look at the universe. PLAYBOY: A black hole is also critical to your theory. Could you explain? HAWKING: A black hole is a region in which the gravitational field is so strong nothing can escape. Within a black hole, there will be a singularity, where space-time comes to an end. This singularity, an infinitely dense point of matter, is rather like the singular­ity that occurred in the big bang and is the beginning of space-time and the whole of the universe.

PLAYBOY: Why is it called a black hole? HAWKING: The gravitational field of the singularity would be so strong that light it­self could not escape from a region around it but would be dragged back by the gravi­tational field. The region from which it is not possible to escape is called a black hole. From 1970 to 1974, I worked mainly on black holes. In 1974, I made perhaps my most surprising discovery: Black holes are not completely black! When one takes small-scale behavior into account, particles and radiation can leak out of a black hole. The black hole emits radiation as if it were a hot body.

PLAYBOY: If your theories are correct, then a black hole will eventually explode in a way similar to how the universe began? HAWKING: Yes.

PLAYBOY: Why does that happen? HAWKING: Because of the uncertainty prin­ciple of quantum mechanics, particles and energy will slowly leak out of the black hole. This will make it grow smaller and smaller and leak energy more rapidly. Eventually, the black hole will disappear in a tremen­dous explosion.

PLAYBOY: Quantum mechanics is the study of the behavior of systems at small scales. HAWKING: Yes. Atoms or elementary par­ticles. In any case, a black hole cannot just suddenly pop out of nothing and explode, because there has to be something there to provide energy.

PLAYBOY: Even though you've made black holes a central part of your life's work, you concede that one has yet to be discovered. In fact, you mention in your book that you have a bet with a colleague that one will not be discovered. Is that true?

HAWKING: Yes. I had a wager with Kip Thome at Caltech that Cygnus X-l was not a black hole. It was an insurance policy, really. I had done a lot of work on black holes, and it all would have been wasted if it had turned out that they didn't exist. But then, at least I would have had the satisfac­tion of winning my bet. [smiles]

PLAYBOY: And?

HAWKING: Well, now I consider the evi­dence for black holes so good, thanks to Cygnus X-l, that I have conceded the bet. Cygnus X-l is a system consisting of a nor­mal star orbiting around an unseen com­panion. It seems that matter is being blown off the normal star and falling on the com­panion. As it falls toward the companion, it develops a spiral motion, like water run­ning out of a bath. It will get very hot and will give off X-rays that are observed. We can show that the mass of the companion is at least six times that of the sun. That's too much to be a white dwarf or a neutron star, so it must be a black hole. PLAYBOY: We feel privileged to hear the news. Can you go beyond deduction and establish what a black hole is, physically? HAWKING: We want a volunteer who will jump into the black hole and find out what happens inside. Unfortunately, he won't be able to signal back to us to let us know. PLAYBOY: Why?

HAWKING: Because of something called a light cone.

PLAYBOY: In your book, you say that in such an event, a person—or any object—would be torn apart by gravitational forces. And the intense gravity would prevent even radio signals from escaping. HAWKING: Yes. A volunteer astronaut would have a sticky end at a singularity. His particles would survive, but that, I sup­pose, is small comfort, [smiles] PLAYBOY: But isn't there a possibility that he or she might escape through what is called a wormhole?

HAWKING: Yes. Particles that fall into a black hole may pass through a thin tube, or wormhole, and come out somewhere else in the universe. But wormholes occur only in imaginary time. The history of the particles, and of an astronaut in real time, will come to a bad end at a singularity. PLAYBOY: What is imaginary time? HAWKING: Imaginary time is another di­rection of time, one that is at right angles to ordinary, real time. It seems that there will be large numbers of imaginary-time worm-holes branching off, and joining on, every­where. We do not notice them directly, but they affect everything we observe directly. It is an exciting area of research. PLAYBOY: And you use imaginary time, and wormholes, to speculate about objects trav­eling through time, don't you? HAWKING: [Smiles] Objects will pass through a thin tube, or wormhole, in imag­inary time, and out into another universe, or another part of our universe. In ordi­nary time, one could pass through a black hole and come out of a white hole. PLAYBOY: A white hole? HAWKING: Yes. The laws of physics are symmetrical, and if there are objects called black holes, which things can fall into but not out of, there ought to be objects that

things can fall out of but not into. One can call these white holes. PLAYBOY: In ordinary time. But you said that was impossible.

HAWKING: A white hole is the time reverse of a black hole. The white hole may be in an­other universe, or another part of our uni­verse. We could use this method for space travel. Otherwise, the distances are so vast it would take millions of years to go to the next galaxy and return. But if you could go through a black hole and out a white hole, you could be back in time for tea. PLAYBOY: And if it were possible, in theory at least, you could travel back in time? HAWKING: Yes. The trouble is, there would be nothing to stop you from getting back before you set out. [smiles] PLAYBOY: Or you could get back and find yourself dead. Or your world dead. HAWKING: Fortunately, for our survival, it seems that space-times in which one can travel back to the past are unstable. The least disturbance, such as a spaceship going through, will cause the passage between a black hole and white hole to pinch off. The history of the spaceship would come to an end, torn apart and crushed out of existence. PLAYBOY: What, exactly, is the relation of imaginary time to real time? HAWKING: By using imaginary numbers, one adds up all the probabilities for all the histories of particles with certain properties—such as passing through cer­tain points at certain times. One then has to extrapolate the result back to real space-time, in which time is different depending on directions in space. This is not the most familiar approach to quantum theory, but it gives the same results as other methods. PLAYBOY: Doesn't that randomness make it difficult—even chaotic—to apply to the laws of science?

HAWKING: Yes. Einstein objected strongly to this randomness with the famous statement

that God does not play dice with the uni­verse! But all evidence points to the prop­osition that God is, indeed, an inveterate gambler, [smiles] He throws the dice to de­termine the outcome of every observation. PLAYBOY: As much—or as little—as we can understand of your work, it again strikes us that most of your ideas depend on obscure mathematical concepts, far removed from ordinary, observable life. HAWKING: Imaginary time may sound like science fiction, but it is a well-defined mathematical concept. PLAYBOY: Yes, to mathematicians and phys­icists, but to most of us, it's beyond immedi­ate understanding. HAWKING: Yes.

PLAYBOY: Then what can the general public gain from trying to understand these con­cepts? Most of us would say we had more immediate problems to deal with. HAWKING: This is why I have spent some of my time attempting to explain what we do. I think knowledge of the general ideas of the recent discoveries in cosmology are useful to the public.

True, understanding cosmology will not help feed anyone. It won't even wash clothes any brighter. But man or woman does not live by bread alone. We all feel the need to come to terms with the universe in which we find ourselves, and to under­stand how we got here. PLAYBOY: And that's why you wrote A Brief History of Time}

HAWKING: There are several reasons why I wrote the book. One was to pay my daugh­ter's school fees. I didn't succeed in that, because by the time the book came out, she was in her last year of high school. But I still have to pay for her college. PLAYBOY: That's an excellent reason. Are there others?

HAWKING: The main reason was that I had written several popular articles and given

a number of popular lectures. They had been well received, and I had enjoyed do­ing them, but I wanted to try something bigger. I felt that we had made tremen­dous progress in the past 25 years in un­derstanding the universe, and I wanted to share this with the general public. I think it is important that the public take some interest in science and have some general understanding of it.

Science has changed our lives a great deal and will change them even more in the future. If we are to decide in a democratic way what direction society should take, it is necessary that the public has some under­standing of science.

PLAYBOY: Then you're doing something political—knowledge as the great lev-eler, not confined to a few who under­stand the language.

HAWKING: Yes. Knowledge and under­standing of how the universe works, and of how it began, had become the preserve of a few specialists. But we all share the hu­man condition, and we all want to know where we came from. My book is an at­tempt to share with the general public the knowledge that the specialists have found. Knowledge is not knowledge unless you share it with someone. Normally, special­ists communicate only with other special­ists; I feel they should communicate with the general public, as well. PLAYBOY: You say that you may succeed in knowing how the universe began, but you will not know why. You do not—as Einstein did not—dismiss the notion of a supreme creator.

HAWKING: I think I'm careful in my book. I leave open the question of whether God exists and what his nature would be. One can never prove that God doesn't exist. What I did was show that it was not neces­sary to appeal to God to decide how the universe began, because that is determined by the laws of science. However, one could say that the laws of science were God's choice for how the universe behaves. PLAYBOY: Apart from now being able to pay your daughter's college fees, has the book made any difference in your life? HAWKING: It has not made that much difference. Even before the book, a cer­tain number of people, mainly Americans [smiles], would come up to me in the street, but it has made that sort of encounter more frequent. And other things like interviews and public lectures have taken up the lim­ited time I have to do research. However, I'm now cutting down on such things and getting back to research. PLAYBOY: We assume that every scientist hopes for recognition for his efforts. You have received a number of honors but not yet the Nobel Prize. Do you think you may someday receive the Nobel? HAWKING: Most of my work has been gen­erally accepted. I have received a lot of recognition recently. But I don't know if I will ever get the Nobel Prize, because that is given only for theoretical work that has been confirmed by observation. It is very, very difficult to observe the things I have worked on. [smiles]