John Wheeler - Session X

EARLY WORK ON GRAVITATION

Now we're talking about this course in gravitation beginning in the fall of 1952. I was learning this subject as I went along. It took some time to get the idea of metric through my thick head, what it really means, that there's a spacetime of events like grains of sand on a sheet of sandpaper with an interval of spacetime between one event and the next.

Relation of relativity to nuclear physics

There was certainly one incentive along the way that was connected with our Los Alamos experience on the equation of state of condensed matter. That was the question of equation of state of matter in a neutron star. It was a question of nuclear physics. I know that there are some of our colleagues who think of surprises even there now. For example, T. D. Lee has talked about the possibility or conceivability of a star in which the matter is so squeezed that it changes from ordinary nuclear matter to quark matter.

Relation of relativity to quantum mechanics

I had been so enthusiastic for the sum-over-histories way of describing quantum mechanics and the transition from quantum mechanics to classical mechanics that I couldn't help looking for a similar transition in the case of relativity. It was a great help to have Valentine Bargmann as a colleague, because he really knew relativity and analytical dynamics, and I can recall his discussing a paper of Asher Peres. Peres at that time, if I remember correctly, was at Syracuse University. Peres had a way to express the Hamilton-Jacobi form of general relativity, which was forerunner of what I later called superspace and the wave equation in superspace. Bargmann helped to clear up exactly what it was that Peres had done.

People today talk of the Wheeler-DeWitt quantum equation for the dynamics of geometry, but, in view of Bargmann's inspiration, it would have been more appropriate to call it the Bargmann-Wheeler equation.

Well, I'm only really happy when I'm swimming in a mystery, and where was the mystery in this gravity business? There was this question of gravitational collapse of a star, but that was hardly a conceptual mystery. It was a mystery, at least so it appeared then and appears now, about detail of the equation of state at high density.

Geometry as everything

I was no longer fired up about trying to get an equivalent of action-at-a-distance treatment of gravitation—half advanced, half retarded potentials. I still hope some student will come around some day who looks as if he's interested in issues of that type, because I think it would be fun to see the consequences. But certainly relativity was enough with its beauty and its appeal of a pure field, and geometry as a field responsible for action between particles—certainly an appeal to give up the idea that interactions between particles are the whole show, action at a distance, and go to the opposite point of view that it's an entirely field-theoretic nature that we deal with.

This was the background for the work that Charlie Misner and I did in a paper in the Annals of Physics, a journal edited at that time by Philip Morse at MIT. This paper we did mostly while we were at the University of Leiden, a paper of 1957. We did the work in '56 at Leiden. "Classical Physics as Geometry . . ." is the title of the paper; "Gravitation, Electromagnetism, Unquantized Charge, and Mass as Properties of Curved Empty Space."

Geons in Geneva

Thinking along that line, thinking in advance before we really got into detail, was, I think, an inspiration for work I did mostly in Geneva. One summer I had gone to the first International Conference on Peaceful Uses of Atomic Energy, as I think it was called, held at the instigation of Eisenhower and his head of the Atomic Energy Commission, Lewis Strauss. There were all kinds of papers on design of engineering reactors, but the Russians and the Americans sneaked off from those meetings and had their own meeting on the physics that they were interested in.

It was a little due to the appeal of this pure field-theory point of view I suppose that led me to consider an object in that work in Geneva in the summer. We stayed in the apartment of an aunt of Janette's overlooking the falls where the Lake of Geneva issues down into the river, a quiet place because the fall suppressed all of the city noise. The idea of light going around held in orbit by its own gravitational attraction was a model for a system made entirely out of field. Gravitational for G, E standing for electromagnetic, ON standing for entity [spelling the word geon]. I didn't realize at the time I published the paper that the object is really unstable. It's like a pencil standing on its tip, which is stable against the pencil bending or collapsing but not stable against the pencil tipping over. Since that time, realizing that point—I think the instability was pointed out to me by somebody else—but realizing that instability, I've been attracted to it as a concept for taking gravitational waves and collapsing them into black holes.

A paper was published this past year by Daniel Holtz of Princeton, who had been a Princeton senior, and Masami Wakano, who had helped with some of the thinking, and Warner Miller, who had also helped us.

COLLECTIVE MODEL OF THE NUCLEUS

Annual Review of Nuclear Science asked me in the 1950s to do a paper on fission physics, and I took that as an excuse to revive the work that I'd done with Bohr on nuclear models. I had the help of David Hill, so we put together a paper, which, however, was too late for the Annual Review, so then we sent it to Physical Review. It was really much longer than the Physical Review normally takes, but Samuel Goudsmit—this is a paper of 1953, Paper No. 56, "Nuclear Constitution and the Interpretation of Fission Phenomena"— Samuel Goudsmit was kind enough to arrange for one of the editors at the Physical Review to move things around so that it would fit. Unfortunately, that made it necessary to put all the pictures at the end instead of putting them in the text to illustrate the text as it went along.

I had people talk to me afterwards in astonishment that one could think of nuclear models in these terms. There was where we really combined the independent-particle picture and the liquid-drop picture. The liquid drop, or its shape, defined the nuclear potential, and in that potential the nucleons moving created a force which was responsible for the potential. There is obviously much more that can be done in that field, for example trying to understand from that point of view why fission gives fragments so different in mass as those which one finds, and why fission sometimes gives rise to other particles and almost always to neutrons. There is some work that's on that line which is reported at an international conference about two years ago in Washington celebrating the anniversary of fission. What work has been done there is promising enough—that was work of other people—to indicate a real incentive to go further.

There were other papers which reported these ideas in much briefer compass and with a better overview, papers given at conferences in Kyoto and Geneva and Glasgow. I've always found that the obligation to give such a paper pays off because it forces me to dream up something new to add to the subject.

VACUUM POLARIZATION

The biggest development in theoretical physics following World War II, I would say, would be the Lamb Shift in the hydrogen spectrum, understanding what it meant, calculating from first principles how much it should be, and comparing with observation. That work I didn't take part in directly, but the polarization of the vacuum by the atomic electron and the hydrogen atom was a topic that did interest me. Robert Euwema, as a graduate student, applied the Kramers-Kronig principle of causality to calculate this polarizability from the ability of the vacuum to absorb photons. I'd always been interested in the absorption of light by the vacuum since I did a paper with Gregory Breit so long ago on the collision between two photons as a mechanism to produce a pair. Now my colleague here at Princeton is working on preparing for an experiment using two high-energy photons to collide and produce particles. Kirk McDonald is his name.

"RELATIVE-STATE" VS. "MANY-WORLDS"

Another graduate student about that time, Hugh Everett, had a very independent mind and was upset by some of the strange features of quantum theory and had a mathematical gift. He later put that to use in the Pentagon. He showed me around the Pentagon and told me how he had reprogrammed the computers in the Pentagon. The draft of a thesis that he brought me seemed to my mind to need a lot of redoing in order to make it truly comprehensible. I can recall our working very late hours at night revising the draft in my office. Well, from reactions around the laboratory I got the feeling that his work would not be well received unless there was something that went along with it, so I wrote a paper called "Assessment of Everett's Relative State Formulation of Quantum Theory." The word [term] "relative state" I had thought was a descriptive term that gave a realistic feeling for what his business was all about, but my colleague Bryce DeWitt gave it the much more exciting term, "many-worlds" interpretation of quantum theory. So this paper of mine which was to defend Everett's point of view has been taken since then as defending the "many-worlds" interpretation of quantum mechanics. I feel very uncomfortable about being viewed as a defender of that term, and I hope someday I can write a book on quantum theory, but how can I if I don't get to teach another course on the subject? But I think the course ought to be taught to young people who have not had advanced physics, because to my mind the greatest ideas are the ones that can be said most simply with the least amount of material.

So if Everett taught me about quantum theory, Brill, another graduate student, taught me about neutrino physic. We did a paper on the interaction of neutrinos with gravitational fields. It was impossible not to be interested in neutrinos, such a strange particle.

Ford: Before you continue with your discussion of your work with Brill on neutrinos, may I ask one question related to that first course on relativity. Do you remember the names of any students who were in it? It must have been a very exciting course, and I'm curious whether any of the students in that first course became researchers in the field themselves.

Who were students in that first course in relativity in the fall of 1952? Lindquist was certainly one. I can believe that Misner was there, although later he was giving a course. And Euwema. I suspect John Klauder. I don't know whether Unruh, William Unruh, had come yet. And Edwin Power.

NEUTRINOS

The neutrino I had just been referring to when our tape ended. I always kept an interest in the neutrino from the days of Los Alamos, talking with Frederick Reines. He [him] I jokingly call Mr. Neutrino. His wonderful push to find some way to detect a neutrino paid off in the end. It was fantastic setting up the permission for him to do an experiment looking for neutrinos at the Hanford reactor. I think that was at the B Site, but I don't swear that was the site. The whole thing had to be written up in advance, every step of the way, in such a form that each operator had an assigned mission so that it would not disrupt the ordinary production operations at the reactor—the production of plutonium.

My du Pont friends had asked me to serve in an advisory capacity on the production reactor they were building at Savannah River, Georgia. Or was it South Carolina?

Ford: I think it's South Carolina.

South Carolina. Because there new problems came up. It was not exclusively plutonium that was being made, but also tritium. It turned out that in the end it was easier for Fred Reines to do his work there than at Hanford.

SCHWARZSCHILD GEOMETRY

The geometry around a spherically symmetric center of attraction, of gravitational attraction, that so-called Schwarzschild geometry, is so simple that it received quite a lot of attention in my course in relativity. I can't recall anything new about the Schwarzschild geometry coming out in that course, but it provided a building block out of which one could build a model universe with some magic number of cells, each cell like the cells in a crystal, approximately spherical, and the geometry there modeled by an exactly spherically symmetric Schwarzschild geometry, and these cells fitted together. This gave a way to derive the dynamics of a model universe in a new way. That work Lindquist did. Edwin Power did another piece of work, taking not radiation going around in a circle, in an intelligent (?) course around the center of attraction of a geon, but rather thermal radiation.

GRAVITATION AND QUANTUM THEORY

I was fortunate at Leiden in 1956 to have the company of Misner and to talk with him about consequences of applying quantum theory to Einstein's general relativity. That led to a paper of mine in the Annals of Physics in which the notion of the Planck length is introduced, and the Planck time and the Planck distance. At the Planck distance, fluctuations in geometry become so great, I argued in that paper, become so great that the very ideas of before and after lose their meaning.

I'm just now writing a review of a book with a theological title. It's a mixture of ideas about quantum theory, cosmology and so on, put together by eight people.

Ford: Did you say theological?

Theological. Yes, it's a book published partly by the Vatican but has such respected physics colleagues writing for it as Christopher Isham and Paul Davies. I've been trying to get the right flavor for that review. Just this morning I fed into it a new title to stimulate me. The title was "Time, Cosmology, Theology, Quantum: Mix, Stir, and Bake Overnight." [laughs]

PARTICLES AS GEOMETRY

One of the graduate students we had about this time was William Unruh from British Columbia—well, actually from Canada. He's in British Columbia now. We never had a student who on both the oral and written general examinations did more spectacularly, and I had hoped that he could find some analog of electric charge. If an electric charge arises from electric lines of force trapped in the topology of multiply connected space, what kind of charge would originate from a gravitational field trapped in the topology of a multiply connected space? He showed there is no such quantity. There is no gravitational analog of the electric charge. But John Klauder did treat the question of a neutrino analog to electric charge. It's an absolutely fascinating fact that we haven't made the most of, I fear, even yet, that when one has a wormhole one has a nonclassical two-valuedness, which was first realized by the French geometer Elie Caftan. As Klauder emphasizes, that has a spin one-half associated with it, as does a neutrino. What's the difference between such a spin one-half purely geometrical object trapped in the topology of space—

what's the difference between that and a neutrino? I just don't know.

WORK WITH REGGE

If Schwarzschild geometry is the key concept and working tool needed in analyzing the wormhole, then it's interesting to ask what one can say about the stability of such a geometry, a Schwarzschild geometry. I was so interested in

that that, without knowing what the answer was, I wrote a paper about it with blanks for the mathematics. I had met a promising graduate student at the annual Rochester Conference on High-Energy Physics. I think it was Marshak that introduced me to this red-headed, tall graduate student, Tullio Regge. Anyway, later, I sent my paper with slots in it to him, and he not only filled it in but came to visit me in Leiden. The visit he describes in his book with the Italian—I think it's a Nobel, but I don't swear to it—writer Primo Levi. It's a book called Conversations with Primo Levi. He tells there how I got him involved in setting off some fireworks in the courtyard of the Institute of Physics over a weekend when we were talking, and that brought the police. But we talked our way out of it.

GETTING "ROPED IN"

Sometimes I got myself roped in in events where I had to give a talk or write a paper on more than detailed physics. For example: "Septet of Sibyls: Aids in the Search for Truth." The Association of Princeton Graduate Alumni had asked me to talk, and in response I dreamed up that topic and talk.

And then the science advisor to the president, Killian, knowing that the first Atoms for Peace Award was going to be given by Dwight Eisenhower to Neils Bohr, asked me to give a talk there on it. So that's how come I wrote this talk called "No Fugitive and Cloistered Virtue" about Bohr. But how did I write a paper called "National Survival and Human Development: Neighborhood Goals in a Rapidly Changing World"? The National Federation of Settlements and Neighborhood Centers in New York was the forum for that, but I don't recall how come.

And then that wonderful person, Jan Oort, the great Dutch astronomer, who died last year, invited me to take part in the 1958 Solvay Congress held in Brussels, this one on the structure and the evolution of the universe. That's where I first encountered the mystery of the missing mass. Some of the students in my course in relativity took part in helping me on that: Adams, Kent Harrison, Klauder, Mjolsness, Wakano, and Willey. Mjolsness was the first student I ever met who shied away from research. I invited him in to talk about some of the problems that there were, and his reaction was "I can hear the clanking of the chains." [laughs] Maybe I shouldn't say anything like that, because he wouldn't like to have it appear on his record, so we'd better leave that out, but—

Ford: Did he in fact do a thesis with you?

Yes. But I can't recall what thesis topic Mjolsness worked on. I should really get a list of them.

FORD-WHEELER PAPERS

How did we get into quantum effects near a barrier maximum and semiclassical description of scattering? What was it that triggered us off? I can't remember what the problem was.

Ford: I only remember that you came to me with the idea and invited me to join and work with you, but I don't recall what triggered your particular interest at that point.

What did we apply the work to? It was just a general treatment, was that it?

Ford: Yes. But it triggered a myriad of applications by others.

MORE WORK TRIGGERED BY SPEAKING OR WRITING COMMITMENTS

Neutrinos and gravitation, the two fascinating fields with zero rest mass, what relation do they have to each other? I tried to explore that as far as I could when I was asked to talk at the Fermi Summer School in northern Italy in 1960.

Another conference that triggered me into doing something was one on nuclear masses in Hamilton, Ontario. Was there any way to get a quick treatment of nuclear masses that would be more detailed or better than what had been given in the past—nuclear mass as a function of nuclear charge and mass number? The surface tension that was put into nuclear models, would that not depend upon the ratio of neutrons and protons? Anyway, Rick Warner and R. Brandt and Masami Wakano and Bob Fuller and I investigated that and reported our conclusions. I suspect I would not have done that if it hadn't been for that conference coming up. And the Encyclopedia of Science and Technology articles on the atomic bomb, on nuclear chain reaction, on critical mass and on nuclear fission, they were all triggered by the urgent invitation of that encyclopedia to contribute.

100TH PAPER

It had been a privilege of being in the Princeton community to meet Leopold Infeld. He had been working with Einstein on trying to derive the equations of motion of masses out of the field equations themselves—in other words, to show that the tensions in the geometry could be thought of as responsible for the forces that tugged masses around in orbit. But there were issues about that subject that were still not clear. That was an incentive for doing a paper on the subject: 1961, Paper No. 100. Somehow that topic doesn't come much into discussion nowadays, and I do not know why.

Gravitational waves, always an interesting subject. The mathematics of gravitational waves is not as simple as one might like, but if one treats the case where the waves have cylindrical symmetry, then they do take on simplicity. Joe Weber and I wrote a paper on such waves.

RESPONSES TO GENERAL QUESTIONS

Here are your questions of March 4th, general questions.

1. Self-confidence: Clearly you had great self confidence about your ability to do meaningful physics, confidence about your ability to succeed (albeit coupled with modesty and humility). Examples: seeking the best physicists in the world for postdoctoral work; diving into forefront topics on which the most renowned physicists were already working; accepting a nontenured position at Princeton and building a house in your first year there. Can you identify factors in your childhood that help to account for this confidence? (Success in school? Support from family? Example of father? . . .)

Well, I know that the family members who know me better than I know myself say I'm a plunger. I think my grandfather was a plunger, my grandfather Archibald.

Ford: How about your own father?

And my father, too, going in for buying this farm in Vermont when it was really financially cuckoo. So sad to go up there nowadays and see the farmhouse itself burned down. The barn's caved in and the land is being farmed by the farmer Almon Charleton that lives on the next farm. If you want to hear real Vermont language, you should talk to Almon Charleton.

Ford: The reason I asked that question, John, is that I've known people even of great achievement who were nevertheless always full of self doubt, unsure of themselves even though they were actually brilliant and did great things. But you don't—at least you don't give the appearance of having ever suffered from such self doubt.

I think my father used to preach in the family those words of Theodore Roosevelt: "Do the best you can with what you have where you are." Theodore Roosevelt is an example of a person who, handicapped in health, made the best of it.

I think one of the fortunate things in my life was being given jobs and told to do it. There's nothing like being told to do something to give you the ability to do it—getting in the cows, for example, when the cows are scattered over a huge pasture and sometimes lost in the woods. Nothing I hated more than having to hoe corn—it was so deadly dull, it was so hot. There I was out in the

open, and I'd sneeze and sneeze, what with my hay fever. There is no sense of adventure in hoeing corn. But some of the work one has to do in life is like hoeing corn, and having to do it was great training for the future.

Accepting a non-tenured position at Princeton. Yes, I had a tenured position at North Carolina, and Johns Hopkins offered me a tenured position, but Princeton was so unusual in its combination of excellent people and great tradition that I felt it was worth taking a risk to take an assistant professorship at Princeton. What about building a house in the first year in Princeton? That would have been impossible without the help of Janette's family. They encouraged us to think of building a house. And if I remember right, it was $13,500 that it cost us to build that house that today I suppose would be $200,000.

Ford: Or more!

My father was always full of more projects than he had a chance to do. One of his projects was to do a book on the design of a house, the architecture of practical houses. The chapter on which I remember the most vivid discussion was the efficient design of a kitchen, the layout for operation of the work. He was tuned into such questions because he had to make public libraries work on minimal budgets, and anything that would allow people to work most efficiently was a help. He read with rapture the works of the man who had done so much on . . . Taylor. There are some people, for example Gerry Piel, who was so long the editor of the Scientific American, who thinks Taylor is the devil's own creation, that his figuring out the proper ratio of rest and work to get the most from workers was cold-blooded exploitation. But if you're doing a job for the public and you're saving money for poor taxpayers, then it's not exploitation but it's protection of poor people. One of the things that he was proud of was the help he could give to people to rise in the world. I recall his telling more than once about the man who was going to take an examination for a job in the Los Angeles area, a job for which he had no experience or training. Now he got books for this man to read and study, and his delight when the man passed [the] examination and got the job.

2. Admiring achievement: You admire achievement, in whatever field—people who get things done, make things happen, people who change the world in some beneficial way. Two aspects of this are interesting: (1) the focus on the person's achievement and impact more than on his or her insight or knowledge; (2) the breadth of your field of view—business, politics, finance, engineering, art—not just science. Can you comment on factors in your early life that may have contributed to this slant in your outlook?

Ford: The reason I asked that question, John, is I think you're quite special in not being narrow in the fields of achievement you admire. Many physicists would only admire achievement in physics or in science, but you have admired achievement in a variety of fields, and not all of them even intellectual— business fields, for instance. Wherever you see a person who does something

unusual and special and with quality, in whatever that field is, my observation is that you have shown admiration and respect for that person.

I must accept Thomas Edison's definition of genius: "the ability to do easy and well what others do badly or not at all."

And that other statement, let's see, it has to do with plagiarizing. I'm trying to remember the little bon mot that ends up with, "Plagiarize, plagiarize, plagiarize."

Ford: "Let no one else's work evade your eyes."

How does that thing begin?

Ford: The song by Tom Lehrer.

Yes, Tom Lehrer. From Omsk to Tomsk. Yes, Lobachevsky. From Omsk to Tomsk, from Minsk to Pinsk to Petrov(?), plagiarize, plagiarize, plagiarize.

Well I think it's so lucky to be alive and look around at all the fascinating things going on in the world. It you take an interest in pigs getting to the feeding trough as you feed them in the morning, then you take immensely more interest in people and doing(?) their way ahead.

3. Flair: Your style of doing physics and reporting your work has a very special flair. This comes across in your use of language, in your use of diagrams (pictures), in your coinages, in your enthusiasm. What were the influences, either in childhood or in your early career in science, that led to this flair?

Use of diagrams and made-up words. I think I've been influenced by my father's background. He helped earn his way through college by painting signs as a sign board artist. So he took a great interest in the impact of a sign, to make it really hit. I think I've mentioned his printing lists of books that could be borrowed from the library, printing them on the cardboards that are inserted in shirts and getting laundries to send these out in the shirts they distributed when they returned a shirt to a customer.

So I've got, I'm afraid, to the point where I can't understand a principle of physics if I can't draw a picture to illustrate it. And then we all know Einstein, how impressive his words were. As I wrote about it in one place, he felt that what was long was lost. You have to [keep it] short and peppy.

4. Bohr: It is often said that your style, your approach to physics, even some of your mannerisms, are derived from Bohr. Do you agree with this assessment? In what ways did your postdoctoral year with Bohr change you as a person and/or as a physicist? Was Bohr's influence a factor much later when you had the courage to tackle fundamental puzzles of the quantum and its relation to the universe?

In what way did my postdoctoral year with Bohr change me as a person or as a physicist or both? I can remember what an inferiority complex I felt as colleagues at the Institute would sit around talking in German or Danish and me having trouble just keeping up with what they were saying, let alone trying to say anything myself. It makes me think of the rule I observed when I visited the Citadel in Charleston, South Carolina a few years ago. The students there were divided very sharply into first-year students and later-year students. The first-year students couldn't walk on the sidewalk; they had to walk in the gutter beside the sidewalk. So I was walking in the gutter. [laughs]

Ford: To show your solidarity. In effect.

It was a great encouragement to know James Franck. He was a marvelous people person. He had been given the Iron Cross in World War I for heroism. Maybe I mentioned, when he was invited to Munich to become a professor there, invited to leave Göttingen, he did not want to accept the job in Munich. Well, he was shown the lecture room where he lectured to the students. He asked how could they justify such a big salary. "Well, you have all these students." "Well, how many will the lecture hall hold?" It was half that number. "Well, how can I in good conscience accept money for teaching X number of students when the lecture hall will only hold X over 2?"

I can recall his concern with what was going on in Germany. He thought it would take 50 years for the bad influences at work to work their way out of the system. Well, the 50 years have passed now.

One of the features about life in Copenhagen, [with] Bohr, Franck and others, [was] the willingness to discuss questions all over the map—politics, business, what-not. The feeling that it was all part of the scene that went on to take an interest in.

I can recall Bohr taking the better part of the summer to write an obituary of Rutherford. He had such an admiration for Rutherford that he wanted to do it right. He had a special responsibility in Denmark, because he occupied the House of Honor. In that status, he was supposed to stand up for learning and matters of principle. It's almost like being named Archbishop, I suppose, except dealing with a wider range of issues. He and his wife, for example, spent quite a little effort in looking after the students in the field of art to give them encouragement, afternoon teas from time to time. The courage to tackle fundamental puzzles of the quantum and its relation to the universe.

Courage is one word, but another word that might be more accurate would be desperation. That is some way to get through. Some day things will look so much simpler than they do today, and a desperate search to find a way through to that later day.

5. Rate of publication: Unlike most physicists, you published at a higher rate in your middle and later years than in your early years. What were the factors that led to this?

Well I suppose the answer is that I didn't have so many students I could exploit in early years.

Ford: Katharine Way was your first student? Yes.

Ford: And was Dick Feynman the second?

Herman Parker was my second student, Herman Parker at North Carolina. I don't know what has happened to him. And then I can't remember the title of his thesis. Another graduate student at that time, but not a thesis student, at North Carolina was Dudley Williams. And still another, Barr. I've forgotten what his first name is.

Ford: Scott Barr?

Scott Barr, yes, who's been doing a series of short biographies of men of the world of physics. And he's aiming to get that published.

[As to] rate of publication, maybe I've become less picky, readier to write what comes into my mind without going over it and over it.

Our friend David Sharp, who is now at Los Alamos, keeps urging me to publish my collected papers. I've held off from that because it would take quite a lot of work to discuss the relation to the state of the subjects, the various subjects, at the present time. But maybe it's not as hard as I think it would be. Maybe it would be easier to just jump in and do it and see what happens.

Ford: Is he willing to work with you?

I don't think he has the financial possibility to do it. But I ought to do it before it's too late. Arthur Wightman has been editing the collected papers of Eugene Wigner, but he's farmed that out to a number a people, the different sections. I haven't looked at the result yet to see what it looks like.

MOST SIGNIFICANT PIECES OF WORK

The most significant piece of work in relativity, as I see it, was establishing the inescapability of gravitational crunch in a star. No equation of state could prevent matter from being crunched. [This is] in contrast to the work of Oppenheimer and Snyder of 1939, which had taken the escapability of resistances for granted and analyzed the time development of crunch. They took for granted that one could arrive at circumstances where resistance of matter to being crunched was negligible and could be forgotten about, whereas the analysis of the equation of state that I had gone through made it clear that no equation of state compatible with special relativity would prevent crunch. That was therefore an intellectual doorway-opener to the black hole.

MOST SATISFYING PIECES OF WORK

What was my most satisfying piece of work? The interaction with the absorber as a mechanism of radiation, the work with Richard Feynman, that was very satisfying in the sense of making radiation a part of statistical mechanics. The absorber particles had to be sufficiently numerous in a great globe of the sky to guarantee that the force of radiative reaction would come out to agree with experience.

The most satisfying pieces of work—that's plural. The book on gravitation, pulling things together and finding slogans to describe the key features of the subject. That was satisfying. For example, putting it all in a single sentence: "Space tells mass how to move, and mass tells space how to curve."

Nuclear physics is not as a whole a satisfying field of physics, at least in its present state, but being able to get a horseback picture of the fission barrier of atomic nuclei, to predict the fissionability of nuclei before that had ever been measured, that was satisfying.

MOST RECOGNIZED PIECES OF WORK

That [work on fission] was also a much recognized piece of work. But I think even more recognized was the scattering matrix. My poor friends that recommended me for this prize that I got in Italy on Saturday had put together, I'm sure, some kind of account, and if my Italian were better I would have picked it up when it was read out on Saturday morning. I would have to look at my bibliography to find out, to be reminded again, about pieces of work that were recognized. I think the paper on the collective model of the nucleus with David Hill received a lot of recognition.

NEAREST MISSES - ALMOST, BUT NOT QUITE

What about nearest misses? One important idea in that paper with David Hill had to do with nuclear deformations. It would have been possible to understand the quadrupole moments of atomic nuclei at an early date. I got the idea how to do that on the train back to Paris from Copenhagen after a visit with Bohr [in 19491, but before I could get to writing it up I learned that the result had already been published by Aage Bohr and a collaborator.

Ford: Rainwater?

Yes. With Rainwater. I can believe that [Niels] Bohr unconsciously acted as a communicator of that idea, either an idea that came to me from Aage Bohr and Rainwater through Neils Bohr's unconscious, serving as a conduit, or the other way.

The paper with Tiomno where we have the triangle, which lots of people call the Puppi triangle, I think came before Puppi, but I should trace out that history, and I would if I only could take the time, because I'd like to recommend Tiomno for an award. He does such good work in Rio de Janeiro and is so poorly recognized.

>MOST TANTALIZING UNSOLVED PROBLEMS

A most tantalizing unsolved problem to me is the quantum. I still think of those words that Einstein had in his letter of 1908 to his friend Michael Besso. "This quantum business is so incredibly important and difficult," he wrote, "that everyone should busy himself with it." I'm giving a talk at Bell Laboratories on this coming Friday where I'm hoping that my principle will work that I should listen to what I say, because sometimes that way I learn something new.

BEST GRADUATE STUDENTS OR POSTDOCS

My best graduate students or postdocs. I am ashamed of myself that I haven't made a list of everybody with his present address and got their publications and kept up. I would certainly like to put out a little newsletter from time to time telling everybody who had been a past student about what others are achieving.

William Wootters at Williams College is somebody who, in my view, needs more encouragement because he has such ability and care(?) and insight.

There was a whole group that got degrees at about the same time, as John Klauder reminded me when I visited Gainesville in January: Klauder, Unruh, Thorne, Misner—but for some reason I'm leaving out someone. There was a group of about five or six or seven.

When I got to Austin, I tried to put into effect the practice, which I'd [done] only a few times at Princeton, of getting a photographer to photograph the candidate with his doctoral committee.

Ford: John, on this subject of students, could you say a few words about Feynman? He's so widely regarded as not merely good, but more than good, so extremely special. What were your impressions early on when he was a graduate student, and what's your assessment now?

One of the great things about Feynman was the fun it was in taking up a problem and discussing it, kicking things around, laughing. I can recall his delight in one of the tricks played when he was a student at MIT, students getting together and hoisting a car and leaving it up on the roof of one of the buildings for the administration to deal with. [laughs] And the same delight he got in opening safes. I think I've told the story about the two safes at General Electric in Schenectady that Feynman opened while the security man was looking on.

Ford: I don't recall that story.

We got to the meeting a little bit early. I always have a bad conscience about our getting to the meeting a little bit early, because on the way there, as we passed a corner, we saw a truck overturned and the body of the driver lying there in it. We assumed the driver was dead, but really we should have stopped and checked to see if there wasn't a pulse and called help. But we didn't do that.

Do it or not, forget it or not, we arrived early, and the only person in the room was the security man. Well, we were chatting with him about this and that, and with each other, and Feynman was leaning against the safe at one corner of the room, idly—or so it seemed—idly spinning the dial. And there came a click and he opened it. Well, the security man's face fell, and he assumed it was some failure—that somebody had not properly closed it. At any rate, he went and leaned against the other one, and the same thing happened, even though the security man had taken care to spin the dial on that one before we went over there.

I think I had a special pleasure in that, because in my high school days, with my good friend Burdett Moke, we set up the Wheeler-Moke Gun and Safe Company, which was just a creation of our imagination. In both cases the parts were rotating parts and they were disks of wood, cut out of wood. The computer had a little pawl inside that ran over a cam attached to a wheel, and each time it completed a revolution the pawl flipped from the up position to the down position, and that, by leverage, transmitted an impulse to the next wheel. So we had moved ahead to take care of the carrying process. But in the case of the safes, of course, it was just a much simpler thing: a series of disks with slots in them; little pegs sticking out from each engaged a corresponding peg on the next wheel so that turning the wheels all to the right got them all turning together in synchronism but not in any way that helped to unlock the safe.

I think that sense of fun that Feynman had—he explained afterward about how so many people use numbers like e and pi and their license number and the telephone number. Those were the numbers that he first tried to use with the greatest chance of solving the safe opening problem.

Ford: John, I can tell such a story on you. You used to carry a little attache case that had a 3-digit code to open it—this was way back in Matterhorn days—and John Toll and I needed to get into your attache case to get a report, so we set it to 137, and sure enough it worked.

[laughs] That's great. Your mentioning 137 reminds me of my kind du Pont friends, who, after we shook hands and said goodbye, put together a sum of money to help elementary-particle research at Princeton. It might have been that that was called 137 Fund, although I don't really know. That fund has been exhausted. I checked up on it the other day, or rather got, through Emily, our finance people to check up, and it's run out.

Ford: The contributions to you, were they personal?

Yes. Individual people.

Ford: Very generous.

Yes, it really was. Ace Vernon, Hood Worthington, Dale Babcock, Charlie Wende. I don't know whether Crawford Greenewalt gave to it, but later he did give to The University of Texas for a John Wheeler Scholarship Fund, which a number of Texas colleagues set up when I left. And when I next visit Texas, I'll be making a special point to talk to the graduate student who occupies that fellowship now.

The best graduate student? I had been deeply interested in the idea of topology in a multiply-connected space, an idea that William Kingdon Clifford had promoted back in the last century. He suffered the fate of Riemann: He died of tuberculosis. His wife, Lucy Clifford, was a distinguished figure in the London literary world for many years afterward. That idea of Clifford, [that] topology comes into the structure of space, Hermann Weyl also touched on, but he did not follow it with full enthusiasm. Charlie Misner and I studied it and spelled out some of the consequences. If that multiply-connected structure is a mechanism by which electric fields can manifest themselves as point charges, so-called point charges, then what about the possibility of gravitational fields manifesting themselves in a similar way as point masses? William Unruh was kind enough to undertake that problem for his Ph.D. thesis and show that it is not so. It doesn't happen for gravitation as it does for electric charges.

The paper where I discussed these quantum fluctuations in the geometry of space did appear in the Annals of Physics, and it was there that I spelled out the Planck length, the Planck mass, and so on and gave them those names which are so much in use today. I'm surprised that a notation or a name which was not accompanied by any great discovery should have spread so widely and thoroughly.

If there's anything that I enjoyed more than anything else in working with students, it was the sense of whacking away together at what I like to call deep happy mysteries. Deep because they look as if they're connected with the most important features of our physical world, and happy in the sense that they offer or might offer an important new insight, and happy too because the line of investigation to get at such issues was just plain fun. Wormholes certainly have had an infectious influence on the theoretical physics community, but I can't cite any single blinding theoretical understanding of an otherwise puzzling experimental fact that came by way of the wormhole approach.

MOST SATISFYING PROFESSIONAL RELATIONSHIPS

My most satisfying professional relationships? Well, I should really talk more with my colleagues than I do because there are some wonderful people around. For example, right now there is this issue on the deck of what happens when two heavy nuclei collide, making a temporary nucleus with a charge number way above 137. It was expected theoretically [that] this is like dipping a pail down in the sea of negative energy states and you could pull up to the surface a lot of water that way, a lot of electrons producing pairs, but they would be in a continuous spectrum. Well, the continuous spectrum has been observed by two groups at the Darmstadt accelerator. The theoretical man there is Greiner. In addition to the continuous spectrum, both the experimental groups report a discrete spectrum. They don't agree on what that discrete spectrum is, and Greiner, whom you might expect to ride herd on it and help get them to clear up the discrepancy, has not succeeded in doing that. Frank Calaprice here at Princeton keeps me up to date with what that situation is there, and as I understand it, the Argonne National Laboratory near Chicago is working up to doing a comparable experiment in hopes to clear up the situation.

When I wrote my application for a Guggenheim fellowship, the one that let me go to Paris, it was primarily to be able to work with Neils Bohr on exploiting and exploring this pair physics in greater detail. However, instead, through his influence, we got going on this collective model of the nucleus so that the paper that finally appeared by David Hill and me would have been—I would have included Neils Bohr as an author if I had had time to stick around longer. That paper, like so many papers, got pushed along and helped because I had been invited to contribute a paper to Annual Review of Nuclear Science. This paper, I had the help of David Hill on it, but it was being done at a time when you, Ken, and I were busy on the Matterhorn Project. I could recall getting home from the Matterhorn and taking a hot bath, trying to get myself into shape to go on and work for the rest of the night on the writing of this paper with David Hill. I think I've said something about that paper somewhere earlier in our talking together.

Ford: Yes.

MOST PLEASING RECOGNITION OR HONOR

The most pleasing recognition or honor that came my way? I think the Neils Bohr International Gold Medal was the most pleasing honor, because Mrs. Bohr was there and my Copenhagen colleagues had had a part in it, although in my talk there, which was on dealing with risk, I was speaking primarily of the risks that people thought of as associated with nuclear power plants. I hadn't realized how anti-nuclear-power-plant Denmark was and is. It even gets the jitters about a nuclear power plant being in Sweden, across the few miles of water from Denmark, even though the power from that plant by undersea cables comes to Copenhagen and a substantial part of the Danish countryside.

MOST SATISFYING EXPERIENCE IN TEACHING OR OUTREACH

My most satisfying experience in teaching or reaching out to the general public? I'd have to go through my recent little book, At Home in the Universe, to see that. Teaching a course in general relativity was so satisfying because I learned so much from it, and that's my justification for saying the reason a university has students is to teach the professors, because that's how I learned so much.

In quantum field theory I made the doctrine of sum over histories the central foundation for the subject, and this at a time when many people were making Feynman diagrams and Schwinger's formalism the center of their approach to quantum electrodynamics. Steven Weinberg tells me of coming as a graduate student to my course meetings and feeling that he could look away from what I was saying, that it wasn't really in line with the approach that most people around the country were using. That was a satisfying experience in teaching. Reaching out to the general public? I'd have a hard time remembering when I did reach out to the general public.

MOST MEMORABLE OR REWARDING FAMILY EVENTS

The most memorable or rewarding family events? The celebration of our 50th wedding anniversary, in which the children took the lead part, and the celebration of Janette's 80th birthday, where we went to New York. I had got us all seats in the theater for Cole Porter's play, and we went afterward to a French restaurant which was closed for the day except to let us all in, so we all sat at a long table, no other customers there to trouble us, and different ones amongst us would get up and say things about Janette.

MOST AGREEABLE TRAVEL

Our most agreeable travel? It was to the little Italian hill town of Asolo, about 35 miles northwest of Venice, where Elizabeth and Robert Browning had lived and written much of what they wrote. While we were there, we had a rental car. Each day we'd drive out in the countryside to a target, one or another town where there was a villa designed by Palladio. So we studied the Palladian architecture. [In] one villa I recall our going into, there was a line stretched between supports that set off the part of the house in use from the part we could visit. We could see in the part in use the Senora, the mistress in the family, at work on her accounts.

We took one time from Austin an automobile trip out to the Big Bend National Park at that part of the State of Texas which dips down in the most southerly extent, where the big bend of the Rio Grande River bounds the state. As we went walking in that desert-like country—because it is part of the Great Chihuahua Desert region—as we walked through that desert-like country, we saw two peccaries going through the brush, these wild hogs. It was especially agreeable because it had some of the feeling of the West, which we find hard to get out of our bones: Texas and New Mexico.

MOST SIGNIFICANT LOSS OR DISAPPOINTMENT

It was October 1944 when my brother was reported missing in action. If there was anything I feel especially bad about, it's not having done more than I did to console my father and mother. They were, of course, in Baltimore. My father finally gave up his position as director of the Baltimore Public Library so that he and my mother could go into the retreat of their life in Vermont.

More immediately, Janette had had a continuing incidence of vaginal bleeding after the birth of our daughter Alison. On one occasion we had to put her on the train so she could go to the hospital in Baltimore, go from Wilmington to Baltimore to the doctor of obstetrics and gynecology there, Dr. Delfs. This happened while I was away on the Manhattan Project in Chicago, and our kind neighbor, Mrs. Donald Notman, took care of the children Letitia and Jamie while Janette was away. Of course I called, and the verdict of Dr. Delfs was that if Janette would stay quiet and didn't have to go far away and could be within reach of that hospital, she could go on and deal with it. But if she was going to be in the West, it would be a risky and tricky situation, and that her best procedure was to have her uterus removed, which it was, although we had hoped to have another child. We, of course, could not after that. So that was a personal loss and a disappointment.

MOST FRUSTRATING COLLABORATION OR PROFESSIONAL INTERACTION

We humans have such a wonderful ability to forget the unpleasant that it will take me a while to resurrect anything. There was one of the people who was in the du Pont group, who had been in some other part of the du Pont organization. I think that the du Pont Company felt that if they were taking some of their best people to help the government, they should now and again be allowed to meet their recruiting quota by one lemon out of their organization. So this chap, how to deal with him? I guess they figured that maybe I could deal with him. But in what way? He was assigned to me at Wilmington. His name, Martin Foss.

The most frustrating collaboration? It was a treat to have the association of David Hill in some of the considerations on fission and on the motion of a particle in a deformed potential well, and I had hoped that his plans for further work in that area would move ahead. But living at Los Alamos, he helped somebody get insurance, and he found he could do so much better that way than this chap would otherwise have been able to do that he thought maybe he could do it for more people, and he became an insurance agent. He later moved to that place in Connecticut that's so beautiful. His wife, Mary, a wonderful person, had been elected to the Tennessee Legislature when she was 21 or 22, and she later become a member of the Democratic National Committee. She was really somebody, but of course had not come from a scientific background or a family with a scientific background, so that I suppose she was not of any particular use in encouraging David to go on with his scientific work. So that was a frustrating business.