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Oral History Transcript — Dr. Robert Dicke

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Interview with Dr. Robert Dicke
By Spencer Weart
At Princeton, New Jersey
November 18, 1975

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Robert Dicke; November 18, 1975

ABSTRACT: A narrowly focused interview on Dr. Dicke's perspective on the field of cosmology and astrophysics at that time in his career, mostly relating to gravitation and relativity.

Transcript

Weart:

This is not a formal history interview. Nobody will use this; nobody will quote it or cite it without your permission and so forth. Itís really mainly just for my own reference purposes. I guess the period. Iíd like to cover with you is sort of the period when you have been active, which I guess goes back to around 1946 or whatever.

Dicke:

Yes, well, I never have been a real cosmologist, as such. Thereís not a great deal I can do to help you on that.

Weart:

No, but youíve been — Iím interested in you because you did have sort of an outsiderís perspective of the field. You have a physicistís perspective, rather than an astronomerís. Iíve mostly been talking with astronomers. Iíd be particularly interested in things like the growth of interest in relativity, things like that. So, I donít know what the best way to start is. Maybe I could just as you what you think have been the main trends, that youíve been aware of, that youíve been interested in, in the general areas of cosmology, astrophysics and so on, since the war.

Dicke:

Yes, well, I can tell you how long Iíve been interested in the field, that might be —

Weart:

Yes, Iíd be particularly interested.

Dicke:

I guess a good place to start on this is, the work that I did back in World War II, with the development of the microwave radiometer.

Weart:

At the Red lab.

Dicke:

The Red Lab, where we made measurements on water vapor absorption in the atmosphere, and in the analysis of that, you looked through the water, you looked through the atmosphere at various elevation angles.

Weart:

Right.

Dicke:

And it was possible, from analyzing the data, to determine — it should have been possible, if youíd had real good accuracy and absolute accuracy, to determine how much radiation was coming in from space. And all we could do without data was set up a limit of about 20 degrees of the temperature radiation coming in. Well, at the time — and this number was published in a paper on the atmosphere absorption — at the time this was done, I really wasnít thinking about a fireball radiation. At the time, I was really thinking about possibility of radiation from the distant Galaxies.

Weart:

Integrated over the —

Dicke:

Integrated, over the past history of the universe, but in a sense, radiation coming from galaxies. My interest in cosmology actually developed as an outgrowth of my interest in gravitational problems.

Weart:

Maybe I should ask first, how did you come to get interested in gravitational problems? Because I think you were doing it at a time when very, few people showed much interest in those problems.

Dicke:

Thatís right. I recall as a graduate student, asking one of my professors about relativity ant gravitation, and he gave me the distinct impression that this really wasnít part of physics. Interesting physical effects were so weak, you couldnít — itís almost impossible to measure them.

Weart:

Was this some experimentalist?

Dicke:

Well, thatís the theorist, it was [???] Bascow. But at the time I was a graduate student, there had been this long period of development of relativity and Einsteinís attempt to make a unified field theory, and so on. And there had been no new observations for a long period of time. On the cosmology end, people were making cosmological, models, paper after paper on cosmological models, but with no particular bearing on the observations. Couple of radio astronomy, expansion of the universe. There hadnít been any real [???] on getting at questions of space closure, and — Well, on the question of interest in gravitation, I got interested in this when I was on sabbatical leave at Harvard. And —

Weart:

— that would have been —?

Dicke:

That was about 1954, Ď55, something like that. Iíd been doing precision measurements of microstructure, that type of thing, making attempts to measure the more important numbers of these micro techniques, and was interested in looking around a little bit at that time. So it occurred to me that there was one experiment that was very important to relativity theory that had not been carried out with modern techniques. That was the [???] experiment. [Frisch ?] and his colleagues had done a very good job. It was towards the end of the 19th century, early 20th, and there had not been any done since then.

Weart:

How did you happen to notice this? You must have had some interest. Was it just that you were looking through the various fundamental measurements?

Dicke:

No. I donĎt know how. Perhaps in connection with some of my reading. I think I got ahold of Whittakerís book on theories of the ether, which was a rather interesting book, and started thinking about gravtationa1 problems, and realized the crucia1 role that this particular experiment plays in sorting theories out. So I decided modern techniques had to be brought to bear on that. I didnít realize at the time how hard this was going to be. Weíve been at this for years. Itís been a very successful experiment.

Weart:

Itís not like you could immediately apply laser or microwave techniques or something to it?

Dicke:

No. I had to develop a new technique. And it just took time. But we were able to make a substantial improvement over the old experiments. It was a significant experiment in that sense. And this is a rather crucial experiment, because it comes into gravitational theory in a number of ways. More than just the question of bodies, whether bodies fall with the same acceleration, is involved here. The implications of this, in terms of the internal structure of an atom being independent of when you put it, ant the ratios of masses of elementary particles not varying with position — those are questions you can raise and answer at a certain level with this experiment. I got interested in the, rather early in the philosophical question of the role that Machís Principle plays in connection with relativity theory and gravitational theory.

Weart:

Were you interested in this already when you were a graduate student, or you became — was it in the fifties that you became interested?

Dicke:

No, I think that — when did I get interested in that? It was in the fifties. It was not — no, I donít think I really thought about it till the middle fifties, about. I saw that one way of interpreting this: at least, seemed to require a scalar component in the gravitation, which led to the scalar-tensor theory — which was actually only a modification of the theory that [???] had constructed earlier.

Weart:

After you did the [???] experiment, then you began to become interested in these other possible approaches.

Dicke:

Yes.

Weart:

So it came in very much from the theoretical, philosophical side?

Dicke:

Yes, thatís — I think Machís Principle rather early was a kind of a strong motivation for work in the area, and led to both the — I canít say that it had a direct experiment on doing the [???] experiment. That was a rather more direct experimental interest. But very definitely, in my work on the scalar -tensor theory, it was —

Weart:

This represented sort of a shift for you, from experimental to theory, didnít it? You hadnít done much theoretical work?

Dicke:

Iíd actually written theoretical papers before that. There was the one, for example, on the role of coherences, super-radiance paper, which I wrote in —

Weart:

— oh, thatís right, with the sort of pre-laser —

Dicke:

Pre-laser stuff. That paper just seems to — keeps influencing the literature.

Weart:

Thereís another reference to it?

Dicke:

Thereís one I just received yesterday.

Weart:

Super-radiance. I see.

Dicke:

Thatís an ancient paper, but it keeps having its usefulness, even now.

Weart:

Right, I see the reference —

Dicke:

Well, letís see. Thatís off the track. Now, letís see, what was I going to say? After realizing that the, at least the way I was interpreting it, the scalar field played a rather crucial role, with Mach Principle, then I noticed the implication of the weakening gravitation, at — with time — with the changing structure of the universe, as the universe grew older, then the scalar field would increase to a far weaker gravitational constant. This carried — this, implication carried with it the whole — a whole host of cosmological implications, which I started, at that point, really started to get interested in both geophysics and astrophysics. Up to then, I hadnít been.

Weart:

I see. So your interest really grew out of — I suppose it could have emerged at almost any time. There wasnít any particular event in the rest of physics that stirred this to happen?

Dicke:

I think I viewed it as a tool, hoping to do some physics by looking at the universe. As far as geophysics is concerned, I think I was pretty well disillusioned on this, about mid-l960ís, I would say. This is another whole question, tangent, but long before the average geologist in the country took this continental drift, and plate tectonicsí to mean anything at all — Harry Hess, over in our geology department, had a clear picture of what was going on. Anyway, itís obvious that as gravitation is getting weaker, the earth should expand slightly, and I noticed in my readings at that time that there were cracks in the mid-Atlantic ridge in the ocean, oceanic cracks. So this suggested that these cracks might be the result of tension, due to the earth expanding, and I made some [???] of this. I went over and talked to Hess about this. We laid out a beautiful picture of the Atlantic Ocean crust moving, and trenches, and island arcs, and all the — the whole plate Techtronic game was laid out for me, and this was the late fifties. He was way ahead of the rest of the boys; I donít think actually that Hess received the credit that he deserves in this respect.

Weart:

Itís a whole other interesting story, this revolution in geophysics and the role that physicists may have played in it, also.

Dicke:

Well, this is not to say that a weakening gravitation and expanding earth might not play an interesting role in the evolution of the earth, but it just seemed to me to be so deeply buried in all the other things that it would be hard to separate it out, in an unambiguous way.

Weart:

Right.

Dicke:

I had one student, for example, look at the heat flow problem from this point of view, because you have heat flowing — if you have the interior hot, as we understand it is, and if the temperature curve for the mantle of the earth is near the melting point, if you lower the pressure inside, the melting point curve shifts, and heat has to flow out, or else the earth melts, one or the other. And you can calculate the way in which heat flows out this way. And it agrees rather well with what is observed, to a factor of two. So this could play a role. But you know, I decided after a while that it was just too hard to try to get fundamental physics out of the earth.

Weart:

Right. I understand. I understand very well,

Dicke:

But then there were a lot of implications for cosmology. I wrote a paper on a hot cosmology, in which scalar tensor theory is used, and you can see that, depending on the assumptions you make, you have a quite different early history of the universe. You can have a fireball expand without producing helium at all, for example. And under certain conditions, producing a little more than you would otherwise expect. Thereís an interesting problem for the temperature history of the earth in this. In fact, I noticed a paper the other day, in which somebody else, somebody noted again that the problem that you face with the origin of life on the earth — if there isnít any weakening gravitation — because the standard history for the way the sun evolves has it somewhat dimmer in the past — but if the oceans freeze, the earth is cold, and itís hard to understand how life could arise under these conditions.

Weart:

Right. Of course, solar evolution is in quite a mire, right now.

Dicke:

Thatís right.

Weart:

Thatís another problem.

Dicke:

There could be other ways of explaining it.

Weart:

It sounds as if you have your finger in almost every one of the completely confused problems.

Dicke:

Thatís right. Just about every confused problem Iíve worried about — without getting any real answers.

Weart:

Maybe youíll all find the solutions at the same time.

Dicke:

Maybe.

Weart:

Well tell me, thereís a lot of things I could ask, but to get back to astrophysics and cosmology, I think a lot of people would agree that thereís been a very great upsurge in interest in general relativity within the last, I donít know, since the fifties, I suppose. What would you say has caused this?

Dicke:

Well, I saw Shander [???] last week, and we were talking about this very problem. I had thought, and I think a lot of people think, that the new sources of observation are what stimulated the theorists to make real progress. And I donít think that may be true. Shander, on the other hand, took the view that the new observations have played a rather minor role, that what had been important is the work of a few key individuals. He mentioned particularly the understanding of gravitational, radiation, of the — that it is a real effect — and so on — the work that Bondi did, in the early sixties. I remember when I first started going to relativity meetings, at international conferences and so on. There was a great deal of confusion about this. People had — some had gotten negative gravitational radiation dampings, some positive some didnít get any at all.

Weart:

Negative gravitational —?

Dicke:

Yes. One of the well-known theorists in the country had a system where he had radiating negative energies. But the straightening out of that confusion, in his view, played a rather important role in getting things moving, understanding the initial value problem.

Weart:

This flowed out of — it probably did not depend too much on the new observations, from what youíve said.

Dicke:

Well, certainly, as I said, I looked to the observations as a means of providing some clues as to whether there was a scalar component in gravitation or not. And this has been a confusing story, at best. Itís just confusing. Iím giving a talk this afternoon — talking again about the solar brightness problem, in relation to the other observations. The observations have come and gone. There are systematic errors, and they disappear.

Weart:

ThatĎs happened to a lot of things in cosmology, I think. Things that are just on the limit of detectability. Well, of course, the discovery of the microwave radiation.

Dicke:

I think that played a very key role. At the time, that this was done, there was a really large number of people that were taking the steady state universe seriously. I remember talking to Shombus (?) some years later, who was one of the strong advocates — a student of Fred Hoyle, who worked closely with him, something like that talking to him about the role of this discovery, and the way he put it was that, that when he threw over steady state cosmology and accepted the Big Bang, it was like putting on sackcloth and ashes. He became more conservative than conservative.

Weart:

There were a lot of people who felt that steady state theory was —?

Dicke:

— there were quite a few that took it seriously, I think. I donít think it was a majority.

Weart:

Did you ever take it seriously?

Dicke:

I didnít. No.

Weart:

You never took it seriously.

Dicke:

And the discovery of the black body radiation was another confused story.

Weart:

Right. Iíve read you — printed a once or twice, I guess. Made a story.

Dicke:

Yeah. Thatís — if you want to know who to talk with about this, and try to get the story straight, I think first of all, Pensy? is one you should talk to. And then Wilkinson here, and Peevis. I think —

Weart:

Are you talking about the microwave theory, or about the whole?

Dicke:

The microwave theory.

Weart:

Who do you think would be good to talk to about, the whole general relativity? The whole general relativity, cosmology story?

Dicke:

Well, — youíre from Boston, is that right?

Weart:

Iím from New York, the AIP. But you know, I can get around.

Dicke:

I was thinking of someone who has not really played an active role in the cosmology, but nonetheless does know more than anyone, I think is Steve Weinberg — in connection with producing his book. You know his book?

Weart:

Iím not sure.

Dicke:

He seems to have read everything, —

Weart:

Oh, Gravitation and Cosmology.

Dicke:

For a theorist, for a particle theorist, he has developed a tremendous background, and — in cosmology. Just from his reading.

Weart:

He seems to know a lot of people, too.

Dicke:

Yes. So he would be a good one to get some leads from, I think. Now, as far as those who have worked in cosmology for a longtime, thereís Sandage, Allan Sandage. And relativity — I think John Wheeler is hard to beat. Itís hard to beat John Wheeler, for someone whoís been in the field for a long time and can give you some perspective about what has happened, if you could get him to talk about the historical development. Another one who could give your perspective, whoís been in it a long time, would be Peter Bergman. Peter, probably more than any person in the country, could be called Mr. Relativity, in the sense of having been working with it a long time, and active. Another one that has also been involved for a long time, although not active in a research way, is Hoffman.

Weart:

I didnít realize that.

Dicke:

He was an assistant to Einstein in the thirties.

Weart:

Thatís right. And heís in New York. Who do you think have been the main contributors? These are people who would be good to talk to, but who do you think have been the big figures in the field? Would it be these same ones or others?

Dicke:

I would say, the primary contribution — the really central figure in this country, who has worked mainly through his students, is John Wheeler, more than anyone, I think. Heís been amazingly successful at attracting bright young people to work with him. And to what extent his studentsí ideas, to what extent his — I think primarily, his ideas, that are then worked out through the students, — but the students go off, elsewhere. You can go down a list, one after another, the active contributors, the young people in the country now, are students of John Wheeler. So he is, in a sense, I think, Mr. Relativity, in terms of the modern developments.

Weart:

Itís true. True. Iím having lunch with him today, by the way, on Center business. I should talk with him about this more. What do you think have been the main centers? Princeton clearly, as you mentioned, but what other places?

Dicke:

Well, now a strong center is Cal Tech, with Kit Thorne. Another center is Chicago. Kit Thorne is one of Johnís students, Chicago, with Geroch [?] whoís a student of Johnís.

Weart:

Howís that spelled?

Dicke:

G-E-R-O-C-H. And also, Chadrasakhar has been involved in relativity in recent years. Then, Eric Dim? I was trying to, think of Burtonís students. University of Texas, where the DeWittís are, Bryce DeWitt — I think through Bergman, Iím not quite sure, got interested in relativity quite a long time ago. Heís been active in the field, probably as long as John Wheeler has. Peter Began and his students —

Weart:

Where is he?

Dicke:

Letís see, I guess heís actually retired now. But Syracuse and Yeshiva in New York.

Weart:

Weíve been talking I guess almost exclusively about the United States.

Dicke:

Oh, thatís true.

Weart:

We should mention some other places.

Dicke:

I donít have a good perception of the foreign work, I think. Thereís — Podanski is here, today, as matter of fact, from Poland. He is — now, letís see, who was the famous Polish physicist that worked with Einstein? Iíve forgotten his name. He died a few years ago. Thereís a group that built up in Poland, and. I canít — Then there is, in Paris, from a rather mathematical point of view, — again, Iíve forgotten the fellowís name. Heís strong in differential geometry. And his students — in Paris. But theyíve been rather mathematical. In England, — Synge, I think. In Denmark, Muller. This is really not a very good review. YouĎd do much better asking John.

Weart:

OK, I should ask him about it. Weíve mostly been talking about — are there any specialists you know that have been mostly defined in groups that have dispersed or havenít held up?

Dicke:

Itís been a rather developing field, and I think, the history in the last 20 years has been quite different — students going out and forming new centers, to the point where there are now dozens of centers in the country, and every one of these, you could say even, is enucleated by the students of one of the other — you know, principal centers. And I guess youíd have to say, the principal centers, if you go back 20 years, are Princeton and Bergman. Incidentally, one of the nice things about what Kip Thorne is doing, and his students, has been to be more directly concerned with the observations, not making formal mathematical theory, but to bring in the observations to test the theory, and to try to think through the theory with the observations.

Weart:

Yes, thatís true. Of course, thatís part of where they are, too — where the observations come in. (Cal Tech)

Dicke:

Thatís certainly a part of it.

Weart:

Now, what about institutions in the broader sense? For example, you mentioned that there was a time when relativity conferences began to start up.

Dicke:

Well, there was an international organization of relativists, started about 1960 — perhaps 1960, somewhere in there. And that has met every two years since then.

Weart:

International, sometimes here, sometimes Europe, whatever.

Dicke:

Yes.

Weart:

What about in the departments — Let me switch this.... (Off tape) What about in the department here? Was there at some point when a relativity seminar, or something like that, began?

Dicke:

Iím trying to think how far back Johnís interests went in relativity. I think he got started being interested in this somewhat before I did. I donít have a clear memory of this now. But probably, a few years before. I canít remember whether he had a relativity seminar going at that time, or whether it was started later. For a long time now, weíve had a relativity seminar which meets Tuesday afternoon, and then a number of gravitation seminars and that sort of thing. Things have changed from time to time. We used to have two different seminars, and combined them. Weíve always had some kind of a seminar in relativity here, for more than 20 years.

Weart:

I see. Now, there was a series of Pixus (?) conferences.

Dicke:

Yes, they started — the first one of those was, I donít know, eight years ago, maybe, ten.

Weart:

Do you know how they got started? What was involved there?

Dicke:

I think — see, what was the primary motivation? If I remember correctly, there was some rather important series of observations that got them interested. It was first devoted to astrophysics, and astrophysics that might have relativity implications. But it, whether it was started by the discovery of the pulsar, or whether it was before that, Iíve forgotten. I think it was motivated primarily by observations that were coming in. It was very successful and active, very large groups, for a while. I havenít been myself, for the last couple. I donít know quite how itís going now.

Weart:

Speaking of observations and things, another question — you havenít mentioned Joe Weber.

Dicke:

Yes.

Weart:

What kind of a role do you think all that has played?

Dicke:

I think that itís probably played a very important role, in stimulating people to work in this area. ItĎs a very imaginative technique, trying to see these very tiny effects in a huge bar and inspired peopleís imagination. A rather large number have jumped into it. The fact that there have been several international conferences now devoted, in part at least, to these gravitational radiation problems —

Weart:

— ďgravity waves,Ē whether or not they are there —

Dicke:

Yes.

Weart:

What is your feeling on that now, by the way? Has your feeling on that changed over the last ten years?

Dicke:

I — I donít know. Iím not really close enough to have a good opinion, a strong opinion. But off-hand, it seems to me that the evidence is rather against it at this point. There have been a number of quite good experiments that failed to see gravitational waves. I was talking with Joe about these things last spring, and — when I was at Cal Tech — and he still very firmly believes that heís seen the real thing, and the others havenít built equipment enough to see it yet.

Weart:

Certainly, I remember, I was impressed, when I first saw how sensitive the darned things could be. That was the really unexpected thing for me, in this experiment. All right — another thing I wanted to ask you. What is your relationship with Brans was and is?

Dicke:

Oh. Thatís an interesting one. I didnít really supervise Bransí thesis. Bran was a young theorist here, working with Charlie Misner, and Charlie didnít have a problem for him to work on. So Charlie sent him to me, and Iíd been thinking about this possibility of combining a scalar field with a temperature field, and suggested an action principle that he could investigate, and see what the field equations were, what the implications were. So he went off and worked on this with Charlie. Charlie, I gather, he didnít really work with him either. He pretty well did it on his own.

Weart:

I see.

Dicke:

It was a rather straightforward mechanical thing, because you just had to calculate the equations. But there was one crucial point at which Charlie did play a role in it. Then, he came back with this, and he and I together, I guess primarily me, wrote that paper, which represents some contributions I made afterwards, sort of complex.

Weart:

How did you happen to think of the scalar field in the first place? I suppose, I havenít looked into the history of it very clearly myself, but I know that there were an awful lot of different ideas floating around, different kinds of cosmologies. What brought your attention to the scalar field?

Dicke:

Well, it was just a feeling that I had, through Machís principle that the gravitational constant ought to be determined by the matter distribution in the universe, if you were going to make sense out of that, without imposing boundary conditions, and without imposing constraints, unreasonable constraints. And then, I recognized one day that, you could construct a theory in which the scalar field generated by the matter distribution in the universe could play the role of a reciprocal gravitational constant, of being a wave equation. And this suggested a very natural way of writing the — an action (?) principle.

Weart:

Tell me, Iíve gotten the impression from some of the things youíve written, that you find this philosophically more interesting, or philosophically better than the field theory in which distribution of matter does not play a role?

Dicke:

Well, yeah. It seems to me, from a point of view, that you have two choices available to you. They really go back to the argument that Bishop Berkeley had with Newton, and their two ways of looking at things. You have the choice of assuming that you have a space which exists, and you put matter in this, and that the — such things as metric tensors and so on had meaning before you ever put the matter in. Now, the matter can influence the metric tensor, but youĎre not in the position of saying that the one exists by virtue of the other. Or, if you have an underlying frame of some kind in which matter moves, thatís one viewpoint, which was — comes back to the space of Newton. Then, the other viewpoint says that the whole thing is one physical system, that the tensor of gravitational theory is only one of many different kinds of fields, that it ties the whole thing together, but you donít single it out for special treatment on the whole, so that tensor is the result of an interaction with the whole universe, if you like. That the whole thing is boot-strapped together.

Weart:

In a way, the metric tensor isnít an underlying space, any more than you would say it for any other field.

Dicke:

In fact, a way of looking at this which I find very attractive and nobody else does is that you donít treat the metric tensor initially as a metric tensor at all; you treat it just as a field that produces forces. And there arenít any inertial forces, from that viewpoint. A particle moves the way it does because all the various kinds of forces which act on it balance out.

Weart:

This is Machís principle, in effect.

Dicke:

Itís effectively Machís principle. Now, itís interesting, when you look at it that way, that formalism comes down to this — there are two reasonable possibilities, as far as formalismís concerned. One is the straight Einstein theory, and the other is the scalar-tensor theory. If you take the viewpoint that its Einsteinís theories, then you have a situation where you start interpreting things, see. The structure of an atom, is the result of the various fields acting — electric field, electromagnetic field, and the tensor field, and then you recognize that the tensor field has the role of changing atoms — changing the structure of an atom from point to point. But if you interpret everything in the sense that the atom hasnít changed, this carries with it the implication of a curved geometry. You measure the geometry with meter sticks, and clocks, constructed of these kinds of atoms, that geometry is a curved geometry. So the metric interpretation comes in through the back door.

Weart:

I see. When youíre talking about an atom changing, itís like the idea of a metric stick stretching or whatever, that same idea. I see. But, do you feel that the scalar is necessary, to have a really, a very solid Machís principle in gravitational theory? Or can one —?

Dicke:

I think it is, but Iím a school of one, on this.

Weart:

Do you feel somewhat isolated from other physicists, by that?

Dicke:

On this particular problem — yes.

Weart:

Do you think that other physicists, cosmologists and so forth, have the same philosophical interests?

Dicke:

There are very few that are really interested in this, I think. John Wheelerís quite interested in this, and I am, but the usual cosmologist is more interested in the observations and their interpretation, and the theoretical structure built usually with standard general physics.

Weart:

I see — not so interested in philosophy or the philosophical view of things.

Dicke:

Right. Also, I think one has to say this about cosmology, that, when I was a graduate student in the early fifties, it was cosmology and the cosmological models, structure of the universe and so on. In later years, thereís been a lot, of interest in other aspects of cosmology which are which have to do with the origin of the elements, fireball structure and its development — in homogeneities in the universe, and how they can lead to formation of galaxies, the whole problem in homogeneities, instabilities. So, instead of it being a global problem, the way it was, people are really much more cornered now with the nitty- gritty of how the elements came into being, and so on.

Weart:

Thatís true; itís more concerned with the contents of space than with space itself, if you like.

Dicke:

Yes.

Weart:

Do you feel that thereís been a corresponding change in the orientation of people? Were people more philosophical, back when they were, concerned with these global properties?

Dicke:

I think, when you have few observations, you can afford to be philosophical. Itís also been my observation, which may well be wrong, that the less you know about a subject, the mole strongly you believe in it, and feel about it. When there were few observations, people had very strongly entrenched positions.

Weart:

— as it gets more complicated, things begin to —

Dicke:

— thatís right, as soon as you have observations, then these preconceived notions begin to crumble.

Weart:

I guess thatís been the story of the whole development of the field, in the last 20 years. Things have gotten more and more complicated. It gets back to increasing complication. Tell me, what do you feel now about the solar oblateners? I remember very well when that first —

Dicke:

Well, Iím giving a talk this afternoon, discussing some work I did in California. Thereís been a paradox connected with these observations, the last couple of years, thatís bothered me. Not because it seemed to invalidate the implication of the oblateners in any way, but because there was some piece of the results I didnít understand. And when thereís any little piece you donít understand, why, you can feel very uncomfortable. But I think I understand it now. This is a strange business that if you — these principal observations, of simple diagonal components — you expect the diagonal component of the oblateners to vary in a well-defined way through the season — the data fit that curve fairly well. But the residuals that you get would scatter around that curve. On the face of it, if you look at that scatter, you would say, thatís just plain noise. At the time that the data were first published, why, I thought they were due to bad seeing at Princeton. Iíll show you — scatter, around that curve —

Weart:

— right, yes, I remember that stuff — (Crosstalk)

Dicke:

— distribution there, if you look at the distributions quite Galson (?) I donít know why I didnít do it sooner, but when I finally got around to taking the correlation function of those residuals, I found they werenít random. They were strongly periodic actually. There was a periodicity of 12 2/3 days — two-thirds — and this

Weart:

(???)

Dicke:

No. No, thatís the interesting thing; to actually discover what was going on there. But 12 2/3 days is obviously also periodic at 25 1/3 days. And I had interpreted it — I had first seen this periodicity that way. And then when I stacked the data, I discovered there was a double peak, there, which carried also the implication that that shorter period was in there. Well, I now have a rather — well, let me say this, that I couldnít find any reasonable physical explanation for this, not in the, atmospheric parameters, not in the telescope (crosstalk) It had to be — and that 25 1/3 day period suggested a period of rotation. The interesting thing was that it was impossible to explain it that way. And the reason I thought it was impossible was that if you take this block of data, thatís symmetric, about this crossing point, the — and make the Fourier expansion of the disturbance, in that basic period, there it should be only odd harmonics.

Weart:

Theyíd be symmetrical, about —

Dicke:

And what you discover, when you do it, is all even harmonics.

Weart:

OK. So whatís the explanation?

Dicke:

Well, I had the wrong period. Itís actually the short period. Then you can account for the rigid rotation. And if you subtract out the effect of that rigid rotation, by being — itís [???] like this.

Weart:

I see. It comes much closer to the —

Dicke:

(crosstalk) ... about how good you can account for it, this is the far spectrum. The solid lists are the far spectrum of the data themselves. The dotted curve is the far spectrum that you calculate from the model, of what — the distortion of the surface of the thing. The distorted surface rotating rigidly.

Weart:

A rigidly rotating distortion —

Dicke:

— distortion in the — rotating at 12 2/3 days, actually 12.

Weart:

(crosstalk) What could support a distortion?

Dicke:

Well, thatís an interesting story, too.

Weart:

I see, wait till you publish it — read it when you publish —

Dicke:

As a matter of fact, I donít have that. I concentrated on statistics. I didnít want to color statistics with —

Weart:

— right —

Dicke:

— notions, so itís straight statistics, up to now. Iíve just started on the physics.

Weart:

Well, I gather youíre pretty excited about a rotating —

Dicke:

— well, I think, very likely the whole thing is right. Itís due to something rotating on the inside more rapidly than on the surface.

Weart:

Although 12 2/3 days is not quite —

Dicke:

Itís not the rapid rotation I was talking about.

Weart:

Right. But then, people havenít detected very great frequency shifts or whatever near the sun, anyway.

Dicke:

Right.

Weart:

You donít require at this point as rapid a rotation as you did at one point. Isnít that right?

Dicke:

No, I still require — itís going to be the inner half of the sun rotating, which is the source of the oblateners. Then I need about factor (?) 20, there, which is a little over a one day period.

Weart:

I see, so you just put it in there.

Dicke:

The other possibility on this, which is actually what fits this better, is a — making an internal magnetic field, which is starting to —

Weart:

Uh huh, I see that would make sense.

Dicke:

Rotating not as fast as — but —

Weart:

How are your feelings toward the solar oblateners theory, over the past ten years or whatever, since you first detected it?

Dicke:

Iím just struck by how, looking at the same data over and over again, you learn more and more about it. Iíve learned a lot more than I knew a year after it was — measurements were made.

Weart:

How have your colleagues reacted to your interest in these things?

Dicke:

I think that they — colleagues, while they have their own problems theyíre worrying about — How do physicists and astronomers view this? I think they donít believe it. But that doesnít matter. That doesnít influence me particularly. After all, I have to deal with the data. Iíd like to say that you donít settle a scientific question by taking a popularity poll. Thatís not the way you settle it. Thatís like establishing pi by going out on the street and asking little boys how much pie is. One says 47, one says 4, one says half — and you take an average.

Weart:

I always said, that when you wrote a book, you should write it for the largest possible audience, which didnít mean the number of people who would read it next year, but the number of people who would read it over the next thousand years.

Dicke:

Thatís right. No, Iím not being swayed in my interpretation of these data by what people think, in the slightest.

Weart:

Tell me something else, too. Here youíre in the physics department and youíve been going, I guess, almost from the start, when you first came back from the Rad Lab, you started doing studies of microwaves and what not — what has been the feeling in the physics department about someone who does things that are not what would be narrowly considered physics, but a more —?

Dicke:

Well, I have a — thatís a very interesting question, and I should answer it I think by telling you that when I came from the Radiation Lab here, I didnít realize what the situation was. I brought with me a radiometer, a microwave radiometer, and was interested in getting into the radio astronomy business. That was 1946, which would have been the first one in this country. But I thought, you know, youíre an assistant professor, youíre doing such offbeat, wild things — you wouldnít last here six months. I couldnít really do that, was my view. So I went over to our astronomy department and tried to interest them in a joint venture of some kind, thinking this would give it a little more respectability. And I couldnít get any interest over there. So I didnít do this. I actually scavengered the equipment and started using, it for laboratory experiments. Well, it took a few years, and I realized that that was a completely wrong approach. This department is so tolerant, I could have gone into radio astronomy and there wouldnít be an eye batted about it. It was an interesting question, though, in that connection. I wasnít concerned about this department at all, but I was a little worried, when we started getting interested in astrophysics, in our research group, how the astronomers would view that. So I went over and talked to a couple of senior astronomers, and they said, ďThe more the merrier.Ē So we have a sort of a strange situation now, where we have a very sizeable part of the total Ďastrophysics effort right in this physics department, with former students of mine. Jim Peebles is one of my students. Dave Wilkinson didnĎt come in as a student, but he came in as a young colleague. So, itís a little bit anomalous, from the standpoint of the structure of the university, but it seems to cause no problems.

Weart:

Both the astronomers and the physicists are glad to have you around?

Dicke:

Astronomy students come over to work with Jim Peebles occasionally. And I think some of our students then go over and do — teach in the astronomy department.

Weart:

This is one of the things that Iím particularly interested in, this whole development over the last twenty yearís or whatever — to show how the physicists and the astronomers have started to merge into one another. I gather from what you said, they were pretty separate when you first came back.

Dicke:

Well, as far as structureís concerned, itís very separate. The astronomers, the last thing in the world they would want would, be to have any formal connection with us. They view themselves as a small department, few students, and they think they would be swallowed up in the superior thing, if there were any formal structure. So there isnít that. But when it comes to day to day interaction, thereís no problem. Our students are interchanged, and —

Weart:

— at what point did you start interacting with the astronomers here?

Dicke:

Oh, about the time when I began to see the implications of a scalar field for astronomy. The evolution of a star, for example. A star would be brighter in the past, according to scalar tensor theories, and lead to its burning its fuel more rapidly. This would mean that the implications for stellar age and stellar evolution would be different. And that sort of thing. Then I went over and started talking with Schwarzschild first — that was perhaps in the early sixties, late fifties.

Weart:

Well, weíve pretty well covered the ground, I think. Do you think of anything else? As you said over the phone, thereís a lot of other things that I could ask you, but just in terms of astronomy, we can stop here.