Interview with Kip Thorne — Part 1

0:00 It's the 14th of June, and I'm talking about Kip Tom, about 5pm. So, well, I just wanted to get an idea of, this is something I usually start off asking everybody, but how you first got involved in problems with gravitational radiation, just to get your I guess I first got involved as a graduate student when Johnny Wheeler suggested various research projects to me. The first project he suggested was dealt with cylindrical systems when I looked at basically the stability of Melbourne's magnetic universe, which involves coupled electromagnetic and gravitational waves. and so then in my thesis I did further work on cylindrical gravitational waves that sort of was a follow on to that not awfully relevant to any of these issues but a big piece of my thesis dealt with cylindrical gravitational waves Chandra Sikhar came out with his classic paper when I was in my graduate studies, his classic paper on spherical perturbations of relativistic stars. And I got interested in that and worked out an action principle for spherical perturbations which appears in an appendix of this little red book by Harrison McConnell, Wheeler and Thorne on gravitation theory and gravitational collapse. and I then quite naturally moved on to non-spherical perturbations of relativistic stars still as a graduate student, started as a graduate student or maybe when I was a post-doc at Princeton for my first year of post-doctoral study. Took on a collaborator, Alfonso Campolotaro, who was an Italian that I met right after I got my PhD when I spent a summer in Naples. And he and I did the first step

2:30 in the theory of non-spherical perturbations for logistic stars, which involved the production of gravitational waves, and then I carried on with Richard Price and myself afterwards. But that was all a natural outgrowth of Chandra's original work on spherical perturbations. So that's basically how I got into it originally. And one thing led to another quite directly. I then suggested to Richard Price that he look at non-spherical perturbations of collapsing stars in connection with the issue of whether a non-spherical collapse produces a black hole or not. And it was there that he discovered the tails of the gravitational waves that are produced and developed the theory of the tails of the gravitational waves. And then that led naturally to perturbations of black holes and Tchaikovsky's work. So sort of one thing led to another in a very natural way through that whole period. Just curious, since you were saying that you started off working in cylindrical ways, probably this wasn't of any direct relevance to your work, but whenever I show my very basic original draft and history to any historians of relativity, they always say, oh, you must mention Guido Beck, who came up with a cylindrical solution before it eventually appeared after much roundabout in the Eisen-Rosen paper. So I was wondering, was he actually known to... I never heard of Guido Beck. He's not known to me now. That's the first I've heard of him. So my first, as far as I knew, the first work on cylindrical waves was Einstein and Rosen. The earliest work on cylindrical systems was Levitici-Vita. which goes back to 1917 or 1919, I forget which. Or he had the vacuum static solution. But I did not know about Beck. Yeah, I would never have encountered him in the whole sentence for interested historians who mentioned. He was apparently an Austrian who went to Brazil, and I guess perhaps for that reason. He wasn't known to other relatives. of stuff was done and forgotten over the years. The field was a backwater during that period

5:00 from 1930 to 1962, roughly. And I found, as a graduate student, things that nobody else around me seemed to know of very interesting stuff that had been written in the 20s and in the early 30s, and the field wasn't sufficiently coherent. People were really very familiar with the literature 10 years earlier at that time. And so regarding this question of the coherence of the field, was it a kind of a gradual process, do you feel, that the field tended to become coherent, sudden break when people became interested in it? Well, of course, I have a very parochial view on it, coming out of the Princeton School. But it is clear that there was a major coalescence of a field around the issues of gravitational collapse and black holes, which was triggered by John Wheeler. And he was a major inspiration, not just for the Princeton group, but also for the Cambridge he went and lectured around 59, 60, 61. Then Penrose came and spent many months with him in the Princeton group. This is all before I came along. But I think he was a major force in causing a coalescence of much of the field and focusing in on astrophysical types of questions. Um, but there clearly also was, uh, a lot of, uh, coalescence around Bondi and the thing that the outgrowth of Bondi's work as well on Britain. True. That the, the Cambridge effort around Dennis Schama really was triggered in many respects by Wheeler rather than by Bondi, I believe. Yeah. So, that's my impression anyway, from talking And I suppose because Rita was placing the synthesis on the astrophysical implication of relativity.

7:30 Well, that was a major factor in pulling relativity back into the mainstream of physics. and the creation of a coherent branch of the field that had contact with the rest of physics. In that period before we had it, there were major schools within relativity, the one around Bondi, the one around Peter Bergman, particularly I think of. And then the Enfield school, and to some extent you could say Landau and Lipschitz, or Landau, but Landau was dabbling in everything. But it really was Wheeler in, I believe, in the West, and Zeldovich in parallel in Russia that brought the subject into serious contact with astrophysics. So in this context, I'm certainly interested in it concerning the question of relativity becoming more mainstream than the rest of physics. In the period, in the late 50s, early 60s, when people were arguing about whether self-gravitating systems emit waves and so on, you can see a number of pointed views. For instance, Feynman sort of saying, well, you know, this seems pretty simple to me. And other people, like Bonnie, for instance, who certainly said it's a much more complex question. But after all, since Feynman... So, as I was saying, at that time, that part of the argument wasn't all that important, because I suppose Feynman wasn't really a part of relativity, even if they weren't a part of the Ministry of Physics. But at the later stage, perhaps in the 70s, the practical formula, I sort of feel I get the impression that here you have more, certainly, an argument between relativists, and the question is a little bit on the one side, saying, well, look, we really ought to get over ourselves a little bit and look at, try and look as much as physical consequences of what we're looking at in the face,

10:00 for instance, in the face of gravitational radiation and radiation reaction. And on the other side, people saying, well, no, no, we're not at all happy with the way things are looking just within the context of our own field, and we feel it much more important to sort things out to our own satisfaction in our own corner of the universe as opposed to trying to link up with the people outside of physics. I was wondering if you feel that there's some justice or something. I would put it a little differently. I would say there were, to some extent, two schools. There were gradations within them, and they are roughly as you described. But the first school, which I would say included largely me, Jim Bardeen, Jim Hardell, people who had come out of the Wheeler-Feyneman orbit, basically. Bardeen was a student of Feynman's, Hardell was a student of Galmons and a postdoc of graduate advisee of leaders. So there was a group of people of that sort whose attitude was, the interestingly important problems are astrophysical, and it would be nice to see more rigorous treatments of things like radiation reaction. It would be aesthetically nice, but we know the answer with 99.9% confidence, and so why should we waste our time on it? We will let the other school clean it up. Sure. And I, perhaps uncharitably, would characterize the other school as a group of people who, by and large, were beautifully trained in the mathematical tools of relativity and knew something like this up, but did not have the right kind of training to even be able to think about astrophysical questions or identify useful astrophysical questions, their degree of understanding of the phenomenology of astrophysics was not adequate, and their understanding

12:30 other branches of physics that you have to bring in in order to deal with astrophysical questions was not adequate. They were very strong on mathematical relativity and just didn't have the tools, didn't know any plasma physics to speak of or nuclear physics or other things that you needed in order to work at the interface area. So I don't think working in the interface area even. And I don't think it appealed to them either. My feeling was that they were pleased to see this happening and pleased to see the field that they worked in become popular with astrophysicists and other physicists. But their particular expertise was not appropriate for them to work in that direction. And I would say to some extent my expertise, Bardeen's, Harlow's, was not particularly appropriate to really clean things up for me on these issues, but we were sure of the results, and so we weren't that interested in doing it anyway. So in many ways it was a cultural difference and a training difference. but probably not a major disagreement on what was worthwhile some disagreement but not not major so this is something that's interesting that maybe don't want to spend too much time on right now but one of the things talking to various people I talk to people who didn't see themselves as being that much, who say, I ask them about the performance, they say, well, I recall it being really bitter and getting really excited, but of course, they ended up sending more because they weren't interested, whereas somebody who feels they were more closely involved doesn't want to put it particularly in those terms at all, especially in that nobody, certainly nobody thinks of themselves in general as being bitter. For instance, when I talked to Demure, he getting into controversies and when I talked to Natalie Darrell she said, well, I try to avoid getting into controversies, Natalie but I left that up to Thiebaud

15:00 so I was wondering what your impression I would have said that most of the bitterness and I don't know how much most of the hard feelings preceded the era when D'Amour and Darrell entered the field and by the time they entered the field And it was probably only, my line suddenly goes blank, Cooperstock and the guy who moved to Utah State was a student of Peter Havish, Rosenblum, probably Cooperstock and Rosenblum were the only people who were really pushing very hard against the standard result. And Juergen Ehlers, perhaps a leader of the people who said we still don't have it sufficiently rigorously. But I think you get a good flavor of what it was like in the early 80s from this thing in the Daryl Perron book, the gravitational radiation that I'll give to you. And certainly there were people like Thiebel himself and like Juergen Ehlers, Abe Ashtikar, any of them who have, who aspire to much higher levels of rigor than I, who remained a little dissatisfied with the simple arguments that Feynman or I found adequate. But they certainly had no doubt, I believe, about the result. Ehlers that late probably did have some doubt about the result. I certainly had a sense that Havosh was rather put out by my cavalier attitudes toward these things if we go back to the 60s. And my attitude really was that, well, we know a very high probability when the answer is, I want to move on and deal with other issues. And I think he, it was my impression that, you know, it's hard to mind the other people and you don't know what they're saying behind your back. But it was my impression that he took that as somewhat personally,

17:30 that if I didn't think it was important enough to focus in on, and I claimed that the answer was known, that this was in some sense an attack on him and his concerns, which in some sense it was, in that I chose not to pay any attention to those issues as a result, as far as I was concerned, except that I would very explicitly say, yes, I would love to see them cleaned up, but we know the answer. Let's the rest of us go on and use it. But I would not characterize I said, it's terribly acrimonious. Sure. Everybody was, we're gentlemen. And so I guess the only ill feeling I would have guessed was the feeling on the part of people like Havosh, maybe to some extent Ehlers, that their work was being ignored by those of us who chose to regard this as, in first approximation, a closed issue. But you've talked to Habas, so you must have some sense of this. Yes, yeah, it was certainly very useful to talk about just that sort of issue here. Um, well, just on this context, I remember that when, on the first occasions that we spoke, you mentioned to me that you'd heard Thomas Kuhn speak while you were a student in Totsdam, and you said that his, what he had to say about normal science and the functions of normal science was something that greatly influenced you. And I was wondering, I got the sense at the time that you meant in a kind of practical sense in your career, and I was wondering in what way that was. Well, first let me clarify, I actually, Thomas Kuhn taught a course on the structure of scientific revolutions. It was either the spring semester of 65 or the spring semester of 66.

20:00 I can't pinpoint for sure which one. I think the first edition of his book had already been printed, I believe, and he was working on a second edition and was probably already under some attack by people in the history of science community. I was the only physicist in the course. It was a discussion course, basically, in which we would read sections of this book and then we would talk and elaborate on it. Everybody else was either history of science or philosophy of science students. registered, I just sat in on it. And I just simply found it made enormous sense to me from my point of view as a physicist, everything that he had to say. And I ate it up and came to really believe in it, or at least believe in a variant of it that made sense to me. and I can't at this stage I don't know probably within a year afterwards I couldn't distinguish my variant from his clearly my variant is obviously quite different from the variant that the critics of Kuhn criticize I should say One other thing very early on for me that reinforced it was Feynman's book on the character of physical law, which I read and I reviewed for engineering and science right after I came here, probably 66, probably summer of 67. Feynman's discussion of the value of having a number of different points of view The value of being able to start from any one of a number of different directions and regard those as the axioms and deriving the rest as the theorems. The value of having a number of different pictures in your mind to go along with it. This fit dovetailed with Kuhn's idea of paradigms.

22:30 And I came to see it as a powerful thing, having several paradigms operating in parallel. paradigms in the sense of Kuhn, and I basically translated Feynman's views into Kuhnian language. And this certainly had a big influence on my work in the 80s on the membrane paradigm for black holes and the issue of going back and forth between thinking about black holes in the membrane paradigm or the standard black hole paradigm. It had to be influencing gravitational wave theory on my liking to spend some of the time thinking of general relativity as a field theory in flat space-time when dealing with certain kinds of problems and switch over to a curved space-time point of view and dealing with other types of problems. Kuhn in that sense of the concept of a paradigm but then paradigms in parallel was a major issue for me. Kuhn in the sense of the history of quantum mechanics and the change of paradigm when quantum mechanics came along and in that case two paradigms in parallel the Heisenberg paradigm matrix mechanics and the wave mechanics, and then the sum over histories, and the paradigm shift when you came into quantum mechanics, and then the development of several paradigms in parallel, which you can go back and forth between. I sort of see physics very much in that sense. Paradigm shifts, but then paradigms in parallel operating hand in hand, which a little different from Kuhn, but it's very much an Akunian spirit. And that's always been very much on my mind in doing research through my whole career. You even see some of it in this course on gravitational wave theory that I talked about, when I talked about field theory and flat space and different ways of thinking about gravitational waves.

25:00 When I look to the future, I anticipate that when quantum gravity comes under control, a very similar sort of thing will occur. We'll have an extremely different paradigm in quantum gravity for the nature of gravity, quite possibly very different any candidate paradigm for the present time. The loop formalism that Ashdakar and Al worked on, some of her histories, some of her topologies, stuff that Hartle and Hawking do, string theory, expect they will all ultimately lead to some paradigm that may be radically different. or less, and then we'll have some ways of thinking about it in parallel, but it will be mentally extremely different from general relativity. I also see historically in the development of physics that these, as we get deeper into fundamental physical law, these paradigms become more and more alien to the human mind. And it's not obvious to me that in the ultimate theory of everything, the human mind will to grasp, because it's so alien to how the human mind is built. But I think of all of history, of physics in that way, the past and future, and I think it's largely triggered by an outgrowth of what I learned in this class of Kuhn. I guess somebody had written a book recently, actually, about, I don't think it's a David about the non-intuitive character of physical theories for people, for humans. One thing that had occurred to me, thinking back to it, when you mentioned Kuhn's influence on you, was wondering if the question of normal science and the idea which in Kuhnian way of looking at things is really the pre-revolutionary period when a science develops for the first time as it were into a normal science. Well, it was characterized, I suppose, by potentially a revolutionary change at the beginning, too.

27:30 I was wondering if you're interested in the idea of how normal science worked, what's influenced by a feeling, I don't know how to put words in your mouth too much or anything, but that your experience of relativity was that it had been developing from something that was a little bit outside the mainstream of science into something that was in the mainstream. I don't know whether that aspect of it was, for me, much influenced by Kuhn. I don't know. I guess the things that I took from Kuhn were more the concept of a paradigm shift. The descriptions of normal science which I don't even recall a great deal about yeah I think like a lot of theories of revolution that didn't have much to say about the actual normal periods and so these shifts in the character of our field I don't think of so much in Kunian terms And I think the character of the field has undergone several shifts over the decades that I've been involved in it. The first was the development of a close contact of astrophysics. The second was a bifurcation or breaking up into pieces of the field, a piece basically going off and joining on to particle physics. It's the way I would characterize what Harlow and Hawking and Al do. Basically, they're in the mainstream of particle physics. And a piece becoming part of hardcore astrophysics. And then the old work on classical general relativity largely dying out is a very interesting subject, at least for the time being. classical general relativity as a research activity in and of itself. Do you mean that it's largely died out and that nobody is interested? Well, the best people aren't that interested in it anymore.

30:00 There are a few interesting important problems such as cosmic censorship. There are several important problems the most The best people, the most exciting work is being done at the astrophysics interface, at the particle physics interface, I think. And then a few spots in classical general relativity such as cosmic censorship, which have been very difficult problems where progress is not being made very fast. One thing that had made me think in terms of this question of how, well, maybe people like Halas and Ava were looking at it in the 70s was reading the interview with Roger Penrose in the book Origins, where he talks about... I haven't read it. Yeah, but there's just one brief part of it, where he discusses the growth of interest in cosmology amongst particle physicists in, I guess, the 60s, 70s, when people like Weinberg and so on became involved in the field. and there was a sort of ambivalence there because he's saying, well, it was really nice that everyone was certainly interested in cosmology, but on the other hand, it was annoying that they came in with a characteristically different viewpoint and that they weren't always very appreciative of the kind of problems and interests that the people who had been there to begin with had. I think he invents a certain amount of displeasure at that. And I was wondering, I was trying to get a feel and when I talk to Havis next I think I might try to bring this up I don't know if it's worthwhile about whether that was a sort of a similar feeling that as you were saying no doubt people were pleased everyone was pleased that relativity was much more interesting but I guess there may have been a certain feeling that well yes that's nice but they're not really appreciating certainly I know that talking to Havis he did stress and we talked about this he said for instance at the Warsaw Conference and he said, well, I talked to another sort of non-religious who was out in Warsaw, but the name escapes my mind. But in any case, but it wasn't fine. But he said, well, I was talking to him there,

32:30 and it turned out that he wasn't aware that the field theory in gravitation restricted the way that the bodies could move, that you couldn't just arbitrarily say, well, the thing goes this way, so it's going to emit gravitational waves. And so, again, he was making this point that he felt that they didn't appreciate the particular problems that were absolutely wrong. Well, I think that's probably true. They didn't. On the other hand, to some extent, they didn't. I think Feynman was, I'm almost sure Feynman was quite aware of that. Wheeler was emphasizing it I'm sure I finally would have picked up on it well in fact it's in there it's in Feynman it's essential it's an essential part of his derivation of the Einstein equations by trying to make everything self-consistent so he understood that and understood that in a pretty deep way in that time frame. Yeah, I certainly, I guess Havis wasn't willing to say one way or the other what he thought about Feynman. I certainly get the impression that Feynman was more sensible to these issues than relatively, although you can see in some of these conferences that he still obviously had a different viewpoint from the relevant side. Shield, I was looking at the 62 proceedings, more or so proceedings, and I think Shield had got up to say, well, look, here is a result that only metric theories that were running in curvature can really explain the thing. And Feynman got up to say, well, I don't think you can say that. I mean, other people have these other theories, and I probably agree with you, but I think it's fair to just dismiss them. Well, Feynman, there was a certain amount of open-mindedness about Feynman. He was fundamentally very open-minded, but he was not very patient with what he thought was bad science or what he thought was wasting time on uninteresting or already obvious problems. He, for example, there was a lot of caustic feeling about Fred Hoyle in the 70s, early 80s here at Caltech. I mean, Fred had been pushing steady state cosmology for decades

35:00 and was still sticking with steady state, or a variant of steady state. And Feynman was probably one of the few people who was really a supporter of Fred's in that period and still would argue that here's a clever guy and it's worth listening to him. So, he was very open-minded and more open-minded in some respects than most of his colleagues. I suppose I was just going to talk about, or just ask you a bit about the binary process. chance to look through all of the literature right yet, and we're starting to get around to it now, but I have been interested in I don't think there's really it seems that Paulson Taylor did such a good job in their bad analysis of their observation there doesn't seem to have been any skepticism, there's been so much in the literature about their results when I talk to Havas about this, who might be expected to be someone who would be inclined to be skeptical he said that in the early stages he had you know looked at their stuff and asked them for some of their data and he had considered with an expert in tempo I guess looking into it because he could see some possible problems but he said he never got time to do a paper and that in any case he felt that they had later sorted out the issues that he thought might It might be problematic. And so since, you know, being of the age that I am, I'm mostly only familiar with the long aftermath of Halsam Taylor, do you recall there being any kind of skepticism about their results to begin with? Well, the only skepticism that I saw was a concern that many people, including me, had in the early years as to whether this pulser was really clean enough that there would not be other non-gravitational effects

37:30 due to mass transfer or mass loss. And the fact that the numbers in the end stayed right with the theory, right down to the level of four-tenths of a percent or whatever it's now at, I find very convincing that that can't be a coincidence due to gravitational radiation reaction being different, say, because of some scalar field component plus some compensation that has come from some mass loss from the system and angular momentum loss from the system due to mass outflow, for example. But in the first few years, when the accuracy was at the 10% level, I think that was where the concern that people I talked to had lay. We didn't know enough about the system, about how clean it was. I didn't see any particular concern about the analysis and putting the analysis into general relativity. Roger Blandford jumped right in very early on and you see Blandford is one of the few people that is acknowledged by Joe Taylor in his Nobel Prize lecture Roger jumped right in and helped Joe to get the relativity right in the analysis and then afterwards Joe hooked up with Thibaut D'Amour and Thiebaud provided really the foundations for doing things to high order and doing it fully correctly. But I think that it was... Taylor had crucial advice from theorists almost from the very beginning, from theorists who were very good, who understood both the astrophysics and the relativity, which Roger did. Yeah, I guess that's sort of the other side of the coin, right? Because I was a little bit taken by a surprise talking to Jim Anderson. He said that, yes, well, of course, the whole state of things sort of proves the quadruple formula, as it were.

40:00 But since he was completely unhappy with everybody's derivation of the quadruple formula, he said, well, the key point was, does it verify the theory? so, and of course he felt that there was only one particular way to show the colorful form of but certainly that was another aspect of the other side and it is interesting, I always think it's interesting about the fact of this question whether the system is clean up, it's oddly reminiscent of the perihelion advance of mercury since you have the same situation where you can imagine a million different ways that the thing could arise perturbations but then it just happens whatever everyone's accounted up to a certain point of the remainder it just happens to the side exactly with the general relativity value so it seems to be an interesting indication of the way people did it but then you'd still have people like as you were saying back in the perihelion advanced case you had people like Dickey later on saying well if we had this other effect it could be masking the real result which is... It's somewhat similar, actually. So there was certainly some concern about that to be... I think you hit on something, though, in describing Jim Anderson that still even now characterizes this subject of radiation reaction and how you analyze the binary pulsar or binary black hole systems, that different people have different ways of handling things like the self-field, different ways of handling the matching between the near zone and the radiation zone. And often people are not very happy with each other's ways. I'm not awfully happy with people's fancy techniques from complex variable theory and analytic continuation. and I much prefer like Jim Anderson to do matched asymptotic expansions and equates the motion without ever going into the interior of a body but I do believe that these are largely a matter of taste and that if any of us if one looks in great care

42:30 at each other's ways of handling it I think one would probably say grudgingly, yeah, okay, well, that's alright. I mean, I don't like it. It's not nearly as pretty as my way, but there's something wrong with it. Yeah, I'm interested to hear you say that, because one thing I did know is talking to everybody. It's certainly the one thing that really sticks in your mind is that very often people had a feeling that there was only one method that was right, and of course, none of them agreed on what that was. No, I think that's not true at all. Tebow is so caustic about divergent integrals that sit there in the methods that say that Chandrasekhar used or that Waggoner and Will use. And I just don't see that it's a major issue because with a little bit of horse sense and knowing that you're always going to differentiate these things, there's no real delicacy in law. You just have to be a little bit sensible about them. And I do am convinced that at least up to some rather high order that any of these approaches can be made to work and have probably been made to work by their proponents. I worry at the orders that one is pushing to for LIGO. maybe that's because that's the frontier right now but that's perhaps appropriate what is the frontier of computation one worries about what methods of reading work and which ones won't but if you pull back from that frontier back to the leading order radiation reaction orders and we oversee beyond, I think that all of these different methods are probably just fine. Well, looking back on the history of the field, one thing that certainly strikes you is that, if anything, the number of various approaches probably proliferated over the years, but that from some imaginary point onwards, people tended to get the same answer. even doing the different methods, which certainly I'm sure helps people's confidence. Whereas previous to that, people got different answers, even maybe doing somewhat...

45:00 Well, I think fundamentally, it's my impression that people started getting almost everybody in the same answer when they abandoned doing fast motion approximation and switched over to slow motion. I think that was the difficulty that getting, even just getting out Newtonian theory right in fast motion, It's not easy. If you look at the series of papers by Kovacs and me on the Grumstrand problem, where we do do fast motion, computer gravitational waves by fast motion, it's horrendous. And as I said in the class, that's the only full fast motion calculation all the way to the end and gotten the radiation field. We didn't try to go in and do the radiation reaction. All we did was computer the radiation field. And when I see how horrendously complicated that was and then imagine without the benefit of having fully understood slow motion or its match into the radiation zone, I imagine Havas and others trying to do this by fast motion. surprised that they couldn't get the right answer. It's just horrendous. This goes right back in a completely different period and probably different things had, but I guess there was an even earlier period when people were, by and large, using slow motion approaches and also getting all sorts of strange answers. And one of the reasons they said, well, let's do the fast motion is that they weren't happy with the earlier Yeah, precisely. That's why they went to the fast motion. But the problems of the slow motion at the time were clearly that people did not yet understand the matching under the radiation zone. I think Troutman, it's my impression, Troutman did basically sort it out in the late 50s. But it didn't really get incorporated into the ethos of the field later, and people didn't recognize the problem as having basically been solved. But I do regard the problem as having been more or less solved in that era, Troutman

47:30 and something by Carmele from that period, I think, or early 60s before I got into it. and I guess in the 60s I regarded Carmelia as having given an adequate treatment and when I was going in and doing it for myself and when Burke introduced the radiation reaction potential, I regarded these as nice ways of looking at something that had been basically already solved that was not a popular view of the time yeah I have to look at I have some of Carmele's I think it was Carmele or no maybe it was Perez it was probably Perez I know that Carmele did a lot of work in the fast nation it was probably Perez I know he gets criticized, but I felt at the time that it was quite adequate. Yeah, it is Paris that you say in the Untitled's book that you say you thought was the first right. Yeah, I guess it's Paris. I get confused. They're both in Israel now. Yeah, I have a bunch of people who are both in. I think that Carmelo Lager did the fast motion. He collaborated with Hamlet. Well, I'll let you go, and then we can... Thank you.

50:00 Thank you. Thank you.

52:30 Thank you.