Interview with FI Cooperstock

0:00 I'm in June at 10.30 a.m. and I'm talking with Professor Frank Cooperstock. So, the one thing I was going to ask you to begin with is how you first got involved in the problem of gravitational radiation. Well, my thesis was on gravitational radiation. And I had been given the problem of working on the detection of gravitational radiation because my thesis advisor, Peter Westerfeld of Brown, was actually an expert in acoustics and he was just learning general relativity at the time. And he was convinced that Weber's analysis was faulty for detecting gravity waves. And Peter got me onto the problem. And I finally got into the direction of worrying about what the effect of the gravity waves were on a continuous stress distribution. because the analysis to that time seemed to be one of just really effectively looking at what gravity waves were doing to the masses at the end of the spring and ignoring what the gravity waves were doing to the spring. And gravity waves are going to interact with all stress energy, including the elastic medium that's going to be at play in the detector. So Peter suggested this very nice electromagnetic oscillator model that I think he was the one that devised it or someone had told him about this, which consists of two capacitor plates, which are charged, oppositely charged, so they're electrostatically attracting. And between them, one bounces an electromagnetic wave, which provides radiation pressure and if you have the right energy density of the electromagnetic waves between them then you can balance the electrostatic attraction with the repulsion from electromagnetic radiation pressure and it is an oscillator in the sense that if you perturb it a little bit then you squeeze the electromagnetic waves

2:30 and increase the radiation pressure whereas you hardly touch the electrostatic attraction so the increase in electromagnetic radiation pressure pushes them apart and they pass the equilibrium point the electromagnetic radiation pressure diminishes beyond the equilibrium value and the coulomb attraction is stronger so it pulls them back it behaves like an oscillator but the advantage of this is that you can look at all the elements from the field theory point of view you can look at the oscillator electromagnetic waves which you can analyze interacting with gravity waves which are coming along and affecting this oscillator through the Einstein Maxwell equations and that's what most of my thesis was involved in that and we we went through that and and came to the conclusion in fact that that the oscillator wouldn't get excited unless it were active. That's to say that if the oscillator were just sitting there, it wouldn't get excited. And the only way to get some action with the gravity waves would be to have the oscillator forced, you know, to have the thing in action and then have the gravity waves interacting when the thing was active. So that's how I got into it. And in fact, that analysis was the basis of the later work I did just fairly recently on laser interferometry because I knew how to do that stuff. It goes back to my old Annals of Physics paper from the 60s. And I recall now that you mentioned that in your paper from Foundations of Physics on the Localization Problem you discussed the Feynman-Bondi-Codd experiment saying that there must be energy in the wave in terms of that system. Okay, so you know about that. Sure. You're aware of that. That's right. So at the time when you were doing your thesis, did this kind of... You were saying that you concluded that the wave wouldn't... Wouldn't excite a passive system. That was the conclusion there. That's right. So is that related to the later result? Well, I sort of put that aside. I was a little bit dubious about the conclusions from that later on.

5:00 I started worrying about that more, and I just didn't pick up on that until very recently with this new localization idea. Well, it just fits in just fine. So this all has come back. And would the... So if the thing is already moving, the way it will somehow maybe affect the phase. Well, we'll interact, yeah, we'll interact with it. But it won't excite it as Weber's bars would be excited just sitting there passively waiting for a gravity wave to get excited by it. But I had some doubts about it at the time and I just left it aside and got into other things. I don't remember why I had those doubts now. It's too long ago. but I did have some lingering doubts I was spurred on by Peter who was very happy with the result because he was convinced that Weber was wrong in his analysis and this was great to see it done this way I was talking to Weber last week actually he was recalling that people were doubtful about his arguments at the time and complaining bitterly that now he has a new calculation of his bar detector cross sections higher than his original calculation. Higher? He says that they have a much greater cross-section than his original calculation. Oh, really? So he should have been seeing events all over the place. Where are they? Well, I guess he claims that he has. He sees they are events. I see. And does he have coincidence with it? Is he still running coincidence experiments? Do you know about that? He is, I think, yes. Well, he had this famous coincidence with the Rome bar from the 1987 from the pulsar well from the not the pulsar, what am I saying from the supernova in 1987-8 1987-8 that's right, so he had this coincidence and I believe that he's still running coincidence experiments But people were very dubious about that coincidence that he was claiming with 1987A. That's true, yes, that's right. But he was complaining that, he said that some of the people who doubt his new cross-section

7:30 will say, well, we believe in your own cross-section. And he said, but nobody believed that back then either, so... And he had a really hard time with it with all of them. He's a nice fellow, I like children. Yes. As you say, it's a lot harder. Very nice fellow. People can be really vicious in this business. It's really a shame. I saw a terrible confrontation that I had years back at this meeting with I think it was one of the Texas conferences. It was in New York. And he had a terrible confrontation with Tyson. really, it was ugly I didn't care for that in front of a thousand people not pleasant this was when not long after he had come out with his results and Tyson went after duplicating them and Tyson claimed he had more greater sensitivity and he was getting nothing and oh boy So did your thesis work lead you on then to getting interested directly in the radiation reaction problem, or did that sort of come later? It seems somewhat later. I got into a variety of things in the intermediate period, going to different subjects and sex, some exact solutions that I was doing. Oh, a variety of things. But then I got back to it again when I went to the Poincaré Institute for a sabbatical in 1973. Oh yeah, that's right. In the intermediate period, I'd gotten interested in biometrics. static axisymmetric metrics. So I became quite familiar with them. And then in discussions with Papa Petro, the Poincaré Institute, he suggested, in fact, that, you know, with my experience with biometrics, why don't I get back to the radiation problem? At that

10:00 stage there was a lot of, still a lot of worry about what's going on with the radiation, how do you analyze it properly what sort of radiation are you getting from free fall systems this was the big word in fact this had been a controversy for many years free fall, you have gravitational radiation and he said why not avoid problems of incoming radiation by starting with an initially static configuration two bodies at rest with an intervening strut problem, static axis symmetric problem, and then break the strut and let the body start to fall together. So there's no previous history of radiation. The original t equals zero metric is static. For some time period you break the strut and then the two start to fall together, analyze the radiation that comes out after you break the strut. And that's how I got into like with the phase that led to various confrontations I had with Walker and Will. I don't know if you know about those, I had heavy confrontations with those people, like the equivalent of what I guess Webber had with Tyson, I had with Walker and Will. This is Mark Walker and Clifford Will. So I had done that work at the Poincaré Institute and I was only that problem. I was not able at that stage to get to free fall yet. It was too difficult. I was only able to get through the stress breaking phase. And then once I got through the stress breaking phase, I had to go to a higher approximation in order to do the free fall. It was only good through the stress breaking period. And then I got Paul Lim, a new graduate student, to work with me subsequently on that. And then we got into free fall analysis. and then suddenly there was the binary pulsar was discovered and then everybody was suddenly interested in this work before it was just an academic problem that the pointy headed relativists worried about but it suddenly became a real problem because there was a real source out there the binary pulsar, everybody was excited about the binary pulsar it finally led to Taylor's Nobel Prize

12:30 So I got a lot of attention from that work that I did, and in the meantime, Walker and Will were doing their own work on this, and they came to the conclusion that we were wrong, and we had a lot of battles back and forth about that, and I don't think anything was ever conclusive from any of that. It's still just left in a big mess. That's basically how the thing went. And now I'm I'm really not sure about the correctness of that whole procedure in terms of getting a really solid answer. To get a really solid answer. I think the work we did is okay but it gets mixed up with It still gets mixed up with considerations of the previous history. That was part of the problem, was to avoid having incoming radiation. If you have incoming radiation and you don't know where you're at, you want to just have outgoing radiation. It's a tricky business to make sure that you only have outgoing radiation. And Papa Petro's initial hope was that by doing this, there wouldn't be any confusion. up being some confusion about it because we had to worry about the stress breaking phase and that was a dynamic phase which involved an energy momentum tensor and a non-freefall period and who knows exactly what role that might have played in the whole thing. To this day I'm really not sure about whether one can really be confident about the answer. Either way, I certainly have no doubt that Walker and Will were not right, were not genuine about their results. But about our own, I increasingly had doubts in terms of how much one can rely on it. And then to try to alleviate some of those doubts, Paul Lim and I launched into an analysis of a binary, a circular binary that had been going on for a long time. So we were hoping that, well, that could wipe out a lot of the problems of a stress-breaking phase, that this would be really like a system that got rid of its past history

15:00 in terms of what you have to worry about for the free-fall phase. I don't know whether that, and again, as I look back on it now, whether that's something that one can be confident about doing, that one can really be confident that one can get rid of past history in doing that. But at any rate, we went through an analysis of the binary, and we were not able to come to the conclusion again. We just got to the level in which we, to decide about free-fall radiation, to be totally confident, we had to analyze some non-compact integrals Which, again, we couldn't do mathematically, and in fact, that was the problem going way back. You'll see remarks about, in Ehlers, Rosenblum, Goldberg, and Hobbes, you know, that review paper, that was another review paper, where they talked about the non-compact integrals that come into play. You don't know what to do with them. So that was left in limbo, too. but now if I'm right about this new hypothesis none of that's a problem in terms of the energetics approach in terms of the energetics approach there wouldn't be any energy emitted there'd be these gravity waves given off and if Tipo D'Amour is right then it could lead to a damping of the orbit say for a binary pulsar which could go on without any energy actually in the sense there would just be a redistribution of the energy in the system between the gravitational, in terms of Newtonian terms, to describe it in a rough way, like a trade-off between kinetic energy and Newtonian binding energy. It would be a trade-off, and the two would keep their conserved total energy. The two aspects summed together would be still conserved, but there would be a redistribution of potential kinetic energy. and everything could go on as people expect it to go on, but it wouldn't be a flow of energy out to infinity if my hypothesis is correct. That's a big hit. in the case of De Moore... I wish I could understand De Moore's calculations. They're very complicated. But I'm willing to buy them because it's not an energy calculation. And in fact, so that doesn't really impinge directly on any of this stuff that we had done then

17:30 or what I'm doing now. It's a different approach. It's an equations of motion approach. And it's not a matter of computing fluxes of energy, which is very, very touchy business in GR. Yeah, sure. That's right. So you mentioned, I've read, I guess, some of Walker and Will's papers, certainly, they had some kind of review papers and so on. So when these discussions were going on, did it largely happen through the papers or was it, for instance, at conferences? All conferences, papers, individual discussions, one-on-one, everything. Just out of interest, you mentioned how visceral Webber and Tyson were getting at it. Was it ever hostile? Oh yeah, we had hostile moments. It's unfortunate now that I look upon it in retrospect. and something I never want to have again it takes all the pleasure away from this business you have to get into personal animosities it's not pleasant it really left me with a sour taste After that happened, I put gravitational wave studies aside and I had gone into other things for a number of years. I was so tired of the confrontation. So I left such a distaste in my mouth that I set it aside. That's a shame. But now I'm back to it to some extent, to a fair extent actually. And so I guess, you mentioned Ehlers, Rosenblum, and Hamlin's paper, so they were, were they all still involved in the kind of discussions up until, well, the time the Cooperstock and Hobo paper, or was that sort of familiar? I guess that particular paper is a 76 or so.

20:00 Well, are they still involved in that? Is that what you're asking? No, up until the early 80s. Well, I think it was really Arnold and Rosenblum that really spurred them on in that because he had done his thesis work, I think it was his thesis work, but certainly near the time of his thesis, on the scattering problem. That's right, Rosenblum did a scattering problem, and he got an answer which was different from the quadruple formula answer, the scattering problem. And so I guess they got, he and Havas got Ehlers into it, and I don't know exactly how Goldberg got into it too, but at any rate, they decided to, you know, to form a little consortium and analyze what had been going on up to that time. And so they came out as sort of criticizing everybody, everybody that had done the work up to that time. Yeah, I was just starting to develop, you know, sort of this fall from rest approach at that time. I hadn't done it at the time that they... I had started it, but I hadn't really gotten any conclusions on free-fall at that stage. So I guess Rosenblum worked in the fast motion approximation. Small angle scattering. And there was, from what I read, someone out of two-ing and throwing, between people saying whether that fast motion approach is better or the slow motion approach is better. Was that, from your point of view, that probably wasn't a big issue? Well, I wasn't, of course, I was doing, you know, using a totally different approach, because I had this visceral distaste for singularities that stayed with me all my life. I still don't like singularities. I don't trust them. To me, it's just mathematics, it's not physics. And any of that work, I just did not have any trust in.

22:30 Who knows what you can conclude from having these singularities flying around. To me, it's a non-starter. And it was interesting that in my more recent years, is I did quite a bit of work with Rosen, with Nathan Rosen. And one of the first things he told me was, and I was really happy to hear this, how distasteful Einstein found singularities. I didn't know it at the time. Rosen told me Einstein hated singularities. I really felt, oh my God, here's the great one. And I never knew this. My feeling was always been the same. I never trusted him. I never could really relate to any of the work with using singularities. If your work relied on the singularity, who knows? Yeah. And, yeah, I was interested, actually, when I was reading your paper with Hobo that you referenced one of Rosen's papers from 79 that I wasn't familiar with, does gravitational radiation use it? Yeah, well, see, Rosen's a real maverick. Not so now, but in his earlier years, he was a real maverick. He was ready to challenge anything, you know, which is good. It's healthy. Right now, well, I shouldn't say right now, for many years now, it's been a matter of conformity. There's a party line. People have told the party line, afraid to, you know, look at it, look at it, consider it new possibilities. I mean, they're such beer. So I always found the Rosen a kindred spirit, and that's why I went to work with him. We had a great time together. Yeah, it seems to be interesting. So I was interested in the paper because I had been looking through the Einstein papers. I was interested in the Einstein Rosen paper on cylindrical waves. Beautiful paper, beautiful. One of the reasons I was interested in is this letter from Eisen to Bohr which had been pointed out by Chandrasekhar and some book now to look it up.

25:00 And also Infield mentions this in his other library, that while they were writing the paper, Eisen and Rosen had thought that maybe gravitational waves didn't exist because they were having trouble finding a metric. I think the problem there rested on the fact that they couldn't find a singularity for any metric to describe the world. Oh, I see. So I was trying to look into what the actual problem was, because unfortunately, Infeld spends a bit of time in his book saying what happened, but he never says what the technical problem was. Oh, really? You mean motion and relativity? The Infeld Pabatsky book? No, it's in a book called Quest, which is his autobiography. Oh, really? Oh, I should look at that. It's quite interesting. He describes, he's talking about when he first met Einstein, and it so happened that he met Einstein while Einstein, just after Einstein, had written this paper with Rosen, who had then gone off to Russia. Oh, yeah. Mm-hmm. And so Rosen was present at the time, but Einstein explained to Infeld how he had just come up with what he thought was a proof that gravitational waves didn't exist, and Infeld was surprised, thought this was strange, but he went away and read, you know, thought about it, and he came up with a similar but alternative version of the same proof, and they were both delighted with it and surprised. And then H.P. Robertson, all Infel tells us is that H.P. Robertson was there, or I think he'd just come back from a sabbatical, and this was all in Princeton, and he said that he discovered a flaw in the person, and so Einstein had to radically change the paper. But unfortunately, the Internet doesn't bother telling us what the flaw was that Robertson pointed out. So I was trying to look up, but I did find some correspondence between Einstein and Rosen and Einstein and the editors and journals about this paper. And it does appear that the original title of the paper was, Do Gravitational Waves Exist? Oh, really? That was sort of struck by the similarity in the titles, but then what they decided was that although the way they were doing it, They had been trying to construct a plane wave metric. They couldn't do this the way they were trying to do it without singularities. It's the best I can judge of what was the problem with it. But then they discovered that they could convert it into a cylindrical metric.

27:30 Well, you still have the line singularity. You still have the line singularity, yeah. You can't get rid of that. Yeah, that's right. But that seemed to be less objectionable than what they had previously seen. And unfortunately, since it's hard to find details of what it was, that was, what the, unfortunately, of course, as far as I can judge, the original version of the paper doesn't exist anymore. Well, I would find it inconceivable that gravitational waves don't exist. To me, that's, I can't imagine that there'd be any hope for that kind of prospect if relativity's right. But radiation, energy carrying, that's another issue. but waves how can you do without waves I guess for them though the two are together they're associated for most people waves and radiation, that's it if you have waves you have radiation you have energy count yeah, that's why I was interested in what they were saying because Infeld in his book does say well, how could you he says it doesn't seem he's describing why he was surprised at first he says if anyone's thinking about relativity have waves of radiation. Yeah. So it would be interesting to know, because I do know that Rosen in the 50s wrote a paper in which he suggested that the waves didn't carry energy based on the fact that you could Oh, you're talking about the Feynman-Wheeler absorber theory. Is that what you're talking about? Well, let me see. This is I don't know if Rosen actually refers to this paper. That's the approach of the paper. Is there gravitational radiation? I remember that paper. And so what Rosen does is he said, well, if we do for gravity what we do with E and M, in Wheeler-Fineman absorber theory, in other words, have incoming radiation, you have to use the time-symmetric solution and have both outgoing and incoming radiation, then what happens is that the absorption cross-section for the final outgoing component is so small for gravity waves

30:00 as compared to the electromagnetic waves that all you're left with is just a total cancellation balance and you don't have any radiation. As opposed to E and M, where the absorption cross-section is much stronger for the outgoing component. I don't remember exactly how it worked. But anyway, it was the difference between the absorption cross-section for electromagnetic radiation versus gravitational radiation. That was the difference. That was in the paper, is there gravitational radiation? Another approach that he took as well? Just another, and a much earlier paper. So it's interesting, I was interested in reading that. That was already post-my-review paper with Hobel. Yes, the gravitational wave. Well, around that same time, I shouldn't say. Yeah, it's already around 1980 at that time. But in 1955, I think it was, he published a paper, and this is at a time, this is one of the reasons that this later paper was interesting to me, because this was at a time where people were doing with half of mass minus half retarded potentials in gravity and finding no gravitational radiation, no energy loss. Oh, it was the same, it was really the same kind of thing then. So, yes, that was interesting. So he came back to that. I didn't know that there was a past history on that approach. That's interesting. And in the 55 paper, one thing that he does is, he mentions, and this is, again, I found a remark you were making about how you can find a transformation in which you can make a pseudotensor go zero everywhere. He brings that up in his 1955 paper. He does? You know, this is really interesting. I'll tell you why it's interesting. It's because where this whole business, my recent business got started, is when I had a discussion. It was in the middle of a discussion with Rosen. And I said, well, you know, Why don't you choose as a gauge condition T0k equals 0, k equals 0, 1, 2, 3. These are four conditions, and then you have no energy and no energy flux. And he's saying, couldn't find anything wrong with that. And I got all excited about this.

32:30 my God, can you imagine the consequences of this? And he was kind of interested, and I said, well, you want to develop this further? And he said, no, I don't know. I don't think I'd like to. I guess I'm just too conservative. And I just took off alone. I said, well, if he doesn't want to work on it with me, I'll work on it myself. But it came in a discussion with him. You know, we were talking, and then I just got this inspiration. And now you're telling me that, in fact, he had done something like this in the old days? Yeah, absolutely. Oh, I have to look this up. I should give you the reference one. Unfortunately, I don't have the paper with me, but it's interesting because one of the reasons anyway, but there were various reasons, but it was partly in response to that paper that people were advancing the Feynman-Bondi thought experiment. Now, just a minute. Did he say no pseudotensor period or no few components of it? Because, you see, you can only have four conditions in general. In general, you have four degrees of coordinate freedom, four conditions. Now, this is not beautiful, because what about the other components? What about the space-space components? You know, it's kind of awkward if you just get rid of those and you have no energy density, no energy flux, but what about momentum density and all the rest of it? It's kind of fantastic that this Kerr-Shield metric gets rid of everything. It's very special. But I'm kind of wondering if you remember whether the Roseman thing was all the pseudotensor or just some of the components. It may have been just some of the components. I'd really like to know. Because that was my inspiration. I don't know how we got into that conversation, but I remember coming up with this inspiration of getting rid of just four components, and that would be enough. he couldn't think of any reason why you shouldn't be able to do that because it's just first derivative conditions it doesn't conflict with the Einstein equations or anything but then people have pointed out to me well in spite of that you should still show that you can do it you should still show that explicitly produce a transformation to do it that's easier said than done now with Kershield I have no problem whatsoever It's done for plane waves, but I haven't been able to do it for the stuff that goes beyond what the Gerzis and Gerzi have done.

35:00 They've done it for, oh, and this is the thing, they've done it, they've shown it's true for plane waves, they've shown it's true for the Kern-Eumann metric, and shown it's true for the Bader metric. So it's true for a significant number of space times that you can put them in Kershield form. I'd really be interested to see that and I'm going to bug him about it if that's the case I would say why did you get involved with me in this because I need help if I had convinced Rosen to work on that with me people might have thought it was just as crazy because people see that Rosen comes up with some pretty maverick ideas they say oh another one of Rosen's maverick ideas Well, this might be, it's all my own responsibility. Yeah, so I was interested, just for that reason, in some of the... It could have been a trap. It could be Rosen was just spurring me on, leading me into it. And then I'd say it, and he'd want me to carry the battle all by my own. That would have been a dirty trick. Well, I want to see that paper of his. Maybe he figured, well, he ran that battle, now let Cooperstock run it. Could be he led me right to it. Who knows? A big Mackey villain. Ah, yes. So, I was interested, actually, in that context, since that led into the Feynman and Bondi argument about the ways I was very interested in your pick, because it's the only example that I've ever come across where anyone actually addressed the Feynman-Bondi thought experiment and said, well, here's why I think that doesn't work. Yeah, right, right. Everybody sort of accepted it. Well, it's really, it's a back of the envelope kind of thing that these people have done. Sure. You know, they never went into it thoroughly. No, it's not. That's right. And in fact, as I say, I left it. I had essentially completed that as a graduate student. That was part of my thesis. And I kind of just let that sit and thinking, well, I don't know whether there's something wrong with it at all. But then it all came into place with this new hypothesis. It just fitted in perfectly. So I was quite excited to be able to use that

37:30 to try to bolster my argument. I've had interesting discussions with my referees. and someone will say, well, you know, it doesn't sound right, but I can't find anything wrong with it. Very well. Yeah. That, you know, I'd imagine it. I get that. And I was going to ask you, just because it's something that I'd only come across very recently, much of that, but you were in Dublin in the 60s, I guess. And I know that Singh was working on the problem of motion. Yeah, he wanted to get me into that. And, I don't know, it just looked so boring what those guys were doing. I just couldn't get excited about it. So I just kind of did my own thing. In fact, I completed my paper on this electromagnetic oscillator thing. I did that there. And then I did some of that work that I just, the papers I just gave you on. I got interested in quasi-stellar sources. That was a hot issue at the time, about gravitational radiation as being a mechanism to produce the jets and quasars. So I did a little bit of analysis of that because I knew how to handle interacting systems. So that's some of the work that I did in Dublin at the time. That's interesting. but I just, Singh wanted me to do this work with him and it looked so boring and also I guess part of it too is that Singh is a great, great old man and he treated his post-docs there like graduate students or less I didn't want to be a graduate student anymore. I wanted to have kind of an independent say about things. But for him, these post-docs were just people that had to do exactly what he wanted them to do, with all due respect. He was a great man, but I was just too independent-minded to be a graduate student or less. Well, I mean, my graduate students have a lot more independence than I would have ever contemplated in my day.

40:00 And I'm happy for it. I like to have people bring up their own ideas and that. It makes for more interesting collaborations. I have a great time with most of my graduate students. Some of them are less successful than others in terms of collaborations, but several of them I have wonderful collaborations, but giving them more independence kind of makes it more of an interesting experience that way. But of course, I'm not Singh. I mean, Singh was one of the grand old men. Even at that time, when I came there, he was an old man. Even then. But I had some interesting correspondence with him going into his 90s. Great, great guy. Really liked Singh. Ian Langsos had wonderful conversations with the Dublin Institute. Every morning, over coffee. we'd come in for coffee everyone would come in for coffee it was tea, not coffee, tea I was going to say this is our and Miss Wills wonderful gal, she'd prepare the tea and we'd do this ritual we'd have these delicious shortbread cookies that ended up ruining all my teeth but it was a great time and he, Singh and Langsos would tea off and they'd have these long arguments were just delightful. That was the best part of being there, was listening to the discussions that he and Langsos had. I ended up being the fortunate recipient of a sublet of Langsos' apartment when Langsos went back to Yale for a half year sabbatical from Dublin. So he asked me, we were kind of kindred spirits, I guess, and he asked me if I wanted to sublet his place and I jumped on the chance. and a wonderful huge apartment and he was letting us have it for a very nominal amount to take care of its to take care of his correspondence and things that came there and we had a great time there what i found interesting is in the apartment you see letters lined around that einstein had written to him they're just kind of just lying around you know these people these are things is a really, would be very valuable thing for historians. I don't know if they're lost or not, just wander around.

42:30 Written in nice, fine German writing, signed A. Einstein or Albert Einstein. I felt like saying, I felt like telling him, you know, you should take care of him, it's none of my business. Just left him there. I guess they're ordinary Well, he was in his cloud nine he sort of modeled himself after Einstein he wore his hair like him and just worshipped his memory I don't know if you've seen some of the Langsos books Albert Einstein and the Cosmic World Order and just worshipped his memory and Singh used to say well, he's not God Oh, it's a great time we had in Dublin. But if you want to talk to people about this approach that Singh took, you know, on the motion work, you should see Bob Das. Bob Das is just across the, you know, Simon Fraser, you know, just outside Vancouver. He's a great old friend of mine, and he worked with Das, Floridis, and Singh, called the DFS, and then that's where they started, the three of them together, DFS, and then Floridis and Singh became FS. They took later and refine the calculations. Oh, I'll have to get in touch with that. Yeah, he's just there across the water in the math department at Simon Fraser. He's a great fellow, Das. Bob Das. A Das, but we call him Bob. He calls himself Bob. Okay. He would be happy to talk to you. And he knows Sing from a much longer period. I didn't know. He worked with him. to you. So if you have a chance before you get back, he'd be just handy for you here, just across the water. It would be interesting because Singh has certainly been involved

45:00 in the history that I'm looking at in a couple of points. He wasn't into the radiation problem No, not particularly, no, but he had influenced Felix Pirani a bit, concerning Pirani's work in the regulation problem, because Pirani was at Dublin as well, and then he did the problem of motion, and then some people at Dublin kind of carried that on, his problem of motion on to apply it to the work, to apply it to the regulation. So there's a couple of people I have to find out just to see the interesting thing. That was kind of a very mathematical and it never excited me, that approach. but you were but you were saying of course that for instance in the case of the way de Moore does it starting with this problem motion thing you're thinking that there's not necessarily a contradiction between those results and the fact that the ways may not be carrying on the truth oh absolutely I think he would agree on that but he probably doesn't believe the lack of energy carrying, but I think he would agree that they're not necessarily directly connected. I think he would agree to that. I haven't discussed this with him. I haven't seen him for some time. In fact, I think when he first even started writing his papers in this vein, I think he remarked that the energy thing is a little bit controversial and is not clear-cut, all that. I think he appreciates the subtle difficulties that are involved in looking at it from an energy approach. I think he does. I wish he could formulate what he's done in a simpler way so we can really grab onto it and really decide whether it's right or not. I don't know if anyone's ever gone into it beyond people like Brilé who who work with him, or Schaeffer, who really know all that mathematics. As far as I know, it's just the two of these, Breley and Schaeffer,

47:30 the only ones, as far as I know, that really know all the stuff that he's done, you know, can understand it. Yeah, it's hard to know. And I know he's resistant to, I guess, to trying to break it down, especially in terms of energy transport, because, for instance, I was trying to, when I spoke to him, when he was describing his work and he talked for quite a while, I was interested in asking about kind of the quadruple form of the disputes and that. And he said, well, he said, I'm not really interested in the quadruple form. I mean, to me, that's a separate problem. I'm just dealing with this question of the motion of the... There you are, yeah. I think that reflects what he said in his papers, too. But he's a smart fellow, Tebow, clever fellow. It is a shame that his papers are so bad. I think people tend to believe, well, he's done all these calculations, they're probably okay. But it's nice to be able to, you know, to really grab on to something and really feel confident yourself that they really are okay. Without going into all the detail, but it seems, you know, I think you have to be pretty much into that kind of mathematics that he's doing. It's stuff that I'm certainly not familiar with. I don't know how many people are. I was going to ask there, but I forgot. Take your time. No problem. If you can't remember, I could tell you another thing about... I don't know whether you're interested in subsequent history, not necessarily on the radiation problem, but on the energy of the universe. This is some of the most recent stuff that I've done. I don't know if you've seen these papers. Yes, I've seen them. I've seen one or two. Yeah. This is a work that I did with Rosen's collaborator, Mark Israelite. He came to conclusion that the energy of the universe is zero. Which is a nice number.

50:00 Yes, I was interested in that. I haven't had a chance to look through the papers in detail, but I saw your conclusion. Kind of a different approach to this energy thing. I'm still interested to know whether that's kind of special about FRW metrics, how the conservation laws lead into a form of an ordinary divergence, which is the energy momentum tensor minus the Einstein tensor. And that's how we come to the conclusion that the energy density of the combo should be that quantity, which is again, if Einstein's equations are held, hold, then it's zero. So I'd really be curious to know whether this is very peculiar to FRW or whether it goes beyond that. to what extent what other metrics would fall into that line would be interesting to know and subsequently someone else came oh this guy what's his name Stanford and a few Indian fellows got the same answer recently they published a paper and then there's some Chinese guys that are coming along with the same thing Once you do something and people want to do it, do it again and see whether they get the same answer. It's not terribly exciting, but they're doing a thing. They say, we're going to do it differently, we're going to do it better. In fact, Rosen came along and did it differently too. Since we did it, there's at least three other groups doing it differently. I think it attracts people's attention. Energy is a great interest in life. I was going to ask, actually, that just came to mind. Do you think, are you trying to think that there's some particular fundamental reason to suspect that there might be why, in the case, comparing electromagnetic and gravitational waves, from the Pew of Hawaii.