Oral History Transcript — Dr. Seth Neddermeyer
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Interview with Dr. Seth Neddermeyer
Seth Neddermeyer; May 31, 1972
ABSTRACT: Topics discussed include: his education, Robert Millikan, Carl Anderson, his dissertation on energy losses of certain high energy electrons, his time at California Institute of Technology (Cal Tech), Bethe-Heitler calculations, his discovery of muons, Yukawa's theory, and his work with the Manhattan project at Los Alamos.
TranscriptSession I | Session II
Weiner:Let me just say for the benefit of this device that today is the 31st of May. I know that for sure. And we're resuming our conversation after approximately a 24 hour interruption. When we left off yesterday, I made a statement that we would try to untangle the many complex events resulting in a series of papers up through the mesitron (?) work, and that we try to place it in the context of what else was going on at Cal Tech and your recollections of the atmosphere, the people, including the various colloquia, and I would have some specific questions in terms of the relation of your work to what other people were doing in nuclear physics, if any, that kind of thing. Then we both said that weíd check on some of the papers, to check on dates. Now, one thing that I did check on, the Bethe-Heitler paper was 1934, so your sequence was correct. There was no mistake at all on that. You probably have all the basic papers here, but it seems to me that the biggest one was the 1936 paper on cosmic rays at 4300 meters, the cloud chamber observations.
Weiner:In that paper, from what I can see, you present evidence on the energy loss basis, that the penetrating particles are not electrons. You don't make a big deal of it. And then other evidences show they weren't protons. But no great conclusions are drawn, from that. You sort of left it there not really spelled out.
Neddermeyer:Yes. Well now, very, very early in these measurements, by rather immediately following the positronÖ I was most interested in pursuing farther the momentum loss measurements and the study of the scattered electrons, to try to understand in more detail what was really going on. Now, I refreshed my memory a little bit since yesterday, by looking at my thesis and looking at some of the old papers briefly. I haven't really reread them in detail so I'm still not completely sure of all the minute details, but I think I can give you the essence of it now correctly. These measurements showed that there were wild fluctuations in the energy losses, that occasionally there were particles that lost very large, a considerable fraction of their momentum, and with no secondary particle appearing, so one could say with considerable certainty that there was some process going on, presumably the radiation of a photon, to account for these losses of momentum. That was a guess. But then you see, now, since the positron, one was assuming that practically all these particles were positive and negative electrons that we saw. That was the most reasonable assumption we could make at that time. So when we were studying momentum losses, I tended to think of it as measurements being made on electron tracks, this just by assumption. So as soon as the Bethe-Heitler calculations came out on the radiative losses, I immediately started comparing our results with those, and so run a new — When one had fairly reliable, fairly reliable theoretical estimates of the loss by collisions and by the high energy transfers to electrons, and then also from the radiation from the Bethe-Heitler calculations — Well, in the data that I had summarized in my thesis, I divided these things up into groups over various energy ranges, and plotted average values of the measured momentum loss for these various groups, in a point 35, .35 centimeter lead plate, a 35 millimeter lead plate, a 3.5 millimeter lead plate, and compared that with the calculated theoretical values, and what We found was that the observed values for it were very roughly, the average values were very roughly in agreement with the Bethe-Heitler calculations at the lower energies, but at high energies the average values just flattened out. Although they still fluctuated wildly, the average values flattened out and did not show this linear increase of energy. Now, one knew one could be reasonably certain — it was one of those guesses but it seemed reasonably certain that these losses were radiated from the character of the large fluctuations, but what this indicated was, either that the theory broke down somewhere about 75 or so , I mean, V — results like — this is not a huge number of particles. The number isn't recorded here, but it's, well, it's tabulated somewhere.
Weiner:Is this the thesis?
Neddermeyer:This is what I put in the paper here, in the thesis. So the question already was arising in the fall of 1934, you see, it was after the London paper that I worked out these data in detail, from the thesis — it was pretty clear that there was something strange. Either the theory broke down or else there was something funny about the particles. Now, even at the time of writing that 1934 paper, we were both aware of the possibility or even probability that there were new kinds of particles there, particles, because we had the argument about the protons, conservational momentum — you know, they couldn't be protons because there were too many high energy secondaries. And now, if you suppose that the theory was right, then they couldn't be electrons. So the question was, is the theory right or isn't it? Now, I continued these measurements, and especially the Pike's Peak data provided me with an enormous number of cases where one had nice examples of these large energy losses and large fluctuations. And I found in the Pike's Peak data that as long as one can find the measurements to the particles that appeared in the groups, in the showers of positive and negative particles that appeared frequently, as long as one restricted the measurement to those, then the mean momentum loss just increased with, increased with the momentum of the particle, just followed right up on this curve. So you see, one then identified the particles with considerable certainty that occurred in these showers as positive and negative electrons, and regarded this as an essential verification of the correctness of the Bethe-Heitler theory. So those results, when one included the Pike's Peak data, were like this. Now, in my thesis I did not recognize the fact that these radiative energy losses are so that the target can no longer be treated as a thin target. I made the calculations on the basis of a thin target. If you allow for the rapid decrease in energy as the particle goes through the target, these multiple large losses, then the actual average energy — the observed energy loss is considerably lower than that that would be characteristic in a thin target of the incident article. So I figured out these corrections. There's a simple exponential factor. This is in terms of, again, not really considering the fluctuations in a proper way, but treating it in the sense of an average loss that decreases as its energy goes down, even though there's a wildly fluctuating thing. You deal with averages and it's pretty close. So I figured out this correction. It really bothered me at first, because even though, you know, the general trend of the theory seemed to be verified, the measured values were lower than I had calculated, when I realized that this correction had to be made. I made the correction. The experimental points came right on the theory, within experimental error. So —
Weiner:How long after the thesis was this correction made?
Neddermeyer:This was —
Neddermeyer:Well, this was after we began analyzing the Pike's Peak data. Yes, this was a year later, roughly a year later. So then I also made a pretty good sample of measurements in copper, just to check, and the copper measurements showed this even better. The correction was not as large, but here's the thin plate approximation, here's the corrected one, and the results. We didn't hang statistics — we were awful sloppy about statistics, I mean, but you know, the flags wouldn't have been too big on these points. I should go back — So here were the lead measurements, and here were the — let me see. Well, these are both Pasadena and Pike's Peak and I forget, both sets of data were partly Pasadena, partly Pike's Peak. I donlt know, ltd have to do a lot of digging to get that straightened out. Anyway, whether one did the measurement at Pikeís Peak or Pasadena, when you looked exclusively at the particles in the showers, they always showed this characteristic high absorbability. So you see, the result of that was that the Ė well, the particles in the showers were definitely identified as positive and negative electrons. The correctness of the theory was verified up to something like, well, several hundred MEV, at least this is 600 on this scale, that's in units MC2 so that would be 300 MEV. Three hundred million volts anyway, those measurements. The correctness of the theory was, in my thesis, taking the sample that I had there, which included everything I could measure, it began breaking down at roughly 60 MEV or something like that. So you see, as the point it was pretty obvious that there was something very exciting and very strange going on. So then I think I was the one that suggested the idea of getting a thick plate of dense material like platinum. We succeeded in getting a pound of platinum made into a very nice bar, Baker and Co. Millikan had some pull and he got this bar. So we ran this experiment at Pasadena. The idea into it? was that this would be such that any electrons that were incident would lose practically all of their energy, on the average, and the other particles would maybe fluctuate in their loss, but the idea was to show that there Were two groups of particles with definitely identifiable different characteristics. And that experiment definitely showed the difference. I mean, the particles definitely, clearly separated into two groups, one penetrating group which showed only small losses, which could be attributed to collision, and there in the low energy loss group, the statistical fluctuations were far greater than the error, I mean than the magnitude of loss. But practically all of the particles that occurred in showers stopped in the plate, or lost practically all of their momentum, and those were the results that were published in May, 1937. So that was the thing that really, really sewed up the new particle question. Now, we held off a long time. See, Anderson was rather conservative, you know. He was very queasy about even the positron paper. He was just terribly worried — I mean, you know, even though it was clear, he still couldn't believe it. I mean, it was hard for anybody to believe. He was very close to withdrawing that paper. I don't know to what extent I may have helped encourage him not to, but it was one of those things that's very difficult. Now comes the Mu-on (?), see, and well, that can't be another crazy particle — so again, same business all over again. Well, finally, well, here I had to exert Dome pressure to get him to publish. But actually we finally never submitted the paper, unfortunately, until Street and Stevenson came out with their abstract, suggesting the apartic1es, and their abstract was based just firmly on our work. If it hadn't been for our work, they couldn't have — drawn— you know.
Weiner:Your work in prior publications.
Neddermeyer:Yes, right. Right. Right. They did an experiment with counters and — well, I forget now the details of that experiment, but Oppenheimer had taken to Harvard the news of our work, and pushed Street and Stevenson into getting off the dime and publishing something. We were still sitting on our data trying to get it sewed up better.
Weiner:Did they write to you at all prior to their publishing?
Neddermeyer:No, I don't think so.
Weiner:You mean, you saw the abstract as published?
Neddermeyer:No, I don't think, we, no, we didn't know about it. So really you see we lost the priority for that discovery, unfortunately.
Weiner:Well, generally, it's treated as — together.
Neddermeyer:Yes, but really our work was primary. There's no question about it.
Weiner:What I mean is, your work is usually treated as the basic work and then they also mention Street and Stevenson.
Neddermeyer:Usually it's mentioned even-steven, even-Stevenson. Well, of course, it doesn't matter, you know, that's one of those things.
Weiner:May I ask about that. There was a colloquium in the spring before the paper was published, before Anderson went to Stockholm for the Nobel Prize job, there was a colloquium where this was discussed, and this was the first public discussion of it.
Neddermeyer:Oh, Anderson submitted a note to SCIENCE, that was it, which came ahead of — wait a minute — when was that? Was it not published in SCIENCE? Oh, his colloquium was
Weiner:— no, the newspapers had it. Let me tell you about that. The newspapers for example had, on April 25, 1937, and then , that is the LA TIMES, and the PASADENA POST on April 25th, and the headline, "Cosmic Ray Secret Believed Found , Cal Tech Scientists Report Discovery of a New Form of Matter Vital for Physics." Then the Pasadena one — do you want to hear this? "Eyes of the scientific world were fastened on Pasadena's California Institute of Technology last night, as discovery of a new atomic particle by youthful Nobel winner Dr. Carl D. Anderson and Dr. Seth H. Neddermeyer was held by colleagues as one of the most important findings of the country, If they meant of the century, "in the field of physics. The discovery was announced yesterday at Cal Tech. The news that...
Neddermeyer:Whats the date of that?
Weiner:That was April 26th. The discovery was announced, according to this —
Neddermeyer:April 26, 1937.
Weiner:But then it went on to say that "Anderson and Neddermeyer were on the trail of an unknown particle, the news that they were on the trail of an unknown particle became public some months ago, but at that time the exact nature of the particle had not been discovered." Now, it seems to me that that news was the colloquium. Still no paper. There was the colloquium, and then he went to Stockholm and in his Stockholm address there was a sentence, which no one seemed to worry about, statement about it, and then this newspaper account. This is his recollection, and I'm not sure— I know the newspaper clippings, I was the one who found those, but then the paper came out, and the date of that — you said you submitted it in May?
Neddermeyer:Well, by golly, I'm not quite certain now. No, it was published May 15.
Weiner:The NATURE paper was a letter to the editor. Yours was an article, right.
Neddermeyer:The paper, the joint paper, was published in the PHYS REV May 15. Now, there was a brief item in SCIENCE or somewhere I think on Anderson's colloquium, perhaps, that he gave at Pasadena on the occasion — wait, this newspaper item was a preliminary announcement of the results of this paper. Oh, but there was a mention in — see Anderson gave a colloquium at Pasadena on the occasion of the Nobel Prize. I forget if that was before or after he went to Sweden.
Weiner:Well, if it was the same one that he recalled, it would be before.
Neddermeyer:It was before he went to Sweden, and in that seminar he mentioned the new particle.
Weiner:He mentioned to me that was the occasion, with the Nobel Prize. It seems quite logical.
Neddermeyer:I think it was.
Weiner:Then that fits in with the dates of the newspaper clipping. They said "Some months ago.Ē What I want to ask now, about, the sequence is pretty clear, and youíre saying there was no contact with Street and Stevenson, that the data they were sending was published data that you had already published in your joint paper in '36, for example.
Weiner:At this colloquium were some of the theorists present? Was Oppenheimer present, do you recall?
Neddermeyer:No, I don't.
Weiner:Was there any discussion with people on this paper, people at Cal Tech?
Neddermeyer:I don't remember any detailed discussion, but I remember Willie Fowler telling me several years ago that he thought I was crazy At that time — you know, these particles.
Weiner:Iíll ask him. I'm going to see him next week.
Neddermeyer:But I don't remember any particular discussion. But I was plenty worried about the thing. I mean, here were these results, It was very clear, I mean obvious, trivially obvious that something very basic was wrong. I mean, I was worried about the conclusion just as much as Anderson was, but still I was always of course much less conservative than Anderson was, and though I didn't exactly have to beat him to get this published — unfortunately, we just didn't publish it as soon as it should have been published. It was kicking around. You see, even in my thesis work — see, we already were aware of this difficulty, even in 1934, and out of deference to Anderson I said nothing about the particles in my thesis. I mean it was sort of a joint thing. I couldn't say anything about that in my thesis. So I interpreted it, without any equivocation, I interpreted these results as indicating the breakdown of the theory, instead of the presence of new particles, although I really —
Weiner:— was the thesis published as an article?
Neddermeyer:No. Of course, this was an extension of some of the results that were published in the London paper. This doesn't have any of the details of the radiated losses or this doesn't include as extensive results on the energy losses as the thesis.
Weiner:You mentioned that Oppenheimer carried the news to Harvard. It might have been in connection with the Harvard Tercentennary, I'm not sure, but Iíll worry about that later. What I want to ask is the implication that these articles were connected with Yukawa's predictions. Now, had that come up at all when your discussion was going on prior to publication of the paper?
Neddermeyer:We didnít know about Yukala's work. We were talking about particles for a long time, starting from the summer or fall of 1934. I remember distinctly a conversation with Oppenheimer, his remark that if you want an excuse for a new particle, then one exists here's a paper by Yukawa that suggests the possible existence of this particle, mass approximately 200 electron masses, to interpret nuclear forces.
Weiner:When did he say this?
Neddermeyer:This would have been in '35 or '36. Yukawa's paper I guess was 1935, wasn't it? This would have been in '36. early '37.
Weiner:But before you published? Or maybe —
Neddermeyer:Oh yes, before we published, yes. This was when we were batting these things around and going crazy trying to decide.
Weiner:So this was the Oppenheimer statement.
Neddermeyer:Right. Oppie said that to me.
Weiner:What was your response to that?
Neddermeyer:Yeah, it was interesting. It was interesting. Of course, I didn't appreciate the agency of Yukawa's argument about the nuclear forces. So there was no — I donít, I think it's fair to say toot Yukawa's theory was not in any way responsible for our searching for a new particle. I mean, we knew it was there long before. In fact, it may be that Yukawa was partly inspired by our earlier experimental results, see, because there was this very vague remark in the paper. In fact, under a direct question from Jerry Wood, I think Yukawa, when Yukawa was here one time, he indicated that he may have been partly influenced by our earlier measurements. Well, this is a long paragraph. It says" "The absence of a large number of secondaries may indicate that's the scattered electrons," may indicate a difference in character between the high energy particles observed in the cloud chamber and those incoming particles constituting the field sensitive portion of the cosmic ray beam. The data however are preliminary" and the purposes of discussion in this report we have assumed the high energy particles traversing our plates to be practically all electrons. As we show they couldn't have been protons, we're assuming they're electrons. But the indications are that they're something else." It took three years, you know, before we got around to really saying
Weiner:— this was of course not published till about 1935. Yukawa was not at the meeting. Piles, by the way, did the abstract of Yukawa's paper for PHYSICS ABSTRACTS. It came in a batch of things that he was given to abstract, sort of a part time job that he had when he was just settling in England, and I talked with him about that, about his reaction to the paper itself. But it had nothing to do with this. I'm just trying to see if they give the publication data on this. Anyway, that's an interesting sequence to check, it was another problem Iíll get at, but in terms of your own thinking — the first knowledge you had that Yukawa had ideas along these lines was when Oppenheimer mentioned it to you, and you don't recall~ precisely, but that was before the spring of '37 paper was published?
Neddermeyer:Oh yes, I'm sure, yes. That was when we were in the big turmoil over whether to pick up these data and make it plain.
Weiner:Was his position essentially a neutral one on this? Or was he pushing you?
Neddermeyer:Oh, I think he was kind of enthusiastic about the possibility, yes. I think maybe he was even a little — he might have been even a little disgusted with us for not getting it published or something. I don't really know, this is just Of course, from the very beginning he took a very strong interest in this work. But very, very complex, very complex guy. I never could understand him. I never was able to learn theory from him, for example.
Weiner:Did you sit in on any of his seminars?
Neddermeyer:Oh yes. Of course, he emerged as a great teacher. He trained a whole generation, of theoretical physicists.
Weiner:One by one, though.
Weiner:Over a period of time, people, two or three at a time, people that went down on post-docs, people like Thurber and Farini and so forth.
Neddermeyer:Over a long period of years — there is a — well, I shouldn't say a whole generation he trained, but there's a very substantial group of theoreticians who became very influential in theoretical physics, his students primarily.
Weiner:Getting back to the Yukawa business, when this was mentioned do you recall his giving you any confidence in going ahead and publishing, or was the final decision made on the basis of the felt your argument was strengthened on the basis of the evidence?
Neddermeyer:I don't think there was really very much influence. I really Donít think there was. Of course, I was also in this nuclear force business — the curious thing was that these particles that we were finding were so penetrating. Why didn't they interact with nucleii? We didn't explicitly ask this question. It worried Oppenheimer a great deal, and he recognized fairly early the seriousness of the difficulty of reconciling the mu-ons with the Dirac particles, When these particles were so weakly interacting with nucleii. You know, like we have them going through many, many meters of platinum, lead and what not without doing anything as far as nucleii were concerned, just going normal electromagnetic scattering. He recognized this as serious difficulty, that they should be so weakly interacting, and yet being produced so copiously. Yet he didn't quite make the step of suggesting that there was an intermediate particle. This was done first by Weiskopf and Marshak. Made the explicit suggestion that you could understand this if there were first created a strongly interacting particle copiously created which then decayed into these things. So they effectively predicted the pion as the primary particle for the production of muons.
Weiner:It was just when evidence was starting to come in which in fact demonstrated that that was the case. For example Marshak presented the two meson theory about '47, and — at Shelter Island.
Neddermeyer:That was ten years later.
Weiner:Is this what you're referring to, the intermediary?
Neddermeyer:Oh, Oppenheimer recognized that difficulty about the time of of this paper.
Weiner:No, I know that's what you said, but I meant the work that you mentioned Marshak on , wasnít that—
Neddermeyer:— oh, that was later, yes, that was '46 or so, just before the discovery of Powell. Marshal and Weiskopf, and Bethe was also involved.
Weiner:The question comes up, though, how this was treated. For example, wasn't the phrase "Mu mesinĒ used or "Mu mesitron, and that is a particle which is — a question of the lifetime of the particle itself new? and if it's mu maybe it doesn't show these effects. Was that something that was introduced during the period? I wonder if I remember the term that was used.
Neddermeyer:Well, the trouble is of course that we ourselves did not really recognize the full significance of these things by any means.
Weiner:But the major problem, once you published the paper, was to really determine the mass, wasn't it? This was the kind of work that you followed up then.
Neddermeyer:Of course, there's one thing. You see, in One of Anderson's earliest photographs of 1941, there was a track that appeared, highly curved track, very heavily ionized, that couldn't be a proton, couldn't like be an electron, so in a sense just that one picture, the positron, Anderson could have written a paper in 1931 suggesting the existence of particles of a mass of only 200 electron masses. So they go through all this hocus pocus and folderol, through the radiative losses. Then later, I did this experiment with the counter inside of the cloud chamber, to look for particles that ended inside the cloud chamber, and finally got this interesting track where a particle actually went through the counter and did stop at the chamber, and I was able then to make that mass estimate. I made an estimate of 235, and then added all the errors in as bad a way as I could, and estimated 220 it was, plus or minus 35, the mass. I later discovered I'd made a slight mistake in my calculations, and actually the mass I would have given was closer to something like 206, you know -Ė of course with considerable uncertainties.
Weiner:But that was the case with the thickness of the glass of the counter?
Neddermeyer:No, it was that I didn't use quite correct range energy relations. I think a recalculation of that would give much more value to the mass, pretty close to the actual value. another of those things.
Weiner:That was published in '38, I guess, the mass. But that's just By this time, once your paper was published and the Street and Stevenson thing was out, how long a period was there before it became quite clear to everyone that this was the Yuaawa particle, because that's what people felt anyway? Was the interpretation agreed by that time?
Neddermeyer:We were really forced to call it the Yukawa particle, and we — I don't think either of us took Yukawa very seriously. Of course the trouble is that — well, the difficulty of interpreting a particle which showed such fantastic penetrating power as the nuclear force particles. It just didn1t hang together. Oppenheimer was very worried, about that difficulty, still — Oh, we tried to make some crummy argument to force it to fit Yukawats idea. We had some vague ideas — very badly stated, in all these papers, you know, just — Well, we were just thoroughly confused about the whole business, and really didnít understand the theories well enough to think properly about it. (crosstalk) But then the theorists themselves couldn't do much better.
Weiner:That's right, not for a long time. As a matter of fact, they didnít really rethink it until new experimental evidence forced them to.
Neddermeyer:See, it never should have been interpreted at all in terms of the Yukawa particle.
Weiner:Talking about the Yukawa particle, that's a way of giving a name to it, how did you arrive at the name for this?
Neddermeyer:Oh, that was Millikan that made that. Of course, it was very bad etymology. Meson, it might have been, intermediate thing — melitron, well, that's a sort of a bastard usage, intermediate "tron" — meaningless.
Weiner:Following proton —
Neddermeyer:Yes, well, it was like positron, just a simple contraction of positive electron called positron. Mesitron was just a continuation of the same type of thing.
Weiner:That was Millikanís influence.
Neddermeyer:It was Millikan's influence. I had considered proposing the possibility of calling it "pentartons" , the phenomenological name, as a temporary expedient, just to call them that on the phenomenological basis that they were penetrating particles. We didn't know how to properly name them.
Weiner:How would you spell it, pentatron? Penetraon?
Neddermeyer:Pentatron, just a penetrating thing. That didn't take. But as a phenomenological name, until one knew better what terminology to use
Weiner:I noticed in the newspaper story that I quoted before they referred to it as Xparticle which is always good for newspapers. At least it wasnít named at the time that they — Letís talk for a minute, let me just take this beyond it. After the publication in May of '37, then there's the work to measure the mass and that's effectively done. Now, how can you characterize the research program in which you were involved from that time on, from about '38, '37?
Neddermeyer:Oh, we wasted an awful lot of time worrying about new apparatus, larger apparatus to measure, to make measurements on these things and try to understand their properties. That was wholly wasted. We got an old Polsenart (?) magnet and set it up in the laboratory, and built a cloud chamber, try to look at it with mirrors, and but that was a very bad system, very complicated optical system to work with, and by the time that was approaching being ready to try, the war came along. I went to Washington and everything terminated.
Weiner:Did the size of the group grow during this period? The two principals were you and Anderson, but did you get more people working?
Neddermeyer:We had an occasional graduate student working with us.
Weiner:Still just a small team, and you were always a team, the two of you in whatever you tackled. You didn't have any independent lines of research, either of you?
Neddermeyer:No. Except — no, it was a joint thing, very ill-defined. We didn't try to define any particular area for either of us. Just a joint effort.
Weiner:Was it the kind of thing where you were very much in tune and could sort of complete each other's sentences?
Neddermeyer:Yes, sort of, yes. Yes, I think there was a certain amount of psychic connection, actually. I think frequently it was difficult to tell whose idea was whose, or what was — you know.
Weiner:What about the temperament of the two of you? Did that seem to mesh pretty well?
Neddermeyer:Yes, I think so. Yes. There was some, a certain amount of what might have turned into acrimony. It was pretty well under control, I think. You see, I never recognized myself as, you know, particularly qualified for university academic standing, anything of that kind. I was just a sort of a research worker.
Weiner:Did that issue every come up again — we talked about this yesterday, but you had were you seeking toward the end of the period, in the light of these successes, seeking a regular appointment there?
Neddermeyer:No. No. No. I was beginning to worry about what I was going to do in the future, I mean, to some extent. Of course I should really have been getting out. I had considered seriously at various times going into industry, and this is probably what I should have done. After the war, I had the opportunity of going to several different places, like Princeton, Chicago, Cornell — later Stanford — but — and the only reason I went to a university was because it seemed to provide the possibility of doing the kind of research that I was interested in doing. However, I didnít feel up to accepting an appointment at Princeton or Chicago, and when the opportunity came to come here, I decided to come here, because I thought there was the possibility of starting some —
Weiner:Princeton was planning a cosmic ray observatory in the immediate postwar period.
Neddermeyer:Yes, well, Wheeler got a fairly large program going there, really very generously supported, doing work like that. But really not a great deal came out of that program. They did some nice work on observing cosmic ray flux at high altitudes, but they never really did much of anything to elucidate the processes going on.
Weiner:But wouldnít you say that perhaps Wheeler's motivation for that was the same motivation that was expressed elsewhere with large accelerators?
Neddermeyer:Right. He wanted to get to the top of the atmosphere, try to learn something about these processes that were going on, so this program was properly organized. But I donít think they really succeeded in getting down to the thing and telling much about what was going on, except possibly in a very, very indirect way.
Weiner:As a person who worked in the thirties in what was then the highest energy physics available, when you began getting toward the beginning of the war and certainly in the immediate postwar period, where high energy physics emerges as a field with a different kind of definition, that is the large machines, did you feel any interest 1n moving over into that, switching, in other words maintaining your interest in high energy but switching from cosmic rays to ?
Neddermeyer:Oh, I felt that cosmic rays had quite a bit of potential. One could do quite a bit, with the right kind of apparatus. But well, I don't know. I never have had enough energy and drive to really get a program going in the way that was required, to really, reallyÖ
Weiner:Let me ask a couple of questions about Cal Tech and the relations to the other work going on. How much were you informed about the work that Fowler and Lauritsen were doing?
Neddermeyer:Oh, we knew pretty much what was going on. Of course there were colloquia. Lauritsen and Fowler gave colloquia, and there were seminars. We didn't go to their seminars regularly, but we knew what was going on. Anderson and I did some work on induced radioactivity, radioactive products of proton bombardment that they produced in their accelerator. We did a number of experiments which they would bombard a target and then we would take it and tear over to the cloud chamber and slip the target into the cloud chamber, and would record, you know, and look at the momentum distribution of the electrons and positrons coming out. Those measurements were, you know, too sloppy and helter-skelter. We measured a number of these spectra and tested to some extent, got some results that fitted to some extent into the Sargent relation, you know energy and lifetime. But that wasn't very good work. And then we felt that we were kind of intruding on Lauritsen's program, we'd better go back and mind our own business. They had their own interests, you know.
Weiner:Did they have their own cloud chamber?
Neddermeyer:Yes, at that time they developed their own cloud chamber program. One of the first things they did was to look into the gamma~ rays , 16 MEV gamma rays. I forget the reaction. But —
Weiner:— that was the only contact you had of actual experimental work with — collaborative experimental work with nuclear physics per se?
Neddermeyer:Yes, that was a fairly brief thing.
Weiner:When was this?
Neddermeyer:That was probably 1934, something like that.
Weiner:Then you wouldn't participate in the seminars, but in the colloquia, if they had something to say they would say it to the whole group?
Weiner:There were not separate colloquia?
Neddermeyer:Well, they had I think semis, private seminars on their own, in addition to the regular colloquia. Then of course there was a series of meetings on nuclear physics and astro-physics. But it seems to me that was after the war.
Weiner:There were some that Bowen told me about, in the thirties, with Fowler and so on.
Neddermeyer:Yes, I never was in on any of those. I didn't even know they existed.
Weiner:That was more nuclear physics. And when Oppenheimer and his entourage would come down, who would he most strongly interact with the campus?
Neddermeyer:Well, he interacted fairly strongly with Anderson and me for a while, then later most strongly with Lauritsen. He and Lannitsen and Fowler made very close connections, and he contributed very greatly to the development of their understanding of nucleii and nuclear processes and reactions. Lauritsen and he became very close, and Fodxer. They were very closely tied.
Weiner:It seems to me that a good deal of Oppenheimer's work and the work of his students with the experimental data which he needed and was interested in was yours, or was coming out of the kind of work that you were doing.
Neddermeyer:He was very interested in our data.
Weiner:Because he was writing papers on showers and —
Neddermeyer:— yes, he was very interested in the shower problem, for example. The question of interpretation of showers. Well, when the — we succeeded in checking pretty well the theory of the radiative losses with the experiments, then of course it became fairly clear that one could interpret the showers. I remember writing down on the board the basic relation of how the shower develops, that is, an electron produces radiation, radiation produces more pairs and so on, but then the total energy is ultimately dissipated in the form of ionization. So one has effectively an exponential increase in the numbers, as one goes down, then builds up, then terminates, and I wrote these relations down, and I think it had an influence on Oppenheimer, the paper toot he and Carlson wrote. In fact, he dressed this up a little and presented it in the first part of his paper as a very crude That is, qualitative representation of the trend of a shower. There was, the the penetration then goes like logarithm of the energy more or less. But then the full diffusion theory shows how it is spread out, you know, instead of just coming up and just sharply terminating, it has a long tail, which is a complicated statistical problem, and various solutions were worked out for this. Finally there are probably pretty good solutions that exist, that were done with the help of computers.
Weiner:That's another question, about the reactions of the overall physics scene. Just taking the case of fission, of how the news reached you, how you learned of it there, what the response was.
Neddermeyer:It was kind of interesting. I remember quite early, after that came out, Oppenheimer immediately got interested in the question of nuclear energy, and I remember his saying, "Well, gee, somebody ought to get some of this stuff and put it together in the field and see what happens. But then of course later he got this group of his former students together and really dug into this problem in a thorough-going highbrow way, and worked out the entire theory. So this provided the essential quantitative interpretation of what actually happened.
Weiner:How did you hear about fission? Did you hear it as a news item or word of mouth, what?
Neddermeyer:I guess it was as a news item, but I don't remember. I don't remember.
Weiner:Let's decide now, whether, for the remaining time — what we can most productively talk about. Let me just talk about the thirties for a minute. Weíve covered the main trend of things. There are loads of things of course we didn't cover, but I don't know at the moment anything — any clever question I can ask which would open up a whole new field, unless you have something you want to bring up on that?
Neddermeyer:Well, of course, looking back on the past, as far as I'm concerned, it's a little bit depressing, because I didn't do nearly what I might have done, you know, if ltd been a little bit more perceptive and a little bit more energetic and pushed myself a little harder. But on the other hand, well, I mean, what happened is just, with me, is just the consequence of my own characteristics and that's that, Somebody else might have done things differently. I remember at one stage or another, being very, very, very excited about all of the business, because, well, when I first went into physics I think I had in the back of my mind so vague idea about, well, philosophical questions — just what is the universe like anyway? And physics seemed to be the discipline that offered the prospect of getting really exciting fundamental answers. That was to some extent borne out in this series of incidents that happened when I was at Pasadena. Of course my involvement was strictly accidental. I mean, I decided to go down there to study astrophysics, and instead I got involved in cosmic rays, which was very exciting. The positron came along. I was involved in that. The meson and so forth. But then, the trouble was, I just got lost in the — I always wanted very much to get a mastery of some of the theoretical ideas, but I always found them completely illusive. I never could really master the theory even to the point where I could use it, you know, adequately for calculations in depth. I could use a formula, but as far as having really an adequate mastery of the theory, really to use it to make calculations, full dress calculations about a problem, I just simply wasn't capable of doing it. I realize now, in different circumstances, I might have been able to learn this. I don't know. One doesn't have to be a hyper-genius in order to achieve a much greater mastery of those things than I ever did. And I'm not exactly stupid, really. But frequently I guess live behaved as if I were stupid, perhaps. But still at the same time, all of this — I don't know to what extent it was a failure to master these theoretical ideas. At the same time, even with all this physics, this - - it's kind of unsatisfying from a philosophical or metaphysical point of view. And I've always been groping around for something deeper. I'm not religious particularly. I donít feel that the concept of God doesn't help me much. You know, I'm interested in it from an intellectual point of view, questions — Well, when I was a graduate student — oh, there are a couple of events I might tell about that might be interesting. When I was a graduate student, well, I was always somewhat interested in the kind of questions that are involved in parapsychology. When this started, I don't know. Some of the talk when I was a kid kind of suggested things that were strange, and very few actual events — mental or psychic events that I experienced myself— well, there have been very few in all that are just vaguely suggestive of something very interesting that ought to be explored, maybe. Well, when I was a graduate student at Tech there was an engineer, not on the staff, he was in a center that was just around there, I don't know whether he was partly supported by the Institute or not but he was partly on his own as an inventor or designer. He was then on the third floor where our apparatus was, in the aeronautics building. We got to talking about things like this, and he knew a psychiatrist in San Diego who was interested in things like this, and so we decided to arrange a meeting, to get her to come up and talk to as about some of the strange things she had been interested in. So we arranged a meeting. It was either at Carmen's house or his sister's house, and there were Carl Henderson and John Strong and I, and this fellow Van Doren, and Von Carmon, and I guess that was the extent of the group. This gal had been using — she was a psychiatrist — had been using automatic writing to make psychoanalyses of children, trying to use it as a means for bringing out things buried in the subconscious and so on. Well, you know what automatic writing is, I don't need to describe it. It was a phenomenon that many people used to relate to communication with the dead, for example, you know, you get the feeling — you know. But she regarded it as a communication with one's unconscious mind or subconscious mind. But she also had done some experiments in telepathy which were quite interesting, long range experiments with another person, and they'd make a time schedule, each would do something and then write about it and the other would do something and write about it, and each would try to see what the other had done, and this information would cross in the mail so that they would have a two way check at least — not adequate to convince an outside skeptic, but at least they could check each other's honesty. These were quite impressive, you know, in sensing in quite some detail events occurring a distance like from California to Alaska, and I was amused at Von Carmon — I would have expected that he would be you know, a very hard skeptic about these things, but Von Carmon apparently accepted these things as normal. He said, Mind is outside of Space. I thought this was — a certain amusing way of representing, you know, our ignorance about these things. I thought it was a fairly perceptive remark and kind of interesting, you know, for a hardboiled engineer theoretician, which is what Von Carmon was. Well, she tried to get us to do automatic writing and of course none of us could. I picked it up later, practiced for a couple of weeks or so and I finally got so it was coming through, but you know, mostly garbage. Then finally it got to the point where I felt as though I were communicating with another personality, so I'd make a program of writing a question, you know, and writing something out, mostly garbage, but then sometimes kind of startling things would happen. I remember one time, I was pressing for something, for an answer, and in comes, "When are you going to quit pestering me?" Things like that. Well, it went on, you know. It was as though there were some personality that existed in the last century or something like that, you know, some crazy thing. I didn't know what to make of it. Finally I began to get a feeling that I was maybe going to go into a trance or something, and then I felt as if maybe I had better quit this, because I began to be afraid that it might, you know, interfere with my normal development as a rational scientist. So I just stopped it cold.
Weiner:About when, mid-thirties?
Neddermeyer:I think that was before my degree. I remember wondering whether maybe this helped me to some extent, you know, shook up my mind in a way that helped me a little bit in passing the exam, which I was by no means sure I would pass, but I actually passed it fairly well. Well, then I never did anything. I remember being very interested in Rhine's work and hearing about that. Then I remember a conversation I had with a colleague at Los Alamos just after the war, 146, or late '45, early '46, whenever it was, just before we left Los Alamos. We were just talking about the future of physics and what was worthwhile and what wasn't, and I got a reaction, kind of amused incredulity from him, when I told him I thought the most important problem for scientists to work on was the mind problem. Even though I didn't have the foggiest idea how to go about it, and of course I can't even define it. Not in any proper sense, you know. But what I mean is, the problem of consciousness, awareness, consciousness of oneself as an individual, and also these strange remote communications between minds. Well, I never really studied the subject seriously, that work. In fact, all the years I've been here, 25 years that I've been here, I never really did any reading in the field. But recently I began digging into it some more, and I've become rather excited about it, and I have a graduate student who's working on a thesis. Hopefully he will get a degree in physics in the field of para-physics or parapsychology.
Weiner:Do you think there'll be some resistance to that on the part of?
Neddermeyer:— there has been. There has been some resistance. For example, he has the largest PhD committee that has ever been appointed in the physics department. It happens to be exactly the size of my own PhD committee, seven people — the normal number is five. He has two extra hard skeptics on this committee of his.
Weiner:I'd love to hear how that comes out. When is he scheduled for it?
Neddermeyer:Well, he has another year yet. Heís scheduled to give a talk to his committee on the 23rd of June. And it's a difficult experiment, very hard to know how to interpret it. So far, it's an attempt to check and extend some ether work that's been done, namely, to predict the outcome of a random number generator, that generates numbers, 1,2,3,4, 1,2,3,4 like this Ė you push a button and it makes a prediction en which channel you intended to end on, and the thing that terminates it is a random precess, namely, the discharge of a geiger counter determines which one it ends on. New, the thing is that some people seem to be able to get statistically significant scores yet it is random, and the question isÖ
Weiner:You were telling me about what the nature of the experiment was. The point is, that it isn't the kind of thing that a normal PhD committee in physics is able to evaluate in terms of the kinds of criteria one is used to.
Neddermeyer:Yes. New, of course, nominally the idea is to find ways of dragging science into this, you knew to try to either extend science to encompass some basis for understanding these things, or maybe discover buried in existing physics things that might be excavated by reinterpretation that could have some relevance. See, the problems are very, very deep, and of course, the people that should be working on it are the top notch scientists, not clods like me. But you see, I believe in it. I'm convinced that there's something terribly exciting and terribly fundamental that's involved, and my neck is out. I've effectively quit the field of particle physics and, for whatever it's worth, Iím trying to do what I can to bring this field out into the open. You see, now, so the last year I've been running a seminar, two hours a week, two hour session every week, with a few students trying to dig into this field, trying to get some familiarity with what's been done, trying to find the most critical, the most important things insofar as possible. It's just been a helter-skelter, pick and choose, trying to find the parts that really look exciting from the point of view of trying to drag science into it, but in general also just getting a broad enough view of the field so that one can have some feeling that one knows about the — all of the things which — a large enough sample of the field so it may have some chance of encompassing all of the really fundamental underlying factors, so you pick and choose and you deliberately ignore some things as maybe not having the fundamental factors that are already contained in the sample you already have, so at least you restrict yourself to some extent. In the course of this seminar, all that's happened is that my ideas have just become more and more radical, and I am feeling more and more strongly that we have to recognize even totally subjective experiences as elements of a wider reality. We have to redefine what we mean by reality, in a certain sense, if you like. In other words, you look at this field. You try to see what you can reasonably accept as — on the basis that intelligent critical people have studied and reported on it. It is necessary to do this, because if you adopted what most people would regard as a properly scientifically critical attitude, you'll spend the rest of your life trying to convince yourself of the existence of this or that and never get anywhere. So my view is to do as well as I can in picking a sample of various parts of this field, and accepting it by hypothesis for the purpose of thinking and hatching up new experiments. So when I say that I accept a large range of what we would call purely subjective experiences as part of an enlarged reality, I am saying that I believe that many of these things will ultimately be related by more or less normal scientific methods to the conventional reality that we think about in physics, you see. And this really isn't going so much farther off the track than we do in physics. The thing that we call reality in physics, we don't know what reality is in physics. It's by definition got something to do with experiment making and interpretation. The world of physics is becoming more and more mental, more and more purely mental. You do experiments, but what about this ordinary so called objective world? That can be illusory as well as the other aspect, as well as the inner aspect.
I stop at this point only because I'm overdue, but let's just say for the record that in a couple of years I'd like to check back with you on this, just for curiosity see how far you've gotten with it.
Session I | Session II