Notice: We are in the process of migrating Oral History Interview metadata to this new version of our website.
During this migration, the following fields associated with interviews may be incomplete: Institutions, Additional Persons, and Subjects. Our Browse Subjects feature is also affected by this migration.
We encourage researchers to utilize the full-text search on this page to navigate our oral histories or to use our catalog to locate oral history interviews by keyword.
Please contact [email protected] with any feedback.
This transcript may not be quoted, reproduced or redistributed in whole or in part by any means except with the written permission of the American Institute of Physics.
This transcript is based on a tape-recorded interview deposited at the Center for History of Physics of the American Institute of Physics. The AIP's interviews have generally been transcribed from tape, edited by the interviewer for clarity, and then further edited by the interviewee. If this interview is important to you, you should consult earlier versions of the transcript or listen to the original tape. For many interviews, the AIP retains substantial files with further information about the interviewee and the interview itself. Please contact us for information about accessing these materials.
Please bear in mind that: 1) This material is a transcript of the spoken word rather than a literary product; 2) An interview must be read with the awareness that different people's memories about an event will often differ, and that memories can change with time for many reasons including subsequent experiences, interactions with others, and one's feelings about an event. Disclaimer: This transcript was scanned from a typescript, introducing occasional spelling errors. The original typescript is available.
In footnotes or endnotes please cite AIP interviews like this:
Interview of Willard Libby by Greg Marlowe on 1979 April 16, Niels Bohr Library & Archives, American Institute of Physics, College Park, MD USA, www.aip.org/history-programs/niels-bohr-library/oral-histories/4743-2
For multiple citations, "AIP" is the preferred abbreviation for the location.
This interview is concerned primarily with two periods in the life of Libby (1927-1940 and 1945-1954). After briefly discussing his early life and education, considerable attention is focused upon Libby's undergraduate, graduate, and post-graduate years (1927-1940) at the University of California, Berkeley. Major topics included are: growth of Berkeley science; Gilbert Lewis, Wendell Latimer and Ernest Lawrence; Libby's development of low-level counters; radiochemistry and discovery of isotopes; cross-disciplinary collaboration; Libby's interest in carbon-14; association with Samuel Ruben and Martin Kamen; hot atom chemistry and nuclear isomerism; Libby's experiences at Princeton during 1940-1941 (hot atom chemistry, development of heterogeneous catalysis and research on tritium) and his work on the chemistry of the diffusion process during WWII at Columbia University (Manhattan Project) are mentioned; the other major portion of the interview concentrates on Libby's development of the radiocarbon dating technique at the University of Chicago (1945-1954); special attention is devoted to: measurement of half-life of carbon-14; importance to Libby of Harold Urey; secrecy policy; collaboration with Aristid von Grosse, James Arnold and Ernest Anderson; improved counting technologies; first contacts with archaeologists; Viking Fund and cross-disciplinary collaboration; communicating ideas; Sunshine Project and fallout; AEC appointment; concluding remarks.
Dr. Libby, toward the end of our last conversation, you were discussing the development of the boron-tri-fluoride counter, the purpose of which is to detect neutrons. In what year did you develop that counter?
I think it was '37.
Who else besides yourself worked on it? Was that a project of both yourself and Ruben?
No that I did by myself.
You mentioned last time about Serge Korff's work on neutrons in New York. Was there any direct collaboration between Korff and you?
No, very strange. We'd never met and yet our paths ran very parallel courses.
Can you tell me what role, if any, did the development and use of the boron-tri-fluoride counter has in relation to yours and Ruben's research on carbon-14 at Berkeley?
Well, the BF3 counter was a very good neutron detector, and we knew we'd have to have neutrons to make carbon-14. So in that indirect way, it had something to do with it.
You mentioned before that Samuel Ruben hoped to find a longer lived isotope, which we now know to be carbon-14, for his work on photosynthesis.
Well, that was his research thesis, which I gave him.
You mentioned, on the other hand, that your interests were more in terms of applications of carbon-14 in general biology and organic chemistry. Could you explain a little more what you mean by that? Could you give some examples of the problems in those two areas that you hoped to attack?
Well, you see, we hadn't discovered radiocarbon dating. And we thought the half-life was about three months. Obviously, radiocarbon dating with a three month isotope wouldn't be very useful. So it didn't really press home. It was kind of a natural division of labor between the physicists and the chemists, and I was on the chemists' side. Sam was leaning towards the physics side. But I won him. He got over onto the chemists' side, and he was doing mainly work on photosynthesis, real chemical problems.
Now, after Carbon-14 was discovered by Ruben and Kamen in February 1940, did you begin to apply Carbon-14 to your own research, to any problems in general biology or chemistry?
Well, I was on sabbatical leave in Princeton, and had no real opportunity to do anything; then came Pearl Harbor. That settled it, till I went to Chicago in the fall of '45.
Ok. You say by February of 1940 you were already in Princeton?
No. I got there in August, I believe it was.
At that time, besides the very important use of your screen wall counter to detect Carbon-14, did you have any other direct involvement in their work by February of 1940, in terms of isolating Carbon-14? Or was that pretty much Ruben?
Well, we were all caught up in the matter of the war. Nobody was doing much in the way of abstract research. And even though I was in Princeton on sabbatical, a Guggenheim Fellow, I had plenty of other things to think about.
Now, when Ruben and Kamen discovered Carbon-14, they posted a half-life of approximately 25,000 years. How did they come up with that figure?
Well, it was a very inaccurate one. And the first thing I did when I got to Chicago was try to determine the half-life. See, this was the real remarkable development. It's still not very well understood. We expected the half-life to be three months.
Do you remember how they came up with a figure of 25,000 years?
I remember very well. My problem is to tell you. You take a beam, and you bombard a target, and you calculate how many you should have produced, and you compare it with the number counts you get. That gives you the half-life. Now, the uncertainties here are very large. That is, uncertainties in the counting, the uncertainty in the beam intensity, and the uncertainties in the cross-section. That is, one deuteron hitting one Carbon-13, what's the chance it will make C-14? They had no idea what that was. So I suspected that the half-life was different from 25,000 years. Fortunately several other people went to work on the problem, and I wasn't the only one, and so we struck an average, and that average came out 5568 years, which still is the basis for radiocarbon dates because we got launched on that. The correct half-life, more accurate one, is 3 percent larger, 5730 years.
In 1940 you received a Guggenheim Fellowship, which a short time later, in August, took you to Princeton. Why did you apply for that sabbatical leave?
Well, I'd been teaching at Berkeley for seven years. I'd been an undergraduate and a graduate student. So it was time I took a look around. Result, I never came back to Berkeley.
But at that time your intention was just to take a sabbatical leave and then return to Berkeley.
What did you do while at Princeton? Were you able to engage in any research?
Yes. I did quite a number of things. I suppose the most important thing I did was to get acquainted with heterogeneous catalysis. I have to say a little bit about what that is. Certain materials, usually solids, can make chemical reactions proceed. For example, if you take powdered platinum, and there's a cigarette lighter made out of this powdered platinum, a very small amount of platinum, you blow alcohol, ethanol or methanol in the air — it'll light. You have a cigarette lighter which has a cotton plug soaked with alcohol, and that comes out, hits the air, you don't have to strike it or anything. We have platinum catalysts in the auto exhausts. They're not working very well but they're there. Platinum is an excellent catalyst. Now, there are many others, palladium — the heart of the oil business is heterogeneous catalysis. Now, most chemists never have an opportunity to learn that. There was nobody at Berkeley to teach me that. I learned it at Princeton, from Dr. (Hugh S.) Taylor — the head of the chemistry department. At the same time, I was teaching them isotope work. One of my senior students at Berkeley (James Black) had gone to Princeton as a graduate student, and so I helped him with his thesis, which was the use of tritium to measure the solubility of benzene in water. Tritium is an isotope of hydrogen. At that time I think I was the only person who could measure tritium.
Then your interest in tritium, and what ultimately came to be tritium dating, and certainly catalytic research, goes back at least to Princeton.
Yes, that's always true. You see a variegated career such as mine, and you'll see that they all had long time roots.
If we could go back to Berkeley a little bit and evaluate it, looking back, those 13 years at Berkeley, 1927-40, in general, if you can, how do you reflect on that period? For example, how did it mold your subsequent scientific career?
Well, it was the most thrilling productive experience of my whole life.
We were talking about Berkeley.
Well, in my opinion, the Berkeley of that period was the finest school in the world. It was by far the best. The reason I didn't return to Berkeley after the war was that I had a magnificent offer from the University of Chicago. But I've never ceased to admire the quality of that period in the Berkeley history.
We have discussed previously the idea that cross disciplinary research and cooperation was both encouraged and readily accepted at Berkeley. Now, could you analyze for me the impact of having participated in such endeavors? For example, working with biologists, and your later work in carbon dating, which also required cooperation among various disciplines? In other words, do you think you were more inclined to venture into other disciplines because of your experience at Berkeley?
I think so. I had every encouragement to be interested in other things, particularly physics and math, but there was the general attitude there that the university was one entity, and we all were part of it. We all belonged to the Faculty Club and would go there and eat. We didn't have sequestered tables particularly. All my life has been interdisciplinary.
While on the topic of crossing the boundaries of disciplines was there anything inherent in the idea or conception or practice of chemistry at Berkeley which facilitated the practice of such activities? For example, in physical chemistry, you covered everything from nuclear physics to biochemistry. What was it about physical chemistry, particularly at Berkeley, that would have encouraged one to range?
Well, we stuck very close to the fundamental laws. We probably had a better knowledge of those laws than most other places. We were all expert in thermodynamics. There are a lot of schools that never teach thermodynamics properly.
That was primarily because of Gilbert Lewis, the emphasis on thermodynamics?
He ran the place. He was very open-minded. Even in the sixties he accepted the notion that isotopes and radio chemistry was chemistry. Very open minded.
I think it would be fair to say, correct me if I'm wrong, that three men in particular at Berkeley influenced you more than others, and that would probably be Gilbert Lewis, Wendell Latimer, and Ernest Lawrence.
Starting with Lewis, could you please tell me what you remember most about them and what specific effect each man had on your scientific life?
Well, the thing I remember most about Gilbert is that — his brilliance, incisiveness, his reasoning, and his contact with recent research. See, many people in their middle age lose touch with the literature. He didn't. He was fantastic. When it turned out that not only was he in touch with chemistry, but many other fields as well — I remember, in 1931, he gave a lecture at the meeting of the American Philosophical Society in Berkeley, and he read a paper, on philosophy; a very important paper. We had just discovered — I say, we, the scientists of the world, had just discovered a method of testing for identity; a rigorous method of testing for identity. His paper was on that subject. I guess we did it at Berkeley, actually — William Giauque — the oxygen molecule. Showing that half the rotational lines in the absorption are missing, if you had 0-16 0-16, and when you had 0-16 0-17, the other half appeared. This had been predicted by the quantum mechanics, but nobody had seen it. He gave this learned paper on the philosophical implications of this discovery. You could tell now two identical things. You could tell it unfailingly. He was a great authority in English literature, wrote beautifully, spoke beautifully. He was a very famous man among scientists, but practically unknown to the average person. He knew the implications of what he was doing when he hired Ernest Lawrence. See, there wasn't an appointment in the whole campus that he didn't have a look at.
Science or otherwise?
Well, I don't know about otherwise, but science, yes.
How about Wendell Latimer?
Well, he was an extremely brilliant guy, but he didn't have Lewis's breadth or grasp of the whole situation. He was a very fine inorganic chemist, physical chemist. I still use the book he wrote 30, 40 years ago. It's the best reference on thermodynamics. He was a good teacher. But best of all, he let me do whatever I wanted to.
Would you say that was the most visible impact he left on you, giving you the ability to range far and wide?
We didn't lack for graduate students. He let me be there. Those were tough days. To get a TA-ship — it was rough.
Tell me a little bit about the nature of the relationship with Ernest Lawrence and his impact. What did Lawrence teach you?
Well, Ernest was younger than Wendell. He was an outgoing fellow. He'd tell anybody about his cyclotron idea — just kept barreling ahead doing it. He wasn't jealous of his ideas at all; large person. I think it was marvelous when Lewis gave Ernest his first drop of heavy water, to put in his cyclotron. Science really took a great leap forward (to speak Chinese) at that point.
I assume it then took a very long time to produce small amounts of heavy water.
It was the first heavy water ever produced. Harold Urey discovered heavy water, in the sense that he discovered deuterium spectroscopically. But Lewis isolated it, and the first heavy water ever produced, Lewis produced. And he gave half of it to a mouse, to see if it would kill him and half to Ernest Lawrence. I thought that was an equal division.
How about Lawrence's consummate skills as a grants-man? He went after money to build a cyclotron. He knew about big science. Did it have an impact on you?
Ernest invented big science. He literally did. He used to tell us, he said, "Now, look, if you've got a good idea, we'll find the money." That was his philosophy. He did, too which was, of course, absolutely perfect for training us for the Manhattan District work. It was only four or five years until we were in the middle of World War II, when we made the atomic bomb. It couldn't have been made without Ernest.
Ok. Your stay at Princeton was cut short by the Japanese bombing of Pearl Harbor. What happened to you next after the bombing of Pearl Harbor?
Well, we stayed at Princeton for a couple of months, but I commuted every day to New York, worked in New York at Columbia, on the gaseous diffusion project under Dr. Urey.
How is it you came to work on that project? Were you invited by somebody or did you volunteer your services?
Well, December 8, 1941, I went up to Columbia, walked into Dr. Urey's office and said, ''Here I am, what can I do?" He said, "We have a big job, chemistry of diffusion plant." I spent four years on it.
On that subject, can you tell me, while working on the project, a little more about your scientific and administrative responsibilities, working on gaseous diffusion?
My problem was mainly to do the chemistry. There were droves, hundreds, even thousands of people working on the engineering aspects. But the chemistry of that problem was kind of central. UF6 is a very corrosive gas, and the holes are very tiny in the barrier, and if you start corroding them, you plug them up. The other thing is, the output — you feed about two tons a day and you get out about two pounds. So if you waste too much of it in corroding, your product goes. So we had very strict limits on the amount of corrosion we could allow. And UF6, it's a gas, but at room temperature its vapor pressure is finite, so they wanted to run the plant hot. If you run the plant hot, the corrosion rate goes up. That's where I came in.
How about in terms of your administrative responsibilities? Were you in charge of a particular group?
I was in charge of about 140 people. It got pretty heavy, and Dr. Urey appointed a friend of mine, Paul Emmett, to be in charge, so I could — well, whatever reason. Paul left about a year and a half later. He saw we were going to win and he had other things to do.
Can you tell me a little bit about the nature of your relationship with Harold Urey?
Well, sure. He was a very outgoing person, extremely intelligent, very influential and somewhat cantankerous — I had problems because he was arguing with some of my other colleagues. But he was the big boss, and he always won the argument. But we were mainly concerned with getting the job done. He backed me 100 percent. Of all the things I've done in my long life, I'm proudest of that chemistry of the diffusion plant. I'm just damn sorry that it's never been published. I guess it won't be for some time.
This may be a bit redundant, but your participation in the Manhattan Project — what do you remember most about it?
Well, the incredible ability of Groves to manage. Here's this general officer, an engineering officer, didn't know a bean about science, but the way he could do it. He used the scientists as advisors and he listened to them. But there was nothing democratic about Leslie Groves. He ran it. Every once in a while he'd send somebody to Burma or some far-away place, just to give an example. He got it done; incredible. I don't really know — he became a vice president, I think it was, of Remington Rand after the war, and I suspect he earned his money very well. Good administrator, very keen. That was one thing, and the other thing was the enormous collection of talent. In my 140 people I had 25 of the leading young chemists working for me. After the war I was offered jobs by industry. I told one of them, "If you will take 25 others I'll come." They turned it down. And they were wrong. These 25 went on and they're running American chemical industry and education.
Can you give me examples of a few individuals?
I'd prefer not to.
Ok. What effect did that experience of working on the Manhattan Project have on your subsequent attitude or ideas about what ought to be the nature of the relationship between scientific research and the federal government?
Well, I'm all for it. See, I worked at Berkeley when we had one telephone. Now I had six secretaries. Nevertheless, though we made rapid progress, there is a place for the Berkeley, the 1930's Berkeley level of effort, where you have to be thinking, else you can't do anything. One of my best friends at Berkeley was the glass blower. Another one was the head mechanic. If you're going to do anything in science, you have to have these skills. You have to have electronics now and eventually some other things.
As you know, toward the end of the war, some scientists, especially the Metallurgical Lab at University of Chicago, began to discuss the immediate as well as the long term implications of use of nuclear weapons. Did similar discussions, formal or informal, occur at Columbia?
No. It may have happened occasionally, but not –
Did you then have any particular views about the propriety or advisability of scientists actively participating in matters of public policy?
I thought they should. But they ought to not just shoot from the hip. They ought to know what they're talking about.
Were you and some of your colleagues aware of those discussions that were going on at the Met Lab?
Maybe some of them were, but I wasn't.
Obviously you were a very busy person during the war, but at any time, did you ever have time to sit back and contemplate or think about the future implications of your Berkeley research, particularly as it might relate to Carbon-14?
Oh sure. I was hoping to get the war over quick. We did, pretty quickly.
After the atomic bombings of Hiroshima and Nagasaki, at that time then did you and any of your colleagues talk about those events. What do you recall?
Oh, of course. See, Groves kept the thing so compartmentalized that practically the first thing we knew was the newspaper report. We'd known some other things, but more by the grapevine, like the July 16 test at Alamogordo. The papers reported, "Giant Ammunition Dump Blows Up." We didn't believe that. But he was a very wise man. He kept it so divided, and (Klaus) Fuchs got all the design secrets and gave them to the Russians, but he didn't get my barrier because of this compartmentalization. Couldn't get in. He tried. But in reverse, we didn't have all that much information ourselves. There's only one way to keep a secret and that is, don't repeat it.
After the hostilities ended, did you consider returning to Berkeley? Was it in your mind before?
Oh, sure. I was on leave from Berkeley.
Can you tell me then, why did you go to the University of Chicago after the war?
Well, you see, I'd worked with Urey and Fermi. They offered me twice the salary I would have gotten at Berkeley. And I'd been at Berkeley a very long time. On balance, I decided to do it; heart wrenching decision. Probably the wisest decision I ever made.
What was about to happen at the end of the war? What was happening at the University of Chicago, in the so-called migration of atomic scientists?
Well, (Robert) Hutchins decided to make it the atomic center. It's that simple. He got fired for doing it. But he did it.
Why was he fired?
Spending money. Probably the wisest decision he ever made.
The Institute for Nuclear Studies — what was its purpose?
Well, to further nuclear studies. We had the Institute for Metals, Institute for Radio Biology, the Institute for Nuclear Studies, and then the regular departments. I was a member of both Nuclear Studies and Chemistry.
Who was in charge of that program? Who was the departmental or Institute head?
Well, there were two heads. There was the head of the Institute and the head of the department. See, the Institute was interdisciplinary, so there would be several departments associated with the Institute. The first director of the Institute was Samuel Allison — A good solid type. Of course, (Enrico) Fermi really ran everything. But even in such a friendly atmosphere, I didn't dare tell them about my radiocarbon dating. They would think, wow, this guy who did the chemistry of diffusion; couldn't he have worked on something important? They'd hired me. I was the youngest full professor in that whole crowd, and they expected (results) — so I didn't dare tell them what I was doing.
When you decided to take up your research and residence at University of Chicago, had you already outlined for yourself in general a research program? ·
Yes. First, we'd measured the half-life. There was a terrible block on the counters, to make a counter that was sensitive enough. And we got around that by leaning on my friend (Aristid von) Grosse to use his isotope enrichment equipment, but that's good only for one or two runs. It doesn't give you carbon dating. Fortunately we were able to get through that block, which led to a whole new method of low level measurements, which is now world wide
While on the topic of institutional attitudes regarding research policies, could you compare the research environment, particularly as related to encouragement, or lack of it, to cross-disciplinary studies. You mentioned that the Institute was cross-disciplinary in nature. Compare the University of Chicago at that time to Berkeley.
They were comparable. Of course, I had a much higher position at Chicago than I had at Berkeley. I was an assistant, then associate professor at Berkeley. See, when I went to Chicago in '45 I was only 37. And I was a full professor. As I say, they were all watching what I was going to do and I wouldn't tell them.
How extensive was the interchange of ideas between, in the Institute, when you had people of various disciplines? How extensive was the interchange of ideas?
Very good as far as they could communicate. But I just told you twice that I didn't tell them what I was doing.
I meant in general. For example, how did people communicate?
Well, we had these seminars, weekly seminars where people would come. The chairman, Joe Mayer, would point to somebody more or less at random, to stand up and tell what he had to say. It was very good.
Were these weekly seminars attended, for example, by biochemists, physical chemists, and nuclear chemists?
Yes. See, the makeup of the faculty of the Institute was very broad.
And were these discussions essentially only on scientific matters; were politics or philosophy discussed?
OK. When you were hired as a full professor, what balance were you expected to maintain between teaching and research duties? Did that change over time?
I had to teach about one course a quarter. But I had a lot of graduate students. See, in my total career I've had 101 PhD's. That's a lot of them. And you know I've been a busy cookie. Only two of them were working on radiocarbon dating. The rest of them were working on a zillion other problems.
Now, your teaching duties, were they essentially in terms of small seminars, or lecture classes?
And did you look forward to teaching as somewhat of a respite, so to speak, from your research activities? Did you enjoy teaching?
I enjoyed teaching; mainly a matter of my hunting for talent. I always chose the honors classes, the best students. When I came to UCLA I did the same thing. Taught honors freshmen for ten years, and half of them became doctors, either MD's or PhD's.
You suggested in the past that you conceived the actual idea of carbon dating at University of Chicago.
Well, I would say it was during World War II. The idea of radiocarbon dating is so simple. As soon as I read Korff's paper, where he'd found neutrons in the cosmic rays, that's carbon dating. So it was all a question of getting your ducks in a row and testing it out.
So you would say it was definitely during the war. The reason I ask, Theodore Berland said one time that you were sitting in your chair at the University of Chicago in the fall of 1945 and the idea came to you. It wasn't that way?
Well, I think he overstressed it.
I see. If the idea was so simple, why, then, (obviously you were working on those isotopic studies and Ruben and Kamen had discovered Carbon-14) but nevertheless, if the idea was so simple, why do you think it was W. F. Libby, and not someone else, who conceived the idea?
Well, there's a fundamental difficulty there. Carbon dating requires you to think of the world as being one system. And… Consider the propositions, simple as they are, but they involve this assumption of worldwide mixing. That was quite a block. Here I was talking about the ocean, I mean the entire ocean mass, the entire biosphere, the entire atmosphere, as though it were in my test tube. I think perhaps that was the block. Once you get over that, the whole carbon dating thing falls into place.
And you had hurdled that block, so to speak, sometime during World War II? Did you finally put it all together one day, or was it something you just gradually pieced together?
Well, over a period of time, I began to understand the mixing problem. You see if there had been poor mixing, carbon dating wouldn't be possible. You'd have had to know the whole itinerary of the subject, where he'd been, what he'd eaten, and all that. Now, it's turned out now that we go back and we can use carbon dates to elucidate the mixing pattern.
I have a kind of a long question here for you. You suggested previously that the idea of dating history with cosmic rays was so to speak, rather unconventional, to say the least. Now, at the time that you were working on this, Harold Urey was conducting research on isotope thermometry. In other words, he was developing an oxygen isotope for measuring temperatures and measuring times. Now, that too, for some, would be a rather odd undertaking for a chemist. Would you say that the combination of Urey's presence at the University of Chicago, and the fact that he was working on a rather unusual project — did that provide you with psychological support?
It helped me a lot. And of course, I was kind of his protégé, you see. I never told him what I was up to. But he got the idea very quickly; he was all for it.
The fact, then, that he was pursuing a similarly unconventional kind of research encouraged you?
Sure. Well, Sam Allison, director, said, "Our research is to study the color of butterfly wings." These are the guys who made bombs. But I still didn't think they would believe what I was saying. See, I was pretty damn sure it was going to work, or else I wouldn't have bet my career on it.
You decided to pursue this line of investigation in secrecy, but your main motivation was not so much a fear of being anticipated. What then, was the reason for the secrecy?
— the road blocks. Look, I had to have a laboratory. I had to have certain minimal funds. I did the whole radiocarbon on $2500; can't even wipe your nose on $2500 today. Of course, I had my salary and I had the lab. But for explicit money, it was $2500. The dean gave it to me when I went to him and I said, "Now, look you've hired a young full professor. Give me $2500." ''Here it is.'' The next money I got was after the announcement of the discovery. Then I got money.
Are you inclined to think that had you come to him and said, "I have this idea of dating through carbon —"
— I wouldn't have got a dime.
So another reason would have been very practical, that you might not have been funded for this.
You were now at the University of Chicago, what was your first task and what technical facilities did you have available to undertake your C-14 research?
Well, see, I had a lot of graduate students working on other problems in chemistry and I'm purposely leaving that out. But my first one was the half-life. Because I didn't think the 25,000 (years) figure was — plus or minus 10,000, maybe 15,000 — It turned out to be, plus or minus 20,000.
Can you tell me what was the actual process you followed? Did you have to produce some Carbon-14? What did you do in order to measure it?
By that time we had reactor C-14, the AEC had it.
Many places. As I recall, our main source was Oak Ridge. But we had it so hot that we could — Mark Ingram actually measured on his mass spectrometer the abundance. Then we had the half-life. Because as soon as we knew that, how many Carbon 14 atoms there were in that bulb, then we could put them in a counter and get their counts per minute and that told us the half-life. But it was a good year and a half's hard work. Some of the best counting went into that.
Now, by February '46, you had an assistant working with you on the problem of isolating Carbon 14 and measuring it. That was James Arnold. Could you tell me, why was he working with you and who was he?
Well, he came from Princeton. He had his PhD already. He was a post-doc, and I got him over into C-14 dating and that's how he spent the rest of his time with me, in radiocarbon dating. We were doing something. I was testing him out here, to see how he worked. I don't think I've ever told him that.
Arnold stayed with you some months and then subsequently left. (And later returned.) Now, in the summer of '46, you hired another assistant, Ernest Anderson. Can you tell me something about him?
No, he was a graduate student.
OK. He came to work with you in the summer of '46 then.
He got his PhD on radiocarbon.
How is it that he came to work under you?
Well, he knocked on my door and said, "Do you have any interesting problems?" I said to him, ''Well, I want to measure the natural abundance of radiocarbon." He said, "I'm your boy." I didn't tell him about radiocarbon dating.
What particular qualifications did Anderson have?
Very fine lab guy. Good in his head, too. He could get straight A's right down the line. He was unique in the laboratory, a very good guy; kept a good notebook. My notebooks now are in the hands of the university library. Actually they're over in (Reiner) Berger's lab right now. But if you look through Anderson's notebooks, you'll see how neatly written everything is and how clearly. Ernie was just the guy I needed at that moment. So was Jim Arnold.
OK, you'd been working on determining the half-life of radiocarbon. Now, you also needed to find out something about its occurrence in nature. How did you go about that? Were you working with anyone outside the university?
We had to, because we hadn't developed a counter that was sensitive enough for it. Our calculations, from Korff's neutron counter data, indicated the expected concentration was way below anything we could hope to see. Remember, I had the most sensitive counters in the world. That's what I'd been doing for ten years. But we knew enough about those counters to know they weren't that sensitive. So we made a deal with a friend of mine who was separating Carbon-13 for the American Cancer Society.
That was Aristid von Grosse?
Von Grosse. And we reasoned, fairly obviously, that if it would do C-13, it would do C-14. So we got A.V. interested and he collected the sample from the Baltimore Sewage Plant. He knew the president of Sun Oil Company, because he'd been a very close associate of Houdry (Process Corporation) and Houdry had largely developed many of the catalysts used in the oil refining business. A.V. was born, I think, in Peking. His father was White Russian ambassador to China; very interesting fellow. We'd become friends over the years because of various projects we had had going. I think he was one of the two or three guys who showed that 235 was the fissioning isotope in uranium at Columbia. But he got intrigued with this idea about finding natural C-14.
What facilities did you use that he had access to, for example from the Houdry Corporation, or did you?
Well, the thermal diffusion column is a tube about three stories tall, along the axis of which is another tube, frequently just a wire, which is heated. The outer tube is cooled, it can be just by the air or by running water, and then the heavy isotopes go to the bottom and the light isotopes go to the top. This is a fairly expensive piece of equipment, and he had this thing going making C-13 enriched materials for the American Cancer Society. But he was using methane. Now, we had a problem because most methane is from oil wells, and there wasn't a prayer there'd be any carbon 14 in it.
Sure. Though at that point in time we hadn't proven that shows the value of theory. So we held out to get some biological methane. A.V. got that from the Baltimore Sewage plant, and enriched it and sent it. Ernie and I counted it in our lowest level counters that we had at that time.
Was that the screen wall counter?
No, this was a gas counter. Now, the most sensitive way you can dispose of a sample is in the gas, if you're fortunate enough to have such a sample. We had methane. Why should we burn it down, make a solid and lose sensitivity?
Now, at this time you were attempting to improve your counting techniques. The screen wall counter itself wasn't sufficient for carbon dating.
Well, our problem was that now that we had the reading on the Baltimore Sewage, we knew we were right: (A) the cosmic rays had been producing more or less constantly; (B) the mixing was worldwide. We knew both things because the observation was within a factor of 2 of our calculations we were in. We had carbon dating, providing we could build a sensitive enough detector to not require 20 kilobytes (20,000) per copy. That run at Marcus Hook (Pennsylvania, home of Houdry Corporation), 20 kilobytes and in 1946 dollars, you know. That's a lot of money. Well, it took us quite a while to do that. First thing we thought of was to go off and get into a coal mine some place. We recognized immediately that our problem was two-fold. One was the local contamination. The other was the mesons from the penetrating cosmic rays. We could get rid of local by just piling lead and iron clean around it. But the mesons were real tough. And the water table at Chicago is about 10 feet below street level. You couldn't have any mines there. So, we came to the following. We had to invent there wasn't any other way to save our necks, because if we had to drive 100 miles every day for a sample, it's just like 20 kilobytes — forget it. We knew now in principle we had radiocarbon dating. The question was, was it practical? Could we do enough to really prove it? That's where Ernie came in very strongly.
You say "we knew now." Was it late '46, early '47?
Early '47, I would say. We did a lot of head scratching, I'll tell you. We used different kinds of lead, even different kinds of iron. Of course we knew from the beginning that wasn't the problem. We took all of our equipment over and stuck it under the yoke of the cyclotron. They were just building the big cyclotron at Chicago, and this thing was 14 feet of steel. We got a 30 percent drop. Well, tough way to make a living.
After trying these other alternatives, what technology did you adopt?
Well, we had the plan of going down a mine. That sure wasn't very practical. We had the other plan, to build a big thermal diffusion plant right in our own lab, and we did do that eventually. Never used it though. See, if you enrich this stuff enough, then you can count it with an ordinary (not too ordinary) counter — ours was the most sensitive in the world — didn't have the AC shield (Anti-coincidence). We discarded both of those. We decided, the thing to do was to really solve the problem, and that's where the AC came in, where we had anti-coincidence shielding for the mesons.
AC shielding meaning anti-coincidence.
Yes, simple idea.
Whose idea was that?
Do you know, I don't remember. You might ask Ernie. He probably doesn't remember either. We were working very closely. Anyhow, we did it. I should say that physicists had been using coincidence for measuring the direction of cosmic rays. From that to our problem wasn't all that difficult. That opened up the whole thing, because now we could measure Ernie's natural level samples. He could produce his thesis. Jim and I could get on to testing out Egyptian archaeological samples. The whole thing was open.
In talking about Anderson's world-wide assay, what was so significant about the assay, had such a task ever been undertaken before?
No. Nobody ever before had measured world-wide mixing.
Of any element?
How did Anderson go about that?
He went to various museums and got pieces of wood, from various localities. Very easy.
Wasn't there a substantial problem in terms of getting materials from around the world?
No. Just pieces of wood, you know, modern wood, that's not a problem.
Around this time, early spring of 1947, you'd come up with the idea of anti-coincidence counting and Anderson was working on the world wide assay. Now you decide to go public, so to speak, to lift the secrecy?
Well, not yet, quite. We had to make some measurements on the Egyptians. I think it was four Egyptians we measured before we told them what we were up to. — I may have the wrong number, but it was a small number. We needed money, you know. But the fact that we could even come close —
At what point would you guess that you realized that your project would probably have important archaeological and geological applications?
Oh, at the beginning. As soon as I read Korff's article in — when he found neutrons in the cosmic rays that was it. Remember, I'm a chemist and Korff is a physicist, and I don't know whether Serge even knows that plants come from the atmosphere. He probably does, but he doesn't believe it.
During the latter part of 1947, you had your first contact with Paul Fejos. Can you tell me something about it?
Well, that was after our original announcement.
Can you tell me, how did that come about, your meeting with Fejos? And who was he?
Well, I gave a seminar at Chicago, and Urey and Fermi heard about it.
When would this have been, approximately?
Early '47. And Harold knew everybody and traveled a great deal. Paul Fejos was the director of the Viking —
Just like that?
Just like that. So we didn't have money problems from there on. Strangely enough, I had a little problem with graduate students, because I couldn't see more than one PhD thesis in this whole thing and one post-doc that was about it. So I had a team, I don't know how many, two dozen, I would guess, between a dozen and two dozen graduate students working on a variety of problems, and I mean working like hell. We were not kidding around. So this had to be a kind of on-the-back-burner or side thing. Of course, they were very pleased to hear what we had been doing. But they didn't know before Paul Fejos knew. Fejos knew about the same time I gave the Chicago seminar. A week later, I was invited to New York to give a seminar to the people Viking Fund had been supporting — archaeologists. The room was packed.
That was in January of '48, right?
I think so. I've kind of lost the sense of time. Then I went to London and I spoke there.
What did you talk about?
Just the principle. It's so simple, you know. They would say, ''Why didn't I think of that?"
Do you recall what the general response was of those archaeologists at that January 1948 meeting of the Viking Fund?
I felt they were mainly favorable. Out of that, I got support from a lot of very important people. They at least thought my thing was interesting enough and deserved a chance. So they gave me the samples. That's all I wanted, was the samples. Very hard to get good samples.
Do you think that they, being archaeologists and not well steeped in physics and chemistry, they really understood what you were talking about? I mean, for example, one of the problems seems to be that they didn't understand the nature of statistical error limits. How do you come up with the idea when you see a radiocarbon date, it will be 1500 years plus or minus 200. How did you arrive at that date; of the statistical error limits?
Well, let's take one question at a time. Now, the archaeologists are essentially humanists. Few of them had much math. To explain the Poisson law was most difficult. But regardless of their understanding, it still is true that if you count 10,000 counts you can't possibly be better than 1 percent. No possibility. That's where our plus or minus comes from. However, there are other sources of error. We were just pretty damn lucky that these other sources didn't amount to more. It turned out; our main error was the counting error. That's how we could calculate our plus or minus, you see. We had the devil's own time trying to get this idea across to them. But they began to see, when they took six samples from one site, they would cluster around this error, that we had something. We had problems. Jarmo (site) and (Robert) Braidwood — and Bob was one of our best supporters. But our scatter on Jarmo was terrible. We finally concluded, it was probably due to the fact that there was a bitumen well within two miles of Jarmo.
This was contaminating the counts.
I don't know whether that's true.
After this January meeting, one of the primary results of it was that you began to get samples, which was what you were after. Were there formal means of communications and organizations established?
Yes, we set up a committee to give me samples. We had the American Geological Society, with Richard Foster Flint from Yale, and three archaeologists, Froelich Rainey, the director of the Pennsylvania Museum, University of Pennsylvania; Donald Collier, the director of the Field museum on 12th and Roosevelt Road, Chicago; and Frederick Johnson, he was the chairman, from the Peabody museum in Andover, Massachusetts, very distinguished. In my book on this, Fred Johnson writes a chapter. They were invaluable because they got us the material. Those museum dogs were not going to give it to a bunch of physical chemists to burn up, no way. You see why I kept it secret? I couldn't possibly, if I told all this craziness… I had no problem getting funds for my other graduate students.
Now that you'd lifted your secrecy policy, how did your colleagues at the Institute for Nuclear Studies respond?
Wonderfully. They were all for it.
In early 1948 now, you're beginning to date some of the Egyptian samples, and James Arnold, in March 1948, rejoined you. Why did he return to the project?
He was fascinated. I'm sure that's right.
Did he possess any particular skills or background that made his participation necessary?
He was a very fine lab man, the same way, Ernie Anderson. We had a good outfit over there. We had to go back and read the counters every four to six hours, clock around.
So radiocarbon dating wasn't your typical 9 to 5 job.
Oh no. We'd take turns getting in there at 3 A.M. and reading and — writing down the counts —
How did you divide up the responsibility among the three of you?
Did each have a particular task?
We'd do the same thing. It had to be done 24 hours around. Some of these samples were so old; we had to count them three and four days, night and day, to get enough counts.
Talking about counting, could you tell me what was essentially the process, once you acquired a sample, how you went about dating it? What was involved?
Well, it depends on the sample. But take a piece of charcoal, for example, and charcoal was one of our most common samples. We'd look at it, and pull out the roots. It seems that plants like to have their roots soaked in charcoal, but you can pull them out, with tweezers. Then we'd wash it in acid, say, normal HCL. That cleans out the limestone. And then we'd wash it in base, sodium hydroxide. That cleans out the humic acids. Then we'd wash it with distilled water, and dry and burn it, and now we'd get CO2. What we did there is to take the CO2 and put it in a bulb. We had an iron pipe in which we packed magnesium turnings. We'd connect the bulb to the iron pipe, and pump all the air out of it. Then we'd let the CO2 come in to the magnesium turning. Then we'd take an oxygen torch and heat up the iron pipe from the outside, and the CO2 and the magnesium would catch fire. Then we'd have to start standing back, because it might burn right through the iron pipe. Anyhow, the manometer would go down like that. Take the sample and convert it into carbon and magnesium oxide just like that. It would cool off. Then we'd throw it into a beaker and start extracting it with hydrochloric acid solution. Get the magnesium oxide out. That would go on sometimes for many hours. In fact, there were some samples that never did get to zero ash. Somehow the carbon seemed to protect the magnesium oxide. Now, at this point, we'd take great care about the sample, because the carbon was very porous, very absorbent, and we'd set it up — put it in the screen wall. The screen wall has a sample cylinder, and we would re-melt the powdered carbon on the inside, and we had our own artistry as to how to make it stick to the wall. The answer is ethyl alcohol. But we had to be very careful about drying off the ethanol, because the air we'd use for drying would have radon in it. Be absorbed. Well, we got around that. Then we put the counter together and proceeded to count it for three or four days. Our background was customarily around 6, and the modern level was about 12, so we had a difference of 6, fairly close skating.
What would you say was the most difficult and critical part of the entire dating process?
Being smart enough to keep it secret until it was in hand. You couldn't get NSF to support that project. I don't care who you are. You couldn't get anybody to support it. It's obviously too crazy. That was the most difficult.
How about, in terms of the actual chemistry of the process? What was the most crucial aspect?
Well, I think this laundry is a pretty important matter, to clean up the sample from dirt.
Now, how long did you continue to date the known samples?
We ran several hundred samples at Chicago, before I went to Washington. (1954) Only one other lab ever managed to date it using that method. The thing that saved carbon dating was that they learned to purify the CO2 and wouldn't have to go through this black carbon.
Did you have any people, when you began producing your dates, particularly samples whose ages had not been established before; did you have any people who were critical?
Yes, we had quite a few people who were critical. We didn't mind that. In fact, we anticipated that.
Do you remember any of them in particular?
Well, Ernst Antevs, who didn't like our 12,000 date for the last glaciation (in North America). Of course, he didn't know what our basis was so it was hard to talk with him. There were several others. Hell, we were plowing up the landscape. And we weren't all that sure. We could check back to 5000 years with the Egyptians, but — and now we can go back 8000 with the bristlecone. We were talking 12, 15, 20 thousand years.
When did individuals interested in perhaps constructing their own laboratories come to Chicago and begin to visit your laboratory?
Almost immediately after the announcement. There was a stream of them and they were building labs like mad.
And did you take these people in and teach them the method?
And how did that work? How would you go about teaching them the method?
Just put them in the crew. “At 3 AM you come over here, bringing your pipe wrench to protect yourself, you go in and change the sample.”
And how long did these people generally remain at your lab? How long did it take you to teach them?
I would say, in three or four weeks they would begin to get the idea. Then they could go home and build up their own. I think the first one was Larry (Lawrence) Kulp from Columbia. I wrote him a letter this morning and reminded him of that. Helmut De Vries from Groninger… There were a lot of them.
During those first two years of dating, 1948-50, what did you find most exciting about the entire experience?
The interdisciplinary character of it. I found it fascinating, that the Egyptians and historians could be so right and reading their evidence, my God! And yet they could figure it out. And now, with our bristlecone corrections, we're checking it even more accurately; fantastic.
During this period you're obviously a very, very busy person. What kind of family and social life did you have?
Lots of it — barely had time to sleep. Get up at 3 AM, go over and change the counter. It's a 10 minute walk, sometimes zero degrees or below that.
Were you involved in any other scientific projects at this time?
Oh, of course. I had about 15 graduate students who weren't working on it.
What are some that stand out in your mind?
You want to get into that?
I'd be interested to know simply because radiocarbon dating was such a time consuming process. It amazes me that anybody would have time to do anything else.
Well, it's a little hard to answer your question. We used to have a lunch every Friday with all the students at the Windermere Hotel and there would be about 20 of us on the average. The radiocarbon always had a prominent part, but only a part. We'd go around the table, and – One of my most active areas was to develop radioisotope uses. Another one was hot atom chemistry, the chemical properties of atoms which have had a nuclear transformation, and therefore are excited. It's a very rich field. And, I had my hands in politics. That's how I became an AEC Commissioner.
OK. Beginning in 1952, several things had happened. Ernie Anderson had left University of Chicago in 1949, and James Arnold was disengaging from Carbon-14 research and other labs were being constructed like mad, as you said.
Now between 1952 and '54, what did you envision as your principal role in terms of carbon dating, as other people were —?
Well, I was really going to Washington. I was also starting something called the Sunshine Project, where we were beginning to measure the metabolism of fallout isotopes — and we were particularly interested in Strontium 90 because it goes into bone. And we used our low level technique to make the only early measurements on the level of Strontium 90 in bone, human bone. And we set that one up. I set up the whole matter of the worldwide circulation of radioactive fallout, based on the carbon-14 experience. (Marlowe: Inadvertently, as we continued to talk for three or four minutes on tape after flipping over the tape to the second side, that portion of the interview was erased. The matters under discussion at the time were essentially some of his reminiscences about his years as an AEC Commissioner. Since that was not a major topic of intended discussion for this interview, no appreciable material was lost. I do think it is important, however, that Dr. Libby be interviewed on those AEC years and I have written a letter to Dr. Spencer Weart requesting that such an interview take place.)…
Dr. Libby, in 1954, you were appointed as a Commissioner of the Atomic Energy Commission. Could you tell me how that came about?
I have a feeling it came about because of my support of the H bomb. I think that's how it came about; President Eisenhower was a general officer. He knew extremely well the value of this weapon. But a Presidential appointment is just that. He may decide everything or he may take his advisor's word. Admiral Lewis Strauss was a good friend of mine and he was very close to the President.
He was then Commissioner of the AEC?
He was Chairman. I don't really know the answer. I think it's probably a combination of all these matters.
Capsulating your experiences on the AEC, did you undertake research? What were your primary responsibilities?
Well, let's answer one at a time. I undertook a little research, but I had no time really. I spent five years there. I had eight assistants, five secretaries, three mail assistants, and I was a very busy cookie. No part time job. I still have about 20 filing cabinets stashed away in Germantown with my name on them. But I did have a little opportunity to do some research and the Carnegie Institution in Washington gave me a laboratory at the Geophysical on 2801 Upton Street, N.W. I used to go over there, have an hour or so at lunch to do some experiments, and I published two papers in the five years. I'm very proud of those papers.
Do you recall what the nature of those papers was?
I sure do. As you gathered, I've done a lot of work on Geiger counters. One of them was about how to use Geiger counters, still an important paper. Most people look up in the catalogue and buy a Geiger counter. They haven't a clue how to use it. The artistry that's required to make some of the measurements which are essential have kind of escaped a lot of people so one paper was about that. The other paper was on how to rid vegetables of radioactive fallout. I published that and I got a lot of comments. Editors said, "Why does this physical chemist, even though he is God Almighty, venture into biology?" My answer was: ''Because you ain't doing it and maybe one or two other things.” I kept track of carbon dating the whole time, but I didn't do any there at all.
How about in terms of a few of the research projects the AEC undertook, under your direction.
Well, we were essentially running the whole damn country, at least physical research. I remember one afternoon authorizing the first hydrogen bubble chamber. I remember going down to see the President, to get his authorization for a special appropriation to build the Stanford Linear Accelerator. All right I could go on far into the night.
Looking back, those eight years at the University of Chicago, particularly your work on carbon dating, aside from the interdisciplinary aspects of it, what gave you the most satisfaction in terms of pioneering new dating areas, archaeology or whatever?
Well, just working with those guys at Chicago. Fermi was a wonderful guy. So was Urey. There were a lot of them around there. I missed Berkeley. But it was a new scene, Chicago. My experience over the years is, it's good to move every ten years or so. It's good.
Those years of working in carbon dating at the University of Chicago, what is the most significant impression it left on your mind?
Well, the power of the human mind, when it's applied, is beyond belief. Those guys cooperated, once they got the idea. But I knew damn well they wouldn't cooperate until I'd done it first. I think that's probably the unique contribution I made, was to do that. I didn't even tell my wife.
Looking back at the whole period from Berkeley through Chicago, is there anything we've left out, anything you'd like to talk about?
Well, I think the value of education, educational values of these researches, — Look, I was teaching undergraduate courses, canned stuff, out of the textbooks. What I was doing was far more exciting and interesting. At Chicago, little of that happened. I think the University of California has an ideal mix, where it's teaching and research. I don't know what's going to happen to the university. It's in trouble; very serious trouble. I've tried very hard in my 20 years here at UCLA to get it to do things to bring it support. I'm not against football, basketball and all that. But it's not the university that Gilbert Lewis put together. Not anymore.
Is there anything else you want to add?
No, I don't think so. I don't want to run anything down.
 Korff, S.A., Danforth, W.E., Physical Review, 55 (1939) 980
 Radioactive Dating, U. Chicago Press, 1952