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Jerome Karle’s Interview

Manhattan Project Locations:

Jerome Karle worked on plutonium chemistry at the Chicago Metallurgical Laboratory during the Manhattan Project, along with his wife, Isabella. After the war, Jerome and Isabella worked for the U.S. Naval Research Laboratory for almost seventy years. Jerome was awarded a Nobel Prize in Chemistry in 1985. In this interview, Karle explains his chemistry work in the Manhattan Project. He recalls his friendship with Glenn Seaborg, and discusses his opinion on dropping the bombs on Japan.

Date of Interview:
September 12, 2022
Location of the Interview:


Jerome Karle: My name is Jerome Karle. And it is J-E-R-O-M-E K-A-R-L-E.

Cindy Kelly: Great. Dr. Karle, can you tell me about what you were doing in the early 1940s and how you happened to become part of the Manhattan Project?

Karle: Well, I had just finished my work in 1943, for my graduation on my degree.

Isabella Karle: Your PhD.

Karle: PhD degree. I was looking for something useful to do. There was a young man who joined the faculty of the University of Michigan. He told me that there was something very interesting going on at the University of Chicago. He could not tell me what it was. But he suggested that I get in touch with them and go down there and talk to them. That is what I did, and that is how I got connected with the Manhattan Project. My wife came about three to four months after that, when she finished her work for a degree. 

The man in charge of the research program in the areas that we were was Glenn Seaborg. Glenn was one of two people who discovered plutonium. Now this was the key factor in what we had to do. And that was to find a way to get the oxygen out of the plutonium oxide. Because with the oxygen in there, it was not useful. With the oxygen out of there, it was the key factor in the explosive devices that came out of the Manhattan Project.

Now, there were various approaches to this, and I had one specific one. When I got there, they had an apparatus that they thought could be used to get the oxygen out. This was new to me. I worked on it for about four or five months unsuccessfully. Slowly, I realized what the problem was. The problem was that the temperature in this particular apparatus was a little less than half the temperature that I needed in order to solve the problem. Ultimately, I did solve the problem.

In those days, you didn’t look up a directory and find out that you can get all kinds of equipment to run a laboratory. In those days, you did everything by yourself. What I did was that I used a piece of equipment that I had to handle in a variety of ways. This equipment was made to run at room temperature. I had to do a lot of it, to get it up to the temperature that was needed. And I did that. I made all the necessary connections and what have you, and brought it to a point where I could get it to a temperature that I thought would work.

This was after a period of time that was probably three-quarters of the year. I started working on what was successful after about half a year, and I got done with it. Finally then, I fixed up this equipment and tested it on substances that were like plutonium, except that they did not explode. And so they were not interesting. But what I was able to do was to set up a series of tests for my equipment, to see that everything was in place and everything seemed to be workable.

The day came to try it for real. The first thing that happened was that everybody but me, for most of the facility that I was working in, were removed from the facility, in case something happened. I was not particularly concerned, because I had made many trials to test whether the instrument that I made would work. I just proceeded to do this. Lo and behold, I made plutonium from plutonium oxide. That is what they wanted, and that is what I did.

After that, things were settling down because the war was almost over. What happened to my wife and I was, there was some project of interest to the US Navy that my doctorate professor was asked to do. He asked me to come back to work with him on it. I spent two years on this project. I am happy to say it also worked out. And after those two years, the war was over.

Both I and Isabella were offered a job at the Naval Research Laboratory. That turned out to be one of the most marvelous things that happened to us. It was a great place to work. And now almost sixty years later, we’re still working there.

So that’s the general picture of what role I played in this work at Chicago, and the nice consequences that came out of it. 

Glenn Seaborg was a very nice man. I enjoyed working under his supervision. In the course of years, we stayed in touch. He would come to Washington in later years, because he had a job in—where was he? I do not remember. 

There was always concern at the University that what they were doing would get out into the public. There was a feeling, which I shared with them, that almost everybody in Chicago knew that there was something going on, but they did not know what. They always wanted to be very careful.

One of the aspects of the project that Isabella worked at, was the production of certain types of materials that were brought from the place where we worked to the University, which was across a grassy knoll, for the purpose of further investigation as to whether what she had synthesized, what she had put together, was actually what was intended. There was a professor there who had the right kind of equipment, and he would do the work.

Well, Isabella was about twenty-two or twenty-three at the time. She looked very young. She looked like she was a student there and not somebody working on the Manhattan Project. One day, somebody—I do not know who it was—saw her walking across the campus to have her latest work tested. This person became very concerned about the fact that she was carrying this across the campus. So what they did was have her accompanied by two men, who were about twice as tall as she was, standing and walking on both sides of her, protecting her from all those people who would be looking for her to be having all these important things going on.

Well, it was absolutely silly. This was as close as you could get to tell people that there really was something going on at the University of Chicago, whereas she was lost in the view of people, when she was by herself. So it was a silly thing, we thought. We had to laugh about it. But that is the way it was.

I had this basic piece of equipment that I thought I could use. What I had to do was, to insert into the equipment facilities that could raise the temperature very much and would also rotate the equipment at a very high speed. That allowed me to put in a little capsule of the plutonium that I wanted to be removed of oxygen, and would be at high enough temperature that the oxygen would essentially leak out.

That required some electrical connections and attachments that allowed high-speed spinning, and also the heating up that was required. It was grateful, and it was not really difficult to put this together. It just seemed to work. I had to guess somewhat as to how high I needed to go on the temperature. But I made a good, lucky guess, and it was just about right.

Kelly: In all your years as a scientist after this, after World War II, how would you say things changed in the research support you had? Was it dramatically different after the war? Was this a turning point, or did you not operate differently?

Karle: The way we get funded in the Naval Research Laboratory is somewhat different, or perhaps even considerably different, than how it works in universities. In universities, each man or woman has a project. They write and write proposals that come through the national facilities that fund these things.

At the lab, what you have is a group of people working in a certain area, usually. That entire area gets funded; certainly, again, on the basis of what you are going to do. But it was particularly easy for us when we first got there, because we needed equipment to be made and we had the shops to make it. We had a gentleman who was the head of our unit. There were, I would say, about eight such people as the head of units—about eight units at that time—in chemistry, physics, and that sort of thing.

The man who was the head of our unit had a philosophy. He said, “You hire the best people you can find, you fund them, and you leave them alone.” I can tell you, that really worked. We and our other colleagues around who were in that atmosphere did marvelous work. So you did not spend half of your life writing proposals.

Kelly: Maybe go to one of the questions that I asked about how you felt about dropping the bomb.

Karle: That is a very interesting question. 

The people in this entire group that I was a part of had written to the President to, “Please not be the first ones to drop the bomb.” This was a general feeling. Everybody signed up. I spent fifty years of my life being disappointed that we were the first ones to use the bomb. And in 1995, which was fifty years later, I learned what really happened. And I will tell you the story.

What really happened was that before we dropped the first bomb, we asked them to quit. That was it. No more fighting. They would not. Then they were preparing the second bomb. We asked them to quit, and they did not. And then the Japanese were again preparing to continue. But after the first two bombs had fallen on them, Hirohito told them to quit. And that is how the war was stopped.

Now why did we do this? We had, I think it was–I may be wrong—but I think it was three million men some distance from Japan who were going to invade Japan. And they were all, I can tell you—I know a lot of them—all scared to death. Because when you invade somebody else’s territory—in particular, Japan has so many mountains just a bit away from the coast that they would be sitting up there. The loss of life would have been horrendous.

I did not know that for the first fifty years. But after I heard that, then I said. “It was too bad. But I do not know what else they could do. And they saved everybody’s life.” After that became known amongst people, that we had worked on the Manhattan Project, there were many people whom we knew here in the Washington area and other parts of the country who were part of that force that was going to have to go into Japan. It was really astonishing, the number of thank yous that we got for working on the Manhattan Project. 

My view, so far as making a point of eliminating such weapons because of the tremendous destructive capabilities, is as follows. Surely nobody in their right mind would want to have these kinds of explosives around. But you have to stop for a while and think about current circumstances. Current circumstances are, that we have gone all the way from World War II to no fighting amongst the big countries that have these great weapons.

I think that there is a very good chance that the fact that they have these weapons has played a role in keeping the powerful countries from fighting with each other. I think that this aspect of the problem needs to be kept in mind, before some arrangement gets made to have all of these types of equipment destroyed.

My feeling is, be careful. These weapons may be preventing big wars to come out again. So that is my point.

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