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Murray Peshkin’s Interview

Manhattan Project Locations:

In this interview, Peshkin discusses his time at Los Alamos working under Richard Feynman. He also talks about espionage and his personal connection with David Greenglass. Peshkin goes into moral questions surrounding the Manhattan Project and the decision to drop the atomic bombs on Japan. Finally, he discusses the persecution of many of the Manhattan Project scientists as alleged communists, especially Phillip Morrison.

Date of Interview:
April 13, 2008
Location of the Interview:


Murray Peshkin:  Well, how did I get involved in the Manhattan Project? I was an undergraduate student at Cornell University. A group of about ten, who were studying physics. It was clear that we could not be kept out of the Army very long. They were looking for programs in which we could serve usefully. I really believed that there was something else behind it.

In the First World War, a man named, I think it was Henry Moseley, who was considered probably the most promising young atomic scientist in the country had, against the advice of his friends and colleagues, volunteered to fight in the infantry and died. That was a shocking thing to the entire science community. I think that our professors were really trying to save us. It wasn’t that Los Alamos needed me.

Cindy Kelly: Tell us about your road to Los Alamos.

Peshkin: I was informed by one of my professors that there was this project where I could serve and make use of what little training in physics I already had, and that it would be a really good thing to do, but it was completely secret. I would be somewhere in the United States, but I would not be able to tell my family where and would not see them again until the end of the war. That was really all he would tell me. Except that, he advised me to go that way. So I did.

What happened was that at the end of the semester, I informed my draft board that I’m ready. I was duly drafted, sent to basic training in Louisiana. Somewhere in the middle of the basic training, I was pulled out and sent very dramatically on a train with about ten other young men with sealed orders, which carried us first east to Oak Ridge, then north to Cincinnati and so on. And finally, to a train which took us to Los Alamos. It was a very interesting demonstration, I realized later, of the power of that project. Because not only could they pull us out just when people were needed to fight in the infantry, but even in traveling, whenever we got to any station we were given immediate priority. In St. Louis, we were given our own railroad car and found a train to pull it for us.

Then when we arrived at Los Alamos—well, Lamy, which was the entry port from the train station to Santa Fe. We got off this train and we found ourselves in the middle of a desert. We were tired and dirty and discouraged. We could have sat down and cried, except that we were ashamed. But after a while, a car came for us and took us to Los Alamos.

Also in the Army was David Greenglass, the notorious spy. He was not in my barracks. My contact with him was indirect. But it had some effects. We had a mutual friend, a fellow soldier who had an apartment in Albuquerque where he met his wife weekends. She was also in the Army but not at Los Alamos, but nearby. At one time, his wife was away for a few months. Greenglass came to him and begged him to let my friend use that apartment for his wife to stay. She was in the last part of pregnancy. He seemed rather pathetic. My friend knew Greenglass and disliked him intensely. As did I, by the way. He asked me my opinion. And I said, “Don’t do it. This guy is nothing but trouble.” But, he did it anyway because he felt like a dog in the manger.

Well, that was the apartment where Greenglass gave his secret information to his brother-in-law, Julius Rosenberg. In the end, my friend had serious problems with security people about that after the war. It even rubbed off a little on me because I defended him, which was not the politic thing to do during the McCarthyism. But the consequences for me were minor. Mainly because I was lucky, the McCarthyism was just about over by the time they got to me.

Kelly:  That’s a great contrast to Klaus Fuchs. Did you know him?

Peshkin:  Very slightly. I don’t think he knew me at all. You have to understand that I was a very insignificant player. I was working for Dick Feynman that was why I knew people at all. But I was working for him on a trivial level. He needed to do numerical calculations that involved very laborious hand computation using an electric desk calculator. Electronic had not been invented at that time. I did that for him a lot. If Dick Feynman had had the kind of electronic programmable electronic pocket calculator that you can buy today for $50, he wouldn’t have needed me at all. Luckily for me, he didn’t have that. I had the opportunity of being with him just lots and lots of the time. It was fascinating. It was wonderful. I don’t think I did so much for him.  

Kelly:  Tell us about Dick Feynman.

Peshkin:  Dick Feynman was different from anybody else I ever met, and I met many very great physicists. He was a very intuitive person. He looked at everything in a different way. His way was always clearer and better than the way you would have thought of by yourself. The key word there is “clearer.” The minute he said it, you could see exactly how you should do that. But it was absolutely impossible to imitate him. I knew him again when I was a student at Cornell, and he was one of my professors, with whom I interacted a lot. Boy, you could learn physics from Dick Feynman wonderfully. You got all these great insights. But you couldn’t learn to do physics like that, because only he could do that.

Dick Feynman’s idea of a proof was to give two examples of a mathematical proof. He had so much insight, that he could pick those two examples in such a way that they tested every weak point. Mere mortals had to actually proof it. When we grumbled, as I sometimes did, that his proofs were not rigorous, he would say, “Do you know what rigor mortis means? It means died of too much rigor.”

One way of explaining how it was with Dick Feynman, was that you could go to his lectures and they were magnificent. But you could no more learn how to do physics that way, than you could learn to dance by watching a ballerina. It just cannot be done.

Exposure to neutrons. I was working on theory so I didn’t have any exposure to neutrons at all. Other people in the laboratory, who were doing experimental work, often took risks that nobody would accept, except under the pressure of a war. I mean, after all, other young men like us were in trenches in France. They did experiments that today would be considered insanely dangerous.

The most extreme example was Louis Slotin. I was in another part of the same group after the war that Louis Slotin was in. They were doing what we called critical assemblies in order to learn more about the interaction of neutrons with plutonium. What they were doing, was they had the two halves of a plutonium bomb. The lower half was on a table, held in place, of course. The upper half was gradually being lowered. As it got closer, the neutron activity became greater and greater, because the neutrons that were created in one half were more and more likely to strike the other half as they came close together. By seeing how the level of neutron activity, which they could monitor and hear a click every time a neutron was detected in the counter, was to see how that depended upon the distance between the two.

Now, you may ask, the war was over. Why were they doing such an insanely dangerous experiment? In fact, it was worse than that. It had been agreed that you never lowered. You only raised the second hemisphere. Because if you dropped it, and the two came together, you had not a bomb that would make a physical explosion, but you had a bomb that would make an explosion of neutrons. For whatever reason, they were lowering it. And they dropped it. Louis Slotin had the upper hemisphere, had his hands on it, and he threw it away.

But of course, it was all over. There was a burst of neutrons. Nobody heard anything. The fact that he threw it away was irrelevant. I think it just had expanded enough to exterminate the reaction. They all ran out the door. I was told, I was not present. There was an armed guard, whenever you had plutonium, there was an armed solider even though we were ringed by layers of soldiers anyway. He was standing next to the door where he was out of the way. He was the last one out of the room, because he didn’t even know anything had happened at all. Ten days later, Louis Slotin died.

Now, I asked at the beginning, why were they doing such an insanely dangerous experiment when the war was over? The only answer I can give, that makes any sense to me—I never asked any of the people who were then involved. The only answer I can give really, is that it was the momentum. This is what they did. They were accustomed to doing these experiments. They were scientifically fascinating. The information wasn’t needed in such a hurry anymore. But it just would have been against the culture of the time and place to stop and say, “This is too dangerous, let’s not do it.”

After the Trinity explosion, Oppenheimer said, “Now the physicists have known sin.” I had not earlier heard any statements doubting that this was a good thing to do. I’m sure that older and wiser people probably did have such discussions. I was a nineteen year-old kid. I don’t know that that statement of Oppenheimer’s really contributed to the discussion afterward. But it was a bit of a shock when we heard about it.

Kelly:  Let’s see. So, up until the Trinity, what was the atmosphere? Were people confident or were they nervous that this would work? What kind of odds would you have guessed this thing was going to work before Trinity?

Peshkin:  The people I talked with all thought it would work. I don’t know what kind of odds, but better than even money. We certainly hoped it would work. We didn’t really think about the consequences.

Let me supplement that a little. The war against Germany ended pretty early. We were fighting Japan. The hatred of Japan and of the Japanese was really pervasive. It was stoked continually by the newspapers and by the government. I would like to think that it wasn’t significantly racial, but it probably was. When the bomb exploded over Hiroshima, we just erupted in cheers. The more people who were dead the better, you know.

Kelly:  How did you feel about the decision to drop the second bomb?

Peshkin:  I questioned it at the time. The decision to drop the second bomb on Nagasaki after such a short time—even at the time, I had my doubts about that. It seemed unnecessary. We had not given them time to organize themselves to surrender. One person, even the Emperor, does not successfully surrender. He had to get the generals to agree to stop fighting.

Kelly:  Now, you didn’t witness the Trinity test, right?

Peshkin:  No. The only people who went to Trinity are the ones who had something to do there. Or who were leaders of the project and could hardly be denied the opportunity.

Kelly:  Did you know what was going on?

Peshkin:  Oh, sure. Sure.

Kelly: I think you already talked about—

Peshkin:  Yes, I did know what was going on.

Kelly:  About a few weeks after the test, you went to Trinity as part of the team, the whole part of getting down to the five naked men.

Peshkin:  Well, life at Los Alamos was not just work. There was fun. In a peculiar way, being in a war tends to be fun, if you are not in danger and are not seeing the terrible destruction and all that stuff, because everybody knows what he has to do. There are no doubts about what you will do in the long term future. It’s an easy life, if you or your loved ones are not really victims of the war.

One of the things that happened to me was almost a comic opera. After the Trinity test, a few weeks later, well, almost immediately after the test, a few people went in, in a lead-lined tank I think to measure the radiation. Went into the crater, which it had left. This was a crater about ten feet deep and, I don’t know, a couple of hundred feet in diameter. I don’t know exactly. Then volunteers were needed to go in and dig out some blast gauges, so that one could figure out how strong the blast had been. I and the other members of my group, there were five of us all together volunteered. I think maybe partly out of curiosity. But partly because we had a feeling that a lot of the experimenters had already been exposed to a lot of radioactivity and we had not.

So the idea was that we would drive across the desert to that spot. Then we would go in and dig out those blast gauges. We had a map that showed where they were before the explosion. In the event, they did not move very much.

So we did that. We drove in there. We got out and walked on this famous green glass that was all over the place. We dug out those gauges. We had radiation gauges on us, very primitive ones. But we never reached the level of radiation which would have caused us to retreat in those days. Today it would have, I suppose. We got these gauges out and we came out.

Of course we were all covered with radioactive dust. So we stripped off all our clothes and threw it in the trunk of the car. There were these five naked men driving in this sedan across the desert. Nobody wore a stitch of clothing, except me. I was driving the car and the pedals were hot. So I wore shoes and socks. When we got back to the base there, we showered and changed into our ordinary clothes and went home. It was very funny.

Kelly:  Let’s see. The next thing I would love to have you tell us about, which is in your notes as well, was Phillip Morrison and what you thought about him, and tell us about him.

Peshkin:  Phil Morrison. After the war ended, my group evaporated. I was left alone in it. That was quite useless. Phil Morrison was building what was then a very novel type of reactor. So I went to see him and ask, could I work with him? Sure, he always had use for hands. So we worked on building this reactor in a canyon that was next to the Mesa where the Technical Area was. It was surrounded by its own gate. It had its own guards. It had its own machine gun tower on one corner.

One night, I had a really scary experience there. I went down to work on something. I was alone in this concrete building that we had built for working on this, to build this reactor. The guards were very nervous, because there had been alleged to be an invasion. I’m sure there had not. But a guard, just doing the rounds to see that the windows were closed properly on the building or just checking things out, the previous night had gone in there to do that and had been found unconscious on the floor. He claimed that an intruder had slugged him. Phil Morrison, who was in charge of the project, speculated that he had been swinging on one of those hooks from the ceiling and crashed into something.

However that may be, there I was alone. These guards were terribly nervous. They told me stay away from the windows. I had not been there a half an hour before I was so nervous that that there was no use my staying. So I wanted to leave. When I wanted to leave, I was to call them, and tell them I was about to come out the door.

By that time, I figured it out and I called them. They said, “Well, just come out the door.”

I said, “Nothing doing, you come in and get me.”

So they did. I tell you this story to illustrate the level of tension around the place.

Now Phil was a remarkable man. He was by trade a theoretical physicist. But he was one of the people who armed the bomb on Tinian. He was leading this project, building this reactor. He was very versatile. Working with him was really quite inspiring. He walked with a cane and could not stand straight. He had been a victim of polio as a child. But he seemed, you know, eight feet tall. After the war, he was one of my professors at Los Alamos.

Now, Phil had been one of the first few people to go into Japan, after the bombing, to talk with people. He was so horrified by what he saw, that he became a tireless crusader against the use of nuclear weapons and tried in many ways to get this thing under control. He was a person who had a lot of trouble during the McCarthyism, because his generation didn’t find communism so threatening in the days before we really found out what its face was like. He was persecuted by one of the congressional committees, [William E.] Jenner’s, I think, I’m not quite sure.

The reason that they were after him is very interesting. They were really after [J. Robert] Oppenheimer. They didn’t have a handle on him yet. So they were going after his former students, of whom Phil was one, and trying to frighten them into implicating Oppenheimer, to saying that he had been a member of the communist party. Which he may well have been.

It was very interesting that Phil, like many of his fellows in that class, was furious with Oppenheimer. Because Oppenheimer was busily throwing these people to the wolves in order to protect himself. But angry as they were at him, they were willing to take horrible risks rather than help bring him down because of his symbolic value and his importance. Phil, I have it only from him, but it’s absolutely, certainly true. Phil, being questioned by this committee, refused to testify on some untried constitutional grounds. That could well have landed him in jail. His good luck was that this was an executive session. If he had defied them that way in an open session, they could not have let him off the hook.

Now Phillip Morrison was a professor at Cornell after the war, where I was remained closely associated with him. Well, after this, or during the time when this Congressional committee was after him, the FBI was trailing him around. We had many humorous incidents of things that they did. But it was pretty darn serious for him.

There was, of course, pressure from the trustees at Cornell to have him fired. Hans Bethe and Bob Wilson defended him. And he had tenure, luckily. Otherwise, they probably would have fired him. But he never let any of those things stop him in his campaign to get nuclear energy under control. He was tireless in his efforts also to fight the McCarthyism. Not only for his own benefit, but for the benefit of others. He was a person to whom this country is enormously in debt.  

Kelly:  What do you think about the degree of emphasis on secrecy?

Peshkin:  Yeah, secrecy. That’s a very hard question. We had Klaus Fuchs and we had David Greenglass and we had Ted Hall. And perhaps there were other leaks too that I don’t know about. General [Leslie] Groves would have liked to treat the places, almost what we would have thought of as a prison camp, you know. But it wasn’t that way. Oppenheimer felt that we would make much better progress if people could share problems and share solutions. I’m sure that if they had really clamped down, if none of us was ever allowed to leave the Mesa, if the external phone lines had been cut, if, if they had monitored closely whom we spoke to and when, instead of relying on us to use discretion internally in the laboratory, I am sure that the leaks would have been slower.

On the other hand, Klaus Fuchs knew the only important secret before he came to Los Alamos. The only important secret was that we thought we could do it and were working on it. All the rest, yeah, it helped them a little to know these things. But that was the big thing. That was when Stalin knew that he had to get his guys working on it.

Kelly: So was that secret available? I mean, the Soviets knew about our project from the get-go.

Peshkin:  They knew about it from Fuchs, yeah. Perhaps from others. But they knew about the project. Fuchs provided them with marvelous technical information, I am sure. I spoke to one Russian who had been at the Kurchatov Institute in Moscow at the time, which was the Russian equivalent of Los Alamos and Oak Ridge. He told me, you know, he told me this in 1980-something. Earlier, 1970-something, long after the war was over. That Kurchatov had this wonderful intuition about nuclear cross-sections, nuclear reaction rates and things like that. They made measurements of various kinds, and he would say “You know, this one looks funny, maybe you better do that one again.” Now we know why. He had the information from Fuchs.

I should add to that, that I know nothing about these things directly. Only what I’ve read. But from everything that I’ve read and also from knowing him very, very slightly, I do not believe that Greenglass could give them anything useful. That he would, sure. Could, I very much doubt it. He was a machinist.

Oh, David Greenglass was a machinist. He was in the Army as I was. And, luckily for me, I did not associate with him because I didn’t like him.

Kelly:  Did you know Ted? Did you know Ted Hall?

Peshkin:  No.

Kelly:  Okay.

Peshkin:  I did not know Ted Hall. Well, I probably met him. But when he became famous later, I barely remembered him.

Kelly: The bomb. At first, when you believed you were in a race with Germany—

Peshkin:  Well, should we have built that bomb? Having built it, should we have used it? Now these are issues, which are just the reflections of a person who has been thinking about it for many years. It has little to do with my experience directly at Los Alamos. I was not part of any of these decision processes, of course. Well, it was known, not by us, that the Germans had given up around 1942, I think. Certainly by 44’. We were building it because we were in a race with the Germans. Boy, that was some powerful incentive to work on it. We certainly knew when the war ended, that we were no longer in a race with Germany.

We continued to work on it at the same pace. Taking the experiments, taking the same deadly risks without giving it a moment’s thought, most of us. There was one person who actually left the project. There must have been others who had grave doubts. I did not. We were working on it; we were still at a war with Japan. The war with Japan was won. But we didn’t pay much attention to it. I think we even relished the idea of using this weapon on the Japanese. At least many of us did. I’m afraid I did.

Well, should we have built that bomb? In retrospect, I think that the answer is yes, but for a totally different reason than the ones I just mentioned. Norman Ramsey, who was on the plane that accompanied the Hiroshima bombing, the Enola Gay, said in a public speech, which I heard, and answered to a similar question. “If we had not used that bomb to end that war, it is highly probable that it would have been used to start the next war, more than likely by us.”

That’s a very interesting statement. We would not have done the experiment that showed us quite how horrible the consequences were. We would have had a lot more of them. Others would have used them on us. It doesn’t speak to the question, should we have built the bomb? But it’s related to it. Because once fission had been discovered in 1939, it was obvious to every physicist in the world that the possibility of making a fission bomb existed. It was not quite obvious that it would succeed. But only a few relatively easy experiments were needed to find out how many extra neutrons per fission, things like that.

We and the Russians, we and the Soviets, could not have trusted each other. They would have had to go for it, and we would have had to go for it. We had the advantage of great industrial superiority. They had a ruined economy. But they had the advantage that Stalin could force all the best people to work on it. We did not have that advantage. It’s not obvious that we could have gotten all these people to leave their universities and go to Los Alamos. One may speculate, but it’s certainly a reasonable speculation that they would have gotten there first. Then what would have happened?

The issue of using the bomb is much more complicated. Important reasons, pro and con, have been given. People have debated that for a long time. The reasons pro, the most obvious reason pro, is that we were about to invade Japan. We anticipated a million causalities, of whom one-fourth would have been dead. We anticipated that in the process, we would have killed many millions, maybe tens of millions of Japanese, innocent Japanese civilians. We could end the war right then and there. That was certainly a powerful reason. Richard Rhodes — no I’m sorry. It wasn’t Richard Rhodes. Richard B. Frank, the military historian, mentioned another reason that I had not heard until I read his book.

The Japanese Army, he said was killing 100,000 people a month in China and Manchuria, civilians that is. And every day that you waited to use that bomb, 3,000 more would be killed. Well, I don’t know whether that would have influenced the decision makers. What surely would have influenced the decision makers is that Russia, was ready to join the war—had joined, in fact, a few days before the bomb was dropped. A few weeks. If we had let them help us with the invasion of Japan, they would have shared in the occupation. That leads to a kind of desperately awful calculus. In that sense, the people of Hiroshima and Nagasaki were the first victims of the Cold War. The awful thing is, that in that sense everybody else in Japan was a beneficiary of our having used the bomb.

I have many Japanese friends. I have gingerly felt them out. I have yet to speak with one who didn’t say in some way, that they were somehow relieved. I’m sure there are such ones. But I have yet to speak with one. So that was a reason for using it. Also, we had cracked the Japanese code. We knew what the Emperor and the Generals and Admirals were saying to each other. And Richard B. Frank, who has read the translated transcripts says, he’s a historian, says that they were not ready to surrender.

On the other hand, Martin Sherwin, who was also a historian, has done that same thing. He thinks that they were ready to surrender. He thinks that he people around President Truman knew that they were ready to surrender, on the condition that they get to keep their Emperor. Which was the condition on which they finally surrendered anyway. Now, I could easily see that Truman and the Generals, faced with the choice between using that bomb or carrying out that dangerous—that dreadful invasion, might have found it a very easy decision to use the bomb.

That is the discussion that one generally hears. But you know, that really begs the issue, the question really was, why invade? The Japanese were defeated. Why not warn them? Why not make an attempt to get them to surrender? I think the historians are all in agreement that no such attempt was made.

So you ask, should we have done it? I’m not quite sure. I think not. By doing it, we caused all that suffering. Which you can maybe write off against the suffering that would have occurred had we not done it. You can say that we did nothing new because on March 9th, 1945, we had conducted a thousand-plane raid over Tokyo and killed at least 100,000 people. But you know, it was really a qualitatively new weapon. A thousand-plane raid is something that you can mount once in a war, maybe. We lost, I don’t know, thirty B-29’s and all that stuff. This was a raid by one airplane. You could do it once a week if you could make the bombs once a week.

It did something else too. It destroyed our moral leadership in the world. Whatever we have been thinking, other people in the world saw that we had used this horrible new weapon on a defenseless unwarned civilian population. And, incidentally, that these civilians were not white, they were not Christian. Other people had to learn a lesson from that. Every country in the world had to face the fact that we might be willing to bomb them under some circumstances. Especially, the third world countries, to which we do not have the same attachment that we have to Europe.

So on balance I think that a well-meaning President made the worst decision that anybody in the world has ever made. As far as my own part in it is concerned, I recognize that we had to do that and that I didn’t have anything to do with the decision. I wish I hadn’t.

Kelly:  What do you think of the argument, that if we hadn’t used it in the Second World War, we might have used it to start the next war? And that would have been a far worse outcome?

Peshkin:  Well, that is what Norman Ramsey indicated. It could easily have been true. The Russians could have gotten there first and attacked us, in fact. But the notion that we would not, unprovoked by what we thought was a survival problem, use that on people is one which I think is very naïve. These decisions are not made by you and by me. They’re made by military people who are used to doing things that you and I shudder to think of. They’re made by presidents who are subject to amazing pressures and may not be thinking that all clearly. Let me tell you, it is not only they.

In November 1948, Bertrand Russell, who was a great pacifist, and at one time a great communist, urged in a public speech that we should use those bombs to attack the Soviet Union before they got them. If Bertrand Russell could suggest such a thing, I think Norman Ramsey is right. We might have done it.

You remember I told you that I went in there to help clean out that lab after Louis Slotin’s accident. It was just funny. There were workers, ordinary janitorial type workers. They were mostly people who lived in the area, whom were to go in and clean up the place. Phil asked them to do that and they refused. Because they said that all the bugs in there were dead. Phil just laughed and said, “I guarantee you; if you put new bugs in they won’t die, because they had died in that explosion or they had died of starvation or something in the time that the lab was closed.” It doesn’t take very long. But they were afraid. So another person and I went in and cleaned it up. It was not dangerous. I mean, there was so little induced radioactivity, it was nothing to consider. So we went in and we cleaned out the stuff.

Kelly: And the bugs.

Peshkin:  It’s only a sidelight on the way that we just continued to go on and do things. Had there been any doubt, it was no hurry about cleaning up that place. The plutonium had already been removed.

The FBI was hounding Phil Morrison. They followed him around everywhere. I knew other people whom they hounded too, and whom they succeeded in getting fired by a series of employers by going in and saying to them, “Oh, we’re so glad this guy is working for you. You can keep an eye on him for us.”

The employer knew what that meant. Phil couldn’t be fired by Cornell because of his tenure and all that.

He came to give a talk in Chicago at a meeting of the American Physical Society. Then he was going to a party that evening at the home of a friend who lived in Highland Park, just north of Chicago. I drove him there. We had this pleasant social evening. My friend’s wife, who was easily made suspicious, kept saying that there were noises outside. This was a quiet suburban place on the shore of Lake Michigan. We all said to her “Oh, Judy, that’s nonsense.” My friend had been renting the place from a third friend for the summer, while the third friend was away.

When the third friend came back, the Chief of Police of that little town, Highland Park, came to him and said, “You don’t want to rent your house to that person again. The FBI came and made us put a twenty-four hour watch on it.” You know, the Highland Park policemen in those days were people who really had no taste for lurking around in the bushes and spying on people. Also, they were not really athletically equipped for that kind of stuff. The most serious crime that they usually had to contend with was overtime parking. 

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