The Manhattan Project

Bruce Cameron Reed's Interview

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Bruce Cameron Reed's Interview

Bruce Cameron Reed is a physicist and a professor at Alma College. In this interview, he discusses a course he teaches at Alma about nuclear weapons and the Manhattan Project. He explains how he became interested in the physics and history of the Manhattan Project. He provides an overview of some of the challenges the Manhattan Project scientists faced and why uranium, plutonium, and polonium are so difficult to work with. Reed describes some of the innovations of the project, including the implosion design and lenses, the tamper, and the polonium initiator. He concludes by sharing his thoughts on some of the ethical issues related to nuclear weapons.
Date of Interview: 
January 30, 2017
Location of the Interview: 
Washington DC
Transcript: 

Cindy Kelly:​ This is Monday, January 30th, 2017. I’m Cindy Kelly, Atomic Heritage Foundation. We are in Washington, D.C., with Bruce Cameron Reed. If you could say your name for us and spell it.

Bruce Cameron Reed: Bruce Cameron Reed, B-R-U-C-E  C-A-M-E-R-O-N  R-E-E-D.

Kelly:​ Great. Bruce, tell us about yourself. I know you’re a professor at Alma College, but maybe you could start at the beginning—when and where you were born and how you got interested in science.

Reed: ​I was born in Toronto in 1954. As a kid, it was the height of the space race. I can remember in grade school watching John Glenn and Alan Shephard and all these guys, and it was so exciting and exotic. I guess that spurred an early interest in science. I was a classic kid science geek with his little telescope. There was that space influence.

When I became a university student, I studied astronomy and physics at the University of Waterloo in Ontario. It had a very strong physics program. I eventually did my Ph.D. there. When I began my academic career, I was doing sort of conventional astronomy research and teaching physics. 

But always in the back of my mind had been this interest in this history. This may sound a little strange, but I can remember when I was about eight years old during the Cuban Missile Crisis, my father had a darkroom in the basement of our house. I remember my parents outfitting this little darkroom as a bomb shelter. That was just part of the culture then, of course. At that age, it seemed like some sort of an adventure. But they must have been scared out of their wits. 

Anyway, that interest was always in the back of my mind. As a physicist, you can’t help but be interested in this sort of thing. I guess like so many people that come to this, I read Richard Rhodes’ book [The Making of the Atomic Bomb] when it first came out. I thought, “I want to learn: what is the physics of this? How does all this stuff work? How did they calculate this stuff? What’s the relevant physics?”

I began slowly reading papers, reading journal papers, digging out my old nuclear physics textbooks, and began calculating things. Then as this built up, I realized that so much of the physics that underlay nuclear weapons is actually quite understandable to a good undergraduate physics student. 

I began publishing some papers in physics journals and contacting people. Then you realize, well, it’s so much more to it than just the physics. You can’t separate the physics from the historical context and the people involved, so you can’t help but get interested in all these other aspects of the project as well. I tell my students, “It’s addictive.” I began just being curious to know, how did they calculate a critical mass? Then it kind of blossomed, because every aspect of this thing connects to so many others, and you can’t just pull them apart one aspect at a time.

It kind of grew from there. I was lucky in the sense that I could let it become a professional obsession, and publish papers on it and go to conferences and write books and speak with people that were involved in this. There’s always something new to learn. It seems almost infinite in its aspects. That’s how I came to be here.

Kelly:​ That’s wonderful. Tell us the span of the courses that you’re teaching at Alma College now. 

Reed:​ We are a small liberal arts college, about 1,400 students. My mainstream, everyday work is traditional physics classes, everything from a first-year physics course for pre-med students up to our senior-level quantum mechanics class. There are only three of us in the department, and so you end up over the years teaching essentially everything in a physics curriculum, pretty much. Which has its advantages, because it lets you, over your career of doing that, see the connections between those things in a better way than you probably appreciated when you were a student yourself. Because you keep dabbling in all those areas, you can build the connections.

Then specifically, when I began getting interested in this Manhattan Project material—I guess now about twenty years ago—after a little while, I realized this would be the perfect topic for one of our general education classes. Every student, no matter what their major in the college, has to take a physical science class. There are the usual things like geology and astronomy. I proposed putting on a class on the history of the Manhattan Project and the relevant background physics, and this sort of thing. I do that typically about every two years. It gets a lot of history students, political science students that have to get a science credit, a physical science credit. They find that looks relevant to their interests. 

I am sure you know this, that our present generation of students, many of them have no idea of the history of this, of the historical context, who was involved, what was involved. I have come to see it as not only teaching them about the physics and the context, but doing a kind of a public service in bringing some of this knowledge to this generation. 

Kelly:​ What is the most important takeaway from the Manhattan Project that you hope your students absorb? 

Reed: ​I think that’s a hard question, because there are so many aspects. One is that you can accomplish such work of enormous complexity with competent people running it, being allowed to appoint competent people to do the jobs. Many students are surprised to learn that this wasn’t just a couple of guys sitting around a coffee pot and deciding to invent a nuclear weapon, that there was a long history of underlying discoveries.

When I begin the course, I begin with the discovery of X-rays and radium, which are buildups for some of that twentieth century physics history. This was by no means preordained. Nobody anticipated the discovery of fission. A lot of these discoveries were just accidental, serendipitous discoveries that then kind of accumulated to the point where nuclear fission was accidentally discovered within weeks. A number of people recognized that this was a possibility, but it would be extremely difficult. 

I think they are often surprised at the vastness, the complexity of the whole project, that so many hundreds of thousands of people were involved, it cost so much money. But it was kept largely secret, which I think would be impossible today, because everybody would have their cellphone inside a factory somewhere.

Then when we come to the part of the course that deals with—after they had worked through the many, many challenges of getting working designs for these weapons, that these were not just willy-nilly dropped somewhere in Japan, that very serious people were giving serious consideration to, “How would this affect the geopolitical strategies?” The Target Committee, the Interim Committee, this went up to very high levels in the government. It was being taken very seriously by very serious people. It wasn’t just some willy-nilly decision.

The entire context of the war, I think, is a surprise to many of my students. They have, in many cases, no idea just how ferocious the war had become and how long it had dragged on. The idea that a prospective invasion of Japan would have been just horrific, had these bombs not come along.

There are multiple takeaway messages: the vastness and the complexity of these things, the organization challenges and the technical challenges. If you look at it in retrospect, any one of those things could have derailed the whole thing. There are so many ways this might not have come to fruition, with all the complexity and difficulties they ran into. But they did succeed in making it work.

Kelly: I’m glad you said that, because I think that, especially students today, you read the book and you know what happened and it just all seems so inevitable.

Reed:​ It was far from inevitable.

Kelly: ​Right. What were some of the challenges? I invite you to talk not just about technical challenges. You mentioned organizational challenges. What kinds of things?

Reed:​ I often wonder if, say compared to the present day, if an equivalent discovery of such potential import were made, how would information on that be gotten to the relevant decision-makers? The architects of this were very fortunate in that they had very competent people, competent engineers who had the access to people like the president to make them aware of the potential of this.

When research began getting organized, it was very disparate. It was in a number of universities and industrial labs across the country. This had to get put together coherently to avoid overlap, but also keep some compartmentalization and things. Because there were really so few people at the top of the heap that really had a comprehensive view of the entire enterprise. Those people faced enormous organizational challenges—keeping all these balls in the air at once.

I think, to my mind, the person that’s always underappreciated is General [Leslie R.] Groves. He was remarkable. Stan’s [Robert S. Norris’] description of him is “The Indispensable Man” [in Racing for the Bomb]. I think before I really began to dig into this, you get influenced by the Hollywood versions of this man as a bit of a blowhard, or something like that. But he was a very smart, dedicated, hardworking man who just must have worked tirelessly for three years to bring this to fruition. To organize one activity like an Oak Ridge or a Hanford or a Los Alamos or a CP-1[Chicago Pile-1] would be a job for anybody. But to keep all of those things running in parallel and solving their problems simultaneously, I think is really remarkable.

In all of the documents one reads, the financial reports and everything, there’s never a hint of anything, not a penny improperly spent of $2 billion. Imagine that now. Yes, there were areas of research they pursued that turned out not to ultimately be used, but of course, they couldn’t know that before they started. But I have never had a sense in anything I have ever looked at that anything improper was done in such a vast enterprise, which was being kept very hush-hush.

Kelly:​ That was great. I’m just pausing, because there are like a million different avenues to pursue. Thinking about innovations in a technical sense then, can you give us one or two examples of what you think—

Reed:​ Oh, I think many.

Kelly: ​Okay. Give many then, just don’t stop.

Reed:​ I was thinking about this when you were speaking with John [Coster-Mullen][0:15:00]. This is going to probably be biased by my own physics background.

He alluded to some of the developments in high-speed electronics for triggering the bombs. In the testing of the implosion bomb, they had something like six different diagnostic tests for the symmetry of the implosion. Some of these were incredibly ingenious, like, as something would implode, they would have electrical wires inside the assembly. The resistance would change as the density of this material changed. By monitoring an electrical current, you could measure the symmetry of the implosion. I think nothing like that had ever been done before.

Reed:​ As a professor would say, consider a spherical lump of plutonium about the size of a softball sitting in my hand. To trigger the nuclear explosion, this has to be compressed to a higher density. Then the issue becomes, how do you compress a metal maybe to half of its initial volume? This requires an enormous amount of pressure.

The technique they developed for achieving this was to essentially wrap it in segments of explosives in a three-dimensional assembly. Think of sort of pyramid-like chunks of explosives that would fit together like a three-dimensional jigsaw puzzle, which when detonated would blow inward to crush this thing. There were 32 segments surrounding that core altogether, and given the speed of the explosive, they all had to trigger within a microsecond. The simultaneity of the detonators—if the implosion, if say a little off-centered or asymmetric, the core might shoot out one side or you get an uneven density compression, you get a much less efficient nuclear explosion than what you were trying to design for.

They invested an enormous amount of effort in getting that symmetry correct, even to the point of testing things such as putting radioactive sources within a test implosion assembly. As that was crushed, radioactive material would be released and you could monitor the radioactivity as this thing went through its microsecond operation.

These things had to be monitored on that timescale. They developed [0:18:00] X-ray cameras that can operate at microsecond exposures to actually image the implosion. These huge developments in electronics and high-speed photography and this sort of thing, all those diagnostic tools for developing that weapon were really remarkable.

I think along with that, sort of on the theoretical side was, there would really be no project, no scientific work prior to that, that used computation to such a degree as they did. In the days before everybody had a computer on their desk, trying to write an algorithm to simulate an implosion, or what happens once the reaction is triggered. People with slide rules and primitive electronic calculators doing these sort of step-by-step simulation calculations at one nanosecond step at a time to simulate the progress of the explosion.

Of course, now computation is such an integral part of anything in the sciences, but that was really revolutionary at the time. Using primitive punch-card machines, basically tube-driven computers—which would take hours to run a simulation that would now be done in milliseconds—would take them weeks. The whole development of computational physics was a huge enterprise at the time. We take it for granted now, but it was enormous.

Some of the techniques for enriching uranium had never been done on a large scale before, like the gaseous diffusion. When it originally was developed, one might get micrograms. The first isolated samples of uranium-235 are nanograms, smaller than the head of a pin. Some of these techniques then had to be scaled up to get tens of kilograms. Almost literally separating uranium into its constituent isotopes, atom-by-atom, and being able to do that on a scale large enough and quickly enough to isolate enough material in a year or two to make one or a few weapons. There had never been such an industrial infrastructure.

Carrying on from that a little bit, I have never tracked [0:21:00] down this figure, and I assume it’s accurate, but I remember reading somewhere that the capital investment in the factories, in the plants, was equivalent to the automobile industry at the time. The contractors built an infrastructure equivalent to the entire automobile industry of 1940 in about two years, and made it work. I want to get a student to go back and check the stock prices of all those companies in 1940.

These facilities were built so well. The original Hanford reactors operated into the 1960s, and they were still operating but had been eclipsed by larger ones. The gaseous diffusion plant operated until 1985, and some of the calutrons into the 1990s. These things were built, they lasted half a century almost. That’s a really remarkable undertaking for something that had never been done on that scale before.

Reed:​ I don’t know if you would put this under the heading of “innovation,” but probably never before had there been such a marriage of science, scientific research, industry and military engineering to such a degree.

These rather disparate entities, these academic scientists and researchers, then within the culture of the military hierarchy and engineering, and then the entire culture of the industrial engineering people, the chemical engineers from DuPont and Westinghouse used to large-scale factories. Probably very removed from the beautiful, pristine calculations of some physicists put into practice on that large scale. Those are very different cultures of people: academic scientists, industrial engineers, the military. Coordinating these very different cultures was probably an enormous challenge in itself.

Kelly:​ Also, you mentioned the challenge of the pristine theories meeting the messy realities of—

Reed:​ The practical reality.

Kelly: —yes, exactly. Can you talk about the relationship with the scientist and the engineer? That’s sort of on that theme.

Reed: ​Many of the folks viewing this video will be familiar with the fact that there were criticality accidents at Los Alamos. A good physicist can calculate a critical mass for uranium-235. But they had to test this in a laboratory by bringing close together two pieces of enriched uranium, yet not letting them get too close together. Monitoring the neutron flux as these things got closer and closer together, and then extrapolating that laboratory experiment to an entirely assembled system. The calculations weren’t just relied upon solely. People were doing hands-on experiments with these very dangerous materials to actually test these theories.

Then they would make these larger and larger critical assemblies as more and more fissile material came from Oak Ridge or Hanford, and they could more closely approximate a finished critical assembly without actually getting there. That is dangerous work. These people really had to know what they were doing.

I cannot imagine standing over an assembly of enriched uranium that is so close to critical that if I lean over too closely, my body will reflect enough neutrons back, if I get a little too intimate with the thing, to induce criticality. They were that close. I think it’s kind of amazing to me that they didn’t have more accidents.

There was a culture of safety consciousness, but also that drive that, “We have to do this. We have to get this job done.” Didn’t have time, I guess, for elaborate precautions that would be taken now.

Reed: Well, when one envisions a person holding a plutonium core or a uranium core in their hand, it’s rather remarkable to me.

Kelly: ​Have you held one?

Reed:​ No. I have held a cubicle lump of pure uranium metal, which came from one of Werner Heisenberg’s reactor experiments. It was unenriched uranium metal, but you can tell it had been machined and deliberately machined. It’s a little cube that weighs about five pounds. You just have the sense of literally holding history in your hand, or something like that.

Kelly:​ It was little, but it felt pretty heavy, I bet.

Reed:​ Yeah. It was about five pounds. It would easily fit in the palm of your hand. I can show you a picture later. It can be fascinating to view some of the artifacts. I was thinking of some of those innovations. I am sure you have seen at Los Alamos the implosion lens molding machine that is in the Bradbury Museum. Here are these people making these casting, molten explosive into a mold in a commercial candy-making machine. Then casting thousands of these, taking them out, perhaps holding them in their laps while they machine off the rough edges of a cast explosive to make sure it all fits together accurately. To see some of these artifacts when one gets into this and to touch some of these things and think of, “Who was involved in this? Who would have been there and seen this stuff and used it?” and the contribution it made can be quite striking.

Kelly:​ There are a lot of good stories about [George] Kistiakowsky, just what you were saying, trying to shave off the explosive lenses. [Richard] Rhodes asked him, “Gee, what happens if when you’re sawing this, you accidentally cause it to explode?” He said, “Well, I would never know.”

Reed: No. They worked with non-conducting tools. They would, to maintain the symmetry of the implosion, these cast chunks couldn’t have air bubbles in them, so they would X-ray all of them. If there was a void inside, they would drill into it with a non-conducting tool, rather like a dentist getting to a cavity, and then melt a little more explosive and pour it in there to patch it up.

These were literally handmade nuclear devices. Every component fitted together by human hands, and taped together. It wouldn’t be like manufacturing widgets on an assembly line. All pieces were assembled by hand.

Kelly:​ Can you talk about the initiator and what that did and how that was made?

Reed:​ What I can give is what I have read of best speculation, because apparently these are still very highly classified—the actual structure a very highly classified device.

The initiator was apparently about a golf ball-sized sphere at the very core of the weapon, which when crushed by the arrival of the projectile piece in the uranium bomb, or the implosion in the plutonium bomb, would emit neutrons to trigger the nuclear reaction.

The physics of this, how it operates, is in any textbook. There’s a process that if you have a radioactive substance that is an alpha-decayer—alpha decay has been known since Ernest Rutherford in 1902. There are some elements such as polonium that are very prolific alpha-emitters. An alpha particle, if it strikes a nucleus of a light element such as beryllium or aluminum will tend to emit neutrons. It’s called an (alpha, n) reaction.

It was involved in the way James Chadwick discovered the neutron in 1932, ironically. I often wonder what he thought. Such a reaction was involved in his discovery of the neutron. Thirteen years later, he finds himself at the Trinity Site seeing what his neutrons could do.

What one would need in one of these devices would be then a sample of something like polonium, some layer to separate it initially from the light element material. I understand beryllium was used so that the alphas couldn’t penetrate that little protective layer before the bomb is triggered. Then when the triggering goes and the device is crushed, the two materials mix. You can do a rough calculation from estimates I have read of the number of grams of polonium there, that in the sort of critical microsecond of assembly, you get about 100 neutrons to then trigger the nuclear reaction.

These were very tricky devices, because the polonium has a short half-life. I’m trying to remember it off the top of my head, but 130 days. They have a limited shelf life. You would have to keep producing this stuff, which was produced in the reactors at Hanford and Oak Ridge. It’s highly radioactive, so it has to be extracted very carefully, then shipped to Los Alamos, configured into these small devices—which would have their limited shelf life—and then plunked into the core of the weapon when you’re getting ready to detonate it.

Initiator design was apparently a very tricky part of the—the material was dangerous, it was highly radioactive. You want this thing to function at the exact microsecond when you want it to function, but not beforehand. There was a whole chemistry component of the Manhattan Project located in Dayton, Ohio, by the Monsanto Chemical Company that was responsible for the extraction and processing of the polonium, which is not well known.

Reed:​ I remember coming across a letter from Oppenheimer to Groves, about the summer of 1943, already beginning to lay out specifications for what sort of neutron flux they would need from these things to get a credible detonation. It was an integral part of the project that had gone on for a good two years before Hiroshima.

Kelly:​ This letter was from or to Oppenheimer?

Reed:​ From Oppenheimer to Groves. Even down to the level of specifying the average number of neutrons they would want to have released during the operation of the initiator, then deriving from that how much radioactive material you would need in these things.

They originally considered radium, apparently, as there is a fair amount of it around, but it’s not nearly as radioactive as polonium. You get away with a much smaller mass of polonium than radium in the initiator.

Kelly:​ I’m interested in seeing Atomic Time [Jim Sanborn] again, because from the photographs the initiator is exquisitely crafted. They had a jeweler create it. There are some gold casings, and it’s remarkable how this is—

Reed: ​Gold would be heavy enough to stop the alpha particles emitted by the polonium.

Kelly:​ Right.

Reed:​ They also, apparently, from what I have read, considered for the tamper materials ofthe bombs to increase their efficiencies using pure gold as a tamper material and tested that as a possible tamper. The notion for these guys of vaporizing a few hundred kilograms of gold was routine. They used other things, ultimately, but that was the level at which they were operating.

Kelly: ​Can you explain what the tamper was?

Reed: ​If we have our uranium or plutonium core, it’s advantageous to surround that with a metal jacket, say a few centimeters thick. Even if it’s not imploded, even if it’s just sort of static, like in the uranium bomb, this serves two functions. As the chain reaction proceeds and neutrons are emitted from the core, if you can reflect those back into the core, they have another chance of causing the fission and increasing the efficiency. You get an [0:39:00] efficiency boost just by the effect of this reflection.

Simultaneously with that, the core heats up and expands very rapidly. I mean, this thing’s expanding at a rate of thousands of meters per second within a microsecond of the initiation of the chain reaction. If there were nothing to restrain it, it would just blow itself apart very quickly. You’ would lose your critical density, and you would have a very low efficiency explosion.

Just the inertial effect of this surrounding shell, which could be several hundred kilograms, retards the explosion for a minute amount of time to allow a bit more efficiency to build up. It has both this reflective and inertial property that enhances efficiency. You can increase your efficiency manifold, even with a modest tamper. It’s certainly worth the trouble of providing one.

Kelly:​ They thought of everything.

Reed: ​I would encourage anybody seeing this to read the Los Alamos Primer. They had worked out by the spring of 1943—even earlier than that, actually. They were well aware of the concept of a tamper by 1941. They had made estimates of what sort of sizes and masses might be involved, and some rough estimates of the efficiency enhancement. It is a remarkable document, because they anticipated so much of what was going to have to be done in experimental physics, in engineering, the theoretical computations, many things were yet to be done.

They didn’t have numbers from any of the experimental parameters, but they had a remarkably clear idea of what sort of experimental program they were going to need to undertake, and sort of ordnance engineering program to make these workable devices. It’s all in about twenty pages.

Kelly:​ That’s a good recommendation. Is there something else other than the tamper that you want to talk about that they might find in the Primer?

Reed: ​Fascinating in the Primer? The Primer covers everything. It is like a mini course on nuclear physics. It helps to have, obviously, some physics background to fill in the gaps. It wasn’t a tutorial document. But it covers everything from the underlying mechanics of the fission process, the energies of the neutrons emitted.

It is remarkable how close a call this was in the sense that—maybe that’s not the way to phrase it. As a physicist, it strikes me as kind of fascinating that there are over 2300 isotopes of over 100 elements are known, you know, have been synthesized. Some occur naturally, a couple hundred, and many, many hundreds more synthesized. Of all those isotopes that have been discovered since Rutherford, only two have proven practicable for nuclear weapons, when one looks at the combination of the physical parameters of the energy needed by a neutron to induce fission, the cross section, the densities, the spontaneous fission problems.

The window just narrows to these two isotopes, one of which occurs naturally, but is incredibly rare[uranium], and the other [plutonium] of which doesn’t occur naturally at all and has to be synthesized by first getting a fission reactor operating and controllable. It’s, to my mind, a remarkable sort of confluence of factors in nature that, to a physicist, it’s just fascinating that all these factors interplay in such a way to narrow it down to this narrow window, what I have come to think of personally as the window of facility.

They were aware in 1943, at the time of the Primer, of the possibility that spontaneous fission could trigger a reaction before intended. But apparently the magnitude of the effect of plutonium came as a very rude surprise, and that prompted the whole development of the implosion technique. It was a classic case of something that in theory looked promising, looked good, but then turns out to have some horrific practical complication that made their lives very difficult.

Kelly:​ Was this illustrated in the test, the first—I guess that was the hydrogen bomb [Castle Bravo], that was so surprising, that they were so far off in—

Reed: Oh, yeah.

Kelly: —their estimate.

Reed: ​I admit that’s much more out of my kind of area of interest and background. I gather in that case [0:45:00] they didn’t anticipate some of the materials in the first thermonuclear weapons contributing so much to the energy release. I think the particular culprit was lithium, which was used in some of the reactions of this thing, a particular isotope of lithium being more fissile than had been anticipated. Now, I am going to want to check this out, because I probably garbled it up, but it resulted in underestimating the energy release.

The predicted energy release of the Trinity device, there were estimates that were sort of all over the place. But they actually had a pretty good handle on estimating by the summer of 1945 that the implosion would work correctly, what sort of efficiency they should get. These guys were good.

Kelly:​  I showed that slide of the Pond Cabin where Emilio Segré—yes, does that tell it like it was? Working with such crude and humble—

Reed:​ Equipment.

Kelly: —equipment.

Reed:​ Table top. That is something to me that I think—I try to show my students, actually, is James Chadwick discovered the neutron with an experimental vacuum chamber that would fit in your hand, would literally fit on the table beside you. Segré must have been doing something with kind of similar—the first prototype diffusion cascade apparatus would sit in a wardrobe cabinet.

Some of these things were literally handmade devices. Alfred Nier’s spectrometer that he isolated the first uranium-235 with was a handmade spectrometer in his lab, made with a budget of a few hundred dollars. He isolates this minute amount of uranium that you could be dramatic and say changed the course of history. The first synthesized samples of plutonium were so small they could only be seen under a microscope, and that had to be scaled up to kilograms.

But I think when I was a student, this is what first attracted me to astronomy, was the combination of every scale of energy and size and time comes into astronomy. Because stars operate by nuclear fusion, so these minute nuclei of atoms, and yet then you have stars, which are the components of galaxies, which are the components of the universe. You could have every time scales from literally the atomic, the subatomic, to billions of years.

In a way, I guess, the nuclear devices are like that, in that these reactions on these most minute scales, individual nuclei, and yet have latent in them, in something that would fit in a size of a softball, latent in them is so much energy that can be released. That’s just staggering.

It’s easy, a physicist comes to this because of the technical stuff and the computational stuff. But I have also found that just reading the personal stories of the people that were involved is fascinating. Even if one of your listeners is not a physics student, but a sociologist or an organizational theory student or something like that, some of the personal stories of the people that were involved are just compelling.

You can’t help but be compelled by the story of an Oppenheimer, in some ways his own worst enemy. Or of Lise Meitner fleeing Germany, and then learning later of the discovery of fission. By the good fortune of [Otto] Frisch and [Rudolf] Peierls ending up in Birmingham and writing their memorandum in the spring of 1940. Or Hans Bethe or Enrico Fermi. Just some of the lives of these people are fascinating.

They are just endlessly fascinating characters. Then to contrast somebody like an Oppenheimer and a Groves—no writer of a Hollywood drama, they would not have to dramatize it, because the story is so good by itself. This mixture of incredible personalities that you wonder in ordinary life just wouldn’t come together.

Reed:​ Something we haven’t sort of talked about: you raised in your discussion with John [Coster-Mullen] a little while ago, some of the ethical issues in the context of the war and the endless historical debates about the use of the bomb or not. I think something that’s easy to forget is what I have come to think of—this is my own terminology—the theory of nuclear inoculation. That if these things had not been developed when they were and affected the end of the war—perhaps one can debate to what degree the bombs were responsible for ending the war. But I think if they hadn’t been used at that time, they could have easily been delayed by a few weeks, any number of problems.

Then what might have happened in a later war when there was more of them held by more countries and they were more powerful, if we had not become aware in 1945 just how powerful these things were. Even Hans Bethe has said that he felt that the bombings of Hiroshima and Nagasaki were necessary to help end the war and inform the world of the nature of these things, that they can’t be used again. Maybe it has had some deterrent effect over the last seventy-five years. What might have happened in Korea or somewhere else?

​I do try to explore some of those things when I put this before my students.

Kelly:​ Yeah, that’s really important.

Reed:​ There was this horrific context. Who would want to be saddled with a decision like that, you know, with an ethical issue like that? But that’s what these guys faced. Here we are.

Kelly:​ Are there other things that you try to get your students to think about in terms of today’s world?

Reed:​ Well, yes. The relationship between scientists and society, and the ethical issues of what they do. Of course, there are so many things now where scientific ethics are important. You could think of genetic engineering or geoengineering, climate change. These have just a myriad of technical issues and ethical issues that are still very much with us. This wasn’t some remote abstract sort of thing. This was real people in their lives involved in this stuff, sometimes torn by it.

Yet in the circumstances of the time—sometimes I ask my students, “What would you have done, knowing what you know, had you been in that situation? Say, if you are President Truman, what would you think about doing?”

Science and physics just isn’t this cut and dried abstract stuff. It has real effects. It affects the world. What about ethical issues of artificial intelligence? Their generation will inherit that. My God, I’m becoming a sociologist. For a physicist, that’s—

Kelly:​ That’s great. Yeah. There’s no boundary, although in curriculum, or curricula, they tend to say, “Here are the humanities courses, here are the science courses,” that they are two worlds.

Reed:​ In real life, it’s not like that.

Kelly:​ Yeah, I know. So it’s good you are preparing your students to be broad-gauged.

Reed: I hope so. They are often horrified to learn that, okay there was the war, the atomic bombings, and [0:57:00] they are often just incredibly surprised to find out how big the nuclear arsenals got, how many tests there were, how many nuclear weapons there still are in the world. They are just astounded. I have had students guess, “Well, maybe we have a few of these things, maybe they tested a dozen or something.” They are just astounded by how enormous this became during the Cold War. They lived through none of that. They have no experience with it, that many times there were close accidents.

I think we can hope for a steady downward trend. One wonders whether they would ever be eliminated altogether. You can’t uninvent this knowledge. Even very conservative military planners say that we don’t need as many of these things as we have, we could do a perfectly credible job of security with half of what we have got.