In Our Time - The Manhattan Project

Episode Date: October 7, 2021

Melvyn Bragg and guests discuss the race to build an atom bomb in the USA during World War Two. Before the war, scientists in Germany had discovered the potential of nuclear fission and scientists in Britain soon argued that this could be used to make an atom bomb, against which there could be no defence other than to own one. The fear among the Allies was that, with its head start, Germany might develop the bomb first and, unmatched, use it on its enemies. The USA took up the challenge in a huge engineering project led by General Groves and Robert Oppenheimer and, once the first bomb had been exploded at Los Alamos in July 1945, it appeared inevitable that the next ones would be used against Japan with devastating results.The image above is of Robert Oppenheimer and General Groves examining the remains of one the bases of the steel test tower, at the atomic bomb Trinity Test site, in September 1945.WithBruce Cameron Reed The Charles A. Dana Professor of Physics Emeritus at Alma College, MichiganCynthia Kelly Founder and President of the Atomic Heritage FoundationAndFrank Close Emeritus Professor of Theoretical Physics at the University of Oxford and a Fellow of Exeter College, OxfordProducer: Simon Tillotson

BBC Sounds, music, radio, podcasts. Thanks for downloading this episode of In Our Time. There's a reading list to go with it on our website, and you can get news about our programs if you follow us on Twitter at BBC In Our Time. I hope you enjoy the programs. Hello, on 16th of July, 1945, the first atomic bomb was detonated at Los Alamos, New Mexico. In less than a month, the second and third bombs were dropped on Hiroshima and Nagasaki, killing hundreds of thousands of people.

This was the outcome of the manhomomous. Manhattan Project, a race by the USA to use a widely known theory about nuclear fission to make a weapon of war before anybody else did. It is a momentous effort, with thousands of scientists, hundreds of thousands of industrial workers, and billions of dollars. Some believe that its use over Japan remains one of the darkest chapters in human history. With me to discuss the Manhattan project are Bruce Cameron Reed, the Charles A. Dana, Professor of Physics at Emeritus at Alma College, Michigan, Cynthia Kelly, founder and president of the Atomic Heritage Foundation, and Frank Close, Emeritus Professor of Theoretical Physics at the University of Oxford and fellow of Exeter College

Oxford. Frank Close, Frank. What was known about nuclear fission in the late 1930s? Well, in 1938, the discovery was made that if you use uranium, the atoms of uranium are the heaviest that occur naturally in the periodic table, they're very fragile. And the discovery was that, If you just almost touch them with a single neutron, that's a nuclear particle, the uranium was like a drop of water. It would just break apart, split in two. And this action of splitting the uranium has become known as fission. And the process of splitting did two things.

One, it liberated a huge amount of energy, huge on the atomic scale, about a billion times larger than one would get in a conventional chemical reaction. but in addition to splitting in two, it liberated a couple of neutrons. So you put one neutron in, you'd created some energy and made two more neutrons. So those neutrons are now freed up to hit two more uranium nuclei in your sample and continue the process, making what's become known as a chain reaction with an exponential increase in the energy production. And that was in 1938.

Where was that done, Frank? That was done in Germany by three scientists in Germany. It was in the open literature. Everybody knew about it. The idea that you could make an explosion, nobody took that seriously at all. The reason being, to draw an analogy with nowadays, if you think of uranium that you dig out of the ground as being like a group of people and a neutron coming along being like a COVID virus, then there are two types of uranium at work. There is uranium 238, which by analogy is the vaccinated people, and 235 have not been vaccinated. So if you hit the U235, something happens, but for the 238, nothing happens.

So if a neutron hits a U235, in the modern language, it's got an R value of about two, and the thing would indeed increase explosively, but for the fact that U235 is very rare, it's about one in every 140. Most of the uranium that you go on and hit are of the blanketing type which stop the reaction. So at best people thought that if you had maybe a ton of uranium, after the wall, perhaps you might be able to make a heat engine what we now call a nuclear reactor,

but that was about the limit of the ambition. Who first saw the potential of nuclear fission for making a weapon? The first people who appeared to have asked the question, but suppose that somehow we were given a lump of uranium 235, the stuff that can in principle fission and produce energy exponentially. How much would we need to make an explosion? And this question was asked by two Jewish emigres from Nazi Germany working at the University of Birmingham in England.

That was Rudolf Piles and Otto Frisch. and what really frightened them was the discovery that if you had a grapefruit size of uranium 235, you could make an explosion that would be equivalent in strength to a thousand tons of conventional explosive. In addition to that, there would be radiation produced, and they wrote a memorandum. It said that this super bomb, as they called it, would be irresistible. because there is no material structure that could resist the force of the explosion, let alone the radiation.

Now, what happened at that moment was that having had the idea and the shock of the discovery, you immediately then think, maybe scientists in Germany have already had the same idea and come to the same conclusions. Could Hitler already be building such a weapon? And in their memorandum, which they wrote and reached the British government,

they said it's conceivable that Germany is, in fact, developing this weapon. And the only defence against it is to have one yourself. So there in 1940, the beginnings of what we call mad, mutually assured, whether it's mutually assured destruction or mutually assured defense or deterrence. But they had that insight way back then. And they had this insight in 1940,

at the same time the Battle of Britain was raging, the possibility that we had discovered a means of making a bomb that if we got there first, could determine the outcome of a war, which we looked to be about to lose, had a huge amount of impact. And so this project was declared top secret, and the beginnings of the project to try to develop such a weapon was given the code name tube alloys, just a name to cover it from anybody. Thank you. In America it was taken up.

Albert Einstein himself was among those who encouraged the Americans to develop a weapon. And how influential was that support and other support? And when did that get going? Cameron. The letter signed by Einstein that went to President Roosevelt was written in the summer of 1939. And as Frank indicated, it alluded to the possibility of explosives. But it was still very speculative. But the important thing there was that Roosevelt was briefed on that letter in October.

and he directed that a research project be initiated by the then Bureau of Standards. And that project became folded into an organization known as the Office of Scientific Research and Development that was coordinating scientific work that might have military application. And that began in 1940 with research on what would be necessary to both build reactors and isolate the uranium 235 that could be used in a bomb. And so the possibility was taken very seriously, and funding began to ramp up in 1940. Was the American president, was he in favor of it,

did he take notice of Einstein's letter? Oh, yes, he was briefed on it. As this organization began work on this project, he received regular reports through 1941, in particular, aided by reports as well from Britain that had been stimulated by the Frisch Pyrals memorandum. And by about two weeks before Pearl Harbor, Roosevelt was briefed on the possibilities

who are now looking more likely and that an expanded program should proceed. And so there's a kind of a popular misconception that not much happened before Pearl Harbor, but things were quite active in both Britain, America. How quickly can you tell us, and in America, did they proceed towards the great engineering necessary for this? The Brits had brought a lot of theoretical knowledge to the table. They were a bit ahead of the time, but the Americans took on the burden of engineering and building the process

plant. Let me go to it that way. That began to advance pretty quickly, of course, just after Pearl Harbor, when it was proposed that since there would have to be a huge amount of construction involved, The only some large secret of organization could undertake this. And so in the summer of 1942, the project was transferred to the Army Corps of Engineers, which of course had an enormous budget and could keep this largely secret. So planning for the construction began in 1942 and was seriously getting underway by early 1943. It went at a terrific pace, didn't it? It was incredible.

I think any modern project manager would just marvel at what was accomplished in such a short time. And of course they were under existential threat and had a huge amount of money at their disposal. But it was still a remarkable undertaking in such a short time against all of the other demands of the war. Cindy Kelly, what do we need to know by General Groves and the difference? difference he made, picking up what Cameron's been saying about the speed of this massive enterprise, deploying over 100,000 people, different scientists, different trays and all sorts of things. What do we need to know about General Groves? Well, as Cameron was saying, the Army Corps of Engineers got the assignment to take charge of

this top secret effort in the summer of 1942. The first person in charge was far too cautious. and the leadership lost patience and looked for someone more dynamic. Well, they found that person in general Leslie R. Groves. He was a dynamo, and many say he was indispensable to the success of the Manhattan Project. He was a West Point graduate. He joined the Army Corps of Engineers' Rate as World War I was ending in 1918 and kind of had various assignments.

none of them in war, but in 1940, he had a chance to prove himself. He was a leader in the Army's huge mobilization efforts before the U.S. entered World War II. He directed a million men and spent $8 billion constructing camps, air bases, munition plants, hospitals, and even the Pentagon. In the process, he came to know the leading industrial and construction firms, such as Union Carbide, Messi Eatsman, DuPont, Chrysler, Monsanto, and others who would play a crucial role in the Manhattan Project. He was driven, hardworking, decisive. Most importantly, he was an astute judge of people. J. Robert Oppenheimer, a brilliant physicist at UC Berkeley, was an unlikely choice to direct the scientific research.

But Groves ignored the critics. The relationship was a delicate balancing act, but Groves and Oppenheimer made it work and produced the world's first atomic bomb in 27 months. My goodness. Where were the main sites? They had to find a site for this. Can you tell the listeners where the main site was found?

Can we go through that and settle it? Where they decided to build all this stuff, masses of stuff? Okay. Well, I just want to refer to Danish physicist Niels Bohr comment who said, before any of this got started, that building an atomic bomb could never be done without turning the United States into one huge factory. And the Manhattan Project did that. It transformed the United States with hundreds of manufacturers large and small in nearly every state.

But there were three main top secret sites that were run by the military for the Manhattan Project, where much of the key work was done. The first was a scientific research laboratory in Los Alamos, New Mexico. Here, scientists took over a boys' ranch school. Second was Oak Ridge, Tennessee. This site was dedicated to producing enriched uranium. As Frank explained, you need the U-235 to make an explosion, so they had to try to separate enough of them.

this from the ore in which it occurs naturally. This was the fuel for the bomb used on Hiroshima. The third location was Hanford in eastern Washington State in the northwest corner of the country. This is where the reactors and other huge facilities were used to produce plutonium. So the huge production facilities at these sites were built and operated by leading U.S. corporations. The Army Corps of Engineers had to reach out to Union Carbide, Tennessee Eastman, Free Oak Ridge, the DuPont Company ran the facilities at Hanford. Dozens of other companies built critical parts. Many universities were engaged. I mentioned the University of California, Berkeley, where Oppenheimer was. University of Chicago

had 5,000 people working on reactor design, including Enrico Fermi, and Columbia University. To pick up on Nielsborg prediction, the nationwide network between the government, U.S. companies, and academia was absolutely essential to the development of the atomic bombs. We told about 130,000 people one way and another were employed. Frank Close, how much of a driving force was the fear that Germany, would get there first? Well, that was certainly the thing that had frightened piles and frisch when they first discovered the possibility of making a bomb.

And having discovered the idea, it seemed so obvious, that they naturally feared that the Germans were already doing it. I mean, we now know that they weren't, but at that time that was the driving force. And I think that Groves's mantra was that the project, the mission statement was to get a bomb, and be able to deliver it before the enemy can. A short of issue statement as there's ever been, I should imagine.

Yes, and probably one of the most effective. Let's talk about, Frank, let's talk about the difficulty getting up enriched uranium. How did they go about it when they've got to get a lot now? They set up this industry. Well, the name of the game was to be able to separate the 235. 235 relative to 238 is a measure of their different masses. And so you had to try to separate these slightly different masses. Today, it's done by using centrifuges.

But back in the 1940s, the technology for centrifuges wasn't really that good. And the way that was chosen was the one that Piles started working on in Britain in 1940, with infamous assistant Klaus Fuchs, of whom more later perhaps, was to use diffusion. Uranium in a gas, I think it's uranium hexafluoride gas. The idea was you have the gas in a cylinder, you have a piston at one end and a membrane at the other, and you push on the piston to force the gas through the membrane. And the 235 versions of uranium being slightly lighter, get through the membrane slightly faster.

So on the far side of the membrane, you've got relatively more 235 than 2.38. So you've now got a new sample which is enriched in 235 to use the jargon. You take that sample, put it in its own piston, repeat the process, and you get an even more enriched. So the sort of questions that they were asking initially in Birmingham and later in the States was how many sequences of enrichment you have to do, how long does it take, what's the optimum temperature pressure, how big a facility in practice do you need? And by the time the Brits moved all across the North America and the project was set up as the Manhattan Project in America,

the initial program that Piles and Fuchs and other Brits were working on in New York was the actual design of the Oak Ridge Lab that we've just heard about where the enrichment took place. And the size of that lab was vast. It was a huge industrial enterprise, as we've already seen. I don't think at the start anybody anticipated. if they'd known at the start what it would have involved, whether it would ever happen is an open question, I think.

One thing that I think that we as Americans forget is that this really was an Anglo effort, not just an American effort, an Anglo-American effort. Cameron, what about the challenges when handling plutonium and how did plutonium come into the picture? To quickly follow up on a point that Frank and Cindy made, I've read that the investment in Los Alamos and Hanford was about equivalent to the automobile industry of the time, to give a sense of the financial scale. Plutonium is a synthetic element.

It occurs only in extremely trace amounts naturally, but can be produced by the inert uranium 238 capturing neutrons and then decays to plutonium 239. So the 238 did play a role. And this was the role of the reactors built out in Hanford, Washington, to irradiate natural uranium fuel. And then the advantage of this was that plutonium being a different element than uranium, once synthesized, it could be extracted by a regular chemical means. Rather, than the complex diffusion apparatus that Frank was just describing. And so Groves left nothing to chance. He invested in both methods.

And this was quite remarkable in that, you know, in 1942, there was no discipline of nuclear engineering. This had to be developed from scratch first with experimental models and then building reactors that operated at power levels of 250 million watts. And this was all built in about 18 months. So the advantage of plutonium is, once synthesized, can be chemically separated,

but it proved to be very nasty to work with. It's intrinsically very radioactive. It spontaneously fissions, which put tremendous constraints on the bomb design. It is toxic, like heavy metal poisoning. and the process was inefficient in the sense that only about one atom in 10,000 gets transmuted in these reactors. So they developed a whole new industry of nuclear engineering and nuclear reactors and the associated chemical processes for separating the plutonium.

And that is left, what's left over is very radioactive waste products that are still with us today. But that is the material. it was used in the Trinity and Nagasaki bombs. Thank you. Cindy, what did the people who were working there? These thousands of people suddenly called into work on these massive factories, no expense spared, as big as the automobile industry. What did they think they were working on? I'd say 95% or more of the participants who are working on the Manhattan Project,

the construction workers, the operators of these vast facilities. were not told what they were working on. It was a joke. They were told they were producing toilet paper because... Really? Toilet paper? One of the children told that to his classmates. He said, I know what they're producing.

They're toilet paper. My dad brings home a wall on his lunchbox every day. There were a lot of jokes about what was going on, But this younger Manhattan Project scientists who were recruited by the Army and found themselves in Los Alamos as part of a special engineer detachment that Groves created in 1944 to supplement the senior scientists at Los Alamos. These younger people had studied at least a year or two of science and physics, and they have all told me that they figured it out. they knew that it must be working on a nuclear weapon of some sort. So that's why I say 95% people didn't know, but 5% either knew because they had to because they were actually at Los Alamos working on the bomb itself or they figured it out.

But in that case, Frank, it must have been very difficult to keep it secret. Groves was determined to keep it secret, top secret. he managed it in a lot of ways but it leaked one way and another it was being breached it was being breached by individuals like Fuchs can you talk about him for a moment or two and around the place

can you just can you give the list of some idea how the real story leaked out well the first thing was very cleverly in the Soviet Union something that Groves could not have done anything at all about a physicist called George Flairoff

was in the army and he was on two weeks leave from the front and he visited the local university to see what had happened in nuclear fission in the previous two years. And he looked in the library and discovered two things. First of all, there was not a single paper in the literature that had been published on nuclear fission in two years, which was a big shock. And secondly, the likes of Niels Bohr and Fermi

and great scientists like that had published nothing themselves. and he put two and two together and realised that they must be operating on a secret project somewhere to develop Fission into a weapon and alerted Stalin to the fact. Actually, Stalin was already aware of this because of spying that had taken place earlier. But that was the first sort of hint

that something was going on that you could have done nothing about. Now, you mentioned Klaus Fuchs and there were other spies. Fuchs somehow evaded vetting. the irony is that he had been a communist in Germany before he left and came over to Britain after escaping Hitler.

But the only evidence that MI5 had about this was papers from the Gestapo. Coming from the Gestapo, they just ignored them and disregarded everything. And so Fuchs went through the vetting process first of all in Britain and then when he arrived in the States at Los Alamos.

Now the way that the spying was done, was that, and the weakness, if you like, that Fuchs and the other spies had to pass their information to a contact. Fuchs would get out from Los Alamos on a couple of occasions down to Santa Fe, which was about 20 miles away, meet his contact, pass the information to his contact. The contact then passed it on to somebody who took it to the Russian embassy. And then the Russian embassy had to code it up

and transmit the information to Moscow. And it turned out that was where the weakness in the whole thing was because if the coding had been done properly, it would have been totally and utterly uncrackable. The Americans were able to read the messages that were going across, but they had no idea what they said. It wasn't until 1949 that these messages were actually decoded, and that is when we got the first indication that there had been spies at work in Los Alamos, leading to Fuchs's arrest, but by that time, the war had ended five years before. So during the war itself, the information was passed across without anybody being aware of it.

I should just add one thing. We now know that the only information that was sent went always the Soviet Union. There was nothing with Germany. There was nothing with Japan or Italy. It was totally driven by political idealism. Cameron, to those working on the project, how inevitable did success seem going at that speed? Do we have any dire enters or any comments from them? and we're not going to get there, we're getting there.

What did they feel about the pace at which they were going, those who knew where they were going? Of course they were working at a breakneck pace, and even once these facilities and reactors are running, it takes time to generate this material. And I think once they, you know, I think in a sense, once fission had been discovered, it was inevitable that this would occur.

And, you know, obviously the war sped it up. and Groves wanted weapons available in time for use in the war. So this is not to say that they didn't run into problems. The plutonium bomb almost didn't come to fruition because of its spontaneous fission problem. They had to develop an implosive technique to assemble a critical mass. There was a very limited amount of uranium 235 available. So they certainly ran into problems. There was a lot of teething problems,

getting these factories going. But by the spring of 1945, both Oak Ridge and Hanford were beginning to produce appreciable amounts of material. Of course, read about the time the war in Europe was ending. So we're talking about the war in Europe ending, Cindy, Cindy Kelly. There was a sense in which this was directed against Germany, the stop German, stop Hitler. So the war ended in Europe in May 1945, why did the Manhattan Project not stop then? Well, the war was being fought in two fronts. It was called a World War for good reason. It was global. The Japanese had started aggressive action in Asia in 1930, invaded China in 37. While the war was over in Europe, the war in the Pacific was unrelenting. The Japanese were fighting fiercely island-island-island in the Pacific.

and held positions on the Chinese mainland and the Philippines. Despite heavy losses of men and material, the military leaders of Japan considered surrender unthinkable. President Truman knew he had an enormously powerful weapon that might shock the Japanese into ending the war. And as with any new promising technology, the military envisioned using it. General Groves worried about 10,000,

testifying before Congress that he spent in today's terms upwards of $26 billion, and then decided not to use it. He put tremendous pressure, as Cameron was just saying, on the scientists and technicians at Los Alamos and elsewhere to deliver at least two bombs shortly after the Trinity test on July 16, 1945. At Los Alamos, Frank, can you briefly tell us why that was? a warning sign, a proof, what significance it had. This was on 16th of July, 945, and that could be called the first atom bomb. It indeed was the first atom bomb. I mean, as it's been said in the program, there were two routes being followed, the uranium 235,

which by that stage was pretty well guaranteed to work. But the plutonium, as Cameron said earlier, was very tricky. And whether that would work or not, nobody was quite sure. So they decided they had to do a test. and that was what the 16th of July Trinity test, as it became known, was. And if one has a moment for the start of the nuclear age, that really was it. And it's very dramatic. I mean, it took place in the New Mexico desert before dawn. The scientists and engineers were bused away from Los Alamos through the night. It was 2,000 meters or so above sea level there.

It was quite cold. The scientists were 20 miles away from where the test explosion was going to take place. And actually nobody really knew what was going to happen. Groves had prepared three versions for the New Mexico governor. The New Mexico governor was aware that the military were going to do something, but of course he didn't know what the details of it were. But Groves had prepared three statements. One, that the test had been okay. The second level was there had been severe damage. And the third one was obituaries of all present, including himself. So that gives you the range of possibilities that they were anticipating. The actual test itself took place at about 5.30 in the

morning before dawn. There was a flash in the sky about 20 miles away, which was described later as being brighter than a thousand suns. Somebody said it bored right through you. And night was turned instantly into day. Some quote I've got down here, like opening heavy curtains of a darkened room to a flood of sunlight. And the heat. That's the thing we don't tend to think about. In addition to the flashes of light, there was heat, and the heat was scorching. It was like an open hot oven with the sun coming out like sunrise. And that is what you saw in an instant when this thing exploded 20 miles away.

Now, when you see these things on the TV, what you see is the flash and an instant bang. Of course, it wasn't like that. This was 20 miles away. It took nearly five minutes for the sound, the show. shockwave to reach the scientists. And the awesome site that they had seen, and already there was this mushroom cloud developing, they must have been wondering what was going to arrive in five minutes when the shockwave came. And what arrived, it was like thunder echoing from the mountains all around, which is continued and continued. And the mushroom cloud continued rising 20,000

feet into the air, changing colour, gradually as it did. Gradually, the light level went down. And then the real sunrise took place in the east. This has all taken place in the south. The word awesome is used, but on that occasion, I think it really was. And from the scientist's perspective, it had worked. And I think that is the thing, at that moment, they didn't realize the implications, perhaps, but it had worked. They had controlled and liberated the energy of the atomic nucleus. It was the moment the nuclear age began.

It was Promethean in its way. It was a triumph of science and technology. Thank you. Cameron, to come back to something we alluded to a few moments ago, what calls were there then to leave it at that, after that first nuclear bomb, let's call it that. What they're called saying, right, we've proved this, we needn't go any further. We can tell people this. Anyway, what calls were, if any, to leave it at that? Well, as Cindy indicated a few minutes ago, of course, the war and the Pacific was still going on with incredible ferocity. An invasion of Japan was set for November 1st, and that would have dwarfed the D-Day invasion.

The plan was to land about three-quarters of a million troops in the first month or so. And so, you know, the war was still going on in its incredible ferocity. And there was some consideration given to giving a Japanese a demonstration test, but it was, there was fear that, first of all, they had. had very little fissile material, just enough for a couple bombs at that point. There was concern that if it was a dud, they would lose the element of surprise, and it would be a tremendous embarrassment. And perhaps the Japanese would bring prisoners of war into any test area.

So it was considered by a committee that advised the Secretary of War. But I think it was essentially a foregone conclusion that when the bombs were ready, they would be used and would just come as a tremendous shock to the Japanese. Cindy Kendi Kendi Kelleck, for those who don't know, can you remind us of the effect of the bombs on the people of Hiroshima and Nagasaki? Well, the atomic bombs claimed as many as 140,000 lives at Hiroshima and 74,000 in Nagasaki and an equal number of people were injured. major portions of both cities were flattened, leaving only a few concrete and brick skeletons of a few buildings made of those materials.

The nuclear radiation released by the fallout from the mushroom cloud that Frank just described, rising 20, 30,000 feet, caused thousands more to suffer from radiation sickness in the weeks, months and years that followed. load. Those who survived the bombings are known as Habakshah. Many of these survivors suffered lifelong psychological trauma. Many are still plagued by anxiety, not knowing when symptoms of radiation sickness may occur. Young women at the time who lived in the two cities were stigmatized and unable to marry for fear of reproductive abernarmament. caused by radiation exposure. Even today, survivors live in fear. As Mayor Tawi of Nagasaki told me in 2019,

their foremost wish is that no one in this world will ever experience what they have gone through. The mayors of Hiroshima and Nagasaki have embraced the mission to convey their wishes to the world and have worked with about 7,000 cities and 160, 70 countries around the world. And as a culmination of their efforts, on January 22, 2021, the United Nations Treaty on the Prohibition of Nuclear Weapons went into force. Frank Lose, among the scientists, what were the most significant responses that they had to these bombing?

Well, I'll just say one thing about the scientists. We know of these great names today. We view them as like 60, 70-year-olds, senior citizens. The average age of the scientists building the bomb was about 28. They were like graduate students and new postdocs. Piles, however, who started the whole thing, he wrote eloquently about it later, and he said nobody could feel any pride in having brought this thing about. But this was war.

and in war, death, suffering and destruction are unavoidable. I think that was the reality of it, I think as Cameron alluded. There were millions potentially going to be killed if the war continued. But with regards to the atomic bomb, Piles also made the following remark, which is the phenomenon of nuclear fission was discovered and could not be undiscovered. What was the most, Cameron, what do you think were the most important and early? earliest lessons from the Manhattan Project. There are several.

I guess one is that, you know, when Fission was discovered, it was probably regarded as a pretty arcane academic science experiment. But, you know, sometimes an arcane discovery can have just enormous consequences that nobody can foresee all of them and can really change the world. And that, you know, the project stands as an example of how, kind of a model of how an effort to address an existential threat can be effectively organized and carried out. You need the right advice getting to the right people, which was one of the problems that was encountered in Germany. You need people who know what they're doing and are trusted to carry out the work.

And perhaps there's a lesson here today for COVID and climate change that these enormous projects can. can be done. Yes, there's a lot of strange what ifs in this story that the original calculation of Fris and Piles that started it all was based upon rather limited knowledge. And we now know that actually they were 10 times more optimistic, if that's the right phrase, than the reality. So if the sums had been correct at the very start and one had realized that to make a uranium bomb would have required 10 times as much as they thought, whether the project would have started at all. Well, of course, we can never know the answers to that.

But there's so many things that had to be just in the right place at the right time or the wrong place at the wrong time, whichever the metaphor in this case is, for it all to have turned out as it did. Cindy, to come at you towards the end of the programme now, this set off chain reactions, which was part of the nuclear vision, but there's a chain reaction in a contract. which got the bomb. America disengaged itself from the UK and wanted to go to loan for a while. Churchill then decided we would have our own bomb. We, the Brits, would have our own bomb. Russia, through one way and another, got the means to make their own bomb, and so went on around the world.

It sometimes said that it's the politicians who were to blame, as it were, for all this, not the scientists. What do you make of that? Is that a distinction? I think that's a very apropos distinction, especially when first you look at who influenced the decision to drop the bomb. There were a few opportunities for the scientists to influence that decision. Some of them signed a petition to urge Truman to think about what it would be like to have the United States the first nation to drop a bomb and atomic bomb. It was signed by 153 scientists. But when General Groves got it, he stamped it classified and put it in a safe. Neither Secretary of War Stimson nor President Truman saw it.

Leo's Lard quipped that the biggest weapon to emerge from the Manhattan Project was the secret stamp. The senior scientists also were kind of marginalized. They felt Oppenheimer believed the decision was essentially a military one, that they were not qualified to make. But after the war, they began to question whether scientists should be, just dedicated, as Richard Feynman says, to figuring out what goes on and to pursuing how nature works, that they should try to think through the consequences of their discoveries

and have some kind of more active role. Of the hundreds of veterans that I've interviewed, hearkening back to Frank's comments, they feel strongly that dropping the bomb was the right thing to do. Others think, no, a well-meaning president made the worst decision. But I think it's a very difficult question. As leading historian of the Manhattan Project Richard Rhodes predicts, the issue of whether the atomic bombs should have been dropped on Japan and what the right wall was where scientists will continue to be debated for decades to come.

Ironically, there was one thing that the scientists did contribute to via the spies. The fact that the Russians got their atomic bomb about 18 months earlier due to the spies than they would have done meant that in 1950, when the Korean War was starting and some American hawks wanted to drop an atomic bomb over there, they were stopped from doing so because by then we knew the Russians had one themselves. So in a strange sense, Klaus Fuchs and the other spies may have contributed to us being here having this discussion. Well, it was a terrific discussion. Thank you very much indeed. Thanks to Cindy Kelly, Frank Close and Cameron Reed, and to our studio engineer Emma Hath. Next week, it's the great Republican experiment in 16th century Europe, the Commonwealth of Poland and Lithuania. Thanks for listening. And the In Our Time podcast gets some extra time now with a few minutes of bonus material from Melvin and his guests. Cindy, why don't we start with you? Okay. As several have mentioned,

the work done in Great Britain, the British mission that included Fuchs and Rudolph Piles and 25 other brilliant scientists who had fled Nazi Germany were instrumental to the success of the scientists in the United States. In addition, we looked to Canada to get uranium ore and there's valuable work going on in Montreal and elsewhere. So it really was not just an American, do it alone, but it was clearly one of the success stories of the war, an allied effort. I'll just add into that. I think one of the great ironies is the number of Jewish emigres

that Hitler had driven out that then were involved in making this bomb. It wasn't actually used against Germany, of course, but that was one of the great ironies that Hitler got rid of the very people who might have been able to do it for him. Exactly. I'd like to throw in a comment on something Frank mentioned a couple of minutes ago

about Klaus Fuchs and the Korean War that is what I have come to think of as a sort of theory of nuclear inoculation that if these things hadn't been used or hadn't been ready in time for the war and we learned how horrible they were, which is a lesson perhaps people are forgetting now. What might have happened in a later war when there was many more of them,

they were more powerful. And we've somehow managed to avoid that fate for the last 75 years. One of the things I just wanted to add about the reactions to the Trinity test itself, this was a shot that I discovered when I was researching my Trinity book about Trinity and Fuchs. and the like. Freem of information in the States, we managed to get hold of official copies of lectures that Enrico Fermi gave immediately following the Trinity Test and through that autumn. And the shock that I had was that within three days of the Trinity test, even before the bombs had actually been dropped over Japan, Fermi had had the insight and gave a lecture that the

heat generated by an atomic explosion was hot enough. to be the spark to ignite what we now call a hydrogen bomb. And he started giving lectures about the possibilities of making a hydrogen bomb by using the atomic bomb as the spark. And I found that quite disturbing in a way, because that says to me that Fermi was so taken over by the wonder, if that's the right word. I'm looking for a word, but the awe of what had just taken place,

the triumph over the atomic nucleus that the same. scientists had experienced, that the exciting possibilities he'd opened up without giving a thought to what the end consequence of all this was going to be. Oppenheimer called it technically sweet. Yes. These sound horrible now when we look back at this distance. It's easy to be wise after the event. I mean, I suppose I'm glad that I was not 60 years younger, if you like, well, 50 years

younger to have been involved in that. you feel you would be tainted by it in a way ever after, even though what you did at the time was absolutely necessary. Cameron and Cindy, what do you think, how do you view the development of the possession of atomic and hydrogen bombs since 1945? Cindy, do you want to go ahead? What do I think of the possession? Yeah, the development in the possession, yes.

Well, it's become the so-called nuclear club. point of pride. It's more of making sure that your country has this stature alongside of these nations that use their industrial prowess to have this terrible weapon. You know, in the aftermath of the war, I guess any country that fancied itself as being a world power and have the resources and scientific and engineering capability, we've just felt compelled to develop these things like Britain and France and Russia and China. And of course, inevitably the information is going to leak out. One thing is a Brit on this program. To me, the irony and sadness is that the way we started this program was the discovery efficient and that

people saw it potentially as something post-war as a way of making a heat engine, what we call a nuclear reactor. And indeed, immediately following the war, British, took over research in making nuclear reactors and led the world. And as a child, I remember, nuclear power was going to be the thing of the future. And sadly, wherever it's being used, Britain is no longer in the lead by a long way. And that's another irony of all this thing. There are some good things that have come out of this along with the bad. I think another irony is that there's so much political pressure in America to develop the hydrogen bomb. and yet it is so powerful that there's really no credible military mission for it.

Thank you very much indeed. In our time with Melvin Bragg is produced by Simon Tillotson. What's the link between poisoned underpants? They wanted something that wraps against your skin. A plot to kill Nelson Mandela. To find a poison that would cause cancer and have him die shortly afterwards. And the deadly riots in South Africa this year. I'm Andrew Harding with a tale of politics and paranoia.

Some people wanted me dead. Oh, and the link is Jacob Zuma, South Africa's former president. And indeed, it was quite a strong poison. That's poison from BBC Radio 4. To listen to all five episodes, just search for seriously on BBC Sounds.