The Science of World War Two

From radar to rockets, we dive into the science of WW2
12 May 2020
Presented by Adam Murphy
Production by Adam Murphy.

WW2-PLANES

Three WW2 planes in formation

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This week, we’re bringing you a special episode, diving into the science and technology of World War Two, to mark the 75th anniversary of Victory in Europe Day...

In this episode

A spitfire aeroplane, flying through the air

Fighting in the air
Craig Murray, Imperial War Museum Duxford

One of the most iconic images of the war is that of aerial combat. The Battle of Britain, which began in 1940, revolved around fighting in the sky, and one of the planes at the centre of it all, is the Supermarine Spitfire aircraft. But just a few short years before the planes were old time biplanes, used for taking photos. How did we we get to the Spitfire from there? Adam Murphy spoke to Craig Murray, curator in the Imperial War Museum in Duxford about aircraft history...

Craig - Most of the changes really come in the 1930s but within the 1920s period after the first world war, you have the allies are left with an awful lot via craft from that period, but there's a lot of economic restrictions post-war and also there's no actual threat. So really the main things that do change here are a movement away from wooden frames to metal frames, but still covered with fabric as they have been already. But also there's much more of an advancement in aero engines, if they're not been weaponised they're certainly performance and streamlining of aircraft has been improved upon. Aircraft have been rather restricted, land aircraft rather, taking off from airfields have been instructed by fixed props and it's not really until the early 1930s when the first viable variable pitch prop comes in that the aircraft on the ground become more efficient.

What I mean by that is when taking off, it requires quite a lot of power for the engine and if you don't have a variable pitch prop, you have to have quite a long airfield to take off in. And what the variable pitch of the prop does is that it makes the engine more efficient at certain points. If you have in on fine pitch, it cranks up the revolutions per minute for taking off. And when you're cruising you can put it on what's called coarse pitch. So the engine's working in its most efficient manner, but I suppose interestingly a lot of the developments come in the civilian field rather than the military field at this point. And it's with flying boat racing basically, you know, the aircraft that can take off. The Schneider Trophy is really this kind of thing. But, as things start to move into the thirties we start to see the move away from these sort of, you have seen with air racing a move away from biplanes into these monoplane designs, low-wing monoplanes because they're more efficient and you start to see a moving into more metal aircraft.

Certainly in that sense the Boeing company in the United States in 1931 were sort of ahead of the game militarily. They sort of saw the coming of the metal, the metal skinned monoplane fighter. So they built a bomber at the time, which was the first sort of metal monoplane and it was quicker than any biplane about at the time. And a few years later there's another, there's another one comes in which advances it further and then they obviously have their famous B17 flying fortress which they come up with in 1935, which is very heavily armed, based on the theory a bomber should be able to always be get through to the target as long as it's got enough guns to fight off the fighters that are incoming.

Adam - And what about those more famous planes? The Hurricane and of course the Spitfire? 

Craig - And sort of concurrently at this time in Britain you have the development of the Spitfire and the Hurricane. The Hurricane is slightly more traditional. It's got metal tubing frame and the rear part of the fuselage is still covered in fabric. But the Spitfire is a pure metal semi-monocoque fighter. Semi-monocoque, meaning this is a stress skin over a frame as opposed to fully monocoque, which is essentially an egg which supports the structure. The difference with the Spitfire is, again, it's all metal like the 109, but it's a pure thoroughbred of a fighter. R.J. Mitchell, a designer who is also designing the Supermarine aircraft that were winning the Schneider Trophy, he's not overly concerned with budget. He just wants to build a pure fighter. Very, very difficult engineering design that has this elliptical wing, other people have tried it. It's been difficult to do or too expensive. Expense is often a big thing, but it's a pure fighter. It's best handled by experienced pilots, whereas the Hurricane is an easier aircraft to fly and is paradoxically more sturdy, even though it's partly fabric, it can take a lot of battle damage. It can turn a lot sharper than say the BF 109, which shall be its main opponent during the battle of Britain in 1940. It's not actually a pure fighter. It's been designed by Willy Messerschmitt as essentially an ambush predator, it bounces aircraft, it comes down from high out of the Sun and ambushes.

Adam - Without these advances in air combat, the landscape of world war two would have been very different. So how does it move quite so fast?

Craig - Well, I mean, you've gone, I mean aircraft technology moves massively quick from the Wright brothers. Even in the first world war, you're going from the Wright brothers, something that was essentially flying at walking pace almost, to fighters that can fly a hundred miles an hour in the space of maybe 10 years or so. So it has jumped exponentially very, very quickly.

 

A stylised radar detection screen, a series of concentric circles split into eight sections

08:28 - Radar revolution

How did radar change the course of the war?

Radar revolution
Craig Murray, Imperial War Museum Duxford

The outcome of the Battle of Britain was heavily affected by radar. Radar, coined by the US Navy as an acronym of Radio Detection and Ranging, works sort of like how bats find prey. A transmitter blasts out a signal, it bounces off incoming objects, and depending on the signal that’s received back, you can tell, what, if anything is inbound. But how did it get developed. Adam Murphy spoke to Craig Murray from the Imperial War Museum in Duxford...

Craig - Radar certainly is not a British invention, but its one perfected for its use by the British to do what it's supposed to do. The Germans have come up with a think for use in the German Navy for ships, but it's never really exploited as such. But the actual technology, the radio direction-finding technology it comes off, has been really around since the early days of radio development and in the early 1900s they're using it to get fixes on things, usually for for weather, for boats. You can't really tell how far something is, but you can get a fix on a where it is, if that makes any sense. It's more 'we know it's there', but the technology is so limited, it can only be used for relatively short-term meteorological stuff like incoming storms or fog that's quite close. What happens in the 1920s is a guy, a Scottish physicist called Robert Watson-Watt, who is with the Met Office but he works with the National Physical Laboratory on the radio research section, that kind of combined labs; he's got an interest in radio waves.

And he develops a system called huff-duff for the Met system, and it basically instantaneously gives you a fix; and the Met Office use it to develop weather reporting for aviators so they can tell when storms are coming in. So he has this. After, I think it's in '27, the labs of the Met Office and National Physical Centre are amalgamated into this new lab, and he's put in charge. And he takes on this guy called Alfred Wilkin in 1931, and they run a report based off of this, that aircraft nearby cause this fading in the signal. It's basically, the strength comes and goes; which is a bit irritating if you're listening to the radio, the sound comes in, it comes out, drops out, distorts, and clips. And so with these three things going on, they've kind of got the basis for something that can work on radar. Because even back in the early 1900s they realised that metal reflects radio signals, and in fact aircraft being present in an area is distorting the signal. It's this idea that there's something there.

Adam - But how does that translate to a full military sensing infrastructure? Well, like with all good spy stories, it starts with a death ray.

Craig - In 1934 the Tizard Committee, who are basically there to look into research for air defence... because the theory up to then, and something that was put forward, was the bomber will always get through, you can't really defend against them because we don't know when they're coming, et cetera, et cetera. And in 1934 the RAF ran a big exercise with some 350 aircraft they split into two: one lot would be the bombers, one lot would be the fighter defenders, and the only information they get would be from observers on the ground reporting incoming raids. And what they found was that 70% of the bombers could hit London without even meeting a fighter. So this wasn't good. And there were also rumours going around at the time - and this is where the Tizard Committee start contacting Watson-Watt - there were rumours of a death ray that could be produced using radio signals. Now anybody with a working brain pretty much knew this was bunk, it was just utter nonsense; but the RAF, the Air Ministry, and the Tizard Committee were like, "well, we need to check this out, because if there is anything in it you don't want the Germans having it; because if they do have it, they're going to knock out air fighters as their bomber come in, and vice versa". So they thought, "we'll at least run it through science. Let science decide if it's bunk or not". Wilkin is given the task by Watson-Watt to have a look at it, and pretty much quickly turns and says, "it's nonsense, it'll never work. But I'll tell you what it does do, the radio waves: it can detect incoming objects." And this is reported back to the Tizard Committee, and they're like, "yeah, thanks for telling us, we kind of knew that. We hoped what you'd say was that the death ray thing is bunk, and it is; but we like this, this is interesting what you've got here on incoming things."

Adam - So with a new potential way to turn the tide in their favour, it was a matter of investing heavily in the science of it all.

Craig - In 1935 they've got something, they can spot something coming in at a hundred miles out. A little bit later than '36 they've managed to get the towers working so they can actually determine height of the incoming raid as well. And it's not until '40 when you've got these rotating radars we think of now that can read inland. As it turns out, because the Germans rule over France relatively quickly, they're basing their aircraft at Calais, so something they thought would be coming from a long way off originally is now coming from 20 miles across the Channel. I always like to think of it as being a bit like the internet invented by the US military in the 1960s. It has no centre that could be knocked out; I mean, this applies to the radar station. Pilots buy instinct don't fly near to pylons, it's a scary thing, because there's wires and that's just asking for trouble; and also bombing them is very difficult because they're a latticework tower, and explosions tend to come out, so it's very hard to destroy. And even if you do manage to destroy them, the neighbouring station can take over its sweep, so they compensate for each other. So it's a nigh-on impossible tasks for the Germans to remove this system, coupled with the fact that they don't fully understand what it does, and they don't really get the radar is picking them up. They just don't seem to get the radar thing at all.

a greyscale image of a large rocket

Rocketry in WW2
Rebecca Charbonneau, University of Cambridge

While the Allied forces were working on weapons, the Nazis were developing their own. They were working on rockets. Weapons that could be fired from a distance and be trusted to stroke their target. These were the Vengence weapons, first the V-1 rocket (which was nicknamed the buzzbomb, because of the sound it made) and later, the V2 rocket. These weapons have an interesting beginning, and left an interesting legacy that would follow the world long after they stopped being used. Adam Murphy spoke to Rebecca Charbonneau from the University of Cambridge about these early rockets...

Rebecca - In the early 20th century there were several hobbyist rocketry groups which were founded all around the world, but most notably in the US, Germany, and Russia. And this happened quite early on. 1898: Konstantin Tsiolkovsky, a Russian schoolteacher, first proposed the use of rockets to explore space; and he became the first to prove that it was mathematically possible, and suggested the use of liquid propellant, which was quite a novel idea. Up until the 20th century it had been largely solid propellant rockets that had been used in warfare. This idea of using a liquid propellant rocket was tested for the first time in 1926 by Robert Goddard, who is an American physicist who launched the first successful liquid propellant rocket. It only flew about 12.5 metres high for about 2.5 seconds, which is not successful by our standards even for just model rocketry. But nonetheless, this set the stage for the space age, right? And then that can take us back to Hermann Oberth who, in 1930, he and his small group successfully launched their own rocket, what they called a Kegeldüse, which was a small cone jet. And assisting him with the project was an 18 year old man which is Werner von Braun.

Adam - But this was all on the American stage. What were the Germans working on?

Rebecca - In 1937 the Peenemünde rocket group, which included people like Oberth and Von Braun, was assembled at the start of World War II. Their mission was to develop new weapons of war, which included the A4 rocket, which we now know as the V-2 rocket; and that was built and launched under the directorship of Werner von Braun. Now the V-2 rocket was meant to be launched from Germany in order to decimate cities, right, such as London. But the rocket was more a weapon of terror than efficacy; it was scary largely because of its unpredictability. Because the V-2 travelled faster than the speed of sound, it couldn't be heard until it landed. So this was of course terrifying. However, since its deployment towards the end of the war, the technology wasn't effective or powerful enough to make a major difference in the outcome of the war. In fact, historian Michael Neufeld says that many more people, prisoners in the concentration camps tasked with making the rocket, actually died while making the rocket than who died as a result of its use in war; but, you know, nonetheless it was still an impressive piece of technology. But in 1944 the V-2 became the first artificial object to pass what we know as the Kármán Line, which is generally considered to be the boundary into outer space, a hundred kilometres up. So this arguably makes the V-2 a contender for the first human object in space.

Adam - After the war, the Americans took in lots of former Nazi scientists to have them work on American scientific projects. This was called Operation Paperclip. One of those scientists was Werner von Braun.

Rebecca - Von Braun and his group were moved to Huntsville, Alabama, where he led the US Army's rocket development team at Redstone Arsenal. And this effort led to the development of the Redstone rocket, which had a dual role in the United States: it was used for the first live nuclear ballistic missile tests conducted by the United States, but also it was the rocket that made Alan Shepard, astronaut Alan Shepard, the first US astronaut to reach outer space. He actually became kind of popular in the public eye; he actually had a role in a Walt Disney film: Man in Space, von Braun, there he is! And several other German, former Nazi scientists are in this Disney film; talking, trying to educate people, with little animations in the background, on how rocketry works, how space exploration works. There's even a case actually to be made that he is part of the reason why Stanley Kubrick's 2001 A Space Odyssey space station looks like that; because in the 50s von Braun wrote a popular article on artificial gravity and space stations. And so he's fundamental also in our public understanding of space and space exploration.

Adam - That means von Braun, and even to an extent the space race, have some ethical issues at their foundation. And that should really be considered.

Rebecca - So von Braun's story is an interesting one, and it's one that raises more questions than it answers. How do we as historians handle a figure who inarguably achieved great things, but also participated in horrendous ones? Methodologically this can be especially tricky because human beings often try to take control of their own narratives, right? We might ask ourselves, "did von Braun use the Nazi party's power to help further his own goals, trying to ignore their acts of terror? Or did he actively support their mission? Was he an anti-semite, or was he a victim of sorts, who was forced by threat of violence into working for the German state? It would be simple to write off the accomplishments of von Braun by claiming he was a Nazi, or an amoral person with one singular goal he aimed to achieve regardless of the cost; or alternatively we might be tempted to entirely dismiss his involvement in the war as being forced upon him, and instead choose to venerate his role in the space race. But I would argue that neither of those characterisations do us much good. History is most valuable when we get our hands in the muddy reality of human existence, with its uncomfortable juxtapositions, tragedies, and cruelty; and attempt to understand why people made certain decisions.

A grayscale photo of the Holocaust Memorial in Berlin

21:44 - The medical experiments of the Holocaust

Identifying and commemorating the victims of the medical experiments

The medical experiments of the Holocaust
Paul Weindling, Oxford Brookes University

A lot of science was carried out during World War Two, and a lot of it was groundbreaking. But a lot of terrible things were done in the name of science as well. Especially the experiments conducted on unwilling people in the concentration camps. What went on there, and who were the people subjected to that? Adam Murphy spoke to Paul Weindling, Professor of the History of Medicine at Oxford Brookes University...

Paul - Himmler regarded the concentration camps as a, really a resource for human experiments and it was a resource which he developed throughout the Second World War. And really went right until the end of the war, and one type of experiments were infectious disease experiments, and they were really to try and find preventive immunisation. Other types of research work was for military purposes, and again in the concentration camp of Dachau, there were experiments on aviation, on low pressure, so that fighter pilots who had to do manoeuvres for rapid descent and so that they shouldn't black out. The question was what the reasons for blacking out was. So low pressure experiments were done on prisoners, and these prisoners were taken right to the point of death. And so the processes of death were grimly studied in these pressure chambers, and then the bodies were dissected. Brains were taken for research by German brain researchers at that time, Others were cold water experiments, hypothermia, what would happen if a fighter pilot bailed out into the Channel into freezing water.

These experiments were not only on concentration camp prisoners, they were on psychiatric patients, who were children. For example, child psychiatric patients were also put in pressure chambers, or they were subjected to immunisation experiments. There would be deaths caused by the experiments. Then the bodies would be dissected. We can see with the Mengele twins, these were twins who were collected from the end of 1943, Mengele experimented on a number of Sinti and Roma twins, some he even killed because of their different coloured eyes. And so it's been important to work out these different groups, who the persons were and how many survived, in order to get a more precise figure, in order to be able to identify each person as a named person and see what they then wrote about their experiences, and what the experience was like for the experimental research subjects.

Adam - How do you do that? Put names to experiments carried out on people more than 75 years ago. It's a monumental task.

Paul - So for some experiments there are the actual research records, so that for malaria experiments in Dachau, although the SS at the end of the war ordered all the experimental records to be destroyed. In fact, some of the prisoners kept the research records, as many as they could. They hid them and kept them because they were convinced firstly, that each person should be identifiable. And secondly, there could well be a trial of the key perpetrator so that they needed evidence. We have diaries with the research results being done from Buchenwald concentration camp. And two of the diaries which were meant to have been destroyed were in fact found. And the other great source is the compensation. Very often the compensation application was unsuccessful. The Mengele twins were always turned down until the mid 1980s. The federal German finance ministry always said, "Oh, that wasn't a human experiment. You were just being measured." But still the testimony of the person from the twin block is an important testimony. So we have a named person and we can collate the named testimonies to see how many there were. And so there is a very, very large number of testimonies and records of these experiments, which simply, and have to be, should be collated. And that's one of the things I've been trying to do. I work with roughly 30,000 testimonies from the time, to try and reconstruct them in terms of what's known about the experiment. So you have to put the testimony into an experiment, which one can document. And so you try and turn anonymous numbers of victims into named persons

Adam - And a task like this isn't easy. There are bound to be roadblocks.

Paul - One difficulty is the idea of patient confidentiality, because some archivists think, Oh it's medical, therefore you cannot divulge the name of the person. I think that's a mistake, because the victim was perfectly healthy before the experiment and the experiment, it's a form of violence, gratuitous violence that was done, and one shouldn't treat it as serious medicine, one needs to treat it as an injury inflicted for ideological purposes, just as if somebody is being beaten, so that Holocaust victims, it's regarded as perfectly acceptable that they're named. And my view is that the victim needs to have primacy, and it is really irrelevant who their descendants may or may not be. They should be named. The experiences which they underwent should be documented, particularly if they were killed. It's important that the documentation is there, that's the least that can be done to commemorate them as named persons, that they should have the dignity of being a person rather than a research object.

So the great roadblock is ironically confidentiality, and I actually think that protects the perpetrators more than the victims. Last August I was sent a list of brain specimens in the Frankfurt University Neurological Institute and I noticed, "Oh, two of these specimens have got the same number as the specimens that were sent from Warsaw in 1940." And I could actually find the brain autopsy reports in the German military archives, and trace these brains all the way through to the Frankfurt Neurological Institute. So that the brains were taken out of circulation for scientific purposes. They were in what was called the show collection and that's not the only incident where we found body specimens of persons killed in the war, kept in museums or scientific collections. And it's really important, these body parts, they offer really a window back into the person who was killed and their life and their, the identity of, it's very important on the one hand to look, to reconstruct the identity of the person:

Who were they? How come they came to have their brains kept by the German military and the occupation on the one hand. And on the other hand, what happened to the body part scientifically, why was it that the Germans during the war and in the postwar period, were perfectly content to hang on to these specimens in large numbers and to say "Oh well, the killing and the retention of the specimen has got nothing to do with the Nazi aims, which is why the person died. And I think that's very questionable. And then there will be the issue of appropriate commemoration of the person, that they shouldn't just be thrown away as surplus scientific material, but the specimen should be given a dignified burial, with identification. And I think it's the identification, which is above all really important.

Adam - One thing you often hear when reading about this topic is "that a lot of terrible things were done, but at least some useful science came out of it. There was some good done in the midst of all that evil." Would that be an accurate assessment?

Paul - This isn't normal science in any way. This is science being done under extreme circumstances for ideological reasons, and this is also unethical science. So we have first issue is can this actually be correct science? Can it be good science, when you might have persons being killed, but there are prisoner research assistants who are often sabotaging the sort of research that was went on. So that's one issue is sabotage. The second issue is the stress on the actual victims. The third issue is there is a faking of results in order to please the Nazi high-ups like Heinrich Himmler and so on. Fake graphs, and fake statistics would be constructed. On the whole, it tells one a lot about Nazi atrocities, and the exploitation and persecution. It doesn't really tell you very much about science and it really is a lesson in how not to do science.

An enigma codebreaking machine behind glass

32:38 - Breaking the Nazi codes

The road to breaking the enigma cipher.

Breaking the Nazi codes
James Grime

The efforts that would put an end to World War Two were underway. In Britain, one of those avenues was breaking the German ciphers, the code they used, called Enigma. Enigma was a tough nut to crack. Complex and constantly changing. Not only did it change every day, it changed every time you typed a key. So "e" would become "q" with one keystroke, then "s" the next. So how did it work, and how did we break it. Adam Murphy spoke to mathematician, and enigma expert James Grime…

James - The Enigma machine was actually invented by a German engineer called Arthur Scherbius. He invented it in 1918 a little bit too late for world war one. And he would sell these machines to businesses who wanted to send secret information. And then the military started to use them as well. It's wood, it's steel, but it's about the size of a typewriter. It has a keyboard and when you type on the keyboard, your code letters actually light up. There's a second set of letters and so when I press a letter like T, then it's going to light up a code letter. Maybe W.

Adam - The Enigma machine was not dissimilar to a typewriter. The code was contained in three wheels, which you chose out of a possible five with 26 starting positions and some wires on the front and a plug board just to add some little extra complexity. And you had to sit down and set that up each morning.

James - For the Germans, they would have a code book and every day it told you how to set up the machine for that day. Without that key sheet, you won't know how to use the machine. So altogether we have three wheels to put into the machine, their position, these wires at the front and the total number of ways you can set up the Enigma machine is a large number. It's 159 million million million possibilities, which is far too many for a codebreaker to check. And it changes every day, which is the hard thing about it. The British code breakers and the Polish code breakers, they were very aware of how it worked, but not maybe the details of the wiring inside the machine. And that's when the Polish were actually able to work out the wiring inside machine without ever seeing the machine itself. Just from the codes, they were able to deduce all the wiring inside the machine and then build their own.

Adam - So how did the British go about cracking it?

James - So the British - thankfully, they had a kind of a headstart because they saw the Polish methods, the Polish passed their information to the British, but the Polish method was based on a flaw in the German procedure. If the Germans changed their procedures, that method won't work anymore. So that's where Alan Turing comes in. Alan Turing had a different method for breaking the Enigma code, which was based on the flaw in the machine itself. When you're using the Enigma machine, if you press a letter like E and if you kept pressing the letter E repeatedly, it keeps changing the code. This is one of the reasons why Enigma is so hard to break. E might not be the same if I keep pressing it over and over again. But, there's one letter that it will never become and it will never become itself. It's not much of a clue, it is a flaw in the machine. So what they can do now is they can try and guess a word that might be in your message. So what the Germans would do every morning is they would send a weather report. So you can use a phrase in that report, let's use the word "weather", maybe "Wetter" in German. So if I can find where that word fits in the code, I can now start to work out the correct position of the wheels that makes that bit of code, say the word, "weather". It's a guess, but using that guess, we might be able to break the code for that day. They could speed it up by building these very large Bombe machines, Bombe machines and these were like simultaneous Enigma machines, like 12 simultaneous Enigma machines, and it was actually a process of elimination. It was faster to reject the incorrect settings then to go looking for the correct. And you could find the settings on a good day in under 20 minutes.

Adam - There was something else at the facility where Enigma was cracked at Bletchley Park. An early computer called Colossus, which you could call a forerunner of the computers that we have today.

James - Colossus, people may have heard of Colossus, and it's another code breaking machine that was at Bletchley park. Colossus was built to break a different code machine that the Germans were using. It was the machine called Lorenz and this machine, even more difficult than Enigma, was used by the top generals of the Nazi party and we broke that code as well. Enigma has three wheels inside and they turn as it goes along and it changes the code. Lorenz had 12 wheels inside, so if you're talking about how many possibilities, well Enigma has a number that's something like 20 digits long. The number of possibilities for setting up Lorenz was a number that was 170 digits long, which is a ridiculous number. It's more than are atoms in the universe. If each atom in the universe was itself a universe, there would be more Lorenz settings than there are atoms in a universe of universes of atoms, and it's too many to check. And Colossus is arguably the world's first digital computer. If that's true, if the Colossus machine can be considered the world's first computer, then it was built in secret at Bletchley Park to break this top secret German code.

Adam - And what happened to Colossus, and all of this work, once the war was won?

James - After the war, there was an order from Winston Churchill to say, destroy all the material. So they had a big bonfire. They burnt all their work. The machines themselves were destroyed. This story was secret under the Official Secrets Act for 30 years, many of these code breakers were not allowed to tell their friends and family. Some died without their family ever knowing what they did during the war. And then in 1974 one of the people who worked at Bletchley Park, who wasn't a code breaker, but he was in charge of sending the information out to the generals in the field. He wrote a book and the secret came out, and it was a bit of a controversy at the time because they weren't supposed to be telling these secrets. Even though this is 1974 we're talking about.

Nuclear weapons test explosion

The Manhattan Project and building the bomb
Alex Wellerstein, Stevens Institute of Technology

It would be remiss to talk about the science of the war, without talking about the science that ended it. World War Two ended on 15th August, 1945, after two atomic bombs had been dropped on the Japanese cities of Hiroshima and Nagasaki. Nuclear historian Alex Wellerstein from the Stevens Institute of Technology in New Jersey told Adam Murphy why they decided to pursue something like that...

Alex - After the discovery of nuclear fission, which is to say that you could split uranium atoms with neutrons, a lot of scientists and many different countries started to wonder whether you could apply that to weapons purposes. And it wasn't really until 1942 they got a copy of report from the United Kingdom where British scientists concluded that it was in fact very doable for a country like the United States to produce nuclear weapons relatively quickly and relatively cheaply and that led to the beginnings of the Manhattan project. The other side of it is they were very afraid at the beginning that the Germans might be building an atomic bomb and any indication that an atomic bomb was buildable they not only saw as an indication that they could do it, but that the Germans could be doing it. And they were assuming, both because nuclear fission was discovered in Germany and because they figured it was safest to assume the worst, that they were behind the Germans. It later became known to them that that wasn't the case but not until much later.

Adam - All atoms have a core called a nucleus that is full of protons and neutrons, but sometimes this gets too full and it makes the atom unstable. That kind of atom is radioactive. And over time it will break down into more stable elements, and every time it does, it will release a tiny bit of energy. But how do you go about taking that tiny amount of energy and turning it into a bomb that can level cities?

Alex - So to build a nuclear bomb the most difficult part is having the fuel for the bomb. So this is what they call fissile material. It's a high enough concentration of atoms that can, at will, be made to split and split other atoms. So this is enriched uranium and this is plutonium. So both of these made up the bulk of the work on the project, both the spending and the effort and the labor and the time, was in making the facilities that would be able to produce this fuel for the bombs. And you also needed a lot of scientists. Pretty early on in this effort the head of the military General Groves was looking for a scientist who could run the whole enterprise and be his sort of right hand man. And he ended up choosing J Robert Oppenheimer. This was a theoretical physicist at University of California Berkeley, also taught at Caltech, and he was an unusual pick because he had never done any kind of large scale management project before. That's not the kind of scientist he was. He was a chain smoking cigarettes while drawing equations on a Blackboard in a small room with 10 students kind of scientist. But he ended up being quite able to the task and quite accomplished at it. They had quite an array of scientific luminaries, both American and foreign involved in the project. And this was part of its success was having sort of the cream of the crop, not only of the United States, but the cream of the crop of many European countries, including many people who had fled the Germans and had very strong vested interests in making sure that the Germans did not win the war or get an atomic bomb before the Americans.

Adam - Just the concept of radioactivity had only been discovered a few decades prior by Marie and Pierre Curie on their lab bench. So did the scientists working on the Manhattan project really understand just the scope of what they had to do?

Alex - They were entering into this entire field with very little information about how to do any of this work on an industrial scale. And so their task was to go from these basically proofs of concepts to full-scale application in basically one step. And that's highly unusual, both for scientists and for industry. And so it turns out, for example, that if you scale up the reactors the way they did, they'll work for a while and then they'll sort of stop working. So this is the sort of difficulty and most of these questions, these scaling questions, they're exactly what would happen if you tried to scale anything up in that amount of time. They did not know the health effects completely of all of these materials. So they're simultaneously trying to develop say, safety guidelines while developing new artificial substances that have never been created before for which they do not know the health effects of them. So they're doing a lot of things that in a more ideal situation, you'd sort of slow things down a bit. Figure out, say, how toxic plutonium was, and then come up with the safety guidelines. And so they're doing these experiments that are incredibly dangerous - they call them the tickling the dragon's tail experiment in which you basically get as close as you can to a chain reaction that you're not in control of, and then back away from it. And they did have several accidents even during the war. After the war, they had two accidents that actually killed people. But even during the war there's, in their files, they have amazing writeup of how they're trying to figure out the critical mass of enriched uranium in water, and it got much more radioactive than they expected. They concluded that everything was fine, it didn't blow up or burn anything down, but one of the hair of the scientist who was working on it did fall out. And you read that in retrospect you think, wow, that's, that's really not very safe. That's not much margin for error at all. If your hair is falling out, it's a pretty bad sign. So these are just some of the examples, but take those couple examples and multiply them by a thousand and you get a sense for how much unknown there was across the entire edifice of this project.

Adam - And how much did they know about what this was going to do? The lives it would take, the cities it would level, and the people who would die from radioactive fall out.

Alex - They knew that it would cause a lot of fire. They knew that it would cause a lot of damage from blast pressure. They had sort of a rough sense of what area would be affected by it, but there were a lot of things they didn't know. Oppenheimer estimated the casualties far too low. He estimated maybe 20,000 people would die at Hiroshima, was more like a hundred thousand and later he said that that bothered him quite a bit to be so wrong. They dramatically underestimated the effects of radiation. They really thought that basically if you were close enough to be hurt by the radiation, you'd be killed by the blast and the fire anyway, and the radiation wouldn't have a large effect. They were wrong on that. And the reason is that, you know, that real life is more complicated than a sort of physical, simple physical simulation. Sometimes you can be in a situation where you somehow survive all of the other effects, but the radiation is the main one you're going to have. And so their later estimates is that maybe as many as 20% of the deaths were directly attributable to the radiation.

A Nobel Prize medal on a black background.

Hiding treasure from Nazis
Ljiljana Fruk, University of Cambridge

After the war ended life began to return to some kind of new normal. And for two scientists, they found something special in their labs in the University of Copenhagen. Max von Laué and James Franck were Nobel Prize winning scientists. In 1940 the Nazi troops invaded Denmark. And the Nazis had a rule that no one could own a Nobel Prize after pacifist Carl von Osseitsky won the Peace Prize. Understandably, they did not want to lose their gold medals, but their colleague George de Hevesy had a plan. To hide them by dissolving them in a chemical called aqua regia. University of Cambridge chemist Ljiljana Fruk told Adam Murphy more about aqua regia...

Ljiljana - So Aqua regia is the mix of nitric acid, concentrated nitric acid, and concentrated hydrochloric acid in a particular ratio. So you would usually have one part of nitric acid and three parts of hydrochloric acid, and then you would get this really powerful acidic mix. And the name stemmed from... It means like kings acid, noble acid, because it was used by all chemists as well to dissolve certain materials that would not dissolve in any other acid or solvent. And one of these materials is gold.

Adam - But is dissolving gold an easy thing to do?

Ljiljana - This is one of the mixes that is dissolving gold in its form. And the reason for this is that gold is so precious because it's very unreactive. So it can survive treatment with acids, it doesn't oxidize, that means it doesn't react with oxygen. So you would never have a gold ring that will change color with time. So not many things will dissolve gold at all. And Aqua regia is almost the only one that will interact with gold. The other material that interacts with gold is mercury and you wouldn't like using mercury.

Adam - Right then the Nobel prize metals have been put in this stuff. How do they dissolve? Chemically what's going on in the jar?

Ljiljana - Well, there are certain acids that can kind of react in a slow way with noble metals like silver and copper and gold, so nitric acid would actually start interacting with gold. But reaction will stop very quickly, so it's not going to go further to dissolving the entire amount of the gold. But if we add hydrochloric acid, this reacts with some of the species that are produced in the first process of interaction between the nitric acid and the gold, and these intermediate pieces are then strong enough to push the equilibrium of the reaction in the direction of the gold dissolution. So what you basically have, you have then the reaction which is pushed from elemental gold, which we know as a gold column, to the ions of the gold, which give out this very nice yellowish orange solution when they are formed.

Adam - Seems like pretty potent stuff. Why would a chemist just be mixing this stuff up in a lab other than thwarting Nazis of course.

Ljiljana - So one of the reasons where you actually can use this as an acid as well is to get the gold ions made. And the gold ions are very useful for nanotechnology. So what we do today is we use some of these gold ions, which are produced, and we use them as precursors, as starting materials to make gold nanoparticles. So what we are basically doing is we dissolve the gold into the ions and then we transform these ions again into the gold, but now using different procedures so that we can get very tiny structures of gold, which have really wonderful properties which have been used for electronics and also in medicine. So it's very useful for kind of producing these gold ions that can be transformed in nanotechnology into the new material.

Adam - Eventually the scientists had to leave Denmark and the jar behind, but it sat there, an unremarkable looking beaker of liquid, until after the war. But when they got back, they didn't want a jar of potent acid did they? How can you get the gold back?

Ljiljana - So you can have, for example, you can simply - one of the ways how you can have the gold back from the solution is simply evaporate what you have left. During the reaction, and this is the beauty of chemistry, during the reaction, if you do the reaction between Aqua regia and gold, you will see the bubbles forming. Because the products of these reactions are gold ions but also gases. And so the gases will get removed. And you are also left with a little bit of water and with these kind of gold ions. And so you can just simply evaporate the water. And then you are left with a really nice powdery compound, which is now the salt of gold ions.

Adam - And then it's a pretty simple reaction to turn that gold salt back into pure gold.

Ljiljana - You know, this is the power of knowledge: how you can hide something also in plain sight. Who would have said that this orange solution is basically gold!

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