Hiroshima and Nagasaki: 71 Years On


On August 6 1945 over 10,000 people were killed in less that a second in the city of Hiroshima in Japan. Many were vaporised, literally obliterated from the face of the Earth with no trace of them left, by the ‘heat pulse’ of an atomic bomb dubbed Little Boy. Nuclear weapons give out heat radiation when detonated which travels at the speed of light, which is why people died so quickly. But this is only the first of three ways in which nuclear weapons kill. Those who were far enough away from the epicentre of the explosion, the point at which the bomb actually went off, to escape death by burning would be struck almost immediately by a shock wave or blast generated by expanding air travelling at 1000 km/hr. Burning buildings were shattered and burnt people killed by the this second effect of the bomb. The further away from the epicentre of the explosion, the better the chances of survival, but even those who escaped the heat and blast were still victims of the third  effect of a nuclear explosion, and one that is unique to this form of weaponry, namely radiation. This comes in two forms: prompt and delayed. The former is radiation that is released directly by the explosion while the latter is released by materials which themselves are irradiated by the explosion, become radioactive and then in turn release their radiation as ‘fallout.  Heat, blast and radiation all killed people in Hiroshima, either singly or ‘synergistically’, in combination. Three days later it all happened again in the Japanese city of Nagasaki, though this time a Fat Man bomb did the killing, Fat Man being fat where Little Boy was thin, reflecting the different designs of the two weapons. Around 100,000 people were killed in both attacks, nearly all of them civilians and nearly all of them women, children and old men.



These terrible events prompt a series of questions, the first of which is this:




1. Why did the Americans drop their bombs on cities which had no strategic value to the war, and which were filled with civilians?




The answer given by the Americans – their ‘official answer’ – is that they needed to end the war as speedily as possible in order to avoid even more casualties. They had seen that Japanese soldiers were very often willing to fight almost to the last man, as had happened at Iwo Jima and Okinawa, and they were willing to sacrifice their own civilians by setting up defensive positions in populated areas. Bombing cities and killing civilians was thus claimed to be a way of putting pressure on the Japanese authorities to surrender, and thus saving the lives of those civilians who would perish in an invasion of the Japanese main islands. By using the atomic bomb, the most efficient killing machine in history, the Americans were applying the utmost pressure. It worked: Japan surrendered a week after Nagasaki. The apologists for the atomic bombings have maintained this position ever since 1945, and it is an attempt at a justification. The atomic bombings killed many innocent people, and that was a terrible thing to do, but it prevented even more deaths, and so it was, if not right, then at least not wrong.




While the bombing of Hiroshima and Nagasaki seems especially horrible and wicked, in some ways it was no different from what the Americans had been doing to Japanese civilians ever since their bombers had been in range of Japanese cities. And before then, when US joined in the strategic bombing of Germany in 1944, their bombers killed German civilians. In fact, a ‘conventional’ bombing raid on Tokyo in March 1945 killed more civilians than either one of the atomic bombings. So we have a kind of explanation of the dropping of the atomic bombs, an explanation to the effect that this was nothing new with reference to what had gone before. I think the atomic bombings have come to be seen as something different, something even worse than what went before. It seems on reflection that the annihilation of the two cities and their inhabitants seemed so easy and hence so terrible, with just one plane carrying one bomb in each case.






2. How was the atomic bomb built?




A short answer is: with a great deal of difficulty over a long period of time, by very clever men and women. The Manhattan Project, as the atomic bomb programme was called, was set up in January 1942, a month after Pearl Harbour and the US entry into WW2, and ended in July 1945 when a Fat Man bomb was tested and the two other bombs that had been made were handed over to the US military. So the programme coincided almost exactly with the US participation in WW2. In January 1942 there was no assurance that an atomic bomb could be built, and the first task for the Manhattan Project was therefore to determine if this was possible. The idea that it was possible had been suggested by recent advances in the new field of nuclear physics. That atoms have a structure, a nucleus plus electrons, was only discovered in 1911, and between that time and 1942 a handful of scientists in Germany, England, France, Italy and the US had been investigating the properties of the nucleus and developing a theory to explain them. It had been found that the nuclei of some atoms were unstable and would split apart. This is called nuclear fission and it gives rise to radioactive decay and is accompanied by the release of parts of the nucleus, particles called neutrons and some energy. The idea for an atomic bomb is this: make a device that causes a very large number of atoms to undergo fission very quickly indeed. If enough atoms can be made to decay fast enough, then the sum of the energies released in each decay event should add up to very large amount, which is what happened at Hiroshima and Nagasaki.




It took the greatest concentration of scientific talent ever assembled, including more than 20 Nobel prize winners, working in ideal conditions for over three years to determine that atomic bombs could indeed to made, to come up with two designs for an atomic bomb, and to build a total of three bombs. Scientists from universities around the country visited Los Alamos, the main bomb design facility, and other Manhattan Project laboratories, for periods of time. Much pure and applied scientific research was conducted, followed by design, development and engineering – the full gamut of what is now referred to as R&D. The Manhattan Project was the largest most intensive research project ever undertaken, something that remains true today. Its main legacy was not, however, what happened it its immediate aftermath, Hiroshima and Nagasaki, but the knowledge of how to make atomic bombs. This knowledge was re-discovered by the Soviet Union, then by the British, French, Chinese and others. It was used to discover an even more terrifying weapon, the thermonuclear bomb. The principle behind this type of weapon is not the fission of (heavy) nuclei, but the fusion of light nuclei, whereby heavier nuclei are made from lighter ones. Thermonuclear weapons have been made that are 2000 times more powerful than Fat Man, and in the arsenals of the US, Russia, China and elsewhere are enough weapons to end virtually all of sentient life on Earth.




With this is mind, we must surely ask




3. Why was the atomic bomb invented?




I mentioned that the idea of the atomic bomb was suggested by developments in the new field of nuclear physics. But the idea did not emerge from some existing institution devoted to exploiting the latest discoveries in science for making weapons. Weapons research, research dedicated to designing new weapons systems and improving existing systems, had not yet been institutionalised in the US, or for that matter in any countries. After WW2 any country with pretensions of being an important power in the world had one or more such institutions, and the US maintained the Los Alamos nuclear weapons laboratory and set up others. The idea of using a chain of fission reactions to create a massive explosion is usually credited to one person, Leo Szilard, a Hungarian physicist who worked with Albert Einstein in Berlin. Szilard left Germany and moved first to London in 1933 and then to the US in 1936. He had his idea in London in 1933 and then tried to get others to help him investigate it, but that was difficult given the very small community of nuclear physicists. After he moved to the US he worked at Columbia and slowly managed to get the interest of other émigré scientists, scientists like himself who had left Europe because of the rise of Nazism in Germany.




Germany was the world-leader in science, especially physics. The new sciences of quantum theory and relativity had been mainly developed in Germany, as had nuclear physics. For example, the experimental verification of the fact that atoms can undergo fission naturally was discovered in Germany in 1938. It seemed to Szilard, and to others, that if they had the idea of an atomic bomb, then so would the scientists left behind in Germany, and if a bomb could in fact be made, then Germany was the most likely candidate to make one. And Germany was turning into one of the most unpleasant and aggressive regimes in history. Szilard therefore desperately wanted Britain and the US to investigate this possibility, and if an atomic bomb were possible, build one as a deterrent to any similar achievement by the Germans. Szilard’s agitations finally paid off in 1942 when the Manhattan Project was founded and which he joined; and his idea was correct, a chain of fission reactions does produce a massive explosion. But he was wrong about German scientists: they also explored the idea but made a crucial mistake and  concluded that an atomic bomb was impossible. In any case, it became increasingly clear that Germany could not have built a bomb in war time. All this was verified in August 1944, when it became clear that there was no German atomic bomb and hence no need to build a deterrent. But only one scientist, Joseph Rotblat, then left the Manhattan Project: all the others stayed on until the end.




The United States invented and built the first nuclear weapons at the urging of scientists from Europe who had witnessed the rise of Nazism in Germany. But the atomic bombs were not needed as a deterrent to any Nazi bomb, and were finally used to kill tens of thousands of Japanese civilians. Many people, including many of the scientists who took part in the Manhattan Project thought that this was wrong. And it was. A number of decisions that were made should not have been made, including the order to drop the bombs on Hiroshima and Nagasaki.




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