The Heisenberg Uncertainty Principle states that you can never simultaneously know the exact position and the exact speed of an object. Why not? Because everything in the universe behaves like both a particle and a wave at the same time. Chad Orzel navigates this complex concept of quantum physics.
The race between J. Robert Oppenheimer and Werner Heisenberg during World War II to develop the atomic bomb is a fascinating chapter in the history of science and warfare.
Oppenheimer, an American theoretical physicist, led the Manhattan Project, the United States’ secret endeavour to develop the first nuclear weapons. He was instrumental in bringing together a diverse group of top scientists, including many European refugees, to work on this project at Los Alamos, New Mexico. Under Oppenheimer’s leadership, the team successfully developed and tested the world’s first atomic bomb in July 1945.
On the other side of the Atlantic, Werner Heisenberg, a German theoretical physicist and one of the key pioneers of quantum mechanics, was leading Nazi Germany’s nuclear weapon project. However, Heisenberg’s efforts were not as successful. There are many theories as to why Germany’s atomic bomb project failed, ranging from lack of resources and Allied bombing campaigns to Heisenberg’s possible moral qualms about creating such a devastating weapon.
In the end, the race was decisively won by Oppenheimer and the Manhattan Project. The atomic bombs they developed were dropped on the Japanese cities of Hiroshima and Nagasaki in August 1945, leading to Japan’s surrender and the end of World War II. The legacy of this race, however, has had profound and lasting impacts on global politics, ethics, and the scientific community.
Heisenberg’s uncertainty principle says that if we know everything about where a particle is located, we know nothing about its momentum. Conversely, if we know everything about its momentum, then we know nothing about where the particle is located. In other words, this principle means that we cannot measure the position and momentum of a particle with absolute precision or certainty.
But waves, as you know, don’t exist in one specific place. However, you can certainly identify and measure specific characteristics of a wave pattern as a whole, most notably, its wavelength, which is the distance between two consecutive crests or troughs. Particles that are as small or even smaller than atoms have large enough wavelengths to be detected, and can therefore be measured in experiments.
Thus, if we have a wave whose wavelength and momentum can be measured accurately, then it’s impossible to measure its specific position. Conversely, if we know the position of a particle with high certainty, then we cannot accurately determine its momentum. This is what Heisenberg’s uncertainty principle is all about.
In 1939, Werner Heisenberg joined the “Uranium Club” to try to make a nuclear bomb for Hitler. Why? He didn’t love the Nazis and he had plenty of opportunities to leave. This is the story of the moral failings of a brilliant man.
Heisenberg’s uncertainty principle tells us that it is impossible to simultaneously measure the position and momentum of a particle with infinite precision. In our everyday lives we virtually never come up against this limit, hence why it seems peculiar. In this experiment a laser is shone through a narrow slit onto a screen. As the slit is made narrower, the spot on the screen also becomes narrower. But at a certain point, the spot starts becoming wider. This is because the photons of light have been so localised at the slit that their horizontal momentum must become less well defined in order to satisfy Heisenberg’s uncertainty principle.
Hungarian-American physicist, Edward Teller (1908-2003), helped to develop the atomic bomb and provided the theoretical framework for the hydrogen bomb. He remained a staunch advocate of nuclear power, calling for the development of advanced thermonuclear weapons. [Listener: John H. Nuckolls]
TRANSCRIPT: I would like to finish my story about Bohr and, in a way, about Heisenberg, by telling you of a very sad fact. When the Nazis came, when Hitler occupied Denmark, Bohr was in danger of his life. He had a Jewish grandfather, I think, at least. He was to escape. Shortly before that, Heisenberg listened- came to him. Bohr came out to America and told us that Heisenberg is working on the atomic bomb for the Nazis. Heisenberg and Bohr have been good friends. Bohr did enormous damage to Heisenberg’s reputation. I heard him say that, I even heard him say that in a one-to-one conversation. I never quite believed it. I went back to Germany, found out – in more ways than in a short time I can tell you – but found out what actually happened. Heisenberg went to visit Bohr, he had to talk with him. He talked with him in his home, the Carlsberg Castle, the, the beer producing Carlsberg people or- I don’t know whether it was beer, but they gave it to Bohr. And when they were talking indoors and Heisenberg was afraid that there might be- that the Nazis might have put in listening apparatus, he said things- I am working for my government and it’s good to work for my country. That is what Bohr quoted. Then they went out into the garden and Heisenberg was no longer afraid. And then he added- I am with a group working on the atomic bomb. I hope we won’t succeed. I hope the Americans won’t succeed either. I cannot do otherwise than give an ab- abbreviated version of all this but here is one point, one generalization which I would like to make. My years in Germany, about which I want to talk a little more later, have been at a wonderful constructive period of science. Hitler destroyed it. You were not allowed to talk about Einstein. A Jewish lie, relativity. Heisenberg resisted it. I have many detailed indications that Heisenberg, if he did not directly sabotage the work on the atomic bomb, he never seriously worked on it. After war he and maybe ten other people were taken to a place in England and kept there and now the British did listen by secret apparatus to what they were saying to each other. I couldn’t get that record until two years ago when it was published. And Heisenberg said about atomic bombs some of things which clearly prove that he did not think about the subject. They were told in August 1945 that we’d dropped an atomic bomb and the Germans didn’t believe it. And then Heisenberg told them- Perhaps they did, and explained to them how the atomic bomb worked, wrongly so. A point about which I am very proud because the mistake that Heisenberg then made, I made a few years earlier when I was starting to think about it – and found out within a few months that it was wrong. That Heisenberg should make the same mistake gives me pleasure. But it shows, in the case of the excellent intelligence of Heisenberg, that he never seriously tried to work on the subject.
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