Broadcast Saturday 13/09/2003
Profile of John Wheeler
Physicist Paul Davies presents a profile of the great American theoretical physicist John Wheeler whose work gave us much of our knowledge about black holes, and indeed gave them their name. John Wheeler talks about his early fascination with the universe, his collaboration with Niels Bohr and his conversations with Albert Einstein.
Paul Davies: John Wheeler was one of the towering intellects of the 20th Century: he worked with Einstein and Bohr, played a key role in the atomic bomb project and went on to transform the subjects of astrophysics and cosmology. He is perhaps best known for coining the term Black Hole. But Wheeler was also a visionary whose passion for exploring the deepest questions of existence inspired generations of scientists. I spoke with him about his life and work.
John Wheeler: I suppose at the age of 4, I was asking my mother about the universe. Where does it end? How far out can you go?’ ‘You can go as far as you can.’ ‘But what then?’ ‘Well, then you can keep on going’ - and so it was and this created a terrible worry in my minds. What’s the answer?
Paul Davies: But in your high school days were you particularly good at physics?
John Wheeler: When I lived on a Vermont farm, went to a country school, went up in the woods to fetch maple syrup every other day amidst the snow, there in the quiet woods I could take along a book, and J Arthur Thompson’s outline of science to somebody at the age of 10 was a marvellous thing. And then this being shortly after the end of WW1, chemists were supposed to have won WW1 and physicists won WW2 but then of course there was electricity. What makes it possible for electricity to go down a wire and these pictures of an electron moving from one atom to another furnished a little atmosphere of understandability to that subject.
Paul Davies: A man who’s left a tremendous impression on is,of course, Niels Bohr. When did you first meet him?
John Wheeler: Niels Bohr I first saw at the World’s Fair held in Chicago in 1931 or 32. He gave a talk and I could not understand of what he what he was saying because it was not very distinct. He once remarked to me: You must think I talk in a very foggy way, but the main point is to be not clear in speaking than one is in thinking.
Paul Davies: So as you came to know him better you had no real problem them communicating on scientific matters.
John Wheeler: Never at all. No, on the contrary, there were the most inspiring encounters over the years.
Paul Davies: Now when you were working with Bohr on the structure of the nucleus and in particular, the problem of nuclear fission, when did you first realise that a chain reaction might be a possibility?
John Wheeler: Well, the idea of a chain reaction was one which Leo Szilard had had even before the discovery of fission. His mind was activated to the subject already and therefore when uranium came on the scene it was very natural to think of that as being the substance.
Paul Davies: And once it had been established that fission and a chain reaction was a real possibility of course, that was the beginning of the establishment of the atomic bomb project at Los Alamos. Now of course most of the world’s nuclear physicists in fact, went to Los Alamos, although you in fact didn’t – is that right?
John Wheeler: Yes, January 16th 1939 Niels Bohr had landed in New York and he had heard the results about the fission of uranium not then published, just a few minutes before he sailed from Copenhagen. Naturally he paced up and down the deck and since he and I had been occupied with nuclear physics in times before, we at once plunged in to the understanding of this act of fission. It was two months to the day, it was March 16th 1939 after that landing that we were sitting in the office that had belonged to Einstein, there was Niels Bohr and Edward Teller and Leo Salar and Eugene Bigner and myself, and Bohr was remarking that yes, a bomb could be made but it would take the entire efforts of a nation to do it. Well, of course, in the end it took the efforts of three nations, Britain, Canada and the US.
Paul Davies: Now why is it that you didn’t in fact go to Los Alamos with the other? Was that a decision that you made or was it simply the way that the project was organised?
John Wheeler: In the beginning there was no organisation, we did not assemble there until after Pearl Harbour. This was February 1942 and this was, of course, a tremendous shot in the arm to getting on with work. Then the problem was to get a nuclear reaction going at all, to see that the chain reaction was possible at all. One could not hope to make a bomb until one had a reactor.
Paul Davies: This was the work that was going on in Chicago.
John Wheeler: Yes, that was the word going at Chicago, the so called metallurgical project, the project I was engaged in was a project doubly impossible, two forms of alchemy in it. First the idea that you stack up these great blocks of black dead looking graphite with uranium threaded through holes in it and that this would come to life when you had enough and neutrons silently fly back and forth and little by little gain in number and build up a heat production and produce chain reaction. But then the second part of the alchemy was that these neutrons would produce, out of the normal uranium, the abundant uranium, produce plutonium 239 which had never then been seen and to do this not in atomic amounts, not in grams but to do it in kilograms.
Paul Davies: This was indeed a precursor of the so-called breeder reactors that we’re familiar with today?
John Wheeler: Exactly.
Paul Davies: The culmination of this whole project was the first successful testing of the atomic bomb. What were your own feelings when you heard of its successful test?
John Wheeler: I’ve been told that the largest hospital ever built in the history of the world was built on an island near the Pacific to take care of the casualties expected in the invasion of Japan, and I know that it was never used and I’ve been thanked by at least half a dozen men who were slated to take part in the first invasion wave, that they wouldn’t be alive.
Paul Davies: Turning to post war Princeton and the interesting assemblage of individuals who have come from all over the world, you must have had many fascinating experiences, conversations for example, with Einstein. Are there any particularly memorable occasions for those immediate post war years?
John Wheeler: The occasion when I first started teaching a course in relativity in 1952 and then in the spring of 1953 Einstein, who had followed what I was doing was kind enough to invite me to bring my students around to his house for tea one afternoon and we all sat around the dining room table as the secretary, Helen Dukas and the step-daughter Margot Einstein brought tea and the students asked questions: Professor Einstein what do you think about the idea of the expanding universe? He felt that was very natural. And then: Professor Einstein what about the nature of electricity, and he went on quite at length on that in a most fascinating way. Another: Professor Einstein you did so much to bring the quantum idea in the world why don’t you any longer agree with it? Of course, that was wonderful. And then at the end one of the students got up his nerve and said: Professor Einstein when you’re no longer living what will happen to this house? And Einstein’s eyes crinkled up and his great bushy hair stood out and then in that slow beautiful way of speaking, even though it had a German accent: This house will never become a place of pilgrimage where the pilgrims to come to look at the bones of the saint.
Paul Davies: And indeed it never did.
John Wheeler: And the tourists drive up now and get out and take pictures of the outside but they don’t go in.
Paul Davies: Can I just turn to somewhat later when you’re interest began to develop in gravitation and then of course subsequently the era of Black Holes, because many people right the way to the Laplace, have been credited with the idea of the invention of a Black Hole, but as I understand it you invented the words Black Hole, is that right?
John Wheeler: The occasion was a meeting in the fall of 1967 at the Institute of Space Studies in New York to consider this marvellous work of Jocelyn Bell and Anthony Hewish on the pulsars. What could be the cause of these absolutely regular pulses from some object out in space, and one obvious possibility was vibration of a white dwarf star, another was the rotation of a neutron star. But then I thought that to keep one’s mind open, to look at all the possibilities one ought really to look at the gravitationally completely collapsed object. Well, the very words sounded so foggy, so ethereal, so far from touchability that nobody resonated to that as a possibility to be investigated. So in desperation I adopted the words Black Hole. Well, here at least was a name.
Paul Davies: Many great scientists throughout their life have a vision. Do you have a vision?
John Wheeler: Well, to me it’s the picture that the whole of this existence of ours will some day have its single, central principle spring to life, that will be so natural we’ll say to ourselves: How could it have been otherwise and how could we have been so stupid all these years not to have seen it.
Guests on this program: