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Guggenheim fellowship to France


Princeton, 1945: cosmic rays and 'Mesic' Atoms. WY Chang
John Wheeler Scientist
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My friends in experimental physics had seen enough of big projects during the war to have dreams built up in their minds of building big accelerators. But I was not inclined that way. My inclination was to think that the cosmic rays are already there, they're a cheap source of high energy particles, let's exploit them. And we had, on the campus, a building that had been used during the war for work on shock waves and resistance of structure to explosion. I managed to snaffle that building to take over for a cosmic ray laboratory. I think I called it Elementary Particle Physics Laboratory, because that was the object of study. But one of the fascinating things about the cosmic rays is the presence in them of these mesons, and what happens when one of these mesons goes into a solid material and slows down, stops. Well, it goes into orbit around the nucleus. And it's the Law of Competition. It's more effective than the electron in wangling its way close to the nucleus in a region of strong attraction. So there's a Bohr Orbit of the meson around the nucleus, so I figured that it would be natural to study the properties of such a - what I called a Mesic Atom. Well, some of the boys in the lab who had got interested in these things set up equipment to detect the mesons coming in, or rather the radiation given out, of the meson, dropped from one Bohr orbit to a closer, tighter, more strongly held Bohr orbit. And the energy given out we could predict and check the predictions. This was a great insight into the coupling between a meson and a nucleus. The chap who did the experiments was W Y Chang. He had been in the physics department during the war, the university. He had been originally sent over from China, and he was married to another Chinese physicist, who worked with a colleague in Michigan. And here, W Y Chang and his wife would meet, generally in Indiana, once a month, see each other and go back to work at their separate places. They were very loyal to China, so after the war, despite the terrible conditions in China, they went back to their native country. And she taught physics in Peking and he managed a nuclear physics laboratory there. But he was assigned, for a time, to the Russian laboratory at Dubna, outside of Moscow. And once again, they would have to meet at some intermediate point, she from Beijing and he from near Moscow. I don't know how important a part he took in any Chinese nuclear weapons project. I certainly never talked about such things with him, and I had no indication that he was interested in such things. Pure physics was what brought us together, and this cosmic ray work, particles stopping in lead, and other nuclei. That made a fascinating study. I would have liked to get that radiation called the Chang Radiation, but the word never took, unfortunately. But in my mind, that's what it is.

John Wheeler, one of the world's most influential physicists, is best known for coining the term 'black holes', for his seminal contributions to the theories of quantum gravity and nuclear fission, as well as for his mind-stretching theories and writings on time, space and gravity.

Listeners: Ken Ford

Ken Ford took his Ph.D. at Princeton in 1953 and worked with Wheeler on a number of research projects, including research for the Hydrogen bomb. He was Professor of Physics at the University of California and Director of the American Institute of Physicists. He collaborated with John Wheeler in the writing of Wheeler's autobiography, 'Geons, Black Holes and Quantum Foam: A Life in Physics' (1998).

Duration: 5 minutes, 44 seconds

Date story recorded: December 1996

Date story went live: 24 January 2008