THE CHAIRMAN OF the physics department at The George Washington University, Dr. T. B. Brown, at first viewed Gamow and me, members of his department selected by President Marvin, with a dubious eye. After a few years, he relented a little as far as I was concerned, and our relationship became comparatively friendly. At the start of my fourth year, Dr. Brown showed his approval by asking me to give a talk about atomic theory to the faculty of the university; nonetheless, his confidence in me was less than absolute. Once I had agreed to speak, he set about examining my adequacy. Not before or since have I been so thoroughly drilled for a lecture. He even put me through a dress rehearsal. 1
During the question period following my lecture, someone asked, "How long before a practical use of nuclear energy might be worked out?" I predicted, "It may take a year, a hundred years, or it may never happen." I was wrong. As I was speaking, two chemists at the Kaiser Wilhelm Institute in Berlin were beginning to examine the first key to unlocking nuclear energy. That key had been lying around unused for half a dozen years.
I have already mentioned that in 1932, Fermi had begun to bombard, systematically, all the elements with neutrons, a process that produces radioactive substances. He found that if a lightweight element captures a neutron, it produces a single radioactive element with a specific half-life. Heavier elements that have three or more naturally occurring isotopes may____________________