I was asked to speak at the honors convocation at Washington University in St. Louis. During the preceding months there had been additional information released about damage done by radioactivity from testing of nuclear weapons, and by the Hiroshima and Nagasaki bombs. So, my talk was about that. It got a tremendous response from the audience when I said, “We have to stop the testing of nuclear weapons in the atmosphere because hundreds of thousands of unborn children and people now living are being damaged.” So with two other professors, Barry Commoner and Ted Condon, I decided to write a petition. The next day we met, each of us had written a version of the petition, and I think mine was, essentially, the one selected by the three of us. We sent immediately, mimeographed it, and sent it out to 25 scientists that we knew. They all sent it right back, signed. So then I got back to Pasadena and my wife and I and some of our students and other people in the lab got busy and sent out hundreds of copies with the names of these first 25 signers — or perhaps there was 25, the three of us and 22 others. And, within a month or two I had 2,000 signatures from American scientists which I presented to Dag Hammarskjold. Scientists from all over the world began signing this petition. Originally, it was a petition by American scientists, but then it became a petition by world scientists. I think it was about 9,000 signatures that I gave, my wife and I gave to Dag Hammarskjold, and ultimately, about 13,000 scientists all over the world had signed this petition. So, that had a great effect, and I think even on President Kennedy, because a few years later he gave a speech about a need for a treaty limiting bomb testing and of course pretty soon this treaty was made.