This is an interesting example of what you can do if you take some time to think. My father was a physiologist who had missed several important discoveries because, as he told me, he was working so hard that he couldn’t take time out to sit and think. The best piece of advice in my scientific career that he ever gave me was to say: "Just sit down and clear your mind and take time to think." And so the night I thought up the neutron time-of-flight method I was following my father’s advice. I'd said to myself, "Let’s just sit down in a chair all evening and see what you can come up with." I think I wrote in my notebook, "I'm sitting down in my chair and I’m going to see if I can think up something useful tonight." And I sat there and let my mind wander around and realized that the velocity of the neutrons was such that by using reasonable distances and the kinds of turn-on times that one could probably get with the cyclotron, one could observe very slow neutrons and ignore the very fast ones. I didn’t think of it as a spectrometer at that time but really as a way of excluding the effects due to fast neutrons. Nowadays one doesn’t think about that because there are such things as thermal columns in reactors where one has a sample of pure thermal neutrons.