I was delighted to find your site, quite by accident, when looking for information on QED. You see, I was an undergraduate at Caltech 1979-83, and had the opportunity of talking to Feynman a few times during my studies, mostly during my freshman year in Physics X. I do have quite a few Feynman stories, but the one I like the most concerns the time I almost stumped him in "Physics X".
As you know, this was an opportunity for freshman at Caltech to ask Feynman questions, or, more often, as the year went along, to listen to his stories. (This was long before Surely You're Joking Mr. Feynman, but obviously he was rehearsing them!) After several weeks of hearing questions ranging from the trivial ("where did I lose the factor of 2 in my homework?") to the preposterous ("tell us everything you know about quantum mechanics"), I was getting embarrassed by my fellow students. I did want to ask him something, though, which had plagued me since reading up on the history of quantum mechanics while in high school.
I had read that Einstein was troubled by QM, as evidenced by his famous line, "god does not play dice with the universe." Einstein believed that there was something wrong with QM, since it was not deterministic. See, in classical physics, once the state of a system is precisely known, all future behavior can be calculated. The clockwork universe depicted by Newton was disrupted terribly by quantum mechanics. In quantum mechanics, knowing the exact state of a system is not possible. Therefore, it is not possible, no matter how hard you try, to predict the future behavior of quantum systems exactly. Rather, QM predicts only probabilities, or likely outcomes. Like shooting craps, the way an atom behaves is random every time it is observed. It is only the averages that can be predicted with precision.
In high school, my two idols were Einstein and Feynman. While Einstein felt that QM must be wrong, Feynman felt it was the ultimate truth of the universe. This discrepancy bothered me, and I wasn't sure who to believe. So, about six weeks into physics X, I screwed up my courage and asked Feynman about the "dice" and Einstein. "Dr. Feynman", I asked, "Einstein was one of the greatest geniuses of physics, and certainly a lot smarter than me. He knew more physics that I ever hope to. But, he didn't believe in quantum mechanics--so why should I?"
Feynman paused -- which surprised all of us -- and smiled. He looked at me and said, in that wonderful Far Rockaway accent, "Nature doesn't care how smart you are. You can still be wrong." He went on to explain some background on Einstein's view of physics, and why he might feel that way.
However, I remember feeling a real change in my view of the world that day. You see, as a freshman in physics, at Caltech, well, it was sometimes a little intimidating. My teaching assistant for freshman physics (not the instructor, but the TA) happened to have a Nobel prize (Max Delbruck). There were a LOT of smart people wandering the halls. However, Feynman's answer to my question made me realize that, no matter how smart these guys were, they could make mistakes. They were, after all, not that different from me. It was a good feeling, and one that has never left me. It gave me a sense that I could contribute to science, even if I wasn't the smartest guy on campus.
I don't remember most of what we discussed in "Physics X" that year. (My memories were, of course, jogged by Surely You're Joking Mr. Feynman.) However, I have a very vivid memory of the one good question I asked him, and his very good answer.