Bethe had done the Lamb shift calculation, non-relativistically, that spring, so that was already published and we knew about it. And then it was clear that that was a makeshift calculation and it was a fudge, but the physics was obviously right and it was a question whether one could make it mathematically correct, and it had to be relativistic, it had to be precise. Bethe got the right answer within 40 megacycles - the total Lamb shift was at that time a thousand and forty, and he got it right, I mean his rough calculation gave a thousand. But the question of whether you could really explain it precisely was open, and it was clear you needed a much more high powered approach. So that was the problem that Hans gave me to work on, only he said, 'Try the spin zero case first, because that's likely to be easier' - so it meant you had relativity, but you didn't have all the complications of the Dirac equation.

[Q] There was... was there actually another student working on the spin one half?

Yes. There was Richard Scalettar who was doing the spin one half. He was my very close friend, and it was sort of painful because he's very slow - he's a good guy, I've kept in touch with him over the years but he just didn't have what it took really. I mean it was a very tough assignment. I think that was a mistake on the part of Hans to give it to him. And so I was racing ahead with the spin zero, which was the unphysical case, which was fine for me because it gave me the sort of experience I needed and I was very happy with it. But for Hans it was actually unsatisfying, because what Hans wanted was to get the right answer for spin one half, which is the physical case. And there was Richard Scalettar struggling and struggling and not getting it, and I was doing a different problem, so for Hans it was rather frustrating, I think. But anyway, I mean we all felt we couldn't snatch it away from Scalettar, it was Scalettar's problem so we kept our hands off it. But it was not all that easy a situation. And Scalettar and I were, both of us, sort of aware of the situation but we were determined to remain friends and we did, so we never stepped on each other's toes.