John D. and Catherine T. MacArthur 教授
Professor Leggett, I would like to begin by thanking you for granting us this interview today. You are now giving a series of lectures on superconductors, so I would like to ask you how the lectures are going.
I think they are going rather well. There has been a good attendance. We started with 40 people and there are now about 30, which in my experience is a good result. Moreover, a lot of very interesting questions have been asked during the lectures; so I think they are being followed with interest and that the attendees are getting something out of them.
I am enjoying the lectures although I find the subject difficult to follow. I always take my computer so that I can quickly check things I don't understand.
Yes, I can understand that for some people, the speed is probably rather tough. That is why I always give students the opportunity to drop into my office to ask questions on things they don't understand in the lectures.
You have a very interesting academic background, Professor Leggett. You originally studied classics at the University of Oxford; then you changed your major to science. What made you change your subject?
Classics is a four year course of twelve trimesters, and for the first five trimesters you study Latin and Greek, languages and literature. You get to the stage at which you are supposed to be able to write poetry in ancient Greek. Some students can, some can't. The last seven trimesters are an even mix of ancient Greek and Roman history and philosophy. The philosophy is mostly modern and doesn't have much connection with Greece or Rome. I did this course and enjoyed it immensely, but it occurred to me that I was eventually going to have to get a job; so I looked around to see what my fellow students were doing. Generally speaking they either went into the civil service or they taught one of the subjects they had studied — classical languages and literature or ancient history or philosophy. I didn't want to go into the civil service; so the obvious thing would have been to continue in one of the subjects I had studied, and end up as a high school or university teacher. Of the three subjects I had studied, the one I had enjoyed most, and perhaps had been best at was philosophy; so that seemed the obvious course. In England, philosophy is not taught at high school, so I would have had to teach at a university.
I considered becoming a university faculty member in philosophy, but then realized that in philosophy everything depended on the precise turn of words you use and even more on the opinions of your colleagues. There seemed to be no objective criterion as to whether what you are doing was right or wrong, or good or bad. But I wanted to work in a subject where there was some kind of external or objective check on what you are doing. I'd had no experience of physics, but I'd had some exposure to modern mathematics. So I first thought of becoming a professional mathematician. Then it occurred to me that in mathematics if you are wrong, it means you are stupid. I like to be wrong without being stupid; so, because I had experience in mathematics, physics seemed the obvious place to go.
Did you find it difficult to change from one subject to the other? Classics and physics are totally different.
Yes it was difficult in various ways, some of which are not so obvious. When I'd been doing my degree in classics, I went to see my tutors every week and they would give me some topic to do an essay on and suggest reading a journal called Mind or the Proceedings of the Aristotelian Society. Then I'd write an essay and argue with the tutor.
When I switched to physics, it was a big shock to find that you just couldn't operate in this kind of way at all at the undergraduate level. You were several years behind the frontier of the subject, and basically you just had to accept everything without being able to argue about it. Another thing I found difficult to get used to in physics was that you went to a course because it was essential for the subject; in classics, you would go if you found it interesting.
There's another aspect. It's a very hierarchical structure certainly, which you don't find so much on the arts side. All these things took some getting used to.
I read that your parents were teachers of physics. Is that why you chose physics?
My mother had been a high school teacher of mathematics and my father was a high school teacher of physics, mathematics and chemistry. He never pressed me to go into physics at all. When I first went into high school, in 1949, the queen of the academic subjects was classics, Latin and Greek. After that came history and modern languages, then mathematics and right at the bottom of the pile was science. It was an ingrained attitude in England in the late 40s, so my father didn't press me to go into science. In fact, he was quite pleased when I went into classics. At my school, if you had some kind of academic ability, and you didn't express a strong desire to the contrary, you were automatically shunted into classics. That's how I ended up there, not really by any coherent process of thought.
I think the study of classics gives you an attitude which is certainly not universal among physicists. Philosophers make a living out of questioning even things that seem obvious, and they never take anything for granted. They will ask: “How do you know that? What do you mean?” And I think I picked up that attitude. Even long after I had switched to physics, I kept in contact with my colleagues who were professional philosophers and I found it very refreshing to talk to them because they would never take anything on trust. They'd ask the most basic questions which physicists tend not to ask, and that has influenced me a lot. It is partly the reason why I've always been interested in the fundamental aspects of quantum mechanics and questions concerning the arrow of time.
Do you prefer a more kind of basic fundamental research rather than specific research?
Yes, but I have to earn my living, so I at least I need to spend a certain amount of my time doing mainline physics, but I very much like to think about more general problems.
You are now lecturing in Japan, and you were also here in 1973 and 74.
Yes, I spent a year at Kyodai 1965, and 9 months at Todai in 1973.
What motivated you to come to Japan in those days?
After I had got my bachelor's degree in physics, I started on a PhD. Halfway through my PhD, I was elected to a junior fellowship at Magdalen College in Oxford. I was looking though the rules of the college that governed my fellowship, and it occurred to me that I didn't have to spend the fellowship in Oxford; so I decided to take advantage of this and take a year off and go some place I couldn't otherwise go. If it had been possible to go to China, I would have gone there. I was interested in the cultural aspects of Northeast Asia, so I decided to visit Japan.
And at that time you studied in Kyoto?
Yes, I was in a group with Professor Matsubara.
Do you like Japan?
Oh yes, obviously I wouldn't keep coming back if I didn't.
Why do you like Japan?
I somehow feel at home here. This is partly because I speak the language. At the end of my stay in 73, I spoke it considerably better than I do now. I could not just get around, but I could have quite interesting conversations in Japanese. I like the way which people have adapted to having to live at a very high population density. I think that if you were to take the population density you get in an average large Japanese city and transfer that to a western city of similar size, you would almost certainly get a slum. People got very good at living and getting on with one another in these very crowded conditions, and somehow I find it somewhat exciting.
My next question is more research-oriented. You are doing many important work on physics, fundamental quantum physics from semiconductors through to information science. What do you think we should have in mind when we do the research? Can you give me some kind of clue for doing good research?
I think the most, probably single most important thing is not to be afraid to follow your own curiosity. I don't think one should ever be afraid of asking what other people think is a stupid question. The example I always take there is Einstein's question about why do all bodies in a vacuum fall at the same rate in the earth's gravitational field? When he first asked that question, people said it was a stupid question and that everybody knows they just do. But he was really fascinated by that question, and he followed it up, and as we know, this was the origin of the general theory of relativity. So I think you should not be embarrassed if people around you say “Look everyone understands that, don't bother about it.” If you really feel that there is something you don't understand about it, just keep away at it and if it's a question you think other people might worry about you should at some stage search the literature. I don't even think you should search the literature too early in the game. It's often a good idea to try to approach a question from scratch without knowing what's been done on it. Then, of course, if you finally come to a conclusion, you don't rush out and publish a paper without looking at the literature. The odds are, even if it has been done, you'll have come at it in a different way, and you'll have leant something from doing that. And sometimes you may find that no one has done it. When I was just at the final stages of my PhD at Oxford, I'd done a particular calculation and got a particular result that I was quite pleased with. I was just scanning through physics abstracts one day, and this was literally a week before my PhD oral, and I was going through physics abstracts, and I came across an abstract and I thought that the writer had done exactly what I had done. I thought he had done the same problem and got the same answer. The article in question was in the Ukrainian Physics Journal and in Ukrainian. The library in Oxford had no Ukrainian-English dictionary but it did have a Ukrainian-French dictionary; so I went away into the library for several hours — luckily, I do know some Russian, so it wasn't totally impossible — and I finally figured out what this article said, and it had absolutely nothing to do with what I had done. So even if you think something has been done, the odds are it hasn't.
So you think we should not be too convinced to follow the general trends?
I'd say follow the questions you think are interesting. Don't worry what other people think. Very often you'll come up with something which is genuinely new in that way.
Basically, don't be afraid of spending time on questions you think are interesting or exciting, even if other people say everyone knows that or that it's not an interesting question. Probably that's the single most important thing. Don't worry too much about researching the literature at an early stage. It's better sometime to address it yourself. And the third thing I usually say is that you may find yourself in a situation where you've started to work on a problem and you've done some quite hard calculations, and in the end it didn't give a result which looked like it had anything to do with the experiment or in one way or another it didn't work. You shouldn't worry about that. What you should do is make sure that you write down everything you've done, try to make a complete account and just put it away in a drawer, and the odds are ten or fifteen years later, it'll come back and help you out. That happened to me when I was working on 2-band superconductors at Kyodai in 1965. It was motivated by a particular experiment which later turned out to be wrong. So at first sight it looked as if that work was completely wasted. But in fact, it was precisely that work which was a key to my later work on the microscopic theory of NMR in superfluid 3-He, a generalization of that work. As I say, it is never wasted. The other thing, perhaps the most important, assuming that you are not just going on to do research, if you are going to become a university faculty member, then your job will involve both research and teaching. And I would say very strongly, take your teaching as least as seriously as you take your research, in fact more so. That's not just good for your students, it's good for you too. I've found lots and lots of useful ideas have sprung out of my teaching activities.