海森堡：我为什么选择物理而不是音乐

翻译 | 廖玮

The Decision to Study Physics (1920)

Werner Heisenberg

That autumn, I saw a great deal of the boy who had played Bach's Chaconne so magnificently in Prunn Castle. We would meet in the house of our mutual friend, Walter, himself a fine cellist, and practice for a private recital of Schubert's B Major Trio. Walter's father had died at an early age, and his mother had been left to care for her two sons in a large and very elegantly furnished house in Elisabeth Strasse, just a few minutes' walk from my parents' house in Hohenzollern Strasse. The magnificent Bechstein grand in the living room was an added reason for our frequent visits. After we had finished playing, we would often talk deep into the night, and it was on one such occasion that the conversation came round to my proposed studies. Walter's mother wondered why I had not decided to make music my career.

"From the way you play and speak about music, I get the impression that you are much more at home with art than with science and technology, that you prefer the muses to scientific instruments, formulae and machinery. If I am right, why ever have you chosen natural science? After all, the future of the world will be decided by you young people. If youth chooses beauty, then there will be more beauty; if it chooses utility, then there will be more useful things. The decision of each individual is of importance not only to himself but to the whole of man- kind."

"I can't really believe that we are faced with that sort of choice," I said rather defensively. "Quite apart from the fact that I probably wouldn't make a very good musician, the question remains in which field one can contribute most. Now I have the dear impression that in recent years music has lost much of its earlier force. In the seventeenth century music was still deeply steeped in the religious way of life; in the eighteenth century came the conquest of the world of individual emotions; in the nineteenth century romantic music plumbed the innermost depths of the human soul. But in the last few years music seems to have quite deliberately entered a strange, disturbed and rather feeble stage of experimentation, in which theoretical notions take precedence over the desire for progress along established paths. In science, and particularly in physics, things are quite different. Here the pursuit of clear objectives along fixed paths--the same paths that led to the understanding of certain electromagnetic phenomena twenty years ago--has quite automatically thrown up problems that challenge the whole philosophical basis of science, the structure of space and time, and even the validity of causal laws. Here we are on terra incognita, and it will probably take several generations of physicists to discover the final answers. And I frankly confess that I am highly tempted to play some part in all this."

My friend Rolf, the violinist, demurred. "As far as I can see, your remarks about modern physics apply equally well to modern music. Here, too, the path seems to be dearly mapped. The old tonal barriers are collapsing and we find ourselves on promising virgin soil, with almost complete freedom to choose what sounds and rhythms we like. Hence the musician has every chance of discovering as many riches as the scientist."

Walter now raised several objections of his own. "I don't really know whether 'freedom of expression' and 'promising virgin soil' are necessarily the same thing. At first sight it admittedly looks as if greater freedom must necessarily mean enrichment, wider possibilities; but this I know to be untrue in art, with which I am more familiar than with science. I would think that progress in art takes place in the following way: First a slow historical process transforms the life of men in spite of themselves, and thereby throws up fresh ideas. A few talented artists then try to give these ideas a visible or audible form by wresting new possibilities of expression from the material with which they work-from colors or musical instruments. This interplay or, if you like, this struggle between the expressive content and the limitations of the expressive medium is, I think, a sine qua non of the emergence of real art. If the limitations of the expressive medium were taken away--if in music, for instance, we could produce any sounds we liked--then the struggle would be over, and the artist's effort would reach into a void. For that reason I am skeptical about too much freedom.    

"In science," Walter continued, "a continuous flow of new experiments is made possible by new techniques; there are new experiences and as a result new contents may be produced. Here the means of expression are the concepts by which the new ideas are grasped and made explicit. For instance, I have read that Einstein's relativity theory, which interests you so much, was born from the failure of certain experiments designed to demonstrate the motion of the earth through space by means of the interference of light rays. When this demonstration misfired, it became clear that the new results, or, what amounts to the same thing, the new ideas, called for an extension of the means of expression, i.e., of the conceptual system proper to physics. Quite likely, no one anticipated that this would demand radical changes in such fundamental concepts as space and time. It was Einstein's great achievement to appreciate before anyone else that the ideas of space and time were not only susceptible to change but, in fact, had to be changed.

"What you have said about recent developments in physics could reasonably be compared with developments in music in the middle of the eighteenth century. At that time, a gradual historical process had led to a growing awareness of the emotional world of the individual--as all of us know from Rousseau and later from Goethe's Werther--and it was then that the great classicists--Haydn, Mozart, Beethoven and Schubert--succeeded in extending the means of expression and so discovered the musical language needed for depicting this emotional world. In modern music, on the other hand, the new contents appear to be highly obscure and implausible, and the plethora of possible expressions fills me with deep forebodings. The path of modern music seems to be determined by a purely negative postulate: the old tonality has to be discarded because we believe that its powers have been exhausted, and not because there are new and more forceful ideas which it is incapable of expressing. Musicians are entirely in the dark about the next step; at best they grope their way forward. In modern science the questions are clearly posed, and the task is to find the right answers. In modern art, however, even the questions are uncertain. But perhaps you had best tell us a bit more about the new fields you intend to explore in the world of physics."

I tried to convey what little bits of knowledge I had gleaned during my illness, mainly from popular books on atomic physics.

"In relativity theory," I told Walter, "the experiments you have mentioned, together with other experiments, caused Einstein to discard the prevailing concept of simultaneity. That in itself was exciting enough. Every one of us thinks that he knows precisely what the word 'simultaneous' means, even if it refers to events that take place at great distances. But we are mis- taken. For if we ask how one determines whether two such events are, in fact, simultaneous and then evaluates the various means of verification by their results, nature herself informs us that the answers are not at all clear-cut but depend on the observer's state of motion. Space and time are therefore not independent of each other, as we previously believed. Einstein was able to express the 'new' structure of space and time by means of a simple and coherent mathematical formula. While I was ill, I tried to probe into this mathematical world, which, as I have since learned from Sommerfeld, has already been opened up fairly extensively and has therefore ceased to be unexplored territory.

"The most interesting problems now lie in a different field, in atomic physics. Here we come face to face with the fundamental question why the material world manifests ever-recurring forms and qualities-why, for example, water with all its characteristic properties is invariably reproduced during the melting of ice, the condensation of steam or the combustion of hydrogen. This has been taken for granted in physics, but has never been fully explained. Let us suppose that material bodies--in our case, water--are composed of atoms. Chemistry has long made successful use of this idea. Now, the Newtonian laws we were taught at school cannot tell us why the motions of the particles involved should be as stable as they, in fact, are. Only quite different natural laws can help us to explain why atoms should invariably rearrange themselves and move in such a way as to produce the same substances with the same stable properties. We first caught a glimpse of these laws twenty years ago, in Planck's quantum theory. Since then, the Danish physicist, Niels Bohr, has combined Planck's theory with Lord Rutherford's atomic model. In so doing, he was the first to throw light on the curious stability of atoms which I have just mentioned. But Sommerfeld believes that in this sphere we are still a long way from a clear understanding of the ways of nature. Here we have a vast unexplored field, in which new relationships may be discovered for decades to come. By the ap- propriate reformulation of natural laws and with correct new concepts we might, for instance, be able to reduce the whole of chemistry to atomic physics. In short, I firmly believe that in atomic physics we are on the track of far more important relations, far more important structures, than in music. But I freely admit that 150 years ago things were the other way round."    

"In other words," Walter asked, "you believe that anyone concerned with cultural progress must necessarily make use of the historical possibilities of the age in which he lives? That, if Mozart had been born in our day, he, too, would be writing atonal and experimental music?"

"Yes, I suspect just that. If Einstein had lived in the twelfth century, he would not have been able to make important scientific discoveries."

"Perhaps it is wrong to keep bringing up such great men as Mozart and Einstein," Walter's mother said. "Few individuals get the chance to play such decisive roles. Most of us must con- tent ourselves with working quietly in a small circle, and ought to ask simply whether playing Schubert's B Major Trio is not more satisfactory than building instruments or writing mathematical formulae."

I agreed that I myself had quite a few qualms and mentioned Sommerfeld's quotation from Schiller: "When kings go a-building, wagoners have more work."

"We all feel the same way about it," Rolf declared. "Those of us who want to become musicians have to take infinite pains to master their instruments, and even then can only hope to play pieces that hundreds of better musicians have played much more proficiently. And you yourself will have to spend long hours with instruments that others have built much more competently, or retrace the mathematical thoughts of the masters. True, when all this has been done, the musical wagoners among us are left with no small sense of achievement: constant intercourse with glorious music and the occasional delight of a particularly successful interpretation. Likewise, you scientists will occasionally manage to interpret a relationship just that little bit better than anyone before you, or determine a particular process more accurately than your predecessors. But none of us ought to count on the fact that he will be doing trail-blazing work, that he will make decisive discoveries. Not even when he works in a field where a great deal of territory has still to be opened up."

Walter's mother, who had been listening attentively, now said something, more to herself than to us, as if she were trying to formulate her thoughts as she spoke:

"The parable of the kings and the wagoners may have quite a different import. Of course, superficially it looks as if the glory is entirely the kings', as if the wagoners' work were purely subsidiary and unimportant. But perhaps the very opposite is true. Perhaps the kings' glory rests on the work of the wagoners, on the fact that the wagoners have put in many years of laborious effort, reaping joy and success. Perhaps men like Bach or Mozart are kings of music only because, for two long centuries, they have offered so many lesser musicians the chance of reinterpreting their thoughts with love and conscientious attention to detail. And even the audience participates in this careful work as it hears the message of the great musicians.

"If you look at historical developments--in the arts no less than in the sciences--you will find that every discipline has long periods of quiescence or of slow growth. Even during these periods, however, the important thing is careful work, attention to detail. Everything that is not done with utter devotion falls into oblivion and, in fact, does not deserve to be remembered. And then, quite suddenly, this slow process, in which general historical developments introduce changes in the contents of a particular discipline, opens up new possibilities, quite unexpected contents. Talented men feel an almost magical attraction for the process of growth they can sense at work here, and so it happens that, within a few decades, a relatively small region of the world will produce major works of art or scientific discoveries of the greatest importance. In the late eighteenth century, for instance, classical music poured forth from Vienna; in the fifteenth and sixteenth centuries painting had its heyday in the Netherlands. True, great men are needed to express the new spiritual contents, to create the forms in which further developments can be molded, but they do not actually produce these new contents.

"Of course, it is quite possible that we are on the threshold of an exceptionally fruitful scientific epoch, in which case it would be wrong to dissuade any young man from participating in it. It seems unlikely that important developments will take place in more than one branch of art or science at one time; we ought to be grateful enough if it happens in any one area, if we can share in its glory either as bystanders or as active participants. It would be foolish to expect more. That is precisely why I find popular attacks on modern art--be it painting or music--so unjust. Once music and the plastic arts had solved the great problems posed to them in the eighteenth and nineteenth centuries, there just had to be a more restful period, in which much of the old could be preserved and new things were tested by trial and error. To compare modern compositions with the finest achievements of the great epoch of classical music seems utterly unfair. Perhaps we ought to finish the evening with the slow movement of Schubert's B Major Trio. Let's see how well you can play it."    

We did as we were asked, and from the way in which Rolf played the somewhat melancholic C major figures in the second part of the movement, I could sense how sad he was at the thought that the great epoch of European music might be gone forever.

A few days later, when I walked into the hall where Sommerfeld usually gave his lectures, I spotted a dark-haired student with a somewhat secretive face in the third row. Sommerfeld had introduced us during my first visit and had then told me that he considered this boy to be one of his most talented students, one from whom I could learn a great deal. His name was Wolfgang Pauli, and for the rest of his life he was to be a good friend, though often a very severe critic.I sat down beside him and asked him if, after the lecture, I might consult him about my preparatory studies. Sommerfeld now entered the hall, and as soon as he started to address us Wolfgang whispered in my ear: "Doesn't he look the typical old Hussar officer?" After the lecture, we went back to the Institute of Theoretical Physics, where I asked Wolfgang two questions. I wanted to know how much experimental work had to be done by someone interested chiefly in theory, and what he thought of the respective importance of relativity and atomic theory………  

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