Einstein

by Philipp Frank

  “It was a cold day. I was still wearing my winter clothes and heavy overcoat. Arriving at Einstein’s country home, beautiful and commodious, I found him seated on the veranda wearing summer flannels. He asked me to sit down. I asked whether I might wear my overcoat. ‘Oh yes,’ he replied. ‘Aren’t you chilly?’ I asked, surveying his costume. ‘No,’ he replied, ‘my dress is according to the season, not according to the weather, it is summer.’

  “We sat then on the veranda and talked until evening, when Einstein invited me to stay to supper. After supper we talked until almost eleven. By that time it was perfectly clear that Einstein and his wife were prepared to come to America. I told him to name his own terms and he promised me to write to me within a few days.”

  As was his custom, Einstein, wearing a sweater and no hat, accompanied his visitor through the rain to the bus station. The last thing he said on bidding Flexner farewell was: “I am full of enthusiasm about it.”

  Einstein soon communicated the conditions under which he would take the new position in a letter to Flexner, who found them much too modest for such an institute and for a man like Einstein. He requested that the negotiations be left to himself and to Mrs. Einstein. The contract was concluded at this time. Einstein pointed out that he was obliged to spend the winter of 1932–3 in Pasadena and could not go to Princeton until the fall of 1933. At that time he still had intentions of spending a part of every year in Berlin, for he preferred not to be unfaithful to his friends in the world of physics there. But he was very much aware of coming events. When the Nazi revolution took place early in 1933, the way had already been prepared for his emigration to America, and in the winter of 1933 Einstein entered upon his new position at the Institute for Advanced Study, which Flexner had founded at Princeton. Now there was naturally no further mention of spending a part of the year in Berlin. Einstein moved to Princeton to become a permanent resident and citizen of the United States. There were still, however, a number of stages through which he had to pass in order to achieve this goal. He had entered the country only as a visitor and for the present had no legal right to remain here permanently, to say nothing of becoming a citizen.

  3. Einstein’s Activities at the Institute

  The institute that Einstein joined was in some respects similar to the Kaiser Wilhelm Institute to which he had belonged in Berlin. Thus he once again occupied a position that in a certain respect had always appeared distasteful to him. As I have already mentioned, he always regarded it as an uncomfortable situation for anyone to be paid only for his research work. One does not always have really valuable ideas, so that there is a temptation to publish papers of no special value. Thus the scientist is subject to a painful coercion. But when one is a teacher with a moderate load one has every day the consoling feeling of having done a job that is useful to the society. In such a situation it is satisfying to carry on research for one’s own pleasure during the leisure hours, without compulsion.

  On the other hand, however, a man of creative ideas like Einstein chafed under the daily routine of teaching. He found the idea of teaching very noble, but when he was actually offered a position where he would be able to devote himself entirely to research, he was unable to refuse it. At the new Institute he was able to guide talented students who had already acquired the doctorate in carrying on their researches. In consequence, however, his contact with students was restricted to a very small group. Einstein often vacillated between a feeling of satisfaction at being spared any routine work and a certain feeling of loneliness due to his isolation from the great mass of students.

  This divided attitude was quite in accord with his divided attitude toward contact with his fellow men in general, which has already been mentioned repeatedly. This division, which has played a large part in his entire life, manifested itself also in his attitude to his environment in Princeton. It would have been simple enough for him to give lectures or to organize a seminar, which many of the students might have attended. Einstein, however, felt that it would not be fair for him, a man with an international reputation, to enter into a contest with the professors of the university, some of whom were still quite young. They could with some justification regard it as “unfair competition.” At any rate Einstein very punctiliously avoided any such competition for students. It is possible, however, that he exaggerated in his mind the touchiness and ambition of his colleagues, since many would gladly have taken advantage of the presence of such an outstanding scientist in Princeton to learn from him themselves. As things were, his presence there has not been utilized so much as it might have been. No one, perhaps not even Einstein himself, can say to what degree this situation is due to his consideration for others and his aversion toward more intimate contact with people.

  By and large, at Princeton Einstein took up his researches where he had left off in Berlin; this is true both of the problems themselves and of the way in which he dealt with them. It was always very characteristic of him to be independent of his environment. Just as at the time of our meeting in Berlin twenty-five years before it had been a matter of indifference to him whether he was working at his problems in his study or on a bridge in Potsdam, so now it made no difference to him that he had moved his office from the western suburb of Berlin to the distinguished American university town of Princeton beyond the ocean.

  Three groups of problems occupied Einstein during this period. In the first place there was the desire to develop his special and general relativity theories of 1905, 1912, and 1916 into an ever more logically connected structure. In one important point Einstein succeeded in making a great advance at Princeton. It will be recalled that Einstein regarded the gravitational field as a geometrical property of space, which can be called in a word the “curvature.” This curvature is determined by the presence of matter in space and can be computed from the distribution of matter. If the curvature of space, or, in other words, the gravitational field, is known, then one also knows how a body that is present in this space will move. This is given by the “equations of motion,” which can be stated briefly as follows: A body moves in such a manner that the representation of the path in a four-dimensional space-time continuum is a geodesic (shortest) line. This would be entirely satisfactory if one assumed that matter and force field were two completely different entities. But one is driven closer and closer to the conception that the mass of a particle is actually nothing but a field of force that is very strong at this point. Consequently “motion of mass” is nothing but a change of the force field in space. The laws for this change are the “field equations” — that is, the laws that determine the force field. But if the motion of the body is already determined by the field equations, then there is no more room for special laws of motion. One cannot make a supplementary assumption, in addition to the field equations, that masses move along geodesic lines. Instead these equations of motion must already be contained in the field equations.

  C. Lanczos, Einstein’s co-worker in Berlin, had sketched the idea of deriving the laws of motion mathematically from the field equations. His derivation, however, did not appear satisfactory to Einstein, and in Princeton he succeeded in showing in a completely convincing way that only the field laws need be known in order to be able to derive the laws of motion from them. This is regarded as a confirmation of the idea that matter is nothing but a concentration of the field at certain points.

  I have already mentioned that Einstein liked to have the assistance of young physicists or mathematicians, especially when he dealt with involved mathematical computations. From Berlin he had brought with him the Viennese mathematician Walter Mayer, who soon obtained an independent position at the Institute of Advanced Study and no longer collaborated with Einstein. During the first few years of Einstein’s residence a very talented Polish physicist, Leopold Infeld, came to Princeton, where he remained several years and with whom Einstein worked out the aforementioned proof of the “unity of field and matter.”

  Einstein liked to discuss with Infe
ld all kinds of problems, including the fundamental problems of physics and their development. These conversations gave rise to the book by Einstein and Infeld, Evolution of Physics, which has achieved a wide circulation. It is certainly one of the best presentations of the fundamental ideas of physics for the public at large.

  Infeld wrote also an autobiography entitled Quest: The Making of a Scientist. This book contains much about Einstein’s life at Princeton as seen by a keen observer and competent collaborator.

  A second group of problems with which Einstein was intensely occupied at this time is the criticism of the development of the quantum theory, which has been described in Ch. IX. Einstein felt impelled to show by concrete examples that the quantum theory, in the “Copenhagen” form in which it had been formulated by Niels Bohr, did not describe a “physical reality,” such as a field, but only the interaction of the field with a measuring instrument. A paper that Einstein published together with N. Rosen and B. Podolsky, two young physicists, was particularly important in this discussion. This paper shows by a simple example that the way in which the quantum theory describes the physical condition in a certain spatial area cannot be called a complete description of physical reality in this area.

  This work stimulated Niels Bohr to formulate more clearly than he had previously done his standpoint on the question of physical reality. Bohr now rejected definitely all the “mystical” interpretations to which his theory had been subjected. Among these was the conception that the “real state” in a spatial area is “destroyed” by observation, and similar ideas. He now stated clearly that the quantum theory did not describe any property of a field, but an interaction between field and measuring instrument. It is plain that one could not decide between the conceptions of Einstein and Bohr by general logical considerations, since they were not opposed assertions, but rather opposed proposals. Einstein proposed to retain tentatively a kind of description of the physical state in an area of space which was not too far from the way in which the language of daily life describes reality. This means that he proposed to describe the physical state in an area in such a manner that the description itself need not state with which measuring instrument it was obtained. Einstein has been well aware that it would not be absurd to abandon this kind of description where the laws of physics are formulated in terms of a “field”; but he would abandon it only if it became necessary beyond any doubt.

  The third and most exciting problem was his attempt to find the actual physical field that permits a formulation of physical laws for the subatomic phenomena in a form that is a generalization of the equations of the electromagnetic and gravitational fields. Einstein has collaborated in this task with two young men, one called Bergmann, the other Bargmann, a similarity that gave rise to many jokes.

  Every forenoon Einstein went regularly to his office at the Institute for Advanced Study, where he met either Peter Bergmann or Valentin Bargmann or both of them. Einstein suggested to them various ways of conceiving the structure of space, not only as four-dimensional, but sometimes also as five-dimensional, so that the magnitudes that describe this geometrical structure could also furnish a description of the unified physical field of force. The real force field would then be found, if one could find relations between the described magnitudes, from which the actual laws of observable phenomena can be derived in all domains of physics, including atomic and nuclear physics.

  The difficulties of this task proved to be even greater than had been supposed. At present it seems that all the paths that have previously been tried do not lead to the goal. Recently, Einstein has probed new field equations and he has by no means abandoned the hope that electrons and protons will turn out to be just particular fields. Despite the tremendous range of experimental confirmation of Bohr’s “positivistic” Theory it remains, according to Einstein, still an open question, whether it is not possible to derive the same observable facts from a field theory and to save the historic conception of a physical reality independent of the devices of observation and measurement.

  Besides the regular work connected with the Institute, Einstein had to occupy a part of his time as an adviser of young men with interest or ambition in science. It had often been Einstein’s fate to be judged not only as an individual, but as a type — indeed, even more, as the symbol of a certain group of people. This fate was all the more painful for him as there was nothing that he liked less than to be classified as a member of a party or a group. As he had come out courageously for the cause of the Jewish people he has been expected to play the part of a leader or at least of a representative of his people both by the enemies of the Jews and by the Jews themselves. The life of Einstein has been regarded as symbolizing the fate of a people, often talented, but often attacked and driven into isolation. Therefore among the people who looked for Einstein’s advice there were many young Jews who wrote letters to him appealing for his help. In some degree he has played the role among the Jews that Tolstoy at one time had played among Russian youth. Poor young Jews looked upon Einstein as one of their people who had made good and who was so world-renowned that boundless power and wealth were ascribed to him. This was, I dare say, a great mistake. Neither his fortune nor his influence has corresponded even remotely to his fame.

  Very often young people of any background turned to him for advice about beginning an academic career for which they felt they were equipped instead of turning to some mechanical work in an office or a shop. Einstein was always ready to advise what he considered proper and was interested in each one’s personal situation. However, as we have learnt, Einstein also believed that it was a good thing to earn a living by means of a “cobbler’s trade” and to devote one’s spare time to study.

  Einstein never liked to speak about the material and moral help he provided for distressed people. I recall several cases, however, that I was able to observe myself. Einstein remained interested in students whom he had helped to enter a university, and continued to watch them as they progressed with their studies. He advised them with which teachers to study, which books to read, and even sent them books himself. I remember one such case very clearly.

  It concerned a student from one of the Balkan countries. Upon Einstein’s advice he had applied to the university in Prague, where he was admitted. Einstein asked me to take an interest in him and so he consulted me when he had trouble. The student lived on a stipend that he received from a big manufacturer in his native land. But this money, which barely sufficed for himself, the student used to enable his brothers and sisters to study as well. The fact that one of the greatest men of our time was watching his studies was the great event of his life and filled even the minutest experience with a remarkable splendor. When the young man first turned to Einstein, the latter was still in Berlin, but when the young man arrived in Prague Einstein was already in America. The student wrote to Einstein telling him about every phase, even the most trivial, of his studies; and frequently he received answers from America that gave him extremely detailed advice. When the student met with difficulties in his relations with teachers or fellow students, he asked Einstein’s advice as to how he should behave. Einstein usually advised him to be conciliatory. This was certainly very good advice for this young man, as he became involved in various conflicts in the unfamiliar environment. He was naturally filled with pride because he was distinguished from all the other students of physics by the fact that he corresponded personally with the greatest physicist of our time.

  There is little wonder that occasionally a student in this situation imagined himself as Einstein’s representative to such a degree that he regarded all insults to him as insults to Einstein. He would even feel that he was a martyr, happy at being permitted to suffer for Einstein, and finally even came to believe that by being connected with Einstein he was making a sacrifice and getting himself into trouble.

  4. Refugee Scholars

  As the persecution of the Jews increased in Germany and her satellite countries, the number of scientists
, writers, artists, teachers, and others who wished to find haven in the United States grew larger and larger. As when a large quantity of good merchandise is thrown on the market at reduced prices, economic repercussions occur, even inflation, so when these refugee scholars offered themselves, great difficulties were encountered.

  The new immigration began while the United States was still in the midst of the great economic crisis. This was, of course, not an accidental coincidence since without the world-wide depression the Nazi revolution in Germany would not have occurred. As the number of immigrants increased, fantastic rumors began to be spread about them. It was frequently said that the refugees were not pioneers; they did not perform any constructive work as the earlier immigrants had done, but they wanted only to get rich without working or to live on charity. Many regarded and feared them as professional competitors, many simply used them as scapegoats whom they could blame for various ills. Skillful agitators were even able to convince people that enormous numbers of such immigrants would soon change the national and racial composition of the people of the United States.

  When Bertrand Russell, the English mathematician and philosopher, because of his critical attitude to traditional views on marriage and religion, was prevented from being appointed as professor of philosophy at the College of the City of New York, Einstein backed him. He felt that it was harmful for the development of science when attacks of personal and political opponents could prevent the appointment of a scientifically outstanding professor. Russell’s enemies, however, used Einstein’s support for their own aims. They wrote letters to newspapers containing such statements as: “How dare the ‘nudist’ Russell and the ‘refugee’ Einstein interfere in the family life of the United States!” The use of the words “nudist” and “refugee” as equally disparaging characteristics is noteworthy.