MY MEMORIES OF EINSTEIN*

Leopold Infeld

I learned of Einstein’s sudden death. Almost all the journals in Poland asked me to write an obituary. I also received a number of telegrams from abroad asking me to send an article about Einstein. But I was too shaken by this news to write anything; I merely dictated to my secretary one little page, rather of a personal character—it was used by Polish Radio, Trybuna Ludu, and some foreign publications. A few days later Jarosław Iwaszkiewicz** telephoned me and asked me to write recollections for Twórczość. I liked this proposal. I was afraid only that the manuscript would grow too long, and I asked Jarosław whether there was any upper limit to its length. In fact, the present article grew out of that idea.

The reader will be surprised that I quote statements made by Einstein twenty years ago. Can they really have remained in my memory? Of course not. But this part of the memoirs is taken from the book Quest, which I wrote in 1938, that is, when only a few months had passed since the time of my close collaboration with Einstein. In addition, my memory was refreshed by letters, of which I have quite a few, although, unfortunately, not all have survived, since I lost or gave away many of them.

Writing these pages was a consolation for me; it even brought me a certain joy. Memories and images of a period of intense scientific collaboration came to life again.

After the completion of our book Evolution of Physics**\ I wrote: “Everyone will speak of this book as one written by Einstein and by someone else whose name he does not remember.” To the end of my life I bear the stamp—“Einstein’s collaborator.” This

* Twórczość, issue 9, 1955; translated from the Polish by I. E. Dudovskaya and G. I. Zalutsky.
** J. Iwaszkiewicz—a well-known Polish writer and fighter for peace, editor-in-chief of the Polish literary journal Twórczość (Creativity).
*** Russian translation: The Evolution of Physics, Gostekhizdat, 1948.

often irritated me. Today I am proud of it. Perhaps only now do I fully appreciate the good fortune that fell to my lot—the good fortune of collaborating with Einstein.

1.

I first heard Einstein’s name in 1917, when I was a second-year student at the Jagiellonian University. It happened in the following way. Theoretical physics was then lectured by Professor Władysław Natanson; he lectured splendidly, so splendidly that difficulties disappeared, that everything seemed already accomplished, solved, clear, and, moreover, once and for all. During the lecture he sipped tea, wrote formulas magnificently, using an unusual technique—a wet chalk on a wet blackboard. He had the face of a sage, a Baroque style, a quiet and calm voice. In the second year of the university he lectured on classical mechanics, five hours a week for two semesters, without seminars, without laboratory classes, without assistants.

In his lectures I saw a beautiful synthesis of mathematics with the liveliness and fascination of reality. I came to love theoretical physics as a young man can love it who has at last found the embodiment of his long-standing dream of a science striving to enclose the laws of the universe in mathematical form.

At the end of the academic year Professor Natanson devoted several hours to Einstein’s special theory of relativity. For the first time I heard this name, for the first time I heard of the Lorentz transformation, which Einstein had formulated. These lectures were a revelation to me. Even now, although nearly 40 years have passed since then, I still see before my eyes the blackboard covered with formulas, and it seems to me that I hear the professor’s voice. I remember how Professor Natanson called Einstein “a genius among geniuses.” I remember the impression made on me by the стройность of the theory of relativity, the boldness with which its author adopted a completely new point of view and arrived at strange conclusions that at times seemed absurd. I did not then have sufficient preparation to understand fully the structure of the theory of relativity, but I knew that I would return to it again.

When, several months later, I was studying Maxwell’s theory from Drude’s book, the first scientific idea arose in my head—to apply the Lorentz transformation to electromagnetic phenomena in order to ascertain whether Maxwell’s equations remain unchanged with respect to these transformations. It seemed to me—then I was in my third year—that I had found something new and important: the invariance of Maxwell’s equations under the Lorentz transformation. I showed the result obtained to Professor Natanson and learned from him that the very same thing, only much better, more beautifully, and more fully, had been done 13 years earlier by Einstein and Poincaré; that this had indeed been the problem which laid the beginning of the theory of rela-

...that subsequently, in 1908, it was Minkowski who gave this research its splendid mathematical form. This served as a good lesson to me. I knew that I had much to learn before I could set to work. The days and sleepless nights devoted to this problem gave me a foretaste of the joys and sufferings connected with creativity.

In my fifth year of student life I found myself in Berlin. I wanted to complete my course there, at one of the best universities in Europe. For a long time, by various means, I tried to gain admission to the university where Planck, Laue, and Einstein lectured. However, all my attempts ran up against a wall of hostility toward Poles. Someone advised me to appeal to Einstein, at that time already the best-known and the most attacked man among scientists. I realized that it was impudence on my part to bother Einstein with my personal affairs. But to get into the University of Berlin seemed to me then a matter of life and death.

I telephoned him at his apartment.

— Is Professor Einstein at home?

— Yes, he is at home, — answered a woman’s voice.

— I am a physics student from Poland; I would like to meet with Professor Einstein. Could he receive me?

— Certainly. It would be best if you came now.

Timid, deeply excited, and in festive spirits at the prospect of meeting face to face the greatest of contemporary physicists, I rang the bell at the door of Einstein’s apartment at Haberlandstrasse 5. Mrs. Einstein invited me into a small room furnished with heavy furniture. I told her the purpose of my visit. She apologized— I would have to wait; her husband was speaking with the Chinese minister of education. I waited. My face was burning with impatience and excitement. At last Einstein opened the door, said good-bye to the Chinese man, and invited me in. He was wearing a black jacket and striped trousers, on which the main button was missing. The very face that I had already seen so many times in newspapers and magazines. But no photograph could convey the brilliance of his eyes.

I completely forgot my carefully prepared speech. Einstein smiled amicably and treated me to a cigarette. It was the first friendly smile I had happened to see since my arrival in Berlin. Stammering, I told him about my difficulties. Einstein listened attentively.

— I would gladly write you a letter of recommendation to the Prussian Ministry of Education, but that will lead to nothing.

— Why?

— Because I have already given very many recommendations. — Then he added quietly, with a smirk: — They are antisemites.

He thought for a minute, pacing back and forth across the room.

— The fact that you are a physicist simplifies matters. I shall write a few words to Professor Planck; his recommendation carries more weight than mine. That will be best of all!

He began looking for letter paper, which was lying right there before him—on the writing desk. I was too timid to point it out to him. At last he found the paper and jotted down a few words. He did this without knowing whether I had any notion at all of physics. The only thing known to him was that I was a student of Professor Natanson, whom he knew and respected. I already felt free enough to ask him several questions connected with the theory of relativity and concerning problems that were troubling me at the time. What did he think of Weyl’s new generalization?

— No! I do not like Weyl’s new theory, though I very much like his book. It is a pity that he spoiled it by including his new theory in the second edition. You see, if you take two hydrogen atoms and transport them by different paths from the Earth to the Sun, then, according to Weyl, they will have different frequencies. I do not believe that the frequencies of atoms can depend on their past. — Then, laughing loudly, he added in a naïve tone: — No, I do not believe that.

I asked him what, properly speaking, the energy–momentum tensor means in the theory of relativity.

— That question is difficult to answer. I say in my lectures that the theory of relativity rests on two columns. One of them is mighty and beautiful, as if carved from marble. This is the curvature tensor. The second is shaky, as though made of straw. This is the energy–momentum tensor. He again laughed loudly, and then added: — We must leave this problem to the future.

I said goodbye. Such was my first, and for the next 16 years my only, personal meeting with Einstein. This first meeting allowed me to convince myself of a simple truth: true greatness and true nobility always go side by side.

2.

During the following years I maintained correspondence with Einstein. I wrote little, only on scientific questions, and I always received replies that helped me in my work. When my first popular book was to appear in English, the publisher (Collancz) persistently urged me to ask Einstein to write a foreword: such a foreword would considerably increase demand for the book. Einstein was at that time in Princeton—the era of Hitlerism had already begun in Germany. I wrote to Einstein and sent him the galley proofs of the book. Twelve days later I received a warm, beautifully written (in German) foreword. Einstein attached to it a letter in which he said that he liked my book very much and that, if for any reason I wished to have a somewhat different foreword, he would gladly make changes.

MY MEMORIES OF EINSTEIN

A year earlier, Einstein, in one of his studies, had referred to a paper of mine written jointly with Van der Waerden.

It was 1936. Poland was becoming more and more fascist. I realized that in such a Poland I would never obtain a chair. At that time I was a docent in Lwów. I wrote to Einstein about the state of affairs, understanding, of course, that this was one of the very many requests for help that were addressed to him. Soon an excellent reply arrived: the Institute for Advanced Study in Princeton, of which Einstein was a professor, was granting me a modest stipend, and the author of the letter was glad that we would soon meet.

I arrived in Princeton on a Saturday, lived through a dead Sunday, and on Monday set off for Fine Hall, the splendid building that housed the Institute of Mathematics and Theoretical Physics of Princeton University, as well as the Institute for Advanced Study. There I asked the secretary when I might see Einstein. The secretary telephoned him and said:

— Professor Einstein wants to see you right away.

I knocked on the door of room 209 and heard a loud “Herein.” Opening the door, I saw a hand energetically extended to me. Einstein had aged greatly since the time of our Berlin meeting—outwardly even more than the 16 years that had passed since then. His long hair had turned gray, his face had become yellowish, and there was a stamp of weariness on it. Only his sparkling eyes remained as before. He was dressed in a brown leather jacket, a shirt without a collar, rumpled brown trousers, and he wore no socks. I expected at least a brief private conversation—questions about when I had arrived, how I had traveled, what was new in Europe, and so on.

Nothing of the sort.

— Do you speak German?

— Yes, I replied.

— Then I shall tell you what I am working on now.

He calmly took a piece of chalk, went up to the board, and began a lecture. He spoke with astonishing calm. In his behavior there was not a trace of the anxiety of a scholar who assumes that a problem, well known to him and with which he has grown accustomed, is understood to the same degree by his listener. Before moving on to formulas and details, Einstein outlined the philosophical background of the problems on which he was working. He paced slowly and with dignity about the room, from time to time approaching the blackboard to write an equation, holding an extinguished pipe in his mouth, and formulated superbly polished phrases. Everything he said could have been printed without any changes, and every sentence would have been irreproachable. The lecture was distinguished by simplicity, depth, and clarity.

I listened attentively and understood everything. Einstein’s ideas, as always, were of a fundamental character. He said why he would

did not like the way in which Bohr, together with me, had tried to solve the problem of a unified field theory; then he spoke of his strenuous attempts to understand matter as a concentration of fields, then of the theory of “bridges” as models of matter, and of the difficulties that he and his collaborators had encountered during a year of intensive work.

The lecture was interrupted by a knock at the door. Laughing, gesticulating vividly, there entered a man of about sixty, very short in stature. He spoke in a mixed Italian-English language. It was Levi-Civita, the well-known Italian mathematician, at that time a professor at the University of Rome, invited for half a year to Fine Hall. This small, physically frail professor had, several years before, refused to take the fascist oath required of university professors in Italy.

Einstein had long known Levi-Civita well. But he greeted him in Princeton in much the same way as he had greeted me. By gestures rather than words, Levi-Civita let us know that he did not wish to disturb us. With both hands he pointed to the door and, trying to express this thought still more clearly, turned his whole small body toward the door.

It was time for me to intervene.

“I can go and come another time.”

Einstein objected:

“No. We can discuss together, all three of us. I shall briefly repeat what I have just been telling Infeld. And then we shall continue.”

We readily agreed. Einstein began to repeat—in a somewhat abbreviated form—his introductory remarks. This time we chose English as the language of our conversation. Since the first part of the lecture was already familiar to me, I could afford not to follow it, and now my eyes rather than my ears were occupied. It cost me great effort to keep from laughing. Einstein’s English was extremely simple. It consisted of about 300 words, pronounced in a peculiar way. As he himself told me later, he had never studied the language seriously. Yet every word could be understood because of the calmness and slowness with which he pronounced them, because of the expressive, very pleasant timbre of his voice. Levi-Civita’s English was far worse; the meaning of his words dissolved in his Italian accent and lively gesticulation. They managed to reach an understanding only because mathematicians have almost no need of words in order to understand one another. At their disposal are symbols and a few technical terms that can be recognized even in distorted form.

I watched attentively the calm Einstein and the small, thin, vividly gesticulating Levi-Civita, while they pointed to the formulas written on the blackboard, using a language which, in their opinion, was English. The whole scene, and the sight of Einstein, every now and then

pulling up his trousers (without a belt or suspenders), was so majestic and comic that I shall probably never forget it. I tried to keep myself from laughing by resorting to autosuggestion.

Here you are talking and discussing physical problems with the most celebrated physicist in the world and laughing because he does not wear suspenders, I thought. The suggestion worked, and I restrained myself from laughter at the moment when Einstein began speaking about his latest, still unpublished, work on gravitational waves.

After hearing Einstein’s arguments refuting the existence of gravitational waves, Levi-Civita explained that he had arranged to have breakfast with someone, gesticulating so vividly as he did so that I felt hungry. Einstein asked me to accompany him home—he wanted to give me the manuscript of his latest work. On the way we continued talking about physics. This large dose of physics tired me; it was already hard for me to understand Einstein. He spoke on a subject to which we later returned more than once. Einstein explained why, from an aesthetic point of view, he was not satisfied with modern quantum theory, why he believed that it was of a temporary character, and why, in his opinion, in the future this theory would undergo radical transformations.

I went with him into the house, into his study with a large window looking out onto a beautiful garden full of the vivid colors of the American autumn, and there I heard from him the first and only remark of the entire day that did not concern physics:

—A beautiful view from this window.

3.

In my notes from that period, printed in English, I find the following paragraph, written in America in 1938:

“A scientist who has achieved success in science and considers himself an idealist, in moments of creativity was probably a materialist, having accepted with his senses the authenticity of the external world, and then creating an artificial philosophical scheme not connected with his creative work and alien to the spirit of that work. Thus there arises a dangerous contradiction between his scientific work and his words. In everyday life, when we are concerned about the health of our children, the fidelity of our wives, or when we are engaged in scientific work, we always act as materialists. This sense of the materiality of the external world is so strong in Einstein that it often takes the form of something directly opposite. When Einstein speaks of God, he always has in mind the inner connection and the logical simplicity of the laws of nature. I would call this a ‘materialistic approach to God.’”

Einstein appealed to his concept of God more often than a pastor. Once I asked him:

—Tomorrow is Sunday. Should I come to you? Shall we work?

—Why should we not work?

— I thought that you wanted to rest on Sunday.

Einstein laughed loudly and said:

— God, too, does not rest on Sunday.

In Fine Hall there is a hall, usually closed, opened only for the reception of honored guests. On the fireplace is carved Einstein’s saying: “Raffiniert ist der Herr Gott, aber boshaft ist er nicht.” (“The Lord God is subtle, but he is not malicious.”)

4.

In America, for the first time in my life, I saw Negro dances, permeated with fire and vital force. The dance hall at the “Savoy,” in Harlem, is transformed into an African jungle with a blazing sun and rich, dense vegetation. The air is full of vibration. Loud music and passionate dances radiate vital force; the spectator loses the sense of reality. In contrast to the Negroes, the whites seem half-alive, ridiculous, and humiliated. They create a background against which the primitive, boundless vitality of the Negroes is even more striking. It seems that no pause is needed, that this intense movement can continue forever.

This picture often stood before my eyes when I observed Einstein. It was as though there existed some mechanism, intensely alive, turning forever in his brain. This was sublimated vital force. At times the observation was simply painful. Einstein could speak about politics, listen with astonishing kindness, so characteristic of him, to requests, answer questions, but behind this external activity one felt the constant work of thought on scientific problems; the mechanism of his brain acted without interruption, and only death cut short the eternal movement of this mechanism.

Several weeks after my arrival in Princeton, our collaboration began. At first I regarded it without any special enthusiasm. Only later, when I found myself among engrossing problems, did the power of Einstein’s logic carry me away. And to this day my scientific work is to a considerable extent concentrated around the problem that can be briefly defined as the problem of motion. The final solution of this question will probably never have any influence on our everyday life or on present-day technology. It is a purely theoretical problem. Work in this field has as its aim a better understanding of the problem of motion, to find a better, deeper, and more logical explanation of it than Newton’s mechanics gave. This is a fundamental problem, reaching with its roots into the very foundations of physics. The longer I work on it, the more it captivates me.

The basic idea is simple. But its realization required the development of a special computational technique, more intensive thinking, and greater labor than any other problem on which I had worked up to that time. For about twenty years—with interruptions—I worked

MY RECOLLECTIONS OF EINSTEIN

over this question, whose chief application is the motion of double stars.

The problem of motion is as old as human thought itself. In Newtonian mechanics we always have a concrete picture: a horse pulls a cart, and the cart moves. A force causes the acceleration of the body on which it acts. This mechanical picture seems simple to us only because we have grown accustomed to it. In this picture we have both force and body—the basic elements of the mechanical worldview, well-known attributes of the old physics. But can we apply this picture to our conceptions of the field, conceptions that have proved so fruitful in another domain? We must once again analyze the problem of motion, using the concepts and methods introduced into physics by field theory.

It turned out to be a difficult task. In Maxwell’s field equations, as well as in Einstein’s gravitational equations, the problem of motion had not been adapted to field theory. The problem of motion remained in the depths of the classical physics of particles. In our investigations we set ourselves the aim, ignoring the existing concepts of pushing, pulling, lifting, to formulate the problem in a new way, to express it in the terminology of field theory, using only the field equations. This problem is important from a fundamental, philosophical point of view, but its practical value is almost equal to zero.

Scientists have devoted days and sleepless nights to problems of this kind, seemingly remote from everyday life. Yet in general, in the final analysis, the efforts of scientists have practical significance: they satisfy existing needs or create new ones.

I do not know how many people have studied our works. Probably few. How could it happen that only a few study works whose author is Einstein? This is explained by the role that Einstein’s name plays in the world of contemporary science. It is easy to say that Einstein is the greatest scientist of our time, perhaps even the greatest scientist of all time. Such a formulation will satisfy only lovers of clichés. To define and understand Einstein’s role in science is much more difficult.

The key to understanding Einstein’s role in science is his solitude. In this respect he differs from all the scientists I have known. Closest to him from this point of view is Dirac, although the difference between them is great. When Einstein in 1905 formulated his special theory of relativity, no one in the scientific world knew his name. He had never studied physics at any well-known university, was not connected with any well-known school of physics, and at that time was serving in a patent office.

Once Einstein said to me:

“Until I was thirty, I had never seen a real theoretical physicist.”

LEOPOLD INFELD

I very much wanted then to ask him whether he ever happened to look in the mirror.

In our time, for every theoretical physicist, a good school—or even several good schools—contact with the leading figures of science, and knowledge of the technique of using the appropriate instruments of thought are considered indispensable. Einstein’s example is unique. For him isolation was a blessing, because it protected him from beaten paths. Solitude, independent reflection on the problems he set himself, the search for his own solitary roads, and the fact that he avoided haste—these are the most characteristic traits of his work. This is not only originality, not only scientific imagination; it is something more, something that can be understood only when we examine Einstein’s problems and methods of work.

When Einstein was 26 years old, he was engaged not only in the theory of relativity. The fundamental ideas of the theory of photons and of Brownian motion are associated with his name. All these achievements were recognized a few years later, and Einstein’s name became known among physicists. So it was in 1909. During this period physicists were little interested in the problem of gravitation. The center of gravity of scientific work in physics was constituted by quantum theory and, to some extent, the special theory of relativity, which removed serious difficulties in the field of classical electrodynamics. The problems and results connected with quantum theory and the special theory of relativity were considered interesting, modern, and worthy of attention. However, no one perceived the existence of serious problems in the theory of gravitation. Calculations based on Newton’s law of gravitation seemed sufficiently precise to astronomers. I do not think that, during the several years following the formulation of the special theory of relativity, there appeared even a single work concerning the problem of gravitation. Einstein devoted the last 10 years of his life to it at a time when no one was already working on this problem, when no one was already interested in it. The special theory of relativity had overcome an annoying difficulty in physics and had eliminated the most important contradictions. It was accepted with enthusiasm by almost the entire world of physicists. As for the general theory of relativity, which attempted to resolve the problem of gravitation, the attitude toward it on the part of physicists (at least at first) can best be expressed in the words: “Who cares about this?” Einstein told me of this complete absence of interest, of the fact that no one believed in the fruitfulness of his approach to solving this problem; to everyone his point of view seemed alien and strange. To spend ten years considering some problem without any encouragement from the world of physicists—is this not proof of an extraordinary strength of will? It is precisely strength of will, perhaps to a greater degree than enormous intuition, to a greater degree than colossal scientific

fantasy, is the source of Einstein’s scientific achievements. Much later, only after he had created the general theory of relativity, came the time of fame and recognition; his renown among physicists grew into world fame such as no other scientist had ever known.

To the very last minutes of his life Einstein remained faithful to his methods of work: he set problems for himself and followed his own paths. Subsequently this method of working alone no longer led to results as outstanding as the special and general theories of relativity. Fewer and fewer physicists were interested in Einstein’s later works. Almost all scientists work collectively, gathering materials and creating theories, often incomplete ones, so long as they correspond to the abundant experimental data. This is especially noticeable in the field of nuclear physics.

Einstein did not like such “engineering physics,” as he called it—that physics which seeks quick results, corresponding to a very limited domain of facts, by means of hypotheses invented ad hoc. He was always interested in root, fundamental problems. Only a few physicists possess such inclinations. The majority are interested in the rapid attainment of results that satisfy the needs of the present day, in the search for theories and methods that die sooner than spring flowers. Thus, for example, a book on nuclear theory can almost always be considered obsolete already at the moment of its publication.

Einstein considered the solution of the problem of gravitation the greatest achievement of his life. He once said to me:

—The special theory of relativity would now have been created even without me. That problem was ripe. But I do not think this applies to the general theory of relativity as well.

By this remark of his Einstein emphasized what I mentioned above: namely, that the interests of physicists were far removed from the problems with which the general theory of relativity was concerned and which it solved.

Einstein’s habit of doing everything himself went very far. Once, when I had to carry out a calculation that was given in many books, I said:

—Let us see how it is done there. We shall save a great deal of time.

But Einstein went on calculating.

—That will be quicker,—he replied.—I have already forgotten how one looks things up in books.

Before we published our work, I suggested to Einstein that I select the literature relating to the subject, in order to name the scientists who had worked on this question. Laughing loudly, he said:

—Oh yes. Certainly. In this respect I have already sinned greatly.

5.

When we began working together on questions of motion, Einstein had already been studying this problem for fifteen years. What, then, did it consist in?

The general theory of relativity formulates the equations of the gravitational field, describing the changes of this field in space and in time. From the point of view of field theory, particles may be regarded as something located where the equations of the field, of the pure field, cease to be valid. An essential task of the field equations is the description of the field between the regions in which the field equations are inapplicable. But how do these particles move? In relativity theory we proceeded from the fact that the motion of these particles takes place along a so-called “geodesic line.” It is not very important what these words mean. It is enough to know that in the mathematical structure of the theory of relativity there were equations of two kinds: 1) the equations of the gravitational field; 2) the equations of motion of particles. The existence of these two kinds of equations had long ceased to satisfy Einstein. In the field equations we tried to go beyond the limits of the mechanical point of view, to cross the boundary of particle physics; in the equations of motion we return to our old concepts. How is this difficulty to be removed?

Is it possible that the equations of motion are already contained in the field equations? And if so, how are they to be derived from these equations? Perhaps the field compels particles—that is, the regions in which the laws of the field lose their force—to move in some definite way? Perhaps the field equations force particles to move along definite trajectories, and additional laws of motion are unnecessary and even incorrect? For it is not impossible that the old equation of motion is only a first approximate expression of a deeper law, which can be derived from the field equations when we look more deeply into their content. Einstein believed that the equations of motion are contained in the field equations, and for years he sought proofs of this theorem; it could have extraordinarily simplified the structure of the general theory of relativity.

The philosophical aspect of this work is not new. The simpler our assumptions are from a logical point of view, the longer the chain of thought leading from the initial propositions to results that can be confirmed or refuted by experience. The paradox is that modern physics seems so complicated because it is so simple. It appears difficult and complex because we must start from fundamental assumptions that seem abstract, and are forced to make a long journey through complex reasoning, link by link, in order from these links to assemble the chain connecting our premises with observations.

This is precisely the picture that obtains with respect to the problem of motion. We began by admitting the existence of two sorts of laws: those of the field and those of motion. The introduction of laws of motion in each particular case was a simple matter, since we proceeded from a general law of motion. However, let us abandon the general law of motion, assuming that it is contained in the field equations. Then we obtain a system that is logically simpler: one kind of equations instead of two. But at the same time we must considerably lengthen the chain of logical reasoning. We must derive the equations of motion from the field equations—this is not an easy task. We pay with technical complication for the logical simplicity obtained. But it is precisely this logical aspect that has extremely essential significance for physicists. They are prepared to accept any technical complications in order to obtain a theory that is more harmonious from the logical point of view.

I should like to cite here one of Einstein’s beautiful definitions, and therefore I am compelled to use certain mathematical terms. Field theories—such as Maxwell’s theory of the electromagnetic field or Einstein’s theory of gravitation—are formulated in the form of differential equations with partial derivatives. In order to find a solution of these equations, in order to derive from them a result that could be compared with experiment, one must use integration. This is often connected with a lengthy and laborious procedure. The logical chain leading from theory to observations consists chiefly in this procedure of integrating differential equations. This is where our principal technical difficulties lie.

When we had been working for months on problems of this kind, Einstein said:

—The Lord God is not interested in our mathematical difficulties. He integrates empirically.

This phrase expresses Einstein’s conviction that the laws of nature can be derived from a simple theory, and that it is precisely simplicity, and not the technical difficulties connected with deduction, that serves as the measure of the beauty of a given theory.

6.

The problem of the logical simplification of the theory of gravitation by neglecting the equations of motion proved to be very difficult. When we delete the equations of motion, only the field equations remain—very complicated ones; we do not know what treasures are hidden in these equations. Theoretical physicists had studied them only superficially; they had not penetrated deeply enough into their content. At that time we did not know whether these equations allow particles to execute arbitrary motion, or whether they restrict the possibilities of their motion. In other words, we did not know whether it follows from them

equations of motion to the field equations, or not.

Long before the beginning of our joint investigations, Einstein had conceived an idea of how to approach this question: he decided to apply the so-called “new method of approximations.” He believed in a double success: that we would be able, first, to show that the equations of motion are contained in the field equations, and, second, to find the hidden treasure that would allow a bridge to be thrown from classical theory to quantum theory. Einstein, it seems to me, believed until the last minutes of his life that there exist fundamental laws valid both for the motion of stars and planets and for the depths of the atom.

He was pondering an unusual mathematical approach to these questions and suggested that we work on it together. He had long had the goal before his eyes: to obtain the equations of motion and to find the connection between classical and quantum physics.

At first I was not convinced that the equations of motion are contained in the field equations. I was even more skeptical about another question. I did not believe that there existed any connection between questions of gravitation and quantum theory. It seemed to me that not accepting Einstein’s views would have been, on my part, unheard-of audacity and presumption. However, I am convinced that in science there is nothing more dangerous than accepting blindly the judgments of authorities and established dogmas. I would like my students in Poland to understand this. I try to instill in them habits of independent thinking. I repeat: in science one’s own reason must invariably remain the highest authority. Penetration into a problem is almost always the result of a painful struggle in which faith and disbelief are intertwined. I wanted Einstein to understand and approve this position of mine, and so once I said to him:

—If I assume that you are always right, there will be nothing left for me but to echo you and mechanically carry out calculations. All satisfaction from scientific work will disappear. I fear that my skepticism will be unpleasant to you, Professor, and that cooperation with me will bring you little benefit.

Thinking back to those times, I admire the patience with which Einstein answered my arguments. In understanding these questions Einstein had gone far ahead; it was very difficult for me to keep up with him. Yet he never lost his temper, returned many times to the same explanations of the methods and modes of reasoning, and calmly disposed of my objections until I understood what the matter was. Once he uttered a phrase that I regarded as a great compliment:

—I understand everything perfectly well,—he observed,—because I, too, am the same way. I do not believe anyone until I myself have properly figured everything out.

At first our collaboration moved forward with difficulty. Instead of seeking proof that the equations of motion are contained in the field equations, for a long time I tried to prove something directly opposite. Einstein did not insist—he was very tactful. Once he said:

“If I had insisted, it would have taken still more time for you to be convinced that you were on the wrong path.”

Suddenly, one fine day, I saw the light. All my skepticism vanished. I began to work with the greatest enthusiasm. When I came to believe in the possibility of success, my attitude toward the matter changed sharply. I was already convinced that the equations of motion really do follow from the field equations, but I did not think that this question could have any relation to quantum theory. I stressed the divergences in our views as directly and freely as one can do with such a person as Einstein.

Thus began the second period of our collaboration, a period full of joyful excitement, successes, and disappointments.

Our task was divided into two different parts: the first came down to complex reasoning leading to the general theory, and the second to long, difficult calculations in order to derive the equations of motion from the field equations explicite.

We worked from day to day—mornings at the Institute, after lunch at Einstein’s, sometimes at my place.

At Einstein’s we worked in his room, on the second floor of the house on Mercer Street. From the time his wife fell ill, the first floor served as a home hospital. There was already no hope then that her life could be saved, although everything possible was being done for that purpose. While his wife was dying, Einstein was calm and worked tirelessly. Soon after his wife’s death he came again to Fine Hall. I visited him in his room. He looked tired; his face had grown more yellow than usual. I shook his hand, but could not utter the banal words of condolence. As though nothing had happened, we began to discuss the serious difficulties that had arisen in our work. Einstein worked with equal intensity both during his wife’s illness and afterward, when she had died. There was no force that could tear him away from work, so long as even a spark of life still glimmered in him.

Although he was extraordinarily attentive, patient, and kind, collaboration with him proved to be no easy matter. The reason lay in the richness of his ideas, in the fact that he always moved forward, compelling me to the maximum activity, and therefore I found myself in a state of continuous excitement.

Often, after returning home, I would spend almost the entire night pondering the content of our conversation. Sometimes an idea would come into my head which seemed to cast new light on the problem. The next day I would hurry to Einstein to tell him about it;

almost always turned out that Einstein had already had this idea and, moreover, one or two other, more successful ones. During our work on the general part of the question, which proved difficult and required a number of new ideas, my original contribution concerned only one essential aspect. I proved that the problem of motion would yield nothing in questions of quantum mechanics. Here my skepticism prevailed. It led me to a proof distinguished by extraordinary simplicity. It is interesting that Einstein objected to this proof, trying to find an error in the course of my reasoning. After careful checking he admitted that the proof was correct, but the next day his suspicions revived. He analyzed every step with unusual scrupulousness. The proof withstood this analysis. Finally he admitted:

— Now I am already convinced that we cannot obtain quantum conditions from the gravitational equations.

I joked:

— And tomorrow you will not change your mind, Professor?

Holding out his hand to me, he said with exaggerated seriousness:

— No. Never. Here is my hand.

And he laughed loudly.

7.

In addition to the difficult problem of formulating the general theory, which was almost entirely the result of Einstein’s ideas, there remained the question of particular calculations. They required a complicated technique, specially developed for this purpose. Here Einstein had complete confidence in me. He never checked my calculations, but always willingly discussed the difficulties that arose in them. In the end, we succeeded in obtaining the equations of motion for double stars.

It follows from Newton’s theory that the Earth, or any other planet, moves along an ellipse, with the Sun at one focus. Only slightly (in Newtonian theory—more) is the derivation concerning double stars complicated, where we cannot assume (as in the case Sun—planet) that the mass of one of them is much greater than that of the other. According to Newtonian mechanics, each of the two stars moves along an ellipse, and the common focus of these ellipses is located at the so-called center of gravity of these two stars. This conclusion, regarded in Newtonian theory as exact, is, from the standpoint of the general theory of relativity, only approximate. There is always some share of truth in the old theory, and the limits of its correctness are visible from the heights of the new theory. A new theory replaces an old one either because it encompasses a broader range of facts, or because it is logically simpler, or for both these reasons at once. It remains dominant in physics until the need again arises to broaden our field of vi—

...by means of the newest theory, which describes our material reality better and more simply from a logical standpoint.

The connection between the old and the new theories is clearly visible in our example of motion. Roughly speaking, our result was the same as in Newtonian mechanics. By another, roundabout route we obtained the same picture: the motion of double stars along ellipses. It was considerably more difficult for us to arrive at this result, because the initial assumptions were simpler. But, in addition, there was yet another difference between the new and the old equations of motion, characteristic of the transition from the old theory to the new. We obtained the Newtonian equations of motion from the new theory only as a first approximation. We asked ourselves: what equations, different from Newtonian ones, will we obtain if we carry our approximation one step further? The calculations went on for months, and we found new equations of motion, following from the general theory of relativity, more exact than the Newtonian equations. The only difference between the conclusions from these new equations and the conclusions drawn from the old ones consisted in the so-called perihelion motion: not only does each of the stars move along an ellipse—each of these ellipses rotates very slowly, making one revolution for millions of revolutions of the star along the ellipse.

8.

Our joint work brought us closer together. We spoke more and more often about social problems, about politics, about relations among people, about science and philosophy, about life, death, and happiness, and most of all about the future of science and its ultimate aims. I came to know Einstein better and better. Often I managed to foresee his reaction. I understood that his position on various questions, although it might seem strange and unusual, always flowed from the peculiarities of his personality.

Few people knew as many people as Einstein did. Everyone longed to make his acquaintance and to win his friendship. It was relatively easy to meet Einstein, but difficult truly to get to know him. Mail brought him letters from all over the world. Einstein tried to answer every letter in which he found some meaning. Despite the turbulent course of events that intruded into his life, despite his association with many people, he remained solitary; he loved that solitude and isolation, which gave him the opportunity to work calmly.

Several years before our meeting, Einstein spoke in London, at Albert Hall, on the question of scholars—exiles from Hitler’s Germany. He said then that there are many occupations, apart from the university, that would suit these scholars. As an example he cited the work of a lighthouse keeper, which, in his opinion, leaves much time for contemplation and scientific research. This remark seemed funny to those present. However

...it is entirely understandable if one adopts Einstein’s point of view. Judging everything from one’s own point of view, the inability to change one’s “coordinate system” by adopting the point of view of one’s neighbor—this is one of the consequences of solitude. I noticed this trait in Einstein quite early. For him a secluded way of life was what he dreamed of—liberation from many unbearable, troublesome obligations. But, as a rule, scientists dream of something else. If I may cite myself as an example, I must say that solitude in scientific work was for eight years the curse of my life. It is generally known that a strong scientific milieu stimulates creative work, whereas solitude destroys the desire to work. Genius is the exception. Einstein could work anywhere. His best works were born in the seclusion of the patent office. It would have been difficult, however, to convince Einstein that in this respect he was an exception.

He considered himself a very happy man because he had never had to struggle for his daily bread. He recalled with special pleasure the time he had spent in Switzerland. There the atmosphere was more humane, more friendly, less saturated with intrigues than at the university; he had more time left for scientific work.

He told me many times that he would gladly have worked physically, engaging in some useful craft, for example shoemaking, but that he would not have wanted to earn his living by teaching physics at a university. These words conceal a deep meaning. They express a kind of “religious feeling” with which he approached scientific work. Physics is so great and important a matter that one must not barter it for money. It is better to earn one’s living by the labor, for example, of a lighthouse keeper or a shoemaker, and to keep physics at a distance from questions of daily bread. Although such a position may seem naive, it is nevertheless characteristic of Einstein.

9.

I learned a great deal from Einstein in the field of physics. But most of all I value what I learned from him outside physics. Einstein was—I know how banal this sounds—the best person in the world. However, even this definition is not as simple as it seems, and requires some explanation.

Compassion is, in general, the source of human kindness. Compassion for others, sympathy for need, for human misfortune—these are the sources of kindness that operate through the resonance of sympathy. Attachment to life and to people through our ties with the external world awakens an echo in our feelings when we look upon the struggle and suffering of others.

But there is also an entirely different source of kindness. It consists in a sense of duty resting upon solitary, clear thought.

MY MEMORIES OF EINSTEIN

Good, clear thought leads a person to kindness, to loyalty, because these qualities make life simpler, fuller, richer, because in this way we reduce the number of calamities in our surroundings, lessen friction with the environment in which we live, and, by increasing the sum of human happiness, strengthen our own inner peace. A proper position in public affairs, help, friendship, kindness can flow from both of the named sources, if we express ourselves anatomically—from the heart or from the head. With the years I learned to value ever more highly the second kind of kindness—the one that flows from clear thinking. Many times I have had occasion to see how destructive feelings are when they are not supported by clear reason.

And here again Einstein presents an extreme example. Never in my life did I have occasion to observe so much kindness, completely detached from any feelings. Although only physics and the laws of nature evoked genuine emotions in Einstein, he never refused help if he found that help was needed and believed that this help could be effective. He wrote thousands of letters of recommendation, gave advice to hundreds of people, spent hours talking with a madman whose family had written to Einstein that he alone could help the sick man. He was kind, pleasant, talkative, smiled, but with an unusual, though secret, impatience awaited the minute when at last he would be left alone and could return to his work.

He wrote about himself:

“My passionate interest in social justice and my feeling of responsibility toward society have always strangely contradicted the obvious prejudice that I felt toward direct association with people. I am like a horse in a one-horse team, unfit to work with others. I have never given myself with my whole heart to a country, to a state, to a circle of my friends, or even to my own family. These ties have always been accompanied by a feeling of loneliness, and the desire to withdraw and shut myself up within myself increases as I grow older.

Such isolation is at times bitter, but I do not regret being cut off from the possibility of understanding and sympathy on the part of other people. Of course, because of this I lose something, but in return I gain independence from the customs, opinions, and prejudices of others and avoid the temptation to build my inner peace on such fragile foundations.”

Few people could be found for whom fame would have less meaning and would be less desirable than it was for Einstein. And yet Einstein came to know the bitter taste of fame, as often happens with people who do not seek it. He told me that from his youth he had always tried to fence himself off from life’s struggle. Fame came to him of itself—and, moreover, the greatest that had ever fallen to the lot of a scholar. I often reflected on this. At that time (in 1937) his ideas had no noticeable practical significance. Neither electri-

...electric light, neither radio nor the telephone were associated with his name. Probably the only important technical discovery at that time connected with Einstein’s name was the discovery of the photoelectric cell. But the source of Einstein’s fame is, of course, not this invention. He owes the brilliance of his fame to his work on the theory of relativity.

Was this caused by the influence of Einstein’s theory on philosophy? Apparently not. Discoveries in the field of quantum mechanics have just as much, and perhaps even greater, significance for philosophy; however, their creators are far less well known than Einstein. It seems to me that the reasons for the enormous renown he enjoys among ordinary people throughout the world—people who do not know and do not understand the theory of relativity—are most likely social in character. Einstein’s fame probably does not depend on the fact that his name is associated with the problem of atomic energy; after all, this fame arose in 1919, and since that time it has been flaring ever brighter.

Indeed, 1919 marked the beginning of Einstein’s celebrity. His great creation, namely the special and general theories of relativity, had been completed four years earlier. One of the conclusions of the general theory of relativity may be stated as follows. If during a solar eclipse we photograph a portion of the sky near the sun, and then photograph the same portion of the sky, i.e. the same positions of the stars, under normal conditions, we shall obtain two photographs somewhat different from one another. It follows from the theory of relativity that the gravitational field of the sun slightly deforms the path of the light emitted by the stars; therefore a photograph of this part of the sky taken during an eclipse will look different from a photograph taken under ordinary circumstances. The general theory of relativity not only predicts the qualitative effect, but also determines quantitatively the degree of difference between these two photographs. English scientific expeditions sent out in 1919—one to South America and the other to Africa—confirmed Einstein’s prediction both quantitatively and qualitatively.

Thus began Einstein’s great fame. It continued throughout his life and will probably only increase after his death. However, the fact that the theory of relativity predicted a phenomenon as remote from our everyday life as these stars, and that it predicted it on the basis of a long chain of abstract arguments—all this, perhaps, cannot serve as sufficient cause for mass enthusiasm. Nevertheless, that is precisely how matters stood. And it seems to me that the reasons here should be sought in postwar psychology.

This happened after the end of the First World War. People were sick of hatred, murder, and international intrigues. Trenches, bombs, and killings had left a bitter aftertaste. Books about the war were not bought and not read. Everyone was waiting for an era of peace and wanted to forget about the war.

My Recollections of Einstein

And this phenomenon was capable of seizing the human imagination. From the earth, covered with graves, gazes were directed toward the sky strewn with stars. Abstract thought carried man away from the sorrows of everyday life. The mystery of the eclipse of the sun and the power of the human mind, the romantic setting, several minutes of darkness, and then the picture of curving rays—all this was so different from the oppressive reality. There was also another reason, apparently the most important one: the new phenomenon had been predicted by a German scholar, and it was verified by English scholars. Physicists and astronomers who had recently belonged to two hostile camps were again working together. Perhaps this was the beginning of a new era, an era of peace? The human yearning for peace was, it seems to me, the chief reason for Einstein’s growing fame.

It is hard to withstand fame, hard to resist its influence. Yet fame did not change Einstein at all. This was a consequence of his isolation and solitude. Fame hindered him when it came into conflict with his way of life; he forgot about it when external circumstances allowed.

Even in Princeton, a small university town, everyone looked at Einstein with greedy, astonished eyes. During our walks we avoided several of the livelier streets and chose fields and deserted lanes. Once, for example, from some automobile we were asked to stop. A woman, no longer young, got out of the car with a camera and, blushing from agitation, asked:

— Professor, allow me to photograph you.

— Please.

He stood quietly for several seconds, and then continued his reflections.

I am certain that after a few minutes he had forgotten about this incident.

Once in Princeton we went to the cinema to see the picture The Life of Émile Zola. Having bought tickets, we entered the crowded foyer, where we learned that we would have to wait another 15 minutes. Einstein suggested going for a stroll. On leaving, I said to the usher:

— We shall return in a few minutes.

Einstein, however, became worried.

— We no longer have any tickets; will you recognize us?

The usher, thinking this a successful joke, replied:

— Yes, Professor, I shall probably recognize you. When I saw the picture, I thought that if not I myself, then my children would probably someday see a film The Life of Albert Einstein, and it would be just as historically truthful as this one.

If circumstances permitted, Einstein was completely unaware of his fame; he is perhaps the only example of a man upon whom the greatest fame had no effect whatever.

...impact. There were, however, moments when the aggressiveness of the outside world disturbed his peace. Once he said to me:

— I envy a simple worker. He has his own private life.

And another time:

— I feel like an impostor because of all this publicity surrounding my person. And there is no reason at all for the publicity.

Einstein understood everyone perfectly well, so long as understanding required logic and reason. Matters were worse when emotions came into play. He had great difficulty grasping motives and feelings different from his own. Once he said to me:

— I address everyone in the same way—the garbage collector and the university rector.

I replied that this was difficult for other people, that when they met him they became shy and embarrassed, that some time had to pass before they felt at ease, that this had been so with me too. Einstein said:

— I do not understand that. Why should anyone be shy in my presence?

10.

Even if my explanation of how Einstein’s fame began is correct, there still remains one question that must be answered. How did this fame last so long in a world that, almost every day, casts down its former idols? It seems to me that this question is not hard to answer.

Everything Einstein did, everything he defended, all his statements corresponded to the conception of him that had taken shape among ordinary people. His voice always defended the oppressed; his signature always served the cause of progress. He was like a saint with two halos. One halo represented the ideas of justice and progress; the other, abstract physical ideas. The less comprehensible the latter were, the more brightly the halo seemed to shine. His name became a symbol of humanity’s progress and of creative thought; he was hated and reviled by those who sowed hatred and attacked the ideas he defended.

During the period of our collaboration, the civil war in Spain was under way. Einstein was fully aware that on the outcome of this war depended not only the fate of Spain, but also the future of the whole world. I remember the sparkle in his eyes when I told him that the daily newspapers had reported a great victory for the Republicans.

— It sounds like the song of angels, — he said with an enthusiasm that I rarely had occasion to observe in him. But two minutes later we were already discussing formulas, and the outside world ceased to exist for us.

MY RECOLLECTIONS OF EINSTEIN

Many months passed before I understood that his solitude and isolation were the key to comprehending his character. And I am sure, for example, that on the day when Einstein received the Nobel Prize he felt no special elation on that account; and if he slept badly that night, the reason was not the high award, but a scientific problem that gave him no peace. The Nobel Prize medal, together with many others and dozens of honorary diplomas, lay in a drawer in the room where the secretary kept them, and I am sure that Einstein did not even have any idea what that medal looked like.

Einstein consciously maintained his solitude and isolation by means of small eccentricities which might have seemed strange, but which left him great freedom and weakened his ties with the outside world. He never read articles about himself, asserting that in this way he felt freer. Once I tried to break this habit of his. An article appeared in a French newspaper and was reprinted in many European countries, even in prewar Poland and in Lithuania. I have never read an article that was farther from the truth than this one. Thus, for example, the author wrote that Einstein wears glasses (never), that he lives in Princeton in one room on the sixth floor (in all of Princeton at that time there was no six-story building), that he comes to the Institute at 7 o’clock in the morning (in reality he never appeared there before ten), wears a black suit (never), keeps his technical inventions secret, and many more such absurdities. The article could have been called the utmost limit of stupidity, if stupidity had a limit. In Fuld Hall everyone was rolling with laughter as they read this article, which someone had posted on the board by the entrance. In my opinion, the article was so funny that it was worth reading aloud to Einstein. At my request he listened, even attentively, but showed no particular interest and found nothing strange in all of it. From the expression on his face I noticed that he did not understand why the article seemed funny to me.

One of my comrades asked me:

“Since Einstein cannot stand fame, why does he do everything ordinary people do not do? Why does he have long hair, a funny jacket, why does he wear neither socks, nor suspenders, nor a belt, nor a collar, nor a tie?”

The answer is simple, and it can easily be derived from Einstein’s solitude, from his inherent striving to weaken his ties with the outside world. By limiting his needs to a minimum, he strove to expand his independence, his freedom. After all, we are slaves to a million things, and our slavish dependence is constantly increasing. We are slaves to bathrooms, fountain pens, automatic lighters, telephones, radios, and so on. Einstein tried to reduce this dependence to the strictest minimum. Long hair spares one from

necessity of going to the barber often. One can do without socks. A single leather jacket makes it possible to settle the question of a jacket for many years. One can do without suspenders, just as without countless shirts or pajamas. Einstein carried out a minimum program—shoes, trousers, a shirt, and a jacket were indispensable. Further reduction would have been difficult.

At times I was amused by the thought of how Einstein would behave in exceptional circumstances. For example: Princeton is subjected to an air raid, people hide in shelters, panic seizes the city, everyone loses his head and by his behavior further increases the general horror and chaos. If, under such circumstances, Einstein found himself in the street, he would surely have been the only person to keep calm. He would think about what to do in such a situation, would do it without quickening his pace, and at the same time would continue to reflect on the problems that interested him. He was not afraid of death. Once he said to me:

“Life is an exciting and magnificent spectacle. I like it. But if I learned that I had to die in three hours, it would not make a great impression on me. I would think about how best to use the remaining three hours. Then I would put my papers in order and lie down calmly to die.”

11.

I arrived in Princeton in September 1936. Five months later our collaboration with Einstein had become well established; we understood each other perfectly and had even achieved partial success, although the problem of formulating the equations of motion was far from a complete solution. It was time to think about what would happen in the coming 1937/38 academic year.

Clouds were gathering over Poland. The Association of Assistants of Jan Kazimierz University in Lwów took the trouble to send me a registered letter informing me that I had been excluded from their honorable circle. My chances of obtaining work in my native country were equal to zero.

I decided to speak with Einstein about my financial situation. It was not easy to make such a decision. I knew that Einstein would want to help me. But I also knew that his means were rather limited. This may seem strange; however, it was known that his letters of recommendation meant far less than the recommendations of certain other professors, much less well known.

Einstein said to me several times:

“My fame begins beyond the borders of Princeton. In Fine Hall my words mean very little.”

But even beyond the borders of Princeton, Einstein’s recommendations had relatively little weight. This was due to his great kindness. In his life he signed so many letters of recommendation that they were regarded rather as valuable autographs. To me,

MY RECOLLECTIONS OF EINSTEIN

For example, they told the story of a vacancy at a hospital, where they were looking for a roentgenologist-physicist. Four physicists who had fled the Hitler regime applied; each applicant had a letter of recommendation from Einstein. I asked him whether this was true, and argued to him that excessive kindness was more harmful than helpful. Einstein, however, did not agree with me. He said:

“Indeed, I recommended four physicists, but all for different reasons; I gave the reasons for which I recommend each of them. They could choose one of the four candidates. That is what they did.”

In any case, it seemed natural to me to turn to Einstein for advice on what should be done in order to spend one more academic year in Princeton. I did this one day after lunch, when we were working in his room. This was during a period when we had run into great difficulties and, in connection with this, were engaged in an almost continuous discussion. But as soon as I told Einstein that I intended to talk about my personal affairs, he put aside the sheet of paper covered with formulas and tried to understand what I wanted. He asked me a number of questions and, it seemed, showed great interest in my words.

“Under the present circumstances you must not return to Poland. We work well together; we have already achieved serious results. I would like you to remain here for another year. I think that obtaining a fellowship for next year as well will present no difficulty.”

They nevertheless refused to extend the fellowship; Einstein immediately telephoned me:

“I do not want you to lose heart, although I must tell you unpleasant news. You have not been given a fellowship. Do not be upset—we shall somehow arrange matters. We shall talk about this after lunch. But I would like you not to lose confidence—a way out will be found.”

I do not know why I did not receive the fellowship. When I saw Einstein, he said:

“I did everything I could. I told them how highly I value you, said that we are working together on a common problem. But they argued that there was not enough money, and that they already had other obligations. They have nothing against you personally. Everyone praised you. I do not know how truthful their arguments are. I used strong expressions such as I had never resorted to before. I told them that, in my opinion, they were committing an injustice.”

Then he again emphasized that he intended to help me.

“I know that outside Princeton I enjoy some renown, and it will not be difficult for me to obtain a fellowship from some organization. Several years ago I gave a violin concert in aid of refugees from Germany, which brought in 6,000 dollars. As you see, I can do something. I want you not to be upset. If”

even if nothing comes of it, you can become my private assistant. I earn more money than I need, and can easily offer you a sum equal to the stipend.

This proposal aroused in me a mixed feeling of being moved, embarrassment, and anger.

I replied:

— I am very touched. But you must understand, Professor, that I cannot accept your proposal. I certainly know that it would be wrong if I accepted it. Since the Institute has refused me a stipend, I want to earn my living by my own labor.

I left Einstein encouraged. That same evening he telephoned again:

— I would like you to know that I have written a very energetic letter concerning your case. In case this does not help, I have another plan. Do not worry—we shall find a way out of the situation.

Over the next several days these worries had an adverse effect on my work. When I justified myself to Einstein, he said:

— Do not take either your worries or the fact that you are not working now too much to heart. The world waited patiently for centuries for the solution of the problem of motion—it can wait another two weeks.

When I was considering my situation, the thought suddenly occurred to me of writing a book together with Einstein. As soon as this idea was born in me, I realized that it would remove my financial difficulties. I knew that even if the book did not have great success, still, written together with Einstein, it could not fail to justify my hopes. In any case, half of the advance that the publisher would give us would be enough for me to live on for a year.

I thought this question over from every side before approaching Einstein with it. I knew him well enough and understood that he would never lend his name to the book unless he were truly a coauthor. A book bearing Einstein’s name is a book actually written together with him. But work on a book requires time. Did I have the right to take time away from Einstein, when the only thing that interested him was science?

I also realized that, if the book was to have historical value, I ought to step into the background and give Einstein the opportunity to express his own thoughts. It seemed to me that this book should contain Einstein’s views on the development of science. His views were known to me, and I was under their strong influence.

Then it remained to think about the actual writing of the book, about making it popular; this too, I thought, would take much time. I could do this work myself and save Einstein’s time.

MY RECOLLECTIONS OF EINSTEIN

Around 1916 Einstein wrote a book on the theory of relativity which, by design, was supposed to be popular, but did not become so. On the cover there appeared the inscription: Gemeinverständlich). Einstein, laughing, told me in his loud voice that the inscription should have been: Gemeinunverständlich*). Einstein wrote beautifully, concisely; in his style one senses the breath of poetry, but at the same time, because of his solitude, this style is inaccessible. It was not easy for Einstein to step beyond the bounds of his isolation and reason as an ordinary person reasons. I was certain that in precisely this respect I could help a great deal. I convinced myself, by arguments of my own, that the book would not take much of Einstein’s time and would not greatly interfere with his scientific work.

There was still another doubt. It was possible that Einstein would reject this idea of popularization, regarding it, as many scientists do, as a profanation that lowers the high level of science. Knowing that this could not be so, I nevertheless feared that Einstein might feel an aversion to presenting the subject outside the exact language of mathematics, without proofs, giving only conclusions, with a simplified description of the problems themselves and their solutions.

But even if that were so, I considered it necessary to persuade Einstein otherwise. I would act in accordance with my conviction that popularization is a matter of social importance, because it creates a bridge between science and society, diminishes the scientist’s isolation, raises the level of thinking by developing intelligent skepticism, combats superstition and dogma, and evokes enthusiasm and admiration for the achievements of the human mind.

Before going to Einstein, I once again mentally reviewed all my arguments, convinced that I was going to him with the right proposal, of which I had nothing to be ashamed.

When I began my well-prepared speech, Einstein, looking at my tense face, listened with Olympian calm.

“Professor, I should like to talk with you again about my personal affairs. I have been thinking about this in recent days. I am afraid it will be difficult for you to obtain a stipend for me, and under no circumstances can I accept money from you. I should like to earn money as conscientiously as possible.”

Einstein interrupted me:

“What are you talking about? It is not so simple. All the positions are occupied. To find work requires, at best, time, while your matter demands an immediate solution.”

“It seems to me,” I replied, “that I have found a way out; I have a plan. Its fulfillment depends on you, Professor; your help is required, but I hope I shall not abuse it.”

*) Generally intelligible.
**) Generally unintelligible.

11 UFN, Vol. LIX, No. 1

—What do you mean?

I tried to set out my plan clearly and logically. We had always discussed everything freely. Here, however, for no apparent reason, I faltered and could not speak. Instead of the carefully prepared speech, I stammered out meaningless phrases.

—It is hard to explain. I hope you will understand me, Professor.

Einstein looked at me in astonishment. Never before had he heard me stammer, unable to express my thoughts. When I stopped, unable to go on, Einstein waited calmly for a minute and at last broke the prolonged silence:

—For God’s sake! Yes, go on! You really have interested me.

I gathered my courage and, haltingly, repeating myself all the while, finally explained what it was about. I concluded my little speech as follows:

—The greatest scientists in the world have written popular books which are still considered classics. Faraday’s popular lectures, Maxwell’s popular book Matter and Motion, and the lectures of Helmholtz and Boltzmann are read and understood even today.

Einstein calmly looked at me, stroking his moustache, and at last said quietly:

—That is not a bad idea. Not bad at all!

Then he rose from his chair, held out his hand to me, and said:

—We shall do it.

Thus our book was born.

We decided to write a book, but we had no idea what exactly we would write about. I suggested making the theory of relativity the subject of the book—to give such an explanation of its basic ideas that any intelligent person could understand them. Einstein showed no particular enthusiasm; he said that too many books about this theory had already appeared on the book market.

The fact that Einstein had accepted the proposal regarding the book removed, for the time being, all my financial difficulties, since publishers were prepared to give a comparatively large advance merely for the promise to write a book together with Einstein.

The idea of the book seized Einstein; he simply caught fire. He approached the work on the book very seriously; with each day the work seemed to him more and more absorbing. He often repeated:

—It was an excellent idea!

We discussed, changed, and revised our book until it was finally completed. Suddenly Einstein lost all interest in it. The book took up exactly as much of his time as our work on it continued. At the very moment when the work was finished, Einstein’s interest faded.

12.

The idea of what to devote the book to was born in Einstein’s mind. He intended to write a popular book containing the basic ideas of physics in their logical development. According to Einstein, in physics there are only a few fundamental ideas, and they can be expressed in words.

“No scientist thinks in formulas,” he often said. In fact, before a physicist begins to calculate, he must have before him some picture or some idea, which can usually be formulated simply. Calculations and formulas are the next step. Thus, our aim was to present the most fundamental ideas in their proper perspective. Einstein believed that this plan could be carried out within the limits of a single volume that would touch upon all branches of physics.

When we discussed the plan for the first time, Einstein was ill. He was lying in bed, as always without a shirt and without pajamas, and a copy of Don Quixote rested beside him on the nightstand. He loved this book more than any other and reread it many times when he wanted to rest. I sat on a chair beside the bed. Einstein was excited by the thought of our book.

“This is drama, the drama of ideas,” he said. “Our book must be interesting, captivating for everyone who loves science.”

I understood his plan perfectly, and after this brief conversation a clear picture of the book formed in my mind, a picture that I tried to develop in detail. The months of collaboration brought remarkable mutual understanding, when a few words replaced an entire discussion. We understood each other from half a word and conversed almost as if stenographically.

I liked Einstein’s plan. It was a difficult subject; the choice of ideas, the selection of those that should be emphasized, the establishment of the connecting links between them—all this depends on the physicist’s personal taste. It was therefore important that Einstein’s views on these questions should become known. No one thought so deeply about the problems of physics as Einstein did. None of the physicists now living (so I thought then) possessed qualifications equal to Einstein’s for coping with this difficult subject. I was no longer much interested in the financial success of the book. The very fact that such a book would appear thanks to my coming to Princeton was remarkable. I felt happy when I thought about it.

The original conception underwent a change. At first we had thought of writing simply a popular book. But now we believed that it should represent something more! It was to be a book from which I and other physicists could draw something—not concrete facts, but a new point of view, ideas arranged in the proper perspective; it was to be a scientific book, but at the

...at the same time written as simply as possible. One should proceed not from the assumption that the reader possesses some knowledge, but rather be guided by his high intellectual development.

When next we spoke on this subject, we both agreed that the style of the book had to be simple. We had identical views on the tasks of popularization; we hated popularization that speculated on the reader’s emotions. In order to keep the unfortunate reader’s attention tense, some writers juggle with witticisms having nothing in common with the subject; as a result, the reader remembers the jokes, but forgets the aim for which the author offered them. Such writers suddenly leap from physics to metaphysics, producing in the reader a metaphysical shudder that prompts him to turn the pages, though he understands exactly nothing. In such books the universe is presented as a collection of enormous nebulae separated from one another by millions of light-years, while man—like a solitary being—gazes in terror at the desolate and savage cosmos. The atom, if compared with the distances between the nebulae, is fantastically small. And religion stands above all! God is the great mathematician; the greatness of science is only a reflection of divine glory. In such books those results are emphasized that contradict the common sense of the ordinary person, in order to show how wise and enlightened the scientists are.

But beauty can be found everywhere! Both in the laws of motion of nebulae and in works on the falling stone. Good popularization can and should arouse feelings not by excursions into the realm of metaphysics, but by the effort of comprehension it evokes—an arduous and at the same time joyful effort toward ever fuller and deeper understanding.

However, in order to venture upon this kind of popularization, one must renounce external effects. This means that one must write clearly and simply, convincing the reader that science rests on mature and developed common sense, and that its aim is to reconstruct the picture of the reality surrounding us.

The problem of language also presented a difficulty. Until then I had not yet written anything in English. But I had friends at Princeton who zealously helped me in this respect. Toward the end of the work on the book I almost forgot that I was writing in a language not my own.

Together with Einstein we planned our work so that these two tasks—the solution of the problem of motion and the creation of a popular book—would not interfere with one another. We discussed what had been written once a week, and sometimes even once every two weeks. At the same time, we worked on the question of motion considerably more often. I remember how I read part of our book aloud to Einstein, who in such cases always said:

— Read slowly, so that I can understand every word.

He did in fact listen very attentively. He would usually suggest minor changes. We discussed them in detail, and our collaboration proceeded remarkably smoothly. Einstein adhered to the principle that the form was my affair. He often said:

— I do not care how you write it. You know best. But this idea absolutely must be in the book.

If I ever had any objections to including some idea or other in the book, this was usually because it seemed to me too complicated; I thought it better not to touch upon it, so as not to frighten off the reader. We always reached a compromise and invariably took into account the level of development of our imagined reader.

After discussing some part that I had drafted, we would go for a walk and discuss the next passage, always trying to come to agreement. Einstein was never authoritarian. Mutual understanding grew stronger as the work progressed. The meetings devoted to the book became ever shorter, and differences of opinion were smoothed out ever more quickly. Each day I wrote about a thousand words. Step by step the book took on real shape.

13.

I have spoken about our book on the basis of my notes from that time. What do I think of it now, when I am again in my homeland? What I think of first of all is the reproach that this book is idealistic. This reproach seems to me justified only to a very insignificant degree. More than 99 percent of the book deals with physics. Both Einstein and I considered ourselves materialists, although neither of us at that time had studied the theoreticians of dialectical materialism. From today’s point of view I would say that in that one percent touching on philosophical questions there are certain formulations that could be interpreted idealistically. But this “idealism” of Einstein’s is considerably more interesting than the dialectical materialism of certain sectarians who attacked the book. I was told, for example, that X. said at a public lecture: “Einstein is an idealist, and Infeld is carrying on his work in Poland.” When I learned of this, I objected: “I prefer to be abused in company with Einstein than praised in company with Mr. X.”

Some reproaches came from philosophers who had no understanding of physics and spoke against the theory of relativity as idealistic. One of the accusations, so unintelligent that it is even difficult to answer, was that we were opposing Copernicus’ theory, writing that the theories of Copernicus and Ptolemy are one and the same, since everything here depends on the frame of reference,

and the frame of reference in the theory of relativity is arbitrary. Therefore we, as some reviewers, obscurantists (“popovshchina”) and, apparently, also (I add this on my own behalf) supporters of the Inquisition maintained, were accused of being insufficiently clear in our formulation of the aforementioned point; but to infer from this that the theory of relativity in some measure underestimates Copernicus’ achievement is to advance an accusation that is not even worth refuting. I discussed this question in greater detail in the article “From Copernicus to Einstein” (Kosmos, 1955).

I quote that article:

“I want to remove at least one of the many misunderstandings in the interpretation of the theory of relativity. It is sometimes said that the theory of relativity denies the distinction between the theory of Copernicus and the theory of Ptolemy, as though from its point of view they were one and the same. Remarks of this kind are caused either by a misunderstanding or by incomprehension. Popularizers, who express themselves insufficiently precisely, are sometimes to blame for this; but a person who has studied the theory of relativity cannot and should not in any case arrive at such a conclusion. If we are speaking of the mathematical structure of the theory of relativity, then there invariance really does mean that the concept of a system is unnecessary and that there is no difference (I repeat, from the point of view of the mathematical treatment) between the systems of Ptolemy and Copernicus. But the matter appears quite different if we are speaking of the physical content.

The mathematical description of a concrete fragment of reality, such as the motion of the planets, the motion of two bodies, the bending of light rays, is entirely objective and is referred either to a system connected with the sun, or to a system connected with the center of mass, i.e. to Copernican systems. The theory of relativity, as an instrument for the cognition of nature, uses the Copernican system to exactly the same extent as does Newton’s theory. It has the advantage over Newton’s theory that it does not need the concept of an inertial system. It has the advantage over Newtonian mechanics that its conclusions correspond more closely to observation than do the conclusions from Newton’s theory. In the theory of measurements, which we must add to every theory, we proceed from the fact that measurements are made by an observer far from the sun and that for him the gravitational field is extremely weak. The earth and the observer intervene only through the application of the theory of measurements; we always need it in order, from the results of measurement, to draw a conclusion about the properties and laws of the objective world existing outside our consciousness. It seems to me entirely beyond dispute that the theory of relativity represents an enormous advance in the domain of our knowledge, that its physical content, agreeing with experience, must be in full accord with the propositions of dialectical materialism. The fact that some formulations of this theory bear

idealistic character, is explained by the fact that this theory is extremely difficult, requires many years of reflection and familiarity with mathematical tools, and that it was formulated in the West, which is inclined toward idealistic interpretations. Often philosophers, even those proceeding from the very best motives, do not understand the theory of relativity. Sometimes there appears a desire to condemn things one does not understand; it is precisely here that the origins lie of attacks on the theory of relativity, which is one of the greatest achievements of the human mind.”

This is my point of view. I do not agree with Professor Fock that certain conditions should be added to the theory of relativity—conditions that single out a harmonic system. During my stay in the Soviet Union (1955), I became convinced, to my great surprise, that Prof. Fock stands apart on this question, and that physicists of such stature as Landau, Tamm, and Ginzburg take a negative view of his position.

In polemicizing with philosophers who are opponents of the theory of relativity, I am, in all probability, breaking through an open door, for much has changed recently in this field, both in the Soviet Union and among us in Poland. Today an especially sharp struggle is being waged against sectarianism, and it is becoming ever more obvious that dogmatism is the enemy of science.

The object of the most embittered attacks became the last three pages of our book. In the final chapter, “Physics and Reality” (“Physics and Reality”), we write that science consists of innovative ideas and concepts that are free creations of the human mind.

To some critics this judgment appeared to be pure Berkeleyanism. But what we meant by this judgment is explained earlier in our book, in the chapter “The Riddle of Motion” (“The Riddle of Motion”), where we write:

“Physical concepts are free creations of the human mind and are not uniquely determined by the external world, as it may sometimes seem. In our striving to understand reality we are like a person who wants to understand the mechanism of a closed watch. He sees the dial and the moving hands, even hears the ticking, but he has no means of opening it. If he is clever, he may form for himself a picture of the mechanism that would account for everything he observes, but he can never be quite sure that his picture is the only one that could explain his observations. He will never be able to compare his picture with the real mechanism, and he cannot even imagine the possibility or the meaning of such a comparison. But he is, of course, convinced that as his knowledge increases, his picture of reality will become simpler and simpler, and will explain an ever wider range of his sensory perceptions.”

He may also believe in the existence of an ideal limit of knowledge and in the fact that the human mind approaches this limit; he may call this ideal limit “objective truth.”

It is apparently clear that there is no one-to-one correspondence between the fragments of reality that we describe and the concepts with whose help we describe them. This becomes immediately evident if we think of the difference between everyday and scientific language. For example, of how a stone will be described by an ordinary person, a mineralogist, a chemist, a physicist, an atomic scientist, a nuclear scientist. But besides this difference (between everyday and scientific languages), as science advances, differences arise within scientific language itself. The concepts we use to describe our real world undergo changes. Think, for example, of the theories of light of Huygens and Newton and of Einstein’s photons. Yet, as we come to know reality better and better, we draw ever closer (I believe this) to an unambiguous description of the material world—that is, we come ever closer to objective truth. Beings living on Mars would have—in the limit—the very same physics that we do.

Probably what I have written here, and what we wrote in the book, is not expressed in the terminology of dialectical materialism; but to accuse the authors of pure idealism is simply either stupidity, or malice, or a mixture of both these human traits, which so often go hand in hand.

14.

The first year of my stay in Princeton was drawing to a close. In summer Princeton is perhaps the most wretched place on earth. The town seems extinct; people, like shadows, wander along the scorching pavements, repeating now and then: “The heat might still be bearable, but this humidity!” I got up at five in the morning in order to write my thousand words before the burning sun had time to turn the little town into hell. Einstein had gone to Long Island, where, as usual, he rested by taking sea excursions. Before he left Princeton, we carefully thought through two chapters. Twice I visited him on Long Island, bringing the completed material.

In September the book was finished. We had worked on it for about six months. When the last chapter had been written, I felt what an enormous responsibility was laid upon me by the fact that Einstein’s name would appear on the cover beside mine.

“I would feel considerably freer and would exercise less caution if I were the sole author,” I once said to Einstein. “Yet I cannot forget that your name will stand on this book.”

Einstein burst into his loud laughter.

— You should not be so cautious in this connection,” he replied. “There are erroneous works also under my name.”

I sent the manuscript to the publisher, and we returned to work on the problem of motion. For me the second academic year in Princeton began: 1937/38. In April 1938 there appeared both our paper on problems of motion (in Annals of Mathematics) and the book, whose title was Evolution of Physics. When the author’s copies were sent, I brought them to Einstein. He was not at all interested in the book; he did not even look at what it looked like, just as he had not looked at our paper when the proofs had been sent. He told me that when a work is finished he is no longer interested in it, does not read reviews, and reluctantly listens to what is said about it. Thus, according to him, he feels freer. I believe that he did not even know what our book looked like. Einstein attached no importance to appearance, and he did not imagine that one or another external design of a book could have any significance for the reader. The publishers held the opposite opinion. Evolution of Physics received a prize as the most beautiful book among those issued during the month. When the publishers asked whether Einstein liked the cover, the type, and the paper, I replied that he liked everything very much, not wishing to offend them by the admission that Einstein had not even opened the book.

On the day the book came out, a reporter from The New York Times, one of the most substantial American newspapers, telephoned Einstein and asked him to say a few words about the book. Einstein replied:

— What I can say about the book is in the book.

The book was vigorously advertised in America and had great success. Properly speaking, my future on the American continent was secured thanks to this book. It was translated into almost all the languages of the world.

15.

I wanted to remain at the Institute for Advanced Study for a third academic year as well. The income from the book made this possible. However, I received an invitation to work from a very serious university in Toronto, Canada. I decided to accept this offer. Einstein also advised me to accept it, although he regretted that I was leaving and that our collaboration would be interrupted.

All the same, our collaboration did not cease, although during the following twelve years, until the time of my departure from Canada, it was already far less close.

During my stay in Toronto, in the course of the first academic year (1938/39), I worked on a generalization of the equations

motion; consequently, on the same problem on which I had worked the preceding year together with Einstein. In theoretical physics, once the first breach has been made and the difficulty overcome, it often turns out that certain assumptions were unnecessary, that the mathematical structure of the theory can be formulated more precisely and more generally. I tried to eliminate the special assumption relating to the coordinate system, to find the equations of motion not, as before, in a definite coordinate system, but in a general coordinate system, which would better accord with the spirit of the general theory of relativity.

I sent Einstein the first draft of my manuscript. He liked the conception, but he made two comments that at once changed the perspective of the whole work. He observed that not only could the equations be formulated in such a general way, but that we could also outline methods for solving them, applying the same approximation procedure to which we had resorted earlier. Then he proposed simplifying the whole question, skillfully altering my argument and considering the problem from another, original point of view. I wanted to discuss all this with him in person.

In May 1939, after an interval of almost a year, I again crossed the threshold of the house on Mercer Street. Some time had to pass before I felt as free in his room as I had then, when we were working on the problem of the equations of motion or on “The Evolution of Physics.” We discussed our new results, already known to us from our exchange of letters. Einstein proposed that we publish them jointly. We decided that I would prepare the manuscript and send it to Einstein for approval. I was happy that our collaboration had overcome geographical distance. Then Einstein told me about his new attempts in constructing a unified field theory, about his disappointments and hopes. He repeated several times: “I am very sorry that you are not in Princeton. We understood each other well. It was pleasant to work together.”

After this meeting I felt depressed. First of all, I realized that the wonderful period of joint work with Einstein was drawing to a close for me. The other reason was that we spoke about social problems, and Einstein was in a more pessimistic mood than ever before. This pessimism affected me. Einstein believed that the future of Europe had been predetermined by the events in Madrid and in Munich, that “fate is approaching.” Never before had he regarded the political situation as so hopeless and chaos as so near.

I was homesick. Later, when we walked in the university garden, flooded with sunshine and full of spring flowers, everything seemed the same as before, in the days of our collaboration.

MY RECOLLECTIONS OF EINSTEIN

16.

In September of that same year the Hitlerites attacked Poland. During the war I worked in science for the sake of victory. As far as I remember, during this period Einstein and I did not see each other, but only exchanged letters from time to time. I did not know what role Einstein played in the matter of applying atomic energy. After the war we established constant contact on the most varied occasions. Some of them were of an external character, others more profound, since they were related to our scientific work. I want to mention here his activity for the cause of peace in America and my activity in Canada, directed toward the same goal. In my work I used Einstein’s statements and, above all, his wise, remarkable article “Only then shall we be free” (“Only then shall we be free”), which he sent me. Our joint work for peace, against atomic blackmail, revived our correspondence. Then my book about Galois appeared, entitled Whom the Gods Love (“Whom the gods love…”). I sent it to Einstein, although I had little hope that he would find time to read it. Not only did he find time, but he sent several splendid and very flattering phrases about this book, authorizing me to let the publisher use them at his discretion.

I was afraid that this contact might become superficial, since it was not based on joint work. As for me, I felt toward Einstein a reverence mixed with timidity. I did not want to write to him too often. From time to time I also received letters from his secretary, Miss Dukas, a very fine person. Whenever Einstein happened to mention me with a kind word, she would immediately inform me of it.

I have preserved many of Einstein’s letters from this period. I shall give the most interesting excerpts.

“23.X.1939

… I can imagine how worried you are about the fate of your sisters in Poland. I hope that women face less danger. Nothing can be done with this gang of criminals. But it seems to me that they await a well-deserved punishment.”

“6.III.1941

… Our work on the equation of motion is arousing, strangely enough, greater interest than we expected…

Our work on a satisfactory field theory has not led to any result. I am increasingly inclined to the conviction that one cannot advance further with the continuum theory, for the Riemannian metric suggests itself here …”

as the only natural concept. However, our efforts to generalize this concept have so far brought no success.”

“29.XI.1945

...First of all, accept my most heartfelt sympathy on account of the terrible reports that you too have received about the fate of your relatives. There is something horrible in this fate of the Jews, and it is clear that the influence of Hitlerite propaganda harbors a serious danger for us for a long time to come...

I hope that I have discovered how gravitation and electricity are connected with each other, although a physical justification is still far away.

“25.XII.1945

I understand your grief, all the more so because the Germans also killed many in my family.

I am shocked that in this country people do not react to these shameful deeds as strongly and spontaneously as one might have expected.

I am very interested in your work and, if you visit me, I shall gladly tell you about a new possibility of creating a unified field theory.

I have written the Polish ambassador a letter of recommendation for Mr. ... After all, I know from your book that he really deserves it.”

In these last letters we see a very significant change in Einstein’s attitude toward the problem with which he had occupied himself for 35 years and over which, probably, he labored until the last moment of his life: this was the problem of a unified field theory, a theory embracing the structure of elementary particles, a theory providing coherent solutions that could represent elementary particles. He undertook very many such attempts and published his considerations in the conviction that they contained part of the truth he had sought all his life. Then he would find a new theory imperfect and become its severest critic; at times he believed that this problem was altogether insoluble, and at times it seemed to him that he saw a new light. Whether the theory he left behind at his death will withstand the test of time’s fire, as the special and general theories of relativity have withstood it, I personally doubt. But it will be an eternal monument to the steadfastness of this mind, which over the course of 35 years was able to work persistently on a single problem, so difficult that its solution exceeded human powers. In fact, many scientists are working on the problem of elementary particles, approaching it from a completely different side. This problem looks different today than it did 35 years ago, thanks to quantum theory, which Einstein helped to create and from which in more

MY MEMORIES OF EINSTEIN

In the late period of his life he decisively turned away from it; he considered it ill-constructed, and believed that a truly beautiful theory describing our reality could not make use of statistical methods.

I quote a letter from Einstein:

“21.IV.1946

I read your article on the atomic bomb with great pleasure, but unfortunately I have not yet had an opportunity to study your latest work.

Today I am sending you a copy of the letter about our common child (i.e., about The Evolution of Physics), which will surely delight you no less than it delighted me.

Do not be offended that I write so little. The demon of problems is mercilessly squeezing me in its claws and forcing me to undertake desperate efforts to overcome mathematical difficulties. I am sending you my latest work, in which a general path to the solution of the problem is proposed, but the field equations still have to be changed. The completed work has already been in print for many months. I shall send it to you as soon as it appears. I think that at last I have grasped the edge of the truth.”

In the last years of his life—or, more precisely, from the time when he began working on questions of a unified field theory—Einstein was isolated in the scientific world. I personally do not believe in the path he chose. I remember even earlier, in 1936, when I came to Princeton, Einstein offered me a choice of two topics. The first was the problem of motion, the second a unified field theory. I then took up the first topic, on which Hoffmann also later began to work, while the young physicist Peter Bergmann chose the second topic and for some time worked together with Einstein on the unified field theory. (In 1949 it seemed to me that, after 13 years of working together with Einstein on the problem of motion, which I shall mention below, this problem had been completely solved. However, even today, after 20 years, I am still working on this question with my students.) It was very painful for me to see Einstein’s isolation and the fact that he stood, as it were, outside the current of physics. Often this greatest—probably the greatest—physicist in the world would say to me in Princeton: “Physicists consider me an old fool, but I am convinced that in the future the development of physics will proceed in a different direction than it has up to now.” Today Einstein’s objections to quantum mechanics have by no means lost their force. Today—it seems to me—he would be less alone in his views than in 1936.

At that time, however, I considered Einstein’s negative attitude toward quantum theory unfounded. (Indeed, it was scarcely reflected in The Evolution of Physics, which we, incidentally,

...did not wish to give it a polemical character.) That is why, when one of the creators of quantum theory stopped in Toronto in 1948 on his way to Princeton, I asked him to talk with Einstein about the foundations of quantum theory. In 1937 the great Bohr was in Princeton and, in a public discussion, tried to convince Einstein—incidentally, unsuccessfully—of the correctness of his position. I wrote to Einstein that Prof. X. (I would not want to mention his name here) would be in Princeton, and asked him to talk with him on this subject. I told him how much I admired Professor X.

In reply I received a letter containing, in particular, the following remarks:

“20.IX.1948

I like Mr. X. extraordinarily. His scientific imagination is worthy of the greatest admiration, and he is full of criticism toward his own ideas. However, a discussion with him is very difficult, for different arguments carry, in his eyes, quite a different weight than in mine. My firm adherence to logical simplicity and my lack of trust in the value of the criteria of theories—even those that make a great impression when fundamental questions are at issue—are incomprehensible to him. He finds such a position isolated and strange, as do all who believe that quantum theory is close to the heart of the matter. I understand this very well and have no intention of misleading anyone. If I am not compelled to do so (as by the authors in Schilpp’s volume, which will appear in the near future), I do not leave my mousehole and quietly work away at my own problems.”

A few words about Einstein’s last remark. The book by Schilpp which he mentions in the letter is a thick collection, edited by Schilpp in the “Library of Living Philosophers.” The book consisted of articles that were to be, at least in part, critical as well. It included, in particular, an article by Bohr and Pauli. It turns out that Einstein was supposed (such was, in general outline, the plan of this library) first to write about himself, about his life, about his work,* and then, at the end, to answer the reproaches of the other authors. I knew the history of this book well, since I myself was the author of one of the articles and kept in contact with the publisher. And so, at the end of the book there is a splendidly written reply by Einstein to the reproaches addressed to him, a reply which, perhaps more clearly and better than his other articles, explains Einstein’s attitude toward quantum theory.

* See the “Autobiographical Notes” by A. Einstein, printed in this issue of the journal. (Editor’s note.)

17.

In 1948 I once received from Einstein a letter concerning our work on the problem of motion. (I must remind the reader once again that during the war I was very far removed from these problems, since I was occupied with other questions connected with the war.) In this letter Einstein cites the reproach made by the mathematician Levinson regarding our work. The reproach amounts to the following: the paper contains no proof that the approximation can be continued arbitrarily, that after each step the next step follows. We had made only two steps in the approximation, the first Newtonian and the second non-Newtonian. Of course, no one will ever carry out a third step. By way of comparison: if taking the first step is as simple as swimming across the English Channel, then taking the second is as difficult (in comparison with the first) as swimming across the Atlantic Ocean. We made this second step, and a third would be as difficult as interplanetary travel in comparison with crossing the Atlantic. Thus there can be no question of anyone ever daring to take a third step. Later, however, together with my pupil, I proved that the need to take this third step never arises. But in 1948 I did not yet know this, and a mathematician demands precision. It was necessary to find a proof that every subsequent step is possible if the preceding one has been made.

Einstein wrote me an extensive letter about this, pointing to the need to supplement our work and proposing a proof which he wished to publish jointly with me. (This proof, however, turned out to be incorrect.) With this letter there began again our intensive collaboration on the problem of motion. This time the work proceeded by means of a very lively correspondence. I had preserved an entire portfolio of these letters from Einstein; unfortunately, they became wet during the wreck of the ship on which my belongings were being transported to Poland, and they are difficult to read, because the seawater washed away the ink.

Einstein’s role at the beginning of this collaboration was that of an enthusiast. Then it turned out that there were still many unresolved questions connected with the problem of motion, and we obtained a whole series of results—either deepening earlier ideas or entirely new ones. Indeed, eleven years had already passed since the beginning of our collaboration—a long enough period of time to see old things in a new perspective. During this time I had created my own school in Canada, and I had an exceptionally capable collaborator, together with whom I published a number of papers and was able to discuss all these questions.

Two or three times a week we exchanged letters with Einstein. However, one fundamental difficulty still remained: how to apply, in a mathematically suitable way, our method

approximation? One day, as I was returning home from the university, a new idea suddenly came into my head: to introduce gravitational dipoles. Their existence should make a solution possible in any approximation. But since in the final analysis they are not needed, we must eliminate them after carrying out the approximation. From the conditions that these dipoles vanish, the equations of motion are obtained.

I came home very excited. I wanted quickly to carry out the calculations in order to make sure whether this method led to the goal. After 15 minutes I knew that it provided a simple way of overcoming the difficulties that had tormented us for so long. After lunch I returned to the institute to discuss this solution with my former student, that capable collaborator and younger colleague whom I mentioned above. It seemed strange to me that this gifted young man, who grasped everything on the fly, had difficulty understanding my conception, which I considered obvious. This was yet another proof of what, strictly speaking, I had long known: if you yourself think something through, then you lose perspective and everything seems simple to you, almost banal, while for a person who stands aside and looks at these conclusions skeptically, difficulties arise—sometimes new ones, and sometimes the very ones that we quickly overcame and no longer remember.

My colleague promised me to check the entire calculation. The next day he reported that he had found an error in the figures. I did not believe this, and it turned out that I was right. It was he who had made the error, not I. That same day I wrote a letter to Einstein, telling him—very briefly—of my conclusion and that this conclusion removed all the difficulties. I awaited the reply impatiently. The reply came, but it greatly disappointed me: there was no admiration in it for my method. In essence, it contained only Einstein’s further reflections concerning these difficulties, which he was trying to overcome by an entirely different path from mine. I found an error in Einstein’s train of thought, wrote to him about it, and earnestly asked him to read my letter, in which, as it seemed to me, there was a good solution of the question. Einstein’s reply began with the words:

“22.XI.1948

Your objections to what was said concerning the discrepancy in the approximate equations are entirely justified. I am writing only today, since I hoped to find your letter with the corresponding proof. However, I did not succeed in doing so. I did not read this letter carefully at the time, since I had no doubt then of the correctness of my proof, based on the expansion of the Bianchi identity. Therefore I ask you to send me your proof once more.”

18.

It seemed to me that our collaboration required a new meeting. I wrote to Einstein that I was coming to Princeton. From New York I telephoned him and learned that he was in a hospital in New York and had asked me to get in touch with him at once. I called the hospital; a doctor came to the telephone. He said that the professor asked me to come as soon as possible. Einstein was then, as far as I remember, in a small private hospital housed in a small building. When I arrived there, I had to wait for some procedures to be completed. At last Einstein appeared in an old, worn dressing gown. He looked considerably worse than nine years earlier (I think it was nine, since we probably had not seen each other since 1939). I asked what was the matter with him.

“Even the doctors do not yet know that,” he replied, laughing loudly. “They will establish it during the autopsy.”

We went up to the reception room and, as usual, immediately began a conversation connected with our common work.

I knew well that Einstein should not be interrupted; he spoke about the difficulties that still remained in our work. Evidently he had already completely forgotten about my letter, in which, as it seemed to me, I had resolved this question. When Einstein had finished, I asked him to listen to me, since I might possibly have succeeded in overcoming the difficulties. I said only two sentences: that gravitational dipoles had to be added, that they ensure the integrability of the equations, and that then the elimination of these dipoles gives the equations of motion. As usual, when he was thinking, he stroked his moustache, and then began asking me questions. I knew that this was characteristic of Einstein, that he did not like lectures, but only discussions. When I had answered three questions, Einstein said with delight:

“Well, in that case our difficulties are over. Why did you never write to me about this?”

As to the last question, I maintained a diplomatic silence. After that we spoke about other things. I thanked him for the marvelous lines which he himself, without any request from me, had written about my book Whom the Gods Love....

He said that he had in fact liked this book very much. And then, with a somewhat venomous smile, he added:

“I know you; you were, essentially, writing about yourself.”

Of course, here Einstein was completely wrong, unless this phrase contained some hidden meaning that I did not understand. In the evening we had dinner together with his host—the doctor—and the doctor’s family. We agreed that I would come again the next day. I was afraid that he would find some new difficulties. Nothing of the kind. He asked me only one additional question, to make sure that, from the mathematical side, everything really was...

turns out well (he himself never checked my calculations). Then we talked about how to prepare this work. We agreed that I would send him the manuscript and then take all his comments into account.

I am afraid that the reader of these lines will get the false impression that the greatest difficulty to be eliminated was eliminated by me. That was not so. In my account I merely noted one of the difficulties whose solution fell to my lot. The rest, as has been said, we settled by correspondence. Here are several excerpts from Einstein’s letters that I received from him after our meeting in New York.

“6.XII.1948

We agree on one thing: the problem has in the main been solved, and now the only matter is to present the question as well as possible. The pedagogical side is indeed important here, since without it the devil himself will make nothing out, and this problem will be gnawed at from all sides in vain. We simply must leave ourselves more time in order to present our beautiful result as well as possible.”

“6.IV.1949

I fully agree with the corrections to the manuscript. You have done a great deal of work. But for the reader this will not be an easy matter, since we have not quite succeeded in separating the matter of principle from the formal, at least in the exposition of the latter idea. However, I agree that after careful review everything should be printed in its present form.”

*

Even before this he had written me a letter that ended with the following words:

“19.XI.1948

… Our collaboration has brought me indescribable joy. It seems to me that neither of us could have carried out this work independently, since the subject is very treacherous.”

Thus was born our third serious work, published in the Canadian Journal of Mathematics.

19.

At that time I received an invitation to visit Poland. At the same time, in connection with my forthcoming trip to Europe, there came an invitation from Dublin from my former Toronto colleague Professor Synge, and somewhat later two invitations from England: from Birmingham and Manchester. I was to give lectures and, of course, the topic of our work with Einstein, which by then was already in print, naturally suggested itself—I had the first page proofs. I wrote to Einstein that I was leaving and asked

MY MEMORIES OF EINSTEIN

his consent to make, at my discretion, minor corrections in his paper, which had been sent to me as editor of the Canadian Journal of Mathematics, and also to referee our joint work in Europe. His reply contained, in particular, the following lines:

“20.III.1949

Thank you for your letter of March 16. I fully agree that you should make small changes in my manuscript. I do not object, of course, to your giving lectures in Poland and/or in Dublin on our work. Naturally, I would be very glad if we could see each other before your departure and discuss all this. I am also grateful to you for not sending congratulations on my birthday. This already would have looked like a funeral while still alive.”

I returned to Canada. In Poland I was offered the chance to come for a year with my family to my homeland. During that time I could decide whether to settle permanently in Poland. After what I had seen in Poland, the prospect of returning there attracted me very much. I said that if the matter concerned only me, I would not hesitate, but the final answer depended on my family. In Canada I was entitled to a year’s leave, and I do not think that the question of using this leave could have caused any complications. However, I attached great importance to what Einstein would say about it. Soon after returning to Canada I wrote to him and received the following reply:

“Saturday, 11.VI.1949

I am glad that you are here again, and I hope that you have not immersed yourself too deeply in world affairs. People walk on shifting sand, and there is never certainty as to what tomorrow will bring. After all, we both could sing about this little song. In any case, it would be very interesting for me to hear something about your general impressions.”

After coming back from Poland, I spent part of the holidays with my whole family in the New York area. From there—in June 1949—I went to visit Einstein. I apparently had a premonition that I was seeing Einstein for the last time, for I wanted him to meet my family: my wife, my son, who was then ten years old, and my six-year-old daughter. Since I expected the usual more or less lengthy conversation, we decided that I would go alone, and that the family would come for me in an hour. For some reason I remember very little from this meeting. I know only one thing: I asked Einstein what he thought of my intention to return permanently to Poland. He thought for a moment, then said:

13 UFN, vol. LIX, issue 1

— There can be no objection to that. It is very noble, but, but...

I waited for him to continue. Einstein said something that surprised me greatly, but did not alarm me.

— What will happen to you if the old regime comes to power again? What will happen if the Soviet Union agrees to this as a result of the final peace treaties?

Such a supposition seemed incredible to me; I believed that it was out of the question, and I tried to explain my point of view to Einstein. I do not know whether I convinced him. Having finished our conversation, we went downstairs, since the secretary had told me that my family was waiting for me.

Before writing these lines, I asked my son whether he remembered that visit. He replied that he did. However, when it came to telling the story, his recollections looked very pale. Einstein, according to him, laughed loudly at some political jokes that I had brought from Europe. Then he recalled that Einstein’s housekeeper gave my children a large bar of chocolate. My son hid the chocolate in the refrigerator and decided that he would never eat it. Later, however, he and his sister together did eat the whole bar. I remember that when we were leaving, Einstein praised my children. Of course, as we said goodbye, we thought that before our departure, which was not planned for sooner than a year later, we would certainly see one another again.

Soon after this meeting I again received from Einstein a letter concerning scientific work. At the end of the letter there was the following paragraph:

“20.VI.1949

I have thought a great deal about whether, because of a certain idealism, you are not involving yourself too deeply in Polish affairs. With all my sympathy for the Polish government, I cannot rid myself of the thought of the precariousness of the relations existing there. After some time the sons of darkness may crawl out of the mouse holes in which they are now hiding. Just as it was in Germany in the 1920s. Then the ‘brothers’ will show you what a pound of flesh means. Although in the Western zone, too, the atmosphere is now rather stifling, still one cannot suppose that the present history will drag on for long, or that the situation will become unbearable. For that, people are living too well. On a full stomach people are not inclined toward fanaticism.”

It is good to know that there is at least one question on which Einstein was not right. This is the question of the USA and the question of Poland. Yet his words moved me. I know, after all, how little he was always interested in human affairs and how deeply he was absorbed in the laws of nature. And these words were clearly prompted by concern for my fate.

In this period we again began joint scientific work. Einstein sent me a letter in which he put forward the idea of simplifying the equations of motion:

“16.VII.1949

...I feel that we have still not fully resolved our problem, but have merely covered it over with formalism. The solution we published is correct, but we both feel that dipoles constitute a roundabout path.”

Einstein wanted to modify the theory in such a way as to obtain a solution of the equations of motion without dipoles. An exchange of letters began again between us. It seemed that we had reached agreement on all the details, and suddenly our opinions diverged again. I had already sent Einstein the completed manuscript of our joint work, but it turned out that once again we did not understand one another. I felt that we had to meet so that this new work—the manuscript of which is still kept in my archives—could finally be published. Unfortunately, events occurred that made a meeting with Einstein impossible. Thus we never published this last work of ours.

I shall quote the beginning of one more letter belonging to this period:

“Saturday, 23.VII.1949

Do not think merely that I am being lazy and for that reason have not expressed my attitude toward your project. I studied it for a long time, until I became convinced that this is not the true Jacob. I tirelessly searched for the natural path; my brain almost burst. I began six letters and each time rejected the chosen path. Now, it seems, a witty idea has come into my head, if only the devil does not lead me by the nose again.”

Again I could not agree with Einstein’s solution, and we postponed the whole question until the next meeting, which, alas, never took place.

I went to Vancouver, a port city on the Pacific Ocean, where I took part in a congress of physicists attended by Dirac and Bhabha. Then I returned to Toronto and submitted an application for leave in order to go to Poland for a year. The dean assured me that neither he nor the president of the university had any objections to my departure.

20.

“Ensign”—that is the name of a weekly Catholic journal sold chiefly in churches. This journal devoted one of its issues entirely to my departure for Poland; I, allegedly an atomic scientist, had divulged atomic secrets to Einstein and was taking them behind the Iron Curtain. Suddenly a storm broke over my head.

As I felt, everything I experienced in the atmosphere of ever-intensifying blackmail aimed at forcing me to abandon the trip to Poland does not belong to the present subject. I write of it only because, as soon as the above-mentioned issue appeared and the opposition leader George Drew asked in Parliament what the government intended to do in order to prevent my departure, I understood that the road to the USA was closed to me and that I would never again see Einstein. A multitude of journalists annoyed Einstein and me with telephone calls, insistently asking whether it was true that I knew the secret of the atomic bomb. (An idiocy all the more obvious since this was already after the first test of the atomic bomb in the Soviet Union.) Thus, almost a year after Einstein and I had seen each other, I left for my homeland.

Already here (in Poland) I received a touching letter, which I hid so well that I cannot find it. In it Einstein writes how lonely he has felt since the death of Professor Ehrenfest (the well-known Dutch physicist) and since the time when I left the American continent. In addition, I have his reply letters to me on various questions, but these are not the long, handwritten letters I used to receive earlier. It vexes me now, when I think how I treated those letters. Many of them I gave to colleagues and friends; some I lost, not realizing what value they would have for me when the author was no longer among the living. I likewise answered by hand, without keeping copies, and often I do not know what Einstein’s replies refer to.

After my arrival I received a letter on a scientific question with the following postscript:

“13.X.1950

Formerly man was, in essence, only a toy in the hands of blind forces; today, in addition, he has become a toy in the hands of bureaucrats. And nevertheless he agrees to this. Do you know Lichtenberg’s saying: ‘Man learns little from experience, since every new stupidity appears to him in a new light’?”

A month later he sent me a new letter, again on scientific questions connected with my work in Poland. At the beginning he is apparently replying to my remark concerning the activity of the supporters of peace.

“13.XI.1950

You know how highly I value the striving for genuine peace. It seems to me that, in the present terrible situation, the direct measures that are at play here have no prospects of success, because everywhere confidence in the honest intentions of the other side has been shaken. I have no direct proposals. At the present moment only …”

My Recollections of Einstein

only certain individual steps by the various camps, capable of gradually restoring trust, without which there are no concrete paths toward the preservation of international security.”

I never had a photograph of Einstein with his signature, and while I lived in America I never sought to obtain one. For some reason (I myself do not know why) I wanted to have such a picture in Poland. When I asked him for it, I received the following reply:

“28.XI.1952

I am glad to send you the photograph for which you ask, and I hope that the wind now blowing will not compel you, should the occasion arise, to hide it carefully.

You asked me about scientific matters, in particular about field theory. At present I have nothing printed on this subject. Still, the situation is such that the internal difficulties and alternatives have been completely removed... However, the possibility of comparison with facts, unfortunately, is a matter of the distant future.”

Two years later:

“8.XII.1954

I am pleased by the good news about your life and work. I agree with your optimistic assessment of the political situation; it was hard to expect so favorable a turn.”

The year 1955, as I write these lines, is the fiftieth anniversary of the theory of relativity. I received two invitations—one to Bern, the other to Berlin. In Bern a scientific congress connected with the fiftieth anniversary of the theory of relativity was to take place (in July). In Berlin, on March 18 and 19, two lectures were delivered. One, on March 18, by Max Born in West Berlin on the fiftieth anniversary of quantum theory*), the second, on March 19, by me in East Berlin on the fiftieth anniversary of the theory of relativity. I thought that, perhaps, I would meet Einstein in one of these two cities. I wrote him a letter in which I asked him to come to Berlin. Although I knew how negligible the chances were that Einstein would visit Europe, I nevertheless wanted to carry out the wish of the committee that had organized these lectures—common to West and East Berlin. The reply I received was written by Einstein three months before his death.

“17.I.1955

Unfortunately (or, I may say, thank God), I am not so healthy as to appear on such official occasions. It seems to me that it would be wonderful if you, in your

*) See p. 119 of this issue of the journal.

sermons explained that the center of gravity of the theory lies in the general principle of relativity. For the majority of contemporary physicists had not yet understood this.”

How I coped with this task the reader may judge for himself, since my Berlin lecture was printed in the journal Die Naturwissenschaften (1955)*). I know only that so many people gathered that the lecture had to be moved from the halls of the Academy to the largest university hall, which was completely filled. Physicists from West Germany and delegates from the countries of people’s democracy were present at this lecture.

21.

On April 18, 1955, Einstein died. A great luminary went out. The greatest, probably, physicist of all time died. A man of inexpressible kindness died—kindness that came rather from the head than from the heart. A man died who was the conscience of the world, a man who always raised his voice in defense of the oppressed, against tyranny. To write these recollections, to look once more through letters filled with a small, even handwriting, was for me a consolation in the loneliness that I feel. I do not know whether these recollections will give even a faint idea of the greatness, the true greatness, with which I had the good fortune to come into contact.

*) For the Russian translation see UFN, vol. 57, no. 2, p. 193 (1955).