In late 1922 and early 1923, Albert Einstein embarked on a five-and-a-half-month trip to the Far East, Palestine, and Spain. In September 1921, Einstein had been invited by the progressive Japanese journal Kaizo to embark on a lecture tour of Japan. The tour would include a scientific lecture series to be delivered in Tokyo, and six popular lectures to be delivered in several other Japanese cities. An honorarium of 2,000 pounds sterling was offered and accepted.
Einstein’s motivation for accepting the invitation to Japan was threefold: to fulfil his long-term desire to visit the Far East, to enjoy two long sea voyages "far from the madding crowds” and to escape from Berlin for several months in the wake of the recent assassination of Germany’s Foreign Minister Walther Rathenau, who had belonged to Einstein’s circle of friends. Rathenau had been gunned down by anti-Semitic right-wing extremists in June 1922 and there was reason to believe that Einstein’s life was also at risk.
Einstein's lecture tour in Japan
The Japan to which Einstein was invited was that of the Taisho era, “a period when internationalism, cosmopolitanism, secularism, and democratization seemed to be replacing the parochial claims” of the Meiji era, when the country had primarily focused on nation building.
The Einsteins set sail for Japan on the SS Kitano Maru on 8 October from Marseille to the Far East via the Suez Canal.
During the voyage, Einstein kept a travel diary in which he meticulously noted his everyday activities on board the steamer, the people he met and the books he read.
After six weeks at sea, the Einsteins arrived in Kobe, Japan. Einstein’s visit to Japan was a sensation. He was greeted by large, enthusiastic crowds wherever he went and his lectures were delivered in auditoriums filled to capacity. The Japanese press reported his every move and utterance.
On 14 December 1922, Einstein attended a student reception at the Kyoto Imperial University.
It appears that he was asked to talk about how he had found the theory of relativity, and complied with this request in an extemporaneous lecture.
Information about the lecture derives from three sources: an entry of this date in Einstein’s travel diary; the prefatory paragraphs, added by Jun Ishiwara to the Japanese version of his notes of Einstein’s address published in the Kaizo journal; and Ishiwara's prefatory remarks to the reprint of this same text that appeared as Einstein kyoju koen-roku (Records of Professor Einstein’s Lectures), published as a separate book in 1923.
The only extant account of the content of the lecture is provided by Ishiwara in his own words, published first in Kaizo and reprinted shortly thereafter as a chapter in his book about Einstein’s Japan lectures, published in 1923.
Ishiwara’s text gives an account of Einstein’s extemporaneous recollections about the creation and development of the theory of relativity many years after its publication. These reminiscences constitute a rich, if indirect, source for historians and philosophers of science and need to be read with all due caution called for by a document of this kind.
In historical literature, the discussion of this document has focused mostly on a single controversial issue: Ishiwara writes that Einstein mentioned Michelson’s experiment and the role it played in shaping his insights into the relativity principle before the publication in 1905 of his paper “On the Electrodynamics of Moving Bodies” (The Collected Papers of Albert Einstein, Vol. 2, Doc. 23).
The question as to when and how Einstein learned about Michelson’s experiment and what influence such knowledge about the experiment may have had on his path toward the theory of relativity has been debated for a long time.
The Kyoto lecture gives us an account not only of the genesis of the special theory of relativity but also about the path toward general relativity. Here again, the document provides one of the most explicit recollections by Einstein on the development that led to the theory of general relativity. This development, however, is amply documented by primary sources, both in correspondence and in manuscripts authored by Einstein and his contemporaries.
These documents enable us to make an independent reconstruction of the historical development of general relativity and therefore also allow an independent assessment of Einstein’s later reflections.
“How I Created the Theory of Relativity”
Einstein's Kyoto Lecture
It is by no means easy to give an account of how I arrived at the theory of relativity. That is because it involves various hidden complex factors which stimulate one’s thinking and influence it in varying degree. I will not mention these factors one by one. Also I will not list the papers I have written.
I will only briefly summarize the key points of the main strand in the development of my thinking.The first time I entertained the idea of the principle of relativity was some seven- teen years ago. From where it came, I cannot exactly tell. I am certain, however, that it had to do with problems related to the optics of moving bodies.
Light travels through the ocean of the ether, and so does the Earth. From the Earth’s perspective, the ether is flowing against the Earth. And yet I could never find proof of the ether’s flow in any of the physics publications. This made me want to find any way possible to prove the ether’s flow against the Earth, due to the Earth’s motion.
When I began pondering this problem, I did not doubt at all the existence of the ether or the motion of the Earth. Thus I predicted that if light from some source were appropriately reflected off a mirror, it should have a different energy depending on whether it moves in the direction of the Earth’s movement, or in the opposite direction. Using two thermoelectric piles, I tried to verify this by measuring the difference in the amount of heat generated in each. This idea was the same as in Michelson’s experiment, but my understanding of his experiment was not yet clear at the time.
I was familiar with the strange results of Michelson’s experiment while I was still a student pondering these problems, and instinctively realized that, if we accepted his result as a fact, it would be wrong to think of the motion of the Earth with respect to the ether. This insight actually provided the first route that led me to what we now call the principle of special relativity. I have since come to believe that, although the Earth revolves around the Sun, its motion cannot be ascertained through experiments using light.
It was just around that time that I had a chance to read Lorentz’s monograph of 1895. Lorentz discussed and managed to completely solve electrodynamics to first order approximation, i.e., neglecting quantities of the second order and higher of the ratio of the velocity of a moving body to the velocity of light. I also started to work on the problem of Fizeau’s experiment and tried to account for it on the assumption that the equations for the electron established by Lorentz also hold when the coordinate system of the vacuum is replaced by that of a moving body. At any rate, I believed at the time that the equations of Maxwell-Lorentz electrodynamics were secure and represented the true state of affairs. The circumstance, moreover, that these equations also hold in a moving coordinate system gives us a proposition called the constancy of the velocity of light. This constancy of the velocity of light, however, is incompatible with the law of the addition of velocities known from mechanics.
Why do these two things contradict one another? I felt that I had come upon an extraordinary difficulty here. I spent almost a year fruitlessly thinking about it, expecting that I would have to modify Lorentz’s ideas somehow. And I could not but think that this was a riddle that was not going to be solved easily.
By chance, a friend of mine living in Bern (Switzerland) helped me. It was a beautiful day. I visited him and I said to him something like: “I am struggling with a problem these days that I cannot solve no matter what I try. Today I bring this battle of mine to you.” I had various discussions with him. Through them it suddenly dawned on me. The very next day I visited him again and told him without further ado: “Thank you. I have already solved my problem completely.”
My solution actually had to do with the concept of time. The point is that time cannot be defined absolutely, but that there is an inseparable connection between time and signal velocity. Using this idea, I could now for the first time completely resolve the extraordinary difficulty I had had before.
After I had this idea, the special theory of relativity was completed in five weeks. I had no doubt that the theory was also very natural from a philosophical point of view. I also realized that it fitted nicely with Mach’s viewpoint. Although the special theory was, of course, not directly connected with Mach’s viewpoint, as were the problems later resolved by the general theory of relativity, one can say that there was an indirect connection with Mach’s analysis of various scientific concepts.
Thus the special theory of relativity was born.
The first thought leading to the general theory of relativity occurred to me two years later, in 1907, and it did in a memorable setting.
I was already dissatisfied with the fact that the relativity of motion is restricted to motion with constant relative velocity and does not apply to arbitrary motion. I had always wondered privately whether this restriction could somehow be removed.
In 1907, while trying, at the request of [Johannes] Stark, to summarize the results of the special theory of relativity for the “Jahrbuch der Radioaktivität und Elektronik” of which he was the editor, I realized that, while all other laws of nature could be discussed in terms of the special theory of relativity, the theory could not be applied to the law of universal gravitation. I felt a strong desire to somehow find out the reason behind this. But this goal was not easy to reach. What seemed to me most unsatisfactory about the special theory of relativity was that, although the theory beautifully gave the relationship between inertia and energy, the relationship between inertia and weight, i.e., the energy of the gravitational field, was left completely unclear. I felt that the explanation could probably not be found at all in the special theory of relativity.
I was sitting in a chair in the Patent Office in Bern when all of a sudden I was struck by a thought: “If a person falls freely, he will certainly not feel his own weight.”
I was startled. This simple thought made a really deep impression on me. My excitement motivated me to develop a new theory of gravitation. My next thought was: “When a person falls, he is accelerating. His observations are nothing but observations in an accelerated system.” Thus, I decided to generalize the theory of relativity from systems moving with constant velocity to accelerated systems. I expected that this generalization would also allow me to solve the problem of gravitation. This is because the fact that a falling person does not feel his own weight can be interpreted as due to a new additional gravitational field compensating the gravitational field of the Earth, in other words, because an accelerated system gives a new gravitational field.
I could not immediately solve the problem completely on the basis of this insight. It would take me eight more years to find the correct relationship. In the meantime, however, I did come to recognize part of the general basis of the solution.
Mach also insisted on the fact that all accelerated systems are equivalent. This, however, is clearly incompatible with our geometry, for if accelerated systems are allowed, Euclidean geometry can no longer hold in all systems. Expressing a law without using geometry is like expressing a thought without using language. We first have to find a language for expressing our thoughts. So what are we looking for in this case?
This remained an unsolved problem for me until 1912. In that year, I suddenly realized that there was good reason to believe that the Gaussian theory of surfaces might be the key to unlock the mystery. I realized at that point the great importance of Gaussian surface coordinates. However, I was still unaware of the fact that Riemann had given an even more profound discussion of the foundations of geometry. I happened to remember that Gauss’s theory had been covered in a course I had taken during my student days with a professor of mathematics named Geiser. From this I developed my ideas, and I arrived at the notion that geometry must have physical significance.
When I returned to Zurich from Prague, my close friend, the mathematician Grossmann, was there. During my days at the Patent Office in Bern, it had been difficult for me to obtain mathematical literature and he had been the one who would help me. This time, he taught me Ricci and, after that, Riemann. So I asked my friend whether my problem could really be solved through Riemannian theory, i.e., whether the invariance of the curved line element completely determines its coefficients, which I had been trying to find. In 1913 we wrote a paper together. We were unable, however, in that paper, to obtain the correct equation for universal gravitation. Although I continued my research into Riemann’s equation, trying various different approaches, I only found many different reasons that made me believe that it could not give me the results I wanted at all.
Two years of hard work followed. Then I finally realized there was a mistake in my previous calculations. I therefore returned to invariance theory and tried to find the correct equation for universal gravitation. Two weeks later, the correct equation finally emerged before my eyes for the first time.
Of the work I did after 1915, I only want to mention the problem of cosmology. This concerned the geometry of the universe and time, and was based, on the one hand, on the treatment of boundary conditions in the general theory of relativity and, on the other hand, on Mach’s observations about inertia. Of course, I do not know specifically what Mach’s opinions were about the relative nature of inertia, but at least on me he definitely exerted an extremely important influence.
At any rate, after trying to find invariant boundary conditions for the equation for universal gravitation, I was finally able to solve the problem of cosmology by regarding the world as a closed space and removing the boundary. From this I derived the following: inertia emerges purely as a property shared by a number of bodies. If there are no other bodies in the vicinity of a particular body, its inertia must vanish. I believe that this made the general theory of relativity epistemologically satisfactory.
The above, I think, gives a brief historical outline of how the essential elements of the theory of relativity were created.
Einstein's tour of Palestine, February 1923
Already in late 1921, Einstein seems to have envisaged a visit to Palestine,where he could view for himself the settlement activities of the Yishuv, the local Jewish community.
At the time, Chaim Weizmann advised him that “there is as yet no great urgency to travel to Palestine.” But shortly before his departure from Berlin for Japan, Einstein conferred with German Zionist Kurt Blumenfeld and confirmed that he had accepted the invitation of Arthur Ruppin, the director of the Palestine bureau, to visit the country for ten days.
Sailing to Palestine December 1922
After a highly successful, intense six-week stay in Japan, the Einsteins set sail for Europe on 29 December 1922. A month later, they arrived in the British Mandate of Palestine where they stayed for 12 days. They toured the country extensively, visiting all the large cities as well as some agricultural settlements. The Einsteins also toured the Jewish community’s main educational, cultural and economic institutions and met with a number of local Arab dignitaries. This would be Einstein’s only visit to Palestine (or Israel, for that matter) throughout his lifetime. After a three-week tour of Spain, the Einsteins returned to Berlin on 21 March 1923. They had been away from Germany for almost six months.
The Einsteins were greeted at the Lod railway station by senior Zionist officials, including Menachem Ussishkin, president of the Zionist Executive; Ben-Zion Mossinson, member of the General Zionist Council and director of the Herzliya Gymnasium; and Colonel Frederick H. Kisch, director of the political department of the Zionist Executive. They continued by train to Jerusalem, where they were reunited with Solomon Ginzberg, the British Mandate’s inspector of education, who had served as Einstein’s secretary during his tour of the United States in spring 1921.
In Jerusalem, the Einsteins were greeted by Captain L.G.A. Cust, aide-de-camp to Sir Herbert Samuel, the British high commissioner, who drove them to the commissioner’s residence on the Mount of Olives. There they met their host, Sir Herbert, about whom Einstein wrote: “English formality. Fine, well-rounded education. Lofty view of life, tempered by humor.” After a walk the next day into the Old City of Jerusalem, Einstein recorded his first impressions in the travel diary he was keeping.
This journal is the first extant journal written by Einstein and, as far as we know, it was the first such diary kept by him. The diary is a fascinating document which provides us for the very first time with gripping insights into the most immediate levels of Einstein’s experience of the journey, in particular of the people he met and the places he visited.
The journal offers us a snapshot of the Jewish community in Palestine at the time of Einstein’s visit - albeit, of course, from the perspective of the document’s author.
“Excerpt from Einstein’s travel diary to Japan, Palestine and Spain, entry for 3 February 1923”.
[3 February]: Walked with S[ir Herbert] Samuel into the city (Sabbath!) on footpath past the city walls to picturesque old gate, walk into town in sunshine. Stern bald hilly landscape with white, often domed white stone houses and blue sky, stunningly beautiful, likewise the city crowded inside the square walls. Further on in the city with [Solomon] Ginzberg.
Through bazaar alleyways and other narrow streets to the large mosque on a splendid wide raised square, where Solomon’s temple stood. Similar to Byzantine church, polygonal with central dome supported by pillars. On the other side of the square, a basilica-like mosque of mediocre taste. Then downwards to the temple wall (Wailing Wall), where dull ethnic brethren, with their faces turned to the wall, bend their bodies to and fro in a swaying motion. Pitiful sight of people with a past but without a present.
Then diagonally through the (very dirty) city teeming with the most disparate of religions and races, noisy, and orientally alien. Gorgeous walk over the accessible part of the city wall. Then to [Solomon] Ginzberg-[Arthur] Ruppin for midday meal with cheerful and serious conversations. Stay owing to heavy rain. Visit to the Bukharian Jewish quarter and to dark synagogue where pious, grimy Jews await the end of the Sabbath in prayer.
Visit with [Hugo] Bergmann, the serious holy man from Prague who is setting up the [university] library with too little space and money. Atrocious rain with even messier streets. Homeward drive with Ginzberg and Bergmann by car.
During his twelve-day tour of the country, Einstein visited the three large cities in Palestine – Jerusalem, Tel Aviv, and Haifa. He also traveled to the Dead Sea and the Galilee. His Zionist hosts arranged for their illustrious guest to tour all the major educational, economic, industrial and agricultural institutions of the Jewish community in Palestine
Einstein also met with Christian and Muslim dignitaries. The highlight of his tour was his lecture on relativity at the future site of the Hebrew University.
Exhibit Curator — Dr. Ze'ev Rosenkranz, The Einstein Papers Project, California Institute of Technology
Exhibit Technical Management — Dalia Mendelsson, The Library Authority, The Hebrew University of Jerusalem
Additional Editorial Texts — Prof. Diana Buchwald, The Einstein Papers Project, California Institute of Technology
Additional Editorial Texts — Dr. Tilman Sauer, The Einstein Papers Project, California Institute of Technology
Source: The Collected Papers of Albert Einstein, Volume 13, Princeton University Press, Princeton, NJ, 2012. — Name, Surname, Job title (optional)