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The emergence of theoretical physicsin Japan: Japanese physics communitybetween the two World WarsDong-Won Kim aa Division of Humanities and Social Sciences , Korean AdvancedInstitute of Science and Technology , 373-1 Kusong-dong, Yusong-gu,Taejon, 305-701, KoreaPublished online: 22 Aug 2006.

To cite this article: Dong-Won Kim (1995) The emergence of theoretical physics in Japan:Japanese physics community between the two World Wars, Annals of Science, 52:4, 383-402, DOI:10.1080/00033799500200301

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ANNALS OF SC1ENCE, 52 (1995), 383--402

The Emergence of Theoretical Physics in Japan: Japanese Physics Community Between the Two World Wars

By DONG-WON KIM

Divis ion of Humani t ies and Social Sciences , Korean Advanced Insti tute of Science and Technology,

373-1 Kusong-dong, Yusong-gu, Tae jon 305-701, Korea

Received 20 June 1994

Summary The paper aims to show how Japanese theoretical physics groups emerged between the First and Second World Wars. First, it will be argued that by the early 1930s the Japanese physics community had been predominantly inclined towards experimental physics and that several academic, cultural, and social factors had worked for the maintenance of this status quo. Next, how the situation slowly changed during the early 1930s, and how the young theoretical physicists successfully established a bridgehead during the mid-1930s will be analysed. Four different elements are suggested: the dazzling success of quantum mechanics and its spread in the West; the dominance of experimental physics and its effect on the university system; cultural/social influence; and the emergence of the research network.

Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 383 2. The dominance of experimental physics over theoretical physics by the

early 1930s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 384 3. The emergence of theoretical physics during the 1930s . . . . . . . . . . . . . . . . . . 394 4. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 402

1. Introduction In an autobiographical essay, the first Japanese Nobel Laureate, Hideki Yukawa,

stated that he decided to major in theoretical physics because he 'was no good at exper iments where one needed to be c lever with o n e ' s hands ' and noted that instead he had 'a s imple, unsophis t ica ted brain ' , r Another Nobel Laureate in physics, Sin-i t i ro Tomonaga was re la t ively more dexterous than Yukawa but not suited to becoming a top-class exper imental is t . It is interesting to point out that these two Japanese physicis ts received their prizes for theoret ical work, and that the Nobel Commi t tee often preferred exper imenta l to theoret ical achievements when it se lected the winners in physics. Theoret ical physics, however , had a very short history in Japan. Its emergence in Japan during the 1930s was neither expected nor encouraged by con temporary Japanese physicis ts who were most ly incl ined to pursue exper imenta l topics. This fact is often neglected by both historians and the public, because Yukawa and T o m o n a g a ' s success

1H. Yukawa, Creativity and Intuition: A Physicist Looks at East and West, translated by John Bester (Tokyo, 1973), 26 and 34.

0003-3790/95 $I0.00 r 1995 Taylor & Francis Ltd.

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was so impressive that the Japanese often thought there must have been a strong tradition of theoretical physics since the late-nineteenth century when the Japanese commenced systematically studying Western science in earnest.

The aim here is to correct this distorted image and to indicate several elements that contributed to the emergence of theoretical physics in Japan. As this paper is an attempt to understand the Japanese physics community compared with its contemporary Western counterparts, several works by Japanese historians of science shall be referred to, and most selected works are either written or translated in English.

2. The dominance of experimental physics over theoretical physics by the early 1930s

Western science had been introduced into Japan since the mid-sixteenth century, through contact with the Jesuits and later with the Dutch. 2 Western astronomy, medicine, botany, navigation, and physics were introduced. Rangaku, or Dutch learning, had flourished on a small scale since 1638 when the Japanese government adopted the closed-door policy. Although the study of Western science had been strictly limited to practical studies, it is nonetheless important that Japan had a group of scholars who were ready to translate Western languages into their native tongue and also ready to understand up-to-date Western science with little resistance. 3 A famous drawing of 1813, which illustrates 'a Japanese version of Nollet's many-person discharge train',4 suggests that Japan was not totally ignorant of Western science prior to 1853, when the country finally reopened its door to Westerners under the threat of US battleships.

However, it was only after 1868 that the Japanese began to learn modern physics systematically along with other branches of sciences. 'The first generation of Japanese physicists' were either popularizers or experimental physicists whose aims were to serve their nation for modernization. 5 Among them, three major figures, Kenjiro Yamagawa (1854-1931), Aikitsu Tanakadate (1856 1952), and Hantaro Nagaoka (1865-1950) played important roles as the founding fathers of the modern physics community.

Yamagawa was the first Japanese professor of physics. At the age of 17 he was sent to Sheffield Scientific School at Yale, and there he majored in civil engineering 'in the hope that it would provide a grounding in physics'.~' After returning to Japan, he was very active in the popularization of physics in Japan where physics had yet to be properly established: he published several popular essays and also edited the Japanese Dictionary of Physics Terminology from the English, French, and German. While he was not a good researcher, he was an influential teacher and a good administrator at Tokyo University. After completing 25 years as professor, he served twice as the

2For information, see K. Koizumi, 'The Development of Physics in Meiji Japan: 1868 1912' (nnpublished PhD dissertation, University of Pennsylvania, 1973), chapter 1. A revised and abridged version of the dissertation was published: 'The Emergence of Japan's First Physicists: 1868-1900', Historical Studies in Physical Sciences, 6 (1975), 3-108.

: When F. Yukichi met a Chinese in l :mdon and asked each other how many natives in their countries could read Western materials directly, they estimated that there were over 500 Japanese and about 11 Chinese. See E. Shimao, "Some Aspects of Japanese Science, 1868 1945", Annals q f&ienee , 46 (1989), 71.

"~ J. L. Hcilbron, Electricio' in the 17lh and 18lh Centuries. A Study ~(kar ly Modern Phy.~ic.~ (Berkeley, 1979), 319 (Figure 13.2).

s Koizumi (footnote 2), chapters 4 and 5. 6 Ibid., 183.

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Theoretical Physics in Japan 385

President of the University, and was instrumental in the founding of both the Institute of Physical and Chemical Research in 1917 and the Aeronautical Research Institute in 1918.

While Yamagawa was the first Japanese professor of physics, Tanakadate was the first serious Japanese physicist. At Tokyo University he was taught electricity and magnetism by J. A. Ewing, future professor of engineering at Cambridge University, and geophysics by T. C. Mendenhall. In 1888, he was sent to Glasgow to study electromagnetism under William Thomson. During the two years there, he published two papers on magnetization of soft iron in the Philosophical Magazine. 7 He then spent one year in Berlin, attending lectures and seminars by H. von Helmholtz, L. Fuchs, M. Planck, A. Kundt, and others. After returning to Japan he became the full professor of physics at Tokyo University along with Yamagawa. He enthusiastically carried out several research projects, such as the measurement of geomagnet ism in Japan, aeronautics, and the measurement of weight. He was a true experimental physicist in every respect.

Nagaoka was a symbol of departure from the past. K. Koizumi has argued that Nagaoka 'chose a career in physics on the basis o f purely personal motivations, and he entered fully into competit ive participation in the world of physics, both theoretically and experimentally ' . ~ In fact, he was the first Japanese physicist whom Westerners recognized. Like the former two physicists, he was also trained in Tokyo University and became the first graduate student when the University became the Imperial University and established the graduate school in 1877. While his predecessors were busy digesting Western physics in some awe, he was determined to compete with Western physicists from the very beginning. In 1893, he received the doctoral degree at the age of 28, and was sent to Europe. There he attended the lectures by Helmholtz, Planck, Kundt, Fuchs, H. A. Schwartz, L. Boltzmann, and others. He did experimental research on magnetostriction and published several papers on the subject. In 1896, he was appointed professor of physics at Tokyo University, and began to teach applied mathematics and physics. As Koizumi points out, his research can be divided into three categories: magnetostriction, geophysics, and spectroscopy. Though he became famous through the so-called 'Saturnian Atomic Model ' or Saturn-ring atomic model, 9 most of his research has been mainly experimental.

It is therefore very difficult to find any serious theoretical physicists among the first generation of Japanese physicists, and the imbalance between theoretical and experimental physics was apparent. In this respect, Nagaoka ' s fame as a theoretical physicist was unusual. It must be noted that his theory was not given much recognition in Japan. It was only after the spread of Rutherford 's model that Nagaoka ' s work was recognized by both Western and Japanese physicists. However, Rutherford confessed that he did not know Nagaoka ' s model prior to receiving Nagaoka ' s letter indicating

v A. Tanakadate, "Mean Intensity of Magnetization of Soft Iron Bars of Various Lengths in a Uniform Magnetic Field', Philosophical Magazine, 26 (1888), 450-6; idem, "The Thermal Effect due to Reversals of Magnetization in Soft Iron,' Philosophical Magazine, 27 (1889), 207 18.

s Koizumi (footnote 2), 215. 9 For Nagaoka's atomic models, see E. Yagi, 'On Nagaoka's Saturnian Atomic Model (1903)', Japanese

Studies in the Histor 3" of Science, 3 (1964), 29-47; idem, 'The Development of Nagaoka's Saturnian Atomic Model 1: Dispersion on Light ( 1905)', Jupanese Studies in the Histor3" of Science, 6 (1967), 19-25; and idem, 'The development of Nagaoka's Saturnian Atomic Model II (1904~05): Nagaoka's Theory of the Structure of Matter', Japanese Studies in the History tg'Science, 11 (1972), 73-89.

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similarity between the two.l~ The reason that Nagaoka became famous among Japanese was that his work was recognized by a leading Western physicist. In other words, for the Japanese it meant that they now no longer needed to merely follow the initiatives of Westerners but could compete with them directly. However, Nagaoka 's case was more a happy parallel development than evidence of strong research activity, since no

further theoretical works followed. The dominance of experimental physics over theoretical physics cont inued among

the next generation. Kotaro Honda, ' founder of the science of metals in Japan' , was a good exampte.l l He studied physics under Nagaoka and went to Germany to major in metal lurgy and magnetism. As he published several important papers on metallurgy in German and English journals, his name was one of the few which Western scientists were familiar with. In 1922 he was awarded the Bessemer Medal for his researches on magnetic properties of iron and steel, lz He founded his own research school in Tohoku Universi ty (the third Imperial Universi ty alter Tokyo and Kyoto) and trained many able researchers for several decades. J3 The establ ishment of the Research Institute for Iron,

Steel and other Metals in 1919, which would serve both military and civil ian shipbuilding, was one of the major accomplishments of his dist inguished career. For many Japanese, Honda provided the symbol of what physicists would do for the welfare

of the country. The outbreak of the First World War was a watershed for the Japanese scientific

communi ty , and the physics communi ty was one of the major beneficiaries. The establishment of several research institutes and laboratories by government agencies, military, universities, and even private companies during and after the War accelerated the growth of the physics community . 14 C. Kamatan i ' s study of the research organizations in Japan shows that the number of new research institutions between 1914 and 1936 is almost 2.5 times more than that between 1868 and 1913.15 With the rapid growth of Japanese industry and the increasing number of research institutes, the demand for both well-trained experimental and applied physicists was growing year by year. As Japan became one of the leading industrial countries after the First World War, it became more urgent to raise competent physicists for industrial research. The establishment of several research laboratories by chemical, electrical, and automobile companies indicated the changing milieu after the War. It is also noteworthy that the Japanese government played a leading role for such a movement for both civilian and

military purposes. The establishment of the Institute of Physical and Chemical Research (often called

Riken) in 1918 was the starting point of Japan 's own research systemJ 6 It was first

l~ his reply to Nagaoka, Rutherford said, 'You will notice that the structure in my atom is somewhat similar to that suggested by you in a paper some years ago. I have not yet looked up your paper; but I remember that you did write on that subject'. (Yagi, 'On Nagaoka's Saturnian Atomic Model,' 47). For Nagaoka's letter to Rutherford, see Cambridge University Library MSS. Add 7653, NI.

t 1 For Honda's work, see Nobuo Kawamiya, 'Kotaro Honda: Founder of the Science of Metals in Japan', Japanese Studies in the Histors' of Science, 15 (1976), 145-58.

12 Ibid., 151-6. 13 Honda's authoritarian style is famous. J. R. Bartholomew, The Formation of Science in Japan (New

Haven, 1989), 187-91. 14Ibid., chapters 7 and 8. 15 C. Kamatani, 'The History of Research Organization in Japan,' Japanese Studies in the Histoo, of

Science, 2 (1963), 1-79. ~6 K. Itakura and E. Yagi, "The Japanese Research System and the Establishment of the Institute of

Physical and Chemical Research', in Science and Society in Modern Japan: Selected Historical Sources, edited by S. Nakayama, D. L. Swain and E. Yagi (Tokyo, 1974), 160. See also 'An Institute of Physical and Chemical Research for Japan', Nature, 102 ( 1918), 294-5.

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proposed that a large-scale chemical laboratory would be necessary for national security, but physics was soon added to the proposal to provide a broader base. In the final proposal dated 21 February 1916, proponents of the Institute explained the necessity of it a s f o l l o w s : 17

Wishing to contribute to world civilization, to enhance the status of our nation, to lay the foundations of various industries and to increase the nation's wealth, it is imperative that we encourage creative research in the discipline of physics and chemistry. The recent war, moreover, has taught us the urgent necessity of independence and self-sufficiency in military supplies and industrial materials and has made us all acutely aware of the need for physical and chemical research. Because these kinds of research facilities have not previously existed in our country, certain public-spirited people are hoping to establish an Institute of Physical and Chemical Research.

As the proposal indicates clearly, the immediate aim of the Institute was to promote and support Japanese industry on a national scale. It is also emphasized the close relationship between pure research and the industry in order to secure both continuous support in the Diet (the Japanese parliament) and financial aid from leading industries, is

Who were the major beneficiaries of this 'blessing from heaven' ?19 Experimental physicists! Owing to the growing demands of industry after the First World War, experimental physics flourished and most Japanese physicists were basically experimentalists or applied physicists.

To prove the dominance of experimental over theoretical physics between the two World Wars, four scientific periodicals were analysed, Scientific Papers of the Institute of Physical and Chemical Research, Proceedings of the Physico-Mathematical Society of Japan (formerly Proceedings of the Tokyo Mathematico-Physical Society), Japanese Journal of Physics, and Philosophical Magazine. The last one is added here to indicate the extent to which Japanese physicists contributed to the world physics community.

The dominance of experimental over theoretical physics in Riken was apparent from the beginning: above all, there was no separate laboratory for the latter in it. Its own journal, Scientific Papers of the Institute of Physical and Chemical Research, proves this. 2~ In its first volume (1922-3), there are seven physics papers among 13, most of which were devoted to experimental subjects such as spectroscopy: for example, there were 'Band Spectra of Mercury' (Nagaoka), 'On a Microbarograph' (Nagaoka and N. Ayabe), and 'The Fine Structure of Mercury Lines and the Isotopes' (Nagaoka, Y. Sugiura and T. Mishima). In its 13th volume (March-July, 1930), the number of physics papers was increased but the subject-matter was almost the same. Some of the titles were: 'The Angular Intensity Distribution of Continuous X-ray Spectrum, II ' (Sugiura). 'On the Combination Series of Helium' (Y. Ishida and T. Tamura), 'Study of the Corona at Large Gap Length in Air' (T. Nishi and Y. Ishiguro), 'Zeeman Effect of Neon' (K. Murakawa and T. Iwama), and 'Isotope Effect in the Spectrum of Neon' (Nagaoka and Mishima). This trend is slightly changed in its 36th volume

WItakura and Yagi (footnote 16), 188-9. Is Ibid., 191-2. J9Bartholomew (footnote 13), 199. 2o Scientific Papers of the Institute of Physical and Chemical Research, l (1922-3), i; 13 (1930), i-ii;

and 36 (1939), i-iii.

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(April-December, 1939) with more variety of topics: 'On the Stark Effect of Ne II Spectrum' (Ishida, Tamura and G. Kamijima), 'Scattering o f " D " Group Neutrons' (M. Kimura), 'Induction Magnetograph for Recording Sudden Changes of Terrestrial Field' (Nagaoka and T. Ikebe), 'On the Elastic Collisions of Protons and Very Fast Neutrons' (M. Nogami), 'On the Ferromagnetism of Impurity-Semiconductors' (T. Muto), 'Note on the Absorption of Slow Mesotron in Matter' (Yukawa and T. Okayama), 'Sex-linked Mutation of Drosophila melanogaster Induced by Neutron Radiations from a Cyclotron' (Y. Nishina and D. Moriwaki), and 'On the Shift of Intensity in N2 + Bands Excited in Helium and Neon' (T. Takamine, T. Suga and Y. Tanaka). These examples clearly indicate the imbalance between experimental and theoretical physics in Riken during the period.

A report published in 1938 for 'the Past Activities of the Institute' also shows this trend. 2~ Among 30 physics and chemical laboratories (including past ones), only four physics laboratories-- ' Ishida Laboratory' , 'Nagaoka Laboratory' , 'Nishikawa Labora- tory', and 'Nishina Labora tory ' - -of ten paid their attention to theoretical interpretation of experimental results. The other physics laboratories seemed to be satisfied with improving accuracy of measurement of analysis of spectra lines, or improvement of instruments.

The Nishina Laboratory, which was established in 1931, was quite unusual. First, the four main fields of research in this l a b o r a t o r y ~ u a n t u m theory, cosmic ray, nuclear physics, and biological studies connected with radioactivity--were all relatively new ones. Second, pure theoretical r e s e a r c h ~ u a n t u m theory--had finally found a place in Riken. Tomonaga 's move from Kyoto to Tokyo in 1932 was an invaluable addition to Nishina's research team, because this young ambitious graduate was determined to devote himself to theoretical physics. It is noteworthy that about 20 papers were solely devoted to quantum theory between 1931 and 1938. The research on cosmic rays and nuclear physics were also carried out with theoretical concerns in mind. For example, Nishina and his colleagues constructed a new cloud chamber that had 'a large magnet 15 tons in weight with a pole face 50 cm in diameter ' , and with it they 'obtained tracks of the Yukawa particle and determined its mass to be about 180 times that of the electron'.22 Third, Nishina's team collaborated with Nishikawa's for the establishment of the Nuclear Research Laboratory in 1935, in which they 'planned the installation of two sources for nuclear disintegration. One is a large cyclotron with an electromagnet at least 100 tons in weight and the other a high tension apparatus of about a million volts' .23 The opening of the Nuclear Research Laboratory meant the close collaboration of practitioners of experimental and theoretical physics as well as more systematic research on nuclear physics in Japan. It is no wonder, therefore, that Nishina's research team became a core group of theoretical and nuclear physicists along with the Yukawa-Kikuchi group in Kyoto-Osaka.

The second example, Proceedings of the Physico-Mathematical Society of Japan (formerly proceedings of the Tokyo Mathematico-Physical Society), also indicates the same direction. The journal traditionally served as the publication of choice for high

21 Editorial , ' S u m m a r y of the Past Act iv i t ies of the Inst i tute ' , Scientific Papers qf the Institute of Physical and Chemical Research, 34 (1938), 1763-892.

22 Ibid., 1846. 23 Ibid., 1847.

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quali ty papers, and cer ta inly was the best place to submit theoret ical papers. For example , a series of Nagaoka ' s papers on his Saturn-r ing model of atomic structure were printed here 24, Jun Ishiwara publ ished several papers on relat ivi ty and quantum theory during the 1910s25; and Yukawa and his col leagues sent their papers on meson theory to this journal . 26

However , as a whole, exper imenta l (or pract ical) papers were more numerous than theoret ical ones. By compar ing three different periods, we can see this. In 1922, 32 mathemat ics and physics papers were publ ished in the journal , and the titles of some physics papers were as follows: 'Magnet ic Fie ld of Circular Currents ' (Nagaoka) , 'Electr i f icat ion by Dipp ing a Heated Metal l ic Sphere into L iqu ids ' (U. Doi), ' S o m e Remarks on the Method of Reduct ion of the Underground Tempera ture Observa t ion ' (K. Aichi) , 'On the Sound of Aeroplane and the Structure of W i n d ' (T. Terada), and 'On the Band Spectrum associated with He l ium' (Y. Takahashi) . 27 In 1930, there were 39 papers, and a few of them were: 'On a Possible Wave- l i ke Structure of an Elec t ron ' (U. Kakinuma) , 'On a New A. C. Potent iometer ' (M. Sase and T. Muto), 'Calcula t ion of S tark-Displacements in Oxygen ' (S. Doi). 'Fur ther Note on the Exis tence of the Transverse Eddy Res is tance ' (S. Sakakibara) , 'Ref lexion of Monochromat ic X-rays from some Crys ta ls ' (Y. Sakisaka) , 'On the Structure of Long Electric Sparks ' (T. Kobayasi ) , and ' Improvemen t of Thin F ihn Caes ium Photoelectr ic Tube ' (S. Asao and M. Suzuki). 2s In 1939, the number of papers rose to 89 owing to the increase of physics papers, and there were: 'On the Creat ion and Annihi la t ion of Heavy Quanta in Mat te r ' (M. Kobayas i and T. Okayama) , 'On the Angu la r Dis t r ibut ion of the Fast Neutrons Scat tered by the A t o m s ' (Kikuchi , Aoki and T. Wakatuki ) , 'The Beta-Ray Spect rum of ~3N' (Kikuchi , Y. Watase , J. Itoh, E. Takeda and S. Yamaguchi ) , 'The Mass and the Life Time o f the Meso t ron ' (Yukawa and Sakata) , 'An Appara tus for Di rec t -Reading the Pitch and Intensity of Sound ' (J. Obata and R. Kobayas i ) 'On the Thermal Effect Conduc t iv i ty of Light ' (I. Osida), 'Zeeman Effect in Sun-spots ' (T. Tanaka and Y. Takagi) , 'On the Photo-Elas t ic Constant of Rock-Sal t Crys ta ls ' (Y. Kidani) , ' Intense Combina t ion-Tones produced by the Flut ter of an Ai r sc rew ' (J. Obata and Y. Yosida) , 'On the Change in Electr ical Resis tance of Alkal i Metals on Mel t ing ' (A. Haras ima) , 'Magne to-Opt ica l A noma ly of Ord inary and Heavy Wate r ' (A. Okazaki) , and 'Structure of Cr Fi lms deposi ted on Rocksa l t ' (S. Shirai). 29 Though the subject-mat ter of papers increased in variety and the number of theoret ical papers was doubled during the 1930s, the dominance of exper imenta l over theoretical subjects did not change during this period.

The superiori ty of exper imenta l over theoretical phys ics was also clear in the third publ icat ion example , Japanese Journal o f Physics. The results of analysis of its

24 H. Nagaoka, "Motion of Particles in an Ideal Atom illustrating the Line and Band Spectra and the Phenomena of Radioactivity,' Proeeedings of the Tokyo Mathematico-Physical Society, 2 (1904), 92-107; and idem, 'Dispersion of Light due to Electron-Atnm,' Proceeding of the Tokyo Mathematico Physical Society, 2 (19l)5), 280-5.

25 ishiwara published more than 20 papers for the journal during the period 1910-20. 2~ H. Yukawa, "On the Interaction of Elementary Particles', Proceedings of the Physico-Mathematical

SocieO, of Japan, 17 (1935), 48-57; idem, 'On a Possible Interpretation of the Penetrating Component of the Cosmic Ray', Proceedings ~[ the Physico-Mathematieal Society o f Japan, 19 (1937), 712-14; Yukawa and S. Sakata, 'The Mass and Life Time of the Mesotron', Proceedings (~fthe Physico-Mathematical Society of Japan, 21 (1939), 138-39.

27 Proceedings of Physico-Mathematical SocieO' of Japan, 4, (1922), i-ii. 28 Proceedings of Physico-Mathematical Society ~1" Japan, 12, (1930), i-iii. 29 Proceedings of Physico-Mathematical Society of Japan, 21, (1939), i-iii.

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transactions are quite similar to the above two cases: in most volumes, theoretical papers did not exceed one-fifth in number. The journal also had a separate section for the abstracts of physics papers published in Japan, which provided valuable information. The abstracts indicated not only the dominance of experimental over theoretical physics but also the rapid growth of the Japanese physics community between the two World Wars. For example, the number of physics papers published in 1923 was 26; in 1930, it rose to 126; in 1936, 271; and in 1938, 366. 3o It owes mostly to the growth of experimental physics rather than that of theoretical physics.

The last publication to be examined, Philosophical Magazine, confirms this dominance, too. During the period 1914-39, 55 Japanese physicists published 75 research papers (including several joint papers) in this prestigious journal. As expected, most papers were on experimental subjects, such as spectroscopy, the nature of several rays, electricity, or metallurgy. For example, 26 papers were printed during the 1920s, but only two papers, Yoshio Nishina's 'On the L-absorption Spectra of the Elements from Sn (50) to W (74) and their Relation to the Atomic Constitution', and Yoshikatsu Sugiura's 'Application of Schrrdinger 's Wave Functions to the Calculation of Transition Probabilities for the Principal Series of Sodium', were seriously theoretical in content. Nishina presented a series of experiments designed to obtain 'more accurate values of the energy levels free from the uncertainty involved in the interpolation and arising from the lack of uniformity of the measurement of different authors',3J and many pages were devoted to theoretical consideration of experimental data. Sugiura tried to 'calculate the transition probabilities for the principal series of the optical spectrum of sodium', which became possible owing to 'the recent development of quantum mechanics of Heisenberg and Schrrdinger ' , especially the latter's wave function. 32 It must be remembered that both Nishina and Sugiura were working in Niels Bohr 's institute at Copenhagen, the heart of quantum physics during the 1920s.

It is also noteworthy that many of the papers found in the Philosophical Magazine were produced by two select groups, Tokyo (Tokyo University, Riken, and other government organizations) and Sendai (Tohoku University), members from both of which presented nine papers each amongst a total of 26. The superiority of these two physics groups was also apparent in Japanese physics journals, and both were strongly inclined towards experimental physics. The Sendai group, for example, focused on metallurgy due to the influence of Honda. In fact, Tokyo and Sendai were two principal research centres until the early 1930s when Kyoto and Osaka emerged.

All the above analyses indicate one common point: the dominance of experimental over theoretical physics between the two World Wars. In short, the Japanese physics community did not respond effectively to the rapidly changing milieu of world physics community during the 1920s and even early 1930s. It is only after the mid-1930s that theoretical physics began to blossom with the advent of a new generation.

Then, why did this imbalance between experimental and theoretical physics last so long? Why was theoretical physics so unpopular among Japanese physicists regardless of their preference for mathematical physics? I strongly believe that the geographical

3~ Journal of Ph3sics: Abstracts, 2 (1923), t -12; 6 (1930), 1-32, 11 (1936), 1~56; 12 (1938), 1-88.

31 y . Nishina, 'On the L-absorption Spectra of the Elements from Sn (50) to W (74) and their Relation to the Atomic Conclusion' , Philosophical Magazine, 49 (1925), 521.

3ey. Sugiura, 'Application of Schr(~dinger's Wave Functions to the Calculation of Transition Probabilities for the Principal Series of Sodium', Philosophical Magazine, 4 (1927), 4 9 5 ~ .

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seclusion argument does not answer all these questions. The explanat ion for them must be found elsewhere, probably within the Japanese physics communi ty or univers i ty system.

First, let us check what physics meant to the Japanese. When modern science was sys temat ica l ly impor ted from the West in the mid-nineteenth century, it usual ly per ta ined to something measurable or something connected with an instrument, and its phi losophical background was often neglected. The fol lowing comment by Erwin Baelz, who taught at the Medica l School of Tokyo Univers i ty for 25 years, on Japanese atti tudes towards Western science is significant in this regard: 33

The Japanese people regard science as a kind of machine which year ly performs a prescr ibed amount of work and can easi ly be t ransferred to any place to have it kept working there. This is a mistake. The western scientific world is not a machine at all, but it is an organism, for the growth of which a certain c l imate and a tmosphere are necessary as is true with the case of all other organisms ...

... The western countries sent many teachers to you [Japanese], and with zeal did these teachers endeavor to t ransplant this spiri t [of the West] in Japan and to make it adopted by the Japanese people. However , their mission was often misunders tood. They were looked upon as traders o f scientific fruits who sell those fruits by the piece, al though they were to be and they themselves intended to be the cult ivators of the trees of science . . . . The Japanese people are content only with receiving the most recent deve lopments and do not care to learn the basic spirit which has y ie lded these results.

In this milieu, physics was regarded as a useful discipl ine for the educat ion of engineers and medical men as wel l for pract ical needs such as se ismology, metal lurgy, and electrici ty. 34 This pract ical aspect of physics was we lcomed by most Japanese who were eager to catch up with the West but ' v iewed basic science with indifference. '35 Therefore, it was natural that exper imenta l rather than theoret ical physics was popular amongst Japanese physicis ts . The es tabl ishment of Riken and its history also confirms this pract ical or ientat ion among Japanese physicists .

Second, the consol idat ion of Japan ' s own univers i ty sys tem also served to promote the dominance of exper imenta l physics. In the Japanese univers i ty system, a professor with a chair had an a lmost absolute power over the field, and jun ior professors and assistants were ass igned l i teral ly to assist him. 36 The career of a young scholar whol ly depended on his p rofessor ' s will, because chaired professors contro l led not only the money that the government or private companies suppl ied but also the academic appointments in universi t ies or other research institutes. This academic ' f euda l i sm ' was worsened often by favour i t i sm or fact ional ism, and somet imes marr iage- l inks worked when vacant posts were filled. 37 The physics communi ty was no except ion in this respect, a l though the tendency was rela t ively less visible. After the First Wor ld War, the power of the es tabl ished professors became more solid and the academic sys tem lost its vitality.

33 M. Watanabe, 'Science Across the Pacific: American-Japanese Scientific and Cultural Contacts in the Late Nineteenth Century', Japanese Studies in the Historv of Science, 9 (1970), 135.

34 For this utilitarian view, see S. Nakayama, Characteristics of Scientific Development of Japan (New Delhi, 1977), chapter 4, and Kamatani (footnote 15).

35 Bartholomew (footnote 13), 115. 36 Ibid., chapter 6. 37 Ibid., 168-76. Marriage links were common in medical faculties.

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It is also noteworthy that the es tabl ished professors often divided the subject -mat ters by themselves and made one or two fields their own domains , and that the students under a professor more often than not fo l lowed their mas t e r ' s path without hesitation. -~ Who control led the laboratory and its apparatus? To whom did senior students go to prepare their graduat ion theses? Who was the most powerful in depar tmental pol i t ics? Or who was the most influential when seeking jobs after graduat ion? The previous analysis of research papers in various physics journals provides clear answers to these questions: an es tabl ished exper imenta l physicis t in an imperia l university. Under these c i rcumstances , it was natural for young and less es tabl ished scholars to depend on the professor ' s choice of subjects for their research, and few dared to fl)llow their own interests without their p ro fessor ' s permission. As the first and second generat ions of Japanese physicis ts were most ly involved in exper imenta l or pract ical subjects, the next generat ion safely fo l lowed the way their predecessors had chosen.

The consol idat ion of physics depar tments in imperial universi t ies (Tokyo, Kyoto and Tohoku universi t ies) also nar rowed the choice for most younger physicists . As these universi t ies were regional ly and cultural ly different, they were very sensit ive about mainta ining the!r own identit ies. Moreover , the supremacy of Tokyo Univers i ty invited j ea lousy from the other two imperia l universi t ies , which accelerated the divis ion rather than the variety among the physics communi ty . Therefore, most universi t ies preferred their own graduates when filling vacant posts. N i sh ina ' s case i l lustrates that this kind of narrow mind worked too well. Even though he was the most wel l - t ra ined Japanese physic is t of his generat ion, producing work such as the K le in -Ni sh ina formula, Nishina, when he returned from Europe in 1928, found that 'no Japanese universi ty would give him a post as a physicist , s imply because he had graduated in electr ical engineering' .39

In this respect, Ishiwara was an except ional figure; he had introduced and deve loped both quantum and relat ivi ty theories before and during the First Wor ld War. 4~ As a d is t inguished graduate of Tokyo Universi ty, he spent two years in Europe and once worked under Einstein at Zurich Polytechnic Institute. When he returned from Europe in 1914, he was promoted to full professor at Tohoku Universi ty. Ishiwara publ ished about 40 research papers on relat ivi ty and quantum theories between 1909 and 1921 (all in German) , which were most ly submit ted to Proceedings o f the Tokyo Mathemat ico-Phys ica l Socieo,, but somet imes to Jahrbuch der Radioaktivitgit und Elektronik, Phvsikalisch ZeitschrOCt, or Annalen der Ph3'sik. 4t Alte r his res ignat ion in 1921 because of a love affair, he became a popular wri ter and publ ished many art icles and books about the new physics for the general public. I sh iwara ' s activit ies influenced the physicis ts of the next generat ion, such as Tomonaga . a: However , his authori ty was too l imited to change the map: first of all, he was in a minor posi t ion to do so as a professor of Tohoku Univers i ty , and his scholar ly life was too short to nurture the next generat ion. Meanwhi le , Nagaoka, as a professor of Tokyo Univers i ty for more than 30

SSR. W. Holne and M. Watanabc. 'Forming New Physics Communities: Australia and Japan. 1914-1950', Annal.s' qf Science, 47 (1990), 329-30. Watanabe indicates that the Japanese traditionally regarded knowledge as a private property 'to be passed on from a master to a chosen disciple rather than being subjected to open and critical examination'.

~ g . . .

E. Shlmao, 'Some Aspects ol Japanese Science, 1868-1945,' Annals of Science, 46 (1989), 89. 4o S. Hiraoka, 'lshiwara Jun" /in Japanese), Kagaku, 50 (1980), 768-74; S. Nisio, 'The Transmission

of Einstein's Work to Japan', Japanese Studies in the Histo O' of Science, 18 (1979), I-8. al For the full list of lshiwara's research papers during the 1910s. see Nisio (footnote 40), 4 5. 42 Ibid., 7.

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Theoretical Physics in Japan 393

years, was well-located to do so. Without the institutional setting, theoretical physics could not emerge.

Third, the Japanese did not show much enthusiasm lk)r sending their best students abroad to learn physics as before, and the influence of physicists who had recently been trained in Europe declined: no Nagaoka or Honda emerged during the 1920s. With its own universities and graduates schools, Japanese universities began to produce their own physicists. Moreover, study abroad did not seem to guarantee the job opportunities upon their returning home. Therefore, most physics students after graduation remained in the same university, and those who had a chance to go abroad spent only one or two years in German or British universities as guests, not as serious researchers.

In case of the Cavendish Laboratory at Cambridge, there were some Japanese physicists who had worked in this mecca of experimental physics during the first 20 years of the twentieth century. When the Cavendish Laboratory surveyed its former researchers, T. Noda reported that he worked in the Cavendish in 1906. 43 In 1916, M. ishino thanked J. J. Thomson 'for his many suggestions during the course of the investigation, and also for his kind permission to carry out this research at the Cavendish Laboratory' .44 In the annual photographs of the Cavendish Researchers, which has been taken every May or June since 1897, few Japanese physicists with short hair (Y. Ishida and T. Shimizu, in 1920, and Y. Nishina in 1922) can be lkmnd. However, after 1922 no Japanese appeared in the annual pictures whereas several Chinese physicists did. Rutherford's archives also confirms that there was little contact between the Cavendish Laboratory and Japanese physics community after the First World War: there was only one letter from Nagaoka dated 30 June 1919, in which he recommended T. Kikuchi to be admitted to the Cavendish, writing that 'Compared with a number of graduates of the Tokyo University, who entered your laboratory in Manchester, Kikuchi stands prominent in scientific ability, so that I have no doubt that he will become one of the leading Japanese physicists under your kind guidance'.45 It is interesting to point out that before and during the First World War, S. Oba, M. Ishino, and S. Kinoshita had worked under Rutherford at Manchester and the first two produced research papers for Philosophical . 46 Magazine. No such contact continued after the war even though Rutherford became the director of the Cavendish Laboratory in 1918. Even in experimental physics, the Japanese developed their own style of research from around 1920, stressing measurements and practical application.

In conclusion, it was apparent that, by the early 1930s, the Japanese physics community favoured experimental research. However, it was not peculiar only to Japan, for the situation was very similar in the USA during the lirst quarter of the century: it was only at the end of the 1920s that a group of theoretical physicists--E.U. Condon, I. I. RaN, J. R. Oppenheimer, and J. H. Van Vleck--succeeded in founding their centres in US universities. 47 In this respect, Japan was just five or six years behind the USA,

4~ j. j. Thomson et al.. A Histo13" (?]'the Cavemtish Laboralot3', 1871 1900 (London, 1910), 331. 44M. Ishino, 'On the Velocity of Secondary Cathode Rays Emitted by a Gas under the Action of

t iigh-Speed Cathode Rays', Philosophical Ma,~a~ine, 32 (1916), 222. 4, Cambridge University Library MSS. Add. 7653, N2. '6S. Oba, 'The Absorption of ,' Rays', Philosophical Maga=ine, 27 (1914), 601 7: M. lshino.

'The Scattering and the Absorption of the ,' Rays', Philosophical Maga=ine, 33 (1917), 129-46. For S. Kinoshita's contact with Rutherford, see Cambridge University Library MSS. Add. 7653, K42 (4 April 19m), 43 (4 February 1912), 44 (22 October 1914).

4/S �9 S. Schweber, "The Empiricist Temper Regnant: Theoretical Physics in the United States 1920-1950', Historical Studies in Physical and Biological Sciences, 17 (1986), 55-98.

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394 D o n g - W o n Kim

al though more than two generat ions behind Germany . One significant difference between the two is that most US theoret ical physicis ts had worked in major Gernlan universit ies, or at Bohr ' s institute at Copenhagen during the late 1920s or early 1930s, while their Japanese counterparts , Yukawa and Tomonaga , had no such exper iences when they began to study theoretical physics. 4s

3. The emergence of theoretical physics during the 1930s How then did theoret ical physics emerge in this exper imenta l ly or ientated Japanese

physics communi ty? Or, how could Yukawa, Tomonaga , and their small circle become the dr iv ing-force for the format ion of theoret ical physics groups in such unfr iendly c i rcumstances? And, why and how did this new generat ion appear in the 1930s? The answers to these quest ions are important in unders tanding not only the background to the dazzl ing success of these young Japanese physic is ts during the 1930s and 1940s but also the nature of the Japanese physics communi ty itself.

Four different e lements contr ibuted to both the emergence and the success of Japanese theoret ical physics groups during the 1930s: the success of quantum mech- anics and its spread in the West ; the dominance of exper imenta l physics and its effect on the univers i ty system; the cul tural /social influence; and the emergence of a research network. They often united their forces and therefore doubled or t r ipled the impact.

The success of true quantum mechanics during the late 1920s was quite remarkable . 49 W. Heisenberg, W. Pauli, P. A. M. Dirac, and E. Schr6dinger presented powerfu l but controvers ia l theoret ical tools which could be appl ied to the invest igat ion of the structure of the atom. Many physicis ts in Europe and the USA, whether they we lcomed this upheaval or not, were eager to s tudy these new theories and began to apply them to exper iments . Bohr ' s insti tute in Copenhagen and Max Born ' s G6tt ingen p layed an important role to nurture or exchange new ideas, while several laborator ies in Germany and the Cavendish were busy apply ing them to experiments . By 1930, when Heisenberg publ i shed his Physical Principles o f Quantum Theory, the new quantum mechanics had become es tabl ished in the minds of the Western physics communi ty .

There is no evidence that the Japanese physics communi ty immedia te ly responded to this rapid change in Europe. The analysis of research papers in physics journals during the per iod 1925-30 indicates that a lmost no theoret ical papers were devoted to the new quantum mechanics . As the previous section indicates, the journals were filled with very conservat ive subjects, most of which were ei ther exper imenta l or mathemat ica l . The Japanese physics communi ty , however , could not avert its eyes from the change in physics for long. It seemed quite certain that the future would belong to those who could ei ther apply the new theories to exper iments or improve upon them. From the early 1930s a few papers on the new quantum mechanics began to appear in Japanese physics

journals : for example , in 1931, T. Muto wrote on 'Note on the Photoelectr ic Effect by Relat ivis t ic Wave Equat ion o f Di rac ' , and, in 1932, T. Sakai publ ished 'On Di rac ' s New Relat ivis t ic Quantum Mechan ics ' .5o It was only after 1933 that the research papers on

4s Tomonaga spent two years (1937-39) under Heisenberg. However, his case is quite different from those of American theoretical physicists, for Tomonaga was already a competent theoretical physicist when he went to Germany. Yukawa first travelled to Europe in 1939 to attend the 8th Solvay Congress.

49A short but vivid narrative for the period is given by Emilio Segr6: From X-rays to Quarks." Modern Physicists and Their Discoveries (New York, 1980), chapter 8.

5o T. Muto, 'Note on the Photoelectric Effect by Relativistic Wave Equation of Dirac', Scientific Papers of the Institute of Physical and Chemical Research, 15 (1931), 111-26; T. Sakai, 'On Dirac's new Relativistic Quantum Mechanics', Proceedings of the Physico-Mathematical Society of Japan, 14 (1932), 355-62.

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Theoretical Physics in Japan 395

the new quantum mechanics and nuclear physics began to fill Japanese physics journals under the leadership of the theoretical group in Nishina's Laboratory.

The new quantum mechanics seemed not to be systematically taught or seriously discussed in Japanese universities during the late 1920s. 5~ Yukawa's autobiography, Tabibito (The Traveler), hints at the situation at that time. In 1926, during his first year in Kyoto University, Yukawa studied Born's Mechanics of the Atom by himself. In the next year 'I [Yukawa] spent all my spare time in the physics library. I had no use for the old books that filled the shelves but wanted to learn, as quickly as possible, the articles that concerned the new quantum theory, those that had been published in foreign, especially German, journals within the past two or three years .. . . Soon I decided to read Schr6dinger's own papers systematically, as they were the easiest to comprehend. '52 In the third year, Yukawa and Tomonaga together worked on the new quantum mechanics 'almost' without help or disturbance, and Yukawa wrote his thesis on Dirac's new electron theory. 53 Yukawa and the new generation literally taught themselves the new quantum mechanics. Yukawa's example illustrates that a few young Japanese recognized the changes in Europe and sensed that their future depended on it. When Heinsenberg and Dirac visited Japan in 1929, their lectures did not shock Yukawa but just gave 'a great stimulus' to him. 54 Similarly, when B. Arikatsu, Sugiura, and Nishina lectured on quantum mechanics between 1929 and 1931 at Kyoto, Yukawa and Tomonaga were not surprised. 55

The emergence of theoretical physics in Japan, therefore, was initiated by young, ambitious, self-taught, and unestablished physicists like Yukawa and Tomonaga: their subject was atomic physics and their weapon was the new quantum mechanics. Here, the second point, the dominance of experimental physic ironically contributed a great deal. First of all, the prevalence of experimental physics and the lack of both teaching staff and organization for theoretical physics freed these young theoreticians from their professors' vigilant eyes: professors of theoretical subjects (hydrodynamics, electro- magnetism, or even relativity theories) seldom paid attention to the new quantum mechanics. In fact, there were no powerful professors or schools in this area around the early 1930s, and Kyoto University was doubly fortunate not to have another Nagaoka. Even though it meant a lack of systematic training, it did more good than harm as a result: there were none to point to a specific direction; they neither worried about philosophical meanings of the new quantum mechanics nor became entrenched in debates about them, which divided the physics community in Europe; and they had a good chance to build their own field. Most established professors turned their eyes from newly emerging theories because their hands were full with experiments; or, they simply disliked it.

Again, Yukawa's memoir provides a good example. During his days in Kyoto University, no professor delivered any lectures on quantum mechanics or gave him advice to study the new theories. He and a small group of ambitious young men then were free to study what they wanted. In his third year, when he had to select a topic

51Yukawa (foomote 1), 35 6. 52H. Yukawa, Tabibito (The Traveler), translated by L. Brown and R. Yoshida (Singapore, 1982),

16061. 53 Ibid., 164~6. 54 Ibid., 171. 53 Ibid., ! 77.

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396 Dong-Won Kim

on which to write his graduation thesis, Yukawa first considered either spectroscopy or thermodynamics but soon realized that both fields required experimental skills that he did not possess. 56 So, he applied to Professor Kajuro Tamaki's laboratory and was admitted along with Tomonaga. Professor Tamaki was educated at Cambridge University and majored in hydrodynamics and relativity theory. As he had experienced the Cambridge style freedom of research, senior students under him enjoyed the privilege of selecting their own research topics, as Yukawa writes: 57

Naturally, there were people studying relativity theory, on which Tamaki had published many papers in his youth. However, the presence of some who studied the new quantum theory was unusual; they were Sotohiko Nishida and Shohei Tamura. Professor Tamaki had little interest in the new quantum theory, and probably he was perplexed by it; but he always respected the freedom of the people in his research room. As long as one did not step beyond the boundary of theoretical physics, there was no pressure, no matter what one studied. Even if after several years one's work did not bear fruit, that person was not dismissed. Everyone studied at his own pace.

This environment was quite unusual in Japan during those days when experimental physicists shared fields, money, and students. Only in this unique milieu could Yukawa and Tomonaga pursue the new quantum mechanics as they planned.

The unique freedom that both Yukawa and Tomonaga had enjoyed continued after their graduation in 1929. They were allowed to remain in Tamaki's laboratory as unsalaried assistants, and, therefore, were able to pursue what they wanted. In 1932, Tomonaga left Kyoto to join Nishina's laboratory at Riken, and Yukawa was appointed as the lecturer for quantum mechanics. Both now had posts from which they could influence the younger and ambitious students around them.

The third point, cultural/social influence, also played an important role for the emergence of theoretical physics during 1930s. For the Japanese, like other East Asian peoples, working with their brains alone had always been more highly regarded than working with hands. Confucianism, which had flourished under Tokugawa Shogum strengthened this attitude: the study of Confucian books along with martial arts became a major part of samurai education. It is noteworthy that most of the first and second generation of Japanese scientists came from these samurai families. 58 In this respect, it is interesting to examine how Japanese translated the words theory (theoretical) and experiment (experimental) into Chinese characters. 59 The word 'theory' was translated as ~ ( ~ , in which ~ means universal principle and ~ the debate or discussion. The word 'experiment', on the other hand, was translated as ~ , which means practical experience. Theretore, 'theoretical' physics is the subject to study the universal principles of nature, while 'experimental' physics is to experience or observe some natural phenomena. It is correct to translate the word 'theoretical' as ~ and 'experimental' as ~ ? Do these translations deliver the exact meaning of the words? Whether the answer is positive or negative, the imbalance between the two is clear. For more than 2000 years Chinese scholars considered studying and discussing the

5~, Ibid., 162-3. s7 Ibid., 164. 5~ Koizumi (fl)otnote 2), chapter 4. s9 In Chinese characters, there is no difference between theoretical (or experimental) and theory (or

experiment).

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Theoretical Physics in Japan 397

universal principles of nature as one of their main intellectual activities, and the Confucian school was the most influential. On the other hand, there had been no equivalent of the word 'experiment' in Chinese. Though some scholars had observed natural phenomena and kept very accurate records, such activities had been regarded as auxiliary ones. Therefore, it is possible that the first and second generation of physicists might have preferred theoretical to experimental physics. However, quite the opposite occurred. As the social pressures to modernize were so strong, traditional Confucian values did not work in the early years: until the outbreak of the First World War most Japanese leaders regarded 'Japanese' or 'Oriental' as backward.

It is only since the 1920s that Japanese and Oriental values began to regain their strength to balance Western ones, along with the rise of militarism and chauvinism. 6~ The embrace of relativity theories and the enthusiastic welcome of Einstein in 1922 could be understood with this cultural background. 6~ For the Japanese, Einstein symbolized the great scholar who had invented a new universal principle with his brain alone, like the great ancient Chinese scholars. Biographies of Einstein also emphasized the above image: most of them write in an exaggerated manner of how he had brought about an intellectual revolution with his brain and pencil in a Swiss patent office, and simply neglected the fact that he had been interested in experimental results and sometimes had been directly involved in experiments. His famous remark that the post of the lighthouse keeper in a remote place is good for a [theoretical] physicist became very popular among Japanese, because the image of physicist in seclusion was quite similar to that of legendary Oriental scholars. Here, traditional Oriental scholars found a new form in modern society--the theoretical physicist! The difficulty of relativity theory also contributed to the rising fame of Einstein because the Japanese had long been familiar with the non-commonsensical theories of great ancient scholars. As a result, Einstein and his theories attracted several talented young students to physics, and helped to change the image of physics.

The rise of Japanese industrial power after the First World War also changed the public attitude toward the physics community during the 1930s. As the Japanese physics community had served the nation well by providing enough manpower, Japanese society could then allow a few eccentrics, such as theoretical physicists, to exist who seemed to possess no practical value. The younger generation after the First World War did not feel any great urge to sacrifice themselves for the modernization of their country as their elders had. They now recognized themselves as legitimate members of the international physics community, regarded themselves as neither followers nor interpreters of Western thinkers but, rather, as competitors to them. For example, as a graduate student, Yukawa was ambitious enough to compete with Heisenberg, Pauli, and Fermi with two research plans 'to develop relativistic quantum mechanics one step further' and 'to apply quantum mechanics to the problems of the atomic nucleus'. ~2 Fermi disappointed him twice with the papers on hyperfine structure and on fl decay: in the latter case, 'I [Yukawa] think 1 must have grown pale as I read it. Had I been

6o See Yukawa, 'The Oriental Approach' (1948), in his Creativi O' and Intuition (footnote 1 ), 51-60. He confessed that he had been greatly influenced by Oriental philosophy, especially Taosirn, and emphasized that intuition, or Japanese kan, is as much useful as rational thinking in science.

oJ For Einstein 's visit to Japan and its impact, see T. Kaneko, 'Einstein 's View of Japanese Culture', Historia Scientiarum, 27 (1984), 51 76; and Kaneko, 'Einstein 's hnpact on Japanese Intellectuals', in The Comparative Reception o['Relativio', edited by T. F. Glick (Dordrecht, 1987 ), 351-79. For the transmission of Einstein 's work, see Nisio (footnote 40).

02 Yukawa (tootnote 52), 171.

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398 Dong-Won Kim

beaten by Fermi a second t ime? '63 Similarly T o m o n a g a ' s research programme of

e lementary particle physics was intended neither to interpret nor to repeat what Western

physicists had done but to achieve world-class fame. 64 Yukawa and Tomonaga might

have been exceptions but similar feelings were often shared by their generation,

especial ly those who pursued theoretical physics during the 1930s.

Who was the first Japanese physicist to achieve world-class fame? It was a

theoretical physicist, Yukawa, who received acclaim with his meson theory. It must be

emphasized that Yukawa ' s theory was not recognized in the West until 1937 when

S. H. Nedderrneyer and C. D. Anderson found a new charged particle with a mass of

about 200 electron masses in cosmic rays and Oppenheimer and R. Serber first

ment ioned Yukawa ' s name in their joint paper. 65 Within Japan, very few physicists

we lcomed his theory when he circulated his idea and first presented to a meeting of the

Physico-Mathemat ica l Society of Japan in 1934. 66 It was only alter 1937, when Western

physicists recognized him, that Yukawa became famous in Japan and attracted several

enthusiastic followers. He even became the first Japanese physicist to be invited to a

Solvay Congress (the 8th) in 1939. The recogni t ion from the West was important to

the Japanese scientific community . It s trengthened the position of newly emerging

theoretical physicists who would claim that they were working hard for the nation.

The success of Yukawa, however , might have become another one-off episode like

that of the work of Nagaoka or Ishiwara. Fortunately, Japanese physicists produced

several top-quali ty research papers on meson theory, nuclear and particle physics, and

cosmic rays during the 1930s and 1940s. The fourth element, the emergence of the

research network, played a pivotal role: Japanese physicists were no longer working

apart like their predecessors but formed an efficient research network to exchange

information among themselves. In this respect, the emergence of theoretical physics had

a profound influence on the Japanese physics community , changing the style of

Japanese physicists. I need not repeat what Yukawa, Tomonaga, Nishina, Kikuchi, and their fol lowers achieved during the period. 67

63 Ibid., 200. 64 For example, the following papers were published by Tomonaga in Scientific Papers of the Institute

of Physical and Chemical Research: Y. Nishina, S. Tomonaga and M. Kobayashi, "On the Creation of Positive and Negative Electrons by Heavy Charged Particles', 27 (19351, 137-78; Nishina, Tomonaga and H. Tamaki, 'A Note on the Interaction of the Neutron and the Proton', 30 (19361, 61-70; K. Umeda, Tomonaga and Y. Ono, 'Eine Bemerkung tiber die gegenseitigen potentiellen Energien zwischen zwei Deuteronen', 32 (19371, 87 96; Tomonaga and Umeda, 'Eine Bemerkung zum Austauschintegral', 32 (19371, 97-102; Tomonaga, 'Bemerkungen tiber die kinetische Kemenergic im Hartree-Fock-Modell', 32 (1937), 229-232; Tomonaga and Tamaki, 'On the Collision of a High Energy Neutrino with a Neutron', 33 (1937), 288-98; Tomonaga and Kobayashi, "Scattering and Splitting of Photons on the Non-linear Ficld Theory of Born and Infeld' 34 (1938), 1643-9. For the complete list of his works during the 1930s, scc T. Miyazima (ed.), Scientifie Papers of Tomonaga (Tokyo, 19711, I.

~,5 S. H. Neddermeyer and C. D. Anderson. 'Note on the Nature of Cosmic-Ray Particles', Physical Review, 51 ( 19371, 884-6; J. R. Oppenheimcr and R. Serber. 'Note on the Nature of Cosmic-Ray Particles', Physical Review, 51 (19371, 1113.

66 Yukawa (footnote 52), 203. 67 See K. Yoshinori, 'The Elementary Particle Theory Group', and T. Hirosige, 'Social Conditions for

Pre-War Japanese Research in Nuclear Physics' in Nakayama, Swain and Yagi (foomotc 161, 2112 20 and 221-52 respectively; Visvapriya Mukherji, 'A History of the Meson Theory of Nuclear Forces from 1935 to 1952', Archive for History ~fExact Science, 13 (1974), 27-102; Joseph L. Spradley, 'Particle Physics in prewar Japan', American Scientists 73 (19851, 563-9; Satio Hayakawa, 'The Development of Meson Physics in Japan', and Takehiko Takabayasi, "Some Characteristic Aspects of Early Elementary Particle Theory in Japan', in L. M. Brown and L. Hoddcson (cds), The Birth of Particle Physics: Based on a Fermilab Symposium (Cambridge, 1983), 82-107 and 294-303 respectively; and L. M. Brown, R. Kawabc, M. Konuma, and Z. Maki (eds), Elementary Particle Theory in Japan, 1935 1960: Japan-USA Collaboration, Second Phase (Kyoto, 19881.

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Theoretical Physics in Japan 399

The network was small in the beginning. In Kyoto and Osaka, Yukawa formed a small theoret ical group in which S. Sakata and M. Taketani were his major partners. Meanwhi le , Seishi Kikuchi , who transferred from the Nish ikawa Labora tory at Riken to Osaka Univers i ty in 1934, was busy operat ing the newly constructed cyclotron with H. Aoki , K. Husimi, Y. Watase , J. Itoh, and others. These two groups were very close and exchanged ideas with each other. For example , the Kikuchi group often expressed its thanks ' to Mr. H. Yukawa and Mr. S. Sakata of this laboratory for valuable d i scuss ion ' , 6s and Aoki employed Yukawa and Saka t a ' s calculat ion for ' the eff iciency of the search counter in the case of gamma- ray emi t ted f rom C u ' . 69 On the other hand, Yukawa and Sakata frequently used the Kikuchi g roup ' s exper imenta l data. v~ Y u k a w a ' s appoin tment to the professorship at Kyo to Univers i ty in 1939, therefore, did not mean the b reakdown of the group but the expans ion of it, because he had held a dual appoin tment as lecturer at both Osaka and Kyoto Universi ty for several years.

In Tokyo, Nishina t ransformed both his laboratory and Nuclear Research Labora tory in Riken into centres of nuclear and part ic le physics . Here research on cosmic rays was another major topic: S. Miyazaki , C. Ishii, R. Sagane, T. Takeuchi , and even Tomonaga once par t ic ipated in it. As Nishina was busy managing several research projects in Riken, Tomonaga became the ma jo r theoret ic ian in the Nishina group, along with H. Tamaki and M. Kobayas i . The job for these young theoret icians was ' to invest igate var ious phenomena involving the creat ion and annihi lat ion of pos i t rons ' in the beginning, 71 but this soon extended to quantum field theory and meson theory. Nishina and his theoretical group also t ranslated Di rac ' s work into Japanese in the summer of 1935, which proved to be no easy task but a great contr ibut ion for the later generat ion. 72

The crucial point is that these two groups, which were located in t radi t ional ly r ival regions (Kansai and Kanto), formed an efficient network. They visi ted each other, t ransferred f rom one group to the other, a t tended o ther ' s seminars, or created jo in t meet ings such as the 'meson c lub ' . 73 For example , Sakata and Kobayas i were the students who had at tended Yukawa ' s first classes. After graduat ing from Kyoto Univers i ty in 1933, Sakata moved to Riken to work with Tomonaga but Kobayas i remained in Kyoto. The lb l lowing year Sakata return to Osaka to jo in Yukawa while Kobayas i moved to Riken. Four years later, Kobayas i too returned to jo in Yukawa group. Al though Sakata and Kobayas i ' s stay in T o k y o was short and they were more product ive under Yukawa, it is noteworthy that they were able to write research papers with Tomonaga and Nishina. This kind o f human exchange was very unusual in the Japanese academic environment at that time.

6s S. K. Kikuchi, H. Aoki and K. Husimi, 'The Emission of the Electron from the Substances Traversed by Fast Neutrons', Proceedings of the Physico-Mathematical Society of Japan, 18 (1936), 744.

69 H. Aoki, 'Excitation of Gamma-Rays by Fast Neutrons', Proceedings of the Physico-Mathematical Society of Japan, 19 (1937), 376.

7~i H. Yukawa and S. Sakata, 'On the Theory of Collision of Neutrons with Deuterons', Proceedings of the Physico-Mathematical SocieO' of Japan, 19 (1937), 547: Yukawa and Sakata, 'On the Interaction of Elementary Particles II', Proceedings of the Physico-Mathematical Society of Japan, 19 (1937), 1090.

71 S. Tomonaga, 'Reminiscences', in Miyazima (footnote 64), H, 464. It was originally published as the Supplement of Progress of Theoretical Physics, extra number, dedicated to Professor Kobayashi on the occasion of his 60th birthday (Kyoto, 1968).

72 Ibid., 466-7. 73 For the details of the meson club, see L. M. Brown, M. Konuma and Z. Maki (eds), Particle Physics

in Japan, 1930-1950 (Koyto, 1980), l, 56~60.

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400 Dong-Won Kim

A few research papers published during the period also prove that the network was working. In his famous paper, "On the Interaction of Elementary Particle. l' (1935), where the theory of meson was first mentioned, Yukawa employed Tomonaga's calculation of 'the mass defect of H 2 and the probability of scattering of a neutron by a proton' and remarked that he 'owes much' to his former classmate. TM Kobayasi and T. Okayama thanked 'Dr. Nishina and Dr. Yukawa for encouragement and discussions' of their research on Yukawa' s heavy quanta (meson). 75 Taketani and Sakata concluded their paper on meson theory with 'their cordial thanks to Professor H. Yukawa, Dr. S. Tomonaga, and Mr. S. Kusaka and Mr. R. Sakata for encouragement and discussions' .76 The last example is Kobayasi and R. Utiyama's paper on the meson in which they thanked 'Dr. Y. Nishina and Professor H. Yukawa for their kind interest in this work. Moreover they are indebted to Dr. S. Tomonaga and Mr. Taketani for valuable advice' .77 It is noteworthy that the writers, mostly from the Osaka-Kyoto group, recognized their debts to Nishina and/or Tomonaga of the Tokyo group.

How did it happen? Among the many possible answers, 1 would emphasize two elements for the birth and expansion of this network: the role of Nishina and the meson theory. It was Nishina who was behind the success of the 1930s: the importance of Nishina in the history of Japanese physics has already been mentioned by several historians of science as well as by Japanese physicists. TM He was the driving-force behind the new quantum mechanics that the young theoretical physicists pursued eagerly. As Yukawa and Tomonaga lacked authority and experience in the early 1930s, Nishina's support was crucial for them: Tomonaga could continue his theoretical research in Nishina's Laboratory at Riken; it was Nishina who first recognized the importance of Yukawa's meson theory at the 1934 Osaka meeting. Moreover, his laboratory at Riken did not become his own domain but a forum for nuclear and elementary particle physicists, with major equipment and generous finance. The meson-club was initiated when Nishina 'invited the theoretical group of Osaka and had a discussion meeting on mesons' in November of 1937. 79 It was Nishina who enabled two distinct groups, the Tokyo and Osaka-Kyoto groups, to build a network. Although he himself was not so productive after his return from Europe, he made a great contribution to Japanese physics community, especially to theoretical physics.

Yukawa's meson theory also played an important role for the expansion of the network. Since the mid- 1930s, theoretical physics had attracted the most talented young men like Saka, Kobayasi and Taketani, and they concentrated on the meson theory and related subjects. As they had worked together and shared the same ethos with their young professors like Yukawa and Tomonaga, theoretical physics and particle physics was to spread rapidly from 1940 onwards, especially after 1945, when they became professors and trained the next generation. According to Yoshinori's statistics about participants in elementary particle physics in 1950, the number of those who graduated

74 H. Yukawa, 'On the Interaction of Elementary Particles. I', Proceedings of the Physico-Mathematical SocieO' of Japan, 17 (1935), 52.

75M. Kobayasi and T. Okayama, 'On the Creation and Annihilation of Heavy Quanta in Matter' , Proceedings of the Physico-Mathematical Society of Japan, 21 (1939), 13.

76M. Taketani and S. Sakata, 'On the Wave Equation of Meson ' , Proceedings of the Physico-mathemat- ical Society of Japan, 22 (194(l), 770.

77 M. Kobayasi and R. Utiyama, 'On the Interaction of Mesons with Radiation Fields' , Proceedings of the Physico-Mathematical Socie~' of Japan, 22 (1940), 898.

78 See Tomonaga, "Professor Nishina' (in Japanese) in T. Miyazima (footnote 64), II, 4 5 9 ~ 1 , which was originally published in Kagaku, 21 (1951), 211-2. See also Home and Watanabe (footnote 38), 336.

79 Brown, Konuma and Maki (footnote 73), 56.

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Theoretical Physics in Japan 401

from universi t ies belk)re 1930 was seven (e.g. Yukawa and Tomonaga) ; the number increased to 18 be tween 1930 and 1939 (e.g. Kobayas i , Sakata, Taketani); it became 41 between 1940 and 1945; and finally 71 between 1946 and 1949. This large increase proves how successful ly the network operated during tile last 15 years. 8~

It is interesting to see that Tokyo Univers i ty did not p lay an important role in this network. In Tokyo, Riken, with Nishina and Tomonaga , rather than Tokyo Univers i ty was a centre of the network. In fact, Tokyo Universi ty was too r igid to transform itself in response to the rapidly changing mil ieu outside as the fo l lowing recol lect ion indicates: ~t

When I was a student in the pre-war days, some of us students wanted to study part icle physics , but there was no professor in that field. The only one who was really related to it was Professor K. Ochiai , but we were all d iscouraged from doing such study, because of his remark that only geniuses can get into that field. We decided to organize ourselves and study and read p a p e r s . . .

... In the p re -war days, because we d idn ' t have any active part icle physics research inside the Universi ty of Tokyo, a few of us including Hayashi , went to listen to the Tomonaga-Nish ina seminars at Riken. I learned quite a bit about cosmic ray physics. Tomonaga and Nishina par t ic ipated in the same seminar. They would exchange ideas, and Tomonaga would discuss any letter he received at the time. For example , there were letters from Sakata in Nagoya ... Tomonaga reported on Saka ta ' s letter on the two-meson theory in the summer.

Even the bri l l iant successes of Yukawa and Tomonaga could not break the inflexibil i ty of Tokyo Universi ty . 82 Whi le the newly opened Osaka Univers i ty (1931) and the tradit ional rival Kyoto Univers i ty became centres o f the network, revolving around the new quantum theory, 83 in Tokyo Univers i ty it was ei ther ' s t rongly opposed by the older generat ion of professors ' or s imply put aside. 84 When the Kikuchi and Yukawa groups exchanged ideas in their informal lunch meet ing every day, there were none in Tokyo Universi ty. 85

By the end of the 1930s, theoretical physics was firmly rooted in the Japanese physics communi ty , and its growth cont inued even during the Second Wor ld War. The recogni t ion o f T o m o n a g a ' s work on quantum e lec t rodynamics by Oppenhe imer and J. Schwinger in 1948, 86 and the announcement of Y u k a w a ' s Nobel Prize in 1949 were the high points of theoret ical physics during the pos t -war period. As Japanese exper imenta l physic is ts had never received such recogni t ion from their Wes te rn counterparts , Yukawa and T o m o n a g a ' s success del ighted the Japanese who suffered total defeat after the Second Wor ld War. When Tomonaga rece ived the Nobel Prize in physics in 1965 along with R. P. Feynman and Schwinger , theoret ical physics had al ready flourished for two decades

8~ (footnote 67), 222-9. s~ Brown, Kawabe, Konuma and Maki lootnote 67), 3-4. This is Y. Nambu's recollection. See also

Brown, Konuma and Maki (footnote 73), 62-64 [T. Takabayasi's recollection]. s2 Nishina, Yukawa and Tomonaga were once lecturers at Tokyo University. 89 Yoshinori (footnote 67), 239. S4Brown, Konuma and Maki (footnote 73), 39. 85 L. M. Brown, M. Konuma, Z. Maki (eds), Particle Physics in Japan, 193~1950, (Kyoto, 1980). II,

42 3. s6 Julian Schwinger, 'Two Shakers of Physics: Memorial Lectures for Sin-itiro Tomonaga', in Brown

and Hoddeson (footnote 67), 345-75.

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402 Theoretical Physics in Japan

4. Conclusion In this article, it has been shown how theoretical physics emerged in Japan during

the 1930s, with the focus on the Japanese physics community rather than on a few individuals or on a specific group. I hope that this provides a framework to accommodate the details made by several historians of science. As Charles Rosenberg commented in his editorial essay in Isis, historians of science always confront the dilemma to see both 'woods and trees'.87 In the case of the history of Japanese physics, a focus on 'trees' rather than the 'woods' has prevailed lor a long time: particle physics and the meson theory were the two main topics in the history of Japanese physics.

The introduction of a sociological approach into history of science, however, begins to change the historiography of Japanese physics. 88 I believe that it will contribute to our understanding of the nature of Japanese physics community. However, it is the future job for the historians of science to find out how to maintain the balance between this newer mode and old ones.

8? Charles E. Rosenberg, 'Woods of Trees: Ideas and Actors in the History of Science', Isis, 79 (1988), 565 70.

8a For example, see Sharon Traweek, 'Big Science and Colonialistic Discourse: Building High-Energy Physics in Japan' , in Big Science: The Growth oflxlrge-Scale Research, edited by P. Galison and B. Hevly (Stanford, 1992), 100 28.

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