The Mystery of Yukawa's "New Insight"

Please read the revised version instead of this article:
The Mystery of Yukawa's "New Insight" (Revised).

Read in Japanese.
(The Japanese version has not yet been revised.)

The crucial point in the development of Hideki Yukawa's meson theory came to him one night in October 1934. He writes in his autobiography Tabibito [1] as follows:

My new insight was the realization that this distance [the effective range of the nuclear force] and the mass of the new particle that I was seeking are inversely related to each other. Why had I not noticed that before?

This passage contradicts the fact that Yukawa used the above relation already in 1933. Namely, in April that year he made his first oral presentation at a meeting of an academic society. It was entitled "A consideration about the problem of electrons within nuclei," and the meeting was the one held in Sendai by Physico-Mathematical Society of Japan. The abstract of the presentation includes the following sentence [2]:

From the fact that the electron has the rest mass, we consider that the strength of the interaction decreases rapidly as the distance between the neutron and the proton becomes large compared with h/(2πmc).

In the work of the above presentation, Yukawa treated the possibility that the electron might be the mediator of the nuclear force between the neutron and the proton. This hypothesis included difficulties related to the spin and statistics of the electron. Therefore, Yukawa totally abandoned the hypothesis later together with the relation of the distance and the mass of the particle that would mediate the nuclear force [3]. Did this abandonment make it necessary for Yukawa to rediscover the relation? If so, this explains the contradictory remark of his "new insight."

We find another possible explanation of the contradictory description in the process of the making of Yukawa's autobiography. Hisao Sawano of the Asahi Shimbun Company helped the publication by editing Yukawa's manuscript [4]. If Sawano's editing had been to such an extent as to change Yukawa's original version into more dramatic one here and there, the passage that began with "My new insight" might have been Sawano's creation. To eliminate the expression different from the fact, Yukawa, perhaps, regularly checked the changes made by Sawano. However, Yukawa finished writing the last section related to the discovery of the meson theory just a few hours before his trip to Europe [5]. Thus, it is quite possible that Yukawa did not check Sawano's modification of that section.

Both Yukawa and Sawano are now in heaven, and the mystery of the "new insight," i.e., which of the above two explanations was the case, cannot be solved easily.

(This article owes much to the discussion we have had at Osaka Science Museum among the members of "Citizens' Study Group on Hideki Yukawa.")

Read the continuation of this article: The Solution to the Mystery of Yukawa's "New Insight"

1. H. Yukawa, Tabibito (The Traveler), translated by L. Brown and R. Yoshida (World Scientific, 1982) p. 202.
2. H. Yukawa, Sūbutu-gakkaisi, Vol. 7, No. 2 (1933) quoted in Nihon-no Buturigaku-shi (History of Physics in Japan) (Tokai University Press, 1978) p. 319 (in Japanese; English translation of the quoted passage by the present author).
3. M. Kawabe and M. Konuma, Butsuri Vol. 37, p. 265 (1982) (in Japanese).
4. H. Yukawa, Atogaki (Afterwords) in Tabibito, (Kadokawa, 1960) (in Japanese).
5. H. Yukawa, Hon-no Naka-no Sekai (The World in Books) (Iwanami, 1963) p. 182 (in Japanese).

Effects of Chinese Classic Literature on H. Yukawa's Work

The following is the outline of my talk to be delivered at Himeji Kyoyukai meeting on February 18, 2010, in Himeji.

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The Nobel-winning physicist Hideki Yukawa developed the theory of elementary domains for particle physics together with his coworkers in his later years [1, 2]. In the preface of a book [3], he writes that the important factor that led him to the idea of this theory was the words of the Chinese poet Li Po (701­­–762), "Heaven and Earth are hotels for everything, and days and nights are travelers of hundreds of generations." He also writes that scientific research and literature are not separate things for him.

Yukawa also writes in a textbook on particle physics [4] that Li Po's words mentioned above was one of the motivations that brought his unconscious idea about the elementary domains to his consciousness. While being rather lengthy for introducing the concept of the elementary domains in a textbook, the paragraphs including the above words are considered the valuable record of Yukawa's processes of thinking.

In his lecture on experimental nuclear physics, Kiichi Kimura, a classmate of Yukawa's at Kyoto University, told us that some words in the Taoist book Zhuangzi might have been a hint on Yukawa's meson theory that brought him the Nobel Prize. I do not remember the words Kimura quoted from Zhuangzi. In his 1961 essay [5] on Zhuangzi, however, Yukawa writes that he had read Taoist books Zhuangzi and Laozi in his middle school days, but was forgetting philosophical thoughts in them for many years after that. This means: When he was thinking about meson theory, Yukawa was forgetting Zhuangzi. Thus, the words of Zhuangzi Kimura mentioned had not been a direct hint, at least, on the idea of the meson.

It was reported [6] that the meson theory had been motivated by the occasion of the childbirth of Yukawa's wife. Namely, the judo expert Sachio Ashida remembered to have been told in a commuting tramcar by Yukawa, "A baby can exert an attractive force between the parents. There may be a similar existence in the nucleus." I suppose that this was Yukawa's jocular explanation of his idea for the layperson. Yukawa should have gotten the idea of the meson from the study of earlier papers by Werner Heisenberg and Enrico Fermi together with the analogy of the electromagnetic field mediated by the photon. Note here that he used a good analogy.

In his essay mentioned above [5], Yukawa writes that he reminded himself of an allegory in Zhuangzi when he was thinking about something at a deeper level than "elementary particles," which amounted to more than 30 kinds those days. The allegory was about the king who lacked all the seven holes in the face, i.e., ears, eyes, nostrils and a mouth, and was named Chaos ("Konton" in Japanese). The underdeveloped state of the king was appropriate for Yukawa to express his idea of something at a deeper level.

Yukawa also liked the following words from Zhuangzi: "On the basis of the beauty of Heaven and Earth, we arrive at the reason of everything." He made these words in Chinese characters use as a watermark of the invitation letter for "International Meeting on Elementary Particles: The Thirtieth Anniversary of the Meson Theory" [7].

To develop a new theory in the field of particle physics, it is necessary to have good mathematical skill of formulating equations to express a physical model, as well as strong imaginative power to think of a new model. One of the important device with which Yukawa cultivated the latter ability should have been Chinese classic literature, which includes a lot of allegories and helps one to develop thinking by the use of an analogy. Thus his reading of Chinese classic literatures in his young days was useful not only directly for the idea of elementary domains, but, quite possibly, also indirectly for the idea of the meson.

(This article owes much to the discussion we have had at Osaka Science Museum among the members of "Citizens' Study Group on Hideki Yukawa.")

References

1. Y. Katayama and H. Yukawa, "Field Theory of Elementary Domains and Particles. I" Progress of Theoretical Physics Supplement No. 41, p. 1 (1968).
2. Y. Katayama, I. Umemura and H. Yukawa, "Field Theory of Elementary Domains and Particles. II" ibid. p. 22 (1968).
3. H. Yukawa, Auto-selection of Hideki Yukawa's Essays Vol. 5 (Asahi-shimbun, Tokyo, 1971) [in Japanese].
4. H. Yukawa, Unified Theories of Particles, in Iwanami Lectures: Foundations of Modern Physics, Vol. 11, H. Yukawa and Y. Katayama, ed., p. 563 (Iwanami, Tokyo, 1974) [in Japanese].
5. H. Yukawa, Zhuangzi, in Auto-selection of Hideki Yukawa's Essays Vol. 3, p. 363 (Asahi-shimbun, Tokyo, 1971) [in Japanese].
6. Personal connections in Japan: The spirit of Judo (8), Asahi-shimbun, Evening issue (May 25, 2006) [in Japanese].
7. The 30th anniversary of Meson theory (1), Asahi-shimbun (September 20, 1965) [in Japanese].

Hideki Matsui Won MVP

The New York Yankees won the 27th World Series title on Wednesday, November 4, 2009. The designated hitter Hideki Matsui (35 years old), drove in six of the Yankee's seven runs in their series-winning victory. He hit .615 with three home runs and eight RBIs in the series, and became the first Japanese-born World Series Most Valuable player. Matui was reported to have said, "Winning the championship is such a great feeling. I guess you can say that this is the best moment of my life right now."

In the summer of 1992, Matsui, as the fourth batter of Seiryo Senior High School team drew five intentional walks in a game at Koshien Stadium. It was the very uncommon strategy of the opposite team not to make him hit home runs and to win cunningly. I watched that game on TV and impressed by Matsui, who did not show any look of embarrassment or angriness and coolly walked to the first base each time. Such a broad mind of Matsui and his continued effort, I believe, has brought him this best moment of his life. I am especially proud of him because I was born in the same prefecture of Ishikawa as he.

Nobel Peace Prize for Words?

President Barack Obama has been chosen to be the recipient of the 2009 Nobel Peace Prize for "his extraordinary efforts to strengthen international diplomacy and cooperation between peoples" [1]. The press release of the Norwegian Nobel Committee says, "The Committee has attached special importance to Obama's vision of and work for a world without nuclear weapons."

In the preface of my book just printed (see the previous article at this blog site), I wrote, "For the realization of this [eternal peace all over the world], we should attach importance to the following words, the sources of which you might guess easily." Then I quoted Article 9 of the Constitution of Japan and Obama's Prague speech on nuclear weapons delivered on April 5, 2009.

On hearing the news of the Peace Prize yesterday evening, however, I wondered if the awarding to Obama was too early because there has been no fruit of his words yet. The New York Times reported the news of the Prize under the title "Surprise Nobel for Obama stirs praise and doubts" [2].

Questions about the earliness of awarding Obama was also raised during the Prize announcement. In answer to them, Norwegian Nobel Committee President Thorbjørn Jagland replied that the Committee wanted to demonstrate its support for the approaches Obama is taking towards global problems [3].

Today I got an e-mail message from the not-for-profit global campaigning organization Avaaz.org, which requested signing the petition for pressing Obama to turn hope into action [4]. They write, "Only by following through with courageous, transformative action for peace can Obama fulfill his promise – and only then will history judge that this Nobel Peace Prize is truly deserved." I completely agree with them and signed the petition.

1. The Nobel Peace Prize for 2009, Nobelprize.org (October 9, 2009).
2. Surprise Nobel for Obama stirs praise and doubts, New York Times (October 10, 2009).
3. Time for Hope, Speed Read page for Nobel Peace Prize 2009 (October 9, 2009).
4. Obama for peace: Turn hope into action

My First Book

The above image shows the cover of my first nonacademic book made at my own expense. In a small number of academic books included in my list of publications, I made partial contributions only. Therefore, this can also be said to be "my" first book." It is entitled "Passage through Spacetime: Random Writings of a Physicist" (Jupiter Corporation, Tokyo, 2009), and is written in English. A friend of mine from Dalian Reizen Elementary School, Takashi Oshio, coordinated the publication for me.

The contents are as follows:

Preface
Part I. Hello Mr. Feynman!
　1. What Little I Know about Feynman
　2. We See Feynman Everywhere
Part II. Book Reviews
　Fiction
　Biography
　Essays
　Religion and Philosophy
　Cosmology
　Life Science
　Mathematics
　Physics
Part III. Vicky: A Novella
　Sorekara and Sanshiro
　Write to You instead of Sam
　Just a "Good-bye"
　Reunions
　The New Year Card
　Stupid Idea?
Index

All the writings contained have been on my Web site for many years, and polishing has been made on this occasion.

The book is not for sale but will be distributed to my friends and acquaintances. Internet friends of mine are welcomed to request a copy by writing their postal address to my e-mail address, which is shown on the top bar of this site.