The Solution to the Mystery of Yukawa's "New Insight"

Previously I wrote the article [1] that can be summarized as follows:

According to his autobiography [2], Yukawa arrived at a crucial point in the development of his meson theory one night in October 1934 by getting a "new insight." It was about the relation between the effective range of the nuclear force and the mass of the new particle he was seeking. However, this contradicts the fact that he used this relation already in 1933. There are two possibilities to explain the contradiction: (1) Yukawa once thoroughly abandoned the idea in which he used the relation, so that he had to rediscover it. (2) The description in Ref. 2 is the change made by Hisao Sawano of the Asahi Shimbun Company, who helped the publication of the autobiography by editing Yukawa's manuscript. Both Yukawa and Sawano passed, and the mystery of the "new insight," i.e., which of the above two explanations was the case, cannot be solved easily.

Reading the autobiographical book* [3] written by Hideki Yukawa's wife, Sumi, I have found a clue to solve the above mystery. Sumi wrote about the days of their visit to Stockholm for Hideki's receiving Nobel Prize. On arriving at a hotel there, they found that many journalists were waiting to interview Hideki. Sumi writes as follows:

One of the questions addressed to him was this: "We hear that the Japanese people study sitting on their legs in a straw-matted room. Did you, Dr. Yukawa, write your paper sitting on your legs or sitting on a chair at the Western-style desk?" Hideki thought a little while and said, "I did in neither of those ways. I put my thoughts together at night in bed." This is true. Hideki wrote the paper that brought him Nobel Prize after he had kept thinking many nights at the age of 27 in the year of Shōwa 9 [Note by T.T.; 1934]. This story seems to have wrongly come across to Japan. Thus, in Japan they believe that the idea flashed to him in the middle of a night. [Translated by T.T. from Japanese.]

This passage by Sumi clearly denies the story in Ref. 2 of the "new insight" that came suddenly. Therefore, the possibility (2) given above should be regarded as the case.

Hideki Yukawa's own autobiography was translated into English, French and German. Therefore, the wrong version of the story modified by Sawano, "The crucial point came to me one night in October. … My new insight was …" has become famous world over. This is unfortunate. Sumi Yukawa's account quoted above should be informed widely.

Note

* The title Kuraku-no-Sono was taken from the street name in Nishinomiya City, where Hideki and Sumi Yukawa lived in the years shortly after their marriage. It has the meaning of "the garden (sono) of joys and sorrows (kuraku)."

References

1. The Mystery of Yukawa's "New Insight," Ted's Coffeehouse (February 27, 2010).
2. H. Yukawa, Tabibito (The Traveler), translated by L. Brown and R. Yoshida (World Scientific, 1982) p. 202.
3. S. Yukawa, Kuraku-no-Sono (Kōdansha, Tokyo, 1976) in Japanese.