Intensity and Anisotropy of Cosmic Rays

Abstract

These are my personal reminiscences. Since 1932, I was a student of Hokkaido University, Sapporo. Through frequent contact with Professor Ukichiro Nakaya (1900–60), I was charmed by many essays of his teacher Torahiko Terada (1878–1935) bearing his wonderful ability of finding many new fields in physics. Nakaya was working with Fumio Yamasaki operating a cloud chamber to study ion formation preceeding to spark discharge. It was suggested in 1929 by Terada after he and Nakaya worked since 1924 on the morphology of a spark to study the growth of an inanimate object (Sekido, 1981) which was pure but not yet a current problem of physics. In 1934, Nakaya let me read C.Bosch’s paper on Elekronenzahlrohr as an exercise before graduation telling me his interest in the growth of a discharge from only one pair of ions. I surveyed every available paper in which the Geiger counter was concerned and found unexpectedly the existence of cosmic ray physics. Nakaya’s favourite book, J.J.Thomson’s Conduction of Electricity through Gas (Fig.1), was also useful for knowing the beginning of cosmic ray physics. I tried to make a Geiger-Miuller counter to detect cosmic rays with batteries and Shimizu type fiber electroscope but could not succeed before it was interupted by the season of snow. In November, I visited Terada’s home at Tokyo wishing personal contact with him. Accidentally on the next day, a monthly meeting of the Physico-Mathematical Society was held, which was my first chance to peep at a scientific meeting. The chairman was the famous Dr. Nishina, but I did not know the lecturer. When the lecture was over, the chairman stood up and said, “It is a matter for congratulation that such an excellent work came out from a member of this Society”. He was Hideki Yukawa and the lecture was his first paper of mesotron theory.