(b. Iwate, Japan, 18 September 1856; d. Tokyo, Japan, 21 May 1952)
One of the most famous first-generation physicists in Japan. Tanakadate was born into a samurai family of the Nambu fief. His father, Inazo, was a teacher of the Jitsuyo school of military tactics, and his mother, Kisei, was from a family of Shinto priests. In preparation to succeed his father, Tanakadate began his education at the age of four, at age eight began training in swordsmanship, and at nine enrolled in a small private school to begin Chinese classical studies. In 1867 his life changed radically with the outbreak of the wars that ended the Tokugawa shogunate and led to the Meiji Restoration, which abolished the samurai and fiefs and set in motion the transformation of Japan to a modern state. Impoverished and no longer able to enjoy the privileges of the governing class, the Tanakadates moved to Tokyo in 1872, where the father sought to make a living as a merchant.
With Western nations increasingly encroaching on Japan, young Tanakadate realized that the survival of the country depended upon the Japanese gaining a knowledge of Western institutions and learning, and so in 1872, while continuing to study traditional Chinese and Japanese subjects privately, he entered Keio Gijuku, a private college in Tokyo, to study English. Soon financial pressures led him to prepare for entrance to a less expensive government school called Kobu Daigakko (school of engineering), which he did by studying such Western subjects as geometry and algebra on his own. When later he saw that the school’s catalogue said not one word about training students to govern the country (which he, as a Confucian-trained samurai, felt to be the true aim of education) but described only courses on such subjects as building bridges and lighthouses and putting up electrical wires, he was shocked and changed his mind about entering. He studied English from 1874 to 1876 at the Gaikokugo Gakko (school of foreign languages), and in 1876 he finally entered Tokyo Kaisei Gakko, which was later to become the Imperial University.
After two years of general education courses, he chose physics as his major for the concluding four-year specialization. Several factors seem to have influenced his decision. Since childhood his samurai education had been predicated upon the assumption that his ultimate role would be to govern, and even after the abolition of his class he believed his proper role was to become a government official and serve the country. Yet Japan lacked Western studies, and so to study science could serve the country. After his first two years of general education, Tanakadate began to believe that learning could be pursued for its own sake, and not merely as moral training, an idea foreign to Confucian thought. And he became convinced that in true learning one must start with the basics and build from there, and physics seemed to constitute the basis of Western science.
From 1878 to 1882 Tanakadate studied under Kenjiro Yamagawa, the first Japanese professor of physics at the university, as well as with two visiting foreign teachers, James Alfred Ewing, from Edinburgh, who had an appointment in mechanical engineering from 1878 to 1883, and Thomas Mendenhall, an American who from 1878 to 1881 had been the university’s very first professor of physics. Upon graduation in 1882 Tanakadate was made a lecturer, and in 1886, by which time the school had been renamed the Imperial University, he was made assistant professor of physics. The university sent Tanakadate abroad in 1888, and he went first to the University of Glasgow, with an introduction from Ewing, to study with William Thomson for two years. While there he published papers in English on such problems as the magnetization of soft iron bars and the thermal effects of magnetization reversals. In 1890 he went to Berlin for a year. He returned to Japan in July 1891 and was immediately promoted to full professor, a title he held until his retirement in 1916. In August 1891 he received the doctor of science degree from the Imperial University. He married Kiyoko Honjuku in 1893, but his wife died the next year due to complications arising from the birth of a daughter.
Tanakadate’s scientific activity centered on four subjects: electricity and magnetism, geophysics, aeronautics, and weights and measures. He was introduced to the subject of electricity and magnetism through Ewing, who was interested in hysteresis. He got Tanakadate and others involved in the experimental investigation of this phenomenon. Mendenhall, who introduced Tanakadate to geophysics, did not limit his laboratory experiments to mere repetition of known experiments but took his students out into the city and countryside to measure, for instance, the force of gravity in Tokyo and at the top of Mt. Fuji to determine the density of the earth. After Mendenhall’s departure Tanakadate became the person responsible for making such measurements at different locations in Japan. Geomagnetic measurement techniques were also studied by the Mendenhall group early on, but in 1887 Tanakadate, Cargill Knott, who was Ewing’s replacement, and their students undertook an extensive geomagnetic measurement project of Japan as a whole. The Nobi earthquake of 1891 brought him a renewed interest in geomagnetism. Preliminary investigation indicated a difference between the 1887 and 1891 measurements, showing that earthquakes change the geomagnetism of an area, and in 1893 Tanakadate organized a four-year expedition sponsored by the university to make new geomagnetic measurements throughout Japan. His interest in geomagnetism gradually was replaced by aeronautics and weights and measures. His contributions in these areas were mostly governmental and administrative, but continued until well after World War II.
Although Tanakadate justified to himself his work in physics by Confucian arguments, he never confined himself inside a Confucian worldview. He saw in experimental physics something that should be pursued in its own right. He further questioned the simplistic dichotomy that was then frequently drawn between so-called Eastern spirituality and Western materialism. To Tanakadate, who traveled abroad more than twenty times during his active years, mostly on scientific missions or to international conferences, physics was his passport. The Japanese government awarded him the Bunka Kunsho (Order of Culture) in 1944 for his contribution to the modernization of Japan.
I. Original Works. “A Magnetic Survey of Japan, Carried Out by Order of the President of the Imperial University,” in Journal of the College of Science, Imperial University of Tokyo, 2 (1888), 163–262, written with C. Knott; “Mean Intensity of Magnetization of Soft Iron Bars of Various Lengths in a Uniform Magnetic Field,” in Philosophical Magazine, 5th ser. 26 (1888), 450–456; “The Thermal Effect Due to Reversals of Magnetization in Soft Iron,” ibid., 5th ser. 27 (1889), 207–218; “The Disturbance of Isomagnetics Attending the Mino-Owari Earthquake of 1891,” in Journal of the College of Science, Imperial University of Tokyo, 5 (1892), 149–192, written with H. Nagaoka.
Tanakadate’s papers are deposited at the National Science Museum in Tokyo.
II. Secondary Literature. Kenkichiro Koizumi, “The Emergence of Japan’s First Physicists: 1868–1900,” in Historical Studies in the Physical Sciences, 6 (1975), 72–81; Seiji Nakamura, Tanakadate Aikitsu sensei (Tokyo, 1946), which contains a list of Tanakadate’s scientific papers; Shigeru Nakayama, “Shushin saika jikoku heitenka to kagaku—Tanakadate Aikitsu o chushin to shite,” in Butsurigakushi kenkyu, 2 (1963), 155–168.