Tanakadate Aikitsu

Physicist. Born in Fukuoka, Ninohe County, Mutsu Province (Ninohe City, Iwate Prefecture). His family had served as military instructors for the Nanbu Domain for generations. He studied Japanese and Chinese at the domain school, and in 1872 (Meiji 5), following his father Inazo's educational policy, he moved his family to Tokyo. He studied English at Keio University and the Foreign Language School, and from the preparatory school of Tokyo Kaisei School, he entered the Faculty of Science at the University of Tokyo in 1878, where he studied under Kikuchi Dairoku, Yamakawa Kenjiro (1854-1931), and foreign teachers Ewing and Mendenhall. Under the guidance of foreign teachers, he worked on measuring gravity and geomagnetic fields, and after Edison invented the phonograph, he immediately built a prototype and analyzed sound and vibration. This marked the beginning of his interest in romaji, and he later became a leader in the romaji movement. Upon graduation in 1882, he became an associate professor, and in 1883, an assistant professor. In 1887, he was in charge of measuring the geomagnetic field in the southern half of Japan and the southern part of the Korean Peninsula during the nationwide geomagnetic survey. In 1888, he studied at the University of Glasgow in England, where he studied under Kelvin, and then transferred to the University of Berlin. In 1891, he returned to Japan and became a professor at the Faculty of Science of the Imperial University of Tokyo (now the Faculty of Science of the University of Tokyo). In October of that year, he investigated the epicenter of the Nobi earthquake, and introduced the Neodani fault in Gifu Prefecture to the world, which caused a great stir. He took this opportunity to propose earthquake prevention measures to the Diet, and the following year, in 1892, when the Earthquake Disaster Prevention Research Committee was established in the Ministry of Education, he played an active role as a committee member. He led Kimura Hisashi and others to establish a latitude observatory in Mizusawa, Iwate Prefecture (now the Mizusawa VLBI Observatory of the National Astronomical Observatory), and contributed to the establishment of geophysics in Japan. He retired from the government on the occasion of his 60th birthday in 1917 (Taisho 6), and became a pioneer of the later mandatory retirement system. He also conducted pioneering research into aerodynamics, and held important positions including chairman of the Aeronautics Research Committee of the Imperial University of Tokyo, member of the Imperial Academy, member of the Academic Research Council, and member of the House of Peers, where he contributed to the promotion of science and technology and was actively involved in international scientific exchange. He also devoted himself to popularizing and educating the public about science by giving lectures to the general public, and in 1907 (Meiji 40) he became the first Japanese member of the International Committee for Weights and Measures, working to popularize the metric system. As a leader in the field of physics in Japan, he contributed to its establishment, and in 1944 (Showa 19) he was awarded the Order of Culture. In addition to his numerous papers, he also published a collection of essays titled Kudzu Root (1936).

[Satoshi Ihara]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

物理学者。陸奥国(むつのくに)二戸(にのへ)郡福岡（岩手県二戸市）生まれ。家は代々南部藩兵法師範を勤めた。藩校で和漢学を修め、1872年（明治5）父稲蔵の教育方針により一家をあげて上京。慶応義塾、外国語学校で英語を学び、東京開成学校大学予科から、1878年東京大学理学部に入学、菊池大麓(だいろく)、山川健次郎（1854―1931）、お雇い外人教師ユーイング、メンデンホールらに学んだ。外人教師の指導の下に重力測定、地磁気測定に取り組み、またエジソンのフォノグラフ発明後、ただちにその試作を行い、音響や振動の解析を手がけた。これがローマ字への関心の端緒となり、のちにローマ字運動の指導者ともなった。1882年卒業とともに準助教授、1883年助教授。1887年全国地磁気測定では日本の南半、朝鮮半島南部の測定を担当した。1888年イギリス、グラスゴー大学に留学、ケルビンに師事し、ついでベルリン大学に転じ、1891年帰国し帝国大学理科大学（現、東京大学理学部）教授となった。この年10月の濃尾地震(のうびじしん)では震源地調査を行い、岐阜県根尾谷(ねおだに)の大断層を世界に紹介し大きな話題をよんだ。これを機に地震の予防策を議会に建議し、翌1892年文部省に震災予防調査会が設置されると委員として活躍。木村栄(ひさし)らを指導して岩手県水沢に緯度観測所（現、国立天文台水沢VLBI観測所）を設立するなど、日本の地球物理学の確立に尽くした。1917年（大正6）還暦を機に退官、その後の定年制の先駆となった。航空力学の開拓的研究もあり、東京帝国大学航空学調査委員長、帝国学士院会員、学術研究会議委員、貴族院議員など要職にあって、科学・技術の振興に尽くすとともに、国際的な科学の交流に精力的に取り組んだ。一方、科学の普及・啓蒙(けいもう)のため通俗講演に力を注ぎ、さらに1907年（明治40）日本人初の国際度量衡委員会委員に就任、メートル法の普及にも努めた。日本物理学界の指導者としてその確立に貢献し、1944年（昭和19）文化勲章を受けた。多数の論文のほか、随筆集『葛の根(くずのね)』（1936）がある。

［井原　聰］

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