was a Japanese

physicist A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate cau ...

and a pioneer of Japanese

physics Physics is the scientific study of matter, its Elementary particle, fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge whi ...

during the

Meiji period The was an era of Japanese history that extended from October 23, 1868, to July 30, 1912. The Meiji era was the first half of the Empire of Japan, when the Japanese people moved from being an isolated feudal society at risk of colonizatio ...

Life

Nagaoka was born in Nagasaki, Japan on August 19, 1865 and educated at the

University of Tokyo The University of Tokyo (, abbreviated as in Japanese and UTokyo in English) is a public research university in Bunkyō, Tokyo, Japan. Founded in 1877 as the nation's first modern university by the merger of several pre-westernisation era ins ...

. After graduating with a degree in physics in 1887, Nagaoka worked with a visiting Scottish physicist, Cargill Gilston Knott, on early problems in magnetism, namely

magnetostriction Magnetostriction is a property of magnetic materials that causes them to change their shape or dimensions during the process of magnetization. The variation of materials' magnetization due to the applied magnetic field changes the magnetostrictive ...

in liquid nickel. In 1893, Nagaoka traveled to Europe, where he continued his education at the universities of Berlin, Munich, and Vienna, including courses on Saturn's rings and a course with

Ludwig Boltzmann Ludwig Eduard Boltzmann ( ; ; 20 February 1844 – 5 September 1906) was an Austrian mathematician and Theoretical physics, theoretical physicist. His greatest achievements were the development of statistical mechanics and the statistical ex ...

on his Kinetic Theory of Gases, two influences which would be reflected in Nagaoka's later work. Nagaoka also attended, in 1900, the first International Congress of Physics in Paris, where he heard

Marie Curie Maria Salomea Skłodowska-Curie (; ; 7 November 1867 – 4 July 1934), known simply as Marie Curie ( ; ), was a Polish and naturalised-French physicist and chemist who conducted pioneering research on radioactivity. She was List of female ...

lecture on radioactivity, an event that aroused Nagaoka's interest in atomic physics. Nagaoka returned to Japan in 1901 and served as professor of physics at

Tokyo University The University of Tokyo (, abbreviated as in Japanese and UTokyo in English) is a public research university in Bunkyō, Tokyo, Japan. Founded in 1877 as the nation's first modern university by the merger of several pre-westernisation era ins ...

until 1925. After his retirement from Tokyo University, Nagaoka was appointed a head scientist at

RIKEN is a national scientific research institute in Japan. Founded in 1917, it now has about 3,000 scientists on seven campuses across Japan, including the main site at Wakō, Saitama, Wakō, Saitama Prefecture, on the outskirts of Tokyo. Riken is a ...

, and also served as the first president of

Osaka University The , abbreviated as UOsaka or , is a List of national universities in Japan, national research university in Osaka, Japan. The university traces its roots back to Edo period, Edo-era institutions Tekijuku (1838) and Kaitokudō, Kaitokudo (1724), ...

, from 1931 to 1934. His granddaughter was pianist Nagaoka Nobuko.

Saturnian model of the atom

By 1900 physicists had begun to consider new models for the structure of the atom. The recent discovery by J. J. Thomson of the negatively charged

electron The electron (, or in nuclear reactions) is a subatomic particle with a negative one elementary charge, elementary electric charge. It is a fundamental particle that comprises the ordinary matter that makes up the universe, along with up qua ...

implied that a neutral atom must also contain an opposite positive charge. In 1904, Thomson suggested that the atom was a sphere of uniform positive electrification, with electrons scattered through it like plums in a pudding, giving rise to the term

plum pudding model The plum pudding model is an obsolete scientific model of the atom. It was first proposed by J. J. Thomson in 1904 following his discovery of the electron in 1897, and was rendered obsolete by Ernest Rutherford's discovery of the atomic nucleus i ...

. Nagaoka rejected Thomson's model on the grounds that opposite charges are impenetrable. In 1904, Nagaoka proposed an alternative planetary model of the

atom Atoms are the basic particles of the chemical elements. An atom consists of a atomic nucleus, nucleus of protons and generally neutrons, surrounded by an electromagnetically bound swarm of electrons. The chemical elements are distinguished fr ...

in which a positively charged center is surrounded by a number of revolving electrons, in the manner of Saturn and its rings. Nagaoka's model featured: * a very massive atomic center (in analogy to a very massive planet) * thousands of electrons revolving around the nucleus, bound by electrostatic forces (in analogy to the rings revolving around Saturn, bound by gravitational forces). For his model to be stable, Nagaoka showed that the central charge had to be 10,000 times the charge on the electron.Helge Kragh (Oct. 2010)
Before Bohr: Theories of atomic structure 1850-1913
RePoSS: Research Publications on Science Studies 10. Aarhus: Centre for Science Studies, University of Aarhus. Based on his model, Nagaoka suggested that radioactive

beta decay In nuclear physics, beta decay (β-decay) is a type of radioactive decay in which an atomic nucleus emits a beta particle (fast energetic electron or positron), transforming into an isobar of that nuclide. For example, beta decay of a neutron ...

resulted from instability in the electron orbits. However this explanation did not account for important aspects of radioactivity such as its random nature and the high energy of alpha particle emission. He also suggested that the model would explain atomic spectra and chemical properties.

Ernest Rutherford Ernest Rutherford, 1st Baron Rutherford of Nelson (30 August 1871 – 19 October 1937) was a New Zealand physicist who was a pioneering researcher in both Atomic physics, atomic and nuclear physics. He has been described as "the father of nu ...

mentions Nagaoka's model in his 1911 paper in which the

atomic nucleus The atomic nucleus is the small, dense region consisting of protons and neutrons at the center of an atom, discovered in 1911 by Ernest Rutherford at the Department_of_Physics_and_Astronomy,_University_of_Manchester , University of Manchester ...

is proposed. However Nagaoka's work probably did not influence Rutherford's proposal. Nagaoka's model was widely discussed by prominent scientists of the day, but a detailed study by George Schott showed the model could not correctly predict atomic spectra. Nagaoka himself abandoned his proposed model in 1908. Rutherford and

Niels Bohr Niels Henrik David Bohr (, ; ; 7 October 1885 – 18 November 1962) was a Danish theoretical physicist who made foundational contributions to understanding atomic structure and old quantum theory, quantum theory, for which he received the No ...

would present the more viable

Bohr model In atomic physics, the Bohr model or Rutherford–Bohr model was a model of the atom that incorporated some early quantum concepts. Developed from 1911 to 1918 by Niels Bohr and building on Ernest Rutherford's nuclear Rutherford model, model, i ...

in 1913.

Other works

Nagaoka later did research in

spectroscopy Spectroscopy is the field of study that measures and interprets electromagnetic spectra. In narrower contexts, spectroscopy is the precise study of color as generalized from visible light to all bands of the electromagnetic spectrum. Spectro ...

and other fields. In 1909, he published a paper on the

inductance Inductance is the tendency of an electrical conductor to oppose a change in the electric current flowing through it. The electric current produces a magnetic field around the conductor. The magnetic field strength depends on the magnitude of the ...

solenoid upright=1.20, An illustration of a solenoid upright=1.20, Magnetic field created by a seven-loop solenoid (cross-sectional view) described using field lines A solenoid () is a type of electromagnet formed by a helix, helical coil of wire whos ...

s. In 1924, he achieved the first successful synthesis of gold, produced from mercury by neutron bombardment. In 1929, Nagaoka became the first person to describe meteor burst communications. Nagoka also did early research on

earthquake An earthquakealso called a quake, tremor, or tembloris the shaking of the Earth's surface resulting from a sudden release of energy in the lithosphere that creates seismic waves. Earthquakes can range in intensity, from those so weak they ...

s, from the 1900s to the 1920s, building upon works published Europe; "One used the principle of elasticity studies against the background of the current that succeeded in France in the first half of the 19th century. The other defined potential functions and explained phenomena from continuous equations of the nature of waves against the background of new currents that emerged in Britain or Germany from the mid-19th century onwards."

Awards and recognition

*For his lifetime of scientific work, Nagaoka was granted the

Order of Culture The is a Japanese Order (decoration), order, established on February 11, 1937. The order has one class only, and may be awarded to men and women for contributions to Japanese Art, Japan's art, Japanese Literature, literature, science, technolog ...

by the Japanese government in 1937. *The Nagaoka crater on the

Moon The Moon is Earth's only natural satellite. It Orbit of the Moon, orbits around Earth at Lunar distance, an average distance of (; about 30 times Earth diameter, Earth's diameter). The Moon rotation, rotates, with a rotation period (lunar ...

is named after him.

References

External links

H. Nagaoka

Historical Figures of RIKEN
{{DEFAULTSORT:Nagaoka, Hantaro 1865 births 1950 deaths Japanese physicists People from Nagasaki Prefecture Recipients of the Order of Culture Academic staff of Osaka University Academic staff of the University of Tokyo University of Tokyo alumni Kaisei Academy alumni Japanese theoretical physicists Honorary members of the USSR Academy of Sciences Riken personnel Fellows of the American Physical Society Members of the Japan Academy Scientists from Nagasaki Prefecture