Hantaro Nagaoka

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Hantaro Nagaoka (August 15, 1865 – December 11, 1950) was a Japanese physicist and a pioneer of Japanese physics in the early Meiji period.

Nagaoka was born in Omura, Nagasaki Prefecture. After receiving his Bachelors degree in physics from the University of Tokyo in 1887, Nagaoka pursued graduate studies in Japan, working on magnetostriction with visiting British physicist C. G. Knott, later delivering an address on the subject before the first International Congress of Physics held by the Curies in Paris in 1900.

Between 1892 and 1896, Nagaoka studied abroad in Vienna, Berlin, and Munich, where he was particularly fascinated by Ludwig Boltzmann's course in the Kinetic Theory of Gases and Maxwell's work on the stability of Saturn's rings, two influences that would later lead to the development of his atomic model.

From 1901 to 1925, Nagaoka was a professor of physics at the University of Tokyo, where his pupils include Kotaro Honda and 1949 Nobel Prize winner Hideki Yukawa.

In 1904 he developed an early, incorrect "planetary model" of the atom (Saturnian Theory). The model was based around an analogy to the explanation of the stability of the Saturn rings

(the rings are stable because the planet they orbit is very, very massive). So, the model made two predictions:

A very massive nucleus (in analogy to a very massive planet)
electrons revolving around the nucleus, bound by electrostatic forces (in analogy to the rings revolving around Saturn, bound by gravitational forces).

Both predictions were successfully confirmed by Rutherford and others. However, other details of the model were incorrect and Nagaoka himself abandoned it in 1908.

He later did research in spectroscopy and other fields. In March 1924 he described studies in which he claimed to have successfully formed a milligram of gold and some platinum from mercury. He was president of Osaka University from 1931 to 1934. For his lifetime of scientific work, Nagaoka was granted the National Cultural Prize by the Japanese government in 1937.

Nagaoka crater on the Moon is named after him.