Hantaro Nagaoka


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(1865–1950) Japanese physicist

Nagaoka was born in Nagasaki, Japan, and educated at Tokyo University. After graduating in 1887 he worked with a visiting British physicist, C. G. Knott, on magnetism. In 1893 he traveled to Europe, where he continued his education at the universities of Berlin, Munich, and Vienna. He also attended, in 1900, the First International Congress of Physicists in Paris, where he heard Marie Curie 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 until 1925.

Physicists in 1900 had just begun to consider the structure of the atom. The recent discovery by J. J. Thomson of the negatively charged electron implied that a neutral atom must also contain an opposite positive charge. In 1903 Thomson had suggested that the atom was a sphere of uniform positive electrification, with electrons scattered through it like currants in a bun.

Nagaoka rejected Thomson's model on the ground that opposite charges are impenetrable. He proposed an alternative model 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 was, in fact, unstable and it was left to Ernest Rutherford and Niels Bohr, a decade later, to present a more viable atomic model.

Subjects: Science and Mathematics.

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