Robert Andrews Millikan

  • From:

    California Institute of Technology │ Pasadena, California

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  • Citation:

    For the measurement of the charge on an electron and description of Planck's constant, and for the study of cosmic radiation.

Robert Andrews Millikan was born in Morrison, Illinois, in 1868. During his undergraduate course at Oberlin College, his favorite subjects were Greek and mathematics; but after his graduation in 1891 he took, for two years, a teaching post in elementary physics. It was during this period that he developed his interest in the subject in which he was later to excel. In 1893, after obtaining his mastership in physics, he was appointed Fellow in Physics at Columbia University. In 1895, he received his Ph.D.

Millikan spent a postgraduate year (from 1895-1896) in Germany, at the Universities of Berlin and Gottingen. He returned at the invitation of A. A. Michelson, to become assistant at the newly established Ryerson Laboratory at the University of Chicago. Millikan was an eminent teacher, and passing through the customary grades he became professor at that university in 1910, a post which he retained until 1921. During his early years at Chicago, he spent much time preparing textbooks and simplifying the teaching of physics.

Millikan made numerous discoveries in the fields of electricity, optics, and molecular physics. His earliest major success was the accurate determination of the charge carried by an electron, using his "falling-drop method"; he also proved that this quantity was a constant for all electrons (1910), thus demonstrating the atomic structure of electricity. Next, he verified experimentally Einstein's all-important photoelectric equation, and made the first direct photoelectric determination of Planck's constant h (1912-1915). In addition, his studies of the Brownian movements in gases put an end to all opposition to the atomic and kinetic theories of matter. During 1920-1923, Millikan occupied himself with work concerning the hot-spark spectroscopy of the elements (which explored the region of the spectrum between the ultraviolet and X-radiation), thereby extending the ultraviolet spectrum downwards far beyond the then known limit. The discovery of his law of motion of a particle falling towards the earth after entering the earth's atmosphere, together with his other investigations on electrical phenomena, ultimately led him to his significant studies of cosmic radiation.

Information as of 1937