Robert Andrews Millikan Biography

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World of Scientific Discovery on Robert Andrews Millikan

Millikan was born in Morrison, Illinois, on March 22, 1868. He grew up in a number of communities in the Mississippi River region, leading a largely rural life. At the age of fourteen, he took a job in a barrelhead factory at wages of one dollar a day.

After graduation from high school in 1885, Millikan worked briefly as a court reporter before entering Oberlin College in 1886. In his sophomore year, Millikan was asked to teach a course in physics, a somewhat peculiar request since he had little interest and only one twelve-week course in the subject. However, he needed the salary the job paid and so accepted the offer. He then spent the summer teaching himself physics.

After receiving his bachelor's degree from Oberlin in 1891, Millikan stayed on to teach physics. Then, in 1893, he received a fellowship to do graduate study in physics at Columbia University. When he enrolled at Columbia, he became its only graduate student in physics and, when he graduated two years later, he became the university's first Ph.D. in the subject in 1895.

Following a brief stint at the universities of Berlin and Göttingen, Millikan returned to the United States to teach physics at the University of Chicago. For a period of time, Millikan devoted his time to teaching and the writing of textbooks. Some of his books remained standards in the field for more than four decades. In his teaching and writing, he advocated a new approach to science education, involving greater emphasis on laboratory work than on lectures.

Millikan began the research for which he became famous--determining the charge on the electron--in 1908. His experiment was exceedingly simple in concept. He sprayed a mist of droplets of, at first, water and, later, oil into a container. He then placed an electrically charged plate above the chamber containing the droplets. Thus, two forces acted on the droplets, gravity, tending to pull them downward, and an electrical field, tending to pull them upward. By varying the electrical potential on the plate, he was able to keep the droplets suspended, motionless, in space.

From time to time, a droplet would pick up an electron or ion produced by x-rays directed into the chamber. The additional electrical charge on the droplet would cause it to move upward or downward under the influence of the electrical field. By adjusting the charge on the electric plate, Millikan could keep the droplet in suspension. The amount by which the charge had to be adjusted was equivalent to the charge on the ion.

From these experiments, Millikan determined the electronic charge to be 1.60 x 10^-19 coulomb. Over the next few years, Millikan refined his equipment and procedure to obtain even more precise values for this fundamental constant.

His next work involved a test of Albert Einstein's theory of the photoelectric effect. In 1915, he was able to confirm experimentally Einstein's equation, E = -W and, in the process, to determine the value of , Planck's constant.

Millikan's research interests extended to a number of other fields. In the early 1920s, he became interested in a powerful form of radiation entering the earth's atmosphere from outer space. Millikan suggested the name cosmic rays for this radiation although for a number of years it was also referred to as Millikan rays.

Millikan left the University of Chicago in 1921 to become president of the California Institute of Technology. Largely through his efforts, the institution became one of the most prestigious in the world for training and research in science. He retired in 1946, but continued to write and do research for twelve hours a day. He eventually received more than twenty-five honorary degrees and most of the major awards and medals available in physics. Included among these was the 1923 Nobel Prize for physics for his measurement of the electronic charge and Planck's constant. Millikan died in Pasadena, California, on December 19, 1953.