See his autobiography (1950).
Robert Andrews Millikan (March 22, 1868 – December 19, 1953) was an American experimental physicist, and Nobel laureate in physics for his measurement of the charge on the electron and for his work on the photoelectric effect. He served as president of Caltech from 1921 to 1945.
Millikan's enthusiasm for education continued throughout his career, and he was the coauthor of a popular and influential series of introductory textbooks, which were ahead of their time in many ways. Compared to other books of the time, they treated the subject more in the way in which it was thought about by physicists. They also included many homework problems that asked conceptual questions, rather than simply requiring the student to plug numbers into a formula.
In 1902 he married Greta Ervin Blanchard. They had three sons - Clark Blanchard, Glenn Allen, and Max Franklin.
The elementary charge is one of the fundamental physical constants and accurate knowledge of its value is of great importance. His experiment measured the force on tiny charged droplets of oil suspended against gravity between two metal electrodes. Knowing the electric field, the charge on the droplet could be determined. Repeating the experiment for many droplets, Millikan showed that the results could be explained as integer multiples of a common value (1.592 × 10−19 coulomb), the charge on a single electron. That this is somewhat lower than the modern value of 1.602 176 53(14) x 10−19 coulomb is probably due to Millikan's use of an inaccurate value for the viscosity of air.
Although at the time of Millikan's oil drop experiments it was becoming clear that there exist such things as subatomic particles, not everyone was convinced. Experimenting with cathode rays in 1897, J.J. Thomson had discovered negatively charged 'corpuscles', as he called them, with a mass 1/1840 times that of a hydrogen atom. Similar results had been found by George FitzGerald and Walter Kaufmann. Most of what was then known about electricity and magnetism, however, could be explained on the basis that charge is a continuous variable; in much the same way that many of the properties of light can be explained by treating it as a continuous wave rather than as a stream of photons.
The beauty of the oil drop experiment is that as well as allowing quite accurate determination of the fundamental unit of charge Millikan's apparatus also provides a 'hands on' demonstration that charge is actually quantised. Charles Steinmetz, of the General Electric Company, who had previously thought that charge is a continuous variable, became convinced otherwise after having a go with Millikan's apparatus.
There is some controversy over the use of selectivity in Millikan's results of his second experiment measuring the electron charge. This work was done by Allan Franklin, a former high energy experimentalist and current philosopher of science at the University of Colorado. Franklin contends that, while Millikan's exclusions of data do not affect the final value of the charge of an e− that he obtained, there was substantial "cosmetic surgery" that Millikan performed which had the effect of reducing the statistical error on the charge of an e−. This enabled Millikan to quote the figure that he had calculated the charge of e− to better than one half of one percent; in fact, if Millikan had included all of the data he threw out, it would have been within 2%. While this would still have resulted in Millikan having measured the charge of e− better than anyone else at the time, the slightly larger uncertainty might have allowed more disagreement with his results within the physics community, which Millikan likely tried to avoid.
Since Millikan's work formed some of the basis for modern particle physics, it is ironic that he was rather conservative in his opinions about 20th century developments in physics, as in the case of the photon theory. Another example is that his textbook, as late as the 1927 version, unambiguously states the existence of the ether, and mentions Einstein's theory of relativity only in a noncommittal note at the end of the caption under Einstein's portrait, stating as the last in a list of accomplishments that he was "author of the special theory of relativity in 1905 and of the general theory of relativity in 1914, both of which have had great success in explaining otherwise unexplained phenomena and in predicting new ones." He is also credited with measuring the value of Planck's constant by using photoelectric emission graphs of various metals.
Robert Millikan was Vice Chairman of the National Research Council during World War I. During that time, he helped to develop anti-submarine and meteorological devices. He received the Chinese Order of Jade. In his private life, Millikan was an enthusiastic tennis player. He was married and had three sons, the eldest of whom, Clark B. Millikan, became a prominent aerodynamic engineer.
In his later life he became interested in the relationship between Christian faith and science, his own father having been a minister. He dealt with this in his Terry Lectures at Yale in 1926–7, published as Evolution in Science and Religion. A more controversial belief of his was eugenics. This led to his association with the Human Betterment Foundation and his praising of San Marino, California for being "the westernmost outpost of Nordic civilization . . . [with] a population which is twice as Anglo-Saxon as that existing in New York, Chicago or any of the great cities of this country."
AT this moment, August 22, 1938, the principles of representative ballot government, such as are represented by the governments of the Anglo-Saxon, French, and Scandinavian countries, are in deadly conflict with the principles of despotism, which up to two centuries ago had controlled the destiny of man throughout practically the whole of recorded history. If the rational, scientific, progressive principles win out in this struggle there is a possibility of a warless, golden age ahead for mankind. If the reactionary principles of despotism triumph now and in the future, the future history of mankind will repeat the sad story of war and oppression as in the past.
Millikan Middle School (formerly Millikan Junior High School) in the suburban Los Angeles neighborhood of Sherman Oaks is named in his honor, as is Robert A. Millikan High School in Long Beach, California. The Millikan Library, the tallest building on the Caltech campus is also named for him. Additionally, a major street through the Tektronix campus in Portland, Oregon, is named after him, with the Millikan Way (MAX station), a station on Portland, Oregon's MAX Blue Line named after the street.