Robert Millikan
Robert Andrews Millikan was an American experimental physicist who received the Nobel Prize in Physics in 1923 "for his work on the elementary charge of electricity and on the photoelectric effect."
As Chairman of the Executive Council of Caltech from 1921 to 1945, Millikan helped to turn the school into one of the leading research institutions in the United States. He also served on the board of trustees for Science Service, now known as Society for Science & the Public, from 1921 to 1953.
Biography
Robert Andrews Millikan was born on March 22, 1868, in Morrison, Illinois, the second son of The Rev. Silas Franklin Millikan and Mary Jane Andrews. He attended Maquoketa Community High School before entering Oberlin College in 1886, where he obtained a B.A. in 1891 and an M.A. in 1893. He received his Ph.D. from Columbia University in 1895 with a thesis on the polarization of light emitted from incandescent surfaces.At the close of my sophomore year my Greek professor asked me to teach the course in elementary physics in the preparatory department during the next year. To my reply that I did not know any physics at all, his answer was, "Anyone who can do well in my Greek can teach physics." "All right," said I, "you will have to take the consequences, but I will try and see what I can do with it." I at once purchased an Avery's Elements of Physics, and spent the greater part of my summer vacation of 1889 at home – trying to master the subject. I doubt if I have ever taught better in my life than in my first course in physics in 1889. I was so intensely interested in keeping my knowledge ahead of that of the class that they may have caught some of my own interest and enthusiasm.
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 1895, Millikan travelled to Germany and spent a year at the Universities of Berlin and Göttingen. The following year, he returned to the United States to become an assistant at the University of Chicago. He was appointed Professor of Physics in 1910.
In 1917, solar astronomer George Ellery Hale convinced Millikan to begin spending several months each year at Throop College of Technology, a small academic institution in Pasadena, California, that Hale wished to transform into a major center for scientific research and education. In 1920, Throop College was renamed the California Institute of Technology, and the following year Millikan left the University of Chicago to become Director of the Norman Bridge Laboratory of Physics at Caltech, a position he held until his retirement in 1945. During this time, he also served as Chairman of the Executive Council of Caltech.
Millikan died on December 19, 1953, in San Marino, California, at the age of 85. He is interred in the "Court of Honor" at Forest Lawn Memorial Park Cemetery in Glendale, California.
Research
Oil drop experiment
In 1909, Millikan worked on an experiment in which he measured the charge of a single electron. J. J. Thomson had already discovered the charge-to-mass ratio of the electron. However, the actual charge and mass values were unknown. Therefore, if one of these two values were to be discovered, the other could easily be calculated. Millikan and his then graduate student, Harvey Fletcher, used the oil drop experiment to measure the charge of the electron.Millikan took sole credit in return for Fletcher claiming full authorship on a related result for his dissertation. Millikan went on to win the 1923 Nobel Prize in Physics, in part for this work, and Fletcher kept the agreement a secret until his death. After a publication on his first results in 1910, contradictory observations by Felix Ehrenhaft started a controversy between the two physicists. After improving his setup, Millikan published his seminal study in 1913.
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, which is the charge of a single electron. That this is somewhat lower than the modern value of 1.602 176 53 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 experiment, 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 charge-to-mass ratio 1840 times that of a hydrogen ion. Similar results had been found by George FitzGerald and Walter Kaufmann. Most of what was then known about electricity and magnetism could be explained on the basis that charge is a continuous variable. This 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 provided a 'hands on' demonstration that charge is actually quantized. General Electric Company's Charles Steinmetz, who had previously thought that charge is a continuous variable, became convinced otherwise after working with Millikan's apparatus.
Data selection controversy
There is some controversy over selectivity in Millikan's use of results from his second experiment measuring the electron charge. This issue has been discussed by Allan Franklin, a former high-energy experimentalist and current philosopher of science at the University of Colorado. Franklin contends that Millikan's exclusions of data do not affect the final value of the charge obtained, but that Millikan's substantial "cosmetic surgery" reduced the statistical error. This enabled Millikan to give the charge of the electron to better than one-half of one percent. In fact, if Millikan had included all of the data he discarded, the error would have been less than 2%. While this would still have resulted in Millikan's 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. David Goodstein argues that Millikan's statement, that all drops observed over a 60 day period were used in the paper, was clarified in a subsequent sentence that specified all "drops upon which complete series of observations were made". Goodstein attests that this is indeed the case and notes that five pages of tables separate the two sentences.Photoelectric effect
When Albert Einstein published his 1905 paper on the particle theory of light, Millikan was convinced that it had to be wrong, because of the vast body of evidence that had already shown that light was a wave. He undertook a decade-long experimental program to test Einstein's theory, which required building what he described as "a machine shop in vacuo" in order to prepare the very clean metal surface of the photoelectrode. His results, published in 1914, confirmed Einstein's predictions in every detail, but Millikan was not convinced of Einstein's interpretation, and as late as 1916 he wrote, "Einstein's photoelectric equation... cannot in my judgment be looked upon at present as resting upon any sort of a satisfactory theoretical foundation," even though "it actually represents very accurately the behavior" of the photoelectric effect. In his 1950 autobiography, however, he declared that his work "scarcely permits of any other interpretation than that which Einstein had originally suggested, namely that of the semi-corpuscular or photon theory of light itself.Although Millikan's work formed some of the basis for modern particle physics, he was 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."
Millikan is also credited with measuring the value of the Planck constant by using photoelectric emission graphs of various metals.
Cosmic rays
At Caltech, most of Millikan's scientific research focused on the study of cosmic rays. In the 1930s, he entered into a debate with Arthur Compton over whether cosmic rays were composed of high-energy photons or charged particles. Millikan thought his cosmic ray photons were the "birth cries" of new atoms continually being created to counteract entropy and prevent the heat death of the universe. Compton was eventually proven right by the observation that cosmic rays are deflected by the Earth's magnetic field.Other work
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. During his wartime service, an investigation by Inspector General William T. Wood determined that Millikan had attempted to steal another inventor's design for a centrifugal gun in order to profit personally. Wood recommended termination of Millikan's army commission, but a subsequent investigation by Frank McIntyre, the executive assistant to the army chief of staff, exonerated Millikan. He received the Chinese Order of Jade in 1940. After the War, Millikan contributed to the works of the League of Nations' Committee on Intellectual Cooperation, with other prominent researchers.In the aftermath of the 1933 Long Beach earthquake, Millikan chaired the Joint Technical Committee on Earthquake Protection. They authored a report proposing means to minimize life and property loss in future earthquakes by advocating stricter building codes.