Robert Andrews Millikan

Millikan in 1891

Robert Andrews Millikan was born on March 22, 1868, in Morrison, Illinois.[5] He went to high school in Maquoketa, Iowa and received a bachelor's degree in the classics from Oberlin College in 1891 and his doctorate in physics from Columbia University in 1895[6] – he was the first to earn a Ph.D. from that department.[7]

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.[8]

Millikan's enthusiasm for education continued throughout his career, and he was the coauthor of a popular and influential series of introductory textbooks,[9] 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.

Millikan's original oil-drop apparatus, circa 1909–1910

Millikan receives a check for over $40,000 for winning the Nobel Prize

Starting in 1908, while a professor at the University of Chicago, Millikan worked on an oil-drop experiment in which he measured the charge on 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 (as well as the electron mass, and Avogadro's number, since their relation to the electron charge was known).

Professor Millikan took sole credit, in return for Harvey Fletcher claiming full authorship on a related result for his dissertation.[10] Millikan went on to win the 1923 Nobel Prize for Physics, in part for this work, and Fletcher kept the agreement a secret until his death.[11] After a publication on his first results in 1910,[12] contradictory observations by Felix Ehrenhaft started a controversy between the two physicists.[13] After improving his setup, Millikan published his seminal study in 1913.[14]

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), which is the charge of 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.[15][16]

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 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.

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,[17] 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 which 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.[18]

Robert Millikan and Albert Einstein at the California Institute of Technology in 1932

When Einstein published his seminal 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,[19] 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 simply 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".[20]

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."

Millikan is also credited with measuring the value of Planck's constant by using photoelectric emission graphs of various metals.[21]

Robert A. Millikan around 1923

In 1917, solar astronomer George Ellery Hale convinced Millikan to begin spending several months each year at the 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. A few years later Throop College became the California Institute of Technology (Caltech), and Millikan left the University of Chicago to become Caltech's "chairman of the executive council" (effectively its president). Millikan served in that position from 1921 to 1945. At Caltech, most of his scientific research focused on the study of "cosmic rays" (a term he coined). In the 1930s he entered into a debate with Arthur Compton over whether cosmic rays were composed of high-energy photons (Millikan's view) or charged particles (Compton's view). 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 (hence must be charged particles).

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. After the War, Millikan contributed to the works of the League of Nations' Committee on Intellectual Cooperation (from 1922, in replacement to George E. Hale, to 1931), with other prominent researchers (Marie Curie, Albert Einstein, Hendrik Lorentz, etc.).[22] Millikan was a member of the organizing committee of the 1932 Los Angeles Olympics,[23] and in his private life was an enthusiastic tennis player. He was married and had three sons, the eldest of whom, Clark B. Millikan, became a prominent aerodynamic engineer. Another son, Glenn, also a physicist, married the daughter (Clare) of George Leigh Mallory of "Because it's there" Mount Everest fame. Glenn was killed in a climbing accident in Cumberland Mountains in 1947.[24]

A religious man and the son of a minister, in his later life Millikan argued strongly for a complementary relationship between Christian faith and science.[25][26][27][28] He dealt with this in his Terry Lectures at Yale in 1926–27, published as Evolution in Science and Religion.[29] He was a Christian theist and proponent of theistic evolution.[30] A more controversial belief of his was eugenics – he was one of the initial trustees of the Human Betterment Foundation and praised 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."[31] In 1936, Millikan advised the president of Duke University in the then-racial segregated southern United States against recruiting a female physicist and argued that it would be better to hire young men.[32]

1931 sketch of California Institute of Technology President Robert A. Millikan

On account of Millikan's affiliation with the Human Betterment Foundation, in January 2021, the Caltech Board of Trustees authorized removal of Millikan's name (and the names of five other historical figures affiliated with the Foundation), from campus buildings.[33]

In 1938, he wrote a short passage to be placed in the Westinghouse Time Capsules.[34]

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.

Robert A. Millikan circa 1953

The former Millikan Library at Caltech in 2010 (renamed Caltech Hall in 2021)

Millikan died of a heart attack at his home in San Marino, California in 1953 at age 85, and was interred in the "Court of Honor" at Forest Lawn Memorial Park Cemetery in Glendale, California.

On January 26, 1982, he was honored by the United States Postal Service with a 37¢ Great Americans series (1980–2000) postage stamp.[35]

Tektronix named a street on their Portland, Oregon, campus after Millikan with the Millikan Way (MAX station) of Portland's MAX Blue Line named after the street.

During the mid to late 20th century, several colleges had named buildings, physical features, awards, and professorships in honor of Robert Millikan.

In 1958, Pomona College named a science building Millikan Laboratory in honor of Millikan. After reviewing Millikan's association with the eugenics movement, the college administration voted in October 2020 to rename the building as the Ms. Mary Estella Seaver and Mr. Carlton Seaver Laboratory.[36]

On the Caltech campus, several physical features, rooms, awards, and a professorship were named in honor of Millikan, most notably the Millikan Library, which was completed in 1966. In January 2021, the Board of Trustees voted to immediately strip Millikan's name from the Caltech campus because of his association with eugenics. The Robert A. Millikan Library has been renamed Caltech Hall.[37] In November 2021, the Robert A. Millikan Professorship was renamed the Judge Shirley Hufstedler Professorship.[38]

In November 2020, Millikan Middle School (formerly Millikan Junior High School) in the suburban Los Angeles neighborhood of Sherman Oaks started the process of renaming their school.[39]

In August 2020, the Long Beach Unified School District established a committee that would examine the need for renaming of their Robert A. Millikan High School.[40][41]

In the Spring of 2021, the American Association of Physics Teachers voted unanimously to remove Millikan's name from the Robert A. Millikan award, which honors "notable and intellectually creative contributions to the teaching of physics."[42] A few months later, AAPT announced that the award would be renamed in honor of University of Washington professor of physics Lillian C. McDermott who died the previous year.[43]