Robert Andrews Millikan was a pioneering American experimental physicist whose meticulous work laid foundational principles for modern physics. Born on March 22, 1868, in Illinois, he initially studied classics at Oberlin College before unexpectedly teaching himself physics and discovering his passion for the field. He earned his PhD in physics from Columbia University in 1895, a degree that Columbia University had awarded to others prior to this date. After early academic challenges at the University of Chicago where he began his career, he rose to prominence through his rigorous experimental approach that established new standards in precision measurement.
Millikan's most enduring contribution was the development of the elegant oil drop experiment, through which he precisely measured the elementary electrical charge of the electron with unprecedented accuracy. His groundbreaking 1910-1913 work not only confirmed the atomic nature of electricity but also provided the first definitive experimental proof of Einstein's photoelectric equation, for which he later received the Nobel Prize. By meticulously varying energies and frequencies, he established the first direct photoelectric determination of Planck's constant, cementing quantum theory's experimental foundations. His comprehensive studies of Brownian motion in gases effectively resolved remaining opposition to atomic theory, while his later investigations into cosmic radiation opened new frontiers in high-energy physics.
Beyond his research, Millikan served as Chairman of the Executive Council of Caltech from 1921 to 1945, transforming the institution into one of America's premier scientific research centers. His influential textbooks educated generations of physics students, establishing him as a major figure in science education alongside his research achievements. As a sought-after lecturer whose cosmic ray presentations regularly attracted thousands of attendees, he played a crucial role in popularizing modern physics concepts to broad audiences. Though he passed away on December 19, 1953, Millikan's legacy endures through the rigorous experimental standards he established and his fundamental contributions that continue to underpin contemporary physics research worldwide.
