Robert Andrews Millikan (March 22, 1868 - December 19, 1953) was an American experimental physicist. In 1908, while a professor at the University of Chicago, he began experiments in which he measured the charge on a single electron. He and his 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). 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 for Physics, in part for this work, and Fletcher kept the agreement a secret until his death. Millikan is also credited with measuring the value of Planck's constant by using photoelectric emission graphs of various metals. He left the University of Chicago to become Caltech's chairman of the executive council. He served in that position from 1921-45. At Caltech most of his scientific research focused on the study of cosmic rays (a term which he coined). He died of a heart attack at his home in 1953 at the age of 85.