Robert Andrews Millikan (1868-1953), US physicist. Millikan studied Classics as an undergraduate, but he then developed an interest in physics, gaining a doctorate from Columbia University in 1895. In Chicago between 1909 and 1913 he determined the charge on an electron by introducing charges onto oil droplets between charged plates. Adjustment of voltage between the plates to counterbalance the force of gravity on the charged droplets allowed the charge on the droplets to be calculated. Millikan found the charges always to be multiples of a single value; the charge on an electron. He also made an accurate measurement of Planck's constant, and was awarded the Nobel prize in 1923.