Robert A. Millikan

By Maria Iglesias

Biography

Robert Andrews Millikan was born March 22, 1868 in Morrison, Illinois. He attended Oberlin College in Oberlin, Ohio, graduating with a degree in classics in 1891. After teaching elementary physics for two years, Millikan went back to school to earn his doctorate in physics from Columbia University. He earned his Ph.D. in 1895, being the first person to do so from that department. Millikan married Greta Ervin Blanchard in 1902. The couple had three children: Clark Blanchard, Glenn Allen, and Max Franklin. In 1908, he became an assistant at the University of Chicago where he later became a professor. Millikan later went on to be the director of the Norman Bridge Laboratory of Physics at the California Institute of Technology in 1921. Robert Millikan died on December 19, 1953 in San Marino, California at the age of 85.

Major Scientific Contributions

Oil Drop Experiment

In 1909, Millikan worked with assistant Harvey Fletcher to create the oil drop experiment.The pair were able to find the charge of electron as well as the smallest unit of an electron charged that can be quantized. In this experiment, oil was sprayed onto a plate with a hole. Droplets of oil fell through the whole into a chamber with electrically charged plates. These plates emitted x-rays that caused the negatively charged oil drops to either fall at a slower rate, stop or rise. By comparing the velocity's of the charged and non-charged drops, Millikan and Fletcher found that all the negatively charged particles had a charged that was multiple of 1.6e-19 coloumbs. Millikan won a Nobel Prize in 1923 for his work on this experiment.

Photoelectric Effect

In 1905, Albert Einstein published describing the particle-like qualities of light known as the photoelectric effect. Millikan did not agree with this idea, since previously light had only been described as a wave. To test this Einstein's theory, he created an experiment in light bulb. The machine he designed was a lightbulb with a wheel inside that had 3 cylinders of metals on it: sodium, lithium and potassium. The wheel rotated inside, a metal would be shaved down by a knife and the cylinder was rotated toward a light using an electromagnet. The results concluded that Einstein was correct.