Robert Millikan and His Oil Drop Experiment

A scientist can truly be viewed as revolutionary when their di Robert Andrews Millikan was born on the 22nd of March in 1868 as the second son of Reverend Silas Franklin Millikan (Father) and Mary Jane Andrews Millikan (Mother) in the town of Morrison, Illinois. He attended the Maquoketa Community High School in Iowa and after he graduated he went to Oberlin College in Ohio from 1886 to 1891 and became an elementary physics teacher. Then Millikan furthered his education at Columbia University from 1893 to 1895. He received his Ph.D in 1895 from Columbia University. Then Millikan spent a year in Germany at the Universities of Berlin and Gottingen. He finally returned to the U.S. after receiving an invitation from A. A. Michelson to become an assistant at the newly established Ryerson Laboratory at the University of Chicago in 1896.

In 1902 Millikan married Greta Erwin Blanchard and they had three sons: Clark Blanchard, Glenn Allen, and Max Franklin. After that Millikan became a professor at the University of Chicago in 1910 a job he kept until 1921. (“The Nobel Prize 1923”).Also Millikan proved Einstein's all-important photoelectric equation in 1912-1915. During World War 1 Millikan was the Vice-Chairman of the National Research Council also helping make anti-submarine and meteorological devices. From 1920-1923 he kept himself busy by exploring hot-spark spectroscopy of the elements. He won the Nobel Prize for physics in 1923. (“The Nobel Prize 1923”).Millikan died on the 19th of December, 1953 in San Marino, California (He was 85 years old). Millikan was a prolific author throughout his life. Millikan liked to play tennis and golf when he wasn’t a scientist. Millikan held honorary doctor’s degrees of some 25 different universities. (“The Nobel Prize 1923”). Millikan discoveries continue to be appreciated even after his death and will still be appreciated for the rest of time.

In 1909, Millikan conducted an experiment that would earn him a Nobel Peace Prize for his discovery. (The Millikan Oil Drop Experiment) This experiment was called the Oil Drop experiment. It consisted of a tube-like chamber with two charged plates, one positively charged and one negatively charged. The positively charged plate was in the middle while the negatively charged plate was on the bottom. It also consisted of a microscope looking into the bottom half of the chamber and an atomizer filled with oil attached to the top of the chamber.

A flashlight was also present at the bottom of the chamber (The Editors of Encyclopædia Britannica). Using the above setup, Millikan was able to precisely measure the electrical charge of a single electron. This was the first time anyone was able to achieve this. He did it by using the atomizer to spray a mist of oil droplets into the top chamber and the force of gravity pulled a few droplets through a hole into the second chamber. When the droplets fell through the hole, they gained a negative charged due to the metal plates that were ionized by radiation. A flashlight illuminated the droplets and through the microscope, Millikan was able to measure the mass of the droplets.

The voltage of the metal plates could then be turned up or down, resulting in the motion of the droplet decreasing or increasing (The Editors of Encyclopædia Britannica). When the voltage was higher, the drop moved up, when the voltage was lower, the drop moved down, and when the voltage was equal to the force of gravity, the drop remained still (Dewitt). Using the amount of voltage needed to cause the drop to remain still, and the mass of the droplet, Millikan was able to calculate the electric charge of the droplet. By repeating this process multiple times, Millikan was able to determine that the electric charge on different drops is always a multiple of a single number, that number being the smallest value. This number, approximately 1.602x10^-9.