Recent Articles



































Robert Millikan



         


Robert Andrews Millikan (March 22, 1868 - December 19, 1953) was an American physicist who won the 1923 Nobel Prize for Physics primarily for his work in determining the value of the charge on the electron and for the photoelectric effect. He later worked on cosmic rays.

He received a Bachelor's degree, in classics, from Oberlin College in 1891, and his PhD, in physics, from Columbia University in 1895.

Millikan explained his transition from classics to physics, told in his own autobiography:

"At the close of my sophomore year [...] my Greek professor [...] asked me to teach the course in elementary physics in the preparatory department during the next year. To my reply that I did not know any physics at all, his answer was, “Anyone who can do well in my Greek can teach physics.” “All right,” said I, “you will have to take the consequences, but I will try and see what I can do with it.” I at once purchased an Avery’s Elements of Physics, and spent the greater part of my summer vacation of 1889 at home … trying to master the subject. [...] I doubt if I have ever taught better in my life than in my first course in physics in 1889. I was so intensely interested in keeping my knowledge ahead of that of the class that they may have caught some of my own interest and enthusiasm.

In 1910 he published the first results of his oil-drop experiment to measure the charge on a single electron (since repeated, with degrees of success, by generations of physics students). The, so-called, elementary charge is one of the fundamental physical constants and accurate knowledge of its value is of great importance. His experiment measured the force on tiny charged droplets of oil suspended against gravity between two metal electrodes. Knowing the electric field, the charge on the droplet could be determined. Repeating the experiment for many droplets, Millikan showed that the results could be explained as integer multiples of a common value (1.592×10-19 coulomb), the charge on a single electron. That this is somewhat lower than the modern value of 1.602×10-19 coulomb is probably due to Millikan's use of an incorrect value for the viscosity of air.

Subsequently, maverick physicist Felix Ehrenhaft claimed to have performed a similar experiment and observed charges smaller than Millikan's elementary charge. This led Millikan to a further series of measurements which he published in 1913 to reassert his original results. Controversy has arisen because, although Millikan states in his paper that It is to be remarked, too, that this is not a selected group of drops, but represents all the drops experimented upon during 60 consecutive days..., his laboratory notebooks show that he recorded data on 175 drops in the period between November 11 1911 and April 16 1912, reporting only 58 in his paper. The reaction was exacerbated because his notebooks feature phrases such as very low something wrong and This is almost exactly right & the best one I ever had!! Though accusations have been made that Millikan was guilty of fraud and pathological science, it seems more likely that he was using his deep experimental insight and subject-matter expertise to reject unreliable observations on sound physical grounds. More recent research has shown that an analysis of the totality of his data does not lead to substantially different results.

In his private life, Millikan was married with 3 sons. He was an enthusiastic tennis player.

[Top]

Bibliography





  View Live Article   This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License