Saturday, March 21, 2009

Robert Millikan: 141st birthday

Joseph Fourier was born 241 years ago, on March 21st. But almost exactly 100 years later, on March 22nd, 1868, another well-known guy was born.

Robert Andrews Millikan grew up in Iowa. He went to Columbia University. Today, we usually think about left-wing extremists and an aggressive, unconstructive crackpot when the name of that university is mentioned (apologies to a few exceptions). But there used to be different people at Columbia in the 1890s.

Millikan always wanted to be ahead of his class - in physics, Greek, and other subjects - and it had a somewhat good reason.

By being so fast, he became the first physics PhD at Columbia University in 1895. His advisors had pretty interesting names, too. One of them was Michael Pupin, of the Pupin Hall fame (a Serbian-born guy doing electromagnetism), and the other was Albert Michelson, famous for the Michelson-Morley experiments.

Needless to say, Millikan is well-known for the measurement of the elementary electric charge. He also verified Einstein's predictions for the photoelectric effect. Millikan was awarded the physics Nobel prize in 1923 for these two things. Between 1921 and 1945, he was the president of Caltech.

I guess that you know Millikan's experiment: we had to reproduce it in the college which was pretty interesting. The electrostatic force acting in one direction (down) and the resistivity of the air in the other direction (up) determine the stationary speed of oil drops which are observed under the microscope. By looking at these things and making some calculations, the electron's charge can be reconstructed and the very quantized character of the charge may be confirmed.

In "Cargo Cult Sciences", Feynman offers his insightful story about the people trying to cheat and keep the previous wrong values of the electric charge, in order not to deviate from others too much. So the initial wrong value was gradually increasing, before reaching 1.602 x 10^{-19} Coulombs. In the ideal world, they should have gotten the right value instantly. I was not able to find any detailed numbers about this story. The only thing I know is that in Stockholm 1923, Millikan already had the value 1.59 x 10^{-19} Coulombs which is pretty good although the error (1%) was 5 times higher than his standard error.

It is an unknown story that Millikan measured the charge together with his student, Harvey Fletcher, who would later study acoustics and physics of medicine. They agreed on a contract that Millikan would be exclusively credited for the oil-drop experiment while Fletcher would become the only author of another experiment that allowed Fletcher to complete his PhD.

Experimenters are reactionary theorists

But I want to mention a negative side of Millikan's physics, namely his opinions about the theory. Although Millikan tried to be ahead of others in his class, he was very slow in comparison with the world's leading theorists.

For example, his more accurate measurements of the photoelectric effect were motivated by Millikan's desire to prove that Einstein was wrong and light couldn't have had any particulate properties. It was known that light behaved as waves, which are not particles, and Millikan felt certain that it couldn't have been both. By succeeding in his accurate verification of all Einstein's predictions, Millikan failed to prove his main point.

Once he accurately confirmed Einstein's theory, he still wrote that "Einstein's photoelectric equation... cannot in my judgment be looked upon at present as resting upon any sort of a satisfactory theoretical foundation" although he didn't hide that all the predictions were verified accurately. Sorry but this was an unscientific approach. He was really a denier, much like the deniers of the natural climate change.

The success of theories depends on their predictions and if one owns a unique theory that can accurately reproduce the experiments, it's damn likely that there is a very important aspect of the truth incorporated in this theory, to put it very mildly.

Well, he was just too reactionary in his physics opinions. In his case, one can attribute it to his general attitudes to life. Following his father, he was a Christian - in a congregational church - and liked to praise California for owning some of the most Western and most Anglo-Saxon towns in the world. ;-)

Although his work after the 1920s resembled one of a 19th century engineer, he was still giving new modern contributions to the body of knowledge called physics. At Caltech, he studied cosmic rays. Equally importantly, he invented the term "cosmic rays". ;-)

Millikan died of heart attack in San Marino, CA at age 85 i.e. in 1953.

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