The Unnatural Nature of Science by Lewis Wolpert

Author:Lewis Wolpert
Language: eng
Format: azw3, epub
ISBN: 9780571317387
Publisher: Faber & Faber
Published: 2014-09-15T04:30:00+00:00

His conjecture had been shown to be right.

Consider now the famous disagreement around 1910 between Robert A. Millikan in Chicago and J. Ehrenhaft in Vienna, which has been studied in detail by the physicist and historian Gerald Holton. Their disagreement concerned the value of the smallest electrical charge found in nature – the charge on the electron. Millikan, in his first major paper, pointed out that this value ranks with the velocity of light as a fundamental physical constant. The value of the charge of the electron could be deduced from Faraday’s work on electrolysis, but he wished to measure it directly – particularly since Ehrenhaft had reported finding charges of only a fraction of that expected to be carried by the electron.

Millikan’s experimental approach was to study the behaviour of oil drops that could be charged such that when a small droplet was moving upwards in an electric field against gravitational pull ‘with the smallest speed that it could take on, I could be certain that just one isolated electron was sitting on its back. The whole apparatus then represented a device for catching and essentially seeing an individual electron riding on a drop of oil.’ Thus Millikan’s technique involved observing single tiny oil droplets in what was effectively a very sensitive balance. In 1910 Millikan put forward a value for e, the charge on the electron, of 4.65 x 10-10 e.s.u. While Ehrenhaft’s average value was similar, he also found much smaller values, and in his results the value of the charge seemed to vary continuously.

Holton has examined Millikan’s papers and notebooks in detail. In the notebooks used for a 1910 publication, each of the thirty-eight observations is given a more or less personal rating from ‘three stars’ to none, and the sets of observations are given a weighting from 1 to 7. Millikan was effectively saying that he knew a good run when he saw one. Some observations were discarded altogether because he was unhappy with the experiments. But he goes on to say, ‘I would have discarded them had they not agreed with the results of other observations.’ In effect he is saying that he has assumed a particular value for the correct results, and that the fundamental charge is a constant. Having examined Millikan’s notebooks for the years 1911 and 1912, Holton writes, ‘it is clear what Ehrenhaft would have said had he obtained such data or had access to this notebook. Instead of neglecting the second observation, and many others like it in these two notebooks that shared the same fate, he would very likely have used all of these.’ The notebooks contain many exclamations such as ‘Very low. Something wrong.’ ‘This is almost exactly right and the best one I ever had!!!’ ‘Agreement poor.’

In the end Millikan’s view prevailed and he was awarded the Nobel Prize. He rejected data that did not fit his basic idea, and he would perhaps have justified that in terms of how good the experiment that produced the data was.

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