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I read in my mechanics textbook written by Goodstein that Robert Millikan cherry-picked his data in his famous oil drop experiment, and now I'm left wondering about the scientific value of his results.

It seems "okay" to me if one gets rid of one or two ridiculous data points: One doesn't get infinite money and time to perform perfect experiments. On the other hand, scientists have to be able to trust the work of others (or reproduce the results themselves, but that's not always feasible). Should Millikan's "creative" way of handling his data be regarded as fraud?

I would be particularly interested in an answer by someone who has professional experience in experimental science.

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  • $\begingroup$ I edited the question to improve the grammar etc: Hope you're okay with the changes. $\endgroup$ – Danu Sep 5 '15 at 11:53
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    $\begingroup$ @Danu No problem at all! It reflects almost exactly what I was thinking. Thank you a lot for your patience for reading it through, understanding it, then rewriting it in a much more comprehensive way :) I will work hard on my English. $\endgroup$ – Shing Sep 5 '15 at 12:46
  • $\begingroup$ Maybe we should ask if Milliken's paper was consistent with common research practices of 1909. And not whether it would pass muster today. $\endgroup$ – Gerald Edgar Aug 22 '17 at 21:32
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In Millikan's publications, he stated categorically that every single oil drop observed had had a charge that was a multiple of $e$, with no exceptions or omissions. But his notebooks are full of notations such as "beautiful data, keep," and "bad run, throw out."

Richard Feynman wrote an essay called "Cargo Cult Science," in which he pointed out:

Millikan measured the charge on an electron by an experiment with falling oil drops, and got an answer which we now know not to be quite right. It's a little bit off because he had the incorrect value for the viscosity of air. It's interesting to look at the history of measurements of the charge of an electron, after Millikan. If you plot them as a function of time, you find that one is a little bit bigger than Millikan's, and the next one's a little bit bigger than that, and the next one's a little bit bigger than that, until finally they settle down to a number which is higher.

Why didn't they discover the new number was higher right away? It's a thing that scientists are ashamed of--this history--because it's apparent that people did things like this: When they got a number that was too high above Millikan's, they thought something must be wrong--and they would look for and find a reason why something might be wrong. When they got a number close to Millikan's value they didn't look so hard.

So basically, the answer is yes. The experiment was fraudulent.

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    $\begingroup$ Doesn't that mean the follow up experiments were fraudulent? $\endgroup$ – Martin Beckett Sep 6 '15 at 22:10
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    $\begingroup$ Might be better to say that the analysis and publication were fraudulent: the experiment does more or less what he claimed, you just can't get the precision he claimed because he cheated. $\endgroup$ – dmckee Oct 17 '15 at 21:22
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    $\begingroup$ To me, there is nothing fraudulent about Millikan's original work, he just had the wrong value & it biased future researchers. $\endgroup$ – Yrast Jan 9 '18 at 5:10
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Note: I present here some information defending Millikan, but please note that I do not necessarily agree with the article it came from.

From the feature article "In Defense of Robert Andrews Millikan" by David Goodstein (American Scientist, January-February 2001):

Awkwardly, an examination of Millikan's private laboratory notebooks indicates that he did not in fact include every droplet for which he recorded data. He published the results of measurements on just 58 drops, whereas the notebooks reveal that he studied some 175 drops in the period between November 11th, 1911 and April 16th, 1912. In a classic case of cooking, the accusation goes, he reported results that supported his own hypothesis of the smallest unit of charge and discarded those contrary results that would have supported Ehrenhaft's position. And, to make matters very much worse, he lied about it. Millikan's 1913 paper contains this explicit assertion: "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, during which time the apparatus was taken down several times and set up anew." (Emphasis in the original). Thus, Millikan is accused of cheating and then compounding his cheating by lying about it in one of the most important scientific papers of the 20th century.

The author defends some of Millikan's actions.

[...] More than one of the entries in his notebooks show the result of a computation and then the comment "very low something wrong," perhaps with an indication of what Millikan thought might have disturbed the measurement. Needless to say, such entries were not included in the 58 drops Millikan published.

At first glance, this procedure certainly appears questionable. But one needs to dig deeper. The notebooks also contain a calculation with the comment "This is almost exactly right, the best one I ever had!!!" And yet Millikan did not include this drop either in his crucial 1913 paper. These discarded measurements, the good and the bad, were all part of a warm-up period during which Millikan gradually refined his apparatus and technique, in order to make the best determination possible of the unit of electric charge. The first observation that passed muster and made it into print was taken on February 13th, 1912, and all of the published data were taken between then and April 16th. This period of roughly two months is what Millikan refers to when he talks about "60 consecutive days," although the interval was actually a bit longer (63 days), in part because 1912 was a leap year.

During these nine weeks Millikan recorded in his notebooks measurements on roughly 100 separate drops. Of these, about 25 series are obviously aborted during the run, and so cannot be counted as complete data sets. Of the remaining 75 or so, he chose 58 for publication. Millikan's standards for acceptability were exacting. If a drop was too small, it was excessively affected by Brownian motion, or at least by inaccuracy in Stokes's law for the viscous force of air. If it was too large, it would fall too rapidly for accurate measurement. He also preferred to have a drop capture an ion a number of times in the course of observation, so that he could investigate changes as well as total charge, which had to be an integer multiple of the fundamental unit, e.

[...] He had no special bias in choosing which drops to discard: Allan Franklin of the University of Colorado reanalyzed Millikan's raw data in 1981 and discovered that his final value for e and for its margin of error would barely have changed had he made use of all the data he had, rather than just the 58 drops he selected.

There is actually much more to this than what I quoted. The article contains the complete story.

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Working as a physicist, I have to say that it depends quite a bit on exactly what happened in those runs, and there isn't enough information to judge.

Perhaps he failed to focus on a droplet or follow it correctly, and knew that the data would be 'bad'. In my judgement, this is okay.

On the other hand, if he was calculating the charge for each run, and deciding on this basis to reject runs, that would be fraudulent.

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There are a lot of things one can question. He was measuring a charge but of exactly what. How would he know he is actually measuring one electron. Worse, there is no proof an electron exists. May as well be measuring the charge of a unicorn. I view it as an arbitrary value. As long as everyone agrees to it, the equations will work out.

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  • $\begingroup$ Your answer would be seen as more helpful if you would spell out your meaning more clearly for readers who might not share all of your particular background and experiences, and if you would also cite references where available to support the points you put forward. $\endgroup$ – terry-s Aug 28 '17 at 15:57

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