In a commencement address given at the California Institute of Technology (Caltech) in 1974 (and reprinted in Surely You’re Joking, Mr. Feynman! in 1985 as well as in The Pleasure of Finding Things Out in 1999), physicist Richard Feynman noted:
We have learned a lot from experience about how to handle some of the ways we fool ourselves. One example: 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. And so they eliminated the numbers that were too far off, and did other things like that …
As of 2014, the accepted value for the elementary charge is 1.602176634×10−19 C, where the (98) indicates the uncertainty of the last two decimal places. In his Nobel lecture, Millikan gave his measurement as 4.774(5)×10−10, which equals 1.5924(17)×10−19 C. The difference is less than one percent, but is six times greater than Millikan’s standard error, so the disagreement is significant.
1.59 - [Millikan 1908] 1.5911 ± 0.0024 [Birge, 1929] : 1.59875 ±0.004796 Erik Bäcklin, Nature vol 123, no. 3098, p. 409 (1929) - Wide error bar overlaps Millikan’s. 1.60709 ±0.011 Gunnar Kellstrom, Phys. Rev. 1935 Revises Millikan’s value based on updated viscosity of air. Wide error bars 1.602⋅10−19 H.R. Robinson, 1937 Rep. Prog. Phys. 4 212: “Backlin and Flemberg’s result, however, comes down to 1.4778 or very nearly to Millikan’s 1917 value! This is a most unfortunate note on which to end the Report.” 1.60203 ± 0.00050 [Birge, 1942] 1.60210 ± 0.00002 [Dummond and Cohen, 1963] 1.602192 ± 0.000007 [Taylor et al, 1969] 1.6021892 ± 0.0000046 [Cohen and Taylor, 1973] 1.6021773 ± 0.00000049 [Cohen and Taylor, 1987]
R. Czujko, “The Physics Bachelors as a Passport to the Workplace:Recent Research Results,” AIP Conf. Proc. 399, 213-223 (1997).
What’s in the box?
The Black Box! - A Golden Oldie–A Black Box Circuit. Keller, Clifton; Wang, Yimin Physics Teacher, v32 n4 p222-23 Apr 1994