Quantum and Nuclear

The Millikan story – a tale of mixed results

Teaching Guidance for 14-16 PRACTICAL PHYISCS

Millikan recorded the results for 175 drops. He used 58 of those to calculate a value for the charge on an electron, e , which he found as 1.592 x 10 -19 coulombs. The accepted value is now 1.602 x 10 -19 C. He won the Nobel Prize in 1923, partly for this work.

In the 1970s, there were some questions raised over Millikan's selective use of data, most famously by Gerald Holton in Subelectrons, Presuppositions and the Millikan-Ehrenhaft Dispute. Holton referred back to Millikan's original laboratory notes and compared them to his published paper. Millikan had rejected over two thirds of his results. His laboratory notes contain comments such as "This is almost exactly right and the best one I ever had!!!", "Error high will not use" and "Too high by 1.5%".

The debate, known as the Millikan-Ehrenhaft dispute has continued amongst historians and philosophers of science since then. The harshest view is that he massaged or fiddled his results. However, many people now accept that he discarded some results for sound experimental reasons – for example, many of his early results were left out; presumably he thought that his technique was improving as time went on. Also, it can be argued that he omitted obvious outliers.

However, the question remains why he did not own up to this. In his published paper he claimed that "this is not a selected group of drops but represents all of the drops experimented on during 60 consecutive days...". Presumably, he was keen to keep his margin of uncertainty as low as possible (quoted as 0.02 x 10 -19 C).

Furthermore, even before Holton, Richard Feynman had referred to the shame felt by physicists who came after Millikan saying that they had ignored perfectly good results for the measurement of e if they did not match Millikan's closely enough. He said that "We have learned a lot from experience about how to handle some of the ways we fool ourselves."

Many aspects of this story would form the basis of an interesting discussion about how science works. A quick search on the internet for "Millikan-Ehrenhaft Dispute" will yield many interesting links.

is a constituent in our description of Beta Decay
is a type of Lepton
can exhibit Wave-Particle Duality
is a constituent of the Plum Pudding Model
has the quantity Charge
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