Wednesday, August 12, 2009

On the Role of the Michelson-Morley Experiment: Einstein in Chicago

I came across this article and had planned on only reading just a few paragraphs since I am in the middle of doing a lot of other things. But I just couldn't pull myself away from it and ended up reading the entire article! :)

This is a treatise on the infamous question on whether Einstein was aware of the Morley-Michaelson experiment BEFORE his 1905 relativity paper, and if he was aware of it, to what degree did it influenced his 1905 paper.

The conventional thought, based on many accounts given by Einstein in his later years, is that he can't quite remember if he was aware of it, and thus, it didn't play any influential role in his formulation of the principles of relativity. This new paper, in press, reveals a slightly different version of what plausible could have happened, based on two accounts : a translation of Einstein's speech he gave in Kyoto in 1922, and a series of speeches he gave in Chicago a year earlier, and especially at the Francis W. Parker school.

The author draws up this conclusion:

What does the Parker school lecture imply for our understanding of Einstein’s relation to the Michelson-Morley experiment, and its influence on the creation of the special theory? Taking the text at face value, there can be no doubt that Einstein knew of the Michelson-Morley experiment prior to 1905. He attributed a significant role to ether drift experiments in general, and singled out the Michelson-Morley experiment for specific mention. It further suggests that Einstein had learned of the experiment before becoming convinced of the principle of relativity—contrary to his later recollections.

Einstein’s reference to his student days leads one to believe that he may have had in mind his ideas for an ether drift experiment of 1899: his comments perhaps concern the experiment that he briefly mentioned in a letter to Mileva of 10 September 1899—“A good idea occurred to me in Aarau about a way of investigating how the bodies’ relative motion with respect to the luminiferous ether affects the velocity of propagation of light in transparent bodies.”25 His next letter to Mileva, dated to 28 September 1899,26 is the letter that informed her that he had just read Wien’s article, i.e. the article containing the Michelson-Morley experiment, among a discussion of other experiments, which confirms Einstein’s usage of the plural—“experiments of this kind”—in his lecture in Chicago.

This is certainly interesting and contrary to what has been historically accepted. So then the question is, why the discrepancy?

There is an evident contradiction between Einstein’s description in Chicago of the role played by the Michelson-Morley experiment and his own words of some decades later. How is this contradiction to be understood? Did Einstein let down his guard in Chicago and allow a historical inaccuracy to slip in—perhaps to please Michelson’s home crowd? His visit was indeed a great success: soon upon his return to Berlin, Einstein received an informal inquiry as to whether he would be interested joining the University of Chicago physics faculty, an offer which he described as attractive but which he politely declined.

When weighing the different accounts that Einstein gave of his relation to the Michelson-Morley experiment, there are good reasons to accord greater credence to his earlier words, spoken in Chicago and, presumably, Kyoto. One compelling reason is that these fit in well with the contemporary evidence, as argued above. Another, less direct but equally strong reason is that recent scholarship has shown that the later Einstein’s recollections of the development of his own research—in particular with regard to the general theory of relativity—were often colored by his subsequent philosophical beliefs and the research program he was pursuing at the time; this would be the highly theoretical unified field theory program, that had virtually no exchange with empirical science.30 This circumstance coincided with his much discussed pilgrimage from an empiricist philosophical position to that of a “believing rationalist” who seeks the unification of natural forces by exclusively mathematical creativity.31 In that process, the role of experiment lost prominence in both Einstein’s practice in physics, as well as in his philosophical thought.

Oh no! You mean he was slowly evolving into a string theorist?

{Sorry, cheap shot, but I couldn't help it!}

Like I said, this was a fascinating read. Hope you find it as entertaining and informative as I did.



Peter Morgan said...

Very interesting link. Thanks Zz.

The Science Pundit said...

Great article! Thanks for the link (and thanks Peter for pointing me here).

It's particularly interesting because (as I understand it) as a young man, Einstein considered himself very much an empiricist and "hands on" type. Funny how people change with age and experience. The older Einstein did have a point that the epistemology of the (capital E) Empiricists and positivists is indeed inadequate. But (imo) he did stray a bit too far into the "pure theorist" realm in that he unjustifiably minimized the (lower case e) empiricism of his youth.