HPS 0410 Einstein for Everyone

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Einstein as the Greatest of the Nineteenth Century Physicists

Note 1. (back to text)

It is interesting to speculate on just how much Einstein was troubled by the loss of determinism in quantum theory.

We can find clear, strong statements of his distaste for indeterminism. One occasion that elicited these statements was a proposal by Niels Bohr, H. A. Kramers and John C. Slater of 1924, known as the "BKS proposal." It was an ambitious sketch lacking precise mathematical development of how to advance the older quantum theory of the 1910s without employing Einstein's notion of the light quantum. It relied on atoms inducing one another to absorb and emit light through virtual radiation fields. These processes occurred in such a way that energy and momentum where not strictly conserved, but only on the average of many processes. That shortly proved its undoing when further experiments vindicated the strict conservation championed by Einstein.

There was much for Einstein to dislike in the proposal. In a private letter to the wife of a fellow physicist (Max Born), Einstein railed against the indeterminism of the BKS proposal:

"Bohr's opinion about radiation is of great interest. But I should not want to be forced into abandoning strict causality [JDN: determinism] without defending it more strongly than I have so far. I find the idea quite intolerable that an electron exposed to radiation should choose of its own free will, not only its moment to jump off, but also its direction. In that case, I would rather be a cobbler, or even an employee in a gaming-house, than a physicist. Certainly my attempts to give tangible form to the quanta have foundered again and again, but I am far from giving up hope. And even if it never works there is always that consolation that this lack of success is entirely mine."

Einstein to Hedwig Born, 29 April 1924, in, Max Born, ed., The Born-Einstein Letters. Walker & Co., New York, 1971, p.82.

Remarking in a similar vein on the BKS proposal to Paul Ehrenfest, Einstein wrote more tersely: "A final abandonment of strict causality is very hard for me to tolerate." Einstein to Ehrenfest, 31 May 1924; quoted in M. J. Klein, "The First Phase of the Bohr-Einstein Dialogue," Historical Studies in the Physical Sciences, 2 (1970), pp. 1-39 on p.33

Was this distaste for indeterminism as important as his later concern that quantum theory was giving up on the notion of a local reality? I'm not sure that Einstein ever makes quite clear in his writings which was the more troubling failing. However we have an indirect report from Wolfgang Pauli, a physicist who knew Einstein well. The following is from a letter Pauli wrote to Max Born on March 31, 1954:

"...Einstein does not consider the concept of 'determinism' to be as fundamental as it is frequently held to be (as he has told me emphatically many times), and he denied energetically that he had ever put up a postulate such as (your [citation to a letter of Born's]): 'the sequence of such conditions must also be objective and real, this is, automatic, machine-like, deterministic'. In the same way, he disputes that he uses as criterion for the admissibility of a theory the question: 'Is it rigorously deterministic?'

Einstein's point of departure is 'realistic' rather than 'deterministic', which means that his philosophical prejudice is a different one..."

Max Born, ed., The Born-Einstein Letters. New York: Walker & Co., 1971.p. 221