Sunday, March 10, 2002

COPENHAGEN FOLLOWUP: Jeremy Olson of We Are Full Of Shit. points out this Slate article by Jim Holt on what people get wrong about Heisenberg and his famous uncertainty principle. And some other things about him:

Heisenberg, one of the inventors of quantum mechanics, was the leader of Hitler's atomic bomb project during World War II. After the war, he claimed that he had deliberately sabotaged the Nazi bomb effort. Many believed him. But last month, his protestations of innocence (indeed, valor) were revealed to have been almost certainly a lie. Letters written by the Danish physicist Niels Bohr, released to the public for the first time, make it pretty clear that Heisenberg was doing everything he could to produce a nuclear weapon for the Third Reich. His failure was due not to covert heroism but to incompetence.

Apparently Heisenberg was one of these genius-klutzes who knew what he knew but probably couldn't open a bottle of wine without hurting somebody. (I exaggerate.) Holt has a larger ax to grind though:

Those who, prior to last month's revelation about Heisenberg, wished to stress the supposed murkiness of his wartime motives often reached for a metaphor from his physics: the uncertainty principle. Michael Frayn did it in Copenhagen, his play about a mysterious 1941 encounter between Heisenberg and Bohr. Thomas Powers did it in Heisenberg's War, the 1993 book that defended Heisenberg's claim to have destroyed the Nazi bomb project from within. David C. Cassidy did it in the very title of his 1991 biography of Heisenberg, Uncertainty. They should all have known better.

And they're hardly alone. No scientific idea from the last century is more fetishized, abused, and misunderstood—by the vulgar and the learned alike—than Heisenberg's uncertainty principle. The principle doesn't say anything about how precisely any particular thing can be known. It does say that some pairs of properties are linked in such a way that they cannot both be measured precisely at the same time. In physics, these pairs are called "canonically conjugate variables." One such pair is position and momentum: The more precisely you locate the position of a particle, the less you know about its momentum (and vice versa). Another is time and energy: The more precisely you know the time span in which something occurred, the less you know about the energy involved (and vice versa).

How could this principle of physics be applied to Heisenberg the man? In the postscript to Copenhagen, Frayn writes, "There is not one single thought or intention of any sort that can ever be precisely established." Well, maybe; but the uncertainty principle applies to pairs of properties. In Heisenberg's case, the relevant pair is motivation and competence. How willing was he to help Hitler? How competent was he to produce an atomic bomb? But notice that there is a positive relationship between our knowledge of one and of the other: The more certain we become that Heisenberg was willing to serve the Third Reich, the more certain we become that he was incompetent to produce a bomb. This is not the uncertainty principle, but its exact opposite. Evidently, knavishness and incompetence are not canonically conjugate variables.

Neat little read. I still want to see Copenhagen, tho'.

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