On 5/12/2012 11:21 PM, scerir wrote:

H. Kragh ("Dirac: a Scientific Biography", Cambridge U.P., 1990) reports
a 1927 discussion between Dirac, Heisenberg and Born, about what
actually gives rise to the so called "collapse" (reduction of waves packet).
Dirac said that it is 'Nature' that makes the choice (of measurement
outcome). Born agreed.  Heisenberg however maintained that, behind

the collapse, and the choice of which 'branch' the wavefunction would

be followed, there was "the free-will of the human observer".


I don't think this does justice to Born's views.

He was not a realist about the wave function

nor about its collapse.  His position was that

the classical world was *logically* prior and

necessary for shared knowledge to exist.

Without it there could be no measured

values and no records.

Brent, maybe so, but Born wrote the following:

"The question of whether the waves are something

"real" or a function to describe and predict

phenomena in a convenient way is a matter of
taste. I personally like to regard a probability

wave, even in 3N-dimensional space, as a real thing,

certainly as more than a tool for mathematical
calculations ... Quite generally, how could we

rely on probability predictions if by this notion

we do not refer to something real and objective?"

(Max Born, Dover publ., 1964, "Natural Philosophy

of Cause and Chance", p. 107)

I stand corrected.


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