From: scerir (scerir@libero.it)
Date: Fri Jun 13 2003 - 14:56:55 MDT
Hal :
> What are "the very conditions which define the possible types of
> predictions"? Isn't this phrase the same as "the experimental setup"?
> That is, it is the experimental setup which defines the possible types
> of predictions which can be made. It is the setup which determines
> whether you are measuring position or momentum. It is the setup which
> determines whether you detect which slit a particle went through in a
> two slit experiment.
> If so, Bohr is referring to the possibility of "an influence on [the
> experimental setup" as a resolution to the EPR paradox. But what
> determines the experimental setup? It is the decision by the scientist,
> the experimenter, about what to measure. Bohr's words, taken literally,
> imply that he is describing an influence on the decision of what to
> measure. That is, our choice of what to measure is not free, but is
> somehow influenced by the non-local correlations. [...]
Bohr wrote two different (obscure) things, about EPR.
In 1935 (Nature, 136, p. 65) he wrote
"It is true that in the measurement under consideration
any direct mechanical interaction of the [second] system and the
measuring agencies is excluded, but a closer examination reveals
that the procedure of measurements has an essential influence
on the conditions on which the very definition of the physical
quantities in question rests."
And later, in 1935 (Physical Review, 48, p. 696) he wrote, i.e.
"there is ... no question of a mechanical disturbance of the
system under investigation ... [but] there is essentially the
question of an influence on the very conditions which define
the possible types of predictions regarding the future behavior
of the system." And he also wrote " ... we are not dealing with
an incomplete description characterized by the arbitrary picking
out of different elements of reality at the cost of sacrificing
other such elements, but with a rational discrimination between
essentially different experimental arrangements and procedures..."
Now, there are, imho, several possible interpretations. I.e.:
- The choice on the left side (of a EPR setup)does have an influence
on the condition that defines what happens (in the future) on the
right side;
- The choice on the left side (of a EPR setup)does have an influence
on the condition that defines the meaning of (the counterfactual
statement about) what might have happened (in the past) on the
right side; that is to say that performing one of the earlier
possible measurements excludes the possibility of performing
an alternative possible one;
- There is an action-at-a-distance (in Bohrian terms, an "influence",
maybe unphysical too) which directly blocks the EPR argument (saying
that subsystems are "separable"); and this is, i.e., what Henry Stapp
believes;
- Much more elaborate suggestions are at quant-ph/0110107 and
quant-ph/0102053.
Btw John Bell suggested - en passant - a sort of iper-determinism,
in the sense that even actions of observers and choices made
by experimenters were pre-determined. In this sense - he thought -
any problem related to EPR was easy solvable.
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