Re: [asa] Many Worlds Interpretation and ID

From: David Heddle <>
Date: Sun Aug 19 2007 - 06:47:57 EDT

Hi Phil,

I think Moorad is correct, although I'll admit as to never being much
interested in the far-out implications of the CI. However, I was always
taught that it is the interaction of the measurement device, which by
definition is strong enough to resolve the eigenstates, that collapses the
wavefunction. Furthermore, repeated "unmanned" measurements would give the
same result, as long there is no interaction that can cause an admixture
of eigenstates (or ifsuccessive measurements are done quickly.)

Thus if I have perfectly aligned magnets and the first measures spin up, so
will the following magnets, as long as nothing interferes in between
measurements to rotate the spin.

Where do I need a conscious observer? To argue that all those measurements
and all those magnets and all the detectors and all those archived data
existed in an admixture of "measured successive spins up" and "measured
successive spins down" is not, it seems to me, a requirement of the CI. CI,
as I have always learned it, states that after the first measurement, the
spin (relative to the direction of the field) collapsed to the measured
value, period.

David Heddle
Associate Professor of Physics
Christopher Newport University &
The Thomas Jefferson National Accelerator Facility

On 8/19/07, <> wrote:
> Moorad wrote:
> > Note that measuring devices force the
> > quantum system into the eigenvalues being measured. The latter is what
> the
> > collapse of the wave function means.
> Hi Moorad,
> at the present I've been changing my views on QM and so I don't hold to CI
> any more (as I once did), but I want to point out that advocates of CI will
> not agree with what you wrote. If something as macroscopic as
> Schroedinger's cat in a box can be supposed to exist in a superposition of
> states, then so can any sort of measuring equipment you might construct. So
> in CI the measuring equipment, photographic film, etc., all remain in a
> superposition of states until a conscious being looks at it. (I always
> wondered why the cat didn't count as conscious...) Then and only then it
> collapses to a single state and it looks to you as if it had been reading
> some specific value before you showed up. So in CI the wavefunction does
> not collapse when entangled with an instrument, but only when observed by a
> conscious being. This view puts consciousness in a role that implies it is
> the most fundamental element of nature, so this is not a physicalist vi ew.
> CI is completely consistent with everything we can observe in physics at
> the present (perhaps until we learn more about consciousness or the nature
> of time, etc.) IMO it is presently a matter of metaphysics or personal
> preference which view we choose to believe.
> Phil
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Received on Sun Aug 19 06:48:31 2007

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