Re: [asa] Spooky Action At A Distance: Still Spooky

Oh, goodie, I'm not alone!

Michael
----- Original Message -----
From: "Christine Smith" <christine_mb_smith@yahoo.com>
To: <asa@calvin.edu>
Sent: Thursday, April 19, 2007 10:11 PM
Subject: Re: [asa] Spooky Action At A Distance: Still Spooky

Um, can someone please translate this into English?? I
never could quite grasp the idea of quantam
mechanics...

Thanks!
Christine

--- Rich Blinne <rich.blinne@gmail.com> wrote:

> On 4/19/07, David Campbell <pleuronaia@gmail.com>
> wrote:
> >
> > > Most working scientists hold fast to the concept
> of 'realism'-a
> > viewpoint
> > > according to which an external reality exists
> independent of
> > observation.
> > > But quantum physics has shattered some of our
> cornerstone beliefs...Our
> > result suggests that giving up the concept of
> locality is not sufficient to
> > be consistent with quantum experiments, unless
> certain intuitive features of
> > realism are abandoned.
> >
> > This seems (the full article won't open for me) to
> address some
> > specific aspects of particular versions of
> realism. However, the new
> > study is still firmly grounded on the assumption
> that an external
> > reality exists independent of observation. It
> asserts that making the
> > observation has an effect on the external reality;
> however, making the
> > same observation has the same effect on the
> external reality. In
> > other words, the existence but not the behavior of
> the external
> > reality is independent of observation. They are
> claiming that anyone
> > with the equipment could make the same experiment
> and reach the same
> > conclusions. Thus, these results do not provide
> legitimate support
> > for relativism of the sort that claims, e.g., that
> science is merely a
> > cultural product or that there cannot be moral
> absolutes.
>
>
> Not only that, but on further looking into it, I
> noted the review article in
> Nature which implied that results are not as earth
> shattering as I had
> originally assumed:
>
>
> > But after Bell's discovery that local realism
> entailed a limit on the
> > correlations - a limit he expressed in his
> celebrated
>
inequalities4<http://www.nature.com/nature/journal/v446/n7138/full/446866a.html#B4>-
> a series of ever more ideal experiments (ref.
> > 5
>
<http://www.nature.com/nature/journal/v446/n7138/full/446866a.html#B5>and
> references therein) has led us to abandon the
> concept. It is then
> > natural to raise the question of whether one
> should drop locality - which
> > equates to the impossibility of any influence
> travelling faster than light -
> > or rather drop the notion of physical reality.
> >
> > There is no logical answer to that question: one
> can choose to abandon
> > either concept, or even both. Tony Leggett has
>
explored6<http://www.nature.com/nature/journal/v446/n7138/full/446866a.html#B6>one
> of these possibilities by considering a particular
> class of physically
> > plausible theories that abandon locality, but
> maintain realism. He found
> > these theories to be incompatible with quantum
> mechanics, and expressed the
> > disagreement by new
>
inequalities6<http://www.nature.com/nature/journal/v446/n7138/full/446866a.html#B6>.
> > As there was no experimental result available to
> test Leggett's
> > inequalities, a new type of measurement was
> necessary.
> >
> > In experiments detailed on page
>
871<http://www.nature.com/nature/journal/v446/n7138/full/nature05677.html>of
> this issue
> > 7
>
<http://www.nature.com/nature/journal/v446/n7138/full/446866a.html#B7>,
> > Gröblacher *et al*. have carried out such
> measurements. They modified an
> > experiment previously used to test Bell's
> inequalities through measurements
> > on two photons (Box
>
1<http://www.nature.com/nature/journal/v446/n7138/box/446866a_BX1.html>)
> > by changing the original linear polarization
> measurement into an elliptical
> > polarization measurement. This is readily done by
> inserting a quarter-wave
> > plate in front of a standard (linear) polarizer.
> From an experimental point
> > of view, however, the new test is more demanding,
> and requires almost ideal
> > optical elements and a high signal-to-noise ratio.
> Thanks to their
> > high-efficiency source of entangled photons, the
> authors meet these
> > requirements, and find a significant violation of
> the generalized Leggett's
> > inequalities that they have established. Following
> Leggett, they conclude by
> > questioning realism rather than locality - at
> variance with the often-heard
> > statement that "quantum mechanics is non-local".
> >
> > Interesting as this conclusion is, it remains a
> matter of personal
> > preference, not of logical deduction. The
> violation of Bell's inequalities
> > implied that realism and locality are not
> simultaneously tenable. Violation
> > of Leggett's inequalities implies only that
> realism and a certain type of
> > non-locality are incompatible: there are *other
> types of non-local models
> > that are not addressed by either Leggett's
> inequalities or the experiment*.
> > [emphasis mine]
> >
> >
> >
> >
>

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Received on Thu Apr 19 18:25:38 2007