On Mon, Dec 10, 2012 at 10:25 AM, meekerdb <meeke...@verizon.net> wrote:

>  On 12/10/2012 2:47 AM, Bruno Marchal wrote:
>  On 10 Dec 2012, at 02:03, Jason Resch wrote:
> On Sun, Dec 9, 2012 at 6:51 PM, meekerdb <meeke...@verizon.net> wrote:
>>   On 12/9/2012 4:37 PM, Jason Resch wrote:
>> On Sun, Dec 9, 2012 at 5:40 PM, meekerdb <meeke...@verizon.net> wrote:
>>>  On 12/9/2012 12:08 PM, Jason Resch wrote:
>>>  And without a doubt the most popular interpretation of Quantum
>>>> Mechanics among working physicists is SUAC (Shut Up And Calculate),
>>>  That's not an interpretation at all.
>>> Well for a more philosophical statement of it see Omnes.  His view is
>>> that once you can explain the diagonalization of the the density matrix
>>> (either by eigenselection, dechoherence, or just assumed per Bohr) then you
>>> have predicted probabilities.  QM is a probabilistic theory - so predicting
>>> probabilities is all you can ask of it.
>> Is science just about its applications or about understanding the world?
>> I would argue that science would not progress so far as it has if we
>> thought finding the equation was the be all and end all of science.  The
>> "shut up and calculate" mindset can be translated as "don't ask
>> embarrassing questions", it is the antithesis of scientific thinking.
>> Student in the 1500s: Does the earth move about the sun, or do the
>> planets merely appear to move as if earth moved about the sun?
>> Professor in the 1500s: We have all the formulas for predicting planetary
>> motion, so shut up and calculate!
>> Fortunately, Copernicus wasn't satisfied with that answer.
>>  So what's your objection to Omnes?  That the world just can't be
>> probabilistic?  So instead there must be infinitely many inaccessible
>> worlds - which happen to mimic a probabilistic world.
> It is fine if QM is a probabilistic theory.  Where I disagree with him is
> in his belief that we can never go beyond that in our understanding of it.
> I am not sure how accurate this statement is, since it is a secondary
> source, but http://en.wikipedia.org/wiki/Roland_Omn%C3%A8s says: "We will
> never, Omnès believes, find a common sense interpretation of quantum law
> itself."  To me, it almost seems as if he says it is not worth trying to
> find an answer.  I lean more towards David Deutsch who says science is
> about finding good explanations.
>  Omnes is very special. His many books gives the best account and defense
> of the MWI, except that in the last paragraph, or chapter, he insist that
> we have to be irrational, in fine, and select one reality. This is really
> cosmo-solipsism, and makes QM indeed no more rational at all.
> What's not rational about it?  I think 'rational' just means 'being able
> to give coherent reasons'.  There's a perfectly good coherent reason for
> 'selecting' one reality - we experience one reality.
It is as rational as clinging to geocentric theories on the basis that we
don't feel the Earth moving when Newtonian mechanics fully explains not
only the motions of the planets but also why we don't feel the Earth move.

Everett argued this point best
http://www.pbs.org/wgbh/nova/manyworlds/orig-02.html :

A crucial point in deciding on a theory is that one does not accept or
reject the theory on the basis of whether the basic world picture it
presents is compatible with everyday experience. Rather, one accepts or
rejects on the basis of whether or not the experience which is predicted by
the theory is in accord with actual experience.

Let me clarify this point. One of the basic criticisms leveled against the
Copernican theory was that "the mobility of the earth as a real physical
fact is incompatible with the common sense interpretation of nature." In
other words, as any fool can plainly see the earth doesn't really move
because we don't experience any motion. However, a theory which involves
the motion of the earth is not difficult to swallow if it is a complete
enough theory that one can also deduce that no motion will be felt by the
earth's inhabitants (as was possible with Newtonian physics). Thus, in
order to decide whether or not a theory contradicts our experience, it is
necessary to see what the theory itself predicts our experience will be.

Now in your letter you say, "the trajectory of the memory configuration of
a real physical observer, on the other hand, does not branch. I can testify
to this from personal introspection, as can you. I simply do not branch." I
can't resist asking: Do you feel the motion of the earth?

In another place: "...Everett's theory contains all possible branches in it
at the same time. In the real physical world we must be content with just
one branch. Everett's world and the real physical world are therefore not
isomorphic." Yet another: "But the real world does not branch, and therein
lies the flaw in Everett's scheme."

I must confess that I do not see this "branching process" as the "vast
contradiction" that you do. The theory is in full accord with our
experience (at least insofar as ordinary quantum mechanics is). It is in
full accord just because it is possible to show that no observer would ever
be aware of any "branching," which is alien to our experience as you point

The whole issue of the "transition from the possible to the actual" is
taken care of in a very simple way—there is no such transition, nor is such
a transition necessary for the theory to be in accord with our experience.


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