Re: multiverse talk

From: Bruno Marchal <marchal.domain.name.hidden>
Date: Tue, 8 Jul 2008 16:03:09 +0200

On 08 Jul 2008, at 01:08, Brent Meeker wrote:

>
> Ronald Held wrote:
>> I am giving a talk on the Multiverse to Star Trek fans in several
>> weeks. I would appreciate any advice and suggestions, since as of
>> now,
>> I have an outline based on Tegmark's four levels.
>>
>>>
>>
>
> One thing I would avoid is presenting the multiverse (of any level)
> as the
> latest "gee-whiz, science has discovered that..." It is interesting
> speculative metaphysics. Good fodder for SciFi fans but not yet
> science.


I disagree. It is the collapse axiom which has been a speculation all
along: to avoid
macroscopic superpositions. I totally agree with David Deutsch that QM
is the science
of parallel universes, except that I have abandoned eventually the
very notion of
"primary physical universe", and I prefer the many histories or many
dreams wording
which fit better with respect to the mind-body problem in the
mechanist frame.
I am not saying that the MW solves all conceptual problems of QM
'course. But the belief
in the existence and unicity of the Physical Universe is equivalent to
saying that
QM is false, and up to now, *that* is the speculation.
Then with just the digital mechanist thesis, the existence of the many
dreams is even
more obvious. That physics has to emerge from those many dreams is
(apparently)
a bit less obvious, but I am not even sure given that I have not yet
heard
any objection but wishful thinking.

If I look to a particle in the state "(UP + DOWN)", the state "I
cross (UP + DOWN)"
evolves (by SWE) to:

"I-seeing-UP cross UP + I-seeing-DOWN cross DOWN",

I don't see how to avoid this without abandoning QM. The collapse can
be explained
*phenomenologically* (first person plural) through MW + decoherence.
And if I make a decision based on what state I measure on the
particle, the divergence will
propagate.

And Weinberg has given a convincing argument that once SWE is made
slightly non
linear, then, not only we keep the Many Worlds/Dreams, but interaction
is made
possible between them (falsifying then thermodynamics though: that is
why I don't
take that the delinearisation of the SWE idea very seriously). That's
speculation.

Bruno
http://iridia.ulb.ac.be/~marchal/




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Received on Tue Jul 08 2008 - 10:03:20 PDT

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