Bruno Marchal wrote:
> 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
>>> 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
> 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
> a bit less obvious, but I am not even sure given that I have not yet
> 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.
If we can't show that a quasi-classical world emerges from QM we will
abandon it - at least as fundamental. Perhaps the long sought quantum
theory of gravity will come to the rescue.
>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
> 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
Do you have a reference for Weinberg? I'd like to read his paper. I
wonder how it would apply to the idea that there is a smallest unit of
Do you agree that the other forms of multiverse, besides Everett's, are
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