Hal:

I usually do not argue your posts (pro or con) because I feel whatever you
write is in a 'different' discipline for me (euphemism: for 'above my
head').
Now I have a fundamental remark:

Whatever you QM etc. abiding minds conclude (including the published
science) is within our PRESENT *knowledge-base* (mindset, actual cognitive
inventory, naming is open). I don't hold myself above such, just acknowledge
that human *k-b* was flimsier in the past and will be less(?) flimsy in the
future (but still flimsy), so our likes/dislikes are no proof for the
actualities of nature (like: simpler, less axioms, etc.). If there is a
'measure' it is our (present) human figment.

MWI: Tegmark is right: (knowledgeable) people hate it at least. I don't, as
a matter of fact I apply it in my 'narrative' with a vengeance: in the
course of origination I do not specify formational qualia (and the negative
is pointing rather to 'ALL may be very very different') so the MW membership
is as diverse as it can - beyond our widest imagination (which is still
based on this little poor universe we have some experience about.)
So those equations derived from mathematical consideration within this one
have not too much credit for (potentially) fundamentally different systems.
This may be one reason why we know nithing about "them". And this ignorance
is the foundation of the 'hate'. People dislike to 'not know'.
I include the ignorance of 'most of it' and consider our information very
very partial so I can accept the 'rest of it' as unknown/unknowable.

Why I accept the possible 'existence' of the multiverse? because I see no
reason not to. Our uniqueness and sole existence should be justified in the
multitude of everything and so far we could not come up with a good reason
for our exclusivity. I know: nescio non est argumentum against, but it is no
argument pro either. (This opinion is just as flimsy as the opposite
position.)

String theory? I don't know the first thing about it (Pun: 1st: what is
'string' - beyond the math-fiction?). A consequence drawn upon it is at
least subject to the credibility of the base. (Understandability? that would
be too human).
I wrote a remark on the new MIT invention that 'spacetime is a liquid'  in
which I humbly asked about the string-loop vibration as QM-al 'waves' and
the straight string endings as the electrically charged subatomix, an
explanation using the non-explained. (I know: this may be the route of
advancement and I use it myself, - you have to 'dare' to innovate.)

The never-never land of substituting math for common sense is disturbing for
simpleminded non-mathematicians, no matter how advanced they want to think.
Multiverse fits, with enough (non-math) imagination, string does not.
This is my way to look at it, I am not ready to defend it. Especially not on
the turf of the opponent.

Regards

John Mikes

On 9/24/07, "Hal Finney" <[EMAIL PROTECTED]> wrote:
>
>
> New Scientist has an article on parallel universes:
>
> > David Deutsch at the University of Oxford and colleagues have shown
> > that key equations of quantum mechanics arise from the mathematics of
> > parallel universes. "This work will go down as one of the most important
> > developments in the history of science," says Andy Albrecht, a physicist
> > at the University of California at Davis. In one parallel universe,
> > at least, it will - whether it does in our one remains to be seen.
>
> It is behind a paywall at
>
> http://space.newscientist.com/article/mg19526223.700-parallel-universes-make-quantum-sense.html
> but I found a copy on Google Groups:
>
> http://groups.google.com/group/alt.kq.p/browse_thread/thread/9631b2e37ba5e7a2/fb3202c9c5b71228?lnk=st&q=%22new+scientist%22+deutsch+albrecht&rnum=1#fb3202c9c5b71228
>
> It has a great quote from Tegmark: "The critique of many worlds is
> shifting from 'it makes no sense and I hate it' to simply 'I hate it'."
>
> The thrust of the article is about recent work to fix the two perceived
> problems in the MWI: non-uniqueness of basis (the universe splits in all
> different ways) and recovering the Born rule. The basis problem is now
> considered (by supporters) to be resolved via improved understanding
> of decoherence. This work (which was not particularly focused on the
> MWI) generally seems to lead to a unique basis for measurement-like
> interactions, hence there is no ambiguity in terms of which way the
> universe splits.
>
> As for the Born rule, the article points to the effort begun by Deutsch in
> 1999 to base things on decision theory. The idea is that we fundamentally
> care about probability insofar as it influences the decisions and choices
> we make, so if we can recover a sensible decision theory in the MWI, we
> have basically explained probability. I've seen a number of critiques of
> Deutsch's paper but according to this article, subsequent work by David
> Wallace and Simon Saunders has extended it to the point where things
> are pretty solid.
>
> Hence the two traditional objections to the MWI are now at least arguably
> dealt with, and given its advantage in terms of formal simplicity (fewer
> axioms), supporters argue that it should be considered the leading
> model for QM. This is where we get claims about it being among the most
> important discoveries in the history of mankind, etc.
>
> It's interesting to see the resistance of the physics community to
> multiverse concepts. It all comes back to the tradition of experimental
> verification I suppose, which is still pretty much impossible. Really
> it is more a question of philosophy than of physics as we currently
> understand these disciplines.
>
> We see the same thing happening all over again in string theory. I
> don't know if you guys are following this at all. String theory is
> going through a crisis as it has turned out in the past few years that
> it does not predict a single universe, rather a multiverse where there
> is a "landscape" of possible sets of parameters, each of which would
> correspond to a universe. The big problem is that there is no natural
> or accepted measure (unlike with QM where everyone knew all along that
> the measure had to be the Born rule and it was just a matter of how
> many hoops you had to jump through to pull it out of your model).  As a
> result it looks like it might be impossible to get even probabilistic
> predictions out of the string theory landscape.
>
> AFAIK no one within the community has followed our path and looked
> at algorithmic complexity as a source of measure (i.e. the Universal
> Distribution, which says that the simplest theories have higher measure).
> Granted, even if that direction were pursued it would probably be
> computationally intractable so they still would not be able to pull much
> out in the way of predictions. Neverthless physicists are skilled at the
> use of approximation and assumptions to get plausible predictions out of
> even rather opaque mathematics so it's possible they might get somewhere.
>
> But at this point it looks like the resistance is too strong. Rather
> than string theory making the multiverse respectable as we might hope,
> it seems likely that the multiverse will kill string theory.
>
> Hal Finney
>
> >
>

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