Earlier, scerir wrote:
>
>
>
> As far as I know the MWI is not a theory about physical, real,
> objective worlds. These worlds are - for the observer - just a
> subjective concept, perceptions, consciousness.
> All these worlds form the universe, which is real, one,
> physical, objective.
It's my understanding that expert opinions differ considerably over this
matter of alternate histories being real or possibly real. David Deutsch
argues for the actual reality of all conceivable branching histories
that could result from different quantum events. Others, like Seth Lloyd
and Murray Gell-Mann, have seemed to indicate that, while Many Worlds is
the best explanation of quantum happenings, the other Worlds should be
looked at as only potentially real, but not actually real? Deutsch and
Lloyd even had a brief debate on the this matter on the Hotwired web
site, back last year sometime, I think.
> But the number or worlds is very far from being defined.
> These worlds continue to multiply!.
I am reminded here that a really worthwhile source of detail on the
general properties of Many Worlds theories is Michael Clive Price's
"Everett FAQ", at http://www.hedweb.com/everett/everett.htm#splitsh
Here, under the slightly misleading heading, "Could we detect other
Everett-worlds?", Price describes an interestingly advanced experiment
for someday "proving" that a alternate worlds exist. *However*, and
unfortunately for the sake of *really* proving this point, what Price
describes is just a more realistic version of the old Shroedinger's Cat
conundrum. In effect, Price just wants to put a special, reversible
computer into a superposition of two different states, then he wants to
reverse the whole procedure so that the computer is gently brought back
out of the superposition, without the whole unusual effect being
"collapsed" or decohered before the end of the experiment. This is not
really anything quite like "detecting another world", and on that level
it might seem a bit disappointing. However, this *is* an advanced idea
for inferring that a really weird superposition "must have happened"
inside a closed box.
As an advanced superposition demo, Price's scenario seems much more
convincing to me than the old Schroedinger's Cat idea ever did. In other
words, if Price's computer could be indirectly shown to have "thought
two ways at the same time", that would represent a superposition that
would be hard not to think of as involving two separate, existing worlds
at that point. Note though, that everything in this superposition has to
be reversed exactly without contacting the outside world in any way, in
order for the inference of two "overlapping computer thoughts" to work.
So nothing can really be proven, since you don't actually get any
message or info from the two separate "worlds" of the superposition!
Looks to me like I have to be an "agnostic forever" on this, since there
is no sure way to tell the reality of indirect inferences of events
previously set up (and then reversed).
David Blenkinsop <blenl@sk.sympatico.ca>
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