----- Original Message -----

From: "Saibal Mitra" <[EMAIL PROTECTED]>

To: "aet.radal ssg" <[EMAIL PROTECTED]>

Subject: Re: Many Pasts? Not according to QM...

Date: Thu, 26 May 2005 19:02:19 +0200

>

> The original posting about this dates back from the beginning of

> this list. I just

> invoked this in this thread to argue why one should consider observer moments

> (identical ones considered as the same) as fundamental concepts.

>

> The suicide paradox I was referring to is just Tegmark's thought

> experiment where the

> experimenter measures the spin of a particle. If it is down he is

> instantly killed, he

> survives if it is up. Then he argues that according to the MWI the

> experimenter should

> always measure that the spin is up, because that's the only branch in which he

> survives.

>

> Saibal

>

> Quoting "aet.radal ssg" <[EMAIL PROTECTED]>:

>

> > For some reason I didn't get the original post about the suicide paradox,

> > so if someone could resend it, sans any "everything" computer lingo, I

> > would appreciate it.

> > The subject of the thread - "Many Pasts? - Not according to QM" taken on

> > its face seems false, at least from the standard MWI model. If you have

> > parallel worlds you have parallel pasts. In fact, that's why MWI is

> > supposed to be the solution to time travel paradoxes. Take an arbitrary

> > moment, when a measurement, or any other trigger, causes a decoherence,

> > move forward in time from that moment and look back - you have parallel

> > pasts that begin from the point of decoherence. ----- Original

> > Message ----- From: "Saibal Mitra" To: everything-list@eskimo.com

> > Subject: Re: Many Pasts? Not according to QM... Date: Wed, 25 May

> > 2005 01:24:23 +0200 > > > > > ----- Oorspronkelijk bericht -----

> > > Van: "Patrick Leahy" > Aan: > Verzonden: Wednesday, May 18,

> > 2005 05:57 PM > Onderwerp: Many Pasts? Not according to QM... > >

> > > > Of course, many of you (maybe all) may be defining pasts from

> > an > > information-theoretic point of view, i.e. by identifying

> > all > > observer-moments in the multiverse which are equivalent

> > as perceived by

> >

> > > > the observer; in which case the above point is quite irrelevant. (But

> > you > > still have to distinguish the different branches to find the total

> > measure > > for each OM). > > This is indeed my position. I

> > prefer to define an observer moment as the > information needed

> > to generate an observer. According to the

> > ''everything'' > hypothesis (I've just seen that you don't

> > subscibe this) an observer

> > moment > defines its own universe. But this universe is very

> > complex and therefore

> >

> > > must have a very low measure. It is thus far more likely that the

> > observer > finds himself embedded in a low complexity universe. >

> > > > One of the arguments in favor of the observer moment picture

> > is that it > solves Tegmark's quantum suicide paradox. If you

> > start with a set of all > possible observer moments on which a

> > measure is defined (which can be > calculated in principle using

> > the laws of physics), then the paradox

> > never > arises. At any moment you can think of yourself as being

> > randomly drawn

> > from > the set of all possible observer moments. The observer

> > moment who has > survived the suicide experiment time after time

> > after time has a very

> > very > very low measure. > > > Even if one assumes only a single

> > universe described by the MWI, one has

> > to > consider simulations of other universes. Virtual observers

> > living in such

> > a > simulated universe will perceive their world as real. The measure of such

> >

> > > embedded universes will probably decay exponentialy with

> > complexity.... > > > Saibal --

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>

>

>

>

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