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

From: Saibal Mitra <smitra.domain.name.hidden>
Date: Fri, 27 May 2005 14:29:07 +0200

----- Oorspronkelijk bericht -----
Van: "Stathis Papaioannou" <stathispapaioannou.domain.name.hidden>
Aan: <smitra.domain.name.hidden>
CC: <smitra.domain.name.hidden>; <everything-list.domain.name.hidden.com>
Verzonden: Friday, May 27, 2005 01:44 AM
Onderwerp: Re: Many Pasts? Not according to QM...


> Saibal Mitra wrote:
>
> >Quoting Stathis Papaioannou <stathispapaioannou.domain.name.hidden>:
> >
> > > On 25th May 2005 Saibal Mitra wrote:
> > >
> > > >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.
> > >
> > > I'm not sure what you mean by "the paradox never arises" here. You
have
> > > said
> > > in the past that although you initially believed in QTI, you later
> >realised
> > >
> > > that it could not possibly be true (sorry if I am misquoting you, this
> >is
> > > from memory). Or are you distinguishing between QTI and QS?
> > >
> >That's correct. In both QTI and QS one assumes conditional probabilities.
> >You just
> >throw away the branches in which you don't survive and then you conclude
> >that you
> >continue to survive into the infinitely far future (or after performing
an
> >arbitrary
> >large number of suicide experiments) with probability 1.
> >
> >But if you use the a priori probability distribution then you see that
you
> >the measure
> >of versions of you that survive into the far future is almost zero.
>
> What does "the measure of versions of you that survive into the far future
> is almost zero" actually mean? The measure of this particular version of
me
> typing this email is practically zero, considering all the other versions
of
> me and all the other objects in the multiverse. Another way of looking at
it
> is that I am dead in a lot more places and times than I am alive. And yet
> undeniably, here I am! Reality trumps probability every time.


You have to consider the huge number of alternative states you could be in.

1) Consider an observer moment that has experienced a lot of things. These
experiences are encoded by n bits. Suppose that these experiences were more
or less random. Then we can conclude that there are 2^n OMs that all have a
probability proportional to 2^(-n). The probability that you are one of
these OMs isn't small at all!

2) Considering perforing n suicide experiments, each with 50% survival
probability. The n bits have registered the fact that you have survived the
n suicide experiments. The probability of experiencing that is 2^(-n). The
2^(n) -1 alternate states are all unconscious.


So, even though each of the states in 1 is as likely as the single state in
2, the probability that you'll find yourself alive in 1 is vastly more
likely than in 2. This is actually similar to why you never see a mixture of
two gases spontaneously unmix. Even though all states are equally likely,
there are far fewer unmixed states than mixed ones.

Saibal
Received on Fri May 27 2005 - 09:07:19 PDT