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

From: John Collins <johnhcollins.domain.name.hidden>
Date: Fri, 27 May 2005 09:00:01 +0100

Stathis Papaioannou wrote:
> 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.
>
> --Stathis Papaioannou
    If there is a continuum of states in the multiverse (or, rather, if the
states are continuously indexed by the position and momentum of each
particle), then any situation that has a finite or countable description,
(in terms of your perception of that state through observer moments, for
instance) will occur with uncountably large measure, however unlikely the
state. If, however, the underlying basis of states in the multiverse has
itself a discrete structure, this would impose a 'cutoff' on very unlikely
events, so there would be a small fraction of universes wherein my trousers
will fall down at the busstop (why is it always busstops?) but literally
none at all wherein my shirt will fall up into the sky, there being no
configuration of the underlyimg physical variables that would
macroscopically correspond to such an event.
-- Chris Collins
Received on Fri May 27 2005 - 04:08:26 PDT