On Mon, Apr 04, 2011 at 02:25:04PM -0700, Nick Prince wrote:
> 
> Hi Russell
> 
> Hi Russell
> 
> Sorry I'm not making it clear what I meant – but I think I may have
> got a handle on it now.  I was thinking about Bruno’s  thought
> experiment. Suppose I am encoded in Brussels, my original is destroyed
> and I am  reconstituted in Moscow and Washington. The reconstitution
> in Moscow is immediate, but in Washington, it  takes  place after a
> delay of a year or so.
> 
> Now this single universe process is assumed to carry over into the
> case of a universe which splits via MWI, at an appropriate time, into
> one where I survive some disaster and another in which I do not.  But
> suppose in the one where I do not survive, the medics manage to make a
> copy of me which gets activated a year or so later.  This then mirrors
> Bruno’s experiment.  Now I think I was getting mixed up about
> Microscopic and macroscopic things and thought that somehow this
> violated QM in some way.  However as long as the copying process
> produces an “appropriate” Hamiltonian representing the “me” which is
> sufficient to encapsulate what was essentially my consciousness and
> “state” prior to the split, then the gap should be just the same as in
> Bruno’s example.  Would you (anyone) disagree?  What constitutes an
> appropriate Hamiltonian of me is another issue, but in principle this
> is what I am thinking is the way to approach the two parallel
> situations.
> 
> Best
> 
> Nick
> 

Thanks Nick. I had got the wrong end of the stick. You have cleverly
highlighted an intuition pump that exposes a potential difference
between QM and COMP. If you took causality to be important for
consciousness then you would have to disagree at Bruno's step 4 of the
UDA. You would also disregard continuations that existed outside our
future light cone - such as the case of Tegmark's level 1 Multiverse
(spatially separated regions of spacetime that happen to have the same
microscopic configuration).

I think that causality is a red herring here (and possibly even a
misleading concept). What counts is consistency between prior and
successor observer moments. Then step 4 goes through in the quantum
multiverse, as it does in Bruno's teleportation experiment.

On a somewhat related issue, let me proved that time machines are
possible, in principle. Consider David Deutsch's discussion of time
travel in which he resolves the grandfather paradox by means of the
multiverse. When you travel back in time, and then folloow the normal
course of history, you will end up (with near certainty - ie
probability 1) in a different branch to where you started. If you kill
your own grandfather, you will definitely end up in a branch in which
your grandfather never had your father.

To travel in time and (multi-) space in the Multiverse has to be
equivalent to selecting a particular book from the Library of
Babel. And how might you do that? There is no catalogue - the
catalogue is somewhere there in the library, along with all its false
cousins. The only possibility is to have the book to start with, then
you could find its copy in the library. Just the same, time travel in
the multiverse requires you to have an accurate description of the
past observer moment - and the machine can only select an OM that is
consistent with your description, it cannot know which of the
infinitely many consistent OMs you had in mind, though.

So all you need to go back in time is a sufficiently powerful virtual
reality generator to generate the experience of what you remembered
being at that time. The future history will, of course, unfold
completely differently, just as in the example above, so any such
machine will be useless for winning the lottery.


Cheers
-- 

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Prof Russell Standish                  Phone 0425 253119 (mobile)
Mathematics                              
UNSW SYDNEY 2052                         hpco...@hpcoders.com.au
Australia                                http://www.hpcoders.com.au
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