You don't need an infinite number of universes, or even an infinite number of states in the one universe (if there is only one universe) to have something approaching immortality. If you limit yourself to the information theoretically containable in even something as small as a human-sized object, it would be many orders of magnitude greater than the amount of information processed by a human brain in a single lifetime. I think it would be relatively straightforward to calculate how many orders of magnitude using the Beckenstein Bound - perhaps someone could comment. If you allow for the potential information content in the whole visible universe, I'm sure that would be plenty of lifetimes for every human that has ever lived. The problem is not the number of possible lifetimes squeezed into the universe, but whether these possibilities will actually be realised.

In a many worlds interpretation of QM, all possibilities WILL be realised in some universe. If the universe is unique but infinite in extent (and hence contains an infinite amount of information), all possibilities will be realised provided that it is homogeneous but non-repeating. If all possible computations are implemented by virtue of their platonic existence, without the need for a "real" physical universe at all, then again all possibilities will be realised and we are immortal in this virtual heaven. If the universe collapses in such a way as to allow an infinite number of computations in a finite amount of time, as per Tipler, then potentially we will experience immortality, although I have not been able to understand how the quantisation of time would allow such a thing.

In a recent post ("All possible worlds in a single world cosmology?") I wondered about this question in a more pessimistic situation: one universe, containing a finite amount of matter/energy/information, expanding and cooling forever. As discussed above, even this model contains the possibility of near-immortality; certainly the possibility of at least every possible future our current limited minds could conceive. As you suggested, even single word interpretations of QM allow for extremely improbable events, such as the Earth quantum tunnelling to another star. I don't accept your notion of a minimal quantum of probability; there seems no reason to postulate such a thing. Given infinite time, such improbable events MUST occur - provided that the probability statys constant or increases per unit time. But if the probability decreases with time, then, even given eternity, it is NOT certain that the given improbable-but-not-impossible event will occur, so that immortality is not guaranteed. Bummer!

So far, no-one has been able to tell me what happens to the probability of bizarre quantum events occurring as t->infinity in a finite, eternally expanding universe, which incidentally seems more likely than the Tipler scenario.

Stathis Papaioannou

From: Danny Mayes <[EMAIL PROTECTED]>
Subject: regarding QM and infinite universes
Date: Mon, 26 Jul 2004 20:54:33 -0400

I posted this today on the Fabric of Reality Yahoo Group, but would like to get responses to it over here as well.

First, regarding the idea of magical universes or quantum immortality for that matter, doesn't this assume a truly infinite number of universes? However, if you start with the idea that the reality we experience is being created by a mechanical/computational process, isn't it more likely that the number of universes is just extremely large? Why should we assume the "creator" (however you choose to define that) has access to infinite resources? Also, everything that makes up our universe appears to have finite characteristics (per QM), so it seems like every possibility within the parameters of the multiverse could be covered by an enormous, but not infinite range of possibility.

My understanding of QM is that it describes possibilities (even if
vanishingly small) of bizarre things occurring in our everyday world.
For instance, I once read a book in which the author calculated the
possibility(incredibly small obviously) that our planet would suddenly
appear in orbit, fully intact, around another star.  He argued that QM
allows for this possibility.

I think we are overlooking something here.  It seems like there should
be a quanta of probabilty, just as there is (apparently) with time,
space, and matter.  In other words, once the probability of something
happening falls below a certain threshold, it is not realized.  Could
there be a Planck scale of probability?  Does decoherence somehow keep
these strange events from occurring on a macro scale?

Also, it seems to me that the violation of other physical laws comes
into play in preventing many scenarios from taking place.  For
instance, with quantum immortality, I understand the concept that if
there are infinite copies of me, there will always be one more
universe in which I survive another second.  But the reality is that
there would seem to be a rate of diminishing return here.  The
probability curve would have a point where it approaches zero, even as
the number of alternatives approached infinity.

Another way to resolve the immortality issue is to presume
consciousness survives death, but I will not remark on that further.

One thing that I think hurts the MWI as a theory is the misconception
among many that everytime a choice is made, the entire universe splits
in two, and there is a proliferation of all of these virtually
identical copies of universes out there somewhere.  In reality there
is only one universe, and there is a proliferation of differences
being created.  The only thing that matters are the recorded
differences, everything else remains unchanged. If you view our
reality as a virtual reality it is much easier to understand this
concept.  For instance a program that predicts the weather doesn't
have to create an entirely new simulation for each outcome it
predicts- it can overlap the various possibilities in one simulation.

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