On 9/27/2011 4:18 PM, nihil0 wrote:

> > 1) There is an infinite number of Hubble
> > volumes in our universe, which are all casually disconnected (as the
> > theory of inflation implies). 2) There is a limit on how much matter
> > and energy can exist within a region of space of a given size, such as
> > a Hubble volume. 3) There is only a finite number of possible
> > configurations of matter, due to the Uncertainty Principle.
> > I can explain any of these ingredients in more depth if you'd like me
> > to, but I hope you see that they lead to the conclusion that all
> > quantum-physical possibilities in our universe are realized infinitely
> > many times.

On Sep 27, 7:47 pm, meekerdb <meeke...@verizon.net> wrote:

> No they don't.   There's an implicit assumption that what happens in these 
> other universes
> has the same or similar probability distribution as we observe in ours.  A 
> reasonable
> assumption, but not a logically necessary one.  I think it's what Bruno means 
> by
> "homogeneous".  It's logically possible that all but a finite number of these 
> universes
> are just exact copies of the same completely empty universe, for example.
> Brent

You imply that it's logically possible that there is only a finite
number of universes that are filled with matter, and you seem to think
few will resemble ours. However, according to Vilenkin, Greene, and
Tegmark, a generic prediction of the theory of inflation is that there
is an *infinite* number of Hubble volumes (what you are calling
universes).  Let's call the hypothesis that all quantum-physical
possibilities are realized infinitely many times "the hypothesis of
Cosmic Repetition". Brian Greene argues for this hypothesis quite
persuasively. He says, "In an infinitely big universe, there are
infinitely many patches [i.e., Hubble volumes]; so, with only finitely
many different particles arrangements, the arrangements of particles
within patches must be duplicated an infinite number of times." (The
Hidden Reality, pg. 33)

As for the probability distribution of matter and/or outcomes, I'll
let Tegmark do the explaining:

"Observers living in parallel universes at Level I observe the exact
same laws of physics as we do, but with different initial conditions
than those in our Hubble volume. The currently favored theory is that
the initial conditions (the densities and motions of different types
of matter early on) were created by quantum fluctuations during the
epoch (see section 3). This quantum mechanism generates initial
conditions that are for all practical purposes random, producing
density fluctuations described by what mathematicians call an ergodic
random field. Ergodic means that if you imagine generating an ensemble
of universes, each with its own random initial conditions, then the
probability distribution of outcomes in a given volume is identical to
the distribution that you get by sampling different volumes in a
single universe. In other words, it means that everything that could
in principle have happened here did in fact happen somewhere else.
Inflation in fact generates all possible initial conditions
with non-zero probability, the most likely ones being almost uniform
with fluctuations at the 10^5 level that are amplified by
gravitational clustering to form galaxies,
stars, planets and other structures. This means both that pretty much
all imaginable matter configurations occur in some Hubble volume far
away, and also that we should
expect our own Hubble volume to be a fairly typical one — at least
typical among those that contain observers. A crude estimate suggests
that the closest identical copy
of you is about ∼ 10^(10^29)m away. . ." (The Multiverse Hierarchy,
section 1B, http://arxiv.org/abs/0905.1283)

Do you still disagree with the hypothesis of Cosmic Repetition? Which
parts of the argument do you accept or deny?

Best regards,


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