On 9/27/2011 9:13 PM, Jason Resch wrote:

On Tue, Sep 27, 2011 at 10:52 PM, meekerdb <meeke...@verizon.net <mailto:meeke...@verizon.net>> wrote:

    On 9/27/2011 8:07 PM, nihil0 wrote:

        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 
                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 
                many times.

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

            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
            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 


        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.

    I don't think that.  I just noted it's logically possible, contrary to 
    that our universe must be duplicated infinitely many times.

If our universe is not duplicated a huge number of times, then quantum computers would not work. They rely on huge numbers of universes different from ours aside from a few entangled particles. Even normal interference patterns are explained by there existing a huge number of very similar universes.

Or by Feynmann paths that zigzag in spacetime. Don't become to enamored of an interpretation.

        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)

    It's plausible - but not logically required.  Suppose all the infinite 
universes are
    number 1, 2, ...  Number 1 is ours.  Number 2 something different.  Numbers 
    ...inf are exact copies of number 2.  So there are only two arrangements of
    particles; in spite of there being infinitely many universes.

Not logically required, but I would say it is not consistent with our current theories and observations.

        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.

    This is questionable.  Most theories of the universe starting from a quantum
    fluctuation or tunneling from a prior universe assume that the universe 
must start
    very small - no more than a few Planck volumes.

The generalized theory of inflation is eternal inflation. It leads to an exponentially growing volume which expands forever.

     This limits the amount of information that can possibly be provided as 
    conditions.  So where does all the information come from?

I haven't heard the theory that there is an upper bound on the information content for this universe set by the big bang.

In one Planck volume there is only room for one bit.  That's the holographic 

As to where information comes from, if all possibilities exist, the total information content may be zero, and the appearance of a large amount of information is a local illusion.

     QM allows negative information (hidden correlations) so that one 
possibility is
    that the net information is zero or very small and the apparent information 
    created by the existence of the hubble horizon.

        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.

That's not what ergodic means. In the theory of stochastic processes it means that ensemble statistics are the same as temporal statistics. In the eternal expansion theory it is not assumed that the physics is the same in each bubble universe. It is hypothesized that the spontaneous symmetry breaking that results in different coupling constants for the weak, strong, EM, and gravity forces is random. That's how it provides and anthropic explanation for "fine-tuning" - we're in the one where the random symmetry breaking was favorable to life.

        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

But it's not initial conditions.  It's random symmetry breaking.

        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.

But this sort of undercuts the need for the anthropic explanation. If our universe is "typical" (i.e. probable) then there's no need to invoke infinitely many others to avoid the "fine-tuning" problem. You could just say it's the more probable one and so it's the one that happened.

"If an explanation could easily explain anything in the given field, then it actually explains nothing."

You received this message because you are subscribed to the Google Groups 
"Everything List" group.
To post to this group, send email to everything-list@googlegroups.com.
To unsubscribe from this group, send email to 
For more options, visit this group at 

Reply via email to