I have trouble with Dr. Tegmark's statement: "The simplest and most popular cosmological model today predicts that you have a twin in a galaxy about 10 to the 10^28 meters from here." This is the first I've heard of such a cosmological model.
One of Tegmark's references (Phys.Rev. D64 (2001) 043511) states: "A generic prediction of inflation is that the thermalized region we inhabit is spatially infinite. Thus, it contains an infinite number of regions of the same size as our observable universe, which we shall denote as $\O$-regions." Nevertheless, the above reference does not assert that I have "a twin in a galaxy about 10 to the 10^28 meters from here."
I agree that "in infinite space and time, anything that can happen must happen, not only once but an infinite number of times." (I can't remember the source of this quote.) I can think of infinite space as a void in which big bangs occur from time to time, each producing a universe. With an infinite number of big bangs, some of these universes must be identical.
However, Tegmark's "parallel universes" seems much more complicated than this notion of random big bangs that I have. Can somebody help me to understand his point of view?
Thanks,
Norm Samish
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> What do you think of Tegmark's concepts for four "levels" of multiverse
> as described at
> http://www.sciam.com/article.cfm?colID=1&articleID=000F1EDD-B48A-1E90-EA5809EC5880000
> or
> http://it.arXiv.org/abs/astro-ph/0302131
>
> Tegmark's four levels are:
>
> 1. In a spatially infinite universe, there should be infinitely many copies
> of ourselves, our planet, and indeed the entire bubble of the universe that
> we are able to see.
>
> 2. In the cosmological model of "inflation", there are an infinite number
> of regions of space where the inflation has stopped, each separate from
> the others, possibly with different dimensionalities and laws of physics.
>
> 3. In the many-worlds interpretation of quantum mechanics, the universe is
> constantly splitting into causally disconnected branches, and we go on
> living in each one.
>
> 4. If everything exists, or at least all mathematical objects or all
> computer programs, then we and the universe would exist as a subset of
> those collections, in all possible variations.
>
> I think the point is that unless you disbelieve all of these, you are
> forced in any case to deal with the philosophical implications of parallel
> worlds, that you do in fact have an infinite number of duplicates.
> And since much of the resistance to the more advanced levels 3 and 4
> comes from concerns over these issues, that should eliminate resistance
> founded on those worries.
>
> Of course logically these are all pretty much independent, and it
> is possible that 1 and 3 are right, 2 and 4 are wrong, or any other
> combination. So you can consistently believe and disbelieve as you
> like.
>
> Hal Finney
>
Received on Fri Apr 18 2003 - 19:28:19 PDT