Without getting into a long hurrang, I think that Tegmark is correct, at least in part. Briefly, there has to be a reason why these alternate worlds exist. I'm referring to the Everett-Wheeler hypothesis and not just wishful thinking. Granted, if I remember correctly, Tegmark does deal with the whole issue in terms of mathematical models, which I don't really care for, however, I can tolerate it.
As for the issue of measurement, all possible worlds can be viewed as still existing, without measurement, in a superpositional state, until they are observed (or "measured"). So you still get a "plurality of worlds".
My question is how does anyone know whether "law-like" worlds vastly outnumber "lawful" ones?
If I have to, I can go look up Tegmark's Scientific American article on it all, to get a refresher on it. I'm just hoping I don't have to.
I met Tegmark about a year ago or so. Nice guy. I stumbled into his office, since the door was open, and introduced myself, mentioning that I was also an "Everett man". "Everett-man?" he replied puzzled. "Yeah, you know - Hugh Everett, Everett/Wheeler hypothesis?" at which point he excitedly jumped out of his seat and shook my hand, laughing.
----- Original Message -----
From: "Patrick Leahy"
To: EverythingList
Subject: White Rabbit vs. Tegmark
Date: Mon, 23 May 2005 00:03:55 +0100 (BST)
>
>
> I looked into this mailing list because I thought I'd come up with
> a fairly cogent objection to Max Tegmark's version of the
> "everything" thesis, i.e. that there is no distinction between
> physical and mathematical reality... our multiverse is one
> particular solution to a set of differential equations, not
> privileged in any way over other solutions to the same equations,
> solutions to other equations, and indeed any other mathemetical
> construct whatsoever (e.g. outputs of UTMs).
>
> Sure enough, you came up with my objection years ago, in the form
> of the "White Rabbit" paradox. Since usage is a bit vague, I'll
> briefly re-state it here. The problem is that worlds which are
> "law-like", that is which behave roughly as if there are physical
> laws but not exactly, seem to vastly outnumber worlds which are
> strictly "lawful". Hence we would expect to see numerous departures
> from laws of nature of a non-life-threating kind.
>
> This is a different objection to the prediction of a complete
> failure of induction... it's true that stochastic universes with no
> laws at all (or where laws abruptly cease to function) should be
> vastly more common still, but they are not observed due to
> anthropic selection.
>
> A very similar argument ("rubbish universes") was put forward long
> ago against David Lewis's modal realism, and is discussed in his
> "On the plurality of worlds". As I understand it, Lewis's defence
> was that there is no "measure" in his concept of "possible worlds",
> so it is not meaningful to make statements about which kinds of
> universe are "more likely" (given that there is an infinity of both
> lawful and law-like worlds). This is not a defense which Tegmark
> can make, since he does require a measure (to give his thesis some
> anthropic content).
>
> It seems to me that discussion on this list back in 1999 more or
> less concluded that this was a fatal objection to Tegmark's version
> of the thesis, although not to some alternatives based exclusively
> on UTM programs (e.g. Russell Standish's Occam's Razor paper).
>
> Is this a fair summary, or is anyone here prepared to defend Tegmark's thesis?
>
> Paddy Leahy
>
> ======================================================
> Dr J. P. Leahy, University of Manchester,
> Jodrell Bank Observatory, School of Physics & Astronomy,
> Macclesfield, Cheshire SK11 9DL, UK
> Tel - +44 1477 572636, Fax - +44 1477 571618
--
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Received on Sun May 22 2005 - 19:57:42 PDT