X-Message-Number: 22224
Date: Fri, 18 Jul 2003 22:25:30 -0700
From: Mike Perry <>
Subject: Re: CryoNet #22219 Re Time Travel etc

> From Yvan Bozzonetti:
>
> >From Mike Perry:
>
> > ." If you stopped Lincoln's assassination, then --
> > contradiction!
>
>Many years ago (in the sixties) Kip S. Thorn, one of the best general
>relativity specialist has pointed out that an object falling in a black 
>hole drawn
>with it all its past interactions: Not only it disappear of the universe, 
>it has
>never existed.

If this were possible then nothing could be said to have definitely 
happened, or so it would seem. Actually, I don't think this is a reasonable 
conclusion (that nothing has definitely happened) even if the universe 
eventually "swallows itself" in somewhat the manner indicated. It seems to 
me that "something happened"--and David Deutsch, one of my favorite 
authorities on cosmological matters (as in *The Fabric of Reality*), would 
almost certainly agree. For he views reality as a sort of collection of 
snapshots in which the impression that time is "flowing" is a peculiarity 
of the observer's perception rather than something fundamentally "real." 
Instead, "time doesn't flow" he tells us--so that once it happened, 
(really, "happened" is not the correct word--the thing is/was always there) 
you can't change that even by the most exotic means (at least so I read 
it). Depends on your point of view.

>assume a cracked nut produces a big aircraft accident with
>many casualties, if we had a BH at hand we could recover the nut from the
>wreckage and drop it in the black hole. The past would be changed, no 
>accident, no
>victims.

To me this amounts to popping into a parallel universe. The "original" has 
been really changed, you say? I think this is a point of view only, because 
I would expect versions of the universe to exist in which you do not drop 
the cracked nut in the BH. Those are still sitting there. Have you 
generated another universe, popped into one that was there all the time, or 
altered one that was there before? Are the three concepts actually 
equivalent in some sense?


>If you stopped Lincoln assassination nobody would recall that there has been
>such a fact.

Again, though, maybe you, in effect, have just popped into a parallel 
universe that was there all along rather than truly "altered" the past. I 
wonder if *you* would "recall that there has been such a fact"?

In any case, this is quite speculative. Cryonics, with its reliance on 
future nanotech based on reasonably verified physics as understood today, 
is, relatively speaking, far more down-to-earth, despite its admitted 
uncertainties. Being signed up makes eminent sense to me despite the 
conjectures about exotic future physics.

Mike Perry

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