Re: expansion of the universe; infinity of "level 1"

Date: Mon Apr 21 2003 - 16:12:42 MDT

"Paul Hughes" <> wrote:
> *Inside* our level 1 multiverse, and depsite its infinite size, does it
> not also have a finite time to go before its demise? And when I say
> demise, I don't mean our visible universe, but our entire infinite
> level 1 multiverse. Demise being defined here as the end of stars,
> galaxies, completion of proton decay, etc.

Yes and no.

All the different regions like our observable universe can be seen as
starting at the same time and evolving at the same speed. (The energy
density is homogeneous in the "internal" space and time coordinates, the
ones where the universe-bubble ("universe", "thermalized region") is
spatially infinite.) This means that far-away parts of the bubble will
become more and more boring in the very long term, just like our part.

So while, say, a world much like Middle-Earth really exists in this
theory, it (and you) will have secondlawed to oblivion by the time you
can get there. :-)

That's the 'yes' part of the answer, with a few reservations: there is no
one moment you can point to as being the "end", and we might be able to
keep alive anyway (in a "Dyson scenario", or if there's a way around the
second law).

The 'no' part of the answer is described somewhere in the paper "Many
worlds in one" by Garriga and Vilenkin, found here:

The second law is only statistical: entropy will actually go down in very
rare cases. This means that for any length of time, there is a very small
but finitesimal (nonzero, "finite") probability that a civilization will
be able to survive for that length of time due to thermal fluctuations.
The longer the time, the smaller the probability; but if there are
infinitely many civilizations, then infinitely many of them will be alive
at any time, even though almost all will have died out. In that sense,
the universe lives forever, fuelled by extreme improbability.

I think this leads to something similar to what people have called
"quantum immortality": if the many-worlds interpretation is true and if,
whenever you die in some worlds and live in some worlds, your
consciousness is always continuous with one of those worlds where you
stay alive, then a consequence is that your consciousness never stops,
and you will experience more and more improbable events that cause you to
stay alive. Something similar would be true in the infinite universe
("big universe immortality", maybe): you would always live on as one of
those versions of you (in different regions of the universe) that happen
to stay alive.

I think this is nonsense, though, based on a wrong view of identity,
probability, and so on. Those who believe their probability measure is
redistributed among their surviving copies should now believe in this
silliness whether they believe in the MWI or not.

A corollary of "quantum immortality" ("big universe immortality") is
"quantum suicide" ("big universe suicide"): if you set up a quantum
experiment that kills you unless you win the lottery, you will find
you're in one of those worlds (parts of the universe) where you won the
lottery. If this is true, then you could also distinguish experimentally
between Copenhagen and many-worlds (between a small and an infinite
universe) by selective suicide, though this wouldn't convince other
people. (If you did this to someone else, it would be "quantum murder",
as in the case of Schrödinger's cat.)

Again, I think this is nonsense; *please* do not try anything like this
at home. Some people have a reckless disregard for their (or their cat's)
probability measure.

Hope this hasn't given anyone unsafe ideas,

"If there are infinitely many goldfinches in the world, it seems that one
cannot increase their total quantity by donating to the Audubon Society."
  -- Knobe/Olum/Vilenkin, "Philosophical Implications of Inflationary
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