Large has a lot to do with old. Universes where conscious life arose
by a lengthy evolutionary process will have larger measure (by vitue
of simpler initial conditions) than do universes whose conscious life
arises spontaneously, or by relatively short evolutionary processes.
It is also interesting to speculate on the observed difficulty in
achieving self-awareness - see Robin Hanson's argument in "Hard Steps"
(do a Google search). This would probably imply that a number of difficult
transitions in the evolutionary sequence is of higher measure than
evolutionary sequences generating self-aware lifeforms without
difficult transitions. And difficult transitions imply large, empty
universes.
Cheers
On Tue, Jun 27, 2006 at 05:38:56PM -0700, "Hal Finney" wrote:
>
> Ron Hale-Evans writes:
> > My favourite answer to the Fermi Paradox has been that the aliens are
> > using nearly-perfect compression or encryption for their radio signals
> > (if they're using radio), and that's why all we can detect is noise.
> >
> > However, tonight another "answer" occurred to me. What if we're living
> > in a finite simulation?
>
> I don't know that multiverse concepts explain the Fermi paradox, but
> they do cast it in a different light.
>
> As Bruno points out, our first-person experiences could be created by
> many different kinds of programs, corresponding to different "realities".
> It could be that everything is pretty much as it seems. Or perhaps we
> are living in a simulation controlled by aliens, or our descendants,
> or robots. Or it's even possible that everything is an illusion and we
> are in effect imagining it. All of these possibilities contribute to the
> measure of our experiences. So in some sense it must be simultaneously
> true that we are in a simulation, and that we are not in a simulation.
> Both situations exist in the multiverse and both contribute to the
> reality of our experiences.
>
> The hard part of the Fermi question still remains. It might be stated,
> why is the universe seemingly so large and so empty? In multiverse
> terms, why is the measure of observers who live in large, empty universes
> so large, compared to the measure of observers who live in universes
> teeming with life? For if the measure of the latter observers were much
> greater than the measure of the former, we would be highly unlikely to
> find ourselves one of that very small set of observers who see sparse
> universes.
>
> (Of course, I am skipping past the various conventional explanations that
> have been offered which allow for the universe to in fact be full of life
> but for it somehow not to be observable. Those have not been generally
> found to be convincing so we should focus on the hard part. Also,
> note that while I write "life" for short I really mean intelligent life.)
>
> A while back I speculated as follows. Presumably there are laws of
> physics which would lead to very densely populated universes. And we
> know that there are laws that lead to very sparse universes, like
> the ones we live in. All universes exist; all laws are instantiated.
>
> For various reasons many of us argue that universes with simpler laws
> are likely to be more common, to have larger measure. Now, we know that
> if the laws are too simple, life cannot exist. Trivial universes are
> not living ones. Presumably, as the laws get more complex, we pass a
> threshold where life can start to exist. But perhaps it is reasonable
> to assume that we will first find laws where life can barely exist,
> before we find laws where life is very common. If so, then there is a
> band of complexity where universes at the simple end of this band have
> very sparse intelligent life, and universes at the complex end have very
> dense intelligent life.
>
> Then, to be consistent with our observations, we have to conclude that
> this band is quite wide - that universes that are just barely complex
> enough for life have much simpler laws than universes that are teeming
> with life. That is how we would explain the fact that we find ourselves
> in one of the first kind. Their boost from having simpler laws must
> outweigh the increase in numbers of intelligent life forms in the more
> complex universes.
>
> I read that the universe is estimated to have about 10^23 stars.
> A universe with a high density of intelligent life might therefore be
> 10^23 times more densely populated than ours. This is about 2^75 times.
> Therefore we would predict that the physical laws necessary to create
> such a densely populated universe would be at least 75 bits longer than
> the simpler laws of our own universe.
>
> This is a prediction of multiverse theory as I interpret it. If it should
> turn out that there are very simple sets of laws that would create very
> numerous observers, then that would contradict the theory in this form.
>
> Hal Finney
>
>
--
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Received on Sun Jul 02 2006 - 23:05:57 PDT