I don't think there are many intelligent beings per cubic Plank length in
our universe at all! In fact, string theorists don't know how to get to the
standard model from their favorite theory, yet they still believe in it.
Simple deterministic models could certainly explain our laws of physics, as
't Hooft explains in these articles:



Determinism beneath Quantum Mechanics:

http://arxiv.org/abs/quant-ph/0212095


Quantum Mechanics and Determinism:

http://arxiv.org/abs/hep-th/0105105

How Does God Play Dice? (Pre-)Determinism at the Planck Scale:

http://arxiv.org/abs/hep-th/0104219


----- Original Message -----
From: Kory Heath <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Sunday, January 18, 2004 1:15 PM
Subject: Re: Tegmark is too "physics-centric"


> At 1/17/04, Hal Finney wrote:
> >But let me ask if you agree that considering Conway's 2D
> >Life world with simply-specified initial conditions as in your example,
> >that conscious life would be extraordinarily rare?
>
> I certainly agree that it would be "extraordinarily rare", in the sense
> that the size of the lattice would need to be very big, and the number of
> clock-ticks required would need to be very large. But "big" and "large"
are
> such relative terms! Clearly, our own universe is very, very big. The
> question is, how can we sensibly determine whether life is more likely in
> our universe or in Conway's Life universe?
>
> I don't believe we have anywhere near enough data to answer this question,
> but I don't think it's unanswerable in principle. Fredkin actually
believes
> that our universe is a 3+1D cellular automata, and if anyone ever found
> such a description of our physics (or some other fundamentally
> computational description), then we could directly compare it with
Conway's
> Life, determining for each one how big the lattice needs to be, and how
> many clock-ticks are required, for life to appear with (say) 90%
> probability. (Of course, this determination might be difficult even when
we
> know the rules of the CAs. But we can try.)
>
> One thing that you'd have to take into account is the complexity of the
> rules you're comparing, including the number of states allowed per cell.
> Not only are the rules to Conway's Life extremely simple, but the cells
are
> binary. All things being equal, I would expect that an increase in the
> complexity of the rules and the number of cell-states allowed would
> decrease the necessary lattice-size and/or number of clock-ticks required
> for SASs to grow out of a pseudo-random initial state. I mention this to
> point out a problem with our intuitions about our universe vs. Conway's
> Life: the description of our universe is almost certainly more complex
than
> the description of Conway's Life with a simple initial state. If Fredkin
> actually succeeds in finding a 3+1D CA which describes our universe, it
> will almost certainly require more than 2 cell-states, and its rules will
> certainly be more complex than those of the Life universe. We have to take
> this difference into account when trying to compare the two universes, but
> we have nowhere near enough data to quantify the difference currently. We
> really don't know what size of space in the Life universe is equivalent to
> (say) a solar system in this universe.
>
> In a way, this is all beside the point, since I have no problem believing
> that one CA can evolve SASs much more easily than some other CA whose
rules
> and initial state are exactly as complex. (In fact, this must be true,
> since for any CA that supports life at all, there's an equally complex one
> that isn't even computation universal.) I have no problem believing that
> the Life universe is, in some objective sense, not very conducive to SASs.
> Perhaps it's less conducive to SASs than our own universe, although I'm
not
> convinced. What I have a problem believing is that CAs as a class are
> somehow less conducive to observers than quantum-physical models as a
> class. In fact, I think it's substantially more likely that there are
> relatively simple CA models (and other computational models) that are much
> more conducive to SASs than either Conway's Life universe or our own.
> Models in which, for instance, neural-net structures arise much more
> naturally from the basic physics of the system than they do in our
> universe, or the Life universe.
>
> >In many ways, our universe seems tailor made for creating observers.
>
> I understand this perspective, but for what it's worth, I'm profoundly out
> of sympathy with it. In my view, computation universality is the real
key -
> life and consciousness are going to pop up in any universe that's
> computation universal, as long as the universe is big enough and/or it
> lasts long enough. (And there's always enough time and space in the
> Mathiverse!) When I think about the insane, teetering, jerry-rigged
> contraptions that we call life in this universe - when I think about the
> tortured complexity that matter has to twist itself into just to give us
> single-celled replicators - and when I think about the insane reaches of
> space we see around us (even if we end up finding life in practically
every
> solar system, there's a crazy amount of space even between planets, not to
> mention stars) - I find it easy to believe that our universe is just one
of
> those countless universes out there in Mathspace which isn't especially
> conducive to life at all, but is simply computation universal, so life
pops
> up eventually.
>
> Because of the above conclusions, the problem of measure is a serious one
> for me. I don't have a clue why I would be more likely to find myself in a
> universe like this one instead of some CA universe. Regarding your
> suggestion that we might judge universes not only by the complexity of
> their rules and initial states, but also by the complexity of the simplest
> program which "finds" SASs within them: as I understand the proposal,
> universes (or observer-moments within the universes) which have simple
> rules and initial states and yet generate SASs easily would have greater
> measure, because the program needed to "find" these very common SASs would
> also be simple. This is an intriguing idea, but it doesn't help me,
because
> I don't (yet) see why simplicity or complexity of any kind should affect
> measure. I can imagine a CA world which is sparsely populated with SASs,
> and one that's densely populated with them, but the number of SASs (or the
> number of observer moments) in both worlds seems exactly the same -
> (countably?) infinite. So why would I be more likely to find myself in one
> of those universes rather than the other?
>
> -- Kory
>

Reply via email to