From: Wei Dai (weidai@eskimo.com)
Date: Wed May 29 2002 - 15:14:41 MDT
On Tue, May 28, 2002 at 12:05:29PM -0700, Hal Finney wrote:
> The bottom line is that in an expanding universe, life is inherently
> finite in what it can accomplish. There is a limit on complexity that
> cannot be broken. I understand that some people take comfort in the
> thought of endlessly cyclying through their old memories, but IMO it
> would be a cruel hoax for the universe to play on us, offering a ghostly
> half-life with no possibility of growth or redemption. It might be
> physically pleasant, but from the philosophical standpoint it sounds
> hellish. Life means growth, and if you're not growing, you're not
> really living.
The fact that growth will be limited by the causal isolation caused by the
expansion of the universe will no doubt be viewed as a great tragedy in a
few billion years. Unless we find some way to work around this causal
isolation, at that time we will have reached the limit of growth and will
be forced to live the rest of our lives without being able to acquire any
new resources that can be used to create more memory storage.
In the mean time, this limit to growth allows us to have some insight on
the peak and final state of cosmic-scale civilizations. Given that the
ultimate resource limit will be matter and energy (which I'll refer to as
just matter) which can be used to construct memory storage, a priority of
any growth-oriented civilization will be to gather as much matter as
possible before they disappear forever beyond the causal horizon. This
means sending out self-replicating probes to propect, mine, and send back
matter. However, beyond a certain radius, but still within the the causal
horizon, it will not be possible to send back the mined matter. (I.e. the
probe can get there but it won't be able to come back because the universe
will have expanded.) Therefore some of the probes will be sent to
establish independent centers of civilization that will be causally
isolated from the original center and from each other.
Once all available matter has been gathered, the question will be how to
organize it for the greatest possible computational efficiency. I propose
the following architecture for consideration: two concentric spherical
shells of computronium, with a black hole in the center. Most of the mass
will be placed between the two shells, as matter/energy reserves and
long-term memory storage. They will have to be spread out to prevent
collapse into black holes. The inner shell will envelop the central black
hole, at a safe distance, and radiate waste heat into the black hole. The
outer shell will radiate waste heat outward into empty space. Eventually
the cosmic background radiation will be at a lower temperature than the
black hole so the outer shell will be able to perform general computations
more efficiently (i.e. less energy used per operation). The inner shell
will then be reserved to perform tasks that require its centrally placed
location or greater density of computational elements.
While the causal isolation is a cruel hoax, it can also be considered a
great favor. It means that the civilization is now completely free from
external threats. Perhaps it's the universe's way of preventing a Blight
from taking over everything in it.
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