From: Robert J. Bradbury (bradbury@aeiveos.com)
Date: Sat Jul 10 1999 - 05:22:00 MDT
> Spike Jones <spike66@ibm.net> wrote:
>
> I did have an idea tho. Consider all the dark matter out there.
That was what got me thinking about this a couple of years ago
when I first realized how significantly our astroengineering
capacites change at the time of the singularity.
> We think we could detect a Dyson Sphere by the low frequency radiation
> that would need to be emitted by reason of conservation of energy.
Depends on the temperature. A "young" M-brain probably doesn't
have enough matter to fill its outer shells, so it might be "warm"
(perhaps 50-1000K). An "old" M-brain could have collected enough
matter to fill the outer shells and therefore be "cold" (slightly
above the microwave background. Cold is good for both
the preservation of long term memories (for data you don't
really need access to for the next 10 million years) and
it gives you the greatest thermodynamic efficiency. I've
considered that the anisotropy in the microwave background
radiation could be due to greater or lesser concentrations
of M-brains in various regions of space. [But I would suggest
that this idea will not make the astronomers happy. :-)]
However, one well informed person I've talked to thinks that
if star dismantlement is feasible, that the optimal architecture
would be diamondoid based shells that could operate @ ~1500-1700K.
I'm not sure it matters much since our observing capabilities at
this point in the mid-to-far IR region are very poor. We have
a difficult time finding warm brown dwarf's (which are hotter
than M-Brains) beyond ~400 ly.
> But what if... the universe is a dangerous place?
I assume you mean dangerous from the perspective of other aggressive
intelligences.
> Then any ETI that has any brains knows to hide.
No, I thought about this after I read "The Killing Star" by
Pellegrino & Zebrowski. For an SI to want to make war
(unless it is suicidal), it has to be able to guarantee
that it can wipe out *all* traces of its enemy. That
would require incinerating, irradiating, or black-hole-izing
*all* possible nanobots in a very large volume of space.
I strongly question if that is possible. This might be
a worthy effort as "revenge", but seems questionable
as an evolutionary strategy in general.
Since the MAD (mutually assured destruction) scenario would
seem to prevail (because all SIs would have berserker-nanobots
hidden somewhere) it would never seem to make sense to
do anything that would trigger the response.
> Could not a really advanced ETI build a Dyson sphere, then
> somehow collect the waste energy, collimate the radiation
> into a narrow beam and focus it out in some harmless (starless)
> direction?
This seems quite feasible. Enough highly reflective layers
(a large multi-layer solar-sail) on one side would cut the
radiation signature significantly. It could also be an
intereresting form of propulsion/navigation.
> Are there SF stories based on this explanation of dark matter?
Not that I know of, but "The Killing Star" (already mentioned),
and "The Wanderer" by Fritz Leiber discuss some aspects of
super-astro-engineering.
>
> Given enough raw material, it seems that a really out-there nanotech
> civilization could make a sphere and keep its surface at 3 kelvin, so
> that it would be undetectable by us less advanced (and therefore more
> dangerous) intelligences. Do we have any thermodynamics experts
> out there who can confirm that such a scheme does not violate the
> third law? Seems to me it doesnt. spike
>
My impression is that it doesn't violate the the laws and does in
fact give you the best computing structure. The problem is that
power in has to equal power out. If you surround the star, to
radiate at ~3K you need a *really* big sphere. This is because
heat radiation scales with T^4 (i.e. hot radiators are much
more efficient (smaller) than cold radiators). Think about Neptune and
perhaps Pluto - the He/H2/Ne/O2 if retained by the gravity isn't "frozen"
solid. They are heated by the sun. [This is true to some degree
with Jupiter & Saturn, but you have to factor in the
heating due to ongoing gravitational collapse as well.]
In our solar system, my calculations show that you don't have
enough mass to get a 3K radiator (at least if you want to
circulate the cooling fluid from the computers and use all
of the power the sun produces). If your only goal is to
"hide" I'm unsure. Given the solar sail idea, I suspect
"hiding" is relatively easy.
Robert
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