From: Robert J. Bradbury (bradbury@aeiveos.com)
Date: Fri Apr 25 2003 - 15:40:37 MDT
On Thu, 24 Apr 2003, Keith M. Elis wrote:
> On another
> track, the Fermi paradox suggests that either life is very uncommon in the
> universe, or we are relatively advanced as a technological civilization.
>
> In short, the two propositions 'life is common in the universe' and 'we are
> a typical civilization' are not compatible. As Fermi asked, if life is
> common, where is it? We must conclude that if life is common, most life is
> not technologically advanced enough to be detectable. If this is true, we
> are atypical.
We are "atypical". There are 3 types of "intelligences" in the universe.
a) Those too simple to produce detectable signs. We can't even detect
Earth like planets now. Perhaps we will have this ability in 15 years.
Even then we have to "go there" to detect such intelligences (whales
and dolphins come to mind).
b) Civilizations like us. The problem is that these civilizations have
extremely short lifetimes. Dyson pointed out that if we grow at the
current rate we exhaust the resources of the solar system in less than
1000 years (except the sun). Add that to a ~2000 year old civilization
and the "typical" lifetime of civilizations like ours is ~3000 years.
Going back to the dawn of civilization in Egypt or Iraq and you might
add perhaps 3000 more years. 6000 years is the blink of an eye in
terms of the evolution and survival of advanced civilizations.
c) Civilizations more advanced than us. If these exist one has to extract
them from the galactic background radiation at temperatures below LN2
and perhaps almost as low as the GBR itself. (This was pointed out
by Minsky as the ideal thermodynamic situation that advanced civilizations
would seek at the first U.S.-Russian SETI conference.)
The bulk of the civilizations in the galaxy should be at stage (c) [in
part because if Lineweaver is correct ~70% of the "Earths" in the galaxy
should be *older* than the Earth -- at least until they get dismantled.]
We are not going to "see" them (class c) without using different methods.
To start with you don't point your detectors (radio or optical) at *stars*
because advanced civilizations "hide" their stars. Second they aren't
going to want to communicate with us because we are way to stupid (they
can probably run a simulation for all of humanity if they wanted to).
Third unless things like subspace communications and transwarp conduits
are *real* interstellar communication is a pointless exercise.
Advanced civilizations are more concerned with:
(a) How do I lengthen the lifetime of my star (i.e. implement star-lifting)
or
(b) How do I determine a least cost method for gathering new material to
myself so I can have greater amounts of computronium (CPU or memory
capacity) and/or lengthen the lifetime of my star.
or
(c) How do I pick the least dangerous path through the galaxy (no
supernovas, neutron star collisions, etc. in my vicinity) with the
requirement that you have to navigate something with the mass of
an entire solar system.
Robert
P.S. Keith, if you haven't read the papers on Matrioshka Brains and
related references, esp. the paper cited by Anders, you may want to
do so. That will give you a fair amount to think about.
See: http://www.aeiveos.com/~bradbury/MatrioshkaBrains/index.html
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