[extropy-chat] Dark matter and ET

[Damien Broderick]

Check out:

   http://arxiv.org/abs/astro-ph/0506110


Galactic Gradients, Postbiological Evolution and the Apparent Failure of SETI

Authors: 
<http://arxiv.org/abs/astro-ph//find/astro-ph/1/au:+Cirkovic_M/0/1/0/all/0/1>Milan 
M. Cirkovic, 
<http://arxiv.org/abs/astro-ph//find/astro-ph/1/au:+Bradbury_R/0/1/0/all/0/1>Robert 
J. Bradbury
Comments: 30 pages, 2 figures
Subj-class: Astrophysics; Physics and Society; Artificial Intelligence
Motivated by recent developments impacting our view of Fermi's paradox 
(absence of extraterrestrials and their manifestations from our past light 
cone), we suggest a reassessment of the problem itself, as well as of 
strategies employed by SETI projects so far. The need for such reevaluation 
is fueled not only by the failure of searches thus far, but also by great 
advances recently made in astrophysics, astrobiology, computer science and 
future studies, which have remained largely ignored in SETI practice. As an 
example of the new approach, we consider the effects of the observed 
metallicity and temperature gradients in the Milky Way on the spatial 
distribution of hypothetical advanced extraterrestrial intelligent 
communities. While, obviously, properties of such communities and their 
sociological and technological preferences are entirely unknown, we assume 
that (1) they operate in agreement with the known laws of physics, and (2) 
that at some point they typically become motivated by a meta-principle 
embodying the central role of information-processing; a prototype of the 
latter is the recently suggested Intelligence Principle of Steven J. Dick. 
There are specific conclusions of practical interest to be drawn from 
coupling of these reasonable assumptions with the astrophysical and 
astrochemical structure of the Galaxy. In particular, we suggest that the 
outer regions of the Galactic disk are most likely locations for advanced 
SETI targets, and that intelligent communities will tend to migrate outward 
through the Galaxy as their capacities of information-processing increase, 
for both thermodynamical and astrochemical reasons. This can also be 
regarded as a possible generalization of the Galactic Habitable Zone, 
concept currently much investigated in astrobiology.