Why don't we see Others?
I think the anthropic principle neatly explains both scenarios: why we're
here, yet nobody else seems to be.
If life nucleation density is arbitrarily low (e.g. 1/visible univers) we
still wouldn't fail to observe our existance.
It is also worthwhile to mention that the deep universe is young, and hasn't
yet bred sufficient amount of metals (in the astronomic, not the chemical
sense), so due to delayed hatching we're not yet in the lightcone of an
advanced culture. I.e., don't look at the visible universe without a
probability bias, proportional but thresholded (no H/He life for sure).
It is relatively straightforward to show that an advanced culture is
expansive, in fact relativistically so, and everything past pioneer wave will
be transformed to become unsuitable for an ursoup. Arguably, we're about to
enter that expansive stage (notice that computational physics seem to allow
cognition at a >>10^6 speedup, so the time from zero to hero is less than
a year), and we've only become observable within less than a century, the
high-power emitters less than three decades.
What's the probability to observe a >>0.9 c pioneer expansion wavefront, which
will kill subexpansive observers (observation window: about a century?), will
prevent emergence of new observers, and will only start in systems with
sufficient metallicity, with a yet unknown (yet probably very low) nucleation
density?
Arbitrarily close to zero, obviously. So I would be very, very surprised if
SETI people actually found the sky hanging full of ~lighthour 300 K
blackbodies, or even if we found independant life nucleation events within
our solar system (which have to compete with impact ejecta
crosscontamination, a very frequent event).
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Received on Sun Jan 11 2004 - 07:39:27 PST