Re: A _Rare Earth_ review (was: Scientific American article on GHZ)

From: Eliezer S. Yudkowsky (
Date: Sun Nov 11 2001 - 08:26:21 MST

"Robert J. Bradbury" wrote:
> Eliezer commented:
> > Is anyone looking for a hypothesis under which intelligent life
> > would happen, not once in a galaxy, but once in a Universe,
> > or once in every 10^8 Universes?
> Why would you care if it happens in other Universes? Are you
> assuming inter-universe travel is possible?

If there are lots and lots of Universes, then it's acceptable to consider
hypotheses of the origins of life-bearing planets that involve extreme
improbabilities - four supernovas arranged in a perfect tetrahedron and so
on - and the Anthropic Principle will still take care of it. This would
also go for accounts of our evolutionary history that require eight
simultaneous mutations to make some key evolutionary transition.

If so, the fact that we appear to be alone in the Universe is easy to
explain, as long as inter-universe travel is impossible or Universes are
reproducing faster than they can colonized.

> > Because a rarity of once in a galaxy isn't enough to explain
> > the Fermi Paradox, not nearly.
> I assume you are saying this because intergalactic travel is
> feasible. Without wanting to startup a whole long discussion
> on the topic (because I should really finish the papers that
> explain it clearly and those papers are 6 levels down in
> my paper push down stack), intergalactic travel suffers
> even more than interstellar travel from the time delay
> effect.

Intergalactic colonization is cheap relative to the resources of a
galactic civilization. Just fire a package of nanobots out of a cannon.
Not all societies may be given to this type of "colonization", but all it
takes is one society, or one individual/organization in a society where
multiple entities have unrestrained access to colonization technologies,
anywhere in our past light cone.

-- -- -- -- --
Eliezer S. Yudkowsky
Research Fellow, Singularity Institute for Artificial Intelligence

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