David Barrett-Lennard, <[EMAIL PROTECTED]>, writes:
> Given the idea of the ensemble for a TOE, it is only necessary that
> SAS's can exist - no matter how improbable. That they exist is of
> course an empirical fact. An SAS will find the universe is fine tuned
> in order for that SAS to exist. Presumably this fine tuning can take
> two forms - in the laws of physics, and in unusual earlier states of the
> universe. It would appear reasonable for life to be "seeded" if it
> otherwise would be unlikely to form by accident. Furthermore, Darwinian
> evolution could be given a "push" in the right direction where it would
> otherwise have trouble making the necessary jumps.
If all universes exist, then presumably all sets of initial conditions
exist for each given law of physics. If it were true that a given set of
laws would support life once it exists but make it extremely unlikely to
evolve spontaneously, then in only a small fraction of the universes would
life evolve. And I think you're right, in that case then in most of the
universes, life would only appear once (assuming the universe is finite).
One argument against that being the case for us is that life apparently
evolved quite early in the lifetime of our planet. Evidence is that
the earliest forms of life appeared within half a billion years or so
of the Earth's formation. Then it took many billion years for life to
evolve to the state where complex forms could appear.
This might still be explained anthropically, that intelligent life is
overwhelmingly unlikely, and that the early formation of simple life is a
necessary prerequisite if we are going to get intelligent life before the
"window" closes and the Sun changes enough that life will be destroyed.
One paper exploring this topic is http://hanson.gmu.edu/greatfilter.html,
where the author shows that if there are several "hard" steps necessary
for the formation of intelligent life, they should be roughly equally
distributed. In that case the apparent early formation of life might
be compatible with intelligent life being extremely rare.
That paper also use the Fermi paradox, or "great silence", the fact
that no intelligent aliens are apparent in the universe, as evidence
that life in our universe is very rare.
The question remains, why do we find ourselves in such a universe?
Wouldn't it be more likely that we would find ourselves in a universe
with many observers rather than few? I suppose the answer must be that
there are many universes that have life only evolve once, and very few
that have widespread evolution of life.