From: Reason (reason@exratio.com)
Date: Sun Jan 13 2002 - 12:34:07 MST
--> Eugene Leitl
>
> > That would have to be way further than we see now. The initial
> > pre-population II population(s) of stars and subsequent mixing of the
> > interstellar medium only lasted n*10^7 years, according to current
> > modelling. That's pretty much an eyeblink -- you can safely assume that
> > galactic and larger scale structures start out at pop II
> metallicities. I
> > don't see that pop II is too little metal for life and civilization.
>
> You're the stellar modeler here. However, we're second or third
> generation?
The whole concept of generation in the sense of parent and child stars is an
artifical one -- it's a constant ongoing process. Stars with lots of metals
are designated Population I, everything else we've seen is (probably)
Population II, and Population III is a hypothetical box in which to throw
hypothetical very-low metal stars. As I recall, there were one or two
candidates for the upper end of Population III in the solar neighbourhood
among the halo population of dwarf stars. In theory, small Pop III stars
could still be in their main sequence now -- yet more support for their mass
function being very high.
(Just to make it more interesting, you have to have a couple of generations
of Population III at a couple million or tens of millions of years each to
get up to Population II metallicities).
> I do not see how you could have had a noticeable population of
> of systems with the amount of small wet rocky worlds in the olden times.
If you can get a solar system like ours on 2% metals, you can do it on 1% or
0.5%.
> The material had to be passed through several times to enrich on the
> heavier elements. Plus, young galaxies are too bright for life. Plus, life
> needs a lot of time to progres to level which is interesting. Unless we're
> extreme freaks.
>
> Dunno, I think due to multiple factors delayed hatching is real.
I think a more rigorous argument with some numbers is probably called for;
too bright for life sounds like the best bet, but bear in mind that you
could be sitting in the plane of an active galaxy and be shielded by dust
and gas from the core.
Reason
http://www.exratio.com/
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