"Brett Aubrey"  wrote in message
news:cjl51l$q4k$1{at}darwin.ediacara.org...
> "TomHendricks474"  wrote in message
> news:cjk7g1$hfk$1{at}darwin.ediacara.org...
> > >No.  I don't think a similar-sized sun would be a necessity,
> > >unless you're being *very, very* lax with "similar", nor a
> > >"orbit sized" life zone.  Just the temperature zone is
> > >likely, such that liquid water needs to exist somewhere
> > >on the planet.  Of course, I don't *absolutely* rule out some
> > >sort of different life form in other unknowable environments,
> > >but that would be far less likely, IMHO.   Regards, Brett.
> >
> > Well lets go further.  The strength of UV varies.Certain distances
> > between the star and its planet may be too weak to break the
> > bonds or form the monomers, etc. that seem to lead to the
> > origin, while certain shorter distance may be too strong.
> > This is something that would be an important aspect, IF I am correct in
> > suggesting that the sun/UV cycle initiated the origin and powered it
> > through every step.  It also would further restrict size, distance etc.
> >
> > Overall I would say this - the fit between star and planet must
> > be such that there is a reasonably constant cyclic temperature
> > liquid zone that allows for water, and a similar reducing atmosphere .
> > as earth probably had.  Its size probably has to allow for volcanic
> > activity - the source of earth's water,  atmosphere etc.
>
> I'll agree, for the sake of ending the thread.  (In reality, I think OOL
> might possibly occur without volcanism, and think cylic is uneccessary
> if you're talking seasonal.  I'm not sure about "similar" reducing
> atmosphere  .And as to your initial point, I would *not* rule out other
> life forms based on your arguments.)  I'd also say that the above
paragraph
> is considerably more relaxed that your initial "same-sized" planet and
sun.

> I think we've beat this to death.  But will respond if required.  Regards,
> Brett.
> > Tom
> Regards, Brett

In spite of having suggested an end to this thread,  I thought you might be
interested in a similar thread over at sci.physics from 04/10/02 8:07 called
"Try", initiated by "Einsteinhoax".  A sentence from
Para. 1 follows:

 "If an Earth sized planet existed 93,000,000 miles from a
  star that was virtually identical to the Sun, it is extremely
  unlikely that it would be capable of supporting life."

Best regards,  Brett.
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