Text 126, 135 rader
Skriven 2004-09-22 06:05:00 av Brett Aubrey (1:278/230)
Ärende: Re: Different Forms of Li
=================================


"TomHendricks474" <tomhendricks474@cs.com> wrote in message
news:cidugp$u11$1@darwin.ediacara.org...
> Brett Aubrey wrote:
> >> I don't think there are other forms of life,
> >> and  I don't think there are other chemical
> >> paths. I think there is only variation
> >> on a single path.
> >I take Shapiro's quote as hypothetical and would think (panspermia
> >aside) that if life exists off this rock that it would be almost
exclusively
> >"other forms" (non-DNA, possibly non-carbon) with other chemical
> >paths.  But we'll likely never know without positive SETI results or
> >exploration.  (Perhaps I'm misreading you.)
> TH
> If life is a reaction to the sun/heat cycle, then
> you can't have life without the sun/heat cycle.
> And you can carry that further (same size
> planet to hold in a similar atmosphere - watery
> such that liquid water is there - temp zone
> between 0-100C, and on and on.

Ah...  Well, the more similar attributes that you abitrarily add between
here and another life-giving planet, the more likely that life will be the
same form, and on and on.  But there's no real reason that the same size is
necessary nor that the atmosphere is similar - after all, life began with a
different atmosphere.

> >> I suggest that no matter its form,
> >(but this statement implies other forms(?))
> TH
> wrong choice of words - perhaps I should have
> said, " I suggest that no matter the variation"
> >> any life is first a production of, and then a
> >> reaction to, a heat cycle, and because
> >> the basic driving force (the sun heat cycle)
> >> and the initial structures of life are
> >> always the same, the chemical
> >> outcome is the same = life.
> >I think you're likely right about the heat cycle, but how
> >can you guess at the initial structure of alien life (even
> >of Eath's life) or the raw materials.
> TH
> Because chemistry obeys laws. You can't change
> the chemical rules. They lead to the same result,
> at the same temp (liquid water range) and under
> the same conditions (liquid water - certain
> atmosphere etc.) with slight variation

True about basic chemicals.  But I'm suggesting that you can't know that
Earth's (raw materials and) chemistry is the only one capable of producing
life.  That is, a different elemental mix might produce a different form of
life.  And for that matter, a similar mix might produce something pretty
profoundly different from DNA-based life (I'm not thinking that we can even
guess at what that might be - after all, did we successfully guess at a
structure for DNA?).

> >> To say otherwise is to suggest you can
> >> cook a cake with each time using completely
> >> different ingredients cooked in
> >> completely  different temperatures
> >> Comment?
> >No.  Many different ingredients make for a very wide variety of cakes
> >(there will not be an infinite variety of chemicals that can produce
life,
> >but there's probably >1 - a wild guess.)  And even with the same
> >chemicals, it might be possible that some sort of non-DNA-based
> >life could result (I even think this would be "likely" - i.e. not
necessarily
> > likely that life would result, but likely that IF life arose it would
not be
> >based on DNA.)  FWIW, from an amateur.  Regards, Brett Aubrey.
> TH
> Amateur here too (as moderator says - this place
> crawls with them) - perhaps a variant of DNA
> may have played a part for sure

I'm suggesting that (panspermia aside) both DNA or any "variant" is most
unlikely.  While there may need to be something functionally analogous to
DNA (especially for complex life to evolve), it will likely be of a
different "form", to use your word.

> - but the basic life result will be the same.

and therefore life will not be the same.

> And I think and
> predict we will find some reason why amino
> acids, and nucleic acids, have a better chance
> chemically reacting with each other, than apart.
> And we'll find this is a key to the origin in every
> case - no matter the place.
>
> Then carry it further.
> If we have a creature formed that is mobile and
> lives in water  - it'll form
> the same shapes to best move through the water
> as our sea creatures (and probably the same
> range of shapes due to the fact that all planets
> with life will have to have reasonably the same
> gravity to hold in the same atmosphere),
> same with air/flying creatures, same with
> underground digging creatures, same with on
> earth running creatures.

Here I'll agree with you - there will be similarities in *some shapes* where
life has evolved enough in specific environments.  But remember that not all
our sea life is similar - sea horses and anenome do not require a "best
shape" (the way I am interpreting you) to move through the water.

> IMO the more we know about life, the more we will
> see how locked in it is to certain conditions.
> Sci-fi lets' us imagine anything as does early
> unproven speculation. But as the origin becomes
> deciferable, we'll find it limits what life is
> and where it can be, much much much more than
> most think now.

Interestingly, the last few decades has taken the opposite direction.
Extremophiles are now found deep in the rocky mantle, high in the atmosphere
and around oceanic vents, where we used to assume life was impossible.  If
life has evolved elsewhere, I think we'll find it can thrive in even more
extremely diverse and "inhospitable" (from our viewpoint) habitats than ones
just here on this planet.  If I were a betting man and thought that any of
this can be proven in my lifetime, I'd even propose a wager that whatever
life we find will not have DNA, nor anything we'd consider a variant, as its
base.  Regards,  Brett.
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