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From: michaelm@bcsaic.UUCP
Newsgroups: talk.origins,net.bio
Subject: Re: What's this LIFE stuff?
Message-ID: <717@bcsaic.UUCP>
Date: Mon, 6-Oct-86 15:26:44 EDT
Article-I.D.: bcsaic.717
Posted: Mon Oct  6 15:26:44 1986
Date-Received: Thu, 9-Oct-86 04:24:49 EDT
References: <45500088@uiucdcs> <7670@tekecs.UUCP> <829@jplgodo.UUCP> <2446@phri.UUCP>
Reply-To: michaelm@bcsaic.UUCP (michael maxwell)
Organization: Boeing Computer Services AI Center, Seattle
Lines: 48
Keywords: assimilation, energy conversion
Xref: watmath talk.origins:120 net.bio:662

In article <2446@phri.UUCP> lonetto@phri.UUCP (Michael Lonetto) writes:
[Lots of proposed definitions of 'life' and discussion thereof omitted]
>The question thus becomes:  What is this metabolism stuff??  
>
>Metabolism is a SELF SUSTAINING, SELF REGULATING network of chemical
>reactions capable of maintaining HOMEOSTASIS.  Homeostasis is a "steady
>state", ie: changes in the rates and directions of the reactions are
>kept within limits, as is the overall chemical activity of the organism.
>This is not the same as stasis (the lack of change), but implies that
>the changes tend toward a specific rate...
>...Metabolism is responsible for ASSIMILATION,
>which is the conversion of environmentally obtained chemicals to
>substances which can be used as part of the organism, and their
>subsequent utilization.  Note that the substances taken in from the
>environment are chemically distinct from the substances produced from
>them by the organism....

Just to throw in a curve ball--if you omit the word 'chemical' in the above,
then stars metabolize.  A star converts H into He for most of its
'lifespan', using the H that it gathered from the environment during its
'birth'.  The interaction between gravitational forces that would cause
collapse, and thermal 'forces' that would cause expansion, results in a more
or less steady state that lasts a large proportion of the star's lifetime
(this steady state is referred to as the 'main sequence'.  Most stars spend
the majority of their lives in the main sequence.)  Before you object that
stars don't assimilate substances during their later lives, two answers: 
(1) There are certain insects that don't eat during their adult lives
  (i.e. after metamorphosis; one could argue that the point at which a star
  begins burning H is its metamorphosis). 
(2) Some stars, in binary systems, do assimilate gas from their environments. 
  These are usually  collapsed stars, and they strip gas from their
  noncollapsed sisters.  Eventually this gas piles up on the collapsed star to
  a depth where fusion starts, which is the phenomena we call a 'nova' (not a
  supernova, which is quite different).

Some stars even reproduce, in a certain sense.  When a interstellar gas
cloud collapses, some regions will collapse into stars long before others.
The first stars produced are often very large, last a short time (10's of
millions of years), then become supernova.  The shock waves from the
supernova propogate through the clouds, triggering local collapses of the
cloud which then form--you guessed it--more stars.

I wouldn't be surprised if there weren't certain cultures that considered
stars to be living creatures.
-- 
Mike Maxwell
Boeing Advanced Technology Center
	...uw-beaver!uw-june!bcsaic!michaelm