Guy Hoelzer  wrote in
news:cfvpm9$2ktn$1{at}darwin.ediacara.org: 

> in article cftapr$1tal$1{at}darwin.ediacara.org, William Morse at
> wdmorse{at}twcny.rr.com wrote on 8/17/04 9:12 AM:
> 
>> Tim Tyler  wrote in
>> news:cfh516$13j6$1{at}darwin.ediacara.org:
>> 
>>> William Morse  wrote or quoted:
>> 
>>>> I think the definition of life has to encompass the use of fuel,
>>>> but it should be something like "the ability to maintain a
>>>> structure against an energy gradient by using an available energy
>>>> source." 
>>  
>>> Practically any self-organising system does that.
>>> 
>>> Look at a whirlpool - for example.
>> 
>> I disagree. Self-organising systems all maintain a structure by using
>> an available energy source, but I do not think that all that many can
>> maintain the structure against an energy gradient, at least for any
>> significant length of time.
> 
> But all structures, including self-organized ones, exhibit energy
> gradients. You cannot have a structure without a gradient.  A key
> gradient for any structural entity, in the context of this discussion,
> is the boundary that separates the entity from its external
> environment.  Therefore, self-organizing systems must do work to build
> and maintain the local gradients (structure) that facilitate their
> functional performance. 


There are several considerations here, all of which involve energy 
gradients, so my initial terminology may be unfortunate. We have 
structures, which themselves require definition, but which certainly (as 
you point out) will exhibit steep energy gradients at their boundary. We 
also have the overall idea of self-organizing entities appearing at 
energy gradients. What I was trying to convey was the idea that some 
entities can transfer energy gained by exploiting  one energy gradient 
(e.g. sunlight for plants, various reduced compounds for chemoautotrophs)
to create a stable long term structure that resists degradation in the 
face of the random environmental changes that reduce unmaintained 
structures to rubble. 

In this sense life is a special case of self-organizing systems in 
general. It appears likely that in order to maintain their structure life 
(and presumably Tim's crystals) have to make use of information - but 
that is starting to infringe on another thread.

  
(snip)
 
>>> Definitions of life should not make any mention of electron
>>> transport - IMHO.
>> 
>> Actually you might be happier with a definition that included
>> electron transport. It would exclude tornados and whirlpools but
>> would include complex crystals. And electron transport is still a
>> general enough quality that it would not exclude things such as
>> robots or non-carbon based life. Hmmm...
> 
> PET PEEVE ALERT:  I think it is a mistake to search for a realistic
> (that is, a definition aimed at accurately describing something real)
> definition by first identifying phenomena that we think should be
> excluded and then using phenomenological details in our definition to
> achieve this exclusion. This strategy always seems to backfire as we
> develop a better understanding of nature.  It reminds me of the
> endless process of redefining intelligence (or other qualities that we
> think set humans apart from other species) based on what we think
> humans can do to the exclusion of other animals. Eventually we find
> that quality in some other animal and decide that we have to think
> harder about the list of our unique cognitive abilities.  This path 
> for the development of semantics seems like a wonderful way to
> comforting self-deception.

I understand your peeve, but the sensitivity may largely be due to the 
continuing attempt to set humans apart from the rest of biology because 
we want to be special. In fact humans are different, but then all species 
are different from other species, or they wouldn't be species. We may be 
different, but we are special only in that we have managed to make our 
ability to acquire language (as opposed to communication) innate, as 
opposed to say chimpanzees that require considerable training to acquire 
language.

Yet I think it is the norm in science (if you want to call it a mistake 
that is your business) to first observe and classify phenomena, and then 
to attempt to create definitions that correspond to the classifications.
Anyone observing life will classify it as a different phenomenon than a 
flame or a tornado (despite the many similarities). The question (which 
is what started this thread) is what makes it different. Flames, 
tornados, viruses, and living creatures all are structures that self-
organize and utilize an energy gradient. My intuition tells me that 
flames and tornados are short term energy minima - they will 
automatically appear rather quickly under the right conditions. Viruses 
are rather a special case, which is why I mentioned them - they don't 
really self-organize in the sense that the other phenomena do, but the 
difference is subtle. Life presumably started out as a short term energy 
minimum, but are far from that now. Cut a flame off from its fuel source 
and it will die, cut some bacteria off from their fuel source and they 
will form spores that can last at least hundreds of years until a fuel 
source reappears. There is a difference - the difficulty is to define it. 

Now I agree that the phenomenological details are likely to be red 
herrings, which is probably why Tim didn't like including electron 
transport and it set off your pet peeve alert. I also don't like it for 
those reasons - but as I thought about it more the knee-jerk reaction 
subsided and it seemed that electron transport might in fact be a very 
basic component of self-organizing systems that could create long-term 
structures utilizing energy gradients.

Yours,

Bill Morse
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