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From: sa209@utb.shv.hb.se (Claes Andersson)
Subject: Re: "What is Life?"
Message-ID: <1995Feb16.180714.11488@gdunix.gd.chalmers.se>
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References: <1995Feb6.125045.15753@gdunix.gd.chalmers.se> <3h6676$btc@engnews2.Eng.Sun.COM> <1995Feb9.233556.29536@gdunix.gd.chalmers.se> <3hgnqt$lk3@engnews2.Eng.Sun.COM>
Date: Fri, 17 Feb 1995 00:26:45 GMT
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holtz@netcord.Eng.Sun.COM (Brian Holtz) wrote:
>In article <1995Feb9.225702.26598@gdunix.gd.chalmers.se>,
>Claes Andersson <sa209@utb.shv.hb.se> wrote:

>
>>lack any self-maintaing mechanism. I refer, once again, to that a
>>tornado don't add any energy to its own system to keep it going.
>
>Repeating this over and over doesn't help convince me that it's true.
>Tornados definitely do extract energy from their environment to keep
>themselves going.

 No they don't. Could you please tell me in which way a tornado is anything
else than the result of a certian meteorological condition. Tornadoes arise
as soon as these conditions are present and the tornado as such is therefor
not distinguisable from its environment, it's just a part of the phenomenon.
It get its energy, without transforming it, from the wind that is caused by
differences in heat etc. etc. It's a very automatic process that can be expected
to be found anywhere there is an atmosphere. Mars for example. I don't say
that this disqualify it as a lifeform but the fact that it doesn't transform energy
in any way, doesn't actively maintain its entropy, disqualifies it.

>
>>>>The tornado can be predicted to last a certain amount of time,
>>>
>>>So can a tree.
>>
>> Yes, you are right but why? Can it be predicted from an analysis
>>of what it's made of? A tornado would be much easier to predict
>>like that.
>
>Hardly.  Both a tree and a tornado will maintain their low entropy as
>long as the environmental conditions are right.

 Not the same thing and you know it. The tree transform one sort of
energy into another that allows it to take incredibly complex forms.
A tornado is propelled by the wind and nothing further happens, just
what could be expected by any non-living thing.

>
>>Take a tree, remove the entropysinking mechanism: the life. Take
>>another tree that is identical to the first one. The dead tree will
>>ofcourse decay just as fast as one could expect but the living
>>tree, even though it is made of exactly the same thing will go
>>on living until it dies.
>
>No dead tree is identical to a living tree.  The difference between
>them is, in terms of entropy maintenance, the same as the difference
>between a tornado and a recently-dispersed tornado.

 No, your'e right. Not really. But remove just one little piece of its
function so it cannot metabolize anymore. There is no such thing
that can be done with a tornado? Do you suggest that the golf-stream
is alive? Perhaps everything is alive? Obviously, everything isn't alive...
the question becomes quite bizarre.. there is a difference between
a tree and a tornado.

>
>It seems kind of silly (and circular) to limit life to only those
>things that don't look much different after they are dead.

 Do it? I mean directly after that they dies. In the moment of death.
It is from then you can compare what happens to the system when it
is alive and when it is dead.

>
>>>>Compare a virus and a tornado. They have one thing in common:
>>>>They do not actively contribute to their low entropy in any way. [...]
>>Don't you see what I mean? It's called metabolism in known living
>>creatures. This is how it manages to keep the entropy low.
>
>Actually, I think I see what you mean more than _you_ do. :-)
>I think that if I were to wring from you what you really mean by
>"active", you would end up with a self-production sort of definition
>like Greg's.  But because entropy is such a neat concept, I don't see
>you letting go of it any time soon, so this discussion may not be
>worth continuing much longer.

 What I was after was the fact that viruses, just like cars, are designed
(viruses are evolutionary designed, and cars by humans) to stay in
the shape they are. They don't have any mechanisms for it. I don't
have to mention entropy but since it points out very well what I'm after
it would be stupid not to.

 The reson why it wouldn't be worth to continue the discussion would
rather be that you, by refusing to see the difference in the self-maintenance
of a tree and a tornado. You take up things like that both take energy
from the environment and that both have a predictable length of life
etc. etc. Of course.. If you accept a tornado as a living system, you will
certainly have to recognise the atmosphere as one, and the whole planet
etc. But we will still have to ask us the question: Is it possible to define
the difference between a pig and a rock?

>>If a tornado would metabolize something (like what it sucks up or something)
>>to maintain its existance even after it would have "died" normally.
>
>I can't fully parse this sentence.  At any rate, why can't we say that
>a tornado metabolizes the temperature differentials in the atmosphere?

 Sorry for the incomplete sentence..

 Why can't we say that the atmosphere metabolize the energy of the sun and
of the earth's core? The sun obviously metabolize the energy of the hydrogen
it once accumulated etc. etc. Perhaps you can say that it does but still there is
something in the metabolism of a pig and a procaryote that is simillar to
eachother and still different to this "metabolism" that a tornado has. There is
something there that makes them last longer than their fragile constitution
would have allowed without this complicated metabolism. Energy can be
used to build molecules in a way that creates a metastable entity: A lifeform.

>
>In article <1995Feb9.233556.29536@gdunix.gd.chalmers.se>,
>Claes Andersson <sa209@utb.shv.hb.se> wrote:
>
>>>a lone terrestrial virus on an outbound spaceprobe becomes
>>>effectively dead upon the destruction of all other terrestrial life.
>>
>>  Say that some earthlife back in time travelled forward and met this
>>dead virus? You never know do you..
>
>The point of my thought-experiment was to stipulate that the virus is
>intact but has zero hope of reproducing.  If you stipulate a much
>higher hope of reproducing, the situation is different.

 Of course, but I understand your point and I agree that it has something
to contribute with.

>>a rabbit on an outbound spaceprobe would die when this
>>happened as well..
>
>No.  In my definition of "alive" I said that living things remain
>alive as long as they are "able to reproduce or interact with their
>environment".  A much better job could be done of defining exactly
>what constitutes death, but this is comp.ai.alife, not comp.ai.adeath.

 Or interact.. Very well. Interact in a meaninful manner.. The meaning
a rabbit could have with interacting with its environment can ultimately
only be reproduction. If it can't reproduce or affect the reproduction
of any other lifeforms, its interactions would be meaningless. A virus
on this probe probably interacts in a meaningless way as well by bumping
into molecules in the air or walls etc. etc.

 What type of interaction do you mean?

>>you surely know the
>>difference between an inductive and a deductive evidence. And
>>that inductive evidences cannot be global. You can say that such
>>a deifnition with reproduction etc. does with great certainity apply
>>to all lifeforms on earth and is likely to apply to other lifeforms
>>as well but you can never define life with it.
>
>What induction?  Definition is about stipulation, not inference.  To
>me, defining life as reproduction and evolution is like defining
>bachelor as an unmarried male.  You seem to be assuming that there is
>some pre-existing platonic category of Life and that we mortals are
>struggling to discern it.  By contrast, I'm just trying to clarify
>this speech habit most of us have concerning the use of the phrase
>'biological life'.

 That's exactly what I don't mean. By setting up one simple rule for what
can be called alive a what cannot I try to ignore all sorts of precognitions
of what life is.

>
>>it is amazing that you refuse to see that a tornado lack any form of
>>entropy sinking mechanism and that trees don't.
>
>There _is_ a difference between the tornado process and the tree
>process, but that difference is _not_ essentially thermodynamic.  It
>has more to do with what Greg calls self-production.

 Well, my definition wasn't entirely about entropy either. It was about
how the entropy is preserved.

>
>>>>Do you see any strategy that a fire use to spread to the right place?
>>>
>>>Fires send out embers on the same air currents that trees use [...]
>>In fact, fires sometimes _create_ those air currents, which is
>>>a trick that trees cannot perform.  Sure, some trees put their seeds
>>>in fruit, but there are many one-celled organisms that do absolutely
>>>nothing to choose where to spread.  Are they not alive?
>>
>>Don't you see what's wrong in what you just wrote?
>
>No.  You asked for a "stategy" used by fire "to spread to the right
>place".  I told you one.  I further pointed out that many living
>organisms employ no such strategy whatsoever.  You ignored both of
>these points, and simply repeated:
>
>>Some trees put their seeds in fruits, no fires
>>fires would ever do that.
>

[Cut alot about what look at a system on]

 It's not about whether we understand the process or not it is about
the level of it. Any short definition like mine will have to assume alot
of what certain words means. With "Actively" I don't mean everything
that the word can mean, I mean that there is a sort of mechanism that
manage to maintain the entropy so that it distinguishes the lifeform from
its environment. Therefor, in our environment, simple mechanisms like
atmospherical currents etc. etc. can't be accepted as life qualifiers.
If a tornado occured in vacuum and wandered about despite the fact
that it normally wouldn't be able to (x grams a carbon, x grams of oxygen,
x grams of calcium etc. etc. wouldn't normally be writing posts) would
perhaps quilify it as a lifeform. A tornado in a vacuum would of course
have to protect itself from diffundation (spell?) and that's where the
life mechanism comes in. Such a mechanism is HIGHLY unlikely to
emerge by chance and therefor, is is highly likely that these vacuum-
living tornadoes also would reproduce.

Regards,

Claes Andersson. University of Bors. Sweden


>--
>Brian Holtz

