What physical property separates the two?
That is a very interesting question, as any attempt to answer it using logic ends up with the conclusion that either everything is alive, including stones, or everything is dead, including ourselves. That can only mean one thing: "life" is a fundamental property of the universe and as such can't be reduced to anything more fundamental, not even physics.
Or that life is a subjective, relativist value.
For a multicellular metazoan, it is that the collective cellular processes still work. This automatically means that such an organism dies in some parts before others (cf. "brain death"), but once the major processes fail, the others will eventually fail too.
Doing my best to evade trying to
define "life" I would say that
what distinguishes that which is
alive from that which is dead for
me is that that which is alive
must be engaged to some
extent in the attempt to improve
or elaborate upon it's status quo.
That which is dead no longer exerts any effort of any kind on
its own behalf and is at the
mercy of any force that acts upon
It is by virtue of this that I
would never consider rocks, or
minerals, or individual elements
to be possessed of life.
Well, since all "living things" are composed of elements, then perhaps life is a property related to complexity. After all, a cell is basically a very complex system of interactions and reactions. Of course, the cell is not a closed system, and a certain amount of interactions and reactions between it and its environment must take place. Maybe after a system becomes complex enough and parts of the system are dedicated to maintaining the system's continuity by interacting with and reacting to its environment, then it could be considered alive. But then, this is only my humble opinion.
Keep that heart-lung machine away from me!
Arggg! Attack of the undead fishies...
This is a good start.
But there is more.
Life als is able of reproducing itself, in more or less the same form.
And life distinguishes itself from the environment.
And life needs to take in sources of energy to sustain itself, it needs a form of metabolism.
I agree with all except the first.
The mule, I beieve is is, which is
a cross between a donkey and a
horse, I believe it is, is not able to reproduce.
Likewise it seems resonable to
propose that throughout evolution
lifeforms came to be that were not
able to reproduce, and these indi-
viduals lineage died with them.
Before these indiiduals died, how-
ever, they were alive.
So does a computer virus. Which is why they are called 'virus'. Are computer viruses alive?
Yes, living beings are different from the environment by virtue of being alive. Like any fundamental principle, such as 'matter', 'space', 'time', life can only be defined tautologically.
So does my car.
What stands in the way of accepting life as a fundamental, irreduceable principle of the universe?
Your car does not sustain itself.
It can never make any effort on
it's own behalf to do so. It
cannot even desire to make such
Nohing your car takes in goes to
sustaining it in it's present
state. All of its parts start to
be acted upon by environmental
agents as soon as they are made.
It's downhill from there: no
growth, no healing.
A car cannot be used as an example
of something that sustains itself
by taking in nutrients.
Douglas Adams at Digital Biota 2
Life, seemingly like all things in our universe, is a phenomenon named by humans, which isn't bounded by a nice neat couple of lines of demarcation. Life, is a part of everything else which does something neat, but nothing which is unique nor removed from everything else which happens.
Just like us humans like to have these neatly defined colours : Red, blue, green, yellow etc... when we find out what colour actually is, we quickly realise that there is no neat defined boundary of where Blue stops, and green starts...there is just a continuum. A morphing from one thing into another.
Life, is a chemical reaction...it just happens to be a type which may become increasigly complex and self-propogating, so when seen in its most extreme form (Eukaryotes) it is easy to define. When u follow this easily defined 'life' back to its origins though...it becomes incresingly hard to find that magical line of demarcation.
The same thing is apparent with 'What is human?' Whether u mean evolutionarily (it is obvious what is human now, but backwards in evolutionary time, the demarcating lines become more blurred, and no line is apparent), or whether u mean individually (Is a Zygote a human, an embryo, a fetus, a baby etc?) The lines simply do not exist.
People need to start understanding this, or else find a real way to define these concepts (ie: Find God and ask him to tell us the lines.)
Another interesting way of targetting this question is: What seperates a living organism, from a dead version of that same organism.
ie: Poison someone, and figure out what it is precisely that makes them dead as opposed to the non poisoned person.
What is the difference between viable and non-viable bacteria?
The heading of the thread seemed
targeted at discussing the polarities: whats the difference
between that which we definitely
consider alive, and that which
we definitely consider dead. This
is a different question than "what
is life?" I didn't observe anyone
getting confused about the parameters.
OK then, how about: "Degrees of complexity"
Life is Universe's way to increase entropy faster. Living beings actively try to decrease entropy (increase order) locally, at least by sustaining their own bodies. More complex organisms, for example we humans, also attempt to decrease entropy at our surroundings (buildings, cleaning). But all this has only local effect, and the entropy of the system as a whole actually increases; the more we increase order locally, the bigger is the entropy increase in the whole system.
So living beings have a tendency to decrease entropy locally.
The tone of that post was frankly
exploratory; speculative, no
assertions were made.
This is true but it can't be used
to distinguish that which is alive
from that which is dead because
of all the non-living natural
forces a person could think of
that do the same thing: the wind
the tides and waves, rain, snow,
UV rays etc.
Hmm, don't forces of nature more like increase entropy, since they are destructive forces? Wind, rain and UV rays don't make buildings or maintain bodies; they erode them. They are tools of entropy a living being must fight against. From this point of view the natural forces seem like the exact opposite of the living.
Well, if you use the same terms as you did with life, they do locally and temporarily decrease entropy. Eg. in the formation of charged clouds for storms. Or they work to drive life along by providing energy, even though the ultimate product is, as you say, an increase in entropy.
In things like ther formation of a snowflake for example, we see an increase in order from a natural process.
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