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Abs like Jesus
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Best of AD Award Winner: Best Topic, Science & Technology, 2002-2003


The Merriam-Webster dictionary afforded to me by America Online offers several definitions when I conduct a search for "life"
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1 a : the quality that distinguishes a vital and functional being from a dead body b : a principle or force that is considered to underlie the distinctive quality of animate beings; compare VITALISM 1 c : an organismic state characterized by capacity for metabolism, growth, reaction to stimuli, and reproduction
2 a : the sequence of physical and mental experiences that make up the existence of an individual...

9 : an animating and shaping force or principle 

16 a : human activities b : animate activity and movement <stirrings of life>...


When looking into scientific circles I begin to see conflicting views over what the definition should be and how it should be considered. Probably the greatest debate in which the definition of life is considered is that of pregnancy and abortion. But I'd like to steer away from that issue here, if possible. I got around to thinking about life because we're sending two Robot Rovers to search Mars for any signs of past or present life this month.

If we don't have an agreed upon definition of life, how can we ever expect to identify possible extraterrestrial sources of it?

Astrobiology Magazine, among others, tackles the issue with additional websites listed for reference (What is Life?, Defining Life, Entropy and Evolution). Metabolism seemed a good way to go for restricting the definition until the Viking Experiments showed Martian soil to have a peculiar chemistry that resulted in something remarkably similar to metabolism. Water has been another characteristic viewed to be necessary for life in the past, but that doesn't appear to be the case in scientific circles.

Benton Clark, an astrobiologist interviewed by Astrobiology Magazine is quoted as saying: "Water doesn't define life, it is just an aspect of our environment."

The general consensus seems to remain that we haven't found a universal definition for life yet. So my question is what do you think life is? Without a uniform definiton can we really expect programs such as the Mars Rover to look for something they possibly can't describe? And finally, what is it that makes life so special to us?

Other sites of possible interest:
Life in Universe
Ask a Scientist
Space.com: The Meaning of Life
Google
Sleeper
Just my 2 cents on this..

The meaning of life....

Why are we here...

What purpose is our life...

These questions are a waste of time and energy(in my opinion).

Every time I hear somebody say they are trying to find themselves it makes me sick..

I think it was a beer commercial that said "Why ask why"

Just enjoy your life, provide for your family, and do what you think is right and you will most likely come out for the better.

Johnny
Abs like Jesus
I didn't ask any of those questions.

I have pondered those questions before, and I have considered opening a related thread in the Religion forum for such discussion, but they are not in any way the questions being asked here.
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So my question is what do you think life is? Without a uniform definiton can we really expect programs such as the Mars Rover to look for something they possibly can't describe? And finally, what is it that makes life so special to us?

Only the last question might be comparable to those you deemed a waste of time and energy. The first question, however, serves many purposes. It serves to fuel the debate over when life starts, what value we should place on life, and what can either separate or unite us in nature.

The second question is one I feel to be of scientific interest and possibly even theological interest, though I would rather save that aspect for the appropriate forum. If we're to hunt for life beyond our planet, shouldn't we have a better idea of what we're looking for?

And the second question, for me, ties into the third question. If we could better define life and somehow detect its presence elsewhere in the universe, what would that mean for us? Certainly it would upset millenia of religious thought that we are somehow unique and special, that this world was created for us, etc.

These questions don't seem to be a waste of time and energy from where I sit. I don't imagine the scientists, philosophers and theologians who ponder them and others consider them such either. Of course, I can't help but wonder why you'd bother even commenting if you viewed it to be such a waste of your time... shifty.gif
nileriver
well, a special rcok recoverd from mars, they say mars, had fossil evidence of bacteria on the lower 200 nano something or other level. fossil evidence that is. but it could be tainted being it was found on earth. as for the difinition you got me, i think that its been up for debate for some time now on what is the exact terms to be used. i think that it would be agreed on anythig less then bacteria that small or smaller will probally be booted out on the base its a chemical reaction biggrin.gif but i have no real idea myself, just thought i would add my opinion.


but to think of the people that are working on this, i imagine that most anything they might find will come under serious scrutiny.
Sleeper
QUOTE(Abs like Jesus @ Jun 8 2003, 05:15 PM)

Of course, I can't help but wonder why you'd bother even commenting if you viewed it to be such a waste of your time...  shifty.gif

becuase, it's a mere annoyance of mine...
Victoria Silverwolf
These are profound questions to which I can offer only a few superficial thoughts.

The boundary between "living" and "not living" is not as sharp as one might think. Are viri alive? They seem to possess only the absolutely minimal complexity needed to reproduce themselves; just nucleic acid surrounded by a protein shell. They require other organisms in order to perform their basic reproductive function. If we grant that viri seem to be as simple a form of life as we can imagine, what about prions? These seem to be nothing more than protein molecules in a particular orientation, yet they create others of their kind, and cause diseases. Based on these examples, I tend to think of "life" as a phenomenon which occurs once chemical structures have reached a certain level of complexity, at which point they react with the environment and reproduce.

Hence, although humanity can seek out "life as we know it" (nucleic acids and proteins in water) through the use of chemical experiments, it will be very difficult to detect "life as we don't know it" in this way. (On a macroscopic level, life will be much easier to detect, as we observe organisms that behave in ways that reveal their living nature.)

What is it that makes life so special to us? Because we are alive; because some forms of life have reached the level of complexity at which consciousness emerges; becuase we are fascinated by the mirror which living things hold up to us.
moif
Abs

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If we don't have an agreed upon definition of life, how can we ever expect to identify possible extraterrestrial sources of it?


laugh.gif Don't you see thats the beauty of it? No matter what we find... if we find anything at all... we keep our options open.
AuthorMusician
Abs,

Seems to me that drawing the line between living and non-living things has to be an arbitrary decision. The very concept of the line's existence is a philosophical premise, and thus the difficulty in determining its position. as Victoria Silverwolf pointed out, complex molecules can display many of the traits that some have attributed to the definition of life.

One way out of the problem is to start with a different premise: All things are alive. In other words, don't propose a duality and the problem disappears. But that doesn't help us to figure out if life exists elsewhere in the Universe.

So, I propose that we put a stake in the ground and define life as an entity that grows, reproduces, and interacts with its environment in a manner that has the potential of developing increasing complexity. This would eliminate things like crystals and free-floating proteins.

One of the fascinating things I learned in college biology was that the mitochondria (the part of the living cell that carries out basic metabolism) may have once been a free-floating entity. So somehow, life also involves the joining together of independent entities into a more complex whole.

My thoughts on why all this is important to us is that we need to understand how life comes about. We also want to establish the viewpoint that life can arise on other planets in the Universe to boost our awareness to new levels. The motivation for this seems to be built into life, and life seems to be built into creation.

We also want to manipulate life, as evidenced by efforts that range from selective breeding to genetic engineering. Well, in a broader sense, we want to manipulate our environments.

For me personally, I am just curious. How the heck does life work? Can there be variations on the theme? How come life happens at all? What makes mud get up, walk around, and wonder?
Wertz
Abs: I'm not ignoring this thread, just trying to work my way through a few of your links. If I feel I can contribute anything in addition to those whose work you've cited, I will...



QUOTE(Abs like Jesus @ Jun 8 2003, 06:15 PM)
I didn't ask any of those questions.

I have pondered those questions before, and I have considered opening a related thread in the Religion forum for such discussion, but they are not in any way the questions being asked here.

Good God - you wouldn't want to start a thread along the lines of what you've outlined above! Those sorts of questions are a waste of time and energy and the are such an annoyance that they make Sleeper sick. If you did start such a thread, he would be forced to waste more of his time - and everyone else's - telling us all what a waste of time such a thread is. And, as we all know, America's Debate exists solely and exclusively to live up to the expectations of Sleeper. dry.gif rolleyes.gif



Back in the real world, I would be interested in you starting a thread such as the one you describe. I'd probably feel better equipped to deal with the philosophic question of "life" than the scientific. wink2.gif
Jaime
QUOTE(Wertz @ Jun 11 2003, 04:18 PM)

Good God - you wouldn't want to start a thread along the lines of what you've outlined above! Those sorts of questions are a waste of time and energy and the are such an annoyance that they make Sleeper sick. If you did start such a thread, he would be forced to waste more of his time - and everyone else's - telling us all what a waste of time such a thread is. And, as we all know, America's Debate exists solely and exclusively to live up to the expectations of Sleeper. dry.gif rolleyes.gif

Don't make this personal and distract from the debate as a whole, please.
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AGiantBean
I believe that the definition of life is anything with Intelligence that can use it. (ex. a dead person couldn't use their intelligence, whereas anything such as a cell on a non-dead person could)
Victoria Silverwolf
QUOTE(AGiantBean @ Jun 11 2003, 04:53 PM)
I believe that the definition of life is anything with Intelligence that can use it.  (ex. a dead person couldn't use their intelligence, whereas anything such as a cell on a non-dead person could)

I'm sorry, I just don't follow this. To you mean to say that an individual cell has intelligence? That everything that lives has intelligence? If so, I would have to strongly disagree. I think life and intelligence are two different phenomena entirely. So far, all intelligent things must be alive, but that may not always be true. It is certainly not true that all living things must be intelligent. (By "intelligence" I mean consciousness or awareness.)
Ultimatejoe
Bean, you're basically suggesting that anything that is capable of a stimulus-reaction response is LIFE. My computer certainly isn't alive.

LIFE is a now defunct magazine. Life is my personal existence, everything else is just a figment of my imagination. (Damn, where's the stoner smiley...)
Wertz
QUOTE(Jaime @ Jun 11 2003, 04:30 PM)
Don't make this personal and distract from the debate as a whole, please.

Sorry - I didn't mean to be overly personal. I just fail to see the point in submitting a post that says nothing more than "I don't like this thread." What's that about? I just thought it was worth mentioning that if one doesn't like a thread, one needn't bother posting to it - which I would've thought was fairly self-evident. blink.gif

:::::::::::::::::::::::::

In terms of the question of life: From a scientific perspective, it seems there's general agreement on a few basic requirements. These would include the potential for growth and reproduction, consumption/metabolism, stimulus/response, and (sometimes) purposive motion and/or a nervous system - though not everyone's definitions include all of these. Regardless of the definition, I don't think that the Mars Rover itself will be specifically "looking" for anything itself, but just investigating and collecting in the hope that those monitoring the Rover know what they're looking for. smile.gif

As to your last question (What is it that makes life so special to us?), that may be the stuff of another thread - along with some of the other, more philosophical questions you raised - for those who aren't annoyed by such things. rolleyes.gif
AGiantBean
Let me rephrase that. Anything with intelligence in the sense that it responds to a stimulus from its natural environment. Just because the sun is shining, your computer doesn't cover its monitor. A cell has intelligence. Although not complex, it's able to respond to a stimulus and divide itself.
Rancid Uncle
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Let me rephrase that. Anything with intelligence in the sense that it responds to a stimulus from its natural environment. Just because the sun is shining, your computer doesn't cover its monitor. A cell has intelligence. Although not complex, it's able to respond to a stimulus and divide itself.

What about coacervates, microspheres or protobionts? They split when they get large and react to their environment, are they alive?

I don't think it is possible to define life with one rule. I think it's more of a spectrum like one one end there is god or jackie Chan, in the middle are microspheres and on the other end are quarks and atomic brick-a-brak.
AGiantBean
I tried to give a definition, but here's my other view. Life doesn't have a distinct definition. It's more of an understood thing, that one can not describe what it is really.......................... sort of like grits.
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