*What is "Life"?

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What is "life"

What defines if something is alive or not?
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Are you looking for a definitive scientific statement or merely a democratic vote on the matter?

I was hoping for a bit of discussion, ( with a vote), about what people believe it is. For instance I was surprised to discover that a fair few scientists do not believe that viruses are a lifeform, but that they are only replicators.

http://en.wikipedia.org/wiki/Life

http://en.wikipedia.org/wiki/Artificial_life

Developments in computer-generated "sensing, reacting, creating, reproducing, etc" "life-forms"/systems, have begun to challenge our idea of what constitutes life.

I haven't voted yet, because I don't know.

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Well, a self-aware AI or seed-AI machine, could be considered an artificial life form, could be considered to be llegaly alive I suppose.

Artificial life, as in simulations, they are, well, simulations.

To paraphrase Popper:
The study of biology has been fruitful with out ever needing to have a universal definition of it's key subject; "life".

Popper used this as an argument against the tendency of some English philosophers at that time to try and solve all philosophical problems by analysis the words used.

Having a universal definition of "life" might not be very useful, certainly much less useful than having a good knowledge of a variety of living and non-living things, however you chose to classify them.

A "living thing" is essentially a self-contained dynamical system that has the following capabilities:


1) Reproduction

2)The ability to reduce entropy by the consumption of energy(metabolism)

Last edited by Haliphron on 17 Sep 2008, 5:09 pm, edited 1 time in total.

Just for kicks...
Lets get pedantic.

1) No life can self reproduce because:
i) Even clones are not strictly reproductions/replicates.
ii) Many animals are born, or become, sterile.
iii) Many animals reproduce sexually and so need more than their self to do so.

2) No animals can "consume" energy. The total energy out is equal to the total energy in (all be it in a different form).

3) A handful of chemical chains will self replicate and reduce entropy in the right conditions. Few would argue that they are life.



Lets see how much we can tighten this up....

Living organisms continually maintain a VERY low state of entropy by capturing energy either from exothermic reactions OR directly from sunlight and using it drive biosynthesis of macromolecules which comprise cellular structures. I am Well Aware of chemical reactions that involve self replication but they do NOT constitute a continuous, self-contained system the way a bacterium does for example. Now if mitosis is not self-replication than What is it pray tell? hmm?

Bacteria and other single-celled organisms self-reproduce through a process called Mitosis, in which the single-celled organism actually replicates its own genetic code, and then splits into two identical single-celled organisms.

As for a working definition of life, living things:

1. Are composed of matter; thus they have mass and take up volume.
   
2. Tend to be more complex, more differentiated, and more highly organized than ordinary 'dead' matter, such as rocks, air, fire, and water.
   
3. Take in energy (through chemosynthesis, matter reduction, and/or photosynthesis) from the environment and transform it for growth and reproduction.
   
4. Grow, develop, and reproduce.
   
5. Tend towards an equilibrium of parameters that define their internal environment ("Homeostasis"), while maintaining a low and slow state of decay ("Entropy").
   
6. Move in response to both internal and external stimuli.
   
7. Manipulate and/or modify their environment through feeding, reproducing, and elimination of waste products.
   
8. Die.

This list is not THE absolute and definitive description of what humans know as life, but it will do for a start.

Last edited by Fnord on 17 Sep 2008, 5:30 pm, edited 2 times in total.

A self-perpetuating chemical reaction, from simple (virus) to complex (elephant).

I chose independent existence.

A being that creates itself? That's getting into metaphysical things.

Well, life has different approaches from science, religion and philosophy and perhaps even politics, which in politics seem to be influenced by all of them in some degree. Although I agree that the religious and philosophic views are of finding meaning of life as part of trying to define it.

The definition or the meaning of Life seem to be debatable when it comes to pro-life vs pro-choice.

Being me, everyone is IS *DEAD* TO ME!! ! ALL OF YOU!! !!


(ok, lame joke) But, there is no real meaningful definition of life other than perhaps a biological one, and that one does not capture all of the mystique we hold towards life. I mean, a bacterium is alive, but does it have meaning or any real purpose? No, it is a freakin' cell!!

There is a difference between being alive and being intelligent. An ant is evidently alive, but not intelligent. A sentient computer would be intelligent, but hardly alive.

More like a self-perpetuating dynamical system.