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*What is "Life"?

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What defines something as alive?
Independent existence. 13%  13%  [ 3 ]
Motor activity/movement, however slow/limited. 0%  0%  [ 0 ]
Sense "organs"/sensory functions which determine reactions. 4%  4%  [ 1 ]
Transformation of energy received/construction of new material. 17%  17%  [ 4 ]
Capable of constructing and maintaining an ion/electrical gradient. 0%  0%  [ 0 ]
"Life force". 25%  25%  [ 6 ]
Other, please explain in thread. 42%  42%  [ 10 ]
Total votes : 24

DentArthurDent
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18 Sep 2008, 3:24 am

What sort of life are we talking about. If NASA finds bacteria on mars they are going to scream that they have found life, on the other hand this is not sentient life. Sentient life needs a whole lot of criteria.


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18 Sep 2008, 10:06 am

If the one criteria agreed on by science is that a lifeform/life "reduces its own entropy by increasing entropy around it", then it looks rather as if the predominant property of life is to be a threat to its surrounding environment, including other lifeforms within that.

Strange way of defining life.

.



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18 Sep 2008, 10:18 am

ouinon wrote:
If the one criteria agreed on by science is that a lifeform/life "reduces its own entropy by increasing entropy around it", ... Strange way of defining life.

Strange, yet accurate.


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18 Sep 2008, 12:11 pm

ouinon wrote:
If the one criteria agreed on by science is that a lifeform/life "reduces its own entropy by increasing entropy around it", then it looks rather as if the predominant property of life is to be a threat to its surrounding environment, including other lifeforms within that.

Strange way of defining life.

.


You forgot the second criterion which is the ability to reproduce.



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18 Sep 2008, 9:49 pm

There is actually some debate over whether viruses are alive or not, since they cannot reproduce their own DNA without a host. Sometimes they are described as 'molecular machines.'



Haliphron
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19 Sep 2008, 12:54 am

LKL wrote:
There is actually some debate over whether viruses are alive or not, since they cannot reproduce their own DNA without a host. Sometimes they are described as 'molecular machines.'



What about Stars? While the entropy inside a star is MUCH greater that inside terrestrial organisms, they DO reproduce.
When a large star explodes into a supernova, the resulting nebula absorbes interstellar hydrogen and new stars form within.



Psimulus
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19 Sep 2008, 4:20 am

Maybe life is the result of an infinite sum,



LKL
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19 Sep 2008, 11:52 am

Stars are relatively simple chemical reactions. They don't count as alive by any stretch of the imagination. Star formation isn't reproduction; there is no duplication or preservation of the 'parent' star's phenotype or genotype. The 'daughter' stars can be any class of star, depending only on the type and quantity of material they absorb.



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19 Sep 2008, 11:58 am

LKL wrote:
Stars are relatively simple chemical reactions.

Nuclear reactions, LKL.


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LKL
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19 Sep 2008, 12:04 pm

?
Nuclear reactions are chemical. It involves protons and neutrons rather than electron bonding, but it's still chemical.



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19 Sep 2008, 12:11 pm

LKL wrote:
?
Nuclear reactions are chemical. It involves protons and neutrons rather than electron bonding, but it's still chemical.

No, chemical reactions involve only the motion of electrons in the forming and breaking of chemical bonds, while the actual elements involved remain unchanged. Nuclei are not involved.

A nuclear reaction involves two or more nuclei or nuclear particles colliding to produce elements that are different from the initial particles. Electrons are not involved.

Thus, the reaction whereby two Hydrogen atoms form an electron bond with one Oxygen atom to form a single water molecule is a chemical reaction, while two Hydrogen nuclei slamming together and sticking form a single Helium nucleus. In the former, the atoms themselves remain unchanged, while in the latter, an entirely new element is formed.

Sorry, kid; that's physics for you!


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19 Sep 2008, 2:30 pm

LKL wrote:
?
Nuclear reactions are chemical. It involves protons and neutrons rather than electron bonding, but it's still chemical.


WRONG. Chemical reactions involve the electromagnetic force exclusively. Nuclear reactions involve the electromagnetic force AND the strong + weak nuclear forces.



monty
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19 Sep 2008, 3:12 pm

LKL wrote:
There is actually some debate over whether viruses are alive or not, since they cannot reproduce their own DNA without a host. Sometimes they are described as 'molecular machines.'


True, but the fact that they rely on other organisms for vital functions is not a good way to distinguish. Humans cannot photosynthesize - we rely on plant hosts, or on animals that eat plants hosts for our basic energy flow.



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19 Sep 2008, 3:13 pm

This is an idea that might also be considered..

The Gaia hypothesis .

----

"Two decades ago, a British scientist named James Lovelock put forth an imaginative and poetic view of how the Earth functions. The planet's living organisms, he said, act together to regulate the global environment: Life interacts chemically and physically with the air, the waters and the rocks to maintain optimum conditions for itself.

In fact, Dr. Lovelock said, the Earth itself appears to behave like a living organism. He named the organism Gaia (pronounced GUY-uh), after the Earth goddess of the Greeks. The Gaia hypothesis beguiled environmentalists and others inspired by the unitary view of Earth from space as a ''dappled sapphire,'' in Dr. Lovelock's phrase. The concept acquired mystical overtones, and not least for that reason it was shunned by other scientists, some of whom ridiculed it as a fairy tale.

But times change and theories with them. And today, as the prospect of global climactic change infuses the ecological sciences with new urgency, the Gaia hypothesis, whether true or false, appears to have significant influence on the way some scientists study the Earth and the questions they ask about it. For these scientists, it has provided an organizing focus for research as they step up their efforts to learn more about how the enormously complex global environment functions, what maintains it and what disrupts it. And it has stimulated a spirited debate over the role of life in governing the Earth's climate."

http://query.nytimes.com/gst/fullpage.h ... A96F948260

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chever
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19 Sep 2008, 3:14 pm

Lovelock has repeatedly said that he never intended that Earth is actually a single organism


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Haliphron
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19 Sep 2008, 3:18 pm

Accelerator wrote:
This is an idea that might also be considered..

The Gaia hypothesis .

----

"Two decades ago, a British scientist named James Lovelock put forth an imaginative and poetic view of how the Earth functions. The planet's living organisms, he said, act together to regulate the global environment: Life interacts chemically and physically with the air, the waters and the rocks to maintain optimum conditions for itself.

In fact, Dr. Lovelock said, the Earth itself appears to behave like a living organism. He named the organism Gaia (pronounced GUY-uh), after the Earth goddess of the Greeks. The Gaia hypothesis beguiled environmentalists and others inspired by the unitary view of Earth from space as a ''dappled sapphire,'' in Dr. Lovelock's phrase. The concept acquired mystical overtones, and not least for that reason it was shunned by other scientists, some of whom ridiculed it as a fairy tale.

But times change and theories with them. And today, as the prospect of global climactic change infuses the ecological sciences with new urgency, the Gaia hypothesis, whether true or false, appears to have significant influence on the way some scientists study the Earth and the questions they ask about it. For these scientists, it has provided an organizing focus for research as they step up their efforts to learn more about how the enormously complex global environment functions, what maintains it and what disrupts it. And it has stimulated a spirited debate over the role of life in governing the Earth's climate."

http://query.nytimes.com/gst/fullpage.h ... A96F948260

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Im very suprised that there have been no attempts to classify stars as primitive living organisms. Even if they arent *alive* they're formation and destruction, and the fact that new stars form from the embers of old ones, does indeed resemble life.