What exactly constitutes life?

[ronthepon]

Well... life is really a mystery.

 

If we make a robot able to drink petrol for itself, make robots like itself just for the fun of it, then teach it to add components on to itself just to have it grow, we can't call it alive!

 

Or... can we...?

[hallenrm]

Like what? I can't think of anything that does not reproduce. :P

 

A mule!!!!:beer:

[questor]

this question has been discussed in other threads on Hypography. the question is: at what particulate level does life exist? is it at the molecular level or lower?

an atom does not have life, carbon is an element, but when combined with other atoms in certain patterns, it can exhibit life, and is necessary for life. is life strictly a chemical interchange? if so, exactly where does the life force start? no one knows.

[HydrogenBond]

Some characteristics of life:

-Has cells

-Converts energy

-Grows

-Reproduces

 

I remember years ago, studying early evolution when prelife became life; This transition is assumed connected to the evolution of simple DNA or RNA replicators, before full cells formed. Someone made an interesting comment. He said that fire fits all the definitions of the DNA replicator definition of life; coverts energy, grows and reproduces.

 

Since life and death are opposites, the definition of one should be the opposite of the other. When is something considered dead? For a human, it is not when biology stops but when the heart stops beating and the brain shows no brain waves. The hair and fingernails will continue to grow even after death. As such, a human life begins when the heart starts beating and the brain waves begin. It is not based on biochemistry alone or else burying dead people with their hair and nails still growing should be considered burying them alive.

[Mercedes Benzene]

A mule!!!!

 

Hahaha. Touche!:eek_big:

I suppose a Liger would also fall under that category... :)

[ronthepon]

Maybe we could temporarily forget reproduction. MULES don't reproduce!!

 

So I guess the active cell theory could hold water.

Here are the points:

The cells must:

 

- Perform nutrition

- Perform catabolism and anabolism reactions including respiration, as normal life processes.

 

Lets also remember about comatose people as alive also.

[GreekTTC]

I'll throw this into the mix. I don't agree with his first assertion, but it's an interesting quote nonetheless.

 

"I think computer viruses should count as life. I think it says something about human nature that the only form of life we have created so far is purely destructive. We've created life in our own image."

-Stephen Hawking

[hallenrm]

Maybe we could temporarily forget reproduction. MULES don't reproduce!!

 

So I guess the active cell theory could hold water.

Here are the points:

The cells must:

 

- Perform nutrition

- Perform catabolism and anabolism reactions including respiration, as normal life processes.

 

Lets also remember about comatose people as alive also.

 

But would you like to limit the concept of life to biological cells found on Earth alone?

 

Couldn't some forms of life be there yhat are not neccesarily based on catabolism and metabolism?:ebluehair

[questor]

if we are to understand life, we must first understand at which particulate level life exists. most of the posts are discussing macro events, but life is a

micro event. cells can be seen and their enzymatic activity determined. life is belowthis level. it is probably electro-chemical, but no one has yet found

exactly where and what it is.

[ronthepon]

But would you like to limit the concept of life to biological cells found on Earth alone?

 

Couldn't some forms of life be there yhat are not neccesarily based on catabolism and metabolism?:doh:

They might not be the life we define for ourselves.

 

An alien might come to earth and call a moving robo a lifeform. Just as we may do.

 

To take other such lifeforms we shall have to expand our concept.

[someguy]

if we are to understand life, we must first understand at which particulate level life exists. most of the posts are discussing macro events, but life is a

micro event. cells can be seen and their enzymatic activity determined. life is belowthis level. it is probably electro-chemical, but no one has yet found

exactly where and what it is.

This is excellent and to the point of my question. How much do we know / speculate about this?

[CraigD]

if we are to understand life, we must first understand at which particulate level life exists.

An excellent observation. Defining the scale at which life can be said to exist, or, to use a more nouveaux term emerge, is important.

most of the posts are discussing macro events,

If, by “macro” we mean something on the order of 10^-8 meters (about 100 atoms), I think most posts focus on this scale, because there’s a consensus that this is the scale at which life emerges. Most of the posts tend toward a definition of life as “having metabolism”, and any smaller than this, there’s just not enough space for the structure of even such questionably “alive” biological machines as viruses. The smallest things nearly everybody would agree is alive has a diameter of about 2*10^-7 m, while most plant and animal cells are about 10^-5 m. DNA is about 2*10^-9 m wide.

but life is a

micro event. cells can be seen and their enzymatic activity determined. life is below this level. it is probably electro-chemical, but no one has yet found exactly where and what it is.

I disagree. Though electrochemical processes, which can be considered to occur down to the atomic crystal scale of about 10^-10 m, can be very complex and energetic, they seem lacking in the structure and information necessary to be considered even vaguely alive.

 

There’s a tradition of scientific speculation that life is a “ghost”, or a “spark” – perhaps simply an electrical one. The 1818 novel “Frankenstein”, and the current “Ghost in the Shell” anime television series, are examples of fictional exploration of these traditions, while the work or Roger Penrose . I think, however, that these traditions, while interesting, are reaching incorrect conclusions, and are, ultimately, pseudoscientific.

 

I’d argue that life is defined more by information density and complexity than by the particular biological specifics. Consider this question: which is more alive – a dish of amino acids, enzyme and heat fractured beyond any potential for cell formation or metabolism, or a computer simulation of a biological cell?

 

Currently, the smallest features of non-biological information systems are about 10^-7 m wide, 100 times larger than those of biological ones. Current computer technology is likely to shrink another 100-fold, approaching the scale of biology. Far-off computer technology involving such exotic materials as degenerate “neutronium” might vastly surpass this scale of miniaturization to something as small as 10^-14, 100,000 times smaller than biology. Such a computer could not only perform information processing equivalent to a complex biological organism, but be physically much smaller. Current, near-future, and far-future, exotic non-biological information technology is likely, I believe, to soon force a radical reevaluation of what it is to say a system is “alive”.

[hallenrm]

They might not be the life we define for ourselves.

 

An alien might come to earth and call a moving robo a lifeform. Just as we may do.

 

To take other such lifeforms we shall have to expand our concept.

To me the essential trait of any living organism is its capacity to diversify over a period of time!

 

The capacity to evolve indeed appears to be a characteristic of all life forms, including mules and ligers!!

 

If we accept this, then even any atom/molecule can be envisioned to be alive (there are a multitude of energy states, and other configurations possible for any atom/molecule !!

 

How's that?

[CHADS]

I think all biological life Reproduces or has the means for reproduction ... but although a sentient robot can reproduce by building others like its self ... it cannot reproduce biologically so isnt a biological life form but is a being within its sentience .....

[HydrogenBond]

Fire can reproduce itself. It can send out baby embers who can grow into a fire that can send out embers, etc.. It can also reproduce with radiant heat, i.e., it can reproduce without matter transfer. It is like immaculant conception. It is an omivorse that can metabolize carbon, nitrogen, almost anything with energy content. It does not have cells, in the biological sense, but can cook them so they taste better.

 

The elemental basis of life is the hydrogen proton. The hydrogen proton is necessary for the properties of water and the replicating properties of the DNA. Life would not be able to reproduce without the hydrogen proton and hydrogen bonding.

[ronthepon]

Interesting bit, about the fire, HydrogenBond, but I'd rather point towards carbon for the basis of life.

 

Hallenrm, by diversify I believe you mean evolve. I guess that will have to be applied as one of the properties of life.

 

Here is another possibly defining concept:

A form who has all it's information stored genetically i.e. in DNA or RNA.

 

Forget that which is in the brain. Thats kinda.... different information...

[HydrogenBond]

Carbon is extremely important. But its primary function is to form molecular polymers like DNA, RNA and proteins. But once they form, the dynamics of life involve the pertubations of hydrogen bonds. Both C and H have important functions with carbon defining the molecular capacitance of life molecules, such as the memory along the DNA. While hydrogen defines the backbone of the low energy dynamics by which life molecules pack, unpack, interact and react to create life.

 

Carbon follows normal chemistry by becoming the backbone for electrons. While hydrogen bonding hydrogen are sort of an another proton layer on top of the electron clouds create by carbon. This is what gives life, life. When the DNA is duplicated, the chemical reactions begin with hydrogen bonding (base pairing). This becomes the foundation for polymerization into more DNA. The new DNA create more chemical matrix for hydrogen bonding hydrogen. Life is creating hydrogen bonding potential, which reflects hydrogen bonding proton potential moving to ever increasing potential. This is the evolutionary path of life.