Where does life come from?

  • #51
2,257
7
you are asking 'what is the meaning of life'.
no doubt there is some religious motive here as well.

thats as philosophical as it gets
I just do physics

the question you should be asking yourself is 'am i even asking the right question'.
 
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  • #52
Siv
Gold Member
84
5
How are you defining "self aware"? Does it just mean the system responds to stimuli in an extremely compicated fashion? Because otherwise I don't even know how you expect to prove that other humans are self-aware, let alone a machine. I'm not saying solipsism is a tenable philosophical position, but it's outside the realm of science to address the question as far as I can see.
Sentience is a very controversial topic, isn't it ?

There's no way we can prove that someone does or does not have sentience. You cant prove that computers or mobile phones dont have sentience. Many scientists and philosophers feel that its very much a material thing, no need to invoke any magic to explain it. Just a property of a certain degree of complexity.

Its true that sentience is far from being an easy thing to define or measure, so using it as a parameter to differentiate living from non-living is really a no-go.
 
  • #53
Siv
Gold Member
84
5
Perhaps "complicated" could be replaced by something more accurate and meaningful. I want a condition that captures the fact that life seems to have an ulterior motive.

Although it feeds on an energy gradient, it's purpose is not simply to deplete that energy gradient.

Life *wants*, in some sense, its own processes to occur, in the same way that dried wood in the hot sun *wants* to burn, or how water *wants* to form a crystal when it gets cold. The formation of crystals and the combustion of flammable materials is tied directly with the basic chemical and physical properties of the materials involved. Any statement about the crystals "wanting to form" can be translated readily into a statement about water molecules having certain properties.

When one asks, however, "why does a cell seem to want to reproduce?", or "why does a cell seem to want to make these proteins?", the answer could not possibly boil down to a statement about the properties of a few common molecules. Any answer would involve not only an uncommon collection of molecules, but also the structure of the cell, many strange interactions working symbiotically, and many facts about its ancestors.

When one asks, for example, "why does this cell seem to want to reproduce?", you can't really understand it by only looking at that cell. I mean, reproduction is expensive energy-wise. The best answer I can think of is that statistically speaking, you are much more likely to come across a cell that wants to reproduce than one which does not: almost all cells in existence were created by other cells which must have had the ability to reproduce.

I feel as though a definition of life ought to capture that aspect of complexity, while ruling out static results of life, such as art, music, etc.
The problem arises because you want to create an artificial and concrete line between living and non-living when non exists.

Although religious folks would like there to be some magical god-given property to life, life simply is a label we give to a certain level of organized complexity.

A cell no more wants to replicate than wood wants to burn. It really does not help at all to project human wishes and desires onto everything.
The elegance of evolution by random mutations and natural selection is precisely the fact that a "non-intelligent" process can give rise to so much organized complexity and beauty. Organisms which survive and replicate more effectively than other organisms do better simply because, by default, more of them remain after a period of time. See the simple elegance of that theory ? Darwin really was a genius.
 
  • #54
2,257
7
some questions like 'have you stopped beating your wife' are best left unanswered.
the only possible answer is that its the wrong question to ask.

I strongly advise you (and anyone else) to leave the whole thing alone till you clearly understand the issues involved.
And it is perfectly clear to me, just from the fact that you are asking the question in the first place, that you dont understand the issues.

Like I said, the question you should be asking yourself is 'am I asking the right question'.

the philosophy forum:
https://www.physicsforums.com/forumdisplay.php?f=112

meaning of life:
https://www.physicsforums.com/showthread.php?t=435874&page=2

consciousness:
https://www.physicsforums.com/showthread.php?t=423084
 
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  • #55
Siv
Gold Member
84
5
Well, "Where does life come from?" really is not such a bad question. But its rarely ever asked innocently, is it ? Esp on forums like these :wink:
 
  • #56
292
1
some questions like 'have you stopped beating your wife' are best left unanswered.
the only possible answer is that its the wrong question to ask.
Ummm...what? :uhh:
 
  • #57
bobze
Science Advisor
Gold Member
647
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The problem arises because you want to create an artificial and concrete line between living and non-living when non exists.

Although religious folks would like there to be some magical god-given property to life, life simply is a label we give to a certain level of organized complexity.

A cell no more wants to replicate than wood wants to burn. It really does not help at all to project human wishes and desires onto everything.
The elegance of evolution by random mutations and natural selection is precisely the fact that a "non-intelligent" process can give rise to so much organized complexity and beauty. Organisms which survive and replicate more effectively than other organisms do better simply because, by default, more of them remain after a period of time. See the simple elegance of that theory ? Darwin really was a genius.
Good post :wink:
 
  • #58
Siv
Gold Member
84
5
  • #59
2,257
7
Ummm...what? :uhh:
you havent been following the thread have you.

I was responding to post 50
Don't be like that. You made a claim about the nature of life, which I didn't think accurately represented it. I offered an alternative definition.

Perhaps "complicated" could be replaced by something more accurate and meaningful. I want a condition that captures the fact that life seems to have an ulterior motive.

Although it feeds on an energy gradient, it's purpose is not simply to deplete that energy gradient.

Life *wants*, in some sense, its own processes to occur, in the same way that dried wood in the hot sun *wants* to burn, or how water *wants* to form a crystal when it gets cold. The formation of crystals and the combustion of flammable materials is tied directly with the basic chemical and physical properties of the materials involved. Any statement about the crystals "wanting to form" can be translated readily into a statement about water molecules having certain properties.

When one asks, however, "why does a cell seem to want to reproduce?", or "why does a cell seem to want to make these proteins?", the answer could not possibly boil down to a statement about the properties of a few common molecules. Any answer would involve not only an uncommon collection of molecules, but also the structure of the cell, many strange interactions working symbiotically, and many facts about its ancestors.

When one asks, for example, "why does this cell seem to want to reproduce?", you can't really understand it by only looking at that cell. I mean, reproduction is expensive energy-wise. The best answer I can think of is that statistically speaking, you are much more likely to come across a cell that wants to reproduce than one which does not: almost all cells in existence were created by other cells which must have had the ability to reproduce.

I feel as though a definition of life ought to capture that aspect of complexity, while ruling out static results of life, such as art, music, etc.

Then again, the concept of "memes" as ideas with a life of their own may be an important concept for higher life. After all, what makes someone human has a lot to do with what they learn. Intellectual thought seems like a self-perpetuating end in itself. Perhaps consciousness is a form of life itself...
the question he is asking isnt 'where does life come from' but 'what is the meaning of life' and is clearly religious in nature.

hence my response:

some questions like 'have you stopped beating your wife' are best left unanswered.
the only possible answer is that its the wrong question to ask.

I strongly advise you (and anyone else) to leave the whole thing alone till you clearly understand the issues involved.
And it is perfectly clear to me, just from the fact that you are asking the question in the first place, that you dont understand the issues.

Like I said, the question you should be asking yourself is 'am I asking the right question'.

the philosophy forum:
https://www.physicsforums.com/forumdisplay.php?f=112

meaning of life:
https://www.physicsforums.com/showthread.php?t=435874&page=2

consciousness:
https://www.physicsforums.com/showthread.php?t=423084
http://en.wikipedia.org/wiki/Loaded_question
A loaded question is a question which contains a controversial assumption such as a presumption of guilt.[1]
Such questions are used rhetorically, so that the question limits direct replies to be those that serve the questioner's agenda.[2] The traditional example is the question "Have you stopped beating your wife?"
 
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  • #60
As for me, I think I can describe life as an organized set of chemical reactions whose sole purpose is to make sure that these reactions continue to exist.
 
  • #61
Ivan Seeking
Staff Emeritus
Science Advisor
Gold Member
7,260
301
There is no doubt that whatever happens in the cell is just a chemistry, but we are still far from knowing all details.
[PLAIN]http://star.psy.ohio-state.edu/coglab/Pictures/miracle.gif [Broken]
http://star.psy.ohio-state.edu/coglab/Miracle.html [Broken]
 
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  • #62
292
1
you havent been following the thread have you.
Sure I have, just seemed like you were suggesting that if someone's beating their wife, you should look the other way.
I guess maybe I misinterpreted it. I was assuming that it was a known fact that the person beat their wife in the past.
 
  • #63
2,257
7
you've never heard that joke before?
groucho marx is famous for it.
you have heard of groucho marx havent you?

http://en.wikipedia.org/wiki/Loaded_question
A loaded question is a question which contains a controversial assumption such as a presumption of guilt.[1]
Such questions are used rhetorically, so that the question limits direct replies to be those that serve the questioner's agenda.[2] The traditional example is the question "Have you stopped beating your wife?"
 
  • #64
Borek
Mentor
28,600
3,079
No, that's classic example of the question that if you decide to answer (especially in terms of Yes/No), you always put yourself in the bad light.
 
  • #65
199
0
As for me, I think I can describe life as an organized set of chemical reactions whose sole purpose is to make sure that these reactions continue to exist.
What instrument measures purpose, in what units is purpose/intent expressed, and what do you use to calibrate the instrument?

Life, then, covers rocks weathering, stars aging, atoms interacting, and most anything then. Isn't that definition too broad? If you were to send an unmanned probe to Mars, what sort of sensor, what instrument, what detector would test best for life and, most important, what indication would it give for the absence of life. How do we test for past life especially in the case of Mars?
 
  • #66
2,257
7
organic life doesnt have a purpose in that sense but it does have a function that it is optimized for.

(its a local optimum not a global optimum)
 
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  • #67
Siv
Gold Member
84
5
What instrument measures purpose, in what units is purpose/intent expressed, and what do you use to calibrate the instrument?
If we draw a line at a certain level of organized complexity that involves replication, and call all those things to the right of that line as "alive" and all the things to the left as "not alive", then thats easy. Use that very line to "measure" life.
 
  • #68
199
0
If we draw a line at a certain level of organized complexity that involves replication, and call all those things to the right of that line as "alive" and all the things to the left as "not alive", then thats easy. Use that very line to "measure" life.
So my Mars probe has to look for a line and find things on the right side of the line. Probably better things to look for. http://en.wikipedia.org/wiki/Life_on_Mars#Viking_experiments". One showed an increase in CO2 from Martian soil being exposed to water and nutrients. The designer of this experiment, called the Labeled Release experiment, said this indicated life. Maybe, but other scientists dispute his conclusion since the CO2 evolved could have resulted from a non-life explanation, that being the presence of super oxidants in the soil.

organic life doesn't have a purpose in that sense but it does have a function that it is optimized for.

(its a local optimum not a global optimum)
How does organic life know of this function and when it has achieved optimization?

To clarify what you mean by organic, do you mean containing the molecules that the Viking experiment did NOT detect with its mass spectrometer and gas chromatograph? Are you referring to general carbon chemistry?

I have to ask this because of the increased ability of the self-replicating programs known as computer viruses, and especially the http://en.wikipedia.org/wiki/Stuxnet" [Broken] that can be said to be optimized for its function of replicating and installing a PLC rootkit in industrial software in order to cause damage to the process under the PLC's control. Can a replicating, evolving computer program be alive?
 
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  • #69
Siv
Gold Member
84
5
So my Mars probe has to look for a line and find things on the right side of the line. Probably better things to look for. http://en.wikipedia.org/wiki/Life_on_Mars#Viking_experiments". One showed an increase in CO2 from Martian soil being exposed to water and nutrients. The designer of this experiment, called the Labeled Release experiment, said this indicated life. Maybe, but other scientists dispute his conclusion since the CO2 evolved could have resulted from a non-life explanation, that being the presence of super oxidants in the soil.
Sure.
My point was that, any search for life should depend on how we define it.

A lot of people assume that something magical appears in an organism if its alive. Which is not true, really.
 
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  • #70
7
0
You have already been given excellent explanations above. bobze explained it very well in post 26. You are hand waving, which doesn't belong in this forum.
No, not for my specific question. I was not hand waving, or if it appears that way it was not my intention.

granpa's post #32 put things into perspective, and #33 answers my question.
Thanks to grandpa for a good explanation.
 

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