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starcanuck64
2013-May-11, 06:10 PM
So what are they?

The way I look on life is it's information contained in a durable form(in the case of Earth organic molecules) that is able to be transmitted and to a certain degree modified.

And its the flow of energy through a system that allows this "life" to exist. So the basic limits on life to me would seem to be an energy gradient and a durable method of storing and transmitting information that can gain complexity over the passage of time.

Hlafordlaes
2013-May-11, 10:27 PM
Given the mood re LiS excesses these days, not gonna engage much in the thread. But you might be interested in the second video on this page (http://www.preposterousuniverse.com/naturalism2012/video.html).

I've forgotten the gentleman's name who is doing most of the speaking, and I find his voice and delivery irritating, but he actually brings up some good points I think you may enjoy.

What's freaking me about the linked discussion is that I followed it! I even knew when a question was "off." Yippee, the CQ forum may actually have increased my science IQ by 0.01 points, a whopping 100% increase!

starcanuck64
2013-May-11, 10:36 PM
Thanks Hlafordlaes,

My intent wasn't to get into another discussion on whether or not alien life existed or how likely there was intelligent life out there, but to try and get some idea of kind of environments we could be looking at locally and through remote sensor like telescopes that may support life.

Basically I'm interested in a limited discussion on the kind of environments that can allow the transmission of information that can make life possible.

Hlafordlaes
2013-May-11, 10:46 PM
Me, too. If you have any thoughts about the vid, pls PM or maybe discuss them here. Let's put on our Sunday best if we do.

starcanuck64
2013-May-11, 10:53 PM
Sounds good, and if anyone has a good book to recommend on the subject please let me know, I tend to take information in better when I can sit down with a hardcopy over a long period of time.

One book I've found and will have to reread is Into the Cool about the role the 2nd law of Thermodynamics plays in regards to life.

Colin Robinson
2013-May-11, 11:05 PM
So what are they?

The way I look on life is it's information contained in a durable form(in the case of Earth organic molecules) that is able to be transmitted and to a certain degree modified.

And its the flow of energy through a system that allows this "life" to exist. So the basic limits on life to me would seem to be an energy gradient and a durable method of storing and transmitting information that can gain complexity over the passage of time.

I think presence of an energy gradient is the one thing all scientists agree is a necessary condition for life.

What are other necessary conditions for life are there? If life is defined in a broad, functional way (rather than in terms of the composition of known life forms) then is conceivable that it could exist in a big range of environments inhospitable to us.

Back in 1980, physicist Gerald Feinberg and biochemist Robert Shapiro wrote a book with the title Life Beyond Earth, which discusses conceivable environments for exotic forms of life that might (for instance) be based on plasma physics rather than chemistry.

iquestor
2013-May-11, 11:23 PM
I think presence of an energy gradient is the one thing all scientists agree is a necessary condition for life.

What are other necessary conditions for life are there? If life is defined in a broad, functional way (rather than in terms of the composition of known life forms) then is conceivable that it could exist in a big range of environments inhospitable to us.

Back in 1980, physicist Gerald Feinberg and biochemist Robert Shapiro wrote a book with the title Life Beyond Earth, which discusses conceivable environments for exotic forms of life that might (for instance) be based on plasma physics rather than chemistry.

A really good book with an approach from the other direction is "Life As We Do Not Know It", By P Ward of Rare Earth fame, which deals with how other forms of life could evolved, not based no carbon. Its relevant here because, in order to explore how other forms of life could evolve, you must first define and put limits on it.

Hlafordlaes
2013-May-11, 11:49 PM
I think that for both the idea of information processing as a definition or condition for life, and for what abiotic, pre-life may also process, that guy I mentioned is interesting.

There is a point in his exposé (which I shall need to review) in which iirc he begins to build the idea of the reflection of the environment on an abiotic system as an imprint of information, but also implies this may much later provide an explanation for reference. This is a tangent I think I'll explore off thread for a while, as it solves a conundrum in consciousness, or may. So I'll bow out here. May take me a while though, before I can make myself sit through it again.

In the meantime, you gents may find this (http://www.rdmag.com/news/2013/04/power-behind-primordial-soup-discovered) of interest. I posted it before in another thread but that was when it had already mostly died out. I'm trying to collect links like this, as I only care for the science more and more. At most, I will confess optimism that we will crack the abiogenesis case one day. After that, there will be science to guide speculation.

eburacum45
2013-May-12, 08:23 AM
I've posted this link many times before, but this on-line book seems to address many of starcanuck64's points;
The limits of Organic Life in Planetary Systems (http://www.nap.edu/openbook.php?record_id=11919&page=1)

although I'm quite sure there is much more to be said.

eburacum45
2013-May-12, 08:31 AM
For instance, I can imagine non-organic, artificial life that has been created by extraterrestrial civilisations in the past; these forms of life might be robotic, or even entirely virtual, like a game of Spore. These forms of artificial life might be the most common and/or the most widespread forms of life-like process in the galaxy, or in the universe. When and if we find, meet or make contact with any extraterrestrial entity that displays some or most of the characteristics of life, we should be aware of the possibility that it could be partially or entirely artificial in nature.

Colin Robinson
2013-May-12, 09:43 AM
I've posted this link many times before, but this on-line book seems to address many of starcanuck64's points;
The limits of Organic Life in Planetary Systems (http://www.nap.edu/openbook.php?record_id=11919&page=1)

although I'm quite sure there is much more to be said.

I've posted links to that book before too, but it does begin by defining life as a chemical system, which is a more restricted definition than the one given by the OP of this thread.

Selfsim
2013-May-12, 10:50 AM
For instance, I can imagine non-organic, artificial life that has been created by extraterrestrial civilisations in the past; these forms of life might be robotic, or even entirely virtual, like a game of Spore. These forms of artificial life might be the most common and/or the most widespread forms of life-like process in the galaxy, or in the universe. When and if we find, meet or make contact with any extraterrestrial entity that displays some or most of the characteristics of life, we should be aware of the possibility that it could be partially or entirely artificial in nature.Wouldn't we become aware of that, once we meet or make contact with it? :confused:
How does being aware of what you've "imagined", constrain our knowledge of the kinds of environments that can make life possible? :confused:

ASTRO BOY
2013-May-12, 10:59 AM
A really good book with an approach from the other direction is "Life As We Do Not Know It", By P Ward of Rare Earth fame, which deals with how other forms of life could evolved, not based no carbon. Its relevant here because, in order to explore how other forms of life could evolve, you must first define and put limits on it.



I would imagine in a Universe of near infinite content and extent, if not infinite, "life as we don't know it" would be a possibility.

Selfsim
2013-May-12, 11:11 AM
I would imagine in a Universe of near infinite content and extent, if not infinite, "life as we don't know it" would be a possibility.Same question: "How does being aware of what you've "imagined", constrain our knowledge of the kinds of environments that can make 'life as we don't know it' a possibility?

eburacum45
2013-May-12, 01:16 PM
Wouldn't we become aware of that, once we meet or make contact with it?
Only if we recognise it. If we are contrained to looking for life-like processes in Earth-like environments, we could miss life-like processes which do not occupy those locations.

How does being aware of what you've "imagined", constrain our knowledge of the kinds of environments that can make life possible? The environments that make the origin of life possible are a separate concept to the locations where artificial life-like processes might occur. Where do you suppose that artificial life-like processes might most likely be found?

iquestor
2013-May-12, 05:53 PM
Same question: "How does being aware of what you've "imagined", constrain our knowledge of the kinds of environments that can make 'life as we don't know it' a possibility?

The context of the book I mentioned first outlined the Author's ideas about what life processes are required in order for cellular metabolism and makes some basic assumptions about LAWDNKI , namely that there would be enough commonality so that we would recognize it as life. The these ideas are applied to other bases, namely silicon and arsenic. He does a good jab at keeing his "imagined" life constrained to physical processes and known limits of cellular metabolisms on the chemical level.


For instance, I can imagine non-organic, artificial life that has been created by extraterrestrial civilisations in the past; these forms of life might be robotic, or even entirely virtual, like a game of Spore. These forms of artificial life might be the most common and/or the most widespread forms of life-like process in the galaxy, or in the universe. When and if we find, meet or make contact with any extraterrestrial entity that displays some or most of the characteristics of life, we should be aware of the possibility that it could be partially or entirely artificial in nature.

Artificial Intelligence I buy; its one of my favorite answers to Fermi ("Organic intelligences who survive evolve into machine intelligences, which don't have any interst in contacting us"); I'm not sure simulated life applies, Ill have to think on that.

We need a good definition for life, and we won't arrive at a satisfactory definition (IMHO) until we have a few more examples.

starcanuck64
2013-May-13, 07:45 PM
If possible it would be nice to stick to the physical basis of life and what that may mean for environments where it may occur.

As the OP says, I'm trying to get as clear an idea I can of what life is from a thermodynamic and information perspective.

If we can't agree what life is, then it's difficult to discuss where it may occur and what form it may take.

Thanks for the articles and links so far, I'm also reading Into the Cool again about the thermodynamic basis for life.

ASTRO BOY
2013-May-13, 09:27 PM
This may help......

It,s a book called "The Limits of Organic Life in Planetary Systems"
The first link is to the "conclusions and recommendations" reached section.....

http://www.nap.edu/openbook.php?record_id=11919&page=84

The whole book at.....

http://books.nap.edu/catalog.php?record_id=11919

ASTRO BOY
2013-May-13, 09:50 PM
Again in a Universe that is probably infinite in extent the question about the limits of Organic life could well be coupled with a question about the limits of evolution.
Could we evolve to the extent that we would be unrecognisable from our present human biology?

I'm sure I remember Stephen Hawking answering that in the affirmative.

starcanuck64
2013-May-13, 10:28 PM
That's interesting but it kinds of takes the discussion into an unlimited area where it's mostly speculation.

As much as possible I'd like to look at the physical role of life in terms of information and thermodynamics. An energy gradient is an essential ingredient for life as is a means to store durable information and modify it over time, under this definition life doesn't have to be organic in nature.

I need to do a lot more reading before I can even ask intelligent questions.

TooMany
2013-May-13, 10:54 PM
Only if we recognise it. If we are contrained to looking for life-like processes in Earth-like environments, we could miss life-like processes which do not occupy those locations.
The environments that make the origin of life possible are a separate concept to the locations where artificial life-like processes might occur. Where do you suppose that artificial life-like processes might most likely be found?

That's an interesting point. It's possible that the transition from an advanced biological civilization (with technologies like radio and television) to an artificial-life civilization occurs in the space of just a few centuries. If that is so, then contacting another biological civilization is an extremely remote possibility. It's a little off-point, but an interesting thought.

Back on subject, organic chemistry provides a fine opportunity for the development of structures that may lead to abiogenesis. There have to be building blocks for life. It has been suggested that there might be similar chemistries involving silicon (in place of carbon) that might emerge on very hot planets. I'm not sure how much backup there is for such a possibility.

Another likely requirement for the emergence of life is a medium in which the building blocks can interact. In other words there should be a solvent for lifes building blocks. Ours is water which has a fairly narrow range of temperatures in which it is liquid. Ammonia has been suggested as a solvent which has a wider but lower range of temperatures. Ammonia might support organic chemistry.

Then there is Titan where organic molecules are formed and may exist in a liquid methane solvent at very low temperatures.

Anyone know if there is a solvent for silicon-based complex molecules?

If life can only emerge from organic chemistry and water is the only plentiful and suitable solvent, then we know what the limitations are and good places to look for it.

Conditions for life evolved into artificial intelligence is anybody's guess.

Selfsim
2013-May-14, 12:13 AM
Another likely requirement for the emergence of life is a medium in which the building blocks can interact. In other words there should be a solvent for lifes building blocks. Ours is water which has a fairly narrow range of temperatures in which it is liquid. Ammonia has been suggested as a solvent which has a wider but lower range of temperatures. Ammonia might support organic chemistry.

Then there is Titan where organic molecules are formed and may exist in a liquid methane solvent at very low temperatures.Titan's liquid (m)ethane is non-polar, and is hence a poor solvent. The idea that Earth-like 'methanogens' could exist there, because of the abundance of liquid (m)ethane on Titan, assumes that Titan's so-called 'methanogens', have somehow overcome the clear limitations of an environment dominated by non-polar solvents.

The usual analogy drawn for Titan, from the functionality of Earth's (water) based methanogens, just doesn't add up, because we know that so far, no liquid water exists on the surface of Titan (Huygens etc data) ... so how could a 'methanogen', which is defined by fundamentally exploiting solubility, (courtesy of liquid water), as its a molecular/atomic transport and diffusion mechanism, possibly turn up on Titan?

I cannot see how the abstracted functionality of Earth's 'methanogens' is applicable in an environment dominated by non-polar solvents.

Nonetheless, the 'takeaway' here, is that solubility is a necessary chemical function for our defined version of life to exist. Therefore, liquid polar solvents would be a target 'of interest'.

Colin Robinson
2013-May-14, 02:06 AM
Titan's liquid (m)ethane is non-polar, and is hence a poor solvent.

Non polar solvents are weaker, but also gentler — less inclined to break stuff up chemically.


The idea that Earth-like 'methanogens' could exist there, because of the abundance of liquid (m)ethane on Titan, assumes that Titan's so-called 'methanogens', have somehow overcome the clear limitations of an environment dominated by non-polar solvents.

The usual analogy drawn for Titan, from the functionality of Earth's (water) based methanogens, just doesn't add up, because we know that so far, no liquid water exists on the surface of Titan (Huygens etc data) ... so how could a 'methanogen', which is defined by fundamentally exploiting solubility, (courtesy of liquid water), as its a molecular/atomic transport and diffusion mechanism, possibly turn up on Titan?

I cannot see how the abstracted functionality of Earth's 'methanogens' is applicable in an environment dominated by non-polar solvents.

Nonetheless, the 'takeaway' here, is that solubility is a necessary chemical function for our defined version of life to exist. Therefore, liquid polar solvents would be a target 'of interest'.

You mean like the sulphuric acid droplets in the clouds of Venus? There we have a substance that's significantly more polar than water is.

Selfsim
2013-May-14, 02:51 AM
One of the lesser known properties of water is the formation of boundaries caused by charge separation in the presence of hydrophyllic and hydrophobic surfaces. Once water is excited by incident radiation, the effect becomes more exacerbated and allows for more complex chemical reactions. Ordering of water molecules has also been observed in high resolution X-Ray crystallographic electron density maps around protein molecules. Some years ago, it was thought that this effect only extended for a few layers. This was found to be incorrect, with further testing:

Water, Energy and Life: Fresh Views From the Water's Edge. (http://www.youtube.com/watch?v=XVBEwn6iWOo&feature=player_embedded)

The point here is that water's influence on the development of life on this planet, may reach far deeper into sub molecular physics, than we'd normally envisage.

This does not necessarily re-inforce the idea that 'where there's water, there's life', but certainly where life (as we know it) is emerging, the role played by water's intrinsic physics, might well be essential.

ASTRO BOY
2013-May-14, 10:58 AM
We need a good definition for life, and we won't arrive at a satisfactory definition (IMHO) until we have a few more examples.

Sure to be some form out their somewhere sometime...even if we confine ourselves to the observable Universe of about 96 billion L/years in diameter.

Paul Wally
2013-May-14, 06:44 PM
We can define life as anything capable of self-replication and evolution. I think it's a good axiomatic starting point. One could then proceed further
to consider a few rules; let's call them laws of physics. The next step is then to ask whether these rules, whatever they may be, allows for the emergence of life as defined above and if so what the possible mechanisms of such a realization would be. In more particular cases one could consider, the laws of this universe like entropy, gravity, chemical reactions etc. and see how they should play out for a number of different particular conditions.

Consider Titan for example. The problem with Titan is that we need more information about the surface chemistry, especially that of the several lakes on the surface. With sufficient information it should be possible work out whether the emergence and/or existence of life, as defined above, is possible on Titan. With such a determination it should then be possible to design instruments to look for such life on Titan.

iquestor
2013-May-14, 06:49 PM
We can define life as anything capable of self-replication and evolution. I think it's a good axiomatic starting point. One could then proceed further
to consider a few rules; let's call them laws of physics. The next step is then to ask whether these rules, whatever they may be, allows for the emergence of life as defined above and if so what the possible mechanisms of such a realization would be. In more particular cases one could consider, the laws of this universe like entropy, gravity, chemical reactions etc. and see how they should play out for a number of different particular conditions.

Consider Titan for example. The problem with Titan is that we need more information about the surface chemistry, especially that of the several lakes on the surface. With sufficient information it should be possible work out whether the emergence and/or existence of life, as defined above, is possible on Titan. With such a determination it should then be possible to design instruments to look for such life on Titan.

You might enjoy Ward's book Life as we do not know it, if you havent already read it. Titan and Europa, to him, should be our first priority to look for life.