What is the anthropic principle and how does it relate to defining life?

[Andy Resnick]

So is dormant life then dead?

It's perfectly reasonable to ask if a seed is alive. I would respond that a seed has the potential to become alive.

 

[Studiot]

I would respond that a seed has the potential to become alive.

I think you already did.

I didn't comment last time but would like to observe that so has a primordial soup of the right kind of chemicals.
All it takes is the chance encounter of the appropriate molecules in that soup.

Don't ask me which ones, if I knew I wouldn't be here.

Cheers.

 

[Max Faust]

chance encounter

If we hypothesise that "life" happened by chance, at least we have something to test. But there seems to be something else going on, perhaps something akin to a natural drive towards complicating systems while at the same way simplifying their interactive qualities.

 

[Sea Cow]

Life needs apparent intention. So, it grows and self-replicates, and it does that which it needs to do in order to grow and self-replicate. Certain actions will lead to its growth and self-replication, others won't, and it will take those actions that do.

The intention is only apparent because natural selection has 'chosen' these behaviours that lead to successful growth and self-replication, but it is nonetheless detectable, and an intentional being (or at least one that thinks of itself as intentional), knowing nothing of the blind forces that caused the development of the life-form, will recognise intention.

This is a question for biology, not physics. Biological processes are not reducible to physics. You will learn nothing of the biological function of a gene or why it was selected by evolution by studying the wave-function of the electrons in its molecules.

 

[Studiot]

If we hypothesise that "life" happened by chance

I cannot discuss how life may or may not have started.

That does not preclude a possibly different initiating mechanism. So if you have a bowl of the primordial soup there is a finite chance that the right molecules will come together, regardless of what happened elsewhere. this chance is even readily defineable using physical chemistry techniques, if you know what the molecules are.

 

[Sea Cow]

It seems perfectly possible and reasonable to me that life started by chance.

You only have to look at how a simple blob of oil can negotiate a maze with a pH gradient to see how apparently intentional behaviours can come about. Obviously, you need to add other ingredients, but it doesn't seem such a problem to me.

What's the alternative? God started it all? That's very silly. 'God' in this context simply means 'that which we do not understand'.

 

[DaveC426913]

It seems perfectly possible and reasonable to me that life started by chance.

What's the alternative?

OK, I was thinking there's only two possible options:
- life started by chance
- life was created by an entity
which means that, if you don't think there's a God, the only possibility is that life happened by chance.


But I just realized there's a third option.

First, let's define "chance" in this context. If life started by "chance" that means that, on one hundred Earths in identical conditions, it is entirely likely life would not develop on any others. It just happened to be so on this one.

That being said, the third option is that life inevitably followed from the conditions that were present. i.e. on one hundred Earths in identical conditions, all of them would develop life.

My money is on this third option.

 

[Andy Resnick]

I think you already did.

I didn't comment last time but would like to observe that so has a primordial soup of the right kind of chemicals.
All it takes is the chance encounter of the appropriate molecules in that soup.

Don't ask me which ones, if I knew I wouldn't be here.

Cheers.

That's perfectly reasonable- at least, that's the attraction of the Miller-Urey experiment.

 

[Andy Resnick]

<snip>

This is a question for biology, not physics. Biological processes are not reducible to physics. You will learn nothing of the biological function of a gene or why it was selected by evolution by studying the wave-function of the electrons in its molecules.

I'm sorry, but this is a terribly limited view of Physics. I refuse to let biologists have all the fun (and grant money).

 

[mgb_phys]

Biological processes are not reducible to physics.

The enlightenment - coming soon to a bio-lab near you ...

 

[Archosaur]

Biological processes are not reducible to physics.

I cannot put into words how strongly I disagree with this. The barrier you perceive between biology and physics, or between any two fields of study, are social constructs, not properties of the universe. Don't departmentalize that which doesn't need to be. Yes, the physics behind a cell is enormously more complicated than a system of pulleys, but can you really argue that that they follow separate rules?

Just as we are debating the level of complexity that warrants the name "life", can you tell me what the simplest form is that falls exclusively under the jurisdiction of biology?

 

[DaveC426913]

Biological processes are not reducible to physics.

I cannot put into words how strongly I disagree with this.

Yeah, I do not understand Sea Cow's stance.

https://www.physicsforums.com/showpost.php?p=2652228&postcount=94" explicitly says SC does not believe.

 

[Max Faust]

the third option is that life inevitably followed from the conditions that were present

I agree. I think it is some kind of simple and yet as of now undiscovered principle which causes as well biological life (under such conditions as will allow this) as other arrangements into complex systems to happen. This is why I think it is a "physics issue" rather than a question which biologists are equipped to handle.

 

[DaveC426913]

I agree. I think it is some kind of simple and yet as of now undiscovered principle which causes as well biological life (under such conditions as will allow this) as other arrangements into complex systems to happen. This is why I think it is a "physics issue" rather than a question which biologists are equipped to handle.

Just one correction: I think what you're looking for is a metaphysics issue.

 

[Sea Cow]

First, let's define "chance" in this context. If life started by "chance" that means that, on one hundred Earths in identical conditions, it is entirely likely life would not develop on any others. It just happened to be so on this one.

That being said, the third option is that life inevitably followed from the conditions that were present. i.e. on one hundred Earths in identical conditions, all of them would develop life.

Well, certainly it raises the question what a probability for something you know has happened might be. Of course, the probability is 1. The question itself is meaningless.

Then you need to define 'identical conditions', and that is where it becomes tricky. We cannot define identical conditions. We can say how many of a billion unstable atoms will decay in a certain time frame, but we can say nothing about when a particular atom will. We can only place bets. That's a 'law' that is not time-reversible.

So either we have incomplete knowledge at present or chance is a feature of the universe. I'm inclined towards incomplete knowledge, but of course if that is right, we can't know it's right until we find out what that incomplete knowledge might be.

The multiverse solves the problem of chance, but it is hardly an economical solution. It is more like an abandoning of the problem – which may, of course, be the wisest thing to do, but I don't like that. You explain how this happened by including it in the set of 'everything that could have happened'. But it's saying the same thing as chance, really – from this point here to that point there, x possible universes can happen and they all do, so the concept of 'chance' is translated into this: given a particular event or set of events, it is the proportion of possible universes that contain the particular feature you're interested in. The 'chance' of life happening, for instance, could be calculated by looking at how many of those possible universes develop life – given that life will occur at different times in different universes, that's an awful lot of calculations, but theoretically possible, I would have thought.

 

[Sea Cow]

I cannot put into words how strongly I disagree with this. The barrier you perceive between biology and physics, or between any two fields of study, are social constructs, not properties of the universe. Don't departmentalize that which doesn't need to be. Yes, the physics behind a cell is enormously more complicated than a system of pulleys, but can you really argue that that they follow separate rules?

They don't follow separate rules, of course. But the explanation for why a particular life form is like this and not that does not come from physics, or at least can only partially come from physics. Once you are at the level of explaining function, you are no longer at a level of physics explanation.

At the level of minimum complexity for life that follows my earlier provisional definition – apparent intention to perform those functions that are necessary for successful reproduction (a definition that certainly includes viruses as life) – you are already firmly in the realm of biological explanation if you are interested in explaining the way that the life form achieves its 'aims' (they are of course not aims at all, but as ever when talking of evolution, it is hard not to talk in these terms – hopefully you can understand this proviso, that evolution has neither direction nor purpose, is implicit).

 

[Max Faust]

I think what you're looking for is a metaphysics issue.

Perhaps so... but I'm not convinced.

Parts of "hard physics" today are unquestionably metaphysical (at least thus far), such as the various shades of string theory, branes, etc., whereas it ought to be relatively simple (in the context) to formulate a simple theory for why complex systems that show negative entropy occur. What kind of mechanism is driving this tendency towards "life"?

 

[binbots]

Life can be whatever ever you want it to be. We can all argue all we want about what it is and we can even come up with the most popular defintion. But the fact will remain that the definition we give was our own defintition. We can define our rules for life and then put all matter into our 2 sections, Living and non-living. But the bottom line is that we make the rules. So in the end it only matters what each person beleives.

 

[Max Faust]

Life can be whatever ever you want it to be.

In that case, I want it to be something which requires no magical concept.
Whether this be "God" or "irreducible complexity" or "random fluctuations in the protein soup".
I want it to be an obvious process which originates in a basic law of physics.

 

[Archosaur]

Life can be whatever ever you want it to be.

I agree, because "life" is a word. However, so is "boat". "Boat" can also be whatever you want it to be, but a long time ago, we all got together to come up with a single definition of "boat", not because there is one inherently true definition of "boat", but because words are only useful when people agree on their definitions. The word "life" isn't too far gone. Most people agree that trees are alive and that rocks are not. But now we're here to whittle down some of the fuzzy edges to create a more useful word.

Also, Sea Cow, your definition of life includes computer viruses (apparent intention that insures it's survival), which can already be completely explained by physics.

 

[Sea Cow]

Parts of "hard physics" today are unquestionably metaphysical (at least thus far), such as the various shades of string theory, branes, etc., whereas it ought to be relatively simple (in the context) to formulate a simple theory for why complex systems that show negative entropy occur. What kind of mechanism is driving this tendency towards "life"?

There is none. We (living things) are part of the drift towards higher entropy. We are organised matter, but we also consume energy and produce a great deal of heat! Overall, we life-forms on Earth are simply a part of the process by which the highly organised, low-entropy Sun burns itself out.

Oh, and is string theory "hard physics"? Quite the reverse, I would have thought. Quantum mechanics is hard physics, as is relativity, but I think to qualify as such, you need at the very least to have some predictive power.

Life can be whatever ever you want it to be. We can all argue all we want about what it is and we can even come up with the most popular defintion. But the fact will remain that the definition we give was our own defintition. We can define our rules for life and then put all matter into our 2 sections, Living and non-living. But the bottom line is that we make the rules.

Yes, I agree with this. Life is a category that we impose on the universe. And whatever your definition, when it first appeared will always be a fuzzy area. It's a little like asking how many water molecules you need to make wetness.

 

[Studiot]

Why is everyone so seemingly hell-bent on an Aristotelian definition?

There is no trouble finding examples that are alive or not alive that we can all agree upon.

The problem is that there are examples 'left over' by this process that defy agreed classification.

Could this be because there is actually a range from definitely alive to definitely not alive?

 

[Max Faust]

We (living things) are part of the drift towards higher entropy.

Maybe so, but it still seems as if there are local "clusters" of "things" that come together in temporally organised structures that show negative entropy. It is this "tendency" that I want a name for. You can call it "life" (because "life" is certainly a modality of this "tendency") or you can look for a common, physical denominator - which perhaps is something akin to the way "gravity" makes "stuff" cluster together into stars and galaxies instead of "smearing" out evenly throughout the available space.

 

[Max Faust]

Oh, and is string theory "hard physics"?

Uh... well maybe not. I think of it as "metaphysics"... but it's still something that a lot of physicists are fervently pursuing.

 

[Sea Cow]

I know this isn't going to go down well here, but I don't think the answer to your question about the appearance of clusters of temporally organised structures lies in physics! Or at least, the answer to how the organisation in some of these structures increases over time doesn't.

It is a question at the level of biology that requires you to examine the environmental drivers behind evolution. Once you step over the line from non-life to life, pretty much however you define life, you're into this level of explanation.

It's an open question, afaik, whether there is even a tendency in evolution towards complexity. Most life hovers on or just above the level of minimal complexity required for life, and it always has done since life appeared. We more complicated forms are exceptions. The most basic forms such as bacteria and archaea are the norm.

The appearance of life in the first place, of something that could then evolve, may well be a question for physics, and you could be right that there is an underlying mechanism there. The problem with this whole question, for me, is that once you have something that you can definitely call life, you're way past that point. We're still a long way from understanding even the basics behind what happened before that point on the way to the first life.

 

[Studiot]

It's an open question, afaik, whether there is even a tendency in evolution towards complexity. Most life hovers on or just above the level of minimal complexity required for life, and it always has done since life appeared. We more complicated forms are exceptions. The most basic forms such as bacteria and archaea are the norm.

Fair comment.

 

[Sea Cow]

That said, we shouldn't underestimate the complexity and organisation of bacteria!

 

[Max Faust]

It is a question at the level of biology that requires you to examine the environmental drivers behind evolution. Once you step over the line from non-life to life, pretty much however you define life, you're into this level of explanation.

Well, then the problem is that I really don't see any "line" here. I don't see "life" as something which suddenly manifests through a mystical process of this or that "genesis". I examine the driving forces behind "evolution" from the most fundamental level possible, which is that of physics. I will accept it if anyone can prove me wrong - which in my opinion would only imply the existence of some other "magical" principle that would lead me to simply reformulate my question - but until this happens, I'm quite convinced that there exists a fundamental law of physics that is as of yet undiscovered, having to deal with local systems of negative entropy; how they form and how long they will last (which is probably a function of their degree of complexity).

 

[Sea Cow]

I examine the driving forces behind "evolution" from the most fundamental level possible, which is that of physics.

I don't understand what this means. You can't explain why a particular trait gives an evolutionary advantage without reference to the biological context.

Could you give me a worked example of how a particular trait has evolved, for instance the duck reflex, purely with reference to physics?

Physics isn't always the most fundamental level of explanation. It depends on the question.

 

[Sea Cow]

Well, then the problem is that I really don't see any "line" here. I don't see "life" as something which suddenly manifests through a mystical process of this or that "genesis".

The line is where you choose to draw it. I agree that there's an unsolved problem considering how you get from something that definitely isn't life to something that definitely is (as a previous poster put it). That doesn't mean mystical processes, just processes we don't understand yet.