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

[DaveC426913]

Common for what age?

At one point, Play-Doh and Elmer's Glue would've been on my list!

True but Elmer's glue was once horses, and I believe Play-Doh is actually alive.

 

[Galap]

Your nature commands you to conjure junk science?

There's lots of books out there on 'The Power of Attraction' and other woo-wooism.

I'm not saying "don't search for something worthy"; I'm saying "this is a road to folly".


There's nothing mystical about emergence. FaceBook is an example of emergent behaviour. Social networking structures have properties that are not detectable in the individual components. The whole is greater than the sum of its parts.

Emergence isn't mystical, but it is easy to think it is, because so little is understood about it.

For example, intricate knowledge of subatomic particles will teach you a great deal about atoms and how they work, but it won't teach you a whole lot about chemistry. What do we do about that? Well, we figure out chemistry on its own and write the rules for that. We don't really think about WHY the emergent properties are there. We know very little about that. The only area where this gets attention is where its magnitude is the greatest, where all the errors/lack of understanding add up, is the difficulty in uniting QM and GR. Emergence essentially explains why they are so difficult to unite.

 

[Max Faust]

Emergence isn't mystical, but it is easy to think it is, because so little is understood about it.

The reason why I call it "mystical" may be somewhat unjustified, but I seem to run into this concept as a supposed "explanation" every now and then, but upon asking the (to me) perfectly legitimate question 'well what is it then?' I usually only get vague and foggy answers, and/or the end-all-discussion-suggestion that I should "look it up".

However, *emergence* may just be what I'm looking for. Is there any way of 'catching' the phenomenon within a simple equation?

Edit: "Equation" is the wrong word. I'm quite good at *imagining* things but I'm a mathematical illiterate.

 

[Max Faust]

You can always jump on the whole "Complexity Theory" bandwagon with Murray Gelman, the creator of Mathematica (I forget his name), et. al.

Do you mean "Bertie"? (Bertrand Russell).

Anyway, thanks for the hint. I shall have a look into said bandwagon.

 

[Phrak]

Well, do computer simulations count? They fit that definition.

Yes, I would include computer simulations. I think most people wouldn't..

 

[Andy Resnick]

This discussion reminds me of another one, where we try to define what is the color 'blue'. Someone says "blue is 450 nm wavelength light", another says it ranges about some spectral band (somewhere between purple and green, with sidebar discussion on where the boundary should be), and yet another (the color blind computer programmer) claims some things are blue but most people disagree.

Clearly the line between alive and dead is not so clear: when we die, most of our cells are still alive (we even harvest them for research). Some of these cells can live for days or longer (chondrocytes, for example). It's also apparent there is *some* difference between living systems and non-living systems: we can convert living to non-living, but not the other way around.

I maintain that Physics has an opportunity to make a real contribution by bringing quantitation to the question of living/nonliving. There's a tradition of physicists making progress on this question, but unfortunately a lack of real results.

 

[Max Faust]

The one I was thinking of is honey. But then again, I guess pollen is technically seeds.

Honey isn't made from pollen! (Pollen is more akin to "sperm", BTW.) Flower-nectar!

My mind went to "dairy products" upon this question - since milk is a body fluid, but not thought of as "alive" as such, in and of itself.

 

[DaveC426913]

Honey isn't made from pollen! (Pollen is more akin to "sperm", BTW.)

DNA packages either way.

Flower-nectar!

Fair enough. So it was once a fluid of a living thing.

My mind went to "dairy products" upon this question - since milk is a body fluid, but not thought of as "alive" as such, in and of itself.

Good point. Honey is no less a product of a living thing than milk is.

 

[Archosaur]

I like to think of life a little more generally, and through more of a physics lens.
Someone has already said something similar, but I like to think of life as local systems of negative entropy, specifically those that become more ordered through cumulatively selective processes. So, I, unlike many, would consider viruses to be alive.

"No, viruses are just a bunch of chemicals," said my bio prof.

"How many chemicals do you have to be, before you're considered alive?" I asked.

It got a laugh out of the class, but no good answer.

 

[mgb_phys]

"No, viruses are just a bunch of chemicals," said my bio prof.

Are viruses alive is a good question - it just doesn't have a good answer.
It was always a favorite university interview question - it gets people thinking rather than just have them parrot out the answer.

It's also worth asking a class for statistical purposes, maths/physics/chemists all say yes (life is just a level of complexity), biologists/medics tend to say no (they have learned the defn of life)

 

[Archosaur]

biologists/medics tend to say no (they have learned the defn of life)

Yea, and that definition includes the qualifier that life has to be composed of cells. How arbitrary is that?! Why not a mass requirement, or favorite color? Of course I'll concede that it is incredibly unlikely that intelligent life would develop with non-cellular structure, but if such "beings" come to our planet looking for a cup of sugar, what then?

"Nope. You guys aren't even alive."

 

[Andy Resnick]

It's not completely arbitrary- a cell is the smallest self-contained unit of living matter. Viruses must hijack a cell to make copies- they cannot reproduce on their own (nor do they 'eat').

I suppose it's possible to imagine other alternatives, but on Earth anyways, cells are the basic building block.

 

[Studiot]

Including cells in the definition adds the complication.

For any aggregate of cells, some living some dead, is the aggregate alive?

Is there any difference between the 'life' of an aggregate and the 'life' of a single cell?

 

[Phrak]

It's not completely arbitrary- a cell is the smallest self-contained unit of living matter. Viruses must hijack a cell to make copies- they cannot reproduce on their own (nor do they 'eat').

I suppose it's possible to imagine other alternatives, but on Earth anyways, cells are the basic building block.

This is an excellent example. The counter-argument is that many cellular organisms rely upon acquisition of preexistant material to live as well.

Somewhere, inbetween, notice that both the virus and the host cell in unison generate more viral particles. In this perspective there is not one living organisms hijacking another, but a synthesis of genetic material in cooperation, as required, to produce more viral particles.

In the process, most of the genetic material of the host cell is unused. This is not a deficit to reproducing more viral particles, as there are plenty of other mates available to supply the missing chromosomes. The same enviromental dependency occurs in sexual reproduction on a more limited number of chromosomes.

A living system need not be physically localized.

 

[Pythagorean]

Viruses are a very Interesting aspect of this discussion. I've always considered them a sort of wrench in the cogwheel, more so than a lifeform.

I would also generalize Q Goest's definition to genes, not the specific DNA type molecules.

 

[Andy Resnick]

Including cells in the definition adds the complication.

For any aggregate of cells, some living some dead, is the aggregate alive?

Is there any difference between the 'life' of an aggregate and the 'life' of a single cell?

That's essentially the 'Delphic boat' parable. Given that living systems constantly replace parts, what does it all mean for the ensemble?

http://en.wikipedia.org/wiki/Delphic_boat

 

[Andy Resnick]

Viruses are a very Interesting aspect of this discussion. I've always considered them a sort of wrench in the cogwheel, more so than a lifeform.

I would also generalize Q Goest's definition to genes, not the specific DNA type molecules.

There's also prions. Prions are infectious proteins. They convert normal proteins into misfolded proteins that resemble themselves.

Again, physics can make some real contributions here- we excel at finding underlying patterns and 'rules'.

 

[DaveC426913]

It would appear that no definition of life can concentrate on the parts; it must concentrate on the processes. So it is not about the cells themselves but about their metabolizing.

 

[Studiot]

So it is not about the cells themselves but about their metabolizing.

So is dormant life then dead?

 

[Andy Resnick]

It would appear that no definition of life can concentrate on the parts; it must concentrate on the processes. So it is not about the cells themselves but about their metabolizing.

I think that's the right approach- 'life' could be defined by how parts functionally relate to (and perhaps modify) each other, not the parts themselves.

 

[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.