Register to reply

On Fine-Tuning and the Functionality of Physics

Share this thread:
friend
#19
Sep16-10, 08:09 AM
P: 969
Quote Quote by ConradDJ View Post
In other words, I would look at all the different formal / mathematical principles of the current model as having different functional roles in relation to "what the universe needs to do" in order to exist. Rather than envisioning some single underlying formal principle -- a single field-equation, for example -- that somehow explains all of them.
You seem to be saying that all things are consistent with some underlying functionality. Even in that case, the functionality becomes the formal principle which determines the rest of physics. So in any case, we are still seeking some underlying principle (functionality perhaps) from which all of physics is derived so that all the fine tuning is inevitable.
oldman
#20
Sep17-10, 04:05 AM
P: 622
Quote Quote by friend View Post
You seem to be saying that all things are consistent with some underlying functionality. Even in that case, the functionality becomes the formal principle which determines the rest of physics. So in any case, we are still seeking some underlying principle (functionality perhaps) from which all of physics is derived so that all the fine tuning is inevitable.
Yes. I agree.

Although physics is good at mathematically describing and rationalising what is observed and measured, it is not quite so good at anticipating the often unexpectedly complicated outcome of clever processes that nature has devised. Especially self-promoting ones; those that make it easier for the same process to continue or repeat itself. Think of how gravitational accretion unexpectedly causes stellar jets to form; how self-promoting fluvial erosion causes complexities like the Grand Canyon and how the self-promoting chemical replication of DNA is responsible for the biological complexities we live among.

Conversely, in an universe filled with complicated stuff, much of which seems to be the ultimate result of various self-promoting tricks-of-nature, I think looking for some 'underlying functionality' is carrying reductionism too far. I can't find 'functionality' in my dictionary, anyway.

It is as if physicists "seek him here, ... seek him there, ... seek him everywhere. Is he in heaven?—Is he in hell? That demmed, elusive Pimpernel."
ConradDJ
#21
Sep17-10, 08:01 AM
PF Gold
P: 302
Quote Quote by friend View Post
You seem to be saying that all things are consistent with some underlying functionality. Even in that case, the functionality becomes the formal principle which determines the rest of physics. So in any case, we are still seeking some underlying principle (functionality perhaps) from which all of physics is derived so that all the fine tuning is inevitable.

Well, I was trying to make a distinction between formal and functional explanation that apparently doesn’t seem significant to you and oldman... and maybe it isn’t very clear in relation to physics. But in biology, it’s not that the structure of organisms is “consistent with” Darwinian evolution, as if reproduction and evolution were “formal principles” that life obeys. And there’s nothing that indicates the evolution of life on Earth is “inevitable”. Nor could we “derive” any of the details of biological structure from evolution.

On the other hand, we can understand most of those details – the “clever processes nature has devised” – as accidents that proved to be very useful in relation to the requirements of staying alive and reproducing the species. Evolutionary theory is very weak at prediction, but very powerful at making the world intelligible.

So if there were an “underlying functionality” in physics, we wouldn’t expect it to “determine the rest of physics.” We would expect it to show us how an essentially random chaos of lawless interaction comes to look so highly structured and precisely lawful, and what each of the different aspect of physics contributes to making the whole thing work.

If our universe evolved, then presumably it could have evolved in many other ways, leading to other laws and spacetime structures very different from ours – that would also have been very “finely-tuned” to work the way they work. And we would be able to understand the details of physics in our universe not as “inevitable” in any way, but as the comprehensible results of a unique history.
ConradDJ
#22
Sep17-10, 08:27 AM
PF Gold
P: 302
Quote Quote by oldman View Post
Conversely, in an universe filled with complicated stuff, much of which seems to be the ultimate result of various self-promoting tricks-of-nature, I think looking for some 'underlying functionality' is carrying reductionism too far. I can't find 'functionality' in my dictionary, anyway.

It is as if physicists "seek him here, ... seek him there, ... seek him everywhere. Is he in heaven?—Is he in hell? That demmed, elusive Pimpernel."
I'm sorry about your dictionary... But anyhow, I hope the above post makes clear that this is not "reductionism". Or is it reductionist to say that all of biology stems from and responds to the necessity that every species find some way to reproduce itself? That doesn't mean, by the way, that all the "self-promoting tricks of nature" have a reproductive function, in biology. Biological evolution makes all kinds of things possible, many of which have no function at all and just happen to evolve through "genetic drift." But reproduction is still the basis of the process.

The other point I was trying to make in the posts above is that the “functionality” we’re talking about is not necessarily something elusive – a mysterious “secret of the universe” we have yet to discover. I suspect on the contrary that we don’t understand it clearly because it’s too obvious and too basic to everything in physics.

That was also true in biology. Darwin was certainly not the first to realize that organisms reproduce themselves! And it was no great discovery either that some members of a species are better at reproducing than others. But he was the first to realize the implications of these obvious facts of life – and he probably wouldn’t have achieved that if the notion of evolution over geological time had not already been “in the air.” Even once he understood that evolution operates the same way pigeon-breeders do, through selective reproduction, it took many years to convince himself and others about something that nowadays is practically self-evident (at least to biologists).

So basically this boils down to a question – since we find ourselves in a physical world that seems to be “finely-tuned” in many respects, is there something very obvious we’re taking for granted about physics, that might lead to a similar kind of understanding? For example, that things in the world are “determinate” and "obey laws" and are “observable”? This is all so basic and necessary to our experience that it’s still very hard for us not to take it for granted, even after many decades of wrestling with the meaning of QM, which calls all of these things into question.

From a “formal” standpoint, there are a lot of complex facts about the world that we’re trying to "derive" from some underlying mathematical principles. But maybe just the fact that there are observable facts has implications for physics that we haven’t understood.
oldman
#23
Sep17-10, 10:16 AM
P: 622
Quote Quote by ConradDJ View Post
..... this is not "reductionism". Or is it reductionist to say that all of biology stems from and responds to the necessity that every species find some way to reproduce itself? That doesn't mean, by the way, that all the "self-promoting tricks of nature" have a reproductive function, in biology. Biological evolution makes all kinds of things possible, many of which have no function at all and just happen to evolve through "genetic drift." But reproduction is still the basis of the process.
.... which process is biological evolution. And the replication of information coded in DNA by stereochemical means is the essence of reproduction, such replication being one of nature's invented self-promoting tricks. Of course it's not the only one, just the one that underlies Darwinian evolution.

The other point I was trying to make in the posts above is that the “functionality” we’re talking about is not necessarily something elusive – a mysterious “secret of the universe” we have yet to discover. I suspect on the contrary that we don’t understand it clearly because it’s too obvious and too basic to everything in physics.
You suspect that 'it' is in full view all the time but unexpected in appearance, and therefore unrecognised --- like The Purloined Letter in Poe's story?

It would be great if this were so. The only obvious feature of physics that to me seems as if it could fit the bill is the self-consistency that physics has. In particle physics there is such an idea --- I think it's called the bootstrap hypothesis --- proposed by Geoffrey Chew quite a while ago, discarded and perhaps again becoming relevant today. Maybe the physical world behaves as it does because this is the one (and only?) way its behaviours can mesh together seamlessly? Rather as the pieces of a jigsaw puzzle fit together.

But the devil is in the details. While electromagnetism and special relativity are seamless partners, there is as yet no seamless meld of say, quantum mechanics and gravity. Not for the want of trying, though, as this forum shows!

.....But maybe just the fact that there are observable facts has implications for physics that we haven’t understood.
Observable facts that all fit together seamlessly?
Fra
#24
Sep17-10, 03:53 PM
Fra's Avatar
P: 2,799
I think you're looking for a discussion, and I've already thrown in my perspective, but here is another question, just to provoce some points...

Quote Quote by ConradDJ View Post
From a “formal” standpoint, there are a lot of complex facts about the world that we’re trying to "derive" from some underlying mathematical principles. But maybe just the fact that there are observable facts has implications for physics that we haven’t understood.
I guess you are hinting that just - MAYBE our preconception that nautre "obeys laws" etc, and thus that there must be some underlying formal system from where all can be derived - is wrong...

...could the QUEST for such "compactified" understandings in of finding formal reductions still be RATIONAL? What is it's utility? What is the "survival value" of such reductions EVEN if they are mistaken for mathematical truth?

(I have an opinon, but maybe someone else may want to comment?)

/Fredrik
apeiron
#25
Sep17-10, 05:27 PM
PF Gold
apeiron's Avatar
P: 2,432
Quote Quote by ConradDJ View Post
But since so many very different aspect of the model seem to be "required" for any of the kinds of physical structure we see in the universe, it makes sense to me to try thinking about the world as pervasively "functional", in the way a living organism is pervasively functional. I.e. many different kinds of structure working together to accomplish something (in the case of an organism, reproducing its species).
If you want to explore a biological analogy properly, then I would say you would need to anchor it in theoretical biology - precise models of what makes live different from non-life, bios different from abios.

For instance, both bios and abios are functional in thermodynamic terms - they arrange themselves into structures that dissipate entropy. So self-organisation and fine-tuning can be explained in that context.

But then actual bios does something else. It does not just develop (which is all a dissipative structure does) but also has the secondary machinery to control and even evolve.

As Howard Pattee puts it, it uses rate-independent information to control rate-dependent processes. So for example, our genes (which store information in a "timeless" fashion), throw enzymes into the mix to control the rate of some metabolic reaction, some self-organising dissipative process.

This genetic information does not develop (it stands apart from the usual molecular wear and tear) but it does evolve - there is a process for mixing up the information every so often and trying out some new combination.

Anyway, the point is that theoretical biology makes some clear distinctions between development and development-with-evolution, between abios and bios. Functionality and fine-tuning are part of both stories, but they are two different stories.

So, if cosmological thinking is now looking for wider inspiration (as it has with Smolin), then the speculation has to respect this very critical distinction.

If you are talking just development, then that is the realm of dissipative structure theory and other "raw" forms of self-organisation.

If you are talking about evolution, or evo-devo, then that would require a universe or multiverse to have something extra, some equivalent of Pattee's epistemic cut (the separation of rate-independent information and rate-dependent processes).

Although, having said all that, Smolin's spawning blackholes story is perhaps a curious hybrid - somewhere inbetween evo and devo. Every blackhole, which is a white hole to the other side, has a "genetic" memory in that it provides a set of initial conditions that are rate-independent so far as the rate-dependent development of the new baby universe is concerned.

But there is then no selection as such to fine-tune the information bound up in a blackhole. An unlimited supply of entropy and "space" is available so that the branching is without limit and there is no actual constraining competition between alternative recipes for particular universes. Some just happen to be more fecund than others over time.

This "biological" theory needs some source of variation so that not all blackholes are alike in the first place, as well as a source of unbounded entropy, and most of all, some reason to believe in white holes.

However, again, I think it shows that biology can be a source of inspiration for cosmological theorising. And there is a well-developed set of definitions in theoretical biology that would allow for a more precise framing of theories based on "fine-tuning from functionality".
apeiron
#26
Sep17-10, 05:49 PM
PF Gold
apeiron's Avatar
P: 2,432
Quote Quote by oldman View Post
While electromagnetism and special relativity are seamless partners, there is as yet no seamless meld of say, quantum mechanics and gravity. Not for the want of trying, though, as this forum shows!
But this could be precisely the key mistake - to expect a seamless meld in the form of a reduction of a higher emergent level of description (such as GR) to a lower foundational level (such as QM).

Yes this is the way physicists think . But it is not necessarily how all biologists think. Instead, complex, hierarchically-structured, worlds or systems arise via the synergistic interaction between bottom-up constructive degrees of freedom and top-down boundary conditions or emergent contraints. A local~global interaction.

So in this view, the systems science view, you always end up with an irreducible two-ness. You need both the local and the global to have anything arising at all.

Now an irreducible two-ness has arisen in fundamental physics - GR and QM. And their interaction quite successfully gives rise to the classical realm in which we live.

To the reductionist who wants only a theory of the local, this is a frustration. But to a systems thinker, it is only natural that we end up with theories describing both the local and the global.

The task then is not to collapse the global to the local but instead to formalise the nature of their interaction. Which is still a big task, but not the same task. It is a different way of thinking about seamless.
oldman
#27
Sep18-10, 01:29 AM
P: 622
Quote Quote by apeiron View Post
But this could be precisely the key mistake - to expect a seamless meld in the form of a reduction of a higher emergent level of description (such as GR) to a lower foundational level (such as QM).

Yes this is the way physicists think . But it is not necessarily how all biologists think.....
Much of what you then say sounds grand and quite profound, Apieron. Some of today's physicists who are indeed frustrated by the inability of their theories to predict observable phenomena might well be tempted to give this biological approach a whirl. You say that:

.....complex, hierarchically-structured, worlds or systems arise via the synergistic interaction between bottom-up constructive degrees of freedom and top-down boundary conditions or emergent contraints.
But can you give frustrated physicists hope by giving specific examples of how 'local-global interactions' actually work? Better still, has this approach succeeded in predicting observable phenomena? Again, examples would help.

Without the element of verifiable prediction physics has an unfortunate tendency to degenerate into a masquerade of words and squiggles. I'd better not give examples.
Fra
#28
Sep18-10, 04:21 AM
Fra's Avatar
P: 2,799
Quote Quote by oldman View Post
But can you give frustrated physicists hope by giving specific examples of how 'local-global interactions' actually work? Better still, has this approach succeeded in predicting observable phenomena? Again, examples would help.
I can't speak for apeiron but I share some of the general traits of his reasoning, and I think that first of all this is a diffucult problem so just because one may have ideas on constructing principels doesn't mean the step to specific predictions is short.

Quote Quote by oldman View Post
how 'local-global interactions' actually work? Better still, has this approach succeeded in predicting observable phenomena?
I personally think that the quantitative description of these interactions lies in evolving interacting inference models. So what is inference models? What I mean with "Inference models" is mathematical models of how to produce various kinds of "expectations" by means of induction/deduction/abduction. These expectations then further guide the actions of the inference system. Further to this, in the generalized inference thinking, we are not talking bout deductons, but generally uncertain inferences, and reasoning based upon incomplete information. So sometimes the optimal actions are not in consistency with the feedback from the environment, then an evolution takes place where the inference system itself evolves (not just the information state, but also the state of the inference machniery).

This is not so common of physics and very underdeveloped, but there are people looking into this. There are also strong analogies to economical system theory, where the predictions are existence of equilibrium points. There are also strong analogies to learning models, similar to the hman brain, which is exactly an evolving interacting inference system, where the inferences determines the actions. Further feedback "drives" learning and evolution of the brain. Predictions could be how two brains interact. From understanding of how an inference systems works, one can make predictions of the interaction properties to two such systems.

The analogy (which is yet of course strongly underdevelped) is to consider two physical systems as two inference systems, then their interaction properties and thus the overall dynamics of the isolated system could in principled be prediced.

This isn't just foggy ideas, I think the outline a precise idea, but this is simply not how physicists traditionally absctract physics. Somehow physics has more of a tradition of reductionism and quest for eternal fixed laws. This is dominating even today. So all mainstream models today are of this structural realist form.

If we think about how GR we developed. Somehow the development of intrinsic differential geometry by Riemann, was almost as it seems a pre-requisite for the understanding of GR.

I think we are in a similar situation. We still lack a developed theory of intrinsic inference. This will be a pre-requisite to understanding & combining the "inference perspective" of QM with the observer dependent views of GR. Unfortunately the structural realist view that IS dominating has lead to another approach: that the observer invariant form of GR, IS what should somehow be subject to inference; RATHER than seeing the set of inferences beeing related by some yet unknown intersubjective rules.

So I think we need more study of mathematical infernece models. We simply lack the right structural framework to pose the questions right. Until we have, I think the ideas expressed in words is the only guide.

/Fredrik
ConradDJ
#29
Sep18-10, 06:44 AM
PF Gold
P: 302
Quote Quote by oldman View Post
...the replication of information coded in DNA by stereochemical means is the essence of reproduction, such replication being one of nature's invented self-promoting tricks.
I think you have this backward. I don't think anyone has seriously suggested that DNA molecules somehow appeared along with all the molecular mechanism needed to replicate them... and then self-replicating systems emerged.

The earliest self-replicating systems would have been nowhere near this well-organized -- maybe something like pools of simple organic molecules capable of mutually-catalyzing reactions... so that when the pool happened to get splashed into several pools, those reactions could produce more of the same set of molecules, and keep themselves going.

It's very hard to imagine what very primitive "life" may have been like... literally all we know about it is that it was able to make copies that were able to make copies that made more copies. Now random physical processes do lots of very interesting things, in dissipative systems, for example. But self-replication is a very special kind of "self-promotion". The particular "trick" of making new versions of a system, which is susceptible to variations that also get reproduced in the new versions -- isn't something we see happen much. And if something like this does ever get going, it's probably very unlikely to continue for long in the generally entropic environment of physics.

But, once you have something that can copy itself, then the longer the process keeps going, the more likely it is to be able to keep going, because this kind of thing can evolve and adapt. So this is the beginning of the story... and DNA comes many chapters later, as a highly stable storage mechanism for encoded protein-building information.

It worked so well that now nearly all life makes use of it. But the point of this story is that the basis of life is a specific and very special "functionality" -- something life does, not the physical mechanisms any particular life-form evolves to do that.

If molecular biology had become possible before Darwin, we might have a situation in biology similar to the one we have now in physics. We might have a vast amount of information about an extremely complicated, very finely-tuned system of cellular mechanics, consisting of many interdependent sub-systems, each with its own modes of operation, but no fundamental principle to explain what's going on or why. We would even have a puzzle similar to QM, in that we'd see very highly ordered and predictable behavior at the "macroscopic" level of the living cell, somehow based on the nearly random activity of individual molecules within the cell.
ConradDJ
#30
Sep18-10, 07:12 AM
PF Gold
P: 302
Quote Quote by apeiron View Post
If you want to explore a biological analogy properly, then I would say you would need to anchor it in theoretical biology - precise models of what makes live different from non-life, bios different from abios.

For instance, both bios and abios are functional in thermodynamic terms - they arrange themselves into structures that dissipate entropy. So self-organisation and fine-tuning can be explained in that context.

But then actual bios does something else. It does not just develop (which is all a dissipative structure does) but also has the secondary machinery to control and even evolve.

As Howard Pattee puts it, it uses rate-independent information to control rate-dependent processes. So for example, our genes (which store information in a "timeless" fashion), throw enzymes into the mix to control the rate of some metabolic reaction, some self-organising dissipative process.

This genetic information does not develop (it stands apart from the usual molecular wear and tear) but it does evolve - there is a process for mixing up the information every so often and trying out some new combination.

This makes sense to me. Life does have the ability to control ongoing entropy-increasing processes and coordinate them with other processes. This is certainly a basic and distinctive “functionality” pertaining to nearly all life-forms (though not perhaps to viruses and prions). And as a result, organisms get to be "finely-tuned" in a great many different respects at once (like our universe), unlike other dissipative systems.

But the point of a functional explanation is not just to come up with a general description that fits nearly all known cases... though that’s obviously a very useful thing! The goal would be to understand how and why this happens. And in biology we do understand where this “rate-independent information” comes from and how and why it evolves. That’s all based on what I think of as the “key functionality” of self-replication.

So “abios” refers to all the random processes that can occur in physical systems as they “slide down the thermodynamic gradient”... And “bios” refers to all those same physical processes, to the extent that they’ve been selected and replicated as in some way useful to the process of self-replication.
ConradDJ
#31
Sep18-10, 08:23 AM
PF Gold
P: 302
Quote Quote by Fra View Post
I guess you are hinting that just - MAYBE our preconception that nautre "obeys laws" etc, and thus that there must be some underlying formal system from where all can be derived - is wrong...

...could the QUEST for such "compactified" understandings in of finding formal reductions still be RATIONAL? What is it's utility?

Well, I don’t think it’s wrong to think that nature “obeys laws” – clearly it does. But you’re right, I think this ability to be lawful must be based on something deeper.

The posts by friend and oldman above reflect a sense that the lawfulness of nature and the mathematical self-consistency of those laws almost have to be the basic explanation for things. As you know, this point of view goes back to the beginnings of philosophy and science. And it is such a remarkable idea, that “the Logos steers all things through all,” as Heraclitus says – and it fits so well the way we philosophers and scientists like to think.

And the quest to uncover underlying laws clearly has tremendous utility, since it gave us science. I think the search for “unification” that led to the Standard Model was the great intellectual accomplishment of the 20th century. But I suspect we now need a different strategy.


But I think what you’re suggesting is that in nature itself there is some “utility” to things “obeying laws” – i.e. having all this random interaction “reduce” to conformity with a relatively small set of relatively simple formal principles. I certainly agree. The problem is describing the underlying “functionality” in terms of which the laws are useful.

I’ve been intrigued by your suggestion that we might find a model for this in the inference process by which scientists “reduce” the welter of phenomena to a relatively compact set of laws. It’s a guessing game in which guesses are tested against specific cases to improve the guess, and where a key part of the game is trading information about which guesses work. But I haven't yet seen where to find that kind of process in physics.

My own guess is that the measurement process is the “key functionality” that makes laws useful. For one thing, it involves literally all observable phenomena, and so all of physics. For another, QM gives us very strong indications that things are “real” and determinate and lawful only to the extent they are measured. And for another, the very difficulty of the question of what constitutes a physical “measurement” points toward a type of anaylsis that seems to me very new and promising.

What I have in mind is that every physical parameter, system, law or event gets observed through its effect on a different kind of parameter, system, etc. Physics has focused on isolating systems and parameters to study them separately – giving us a huge amount of excellent information – and then looks for ways to “reduce” or “unify” these descriptions, which has also worked very well, up to a point.

But now we may need to ask a different type of question, about the role each physical parameter, each type of field or particle plays in making other parameters and other kinds of systems observable. In other words, the question about measurement suggests the need to understand the relationships between the different kinds of forces, etc., so that they provide a context for measuring each other. If the world were a single, simple mathematical pattern, that might be lovely, but how would it be observable?

We take being “observable” for granted – we assume that if there’s something there in the world, then of course there must be some way to measure it. But there’s no logic to that. In fact, measuring any specific type of physical information requires other specific types of information to be known. So what kind of information-structure is this, that can measure all its own parameters by means of other parameters?

And can we imagine simpler kinds of systems that can do this “trick”... out of which our universe might perhaps have evolved?
oldman
#32
Sep18-10, 08:23 AM
P: 622
Quote Quote by ConradDJ View Post
I think you have this backward. I don't think anyone has seriously suggested that DNA molecules somehow appeared along with all the molecular mechanism needed to replicate them... and then self-replicating systems emerged.
More a case of you and I having crossed wires of communication, than looking at things backward. What you say about DNA not appearing fully-blown, as it were, is of course correct. I'm no creationist, and think that your follow-up is a very reasonable shot at telling the beginning of the story. But I prefer discussing histories that don't begin with guess-work.

So this (may be) the beginning of the story... and DNA comes many chapters later, as a highly stable storage mechanism for encoded protein-building information.
Yes indeed. But this whole self replication story is about a clever trick of nature's (even if DNA took billions of years of mysteious stereochemistry to perfect). It's a trick of the self-promoting kind, akin to fluvial erosion, safe-cracking and sex; once it happens it tends to happen again because nothing succeeds like success. Perhaps biologists should recognise the generic type, rather than the particular case.

.... But the point of this story is that the basis of life is a specific and very special "functionality" -- something life does, not the physical mechanisms any particular life-form evolves to do that.
Are you saying here that life 'does the reproduction dance' rather than act as an agent for reproducing DNA? You then disagree with that polemic biologist, Richard Dawkins? Not that this is a bad thing, of course --- he is very strident. Your invention, "functionality", is I think too unspecific to separate such possibilities.
apeiron
#33
Sep18-10, 04:47 PM
PF Gold
apeiron's Avatar
P: 2,432
Quote Quote by oldman View Post
But can you give frustrated physicists hope by giving specific examples of how 'local-global interactions' actually work? Better still, has this approach succeeded in predicting observable phenomena? Again, examples would help.
You are right that the approach I suggest is more philosophy than science in its current stage of development. But one of the "observables" it predicts (which other approaches don't predict) is precisely that a complete model of a system would throw up a tale of the local constructive substances (ie: QM) and the globally constraining form (ie: relativity). And that furthermore, their interaction over all scales would result in a powerlaw outcome (ie: renormalisation).

Anyway, some familiar examples of physical systems with a local~global logic. A bar magnet (local dipoles, global magnetic field). A Rayleigh-Bénard convection cell (local thermal jostling, globally organising convection currents).

Now these are only examples of partially self-organising systems. A bar magnet does not create its own dipoles, just aligns them. A Benard cell does not create the boundary constraint that is the sides of its heated metal pan, it just responds to their given existence. But it is very difficult to find everyday physical examples of what I am talking about - a totally bootstrapping self-organisation - because the everyday world is already so full of strong physical constraint.

The physical world looks like it is made of solid stuff (atoms, matter) and it takes a lot of energy to melt that state of strong self-organisation. It takes an LHC or a quantum level experiment to melt the familiar world of classical local matter and classical global laws and so discover that what we see has self-organised in local~global fashion.

But biology and other "soft" sciences are a better place to see a systems logic at work because - due to their exploitation of entropy gradients - they do have still degrees of freedom that can be shaped, informational constraints that can be developed.

So take an example like a body organ, it has some global function - a purpose. And it is composed of cells that could be many different type of cells (they originally had the pleni-potential of stem cells) but they have become shaped by a particular organ's purpose. So a liver is made of liver cells, not heart cells.

Or you could take other examples such as the way the receptive fields of neurons are shaped by a prevailing state of attention/anticipation.

But you would still be correct that all this is still more about explaining what is already observed than predicting what will be observed.

There are some proto-mathematical tools - hierarchy theory, fractal geometry, complex adaptive systems, scalefree networks, constructal theory, generative neural networks, dissipative structure theory, etc, that "talk around the subject". But it is far from a "shut up and calculate" level of development.

However, that is also why it is an "opportunity". Either physics is so close to unifying QM and GR that just another little push with one of its 50 or 60 varieties of GR-reduction and it will all click into place. Or there is actually a reason why nature resists such a collapse and so room to consider other ways of framing the task.
apeiron
#34
Sep18-10, 07:15 PM
PF Gold
apeiron's Avatar
P: 2,432
Quote Quote by oldman View Post
Yes indeed. But this whole self replication story is about a clever trick of nature's (even if DNA took billions of years of mysteious stereochemistry to perfect). It's a trick of the self-promoting kind, akin to fluvial erosion, safe-cracking and sex; once it happens it tends to happen again because nothing succeeds like success. Perhaps biologists should recognise the generic type, rather than the particular case.
Yes and what is the generic case here?

The reason for the "unreasonable effectiveness" of DNA molecules - and also, serial human speech - is a constraint of dimensionality, a global constraint of local degrees of freedom.

The key to bios is an ability to store rate-independent information about rate-dependent processes. You have to have some kind of memory mechanism that stands apart from the usual thermodynamic fray, so as to be able to harness these very same dissipative processes.

And nature does this via the addition of further constraints. A DNA molecule is not 3D like a protein molecule, or even 2D like a membrane (membranes are used in cells to constrain reaction dynamics of course - a film has a different rate than a volume). It is a reduction of a structure to 1D, which in turn allows a further constraint to the 0D of a point - or in DNA's case, a codon.

The only thing that matters to a codon is its place in a serial sequence. The other directions of space are frozen out and don't exist so far as the coding structure of DNA is concerned (and even the dimension of time, because DNA is by far the most robust kind of molecule, other cellular molecules, even structural ones like microtubules, can half-lives measured in seconds).

So nature uses constraint over dimensionality all over the place to harness dynamics - cells use membrane, pores, and all sorts of other physical constraints. But the really big trick was a result of the most extreme possible dimensional reduction - that to a serial code which put the information as far away as physically possible from the real world of dissipative process...so as to be able to turn around and control those processes by imposing yet further boundary constraints on them (in the form of enzymes, etc).

And nature discovered this trick at least twice. So as well as DNA as a serial coding mechanism, humans also evolved serial speech. A limitation on vocalisation (the ability to articulate only a single phoneme at a time) became also the constraint that unlocked the coding potential of human language - a new kind of DNA to undepin socio-cultural evolution.

All this seems a long way from physics. But in fact it is the physics - a generic model based on the notion of constraints on degrees of freedom - of modern theoretical biology.

So again, if we follow Schrodinger's advice in What is Life, then biology really can offer a broader view of how the world works.
oldman
#35
Sep19-10, 03:42 AM
P: 622
Quote Quote by apeiron View Post

.....Either physics is so close to unifying QM and GR that just another little push with one of its 50 or 60 varieties of GR-reduction and it will all click into place. Or there is actually a reason why nature resists such a collapse and so room to consider other ways of framing the task.
Thanks for these two discursive and illuminating replies, Apieron. They provide lots of food for thought. A comment: The reason why 'nature resists such a collapse' may simply be that we're not smart enough to do the job; I do hope this is not so; we may not have fully exploited one skill we excel at --- a facility for recognising patterns. We should use all we've got.

Such as your noting that: "nature uses constraint over dimensionality all over the place to harness dynamics - cells use membrane, pores, and all sorts of other physical constraints." I would call this one of nature's tricks; a trick being something surprising in both outcome and underlying simplicity with some tricks being more effective than others. It seems to me that recognising effective tricks, or a class of effective tricks, like those that are self-promoting, may help us to understand nature better.

Here's an example of a trick that involves 'dimensional reduction' and is also 'self promoting'. You're probably aware of it:

Three-dimensional crystals grow at surprisingly low supersaturations because their translational symmetry is in practice hardly ever perfect. A one-dimensional linear defect can convert a three-dimensional lattice into a two-dimensional spiral ramp (like a multi-level parking garage). A surface intersected by this defect then becomes a self promoting site for growth at theoretically impossible low supersaturations. Perhaps this trick has 'global' (the lattice) as well as 'local' (the defect) aspects as well, and could be called a local-global trick.

The point I'm trying to make is that nature, with its huge bag of tricks, seems to be much smarter than we are. Even the clever fellow who recognised this trick (Charles Frank) didn't fully unravel the almost biological complexities that such defects can create in crystals. Makes one wonder about the potential complexities of defects in the now-being-considered symmetries of fundamental physics.
ConradDJ
#36
Sep19-10, 10:25 AM
PF Gold
P: 302
Quote Quote by oldman View Post
Are you saying here that life 'does the reproduction dance' rather than act as an agent for reproducing DNA? You then disagree with that polemic biologist, Richard Dawkins? Not that this is a bad thing, of course --- he is very strident. Your invention, "functionality", is I think too unspecific to separate such possibilities.
Dawkins may be pretty dumb about some things, judging on hearsay about a recent book of his that takes on religion. But the "selfish gene" thing is good, and I especially like his little book River out of Eden as a reminder how evolution works and how powerful this self-replication business is.

"Functionality" is purposely un-specific, because I'm more interested in raising the question about what the basic functionality is, than coming up with a definitive answer. Even in biology where we know the thing quite well, conceptually, evolution is complicated and gets more and more so over time. So while it's accurate to say it's essentially all about things making copies that make copies... really what "functionality" points to here is whatever it is that evolves, so that it can keep on evolving.

In case it's not obvious, I'm using the term in the sense of the functionality of a button on your computer screen, or of a piece of software or hardware --i.e. a description of what it does, what it's good for.

In the case of physics, I think that to describe the "basic functionality" as measurement, or observation, or the communication of information, comes close. But none of these terms are really well-defined yet, in physics, though we know what they mean well enough in daily life. But I'm not trying to give a precise definition, at this point. First we need to get a feel for what's going on with this business of determining information through interaction that then gets passed on as part of the context for determining other information, and so on.

I'm thinking that eventually we may be able to picture this process as the kind of thing that can evolve, just as we can picture the evolution of self-reproduction in biology. Then we'll be in a better position to describe just what's needed to make this work.


Register to reply

Related Discussions
Fine-tuning problem Beyond the Standard Model 0
Fine-Tuning from First Principles... don't laugh... General Physics 0
Fine tuning or dumb luck? General Discussion 29
Fine tuning Astronomy & Astrophysics 6