Bénard cells

[Diane]

Has anyone else had a chance to take a look at these? I don't know much about them yet, but I'm interested. They are cells that form spontaneously and predictably under thermodynamic conditions that are far from equilibrium. I first came across the term in Schneider and Sagan's book, Into the Cool.

I'll be back to quote large chunks of the book. There's a large amount of info about Bénard cells on the net, densely scientific, but in plain English in Into the Cool.

Diane

[nari]

I had a look at what Google brought up on Benard cells - and I think I have the gist of it, but the explanations are a bit beyond my full comprehension. Shall look forward to Sagan's transcription!

Nari

[Diane]

In Chapter 8 of Into the Cool, called "Swirl World", an opening quote from another of my favorite science authors, Mae-Wan Ho, appears:
The space-time structure of living organisms arises as the consequence of energy flow, and is strongly reminiscent of the non-equiibrium phase transitions that can take place in physicochemical systems far from thermodynamic equilibrium. Energy flow organizes and structures the system in such a way as to reinforce the energy flow. This organized space-time structure suggests that both quasi-equilibrium and non-equilibrium descriptions are applicable to living systems, depending on the characteristic times and volumes of the processes involved.

The whole chapter that follows discusses such topics as The Fluidity of Self, Bénard's Hexagons, Irreducible Complexity (a refutation of ID, ongoingly refuted painstakingly throughout the whole book), The Rayleigh Number, Complexity without Selection, Koschmieder and Spirals under Sapphire, Function from Flux.

I will start writing excerpts beginning with Fluidity of Self:
Separate from the world, we are yet inextricably connected to it..In this section we seek the roots of real-world complexity, including the origins of physiology and selves from non-living systems. A transition from noncoherent, molecule to molecule heat transfer to coherent convection occurs in some heated fluids. During the process more than 10 to the 22 molecules come into concert. From a statistical point of view, this is ridiculously improbable. Yet the coherence arises naturally from an applied temperature gradient. Nature creates systems, sometimes quite complex ones,"in order to" get rid of gradients and export atomic chaos into the surroundings. "Centripital," selflike structures arise from material cycles, energy-driven, self-reinforcing networks. Despite the term selfish genes, genes do not have selves: true selves are cells; without proteins and metabolic networks of recursive amino acids and intermediary molecules genes are impotent, no more "selfish" than an unplugged toaster.... Metastable processes underlie the selves we mistake for things. Selves are not closed or isolated but arise as metastable open systems in a sea of energy and flows. .. Even entirely physical swirling systems show a glimmer of selfhood - the beginning of a border between inside and outside. Their swirling metastability anticipates our biological selves and proper names. Discrete and independent as we imagine ourselves to be, we too are metastable flow systems with billions of years of history as dissipative structures.

Thermodynamic selfhood comes from dissipative systems that establish boundaries. Far from sealing themselves off from the outside world, their boundaries allow them to continue their operations. Biological self-hood on Earth depends on the semi-permeable layer, the ubiquitous lipid cell membrane, which provides a place, at first microscopic, for expansion of non-equilibrium processes. Less complex swirling systems grow and even seem to reproduce without biochemistry, or even chemistry.

More to come.
Diane

[bernard]

Benard Cells (http://www.physiology.rwth-aachen.de/user/jaeger/diplom/index_e.html)

Here is some nice videos. It's the first time I heard the term but had had already seen similar pictures.

[Diane]

Thanks Bernard,
There's a similar picture in the book, and it is really good to have something in the thread that shows how they look. (And apologies for having a keyboard that can't put accents over letters to spell French names properly. "Bénard" has an accent over the "e" :o.) (*note for Sept 3.. accent problem solved, thanks to Bernard's capable tutoring!)

Here is a chapter excerpt from Into the Cool, p 112:
Bénard's Hexagons
Consider Bénard's completely nonliving, honeycomb like "cells". Henri Bénard, a student at the University of Paris, had heard, in 1897, of polygonal flow structures arising in an unused photographic developing tray. After investigating convection, Bénard (1900) submitted his PhD thesis: "Les tourbillions cellulaires dans une nappe liquid" (Cellular eddies in a horizontal liquid layer) was the first in-depth study of these shapes, often hexagonal. With 100 degree C steam, Bénard heated, from below, sperm whale oil - spermaceti - in a brass apparatus. Spermaceti, a waxy substance at 20 degrees C, loosens into a viscous fluid at 46 degrees C. The system was an open one, with the upper surface of the oil in direct contact with the over-lying air. The air was at room temperature - 20 degrees C - meaning that Bénard had set up an 80 degree thermal gradient through a thin, one millimeter layer of whale oil. This was a steep gradient - equivalent to an 800-degree gradient across a mere centimeter.

Fueled by the gradient, symmetrical hexagons rose up out of the liquid chaos. Whereas conduction transfers heat without detectible organization, convection drives heat out in organized cycles. The cycles last forever if the gradient is maintained. They represent the natural ability, implicit in thermodynamic nature, of how best, under the given chemical or physical conditions, to solve the problem of reducing a gradient. The switch from conduction to convection shows that there is more than one way of doing the same gradient-reducing job. Here, as the temperature gradient increases, a new, more effective way to reduce it kicks in. It is as if the presence of a near-by gradient puts pressure, sometimes literally, on particles moving willy-nilly to come together, however fleetingly, into gradient-reducing "selves." A most important observation is that when these systems bifurcate from conduction to convection, from random to organized, the system's heat flow - its entropy production- goes up. Thus, the more organized system is also better at producing wastes.

From this thermodynamic point of view, that is why we are here: to even out gradients by producing entropy. Nice 'meaning of life', eh? :) Small wonder that religion doesn't want to go here.. not very placeboic... :angel:

Bénard watched more closely by sprinkling very fine metal flakes onto the spermaceti oil. Using this technique with time-lapse photography, convection can be visualized. Rising in the middle, the oil descends along the edges of each hexagonal convection cell.

Bénard tried to find the factors responsible for the forms he observed. Varying heat flux, temperature, and fluid depth, he found he could control the size of the cells and whether they appeared. Although it would not be described in theoretical detail until sixty years later, Bénard had discovered the critical temperature difference necessary for the appearance of his hexagons. Complex kinetic structures pop up only within gradients of the right steepness: the gradient must be steep enough, but not too steep - and other constraints must be in place, as in the story "Goldilocks and the Three Bears," where Goldilocks eats the "just right" (not too hot, not too cold) porridge. Once the cycles start, if they have access to new materials from the environment, they can grow. Moreover, complex systems may regulate gradients by reducing them, themn cutting back their operations when the gradient (as a result of being devoured by the complex system) temporarily decreases. The gradient is then free to grow back, renewing the cycle. This is incipient physiology.

When one looks at the almost perfect hexagonal Bénard cells it is hard to believe the almost magical nature of the processes. These cells are not chemical reactions or biological life but simple physical processes driven by a temperature gradient.
(snip)

Bénard's little experiment had big implications. Although the intermolecular distances of whale oil are on the order of 10 to the 8 centimeter, the liquid resolved into organized structures 0.1 centimeter in size: a simple heat gradient brings some hundred billion billion (10 to the 20) molecules into lockstep. They line up, show coherent motion. Such correlation among molecular trajectories and speeds are striking. Thay would neither appear nor be predicted in an isolated system. But these systems do not occur in an isolated system. They occur within the organizing confines of a gradient. Open systems naturally compute answers to the thermodynamic problem of how to come to equilibrium. If we do not see the organized context, the gradients around such structures, we will be mystified. The Bénard instability does not come from a vacuum or a creator. Rather it works out a previous improbability. It manifests in concentrated form the differentiation it helps destroy.

That's it for Bénard cells as discussed specifically.. they are brought into the book as a thread helping weave the tapestry of the entire book, which is a science-based explanation of why life exists on our planet. I can't help myself, I l-o-v-e this book!
Diane

[nari]

Diane

I think Gribbin is talking about a similar behaviour of cells in Deep Simplicity, but doesn't specify Benard cells. Gradients and organised movement, looking chaotic but quite ordered....

But I have the feeling that the ID proponents would say: this is an excellent way to 'prove' Design...this behaviour couldn't happen if the system was left to itself!! (my italics)

Nari

[Diane]

ID people will seize whatever they can to try to "prove" their point..
http://www.chem1.com/acad/sci/pseudosci.html
Which links to
http://www.talkorigins.org/origins/faqs-creationists.html

On the contrary, the explanation presented in Into the Cool supports the idea that life arose from the need of nature/the universe to try to reconcile a gradient by creating entropy. It's part of the solution. It's helping to bring about eventual entropy. No celestial designer needed, not any intelligence, just certain conditions. Not very poetic, or religiously comforting, I realize, but a wonderful mystery in and of itself.
Diane

[nari]

MAde a mistake with my previous statement - Gribbin does mention Benard and open systems....p 107-8.

Hadn't got to that bit yet when I posted.

I guess Brownian movement is along similar lines.


Quote: (p108) by Gribbin:

"..whenever you are confronted by the existence of order, and especially by the existence of life, and you are wondernig how it got to be like that, you can always say to yourself 'remember the hexagonal cells of the Benard convection...it's the same thing.' "

I am slow reading Gribbin at present as I keep being distracted by West Canada geology...

Nari

[bernard]

Hello All,

Diane,

Here is a way to type accents for a mac => Macintosh Accent codes (http://tlt.its.psu.edu/suggestions/international/accents/codemac.html)

and for all users:
Accents for your computer (http://tlt.its.psu.edu/suggestions/international/accents/index.html)

If I understand your point of view, cells were organized in this simple way? Membranes were formed by convection and because they are sites of natural convection, they are automatically devoted to exchanges.

But in a melting solution that contains oil and water there is also natural formation of cells.

Nature is ruled by some Sciences and Mathematics. Man tried to describe the behaviours of Nature with his Sciences. That does not means that our sciences are fortunately exact. The rules used by Nature are exact because they are applied everywhere.

[Diane]

Thanks for the pages on code and accents Bernard! I will go back and try to fix the spelling in my posts.

The thing to remember is that conditions on the planet were of a certain favorable sort back 4 billion years ago, and can't be duplicated, obviously, so there's no way to test the theory precisely... the IDers use this as a crowbar to try to lever their way into schools, after all a theory is a theory, right? Well, not exactly..;)

Nari, Brownian movement has fascinated me ever since I first learned about it.
Richard Feynman wrote a great article for scientific American a few years ago describing what he called "Brownian Ratchets"; he hypothesized small protein paddle boats in the cell moving along unidirectionally in spite of, in the face of all the water molecules pelting from on all sides.. he figured the proteins moved not in spite of the Brownian movement but that cells had adapted to it, had figured out a way of harnessing such spontaneous mechanical energy to help them do their work.

Diane

[bernard]

I will go back and try to fix the spelling in my posts.
It wasn't really necessary. It was just a computer tip...
Fine job, anyway. I changed the title to reflect the same...:angel:

[Diane]

I changed the title to reflect the same...
Thank you Bernard! I'm sure it must read a lot better now, to you. I thought I had fixed the title, but apparently it didn't fix when I did it. And now I have a whole new toolkit! I can make new symbols and spell non-English words correctly. Very cool.
Diane

[bernard]

I thought I had fixed the title, but apparently it didn't fix when I did it.

When you use the edit button you are editing only the message but not the title.
If you want to edit the title you must use the thread tools menu and choose edit thread. (edits only the title)

[Diane]

Thanks, I'll remember that for next time. :)
Diane

[Diane]

I found this link (http://www.intothecool.com/) today, about this very book, Into the Cool. It is extensive.. when one goes to the biographies of the authors, it takes one deep into a page called ScienceWriters... filled with treasure.

[bernard]

Many thanks for this golden mine!