Leonard J. Soltzberg Simmons College. Boston. MA 021 15 This symposium deals with a flourishing new area of scientific inquiry that spans all the sciences. Like the nroverbial elephant perceived so differently from differeit vantage points, self-organizing systems can be viewed from a variety of intellectual perspectives; nonequilibrium thermodynamics, catastrophe theory, nonlinearity, and deterministic chaos are all keywords that will lead one into the realm of selforganizing systems. Cutting across these different viewpoints and the various disciplines they represent is the surprising, often counterintuitive character of the phenomena of self-organization, which have been observed in such diverse contexts as chemical reactions, fluid flow, electronic circuits, laser light emission, and the behavior of biological rhythms. For the chemist, the oscillating reaction is the best-known example of self-organization, but this phenomenon is just one exhibit from what has been called a "zoo" of surprising phenomena. The most freouentlv referred-to archetvne of self-oreanization seems to'be ~ i n a r dconvection (lj.'when a shallow pool of liauid is heated from below. the onset of convection it a criticd temperature differencd between the lower and upper surface is accompanied hv the spontaneous annear.. a k e of either a conveckve honeycomb pattern or parallel convection rolls. Although the organized state has a lower entropy than its homog&eous antecedent, the throughput of energy that maintains the organization produces an overall increase in the entropy of the universe,-so the second law of thermodynamics remains inviolate. Turhulcnt flow of gases and liquids displays rirh spatial patterns resulting from self-organization of the moving fluid (21. At very high flow rates, fluid flow patterns take on a particularly curious variety of self-organization called chaos (see fiaure). Chaos is the asDect of self-organization that has received the most popular publicity (3).in studying chaos, we find that even simple driven far enough from . svstems, . equilibrium, can show very complicated, unpredictable hehavior. When a simple steady state gives way t o oscillation, we have self-organization in time. There can also he self-organization in space. in which a homoeeneous svstem soontaneously deveiops spatial patterns (4j.The co;er photo for this issue of the Journal shows snatial patterns that can be eenerated with the simplest of materials. Self-organization is not limited to the laboratory. The world around us is populated with structures and proresses which arise from self-organization. There is serious analysis which suggests that life on Earth could have originated spontaneously thrnugh the mechanism of self-organization (5). The relative unpredictahility of weather is due to the chaotic character of atmospheric dynamics. The following three papers in this symposium will serve the reader as a good introduction to self-organization in chemical svstems. Field law the rroundwork bv definine the essential concepts and terms. ~ o y e sshows how chemical reaction mechanisms can actually lead t o oscillatory hehavior. Finally, Epstein explains the pivotal role of flow-reactor studies, from which much of our present understanding of chemical self-organization has come. The readings suggested ~
-~
throughoutave been selected for accessibility to the novice in this field. Literature Clted
4. w i n f r & , ~ .T. ~ c i ~m:lW4, . ~ 0 ( 6 i82. , 5. Prigogine. I.; Nimlis, G.; Bab1ayantz.A. Phya Todor 1972,25111),23: 25112). 88
Dernonstratlons and Experlrnents
p&iods. A gas e~olutionoaeillstor (updated instructions and analysis in "A Simple DemonaVationofaGas EvalutionOscillator", Kaushik. S. M.;Yuan,Z.; Noyss,R. M.
J. Cham.Educ. 1986.63.761. Liesegangrings.Travelingoridatiodrldvetionwaveain en excitable medium (can be done on overhead projector). Chapter begin8 d t h s
simplined explanation of the mechanism of chemical a d l a t i o n . '"The Salt-Water Oscillat~r.~ Yoahikawa, K. with explanatory companion paper by R M. NoyesJ. Chsrn.Edue. 1989.66,205,207. An essilyconstructed hydrodynamicsystem, the behavior of which illustrates the role of flunuations in triggering millation around unstab1eatatea. "Far from Equilibrium-The Gaa Pendulum", Soltrbarg, L. J. J. Chem. Edue. 1988,63, 1015. Simple system illultrating s b r p transition from steady state to Limit cycle behavior st a liquid surface. Can be doneon an overhead projector for large elaasea. "Far hom Equilibrium-The Continuous-Flow Bottle", Solfeberg. L. J. J. Chem. Educ. 1987.64.147, Lab demonatration or exereiae she-g bitability. oscillstion between two unstable stationary states, chaos. Baaed on Field'a anelom with flow fmm beer bottle (Am. Sei. 1985.73,1421. "Far from Equilibrium-The Flashback Oscillator", S o l t z b g , L. J.; Bowher. M. M.; Cran.. D. M.; Pazar, S. S. J. C k m . Edua 1987, €4,1043.A dramatic lecture demonstration involvineoscihtorv m1asion ina small torch. 111uatratesb i s t a b i h . bifurca-
. . a1 onciaator, non1inesr solid-state oscillator, bi-
""
enfsolid-stateoseillatorj,spioningmsgnctlkickedrotator),mecbaniealDuffingoseil-
lator, bounung ball.
A draotic or "strange" a n r a c t a (the Roessler amactor). This projection of a three-dimensional p h a s e partran on t h e x-y plane s h o w s me bajectory of a Chaotic system. The tangled a p p e a r a n c e and me f a c t that magnification would reveal unlimited levels of additional detall m e a n that t h e behavior of the chaotic System never r e p e a t s itself. See Field, this issue, p. 189.
Volume 66 Number 3 March 1989
187
