COSMOS:
DESIGN AND ORDER
Many non-living physical and chemical systems have the capacity to generate order from chaos. This capacity is known as self-organization.
Self-organization has long been familiar in the transitions between states of matter - especially from liquid to solid. Water or water vapour are usually in a disordered homogeneous state because differences in temperature or density are evened out by continual motion and collision. Lower the temperature to freezing point, and crystals of incredible beauty and complexity begin to form: stars, hexagons, ferns. A similar miracle occurs when minerals crystallize.
Fluids can make a "phase transition" into more ordered states even while they are still fluid. The following experiment was first conducted in 1900 by Benard, with a tank which is taller than it wide, and with metal plates at top and bottom. Normally, liquid in the tank exists in a homogeneous state in which warmth is evenly distributed. If the tank is warmed gently through the bottom plate, then the heat spreads gradually, and forms a gradient, with the warmer liquid below and cooler liquid towards the top. These situations are states of stable equilibrium, or symmetry - that is, they are homogeneous in space and in time. There is no way of telling the difference between one place and another or one time and another.
However, if the bottom plate is heated to a certain threshold temperature, then the liquid re-organizes itself into a honeycomb of hexagonal convection cells known as Benard cells (see illustration). In these cells liquid is rising on one side, and descending on the other.(1) Convection cells are common in the earth's molten interior, in the atmosphere, and in the sun.
Phenomena of self-organization have been discovered in chemistry. Normally, different chemical reagents put together react until they reach an homogeneous equilibrium state called "detailed balance."
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