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Self Organising Systems

Pattern Formation in Nature

What do ice wedge networks, meandering rivers, sorted patterned ground, beach cusps, sand dunes, and humans have in common?

All are examples of complexity emerging over time from stochastic processes that are selected for via feedback mechansisms.

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Dynamic Self Organisation of Ferrofluid

In this experiment Ferrofluid shows a continuos cycle of diffusion and concentration. Some thinner is added to a drop of ferrofluid which is on a dish over a permanent magnet. When spreading out, the thinner takes a low concentration of ferrofluid with it, too low to be bound to the magnet.

The flow is limited by the wetting border of the spot. Increased evaporation increases the flow towards the border. At the end of its way, the concentration of the fluid is increased by evaporation, in a circle around the centre.

At the according level of concentration the fluid on the circle joins to Rosensweig peaks, dots of further increased concentration. These peaks are sufficiently attracted to move back against the continuos outward flow, leaving a track of ferrofluid behind.

Near the centre the peaks are repelled by the centre material which has the same magnetic orientation. In the flowing environment, with much thinner, the Rosensweig peaks "tunnel" to the centre, while the rest of the trace is repelled and partly washed away.

With decreasing thinner and higher concentration, peaks are formed in the centre. The material is regrouped with new material returning to the centre. At the end the peaks at the centre stay separate and more peaks are joining.

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Jimmy Wales: How a ragtag band created Wikipedia

Jimmy Wales recalls how he assembled "a ragtag band of volunteers," gave them tools for collaborating and created Wikipedia, the self-organizing, self-correcting, never-finished online encyclopedia.

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