Ring-Around-a-Rosie
In this case, the turtles aren't drawing a circle; they are a circle. Two simple rules govern the interactions among the turtles. The circle is not mentioned explicitly in the rules; it emerges from them. This circle is like a two-dimensional balloon. The particles in a balloon are pushed apart by the air inside the balloon. But because the balloon is made of an elastic material, the balloon particles try to stay as close to one another as possible. In other words, the balloon tries to minimize its surface area. In two dimensions, the resulting shape is a circle. In three dimensions, the shape that minimizes surface area for a given volume is a sphere. That's why soap bubbles assume a spherical shape. Go to the next page or the previous page or the contents page. Mitchel Resnick and Brian Silverman Epistemology and Learning Group MIT Media Laboratory Last modified: 2/4/96
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