venerdì 10 aprile 2009

chinese cuisine and biological fractals

 Every mathematician knows that snowflakes are a kind of fractal (here there is a well-known snowflake-like fractal), but not so many of them know that also living creatures give rise to snowflake fractals. 

 Indeed, reaction-diffusion equations give rise to fractals through their bifurcations. The most famous of those fractals are the ones given by bacterial colony growth: see also this beautiful gallery (ok, the colours are artificial, but they do look very nice also in black and white).
 This is how they are made, basically: take a Petri-dish, put in its center a point-like colony of bacteria, and let it evolve. The colony will split, and the "daughters" will create some bifurcating paths through the petri dish, giving rise to a snowflake-like pattern.

Before today I would think these snowflakes are, however, quite artificial (where do you find a point-like colony of bacteria put in a "sterile" medium like a Petri dish, in nature??) .. however here is an example!!! 
 It is a chinese food ( the "century egg") made of an egg, which is put in a clay coat for a long period. Bacteria penetrate through some pores of the egg crust, and form exactly the snowflake patterns seen in a lab.. very amazing!

here  are other photos of century eggs 
here  with similar patterns.. I could not 
here  resist looking for other images!
here  Happy easter to you!! ^.^