The cellular automatons we have seen so far are not physical models; that is, they are not intended to describe systems in the real world. But some CAs are intended as physical models.
In this chapter we consider a CA that models chemicals that diffuse (spread out) and react with each other, which is a process Alan Turing proposed to explain how some animal patterns develop.
And we’ll experiment with a CA that models percolation of liquid through porous material, like water through coffee grounds. This model is the first of several models that exhibit phase change behavior and fractal geometry, and we will explain what both of those mean.