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complicated type → chaos type”, through adjusting the parameter
ȹ
of rules
which describe the cellular automata. Thus, he proposed that the state of
complicated cellular automaton was between order (fixed-value type, periodic
type) and chaos, which he named “the edge of chaos”. Besides, it is not difficult
to find that, all the complicated phenomena of the nature, including life,
intelligence, and society, are at the edge between order and chaos in fact. If a
system needs to be complicated enough, it can neither be too ordered to become
ossified, nor be too chaotic to become disordered. So these systems should
skillfully keep the balance between the states of order and chaos.
15.8 Experimental Systems of Artificial Life
The goal of the research platforms of artificial life is to simulate the behavioral
characteristics of life using computers, which can form the life computing theory
finally. That is to say, the computer will not become the life body, but can be
regarded as a strong tool for studying artificial life. These platforms can display
some basic behavior of life, as well as some special behavior of life, such as
self-organizing, self-learning, etc. On the one hand, to study these platforms
facilitate explaining the overall picture of life and exploring the origin and
evolution of life. On the other hand, they also provide the new approaches for
biological research, and offer the beneficial tools for the research on artificial
life.
15.8.1
Digital life evolutionary model Tierra
In 1991, Thomas S. Ray, who is a biologist of the University of Oklahoma in
USA, implemented a computer simulation program called Tierra (in Spanish,
which means the earth). Thomas S. Ray researches on the evolution of tropical
rain forests and the ecological problems. In Tierra system, a virtual life world is
constituted by many digital living beings which are capable of self-replicating.
The evolving process goes on in the physical environment made up of the CPU
and the memory of computer. The time of CPU represents quantity, while the
space of memory represents resource. These digital living beings or
self-replicating programs change their evolution strategies repeatedly, and
compete to survive in Tierra world. Those programs, which obtain more time and
memory space, can leave more copies for the future generation. On the contrary,
those having less time and space will be eliminated. The running of this system
