Civilizations have two important properties:
- they are dissipative systems, and
- they are creative systems.
A dissipative system is a physical system that maintains its state by turning resources from a usable form into an unusable waste form.
In terms of physics (specifically: thermodynamics) one can describe them as dynamic systems that produce entropy (i.e. they become more disordered) and they maintain their ordered state by transferring that entropy onto some resource that is thus changed from a low-entropy form to a high entropy form (for example: electric energy (low entropy) is turned into heat radiation (high entropy)).
Moreover, civilizations are creative systems. This means that they can invent new ways of interacting with each other and with their environment (i.e. by inventing new technologies). Specifically, civilizations can open up new ways of using new resources that could not be used before.
One could take this as a definition of a civilization: a civilization is a creative dissipative system.
Civilizations can grow. When a civilization grows, the size of the dissipative system that has to be maintained is increasing. As a result, the amount of entropy produced by the system increases. As a result, the amount of resources used and destroyed by the system is increasing. The system will also compete with other dissipative systems using the same resources.
(To be continued.)
(The picture is from http://commons.wikimedia.org/wiki/File:MidtownApril2014.jpg)