## Some DefinitionsEdit

- Quiescent state
- A cell is in a quiescent state , if all cells in its neighborhood are the same quiescent state.

- Nilpotent rule (of order n)
- Any configuration evolves in at most steps into a configuration with all cells in any quiescent state .

- Idempotent configuration (of order n)
- A configuration that in at most steps evolves into a steady configuration (C^{t+1}=C^t).

- Idempotent rule
- A rule for which all configurations are idempotent.

- Superluminal configuration
- A configuration for which the phase speed is greater than the speed of light. The phase speed is the shift of the configuration per time.

- Glider

- Eather pattern
- A background for gliders, sometimes the most common background.