The background for the Computer Science web pages depicts an example of a simple one- dimensional cellular automaton (CA) evolved over time to produce a 2D image. 

Cellular automata (CA) are computational systems consisting of a (hypothetically infinite) grid of cells, each of which can exist in any of several predefined states. Grids may be one, two, or any number of dimension. State changes to a cell are based exclusively on its current state and the current state of its neighbors (over some specified neighborhood) based on a collection of predefined rules. All cells are updated in parallel (or such an update is at least simulated).

For the current background, any given row of small squares represent the cells in the 1D CA at some point in time and the row immediately below represents the CA at the next time step when subjected to a specified set of rules. Cells may exist in one of two states (colored or not, which can be represented numerically as 0 or 1). The neighborhood for a cell is the cell itself and the cell to its immediate left and its immediate right. This means that the new state of a cell depends upon its current state and the current state of the two cells adjacent to it. Since there are therefore three cells responsible for producing the new state for any given cell, there are 8 parent combinations (000, 001, …, 111). Because the new state can only be 0 or 1, there are thus 2⁸ = 256 possible rule sets (e.g. 000=>0/1, 001=>0/1, …, 111=>0/1 where the child occupies the center position). Consequently, it takes three parents to produce a child under this scenario (and you thought real life was getting weird!). As previously mentioned, successive generations are displayed one under the other to create the 2D effect. The current background for the Computer Science web pages is generated from only one of the 256 possible rule sets. Not all of the rule sets produce such interesting patterns. Note that, although the pattern is regular, it does not repeat in its details.

The interesting thing to note is that this basic process can produce a rather intricate result. The name for this effect is “emergence,” which is the concept that complex properties can arise from a simple set of rules. Researchers in the Computer Science field called Artificial Life have observed that patterns similar to the ones shown here can be found in nature and speculate that a variety of apparently complex biological (and other phenomena) may actually be describable in terms of a simple set of rules. Finding such rules is one of the challenges scientists enjoy and this is a great example of one of many potential interfaces between Computer Science and the other scientific disciplines.