BioWall

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Life
The second experiment, named after the famous "Game of Life" invented by John Conway, involves a colony of molecules. Each molecule's existence depends on the number of living neighbours it has. The visitor can give life to the molecules and observe the evolution of the colony.

Life : When complexity suddenly appears from nothingness, or the surprises of emergent behaviour

Life is complexity. The way a spider weaves its web or an ant colony builds its nest suggests that these creatures are intelligent. They are nothing of the sort. Biologists have demonstrated that, by blindly following basic rules that have been gradually developed through natural selection, every animal behaves in ways which are sometimes extremely complex.
In the world and language of computer science, the appearance on the screen of complex motifs generated by simple rules is known as "emergent behaviour". In the Life experiment, each BioWall molecule is either dead (dark) or alive (lit up). Every second, each molecule gains a new status (either dead or alive), which depends solely on the number of living molecules within its immediate vicinity. A colony of living molecules then forms a motif which either becomes distorted with time, grows and aggressively colonizes the space or, on the contrary, gradually disappears. Visitors can help this artificial population to survive by pressing a dead molecule, thus reviving it and changing the colony's collective behaviour at local level.

Instructions for use
The current BioWall prototype has a surface of 2,000 molecules, each one either dead (dark) or alive (lit up). Whether a molecule survives depends only on the status of its eight immediate neighbours (figure 1) and on the following rules:

if the number of living neighbours is too small (zero or one), the molecule dies of isolation and its future status is "dead";
if a molecule has exactly two living neighbours, it survives and its current status, either "dead" or "alive", is unchanged;
if a molecule has exactly three living neighbours, a new molecule is born and its status is "alive";
if a molecule has too many living neighbours (four or more), it dies of overpopulation and its status is "dead".

Figure 1: Rules of the "Game of Life" (red = alive, black = dead).

Molecule colonies
You will notice that some motifs are stable, eg the square (figure 2). Some, such as the blinker, form a cycle, while others move around without changing shape, eg the glider.

Figure 2: Various motifs from the "Game of Life".

Behind the scenes
The emergence of complex motifs from simple rules is a characteristic of very popular computer structures known as "cellular automata". Mathematician John Conway devised the "Game of Life" in accordance with the aforementioned rules.

For further information

E.R. Berlekamp, J.H. Conway, R.K. Guy: Winning Ways for your Mathematical Plays. Vol.2: Games in Particular. Academic Press, London, 1985.

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