Brian's Brain is a

cellular automaton A cellular automaton (pl. cellular automata, abbrev. CA) is a discrete model of computation studied in automata theory. Cellular automata are also called cellular spaces, tessellation automata, homogeneous structures, cellular structures, tess ...

devised by

Brian Silverman Brian Silverman is a Canadian computer scientist, the creator of many programming environments for children,Seeds A seed is an Plant embryogenesis, embryonic plant enclosed in a testa (botany), protective outer covering, along with a food reserve. The formation of the seed is a part of the process of reproduction in seed plants, the spermatophytes, includ ...

rule.

Rules

Brian's Brain consists of an infinite two-dimensional grid of cells, but unlike Seeds, each cell may be in one of three states: on, dying, or off. Each cell is considered to have eight neighbors (the

Moore neighborhood In cellular automata, the Moore neighborhood is defined on a two-dimensional square lattice and is composed of a central cell and the eight cells that surround it. Name The neighborhood is named after Edward F. Moore, a pioneer of cellular a ...

), as in Seeds and

Conway's Game of Life The Game of Life, also known simply as Life, is a cellular automaton devised by the British mathematician John Horton Conway in 1970. It is a zero-player game, meaning that its evolution is determined by its initial state, requiring no furt ...

. In each time step, a cell turns on if it was off but had exactly two neighbors that were on, just like the birth rule for Seeds. All cells that were "on" go into the "dying" state, which is not counted as an "on" cell in the neighbor count, and prevents any cell from being born there. Cells that were in the dying state go into the off state.

Behavior

Because of the cellular automaton's name, some websites compare the automaton to a brain and each of its cells to a neuron, which can be in three different states: ready (off), firing (on), and refractory (dying). The "dying state" cells tend to lead to directional movement, so almost every pattern in Brian's Brain is a spaceship. Many spaceships are rakes, which emit other spaceships. Another result is that many Brian's Brain patterns will explode messily and chaotically, and often will result in or contain great diagonal waves of on and dying cells. For example, a 2×2 block of on cells will result in an ever-expanding diamond consisting of four diagonal waves that move across the plane at the pattern's

speed of light The speed of light in vacuum, commonly denoted , is a universal physical constant that is important in many areas of physics. The speed of light is exactly equal to ). According to the special theory of relativity, is the upper limit fo ...

. Nevertheless,

oscillators Oscillation is the repetitive or periodic variation, typically in time, of some measure about a central value (often a point of equilibrium) or between two or more different states. Familiar examples of oscillation include a swinging pendulum ...

have been constructed in Brian's Brain. An example has just four on cells and four dying cells, and oscillates with period 3.

References

*{{cite web , last = Resnick , first = Mitchel , authorlink = Mitchel Resnick , author2 = Silverman, Brian , title = Exploring Emergence: The Brain Rules , publisher = MIT Media Laboratory, Lifelong Kindergarten Group , date = 1996-02-04 , url = http://llk.media.mit.edu/projects/emergence/mutants.html , accessdate = 2008-12-15 , url-status = dead , archiveurl = https://web.archive.org/web/20081223050254/http://llk.media.mit.edu/projects/emergence/mutants.html , archivedate = 2008-12-23 Cellular automaton rules