Day and Night 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 ...

rule in the same family as

Game of Life ''The Game of Life'', also known as ''Life'', is an 1860 board game by Milton Bradley. Game of Life also often refers to: *Conway's Game of Life, in mathematics, a cellular automaton Game of Life or The Game of Life may also refer to: Games * ' ...

. It is defined by rule notation B3678/S34678, meaning that a dead cell becomes live (is born) if it has 3, 6, 7, or 8 live neighbors, and a live cell remains alive (survives) if it has 3, 4, 6, 7, or 8 live neighbors, out of the eight neighbors in 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 ...

. It was invented and named by Nathan Thompson in 1997, and investigated extensively by David I. Bell. The rule is given the name "Day & Night" because its ''on'' and ''off'' states are symmetric: if all the cells in the Universe are inverted, the future states are the inversions of the future states of the original pattern. A pattern in which the entire universe consists of ''off'' cells except for finitely many ''on'' cells can equivalently be represented by a pattern in which the whole universe is covered in ''on'' cells except for finitely many ''off'' cells in congruent locations. Although the detailed evolution of this cellular automaton is very different from Conway's Game of Life, it exhibits complex behavior similar to that rule: there are many known small ''

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 ...

'' and '' spaceships'', and ''

guns A gun is a ranged weapon designed to use a shooting tube (gun barrel) to launch projectiles. The projectiles are typically solid, but can also be pressurized liquid (e.g. in water guns/cannons, spray guns for painting or pressure washing, ...

'' formed by combining oscillators in such a way that they periodically emit spaceships of various types.

References

* . See also Bell'
Day & Night pattern archive
{{DEFAULTSORT:Day and Night Cellular automaton rules