In Conway's Game of Life

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....

 and similar cellular automaton rules

Life-like cellular automaton

A cellular automaton is Life-like if it meets the following criteria:* The array of cells of the automaton has two dimensions....

, a spark is a small collection of live cells that appears at the edge of some larger pattern such as a spaceship or oscillator, then quickly dies off.

Sparks are commonly separated by some distance from the main body of the pattern -- the analogy is to an object "throwing off sparks" -- but the minimum requirement is a set of cells on the pattern boundary that are alive in one phase but dead in a later phase, and that are unaffected by other parts of the pattern (they would die in the same way if the rest of the pattern were removed). The converse is not necessarily true: for example, removing the spark in the accompanying illustration would destabilize the fumarole.

Sparks are an important way for components of a larger pattern to interact with each other; for instance, Niemiec describes the use of sparks formed by colliding gliders

Glider (Conway's Life)

The glider is a pattern that travels across the board in Conway's Game of Life. It was first discovered by Richard K. Guy in 1970, while John Conway's group was attempting to track the evolution of the R-pentomino. Gliders are the smallest spaceships, and they travel diagonally at a speed of c/4...

 as part of the synthesis of other life objects. Bell writes that lightweight, mediumweight, and heavyweight spaceships in Life are especially useful because they all have small sparks which may be used to perturb nearby puffer trains and stationary patterns as the spaceships pass by them.

External links

• Stephen Silver's Life Lexicon home page
• Spark, from Eric Weisstein's Treasure Trove of Life C.A.