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Genetic Laws. Computer specialists everywhere have developed such a mania for Life that millions of dollars in illicit computer time may have already been wasted by the game's growing number of addicts. This week Life reached maturity when a paper discussing its problems and potential was on the agenda at a major computer conference in Washington, D.C.
Invented in 1970 by a Cambridge University mathematician named John Horton Conway and popularized by Mathematical Games Expert Martin Gardner in the pages of Scientific American, Life is a kind of solitaire played by one person on a checkerboard or graph paper, or indeed any gridlike field that contains adjoining squares of equal size. The playing pieces, or counters, are chips (any number) that are placed at random on squares across the board. They are then manipulated by what Conway calls his three "genetic laws"—for birth, death and survival. Under the Law of Birth, each empty square adjoined by three—no more, no fewer—counters on neighboring squares will yield a new counter in the next move, or "generation." Thus configuration 1 becomes 2. The Law of Death is more complex. Each counter with only one piece, or none, ajacent to it dies of isolation and is removed. Thus 3 becomes 4 and in the next generation 5. In addition, each counter with four or more immediate neighbors dies of overpopulation, as in 6, which becomes 7.* Under the Law of Survival, where conditions do not lead to either birth or death, each counter with two or three neighbors simply survives, as in configuration 8.
When all of the laws have been applied to the first placement of the chips, the move, or generation, is completed. Then the next generation applies the laws of Life to the newly formed pattern. The game goes on through a succession of generations until all of the pieces die off, a stable pattern is reached, or the counters can move no further because of limits of the board.
Though Life is rewarding enough when played manually, it takes on an added dimension when played on the computer, which causes the varied patterns to unfold much more rapidly. The computer can either place the counters at random or follow the operator's placement instructions. Readily programmed to obey Life's rules, it can then perform the necessary calculations in a flash and display the changing patterns on a cathode ray tube, providing a remarkable kaleidoscopic show. Sometimes the counters quickly settle into what Conway calls "still lifes" — stable, unchanging figures, including those known in the game's already rich jargon as "bee hives," 9, "snakes," 10 or "long ships," 11 . At other times the patterns may pulse, like the "traffic lights," which flip-flop between patterns 12 and 13. Other figures, including "gliders" and "spaceships," actually move across the board. Some seem to leave clouds of debris behind in their travels ("puffer trains") or climb in a diagonal line ("fuses") and give off clusters of "sparks." One of the more unusual shapes to emerge in Life's repertory of patterns is the "Cheshire cat," 1 4. It gradually changes and shrinks until, after six genertions, only the "grin," 15, is left. Finally it reaches a stable pattern: a "paw print," 1 6.