glider gun

Way back when, when John Conway's game of life was first introduced in Scientific American's Mathematical Recreations column, it was introduced with a challenge. Conway suggested that it was impossible to have a bounded initial set of live cells which would grow without bound. After much mucking about on computer time which was expensive in the early 1970s, a group of Honeywell developed the glider gun, which is a large-ish collection of a few dozen live cells which spits out a glider every so often. This satisfied the ``finite initial size'' and unboundedness criteria, since (with sufficient memory and time), the seed of a glider gun could send out an arbitrary number of gliders (which wouldn't hit anything, and so wouldn't die). Conway coughed up the bounty, I think, which amounted to about $50 U.S.

Gosper's glider gun is the first known gun, and and the first known finite pattern with unbounded growth (termed infinite growth). It was discovered by Bill Gosper in November 1970. To date, it remains by far the smallest known gun, though numerous other guns have been found (many by Gosper).

        ........................O...........
        ......................O.O...........
        ............OO......OO............OO
        ...........O...O....OO............OO
        OO........O.....O...OO..............
        OO........O...O.OO....O.O...........
        ..........O.....O.......O...........
        ...........O...O....................
        ............OO......................

Technically, this pattern is a member of the class of blinkers within Life. The period of the glider gun is 30 - every 30 iterations it returns to the initial state with one exception - the creation of a glider.

Within the terminology of life enthusiasts, the gun is made of a two queen bee shuttles (shown above in various stages of movement). When they collide just right the debris form a glider. The queen bee shuttle is the basis for all true period 30 glider guns.

There are faster period glider producers though none are as elegant as the original. A period 15 glider gun was constructed however it comprises of 542 cells (much larger than can reasonably be shown within the confines of E2), though these are pseudo guns that have multiple guns that oscillate and produce gliders in the space left between gliders of other guns.