I have discovered an interesting cellular automaton. This automaton is defined on the edges of a square grid: each edge has six neighbors, three at each end. Like Conway's Life, each edge can be in one of two states: on or off; and its state in the next generation depends only on the current state of the edge itself and how many of its neighbors are on. The rule for this automaton is that an edge that was off becomes on when exactly two of its neighbors are on; and an edge that was on remains on only if exactly one of its neighbors is on. Or, more simply put, an edge is on in the next generation iff exactly two of the edges in its seven edge neighborhood - including the edge itself - are on. Small patterns with this automaton are a bit more fragile than in Life. For example, a row of two edges (you'll need a fixed-width font to properly view these pictures): -.- goes in the next step to _|_ .|. which then dies out. The alternator is a simple period 2 pattern, alternating between |.| and ._ ._ It is difficult to construct stable patterns, as they must be composed of pairs of lines, with their growth blocked off. I believe the smallest is ...|..... _|.|.|_.. .._....._ ...|.|.|. .....|... However, the really interesting part is what happens when we start with 3 sides of a square: ..._ ..|_ This goes in the next generation to: ._|_. ._._| ..|.. which looks like an airplane (which is what I call this pattern). The next generation it seems to fall apart: ....|_ |...._ ....|. but the next generation is ..._|_. ..._._| ....|.. and it flies! Can anyone find other interesting patterns? It would be especially interesting if someone can find an "airplane gun", which generates airplanes at regular intervals. Any other patterns that move, and any other periodic patterns - especially with a period greater than two - would also be of interest. Franklin T. Adams-Watters P.S. Does anyone know of a forum where cellular automata are being actively discussed? I see that Yahoo has a group, but it has been inactive for several years. ________________________________________________________________________ Check Out the new free AIM(R) Mail -- 2 GB of storage and industry-leading spam and email virus protection.