x66 is a period-4 spaceship with speed c/2 that was found by Hartmut Holzwart in July 1992. One of the symmetric halves can alternatively be escorted by a heavyweight spaceship. Its name refers to the fact that every cell (alive or dead) has at most 6 live neighbours (in contrast to spaceships based on lightweight spaceships, middleweight spaceships, or heavyweight spaceships). In fact, this spaceship was found via a search with this restriction. From this follows that the spaceship is stable also in Life-like rules allowing birth or survival for a cell with 7 or 8 neighbors.
x66 was first synthesized on January 11, 2015, requiring 162 gliders.[1] After the emergence of this spaceship in a symmetrical soup on March 8, 2015,[2] this was drastically reduced to 13 gliders,[3] and then to 12 gliders in 2018.[4]
Half of x66 can be supported by a heavyweight spaceship. A 9-glider synthesis for this variant was found on March 8, 2015, from the same reaction used to create the full x66 in 13 gliders.[5] Since the heavyweight spaceship is glide symmetric, it can support two halves at once, or one half alongside a sidecar.
Image gallery
 Half of x66 supported by a heavyweight spaceship RLE: here |
See also
References
External links
- 34P4H2V0.23 at Heinrich Koenig's Game of Life Object Catalogs
