This week's featured article
|A still life is a pattern that does not change from one generation to the next, and thus may be thought of as an oscillator with period 1. Still lifes are sometimes assumed to be finite and non-empty. The two main subgroups of still lifes are strict still lifes and pseudo still lifes. In some contexts, the term "still life" may refer to strict still lifes.
A strict still life is a still life that is either connected (i.e., has no islands), or is such that removing one or more its islands destroys the stability of the pattern. For example, beehive with tail is a strict still life because it is connected, and table on table is a strict still life because neither of the tables are stable by themselves.
A pseudo still life consists of two or more islands which can be partitioned (either individually or as sets) into non-interacting subpatterns which are by themselves each still lifes. Furthermore, there must be at least one dead cell that has more than three alive neighbours in the overall pattern but has less than three alive neighbours in the subpatterns. This final restriction removes patterns such as bakery, blockade and fleet from consideration, as the islands are not "almost touching".
In the news
- Jan. 13: Matthias Merzenich sets up a new "manually distributed" search (table here), to find out whether a symmetric c/8 spaceship exists at width 19.
- Jan. 9: Nathaniel Johnston completes a long-running enumeration of 34-bit still lifes, finding 35,422,864,104 strict still lifes with 34 bits, and 41,058,173,683 pseudo still lifes with the same bit count, including 26 triple pseudo still lifes.
- Jan. 5: A Rules namespace update on the LifeWiki allows LifeViewer to display in-browser many patterns using rule tables and trees, which previously couldn't be simulated without copying them into Golly.
- Dec. 30: Andrew J. Wade uses his search program, life_slice_ship_search, to find the second elementary 2c/7 spaceship, scholar.
- Dec. 29: Goldtiger997 synthesises a variant of David Hilbert.
- Dec. 28: Martin Grant finds a counterexample to a 22-year old conjecture by Dean Hickerson about still-life finitization.
- Dec. 25: Pavgran assembles Slavic , a quadratic-growth pattern similar to Hydra that doesn't need a central gun.
- Dec. 9: Goldtiger997 reduces the cost of the spider synthesis by over 100 gliders.
- Dec. 1: Martin Grant discovers a new period-49 oscillator based on a partial result by Jason Summers.
|The LifeWiki contains one of the most comprehensive catalogues of patterns available on the internet. Within it you will find:
Did you know...
- ... that there are no known direct reflectors for lightspeed wire signals, or for signals in 2c/3 wires, but that very large reflectors for these signals can be constructed using stable or periodic circuitry?
- ... that 24 ten-cell patterns exhibit infinite growth, with 17 unique pattern types, but that it has been proven that no nine-cell pattern exhibits infinite growth?
- ... that all still lifes up to 18 bits have a known glider synthesis, but it is still not known whether all still lifes are synthesizable?
- ... that the French kiss remained without a glider synthesis until 2013?
- ... that Adam P. Goucher's distributed Catagolue soup-search project, started in February 2015, has already tested more random soups than any previous such project, and has contributed to the reduction of many glider construction recipes?
- ... that with the appearance of the 0E0P metacell, the number of periods for which strict volatility 1 oscillators were known went from 12 to infinity?
- ... that Copperhead is not only the first c/10 orthogonal spaceship ever found, but also remarkably compact for a pattern not discovered until 2016?
- ... that loafer is the fifth smallest non-flotilla spaceship, but was discovered 43 years after the four spaceships smaller than it?
- ... that despite being the fourth smallest non-flotilla orthogonal spaceship, loafer has never appeared from a single randomly generated soup?
- ... that all known glider eaters take at least four ticks to recover to their original state after eating a glider?