Domino
| Domino | |||||||||
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| Pattern type | Spark | ||||||||
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| Number of cells | 2 | ||||||||
| Bounding box | 2 × 1 | ||||||||
| Static symmetry | D4_+2 | ||||||||
| Discovered by | John Conway | ||||||||
| Year of discovery | 1969 | ||||||||
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A domino is two cells connected orthogonally, and it is the only possible 2-cell polyomino. It almost exclusively appears as a spark, in which case it is referred to as a domino spark. A domino-shaped rotor is known as orthogonal on-off.
Domino sparks are arguably the most common type of spark of all, as they arise as the last living state of larger sparks such as the banana spark (and therefore cavity), V spark (and therefore the phi spark and line-of-six spark).
Production of dominoes as sparks
Domino sparks can either be produced parallel or perpendicular to an oscillator's bounding box. In order to be considered a true domino sparker, the spark cannot be a descendant of a higher spark in the same place such as a V spark.
Parallel sparkers
Parallel domino sparkers are the most common type of domino sparker. The heavyweight spaceship is a small spaceship which produces domino belly sparks, which can pose useful for deleting many small objects produced by puffers such as blinkers, blocks and gliders, as well as perturbing larger reactions. The "heavyweight" namesake is carried on to the stationary oscillators heavyweight emulator and heavyweight volcano, which produce domino sparks in much the same way at periods 4 and 5, respectively.
Other important domino sparkers include the pentadecathlon and Merzenich's p31. The fumarole also produces a domino which is usable for perturbation, however the existence of the domino is integral to the oscillator's continued evolution and as such must be used more carefully than more distant sparkers like those mentioned previously.
Perpendicular sparkers
- Main article: Pipsquirter
Oscillators which provide domino sparks oriented perpendicularly to the bounding box are referred to as pipsquirters and are documented on a separate page. Most of the useful pipsquirters have been found by Noam Elkies, including p6 pipsquirter and p7 pipsquirter. They are a type of functional dot sparker.
Much like the T-noses, the edge of the domino farthest from the oscillator must be off for all other cycles of the oscillator to qualify as a pipsquirter, as said cell being present during any other generations has the capability to be disruptive to catalysis. As such, patterns such as a p29 shuttle, despite producing a perpendicular domino spark, have it be generated through dying debris in the same place.
Use in oscillators
There exist two wicks which can be constructed solely from disjoint dominoes. A diagonal spacing of dominoes will consist of dominoes in all phases, whereas a more knightwise arrangement will be composed of sparse dots in every other generation. Both wicks can be stabilised by period-2 components.
| Two possible period-2 wicks composed entirely of dominoes (click above to open LifeViewer) RLE: here Plaintext: here |
The squaredance agar is entirely comprised of dominoes in all phases.
In other rules
In Just Friends (B2-a/S12) and similar S1e rules such as Flock, the domino is a still life.
In Logic Rule (B2ae/S) and similar B2a rules, the domino is a lightspeed one-dimensional parity rule replicator.
See also
- Domino sparkers (category)