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:S Usually means big S, but may sometimes mean paperclip.

:sailboat (p16) A boat hassled by a Kok's galaxy, a figure-8 and two eater3s. Found by Robert Wainwright in June 1984.

	........O...........O........
	.......O.O.........O.O.......
	........O...........O........
	.............................
	......OOOOO.......OOOOO......
	.....O....O.......O....O.....
	....O..O.............O..O....
	.O..O.OO.............OO.O..O.
	O.O.O.....O.......O.....O.O.O
	.O..O....O.O.....O.O....O..O.
	....OO..O..O.....O..O..OO....
	.........OO.......OO.........
	.............OO..............
	.............O.O.............
	........O..O..O..............
	.......O.....................
	.....OO..........OOO.........
	..O......OO.O....OOO.........
	.....O...O..O....OOO.........
	.....OOO.O...O......OOO......
	..O...........O.....OOO......
	...O...O.OOO........OOO......
	....O..O...O.................
	....O.OO......O..............
	..........OO.................
	.........O...................
	.....O..O....................

:salvo A collection of spaceships, usually gliders, all traveling in the same direction. Any valid glider construction recipe can be partitioned into no more than four salvos. Compare flotilla. In contrast with a convoy, the spaceships in a salvo are usually consumed by the reactions that they cause. Simple examples include block pusher and block pull.

Salvos may be slow or synchronized. The following partially synchronized three-glider salvo produces an LWSS from a block.

	OO........
	OO........
	..........
	..........
	OOO.......
	O.........
	.O........
	..........
	.......OOO
	.......O..
	........O.
	..........
	..........
	..........
	..........
	..........
	..........
	.......OOO
	.......O..
	........O.
The above is a synchronized salvo and not a slow salvo, because the second glider must follow the first with the exact separation shown. The third glider can be considered to be a slow glider, because it will still delete the temporary loaf no matter how many ticks it is delayed. The slow glider construction entry includes an example of a true slow salvo.

:sawtooth Any finite pattern whose population grows without bound but does not tend to infinity. (In other words, the population reaches new heights infinitely often, but also infinitely often returns to some fixed value.) Conway's preferred plural is "sawteeth".

The first sawtooth was constructed by Dean Hickerson in April 1991. The current smallest known sawtooth was found by a conwaylife.com forum user with the online handle 'thunk'. It has a bounding box of 74×60, and is the smallest known sawtooth in terms of its minimum repeating population of 177 cells. The following variant has a higher repeating population of 195 and an optimized bounding box of 62×56:

	.....................................................OO.O.....
	.....................................................O.OO.....
	..............................................................
	...........OO.................................................
	...........OO.................................................
	..............................................................
	..............................................................
	..............OO............................OO.......OO.....OO
	....OO........OO.....................................OO.....OO
	.....O.....................................O.O................
	....O......OO............................O..............OO....
	....OO.....OO........................OO.O.OO............OO....
	......................................O.OO....................
	.......................................O......................
	..............................................................
	.................................OO...........................
	........OO.......................OO...........................
	........O.O...................................................
	........O....................OO.....OO........................
	.............................OO.....OO........................
	..............................................................
	..............................................................
	..............................................................
	.....................OOO......................................
	.....................O..O.....................................
	.....................O.OO.....................................
	..............................................................
	..............................................................
	..............................................................
	....................OO............O.........O.................
	....................O..O..........O.O.....OOO.................
	..OOOO...............OOO..........OO.....O....................
	OO....OO.................................OO...................
	OO.....O......................................................
	..OO.O.O..............OO......................................
	.......O..............OO......................................
	...O...O..........................O....O......................
	...O....O.......................OO.....O......................
	.....OOO...O.....................OO...O.O.....................
	.....OO....O.........................OO.OO....................
	...........OO.......................O.....O...................
	.............O.........................O......................
	.............OOO....................OO...OO...................
	..............................................................
	..............................................................
	................O.....................O.......................
	...............O.OOOOO................O.......................
	..............OO.....O...............O........................
	..............OO...O..O.......................................
	......................O.......................................
	................OO.O..O................OO.....................
	...................O..O................OO.....................
	....................OO........................................
	....................OO.....O....O.............................
	.........................OO.OOOO.OO...........................
	...........................O....O.............................
Patterns combining a fast puffer with a slower spaceship have also been constructed (see moving sawtooth). See also tractor beam.

:SBM = sliding block memory

:Schick engine (c/2 orthogonally, p12) This spaceship, found by Paul Schick in 1972, produces a large spark (the 15 live cells at the rear in the phase shown below) which can be perturbed by other c/2 spaceships to form a variety of puffers. See blinker ship for an example perturbation of the spark. The diagram below shows the smallest form of the Schick engine, using two LWSS. It is also possible to use two MWSSes or two HWSSes, or even an LWSS and an HWSS.

	OOOO..............
	O...O.........O...
	O...........OO....
	.O..O..OO.....OOO.
	......OOO......OOO
	.O..O..OO.....OOO.
	O...........OO....
	O...O.........O...
	OOOO..............

:Schick ship = Schick engine

:scorpion (p1)

	...O...
	.OOO...
	O...OO.
	O.O.O.O
	.OO.O.O
	.....O.

:scrubber (p2) Found in 1971.

	....O......
	..OOO......
	.O.........
	.O..OOO....
	OO.O...O...
	...O...O...
	...O...O.OO
	....OOO..O.
	.........O.
	......OOO..
	......O....

:SE = switch engine

:seal (c/6 diagonally, p6) The first diagonal c/6 spaceship, found by Nicolay Beluchenko in September 2005.

	...O..OO..........................
	.OOO.O.O.O........................
	.O..OOO..OO.......................
	O..OOOOOO.O.OOO...................
	.O..OOO.O.OOOOO...................
	......O.O.O.O.....................
	O.O...O.O.OOOOO...................
	O..O.O..O.OO...O..................
	...O..OO.......OOO................
	.O...OOOOO.OOO..OO................
	....O.........O...................
	..O.O.........O...................
	....OO.OOOOO...O..................
	......O.OOO..O.....OO.............
	......O..O...O.OOO.OO.............
	........OO...OOO.O..O...O.........
	........OO....OO.OOOO...OOO.......
	...................O.O..O.........
	.............O.O.....OO..OO.......
	.............O..O.....O.OOO.....O.
	.............O...O....OO..O...O..O
	...............OOO.....OO........O
	...............O.O..O..O.....OO..O
	.................O..OO.OO.O..O....
	................O.......O.O.......
	.................O...OOOO.........
	..................O...O...........
	..................................
	.......................O..........
	......................O.O.........
	.....................OO...........
	.....................O.O..........
	.....................OO...........
	.......................O..........
	......................O...........

:search program A computer program or script which automates the search for Life objects having certain desired properties. These are used because the difficulty of finding previously unknown Life objects now commonly exceeds the patience, speed, and accuracy of humans. Various types of search programs are used for finding objects such as spaceships, oscillators, drifters, catalysts, soups, Gardens of Eden, and slow salvos.

Some search programs generate partial results as they are running, so even if they don't complete successfully, something of use might still be salvaged from the run.

Example search programs are dr, lifesrc, gfind, and Bellman.

There are other types of programs which don't perform searches as such, but instead perform large constructions. These are used to correctly complete very complicated objects such as the Caterpillar, Gemini, Caterloopillar, and universal constructor-based spaceships such as the Demonoids and Orthogonoid.

:second glider domain The second glider domain of an edge shooter is the set of displacements (in space and time, relative to the glider stream emitted by the edge shooter) that a glider stream may have without interfering with the edge shooter. This is useful to know, because edge shooters are often used to generate glider streams very close to other glider streams.

:second natural glider The glider produced at T=72 during the evolution of a Herschel. This is the common edge-shooting glider output used in the NW31 converter and several other converter variants.

:seed A constellation of still lifes and/or oscillators, which can be converted into another Life object when it is struck by one or more gliders. Usually the resulting object is a rare still life or spaceship, more complex than the original constellation. Spartan single-glider (1G) seeds are more commonly seen than multi-glider seeds, because a Spartan 1G seed can be readily constructed and triggered using a slow salvo. See also freeze-dried. For example, the following is a 14sL 1G seed for a c/7 loafer spaceship.

	...................................O..........
	..................................O...........
	..................................OOO.........
	.............OO...............................
	..............O...............................
	..............O.O.............................
	...............OO.............................
	..............................................
	...O..........................................
	..O.O.........................................
	.O.O..........................................
	.OO...........................................
	..............OO..............................
	.............O.O..............................
	.............OO...............................
	..............................................
	..............................................
	..............................................
	....................OO........................
	...................O.O........................
	..........O.........O.........................
	.........O.O....O.............................
	..........OO...O.O............................
	..............O.O.............................
	..............OO..............................
	..............................................
	.............................................O
	.........................OO................OOO
	....................OO...OO...............O...
	...................O..O...................OO..
	.O.................O..O.......................
	O.O.................OO........................
	.OO...........................................
	..............................................
	..............................................
	..............................................
	.....................OO.......................
	.....................O.O....OO................
	......................O.....O.O...............
	.............................OO...............
	.................................OO...........
	.................................OO...........
	..............................................
	..............................................
	......................OO......................
	.....................O..O.....................
	.....................O..O.....................
	......................OO......................

:Seeds of Destruction Game An interactive search application written by Paul Chapman in 2013. Its primary purpose was to assist in the design of self-destruct circuits in self-constructing circuitry. It has also regularly been helpful in completing glider syntheses, and was used to find the 31c/240 base reaction for the shield bug and Centipede spaceships.

:self-constructing A type of pattern, generally a macro-spaceship, that contains encoded construction information about itself, and makes a complete copy of itself using those instructions. The Gemini, linear propagator, spiral growth patterns, Demonoids and Orthogonoid are examples of self-constructing patterns. Self-constructing spaceships often have trivially adjustable speeds. In many cases, the direction of travel can also be altered, less easily, by changing the encoded construction recipe. Compare self-supporting, elementary.

:self-supporting A type of pattern, specifically a macro-spaceship, that constructs signals or tracks or other scaffolding to assist its movement, but does not contain complete information about its own structure. Examples include the Caterpillar, Centipede, half-baked knightship, waterbear, and the Caterloopillars. Caterpillar has been used as a general term for self-supporting spaceships, but it is not very appropriate for the HBKs.

In general a self-supporting pattern cannot be trivially adjusted to alter its speed or direction. The variable speeds of the HBKs and the Caterloopillars are exceptions, but their direction of travel is fixed, and a specific Caterloopillar can't be made to change its speed without completely rebuilding it. Compare self-constructing, elementary.

:semi-Snark Any small stable signal conduit that produces one output glider for every two input gliders, with a 90 degree reflection. These can act as period-doublers for any glider stream whose period is at least equal to their repeat time, and so adding one of these to a single glider gun often results in a pattern much smaller than the older technology of crossing the output of two guns.

The available semi-Snarks differ in their complexity, size, repeat time, and the colour of their output gliders. The CC semi-Snark was the first one found, and the term "semi-Snark" is often used specifically for this object. The "CC" prefix stands for colour-changing, by contrast with the more recently discovered colour-preserving CP semi-Snark. There are also CC and CP variants of a semi-Snark discovered by Tanner Jacobi in November 2017, based on a two-glider to century converter.

:sesquihat (p1) Halfway between a hat and a twinhat.

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

:SGR Abbreviation for stable glider reflector. This term is no longer in use.

:shield bug (31c/240 orthogonally, p240) The first 31c/240 macro-spaceship, constructed by Dave Greene on September 9, 2014.

:shillelagh (p1)

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

:ship (p1) The term is also used as a synonym of spaceship.

	OO.
	O.O
	.OO

A ship can be used as a catalyst in some situations. For example, it can suppress two of the blinkers from an evolving traffic light:

	...OO.
	...O.O
	....OO
	......
	O.....
	OO....
	O.....
It is also a one-glider seed for the engine of the queen bee shuttle:
	OOO..OO.
	..O..O.O
	.O....OO

:ship in a bottle (p16) Found by Bill Gosper in August 1994. See also bottle.

	....OO......OO....
	...O..O....O..O...
	...O.O......O.O...
	.OO..OOO..OOO..OO.
	O......O..O......O
	O.OO..........OO.O
	.O.O..........O.O.
	...OO...OO...OO...
	.......O.O........
	.......OO.........
	...OO........OO...
	.O.O..........O.O.
	O.OO..........OO.O
	O......O..O......O
	.OO..OOO..OOO..OO.
	...O.O......O.O...
	...O..O....O..O...
	....OO......OO....

:ship on boat = ship tie boat

:ship on ship = ship-tie

:ship-tie (p1) The name is by analogy with boat-tie.

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

:ship tie boat (p1)

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

:short keys (p3) Found by Dean Hickerson, August 1989. See also bent keys and odd keys.

	.O........O.
	O.OOO..OOO.O
	.O..O..O..O.
	....O..O....

:shoulder The fixed upper end of a construction arm, generally consisting of one or more glider guns or edge shooters aimed at an elbow object.

:shuttle Any oscillator which consists of an active region moving back and forth between stabilizing objects. The most well-known examples are the queen bee shuttle (which has often been called simply "the shuttle") and the twin bees shuttle. See also p54 shuttle and Eureka. Another example is the p72 R-pentomino shuttle that forms part of the pattern given under factory.

:siamese A term used in naming certain still lifes (and the stator part of certain oscillators). It indicates that the object consists of two smaller objects sharing two or more cells. See snake siamese snake and loaf siamese barge for examples.

:side Half a sidewalk. In itself this is unstable and requires an induction coil.

	OO...
	O.OOO
	....O

:sidecar A small tagalong for an HWSS that was found by Hartmut Holzwart in 1992. The resulting spaceship (shown below) has a phase with only 24 cells, making it in this respect the smallest known spaceship other than the standard spaceships and some trivial two-spaceship flotillas derived from them. Note also that a HWSS can support two sidecars at once.

	.O......
	O.....O.
	O.....O.
	OOOOO.O.
	........
	....OO..
	..O....O
	.O......
	.O.....O
	.OOOOOO.

:side-shooting gun = slide gun

:sidesnagger A Spartan eater found by Chris Cain in May 2015 with functionality similar to the eater5, as shown below. It has one lane less diagonal clearance on the high-clearance side than other eater5 variants, due to the presence of the boat. See also highway robber.

	..O.............
	O.O.............
	.OO.............
	................
	................
	................
	.........O......
	........O.......
	........OOO.....
	................
	................
	.........O......
	........O.O.....
	.......O..O...OO
	........OO....OO
	....O...........
	...O.O..........
	...OO...........
	.........OO.....
	.........OO.....

:side-tracking See universal constructor.

:sidewalk (p1)

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

:siesta (p5) Found by Dave Buckingham in 1973. Compare sombreros.

	...........OO...
	...OO.....O.O...
	...O.O....O.....
	.....O...OO.O...
	...O.OO.....OOO.
	.OOO.....O.O...O
	O...O.O.....OOO.
	.OOO.....OO.O...
	...O.OO...O.....
	.....O....O.O...
	...O.O.....OO...
	...OO...........

:signal Movement of information through the Life universe. Signals can be carried by spaceships, fuses, drifters, or conduits. Spaceships can only transfer a signal at the speed of the spaceship, while fuses can transfer a signal at speeds up to the speed of light.

In practice, many signals are encoded as the presence or absence of a glider or other spaceship at a particular point at a particular time. Such signals can be combined by the collision of gliders to form logic operations such as AND, OR, and NOT gates. Signals can be duplicated using glider duplicators or other fanout devices, and can be used up by causing perturbations on other parts of the Life object.

Signals are used in Herschel conduit circuitry, universal constructors, macro-spaceships, and other computational patterns such as the pi calculator and Osqrtlogt patterns.

:signal elbow A conduit with signal output 90 degrees from its input. This term is commonly used only for signal wires, particularly 2c/3 signals. A Snark could reasonably be called a "glider elbow", but glider reflector is the standard term. A signal elbow with a recovery time less than 20 ticks would enable a trivial proof that Conway's Life is omniperiodic.

A near miss is the following elbow-like converter found by Dean Hickerson. It successfully turns a 2c/3 signal by 90 degrees, but unfortunately changes it to a double-length signal in the process. This means that further copies of the converter can not be appended (e.g., to make a closed loop).

	........................O..O......
	........................OOOOOO....
	..............................O.OO
	......................OOOOO.O.O.OO
	.....................O......O.O...
	.....................OOOOO..O.O...
	..................O.......O.OO....
	..................OOOOOO..O.......
	........................O.O.......
	................OOOOOO..O.OO......
	..........OO...O......O.O.........
	.........O..O..OOOOO..O.O.........
	........O.OOO.......O.OO..........
	....OO.O.O...OOOOO..O.............
	.....O.O...O......O.O.............
	.....O.O..OOOOOO..O.OO............
	...O.O.O.O......O.O...............
	..O.OO..O.OOOO..O.O...............
	..O...O.O.O...O.OO................
	OO.OO.O.O...O.O...................
	.O.O..O.OOOO.O.OOO................
	O..O.O.......O...O................
	.OOO..OOOOOOOO....................
	....O.O...........................
	...OO.O..OOOOOOO..................
	..O..OO.O.......O.................
	..OO....O..OOOOOO.................
	........O.O.......................
	.......OO.O..OOOOOO...............
	..........O.O......O..............
	..........O.O..OOOOO..............
	...........OO.O.......O...........
	..............O..OOOOOO...........
	..............O.O.................
	.............OO.O..OOOOOO.........
	................O.O......O.OO.....
	................O.O..OOOOO.OO.....
	.................OO.O.............
	....................O..OOOOOO.....
	....................O.O.....O.....
	...................OO.O..OOO......
	......................O.O.....OO..
	......................O..O....OO..
	.......................OO.........

Relatively small composite MWSS elbows can now be constructed, using Tanner Jacobi's 2015 discovery of a small H-to-MWSS component. For example, the Orthogonoid includes a constructor/reflector that reflects an MWSS stream by 180 degrees, but it can be trivially reconfigured to make a 90-degree MWSS elbow.

:Silver G-to-H A variant of the Silver reflector made by substituting an Fx119 conduit for the final NW31, allowing a Herschel output as well as the beehive-annihilating reset glider. It is still Spartan, and as long as the Fx119 is followed by a dependent conduit, it retains the faster 497-tick recovery time.

:Silver reflector A stable glider reflector found by Stephen Silver in November 1998, by substituting an NW31 converter for the second Fx77 conduit in the Callahan G-to-H found a few days previous. The repeat time is 497 ticks:

	........O.............O.......................................
	......O.O...........OOO.......................................
	.......OO..........O..........................................
	...................OO.........................................
	....OO........................................................
	.....O........................................................
	.....O.O......................................................
	......OO..........O...........................................
	.................O.O..........................................
	.................O.O..........................................
	..................O....OO.....................................
	......OO...............O.O....................................
	.....O.O.................O....................................
	.....O...................OO...................................
	....OO........................................................
	..............................................................
	..............................................................
	..............................................................
	..............................................................
	..............................................................
	...............OO.............................................
	...............OO.............................................
	..............................................................
	..............................................................
	..............................................................
	..............................................................
	..............................................................
	..............................................................
	..............................................................
	..............................................................
	...OO.........................................................
	....O.........................................................
	....O.O.......................................................
	.....OO.......................................................
	..............................................................
	..............................................................
	..............................................................
	..............................................................
	..............................................................
	..............................................................
	..............................................................
	..............................................................
	..............................................................
	..............................................................
	..............................................................
	......OO...............OO.....................................
	......OO...............O.O....................................
	.........................O....................................
	.........................OO...................................
	..............................................................
	..............................................................
	..............................................................
	..............................................................
	..............................................................
	...................O..........................................
	.................OOO..........................................
	................O.............................................
	................OO...................OO.......................
	....................OO................O.......................
	.....................O................O.O.....................
	...................O...................OO.....................
	...................OO.........................................
	..............................................................
	..............................................................
	............................................................OO
	............................................................OO
	..............................................................
	......................OO......................................
	...OO.................OO......................................
	...OO.........................................................
	..............................................................
	..............................................................
	..OO..........................................................
	...O..........................................................
	OOO............OO.............................................
	O..............O..............................................
	................OOO...........................................
	..................O...........................................
	..............................................................
	..................................................OO..........
	..................................................OO..........

:Silver's p5 (p5) The following oscillator found by Stephen Silver in February 2000:

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

As this has no spark, it appears useless. Nonetheless, in March 2000, David Eppstein found a way to use it to reduce the size of Noam Elkies' p5 reflector.

:Simkin glider gun (p120) A Herschel-based glider gun discovered by Michael Simkin in April 2015. It consists of a Herschel running through two B60 conduits. In terms of its 36-cell minimum population, it is one of the smallest known guns, sharing the record with the Gosper glider gun. In the double-barreled form, as well as the pseudo-period, snake-stabilized form shown below, it is the absolute record holder.

	OO.....OO........................
	OO.....OO........................
	.................................
	....OO...........................
	....OO...........................
	.................................
	.................................
	.................................
	.................................
	......................OO.OO......
	.....................O.....O.....
	.....................O......O..OO
	.....................OOO...O...OO
	..........................O......
	.................................
	.................................
	.................................
	.................................
	........................O.OO.....
	........................OO.O.....

:single-arm A type of universal constructor using just one construction arm and slow salvo techniques to construct, usually, Spartan or near-Spartan circuitry. Compare two-arm.

:single-channel A type of universal constructor discovered and developed by Simon Ekström and others starting in December 2015. The initial elbow operation toolkit was near-minimal, with just one push, one pull, and one output glider of each colour (see colour of a glider). Later searches produced a much larger and more efficient library.

Single-channel recipes consist of a stream of gliders on a single lane and aimed at a construction elbow, usually separated from each other by at least 90 ticks. In spite of these strict limitations, single-channel recipes can be made to do surprising things. For example, it is possible to build a Snark directly on the construction lane of an active construction arm, starting from a single elbow block. This can allow the arm to reach efficiently around complex obstructions by bending itself through multiple lossless elbows. Known recipes can also remove an elbow when it is no longer needed, by controlled demolition of the Snark.

As of November 2017, almost all single-channel recipes are made up of singletons and synchronized pairs of gliders, but no synchronized triplets or larger groups. This is not an inherent limitation of single-channel construction, but rather a limitation in the search program used to find currently known single-channel toolkits.

A useful byproduct of this limitation is that single-channel recipes can be trivially adjusted to allow them to safely cross perpendicular data streams, including other single-channel recipes (or earlier parts of the same recipe). To avoid collisions with a crossing stream, each singleton glider or glider pair can safely be delayed by any even number of ticks, or technically by any multiple of the period of the current intermediate target. The final result of the construction will not be affected.

:single-channel Demonoid See Demonoid.

:single-lane = single-channel.

:singleton In single-channel recipes, a glider that is not synchronized with a neighboring glider in its stream. Compare glider pair.

:singular flip flop (p2) Found by Robert Wainwright, July 1972.

	..O...
	..O.O.
	O....O
	OOOOOO
	......
	..OO..
	..OO..

:sinking ship = canoe

:six Ls (p3) This is a compact form of loading dock.

	...O...
	.OOO..O
	O...OOO
	OOO....
	....OOO
	OOO...O
	O..OOO.
	...O...

:sixty-nine (p4) Found by Robert Wainwright, October 1978.

	.........O...........
	........O.O..........
	.....................
	......O...OO.........
	.....O.....O.........
	......O.O............
	........OO......O....
	................O....
	..O.....OO....OOO....
	..O...........OO.....
	OOO.......OO..OO..OOO
	OO......O.OO....OOO..
	OO..OOO.O.O.....OOO..
	..OOO................
	..OOO......O.........
	..........O.O........
	.....................
	........O...OO.......
	.......O.....O.......
	........O.O..........
	..........OO.........

:skewed quad (p2)

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

:skewed traffic light (p3) Found by Robert Wainwright, August 1989.

	.............OO.........
	............O..O........
	.............O.O........
	.........OO...O.........
	..........O.OO..........
	............O...........
	............O...........
	........................
	OO........OOO......O....
	OOOO.O........O...OO....
	O.O..OOO.O....O.........
	.........O....O.OOO..O.O
	....OO...O........O.OOOO
	....O......OOO........OO
	........................
	...........O............
	...........O............
	..........OO.O..........
	.........O...OO.........
	........O.O.............
	........O..O............
	.........OO.............

:sL Abbreviation for still life, used most often in rough measurements of the complexity of a Spartan constellation.

:slide gun A gun which fires sideways from an extending arm. The arm consists of streams of spaceships which are pushing a pattern away from the body of the gun and releasing an output spaceship every time they do so. Each output spaceship therefore travels along a different path.

Dieter Leithner constructed the first slide gun in July 1994 (although he used the term "side shooting gun"). The following pattern shows the key reaction of this slide gun. The three gliders shown will push the block one cell diagonally, thereby extending the length of the arm by one cell, and at the same time they release an output glider sideways. (In 1999, Jason Summers constructed slide guns using other reactions.)

	..............OO.
	..............OO.
	........OOO......
	..........O......
	.........O.....OO
	..............O.O
	................O
	.................
	.................
	.................
	.................
	.................
	.................
	.................
	.................
	.................
	.................
	.O...............
	.OO..............
	O.O..............

:sliding block memory A memory register whose value is stored as the position of a block. The block can be moved by means of glider collisions. See block pusher for an example.

In Conway's original formulation (as part of his proof of the existence of a universal computer in Life) two gliders were used to pull the block inwards by three diagonal spaces, as shown below, and thirty gliders were used to push it out by the same amount.

	OO..........
	OO..........
	............
	............
	............
	.........OOO
	OOO......O..
	O.........O.
	.O..........

Dean Hickerson later greatly improved on this, finding a way to pull a block inwards by one diagonal space using 2 gliders, and push it out the same distance using 3 gliders. In order for the memory to be of any use there also has to be a way to read the value held. It suffices to be able to check whether the value is zero (as Conway did), or to be able to detect the transition from one to zero (as Hickerson did).

Dean Hickerson's sliding block memory is used in Paul Chapman's URM, and several other complex constructions such as Adam P. Goucher's pi calculator and Spartan universal computer-constructor.

:slmake A search program published by Adam P. Goucher in May 2017. It accepts as input a constellation of sufficiently widely separated still lifes, and produces a glider stream that will perform a complete slow glider construction of that constellation, starting from a single block.

One of slmake's primary uses is to make self-constructing patterns much easier to design and build. It is capable of finding recipes not only for Spartan stable circuitry, but also for other useful non-Spartan circuits such as Snarks, syringes, and H-to-MWSS converters, provided that they are separated from other nearby objects by a sufficient amount of empty space.

:slow See slow glider construction.

:slow elbow A movable elbow in a construction arm toolkit that is controlled by a slow salvo, which most likely comes from a previous construction elbow. Unlike a standard elbow which is generally fixed on a single construction lane or at least within a narrow range, a slow elbow can move freely in two dimensions as long as there is room for it. Each slow elbow added to a construction arm results in an exponential increase in the cost (in gliders) of the final construction. Compare lossless elbow.

:slow glider construction Construction an object by a "slow salvo" of gliders all coming from the same direction, in such a way that timing of the gliders does not matter as long as they are not too close behind one another. This type of construction requires an initial seed object, such as a block, which is modified by each glider in turn until the desired object is produced.

In May 1997, Nick Gotts produced a slow glider construction of a block-laying switch engine from a block, using a slow salvo of 53 gliders. Constructions like this are important in the study of sparse Life, as they will occur naturally as gliders created in the first few generations collide with blonks and other debris.

Slow glider constructions are also useful in some designs for universal constructors. However, in this case the above definition is usually too restrictive, and it is desirable to allow constructions in which some gliders in the salvo are required to have a particular timing modulo 2 (a "p2 slow salvo"). This gives much greater flexibility, as blinkers can now be freely used in the intermediate construction steps. The Snarkmaker is a very large p2 slow salvo. A much smaller example is the following edgy construction of an eater1 starting from a block.

	OO..OOO...............................................
	OO..O.................................................
	.....O................................................
	......................................................
	......................................................
	......................................................
	......................................................
	......................................................
	......................................................
	......................................................
	................OOO...................................
	................O.....................................
	.................O....................................
	......................................................
	......................................................
	......................................................
	......................................................
	.......................OOO............................
	.......................O..............................
	........................O.............................
	......................................................
	......................................................
	......................................................
	......................................................
	......................................................
	......................................................
	......................................................
	..............................O.......................
	........................O....OO.......................
	.......................OO....O.O......................
	.......................O.O............................
	......................................................
	......................................................
	..........................O...........................
	.........................OO...........................
	.........................O.O..........................
	......................................................
	.............................OOO....................OO
	.............................O.....................OO.
	..............................O......................O

Adam P. Goucher's slmake search program, made available in May 2017, makes it much easier to find a slow glider construction for a wide variety of stable circuitry.

:slow salvo See slow glider construction.

:small fish = LWSS

:small lake (p1) See also lake.

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

:smiley (p8) Found by Achim Flammenkamp in July 1994 and named by Alan Hensel.

	OO.O.OO
	...O...
	O.....O
	.OOOOO.
	.......
	.......
	OOO.OOO

:SMM breeder See breeder.

:smoke Debris which is fairly long-lived but eventually dies completely. Basically, a large spark. This term is used especially when talking about the output from a spaceship such as the smoking ship.

:smoking ship A spaceship which produces smoke. If the smoke extends past the edge of the rest of the spaceship, then it can be used to perturb other objects as the spaceship passes by. Running gliders into the smoke is often a good way to turn or duplicate them, or convert them into other objects. Sometimes the smoke from a smoking ship may itself be perturbed by accompanying spaceships in order to form a puffer. A simple example of a smoking ship is the Schick engine.

:snacker (p9) Found by Mark Niemiec in 1972. This is a pentadecathlon with stabilizers which force it into a lower period.

	OO................OO
	.O................O.
	.O.O............O.O.
	..OO............OO..
	.......O....O.......
	.....OO.OOOO.OO.....
	.......O....O.......
	..OO............OO..
	.O.O............O.O.
	.O................O.
	OO................OO
The stabilizers make the domino spark largely inaccessible, but the snacker is extensible, as shown in the next diagram, and so a more accessible p9 domino spark can be obtained. In April 1998 Dean Hickerson found an alternative stabilizer that is less obtrusive than the original one, and this is also shown in this diagram.
	OO................................
	.O................................
	.O.O.........................OO...
	..OO.......................O..O...
	.......O....O..............OOO....
	.....OO.OOOO.OO...O....O......OOO.
	.......O....O...OO.OOOO.OO...O...O
	..OO..............O....O......OOO.
	.O.O.......................OOO....
	.O.........................O..O...
	OO...........................OO...
An end can also be stabilized by killer candlefrobras.

:snail (c/5 orthogonally, p5) The first known c/5 spaceship, discovered by Tim Coe in January 1996. For some time it was the slowest known orthogonal spaceship.

	.O....................................
	.O....................................
	O.....................................
	.OOO.................OOO...OOO........
	.OO.O.........O...O.O......OOO........
	..O...........OO.O.......O....OOOO....
	......O......O...O.O...OO.O.....OO....
	...O..O.OOO...OO.........O........OO.O
	...OO.O.....O.....O.................O.
	.........O.OOOOOOO....................
	......................................
	.........O.OOOOOOO....................
	...OO.O.....O.....O.................O.
	...O..O.OOO...OO.........O........OO.O
	......O......O...O.O...OO.O.....OO....
	..O...........OO.O.......O....OOOO....
	.OO.O.........O...O.O......OOO........
	.OOO.................OOO...OOO........
	O.....................................
	.O....................................
	.O....................................

:snake (p1)

	OO.O
	O.OO

:snake bit An alternative name for a boat-bit. Not a very sensible name, because various other things can be used instead of a snake. A snake, or alternatively an aircraft carrier, is the smallest object that can consume a glider stream by effectively acting as an eater for every two incoming gliders. The one-cell reduction from the smallest real eater, the seven-cell eater1, has been important when trying to construct recent sawtooths where the population must be minimized.

:snake bridge snake (p1)

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

:snake dance (p3) Found by Robert Wainwright, May 1972.

	...OO.O..
	...O.OO..
	OO.O.....
	.O..O.OOO
	O..O.O..O
	OOO.O..O.
	.....O.OO
	..OO.O...
	..O.OO...

:snake pit This term has been used for two different oscillators: the p2 snake pit (essentially the same as fore and back)

	O.OO.OO
	OO.O.O.
	......O
	OOO.OOO
	O......
	.O.O.OO
	OO.OO.O
and the p3 snake pit.
	.....OO....
	....O..O...
	....O.OO...
	.OO.O......
	O.O.O.OOOO.
	O.........O
	.OOOO.O.O.O
	......O.OO.
	...OO.O....
	...O..O....
	....OO.....

:snake siamese snake (p1)

	OO.OO.O
	O.OO.OO

:Snark A small stable 90-degree glider reflector with a repeat time of 43 ticks, discovered by Mike Playle on 25 April 2013 using a search utility he wrote called Bellman. Compare boojum reflector. Four common Snark variants are shown below: Playle's original at the top, and variants by Heinrich Koenig, Simon Ekström, and Shannon Omick to the left, bottom, and right, respectively. As of November 2017, only Playle's variant has a known slow glider construction recipe for all orientations.

	.............................OO....................
	............................O.O....................
	......................OO....O......................
	....................O..O..OO.OOOO..................
	....................OO.O.O.O.O..O..................
	.......................O.O.O.O.....................
	.......................O.O.OO......................
	........................O..........................
	...................................................
	.....................................OO............
	............................OO.......O.............
	............................OO.....O.O.............
	.........O.........................OO..............
	.........OOO.......................................
	............O........O.............................
	...........OO.......O..............................
	....................OOO............................
	...................................................
	...OO..............................................
	...O.....................OO........................
	OO.O......................O........................
	O..OOO....OO...........OOO.........................
	.OO...O...OO...........O......................O....
	...OOOO.....................OO..............OOOOO..
	...O...............OO........O.............O.....O.
	....OOO............O.O.......O.O............OOO..O.
	.......O.............O........OO...............O.OO
	..OOOOO..............OO.....................OOOO..O
	.O..O......................O...........OO...O...OO.
	.OO......................OOO...........OO....OOO...
	........................O......................O...
	........................OO.....................O.OO
	..............................................OO.OO
	...................................................
	...................................................
	......................................OO...........
	......................................O............
	.......................................OOO.........
	..............OO.........................O.........
	.............O.O.....OO............................
	.............O.......OO............................
	............OO.....................................
	...................................................
	..........................O........................
	................OO....OO.O.O.......................
	...............O..O..O.O.O.O.......................
	................OO...O.O.O.OO......................
	..................OOOO.OO..O.......................
	..................O...O....O.......................
	...................O..O.OOO........................
	....................O.O.O..........................
	.....................O.............................

:Snarkmaker A single-channel stream of gliders that, when aimed to collide with an elbow block in a specific location, will perform a slow glider construction of a Snark, directly on the same lane as the incoming gliders. This allows a construction arm to add one or more lossless elbows, so that it can bend around multiple corners without an exponential increase in construction cost.

The Snarkmaker recipe used in the first single-channel Demonoid, Orthogonoid, and spiral growth patterns contains 2,254 gliders. This could be considerably reduced with a customized search program.

:SNG = second natural glider.

:SODGame = Seeds of Destruction Game

:sombrero One half of sombreros or siesta.

:sombreros (p6) Found by Dave Buckingham in 1972. If the two halves are moved three spaces closer to one another then the period drops to 4, and the result is just a less compact form of Achim's p4. Compare also siesta.

	...OO........OO...
	...O.O......O.O...
	.....O......O.....
	...O.OO....OO.O...
	.OOO..........OOO.
	O...O.O....O.O...O
	.OOO..........OOO.
	...O.OO....OO.O...
	.....O......O.....
	...O.O......O.O...
	...OO........OO...

:soup A random initial pattern, either contained within a small area, or alternatively filing the whole Life universe.

Finite soups probably have behaviors very different than infinite soups, but this is obviously unknown. Infinite soups may remain chaotic indefinitely since any reaction, no matter how rare, is bound to happen somewhere.

Soups can have an average density, with results varying based on that. See sparse Life for a discussion of what can happen at a low density.

Finite soups for sizes such as 16×16 (asymmetric) have been examined by the billions by scripts such as apgsearch to find interesting results. Many new oscillators and synthesis recipes have been discovered, as well as previously known rare patterns such as stabilized switch engines. In addition, soups are used to generate statistical census data, and to decide whether specific objects can be considered natural.

Soups can be fully random, or they can be forced to be symmetric. The results for these two types of soups can differ since symmetric soups tend to create large symmetrical objects at a much higher rate. Shown below is an unusual mirror-symmetric soup that produces a pufferfish and nothing else.

	OOOO..OO.OOO.O...O.OOO.OO..OOOO
	.O.O.OO.O.............O.OO.O.O.
	..OOO..O.O.O.......O.O.O..OOO..
	O.OO.OOO.O..O.....O..O.OOO.OO.O
	.OOOO.O...OO.OOOOO.OO...O.OOOO.
	.....OO...OO.O.O.O.OO...OO.....
	..OOO...OO...O...O...OO...OOO..
	O..O..O.OO...OO.OO...OO.O..O..O
	OO.O..O...O.........O...O..O.OO
	O.O.O...OOOO..OOO..OOOO...O.O.O
	O.OOO.OO..OO...O...OO..OO.OOO.O
	..O.....OO...O...O...OO.....O..
	OOOOO.O.OOO..O...O..OOO.O.OOOOO
	.O....O....O..OOO..O....O....O.
	.OO.O...OOOOOOOOOOOOOOO...O.OO.
	OOOO.OOO......O.O......OOO.OOOO

:space dust A part of a spaceship or oscillator which looks like a random mix of ON and OFF cells. It is usually very difficult to find a glider synthesis for an object that consists wholly or partly of space dust. As examples, the 295P5H1V1, fly, and seal spaceships contain large amounts of space dust.

:spacefiller Any pattern that grows at a quadratic rate by filling space with an agar. The first example was found in September 1993 by Hartmut Holzwart, following a suggestion by Alan Hensel. The diagram below shows a smaller spacefiller found by Tim Coe. See also Max. Spacefillers can be considered as breeders (more precisely, MMS breeders), but they are very different from ordinary breeders. The word "spacefiller" was suggested by Harold McIntosh and soon became the accepted term.

	..................O........
	.................OOO.......
	............OOO....OO......
	...........O..OOO..O.OO....
	..........O...O.O..O.O.....
	..........O....O.O.O.O.OO..
	............O....O.O...OO..
	OOOO.....O.O....O...O.OOO..
	O...OO.O.OOO.OO.........OO.
	O.....OO.....O.............
	.O..OO.O..O..O.OO..........
	.......O.O.O.O.O.O.....OOOO
	.O..OO.O..O..O..OO.O.OO...O
	O.....OO...O.O.O...OO.....O
	O...OO.O.OO..O..O..O.OO..O.
	OOOO.....O.O.O.O.O.O.......
	..........OO.O..O..O.OO..O.
	.............O.....OO.....O
	.OO.........OO.OOO.O.OO...O
	..OOO.O...O....O.O.....OOOO
	..OO...O.O....O............
	..OO.O.O.O.O....O..........
	.....O.O..O.O...O..........
	....OO.O..OOO..O...........
	......OO....OOO............
	.......OOO.................
	........O..................

:space nonfiller Any pattern that expands indefinitely to affect every cell in the Life plane, but leaves an expanding region of vacuum at its center. Compare spacefiller; see also antstretcher. The first nonfiller was discovered by Jason Summers on 14 April 1999:

	...................OOO...............
	..................O..O...............
	............OOO......O....OOO........
	............O..O.O...O....O..O.......
	............O..O.O...O....O..O.......
	..........O..........O..O.O.OOO......
	..........OO..OO..O.O....O.....O.....
	........O................OO..OOO.....
	........OOO.O.OO..........O......O...
	......O........O.........O.O...OOO...
	......OOO.....O..........O........O..
	...O.O.........................O.OOO.
	..OOOOO.O..........................O.
	.OO......O.....................OOOOO.
	OO....OO..................O.O........
	.O.O...O..O...............O..O...O.O.
	........O.O..................OO....OO
	.OOOOO.....................O......OO.
	.O..........................O.OOOOO..
	.OOO.O.........................O.O...
	..O........O..........O.....OOO......
	...OOO...O.O.........O........O......
	...O......O..........OO.O.OOO........
	.....OOO..OO................O........
	.....O.....O....O.O..OO..OO..........
	......OOO.O.O..O..........O..........
	.......O..O....O...O.O..O............
	.......O..O....O...O.O..O............
	........OOO....O......OOO............
	...............O..O..................
	...............OOO...................

:space rake The following p20 forwards glider rake, which was the first known rake. It consists of an ecologist with a LWSS added to turn the dying debris into gliders.

	...........OO.....OOOO
	.........OO.OO...O...O
	.........OOOO........O
	..........OO.....O..O.
	......................
	........O.............
	.......OO........OO...
	......O.........O..O..
	.......OOOOO....O..O..
	........OOOO...OO.OO..
	...........O....OO....
	......................
	......................
	......................
	..................OOOO
	O..O.............O...O
	....O................O
	O...O............O..O.
	.OOOO.................

:spaceship Any finite pattern that reappears (without additions or losses) after a number of generations and displaced by a non-zero amount. By far the most natural spaceships are the glider, LWSS, MWSS and HWSS, followed by the Coe ship which has also evolved multiple times from random asymmetric soup starting conditions. See also the entries on individual spaceship speeds: c/2 spaceship, c/3 spaceship, c/4 spaceship, c/5 spaceship, c/6 spaceship, c/7 spaceship, c/10 spaceship, c/12 spaceship, 2c/5 spaceship, 2c/7 spaceship, 3c/7 spaceship, and 17c/45 spaceship.

It is known that there exist spaceships travelling in all rational directions and at arbitrarily slow speeds (see universal constructor). Before 1989, however, the only known examples travelled at c/4 diagonally (gliders) or c/2 orthogonally (everything else).

In 1989 Dean Hickerson started to use automated searches to look for new elementary spaceships, and had considerable success. Other people have continued these searches using tools such as lifesrc and gfind, and as a result we now have a great variety of elementary spaceships travelling at fifteen different velocities. The following table details the discovery of elementary spaceships with new velocities as of November 2017.

	--------------------------------------------------------------
	Speed Direction  First Discovery   Discoverer             Date
	--------------------------------------------------------------
	c/4   diagonal   glider            Richard Guy            1970
	c/2   orthogonal LWSS              John Conway            1970
	c/3   orthogonal 25P3H1V0.1        Dean Hickerson     Aug 1989
	c/4   orthogonal 119P4H1V0         Dean Hickerson     Dec 1989
	c/12  diagonal   Cordership        Dean Hickerson     Apr 1991
	2c/5  orthogonal 44P5H2V0          Dean Hickerson     Jul 1991
	c/5   orthogonal snail             Tim Coe            Jan 1996
	2c/7  orthogonal weekender         David Eppstein     Jan 2000
	c/6   orthogonal dragon            Paul Tooke         Apr 2000
	c/5   diagonal   295P5H1V1         Jason Summers      Nov 2000
	c/6   diagonal   seal              Nicolay Beluchenko Sep 2005
	c/7   diagonal   lobster           Matthias Merzenich Aug 2011
	c/7   orthogonal loafer            Josh Ball          Feb 2013
	c/10  orthogonal copperhead        zdr                Mar 2016
	3c/7  orthogonal spaghetti monster Tim Coe            Jun 2016
	--------------------------------------------------------------

Several infinite families of adjustable-velocity macro-spaceships have also been constructed, of which the first was Gabriel Nivasch's Caterpillar from December 2004. The macro-spaceship with the widest range of possible speeds is Michael Simkin's Caterloopillar from April 2016; in theory it supports any rational speed strictly less than c<4. A somewhat similar design supporting any rational speed strictly less than c/2 has been shown to be feasible, but as of November 2017 no explicit examples have been constructed.

A period p spaceship that displaces itself (m,n) during its period, where m>=n, is said to be of type (m,n)/p. It was proved by Conway in 1970 that p>=2m+2n. (This follows immediately from the easily-proved fact that a pattern cannot advance diagonally at a rate greater than one half diagonal step every other generation.)

:Spaceships in Conway's Life A series of articles posted by David Bell to the newsgroup comp.theory.cell-automata during the period August-October 1992 that described many of the new spaceships found by himself, Dean Hickerson and Hartmut Holzwart. Bell produced an addendum covering more recent developments in 1996.

:spaghetti monster The first 3c/7 spaceship, found by Tim Coe in June 2016. The spaceship travels orthogonally, has a minimum of 702 live cells and fits in a 27×137 bounding box.

:spark A pattern that dies. The term is typically used to describe a collection of cells periodically thrown off by an oscillator or spaceship, but other dying patterns, particularly those consisting or only one or two cells (such as produced by certain glider collisions, for example), are also described as sparks. For examples of small sparks see unix and HWSS. Examples of much larger sparks are seen in Schick engine and twin bees shuttle spark.

:spark coil (p2) Found in 1971.

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

:sparker An oscillator or spaceship that produces sparks. These can be used to perturb other patterns without being themselves affected.

:sparking eater One of two eaters found in April 1997 and November 1998 by Dean Hickerson using his dr search program, shown below to the left and right respectively. These both absorb gliders as a standard eater does, but also produce separated single-bit sparks at the upper right, which can be used to delete antiparallel gliders with different phases as shown.

	..O.........OO........O..........OO.
	O.O........OO.......O.O..........O.O
	.OO..........O.......OO..........O..
	....OO..OO...............OO..OO.....
	.O...O..OO............O...O..OO.....
	.OOOO.............OO..OOOO..........
	..................O.................
	.OO................OOOOO............
	.OO.....................O...........
	.....................OOO............
	.....................O..............
The above mechanisms can be used to build intermitting glider guns. The left-hand eater produces a spark nine ticks after a glider impact, with the result that the period of the constituent guns can't be a multiple of 4. The right-hand eater produces the same spark ten ticks after impact, which allows p4N guns to be used.

The separation of the spark also allows this reaction to perform other perturbations "around the corner" of some objects. For example, it was used by Jason Summers in 2004 to cap the ends of a row of ten AK47 reactions to form a much smaller period 94 glider gun than the original one. (This is now made obsolete by the AK94 gun.)

:sparky A certain c/4 tagalong, shown here attached to the back of a spaceship.

	..........O....................
	..........O...............OO...
	......OO.O.OOO..........OO...O.
	O.OO.OO.OO..O.O...OO.OOOO......
	O...OO..O.OO..OOO..O.OO..OO...O
	O.OO....OOO.O.OOO......OO..O...
	........OO.O...............O..O
	O.OO....OOO.O.OOO......OO..O...
	O...OO..O.OO..OOO..O.OO..OO...O
	O.OO.OO.OO..O.O...OO.OOOO......
	......OO.O.OOO..........OO...O.
	..........O...............OO...
	..........O....................

:sparse Life This refers to the study of the evolution of a Life universe which starts off as a random soup of extremely low density. Such a universe is dominated at an early stage by blocks and blinkers (often referred to collectively as blonks) in a ratio of about 2:1. Much later it will be dominated by simple infinite growth patterns (presumably mostly switch engines). The long-term fate of a sparse Life universe is less certain. It may possibly become dominated by self-reproducing patterns (see universal constructor), but it is not at all clear that there is any mechanism for these to deal with the all junk produced by switch engines.

:Spartan A pattern composed of subunits that can be easily constructed in any orientation, usually with a slow salvo. Generally this means that the pattern is a constellation of Spartan still lifes: block, tub, boat, hive, ship, loaf, eater1, or pond. Other small objects may sometimes be counted as Spartan, including period-2 oscillators - mainly blinkers, but also beacons or toads, which may occur as intermediate targets in slow salvo recipes. Most self-constructing patterns are Spartan or mostly Spartan, to simplify the process of self-construction.

:speed booster Any mechanism which allows a signal (indicated by the presence or absence of a spaceship) to move faster than the spaceship could travel through empty space. The original speed booster is based on p30 technology, and is shown below:

	....................O........................
	.....................O.......................
	...................OOO.......................
	.............................................
	...........................O.O...............
	.........................O...O...............
	.................O.......O...................
	................OOOO....O....O........OO.....
	...............OO.O.O....O............OO.....
	....OO........OOO.O..O...O...O...............
	....OO.........OO.O.O......O.O...............
	................OOOO.........................
	.................O...........................
	..........................OOO................
	..........................O.O...OO...........
	.........................OO.....O..O.........
	..................O.O.....O.........O......OO
	................O...O..OO...........O......OO
	.........OO.....O..........O........O........
	.O.......OO....O....O.......OO..O..O.........
	..O.............O.......O.O..O..OO...........
	OOO.............O...O.....OOO................
	..................O.O........................
Here the top glider is boosted by passing through two inline inverters, emerging 5 cells further along than the unboosted glider at the left.

The fastest speed boosters are the telegraph and p1 telegraph, which can transfer a orthogonal signal at the speed of light, although their bit rate is rather slow.

Diagonal speed boosters have also been built using 2c/3 wires or other stable components. See stable pseudo-Heisenburp.

The star gate seems like it can transfer a signal faster than the speed of light. The illusion is explained in Fast Forward Force Field.

:speed of light A speed of one cell per generation, the greatest speed at which any effect can propagate. Usually denoted c.

:S-pentomino Conway's name for the following pentomino, which rapidly dies.

	..OO
	OOO.

:spider (c/5 orthogonally, p5) This is the smallest known c/5 spaceship, and was found by David Bell in April 1997. Its side sparks have proved very useful in constructing c/5 puffers, including rakes. See also PPS.

	......O...OOO.....OOO...O......
	...OO.OOOOO.OO...OO.OOOOO.OO...
	.O.OO.O.....O.O.O.O.....O.OO.O.
	O...O.O...OOOOO.OOOOO...O.O...O
	....OOO.....OO...OO.....OOO....
	.O..O.OOO.............OOO.O..O.
	...O.......................O...

:spiral (p1) Found by Robert Wainwright in 1971.

	OO....O
	.O..OOO
	.O.O...
	..O.O..
	...O.O.
	OOO..O.
	O....OO

:spiral growth A self-constructing pattern built by Dave Greene in August 2014 that uses four universal constructors (UCs) arranged in a diamond to build four more UCs in a slightly larger diamond. This was the first B3/S23 pattern that exhibited spiral growth. Much smaller versions have now been constructed using the single-channel construction toolkit.

:splitter A signal converter that accepts a single input signal and produces two or more output signals, usually of the same type as the input. An older term for this is fanout, or "fanout device".

A sub-category is the one-time splitter, which is not technically a converter because it can only be used once. One-time splitters are usually small constellations that produce two or more clean gliders when struck by a single glider. In other words, they are multi-glider seeds. These are important for constructing self-destruct circuitry in self-constructing spaceships.

:SPPS (c/5 orthogonally, p30) The symmetric PPS. The original PPS found by David Bell in May 1998. Compare APPS.

:sqrtgun Any glider-emitting pattern which emits its nth glider at a time asymptotically proportional to n2. The first examples were constructed by Dean Hickerson around 1991. See also quadratic filter, exponential filter, recursive filter.

:squaredance The p2 agar formed by tiling the plane with the following pattern. Found by Don Woods in 1971.

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

:squirter = pipsquirter

:S-spiral = big S

:stabilized switch engine A single switch engine which survives indefinitely by interacting with the appropriate exhaust such that it prevents the engine from ever being destroyed.

The only known types of stabilized switch engines were found by Charles Corderman soon after he discovered the switch engine itself. There is a p288 block-laying type (the more common of the two) and the p384 glider-producing type. These two puffers are the most natural infinite growth patterns in Life. As of November 2017 they are the basis for every infinite growth pattern ever seen to occur from a random asymmetric soup, even after trillions of census results by apgsearch and similar projects.

Patterns giving rise to block-laying switch engines can be seen under infinite growth, and one giving rise to a glider-producing switch engine is shown under time bomb.

:stable A pattern is said to be stable if it is a parent of itself. Stable objects are oscillators with period 1 (p1), and are generally called still lifes.

:stable pseudo-Heisenburp A multi-stage converter constructed by Dave Greene in January 2007, using a complex recipe found by Noam Elkies to insert a signal into a 2c/3 wire. The wire's high transmission speed allows a signal from a highway robber to catch up to a salvo of gliders. Ultimately the mechanism restores the key glider, which was destroyed by the highway robber in the first stage of the converter, to its exact original position in the salvo.

Much smaller stable pseudo-Heisenburp devices have since been designed that use simple 0-degree glider seed constellations instead of a 2c/3 wire.

These patterns are labeled "pseudo-Heisenburp", because a true Heisenburp device does not even temporarily damage or affect a passing glider, yet can still produce an output signal in response. However, it is impossible to construct a stable device that can accomplish this for gliders. True stable Heisenburp devices are possible with many other types of spaceships, but not with gliders which have no usable side sparks to initiate an output signal.

:staged recovery A type of signal-processing circuit where the initial reaction between catalysts an incoming signal results in an imperfect recovery. A catalyst is damaged, destroyed completely as in a bait reaction, or one or more objects are left behind that must be cleaned up before the circuit can be reused. In any of these three cases, output signals from the circuit must be used to complete the cleanup. In theory the cleanup process might itself be dirty, requiring additional cleanup stages. In rare cases this might theoretically allow the construction of special-purpose circuits with a lower recovery time than would otherwise be possible, but in practice this kind of situation does not commonly arise.

An example is the record-breaking (at the time) 487-tick reflector constructed by Adam P. Goucher on 12 April 2009. 487 ticks was a slight improvement over the repeat time of the Silver reflector. The reflector featured a standard Callahan G-to-H, with cleanup by an internal dirty glider reflector found by Dieter Leithner many years before. This in turn was cleaned up by the usual ungainly Herschel plumbing attached to the G-to-H's output. The dirty glider reflector is not actually fully recovered before a second p487 signal enters the full reflector. However, it has been repaired by the time the internal reflector is actually needed again, so the cycle can be successfully repeated at p487 instead of p497.

:stairstep hexomino (stabilizes at time 63) The following predecessor of the blockade.

	..OO
	.OO.
	OO..

:stamp collection A collection of oscillators (or perhaps other Life objects) in a single diagram, displaying the exhibits much like stamps in a stamp album. The classic examples are by Dean Hickerson (see http://conwaylife.com/ref/DRH/stamps.html).

Many stamp collections contain "fonts" made of single cells (which cleanly die) to annotate the objects or to draw boxes around them. For example, here is a stamp collection which shows all the ways that two gliders can create a loaf or an eater:

	.O......O.O.....O....O.O.O...................O.
	............................................O..
	.O.....O...O...O.O...O......................OOO
	...............................................
	.O.....O...O..O...O..O.O.O.....................
	...............................................
	.O.....O...O..O.O.O..O.........................
	........................................OO.....
	.O.O.O..O.O...O...O..O.................O.O.....
	.........................................O.....
	...............................................
	...............................................
	.............................................O.
	............................................O..
	O.O.O....O....O.O.O..O.O.O..O.O.............OOO
	................................O..............
	O.......O.O.....O....O......O..................
	................................O..............
	O.O.O..O...O....O....O.O.O..O.O................
	...............................................
	O......O.O.O....O....O......O..O...........O...
	..........................................OO...
	O.O.O..O...O....O....O.O.O..O...O.........O.O..

Alternatively, stamp collections can use LifeHistory for their annotations, but this requires a more sophisticated Life program to handle. Numbers, or more rarely letters, are sometimes constructed from stable components such as blocks or snakes, but their readability is somewhat limited by placement constraints.

:standard spaceship A glider, LWSS, MWSS or HWSS. These have all been known since 1970.

:star (p3) Found by Hartmut Holzwart, February 1993.

	.....O.....
	....OOO....
	..OOO.OOO..
	..O.....O..
	.OO.....OO.
	OO.......OO
	.OO.....OO.
	..O.....O..
	..OOO.OOO..
	....OOO....
	.....O.....

:star gate A device by Dieter Leithner (October 1996) for transporting a LWSS faster than the speed of light. The key reaction is the Fast Forward Force Field.

:stator The cells of an oscillator that are always on. Compare rotor. (The stator is sometimes taken to include also some of those cells which are always off.) The stator is divided into the bushing and the casing.

By analogy, the cells of an eater that remain on even when the eater is eating are considered to constitute the stator of the eater. This is not always well-defined, because an eater can have more than one eating action.

:statorless A statorless oscillator is one in which no cell is permanently on - that is, the stator is empty.

:step Another term for a generation or tick. This term is particularly used in describing conduits. For example, a 64-step conduit is one through which the active object takes 64 generations to pass.

:stillater (p3) Found by Robert Wainwright, September 1985. This is one of only three essentially different p3 oscillators with only three cells in the rotor. The others are 1-2-3 and cuphook.

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

:still life Any stable pattern, usually assumed to be finite and nonempty. For the purposes of enumerating still lifes this definition is, however, unsatisfactory because, for example, any pair of blocks would count as a still life, and there would therefore be an infinite number of 8-bit still lifes.

For this reason a stricter definition is often used, counting a stable pattern as a strict still life only if its islands cannot be divided into two or more nonempty sets both of which are stable in their own right. If such a subdivision can be made, the pattern can referred to as a constellation. If its cells form a single cluster it is also, more specifically, either a pseudo still life or a quasi still life.

In rare cases above a certain size threshold, a pattern may be divisible into three or four stable nonempty subsets but not into two. See the 32-bit triple pseudo (32 bits) and the 34-bit quad pseudo for examples.

All still lifes up to 18 bits have been shown to be glider constructible. It is an open question whether all still lifes can be incrementally constructed using glider collisions. For a subset of small still lifes that have been found to be especially useful in self-constructing circuitry, see also Spartan.

The smallest still life is the block. Arbitrarily large still lifes are easy to construct, for example by extending a canoe or barge. The maximum density of a large still life is 1/2, which can be achieved by an arbitrarily large patch of zebra stripes or chicken wire, among many other options. See density for more precise limits.

	...O..O..O..O..O..O...
	.OOOOOOOOOOOOOOOOOOOO.
	O....................O
	OOOOOOOOOOOOOOOOOOOOOO
	......................
	OOOOOOOOOOOOOOOOOOOOOO
	O....................O
	.OOOOOOOOOOOOOOOOOOOO.
	......................
	.OOOOOOOOOOOOOOOOOOOO.
	O....................O
	OOOOOOOOOOOOOOOOOOOOOO
	......................
	OOOOOOOOOOOOOOOOOOOOOO
	O....................O
	.OOOOOOOOOOOOOOOOOOOO.
	......................
	.OOOOOOOOOOOOOOOOOOOO.
	O....................O
	OOOOOOOOOOOOOOOOOOOOOO
	......................
	OOOOOOOOOOOOOOOOOOOOOO
	O....................O
	.OOOOOOOOOOOOOOOOOOOO.
	...O..O..O..O..O..O...

:still life tagalong A tagalong which takes the form of a still life in at least one phase. An example is shown below.

	..OO...............
	.OO.OO.............
	..OOOO.............
	...OO..............
	...................
	...OOOOO...........
	..OOOOOOO..........
	.OO.OOOOO..........
	..OO...............
	...................
	........O.O.....OO.
	......O....O...O..O
	......OO.....O.O..O
	.O..O..OOOO.O...OO.
	O.......OO.........
	O...O..............
	OOOO...............

:stop and go A pattern by Dean Hickerson in which a period 46 shuttle converts a glider into a block on one oscillation, and then converts the block back into a glider on the next oscillation. The glider is reflected back onto its own path, but with a delay.

	........................................O.
	.......................................O..
	OO..............OO.........OO..........OOO
	OO...............OO........OO.............
	.............OOOOO........................
	.............OOOO.........................
	..........................................
	.............OOOO.........................
	.............OOOOO........................
	OO...............OO.......................
	OO..............OO........................

:stop and restart A type of signal circuit where an input signal is converted into a stationary object, which is then re-activated by a secondary input signal. This can be used either as a memory device storing one bit of information, or as a simple delay mechanism. In the following January 2016 example by Martin Grant, a ghost Herschel marks the output signal location, and a "ghost beehive" marks the location of the intermediate still life.

	........................................................O.
	.......................................................O..
	.......................................................OOO
	..........................................................
	..........................................................
	..........................................................
	..........................................................
	..........................................................
	..........................................................
	..........................................................
	..........................................................
	..........................................................
	..........................................................
	..........................................................
	..........................................................
	............O.............................................
	............OOO...........................................
	...............O..........................................
	..............OO..........................................
	........O.................................................
	.......O.O.......OO.......................................
	.......O.O......O.O.......................................
	.....OOO.OO.....OO........................................
	....O.....................................................
	.....OOO.OO...............................................
	.......O.OO...............................................
	..........................................................
	..........................................................
	..........................................................
	OO........................................................
	.O........................................................
	.O.O......................................................
	..OO......................................................
	..........................................................
	....................O.....................................
	...................O.O....................................
	...................O...................................O..
	....................O................................OOO..
	....................................OO...............O....
	..O.................................OO...............O....
	..O.O.....................................................
	..OOO.....................................................
	....O....................O................................
	........................O.O...............................
	........................OO................................
	...................OO............OO.......................
	...................OO............O........................
	..................................O.......................
	.................................OO.......................
	..........................................................
	..........................................................
	..........................................................
	..........................................................
	..........................................................
	..........................................................
	..OO..........OO..........................................
	...O..........O...........................................
	OOO............OOO........................................
	O................O........................................
The eater1 in the lower left corner catches the restart glider if no input signal has come in to create the beehive. This eater could be removed if it is useful to have both a "0" and a "1" output for a memory cell mechanism.

The catch and throw technology in a Caterpillar is a somewhat similar idea. See also stop and go and reanimation.

:stream A line of identical objects (usually spaceships), each of which is moving in a direction parallel to the line, generally on the same lane. In many uses the stream is periodic. For example, the new gun produces a period 46 glider stream. The stream produced by a pseudo-random glider generator can have a very high period. Compare with wave. See also single-channel for a common use of non-periodic glider streams.

:stretcher Any pattern that grows by stretching a wick or agar. See wickstretcher and spacefiller.

:strict still life A still life that is either a single connected polyplet, or is arranged such that a stable smaller pattern cannot be formed by removing one or more of its islands. 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. See also triple pseudo, quad pseudo.

Still lifes have been enumerated by Conway (4-7 bits), Robert Wainwright (8-10 bits), Dave Buckingham (11-13 bits), Peter Raynham (14 bits), Mark Niemiec (15-24 bits), and Simon Ekström and Nathaniel Johnston (25-32 bits). The resulting figures are shown below; see also https://oeis.org/A019473. The most recent search by Nathaniel Johnston has also confirmed that the triple pseudo pattern found by Gabriel Nivasch is the only such still life with 32 bits or less. It is therefore included in the pseudo still life count and not in the table below.

	--------------
	Bits    Number
	--------------
	 4           2
	 5           1
	 6           5
	 7           4
	 8           9
	 9          10
	10          25
	11          46
	12         121
	13         240
	14         619
	15        1353
	16        3286
	17        7773
	18       19044
	19       45759
	20      112243
	21      273188
	22      672172
	23     1646147
	24     4051711
	25     9971377
	26    24619307
	27    60823008
	28   150613157
	29   373188952
	30   926068847
	31  2299616637
	32  5716948683
	--------------

:strict volatility A term suggested by Noam Elkies in August 1998 for the proportion of cells involved in a period n oscillator which themselves oscillate with period n. For prime n this is the same as the ordinary volatility. Periods with known strictly-volatile oscillators include 1, 2, 3, 5, 6, 8, 13, 15, 22, 30, 33, and 177. Examples include figure-8, Kok's galaxy, smiley, and pentadecathlon. A composite example is the following p22, found by Nicolay Beluchenko on 4 March 2009:

	...........OO...
	..........O.O...
	..O.....O....O..
	OO.OO..OO.O.O...
	O.......O...O...
	.O.O............
	................
	..OOO.......O...
	...O.......OOO..
	................
	............O.O.
	...O...O.......O
	...O.O.OO..OO.OO
	..O....O.....O..
	...O.O..........
	...OO...........

:super beehive = honeycomb

:superfountain (p4) A p4 sparker which produces a 1-cell spark that is separated from the rest of the oscillator by two clear rows of cells. The first superfountain was found by Noam Elkies in February 1998. In January 2006 Nicolay Beluchenko found the much smaller one shown below. See also fountain.

	...........O...........
	.......................
	.......................
	.....O..O.....O..O.....
	...OO..O.OOOOO.O..OO...
	.....O...........O.....
	...O.OO.........OO.O...
	.O.O...OOO...OOO...O.O.
	OOO.O.............O.OOO
	..........O.O..........
	....OOO...O.O...OOO....
	....O..O...O...O..O....
	...OOOO..O.O.O..OOOO...
	...OO..OOO.O.OOO..OO...
	..O...O...O.O...O...O..
	...O..O.O.O.O.O.O..O...
	....O.O.OO...OO.O.O....
	.....O...........O.....

:superlinear growth Growth faster than any rate proportional to T, where T is the number of ticks that a pattern has been run. This term usually applies to a pattern's population growth, rather than diametric growth or bounding-box growth. For example, breeders' and spacefillers' population asymptotically grows faster than any linear-growth pattern. It may also be used to describe the rate of increase in the number of subpatterns present in a pattern, such as when describing a replicator's rate of reproduction. Due to limits enforced by the speed of light, no pattern's population can grow at an asymptotic rate faster than quadratic growth.

:superstring An infinite orthogonal row of cells stabilized on one side so that it moves at the speed of light, often leaving debris behind. The first examples were found in 1971 by Edward Fitzgerald and Robert Wainwright. Superstrings were studied extensively by Peter Rott during 1992-1994, and he found examples with many different periods. (But no odd periods. In August 1998 Stephen Silver proved that odd-period superstrings are impossible.)

Sometimes a finite section of a superstring can be made to run between two tracks ("waveguides"). This gives a fuse which can be made as wide as desired. The first example was found by Tony Smithurst and uses tubs. (This is shown below. The superstring itself is p4 with a repeating section of width 9 producing one blinker per period and was one of those discovered in 1971. With the track in place, however, the period is 8. This track can also be used with a number of other superstrings.) Shortly after seeing this example, in March 1997 Peter Rott found another superstring track consisting of boats. At present these are the only two waveguides known. Both are destroyed by the superstring as it moves along. It would be interesting to find one that remains intact.

See titanic toroidal traveler for another example of a superstring.

	.OO..........................................................
	O..O...O...O...O...O...O...O...O...O...O...O...O...O...O...O.
	....O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O
	O..O...O...O...O...O...O...O...O...O...O...O...O...O...O...O.
	.OOO.........................................................
	..OO.........................................................
	..OO.........................................................
	...O.........................................................
	...O.........................................................
	...O.........................................................
	...O.........................................................
	...O.........................................................
	...O.........................................................
	...O.........................................................
	..OO.........................................................
	..OO.........................................................
	.OOO.........................................................
	O..O...O...O...O...O...O...O...O...O...O...O...O...O...O...O.
	....O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O
	O..O...O...O...O...O...O...O...O...O...O...O...O...O...O...O.
	.OO..........................................................

:support Those parts of an object which are only present in order to keep the rest of the object (such an engine or an edge spark) working correctly. These can be components of the object, or else accompanying objects used to perturb the object. In many cases there is a wide variation of support possible for an engine. The arms in many puffers are an example of support.

:surprise (p3) Found by Dave Buckingham, November 1972.

	...O....OO
	...OOO..O.
	.OO...O.O.
	O..OO.O.OO
	.O......O.
	OO.O.OO..O
	.O.O...OO.
	.O..OOO...
	OO....O...

:SW1T43 A Herschel-to-glider converter that produces a tandem glider useful in the tee reaction. It is classified as a "G3" converter because its two gliders are three lanes apart.

	.......OO........
	.......O.........
	.....O.O.........
	....O.O..........
	OO...O...........
	OO...............
	...........OO....
	...........O.O...
	.............O...
	.............O.OO
	..........OO.O.OO
	O........O..O....
	O.O.......OO.....
	OOO..............
	..O.......OOOO...
	...........O..O..
	.........O...OO..
	.........OO......
Besides the southwest-traveling glider on lane 1, the converter also emits the Herschel's standard first natural glider, SW-2. The converter's full standard name is therefore "HSW1T43_SW-2T21". See NW31T120 for an explanation of H-to-G naming conventions.

:SW-2 The simplest type of H-to-G converter, where the converter's effect is simply to suppress a Herschel cleanly after allowing its first natural glider to escape. The name should be read as "SW minus two", where -2 is a glider lane number. The complete designation is SW-2T21. See NW31T120 for a discussion of the standard naming conventions used for these converters.

An unlimited number of converters have the SW-2T21 classification. The variants most often used consist of just one or two small still life catalysts.

	...................................OO.....
	...................................O......
	.................................O.O......
	.............................OO..OO.......
	.............................OO...........
	.....OO...................................
	.....OO...................................
	.............................OO...........
	.............................OO...........
	..........................................
	..........................................
	..........................................
	.........OO...............................
	.........OO...............................
	..........................................
	O........................O................
	O.O......................O.O..............
	OOO......................OOO..............
	..O........................O..............
	..........................................
	..........................................
	..........................................
	..........................................
	..........................................
	..........................................
	..........................................
	..........................................
	..........................................
	..........................................
	..........................................
	..........................................
	..........................................
	..........................................
	..........................................
	..........................................
	........................................O.
	...........O...........................O.O
	..........O.O...........................OO
	..........O.O.............................
	...........O............................OO
	O........................O.............O.O
	O.O......................O.O............O.
	OOO......................OOO..............
	..O........................O..............

:SW-2T21 = SW-2

:swan (c/4 diagonally, p4) A diagonal spaceship producing some useful sparks. Found by Tim Coe in February 1996.

	.O..........OO..........
	OOOOO......OO...........
	O..OO........O.......OO.
	..OO.O.....OO......OOO.O
	...........OO...O.OO....
	.....O.O......OO........
	..........OOO.O....O....
	.......OOO...O....O.....
	........O.......O.......
	........O......O........
	........................
	...........O............

:swimmer = switch engine.

:swimmer lane = switch engine channel.

:switch A signal-carrying circuit that can be modified so that it cleanly absorbs any future signals instead of allowing them to pass. Optionally there may be a separate mechanism to restore the circuit to its original function.

In the following example, a glider from the northeast (shown) will perform a simple block pull that switches off an F166 conduit, so that any future Herschel inputs will be cleanly absorbed. A glider from the southwest (also shown) can restore the block to its original position.

	.OO........................................................
	..O........................................................
	.O.........................................................
	.OO...............................................OO.......
	...................................................O.......
	..................................................O........
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:switchable gun A gun that includes a mechanism to turn the output stream off and on with simple signals, often gliders. A small example is Dieter Leithner's switchable LWSS gun from July 8, 1995. The ON signal enters from the northeast, and the OFF signal from the northwest:

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:switch engine The following pattern discovered by Charles Corderman in 1971, which is a glide symmetric unstable puffer which moves diagonally at a speed of c/12 (8 cells every 96 generations).

	.O.O..
	O.....
	.O..O.
	...OOO

The exhaust is dirty and unfortunately catches up and destroys the switch engine before it runs 13 full periods. Corderman found several ways to stabilize the switch engine to produce puffers, using either one or two switch engines in tandem. See stabilized switch engine and ark.

No spaceships were able to be made from switch engines until Dean Hickerson found the first one in April 1991 (see Cordership). Switch engine technology is now well-advanced, producing many c/12 diagonal spaceships, puffers, and rakes of many periods.

Small polyominoes exist whose evolution results in a switch engine. See nonomino switch engine predecessor.

Several three-glider collisions produce dirty reactions that produce a stabilized switch engine along with other ash, making infinite growth. Until recently the only known syntheses for clean unstabilized switch engines used four or more gliders. There are several such recipes. In the reaction shown below no glider arrives from the direction that the switch engine will travel to, making it easier to repeat the reaction:

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Running the above for 20 ticks completes a kickback reaction with the top two gliders, resulting in the three-glider switch engine recipe discovered by Luka Okanishi on 12 March 2017.

:switch engine channel Two lines of boats (or other suitable objects, such as tub with tails) arranged so that a switch engine can travel between them, in the following manner:

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David Bell used this in June 2005 to construct a "bobsled" oscillator, in which a switch engine factory sends switch engines down a channel, at the other end of which they are deleted.

:switch engine chute = switch engine channel

:switch-engine ping-pong A very large (210515×183739) quadratic growth pattern found by Michael Simkin in October 2014. Currently this is the smallest starting population (23 cells) known to result in a quadratic population growth rate.

:symmetric Any object which can be rotated and/or flipped over an axis and still maintain the same shape. Many common small objects such as the block, beehive, pond, loaf, clock, and blinker are symmetric. Some larger symmetric objects are Kok's galaxy, Achim's p16, cross, Eureka, and the pulsar.

Large symmetric objects can easily be created by placing multiple copies of any finite object together in a symmetrical way. Unless the individual objects interact significantly, this is considered trivial and is not considered further here (e.g., two LWSSs travelling together a hundred cells apart).

Because the Life universe and its rules are symmetric, all symmetric objects must remain symmetric throughout their evolution. Most non-symmetric objects keep their non-symmetry as they evolve, but some can become symmetric, especially if they result in a single object. Here is a slightly more complicated example where two gliders interact to form a blockade:

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

Many useful objects are symmetric along an orthogonal axis. This commonly occurs by placing two copies of an object side by side to change the behaviour of the objects due to the inhibition or killing of new cells at their gutter interface. Examples of this are twin bees shuttle, centinal, and the object shown in puffer. Other useful symmetric objects are created by perturbing a symmetric object using nearby oscillators or spaceships in a symmetric manner. Examples of this are Schick engine, blinker ship, and hivenudger.

Many spaceships found by search programs are symmetric because the search space for such objects is much smaller than for non-symmetrical spaceships. Examples include dart, 60P5H2V0, and 119P4H1V0.

:synchronized Indicates that precise relative timing is required for two or more input signals entering a circuit, or two or more sets of gliders participating in a glider synthesis. Compare asynchronous. See also salvo and slow glider construction.

:synchronous = synchronized

:synthesis = glider synthesis

:syringe A small stable converter found by Tanner Jacobi in March 2015, accepting a glider as input and producing an output Herschel As of November 2017 it is the smallest known converter of this type, so it is very often used to handle input gliders in complex signal circuitry, as described in Herschel circuit. A second glider can safely follow the first any time after 78 ticks, but overclocking also allows the syringe to work at a repeat time of 74 or 75 ticks. If followed by a dependent conduit a simple eater2 can be used instead of the large welded catalyst shown here. A ghost Herschel marks the output location.

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Introduction | 1-9 | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | Bibliography