Definitions of Life Terms

Life | Terms | Object | Pseudo-object | Still-life | Eater | Rock | Pseudo-still-life | Oscillator | Sparker | Pseudo-oscillator | Spaceship | Pseudo-spaceship | Flotilla | Gun | Puffer | Breeder | Inductor | Constellation | Methuselah


Life is a cellular automata invented by professor John Horton Conway in the early 1970s.

The universe is an infinitely large array of square cells. Each cell can be in one of two distinct states: dead or alive, empty or full, 0 or 1, etc. Each cell is adjacent to eight other neighboring cells.


In every generation, a cell changes state according to its current state and the state of its eight neighbors:

All cells change state simultaneously. By successively repeating this operation, patterns evolve.

To avoid confusion, on these pages, the term cell refers to a cell as an entity that can be in one of several different states, while the term bit always refers to a cell that is alive, and is generally used for counting purposes. For example, a 12-bit still-life is a still-life that has exactly 12 living cells.

Most of the other definitions on this page apply not only to Life, but also to many other cellular automata with different states, neighborhoods or transition rules.

Patterns are usually characterized by their behavior:


The following terms are used frequently when discussing Life and other cellular automata. These are all basic terms that require little explanation. Terms with more complex definitions are described separately in subsequent sections.


An object is a pattern consisting of one or more closely-connected bits. In order to provide an unambiguous method of distinguish objects from non-objects, the definition of "close" is defined precisely:

Any bit (i.e. living cell) forms an object.

bit object

If two objects contains any bits that are neighbors of each other, they are a single connected object. In Life, this includes any bits adjacent to each other either orthogonally or diagonally.

connected objects

If two unconnected objects interact with each other so that they cause births that would otherwise not occur, or suppress births that would otherwise occur, they form a single spatially-connected object.

spatial objects

Carrier [4] 10.25; Block on table [4] 13.221; Up bun on snake [7] Glider- snake collision adding "boat-bit" [3] MWSS on MWSS #1 [7]

If two or more unconnected objects are adjacent to each other in such a way that some empty cells change from being sterile due to under-population to being sterile due to over-population, but they do not affect each other, they do not automatically form an object; these form a pseudo-object.

simple pseudo-objects

Block on block [2] Down snake below snake [8] Block on beacon [4] HWSS on HWSS #3 [7]

If three or more unconnected objects are adjacent to each other in such a way that there exists any way of partitioning these objects into two distinct sets, such that the combined objects in one set do not affect the combined objects in the other set, these objects do not automatically form a single object, even if there is some partition where they do affect one another. They form a pseudo-object. The third example, found by Pavel Podgoretsky, was the first pseudo-object where the pieces must be partitioned into more than two distinct sets. Gabriel Nivasch subsequently found the next two examples. The fourth example is a smaller one with similar properties, and the fifth one requires partitioning into four distinct sets. The Four Color Map Theorem can show that no more than four distinct sets will ever be required.

complex pseudo-objects

Two blocks on two blocks [4] Two blocks on snake siamese snake [18] Four blocks on table around block [x+34] Two hooks w/ tail and two snakes on block [x] Hook w/ tail bit snake on snake and hat and block [x]

When dealing with periodic objects over their entire lifespan, such as oscillators and spaceships, if any components form a single object together in any generation, they are considered to form a single object in all generations. (This only applies when considering all generations as a whole; when only considering a single generation at a time, this rule is not applicable.)

simple temporal objects

Beacon [3] Unix [6] Blocker [6] Penta- decath- lon [3] Penta- decath- lon on penta- decath- lon #7 [8] HWSS on HWSS #7 [7] LWSS on 7WSS on LWSS #1 [12]

The above also applies, even if the interaction between individual components is completely trivial, either forming attachments between dying bits, or creating additional births that die unobtrusively, or suppressing births that would otherwise die unobtrusively.

complex temporal objects

Pentadec- athlon on pentadec- athlon #4 [8] Eater eating pentadec- athlon [6] Two trans blockers [16] Two trans unices [14] HWSS on HWSS #4 [6]


A pseudo-object is a pattern that, although not quite meeting the criteria necessary to be a single object, is nevertheless closely connected.

If two unconnected objects are adjacent to one another in such a way that any empty cells between then do not cause new births, but have a neighborhood that could form a birth if some if its cells were removed (in Life, this means four or more neighbors), the objects combine to form a pseudo-object. (See previous section for a more rigorous description).


A still-life is an object where all bits survive, and no new births are formed. For example:


Block [2] Carrier [6] 10.25; Block on table [4] 12.121; Super beehive [6] 14.79; Paperclip [3] 15.243; Moose antlers [4] 20. 88034; Small lake [10]


An eater is a still-life (or sometimes an pseudo-still-life or constellation) that can eat other objects, or parts of other objects, which may temporarily damage or destroy the eater, but the eater later re-appears unchanged. For example:


Block [2] Tub [3] Eater; Eater-1; Fishhook [2] Eater-5 [6] 18.13721; Century eater [9] 19.11763; Eater-2 [16] Glider eater [12-14] B1 glider eater [21] Eater-3 [72] Variant eater-3 [42]


A rock is a still-life (or sometimes a pseudo-still-life or oscillator) that is an eater, but with the additional property that its own behavior is never altered in the process. For example:


Block [2] Eater; Eater-1; Fishhook [2] Blinker [2] Clock [4] Killer toads [6] Killer candel- frobras [12-16]


A pseudo-still-life is a pseudo-object where all bits survive, and no new births are formed. For example:


Block on block [2] Down snake below snake [8] Block on block on block [4] Two blocks on two blocks [4] Two blocks on snake siamese snake [18] Two hooks w/ tail and two snakes on block [x] Hook w/ tail bit snake on snake and hat and block [x] Four blocks on table around block [x+34]


An oscillator is an object that, after several generations, returns to its original state. Objects that return to their original state in 1 generation are still-lifes, and are not considered oscillators.

Terms used to describe electric motors can also describe parts of oscillators:

Oscillators are often classified by their form or function:


Blinker [2] (flip- flop, muttering moat) Beacon [3] (on-off, babbling brook) Phoenix [10] (flip- flop, phoenix) Caterer [11] (puls- ator, hassler) Tumbler [6] (puls- ator, in- ductor) Hertz oscillator [11] (BTC) Al Jolson [13] (sparked)
Cis buckaroo [6] (shuttle, eater- bound, sparker) Loaf hassled by two blocks and two caterers [52] (eater- bound, hassled)


A sparker is a special kind of oscillator that throws off sparks, i.e. dying bits at the edge of the object, or a part of the object at the edge that protrudes. These can be useful to provide momentary alterations of neighborhoods of cells in another object, to either cause additional births, or suppress unwanted ones. There are several categories of sparks that are commonly seen:


A pseudo-oscillator is a pseudo-object that, after several generations, returns to its original state. Pseudo-objects that return to their original state in 1 generation are pseudo-still-lifes, and are not considered pseudo-oscillators.


Up toad on toad [5] Block on beacon [4] Pentadec- athlon on pentadec- athlon #3 [7]


A spaceship is an object that, after several generations, returns to its original state, but translated in space. Objects that return to their original state without moving are oscillators, and are not considered spaceships. Many spaceships also produce sparks. Sparks at the back of the spaceship are called tails parks, while those at the sides are called belly sparks.


Glider [2] Light- weight space- ship (LWSS) [3] Middle- weight space- ship (MWSS) [3] Heavy- weight space- ship (HWSS) [3] Sidecar on HWSS [8] Half of X66 on HWSS [x] Schick ship behind two LWSS [10] LWSS on Coe ship [8]


A pseudo-spaceship is an pseudo-object that, after several generations, returns to its original state, but translated in space. Pseudo-objects that return to their original state without moving are pseudo-oscillators, and are not considered pseudo-spaceships.


LWSS on LWSS [7] LWSS on HWSS #8 [7] HWSS on HWSS #3 [7]

Spaceship Flotilla (Flotilla)

An spaceship flotilla (or just flotilla) is a collection of two or more spaceships traveling in tandem. Some of the spaceships may escort mechanisms that are not able to travel by themselves, or they may interact trivially with each other. Many flotillae are themselves technically just spaceships or pseudo-spaceships; however, it is usually easier to discuss them separately. Flotillae that are not objects (i.e. multiple independent spaceships traveling in tandem, separated by a small distance) are not detailed on these pages, because there are infinitely many of them.

spaceship flotillae

LWSS on MWSS #3 [7] Sidecar on HWSS [8] Half of X66 on HWSS [x] LWSS on 7WSS on LWSS #1 [12] LWSS on Coe ship [8]

Spaceship Gun (Gun)

A spaceship gun (or gun) is an oscillator that creates eggs that are spaceships that can safely escape. The population of a gun increases linearly with time.

Guns that emit puffer trains are SMM breeders, and have populations that increase quadratically with time.

Glider guns (i.e. guns that emit gliders) can be constructed for all periods 56 and higher, and guns of many lower periods are known. Guns that emit glider streams of any period 14 and up can be constructed, but even though the glider stream has a period as low as 14, the the gun itself typically has a period that is some larger multiple of the stream period.

For example, one can construct a gun that shoots gliders 14 generations apart using base period 30 guns by creating a slow period 210 gun by using several base guns and a reaction that divide the period by seven, then using many such gun to create and align 15 period 210 glider streams in the same lane.

Since the three simple c/2 orthogonal spaceships can be constructed from gliders, guns (also known as factories) for these spaceships of the same periods can be constructed. Light-weight spaceship streams must at least period 24. Middle-weight spaceship streams must at least period 28. Heavy-weight spaceship streams must at least period 32. (Theoretically, streams as dense as periods 14, 16, and 18 respectively could be created, but there are currently no known synthesis techniques to do so).

spaceship guns

Period-30 glider gun [8] Period-46 glider gun
Period-30 LWSS factory

Puffer Train (Puffer)

A puffer train (or puffer) is a spaceship that emits debris, that may be anything that does not move with the same velocity as the puffer train, such as still-lifes, oscillators, or spaceships.

puffer trains

Corderman's block-making switch engine [5] Wainwright's P8 blinker puffer [10] Buckingham's P24 tub puffer [9] Gosper's P20 puffer [9]


A breeder is a pattern whose population increases forever, and whose population is greater than a linear function of time. Breeders are generally factories that build producers that produce debris, and their population normally increases quadratically with respect to time. Breeders that produce a fixed number of objects of quadratically-increasing population are called space-fillers. The four categories of breeders are categorized by which of the three parts are stationary:

  1. SMM breeder (stationary factory): guns that builds puffer trains that emit spaceships.
  2. MSM breeder (stationary producer): puffer trains that build guns that emit spaceships (this is the first type of breeder ever built).
  3. MMS breeder (stationary debris): puffer trains that build puffer trains that emit still-lifes and/or oscillators.
  4. MMM breeder (nothing stationary): puffer trains that build puffer trains that emit spaceships.

There are also many other hybrid categories possible, including many variations whose population increases at other rates. Dean Hickerson has created many such patterns, with populations of O(√n), O(n log n), etc.

Induction Coil (inductor)

An induction coil (or inductor) is an unstable object that, by itself, would produce several unwanted births on its outside. These births can be suppressed by placing another object beside the induction coil. This birth-suppression is referred to as induction.

This is a sampling of inducted objects (named below), with their corresponding inductors (named above) shown in teal.

induction coils

Table Side Bookend Cover Tear- drop Very long house, siamese bookends Cup- hook with tail Long bookend eating eater Candel- frobra
Down beacon on table [6] Snake on side (13.214) [10] Up snake on bookend (13.223) [7] Block with cover (12.111) [4] Two bridged carriers on teardrop (21. 198031) [6] Tub on very long house (16.1858) [7] Block on up cuphook w/ tail; M.I.T. Oscillator [8] Eater eating block on up long bookend [11] Block on up candel- frobra [12]


A constellation is a collection of several periodic objects or pseudo-objects. Since there are so many possible constellations (for example, there are an infinite number of arrangements of two blocks alone), most constellations are not interesting in themselves. Exceptions include constellations that occur naturally, or that have some functional significance, or that can be constructed for a cost less than their individual components.


Two blocks offset (1, 4) [2] Teardrop [2] Fleet [3] Honey- farm [2] Bakery [3] Loaf and blinker [2] Traffic light [2] Loaf and tub and block and blinker [2]


A methuselah is a small unstable object that lives for an unusually long time before becoming stable. (The name is derived from the biblical patriarch of the same name, who had the longest recorded human life span: 969 years.) In Life, this was originally defined as any object of 8 bits or less that survives at least 50 generations before becoming stable. In colloquial usage, and on these pages, this definition is relaxed somewhat to also include some larger long-lived objects or pseudo-objects, or even patterns that are neither, and focuses on the results (that can be obtained from several predecessors), rather than dwelling on specific predecessors. The key feature methuselahs share is that they start small and run for a disproportionately long time.


Pi hept- omino [2] R pent- omino [3] B hept- omino [2] Bookend [3] Thunder- bird [4] Acorn [4] (2 glider) Oct- omino [2] Gliders by the dozen [3] Rabbits [5] Two glider mess [2]

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This page was last updated on 2015-02-19.