Glossary
Fifty years of enthusiasts naming things produced a vocabulary. Here it is, alphabetically.
- Agar
- A pattern that fills the plane with a repeating periodic texture, in the way a wick fills a line.
- Ash
- The stable and oscillating debris left behind once a random soup has settled. Its statistics - which objects appear, and how often - are a genuine field of study.
- B/S notation
- The standard way of writing a Life-like rule: B followed by the neighbour counts that cause a birth, then S followed by the counts that permit survival. Conway's Life is B3/S23.
- Billiard table
- An oscillator whose active cells are enclosed by a stable border, like balls rattling around inside a frame.
- Blinker
- The smallest and most common oscillator: three cells in a row, flipping between horizontal and vertical every generation.
- Block
- The smallest and most common still life - a 2x2 square. Also the standard building material for Life engineering.
- Breeder
- A pattern whose population grows quadratically, typically by leaving a trail of guns behind it, each of which then emits spaceships forever.
- c
- The speed of light in Life: one cell per generation. Nothing can travel faster, because information cannot propagate beyond the neighbourhood in a single step. A glider moves at c/4.
- Catagolue
- A distributed census of random soups. Volunteers run trillions of random starting patterns and the results are catalogued automatically, which is how most new objects are now discovered.
- Cell
- One square of the grid. In Life it holds one bit: alive or dead.
- Conduit
- A stable arrangement of still lifes that moves an active object from one place to another without being destroyed, letting engineers route signals.
- Eater
- A still life that absorbs an incoming object and repairs itself. The fishhook eater consumes a glider in four generations and is the standard component.
- Fuse
- A pattern that burns steadily from one end, sometimes leaving debris and sometimes leaving nothing.
- Garden of Eden
- A configuration with no possible predecessor. It can be drawn, but it can never arise from any earlier generation.
- Generation
- One application of the rule to the entire board. Also called a tick or a step.
- Glider
- The smallest spaceship: five cells travelling diagonally at c/4. The emblem of the whole field.
- Golly
- The standard open-source Life program, implementing HashLife and handling patterns of astronomical size.
- Gun
- A pattern that returns to its original state while emitting spaceships, so its population grows without bound.
- HashLife
- Bill Gosper's algorithm for advancing a Life pattern by memoising repeated regions of space and time. Highly regular patterns can be advanced by billions of generations in seconds; chaotic ones cannot.
- Methuselah
- A small pattern that takes an extraordinarily long time to stabilise. The R-pentomino runs 1,103 generations from five cells; Bunnies runs 17,332 from nine.
- Moore neighbourhood
- The eight cells surrounding a cell - four edge-adjacent and four corner-adjacent. Life's neighbourhood.
- Oscillator
- A pattern that returns to its exact starting configuration after a fixed number of generations. That number is its period.
- Period
- The number of generations after which an oscillator or spaceship repeats. A still life has period 1.
- Puffer
- A spaceship that leaves debris behind as it travels.
- Rake
- A puffer whose debris consists of spaceships - effectively a moving gun.
- Reflector
- A construction that changes the direction of a passing glider, letting signals be routed around a circuit.
- RLE
- Run Length Encoded - the standard text format for Life patterns since 1980. 'b' is a dead cell, 'o' is a live one, '$' ends a row, '!' ends the pattern, and a leading number repeats the next symbol.
- R-pentomino
- The five-cell methuselah that Conway's group tracked by hand on a Go board. It runs for 1,103 generations and throws off six gliders.
- Rotor and stator
- In an oscillator, the rotor is the set of cells that change and the stator is the set that stays put.
- Sawtooth
- A pattern whose population grows without bound but returns to its original value infinitely often, so the population graph looks like a saw blade.
- Soup
- A random starting configuration, usually confined to a small square.
- Spaceship
- A pattern that returns to its original shape displaced by some distance - an oscillator that travels.
- Spark
- A transient cell or small group appearing briefly at the edge of an oscillator. Sparks do nothing alone but can perturb passing objects, which makes sparkers valuable components.
- Still life
- A pattern that never changes. Strictly, a stable pattern that cannot be split into two independent stable pieces.
- Stabilisation
- The point at which a pattern has become entirely still lifes, oscillators and escaping spaceships, so nothing new will ever happen.
- Synthesis
- Building a target pattern by colliding gliders in a carefully arranged sequence. Reducing the glider count for a given object is a competitive sport.
- Torus
- A grid whose left edge is joined to its right and whose top is joined to its bottom, so nothing ever falls off. The Lab uses one by default.
- Turing complete
- Capable of performing any computation a Turing machine can. Life was proved Turing complete in 1982.
- Universal constructor
- A machine that can build any pattern - including a copy of itself - from a description tape. Von Neumann's original goal, achieved inside Life in 2010.
- Wick
- A one-dimensional repeating pattern, typically burned from one end by a fuse.
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