:oblique Neither diagonal nor orthogonal. See also knightship.
:obo spark A spark of the form O.O (so called after its rle encoding).
:octagon II (p5) The first known p5 oscillator, discovered in 1971 independently by Sol Goodman and Arthur Taber. The name is due to the latter.
...OO... ..O..O.. .O....O. O......O O......O .O....O. ..O..O.. ...OO... |
:octagon IV (p4) Found by Robert Wainwright, January 1979.
:octomino Any 8-cell polyomino. There are 369 such objects. The word is particularly applied to the following octomino (or its two-generation successor), which is fairly common but lacks a proper name:
..OO ..OO OOO. .O.. |
:odd keys (p3) Found by Dean Hickerson, August 1989. See also short keys and bent keys.
..........O. .O.......O.O O.OOO..OO.O. .O..O..O.... ....O..O.... |
:omniperiodic A cellular automaton is said to be omniperiodic if it has oscillators of all periods. It is not known if Life is omniperiodic, although this seems likely. Dave Buckingham's work on Herschel conduits in 1996 (see My Experience with B-heptominos in Oscillators) left only a finite number of unresolved cases, further reduced by Noam Elkies between 1999 and 2002. At the time of writing (August 2017) no oscillators are known for periods 19, 23, 38, or 41. If we insist that the oscillator must contain a cell oscillating at the full period, then 34 should be added to this list. Period 43 and 53 oscillators were made possible in 2013 by Mike Playle's Snark.
Note that if we were to allow infinite oscillators, then all periods are certainly possible, as any period of 14 or more can be obtained using a glider (or LWSS) stream.
:one per generation See grow-by-one object.
:one-sided spaceship synthesis A glider synthesis of a spaceship in which all gliders come from the same side of the spaceship's path. Such syntheses are used extensively in the 17c/45 Caterpillar.
:one-time A concept used for turners and splitters, specifying that the reaction in question is not repeatable as it would be in a reflector or fanout device. Instead, the constellation is used up in the course of the reaction, usually leaving nothing behind.
:onion rings For each integer n>1 onion rings of order n is a stable agar of density 1/2 obtained by tiling the plane with a certain 4n x 4n pattern. The tile for order 3 onion rings is shown below - the reader should then be able to deduce the form of tiles of other orders.
......OOOOOO .OOOO.O....O .O..O.O.OO.O .O..O.O.OO.O .OOOO.O....O ......OOOOOO OOOOOO...... O....O.OOOO. O.OO.O.O..O. O.OO.O.O..O. O....O.OOOO. OOOOOO...... |
:Online Life-Like CA Soup Search = The Online Life-Like CA Soup Search.
:on-off Any p2 oscillator in which all rotor cells die from overpopulation. The simplest example is a beacon. Compare flip-flop.
:O-pentomino Conway's name for the following pentomino, a traffic light predecessor, although not one of the more common ones.
OOOOO |
:orbit A term proposed by Jason Summers to refer to a natural stabilization of a puffer. For example, the switch engine has two (known) orbits, the block-laying one and the glider-producing one.
:Orion (c/4 diagonally, p4) Found by Hartmut Holzwart, April 1993.
.OO.......... OO........... ..O.......... ....O....OOO. ....OOO....OO .....OOO.O.O. ............O .....O.O..... ....OO.O..... .....O....... ...OO.O...... ......O...... ....OO....... |
:orphan Conway's preferred term for a Garden of Eden. According to some definitions, a orphan consists of just the minimum living and dead cells needed to ensure that no parent is possible -- whereas a GoE is an entire infinite Life plane that contains an orphan.
:Orthogonoid (256c/3476016, p3476016) A self-constructing spaceship with a slow orthogonal direction of travel, analogous to the Demonoids but using MWSSes instead of gliders in the construction recipe. The first example was completed by Dave Greene on 29 June 2017.
:oscillator Any pattern that is a predecessor of itself. The term is usually restricted to non-stable finite patterns. An oscillator is divided into a rotor and a stator. See also omniperiodic.
In general cellular automaton theory the term "oscillator" usually covers spaceships as well, but this usage is not normal in Life.
:Osqrtlogt (p1 circuitry) A pattern constructed by Adam P. Goucher in 2010, which uses an unbounded triangular region as memory for a binary counter. Empty space is read as a zero, and a boat is a 1. The pattern's diametric growth rate is O(sqrt(log(t))), which is the slowest possible for any Life pattern, or indeed any 2D Euclidean cellular automaton. Since the population returns infinitely often to its initial minimum value (during carry operations from 11111...1 to 100000...0, it can be considered to be an unusual form of sawtooth.
:OTCA metapixel (p46 circuitry) A 2048 x 2048 period 35328 metacell constructed by Brice Due in 2006. It contains a large "pixel" area that contains a large population of LWSS spaceships when the cell state is ON, but is empty when the cell state is OFF. This allows the state of the cell to be visible at high zoom levels, unlike all previous unit cells where the state was signaled by the presence or absence of a single glider in a specific location.
:overclocking A term used when a circuit can accept a signal at a specific period which it cannot accept at a higher period. A syringe is a simple example. A better example is a Silver reflector, where overclocking creates a situation where the circuit can process input gliders much faster than the normal repeat time of 497 ticks, but the stream of gliders has to be continuous. Any interruption of the stream will cause the destruction of the reflector.
Some staged recovery circuits also permit overclocking, and can function successfully at a rate faster than their recovery time. A Silver reflector has a recovery time of 497 ticks, but can be overclocked to reflect a period 250 glider stream, or any nearby period above 248, simply by removing a beehive after the first glider enters the reflector. However, a continuous stream of gliders is then required to maintain the circuit, with timing within a tightly bounded range.
:overcrowding = overpopulation
:over-exposure = underpopulation
:overpopulation Death of a cell caused by it having more than three neighbours. See also underpopulation.
:OWSS A would-be spaceship similar to LWSS, MWSS and HWSS but longer. On its own an OWSS is unstable, but it can be escorted by true spaceships to form a flotilla.
:Ox A 1976 novel by Piers Anthony which involves Life.