:early universe Conway's somewhat confusing term for sparse Life.
:eater Any still life that has the ability to interact with certain patterns without suffering any permanent damage. (If it doesn't suffer even temporary damage then it may be referred to as a rock.) The eater1 is a very common eater, and the term "eater" is often used specifically for this object. Other eaters include eater2, eater3, eater4 and even the humble block. (In fact the block was the first known eater, being found capable of eating beehives from a queen bee.) Another useful eater is shown below, feasting on a glider.
...O..... ...O.O... ...OO.... ......... .......OO ...O...OO ..O.O.... .O.O..... .O....... OO....... |
:eater1 (p1) Usually simply called an eater, and also called a fishhook. Its ability to eat various objects was discovered by Bill Gosper in 1971.
OO.. O.O. ..O. ..OO |
:eater2 (p1) This eater was found by Dave Buckingham in the 1970s. Mostly it works like the ordinary eater (see eater1) but with two slight differences that make it useful despite its size: it takes longer to recover from each bite, and it can eat objects appearing at two different positions.
...O.OO .OOO.OO O...... .OOO.OO ...O.O. ...O.O. ....O.. |
The following eater2 variant (Stephen Silver, May 1998) can be useful for obtaining smaller bounding boxes. A more compact variant with the same purpose can be seen under gliderless.
:eater3 (p1) This large symmetric eater, found by Dave Buckingham, has a very different eating action from the eater1 and eater2. The loaf can take bites out things, being flipped over in the process. The rest of the object merely flips it back again.
.........OO. ....OO..O..O .O..O....O.O O.O.O.....O. .O..O.OO.... ....O..O.... .....O....O. ......OOOOO. ............ ........O... .......O.O.. ........O... |
:eater4 (p1) Another eater by Dave Buckingham, which he found in 1971, but did not recognize as an eater until 1975 or 1976. It can't eat gliders, but it can be used for various other purposes. The four NE-most centre cells regrow in a few generations after being destroyed by taking a bite out of something.
:eater5 (p1) A compound eater that can eat gliders coming from two different directions. Also called the tub-with-tail eater (TWIT), it is often placed along the edges of glider lanes to suppress unwanted gliders in conduits. Below is the standard form, a compact form with a long hook, and an often-useful conjoined form found with Bellman. The sidesnagger is a Spartan constellation that has a similar glider-absorbing function, using a loaf. See also 7x9 eater.
:eater/block frob (p4) Found by Dave Buckingham in 1976 or earlier.
.OO....... ..O....... ..O.O..... ...O.O.... .....OO.OO ........OO ..OO...... ...O...... OOO....... O......... |
:eater-bound pond = biting off more than they can chew
:eater-bound Z-hexomino = pentoad
:eater eating eater = two eaters
:eater plug (p2) Found by Robert Wainwright, February 1973.
.......O .....OOO ....O... .....O.. ..O..O.. .O.OO... .O...... OO...... |
:eaters plus = French kiss
:ecologist (c/2 orthogonally, p20) This consists of the classic puffer train with a LWSS added to suppress the debris. See also space rake.
:edge-repair spaceship A spaceship which has an edge that possesses no spark and yet is able to perturb things because of its ability to repair certain types of damage to itself. The most useful examples are the following two small p3 c/3 spaceships:
................O....... O..............OOOO..... O.O.......O...O...OO.OO. OOO......OOOO.....O..OO. ..O.....O...O.......O..O .........O.O..O......... .............O.......... |
:edge shooter A gun which fires its gliders (or whatever) right at the edge of the pattern, so that it can be used to fire them closely parallel to others. This is useful for constructing complex guns. Compare glider pusher, which can in fact be used for making edge shooters.
The following diagram shows a p46 edge shooter found by Paul Callahan in June 1994.
:edge spark A spark at the side of a spaceship that can be used to perturb things as the spaceship passes by.
:edge sparker A spaceship that produces one or more edge sparks.
:edgy In slow salvo terminology, an edgy glider construction recipe is one that places its final product at or very near the edge of its construction envelope.
:egg = non-spark. This term is no longer in use.
:E-heptomino Name given by Conway to the following heptomino.
.OOO OO.. .OO. |
:elbow Depending on context, this term may refer to a signal elbow or a construction elbow. See also elbow ladder.
:elbow ladder Scot Ellison's name for the type of pattern he created in which one or more gliders shuttle back and forth (using the kickback reaction) deleting the output gliders from a pair of slide guns.
:elbow operation A recipe, usually a salvo of gliders traveling on one or more construction lanes, that collides with an elbow constellation and performs one of the standard transformations on it -- push, pull, or fire for simple construction arms, along with possible construct, duplicate-elbow, or delete-elbow ops for more complicated systems. See construction elbow.
:electric fence (p5) A stabilization of ants. Dean Hickerson, February 1993.
:elementary Not reducible to a combination of smaller parts. Elementary spaceships in particular are usually those found by search programs, and they can't be subdivided into smaller spaceships, tagalongs, and supporting reactions, as contrasted with engineered macro-spaceships.
:elementary conduit A conduit with no recognizable active signal stage besides its input and output. Theoretically an elementary conduit may become a composite conduit, if another conduit can be found that shares the beginning or end of the conduit in question. In practice this happens only rarely, because many of the most likely branch points have already been identified: glider, standard *WSS spaceship, Herschel, B-heptomino, R-pentomino, pi-heptomino, queen bee shuttle, century or bookend, dove, and wing.
:elevener (p1)
OO.... O.O... ..O... ..OOO. .....O ....OO |
:Elkies' p5 (p5) Found by Noam Elkies in 1997.
.O....... O..OOO... ..O...... ...O.O..O ..OO.OOOO ....O.... ....O.O.. .....OO.. |
:emu Dave Buckingham's term for a Herschel loop that does not emit gliders (and so is "flightless"). All known Herschel loops of periods 57, 58, 59 and 61 are emus. See also Quetzal.
:emulator Any one of three p4 oscillators that produce sparks similar to those produced by LWSS, MWSS and HWSS. See LW emulator, MW emulator and HW emulator. Larger emulators are also possible, but they require stabilizing objects to suppress their non-sparks and so are of little use. The emulators were discovered by Robert Wainwright in June 1980.
:engine The active portion of an object (usually a puffer or gun) which is considered to actually produce its output, and which generally permits no variation in how it works. The other parts of the object are just there to support the engine. For examples, see puffer train, Schick engine, blinker puffer, frothing puffer and line puffer.
:engineless A rake or puffer which does not contain a specific engine for its operation. Instead it depends on perturbations of gliders or other objects by passing spaceships. The period of such objects is often adjustable, and in some cases the speed as well. An early example was the creation of c/5 rakes in September 1997, using gliders circulating among a convoy of c/5 spaceships. More recently, the passing spaceships themselves are also constructed, as in the Caterloopillar.
:en retard (p3) Found by Dave Buckingham, August 1972.
.....O..... ....O.O.... OO.O.O.O.OO .O.O...O.O. O..O.O.O..O .OO.....OO. ...OO.OO... ...O.O.O... ....O.O.... ..O.O.O.O.. ..OO...OO.. |
:Enterprise (c/4 diagonally, p4) Found by Dean Hickerson, March 1993.
:envelope See construction envelope, reaction envelope.
:Eureka (p30) A pre-pulsar shuttle found by Dave Buckingham in August 1980. A variant is obtained by shifting the top half two spaces to either side.
:evolutionary factor For an unstable pattern, the time to stabilization divided by the initial population. For example, the R-pentomino has an evolutionary factor of 220.6, while bunnies has an evolutionary factor of 1925.777... The term is no longer in use.
:exponential filter A toolkit developed by Gabriel Nivasch in 2006, enabling the construction of patterns with asymptotic population growth matching O((log log ... log(t)) for any number of nested log operations. See also quadratic filter, recursive filter.
:exposure = underpopulation
:extensible A pattern is said to be extensible if arbitrarily large patterns of the same type can be made by repeating parts of the original pattern in a regular way.
:extremely impressive (p6) Found by Dave Buckingham, August 1976.
....OO...... ...O.OOO.... ...O....O... OO.O...OO... OO.O.....OO. ....OOOOO..O ..........OO ......O..... .....O.O.... ......O..... |