lexicon.txt

LIFE LEXICON
  Release 20, 2002 Feb 8
  ASCII version

INTRODUCTION
  This is a lexicon of terms relating to John Horton Conway's
Game of Life.  It is also available in single-page and multipage
HTML versions.
  This lexicon was compiled by Stephen A. Silver - see
below for additional credits.  I can be contacted at
life@argentum.freeserve.co.uk.
  The lastest versions of this lexicon (both HTML and ASCII)
should always be available from the Life Lexicon Home Page at
http://www.argentum.freeserve.co.uk/lex_home.htm.

CREDITS
  The largest single source for the early versions of this lexicon was
a glossary compiled by Alan Hensel "with indispensable help from John
Conway, Dean Hickerson, David Bell, Bill Gosper, Bob Wainwright, Noam
Elkies, Nathan Thompson, Harold McIntosh, and Dan Hoey".
  Other sources include the works listed in the bibliography at the
end of this lexicon, as well as pattern collections by Alan Hensel and
David Bell (and especially Dean Hickerson's file stamp.l in the latter
collection), and the web sites of Mark Niemiec, Paul Callahan, Achim
Flammenkamp, Robert Wainwright and Heinrich Koenig.  Recent releases
also use a lot of information from Dean Hickerson's header to his
1995 stamp file (http://math.ucdavis.edu/~dean/RLE/stamps.html).
  Most of the information on recent results is from the discoverers
themselves.
  David Bell, Nick Gotts, Alan Hensel, Dean Hickerson, Dieter Leithner,
Peter Rott and Malcolm Tyrrell all provided useful comments on earlier
releases of this lexicon.
  The format, errors, use of British English and anything else you
might want to complain about are by Stephen Silver.

COPYING
  This lexicon is copyright (C) Stephen Silver, 1997-2002.  It may be
freely copied and/or modified as long as due credit is given.  This
includes not just credit to those who have contributed in some way to
the present version (see above), but also credit to those who have made
any modifications.

LEXICOGRAPHIC ORDER
  I have adopted the following convention: all characters (including
spaces) other than letters and digits are ignored for the purposes of
ordering the entries in this lexicon.  (Many terms are used by some
people as a single word, with or without a hyphen, and by others as two
words.  My convention means that I do not have to list these in two
separate places.  Indeed, I list them only once, choosing whichever
form seems most common or sensible.)  Digits lexicographically precede
letters.

FORMAT
  The format used in the ASCII version of this lexicon is loosely
based on that of the Jargon File.  In particular, the keywords are
enclosed in colons and selected references to them are enclosed in
curly brackets.  The curly brackets will not be of much use unless
you have a programmable text editor, in which case you could program
it to jump from a reference to the corresponding definition when you
hit a certain key.  (The file lifelex.el, which you should have
received with this lexicon, provides such a facility for GNU Emacs.)
If you don't want the curly brackets you can safely remove them with
two find and replace operations, since they are not used for any other
purpose in this file.  The colons are more generally useful.  For
example, a search for ":foo" will take you straight to the definition
of the first word beginning with "foo" (or at least it would if there
were any).
  The diagrams in this lexicon are in a very standard format.  You
should be able to simply copy a pattern, paste it into a new file and
run it in your favourite Life program.  If you use Johan Bontes' Life32
or Mirek Wojtowicz' MCell then you can, of course, paste the pattern
directly into the Life program.  If you view this lexicon in GNU Emacs
and use lifelex.el then you should be able to load a pattern into
your Life program with a single keypress, without needing to copy or
paste.
  The diagrams use an asterisk to represent a live cell.  If this looks
ugly with the font you use then you can change to O or o with a global
replace.  I have restricted myself to diagrams of size 64x64 or less.
  Most definitions that have a diagram have also some data in brackets
after the keyword.  Oscillators are maked as pn (where n is a positive
integer), meaning that the period is n (p1 indicates a still life).
Wicks are marked in the same way but with the word "wick" added.  For
spaceships the speed (as a fraction of c, the speed of light), the
direction and the period are given.  Fuses are marked with speed and
period and have the word "fuse" added.  Wicks and fuses are infinite in
extent and so have necessarily been truncated, with the ends stabilized
wherever practical.

SCOPE
  This lexicon covers only Conway's Life, and provides no information
about other cellular automata.  David Bell has written articles on
two other interesting cellular automata: HighLife (which is similar
to Life, but has a tiny replicator) and Day & Night (which is very
different, but exhibits many of the same phenomena).  These articles
can be found on his web-site (http://www.canb.auug.org.au/~dbell/).

ERRORS AND OMISSIONS
  If you find any errors (including typos) or serious omissions, then
please let me know.

NAMES
  When deciding whether to use full or abbreviated forms of forenames
I have tried, wherever possible, to follow the usage of the person
concerned.

QUOTE
  Every other author may aspire to praise; the lexicographer can only
hope to escape reproach.  -- Samuel Johnson, 1775

DEDICATION
  This lexicon is dedicated to the memory of Dieter Leithner, who died
on 26 February 1999.

-----------------------------------------------------------------------

:101: (p5)  Found by Achim Flammenkamp in August 1994.  The name was
   suggested by Bill Gosper, noting that the phase shown below displays
   the period in binary.
	....**......**....
	...*.*......*.*...
	...*..........*...
	**.*..........*.**
	**.*.*..**..*.*.**
	...*.*.*..*.*.*...
	...*.*.*..*.*.*...
	**.*.*..**..*.*.**
	**.*..........*.**
	...*..........*...
	...*.*......*.*...
	....**......**....

:1-2-3: (p3)  Found by Dave Buckingham, August 1972. This is one of only
   three essentially different p3 {oscillator}s with only three cells in
   the {rotor}.  The others are {stillater} and {cuphook}.
	..**......
	*..*......
	**.*.**...
	.*.*..*...
	.*....*.**
	..***.*.**
	.....*....
	....*.....
	....**....

:1-2-3-4: (p4)  See also {Achim's p4}.
	.....*.....
	....*.*....
	...*.*.*...
	...*...*...
	**.*.*.*.**
	*.*.....*.*
	...*****...
	...........
	.....*.....
	....*.*....
	.....*.....

:14-ner: = {fourteener}

:2 eaters: = {two eaters}

:4-8-12 diamond:  The following {pure glider generator}.
	....****....
	............
	..********..
	............
	************
	............
	..********..
	............
	....****....

:4 boats: (p2)
	...*....
	..*.*...
	.*.**...
	*.*..**.
	.**..*.*
	...**.*.
	...*.*..
	....*...

:4F: = {Fast Forward Force Field}

:Achim's p144: (p144)  This was found (minus the blocks shown below)
   on a cylinder of width 22 by Achim Flammenkamp in July 1994.  Dean
   Hickerson reduced it to a finite form using {figure-8}s the same day.
   The neater finite form shown here - replacing the figure-8s with
   blocks - was found by David Bell in August 1994.  See {factory} for
   a use of this oscillator.
	**........................**
	**........................**
	..................**........
	.................*..*.......
	..................**........
	..............*.............
	.............*.*............
	............*...*...........
	............*..*............
	............................
	............*..*............
	...........*...*............
	............*.*.............
	.............*..............
	........**..................
	.......*..*.................
	........**..................
	**........................**
	**........................**

:Achim's p16: (p16)  Found by Achim Flammenkamp, July 1994.
	.......**....
	.......*.*...
	..*....*.**..
	.**.....*....
	*..*.........
	***..........
	.............
	..........***
	.........*..*
	....*.....**.
	..**.*....*..
	...*.*.......
	....**.......

:Achim's p4: (p4)  Dave Buckingham found this in a less compact form
   (using two halves of {sombreros}) in 1976.  The form shown here was
   found by Achim Flammenkamp in 1988.  The {rotor} is two copies of
   the rotor of {1-2-3-4}, so the oscillator is sometimes called the
   "dual 1-2-3-4".
	..**...**..
	.*..*.*..*.
	.*.**.**.*.
	**.......**
	..*.*.*.*..
	**.......**
	.*.**.**.*.
	.*..*.*..*.
	..**...**..

:Achim's p5: = {pseudo-barberpole}

:Achim's p8: (p8)  Found by Achim Flammenkamp, July 1994.
	.**......
	*........
	.*...*...
	.*...**..
	...*.*...
	..**...*.
	...*...*.
	........*
	......**.

:acorn: (stabilizes at time 5206)  A {methuselah} found by Charles
   Corderman.
	.*.....
	...*...
	**..***

:A for All: (p6)  Found by Dean Hickerson in March 1993.
	....**....
	...*..*...
	...****...
	.*.*..*.*.
	*........*
	*........*
	.*.*..*.*.
	...****...
	...*..*...
	....**....

:agar:  Any pattern covering the whole plane that is periodic in both
   space and time.  The simplest (nonempty) agar is the {stable} one
   extended by the known {spacefiller}s.  For some more examples see
   {chicken wire}, {houndstooth agar}, {onion rings}, {squaredance}
   and {Venetian blinds}.  Tiling the plane with the pattern O......O
   produces another interesting example: a p6 agar which has a phase of
   {density} 3/4, which is the highest yet obtained for any phase of an
   oscillating pattern.

:aircraft carrier: (p1)  This is the smallest {still life} that has more
   than one {island}.
	**..
	*..*
	..**

:airforce: (p7)  Found by Dave Buckingham in 1972.  The rotor consists
   of two copies of that used in the {burloaferimeter}.
	.......*......
	......*.*.....
	.......*......
	..............
	.....*****....
	....*.....*.**
	...*.**...*.**
	...*.*..*.*...
	**.*...**.*...
	**.*.....*....
	....*****.....
	..............
	......*.......
	.....*.*......
	......*.......

:AK47 reaction:  The following reaction (found by Rich Schroeppel and
   Dave Buckingham) in which a honey farm predecessor, catalysed by
   an eater and a block, reappears at another location 47 generations
   later, having produced a glider and a traffic light.  This is the
   basis of a very small (but {pseudo}) p94 glider gun found by Paul
   Callahan in July 1994, and was in 1990 the basis for the Dean
   Hickerson's construction of the first {true} p94 gun.  (This latter
   gun was enormous, and has now been superceded by comparatively small
   {Herschel loop} guns.)
	.....*....
	....*.*...
	...*...*..
	...*...*..
	...*...*..
	....*.*...
	.....*....
	..........
	..**......
	...*......
	***.....**
	*.......**

:Al Jolson: = {Jolson}

:almosymmetric: (p2)  Found in 1971.
	....*....
	**..*.*..
	*.*......
	.......**
	.*.......
	*......*.
	**.*.*...
	.....*...

:antlers: = {moose antlers}

:ants: (p5 wick)  The standard form is shown below.  It is also
   possible for any ant to be displaced by one or two cells relative
   to either or both of its neighbouring ants.  Dean Hickerson found
   {fencepost}s for both ends of this wick in October 1992 and
   February 1993.  See {electric fence}, and also {wickstretcher}.
	**...**...**...**...**...**...**...**...**..
	..**...**...**...**...**...**...**...**...**
	..**...**...**...**...**...**...**...**...**
	**...**...**...**...**...**...**...**...**..

:anvil:  The following {induction coil}.
	.****.
	*....*
	.***.*
	...*.**

:APPS: (c/5 orthogonally, p30)  An asymmetric {PPS}.  The same as the
   {SPPS}, but with the two halves 15 generations out of phase with one
   another.  Found by Alan Hensel in May 1998.

:ark:  A pair of mutually stabilizing {switch engine}s.  The archetype
   is {Noah's ark}.

:arm:  A long extension hanging off from the main body of a {spaceship}
   or {puffer} perpendicular to the direction of travel.  A lot of
   known spaceships, particularly c/3 ones, have multiple arms.  This
   is an artefact of the search methods used to find such spaceships,
   rather than an indication of what a "typical" spaceship might look
   like.

:ash:  The ({stable} or oscillating) debris left by a random reaction.
   Experiments show that for random {soup}s with moderate initial
   densities (say 0.25 to 0.5) the resulting ash has a density of about
   0.0287.  (This is, of course, based on what happens in finite fields.
   In infinite fields the situation may conceivably be different in the
   long run because of the effect of certain initially very rare objects
   such as {replicator}s.)

:aVerage: (p5)  Found by Dave Buckingham, 1973.
	...**........
	....***......
	..*....*.....
	.*.****.*....
	.*.*....*..*.
	**.***..*.*.*
	.*.*....*..*.
	.*.****.*....
	..*....*.....
	....***......
	...**........

:B: = {B-heptomino}

:B-52 bomber:  The following p104 {double-barrelled} {glider} {gun}.
   It uses a {B-heptomino} and emits one glider every 52 generations.
   It was found by Noam Elkies in March 1996, except that Elkies used
   {blocker}s instead of {mold}s, the improvement being found by
   David Bell later the same month.
	.**....................................
	.**.................*..................
	...................*.*............*.*..
	....................*............*.....
	**.......**.......................*..*.
	**.*.....**.......................*.*.*
	...*.......................*.......*..*
	...*.......................**.......**.
	*..*.................**.....*..........
	.**..................*.................
	.....................***...............
	....................................**.
	....................................**.
	.**....................................
	*..*...................................
	*.*.*................*.*....**.....**..
	.*..*.................**....**.....**.*
	.....*............*...*...............*
	..*.*............*.*..................*
	..................*................*..*
	....................................**.

:babbling brook:  Any {oscillator} whose {rotor} consists of a string
   of cells each of which is adjacent to exactly two other rotor cells,
   except for the endpoints which are adjacent to only one other rotor
   cell.  Compare {muttering moat}.  Examples include the {beacon}, the
   {great on-off}, the {light bulb} and the {spark coil}.  The following
   less trivial example (by Dean Hickerson, August 1997) is the only
   one known with more than four cells in its rotor.  It is p4 and has
   a 6-cell rotor.
	.......*........
	.....***....**..
	....*...**..*...
	.*..*.**..*.*...
	*.*.*....**..**.
	.**..**....*.*.*
	...*.*..**.*..*.
	...*..**...*....
	..**....***.....
	........*.......

:backrake:  Another term for a backwards {rake}.  A p8 example by
   Jason Summers is shown below.  See {total aperiodic} for a p12
   example.
	.....***...........***.....
	....*...*.........*...*....
	...**....*.......*....**...
	..*.*.**.**.....**.**.*.*..
	.**.*....*.**.**.*....*.**.
	*....*...*..*.*..*...*....*
	............*.*............
	**.......**.*.*.**.......**
	............*.*............
	......***.........***......
	......*...*.........*......
	......*.*....***...........
	............*..*....**.....
	...............*...........
	...........*...*...........
	...........*...*...........
	...............*...........
	............*.*............

:backward glider:  A {glider} which moves at least partly in the
   opposite direction to the {puffer}(s) or {spaceship}(s) under
   consideration.

:baker: (c p4 fuse)  A {fuse} by Keith McClelland.
	..............**
	.............*.*
	............*...
	...........*....
	..........*.....
	.........*......
	........*.......
	.......*........
	......*.........
	.....*..........
	....*...........
	...*............
	***.............
	.*..............

:baker's dozen: (p12)  A {loaf} {hassle}d by two {block}s and two
   {caterer}s.  The original form (using p4 and p6 oscillators to
   do the hassling) was found by Robert Wainwright in August 1989.
	**.........**..........
	****.*.....**..........
	*.*..***...............
	...........*...........
	....**....*.*..........
	....*.....*..*....*....
	...........**....**....
	.......................
	...............***..*.*
	..........**.....*.****
	..........**.........**

:bakery: (p1)  A common formation of two bi-loaves.
	....**....
	...*..*...
	...*.*....
	.**.*...*.
	*..*...*.*
	*.*...*..*
	.*...*.**.
	....*.*...
	...*..*...
	....**....

:barberpole:  Any p2 oscillator in the infinite sequence {bipole},
   {tripole}, {quadpole}, {pentapole}, {hexapole}, {heptapole} ...
   (It wasn't my idea to suddenly change from Latin to Greek.)
   This sequence of oscillators was found by the MIT group in 1970.
   The term is also used (usually in the form "barber pole") to
   describe other extensible sections of oscillators or spaceships,
   especially those (usually of period 2) in which all generations
   look alike except for a translation and/or rotation/reflection.

:barberpole intersection: = {quad}

:barber's pole: = {barberpole}

:barge: (p1)
	.*..
	*.*.
	.*.*
	..*.

:basic shuttle: = {queen bee shuttle}

:beacon: (p2)  The third most common {oscillator}.  Found by Conway,
   March 1970.
	**..
	*...
	...*
	..**

:beacon maker:  (c p8 fuse)
	..............**
	.............*.*
	............*...
	...........*....
	..........*.....
	.........*......
	........*.......
	.......*........
	......*.........
	.....*..........
	....*...........
	...*............
	***.............
	..*.............
	..*.............

:beehive: (p1)  The second most common {still life}.
	.**.
	*..*
	.**.

:beehive and dock: (p1)
	...**.
	..*..*
	...**.
	......
	.****.
	*....*
	**..**

:beehive on big table: = {beehive and dock}

:beehive pusher: = {hivenudger}

:beehive with tail: (p1)
	.**...
	*..*..
	.**.*.
	....*.
	....**

:belly spark:  The spark of a {MWSS} or {HWSS} other than the
   {tail spark}.

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

:B-heptomino: (stabilizes at time 148)  This is a very common
   pattern.  It often arises with the cell at top left shifted one
   space to the left, which does not affect the subsequent evolution.
   B-heptominoes acquired particular importance in 1996 due
   to Dave Buckingham's work on {B track}s - see in particular
   {My Experience with B-heptominos in Oscillators}.
	*.**
	***.
	.*..

:B-heptomino shuttle: = {twin bees shuttle}

:bi-block: (p1)  The smallest {pseudo still life}.
	**.**
	**.**

:bi-boat: = {boat-tie}

:biclock:  The following {pure glider generator}.
	..*....
	**.....
	..**...
	.*...*.
	...**..
	.....**
	....*..

:big beacon: = {figure-8}

:big fish: = {HWSS}

:big glider: (c/4 diagonally, p4)  This was found by Dean Hickerson in
   December 1989 and was the first known diagonal {spaceship} other than
   the {glider}.
	...***............
	...*..***.........
	....*.*...........
	**.......*........
	*.*....*..*.......
	*........**.......
	.**...............
	.*..*.....*.**....
	.*.........**.*...
	...*.*......**..*.
	....**.*....**...*
	........*.......*.
	.......****...*.*.
	.......*.**...****
	........*...**.*..
	.............**...
	.........*.***....
	..........*..*....

:big S: (p1)
	....**.
	...*..*
	...*.**
	**.*...
	*..*...
	.**....

:big table: = {dock}

:billiard table configuration:  Any {oscillator} in which the {rotor}
   is enclosed within the {stator}.  Examples include {airforce},
   {cauldron}, {clock II}, {Hertz oscillator}, {negentropy},
   {pinwheel}, {pressure cooker} and {scrubber}.

:bi-loaf:  This term has been used in at least three different senses.
   A bi-loaf can be half a {bakery}:
	.*.....
	*.*....
	*..*...
	.**.*..
	...*.*.
	...*..*
	....**.
   or it can be the following much less common {still life}:
	..*....
	.*.*...
	*..*...
	.**.**.
	...*..*
	...*.*.
	....*..
   or the following {pure glider generator}:
	..*.
	.*.*
	*..*
	.**.
	*..*
	*.*.
	.*..

:bipole: (p2)  The {barberpole} of length 2.
	**...
	*.*..
	.....
	..*.*
	...**

:bi-pond: (p1)
	.**....
	*..*...
	*..*...
	.**.**.
	...*..*
	...*..*
	....**.

:bi-ship: = {ship-tie}

:bit:  A live {cell}.

:biting off more than they can chew: = {eater-bound pond}

:Black&White: = {Immigration}

:blasting cap:  The {pi-heptomino} (after the shape at generation 1).
   A term used at MIT and still occasionally encountered.

:blinker: (p2)  The smallest and most common {oscillator}.  Found by
   Conway, March 1970.
	***

:blinkers bit pole: (p2)  Found by Robert Wainwright, June 1977.
	.....**
	***.*.*
	.......
	.*.*..*
	*....*.
	**...*.

:blinker ship:  A {growing spaceship} in which the wick consists of
   a line of {blinker}s.  An example by Paul Schick based on his
   {Schick engine} is shown below.  Here the front part is p12 and
   moves at c/2, while the back part is p26 and moves at 6c/13.  Every
   156 generations 13 blinkers are created and 12 are destroyed, so the
   wick becomes one blinker longer.
	..........****.............
	..........*...*............
	..........*................
	.**........*..*............
	**.**......................
	.****...*..................
	..**...*.**........*....***
	......*...*........*....*.*
	..**...*.**........*....***
	.****...*..................
	**.**......................
	.**........*..*............
	..........*................
	..........*...*............
	..........****.............

:block: (p1)  The most common {still life}.
	**
	**

:blockade: (p1)  A common formation of four blocks.  The final form
   of {lumps of muck}.
	**.....................
	**.....................
	.......................
	.......................
	.**.................**.
	.**.................**.
	.......................
	.......................
	.....................**
	.....................**

:block and dock: (p1)
	...**.
	...**.
	......
	.****.
	*....*
	**..**

:block and glider: (stabilizes at time 106)
	**..
	*.*.
	..**

:blocker: (p8)  Found by Robert Wainwright.  See also {filter}.
	......*.*.
	.....*....
	**..*....*
	**.*..*.**
	....**....

:block on big table: = {block and dock}

:block on table: (p1)
	..**
	..**
	....
	****
	*..*

:block pusher:  A pattern emitting streams of {glider}s which can
   repeatedly push a block further away.  The following pattern,
   in which three gliders push a block one cell diagonally, is an
   example of how this can work.
	...................*.*
	...................**.
	....................*.
	......................
	......................
	......................
	...*..................
	..*...................
	..***.................
	......................
	......................
	......................
	......................
	**...*................
	**...*.*..............
	.....**...............

:blonk:  A {block} or a {blinker}.  This term is mainly used in the
   context of {sparse Life} and was coined by Rich Schroeppel in
   September 1992.

:boat: (p1)  The only 5-pixel {still life}.
	**.
	*.*
	.*.

:boat-bit:  A binary digit represented by the presence of a
   {boat} next to a {snake} (or other suitable object, such as
   an {aircraft carrier}).  The bit can be toggled by a {glider}
   travelling along a certain path.  A correctly timed glider on a
   crossing path can detect whether the transition was from 1 to 0
   (in which case the crossing glider is deleted) or from 0 to 1 (in
   which case it passes unharmed).  Three gliders therefore suffice for
   a non-destructive read.  The mechanisms involved are shown in the
   diagram below.  Here the bit is shown in state 0.  It is about to be
   set to 1 and the switched back to 0 again.  The first crossing glider
   will survive, but the second will be destroyed.  (In January 1997
   David Bell found a method of reading the bit while setting it to 0.
   A {MWSS} is fired at the boat-bit.  If it is already 0 then the
   MWSS passes unharmed, but if it is 1 then the boat and the MWSS are
   destroyed and, with the help of an {eater1}, converted into a glider
   which travels back along exactly the same path that is used by the
   gliders that toggle the boat-bit.)
	......*..................
	.......*.................
	.....***.................
	.........................
	.........................
	.........................
	.........................
	.........................
	.........................
	.........................
	................*........
	..............*.*........
	..........**...**........
	...........**............
	..........*..........*.**
	.....................**.*
	.........................
	.........................
	.........................
	.........................
	.........................
	.*.......................
	.**......................
	*.*......................

:boat maker: (c p4 fuse)
	................**
	...............*.*
	..............*...
	.............*....
	............*.....
	...........*......
	..........*.......
	.........*........
	........*.........
	.......*..........
	......*...........
	.....*............
	*****.............
	....*.............
	....*.............
	....*.............
	....*.............

:boat on boat: = {boat-tie}

:boat-ship-tie: = {ship tie boat}

:boatstretcher:  Any {wickstretcher} that stretches a boat.  The first
   one was found by Hartmut Holzwart in June 1993.  The following
   example is by Noam Elkies (February 1996) and uses Tim Coe's {swan}.
   Note that in any boatstretcher the point of the boat can be removed
   to get a tubstretcher.
	............**..........
	***.........*.*.........
	*..***......*.........*.
	.*.*................**.*
	......*....**..*...**..*
	....*......**..*.**..*..
	......*.**.*...*****....
	...............**.......
	.......*..******........
	........*******.........
	..........***...........
	........................
	.............*..........
	............*.*.........
	.............**.........

:boat-tie: (p1)  The name is a pun on "bow tie".
	.*....
	*.*...
	.**...
	...**.
	...*.*
	....*.

:bookend:  The following {induction coil}.  It is generation 1 of
   {century}.
	..**
	*..*
	***.

:bookends: (p1)
	**...**
	*.*.*.*
	..*.*..
	.**.**.

:boss: (p4)  Found by Dave Buckingham, 1972.
	.....*.....
	....*.*....
	....*.*....
	...**.**...
	..*.....*..
	.*.*.*.*.*.
	.*.*...*.*.
	**.*...*.**
	*..*.*.*..*
	..*.....*..
	...**.**...
	....*.*....
	....*.*....
	.....*.....

:bottle: (p8)  Found by Achim Flammenkamp in August 1994.  The name is
   a back-formation from {ship in a bottle}.
	....**......**....
	...*..*....*..*...
	...*.*......*.*...
	.**..***..***..**.
	*......*..*......*
	*.**..........**.*
	.*.*..........*.*.
	...**........**...
	..................
	..................
	...**........**...
	.*.*..........*.*.
	*.**..........**.*
	*......*..*......*
	.**..***..***..**.
	...*.*......*.*...
	...*..*....*..*...
	....**......**....

:bounding box:  The smallest rectangular array of cells that contains
   the whole of a given pattern.  For {oscillator}s and {gun}s this
   usually is meant to include all phases of the pattern, but excludes,
   in the case of guns, the outgoing stream(s).

:bow tie: = {boat-tie}

:brain: (c/3 orthogonally, p3)  Found by David Bell, May 1992.
	.***.........***.
	*.*.**.....**.*.*
	*.*.*.......*.*.*
	.*.**.**.**.**.*.
	.....*.*.*.*.....
	...*.*.*.*.*.*...
	..**.*.*.*.*.**..
	..***..*.*..***..
	..**..*...*..**..
	.*....**.**....*.
	.*.............*.

:breeder:  Any pattern whose {population} grows at a quadratic rate,
   although it is usual to exclude {spacefiller}s.  It is easy to see
   that this is the fastest possible growth rate.
     The term is also sometimes used to mean specifically the breeder
   created by Bill Gosper's group at MIT, which was the first known
   pattern exhibiting superlinear growth.
     There are four basic types of breeder, known as MMM, MMS, MSM and
   SMM (where M=moving and S=stationary).  Typically an MMM breeder is a
   {rake} {puffer}, an MMS breeder is a puffer producing puffers which
   produce stationary objects ({still life}s and/or {oscillator}s),
   an MSM breeder is a {gun} puffer and an SMM breeder is a rake gun.
   There are, however, less obvious variants of these types.  The
   original breeder was of type MSM (a p64 puffer puffing p30 glider
   guns).
     The known breeder with the smallest initial population is the
   {metacatacryst}.

:bridge:  A term used in naming certain {still life}s (and the {stator}
   part of certain {oscillator}s).  It indicates that the object
   consists of two smaller objects joined edge to edge, as in
   {snake bridge snake}.

:broth: = {soup}

:BTC: = {billiard table configuration}

:B track:  A {track} for {B-heptomino}es.  The term is more-or-less
   synonymous with {Herschel track}, since a B-heptomino becomes a
   Herschel plus a block in twenty generations.

:buckaroo:  A {queen bee shuttle} stabilized at one end by an eater
   in such a way that it can turn a glider, as shown below.  This was
   found by Dave Buckingham in the 1970s.  The name is due to Bill
   Gosper.
	..*.....................
	*.*.....................
	.**.....................
	...........*............
	.........*.*............
	........*.*.............
	.......*..*...........**
	........*.*...........**
	...**....*.*............
	..*.*......*............
	..*.....................
	.**.....................

:bullet heptomino:  Generation 1 of the {T-tetromino}.
	.*.
	***
	***

:bun:  The following {induction coil}.  By itself this is a common
   {predecessor} of the {honey farm}.  See also {cis-mirrored R-bee}.
	.**.
	*..*
	.***

:bunnies: (stabilizes at time 17332)  This is a {parent} of {rabbits}
   and was found independently by Robert Wainwright and Andrew
   Trevorrow.
	*.....*.
	..*...*.
	..*..*.*
	.*.*....

:burloaf: = {loaf}

:burloaferimeter: (p7)  Found by Dave Buckingham in 1972.  See also
   {airforce}.
	....**....
	.....*....
	....*.....
	...*.***..
	...*.*..*.
	**.*...*.*
	**.*....*.
	....****..
	..........
	....**....
	....**....

:bushing:  That part of the {stator} of an {oscillator} which is
   adjacent to the {rotor}.  Compare {casing}.

:butterfly:  The following pattern, or the formation of two beehives
   that it evolves into after 33 generations.  (Compare {teardrop},
   where the beehives are five cells closer together.)
	*...
	**..
	*.*.
	.***

:by flops: (p2)  Found by Robert Wainwright.
	...*..
	.*.*..
	.....*
	*****.
	.....*
	.*.*..
	...*..

:c: = {speed of light}

:CA: = {cellular automaton}

:caber tosser:  Any pattern whose {population} is asymptotic to c.log(t)
   for some constant c, and which contains a {glider} (or other
   {spaceship}) bouncing between a slower receding spaceship and a
   fixed {reflector} which emits a spaceship (in addition to the
   reflected one) whenever the bouncing spaceship hits it.
     As the receding spaceship gets further away the bouncing spaceship
   takes longer to complete each cycle, and so the extra spaceships
   emitted by the reflector are produced at increasingly large
   intervals.  More precisely, if v is the speed of the bouncing
   spaceship and u the speed of the receding spaceship, then each
   interval is (v+u)/(v-u) times as long as the previous one.  The
   population at time t is therefore n.log(t)/log((v+u)/(v-u))+O(1),
   where n is the population of one of the extra spaceships (assumed
   constant).
     The first caber tosser was built by Dean Hickerson in August 1994.

:Cambridge pulsar CP 48-56-72: = {pulsar}  (The numbers refer to
   the populations of the three phases.  The Life pulsar was indeed
   discovered at Cambridge, like the first real pulsar a few years
   earlier.)

:Canada goose: (c/4 diagonally, p4)  Found by Jason Summers, January
   1999.  It consists of a {glider} plus a {tagalong}.
	***..........
	*.........**.
	.*......***.*
	...**..**....
	....*........
	........*....
	....**...*...
	...*.*.**....
	...*.*..*.**.
	..*....**....
	..**.........
	..**.........
   At the time of its discovery the Canada goose was the smallest known
   diagonal {spaceship} other than the glider, but this record has since
   been beaten, first by the second spaceship shown under {Orion}, and
   more recently by the following 25-cell spaceship (Jason Summers,
   September 2000):
	........**...
	.......**....
	.........*...
	...........**
	..........*..
	.............
	.........*..*
	.**.....**...
	**.....*.....
	..*....*.*...
	....**..*....
	....**.......

:candelabra: (p3)  By Charles Trawick.  See also the note under {cap}.
	....**....**....
	.*..*......*..*.
	*.*.*......*.*.*
	.*..*.****.*..*.
	....*.*..*.*....
	.....*....*.....

:candlefrobra: (p3)  Found by Robert Wainwright in November 1984.
	.....*....
	.*.**.*.**
	*.*...*.**
	.*....*...
	.....**...
   The following diagram shows that a pair of these can act in some ways
   like {killer toads}.  See also {snacker}.
	....*...........*....
	**.*.**.*...*.**.*.**
	**.*...*.*.*.*...*.**
	...*....*...*....*...
	...**...........**...
	.....................
	.....................
	.........***.........
	.........*..*........
	.........*...........
	.........*...*.......
	.........*...*.......
	.........*...........
	..........*.*........

:canoe: (p1)
	...**
	....*
	...*.
	*.*..
	**...

:cap:  The following {induction coil}.  It can also be easily be
   stabilized to form a p3 oscillator - see {candelabra} for a slight
   variation on this.
	.**.
	*..*
	****

:carnival shuttle: (p12)  Found by Robert Wainwright in September 1984
   (using {MW emulator}s at the end, rather than {monogram}s).
	.................................*...*
	**...**..........................*****
	.*.*.*...*..*......**...*..*.......*..
	.**.**..**...**....**..**...**....*.*.
	.*.*.*...*..*......**...*..*.......*..
	**...**..........................*****
	.................................*...*

:carrier: = {aircraft carrier}

:casing:  That part of the {stator} of an {oscillator} which is not
   adjacent to the {rotor}.  Compare {bushing}.

:catacryst:  A 58-cell quadratic growth pattern found by Nick Gotts
   in April 2000.  This was formerly the smallest known pattern with
   superlinear growth, but has since been superceded by the related
   {metacatacryst}.  The catacryst consists of three {ark}s plus a
   glider-producing {switch engine}.  It produces a block-laying switch
   engine every 47616 generations.  Each block-laying switch engine has
   only a finite life, but the length of this life increases linearly
   with each new switch engine, so that the pattern overall grows
   quadratically, as an unusual type of MMS {breeder}.

:catalyst:  An object that participates in a reaction but emerges from
   it unharmed.  The term is mostly applied to {still life}s, but can
   also be used of {oscillator}s, {spaceship}s, etc.  The still lifes
   and oscillators which form a {conduit} are examples of catalysts.

:caterer: (p3)  Found by Dean Hickerson, August 1989.  Compare
   with {jam}.  In terms of its minimum {population} of 12 this is
   the smallest p3 {oscillator}.  See also {double caterer} and
   {triple caterer}.
	..*.....
	*...****
	*...*...
	*.......
	...*....
	.**.....
   More generally, any oscillator which serves up a {bit} in the
   same manner may be referred to as a ceterer.

:Catherine wheel: = {pinwheel}

:cauldron: (p8)  Found in 1971 independently by Don Woods and Robert
   Wainwright.  Compare with {Hertz oscillator}.
	.....*.....
	....*.*....
	.....*.....
	...........
	...*****...
	*.*.....*.*
	**.*...*.**
	...*...*...
	...*...*...
	....***....
	...........
	....**.*...
	....*.**...

:cavity: (p2)
	**......
	.*......
	.*.**...
	..*..*..
	.....*..
	....*...
	.....***
	.......*

:cell:  The fundamental unit of space in the Life universe.  The term is
   often used to mean a live cell - the sense is usually clear from the
   context.

:cellular automaton:  A certain class of mathematical objects of which
   {Life} is an example.  A cellular automaton consists of a number of
   things.  First there is a positive integer n which is the dimension
   of the cellular automaton.  Then there is a finite set of states S,
   with at least two members.  A state for the whole cellular automaton
   is obtained by assigning an element of S to each point of the
   n-dimensional lattice Z^n (where Z is the set of all integers).
   The points of Z^n are usually called cells.  The cellular automaton
   also has the concept of a neighbourhood.  The neighbourhood N of the
   origin is some finite (nonempty) subset of Z^n.  The neighbourhood
   of any other cell is obtained in the obvious way by translating that
   of the origin.  Finally there is a transition rule, which is a
   function from S^N to S (that is to say, for each possible state of
   the neighbourhood the transition rule specifies some cell state).
   The state of the cellular automaton evolves in discrete time, with
   the state of each cell at time t+1 being determined by the state
   of its neighbourhood at time t, in accordance with the transition
   rule.
     There are some variations on the above definition.  It is common
   to require that there be a quiescent state, that is, a state such
   that if the whole universe is in that state at generation 0 then it
   will remain so in generation 1.  (In Life the OFF state is quiescent,
   but the ON state is not.)  Other variations allow spaces other than
   Z^n, neighbourhoods that vary over space and/or time, probabilistic
   or other non-deterministic transistion rules, etc.
     It is common for the neighbourhood of a cell to be the 3x...x3
   (hyper)cube centred on that cell.  (This includes those cases
   where the neighbourhood might more naturally be thought of as a
   subset of this cube.)   This is known as the Moore neighbourhood.

:centinal: (p100)  Found by Bill Gosper.  This combines the mechanisms
   of the p46 and p54 shuttles (see {twin bees shuttle} and
   {p54 shuttle}).
	**................................................**
	.*................................................*.
	.*.*.....................**.....................*.*.
	..**........*............**............**.......**..
	...........**..........................*.*..........
	..........**.............................*..........
	...........**..**......................***..........
	....................................................
	....................................................
	....................................................
	...........**..**......................***..........
	..........**.............................*..........
	...........**..........................*.*..........
	..**........*............**............**.......**..
	.*.*.....................**.....................*.*.
	.*................................................*.
	**................................................**

:century: (stabilizes at time 103)  This is a common pattern which
   evolves into three {block}s and a {blinker}.  In June 1996 Dave
   Buckingham built a neat p246 glider {gun} using a century as the
   engine.  See also {bookend} and {diuresis}.
	..**
	***.
	.*..

:chemist: (p5)
	.......*.......
	.......***.....
	..........*....
	.....***..*..**
	....*.*.*.*.*.*
	....*...*.*.*..
	.**.*.....*.**.
	..*.*.*...*....
	*.*.*.*.*.*....
	**..*..***.....
	....*..........
	.....***.......
	.......*.......

:C-heptomino:  Name given by Conway to the following {heptomino}, a less
   common variant of the {B-heptomino}.
	.***
	***.
	.*..

:Cheshire cat:  A block {predecessor} by C. R. Tompkins that
   unaccountably appeared both in Scientific American and in
   {Winning Ways}.  See also {grin}.
	.*..*.
	.****.
	*....*
	*.**.*
	*....*
	.****.

:chicken wire:  A type of {stable} {agar} of {density} 1/2.  The
   simplist version is formed from the tile:
	**..
	..**
   But the "wires" can have length greater than two and need not
   all be the same.  For example:
	**...****.....
	..***....*****

:cigar: = {mango}

:cis-beacon on anvil: (p2)
	...**.
	....*.
	.*....
	.**...
	......
	.****.
	*....*
	.***.*
	...*.**

:cis-beacon on table: (p2)
	..**
	...*
	*...
	**..
	....
	****
	*..*

:cis-boat with tail: (p1)
	.*...
	*.*..
	**.*.
	...*.
	...**

:cis fuse with two tails: (p1)  See also {pulsar quadrant}.
	...*..
	.***..
	*...**
	.*..*.
	..*.*.
	...*..

:cis-mirrored R-bee: (p1)
	.**.**.
	*.*.*.*
	*.*.*.*
	.*...*.

:cis snake: = {canoe}

:clean:  Opposite of {dirty}.  A reaction which produces a small number
   of different products which are desired or which are easily deleted
   is said to be clean.  For example, a {puffer} which produces just one
   object per period is clean.  Clean reactions are useful because they
   can be used as building blocks in larger constructions.
     When a {fuse} is said to be clean, or to burn cleanly, this usually
   means that no debris at all is left behind.

:clock: (p2)  Found by Simon Norton, May 1970.  This is the fifth or
   sixth most common {oscillator}, being about as frequent as the
   {pentadecathlon}, but much less frequent than the {blinker}, {toad},
   {beacon} or {pulsar}.  But it's surprisingly rare considering its
   small size.
	..*.
	*.*.
	.*.*
	.*..

:clock II: (p4)  Compare with {pinwheel}.
	......**....
	......**....
	............
	....****....
	**.*....*...
	**.*..*.*...
	...*..*.*.**
	...*.*..*.**
	....****....
	............
	....**......
	....**......

:cloud of smoke: = {smoke}

:cloverleaf:  This name was given by Robert Wainwright to his p2
   oscillator {washing machine}.  But Achim Flammenkamp also gave this
   name to {Achim's p4}.

:cluster:  Any pattern in which each live cell is connected to every
   other live cell by a path that does not pass through two consecutive
   dead cells.  This sense is due to Nick Gotts, but the term has also
   been used in other senses, often imprecise.

:CNWH:  Conweh, creator of the Life universe.

:Coe ship: (c/2 ortogonally, p16)  A {puffer engine} discovered by Tim
   Coe in October 1995.
	....******
	..**.....*
	**.*.....*
	....*...*.
	......*...
	......**..
	.....****.
	.....**.**
	.......**.

:Coe's p8: (p8)  Found by Tim Coe in August 1997.
	**..........
	**..**......
	.....**.....
	....*..*....
	.......*..**
	.....*.*..**

:colorized Life:  A {cellular automaton} which is the same as Life
   except for the use of a number of different ON states ("colours").
   All ON states behave the same for the purpose of applying the Life
   rule, but additional rules are used to specify the colour of the
   resulting ON cells.  Examples are {Immigration} and {QuadLife}.

:complementary blinker: = {fore and back}

:compression: = {repeat time}

:conduit:  Any arrangement of {still life}s and/or {oscillator}s which
   move an active object to another location, perhaps also transforming
   it into a different active object at the same time, but without
   leaving any permanent debris (except perhaps gliders, or other
   spaceships) and without any of the still lifes or oscillators being
   permanently damaged.  Probably the most important conduit is the
   following remarkable one (Dave Buckingham, July 1996) in which a
   {B-heptomino} is transformed into a {Herschel} in 59 generations.
	.........**.*
	*.**......***
	**.*.......*.
	.............
	.........**..
	.........**..

:confused eaters: (p4)  Found by Dave Buckingham before 1973.
	*..........
	***........
	...*.......
	..*........
	..*..*.....
	.....*.....
	...*.*.....
	...**..**..
	.......*.*.
	.........*.
	.........**

:converter:  A {conduit} in which the input object is not of the same
   type as the output object.  This term tends to be preferred when
   either the input object or the output object is a {spaceship}.
     The following diagram shows a p8 {pi-heptomino}-to-{HWSS}
   converter.  This was originally found by Dave Buckingham in a
   larger form (using a {figure-8} instead of the {boat}).  The
   improvement shown here is by Bill Gosper (August 1996).  Dieter
   Leithner has since found (much larger) oscillators of periods 44,
   46 and 60 to replace the {Kok's galaxy}.
	.*.*..*........
	.***.*.**......
	*......*.....*.
	.*.....**...*.*
	.............**
	**.....*.......
	.*......*......
	**.*.***.......
	..*..*.*.......
	............***
	............*.*
	............*.*

:convoy:  A collection of {spaceship}s all moving in the same direction
   at the same speed.

:Corder engine: = {switch engine}

:Cordership:  Any {spaceship} based on {switch engine}s.  These
   necessarily move at a speed of c/12 diagonally with a period of 96
   (or a multiple thereof), and the first was found by Dean Hickerson
   in April 1991.  Corderships are by far the slowest spaceships yet
   constructed, although arbitrarily slow spaceships are known to exist
   (see {universal constructor}).  Hickerson's original Cordership used
   13 switch engines.  He soon reduced this to 10, and in August 1993
   to 7.  In July 1998 he reduced it to just 6, and this is shown below.
	..........................................**...................
	......................................**...*...................
	...........................***.......*......*..................
	..............................***.....*...*****................
	..............................***......*...*...................
	...............................*...........*..*................
	............................................**.......**........
	.....................................................**........
	...............................................................
	...............................................................
	...............................................................
	...............................................................
	....................***........................................
	....................***..................*.....................
	........................................*.*..................**
	....................*.**................*..*.................**
	....................*...*................**....................
	......................***......................................
	.....................................**........................
	.....................................**........................
	...............................................................
	...............................................................
	..............................*................................
	.....*.......................*.*.........................*.....
	.****.**.....***.............*.*.....................****.**...
	**.***.**....***..............*.....................**.***.**..
	.*.***.*.......**....................................*.***.*...
	..*...****....**......................................*...****.
	.....**.***..............................................**.***
	......*****.........**....................................*****
	.......*............**.....................................*...
	...............................................................
	...............................................................
	...............................................................
	...........................................*...................
	..........................................***..................
	..........................***.............*..*.................
	......................*....**.............***..................
	....................****..................***..................
	............*......**.**.................*.**.*................
	.........**....*..*.*.....................*..***...............
	....**.....**...*.........................****.**..............
	....**.......*.**...***..**................*.***...............
	.....................**..**..................***...............
	..............................................**...............
	...............................................................
	...............................................................
	.............................*.................................
	.........................****.**....*...**.***.................
	............**..........**.***.**...**...*****.................
	............**...........*.***.*....***...***..................
	..........................*...****....**.......................
	.............................**.***............................
	..............................*****............................
	...............................*...............................
	...............................................................
	...............................................................
	....................**.........................................
	....................**.........................................

:cousins: (p3)  This contains two copies of the {stillater} {rotor}.
	.....*.**....
	...***.*.*...
	*.*......*...
	**.**.**.*.**
	...*.*....*.*
	...*.*.***...
	....**.*.....

:cover:  The following {induction coil}.  See {scrubber} for an example
   of its use.
	....*
	..***
	.*...
	.*...
	**...

:covered table: = {cap}

:cow: (c p8 fuse)
	**.......**..**..**..**..**..**..**..**..**..**..**..**.....
	**....*.***..**..**..**..**..**..**..**..**..**..**..**...**
	....**.*.................................................*.*
	....**...*************************************************..
	....**.*..................................................*.
	**....*.***..**..**..**..**..**..**..**..**..**..**..**..**.
	**.......**..**..**..**..**..**..**..**..**..**..**..**.....

:CP pulsar: = {pulsar}

:cross: (p3)  Found by Robert Wainwright in October 1989.
	..****..
	..*..*..
	***..***
	*......*
	*......*
	***..***
	..*..*..
	..****..
   In February 1993, Hartmut Holzwart noticed that this is merely the
   smallest of an infinite family of p3 oscillators.  The next smallest
   member is shown below.
	..****.****..
	..*..*.*..*..
	***..***..***
	*...........*
	*...........*
	***.......***
	..*.......*..
	***.......***
	*...........*
	*...........*
	***..***..***
	..*..*.*..*..
	..****.****..

:crowd: (p3)  Found by Dave Buckingham in January 1973.
	...........*..
	.........***..
	.....**.*.....
	.....*...*....
	.......**.*...
	...****...*...
	*.*.....*.*.**
	**.*.*.....*.*
	...*...****...
	...*.**.......
	....*...*.....
	.....*.**.....
	..***.........
	..*...........

:crown:  The p12 part of the following p12 {oscillator}, where it is
   {hassle}d by {caterer}, a {jam} and a {HW emulator}.  This oscillator
   was found by Noam Elkies in January 1995.
	..........*...........
	..........*......*....
	...*....*...*...**....
	...**....***..........
	.........***..***..*.*
	.*..***.........*.****
	*.*.*...............**
	*..*..................
	.**........**.........
	......**.*....*.**....
	......*..........*....
	.......**......**.....
	....***..******..***..
	....*..*........*..*..
	.....**..........**...

:crucible: = {cauldron}

:cuphook: (p3)  Found by Rich Schroeppel, October 1970.  This is one of
   only three essentially different p3 {oscillator}s with only three
   cells in the {rotor}.  The others are {1-2-3} and {stillater}.

	....**...
	**.*.*...
	**.*.....
	...*.....
	...*..*..
	....**.*.
	.......*.
	.......**
   The above is the original form, but it can be made more compact:
	....**.
	...*.*.
	...*...
	**.*...
	**.*..*
	...*.**
	...*...
	..**...

:curl: = {loop}

:dart: (c/3 ortogonally, p3)  Found by David Bell, May 1992.
	.......*.......
	......*.*......
	.....*...*.....
	......***......
	...............
	....**...**....
	..*...*.*...*..
	.**...*.*...**.
	*.....*.*.....*
	.*.**.*.*.**.*.

:dead spark coil: (p1)  Compare {spark coil}.
	**...**
	*.*.*.*
	..*.*..
	*.*.*.*
	**...**

:density:  The density of a pattern is the limit of the proportion of
   live cells in a (2n+1)x(2n+1) square centred on a particular cell as
   n tends to infinity, when this limit exists.  (Note that it does not
   make any difference what cell is chosen as the centre cell.  Also
   note that if the pattern is finite then the density is zero.)  There
   are other definitions of density, but this one will do here.
     In 1994 Noam Elkies proved that the maximum density of a stable
   pattern is 1/2, which had been the conjectured value.  See the paper
   listed in the bibliography.  Marcus Moore provided a simpler proof
   in 1995, and in fact proves that a {still life} with an m x n
   {bounding box} has at most (mn+m+n)/2 cells.
     But what is the maximum average density of an oscillating pattern?
   The answer is conjectured to be 1/2 again, but this remains unproved.
   The best upper bound so far obtained is 8/13 (Hartmut Holzwart,
   September 1992).
     The maximum possible density for a phase of an oscillating pattern
   is also unknown.  An example with a density of 3/4 is known (see
   {agar}), but densities arbitrarily close to 1 may perhaps be
   possible.

:D-heptomino: = {Herschel}

:diamond: = {tub}

:diamond ring: (p3)  Found by Dave Buckingham in 1972.
	......*......
	.....*.*.....
	....*.*.*....
	....*...*....
	..**..*..**..
	.*....*....*.
	*.*.**.**.*.*
	.*....*....*.
	..**..*..**..
	....*...*....
	....*.*.*....
	.....*.*.....
	......*......

:diehard:  Any pattern that vanishes, but only after a long time.  The
   following example vanishes in 130 generations, which is probably the
   limit for patterns of 7 or fewer cells.  Note that there is no limit
   for higher numbers of cells - e.g., for 8 cells we could have a
   glider heading towards an arbitrarily distant blinker.
	......*.
	**......
	.*...***

:dinner table: (p12)  Found by Robert Wainwright in 1972.
	.*...........
	.***.......**
	....*......*.
	...**....*.*.
	.........**..
	.............
	.....***.....
	.....***.....
	..**.........
	.*.*....**...
	.*......*....
	**.......***.
	...........*.

:dirty:  Opposite of {clean}.  A reaction which produces a large amount
   of complicated junk which is difficult to control or use is said
   to be dirty.  Many basic {puffer engine}s are dirty and need to
   be {tame}d by accompanying {spaceship}s in order to produce clean
   output.

:diuresis: (p90)  Found by David Eppstein in October 1998.  His original
   stabilization used {pentadecathlon}s.  The stabilization with
   complicated {still life}s shown here (in two slightly different
   forms) was found by Dean Hickerson the following day.  The name is
   due to Bill Gosper (see {kidney}).
	.....**................**....
	......*................*.....
	......*.*............*.*.....
	.......**............**......
	.............................
	....**..................**...
	....*.*..........**....*.*...
	.....*..........*.*.....*....
	..*.............**.........*.
	..******........*.....******.
	.......*..............*......
	....**..................**...
	....*....................*...
	.....*..................*....
	..***..*..............*..***.
	..*..***........*.....***...*
	...*............**.......***.
	....**..........*.*.....*....
	......*..........**....*..**.
	....**..................**.*.
	.*..*....................*...
	*.*.*..**............**..*...
	.*..*.*.*............*.*.**..
	....*.*................*..*..
	.....**................**....

:dock:  The following {induction coil}.
	.****.
	*....*
	**..**

:domino:  The 2-cell {polyomino}.  A number of objects, such as the
   {HWSS} and {pentadecathlon}, produce domino {spark}s.

:double-barrelled:  Of a {gun}, emitting two streams of {spaceship}s
   (or {rake}s).  See {B-52 bomber} for an example.

:double block reaction:  A certain reaction that can be used to
   stabilize the {twin bees shuttle} (qv).  This was discovered by
   David Bell in October 1996.
     The same reaction sometimes works in other situations, as shown in
   the following diagram where a pair of blocks eats an {R-pentomino}
   and a {LWSS}.  (The LWSS version was known at least as early 1994,
   when Paul Callahan saw it form spontaneously as a result of firing
   a LWSS stream at some random junk.)
	.****.....**....
	*...*......**.**
	....*......*..**
	*..*............
	................
	.............**.
	.............**.

:double caterer: (p3)  Found by Dean Hickerson, October 1989.  Compare
   {caterer} and {triple caterer}.
	.....**...*........
	....*..*..***......
	....**.*.....*.....
	......*.****.*.....
	..***.*.*...*.**...
	.*..*..*...*..*.*..
	*.*..*...*.**....*.
	.*..........**.***.
	..**.**.**...*.....
	...*...*.....*.***.
	...*...*......**..*
	.................**

:double ewe: (p3)  Found by Robert Wainwright before September 1971.
	......**............
	.......*............
	......*.............
	......**............
	.........**.........
	......***.*.........
	*.**.*..............
	**.*.*..............
	.....*...*..........
	....*...**....**....
	....**....**...*....
	..........*...*.....
	..............*.*.**
	..............*.**.*
	.........*.***......
	.........**.........
	............**......
	.............*......
	............*.......
	............**......

:double wing: = {moose antlers}

:dove:  The following {induction coil}.
	.**..
	*..*.
	.*..*
	..***

:down boat with tail: = {cis-boat with tail}

:dragon: (c/6 orthogonally, p6)  This {spaceship}, discovered by
   Paul Tooke in April 2000, was the first known c/6 spaceship.
   All other known c/6 spaceships are {flotilla}s involving at
   least two dragons.
	.............*..**......*..***
	.....*...****.******....*..***
	.*****....*....*....***.......
	*......**.*......**.***..*.***
	.*****.***........****...*.***
	.....*..*..............*......
	........**..........**.**.....
	........**..........**.**.....
	.....*..*..............*......
	.*****.***........****...*.***
	*......**.*......**.***..*.***
	.*****....*....*....***.......
	.....*...****.******....*..***
	.............*..**......*..***

:drain trap: = {paperclip}

:drifter:  A perturbation moving within a stable pattern.  Dean
   Hickerson has written a program to search for drifters, with the
   hope of finding one which could be moved around a track.  Because
   drifters can be very small, they could be packed more tightly than
   {Herschel}s, and so allow the creation of {oscillator}s of periods
   not yet attained, and possibly prove that Life is {omniperiodic}.
   Hickerson has found a number of components towards this end, but
   it has proved difficult to change the direction of movement of a
   drifter, and so far no complete track has been found.  However,
   Hickerson has had success using the same search program to find
   {eater}s with novel properties, such as that used in {diuresis}.

:dual 1-2-3-4: = {Achim's p4}

: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.
	...*.....
	...*.*...
	...**....
	.........
	.......**
	...*...**
	..*.*....
	.*.*.....
	.*.......
	**.......

: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.
	**..
	*.*.
	..*.
	..**

: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 acts like an eater in two
   directions.  The first property means that, among other things, it
   can eat a {glider} in a position that would destroy a fishhook.  This
   novel glider-eating action is occasionally of use in itself, and
   combined with the symmetry means that an eater2 can eat gliders along
   four different paths.  An eater2 variant noticed by Stephen Silver in
   May 1998 that is useful for obtaining smaller {bounding box}es 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.
	.........**.
	....**..*..*
	.*..*....*.*
	*.*.*.....*.
	.*..*.**....
	....*..*....
	.....*....*.
	......*****.
	............
	........*...
	.......*.*..
	........*...

: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 {glider}s, 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.
	...**.........
	...*..........
	**.*..........
	*..**.........
	.**....*......
	...*****......
	...*....**....
	....**..*.....
	......*.*.....
	......*.*.*..*
	.......**.****
	.........*....
	.........*.*..
	..........**..

:eater/block frob: (p4)  Found by Dave Buckingham in 1976 or earlier.
	.**.......
	..*.......
	..*.*.....
	...*.*....
	.....**.**
	........**
	..**......
	...*......
	***.......
	*.........

:eater-bound pond: (p3)  Found by Peter Raynham, July 1972.
	*...........
	***.........
	...*........
	..**........
	...**.......
	....**......
	...*..*.....
	...*..**....
	....**.***..
	........*.*.
	..........*.
	..........**

:eater-bound Z-hexomino: = {pentoad}

:eater eating eater: = {two eaters}

:eater plug: (p2)  Found by Robert Wainwright, February 1973.
	.......*
	.....***
	....*...
	.....*..
	..*..*..
	.*.**...
	.*......
	**......

:eaters +: = {French kiss}

: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: (c/3 orthogonally, p3)  Any of a family of
   {spaceship}s whose left-hand edge can be used to {perturb} things,
   since it can often repair damage done to itself.  Below are shown
   the two smallest and most useful members of this family, both found
   by David Bell in 1992.  The usefulness of the edge-repair property
   wasn't recognised until July 1997.
	..................................*.....
	........*.......................***.***.
	.......****....................**......*
	..*...*...**.**...........*...*..*...**.
	.****.....*..**..........****...........
	*...*.......*..*........*...*...........
	.*.*..*..................*.*..*.........
	.....*.......................*..........
   The following diagram (showing an edge-repair spaceship deleting a
   {Herschel}) demonstrates the self-repairing action.
	................*.......
	*..............****.....
	*.*.......*...*...**.**.
	***......****.....*..**.
	..*.....*...*.......*..*
	.........*.*..*.........
	.............*..........

: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 spark}s.

:egg: = {non-spark}

:E-heptomino:  Name given by Conway to the following {heptomino}.
	.***
	**..
	.**.

:elbow ladder:  Scot Ellison's name for the type of pattern he
   created in which a glider shuttles back and forth (using the
   {kickback reaction}) deleting the output gliders from a pair of
   {side-shooting gun}s.

:electric fence: (p5)  A stabilization of {ants}.  Dean Hickerson,
   February 1993.
	..........*...................................................
	.........*.*........................**........................
	..*....***.*.....*...................*...*..*......*........**
	.*.*..*....**...*.*..................*.***..***...*.*......*.*
	.*.*..*.**.......*....................*...**...*.*..*......*..
	**.**.*.*.*****.....*..................**...*..*.*.**.**..**..
	.*.*..*...*..*..*.......**...**...**....**.**..*.*..*.*.*.....
	.*..**....**......***.**...**...**...***.....****.***.*...**..
	..*..***..*..*.****...**...**...**...***.**..*....*.*....*..*.
	...**...*.*..*.....**...**...**...**......*............*...**.
	.....**.*.**.*.**..*......................*........**.*.......
	.....*.**.*..*.**....*.................**.*.*.................
	...........**.......**..................*..**.................
	......................................*.*.....................
	......................................**......................

:elevener: (p1)
	**....
	*.*...
	..*...
	..***.
	.....*
	....**

:Elkies' p5: (p5)  Found by Noam Elkies in 1997.
	.*.......
	*..***...
	..*......
	...*.*..*
	..**.****
	....*....
	....*.*..
	.....**..

:emu:  Dave Buckingham's term for a {Herschel loop} that does not emit
   {glider}s (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 {spark}s
   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-spark}s and so are of little use.  The emulators were
   discovered by Robert Wainwright in June 1980.

:en retard: (p3)  Found by Dave Buckingham, August 1972.
	.....*.....
	....*.*....
	**.*.*.*.**
	.*.*...*.*.
	*..*.*.*..*
	.**.....**.
	...**.**...
	...*.*.*...
	....*.*....
	..*.*.*.*..
	..**...**..

:Enterprise: (c/4 diagonally, p4)  Found by Dean Hickerson, March 1993.
	.......***...........
	.....*.**............
	....****.............
	...**.....*..........
	..***..*.*.*.........
	.**...*.*..*.........
	.*.*.*****...........
	**.*.*...*...........
	*........**..........
	.**..*...*.*.........
	....**..*.**......*..
	...........**.....***
	............*..***..*
	............*..*..**.
	.............*.**....
	............**.......
	............**.......
	...........*.........
	............*.*......
	...........*..*......
	.............*.......

: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.
	.*..............*.
	*.*....*.......*.*
	.*...**.**......*.
	.......*..........
	..................
	..................
	..................
	.......*..........
	.*...**.**......*.
	*.*....*.......*.*
	.*..............*.

:exposure: = {underpopulation}

:extremely impressive: (p6)  Found by Dave Buckingham, August 1976.
	....**......
	...*.***....
	...*....*...
	**.*...**...
	**.*.....**.
	....*****..*
	..........**
	......*.....
	.....*.*....
	......*.....

: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.

:extra extra long: = {long^4}

:extra long: = {long^3}

:factory:  Another word for {gun}, but not used in the case of glider
   guns.  The term is also used for a pattern that repeatedly
   manufactures objects other than {spaceship}s or {rake}s.  In this
   case the new objects do not move out of the way, and therefore must
   be used up in some way before the next one is made.  The following
   shows an example of a p144 gun which consists of a p144 block
   factory whose output is converted into gliders by a p72 oscillator.
   (This gun is David Bell's improvement of the one Bill Gosper found
   in July 1994.  The p72 oscillator is by Robert Wainwright, 1990, and
   the block factory is {Achim's p144} minus one of its stabilizing
   blocks.)
	.......................**........................**
	.......................**........................**
	.........................................**........
	........................................*..*.......
	.........................................**........
	...................................................
	....................................***............
	....................................*.*............
	.........**.........................***............
	.........**.........................**.............
	........*..*.......................***.............
	........*..*.**....................*.*.............
	........*....**....................***.............
	..........**.**....................................
	...............................**..................
	.....................**.......*..*.................
	.....................**........**..................
	.................................................**
	.................................................**
	...................................................
	....**..................*..........................
	**....****..........**..**.***.....................
	**..**.***..........**....****.....................
	....*...................**.........................

:familiar fours:  Common patterns of four identical objects.  The
   five commonest are {traffic light} (4 blinkers), {honey farm}
   (4 beehives), {blockade} (4 blocks), {fleet} (4 ships, although
   really 2 ship-ties) and {bakery} (4 loaves, although really 2
   bi-loaves).

:fanout:  A mechanism that emits two or more objects of some type for
   each one that it receives.  Typically the objects are {glider}s or
   {Herschel}s.

:Fast Forward Force Field:  The following reaction found by Dieter
   Leithner in May 1994.  In the absence of the incoming LWSS the
   gliders would simply annihilate one another, but as shown they
   allow the LWSS to advance 11 spaces in the course of the next 6
   generations.  A neat illusion.  See also {star gate}.  (Leithner
   named the Fast Forward Force Field in honour of his favourite
   science fiction writer, the physicist Robert L. Forward.)
	.......*......*..
	........*......**
	..**..***.....**.
	**.**............
	****.........*...
	.**.........**...
	............*.*..

:father: = {parent}

:featherweight spaceship: = {glider}

:fencepost:  Any pattern that stabilizes one end of a {wick}.

:Fermat prime calculator:  A pattern constructed by Jason Summers in
   January 2000 that exhibits {infinite growth} if and only if there
   are no Fermat primes greater than 65537.  The question of whether
   or not it really does exhibit infinite growth is therefore equivalent
   to a well-known and long-standing unsolved mathematical problem.
   It will, however, still be growing at generation 10^2585827975.
   The pattern is based on Dean Hickerson's {primer} and {caber tosser}
   patterns and a p8 beehive puffer by Hartmut Holzwart.

:F-heptomino:  Name given by Conway to the following {heptomino}.
	**..
	.*..
	.*..
	.***

:figure-8: (p8)  Found by Simon Norton in 1970.
	***...
	***...
	***...
	...***
	...***
	...***

:filter:  Any {oscillator} used to delete some but not all of the
   {spaceship}s in a stream.  An example is the {blocker}, which can
   be positioned so as to delete every other {glider} in a stream of
   period 8n+4, and can also do the same for {LWSS} streams.  Other
   examples are the {MW emulator} and {T-nosed p4} (either of which
   can be used to delete every other LWSS in a stream of period 4n+2),
   the {fountain} (which does the same for {MWSS} streams) and a number
   of others, such as the p6 {pipsquirter}, the {pentadecathlon} and
   the p72 oscillator shown under {factory}.  Another example, a p4
   oscillator deleting every other HWSS in a stream of period 4n+2, is
   shown below.  (The p4 oscillator here was found, with a slightly
   larger {stator}, by Dean Hickerson in November 1994.)
	..........****............
	....**...******...........
	****.**..****.**..........
	******.......**...........
	.****.....................
	..........................
	................**........
	..............*....*......
	..........................
	.............*.*..*.*.....
	...........****.**.****...
	........*.*....*..*....*.*
	........**.**.*....*.**.**
	...........*.*......*.*...
	........**.*.*......*.*.**
	........**.*..........*.**
	...........*.*.****.*.*...
	...........*.*......*.*...
	..........**.*.****.*.**..
	..........*..***..***..*..
	............*..****..*....
	...........**.*....*.**...
	...........*..*....*..*...
	............*..*..*..*....
	.............**....**.....

:fish:  A generic term for {LWSS}, {MWSS} and {HWSS}, or, more
   generally, for any {spaceship}.

:fishhook: = {eater1}

:fleet: (p1)  A common formation of two {ship-tie}s.
	....**....
	....*.*...
	.....**...
	.......**.
	**.....*.*
	*.*.....**
	.**.......
	...**.....
	...*.*....
	....**....

:flip-flop:  Any p2 {oscillator}.  However, the term is also used
   in two more specific (and non-equivalent) senses: (a) any p2
   oscillator whose two phases are mirror images of one another,
   and (b) any p2 oscillator in which all {rotor} cells die from
   {underpopulation}.  In the latter sense it contrasts with {on-off}.
   The term has also been used even more specifically for the 12-cell
   flip-flop shown under {phoenix}.

:flip-flops:  Another name for the flip-flop shown under {phoenix}.

:flipper:  Any {oscillator} or {spaceship} that forms its mirror image
   halfway through its period.

:flotilla:  A {spaceship} composed of a number of smaller interacting
   spaceships.  Often one or more of these is not a true spaceship and
   could not survive without the support of the others.  The following
   example shows an {OWSS} escorted by two {HWSS}.
	....****.......
	...******......
	..**.****......
	...**..........
	...............
	...........**..
	.*............*
	*..............
	*.............*
	**************.
	...............
	...............
	....****.......
	...******......
	..**.****......
	...**..........

:fly:  A certain c/3 {tagalong} found by David Bell, April 1992.
   Shown here attached to the back of a small spaceship (also by Bell).
	..*...............................
	.*.*..............................
	.*.*......................*.*...*.
	.*.......................**.*.*..*
	...........***........*.........*.
	**.........**..*.**...*..****.....
	.*.*.........****..*.*..**....**..
	.**........*..*...***.....***.....
	..*.......*....*..**..**..*..*....
	...*..*...*....*..***.*.*....**...
	.......*.**....*..****.....*......
	....**...**....*..****.....*......
	....*.*...*....*..***.*.*....**...
	...**.....*....*..**..**..*..*....
	....*.*....*..*...***.....***.....
	.....*.......****..*.*..**....**..
	...........**..*.**...*..****.....
	...........***........*.........*.
	.........................**.*.*..*
	..........................*.*...*.

:flying machine: = {Schick engine}

:fore and back: (p2)  Compare {snake pit}.  Found by Achim Flammenkamp,
   July 1994.
	**.**..
	**.*.*.
	......*
	***.***
	*......
	.*.*.**
	..**.**

:forward glider:  A {glider} which moves at least partly in the same
   direction as the {puffer}(s) or {spaceship}(s) under consideration.

:fountain: (p4)  Found by Dean Hickerson in November 1994, and named by
   Bill Gosper.  See also {filter}.
	.........*.........
	...................
	...**.*.....*.**...
	...*.....*.....*...
	....**.**.**.**....
	...................
	......**...**......
	**...............**
	*..*...*.*.*...*..*
	.***.*********.***.
	....*....*....*....
	...**.........**...
	...*...........*...
	.....*.......*.....
	....**.......**....

:fourteener: (p1)
	....**.
	**..*.*
	*.....*
	.*****.
	...*...

:fox: (p2)  This is the smallest asymmetric p2 oscillator.  Found by
   Dave Buckingham, July 1977.
	....*..
	....*..
	..*..*.
	**.....
	....*.*
	..*.*.*
	......*

:French kiss: (p3)  Found by Robert Wainwright, July 1971.
	*.........
	***.......
	...*......
	..*..**...
	..*....*..
	...**..*..
	......*...
	.......***
	.........*

:frog II: (p3)  Found by Dave Buckingham, October 1972.
	..**...**..
	..*.*.*.*..
	....*.*....
	...*.*.*...
	...**.**...
	.**.....**.
	*..*.*.*..*
	.*.*...*.*.
	**.*...*.**
	....***....
	...........
	...*.**....
	...**.*....

:frothing puffer:  A frothing puffer (or a frothing spaceship) is a
   {puffer} (or {spaceship}) whose back end appears to be unstable and
   breaking apart, but which nonetheless survives.  The exhaust festers
   and clings onto the back of the puffer/spaceship before breaking off.
   All known frothing puffers are c/2, and most were found as the result
   of slightly modifying the back ends of p2 spaceships.  A number of
   them have periods which are not a multiple of 4.  (In this respect,
   see also {line puffer}.)  The following p78 frothing puffer was found
   by Paul Tooke in April 2001.
	.......*.................*.......
	......***...............***......
	.....**....***.....***....**.....
	...**.*..***..*...*..***..*.**...
	....*.*..*.*...*.*...*.*..*.*....
	.**.*.*.*.*....*.*....*.*.*.*.**.
	.**...*.*....*.....*....*.*...**.
	.***.*...*....*.*.*....*...*.***.
	**.........**.*.*.*.**.........**
	............*.......*............
	.........**.*.......*.**.........
	..........*...........*..........
	.......**.*...........*.**.......
	.......**...............**.......
	.......*.*.*.***.***.*.*.*.......
	......**...*...*.*...*...**......
	......*..*...*.*.*.*...*..*......
	.........**....*.*....**.........
	.....**....*...*.*...*....**.....
	.........*.**.*...*.**.*.........
	..........*.*.*.*.*.*.*..........
	............*..*.*..*............
	...........*.*.....*.*...........

:frothing spaceship:  See {frothing puffer}.

:fumarole: (p5)  Found by Dean Hickerson in September 1989.  In terms of
   its 7x8 bounding box this is the smallest p5 oscillator.
	...**...
	.*....*.
	.*....*.
	.*....*.
	..*..*..
	*.*..*.*
	**....**

:fuse:  A {wick} burning at one end.  For examples, see {baker},
   {beacon maker}, {blinker ship}, {boat maker}, {cow}, {harvester},
   {lightspeed wire}, {pi ship}, {reverse fuse}, {superstring} and
   {washerwoman}.  Useful fuses are usually {clean}.

:galaxy: = {Kok's galaxy}

:Game of Life: = {Life}

:Garden of Eden:  A configuration of ON and OFF cells that can only
   occur in generation 0.  (This term was first used in connection with
   cellular automata by John W. Tukey, many years before Life.)  It was
   known from the start that there are Gardens of Eden in Life, because
   of a theorem by Edward Moore that guarantees their existence in
   a wide class of cellular automata.  Explicit examples have since
   been constructed, the first by Roger Banks, et al. at MIT in 1971.
   This example was 9 x 33.  In 1974 J. Hardouin-Duparc, et al. produced
   a 6 x 122 example.  The following shows a 14 x 14 example (with 143
   ON cells) by Achim Flammenkamp (1991 or 1992).
	**.*.*.*.**.*.
	*.***.***.**.*
	****.***.**.*.
	***.*.*.*.****
	.***.*.***.**.
	*******.****.*
	.*.*.********.
	*.***.**.*.*.*
	******.******.
	*.**.*****.*.*
	***.*********.
	.***.*.*.*.***
	***.*.*.*.**.*
	*.************

:generation:  The fundamental unit of time.  The starting pattern is
   generation 0.

:germ: (p3)  Found by Dave Buckingham, September 1972.
	....**....
	.....*....
	...*......
	..*.****..
	..*....*..
	.**.*.....
	..*.*.****
	*.*.*....*
	**...***..
	.......**.

:gfind:  A program by David Eppstein used for searching for new
   {spaceship}s.  It was with gfind that Eppstein found the
   {weekender}, and Paul Tooke later used it to find the {dragon}.
   Compare {lifesrc}.

:glasses: (p2)  Compare {scrubber} and {spark coil}.
	....*........*....
	..***........***..
	.*..............*.
	.*..***....***..*.
	**.*...*..*...*.**
	...*...****...*...
	...*...*..*...*...
	....***....***....
	..................
	....**.*..*.**....
	....*.**..**.*....

:glider: (c/4 diagonally, p4)  The smallest, most common and first
   discovered {spaceship}.  This was found by Richard Guy in 1970
   while Conway's group was attempting to track the evolution of the
   {R-pentomino}.  The name is due in part to the fact that it is
   {glide symmetric}.  (It is often stated that Conway discovered the
   glider, but he himself has said it was Guy.  See also the cryptic
   reference ("some guy") in {Winning Ways}.)
	***
	*..
	.*.
   The term "glider" is also occasionally (mis)used to mean "spaceship".

:glider-block cycle:  An infinite {oscillator} based on the following
   reaction (a variant of the {rephaser}).  The oscillator consists of
   copies of this reaction displaced 2n spaces from one another (for
   some n>6) with blocks added between the copies in order to cause the
   reaction to occur again halfway through the period.  The period of
   the resulting infinite oscillator is 8n-20.  (Alternatively, in a
   cylindrical universe of width 2n the oscillator just consists of two
   gliders and two blocks.)
	...**...
	...**...
	........
	........
	..*..*..
	*.*..*.*
	.**..**.

:glider construction: = {glider synthesis}

:glider gun:  A {gun} which fires {glider}s.

:gliderless:  A {gun} is said to be gliderless if it does not use
   {glider}s.  The purist definition would insist that a glider does
   not appear anywhere, even incidentally.  For a long time the only
   known way to construct {LWSS}, {MWSS} and {HWSS} guns involved
   gliders, and it was not until April 1996 that Dieter Leithner
   constructed the first gliderless gun (a p46 LWSS gun).  The following
   diagram shows Leithner's p44 MWSS gun which he discovered in April
   1997 (shown with Stephen Silver's May 1998 improvement to the
   {bounding box} using a modified {eater2}).  This is the smallest
   known gliderless gun, and also the smallest known MWSS gun.  It is
   based on an important p44 oscillator discovered by Dave Buckingham
   in early 1992.  (Note that a glider shape appears in this gun for
   three consecutive generations, but always as part of a larger
   {cluster}, so even a purist would regard this gun as gliderless.)
	.........**....**....**...........................
	........*..*.*....*.*..*..........................
	........***..........***..........................
	...........**......**.............................
	..........*..******..*............................
	..........**........**............................
	.................................*................
	...............................***................
	..............................*........***........
	..............................**.......*..*.......
	.........................*.............*..........
	........................*..............*...*......
	.........................**............*..........
	........................*.*.............*.*.......
	..................................................
	.......................*.*.....***..............**
	........................*.....*..*...............*
	**............***.......*......**...........**.*..
	**...........*...*..........................**.**.
	.............**.**................................
	.................................**.........**.**.
	..............................**.............*.*..
	.............................................*.*..
	..............................................*...
	.............**.**.............*.*................
	**...........*...*.............**.................
	**............***.................................
	...........................**.....................
	...........................*.*....................
	.............................*....................
	.............................**...................
	..................................................
	..................................................
	..................................................
	..................................................
	..................................................
	..................................................
	..................................................
	..........**........**............................
	..........*..******..*............................
	...........**......**.............................
	........***..........***..........................
	........*..*.*....*.*..*..........................
	.........**....**....**...........................

:glider pusher:  An arrangement of a {queen bee shuttle} and a
   {pentadecathlon} that can push the path of a passing glider
   out by one half-diagonal space.  This was found by Dieter Leithner
   in December 1993 and is shown below.  It is useful for constructing
   complex {gun}s where it may be necessary to produce a number of
   gliders travelling on close parallel paths.  See also {edge shooter}.
	.........**..............
	.........**..............
	.........................
	..........*..............
	.........*.*.............
	.........*.*.............
	..........*..............
	.........................
	.........................
	.......**.*.**...........
	.......*.....*...........
	........*...*............
	.*.......***.............
	..*......................
	***......................
	.........................
	.........................
	.................*....*..
	...............**.****.**
	.................*....*..

:gliders by the dozen: (stabilizes at time 184)  In early references
   this is usually shown in a larger form whose generation 1 is
   generation 8 of the form shown here.
	**..*
	*...*
	*..**

:glider synthesis:  Construction of an object by means of {glider}
   collisions.  It is generally assumed that the gliders should be
   arranged so that they could come from infinity - that is, gliders
   should not have had to pass through one another to achieve the
   initial arrangement.
     Glider syntheses for all {still life}s and known {oscillator}s with
   at most 14 cells were found by Dave Buckingham.
     Perhaps the most interesting glider syntheses are those of
   {spaceship}s, because these can be used to create corresponding
   {gun}s.  Many of the c/2 spaceships that are based on
   {standard spaceship}s have been synthesized, mostly by Mark Niemiec.
   In June 1998 Stephen Silver found syntheses for some of the
   {Cordership}s (although it was not until July 1999 that Jason Summers
   used this to build a Cordership gun).  All other spaceships (except
   the glider itself, of course) have so far eluded synthesis.  Many of
   them are {space dust}.
     A 3-glider synthesis of a {pentadecathlon} is shown in the diagram
   below.  This was found in April 1997 by Heinrich Koenig and came as
   a surprise, as it was widely assumed that anything using just three
   gliders would already be known.
	......*...
	......*.*.
	......**..
	..........
	***.......
	..*.......
	.*.....**.
	........**
	.......*..

:glider train:  A certain {puffer} that produces two rows of {block}s
   and two backward {glider} waves.  Ten of these were used to make the
   first {breeder}.

:glide symmetric:  Undergoing simultaneous reflection and translation.
   A glide symmetric {spaceship} is commonly called a {flipper}.

:gnome: = {fox}

:GoE: = {Garden of Eden}

:GoL: = {Game of Life}

:Gosper glider gun:  The first known {gun}, and indeed the first
   known finite pattern with unbounded growth, found by Bill Gosper
   in November 1970.  It remains by far the smallest known gun.
   Gosper has since found other guns, see {new gun} and the p144
   gun shown under {factory}.
	........................*...........
	......................*.*...........
	............**......**............**
	...........*...*....**............**
	**........*.....*...**..............
	**........*...*.**....*.*...........
	..........*.....*.......*...........
	...........*...*....................
	............**......................

:gourmet: (p32)  Found by Dave Buckingham in March 1978.  Compare with
   {pi portraitor} and {popover}.
	..........**........
	..........*.........
	....**.**.*....**...
	..*..*.*.*.....*....
	..**....*........*..
	................**..
	....................
	................**..
	*.........***..*.*..
	***.......*.*...*...
	...*......*.*....***
	..*.*..............*
	..**................
	....................
	..**................
	..*........*....**..
	....*.....*.*.*..*..
	...**....*.**.**....
	.........*..........
	........**..........

:grammar:  A set of rules for connecting components together to make
   an object such as a {spaceship}, {oscillator} or {still life}.

:grandfather: = {grandparent}

:grandparent:  A pattern is said to be a grandparent of the pattern it
   gives rise to after two generations.  See also {parent}.

:Gray counter: (p4)  Found in 1971.  If you look at this in the right
   way you will see that it cycles through the Gray codes from 0 to 3.
   Compare with {R2D2}.
	......*......
	.....*.*.....
	....*.*.*....
	.*..*...*..*.
	*.*.*...*.*.*
	.*..*...*..*.
	....*.*.*....
	.....*.*.....
	......*......

:great on-off: (p2)
	..**....
	.*..*...
	.*.*....
	**.*..*.
	....**.*
	.......*
	....***.
	....*...

:grey counter: = {Gray counter}  (This form is erroneous, as Gray is
   surname, not a colour.)

:grin:  The following common {parent} of the {block}.  This name relates
   to the infamous {Cheshire cat}.  See also {pre-block}.
	*..*
	.**.

:growing spaceship:  An object that moves like a {spaceship}, except
   that its front part moves faster than its back part and a {wick}
   extends between the two.  Put another way, a growing spaceship is
   a {puffer} whose output is burning {clean}ly at a slower rate than
   the puffer is producing it.  Examples include {blinker ship}s and
   {pi ship}s.

:gull: = {elevener}

:gun:  Any stationary pattern that emits {spaceship}s (or {rake}s)
   forever.  For examples see {double-barrelled}, {edge shooter},
   {factory}, {gliderless}, {Gosper glider gun}, {new gun} and {true}.

:gunstar:  Any of a series of glider {gun}s of period 144+72n (for all
   non-negative integers n) constructed by Dave Buckingham in 1990
   based on his {transparent block reaction} and Robert Wainwright's
   p72 oscillator (shown under {factory}).

:half bakery:  See {bi-loaf}.

:half fleet: = {ship-tie}

:hammer:  To hammer a {LWSS}, {MWSS} or {HWSS} is to smash things into
   the rear end of it in order to transform it into a different type
   of {spaceship}.  A hammer is the object used to do the hammering.
   In the following example by Dieter Leithner a LWSS is hammered by
   two more LWSS to make it into a MWSS.
	*..*................
	....*...**..........
	*...*..***.....****.
	.****..**.*....*...*
	........***....*....
	.........*......*..*

:hammerhead:  A certain front end for c/2 spaceships.  The central
   part of the hammerhead pattern is supported between two {MWSS}.
   The picture below shows a small example of a {spaceship} with a
   hammerhead front end (the front 9 columns).
	................*..
	.**...........*...*
	**.***.......*.....
	.*****.......*....*
	..*****.....*.****.
	......***.*.**.....
	......***....*.....
	......***.***......
	..........**.......
	..........**.......
	......***.***......
	......***....*.....
	......***.*.**.....
	..*****.....*.****.
	.*****.......*....*
	**.***.......*.....
	.**...........*...*
	................*..

:handshake:  An old MIT name for {lumps of muck}, from the following
   form (2 generations on from the {stairstep hexomino}):
	..**.
	.*.**
	**.*.
	.**..

:harbor: (p5)  Found by Dave Buckingham in September 1978.  The name is
   by Dean Hickerson.
	.....**...**.....
	.....*.*.*.*.....
	......*...*......
	.................
	.....**...**.....
	**..*.*...*.*..**
	*.*.**.....**.*.*
	.*.............*.
	.................
	.*.............*.
	*.*.**.....**.*.*
	**..*.*...*.*..**
	.....**...**.....
	.................
	......*...*......
	.....*.*.*.*.....
	.....**...**.....

:harvester: (c p4 fuse)  Found by David Poyner, this was the first
   published example of a {fuse}.  The name refers to the fact the
   it produces debris in the form of {block}s which contain the same
   number of cells as the fuse has burnt up.
	................**
	...............*.*
	..............*...
	.............*....
	............*.....
	...........*......
	..........*.......
	.........*........
	........*.........
	.......*..........
	......*...........
	.....*............
	*****.............
	****..............
	*.**..............

:hashlife:  A Life algorithm by Bill Gosper that is designed to take
   advantage of the considerable amount of repetitive behaviour in many
   large patterns of interest.  This algorithm is described by Gosper
   in his paper listed in the bibliography at the end of this lexicon.
   Roughly speaking, the idea is to store subpatterns in a hash table so
   that the results of their evolution don't have to be recomputed if
   they arise again somewhen, or somewhere, else.  This does, however,
   mean that complex patterns can require substantial amounts of memory.
   Hashlife provides a means of evolving repetitive patterns millions
   (or even billions or trillions) of generations further than normal
   Life algorithms can manage in a reasonable amount of time.  It is
   not, however, suitable for showing a continuous display of the
   evolution of a pattern, because it works asynchronously - at any
   given moment it will usually have evolved different parts of the
   pattern through different numbers of generations.

:hassle:  See {hassler}.

:hassler:  An {oscillator} that works by hassling (repeatedly moving
   or changing) some object.  For some examples, see {Jolson},
   {baker's dozen}, {toad-flipper}, {toad-sucker} and {traffic circle}.

:hat: (p1)  Found in 1971.  See also {twinhat} and {sesquihat}.
	..*..
	.*.*.
	.*.*.
	**.**

:heat:  For an {oscillator} or {spaceship}, the average number of cells
   which change state in each generation.  For example, the heat of a
   {glider} is 4, because 2 cells are born and 2 die every generation.
     For a period n oscillator with an r-cell {rotor} the heat is at
   least 2r/n and no more than r(1-(n mod 2)/n).  For n=2 and n=3 these
   bounds are equal.

:heavyweight emulator: = {HW emulator}

:heavyweight spaceship: = {HWSS}

:heavyweight volcano: = {HW volcano}

:hebdarole: (p7)  Found by Noam Elkies, November 1997.  Compare
   {fumarole}.  The smaller version shown below was found soon after by
   Alan Hensel using a component found by Dave Buckingham in June 1977.
   The top tens rows can be stabilized by their mirror image (giving
   an {inductor}) and this was the original form found by Elkies.
	...........**...........
	....**...*....*...**....
	.*..*..*.*....*.*..*..*.
	*.*.*.**.*....*.**.*.*.*
	.*..*..*.*.**.*.*..*..*.
	....**....*..*....**....
	...........**...........
	.......*..*..*..*.......
	......*.**....**.*......
	.......*........*.......
	........................
	...**..............**...
	...*..****....****..*...
	....*.*.*.*..*.*.*.*....
	...**.*...****...*.**...
	.......**......**.......
	.........**..**.........
	.........*..*.*.........
	..........**............

:hectic: (p30)  Found by Robert Wainwright in September 1984.
	......................**...............
	......................**...............
	.......................................
	.......................................
	.......................................
	.......................................
	.......................................
	.......................................
	.......................................
	.......................................
	.......................................
	.......................................
	.........*..........**...**............
	.......*.*............***..............
	......*.*............*...*.............
	**...*..*.............*.*..............
	**....*.*..............*...............
	.......*.*......*.*....................
	.........*......**.....................
	.................*...*.................
	.....................**......*.........
	....................*.*......*.*.......
	...............*..............*.*....**
	..............*.*.............*..*...**
	.............*...*............*.*......
	..............***............*.*.......
	............**...**..........*.........
	.......................................
	.......................................
	.......................................
	.......................................
	.......................................
	.......................................
	.......................................
	.......................................
	.......................................
	.......................................
	...............**......................
	...............**......................

:Heisenburp device:  A pattern which can detect the passage of a
   {glider} without affecting the glider's path or timing.  The first
   such device was constructed by David Bell in December 1992.  The
   term is due to Bill Gosper.
     The following is an example of the kind of reaction used at the
   heart of a Heisenburp device.  The glider at bottom right alters
   the reaction of the other two gliders without itself being affected
   in any way.
	*.....*....
	.**...*.*..
	**....**...
	...........
	...........
	...........
	.........**
	........*.*
	..........*


:heptaplet:  Any 7-cell {polyplet}.

:heptapole: (p2)  The {barberpole} of length 7.
	**........
	*.*.......
	..........
	..*.*.....
	..........
	....*.*...
	..........
	......*.*.
	.........*
	........**

:heptomino:  Any 7-cell {polyomino}.  There are 108 such objects.
   Those with names in common use are the {B-heptomino}, the
   {Herschel} and the {pi-heptomino}.

:Herschel: (stabilizes at time 128)  The following pattern which
   occurs at generation 20 of the {B-heptomino}.
	*..
	***
	*.*
	..*

:Herschel conduit:  A {conduit} that moves a {Herschel} from one place
   to another.  See also {Herschel loop}.
     Sixteen simple {stable} Herschel conduits are currently known,
   having been discovered from 1995 onwards by Dave Buckingham (DJB)
   and Paul Callahan (PBC).  These are shown in the following table.
   In this table "steps" is the number of {step}s, "m" tells how the
   Herschel is moved (R = turned right, L = turned left, B = turned
   back, F = unturned, f = flipped), and "dx" and "dy" give the
   displacement of the centre cell of the Herschel (assumed to start
   in the orientation shown above).
	------------------------------------
	steps  m     dx   dy     discovery
	------------------------------------
	  64   R    -11    9   DJB, Sep 1995
	  77   Ff   -25   -8   DJB, Aug 1996
	 112   L    -12  -33   DJB, Jul 1996
	 116   F    -32    1   PBC, Feb 1997
	 117   F    -40   -6   DJB, Jul 1996
	 119   Ff   -20   14   DJB, Sep 1996
	 125   Bf     9  -17   PBC, Nov 1998
	 153   Ff   -48   -4   PBC, Feb 1997
	 156   L    -17  -41   DJB, Aug 1996
	 158   Ff   -27   -5   DJB, Jul 1996
	 166   F    -49    3   PBC, May 1997
	 176   Ff   -45    0   PBC, Oct 1997
	 190   R    -24   16   DJB, Jul 1996
	 200   Lf   -17  -40   PBC, Jun 1997
	 202   Rf    -7   32   DJB, May 1997
	 222   Bf     6  -16   PBC, Oct 1998
	------------------------------------

:Herschel loop:  A cyclic {Herschel track}.  Although no loop of length
   less than 256 generations has been constructed it is possible to make
   {oscillator}s of smaller periods by putting more than one Herschel in
   the track.  In this way oscillators, and in most cases {gun}s, of all
   periods from 54 onwards can now be constructed (although the p55 case
   is a bit strange, shooting itself with gliders in order to stabilize
   itself).  See also {emu} and {omniperiodic}.

:Herschel track:  A {track} for {Herschel}s.  See also {B track}.

:Hertz oscillator: (p8)  Compare {negentropy}, and also {cauldron}.
   Found by Conway's group in 1970.
	...**.*....
	...*.**....
	...........
	....***....
	...*.*.*.**
	...*...*.**
	**.*...*...
	**.*...*...
	....***....
	...........
	....**.*...
	....*.**...

:hexadecimal: = {beehive and dock}

:hexaplet:  Any 6-cell {polyplet}.

:hexapole: (p2)  The {barberpole} of length 6.
	**.......
	*.*......
	.........
	..*.*....
	.........
	....*.*..
	.........
	......*.*
	.......**

:hexomino:  Any 6-cell {polyomino}.  There are 35 such objects.
   For some examples see {century}, {stairstep hexomino}, {table},
   {toad} and {Z-hexomino}.

:H-heptomino:  Name given by Conway to the following {heptomino}.  After
   one generation this is the same as the {I-heptomino}.
	**..
	.*..
	.***
	..*.

:hive: = {beehive}

:hivenudger: (c/2 orthogonally, p4)  A {spaceship} found by Hartmut
   Holzwart in July 1992.  (The name is due to Bill Gosper.)  It
   consists of a {pre-beehive} escorted by four {LWSS}.  In fact any
   LWSS can be replaced by a {MWSS} or a {HWSS}, so that there are 45
   different single-hive hivenudgers.
	****.....*..*
	*...*...*....
	*.......*...*
	.*..*...****.
	.............
	.....**......
	.....**......
	.....**......
	.............
	.*..*...****.
	*.......*...*
	*...*...*....
	****.....*..*

:honeycomb: (p1)
	..**..
	.*..*.
	*.**.*
	.*..*.
	..**..

:honey farm: (p1)  A common formation of four beehives.
	......*......
	.....*.*.....
	.....*.*.....
	......*......
	.............
	.**.......**.
	*..*.....*..*
	.**.......**.
	.............
	......*......
	.....*.*.....
	.....*.*.....
	......*......

:hook:  Another term for a {bookend}.  It is also used for other
   hook-shaped things, such as occur in the {eater1} and the
   {hook with tail}, for example.

:hook with tail: (p1)  For a long time this was the smallest
   {still life} without a well-established name.  It is now a vital
   component of the smallest known {HWSS} {gun}, where it acts as a
   {rock}.
	*.*..
	**.*.
	...*.
	...**

:houndstooth agar: The p2 {agar} that results from tiling the plane
   with the following pattern.
	.***
	.*..
	..*.
	***.

:house:  The following {induction coil}.  It is generation 3 of the
   {pi-heptomino}.  See {spark coil} and {dead spark coil}.
	.***.
	*...*
	**.**

:hustler: (p3)  Found by Robert Wainwright, June 1971.
	.....**....
	.....**....
	...........
	...****....
	*.*....*...
	**.*...*...
	...*...*.**
	...*....*.*
	....****...
	...........
	....**.....
	....**.....

:hustler II: (p4)
	....*...........
	....***.........
	.......*........
	......*..**.....
	*.**.*.**..*....
	**.*.*.....*....
	.....*....*.....
	....*.....*.*.**
	....*..**.*.**.*
	.....**..*......
	........*.......
	.........***....
	...........*....

:HW emulator: (p4)  Found by Robert Wainwright in June 1980.  See also
   {emulator}.
	.......**.......
	..**.*....*.**..
	..*..........*..
	...**......**...
	***..******..***
	*..*........*..*
	.**..........**.

:HWSS: (c/2 orthogonally, p4)  The fourth most common {spaceship}.
   Found by Conway in 1970.
	...**..
	.*....*
	*......
	*.....*
	******.

:HWSS emulator: = {HW emulator}

:HW volcano: (p5)  A p5 {domino} {sparker}, found by Dean Hickerson in
   February 1995.  There are at least two known forms for this, one of
   which is shown below.
	.........*..........................
	........*.*.........................
	......***.*.........................
	.....*....**.*......................
	.....*.**...**......**..............
	....**.*.**.........*.*.............
	.........*.*****......*..*.**.......
	..*.**.**.*.....*....**.*.**.*......
	.....**.....****........*....*......
	*...*.*..*...*.*....**.*.****.**....
	*...*.*..**.*.**.**....*.*....*.*...
	.....**...***.**.*.***.*..***...*...
	..*.**.**.**.............*.*..*.*.**
	...........*......*.*.*.*..**.*.*.*.
	....**.*.*.**......**.*.*.*...*.*.*.
	.....*.**.*..*.......*.**..****.**..
	.....*....*.*........*...**.........
	....**....**........**...*..*.......
	...........................**.......

:I-heptomino:  Name given by Conway to the following {heptomino}.  After
   one generation this is the same as the {H-heptomino}.
	**..
	.*..
	.**.
	..**

:IMG: = {intermitting glider gun}

:Immigration:  A form of {colorized Life} in which there are two types
   of ON cell, a newly-born cell taking the type of the majority of its
   three {parent cells} and surviving cells remaining of the same type
   as in the previous generation.

:induction coil:  Any object used to stabilize an edge (or edges)
   without touching.  The tubs used in the {Gray counter} are examples,
   as are the blocks and snakes used in the {Hertz oscillator} and the
   heptomino at the bottom of the {mathematician}.

:inductor:  Any {oscillator} with a row of dead cells down the middle
   and whose two halves are mirror images of one another, both halves
   being required for the oscillator to work.  The classic examples are
   the {pulsar} and the {tumbler}.  If still lifes are considered as
   p1 oscillators then there are numerous simple examples such as
   {table on table}, {dead spark coil} and {cis-mirrored R-bee}.
   Some spaceships, such as the {brain}, the {snail} and the {spider}
   use the same principle.

:infinite glider hotel:  A pattern by David Bell, named after Hilbert's
   "infinite hotel" scenario in which a hotel with an infinite number of
   rooms has room for more guests even if it is already full, simply by
   shuffling the old guests around.
     In this pattern, two pairs of {Cordership}s moving at c/12 are
   pulling apart such that there is an ever-lengthening {glider} track
   between them.  Every 128 generations another glider is injected into
   the glider track, joining the gliders already circulating there.
   The number of gliders in the track therefore increases without limit.
     The tricky part of this construction is that even though all
   the previously injected gliders are repeatedly flying through the
   injection point, that point is guaranteed to be empty when it is
   time for the next glider to be injected.

:infinite growth:  Growth of a finite pattern such that the
   {population} tends to infinity, or at least is unbounded.
   The first known pattern with infinite growth was the
   {Gosper glider gun}.
     An interesting question is: What is the minimum population of a
   pattern that exhibits infinite growth?  In 1971 Charles Corderman
   found that a {switch engine} could be stabilized by a {pre-block}
   in a number of different ways, giving 11-cell patterns with
   infinite growth.  This record stood for more than quarter of a
   century until Paul Callahan found, in November 1997, two 10-cell
   patterns with infinite growth.  The following month he found the
   one shown below, which is much neater, being a single {cluster}.
   This produces a stabilized switch engine of the block-laying type.
	......*.
	....*.**
	....*.*.
	....*...
	..*.....
	*.*.....
   Nick Gotts and Paul Callahan have also shown that there is no
   infinite growth pattern with fewer than 10 cells, so that the
   question has now been answered.
     Also of interest is the following pattern (again found by
   Callahan), which is the only 5x5 pattern with infinite growth.
   This too emits a block-laying switch engine.
	***.*
	*....
	...**
	.**.*
	*.*.*
     Following a conjecture of Nick Gotts, Stephen Silver produced, in
   May 1998, a pattern of width 1 which exhibits infinite growth.  This
   pattern was very large (12470x1 in the first version, reduced to
   5447x1 the following day).  In October 1998 Paul Callahan did an
   exhaustive search, finding the smallest example, the 39x1 pattern
   shown below.  This produces two block-laying switch engines,
   stability being achieved at generation 1483.
	********.*****...***......*******.*****
     Although the simplest infinite growth patterns grow at a rate that
   is (asymptotically) linear, many other types of growth rate are
   possible, quadratic growth (see {breeder}) being the fastest.  Dean
   Hickerson has found many patterns with unusual growth rates, such as
   {sawtooth}s and a {caber tosser}.
     See also {Fermat prime calculator}.

:initials: = {monogram}

:integral: = {integral sign}

:integral sign: (p1)
	...**
	..*.*
	..*..
	*.*..
	**...

:intentionless: = {elevener}

:interchange: (p2)  A common formation of six blinkers.
	..***....***..
	..............
	*............*
	*............*
	*............*
	..............
	..***....***..

:intermitting glider gun:  Despite the name, an intermitting glider gun
   (IMG) is more often an {oscillator} than a {gun}.  There are two
   basic types.  A type 1 IMG consists of two guns firing at one another
   in such a way that each gun is temporarily disabled on being hit
   by a glider from the other gun.  A type 2 IMG consists of a single
   gun firing at a 180-degree glider {reflector} in such a way that
   returning gliders temporarily disable the gun.
     Both types of IMG can be used to make glider guns of periods that
   are multiples of the base period.  This is done by firing another
   gun across the two-way intermittent glider stream of the IMG in such
   a way that gliders only occasionally escape.

:island:  The unconnected {polyplet}s of which a {stable} pattern
   consists are sometimes called islands.  So, for example, a {boat}
   has only one island, while an {aircraft carrier} has two, a
   {honey farm} has four and the standard form of the {eater3} has five.

:J: = {Herschel}

:jack: (p4)  Found by Robert Wainwright, April 1984.
	...*.....*...
	...**...**...
	*..**...**..*
	***..*.*..***
	.....*.*.....
	***..*.*..***
	*..**...**..*
	...**...**...
	...*.....*...

:jam: (p3)  Found by Achim Flammenkamp in 1988, but not widely known
   about until its independent discovery (and naming) by Dean Hickerson
   in September 1989.  Compare with {mold}.  In fact this is really very
   like {caterer}.  In terms of its 7x7 {bounding box} it ties with
   {trice tongs} as the smallest p3 {oscillator}.
	...**.
	..*..*
	*..*.*
	*...*.
	*.....
	...*..
	.**...

:Jaws:  A {breeder} constructed by Nick Gotts in February 1997.  In the
   original version Jaws had an initial {population} of 150, which at
   the time was the smallest for any known pattern with superlinear
   growth.  In November 1997 Gotts produced a 130-cell Jaws using
   some {switch engine} {predecessor}s found by Paul Callahan.  Jaws
   has since been beaten by the even smaller {mosquito}s, {teeth},
   {catacryst} and {metacatacryst}.
     Jaws consists of eight pairs of switch engines which produce a
   new block-laying switch engine (plus masses of junk) every 10752
   generations.  It is therefore an MMS breeder.

:JC: = {dead spark coil}

:JHC:  John Horton Conway.  Also another name for {monogram}.

:J-heptomino: = {Herschel}

:Jolson: (p15)  Two {block}s {hassle}d by two {pentadecathlon}s.
   Found by Robert Wainwright in November 1984 and named by Bill
   Gosper.  A p9 version using {snacker}s instead of pentadecathlons
   is also possible.
	.**......**..
	*..*....*..*.
	*..*....*..*.
	*..*....*..*.
	.**......**..
	.............
	.............
	.......*.....
	.....*..*.**.
	......**..**.
	.............
	.............
	......****...
	.....******..
	....********.
	...**......**
	....********.
	.....******..
	......****...

:keys:  See {short keys}, {bent keys} and {odd keys}.

:kickback reaction:  The following collision of two {glider}s whose
   product is a single glider travelling in the opposite direction
   to one of the original gliders.  This is important in the proof
   of the existence of a {universal constructor}, and in Bill Gosper's
   {total aperiodic}, as well as a number of other constructions.
	.....*..
	......**
	.**..**.
	*.*.....
	..*.....

:kidney:  A Gosperism for {century}.  See also {diuresis}.

:killer toads:
   A pair of {toad}s acting together so that they can eat things.
   Here, for example, are some killer toads eating a {HWSS}.  Similarly
   they can eat a {MWSS} (but not a {LWSS}).  For another example see
   {twirling T-tetsons II}.  See also {candlefrobra}.
	..**.......***
	*....*....***.
	......*.......
	*.....*.......
	.******.......
	..........***.
	...........***

:knightship:  Any {spaceship} of type (2m,m)/n.  Such spaceships do
   exist (see {universal constructor}), but no concrete example is
   known.  A knightship must be asymmetric and its period must be at
   least 6, which makes searching for them using programs like {lifesrc}
   very difficult.
     By analogy with the corresponding fairy chess pieces, spaceships of
   types (3m,m)/n, (3m,2m)/n and (4m,m)/n would presumably be called
   camelships, zebraships and giraffeships, respectively.  But no
   examples of these are known either, and they are even more difficult
   to search for.

:Kok's galaxy: (p8)  Found by Jan Kok in 1971.  See {converter} for a
   use of this {sparker}.
	******.**
	******.**
	.......**
	**.....**
	**.....**
	**.....**
	**.......
	**.******
	**.******

:lake:  Any still life consisting of a simple closed curve made from
   diagonally connected {domino}es.  The smallest example is the
   {pond}, and the next smallest is this (to which the term is
   sometimes restricted):
	....**....
	...*..*...
	...*..*...
	.**....**.
	*........*
	*........*
	.**....**.
	...*..*...
	...*..*...
	....**....

:Laputa: (p2)  Found by Rich Schroeppel, September 1992.
	...**.**....
	...**.*...**
	........*..*
	.******.***.
	*..*.*......
	**...*.**...
	....**.**...

:large S: = {big S}

:Life:  A 2-dimensional 2-state {cellular automaton} discovered by
   John Conway in 1970.  The states are referred to as ON and OFF (or
   live and dead).  The transistion rule is as follows: a cell that is
   ON will remain ON in the next generation if and only if exactly 2
   or 3 of the 8 adjacent cells are also ON, and a cell that is OFF will
   turn ON if and only if exactly 3 of the 8 adjacent cells are ON.
   (This is more succinctly stated as: "If 2 of your 8 nearest
   neighbours are ON, don't change.  If 3 are ON, turn ON.  Otherwise,
   turn OFF.")

:Life32:  A freeware Life program by Johan Bontes for Microsoft Windows
   95/98/ME/NT/2000.

:LifeLine:  A newletter edited by Robert Wainwright from 1971 to 1973.
   During this period it was the main forum for discussions about Life.
   The newletter was nominally quarterly, but the actual dates of its
   eleven issues were as follows:
	Mar, Jun, Sep, Dec 1971
	Sep, Oct, Nov, Dec 1972
	Mar, Jun, Sep 1973

:Lifenthusiast:  A Life enthusiast.  Term coined by Robert Wainwright.

:lifesrc:  David Bell's Life search program, for finding new
   {spaceship}s and {oscillator}s.  This is a C implementation of an
   algorithm developed by Dean Hickerson in 6502 assembler.  Most of
   the spaceships and many of the oscillators shown in this lexicon
   were found with lifesrc or by Hickerson's original program.
     The lifesrc algorithm is only useful for very small periods, as
   the amount of computing power required rises rapidly with increasing
   period.
     Compare {gfind}.

:light bulb: (p2)  Found in 1971.
	.**.*..
	.*.**..
	.......
	..***..
	.*...*.
	.*...*.
	..*.*..
	*.*.*.*
	**...**
   The same {rotor} can be embedded in a slightly smaller {stator}
   like this:
	...*.....
	.***.....
	*........
	******...
	......*..
	..*...*..
	..**.*...
	......***
	........*

:lightspeed ribbon: = {superstring}

:lightspeed wire:  Any {wick} that can burn non-destructively at the
   speed of light.  These are potentially useful for various things,
   but so far no-one has found the necessary mechanisms.  The
   following diagram shows an example of a lightspeed wire, with a
   small defect that travels along it at the speed of light.
	....**..**..**..**..**..**..**..**..**..**..**..**..**....
	....**..**..**..**..**..**..**..**..**..**..**..**..**....
	..........................................................
	..******************************************************..
	.*......*...............................................*.
	*.*****....*********************************************.*
	.*.....*................................................*.
	..******************************************************..
	..........................................................
	....**..**..**..**..**..**..**..**..**..**..**..**..**....
	....**..**..**..**..**..**..**..**..**..**..**..**..**....

:lightweight emulator: = {LW emulator}

:lightweight spaceship: = {LWSS}

:lightweight volcano: = {toaster}

:line puffer:  A {puffer} which produces its output by means of an
   orthogonal line of cells at right angles to the direction of travel.
   The archetypal line puffer was found by Alan Hensel in March 1994,
   based on a {spaceship} found earlier that month by Hartmut Holzwart.
   The following month Holzwart found a way to make extensible c/2 line
   puffers, and Hensel found a much smaller stabilization the following
   day.  But in October 1995 Tim Coe discovered that for large widths
   these were often unstable, although typically lasting millions of
   generations.  In May 1996, however, Coe found a way to fix the
   instability.  The resulting puffers appear to be completely stable
   and to exhibit an exponential increase in period as a function of
   width, although neither of these things has been proved.
     Line puffers have enabled the construction of various difficult
   periods for c/2 spaceships and puffers, including occasionally
   periods which are not multiples of 4 and which would therefore be
   impossible to attain with the usual type of construction based on
   {standard spaceship}s.  (See {frothing puffer} for another method
   of constructing such periods.)  In particular, the first c/2 {rake}
   with period not divisible by 4 was achieved in January 2000 when
   David Bell constructed a p42 {backrake} by means of line puffers.
     See also {puff suppressor}.

:loading dock: (p3)  Found by Dave Buckingham, September 1972.
	....*....
	..***....
	.*...**..
	*.**...*.
	.*...**.*
	..**...*.
	....***..
	....*....

:loaf: (p1)
	.**.
	*..*
	.*.*
	..*.

:loaflipflop: (p15)  Here four {pentadecathlon}s {hassle} a {loaf}.
   Found by Robert Wainwright in 1990.
	................*.................
	...............***................
	..................................
	..................................
	...............***................
	..................................
	...............*.*................
	...............*.*................
	..................................
	...............***................
	..................................
	..................................
	...............***................
	................*.................
	..................................
	.*..*.**.*..*...............**....
	**..*....*..**...**.......*....*..
	.*..*.**.*..*...*..*.....*......*.
	................*.*.....*........*
	.................*......*........*
	........................*........*
	.........................*......*.
	..........................*....*..
	............................**....
	..................***.............
	.................*...*............
	................*.....*...........
	..................................
	...............*.......*..........
	...............*.......*..........
	..................................
	................*.....*...........
	.................*...*............
	..................***.............

:loaf on loaf: = {bi-loaf}

:loaf siamese barge: (p1)
	..**.
	.*..*
	*.*.*
	.*.*.
	..*..

:LoM: = {lumps of muck}

:lone dot agar:  An {agar} in which every live cell is isolated in every
   generation.

:lonely bee: = {worker bee}

:long:  A term applied to an object that is of the same basic form
   as some standard object, but longer.  For examples see {long barge},
   {long boat}, {long bookend}, {long canoe}, {long shillelagh},
   {long ship} and {long snake}.

:long^3:  The next degree of longness after {long long}.  Some people
   prefer "extra long".

:long^4:  The next degree of longness after {long^3}.  Some people
   prefer "extra extra long".

:long barge: (p1)
	.*...
	*.*..
	.*.*.
	..*.*
	...*.

:long boat: (p1)
	.*..
	*.*.
	.*.*
	..**

:long bookend:  The following {induction coil}.
	...**
	*...*
	****.

:long canoe: (p1)
	....**
	.....*
	....*.
	...*..
	*.*...
	**....

:long hat: = {loop}

:long hook: = {long bookend}

:long house: = {dock}

:long integral: (p1)
	..**
	.*.*
	.*..
	..*.
	*.*.
	**..

:long long:  The next degree of longness after {long}.  Some people
   prefer "very long".

:long long barge: (p1)
	.*....
	*.*...
	.*.*..
	..*.*.
	...*.*
	....*.

:long long boat: (p1)
	.*...
	*.*..
	.*.*.
	..*.*
	...**

:long long canoe: (p1)
	.....**
	......*
	.....*.
	....*..
	...*...
	*.*....
	**.....

:long long ship: (p1)
	**...
	*.*..
	.*.*.
	..*.*
	...**

:long long snake: (p1)
	**....
	*.*...
	...*.*
	....**

:long shillelagh: (p1)
	**..**
	*..*.*
	.**...

:long ship: (p1)
	**..
	*.*.
	.*.*
	..**

:long sinking ship: = {long canoe}

:long snake: (p1)
	**...
	*.*.*
	...**

:loop: (p1)
	.**..
	*..*.
	.*.*.
	**.**

:low-denisty Life: = {sparse Life}

:lumps of muck:  The common evolutionary sequence that ends in the
   {blockade}.  The name is sometimes used of the blockade itself,
   and can in general be used of any stage of the evolution of the
   {stairstep hexomino}.

:LW emulator: (p4)  The smallest (and least useful) {emulator}, found by
   Robert Wainwright in June 1980.
	..**.*..*.**..
	..*........*..
	...**....**...
	***..****..***
	*..*......*..*
	.**........**.

:LWSS: (c/2 orthogonally, p4)  The known smallest orthogonally
   moving {spaceship}, and the second most common (after the
   {glider}).  Found by Conway in 1970.
	.*..*
	*....
	*...*
	****

:LWSS emulator: = {LW emulator}

:LW volcano: = {toaster}

:mango: (p1)
	.**..
	*..*.
	.*..*
	..**.

:mathematician: (p5)  Found by Dave Buckingham, 1972.
	....*....
	...*.*...
	...*.*...
	..**.**..
	*.......*
	***...***
	.........
	*********
	*.......*
	...****..
	...*..**.

:Max:  A name for the smallest known {spacefiller}.  The name represents
   the fact that the growth rate is the fastest possible.  (This has not
   quite been proved, however.  There remains the possibility, albeit
   not very likely, that a periodic {agar} could have an average
   {density} greater than 1/2, and a spacesfiller stretching such an
   agar at the same speed as the known spacefillers would have a faster
   average growth rate.)

:mazing: (p4)  In terms of its minimum {population} of 12 this ties with
   {mold} as the smallest p4 {oscillator}.  Found by Dave Buckingham in
   December 1973.
	...**..
	.*.*...
	*.....*
	.*...**
	.......
	...*.*.
	....*..

:medium fish: = {MWSS}

:metacatacryst:  A 52-cell pattern exhibiting quadratic growth.  Found
   by Nick Gotts, December 2000.  This is currently the smallest known
   pattern (in terms of initial population) with superlinear growth.
   See also {catacryst}.

:metamorphosis:  An {oscillator} built by Robert Wainwright that uses
   the following reaction (found by Bill Gosper) to turn {glider}s into
   {LWSS}, and converts these LWSS back into gliders by colliding them
   head on.  (There are in fact two ways to do the following reaction,
   because the {spark} of the {twin bees shuttle} is symmetric.)
	...................*.........
	....................*........
	..................***........
	.............................
	.............................
	.............................
	.............................
	.............................
	............*...*.....*.**...
	**.........*.....*....*.*.*..
	**.........*.........*....*..
	...........**...*.....*.*.*..
	.............***......*.**...
	.............................
	.............***.............
	...........**...*............
	**.........*...............**
	**.........*.....*.........**
	............*...*............

:metamorphosis II:  An oscillator built by Robert Wainwright in
   December 1994 based on the following p30 {glider}-to-{LWSS}
   {converter}.  This converter was first found by Paul Rendell,
   January 1986 or earlier, but wasn't widely known about until
   Paul Callahan rediscovered it in December 1994.
	......................*.
	.....................*..
	.....................***
	........................
	........................
	.........*.*............
	.........*..*...........
	**..........**..........
	**........*...**........
	.....**.....**..........
	....*....*..*...........
	.........*.*............
	........................
	........................
	........................
	........................
	................*.......
	...............***......
	..............*****.....
	.............*.*.*.*....
	.............**...**....
	........................
	........................
	................*.......
	...............*.*......
	...............*.*......
	................*.......
	...............**.......
	...............**.......
	...............**.......

:methuselah:  Any small pattern that stabilizes only after a long
   time.  Term coined by Conway.  Examples include the {R-pentomino},
   {acorn} and {bunnies}.

:Mickey Mouse: (p1)  A name proposed by Mark Niemiec for the following
   {still life}:
	.**....**.
	*..*..*..*
	*..****..*
	.**....**.
	...****...
	...*..*...
	....**....

:middleweight emulator: = {MW emulator}

:middleweight spaceship: = {MWSS}

:middleweight volcano: = {MW volcano}

:mini pressure cooker: (p3)  Found by Robert Wainwright before
   June 1972.  Compare {pressure cooker}.
	.....*.....
	....*.*....
	....*.*....
	...**.**...
	*.*.....*.*
	**.*.*.*.**
	...*...*...
	...*.*.*...
	....*.*....
	.....*.....

:M.I.P. value:  The maximum {population} divided by the initial
   population for an unstable pattern.  For example, the
   {R-pentomino} has an M.I.P. value of 63.8, since its maximum
   population is 319.  The term is no longer in use.

:MIT oscillator: = {cuphook}

:MMM breeder:  See {breeder}.

:MMS breeder:  See {breeder}.

:mod:  The smallest number of generations it takes for an
   {oscillator} or {spaceship} to reappear in its original form,
   possibily subject to some rotation or reflection.  The mod may
   be equal to the {period}, but it may also be a quarter of the period
   (for oscillators that rotate 90 degrees every quarter period) or half
   the period (for other oscillators which rotate 180 degrees every half
   period, and also for {flipper}s).

:mold: (p4)  Found by Achim Flammenkamp in 1988, but not widely known
   until Dean Hickerson rediscovered it (and named it) in August 1989.
   Compare with {jam}.  In terms of its minimum {population} of 12 it
   ties with {mazing} as the smallest p4 {oscillator}.  But in terms
   of its 6x6 {bounding box} it wins outright.  In fact, of all
   oscillators that fit in a 6x7 box it is the only one with {period}
   greater than 2.
	...**.
	..*..*
	*..*.*
	....*.
	*.**..
	.*....

:monogram: (p4)  Found by Dean Hickerson, August 1989.
	**...**
	.*.*.*.
	.**.**.
	.*.*.*.
	**...**

:moose antlers: (p1)
	**.....**
	*.......*
	.***.***.
	...*.*...
	....*....

:mosquito:  See {mosquito1}, {mosquito2}. {mosquito3}, {mosquito4} and
   {mosquito5}.

:mosquito1:  A {breeder} constructed by Nick Gotts in September 1998.
   The original version had an initial population of 103, which was
   then the smallest for any known pattern with superlinear growth
   (beating the record previously held by {Jaws}).  This was reduced
   to 97 by Stephen Silver the following month, but was then almost
   immediately superceded by {mosquito2}.
     Mosquito1 consists of the classic {puffer train} plus four
   {LWSS} and four {MWSS} (mostly in {predecessor} form, to keep the
   population down).  Once it gets going it produces a new block-laying
   {switch engine} (plus a lot of junk) every 280 generations.  It is
   therefore an MMS breeder, albeit a messy one.

:mosquito2:  A {breeder} constructed by Nick Gotts in October 1998.
   Its initial population of 85 was for a couple of hours the smallest
   for any known pattern with superlinear growth, but was then beaten by
   {mosquito3}.
     Mosquito2 is very like {mosquito1}, but uses two fewer {MWSS} and
   one more {LWSS}.

:mosquito3:  A {breeder} constructed by Nick Gotts in October 1998.
   Its initial population of 75 was at the time the smallest for any
   known pattern with superlinear growth, but was beaten a few days
   later by {mosquito4}.
     Mosquito3 has one less {LWSS} than {mosquito2}.  It is somewhat
   different from the earlier mosquitos in that the {switch engine}s
   it makes are glider-producing rather than block-laying.

:mosquito4:  A slightly improved version of {mosquito3} which Stephen
   Silver produced in October 1998 making use of another discovery of
   Nick Gotts (September 1997): an 8-cell pattern that evolves into a
   {LWSS} plus some junk.  Mosquito4 is a {breeder} with an initial
   population of 73, at the time the smallest for any known pattern
   with superlinear growth, but superceded a few days later by
   {mosquito5}.

:mosquito5:  A slightly improved version of {mosquito4} which Nick Gotts
   produced in October 1998.  The improvement is of a similar nature
   to the improvement of mosquito4 over mosquito3.  Mosquito5 is a
   {breeder} with an initial population of 71.  At the time, this was
   the smallest population for any known pattern with superlinear
   growth, but it has since been superceded by {teeth}, {catacryst} and
   {metacatacryst}.

:mould: = {mold}

:MSM breeder:  See {breeder}.

:multi-state Life: = {colorized Life}

:multum in parvo: (stabilizes at time 3933)  A {methuselah} found by
   Charles Corderman, but not as long-lasting as his {acorn}.
	...***
	..*..*
	.*....
	*.....

:muttering moat:  Any {oscillator} whose {rotor} consists of a closed
   chain of cells each of which is adjacent to exactly two other rotor
   cells.  Compare {babbling brook}.  Examples include the {bipole},
   the {blinker}, the {clock}, the {cuphook}, the {Gray counter}, the
   {quad}, the {scrubber}, the {skewed quad} and the p2 {snake pit}.
   The following diagram shows a p2 example (by Dean Hickerson, May
   1993) with a larger rotor.  See {ring of fire} for a very large one.
	**.....
	*.*.**.
	.....*.
	.*..*..
	..*....
	..*.*.*
	.....**

:MW emulator: (p4)  Found by Robert Wainwright in June 1980.  See also
   {emulator} and {filter}.
	.......*.......
	..**.*...*.**..
	..*.........*..
	...**.....**...
	***..*****..***
	*..*.......*..*
	.**.........**.

:MWSS: (c/2 orthogonally, p4)  The third most common {spaceship}.
   Found by Conway in 1970.
	...*..
	.*...*
	*.....
	*....*
	*****.

:MWSS emulator: = {MW emulator}

:MWSS out of the blue:  The following reaction, found by Peter Rott
   in November 1997, in which a {LWSS} passing by a p46 {oscillator}
   creates a {MWSS} travelling in the opposite direction.  Together
   with some reactions found by Dieter Leithner, and a LWSS-turning
   reaction which Rott had found in November 1993 (but which was not
   widely known until Paul Callahan rediscovered it in June 1994)
   this can be used to prove that there exist {gliderless} guns for
   LWSS, MWSS and {HWSS} for every period that is a multiple of 46.
	*..*.................................
	....*................................
	*...*................................
	.****................................
	.....................................
	.....................................
	.....................................
	.....................................
	.....................................
	...................**..............**
	..................**...............**
	...................*****.............
	..**................****.............
	..**.....*...........................
	........***.........****.............
	.......*.*.*.......*****.............
	........*..*......**...............**
	........***........**..............**
	.........*...........................
	.....................................
	.....................................
	.....................................
	.....................................
	..*.......*..........................
	.....................................
	***.......***........................
	.**.**.**.**.........................
	..***...***..........................
	...*.....*...........................
	.....................................
	.....................................
	.....................................
	.....................................
	.....................................
	.....................................
	.....................................
	.....................................
	.....................................
	.....................................
	..**.....**..........................
	..**.....**..........................

:MW volcano: (p5)  Found by Dean Hickerson in April 1992.
	......*......
	....*...*....
	.............
	...*.....*...
	.***.***.***.
	*...**.**...*
	*.***.*.****.
	.*...........
	...*.*.*.**.*
	..**.***.*.**
	...*.*..*....
	...*..**.....
	..**.........

:My Experience with B-heptominos in Oscillators:  An article by
   Dave Buckingham (October 1996) that describes his discovery of
   {Herschel conduit}s, including sufficient (indeed ample) {stable}
   conduits to enable, for the first time, the construction of period n
   oscillators - and true period n guns - for every sufficiently large
   integer n.  (See {Herschel loop} and {emu}.)

:natural:  Occurring often in random patterns.  There is no precise
   measure of naturalness, since the most useful definition of "random"
   in this context is open to debate.  Nonetheless, it is clear that
   objects such as {block}s, {blinker}s, {beehive}s and {glider}s are
   very natural, while {eater2}s, {dart}s, {gun}s, etc., are not.

:negentropy: (p2)  Compare {Hertz oscillator}.
	...**.*....
	...*.**....
	...........
	....***....
	...*.*.*.**
	...**..*.**
	**.*...*...
	**.*...*...
	....***....
	...........
	....**.*...
	....*.**...

:neighbour:  Any of the eight cells adjacent to a given cell.  A cell
   is therefore not considered to be a neighbour of itself, although
   the neighbourhood used in Life does in fact include this cell (see
   {cellular automaton}).

:new five: (p3)  Found by Dean Hickerson, January 1990.
	..**.....
	.*..*....
	.*.*..*..
	**.*.**..
	*........
	.***.****
	.....*..*
	*.**.....
	**.**....

:new gun:  An old name for the second known basic {gun} (found, like
   the first, by Bill Gosper), shown below.  A number of other ways of
   constructing a gun from two {twin bees shuttle}s have since been
   found - see {edge shooter} for one of these.
	.........................**.....**
	.........................**.....**
	..................................
	..................................
	..................................
	..................................
	..................................
	..................................
	..................................
	..................................
	..................................
	..................................
	..................................
	...........................**.**..
	..........................*.....*.
	..................................
	.........................*.......*
	.........................*..*.*..*
	.........................***...***
	..................................
	..................................
	..................................
	..................................
	.................*................
	**...............**...............
	**................**..............
	.............**..**...............
	..................................
	..................................
	..................................
	.............**..**...............
	**................**.......**.....
	**...............**........**.....
	.................*................

:Noah's ark:  The following diagonal {puffer} consisting of two
   {switch engine}s.  This was found by Charles Corderman in 1971.
   The name comes from the variety of objects it leaves behind: blocks,
   blinkers, beehives, loaves, gliders, ships, boats, long boats,
   beacons and block on tables.
	..........*.*..
	.........*.....
	..........*..*.
	............***
	...............
	...............
	...............
	...............
	...............
	.*.............
	*.*............
	...............
	*..*...........
	..**...........
	...*...........

:n-omino:  Any {polyomino} with exactly n cells.

:non-spark:  Something that looks like a spark, but isn't.  An {OWSS}
   produces one of these instead of a {belly spark}, and is destroyed
   by it.

:non-standard spaceship:  Any {spaceship} other than a {glider}, {LWSS},
   {MWSS} or {HWSS}.

: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.
	...**...
	..*..*..
	.*....*.
	*......*
	*......*
	.*....*.
	..*..*..
	...**...

: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:
	..**
	..**
	***.
	.*..

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

:omino: = {polyomino}

:omniperiodic:  A {cellular automaton} is said to be
   omniperiodic if it has {oscillator}s of all {period}s.
   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})
   reduced the number of unresolved cases to a finite number.
   At the time of writing the only periods for which no oscillator
   is known are 19, 23, 27, 31, 37, 38, 41, 43 and 53.  If we
   insist that the oscillator must contain a cell oscillating at
   the full period, then 34 and 51 should be added to this list.
   The most recently achieved periods are 49, a glider loop which
   Noam Elkies constructed in August 1999 using p7 {reflector}s
   built from his new p7 {pipsquirter}, and 39 (formerly only possible
   without a p39 cell), which Elkies contructed in July 2000.

: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.
	......******
	.****.*....*
	.*..*.*.**.*
	.*..*.*.**.*
	.****.*....*
	......******
	******......
	*....*.****.
	*.**.*.*..*.
	*.**.*.*..*.
	*....*.****.
	******......

: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.
	*****

:Orion: (c/4 diagonally, p4)  Found by Hartmut Holzwart, April 1993.
	...**.........
	...*.*........
	...*..........
	**.*..........
	*....*........
	*.**......***.
	.....***....**
	......***.*.*.
	.............*
	......*.*.....
	.....**.*.....
	......*.......
	....**.*......
	.......*......
	.....**.......
   In May 1999, Jason Summers found the following smaller variant:
	.**..........
	**...........
	..*..........
	....*....***.
	....***....**
	.....***.*.*.
	............*
	.....*.*.....
	....**.*.....
	.....*.......
	...**.*......
	......*......
	....**.......

:orphan:  Conway's preferred term for a {Garden of Eden}.

: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 {spaceship}s as well, but this usage is not normal in
   Life.

:overcrowding: = {overpopulation}

:over-exposure: = {underpopulation}

:overpopulation:  Death of cell caused by it having more than three
   {neighbour}s.

:overweight spaceship: = {OWSS}

: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.

:p: = {period}

:p30 shuttle: = {queen bee shuttle}

:p46 shuttle: = {twin bees shuttle}

:p54 shuttle:  (p54)  A surprising variant of the {twin bees shuttle}
   found by Dave Buckingham in 1973.  See also {centinal}.
	**.........................**
	.*.........................*.
	.*.*.......*.............*.*.
	..**.....*..*.....*......**..
	............*.....**.........
	........*..........**........
	........*...**....**.........
	.........*****...............
	.............................
	.........*****...............
	........*...**....**.........
	........*..........**........
	............*.....**.........
	..**.....*..*.....*......**..
	.*.*.......*.............*.*.
	.*.........................*.
	**.........................**

:pair of bookends: = {bookends}

:pair of tables: = {table on table}

:paperclip: (p1)
	..**.
	.*..*
	.*.**
	**.*.
	*..*.
	.**..

:parent:  A pattern is said to be a parent of the pattern it gives
   rise to after one generation.  Some patterns have infinitely many
   parents, but other have none at all (see {Garden of Eden}).

:parent cells:  The three cells that cause a new cell to be born.

:PD: = {pentadecathlon}

:pedestle: (p5)
	.....*.....
	....*.*....
	.*..**.....
	.***.......
	.....***...
	...**...*..
	..*....*..*
	.*.*.*.*.**
	.*.*...*.*.
	**.*.*.*.*.
	*..*....*..
	..*...**...
	...***.....
	.......***.
	.....**..*.
	....*.*....
	.....*.....

:penny lane: (p4)  Found by Dave Buckingham, 1972.
	...**.....**...
	...*.......*...
	**.*.......*.**
	**.*.*****.*.**
	....*..*..*....
	.....*****.....
	...............
	.......*.......
	......*.*......
	.......*.......

:pentadecathlon: (p15)  Found in 1970 by Conway while tracking the
   history of short rows of cells, 10 cells giving this object, which is
   the most {natural} {oscillator} of period greater than 3.  In fact
   it is the fifth or sixth most common {oscillator} overall, being
   about as frequent as the {clock}, but much less frequent than the
   {blinker}, {toad}, {beacon} or {pulsar}.
	..*....*..
	**.****.**
	..*....*..
   The pentadecathlon is the only known oscillator which is a
   {polyomino} in more than one phase.

:pentant: (p5)  Found by Dave Buckingham, July 1976.
	**........
	.*........
	.*.*......
	..**....**
	.........*
	.....****.
	.....*....
	..*...***.
	..****..*.
	.....*....
	....*.....
	....**....

:pentaplet:  Any 5-cell {polyplet}.

:pentapole: (p2)  The {barberpole} of length 5.
	**......
	*.*.....
	........
	..*.*...
	........
	....*.*.
	.......*
	......**

:pentoad: (p5)  Found by Bill Gosper, June 1977.  This is extensible:
   if an eater is moved back four spaces then another {Z-hexomino} can
   can be inserted.  (This extensibility was discovered by Scott Kim.)
	...........**
	...........*.
	.........*.*.
	.........**..
	.....**......
	......*......
	......*......
	......**.....
	..**.........
	.*.*.........
	.*...........
	**...........

:pentomino:  Any 5-cell {polyomino}.  There are 12 such patterns,
   and Conway assigned them all letters in the range O to Z, loosely
   based on their shapes.  Only in the case of the {R-pentomino}
   has Conway's label remained in common use, but all of them can
   nonetheless be found in this lexicon.

:period:  The smallest number of generations it takes for an
   {oscillator} or {spaceship} to reappear in its original form.  The
   term can also be used for a {puffer}, {wick}, {fuse}, {superstring},
   stream of {spaceship}s, {factory} or {gun}.  In the last case there
   is a distinction between {true} period and {pseudo} period.  There
   is also a somewhat different concept of period for {wicktrailer}s.

:perturb:  To change the fate of an object by reacting it with
   other objects.   Typically, the other objects are sparks from
   {spaceship}s or {oscillator}s, or are {eater}s or impacting
   spaceships.  Perturbations are typically done to turn a {dirty}
   reaction into a {clean} one, or to change the products of a reaction.
   In many desirable cases the perturbing objects are not destroyed by
   the reaction, or else are easily replenished.

:phi:  The following common {spark}.  The name comes from the shape in
   the generation after the one shown here.
	.***.
	*...*
	*...*
	.***.

:phoenix:  Any pattern all of whose cells die in every generation,
   but which never dies as a whole.  A {spaceship} cannot be a phoenix,
   and in fact every phoenix eventually evolves into an {oscillator}.
   The following 12-cell oscillator (found by the MIT group in December
   1971) is the smallest known phoenix, and is sometimes simply called
   "the phoenix".
	....*...
	..*.*...
	......*.
	**......
	......**
	.*......
	...*.*..
	...*....

:pi: = {pi-heptomino}

:pi-heptomino: (stabilizes at time 173)  A common pattern.  The name is
   also applied to later generations of this object - in a {pi ship},
   for example, the pi-heptomino itself never arises.
	***
	*.*
	*.*

:pincers: = {great on-off}

:pinwheel: (p4)  Found by Simon Norton, April 1970.  Compare {clock II}.
	......**....
	......**....
	............
	....****....
	**.*....*...
	**.*..*.*...
	...*...**.**
	...*.*..*.**
	....****....
	............
	....**......
	....**......

:pi orbital: (p168)  Found by Noam Elkies, August 1995.  In this
   {oscillator}, a {pi-heptomino} is turned ninety degrees every 42
   generations.
	..............**....**....**...............................
	.............*..*.*....*.*..*..............................
	.............***..........***..............................
	................**......**.................................
	...............*..******..*................................
	...............**........**................................
	...........................................................
	........*.............................**..........*........
	.......*...***......*.........*.......**.........*.*.......
	........*.*****..........***...*...........................
	............*...*.....*.*****.*..................*.........
	............**....***.....*......................**........
	............**....***....**...................*****........
	...................*.....**...................**.**.....**.
	.................................................*......*.*
	.....................................................**.*.*
	.....................................................*.*.*.
	.......................................................*...
	...................................***.........*.*...*..*..
	.......**..........................*..*........*..*.....*..
	.......**..............................*.......*.*..*...*..
	...................................*..*.............*...*..
	...................................***..................*..
	.....................................................*..*..
	................................................*......*...
	.............................................**.**...*.*.*.
	.............................................*****...**.*.*
	.........*......................................**......*.*
	........*.*.....................................*.......**.
	...........................................................
	.**.......*.....................................*.*........
	*.*......**......................................*.........
	*.*.**...*****.............................................
	.*.*.*...**.**.............................................
	...*......*................................................
	..*..*.....................................................
	..*........................................................
	..*...*....................................................
	..*...*..*.*......................................**.......
	..*.....*..*......................................**.......
	..*..*...*.*...............................................
	...*.......................................................
	.*.*.*.....................................................
	*.*.**.....................................................
	*.*......*.................................................
	.**.....**.**...................**.....*...................
	........*****...................**....***....**............
	........**......................*.....***....**............
	.........*..................*.*****.*.....*...*............
	...........................*...***..........*****.*........
	.......*.*.........**.......*.........*......***...*.......
	........*..........**.............................*........
	...........................................................
	................................**........**...............
	................................*..******..*...............
	.................................**......**................
	..............................***..........***.............
	..............................*..*.*....*.*..*.............
	...............................**....**....**..............

:pi portraitor: (p32)  Found by Robert Wainwright in 1984 or 1985.
   Compare with {gourmet} and {popover}.
	...........**...........
	......**.*....*.**......
	......*..........*......
	.......**......**.......
	....***..******..***....
	....*..*........*..*....
	.**.*.*..........*.*.**.
	.*.*.*............*.*.*.
	...*................*...
	.*..*..............*..*.
	....*.......***....*....
	*...*.......*.*....*...*
	*...*.......*.*....*...*
	....*..............*....
	.*..*..............*..*.
	...*................*...
	.*.*.*............*.*.*.
	.**.*.*..........*.*.**.
	....*..*........*..*....
	....***..******..***....
	.......**......**.......
	......*..........*......
	......**.*....*.**......
	...........**...........

:pipsquirt: = {pipsquirter}

:pipsquirter:  An {oscillator} that produces a {domino} {spark} that
   is orientated parallel to the direction from which it is produced
   (in contrast to domino sparkers like the {pentadecathlon} and
   {HWSS}, which produce domino sparks perpendicular to the direction
   of production).  The following is a small p6 example found by Noam
   Elkies in November 1997.
	.....*.........
	.....*.........
	...............
	...*...*.......
	.***.*.***.....
	*...**....*....
	*.**..**.*.*...
	.*..**..**.*...
	..**..**.*.*.**
	....*..*.*.*.**
	....****.**....
	........*......
	......*.*......
	......**.......

:pi ship:  A {growing spaceship} in which the back part consists of
   a {pi-heptomino} travelling at a speed of 3c/10.  The first example
   was constructed by David Bell.  All known pi ships are too large to
   show here, but the following diagram shows how the pi fuse works.
	............*............
	...........*.*...........
	**........**.**........**
	**.....................**

:piston: (p2)  Found in 1971.
	**.......**
	*.*..*..*.*
	..****..*..
	*.*..*..*.*
	**.......**

:pixel: = {cell}

:plet: = {polyplet}

:polyomino:  A finite collection of orthogonally connected cells.  The
   mathematical study of polyominoes was initiated by Solomon Golomb
   in 1953.  Conway's early investigations of Life and other cellular
   automata involved tracking the histories of small polyominoes,
   this being a reasonable way to ascertain the typical behaviour of
   different cellular automata when the patterns had to be evolved
   by hand rather than by computer.  Polyominoes have no special
   significance in Life, but their extensive study during the early
   years lead to a number of important discoveries and has influenced
   the terminology of Life.  (Note on spelling:  As with "dominoes"
   the plural may also be spelt without an e.  In this lexicon I have
   followed Golomb in using the longer form.)
     It is possible for a polyomino to be an {oscillator}.  In fact
   there are infinitely many examples of such polyominoes, namely the
   {cross} and its larger analogues.  The only other known examples
   are the {block}, the {blinker}, the {toad}, the {star} and (in two
   different phases) the {pentadecathlon}.
     A polyomino can also be a {spaceship}, as the {LWSS}, {MWSS} and
   {HWSS} show.

:polyplet:  A finite collection of orthogonally or diagonally connected
   cells.  This king-wise connectivity is a more natural concept in
   Life than the orthogonal connectivity of the {polyomino}.

:pond: (p1)
	.**.
	*..*
	*..*
	.**.

:pond on pond: (p1)  This term is often used to mean {bi-pond}, but may
   also be used of the following {pseudo still life}.
	.**...**.
	*..*.*..*
	*..*.*..*
	.**...**.

:popover: (p32)  Found by Robert Wainwright in August 1984.  Compare
   with {gourmet} and {pi portraitor}.
	.....................*..........
	.....................*..........
	.....................***........
	.............**.......**........
	.............**..***..**........
	...................***..........
	...................***..........
	..............**................
	..***........*..*...............
	..***........*.*................
	***..**...*...*....***..........
	.....**...*.....................
	....***...*.....................
	....*.................**...**...
	....*...........***..*..*..**...
	........*.......*.*...*.*.......
	.......*.*......*.*....*........
	...**..*..*................*....
	...**...**.................*....
	.....................*...***....
	.....................*...**.....
	..........***........*...**..***
	.................**........***..
	................*..*.......***..
	................*.*.............
	..........***....*..............
	..........***...................
	........**..***..**.............
	........**.......**.............
	........***.....................
	..........*.....................
	..........*.....................

:population:  The number of ON cells.

:P-pentomino:  Conway's name for the following {pentomino}, a common
   {spark}.
	**
	**
	*.

:PPS:  (c/5 orthogonally, p30)  A pre-pulsar spaceship.  Any of three
   different p30 c/5 orthogonal {spaceship}s in which a {pre-pulsar} is
   pushed by a pair of {spider}s.  The back sparks of the spaceship can
   be used to perturb gliders in many different ways, allowing the easy
   construction of c/5 puffers.  The first PPS was found by David Bell
   in May 1998 based on a previous p15 pre-pulsar spaceship found by
   Noam Elkies in December 1997.  See also {SPPS} and {APPS}.

:pre-beehive:  The following common {parent} of the {beehive}.
	***
	***

:pre-block:  The following common {parent} of the {block}.  Another
   such pattern is the {grin}.
	*.
	**

:precursor: = {predecessor}

:predecessor:  Any pattern that evolves into a given pattern after
   one or more generations.

:pre-pulsar:  A common {predecessor} of the {pulsar}, such as that
   shown below.  This duplicates itself in 15 generations.  (It fails,
   however, to be a true {replicator} because of the way the two copies
   then interact.)
	***...***
	*.*...*.*
	***...***
     A pair of {tub}s can be placed to eat half the
   pre-pulsar as it replicates; this gives the p30 oscillator {Eureka}
   where the pre-pulsar's replication becomes a movement back and forth.
   (See {twirling T-tetsons II} for a variation on this idea.)  By
   other means the replication of the pre-pulsar can be made to occur
   in just 14 generations as half of it is eaten; this allows the
   construction of p28 and p29 oscillators, and is in fact the only
   known method for creating a p29 oscillator.  The pre-pulsar is also
   a vital component of the only known p47 oscillator.
     See also {PPS}.

:pre-pulsar spaceship:  See {PPS}.

:pressure cooker: (p3)  Found by the MIT group in September 1971.
   Compare {mini pressure cooker}.
	.....*.....
	....*.*....
	....*.*....
	...**.**...
	*.*.....*.*
	**.*.*.*.**
	...*...*...
	...*...*...
	....***....
	...........
	...*.**....
	...**.*....

:primer:  A pattern constructed by Dean Hickerson in November 1991 that
   emits a stream of {LWSS}s representing the prime numbers.

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

:pseudo:  Opposite of {true}.  A {gun} emitting a period n stream of
   spaceships (or rakes) is said to be a pseudo period n gun if its
   mechanism oscillates with a period different from n.  This period
   will necessarily be a multiple of n.  Pseudo period n glider guns
   are known to exist for all periods greater than or equal to 14, with
   smaller periods being impossible.  The first pseudo p14 gun was built
   by Dieter Leithner in 1995.
     Exactly the same distinction between true and pseudo also exists
   for {puffer}s.

:pseudo-barberpole: (p5)  Found by Achim Flammenkamp in August 1994.
   In terms of its minimum {population} of 15 this is the smallest known
   p5 {oscillator}.
	..........**
	...........*
	.........*..
	.......*.*..
	............
	.....*.*....
	............
	...*.*......
	............
	..**........
	*...........
	**..........

:pseudo still life:  The strict definition of {still life} rules out
   such stable patterns as the {bi-block}.  In such patterns there are
   dead cells which have more than 3 neighbours in total, but fewer than
   3 in any component still life.  These patterns are called pseudo
   still lifes.  Mark Niemiec has enumerated the pseudo still lifes
   up to 24 bits, and his figures are shown below.
	-------------
	Bits   Number
	-------------
	  8        1
	  9        1
	 10        7
	 11       16
	 12       55
	 13      110
	 14      279
	 15      620
	 16     1645
	 17     4067
	 18    10843
	 19    27250
	 20    70637
	 21   179011
	 22   462086
	 23  1184882
	 24  3068984
	-------------

:puffer:  An object that moves like a {spaceship}, except that it
   leaves debris behind.  The first known puffers were found by Bill
   Gosper and travelled at c/2 orthogonally (see diagram below for
   the very first one, found in 1971).  Not long afterwards c/12
   diagonal puffers were found (see {switch engine}).  Discounting
   {wickstretcher}s (which are not puffers in the conventional sense),
   no new velocity was obtained after this until David Bell found the
   first c/3 orthogonal puffer in April 1996.  Since then c/5 orthogonal
   puffers have also been found, the first by Tim Coe in May 1997.
   Jason Summers built the first c/4 orthogonal puffer in January 1999,
   and the first 2c/5 orthogonal puffer in February 1999.
	.***......*.....*......***.
	*..*.....***...***.....*..*
	...*....**.*...*.**....*...
	...*...................*...
	...*..*.............*..*...
	...*..**...........**..*...
	..*...**...........**...*..

:puffer engine:  A pattern which can be used as the main component of
   a {puffer}.  The pattern may itself be a puffer (e.g. the classic
   {puffer train}), it may be a spaceship (e.g. the {Schick engine}),
   or it may even be unstable (e.g. the {switch engine}).

:puffer train:  The full name for a {puffer}, coined by Conway before
   any examples were known.  The term was also applied specifically
   to the classic puffer train found by Bill Gosper and shown below.
   This is very {dirty}, and the tail does not stabilize until
   generation 5533.  It consists of a {B-heptomino} (shown here one
   generation before the standard form) escorted by two {LWSS}.  (This
   was the second known puffer.  The first is shown under {puffer}.)
	.***...........***
	*..*..........*..*
	...*....***......*
	...*....*..*.....*
	..*....*........*.

:puff suppressor:  An attachment at the back of a {line puffer} that
   suppresses all or some of its puffing action.  The example below (by
   Hartmut Holzwart) has a 3-cell puff suppressor at the back which
   suppresses the entire puff, making a p2 {spaceship}.  If you delete
   this puff suppressor then you get a p60 double {beehive} {puffer}.
   Puff suppressors were first recognised by Alan Hensel in April 1994.
	............*....................
	..........**.*...................
	..........**...*.................
	........*...**.*.....*...........
	........****.**...****.......*.*.
	......*......*....***.....*.*..*.
	......*******...*...*....*..*....
	...*.*......**..*...*.*.**....*..
	..*********.....*..**........*...
	.**..............*.**.****...*..*
	**....**.*..........*...*..*.*...
	.**....*........***......*.*.*..*
	.........*......**......*....**..
	.**....*........***......*.*.*..*
	**....**.*..........*...*..*.*...
	.**..............*.**.****...*..*
	..*********.....*..**........*...
	...*.*......**..*...*.*.**....*..
	......*******...*...*....*..*....
	......*......*....***.....*.*..*.
	........****.**...****.......*.*.
	........*...**.*.....*...........
	..........**...*.................
	..........**.*...................
	............*....................

:pulsar: (p3)  Despite its size, this is the fourth most common
   {oscillator} (and by far the most common of period greater than 2)
   and was found very early on by Conway.  See also {pre-pulsar} and
   {pulsar quadrant}.
	..***...***..
	.............
	*....*.*....*
	*....*.*....*
	*....*.*....*
	..***...***..
	.............
	..***...***..
	*....*.*....*
	*....*.*....*
	*....*.*....*
	.............
	..***...***..

:pulsar 18-22-20: = {two pulsar quadrants}

:pulsar CP 48-56-72: = {pulsar}  (The numbers refer to the populations
   of the three phases.)

:pulsar quadrant: (p3)  This consists of a quarter of the outer part of
   a {pulsar} stabilized by a {cis fuse with two tails}.  This is
   reminiscent of {mold} and {jam}.  Found by Dave Buckingham in July
   1973.  See also {two pulsar quadrants}.
	.....*..
	...***..
	..*...**
	*..*..*.
	*...*.*.
	*....*..
	........
	..***...

:pulse: = {pulsar quadrant}

:pulse divider:  A mechanism that lets every n-th object that reaches
   it pass through, and deletes all the rest, where n > 1 and the
   objects are typically {spaceship}s or {Herschel}s.
     The following diagram shows a p5 glider pulse divider by Dieter
   Leithner (February 1998).  The first glider moves the centre block
   and is reflected at 90 degrees.  The next glider to come along will
   not be reflected, but will move the block back to its original
   position.  The small size and low period of this example make it
   useful for constructing glider {gun}s of certain periods.  p7, p22,
   p36 and p46 versions of this pulse divider are also known.
	.....**...................
	.....**...................
	..........................
	..................**......
	.................*..*.....
	.................*.*..*..*
	*...............**.*.*****
	.**...........*...**......
	**...............**..***..
	.............*...*.*..*.*.
	........**.......**..**.*.
	........**....*...**...*..
	................**.*.**...
	.................*.*.*....
	.................*.*..*...
	..................*..**...
	..**......................
	...*......................
	***.......................
	*.........................
	..........................
	............**............
	............*.............
	.............***..........
	...............*..........

:pulshuttle V: (p30)  Found by Robert Wainwright, May 1985.
   Compare {Eureka}.
	.............*..............*.............
	............*.*.......*....*.*............
	.............*......**.**...*.............
	......................*...................
	..**......**..................**......**..
	*....*..*....*..............*....*..*....*
	*....*..*....*..............*....*..*....*
	*....*..*....*........*.....*....*..*....*
	..**......**........**.**.....**......**..
	......................*...................
	..........................................
	..........................................
	..**......**..................**......**..
	*....*..*....*........*.....*....*..*....*
	*....*..*....*......**.**...*....*..*....*
	*....*..*....*........*.....*....*..*....*
	..**......**..................**......**..
	..........................................
	..........................................
	......................*...................
	..**......**........**.**.....**......**..
	*....*..*....*........*.....*....*..*....*
	*....*..*....*..............*....*..*....*
	*....*..*....*..............*....*..*....*
	..**......**..................**......**..
	......................*...................
	.............*......**.**...*.............
	............*.*.......*....*.*............
	.............*..............*.............

:pure glider generator:  A pattern that evolves into one or more
   {glider}s, and nothing else.  There was some interest in these
   early on, but they are no longer considered important.  Here's
   a neat example:
	..*............
	..*............
	***............
	...............
	......***......
	.......*.......
	............***
	............*..
	............*..

:pushalong:  Any {tagalong} at the front of a spaceship.  The following
   is an example (found by David Bell in 1992) attached to the front of
   a {MWSS}.
	..***.*.....
	.****.*.....
	**..........
	.*.*........
	..****.*....
	...***......
	............
	............
	......*****.
	......*....*
	......*.....
	.......*...*
	.........*..

:pyrotechnecium: (p8)  Found by Dave Buckingham in 1972.
	.......*........
	.....*****......
	....*.....*.....
	.*..*.*.**.*....
	*.*.*.*....*..*.
	.*..*....*.*.*.*
	....*.**.*.*..*.
	.....*.....*....
	......*****.....
	........*.......

:pyrotechneczum:  A mistaken spelling of {pyrotechnecium}, caused by an
   early transcription error.

:python: = {long snake}

:Q: = {Quetzal}

:Q-pentomino:  Conway's name for the following {pentomino}, a
   {traffic light} {predecessor}.
	****
	...*

:quad: (p2)  Found by Robert Kraus, April 1971.  Of all {oscillator}s
   that fit in a 6x6 box this is the only {flipper}.
	**..**
	*..*.*
	.*....
	....*.
	*.*..*
	**..**

:QuadLife:  A form of {colorized Life} in which there are four types of
   ON cell.  A newly-born cell takes the type of the majority of its
   three {parent cells}, or the remaining type if its parent cells are
   all of different types.  In areas where there are only two types of
   ON cell QuadLife reduces to {Immigration}.

:quadpole: (p2)  The {barberpole} of length 4.
	**.....
	*.*....
	.......
	..*.*..
	.......
	....*.*
	.....**

:quapole: = {quadpole}

:quasar: (p3)  Found by Robert Wainwright, August 1971.  See {pulsar}.
	..........***...***..........
	.............................
	........*....*.*....*........
	........*....*.*....*........
	........*....*.*....*........
	..........***...***..........
	.............................
	........***.......***........
	..***..*....*...*....*..***..
	.......*....*...*....*.......
	*....*.*....*...*....*.*....*
	*....*.................*....*
	*....*..***.......***..*....*
	..***...................***..
	.............................
	..***...................***..
	*....*..***.......***..*....*
	*....*.................*....*
	*....*.*....*...*....*.*....*
	.......*....*...*....*.......
	..***..*....*...*....*..***..
	........***.......***........
	.............................
	..........***...***..........
	........*....*.*....*........
	........*....*.*....*........
	........*....*.*....*........
	.............................
	..........***...***..........

:queen bee:  See {queen bee shuttle}.

:queen bee shuttle: (p30)  Found by Bill Gosper in 1970.  There are a
   number of ways to stabilize the ends.  Gosper originally stabilized
   shuttles against one another in a square of eight shuttles.
   Two simpler methods are shown here; for a third see {buckaroo}.
   The queen bee shuttle is the basis of all known {true} p30 {gun}s
   (see {Gosper glider gun}).
	.........*............
	.......*.*............
	......*.*.............
	**...*..*.............
	**....*.*.............
	.......*.*........**..
	.........*........*.*.
	....................*.
	....................**

:Quetzal:  Dieter Leithner's name for the {true} p54 glider gun he built
   in January 1998.  (This is short for {Quetzalcoatlus} and expresses
   the fact that the gun was a very large {Herschel loop} that was not
   an {emu}.)  Shortly afterwards Leithner also built a p56 Quetzal
   using a mechanism found by Noam Elkies for this purpose.  In October
   1998 Stephen Silver constructed a p55 Quetzal using Elkies' p5
   {reflector} of the previous month.

:Quetzalcoatlus:  A giant flying dinosaur after which Dieter Leithner
   named his p54 gun.  Usually abbreviated to {Quetzal}, or simply Q
   (as in Q54, Q55, Q56, Q-gun, etc.).

:quilt: = {squaredance}

:R: = {R-pentomino}

:R2D2: (p8)  This was found, in the form shown below, by Peter Raynham
   in the early 1970s.  The name derives from a form with a larger
   and less symmetric {stator} discovered by Noam Elkies in August
   1994.  Compare with {Gray counter}.
	.....*.....
	....*.*....
	...*.*.*...
	...*.*.*...
	**.*...*.**
	**.*...*.**
	...*...*...
	...*.*.*...
	....*.*....
	.....*.....

:r5: = {R-pentomino}

:rabbits: (stabilizes at time 17331)  A {methuselah} found by Andrew
   Trevorrow in 1986.
	*...***
	***..*.
	.*.....

:rake:  Any {puffer} whose debris consists of {spaceship}s.  A rake is
   said to be forwards, backwards or sideways according to the direction
   of the spaceships relative to the direction of the rake.  Originally
   the term "rake" was applied only to forwards c/2 glider puffers (see
   {space rake}).  Many people prefer not to use the term in the case
   where the puffed spaceships travel parallel or anti-parallel to the
   puffer, as in this case they do not rake out any significant region
   of the Life plane (and, in contrast to true rakes, these puffers
   cannot travel in a stream, and so could never be produced by a
   {gun}).
     Although the first rakes (circa 1971) were c/2, rakes of other
   velocities have since been built.  Dean Hickerson's construction of
   {Cordership}s in 1991 made it easy for c/12 diagonal rakes to be
   built, although no-one actually did this until 1998, by which time
   David Bell had constructed c/3 and c/5 rakes (May 1996 and September
   1997, respectively).  Jason Summers constructed a 2c/5 rake in June
   2000 (building on work by Paul Tooke and David Bell) and a c/4
   orthogonal rake in October 2000 (based largely on reactions found
   by David Bell).
     The smallest possible period for a rake is probably 7, as this
   could be achieved by a 3c/7 orthogonal backwards glider puffer.  The
   smallest period attained to date is 8 (Jason Summers, March 2001) -
   see {backrake}.

:$rats: (p6)  Found by Dave Buckingham, 1972.
	.....**.....
	......*.....
	....*.......
	**.*.****...
	**.*.....*.*
	...*..***.**
	...*....*...
	....***.*...
	.......*....
	......*.....
	......**....

:R-bee: = {bun}

:reflector:  Any {stable} or oscillating pattern that can reflect some
   type of {spaceship} (usually a {glider}) without suffering permanent
   damage.  The first known reflector was the {pentadecathlon}, which
   functions as a 180-degree glider reflector (see {relay}).  Other
   examples include the {buckaroo}, the {twin bees shuttle} and some
   oscillators based on the {traffic jam} reaction.  Glider {gun}s can
   also be made into reflectors, although these are mostly rather large.
     In September 1998 Noam Elkies found some fast small-period glider
   reflectors.  The p8 version is shown below.  Replacing the {figure-8}
   by the p6 {pipsquirter} gives a p6 version.  A more complicated
   construction allows a p5 version (which, as had been anticipated,
   soon led to a {true} p55 gun - see {Quetzal}).  And in August 1999
   Elkies found a suitable p7 {sparker}, allowing the first p49
   oscillator to be constructed.
	......**.....**..
	*.*...**.....*...
	.**........*.*...
	.*.........**....
	.......**........
	.......*.*.......
	........*........
	.................
	...........***...
	...........***...
	...........***...
	..............***
	..............***
	..............***
     Stable reflectors are special in that if they satisfy certain
   conditions they can be used to construct {oscillator}s of all
   sufficiently large periods.  It was known for some time that stable
   reflectors were possible (see {universal constructor}), but no one
   was able to construct an explicit example until Paul Callahan did
   so in October 1996.
     All known stable reflectors are very slow.  Callahan's original
   reflector has a {repeat time} of 4840, soon improved to 1686 and
   then 894 and then 850.  In November 1996 Dean Hickerson found a
   variant in which this is reduced to 747.  Dave Buckingham reduced
   it to 672 in May 1997 using a somewhat different method, and in
   October 1997 Stephen Silver reduced it to 623 by a method closer
   to the original.  In November 1998 Callahan reduced this to 575
   with a new initial reaction.  A small modification by Silver a few
   days later brought this down to 497.
     But in April 2001 Dave Greene found a 180-degree stable reflector
   with a repeat time of only 202.  This reflector also won the $100
   prize that Dieter Leithner had offered in April 1997 for the first
   stable reflector to fit in a 50x50 box, and the additional $100
   that Alan Hensel had offered in January 1999 for the same feat.
   This reflector is shown below, with a glider entering at top left.
   Dave Greene has subsequently offered $50 for the first 90-degree
   stable glider reflector that fits in a 50x50 box, and a further
   $50 for the first in a 35x35 box.
	....*.*......**.............................
	.....**......**.............................
	.....*......................................
	............................................
	............................................
	............................................
	............................................
	............................................
	............................................
	........................................*...
	.......................................*.*..
	.......................................*.*..
	....................**................**.**.
	....................**......................
	......................................**.**.
	..**..................................**.*..
	.*.*.......................................*
	.*........................................**
	**..........................................
	............................................
	..................................**........
	..................................**....**..
	...........**...........................*.*.
	..........*.*.............................*.
	..........*...............................**
	.........**.......................**........
	..................................**........
	............................................
	............................................
	.............................*..............
	............................*.*.............
	.............................*..............

:relay:  Any {oscillator} in which {spaceship}s (typically {glider}s)
   travel in a loop.  The simplest example is the p60 one shown below
   using two {pentadecathlon}s.  Pulling the pentadecathlons further
   apart allows any period of the form 60+120n to be achieved - this
   is the simplest proof of the existence of oscillators of arbitrarily
   large period.
	...........................*....*..
	................**.......**.****.**
	.................**........*....*..
	................*..................
	..*....*...........................
	**.****.**.........................
	..*....*...........................

:repeater:  Any {oscillator} or {spaceship}.

:repeat time:  The minimum number of generations that is possible
   between the arrival of one object and the arrival of the next.  This
   term is used for things such as {reflector}s or {conduit}s and the
   objects (gliders or Herschels, for example) will interact fatally
   with each other (or one will interact fatally with a disturbance
   caused by the other) if they are too close together.  For example,
   the repeat time of Dave Buckingham's 59-step B-heptomino to Herschel
   conduit (shown under {conduit}) is 58.

:rephaser:  The following reaction that shifts the phase and path of a
   pair of gliders.  In fact there is another form of this reaction that
   reflects the gliders 180 degrees - see {glider-block cycle}.
	..*..*..
	*.*..*.*
	.**..**.
	........
	........
	...**...
	...**...

:replicator:  A finite pattern which repeatedly creates
   copies of itself.  Such objects are known to exist (see
   {universal constructor}), but no concrete example is known.

:reverse fuse:  A {fuse} that produces some initial debris, but then
   burns {clean}ly.  The following is a simple example.
	.............**
	............*.*
	...........*...
	..........*....
	.........*.....
	........*......
	.......*.......
	......*........
	.....*.........
	....*..........
	...*...........
	..*............
	**.............

:revolver: (p2)
	*............*
	***....*...***
	...*.*.*..*...
	..*......*.*..
	..*.*......*..
	...*..*.*.*...
	***...*....***
	*............*

:ring of fire: (p2)  The following {muttering moat} found by Dean
   Hickerson in September 1992.
	................*.................
	..............*.*.*...............
	............*.*.*.*.*.............
	..........*.*.*.*.*.*.*...........
	........*.*.*..**.*.*.*.*.........
	......*.*.*.*......*..*.*.*.......
	....*.*.*..*..........*.*.*.*.....
	.....**.*..............*..*.*.*...
	...*...*..................*.**....
	....***....................*...*..
	..*.........................***...
	...**...........................*.
	.*...*........................**..
	..****.......................*...*
	*.............................***.
	.***.............................*
	*...*.......................****..
	..**........................*...*.
	.*...........................**...
	...***.........................*..
	..*...*....................***....
	....**.*..................*...*...
	...*.*.*..*..............*.**.....
	.....*.*.*.*..........*..*.*.*....
	.......*.*.*..*......*.*.*.*......
	.........*.*.*.*.**..*.*.*........
	...........*.*.*.*.*.*.*..........
	.............*.*.*.*.*............
	...............*.*.*..............
	.................*................

:rle:  Run-length encoded.  Run-length encoding is a simple (but not
   very efficient) method of file compression.  In Life the term refers
   to a specific ASCII encoding used for Life patterns (and patterns
   for other similar cellular automata).  This encoding was introduced
   by Dave Buckingham and is now the usual means of exchanging Life
   patterns (especially large ones) by e-mail.

:rock:  Dean Hickerson's term for an {eater} which remains intact
   throughout the eating process.  The {snake} in Dave Buckingham's
   59-step B-to-Herschel conduit (shown under {conduit}) is an
   example.  Other still lifes that sometimes act as rocks include the
   {tub}, the {hook with tail}, the {eater1} (eating with its tail)
   and the {hat} (in Heinrich Koenig's stabilization of the
   {twin bees shuttle}).

:roteightor: (p8)  Found by Robert Wainwright in 1972.
	.*............
	.***........**
	....*.......*.
	...**.....*.*.
	..........**..
	..............
	.....***......
	.....*..*.....
	.....*........
	..**..*...*...
	.*.*......*...
	.*.......*....
	**........***.
	............*.

:rotor:  The cells of an {oscillator} that change state.  Compare
   {stator}.  It is easy to see that any rotor cell must be adjacent
   to another rotor cell.

:R-pentomino:  This is by far the most active {polyomino} with less
   than six cells: all the others stabilize in at most 10 generations,
   but the R-pentomino does not do so until generation 1103, by which
   time it has a {population} of 116.
	.**
	**.
	.*.

:rule 22:  Wolfram's rule 22 is the 2-state 1-D {cellular automaton}
   in which a cell is ON in the next generation if and only if exactly
   one of its three neighbours is ON in the current generation (a cell
   being counted as a neighbour of itself).  This is the behaviour of
   Life on a cylinder of width 1.

:rumbling river:  Any {oscillator} in which the {rotor} is connected and
   contained in a strip of width 2.  The following p3 example is by Dean
   Hickerson, November 1994.
	..............**......**......**...*.**..........
	....*........*..*....*..*....*..*..**.*..........
	*..*.*....*...**..*...**..*...*.*.....*.**.......
	****.*..******..******..******..******.*.*.......
	.....*.*.....*.*.....*.*.....*.*.....*.*......**.
	..**.*.*.*.*...*.*.*...*.*.*...*.*.*...*.*.....*.
	.*.....*.*...*.*.*...*.*.*...*.*.*...*.*.*.*.**..
	.**......*.*.....*.*.....*.*.....*.*.....*.*.....
	.......*.*.******..******..******..******..*.****
	.......**.*.....*.*...*..**...*..**...*....*.*..*
	..........*.**..*..*....*..*....*..*........*....
	..........**.*...**......**......**..............

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

:sailboat: (p16)  A {boat} {hassle}d by a {Kok's galaxy}, a {figure-8}
   and two {eater3}s.  Found by Robert Wainwright in June 1984.
	........*...........*........
	.......*.*.........*.*.......
	........*...........*........
	.............................
	......*****.......*****......
	.....*....*.......*....*.....
	....*..*.............*..*....
	.*..*.**.............**.*..*.
	*.*.*.....*.......*.....*.*.*
	.*..*....*.*.....*.*....*..*.
	....**..*..*.....*..*..**....
	.........**.......**.........
	.............**..............
	.............*.*.............
	........*..*..*..............
	.......*.....................
	.....**..........***.........
	..*......**.*....***.........
	.....*...*..*....***.........
	.....***.*...*......***......
	..*...........*.....***......
	...*...*.***........***......
	....*..*...*.................
	....*.**......*..............
	..........**.................
	.........*...................
	.....*..*....................

: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
   drops below some fixed value.)  The first such pattern was
   constructed by Dean Hickerson in April 1991.  Conway's preferred
   plural is "sawteeth".

: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 {perturb}ed by
   other c/2 spaceships to form a variety of {puffer}s.  The diagram
   below shows the smallest form of the Schick engine, using two
   {LWSS}.  It is also possible to use two {MWSS} or two {HWSS}, or
   even a LWSS and a HWSS.
	****..............
	*...*.........*...
	*...........**....
	.*..*..**.....***.
	......***......***
	.*..*..**.....***.
	*...........**....
	*...*.........*...
	****..............

:Schick ship: = {Schick engine}

:scorpion: (p1)
	...*...
	.***...
	*...**.
	*.*.*.*
	.**.*.*
	.....*.

:scrubber: (p2)  Found in 1971.
	....*......
	..***......
	.*.........
	.*..***....
	**.*...*...
	...*...*...
	...*...*.**
	....***..*.
	.........*.
	......***..
	......*....

:SE: = {switch engine}

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

:SGR:  Abbreviation for {stable} {glider} {reflector}.

:shillelagh: (p1)
	**...
	*..**
	.**.*

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

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

:ship on boat: = {ship tie boat}

:ship on ship: = {ship-tie}

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

:ship tie boat: (p1)
	**....
	*.*...
	.**...
	...**.
	...*.*
	....*.

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

: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 life}s (and the {stator}
   part of certain {oscillator}s).  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}.
	**...
	*.***
	....*

:sidecar:  A small {tagalong} for a {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 spaceship}s and some trivial
   two-spaceship {flotilla}s derived from them.  Note also that a HWSS
   can support two sidecars at once.
	.*......
	*.....*.
	*.....*.
	*****.*.
	........
	....**..
	..*....*
	.*......
	.*.....*
	.******.

:side-shooting gun:  A {gun} which fires sideways from an extending
   arm.  The arm consists of streams of {spaceship}s which are pushing
   a pattern away from the body of the gun and releasing an output
   spaceship every time they do so.
     The following pattern, from a side-shooting gun by Dieter Leithner
   (July 1994), shows how this can be achieved.  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.
	..............**.
	..............**.
	........***......
	..........*......
	.........*.....**
	..............*.*
	................*
	.................
	.................
	.................
	.................
	.................
	.................
	.................
	.................
	.................
	.................
	.*...............
	.**..............
	*.*..............

:side-tracking:  See {universal constructor}.

:sidewalk: (p1)
	.**.**
	..*.*.
	.*..*.
	.*.*..
	**.**.

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

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

:sinking ship: = {canoe}

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

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

:skewed quad: (p2)
	.**....
	.*...**
	..*.*.*
	.......
	*.*.*..
	**...*.
	....**.

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

:slide gun:  A {gun} that fires {glider}s each along a different path.
   These work by firing {spaceship}s at some object so as to push it
   away from the guns and at the same time release a glider.  The
   first one was constructed by Dieter Leithner and Dean Hickerson in
   February 1997.  Jason Summers constructed a number of new ones in
   1999.

: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.  In Conway's original formulation (as part of his proof
   of the existence of a {universal computer} in Life) 2 gliders were
   used to pull the block inwards by three diagonal spaces, and 30
   gliders were used to push it out by the same amount.  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 using
   3 gliders.  In order for the memory to be of any use there also has
   to be a way of reading 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).

:small fish: = {LWSS}

:small lake: (p1)  See also {lake}.
	....*....
	...*.*...
	...*.*...
	.**...**.
	*.......*
	.**...**.
	...*.*...
	...*.*...
	....*....

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

: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} -
   see {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 the
   gliders, 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.
	**................**
	.*................*.
	.*.*............*.*.
	..**............**..
	.......*....*.......
	.....**.****.**.....
	.......*....*.......
	..**............**..
	.*.*............*.*.
	.*................*.
	**................**
   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.
	**................................
	.*................................
	.*.*.........................**...
	..**.......................*..*...
	.......*....*..............***....
	.....**.****.**...*....*......***.
	.......*....*...**.****.**...*...*
	..**..............*....*......***.
	.*.*.......................***....
	.*.........................*..*...
	**...........................**...
   An end can also be stabilized by killer {candlefrobra}s, although
   this isn't efficient.

:snail: (c/5 orthogonally, p5)  The first known c/5 {spaceship},
   discovered by Tim Coe in January 1996.
	.*....................................
	.*....................................
	*.....................................
	.***.................***...***........
	.**.*.........*...*.*......***........
	..*...........**.*.......*....****....
	......*......*...*.*...**.*.....**....
	...*..*.***...**.........*........**.*
	...**.*.....*.....*.................*.
	.........*.*******....................
	......................................
	.........*.*******....................
	...**.*.....*.....*.................*.
	...*..*.***...**.........*........**.*
	......*......*...*.*...**.*.....**....
	..*...........**.*.......*....****....
	.**.*.........*...*.*......***........
	.***.................***...***........
	*.....................................
	.*....................................
	.*....................................

:snake: (p1)
	**.*
	*.**

: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.

:snake bridge snake: (p1)
	....**
	....*.
	.....*
	....**
	**.*..
	*.**..

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

:snake pit:  This term has been used for two different {oscillator}s:
   the p2 snake pit (essentially the same as {fore and back})
	*.**.**
	**.*.*.
	......*
	***.***
	*......
	.*.*.**
	**.**.*
   and the p3 snake pit.
	.....**....
	....*..*...
	....*.**...
	.**.*......
	*.*.*.****.
	*.........*
	.****.*.*.*
	......*.**.
	...**.*....
	...*..*....
	....**.....

:snake siamese snake: (p1)
	**.**.*
	*.**.**

: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}.
	...**........**...
	...*.*......*.*...
	.....*......*.....
	...*.**....**.*...
	.***..........***.
	*...*.*....*.*...*
	.***..........***.
	...*.**....**.*...
	.....*......*.....
	...*.*......*.*...
	...**........**...

:soup:  A random initial pattern, often assumed to cover the whole
   Life universe.

: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.

: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 {breeder}s (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.
	..................*........
	.................***.......
	............***....**......
	...........*..***..*.**....
	..........*...*.*..*.*.....
	..........*....*.*.*.*.**..
	............*....*.*...**..
	****.....*.*....*...*.***..
	*...**.*.***.**.........**.
	*.....**.....*.............
	.*..**.*..*..*.**..........
	.......*.*.*.*.*.*.....****
	.*..**.*..*..*..**.*.**...*
	*.....**...*.*.*...**.....*
	*...**.*.**..*..*..*.**..*.
	****.....*.*.*.*.*.*.......
	..........**.*..*..*.**..*.
	.............*.....**.....*
	.**.........**.***.*.**...*
	..***.*...*....*.*.....****
	..**...*.*....*............
	..**.*.*.*.*....*..........
	.....*.*..*.*...*..........
	....**.*..***..*...........
	......**....***............
	.......***.................
	........*..................

: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 {glider}s.
	...........**.....****
	.........**.**...*...*
	.........****........*
	..........**.....*..*.
	......................
	........*.............
	.......**........**...
	......*.........*..*..
	.......*****....*..*..
	........****...**.**..
	...........*....**....
	......................
	......................
	......................
	..................****
	*..*.............*...*
	....*................*
	*...*............*..*.
	.****.................

: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}.  For further examples see {big glider},
   {brain}, {Canada goose}, {Coe ship}, {Cordership}, {dart}, {dragon},
   {ecologist}, {edge-repair spaceship}, {Enterprise}, {flotilla},
   {fly}, {hammerhead}, {hivenudger}, {Orion}, {puff suppressor},
   {pushalong}, {Schick engine}, {sidecar}, {snail}, {sparky}, {swan},
   {turtle}, {wasp} and {weekender}.
     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 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 spaceships travelling at ten different velocities.  The following
   table details the discovery of spaceships with new velocities.
	---------------------------------------------
	Speed  Direction    Discoverer         Date
	---------------------------------------------
	c/4    diagonal     Richard Guy          1970
	c/2    orthogonal   John Conway          1970
	c/3    orthogonal   Dean Hickerson   Aug 1989
	c/4    orthogonal   Dean Hickerson   Dec 1989
	c/12   diagonal     Dean Hickerson   Apr 1991
	2c/5   orthogonal   Dean Hickerson   Jul 1991
	c/5    orthogonal   Tim Coe          Jan 1996
	2c/7   orthogonal   David Eppstein   Jan 2000
	c/6    orthogonal   Paul Tooke       Apr 2000
	c/5    diagonal     Jason Summers    Nov 2000
	---------------------------------------------
     A period p spaceship which 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.)
     The following diagram shows the only known c/5 diagonal spaceship
   (Jason Summers, November 2000).
	.............**.....................................
	.....**....**.*.*...................................
	....***....****.....................................
	...**......**.....*.................................
	..**..**...*..*..*..................................
	.**.....*.......*..**...............................
	.**.*...****........................................
	....*...**..**.*....................................
	.....***....*.*.....................................
	......**...**..*....................................
	......*.....*.......................................
	.****.*..*..*...*...................................
	.***...*****..*******.*.............................
	*.*....*..........*..**.............................
	***.*...*...*.....***...............................
	.......*.*..*.......**..............................
	.*...*.....**........**..*.*........................
	....*.......*........***.*.***......................
	...*........***......*....*.........................
	.....*......*.*.....*.*.............................
	.....*......*.**...*....*...........................
	.............*.****...*.....*..*....................
	............**..**.*.*...*.***......................
	.................*......*..***...***................
	....................*..*......**....................
	................**....*..*..........**..............
	..................*.............*...*...............
	................**....**........*...................
	.................*...***........*.*.*.*.............
	.................*....**........*.....**............
	........................*........*..***.............
	.....................*..*........*........*.........
	..........................****........**...*........
	.......................*......**......**...*........
	.......................*....*............*..........
	.......................*...............*............
	.........................**.*.*.......*..*..........
	.........................*....*.........***.........
	............................***.**..*...*...*.**....
	.............................*..**.*.....*...*..*...
	.....................................**..*...*......
	..................................*.**.**.*..**...*.
	...............................*.....*...*.......*.*
	................................**............**...*
	......................................*.......**....
	.......................................***...**..*..
	......................................*..*.***......
	......................................*....**.......
	.......................................*............
	..........................................*..*......
	.........................................*..........
	..........................................**........

: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 {spaceship}s found
   by himself, Dean Hickerson and Hartmut Holzwart.  Bell produced an
   addendum covering more recent developments in 1996.

: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, particulary 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}.  For an example
   of a much larger spark see {Schick engine}.

:spark coil: (p2)  Found in 1971.
	**....**
	*.*..*.*
	..*..*..
	*.*..*.*
	**....**

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

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

: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 {block}s and {blinker}s (often referred to collectively
   as {blonk}s) in a ratio of about 2:1.  Much later it will be
   dominated by simple {infinite growth} patterns (presumably mostly
   {switch engine}s).  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.

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

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

:spider: (c/5 orthogonally, p5)  This is the smallest known c/5
   {spaceship}, and was found by David Bell in April 1997.  Its
   side {spark}s have proved very useful in constructing c/5
   {puffer}s, including {rake}s.  See also {pre-pulsar}.
	......*...***.....***...*......
	...**.*****.**...**.*****.**...
	.*.**.*.....*.*.*.*.....*.**.*.
	*...*.*...*****.*****...*.*...*
	....***.....**...**.....***....
	.*..*.***.............***.*..*.
	...*.......................*...

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

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

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

:squirter: = {pipsquirter}

:S-spiral: = {big S}

:stable:  A pattern is said to be stable if it is a {parent} of itself.
   See {still life}.

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

:stamp collection:  A collection of {oscillator}s (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.

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

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

: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 necessarily well-defined, because the eater may have more
   than one eating action.

:step:  Another term for a {generation}.  This term is particularly
   used in describing {conduit}s.  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 {oscillator}s with only
   three cells in the {rotor}.  The others are {1-2-3} and {cuphook}.
	...*....
	..*.*.**
	..*.**.*
	**......
	.*.*.**.
	.*.*..*.
	..*..*..
	...**...

: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
   single still life only if its {island}s cannot be divided into two
   nonempty sets both of which are stable in their own right.  Compare
   {pseudo still life}.
     The requirement that a still life not be decomposable into two
   separate stable patterns may seem a bit arbitrary, as it does not
   rule out the possibility that it might be decomposable into more
   than two.  This is shown by the patterns in the following diagram,
   both found by Gabriel Nivasch in July 2001.  On the left is a 32-cell
   pattern that can be broken down into three stable pieces but not into
   two.  On the right is a 34-cell pattern that can be broken down into
   four stable pieces but not into two or three.  (Note that, as a
   consequence of the Four-Colour Theorem, four is as high as you need
   ever go.)  It is arguable that patterns like these ought not to be
   considered as single still lifes.
	......**...........**.
	..*.*..*......**.*..*.
	.*.**.*.......*.**.*..
	.*....**...........**.
	**.**.........*.**...*
	...**.**....***.**.**.
	**....*....*.......*..
	.*.**.*.....***.**.*..
	*..*.*........*.*.*...
	**....................
     Still lifes have been enumerated by Conway (4-7 bits), Robert
   Wainwright (8-10 bits), Dave Buckingham (11-13 bits), Peter Raynham
   (14 bits) and Mark Niemiec (15-24 bits).  The resulting figures are
   shown below.  (These figures shouldn't be affected by the above
   discussion of the strict definition of "still life", because it is
   unlikely that there are any doubtful cases with much less than 32
   cells.)
	-------------
	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
	-------------

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

: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}.

:super beehive: = {honeycomb}

:superfountain: (p4)  This {sparker} was found by Noam Elkies in
   February 1998 (shown here with a slightly smaller {stator}).
   The resulting {spark} is more isolated than in the {fountain}.
	...............**......**......**..**.........
	.........**.....*......*.....*..*..*..*.**....
	....*....*.*.***....**.*.....**.....***.*.*...
	...*.*.....*.*.....*..*........*****....*..*..
	....*.....*..*....*.*......****..*...**..*.*..
	....*.......****..*.**....*....*****...*.*..**
	....***...*.....*.*..*....**..*...*..**.*.*.*.
	........**..*.**.*.**....**..*....*......**.*.
	....*...*......*.*...**.**...****....**.*..*..
	...*.....*.*.....*...*.*.*****.*......*.***...
	....*...***.....*....*..........***..*........
	....***.**..**..*..****..*.*.**.*.*..*.**.....
	*...*.........*...**.**.*..*......*..*..*.....
	....***.**..**..*..*...***......**....**......
	....*...***.....*...*...*.....................
	...*.....*.*.....*.....*...*..................
	....*...*......*.*..***...**..................
	........**..*.**.*.*...**.....................
	....***...*.....*..*.*...***..................
	....*.......****...*.****..*..................
	....*.....*..*......*....*....................
	...*.*.....*.*........*..**...................
	....*....*.*.***.....**.......................
	.........**.....*.............................
	...............**.............................

: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 {tub}s.  (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 {boat}s.  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.
	.**..........................................................
	*..*...*...*...*...*...*...*...*...*...*...*...*...*...*...*.
	....*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*
	*..*...*...*...*...*...*...*...*...*...*...*...*...*...*...*.
	.***.........................................................
	..**.........................................................
	..**.........................................................
	...*.........................................................
	...*.........................................................
	...*.........................................................
	...*.........................................................
	...*.........................................................
	...*.........................................................
	...*.........................................................
	..**.........................................................
	..**.........................................................
	.***.........................................................
	*..*...*...*...*...*...*...*...*...*...*...*...*...*...*...*.
	....*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*
	*..*...*...*...*...*...*...*...*...*...*...*...*...*...*...*.
	.**..........................................................

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

:swan: (c/4 diagonally, p4)  A diagonal {spaceship} producing some
   useful sparks (see {boatstretcher} for one simple use).  Found
   by Tim Coe in February 1996.
	.*..........**..........
	*****......**...........
	*..**........*.......**.
	..**.*.....**......***.*
	...........**...*.**....
	.....*.*......**........
	..........***.*....*....
	.......***...*....*.....
	........*.......*.......
	........*......*........
	........................
	...........*............

:switch engine:  The following pattern, which in itself is unstable,
   but which can be used to make c/12 diagonal {puffer}s and
   {spaceship}s.
	.*.*..
	*.....
	.*..*.
	...***
     The switch engine was discovered by Charles Corderman in 1971.
   He also found the two basic types of stabilized switch engine:
   a p288 block-laying type (the more common of the two) and p384
   glider-producing type.  These two puffers are the most {natural}
   infinite growth patterns in Life, being the only ones ever seen
   to occur from random starting patterns.
     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}.  See also {Cordership}
   and {ark}.

:synthesis: = {glider synthesis}

:T: = {T-tetromino}

:table:  The following {induction coil}.
	****
	*..*

:table on table: (p1)
	*..*
	****
	....
	****
	*..*

:tag: = {tagalong}

:tagalong:  An object which is not a {spaceship} in its own right, but
   which can be attached to one or more spaceships to form a larger
   spaceship.  For examples see {Canada goose}, {fly}, {pushalong},
   {sidecar} and {sparky}.  See also {Schick engine}, which consists of
   a tagalong attached to two LWSS (or similar).

:tail spark:  A {spark} at the back of a spaceship.  For example, the
   1-bit spark at the back of a {LWSS}, {MWSS} or {HWSS} in their less
   dense phases.

:tame:  To {perturb} a {dirty} reaction using other patterns so as to
   make it {clean} and hopefully useful.  Or to make a reaction work
   which would otherwise fail due to unwanted products which interfere
   with the reaction.

:taming:  See {tame}.

:teardrop:  The following {induction coil}, or the formation of two
   beehives that it evolves into after 20 generations.  (Compare
   {butterfly}, where the beehives are five cells further apart.)
	***.
	*..*
	*..*
	.**.

:technician: (p5)  Found by Dave Buckingham, January 1973.
	.....*.....
	....*.*....
	....**.....
	..**.......
	.*...***...
	*..**...*.*
	.**....*.**
	...*.*.*...
	...*...*...
	....***....
	......*.*..
	.......**..

:technician finished product: = {technician}

:teeth:  A 65-cell quadratic growth pattern found by Nick Gotts in March
   2000.  This (and a related 65-cell pattern which Gotts found at about
   the same time) beat the record previously held by {mosquito5} for
   smallest population known to have superlinear growth.  Now superceded
   by {catacryst} and {metacatacryst}.

:ternary reaction:  Any reaction between three objects.  In particular,
   a reaction in which two gliders from one stream and one glider from
   a crossing stream of the same period annihilate each other.  This
   can be used to combine two glider guns of the same period to produce
   a new glider gun with double the period.

:test tube baby: (p2)
	**....**
	*.*..*.*
	..*..*..
	..*..*..
	...**...

:tetraplet:  Any 4-cell {polyplet}.

:tetromino:  Any 4-cell {polyomino}.  There are five such objects,
   shown below.  The first is the {block}, the second is the
   {T-tetromino} and the remaining three rapidly evolve into
   {beehive}s.
	**......***......****......***......**.
	**.......*...................*.......**

:The Recursive Universe:  A popular science book by William
   Poundstone (1985) dealing with the nature of the universe,
   illuminated by parallels with the game of Life.  This book
   brought to a wider audience many of the results that first
   appeared in {LifeLine}.  It also outlines the proof of the
   existence of a {universal constructor} in Life first given
   in {Winning Ways}.

:thunderbird: (stabilizes at time 243)
	***
	...
	.*.
	.*.
	.*.

:tick: = {generation}

:tie:  A term used in naming certain {still life}s (and the {stator}
   part of certain {oscillator}s).  It indicates that the object
   consists of two smaller objects joined point to point, as in
   {ship tie boat}.

:time bomb:  The following pattern by Doug Petrie, which is really
   just a glider-producing {switch engine} in disguise.  See
   {infinite growth} for some better examples of a similar nature.
	.*...........**
	*.*....*......*
	.......*....*..
	..*..*...*..*..
	..**......*....
	...*...........

:titanic toroidal traveler:  The {superstring} with the following
   repeating segment.  The front part becomes p16, but the eventual
   fate of the detatched back part is unknown.
	******
	***...

:TL: = {traffic light}

:T-nosed p4: (p4)  Found by Robert Wainwright in October 1989.  See also
   {filter}.
	.....*.....
	.....*.....
	....***....
	...........
	...........
	...........
	...*****...
	..*.***.*..
	..*.*.*.*..
	.**.*.*.**.
	*..**.**..*
	**.......**

:T-nosed p6: (p6)  Found by Achim Flammenkamp in September 1994.
   There is also a much larger and fully symmetric version found
   by Flammenkamp in August 1994.
	......**...**......
	......*.*.*.*......
	.......*...*.......
	...................
	..*.*.*.....*.*.*..
	***.*.**...**.*.***
	..*.*.*.....*.*.*..
	...................
	.......*...*.......
	......*.*.*.*......
	......**...**......

:toad: (p2)  Found by Simon Norton, May 1970.  This is the second most
   common {oscillator}, although {blinker}s are more than a hundred
   times more frequent.
	.***
	***.

:toad-flipper:  A {toad} {hassler} that works in the manner of the
   following example.  Two {domino} {sparker}s, here {pentadecathlon}s,
   apply their {spark}s to the toad in order to flip it over.  When the
   sparks are applied again it is flipped back.  Either or both domino
   sparkers can be moved down two spaces from the position shown and
   the toad-flipper will still work, but because of symmetry there are
   really only two different types.  Compare {toad-sucker}.
	.*..............*.
	.*..............*.
	*.*............*.*
	.*..............*.
	.*......*.......*.
	.*......**......*.
	.*......**......*.
	*.*......*.....*.*
	.*..............*.
	.*..............*.

:toad-sucker:  A {toad} {hassler} that works in the manner of the
   following example.  Two {domino} {sparker}s, here {pentadecathlon}s,
   apply their {spark}s to the toad in order to shift it.  When the
   sparks are applied again it is shifted back.  Either or both domino
   sparkers can be moved down two spaces from the position shown and the
   toad-sucker will still work, but because of symmetry there are really
   only three different types.  Compare {toad-flipper}.
	.*................
	.*..............*.
	*.*.............*.
	.*.............*.*
	.*......*.......*.
	.*......**......*.
	.*......**......*.
	*.*......*......*.
	.*.............*.*
	.*..............*.
	................*.

:toaster: (p5)  Found by Dean Hickerson, April 1992.
	....*......**..
	...*.*.**..*...
	...*.*.*.*.*...
	..**.*...*.**..
	*...**.*.**...*
	...*.......*...
	...*.......*...
	*...**.*.**...*
	..**.*...*.**..
	...*.*.*.*.*...
	...*.*.**..*...
	....*......**..

:total aperiodic:  Any finite pattern which evolves in such a way that
   no cell in the Life plane is eventually periodic.  The first example
   was found by Bill Gosper in November 1997.  A few days later he found
   the following much smaller example consisting of three copies of a
   p12 {backrake} by Dave Buckingham.
	.........................................*.................
	........................................***................
	.......................................**.*.....*..........
	.......................................***.....***.........
	........................................**....*..**...***..
	..............................................***....*..*..
	........................................................*..
	........................................................*..
	........................................................*..
	........................................***............*...
	........................................*..*...............
	........................................*..................
	........................................*..................
	.........................................*.................
	...........................................................
	...........................................................
	...........................................................
	...........................................................
	...........................................................
	...........................................................
	......................................***..................
	......................................*..*...........*.....
	......................................*.............***....
	......................................*............**.*....
	......................................*............***.....
	.......................................*............**.....
	...........................................................
	...........................................................
	...................................***.....................
	..................................*****....................
	..................................***.**.......**.....*..*.
	.....................................**.......****........*
	..............................................**.**...*...*
	................................................**.....****
	...........................................................
	...........................................................
	....................*......................................
	.....................*.....................................
	.**.............*....*................................***..
	****.............*****..................................*..
	**.**...................................................*..
	..**...................................................*...
	....................................*......................
	.....................................*.....................
	.....................**..........*...*.....................
	......................**..........****...............**....
	.....................**...........................***.**...
	.....................*............................*****....
	...................................................***.....
	...........................................................
	......................**...................................
	.............****....****..................................
	............*...*....**.**.................................
	.*****..........*......**..................................
	*....*.........*...........................................
	.....*.....................................................
	....*......................................................

:T-pentomino:  Conway's name for the following {pentomino}, which is a
   common {parent} of the {T-tetromino}.
	***
	.*.
	.*.

:track:  A path made out of {conduit}s, often ending where it begins
   so that the active object is cycled forever, forming an {oscillator}
   or a {gun}.

:traffic circle: (p100)
	.....................**....**...................
	.....................*.*..*.*...................
	.......................*..*.....................
	......................**..**....................
	.....................***..***...................
	.......................*..*.....................
	...............................*................
	..............................*.**..............
	..................................*.............
	..........................*...*..*.*............
	..........................*.....*..*............
	..........................*......**.............
	.........**.....................................
	........*..*..........***...***.................
	.......*.*.*....................................
	......***.*...............*.....................
	......***.................*.....................
	..........................*.....................
	............***.................................
	**..*................***........................
	*..**.....*.....*...............................
	.*****....*.....*..*.....*.................*..**
	..........*.....*..*.....*.................**..*
	...................*.....*.......***......*****.
	.*****......***.................................
	*..**................***.......*.....*..........
	**..*..........................*.....*....*****.
	...............................*.....*.....**..*
	...........................................*..**
	.................................***............
	.......................................**.......
	......................................***.......
	.....................................*.**.......
	....................................*.*.........
	....................***.............*..*........
	.....................................**.........
	.............**....*..*.........................
	............*..*................................
	............*.*.*...............................
	.............*..*...............................
	.................*..............................
	..............*.*...............................
	.....................*..*.......................
	...................***..***.....................
	....................**..**......................
	.....................*..*.......................
	...................*.*..*.*.....................
	...................**....**.....................

:traffic jam:  Any {traffic light} {hassler}, such as {traffic circle}.
   The term is also applied to the following reaction, used in most
   traffic light hasslers, in which two traffic lights interact in such
   a way as to reappear after 25 generations with an extra 6 spaces
   between them.
	..***...........
	...........***..
	*.....*.........
	*.....*..*.....*
	*.....*..*.....*
	.........*.....*
	..***...........
	...........***..

:traffic light: (p2)  A common formation of four blinkers.
	..***..
	.......
	*.....*
	*.....*
	*.....*
	.......
	..***..

:trans-beacon on table: (p2)
	....**
	.....*
	..*...
	..**..
	......
	****..
	*..*..

:trans-boat with tail: (p1)
	**...
	*.*..
	.*.*.
	...*.
	...**

:trans-loaf with tail: (p1)
	.*....
	*.*...
	*..*..
	.**.*.
	....*.
	....**

:transparent block reaction:  A certain reaction between a block and
   a {Herschel} {predecessor} in which the block reappears in its
   original place some time later, the reaction having effectively
   passed through it.  This reaction was found by Dave Buckingham in
   1988.  It has been used in some {Herschel conduit}s, and in the
   {gunstar}s.  Because the reaction involves a Herschel predecessor
   rather than an actual Herschel, the following diagram shows instead
   a {B-heptomino} (which by itself would evolve into a block and a
   Herschel).
	*.............
	**..........**
	.**.........**
	**............

:transparent debris effect: = {transparent block reaction}

:trice tongs: (p3)  Found by Robert Wainwright, February 1982.  In terms
   of its 7x7 {bounding box} this ties with {jam} as the smallest p3
   {oscillator}.
	..*....
	..***..
	**...*.
	.*.*.*.
	.*.....
	..**..*
	.....**

:triomino:  Either of the two 3-cell {polyomino}es.  The term is
   rarely used in Life, since the two objects in question are simply
   the {blinker} and the {pre-block}.

:triple caterer: (p3)  Found by Dean Hickerson, October 1989.  Compare
   {caterer} and {double caterer}.
	.....**.........
	....*..*..**....
	....**.*...*....
	......*.***....*
	..***.*.*....***
	.*..*..*....*...
	*.*..*...*..**..
	.*..............
	..**.**.**.**...
	...*...*...*....
	...*...*...*....

:triplet:  Any 3-cell {polyplet}.  There are 5 such objects, shown
   below.  The first two are the two {triomino}es, and the other three
   vanish in two generations.
	*..................*.......*.......*..
	**......***......**.......*.*.......*.
	.....................................*

:tripole: (p2)  The {barberpole} of length 3.
	**....
	*.*...
	......
	..*.*.
	.....*
	....**

:tritoad: (p3)  Found by Dave Buckingham, October 1977.
	.........**.......
	.........*........
	..........*..**...
	.......***.*..*...
	......*....**.*.**
	......*.**..*.*.**
	...**.*...**..*...
	...*..**...*.**...
	**.*.*..**.*......
	**.*.**....*......
	...*..*.***.......
	...**..*..........
	........*.........
	.......**.........

:true:  Opposite of {pseudo}.  A {gun} emitting a period n stream of
   {spaceship}s (or {rake}s) is said to be a true period n gun if
   its mechanism oscillates with period n.  (The same distinction
   between true and pseudo also exists for {puffer}s.)  True period
   n guns are known to exist for all periods greater than 61 (see
   {My Experience with B-heptominos in Oscillators}), but only a
   few smaller periods have been achieved, namely 22, 24, 30, 44,
   46, 48, 50, 54, 55, 56 and 60.  (Credits for these small period
   guns are: p30, p46 and p60 by Bill Gosper in 1970-1971, p44 by
   Dave Buckingham in 1992, p50 by Dean Hickerson in 1996, p24 and p48
   by Noam Elkies in 1997, p54 and p56 by Dieter Leithner in early 1998,
   p55 by Stephen Silver in late 1998 and p22 by David Eppstein in
   2000.)
     The following diagram shows the p22 gun (David Eppstein, August
   2000, using two copies of a p22 oscillator found earlier the same
   day by Jason Summers).
	..................**.........................
	...................*.......*.................
	...................*.*..............**.......
	....................**............**..*......
	........................***.......**.**......
	........................**.**.......***......
	........................*..**............**..
	.........................**..............*.*.
	...................................*.......*.
	...........................................**
	.............................................
	**.......................*...................
	.*.....................*.*...................
	.*.*.............***....**...................
	..**...*........*...*........................
	......*.**......*....*.......................
	.....*....*......**.*.........*..............
	......*...*........*...**......*.............
	.......***.............*.*...***.............
	.........................*...................
	.........................**..................

:T-tetromino:  The following common {predecessor} of a {traffic light}.
	***
	.*.

:tub: (p1)
	.*.
	*.*
	.*.

:tubstretcher:  See {boatstretcher}.

:tub with tail: (p1)
	.*...
	*.*..
	.*.*.
	...*.
	...**

:tubber: (p3)  Found by Robert Wainwright before June 1972..
	....*.*......
	....**.*.....
	.......***...
	....**....*..
	**.*..**..*..
	.*.*....*.**.
	*...*...*...*
	.**.*....*.*.
	..*..**..*.**
	..*....**....
	...***.......
	.....*.**....
	......*.*....

:tugalong: = {tagalong}

:tumbler: (p14)  The smallest known p14 {oscillator}.  Found by
   George Collins in 1970.
	.*.....*.
	*.*...*.*
	*..*.*..*
	..*...*..
	..**.**..

:tumbling T-tetson: (p8)  A {T-tetromino} {hassle}d by two {figure-8}s.
   Found by Robert Wainwright.
	.***.................
	*..................**
	*...*............*.**
	*..*.*..........*....
	..*.*..*...........*.
	...*...*.......**.*..
	.......*.......**....
	....***....*.........
	.........**..........
	...........*.........

:turning toads: (p4 wick)  Found by Dean Hickerson, October 1989.
	..............**.....**.....**.....**.....**..............
	.......*.....*......*......*......*......*................
	......**...*....*.*....*.*....*.*....*.*....*.*.*.**......
	..**.*.***.*..**..*..**..*..**..*..**..*..**..*..*..*.**..
	*..*.**.........................................*****.*..*
	**.*..............................................**..*.**
	...*..................................................*...
	...**................................................**...

:turtle: (c/3 orthogonally, p3)  Found by Dean Hickerson.
	.***.......*
	.**..*.**.**
	...***....*.
	.*..*.*...*.
	*....*....*.
	*....*....*.
	.*..*.*...*.
	...***....*.
	.**..*.**.**
	.***.......*

:twin bees shuttle: (p46)  Found by Bill Gosper in 1971, this is the
   basis of all known p46 oscillators, and so of all known {true} p46
   {gun}s (see {new gun} for an example).  There are numerous ways to
   stabilize the ends, two of which are shown in the diagram.  On the
   left is David Bell's {double block reaction} (which results in a
   shorter, but wider, shuttle than usual), and on the right is the
   stabilization by a single block.  This latter method produces a
   very large {spark} which is useful in a number of ways (see, for
   example, {metamorphosis}).  Adding a symmetrically placed block
   below this one suppresses the spark.  See also {p54 shuttle}.
	.**........................
	.**........................
	...........................
	...............*...........
	**.............**........**
	**..............**.......**
	...........**..**..........
	...........................
	...........................
	...........................
	...........**..**..........
	**..............**.........
	**.............**..........
	...............*...........
	...........................
	.**........................
	.**........................

:twinhat: (p1)  See also {hat} and {sesquihat}.
	..*...*..
	.*.*.*.*.
	.*.*.*.*.
	**.*.*.**
	....*....

:twin peaks: = {twinhat}

:twirling T-tetsons II: (p60)  Found by Robert Wainwright.  This is
   a {pre-pulsar} {hassle}d by {killer toads}.
	.......**...**..........
	......*.......*.........
	.........*.*............
	.......**...**..........
	........................
	........................
	........................
	.....................***
	....................***.
	.............*..........
	***.........***.........
	.***....................
	....................***.
	.....................***
	........................
	.***....................
	***.........***.........
	.............*..........
	........................
	........................
	..........**...**.......
	............*.*.........
	.........*.......*......
	..........**...**.......

:two eaters: (p3)  Found by Bill Gosper, September 1971.
	**.......
	.*.......
	.*.*.....
	..**.....
	.....**..
	.....*.*.
	.......*.
	.......**

:two pulsar quadrants: (p3)  Found by Dave Buckingham, July 1973.
   Compare {pulsar quadrant}.
	....*....
	....*....
	...**....
	..*......
	*..*..***
	*...*.*..
	*....*...
	.........
	..***....

:underpopulation:  Death of cell caused by it having fewer than two
   {neighbour}s.

:unit Life cell:  A rectangular pattern, of size greater than 1x1,
   that can simulate Life in the following sense.  The pattern
   by itself represents a dead Life cell, and some other pattern
   represents a live Life cell.  When the plane is tiled by these
   two patterns (which then represent the state of a whole Life
   universe) they evolve, after a fixed amount of time, into another
   tiling of the plane by the same two patterns which correctly
   represents the Life generation following the one they initially
   represented.  It is usual to use capital letters for the simulated
   things, so, for example, for the first known unit Life cell
   (constructed by David Bell in January 1996), one Generation is
   5760 generations, and one Cell is 500x500 cells.

:universal computer:  A computer that can compute anything that is
   computable.  (The concept of computability can be defined in terms
   of Turing machines, or by Church's lambda calculus, or by a number
   of other methods, all of which can be shown to lead to equivalent
   definitions.)  The relevance of this to Life is that both Bill
   Gosper and John Conway proved early on that it is possible to
   construct a universal computer in the Life universe.  (To prove
   the universality of a {cellular automaton} with simple rules was
   in fact Conway's aim in Life right from the start.)  Conway's proof
   is outlined in {Winning Ways}, and also in {The Recursive Universe}.
     No universal Life computer has ever been built in practice, because
   it would be enormous, even with the improvements that have since been
   devised.
     See also {sliding block memory} and {universal constructor}.

:universal constructor:  A pattern that is capable of constructing
   almost any pattern that has a {glider synthesis}.  This definition is
   a bit vague.  A precise definition seems impossible because it has
   not been proved that all possible glider fleets are constructible.
   In any case, a universal constructor ought to be able to construct
   itself in order to qualify as such.  An outline of Conway's proof
   that such a pattern exists can be found in {Winning Ways}, and also
   in {The Recursive Universe}.  The key mechanism for the production
   of gliders with any given path and timing is known as side-tracking,
   and is based on the {kickback reaction}.  A universal constructor
   designed in this way can also function as a universal destructor
   - it can delete almost any pattern that can be deleted by gliders.
     A universal constructor is most useful when attached to a
   {universal computer}, which can be programmed to control the
   constructor to produce the desired pattern of gliders.  In what
   follows I will assume that a universal constructor always includes
   this computer.
     The existence of a universal constructor/destructor has a number of
   theoretical consequences.
     For example, the constructor could be programmed to make copies of
   itself.  This is a {replicator}.
     The constructor could even be programmed to make just one copy
   of itself translated by a certain amount and then delete itself.
   This would be a (very large, very high period) {spaceship}.  Any
   translation is possible (except that it must not be too small), so
   that the spaceship could travel in any direction.  It could also
   travel slower than any given speed, since we could program it to
   perform some time-wasting task (such as repeatedly constructing and
   deleting a block) before copying itself.  Of course, we could also
   choose for it to leave some debris behind, thus making a {puffer}.
     It is also possible to show that the existence of a universal
   constructor implies the existence of a {stable} {reflector}.  This
   proof is not so easy, however, and is no longer of much significance
   now that explicit examples of such reflectors are known.

:universal destructor:  See {universal constructor}.

:unix: (p6)  Two {block}s eating a {long barge}.  This is a useful
   {sparker}, found by Dave Buckingham in February 1976.  The name
   derives from the fact that it was for some time the mascot of the
   Unix lab of the mathematics faculty at the University of Waterloo.
	.**.....
	.**.....
	........
	.*......
	*.*.....
	*..*..**
	....*.**
	..**....

:up boat with tail: = {trans-boat with tail}

:U-pentomino:  Conway's name for the following {pentomino}, which
   rapidly dies.
	*.*
	***

:vacuum:  Empty space.  That is, space containing only dead {cell}s.

:Venetian blinds:  The p2 {agar} obtained by using the pattern O..O to
   tile the plane.

:very long: = {long long}

:very long house:  The following {induction coil}.
	.*****.
	*..*..*
	**...**

:volatility:  The volatility of an {oscillator} is the size (in cells)
   of its {rotor} divided by the sum of the sizes of its rotor and its
   {stator}.  In other words, it is the proportion of cells involved in
   the oscillator which actually oscillate.  For many periods there are
   known oscillators with volatility 1, see for example {Achim's p16},
   {figure-8}, {Kok's galaxy}, {mazing}, {pentadecathlon}, {phoenix},
   {relay}, {smiley} and {tumbler}.  The smallest period for which the
   existence of such statorless oscillators is undecided is 3, although
   Dean Hickerson showed in 1994 that there are p3 oscillators with
   volatility arbitrarily close to 1 (as is the case for all but
   finitely many periods, because of the possibility of feeding the
   gliders from a {true} period n {gun} into an {eater}).
     The term "volatility" is due to Robert Wainwright.  See also
   {strict volatility}.

:volcano:  Any of a number of p5 oscillators which produce
   sparks.  See {lightweight volcano}, {middleweight volcano}
   and {heavyweight volcano}.

:V-pentomino:  Conway's name for the following {pentomino}, a {loaf}
   {predecessor}.
	*..
	*..
	***

:washerwoman: (2c/3 p18 fuse)  A {fuse} by Earl Abbe.
	*.......................................................
	**....*.....*.....*.....*.....*.....*.....*.....*.....*.
	***..*.*...*.*...*.*...*.*...*.*...*.*...*.*...*.*...*.*
	**....*.....*.....*.....*.....*.....*.....*.....*.....*.
	*.......................................................

:washing machine: (p2)  Found by Robert Wainwright before June 1972.
	.**.**.
	*.**..*
	**....*
	.*...*.
	*....**
	*..**.*
	.**.**.

:wasp: (c/3 orthogonally, p3)  The following {spaceship} which produces
   a {domino} {spark} at the back.  It is useful for {perturb}ing other
   objects.  Found by David Bell, March 1998.
	..........**.**.......
	........**.*.**.**....
	.....***.*..***..****.
	.***....***.....*....*
	*.*.*.***.*........**.
	*.*.*.****............
	.*.*....*..*..........
	..........*...........
	..*...................
	..*...................

:wavefront: (p4)  Found by Dave Buckingham, 1976 or earlier.
	........**...
	........*....
	.........*...
	........**...
	.....**...**.
	....*..***..*
	....*.....**.
	.....*...*...
	**.*.*...*...
	*.**.*.**....
	....*.*......
	....*.*......
	.....*.......

:waveguide:  See {superstring}.

:weekender: (2c/7 orthogonally, p7)  Found by David Eppstein in
   January 2000.  In April 2000 Stephen Silver found a tagalong for a
   pair of weekenders.  At present, n weekenders pulling n-1 tagalongs
   constitute the only known {spaceship}s of this speed or period.
	.*............*.
	.*............*.
	*.*..........*.*
	.*............*.
	.*............*.
	..*...****...*..
	......****......
	..****....****..
	................
	....*......*....
	.....**..**.....

:weld:  To join two or more {still life}s or {oscillator}s together.
   This is often done in order to fit the objects into a smaller space
   than would otherwise be possible.  The simplest useful example is
   probably the {integral sign}, which can be considered as a pair of
   welded {eater1}s.

:Wheels, Life, and other Mathematical Amusements:  One of Martin
   Gardner's books (1983) that collects together material from his
   column in Scientific American.  The last three chapters of this
   book contain all the Life stuff.

:why not: (p2)  Found by Dave Buckingham, July 1977.
	...*...
	...*.*.
	.*.....
	*.*****
	.*.....
	...*.*.
	...*...

:wick:  A stable or oscillating linearly repeating pattern that can be
   made to burn at one end.  See {fuse}.

:wickstretcher:  A {spaceship}-like object which stretches a {wick}
   that is fixed at the other end.  The wick here is assumed to be
   in some sense connected, otherwise most puffers would qualify as
   wickstretchers.  The first example of a wickstretcher was found in
   October 1992 (front end by Hartmut Holzwart and back end by Dean
   Hickerson) and stretches {ants} at a speed of c/4.  This is shown
   below with an improved back end found by Hickerson the following
   month.
	.................**..............................
	.............**....*.............................
	............***.*................................
	*.**..**...*...****.*.*....**.......**...........
	*....**..*........*.***....*....**.*..*.**.*.....
	*.**....**.**....*...........*...*.*.**.*.**.....
	......*.......*.............**.....*..*.*...**...
	.....*.........*.*....***...*....*..*.*.***...*..
	.....*.........*.*....***.**.*..**.*.*...*..**.*.
	......*.......*.............**.*...**....**....*.
	*.**....**.**....*..........*........**.*.*.**.**
	*....**..*........*.***........*...*...**.*..*.*.
	*.**..**...*...****.*.*.......*.*...**....*..*.*.
	............***.*..............*.....*.***....*..
	.............**....*.................*.*.........
	.................**...................*..........
   Diagonally moving c/4 wickstretchers have also been built (see
   {boatstretcher}).  In March 1999 Jason Summers constructed a very
   large c/12 wickstretcher using {switch engine} based puffers found
   earlier by Dean Hickerson.  The wick in this last case is the
   simplest possible one: a single line of diagonal cells.  In July
   2000 Summers also constructed a c/2 wickstretcher, stretching a
   p50 {traffic jam} wick.  This was based on an earlier (October
   1994) pattern by Hickerson.

:wicktrailer:  Any extensible {tagalong}, that is, one which can
   be attached to the back of itself, as well as to the back of a
   {spaceship}.  The number of generations which it takes for the
   tagalong to occur again in the same place is often called the
   period of the wicktrailer - this has little relation to the period
   of the tagalong units themselves.

:windmill: (p4)  Found by Dean Hickerson, November 1989.
	...........*......
	.........**.*.....
	.......**.........
	..........**......
	.......***........
	..................
	***...............
	...**..***.**.....
	..........*******.
	.*******..........
	.....**.***..**...
	...............***
	..................
	........***.......
	......**..........
	.........**.......
	.....*.**.........
	......*...........

:wing:  The following {induction coil}.  This is generation 2 of
   {block and glider}.
	.**.
	*..*
	.*.*
	..**

:Winning Ways:  A two-volume book (1982) by Elwyn Berlekamp, John
   Conway and Richard Guy on mathematical games.  The last chapter
   of the second volume concerns Life, and outlines a proof of the
   existence of a {universal constructor}.

:worker bee: (p9)  Found by Dave Buckingham in 1972.  Unlike the similar
   {snacker} this produces no {spark}s, and so is not very important.
   Like the snacker, the worker bee is extensible - it is, in fact, a
   finite version of the infinite oscillator which consists of six ON
   cells and two OFF cells alternating along a line.  Note that Dean
   Hickerson's new snacker ends also work here.
	**............**
	.*............*.
	.*.*........*.*.
	..**........**..
	................
	.....******.....
	................
	..**........**..
	.*.*........*.*.
	.*............*.
	**............**

:W-pentomino:  Conway's name for the following {pentomino}, a common
   {loaf} {predecessor}.
	*..
	**.
	.**

:x66:  (c/2 orthogonally, p4)  Found by Hartmut Holzwart, July 1992.
   Half of this can be escorted by a HWSS.  The name refers to the
   fact that every cell (live or dead) has at most 6 live neighbours
   (in contrast to {spaceship}s based on {LWSS}, {MWSS} or {HWSS}).
   In fact this spaceship was found by a search with this restriction.
	..*......
	**.......
	*..***..*
	*....***.
	.***..**.
	.........
	.***..**.
	*....***.
	*..***..*
	**.......
	..*......

:Xlife:  A popular freeware Life program that runs under the X Window
   System.  The main Life code was written by Jon Bennett, and the X
   code by Chuck Silvers.

:X-pentomino:  Conway's name for the following {pentomino}, a
   {traffic light} {predecessor}.
	.*.
	***
	.*.

:Y-pentomino:  Conway's name for the following {pentomino}, which
   rapidly dies.
	..*.
	****

:Z-hexomino:  The following {hexomino}.  The Z-hexomino features in
   the {pentoad}, and also in {Achim's p144}.
	**.
	.*.
	.*.
	.**

:Z-pentomino:  Conway's name for the following {pentomino}, which
   rapidly dies.
	**.
	.*.
	.**

:zweiback: (p30)  An oscillator in which two {HW volcano}es {hassle} a
   {loaf}.  This was found by Mark Niemiec in February 1995 and is too
   big to show here.

-----------------------------------------------------------------------

Bibliography.

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David I. Bell, "Speed c/3 Technology in Conway's Life", 17 December
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Elwyn R. Berlekamp, John H. Conway and Richard K. Guy, "Winning Ways
  for your Mathematical Plays, II: Games in Particular".  Academic
  Press, 1982.

David J Buckingham, "Some Facts of Life".  BYTE, December 1978.

Dave Buckingham, "My Experience with B-heptominos in Oscillators".
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David J. Buckingham and Paul B. Callahan, "Tight Bounds on Periodic Cell
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  Available at http://www.expmath.org/restricted/7/7.3/callahan.ps.gz .

Noam D. Elkies, "The still-Life density problem and its
  generalizations", pp228-253 of "Voronoi's Impact on Modern Science,
  Book I", P. Engel, H. Syta (eds), Institute of Mathematics,
  Kyiv 1998 = Vol.21 of Proc. Inst. Math. Nat. Acad. Sci. Ukraine,
  math.CO/9905194 (http://front.math.ucdavis.edu/math.CO/9905194).

Martin Gardner, "Wheels, Life, and other Mathematical Amusements".
  W. H. Freeman and Company, 1983.

R. Wm. Gosper, "Exploiting Regularities in Large Cellular Spaces".
  Physica 10D (1984) 75-80.

N. M. Gotts and P. B. Callahan, "Emergent structures in sparse fields of
  Conway's 'Game of Life'", in "Artificial Life VI: Procedings of the
  Sixth International Conference on Artificial Life", MIT Press, 1998.

Mark D Niemiec, "Life Algorithms".  BYTE, January 1979.

William Poundstone, "The Recursive Universe".  William Morrow and
  Company Inc., 1985.