Life Lexicon (L)
Author: Stephen A. Silver
Description: Part of Stephen Silver's Life Lexicon.

Introduction | Bibliography

1-9 | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

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

    ....OO....
    ...O..O...
    ...O..O...
    .OO....OO.
    O........O
    O........O
    .OO....OO.
    ...O..O...
    ...O..O...
    ....OO....

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

    ...OO.OO....
    ...OO.O...OO
    ........O..O
    .OOOOOO.OOO.
    O..O.O......
    OO...O.OO...
    ....OO.OO...

:large S = big S

:Lidka (stabilizes at time 29053) A methuselah found by Andrzej Okrasinski in July 2005.

    ..........OOO..
    ..........O....
    ..........O...O
    ...........O..O
    ............OOO
    ...............
    .O.............
    O.O............
    .O.............

The following variant, pointed out by David Bell, has two fewer cells and lasts two generations longer.

    ..........OOO..
    ...............
    ...........OO.O
    ............O.O
    ..............O
    ...............
    .O.............
    O.O............
    .O.............

: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 transition 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/XP: http://www.xs4all.nl/~jbontes/.

:LifeLab A shareware Life program by Andrew Trevorrow for the Macintosh (MacOS 8.6 or later): http://www.trevorrow.com/lifelab/.

:LifeLine A newsletter edited by Robert Wainwright from 1971 to 1973. During this period it was the main forum for discussions about Life. The newsletter 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 spaceships and oscillators. 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.

Although lifesrc itself is a command-line program, Jason Summers has made a GUI version called WinLifeSearch for Microsoft Windows.

The lifesrc algorithm is only useful for very small periods, as the amount of computing power required rises rapidly with increasing period. For most purposes, period 7 is the practical limit with current hardware.

Lifesrc is available from http://www.canb.auug.org.au/~dbell/ (source code only).

Compare gfind.

:light bulb (p2) Found in 1971.

    .OO.O..
    .O.OO..
    .......
    ..OOO..
    .O...O.
    .O...O.
    ..O.O..
    O.O.O.O
    OO...OO

The same rotor can be embedded in a slightly smaller stator like this:

    ...O.....
    .OOO.....
    O........
    OOOOOO...
    ......O..
    ..O...O..
    ..OO.O...
    ......OOO
    ........O

: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.

    ....OO..OO..OO..OO..OO..OO..OO..OO..OO..OO..OO..OO..OO....
    ....OO..OO..OO..OO..OO..OO..OO..OO..OO..OO..OO..OO..OO....
    ..........................................................
    ..OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO..
    .O......O...............................................O.
    O.OOOOO....OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO.O
    .O.....O................................................O.
    ..OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO..
    ..........................................................
    ....OO..OO..OO..OO..OO..OO..OO..OO..OO..OO..OO..OO..OO....
    ....OO..OO..OO..OO..OO..OO..OO..OO..OO..OO..OO..OO..OO....

: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 spaceships. (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 hivenudger and puff suppressor.

:line ship A spaceship in which the front end is a linestretcher, the line being eaten by the back end.

:linestretcher A wickstretcher that stretches a single diagonal line of cells. The first example was constructed by Jason Summers in March 1999; this was c/12 and used switch engine based puffers found earlier by Dean Hickerson. The first c/4 example was found by Hartmut Holzwart in November 2004.

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

    ....O....
    ..OOO....
    .O...OO..
    O.OO...O.
    .O...OO.O
    ..OO...O.
    ....OOO..
    ....O....

:loaf (p1)

    .OO.
    O..O
    .O.O
    ..O.

:loaflipflop (p15) Here four pentadecathlons hassle a loaf. Found by Robert Wainwright in 1990.

    ................O.................
    ...............OOO................
    ..................................
    ..................................
    ...............OOO................
    ..................................
    ...............O.O................
    ...............O.O................
    ..................................
    ...............OOO................
    ..................................
    ..................................
    ...............OOO................
    ................O.................
    ..................................
    .O..O.OO.O..O...............OO....
    OO..O....O..OO...OO.......O....O..
    .O..O.OO.O..O...O..O.....O......O.
    ................O.O.....O........O
    .................O......O........O
    ........................O........O
    .........................O......O.
    ..........................O....O..
    ............................OO....
    ..................OOO.............
    .................O...O............
    ................O.....O...........
    ..................................
    ...............O.......O..........
    ...............O.......O..........
    ..................................
    ................O.....O...........
    .................O...O............
    ..................OOO.............

:loaf on loaf = bi-loaf

:loaf siamese barge (p1)

    ..OO.
    .O..O
    O.O.O
    .O.O.
    ..O..

: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)

    .O...
    O.O..
    .O.O.
    ..O.O
    ...O.

:long boat (p1)

    .O..
    O.O.
    .O.O
    ..OO

:long bookend The following induction coil, longer than a bookend.

    ...OO
    O...O
    OOOO.

:long canoe (p1)

    ....OO
    .....O
    ....O.
    ...O..
    O.O...
    OO....

:long hat = loop

:long hook = long bookend

:long house = dock

:long integral (p1)

    ..OO
    .O.O
    .O..
    ..O.
    O.O.
    OO..

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

:long long barge (p1)

    .O....
    O.O...
    .O.O..
    ..O.O.
    ...O.O
    ....O.

:long long boat (p1)

    .O...
    O.O..
    .O.O.
    ..O.O
    ...OO

:long long canoe (p1)

    .....OO
    ......O
    .....O.
    ....O..
    ...O...
    O.O....
    OO.....

:long long ship (p1)

    OO...
    O.O..
    .O.O.
    ..O.O
    ...OO

:long long snake (p1)

    OO....
    O.O...
    ...O.O
    ....OO

:long shillelagh (p1)

    OO..OO
    O..O.O
    .OO...

:long ship (p1)

    OO..
    O.O.
    .O.O
    ..OO

:long sinking ship = long canoe

:long snake (p1)

    OO...
    O.O.O
    ...OO

:loop (p1)

    .OO..
    O..O.
    .O.O.
    OO.OO

:low-density 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.

    ..OO.O..O.OO..
    ..O........O..
    ...OO....OO...
    OOO..OOOO..OOO
    O..O......O..O
    .OO........OO.

:LWSS (c/2 orthogonally, p4) A lightweight spaceship, the smallest known orthogonally moving spaceship, and the second most common (after the glider). Found by Conway in 1970. See also MWSS and HWSS.

    .O..O
    O....
    O...O
    OOOO

:LWSS emulator = LW emulator

:LWTDS Life Worker Time Deficiency Syndrome. Term coined by Dieter Leithner to describe the problem of having to divide scarce time between Life and real life.

:LW volcano = toaster

1-9 | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z