In case you didn't know, there are a total of twelve LifeLine magazines, published quarterly from 1971 - 1973. I only have the first and second issues; the second is below:
Code: Select all
{2:1}
A QUARTERLY NEWSLETTER FOR ENTHUSIASTS OF JOHN CONWAY'S GAME OF LIFE
..................................................................
.........O.....OOOOO.OOOOO.OOOOO.O.....OOOOO.O...O.OOOOO..........
.........O.......O...O.....O.....O.......O...OO..O.O..............
.........O.......O...OOO...OOO...O.......O...O.O.O.OOO............
.........O.......O...O.....O.....O.......O...O..OO.O..............
.........OOOOO.OOOOO.O.....OOOOO.OOOOO.OOOOO.O...O.OOOOO..........
..................................................................
NUMBER 2 JUNE 1971
. Editor and Publisher - Robert T. Wainwright .
The response to LIFELINE Number One and Martin Gardner's announcement in the April issue of Scientific American regarding this endeavor has been overwhelming! More than 340 inquiries have been received from readers in many industrial organizations, schools, and universities in fourteen different countries 0 and mail is still flowing in. The administrative burden accounts for what may seem to some of you (especially the early respondents) an indifference on my part. Following the establishment of a mailing list of subscribers, I will attempt to answer many of your individual inquiries via LIFELINE, an informal but relatively rapid and specific response to your area of interest.
LIFELINE Number Two extends and refines the ideas presented in the first issue and incorporates information from many of your responses. The main objective of this issue is to further the base of classification and common definition using your own developments as examples.
The fates of the unknown heptominoes E, F, H, and I were first sent in by Robert Bison of Hopewell Jct., N.Y. and subsequently confirmed by David W. Bray of Syracuse, N.Y., Charles L. Corderman of Winchester, Mass., Gary Goodman of Stanford, Calif., Stephen B. Gray of Los Angeles, Calif., Maxwell E. Manowski of New York (FPO), and Don Woods of Natick, Mass. The histories and final 'census' (an apt term coined by Woods) of these four interesting Life objects are shown here:
{Figure 2.1}
+------------------------------------------------------------------+
| Fates of the last four unknown heptominoes |
+------------------------------------------------------------------+
| Heptomino | Age | Census |
+-----------+-----+------------------------------------------------+
| E | 343 | 5 blocks, 4 beehives, 1 blinker, and 1 glider |
| | | |
| F | 437 | 3 blocks, 1 tub, 1 boat, 1 beehive, 1 pond |
| | | 7 blinkers (1+3/4 traffic lights), and 1 glider|
| | | |
| H and I | 247 | 3 blocks, 1 boat, 1 beehive, 1 ship, |
| | | and 2 gliders |
+-----------+-----+------------------------------------------------+
To save unnecessary effort on the part of those receiving issue Number One later than April, I appended a note to the effect that these results were known. Like seven other heptominoes (No. 1, Table 2), they all give birth to one or more gliders during their history. Interestingly, the direction of glider escape in all cases is to the northeast from the initial positions originally shown.
With many more objects being discovered in Classes I, II, and V it becomes tempting to subclassify them within the system proposed in issue Number One. The writer had previously arranged all Life objects into six primary classes based upon characteristics of their history and now proposes further definition (subclassification).
{2:2}
{Figure 2.2}
+---------------------------------------------------------------------------+
| AN EXPANDED CLASSIFICATION SYSTEM FOR FINITE LIFE OBJECTS |
+---------------+-----------------------------+--------+--------------+-----+
| Primary Class | Subclassified According To: |Subclass| Example* |Size |
+---------------+---------+-------------------+--------+--------------+-----+
| | | 2-way orthogonal, | |block | 4 |
| | | 2-way diagonal, | I.A | | |
| | | 90@ rotational | | | |
| | +-------------------+--------+--------------+-----+
| | | 2-way orthogonal, | I.B.1 |beehive | 6 |
| | | 180@ rotational | | | |
| | +-------------------+--------+--------------+-----+
| | | 2-way diagonal, | I.B.2 |ship | 6 |
|I-Still Lifes |Degree of| 180@ rotational | | | |
| |symmetry +-------------------+--------+--------------+-----+
| | | 90@ rotational | I.B.3 |spiral | 20 |
| | +-------------------+--------+--------------+-----+
| | | 1-way orthogonal | I.C.1 |hat | 9 |
| | +-------------------+--------+--------------+-----+
| | | 1-way diagonal | I.C.2 |boat | 5 |
| | +-------------------+--------+--------------+-----+
| | | 180@ rotational | I.C.3 |snake | 6 |
| | +-------------------+--------+--------------+-----+
| | | none | I.D |fishhook | 7 |
+---------------+---------+-------------------+--------+--------------+-----+
| | | flip-flops | II.A |blinker | 3 |
| | | (all period two) | | | |
| | +-------------------+--------+--------------+-----+
| | | billiard table | II.B |pinwheel | 35 |
| | | configurations | | | |
| | +-------------------+--------+--------------+-----+
|II-Oscillators | | inductors | II.C |tumbler | 16 |
| | +-------------------+--------+--------------+-----+
| | | pulsators | II.D |pentadecathlon| 12 |
| | +-------------------+--------+--------------+-----+
| | | shuttles | II.E |queen bee | 20 |
| | +-------------------+--------+--------------+-----+
| | | miscellaneous | II.F |M.I.T. osc. | 18 |
+---------------+---------+-------------------+--------+--------------+-----+
| |Motion of| orthogonal | III.A |lt. wt. s.s. | 8 |
|III-Spaceships |spaceship+-------------------+--------+--------------+-----+
| | | diagonal | III.B |glider | 5 |
+---------------+---------+-------------------+--------+--------------+-----+
| |Nature of| spaceship guns | IV.A |the Gun | 36 |
|IV-Propagators |activity +-------------------+--------+--------------+-----+
| | | puffer trains | IV.B |? | ? |
+---------------+---------+-------------------+--------+--------------+-----+
| | | dies ({theta}) | V.A |bit | 1 |
| | +-------------------+--------+--------------+-----+
| | | Class I | V.B |latent block | 3 |
| | +-------------------+--------+--------------+-----+
| | | Class II | V.C |blinker pred. | 4 |
|V-Unstable | +-------------------+--------+--------------+-----+
| (all objects | Final | Class III | V.D.1 |R-pentomino | 5 |
| not in above)| census +-------------------+--------+--------------+-----+
| | | Class III (only) | V.D.2 |glider pred. | 5 |
| | +-------------------+--------+--------------+-----+
| | | Class IV | V.E |Gun pred. | 26 |
| | +-------------------+--------+--------------+-----+
| | | unknown | V.F |acorn** | 7 |
+---------------+-----------------------------+--------+--------------+-----+
| * smallest known object (for Classes II, III, IV - minimum phase) |
| ** 'apparently' unknown - see text, page six [LifeLine 2:6] |
+---------------------------------------------------------------------------+
{2:3}
A modified classification system is presented on page two [LifeLine 2:2] which attempts to recognize the specific, key characteristics of _finite_ Life objects of each class. The examples shown represent, for each subclass, the smallest object (minimum number of bits) known to the writer. Most examples given are well known and have been previously described in either Scientific American or LIFELINE Number One. Those that are new are described in this newsletter. If anyone knows of smaller objects than any of these I will publish them in the next issue.
In general the number of new Class I objects reported is too large and common to mention. The 'spiral' was suggested by the writer merely to provide an example of a small Class I.B.3 object since none had previously been mentioned. The 'hat' a name given by Corderman and known by several other readers can be used to construct larger stable forms and is probably the smallest Class I.C.1 object. Class I.D objects exhibiting no symmetry whatsoever are the least common.
{Figure 2.3}
-------------------------------------------------------
Some interesting examples of still life symmetry:
Hat Fishhook Spiral Shillelagh Tub w/tail
.......................OO....O.......................
........................O..OOO.......................
......O.......OO........O.O........OO.........O......
.....O.O.......O.........O.O.......O.O.......O.O.....
.....O.O.......O.O........O.O........O........O.O....
....OO.OO.......OO.....OOO..O.......O...........O....
.......................O....OO......OO..........OO..
-------------------------------------------------------
The 'fishhook', a name independently coined by Clement A. Lessner III of W. Lafayette, Ind. and William P. Webb of San Rafael, Calif., was sent in by a number of readers and certainly must be the smallest possible nonsymmetrical still life. The two made of eight bits were given by Corderman and Hugh Thompson of Lefrak City, N.Y., who suggested the name 'shillelagh'.
Many Class II.A objects were reported, again too numerous and common to mention. Class II.B objects are fairly easy to develop starting with an empty m by n area (billiard table) bounded by 'inductor coils' and experimenting with various random patterns within. But if one excludes period two oscillators from this subclass, only a few are known. Other than the familiar Hertz oscillator (period eight) and pinwheel (period four) only the 'hustler' of an uneven period of three shown here has been added to this subclass. Note the now familiar fishhook used as an inductor coil for the crooked sides of the billiard table. Classes II.C and II.D are very uncommon and to date no one has reported anything new in either of these groups.
{Figure 2.4}
-----------------
The hustler:
......O........
.....O.O.......
......O........
...............
....OOOOO......
OO..O....O.OO..
.O...O...O.O.O.
.O.O.O...O...O.
..OO.O....O..OO
......OOOOO....
...............
........O......
.......O.O.....
........O......
-----------------
{2:4}
If one uses the Gun, many Class II.E objects may be constructed, for example, the pentadecathlon 'eating' gliders (February column, page 114. Incidentally, the illustration as shown is incorrect. The pentadecathlon and glider nearest it should be moved to the right one unit and in addition, an extra bit should be placed in the cell directly to the southeast of the glider). Earl C. Abbe of McLean, Va. has similarly positioned a queen bee near the glider stream. In this case however, the object eating the gliders will die if it is not fed every thirty generations!
{Figure 2.5}
------------------------------------------------------------
The hungry bee:
.........................OO...............................
.......................O..O.......O.......................
..........O.O.........O.......OO...O......................
..........O...O.......O......O.....O......................
OO............O.......O.......OOOOO.......................
OO........O....O.......O..O...............................
..............O..........OO...............................
..........O...O...........................................
..........O.O........O.O..................................
......................OO..................................
......................O...................................
..........................................................
..........................................................
..........................................................
..........................................................
.............................O............................
..............................OO..........................
.............................OO...........................
..........................................................
..........................................................
..........................................................
..........................................................
..........................................................
....................................O.O......OO...........
.....................................OOO.....O.O..........
.....................................OOOOO....OOO.......OO
.......................................O..O....OOO......OO
........................................OO....OOO.........
.............................................O.O..........
.............................................OO...........
------------------------------------------------------------
Abbe has also placed two shuttles between two blocks to create a 'queen bees' oscillator of period thirty. Does anyone know of an 'active element' which can be used for these type of constructions other than the glider or shuttle?
{Figure 2.6}
---------------------------------------
Queen bees:
............O...........O............
...........OO...........OO...........
OO........OO....OO.OO....OO........OO
OO.......OOO....OO.OO....OOO.......OO
..........OO....OO.OO....OO..........
...........OO...........OO...........
............O...........O............
---------------------------------------
The miscellaneous category II.F is unusual and had the single addition presented below with all its phases shown. Charles Trawick of Decatur, Ga, calls his discovery 'candelabra' and, like the M.I.T. oscillator (No. 1, [LifeLine 1:5]) [it] is also of period three.
{Figure 2.7}
------------------------------------
Candelabra:
....OO....OO.OO....OO.OO....OO....
.O..O......O.O......O.O......O..O.
O.O.O......O.O..OO..O.O.O..O.O.O.O
.O..O.OOOO.O.O.OOOO.O.O.O..O.O..O.
....O.O..O.O.O.O..O.O.O.O..O.O....
.....O....O...O....O...O....O.....
------------------------------------
Not surprisingly, no new spaceships (Class III) were reported. However, several intriguing (and delightfully simple) infinite patterns have been discovered that move orthogonally at the speed of light! These are discussed later in this newsletter. Notice Class III is now subdivided by the object's direction of motion.
Class IV, consisting only of the Gun, may (for the fun of it) be subclassified by type of activity into spaceship guns and puffer trains. In a sense, all Class III.A objects are puffer trains whose 'sparks' die rather than create any Class I or II objects. More will be said about puffer trains later.
{2:5}
Class V includes anything not in Classes I through IV and is now subdivided according to the object's final census. The single bit is, of course, the smallest object (Class V.A) that dies. I coined theta ({theta}), [which is] the Greek symbol for death and which appears on the ecology flags, to represent this subclass. A latent block (o$oo!) is the smallest object (Class V.B) that becomes a still life. The blinker predecessor shown here (oboo$$bbo!) is not only one of the smallest objects (Class V.C) that becomes periodic but does so in only a single generation. The tetromino (bo$3o!) and two other four-bit objects, of course, form the traffic light but only after a varying number (nine or more) of generations. These three objects were the subject of issue Number One (p.6) and are discussed later in this issue. Can you identify the five other four-bit objects besides the one shown here that become a blinker?
{Figure 2.8}
------------------------------------
A small predecessor to the blinker:
O.OO
....
..O.
------------------------------------
Class V.D objects are less common and very fascinating because of the one or more gliders created during their history. They include the R-pentomino, a hexomino, and the eleven heptominoes mentioned earlier. Of these, three heptominoes are of the 'pure glider generator' variety (Class V.D.2) one of which is shown at the left {Figure 9}. Although not an omino, the five-bit object to the right {Figure 10} is one of the several smallest known predecessors to the glider. Glider-a {alpha} (bo$bbo$3b!) and glider-b {beta} (obo$boo$bo!) are not included in the list even though they do evolve into a glider. Can you identify any of these objects including the two other heptominoes before I present them in the next issue?
{Figure 2.9}
------------------------------------
A pure glider generating heptomino:
..O.O
OOOOO
------------------------------------
A small predecessor to the glider:
.O..
..OO
OO..
------------------------------------
Many readers have reported Class V.D.2 objects like the 4-8-12 diamond and biloaf presented in the first issue and also described by Martin Gardner in the April column. Shown below are two symmetrical objects yielding two gliders each and three nonsymmetrical single glider generators. 'No name' was sent in by Bray and also Roger H. Rosenbaum of Seattle, Wash., who supplied the two long undecominoes. You may recognize the third one as appearing in the spaceship conversion last issue. There seems to be an inordinate number (four now including the one mentioned last issue, p. 3) of undecominoes in this subclass. Dale Edwin Cole of San Bernardino, Calif. sent in his 'biclock'.
{Figure 2.10}
----------------------------------
Some more pure glider generators:
no name:
O........
O........
O........
O........
O.OOOOO.O
........O
........O
........O
........O
----------------------------------
three undecominoes:
.OO.O.O
OOOOOOO
.O.
.O.
.O.
.O.
.O.
OO.
.O.
.O.
.OO
..OO
OOOO
OO.O
.OO.
{sic -- without a mirror-image copy to its right, this is a century predecessor}
----------------------------------
biclock:
.....O.
...O.O.
....O.O
..O.O..
O.O....
.O.O...
.O.....
----------------------------------
You might be interested in following the pattern made up entirely of ominoes at the top of the next page for a real surprise!
{2:6}
{Figure 2.11}
---------------------------------------------------------
A family of ominoes with interesting great-grandchildren:
..OO..OO.OO..OO..
..O...O...O...O..
......OO.OO......
O...............O
OOO...........OOO
..O...........O..
---------------------------------------------------------
No one responded to the challenge of finding a minimum predecessor pattern for the Gun (Class V.E). The 26-bit pattern mentioned in March (p.3) {LifeLine 1:3} is shown here and the challenge still stands: Does a 25 or less bit pattern exist? This was given as the example for Class V.E even though it is not a true object since the idea was to get the _minimum_ configuration (object or pattern). However, there undoubtedly are true objects that evolve into the Gun. More will be said about the meaning of an object later.
{Figure 2.12}
----------------------------------------
The smallest known ancestor of the Gun:
..................O.................
...................OO...............
..................OO......OO........
...........OO............O.O......O.
..........O..............OO.......OO
O........O..........................
OO.......O..........................
.........O..........................
..........O.........................
...........OO.......................
----------------------------------------
Class V.F is a catchall for anything whose outcome is not known. Notice the old Class VI is now defunct. The example mentioned on page two {Lifeline 2:2} and shown to the left {Figure 13} is a mere seven-bit object that is for all practical purposes unknown (to all but a few) because of its unusual history. Unless you have the resources of a large computer (and program), the patience, and are willing to spend a lot of time please do not try to determine its fate. As a surprise for LIFELINE Number Three, I will give its discoverer as well as present the fate of the 'acorn' - a term I coined after seeing its final census. It is given as a Class V.F example only to show how a simple object can, until census verified, be classified as unknown (just like the four heptominoes previously given.)
{2:7}
A large unexplored area of Life that is fast gaining popularity (with some real surprises!) involves 'transfinite objects'. In general, these are objects consisting of an infinite stable portion and (if activated) a finite unstable portion and (if activated) a finite unstable portion which 'feeds' on the stable portion. The stable portion may be a single infinite object (or an infinite set of finite objects) of Class I, II, III, or IV. The object (or set) may be infinite in one dimension (a fuse) or infinite in two dimensions (an agar). In a sense, transfinite objects (activated) may be considered very large Class V objects. But, for the fuses, the active portion exhibits characteristics of:
1. Periodicity.
2. Motion (speed).
3. Some visible rate of change of population (decreasing, constant, or _increasing_).
and most importantly:
4. _An_ _infinite_ _life_ (as do classes I thru IV).
Fuses, therefore, seem most like the hypothetical puffer trains with the difference (_very_ significant) being that they (the fuses) have an infinite mass provided (gratis) whereas a genuine puffer train, like the Gun, creates its own mass.
If the stable portion is infinite in two dimensions (an agar), the active portion will be an ever expanding oval boundary around an area which may continue to 'ferment'. Examples of the stable portion of these types of objects, many of which are familiar to you, are shown:
{Figure 2.13}
+-----------------+---------------------+---------------------+
| Stable portion | Fuse example | Agar example |
+-----------------+---------------------+---------------------+
| Class I | diagonal | 'chicken wire' |
| | | |
| Class II | barber pole | oscillating field* |
| | | |
| Class III | flotilla | field of spaceships*|
| | | |
| Class IV | 'multibarreled Gun' | none |
+-----------------+---------------------+---------------------+
| * described with specific examples in the newsletter |
+-------------------------------------------------------------+
Note that in all cases, the examples given are true (single) objects and in order to exist must be infinite. In some cases, methods are known to stabilize the boundary thereby making it possible to construct a finite object of the desired size - for instance, the 'fencepost' (boo$obo!) for the diagonal. Whatever their class, transfinite objects, and fuses especially, display a variety of interesting phenomena.
The number of fuses reported is increasing rapidly so I will present here only those that display some variation on what we have previously seen reported with these objects. [Regarding fuses, Woods points out an error in the Scientific American illustration (April, page 116) in fuse b. The bottom row of two bits should be one row lower in order to work properly.]
The top of page eight [LifeLine 2:8] shows two orthogonal fuses both of which, unlike all of the diagonal ones, 'burn' slower than the speed of light. 'Washerwoman' was sent in by Abbe and every 18 generations converts two tubs into a pair of 'clotheslines' (traffic lights). 'Honey farm-II' supplied by the writer converts three fenceposts into a beehive every 12 generations.
{2:8}
{Figure 2.14}
-------------------------------------------------------------------
Washerwoman:
............................................................O....
............................................................O....
.....................................O...........O..........O....
.O.....O.....O.....O.....O.....O....OO.........O.................
O.O...O.O...O.O...O.O...O.O...O.O..OOO.........O........OOO...OOO
.O.....O.....O.....O.....O.....O....OO.........O.................
.....................................O...........O..........O....
............................................................O....
............................................................O....
-------------------------------------------------------------------
Honey farm-II:
..............................................O..................
.O.OO.OO.OO.OO.OO.OO.OO.OO.OO.OO.OO.OO.OO.OO.O.O.................
.OO.OO.OO.OO.OO.OO.OO.OO.OO.OO.OO.OO.OO.OO.OO.O..................
...................................................OO.......OO...
..................................................O..O.....O..O..
...................................................OO.......OO...
-------------------------------------------------------------------
Many fuses may be constructed by using objects other than the simple, single diagonal. Shown below are two such fuses which, at the speed of light, convert their fuse material into Class I and Class III (!) objects respectively. The first one converts its wavy diagonal (half-pond pieces) into a pond every six generations making it one of the two only known fuses that burns with a period not of multiple four. The other converts its double fuse into a glider every four generations thus creating a stream of gliders (20 generations apart in space). Question: what is the closest possible spacing for a stream of gliders in the same 'flight path'?
{Figure 2.15}
---------------------------------------------------------------------
Two unusual fuses
....................................OO..............................
...................................O..O...........................OO
...................................O..O..........................O.O
....................................OO.............................O
....................................................................
....................................................................
............................OO...............................OO.....
............................OOO.........................O.....O...O.
.............................O...............................O..O..O
.......................................................O....O.......
........................O.............................OOOOO.......O.
..........................O..........................O.........O.O..
......................OOO...........................O..........OO...
.....................O.O...........................O..........O.....
.....................O............................O.........OO......
...................OO............................O..................
..................O.............................O.........OO........
..................O............................O....................
................OO............................O.........OO..........
...............O.............................O......................
...............O............................O.........OO............
.............OO............................O........................
............O.............................O.........OO..............
............O............................O..........................
..........OO............................O.........OO................
.........O.............................O............................
.........O............................O.........OO..................
.......OO............................O..............................
......O.............................O.........OO....................
......O............................O................................
....OO............................O.........OO......................
**.O.............................O..................................
*.*O............................O.........OO........................
{*'s added to stabilize infinite fuse}
---------------------------------------------------------------------
{2:9}
I would now like to describe five unusual agars (not activated) all of which are periodic. The one shown to the right [Figure 2.15] oscillates with a period of two. 'Squaredance', a name I gave (because the bit pairs seem to move in and out around an open square) was sent in by Woods who actually named it the 'quilt'. The one below-left [Figure 2.16] sent in by Steve Tower (no address given) looks as if it will completely die out ({theta}). It does but only after creating an appropriate dispersion of bit pairs to replace it. Another oscillator discovered by Tower is truly unique for it is of period three! Each of its phases are shown. Can you detect anything unusual about this oscillator (besides the period) before it is revealed in Issue Three?
{Figure 2:16}
------------------------------------------
Squaredance:
...O..O....O..O....O..O....O..O...
...O..O....O..O....O..O....O..O...
OO......OO......OO......OO......OO
....OO......OO......OO......OO....
..O....O..O....O..O....O..O....O..
..O....O..O....O..O....O..O....O..
....OO......OO......OO......OO....
OO......OO......OO......OO......OO
...O..O....O..O....O..O....O..O...
...O..O....O..O....O..O....O..O...
OO......OO......OO......OO......OO
....OO......OO......OO......OO....
..O....O..O....O..O....O..O....O..
..O....O..O....O..O....O..O....O..
....OO......OO......OO......OO....
OO......OO......OO......OO......OO
...O..O....O..O....O..O....O..O...
...O..O....O..O....O..O....O..O...
OO......OO......OO......OO......OO
....OO......OO......OO......OO....
..O....O..O....O..O....O..O....O..
..O....O..O....O..O....O..O....O..
....OO......OO......OO......OO....
OO......OO......OO......OO......OO
...O..O....O..O....O..O....O..O...
...O..O....O..O....O..O....O..O...
------------------------------------------
Surviving bits:
O.O.....O.O......O.O.....O.O......
....O.O......O.O.....O.O......O.O.
O.O......O.O.....O.O......O.O.....
.....O.O.....O.O......O.O.....O.O.
.O.O.....O.O......O.O.....O.O.....
.....O.O......O.O.....O.O......O.O
.O.O......O.O.....O.O......O.O....
......O.O.....O.O......O.O.....O.O
..O.O.....O.O......O.O.....O.O....
......O.O......O.O.....O.O......O.
..O.O......O.O.....O.O......O.O...
O......O.O.....O.O......O.O.....O.
...O.O.....O.O......O.O.....O.O...
.O.....O.O......O.O.....O.O......O
...O.O......O.O.....O.O......O.O..
.O......O.O.....O.O......O.O.....O
....O.O.....O.O......O.O.....O.O..
O.O.....O.O......O.O.....O.O......
....O.O......O.O.....O.O......O.O.
O.O......O.O.....O.O......O.O.....
.....O.O.....O.O......O.O.....O.O.
.O.O.....O.O......O.O.....O.O.....
.....O.O......O.O.....O.O......O.O
.O.O......O.O.....O.O......O.O....
......O.O.....O.O......O.O.....O.O
..O.O.....O.O......O.O.....O.O....
......O.O......O.O.....O.O......O.
..O.O......O.O.....O.O......O.O...
O......O.O.....O.O......O.O.....O.
...O.O.....O.O......O.O.....O.O...
.O.....O.O......O.O.....O.O......O
...O.O......O.O.....O.O......O.O..
.O......O.O.....O.O......O.O.....O
....O.O.....O.O......O.O.....O.O..
------------------------------------------
The three phases of an oscillating field:
OO.....OO.....OO.....OO.....
....OO.....OO.....OO.....OO.
.OO.....OO.....OO.....OO....
.....OO.....OO.....OO.....OO
..OO.....OO.....OO.....OO...
O.....OO.....OO.....OO.....O
...OO.....OO.....OO.....OO..
OO.....OO.....OO.....OO.....
....OO.....OO.....OO.....OO.
.OO.....OO.....OO.....OO....
.....OO.....OO.....OO.....OO
..OO.....OO.....OO.....OO...
O.....OO.....OO.....OO.....O
...OO.....OO.....OO.....OO..
OO.....OO.....OO.....OO.....
....OO.....OO.....OO.....OO.
.OO.....OO.....OO.....OO....
.....OO.....OO.....OO.....OO
..OO.....OO.....OO.....OO...
O.....OO.....OO.....OO.....O
...OO.....OO.....OO.....OO..
OO.....OO.....OO.....OO.....
....OO.....OO.....OO.....OO.
.OO.....OO.....OO.....OO....
.....OO.....OO.....OO.....OO
..OO.....OO.....OO.....OO...
O.....OO.....OO.....OO.....O
...OO.....OO.....OO.....OO..
OO.....OO.....OO.....OO.....
------------------------------------------
...O.O....O.O....O.O....O.O.
O.O....O.O....O.O....O.O....
....O.O....O.O....O.O....O.O
.O.O....O.O....O.O....O.O...
O....O.O....O.O....O.O....O.
..O.O....O.O....O.O....O.O..
.O....O.O....O.O....O.O....O
...O.O....O.O....O.O....O.O.
O.O....O.O....O.O....O.O....
....O.O....O.O....O.O....O.O
.O.O....O.O....O.O....O.O...
O....O.O....O.O....O.O....O.
..O.O....O.O....O.O....O.O..
.O....O.O....O.O....O.O....O
...O.O....O.O....O.O....O.O.
O.O....O.O....O.O....O.O....
....O.O....O.O....O.O....O.O
.O.O....O.O....O.O....O.O...
O....O.O....O.O....O.O....O.
..O.O....O.O....O.O....O.O..
.O....O.O....O.O....O.O....O
...O.O....O.O....O.O....O.O.
O.O....O.O....O.O....O.O....
....O.O....O.O....O.O....O.O
.O.O....O.O....O.O....O.O...
O....O.O....O.O....O.O....O.
..O.O....O.O....O.O....O.O..
.O....O.O....O.O....O.O....O
...O.O....O.O....O.O....O.O.
------------------------------------------
OOO...OOOO...OOOO...OOOO...O
...OOOO...OOOO...OOOO...OOOO
OOOO...OOOO...OOOO...OOOO...
O...OOOO...OOOO...OOOO...OOO
.OOOO...OOOO...OOOO...OOOO..
OO...OOOO...OOOO...OOOO...OO
..OOOO...OOOO...OOOO...OOOO.
OOO...OOOO...OOOO...OOOO...O
...OOOO...OOOO...OOOO...OOOO
OOOO...OOOO...OOOO...OOOO...
O...OOOO...OOOO...OOOO...OOO
.OOOO...OOOO...OOOO...OOOO..
OO...OOOO...OOOO...OOOO...OO
..OOOO...OOOO...OOOO...OOOO.
OOO...OOOO...OOOO...OOOO...O
...OOOO...OOOO...OOOO...OOOO
OOOO...OOOO...OOOO...OOOO...
O...OOOO...OOOO...OOOO...OOO
.OOOO...OOOO...OOOO...OOOO..
OO...OOOO...OOOO...OOOO...OO
..OOOO...OOOO...OOOO...OOOO.
OOO...OOOO...OOOO...OOOO...O
...OOOO...OOOO...OOOO...OOOO
OOOO...OOOO...OOOO...OOOO...
O...OOOO...OOOO...OOOO...OOO
.OOOO...OOOO...OOOO...OOOO..
OO...OOOO...OOOO...OOOO...OO
..OOOO...OOOO...OOOO...OOOO.
------------------------------------------
The last two agars (which were referred to on page four [LifeLine 2:4]) are actually spaceships! The first of these shown at the left below was discovered by Robert Kraus of Chicago, Ill. Each member can be made any length desired (greater than four) by extending the two 'fins'. The second one discovered by the writer only comes in two sizes. The smaller version (not shown) is four units long and without the single bit. Both of these period one objects move orthogonally at the speed of light!
{Figure 2:17}
-----------------------------------------------------
Two spaceship flotillas moving at the speed of light:
OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO.
..OO...OO...OO...OO...OO...OO...OO...OO...OO...OO
OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO.
.................................................
OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO.
..OO...OO...OO...OO...OO...OO...OO...OO...OO...OO
OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO.
.................................................
OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO.
..OO...OO...OO...OO...OO...OO...OO...OO...OO...OO
OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO.
.................................................
OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO.
..OO...OO...OO...OO...OO...OO...OO...OO...OO...OO
OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO.
.................................................
OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO.
..OO...OO...OO...OO...OO...OO...OO...OO...OO...OO
OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO.
.................................................
OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO.
..OO...OO...OO...OO...OO...OO...OO...OO...OO...OO
OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO.
.................................................
OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO.
..OO...OO...OO...OO...OO...OO...OO...OO...OO...OO
OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO.
.................................................
OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO.
..OO...OO...OO...OO...OO...OO...OO...OO...OO...OO
OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO.
.................................................
OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO.
..OO...OO...OO...OO...OO...OO...OO...OO...OO...OO
OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO.
.................................................
OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO.
..OO...OO...OO...OO...OO...OO...OO...OO...OO...OO
OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO.
.................................................
OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO.
..OO...OO...OO...OO...OO...OO...OO...OO...OO...OO
OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO.
.................................................
OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO.
..OO...OO...OO...OO...OO...OO...OO...OO...OO...OO
OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO..OOO.
-----------------------------------------------------
OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..
....OO.....OO.....OO.....OO.....OO.....OO.....OO.
..O..O...O..O...O..O...O..O...O..O...O..O...O..O.
....OO.....OO.....OO.....OO.....OO.....OO.....OO.
OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..
.................................................
OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..
....OO.....OO.....OO.....OO.....OO.....OO.....OO.
..O..O...O..O...O..O...O..O...O..O...O..O...O..O.
....OO.....OO.....OO.....OO.....OO.....OO.....OO.
OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..
.................................................
OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..
....OO.....OO.....OO.....OO.....OO.....OO.....OO.
..O..O...O..O...O..O...O..O...O..O...O..O...O..O.
....OO.....OO.....OO.....OO.....OO.....OO.....OO.
OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..
.................................................
OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..
....OO.....OO.....OO.....OO.....OO.....OO.....OO.
..O..O...O..O...O..O...O..O...O..O...O..O...O..O.
....OO.....OO.....OO.....OO.....OO.....OO.....OO.
OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..
.................................................
OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..
....OO.....OO.....OO.....OO.....OO.....OO.....OO.
..O..O...O..O...O..O...O..O...O..O...O..O...O..O.
....OO.....OO.....OO.....OO.....OO.....OO.....OO.
OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..
.................................................
OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..
....OO.....OO.....OO.....OO.....OO.....OO.....OO.
..O..O...O..O...O..O...O..O...O..O...O..O...O..O.
....OO.....OO.....OO.....OO.....OO.....OO.....OO.
OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..
.................................................
OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..
....OO.....OO.....OO.....OO.....OO.....OO.....OO.
..O..O...O..O...O..O...O..O...O..O...O..O...O..O.
....OO.....OO.....OO.....OO.....OO.....OO.....OO.
OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..
.................................................
OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..
....OO.....OO.....OO.....OO.....OO.....OO.....OO.
..O..O...O..O...O..O...O..O...O..O...O..O...O..O.
....OO.....OO.....OO.....OO.....OO.....OO.....OO.
OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..OOOOO..
-----------------------------------------------------
{2:10}
The next three examples actually involve finite fuses but in all cases the length of the fuse may be increased in multiples of four to achieve the same effect. They all illustrate how a glider's direction may be altered using fuses. I will, in a scenario of events, show how three fuses can be placed to demonstrate these findings. The creative staff includes (in order of occurrence) Rosenbaum, Webb, and Woods. The sequence of exhibits on this and the opposite page show, first, the three fuses at generation zero, then a glider (created by the short clean fuse) heading in generation eight towards the diagonal fuse (burning at both ends) where in generation twelve it is altered in flight and directed toward the 'synapse fuse' which gets activated by the glider (a signal) transmitting the signal thru the network (shown at generation 44) until reaching the other end where the signal is returned in generation 66 (as a glider displaced in time and space).
One of the most appealing features of fuses, from an experimental standpoint, is their ease of tracking. As stated in issue Number One (p.6) [LifeLine 1:6] you need only a good supply of graph paper and not as much patience. The fact that fuses are periodic means that after a fairly small number of generations you can determine the period and identify each phase.
For anyone new to the game, LIFEFILE contains, among other things, a brief description of a convenient and reliable method for manually calculating Life object histories. Also, for anyone with access to a computer, but no program, I have provided an efficient program (FORTRAN source listing) written by Paul Boltwood of Ottawa, Ontario. The program calculates about three generations per second on an 80 by 80 matrix.
{Figure 2.18}
----------------------------------
[Finite fuses turning a glider]
Generation: 0
..............................OO
...............................O
..............................O.
.............................O..
............................O...
...........................O....
..........................O.....
.........................O......
........................O.......
.......................O........
......................O.........
.....................O..........
....................O...........
...................O............
..................O.............
.................O..............
................O...............
...............O................
..............O.................
.............O..................
............O.....O.O...........
O..........O.....OOO............
.O......O.O......OO.............
..O.....OO......OO..............
...O...........O................
....O.........O.................
.....O.......O..................
......O.....O...................
.......O....OO..................
........O.......................
.........O......................
..........O.....................
...........O....................
............O...................
.............O..................
..............O.................
...............O................
................O...............
.................O..............
..................O.............
...................O............
----------------------------------
{2:11}
{Figure 2.19}
----------------------------------
[Finite fuses turning a glider]
Generation: 8
O.............................OO
...............................O
..............................O.
.............................O..
............................O...
...........................O....
..........................O.....
.........................O......
........................O.......
.......................O........
......................O.........
.....................O..........
....................O...........
...................O............
..................O.............
.................O..............
................O...............
...............O................
..............O.................
.............O..................
............O...................
...........O....................
........O.O.....................
........OO......................
................................
................................
................................
...........O.O..................
...........OO...................
........O...O...................
.........O......................
..........O.....................
...........O....................
................................
................................
................................
................................
................................
................................
................................
................................
----------------------------------
Generation: 12
..............................OO
...............................O
..............................O.
.............................O..
............................O...
...........................O....
..........................O.....
.........................O......
........................O.......
.......................O........
......................O.........
.....................O..........
....................O...........
...................O............
..................O.............
.................O..............
................O...............
...............O................
..............O.................
.............O..................
............O...................
...........O....................
........O.O.....................
........OO......................
................................
................................
................................
................................
..........OO....................
.........OO.....................
...........O....................
................................
................................
................................
................................
................................
................................
................................
................................
................................
................................
----------------------------------
Generation: 44
..............................OO
...............................O
..............................O.
.............................OO.
..........................O..O..
................................
.........................OO.O...
.......................O...O....
......................O.........
.......................O........
.......................O........
................................
................................
................................
................................
.................O.O............
.................OOO............
...............O................
........O.......O...............
........O........O..............
........O.O.....................
................O...............
................................
................................
................................
.......OO.......................
......O..O......................
......O..O......................
.......OO.......................
................................
................................
................................
................................
................................
................................
................................
................................
................................
................................
................................
................................
----------------------------------
Generation: 66
...........................O.O..
............................OO..
............................O...
................................
................................
................................
................................
................................
......................OO........
......................OO........
................................
................................
................................
................................
................................
.................O..............
.................O..............
.................O..............
................................
................................
................................
................................
................................
................................
................................
.......OO.......................
......O..O......................
......O..O......................
.......OO.......................
................................
................................
................................
................................
................................
................................
................................
................................
................................
................................
................................
................................
----------------------------------
{2:12}
At this time we must deal with the inevitable question: what do we mean by an "object"? My own criteria (arbitrary, of course) for determining if a pattern (of bits) is a single object are these:
1. Patterns whose bits are all connected (either orthogonally and/or diagonally) are objects.
2. Spatially connected patterns (a collection of objects, each of which is defined as above) are single objects if an empty cell between two or more of the 'subparts', and _because_ _of_ _the_ _subparts_, is either a birth cell (when, without the subparts, [it] would not have been) or a non-birth cell (when, without all the subparts, [it] would have been.)
In other words, the subparts must have a mutual effect upon each other. The pattern at the left below {Figure 2.18, first pattern} is _not_ a single object, but its next generation, center below, is a single object (by the definition just given). The smallest example of a stable spatially connected object is the 'aircraft carrier' (Conway's term) shown at the right below.
{Figure 2.20}
------------------
A pattern:
O....
.O.OO
.O.O.
------------------
An object:
.....
OO.OO
...OO
------------------
Aircraft carrier:
OO..
O..O
..OO
------------------
Obvious exceptions to this definition include all objects in Classes II.E and IV.A because they are, by definition, 'shuttles' whose activity necessitates a movement thru open space. On page two {LifeLine 2:2} my example given for Class V.E was purposely called a pattern (No.1, p.3) {LifeLine 1:3} since it is not a true object. The idea there was to find the _minimum_ pattern (object or not). Finally, members of Classes II.C, II.D, and the beacon may be considered objects since at least one of their phases meets the definition. This definition is important (at least for Class V objects) to preserve any meaning for the E.F. ratio discussed in March (page 6) {LifeLine 1:6) since it excludes defining as an object (as was suggested by several readers) such things as 'a glider a long distance away from and heading towards a blinker, say'.
This brings us to the challenges proposed last issue of finding objects with maximum M.I.P. and E.F. ratios. Philip M. Cohen of Aliquippa, Pa. and Woods pointed out the only two other four-bit objects with an M.I.P. value of 5.0. These are shown at the right {Figure 2.20} along with the tetromino to illustrate their varying E.F. values. The third one, incidentally, sets the record for all four-bit objects.
{Figure 2.21}
-----------------
Three relatives:
E.F.: 2.25
.O.
OOO
-----------------
E.F.: 2.50
O.O
.O.
.O.
-----------------
E.F.: 2.75
.O.
...
OOO
-----------------
Shown at the top of the next page are eight predecessor objects to the R-pentomino. The first three (a, b, and c) are the ones (all orthogonally-diagonally connected) that the writer had in mind when discussing this subject in March. The other five, all spatially connected, were sent in by Cohen (f), Corderman (a, c, and h), and Woods (a, b, d, e, f, and g). Three of these (a, c, and h) are all 'grandfathers' to the R-pentomino and therefore have an E.F. value (the one Woods had in mind) of 221.0. Does anyone know of a five-bit great grandfather to the R-pentomino?
{2:13}
{Figure 2.22}
-------------------------------------------
A host of predecessors to the R-pentomino:
a:
OOO.
...O
...O
-------------------------------------------
b:
O..
OO.
O.O
-------------------------------------------
c:
O...
.OO.
...O
..O.
-------------------------------------------
d:
.O.
.O.
OO.
...
..O
-------------------------------------------
e:
...O
O...
..OO
.O..
-------------------------------------------
f:
...O
O...
.OO.
O...
-------------------------------------------
g:
..O
.O.
.O.
O..
..O
-------------------------------------------
h:
O..
OOO
...
.O.
-------------------------------------------
Another interesting measure is the ratio of age to initial population for Class V.A objects. For example, five generations is the longest any four-bit object can last before dying (E.F.=1.25) and apparently eight generations is the longest any five-bit object can survive before death (E.F.=1.6). Can you identify either of these? Rosenbaum has discovered the object at the right of a mere eight bits that manages to stay alive 118 generations before death (E.F.=14.75)! Even though E.F.[sub]V.A. max <= E.F.(sub)V max for objects of the same size, I think this represents a very interesting challenge by virtue of the final extinction requirement. Any information received regarding this or the other two ratios will be presented in issue Three.
Practically any variation to Life that you can think of is probably being investigated by at least one individual. I would now like to mention several areas of Life and Cellular Automata Theory in general that are being investigated. It is still too early to report many detailed results on these subjects, however.
Several readers have tried playing Life on boards finite in either one or two dimensions which is analogous to playing on a cylindrical or a toroidal (doughnut) surface. The most noteworthy of these involves the work of Donovan Smith of El Cerritor, Calif. who has investigated families of 'necklaces' and 'radicals' as he calls them, on 4 by n toroidal surfaces (see example).
{Figure 2.23}
--------------
A necklace:
O..........O
.O........O.
..O......O..
...OOOOOO...
--------------
A radical:
O.....OOOOOO
.O...O......
..O.O.......
...O........
--------------
Oscillators with periods greater than two are very common (usually a multiple of four) and shown below at the left is one Smith discovered of period five (!) which begins in generation seven starting with a 4 by 12 necklace. Interestingly, the very same finite surface will support a period four oscillator sent in by Trawick shown below at the right.
{Figure 2.24}
--------------
Period 5:
...O....O...
...O....O...
...O....O...
...O....O...
--------------
Period 4:
...O...O....
...O...O....
...O...O....
...O...O....
--------------
{2:14}