Lifeline Volume 10

Lifeline Volume 10
Published in	June 1973
Preceded by	Volume 9
Succeeded by	Volume 11

This page is a transcript of Volume 10 of the Lifeline newsletter
This article may contain spelling mistakes and/or errors that will not be corrected. It is preserved in this way for history's sake. A record of such errors can be found at Lifeline/Errata.

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 10
JUNE 1973

• Editor and Publisher: Robert T. Wainwright •

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Since publishing the last issue of LIFELINE, I received a unique letter which I am including in this issue in its entirety and without any editing. This reply is not only laid out in newsletter fashion but also includes a kaleidoscope of new and interesting discoveries. I certainly welcome any and all letters of this nature no matter how long or short!

As usual, I will present a cross-section of the new and more recent discoveries reported by all the readers who have taken the time and effort to reply.

Petrie's pentadecathlon, profound, and Prolific predecessors

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The glider arrangements shown on this cover page of LIFELINE Number Ten are described in the previously mentioned letter sent in by Douglas G. Petrie of Lake Oswego, Ore. These patterns discovered by Petrie pro- duce respectively in a varying number of generations, the pentedeca- thlon(!), Conway's heavyweight spaceship(!!), and Corderman's Switch Engine(!!!). Details of these reactions and other newsworthy events are described in Petrie's letter which begins on page three. Is there anything beside Gardens of Eden that can not be constructed with gliders?

Lifequote submitted by Mark Linimon of Houston, Tx:

'Life is too important a matter to be taken seriously.'

. . . Oscar Wilde

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Class E, Evolutionaries, Exercises, Events, Et. cetera . . .

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In keeping up with the new and exciting series of glider(s) and block(s) collisions reported last issue, Dave Filpus of East Lansing, Mi. submits the following reaction of a single glider and two blocks which in 113 generations yields a glider (reflected 180 degrees) and three blocks!

Additionally, Peter Raynham of Sarnia, Ontario, Canada submits the following collision of a block and two gliders which in 47 generations results in two gliders (reflected 90 degrees) and three beehives!

The fates of the two unknown nonominoes introduced last issue were first discovered and sent in by Robert Bison of Hopewell Jct., N.Y. and then later by Bryan Drake of Lansing, Mi. and Harvey Lerman of Maitland, Fla. Incidentally, Drake supplied some very nice Polaroid photographs of these final populations that were left on the screen of the IMLAC device described last issue. A summary of these results as submitted by Bison follows:

 Non-  Age  Maximum    Final   Final     Census
 omino      Population  Pop    Area
 
  N-1 1451  536(@439)   291   =160x180   29 blocks, 2 tubs, 5 beehives,
                                         3 ships, 2 loaves, 1 long boat,
                                         1 fleet, 13 blinkers, 6 gliders.
                                         
  N-2 2925  562(@2110)  388   =140x160   31 blocks, 1 tub, 4 boats,
                                         17 beehives, 4 loaves, 3 ponds,
                                         12 blinkers, and 10 gliders!

Additionally, Bison notes that the Filpus-Karplus glider-blocks col- lision described last issue (p.2) goes to 3360 generations after spawning 15 gliders (!) for a Final population of 457 (max was 769 @2931). During its history it expanded to 160x200 (@2592) before settling down to within 150x180.

A spaceship collision resulting in an unusual still life has been reported by D. R. Mc Entee of St. Louis, Mo. Shown below are two light- weight spaceships colliding to form a 14-bit stable object.

Additionally, Raynham sub- mits the following four-. glider collision which also forms a still life.

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Reader Reply . . .

May 2, 1973

Robert Wainwright LIFELINE Editor

Dear Sir,

    I was glad to receive copies of all the newer LIFELINEs in the mail recently.

Some general comments: I notice that the newsletter is now being held to a limit of eight pages, and when rereading the "Coming Events" notices I get the impression thar a number of interesting items are, because of this limitation, being withheld. If the reason for the limit is cost rather than some other factor (taking too much of your time?), I for one would be willing to kick in more money for a subscription. As far as the articles printed went, most were quite interesting (but, please, don't go overboard on the occult symbology). I strongly hope that the next issue will include something about glider logic circuitry. Everett Boyer ought to be keeping you informed of the rather extensive work he and I have done in that field, but I would also Like to see what others might have done -- I can't believe we are the only ones working on computer design.

    Following are some recent discoveries of mine, of var31ng Importance:

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The ordinary-looking object at right has a very un-ordinary his- tory: its final population is infinite! This (along with a few relatives of similar structure) is the smallest single ob- ject known to achieve infinite growth. You may recognize it as a cousin Of the switch engine puffer shown in #4 p.1.

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Following a suggestion by Parrello and Tetenbaum (#7 p.7) I have used :Immigration" rules on about 20 pre- viously known collisions in order to determine the exact parentage of the resultant patterns; in only two cases did the final census include both types of live bits. These are Illustrated at the right. In view of their rarity, any further examples of mixed populations that people might discover would be of interest, and in particular, any reaction that results in an allied glider, (such as glider-toad, #9 p.5) would be noteworthy. There are two 2-g1ider collisions whose result is a single glider each; in both cases the new glider is shown to be produced by a 180° reflection of one of the original gliders.

Addendum: Boyer has just informed me that three glider-blinker collisions result in a hybrid ship, a hybrid loaf, and a hybrid pond, respectively. EN: any others?

Enclosed with this letter is a list of 121 12-bit Class I objects which was com- piled jointly by Boyer and myself. There may still be some missing, but not many. It is noteworthy that out of the entire list only one object (the half-fleet) has yet been reported to result from a "naturally-occurring" reaction.

EN: see 23,5 on next page.

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ERRATA: The "race against time" scenario (#3 p.14) will not work as shown; the correct form is pictured here. Also, in the table of 3x3 patterns (#9 p.4) note that A10=D11, E11=H10, so the number of unique arrangements is actually 102.

EN: thanks, I missed that.

By using eaters instead of blocks for shuttle-stabilizers (#3 p.5) it is possible to stack glider guns as close as 20 spaces apart, rather than 24 as reported in #9 p.5.

EN: I would still be satisfied to see a period 48 NEWBREEDER!

Now that Boyer's procrastination quotient has appeared, readers might be interested in trying to find the most procrastinating ancestor of each of the common terminal forms. For the blinker and the beehive the objects reported by Thompson (#8 p.5) will surely hold the record. Presented here as further candidates are (A) an interchange ancestor (21 gens., PQP=.167), and (B) a traffic lights ancestor (28 gens., PQP=.333).

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As a number of readers probably know, in the multitude of glider collisions can be found methods for constructing almost all of the familiar Class I&II objects. Two unusual examples are illustrated at the left. In Class III, ways of making light Or medium spaceships have long been known, but as yet no one has reported any method to build the heavy spaceship. This hole has now been filled. Shown at the right is a com- plex reaction between three gliders, a ship, and an eater which produces a heavy spaceship in ten generations. Shown also is one of many three-glider collisions which results in a ship. Since two gliders react to form an eater, making a heavy spaceship therefore requires a total of eight gliders. Using this mechanism a P60 heavy spaceship factory can probably be built, but in the present state of the art such a factory would require about 25 P30 glider guns. Perhaps future collision discoveries will allow simplification.

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In #7 p.4 there were presented several examples of objects which, when attacked by a virus, would reproduce themselves. Another "friendly" virus has now come to light, one which stimulates growth rather than reproduction. A spaceship of any length (including overweight ones) with a virus attached as shown will immediately turn into a spaceship of the next larger size. This reaction is more important than might first appear; it is vital to the heavy-spaceship con- struction described earlier.

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With various rather complicated collision scenarios a number of Class IV patterns can be produced, too. A new and surprisingly simple construction of this nature was recently discovered: six gliders collid- ing to form a puffer train. Gen. 6 at right is the same as gen. 2 of the pattern pictured in #4 p.1.

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By now ways are known to form from glider collisions almost all of the "significant" objects or patterns, including eaters, pentadecathlons, both major types of shuttle, the three basic orthogonal spaceships, both glider guns, and two of the three types of puffer train. (For completeness, the simplest pentadecathlon- forming collision I know of is shown here.) "Signi- ficant" in this case refers to all objects which might prove essential to such large-scale constructions as puffer train factories, a p31 glider gun, glider logic circuitry, or a pattern capable of self-replication. Still missing from the list is any method of producing "Schick's Flying Machine". Why bother with these collisions at all? For one thing, any pattern able to reproduce itself must entirely be composed of objects which can be created with glider collisions; we now have a wide variety of objects which might be used to build such a pattern. For another, it keeps me off the streets and out of trouble. (Regarding the question (#9 p.2) concerning the purpose of LIFE, the most practical result I have seen is the prevention of bore- dom among computer programmers.)

That's all for now; more to follow later on, including more results obtained in collaboration with Boyer.

Sincerely yours,

Douglas G. Petrie

Enclosure: 12-bit objects.

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EN: these four and p.4.

Lifequote:

'Life is very short
      and there's no ti i
                          i
                           i
                            i
                              i me . . . '

. . . Paul and John

Reader Brief . . .

Philip Cohen of Aliquippa, Pa.: 'I may have mentioned this before, but - of the 10,000's of possible 8-bit figures consisting of an R-pentomino and a [insert image here] tromino at a greater or lesser distance, isn't it likely that at least one grows to infinity? It would seem worth- while to investigate a dozen or so randomly chosen block sites to see if there is a significant change in any of the Life histories; if not, the speculation becomes rather less likely. Has it been tried?

EN: does anyone have a handle on the number of these combinations?

  (also for R-pentomino and a single blinker); try: [insert viewer? image? here]

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Lifeobservation . . . SOME EQUIVALENT GLIDER PREDECESSERS

Anyone who plays life regularly knows that the alteration in position of even a single bit in a pattern can alter considerably the final census. Patterns which can be so altered and still produce identical output we call equivalent. For example, A is the glider predescessor heptomino discovered by Thompson. B and C show how the end bit can be moved around without destroying the pattern's identity- for all three produce the same glider in the game generation(4) occupying the same position in the matrix.

D and E are another case in point. Both of these patterns - differing from each other by the dislocation of a single bit - produce a single glider fleeing a set of traffic lights.

F is perhaps the most remarkable example I have to offer. Structurally it is a glider connected to a latent block. In Practice the latent block may as while not even exist, for the glider is alone in the field in the sixth generation, occupying the same position as it would have had it started out alone.

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Harry J. Riley of Trenton, N.J.

Additionally, Curt Gibson of New York, N.Y. notes that: [insert image here] and [insert image here] have identical results (traffic lites in exactly the same position and in exactly the same number of gens.

Lifemerick:

An eager young Lifeman named Draper
Played all night by the light of a taper,
    But, excessively tired,
    He quite soon expired,
So they buried him, wrapped in squared paper!

. . . J.E. Still of Wembley,

     Middlesex, England

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LIFEXPLAINATIONS . . .

Tom Du Bois of Hawthorne, N.Y. has noted a surprising phenomenon in Life regarding hollow block objects. In all cases investigated up to order sixteen, the resultant census contains still lifes composed of bits with either 2 or 3 neighbors but never both.

Eric A. Haines of Moorestown, N.J. has noted the same phenomenon regarding solid block objects. In all cases investigated up to order nine, the census never contained a common 2/3 type still life.

Henrik Bjurstrom of Uppsala, Sweden in studying all solid rectangu- lar objects up to ten by ten, has neverseen a census containing a common 2/3 type still life.

These Lifexplainations are very unusual since still lifes are almost always composed of bits with both 2 and 3 neighbors. In fact, of all the 60,000 still lifes of 20 or less bits (conservative estimate), there are only nine known to the writer. See table below showing this distribution:

Still Life Structure Data [insert table here]

The smaller ones should be obvious to the seasoned Lifenthusiast. Can you identify all nine? I'll print results of anyone with more in No. 11. EN: how long can these generalities possibly last?

Reader Brief . . .

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R.J. Best of Miami, Fla. reports that an order twenty-one 'hooked cross' yields in 87 generations, a group of four pulsars with two extra beehives. Best ran this in four seconds on homemade device that outputs the results on a T-V like device.

COMING EVENTS:

. Neal'sgame - an exciting and new biocolony simulation . The 'Blinker-Tee' family . Life on a small doughnut - is it alive? . more local Lifeclub news . a four-glider pentadecathlon predecessor . other exotic n-glider collisions . a period 92 Slogun! . a period 76 pseudo spaceship . a period 14 pseudo oscillator

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