Life Period-2 Oscillators

Size in bits: 3 | 6 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | Larger | Scrubbers
Cost in gliders: 2 | 3 | 4 | 5 | 6 | 1 glider/bit | >1 glider/bit | unknown
Frequency of occurrence | Methuselahs with P2 censuses | Not quite oscillators



The 1 three-bit period 2 oscillator

3b P2

Blinker [2]


The 3 six-bit period 2 oscillators

6-bit P2

Toad [3] Clock [4] Beacon [3]

Clocks have thumbs that can sometimes be used to suppress diagonal bit-sparks, allowing clocks to be used as rocks to stabilize some larger oscillators.

Toads have no stable surfaces, but one side vacillates between one and two bits, making it possible to form pseudo-objects with other toads or similar oscillators, or with even-period oscillators that create domino sparks, like the Figure-8.

Their other sides can also be placed between pairs of domino sparks in several ways, resulting in two reactions: toad-flipping, where the toad is reflected, and toad-sucking, where the toad is moved sideways one position. Since each step must occur twice to return the toad to the original period, this usually results in an oscillator of double the original period (or quadruple, if the original period is odd). Several examples are shown in the period 60 versions of a toad between two pentadecathlons. Several additional period 8 versions using Figure-8s do not double the period, because the Figure-8's domino sparks have an extra bit-spark that produces a second domino hassling the toad twice in immediate succession each cycle. Toad-sucking can also occur be done by pairs of c/4 or c/6 orthogonal spaceships that produce domino sparks each time they advance. This could theoretically also work with spaceships of any slower even base period that move one step each period and produce one domino spark each period.

Pairs of toads, known as killer toads, can also eat expanding objects like middle-weight and heavy-weight spaceships, and forming 3/4 traffic light. These are most useful for eating spaceship streams whose period is a multiple of 2. For those whose period is a multiple of 3, killer candelfrobras are more appropriate.


The 1 eight-bit period 2 oscillator

8b P2

Bipole [5]


The 1 nine-bit period 2 oscillator

9b P2

Tripole [7]


The 1 ten-bit period 2 oscillator

10b P2

Quadpole [6]


The 1 eleven-bit period 2 oscillator

11b P2

Pentapole [10]


The 6 twelve-bit period 2 oscillators

12-bit period 2 oscillators

Up beacon on table; Cis- beacon and table [6] 12-bit P2 #1 [18] Fox; Gnome [12] Down beacon on table; Trans- beacon and table [6] Phoenix [10] Hexapole [12]


The 3 thirteen-bit period 2 oscillators

13-bit P2

Byflops; Butterfly; Griddles on two Ys [21] Bipole tie boat [8] Heptapole [16]


The 20 fourteen-bit period 2 oscillators

14-bit period 2 oscillators

Up beacon on cap; Cis-beacon and cap [6] 14-bit P2 #1 [28] Up beacon on up long bookend; Cis-beacon up and long hook [6] Test tube baby [6] Up beacon on down long bookend; Cis-beacon down and long hook [6] Up bipole on table [8] Down beacon on cap; Trans-beacon and cap [8] Down beacon on down long bookend; Trans-beacon up and long hook [6] Why not; Griddles on tub and Y [24] Beacon w/ cover; Beacon and two tails [9]
14-bit P2 #3 [17] 14-bit P2 #4 [x] Down bipole on table [9] Down beacon on up long bookend; Trans-beacon down and long hook [6] Bipole tie snake [8] Cavity; Eater plug [8] Bipole tie ship; Bipole on ship [8] Bipole tie carrier [12] Tripole tie boat [13] Octopole [20]


The 29 fifteen-bit period 2 oscillators

15-bit period 2 oscillators

15-bit P2 #1 [x] Down beacon on up long bookend w/ hook [9] Test tube baby w/ hook [9] Up beacon on down long bookend w/ hook [9] Block on griddle; Griddle and block; Singular flip- flop [11] Blinkers bit pole [x] 15-bit P2 #3 [34] Down beacon on up long bookend w/ tub [9] Test tube baby w/ tub; Odd test tube baby [9] Down beacon on down long bookend w/ hook [9]
Down beacon on down long bookend w/ tub [9] Up beacon on down long bookend w/ tub [9] Up tripole on table [10] Mutter- ing moat 1 [x] 15-bit P2 #6 [21] 15-bit P2 #7 [23] Up beacon on up long bookend w/ hook [9] Bipole tie eater tail [13] Phoenix w/ cavity [11] Up beacon on up long bookend w/ tub [9]
Down tripole on table [9] Bipole tie python [12] Tripole tie snake [12] Tripole tie ship [12] Bipole tie eater head [12] Bipole tie long boat [10] Tripole tie carrier [15] Quad- pole tie boat; Quad- pole on boat [7] Nono- pole [24]  


The 98 sixteen-bit period 2 oscillators

16-bit period 2 oscillators


The 199 seventeen-bit period 2 oscillators

Due to space limitations, these and their syntheses are shown on a separate page.


The 484 eighteen-bit period 2 oscillators

Due to space limitations, these and their syntheses are shown on a separate page.


The 1083 nineteen-bit period 2 oscillators

Due to space limitations, these are shown without syntheses on a separate page. Syntheses for 9 of them are shown here.

19-bit P2

Two blocks on griddle [34] Pond on griddle [12] Test tube baby siamese cover on block [22] Up beacon on up anvil; Cis- beacon and anvil [7] 19-bit P2 #2 [59] Spark coil w/ tub [6] Bun on beacon beside carrier [11] Bun on beacon beside snake [11] 19-bit P2 #1 [59]


The 2722 twenty-bit period 2 oscillators

Due to space limitations, these are shown without syntheses on a separate page. Syntheses for 8 of them are shown here.

20-bit period 2

Spark Coil w/ cis tubs [10] Toad and snake on Z [31] Pre- block on very long table w/ tail and curl [10] Pre- block on very long table w/ feather and curl [9] Hook w/ tail on griddle w/ tub [40] Up bipole on table siamese canoe [20] Two tied book- ends on beacon [10] Two snakes on butter- fly [26] Cavity w/ two tubs [8]


The 6596 21-bit period 2 oscillators

Due to space limitations, these are shown without syntheses on a separate page. Syntheses for 2 of them are shown here.

21b P2

Beacon on bookend siamese long integral [12] Up beacon on down dock w/ down mango [6]


4 22-bit period 2 oscillators

22-bit period 2 oscillators

Test tube baby between cis snakes [30] Test tube baby between trans snakes [30] Two blocks on armpit [10] Two eater tails on butterfly [15]


6 23-bit period 2 oscillators

23-bit period 2 oscillators

Piston [46] Spark coil from tub on D on house [12] Spark coil from pre- block on D w/ tub on house [21] Light bulb*; Snake on light bulb [30] Spark coil tie boat; Boat on spark coil [5] Block and down boat on armpit [11]

(* Q: How many gliders does it take to screw in a light bulb?
A: 11-30, depending on the socket.)


11 24-bit period 2 oscillators

24-bit period 2 oscillators

Spark coil from boat on D on house [10] Test tube baby between up bookends [13] Cis sparking tets [7] Washing machine [8] Fore and back; Complem- entary blinker [20] Test tube twins [25]
Trans sparking tets [8] Bookend on light bulb [12] Two boats on two loaves [15] Diagonal light bulb on two snakes [65] 2x2 Phoenix [29]


2 25-bit period 2 oscillators

larger period 2 oscillators

Test tube baby between snake and house [11] Block and down long boat on armpit [12]


34 period 2 oscillators 26 bits and larger

larger period 2 oscillators

Double piston; Long piston [10] House on light bulb [11] Two boats on two ponds [16] Diagonal light bulb on two eater tails [58] Two tied paper- clips [9] House w/ tub on light bulb [14] Block and down very long boat on armpit [12] Double spark coil [6]
Test tube baby between houses [9] Test tube twins w/ 2 curls [16] Test tube baby between cis skewed houses [8] Test tube baby between house and skewed house [8] Spark coil tied to two boats (up) [6] Test tube baby between trans skewed houses [8] Spark coil tied to two boats (down) [6]  
Beacon and boat on two ponds [13] Test tube twins between down bookend [16] Test tube twins between up bookend [16] Half pseudo- jack [25] Spark coil w/ 4 barges [8] Semifore; Two beacons on two ponds [14] Triple piston [48]
Quadruple piston [18] Test tube twins between trans houses [11] Test tube twins between cis houses [12] 36-bit P2 #1 [14] Double kiss [14] Sextuple piston [30]
Quintuple piston [60] Test tube twins between house and two bookends [17] Test tube triplets between house and two bookends [20] Test tube triplets between pairs of two bookends [26] Test tube quadruplets between pairs of two bookends [29] Four armpits [23] 60-bit P2 #1 [20]

Pistons are infinitely extensible. Pistons of any even length can be made by starting with the double piston synthesis, and adding as many additional copies of down-beacon-on-table as necessary for the desired length. (The first one is easiest, e.g. the quadruple piston; all others can use the method to extend this to the sextuple piston). Pistons of any odd length can be made by shortening an even-length piston by one unit, e.g. the triple and quintuple pistons.

NOTE: Because there are so many scrubbers, they are omitted from this list, and shown in the next section.


18 period 2 Scrubbers

The Scrubber is a billiard table oscillator consisting of a traffic light predecessor surrounded by induction coils. There are many different ways to stabilize the exterior sides. Here are several synthesizable variations.

larger period 2 scrubbers

1x1 Scrubber #1 [10] 1x1 Scrubber #3 [16] 1x1 Scrubber #2 [13] 1x1 Scrubber #4 [13] 1x1 Scrubber #5 [23] 1x1 Scrubber #6 [10] Scrubber piston [12]
2x1 Scrubbers #1 [23] 2x1 Scrubbers #2 [24] 2x1 Scrubbers #3 [17] 2x1 Scrubbers #4 [18] 2x1 Scrubbers #5 [18] 2x1 Glasses [17]
2x2 Scrubbers #1 [23] 2x2 Scrubbers #2 [24] 2x2 Scrubbers #3 [28] 3x2 Scrubbers [37] 4x2 Scrubbers [55]

Glasses are pairs of scrubbers with out-of-phase spark coils between them.



The 1 period 2 oscillator buildable from 2 gliders

2gl osc

Blinker [2]


The 2 period 2 oscillators buildable from 3 gliders

3g P2

Toad [3] Beacon [3]

Toads have no stable surfaces, but one side vacillates between one and two bits, making it possible to form pseudo-objects with other toads or similar oscillators, or with even-period oscillators that create domino sparks, like the Figure-8.

Their other sides can also be placed between pairs of domino sparks in several ways, resulting in two reactions: toad-flipping, where the toad is reflected, and toad-sucking, where the toad is moved sideways one position. Since each step must occur twice to return the toad to the original period, this usually results in an oscillator of double the original period (or quadruple, if the original period is odd). Several examples are shown in the period 60 versions of a toad between two pentadecathlons. Several additional period 8 versions using Figure-8s do not double the period, because the Figure-8's domino sparks have an extra bit-spark that produces a second domino hassling the toad twice in immediate succession each cycle. Toad-sucking can also occur be done by pairs of c/4 or c/6 orthogonal spaceships that produce domino sparks each time they advance. This could theoretically also work with spaceships of any slower even base period that move one step each period and produce one domino spark each period.

Pairs of toads, known as killer toads, can also eat expanding objects like middle-weight and heavy-weight spaceships, and forming 3/4 traffic light. These are most useful for eating spaceship streams whose period is a multiple of 2. For those whose period is a multiple of 3, killer candelfrobras are more appropriate.


2 period 2 oscillators buildable from 4 gliders

4g P2

Clock [4] Spark coil [4]

Clocks have thumbs that can sometimes be used to suppress diagonal bit-sparks, allowing clocks to be used as rocks to stabilize some larger oscillators.


3 period 2 oscillators buildable from 5 gliders

5g P2

Bipole [5] Great on-off; Pincers [5] Spark coil tie boat; Boat on spark coil [5]


14 period 2 oscillators buildable from 6 gliders

6-glider period 2 oscillators

Quadpole [6] Up beacon on cap; Cis- beacon and cap [6] Up beacon on up long bookend; Cis- beacon up and long hook [6] Test tube baby [6] Up beacon on down long bookend; Cis- beacon down and long hook [6] Down beacon on down long bookend; Trans- beacon up and long hook [6] Down beacon on up long bookend; Trans- beacon down and long hook [6]
Up beacon on table; Cis- beacon and table [6] Down beacon on table; Trans- beacon and table [6] Spark coil w/ tub [6] Up beacon on down dock w/ down mango [6] Spark coil tie cis boats [6] Spark coil tie trans boats [6] Double spark coil [6]


The 16 period 2 oscillators up to 17 bits costing 1 glider/bit

1 glider/bit p2 oscillators

Fox; Gnome [12] Hexa- pole [12] Tripole tie carrier [15] Quad; Square quad; Barber- pole inter- section [16] Down beacon on snake siamese snake [16] Bipole tie hook w/ tail [16] Bipole tie tub w/ tail [16] Tripole tie eater tail [16] Tripole tie python [16]
Up beacon on Z w/ feather [17] Up beacon on up bookend siamese snake [17] Down beacon on Z w/ feather [17] Down beacon on bookend siamese snake [17] Down beacon on snake siamese python [17] Tripole tie hook w/ tail [17] Tripole tie canoe [17]  


The 54 period 2 oscillators up to 17 bits costing >1 glider/bit

gt. 1 glider/bit p2 oscillators


The 48 period 2 oscillators up to 17 bits without any known syntheses

At present, the technology for synthesis of oscillators containing large number of disconnected bits is sorely lacking.

unknown period 2 oscillators



The top 41 naturally-occurring period 2 oscillators

natural period 2 oscillators

Blinker [2] (3.038) Toad [3] (373.6) Beacon [3] (1221) Clock [4] (1.7e6) Bipole [5] (7.5e6) Quad- pole [6] (8.2e6) Great on-off [5] (1.2e7) Spark coil [4] (3.6e7) Quadpole tie ship [7] (1.1e8)
Tripole [7] (2.1e8) Up beacon on dock; Cis- beacon and dock [7] (7.0e8) Up beacon on table; Cis- beacon and table [6] (9.0e8) Down beacon on table; Trans- beacon and table [6] (9.3e8) Up beacon on up anvil; Cis- beacon and anvil [7] (1.1e9) Test tube baby [6] (1.3e9) Test tube baby w/ two tubs; Tub test tube baby [8] (2.4e9) Down beacon on dock; Trans- beacon and dock [7] (2.5e9) Up beacon on up long bookend; Cis- beacon up and long hook [6] (3.0e9)
Up beacon on cap; Cis- beacon and cap [6] (3.3e9) 1beacon [10] (3.3e9) Up beacon on down dock w/ down mango [6] (3.6e9) Up beacon on down long bookend; Cis- beacon down and long hook [6] (3.9e9) Block on griddle; Griddle and block; Singular flip- flop [12] (7.2e9) Spark coil tie boat; Boat on spark coil [5] (7.2e9) Pre- block on very long table w/ tail [11] (8.4e9) Fore and back; Complem- entary blinker [20] (8.4e9) Down beacon on up long bookend; Trans- beacon up and long hook [6] (1.0e10)
Beehive on griddle; Griddle and beehive [10] (1.3e10) Bipole tie ship; Bipole on ship [8] (1.7e10) Quad- pole tie boat; Quad- pole on boat [7] (1.7e10) Down beacon on up bookend siamese table [10] (1.7e10) Pre- block on very long table w/ tail and curl [10] (1.7e10) Down beacon on cap; Trans- beacon and cap [8] (2.5e10) Down beacon on down long bookend; Trans- beacon down and long hook [6] (2.5e10) Beacon w/ cover [9] (2.5e10) Cavity; Eater plug [8] (2.5e10)
Test tube baby w/ tub; Odd test tube baby [9] (2.5e10) Boat on griddle; Griddle and boat [13] (2.5e10) Pre- block on very long table w/ tail siamese tail [29] (2.5e10) Pre- block on very long table w/ tail and head [14] (2.5e10) Pre- block on very long table w/ feather and curl [9] (2.5e10)  



8 methuselahs whose censuses are period 2

P2 methuselahs

Pi Heptomino (@2); Blasting cap (@2); House (@5) [2] Thompson's 6-bit methuselah [6] Century (@1); Bookend (@2); Hook (@2); Kidney (@2) [3] Thunder- bird (@1) [4] (2 glider) Octomino (@4) [2] Dove (@1); R-mango (@1) [3] Pike; Pi heptomino and block (@3) [3] Two-glider mess [2]
2 Ponds, 6 blocks, 5 blinkers (@175) Loaf, 6 blocks and 12 blinkers (@608) Blinker and 3 blocks (@103) 4 Beehives, 2 boats, 2 blinkers (@244) 2 Traffic lights and 4 beehives (@388) 3 Blocks and 2 blinkers (@201) Toad, 9 beehives, 2 boats, 7 blocks, 9 blinkers (@991) Ship, beehive, 4 blocks, 8 blinkers, 4 gliders (@530)

These all have a period of 2 because of blinkers (and also, in Pike, a toad).



1 Not quite period 2 oscillator

bad P2

Eater tie beacon [11]



Related: period-2 pseudo-oscillators.

Other oscillators by period: 2, 3, 4, 5, 6, 8, 10, 12, 14, 15, 24, 30, 36, 60, other.

Other types: still-lifes, pseudo-still-lifes, oscillators, pseudo-oscillators, oscillators by period, pseudo-oscillators by period, guns, multi-colored Life, basic spaceships and pseudo-spaceships, exotic spaceships, spaceships flotillae, puffers, constellations, methuselahs, not quite stable objects.

See also: Life objects sorted by: counts, frequency of occurrence, cost in gliders, name, size in bits, or type.

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This page was last updated on 2015-02-19.