Oscillator

An oscillator is a pattern that is a predecessor of itself. That is, it is a pattern that repeats itself after a fixed number of generations (known as its period). The term is usually restricted to finite patterns that are not still lifes, though still lifes may be thought of as oscillators with period 1. An oscillator is divided into a rotor (the individual cells that actually oscillate) and a stator (the cells which remain alive throughout its whole period).

Cellular automaton theory recognizes shift periodicity, which refers to a configuration reappearing in shifted form after a lapse of one or more generations. Without the shift, it is an oscillator, but if it moves it would be called a spaceship.

Important oscillators by period

A list of the first-discovered oscillator of each period, as well the current smallest-known oscillator of that period, is provided here. Note that only non-trivial oscillators are considered here, in the sense that there must be at least one cell that oscillates at the full period. In some cases, it is not known for certain what the first-discovered oscillator of a given period is, and in such situations all possible candidates are listed. For any period 61 or greater an oscillator can be constructed using the Herschel track method. In April, 2013 Mike Playle found a small 90-degree stable reflector known as the Snark that allows oscillators of all periods 43 or greater to be constructed.

*An oscillator of this period can also be constructed from two sparkers both of which were known by an earlier date. However, this type of oscillator is generally considered "boring", and thus not listed here despite technically being non-trivial.
Period First discovered Discoverer Year of discovery                      Smallest known Minimum # of cells
2 blinker John Conway 1970 blinker 3
3 pulsar John Conway 1970 caterer 12
4 pinwheel Simon Norton 1970 mazing, mold 12
5 octagon 2 Sol Goodman, Arthur Taber 1971 pseudo-barberpole 15
6 $rats David Buckingham 1972 unix 16
7 burloaferimeter David Buckingham 1972 28P7.1, 28P7.2, 28P7.3, burloaferimeter 28
8 figure eight Simon Norton 1970 figure eight 12
9 worker bee David Buckingham 1972 29P9 29
10 42P10.3 David Buckingham ≤1976 24P10 24
11 38P11.1 David Buckingham 1977 rattlesnake 33
12 dinner table Robert Wainwright 1972 dinner table 33
13 Buckingham's p13 David Buckingham 1976 Beluchenko's p13 34
14 tumbler George Collins 1970 tumbler 16
15 pentadecathlon John Conway 1970 pentadecathlon 12
16 two pre-L hasslers Robert Wainwright 1983 Rob's p16 21
17 54P17.1 Dean Hickerson 1997 honey thieves 36
18 117P18* David Buckingham ≤1991 p18 bi-block hassler 43
19 None found
20 145P20* Noam Elkies 1995 mold on fumarole 30
21 124P21* Robert Wainwright 1995 caterer on 28P7.3 40
22 168P22.1 Noam Elkies 1997 Jason's p22 36
23 David Hilbert Luka Okanishi, Aidan F. Pierce 2019 David Hilbert 122
24 186P24* Bill Gosper 1994 caterer on figure eight 24
25 134P25 Noam Elkies 1994 p25 honey farm hassler 88
26 p26 pre-pulsar shuttle David Buckingham 1983 87P26 87
27 123P27.1 Noam Elkies 2002 56P27 56
28 newshuttle David Buckingham 1973 mold on 34P14 shuttle 46
29 p29 pre-pulsar shuttle David Buckingham 1980 p29 pre-pulsar shuttle 54
30 queen bee shuttle Bill Gosper 1970 queen bee shuttle 20
31 Merzenich's p31 Matthias Merzenich 2010 Merzenich's p31 48
32 gourmet David Buckingham 1978 gourmet 66
33 258P3 on Achim's p11 Noam Elkies, Achim Flammenkamp 1997 caterer on rattlesnake 46
34 No non-trivial examples found
35 p35 beehive hassler* Dean Hickerson 1995 p35 honey farm hassler 44
36 p36 toad hassler* Robert Wainwright 1984 22P36 22
37 Beluchenko's p37 Nicolay Beluchenko 2009 Beluchenko's p37 124
38 None found
39 134P39.1 David Buckingham, Noam Elkies 2000 caterer on Beluchenko's p13 46
40 p40 B-heptomino shuttle* David Buckingham ≤1991 Beluchenko's p40 26
41 None found
42 p42 glider shuttle* Noam Elkies 1994 unix on 34P14 shuttle 50
43 p43 glider loop Mike Playle 2013 p43 glider loop 228
44 p44 pi-heptomino hassler David Buckingham 1992 mold on rattlesnake 45
45 pentadecathlon on snacker ? ≤1995 pentadecathlon on thumb 1 48
46 twin bees shuttle Bill Gosper 1971 twin bees shuttle 28
47 p47 pre-pulsar shuttle David Buckingham 1982 p47 pre-pulsar shuttle 84
48 p48 toad hassler Bill Gosper 1994 unix on Rich's p16 52
49 p49 glider shuttle Noam Elkies 1999 p49 bumper loop 206
50 p50 glider shuttle Dean Hickerson 1992 p50 traffic jam 92
51 Beluchenko's p51 Nicolay Beluchenko 2009 92P51 92
52 Four eaters hassling lumps of muck David Buckingham 1977 Four eaters hassling lumps of muck 35
53 p53 glider loop Mike Playle 2013 p53 glider loop 228
54 p54 shuttle David Buckingham 1973 p54 shuttle 48
55 p55 pre-pulsar hassler David Buckingham 1986 pseudo-barberpole on rattlesnake 49
56 p56 B-heptomino shuttle* David Buckingham ≤1991 p56 B-heptomino shuttle 45
57 p57 Herschel loop 1 Dietrich Leithner 1997 p57 bumper loop 152
58 p58 toadsucker Bill Gosper 1994 p58 pre-pulsar shuttle 104
59 p59 Herschel loop 1 David Buckingham 1997 p59 glider loop 228
60 p60 glider shuttle David Buckingham ≤ 1971 mold on pentadecathlon 24
61 p61 Herschel loop 1 David Buckingham 1996 p61 glider loop 228
62 ? ? ? 110P62 110
63 ? ? ? snacker on 38P7.2 78
64 ? ? ? Merzenich's p64 34
65 ? ? ? fumarole on Beluchenko's p13 52
66 ? ? ? caterer on 36P22 48
67 ? ? ? ? ?
68 ? ? ? ? ?
69 ? ? ? ? ?
70 ? ? ? fumarole on 34P14 shuttle 52
71 ? ? ? ? ?
72 two blockers hassling R-pentomino Robert Wainwright 1990 figure eight on 22P36 36
73 ? ? ? ? ?
74 ? ? ? ? ?
75 ? ? ? 6 bits 49
76 ? ? ? ? ?
77 ? ? ? 77P77 77
78 ? ? ? p6 thumb on Beluchenko's p13 61
79 ? ? ? ? ?
80 ? ? ? fumarole on Rob's p16 39
81 ? ? ? ? ?
82 ? ? ? ? ?
83 ? ? ? ? ?
84 ? ? ? 52P84 52
85 ? ? ? ? ?
86 ? ? ? ? ?
87 ? ? ? 84P87 84
88 p88 pi-heptomino hassler Dean Hickerson 1994 figure eight on rattlesnake 45
89 ? ? ? ? ?
90 ? ? ? fumarole on 43P18 61
91 ? ? ? ? ?
92 ? ? ? twin bees shuttle on 22P4.3 50
93 ? ? ? caterer on Merzenich's p31 60
94 ? ? ? capped AK-94 110
95 ? ? ? ? ?
96 ? ? ? caterer on 68P32 80
97 ? ? ? ? ?
98 ? ? ? ? ?
99 ? ? ? ? ?
100 centinal Bill Gosper ≤1987 centinal 70
104 ? ? ? figure eight on Beluchenko's p13 46
105 ? ? ? pentadecathlon on 37P7.1 49
108 ? ? ? 22P4.3 on 56P27 78
110 p110 traffic jam Bill Gosper 1994 pseudo-barberpole on 36P22 51
120 ? ? ? figure eight on pentadecathlon 24
124 p124 lumps of muck hassler Dean Hickerson 1994 mold on Merzenich's p31 60
132 p132 pi-heptomino hassler David Buckingham ≤1994 ? ?
135 106P135 Bill Gosper 1989 pentadecathlon on 56P27 68
138 ? ? ? Gabriel's p138 36
144 Achim's p144 Achim Flammenkamp 1994 Achim's p144 42
156 p156 Hans Leo hassler Noam Elkies 1995 Jason's p156 92
177 ? ? ? Karel's p177 104
200 p200 traffic jam Bill Gosper 1994 figure eight on centinal 82
312 period-tripled p104 gun Dave Greene 2004 60P312 60
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