T-tetromino

T-tetromino is one of 5 tetrominoes. It is a common predecessor of the traffic light, and when paired with another T-tetromino it can become a predecessor of the pulsar.

T-tetromino
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Pattern type Miscellaneous
Number of cells 4
Bounding box 3×2
Discovered by John Conway
Year of discovery 1970

In a cylindrical grid with a width of 6, the T-tetromino is always a replicator. It copies itself on the 15th and 40th generations of every 40 generations. However, because it leaves behind blocks, blinkers, and sparks, it doesn't cleanly replicate itself until after 200 generations. It acts much the same way as the replicator in Highlife because the two copies of the T-tetromino appear offset in opposite directions of the original. Also, two replicators will destroy each other if they are next to each other. The T-tetromino replicates orthogonally and 35 cells away from the original.

It is the daughter of the T-pentomino.

In other rules

The T-tetromino exhibits interesting behaviour in other life-like cellular automata. It is a c/4 orthogonal spaceship in 32 totalistic rules, B345/S126 to B345678/S12678, with the tip of the T being the trailing edge; it is also a c/4 orthonal spaceship in various non-totalistic rules, e.g. GlideLife, though it evolves differently.

In the non-totalistic automaton tlife, the T-tetromino is an extremely common c/5 orthogonal spaceship, with the tip of the T being the leading edge.

In the rule B34tw5y/S23, it acts almost like a two-dimensional replicator, however the copies react with each other to form 4 17c/47 orthogonal glider rakes. A similar reaction happens in wlife (B34w/S23), forming 4 2c/5 orthogonal beehive puffers.

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See also
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