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  • H.Koenig
  • Adam Goucher
  • Dave Greene

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2010 May 19

Oblique Life spaceship created

Andrew J. Wade has recently built a self-replicating configuration in Life. It consists of two stable configurations equipped with Chapman-Greene construction arms, and a volley of gliders circulating between them. The tape contains a recipe for both constructing a daughter machine and cannibalising its parent configuration. In other words, it 'cleans up after itself', forming a spaceship.

The announcement was made on this forum thread. Amazingly, Andrew managed this feat independently, despite the fact that he had access to limited knowledge and resources. In fact, that may have actually helped him -- he was not familiar with, and therefore not constrained by, the preliminary work in this field.

The spaceship propagates at the impressively slow speed of (5120,1024)c/33699586. This is the first spaceship that travels neither orthogonally nor diagonally. This is truly groundbreaking work, solving the 40-year-old ambition of producing a self-replicating configuration in Life. In fact, this is arguably the single most impressive and important pattern ever devised.

Undoubtedly, this creation will lead to an avalanche of discoveries in Life.

It differs from the Standard Architecture in a variety of ways. Firstly, the data is stored within an active salvo of synchronised gliders, rather than as a passive tape of still lifes. This makes reproduction much faster; it replicates in linear, rather than quadratic, time. Indeed, it copies itself in 33699586 generations, whereas the estimated period of a replicator via a Universal Computer-Constructor would be approximately 10^16 generations.

The configuration uses three Chapman-Greene construction arms at each end of the tape: two perpendicular arms for construction, and a third arm for destruction. In principle, this could all be accomplished using one asynchronous arm, but this approach is immeasurably faster.

This is the thirteenth explicitly constructed spaceship velocity in Life, although it facilitates an infinite number of related velocities. One could, for example, translate one of the ends of the spaceship by one diagonal cell and reposition the gliders to increase the period by eight generations. Dave Greene has managed to do the inverse, to reduce the period by eight generations.