One-cell-thick pattern

A unidimensional pattern is a pattern that is only one cell thick; that is, it is contained entirely within one dimension of the Life plane. Put another way, it is a pattern with bounding box of the form y×1 for some natural number y. Because of their size restriction, exhaustive computer searches have been carried out to explore unidimensional patterns up to size about 40×1. Despite their inherent limitations, unidimensional patterns can exhibit quite complex behavior, even at reasonably small sizes.

Infinite growth

Generation 2000 of Callahan's pattern

In May 1998, Stephen Silver produced a unidimensional pattern that exhibits infinite growth, following a conjecture of Nick Gotts that such patterns exist. This pattern was extremely large (12470×1 in the first version, reduced to 5447×1 the following day).

In October 1998, Paul Callahan performed an exhaustive computer search to find the following pattern that exhibits infinite growth. It is probably the most well-known unidimensional pattern, and Callahan showed that it is the smallest such unidimensional pattern (in terms of its bounding box) to exhibit infinite growth. It contains 28 alive cells and has a 39×1 bounding box.

Paul Callahan's unidimensional infinite growth pattern
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Indeed, this pattern produces two block-laying switch engines at about generation 700. The image to the right shows what it looks like at generation 2000.