If someone asked you to walk in a straight line over a constantly shifting floor, you would probably declare it impossible after a few tries and a couple of grazed knees. Researchers studying a version of this task inside a particular mathematical universe felt the same – but now a nimble traveller capable of navigating a clear path has emerged.
The walk in question takes place inside a particular, irregular cellular automaton, a theoretical universe in which patterns of cells evolve, and appear to move, just by following simple rules. The traveller, meanwhile, is a highly repetitive object known as a glider.
Its creation is an achievement because gliders were previously thought to exist only in regular cellular automata, such as the most famous one, the Game of Life – and because these objects are building blocks for more complex creations.
Invented by mathematician John Conway in the 1970s, Life is composed of an infinite grid of identical square cells, which can either be "live" or "dead". Play consists of simply choosing an initial pattern of cells. The pattern then evolves according to a short set of rules that state how cells should switch their state depending on the exact patterns of cells that surround them. The result can be a variety of patterns, some of which appear to morph or even move across the grid.
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