Wang's Carpets

Greg Egan

4 ideas

1. The Wang carpets of Orpheus

   Software-based human explorers reach the ocean planet Orpheus, orbiting Vega, hoping to find extraterrestrial life. The only organisms they find are simple floating polymer 'carpets' whose molecular units behave like Wang tiles, which replicate by matching edges. When one explorer analyses the carpets' tile dynamics mathematically, the patterns turn out to compute an entire ecosystem of complex, apparently conscious creatures that have no knowledge of the chemistry that runs them.

2. Tiling rules as universal computation

   Wang tiles are square tiles with coloured edges that may only be placed where adjoining edges match. Suitable sets of such tiles can emulate any Turing machine, so a local, purely mechanical matching rule can carry out arbitrary computation. A physical system that self-assembles by edge-matching can therefore host a full computation, including a mind, without any designer intending it.

3. Life hidden at another level of description

   Viewed directly in physical space, the carpet is a dull repetitive polymer. Its rich structure only appears after a mathematical transformation, such as moving to frequency space, where the patterns form coherent, interacting entities. Whether you find life depends on the representation you examine, not just on the matter in front of you, so a search for life framed around chemistry and morphology can miss the most complex thing present.

4. Computed minds are fully real minds

   Beings made of computation are as real as beings made of flesh, and they can have genuine experience while being entirely unaware of the substrate running them. This undercuts any claim that the explorers, who are themselves software, occupy a privileged kind of existence.

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