"Konrad Zuse (1910-1995; pronounce: "Conrud Tsoosay") not only built the first programmable computers (1935-1941) and devised the first higher-level programming language (1945), but also was the first to suggest (in 1967) that the entire universe is being computed on a computer, possibly a cellular automaton (CA). He referred to this as "Rechnender Raum" or Computing Space or Computing Cosmos. Many years later similar ideas were also published / popularized / extended by Edward Fredkin (1980s), Jürgen Schmidhuber (1990s - see overview), and more recently Stephen Wolfram (2002) (see comments and Edwin Clark's review page ). Zuse's first paper on digital physics and CA-based universes was:
Konrad Zuse, Rechnender Raum, Elektronische Datenverarbeitung, vol. 8, pages 336-344, 1967.
Zuse is careful: on page 337 he writes that at the moment we do not have full digital models of physics, but that does not prevent him from asking right there: which would be the consequences of a total discretization of all natural laws? For lack of a complete automata-theoretic description of the universe he continues by studying several simplified models. He discusses neighbouring cells that update their values based on surrounding cells, implementing the spread and creation and annihilation of elementary particles. On page 341 he writes "In all these cases we are dealing with automata types known by the name "cellular automata" in the literature" and cites von Neumann's 1966 book: Theory of self-reproducing automata. On page 342 he briefly discusses the compatibility of relativity theory and CAs."