Digital physics

Digital physics is a family of speculative proposals in philosophy, holding that the universe is at its most fundamental level digital, informational or computational in character: that physical reality is either the output of a computer program or is itself a computational process. This metaphysical position is also known as pancomputationalism.

The hypothesis that the universe is a digital computer was first set out by Konrad Zuse in a 1967 paper and in his 1969 monograph Rechnender Raum ("Calculating Space"). The term "digital physics" was coined in 1978 by Edward Fredkin, who taught a graduate course under that name at MIT and later came to prefer the label "digital philosophy". Fredkin's collaborations with Tommaso Toffoli and Norman Margolus on reversible and conservative logic made MIT's Information Mechanics group the principal early institutional home of the programme.

Digital physics is not a single theory but a cluster of positions that differ over what is claimed to be discrete (space, time, state, or information), over which computational formalism is taken to be exact (cellular automata, Turing machines, quantum circuits, graph rewriting systems), and over whether the claim is empirical, metaphysical, or both. It overlaps with, but is distinct from, the simulation hypothesis, which concerns whether our universe is being run by agents in some other universe rather than whether it is computational at all.

Digital physics is not broadly accepted. No version of it has yielded a confirmed novel prediction, and existing discrete models are in tension with several continuous symmetries of established theory, such as rotational symmetry, Lorentz symmetry and gauge invariance. Deterministic classical variants also fall within the class of local hidden-variable theories constrained by Bell's theorem and the experiments that test it.