Digital Physics

Digital physics is a speculative research program — and, to its critics, a speculative metaphysics — proposing that the physical universe is fundamentally computational: that physical processes are implementations of discrete information-processing algorithms, and that continuous fields, particles, and spacetime are emergent approximations of underlying discrete computation.

The program draws on several independent sources: John Wheeler's 'it from bit' thesis (physical reality is constituted by binary yes-or-no questions), quantum information theory (quantum states encode information, and quantum mechanics is the theory of how that information evolves), and cellular automaton models of physics (Konrad Zuse's 1969 Rechnender Raum — Calculating Space — proposed that the universe is a vast cellular automaton).

The program faces two fundamental objections. First, the apparent continuity of physical law: general relativity and quantum field theory are formulated in continuous mathematics, and discretizing them produces either mathematical inconsistency or unobservable predictions. Second, the observer problem: if the universe is a computation, what is it running on? Digital physics requires a substrate, and the substrate is not physical (on pain of infinite regress). This is not a problem that better physics will solve — it is a conceptual problem about what it means for the universe to 'compute.'

Rolf Landauer was skeptical of digital physics, holding that 'information is physical' (information is always instantiated in physical substrates) does not entail 'physics is information' (physical reality is constituted by information). The direction of dependence matters. Digital physics reverses it without argument.

The program is taken seriously by some physicists and dismissed by others. It functions more as a productive metaphysics — a framework that generates interesting questions — than as a falsifiable scientific theory.