Digital physics#Pancomputationalism

{{short description|The idea that the universe is a digital computation device}}

{{Distinguish|Computational physics|Computational philosophy}}

Digital physics is a speculative idea suggesting that the universe can be conceived of as a vast, digital computation device, or as the output of a deterministic or probabilistic computer program.{{Citation |last= Schmidhuber |first=Jürgen |title=A computer scientist's view of life, the universe, and everything |date=1997 |url= https://doi.org/10.1007/BFb0052088 |work= Foundations of Computer Science: Potential — Theory — Cognition |series= Lecture Notes in Computer Science |volume= 1337 |pages= 201–208 |editor-last= Freksa |editor-first= Christian |place= Berlin, Heidelberg |publisher= Springer |language= en |doi= 10.1007/bfb0052088 |isbn= 978-3-540-69640-7 |s2cid= 17830241 |access-date= 2022-05-23 |editor2-last= Jantzen |editor2-first= Matthias |editor3-last= Valk |editor3-first= Rüdiger |arxiv= quant-ph/9904050 }} The hypothesis that the universe is a digital computer was proposed by Konrad Zuse in his 1969 book Rechnender Raum{{Cite web |title=Das Jahr des rechnenden Raums |url= https://blog.hnf.de/das-jahr-des-rechnenden-raums/ |access-date=2022-05-23 |website=blog.hnf.de |language=de}} (Calculating-space).{{Cite book |last= Zuse |first= Konrad |title= Rechnender Raum |date= 1969 |publisher=Springer Vieweg |isbn= 978-3-663-02723-2 |location= Braunschweig}} The term "digital physics" was coined in 1978 by Edward Fredkin,[http://simson.net/ref/1978/6.895%20Digital%20Physics/1978-01-17%20Digital%20Physics%20Lecture%20Outline.pdf 6.895 Digital Physics Lecture Outline], MIT Course Catalog Listing, 1978 (PDF) who later came to prefer the term "digital philosophy".{{Cite web |archivedate=2021-01-26 |title= Digital Philosophy {{!}} A New Way of Thinking About Physics |url=http://www.digitalphilosophy.org/ |archiveurl= https://web.archive.org/web/20210126115736/http://www.digitalphilosophy.org/ |website=digitalphilosophy.org}} Fredkin taught a graduate course called "digital physics" at MIT in 1978, and collaborated with Tommaso Toffoli on "conservative logic" while Norman Margolus served as a graduate student in his research group.{{Cite web |title=Tomorrow’s computer, yesterday |url=https://www.technologyreview.com/2021/04/27/1021714/tomorrows-computer-yesterday/ |access-date=2025-04-07 |website=MIT Technology Review |language=en}}

Digital physics posits that there exists, at least in principle, a program for a universal computer that computes the evolution of the universe. The computer could be, for example, a huge cellular automaton.Zuse, Konrad, 1967, Elektronische Datenverarbeitung vol 8., pages 336–344 It is deeply connected to the concept of information theory, particularly the idea that the universe's fundamental building blocks might be bits of information rather than traditional particles or fields.

However, extant models of digital physics face challenges, particularly in reconciling with several continuous symmetries{{Cite journal|last= Fritz|first= Tobias|date= June 2013|title= Velocity polytopes of periodic graphs and a no-go theorem for digital physics|journal= Discrete Mathematics|language= en|volume= 313|issue= 12|pages= 1289–1301|doi= 10.1016/j.disc.2013.02.010|doi-access= free|arxiv= 1109.1963}} in physical laws, e.g., rotational symmetry, translational symmetry, Lorentz symmetry, and the Lie group gauge invariance of Yang–Mills theories, all of which are central to current physical theories. Moreover, existing models of digital physics violate various well-established features of quantum physics, as they belong to a class of theories involving local hidden variables. These models have so far been disqualified experimentally by physicists using Bell's theorem.{{Cite journal |last= Aaronson |first= Scott |date= 2014 |title= Quantum randomness: if there's no predeterminism in quantum mechanics, can it output numbers that truly have no pattern? |url= https://link.gale.com/apps/doc/A373474677/AONE?u=mlin_oweb&sid=googleScholar&xid=62475a52 |journal= American Scientist |volume= 102 |issue= 4 |pages= 266–271|doi= 10.1511/2014.109.266 |doi-access= free }}{{Cite book |doi = 10.1007/978-3-319-74971-6_8

|title = Quantum Foundations, Probability and Information |year = 2018 |last1 = Jaeger |first1 = Gregg | chapter= Clockwork Rebooted: Is the Universe a Computer? | series=STEAM-H: Science, Technology, Engineering, Agriculture, Mathematics & Health |pages = 71–91| isbn=978-3-319-74970-9 }}