John Archibald Wheeler is a bit of a hero for me (and also, like all good heroes a bit of a villain). Discovering his paper “It from Bit” was definitely a huge inspiration for me to get into the field. When I found Wheeler’s paper it led me to Bill Wootters work, and I immediately charged my parents hundreds of dollars to get a copy of very paper Bill had written (I mean who wouldn’t want to read “Quantum mechanics without probability amplitudes“) Amusingly these days I think many who claim the mantle of “it from bit” have not actually read the paper, which is quite radical, you should definitely stop reading this blog and read the paper if you have not.
Because Wheeler is someone who I’ve always been interested in, I was Googling (company plug) around the other day and found out the the American Philosophical Society has a collection with papers, notes, etc from Wheeler. Among these is a typed up note that I don’t think ever made it into a paper, but which I really loved. The title of the note is “THE UNIVERSE AS A COMPUTER”, and is dated “[1980?]”. In it Wheeler first lists possible meanings for the expression “the universe as a computer” followed by possible implications for this metaphor. And by list, I don’t mean a small list, he puts down 48 possible meanings. I love it.
Here are Wheeler’s possible meanings for the metaphor:
THE UNIVERSE AS A COMPUTER | [1980?]
Possible Meanings of the Metaphor
NOTE: Such metaphors tend to be at once useful and misleading. They are understood only intuitively, vaguely, partially, ambiguously, and abstractly by their authors and users. They are apt to be polysemous–possessed of multiple and complex meanings, both relevant and irrelevant. Moreover, in the present instance the utilitarian and natural meaning of the very words universe and computer is unknown to an indefinite degree! Physicists who are trying to conceive a new cosmology based in part on the metaphor of the universe as a computer may find the following list clarifying, heuristic, provocative, useful for self-criticism or discussion, &c. It is a partial list that needs to be extended, systematized, edited, explained, and illuminated by examples and corollaries.
1. May be more or less similar or identical to a Turing machine or serial computer, or be wholly or partly I-dimensional.
2. May comprise the equivalent of serial computers operating, either independently or interdependently, in a parallel array.
3. May resemble more nearly a completely parallel computer whose elements are not sub-computers.
4. May represent a hybrid serial and parallel computer.
5. May represent a hierarchy, network, and/or series of many serial or parallel computers.
6. May represent an infinite or finite set of computers.
7. May represent a computer of infinite size, complexity, subdivisibilit (componentry), age, lifespan, sophistication, perfection, power, connectivity, programming, knowledge, intelligence, dimensionality, activity, strangeness, and/or the like.
8. May (or physics may) reduce to pure mathematics, numbers, or ‘order’.
9. May use or reduce entirely to information, symbols, computer-like rules, states, decisions, operations, markers, pointers, arrays, structures, programs, sets, and/or the like.
10. May be like a computer in being instructible and programmable–or re-instructible, re-programmable, controllable, and manipulable. |
11. May reduce to a computer at a higher, lower, or ultimate level (scale).
12. May be treated as equivalent to a computer if the treatment is sufficiently elaborate, universal, clever, and/or absolute.
13. May represent a set of (finitely or infinitely) homogeneous or heterogeneous computers.
14. May represent a digital or binary computer.
15. May represent an analogue computer of finite, infinite, or infinitesimal self-similarity.
16. May be mechanical in the sense of being possessed of machinelike entities or phenomena–or of parts, operations, laws, &c that are surprisingly or absolutely simple, regular, interchangeable, interlocking, perfect, universal, reliable, deterministic, knowable, predictable, finite, utilitarian, teleological, rational, constructible, symmetric, efficient, irreducible, repetitive, and/or the like.
17. May behave like a computer on occasion or in special situations.
18. May use a (central or omnipresent) model of itself.
19. May be simulated by a computer with arbitrarily great accuracy.
20. May represent a superficial pattern projected, in effect, on a background–or something like a program or simulation of a universe that is running on an independent and truly real computer but 1s not itself real or fundamental.
21. All natural phenomena, entities, and systems (be they trees, rocks, : molecules, bacteria, men, societies, rivers, stars, diseases, clouds, or whatever) may be computers or computer-like (have programs, perform computations, use circuitry, possess memory, use languages, process information, use Boolean logic, or the like).
22. May be clock-like or use universally or locally synchronized parts or processes.
23. All known laws may be controlled or created by higher laws (possibly arranged in a hierarchy or network). :
24. The universe or all physical phenomena may be reducible to computation or a single great calculation.
25. May reduce to or be controlled by, or be expressible as, pure (Boolean or non-Boolean) logic.
26. May be a mind, mind-like, or thought-like, or be reducible to or treatable by pure thought.
27. May possess a (finite or infinite) computer-like or other memory; or memories and memory processes may exist in all natural phenomena (trees, rocks, genomes, &c).
28. May wholly or in part consist of cellular automata, or be a single great or infinite cellular automaton.
29. Physical processes, phenomena, entities, events, quantities, laws, states, and relationships (such as apparent movement, mass, fundamental physical constants, particle populations, 3-space, spacetime, volcanoes, and ocean waves) may be representational, programmatic, or computational illustons~~-or be infinitely ambiguous–rather than truly fundamental or real; and per se, may be alterable or transcendable by gaining knowledge of and control over their ‘programs’ or an equivalent. Put otherwise, all phenomena, &C may appear or behave as they do because of internal programs, self-models, rules, or computation to which man can gain access.
30. May be a lattice–or spacetime may be wholly quantized.
31. All quantum numbers may reduce to a single quantum number.
32. May essentially represent but a single, individual particle, event, or computer (that somehow generates the illusion of a multifarious world); or a single iterative or recursive operation repeating itself forever or toward a finite future destiny.
33. May represent more or less homogeneous or heterogeneous iterative or recursive processes, entities, phenomena, laws, quanta, measurements, disturbances, &c.
34. It may be possible to show that information and computation are fundamentally indistinguishable and hence equivalent, or that all of the following must in a similar way be equivalent: information, computation, energy, mass, space, time, and/or the like.
35. May be an asynchronous computer (computer with asynchronous parts).
36. May be a computer that functions statistically and indeterministically.
37. May be more or less lifelike (possessed of biological features such as homeostasis, growth, self-reproduction, self-evolution, competition, purpose, or memory).
38. As science progresses and becomes more complex, difficult, mathematical, and abstract, reliance on the computer may become total; and this may make a purely computational representation of the universe expedient, and justify present-day steps in that direction.
39. No one knows how simple, powerful, universal, natural, and/or complex computers might ultimately become–and it might be in these ultimate senses that the universe is or resembles a ‘computer’. (It might even be possible to devise revolutionary types of computers by studying and applying computational or computer-like properties of the universe.)
40. May function in ways similar or identical to such computer or mental processes as generalization, recognition, categorization, error correction, time sequence retention, induction, symbolic logic, analogical reasoning, and/or the like.
41. May use holonomical memory, correlations, or laws, something like a computer’s content-addressable memory, and/or the like. |
42. May represent an anastomotic network of everywhere diverging, converging,and interacting causes and effects, and in this way resemble a computer’s structure and functioning.
43. May be in some profound sense a function of the mind, and hence half-mental; or respond in entirely different ways dependent on how it is ‘addressed’.
44. Local phenomena may be controlled from a distance or by larger systems.
45. May represent a great hierarchical network of specialized ‘administrators’ or ‘administrative! processes, functions, systems, laws, constraints, &c. Also, may contain things analogous to questions, answers, experiments, orders, requests, negotiations, conversations, messages, traffic cops, supervisors, inspectors, translators, arbitrators, pioneers, &c.
46. May be totally finitistic–or finite everywhere and in every way.
47. May be ‘centralized’ and ‘centralistically’ controlled.
48. All that exists in the universe (including relationships, entities, interactions, laws, &c that are conventionally thought of as being inert, static, or time-invariant) may in fact be time-asymmetric or an uninterrupted process of change or of cosmoplastic or cosmopoietic interadjustments and interchanges; in this ‘everywhere~ always~novel universe! work and information-processing could be omnipresent and quintessential.
–THE UNIVERSE AS A COMPUTER
There are a couple of things that struck me in this list. The first is number 39. “39. No one knows how simple, powerful, universal, natural, and/or complex computers might ultimately become–and it might be in these ultimate senses that the universe is or resembles a ‘computer’. (It might even be possible to devise revolutionary types of computers by studying and applying computational or computer-like properties of the universe.) ” If this is truly 1980, this is pretty amazing because it is at its heart a statement that the universe’s computation may be very powerful, and that this might lead us to more powerful computers. This is right around the time Manin is credited with mentioning the idea of quantum computation in his book Computable and Uncomputable and before the 1981 Physics of Computation conference, which I think is rightfully considered a good point to take as the starting time for quantum computing.
The second thing that I love is Wheeler. “may in fact be time-asymmetric or an uninterrupted process of change or of cosmoplastic or cosmopoietic interadjustments and interchanges” I mean come on this is awesome who writes like that these days? Wheeler’s writing was so full of this crazy poetry, that it famously got parodied in “Rasputin, Science, and the Transmogrification of Destiny” by “John Archibald Wylers”. Excellent stuff.
I was lucky enough to work with a brilliant graduate student, Ben Toner, where we looked at the information cost of simulating entanglement. When we completed that work, Ben was able to attend a conference in honor of Wheeler, and I believe he told him about our work. I’m sad I never got to meet him, but I hope he could recognize in Ben talking with him, the long echo of his impact on those of us who still dream more about computation and the universe.
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