Comment by A_D_E_P_T
4 days ago
Oh man, Stephen Wolfram and Jürgen Schmidthuber are probably fuming at the fact that this is called a "new" mathematical framework. It's all very old, and quite conventional, even popular -- not exactly the road not taken.
What the author did was use the Physical Church-Turing thesis, and Kleene's second recursion theorem, to show that: (1) If a universe’s dynamics are computable (PCT), and (2) the universe can implement universal computation (RPCT), then (3) the universe can simulate itself, including the computer doing the simulating.
That's basically all. And thus "there would be two identical instances of us, both equally 'real'." (Two numerically distinct processes are empirically identical if they are indistinguishable. You might remember this sort of thing from late 20th c. philosophy coursework.)
He also uses Rice’s theorem (old) to show that there is no uniform measure over the set of "possible universes."
It's all very interesting, but it's more a review article than a "new mathematical framework." The notion of a mathematical/simulated universe is as old as Pythagoras (~550 BC), and Rice, Church-Turing, and Kleene are all approaching the 100-year mark.
I'm no mathematician, but doesn't this come up against Gödel's incompleteness theorem? My brain has that roughly as "If you have a system and a model of that system, but the model is also part of the same system, something something, impossible"
Isn't GIT you can have a statement that is valid in a system, but can't be proven this way or that given the systems' axioms? And this is true for all such axiom systems? In other words the axioms are an incomplete description of the system.
Maybe the problem is axiomative deduction, we need a new inference-ology?
No, this sort of self-reflection is exactly what makes Gödel/Turing/etc impossibility results work ("strange loops" and all that).
Can you explain further?
Maybe I'm too out of this scope but if you want to simulate Universe X plus the computer Y that simulates X then you'd need at least 1 extra bit of memory (likely way more) to encompass the simulation plus the computation running the simulation (X+Y). The computer running the simulation by definition is not part of the simulation, so how can it be that it can truly simulate itself?
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Godel's incompleteness theorem is about the limits of proof / mathematical knowledge. Algebra is still useful and true, even though the proof shows it must be incomplete.
Any decent Lisp can reimplement eval, apply and the rest of functions/atom within itself.
It’s also a little silly for the same reasons discussions of theoretical computability often are: time and space requirements. In practice the Universe, even if computable, is so complex that simulating it would require far more compute than physical particles and far more time than remaining until heat death.
Hehe yeah.. For me, its just inverted search for the God. There must be somethink behind it, if its not God, then it must be simulation! Kinda sad, I would expect more from scientist.
The big riddle of Universe is, how all that matter loves to organize itself, from basic particles to Atoms, basic molecues, structured molecues, things and finally live.. Probably unsolvable, but that doesnt mean we shouldnt research and ask questions...
>The big riddle of Universe is, how all that matter loves to organize itself, from basic particles to Atoms, basic molecues, structured molecues, things and finally live.. Probably unsolvable, but that doesnt mean we shouldnt research and ask questions...
Isn't that 'just' the laws of nature + the 2nd law of thermodynamics? Life is the ultimate increaser of entropy, because for all the order we create we just create more disorder.
Conway's game of life has very simple rules (laws of nature) and it ends up very complex. The universe doing the same thing with much more complicated rules seems pretty natural.
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For me the biggest riddle is: why something instead of nothing ?
That's the question that prevent me from being atheist and shift me to agnosticism.
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> The big riddle of Universe is, how
A lot of people are more interested in the Why of the Universe than the How, though.
How is an implementation detail, Why is "profound". At least that's how I think most people look at it.
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You expect scientists to not ask :‘what is behind all this?’
Ha
Yes, is that (obvious) point being addressed in the paper? At first skimming, it just says that a "sufficiently souped up laptop" could, in principle, compute the future of the universe (i.e. Laplace's daemon), but I haven't seen anything about the subsequent questions of time scales.
Computing the future is cool, but computing the past state is also really cool as it essentially allows time travel into (a copy of) the past.
The real universe might be different and far more complex than our simulated reality. Maybe a species that can freely move within 4 or 5 dimensions is simulating our 3D + uni directional time reality just like we „simulate“ reality with Sim City and Sims.
but then we don't have a universe simulating itself, but simulating a low-fi imitation
You're predicating on particles, heat death, etc as you understand it being applicable to any potential universe. Such rules are only known to apply in this universe.
A universe is simply a function, and a function can be called multiple times with the same/different arguments, and there can be different functions taking the same or different arguments.
The issue with that in terms of the simulation argument, is that the simulation argument doesn't require a complete simulation in either space or time.
It also doesn't require a super-universe with identical properties and constraints.
There's no guarantee their logic is the same as our logic. It needs to be able to simulate our logic, but that doesn't mean it's defined or bound by it.
Thanks for this great comment!
> He also uses Rice’s theorem (old) to show that there is no uniform measure over the set of "possible universes."
I assume a finite uniform measure? Presumably |set| is a uniform measure over the set of "possible universes".
Anyway if I understood that correctly, than this is not that surprising? There isn't a finite uniform measure over the real line. If you only consider the possible universes of two particles at any distance from eachother, this models the real line and therefore has no finite uniform measure.
Okay, here's the thing: this is creating revenue, this is fascinating literature for a huge class of armchair scientists that want to believe, want to play with these mental toys, and are willing to pay for the ability to fantasize with ideas they are incapable of developing on their own. This is ordinary capitalism, spinning revenues out of sellable stories.