5 ms·

>doesn't evolve deterministically Isn't that still debated?

titzer 2y ago
Not really. The best models that we have to explain measurable physical phenomenon are wave equations from quantum mechanics that describe probably distributions. There have been proposals for nearly a century that a deterministic model underlies this, but they have to contend with observed phenomenon and inconveniences like Bell's Theorem that suggest that our universe just isn't deterministic. That said, we don't have a unified theory of the universe. General relativity, the dark matter question, and quantum mechanics have not been unified into any mathematical theory. All of those theories are pretty weird, mathematically. And we have no efficient way to simulate on classical computers the models that we do have. We don't live in a billiard ball universe. It's a CS fantasy that evaporates as soon as you start doing experiments on matter and energy in the actual universe we are in.
- mjburgess 2y ago
  Yes, the biggest problem with this mere mechanistic picture is why anything should move at all. The csci view is essentially a divine command one: the machine runs because of it's 'program' which is somehow external to the machine. But this is a metaphor/illusion for programmable devices like electronic computers, which breaks down for the actual universe. The universe must be inherently dynamical, ie., not mere discrete states that change by rules, but properties whose nature is to interact with the world... This is why the abstract mathematical conception of "computer" cannot describe anything physical: mathematical objects do not have temporal properties; they do not change. This leads to the illusion, for electric devices, that the change is extrinsic to the physics of the system since we can specify the algorithm (somewhat) abstractly. But it isnt.. your pieces of meat, are in the end, the causal power which moves the liquid crystal, electric field, etc.
  - fellowmartian 2y ago
    I think this a caricature or at least a shallow view of computationalism. Nobody is claiming that the universe is a computer of the same kind as the ones we have. Instead, I think, it claims that the universe has to necessarily be computational in order to be real - everything has to be computational to be real, otherwise how can it ever be implemented. On your "divine command" bit: I don't think any theory has a good claim on the ultimate ontology of reality, so I don't see how one view is better than another. It's all some kind of divine command at the moment. Computationalism at least constrains the necessary properties the divine must have.
    - titzer 2y ago
      > everything has to be computational to be real But that's just circular logic. It begs the question as to what is "computational" and what is "mathematical". E.g. Tegmark has good points in the "Mathematical Universe" that describe possible interpretations of what it means to be mathematical. But how is computation different than math? I'd argue that computation is primarily stateful, logical, and (mostly) deterministic with a clear flow of time, whereas mathematical models are often time-reversible (as most, if not of QM is), stateless, and not necessarily "logical" in the sense of relating finite symbolic quantities. Rather mathematical models happily relate infinite series, manifolds, surfaces, high-dimensional spaces, they talk about fields and operate on functions, etc.
- openrisk 2y ago
  > It's a CS fantasy that evaporates as soon as you start doing experiments The interesting bit (pun) is that this seems to be a recurring pattern. Whenever there is a intellectual revolution that establishes new ways of thinking / acting, there is a tendency to apply its toolkit to everything in sight, including "the big questions". So it was with the industrial revolution and the hordes of related engineers: the universe was invariably seen as "a machine". With the digital revolution and the hordes of computer engineers, the universe is invariably "a computer". Effectively just a glorified version of the law of the instrument [1] "to a person with a hammer everything looks like a nail". The controversial question (and one that cannot be dismissed easily) is whether the universe is in some broader sense "mathematical". The huge success of mathematical descriptions around certain corners of the universe makes people think there might be something to it. But maybe mathematics too, is just our hammer. [1] https://en.wikipedia.org/wiki/Law_of_the_instrument https://en.wikipedia.org/wiki/Law_of_the_instrument
  - flawsofar 2y ago
    Perhaps the irreconcilibility of 3 weird mathematical theories is a sign that the universe isn’t mathematical? but what would be the alternative?
    - openrisk 2y ago
      Its possible that we simply havent evolved yet the mental faculties to reconcile them. After all none of these theories were around even like 200 years ago - we had in fact no clue whatsoever about any of that stuff. Mathematics is an evolving process and it can make leaps. The current knowledge might be like distinct coordinate patches on an underlying manifold that we will asymptotically cover with a consistent collection. On the other hand it may indeed be a remarkable feature of the human mind that it can "make mathematical sense" of subsets of reality, but there is no overarching system and no reason to expect that we will be able to make simultaneous mathematical sense of "everything". It might take a long time to collect sufficient such "metadata" to help tilt the balance.
  - RetroTechie 2y ago
    > The controversial question (and one that cannot be dismissed easily) is whether the universe is in some broader sense "mathematical" A similar question: does time evolve in discrete steps, or is it continuous? The passage of time can only be established by comparing with physical phenomena that evolve over time. Even if that comparison would suggest "discrete steps", that doesn't exclude the possibility of time evolving continuously, but instrument / experiment too 'crude' to see between steps. Right up there with "are we living in a simulation?", and "does $DEITY exist?". As long as you can't break into a deeper layer (assuming that exists!), it's undecidable, and a philosophical rather than a scientific question, imho.
- kawa 2y ago
  > The best models Yes, models. But a model doesn't need to be "real", it just models something real to a certain extent. But models tend to break down if you look close enough, and I think this may also happen to QM at some point. Bell's Theorem doesn't rule out determinism, it only rules out hidden variables. If the universe is non-local, Bell's theorem fits well with determinism. > We don't live in a billiard ball universe We do - at least as long we look at clumps of matter. The billiard ball universe breaks down if we look at the constituents of matter but somehow it re-remerges if we put enough of those constituents together. It's probably the biggest riddle in Physics why this happens. But it does.
  - titzer 2y ago
    > But models tend to break down if you look close enough, and I think this may also happen to QM at some point. Sure, but there's absolutely nothing to suggest that it will be some kind of deterministic computation underneath. > We do - at least as long we look at clumps of matter. Not even. Even non-quantum clumps of matter are influenced by continuous fields and dilation effects from both special and relativity. Even without QM, our universe is not efficiently simulatable on our computational models because of general relativity.
    - kawa 2y ago
      > Sure, but there's absolutely nothing to suggest that it will be some kind of deterministic computation underneath The universe behaves very deterministically if we look at "clumps of matter". Why is it this way when this determinism isn't already part of the "base"? For me that's at least a "suggestion". Not a proof of course, but still a hint. > ... because of general relativity. General relativity doesn't fits together with QM, so either one is (or both are) "wrong" (in the sense that they only approximate reality to a certain degree). I'm even sceptical about special relativity: It's a good model and works well in most occasions, but it may still be wrong on a fundamental level. Most of the assumptions under which Einstein proposed SR (no QM, static universe) don't hold anymore.
      - LegionMammal978 2y ago
- eigenket 2y ago
  I mostly agree with this but I would like to emphasise that Bell's theorem emphatically doesn't tell you the universe isn't deterministic. It tells you there isn't a local hidden variables model for it (under appropriate assumptions). There are deterministic models which "escape" Bell's theorem's assumptions. In particular you can assume superdeterminism (which makes it very hard to do physics) or alternatively Everettian "many worlds" quantum mechanics is completely consistent with Bell's theorem.
  - pilebunker7 2y ago
    what do you mean by "makes it very hard to do physics"?
    - eigenket 2y ago
      Super determinism gets around the "problem" of Bell's inequality experiments by saying that the choices of experiment settings chosen by the experimenters are correlated with things we usually wouldn't expect them to be correlated with (like the system being measured). This makes it really hard to do physics because we usually assume you can choose to measure whatever the hell you want independent of the state of the system. Say we have some toy physical system which changes color reguarly, for 10 seconds it's red and for the next 10 seconds it's green and so on. We assume that we'll be able to gain physical understanding of such thing by measuring it whenever we like, but in a superdeterministic universe our choice to do the experiment can be correlated with the system, so we might be "forced" to only measure it when it happens to be red. We'll only ever see it be red and we will end up framing an incorrect "law of physics" that says the thing is red.
- goatlover 2y ago
  The MWI is the second most popular interpretation of QM, and it's deterministic, because Schrodinger's equation evolves deterministically. The probability comes in when making measurements. But in MWI, that's just a function of decoherence hiding the other branches.

Not really. The best models that we have to explain measurable physical phenomenon are wave equations from quantum mechanics that describe probably distributions. There have been proposals for nearly a century that a deterministic model underlies this, but they have to contend with observed phenomenon and inconveniences like Bell's Theorem that suggest that our universe just isn't deterministic. That said, we don't have a unified theory of the universe. General relativity, the dark matter question, and quantum mechanics have not been unified into any mathematical theory. All of those theories are pretty weird, mathematically. And we have no efficient way to simulate on classical computers the models that we do have. We don't live in a billiard ball universe. It's a CS fantasy that evaporates as soon as you start doing experiments on matter and energy in the actual universe we are in.

mjburgess 2y ago
Yes, the biggest problem with this mere mechanistic picture is why anything should move at all. The csci view is essentially a divine command one: the machine runs because of it's 'program' which is somehow external to the machine. But this is a metaphor/illusion for programmable devices like electronic computers, which breaks down for the actual universe. The universe must be inherently dynamical, ie., not mere discrete states that change by rules, but properties whose nature is to interact with the world... This is why the abstract mathematical conception of "computer" cannot describe anything physical: mathematical objects do not have temporal properties; they do not change. This leads to the illusion, for electric devices, that the change is extrinsic to the physics of the system since we can specify the algorithm (somewhat) abstractly. But it isnt.. your pieces of meat, are in the end, the causal power which moves the liquid crystal, electric field, etc.
- fellowmartian 2y ago
  I think this a caricature or at least a shallow view of computationalism. Nobody is claiming that the universe is a computer of the same kind as the ones we have. Instead, I think, it claims that the universe has to necessarily be computational in order to be real - everything has to be computational to be real, otherwise how can it ever be implemented. On your "divine command" bit: I don't think any theory has a good claim on the ultimate ontology of reality, so I don't see how one view is better than another. It's all some kind of divine command at the moment. Computationalism at least constrains the necessary properties the divine must have.
  - titzer 2y ago
    > everything has to be computational to be real But that's just circular logic. It begs the question as to what is "computational" and what is "mathematical". E.g. Tegmark has good points in the "Mathematical Universe" that describe possible interpretations of what it means to be mathematical. But how is computation different than math? I'd argue that computation is primarily stateful, logical, and (mostly) deterministic with a clear flow of time, whereas mathematical models are often time-reversible (as most, if not of QM is), stateless, and not necessarily "logical" in the sense of relating finite symbolic quantities. Rather mathematical models happily relate infinite series, manifolds, surfaces, high-dimensional spaces, they talk about fields and operate on functions, etc.
openrisk 2y ago
> It's a CS fantasy that evaporates as soon as you start doing experiments The interesting bit (pun) is that this seems to be a recurring pattern. Whenever there is a intellectual revolution that establishes new ways of thinking / acting, there is a tendency to apply its toolkit to everything in sight, including "the big questions". So it was with the industrial revolution and the hordes of related engineers: the universe was invariably seen as "a machine". With the digital revolution and the hordes of computer engineers, the universe is invariably "a computer". Effectively just a glorified version of the law of the instrument [1] "to a person with a hammer everything looks like a nail". The controversial question (and one that cannot be dismissed easily) is whether the universe is in some broader sense "mathematical". The huge success of mathematical descriptions around certain corners of the universe makes people think there might be something to it. But maybe mathematics too, is just our hammer. [1] https://en.wikipedia.org/wiki/Law_of_the_instrument https://en.wikipedia.org/wiki/Law_of_the_instrument
- flawsofar 2y ago
  Perhaps the irreconcilibility of 3 weird mathematical theories is a sign that the universe isn’t mathematical? but what would be the alternative?
  - openrisk 2y ago
    Its possible that we simply havent evolved yet the mental faculties to reconcile them. After all none of these theories were around even like 200 years ago - we had in fact no clue whatsoever about any of that stuff. Mathematics is an evolving process and it can make leaps. The current knowledge might be like distinct coordinate patches on an underlying manifold that we will asymptotically cover with a consistent collection. On the other hand it may indeed be a remarkable feature of the human mind that it can "make mathematical sense" of subsets of reality, but there is no overarching system and no reason to expect that we will be able to make simultaneous mathematical sense of "everything". It might take a long time to collect sufficient such "metadata" to help tilt the balance.
- RetroTechie 2y ago
  > The controversial question (and one that cannot be dismissed easily) is whether the universe is in some broader sense "mathematical" A similar question: does time evolve in discrete steps, or is it continuous? The passage of time can only be established by comparing with physical phenomena that evolve over time. Even if that comparison would suggest "discrete steps", that doesn't exclude the possibility of time evolving continuously, but instrument / experiment too 'crude' to see between steps. Right up there with "are we living in a simulation?", and "does $DEITY exist?". As long as you can't break into a deeper layer (assuming that exists!), it's undecidable, and a philosophical rather than a scientific question, imho.
kawa 2y ago
> The best models Yes, models. But a model doesn't need to be "real", it just models something real to a certain extent. But models tend to break down if you look close enough, and I think this may also happen to QM at some point. Bell's Theorem doesn't rule out determinism, it only rules out hidden variables. If the universe is non-local, Bell's theorem fits well with determinism. > We don't live in a billiard ball universe We do - at least as long we look at clumps of matter. The billiard ball universe breaks down if we look at the constituents of matter but somehow it re-remerges if we put enough of those constituents together. It's probably the biggest riddle in Physics why this happens. But it does.
- titzer 2y ago
  > But models tend to break down if you look close enough, and I think this may also happen to QM at some point. Sure, but there's absolutely nothing to suggest that it will be some kind of deterministic computation underneath. > We do - at least as long we look at clumps of matter. Not even. Even non-quantum clumps of matter are influenced by continuous fields and dilation effects from both special and relativity. Even without QM, our universe is not efficiently simulatable on our computational models because of general relativity.
  - kawa 2y ago
    > Sure, but there's absolutely nothing to suggest that it will be some kind of deterministic computation underneath The universe behaves very deterministically if we look at "clumps of matter". Why is it this way when this determinism isn't already part of the "base"? For me that's at least a "suggestion". Not a proof of course, but still a hint. > ... because of general relativity. General relativity doesn't fits together with QM, so either one is (or both are) "wrong" (in the sense that they only approximate reality to a certain degree). I'm even sceptical about special relativity: It's a good model and works well in most occasions, but it may still be wrong on a fundamental level. Most of the assumptions under which Einstein proposed SR (no QM, static universe) don't hold anymore.
    - LegionMammal978 2y ago
eigenket 2y ago
I mostly agree with this but I would like to emphasise that Bell's theorem emphatically doesn't tell you the universe isn't deterministic. It tells you there isn't a local hidden variables model for it (under appropriate assumptions). There are deterministic models which "escape" Bell's theorem's assumptions. In particular you can assume superdeterminism (which makes it very hard to do physics) or alternatively Everettian "many worlds" quantum mechanics is completely consistent with Bell's theorem.
- pilebunker7 2y ago
  what do you mean by "makes it very hard to do physics"?
  - eigenket 2y ago
    Super determinism gets around the "problem" of Bell's inequality experiments by saying that the choices of experiment settings chosen by the experimenters are correlated with things we usually wouldn't expect them to be correlated with (like the system being measured). This makes it really hard to do physics because we usually assume you can choose to measure whatever the hell you want independent of the state of the system. Say we have some toy physical system which changes color reguarly, for 10 seconds it's red and for the next 10 seconds it's green and so on. We assume that we'll be able to gain physical understanding of such thing by measuring it whenever we like, but in a superdeterministic universe our choice to do the experiment can be correlated with the system, so we might be "forced" to only measure it when it happens to be red. We'll only ever see it be red and we will end up framing an incorrect "law of physics" that says the thing is red.
goatlover 2y ago
The MWI is the second most popular interpretation of QM, and it's deterministic, because Schrodinger's equation evolves deterministically. The probability comes in when making measurements. But in MWI, that's just a function of decoherence hiding the other branches.