6 ms·

Does having inherently unpredictable phenomena have philosophical implications?

by seventhtiger 3y ago

widea 3y ago
The variation of philosophical implications are possibly unpredictable by themselves...
- richardfey 3y ago
  Ha! Gödel would be so proud of this conjecture
jbotz 3y ago
Certainly. One of the most fundamental philosophical questions is about the nature of time, precisely because all of our "laws" of physics are time reversible, so from the perspective of physics time doesn't really exist or is just a space-like dimension (no arrow). And so the Universe should be perfectly deterministic and with enough computing power and precise enough knowledge of the initial conditions everything should be perfectly predictable and the future should be "fixed". In some way or another probably most of philosophy is arguing about whether or not this is true and what it means. This paper claims that 5% of 3-body systems in the Universe can't be predicted even in principle, because you would need to measure initial conditions to greater precision than the planck length, which is impossible. And of course N-body systems where N > 3 are even more unpredictable, and the whole of the Universe is an N-body system, so if correct it would mean the end of determinism. For a good treatment of this topic for a lay audience see Lee Smolin's recent book "Time Reborn".
- lordfrito 3y ago
  > And of course N-body systems are even more unpredictable, and the whole of the Universe is an N-body system, so if correct it would mean the end of determinism. I read this as the systems are, for all intents and purposes, practically unpredictable, not fundamentally unpredictable. Just because we can't measure beyond the plank length doesn't mean there aren't deterministic rules down there. So my take is that the universe could still be deterministic, but that can't be knowable to us since we'd have to be able to peer below the plank length. Maybe I'm reading this wrong.
  - nine_k 3y ago
    "Fundamentally"as in "QM forbids this". If our universe were different, a simpler kind which Laplace dealt with, it could be completely predicable, as theories of 18th century stated.
    - simonh 3y ago
      I think an appeal to quantum mechanics is a different argument from the one under discussion, which is based on discrete physics.
      - TheOtherHobbes 3y ago
        It's a different view of the same problem.
      - mannykannot 3y ago
        I'm not sure it is a different argument, given its dependence on the Planck length.
  - layer8 3y ago
    Indeed. The evolution of the universal wave function as described by the Schrödinger equation is perfectly deterministic. If you believe in that as the fundamental description of reality (which also means not believing in wave-function collapse), the result is the many-worlds interpretation of QM. Similarly, hidden-variable theories are deterministic.
    - TheOtherHobbes 3y ago
      If hidden variable theories exist, they're non-local. Which is a whole other philosophical problem. As for many worlds - when everything is possible, nothing is explained.
      - layer8 3y ago
        Many-worlds doesn’t mean that everything is possible, it rather means that everything that is possible becomes actual. It is arguably strongest in explanation, in the sense that it relies on the least amount of assumptions (just the Schrödinger equation).
- seventhtiger 3y ago
  So this would be a totally separate source of indeterminism than quantum mechanics. So you could have a schrodinger's rocket fired at a indeterministic 3-body system which means multiple sources of indeterminism interact. Entropy could be viewed as the simple addition of information due to indeterminism. How can causality survive in a universe like that.
  - MattPalmer1086 3y ago
    Why does causality require determinism? Surely effect can still follow cause, even if it is not predictable in advance?
    - seventhtiger 3y ago
      The scientific method tests its understanding of causation using prediction. If something is not predictable in principle, then it is impossible to show that it has causation.
      - rolisz 3y ago
        Doesn't the Turing halting problem also imply that (some) things are not predictable (the halting of certain algorithms)? But I don't think that interferes with causality.
        deleted 3y ago
        [deleted]
      - mannykannot 3y ago
        Causality in physics survived the discovery of quantum uncertainty, though it was changed by it. What parts of current physics would have to be abandoned if our current inability to predict outcomes with complete precision turned out to be fundamental?
      - tsimionescu 3y ago
        That only matters if you assume infinite measurement accuracy, and the scientific method has never assumed that. Even if we assume the world is 100% fully deterministic, as long as our measurements are not 100% accurate we will have some amount of measurement noise which is completely indistinguishable, even in principle, from true fundamental randomness. In fact, fundamental randomness is much easier to work around than measurement noise, since there is no risk of it being correlated with your experimental design. In contrast, measurement errors are often correlated to the measurement method, which makes them much harder to eliminate statistically.
- simonh 3y ago
  >'One of the most fundamental philosophical questions is about the nature of time, precisely because all of our "laws" of physics are time reversible' Many of our theories are, but the thing is we have several direct observations of time reversal symmetry violation (below), independent of the experimental demonstrations of CP violation which also imply T-Symmetry violation. https://arxiv.org/abs/1409.5998 https://arxiv.org/abs/1409.5998 https://pubs.aip.org/physicstoday/article-abstract/52/2/19/410762/Two-Experiments-Observe-Explicit-Violation-of-Time?redirectedFrom=fulltext https://pubs.aip.org/physicstoday/article-abstract/52/2/19/4...
  - MengerSponge 3y ago
    Yes! This is important. It's a finding from 1964, nearly 60 years ago, and it is included in the Standard Model of physics. One interesting thing is that unlike the other discrete symmetries, we haven't found a system that has a large Time-reversal symmetry violation. Not having a large enough source of T-violation is actually one of the major problems with the SM! Related supplemental reading on the Strong CP problem: https://www.forbes.com/sites/startswithabang/2019/11/19/the-strong-cp-problem-is-the-most-underrated-puzzle-in-all-of-physics/?sh=313919bd1ea7 https://www.forbes.com/sites/startswithabang/2019/11/19/the-...
- bufferoverflow 3y ago
  The universe is not an N-body problem. Because we have things behaving like waves. Which are much harder to simulate. We can't even simulate a 2-electron collision precisely.
daxfohl 3y ago
See Norton's Dome as an example of nondeterministic behavior in classical mechanics. No quantum or chaos etc required. https://en.m.wikipedia.org/wiki/Norton%27s_dome https://en.m.wikipedia.org/wiki/Norton%27s_dome
- tsimionescu 3y ago
  Note that this is not an actual physical experiment - it only works with an infinitely accurate and smooth shape of the dome, which contradicts all of the models of how matter exists at least since the ancient greeks. Any dome made up of atoms, even if arranged perfectly accurately up to the position of each individual atom, does not exhibit any kind of non-deterministic behavior in classical mechanics.

Does having inherently unpredictable phenomena have philosophical implications?

widea 3y ago

The variation of philosophical implications are possibly unpredictable by themselves...

richardfey 3y ago
Ha! Gödel would be so proud of this conjecture

jbotz 3y ago

Certainly. One of the most fundamental philosophical questions is about the nature of time, precisely because all of our "laws" of physics are time reversible, so from the perspective of physics time doesn't really exist or is just a space-like dimension (no arrow). And so the Universe should be perfectly deterministic and with enough computing power and precise enough knowledge of the initial conditions everything should be perfectly predictable and the future should be "fixed". In some way or another probably most of philosophy is arguing about whether or not this is true and what it means. This paper claims that 5% of 3-body systems in the Universe can't be predicted even in principle, because you would need to measure initial conditions to greater precision than the planck length, which is impossible. And of course N-body systems where N > 3 are even more unpredictable, and the whole of the Universe is an N-body system, so if correct it would mean the end of determinism. For a good treatment of this topic for a lay audience see Lee Smolin's recent book "Time Reborn".

lordfrito 3y ago
> And of course N-body systems are even more unpredictable, and the whole of the Universe is an N-body system, so if correct it would mean the end of determinism. I read this as the systems are, for all intents and purposes, practically unpredictable, not fundamentally unpredictable. Just because we can't measure beyond the plank length doesn't mean there aren't deterministic rules down there. So my take is that the universe could still be deterministic, but that can't be knowable to us since we'd have to be able to peer below the plank length. Maybe I'm reading this wrong.
- nine_k 3y ago
  "Fundamentally"as in "QM forbids this". If our universe were different, a simpler kind which Laplace dealt with, it could be completely predicable, as theories of 18th century stated.
  - simonh 3y ago
    I think an appeal to quantum mechanics is a different argument from the one under discussion, which is based on discrete physics.
    - TheOtherHobbes 3y ago
      It's a different view of the same problem.
    - mannykannot 3y ago
      I'm not sure it is a different argument, given its dependence on the Planck length.
- layer8 3y ago
  Indeed. The evolution of the universal wave function as described by the Schrödinger equation is perfectly deterministic. If you believe in that as the fundamental description of reality (which also means not believing in wave-function collapse), the result is the many-worlds interpretation of QM. Similarly, hidden-variable theories are deterministic.
  - TheOtherHobbes 3y ago
    If hidden variable theories exist, they're non-local. Which is a whole other philosophical problem. As for many worlds - when everything is possible, nothing is explained.
    - layer8 3y ago
      Many-worlds doesn’t mean that everything is possible, it rather means that everything that is possible becomes actual. It is arguably strongest in explanation, in the sense that it relies on the least amount of assumptions (just the Schrödinger equation).
seventhtiger 3y ago
So this would be a totally separate source of indeterminism than quantum mechanics. So you could have a schrodinger's rocket fired at a indeterministic 3-body system which means multiple sources of indeterminism interact. Entropy could be viewed as the simple addition of information due to indeterminism. How can causality survive in a universe like that.
- MattPalmer1086 3y ago
  Why does causality require determinism? Surely effect can still follow cause, even if it is not predictable in advance?
  - seventhtiger 3y ago
    The scientific method tests its understanding of causation using prediction. If something is not predictable in principle, then it is impossible to show that it has causation.
    - rolisz 3y ago
      Doesn't the Turing halting problem also imply that (some) things are not predictable (the halting of certain algorithms)? But I don't think that interferes with causality.
      - deleted 3y ago
        [deleted]
    - mannykannot 3y ago
      Causality in physics survived the discovery of quantum uncertainty, though it was changed by it. What parts of current physics would have to be abandoned if our current inability to predict outcomes with complete precision turned out to be fundamental?
    - tsimionescu 3y ago
      That only matters if you assume infinite measurement accuracy, and the scientific method has never assumed that. Even if we assume the world is 100% fully deterministic, as long as our measurements are not 100% accurate we will have some amount of measurement noise which is completely indistinguishable, even in principle, from true fundamental randomness. In fact, fundamental randomness is much easier to work around than measurement noise, since there is no risk of it being correlated with your experimental design. In contrast, measurement errors are often correlated to the measurement method, which makes them much harder to eliminate statistically.
simonh 3y ago
>'One of the most fundamental philosophical questions is about the nature of time, precisely because all of our "laws" of physics are time reversible' Many of our theories are, but the thing is we have several direct observations of time reversal symmetry violation (below), independent of the experimental demonstrations of CP violation which also imply T-Symmetry violation. https://arxiv.org/abs/1409.5998 https://arxiv.org/abs/1409.5998 https://pubs.aip.org/physicstoday/article-abstract/52/2/19/410762/Two-Experiments-Observe-Explicit-Violation-of-Time?redirectedFrom=fulltext https://pubs.aip.org/physicstoday/article-abstract/52/2/19/4...
- MengerSponge 3y ago
  Yes! This is important. It's a finding from 1964, nearly 60 years ago, and it is included in the Standard Model of physics. One interesting thing is that unlike the other discrete symmetries, we haven't found a system that has a large Time-reversal symmetry violation. Not having a large enough source of T-violation is actually one of the major problems with the SM! Related supplemental reading on the Strong CP problem: https://www.forbes.com/sites/startswithabang/2019/11/19/the-strong-cp-problem-is-the-most-underrated-puzzle-in-all-of-physics/?sh=313919bd1ea7 https://www.forbes.com/sites/startswithabang/2019/11/19/the-...
bufferoverflow 3y ago
The universe is not an N-body problem. Because we have things behaving like waves. Which are much harder to simulate. We can't even simulate a 2-electron collision precisely.

daxfohl 3y ago

See Norton's Dome as an example of nondeterministic behavior in classical mechanics. No quantum or chaos etc required. https://en.m.wikipedia.org/wiki/Norton%27s_dome https://en.m.wikipedia.org/wiki/Norton%27s_dome

tsimionescu 3y ago
Note that this is not an actual physical experiment - it only works with an infinitely accurate and smooth shape of the dome, which contradicts all of the models of how matter exists at least since the ancient greeks. Any dome made up of atoms, even if arranged perfectly accurately up to the position of each individual atom, does not exhibit any kind of non-deterministic behavior in classical mechanics.