4 ms·

There's a quote, in I believe one of Greg Egans books, about the idea that the probable end state of physics will be just a bunch of isomorphic theories, which

by tw1010 8y ago

There's a quote, in I believe one of Greg Egans books, about the idea that the probable end state of physics will be just a bunch of isomorphic theories, which I wish I could find right now.

westoncb 8y ago
For understanding why that might be, I find this to be an elegant little example: take a pattern of black and white stripes; is it white with black stripes, or is it black with white stripes? The two formulations are identical in consequence of what they describe, even though they frame things inversely. (Of course this is just a metaphor to hint toward something in the nature of language, and is not really a deep scenario if you dig into it.) It seems likely that the descriptions we formulate in physical theories work because they create a pattern which is isomorphic to patterns we extract in physical measurements—but there's something in the nature of the universe and/or language so that there tends to be many ways to create some linguistic thing which produces exactly the same pattern.
- whatshisface 8y ago
  That's actually one of the main ideas of positivism: that if two theories lead to the same physical predictions, they are the same theory. When positivism is presented as "every true thing is empirically knowable" it sounds kind of shaky, but if you instead go for, "you can't tell the difference between two internally-consistent claims unless you compare them with the world," then it sounds a lot more likely to be true.
  - goatlover 8y ago
    > "you can't tell the difference between two internally-consistent claims unless you compare them with the world," then it sounds a lot more likely to be true. But only if it's the case that we end up with more than one theory which explains the phenomena equally well. That doesn't seem to be what ends up happening. We don't have an equivalent to GR, QM, Evolution, or any other well established, large scale theory. Positivism sounds closer to math than it does science. And that's because nature is a certain way, which means you probably can't have equivalent theories at sufficiently granular levels.
    - westoncb 8y ago
      My understanding is that there are multiple precisely equivalent formulations of classical mechanics (Newtonian mechanics being one of them, but then there's e.g. Lagrangian mechanics[0] and other more exotic things). Perhaps that doesn't cross your threshold for 'sufficient granularity'—but it took quite a bit of time to find the alternate formulations in classical mechanics (after Newton I mean), so just because we don't yet have them for certain more modern theories doesn't mean they aren't forthcoming. Also, I'm pretty sure there are at least very nearly equivalent formulations of QM, e.g. the de broglie pilot wave stuff (often termed as an alternate 'interpretation', but my understanding is that the differences extend even to the level of mathematical formulation, and are not just some detached reflections on the 'meaning' of the theory or whatever. [0] https://en.wikipedia.org/wiki/Lagrangian_mechanics https://en.wikipedia.org/wiki/Lagrangian_mechanics
      - whatshisface 8y ago
        >so just because we don't yet have them I think the strongest argument for positivism is that you can generate arbitrarily many trivial "different but the predictions are the same" theories from any parent theory just by doing algebra. You can also generate arbitrarily many "the predictions are slightly different but our present experiments can't resolve it" theories from a parent theory by littering it with new, small constants and tiny interactions. Occam's razor will lead you astray about that, too: most of modern physics was at one time a small constant or a tiny interaction.
    - deleted 8y ago
      [deleted]
Florin_Andrei 8y ago
Well, Egan was just repeating things that others were saying before. This is M-theory basically, and Stephen Hawking, among others, has mentioned it as a possible "theory of everything".
gowld 8y ago
What else could be? The universe is outside our language(s) to describe it, so there's no reason to have only one isomorphic theory. The only alternative is to have two (or more) incomplete theories, but then combining them makes one "unified" theory. Even in pure math, outside of physics, the same applies. The only other possible alternative would be , what, one tiny theory that is essentially simple and minimal in every possible way, yet somehow models everything, in the spirit of ANKOS?

by tw1010 8y ago

There's a quote, in I believe one of Greg Egans books, about the idea that the probable end state of physics will be just a bunch of isomorphic theories, which I wish I could find right now.

westoncb 8y ago

For understanding why that might be, I find this to be an elegant little example: take a pattern of black and white stripes; is it white with black stripes, or is it black with white stripes? The two formulations are identical in consequence of what they describe, even though they frame things inversely. (Of course this is just a metaphor to hint toward something in the nature of language, and is not really a deep scenario if you dig into it.) It seems likely that the descriptions we formulate in physical theories work because they create a pattern which is isomorphic to patterns we extract in physical measurements—but there's something in the nature of the universe and/or language so that there tends to be many ways to create some linguistic thing which produces exactly the same pattern.

whatshisface 8y ago
That's actually one of the main ideas of positivism: that if two theories lead to the same physical predictions, they are the same theory. When positivism is presented as "every true thing is empirically knowable" it sounds kind of shaky, but if you instead go for, "you can't tell the difference between two internally-consistent claims unless you compare them with the world," then it sounds a lot more likely to be true.
- goatlover 8y ago
  > "you can't tell the difference between two internally-consistent claims unless you compare them with the world," then it sounds a lot more likely to be true. But only if it's the case that we end up with more than one theory which explains the phenomena equally well. That doesn't seem to be what ends up happening. We don't have an equivalent to GR, QM, Evolution, or any other well established, large scale theory. Positivism sounds closer to math than it does science. And that's because nature is a certain way, which means you probably can't have equivalent theories at sufficiently granular levels.
  - westoncb 8y ago
    My understanding is that there are multiple precisely equivalent formulations of classical mechanics (Newtonian mechanics being one of them, but then there's e.g. Lagrangian mechanics[0] and other more exotic things). Perhaps that doesn't cross your threshold for 'sufficient granularity'—but it took quite a bit of time to find the alternate formulations in classical mechanics (after Newton I mean), so just because we don't yet have them for certain more modern theories doesn't mean they aren't forthcoming. Also, I'm pretty sure there are at least very nearly equivalent formulations of QM, e.g. the de broglie pilot wave stuff (often termed as an alternate 'interpretation', but my understanding is that the differences extend even to the level of mathematical formulation, and are not just some detached reflections on the 'meaning' of the theory or whatever. [0] https://en.wikipedia.org/wiki/Lagrangian_mechanics https://en.wikipedia.org/wiki/Lagrangian_mechanics
    - whatshisface 8y ago
      >so just because we don't yet have them I think the strongest argument for positivism is that you can generate arbitrarily many trivial "different but the predictions are the same" theories from any parent theory just by doing algebra. You can also generate arbitrarily many "the predictions are slightly different but our present experiments can't resolve it" theories from a parent theory by littering it with new, small constants and tiny interactions. Occam's razor will lead you astray about that, too: most of modern physics was at one time a small constant or a tiny interaction.
  - deleted 8y ago
    [deleted]

Florin_Andrei 8y ago

Well, Egan was just repeating things that others were saying before. This is M-theory basically, and Stephen Hawking, among others, has mentioned it as a possible "theory of everything".

gowld 8y ago

What else could be? The universe is outside our language(s) to describe it, so there's no reason to have only one isomorphic theory. The only alternative is to have two (or more) incomplete theories, but then combining them makes one "unified" theory. Even in pure math, outside of physics, the same applies. The only other possible alternative would be , what, one tiny theory that is essentially simple and minimal in every possible way, yet somehow models everything, in the spirit of ANKOS?