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Macroscopic decoherence (and therefore many worlds) is a straightforward prediction of the Schrödinger equation. It's not something you can just dismiss as ima

Macroscopic decoherence (and therefore many worlds) is a straightforward prediction of the Schrödinger equation. It's not something you can just dismiss as imaginary.

TheOtherHobbes 10y ago
Apart from that minor "Let's create an infinite number of universes out of nothing" problem. Mathematical solutions are never guaranteed to be physical, or even potentially realisable.
- bmh100 10y ago
  What is your preferred interpretation? Mine is pilot wave, treating the wave function as a purely mathematical and nonphysical concept.
  - Filligree 10y ago
    Pilot wave theory still requires the wavefunction to exist, with all the same detail as many-worlds, all the same computations. It just then picks a particular timeline and declares that this one is real, these are real particles, and everything else is shadows on the wall. It's thus incompatible with computationalism. I consider this scenario improbable.
    - bmh100 10y ago
      My limited understanding is that the pilot wave is more of a concept regarding embodied in the exact state of the universe. In other words, the pilot wave is the seed in the pseudorandom number generator of the universe.
      - Filligree 10y ago
        I'll admit it does get a little philosophical, but: No. The "pilot wave", in pilot wave theory, is a mathematical object identical to the universal wavefunction of the many-worlds interpretation. As such, if you believe that computation is all is required for consciousness to exist (and there's no separate "is real" tag on the math), then it's an incoherent concept. I fall on that side myself, but I can't convincingly argue that it's the right philosophical stance to take. I've yet to see anyone give a proof, it just seems most likely.
    - openasocket 10y ago
      Isn't this equivalent to a universe with non-determinism?
      - Filligree 10y ago
        No, non-determinism on its own can't reproduce all the predictions of quantum mechanics. That'd be a different theory, and one I believe has been disproven experimentally.
- wyager 10y ago
  The cardinality of a many-worlds multiverse isn't clear. It might be finite if all physical systems are in a superposition of a finite number of eigenstates in the collapse/split basis. You're also not creating anything out of nothing. The correct version of your complaint is "Let's create x > n things out of n things" (where "things" are quantum states), which happens all the time when you take the tensor product of two quantum systems, evolve the new overall system, and end up with a state that's not factorizable into a tensor product of two states.
- bduerst 10y ago
  Or that every probable action guarantees the creation of a new universe where the action didn't happen.
- fizx 10y ago
  Keep in mind that the infinite universes still obey conservation laws collectively. I tend to think of it like the number line. There are infinite numbers between 0 and 1. If we decide to define infinite unique ranges between 0 and 1, the space each one occupies becomes infinitely small and the total range is conserved. But we don't know whether the multiverse is infinite or not, so that corresponds to the question of whether the range is from 0 to 1, or 0 to infinity. Either way, the original point stands, and unitarity of the wavefunction (the most notable conservation law) is maintained in Many-worlds. Where people get confused seems to be a mix-and-match of incompatible parts of the Copenhagen and Many-worlds interpretations, where you have both universe-splitting and the non-unitary wave function collapse in the same flawed interpretation.
bmh100 10y ago
What makes it seem imaginary to me is this: in what dimension(s) do all of these infinite "universes" reside? Why do they not interact in any way? What causes this creation of matter and energy?
- srssays 10y ago
  If we didn't have telescopes, you could make the same argument about the existence of other galaxies.
  - bmh100 10y ago
    You could, and that's a fair point, but you're more talking about philosophy of science and epistemology. My point is that Many Worlds seems to die to Occam's Razor, because of all the additional requirements to accept Many Worlds over something like wave function collapse.
    - mrec 10y ago
      Back when I read about this stuff I had the exact opposite reaction - Occam's Razor seemed to favour Many-Worlds. Given direct experience of one universe, I think it's more ontologically conservative to introduce multiple universes than it is to introduce a whole new unprecedented category of cats that are simultaneously dead and alive. Very loose analogy: if I see a mouse in front of me and simultaneously hear a squeak behind me, I'd probably assume two mice rather than one mouse which has learned ventriloquism.
      - osullivj 10y ago
        Interesting. Occam's Razor says "don't multiply entities beyond need", not "don't multiply types of entities beyond need". Of course, you could argue that types are entities too. So many worlds minimizes entity types at the expense of total entity count.
        mrec 10y ago
mannykannot 10y ago
> Macroscopic decoherence (and therefore many worlds) is a straightforward prediction of the Schrödinger equation. I was not aware of that development. in what way is the Copenhagen interpretation inconsistent with the Schrödinger equation?

Macroscopic decoherence (and therefore many worlds) is a straightforward prediction of the Schrödinger equation. It's not something you can just dismiss as imaginary.

TheOtherHobbes 10y ago

Apart from that minor "Let's create an infinite number of universes out of nothing" problem. Mathematical solutions are never guaranteed to be physical, or even potentially realisable.

bmh100 10y ago
What is your preferred interpretation? Mine is pilot wave, treating the wave function as a purely mathematical and nonphysical concept.
- Filligree 10y ago
  Pilot wave theory still requires the wavefunction to exist, with all the same detail as many-worlds, all the same computations. It just then picks a particular timeline and declares that this one is real, these are real particles, and everything else is shadows on the wall. It's thus incompatible with computationalism. I consider this scenario improbable.
  - bmh100 10y ago
    My limited understanding is that the pilot wave is more of a concept regarding embodied in the exact state of the universe. In other words, the pilot wave is the seed in the pseudorandom number generator of the universe.
    - Filligree 10y ago
      I'll admit it does get a little philosophical, but: No. The "pilot wave", in pilot wave theory, is a mathematical object identical to the universal wavefunction of the many-worlds interpretation. As such, if you believe that computation is all is required for consciousness to exist (and there's no separate "is real" tag on the math), then it's an incoherent concept. I fall on that side myself, but I can't convincingly argue that it's the right philosophical stance to take. I've yet to see anyone give a proof, it just seems most likely.
  - openasocket 10y ago
    Isn't this equivalent to a universe with non-determinism?
    - Filligree 10y ago
      No, non-determinism on its own can't reproduce all the predictions of quantum mechanics. That'd be a different theory, and one I believe has been disproven experimentally.
wyager 10y ago
The cardinality of a many-worlds multiverse isn't clear. It might be finite if all physical systems are in a superposition of a finite number of eigenstates in the collapse/split basis. You're also not creating anything out of nothing. The correct version of your complaint is "Let's create x > n things out of n things" (where "things" are quantum states), which happens all the time when you take the tensor product of two quantum systems, evolve the new overall system, and end up with a state that's not factorizable into a tensor product of two states.
bduerst 10y ago
Or that every probable action guarantees the creation of a new universe where the action didn't happen.
fizx 10y ago
Keep in mind that the infinite universes still obey conservation laws collectively. I tend to think of it like the number line. There are infinite numbers between 0 and 1. If we decide to define infinite unique ranges between 0 and 1, the space each one occupies becomes infinitely small and the total range is conserved. But we don't know whether the multiverse is infinite or not, so that corresponds to the question of whether the range is from 0 to 1, or 0 to infinity. Either way, the original point stands, and unitarity of the wavefunction (the most notable conservation law) is maintained in Many-worlds. Where people get confused seems to be a mix-and-match of incompatible parts of the Copenhagen and Many-worlds interpretations, where you have both universe-splitting and the non-unitary wave function collapse in the same flawed interpretation.

bmh100 10y ago

What makes it seem imaginary to me is this: in what dimension(s) do all of these infinite "universes" reside? Why do they not interact in any way? What causes this creation of matter and energy?

srssays 10y ago
If we didn't have telescopes, you could make the same argument about the existence of other galaxies.
- bmh100 10y ago
  You could, and that's a fair point, but you're more talking about philosophy of science and epistemology. My point is that Many Worlds seems to die to Occam's Razor, because of all the additional requirements to accept Many Worlds over something like wave function collapse.
  - mrec 10y ago
    Back when I read about this stuff I had the exact opposite reaction - Occam's Razor seemed to favour Many-Worlds. Given direct experience of one universe, I think it's more ontologically conservative to introduce multiple universes than it is to introduce a whole new unprecedented category of cats that are simultaneously dead and alive. Very loose analogy: if I see a mouse in front of me and simultaneously hear a squeak behind me, I'd probably assume two mice rather than one mouse which has learned ventriloquism.
    - osullivj 10y ago
      Interesting. Occam's Razor says "don't multiply entities beyond need", not "don't multiply types of entities beyond need". Of course, you could argue that types are entities too. So many worlds minimizes entity types at the expense of total entity count.
      - mrec 10y ago

mannykannot 10y ago

> Macroscopic decoherence (and therefore many worlds) is a straightforward prediction of the Schrödinger equation. I was not aware of that development. in what way is the Copenhagen interpretation inconsistent with the Schrödinger equation?