4 ms·

Observations in MWI are just ordinary physical interactions. Specifically they're perturbative-regime interactions between the thing being observed and large th

Observations in MWI are just ordinary physical interactions. Specifically they're perturbative-regime interactions between the thing being observed and large thermalized systems (e.g. humans). From the perspective of the thermal bath, you get exponential suppression of everything but the eigenstates of the interaction Hamiltonian, which is why our observations "look classical".

kgwgk 3y ago
Will other large thermalised system (e.g. rocks) also experience observations that "look classical"? Another MWI proponent here is talking about how the "look classical" thing is "simply an artifact of being a conscious being that can only observe one value". Is there something special about "large thermalised systems" (and/or humans)? How large have they to be to allow for "our observations"? Where is the boundary between the thing being observed and the observing thing? MWI seems to still face most of the difficult questions - it not all.
- consilient 3y ago
  > Will other large thermalised system (e.g. rocks) also experience observations that "look classical"? The inner life of rocks is somewhat beyond our reach, I'm afraid. But they'll induce decoherence in the same way as a human, yes. > Is there something special about "large thermalised systems" (and/or humans)? Aside from being large and thermalized? No. > How large have they to be to allow for "our observations"? It's a continuum. The more internal degrees of freedom you have, and the more thoroughly they're mixed, the faster you'll decohere things. > Where is the boundary between the thing being observed and the observing thing? At the level of fundamental physics, there isn't one. "Observation" is an approximate and thermodynamic notion.
  - kgwgk 3y ago
    > But they'll induce decoherence in the same way as a human, yes. From the perspective (?) of the (non-human) thermal bath, will that decoherence result in a single (diagonal, mixture) state or in a particular state of those N separate states that would "look classical"? Decoherence doesn't make things "look classical" by itself - at least until you define what "looking" is.
    - consilient 3y ago
      Depends on whether you're talking about the "perspective" of the whole joint |Rock>|Interaction Eigenstate 1> + |Rock>|Interaction Eigenstate 2> ... system or just one of its components. > Decoherence doesn't make things "look classical" by itself - at least until you define what "looking" is. Of course; but that's true of every scientific theory. Decoherence solves the preferred basis problem, not the hard problem of consciousness.
      - kgwgk 3y ago
        > Decoherence solves the preferred basis problem, not the hard problem of consciousness. Ok, I guess I misunderstood the scope of "There's also nothing special about observing." It's not clear to me if you (MWI) would say that rocks had defined positions when nobody was observing them - or whether the question of things having definite positions (and the very existence of those things) wouldn't even make sense in the absence of consciousness.
        consilient 3y ago
        > Ok, I guess I misunderstood the scope of "There's also nothing special about observing." There's nothing special about the physical processes constituting a scientific experiment. They're unitary evolution like everything else. Whether there's anything special about conscious experience (for my money: obviously yes) is outside the scope of physics. > or whether the question of things having definite positions (and the very existence of those things) wouldn't even make sense in the absence of consciousness. If you want to be perfectly precise, the MWI does not contain discrete things at all, any more than the Earth objectively has discrete continents and seas. But the most accurate map is not always the most useful one.
        kgwgk 3y ago
        If the MWI doesn’t contain the Earth, the seas or the molecules of water it may not be providing a very useful map until we add a lot of things to it.

kgwgk 3y ago

Will other large thermalised system (e.g. rocks) also experience observations that "look classical"? Another MWI proponent here is talking about how the "look classical" thing is "simply an artifact of being a conscious being that can only observe one value". Is there something special about "large thermalised systems" (and/or humans)? How large have they to be to allow for "our observations"? Where is the boundary between the thing being observed and the observing thing? MWI seems to still face most of the difficult questions - it not all.

consilient 3y ago
> Will other large thermalised system (e.g. rocks) also experience observations that "look classical"? The inner life of rocks is somewhat beyond our reach, I'm afraid. But they'll induce decoherence in the same way as a human, yes. > Is there something special about "large thermalised systems" (and/or humans)? Aside from being large and thermalized? No. > How large have they to be to allow for "our observations"? It's a continuum. The more internal degrees of freedom you have, and the more thoroughly they're mixed, the faster you'll decohere things. > Where is the boundary between the thing being observed and the observing thing? At the level of fundamental physics, there isn't one. "Observation" is an approximate and thermodynamic notion.
- kgwgk 3y ago
  > But they'll induce decoherence in the same way as a human, yes. From the perspective (?) of the (non-human) thermal bath, will that decoherence result in a single (diagonal, mixture) state or in a particular state of those N separate states that would "look classical"? Decoherence doesn't make things "look classical" by itself - at least until you define what "looking" is.
  - consilient 3y ago
    Depends on whether you're talking about the "perspective" of the whole joint |Rock>|Interaction Eigenstate 1> + |Rock>|Interaction Eigenstate 2> ... system or just one of its components. > Decoherence doesn't make things "look classical" by itself - at least until you define what "looking" is. Of course; but that's true of every scientific theory. Decoherence solves the preferred basis problem, not the hard problem of consciousness.
    - kgwgk 3y ago
      > Decoherence solves the preferred basis problem, not the hard problem of consciousness. Ok, I guess I misunderstood the scope of "There's also nothing special about observing." It's not clear to me if you (MWI) would say that rocks had defined positions when nobody was observing them - or whether the question of things having definite positions (and the very existence of those things) wouldn't even make sense in the absence of consciousness.
      - consilient 3y ago
        > Ok, I guess I misunderstood the scope of "There's also nothing special about observing." There's nothing special about the physical processes constituting a scientific experiment. They're unitary evolution like everything else. Whether there's anything special about conscious experience (for my money: obviously yes) is outside the scope of physics. > or whether the question of things having definite positions (and the very existence of those things) wouldn't even make sense in the absence of consciousness. If you want to be perfectly precise, the MWI does not contain discrete things at all, any more than the Earth objectively has discrete continents and seas. But the most accurate map is not always the most useful one.
        kgwgk 3y ago
        If the MWI doesn’t contain the Earth, the seas or the molecules of water it may not be providing a very useful map until we add a lot of things to it.