4 ms·

I mean, obviously. If you let a system interact with the external world that system on its own will not follow the schrodinger equation. Carroll is suggesting

I mean, obviously. If you let a system interact with the external world that system on its own will not follow the schrodinger equation. Carroll is suggesting we try to observe this behavior from a sufficiently large isolated system.

pdonis 2y ago
> If you let a system interact with the external world that system on its own will not follow the schrodinger equation. Not only that--even the combined system + what it is interacting with won't. > Carroll is suggesting we try to observe this behavior from a sufficiently large isolated system. But you can't, even with the entire universe, if measurements have single results. In the MWI, they don't; any measurement has all possible results. But we don't observe that, we observe measurements to have single results, so the MWI has to jump through hoops to explain that discrepancy away--and in doing so, makes itself unfalsifiable.
- whimsicalism 2y ago
  sure it’s unfalsifiable in that there is always an interpretation of copenhagen that will predict the same thing as MWI, but if we are able to construct a very large object that doesn’t show “collapse”, it seems vibe-wise that the same process is what is happening to us when we make a measurement, just more chaotically (aka decoherence)
- mitthrowaway2 2y ago
  > But we don't observe that, we observe measurements to have single results What do you think it would feel like to observe a measurement to have multiple results simultaneously? And do you think MWI predicts any branch of the wavefunction would exist in which a human would be experiencing that sensation? It doesn't; it predicts a superposition of (human observes result A + human observes result B), with ~zero probability of (human observes both results A + B). So I'm not sure which hoops you think MWI needs to jump through to match our subjective experience.
  - pdonis 2y ago
    > What do you think it would feel like to observe a measurement to have multiple results simultaneously? I have no idea. > do you think MWI predicts any branch of the wavefunction would exist in which a human would be experiencing that sensation? No. As you say, the MWI claims that in each branch of the wave function, the human experiences a single result of a measurement. However, that is completely different from the way QM normally treats individual branches of the wave function in an entangled superposition, which is what we are talking about--"measurement" in the MWI is just an interaction that entangles a "measured system" with a "measuring device" (and eventually with "the brain of a human who looks at the measuring device to read off its result") and results in an entangled superposition of all of those subsystems. Normally, in individual branches of an entangled superposition of multiple subsystems, each subsystem has no well-defined state at all. Only the full system, including all branches of the superposition, has a well-defined state. That would imply that in the case of a "measurement", the measuring device in each individual branch, and the brain of the human that looks at it, would have no well-defined state at all. It would not imply that in each branch, the measuring device and the brain of the human that looks at it has a well-defined state that corresponds to a particular measurement result being recorded and observed. In terms of your "feel like", the way QM normally treats individual branches of the wave function in an entangled superposition, it should not "feel like" anything in any individual branch. The human should only "feel like" something, if at all, in the full wave function, containing all the branches. And of course nobody has any idea what it would "feel like" in such a state--but it clearly would not "feel like" having observed a particular result of a measurement. > I'm not sure which hoops you think MWI needs to jump through to match our subjective experience. It needs to explain why, somehow, when a "measuring device" or a human observer is involved, the way QM treats individual branches of entangled superpositions drastically changes. See above.

pdonis 2y ago

> If you let a system interact with the external world that system on its own will not follow the schrodinger equation. Not only that--even the combined system + what it is interacting with won't. > Carroll is suggesting we try to observe this behavior from a sufficiently large isolated system. But you can't, even with the entire universe, if measurements have single results. In the MWI, they don't; any measurement has all possible results. But we don't observe that, we observe measurements to have single results, so the MWI has to jump through hoops to explain that discrepancy away--and in doing so, makes itself unfalsifiable.

whimsicalism 2y ago
sure it’s unfalsifiable in that there is always an interpretation of copenhagen that will predict the same thing as MWI, but if we are able to construct a very large object that doesn’t show “collapse”, it seems vibe-wise that the same process is what is happening to us when we make a measurement, just more chaotically (aka decoherence)
mitthrowaway2 2y ago
> But we don't observe that, we observe measurements to have single results What do you think it would feel like to observe a measurement to have multiple results simultaneously? And do you think MWI predicts any branch of the wavefunction would exist in which a human would be experiencing that sensation? It doesn't; it predicts a superposition of (human observes result A + human observes result B), with ~zero probability of (human observes both results A + B). So I'm not sure which hoops you think MWI needs to jump through to match our subjective experience.
- pdonis 2y ago
  > What do you think it would feel like to observe a measurement to have multiple results simultaneously? I have no idea. > do you think MWI predicts any branch of the wavefunction would exist in which a human would be experiencing that sensation? No. As you say, the MWI claims that in each branch of the wave function, the human experiences a single result of a measurement. However, that is completely different from the way QM normally treats individual branches of the wave function in an entangled superposition, which is what we are talking about--"measurement" in the MWI is just an interaction that entangles a "measured system" with a "measuring device" (and eventually with "the brain of a human who looks at the measuring device to read off its result") and results in an entangled superposition of all of those subsystems. Normally, in individual branches of an entangled superposition of multiple subsystems, each subsystem has no well-defined state at all. Only the full system, including all branches of the superposition, has a well-defined state. That would imply that in the case of a "measurement", the measuring device in each individual branch, and the brain of the human that looks at it, would have no well-defined state at all. It would not imply that in each branch, the measuring device and the brain of the human that looks at it has a well-defined state that corresponds to a particular measurement result being recorded and observed. In terms of your "feel like", the way QM normally treats individual branches of the wave function in an entangled superposition, it should not "feel like" anything in any individual branch. The human should only "feel like" something, if at all, in the full wave function, containing all the branches. And of course nobody has any idea what it would "feel like" in such a state--but it clearly would not "feel like" having observed a particular result of a measurement. > I'm not sure which hoops you think MWI needs to jump through to match our subjective experience. It needs to explain why, somehow, when a "measuring device" or a human observer is involved, the way QM treats individual branches of entangled superpositions drastically changes. See above.