I Interpretation of Schrodinger's Cat

  • Thread starter Pleonasm
  • Start date
317
18
. But it raises a problem that nobody, AFAIK, has ever been able to solve: "the probability of me being one of the me's that sees a live cat" doesn't make sense, because both of the branches after the measurement are "you". "You" before the measurement does not become one or the other branch after the measurement, with some chance of each; "you" before the measurement becomes both branches after the measurement. This is the issue I referred to before as the problem of explaining where the Born rule comes from in the MWI.
That appears to be a conceptual objection, rather than a scientific one. Not gonna refute a theory that way.

Anyway, we don't need to go down this path. The equations work. The wave function evolves deterministically regardless of which interpretation one takes. Determinism and probabilities is not an oxymoron. The probabilities most likely (no pun intended) represent our knowledge of the system. As long as it obeys the laws of physics, I can sleep well at night.
 
24,312
5,990
That appears to be a conceptual objection, rather than a scientific one
Agreed; it's an objection against a particular interpretation, but there's no way to test it by experiment.

The wave function evolves deterministically regardless of which interpretation one takes
Except when a measurement occurs and you either have a collapse (if you are using a collapse interpretation) or you have to treat the wave function as if there had been a collapse (if you are using a no collapse interpretation like the MWI). The MWI claims that the "whole" wave function, including the branches that you did not actually observe as the result of the measurement (which is what deterministic evolution of the wave function would give you), is still "there", but nobody actually uses that "whole" wave function to make predictions about future experiments. They use the reduced wave function that describes just the result that was actually observed.
 
317
18
Agreed; it's an objection against a particular interpretation, but there's no way to test it by experiment.



Except when a measurement occurs and you either have a collapse (if you are using a collapse interpretation) or you have to treat the wave function as if there had been a collapse (if you are using a no collapse interpretation like the MWI). The MWI claims that the "whole" wave function, including the branches that you did not actually observe as the result of the measurement (which is what deterministic evolution of the wave function would give you), is still "there", but nobody actually uses that "whole" wave function to make predictions about future experiments. They use the reduced wave function that describes just the result that was actually observed.
Wrong. We have determinism regardless:

"Quantum physics is completely deterministic, as far as the time-evolution of the solution of the equation of state is concerned. In the early days of QM, some people were disturbed because the solution itself is in terms of probability amplitudes, but it remains true that those amplitudes evolve deterministically."

/Rory Coker
 
24,312
5,990
Quantum physics is completely deterministic, as far as the time-evolution of the solution of the equation of state is concerned. In the early days of QM, some people were disturbed because the solution itself is in terms of probability amplitudes, but it remains true that those amplitudes evolve deterministically.
As long as no measurement takes place, yes. Not once a measurement takes place. Ask anyone who actually does QM for a living.
 
317
18
As long as no measurement takes place, yes. Not once a measurement takes place. Ask anyone who actually does QM for a living.
Why are you being so persistent? I just told you that it's wrong, and quoted an actual physicist. I don't know if it's appropriate to reproduce lectures from Hawkings since he is dead (is it still not allowed?), but you know where to find it (does god play dice). He explains how we still have determinism, but not Laplace kind in QM, and that includes observations.
 
24,312
5,990
I just told you that it's wrong, and quoted an actual physicist.
You gave no link, so I have no idea what kind of source you're quoting from. You know the rules, and you've been warned before for not adhering to that one.

I don't know if it's appropriate to reproduce lectures from Hawkings
You don't have to reproduce them, just link to them.

He explains, if you read the full lecture, how we still have determinism, but not Laplace kind in QM, and that includes observations.
Do you mean this lecture?


If so, it's not a textbook or peer-reviewed paper, so it's not a valid source. Pop science articles or lectures, even by scientists, are not reliable if you want to learn the actual science. Plus, even leaving that aside, the lecture does not say what you claim it says; note that at one point, Hawking says (referring to black holes) that not only does God play dice, but he sometimes throws them where they can't be seen.

Rory is second
Quora answers aren't valid sources either. Plus, it says nothing whatever about measurement. Note that the first response does address precisely that point--and says what I have been saying, not what you have been saying. So even if this Quora page were a valid source, it wouldn't support your claim.

This thread is closed.
 

Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving

Hot Threads

Top