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> Quantum Physics - Everything is non-local Not true in the slightest. The Many-Worlds interpretation is local.

ThomPete 11y ago
But it's an interpretation not the actual mathematical and observational data no? I.e. Bells Theorem predict non-locality. Many worlds is a way to interpret not the actual theory? Or am I wrong?
- spacehome 11y ago
  Contrary to the name, Many Worlds is a complete theory. Bell's Theorem does not predict non-locality, rather it says that any local realist theory must satisfy a certain inequality which is violated in practice. An assumption of Bell's Theorem which is so deep of an assumption that people don't even know they're making it is is that there's only one outcome to any measurement.
tim333 11y ago
>The Many-Worlds interpretation is local I'm not sure it is even though Wikipedia currently says that it is local. The recent experiment http://www.nytimes.com/2015/10/22/science/quantum-theory-experiment-said-to-prove-spooky-interactions.html http://www.nytimes.com/2015/10/22/science/quantum-theory-exp... seems to show clear non local effects. I don't think that contradicts Many-Worlds. Much of the question comes down to an aspect that Everett, the inventor of Many-Worlds kind of hand waved over and didn't really explain. He said roughly lets assume all outcomes happen and assign a probability P to each one without really explaining where the Ps came from. In the NYT described experiment the probabilities seem to be such as to show non local effects but Everett and his theory don't really say much as to how they got that way.
- spacehome 11y ago
  The experiment you liked is just a supped up version of the experiments that first showed that Bell's Inequality is violated in our reality. The experiment didn't really have any theoretical import. I don't think anybody really thought that Freedman and Clauser's experimental outcome was due to some "loophole" that, when closed, would let Bell's Inequality be satisfied. And despite what the experimenters seem to believe, the experiment you linked to does not show non-local effects. That's not really the way that science and experimentation work. The experimental result rules out a particular class of physical theory - specifically any theory that's local and real, but a deep assumption of the derivation (so deep that one doesn't realize one is making it) is that every measurement has one outcome, which of course Many Worlds does not assume. I don't think that anyone is hand waving about where probabilities come from -- they are the integral of the squared modulus of the wave function. Nothing ambiguous about the mathematics of the theory. If you're asking why this equation rather than some other equation, it's an open question, and an interesting one. But the Many Worlds Theory can perfectly well do its job as a predictor of experiment without justification of where the equation comes from. You may as well ask "Why the Schrodinger Equation rather than some other equation?". It's also worth pointing out that all interpretations of QM have the same open question because they all have some form of the Born Rule without justification.

But it's an interpretation not the actual mathematical and observational data no? I.e. Bells Theorem predict non-locality. Many worlds is a way to interpret not the actual theory? Or am I wrong?

spacehome 11y ago
Contrary to the name, Many Worlds is a complete theory. Bell's Theorem does not predict non-locality, rather it says that any local realist theory must satisfy a certain inequality which is violated in practice. An assumption of Bell's Theorem which is so deep of an assumption that people don't even know they're making it is is that there's only one outcome to any measurement.

tim333 11y ago

>The Many-Worlds interpretation is local I'm not sure it is even though Wikipedia currently says that it is local. The recent experiment http://www.nytimes.com/2015/10/22/science/quantum-theory-experiment-said-to-prove-spooky-interactions.html http://www.nytimes.com/2015/10/22/science/quantum-theory-exp... seems to show clear non local effects. I don't think that contradicts Many-Worlds. Much of the question comes down to an aspect that Everett, the inventor of Many-Worlds kind of hand waved over and didn't really explain. He said roughly lets assume all outcomes happen and assign a probability P to each one without really explaining where the Ps came from. In the NYT described experiment the probabilities seem to be such as to show non local effects but Everett and his theory don't really say much as to how they got that way.

spacehome 11y ago
The experiment you liked is just a supped up version of the experiments that first showed that Bell's Inequality is violated in our reality. The experiment didn't really have any theoretical import. I don't think anybody really thought that Freedman and Clauser's experimental outcome was due to some "loophole" that, when closed, would let Bell's Inequality be satisfied. And despite what the experimenters seem to believe, the experiment you linked to does not show non-local effects. That's not really the way that science and experimentation work. The experimental result rules out a particular class of physical theory - specifically any theory that's local and real, but a deep assumption of the derivation (so deep that one doesn't realize one is making it) is that every measurement has one outcome, which of course Many Worlds does not assume. I don't think that anyone is hand waving about where probabilities come from -- they are the integral of the squared modulus of the wave function. Nothing ambiguous about the mathematics of the theory. If you're asking why this equation rather than some other equation, it's an open question, and an interesting one. But the Many Worlds Theory can perfectly well do its job as a predictor of experiment without justification of where the equation comes from. You may as well ask "Why the Schrodinger Equation rather than some other equation?". It's also worth pointing out that all interpretations of QM have the same open question because they all have some form of the Born Rule without justification.