4 ms·

>is not true, either. I didn't think this was settled and depends on your interpretation of QM: https://en.wikipedia.org/wiki/Action_at_a_distance https://en.w

>is not true, either. I didn't think this was settled and depends on your interpretation of QM: https://en.wikipedia.org/wiki/Action_at_a_distance https://en.wikipedia.org/wiki/Action_at_a_distance

codethief 8y ago
…and on your precise definition of "action and a distance", yes. But there is something like standard textbook quantum mechanics which most physicists subscribe to, i.e. the Copenhagen interpretation, and while I'm not saying this is the interpretation everyone should follow and believe in (in fact, there are good reasons to be dissatisfied with this interpretation), the term "action at a distance" was coined in the context of the Copenhagen interpretation, so I think should therefore also be interpreted in this context. Now, Copenhagen is a local and non-realist theory, the latter of which meaning among other things that the wave function is not believed to be an object of reality. Therefore, in this interpretation, the collapse of the wave function is merely a tool for predicting the outcome of a measurement and not something that's believed to actually happen. The same thing goes for an "instantaneous collapse" at a distance — this action does not exist in reality. I know there is probably going to be someone who objects to me saying that Copenhagen is non-realist and local. But those people will have to explain to me how they would bring the actual existence of the wave function and its collapse into agreement with relativity and, in particular, with different observers who come to different conclusions about when the wave function collapses. For instance, for one observer, it might be Alice who causes the wave function to collapse and, thus, Bob to measure a certain outcome but then there is always going to be another observer who will say the exact opposite, namely that Bob caused the collapse. So, essentially, if you really think the wave function is an object of reality, all hell breaks lose. Needless to say, even if you completely disregard these issues and still want to think of Copenhagen as a realist but then necessarily non-local theory (in which case I'd say you should really give your theory a different name), this is all just splitting hairs because the only thing that matters is that there's no FTL transfer of information. This is the only experimentally verifiable statement we can make.

>is not true, either. I didn't think this was settled and depends on your interpretation of QM: https://en.wikipedia.org/wiki/Action_at_a_distance https://en.wikipedia.org/wiki/Action_at_a_distance

codethief 8y ago

…and on your precise definition of "action and a distance", yes. But there is something like standard textbook quantum mechanics which most physicists subscribe to, i.e. the Copenhagen interpretation, and while I'm not saying this is the interpretation everyone should follow and believe in (in fact, there are good reasons to be dissatisfied with this interpretation), the term "action at a distance" was coined in the context of the Copenhagen interpretation, so I think should therefore also be interpreted in this context. Now, Copenhagen is a local and non-realist theory, the latter of which meaning among other things that the wave function is not believed to be an object of reality. Therefore, in this interpretation, the collapse of the wave function is merely a tool for predicting the outcome of a measurement and not something that's believed to actually happen. The same thing goes for an "instantaneous collapse" at a distance — this action does not exist in reality. I know there is probably going to be someone who objects to me saying that Copenhagen is non-realist and local. But those people will have to explain to me how they would bring the actual existence of the wave function and its collapse into agreement with relativity and, in particular, with different observers who come to different conclusions about when the wave function collapses. For instance, for one observer, it might be Alice who causes the wave function to collapse and, thus, Bob to measure a certain outcome but then there is always going to be another observer who will say the exact opposite, namely that Bob caused the collapse. So, essentially, if you really think the wave function is an object of reality, all hell breaks lose. Needless to say, even if you completely disregard these issues and still want to think of Copenhagen as a realist but then necessarily non-local theory (in which case I'd say you should really give your theory a different name), this is all just splitting hairs because the only thing that matters is that there's no FTL transfer of information. This is the only experimentally verifiable statement we can make.