The EPR paradox (Einstein-Podolsky-Rosen paradox) is a set of experiments that suggest ‘spooky action at a distance’ because particles appear to share information instantaneously, at a distance, long after an interaction between them.
People applying “common sense” would like to argue that there is some way that the information is being shared—some hidden variable that collects and shares the information between them.
Bell’s Inequality only assumes there there is some such hidden variable operating locally* -- with no specifications of any kind on how it works—and deduces correlations between particles sharing information that is in contradiction with experiments.
* that is, mechanically rather than ‘magically’ at a distance
Well, actually everything has to follow them because of Bell’s Theorem.
Edit: The second link should be to this explanation, which is somewhat less funny, but actually explains the experiments that violate the theorem. Sorry that I took so long, but it appeared that the server was down when I first tried to fix it, so I went and did other things for half an hour.
What are Bell’s inequalities, and why do quantumly-behaving things with deterministic causes have to follow them?
Alicorn, if you’re free after dinner tomorrow, I can probably explain this one.
The EPR paradox (Einstein-Podolsky-Rosen paradox) is a set of experiments that suggest ‘spooky action at a distance’ because particles appear to share information instantaneously, at a distance, long after an interaction between them.
People applying “common sense” would like to argue that there is some way that the information is being shared—some hidden variable that collects and shares the information between them.
Bell’s Inequality only assumes there there is some such hidden variable operating locally* -- with no specifications of any kind on how it works—and deduces correlations between particles sharing information that is in contradiction with experiments.
* that is, mechanically rather than ‘magically’ at a distance
Um… am I missing something or did no one link to, ahem:
http://lesswrong.com/lw/q1/bells_theorem_no_epr_reality/
Thank you, although I find this a little too technical to wrap my brain around at the moment.
Well, actually everything has to follow them because of Bell’s Theorem.
Edit: The second link should be to this explanation, which is somewhat less funny, but actually explains the experiments that violate the theorem. Sorry that I took so long, but it appeared that the server was down when I first tried to fix it, so I went and did other things for half an hour.
There’s no good explanation anywhere. :(