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This article completely misses the point. You can never disprove hidden variable theories in a stochastic system, because hidden variable theories make the exac

This article completely misses the point. You can never disprove hidden variable theories in a stochastic system, because hidden variable theories make the exact same predictions as 'true random' theories - the difference is only philosophical. What you can disprove are local hidden variable theories, which were somewhat popular (and favored by Einstein, for example) prior to Bell's thought experiment being empirically supported. See what Einstein wanted was for all of quantum mechanic's weird results to be explainable by local interactions that took place when two particles interact - so that when they become entangled and subsequently drift apart, you don't have to have any "spooky action at a distance" to explain the results of experiments you do on them separately. However, what Bell's experiment shows is that the dice don't get rolled until one of the particles is measured - and that the way in which a measurement is performed on one particle affects its correlation with the other. So in fact you do need instantaneous nonlocal interaction to explain the real world. The result, unfortunately, has nothing to do with 'hidden variables' vs. 'true randomness'. What it does say though, is that you can't just explain away the weirdness of quantum mechanics as the result of some yet-to-be-found local hidden variables.

encoderer 13y ago
"So in fact you do need instantaneous nonlocal interaction to explain the real world." Do you just mean quantum entanglement, or some other "spooky action"? (love that quote btw -- like many)
- Russell91 13y ago
  Haha, well the instances of Bell's experiment that I've seen so far all refer to entanglement. It's pretty easy to think about some unknown quantity having a probability distribution on its states. If you have an electron, and you don't know the spin yet, you say that it can be either up or down. What's special about entanglement between 2 particles is that it says the distributions on the two are not independent. In the classic example, one can only be spin up if the other is spin down - so they have a statistical dependence on each other. Bell's experiment tells us that the strength of this statistical dependence depends on how you measure the particles, which isn't determined until measurement time, when the particles are far away. But that being said, you could imaging all other sorts of spooky action at a distance - like 2 particles that have never been local to one another having some sort of statistical dependence. But that would be really hard to show until you found what type of nonlocal statistical dependence to look for, so usually when we're trying to figure out a good model we end up thinking about entanglement.
rsp1984 13y ago
Thank you for this explanation, this makes so much more sense now.
thisisdave 13y ago
My understanding is that Bell's inequality is a little more devastating for hidden variable theories. To make hidden variable theories work, you don't just need spooky action at a distance: you need that spooky action to travel faster than light.

encoderer 13y ago

"So in fact you do need instantaneous nonlocal interaction to explain the real world." Do you just mean quantum entanglement, or some other "spooky action"? (love that quote btw -- like many)

Russell91 13y ago
Haha, well the instances of Bell's experiment that I've seen so far all refer to entanglement. It's pretty easy to think about some unknown quantity having a probability distribution on its states. If you have an electron, and you don't know the spin yet, you say that it can be either up or down. What's special about entanglement between 2 particles is that it says the distributions on the two are not independent. In the classic example, one can only be spin up if the other is spin down - so they have a statistical dependence on each other. Bell's experiment tells us that the strength of this statistical dependence depends on how you measure the particles, which isn't determined until measurement time, when the particles are far away. But that being said, you could imaging all other sorts of spooky action at a distance - like 2 particles that have never been local to one another having some sort of statistical dependence. But that would be really hard to show until you found what type of nonlocal statistical dependence to look for, so usually when we're trying to figure out a good model we end up thinking about entanglement.

rsp1984 13y ago

Thank you for this explanation, this makes so much more sense now.

thisisdave 13y ago

My understanding is that Bell's inequality is a little more devastating for hidden variable theories. To make hidden variable theories work, you don't just need spooky action at a distance: you need that spooky action to travel faster than light.