Quote:
Originally Posted by CraigS
So, I'm having a lot of difficulty in translating all this into plain English.
Is it reasonable to say that Bell's theorem is saying that faster than light changes can happen, and can be reproduced as per quantum mechanical predictions, whereas Special Relativity says this cannot happen ?
I'm mystified as to whether any of these concepts are implying anything about the causes of entanglement.
It seems to be more about predictions of correlated events (??)
Cheers
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Craig,
Here is simple example of the significance of Bell's Inequality for an experiment.
Suppose you performed a machine washability test on gloves at different temperatures. The gloves are dyed in different colours but are made of the same material. Let's assume that the dye is stable at all temperatures and doesn't wash off. Hence each glove is expected to react in the same way when tested. By testing large numbers of gloves you can calculate the probabilities of whether or not the gloves survive a test at a given temperature.
The probabilities are the same if you are testing left hand gloves or right hand gloves.
If you pair off the gloves according to their colours, the probabilities are still the same. This is because the result on a left hand glove doesn't effect the result on a right hand glove and vice versa for any given test.
For this test Bell's inequality isn't violated as the left hand and right hand gloves have separate realities. Each glove has a local reality.
Local hidden variable theories which maintain that local reality exists, run into trouble when for example the test on a right hand (or left hand) glove does effect the other glove. Since the gloves have a separate reality and exist at different points in space-time there must be an instantaneous transfer of information which of course would exceed the speed of light.
When Bell's inequality is violated this means there cannot be separate realities. In the case of a pair of photons, the photons exist in a delocalized or entangled state.
The photons are in "contact" prior to a measurement being made in an experiment.
Regards
Steven