In our day-to-day world, we are accustomed to the idea that two events are unlikely to be correlated unless there is a clear connection of cause and effect. Pulling a red sock onto my right foot in no way ensures that my left foot will also be clad in red - unless I purposely reach into the drawer for another red sock. In 1964, John Bell of the CERN particle physics laboratory near Geneva, Switzerland, described the degree of correlation that classical theories allow. Bell's result relied on two concepts: realism and locality.The only time this ever happens in the macro world, in my own life experience, is if someone is fool enough to put dyed clothes in the javel water bleach wash. If you like white, buy it off the rack.
Realism amounts to saying that the properties of an object exist prior to, and independent of, measurement. In the classical world, that second sock in my drawer is red regardless of whether or not I "measure" its state by looking at it. Locality is the assumption that these properties are independent of any remote influence.
In the quantum world, these are dangerous assumptions. "It turns out that either one or both of Bell's principles must be wrong," says Brukner. If quantum effects were visible in our everyday world, I might well find that my pulling on a red sock leads to the colour of the sock left in my drawer automatically changing to red.
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A world with this degree of interconnection would be weird indeed. I might find that by selecting a red sock from my drawer in the morning, I had predetermined the colour not just of my other sock, but that of my shirt, underpants and of the bus I ride to work.
( - New Scientist 23 August 2010)
More quantum stories here.