Paul Davies
Well, let me tell you about them, and then you'll be able to change your mind. Most of the experiments used to discriminate between Einstein's and
Bohr's view of the world involve two particles that interact and then move a long way apart, and then measurements are performed simultaneously on
these separated particles. Now it's possible to prove a very general theorem, making only three assumptions. One is that normal logical rules apply.
So if we agree that we want to be bound by ordinary logical reasoning then the theorem follows. And then the two physical assumptions are, one, that
there should be no faster than light signalling - that's a consequence of Einstein's theory of relativity, and Einstein for one would be reluctant to
give that up (...)
--and the other is that there is some type of reality of the type you were talking about, in which objects have well- defined properties prior to our
making measurements - in other words, they really exist in certain states and so on. Normal, old-fashioned, cause and effect if you like. You can show
that, subject to those three conditions, there are strict mathematical limits to the degree of correlations that can exist between these separated
particles. And you can do the experiment and what you find is that those limits are violated. The limits are called "Bell's Inequalities", after John
Bell. And so you have three choices. One is to abandon ordinary logical reasoning - most people wouldn't want to do that. The other is to say that
there's some sort of faster than light signalling - "ghostly action at a distance" is what Einstein called it. (...)
(Or that they're somehow connected.)
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