Does time's arrow point in the wrong direction?
Jun 1, 2003
Perhaps the deepest mystery in all of physics is quantum non-locality - the ability of two distant systems to instantaneously know about each other. Non-locality means that two particles in a quantum system can be "entangled" such that the state of one particle affects the state of the other, regardless of how far apart they are. As well as challenging our common sense, non-locality suggests that the ultimate speed limit - the speed of light - is violated. Einstein spent many years worrying about this problem because such "superluminal" interactions seem to be incompatible with special relativity.
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