  In a famous theorem, John Bell (1964) demonstrated that granted some plausible assumptions, any local model of the EPR/B experiment is committed to certain inequalities about the probabilities of measurement outcomes, ‘the Bell inequalities,’ which are incompatible with the quantum-mechanical predictions. When Bell proved his theorem, the EPR/B experiment was only a thought experiment. But due to technological advances, various versions of this experiment have been conducted since the 1970s, and their results have overwhelmingly supported the quantum-mechanical predictions (for brief reviews of these experiments and further references, see the entry on Bell's theorem and Redhead 1987, chapter 4, section 4.3 and ‘Notes and References’). Thus, a wide consensus has it that the quantum realm involves some type of non-locality.