Ghostly action at a distance: a non-technical explanation of the Bell inequality

ABSTRACT

We give a simple non-mathematical explanation of Bell's inequality. We describe how, when applied to the results of Einstein-Podolsky-Rosen (EPR) experiments (and combined with some auxiliary assumptions), the inequality shows that some sort of faster-than-light influence is present in nature. We discuss the implications, emphasizing the distinction between causal influences and signals, the tension between EPR and determinism, and the challenge of reconciling the Principle of Relativity with the EPR results.