How Bell’s Theorem Proved ‘Spooky Action at a Distance’ Is Real
How Bell’s Theorem Proved ‘Spooky Action at a Distance’ Is Real By BEN BRUBAKER July 20, 2021 The root of today’s quantum revolution was John Stewart Bell’s 1964 theorem showing that quantum mechanics really permits instantaneous connections between far-apart locations 103 READ LATER Samuel Velasco/Quanta Magazine We take for granted that an event in one part of the world cannot instantly affect what happens far away. This principle, which physicists call locality, was long regarded as a bedrock assumption about the laws of physics. So when Albert Einstein and two colleagues showed in 1935 that quantum mechanics permits “spooky action at a distance,” as Einstein put it, this feature of the theory seemed highly suspect. Physicists wondered whether quantum mechanics was missing something. Then in 1964, with the stroke of a pen, the Northern Irish physicist John Stewart Bell demoted locality from a cherished principle to a testable hypothesis. Bell proved that quantum mechan