The EPR Paradox
Measure one particle here and you instantly know something about its partner light-years away. Einstein thought this proved physics was unfinished.
1935 (argument), 1964 (Bell's theorem), 2015 (loophole-free tests)21 min read
Northern Irish theoretical physics
John Stewart Bell
1928 – 1990
Belfast-born physicist who spent most of his career at CERN doing accelerator and particle theory, and pursued quantum foundations as what he called his "hobby". His 1964 paper turned Einstein's philosophical complaint into an inequality that experiments could test, and his 1966 review dismantled von Neumann's supposed proof that hidden variables were impossible. He died of a stroke in 1990, the year he had been nominated for a Nobel Prize.