Por João Lopes dos Santos (Departamento de Física e Astronomia, Faculdade de Ciências, Universidade do Porto, Portugal).

At the end of the second decade of the last century, the discussion on the nature of Quantum Mechanics occupied central stage, with Einstein and Bohr as leading actors. Then it moved into the side lines, such was its success atomic physics. "Shut up and calculate" became the dominant paradigm in the community. Einstein stayed unconvinced, but when in 1935 he proposed, with Podolsky and Rosen, a new challenge - the EPR gedanken experiment -, most physicists delegated the answer to Bohr and considered the matter closed. Not so John Bell, who in the sixties gave a crucial impulse to the discussion by shifting it to the field of experiment. Without him the 2022 Nobel prize in Physics would have been different.