Part 4/9:
The clash between Niels Bohr and Albert Einstein illuminates the divide between quantum mechanics and classical physics. Bohr's Copenhagen interpretation posited that without observation, quantum systems exist in a superposition of possibilities, lacking definitive properties. In contrast, Einstein championed the notion of an objective reality, proposing that unseen properties must exist as hidden variables, thus rejecting the idea of a universe dependent on observation.
Einstein's argument stretched to the concept of locality: that influences in the universe operate only at immediate distances, a core principle of relativity. He, together with Doris Podolsky and Nathan Rosen, posited the EPR paradox, introducing quantum entanglement as a profound contradiction to locality.