The Many Worlds Interpretation
Hugh Everett completes his Ph.D. thesis in 1956. It is titled "'Relative State' Formulation of Quantum Mechanics" but becomes generally known as the Many Worlds Interpretation or the theory of parallel worlds. Everett's theory provides one solution to the paradox inherent in the Copenhagen Interpretation, as seen in Schrödinger's thought experiment. The Copenhagen Interpretation relies on the idea of a waveform collapse, but Everett suggests something entirely different—a waveform "branching." Although we only see one outcome—the cat is either alive or dead—there are actually multiple parallel worlds that collectively contain all of the outcomes that we don't see.