hidden variable

In quantum mechanics, the concept of "hidden variables" arises from the theory's inherent randomness and indeterminacy. Unlike classical physics, where apparent randomness often stems from incomplete knowledge of initial conditions, quantum mechanics asserts that outcomes like radioactive decay are fundamentally unpredictable.1

Physicists like Albert Einstein found this indeterminacy unsettling and proposed that unknown properties, or "hidden variables," might exist that could restore determinism. If these variables were known, it would be possible to predict outcomes with certainty. However, attempts to construct theories based on hidden variables have proven complex and lack widespread support among physicists. Experiments, particularly those related to the Einstein-Podolsky-Rosen (EPR) paradox, suggest that nature is non-local, meaning measurements on one particle can instantaneously affect another, regardless of distance, contradicting the idea of hidden variables that adhere to locality. The prevailing view, known as the Copenhagen interpretation, accepts this fundamental indeterminacy as a feature of nature rather than a reflection of incomplete knowledge.123