Bell's theorem

Bell's theorem demonstrates that certain predictions of quantum mechanics cannot be explained by any theory that relies on local hidden variables—that is, properties determined at a distance without faster-than-light influence. When particles become entangled, measurements on one instantly influence the other, regardless of the distance separating them. Bell's theorem provides inequalities that—if violated by experimental results—show that nature doesn't adhere to local realism. Experiments have confirmed these violations, suggesting that the universe allows for such non-local correlations, challenging classical notions of how information and reality behave at a fundamental level.