https://en.wikipedia.org/wiki/Objective-collapse_theory
Objective-collapse theories, also known as models of spontaneous wave function collapseor dynamical reduction models,[1][2] are proposed solutions to the measurement problem in quantum mechanics.[3] As with other theories called interpretations of quantum mechanics, they are possible explanations of why and how quantum measurements always give definite outcomes, not a superposition of them as predicted by the Schrödinger equation, and more generally how the classical world emerges from quantum theory. The fundamental idea is that the unitary evolution of the wave function describing the state of a quantum system is approximate. It works well for microscopic systems, but progressively loses its validity when the mass / complexity of the system increases.
