>[!abstract] >Objective-collapse theories are proposed solutions to the [[Measurement problem|measurement problem]] in quantum mechanics. As with other 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. ("Objective-collapse theory", 2025). > >According to objective-collapse theories, wave-function collapse occurs when a superposed system reaches a certain objective threshold of size or complexity. Objective-collapse proponents would expect a system as macroscopic as a cat to have collapsed before the box was opened, so the question of observation-of-observers does not arise for them. If the measured system were much simpler (such as a single spin state), then once the observation was made, the system would be expected to collapse, since the larger system of the scientist, equipment, and room would be considered far too complex to become entangled in the superposition. ("Wigner’s Friend", 2025). ## References - Objective-collapse theory. (2025, February 15). In *Wikipedia*. https://en.wikipedia.org/w/index.php?title=Objective-collapse_theory&oldid=1258797217 - Wigner’s Friend. (2025, February 15). In *Wikipedia*. https://en.wikipedia.org/w/index.php?title=Wigner%27s_friend&oldid=1272114083