Title: What does it mean to say a wave-function collapses? - Quora
Headings: What does it mean to say a wave-function collapses?
What does it mean to say a wave-function collapses?
Let us talk about spin of an electron:
Clifford Chafin
Doug Mason
Doug Morris
D. B. G. Tilak
Anonymous
Priyam Chaudhuri
Stephon Henry

Content: If that's true, then this universal wavefunction could be regarded as objectively real, rather than epistemic. And it is clear that if you accept the wavefunction as real, as Everett did, it never collapses. As interesting as this proposal is, it's still regarded as controversial among most physicists. Some believe in it, others do not, and still others shrug the question off as metaphysical and essentially meaningless. But it doesn't affect the question of whether wavefunction collapse is a physical process--just about everyone on both sides agrees that it is not. It's merely a useful representation of how an observer gains information about a system. An important difference between the wavefunction in classical statistical mechanics and quantum mechanics is that in classical mechanics, there is no interference between different possibilities in the superpostion, at least for the normal observables like position and momentum that physicists usually care about. In quantum mechanics, different possibilities can interfere constructively or destructively before a final outcome is registered. But when you have large ensembles of particles, there is enough noise that the different possibilities are always decoherent, which guarantees that they cannot interfere with one another. Because of the interference, and the uncertainty principle (both of which arise as consequences of the non-commutativity of observables), the Hilbert space formalism is a much more natural way to view things in quantum mechanics than it is in classical mechanics, which is why it's used so much more in quantum mechanics.