why does measuring a particle make its wavefunction collapse?

Question

Well base on reading Particles don't behave like tiny balls, but rather like waves that are spread over a large area. Each particle is described by a wavefunction or probability which tells what its location may be but not exact and velocity may be but not exact and other properties are more likely to be, but not what those properties are...The particle actually has a range of values for all the properties until you measure one of them like velocity or its location for example at which point the particle's wavefunction collapses and it adopts just one location..... But it does not explain why measuring it collapse.

Answer 1

I'll bet its similar to the reason why some have said the universe will disappear just after we totally figure it out. Once we know- game over.

Answer 2

No one knows, but The up and coming HUT (Holographic Universe Theory) Physics gives a clue.  One aspect of HUT is that Particles with a LOCATION in 3D space are an "illusion" of sorts of our Conscious Perception.---that is, all particles exist in an UPPER REALITY where there is no space between them.  Our 3D universe is a result of our perception of certain wave attributes of the particles that we perceive as a POSITION in a 3D space---(Sort of like how our senses perceive a given frequency of EMR(light) as a color)----Thus CONCIOUSNESS is involved in the LOWER REALITY or 3D universe.    David Bohn, Einstein's Protégé, said this also explains "quantum entanglement"---how another particle can affect another, instantly, light years apart.   We may Perceive them far apart on our level of reality, but they are in physical contact in the Higher reality. 



This also explains the "observer effect".  As it is Consciousness and perception that creates our lower reality 3D universe.  So if we FOCUS in an individual particle, which is illusionary to us anyway, we may NOT perceive it as the WAVE it really is--but as a particle, our senses make it out to be.----thus it loses its "wave nature" relative to us.



Check out HUT---it is quite fascinating and is rapidly gaining favor with major Physics institutions----Likely the way REAL things are.



I accept the prize  ;)    

Answer 3

Your understanding of quantum mechanics is very good. Books don't say why measurement causes the wavefunction to collapse because nobody knows! That is called the measurement problem. Collapse is not part of Schrodinger's equation. It is a separate postulate. How and why wavefunctions collapse is a complete mystery. 

Answer 4

Might as well throw my 2 cents in .....



We need to recognize that wave function ‘collapse’ is just an example of more general quantum state reduction. Everything that applies to wave functions also applies to a spin state in a superposition of two possible spins, and as it does with any quantum state that can be in superposition of multiple possible states.



We don’t understand the measurement problem because we don’t understand what superposition is in reality. Anyone of the very smart people that have answered this question can easily describe superposition mathematically, but no one can say what the reality is that underlies the mathematics. Hard to describe the transition process without understanding what is transitioning.

Answer 5

How about the unappealing answer of, " it has too".  

When you make a measurement the particle has that position, or energy, or momentum, or whatever you are measuring.  If you immediately measure it again it better have the same value or measurement has no meaning, but if the wave function stays intact the measurement will most likely not be the same because of the probabilistic nature of the function, so the function has to collapse to the measured value or the universe makes no sense.  I know this isn't satisfying an answer but sometimes that's the best we got, at least for now.

Answer 6

That's (probably) the biggest unanswered question in quantum mechanics.  It is often referred to as 'the measurement problem' (because measuring somethng causes its wave-function to collapse).



One solution is the 'many-worlds theory' (which I don't like). E.g. see https://thereader.mitpress.mit.edu/the-many-worlds-theory/



As Zirp said, anyone who can answer it will almost certainly get a Nobel prize.

Answer 7

There's a nobel-prize waiting for whoever figures it out