“Really exist in some physical definite state” = collapse. — khaled
But how do we know this? We observe the world and see a definite state?
How do we know we've observed the world to see a definite state? We become conscious of the observation.
If we just had the wave function we can have as many particles as we like, and nothing in the math of the wave function "forces" us to collapse our possible states to more definite states.
The reason viewing the reality as "just the wave function" is that it conflicts with our being conscious of definite states.
Correct. And MWI is the idea that this is what happens, for each possible universe. Again, you have each possible single path block, not a single multi path block (though that’s what you get if you were to superimpose all the blocks on each other) — khaled
You do not understand my point.
There is nothing in quantum mechanics that prevents setting up a wave function state of however many things you want, and simply propagating it forward in time to the end of the universe.
There's nothing preventing a "spacial" view of time in such a mathematical structure so everything is "one block" and all the particles represented by all their possible world lines and spacially representing the probability density of each world line, and having one block.
What's "wrong" with such a view of the universe? (And whether the block-universe we're considering we define as Newtonian, General Relativity or Quantum terms )
The problem is the supposition that there are conscious beings that experience the flow of time. The idea the universe, however it is mathematically described, is one "single block" with past, present and future coexisting (just as up and down direction co-exist) is that it conflicts with the idea of conscious beings inhabiting the universe and experiencing time, and we get that idea from being conscious ourselves.
The point is that it is an analogous problem of a perfectly "fine" interpretation of a mathematical structure of which the only problem is the supposition of conscious beings experiencing time and change (rather than experiencing no time and no change as something existing as a solid changeless block would suggest).
Likewise, that wave functions just propagate indefinitely and never collapse is a perfectly "fine" interpretation of the mathematics of the wave function, of which the only problem is the supposition of conscious beings experiencing definite states represented by real numbers and not these probability distributions represented by complex numbers.
In both cases, since consciousness is "the problem" that prevents, it is entirely reasonable to consider some special relationship between consciousness and these things.
So a single path, for every possible path a world. — khaled
Again, you do not understand my point nor the mathematics of quantum mechanics.
It is not the case that when the wave functions "collapses" that a particle is then considered to have taken a definite path, only the properties observed become more definite for the time of observation, but it is still the case that the particle in some way (we really don't understand) when through all possible paths to get to that observation point: which is why interference patterns emerge (the particle went through, in some sense, both slits and then interfered with itself).
No the point is this isn’t the “result” of the experiment. The variable we want to examine is whether or not the wave function can collapse without our conscious interference. If we get a cookie, where was the conscious interference? We definitely didn’t measure which slit the electron went through. And we didn’t interpret the results on the screen. All that was done by things that aren’t conscious. Yet in the end, when we look at the cookie dispenser, it won’t be “in a superposition of dispensing and not dispensing a cookie” it will either dispense or not dispense a cookie. Based on that we can know whether or not collapse happened without measuring which slit the electrons are going through. That’s the point. Same with the cat. All you’d need is a cookie dispenser there too to know specifically whether or not the cat is alive without observing the cat, just the dispenser.
And, again, address the historical argument: — khaled
Wave function collapse is not a variable.
Variables are states of particles or fields that we can observe. "Wave function collapse" is simply what the "other possibilities" going away is referred to.
For instance, you can have a "probability wave" of a particle in classical mechanics, such as a random walk of a particle Brownian motion or someone who fell of a boat and is adrift at sea. Take the person at sea, based on known constraints, relevant laws of physics etc, a probability distribution of where we are likely to find the person after some time t can be calculated. "Our probability wave" representing where the person might be is the exact same sense of probability as where we might find a particle in a quantum mechanics experiment.
We then go and find the person, and the "wave function" or where they could have been "collapses" in our model because we have new information. This the exact same process as quantum physicists doing measurements and "collapsing" other possibilities that didn't happen when they find one possibility that did happen, they update the model with new information and continue. For instance, finding the persons boot (or what is evaluated as 50% likely to be the persons boot) would update the "lost at sea" model based on this new constraint of observing a boot at location x,y.z at time t.
The difference between classical and quantum probability "wave collapse", is that classical probabilities of the above scenario act only as a one sort of "blobbty diffusion" wave and don't have tell-tale characteristics we'd associate with classic waves such as waves in water.
Critically, as the classical "probability wave / blob" diffuses in space, it always remains cohesive. The probability wave representing where a person maybe based on some initial condition, has no disconnected regions. A person might fall down an elevator shaft, and so is very "unlikely" we'd observe the person in the state of falling down the elevator shaft, but it's not zero probability; we could open one of the other elevator doors on the way down and see the person falling. It's more likely we'd observe the person either just sitting somewhere at the top or then just lying t the bottom of the shaft, than it is to go and observe happen to open an elevator door in the middle and see the falling state, but obviously not impossible.
The classical probability blobs diffuse through space, but never disconnect entirely.
Likewise, someone in a house maybe more probable to be observed in one room or another and less likely we'd observe them right at the moment of going through a door, but obviously we might and people do need to walk through doors to be in different rooms.
We do not believe someone lost at sea somehow "really exists" in all the places we might find them, it is just a mathematical description of probabilities to help us find them. Likewise, we do not believe someone is in "all the rooms" they could be at once, it's just a mathematical description of where we might find them.
Critical to this view that someone lost at sea is a definite state or someone in a house is in a definite state, before we go and check where they actually are, is the probability regions never disconnect (there is a continuous connection of everywhere "they might be", just different probabilities for each place, and we might really find them anywhere in this region; we can run experiments to find that 1/10000 chance of randomly opening the elevator shaft over some time span at the moment someone, let's hope a dummy, is falling).
In quantum mechanics, regions of probability states can be entirely disconnected, and this completely breaks our normal intuition of probability diffusion of "little ball particle" at definite positions through space at each moment in time. How does the electron exist in a definite state but "move" between disconnected regions A and B without any possibility of us finding the electron in some connected bridge state between A and B (i.e. in the doorway)? Likewise, how does an electron interfere with itself so that it's probability of hitting certain regions of a detector is zero, and that even one at a time, electrons produce interference patterns?
The only way to make sense of this is to say the electron does not "move" in a classical sense between A and B and when we look we find where it "really is" but rather the electron somehow co-exists in some sense in both regions, but when we look to find the electron in region A, then somehow it's "existence" in region B disappears. This is what happens mathematically, and "collapsing the wave of probabilities" to the new reality, is a sensical way to describe the mathematical process of updating a model with new information (just as with updating a model of someone lost at sea with information about their probable shoe or then finding the person themselves).
What we cannot easily make sense of is what sort of "substance" the electron (or quantum fields if you prefer) really is to have these characteristics, nor can we easily make sense of how our observations affect the situation (to resolve such questions, we need to make observations, but obviously that is no longer the same question).
Again, address this: Consciousness evolved yes? In order for that to happen we needed to have collapsed, well defined molecules at least yes? And eventually after enough time a conscious thing evolved from these molecules yes?
Then how can consciousness be a requirement for wave function collapse? If it was, it would’ve never evolved. — khaled
The consciousness relation to wave collapse can solve this in different ways; such as simply stating first wave collapsing at some threshold of consciousness or something along those lines (evolution happens in every possibility, and then collapses to the first possibility of consciousness; explaining why there's more matter than antimatter, as only in these probability edge cases does matter outnumber anti-matter, and stars and evolution can happen etc.); but we have no experiment that even shows what is and isn't conscious so this is pseudoscience speculation; not anyway to go back and "observe" the universe before it collapsed to a definite state due to the first observation.
What we do know (or what I know) is that I'm conscious and observe a definite state of the universe around me (certainly more definite than observing "all possibilities" simultaneously). I can know what I observe; I cannot "know" what existence is "really like" prior to my observations. I can note that quantum mechanics basically prevents any intuitive visualizations of what "things are really like at all", but, as a Kantian, it's not really surprising that whatever we can say of the "noumena" always remains fundamentally speculative anyways (maybe new physical theories will lend themselves back to a more "Newtonian" view just to be overturned once again by something even more bizarre than quantum mechanics).