MWI and path of single electron

[PeterDonis]

MWI says (roughly) that each time you toss a coin two universes are "produced": one universe in which you threw a head and one universe in which you threw a tail. But, definitely not a universe in which the coin was both heads and tails.

The word "universe" can be confusing here. That's why I specifically used the term "wave function" in my previous post. The math plus the MWI interpretation of the math can be described as "different terms in the wave function are different copies of the universe", or as "the wave function is the universe, different terms are just different parts of the same universe"; both of these are just different ways of trying to convey in words something that doesn't really fit into the categories embedded in our language. (The same applies if you substitute "world" for "universe".) The first set of words would make your statement quoted above true; but the second set of words would make it false. But it's the same math and the same basic interpretation (no collapse) in both cases; so the apparent difference is not there in the math (or the physics), it's a confusion due to the limitations of our words. The only way to avoid this kind of confusion is to taboo the words and go back to the math.

 

[PeroK]

The only way to avoid this kind of confusion is to taboo the words and go back to the math.

Reading the Lev Vaidman piece in more detail, it seems to me that the MWI walks a fine line between a rigorous all-encompasing view of the universe based on QM and a philosophical investigation that (IMHO) defies rigorous analysis using QM. To take an example of the cat. Vaidman makes the point himself that a cat is not well-defined. But, also, is the state of the cat in terms of any macroscopic property really an observable in any QM sense?

In particular, do we have an observable with the two outcomes of alive and dead? Or, do the terms "cat" "alive" and "dead" simply make no sense within QM? Forensic science can tell how long an animal has been dead, so do you have a "dead for time t" outcome? Clearly the state of a cat that has just died is very different from the state of a cat that has been dead for a week!

I know that Vaidman is an expert in his field, but I personally can't help feeling his whole edifice is based on a potentially false premise: that everything can be understood directly from the laws of particle physics.

As a contrast, I was watching one of the Feyman lectures recently and he said:

"The understanding [of the real world] is not prima facie available by knowing about the laws ... The laws of physics do not have a direct relevance to the experience, but the laws are abstract from the experience to varying degrees ... There are often great distances between the detailed laws and the main aspects of real phenomema ... One does not by knowing all the fundamental laws as we know them today immediately obtain an understanding of anything much."

Brilliant stuff! and I could quote more. My interpretation of this is that in order to understand a cat, you need QM to explain the behaviour of the atomic nucleii, chemistry to understand the bonding of molecules, cell biology to understand the organic processes within the cat, a medical understanding of the cat's organs etc,, which eventually leads to an understanding of the cat and a method of ascribing "alive" or "just died" or "dead for a week" to a cat.

But, IMHO, as soon as one writes down $\Psi_{cat}$ for the wave-function of a cat, one is potentially misapplying the laws of particle physics and the concept of the wave-function for a cat is on very shaky ground.

That's not to say that the alternatives do not have their flaws, but I find the MWI presented by Vaidman to be based on the unsatisfactory premise that the laws of particle physics explain everything.

 

[PeterDonis]

do we have an observable with the two outcomes of alive and dead?

As long as one can partition the cat's state space into two disjoint subspaces, an "alive" one and a "dead" one, then there must be some observable that has those two subspaces as eigensubspaces. In other words, as long as "alive" and "dead" name two mutually exclusive conditions on the cat, there must be an "alive/dead" observable, which gives the output "yes" (or 1 or whatever) if the cat is "alive" (i.e., if its state is in the "alive" subspace) or "no" (or 0 or whatever) if the cat is "dead" (i.e., if its state is in the "dead" subspace).

Whether one can actually partition the cat's state space in this way is really a question about definitions, not physics: how do we want to define the terms "alive" and "dead"? There are certainly cat states which are unproblematically described by one of these two terms; the question becomes where in the state space we want to draw the boundary between them. But any such boundary will be arbitrary, so we can just pick one that meets our intuitions reasonably well.

Clearly the state of a cat that has just died is very different from the state of a cat that has been dead for a week!

That just means you have to draw the boundary in the cat's state space so that both of these states are in the "dead" subspace.

You could also observe that the state of a live cat today is very different from the state of the live kitten that grew into the cat. The same response applies.

 

[FallenApple]

Also, though the distinction may be philosophical, the differences in ideas may affect how future theories turn out. Feynman explains it very well here.

 

[bubsir]

I'm currently trying and really struggling to understand that same thing. Problem is, it seems like the more I read, the less I understand.

“Young man, in mathematics you don't understand things. You just get used to them.”
―John von Neumann

 

[Blue Scallop]

According to the MWI, the physical reality is the wave function; that's it. So whatever happens to the wave function is what happens in physical reality. In the double slit experiment, each time an electron goes through the experiment, the wave function ends up with one term for each possible position on the detector that the electron could end up at: each such term is just the piece of the electron wave function that ends up at that position, multiplied by the piece of the detector wave function that describes an electron being detected at that position. Each such term is multiplied by the amplitude for the electron to end up at that position.

But, as I said before, there is no way to show that physical reality actually works this way, because the MWI makes the same predictions as all the other interpretations, which have very different descriptions of what is happening in physical reality.

I've searched your previous statements. Let's tackle the issue head one. In the above you yourself stated that : "According to the MWI, the physical reality is the wave function; that's it." So you admit that the physical particle is the wave function. But elsewhere you stated that "No. Physical objects are physical objects. State vectors are mathematical objects that appear in mathematical models. They are not the same.". But in MWI, you admit they are the same? Please clarify.

Now to distinguish or test if MWI is correct. Then if we can change the wave function, and we can change the reality... then MWI is the right one. This is logically right and reasonable argument, right? Why not?

 

[PeterDonis]

Let's tackle the issue head on

That's not what you're doing. What you're doing is trying to give a precise interpretation to vague ordinary language. That doesn't work. Yes, the descriptions I've tried to give in different discussions, in ordinary language, might seem contradictory to you when put alongside each other. That's because they were different descriptions given in different contexts for different purposes, none of which were the purpose you're trying to put them to here. Trying to fit all those ordinary language descriptions, as they stand, into a single consistent picture is a fool's errand; there isn't one if the only tool you have to reason with is ordinary language.

If you really want to understand what the MWI, or any other interpretation of QM, says, you first have to learn the basic underlying math that all of the interpretations are based on. You have to learn the math of wave functions, state vectors, operators, Hamiltonians, Schrödinger picture vs. Heisenberg picture, etc., etc. (And if you really want to do it right, you then have to unlearn a good chunk of all that in order to learn quantum field theory, which you need to do in order to be relativistically correct.) Then you have to learn how all this math relates to what we actually observe in experiments, free of any interpretation. (Some physicists call what I am describing the "shut up and calculate" interpretation, but it's not really an "interpretation", it's just a description of the mathematical model and how it makes predictions and how those predictions are compared with experimental results.) If you don't understand all that, you won't even understand the questions that the various interpretations are trying to answer.

Actually learning all that stuff takes years, but if you want to take one small step, go back and read my post #12 in this thread. Notice that I don't use the words "physical reality" once. Nor do I make any of the claims that are apparently confusing you.

Then read my post #15 in this thread, and note carefully the statement of Manyme's that I quoted in that post and responded to. That's what I'm going to fall back on any time it looks like someone is misinterpreting my ordinary language attempts to explain claims that the various interpretations make.

 

[bhobba]

I never said philosophy was rubbish, just that it's not physics and isn't what we concern ourselves with on this forum.

Philosophy isn't rubbbish - its a perfectly legit disipine of much academic value.

The trouble with philosophy however is it never really resolves anything. Science has a resolving mechanism built right into its foundations:


That's the key difference. The reason we don't discuss it here is it leads to threads that go on and on but get nowhere. We actually want to help people understand science not be confused.

That said, since this is about MW there is a good textbook available on it by David Wallace who just happens to have a PhD is both philosophy and particle physics:
https://www.amazon.com/dp/0198707541/?tag=pfamazon01-20

Its not for the beginner though. But it does give the modern version of MW, which is basically the same as Consistent Histories, but it doesn't have the many worlds. In Consistent Histories QM is the stochastic theory about histories. In MW each history is a world.

Thanks
Bill

 

[bhobba]

“Young man, in mathematics you don't understand things. You just get used to them.”
―John von Neumann

Von Neumann, a man of great mathematical ability, was speaking from his rather lofty perspective as likely one of the 10 greatest mathematicians of all time. He was also a polymath - one of the greatest ever. What he saw easily the rest of us have to work very hard at - and yes through that work you do gain understanding.

Thanks
Bill

 

[bhobba]

But, also, is the state of the cat in terms of any macroscopic property really an observable in any QM sense?

Its a difficult issue, that, without going into the details (start a new thread if interested) is part of the Schrodenger Cat resolution, its very difficult to decide where the cat ends and environment begins. Feynman somewhere in the early chapters of his famous lectures looks at the issue from the viewpoint of what the surface of a table is. Look at deciding where it starts and ends is - well not even possible. Again this is part of the explanation of why things like tables etc have classical properties via decoherence.

Thanks
Bill

 

[bhobba]

I understand it's the wave that interferes and how waves can result interference patterns, but I'm having a problem with it being just something mathematical and non-physical.

This is the diffference betweeen pure and applied math.

A good example to understand this is good old probability theory which is based on the Kolmogorov axioms. These axioms speak of events. Pure mathematics doesn't worry what events are. Applied math, as you gradually learn how to use it, builds up the concept of what an event is in practice.

The best book for doing that in QM I know is - Ballentine - QM - A Modern Development
https://www.amazon.com/dp/9814578584/?tag=pfamazon01-20

Contrast this with a pure math appproach:
https://www.amazon.com/dp/0387493859/?tag=pfamazon01-20

Glance through both and you will see the difference.

Thanks
Bill

 

[mieral]

About quantum suicide or sorta..

Say your state is entangled with the system. If the electron is spin up.. you survive.. if the electron is spin down.. you commit suicide. After the experiment.. will you be alive or dead if it's MWI? It is emphasized the there is only one quantum system and there is only entanglement. I understand this and I know nothing gets duplicated in MWI. But is it not after the experiment.. one of you will come up dead and one alive? If nothing gets duplicated. Where did the alive version of you go and the dead version of you go?

 

[PeterDonis]

After the experiment.. will you be alive or dead if it's MWI?

In the MWI this question is not well-defined; "you" do not have a definite state after the experiment. Your state is entangled with the state of the electron. It's no different from two electrons being entangled--neither electron by itself has a definite state, only the system consisting of both of them does. Here instead of one electron, there's you: so neither you nor the electron have a definite state, only the system consisting of both you and the electron does.

is it not after the experiment.. one of you will come up dead and one alive?

No.

Where did the alive version of you go and the dead version of you go?

There are no such "versions" of you in the MWI. So this question is also not well-defined.

 

[mieral]

In the MWI this question is not well-defined; "you" do not have a definite state after the experiment. Your state is entangled with the state of the electron. It's no different from two electrons being entangled--neither electron by itself has a definite state, only the system consisting of both of them does. Here instead of one electron, there's you: so neither you nor the electron have a definite state, only the system consisting of both you and the electron does.
No.
There are no such "versions" of you in the MWI. So this question is also not well-defined.

But in the double slit experiment. The electron passes thru both slits in different branches/worlds. So they explain that we saw it hits one location in the screen in this world.. But in other worlds.. they hit different parts of the screen.. so how can you say the other worlds aren't there and actually duplicated? If someone else knows the answer to this. Please let us know because Peterdonis wil be back after 12 hours at this time and it is too long to wait for the answer. Thanks.

 

[PeterDonis]

in the double slit experiment. The electron passes thru both slits in different branches/worlds

No, it doesn't. The "branching" in the MWI--entanglement of a system with a measuring device--doesn't happen until a measurement is made. In the double slit experiment, that happens when the electron hits the detector screen and the position where it arrives is recorded. So according to the MWI, one run of the double slit experiment, with one electron, creates an entangled state with many terms (many more than two--how many depends on how accurately the detector screen detects position), each of which consists of the electron hitting the detector at a particular position and the detector showing a bright spot at that position.

how can you say the other worlds aren't there and actually duplicated?

The answer to this question is the same as all the previous times you asked it. What is going on is not a duplication of anything. It's just entanglement: the state of the system (electron in this case) gets entangled with the state of the measuring device (detector screen in this case). That's it. Do not ask this question again.

 

[mieral]

No, it doesn't. The "branching" in the MWI--entanglement of a system with a measuring device--doesn't happen until a measurement is made. In the double slit experiment, that happens when the electron hits the detector screen and the position where it arrives is recorded. So according to the MWI, one run of the double slit experiment, with one electron, creates an entangled state with many terms (many more than two--how many depends on how accurately the detector screen detects position), each of which consists of the electron hitting the detector at a particular position and the detector showing a bright spot at that position.
The answer to this question is the same as all the previous times you asked it. What is going on is not a duplication of anything. It's just entanglement: the state of the system (electron in this case) gets entangled with the state of the measuring device (detector screen in this case). That's it. Do not ask this question again.

Oh you are still awake.
But why do we only see one hit in the screen, what happens to the other hits.. do they just vanish. I can wait for the answer many hours later.
Meantime. Hope others can confirm if this is what orthodox Many World actually says in MWI.. because for many years.. I thought otherwise.

 

[PeterDonis]

why do we only see one hit in the screen, what happens to the other hits

According to the MWI, if we look at the screen, our state becomes entangled with the screen's state, just as the screen's state became entangled with the electron's state. So the state of the system as a whole--electron + screen + us--now includes multiple terms, each of which is a product of an eigenstate of electron position (corresponding to some location on the screen), an eigenstate of screen measurement of position (corresponding to the screen showing a spot at some location), and an eigenstate of us observing the screen (corresponding to us seeing the spot at some location on the screen). So now we, like the electron and the screen, no longer have a definite state: only the total system does.

This is how the MWI deals with any kind of interaction, so no matter what experiment or scenario you ask about, the answer will look the same.

 

[mieral]

According to the MWI, if we look at the screen, our state becomes entangled with the screen's state, just as the screen's state became entangled with the electron's state. So the state of the system as a whole--electron + screen + us--now includes multiple terms, each of which is a product of an eigenstate of electron position (corresponding to some location on the screen), an eigenstate of screen measurement of position (corresponding to the screen showing a spot at some location), and an eigenstate of us observing the screen (corresponding to us seeing the spot at some location on the screen). So now we, like the electron and the screen, no longer have a definite state: only the total system does.

This is how the MWI deals with any kind of interaction, so no matter what experiment or scenario you ask about, the answer will look the same.

Thanks. For me I had hard time believing in Many worlds before because I thought the excess baggage was multiplicities of worlds where at the end of the day.. I have many me in other worlds and I can't believe this. But with the context of what you describe. Then I think Many world is really elegant and possible and I may just become a many worlder now. Thanks again for explaining something that removes many years of wrong thinking!

 

[PeterDonis]

Then I think Many world is really elegant and possible

Bear in mind that, when we talk about conscious observers like ourselves, the MWI is making an assumption (IMO a very big one): that each term in the entangled state I described has a separate consciousness associated with it.

(Note that, at least as I understand it, Schrödinger's original motivation in constructing his cat thought experiment was to produce a reductio ad absurdum of this idea--he expected that people would recognize as obvious nonsense the claim that a sentient being like a cat could end up in an entangled state where one branch was "alive" and the other was "dead". But for the MWI to work, this has to actually be the case.)

 

[bhobba]

Schrödinger's original motivation in constructing his cat thought experiment was to produce a reductio ad absurdum of this idea--he expected that people would recognize as obvious nonsense the claim that a sentient being like a cat could end up in an entangled state where one branch was "alive" and the other was "dead". But for the MWI to work, this has to actually be the case.)

True

But he went further and claimed an actual superposition of alive and dead states which a little thought shows it utterly impossible.

Without going into why, but we know it's an observed fact here in the macro world (we do know why but its not really relevant here here) the cats constituent parts have definite position. The position of those parts of alive and dead cats are totally different eg alive cats breathe and their heart beats - dead cats do not. Since cats actually have definite position, like virtually all objects here in the macro world, you can't have a superposition of position - this is from the very foundations of QM. So you can't have a macro object like a live and a dead cat in superposition. Yes I know the great Dirac states in principle you can have a superposition of any two states - but what is, for theoretical convenience considered true, in principle (it's given a name BTW the strong superposition principle and is used a lot in the the foundations of QM) is not always true in practice for various reasons like the above.

Thus the issue is exactly as Peter said - one branch is alive - the other dead - an actual superposition is not possible.

Personally my view is MW is just the consistent histories interpretation where QM is the stochastic theory of histories with the twist each history happens in its own world. In that way we just have an evolving state for the whole universe - or maybe multiverse if some cosmological theories are correct. Which is better - it's purely a matter of taste.

Thanks
Bill

 

[bhobba]

Bear in mind that, when we talk about conscious observers like ourselves, the MWI is making an assumption (IMO a very big one): that each term in the entangled state I described has a separate consciousness associated with it.

Indeed. Its goes right to the foundations of the decision theory approach they use to derive the Born Rule. Its a not usually talked about way to view probability. But some areas of applied math use it like credibility theory used in actuarial science.

Thanks
Bill

 

[mieral]

Bear in mind that, when we talk about conscious observers like ourselves, the MWI is making an assumption (IMO a very big one): that each term in the entangled state I described has a separate consciousness associated with it.

You just mentioned earlier that "There are no such "versions" of you in the MWI. So this question is also not well-defined.". And yet above you said MWI is making an assumption that each term in the entangled state I described has a separate consciousness associated with it.

You mean your MWI or PF MWI is different from the mainstream MWI? Who are the public authors who said that in MWI each term in the entangled state has a separate consciousness associated with it?

(Note that, at least as I understand it, Schrödinger's original motivation in constructing his cat thought experiment was to produce a reductio ad absurdum of this idea--he expected that people would recognize as obvious nonsense the claim that a sentient being like a cat could end up in an entangled state where one branch was "alive" and the other was "dead". But for the MWI to work, this has to actually be the case.)

 

[PeterDonis]

it's an observed fact here in the macro world (we do know why but its not really relevant here here) the cats constituent parts have definite position

No, it isn't. We don't observe the position of every atom in the cat. We observe the cat's position--which is to say, we measure an operator which is, at best, some kind of average position of all the atoms (center of mass position, perhaps), plus a very coarse set of relationships between parts of the cat (the head's at this end, the tail's at this end, the legs are sticking out this way, etc.) Going from that to the claim that all $10^{25}$ or so atoms in the cat have definite positions is a huge leap: the macroscopic state we observe is perfectly compatible with every atom in the cat being in a superposition of position states with a fair bit of spread, atomically speaking.

the issue is exactly as Peter said - one branch is alive - the other dead - an actual superposition is not possible

This is self-contradictory. "One branch is alive - the other dead" means that the state of the system as a whole--cat entangled with radioactive device that does or does not decay, and does or does not release poison--is in a superposition, of two terms (atom not decayed-cat alive, and atom decayed-cat dead), which describes an entangled state. The system as a whole does not have an alive cat or a dead cat in it; it has a cat entangled with a radioactive atom. This is an actual superposition--it's just not an actual superposition of "alive cat" and "dead cat". It's a different superposition, describing entanglement of the cat with the radioactive atom.

 

[PeterDonis]

you said MWI is making an assumption that each term in the entangled state I described has a separate consciousness associated with it

That's because the MWI, at least in the form in which it purports to explain our everyday observations, in which we observe measurements to have definite single results, has to explain how that can be the case given the entangled state that comes out of a measurement. The explanation is that, when we write down such an entangled state, for example, this one:

$$
\Psi_\text{final} = a \vert u \rangle \vert U \rangle \vert O_U \rangle + b \vert d \rangle \vert D \rangle \vert O_D \rangle
$$

where $u, d$, $U, D$, and $O_U, O_D$ are, respectively, the eigenstates of the electron (up/down), the measuring device (measured up/measured down), and the observer (observed up result/observed down result), the observer states have to include conscious experience--so, for example, $O_U$ has to mean "the observer consciously experienced seeing the measuring device give an up result", and similarly for $O_D$ with down. So this entangled state describes an entanglement that includes two different conscious experiences in it, which are separate and cannot communicate at all with each other, but it's still one single state of the overall system. That's what the MWI has to claim, in order to explain our everyday experience of measurements. (And it's also where all the talk about "splitting of worlds" and so forth comes from.)

You mean your MWI or PF MWI is different from the mainstream MWI?

No.

Who are the public authors who said that in MWI each term in the entangled state has a separate consciousness associated with it?

Any author that says that the MWI can explain our everyday experience of measurements. See above.

 

[mieral]

No, it isn't. We don't observe the position of every atom in the cat. We observe the cat's position--which is to say, we measure an operator which is, at best, some kind of average position of all the atoms (center of mass position, perhaps), plus a very coarse set of relationships between parts of the cat (the head's at this end, the tail's at this end, the legs are sticking out this way, etc.) Going from that to the claim that all $10^{25}$ or so atoms in the cat have definite positions is a huge leap: the macroscopic state we observe is perfectly compatible with every atom in the cat being in a superposition of position states with a fair bit of spread, atomically speaking.
This is self-contradictory. "One branch is alive - the other dead" means that the state of the system as a whole--cat entangled with radioactive device that does or does not decay, and does or does not release poison--is in a superposition, of two terms (atom not decayed-cat alive, and atom decayed-cat dead), which describes an entangled state. The system as a whole does not have an alive cat or a dead cat in it; it has a cat entangled with a radioactive atom. This is an actual superposition--it's just not an actual superposition of "alive cat" and "dead cat". It's a different superposition, describing entanglement of the cat with the radioactive atom.

But is it not most popular books describe the superposition as an actual superposition of alive cat and dead cat? My dozens of popular books about QM is tucked in wooden crates and it's difficult to look for the physical books.. But if anyone here has any popular books on QM.. please review if it says the superposition has actual alive cat and dead cat or it is as Peterdonis described that although it is an actual superpostion.. it's a a different superposition thing describing the entangement of the cat with the radioactive atom. Peterdonis explanation makes sense and more elegant but I need to actually see the popular QM books also state it like Peterdonis does. So others please verify this.

And Peterdonis. I need to know something. When you stare at the screen detectors in the double slit experiment. How long does the entanglement last? Is it like split milliseconds or say 0.00000001 seconds where the different terms in the superposition exist or does it last many seconds such that when I'm looking at the detector.. I can say "Oh, the other me is seeing the hits in other positions and I'm just part of the terms of this different superposition thing and when I close my eyes. All those me won't exist anymore and they are really not separate me but this different entanglement thing that Peterdonis is describing". Or does the entanglement occurs like in 0.0000001 second that I won't be able to even think or say the words?

 

[PeterDonis]

is it not most popular books describe the superposition as an actual superposition of alive cat and dead cat?

Popular books are not valid sources here on PF. You are illustrating one of the reasons why: they misstate the actual physics.

I need to actually see the popular QM books

No, you don't. You need to learn QM from an actual textbook. Then you need to work out the math for yourself and understand what it is actually telling you.

When you stare at the screen detectors in the double slit experiment. How long does the entanglement last?

According to the MWI, the entanglement never goes away, because once you've seen the detector showing a spot in a particular place, you remember seeing it that way, and everything else you observe is consistent with it being that way. So the entanglement has to involve everything that could possibly be affected by the location of the spot, your perception and memory of the location of the spot, etc.

does the entanglement occurs like in 0.0000001 second

We don't know how fast the entanglement actually occurs, because we don't observe it continuously in the process of occurring. We just run the experiment and see a spot in a particular place on the screen. It might not even be meaningful to assign a "length of time" in which the entanglement occurs--except that it must happen much faster than our conscious perceptions happen, which is pretty slow on the atomic scale (tens to hundreds of milliseconds).

 

[Nugatory]

But is it not most popular books describe the superposition as an actual superposition of alive cat and dead cat? My dozens of popular books about QM is tucked in wooden crates and it's difficult to look for the physical books..

Leave them there. One good textbook is what you need.

Is it like split milliseconds or say 0.00000001 seconds where the different terms in the superposition exist or does it last many seconds such that when I'm looking at the detector.

The different terms never go away - that's what makes MWI what it is.

 

[mieral]

Popular books are not valid sources here on PF. You are illustrating one of the reasons why: they misstate the actual physics.
No, you don't. You need to learn QM from an actual textbook. Then you need to work out the math for yourself and understand what it is actually telling you.
According to the MWI, the entanglement never goes away, because once you've seen the detector showing a spot in a particular place, you remember seeing it that way, and everything else you observe is consistent with it being that way. So the entanglement has to involve everything that could possibly be affected by the location of the spot, your perception and memory of the location of the spot, etc.

You wrote above the entanglement never goes away or forever.

We don't know how fast the entanglement actually occurs, because we don't observe it continuously in the process of occurring. We just run the experiment and see a spot in a particular place on the screen. It might not even be meaningful to assign a "length of time" in which the entanglement occurs--except that it must happen much faster than our conscious perceptions happen, which is pretty slow on the atomic scale (tens to hundreds of milliseconds).

Yet above you wrote it it must happen much faster than our conscious perceptions or an instance in time.

I kept reading them again and again to see how you can describe two paragraphs in totally opposing views.. forever vs an instant in time. perhaps there are two you in different terms of the entanglement and each paragraph occurs in different branches? But you said there is only one you.. maybe our thoughts came from different us.

But let's take the first paragraph where you said the entanglement never goes away. What happens to the other awareness where you see other hits? This is the part I don't understand. I think some book said they evolve their own. meaning in another worlds or branches, there are other hits with separate history. Even Bill mentioned this.

I hope others can share how they understood the MWI.. what happens to the other hits if the entanglement never goes away? pls answer this specifically and let's focus on this aspect. Thanks!

 

[Nugatory]

Yet above you wrote it it must happen much faster than our conscious perceptions or an instance in time.

The entanglement is result of the interaction between the system we're measuring and the measuring device, so happens more or less quickly according to the details of that interaction. This is when the wave function is changing from $\Psi_{initial}$ to $\Psi_{final}$. The entangled state $\Psi_{Final}$ then continues to evolve forward in time, more or less forever. So the transition from the pre-measurement state to the post-measurement state happens quickly, but the results of the measurement persist.

 

[PeterDonis]

I kept reading them again and again to see how you can describe two paragraphs in totally opposing views.. forever vs an instant in time.

It takes an instant of time (or at least a very short time) to go from "not entangled" to "entangled". Once that happens, "entangled" lasts forever. What's the problem?