Scientific Proof For The Existence of God/ Heaven

[Chesterton]

Well, the corollary to that is that you as a superposition of observers see every possible outcome. The 'many worlds' are all part of the same universe, they're non-interacting branches of the universal wavefunction - they're predicted by the quantum formalism, so they're not really imaginary - much as black holes and the Higgs boson were predicted by General Relativity (or even Newtonian gravity) and the Standard Model of particle physics, respectively. It's hard to see how the QM interpretation with the simplest ontology, the unitary evolution of the wavefunction according to Schrodinger's equation, can be criticised as not being science without calling QM itself unscientific... it is what it is.

As with any multiverse hypothesis, the separate worlds or universes themselves are inaccessible by definition, but it's a mistake to think that therefore they can't be scientific or real - model prediction together with indirect and circumstantial evidence can be sufficient to establish inaccessible entities; black holes are a canonical example. But you're right that there is a philosophical debate about precisely what the criteria for the label 'science' should be. In practice, scientists just use whatever model works for their purposes, and in the case of QM interpretations, they use the interpretation they feel most comfortable with, or none at all. They're just different interpretations consistent with the formalism.

Of course, it's possible that the QM formalism is incomplete - maybe a wavefunction collapse mechanism will be discovered and verified, or pilot waves will be found to be real, or some other interpretation. But for now, that's not the case. Copenhagen (wavefunction collapse) and other interpretations are the ones that add speculative mechanisms to the formalism, so if you want interpretations that involve imagination, choose one of them rather than MWI.

I don't know what to say, except to remind you of the scientific method. An idea needs to be experimented on, needs to be testable, and falsifiable. That's impossible with MW.

If the wavefunction of the system to be observed describes multiple possible measurement outcomes, a measurement will produce a branch of the wavefunction for every possible outcome.

Let me try something further. Let's say a man sets up the "wheel" experiment as I described, with this twist: he has another man design and install the wheel while the experimenter is not around. He instructs the designer to make the wheel with any random number of slots he chooses, and to keep it secret from the experimenter. The result (where the wheel stops) will be displayed on a digital display on the wall. The experimenter will never see the wheel, so will not know the number of possible measurement outcomes, but will only see the result displayed. Also, the guy who designed the wheel will conveniently not be around that day, and will not observe the result. How many branches of the wavefunction will be produced?

Sorry about that!

I certainly wasn't talking about you.

 

[FrumiousBandersnatch]

I don't know what to say, except to remind you of the scientific method. An idea needs to be experimented on, needs to be testable, and falsifiable. That's impossible with MW.

But also with the other interpretations - they're all in the same epistemic position.

Let me try something further. Let's say a man sets up the "wheel" experiment as I described, with this twist: he has another man design and install the wheel while the experimenter is not around. He instructs the designer to make the wheel with any random number of slots he chooses, and to keep it secret from the experimenter. The result (where the wheel stops) will be displayed on a digital display on the wall. The experimenter will never see the wheel, so will not know the number of possible measurement outcomes, but will only see the result displayed. Also, the guy who designed the wheel will conveniently not be around that day, and will not observe the result. How many branches of the wavefunction will be produced?

You have to be careful not to confuse the possible outcomes of a quantum measurement with some conscious observer's knowledge of the outcomes. An observation or measurement really means any interaction between quantum systems that causes the superposition to decohere into the environment. The nomenclature is a hang-over from the early days of QM thought experiments.

After a measurement in MWI, there will be a branch of the wavefunction for every outcome the measuring instrument is set up to detect. It makes no difference whether a conscious observer knows what the outcome is or not - if something, e.g. measuring apparatus, interacts with the quantum system, the quantum system's superposed states will rapidly decohere into the environment as branches of the wavefunction, and a conscious observer will have become part of that superposition long before she becomes aware of the outcome; i.e. each branched version of her will see whatever outcome her branch of the wavefunction carries.

Ironically, a conscious observer becoming aware of a measurement outcome is not itself an observation of a quantum system in the QM sense of observation, it's just information processing.

I certainly wasn't talking about you.

Ah, so I can continue to drone on...

 

[Chesterton]

You have to be careful not to confuse the possible outcomes of a quantum measurement with some conscious observer's knowledge of the outcomes. An observation or measurement really means any interaction between quantum systems that causes the superposition to decohere into the environment. The nomenclature is a hang-over from the early days of QM thought experiments.

After a measurement in MWI, there will be a branch of the wavefunction for every outcome the measuring instrument is set up to detect. It makes no difference whether a conscious observer knows what the outcome is or not - if something, e.g. measuring apparatus, interacts with the quantum system, the quantum system's superposed states will rapidly decohere into the environment as branches of the wavefunction, and a conscious observer will have become part of that superposition long before she becomes aware of the outcome; i.e. each branched version of her will see whatever outcome her branch of the wavefunction carries.

But how would the wavefunction know how many possible outcomes there were? We're talking about a wheel with some number of little pegs in it.

Also, let's make it a blank wheel (a wheel of no fortune ). No numbers, no pegs, yet it spins and stops. The branching would have to be infinite, right?

Ironically, a conscious observer becoming aware of a measurement outcome is not itself an observation of a quantum system in the QM sense of observation, it's just information processing.

Measurement requires conscious observation. Unconscious matter does not measure. I can place a ruler next to my pencil to see how long it is, but it is I who is doing the measuring.

 

[Chesterton]

Ah, so I can continue to drone on...

Sure if you want to, I probably have dozens of questions. Like, if you say a macro object is a "quantum system", how does that break down? Am I one system, or are my eyeballs, hands, taste buds, etc. all separate systems within a system? Is my car one system or many?

 

[FrumiousBandersnatch]

But how would the wavefunction know how many possible outcomes there were? We're talking about a wheel with some number of little pegs in it.

Also, let's make it a blank wheel (a wheel of no fortune ). No numbers, no pegs, yet it spins and stops. The branching would have to be infinite, right?

Frankly, I don't know the details of how the MWI handles time-dependent quantum events such as radioactive decay (I don't think the superficial account in Carroll's blog post was intended to be strictly accurate); but it wouldn't depend on how many numbers were or were not on the spinning wheel - everything that happens after the measurement, i.e. the Geiger counter detecting the particle ejected from the atom (and I doubt even that is a quantum measurement), is, to all intents & purposes, classical.

It seems to me that, under MWI, the result is either two branches, decay and no decay, or no decay and as many decay branches as can occur in the lifetime of the atom (which is indefinite). The latter option doesn't smell right.

The problem I have is what constitutes a measurement or observation in the situation of radioactive decay. If the atom's wavefunction describes the possible results of measurement, and a measurement involves interaction with the quantum system in question, then it appears that a radioactive atom does not interact with the measuring instrument until it spontaneously decays and spits out a particle that can be detected, at which point it's no longer an atom in superposition of decay + no decay.

I'd like to get chapter and verse from an expert...

Measurement requires conscious observation. Unconscious matter does not measure. I can place a ruler next to my pencil to see how long it is, but it is I who is doing the measuring.

I don't agree (although it may just be a semantic issue). Consider any autonomous device with a sensor; for example, the thermostat on your freezer. That measures the freezer temperature, compares it with a reference value, and takes action if the measured temperature exceeds that value. No consciousness involved.

But what constitutes a measurement for the purpose of QM has been a problem for a long time (it's actually called the Measurement Problem). The commonly accepted answer is that a measurement occurs when the relevant state of the quantum system under consideration leaves a macroscopic and irreversible trace in the measuring device (and, by extension, the environment). This is also called decoherence. A 'macroscopic trace' is effectively something that can be described using statistical mechanics, i.e. classically.

The introductory undergraduate QM textbook by David Griffiths, "Introduction to Quantum Mechanics" says (with reference to Schrodinger's Cat):

"The most widely accepted answer is that the triggering of the Geiger counter constitutes the "measurement," in the sense of the statistical interpretation, not the intervention of a human observer. It is the essence of a measurement that some macroscopic system is affected (the Geiger counter, in this instance). The measurement occurs at the moment when the microscopic system (described by the laws of quantum mechanics) interacts with the macroscopic system (described by the laws of classical mechanics) in such a way as to leave a permanent record.
...
Part of the problem is the word "measurement" itself, which certainly carries a suggestion of human participation. Heisenberg proposed the word "event," which might be preferable. But I'm afraid "measurement" is so ingrained by now that we're stuck with it."
​

 

[FrumiousBandersnatch]

Sure if you want to, I probably have dozens of questions. Like, if you say a macro object is a "quantum system", how does that break down? Am I one system, or are my eyeballs, hands, taste buds, etc. all separate systems within a system? Is my car one system or many?

Everything is part of a quantum system (which really means a subset of the universal wavefunction that can be treated to some extent as an identifiable object), but macro scale objects have extremely complex wavefunctions comprising all the wavefunctions of their constituent parts, and all in close proximity, so their potential superpositions decohere almost instantaneously, which means we don't normally see quantum effects at macro scales. The result is that they closely approximate to classical objects.

An analogy would be the difference between dropping two stones into a still pond, when you could clearly see the expanding ripples and their interference patterns, and dropping a lorryload of stones into the pond, which would produce an indecipherable mess in which you would be unable to see any individual ripples or interference patterns.

 

[Michael]

FYI, thanks FB for your responses in this thread. There are a lot of subtle (and less than subtle) aspects about QM that I don't fully understand, and your insights are quite enlightening.

 

[Michael]

By the way, you might find this paper interesting:

Experimental rejection of observer-independence in the quantum world

 

[Chesterton]

Frankly, I don't know the details of how the MWI handles time-dependent quantum events such as radioactive decay (I don't think the superficial account in Carroll's blog post was intended to be strictly accurate); but it wouldn't depend on how many numbers were or were not on the spinning wheel - everything that happens after the measurement, i.e. the Geiger counter detecting the particle ejected from the atom (and I doubt even that is a quantum measurement), is, to all intents & purposes, classical.

It seems to me that, under MWI, the result is either two branches, decay and no decay, or no decay and as many decay branches as can occur in the lifetime of the atom (which is indefinite). The latter option doesn't smell right.

I agree the latter doesn't smell right, but how could the branching be limited? In the case of the circle, with a theoritically infinite number of points and divisions between points, you'd have to get an infinite number of universes from one simple spin of the wheel. And add to that all the other sets of infinite universes which are constantly being created and have been since the Big Bang. Talk about an indecipherable mess!

The problem I have is what constitutes a measurement or observation in the situation of radioactive decay. If the atom's wavefunction describes the possible results of measurement, and a measurement involves interaction with the quantum system in question, then it appears that a radioactive atom does not interact with the measuring instrument until it spontaneously decays and spits out a particle that can be detected, at which point it's no longer an atom in superposition of decay + no decay.

I'd like to get chapter and verse from an expert...

Yes, the way you stated it is the way I've always heard it.

I don't agree (although it may just be a semantic issue). Consider any autonomous device with a sensor; for example, the thermostat on your freezer. That measures the freezer temperature, compares it with a reference value, and takes action if the measured temperature exceeds that value. No consciousness involved.

Okay, but I think that just means a consciousness automated a conscious process. It's just a labor saving device.

But what constitutes a measurement for the purpose of QM has been a problem for a long time (it's actually called the Measurement Problem). The commonly accepted answer is that a measurement occurs when the relevant state of the quantum system under consideration leaves a macroscopic and irreversible trace in the measuring device (and, by extension, the environment). This is also called decoherence. A 'macroscopic trace' is effectively something that can be described using statistical mechanics, i.e. classically.

The introductory undergraduate QM textbook by David Griffiths, "Introduction to Quantum Mechanics" says (with reference to Schrodinger's Cat):

"The most widely accepted answer is that the triggering of the Geiger counter constitutes the "measurement," in the sense of the statistical interpretation, not the intervention of a human observer. It is the essence of a measurement that some macroscopic system is affected (the Geiger counter, in this instance). The measurement occurs at the moment when the microscopic system (described by the laws of quantum mechanics) interacts with the macroscopic system (described by the laws of classical mechanics) in such a way as to leave a permanent record.
...
Part of the problem is the word "measurement" itself, which certainly carries a suggestion of human participation. Heisenberg proposed the word "event," which might be preferable. But I'm afraid "measurement" is so ingrained by now that we're stuck with it."
​

Maybe I misunderstand it, but I thought the "delayed choice double eraser" experiment tends to disprove this.

So how exactly does any measuring apparatus interact with a particle? Mere physical proximity? Does it interact in a way that the walls and furniture and air don't?

And another question, which may be a bit of sophistry. If MW is true, doesn't that mean there is necessarily a universe where MW is not true? If your brain is a quantum system which generates the idea of MW, and if there is even the slightest probability that the idea is false, then the idea will actually be false somewhere, no?

 

[Chesterton]

Everything is part of a quantum system (which really means a subset of the universal wavefunction that can be treated to some extent as an identifiable object), but macro scale objects have extremely complex wavefunctions comprising all the wavefunctions of their constituent parts, and all in close proximity, so their potential superpositions decohere almost instantaneously, which means we don't normally see quantum effects at macro scales. The result is that they closely approximate to classical objects.

An analogy would be the difference between dropping two stones into a still pond, when you could clearly see the expanding ripples and their interference patterns, and dropping a lorryload of stones into the pond, which would produce an indecipherable mess in which you would be unable to see any individual ripples or interference patterns.

Trying to figure out whether that's a "yes" or a "no".

 

[FrumiousBandersnatch]

I agree the latter doesn't smell right, but how could the branching be limited? In the case of the circle, with a theoritically infinite number of points and divisions between points, you'd have to get an infinite number of universes from one simple spin of the wheel.

No; not even the measuring device can influence when the atom decays. Downstream gadgets set up to time the event aren't relevant. If multiple branching applies, its frequency would (at least) be limited by the speed of light.

And add to that all the other sets of infinite universes which are constantly being created and have been since the Big Bang. Talk about an indecipherable mess!

Very large numbers, but not infinite - unless the universe itself is infinite, in which case, no problem; and not a mess, but a very complex ordered tree structure in Hilbert space.

Okay, but I think that just means a consciousness automated a conscious process. It's just a labor saving device.

OK, what about when a tree measures the time of year and drops its leaves? It's just a matter of semantics - does water measure the temperature when it turns to ice, or when it melts?

As I (and Griffiths) already said, it happens that the terms 'measurement' and 'observation' in QM don't mean quite what they mean in colloquial use, they're now part of QM jargon; much as 'hypothesis' is science jargon for the colloquial 'theory'.

Maybe I misunderstand it, but I thought the "delayed choice double eraser" experiment tends to disprove this.

How so?

So how exactly does any measuring apparatus interact with a particle? Mere physical proximity? Does it interact in a way that the walls and furniture and air don't?

It depends on what's being measured; as already mentioned, it's any means by which the relevant state of the system can be recorded - in everyday circumstances, this will be electromagnetic.

If MW is true, doesn't that mean there is necessarily a universe where MW is not true? If your brain is a quantum system which generates the idea of MW, and if there is even the slightest probability that the idea is false, then the idea will actually be false somewhere, no?

No, MWI doesn't imply that everything conceivable happens, it doesn't even imply that everything physically possible happens; only measurement interactions with quantum systems in a superposition branch the universal wavefunction.

The activity of your brain is effectively classical information processing, i.e. the 'averaged' result of all the QM activity of the constituents of a complex macro-scale system. And thoughts are just patterns of neural activity, they don't branch the wave function or create real 'worlds'.

 

[FrumiousBandersnatch]

Trying to figure out whether that's a "yes" or a "no".

It depends what level you want to consider - your car is a quantum system and has a wavefunction which is made up of the sum of the wavefunctions of its components, which are themselves the sum of the wavefunctions of the parts they're made of; ultimately, they're all part of the overall wavefunction of the universe.

 

[Chesterton]

No; not even the measuring device can influence when the atom decays. Downstream gadgets set up to time the event aren't relevant. If multiple branching applies, its frequency would (at least) be limited by the speed of light.

Why? Entanglement isn't limited by the speed of light.

Very large numbers, but not infinite - unless the universe itself is infinite, in which case, no problem; and not a mess, but a very complex ordered tree structure in Hilbert space.

I thought that a circle has infinite points. If so, then there are infinite measurement outcomes.

OK, what about when a tree measures the time of year and drops its leaves? It's just a matter of semantics - does water measure the temperature when it turns to ice, or when it melts?

As I (and Griffiths) already said, it happens that the terms 'measurement' and 'observation' in QM don't mean quite what they mean in colloquial use, they're now part of QM jargon; much as 'hypothesis' is science jargon for the colloquial 'theory'.

No, trees and water don't measure anything, but I get your point. I'm also willing to chalk it up to semantics.

How so?

By demonstrating that knowledge makes the difference, not measurement. They take the measurement, throw away the "which path" data so that there's no knowledge of which slit the particle went through, and they get the diffraction pattern every time. But if they keep the data and look at it, they get clump pattern every time. How do those who deny "conscious collapse" explain this? I'd honestly like to hear if you know.

It depends on what's being measured; as already mentioned, it's any means by which the relevant state of the system can be recorded - in everyday circumstances, this will be electromagnetic.

But if everything is a quantum system, why is that limited to a recording apparatus? Why not a chair?

No, MWI doesn't imply that everything conceivable happens,...

But it gives a bell curve of probabilty, which would have to include the idea being wrong, right?

...it doesn't even imply that everything physically possible happens; only measurement interactions with quantum systems in a superposition branch the universal wavefunction.

I don't know if you remember Wiccan Child. He was a respected theoretical physicist on CF (hasn't been around for some years). He once told me exactly that - that QM allows for everything physically possible to happen, that the chair I'm sitting in could spontaneously turn into a golden elephant, but it's just that the probability is very, very tiny. I've heard other physicists express the same. And it makes sense to me; we're talking about about mere waves of potentiality after all.

The activity of your brain is effectively classical information processing, i.e. the 'averaged' result of all the QM activity of the constituents of a complex macro-scale system. And thoughts are just patterns of neural activity, they don't branch the wave function or create real 'worlds'.

Is that what the classical world is, the averaged result of all the QM activity?

It depends what level you want to consider - your car is a quantum system and has a wavefunction which is made up of the sum of the wavefunctions of its components, which are themselves the sum of the wavefunctions of the parts they're made of; ultimately, they're all part of the overall wavefunction of the universe.

You sound like a hippie. But I guess that's how any discussion of any interpretation of QM has to sound, lol.

 

[Michael]

You sound like a hippie. But I guess that's how any discussion of any interpretation of QM has to sound, lol.

Ya, I think it comes with the territory.

By the way, I'm really appreciating the discussion you and FB are having. I'm learning a lot of subtleties about QM theory and I appreciate the questions you've raised. Cool conversation.

 

[FrumiousBandersnatch]

Why? Entanglement isn't limited by the speed of light.

You may be thinking of the correlation between entangled objects (Einstein's 'spooky action at a distance'). That's something else.

I thought that a circle has infinite points. If so, then there are infinite measurement outcomes.

When you look in the box, you're not making a quantum measurement, you're just seeing where the wheel stopped. The wheel has no influence on the radioactive decay or when it happens; it's effectively just a crude timer. So while there may be a large number of possible positions (not infinite) the wheel could be stopped at, it just tells you that the radioactive decay can happen at any time - that's not a measurement outcome in the quantum sense. As I've already said, the wavefunction of the radioactive atom describes the possible measurement outcomes - decay or no decay.

By demonstrating that knowledge makes the difference, not measurement. They take the measurement, throw away the "which path" data so that there's no knowledge of which slit the particle went through, and they get the diffraction pattern every time. But if they keep the data and look at it, they get clump pattern every time. How do those who deny "conscious collapse" explain this? I'd honestly like to hear if you know.

See post #1 here, which explains it using the main QM interpretations. MWI is item 6 (item 3 mentioned below is a wavefunction collapse interpretation - follow the link for full details):

6. Many-world interpretation: The wave always goes through both slits. However, due to decoherence, at the instant of measurement (and at the position of the measurement apparatus) the wave splits into many non-communicating branches, which makes the illusion of collapse as in 3. This branching does not modify the wave function in the past.
Reference Who is puzzled by the delayed choice?​

The experimental setup is all mechanical & electronic and can work the same whether there's anyone around to see it or not; conscious observation not required. There's plenty of explanatory discussion about it on the Physics Forums, and PBS Space Time has a nice video about it.

But if everything is a quantum system, why is that limited to a recording apparatus? Why not a chair?

If a chair can make a record of the relevant state, then a chair can be a measuring instrument. As I've already said, a measuring apparatus is any quantum system that can interact with the quantum system in question and make a macro-scale record of the state in question.

But it gives a bell curve of probabilty, which would have to include the idea being wrong, right?

No. The probability amplitudes described by quantum wavefunctions are different for different states and may include amplitudes of zero, meaning some measurement outcomes will never occur. None of that has any relevance to whether MWI is correct or not.

But logically, what you suggest is paradoxical; you can't use the assumed truth of statement or idea to prove that statement or idea false - it's related to the Liar paradox.

I don't know if you remember Wiccan Child. He was a respected theoretical physicist on CF (hasn't been around for some years). He once told me exactly that - that QM allows for everything physically possible to happen, that the chair I'm sitting in could spontaneously turn into a golden elephant, but it's just that the probability is very, very tiny. I've heard other physicists express the same. And it makes sense to me; we're talking about about mere waves of potentiality after all.

I used to think that was the case too.

Is that what the classical world is, the averaged result of all the QM activity?

Loosely, yes. It might be more accurate to say that the classical world is emergent from the quantum world. An analogy is temperature and pressure, which are emergent statistical properties of the frenetic activity of billions of atoms & molecules.

You sound like a hippie. But I guess that's how any discussion of any interpretation of QM has to sound, lol.

Wow dude, far out... totally, like, yeah...

 

[FrumiousBandersnatch]

FYI, thanks FB for your responses in this thread. There are a lot of subtle (and less than subtle) aspects about QM that I don't fully understand, and your insights are quite enlightening.

You're welcome, but don't take my views as gospel - without an understanding of the underlying mathematics, I rely on the explanations of people in the field who do understand it, and who I think are likely to have thought about it in depth. I can't guarantee that I have their explanations straight.

 

[FrumiousBandersnatch]

By the way, you might find this paper interesting:

Experimental rejection of observer-independence in the quantum world

It's interesting in that it shows that what were previously only thought experiments can actually be done for real, but it doesn't really say anything new.

Here's a good summary on Quora, and here's what some (rather critical) philosophers of quantum mechanics had to say: Philosophers On a Physics Experiment.

 

[Chesterton]

See post #1 here, which explains it using the main QM interpretations. MWI is item 6 (item 3 mentioned below is a wavefunction collapse interpretation - follow the link for full details):

6. Many-world interpretation: The wave always goes through both slits. However, due to decoherence, at the instant of measurement (and at the position of the measurement apparatus) the wave splits into many non-communicating branches, which makes the illusion of collapse as in 3. This branching does not modify the wave function in the past.
Reference Who is puzzled by the delayed choice?​

The experimental setup is all mechanical & electronic and can work the same whether there's anyone around to see it or not; conscious observation not required. There's plenty of explanatory discussion about it on the Physics Forums, and PBS Space Time has a nice video about it.

Is saying that the the branching/collapse occurs at the instant of measurement just a bald assertion?

If a chair can make a record of the relevant state, then a chair can be a measuring instrument. As I've already said, a measuring apparatus is any quantum system that can interact with the quantum system in question and make a macro-scale record of the state in question.

Why does it have to be a quantum system which can record? Why not any quantum system?

No. The probability amplitudes described by quantum wavefunctions are different for different states and may include amplitudes of zero, meaning some measurement outcomes will never occur. None of that has any relevance to whether MWI is correct or not.

But logically, what you suggest is paradoxical; you can't use the assumed truth of statement or idea to prove that statement or idea false - it's related to the Liar paradox.

But you seem to have responded with a paradox. You're saying it's impossible for MW to be false ("that outcome will never occur"), and also that the possibility of MW being false has no relevance to MW.

 

[FrumiousBandersnatch]

Is saying that the the branching/collapse occurs at the instant of measurement just a bald assertion?

No, it's decoherence (when the superposition spreads out into the environment like a chain-reaction). The consensus QM definition of a measurement implies decoherence. Under MWI that means a branching of the wavefunction; under wavefunction collapse interpretations, the collapse must occur prior to or at the start of decoherence so that only one state of the quantum superposition survives to be recorded.

Why does it have to be a quantum system which can record? Why not any quantum system?

A 'record' just means that the quantum state in question changes the state of the measuring apparatus in such a way that it is irreversible and macro-scale. Crudely, it has a signficant effect.

If a particle in a superposition collides with a photon or another free particle, that doesn't count as a measurement, as it doesn't create an irreversible change (a record) in the rest of the environment - although when the photon or particle do eventually make an impact on a measuring apparatus, a measurement may well occur.

You should be able to see why this is more of a problem for wavefunction collapse theories than MWI, because they have to pick some suitable point for the wavefunction to collapse as a measurement occurs, before it has macro-scale impact, and come up with a plausible physical reason for it to do so. Under MWI, the wavefunction just evolves smoothly, spreading the superposition into the environment until it is effectively irreversible, becoming separate branches of the wavefunction.

But you seem to have responded with a paradox. You're saying it's impossible for MW to be false ("that outcome will never occur"), and also that the possibility of MW being false has no relevance to MW.

No; MWI, Copenhagen, Bohmian mechanics, transactional, relational, consistent histories, etc., are all interpretations of what quantum mechanics means. If one of them is the correct interpretation, that is how QM works, and the others are incorrect.

If MWI is correct, all the branches of the wavefunction that make up the many worlds are all a result of MWI quantum mechanics in operation since the big bang - it would be an MWI universe/multiverse; it doesn't make physical or logical sense to wonder if the correct interpretation can result in a universe where it is not the correct interpretation.

 

[Chesterton]

No, it's decoherence (when the superposition spreads out into the environment like a chain-reaction). The consensus QM definition of a measurement implies decoherence. Under MWI that means a branching of the wavefunction; under wavefunction collapse interpretations, the collapse must occur prior to or at the start of decoherence so that only one state of the quantum superposition survives to be recorded.

Well I don't know what to say. The last few days I've been reading a little more on this stuff, and Sean Carroll has some good talks online about MW. I'm just not convinced, for now anyway. I don't know what it means to speak of probabilities while simultaneously asserting that every possibility will happen. Also, some people think MW is a way to avoid the weirdness of consciousness being in control of reality, so to speak. It seems to me, though, it makes the problem worse. If I can consciously choose to do an experiment which splits the universe, I become a creator of worlds. Or at least an influencer of many worlds besides this one.

BTW, have you ever read the Wiki page on Everett? Some interesting trivia about him there. I don't mean that as character assassination, just that it's interesting.

Like Tipler, he believed in some kind of human-immortality-through-physics. Also, he apparently was a fan of science fiction comics, including L. Ron Hubbard's original Dianetics. Interestingly, the first mention of the multiverse concept was in a 1940 DC comic book. If WM is ever proven, I think the Nobel Prize should go to Stan Lee.