Does Many Worlds Explain Quantum Probabilities? 

Why are scientists ignoring the 'Mandela effect' phenomenon. Its real and can't argued otherwise and it is an amazing sign of the multiverse at work.

Cool logo, congrats!

Please stop playing the xylophone when you're speaking

While you're at it, can you fix the bg music? It's too distracting from Matt's story. Or remove it completely.

@@DaleSteel your comment is the definition of the Dunning-Kruger effect at its finest 😆🤣

I was married to a quantum chemist for 20 years (Sarah J. Edwards, she wrote TagDock). She passed away unexpectedly earlier this year, and I watch these and miss her and our conversations every night. I keep hoping conservation of information exists so she'll be around forever and I am comforted that she still exists, just not in my time reference any more. Grief and science are an odd pairing.

YES another person who enjoys having their brain expanded. It's awesome isn't it?

you trash chemists have no real understanding of these topics. you just compute

What's the most fascinating thing about quantum chemistry that you think a layperson ought to know?

@@prdoyle seconded

This explanation was an odd blend of rigorous and analogous... I've understood all of this for several years now, but I had trouble finding a clear path through the analogies. I think there are easier, more intuitive ways to explain it, but they don't _quite_ pinpoint that Many Worlds more naturally explains the Born rule. This is really Sean Carroll's argument, and he explains it in a way that I find much more intuitive... it's just also a bit less precise in its implications. I do think there's value in this kind of rigor, even within the framework of popular science communication, but I can't say for sure whether it's effective at conveying the information to someone who doesn't yet understand it, since I had that revelation, personally, well before this episode. You say it's one of the hardest to grasp... does that imply that you feel like you _did_ grasp it in the end? If so, then it was a successful explanation for at least one person. Still, I'd suggest watching one of Sean Carroll's lectures on the subject. He did a whole bunch of them while doing the publishing tour for his previous book, Something Deeply Hidden (and the book itself, of course, makes the same points in the same ways, it just goes a little deeper). The easiest to find is probably his lecture at the Royal Institution a few years ago, though it's not his clearest, best presentation of it (probably owing to the time constraints).

​@@barefootalienthanks

I don't think it is super hard to understand but any simple version of it would be more of a metaphor than accurate description and this channel leans toward accurate. My best summary (and I am not expert others add or correct as needed) is that many worlds matches what we know about quantum physics and math already, we can't falsify it, but the math is straight forward. Other interpretations can use the same math but they don't explain why the other realities don't exist. I think we intuitively want to think that there is 1 reality and that may be the shortcoming here, that we as humans want it to match our intuition but doing so requires some other effect or mechanism to be in play that we don't yet understand. It doesn't mean that it doesn't exist, but this argument is that many worlds is a more simple explanation. An Occam's razor of sorts.

Yeah they've blasted through all the 'easy' stuff, I'm honestly excited to see how they'll present the truly mind-shredding topics to the general public.

It was hard to grasp because they barely explained it at all. The crux of the math is that a. all the vector amplitude has to be 1 (which was why 1/√2 appeared out of nowehere when |T⟩ was broken into |T1⟩ and |T2⟩) and b. length addition follows usual euclidean rules (I mean, special relativity as a theory has its own peculiar way to "add" length, not to mention this is some abstract space and not normal space either, we can't just assume usual rules apply). I'm sure these are very basic quantum mechanics facts but I can't immediately see why, because I'm a layman, and they didn't explain.

I think I'm having a stroke now

I have a serious headache now.

We are living in the 2nd plane of existence from the 31 planes. Humans live in 4 different planes with 4 different great oceans. Devas (gods) and Brahmas live in higher planes of existence in mount Meru, and the earth is a part of that mountain.

Yes

@@smlanka4uare you a Hindu? 😊

As someone who specializes in literature, as soon as it goes into deep mathematics, I'm lost.

@@PrincipalSkinner3190 Same here as software engineer. I know what sigma, delta, and that fork symbol are, but some of those pipes don't seem to indicate a limit. It would be nice to make the math readable with Python.

"I may be capable of explaining it to you, or I may not be capable of explaining it to you. Until I attempt to explain it to you and you observe my explanation, neither of us knows if I can, therefore I am in a superposition of simultaneously able and unable to explain to you until you attempt to listen to me"

@@foxbruner There's a world in which I can, and a world in which I can't, shall we figure out which we're in?

@@shipwreck9146 Better. Thumbs up.

😂 Exactly why I am more of a GR guy. QM needs to figure out how to measure before I try understanding the religious nature of the interpretations since many are not testible.

When you add the integers 2 and 3 what "happens" before it collapses to become 5? I find the question of the measurement problem silly.

Wow!! Well spotted!!

For a moment I thought he may make this exact comparison in the video.

Sound like Qbism to me

информация несет эффект в будущее.) кто то знает заранее что произойдет?

@@antm9771 Many Worlds and QBism are distinct; in QBism there is a single world and the wavefunction encodes subjective beliefs about it whereas in Many Worlds the branching wavefunction exists objectively and observers within it have "indexical uncertainty" that is treated in a Bayesian way using the principle of indifference

@@kisskaspeik5220 go kick Putin in the balls and then ask that question again.

That is: until someone reads your comment and thinks "Yepp. This guy has got it!" 😁

The problem with superposition might be solved by more understanding of the quark mechanics. I feel like our understanding of quarks is muddied because of our misunderstanding of superposition because it's a fallacy.

Me too, I'm wondering whether this is the kind of episode that the folks who liked reading the proof that 1+1=2 would enjoy. Handy that someone put the effort in to actually put the proof on paper since it's the foundation of an entire branch of study, but a lot of people intuitively see it as a "well, yeah" statement without grasping the level of thinking that went into proving it's actually the case. It's hard for me to tell though as I'm usually in the other camp and playing with tensor fields and wavefunctions in my head. Maybe Feynman has finally infiltrated my brain 😬

@@thedeadmoneyallstars Just shut up and calculate!

You can however split the worlds where you understand and those where you don't into stacks... It's easy sailing from there.

The monty hall problem is easily explained when looking at it like this: In order, for the showrunner to pick a door that is wrong, he MUST know whats behind each of the doors. So at the exact moment he opens a false door, information is being shared. That information in of itself gives the higher odds at the third door. Because he knew and now told you part of it.

@@gorgit Of course the Monty Hall problem is easily explained. The inversion joke wouldn't work if it was difficult.

@@gorgit Also, the trick to Monty Hall problem isn't that he knows which door is wrong, it's that him eliminating the wrong door changes the set structure. Intuitively, each door has a 1-in-set size chance of being right, which is correct, but by revealing a door after you pick, he is binding the 2 unselected doors into a set. People intuitively think of it as bare selection between 2 doors, and thus a 1-in-2 chance, but because the revealed door is selection entangled you are actually picking between your 1 door and the pair of other doors. So your original door is still 1-in-3 odds while the other doors collectively are 2-in-3 odds.

@@Merennulli thought you were joking about qm being easy compares to the monty hall problem.

@@Merennulli Yes, but thats all because he KNOWS which door is wrong. That means information is being communicated by opening the wrong door. You are just going into the details what information actually is being communicated.

Absolutely. When you observe a particle to see whether it has property P or not-P, your brain and the particle will become an entangled superposition of the following two states: 1. The particle had property P and your brain contains the memory of having seen it as having property P, and 2. The particle had property not-P and your brain contains the memory of having seen it as having property not-P. And the "wave function collapse" that other quantum interpretations talk about, is simply the transition of going from an un-entangled state (prior to making the measurement) to the entangled state (post measurement).

Totally agree.

The measurement problem is a pseudoproblem. The measurement problem arises from the measurement postulate, as the Copenhagen interpretation claims particles "spread out" into all possible states as a postulate, but if they do this, why don't we ever measure particles in all possible states? Copenhagen fixes this by adding on the measurement postulate to bring everything back together, to "collapse' the "spread out" state into a determinate state. MWI tries to "solve" the measurement problem by deleting the measurement postulate, by saying there is no "collapse," but then they're left with reality itself spreading out into a grand multiverse which we can't even observe. Einstein had correctly pointed out a century ago that all this confusion comes from the postulate that particles really do "spread out" into all possible states in the first place. If you drop this postulate, there is no need for a measurement postulate either because nothing ever "spreads out" that needs to be "collapsed," and you don't get grand multiverses, because, again, nothing spreads out at all. The percentages derivative of the Born rule are interpreted as a sort of "best guess" of what path the particle took, and not that the particle literally spread out into all possible paths, it only ever takes one path. Einstein had already given a lot of great arguments into why this "spreading out" postulate is absurd and that there is nothing in quantum mechanics that provides a convincing enough reason to adopt it. Einstein's biggest problem with it is that it inherently requires you to reject the existence of objective reality that is independent of the observer. He gave an example of atomic decay. As time passes, quantum mechanics would predict an increasing probability that the atom has decayed, but it never hits one-hundred percent. This means, if you interpret the wave function as ontologically real, you have to believe the atom really never does decay until you look at it, and so you cannot even say the atom has a real state independent of the observer. (Eugene Wigner also pointed out in his "Wigner's friend" thought experiment that under certain conditions two observers would come to experience entirely different realities, and thus you could not say there is an objective reality independent of the observer from a purely psi-ontological standpoint.) Believe it or not, Schrodinger had also initially put forwards his "cat" thought experiment also as a way to criticize Copenhagen, pointing out that if individual particles can "smear out," then there's no reason that particle could not then trigger a chain of events that would affect macroscopic objects, like a cat, and then you'd have to claim the cat is "smeared out" as well, which is an absurdity, and so it should be rejected. Yet people these days repeat Schrodinger's thought experiment as if he was arguing _in favor of_ believing "smeared out" cats exist, which is the opposite of what he was saying. Even John Bell is often misrepresented as saying he "proved hidden variables don't exist" and therefore objects really don't have real states until you look at them and are fundamentally indeterminate. John Bell did not believe this and also criticized Copenhagen in his paper "Against Measurement" because of its measurement postulate which makes it incapable of scaling the theory up to large scale systems. While Bell did not take on Einstein's approach, he became infatuated with Bohm's "pilot wave theory" and even contributed to it in his paper "On the impossible pilot wave."

@@amihart9269 thanks a lot for this valid explanation👍. Hope some other guys read it too.

You did better than me, that's for sure.

"states with any coefficient can be represented as a sum of substates with equal coefficients" - Doesn't it seem too convenient that the state with the larger coefficient is allowed to be broken up into substates but the one with the smaller coefficient isn't, just to make 3 states with the same coefficient? Both states correspond to one macro observable. What makes one worthy of being broken up but not the other, except the motivation to force emergence of the born rule from many worlds? Not a rhetorical question. Genuinely wondering if I have missed something.

@@kanishkchaturvedi1745 That's one of the things that's tripping me up too, honestly

​@kanishkchaturvedi1745 The idea is that you can always arrive at a consistent coefficient based on a common denominator. Like, let's say that the probability spread was 3/5 heads and 2/5 tails. These can be broken into 3 head worlds and 2 tail worlds out of a potential 5, all with a coefficient of 1. So we only break apart one side in Matt's example because that's all we need to do. He could just as easily have broken one side into 2 branches and the other into 4, all with a coefficient of .5 and the math wouldn't care.

@@umbrascitor2079 This is fine for showing that the born rule is a good mathematical tool for a physicist to calculate a probability from the schrodinger equation. But it does nothing at all to explain how the branching of the wave function would phsyically but you in a tails-flip branch twice as often as a heads-flip branch. The card explanation reveals the problem. The only reason it worked in that case was because there were more cards in one stack than the other to begin with. The analogy for many worlds would be that there were more quantum states in the tails world than the heads world to begin with. Exactly twice as many, in fact.

You're not looking at the experiment through the eyes of a quantum observer. While the outcome of an experiment can appear to be along a continuum logically, the uncertainty principle ensures that many states along that continuum share a common outcome. No measurement apparatus, including our eyes and our memories, can discern an infinite number of measurements. Therefore, the number of outcome states is always an integer at some level.

Thanks. I've had a long-standing intuitive sense that MWI doesn't handle irrational numbers consistently, and it's nice to know which resources to turn to (Carroll's paper) if I want to develop a more rigorous belief.

​@@davidhand9721let's say the wavefunction for the coin is (2^(1/4)/a)|H>+(√(1-√2)/a)|T>, for some number a so that the coefficients square to 1. How would many worlds tell us about the probabilities of obtaining each measurement?

There's no reason to stop because no conclusion is ever reached. This ensures the jobs in some realities are secure.

You bring up a good point. I think that the proof is flawed in that the fact that the states add as orthogonal vectors is coming as a result of Born's rule.

Yeah, I don’t understand because tails isn’t orthogonal to tails. It’s obviously orthogonal to heads. The whole point of superposition is that 2 or more different states exist together. It doesn’t make sense to talk about the superposition of the same state. I think it’s not a satisfactory solution but an ad hoc attempt to get proper probabilities from MWI.

Agree, you find the same future depending input in superdeterminism and in classical physics in the principle of least action. No necessity of measurement independence.

MWI seems to pose no problem with conservation. It is just QM, and QM does not violate conservation. but i think we need an explanation for it because it seems contradictory

@@nmarbletoe8210 What do you mean by "QM"?

@@Pit.Gutzmann quantum mechanics

​@@nmarbletoe8210thanx. I still think, yes a universe can start out of quantum fluctuations, but generating a 13.8 billion years old universum at each quantum event...?

@@Pit.Gutzmann It does seem extraordinary. But it seems to be required even without Many Worlds. In Feyman's Sum over Histories, all possible paths combine to form the probability wave function. Each path is like a world in the Many Worlds. Since information requires some material carrier, perhaps this means the MW are material as well...?

Good question. I don't think that many worlds has a definite answer to this. I also think that there are issues when the number of possible outcomes is infinite.

You can take a limit of closer and closer rational approximations, perhaps?

Water molecules move relative to each other.

Thanks, but the physicist in these videos is named Matt.

interesting question

Indifference should be not attributing any belief equally, rather than attributing equal belief evenly. The latter sounds more like apportion.

They're related in that both of these theoretical areas draw on probability theory. It is insightful to pull a bit on why each does: Statistical physics and quantum physics both use the language of probabilities because we (a user of the theory) have some necessary ignorance about what is going on. In SM this is because knowing the microstate of an avogadro number of particles is impractical; in QM it is because a closed system, as described by the Schrodinger equation, is fundamentally inaccessible to external degrees of freedom (i.e. the closed system is no longer closed when we force a measurement device to interact with it). I think that starts to get at some of what your question intuits. As an aside, you might find some interesting follow up on those thoughts by 1) reading a bit about the Quantum Bayesian (QBist) interpretation of quantum theory, and 2) reading about the Maxwell Demon thought experiment from statmech, and it's analogs in the quantum context. There are some reasonably accessible articles around that can get you started on the latter (Quanta magazine has some nice articles about Maxwell's Demon, for instance). Connect those dots and you'll have understood a great deal about your excellent question!

It indeed is, see the paper _"Epistemic Separability and Everettian Branches: A Critique of Sebens and Carroll"_ by Richard Dawid and Simon Friederich, which is the paper this video is based upon, which precisely demonstrates that the derivation of the Born rule from this method requires arbitrary assumptions that are clearly chosen just for the purpose of deriving the Born rule and would not be chosen as assumptions otherwise.

​@@amihart9269Thank you! I'll read the paper

They already did that episode.

y'all should play the banjo more

What does it even mean to say "what is real are observer dependent"? This is an abuse of philosophical terminology. The term "realism" refers to an objective reality that is independent of the observer. "Observer-dependent reality" is nonsensical.

Yes. The MWI is ridiculously extravagant.

what do you mean by a non-quantum interaction? every interaction is at some point quantum if you zoom in enough, no?

I don't think it would have anything to do with relativity. Information can't travel ftl in MWI. Also MWI is both local and deterministic so problems with entanglement don't really appear in it. All of the quantum weirdness is stuffed into the MW part of MWI.

@@AwfulnewsFM MWI is only "local" if you redefine "locality" to be something entirely different. People who claim MWI is "local" remind me of compatibilists who come into the "free will" vs "determinism" debate and just say, "hey, why don't we just change the definition of 'free will' so the two are compatible?" I mean, sure, you can do that, but it doesn't really end the debate but just kind of misses the entire point of the debate in the first place. The same is true of silly MWI claims that it is "local." MWI is only "local" in an extremely intangible and unverifiable metaphysical sense of locality in terms of the multiverse, but nobody who cares about locality actually cares about locality as some vague philosophical principle. Most of physics was nonlocal up until Einstein. Newtonian gravity is treated as instantaneous and the speed of light was also treated as instantaneous. The desire for a local theory arose very specifically in the 20th century with the development of Einstein's General Relativity where not only is the theory entirely local and these speeds are actually finite, but locality is baked deeply into the theory, i.e.if you could travel at superluminal speeds it would lead to nonsense predictions like distances contracting to imaginary values. MWI claims about it being "local" entirely miss the point of the locality debate. Locality isn't desirable as some vague abstract principle, but very specifically due to a desire to one day make QM compatible with GR. That means the only locality that matters is locality in the GR sense. Any other form of "locality" is irrelevant and there is no reason to care about it. MWI is not local in terms of GR as it is only "local" in terms of its multiverse but still contains _apparent_ nonlocality when a single "branch" is considered in isolation. See the paper _"An Elementary Proof That Everett's Quantum Multiverse Is Nonlocal: Bell-Locality and Branch-Symmetry in the Many-Worlds Interpretation"_ by Aurélien Drezet. Also see the paper _"Einstein, incompleteness, and the epistemic view of quantum states"_ by Harrigan and Spekkens which provides a no-go theorem showing it is not even possible to have a purely ontological interpretation of quantum mechanics that is local. MWI is only "local" in a vague sense which is only defined in terms of itself, which misses the entire point of why people actually care about locality and debate whether or not it is real.

​​​​@@amihart9269You made some good points here, but there's an important clarification needed: All versions of ( unmodified) QM are "weakly" non local, because the light cone structure ( that defines Causality and temporal order in both special and General Relativity) still defines how signals ( particles , anything with four-momentum) are transmitted in a quantum world. It's not strong non-locality. This clarification is important , because still many people are confusing the quantum non locality ( non separability) with the strong non locality ( that exists only in science fiction...) But you're right of course, that MW is indeed weakly non local , like the other interpretations. (Bohmian mechanics has a more serious problem with relativity, because it breaks Lorentz Invariance).

Who says the probabilities are uncountable by definition?

What symmetry are you referring to?

Perhaps you mean linearity. The reason is that the Schrodinger equation is linear so any operation applies equally to all terms of it.

@@d95mback I mean symmetry and for exactly or the reason you stated. My only issue with the video is that this symmetry is implicitly stated amongst a lot of talk about vectors and equations and so on. Not that any of it is wrong, it certainly isn't, but that it's easy for a viewer's eyes to start glazing over. It might have been better at one point to just say something like "Forget about the weird equations that only some people can read/understand, this is fundamentally an issue with symmetry" and explain why in a more easily digestible manner. There is a symmetry in MWI between the number of outcomes which are possible and the number of outcomes which happen. The outcomes are not symmetric individually, obviously; but they do, by definition, respect a symmetry as a whole. This is not true for CI, for instance, because it requires that only one outcome happens regardless of the number of possible outcomes. It requires that symmetry is broken but without any justification for what causes the breaking.

spins. there are only two possible spins, up and down

@@nmarbletoe8210 Alright, Thanks for explaining. ^⁠_⁠^

getting rid of unnecessary data is a great way to better understand your situation - it's just good advice, not just in physics.

An inability to measure a difference is another definition of a symmetry. It shouldn't be surprising that we have gained so much knowledge by considering the innate symmetries of nature with mathematical rigor. In combination with Noether's theorem, symmetries are also conservation laws. Thus, situations which we cannot discern are the source of all deep physical principles.

An accelerating rocket is a 'gravity' field. There is no difference between the earth accelerating you or a rocketship accelerating you. One is accelerating you in a curve, the other a more or less straight line. The laws of physics apply equally in all frames of reference. It doesn't matter if the frame is vertical, horizontal or curved. This is what Einstein and his flat Earth followers don't understand.

I think we sooner or later will find that space and time are discrete. Nothing else makes much sense.

The waavefunction is continuous, we observe a smear on the screen after passing through observed slits. I don't think what you're stating is necessarily more than a Zeno's paradox type thing. We can do continuous probaability can we not?

Well you can’t really measure accurately down to a point because of the Heisenberg uncertainty principle. The uncertainty in position times the uncertainty in momentum needs to be greater than some constant, and a point position would have zero uncertainty. So you can never find yourself in a world that has zero probability to be measured (which kind of makes sense when put that way)

@@d95mback Isn't discreteness already proven by Planck length and the Zeno paradox?

@@CTimmerman not sure what you mean by "proven". The Planck length is a very small length indeed, but it's just what you get when combining the Planck units. The smallest possible length could be much smaller than that.

"The wave property of particles appears when we start looking into the future of that particle" Isn't that notion inherently completely contrary to general relativity?

@@asd-wd5bjThat's the point.

I saw that too!

I thought the principle of least action applies to both quantum and classical theories

When summing all possible paths, the principle of stationary/least action is what you get as a consequence, for free, it's not like you add it in explicitly. Classical mechanics with its least action principle comes from this, from the quantum world where we sum over all paths.

@@thedeemon This!

Yeah, you know, I've noticed a trend of interactivity on RU-vid decreasing in some niches/genres, science communication being one of them. The Royal Institution has seemingly stopped doing Q&A sessions after lectures, or at least has stopped recording and publishing them on their channel... SpaceTime doesn't seem to do comment responses much if at all anymore... I wonder if engagement with those kinds of content is just too low according to analytics and metrics... 🤔

I for one switch off after the main topic is done and dusted. I suspect I'm not alone. Which would count as only partially watched in the stats.

Universe / physics has no obligation to be describable with computable functions and decidable problems. I agree that explanations of MWI should do a better job of describing what a "world" is. MWI is very much compatible with relativity and can describe most everything without non-locality, while having basically one "non-local" hidden parameter - which world you're in. For instance, if we create an entangled pair of particles and measure them later (getting spins +1 or -1, unpredictable but always opposite), the way MWI describes it, at the moment of creation of the pair the worlds "split" (start to evolve differently, they've always been split but just remained in sync previously) such that in one world the particles will measure +1, -1 and in another world -1, +1. Both worlds evolve using locality-respecting rules of SR, all changes propagate at speeds

I'm pretty sure this episode is based on Carroll's paper about deriving the Born rule in many worlds. Edit: it's not. It's based on the paper linked in the description.

@@narfwhals7843 the paper in the description is based on Carroll’s work (it says so at the end), so you were right

It's based on Carroll's paper which is incredibly unconvincing and the circular nature of it is already obvious in this video. Notice at 15:12 if you apply the "principle of indifference" (what Sean Carroll actually called the "epistemic separability principle," i.e. ESP) you would get the wrong answer, so you have to intentionally rearrange the mathematics in order for it to get you the right answer. This is because Carroll does not rely on the ESP but a derivative he calls ESP-QM, which adds on a postulate that the probability one should assign to being in a certain branch depends on the reduced density matrix that describes the combined system of the agent and the detector... but density matrices give you Born rule probabilities, i.e. ESP-QM implicitly assumes the Born rule. Carroll's paper assumes the Born rule in order to derive the Born rule. I recommend Richard Dawid and Simon Friederich's paper _"Epistemic Separability and Everettian Branches: A Critique of Sebens and Carroll"_ which goes over this, ultimately showing that an assumption of ESP does not entail ESP-QM without additional assumptions, and these assumptions are arbitrarily chosen specifically to reproduce the Born rule. James Hartle's paper _"What Do We Learn by Deriving Born's Rule"_ also points out that you cannot derive the Born rule without additional assumptions. If the Born rule is not assumed as a postulate, you need some other postulate from which it can be derived. Carroll's ESP-QM really is of the same type as the "quantum non-equilibrium" postulate in Bohmian mechanics, that is to say, yes, you can derive the Born rule from such a postulate, but it is clear the postulate is chosen _specifically to derive the Born rule,_ and thus the postulate is just as arbitrary as just assuming the Born rule as its own postulate.

@@amihart9269 I think you’ve misunderstood a few things here. The Principle of Indifference (POI) and ESP are two different ideas. The video skips through some of the details that are shown in the doc linked in the description, but the basic idea is that you can show that the POI is valid when branches have equal amplitudes, and that it is invalid when they do not. So when you encounter a wavefunction with unequal amplitudes, you must re-express it in terms of equal amplitude terms to use POI and get the correct probabilities. The argument for when POI is valid and when it is not does *not* require knowing the Born Rule in advance, so this is not circular.

@@skewlkid521 You say are different but fail to show how they are different, and yes, you have to break them up in a specific way precisely to get the Born rule. The validity of the Born rule is a starting assumption and arbitrary postulates are added to get to this conclusion, but those postulates have no justification outside of the fact you could derive the Born rule with them. If we discard the Born rule, why should believe anything about your mathematical operation to break up the wave function?

I second this, the principle of indifference requires a finite number of "cards" (here: multiverses) at each split. Unless we propose a mechanism that changes the number of cards between splits that is a common multiple of both splits without changing probabilities, it also means that the number of multiverses since the big bang is a finite constant. If that's true (and irrational probabilities are just approximations of a rational reality), I'd be curious what that number could be. And at some point in the future we will run out of multiverses to accurately approximate probabilities using distinct multiverses.

That would "just" mean that the eternal wave function has uncountable infinite granularity (i.e. uncountable infinite number of branches) and you are either in one of the uncountably infinitely many "α branches", or one of the uncountably infinitely many "β branches".

This is why I hate it when they describe Many Worlds as "branching". There is only one world, but states within it lose coherence with other states. Thanks to the uncertainty principle, there can't be a continuum of outcomes forever; they must get pooled into a finite number of distinguishable outcomes. Even when outcomes appear to be continuously distributed in reality, there are, in fact, a finite integer number of results that any measurement device (e.g. your eyes) can distinguish.

​@@db7213 yeah, like, I get that the many worlds interpretation seems like the most parsimonious interpretation of quantum theory, as in, it is the one which gels the easiest with it's formalism and etc. But what it says about the world is just about as un-parsimonious as anything could ever be, specially if we go down this uncountably infinitely path. Another thing you could say about reality, outside the formalism of quantum theory, would be that quantum theory is just not complete enough to offer a great interpretation for the measurement problem. To me, that just sounds quite a bit less out there, you know?

@@user-sl6gn1ss8p So we have a way to accurately predict and describe what happens at the quantum level, but you choose to ignore it and instead claim that it's not "complete enough", even though there is nothing that's missing about it. What theory would then be "complete enough"?

Schrodinger equation applies to the big wave function and changes amplitude of each point/"world" depending on its difference with its neighbor points ("worlds"), so nearby points in wave function influence each other.

Man, the Jason Bourne movies keep getting more complicated.

Well... ultimately that's why Schrödinger came up with his cat thought experiment. The coin flip is a much less convoluted analogy, but also admittedly less rigorous. Schrodinger's Cat is much more rigorous, presenting a pathway to amplify a truly random quantum effect to a macroscopic observable. The intended conclusion he meant for people to draw, however, was "Surely you can't actually _believe_ this nonsense..." Sadly, the "shut up and calculate" crew lead by Niels Bohr pretty much said, "Ooh, cool, yeah, that's exactly how crazy this stuff is, good job Erwin!" Humans.

Pilot-wave Theory is basically just the Everett Interpretation with unnecessary extra steps.

Does there need to be a difference? I think the intended difference is what comes after, like how the corpuscles disappear compared to the many worlds that persist.

He already did make a video about it: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-BUHW1zlstVk.html

@@n0tthemessiah No, it is not, as Everett's interpretation fails to explain why we find ourselves in one branch over another if all outcomes occur. It is just an empirical fact that only one outcome occurs, and if both X and Y are possible, and X occurs, why did we measure X and not Y? While I do not endorse pilot wave, Copenhagen, or MWI, pilot wave at least has a specific reason for why X would be measured instead of Y, that it depends on the particle position.

It doesn't matter how you chose the basis. Nature doesn't care about your coordinate systems, neither in physical, nor in Hilbert space. ;-)

Sean Carroll is simply pulling your leg with MWI to get book sales up. Forget about him. There is nothing he can teach you about quantum mechanics.

At what point has someone made a compelling case for Pilot Wave? If the comparative inelegance alone doesn't turn you over to Many Worlds, then you still have to deal with non-locality and other contradictions with relativity. Many Worlds works with fewer axioms, never fails, and isn't ridiculous like Copenhagen. In an unbiased evaluation, Pilot Wave should be the inferior interpretation.

@@davidhand9721 -- What are the other contradictions with general relativity?

@@davidhand9721Copenhagen is far less ridiculous than the Many Worlds interpretation. I’d buy the boltsman brain or simulation theory before Many Worlds. The idea that every quantum event essentially results in two distinct universes and macroscopically an infinite number of universes is one of the most ridiculous scientific theories.

Yep. Many Worlds is the null hypothesis. All evidence ever discovered supports it without fail, because it is the simplest model devised to fit all available evidence. The other real _theories_ of quantum mechanics "interpretations" each make verifiable predictions. For example, a Hidden Variables theory like Pilot Wave Theory predicts that there exist hidden variables. The discovery or verification of one of them would prove it correct and eliminate the null hypothesis. Spontaneous Collapse theories predict that from time to time, a wave function of a particle will spontaneously collapse into a point function with no external stimulus. If we ever observe such a collapse (and can eliminate all extrinsic causes to a significant degree of certainty), it will prove that theory and eliminate the null hypothesis. Until one of those other theories has its predictions verified to 6 sigma significance, the null hypothesis _should_ remain the default and be what is taught in schools. It isn't. Because humans. Mostly because Bohr was apparently quite the force of personality, and, more cynically, because it's fun to watch students' faces scrunch up in confusion as we teach them the same magical gobbledygook of paradox and contradiction that we were taught. For a century now. Go humans!

I have never seen a compelling argument for Copenhagen, Many Worlds, or Pilot Wave. All of them rely on arbitrary postulates that Einstein had already eviscerated.

@@armandaneshjoo So you have proved otherwise? I look forward to reading about your nobel prize.

I'm pretty sure everyone has a gut feeling preference based on some combination of what hand waviness they'll most easily overlook (and all of the interpretations have hand-waviness) and what is most emotionally appealing to them. It makes sense to me that a lot of physicists like this interpetation, because, as they like to say, "it's just taking the math [that we know so far]" and taking it literally! Physicists are immersed in the math, so they prefer the interpretation that takes the math literally, and that handwaves everything else (kidding. Sorta.) It's fine to have a gut-level preference, but given that there is absolutely no way to test this interpretation compared to most others (not even in principle I don't think), scientists like Sean Carroll should know better than to be out arguing in favor of a particular interpretation. It's much more scientific to say that we don't know, and to keep working on further developing the theory in ways that ARE testible.It seems far more likely to me that QM is an approximation and/or that there's something deeper or more subtle going on that we don't understand yet, than that any of our current problematic interpretations is correct. What Sean Carroll is engaging in is philosophy, not science, but given that he's not rigorously trained as a philosopher, he's probably not very good at it. This is one of the things I love so much about Roger Penrose. He comes up with some pretty crazy ideas, but they are all testable via experiment. And cases where they are testible in principle but our equipment isn't good enough to test yet, he refrains from saying how likely his theory is to be RIGHT, and just works on developing the theory.

@@ReivecS It's ironic you say this when MWI is unfalsifiable...

@@amihart9269 There are many papers (and even more when just doing a quick check) that makes claims of ways to test MWI, but even if that weren't the case, my statement was about the ability to prove something else, so this comment still doesn't hold up. Nice try though.

@@ReivecS There are no ways to test MWI. You are appealing to vague amorphous papers which don't exist. Your comment was also about disproof and not about proof, and proof only exists in mathematics not in experimentation which can only show evidence with varying levels of confidence, and the Nobel prize cannot be awarded based on mathematical proof. Nice try though.

Wow, Did they preform those 350.757 coin flips with their hands like regular natural coin flips or did they used a mechanic coin flip machine for the study? Both would be equal impressie for sure. If they relay on the secret ninja one second coin flip methode it would still take them four days straight to complete all those coin flips.

Pedantic.

@@amihart9269 When talking about science, you need to be thorough and precise.

nor do they seem to be conducted in reality. i dont think superpositions exist in reality, object permence and all

The math doesn’t help with the understanding. It just gets you the answer that matches measurements.

The observed violation of the Bell inequalities is most often understood as a proof against the "hidden variable" scenario you've described, wherein there is some deeper system to which we are denied access that would make perfect sense of the quantum world. At least under Copenhagen, no hidden system obeying locality can account for quantum oddity. If you can tolerate non-locality, I guess that's fine, but Many Worlds offers the most sensible and elegant explanation: the hidden variable is the observer, who is just as quantum as the system they observe.

@@davidhand9721 Why, if I may ask, is locality so universally agreed upon as an essential characteristic for a successful model of QM? What is it about a local universe that is so much more attractive to physicists than the idea of a non-local universe?

Its a base philosophical assumption about how the world works, i.e. so far back in the chain of assumptions that they really don't want to ditch it too readily. From any experiment we can ask if the result is understood or if we should go back and change our major basic assumptions and this is a very major one, like causality. Results of any experiment give rise to a debate about which part of the holistic set of theories and observations we can change. Usually major philosophical assumptions are taken as a bedrock for which we imply something is wrong in observation or theory (although we haven't found that so still looking, didn't it take a while to accept an unseen planet didn't cause anomalies in the transit of Mercury but rather we had to find a whole new theory of gravity?).

@@davidhand9721 Someone should've told John Bell that, I'm sure he would've been interested in knowing that "Bell inequalities" disprove "hidden variables"... lol What you say is literally just an old wives' tale. There is no relevant at all to Bell's theorem and hidden variables, which is why John Bell himself was a major advocate and worked on developing hidden variable theories (see his paper "On the impossible pilot wave"). All Bell's theorem shows is that if there are hidden variables, they would have to be nonlocal (setting aside superdeterminism). Both MWI and Copenhagen are equally overly complicated interpretations that rely on an arbitrary and unfounded assumption that the statistics used in quantum mechanics differ fundamentally from statistics used in all other fields in all other sciences, that a particle having a 50% chance to be in one state and 50% chance of being in another is not due to an epistemic restriction in reference to the observer but somehow it actually exists in both states simulatenously. This assumption is entirely unfounded but is beloved by the mystics who want to believing in grand multiverses or collapsing wave functions.

Personally, I think the simplest and most intuitive way to think about quantum mechanics is not that there is some underlying hidden information we can't access that prevents us from predicting the outcome exactly, but that the probabilistic nature of QM is instead caused by precisely all the things we _can_ access. From such a point of view, it is not correct to even interpret classical mechanics as causally deterministic, because it is only causally deterministic in an ideal sense where you can fully isolate a system from its environment, which is not possible in reality. In reality, there are always some deviations, some _error,_ between the idealized predictions of classical mechanics and the actual measurement results. Typically, we think of the idealized mathematical laws as describing the system "in perfect isolation," but you could instead consider the idealized system as what Einstein had called an "ensemble." An ensemble is not a system in isolation, rather, an ensemble is formed when you repeat an experiment with the same initial setup an infinite number of times. As you continue to repeat the experiment and average out the results, the errors should cancel out, and you'll _converge_ towards the idealized mathematical law. If you think about classical mechanics this way, then there is not a fundamental distinction between the probability in QM and in classical mechanics. The wave function represents an ensemble, the Born rule gives you a probability distribution that the system will converge towards if you repeat the experiment an infinite number of times. If you only carry out the experiment once or a small number of times, you get deviation from the idealized prediction and the actual outcome, but this deviation is not caused by some underlying brand new phenomenon we haven't discovered, but is caused precisely by all the phenomena we already know able---the entire universal context in which the experiment is conducted. You can't account for this even in principle, so there is no way you'll be able to predict the outcome precisely, but the same is true also in classical mechanics. You have to get rid of the conception in your head of trying to imagine that idealized mathematical laws have any relationship to things "in perfect isolation," because things in perfect isolation can't exist, and consider how these idealized mathematical laws are actually produced if we can never isolate anything. Usually we can isolate things _enough_ so that the error is small enough that we can pretend it's possible to imagine some truly isolated system where that error doesn't exist, but when you get down to the atomic scale this mental trick doesn't work, you have to actually acknowledge that there is always error and that it stems from deviations from the ideal due to the fundamental inability to isolate systems form their environment. If you think about it that way, then the "measurement problem" is solved because there is no measurement problem in the first place. The measurement problem arises from a belief that particles in a sense "spread out" and take all possible paths described by the wave function, but we only ever measure a particle taking a single path, and so you have to explain how the particle seems to come back together into a single point whenever you make a measurement. Copenhagen claims things "spread out" as a postulate and then needs another postulate to explain how things "collapse" back together again. MWI denies things come back together but maintains the postulate that things "spread out," so it forced to then declare there's a grand multiverse composed of an infinite number of parallel universes. But the view I'm presenting here from Blokhintsev denies that particles "spreads out" in the first place, so there is no need to bring them back together, and thus there is no "measurement problem." Particles only ever take a single path, but the path does not have a singular essential cause but is instead caused by its universal context. All the _particulars_ of its context are knowable in principle but they work together to overdetermine the outcome of the experiment, and so you need to know all the _particulars_ in order to predict the outcome, and it is not possible to know the entire universal context simulatenously, so you will always have some error and deviation. A "correct" interpretation of QM from this point of view would thus be one that is both epistemic but also does not contain hidden variables because there is no essential cause that the error could be reduced down to, in the same sense you do not need to add hidden variables to classical mechanics to explain deviations that can be attributed to error. The error arises from epistemic reasons due to universal context which the observer did not (and could not) fully account for.

The simple answer is that you don't get irrational numbers when you are dealing with probabilities. If you are looking for one event out of n outcomes, then your chance is 1/n. That is a rational number by definition. Another way of looking at it, is that all the probabilities of different outcomes must add up to 1 (again by definition). That would never happen if one of your probabilities was irrational.

@@waynerobertson511 Yes, they have to add up to 1, but I am talking about the ratio of the probabilities to each other. An easy example is the Buffon’s needle problem, where you throw a match onto a set of parallel lines, I can’t remember the exact ratio, but the probability that a match will land on a line is some ratio of pi. Obviously, the ratio that the match will NOT land on a line is the inverse. So the multiply up to 1. But the argument in this video is that you can create enough many-worlds so that it reflects the ratio of the outcome probabilities to each other. In the case of 6 cards, it was just 2 or 3, but there will always be a case where you have to create an infinite number of many-worlds to match up to an irrational ratio of probabilities, Do this twice, and have the 2 quantum “collapses” be entangled with each other and like I said, an infinite number of many-worlds is not enough. Or am I wrong?

On the number line, rational numbers are dense amongst irrational ones. So if you have an irrational amplitude, you can just take two “nearby” rational numbers, calculate the probability for those, and then interpolate.

@@skewlkid521 Yes, but this is supposed to be science, so if you want the many-worlds interpretation to be a real and accurate way to reflect reality, then you will get such a confluence of infinite numbers of infinite numbers of worlds, that it seems like the many-world interpretation doesn't really work. But I am actually one of the people who think that there isn't actually a problem. I'm all for "shut up and calculate!".

@@waynerobertson511 may be that looks like single states objects at larger scales than plank length, is in fact at scales smallers than pl an high entropy environnement . and because we only mesure effects of this unknown underlaying reality smaller than pl by its effect on quantum objects that we have to mesure, we trust entropy is low and there is a probability , but in fact there is an High entropy environnement with its own rules that we are interpreting with probabilities, so probability is just our point of view , and so we observe patterns at one precise instant of a continuously moving hidden kinda reality out (inward?)of space time, but sufficiently organised to let emerge at higher scale mesurable patterns we call particules and/or wave functions and so there are no many world interpretarions but an hidden realm we cannot reach . Philosophically speaking it makes more sense to me than playing dices with half dead cats . Ps: my mind is bullshit and english second language. The Alice one world interpretation lol.

I'm pretty sure he just tried it and it worked--squaring the result produced the right predictions. So he basically derived it by throwing darts and testing the results.

From what I understand, time in many worlds is Einsteinian and deterministic - all possibilities exist already 'somewhere there' and its the observer that follows one of 'predestined path' of events. Otherwise we'd have to assume that with every ongoing event reality splits into infinite number of possible options and that such process is ongoing constantly. Personally I find both options equally stupid :)

Mathematically time in QM is an external parameter, it just goes linearly and states evolve with time, everything if some function F(t). There is no time operator, no time quantization etc. Many Worlds Interpretation usually doesn't add anything new to this picture. Quantum Field Theory uses maths from Special Relativity, flat 4D spacetime, where different observers may have somewhat differently inclined time axes, and use Lorentz transformation to convert from one frame of reference to another. Interestingly though, and not many people think about it, time becomes a real puzzle in MWI: if we're inside some branch of a wave function, and wave function is all there is, and its amplitude is not observable from inside, and Schrodinger equation only changes amplitudes, this would mean from inside our world we should not be able to see any changes at all, so how the heck we see time passing is a riddle.

Hence my question really. I feel the whole premise of us observing and measuring the outcomes of an experiment, implies some sort of sequential order by default. So really it is at the centre of the entire concept, and yet i havent seen or heard much about it, admittedly im not an expert, but find it odd. @@thedeemon

Could it be that these are all artefacts of the limitations of our consciousness? We dont really understand consciousness very well, so perhaps a more advanced form of it could deal with seeing all possible worlds simultaneously. We are unable to observe all possible outcomes simultaneously, so we only do one at a time. Similarly we have invented the time concept to aid us with seeing logic in the whole process.@@thedeemon

What happened after you outed yourself as a loser? Nothing. They didn't give a crap. ;-)

That's awesome. I thought I got most of it, but still had to watch it again to make sure I wasn't fooling myself.

Uh-huh. My mind immediately went to the ramifications of this to the Monty Hall problem, and there was an Elder God behind door number two.

Because it's already debunked. It tries to present itself as the "inevitable" and "obvious" consequence of a single premise, yet the premise presented in the video is actually immediately abandoned in the original paper it references when it tries to derive the Born rule for an updated version of the premise which is incredibly arbitrary and clearly chosen just to derive the Born rule, meaning most of the video is an irrelevant red herring. See the paper _"Epistemic Separability and Everettian Branches: A Critique of Sebens and Carroll."_

I never thought justification of born rule was “to avoid complex values”. If you have a bounded observable, some self-adjoint operator, it will be diagonalizable, and so you can take an eigenbasis, and split whatever state into a sum of orthogonal eigenstates of the observable. And, the born rule just says that the probabilities of each observation are proportional to the norm squared of the lengths of these? Which, like, well, if the different lengths are to correspond to the probabilities in some way, and probabilities sum to one, then, well, the squared lengths of orthogonal vectors sum to the squared length of the sum of those vectors (which is 1 if we assume state vector is normalized), so it all works out? So like, it’s a consequence of using the l^2 norm over the l^1 norm , and the l^2 norm is the natural thing to use, and also, like, rotations.

The measurement problem is derivative of the arbitrary assumption, which Schrodinger was the first to criticize, that particles should be interpreted in "smeared out" states (to use his terminology). No one has ever observed a particle in a "smeared out" state, we've only observed particles in discrete states. So if the particle "smears out," you need something to bring it back together again upon measurement, and this gives rise to the _measurement problem._ Many Worlds deletes the "bringing it back together again" postulate (the "collapse") but keeps the "smeared out" postulate (ontological wave functions), and thus it is forced to conclude that reality "smears out" into a branching multiverse, and then has to run in circles trying to come up with deep philosophical reasons to explain why we don't observe this. Einstein already pointed out a century ago that this difficulty is resolved if we just abandon the "smeared out" postulate, i.e. we stop assuming that particles somehow spread out into "all possible paths" when they're not being observed. Once you abandon that postulate, you can (philosophically) reformulate quantum mechanics in a way where the measurement problem never even shows up, because the particle only ever takes one path, and when you measure it you just reveal the path it took.