for a loooong time I've been puzzled with these "quantum algebra" equations to no end, your video explained it so cleary, I just got a new motivation to dive right back in... Thank you for your work!
It's called Dirac notation. Oversimplifying, a bra such as is a column vector. That makes the inner product (assuming there is one in the particular vector space in question). See en.wikipedia.org/wiki/Bra%E2%80%93ket_notation
You shouldn't put much importance on Dirac notation: it's just a conceptually ugly notation that physicists use in order to make elementary linear algebra appear esoteric :-))
I still don't understand. This seems like a tautology. "Why did I observe state X?" "Because you're in a state of observing state X." "Right, but why didn't I observe the superposition state Y?" "Because you're not in a state of observing state Y." It feels like instead of answering the question, MWI is defining the answer as being the essence of the answer to the question. "What's 2+2=?" "It's the answer to the question, 'what's 2+2=?'" It feels like I'm left the illusion of an answer to my question, a more complicated framework, and still no answer to any situation other than a 50/50 split, despite this addressing far too few issues with locality and probability distributions. How is MWI not just a complicated tautology?
Because like a lot of other interpretations, it's just a cop-out, and not really based on any physical evidence. It sounds nice, but ultimately ridiculous, and brings with it a whole host of needless complications.
Uh oh, we have a thinker over here. Stop it! Don't point out the obvious flaws in the unscientific bullshit. Gobble it up! Don't you see it's just like in all those cool Marvel comics and movies? The multiverse is totally real, mmmkay?
Exactly, and this is not only a problem for MWI. I think the reason that these explanations seems to resolving the problem is that people are accepting the "definition" that feelings are an emergent behavior of brain electric-chemical activities. Because if everything is simply an object in different positions and velocities, there is no feelings, there's only "state". And what about feelings, they tell you it's an illusion. In my opinion what people do is that, if I just pretend other people don't have consciousness, pretend they can be perfectly and entirely described by brain electro-chemical activites and other materialistic objects, and ignore the existence of my own consciousness, then suddenly I can pretend the issue is resolved, the model is perfect and I can explain why Bob's observation on Alice's observation on electron is always consistent. Then we can keep telling people that "consciousness" or "feelings" are no more an illusion of brain electro-chemical activities. Circular logic, isn't it? And it can be applied to any level of theory, classical physics, "why am I observing this", "because your brain cell are wired in such a state, the electron orbit around nucleus, bioelectricity, etc, that gives you an illusion that you're seeing this"
@@xuanyuzhu6779: Yep, that's ultimately the fatal flaw of all materialism, the hard problem of consciousness, as well as what I've started to dub "the even harder problem of will", another thing most materialist scientists today want to sweep under the rug (as well as people like Yuval Noah Harari talking about how stupid it is to think free will exists, how we are hackable, and how we should submit to the materialist new world order).
I know this is two years later, but I hope this helps: If you believe the schorindger equation works for macroscopic objects, you are forced to conclude (at least from an outside reference frame) that observers can be described as being entangled with the environment. The moment "you" are the one observing the system, however, we then switch to saying that there is a collapse, which is highly unmotivated and without reasoning. Yes, there is no explanation for why you're in one world and not the other, but at least it doesn't outright reject the schrodinger equation's solvency arbitrarily like the Copenhagen interpretation does. Because remember: you can't say that there's an objective collapse and say that an observer and a particle can be entangled at the same time. So you can either have an interpretation with a set of axioms that you just have to accept (every consistent and well defined interpretation/theory like MW), or you can have an interpretation that has extremely arbitrary and seemingly contradictory axioms. Why people accept the ill-defined or contradictory one is beyond me. (You could also have a theory that doesn't work for macroscopic observers, but then you're not describing quantum mechanics anymore; you're describing another theory that makes different predictions). Note that ultimately I think relational quantum mechanics solves a couple of problems that the MWI has (the EPR paradox ends up not being a paradox at all if you give up on the idea of an objective wavefunction, and the idea of a "wavefunction of the universe" is ill-defined because wavefunctions only make sense with respect to a given observer) but MWI is still much better than copenhagen.
No, it's deflection. It answers the easy problem of determination in MWI (why we find ourselves isolated to one outcome and not all of them at once) and not the hard problem of determination in MWI (why we observe one specific outcome over another specific outcome, or vice-versa). Obviously if we branch with the multiverse we will observe X or Y and not X and Y. But if we measure X, it does not tell us why we measured X rather than Y. It's supposedly a deterministic theory, yet there is nothing to determine what we actually measure.
I just started my journey in physics after switching from computer science. Its been pretty awesome, thank God, in terms of mathematics but for this physics class I'm taking, which basically gives an overview of modern physics, its been rough as the teacher doesn't have the passion to teach physics and it does bring me down a bit. Did you ever encounter teachers like this? Thanks and the videos are awesome!
r u at UK university? why don't you share ur bad experiences in Social media? for example if the teacher bullies students like u ,or humiliates u in front of class then you can record it live then upload it in social media, then see the magic, as in India great History. The RAMAYAN say. mean people needs to punished
Thank you so much for continuing with "many worlds" videos. And while still on holiday, no less. You sincerely rock. Your videos blow my mind. What is this strange place in which we live?!
Wonderful video!! I am 1 week away from finishing my quantum physical chemistry class, and it’s been one of my favorite (and toughest!) classes I’ve taken. Great job explaining everything. I just found your channel!
"Yes, this is my phone taped to a box, balanced on another box... I'm a professional." :D Thanks for taking the time out of your vacation to make great content! Would be curious to hear what you think about Travis Norsen's paper "Against 'Realism'" (its on arxiv) and his criticism of MWI therein. Looking forward to any further videos you have for this series. :)
These videos are so good. It's so nice to see videos on these subjects from someone who doesn't avoid the maths, but also doesn't overcomplicate it. Would you consider doing a video on how the many worlds interpretation deals with probabilities? In all your examples, you're using a superposition where both states have equal magnitude, so it's always 50/50 chance. The bit that seems most weird to me about many worlds is when this isn't the case, and one possibility is more likely than the other. If we split into two or more copies when measurement happens, why would it be that we're "more likely" to inhabit one copy of the universe than the other? I know there are explanations, but none of them seem intuitive to me, and I'd love a video on it. Thanks for all the great content.
Great explanations! Here’s something I still don’t get: we can describe how this electron interacting with stuff puts the electron and the stuff in an entangled state, but surely everything is interacting with everything else all the time right? So the universe must be one giant superposition of entangled states in this interpretation, cause nothing ever gets collapsed. In that case, how is it still valid to describe the electron as being in a fairly simple state of up + down at the beginning of the experiment, neglecting all other parts of the universe the electron has touched since the dawn of time? What part of the math allows us to sort of ignore the rest of the system and talk about the electron as if it has its own state?
You are correct - because any charge in the past light cone surface is essentially measuring the electron with a probability of 1/137 … not to mention gravitons if they exist. But theorists like Sean Carroll posit without evidence that you can isolate single particles (single oscillators in the quantum field lattice). It’s fraught with issues. There is really one one wave function of the Universe- yet you get all these stories about two particle “maximally entangled states” - this causes paradoxes like the AMPS paradox for black holes that you can see Leonard Susskind lecture about - the genesis of his and Juan Maldecena’s ER=EPR proposition.
I think, as far as the maths would go, it has to do with the basis in which you look at it. If you look at it from the basis of the wave function of the whole universe, adding up every interaction since the Big Bang, then it'd look like you say. But if you look at it from the basis of the electron's creation or last interaction, it's in a simple up+down state (or whatever entangled state that event left it in), and every other historical interaction cancels out to zero by decoherence, and even that basis will be short lived and replaced by a new basis as soon as it gets entangled enough.
Have they actually got proof that entanglement works across the galaxy of universe? I don't think so. All elemental particles are "vibrating" at or near light speed and if propelled will move like a wave. There is only one particle & one path ... but different positions at any moment in time. The Multiverse & other worlds are from the mind of an intelligence, and are an UNNATURAL existence. Heaven & Hell are UNNATURAL existences from the mind of an intelligence. Only an intelligence ... has free will ... to think, believe, say & do as he/she wants .. and ... make abstract & physical constructs. Only an intelligence makes Laws ( of nature) & things ( of the Universe) with clear purpose,, form, design & FUNCTION. Man has always known that the Universe has an UNNATURAL origin by an intelligence ... more powerful than Man.
While I agree with you that the many wolds interpretation of QM is a simplification, and I would say that it's probably also my preferred interpretation, the part I struggle with is the actual assigning of the 'many worlds' to the math. That is to say, what we initially mean by the many worlds interpretation is simply QM without the collapse axiom, and this is perfectly mathematically consistent and makes its predictions. But interpreting these predictions in real experiments to me seems to require more structure than the pure math has. Namely, we have to additionally define what it means to experience something as a detector/experimenter. The definition presented is that it means 'to have evidence for', but this is nevertheless more information on how to construe the results of the math.
I think Sean Carroll says that all the different states already exist ab initio, as part of the block universe. We're just only experiencing one of them at any given time, and our consciousness tracks along with the outcomes that are real for us. There is only one wave equation, and it encompasses everything. All possible futures and possible pasts exist already. I'm a) not a physicist, and b) drunk at this particular moment, so forgive me if that makes no sense.
I feel like these questions, while valid, aren't specific to this problem. Whether or not many worlds is true, or even if we found ourselves in a universe that wasn't quantum in nature at all, we would have to define experience and evidence. For understanding the nature of evidence I would recommend Bayes Theorem, and for understanding the nature of experience I would recommend this moment.
I don't think MWI requires any definition of "to experience something" or "to have evidence for". The cute drawings with the (sooo long!) tensor products of kets in the video are, in a sense, a discrete approximation of what happens in reality: the transition from the initial state to the final complicatedly entangled one happens with continuity; and also the factorization of the Hilbert space into tensor factors for System, Device, Environment, and what not, is conventional. ---- But you're right that a bare Hilbert space, together with a state vector in it, isn't enough for reconstructing reality from the math. Indeed, a Hilbert space is a very homogeneous entity: the group of unitary transformations acts transitively on the set of unit vectors... Everything looks the same in a Hilbert space! So the "structure" of the world should be reconstructed from some additional piece of data. What this further piece of data is and how it is "selected" by nature, as far as I understand, has something to do with the so-called Preferred Basis Problem. A "world" is in fact just a (normalized) component (just in the sense of linear algebra) of the Universe's state vector; the question is: what component? The answer is: a component with respect to a special eigenbasis of a "macroscopic" observable, which is somehow automatically selected by decoherence and is significant from our human descriptive point of view. This basis has something to do with the position of macroscopic objects, such as pointers in measurement devices (hence the name "pointer basis"). But it is not very clear to me how this works.
If you consider a quantum computer program that is performing some sort of inference task (like estimating how often a qubit prepared in a particular way ends up ON), you can derive that this results in almost all amplitude ending up in states where its estimates follow the Born rule. Basically you can derive that all of the statistical conclusions made by an automated quantum agent will match up with what we experience. The part that's missing is the "something experiences making these statistical conclusions". But it's not a new complaint that reducing people to physics doesn't seem to explain experience. That's the hard problem of consciousness, and it also occurs in classical mechanics.
@@rv706 Isn't the additional data that provides the structure just the Lagrangian, or equivalently the time evolution operator? And the preferred basis comes from the fact that the Lagrangian is a local operator? That of course poses the question what makes time and space special and why are the laws of nature local, so I don't know if that helps.
Thanks so much for another amazing video, I think you make the most interesting videos on youtube. I love that you try to understand and explain what's happening under the hood, rather than just dismissing those deeper questions (which a lot of physicists seem to do!). I have a question I'm stumped on - in many worlds, what's actually happening when you see an interference pattern in the double slit experiment? Is this the different "worlds" interfering with each other? What does that even mean? Thanks again!
Great question! Interference is when two branches of the wavefunction interfere. A world in many worlds is a branch of the wavefunction where this sort of interference is difficult to get (because the experiment might involve too many particles etc). So in the first case I wouldn’t say that those branches are “worlds”.
Really nice video. Glad I found your channel again, after having seen your vids years ago. One of my issues with Many Worlds is that it relies on these binary analogies to talk about a split. But say you fire a photon through a double slit and it hits a detector. The two slits are binary, but the detector has essentially infinite locations the photon could hit. How many splits happened in this experiment? More universes would see the photon hit the detector in one of the more likely positions; but how many? What is the "resolution" of the willingness of the universe to create a split? If something has a 0.00000000000000000000001% chance of happening, does the universe split into 10000000000000000000000000 universes to accommodate that chance? This would imply that there are essentially infinite splits happening at every instant of time.
@@LookingGlassUniverse : I hope you'll also deal with how conservation of mass/energy does or doesn't work in Many Worlds. Does the total mass of the universe(s) double when the measurement of the superposed Up+Down electron splits the universe into an Up universe and a Down universe? Or does the total mass remain the same so that everything in the Up universe has half the mass that it had in the superposition universe? Or some other alternative, such as David Deutsch's variation of Many Worlds (described in one of the chapters of his book "The Beginning of Infinity) which postulates that there was an infinity of universes before the measurement, and half of the infinity of universes are Up, half are Down, the infinite mass remains unchanged and the mass in each universe remains unchanged.
@@brothermine2292 Sean Carroll explained (his view on) this when he was on the Lex Fridman podcast. FWIW Many Worlds makes most sense to me, but I found out recently that Sabine thinks it's nonsense. And when Sabine speaks I think we should listen :-)
@@guest_informant I share your respect for Sabine, but I wonder whether you might have misunderstood her. Her feelings about Many Worlds are in this video: czcams.com/video/kF6USB2I1iU/video.html Basically her claim is that Many Worlds does not solve the measurement problem, so it is EQUALLY as troubled as the other interpretations. Sabine also has a video about "the multiverse" in which she says that the idea is not scientific. Could that be what you are referring to? She is not talking about Many Worlds there. czcams.com/video/-dSua_PUyfM/video.html Even there, she's not saying the idea is wrong, necessarily.
Ok, that´s the second video I've watched from the channel. They are amazing!! I am from Brazil and studied Physics and Mathematics at the University of São Paulo in the late 70"s - by that time some physicists believed that the observer could cause the wave collapse. It was clear to me that it should be something simpler as an interaction. What about the MWI? Where´s the real magics? I don´t really know yet. I'am bewildered by that. In his book THE FABRIC OF REALITY, David Deutsch says that predicting phenomena is much less fundamental then explaining how things happen. I agree totally. I hate that "Shut up and do the calculation" rule. Explaining stuff is fundamental, and these videos aim to this honorable objetive. Just Great! Thank you!!
I can either listen or watch you speak, can't do both at the same time. It's because I find you to be beautiful 😍 Great explanation - as I came to realize at listening it the second time. 😁
Thank you for this great explanation. Your videos are always easy to follow! When you were talking about interaction, I was wondering, can neutrinos cause the collapse of the superposition?
Thank you for doing this on your holiday (hope it's relaxing)! I've been highly sceptical about the Many Worlds Interpretation, but you've done the best job so far at making it sound reasonable. However, if we were to ever get a clearer physical understanding of other "weird" quantum phenomena (eg some recent arguments by Charles Sebens claim that spin can be explained by something actually spinning), I wonder whether this could ever lead to a more intuitive idea behind superposition. (Another thing I've wondered about is how gravity would tie into all of this - would its interaction with particles affect the "branching" into worlds at all?)
There actually is an "objective collapse" theory proposed by Roger Penrose, in which gravity causes wave function cpllapse, essentially adding an explanation to the Copenhagen interpretation. But Idk how gravity would play into Many Worlds, that is an interesting question…
@@vauchomarx6733 Yeah, the Penrose interpretation is actually my favourite. I think his view is that Many Worlds simply can't be explained if you consider gravity
Regarding the interaction of "many worlds" and gravity an interesting clue for how they might work together comes from the Wolfram physics project which is an interesting project extending Turing's work looking into the consequences of Gödel's incompleteness theorems on Turing machines specifically a property generalizing the conditions to ensure logical internal consistency via the logical conclusions needed to avoid the pitfalls of the Halting problem that called computational irreducibility. Basically it turns out you can show that you can in this model as the size of the Turing machine system becomes large derive an emergent space relative to a rate or flux. In the case of the rate at which changes in the system propagate this can be shown in this limit to converge to the Einstein field equations with causal space as formulated being the type of space known in General Relativity. Attempting this same emergent spatial property to resolve any and all combinations in which the system can operate in a superposition of states where the rate at which these possible combinations resolve through indistinguishable states recombining interestingly allows you to define an additional, distinct type of spatial dimensions representing the superposition of all these possible branches of the system which Wolfram calls "branchial space" which like the causal space is a rate of interactions between branch states. This emergent branchial space has been shown to be identical to the Feynman path integral formulation of Quantum field theory which also follows the Einstein field equations with the analog of distance for quantum states in these dimensions represented by the Hamiltonian of the universal wave function that is to say the units of distance are energy. What matters here is it appears that mathematically the branchial components of curvature within this energy space of quantum states corresponds to the probability of measuring a given state for any branchial frame of reference within the cone of entanglement.(basically constructive interference means more paths within a given cone of entanglement, the light cone analog of branchial space, curve in toward that state in branchial space-time with the collision in branchial space of two states representing the reconvergence of those two states into a superposition. In principal it may be that any act of measurement to distinguish between the two states by observers would then amount to costing the appropriate amount of energy to try and separate(distinguish) the two or more effectively indistinguishable quantum states which is a very different way to think about this. While it may be premature in principal one of the most natural ways you can attempt to combine these two results borrowing from both objective collapse and many worlds would be to extend the dimensions of the Einstein field equations to now incorporate causal space, branchial space and time as different types of space (noting that like the speed of light represents the geometric parameter converting between causal space and time there will be an equivalent geometric conversion constant between branchial space and time, a speed of entanglement if you will) into a single higher dimensional Einstein field equation with us as observers being constrained to the 3 dimensions of causal space and 1 dimension of time. Quantum weirdness in this limit is a limitation that we can only observe a causal projection of the universe and the states associated with "many worlds can then be thought of as places which we can only observe through indirect interactions projecting into our reality or rather our frame of reference with anything outside our cone of entanglement being unreachable via any branchial acceleration or measurement. If this interpretation is valid then gravity may in essence as some have theorized leak out and effect the other branches of the wavefunction and thus could be expected to leak into our branch of the wave function as a superposition of all projections of those disentangled states. As you wouldn't be able to observe the individual states you would see a cloud of invisible and otherwise undetectable apparent gravitational mass which would resemble a quantum superposition largely devoid of any apparent internal structure. (In effect perhaps able to be thought of as the equivalent of gravitons leaking information to pull the branches of the wave function back together i.e. causing them to evolve towards a indistinguishable higher entropy state) This might even suggest that gravity, quantum probability and entropy might be aspects of a single underlying entanglement field within some more generalized counterpart to Anti-De Sitter Conformal Field Theory correspondence. (I'm actually wondering if the extra dimensions of string theory or similar attempts to extend the standard model into a "theory of everything" might be dimensions in branchial space rather than causal space that in effect have been staring us in the face all the time.
@@joelbeckles3490 I don't think we can really know until we understand more about gravity. If gravity is created by real physical spacetime curvature, then I don't think MW could be true. If gravity is created by graviton particles whose effects can be *modeled* as spacetime curvature, but nothing is actually curving, then that probably wouldn't rule out MWI, the graviton particles would just exist in superpositions like everything else.
I'd like to add, that even if you were able to get all the particles including the experimenter together and tried to get interference between the "worlds", a necessary condition for that to happen is that the experimenter forgets what she has seen. This is because the states of the brain remembering different things are certainly orthogonal. The same is true for any other system storing information.
As a Black and White photographer and darkroom printer. I love your photos on the Wall. I have seen the originals in the Weston gallery in Carmel California and just beautiful.
Why can I use thumbs up only once?? Again, such a great explanation! It sparked a thought: I think you can determine big objects being in a super position more easily like this: Entangle 2 electrons. Measure one's left-rightness, so you know the other one's up-downness is definitely in superposition. Setup a detector so that it will measure the other particle in a minute from now. This way, you know that the future detector state is in superposition. It's like, disconnecting a big object from information leaking out, by hiding it in the future. And also I think, this is the way the future evolves. Over time we know more and more of it until the superposition seamingly disappears because we completely entangle with it. That is when it is 'happening'.
Very interesting! You may wish to check out Lee Smolin lectures on the Perimeter Institute channel - he’s the only mainstream theorist I know that has equations on how he believes the future becomes the present … how energy/momentum is transferred.
Superbly explanined. I find the many-worlds-interpretation the pure "HORROR", but my friends don't understand why I believe in this interpretation if I don't like it. It is not a matter of like or don't like it. Maybe if they could see your explanation they would understand it.
Thanks for another interesting video!! I was wondering if you started with a horizontal gerlach machine, then attached a vertical gerlach to the left output, and a vertical gerlach machine to the right (x2 vertical gerlach machines in parallel) would the 2 vertical machines produce the same result?
Great question! Yes, they would, because the first machine is basically a measurement of left right. A left or right electron will go up or down with 50/50 probability
Thanks for this explanation. I had assumed something different in my understanding of many worlds. At the point when we are looking at the results of a double slit experiment, I thought that meant that we were seeing a superposition of time-lines in the multiverse. At that point we, as quantum beings in the quantum multiverse, are observing multiple timelines where or particle goes through both slits. When we measure, we are, in effect, selecting the timeline we are on, so no longer see the results of observing this superposition. I assume from your description that I am wrong, but can you explain how we see the results of the double slit, or similar, if we aren’t observing multiple timelines please?
I understand that the "-ket" notation denotes a column vector. So what does it mean when you juxtapose tokens of that notation horizontally? Usually juxtaposed mathematical symbols denote multiplication, but we usually don't multiply column by column. We multiply row by column. So, what do you intend by the juxtaposition?
Mithuna, I really liked your video on many worlds. Many people are spewing this crap out there making themselves to be great physics gurus but few have done this with the quality that you have. While not perfect I think your explanation is the best ive seen on this on youtube. The other being a colloquium by Zurek. By the way
This was really interesting, thanks! A question I have is: the experiments showed that given a certain initial conditions you get particular end states and those end states were always consistent with the electron being up or down, so (ignoring the initial state) what would an end state look like if it were possible to see if you were in a superposition? Apologies if this sounds like nonsense, I'm clearly not a physicist.
To understand from the measurement what state the electron was in, it is necessary to carry out many measurements of electrons prepared in the same state. If from the measurements you always get up, then it was up. If he always gets down then he was down. If you get about 50% of the time up and 50% down then the electron was in a quantum superposition state.
at 14:23, are you saying that a particle in the up-down superposition along the vertical axis will always give the same value when measured along the horizontal axis?
One serious question from the philosophy of science point of view: if there is (probably) no hope of ever detecting evindence for this interpretation, where does this stand in the demarcation problem(i.e. is it still science?) This reminds me a lot of one of my favorite physics theorems, the "Ewald-Oseen extinction theorem". Usually when we speak of light traveling in a medium we say "it slows down", giving us the definition of n, index of refraction. However, from a microscopic perspective that doesn't make sense! We only had photons/EM waves traveling through vacuum, other EM fields and sometimes scattering with other fermions. These photons should always move at "c" speed and never slower. So what happened? The theorem states that what we observe actually is the superposition of many, many scattered photons/EM waves, all traveling at "c", and if you add then all those wavelets together with their amplitude and phases, you get a wave that, mathematically, propagates at a slower speed (agreeing with n), but that wave is only a mathematical construct, a device to help our intuition. It on looks *as if* light slowed down. All the "real" wavelets never slowed down (as they shouldn't). Couldn't many worlds be like this? It is a story we can tell, and the math adds up, but it still cannot be assigned or identify to carry "an element of reality".
Im not sure, it might be like that! On the other hand, it is in principle testable. You’d just need extremely fine control of quantum objects to test it (eg, doing the test I mentioned at the end)
we are able to "experience" all outcomes in our heads, in imagination, the field of all possibilities and then we make a choise and only one outcome is manifested into our reality. That's how we are living.
After your great explanation, just to proof that as a probabilistic tautology, the craziest thing is the posibility of someone else replicating the experiment to find the person checked in the down world. The theory of linving in superposition is near enough to realize we are the superposition, entanglement and supersymmenty at once.
I really appreciate you explaining this, I'm trying to wrap my head around it. So let me ask a question by proposing a counter idea and see if that spurs a conversation: I'm sure the superstate concept is understood... mathematically, but does it translate to reality? What if the superstate is like a bag of colored marbles and you're only allowed to remove one marble... so when you make a measurement you remove the one marble and that is the answer to the question: up or down... so now that's the one marble that is sitting on the outside of the bag and you can't can't pull out any other marble(s) after that one is removed. This pushes whole the notion of the superposition state purely into the "bag", and thus it cannot extend past the bag into other worlds/realities... As you described the observer that observes the observer ad infinitum, it is merely a downstream effect from a cause of making that measurement... i.e. a one-way chain, downstream of cause-and-effect... there is no spoon... I mean... no other worlds created of the opposite measurement, etc., etc., etc. I'm sure there's a hole big enough to drive a semitruck through, but maybe my ignorance of the subject matter can serve as a foil and it gives you an opportunity to help us "mere mortals" (LOL) understand Quantum Mechanics better... I'd be interested in hearing your response; This stuff is so fascinating!
It's best to think of "measurement" as a state change of the system. For instance, if Schrödinger put a cat in a box, then the cat also changed Schrödinger during this process, as Schrödinger had to physically put the cat in the box. Schrödinger, the cat, the box, the room, the building, the planet, the solar system, and the galaxy are all part of the same closed system. Schrödinger's hypothetical air-gapped box barrier is entirely arbitrary and artifical. If you think of yourself as the cat in the box... czcams.com/video/5P38r-J3Ay8/video.html
Hi Mithuna! I'm just seeing this now about 1 year later😂 but just checking: at 11:48 there was a tiny error in the girl's state in the 2nd half of your bottom equation, correct? It shows "up" arrow but it should be "down".... Am I correct or crazy? (Either is ok because there is evidence of both correct & crazy in my case 😂)
What happens if you have contradictory information? For example, detector says up, the observer sees up but writes down. Other people reading the notes would then believe it to be down and if the detector didn't keep records and the initial observer didn't remember other than the note, would state of the particle be down? Would it return to superposition?
Can't get enough of these many worlds videos. I have a dumb question though, do entangled particles act this way for the same reason superposition works? I mean we assume a single particle is almost anywhere until it's measured. If so, then wouldn't the idea of "faster than light communication" still be a factor vs the many worlds construct?
Evidence would mean that you can interact with it in some way, or see that matter in your world line is influenced by matter in another world line. If we hypothesized that there is some kind of evidence to the existence of many worlds, what kind of interactions would we look for, and what types of bosons should we consider looking at? Like, could darkmatter result from four dimensional gravity in a many worlds universe?
A question from a very non-physicist. If you had enough computing power, could you simulate the experimenters and all their various entanglements? Like a digital proxy of the “up world” that could let us glimpse both states at once? Thank you for your videos! Just found you today, and your explanations are totally mind blowing!
As you point out at the end of the video, seeing evidence for both worlds when the components are a person, detector, electron, the surrounding environment, etc. is impractical. Is it more practical in principle (though still a very challenging engineering problem) to see evidence for both worlds if a quantum computer with enough qubits was designed to have sub-components interact with each other in ways analogous to how the person, detector, etc. do? If so, and such evidence was found, would that be incompatible with the Copenhagen interpretation?
Is the direction the electron takes in the Stern-Gerlach itself a "measurement"? So, when the electron leaves the S/G, but before it gets to the monitor, the world has already decohered?
What happens if you use a device that reads the measurement and flip it like if its down it becomes up and get someone (who don't know that this device flip the result) and she write it on paper up then we use the original read to another one who says it's down and write it as down. And they interacted without letting the creator of this trick knows about results and use a fourth person to ask those 2 about their opposite evidences and destroy the machines and the evidences and then let those two interact would they be in different dimensions? I know we can use devices instead of human beings but I wonder can we trick the quantum?
The more I learn about this the more I become really convinced that information must be at the heart of the whole mystery. Someone gains information from an experiment and now exists in the world where they must be consistent with that information, cascading out as the informations conveyed to the world. it's almost like we exist on branches in a sort of complex, infinite dimensional, information-vector space, constantly splitting off diverging branches when values in one direction are forced into certain states.
Ultimately the problem I have with the MWI is the "individual experience" of a particular branch. At this level you have invoked something special. Does a rock "experience" only a single world? How about an amoeba? What about kittens? Such questions were asked about the experiment of Frauchiger and Renner who considered measurement from a photon's perspective. My preference is for theory-independent no-go theorems such as Bell's theorem. All interpretations must be consistent with such theorems, and then you have some understanding of the properties of "reality". Such a no-go theorem has been developed from the extended Wigner's friend paradox. There, three properties of reality are considered: locality, determinism, and observer-independent facts. No interpretation of quantum theory can satisfy all three properties. This means that for each interpretation you are making a choice to reject a particular property. Thus, if all the above properties are reasonable, then some element of strangeness must arise in all interpretations. By far most physicists that I know remain agnostic about interpretations.
Thanks for introducing this interesting topic! But I don't think it resolves the question, it's difficult to explain but please see if my explanation also make sense for you. I also thought about this entanglement formulation for a long time, and I'm pretty sure that these math consistency that you showed really only explained this: for Bob who is observing Alice observing an electron spin, it only explained why Alice always reports the electron is spin up when electron is spin up, and Alice reports spin down when electron is spin down, but it really don't explain why Bob consciousness only "feels" one out of the two possible realities. Let me explain what I meant: When I say Bob observing Alice observing an electron spin, it is *by definition* that we treat Alice as an object and "she" is not different than an electron, then of course for Bob, the system may either collapse into Alice reporting up with electron being up, or Alice reporting down with electron being down, it's consistent, because why not. But this is like getting around the problem by not answering it, because the whole problem is, we wouldn't have a problem understanding the measurement device entangled with the electron spin, at least we don't imagine the machine will "feel" the collapse of the electron, it's simply an object, it doesn't feel. (To attempt to put it precisely, the quantum model we are presenting here doesn't contain any fundamental components that give rise to feelings. The materialistic model only contain fundamental components that give rise to the phenomenon such that if someone sees some object exhibiting some phenomenon, it appears as if that object has feelings, but that's only *phenomenon* which is completely encompassed by "expressions", "screaming", for example, which basically decomposes into coordinates and momentum of objects if I'm talking about classical physics, but same idea for quantum. This is entirely a fact that a model is restricted by it's fundamental components and it cannot give rise to something that the model does not have.) The problem is that, for Bob, he can't understand why he only experiences only one of the two possibilities, but I can claim to solving the problem by defining Bob as an object in the system I'm observing, in my model I claim Bob is an object, so I will always either see Bob sees Alice reporting up with electron up, or I Bob sees Alice reporting down with electron down, and within my model I can see they are consistent. But my claim of solving the problem is false, because I cannot explain why I only sees one of the two possibilities. But this is not a problem for you because you are observing me as if I am a object, so it's nothing but consistency in the two possibilities that you could see, and it goes on. The biggest reason that these explanations seems to resolving the problem is that people are accepting the "definition" that feelings are an emergent behavior of brain electric-chemical activities. I really want to say that this definition of feelings are really problematic, it's not even an "hypothesis" in my opinion, it's simply wrong, by definition of models, if you think about it. Here's two statements that I take as facts. Statement 1: I know I have feelings, but I can only see your materialistic representations, velocities, positions of your particles, so I have no evidence that you have feelings. You could have, or not have feelings, from my perspective. You can think about it, is it true for you too. [end of statement 1] Statement 2: our models don't contain feelings. [End of statement 2] So for me, I think it's clear that the model isn't entirely compatible with the reality, because it does not have any component that contains feelings and I do have feelings. But the model could *possibly* describe everything I see from you, because everything I see from you is materialistic and the model contains everything needed to describe that, but it could also *possibly* not be able to describe everything about you because I don't know if you have some element that cannot be described by the model, for example feelings. In my opinion what people do is that, I just pretend I know that other people don't have real consciousness, pretend I know they can be perfectly and entirely described by brain electro-chemical activites and other materialistic objects, and ignore the existence of the consciousness of myself, then suddenly I can pretend the issue is resolved, the model is perfect and I can explain why Bob's observation on Alice's observation on electron is always consistent. Then we can keep telling people that "consciousness" or "feelings" are no more an illusion of brain electro-chemical activities. Do you see the circular logic here?
As I model reality, we regularly experience many of the different paths/timelines simultaneously, as patterns branch and merge and branch and merge. When we stop remembering specifics, that might be because we have merged past timelines. This is similar to when two separate biological species split and then mate again, producing a new merged species, similar, but different, from the original species that existed before the two species split.
How does down quark convert into up quark in beta minus decay? In wiki it says that down quark enters into superposition of up quarks while converting into up quark what causes this superposition?
I always wondered: What if you check for the input twice? It always seemed to me that the act of checking. The moment of measuring created what we erceive as the parallel universe. Did you do the theory of entanglement somewhere already? (I am a new subscriber). Really curious about your clear-cut explanation. Everett's MW Interpretation inspired the first film I made. Where the universes collide at one point and reset into an ambiguious ending. Making the audience one in the up state the other in the down state ;) QM is just way too interesting even for someone who never studied the field.
I suppose you did answer it at the end a little btw. once checked, you are in that universe forever right? It's just so mysterious to me why that is, and how it can't be undone.
How do you interpret the probabilities of measurements that weren’t made? For instance the double slit, where you didn’t measure which slit the particle went through, but the interference pattern tells you that the particle was 50% slit A and 50% slit B?
The interpretation that I‘m considering at the moment is that the question „which slit did the particle go through“ actually reduces to „at which slit did the particle not interact with anything so it could reach the screen on the other side?“ to which the answer is: both! Neither the particle nor the rest of the world have the necessary information to decide which slit the particle went through. Thus, it didn’t. There is no universal coordinate system where particles would have a clear position and momentum. Instead, the particles have to carry all information themselves. Which is too much of a burden for individual particles without inner structure: when they were hit, they immediately forget about it and about the direction of the blow; ensembles of particles on the other hand do exhibit memory, as a ball of play dough clearly indicates that it was punched and from which angle once I did so. I feel that this perspective of mine - inspired by Boltzmann‘s explanation of the time arrow and Einstein’s approach of removing observers that appear to live outside the model - should be intimately related to the model you describe as „many worlds“, possibly getting rid of a few last philosophical problems. I just can’t quite grasp how to bridge the gap here. And oh, I‘m a mathematician, not a physicist, and I left academia for a job where I get paid, so I didn’t write a paper that could be peer reviewed.
I was just curious about something called parallel worlds shown in the super hero webseries or movies. So I just Saw this title many words. But after watching this video it seems possible that their is a parallel word in the universe that we do not know about and we don't have proof about it because the reason stated in this video. Can we make something from quantum computers to get proof about parallel world's?
I've always considered the 4th dimension to just be a field of infinite possibilities within a set of limited parameters, and our experience of time is just a result of how we navigate through these possibilities with our choices. It seems to me that physicists are simply observing the phenomena of movement through this 4th dimension as it pertains to the simple observation of quantum occurrences where the results are binary. I'm interested in your thoughts on this perspective.
Hypothesis: Penrose is right about consciousness being mediated by quantum effects in cytoplasmic microtubules, being drunk interferes with tubule structure, so seeing double when you're tanked to the gills is being able to collapse superpositions from nearby parallel worlds.
I've often heard people postulate that there is still randomness in many worlds because our consciousness seems to get pulled at random into one of these many parallel worlds instead of experiencing all of them. I wonder however if our experience of reality does actually consist of perceiving all of the many worlds at once, it's just that we experience them to varying degrees based on how "probable" that world is. In the same way that two quantum states don't need to be equally likely, two worlds don't need to be either. Maybe in this experiment you showed here, multiple interactions in the down world come together to just make the down world less probable than the up world, and the probability has some kind of feedback loop that makes it trend towards being less and less the world that exists. The whole down world does exist in the wave equation, just at a way lower amplitude than the up world. It's the same as how an electron exists spread out over the whole universe, but the maths of the universe say that it's 99.999% right here. In the same way, we would just be 99.999% in the up world. I guess that's more going into objective collapse theory, except that I'm specifically saying collapse never happens. In that context probability shouldn't be called probability and should just be called amplitude or something.
As usual, I still have trouble groking the MWI. The questions I would raise would be the following: 1. What happens if the person is perverse, decides to record the opposite in pen and paper of what was observed in the experiment? (Or toss a coin, put down something random?). Does this really affect the results of the experiment (the physicality of the experimental setup)? Or there are two different books for the experiment? One good. The other bad. 2. How is the interpretation a "science", when there is no way to tell whether the theory is true or not? (Maybe this is why it's called an "interpretation", and not a "theory"?). Something regarding the "falsifiability" principle in science (?). Also, assuming MWI, you still wind up with the same problem. Calculating the probability one winds up in one world vs. another. 3. This seems to want to satisfy some assumption (aesthetic?) that the math is primary, and the empiricism is secondary. Is it possible it's the other way around? That math is a modeling tool, probably imperfect in some ways, and the physical reality should be regarded as primary. What if we question linearity assumption? (This question was raised by Sabine Hossenfelder raised, in some of her videos.) As oppose to the double slit experiment, the spin example, presents an interesting image. It's like a bar magnet. Somehow, with the measuring device (up or down), the bar magnet is "coerced" into one direction. (I haven't figured out the left right case. And this could be a reflection of my own misunderstandings.). The universe, as we already know it (since the big bang), is the way it is. Stuff is coerced (entangled) into it, when "measured" (though we don't understand all the details). 4. Can you say more about de-coherence theory? Does it require the MWI, or can it fit into a theory such as one suggested by Lee Smolin?
1. Quantum Mechanics nor Quantum Field theory predict anything about consciousness - most theorists appear to not believe in ‘decisions’ - so they certainly can’t say anything about it. 2. It’s a theory from which you could create models to predict things - but right now MWI isn’t leading to any actual models - I haven’t seen any equations for predicting how many worlds are created based on the amplitudes of a continuous variable like a position or momentum measurement. Sean Carroll and others studying it actively are undecided on many questions. I don’t know of an actual model yet. 3. I agree with that - there should only be one wave function- that of the universe- anything else is an ‘effective’ theory. Bohr and others wanted to treat everything that performs the “C” operation as classical and not quantum. Since 1970, they prefer handy-wavy decoherence… never explaining when the “split”/“collapse” occurs. Roger Penrose has an actual equation for objective collapse, but no ontological mechanism of how it happens. 4. To definitively understand decoherence math, you will probably need to understand Density Matrices … one easy approach to get there is the Leonard Susskind book “Quantum Mechanics - The Theoretical Minimum” … Stanford University has the corresponding lectures on CZcams.
1. Look, there are worlds in which every law of statistics is falsified. But they carry a _very_ small measure. I haven't thought about what happens in your scenario, but whatever happens it certainly won't be a logical problem because whatever happens is just Schroedinger unitary evolution. 2. exactly: the goal of interpretations of QM is to solve the Measurement Problem, _not_ to make new empirical predictions. Their empirical predictions are the same as traditional QM up to our current precision range. There _are_ some interpretations of QM that happen to also make new predictions: e.g. some objective collapse theories disagree with the Schroedinger equation (obviously only for tiny variations that go beyond previous experiments that of course confirmed traditional QM). 3. as I explained in point 2, the MWI doesn't sacrifice empirical predictions: it makes _at least_ the _same_ empirical predictions as traditional QM. I say "at least" because I don't know whether to count the description of what happens during measurements as new predictions or not. And, by the way, the "other worlds" shouldn't count as empirical predictions at all: think of them as useful mathematical fictions, in the same way as you think as virtual particles inside Feynman diagrams. 4. decoherence theory is a set of models that describe what happens when a quantum system interacts with certain types of environment whose information is not accessible ("the system leaks information into the environment"). The word also denotes the physical process itself. A consequence of decoherence is that interaction with the environment heavily dampens down interference effects. It does not require the many worlds interpretation (but fits nicely within it). Decoherence theory is a concrete physical theory in the usual sense of the term, like that of phase transitions or scattering or whatever. It is not an interpretation of QM (see point 2). But, from the philosophical point of view, it explains an aspect of the "quantum-to-classical transition".
To answer 2, the answer is: it's not scientific at all, and this bullshit artist, like Everett, is peddling pure hogwash with zero basis in reality, and she probably knows it too.
Why is it always Up or Down? Is there no neutral state? Or is it like a two pole magnet? What do you even call the part of a magnet that is the center of the poles?
Another impossibility in physics is traveling back in time. It leads to paradoxes such as the Grandfather paradox. Are there similar paradoxes if we try and communicate with the other world? Wonderful explanation, thank you.
Actually I'd say that many worlds is a solution to the grandfather paradox. When you'd be able to travel back in time and kill your grandpa, you'd live on in a different timeline where different 'splits' have happened. Since all other possible timelines are also still there, you'd just keep on living and not disappear like in Back to the Future :)
General relativity allows Closed Timelike Loops … and there are physically realizable situations - e.g. Tipler Cylinder - in which it’s predicted. Quantum Mechanics ALSO has paradoxes - e.g. Hawking Radiation be maximally entangled BOTH with things inside and outside of a black hole horizon.
Entanglement certainly seems a better candidate for explaining an arrow of time. Is there a speed of entanglement? Does the speed of entanglement correspond to the speed of causality? Is entanglement what drives causality?
Thank you for an interesting video. Maybe I am missing the point, but isn't this many worlds interpretation one of many models (maybe an infinite class of models) that could be constructed to explain the quantum measurement problem? The many worlds model is maybe be nice and elegant but does that necessarily mean it is the model that is correct? Aren't we back to the argument that "naturalness" in the maths is used as evidence in the absence of experimental evidence?
It's true, there is no direct physical evidence for Many Worlds, nor for any other Interpretation of Quantum Mechanics really (including Copenhagen/Orthodox Quantum Mechanics). But there _is_ this principle called "Occam's Razor", which you may have heard of, and Many Worlds does in fact abide by Occam's Razor the best out of all Interpretations of Quantum Mechanics.
Regarding the testing proposal of MWI at the end... Assuming the external verifier manages to isolate the entire quantum system of the experiment, wouldn't the measurement performed by the verifier necessarily entangle him and the whole external experiment setting with the quantum system of the internal experiment? The way I see it, according to MWI, the only way to perform an observation is by being inside a superposition of all the involved parts in the first place (one of the many worlds). Now, this is some complicated stuff, maybe I missed the point altogether, but I was reading that even MWI proponents agree that (as with all theories) many of the implications of MWI, specifically the many worlds part, are not testable. This doesn't mean that the postulates of the theory are not testable. The postulates of MWI seem to be the same as those of many other interpretations, so it should be equivalent in this regard.
OK. Very little background here. What does measuring and getting "superposition" as a result even mean? Isn't that *in principle) not available as an outcome?
What are the odds that we are “trapped” in the world with a normal distribution for random events? (Some worlds have extreme statistical deviations, eg whenever they roll a die, they always roll a die; whenever they flip a coin they always get a head, etc. However, somehow we were lucky/unlucky enough to end up in the world where every single random event has an equal probability!
So if I understand correctly, you can see that a system is in a superposition as long as you are not part of the system itself. The interference experiment only works for people outside the system. Is that correct? Then the universe could be in a superposition of two (or more) states but we cannot know unless we were somehow outside the universe, and we can't communicate that to someone inside the universe. God could see the many worlds unfolding but they can't tell us. Right?
With careful consideration of sync-duration coherence-cohesion phase-locked states, it's possible to imagine, using the unit circle representation of inside-outside relative-timing turned insideout and forming fields of bubble-mode coordination that is "in the now" but not 0-1-2-3-4-etc connection. We can think about it, but technically, it is something that is just an idea we're floating.., and it is as a consequence of time-timing projection that a boat floats, planets orbit and chemicals are bonded. Because every point of existence floats around every other point, it's the same point displaced in relative-timing. Still reckon we can build Quantum Computers?
Thank you for talking about QM without calling it confusing, or unintuitive. And for taking many worlds seriously.
Many worlds is pseudo-science. For reference, see Sabine Hossenfelder on the multiverse. Many would say it’s religion dressed up as science.
Reminds me of Christians thanking the video creator for taking Jesus seriously.
for a loooong time I've been puzzled with these "quantum algebra" equations to no end, your video explained it so cleary, I just got a new motivation to dive right back in... Thank you for your work!
It's called Dirac notation. Oversimplifying, a bra such as is a column vector. That makes the inner product (assuming there is one in the particular vector space in question). See en.wikipedia.org/wiki/Bra%E2%80%93ket_notation
You shouldn't put much importance on Dirac notation: it's just a conceptually ugly notation that physicists use in order to make elementary linear algebra appear esoteric :-))
I still don't understand. This seems like a tautology. "Why did I observe state X?" "Because you're in a state of observing state X." "Right, but why didn't I observe the superposition state Y?" "Because you're not in a state of observing state Y." It feels like instead of answering the question, MWI is defining the answer as being the essence of the answer to the question. "What's 2+2=?" "It's the answer to the question, 'what's 2+2=?'"
It feels like I'm left the illusion of an answer to my question, a more complicated framework, and still no answer to any situation other than a 50/50 split, despite this addressing far too few issues with locality and probability distributions. How is MWI not just a complicated tautology?
Because like a lot of other interpretations, it's just a cop-out, and not really based on any physical evidence. It sounds nice, but ultimately ridiculous, and brings with it a whole host of needless complications.
Uh oh, we have a thinker over here. Stop it! Don't point out the obvious flaws in the unscientific bullshit. Gobble it up! Don't you see it's just like in all those cool Marvel comics and movies? The multiverse is totally real, mmmkay?
Exactly, and this is not only a problem for MWI. I think the reason that these explanations seems to resolving the problem is that people are accepting the "definition" that feelings are an emergent behavior of brain electric-chemical activities. Because if everything is simply an object in different positions and velocities, there is no feelings, there's only "state". And what about feelings, they tell you it's an illusion. In my opinion what people do is that, if I just pretend other people don't have consciousness, pretend they can be perfectly and entirely described by brain electro-chemical activites and other materialistic objects, and ignore the existence of my own consciousness, then suddenly I can pretend the issue is resolved, the model is perfect and I can explain why Bob's observation on Alice's observation on electron is always consistent. Then we can keep telling people that "consciousness" or "feelings" are no more an illusion of brain electro-chemical activities. Circular logic, isn't it? And it can be applied to any level of theory, classical physics, "why am I observing this", "because your brain cell are wired in such a state, the electron orbit around nucleus, bioelectricity, etc, that gives you an illusion that you're seeing this"
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Yep, that's ultimately the fatal flaw of all materialism, the hard problem of consciousness, as well as what I've started to dub "the even harder problem of will", another thing most materialist scientists today want to sweep under the rug (as well as people like Yuval Noah Harari talking about how stupid it is to think free will exists, how we are hackable, and how we should submit to the materialist new world order).
I know this is two years later, but I hope this helps:
If you believe the schorindger equation works for macroscopic objects, you are forced to conclude (at least from an outside reference frame) that observers can be described as being entangled with the environment. The moment "you" are the one observing the system, however, we then switch to saying that there is a collapse, which is highly unmotivated and without reasoning. Yes, there is no explanation for why you're in one world and not the other, but at least it doesn't outright reject the schrodinger equation's solvency arbitrarily like the Copenhagen interpretation does. Because remember: you can't say that there's an objective collapse and say that an observer and a particle can be entangled at the same time.
So you can either have an interpretation with a set of axioms that you just have to accept (every consistent and well defined interpretation/theory like MW), or you can have an interpretation that has extremely arbitrary and seemingly contradictory axioms. Why people accept the ill-defined or contradictory one is beyond me. (You could also have a theory that doesn't work for macroscopic observers, but then you're not describing quantum mechanics anymore; you're describing another theory that makes different predictions).
Note that ultimately I think relational quantum mechanics solves a couple of problems that the MWI has (the EPR paradox ends up not being a paradox at all if you give up on the idea of an objective wavefunction, and the idea of a "wavefunction of the universe" is ill-defined because wavefunctions only make sense with respect to a given observer) but MWI is still much better than copenhagen.
Your presentation, articulacy, and intellectual projection of an idea is so nice to hear aloud... better than Netflix! Bravo :)
No, it's deflection. It answers the easy problem of determination in MWI (why we find ourselves isolated to one outcome and not all of them at once) and not the hard problem of determination in MWI (why we observe one specific outcome over another specific outcome, or vice-versa). Obviously if we branch with the multiverse we will observe X or Y and not X and Y. But if we measure X, it does not tell us why we measured X rather than Y. It's supposedly a deterministic theory, yet there is nothing to determine what we actually measure.
I just started my journey in physics after switching from computer science. Its been pretty awesome, thank God, in terms of mathematics but for this physics class I'm taking, which basically gives an overview of modern physics, its been rough as the teacher doesn't have the passion to teach physics and it does bring me down a bit. Did you ever encounter teachers like this? Thanks and the videos are awesome!
r u at UK university? why don't you share ur bad experiences in Social media? for example if the teacher bullies students like u ,or humiliates u in front of class then you can record it live then upload it in social media, then see the magic,
as in India great History. The RAMAYAN say. mean people needs to punished
Thank you so much for continuing with "many worlds" videos. And while still on holiday, no less. You sincerely rock.
Your videos blow my mind. What is this strange place in which we live?!
Love these videos! Thank you for sharing this! ✨
Wonderful video!! I am 1 week away from finishing my quantum physical chemistry class, and it’s been one of my favorite (and toughest!) classes I’ve taken.
Great job explaining everything. I just found your channel!
Good luck! I’ve always wanted to understand physical chemistry
Love your channel and unique insights
Excellent visual demonstration! :) Thank you!! Bless you!!!
"Yes, this is my phone taped to a box, balanced on another box... I'm a professional." :D Thanks for taking the time out of your vacation to make great content!
Would be curious to hear what you think about Travis Norsen's paper "Against 'Realism'" (its on arxiv) and his criticism of MWI therein. Looking forward to any further videos you have for this series. :)
The next time somebody asks me what I'm doing "this weekend," I'm going to say, "Everything."
These videos are so good. It's so nice to see videos on these subjects from someone who doesn't avoid the maths, but also doesn't overcomplicate it.
Would you consider doing a video on how the many worlds interpretation deals with probabilities? In all your examples, you're using a superposition where both states have equal magnitude, so it's always 50/50 chance. The bit that seems most weird to me about many worlds is when this isn't the case, and one possibility is more likely than the other. If we split into two or more copies when measurement happens, why would it be that we're "more likely" to inhabit one copy of the universe than the other? I know there are explanations, but none of them seem intuitive to me, and I'd love a video on it.
Thanks for all the great content.
Great question! That’s one I’m working on a video for now :)
(She never finished the video because MWI is sophistry.)
Great explanations! Here’s something I still don’t get: we can describe how this electron interacting with stuff puts the electron and the stuff in an entangled state, but surely everything is interacting with everything else all the time right? So the universe must be one giant superposition of entangled states in this interpretation, cause nothing ever gets collapsed. In that case, how is it still valid to describe the electron as being in a fairly simple state of up + down at the beginning of the experiment, neglecting all other parts of the universe the electron has touched since the dawn of time? What part of the math allows us to sort of ignore the rest of the system and talk about the electron as if it has its own state?
You are correct - because any charge in the past light cone surface is essentially measuring the electron with a probability of 1/137 … not to mention gravitons if they exist. But theorists like Sean Carroll posit without evidence that you can isolate single particles (single oscillators in the quantum field lattice). It’s fraught with issues. There is really one one wave function of the Universe- yet you get all these stories about two particle “maximally entangled states” - this causes paradoxes like the AMPS paradox for black holes that you can see Leonard Susskind lecture about - the genesis of his and Juan Maldecena’s ER=EPR proposition.
Great question! This is one I’d like to make a video on
Short answer: linearity of the Schroedinger equation.
I think, as far as the maths would go, it has to do with the basis in which you look at it. If you look at it from the basis of the wave function of the whole universe, adding up every interaction since the Big Bang, then it'd look like you say. But if you look at it from the basis of the electron's creation or last interaction, it's in a simple up+down state (or whatever entangled state that event left it in), and every other historical interaction cancels out to zero by decoherence, and even that basis will be short lived and replaced by a new basis as soon as it gets entangled enough.
Have they actually got proof that entanglement works across the galaxy of universe? I don't think so.
All elemental particles are "vibrating" at or near light speed and if propelled will move like a wave.
There is only one particle & one path ... but different positions at any moment in time.
The Multiverse & other worlds are from the mind of an intelligence, and are an UNNATURAL existence.
Heaven & Hell are UNNATURAL existences from the mind of an intelligence.
Only an intelligence ... has free will ... to think, believe, say & do as he/she wants .. and ... make abstract & physical constructs.
Only an intelligence makes Laws ( of nature) & things ( of the Universe) with clear purpose,, form, design & FUNCTION.
Man has always known that the Universe has an UNNATURAL origin by an intelligence ... more powerful than Man.
While I agree with you that the many wolds interpretation of QM is a simplification, and I would say that it's probably also my preferred interpretation, the part I struggle with is the actual assigning of the 'many worlds' to the math. That is to say, what we initially mean by the many worlds interpretation is simply QM without the collapse axiom, and this is perfectly mathematically consistent and makes its predictions. But interpreting these predictions in real experiments to me seems to require more structure than the pure math has. Namely, we have to additionally define what it means to experience something as a detector/experimenter. The definition presented is that it means 'to have evidence for', but this is nevertheless more information on how to construe the results of the math.
I think Sean Carroll says that all the different states already exist ab initio, as part of the block universe. We're just only experiencing one of them at any given time, and our consciousness tracks along with the outcomes that are real for us. There is only one wave equation, and it encompasses everything. All possible futures and possible pasts exist already.
I'm a) not a physicist, and b) drunk at this particular moment, so forgive me if that makes no sense.
I feel like these questions, while valid, aren't specific to this problem. Whether or not many worlds is true, or even if we found ourselves in a universe that wasn't quantum in nature at all, we would have to define experience and evidence. For understanding the nature of evidence I would recommend Bayes Theorem, and for understanding the nature of experience I would recommend this moment.
I don't think MWI requires any definition of "to experience something" or "to have evidence for". The cute drawings with the (sooo long!) tensor products of kets in the video are, in a sense, a discrete approximation of what happens in reality: the transition from the initial state to the final complicatedly entangled one happens with continuity; and also the factorization of the Hilbert space into tensor factors for System, Device, Environment, and what not, is conventional. ----
But you're right that a bare Hilbert space, together with a state vector in it, isn't enough for reconstructing reality from the math. Indeed, a Hilbert space is a very homogeneous entity: the group of unitary transformations acts transitively on the set of unit vectors... Everything looks the same in a Hilbert space! So the "structure" of the world should be reconstructed from some additional piece of data. What this further piece of data is and how it is "selected" by nature, as far as I understand, has something to do with the so-called Preferred Basis Problem. A "world" is in fact just a (normalized) component (just in the sense of linear algebra) of the Universe's state vector; the question is: what component? The answer is: a component with respect to a special eigenbasis of a "macroscopic" observable, which is somehow automatically selected by decoherence and is significant from our human descriptive point of view. This basis has something to do with the position of macroscopic objects, such as pointers in measurement devices (hence the name "pointer basis"). But it is not very clear to me how this works.
If you consider a quantum computer program that is performing some sort of inference task (like estimating how often a qubit prepared in a particular way ends up ON), you can derive that this results in almost all amplitude ending up in states where its estimates follow the Born rule. Basically you can derive that all of the statistical conclusions made by an automated quantum agent will match up with what we experience. The part that's missing is the "something experiences making these statistical conclusions". But it's not a new complaint that reducing people to physics doesn't seem to explain experience. That's the hard problem of consciousness, and it also occurs in classical mechanics.
@@rv706 Isn't the additional data that provides the structure just the Lagrangian, or equivalently the time evolution operator? And the preferred basis comes from the fact that the Lagrangian is a local operator?
That of course poses the question what makes time and space special and why are the laws of nature local, so I don't know if that helps.
Always relaxing to watch your videos. Very nice 👌
So glad you're uploading again. (:
Interesting. From a layman's point of view, it seems super position could prove anything you want it to prove.
Thanks so much for another amazing video, I think you make the most interesting videos on youtube. I love that you try to understand and explain what's happening under the hood, rather than just dismissing those deeper questions (which a lot of physicists seem to do!).
I have a question I'm stumped on - in many worlds, what's actually happening when you see an interference pattern in the double slit experiment? Is this the different "worlds" interfering with each other? What does that even mean?
Thanks again!
Great question! Interference is when two branches of the wavefunction interfere. A world in many worlds is a branch of the wavefunction where this sort of interference is difficult to get (because the experiment might involve too many particles etc). So in the first case I wouldn’t say that those branches are “worlds”.
Really nice video. Glad I found your channel again, after having seen your vids years ago.
One of my issues with Many Worlds is that it relies on these binary analogies to talk about a split. But say you fire a photon through a double slit and it hits a detector. The two slits are binary, but the detector has essentially infinite locations the photon could hit. How many splits happened in this experiment? More universes would see the photon hit the detector in one of the more likely positions; but how many? What is the "resolution" of the willingness of the universe to create a split? If something has a 0.00000000000000000000001% chance of happening, does the universe split into 10000000000000000000000000 universes to accommodate that chance? This would imply that there are essentially infinite splits happening at every instant of time.
Great question! I really disliked this too, but there is actually a nice resolution. I’ll put it on the video list
@@LookingGlassUniverse : I hope you'll also deal with how conservation of mass/energy does or doesn't work in Many Worlds. Does the total mass of the universe(s) double when the measurement of the superposed Up+Down electron splits the universe into an Up universe and a Down universe? Or does the total mass remain the same so that everything in the Up universe has half the mass that it had in the superposition universe? Or some other alternative, such as David Deutsch's variation of Many Worlds (described in one of the chapters of his book "The Beginning of Infinity) which postulates that there was an infinity of universes before the measurement, and half of the infinity of universes are Up, half are Down, the infinite mass remains unchanged and the mass in each universe remains unchanged.
@@brothermine2292 Sean Carroll explained (his view on) this when he was on the Lex Fridman podcast. FWIW Many Worlds makes most sense to me, but I found out recently that Sabine thinks it's nonsense. And when Sabine speaks I think we should listen :-)
@@guest_informant Think for yourself
@@guest_informant I share your respect for Sabine, but I wonder whether you might have misunderstood her. Her feelings about Many Worlds are in this video:
czcams.com/video/kF6USB2I1iU/video.html
Basically her claim is that Many Worlds does not solve the measurement problem, so it is EQUALLY as troubled as the other interpretations.
Sabine also has a video about "the multiverse" in which she says that the idea is not scientific. Could that be what you are referring to? She is not talking about Many Worlds there.
czcams.com/video/-dSua_PUyfM/video.html
Even there, she's not saying the idea is wrong, necessarily.
Here from the kurt interview. :P Very glad to have found you. Insta subbed obviously!
Ok, that´s the second video I've watched from the channel. They are amazing!! I am from Brazil and studied Physics and Mathematics at the University of São Paulo in the late 70"s - by that time some physicists believed that the observer could cause the wave collapse. It was clear to me that it should be something simpler as an interaction. What about the MWI? Where´s the real magics? I don´t really know yet. I'am bewildered by that. In his book THE FABRIC OF REALITY, David Deutsch says that predicting phenomena is much less fundamental then explaining how things happen. I agree totally. I hate that "Shut up and do the calculation" rule. Explaining stuff is fundamental, and these videos aim to this honorable objetive. Just Great! Thank you!!
I can either listen or watch you speak, can't do both at the same time. It's because I find you to be beautiful 😍
Great explanation - as I came to realize at listening it the second time. 😁
wow youre a great teacher ive often wondered about this but failed to understand till now
Thank you for this great explanation. Your videos are always easy to follow! When you were talking about interaction, I was wondering, can neutrinos cause the collapse of the superposition?
Thank you for doing this on your holiday (hope it's relaxing)! I've been highly sceptical about the Many Worlds Interpretation, but you've done the best job so far at making it sound reasonable. However, if we were to ever get a clearer physical understanding of other "weird" quantum phenomena (eg some recent arguments by Charles Sebens claim that spin can be explained by something actually spinning), I wonder whether this could ever lead to a more intuitive idea behind superposition.
(Another thing I've wondered about is how gravity would tie into all of this - would its interaction with particles affect the "branching" into worlds at all?)
There actually is an "objective collapse" theory proposed by Roger Penrose, in which gravity causes wave function cpllapse, essentially adding an explanation to the Copenhagen interpretation. But Idk how gravity would play into Many Worlds, that is an interesting question…
@@vauchomarx6733 Yeah, the Penrose interpretation is actually my favourite. I think his view is that Many Worlds simply can't be explained if you consider gravity
Regarding the interaction of "many worlds" and gravity an interesting clue for how they might work together comes from the Wolfram physics project which is an interesting project extending Turing's work looking into the consequences of Gödel's incompleteness theorems on Turing machines specifically a property generalizing the conditions to ensure logical internal consistency via the logical conclusions needed to avoid the pitfalls of the Halting problem that called computational irreducibility.
Basically it turns out you can show that you can in this model as the size of the Turing machine system becomes large derive an emergent space relative to a rate or flux. In the case of the rate at which changes in the system propagate this can be shown in this limit to converge to the Einstein field equations with causal space as formulated being the type of space known in General Relativity.
Attempting this same emergent spatial property to resolve any and all combinations in which the system can operate in a superposition of states where the rate at which these possible combinations resolve through indistinguishable states recombining interestingly allows you to define an additional, distinct type of spatial dimensions representing the superposition of all these possible branches of the system which Wolfram calls "branchial space" which like the causal space is a rate of interactions between branch states.
This emergent branchial space has been shown to be identical to the Feynman path integral
formulation of Quantum field theory which also follows the Einstein field equations with the analog of distance for quantum states in these dimensions represented by the Hamiltonian of the universal wave function that is to say the units of distance are energy. What matters here is it appears that mathematically the branchial components of curvature within this energy space of quantum states corresponds to the probability of measuring a given state for any branchial frame of reference within the cone of entanglement.(basically constructive interference means more paths within a given cone of entanglement, the light cone analog of branchial space, curve in toward that state in branchial space-time with the collision in branchial space of two states representing the reconvergence of those two states into a superposition. In principal it may be that any act of measurement to distinguish between the two states by observers would then amount to costing the appropriate amount of energy to try and separate(distinguish) the two or more effectively indistinguishable quantum states which is a very different way to think about this.
While it may be premature in principal one of the most natural ways you can attempt to combine these two results borrowing from both objective collapse and many worlds would be to extend the dimensions of the Einstein field equations to now incorporate causal space, branchial space and time as different types of space (noting that like the speed of light represents the geometric parameter converting between causal space and time there will be an equivalent geometric conversion constant between branchial space and time, a speed of entanglement if you will) into a single higher dimensional Einstein field equation with us as observers being constrained to the 3 dimensions of causal space and 1 dimension of time. Quantum weirdness in this limit is a limitation that we can only observe a causal projection of the universe and the states associated with "many worlds can then be thought of as places which we can only observe through indirect interactions projecting into our reality or rather our frame of reference with anything outside our cone of entanglement being unreachable via any branchial acceleration or measurement.
If this interpretation is valid then gravity may in essence as some have theorized leak out and effect the other branches of the wavefunction and thus could be expected to leak into our branch of the wave function as a superposition of all projections of those disentangled states. As you wouldn't be able to observe the individual states you would see a cloud of invisible and otherwise undetectable apparent gravitational mass which would resemble a quantum superposition largely devoid of any apparent internal structure. (In effect perhaps able to be thought of as the equivalent of gravitons leaking information to pull the branches of the wave function back together i.e. causing them to evolve towards a indistinguishable higher entropy state)
This might even suggest that gravity, quantum probability and entropy might be aspects of a single underlying entanglement field within some more generalized counterpart to Anti-De Sitter Conformal Field Theory correspondence. (I'm actually wondering if the extra dimensions of string theory or similar attempts to extend the standard model into a "theory of everything" might be dimensions in branchial space rather than causal space that in effect have been staring us in the face all the time.
@@joelbeckles3490 I don't think we can really know until we understand more about gravity. If gravity is created by real physical spacetime curvature, then I don't think MW could be true. If gravity is created by graviton particles whose effects can be *modeled* as spacetime curvature, but nothing is actually curving, then that probably wouldn't rule out MWI, the graviton particles would just exist in superpositions like everything else.
I'd like to add, that even if you were able to get all the particles including the experimenter together and tried to get interference between the "worlds", a necessary condition for that to happen is that the experimenter forgets what she has seen. This is because the states of the brain remembering different things are certainly orthogonal. The same is true for any other system storing information.
As a Black and White photographer and darkroom printer. I love your photos on the Wall. I have seen the originals in the Weston gallery in Carmel California and just beautiful.
someone should tell the electron to stop being so negative.
😂
Makes you appreciate how difficult it is to build a Quantum Computer, when any particle can just walk in and make a measurement you didn't want.
I can only figure why the electrons are sad when you answer if the positrons are happy
If your electron hooks up with a positive ion does it become happy?
You're on a roll! More-yes please!
Why can I use thumbs up only once?? Again, such a great explanation!
It sparked a thought: I think you can determine big objects being in a super position more easily like this:
Entangle 2 electrons. Measure one's left-rightness, so you know the other one's up-downness is definitely in superposition. Setup a detector so that it will measure the other particle in a minute from now.
This way, you know that the future detector state is in superposition.
It's like, disconnecting a big object from information leaking out, by hiding it in the future.
And also I think, this is the way the future evolves. Over time we know more and more of it until the superposition seamingly disappears because we completely entangle with it. That is when it is 'happening'.
Very interesting! You may wish to check out Lee Smolin lectures on the Perimeter Institute channel - he’s the only mainstream theorist I know that has equations on how he believes the future becomes the present … how energy/momentum is transferred.
Superbly explanined. I find the many-worlds-interpretation the pure "HORROR", but my friends don't understand why I believe in this interpretation if I don't like it. It is not a matter of like or don't like it. Maybe if they could see your explanation they would understand it.
Thanks for another interesting video!! I was wondering if you started with a horizontal gerlach machine, then attached a vertical gerlach to the left output, and a vertical gerlach machine to the right (x2 vertical gerlach machines in parallel) would the 2 vertical machines produce the same result?
Great question! Yes, they would, because the first machine is basically a measurement of left right. A left or right electron will go up or down with 50/50 probability
Thanks for this explanation. I had assumed something different in my understanding of many worlds. At the point when we are looking at the results of a double slit experiment, I thought that meant that we were seeing a superposition of time-lines in the multiverse. At that point we, as quantum beings in the quantum multiverse, are observing multiple timelines where or particle goes through both slits. When we measure, we are, in effect, selecting the timeline we are on, so no longer see the results of observing this superposition. I assume from your description that I am wrong, but can you explain how we see the results of the double slit, or similar, if we aren’t observing multiple timelines please?
Question: How is something placed into superposition?
I really really loved the explanation and your method of explaining. Please take some time to write a book for lay quantum physicist.
Love this. Do you think that measurements impacting a particle's state is evidence of some form of consciousness on the part of particles?
I understand that the "-ket" notation denotes a column vector. So what does it mean when you juxtapose tokens of that notation horizontally? Usually juxtaposed mathematical symbols denote multiplication, but we usually don't multiply column by column. We multiply row by column. So, what do you intend by the juxtaposition?
Mithuna, I really liked your video on many worlds. Many people are spewing this crap out there making themselves to be great physics gurus but few have done this with the quality that you have.
While not perfect I think your explanation is the best ive seen on this on youtube. The other being a colloquium by Zurek. By the way
This was really interesting, thanks! A question I have is: the experiments showed that given a certain initial conditions you get particular end states and those end states were always consistent with the electron being up or down, so (ignoring the initial state) what would an end state look like if it were possible to see if you were in a superposition? Apologies if this sounds like nonsense, I'm clearly not a physicist.
To understand from the measurement what state the electron was in, it is necessary to carry out many measurements of electrons prepared in the same state.
If from the measurements you always get up, then it was up.
If he always gets down then he was down.
If you get about 50% of the time up and 50% down then the electron was in a quantum superposition state.
at 14:23, are you saying that a particle in the up-down superposition along the vertical axis will always give the same value when measured along the horizontal axis?
What is your opinion of what you could broadly call the UFO phenomenon?
Thanks!
Jim
Chattanooga, Tennessee
Frowny particle knows it’s about to be experimented on
One serious question from the philosophy of science point of view: if there is (probably) no hope of ever detecting evindence for this interpretation, where does this stand in the demarcation problem(i.e. is it still science?)
This reminds me a lot of one of my favorite physics theorems, the "Ewald-Oseen extinction theorem". Usually when we speak of light traveling in a medium we say "it slows down", giving us the definition of n, index of refraction. However, from a microscopic perspective that doesn't make sense! We only had photons/EM waves traveling through vacuum, other EM fields and sometimes scattering with other fermions. These photons should always move at "c" speed and never slower. So what happened?
The theorem states that what we observe actually is the superposition of many, many scattered photons/EM waves, all traveling at "c", and if you add then all those wavelets together with their amplitude and phases, you get a wave that, mathematically, propagates at a slower speed (agreeing with n), but that wave is only a mathematical construct, a device to help our intuition. It on looks *as if* light slowed down. All the "real" wavelets never slowed down (as they shouldn't).
Couldn't many worlds be like this? It is a story we can tell, and the math adds up, but it still cannot be assigned or identify to carry "an element of reality".
Im not sure, it might be like that! On the other hand, it is in principle testable. You’d just need extremely fine control of quantum objects to test it (eg, doing the test I mentioned at the end)
Electrons are sad because positrons are happy!
we are able to "experience" all outcomes in our heads, in imagination, the field of all possibilities and then we make a choise and only one outcome is manifested into our reality. That's how we are living.
Thanx.
After watching your vid, i feel like more as a electron in Superposition *smile.
Have a nice time.
After your great explanation, just to proof that as a probabilistic tautology, the craziest thing is the posibility of someone else replicating the experiment to find the person checked in the down world. The theory of linving in superposition is near enough to realize we are the superposition, entanglement and supersymmenty at once.
I really appreciate you explaining this, I'm trying to wrap my head around it. So let me ask a question by proposing a counter idea and see if that spurs a conversation: I'm sure the superstate concept is understood... mathematically, but does it translate to reality? What if the superstate is like a bag of colored marbles and you're only allowed to remove one marble... so when you make a measurement you remove the one marble and that is the answer to the question: up or down... so now that's the one marble that is sitting on the outside of the bag and you can't can't pull out any other marble(s) after that one is removed. This pushes whole the notion of the superposition state purely into the "bag", and thus it cannot extend past the bag into other worlds/realities... As you described the observer that observes the observer ad infinitum, it is merely a downstream effect from a cause of making that measurement... i.e. a one-way chain, downstream of cause-and-effect... there is no spoon... I mean... no other worlds created of the opposite measurement, etc., etc., etc.
I'm sure there's a hole big enough to drive a semitruck through, but maybe my ignorance of the subject matter can serve as a foil and it gives you an opportunity to help us "mere mortals" (LOL) understand Quantum Mechanics better... I'd be interested in hearing your response; This stuff is so fascinating!
It's best to think of "measurement" as a state change of the system. For instance, if Schrödinger put a cat in a box, then the cat also changed Schrödinger during this process, as Schrödinger had to physically put the cat in the box. Schrödinger, the cat, the box, the room, the building, the planet, the solar system, and the galaxy are all part of the same closed system. Schrödinger's hypothetical air-gapped box barrier is entirely arbitrary and artifical. If you think of yourself as the cat in the box... czcams.com/video/5P38r-J3Ay8/video.html
Hi Mithuna! I'm just seeing this now about 1 year later😂 but just checking: at 11:48 there was a tiny error in the girl's state in the 2nd half of your bottom equation, correct? It shows "up" arrow but it should be "down".... Am I correct or crazy? (Either is ok because there is evidence of both correct & crazy in my case 😂)
These videos are great!
What happens if you have contradictory information? For example, detector says up, the observer sees up but writes down. Other people reading the notes would then believe it to be down and if the detector didn't keep records and the initial observer didn't remember other than the note, would state of the particle be down? Would it return to superposition?
Can't get enough of these many worlds videos. I have a dumb question though, do entangled particles act this way for the same reason superposition works? I mean we assume a single particle is almost anywhere until it's measured. If so, then wouldn't the idea of "faster than light communication" still be a factor vs the many worlds construct?
Evidence would mean that you can interact with it in some way, or see that matter in your world line is influenced by matter in another world line.
If we hypothesized that there is some kind of evidence to the existence of many worlds, what kind of interactions would we look for, and what types of bosons should we consider looking at? Like, could darkmatter result from four dimensional gravity in a many worlds universe?
A question from a very non-physicist. If you had enough computing power, could you simulate the experimenters and all their various entanglements? Like a digital proxy of the “up world” that could let us glimpse both states at once? Thank you for your videos! Just found you today, and your explanations are totally mind blowing!
Yes.
Maxwell’s demon…
Are you working with Quantum Gravity Research on the QSN/E8 Code Theoretic??? If not, I think you should consider...
As you point out at the end of the video, seeing evidence for both worlds when the components are a person, detector, electron, the surrounding environment, etc. is impractical.
Is it more practical in principle (though still a very challenging engineering problem) to see evidence for both worlds if a quantum computer with enough qubits was designed to have sub-components interact with each other in ways analogous to how the person, detector, etc. do? If so, and such evidence was found, would that be incompatible with the Copenhagen interpretation?
Brings a whole new meaning to "seeing is believing."
Is the direction the electron takes in the Stern-Gerlach itself a "measurement"? So, when the electron leaves the S/G, but before it gets to the monitor, the world has already decohered?
Really interesting as always, though Sabine Hossenfelder refuted this in her video. Did you have a reaction to her video? Thank you
Great video, have you met David Deutsche? It would be so cool to chat with him about this stuff and on his work with quantum computers
What happens if you use a device that reads the measurement and flip it like if its down it becomes up and get someone (who don't know that this device flip the result) and she write it on paper up then we use the original read to another one who says it's down and write it as down. And they interacted without letting the creator of this trick knows about results and use a fourth person to ask those 2 about their opposite evidences and destroy the machines and the evidences and then let those two interact would they be in different dimensions? I know we can use devices instead of human beings but I wonder can we trick the quantum?
The more I learn about this the more I become really convinced that information must be at the heart of the whole mystery. Someone gains information from an experiment and now exists in the world where they must be consistent with that information, cascading out as the informations conveyed to the world. it's almost like we exist on branches in a sort of complex, infinite dimensional, information-vector space, constantly splitting off diverging branches when values in one direction are forced into certain states.
Ultimately the problem I have with the MWI is the "individual experience" of a particular branch. At this level you have invoked something special. Does a rock "experience" only a single world? How about an amoeba? What about kittens? Such questions were asked about the experiment of Frauchiger and Renner who considered measurement from a photon's perspective.
My preference is for theory-independent no-go theorems such as Bell's theorem. All interpretations must be consistent with such theorems, and then you have some understanding of the properties of "reality". Such a no-go theorem has been developed from the extended Wigner's friend paradox. There, three properties of reality are considered: locality, determinism, and observer-independent facts. No interpretation of quantum theory can satisfy all three properties. This means that for each interpretation you are making a choice to reject a particular property. Thus, if all the above properties are reasonable, then some element of strangeness must arise in all interpretations. By far most physicists that I know remain agnostic about interpretations.
I’m curious what you think of Sabine Hossenfelder’s videos on quantum physics. Do they seem accurate in your inexperience?
The electron is sad because… it is negative 🙁
You can be negative and unsad.
@@skebess You can be positively contrary.
@@MNbenMN You can be pessimistically optimist.
I want to ask a dumb question here . So should we say something like in "this" universe , for an electron , the spin will be 0 or 1 ?
Thanks for introducing this interesting topic! But I don't think it resolves the question, it's difficult to explain but please see if my explanation also make sense for you. I also thought about this entanglement formulation for a long time, and I'm pretty sure that these math consistency that you showed really only explained this: for Bob who is observing Alice observing an electron spin, it only explained why Alice always reports the electron is spin up when electron is spin up, and Alice reports spin down when electron is spin down, but it really don't explain why Bob consciousness only "feels" one out of the two possible realities. Let me explain what I meant: When I say Bob observing Alice observing an electron spin, it is *by definition* that we treat Alice as an object and "she" is not different than an electron, then of course for Bob, the system may either collapse into Alice reporting up with electron being up, or Alice reporting down with electron being down, it's consistent, because why not. But this is like getting around the problem by not answering it, because the whole problem is, we wouldn't have a problem understanding the measurement device entangled with the electron spin, at least we don't imagine the machine will "feel" the collapse of the electron, it's simply an object, it doesn't feel. (To attempt to put it precisely, the quantum model we are presenting here doesn't contain any fundamental components that give rise to feelings. The materialistic model only contain fundamental components that give rise to the phenomenon such that if someone sees some object exhibiting some phenomenon, it appears as if that object has feelings, but that's only *phenomenon* which is completely encompassed by "expressions", "screaming", for example, which basically decomposes into coordinates and momentum of objects if I'm talking about classical physics, but same idea for quantum. This is entirely a fact that a model is restricted by it's fundamental components and it cannot give rise to something that the model does not have.) The problem is that, for Bob, he can't understand why he only experiences only one of the two possibilities, but I can claim to solving the problem by defining Bob as an object in the system I'm observing, in my model I claim Bob is an object, so I will always either see Bob sees Alice reporting up with electron up, or I Bob sees Alice reporting down with electron down, and within my model I can see they are consistent. But my claim of solving the problem is false, because I cannot explain why I only sees one of the two possibilities. But this is not a problem for you because you are observing me as if I am a object, so it's nothing but consistency in the two possibilities that you could see, and it goes on. The biggest reason that these explanations seems to resolving the problem is that people are accepting the "definition" that feelings are an emergent behavior of brain electric-chemical activities. I really want to say that this definition of feelings are really problematic, it's not even an "hypothesis" in my opinion, it's simply wrong, by definition of models, if you think about it. Here's two statements that I take as facts. Statement 1: I know I have feelings, but I can only see your materialistic representations, velocities, positions of your particles, so I have no evidence that you have feelings. You could have, or not have feelings, from my perspective. You can think about it, is it true for you too. [end of statement 1] Statement 2: our models don't contain feelings. [End of statement 2] So for me, I think it's clear that the model isn't entirely compatible with the reality, because it does not have any component that contains feelings and I do have feelings. But the model could *possibly* describe everything I see from you, because everything I see from you is materialistic and the model contains everything needed to describe that, but it could also *possibly* not be able to describe everything about you because I don't know if you have some element that cannot be described by the model, for example feelings. In my opinion what people do is that, I just pretend I know that other people don't have real consciousness, pretend I know they can be perfectly and entirely described by brain electro-chemical activites and other materialistic objects, and ignore the existence of the consciousness of myself, then suddenly I can pretend the issue is resolved, the model is perfect and I can explain why Bob's observation on Alice's observation on electron is always consistent. Then we can keep telling people that "consciousness" or "feelings" are no more an illusion of brain electro-chemical activities. Do you see the circular logic here?
As I model reality, we regularly experience many of the different paths/timelines simultaneously, as patterns branch and merge and branch and merge. When we stop remembering specifics, that might be because we have merged past timelines. This is similar to when two separate biological species split and then mate again, producing a new merged species, similar, but different, from the original species that existed before the two species split.
Would there ever be a practical application for this equation or is it only an experiment to prove entanglement
How does down quark convert into up quark in beta minus decay? In wiki it says that down quark enters into superposition of up quarks while converting into up quark what causes this superposition?
I always wondered: What if you check for the input twice?
It always seemed to me that the act of checking. The moment of measuring created what we erceive as the parallel universe.
Did you do the theory of entanglement somewhere already? (I am a new subscriber). Really curious about your clear-cut explanation.
Everett's MW Interpretation inspired the first film I made. Where the universes collide at one point and reset into an ambiguious ending. Making the audience one in the up state the other in the down state ;) QM is just way too interesting even for someone who never studied the field.
I suppose you did answer it at the end a little btw. once checked, you are in that universe forever right?
It's just so mysterious to me why that is, and how it can't be undone.
How do you interpret the probabilities of measurements that weren’t made? For instance the double slit, where you didn’t measure which slit the particle went through, but the interference pattern tells you that the particle was 50% slit A and 50% slit B?
The interpretation that I‘m considering at the moment is that the question „which slit did the particle go through“ actually reduces to „at which slit did the particle not interact with anything so it could reach the screen on the other side?“ to which the answer is: both!
Neither the particle nor the rest of the world have the necessary information to decide which slit the particle went through. Thus, it didn’t. There is no universal coordinate system where particles would have a clear position and momentum. Instead, the particles have to carry all information themselves. Which is too much of a burden for individual particles without inner structure: when they were hit, they immediately forget about it and about the direction of the blow; ensembles of particles on the other hand do exhibit memory, as a ball of play dough clearly indicates that it was punched and from which angle once I did so.
I feel that this perspective of mine - inspired by Boltzmann‘s explanation of the time arrow and Einstein’s approach of removing observers that appear to live outside the model - should be intimately related to the model you describe as „many worlds“, possibly getting rid of a few last philosophical problems. I just can’t quite grasp how to bridge the gap here. And oh, I‘m a mathematician, not a physicist, and I left academia for a job where I get paid, so I didn’t write a paper that could be peer reviewed.
I was just curious about something called parallel worlds shown in the super hero webseries or movies. So I just Saw this title many words. But after watching this video it seems possible that their is a parallel word in the universe that we do not know about and we don't have proof about it because the reason stated in this video. Can we make something from quantum computers to get proof about parallel world's?
I’d like your opinion on superdeterminism, it would seem to explain a lot of physics is trying to still explain.
I've always considered the 4th dimension to just be a field of infinite possibilities within a set of limited parameters, and our experience of time is just a result of how we navigate through these possibilities with our choices. It seems to me that physicists are simply observing the phenomena of movement through this 4th dimension as it pertains to the simple observation of quantum occurrences where the results are binary. I'm interested in your thoughts on this perspective.
It would be really interesting to actually see this experiment in real time with a S G device. Thanks for your videos.
Hypothesis: Penrose is right about consciousness being mediated by quantum effects in cytoplasmic microtubules, being drunk interferes with tubule structure, so seeing double when you're tanked to the gills is being able to collapse superpositions from nearby parallel worlds.
Lol... but what is, when your world is only rotating in front of your eyes (and inside your stomach)?
@@MsSonali1980 That's what they call spin
I've often heard people postulate that there is still randomness in many worlds because our consciousness seems to get pulled at random into one of these many parallel worlds instead of experiencing all of them. I wonder however if our experience of reality does actually consist of perceiving all of the many worlds at once, it's just that we experience them to varying degrees based on how "probable" that world is. In the same way that two quantum states don't need to be equally likely, two worlds don't need to be either.
Maybe in this experiment you showed here, multiple interactions in the down world come together to just make the down world less probable than the up world, and the probability has some kind of feedback loop that makes it trend towards being less and less the world that exists. The whole down world does exist in the wave equation, just at a way lower amplitude than the up world. It's the same as how an electron exists spread out over the whole universe, but the maths of the universe say that it's 99.999% right here. In the same way, we would just be 99.999% in the up world.
I guess that's more going into objective collapse theory, except that I'm specifically saying collapse never happens. In that context probability shouldn't be called probability and should just be called amplitude or something.
I'm putting here my much more simple minded question: how can you explain us probability on this model?
As usual, I still have trouble groking the MWI. The questions I would raise would be the following:
1. What happens if the person is perverse, decides to record the opposite in pen and paper of what was observed in the experiment? (Or toss a coin, put down something random?). Does this really affect the results of the experiment (the physicality of the experimental setup)? Or there are two different books for the experiment? One good. The other bad.
2. How is the interpretation a "science", when there is no way to tell whether the theory is true or not? (Maybe this is why it's called an "interpretation", and not a "theory"?). Something regarding the "falsifiability" principle in science (?). Also, assuming MWI, you still wind up with the same problem. Calculating the probability one winds up in one world vs. another.
3. This seems to want to satisfy some assumption (aesthetic?) that the math is primary, and the empiricism is secondary. Is it possible it's the other way around? That math is a modeling tool, probably imperfect in some ways, and the physical reality should be regarded as primary. What if we question linearity assumption? (This question was raised by Sabine Hossenfelder raised, in some of her videos.)
As oppose to the double slit experiment, the spin example, presents an interesting image. It's like a bar magnet. Somehow, with the measuring device (up or down), the bar magnet is "coerced" into one direction. (I haven't figured out the left right case. And this could be a reflection of my own misunderstandings.). The universe, as we already know it (since the big bang), is the way it is. Stuff is coerced (entangled) into it, when "measured" (though we don't understand all the details).
4. Can you say more about de-coherence theory? Does it require the MWI, or can it fit into a theory such as one suggested by Lee Smolin?
1. Quantum Mechanics nor Quantum Field theory predict anything about consciousness - most theorists appear to not believe in ‘decisions’ - so they certainly can’t say anything about it.
2. It’s a theory from which you could create models to predict things - but right now MWI isn’t leading to any actual models - I haven’t seen any equations for predicting how many worlds are created based on the amplitudes of a continuous variable like a position or momentum measurement. Sean Carroll and others studying it actively are undecided on many questions. I don’t know of an actual model yet.
3. I agree with that - there should only be one wave function- that of the universe- anything else is an ‘effective’ theory. Bohr and others wanted to treat everything that performs the “C” operation as classical and not quantum. Since 1970, they prefer handy-wavy decoherence… never explaining when the “split”/“collapse” occurs. Roger Penrose has an actual equation for objective collapse, but no ontological mechanism of how it happens.
4. To definitively understand decoherence math, you will probably need to understand Density Matrices … one easy approach to get there is the Leonard Susskind book “Quantum Mechanics - The Theoretical Minimum” … Stanford University has the corresponding lectures on CZcams.
1. Look, there are worlds in which every law of statistics is falsified. But they carry a _very_ small measure. I haven't thought about what happens in your scenario, but whatever happens it certainly won't be a logical problem because whatever happens is just Schroedinger unitary evolution.
2. exactly: the goal of interpretations of QM is to solve the Measurement Problem, _not_ to make new empirical predictions. Their empirical predictions are the same as traditional QM up to our current precision range. There _are_ some interpretations of QM that happen to also make new predictions: e.g. some objective collapse theories disagree with the Schroedinger equation (obviously only for tiny variations that go beyond previous experiments that of course confirmed traditional QM).
3. as I explained in point 2, the MWI doesn't sacrifice empirical predictions: it makes _at least_ the _same_ empirical predictions as traditional QM. I say "at least" because I don't know whether to count the description of what happens during measurements as new predictions or not. And, by the way, the "other worlds" shouldn't count as empirical predictions at all: think of them as useful mathematical fictions, in the same way as you think as virtual particles inside Feynman diagrams.
4. decoherence theory is a set of models that describe what happens when a quantum system interacts with certain types of environment whose information is not accessible ("the system leaks information into the environment"). The word also denotes the physical process itself. A consequence of decoherence is that interaction with the environment heavily dampens down interference effects. It does not require the many worlds interpretation (but fits nicely within it). Decoherence theory is a concrete physical theory in the usual sense of the term, like that of phase transitions or scattering or whatever. It is not an interpretation of QM (see point 2). But, from the philosophical point of view, it explains an aspect of the "quantum-to-classical transition".
To answer 2, the answer is: it's not scientific at all, and this bullshit artist, like Everett, is peddling pure hogwash with zero basis in reality, and she probably knows it too.
Alphabet, you say there are three replies! Why don't you show them?
12:13, small typo - in the last term one arrow is wrong.
Amazing video, by the way.... :-)
It's fixed at 13:49.
Why is it always Up or Down? Is there no neutral state? Or is it like a two pole magnet? What do you even call the part of a magnet that is the center of the poles?
How would you draw an electron of anti-matter?
Another impossibility in physics is traveling back in time. It leads to paradoxes such as the Grandfather paradox. Are there similar paradoxes if we try and communicate with the other world? Wonderful explanation, thank you.
Actually I'd say that many worlds is a solution to the grandfather paradox. When you'd be able to travel back in time and kill your grandpa, you'd live on in a different timeline where different 'splits' have happened. Since all other possible timelines are also still there, you'd just keep on living and not disappear like in Back to the Future :)
@@Jopie65 : Is there a reason to treat the quantum Many Worlds Interpretation as if it's the same theory as the Many Timelines Interpretation?
General relativity allows Closed Timelike Loops … and there are physically realizable situations - e.g. Tipler Cylinder - in which it’s predicted. Quantum Mechanics ALSO has paradoxes - e.g. Hawking Radiation be maximally entangled BOTH with things inside and outside of a black hole horizon.
@@brothermine2292 They both involve causative entities?
Are we not seeing stars as they were many years ago?
Entanglement certainly seems a better candidate for explaining an arrow of time. Is there a speed of entanglement? Does the speed of entanglement correspond to the speed of causality? Is entanglement what drives causality?
Thank you for an interesting video. Maybe I am missing the point, but isn't this many worlds interpretation one of many models (maybe an infinite class of models) that could be constructed to explain the quantum measurement problem? The many worlds model is maybe be nice and elegant but does that necessarily mean it is the model that is correct? Aren't we back to the argument that "naturalness" in the maths is used as evidence in the absence of experimental evidence?
It's true, there is no direct physical evidence for Many Worlds, nor for any other Interpretation of Quantum Mechanics really (including Copenhagen/Orthodox Quantum Mechanics). But there _is_ this principle called "Occam's Razor", which you may have heard of, and Many Worlds does in fact abide by Occam's Razor the best out of all Interpretations of Quantum Mechanics.
Regarding the testing proposal of MWI at the end...
Assuming the external verifier manages to isolate the entire quantum system of the experiment, wouldn't the measurement performed by the verifier necessarily entangle him and the whole external experiment setting with the quantum system of the internal experiment?
The way I see it, according to MWI, the only way to perform an observation is by being inside a superposition of all the involved parts in the first place (one of the many worlds).
Now, this is some complicated stuff, maybe I missed the point altogether, but I was reading that even MWI proponents agree that (as with all theories) many of the implications of MWI, specifically the many worlds part, are not testable. This doesn't mean that the postulates of the theory are not testable. The postulates of MWI seem to be the same as those of many other interpretations, so it should be equivalent in this regard.
Beautiful, smart, and with a great personality. Thanks for the content ❤️
OK. Very little background here. What does measuring and getting "superposition" as a result even mean? Isn't that *in principle) not available as an outcome?
What are the odds that we are “trapped” in the world with a normal distribution for random events? (Some worlds have extreme statistical deviations, eg whenever they roll a die, they always roll a die; whenever they flip a coin they always get a head, etc.
However, somehow we were lucky/unlucky enough to end up in the world where every single random event has an equal probability!
Amazing.
Is the electron sad because no two can exist in the same state; forever alone?
So if I understand correctly, you can see that a system is in a superposition as long as you are not part of the system itself. The interference experiment only works for people outside the system. Is that correct?
Then the universe could be in a superposition of two (or more) states but we cannot know unless we were somehow outside the universe, and we can't communicate that to someone inside the universe. God could see the many worlds unfolding but they can't tell us. Right?
With careful consideration of sync-duration coherence-cohesion phase-locked states, it's possible to imagine, using the unit circle representation of inside-outside relative-timing turned insideout and forming fields of bubble-mode coordination that is "in the now" but not 0-1-2-3-4-etc connection. We can think about it, but technically, it is something that is just an idea we're floating.., and it is as a consequence of time-timing projection that a boat floats, planets orbit and chemicals are bonded. Because every point of existence floats around every other point, it's the same point displaced in relative-timing.
Still reckon we can build Quantum Computers?
lovely!
You had my upvote at "I am a professional".