If there are “Many Worlds" why don’t you experience it?

[@32rq]

Thank you for talking about QM without calling it confusing, or unintuitive. And for taking many worlds seriously.

[@SimonBrisbane]

Many worlds is pseudo-science. For reference, see Sabine Hossenfelder on the multiverse. Many would say it’s religion dressed up as science.

[@QuantumPolyhedron]

Reminds me of Christians thanking the video creator for taking Jesus seriously.

[@thomashall8701]

​@@QuantumPolyhedronNo one should take Jesus, pilot wave or the cope interpretation seriously

[@Alejandro388]

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!

[@michaelsommers2356]

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

[@rv706]

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 :-))

[@markwebb7179]

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?

[@Lolwutdesu9000]

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.

[@outisnemo8443]

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?

[@xuanyuzhu6779]

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"

[@outisnemo8443]

@@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).

[@ret2pop]

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.

[@nathankopp9363]

Your presentation, articulacy, and intellectual projection of an idea is so nice to hear aloud... better than Netflix! Bravo :)

[@QuantumPolyhedron]

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.

[@nathanielsaxe3049]

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?

[@enterprisesoftwarearchitect]

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.

[@LookingGlassUniverse]

Great question! This is one I’d like to make a video on

[@rv706]

Short answer: linearity of the Schroedinger equation.

[@cademosley4886]

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.

[@abelincoln8885]

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.

[@philochristos]

The next time somebody asks me what I'm doing "this weekend," I'm going to say, "Everything."

[@ace9924]

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!

[@UPAKHOSALA]

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

[@aleksandarivanov8737]

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.

[@grayaj23]

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.

[@paulfoss5385]

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.

[@rv706]

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.

[@CraigGidney]

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.

[@Kaepsele337]

@@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.

[@mikerogu5089]

She's as intelligent as she is beautiful, wow

[@joemoya9743]

Interesting. From a layman's point of view, it seems super position could prove anything you want it to prove.

[@diseris23]

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.

[@lukasm5254]

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.

[@Kaepsele337]

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.

[@thecenter26]

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.

[@nullifier_]

I can only figure why the electrons are sad when you answer if the positrons are happy

[@bioartmivideocorporativo1008]

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.

[@stevenjones8575]

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]

Great question! I really disliked this too, but there is actually a nice resolution. I’ll put it on the video list

[@brothermine2292]

@@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.

[@guest_informant]

@@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 :-)

[@The_Canonical_Ensemble]

@@guest_informant Think for yourself

[@ClearerThanMud]

@@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: kzbin.info/www/bejne/oXeZhoZ4Z65kn7c 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. kzbin.info/www/bejne/Y5W2ppSVhbqsnK8 Even there, she's not saying the idea is wrong, necessarily.

[@williamchamberlain2263]

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.

[@MsSonali1980]

Lol... but what is, when your world is only rotating in front of your eyes (and inside your stomach)?

[@Tom_Quixote]

@@MsSonali1980 That's what they call spin

[@Self-Duality]

Excellent visual demonstration! :) Thank you!! Bless you!!!

[@terrywbreedlove]

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.

[@sethhhhhhhhhhhhhhh]

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!

[@LookingGlassUniverse]

Good luck! I’ve always wanted to understand physical chemistry

[@christopherleubner6633]

The electron is sad because it gets too much resistance, which limits it's potential, and is in a state of confusion until it's mind is made up for it by someone.

[@adomasgaudiesius]

damn

[@markfernee3842]

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.

[@Danyel615]

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".

[@LookingGlassUniverse]

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)

[@PixelPi]

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... kzbin.info/www/bejne/a4GWaaVjf5h0r5o

[@jeffbguarino]

You need a sealed box that can't communicate the state of what is going on inside. This is the hard part and that is why you probably can't do the cat experiment. If the cat dies, then this information leaks out and reaches you and you are entangled with it. So the super position is destroyed very easily. If is easier if you stick to a smaller system like a bunch of atoms that you can get into a superposition. The principle is the same but from a practical point you can't do the cat experiment. Some radiation, will pass though a box, neutrinos pass through and hit the cat. The cat radiates and the box could vibrate. You need to isolate what is going on in the box completely. I imagine you could do this by putting the box in another galaxy or light years away from you ? I don't know how that would work ? You can still have entangled particles even lights years apart.

[@ricardoabh3242]

Electrons are sad because positrons are happy!

[@mintakan003]

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?

[@enterprisesoftwarearchitect]

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 KZbin.

[@rv706]

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".

[@outisnemo8443]

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.

[@b43xoit]

Alphabet, you say there are three replies! Why don't you show them?

[@blblblblblbl7505]

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.

[@LookingGlassUniverse]

Great question! That’s one I’m working on a video for now :)

[@QuantumPolyhedron]

(She never finished the video because MWI is sophistry.)

[@MatthewDickau]

"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. :)

[@Ggdivhjkjl]

@4:35 Why am I wearing a bow?

[@ImranSahir1]

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. 😁

[@pbp6741]

If your electron hooks up with a positive ion does it become happy?

[@majfauxpas]

Frowny particle knows it’s about to be experimented on

[@davidrandell2224]

QM classicalized in 2010:Juliana Mortenson website Forgotten Physics. “Hidden variables “ no longer hidden. “The Final Theory: Rethinking Our Scientific Legacy “, Mark McCutcheon for proper physics.No energy, charge, photons, waves, spin, fields, potential,information,etc.

[@ChitChat]

Brings a whole new meaning to "seeing is believing."

[@chongxina8288]

Here from the kurt interview. :P Very glad to have found you. Insta subbed obviously!

[@Sluppie]

someone should tell the electron to stop being so negative.

[@anbublackops3394]

😂

[@GLBXA]

If the whole universe is a wave function and everything is entangled with everything, then I might guess that every possible outcome exists, and is perception / consciousness that navigates through outcomes, and the wave function never collapses at all. It’s our perception jumping through outcomes that looks like a wave collapsing.

[@buktoptravel9314]

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?

[@cademosley4886]

1. If you had your third party (Mithuna's friend? a la Wigner's friend) do the experiment with the whole complex superposition in a box and measure the contents to get a result consistent with demonstrating a superposition (by an interference type of experiment that doesn't disturb the state), and she writes on her own piece of paper "result supports superposition", could the friend then open the box (which I think would then entangle its contents with the friend's environment, so she then finds just one person in the box who definitely saw only the up or down state, and the friend is now entangled with that state too, so the friend definitely sees only an up or down written on the paper in the box) ... BUT then the friend tells the person she finds inside the box her finding (actually I made a measurement demonstrating the superposition before I opened the box, here I wrote it on this piece of paper)? Would that count as evidence one was in a superposition? Does or can (in principle) the person in the box see the friend's piece of paper that says "result supports superposition" AND her own "definitely up" piece of paper still in her hand at the same time? And if not, what happened when and where that made that not possible? 2. I've been reading this stuff and at one point it started to sound to me like encryption, and linked to the monogamy of entanglement. That is, when two wave bodies scatter off each other, they get entangled (there's your first-level superposition, like a double slit experiment). But then when those scatter products run into new waves, because of monogamy of entanglement, they don't appear to scatter. The wave function collapses right at that moment. In MWI it's really scattered again into countless little point-like pieces of the earlier wavefront (second level superposition), each one defining the basis of a new "branch", and then to take just one point-basis, it's the basis for a new wave that races out at the speed of that wave (like light speed) and it "eats up" everything it touches in its new basis, I mean it communicates just its basis to the waves it scatters off of, setting a new basis / branching every piece of that scattering again (monogamy of entanglement again), but all the new scatters "agree" on the original basis (so the history of branchings is maintained), and that's what we call a branch world (actually two branches of one world, a foilation), but from people "in the world" it looks like a wave function collapse. If a story like that is right, it sounds like the basis wave is like an encryption key that encrypts everything it touches according to in its own crazy complex phase. So you have all these complex waves on top of each other. But if you "run them through" different bases reference waves, like de-encryption reference keys / reference beams, then the different worlds "emerge", but all the other worlds are left encrypted as random noise to each other (random quantum fluctuations?). I mean all the worlds are mutually encrypted to each other, but the new basis of wave function collapses are de-encryption keys or reference beams that can each "change the channel". By reference beam I mean like in holography. You hit an object with a reference beam in a phase, then its scatter hits a material and displaces it just according to that reference beam, so when you run the reference beam back through the material, it will reconstruct the original phase so you see the object as a 3D hologram. But if you ran any other reference beam (a beam at any other phase or just random light) through that material, you'll only get back purely random noise. The object will be invisible. Or you could actually imprint two holograms in the same material, one set to reference beam A, the other to reference beam B, and the objects only emerge when you hit it with reference beam without interference from the other. Is the MWI like that? Sorry, I guess I don't have a more specific question. But does any of that sound right or a productive way to think about it? 3. I've been reading David Wallace's book. Great recommendation from your last video! Thanks! I recommend it to everyone watching these. The most interesting revelation from this book for me is that the "magic" of the MWI actually doesn't have anything to do with superposition or the wave function itself. It's just linear combinations of waves all the way down. It doesn't care about or even recognize one level of superposition as different from any another. The magic is that at the lowest level of superposition (the monogamy of entanglement level), classical-like objects "emerge" and are stable over time to make chemistry, biology, civilization, etc. possible. That was the really fascinating part to me. (Also sorry for the long post. It's hard to keep things short for a topic so hard to wrap one's head around!)

[@cademosley4886]

Wait, yeah, because you can do the spin left-right experiment on an electron, get a result consistent with spin up-down superposition, write it down, and then measure if it's up or down, get only one of those, write that down, and that electron can "see" both of those results, won't it? I think that's the same.

[@enterprisesoftwarearchitect]

The wave function could be just “book keeping” - nobody has ever seen a wavefunction nor seen a superposition - it’s probably like ‘virtual particles’ where they don’t have ontological existence but do produce (in most cases) the same predictions as an Amplituhedron or Spinor Helicity Variable method of calculating scattering probabilities. This MWI is still just an episistemic storyline to other theories.

[@rv706]

Your first paragraphs are definitely beyond my background (but they sound interesting!). The book by Wallace, yeah, great book! (even though I have probably understood only part of it) - I was a MWI skeptic and now it's my favorite interpretation by far. In a sense, in my opinion MWI is what "QM _really_ wants to be", regardless from human metaphysical preconceptions. Linear algebra and a linear dynamical system on Hilbert space. That's it. But a Hilbert space together with a unit vector is not enough to describe nature: it's too homogeneous/structureless: everywhere looks the same. What really happens is not described merely by the wandering of a vector ψ in Hilbert space, but by the changing relative position of a vector ψ _with respect to a special basis._ How is this basis defined/selected? How natural and how conventional is this? I also have another question that you may be able to answer. What's the relationship between MWI and the "locality" of fields (by which I believe I mean interactions propagating through space at a finite speed)? Does entanglement "spread/propagate"? If the spin of a particle is measured here, does an alien on Proxima Centauri become split into two copies (according to whatever emergent notion of "world" we're using)? Even disregarding Einsteinian relativity, do worlds split (almost) instantaneously or bigger and bigger "sectors" of a world get split as the entanglement "spreads" over space? What I've written probably doesn't make any sense whatsoever...

[@enterprisesoftwarearchitect]

@@rv706 for this, search for “density matrices” and “decoherence” - this will take you to explanations that popularizers of QM seldom/never talk about that describe the coupling between a system and its environment

[@cademosley4886]

@@rv706 I can try to answer your questions. I might do a more proper explanation in a blog post later and give a link here, since I want to think about it more. 1. What is special about the "selected basis"? If any basis is as equal as any other, why do we see this one? The short answer is, because the "selected bases" have stable wave packets that allow chemistry and biology (and observers!) to happen as an emergent phenomenon, and the others don't. I think it may help to distinguish two kinds of processes: (1) "measurements", which are maximally entangling events, or wave packet shattering events, where the only part of a wave packet that can maintain a stable signal will be the basis defined at one point (but that will apply to all points). We call it “decoherence” because the shattered wave bits are now out of coherent phase with each other. (Little aside: I think the importance of "coherence" is a little misleading. Of course the shattered wave bits are still interfering with each other; they don’t care about phase. But the amplitudes of that interference are total chaos that cancels itself all out. The magical thing is, from the basis of one point in that chaos, all that surrounding chaos disappears, and all it sees now are objects still coherent in its basis-history that the expanding wave in its new basis smash into.) An example is when a photon smashes into a giant complex protein like rhodopsin in your retina, signaling "I see you here!" The visual image to have is a small creek wave smashing into a boulder so that it shatters into a billion little fragment wavelets. Each wavelet bit is completely out of phase with the other bits. So each "bit" becomes its own basis. And those are the "special" ones. Whenever the simplest coherent wave shatters, that defines the "special basis" at one point of the shattering. And then (2) minimally entangling quantum events, where quantum interference happens all in the same basis (already defined by #1) because the wave is in phase with itself everywhere. The example is a photon in a double slit experiment. The image here is an ocean wave rolling over a pebble, or through two giant gaps. There may be a few little ripples, but the photon wave generally just rolls right through intact, stays in phase with itself, interferes with itself, hits the back wall, and it keeps the info of that interference up until it hits that rhodopsin in our retina and then it shatters (or maybe it hits some air molecule along the way). So the special "wave collapsing" basis is the one defined by a "measurement" or a "shattering event", and it's special because the new point-based basis is the only ones where stable wave packets are maintained, making it the topography where chemistry & biology happen. It's an emergent property, nothing to do with the waves or the rules by which they move. They don't care; they just wave on. 2. MWI and locality. I don't know if this is special to MWI, since I think most quantum interpretations say the same thing, but: Action at a distance: No. Properties of entangled systems are nonlocal: Yes. "Quantum theory is a theory of local interactions and nonlocal states." My visual image is, signals are communicated by positive value measurements (PVMs) or wave packets. PVMs in the position basis don't jump around; they move at a finite speed. And an interaction requires wave packets to be touching to happen. So if you measure a spin, that result is a wavelet shattering off a boulder and moving out at a finite speed (like light speed). So no, it does not branch the whole universe instantly. All those little wavelets (some carrying "up", some carrying "down" weirdo angular momentum) have to actually fly out to another galaxy over a million years. Once it is possible for them to be "measured" there, they will all shatter against lots of particles there, maybe some alien retina proteins, and each point-like bit will communicate the result that only that little bit is carrying (up or down), each one the basis for a new branch. That's when the branching actually happens in the distant place, a million years after the measurement. There is still this part that the properties of entangled systems are nonlocal, even if it takes time to communicate them. If you have an event emitting two entangled electrons, they're both in a superpositions of up and down spins, but even if you allow them to fly out even light years apart, to maintain conservation of angular momentum, if you measure one up, the other will instantly be down in that basis no matter how far away it is (even though, again, it may take years for the branches to come back into contact to communicate that info to each other at the places they were both measured). I think this may have something do with the fact that quantum states are defined for “all of space”. Like in nonrelativistic QM, position can be defined (in the position basis) by a combination of lots of sine & cos waves in complex space, each with a definite amplitude, frequency, wave length, etc., from here to infinity, even for a wave packet localized here, those sine waves out in Alpha Centuri still contribute, even by just canceling out to zero. For spin, it’s relativistic QM, so there’s the more complicated Dirac Equation. There are more values at each point in space. I don’t think I understand this part well enough to talk about it any more than this though.

[@benmcreynolds8581]

Is your Electron feeling Negative 🙁

[@Ggdivhjkjl]

How would you draw an electron of anti-matter?

[@mariorqmsilveira3270]

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!!

[@gurmeet0108]

12:13, small typo - in the last term one arrow is wrong. Amazing video, by the way.... :-)

[@32rq]

It's fixed at 13:49.

[@MichaelNiles]

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?

[@jesperdj]

The electron is sad because… it is negative 🙁

[@Melomathics]

You can be negative and unsad.

[@MNbenMN]

@@Melomathics You can be positively contrary.

[@Melomathics]

@@MNbenMN You can be pessimistically optimist.

[@banenewton4559]

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?!

[@ChumX100]

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.

[@MichaelPrice917]

If anyone is interested, Hugh Everett showed that all measurements would be consistent with each other. So you never see two different result.

[@Kelticfury]

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?

[@MrFlaviojosefus]

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.

[@ClearerThanMud]

I find it a useful analogy -- but just an analogy! -- to imagine shining a light on an object, say a cylinder, and then observing its shadow on the wall. Depending on the orientation of the cylinder, the result might be a rectangle or a circle (or something else). If you were a being that lived in the space of projections, then you might see a rectangle or a circle, but you wouldn't see both. And there is another wall where, if you are seeing a rectangle, they are seeing a circle. These are two different "worlds" in a sense, but they do not require the creation of a copy of the universe.

[@ClearerThanMud]

@Counterfactual Definiteness I had never heard of it, somehow, so thanks -- I'll take a look.

[@ClearerThanMud]

@Counterfactual Definiteness Wikipedia's brief comparison of the two seems to focus on one point as the essential difference: that in Many Worlds there is an actual reality described by the wavefunction for the universe (which may of course involve lots of superpositions and entanglements), while in RQM there are ONLY views of the universe relative to observers (as in Relativity). I'd love to see a deeper dive into that distinction, e.g. by Sean Carroll. en.wikipedia.org/wiki/Relational_quantum_mechanics#Relative-state_formulation

[@ClearerThanMud]

@Counterfactual Definiteness Found it; thanks! kzbin.info/www/bejne/aYvSlo1qhN-bmJo

[@GGrev]

So glad you're uploading again. (:

[@ChitChat]

Question: How is something placed into superposition?

[@roing747]

This is almost a philosophical discussion, since it is very hard to prove anything. Did I flush the toilet? Is me flushing the toilet in a superposition until I go check, and once I do, I get entangled with the toilet's state? Is every person in a superposition of being dead and alive, but only observations of other people keep us alive? Does the world behind me really exist? So hard to comprehend all this.

[@rv706]

This is not _almost_ a philosophical discussion, this _is_ a philosophical discussion. :-) Interpretations of QM aren't designed to make new empirically testable predictions, they're designed to (keep all the empirical predictions of traditional QM and) solve the Measurement Problem.

[@failfection]

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?

[@joshuawalker3749]

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!

[@mrblank-zh1xy]

Yes.

[@Clevertechly]

Maxwell’s demon…

[@johndbro1]

Do you think that the Many Worlds model implies Quantum Immortality? Why or why not?

[@peterwegwerth64]

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?

[@thewiseturtle]

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.

[@mygirldarby]

Since virtual particles can pop in and out of existence from our point of view, who is to say that these aren't in actuality evidence of the other state when a measurement was taken? So an electron in superposition is measured, thereby forcing a choice. The other state splits off, pops into existence and then out. The other world that was created at the moment the measurement was taken pops into and out of existence in a flash thereby leaving one world, but the collapse doesn't happen at the moment of measure, but at a moment later. Is that possible?

[@guest_informant]

2:05 Electrons are sad bc they are negative?

[@davidwilkie9551]

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?

[@UpstateAlgaeLaboratory]

(Warning: "theory" from a nonexpert🤣) I feel the "many worlds" is not splitting into different worlds. Imagine a radio (old dial analog one). If each note in music/voice is like a subatomic particle, the state of one note is like the pitch or volume of the note. (Sorry, I know less about acoustics than quantum mechanics) If you looked at particular note pitch from one end of the dial to the other, it is like the wave function of the particle. As you move the dial right to left, you will hear the music slowly change to static then back to a new song. This is like moving through all the "worlds." All the possible notes are like all the particles of the universe. The wave functions of your body are smeared across this "radio dial." So your particles could be part of someone else if you move the "dial" enough. The quantum issues arise (i.e. double slit) the lack of interaction causes a decoerance that allows the wave function to no longer be constrained by the other particles. The result is that when the particles become constrained again, (electrons hit the detector wall) the pattern will be a jumbled mix of results from the other dials. There is not a you in other worlds. You are that person as well. Just as a song sounds slightly static as you turn the dial, as you move through the many worlds, you would see a person change slightly based on the cumulative wave function of the person you are observing.

[@mikebrowning1624]

Is the electron sad because no two can exist in the same state; forever alone?

[@davidgeffeney1283]

Love your channel and unique insights

[@whatitis4872]

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

[@hyperactivists9390]

wow youre a great teacher ive often wondered about this but failed to understand till now

[@Siluetae]

Are you working with Quantum Gravity Research on the QSN/E8 Code Theoretic??? If not, I think you should consider...

[@cmacmenow]

Can I concluded that: 1 Everything and everyone is connected. 2 Everything is in superposition prior to observation. 3. We are not living in a block universe. 4. Compatibilism is probably correct.

[@Charon0]

How could the electron not be sad if it's negative?

[@14s0cc3r14]

I’m curious what you think of Sabine Hossenfelder’s videos on quantum physics. Do they seem accurate in your inexperience?

[@markuspfeifer8473]

For two entangled particles, we can prove they’re entangled by correlation measurements. Why doesn’t this work for us? Shouldn’t a second, spatially separated observer find us and the particle in a provable entanglement? And why do we have to assume the other worlds existing rather than the universe keeping track of options that haven’t materialized?

[@FairyEvergardens]

Love these videos! Thank you for sharing this! ✨

[@michaelransom5841]

I argue that there are no many worlds, at least not in the sense of the "Many Worlds" interpretation. The equations work just as well if we let go of the idea that information is always conserved in every temporal symmetry, and that the wave function of the collective system is additive and can change the information contained in the current state about prior states will align with the conditions of the current state. Much like this explanation of why we can only experience a single state, we can not directly "experience" "retroactive" information reformatting, but we could infer the effect under certain conditions such as what we see with the delayed choice quantum eraser experiment. So I argue the no hiding theorem is an illusion created by how memory works.. we can only experience a forward trajectory of time and the accumulation of information. No need to split the universe, and no need for all states at all time to have to had always existed, so no need for super determinism.

[@outisnemo8443]

All correct. The many-worlds "interpretation" is pure nonsense with zero basis in reality, literally unfalsifiable and unscientific bullshit.

[@jonfr]

The possibility that is not used gets deleted from reality. Time does not mess around and creating branches of possible realities within in any given time flow would be messy and does not align with multiverse (a different thing).

[@karasu.a]

The act of think on result, will it create the result in the future measurement? 🤔

[@joelbeckles3490]

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?)

[@vauchomarx6733]

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…

[@joelbeckles3490]

@@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

[@Dragrath1]

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.

[@erinm9445]

@@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.

[@wallacecarvalho5032]

Is the electron sad because he's negative?

[@praveenb9048]

Mithuna seems to be saying (if i understand correctly) that the information available within one "world" or "branch" is sufficient to deduce the existence of other worlds, and to know something of what goes on in them. I'm not an expert, but this may not be the case. As i understand it, each World or branch just corresponds to one product term among all the product terms that sum up to give the state of the system, including the particle, instrument, observer etc. I think that an observer can only access data about one term, so their experience can not be a function of data from another term

[@praveenb9048]

To clarify, she is saying that it is possible in principle, but highly impractical because of complexity. But it seems to me that it is not possible even in principle.

[@ronleblanc1094]

Consider your reality as being one where you see up and your other you sees down. An instant later you see another up while your other you observes down and on and on. All realities exist, endlessly splitting into new forks in the road. The "instant" I speak of only exists in the fork in the road where we imagine that time is real. All realities have happened, happen and will happen in the present

[@Jim-jx5ds]

What is your opinion of what you could broadly call the UFO phenomenon? Thanks! Jim Chattanooga, Tennessee

[@kreynolds1123]

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?

[@ricardosantos6721]

is the electron alone and sad because of 1 electron universe?

[@docopoper]

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.

[@Maikl717]

I'm putting here my much more simple minded question: how can you explain us probability on this model?

[@sunritpal9596]

Always relaxing to watch your videos. Very nice 👌

[@Carlos-kt1wo]

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!

[@DNNYMc-ux7fk]

What if, a few months later, she remembers writing "up" on paper and everyone who was there when she wrote, "up" on paper, also remembers it being "up". But when she goes back and looks at the paper, she finds that she actually originally wrote, "down"? Did something change? Is everyone's memory wrong? Did the two universes collide? Could the Mandela Effect be real?

[@mrfranksan]

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?

[@coffeeisgood102]

It would be interesting to see the math where the person finds out by accident that there is another version of themselves. In my case I found out very subtlety when I noticed very minor changes in my surroundings. It is obvious that the other people around me do not appear to see anything odd which tells me that for them there have been no changes. This seems to indicate that I stepped into their world and at that instant the other version of me entered my former world. That version of myself would likely notice very subtle changes in the same way that I have. There is no way for me to prove the existence of my other self. If I were to mention to my associates that the wall is a different colour and the placement of objects around the room has changed they would have no idea what I am talking about. They would be adamant that it has always been this way, etc. This has only happened several times, leading me to believe that on more than one occasion I have switched back and forth between the worlds. It likely also happens to others but they just shrug it off as a bad hang-over or effects from some chemical they used previously. In my case I don’t drink or do drugs so I have nothing to blame it on.

[@oblivion5683]

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.

[@MN-vz8qm]

Well, our brain (the support of our mind) is matter too, hence in the continuous wavefunction which is our brain, the brain state where the experiment has the "up" result is bound to it and not to the "down" result which it hence cannot perceive. The ability to see both would be fascinating tho, we would see the universe like a giant wave of all possibilities happening at the same time. It would be in the same vein as if we were able to get out of time and perceive the space-time in its entirety. What I don't like about the "many world" name is that it implies semantically that there are parallel universes, while my understanding is that there is only one wave-like universe, that the state of mind we are in right now can only experience in a classical state. The wave universe theory would have been a better name.

[@prosimulate]

I’d like your opinion on superdeterminism, it would seem to explain a lot of physics is trying to still explain.

[@mitchellchyette6537]

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?

[@b43xoit]

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?

[@alistairmills7608]

It takes two laps around the nucleus to return back to the original orientation.

[@shashankchandra1068]

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?

[@TheWyrdSmythe]

The MWI claims simplicity by removing the “measurement problem” but makes the big unproven assumption that quantum behavior applies to classical objects. Usually, producing quantum behavior requires extreme isolation from the environment. It seems far more likely we’ll solve the measurement problem, perhaps through a theory of quantum gravity, than that uncountable copies of the entire universe exist. (And what about the uncountable worlds being created in other galaxies? Do they eventually impact us?) Is it easier to believe that we “decohere” into countless non-interacting, non-interfering copies or that quantum effects are swamped out in emergent classical reality? The latter is certainly what _appears_ to happen…

[@lepidoptera9337]

There is no measurement problem to begin with. Every day experimentalists are making trillions of quantum measurements. Not once will you see a problem with any of them. Some (very few, it's really just a handful, really) theorists simply can't separate the approximations in the theory from reality.

[@davefarley77]

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?

[@andrewharrison8436]

You had my upvote at "I am a professional".