Does the Many Worlds Interpretation make sense?
ฝัง
- เผยแพร่เมื่อ 7 พ.ค. 2024
- Expand your scientific horizon with Brilliant! First 200 to use our link brilliant.org/sabine will get 20% off the annual premium subscription.
This video comes with a quiz which you can take here: quizwithit.com/start_thequiz/...
The idea of parallel universes has captured the imagination of many. In physics, it's prominently represented by the “Many Worlds” interpretation of quantum mechanics. In this video, I want to explain how the Many Worlds Interpretation works. Is it science? Does it solve any problems? And are the parallel universes real?
🤓 Check out our new quiz app ➜ quizwithit.com/
💌 Support us on Donatebox ➜ donorbox.org/swtg
📝 Transcripts and written news on Substack ➜ sciencewtg.substack.com/
👉 Transcript with links to references on Patreon ➜ / sabine
📩 Free weekly science newsletter ➜ sabinehossenfelder.com/newsle...
👂 Audio only podcast ➜ open.spotify.com/show/0MkNfXl...
🔗 Join this channel to get access to perks ➜
/ @sabinehossenfelder
🖼️ On instagram ➜ / sciencewtg
00:00 Intro
00:53 Standard Quantum Mechanics
02:33 Why Quantum Mechanics is Weird
06:45 The Many Worlds Interpretation
09:18 Is the Many Worlds Interpretation Simple?
11:51 Is the Many Worlds Interpretation Local?
15:32 Is Many Worlds wrong?
16:53 Learn More with Brilliant.org
#science #physics #quizwithit - วิทยาศาสตร์และเทคโนโลยี
As an engineer, I performed a quick estimate and determined that we have at least one world in existence. The remaining calculations are beyond the scope of our current budget.
It's the correct order of magnitude :-)
Haha, right! XD
If you know that one world exists, then you know that all the worlds exist because the information complexity of existence in the multiverse must be zero.
LOL
Lol, good one 😂
“Friends don’t let friends go through beam splitters” - wise words to live by 😂
The rivalry between physicists at times weakens an exact definition of 'friendship'. Especially when they look upon each other as barely acquaintances.
With metaphysical friends it's different, that's kind of what Easter is about, but local-friends definitely don't let local-friends go through beam or any other kind of splitter.
@Dr.M.VincentCurley how sad.
I don't think the universe is the problem. I think humanity is the problem.
7:40 I always assumed that the observers *did* split. So the question 'why do we only experience one of the worlds' would be answered when we realise that there would be a gazillion other 'replicas' of us asking the same question in their own world.
Yes, this is correct. Computation favours a local basis, as all forces act locally (decay by distance), so your brain has a different thought process in each branch, each thinking about their observation.
I had exactly the same thoughts. That observers split means to me that the other "you" experiences the slightly different universe. It wouldn't mean that you'd suddenly have multiple concurrent experiences
I could be wrong but I think Sean Carroll said that observation was the observer becoming entangled with the experiment. That the observation problem stems from assuming we sit outside the experiment even though we are made of elementary particles too. So yes I thought the observer would branch also.
I think it's funny how physicists are fine with virtual particles being unobservable and taking every possible uncountably infinte path including escaping black holes but are not OK with the universe branching in an uncountably infinite way. To me the gini is already out of the bottle.
This is really annoying to me about this video. The observer *does* split with the world. But in this video, Sabine argues against the interpretation, assuming wrongly that the observer doesn't split and that there have to be additional axioms because of that. Also, the theory of decoherence gives a good account of when the measurement happens and why the worlds seem to branch in the first place.
PS: Also in this video she very often says something that "they" apparently say, and then argues against that strawman. In total a very frustrating video. That there are many people who have a wrong understanding of Everetts theory, is not an argument against the theory itself.
@@RobinCarter This seems like an odd explanation to me though. The observer (the experimenter) is not some special entity that has a connection to the collapse of the wave function. They're basically the same as the chair they sit on, from a physics standpoint. The actual wave function collapse is because of an interaction with another particle, or a photon. Physics doesn't care about why this interaction happens. The fact that the experimenter is the one who uses a machine to shoot out that particle or photon is completely irrelevant. Wave function collapse happens all the time. Probably an infinite amount of times per second. Doesn't matter if it's part of an experiment or not. I always disliked the term "observer" for this reason.
The point that hidden variables theories have NOT been ruled out by experiment is an extremely important one, and it should be hammered over and over until the myth is dispelled (and then some more to kill it while it still goes around as a zombie). And I think you're doing a huge service to physics in highlighting it once more. Thank you!!
Yeah, I'm not a physicists, though I'm interested in it.
And most of the lay discussion around these concepts are actually just a discussion of the supernatural or excuses to support religion/spirituality. But experiments have not been ruled out. As far as i understand Bells Theorem is basically just a bias check and magic still doesn't exist.
Bell's results effectively rule out local hidden variables. But it doesn't say anything about global hidden variables. But to most, abandoning locality is a much bigger leap of faith than for hidden variables.
@@JustinLe Bell's theorem with confirmatory experiment is more than that, it proves the world is non-local. Physicists tie themselves into knots trying to deny non-locality.
@@JustinLe I agree with the last sentence. On the first one, _i think_ it might depend on what you mean by local. If you allow for retrocausality for example then local can be something near but in the future cone, and that would work fine as a local theory that satisfies Bell's inequality, i guess (?). OTOH, while I've studied QM in my third year of EE, and i am interested in the subject, i am NOT a physicist so what i just said might not make sense or be flat out wrong.
There's been some experiments that indicate "spin" of an atom determine the result of Quantum collapse.
(Quantum worlds theory is a weird religion though.)
Hi Sabine. Here in Brazil, "quantum mechanics" means whatever you like!!! I have a coworker who is a civil engineer and she was teaching "quantum mechanics" to a handful of people from my job. I was like "well she returned to college to study physics". One day she started talking to me about such QM. Turns out it's a religion!!! More like horoscupus and sign mixed with spiritism (I guess?). The term "quantum dynamics " seemed to be for cosmetic purposes only... I was astonished!!! Can't believe it up to this day.
Oh dear
@@SabineHossenfelder🤣🤣🤣 this is worse than the phone ringing I suspect
Sure she was not talking about "climate change"? That's a religion, too!
Fellow Brazilian here and, unfortunately, I can confirm there are people who believe in stuff like that. 😬
@@jovetjoh boy
Asking why the observer "doesnt branch and observe all worlds" feels like asking why identical twins don't have telepathy. The observer *does* branch, and by definition, to branch is to become a different thing, with different experiences.
yes, the observer can only see the outcome of the own branch because different branches can't interact with each other. To me it sounds like the Copenhagen interpretation and the many worlds interpretation are the same thing, just worded differently and which one is "simpler" depends on the person who tries to understand it.
@@dennismuller1141 The Copenhagen Interpretation is a non-starter, as it postulates a classical world in which measurements take place. But the measuring instrument is made of atoms which are themselves governed by QM...
@@kevinvanhorn2193no it makes just as much sense to take the classical limit of the measuring apparatus
I think that Sabine makes a good point because there is a failure in how many-world's is often explained: it isn't that it removes the collapse postulate but rather it *generalizes* it: i.e. it says that the 'final' measurement of the Copenhagen interpretation is itself not final and thus there must be many worlds (i.e. constant collapses/decoherence all through the process of a quantum mechanical process).
That's why its superior: the Copenhagen interpretation want's this giant exception to the quantum mechanical process. Here the real problem is the focus on 'non-locality' rather than non-realness. Its the non-realness which the MWI embraces (and which is, I feel, the correct path since everywhere else locality holds and you need locality to make time make sense). The cost of non-realness is a reality explosion (all things happen) and some people will want to come in and say that Occam's razor eliminates it for this reason, but the problem is that reality explosion is, actually, very simple explanation for reality (complexity exists in the middle between infinity and 'one' --- you can pick either 'infinity' or 'one' and maintain simplicity).
Yeah I agree and don’t get the objection. Basically noninteracting observes follows from the definition of “worlds.” What am I missing?
The way Sabine says ‘today’ is everything
Hi Sabine. I love your passion and commitment to getting physics right!
well this video did not confirm your claim at all.
It’s never right
I would love to see a discussion about this between Sabine and Sean Carroll. He's a very smart physicist (formerly at Caltech, now at Johns Hopkins) who favors Many Worlds and who, like Sabine, has a great youtube channel (featuring lengthy interviews of other very smart people).
The problem with discussion about physics is that there is not really anything to discuss with words. Any discussion about it among smart people will result in a battle of math equations that normal people will not understand.
@@yaldabaoth2 I would agree on that under normal circumstances, but this is really a matter of elementary logic, it doesn't require a lot of maths to understand.
I feel confident that @seancarroll would pretty easily win that battle, but I would love to see it also.
I came here to say this. Many Worlds seems obviously correct to my very limited understanding, but if anyone can change my mind about that it would be Sabine.
Yeah, this topic is more complex than its title reads.
"The major challenge [of MWI] is to explain why the thing we call an observer does not itself branch with the worlds"
But in MWI, the observer *does* branch with the worlds. Suppose that, like Two-Face, I decide whether to comment on this video by flipping a truly random coin that's dependent on some random quantum event. Some other world has a me that decided not to comment on this video. I can no longer see the world thru his eyes, nor he thru mine, but we each see a consistent world, and we each see a single outcome for the coin-flip, even though in the larger picture both outcomes happened.
"Not simpler [because] as we saw earlier, you need the collapse postulate to calculate probabilities"
That's circular, since you couched the earlier discussion in the Copenhagen paradigm or something similar in the first place. As I was watching it, I was thinking "That's not right, observer-splitting does the same thing just fine"
But I do want to thank you for introducing QB-ism, which I will have a look at.
If Many Worlds actually exist? Since we can only see one, we'll never know for sure.
Indeed!
In fact it's the Copenhagen interpretation that has the trouble of explaining why the observer does not branch. It reconciles this through the artificial and awkward band-aid of wave-function collapse. Nobody can explain how it comes about, how it actually works, what a measurement or an observer even is, and yet it is widely accepted.
The observer definitely does branch unless their time evolution is not governed by the Schrödinger equation in which case all of QM is just wrong. The observer in each branch will, however, discard all other branches as not being real and happily claim that there is only one world, namely theirs and everything else collapsed into nothingness for some reason.
Instantaneous collapse of the wave function = FASTER THAN LIGHT communication!
Probability can travel faster than light -- spooky action at a distance.
Wave function collapse implies that probability travels instantaneously and is therefore by definition travelling faster than light.
Nothing can travel faster than light -- Einstein.
Spooky action at a distance = FASTER THAN LIGHT!
"Always Two there are! -- Yoda.
Probability collapse has infinite velocity?
You can build a double or dual split experiment to confirm this with a very large screen placed on the moon!
@@hyperduality2838 Einstein's theories do not prohibit faster than light travel. Only the acceleration of mass from below light speed to light speed takes infinite energy.
'Probability' does not have weight, but also does not travel in any logical sense. Furthermore, the collapse of the wave function does not carry any information and thus there is no FTL communication.
@@olejurgensen2489 Exactly!
7:25 "The major challenge for many worlds is to explain why the thing we call an observer does not itself branch with those worlds and therefore see all the outcomes, but somehow randomly only experiences one of those worlds. I've never found a good explanation for that."
Wait, what? But, that's precisely the major challenge for Copenhagen, not many worlds! Actually, that's WHY MWI is so nice: it's an interpretation QM that even *laypeople* can understand, and that, as you've admitted, *accurately* explains QM effects, including entanglement AND randomness. Except, in MWI, the source of both randomness and entanglement are incredibly intuitive: they're only "weird" when wearing a Copenhagen hat.
Why would the branched observer be able to see all outcomes? If there is anything in the theory, then you become a branched observer in every new instance of time and are only able to observe that which branched with you? No? What am I missing?
@@Strange_Club you're not missing anything. Apparently Sabine is missing something, because she is the one who asked the silly question I quoted.
You are a most wonderful example of a thinker.
Examine, test, observe, think.
Love your videos and thoughts.
❤
Seems like Many Worlds violates Occam's Razor. Also, an untestable theory is not scientific.
Sabine, which universe has a new video from you everyday? That's the one I want to be in.
It's the one in which I never sleep ;)
@@SabineHossenfelderIt's all good if sleep is not a requirement in the other universe. That universe must exist.
It's where the day has 72 hours.
@@imacmill your logic doesn't follow. Infinite possibilities doesn't mean all things are possible.
You can have an infinite amount of numbers between 1 and 0, and never once count a 2.
@@hieronymusbutts7349 there is no law of physics that states there can't be a creature that never sleeps, if I recall correctly there are animals who sleep one hemisphere at a time or not at all. If he said something like "I wish there was a word where you were able to record two constant streams of videos non-stop, each of them being different", that would fit your "number between 0 and 1 can't be 2" statement. Just because you came up with a random sentence doesn't mean it is in any way proving your point whatsoever
Your videos are Great Sabine, thank you 😁
This is an awesome video on the subject! I would love a dissection of the observer vs measurement aspect of this subject as well.
Instantaneous collapse of the wave function = FASTER THAN LIGHT communication!
Probability can travel faster than light -- spooky action at a distance.
Wave function collapse implies that probability travels instantaneously and is therefore by definition travelling faster than light.
Nothing can travel faster than light -- Einstein.
Spooky action at a distance = FASTER THAN LIGHT!
"Always Two there are! -- Yoda.
Probability collapse has infinite velocity?
You can build a double or dual split experiment to confirm this with a very large screen placed on the moon!
Hi sabine!!! Thank you for keeping us all updated on science news. I one day aspire to get a degree in physics, so thank you for keeping that sense of wonder alive!!
Thank you for these amazing videos ! I always love when you talk about quantum mechanics.
Can you please explain Nelson mechanics, whether it is equivalent to QM and what is entanglement in it ?
Beautifully said and point well made. Bravo.
8:38 - I love your stuff, Sabine and I am so, so thankful for all the knowledge you share. At that timestamp, I've often wondered the same thing about energy conservation and many worlds. Maybe I'm just bad with the math here, but I'm having a hard time trying to understand why the "branching universes / probability calculation explains why conservation of energy isn't violated" point you made. Maybe this is something you could do its own video on at some point?
I also don't understand how creating a whole new universe for each time a photon goes left and right doesn't require twice as much energy as the universe had before that point. And as Sabine says, this is happening gazillions of times a second.
I think I can try to explain... I'll start with, say, 3 units of energy, and then perform an experiment that has two possible outcomes A and B. In the A universe, we still have 3 units of energy, and the same for B. Stepping back to view my mini multiverse, I would see this as a 50% probability of A (or, technically speaking, A's wavefunction is scaled by 1/√2) with 3 units of energy, and 50% probability for B, so my overall energy (again technically the "expectation value") is 0.5*3 +0.5*3 = 3 units still.
Analogies are always dangerous, but you could think of this like a block of modelling clay. I can make a model, or I could split the block in half and make two models. I have the same amount of clay in each, despite doubling the number of models. As I split the clay further, I'd need smaller and smaller tools, which is a problem for me, but not for wavefunctions.
Incidentally, the maths behind that calculation is the same for _any_ version of quantum mechanics, just applied here to the total energy, which is normally quite a boring thing to do because it doesn't ever change (conservation of energy)
@@mikeflowerdew7877 I appreciate your attempt here, and I am truly sorry that I'm still not understanding this. I assume I'm missing something conceptually that perhaps people steeped in the math are able to intuit? Let me give you an example of how the Many Worlds concept comes across to us laypeople (or at least how it comes across to me):
Think of a cell dividing. A cell has to intake energy in order to divide. At one point in time, there's only one universe, then "something quantum happens," and the universe "divides" into two - nearly identical except for one small difference - universes. Like the dividing cell, this requires energy because every single thing in the universe is doubling. So if there is Telephone A in Universe 1, when Universe 1 divides into Universes 2 and 3, it creates (because it wasn't previously there before) an additional copy of the telephone. So now there's Telephone B and Telephone C. Where'd you get the energy for this new telephone?!?
If I'm understanding your explanation correctly (which, I'm probably not, so fair warning!), your approach here seems to me to be kind of more like a "Block Universe" approach to things. If I can try to translate your explanation into my understanding of the Many Worlds theory, then Many Worlds doesn't have any "randomness" in it, because ALL possible quantum variations are "already accounted for" at the beginning of the universe. Basically, there's no "time," so there's no "division" from one thing into two things. Instead, all of the (possibly) infinite universes essentially "already exist," and causality grants the illusion of time passing in each. So, in the "overlap" between these universes, at one specific location in the "shape," there's one telephone, and in the very next... Planck-second there are two, but the energy that creates both of the telephones is essentially the same energy shared between them?
TL;DR: I think I'm having an issue with the concept that at minute 1:00 you have a single object, a telephone let's say, and then at 1:01 you now have two telephones. Before the quantum event, 1 telephone. After the quantum event, 2 telephones. Where'd the energy for the second telephone come from???
@mikeflowerdew7877 I have two Questions: 1. If after branching, both A and B exist (albeit each one on its own parallel universe) then why probability is 50% for each? Shouldn't it be 100% for both? 2. Doesn't a wavefunction need something like clay (being it energy or anything else that is being cut in half to create the 2 universes?) Could a finite universe be cut in half infinite times? You suggest that "clay" is similar to "probability" ?
Bumblebees have no idea how humans can walk with those ridiculous legs
Humans limit themselves to a mainly 2D world
It should be impossible!! 😁
But humans walk regardless because they're not interested in what bees think
(Only in what they secrete)
@@wb3904 I can assure you, most humans experience a very 3D world, as anyone who has tripped and fell will tell you. Or anyone who has tried climbing the stairs to the bathroom after too much alcohol... that 3rd dimension can be quite annoying, and sometimes quite painful. 😂
7:28 - oh, c'mon, I didn't expect such a misconception from Sabine - observer also branches altogether with his/its consciousness if applied - every version of observer observe (or "experience") only its branch
I just love the topics and discussions! It keeps our brains from rusting out!! 😂😂🙏❤️❤️
"We can neither confirm them nor rule them out" sounds exactly like the definition of unscientific to me.
I love this channel. Your standup keeps getting better & better. Keep it up!
As an observer you can branch into several realities just fine. They have very special pills for that.
Idk about very special. You have literally thousands of options. And who knows how many analogues and things we haven't even discovered yet.
An observer can only see one outcome because he has finite vision it cannot see ALL possibilities only that which his vision will allow him to see. That is why the red wave is not good anymore we seen that which we couldn’t before
thanks for the reminder to take my dried frog pills for today
And magical mushrooms🤪
How could it possibly be scientific if you can never prove it?
that is the same as god, santa or string theory
its just a different way of looking at things that doesnt necessarily mean anything of substance.
My understanding is that some variants of many worlds feature all the worlds pre-existing in some sense, rather than literally splitting. In these versions, measurement is simply a local knowledge update, so the theory is local in the sense that there is nothing “causal” happening at a distance. Of course, the more serious problem is how you are supposed to derive probabilities from within the interpretation
Instantaneous collapse of the wave function = FASTER THAN LIGHT communication!
Probability can travel faster than light -- spooky action at a distance.
Wave function collapse implies that probability travels instantaneously and is therefore by definition travelling faster than light.
Nothing can travel faster than light -- Einstein.
Spooky action at a distance = FASTER THAN LIGHT!
"Always Two there are! -- Yoda.
Probability collapse has infinite velocity?
You can build a double or dual split experiment to confirm this with a very large screen placed on the moon!
My understanding of many worlds is there is no collapse because the observation (or measurement) gets entangled with the result. The simplification of many worlds is the wave equations are reality and there is no collapse. They just keep deterministically following physics. However, when we observe some QM event, we get entangled and get all probabilities. However, we cannot communicate with the parts of us that saw different outcomes. It also sounded less like branching and more like subsets. Like there are an infinite number of points between 0 and 1. If you have an event that is 50/50, then one part of you gets 0 to 0.5 and another part gets from 0.5 to 1. However, both sections still contain an infinite number of points can be further subdivided.
Hello Sabine, I was once enamoured with MWI thanks to Sean Caroll but since than I grew more and more sceptical with it. Its there any video on youtube where you debate with him, or another MWI proponents about this topic?
Although Sean Caroll is still one my favourite science communicators:).
I know Sean and would be surprised if he wouldn't remember me, but I think we're mostly living in parallel worlds that don't intersect very often.
@@SabineHossenfelder
Which surprising. Aren't you both science communicators and both interested in the foundations of quantum physics?
How could it possibly be scientific if you can never prove it?
that is the same as god, santa or string theory
its just a different way of looking at things that doesnt necessarily mean anything of substance.
@@nahoj.2569 Santa does exist in our universe.
@@viralsheddingzombie5324 I assumed Santa wasn't real when I noticed he had the same handwriting as my mom. Every gift that said ''To Stevie, From Santa'' looked exactly like all the gifts from my ma.
I don't think it is an additional postulate that observers can only experience one branch rather than multiple ones. This comes out of the theory because you find that different branches evolve independently. Any scenario where you could feel yourself in a superposition would violate this.
She does not have a valid argument against it so she made one up.
I think it would be fascinating to have dinner with you and be able to ask you questions about the universe and science then sit back and listen to you explain!! Maybe in another universe I could..wish it was this one!!!!
Hi Sabine, great job! I have to say the insistence on confusing model with reality is really a big problem for me, and a lot of physicists, specially particle physicist, seem to be tirelessly focused on that misguided assumption.
My understanding was that MWI was local because the "splitting" propagates out locally from the measurement. When A and B finally compare measurements locally that too is a split, except that impossible universes (where A and B both detected the photon) are excluded. But as far as A is concerned after her measurement B is still technically in superposition until B's measurement information actually reaches her, which is STL.
Could be this is wrong but I've definitely seen this explanation before to justify MWI being local.
07:40 The observer IS branched to the other worlds but since there’s no communication between the branches each branched observer sees only his version of the measurement.
Or not.
You guess?
It must be so! Because I imagined it to be so!
@@brownro214 no, it’s how Sean Carroll explains it. Google him
This!
This is what the Schrödinger equation tells us what happens. So either it's fundamentally wrong and yet magically works everytime we check, or reality is indeed branched. I don't see any issue with the many-worlds interpretation, but we need to come up with all kinds of awkward band-aids like wave-function collapse to get around it.
Sabine! I just heard about the double "time" slit experiment and I definitely want to hear you explain it! Please, please make a video covering the experiment where a laser beam goes through indium tin oxide and reflects onto a detector within a time frame of a few femtoseconds and the scientists measured an interference pattern in the wave's frequency.
I always have a preference for the simplest explanations. They're usually the ones that turn out to be correct, once we have a way to prove them.
For that reason, while it may be an interesting exercise to consider the possibility of infinite parallel universes, it does seem to a bit of stretch for something that can be explained by something as simple as hidden variables (just properties we can't measure). That's not something we generally do in other areas of life.... thankfully.
Occam'z razor is about the simplest explanation though, not about the fewest existing things or anything like this. If Many Worlds works without postulating any additional hidden variables, then it is the simpler explanation, regardless of how many worlds exist in it.
Instantaneous collapse of the wave function = FASTER THAN LIGHT communication!
Probability can travel faster than light -- spooky action at a distance.
Wave function collapse implies that probability travels instantaneously and is therefore by definition travelling faster than light.
Nothing can travel faster than light -- Einstein.
Spooky action at a distance = FASTER THAN LIGHT!
"Always Two there are! -- Yoda.
Probability collapse has infinite velocity?
You can build a double or dual split experiment to confirm this with a very large screen placed on the moon!
@@hyperduality2838nope. The tree is falling whitout onlookers.
Non-locality as defined in the video is unimpressive and not unique to quantum mechanics.
06:20
"a measurement in one place provides information about the measurement outcome in another place"
If I compete in a fotography competition and someone calls me and tells me, that I won, I instantly know, that others did not win, although they are far away and I don't observe their result announcement.
If you place 2 boxes with only 1 ball in one of them, then let me open one box, I will know, if the ball is or isn't inside the other still closed unobserved box.
That is what happened with the photon 50/50 deflection example.
Absolute banality.
This is not physics. This is logic. No unintuitive physics is happening here.
Isn't this the Bayesian QM interpretation that Sabine mentioned?
@@happyduck1 Occam's razor is about making things not overly complicated - for the sole purpose of fitting your expectations. Many worlds is just that, it sounds nice, but doesn't solve any problem and has nothing confirming it. As long as nothing changes it's just wishful thinking.
The collapse of the wave function has always struck me as a mathematical artifact that only appears because of our insistence on stitching quantum systems with classical measurements.
I view it as not a collapse at all. We "sample" a particle's value by interacting fundamentally with it. The particle dutifully tells us its value at that instant of time. It's like asking the temperature outside. One has to look at the thermometer to tell its value. The thermometer doesn't care.
@@palancar4262this is very wrong interpretation. What you are talking about is hidden variables, which has been debunked by careful quantum experiments. Do you think scientists have not thought about it?
How can you explain entanglement? The partial also needs to know what answer the other particle gave no matter how much distance separates them.
I consider the "collapse" of the wave as two waves, observer and observed, synchronizing. They each STAY waves and do not change in the slightest, but now there is a connection which creates the appearance of a particle that can be measured.
Try e=ymc² where y is the Lorentz factor. And time is only ever now.
Relativistic stuff has an implied plurality of datum. Take as analogous the proposition that the single overarching reality iterates a sum total through the lens of all its existing member components, and attaches the space-time qualifier "Now". I don't know if thats factorial but every single unique datum requires a construct of its moment relative to the rest of the entire universe. In this way, I reconcile what IS and the many worlds.
In a fraction of a second, we would have more universes as there are particles in the one we are living in. This seems like nonsense to me.
Does it seem like nonsense when they describe "spooky effects at distance" where what happens here affects the galaxies billions of light years away? Does it sound like nonsense when they say some particles have no mass, or gravity is the bending of "spacetime"? The universe was "nothing" until a big bang, and it became something from nothing. If so, I'd agree with you... some scientists are clearly high on drugs much of the time. 😂
That's does not follow. It's the simplest explination, Sounding like nonsense cause it's hard to picture in ur head is a nonsensical argument.
The math has been right for any experiment we can throw at it. It's just that the math itself makes no goddamn sense and nobody knows why it works. There has to be _some_ reason it works, but all the _sane_ explanations contradict both the math and observation, so all that's left for the scientists to consider are the _insane_ explanations.
Actually, it all seems like nonsense to me. Theorizing that there must be other dimensions to support an idea of how things work seems like grasping at straws to prove a theory that doesn't exist in the real world. Maybe someone will have the fortitude to say "the emperor has no clothes".
many worlds is just another compounding error resulting from faulty fundamental premises. obviously at some point ridiculousness of those unverifiable theories and interpretations becomes unacceptable and illusion shatters - individual thresholds vary
Your sense of humour is wonderful 😊
You briefly touched on Qbism in this video. Would love to see a whole video with just your take on that! It's an interesting shift in perspective, but I don't see how it really affects calculations?
Maybe the observer branches too. Each observer sees one outcome, the one that happens in his universe. But collectively, the observers see them all. Or most of them. In some universes, the observer might die the instant that the observation is made or would have been made.
She is extremely wrong, watch D. Deutsch. You will thank me later, cheers.
It's could be "explanation" of literally anything. "Why did my poop smell bad the other day? Oh its because I just happen to live in a universe where it did. There were other universes where it smelled like a summer's day. There now I've explained it."
A good explanation for the fact that an observer only experiences one 'path' down the tree may be that that is the nature of consciousness. Suppose consciousness only makes sense in a causally connected world, then, because the branches in the tree are no longer causally connected, it can only experience one branch. It'll experience all of course, but since these are causally disconnected, there are just many 'split' consciousnesses that are unaware of each other: hence "many" worlds.
I like how she makes up the word "update" for wave function collapse to make it sound less ridiculous and how she still pines for hidden variable theories after Bell's inequalities experiments.
To believe in the Many Worlds Interpretation of QM, because it can be neither proved nor disproved, even in principle, is tantamount to holding a religious belief - It is an act of faith.
All of the interpretations can neither be proven or disproven with greater utility than any other, and mathematically they are all exquisitely accurate and have made phenomenal predictions that have measured experiments backing them up. Religion has none of those things and is demonstrably false to anything with rationality.
around 7:25 you ask why observers only experience one of the branch worlds. This seems fairly easily answered if one considers an observation an update in an observers wavefunction. I.e. an observation behaves the same way as that which is being observed, with an update to its wavefunction.
Thank you for this complete and correct presentation.
You may want to correct the spelling in the slide that starts around 2:10.
Also, I think the main problem with many worlds is they assume a correlation of outcomes; that the different worlds statistically matches the probabilities of different outcomes in this world. If that's the case, there must be a mechanism of correlation and so the other worlds will be in principle observable.
I give you an apple. The optical image of that apple is correlated with the optical images of all other apples in this world. Please use your apple to count the total number of apples in the universe. :-)
There is a correlation predicted by MWI. But it is the same correlation between outcomes predicted by standard run-of-the-mill textbook QM, aka, Copenhagen. And so these interpretations still seem practicaly the same.
@@felipealmeidabarretto3396 Except that they are not. Copenhagen actually explains the physics behind quantum mechanics, MWI does not. That most people don't know this is the result of abysmally poor teaching of QM at the undergrad level. It is, however, not the result of our actual physics knowledge. So, no, Copenhagen and MWI are not identical. One tells you all you need to know, the other only tells you that Everett and his believers are clueless. ;-)
And just as many not asking the question 🙂
@@Bgrosz1 You can ask the question but most people won't be able to give you the correct answer. ;-)
@02:14 The Copenhagen Interpretation !!
Yeah something is rotten in the state of Denmark.
I've casually accepted Many Worlds as a layperson for a long while and have done a lot of personal sci-fi exploration on the topic. As in, I assumed it was the prevailing accepted theory among academics. This is the first time I've seen someone break down why wave function collapse and many worlds are more equally matched than I otherwise realized and has shed some light on the process of academic disagreements. Makes you wonder if many worlds has so many staunch supporters _because_ of its sci-fi implications. Thanks, Sabine!
I have never met a physicist who actually uses MWI. Sean Carroll preaches MWI but when he does calculations he uses Copenhagen. :-)
@@schmetterling4477Woah, is thst true? Do you have any sources I can look at where Carroll does that?
@@HOTD108_ You can't calculate anything with MWI. It's exactly the same math as in Copenhagen except that they pretend that they don't need the Born rule. Which they do... to calculate the distribution of multiple universes. ;-)
Probabilistically, there are more realities in which Sabine believes in Many Worlds.
Which gives me comfort
Good video. Lots of food for thought. You mentioned QBism in this video. I'd welcome a video on that interpretation of QM.
Hey Sabine, could you please make a detailed video on energy conservation in many world theory. Also, your videos are amazing.
This is my question also! You have to photocopy the entire universe each time a photon takes path-A or B, that's got to take a fair bit of energy!
In any case, the wave function describes my incomplete knowledge of everything.
That is more true than you know!!!
@@jovetj Trust me, I don't know.
U don't know but the wave function knows.... If ur wavefunction knows so u should be happy that a part of u knows
Your knowledge or lack thereof cannot go through two slits at once
The universe has no obligation to make sense to us.. Our persistence of “one theory” is what’s leading us to fantastical ideas.. If the model works, let it be and move on rather than romanticising about its implications.
Thanks for the video; I always appreciate your common-sense takes. Notice also that for continuous variables, the number of worlds spawned is uncountably infinite. Good luck with the quiz app! I can only speak for myself, but I come here to get information, not to take a test.
2:05 @Sabinehossenfelder: excellent video, as always. Your clarifications are very helpful!
(Note: Copenhagen Interpretation is almost correct, except the Interpretation is missing the first T.)
Instantaneous collapse of the wave function = FASTER THAN LIGHT communication!
Probability can travel faster than light -- spooky action at a distance.
Wave function collapse implies that probability travels instantaneously and is therefore by definition travelling faster than light.
Nothing can travel faster than light -- Einstein.
Spooky action at a distance = FASTER THAN LIGHT!
"Always Two there are! -- Yoda.
Probability collapse has infinite velocity?
You can build a double or dual split experiment to confirm this with a very large screen placed on the moon!
I watched a debate with Sabine, Penrose, another guy (sorry other guy, didn't remember your name) and one of the String Theory/Many Worlds enthusiasts, from about a year ago. It left me pretty convinced that String Theory/Many Worlds is a dead end - partly because they seem to be making it up as they go along, but mostly because the String Theory guy almost instantly resorted to whataboutery and evasion when challenged. I'm no physicist (but numerate degree educated), but viewing the discussion as a debate I was left with the distinct impression that there is no need for Many Worlds other than to satisfy some mathematical ideas, rather than explaining the 'real' universe.
Remember, that Sabine talked the less, but said the most.
String theory has nothing to do with many worlds as far as I know. Many-worlds is a consequence of taking quantum mechanics seriously as a universal theory of reality.
the guy was Michio Kaku and he gave possible ideas for ways to test string theory, so maybe you wern't watching very closely. And a Nobel prize was given to physicists who proved that the universe is not locally real, so your comment about the "real universe" makes no sense.
@@richardpreston5154 You have highlighted another problem there, also covered in that debate, that there are at least three different versions of 'parallel universes'.
@@nextlevelenglish5858 If you note, I said he lost the debate - I didn't say he was wrong, just very unconvincing in his argument. Also, Fred Hoyle would have had a Nobel if he hadn't upset the jury - being right about one thing does make someone right about everything.
The magic of Many Worlds comes from reframing a Measurement as Entanglement. That is the only thing about it I find convincing. I find it incredibly philosophically convenient to think about the wavefunction collapsing as entangling myself with the system I'm measuring. It also helps me to think about the distinction between classical and quantum systems as "systems where the objects are or are not initially entangled."
I'm not really a fan of ascribing physical reality to those "extra worlds," as I'm not sure it's sensible to think about "the rest of the wavefunction" once you are entangled with it.
Or... you could have paid attention in undergrad physics and then you would know that measurements are irreversible energy transfers... which saves you all the philosophy and puts everything on a solid physical footing. ;-)
@@schmetterling4477que sera, sera
@@ralphmacchiato3761 True that...
This one is really good. Clarifies and cuts through.
I think Sabine is generous to this pseudoscience for no good reason.
It's the sociological pressure of Academia. Playing nice with the many world cultists.
Cultists? Lol
@GlazeonthewickeR yep. They are pretty much a cult. In some branch universe, they are all sacrificing virgins to the great beam splitter. According to their own theory, that's not only possible but unavoidable.
My issue with Many World is that if there is one world for every measurable outcome, then then all outcomes must be equally probable because they are each associated with one-and-only-one world. This results in non-unitary probability, and therefore must be false.
There's an equation showing how you can have an infinite number of different quantities. For example, I could have an infinite number of 3 leaf clovers or 4 leaf clovers. Technically there should be an equal amount of leaves if they're infinite, whether 3 or 4 leaf, but there always appears a different number of leaves in a specific location. Depending if they are infinite 3 or 4 leaves.
Great explanation!!!
Thanks for the video. My personal version of the many-worlds interpretation is as follows: I accept that it's as non-local as the other non-hidden-variable interpretations of quantum mechanics. And personally, I consider non-local correlation, though not non-local causation, to be perfectly acceptable (as the latter is forbidden by the speed of light, while the former isn't). The only motivation behind it is the idea that the collapse postulate is counterintuitive and that one runs into the thorny issues of, "well, what is an observer?" or "what if a dog uses the measurement device without your knowledge and you never find out directly what the dog measured?". Hence, I replace the collapse postulate with the idea that when you conduct a measurement, instead of the wave-function collapsing, your state becomes entangled with that of the wave-function. Entanglement has already been observed in experiments, with the Bell inequality tests being an example: the "Bell states" that have been observed to violate Bell's theorem (an example of this is a superposition of 2 electrons getting deflected and the same 2 not getting deflected). Let's say an electron is in a superposition of being deflected by a beam-splitter and not being deflected. A measurement would put the system in a superposition of the electron being deflected and the measurement happening accordingly and the electron not being deflected and the measurement happening accordingly. Entanglement of the observer with the system observed would appear to an observer to be a collapse, because there are no physical methods for consciousness of different states to talk to each other. And this solves the thorny issue of "what is an observer?": an observer can be anything that can be entangled with something else. As for the case with the dog: the state becomes a superposition of the electron being deflected and the dog observing it that way and the electron being not deflected and the dog observing it that way, and the probabilities of you measuring this new state is similar to what you'd get from a measuring (or rather, getting entangled with) a superposition of 2 electrons getting deflected and the same 2 electrons not getting deflected.
To my understanding, this is similar to Everett's original argument, but I don't claim it's local, in the sense that when you get entangled with a state, you (as a rule) get entangled with everything that you're getting entangled with was already entangled with, no matter how far away it is. (that said, all entanglements must be caused by a local event)
The world is perfectly local. Your premise is already wrong. ;-)
you are the person who better explains concepts in the whole internet. thanks you are brilliant Sabine
10:19 I think you mean the many "many worlds interpretation" interpretations.
Dang. Just when I thought I had it figured out. Thanks Sabine .
Sabina, can you do a clip on Penroses objective reduction hypothesis? AFAIK, I’d does away with the need for interpretation altogether. Poses a bigger challenge instead, of course :)
Dang, it was cool to consider that the universe easily deals with unfathomable (to us animals) infinity, and that it already had, neatly self-contained in some sort of hypersphere, not only the knowledge of the universe from start to finish (already 😮), but casually also the awesome infinite possibilities of everything that ever could happen, from start to finish; and we were simply metaphorical ants near blindly traversing that, from one possible moment to another, believing we're on a much more simplistic plane. 😳🐜🌌
Sabine casually talks about things that I could almost could if I sat and thought about them and nothing else for fifty years.
Keep doing so, all Sabine's videos on MWI prove is that she is curiously ignorant of what the theory actually says and what it implies.
To illustrate this there's a point in this video where she literally asks for an explanation about why conscious perception doesn't encompass all of the outcomes of experiments seen by different copies of itself, this when she knows full well those copies are each in their own causally disconnected universes.
Her critique's of the theory are like this in general; almost seemingly intellectually disingenuous and flawed logically on a basic level. Most of the time it requires advanced knowledge of the subject to see this is the case but I point out the example above as it doesn't and even someone only aware of her own provided description of it can see isn't valid.
If you want me to explain the issues with most of her other dismissive claims about the theory feel free to ask, there's too much to go into everything.
@@jyjjy7say hi to Elvis for me.
In the Many Worlds Interpretation, the observers also fork and each observes their own outcomes. Why would an observer see into other worlds? That would suddenly make the 'observer' definition problematic too.
Averaging all the parallel words, we get the expected probability distributions that QM gives us.
If one outcome is more probable than others, then does that mean that that outcome branches off multiple times? How exactly does that work? For the probabilities to pan out, you don't just need a new world for each possible outcome, you need many, many new worlds for each possible outcome.
@@erinm9445 I think a many worlder would say that the branching happens at the moment of the quantum event going one way or another even though there might be a higher probability of one over the other therefore there is no need for muliple branches.
Personally I'm not convinced though there's no way we can know.
Your many branches depending on probability idea might be consistant with the existance of other dimensions undetectable by us. I've read that the many worlds branching is not consistant with extra dimensions but I would say we have to expand our understanding of what a dimension could be. After all we already have two kinds of dimension, why not more.
6:40 the technical term of the combination of the two reasons of QM non locality is that correlations of QM are holistic (essentially what "entanglement" wants to express).
Thank you for bringing up this point about how a pure many worlds interpretation doesn't replicate born probabilities. Attempts to derive the Born Rule always seem to work by invoking a seemingly enticing assumption that ends up being equivalent to what they were trying to prove.
In the many-worlds interpretation, the many-worlds interpretation can have infinite names. 😂
Hey Sabine, I'm loving the quizwithit experience! It's really quick so it barerly adds to the length of the video. I'd like to offer some feedback: when you complete the quiz, some of the answers are provided to us, but then the page blocks the rest of them with the message: "Join now to uncover your rest quiz results!". Shouldn't it say "Join now to uncover the rest of your quiz resuts!"?
2:16 Sabine talking about too much beer……whilst misspelling “interpretation” cracked me up😂
The problem is right there in the title: it includes the word interpretation. So, any physics discussion that involves an interpretation will be just that - a discussion with no hard and fast conclusion.
"The major challenge for many worlds is to explain why the thing we call many worlds does not itself branch with those worlds and therefore sees all the outcomes, but somehow randomly only experiences one of those worlds." (7:25)
I don't see this as a problem if the observer is branched off with the rest universe into many worlds, but can only observe the world they are in and cannot know if the other worlds exist. So if the observer is Sabine there may be many, perhaps an infinite number of Sabines in many, perhaps an infinite number of worlds. I'm sure we all consider that a delightful prospect.
Mind you in some of those worlds Sabine will be not very bright, not very attractive and perpetually grumpy. Not in this world of course.
Yes!
An easy mistake to make, but QM never predits anybody to experience themselves in a superposition. The challenge Sabine talks about simply does not come up.
It only does if the scientist takes themselves out of the equation as if they were not also subject to the same time propagation governed by the Schrödinger equation. We like to do that, because it feels so very uncomfortable to continuously branch and not be unique.
I look forward to seeing a discussion between Sabine and Sean Carroll.
I still see the MWI as the simpler explanation and think Sabine looked at some bad explanation of it. It removes extra rules and only comes at the cost of introducing a huge probability multiverse. A small price to pay for simplicity.
Yes, MWI is a simple logical error. You can find it in the second sentence of Everett's thesis. ;-)
What is the logical error in his sentence: "A physical system is described completely by a state function PSI,
which is an element of a Hilbert space, and which furthermore gives information only concerning the probabilities of the results of various observations which can be made on the system"@@schmetterling4477
@@schmetterling4477 what type of logic error?
@@rsm3t He didn't understand that the wave function describes an ensemble average, i.e. an infinite number of independent repetitions of an experiment. He then assigns it as a state function to a single system. It is this counting error that creates infinite copies of the universe. Everett could simply not count properly.
I asked what type of logic error and instead, you made claims (unsupported of course) about what Everett did or didn't understand.
"Let not your heart be troubled. In my father's house there are many rooms I will go and make a place for you." I'm going with Universes branching off like cells divide in mitosis or some other micro division which is re-presented in the macro. I feel like there is many things we can draw cues from in viewing the Universe as a fractal. The etymology of words also seems like an important place to look for answers as to how the Universe works. Interpreting the syllables of words to form a sentence I think also gives many amazing clues especially scientific words. Like biology (mode of life the word), phospholipids (light bearer which gives form to the word as what appears), Ribosomes represent the process described in the story of Adam and Eve and the conscious - subconscious reflection like the evening reflects the day or energy radiates out as everything like E equals MC2. Cytoplasm is the word across the waters.
👍⚛️🔯⚕️
Whales need plankton so no worries
Good morning Mam
Mam I have been following your channel since a while trying to learn new things about various aspects of physics
Mam recently I have to resolve one of the great mysteries of the universe that is the black holes and I have formulated a mathematical equation which tells us the exact speed to move through different black holes
Mam I request you to please guide me on this topics
I hope with your precious help I may be able to bring this formula in front of the whole World
We can't deny a flying spaghetti monster either. But if we have a Word for universe then it better actually mean universe. One thing to group everything, absolutely everything. Including multiple words. In other words a house with many rooms that also contains it self.
FLat earthers doing extra thinking.
I think the biggest thing that makes MWI persuasive, is asking the question... why did we find a particle in one place but not another place? Why is it not deterministic? MWI basically says... well it is deterministic. The particle is all of those places, but you as a large quantum mechanical object can't exist in multiple branches of the universe at once, so you can only see one result. The result you see can't be fully predicted because you can't travel the multiverse to enter a branch of your own choosing, however you can make a good estimation. So when you make the measurement you are measuring your own position too.
In other words it's a lot like being puzzled at how a coin can come up both heads and tails despite seemingly being a single object. It makes more sense to realise that the coin is a simple object which has both heads and tails, and the complexity arises because you can only see one face of the coin at a time. If you could see both sides at once, it would cease to be an object of chance, and be very predictable.
We are never finding "particles" anywhere. We are only detecting quanta of energy. Quanta of energy are always being detected where the detector is. Their "position" is not "their position". It's the position of the detector.
1:36: 🌌 The Many Worlds Interpretation of quantum mechanics suggests that parallel universes exist where anything that can happen, does happen.
1:36: The wave-function of small particles, like electrons, describes the probability of finding them in a particular place.
2:00: According to the Copenhagen Interpretation, nothing has definite properties until it is measured.
2:28: The measurement problem in quantum mechanics refers to the switch from a particle described by a wave-function to a particle with a definite property after measurement.
3:07: Sending a photon through a beam splitter creates a superposition of possibilities, but measurement collapses the wave-function and determines the outcome.
3:45: 🔬 The video discusses the non-locality of quantum mechanics and the possibility of hidden variables models and the Many Worlds interpretation to restore locality.
3:45: Updating the wave-function is necessary to obtain correct probabilities in quantum mechanics.
4:14: The wave-function update is instantaneous and non-local, leading to the concept of 'spooky action at a distance.'
4:45: The non-locality of quantum mechanics depends on whether it is fundamentally correct or just a description of an underlying reality.
4:57: Hidden variables models propose that there is an underlying reality determining measurement outcomes, making it possible for the world to be local.
6:43: Many Worlds interpretation suggests that all outcomes of a measurement happen in separate universes, explaining the appearance of wave-function collapse.
6:57: The challenge for Many Worlds is explaining why observers do not branch with the worlds and see all outcomes.
7:38: 🌍 The Many Worlds interpretation of quantum mechanics suggests that every possible outcome of a measurement exists in a parallel universe.
7:38: The Many Worlds interpretation assumes that observers only experience one outcome, but the reason for this is unclear.
8:06: Each time a quantum particle interacts with another, the universe splits into multiple branches, allowing for all possible outcomes to occur.
8:43: Energy conservation is maintained in the Many Worlds interpretation by assigning probabilities to each branch based on its existence.
9:18: Supporters of Many Worlds argue that it is simpler than the standard interpretation, but it still requires assumptions about measurements and probabilities.
9:43: There are multiple versions of the Many Worlds interpretation, each with slight differences in how they handle branching and measurements.
10:25: To make the Many Worlds interpretation work, additional axioms need to be added, which essentially perform the same function as the collapse postulate in standard quantum mechanics.
10:51: Different interpretations of quantum mechanics, such as QuBism, offer alternative ways to update the wave-function without the collapse postulate.
11:25: 🔍 The Many Worlds interpretation of quantum mechanics is not simpler or more local than the standard interpretation, and it cannot avoid Bell's theorem.
11:25: The Many Worlds interpretation replaces the collapse postulate with other axioms, making it just as non-local as the standard interpretation.
13:07: Physicists have written papers on making Many Worlds local, but this would require introducing hidden variables to transport information locally.
13:21: The EPR paper by Einstein, Podolsky, and Rosen argued that quantum mechanics is incomplete because it lacks a local element of reality.
13:57: Bell's theorem shows that all local theories predict correlations that conflict with observations, which includes the Many Worlds interpretation.
14:28: Many Worlds supporters want to believe their theory is local, but it is not supported by the evidence.
14:39: Many Worlds adherents claim to avoid Bell's theorem by introducing the 'one world' assumption, but this assumption is not hidden and removing it makes the theorem irrelevant.
14:50: Observational fact shows that we only observe one outcome of a measurement, which is the basis for Bell's theorem.
15:20: 🌌 The Many Worlds interpretation of quantum mechanics is neither wrong nor unscientific, but it is as problematic as standard quantum mechanics.
15:20: The Many Worlds interpretation does not introduce anything new and is still non-local.
15:31: The Many Worlds interpretation gives the same results as the standard interpretation when the collapse postulate is replaced with assumptions about branching worlds.
15:47: The existence of other worlds in the Many Worlds interpretation cannot be observed or proven.
16:09: The Many Worlds interpretation is not related to the path integral.
16:21: The paths in the path integral only exist before the measurement, while the branches in the Many Worlds interpretation exist after the measurement.
16:35: The Many Worlds interpretation is as problematic as standard quantum mechanics.
16:50: Believing in the existence of parallel universes is a personal choice as it cannot be confirmed or ruled out.
Recap by Tammy AI
Some people who play with mathematics make the mistake of thinking that they are dealing with the real world. Maths is fun, but let's keep our feet on the ground.
I have a firm belief that nothing is verifiably 'true' until both an engineer and physicist agree that it is. Theoretical physicists seem to forget that whole 'theoretical' thing.
This video comes with a quiz which you can take here: quizwithit.com/start_thequiz/1696811301328x301364883622124100
A theory can be accurate or useful and at the same time incorrect.
Quantum Mechanics is very clever nonsense
For an observer to see the totality of outcomes, they would have to exist in all of those universes simultaneously while their neural firings still manage to converge on a single interpretation - the everywhere all at once interpretation. Doesn't seem that hard to grok to me why it's not a feasible possibility.
We already know based on testable empirical material evidence that the hidden variable does exist and it is non-local... so you’re wrong assuming that the existence of a hidden variable would mean QM is n’t fundamentally correct.
Nothing is deterministic but the probability and likelihood of the same thing repeating itself is very high... one thing I can determine is that you can't get Superman powers and take off and fly around and save the world... your choices are limited therefore there's no free will.
What are the problems with observation in a mini worlds interpretation is that the past doesn't really exist nor does the future. You can't die until it's your time to die. You will just switch Universe versions with different versions of everyone and everything until all existence feels completely alien...
This is absolutely convoluted reasoning. Quantum particles (energy perturbations) in a field, definitely have a position at any instance in time…but they are moving at such an unbelievably high velocity that you need to guess their position using a wave function ( because they move like waves). When you measure them, duh…there they are…stopped by the detectors (which also collapses the wave properties of the particle). The sooner we get off the denial train the better!
What I find compelling is this:
If you have an electron in a superposition of A and B, then you fire another electron at it and it interacts in a way that's affected by the state of the first, it'll then be in a superposition of A* and B*. And the whole system will be in a superposition of |AA*>+|BB*>.
I'm not sure if this is the Many Worlds Interpretation, but I suspect that's how measurement works - we don't actually collapse the particle, we just join the superposition. So if we measure an electron in that same superposition, then the electron-physicist system is now in a superposition of |Am(A)>+|BM(B)>.
And in that instance, there's no reason to expect the split physicists to have any knowledge of one another - after all, the split realities of the electron don't interact with one another.
Is that the Many Worlds Interpretation? Or is it subtlety different?
You will never find an individual electron in superposition. That's just a complete misunderstanding of actual physical observations.
Im not a physicist, but an IT guy. Hearing all this makes me think of the nyquist theorem (aliasing when measuring signals). It states that you must measure at least twice as frequently as the highest frequency of signal you are trying to measure so that you can reconstruct it. Is it possible we aren't measuring frequently enough and therefore can't reconstruct the wave function?
No, it's not about the frequency of measurement. We know the multiple branches (or superposition components) exist because they interfere with each other, even in very carefully designed experiments. See, e.g., the delayed choice eraser.
No, that isn't possible, because the wave function is not physically observable, it is a purely abstract mathematical construct we invoke to *explain* what we observe. Also keep in mind, it's not just humans that can "observe" things, it's all particles in the universe. Photons of light, make our observations, and they travel at the speed limit for causality / information. So you quite literally cannot measure things faster than that. I am pretty sure we have even measured things in planck time (the shortest possible length traveled at the fastest possible speed our theories allow) and the wave function persists.
In IT you don't have these difficulties, because you're not trying to explain observation at the quantum level. it's simply sufficient for you to say the frequencies you observe on the screen, explain what you observe. But that's not sufficient at the fundamental level of particle physics.
@@Google_Censored_Commenter Sabine never brought up that the Copenhagen interpretation is often associated with needing a sentient observer for quantum physics to function, something I find more laughable than many worlds.
@@hugegamer5988 that's because that association is false, and Sabine doesn't want to spread misinformation?
@@Google_Censored_CommenterThat's not entirely true. You can't measure one particle's wave function, but you can measure lots of particles and reconstruct a wave function.
Mary Jane Rubinstein has described the many worlds hypothesis as essentially having all of the characteristics of a religious belief system.
By that logic, really any scientific hypothesis or interpretation of any scientific theory should be considered to have the "characteristics of a religious belief system" for the proponents of said hypothesis/interpretation.
@@frede1905"... really any scientific hypothesis..." ??
Where are all these other scientific hypotheses that have such zealots as proponents and so little evidence ( better saying " not evidence at all") that is specific for them?
@@frede1905Only just two come in mind: supersymmetry and holographic principle.
But , at least, these two have some theoretical motivation and they're related to AdS/ CFT correspondence ( that is arguably a conjecture, too, but is supported by theoretical evidence and so on...). Now that I'm thinking about it, these also have some proponents that look like zealots too...
Isn't any religious belief a hypothesis? They believe something that has not yet been proven?
@@dimitrispapadimitriou5622 What makes you think the proponents of MW are "zealots"? Even if you think there are some proponents that are, then why generalize it to all proponents? Do you consider everyone who has contributed to developing MW as a "zealot"?
When I think of the multi-world hypothesis I think of Florida in the winter time. It gets terribly crowded
. Traffic moves at a crawl. The number of accidents goes way up. And that's the way the universe ends, not with a whimper but a big bang.
I never understood how we go from "anything that can happen does happen" to "anything can happen." Maybe pizza on Mars was an impossibility?
It would've been better to include many worlds supported ideas as well. In my understanding, the math is the same, but the wave function collapse is just replaced with entanglement of the observer with the result, so a particular version only sees one possible result.
The entanglement with the observer is not a many worlds specific idea. It is one of the ways of giving physicality to the wave function update. Understanding that very solipsistic mechanism is key to understanding most if not all the really mind bending interpretations of quantum mechanics.
Instantaneous collapse of the wave function = FASTER THAN LIGHT communication!
Probability can travel faster than light -- spooky action at a distance.
Wave function collapse implies that probability travels instantaneously and is therefore by definition travelling faster than light.
Nothing can travel faster than light -- Einstein.
Spooky action at a distance = FASTER THAN LIGHT!
"Always Two there are! -- Yoda.
Probability collapse has infinite velocity?
You can build a double or dual split experiment to confirm this with a very large screen placed on the moon!
I am confused. Why does many worlds need something to transport information? If I have a machine that puts an apple in 1 box and an orange in another, when I open a box I instantly know what is in the other box, but has any information been transported? Isn't this what many world's does?
Yes. I think in this case Sabine may be confused ;)
Well, no, in many worlds you open the box, and in an infinite amount of the universes you get an apple, which then tells the other box contents to transform into an orange. In an infinite amount of universes it happens the other way.
Putting fruit in boxes isn't anything to do with quantum mechanics and would be entirely deterministic.
There would be no branching under many words.
If you put a particle in each box and measure its spin in many worlds you have a split. Rather than the super position collapsing the universe branches. Or in some versions the superposition extends to the rest of the universe.
Thanks. Going to Neil.
What is many worlds interpretation and how it can be explained by string theory
The Many-Worlds Interpretation (MWI) is a quantum physics interpretation that suggests that every possible outcome of a quantum measurement actually occurs in its own separate branch of the universe, resulting in a vast number of parallel universes.
In the context of string theory, which is a theoretical framework aiming to unify fundamental forces and describe the universe at the quantum level, the MWI can be seen as a consequence of the fundamental principles of quantum mechanics. String theory doesn't directly explain MWI, but it provides a framework for understanding the quantum behavior of particles, which can be used to discuss MWI within a multiverse perspective. However, it's important to note that MWI remains a topic of debate and interpretation within the broader field of quantum mechanics and isn't exclusive to string theory.
I see another big problem with the MWI: It tries to describe a nonlinear reality with a linear equation. If the universal wave function governed by some linear Schrödinger type equation were all that exists, then the multiverse could isomorphically be described in a diagonal basis of the associated Hamiltonian. In this basis, the "many worlds" are non-interacting due to the superposition principle and have each an eigenvalue of the Hamiltonian as their definite energy, which means their wave function branches are stationary and the only thing that happens is phase rotating. It doesn't make any sense that reality as we now it should be equivalent to a collection of non-interacting universes, in each of which nothing ever happens.
Are mushrooms or LSD involved with the people who came up with this theory?
The Many Worlds theory is a fantastic, robust, and versatile tool for science fiction. This is its primary purpose.
The Many Dinosaurs interpretation of fossils is a fantastic, robust, and versatile tool for science fiction. This is its primary purpose.
So when you die there is only heaven or hell
The popular image of Many Worlds can indeed make for good sci-fi, but a more accurate image of Many Worlds can make for _better_ sci-fi.
"You do _not_ want to see the equations."
Instantaneous collapse of the wave function = FASTER THAN LIGHT communication!
Probability can travel faster than light -- spooky action at a distance.
Wave function collapse implies that probability travels instantaneously and is therefore by definition travelling faster than light.
Nothing can travel faster than light -- Einstein.
Spooky action at a distance = FASTER THAN LIGHT!
"Always Two there are! -- Yoda.
Probability collapse has infinite velocity?
You can build a double or dual split experiment to confirm this with a very large screen placed on the moon!
Hehehe, I admit, my eyes started rolling before I got to the twist ending of your comment. Well done! 😄👏🏻
9:01 Hang on, though. That means the Universe we actually measure can only be assigned an energy proportional to the probability of its occurrence. Which is vanishingly small. And which is not conserved, because it decreases by some huge factor every time there is another branching point.
So the only “energy” being conserved would be “total energy of all the Universes”, which is something we can never measure, and therefore seems meaningless.
The MW interpretation is the reason I can't find my keys when I know I put them in a particular place. In one branch, I put them there, but in my present world I didn't. I've slipped into another world. Give me excuses for a lot of my mishaps.
Or it's the 'little people'. But that's a special case of the Mandela Effect.