The Biggest Ideas in the Universe | 8. Entanglement

[@jeremyroy99]

Physics students of the 60s had the Feynman Lectures in print form. We have a Sean Carroll KZbin playlist. What a time to be alive.

[@richardlinter4111]

@Astute Cingulus : Quite right, but GR can be extrapolated to the Planck scale. It's just that doing so we find it disagrees with QM. This I believe is actually Sean's point, or one of them.

[@richardlinter4111]

Amen.

[@ssshurley]

Jeremy Roy Your right. I bet they were loving the print lectures. Hahah

[@tricky778]

In the 60s they had Feynman lectures on cine film, in person, and had tutorials with him directly, plus drinking with him I bet

[@GuRuGeorge03]

we are living in the McDonalidization of knowledge. Type a few words into google on a device the size of your hand and nearly all knowledge of humanity is literally at your fingertips. Now we just need people to enjoy it as much as they do McDonald's

[@seancarroll]

Hey, sorry for the mixup with the previous version of this video! Somehow I uploaded the wrong version, I had to delete it. This one should be better in both audio and video quality.

[@Nietzsche_K_Gote]

I love listening to you explain about things I never and always knew I as curious about

[@CuriousCauliflowerX]

Less tearducts, more physics, great!

[@seandimmock5813]

Sean Carroll let us know when that textbook is out!!!! Can’t wait!!!!!!

[@coecovideo]

All good, thanks

[@bombproofmetal]

All of these videos have been amazing thank you so much for your hard work.

[@robbyjohnson6531]

I am artist with very little understanding of physics. I have been so interested in my whole life, and five or so years ago, gave up on my attempt to understand or appreciate the subjects that you've been teaching in this series. This is exactly what I've been hoping for for so damn long! I have the drive to learn more about this stuff again. Every episode starts with me doubting myself, that I'm too stupid to get it, and ends with my mind being blown, and feeling like I have a new outlook on my ability to understand... well, anything.

[@schmetterling4477]

You are correct. You have very little understanding of physics. :-)

[@Dr10Jeeps]

How lucky we are to have people like Dr. Carroll willing to share their knowledge of physics with us! I love it.

[@dude124353]

Entanglement, yes! Been trying to get my head around it for awhile now, every time I think I have it there's more around the corner, angular momentum was an entire rabbit-hole on its own. Thank you for sharing your knowledge Sean, your videos are my favourite for explanations of complex ideas.

[@scottmiller4295]

this may be off, but i simply think of it as particles sharing information aka energy and the more they share the more entangled that they become. to the point you get stuff like us. any time particles interact in the universe and share information i tend to think entaglement is all over all the time and not wierd at all. i look at information as the key and the type of information secondary. but i could be and probably am way the hell off.

[@billyjoe2128]

Complex ideas?? Just being plugged in and realizing nothing is impossible. Upward and onwards All day everyday

[@Wandering_Chemist]

I would read Nobel Prize winning John Bell’s book, “Speakable and Unspeakable in Quantum Mechanics.” To really understand his Nobel Prize winning theory that was confirmed experimentally, Bell’s Theorem.

[@harstar12345]

quickly becoming my favourite series on KZbin.

[@rage9715]

Hope it continues after the lockdown even if he does them less frequently.

[@rage9715]

@Astute Cingulus I miss carolin crawford/Ian Morison both fantastic speakers.

[@yishaimendelsohn620]

Ditto

[@jolly39j]

@@yishaimendelsohn620 too For for the day that we wayHome From At f get rest f, to get d74^3

[@cmacmenow]

Love that every so often Sean's hand slips in and out of "phase spacetime" when he becomes more demonstratively excited! Always thought he might actually be a many worlds traveler. Confirmation; seeing is believing!

[@eminem2]

If you want to see a great man with no pretentious ego, Sean Carroll is one such !!!

[@DomainRider]

Wow! - Entanglement in a purple hot tub! Isolation doesn't get much better than this!! Thank you Sean, for the highlight of my week :)

[@rc5989]

Another great video, Professor Carroll! Also, I have read the professor’s latest book, Something Deeply Hidden, and I highly recommend it to anyone who really enjoys this video and wants to learn more about the foundations of QM.

[@tripp8833]

Learn linear algebra if you want to actually get the foundations of QM

[@johnp1]

Another good reading: Sean's CV. It's impressive. www.preposterousuniverse.com/cv/

[@avadhutd1403]

Please share Ur insight 1.whats Ur thought on experiment that monkey is sit on type writer and one of possible worlds it creates Shakespeare play ,or quantum immortality,these are the weird implications What's Ur thought folks please share

[@isabelab6851]

tripp I look that in my first year of college in 1981! I have not used real math graduation

[@sevrjukov]

These talks are absolutely phenomenal. Prof. Carroll is an excellent educator, who is able to convey very difficult topics in an easy, understandable manner, making them reachable for broad audience without scientific training. Thank you, prof. Carroll!

[@Bronett]

I so enjoy these lectures! With the entanglement episode, you made me think of the story about the blind men and the elephant. Each touching a different part of the animal and from that having an opinion about the nature of the creature. It is hard to state what the entirety of something is (and exciting!) - not knowing the whole creature… Thank you so much! Henry B.

[@life42theuniverse]

47:00 A interesting observation I had one day. I was entering the mall one day and some doors were automatic some were of the manual variation. You could see by the wear in the ground how much each was used. It reminded me of the double slit experiment. But it was people and shopping destinations.

[@longFlatTable]

Sean, very smooth talk, I really like it. You used two particles/waves collision as an example for entanglement. It makes sense to me but this is the first time I hear that kind of use case in entanglement. The two particles collision case can be seen as following Newton’s 3rd law of action vs reaction, although this is QM which makes Newton’s law dubious. A more interesting case is the action over distance in gravitational force. Has anybody tried to apply the entanglement idea to explain action over distance in gravitational force? It seems there are different types of entanglement. The spin-based entanglement is one type, the two particles/waves collision you mentioned here is another and the action over distance in gravitational force is yet another.

[@incoathwetrust4612]

Sean, thanks for putting out these amazing lectures. You are an incredible teacher! I honestly feel that these videos have much more utility than all the nonsensical and pseudo-sophisticated "Theory of Everything" garbage being propagated by certain individuals (e.g. Weinstein and Wolfram) who are not even directly involved with the established physics community. Kudos to your efforts! I'll be looking for your undergrad QM textbook when it comes out.

[@jonathansharir-smith6683]

Is he actually working on an undergrad QM textbook? Asking because I have no doubt that would be an amazingly lucid intro to a difficult subject. Maybe he can answer on his next Q&A!

[@jonathansharir-smith6683]

Aaaaand lo and behold, 3 minutes in he answers my question. Looking forward to it.

[@FreekaPista]

I think what Wolfram and Weinstein are doing is still massively important to the physics community, but their efforts are *very* niche in application. We are at a point where string theory isn't able to be confirmed experimentally (yet) so having some other theories is definitely beneficial in case string theory doesn't pan out. But those new theories really aren't relevant yet either, especially not to those without a career in physics that can make sense of their arguments and mathematics. An overabundance of ideas is never a problem in science, but if understanding Quantum theories is just a hobby for you, it's worth cutting out most of the noise until scientists can reach a new consensus (or at least start moving towards one).

[@dustinirwin1]

@@nihlify True, but these vids are based in what we know of the universe and our theories of the implications of this knowledge. Weinstein is talking about rulers and protractors in a way that I find to be completely incoherent. His "hidden knowledge" that he's been afraid to reveal for the trauma it might bring us. OK fine. But perhaps he could discuss with an educated peer who has the knowledge to at least work through what he's trying to say and challenge him in the foundational ideas.

[@evanbauer2590]

@@dustinirwin1 Weinstien is talking nonsense clearly. A decent analogy would be Jay-z and Nas (just because he wear a kufi doesn't mean that he bright.) He uses big words and obfuscates the point. He is the type of person who seems smart to dumb people.

[@deansundquist9601]

Favorite video in the series thus far! Thanks Dr C.

[@philjamieson5572]

I'm glad that I live in a universe that has people like Sean Carroll. I never get tired of reading his stuff.

[@NikkiTrudelle]

You’re really good at making the equations seem less scary, and explaining the reason behind the numbers.

[@DeanBatha]

The best explanation of entanglement I've ever heard.

[@joshoowa]

It confuses me that you say the observation itself collapses a wave into a particle. What seems to be the case is that, in order to observe, you’re introducing an environment which collapses the wave into a particle. It isn’t the act of observing itself that does anything at all but rather the other matter introduced to the subject which has the effect.

[@peterb9481]

I think in episode two of this series ‘Carroll’s Cat’ certainly was not sleeping. Good video.

[@stephenbryant7873]

Feynman, Susskind, Carroll ... three great explainers, but with very different styles and emphases. I can’t say which is more influential, but I am so glad that Sean has decided that this is a good use of his time. For me, these talks are very accessible.

[@veronicanoordzee6440]

Susskind, the cookies-munster?

[@Thedudeabides803]

I barely understand algebra, but I still listen to these beginning to end with complete interest. thanks sean

[@_Nibi]

k

[@ToriKo_]

36:00 Adam Becker’s book What is Real, and Bell’s theorems, non-local and local hidden variables, 42:00 superdeterminism, 1:13:00 a short explanations of how Many Worlds is falsifiable, and objections to do with ontology (?)/ metaphysics (?), hermeneutics (interpretation?), etc etc

[@davegrundgeiger9063]

I just discovered this series of videos, and I'm like a vegan in a tofu store. Any update on the undergrad quantum physics textbook mention at 1:38? I searched on Amazon and at preposterousuniverse and didn't find anything. Thanks so much for this great series!

[@jeffbass1165]

Wooo! Been refreshing the page all day waiting for this :)

[@paulmichaelfreedman8334]

Or you can click the bell icon.....

[@FulguroGeek]

The fact that im listening to many quantum physic explaination doccument video or podcast or conference show how small we know about it because almost if i click anywhere in the video after 5 minutes we always comeback to talk about the particules react diferently in the observer point of view and in real life situation when the influence of the observeris not there or because the observer cannot see because its something to see its something that behave and change state. if find it really interresting to listen because i dont dont know if its the same thing as someone who is learning a language and by listening a lot of it you are able to figuere it out more and more in your head. Now that its been almost 5 years where i listen almost everything i can find on the subject i can more and more represent it in my head . Thanks for doing your job that way thats a great way you are a great speaker too .

[@jcpmac1]

Dear Professor Carroll Many thanks indeed for your very clear explanation. One particular puzzle stood out for me, though. You point out (at about 21:03) that in the wavefunction Psi [2] measurement the result of Alice finding her particle having spin up is that she instantly knows that Bob's will also be spin up too. You then go on to say that in a variation of the measurement, wavefunction Psi [3], particles can be anti-correlated, so that when Alice measures her particle to be spin up, Bob will measure his to be spin down. How are Alice and Bob able tell which of the two types of wavefunction they're dealing with? I suppose they must have some way of telling otherwise neither Alice nor Bob can have any knowledge of the other's particle. Does this mean, then, that it's possible for the two wavefunctions Psi [2] and Psi [3] to be set up in advance to be either correlated or uncorrelated, thus having some control of the outcome of the measurement?

[@resurrectedstarships]

26:45 what if you could change the spin of the eelctron, forcing the opposite spin on the other side, which would then be communications....is that possible? Aren't the spins of electrons altered all the time as a matter of course??

[@schmetterling4477]

No, it is not possible.

[@petrt88]

I have heard about entanglement many times. But this was super duper explanation Professor! Finally it does not seem as a pure magic for me anymore. Thank you for this.

[@RolandRhodes1]

This is so enjoyable. Great teaching. Thank you for doing this.

[@dustinirwin1]

I really appreciate how neutral you are with your preferred theory while being objective in fairly expressing the alternatives. That said, many worlds feels an awful lot like string theory to me, though instead of making up n dimensions, we make up n worlds. Something about it feels off to me. But that's just a suspicion!

[@KungFuKeni]

I suggest you watch the many worlds part of the video again. Sean Carrol is trying to stress really hard that the many world's theory does not 'predict/assume' the existence of other worlds/universes. The theory just states two postulates which IMO are unequivocally true. The 'other worlds' come about when you try and attach meaning to the theory, ie how you INTERPRET the theory. Ofc the other branches of the wavefunction cannot just be ignored, after all they must be there for some reason, but you shouldn't be dismissing the theory just because it's hard to interpret.

[@ToriKo_]

13:00 Sean gives a solid definition of entanglement after motivating it the previous 13 mins. I have a feeling this episode is going to be crucial for a lot of moving parts. I think now in part I am able to articulate some thoughts around the (DSE) double split experiment, which is supposed to highlight the wave-ness of stuff, which collapses into particle-ness when we detect/observe it. We also have this idea and assumption of “a (physical) system”, which might come into play as confusing. So we have some electrons that are being fired out of a gun, through two slits as wave-like, and collapse as they (singular) hit the detector. My sense, which may be wrong, is that the wave collapses as we observe it, which means we are detecting it, which really means it is being entangled with the physical system of the detector. But how does this wave like form leave the gun, which is also a physical system, go through the slits, the walls of which are physical systems, and then hit the detector, a physical system, but only get entangled (collapsed) at the last step? If we are all in the same universe, kind of by definition a universe entangled with itself, how could we ever see directly or indirectly, wave like properties?

[@ph6560]

I can't wait for the upcoming class/episode! Mr. Carroll is the best "teacher" (I've watched quite a few online) in QM I've come across. Really hope he continues to produce classes (and alike) about QM for the unforeseeable future!

[@TheAuriconGroup]

I had some sadness in my life related to the covad-19 thing. The only way I could remove my self from the sadness was to watch this video (I read your latest book). Your talk took me to another place where I had to think really hard to follow along. Not that I understand it all, but it is so very helpful. Thank you.

[@brucegoodwin634]

I hear your pain. Take a hug? Keep plugging…

[@TheAuriconGroup]

@@brucegoodwin634 Thank you so much Bruce. Yea, I will take that hug and back at 'ya. I am so very pleased that Dr. Carroll is doing this series. It expands my mind. What a wonderful thing for him to do. It is like the best collage teacher you ever had.

[@jerryrobbins5013]

best podcast ever. i had to rewind a few times to get things again. you're a great science communicator, thank you so much.

[@Villinos]

This man's voice makes my day.

[@DeanBatha]

Sean, I downloaded the "Universe Splitter" app that you mentioned In your book, "Something Deeply Hidden," which I am still enjoying reading. I asked it if I should "Study physics" or "Waste my time." It told me to waste my time. A few minutes later, I asked the same question again. It told me to "Study physics." I now feel myself in a superposition between studying physics and wasting my time.

[@Cooldrums777]

Dean Batha No. You have split into two worlds. In one world Dean studies physics, in the other world Dean wastes his time. Since you are watching this videos the Dean I'm responding to now is studying physics. In the other world, Dean never bothered to post this comment on KZbin and is wasting his time. LOLOLOL. Dean was in a superposition BEFORE you used the "Universe Splitter" app. That in a nutshell is many worlds.

[@wgcar]

Three comments: 1. Thanks for another fantastic discussion. I now feel much better about “Entanglement.” (Meaning I will no longer fall asleep wondering about it.) 2. I agree 100% with Jeremy Roy's comment below. 3. I certainly did not know it, but it now looks like I am a “fan of” some Alternative Theorem. The cat still gets me but I’ll wait for your discussion on “measurement” before firmly taking a position.

[@walkercatenaccio]

This is probably the best talk so far of a great series. I finally understand (a little) "Many Worlds," which had always seemed ridiculous to me. It was the orthogonal axes that did it.

[@expchrist]

1:10:58 "many worlds is plug and play ... for those of us who are interested in pushing the laws of physics beyond what we currently know into more speculative realms ... hidden variables are not nearly as compelling as many worlds." I seem to remember that Feynman stressed this point quite a bit. So can you elaborate a little bit and make some predictions to help better explain this point? The next big breakthrough in QM and QFT that incorporates gravity or solves some big problem, can you assign probabilities to what the authors of that paper are likely to believe as their preferred interpretation of Quantum Mechanics? Probability that the author is a believer in Everettian interpretations of QM? Probability that the author is a believer in Bohmian Mechanic interpretations of QM? Spontaneous Collapse? Cubism? Some variant of the Copenhagen interpretation?

[@alexrsnh]

This was my favorite of this series so far, and they're all great. Brian Greene also provides a really good explanation of Bell's Theorem in "The Fabric of the Cosmos."

[@thoel1]

OMG! From the 1st lesson about basic calculus, Sean reached the point of negotiating the deepest questions of the present. I'm afraid this means that gradually this wonderful series is coming to an end... :( Anyway thank you so much Sean...

[@robinbrowne5419]

Tralfamadorian teacher: "Joey, did you copy your cousin's homework?" "Ummmmm....." "Well. We measured his homework and yours was exactly the opposite."

[@QuantumBell-xp1qg]

This is the best description of the problem I have seen so far. I'm not convinced of the many worlds or super determinism interpretations. Adam Becker's book (What is Real) -- mentioned in the talk, is an excellent perspective. Nonetheless , I would recommend to everyone on my team, and our collaborators, to watch this to escape their comfort zone of the façade of Newtonianism.

[@schmetterling4477]

And your team are three fish and an ant farm? ;-)

[@thiennganguyen]

This is the best ‘Many World Interpretation’ that I have heard! Thank you so much! I still don’t believe this is how it works. I personally like the ‘Wave Collapsing’ theory better! I’ll wait to see how it turns out!

[@sambarta9865]

The wave collapse almost seems more magical and hence probably wrong to me. It gives too much to consciousness and woo talk. Many world's seems magically unreal in a different way but entanglement makes it seem more intuitive

[@argyriosvlastos321]

Thank you! for making more accessible, these highly abstract and technical concepts to those of us who love physics and...and assuming we're not stupid! SC a fantastic human being, thank you sir for sharing!

[@cl37167]

Dang! I thought I understood Sean's answer to the question in the last video of "What is waving in the wave function?" until this video came and shattered that perception. I thought he was talking about spacetime, but now I see he wasn't. It goes deeper than that. Incredibly fascinating stuff, but I am continually cursing the limits of my intellect. I know I wont' ever fully comprehend these concepts, but the challenge is great fun. Keep 'em coming, Sean.

[@3dlabs99]

Amazing how fast you can make these videos -- I love the quarantine :)

[@goltltamas]

The real “Mr. Universe”! Just awesome! Thank you for this video (too) Mr. Carroll! Me: never stop learning just sometimes “sleep a bit longer”! 😉

[@sleepyangel22]

Thank you so much Mr. Carroll for these series of videos. It's my end of day everyday and I've been learning a lot about these subjects. More than the lectures and I've seen a lot of them. Thank you so much!

[@henrydavidpurple8323]

You’re the man Sean. Thank you for doing these.

[@Markoul11]

Thank you Prof. Sean Carroll for this passionate thorough and science loving presentation about the subject of QE and not only and specially for its interpretation in the the many worlds theory context. I kept and cherished specially your phrase that decoherence is the entanglement of the quantum particle with the "environment". QE, superposition and all the "quantum weirdness" could be resolved by simply examining that what is very obvious possibility for me and was all the time in front of our nose, that vacuum 3D Cartesian space is a medium in an underlying intrinsic superluminal energy state and that our matter Universe is actually the phase transition of this superluminous medium to luminous or lower energy states. In this context, all "spooky actions at a distance" in our spacetime domain and frame of reference, would appear instantaneous as actions would propagate instantly as it would appear to us and timeless intrinsically in this underlying vacuum space superluminous energy state connecting all actions and phenomena like a gel. Einstein said that there can be no superluminous energy state but he was referring to our spacetime 3D reality domain. That necessarily does not mean that there can not be an underlying higher energy state to our Universe which is completely invisible to us... well not completely, QE is one hint.

[@ausblob263]

Thank you for taking the time to do these videos they are great. You are respectful and dont assume you are talking to a room full of kids thanks for all the details and real explanantion this is a very valuable video series.

[@Avenged7Xsick]

A few questions: What relation does many worlds have to the arrow of time? Can wave functions branch "backward" in time? If not, why is the wave function time asymmetric? Does the present moment have multiple possible pasts? Is entropy related to many worlds in any way? Could many worlds be emergent from a more fundamental law of the universe, such as for example, "all things that can exist do" and the branching then happens when different logically consistent possible realities can no longer logically exist together anymore? Could the laws of physics as we observe them be the original branches of the universe? Could other branches have other laws of physics or different values for universal constants? Also, thanks so much for making these videos! I hope you truly understand and internalize the impact they have on the world and especially to your viewers.

[@tomhepz]

As for the entropy and the arrow of time, QM has the exact same princple, the worlds decohere, and there are many more decohered states, and so statistically you move to a state of 'lower entropy' but there is a tiny tiny change just as there is with entropy that they will 'recohere' but it's so insignificant that you don't need to worry about it

[@dajandroid]

I think that the entropy question with regard to the Everettian interpretation was briefly mentioned in Professor Carroll’s Google lecture but I wonder if he could expand on it here in this “The Biggest Ideas” series?

[@iainmackenzieUK]

7:00. When two 'waves' meet, my sense is that they disturb one another at the moment of 'impact' but then move on through undisturbed. (This is what I teach my A-level students about superposition.) So could you please tell us in the QnA session: Why is this different with the wave function? Why do we get this 'spherical resultant wavefunction'. What is it about the wavefunction that makes it NOT like an emag wave for example...

[@kindlin]

I think it's just because these are not just waves, but particles that interact. If you take two photons, they can pass right through each other and emerge unchanged at the other end of the 'collision,' but if you take a photon and electron, or any other pair of particles that interact with each other, when they are 'close enough' they pass information back and forth and scatter, or annihilate, or what have you.

[@inanconur9220]

A 1:20:29 long video on solely entanglement. This is unique

[@arpansircar8858]

Questions: - 1. In the spin example, can the wave function be of the form: 1/sqrt(3) [ (up,up) (down,down) (up,down) ] - in that case if A measures up, the measurement of B is not immediately determined - is this also an entangled system then ? 2. It seems that the concept of many worlds comes out as a result of Everett's 2 postulates. However, is it possible to design an experiment to test the concept of many worlds ? 3. A request: would you please re-do the double-slit experiment explanation from the point of view of many worlds rather than Copenhagen

[@arpansircar8858]

2) Yeah I think he may have said something like that 3) As far as I can recall, in PBS Space Time they used the Copenhagen explanation, I can re-check. Do let me know if you have any link to a video which explains the Double Slit using Many-Worlds

[@JohnDlugosz]

@@chriswarburton4296 *affects

[@rufusapplebee1428]

Live Forever and Prosper, Sean Carroll. Live Forever Young and Prosper, Sean Carroll.

[@damianerangey]

This has finally answered my questions on entanglement, I love popular science descriptions, however at times, you just need to run through the fundamentals.

[@Les537]

You have quite the visual style, Dr. Carroll. It reminds me of '80s era VCR tapes for some reason. Love all your content.

[@stephenkamenar]

i like the intro with his floating head in space

[@DEFIT_Riddlix]

Very interesting stuff explained in a way everyone can understand it. Thanks, Sean.

[@bartk07]

The perfect duet - Sean Carroll with The Biggest Ideas and Brian Greene with Your daily equation. I could hear and learn from them all day long.

[@stephenkamenar]

i sometimes get those 2 guys mixed up

[@adriancook9742]

Thanks for these videos. Wish I could buy them.

[@bendavis2234]

The book you mentioned, "What is Real", is an amazing read that covers the history of QM interpretations and the measurement problem. It's a must read for anyone fascinated about the story of Quantum Mechanics and all of the controversy surrounding it.

[@bruinflight]

OH MY LORD. I never thought I would understand entanglement. Sean you are AMAZING.

[@puppetpron2073]

Thank you for all of your lectures, you make complex subjects more understandable, (although I can't follow the math). I wish I had a instructor or they told us this stuff when I was a kid I might have gone into Quantum Mechanics.

[@VideoFunForAll]

Fantastic work! The main three issues I have are: 1. I am having some trouble with the given description of what superdeterminism is. I understand it differently and I am not sure superdeterminism is getting a fair chance by the given explanation. 2. Electrons do not spin in a classical way, a small disclaimer that quantum spinning is yet another strange quantum phenomenon would have avoided people taking spinning literally. 3. The decoherence argument I find totally unconvincing. To quote: "they evolve completely independently, they do not affect each other....", well, that's not true since they are in superposition so one does have to continue to take the "sum" of it.

[@Czeckie]

This was so good, thank you Sean. Additionally, I really enjoyed Mindscape episodes with Adam Becker and your solo episode about this very topic, I really liked the idea how space is basically and emergent property - two things being close is defined as being able to entangle with each other. I've bought myself a copy, but haven't got the chance to read it yet. I have two questions about the video: 1) Decoherence. Why don't atoms destabilize? We saw that electron fired into a cloud chamber is behaving pretty classically and not like a blob of uncertainty. You explain it like it's getting entangled with everything around. I like that. But how come the electrons in atoms don't de-cohere when every other atom from vicinity is bouncing into them? As we've seen in the previous lecture, the work of Planck-Bohr-de Broglie-Schrödinger explained the electron in an atom needs to be quantum and classical particle just doesn't work. 2) There're projects of 'quantum reconstruction.' Mathematically minded people are trying to rediscover quantum mechanics from simple foundations and derive it mathematically. This is because some people are uneasy because Planck, Heisenberg, Schrödinger and others basically just guessed it. Some of these are based on quantum thermodynamics or quantum information theory. Are these approaches compatible with many worlds?

[@davidcrabtree4718]

Let a thousand flowers 🌺 bloom across the multiverse of speculative ideas.

[@TanioDiazSantos]

Thanks a lot for the videos. I have some Qs for the Q&A: 1) Is there any kind of "profound" connection between each of the conservation laws and each pair of conjugate variables in Heisenberg's unc. principle(s)? Is there a one-to-one relation, or one can arise from the other? 2) Isn't the dismissal of "super-determinism" at odds with the acceptance of the Anthropic principle (which I'm also fond of but...)? If I understand well, it's not about the experiments being able to be imagined, but whether some outcomes will ever happen or not. Accepting the Anthropic principle implies that many of them won't, because those are not the outcomes that would allow us to be here to measure them. And that's very similar to the idea of "super-determinism". 3) Could you comment a bit more on how non-locality fits in the MW interpretation? The idea of decoherence being triggered by the environment seems somewhat local to me (or at least it appears; maybe it's just the word). Does decoherence/branching happen instantaneously everywhere or does it propagate at c? Also, can be particles entangled in any property that is not part of any of the Heisenberg unc. principle(s)? (or conservation laws?). Thanks again!

[@Nixontheman]

Thanks for posting, surprisingly easy to follow. 👍

[@psmoyer63]

Sean Carroll, you did an excellent job. Even your Everettian bias was exceptionally well tempered. But you murdered superdeterminism. Where you could have used some creativity to show how Schroedinger's sleepy cat's lack of free will might be predetermining some of the elements of the experiment to begin with, you simply killed him off. So much for the kinder gentler Sean.

[@Wandering_Chemist]

32:50 This far in and I’m not hearing anything about Bell’s Theorem! He better not disappoint me 😅 36:10 And of Dr. Carroll comes through again!

[@charonme]

in which videos do you talk more about the probabilities mentioned at 1:07:56 ?

[@smoozerish]

Fantastic body of work with these videos. Well done. Keep it up.

[@SandyCameron]

This is really good informative stuff Prof Carroll. I really want to thank you for making all these videos - this one in particular. The nature of entanglement and quantum decoherence leaves me wondering if it will be possible to actually build a useful quantum computer - or if decoherence will present insurmountable technical problems

[@reinerwilhelms-tricarico344]

This is what went through my head following your interesting lecture: Isn't the Schrödinger cat problematic just a consequence of our thinking in categories, which we turn in a slight of hand into discrete states of nature? It reminds very much of the cow as a point mass. I have never seen a cat that is in the state of being asleep, or in the state of hunting mice (but I have seen a cat sleeping and possibly dreaming about hunting mice). This whole idea of physical state is great, especially when you can assess it quantitatively and make predictions about it, but for almost everything else of greater complexity it remains just an empty abstraction. How many possible states has a large molecule made up of 10,000 atoms? How many states has your brain with all its10^11 neurons, each one of which being as complex as a little universe? And, since you mention of course the Schrödinger equation of which that monstrosity is supposed to be a solution, one might challenge you to write down the Hamiltonian for that :-) The "solution" of integrating the cat, the entire apparatus, and the observer (with brain and guts and laptop) into one grand wave function seems attractive on first glance, but it is still an unbelievably great leap of faith to generalize from an entangled state of a few atoms (or even a million atoms) to "the Psi function of the universe". Some religious person might ask - does it include God? How far have we really moved away from trying to answer the question how many angels fit on a needle tip?

[@dcquence]

I like this format with the virtual blackboard

[@pettiprue]

Biggest entanglement in your lockdown hair X I so enjoy your stuff. Thank you.

[@nickstu2355]

Your version of Schroedinger's cat doesn't work because the cat is likely to be asleep either way

[@jeffbass1165]

This all makes perfect sense for simple entanglement like spin-up and spin-down, but I still just can't wrap my head around position entanglement. Wouldn't the universe split infinitely often for every different position that an electron could be in, for example?

[@jimlake5404]

This raises a question in my mind. You have two balls, a red one and a blue one. Pick one at random, don't look at it, and send it to Pluto. Then look at the one you kept. If it is red, you know the other one on Pluto is blue. There's nothing spooky about that. No FTL travel required. Please explain how what you are saying is different.

[@ArnoldBlues]

Those balls are not quantum in nature. The real revelation of quantum mechanics is that the state of a quantum system is not definite until it is measured. I’d suggest reading more about Bell’s Theorem and the tests of it.

[@etienga]

Entanglement finally clicked! While the spin example is simpler to write down, the conservation of momentum illustration is much more intuitive.

[@posseydon6891]

Q: Can you please show us exactly why the "glove analogy" fails in explaining quantum entanglement ? (We buy 1 pair of gloves, put each individual glove into a box at random. Bob takes one box on a trip to some distant star. Once he opens the box and see right glove, he instantly knows that Alice has the left one) BTW. awesome video, thanks!

[@posseydon6891]

​@@nihlify thx a lot, indeed well explained by Brian Greene in "Your Daily Equations #21" kzbin.info/www/bejne/i4vMqKecp86mirM, and the answer boils down to >5/9 vs 50-50 as shown in the experiment.

[@Filipe9171]

This playlist is gold

[@AndrewCMumm-sf2yo]

If I was studying quantum mechanics at uni, I would be thrilled to have these "big picture" videos

[@ABuffaloDub]

Thanks for the podcasts and videos. I appreciate you.

[@zoranivanic3543]

I am a simple man. I see Sean Carroll channel. I subscribe.

[@JoeHynes284]

it helped me so much to read his book first and then watch these videos :)

[@johnlawrence2757]

Entanglement: one of those words whose meaning changes as the year passes. Like iconic. I am old enough to remember when it involved splitting a quantum particle in two, consigning each of the halves to opposite sides of the universe, then tapping one to make the other jump simultaneously. The logistics of such an experiment were always rather fascinating, I thought. But then I can remember when an icon was a small painting on wood of a Christian subject created in the Byzantine era of the Roman Empire in Constantinople Ah me, those were the days

[@johnwollenbecker1500]

Fun times to be so entangled with KZbin.

[@michaeljames5936]

All well and good Herr Schrodinger, but let's see you get the cat into the box in the first place. Might i suggest you propose a simpler and less painful experiment such as 'Schrodinger's tortoise.'

[@charlesmurphy8978]

I have a question, Mr Carroll. Why do complex numbers are necessary to describe a wave function? I've never had a satisfactory answer to this question during my undergraduate studies in physics.

[@fkafka123]

Dr. Carroll, I enjoy this series immensely. But as a layperson, I'm unsure how to conceptualize many worlds. When I consider the myriad branch points of the wave function, am I to think that the physical realization of each term occupies different dimensions of Hilbert space? Is this the barrier between worlds? Does the Born Rule have any impact on what space is occupied? What is the relationship in physical space? Does the matter making up the new world come into existence after the branch? How can it be generated to keep up with an infinite number of splits in an infinite number of worlds?

[@sirilandgren]

This superdeterminism thing sounds a bit like how some people say that the laws of nature seem to "conspire" to prevent time travel to the past (and any paradoxes that might entail). Can you say something about this?

[@dimitrispapadimitriou5622]

I'm late to this but it's an interesting question. Superdeterminism is a " conspiracy theory" in the sense that presupposes extremely fine tuned initial conditions ( to mimic standard QM), so ot rejects " statistical independence". All conspiratorial hypotheses are based on the belief that something ( in this case " Nature") is cheating us, so we can't trust our observations. For Closed Timelike Curves( CTCs) , that could allow time travel to the past, the situation is very different: In this case the physical laws, although they allow CTCs theoretically, prevent them for existing in most physically possible situations. This does not require pre-adjusted initial conditions: On the contrary, fine tuned conditions are required for a CTC to exist. Imagine, for example, a complicated living organism that exists on a closed loop in time: We cannot isolate this being from the environment ( the air etc), so for this time loop to exist everything must be exactly the same; the loop happens only once, nothing can change. This is physically very implausible . Superdeterminism is even more implausible, because it's based on two coincidences: not only there have to be infinitely precise initial conditions, but these have to mimic, exactly, the correlations of standard quantum mechanics.

[@traelstechnologytmalsantua3471]

One way to shorten the variables between quantum gravity and any other equation relevant to gravity, is use an object for reference, so a chair for example would be, weight(w)+gravity? Being relative, but we'll Earth gravity for example, being so much amount of pressure being applied to an object. Weight+ Earth gravity+ anything seated on it or applying pressure to it= quantum gravity around the chair^2 basically creating a pi formula in which to reference for measurements.

[@HenrikScheel_]

The 2 slit experiment question; If you have a measurement device used to observe the electron which will only observe when switched on then the pattern will change as you switch the device on/off`?

[@mby_dk]

At 9:12 Sean refers to particle 1, but he should have said particle 2. At least as I see it. Afterwards he explains what happens in more detail, and here he gets it right.

[@clawpuss2]

Sean is making lockdown bearable.