Pilot Waves vs Many Worlds | Wife Reacts to Quantum Mechanics (Part 2)

the interactions aren't classical but the properties are okay i'm glad that we can be so choosy about how we're doing this this is wonderful [Music] this episode was made possible by generous supporters on patreon something that's very important to keep in mind as we move forward right that quantum mechanics sort of brings to light a discrepancy in how people view physics sure we like to view physics as though we're finding some deeper understanding about the universe but it's not really what physics is about physics is about making predictions okay right we want to be able to science is about making predictions right well exactly so this what we try to do in physics is we try to come up with a model that's going to predict future behaviors of things right so in this case quantum mechanics is predicting future behaviors of quantums or you know little quantum particles right okay it allows us to make accurate predictions correct using this branch of science right but this video this video is about what we call interpretations of quantum mechanics okay so even though this model is very good at making predictions and everyone agrees that that's true many of us still want it to also give us a deeper understanding of physics and of the universe the problem is there are a lot of possible ways to interpret it that haven't been ruled out by experiment yet i'm sure that that's difficult it is it's very difficult cutting edge science you know and i guess just uh just to be clear this video is not a comprehensive list of interpretations of quantum mechanics it is just we're just covering a few examples to get an idea of why it's so difficult to do this one cannot cover everything right one of the first major interpretations is called the copenhagen interpretation and don't don't get on my case about this i'm just talking about history here i know there's a lot of are we feeling a little defensive here all right there are a lot of a lot of copenhagen interpretation haters out there okay you're not condoning it you're just stating that this is an interpretation that exists right but first we're going to start with there's actually like two different kinds there's something we call the weak copenhagen interpretation and the strong copenhagen interpretation and i assume that this does not actually have to do with like how scientifically like verbose they are no it has to do with how strongly it speaks about the nature of the universe okay so the original one the one that they i think it was heisenberg in 1929 talked about this interpretation and this one is the weak interpretation okay we're basically it's called weak because it doesn't really interpret anything it takes the stance that you were saying earlier where well maybe it doesn't actually say anything about the universe it's just a really good model that makes great predictions sure and if it's a good model that makes great predictions i mean it doesn't it's not useless you know what i mean right that was uh a pretty decent place to be it's it's summarized in one one statement that a lot of quantum physics teachers like to use shut up and calculate oh sure i've heard this before yeah okay i'm sure i've said it before i'm sure that's where i've heard it before right that's sort of the idea like stop trying to read into any of any of this stuff just shut up calculate the prediction and move on with your life i mean i have to be honest if i was a physicist this would be appealing to me that's very much my personality type right it takes the philosophy out of it it does uh it's a very experimental approach as a theoretical physicist uh i can't stand for that so we're gonna try and take some more uh we're gonna take some stronger approaches to this all right so next up the strong copenhagen interpretation which is something that's developed over the last you know the several decades after heisenberg gave this talk which was in 29 29 yeah it takes it one step further and says not only does this wave function for an electron describe the electrons behavior once it's used to calculate something the wave function before the collapse is also something that physically exists it is at a thing that is real and says something about the universe okay about that electron that we're trying to examine okay so the weak one says this isn't actually real it's just math that helps us predict things right and the strong one says it is math and it does help us predict things and also it's real right okay right that the wave function is a very real thing and that is literally how the electron exists before it collapses into one of these regular states so for the weak one what do they think the electron exists as if not the wave function they don't they don't think electrons exist it is a very agnostic approach to quantum mechanics we're not going to make any judgments at all i see about the electron i see i feel like that's not useful or helpful because the electron does exist though right so somehow the point because it like i said it's a very experimental approach so it's very useful in just setting your preconceived notions aside making the calculations maybe building something like a transistor which is the foundation of all modern electronics i find it so interesting that this ends up being i mean we're not going to make any judgments about electrons but also we're going to go ahead and make an actual thing that utilizes electrons i feel like these two things don't don't go together as you can imagine like i mean none of these interpretations we're going to be talking about today would exist if people were satisfied with that okay fair enough it was just uh let's just put this aside and move on but then you know people would come up and be like hold on a second we need all types right okay all right right one of the things that we're going to find as we go through today is that all interpretations of quantum mechanics have a problem different problems diff different problems for example the strong copenhagen interpretation that says electrons exist as this superposition the major problem that that has is something we call determinism that things are planned out ahead of time right things are not random the universe is not random then everything is determined right right it takes things like free will out of the picture right there are a lot of physicists out there that have a really huge problem with quantum mechanics being non-deterministic and so this idea this strong copenhagen interpretation that that these particles are inherently probabilistic is a problem for people but it because it violates determinism it says that the universe is not deterministic we'll hate to be the bearer of bad news but if the science says that it's not deterministic it's probabilistic then like update yourselves that's my opinion on that quantum physicists have tried to come up with a way for quantum mechanics to be deterministic okay they've tried to force it i was going to say let's squeeze it into the box the problem with a lot of these different interpretations is that when you you come up with a way to interpret quantum mechanics so that it fixes one problem it creates a different one sure believable also i would just like to say that i am innately against doing science with a particular goal in mind that's not how science is done you're not doing good science so i'm i'm going into this interpretation judging it what ends up getting sacrificed when you force determinism onto quantum mechanics is something we call causality okay the order of cause and effect the best ways i've found to define each of these things determinism and causality is that determinism is that the universe is is not random probabilities are only zero or one zero or a hundred percent okay there is no fifty percent chance of anything it either is going to happen or it isn't going to happen that's determinism okay causality is like i said it's the the order of cause and effect it's that causes in the past lead to effects or events in the future the idea that if we knew everything about all of the particles in the universe right now we could predict the entire history past and future and so this new interpretation doesn't abide by that right in order to get determinism back into quantum mechanics we have to sacrifice causality usually okay there is an entire category of interpretations of quantum mechanics called retrocausality not only can effects travel into the future from the past they can also travel into the past from the future wonderful they can retro retroactively cause something so retro causality right so that's the that's the idea okay why how tell me how we came to this conclusion uh i mean it's not really a conclusion it's just a guess tell me how we came to this guess all right so there's one example it's called the uh the transactional interpretation where basically a particle like an electron creates and it has a wave function associated with it right okay and so what ends up happening is this wave function which it is affected by wave functions traveling from the past right some other particle in the past its wave function moves forward into the future and it affects this electron sure that makes sense right now the idea is that particles complete wave function is a past and future wave function so not only are things sending information into the future to affect particles and events in the future they're also sending wave function another half of their wave function into the past to affect events in the past are all events affected by each wave function that is produced it can get rather complicated if your system isn't isolated but that's true of anything in quantum mechanics isolated systems don't exist right unless you're talking about the universe right right right so technically it's not possible but we get close enough that these effects start to show up not the retro causality effects but probably probability quantum mechanics stuff all right so the idea is that when you have you take a measurement in the future the particles involved in that experiment that measurement can travel back in time and change the behavior of the particle you measured so anyway the point is retrocausality yes fixes the determinism problem right so we can look back and we can say oh well these two entangled particles they had they had stuff you know they they were they were predetermined to do what they were going to do but like it's only because there are signals traveling forward and backward in time and because the experiment sent information back in time to affect the particles to make them do certain things because they know that you did the experiment in the future because retro causality okay that's complicated i think that you all should know that i hate time travel uh innately in movies or whatever it always is so complicated right so i am not inclined to jump on board with this one uh and if you've seen any of my videos you know that i don't think time travel is possible so i'm sure you can guess how i feel about retro causality okay so retro causality is something that fixes determinism some of the time right but quantum entanglement also brings up another problem okay we have two other issues that come into play not just determinism and causality but also something we call locality and realism locality and realism right okay locality is essentially that a particle can only be influenced by things adjacent to its location right next to it well so that would innately disagree with the quantum entanglement thing that we just talked about right so that's that's a problem that quantum entanglement we need to address okay essentially locality means that the speed of light limit is maintained in all circumstances okay things cannot travel faster than light now realism is that particles always have single classical properties they behave just like billiard balls okay it's just that we don't understand what's happening enough but they do exist classically they exist classically but we don't understand how they work right i feel like that's an oxymoron that will make sense as we cover some of these next couple of interpretations okay but in 1965 there's this guy named john stewart bell he came up with and designed an experiment that proves without a doubt that locality and realism cannot happen at the same time it is physically impossible it either follows classical mechanics or it has classical properties or it interacts with local particles right but not at the same time right and so what we say is that local realism not a thing now you can have non-local realism where particles interact over vast distances violating the speed of light limit but are real and have real properties or can you be real and have real properties while violating the speed of light apparently some people think so i feel like that doesn't make sense so that's one option the other option is that you have non-real locality the speed of light limit is maintained but these particles don't have properties before you measure them i think that's my favorite one that seems to make the most sense to me okay that one happens to be a at least the example we're going to talk about that does that is going to be the one that is is gaining a lot of popularity lately so let's start with the one that violates locality okay that lets particles interact over any distance instantaneously but classically but exist with actual properties okay the interactions aren't classical but the properties are okay i'm glad that we can be so choosy about how we're doing this this is wonderful so this first one is something called the pilot wave model pilot as in like a pilot or pilot as in like the first one pilot is in like a pilot okay the idea is that the waves that are described in quantum mechanics aren't the actual particles they're just these waves that exist in the space in some other something that we don't understand we said we're doing non-local realism right now right yes okay yes the idea is that there's some kind of substance that we don't understand not an actual like substance but okay there is something that fills the universe that has waves in it and those waves guide the particles and so they only look like they behave randomly because there's this very complex wave stuff happening underneath them on the quantum level right and so these little tiny itty-bitty quantum waves if you were to imagine some kind of like little i don't know like a little styrofoam ball floating on the surface of a tank of water and then you put waves in the water the particle's gonna do all sorts of weird stuff right right because this wave is affecting it a wave that we can't see sure and quantum mechanics describes describes the wave in that stuff okay it doesn't describe the actual particles i am what disinclined to or whatever i don't like it i i know it sounds completely ridiculous it does but i feel like we're not following occam's razor at this point right i don't think we are with the other one either but we'll get to that in a minute oh no okay so the idea there is that the particles are like billiard balls they have properties they do exist in the way that we understand particles to exist they're just affected by this complex like undercurrent they are not the wave but there are waves and they affect them yes okay and whatever this stuff is that's waving can violate the speed of light limit even though the particles themselves can't this is very complex yes now this does address the quantum entanglement problem because if this substance can yes and i say that with sarcasm in my voice this substance communicates faster than light then it's okay for one particle to immediately collapse the wave function of the other particle because these waves are happening in this like under material sure this under substance that's controlling the quantum world it's the under substance right i'm i'm making it sound like science fiction uh but like it's pretty it's pretty close i mean think about it yeah i mean technically it's all science fiction until it's experimentally validated right right so this one is called the many worlds interpretation oh here we are here we are heard of that one before uh i think a lot of people would have been very disappointed if i didn't talk about this today well let's do it then the idea with the many worlds model interpretation i should say is that there are an infinite number of universes and there is essentially one wave function that describes the entire multiverse okay a very complex wave function and as certain interactions take place and measurements happen the wave functions the sort of subway functions of each individual universe become unentangled or they start in this sort of entangled state where they're all related to each other and then once measurements are made once it becomes known to the universe not necessarily to a person once it becomes known what kind of state the particle is in the universe kind of splits it sounds like you're saying that all of these waves that there are enough waves for like all of the splitting that it's eventually going to be doing like all of those waves exist yes but that would also sound pretty deterministic though yes yes because it has to you already have to have that wave existing in order for it to split yes right right and so that's this is a major a major reason that this model this interpretation is so popular it's because it's only problem is realism okay it is deterministic it's causal and it's local it just isn't real it's not real right no big deal this is fine we're fine okay so so the idea is that these universes split apart now it doesn't mean that an entire universe is created at the measurement it's often described like that and that's completely ridiculous that's not what's happening we're saying that is the ridiculous thing here glad we ironed that out we're gonna draw the line the idea is that all these universes already exist it's just that they become unentangled and separate from each other they existed before they were just entangled and now they're not okay when that information becomes known to the universe about these particles they become separated in the multiverse the quantum multiverse this is wild yes i just feel like when you're talking about particles the number of universes that we're talking about is absurd right i mean particles and events with those particles right i mean because you're not even talking about people doing something you know what i mean you're talking about particles doing something and there's there's so many so many it's an unimaginable number of universes that's what i'm trying to say right but it's not real so it's okay well we're saying that the particles aren't particles i know it's funny to say that it's not real but that's not really what realism is saying so that's the idea right that the the universe is you can map them across time so it's causal the probability of something an event happening in the multiverse somewhere is equal to one or one hundred percent you just might not be in the universe where it happens but it does happen so it is deterministic and so if there's a 50 50 chance in quantum mechanics that says oh well this event is going to happen or it's not going to happen like a radioactive decay of a particle or something what the many worlds interpretation says is well that does happen in half the universe is and it doesn't in the other half sure but it happens somewhere right if there's a chance if there's a non-zero chance it's going to happen it happens somewhere in the multiverse right i mean which is kind of comforting on one side sure and uh concerning on the other side right but the effects are local right so there's localities maintained because the interaction happens locally right it doesn't happen over vast distances this is okay with quantum entanglement because everything's deterministic and causal the the particle on earth and the particle on mars don't have to communicate with each other they were already predetermined to be the way they were we just didn't know about it i don't love that determinism isn't my favorite thing well because it doesn't allow for free will and i i have a problem with that sure which is why i am very very firmly under the non-deterministic umbrella yeah whatever interpretation i get behind it better be non-deterministic or i'm not getting behind it sure the hardcore physicists are starting to get really get behind this mini world's interpretation but not the softcore physicist definitely not me when i was starting to like really dive into this and learn about it i i can understand why it's so appealing to people it solves so many problems but it does it in a way that i feel violates the most important tenet of coming up with a model and that is occam's razor right agree we have to assume a a an infinite or nearly infinite number of universes exist even though we have no physical evidence whatsoever that they exist right that cannot be the like least complicated answer right occam's razor does not say that explanations can't be complicated it just says that we need to start with the simpler ones right and if we rule them all out and we arrive at something that's complicated then so be it uh that's how quantum mechanics happened but i think that i think there are better options i think it's good to have many hypotheses right yes because it's it's good to be able to like get a new idea and assess it see how it works see how it doesn't work and then when you see that like there are x y and z reasons why this doesn't appear to be the one let's move on to the next one you know what i mean i think that it's not good science to get caught on one hypothesis and just keep beating it to death trying to make it work for you and i'm not talking about the many worlds specifically i mean for any of them in general something we expect out of scientists in general right if you're gonna oppose if you're going to propose an alternative explanation for something you better also at the same time propose a way to test it yeah or else what good is it what good is is a proposed explanation without an experiment that you can do to test it right agree and i acknowledge that our whole conversation today existed because we just don't have the experimental means to test these right hypotheses but that means that they do need to be treated as such though right i think that's the biggest problem with the many worlds interpretation is that it's it is completely untestable right there is literally no experiment you can come up with that allows us to test whether or not other universes exist at least as far as we know as right now right i'm not discounting it in the future but i it there's we can't see any way to do that and that sort of extends to all of the interpretations right the reason we have so many that still work is because we don't have a way to test any of them yet yet just gotta give it give it some time scientists get on it it's not gonna be us it's gotta be you right right now the thing is none of these interpretations go against what quantum the math and quantum mechanics says the math supports them all right the idea here is that we're trying to explain what the math means what do the probabilities in quantum mechanics actually mean about the universe okay out of all four of these things determinism causality locality and realism in my personal opinion locality is the most important of the four you like things being able to interact with each other right so it would go in order of importance i would say locality causality determinism and then realism okay i'm generally okay with that i'm open to a discussion about the last two realism versus determinism but i think locality is more important than realism and so i am willing to sacrifice realism to maintain locality and there are so many times in the history of physics where we have like we've come across a situation where we we thought locality was broken only to discover a few years later that it wasn't actually broken that we just didn't understand what was going on sure right and i i don't think that this is an exception so i think locality is maintained okay on that note do you feel like you have a deeper understanding of the problems that quantum physicists face i do feel like i have a deeper understanding of the problems i didn't know where that question was gonna go and i honestly didn't know if i was gonna be able to answer yes to it but that question absolutely yes i can answer awesome the goal of this video was to give people an idea of like why this this process is so difficult and like what obstacles we're facing as we try to answer these questions sure and what some of the issues are with the different not just the issues like some of the good things that they have going for them and then also the the things they don't have going for them right sure what about you guys did you feel like you got a decent idea of why this problem is so hard let us know in the comments and until next time remember it's okay to be a little crazy right things don't just teleport like that i mean they can under some circumstances but it's okay it's not like the star trek transporter well it's not like the star trek is it

Channel: The Science Asylum

Views: 207,065

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Id: MYX5Mo7IRqA

Length: 27min 57sec (1677 seconds)

Published: Wed Dec 23 2020