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Could quantum mechanics be deterministic? · Daniel and Kelly’s Extraordinary Universe

0:09
Speaker 1: Quantum mechanics just doesn't seem to make sense. It tells
0:13
Speaker 1: us that the universe is fundamentally random, that some questions
0:17
Speaker 1: just don't have answers, that there's a limit to what
0:20
Speaker 1: can be known about reality, and that things change when
0:25
Speaker 1: we look at them. More than that, it tells us
0:27
Speaker 1: that reality is fundamentally different from what we have imagined.
0:31
Speaker 1: But what if that's not true? What if that's wrong?
0:34
Speaker 1: What if it were possible to build a theory of
0:37
Speaker 1: quantum mechanics that doesn't describe the universe as bizarrely random,
0:42
Speaker 1: that doesn't have any special role for observers, that doesn't
0:46
Speaker 1: suffer from the famous measurement problem, and that lets us
0:50
Speaker 1: think of the microscopic world as very similar to our
0:54
Speaker 1: familiar intuitive world. And what if this theory actually worked
0:58
Speaker 1: and was able to describe I've been predict experiments. That is,
1:02
Speaker 1: what if there's an intuitive alternative to mainstream quantum mechanics.
1:08
Speaker 1: If there were, why on Earth wouldn't it be embraced? Hi,
1:28
Speaker 1: I'm Daniel. I'm a particle physicist and a professor of
1:31
Speaker 1: physics that you see, Irvine, and I want to believe
1:34
Speaker 1: that the world makes sense. We are all drawn to
1:37
Speaker 1: basic questions about the nature of the universe. How does
1:40
Speaker 1: it work, why is it this way and not some
1:42
Speaker 1: other way? How did it all begin? And how will
1:45
Speaker 1: it all end? Physics is supposed to be a way
1:47
Speaker 1: to get answers to those questions, and so welcome to
1:51
Speaker 1: the podcast Daniel and Jorge explained the Universe and production
1:54
Speaker 1: of My Heart Radio, where this is precisely the kind
1:57
Speaker 1: of question we ask and the kind of answer we
2:00
Speaker 1: reach for. And the amazing thing is that physics kind
2:03
Speaker 1: of seems to work. It offers explanations, explanations that not
2:07
Speaker 1: only work because they could predict what happens in experiments,
2:11
Speaker 1: but explanations that usually make some kind of sense. The
2:15
Speaker 1: stories they tell us are mathematical and could be very
2:18
Speaker 1: different from the stories we guessed at. It turns out
2:20
Speaker 1: the Earth is billions of years old and not thousands,
2:23
Speaker 1: that stars are massive balls of fusion in the sky
2:26
Speaker 1: rather than tiny pin pricks in the screen. But in
2:28
Speaker 1: the end, these mathematical stories that physics tells us about
2:31
Speaker 1: the universe, they are coherent, they are sensible. We can
2:34
Speaker 1: use them to understand how the universe really is. Except
2:38
Speaker 1: in one area, quantum mechanics. While we do have a
2:42
Speaker 1: working theory, we struggle to make sense of it. What
2:45
Speaker 1: does it really mean? What is it telling us about
2:48
Speaker 1: how the world really is? And while we have lots
2:51
Speaker 1: of different interpretations, we struggle to accept the story that
2:55
Speaker 1: they tell us. Is the universe really random? Is everything
2:58
Speaker 1: really described by the wave function? Does it collapse when
3:02
Speaker 1: you observe it? Or split into millions of meta universes?
3:05
Speaker 1: Or do objects not really have any properties on their
3:08
Speaker 1: own to observe or all properties relative to the observer.
3:12
Speaker 1: None of these are easy to absorb, to click into
3:15
Speaker 1: our minds and let you say, oh, yeah, I get it,
3:18
Speaker 1: that's how the universe is. But what if there was
3:21
Speaker 1: a version of quantum mechanics that was more intuitive, that
3:24
Speaker 1: was deterministic, that didn't need some observer effect or multiple
3:29
Speaker 1: universes or a redefinition of the nature of reality. Well,
3:32
Speaker 1: today we will be exploring a less popular theory of
3:36
Speaker 1: quantum mechanics that doesn't rely on randomness and uncertainty. It
3:41
Speaker 1: tells us that what is happening to tiny particles is
3:44
Speaker 1: much simpler and easier to swallow, and we'll talk about
3:48
Speaker 1: why it's been overlooked by mainstream physics. So today on
3:52
Speaker 1: the podcast, we'll be asking the question the quantum mechanics
4:01
Speaker 1: have to be so random? My friend and co host
4:05
Speaker 1: Orges on a break, so I'm continuing our series of
4:07
Speaker 1: conversations with experts in quantum mechanics. We spoke to Adam
4:12
Speaker 1: Becker about mainstream quantum mechanics, to Carlo Rovelli about his
4:16
Speaker 1: theory of relational quantum mechanics, to Sean Carroll about the
4:21
Speaker 1: many world interpretation, and today we are speaking to an
4:24
Speaker 1: expert on pilot wave theory, also known as Boemian mechanics.
4:31
Speaker 1: So it's my great pleasure today to introduce all of
4:34
Speaker 1: you to Professor Valia Alori, who, if I understand correctly,
4:37
Speaker 1: holds two pH d s, one in physics and one
4:41
Speaker 1: in philosophy, so she's the perfect person for us to
4:44
Speaker 1: talk to about the crazy philosophical consequences of quantum mechanics.
4:48
Speaker 1: She's also a full professor in the Department of Philosophy
4:51
Speaker 1: at Northern Illinois University and a fellow at the John
4:54
Speaker 1: Bell Institute for Foundations of Physics. Professor A Lorii, welcome
4:58
Speaker 1: the podcast. Thank you for having me, well, thank you
5:01
Speaker 1: for coming here to talk to us about the mysteries
5:04
Speaker 1: of quantum mechanics. Before we get into the details of
5:07
Speaker 1: pilot wave theory, I thought we should take a step
5:09
Speaker 1: back and remind ourselves why we have so many theories
5:13
Speaker 1: of quantum mechanics and why there are still so many
5:16
Speaker 1: questions about it. To me, the basic question we have
5:19
Speaker 1: about quantum mechanics is what is going on? How do
5:23
Speaker 1: we understand the story that it's telling us. Our intuition
5:27
Speaker 1: is to think of particles as tiny dots of matter,
5:29
Speaker 1: but quantum mechanics usually tells us that they are basically different,
5:33
Speaker 1: that they are fundamentally different kinds of things because they
5:36
Speaker 1: can maintain two contradictory possibilities at once. There's also this
5:42
Speaker 1: wave function that seems to control what happens, but then
5:45
Speaker 1: it collapses when you touch it, but it's not clear
5:47
Speaker 1: what the rules of that collapse are. It's so hard
5:50
Speaker 1: to get a mental picture of what's going on with
5:53
Speaker 1: the little particles. So how do you approach this question
5:56
Speaker 1: of trying to understand what quantum mechanics? So first of all,
6:01
Speaker 1: let me just say that I'm not sure that we
6:04
Speaker 1: should understand quantum mechanics philosophically there is a sense in
6:09
Speaker 1: which we don't understand quantum mechanics even physically as a
6:13
Speaker 1: physical theory, because I mean, the theory seems to be
6:17
Speaker 1: talking about you know, electrons and protons and matter in
6:22
Speaker 1: general and fields, but when you actually look at the formalism,
6:26
Speaker 1: it's unclear exactly what plays the rollers of what. So
6:30
Speaker 1: we do have a an equation, the Shouldinger equation, which
6:33
Speaker 1: is a question of the evolution of the wave function.
6:35
Speaker 1: Should we understand the way function as a physical object.
6:39
Speaker 1: If the wave function is a physical object, what does
6:41
Speaker 1: it represent? Does it represent particles, does it represent fields?
6:45
Speaker 1: Since I was a student, just to put it bluntly,
6:48
Speaker 1: I really had trouble relating to the theory as a
6:51
Speaker 1: physics student. But even granting that the it's accurate to
6:55
Speaker 1: talk about that as a theory about something. Let's put
6:58
Speaker 1: it this way. The ory, I would say, is either
7:02
Speaker 1: empirically inadequate or it's incomplete. Why is that? Well, because
7:09
Speaker 1: I just said that, you do have this equation, which
7:11
Speaker 1: is the shrining equation, which is a again equestion of
7:15
Speaker 1: evolution of an objicle the wave function, and the wave
7:18
Speaker 1: function is a called like that because it's a wave
7:22
Speaker 1: so and wave can superimpose. You know, you throw a
7:26
Speaker 1: rock in the pond, right, throw another rock in the pond.
7:29
Speaker 1: Then you see waves from one rock and then you
7:32
Speaker 1: see the other rock. They superimposed. You have interference and
7:35
Speaker 1: the fraction of this kind of behavior that you would
7:37
Speaker 1: attribute to waves. Okay, And so since there's two superimposed.
7:42
Speaker 1: If you think of the wave functions are presenting objects
7:45
Speaker 1: of physical objects right at the microscopic level, they could
7:48
Speaker 1: be in a superposition state, right, and nucluse that adioactive
7:52
Speaker 1: substance of subsort could be in the superposition of a
7:55
Speaker 1: decade state or a non decade state. And by superposition
7:59
Speaker 1: you mean that there's two possibilities for an object. It
8:02
Speaker 1: could be spin up or spin down, or decade or
8:04
Speaker 1: not decade. There's two options for the situation. It can
8:08
Speaker 1: actually be in yes, in a sense, yes, more generally,
8:11
Speaker 1: I mean mathematically, this is the mathematical property of the equation, right.
8:14
Speaker 1: I mean the prototype example is the problem of the
8:17
Speaker 1: shrilling a cat, right, in which you do have this
8:19
Speaker 1: cat which is in a box. Right in the box
8:21
Speaker 1: that is this vial of poison. De vial of poison
8:24
Speaker 1: will break because it's connected to this radioactive substance, so
8:30
Speaker 1: it will break if the substance will decay. If nothing happens,
8:34
Speaker 1: it will not break. So what happens is that if
8:37
Speaker 1: the nucleus decase, bile of poison breaks and the cat dies. Okay,
8:42
Speaker 1: So that's a possible state of affairs. Otherwise nothing happens
8:46
Speaker 1: in the cat stays alive, okay. And so what happens
8:49
Speaker 1: is that, however, given the superposition state possibility, given the
8:54
Speaker 1: fact that there is a possibility of having a superposition
8:57
Speaker 1: state as a true physical state for this system, then
9:01
Speaker 1: you could also have this microscopic superposition of decade and
9:05
Speaker 1: not decayed, which actually spread out of the cat. And
9:08
Speaker 1: so the theory predicts this microscopic superposition which we never
9:13
Speaker 1: ever observed. They are not observable. That's not what we
9:16
Speaker 1: have experienced. Off So there is a very strong sense
9:20
Speaker 1: in which the theory as it is is empirically inadequate,
9:24
Speaker 1: because when we open the box and we when we
9:27
Speaker 1: check on the cat, the cat is either dad or alive.
9:30
Speaker 1: So what I'm hearing you saying is that quantum mechanics
9:33
Speaker 1: is useful as a description of these microscopic states. But
9:37
Speaker 1: which I think you mean like quantum particles, electrons and photons, etcetera.
9:41
Speaker 1: But that we don't really understand what it means and
9:44
Speaker 1: we can't access it directly. We can't like see these things.
9:47
Speaker 1: We have to interact with them using macroscopic objects like
9:50
Speaker 1: detectors or our fingers or cats, etcetera, which don't have
9:54
Speaker 1: the same quantum properties, And so it doesn't really answer
9:56
Speaker 1: the question of like, what's actually going on in the
9:59
Speaker 1: microscopic leve Is that a summary of the problem. Yes,
10:02
Speaker 1: Actually it's more than that. So not only doesn't explain
10:05
Speaker 1: what's going on intuitively at the microscopic level, but also
10:09
Speaker 1: if you try to apply the theory to everything, including
10:13
Speaker 1: cats and detectors and stuff like that, the theory doesn't
10:16
Speaker 1: give you what you observe. So it's really bad for
10:19
Speaker 1: the theory. The theory doesn't I mean, it is actually
10:22
Speaker 1: falsified directly by the fact that the training Garry question
10:25
Speaker 1: is it's a linear I think because you're saying that
10:28
Speaker 1: they suggest that cats should also be in superpositions, and
10:30
Speaker 1: fingers and detectors and everything should be in superpositions. But
10:33
Speaker 1: that's not what we observe. That's what you mean by
10:35
Speaker 1: experimentally falsifying, Yes, exactly, and of course, I mean, you know,
10:40
Speaker 1: the family fathers were not naive and the newness okay,
10:43
Speaker 1: and that's why they proposed, at least that's what for
10:45
Speaker 1: Neuman did, right. He proposed that there is actually a
10:49
Speaker 1: second evolution a question for the wave function. And so
10:52
Speaker 1: they say, okay, right, you don't want macroscopy superposition. Okay,
10:56
Speaker 1: So when do you get them again? Oh, when there
10:57
Speaker 1: is a measurement. Uh huh. So when the measurement is performed,
11:01
Speaker 1: then there is a different evolution equation. The wave function
11:04
Speaker 1: randomly collapses in one of the terms a superpositional when
11:08
Speaker 1: you open the door and you see the cat ha ha,
11:11
Speaker 1: the wave function actually collapses. So you write in a
11:15
Speaker 1: sense right as a detector, right, you collapse the wave function.
11:19
Speaker 1: The issue there is that we don't have a clear
11:20
Speaker 1: definition of what a measurement is and when it happens.
11:23
Speaker 1: Because you can imagine, you know, if I'm poking something
11:25
Speaker 1: with my finger, the tip of my finger is still
11:27
Speaker 1: a microscopic particle, So why should it collapse the way
11:30
Speaker 1: function and two particles on the tip of my fingers
11:32
Speaker 1: should still be a quantum mechanical system. So there's no
11:34
Speaker 1: like clear line when something becomes classical or microscopic when
11:38
Speaker 1: the wave function should collapse. Yes, exactly. I mean we
11:41
Speaker 1: don't know who does the collapsing, who kills the cat? Right?
11:45
Speaker 1: So is it me when I open the door, or
11:48
Speaker 1: is it my consciousness? We don't really want to enter
11:51
Speaker 1: into that. So it is a problem that you're suggesting. Namely,
11:55
Speaker 1: it's not a precise physical theory. It doesn't really define
11:59
Speaker 1: what a measurement is. Because I mean, this is puzzling,
12:02
Speaker 1: because we just would like measurement just to be physical
12:05
Speaker 1: processes like anything else, right, I mean, they're made of particles,
12:08
Speaker 1: quantum particles, and so why are they special? So there
12:12
Speaker 1: is a sense in which started from this, which is
12:14
Speaker 1: called the measurement problem, because I mean, we are actually
12:18
Speaker 1: measuring what is the state of the cat, and the
12:21
Speaker 1: cat is actually measuring what is the state of the particle.
12:24
Speaker 1: Another way of putting this would be that measurements, when
12:28
Speaker 1: you're performing a measurement. Quantum theory says that measurements do
12:31
Speaker 1: not have a precise result. Okay, so like the cat
12:35
Speaker 1: doesn't have a precise state, and so various people call
12:40
Speaker 1: them interpretation. But I actually think that they are different theories,
12:43
Speaker 1: but they have different solutions of these problem so to speak.
12:46
Speaker 1: So bo mechanics is one of those. It does solve
12:51
Speaker 1: this problem, even if I do think that's not the way.
12:54
Speaker 1: The reason why it was proposed. So this theory was
12:58
Speaker 1: proposed by I mean, the first version of this was
13:01
Speaker 1: proposed by the Brody in ninety three as part of
13:05
Speaker 1: his dissertation. So according to this theory, what happens is
13:09
Speaker 1: that I just like very very some people like to
13:13
Speaker 1: put it and romantic, right, something very plan and boring
13:17
Speaker 1: in a sense obvious because it's according to this theory,
13:20
Speaker 1: matter is made of particles, just liking classical mechanics, but
13:25
Speaker 1: they do have a different evolution equation than quantum theories.
13:28
Speaker 1: In this theory there is this object which is the
13:30
Speaker 1: wave function, which is the same guy as ordinary quantum theory,
13:34
Speaker 1: but it devolves according to Shrinninger equation. So you do
13:37
Speaker 1: have this an evolution a question for the particles, which
13:40
Speaker 1: is first to order, and then you have an object
13:43
Speaker 1: which is the wave function, which evolves like in regular
13:46
Speaker 1: quantum mechanics according to the Shrininger equation. So then in
13:49
Speaker 1: the Copenhagen interpretation, the one most people are familiar with.
13:52
Speaker 1: The wave function is supposed to be everything is supposed
13:54
Speaker 1: to describe the whole system, and particles when we're not
13:57
Speaker 1: looking at them, sort of operated according to this wave auction,
14:00
Speaker 1: which you know evolves according to the Shortinger equation. But
14:03
Speaker 1: then there's this weird second bit where things collapse to
14:06
Speaker 1: particle like behavior that we observe when you look at them. So,
14:09
Speaker 1: for example, you have a particle that's supposed to hit
14:11
Speaker 1: the screen, the whole wave hits the whole screen, but
14:14
Speaker 1: at some point when it interacts, when that measurement happens,
14:17
Speaker 1: then it becomes a single point, a flash of light
14:19
Speaker 1: on that screen. And so you're saying that Bomian mechanics
14:21
Speaker 1: is different because not only do you have the wave function,
14:24
Speaker 1: but you also have the particles. It's not like this.
14:27
Speaker 1: There's sometimes waves and then sometimes particles. They're always particles,
14:31
Speaker 1: but they're governed by this wave that sort of guides
14:34
Speaker 1: them through their path. Yes, so there are always particles.
14:38
Speaker 1: That's what matter is made off. Tables and chairs and
14:40
Speaker 1: people and screens and detectors and whatever are all made
14:43
Speaker 1: of particles. So what happens is that these particles their
14:47
Speaker 1: trajectories is mathematically written down in terms of this wave function,
14:52
Speaker 1: and this way function in itself evolves according to a
14:55
Speaker 1: given equation. Okay, So usually what you said is kind
14:57
Speaker 1: of important because some I mean, very common way of
15:00
Speaker 1: describing the theory, which is also called because of this reason,
15:04
Speaker 1: the pilot wave theory, is that this particle are pushed
15:08
Speaker 1: around by this wave. Okay. So the user slogan is, oh,
15:14
Speaker 1: it's not particle end waves or waves, it's particle end waves. Okay.
15:20
Speaker 1: So there is a sense in which this is true,
15:23
Speaker 1: in the sense that there are particles and there is
15:24
Speaker 1: also this wave function. However, I think that it is
15:28
Speaker 1: kind of misleading to think of that in these terms,
15:32
Speaker 1: because if you think about what kind of entity the
15:35
Speaker 1: wave function is, it is a wave, but not a
15:38
Speaker 1: wave in three dimensional space. Okay. If you think of
15:42
Speaker 1: how to represent the wave function, what the wave function
15:44
Speaker 1: really is, It's a function of all the particles, right,
15:49
Speaker 1: It is a function of the configuration in the case
15:52
Speaker 1: of bow Mean mechanics, the function of the configuration about
15:55
Speaker 1: the particles. So it has three dimensions for every particle.
15:59
Speaker 1: So in total it has three n dimensions. If the
16:02
Speaker 1: universe is composed of and particles, so it's not a
16:05
Speaker 1: field into adimensional space. The way function, then, just to
16:08
Speaker 1: be clear, talks about the trajectory of all of the
16:10
Speaker 1: particles in the universe, and so they're all sort of
16:14
Speaker 1: combined into this one grand object. The way function mechanics
16:18
Speaker 1: talks about is the way function of the universe. So
16:22
Speaker 1: the one that evolves according to the shooting their question
16:25
Speaker 1: is the way function of the universe. So I do
16:28
Speaker 1: have two things to clarify here. So the first thing is,
16:32
Speaker 1: so how we should interpret this wave function physically. It's
16:36
Speaker 1: an open question. I mean, philosophers and physicists are talking
16:38
Speaker 1: about this all the time. But I do think if
16:41
Speaker 1: you describe b My mechanics as I just did name
16:43
Speaker 1: it is a theory of particles with the wave function
16:45
Speaker 1: defining that trajectory, and you can understand that the way
16:49
Speaker 1: function as pushing the particles just in the same way
16:52
Speaker 1: as you understand gravity is pulling stuff right on the ground. Okay,
16:58
Speaker 1: So it's I think that the best this is my
17:00
Speaker 1: personal take on this, is that the best way of
17:03
Speaker 1: understanding the way function in Bowman mechanics is to think
17:06
Speaker 1: of that as law like right, It's part of the
17:09
Speaker 1: ingredients of the law of nature, something that you need
17:12
Speaker 1: right in order to specify the right trajectory, the one
17:14
Speaker 1: that you observe. And so the other thing was about
17:18
Speaker 1: the way function of the universe. So the fact that
17:21
Speaker 1: the way function is a function of all these particles
17:24
Speaker 1: is something that leads to a very important feature of
17:26
Speaker 1: Bonan mechanics, which is it's no locality. And I want
17:30
Speaker 1: to talk about non locality in a minute, but first
17:32
Speaker 1: I just want to make sure that we have a
17:33
Speaker 1: clear sense of what's going on here. So we talked
17:35
Speaker 1: about how the problem with quantum mechanics was this measurement
17:38
Speaker 1: problem that what happens when you measure this wave and
17:41
Speaker 1: it collapses into a particle. So how exactly does bow
17:44
Speaker 1: mean mechanics solve that problem? Is it because things are
17:47
Speaker 1: always a particle and so when you look at them,
17:49
Speaker 1: they were a particle and it's no big deal, and
17:51
Speaker 1: this is where it was, and it has like a
17:53
Speaker 1: well defined trajectory that in bow Mean mechanics you really
17:56
Speaker 1: can think about like electrons as tiny little dots of
17:59
Speaker 1: matter flying through the universe, the way planets fly through
18:02
Speaker 1: the Solar system. Yes, I think that's right in the
18:05
Speaker 1: case of the cat. The cats made of particles like
18:08
Speaker 1: everything else, So it is either dead or alive. Okay.
18:12
Speaker 1: The cat is either dead or alive at all times. Okay,
18:17
Speaker 1: So the macroscopic superposition should not belong to the wave functions.
18:20
Speaker 1: But the wave function is not what cat is made of.
18:23
Speaker 1: The cat was made of particles and particulars a precise location,
18:26
Speaker 1: which is what it is right, either in the dead
18:28
Speaker 1: camp or a in the life camp. So this is
18:31
Speaker 1: really different from the way people are sort of taught
18:33
Speaker 1: to think about quantum mechanics. That information isn't there until
18:36
Speaker 1: you measure it, that there's a fuzziness to the universe
18:39
Speaker 1: that is fundamentally random, all these really alien elements of
18:42
Speaker 1: quantum mechanics that make it so weird. Bo Mean mechanics
18:45
Speaker 1: seems to sort of like chuck that out the window
18:47
Speaker 1: and say, no, everything actually is determined. There is no
18:50
Speaker 1: randomness or uncertainty. There's just some information you sometimes haven't
18:54
Speaker 1: measured yet, but it's really there. That the cat really
18:56
Speaker 1: is dead or is alive. It's never sort of uncertain.
19:00
Speaker 1: Is that true? That there's really no randomness, no true
19:03
Speaker 1: randomness In Boomian mechanics. It depends on what is meant
19:06
Speaker 1: by that. So it is true that the cat is
19:08
Speaker 1: either dead or alive. It is true that the particles
19:11
Speaker 1: even passes through one sleet or the other sleet. It
19:14
Speaker 1: is true that when you observe a flash on the screen,
19:16
Speaker 1: that was coming from a particle that traveled all the
19:19
Speaker 1: way from the source to the screen. And it is
19:22
Speaker 1: true that there is no fuzziness. That's why I think
19:26
Speaker 1: that Bomian mechanics is physically clear. And the question is okay,
19:30
Speaker 1: so is there no randomness? Well, now there is randomness
19:33
Speaker 1: because the prediction of Bomian mechanics are provable to be
19:36
Speaker 1: the same as quantum mechanics. And quantum mechanics predicts probabilities. Right,
19:41
Speaker 1: the traditional stories that you do get only the probabilities
19:46
Speaker 1: of the results. Right, you obtain this, this or that
19:49
Speaker 1: not with a definite outcome. For sure, you have a
19:52
Speaker 1: probability distribution of the experimental results. So the legitimate question
19:56
Speaker 1: is where is the probability is coming from in Bomia mechanics.
20:00
Speaker 1: They come from the fact that So I mean, this
20:04
Speaker 1: is more general question about how is it possible to
20:09
Speaker 1: get probabilities if you have a deterministic theory. Deterministic theory,
20:13
Speaker 1: you have one past, one future, right if you know
20:15
Speaker 1: the law. If you not the initialis condition, you know everything, right,
20:18
Speaker 1: everything is determined. If you have this laplacean demon knows
20:21
Speaker 1: it at all and everything he knows everything. So this
20:24
Speaker 1: is a deterministic theory. So where the probability is coming from.
20:27
Speaker 1: They're coming from the initiative conditions. Okay, so there are
20:30
Speaker 1: two elements here, right. In determinism is something like that,
20:34
Speaker 1: given the initiative conditions and given the laws, you know everything.
20:38
Speaker 1: So if you do know the laws and you do
20:40
Speaker 1: know that, I mean principle, you can predict anything. I
20:43
Speaker 1: want to talk more about this randomness and initial conditions,
20:46
Speaker 1: but first let's take a quick break. All right, we're back,
21:01
Speaker 1: and we are talking about Bomian mechanics, a really fascinating
21:05
Speaker 1: quantum theory that describes the universe as filled with actual,
21:09
Speaker 1: tiny little dots of matter moving on what are like
21:12
Speaker 1: classical paths, but guided by a wave function that gives
21:16
Speaker 1: them the appearance of wave like behavior. And the element
21:19
Speaker 1: that we're talking about right now is this question of randomness.
21:22
Speaker 1: In traditional quantum mechanics, we are told that the universe
21:25
Speaker 1: is fundamentally random, that there aren't hidden variables that control
21:29
Speaker 1: what actually happens. But Boian mechanics says the opposite. It
21:32
Speaker 1: says that things are actually determined by the initial conditions,
21:35
Speaker 1: and that if you do the same experiment multiple times
21:38
Speaker 1: with exactly the same initial conditions, you should get the
21:41
Speaker 1: same output. So I'm a particle physicist and at the
21:43
Speaker 1: Large Hadron Collider we smash protons together multiple times, and
21:46
Speaker 1: we often say that if we smash those protons together
21:50
Speaker 1: with exactly the same initial conditions, we would still get
21:53
Speaker 1: different outcomes every time. That is quantum mechanical, and that
21:56
Speaker 1: it's drawn from some probability distribution that somewhere seriously, the
22:00
Speaker 1: universe is like rolling the dye based on this probability
22:03
Speaker 1: distribution and deciding what happens on the giving collision. But
22:06
Speaker 1: you're saying that Bomian mechanics is deterministic, and that if
22:10
Speaker 1: I get two different collisions giving me two different outcomes,
22:13
Speaker 1: that's because the initial conditions were slightly different, the protons
22:16
Speaker 1: that a slightly different energy or slightly different angle, and
22:19
Speaker 1: that if it was actually able to repeat the same
22:21
Speaker 1: exact experiment, I should get the same exact outcome, is
22:24
Speaker 1: that right? So yes, so so so if you say
22:26
Speaker 1: that you do have this distribution of the particles, the
22:30
Speaker 1: particles of distributed according to quantum ecalibbon distribution, and it
22:33
Speaker 1: is an equilibient distribution and nothing changes anymore, then that's
22:37
Speaker 1: the most complete information that you may have about this particles.
22:41
Speaker 1: And so we don't have more knowledge than this about
22:43
Speaker 1: the particles. Then we have absolute tons certainty about the
22:48
Speaker 1: precise positions of the particles. And so this plays out
22:52
Speaker 1: into having a distribution of the outcomes at the end
22:56
Speaker 1: of the experiment. I see. So we have particles which
22:59
Speaker 1: go through the experiment using deterministic laws. So the entire
23:03
Speaker 1: outcomes determined for each particle based on how it came
23:06
Speaker 1: into the experiment. But we have some distribution of inputs
23:10
Speaker 1: at the particles when they come into the experiment. They're
23:12
Speaker 1: never all actually at the same angle or location or whatever.
23:16
Speaker 1: There's some variation there and that gives a variation in
23:19
Speaker 1: the output. So not a randomness, but you have sort
23:21
Speaker 1: of variation and the inputs gets translated to a variation
23:24
Speaker 1: on the outputs, sort of like you know that game
23:26
Speaker 1: where you drop a ball and it goes left and right,
23:28
Speaker 1: and left and right and left and right. It sort
23:29
Speaker 1: of chaotic. It's very hard to predict exactly what slot
23:32
Speaker 1: it's going to go into. But in theory, if you
23:35
Speaker 1: did drop it exactly the same place twice, it should
23:37
Speaker 1: end up in the same slot twice. So boomy and
23:40
Speaker 1: mechanics describes the universe that way that you have some
23:42
Speaker 1: like variation in how the balls start to drop, which
23:45
Speaker 1: is how you get a variation in the output. But
23:47
Speaker 1: each trajectory of each one really is like a tiny,
23:50
Speaker 1: classical little baseball. That's crazy to me. I mean that
23:53
Speaker 1: requires like a whole rethinking of the idea of quantum mechanics,
23:56
Speaker 1: because I've spent twenty years getting used to this concept
23:59
Speaker 1: of the universe being random and unavailable and fuzzy, and
24:02
Speaker 1: this is now saying, oh, no, you actually don't have
24:04
Speaker 1: to take that whole weird route after all. Yes, that's right,
24:08
Speaker 1: so you don't have to and so why go for it?
24:11
Speaker 1: So I I mean, there is this is uncertainty that
24:13
Speaker 1: you have regarding the nition then the configuration, right, initial configuration,
24:16
Speaker 1: But that's it, right, you don't have to transform that
24:19
Speaker 1: into in the necessarily into somehow random trajectories or randomness
24:24
Speaker 1: more radical levels. But where is the fuzziness come from
24:27
Speaker 1: in the beginning? I mean, does the universe start with fuzziness?
24:30
Speaker 1: Because the standard picture we have, like why the universe
24:33
Speaker 1: is not totally smooth while we have galaxies here and
24:35
Speaker 1: not over there, is that we had some like quantum
24:38
Speaker 1: fluctuations in the early universe that gave us densities which
24:41
Speaker 1: you know, dot dot dot. Billions of years later we
24:43
Speaker 1: have galaxies. Where did those fluctuations in the density of
24:46
Speaker 1: the early universe come from, If not from quantum randomness,
24:50
Speaker 1: is it some pre pre initial condition before the Big Bang? Yeah, well,
24:53
Speaker 1: I have no idea, I mean, but I mean this
24:57
Speaker 1: is I think it's a very very important thing to notice. Right. So,
25:00
Speaker 1: if you do have a theory, which is like moving mechanics,
25:03
Speaker 1: is precise mathematically and physically, meaning you do have equations
25:07
Speaker 1: right written there, they apply every time, right, it's not like, oh,
25:10
Speaker 1: you use this or use that measurement or no measurement. No,
25:12
Speaker 1: it's precise, okay, And it's precise physically gives you a
25:16
Speaker 1: picture of what's going on, which is exactly how it
25:19
Speaker 1: was in the classical you know, when we're thinking about
25:21
Speaker 1: classical physics, and one of the you know, the marriage
25:24
Speaker 1: is that you can visualize. Okay. So but if you
25:26
Speaker 1: do have this theory and there are crazy things about it,
25:29
Speaker 1: you know how to which questions are needed? Right? Which
25:34
Speaker 1: questions are really the ones that we should focus on? Okay?
25:38
Speaker 1: So one question is where is this absolute ansertainty coming from?
25:43
Speaker 1: Another question, right, is what about the fact the way
25:47
Speaker 1: function is a function of all the configuration. There is
25:50
Speaker 1: a sense in which you may think that, you know,
25:53
Speaker 1: bombing mechanics removes all the romance from from physics, and
25:57
Speaker 1: that I think that's you know, a merriage romance. I
26:00
Speaker 1: would say, removes all the headaches the head Oh yeah, exactly.
26:04
Speaker 1: I mean to me, it removes all the headaches. But
26:05
Speaker 1: some people, you know, they think of that, Oh yeah,
26:08
Speaker 1: but I mean the observer, you know, gains again, right,
26:11
Speaker 1: the center of the attention. I'm not sympathetic at all
26:14
Speaker 1: about this kind of talk, but I mean some people
26:17
Speaker 1: are attracted by the craziness, right, and so when they
26:21
Speaker 1: hear about Bowman mechanics, they think, oh, what is the
26:24
Speaker 1: all the fun? What is this? I mean, physics is fun,
26:27
Speaker 1: but maybe in a different way. I'm sympathetic to that,
26:30
Speaker 1: because I think we want physics to teach us the
26:33
Speaker 1: truth of the universe, and we hope in our hearts
26:35
Speaker 1: somehow the truth of the universe is not what we
26:38
Speaker 1: imagine that we're gonna be learning something that requires some
26:40
Speaker 1: sort of like mental revolution to be like, wow, the
26:43
Speaker 1: universe is so weird and different from what we imagine.
26:45
Speaker 1: And so if you're just telling me, know, the universe
26:48
Speaker 1: at the tiny scale, it's just a tiny little bunch
26:50
Speaker 1: of baseballs, the way it is sort of like at
26:52
Speaker 1: the atomic scale and the macroscopic scale and the scale
26:55
Speaker 1: of planets and stars, then yeah, I guess that does
26:57
Speaker 1: remove a little bit of the mystery. But you know what,
26:59
Speaker 1: I was struggling to learn quantum mechanics and absorb it
27:02
Speaker 1: intuitively as a college student. The thing that really got
27:05
Speaker 1: me over the hump were these bells, theorems, and these
27:08
Speaker 1: bells and equalities that really seemed like definitive proof that
27:12
Speaker 1: quantum mechanics was random. And we have these experiments and
27:16
Speaker 1: very clever people have shown that there are these correlations
27:19
Speaker 1: among entangled particles that simply cannot happen if quantum mechanics
27:25
Speaker 1: was not fundamentally random that you can't like secretly hide
27:28
Speaker 1: all the information that it can't be the things are
27:31
Speaker 1: really just one way or not the other way that
27:33
Speaker 1: you know before you look at the electronic always was
27:36
Speaker 1: spin up in my mind. Those bells and equality really
27:39
Speaker 1: sort of like killed that possibility. Said, no, you have
27:42
Speaker 1: to accept fundamental randomness. Why don't these theorems, these bills
27:46
Speaker 1: and equalities and those experiments, why don't they kill Bonian mechanics?
27:50
Speaker 1: They did kill it for a long time. Actually, you
27:53
Speaker 1: know the first theorem that was the theory which allegedly
27:56
Speaker 1: proved that heat and variable something impossible. It was still
28:00
Speaker 1: too for Neuman in nine five or something like that,
28:04
Speaker 1: and so he basically wanted to put an end to
28:08
Speaker 1: all uh for reasons that are you know, maybe historically interesting,
28:13
Speaker 1: but I mean what he wanted to provide was a
28:15
Speaker 1: proof and mathematical proof that you cannot do better than
28:18
Speaker 1: quantum theory. So that was just like kind of you know, oh,
28:21
Speaker 1: we all would like to have a pictorial view of
28:24
Speaker 1: visualized visualize about theory, right, but we cannot. That's what
28:28
Speaker 1: he wanted to prove, and so he went by contradiction. Okay,
28:31
Speaker 1: so he said, Okay, let's pretend for a second that
28:34
Speaker 1: we can complete quantum mechanics. Let's pretend for a second
28:37
Speaker 1: that we can add these hidden variables right to the theory.
28:41
Speaker 1: The theory is not complete, right, it is, there are
28:43
Speaker 1: these even variables. At first, their hidden for them in
28:46
Speaker 1: the sense that quantum theory doesn't specify what they are.
28:49
Speaker 1: And so he said, okay, let's pretend let's start with
28:51
Speaker 1: this theory, let's work it out, let's work the consequences out.
28:54
Speaker 1: And what he obtained was that there is some sort
28:58
Speaker 1: of a contradiction, like five is greater than seven. I mean,
29:02
Speaker 1: it's not really the case, but I mean you can
29:03
Speaker 1: imagine something like that. Okay. So he said, okay, what
29:06
Speaker 1: are the assumptions? I mean the reasonable assumption. So the
29:08
Speaker 1: only assumption that so we had reasonable assumption, we started
29:12
Speaker 1: from this hidden variable theory, we get contradictions. So the
29:15
Speaker 1: only way out is just to say there are no
29:17
Speaker 1: hidden variables. The quantum world is weird. For those of
29:20
Speaker 1: you who don't know of Annoyingment is one of the
29:22
Speaker 1: great mathematical geniuses of the century and really credited with
29:25
Speaker 1: like pulling together the mathematics of modern quantum theory, and
29:30
Speaker 1: so when he said something, people tended to listen, and
29:32
Speaker 1: you know, it was sort of difficult to stand up
29:34
Speaker 1: to Vannyman. You know, back in the forties when he
29:36
Speaker 1: was in his hey day, he was very influential exactly.
29:39
Speaker 1: I mean, there is actually something normal. It's not like
29:42
Speaker 1: you can charge these people to have listened and just
29:45
Speaker 1: relied on the authority. It was just like kind of normous.
29:48
Speaker 1: It's not for Noyman process theory. I mean, there's not
29:50
Speaker 1: much of a reason to suspect that he was wrong.
29:53
Speaker 1: But he was wrong because he assumed something, which is
29:57
Speaker 1: the start that assumption of quantum theory. The experiment doesn't
30:01
Speaker 1: really change the system, Okay, The interaction is small enough
30:05
Speaker 1: that the property that you're trying to measure is left
30:08
Speaker 1: the same. Okay, like I was talking about before, right,
30:11
Speaker 1: I do believe I have a fever. Say, okay, I
30:14
Speaker 1: want to measure my temperature and making an experiment, put
30:17
Speaker 1: the thermometer under my arm. Wait a second, wait for
30:19
Speaker 1: the interaction. Than the mercury or whatever, the gallium or
30:22
Speaker 1: whatever it is, expands and it gives me the temperature. Okay,
30:26
Speaker 1: So but the temperature that I read it's not really
30:29
Speaker 1: my temperature before I actually put the thermometer under my army.
30:33
Speaker 1: It's actually the equilibrium temperature between the thermometermy and me. Okay, so,
30:41
Speaker 1: but what I read is we forget about this all
30:43
Speaker 1: the time because we believe that, I mean, this is
30:45
Speaker 1: the property of the thermometer, which was the thermometer in
30:47
Speaker 1: such a way that it doesn't affect too much that
30:50
Speaker 1: the equilibrium temperature is really close to my original temperature.
30:53
Speaker 1: So you're saying that, for example, when you measure your temperature,
30:56
Speaker 1: you actually measure slightly lower temperature than your actual temperature
30:59
Speaker 1: because the thermometer is slightly cooler than you and you
31:02
Speaker 1: guys have come into equilibrium, and it's sort of like
31:04
Speaker 1: putting a tiny little piece of ice on you and
31:06
Speaker 1: it's cooled you down a little bit. And in the
31:08
Speaker 1: same way, you need to take that into account. And
31:11
Speaker 1: van Neuman ignored the impact of the measurement on the
31:14
Speaker 1: system when he was making all of his calculations and
31:17
Speaker 1: proof that quantum mechanics had to be random, that you
31:20
Speaker 1: couldn't have any hidden variables. Right, It's actually worse than that,
31:24
Speaker 1: because I mean, this is a general assumption that we
31:26
Speaker 1: all make when you're doing quantum theory, right, we do
31:28
Speaker 1: assume that I mean the operators represent properties. The problem
31:32
Speaker 1: is that most of the time the experiments are such
31:36
Speaker 1: that they perturbed the system so much that they don't
31:40
Speaker 1: measure anything about the system. They tell you something about
31:43
Speaker 1: the interaction. Think about you want to know where the
31:46
Speaker 1: table is, Okay, so you switch on the light. Basically
31:49
Speaker 1: what happens you hit the table surface with photons, the
31:52
Speaker 1: photos going to your retina, and the retina records the result. Right,
31:56
Speaker 1: but I mean the photo world bounce back, but also
31:59
Speaker 1: the table ricoisly to bit. You forget about that, okay,
32:02
Speaker 1: because the mass and blah blah blah. Okay, it's much bigger. However, instead,
32:07
Speaker 1: if you instead of willing to try and find the
32:09
Speaker 1: position of the table, you want to try and find
32:11
Speaker 1: the position of an electron. Okay, you switch on the light.
32:13
Speaker 1: The photon hits the electron, and the electron goes. So
32:17
Speaker 1: what you measure the electron is going to click somewhere
32:19
Speaker 1: in some detectors somewhere, So the position what you're measuring
32:22
Speaker 1: is not the position of the electron before, it's the
32:25
Speaker 1: position afterwards, Okay, which is totally fine, but I mean
32:29
Speaker 1: what is tricky and sometimes what you want is that
32:32
Speaker 1: not What for no, Himan actually proved was not that
32:36
Speaker 1: hidden variables are impossible, but that he proved that not
32:39
Speaker 1: all experiments are actually measurement. So all these certain experiments
32:44
Speaker 1: are able to measure, namely those experiments where the interaction
32:50
Speaker 1: is not that high to destroy the system or perturbit
32:52
Speaker 1: too much. And how does that connect with hidden variables?
32:55
Speaker 1: Like I get that he's showing that you can only
32:57
Speaker 1: make a measurement if you're making it very small, all
33:00
Speaker 1: negligible interaction on the system, that you're extracting information from
33:03
Speaker 1: what happened before he measured it. How does that connect
33:05
Speaker 1: to the question of whether quantum mechanics is really random
33:08
Speaker 1: or whether there's sort of hidden information in there that
33:11
Speaker 1: controls what's happening. It doesn't have much to do with
33:13
Speaker 1: him invariables. That for sure. His theorem was supposed to
33:16
Speaker 1: be showing that he did invariables are impossible, Okay, But
33:20
Speaker 1: he didn't show that because he had this assumption in it.
33:22
Speaker 1: He came out with the contradiction because he was assuming
33:25
Speaker 1: this and so he was assuming that there are properties
33:28
Speaker 1: and these properties have actually weird behavior. So he set
33:32
Speaker 1: out to prove that hidden variables couldn't exist, and he
33:35
Speaker 1: did by contradiction, but instead of a false assumption into
33:38
Speaker 1: his proof, which is the thing that led to the contradiction.
33:41
Speaker 1: So his conclusion about hiddenvariables was therefore invalid because the
33:44
Speaker 1: contradiction came from somewhere else. And then this stood for decades. Right,
33:48
Speaker 1: people thought, oh no, him improved, the quantum mechanics must
33:50
Speaker 1: be random, so this the burglary theory, This, this deterministic
33:54
Speaker 1: idea of quantum mechanics, We shouldn't even think about that.
33:57
Speaker 1: And then what happened? When did people realize, oh, hold,
34:00
Speaker 1: the second pandomen was wrong and it's possible to have
34:03
Speaker 1: determinist e quantum mechanics. Yeah, well, some people actually figured
34:06
Speaker 1: this out immediately, but we're ignored either because they were
34:10
Speaker 1: you know, not very well known figure, or because they
34:13
Speaker 1: didn't really want to batter. I mean, according to some people,
34:16
Speaker 1: did Einstein figured this out immediately, but he didn't bother
34:20
Speaker 1: to reply. And it is also true that the original
34:23
Speaker 1: proof of phen nomen had other issues, which, however, where
34:28
Speaker 1: you know, taking care of in proofs that came later.
34:31
Speaker 1: But the person who actually figured this out was Bell
34:33
Speaker 1: John Bell, who actually came back to this for no
34:37
Speaker 1: human proof and figure out where he was wrong, namely
34:41
Speaker 1: the assumption that operators necessarily mean you can understand experiments
34:45
Speaker 1: always as measurement, which is not necessarily the case. So
34:48
Speaker 1: the same Bell who is responsible for most people thinking
34:51
Speaker 1: that equantum mechanics has to be random because he showed
34:54
Speaker 1: these crazy inequalities, is the one who also revealed that
34:57
Speaker 1: no Eman was wrong improving the quantum exist random. So
35:01
Speaker 1: this Bell guy had a pretty big role to play
35:03
Speaker 1: in our understanding one of mechanics. Yes, yes, and I mean.
35:06
Speaker 1: And also it is the case that he was often
35:07
Speaker 1: misunderstood for many years, even if he clearly wrote down
35:11
Speaker 1: what he was trying to prove. So I mean indeed
35:15
Speaker 1: he was writing about for Annoyman's proven very shortly after
35:18
Speaker 1: he came up with his own belt inequality. So he
35:22
Speaker 1: did try to provide a didn't variable theory. So he
35:26
Speaker 1: was trying to do the same as for Annoyman and say, okay,
35:28
Speaker 1: so if we do have it, this is it an
35:30
Speaker 1: a variable? Here? What do we get? There is a
35:32
Speaker 1: sense in which you can take as you were doing
35:34
Speaker 1: at the beginning, right, he's inequality, just like a different
35:38
Speaker 1: variety of impossibility proof against the invariable. But actually, as
35:43
Speaker 1: many people would say, even if there is a sense
35:46
Speaker 1: in which is it's controversial, I mean it's it's controversial
35:49
Speaker 1: whether he actually proved it. What it's not controversially is
35:52
Speaker 1: what he thought, Namely, he thought to have proven that
35:56
Speaker 1: at the end of the name, if you have a
35:57
Speaker 1: theory which respects the prediction of quantum kind of extent,
36:00
Speaker 1: this theory has to be non no com right, So
36:02
Speaker 1: let's unpack what that means for a moment. Because bells
36:05
Speaker 1: inequality tells us that the universe has to be random,
36:07
Speaker 1: there can't be any hidden variables. But it turns out
36:10
Speaker 1: there's a caveat. That's only true if you're talking about
36:12
Speaker 1: so called local information, right, and information which is accessible
36:17
Speaker 1: to somebody like in their immediate environment. You know, like
36:20
Speaker 1: I can know what's near me, I can measure something nearby,
36:23
Speaker 1: but I don't know anything about what's happening in Andromeda
36:27
Speaker 1: right now because this sort of limited passage of information.
36:30
Speaker 1: And I want to talk more about entanglement and locality,
36:34
Speaker 1: but first let's take another quick break. Okay, we're back
36:51
Speaker 1: and we are talking about whether quantum mechanics is what
36:55
Speaker 1: we call local. We know that there's a limit on
36:58
Speaker 1: how fast in formation can move, that there's this speed
37:02
Speaker 1: limit of information in the universe, and that information cannot
37:05
Speaker 1: move instantaneously. But this gets confusing when we talk about
37:10
Speaker 1: entangled particles. You create two electrons so that they have
37:14
Speaker 1: to have opposite spin, but you don't know which electron
37:17
Speaker 1: has spin up and which one is spinned down. But
37:19
Speaker 1: as soon as you measure one to be spin up,
37:22
Speaker 1: for example, you know instantaneously that the other one has
37:25
Speaker 1: to be spinned down. And that seems sort of nonlocal
37:29
Speaker 1: because the particles can be entangled, but they can also
37:31
Speaker 1: be really far apart. So all of a sudden, when
37:35
Speaker 1: you measure the spin of one particle, the other one,
37:37
Speaker 1: which is many many kilometers or maybe light years away,
37:41
Speaker 1: instantaneously collapses to have the other possibility. So I would
37:46
Speaker 1: put it slightly differently in the sense that I would
37:48
Speaker 1: say that in general, what Bell proofed is that you
37:51
Speaker 1: do have no locality. In general, at the beginning particle
37:55
Speaker 1: one didn't have any spin property because of the entire state.
37:59
Speaker 1: When it's measured. Instead, oh, it turns up up so
38:02
Speaker 1: and the other immediately down. And the issue there, of course,
38:05
Speaker 1: is that these things can be separated. Right, so if
38:08
Speaker 1: these two particles, they have to have opposite spins, and
38:11
Speaker 1: classical or in the traditional equantum mechanics tells us that
38:15
Speaker 1: both of them have the possibility to be up and down.
38:17
Speaker 1: And so when you measure one of them and it
38:19
Speaker 1: becomes up, then the other one, now hundreds of miles
38:22
Speaker 1: away or thousands of miles away, somehow instantaneously goes from
38:26
Speaker 1: being up or down to only being down. And that's
38:29
Speaker 1: this question of nonlocality, right, how does the information get
38:33
Speaker 1: from one particle, you know, to the other particle faster
38:36
Speaker 1: than the speed of light. Yes, that's a problem. That's
38:39
Speaker 1: something that the scars and regarded as a non starter.
38:43
Speaker 1: That was just like thinking about, I mean, that's one
38:46
Speaker 1: possibility and the other possibilities instead that they really had
38:50
Speaker 1: a property or spin since the beginning. Right, So you
38:54
Speaker 1: measure spin up because the first guy always had spin
38:57
Speaker 1: up from the start, okay, And so they don't actually talk, right,
39:02
Speaker 1: they were prepared and up and down and you detect
39:04
Speaker 1: them up and down. And that's this hidden variables interpretation
39:06
Speaker 1: that they always are something. It's just you don't know
39:09
Speaker 1: about it. It's sort of hidden from you until you
39:11
Speaker 1: measure it. But that there's no like actual uncertainty. It's
39:13
Speaker 1: not like there's the particles actually in up and down
39:16
Speaker 1: until you measure it. And so that's this problem with nonlocality, right,
39:20
Speaker 1: And you're saying, einstein collaborators were suggesting this is ridiculous
39:24
Speaker 1: because it requires a theory that's nonlocal, that somehow these
39:27
Speaker 1: things have to you know, coordinate to make sure that
39:29
Speaker 1: they're always opposite spins. And so what did Bell showed?
39:32
Speaker 1: Bell showed that every theory of quantum mechanics has to
39:35
Speaker 1: be nonlocal, Yes, because I mean he started off with
39:39
Speaker 1: a theory like that and he predicts inequality, and so
39:44
Speaker 1: they eat in variables. You have to imagine something like this,
39:47
Speaker 1: so you have quantum mechanics. Quantum mechanics implies that there
39:51
Speaker 1: has to be eating variables. So one of the main
39:54
Speaker 1: objections people might have to this theory of deterministic particles
39:58
Speaker 1: being guided by the way function information is actually there,
40:01
Speaker 1: it's just that we don't know it sometimes is that
40:04
Speaker 1: we thought that quantum mechanics have to be random because
40:06
Speaker 1: of these arguments by Bell and these experiments that showed
40:09
Speaker 1: that you couldn't explain these experiments using some hidden variables.
40:13
Speaker 1: But it turns out then you couldn't explain those experiments
40:16
Speaker 1: using local hidden variables, but you can explain those experiments
40:19
Speaker 1: using non local hidden variables. So Bonian mechanics works and
40:23
Speaker 1: is consistent with experiments if you have nonlocality, this idea
40:28
Speaker 1: that particles that are not in the same place, that
40:30
Speaker 1: are not near each other, can somehow you know, communicate
40:33
Speaker 1: or coordinate their arrangements. And you might think, well, that's crazy,
40:37
Speaker 1: that it's bonkers, how could that be possible? And that
40:40
Speaker 1: seems like a pretty big objection, But I think, as
40:43
Speaker 1: you're saying, Bell showed that this is actually true and
40:45
Speaker 1: required for all theories of quantum mechanics, not just Bomian mechanics,
40:49
Speaker 1: And so it's not really a strike against Bomian mechanics
40:52
Speaker 1: to say that requires non local information. Yes, that's true,
40:56
Speaker 1: because I mean he did prove his inequality. And if
40:59
Speaker 1: you if right, then down in the in the appropriate way,
41:02
Speaker 1: you will see that the hidden variable is just a
41:05
Speaker 1: passage in the deduction, but it's actually something that you
41:08
Speaker 1: don't require so that arguably what's going on is that
41:13
Speaker 1: every single theory that has the same predictions fantum mechanics
41:16
Speaker 1: will turn out to be non local. But doesn't nonlocality
41:20
Speaker 1: seems sort of crazy. I mean, special relativity tells us
41:24
Speaker 1: that information takes time to propagate through the universe. That
41:27
Speaker 1: what's happening in Andromeda can't influence me right now because
41:30
Speaker 1: I'm outside of its light cone. So if you're telling
41:33
Speaker 1: me that not only does Bonian mechanics, which seems like
41:35
Speaker 1: a beautiful description of the universe and nicely deterministic, require nonlocality,
41:40
Speaker 1: but all theories of econom mechanics require nonlocality, how do
41:43
Speaker 1: I then accept that? How do I think about the
41:45
Speaker 1: universe as nonlocal? Does it mean that every particle in
41:47
Speaker 1: Andromeda potentially can influence me right now? Yeah? Okay, so
41:51
Speaker 1: that's the craziness, right. So that's a good thing about
41:54
Speaker 1: Bona mechanics because in this theory the non locality is obvious.
41:57
Speaker 1: It's clear right there in the wave functions. So then
41:59
Speaker 1: that thing that we need to do as physicist is
42:03
Speaker 1: to investigate how it's possible for a theory like that
42:07
Speaker 1: to be compatible with relativity theory, right, so we just
42:11
Speaker 1: give access to the right questions again before I actually
42:13
Speaker 1: talk a little bit about that. I mean, so you
42:15
Speaker 1: don't really have to go into the interpretation and show
42:19
Speaker 1: that all the other interpretation are no local. Just think
42:21
Speaker 1: about the regular theory, okay, with the collapse. When you
42:26
Speaker 1: do have the collapse, the collapse is no local, right,
42:29
Speaker 1: I mean, think about the original EPR argument. Right, how
42:32
Speaker 1: do you explain the compa relation over there? It's no local, right,
42:36
Speaker 1: You measure one, the other has to tell the first
42:38
Speaker 1: one has to tell the other one. Right, that's no
42:40
Speaker 1: locality right there. It's not a problem of the hidden variables.
42:44
Speaker 1: I mean the regular I mean, the textbook theory has
42:46
Speaker 1: it right there. Indeed, Heisenberg accepted that, yes, there are
42:52
Speaker 1: some lectures that I forgot the year the precise here
42:55
Speaker 1: in which he talks about exactly this. Right, the collapse
42:59
Speaker 1: is no local, But then he says it doesn't contradict relativity.
43:03
Speaker 1: He did really take it seriously that much because he
43:06
Speaker 1: thought that you kind of use the non locality of
43:09
Speaker 1: the collapse transfer information. So if you think of relativity
43:14
Speaker 1: as a theory of sicknals, there is not I mean,
43:17
Speaker 1: you can't get around, there's no locality, right, And so
43:20
Speaker 1: for our listeners who are curious, it does seem like
43:22
Speaker 1: there's some weird nonlocal features of quantum mechanics, but it
43:26
Speaker 1: is not possible to use that nonlocality to send information
43:29
Speaker 1: faster than the speed of light. And Jorge and I
43:31
Speaker 1: did a whole podcast on that, so check that out
43:33
Speaker 1: in detail. We don't have time to get into all
43:35
Speaker 1: of that today, but if you're curious about why you
43:37
Speaker 1: can't send information fast in the speed of light using
43:40
Speaker 1: quantum entanglement, we did cover that in the whole podcast episode.
43:43
Speaker 1: All right, So this is really fascinating and I don't
43:45
Speaker 1: want to use too much more of your time, so
43:46
Speaker 1: I just want to ask you if Bowman mechanics, you know,
43:49
Speaker 1: is a nice, beautiful picture of the universe and explains
43:52
Speaker 1: all the experiments that we have and doesn't require us
43:55
Speaker 1: to accept some strange, alien uncertainty and randomness that's counterintuited
44:00
Speaker 1: and only requires the acceptance of this concept of nonlocality,
44:04
Speaker 1: which already is present in all other quantum theories. Then
44:08
Speaker 1: why isn't it the dominant quantum theory? What are the
44:10
Speaker 1: objections against it? Is? It's still sort of like historical
44:13
Speaker 1: inertia because von Neuman didn't like it, or there you know,
44:16
Speaker 1: real philosophical objections to it. So I mean, I think
44:19
Speaker 1: that part of the problem has to do with the
44:21
Speaker 1: fact that historically it was blocked. I mean there is
44:23
Speaker 1: all this, you know, historical accidents that happened one after
44:27
Speaker 1: the other. I mean the first bomb was you know,
44:30
Speaker 1: ostracized for various reasons, and then for Neuman contributed to this,
44:34
Speaker 1: there seemed to be no real reason to reject this
44:37
Speaker 1: theory from from a rational point of view. I mean,
44:40
Speaker 1: it provides a clear mathematical picture. It's a clear physical
44:43
Speaker 1: picture as well. You do have to accept no locality,
44:46
Speaker 1: as you said, but I mean it's something that we
44:48
Speaker 1: have to deal with. Some people sometimes mentioned that, oh,
44:52
Speaker 1: it's not testable in the sense that probably the prediction
44:56
Speaker 1: of the Boomian mechanics are the same as quantum theory.
45:00
Speaker 1: That's not a good objection for a variety of reason. First,
45:02
Speaker 1: because I mean, you have a piece of evidence. You
45:05
Speaker 1: have two theories, right, and so which one of the
45:08
Speaker 1: theories the evidence confirming, assuming that you can confirm a
45:11
Speaker 1: theory the first? Okay, so who came first? The brawl
45:14
Speaker 1: nine twenty three. Right, uh, and so because no, no, no, no,
45:19
Speaker 1: but it's simpler, right, you come to mechanics is simpler,
45:22
Speaker 1: that's just one equation, but the mechanics has two equations,
45:25
Speaker 1: one equation with two evolution equation. Okay, so what about
45:28
Speaker 1: time of light? You have particle physicists, right, you measure
45:31
Speaker 1: time of flight, You measure where the particle how long
45:33
Speaker 1: they take to go from here to there? But there
45:35
Speaker 1: is no time open it. And so what are this
45:37
Speaker 1: time of light results? Well, I mean the drugular quantum
45:40
Speaker 1: theory have resorts to this kind of approximation. Right. If
45:43
Speaker 1: you approximate the time measurement in one way or in
45:45
Speaker 1: another way, you get different distribution of results. Booming mechanics
45:49
Speaker 1: gives you uh, you know their particles, right, So you
45:52
Speaker 1: don't need the operators, right, you just do you use
45:55
Speaker 1: the particles trajectories and do the calculation that you would
45:57
Speaker 1: do classically, but with quantum tra actorism. And so there
46:01
Speaker 1: is the possibility of actually making an experiment. So there
46:05
Speaker 1: are some cases in which you can put yourself in
46:08
Speaker 1: a situation in which the prediction from quantum theory are
46:10
Speaker 1: different from boom mechanics. This can happen because you know,
46:16
Speaker 1: quantum mechanics is not precise, some bigues in disrespect, so
46:20
Speaker 1: you can test out. So there is a strong sense
46:23
Speaker 1: in which you can, you know, falsify quantum theory or
46:28
Speaker 1: quantum mechanics. So even if your physicists are usually strong
46:32
Speaker 1: about this undetectability business, but I mean, no, you can detect. So,
46:37
Speaker 1: I mean, I really don't understand that much about the
46:39
Speaker 1: reasons why quantum mechanics hasn't been taken more seriously by physicists.
46:45
Speaker 1: And I hope the situation we've changed. Well, what it
46:48
Speaker 1: might require for to change is maybe for us to
46:51
Speaker 1: meet alien intelligence and talk to them about quantum mechanics
46:54
Speaker 1: and you know, maybe their way in and will say, sorry, folks,
46:57
Speaker 1: we think it's many worlds or no, what you call
46:59
Speaker 1: booming mechanics is what makes most sense to us. So
47:02
Speaker 1: on the topic, let me ask you are totally off
47:04
Speaker 1: the wall question, what do you think are the chances
47:06
Speaker 1: of that that if we meet alien intelligence that they
47:09
Speaker 1: will have sort of similar concepts about the universe. I mean,
47:12
Speaker 1: it's really another way to ask the question, do you
47:14
Speaker 1: think what we're doing here are playing games inside our
47:18
Speaker 1: own minds? To try to tell mathematical stories about the
47:21
Speaker 1: universe it makes sense to us, or do you think
47:23
Speaker 1: we're actually probing something deep and universal which we could
47:26
Speaker 1: present without embarrassment at the first Interstellar Physics meeting after
47:30
Speaker 1: we meet the aliens. I really do hope that we
47:33
Speaker 1: can meaningfully talk about the universe, and it seems like
47:37
Speaker 1: we are actually succeeding in that right. We explained so
47:40
Speaker 1: many things since the beginning that we started doing science. No,
47:44
Speaker 1: we've made many hypothesis and constructive many theories, and some
47:48
Speaker 1: some of them were bad ideas, some of them are
47:50
Speaker 1: better ideas. I think that the fact that we are
47:53
Speaker 1: explaining so much is an indication that maybe we are
47:57
Speaker 1: onto something, but I don't know. I hope that we
48:02
Speaker 1: can contribute to the alien meeting in some way. Maybe
48:06
Speaker 1: they have their own version of bondingment and they've made
48:08
Speaker 1: their own mistakes along the way, so we can help
48:10
Speaker 1: them understand some of the things that we have learned.
48:13
Speaker 1: I hope also that when we meet the aliens, we
48:14
Speaker 1: can talk physics with them, because I hope that they
48:16
Speaker 1: are advanced and that millions of years ago they were
48:19
Speaker 1: struggling with these questions and now to them. It's child's play.
48:22
Speaker 1: But I fear honestly that everything we've learned is sort
48:25
Speaker 1: of centered in the human mind. We're asking human questions,
48:28
Speaker 1: we're telling human stories using mathematical tools that makes sense
48:31
Speaker 1: to humans, and that it might be frankly impossible to
48:34
Speaker 1: translate into this knowledge to any other intelligence. But it
48:37
Speaker 1: remains to be seen, and the universe has filled with surprises.
48:39
Speaker 1: So I look forward to having hard quantum mechanics conversations
48:42
Speaker 1: with alien physicists. All right, And with that, I'll say
48:45
Speaker 1: thank you very much for coming out a podcast and
48:47
Speaker 1: talking to us about this crazy concept of boom and mechanics.
48:50
Speaker 1: It seems to me like sort of a beautiful theory
48:52
Speaker 1: that lets us recover the sense that the universe makes sense,
48:56
Speaker 1: that these particles are flying through the air, and they
48:59
Speaker 1: have victories, and they were here and then they're there,
49:02
Speaker 1: which means that they were sort of in between in
49:03
Speaker 1: the middle. That you can still think about the universe
49:06
Speaker 1: in a way that's intuitive to you, and that you
49:08
Speaker 1: can sort of get rid of a lot of this
49:10
Speaker 1: quantum weirdness and uncertainty. In some ways, it even hangs
49:13
Speaker 1: together better than other theories, and it's a sort of
49:16
Speaker 1: unfortunate that it was cast aside for so many decades
49:19
Speaker 1: because of the mistake of eminent physicists. But we'll see
49:22
Speaker 1: what the future holds and how much progress we have
49:25
Speaker 1: to make. So thanks again very much for coming on
49:27
Speaker 1: the podcast. It was a pleasure. Thank you, Thank you
49:29
Speaker 1: very much. Thanks for listening, and remember that Daniel and
49:39
Speaker 1: Jorge explained. The Universe is a production of I Heart
49:42
Speaker 1: Radio or more podcast. For my heart Radio, visit the
49:45
Speaker 1: I heart Radio app, Apple Podcasts, or wherever you listen
49:49
Speaker 1: to your favorite shows.