Latest / Drawn of History / Theoretical Physicist Carlo Rovelli Explains the Observer Effect(M4A_128K)

Transcript

Theoretical Physicist Carlo Rovelli Explains the Observer Effect(M4A_128K) · Drawn of History

• 0:00
  Speaker 1: The Joe Rogan experience. And quantum mechanics is one of
• 0:04
  Speaker 1: these jumps. Now, Joe, we're still debating about us, right?
• 0:09
  Speaker 1: Physicists are debating about themselves and philosophers are debating. What
• 0:14
  Speaker 1: the hell have we understood with quantum mechanics? Quantum mechanics
• 0:17
  Speaker 1: telling us the world is not what we thought it is.
• 0:21
  Speaker 1: And there's a conversation that's going on, a debate, sometimes furious.
• 0:25
  Speaker 1: And somebody says, oh, you know, there is this... immense
• 0:29
  Speaker 1: wave function of the universe, other universes and stuff like that.
• 0:35
  Speaker 1: Trying to hang on on the existence of something absolutely
• 0:38
  Speaker 1: objective down there. Trying to multiply reality to make it objective.
• 0:43
  Speaker 1: But I think it's this dream of an absolute objectivity
• 0:47
  Speaker 1: which is a mistake.
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  Speaker 2: The dream of an absolute objectivity is a mistake. That's
• 0:52
  Speaker 2: really fascinating. When they first started understanding that observing quantum
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  Speaker 2: interactions changes them.
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  Speaker 1: Yeah.
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  Speaker 2: What, what was, how long did it take for them
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  Speaker 2: to even accept that? Like how many times did they
• 1:10
  Speaker 2: have to run those experiments with particles and waves with
• 1:15
  Speaker 2: observers versus not before they said, okay, something's going on
• 1:19
  Speaker 2: here where it seems that we, when we watch things,
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  Speaker 2: it has an effect on them and a measurable effect.
• 1:25
  Speaker 2: This is a real thing that's happening. This isn't, This
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  Speaker 2: isn't woo-woo.
• 1:29
  Speaker 1: No, it's not voodoo. Exactly. What was that like for them?
• 1:35
  Speaker 1: Smoking joint and getting high. These are the physicists, the
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  Speaker 1: ones who were supposed to be the most rational objective guys. Well,
• 1:42
  Speaker 1: what happened is that measurement piled up all through the
• 1:46
  Speaker 1: first 20 years of the 20th century. The measurements were
• 1:52
  Speaker 1: simple measurements, right? Atoms emit light. And the light has
• 1:57
  Speaker 1: special colors. This color is a spectrum of the light.
• 2:00
  Speaker 1: And they were trying to make sense of that. I mean,
• 2:01
  Speaker 1: how does the electron move to produce that light? It
• 2:04
  Speaker 1: didn't work, didn't work, didn't work. Then in Copenhagen, there
• 2:10
  Speaker 1: was a school in which they were debating almost that.
• 2:13
  Speaker 1: And Niels Bohr is the first one who started saying, look,
• 2:18
  Speaker 1: to understand the atom, we should not just look at
• 2:20
  Speaker 1: the atom. We should understand how we look at it.
• 2:22
  Speaker 1: If we look at it in one way, we see
• 2:24
  Speaker 1: one thing. If we look at it another way, we
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  Speaker 1: see another thing. That was very confused. But then what
• 2:29
  Speaker 1: happened is that mathematics for describing the atoms came out.
• 2:34
  Speaker 1: This is the theory, the mathematical theory of quantum mechanics.
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  Speaker 1: It works very well. It's used today everywhere. I mean,
• 2:39
  Speaker 1: we talk with this microphone. There's quantum stuff inside. Circuits
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  Speaker 1: are designed with quantum properties of matter. So quantum mechanics
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  Speaker 1: is a solid thing. We know how to use it.
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  Speaker 1: It tells us, if you do this, you see this.
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  Speaker 1: If you do that, you see that. But it doesn't
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  Speaker 1: tell us in between. You do this, and then if
• 3:01
  Speaker 1: you do one thing, you see one thing. If you
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  Speaker 1: do another thing, you see another thing. And it doesn't
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  Speaker 1: give a story of what happened to the electron, to
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  Speaker 1: the quantum system itself. So people got confused. The physicists
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  Speaker 1: got confused. And they started discussing how to think about that.
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  Speaker 1: So quantum mechanics is a strange theory. We know how
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  Speaker 1: to use it. It's like a black box, but we
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  Speaker 1: don't know what's inside the box. It gives the right answer,
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  Speaker 1: but we can't make a picture in our mind of
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  Speaker 1: what happened in the atoms, in the things, in the
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  Speaker 1: electronic circuits. Even in a quantum computer, we don't know
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  Speaker 1: really what happened inside.
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  Speaker 2: That's so strange.
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  Speaker 1: Yes, but it works fantastically. And so physicists disagree. And
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  Speaker 1: some say, you know, there are extra variables that are
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  Speaker 1: in principle impossible to see who are– that's somebody who
• 3:53
  Speaker 1: says that– who determines what happens. And they are a
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  Speaker 1: priori invisible. Others say, you know, there are parallel worlds
• 4:01
  Speaker 1: in which– worlds. Worlds. Worlds.
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  Speaker 2: I know your talent.
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  Speaker 1: Sorry.
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  Speaker 2: Yeah.
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  Speaker 1: Then there are others, me included, who think, no, no, no,
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  Speaker 1: it's really philosophical here. We have to get rid of
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  Speaker 1: the idea that there is something there just by itself.
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  Speaker 1: What is there is what affects me or what affects
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  Speaker 1: you or what affects another piece of matter. So we
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  Speaker 1: have to think of reality as processes of things affecting
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  Speaker 1: one another, relations, relations. And, you know... In a sense,
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  Speaker 1: down there, the simple physics is more like our everyday
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  Speaker 1: life than what we imagined in thinking that it was
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  Speaker 1: so objective and abstract. Everyday life, you know, who are you,
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  Speaker 1: Joe Rogan? What I see, what he sees, what people
• 5:00
  Speaker 1: listen to you, you're a multiplicity of things. Which one
• 5:03
  Speaker 1: is the real one? Well, you are this collection. of
• 5:07
  Speaker 1: perspectives on you, including your own perspective on yourself, there's
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  Speaker 1: no final one. What is a final description of you?
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  Speaker 1: Or what is a final description of a cup of water?
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  Speaker 1: Is that the one given by chemistry, by physics? Which physics?
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  Speaker 1: Quantum physics? Quantum gravity? By psychology? A cup of water
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  Speaker 1: is because we drink. That's why we call it a
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  Speaker 1: cup of water. So it's a human picture of what
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  Speaker 1: is going on. Which one is the final one? I
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  Speaker 1: don't think there is a final one. There is a
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  Speaker 1: collection of perspective on the same cup of water, and
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  Speaker 1: that's a cup of water.
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  Speaker 2: So when they first started measuring this observer effect, what
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  Speaker 2: was the reaction? Like how long did it take for
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  Speaker 2: them to accept it? Because that seems like such a
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  Speaker 2: completely new chapter of science.
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  Speaker 1: Yeah. It worked so well. that people accepted even if
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  Speaker 1: it was confused.
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  Speaker 2: Could you explain to people that maybe don't know what
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  Speaker 2: we're talking about, how those experiments work?
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  Speaker 1: These were the first experiments with atoms. People had this
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  Speaker 1: idea that an atom is a nucleus, a central nucleus,
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  Speaker 1: and an electron is moving around. So the property of
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  Speaker 1: the atom, the way it makes molecules, the way it
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  Speaker 1: produces light, had to be computed from the movement of
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  Speaker 1: the electrons. And the mathematical theory was developed for doing that.
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  Speaker 1: And then people started making experiments in laboratories about how
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  Speaker 1: atoms move, how molecules move, small things move. And the
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  Speaker 1: mathematical theory predicts them perfectly. And the mathematical theory predicts
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  Speaker 1: the property of matter The success was really spectacular. Let
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  Speaker 1: me just tell you one example of the success. You
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  Speaker 1: remember the periodic table of the elements, right? We had
• 7:17
  Speaker 1: it in, I don't know, in Italy, we had it
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  Speaker 1: in primary school, we had it on the classroom, on
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  Speaker 1: the wall. Hydrogen, helium, all the, there are about 100
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  Speaker 1: atoms and 100 elements and everything we see is just
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  Speaker 1: a composition of these 100 elements. This is what the
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  Speaker 1: chemists have figured out through the 18th, 19th, 20th century.
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  Speaker 1: All right, so why this hundred elements? Why those particular properties?
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  Speaker 1: Why this strange structure of the periodic table of the element?
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  Speaker 1: You know, there are two and then seven, and then
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  Speaker 1: this is a peculiar structure. Well, it turns out if
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  Speaker 1: you use quantum mechanics, you just write an equation and bingo,
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  Speaker 1: it has exactly a number of solutions, one per each element.
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  Speaker 1: So you understand exactly what is going on. You understand
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  Speaker 1: why there are these elements. You can predict the elements. People,
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  Speaker 1: in fact, could predict properties of the element without having
• 8:09
  Speaker 1: measuring them, before measuring them, and then check. That's the
• 8:13
  Speaker 1: magic of physics, right?
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  Speaker 1: You predict things before seeing them. The electromagnetic waves that
• 9:38
  Speaker 1: we use to send your broadcast all over the planet...
• 9:43
  Speaker 1: This is an electromagnetic wave. Well, they were not discovered
• 9:46
  Speaker 1: by seeing them. They were predicted by Maxwell and Hertz.
• 9:52
  Speaker 1: They wrote a question and said, well, if you do that,
• 9:54
  Speaker 1: you make a little circuit with some electricity that goes on,
• 9:57
  Speaker 1: then the other side of the room, you can have
• 9:58
  Speaker 1: another one, and there's a wave. that goes by, and bingo,
• 10:02
  Speaker 1: it worked. And then it worked between Europe and US.
• 10:06
  Speaker 1: You can send waves. You can predict things. That's the
• 10:09
  Speaker 1: strength of science. You know, black holes were discovered in
• 10:12
  Speaker 1: the sky, but not because somebody said, oh, look, there's
• 10:15
  Speaker 1: a black hole. They were predicted by Einstein. So, because
• 10:20
  Speaker 1: of the equations of gravity, blah, blah, you should expect
• 10:23
  Speaker 1: to see black holes. And then they were found. So
• 10:25
  Speaker 1: there is this extraordinarily predictive power. Today in engineering that
• 10:32
  Speaker 1: put together circuits, quantum circuits, doesn't have to go trial
• 10:37
  Speaker 1: and effort. You make a calculation, it predicts what's going
• 10:39
  Speaker 1: to happen. It works. It works fabulously. So quantum mechanics works.
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  Speaker 1: It gives good predictions. The question open is that you
• 10:49
  Speaker 1: can have something that works very, very well and you
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  Speaker 1: don't know why.
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  Speaker 2: Could you explain what it does, like what that experiment
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  Speaker 2: does and why it was so confusing to them? When
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  Speaker 2: they were sending the double slit?
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  Speaker 1: Yeah, there were a number of extremely confusing experiments. Here
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  Speaker 1: is one, if I can try to make it in
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  Speaker 1: a few words. you have a wall with two holes,
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  Speaker 1: two slits, okay? And you send one particle from one
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  Speaker 1: side to the other side. Okay, that's easy. You can
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  Speaker 1: try to do many times. It goes through one of
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  Speaker 1: the two slits and it gets to the other time. Now,
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  Speaker 1: if you look which slits it goes through, it only
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  Speaker 1: goes through one slit or the other, okay? So never both, never...
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  Speaker 1: So if you go through one and you check, it
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  Speaker 1: goes through one and the other. So far, so good.
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  Speaker 1: But that is a magic. If you send it, the
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  Speaker 1: particle can go to one point on the screen of
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  Speaker 1: the other side if you have one screen open. It
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  Speaker 1: can go to the same point if you have one
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  Speaker 1: hole open. It can get to the same point if
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  Speaker 1: you have the other hole open, but it does never
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  Speaker 1: get there if you have both open. And that's, if
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  Speaker 1: you start thinking The more you think, the more it
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  Speaker 1: makes no sense at all. Because if you can get
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  Speaker 1: there through one hole, why cannot it go there if
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  Speaker 1: two holes are open? So the only possibility is that
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  Speaker 1: in some senses go through both. And somehow part go
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  Speaker 1: through one, part go through the other, and the two
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  Speaker 1: parts forbid each other to go to that particular place.
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  Speaker 1: But then you look at the two holes, and it
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  Speaker 1: never goes through both, only one. Now, do you find
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  Speaker 1: this confusing? Yes. And for a century, people have been
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  Speaker 1: confused about that. So what's the way out? The way
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  Speaker 1: out is that the question, where is the particle if
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  Speaker 1: you're not checking, if it's not interacting with something else,
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  Speaker 1: it's a wrong question. There's just no particle. The particle
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  Speaker 1: is only the effect it has on the screen, on
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  Speaker 1: the detectors. You cannot make sense of the particle as
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  Speaker 1: something which always has a position. It only has a
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  Speaker 1: position when it interacts with something else. That's a mystery
• 13:18
  Speaker 1: of quantum mechanics, the magic of quantum mechanics, and a
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  Speaker 1: challenge to our idea of an objective, always-existing particle independent
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  Speaker 1: of its interaction.
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  Speaker 2: What do you think is happening? Do you have any
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  Speaker 2: theories of what is happening that's causing it to behave
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  Speaker 2: differently when observed? Or when measured? So the measurement itself
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  Speaker 2: is something. Something is going on, it interacts with the measurement,
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  Speaker 2: and it changes the way it makes a pattern.
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  Speaker 1: Yes. But it's not a measurement in the sense of,
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  Speaker 1: you know, some physicists making a measurement. It's just interaction
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  Speaker 1: with anything. It's a.
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  Speaker 1: If there is something to interact with, or if there isn't,
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  Speaker 1: the physics is completely different. And if there isn't, the
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  Speaker 1: question where the particle is is a badly posed question.
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  Speaker 1: So the particle is something... We shouldn't think of the
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  Speaker 1: particle as an entity which always has a position. We
• 14:29
  Speaker 1: should think of it as an entity like it snaps here,
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  Speaker 1: and then it snaps there, and then it snaps there.
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  Speaker 1: And when it snaps is when it hits something. And
• 14:37
  Speaker 1: the These snaps are connected by, we can predict probabilistically
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  Speaker 1: where they're going to happen, but if we ask what
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  Speaker 1: happened in between, it makes no sense. The particle is
• 14:50
  Speaker 1: just these interactions.
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  Speaker 2: Do you think we'll ever understand what's happening?
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  Speaker 1: Yes, I do. I do because historically, every time we
• 15:03
  Speaker 1: have found something strange, it seemed... totally incomprehensible at first.
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  Speaker 1: And then we get used to it. And we start learning.
• 15:12
  Speaker 1: Let me give you an example. This is much older.
• 15:16
  Speaker 1: I don't think science is modern stuff. Learning about the
• 15:21
  Speaker 1: world is an ancient thing. So about 2,000 years ago,
• 15:25
  Speaker 1: humankind realized that the Earth is a ball, is a sphere.
• 15:30
  Speaker 1: It's not a flat thing. Not everybody's convinced, but.
• 15:34
  Speaker 2: A lot of people aren't.
• 15:36
  Speaker 1: But it is a book. And why not everybody's convinced?
• 15:41
  Speaker 1: Because indeed, it's incredibly counterintuitive, right? You're now here, and
• 15:46
  Speaker 1: in Sydney, people are upside down. Why don't they follow?
• 15:50
  Speaker 1: I don't know. Do you remember when you learned it
• 15:52
  Speaker 1: the first time you were a kid?
• 15:53
  Speaker 2: I've always learned it, so it's... I mean, it seemed weird.
• 15:57
  Speaker 1: It seems weird.
• 15:58
  Speaker 2: But I mean, I can't remember a time where I
• 16:01
  Speaker 2: didn't know it. I mean, I guess they taught it
• 16:04
  Speaker 2: in science when I was in grade school.
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  Speaker 1: Exactly. Exactly. So you're a kid. You're told that.
• 16:10
  Speaker 2: I'm just like, well, they're smarter than me. So, well,
• 16:12
  Speaker 2: it seems crazy. But I guess the Earth is round,
• 16:15
  Speaker 2: just like the sun and the moon.
• 16:16
  Speaker 1: And it spins.
• 16:17
  Speaker 2: And we're stuck to it somehow because of this thing
• 16:20
  Speaker 2: called gravity that they can't totally explain. It has something
• 16:22
  Speaker 2: to do with mass.
• 16:25
  Speaker 1: Right, right.
• 16:26
  Speaker 2: And it's something you can measure.
• 16:27
  Speaker 1: But how the hell do people in Sydney can live
• 16:29
  Speaker 1: upside down? Right. Don't they fall?
• 16:31
  Speaker 2: It's all strange. Why does the ocean stay in place?
• 16:34
  Speaker 1: Why the ocean stay in place?
• 16:35
  Speaker 2: That's the flat earthers. They love that one.
• 16:38
  Speaker 1: Exactly.
• 16:38
  Speaker 2: A ball spinning 1,000 miles an hour.
• 16:40
  Speaker 1: Exactly. So some people just refuse to believe that.
• 16:43
  Speaker 2: What?
• 16:44
  Speaker 1: What do they refuse to believe? That reality is a
• 16:47
  Speaker 1: bit different than what we think.
• 16:48
  Speaker 2: Yes.
• 16:49
  Speaker 1: That's the point. Reality is different than what we think.