Latest / Daniel and Kelly’s Extraordinary Universe / Classic Episode - Is Light a Particle or a Wave?

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Classic Episode - Is Light a Particle or a Wave? · Daniel and Kelly’s Extraordinary Universe

• 0:08
  Speaker 1: Is it possible to be two different things at the
• 0:11
  Speaker 1: same time?
• 0:13
  Speaker 2: Can you like dogs and cats?
• 0:16
  Speaker 1: Can you be a horse and a giraffe at the
• 0:18
  Speaker 1: same time?
• 0:19
  Speaker 2: Can something taste salty and sweet? Can a dress be
• 0:23
  Speaker 2: black and blue and white and gold?
• 0:26
  Speaker 1: In today's podcast, we talk about the centuries old scientific
• 0:30
  Speaker 1: debate about light.
• 0:32
  Speaker 2: Is light a particle or a wave?
• 0:35
  Speaker 1: Or is it both? Hello, I'm Jorge and I'm Daniel.
• 0:57
  Speaker 2: Welcome to Daniel and Jorge Explain the Universe.
• 1:00
  Speaker 1: In which we try to explain the whole universe and
• 1:03
  Speaker 1: everything in it, including light.
• 1:05
  Speaker 2: Now, I'm a cartoonist. I draw something called PhD comics.
• 1:08
  Speaker 1: And I'm a particle physicist. During the day, I smash
• 1:11
  Speaker 1: particles together at the large Hadron Collider.
• 1:14
  Speaker 2: Yeah. Well, today on the program, we're going to talk
• 1:16
  Speaker 2: about the nature of light.
• 1:22
  Speaker 1: That's right. People have been arguing for centuries what is light?
• 1:26
  Speaker 1: Is it made out of particles? Is it made out
• 1:28
  Speaker 1: of waves? It's something else? Is it tiny little puppies
• 1:31
  Speaker 1: screaming through space? People have gone back and forth on
• 1:33
  Speaker 1: the issue, and today even the topic is not yet
• 1:37
  Speaker 1: totally settled. So we're going to be taking you through
• 1:39
  Speaker 1: that history and breaking it down.
• 1:41
  Speaker 2: It's one of the most mind blowing questions in human
• 1:44
  Speaker 2: scientific history.
• 1:45
  Speaker 1: That's right, what is light made out of? So, as usual,
• 1:48
  Speaker 1: before we dig into it, we went out and we
• 1:50
  Speaker 1: asked people on the street. What do you think light
• 1:52
  Speaker 1: is made out of? What do people know about light?
• 1:54
  Speaker 2: Is light a particle or is it a wave?
• 1:57
  Speaker 1: Here's what people had to say. Do you think light
• 1:59
  Speaker 1: is made out of particles or waves or both or neither? Photons? Yeah? Photons? Yeah,
• 2:05
  Speaker 1: so you think light it's a particle. I think it's waves,
• 2:08
  Speaker 1: youth waves. Yeah, cool, it's both, I think because it
• 2:13
  Speaker 1: moves like a wave, but it also has properties of
• 2:16
  Speaker 1: a particle and there's nothing saying it can't people. Okay, light,
• 2:23
  Speaker 1: I think they're made of wavelength.
• 2:27
  Speaker 2: Yeah all right. Well it's interesting because I think all
• 2:31
  Speaker 2: of the answers are right.
• 2:35
  Speaker 1: Or none of them are or both.
• 2:39
  Speaker 2: Yeah.
• 2:39
  Speaker 1: Well, it seems like a lot of people reflected the
• 2:42
  Speaker 1: fact that there is a controversy like that. You know,
• 2:44
  Speaker 1: it's not really well described, but either those some people
• 2:47
  Speaker 1: went all in, you know, like it's a photon or
• 2:49
  Speaker 1: it's a wave, or it's a wave.
• 2:51
  Speaker 2: Length right, Yeah, that was my favorite one.
• 2:54
  Speaker 1: I want to be a wavelength.
• 2:55
  Speaker 2: Like I've heard of this word. It sounds really cool
• 2:58
  Speaker 2: and scientific. I'm just going to throw it up.
• 3:00
  Speaker 1: There, that's right. Yeah, maybe I get some points. We
• 3:04
  Speaker 1: award no points to people, no points, that's right. There's
• 3:07
  Speaker 1: no price. Your price is you get to be on
• 3:09
  Speaker 1: our podcast and maybe we even make fun of you. Yeah.
• 3:12
  Speaker 2: Yeah, but yeah, I guess what you mean is nobody
• 3:14
  Speaker 2: sort of fell for the trap, right, Like nobody said,
• 3:17
  Speaker 2: oh of course it's a particle, or nobody said, oh
• 3:19
  Speaker 2: of course it's a wave. Most people sort of knew
• 3:21
  Speaker 2: that there's some sort of duality there, something weird going on.
• 3:24
  Speaker 1: That's right. That science is having some trouble, some difficulty
• 3:28
  Speaker 1: coming up with a way to describe what light is.
• 3:31
  Speaker 1: And that might seem surprising you because light is everywhere, right,
• 3:34
  Speaker 1: and it runs the universe. It's streaming through the Solar
• 3:37
  Speaker 1: system from the Sun, illuminating our lives, empowering everything on Earth.
• 3:41
  Speaker 1: So you think this would be sort of a high
• 3:43
  Speaker 1: priority topic to figure out, like what is this stuff?
• 3:45
  Speaker 1: What is it made out of?
• 3:47
  Speaker 2: Yeah? I mean, like, what are we paying you for, Daniel,
• 3:49
  Speaker 2: if not to figure these kinds of questions out.
• 3:52
  Speaker 1: I was just about to figure out what light was
• 3:54
  Speaker 1: when you called and said it's time to do this podcast.
• 3:57
  Speaker 2: Sorry, science was totally you're a train of thought there,
• 4:01
  Speaker 2: that's right.
• 4:02
  Speaker 1: Reflect on that for a minute.
• 4:03
  Speaker 2: Or but no, Yeah, I'm a California taxpayer. Part of
• 4:09
  Speaker 2: my salary goes to paying your salary, like you know,
• 4:12
  Speaker 2: one million of a percent.
• 4:13
  Speaker 1: That's true. Yeah, so you're saying you did pay taxes
• 4:15
  Speaker 1: last year.
• 4:17
  Speaker 2: There you go again.
• 4:18
  Speaker 1: That's another topic.
• 4:19
  Speaker 2: Seekers on air, Daniel. Anyway, So that's an interesting question,
• 4:27
  Speaker 2: like is light a waver particle? And it's weird that
• 4:29
  Speaker 2: we don't know, But maybe let's break it down a
• 4:32
  Speaker 2: little bit. What is it? Like, what are we actually
• 4:34
  Speaker 2: talking about when we say that light could be a
• 4:36
  Speaker 2: particle or light could be a wave, like you know,
• 4:39
  Speaker 2: most people probably think of light as just like just
• 4:42
  Speaker 2: like brightness, right.
• 4:43
  Speaker 1: Yeah. The thing to understand here is that we try
• 4:47
  Speaker 1: to describe light in terms of things we know, and
• 4:50
  Speaker 1: that's what science is. Right. You see something weird and
• 4:53
  Speaker 1: new and you wonder, oh, is it like this other
• 4:55
  Speaker 1: thing I know? So we've observed different kinds of phenomena
• 4:58
  Speaker 1: in the world, like you've seen waves, right, you go
• 5:01
  Speaker 1: to the beach, you see waves and water, you drop
• 5:03
  Speaker 1: a rock in a small puddle, you see waves. We
• 5:06
  Speaker 1: know what waves are, and we see different phenomena. We
• 5:09
  Speaker 1: try to categorize them in terms of things we know, right,
• 5:11
  Speaker 1: So like when people were studying sound, they discovered, oh,
• 5:15
  Speaker 1: sound is actually a wave. You know, it's a compression
• 5:17
  Speaker 1: wave in the air. And that's cool because he says, oh,
• 5:20
  Speaker 1: I already know how the math for waves works. Right,
• 5:23
  Speaker 1: I've seen waves and water. I've seen waves and other stuff.
• 5:26
  Speaker 2: You can describe it with like equations, right, yeah, wavy equations.
• 5:31
  Speaker 1: That's right, very solid unwavy physics to describe waves. And
• 5:35
  Speaker 1: there's a lot of science that's gone into understanding waves.
• 5:38
  Speaker 1: So if you can cram it into that box and say, oh,
• 5:40
  Speaker 1: this is just another example of something we already know,
• 5:43
  Speaker 1: then you're taking a huge leap forward. Right. So that's
• 5:47
  Speaker 1: something people try to do, is say, like, look, can
• 5:49
  Speaker 1: we describe this in terms of other things we know?
• 5:50
  Speaker 2: So we need like, you know, we know about light,
• 5:54
  Speaker 2: but we want to know how it behaves and what
• 5:56
  Speaker 2: makes it work.
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  Speaker 1: Yeah, and just on a more general level, you try
• 5:58
  Speaker 1: to see something new, try to describe in terms of
• 6:01
  Speaker 1: things you know, Like say you taste a new kind
• 6:03
  Speaker 1: of fruit and you'd be like, Oh, it's a little
• 6:05
  Speaker 1: bit like a cherry, and a little bit like an apple,
• 6:07
  Speaker 1: and a little bit like you know, it's got a
• 6:08
  Speaker 1: hint of smokiness to it or whatever. You know.
• 6:10
  Speaker 2: You're like, it's a chapel.
• 6:12
  Speaker 1: It's a chapel. How has nobody ever invented that? The
• 6:15
  Speaker 1: cherry apple chapel? Oh my gosh, somebody, if our lawyer
• 6:19
  Speaker 1: is listening, get on that right away. Copyright that idea.
• 6:22
  Speaker 2: I'll reserve ww dot chapel dot com. Up.
• 6:24
  Speaker 1: That's right. So that's the basic idea is we have
• 6:26
  Speaker 1: these things we've seen. You see something new, you don't
• 6:29
  Speaker 1: want to create a whole new category. You want to
• 6:31
  Speaker 1: fit into one of the existing categories.
• 6:33
  Speaker 2: So we sort of knew about light. It came from
• 6:35
  Speaker 2: the sun. It you know, if you light a fire,
• 6:37
  Speaker 2: it spreads out into a room. And so we're like,
• 6:40
  Speaker 2: what's going on? Like what what best describes how this
• 6:45
  Speaker 2: light you know, comes from a source and bounces off
• 6:47
  Speaker 2: the walls and stuff.
• 6:49
  Speaker 1: Exactly exactly, that's the question. And so we'd seen things
• 6:52
  Speaker 1: like waves, So what do we mean when we say
• 6:54
  Speaker 1: a wave? Like how could a light be a wave?
• 6:55
  Speaker 2: Well, how can anything be a wave?
• 6:58
  Speaker 1: Yeah? How can anything be a wave? A wave is
• 7:00
  Speaker 1: a funny thing because it's not a thing itself. It's
• 7:03
  Speaker 1: a property of some medium.
• 7:05
  Speaker 2: Like it's the words like a ripple on something.
• 7:07
  Speaker 1: Yeah, that's right. Like if you do the wave at
• 7:09
  Speaker 1: a baseball game, you know, there's nothing to the wave itself.
• 7:13
  Speaker 1: It's just a bunch of people moving up and down
• 7:15
  Speaker 1: and waving their hands, right.
• 7:16
  Speaker 2: Or like a sound wave is just like air molecules
• 7:19
  Speaker 2: kind of bumping forward.
• 7:21
  Speaker 1: That's right, yeah, exactly. Or a wave in the ocean
• 7:24
  Speaker 1: is just it's an arrangement of the water, right, It's
• 7:27
  Speaker 1: a way the water gets compressed and then stretched out
• 7:29
  Speaker 1: and compressed and then gets stretched out. So that's an
• 7:32
  Speaker 1: important thing about a wave is that it moves in
• 7:33
  Speaker 1: this way through a medium.
• 7:35
  Speaker 2: M Okay, so that's a wave. It's like a propagation,
• 7:39
  Speaker 2: it's like a ripple through something. But then, so then
• 7:41
  Speaker 2: what what would you call a particle? A particle is
• 7:43
  Speaker 2: different than that.
• 7:44
  Speaker 1: A particle is different than that, and it's a totally
• 7:47
  Speaker 1: different kind of thing, you know, And to be a
• 7:49
  Speaker 1: particle physicist, it's kind of odd, but The concept of
• 7:52
  Speaker 1: a particle is not that really well defined, you know.
• 7:55
  Speaker 1: But when I think of a particle, I think of
• 7:57
  Speaker 1: taking matter and breaking it down to its smallest pieces.
• 8:00
  Speaker 1: If something's made out of particles, it means that at
• 8:02
  Speaker 1: its smallest level, it's made out of these little bits
• 8:05
  Speaker 1: that can't be chopped into smaller bits, and that they're localized.
• 8:09
  Speaker 1: They're like small and contained. Right. If you discover that
• 8:14
  Speaker 1: something is made of particles, you expect it to be
• 8:17
  Speaker 1: like mostly empty space, but with these little dots of matter, right.
• 8:21
  Speaker 2: Like you would take something and then you smash it
• 8:23
  Speaker 2: to bit and just keep smashing, and at some point
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  Speaker 2: you're going to get to these little baby balls or
• 8:28
  Speaker 2: like little tiny pellets that you can't break down anymore.
• 8:31
  Speaker 1: That's right. Yeah, It's like seeing a picture on your
• 8:35
  Speaker 1: computer screen and discovering it's made out of pixels, right,
• 8:38
  Speaker 1: and that those pixels are the basic elements and they
• 8:40
  Speaker 1: come together to make the whole picture. So figuring out
• 8:43
  Speaker 1: that something is made of particles means that there's made
• 8:46
  Speaker 1: out these these little bits that are not connected to
• 8:50
  Speaker 1: each other, right, they're separated. So a wave and a
• 8:53
  Speaker 1: particle in nature are totally different. Kinds of things. Right. Now,
• 8:56
  Speaker 1: water of course is made of particles, but can have
• 8:59
  Speaker 1: waves in it.
• 9:00
  Speaker 2: Right, But I think maybe what's important here is that,
• 9:03
  Speaker 2: you know, particles we tend to think of as little
• 9:05
  Speaker 2: tiny bits that can bounce around, right, and like go
• 9:08
  Speaker 2: in a street line and then hit something else and
• 9:12
  Speaker 2: then bounce back, or you know, kind of fly through
• 9:15
  Speaker 2: space right in a discrete little package exactly.
• 9:19
  Speaker 1: That's exactly the right way to say. It's a discrete
• 9:21
  Speaker 1: little package. Right. So things that are made of particles
• 9:23
  Speaker 1: we think of as being discrete little bits, and they
• 9:26
  Speaker 1: they're broken up into these little pieces, and you're right,
• 9:30
  Speaker 1: they move in straight lines. Right, Like you throw a rock,
• 9:33
  Speaker 1: you roll a smooth ball across the surface, you expect
• 9:36
  Speaker 1: it to move in a straight line.
• 9:38
  Speaker 2: So that's kind of what we mean by a wave
• 9:40
  Speaker 2: and a particle, that's right.
• 9:41
  Speaker 1: Yeah.
• 9:42
  Speaker 2: And so the question is like, is light a ripple
• 9:45
  Speaker 2: on a medium? Is that what light is? Or is
• 9:47
  Speaker 2: it like actual little things and move around in space?
• 9:50
  Speaker 1: Right? Does it have its own stuff to it? Right?
• 9:53
  Speaker 1: Or is it just a way something else moves right?
• 9:55
  Speaker 1: That's sort of another way to phrase the question.
• 9:58
  Speaker 2: Right, And those are two pretty different pictures. Is of reality, right, Yeah,
• 10:01
  Speaker 2: light could be little pellets flying around, or it could
• 10:04
  Speaker 2: be some sort of ripple on a medium. To us
• 10:06
  Speaker 2: in our intuitive sense, it couldn't be any more different, right.
• 10:10
  Speaker 1: That's right. Yeah. It's like you can't be a Democrat
• 10:12
  Speaker 1: and a Republican, you know, just you have to pick one,
• 10:14
  Speaker 1: you know. Yeah, if you vote, you can be or
• 10:19
  Speaker 1: you could be neither. I suppose you shouldn't be both though, Yeah,
• 10:23
  Speaker 1: that would be a violation of some election law not
• 10:27
  Speaker 1: recommended to violate elections, right, that's right. Yeah. So, speaking
• 10:31
  Speaker 1: of political shouting matches, this one, this historical scientific shouting match,
• 10:35
  Speaker 1: began all the way back with the Greeks, right, Democratus
• 10:38
  Speaker 1: he's the guy sort of the first atomist. He's the
• 10:40
  Speaker 1: first person to look at the world and to say,
• 10:43
  Speaker 1: you know, maybe everything's made out of tiny little bits,
• 10:46
  Speaker 1: not just light, but also matter. And that was sort
• 10:48
  Speaker 1: of the birth of that idea that maybe everything around
• 10:52
  Speaker 1: us that seems macroscopic is made out of tiny little things,
• 10:55
  Speaker 1: smaller than we can see. And you know, as usual,
• 10:58
  Speaker 1: when somebody comes up with a good idea, they overextended.
• 11:01
  Speaker 1: They're like, well, maybe if rocks were made out of stuff.
• 11:03
  Speaker 1: Then water is also made out of particles, and maybe
• 11:06
  Speaker 1: even light is made out of particles. You know, at
• 11:08
  Speaker 1: the time, seemed like a totally a crazy reach, And.
• 11:12
  Speaker 2: That makes sense, right, because light seems to go in
• 11:14
  Speaker 2: a straight line. It seems to bounce off of things.
• 11:17
  Speaker 2: So why couldn't light just be like little tiny little
• 11:19
  Speaker 2: pellets that bounce around the room and then eventually hit
• 11:23
  Speaker 2: your eye and then that's how you see something.
• 11:24
  Speaker 1: Yeah, it certainly seems to have some of those particle
• 11:27
  Speaker 1: like properties, right, it moves in straight lines, it certainly
• 11:30
  Speaker 1: would be going really really fast. At the time, people
• 11:32
  Speaker 1: thought that light traveled instantly, right. They thought that light
• 11:36
  Speaker 1: instantaneously went from like the sun to the Earth, or
• 11:40
  Speaker 1: or if you started a fire, that the light would
• 11:42
  Speaker 1: immediately illuminate the room. Now, we of course know that
• 11:45
  Speaker 1: it just happens super duper crazy fast, too fast for
• 11:48
  Speaker 1: those folks to ever measure, so it's almost like it's instantaneous.
• 11:51
  Speaker 1: But they thought that these things just moved instantly through
• 11:54
  Speaker 1: space and filled up the room. Okay, and I want
• 11:56
  Speaker 1: to talk a little bit more about that, but first
• 11:58
  Speaker 1: a quick break.
• 12:12
  Speaker 2: So, initially we thought light was or the Greeks thought
• 12:15
  Speaker 2: that light was a.
• 12:16
  Speaker 1: Particle, right, And I think we have to qualify that
• 12:19
  Speaker 1: because it makes the Greeks sound really smart. Just come
• 12:22
  Speaker 1: up with this idea of atoms and all that stuff.
• 12:25
  Speaker 2: And you say this before you're really down into Greeks.
• 12:27
  Speaker 1: Well, I think people give the Greeks too much credit
• 12:29
  Speaker 1: for that, because, as I've probably said to you before,
• 12:32
  Speaker 1: the Greeks had lots and lots of ideas. You know,
• 12:34
  Speaker 1: they had like thousands of these ideas about how the
• 12:36
  Speaker 1: way the world works, and yeah, one of them was
• 12:38
  Speaker 1: close to true. But like, if we're going to do
• 12:40
  Speaker 1: some accounting, let's also remember the nine hundred and ninety
• 12:43
  Speaker 1: nine ones that were totally off base, you know, and
• 12:46
  Speaker 1: give them credit for those.
• 12:48
  Speaker 2: Yeah, find that Greek who thought life was just little puppies,
• 12:51
  Speaker 2: and be like seeing you guys also thought they were puppies.
• 12:53
  Speaker 2: You can't be that.
• 12:54
  Speaker 1: Smart, that's right. But he's a cool idea. So give
• 12:58
  Speaker 1: them credit for having that idea. Know what they were
• 13:00
  Speaker 1: smoking when they came up with it, But I'd like
• 13:02
  Speaker 1: to figure out where to find some. And then it
• 13:05
  Speaker 1: was thousands of years later before people had another idea.
• 13:07
  Speaker 1: It was a Descartes, the guy who's famous for. You know,
• 13:10
  Speaker 1: I think therefore I am he thought about He was
• 13:13
  Speaker 1: one of the earliest scientists, not just philosopher, but a scientist,
• 13:16
  Speaker 1: back in the day when you know, science really was
• 13:18
  Speaker 1: part of philosophy, and he thought that light was waves.
• 13:22
  Speaker 2: What made him think it was waves?
• 13:23
  Speaker 1: You know, I don't think he had much justification for it.
• 13:26
  Speaker 1: This is back in the early days when science wasn't
• 13:29
  Speaker 1: really an empirical study where you didn't like go out
• 13:31
  Speaker 1: and do experiments to test your hypothesis. It just made
• 13:34
  Speaker 1: more sense to him for light to be like these
• 13:37
  Speaker 1: wavelike disturbances.
• 13:39
  Speaker 2: Right, which kind of makes sense, right, Like if you
• 13:41
  Speaker 2: have a speaker in a room emitting sound waves, it's
• 13:45
  Speaker 2: not that different from like a light bulb in the
• 13:47
  Speaker 2: middle of the room emitting light all around it.
• 13:50
  Speaker 1: Right. Yeah. And there's some things that light does that
• 13:53
  Speaker 1: don't really that don't really seem consistent with particles, you know,
• 13:57
  Speaker 1: like the way light bends through a lens, right, it's
• 14:00
  Speaker 1: called we call it in science, we call that refraction.
• 14:03
  Speaker 1: You know, with light changes from going through air to glass,
• 14:05
  Speaker 1: it bends in this weird way. That's something that's very
• 14:08
  Speaker 1: common for waves, right.
• 14:10
  Speaker 2: And a particle wouldn't bend inside of a lens.
• 14:15
  Speaker 1: No, No, a particle that's definitely a wave like behavior. Yeah, oh,
• 14:19
  Speaker 1: not particle like behavior. And so Descartes saw that and
• 14:22
  Speaker 1: he's like, oh, you know, we have optics, we have
• 14:24
  Speaker 1: these lenses, so maybe light is a wave. But if
• 14:26
  Speaker 1: light is a wave, then it opens this other question.
• 14:29
  Speaker 1: What's doing the waving? Right? I mean with sound, you
• 14:32
  Speaker 1: know it's the air and the water waves. Obviously it's
• 14:34
  Speaker 1: the water. But if light is a wave, then what
• 14:37
  Speaker 1: is waving?
• 14:38
  Speaker 2: Meaning? Like, if light is a ripple, what is it a.
• 14:41
  Speaker 1: Ripple of that's right? Yeah, what's doing the rippling? Right?
• 14:44
  Speaker 1: If it's a wave, it has to be a wave
• 14:45
  Speaker 1: in something, because a wave is just a description of
• 14:48
  Speaker 1: some other form of matter rippling, right.
• 14:52
  Speaker 2: It couldn't just be like stuff that we can't see.
• 14:56
  Speaker 1: Yeah, and so you have to invent some stuff that
• 14:58
  Speaker 1: we can't see. Right. To explain light being a wave,
• 15:01
  Speaker 1: you have to invent this universe filled with stuff, or
• 15:03
  Speaker 1: there has to be that stuff between us and the
• 15:05
  Speaker 1: sun for example, right, which is a huge amount of
• 15:07
  Speaker 1: this new stuff you're inventing. And if you're looking at
• 15:10
  Speaker 1: the stars, there has to be that stuff between you
• 15:12
  Speaker 1: and the stars. Right, So now we're talking about billions
• 15:14
  Speaker 1: of miles of this new stuff, and Dick Cart, you know,
• 15:17
  Speaker 1: didn't know, so he just gave it a name. He's
• 15:20
  Speaker 1: called I don't even know how to pronounce it, but
• 15:21
  Speaker 1: he called it plenum. And he thought, well, there must
• 15:24
  Speaker 1: be if light is a wave, there must be some
• 15:26
  Speaker 1: stuff that's doing the waving, and we'll just give it
• 15:28
  Speaker 1: a name and maybe we'll be right, and then we'll
• 15:30
  Speaker 1: be famous forever.
• 15:31
  Speaker 2: Isn't it is that different than the ether?
• 15:33
  Speaker 1: It's similar in concept, right, It's a different idea, but
• 15:36
  Speaker 1: it's similar in concept that like, if light is a wave,
• 15:38
  Speaker 1: it must be waving through something, and we don't know
• 15:41
  Speaker 1: what it is, which is invents something to and give
• 15:43
  Speaker 1: it a name as a placeholder so when later people
• 15:45
  Speaker 1: do the hard work of actually discovering it, we'll still
• 15:48
  Speaker 1: get credit.
• 15:49
  Speaker 2: Okay, So it was a particle. Light was a particle,
• 15:51
  Speaker 2: then was a wave, and then what happened?
• 15:53
  Speaker 1: Well, then Newton came along, right, And Newton's a really
• 15:55
  Speaker 1: smart guy, and everybody knows that he's famous for thinking
• 15:58
  Speaker 1: about gravity, but he also like to think about optics
• 16:01
  Speaker 1: and lenses and he thought for sure that light was
• 16:04
  Speaker 1: a particle because he saw it moving in straight lines
• 16:07
  Speaker 1: and he saw distinct shadows. But you know, Newton also
• 16:11
  Speaker 1: did a lot of experiments with optics. He studied prisms,
• 16:14
  Speaker 1: and he saw light bending, and he saw light splitting
• 16:16
  Speaker 1: into colors. And you can't explain that if light is
• 16:19
  Speaker 1: a particle, but he tried. You know, he's like, well,
• 16:21
  Speaker 1: maybe when a particle hits the glass, it gets some
• 16:25
  Speaker 1: sort of weird sideways force and that makes it bend.
• 16:29
  Speaker 1: But you know, that's not really an explanation. That's just
• 16:32
  Speaker 1: sort of like a I don't really understand it. But
• 16:34
  Speaker 1: maybe it's something like this.
• 16:36
  Speaker 2: Like, if light is a particle, why does it split
• 16:39
  Speaker 2: into the rainbow kind of thing?
• 16:40
  Speaker 1: Yeah, exactly. And you know this is again back in
• 16:43
  Speaker 1: the day when empirical studies of science weren't the main
• 16:46
  Speaker 1: way to answer questions. It was mostly thinking in your
• 16:49
  Speaker 1: head about things that made sense to you, and then
• 16:52
  Speaker 1: they would argue about them. Right. A lot of the
• 16:54
  Speaker 1: way scientific disputes used to be resolved was people would
• 16:57
  Speaker 1: argue about it and then say, well, that makes no sense,
• 16:59
  Speaker 1: so it can't be true. And we know now, of
• 17:02
  Speaker 1: course that the universe doesn't always make sense to us.
• 17:04
  Speaker 1: What's real isn't necessarily the things that we would have
• 17:08
  Speaker 1: accepted as true or accepted as a reasonable way to
• 17:11
  Speaker 1: describe the universe. But you know, if that's the way
• 17:14
  Speaker 1: nature works, that's the way nature works, you have to
• 17:15
  Speaker 1: accept it. But that's the sort of primacy of experimental
• 17:19
  Speaker 1: results came later on. So back in the day, people
• 17:22
  Speaker 1: just sort of used to argue for an explanation that
• 17:24
  Speaker 1: made sense to them.
• 17:25
  Speaker 2: Right, Well, it was kind of hard for them to
• 17:27
  Speaker 2: build a particle collider, right.
• 17:29
  Speaker 1: That's right, Yeah, exactly, They didn't have the massive government
• 17:34
  Speaker 1: funding to do that. These were men of leisure studying
• 17:36
  Speaker 1: science and the spare time.
• 17:38
  Speaker 2: In fact, it was called like natural philosophy, right, It
• 17:41
  Speaker 2: wasn't called science at the time, was it.
• 17:43
  Speaker 1: Yeah, that's right exactly. All science grew out of philosophy.
• 17:48
  Speaker 1: It was called these folks were natural philosophers. Okay, But
• 17:51
  Speaker 1: you know, later on then people started doing experiments, and
• 17:54
  Speaker 1: there were a bunch of French guys who did a
• 17:57
  Speaker 1: bunch of experiments and some of some English folks, and
• 17:59
  Speaker 1: they they were studying how light behaved and refraction and reflection,
• 18:03
  Speaker 1: and they saw it doing these things, and they thought,
• 18:05
  Speaker 1: there's no way Newton's right, this has to be a wave,
• 18:08
  Speaker 1: you know. They saw things like interference patterns, right. Interference
• 18:13
  Speaker 1: patterns is when you have two waves and sometimes one
• 18:16
  Speaker 1: is rippling up at the same time another one is
• 18:19
  Speaker 1: rippling down. Right. So imagine, for example, you have a
• 18:23
  Speaker 1: bathtub of water in front of you, and you slap
• 18:25
  Speaker 1: it with two hands at once, right, each one is
• 18:28
  Speaker 1: going to send waves out, and then when those end,
• 18:31
  Speaker 1: those waves are either rippling up or rippling down. And
• 18:34
  Speaker 1: when they reach each other, if they're both rippling up
• 18:37
  Speaker 1: at the same time, then they constructively interfere to get
• 18:40
  Speaker 1: a double wave. If they're both rippling down at the
• 18:43
  Speaker 1: same time, they constructively interfere to get a double down wave.
• 18:47
  Speaker 1: If one is rippling up and the other's rippling down,
• 18:49
  Speaker 1: then then they cancel each other.
• 18:51
  Speaker 2: Out right, And so you would see no light.
• 18:54
  Speaker 1: Yeah, exactly, And so you can do this kind of stuff,
• 18:58
  Speaker 1: you know, in your bathtub. You can see interference patterns.
• 19:01
  Speaker 1: And what happens if you have two sources like that,
• 19:03
  Speaker 1: like one from each of your hands, is you get
• 19:05
  Speaker 1: some areas where the waves are high, in some areas
• 19:08
  Speaker 1: where the waves are low in some areas where there
• 19:10
  Speaker 1: are no waves, and so as you say, if you
• 19:12
  Speaker 1: do it with light, then you see these patterns of
• 19:14
  Speaker 1: dark and light, these stripes.
• 19:16
  Speaker 2: And you couldn't do that with particles, right, like a
• 19:18
  Speaker 2: particle wouldn't cancel another particle.
• 19:20
  Speaker 1: Yeah, there's no way to explain that with particles. People thought, well, look,
• 19:24
  Speaker 1: this is something that waves do and light is doing it,
• 19:26
  Speaker 1: and there's no way to explain it with particles, so
• 19:28
  Speaker 1: light must be a wave. Right. In fact, there's even
• 19:32
  Speaker 1: famous cases where they said, well, you know, if light
• 19:35
  Speaker 1: is a wave, then you know, if you set up
• 19:37
  Speaker 1: this various experiment, you would get this crazy effect and
• 19:40
  Speaker 1: so that's absurd and so it definitely can't be true.
• 19:44
  Speaker 1: And then they went and did the experiment and saw
• 19:45
  Speaker 1: the crazy wave effect and they're like, oh, that is true.
• 19:48
  Speaker 1: You know this is a I love that because it's
• 19:52
  Speaker 1: the primacy of experiment experimentalism, right, like, go and check
• 19:55
  Speaker 1: the data, Go and actually get some data and see
• 19:57
  Speaker 1: what the universe tells you.
• 19:59
  Speaker 2: Yeah, Like you're like, a doughnut can't possibly be a
• 20:02
  Speaker 2: croissant at the same time, But it turns out that
• 20:06
  Speaker 2: you can bake something called a cronat.
• 20:08
  Speaker 1: Yeah exactly. I think that's a big debate in pastry
• 20:11
  Speaker 1: science still though. Yeah, is it from a donut like
• 20:14
  Speaker 1: that's like a croissant or is it a croissant that's
• 20:15
  Speaker 1: like a donut.
• 20:16
  Speaker 2: Yeah. I'm getting my degree in a particle baking.
• 20:21
  Speaker 1: Yeah, the large Pastry Collider. I'm looking forward to the
• 20:24
  Speaker 1: construction of that project.
• 20:29
  Speaker 2: But that's kind of what you mean. It's like you,
• 20:30
  Speaker 2: people don't think it's possible until they actually see it.
• 20:33
  Speaker 2: And waves and light has been doing this to people
• 20:36
  Speaker 2: for hundreds of years, or they're like, they can't possibly
• 20:38
  Speaker 2: be doing this, or they can't it can't possibly be
• 20:40
  Speaker 2: doing that, but it just keeps doing all these weird things.
• 20:43
  Speaker 1: Yeah, exactly. And that was the experiment it's called the
• 20:46
  Speaker 1: double slit experiment, the one that really convinced people that
• 20:50
  Speaker 1: light is a wave because they've shone a strong light
• 20:54
  Speaker 1: and they had just two little narrow slits which act
• 20:56
  Speaker 1: like as sources like slapping your hands in the bath
• 20:58
  Speaker 1: to water, and then on a screen behind it. They
• 21:01
  Speaker 1: saw these interference patterns, right, is that you could definitely
• 21:04
  Speaker 1: only get if light was a wave. And so that
• 21:07
  Speaker 1: was the early eighteen hundreds, and everybody was absolutely certain
• 21:10
  Speaker 1: light was totally a wave. The question was settled. We
• 21:13
  Speaker 1: knew forever light was a wave, and we still didn't
• 21:16
  Speaker 1: know what was it waving through.
• 21:19
  Speaker 2: But how did they explain all those particle experiments?
• 21:21
  Speaker 1: Well, this was before we even really knew about particles, right,
• 21:25
  Speaker 1: No real particles had been discovered at this point. With
• 21:28
  Speaker 1: this idea from the Greeks of thousands of years ago
• 21:31
  Speaker 1: that maybe things were made out of particles, and chemistry
• 21:33
  Speaker 1: was getting warmed up, and you know, people are starting
• 21:36
  Speaker 1: to think about atoms and molecules and stuff, but they
• 21:39
  Speaker 1: hadn't really seen any actual particles yet. And it was
• 21:41
  Speaker 1: decades later when the electron was discovered that people started
• 21:46
  Speaker 1: to think about the particle model again. But you know,
• 21:48
  Speaker 1: the wave theory was definitely ascended, right, Everybody definitely looked
• 21:51
  Speaker 1: at these double slit experiments and saw light doing all
• 21:53
  Speaker 1: this wavy stuff, and they were sure that light was
• 21:56
  Speaker 1: a wave.
• 21:57
  Speaker 2: Now did people extend that to other things, like, you know,
• 22:00
  Speaker 2: they thought, oh, light is this weird wavy thing, but
• 22:02
  Speaker 2: surely us, we're made out of little tiny atoms.
• 22:05
  Speaker 1: Yeah, that's a good question. I wonder if people thought,
• 22:08
  Speaker 1: hm light's a wave. Maybe we're a wave too, right.
• 22:11
  Speaker 2: Yeah, or like everything is just like a wave.
• 22:14
  Speaker 1: Yeah, probably not, because nobody thought that light had any
• 22:18
  Speaker 1: mass to it, right, whereas we definitely know that we
• 22:21
  Speaker 1: have mass. Right, we feel pretty heavy sometimes after a
• 22:24
  Speaker 1: big meal. Even before the discovery particles, though, there was
• 22:27
  Speaker 1: a huge advance in the theory of light, which was
• 22:31
  Speaker 1: a Scottish guy named Maxwell. He was working on electricity
• 22:35
  Speaker 1: and magnetism, and he put together all these equations to
• 22:38
  Speaker 1: describe electricity magnetism, and he just sort of wrote them
• 22:42
  Speaker 1: down in a new way. This is like the way
• 22:44
  Speaker 1: you could do theoretical physics back in the days. You
• 22:46
  Speaker 1: just take existing ideas and you find a new way
• 22:48
  Speaker 1: to write them down. But he wrote them down in
• 22:51
  Speaker 1: this way that looked like the mathematics of a wave.
• 22:55
  Speaker 1: We have this equation, it's called a wave equation, and
• 22:57
  Speaker 1: it describes how waves moved through a medium.
• 23:00
  Speaker 2: Meaning like it could be described by equations that looked
• 23:03
  Speaker 2: like sine waves and cosine waves, right, I mean, just
• 23:06
  Speaker 2: in case anyone remembers high school math, that's kind of
• 23:10
  Speaker 2: what we mean by mathematical equations. So you can describe
• 23:13
  Speaker 2: it as a sine wave ors cosine wave.
• 23:15
  Speaker 1: Right, that's right. Yeah, The solution to these equations are
• 23:18
  Speaker 1: sine waves and cosine waves. These are differential equations to
• 23:21
  Speaker 1: describe how things move through the medium, and if things
• 23:24
  Speaker 1: follow these equations, then they're waves, right, okay. And so
• 23:28
  Speaker 1: he looked at the equations for electricity and for magnetism
• 23:32
  Speaker 1: and he rewrote them and he realized, you can rewrite
• 23:34
  Speaker 1: them in a way that looks just like the wave equation. Right,
• 23:38
  Speaker 1: So he said, oh, electricity magnetism has the same equation
• 23:42
  Speaker 1: as waves moving through water or waves moving through air.
• 23:47
  Speaker 1: And in fact, if you write it in terms of
• 23:49
  Speaker 1: this wave equation, you can pull out what the speed
• 23:52
  Speaker 1: of those waves must be. And the speed that he
• 23:55
  Speaker 1: pulled out from this from these equations was the speed
• 23:57
  Speaker 1: of light. So he had this moment of epift. He
• 24:00
  Speaker 1: must have been like in his office late one night,
• 24:03
  Speaker 1: rearranged these equations and realized, oh, my gosh, light is
• 24:07
  Speaker 1: a wave and it's a wave of electromagnetism.
• 24:10
  Speaker 2: So like a light bulb turned on on top of
• 24:12
  Speaker 2: his head, emitting waves.
• 24:14
  Speaker 1: Exactly the first appropriate light bulb ever.
• 24:17
  Speaker 2: Yeah, so then that seems pretty definitive. The double slit
• 24:24
  Speaker 2: experiment shows it light interferes with itself. And also this
• 24:29
  Speaker 2: guy figured out that it's mathematically describable by sine ways
• 24:34
  Speaker 2: and cosine waves right.
• 24:35
  Speaker 1: Right right, That light is waves of electromagnetism. Yeah, exactly.
• 24:40
  Speaker 1: So then it all seems really nice and tidy. But
• 24:42
  Speaker 1: then the particle revolution comes, right. People discover the electron,
• 24:46
  Speaker 1: people discover the neutron, people discovering all these particles. But
• 24:50
  Speaker 1: then they were doing experiments where they were shining light
• 24:52
  Speaker 1: onto materials and trying to get it to kick off electrons.
• 24:57
  Speaker 1: So you shine a really bright light at something and
• 24:59
  Speaker 1: you hope that some of the electrons in the material
• 25:01
  Speaker 1: absorb that light and get enough energy to be free
• 25:05
  Speaker 1: to run away. And so this is called the photoelectric effect.
• 25:08
  Speaker 1: You shine light at something and you measure the electrons
• 25:10
  Speaker 1: that come off. So what they saw in this experiment
• 25:13
  Speaker 1: only made sense if the energy of the light comes
• 25:17
  Speaker 1: in little packets rather than a continuous stream like waves.
• 25:20
  Speaker 1: So they turned up the intensity of the light and
• 25:22
  Speaker 1: they made it brighter, but that didn't increase the energy
• 25:26
  Speaker 1: the electrons that were coming off, which doesn't make sense
• 25:29
  Speaker 1: if it's a wave. It only makes sense if photons
• 25:31
  Speaker 1: come in little packets, so that increasing the intensity of
• 25:35
  Speaker 1: the light means more photons, but it doesn't give more
• 25:38
  Speaker 1: energy to any one electron because each electron can only
• 25:42
  Speaker 1: absorb one photon. And nobody understood this at all. This
• 25:46
  Speaker 1: made no sense to anybody. It was a huge puzzle.
• 25:49
  Speaker 1: We totally believe that it acted like a wave. We
• 25:51
  Speaker 1: had the double slit experiment told us it was a wave.
• 25:53
  Speaker 1: Maxwell's equations told us it was a wave. But then
• 25:57
  Speaker 1: we had the photoelectric effect, which didn't quite make sense
• 25:59
  Speaker 1: to anybody. Okay, And then Einstein said, well, what if
• 26:03
  Speaker 1: light comes in these little packets like you were saying before,
• 26:07
  Speaker 1: What if light is not this continuous stream of energy
• 26:10
  Speaker 1: like a wave is right, a wave is continuous stream
• 26:12
  Speaker 1: of energy. What if it comes in these little bits?
• 26:15
  Speaker 1: And that explained everything if you if you thought that
• 26:18
  Speaker 1: light was came in these little packets, it explained the
• 26:20
  Speaker 1: photo electric effect, explained these all these other mysteries in physics,
• 26:25
  Speaker 1: and that was the birth of quantum mechanics.
• 26:27
  Speaker 2: Did they think that maybe it was little packets of waves?
• 26:29
  Speaker 2: Do you know what I mean? Like little short bursts
• 26:32
  Speaker 2: of ripples, you know, do you know what I mean?
• 26:34
  Speaker 2: Like could that explain how it's both things that run
• 26:37
  Speaker 2: through his brain.
• 26:38
  Speaker 1: Yes, absolutely, I think that's probably the first way he
• 26:41
  Speaker 1: thought about it. Is like a little localized ripple, right,
• 26:44
  Speaker 1: like a little Yeah, that's the best way to put it,
• 26:48
  Speaker 1: a little localized ripple, like the way you can send
• 26:51
  Speaker 1: a little ripple of water, Yeah, through a swimming pool,
• 26:54
  Speaker 1: or something.
• 26:54
  Speaker 2: Like a chirp or like a little sound burst.
• 26:57
  Speaker 1: Yeah, exactly, like a little chirp. But it's strange because
• 27:02
  Speaker 1: you know, you can make a chirp of any size.
• 27:03
  Speaker 1: You can make a big one, a little one, a
• 27:05
  Speaker 1: long one, a fat one. But light, for some reason,
• 27:07
  Speaker 1: wanted to come only these in these little distinct chirps
• 27:11
  Speaker 1: of a specific size, and the size of those chirps
• 27:14
  Speaker 1: was controlled by their color or their frequency. And so
• 27:17
  Speaker 1: that was the birth of quantum mechanics, which we could
• 27:19
  Speaker 1: spend a whole other podcast talking about, but it was
• 27:22
  Speaker 1: the first clue that maybe light did come in these
• 27:24
  Speaker 1: distinct little packages.
• 27:26
  Speaker 2: Yeah, let's talk about that, but first let's take a
• 27:29
  Speaker 2: quick break.
• 27:41
  Speaker 1: And that's what we talked about, Like, what is a particle.
• 27:43
  Speaker 1: It's a distinct little package. And then here's the part
• 27:47
  Speaker 1: that blew my mind. Is that. Then they went back
• 27:49
  Speaker 1: and they did that double slit experiment again, but they
• 27:52
  Speaker 1: slowed it down. Instead of shining a really big beam
• 27:55
  Speaker 1: of light, they just shown one photon at a time, right, Okay,
• 27:59
  Speaker 1: because they wanted to see what's going to happen. Right,
• 28:02
  Speaker 1: if light comes in these little packets, how does that
• 28:04
  Speaker 1: explain the interference effect? How can light interfere if it's
• 28:07
  Speaker 1: a particle?
• 28:08
  Speaker 2: So like, instead of like pointing the hose of water
• 28:11
  Speaker 2: at these two little holes and just seeing what happens
• 28:14
  Speaker 2: on the other side, they were throwing one droplet of
• 28:17
  Speaker 2: water at a.
• 28:18
  Speaker 1: Time, yes, exactly. And what they expected to see was
• 28:22
  Speaker 1: that there'ld be no interference pattern, right, because the interference
• 28:25
  Speaker 1: comes from having two sources. Right. You have interference when
• 28:28
  Speaker 1: you have two waves that are either adding up or
• 28:30
  Speaker 1: canceling out.
• 28:31
  Speaker 2: Meaning like a huge stream of light is going through
• 28:34
  Speaker 2: these two little slits. Then the two little slits act
• 28:38
  Speaker 2: like little sources, like little sorts of ripples, which can
• 28:41
  Speaker 2: cancel az exactly. But if you throw one drop at time,
• 28:43
  Speaker 2: it's either going to go in one slit or it's
• 28:46
  Speaker 2: going to go on the other slid, right.
• 28:47
  Speaker 1: That's right. Yeah, And so there should be nothing to interfere, right,
• 28:51
  Speaker 1: So that's what they expected. But what they what they
• 28:53
  Speaker 1: saw blew their minds. Right. What happens if you slow
• 28:56
  Speaker 1: the experiment down, you send one photon at a time,
• 28:59
  Speaker 1: is that you'll get an interference pattern. It's just that
• 29:01
  Speaker 1: it builds up piece by piece. So you used to
• 29:04
  Speaker 1: throw one photon through and it lands someplace on the screen.
• 29:08
  Speaker 1: Throw another photon through, it lands somewhere else on the screen.
• 29:11
  Speaker 1: After you add up a million photons, you rebuild the
• 29:14
  Speaker 1: original interference pattern you saw.
• 29:16
  Speaker 2: That's crazy.
• 29:17
  Speaker 1: What light is a particle, but it's acting like a wave? Right?
• 29:21
  Speaker 1: How is that? How can that even be? Right?
• 29:23
  Speaker 2: It's not just that it's like it's a particle that's
• 29:26
  Speaker 2: acting like a wave, as if it was in a
• 29:29
  Speaker 2: huge stream of other particles.
• 29:31
  Speaker 1: Right, that's right, And this blew everybody's mind. And the answer,
• 29:36
  Speaker 1: of course, is that light is a particle. But like
• 29:40
  Speaker 1: every kind of matter, like every particle, how it moves
• 29:44
  Speaker 1: is governed by mathematics of wave equations. So every particle
• 29:49
  Speaker 1: carries with it some quantum mechanical wave that determines where
• 29:53
  Speaker 1: it goes. But what was happening in that experiment was
• 29:56
  Speaker 1: that a particle photon was approaching the experiment and then
• 30:00
  Speaker 1: it could either go through the left hand side or
• 30:02
  Speaker 1: the right hand side slit right, And because it's quantum mechanical,
• 30:07
  Speaker 1: it did both. It had a chance to do both,
• 30:10
  Speaker 1: and what was interfering was the probability to go through
• 30:13
  Speaker 1: the left slit or the right slit.
• 30:15
  Speaker 2: So that's interesting. I don't think i've heard that explanation before,
• 30:18
  Speaker 2: that it's a particle and a wave in the sense
• 30:21
  Speaker 2: that it is a particle, but it moves according to
• 30:24
  Speaker 2: wave equations.
• 30:26
  Speaker 1: Yes, everything moves according to wave equations. It's just that
• 30:30
  Speaker 1: the wavelength for things depends on how much energy they have.
• 30:33
  Speaker 1: So that was this guy, Tobroguely. He came up with
• 30:36
  Speaker 1: this equation. And maybe you've heard the expression to broguely wavelength.
• 30:39
  Speaker 2: I've heard the expression wavelength. That seems to be a.
• 30:41
  Speaker 1: Yeah, everything is wavelengths. We were making fun of that guy.
• 30:46
  Speaker 1: Turns out he was right, oh twist ending, No, everything
• 30:52
  Speaker 1: has a wavelength. Right, you can describe the motion of
• 30:56
  Speaker 1: anything in terms of a wave. Now, the wavelength depends
• 31:00
  Speaker 1: on the mass and the momentum, and for most things
• 31:02
  Speaker 1: like me or you or a cantalope. The wavelength of
• 31:06
  Speaker 1: its quantum mechanical wave function is tiny, and so you
• 31:10
  Speaker 1: can't even notice, right, the wave effects of you and
• 31:14
  Speaker 1: your son walking down the hallway and interfering with each
• 31:16
  Speaker 1: other are basically negligible. But on the scale of particles,
• 31:20
  Speaker 1: these wave functions interfere with each other.
• 31:23
  Speaker 2: Yeah, that's a crazy thodd that, you know. We I
• 31:27
  Speaker 2: think people think quantum is something that doesn't affect their lies,
• 31:29
  Speaker 2: but quantum ideas and concepts are everywhere, right, Like you
• 31:36
  Speaker 2: have a sort of like a quantum superposition, or you
• 31:39
  Speaker 2: you're not really there. You sort of there's a cloud
• 31:42
  Speaker 2: of you that is.
• 31:43
  Speaker 1: I'm not really here, I'm just an AI on the internet.
• 31:46
  Speaker 1: But that's that's differently cloud. Yeah, there is this quantum
• 31:51
  Speaker 1: mechanical certainly and everything.
• 31:53
  Speaker 2: Guess yeah, yeah, it's just that you can't notice.
• 31:55
  Speaker 1: That really blew people's minds. This concept that like, okay,
• 31:58
  Speaker 1: light is a particle, but it's sort of acts like
• 32:00
  Speaker 1: a wave. We can use these wave equations to describe it.
• 32:05
  Speaker 1: And you know, there's another layer to that experiment which
• 32:08
  Speaker 1: is even crazier, right, which is if what's interfering is
• 32:12
  Speaker 1: the probability to go through the left slit or the
• 32:14
  Speaker 1: right slit right. When the photon approaches the experiment, it
• 32:18
  Speaker 1: can go through one or the other. The interference pattern
• 32:20
  Speaker 1: comes from the uncertainty of which it's going to go through.
• 32:24
  Speaker 1: So what you can do is you can add a
• 32:25
  Speaker 1: little detector to one slit that like gives you a
• 32:28
  Speaker 1: ping if it goes through that slit right, so you
• 32:30
  Speaker 1: know for sure if it goes through one slit or
• 32:32
  Speaker 1: the other. If you do that, the interference pattern disappears.
• 32:37
  Speaker 1: WHOA why does it disappear? It disappears because the interference
• 32:41
  Speaker 1: only came from the interference of the possibility of the
• 32:44
  Speaker 1: particles to go through the left slit or the right slit,
• 32:47
  Speaker 1: our lack of knowledge. Once you know it goes through
• 32:50
  Speaker 1: the right slit of left slit, there's no more uncertainty.
• 32:52
  Speaker 1: There's nothing to interfere. It just goes through the left
• 32:55
  Speaker 1: or it goes through the right.
• 32:56
  Speaker 2: It's like you're throwing a box is full of cats
• 33:00
  Speaker 2: that are either dead or alive, and you see what
• 33:04
  Speaker 2: happens on the other side. It's different if you take
• 33:06
  Speaker 2: a peek inside the box before it gets.
• 33:08
  Speaker 1: There, exactly exactly, and no cats were harmed in the
• 33:13
  Speaker 1: making of this podcast, I now feel energe to point
• 33:15
  Speaker 1: out that's sort of where we are today, is that
• 33:22
  Speaker 1: we know that light is a particle and then it
• 33:24
  Speaker 1: comes in these little discrete packets become photons, right, Yeah,
• 33:28
  Speaker 1: But we also know that, like everything else, light is
• 33:31
  Speaker 1: determined by how its wave function moves. Every particle and
• 33:34
  Speaker 1: every object has this wave function, and how it moves
• 33:38
  Speaker 1: is controlled by wave equations.
• 33:40
  Speaker 2: It's not like it's both a particle and a wave
• 33:43
  Speaker 2: and people don't really know which one it is, or
• 33:45
  Speaker 2: people are still confused about that. But it sort of
• 33:47
  Speaker 2: sounds like you're not that confused about it, right, It
• 33:49
  Speaker 2: sort of sounds like you know it's a particle, but
• 33:52
  Speaker 2: it moves around like a wave.
• 33:54
  Speaker 1: Yeah, but it's still confusing. I mean, I think you could.
• 33:57
  Speaker 1: It's totally reasonable to say it's both. It's a particle
• 34:01
  Speaker 1: but it acts like a wave. Right. It's also totally
• 34:03
  Speaker 1: reasonable to say it's neither. It's not a particle, it's
• 34:07
  Speaker 1: not a wave, it's something else. It's something weird, something
• 34:10
  Speaker 1: totally strange, we've never seen before. It's a war we can.
• 34:17
  Speaker 2: Or a pave.
• 34:18
  Speaker 1: You are on fire.
• 34:20
  Speaker 2: I am simple spelling.
• 34:25
  Speaker 1: But that's that's a joke. But it's also serious because
• 34:28
  Speaker 1: sometimes we discover things which are unlike anything else we've seen,
• 34:32
  Speaker 1: and how do you describe them?
• 34:33
  Speaker 2: I mean, we should stop using these words. We should
• 34:36
  Speaker 2: maybe come up with a new word to describe what
• 34:38
  Speaker 2: it is, because it's not, yes, not described by either
• 34:41
  Speaker 2: word particle.
• 34:42
  Speaker 1: That's right, it's a chapel, it's a cherry apple combination.
• 34:45
  Speaker 2: Yeah, let's not call it a particle or a wave.
• 34:48
  Speaker 2: Let's just make up anyw word that embodies these two
• 34:51
  Speaker 2: ways to behave that's right.
• 34:52
  Speaker 1: But here we've discovered something which is different from anything
• 34:55
  Speaker 1: in our microscopic world. There's nothing in our world particles, wave,
• 35:00
  Speaker 1: little puppies that is a good analogy for what light is.
• 35:03
  Speaker 1: So we have to try to sort of describe it
• 35:05
  Speaker 1: in terms of sometimes it's like this, sometimes like this.
• 35:08
  Speaker 1: My personal belief is that it's it's not like anything else,
• 35:11
  Speaker 1: and that these are approximations. But you know, like we
• 35:15
  Speaker 1: were talking about earlier, you can be different contradictory things
• 35:17
  Speaker 1: like how would you describe yourself? You know, sometimes your husband,
• 35:21
  Speaker 1: sometimes your father, Sometimes you're a cartoonist, sometimes you're just asleep.
• 35:24
  Speaker 1: You know, like all these things describe you, they're contradictory.
• 35:28
  Speaker 1: There are different facets of who you are at your core,
• 35:30
  Speaker 1: and none of them define you.
• 35:32
  Speaker 2: Right right, But if you don't have to have the
• 35:35
  Speaker 2: right label, you make up and you know that's right.
• 35:37
  Speaker 1: Yes, we need a new thing, right. Light is definitely
• 35:40
  Speaker 1: its own weird kind of thing.
• 35:44
  Speaker 2: All right, Well, until next time.
• 35:54
  Speaker 1: If you still have a question after listening to all
• 35:56
  Speaker 1: these explanations, please drop us a line. We'd love to
• 36:00
  Speaker 1: hear from you. You can find us at Facebook, Twitter,
• 36:02
  Speaker 1: and Instagram at Daniel and Jorge That's one word, or
• 36:06
  Speaker 1: email us at Feedback at Danielanorge dot com