WEBVTT - Is Light a Particle or a Wave? 0:00:08.560 --> 0:00:11.720 Is it possible to be two different things at the 0:00:11.760 --> 0:00:16.360 same time? Can you like dogs and cats? Can you 0:00:16.440 --> 0:00:18.720 be a horse and a giraffe at the same time? 0:00:19.320 --> 0:00:23.479 Can something taste salty and sweet? Can address be black 0:00:23.520 --> 0:00:27.560 and blue and white and gold? In today's podcast, we 0:00:27.640 --> 0:00:32.400 talked about the centuries old scientific debate about light. Is 0:00:32.520 --> 0:00:55.440 light a particle or a wave? Or is it both? Hello? 0:00:55.480 --> 0:00:58.800 I'm Organ and I'm Daniel. Welcome to Daniel and Jorge 0:00:58.880 --> 0:01:01.760 Explain the Universe, in which we try to explain the 0:01:01.840 --> 0:01:05.840 whole universe and everything in it, including light. Now, I'm 0:01:05.880 --> 0:01:08.959 a cartoonist. I draw something called PhD comics, and I'm 0:01:09.000 --> 0:01:12.200 a particle physicist. During the day, I smash particles together 0:01:12.240 --> 0:01:15.679 with the large hadron collider. Yeah. Well, today on the program, 0:01:15.760 --> 0:01:23.000 we're going to talk about the nature of light. That's right. 0:01:23.040 --> 0:01:26.440 People have been arguing for centuries what is light? Is 0:01:26.440 --> 0:01:28.520 it made out of particles? Is it made out of waves? 0:01:28.560 --> 0:01:32.040 It's something else? Is it tiny little puppies screaming through space? 0:01:32.560 --> 0:01:34.440 People have gone back and forth on the issue, and 0:01:34.520 --> 0:01:38.280 today even the topic is not yet totally settled. So 0:01:38.319 --> 0:01:40.520 we're gonna be taking you through that history and breaking 0:01:40.560 --> 0:01:43.119 it down it's one of the most mind blowing questions 0:01:43.400 --> 0:01:47.080 in human scientific history. That's right, what is light made 0:01:47.120 --> 0:01:49.480 out of? So, as usual, before we dig into it, 0:01:49.520 --> 0:01:51.160 we went out and we asked people on the street. 0:01:51.280 --> 0:01:52.560 What do you think light is made out of? What 0:01:52.600 --> 0:01:55.920 do people know about light? Is light a particle or 0:01:56.080 --> 0:01:58.600 is it a wave? Here's what people had to say. 0:01:58.920 --> 0:02:01.560 Do you think light? Is it out of particles or waves? 0:02:01.640 --> 0:02:05.480 Or both? Are neither? Photos? Yeah? Photons? Yeah, so you 0:02:05.480 --> 0:02:10.840 think it's a particle. I think it's waves. Yeah, it's both, 0:02:11.000 --> 0:02:15.800 I think because it moves like a wave, but it 0:02:15.840 --> 0:02:19.040 also has properties of a particle and there's nothing saying 0:02:19.080 --> 0:02:25.360 it can't people. Okay, um, light, I think they're made 0:02:25.360 --> 0:02:30.680 of wavelength Yeah all right. Well, um, it's interesting because 0:02:30.680 --> 0:02:35.720 I think all of the answers are right or none 0:02:35.720 --> 0:02:40.600 of them, or or both. Yeah. Well, it seems like 0:02:40.639 --> 0:02:42.600 a lot of people reflected the fact that there is 0:02:42.600 --> 0:02:45.679 a controversy like that. You know, it's not really well 0:02:45.720 --> 0:02:48.120 described by either those. Some people went all in, you know, 0:02:48.160 --> 0:02:50.680 like it's a photon or it's a wave, or it's 0:02:50.680 --> 0:02:53.399 a wave length right, Yeah, that was my favorite one. 0:02:54.400 --> 0:02:56.200 I want to be a wavelength like I've heard of 0:02:56.240 --> 0:02:59.320 this word. It sounds really cool and scientific. I'm just 0:02:59.320 --> 0:03:02.520 gonna throw it out there, that's right. Yeah, maybe I 0:03:02.520 --> 0:03:06.200 get some points. We award no points, people, no points. 0:03:06.480 --> 0:03:09.160 That's right. There's no prize, your prices. You get to 0:03:09.200 --> 0:03:11.320 be on our podcast, and maybe we even make fun 0:03:11.360 --> 0:03:13.919 of you. Yeah, but yeah, I guess what you mean 0:03:14.000 --> 0:03:16.320 is nobody sort of fell for the trap, right, Like 0:03:16.360 --> 0:03:18.799 nobody said, oh, of course it's a particle, or nobody said, 0:03:18.800 --> 0:03:21.320 oh of course it's a wave. Most people sort of 0:03:21.360 --> 0:03:24.280 needed that there's some sort of duality there, something weird 0:03:24.360 --> 0:03:27.600 going on. That's right. That science is having some trouble, 0:03:27.720 --> 0:03:30.400 some difficulty coming up with a way to describe what 0:03:30.520 --> 0:03:33.000 light is. And that might seem surprising to you because 0:03:33.160 --> 0:03:35.600 light is everywhere, right, and it runs the universe. It's 0:03:35.680 --> 0:03:39.600 streaming through the Solar system from the Sun, illuminating our lives, 0:03:39.640 --> 0:03:42.440 empowering everything on Earth. So you think this would be 0:03:42.440 --> 0:03:44.720 sort of a high priority topic to figure out, like 0:03:44.800 --> 0:03:47.240 what is this stuff? What is it made out of? Yeah? 0:03:47.240 --> 0:03:49.280 I mean, like, what are we paying you for, Daniel, 0:03:49.440 --> 0:03:52.760 if not to figure these kinds of questions out. I 0:03:52.880 --> 0:03:55.040 was just about to figure out what light was when 0:03:55.040 --> 0:03:58.520 you called and said it's time to do this podcast. 0:03:58.240 --> 0:04:02.080 Totally about your thin train of thought there, that's right, 0:04:02.120 --> 0:04:06.960 reflect on that for a minute or but no, Yeah, 0:04:06.960 --> 0:04:10.400 I'm a California taxpayer. Part of my salary goes to 0:04:10.480 --> 0:04:13.480 being your salary, like you know, one million of a present. 0:04:13.800 --> 0:04:15.400 That's true. Yeah, so you're you're saying you did pay 0:04:15.440 --> 0:04:25.520 taxes very against another topics on air Daniel. Anyway, So 0:04:25.640 --> 0:04:28.720 that's an interesting question, like is light a waiver particle? 0:04:28.800 --> 0:04:31.560 And it's weird that we don't know, um, but maybe 0:04:31.600 --> 0:04:33.440 let's bring it down a little bit. What is it? Like, 0:04:33.480 --> 0:04:35.480 what are we actually talking about when we say that 0:04:35.600 --> 0:04:38.080 light could be a particle or light could be a wave, 0:04:38.240 --> 0:04:41.359 like you know, most people probably think of light is 0:04:41.400 --> 0:04:45.520 just like just like brightness, right. Yeah. The thing to 0:04:45.600 --> 0:04:48.839 understand here is that we try to describe light in 0:04:48.960 --> 0:04:51.920 terms of things we know, and that's what science is. Right. 0:04:52.240 --> 0:04:54.640 You see something weird and new and you wonder, is 0:04:54.680 --> 0:04:57.719 it like this other thing I know? So we've observed 0:04:57.720 --> 0:05:00.720 different kinds of phenomenon in the world. Like you see waves, right, 0:05:00.720 --> 0:05:02.400 you go to the beach, you see waves and water. 0:05:02.720 --> 0:05:05.920 You drop a rock in a small puddle. You see waves. 0:05:06.120 --> 0:05:09.200 We know what waves are, and we see different phenomena. 0:05:09.240 --> 0:05:11.680 We try to categorize them in terms of things we know. Right, 0:05:11.720 --> 0:05:15.040 So like when people were studying sound, they discovered, oh, 0:05:15.080 --> 0:05:17.719 sound is actually a wave. You know, it's a compression 0:05:17.800 --> 0:05:20.760 wave in the air. And that's cool because he says, oh, 0:05:20.800 --> 0:05:23.600 I already know how the math for waves works. Right, 0:05:23.600 --> 0:05:26.200 I've seen waves and water. I've seen waves and other stuff. 0:05:26.480 --> 0:05:30.320 You can describe it with like equations, right, yeah, wavy equations, 0:05:31.040 --> 0:05:35.520 that's right, very solid unwavy physics to describe waves. And 0:05:35.560 --> 0:05:38.080 there's a lot of science that's gone into understanding ways. 0:05:38.120 --> 0:05:40.720 So if you can cram it into that box and say, oh, 0:05:40.760 --> 0:05:43.039 this is just another example of something we already know, 0:05:43.400 --> 0:05:47.080 then you're taking a huge leap forward. Right. So that's 0:05:47.120 --> 0:05:48.920 something people try to do is say, like, look, can 0:05:48.960 --> 0:05:50.800 we describe this in terms of other things we know? 0:05:50.920 --> 0:05:53.640 So we need like we you know, we know about light, 0:05:54.000 --> 0:05:55.839 but we want to know how it behaves and what 0:05:55.920 --> 0:05:58.279 makes it work. Yeah, and just on a more general level, 0:05:58.279 --> 0:06:00.520 you try to see something new you are to describe 0:06:00.560 --> 0:06:02.720 in terms of things you know, Like, say you taste 0:06:02.720 --> 0:06:04.600 a new kind of fruit and you'd be like, Oh, 0:06:04.640 --> 0:06:06.279 it's a little bit like a cherry and a little 0:06:06.320 --> 0:06:08.000 bit like an apple, and a little bit like you know, 0:06:08.040 --> 0:06:10.440 it's got a hint of smokiness to it or whatever. 0:06:10.520 --> 0:06:13.320 You know. You're like, it's a chapel. It's a chapel. 0:06:13.920 --> 0:06:16.880 How has nobody ever invented that? The cherry apple chapel? 0:06:16.960 --> 0:06:20.080 Oh my gosh, somebody, if our lawyer is listening, get 0:06:20.080 --> 0:06:24.599 on that right away. Copyright that idea chapel dot com. 0:06:24.880 --> 0:06:26.680 That's right. So that's the basic idea is we have 0:06:26.800 --> 0:06:29.000 these things we've seen. You see something new, you don't 0:06:29.000 --> 0:06:30.919 want to create a whole new category. You want to 0:06:30.960 --> 0:06:33.159 fit in into one of the existing categories. So we 0:06:33.279 --> 0:06:35.400 set a new about light. It came from the sun. 0:06:35.960 --> 0:06:38.240 You know, if you light a fire, it spreads out 0:06:38.400 --> 0:06:41.200 into a room. And so we're like, what's going on? 0:06:41.279 --> 0:06:46.000 Like what? Um? What best describes how this light you know, 0:06:46.160 --> 0:06:48.760 comes from a source and bounces off the walls and stuff? 0:06:49.000 --> 0:06:52.520 Exactly exactly, that's the question. And so we've seen things 0:06:52.520 --> 0:06:54.160 like waves, So what do we mean when we say 0:06:54.160 --> 0:06:56.080 a wave? Like, how could a light be a wave? Well? 0:06:56.520 --> 0:06:58.880 How can anything be a wave? Yeah? How can anything 0:06:58.920 --> 0:07:01.480 be a wave. A wave is a funny thing because 0:07:01.520 --> 0:07:04.799 it's not a thing itself. It's a property of some medium. 0:07:04.960 --> 0:07:08.360 Like it's like a ripple on something. Yeah, that's right. 0:07:08.440 --> 0:07:10.480 Like if you do the wave at a baseball game, 0:07:10.560 --> 0:07:13.520 you know, there's nothing to the wave itself. It's just 0:07:13.560 --> 0:07:16.480 a bunch of people moving up and down waving their hands, right, 0:07:16.640 --> 0:07:19.320 Or like a sound wave is just like air molecules 0:07:19.640 --> 0:07:23.360 kind of bumping forward. That's right, yeah, exactly. Or a 0:07:23.400 --> 0:07:24.960 wave in the in the ocean, it's just it's an 0:07:25.080 --> 0:07:27.520 arrangement of the water, right, It's it's the way the 0:07:27.520 --> 0:07:30.320 water gets compressed and then stretched out and compressed and 0:07:30.320 --> 0:07:32.800 then get stretched out. So that's the important thing about 0:07:32.840 --> 0:07:35.000 a wave is that it moves in this way through 0:07:35.040 --> 0:07:39.160 a medium. Okay, so that's a wave. It's like a propagation, 0:07:39.280 --> 0:07:41.800 it's like a ripple through something. But then so then 0:07:41.800 --> 0:07:44.080 what what would you call a particle? Particle is different 0:07:44.080 --> 0:07:46.400 than that. A particle is different than that, and it's 0:07:46.400 --> 0:07:48.920 a totally different kind of thing, you know, and uh, 0:07:49.200 --> 0:07:51.120 to be a particle physicist, it's kind of odd, but 0:07:51.200 --> 0:07:53.640 the concept of a particle is not that really well 0:07:53.680 --> 0:07:55.760 to find you know, um, But when I think of 0:07:55.800 --> 0:07:58.400 a particle, I think of taking matter and breaking it 0:07:58.440 --> 0:08:00.920 down to its smallest pieces. Like, if something is made 0:08:00.920 --> 0:08:03.520 out of particles, it means that at its smallest level, 0:08:03.520 --> 0:08:05.920 it's made out of this these little bits that can't 0:08:05.920 --> 0:08:09.280 be chopped into smaller bits, and that they're localized. They're 0:08:09.320 --> 0:08:14.200 like um, small and contained. Right. If if you discover 0:08:14.400 --> 0:08:16.760 that something is made of particles, you expect it to 0:08:16.760 --> 0:08:20.280 be like mostly empty space, but with these little dots 0:08:20.320 --> 0:08:22.440 of matter, Like it would take something and then you 0:08:22.560 --> 0:08:24.600 smash it to bits and just keep smashing, and at 0:08:24.640 --> 0:08:26.760 some point you're going to get to these little like 0:08:26.920 --> 0:08:30.680 baby balls or like little tiny pellets that you can't 0:08:30.680 --> 0:08:33.800 break down anymore, that's right. Yeah, It's like seeing a 0:08:33.840 --> 0:08:36.719 picture on your your computer screen and discovering it's made 0:08:36.760 --> 0:08:39.480 out of pixels, right, and that those pixels are the 0:08:39.480 --> 0:08:42.640 basic elements and they come together to make the whole picture. Um. 0:08:42.679 --> 0:08:46.000 So figuring out this something is made of particles means 0:08:46.080 --> 0:08:48.559 that there's made of these these little bits that are 0:08:48.640 --> 0:08:52.240 not um connected to each other, right, they're separated. So 0:08:52.360 --> 0:08:54.920 a wave and a particle in nature are totally different 0:08:54.960 --> 0:08:58.120 kinds of things, right Now, water of course is made 0:08:58.120 --> 0:09:00.760 of particles, but can have waves in it, right, But 0:09:00.800 --> 0:09:03.120 I think maybe maybe what's important here is that, you know, 0:09:03.200 --> 0:09:06.440 particles we tend to think of as little tiny bits. 0:09:06.480 --> 0:09:08.560 They can bounce around, right, and like go in a 0:09:08.600 --> 0:09:13.160 straight line and then hit something else and then bounce back, 0:09:13.440 --> 0:09:17.000 or you know, kind of fly through space right in 0:09:17.040 --> 0:09:20.040 a discrete little package. Exactly. That's exactly the right way 0:09:20.040 --> 0:09:22.439 to say. It is a discrete little package. Right. So 0:09:22.559 --> 0:09:24.120 things that have made of particles we think of as 0:09:24.160 --> 0:09:27.679 being discrete little bits um and they they've broken up 0:09:27.720 --> 0:09:30.319 into these little little pieces, and you're right, they move 0:09:30.360 --> 0:09:33.280 in straight lines. Right, Like you throw a rock, your 0:09:33.400 --> 0:09:36.760 your roll a smooth ball across the surface, you expected 0:09:36.800 --> 0:09:38.840 to move in a straight line. So that's kind of 0:09:38.840 --> 0:09:41.880 what we mean by a wave and a particle, that's right. Yeah. 0:09:41.960 --> 0:09:44.520 And so the question is is like is light a 0:09:44.600 --> 0:09:47.080 ripple on a medium? Is that what light is? Or 0:09:47.200 --> 0:09:50.319 is it like actually little things and move around in space? Right? 0:09:50.320 --> 0:09:53.000 Does it have its own stuff to it? Right? Or 0:09:53.040 --> 0:09:55.959 is it just a way something else moves right? That's 0:09:56.000 --> 0:09:58.360 sort of another way to phrase the question, right, And 0:09:58.360 --> 0:10:01.280 those are two pretty different picture is a reality? Right? Yeah? 0:10:01.360 --> 0:10:03.679 The light could be little pellets flying around, or it 0:10:03.720 --> 0:10:06.679 could be some sort of ripple on a medium. To us, 0:10:06.679 --> 0:10:09.840 in our intuitive sense, it couldn't be any more different, right, 0:10:10.160 --> 0:10:12.480 that's right. Yeah, it's like you can't be a Democrat 0:10:12.520 --> 0:10:14.680 and a Republican, you know, just you have to pick one, 0:10:14.880 --> 0:10:19.640 you know. Yeah, if you can be or you could 0:10:19.640 --> 0:10:23.080 be neither as opposed, Um, you shouldn't be both though, Yeah, 0:10:23.200 --> 0:10:26.040 that would be a violation of some some election law 0:10:27.080 --> 0:10:31.240 not recommended to violate election that's right. Yeah. So, speaking 0:10:31.240 --> 0:10:35.040 of political shouting matches, this one, this historical scientific shouting match, 0:10:35.120 --> 0:10:37.960 began all the way back with the Greeks, right Democratus 0:10:38.400 --> 0:10:40.800 he's the guy sort of the first atomist. He's the 0:10:40.800 --> 0:10:42.880 first person to look at the world and to say, 0:10:43.240 --> 0:10:45.760 you know, maybe everything's made out of tiny little bits, 0:10:46.080 --> 0:10:48.880 not just light, but also matter. And that was sort 0:10:48.920 --> 0:10:51.960 of the birth of that idea that maybe everything around 0:10:52.080 --> 0:10:55.400 us that seems macroscopic is made out of tiny little things, 0:10:55.440 --> 0:10:58.600 smaller than we can see. And you know, as usual, 0:10:58.640 --> 0:11:01.319 when somebody comes up with a good idea, they overextended. 0:11:01.360 --> 0:11:03.480 They're like, well, maybe if rocks are made out of stuff, 0:11:03.600 --> 0:11:06.160 then water is also made out of particles, and maybe 0:11:06.240 --> 0:11:08.760 even light is made out of particles. You know. It's 0:11:08.760 --> 0:11:11.680 at the time seemed like a totally a crazy reach. 0:11:12.080 --> 0:11:13.920 And that makes sense, right, because light seems to go 0:11:13.960 --> 0:11:16.880 in a straight line. It seems to bounce off of things. 0:11:17.040 --> 0:11:19.439 So why couldn't light just be like a little tiny 0:11:19.520 --> 0:11:22.239 little pellets that bounce around the room and then eventually 0:11:22.720 --> 0:11:25.040 hit your eye and then that's how you see something. Yeah, 0:11:25.080 --> 0:11:27.800 it certainly seems to have some of those particles like properties, right, 0:11:27.840 --> 0:11:30.520 it moves in straight lines. Uh, it certainly would be 0:11:30.520 --> 0:11:33.160 going really really fast. At the time, people thought that 0:11:33.240 --> 0:11:37.559 light traveled instantly, right. They thought that light um instantaneously 0:11:37.559 --> 0:11:40.040 went from like the sun to the earth, or or 0:11:40.200 --> 0:11:42.120 um if you started a fire, that the light would 0:11:42.160 --> 0:11:44.840 immediately illuminate the room. Now, we of course know that 0:11:44.880 --> 0:11:47.880 it just happens super duper crazy fast, too fast for 0:11:47.920 --> 0:11:51.439 those folks to ever measure, so it's almost like it's instantaneous. 0:11:51.720 --> 0:11:54.040 But they thought that these things just moved instantly through 0:11:54.080 --> 0:11:56.360 space and filled up the room. Okay, and I want 0:11:56.360 --> 0:11:58.480 to talk a little bit more about that, but first 0:11:58.520 --> 0:12:14.320 a quick break. So, initially we thought light was or 0:12:14.320 --> 0:12:18.520 the Greeks thought that light was a particle, right, And 0:12:18.679 --> 0:12:20.400 I think we have to qualify that because it makes 0:12:20.400 --> 0:12:22.880 the Greek sound really smart. Just come up with this 0:12:22.960 --> 0:12:25.840 idea of atoms and all that stuff, and you say 0:12:25.880 --> 0:12:28.040 this before you're really really down in the Greeks. Well, 0:12:28.080 --> 0:12:30.440 I think people give the Greeks too much credit for that, because, 0:12:30.640 --> 0:12:33.240 as I've probably said to you before, Um, the Greeks 0:12:33.240 --> 0:12:34.880 had lots and lots of ideas. You know, they had 0:12:34.920 --> 0:12:36.679 like thousands of these ideas about how the way the 0:12:36.679 --> 0:12:39.320 world works, and yeah, one of them was close to true. 0:12:39.360 --> 0:12:41.720 But like, if we're going to do some accounting, let's 0:12:41.720 --> 0:12:46.080 also remember the n that were totally off base, you know, 0:12:46.160 --> 0:12:48.839 and and give them credit for those. Yeah, find that 0:12:48.920 --> 0:12:52.040 Greek we thought life was just little puppies, and be like, see, 0:12:52.120 --> 0:12:54.120 you guys also thought they were puppies. You can't be 0:12:54.120 --> 0:12:57.760 that smart, that's right. But it's a cool idea. So 0:12:58.000 --> 0:13:00.160 give them credit for having that idea and know what 0:13:00.200 --> 0:13:01.760 they were smoking when they came up with it. But 0:13:02.000 --> 0:13:04.800 I'd like to figure out where to find something. Um. 0:13:04.840 --> 0:13:07.040 And then it was thousands of years later before people 0:13:07.080 --> 0:13:09.360 had another idea. It was a Descartes, the guy who's 0:13:09.400 --> 0:13:12.440 famous for you know, I think therefore I am he 0:13:12.559 --> 0:13:14.680 thought about He was one of the early scientists, not 0:13:14.760 --> 0:13:17.280 just philosopher, but a scientist, back in the day when 0:13:17.440 --> 0:13:20.040 you know, science really was part of philosophy, and he 0:13:20.160 --> 0:13:23.040 thought that light was waves. What made him think it 0:13:23.120 --> 0:13:25.320 was waves? You know, I don't think he had much 0:13:25.400 --> 0:13:27.760 justification for it. This is back in the early days 0:13:27.840 --> 0:13:30.680 when science wasn't really an empirical study where you didn't 0:13:30.720 --> 0:13:34.320 like go out and do experiments to test your hypothesis. Um, 0:13:34.320 --> 0:13:36.840 it just made more sense to him for light to 0:13:36.840 --> 0:13:40.520 be like these wave like disturbances, which kind of makes sense, right, 0:13:40.600 --> 0:13:43.320 Like if you have a speaker in a room emitting 0:13:43.360 --> 0:13:46.520 sound waves, Um, it's not that different from like a 0:13:46.640 --> 0:13:49.240 light bulb in the middle of the room emitting light 0:13:49.360 --> 0:13:52.280 all around it. Right. Yeah. And there's some things that 0:13:52.400 --> 0:13:55.800 light does that don't really that don't really seem consistent 0:13:55.840 --> 0:13:58.880 with particles, you know, like the way light bends through 0:13:59.280 --> 0:14:02.040 a lens, right, it's called we call in science, we 0:14:02.080 --> 0:14:04.920 call that refraction. You know, with light changes from going 0:14:04.920 --> 0:14:07.240 through air to glass, it bends in this weird way. 0:14:07.640 --> 0:14:12.120 That's something that's very common for waves, right, And a 0:14:12.200 --> 0:14:16.720 particle wouldn't bend inside of a lens. No particle, that's 0:14:16.760 --> 0:14:20.720 definitely a wave like behavior, yeah, not particle like behavior. 0:14:21.280 --> 0:14:23.400 And so Descartes saw that and he's like, oh, you know, 0:14:23.640 --> 0:14:26.000 we have optics, we have these lenses, so maybe light 0:14:26.080 --> 0:14:27.840 is a wave. But if light is a wave, then 0:14:27.840 --> 0:14:31.160 it opens this other question. What's doing the waving? Right? 0:14:31.320 --> 0:14:33.280 I mean with sound, you know it's the air, and 0:14:33.320 --> 0:14:36.120 in water waves obviously it's the water. But if light 0:14:36.200 --> 0:14:38.840 is a wave, then what is waving? Meaning? Like, if 0:14:39.120 --> 0:14:41.600 light is a ripple, what is it a ripple of 0:14:42.000 --> 0:14:44.920 that's right? Yeah, what's doing the rippling? Right? If it's 0:14:44.920 --> 0:14:46.280 a wave, it has to be a wave in something, 0:14:46.320 --> 0:14:49.000 because a wave is just a description of some other 0:14:49.480 --> 0:14:53.120 form of matter rippling, right, It couldn't just be like 0:14:53.200 --> 0:14:56.920 a stuff that we can't see. Yeah, and so you 0:14:56.960 --> 0:14:59.480 have to invent some stuff that we can't see, right, 0:14:59.760 --> 0:15:01.920 So explain light being a wave. You have to invent 0:15:01.960 --> 0:15:04.040 this universe filled with stuff or there has to be 0:15:04.080 --> 0:15:06.520 that stuff between us and the sun for example, right, 0:15:06.520 --> 0:15:08.760 which is a huge amount of this new stuff you're inventing. 0:15:09.040 --> 0:15:10.960 And if you're looking at the stars, there has to 0:15:10.960 --> 0:15:13.120 be that stuff between you and the stars. Right, So 0:15:13.120 --> 0:15:16.000 now we're talking about billions of miles of this new stuff, 0:15:16.520 --> 0:15:19.000 and Decart, you know, didn't know. So he just gave 0:15:19.040 --> 0:15:20.680 it a name. He's called I don't even know how 0:15:20.680 --> 0:15:23.680 to pronounce it, but he called it plenum. And he thought, well, 0:15:23.720 --> 0:15:25.600 there must be if light is a wave, there must 0:15:25.600 --> 0:15:27.840 be some stuff that's doing the waving, and we'll just 0:15:27.920 --> 0:15:29.680 give it a name and maybe we'll be right, and 0:15:29.720 --> 0:15:32.560 then we'll be famous forever. Isn't it is that different 0:15:32.600 --> 0:15:36.120 under either it's similar in concept, right, it's a different idea, 0:15:36.160 --> 0:15:38.200 but it's similar in concept that like, if light is 0:15:38.200 --> 0:15:40.680 a wave, it must be waving through something, and we 0:15:40.720 --> 0:15:42.640 don't know what it is, which is invents something to 0:15:43.240 --> 0:15:45.600 give it a name as a placeholder so when later 0:15:45.600 --> 0:15:48.360 people do the hard work of actually discovering it will 0:15:48.360 --> 0:15:51.320 still get credit. So it was a particle. Light was 0:15:51.320 --> 0:15:53.600 a particle, then it was a wave, and then what happened, Well, 0:15:53.640 --> 0:15:55.680 then Newton came along, right, And Newton is a really 0:15:55.720 --> 0:15:58.240 smart guy, and everybody knows that he's famous for thinking 0:15:58.280 --> 0:16:01.480 about gravity, but he also like to think about optics 0:16:01.560 --> 0:16:04.760 and lenses. And he thought for sure that light was 0:16:04.760 --> 0:16:07.160 a particle because he saw it moving in straight lines, 0:16:07.720 --> 0:16:10.960 and he saw distinct shadows. But you know, Newton also 0:16:11.000 --> 0:16:13.080 did a lot of experiments with optics. He did he 0:16:13.120 --> 0:16:15.560 studied prisms, and he saw light bending, and he saw 0:16:15.640 --> 0:16:18.600 light splitting into colors. And you can't explain that if 0:16:18.680 --> 0:16:21.640 light is a particle, but he tried. You know, He's like, well, 0:16:21.680 --> 0:16:25.000 maybe when a particle hits the glass, it gets some 0:16:25.040 --> 0:16:29.520 sort of weird sideways force, um, and that makes it bend. 0:16:29.680 --> 0:16:32.120 But you know, that's not really an explanation. That's just 0:16:32.160 --> 0:16:34.560 sort of like a I don't really understand it. But 0:16:34.720 --> 0:16:37.920 maybe it's something like this, like, if light is a particle, 0:16:38.240 --> 0:16:41.560 why does it split into the rainbow kind of thing? Yeah, exactly. 0:16:42.320 --> 0:16:44.040 And you know this is again back in the day 0:16:44.040 --> 0:16:47.040 when empirical studies of science weren't the main way to 0:16:47.080 --> 0:16:50.200 answer questions. It was mostly thinking in your head about 0:16:50.200 --> 0:16:52.680 things that made sense to you, and then they would 0:16:52.760 --> 0:16:55.360 argue about them. Right. A lot of a way scientific 0:16:55.360 --> 0:16:57.880 disputes he used to be resolved was people would argue 0:16:57.880 --> 0:16:59.520 about it and then say, well, that makes no sense, 0:16:59.520 --> 0:17:01.960 so it can't be true. Um. And we know now, 0:17:02.000 --> 0:17:04.479 of course, that the universe doesn't always make sense to us. 0:17:04.520 --> 0:17:07.760 What's real doesn't isn't necessarily the things that we would 0:17:07.800 --> 0:17:11.480 have accepted as true or or accepted as a reasonable 0:17:11.520 --> 0:17:13.760 way to describe the universe. But you know, if that's 0:17:13.800 --> 0:17:15.560 the way nature works, that's the way nature works, you 0:17:15.600 --> 0:17:18.560 have to accept it. But that's the sort of primacy 0:17:18.600 --> 0:17:21.880 of experimental results came later on. So back in the day, 0:17:21.880 --> 0:17:24.320 people just sort of used to argue for an explanation 0:17:24.320 --> 0:17:26.720 that made sense to them. Right, Well, it was kind 0:17:26.720 --> 0:17:29.000 of hard for them to build a particle collider, right, 0:17:29.800 --> 0:17:34.240 that's right, yeah, exactly. They they didn't have the massive 0:17:34.240 --> 0:17:36.159 government funding to do that. These were men of leisure 0:17:36.160 --> 0:17:39.000 studying science in the spare time. In fact, it was 0:17:39.000 --> 0:17:43.040 called like natural philosophy, right, It wasn't called science at 0:17:43.040 --> 0:17:45.840 the time, wasn't. Yeah, that's right exactly. Science All science 0:17:45.960 --> 0:17:49.359 grew out of philosophy. Um, it was called these folks 0:17:49.400 --> 0:17:52.640 were natural philosophers. But you know, later on then people 0:17:52.680 --> 0:17:55.399 started doing experiments. And there were a bunch of French 0:17:55.440 --> 0:17:58.320 guys um who did a bunch of experiments, and some 0:17:58.400 --> 0:18:01.400 of some English folks, and they were studying how life 0:18:01.400 --> 0:18:04.600 behaved and refraction and reflection, and they saw it doing 0:18:04.640 --> 0:18:06.560 these things, and they thought, there's no way Newton's right, 0:18:06.720 --> 0:18:09.080 this has to be a wave. Um. You know, they 0:18:09.119 --> 0:18:14.560 saw things like interference patterns. Right. Interference patterns is when 0:18:14.560 --> 0:18:17.560 you have two waves and sometimes one is rippling up 0:18:17.840 --> 0:18:20.480 at the same time another one is rippling down. Right. 0:18:20.520 --> 0:18:23.960 So imagine, for example, you have a bathtub of water 0:18:24.000 --> 0:18:26.200 in front of you, and you slap it with two 0:18:26.280 --> 0:18:28.920 hands at once, right, each one is going to send 0:18:28.920 --> 0:18:32.119 waves out, and then when those end, those waves are 0:18:32.119 --> 0:18:35.120 either rippling up or rippling down. And when they reach 0:18:35.200 --> 0:18:38.240 each other, if they're both rippling up at the same time, 0:18:38.280 --> 0:18:41.560 then they constructively interfere to get a double wave. If 0:18:41.560 --> 0:18:44.320 they're both rippling down at the same time, they constructively 0:18:44.359 --> 0:18:47.359 interfered to get a double down wave. If one is 0:18:47.400 --> 0:18:50.159 rippling up and the others rippling down, then they then 0:18:50.200 --> 0:18:53.000 they cancel each other out right, And so you would 0:18:53.080 --> 0:18:57.040 see no light, yeah, exactly, And so you can do 0:18:57.080 --> 0:18:59.280 this kind of stuff in you know, in your bathtub, 0:18:59.280 --> 0:19:02.280 you can see interfe Auran's patterns, um. And what happens 0:19:02.280 --> 0:19:04.199 if you have two sources like that, like one from 0:19:04.240 --> 0:19:06.800 each of your hands, is you get some areas where 0:19:06.960 --> 0:19:08.800 the waves are high in some areas where the waves 0:19:08.840 --> 0:19:11.040 are are low, in some areas where there are no waves. 0:19:11.119 --> 0:19:12.720 And so as you say, if you do with light, 0:19:13.119 --> 0:19:15.960 then you see these patterns of dark and light, these stripes, 0:19:16.280 --> 0:19:18.600 And you couldn't do that with particles, right, like a 0:19:18.680 --> 0:19:21.600 particle wouldn't cancel another particle. Yeah, there's no way to 0:19:21.640 --> 0:19:24.480 explain that with particles. People thought, well, look, um, this 0:19:24.560 --> 0:19:26.800 is something that waves do and light is doing it, 0:19:26.880 --> 0:19:28.720 and there's no way to explain it with particles, so 0:19:28.880 --> 0:19:32.399 light must be a wave. In fact, there's even famous 0:19:32.400 --> 0:19:35.080 cases where they said, well, you know, um, if light 0:19:35.160 --> 0:19:37.480 is a wave, then you know, if you set up 0:19:37.480 --> 0:19:40.720 this various experiment, you would get this crazy effect and 0:19:40.760 --> 0:19:43.520 so that's absurd and so it definitely can't be true. 0:19:43.960 --> 0:19:45.760 And then they went and did the experiment and saw 0:19:45.800 --> 0:19:48.760 the crazy wave effect and they're like, oh, that is true. 0:19:48.840 --> 0:19:51.960 You know, this is a I love that because it's 0:19:51.960 --> 0:19:55.640 the primacy of experimental experimentalism, right, like, go and check 0:19:55.680 --> 0:19:57.880 the data, Go and actually get some data and see 0:19:57.880 --> 0:20:00.520 what the universe tells you. Yeah, Like you're like a 0:20:00.640 --> 0:20:03.879 doughnut can't possibly be a croissant at the same time, 0:20:04.359 --> 0:20:07.680 But it turns out that you can bake something called 0:20:07.680 --> 0:20:10.439 the cronut. Yeah exactly. I think that's a big debate 0:20:10.480 --> 0:20:13.080 in pastry science still though. And is it from a 0:20:13.119 --> 0:20:15.119