WEBVTT - How do LEDs work? 0:00:08.440 --> 0:00:11.319 Hey, Daniel, I have a question about Noble prices. Well, 0:00:11.360 --> 0:00:13.880 you know they aren't awarded until much later this year 0:00:13.960 --> 0:00:16.480 or so, don't stay up late and wait by your phone. Really, 0:00:16.480 --> 0:00:19.119 they don't give one for podcasts. No, and they also 0:00:19.200 --> 0:00:21.720 don't give a banana prize. Well, my question is about 0:00:21.720 --> 0:00:24.400 the Physics Nobel Prize. Well, I'm not staying up late 0:00:24.440 --> 0:00:26.479 and waiting by the phone either. Well, my question is 0:00:26.480 --> 0:00:30.040 whether it's given to some discovery that is deep or 0:00:30.200 --> 0:00:32.879 a discovery that's useful to humanity. Why does it have 0:00:32.960 --> 0:00:36.400 to be one or the other. Isn't deep knowledge also useful? 0:00:36.880 --> 0:00:39.360 Have you found new trinos to be useful to humanity? 0:00:39.440 --> 0:00:42.560 Not yet? Actually, I'm still waiting for aliens to teach 0:00:42.600 --> 0:00:45.320 us how to use new trinos to get a safe tan. Yeah, 0:00:45.400 --> 0:00:49.080 don't wait by the phone for that. Sweden call me, Jupiter, 0:00:49.200 --> 0:00:52.680 call me? What does that even mean? If they're Aliens 0:00:52.680 --> 0:00:55.480 and Jupiter? I want the Jovia Noble Prize for Best 0:00:55.520 --> 0:01:14.440 Podcast Sidekick. You're not the sidekick. I'm what what I am? 0:01:14.480 --> 0:01:17.040 John make cartoon is and the creator of PhD comments 0:01:17.360 --> 0:01:20.600 I'm Daniel. I'm a particle physicist, and until a moment ago, 0:01:20.640 --> 0:01:23.360 I thought I was the sidekick on this podcast, and 0:01:23.440 --> 0:01:26.720 so welcome to our podcast, the award winning science and 0:01:26.760 --> 0:01:30.319 physics podcast called Daniel and Jorge Explained the Universe. Remind 0:01:30.360 --> 0:01:33.560 me which award we won. We won the award for 0:01:33.840 --> 0:01:37.840 having no awards yet, the award for best podcast that 0:01:37.880 --> 0:01:42.000 features only two sidekicks. We're sidekicking it here on our podcast. 0:01:42.080 --> 0:01:44.960 But yeah, it's our podcast about physics and science and 0:01:45.040 --> 0:01:48.760 astronomy and the universe and everything in between. Our podcast 0:01:48.800 --> 0:01:52.200 in which we share with you the gorgeous, amazing mysteries 0:01:52.280 --> 0:01:54.120 of the universe. We take you on a mental tour 0:01:54.200 --> 0:01:57.200 to all the crazy stuff that's out there, that's in here, 0:01:57.440 --> 0:02:00.080 the tiny stuff, the huge stuff, and we explain it 0:02:00.160 --> 0:02:02.040 all to you in a way that we hope also 0:02:02.320 --> 0:02:04.000 makes you chuckle, yeah, because you know, we hope to 0:02:04.120 --> 0:02:07.240 open up your mind to the amazing and incredible things 0:02:07.240 --> 0:02:09.400 that are happening right now and the far reaches of 0:02:09.440 --> 0:02:12.240 the universe and the far corners of the Solar System. 0:02:12.360 --> 0:02:14.200 But we also kind of want to open your eyes 0:02:14.360 --> 0:02:17.400 to see you all of the amazing signs that's happening 0:02:17.560 --> 0:02:19.239 all around you right now. Because one of the most 0:02:19.240 --> 0:02:22.200 amazing things about physics is that the same laws of 0:02:22.240 --> 0:02:26.680 physics operate on black holes and nebula and neutron stars 0:02:26.960 --> 0:02:30.120 and you and me and everything in our world. This 0:02:30.160 --> 0:02:33.040 is one of the most earth shattering revelations of physics 0:02:33.080 --> 0:02:35.360 in the last few hundred years, that the physics of 0:02:35.400 --> 0:02:37.760 the cosmos and the physics of the every day are 0:02:37.880 --> 0:02:40.680 the same physics, which means that we can discover the 0:02:40.720 --> 0:02:44.280 secrets of the universe just by doing experiments in our laboratory. Yeah, 0:02:44.280 --> 0:02:46.120 it's all the same being trapped in a black hole 0:02:46.240 --> 0:02:50.040 or being trapped in your apartment for an indefinite amount 0:02:50.040 --> 0:02:52.359 of time. It's all the same. You can do physics anywhere. 0:02:52.400 --> 0:02:55.440 They're crushing in different ways. But it also means that 0:02:55.520 --> 0:02:59.240 we can look around us and find amazing crazy stuff 0:02:59.240 --> 0:03:02.200 that reveals the grits of the universe. Like quantum mechanics 0:03:02.240 --> 0:03:04.720 was not discovered inside a black hole. It was found 0:03:05.040 --> 0:03:07.880 just by shooting photons that weird kinds of metal. And 0:03:07.919 --> 0:03:10.480 so today we'll be talking about an invention. Dad, I 0:03:10.480 --> 0:03:13.239 would argue maybe is one of the most commonplace or 0:03:13.400 --> 0:03:18.359 most prevalent technologies out there in human technology human kind. Right, 0:03:18.440 --> 0:03:22.040 are you talking about the wheel fire the hoverboard, and 0:03:22.280 --> 0:03:26.800 I was hoping for the hoverboard. Hasn't had that happened yet, Daniel, No, 0:03:26.800 --> 0:03:29.239 it is not. But I'm sure somebody accidentally ordered a 0:03:29.280 --> 0:03:31.800 hoverboard on Amazon and got something else. You know. Well, 0:03:31.840 --> 0:03:35.040 it's a technology that I think basically almost every human 0:03:35.080 --> 0:03:38.280 looks at on a daily basis, maybe even an hourly basis. 0:03:38.320 --> 0:03:39.480 Now you have me at the edge of my seat. 0:03:39.520 --> 0:03:41.560 What are we talking about today? What do you mean? 0:03:41.840 --> 0:03:44.040 I thought you knew what we were talking about today. 0:03:44.200 --> 0:03:46.920 I'm the sidekick here. Remember you're in charge. Oh I see, 0:03:47.120 --> 0:03:49.200 I see. Well, it's in our phones, you know, everyone 0:03:49.280 --> 0:03:51.200 looks at their phone every couple of minutes. It's on 0:03:51.240 --> 0:03:53.800 our computer screens and our televisions, which I'm sure a 0:03:53.840 --> 0:03:55.800 lot of people are watching a lot of these days. 0:03:55.920 --> 0:03:59.800 So it illuminates everything you're talking about. My sheer genius, right, 0:04:00.040 --> 0:04:04.480 my brilliance about Netflix. I'm just kidding. Well, it's I 0:04:04.560 --> 0:04:07.160 just figured out it's on the title of our podcast. 0:04:07.200 --> 0:04:09.760 So I'm guessing that people will already know by the 0:04:09.760 --> 0:04:12.680 time they click that's right. I hope they haven't been misled. 0:04:13.520 --> 0:04:16.240 That's right. We'll lead him to the light. That's right, 0:04:16.279 --> 0:04:22.960 So to have the podcast, we'll be talking about l 0:04:23.000 --> 0:04:25.120 E d S. How do elds work, what are the 0:04:25.240 --> 0:04:28.120 physics of it? And why did somebody win a Nobel 0:04:28.160 --> 0:04:31.680 Prize for inventing a particular color of it? That's right, 0:04:31.760 --> 0:04:35.680 We have physics Nobel Prizes for things like understanding quantum 0:04:35.680 --> 0:04:39.520 mechanics and figuring out what the basic particles are, or 0:04:39.560 --> 0:04:42.680 for you know, an observation of gravitational ways. Things really 0:04:42.800 --> 0:04:46.000 reveal the fundamental fabric and nature of the universe. And 0:04:46.080 --> 0:04:49.200 then we have Nobel Prizes for the invention of the 0:04:49.240 --> 0:04:52.599 blue led blue eled, not the red led. That one 0:04:52.720 --> 0:04:57.400 did not win. It was blued, Nobel's favorite color. Not 0:04:57.480 --> 0:05:00.240 at all, not at all. And so today we wanted 0:05:00.279 --> 0:05:02.640 to dive into, like what are the physics of L 0:05:02.640 --> 0:05:05.000 E d S. Is it's really worth a Nobel Prize? 0:05:05.200 --> 0:05:07.400 What are the sort of obstacles that they had to 0:05:07.480 --> 0:05:10.279 leap over in order to make this thing work? And 0:05:10.320 --> 0:05:12.320 what physics did they have to solve along the way. 0:05:12.360 --> 0:05:14.880 What does it reveal about the nature of our universe 0:05:15.120 --> 0:05:17.600 that we can now make L d's globe blues? So 0:05:17.640 --> 0:05:19.520 what do you think about my idea that it's maybe 0:05:19.520 --> 0:05:21.760 one of the most prevailing technologies out there, you mean 0:05:21.960 --> 0:05:25.720 lights in general, or LED specifically, L E D specifically, 0:05:25.760 --> 0:05:27.880 you know, because they're they're basically in every phone, and 0:05:27.920 --> 0:05:30.520 there's billions of phones out there, and it's on every 0:05:30.560 --> 0:05:33.560 computer screen now in TV screen, most of the TV 0:05:33.680 --> 0:05:35.479 screens have them. I would say it's up there along 0:05:35.520 --> 0:05:39.480 with a concrete and toilet paper as the current most 0:05:39.480 --> 0:05:42.640 important technology. Yeah. You know, people have been stockpiling L 0:05:42.640 --> 0:05:44.800 e d s ever since the coronavirus came out, you know, 0:05:44.920 --> 0:05:47.960 just in case, yeah, you know, just in case we 0:05:48.120 --> 0:05:49.520 run out of lights. I think you're right. Just had 0:05:49.520 --> 0:05:52.320 a really big impact on everyday life. You see them 0:05:52.320 --> 0:05:54.280 in screens, you see them in lights, you see them 0:05:54.320 --> 0:05:57.200 on trucks, you see them everywhere now. Yeah. Yeah, So 0:05:57.240 --> 0:05:59.599 it's a pretty important technology that's all around us, that 0:05:59.800 --> 0:06:02.839 is hitting our eyeballs all of the time. But as usually, 0:06:02.839 --> 0:06:04.800 we were wondering how many people out there know how 0:06:04.920 --> 0:06:07.159 L e d s work or what it even stands for. 0:06:07.400 --> 0:06:09.880 L E ED. So, as usual, Daniel went out into 0:06:09.880 --> 0:06:12.440 the world and ask people if they do how an 0:06:12.560 --> 0:06:15.600 LED works. That's right, and these questions actually pre date 0:06:15.960 --> 0:06:20.000 the coronavirus pandemic and so these are historical records of 0:06:20.279 --> 0:06:23.880 in person interviews back when that was still possible. Really, Oh, 0:06:24.080 --> 0:06:26.080 this is an actual on the street. These are from 0:06:26.120 --> 0:06:28.720 the archive. We haven't had a chance to pull this 0:06:28.760 --> 0:06:31.040 episode out yet. I see. Do you think people's opinions 0:06:31.040 --> 0:06:33.240 about l E d S would have changed by now? 0:06:33.360 --> 0:06:36.200 While people are spending more time inside under the life 0:06:37.360 --> 0:06:39.840 of a deeper relationship with L E d S. Now, 0:06:39.960 --> 0:06:43.160 maybe hypnotizes a little bit more since Yeah, well you know, 0:06:43.320 --> 0:06:45.200 people are looking at more screens and so they have 0:06:45.440 --> 0:06:47.960 hopefully more affection for L D. Yeah. So think about 0:06:47.960 --> 0:06:49.800 it for a second. If someone asked you how an 0:06:49.880 --> 0:06:52.359 LED works, would you know what to answer. Here's what 0:06:52.400 --> 0:06:54.640 people had to say. No, but I just know it's 0:06:54.640 --> 0:06:56.440 a better life. Part of me really wants you to 0:06:56.480 --> 0:07:00.320 say electricity, but uh, isn't it No, that's fluorescence. Remind 0:07:00.600 --> 0:07:06.200 I was gonna say gas, but let's just fluorescence light. Yeah, 0:07:06.920 --> 0:07:10.840 I'm going to assume it's due to a residents frequency 0:07:11.120 --> 0:07:16.920 within within the LED. I'm not sure. Essentially, it's just 0:07:17.000 --> 0:07:21.760 a PM junction. Um one side has holes in side 0:07:21.800 --> 0:07:26.400 has an accessible electrons, especially transitions in the state of 0:07:26.400 --> 0:07:34.680 the PM junction. Really slight. So yeah, oh shoot, um, honestly, 0:07:34.880 --> 0:07:40.520 I don't know. I literally don't know. Kind of yeah, yeah, 0:07:40.560 --> 0:07:46.080 I know, um excited Adams, but I forgot like which 0:07:46.080 --> 0:07:51.840 Adam like maybe alien They excited to higher state energy 0:07:51.880 --> 0:07:58.880 state and wave falls generated energy. But yeah, that's kind 0:07:58.880 --> 0:08:03.960 of isn't that. Florescen no similar, but fluorescence like much 0:08:04.000 --> 0:08:06.560 weaker energy. So what do you think of these responses? 0:08:06.600 --> 0:08:09.080 Pretty good? I feel like they fall in live with 0:08:09.120 --> 0:08:10.960 how I think about l d S, which is that 0:08:11.080 --> 0:08:12.960 I don't know much about him. Yeah, I was a 0:08:13.000 --> 0:08:16.040 little surprised. Some people had no idea. Some people thought 0:08:16.120 --> 0:08:18.880 they understood it, but we're actually talking about a completely 0:08:18.960 --> 0:08:22.680 different type of light generation that's fluorescence. People got them 0:08:22.680 --> 0:08:25.520 confused with fluorescent, Like yeah, yeah, In turns out there's 0:08:25.720 --> 0:08:27.400 lots of different ways to make light. You know, you 0:08:27.560 --> 0:08:29.720 incandescent light, we have fluorescent lights, and then we have 0:08:29.840 --> 0:08:34.200 led lights, and they all operate on really different physical principles. Yeah, 0:08:34.240 --> 0:08:36.800 because maybe maybe people have got them confused, because I 0:08:36.800 --> 0:08:39.560 feel like fluorescent lights, I know, they've been around for 0:08:39.600 --> 0:08:41.840 a long time, you know, like neon signs and things 0:08:41.880 --> 0:08:44.000 like that, and fluorescent bulbs, but they sort of made 0:08:44.000 --> 0:08:47.600 it into people's homes more recently, but then right away 0:08:47.600 --> 0:08:50.719 elid sort of came about and then totally replaced them. Yeah, well, 0:08:50.760 --> 0:08:52.920 fluorescent lights have been around for quite a long time, 0:08:53.200 --> 0:08:55.160 but yeah, they didn't make it into people's homes until 0:08:55.200 --> 0:08:57.839 recently with the compact fluorescence. But there's actually sort of 0:08:57.840 --> 0:09:01.520 a fascinating legal drama aout florescent lights because they were 0:09:02.000 --> 0:09:05.360 first developed pretty soon after incandescent lights, but then General 0:09:05.400 --> 0:09:08.439 Electric bought up all the patents and prevented anybody from 0:09:08.480 --> 0:09:12.240 developing them or using them, and basically kept fluorescent lights 0:09:12.240 --> 0:09:15.520 out of the market for decades just because they also 0:09:15.559 --> 0:09:18.120 owned the patents for incandescent lights. So it's sort of 0:09:18.160 --> 0:09:20.800 a legal political drama that we probably won't even get 0:09:20.800 --> 0:09:23.120 into today. They're like fluorescence that that works with gas, 0:09:23.200 --> 0:09:25.640 it's not electric. It's on brand with us, so we'll 0:09:25.679 --> 0:09:27.600 just sit in it. Yeah, they just sort of bought 0:09:27.600 --> 0:09:29.559 it up and sat on it as a dangerous technology 0:09:29.600 --> 0:09:32.719 that they thought would sort of endanger their business. Well, 0:09:32.800 --> 0:09:36.560 let's get into how LEDs work, but first let's maybe 0:09:36.600 --> 0:09:38.560 talk about how some of the other lights that people 0:09:38.600 --> 0:09:41.360 are familiar with work. So take us back, Daniel, how 0:09:41.360 --> 0:09:44.840 does it torch work. You know, that's a really awesome 0:09:44.920 --> 0:09:47.800 question actually, like what is fire and how does it work? 0:09:48.080 --> 0:09:50.240 And I want to do a whole podcast episode, Um, 0:09:50.240 --> 0:09:52.480 what is fire and what is the thing you're seeing 0:09:52.520 --> 0:09:56.520 that's glowing? And remember it's it's gonna be totally lit. 0:09:56.800 --> 0:09:58.640 M We're gonna brighten your life with that one. And 0:09:58.679 --> 0:10:01.040 remember on our live streams, somebody asked about that whether 0:10:01.120 --> 0:10:04.400 fire can have a shadow, which is a totally awesome question. 0:10:04.600 --> 0:10:06.400 But I think the first light that we should talk 0:10:06.400 --> 0:10:09.000 about is incandescent lights. And these are the ones that 0:10:09.120 --> 0:10:11.480 Edison invented, you know, the ones that people have had 0:10:11.480 --> 0:10:14.560 in their homes until very recently. It has a little 0:10:14.679 --> 0:10:18.880 filament in it that glows and eventually it breaks, right. Yeah, 0:10:18.960 --> 0:10:20.559 basically what people think of when they think of a 0:10:20.640 --> 0:10:22.800 light bulb, like a round thing with a little wire 0:10:22.920 --> 0:10:25.200 through the middle. Yeah, that's your classic light bulb. And 0:10:25.240 --> 0:10:27.880 all the technologies that we're gonna talk about today operate 0:10:28.000 --> 0:10:32.719 under the same essential goal, which is turned electricity into photons. 0:10:32.920 --> 0:10:34.680 Do you think when Edison had the idea for the 0:10:34.800 --> 0:10:36.559 light bulb, do you think he had a light bulb 0:10:36.600 --> 0:10:39.200 over his head? Like, was that the only time in 0:10:39.280 --> 0:10:42.400 history when like somebody was actually thinking of a light bulb, 0:10:42.400 --> 0:10:44.400 when they had an idea. Yeah, that's where it comes from, right, 0:10:44.400 --> 0:10:46.480 that was the first great idea, That was the first 0:10:46.520 --> 0:10:51.400 idea worthy of having a light bulb over your head. Technically, 0:10:51.400 --> 0:10:53.760 that's true. Yeah, And so the idea for incandescent lights 0:10:54.280 --> 0:10:58.120 is to find some material where you can deposit the 0:10:58.240 --> 0:11:00.800 energy from your electrons and it will give off light. 0:11:01.200 --> 0:11:03.760 All right, So every one of these strategies you want 0:11:03.760 --> 0:11:07.880 to turn fast moving electrons into shooting off photon photons 0:11:07.920 --> 0:11:11.560 to the surrounding areas. Okay, so how do incandescent lights work? 0:11:11.679 --> 0:11:14.080 How do light bulbs work? Regularly? The amazing thing about 0:11:14.160 --> 0:11:16.400 light bulbs that people probably don't understand is that they 0:11:16.440 --> 0:11:21.199 glow even when they're off. What. Yeah, everything glows. It's 0:11:21.240 --> 0:11:25.400 called black body radiation. Everything in the universe gives off photons, 0:11:25.480 --> 0:11:28.520 gives off radiation, even if it's totally black, even if 0:11:28.520 --> 0:11:32.280 it's a black hole, daddy. Well, technically, yes, black holes 0:11:32.320 --> 0:11:35.280 do give up a radiation all right, Yeah, that's true. Correct, 0:11:35.600 --> 0:11:37.880 Even black holes have a temperature. Right, Everything in the 0:11:37.920 --> 0:11:42.280 universe that's not an absolute zero glows at some spectrum. Now, 0:11:42.400 --> 0:11:45.040 usually you don't see it because it's invisible. It glows 0:11:45.160 --> 0:11:49.640 very very very long wavelengths, very low frequencies, and so 0:11:49.679 --> 0:11:52.600 you don't see it. So but this is why, for example, 0:11:52.960 --> 0:11:56.480 you know infrared telescopes like the James web Space telescope 0:11:56.720 --> 0:12:00.120 that looks for infrared light. It sees a lot out 0:12:00.120 --> 0:12:01.920 of noise that you don't even see and have to 0:12:02.000 --> 0:12:04.720 keep it cold a like negative fifty degrees or whatever. 0:12:05.400 --> 0:12:08.640 So everything in the universe is already glow, but it's 0:12:08.679 --> 0:12:10.760 not so useful, right, What you want is something that 0:12:10.800 --> 0:12:14.040 glows with light that you can see a lot. Right. Oh, 0:12:14.120 --> 0:12:16.480 I see black body radiation is in the infrared. It's 0:12:16.559 --> 0:12:19.840 much lower than the infrared. Yet most black body radiation, 0:12:19.920 --> 0:12:23.720 like the cosmic Marcrowave background radiation, is black body radiation 0:12:23.800 --> 0:12:26.679 from that initial plasma of the universe. And is it 0:12:26.800 --> 0:12:29.320 like you know, three degrees kelvin. It's a very very 0:12:29.320 --> 0:12:32.280 long wavelength. But what about something that's at zero degreek kelvin, 0:12:32.559 --> 0:12:35.240 like absolute zero? Would that still glow? You know, something 0:12:35.240 --> 0:12:37.560 that absolute zero can't glow. But there is nothing in 0:12:37.559 --> 0:12:40.480 the universe at absolute zero. So if you're like at 0:12:40.520 --> 0:12:45.440 point oh one degrees kelvin, from absolute zero, you would 0:12:45.520 --> 0:12:47.480 be glowing a little bit exactly. And that's why the 0:12:47.520 --> 0:12:50.120 black hole stuff is actually quite fascinating because when Stephen 0:12:50.160 --> 0:12:53.679 Hawking developed his ideas of black holes having a temperature, 0:12:54.120 --> 0:12:58.600 that automatically suggests that black holes should radiate, because like 0:12:58.640 --> 0:13:01.280 everything else that has a temperature, should radiat And that's 0:13:01.280 --> 0:13:04.439 why Hawkings results are sort of black hole thermo dynamics, 0:13:04.600 --> 0:13:06.760 because he's thinking about the temperature of black holes and 0:13:06.760 --> 0:13:08.720 how that connects to how they radiate. All right, so 0:13:08.840 --> 0:13:11.040 everything glows into infrared, So how do we get things 0:13:11.080 --> 0:13:13.240 to glow in the in the visible light the white 0:13:13.320 --> 0:13:15.560 light spectrum. Yes, so the spectrum in which you glow 0:13:15.640 --> 0:13:19.520 depends on your temperature. So really cold stuff glows in 0:13:19.559 --> 0:13:22.280 the infrared. If you heat something up, then its emissions 0:13:22.520 --> 0:13:25.280 move into the visible spectrum. So you want to make 0:13:25.320 --> 0:13:27.400 your filament glow in the visible light instead of in 0:13:27.440 --> 0:13:29.360 the infrared light. Than what you do is you make 0:13:29.400 --> 0:13:32.640 it hot, hotter and hotter. It turns the light from 0:13:32.640 --> 0:13:35.040 it not just glows more, but it changes color. It 0:13:35.120 --> 0:13:37.600 changes color. And that's why for example, you heat up 0:13:37.640 --> 0:13:39.959 metal right and you see it glows blue, it glows red, 0:13:40.000 --> 0:13:43.000 It glows white, for example, and the temperature of the 0:13:43.040 --> 0:13:45.840 metal determines the frequency at which it's glowing, right, Like 0:13:45.920 --> 0:13:49.679 white hot and red hot are different temperatures of metal R. 0:13:50.400 --> 0:13:52.200 And so this is a basic principle. And what's going 0:13:52.240 --> 0:13:54.160 on in the physics sense, like what's going on with 0:13:54.200 --> 0:13:56.760 the electrons on the atoms, why is it changing color? 0:13:56.920 --> 0:13:58.920 And how is it giving off the light. So it's 0:13:58.920 --> 0:14:01.439 always a good idea to try to think about stuff microscopically. 0:14:01.440 --> 0:14:03.599 And that's not just because I'm a particle physicist that 0:14:03.640 --> 0:14:06.079 I think we should always be thinking about the tiny stuff. 0:14:06.120 --> 0:14:08.840 I think it really does lead to some inside And 0:14:08.880 --> 0:14:12.400 so what's happening microscopically when you heat something up is 0:14:12.400 --> 0:14:15.160 that the electrons inside of the particles inside it have 0:14:15.360 --> 0:14:18.240 more ways to move. They're wiggling more, they're bouncing more. 0:14:18.559 --> 0:14:21.240 So there's just a lot more energy there. Now. The 0:14:21.280 --> 0:14:24.600 way something glows is when something moves from a higher 0:14:24.680 --> 0:14:27.080 energy level to a lower energy level. I mean, like 0:14:27.120 --> 0:14:30.000 the atoms in a decay or sort of degrade a 0:14:30.080 --> 0:14:32.160 little bit or chill out. And when they do that, 0:14:32.240 --> 0:14:34.840 they admit a hotel. Yeah, they're excited. They have some 0:14:34.960 --> 0:14:37.360 energy stored in them, and that energy comes from you know, 0:14:37.400 --> 0:14:40.600 whatever you did to heat up this material. Right, Heat 0:14:41.080 --> 0:14:44.400 means internal energy stored in the motion of these objects, 0:14:44.400 --> 0:14:46.960 and we had a whole podcast about what temperature means 0:14:46.960 --> 0:14:49.600 and it turns out to be very confusing and amazing, 0:14:49.840 --> 0:14:51.760 like everything else in the universe. But the way to 0:14:51.760 --> 0:14:55.560 think about microscopically is that these atoms are excited. Either 0:14:55.720 --> 0:14:58.360 the electrons that are whizzing around them have gone up 0:14:58.680 --> 0:15:00.960 one ladder in the energy level, or two ladders or 0:15:00.960 --> 0:15:04.080 three ladders, or maybe they're vibrating in new ways or 0:15:04.200 --> 0:15:06.320 rotating in new ways. These are all ways that they 0:15:06.320 --> 0:15:08.880 can store energy. The electrons are that are the atoms. 0:15:08.960 --> 0:15:11.120 The electrons can move up energy levels, but the atoms 0:15:11.160 --> 0:15:13.720 also they can vibrate. Remember a lot of these are 0:15:13.760 --> 0:15:16.520 in bonds, right. Metals are not just free floating gases. 0:15:16.760 --> 0:15:20.040 These lattices of things tied together and they're like you 0:15:20.080 --> 0:15:22.680 can imagine little springs between them, and then you can 0:15:22.680 --> 0:15:25.280 imagine those things vibrating and vibrating in different ways. They 0:15:25.280 --> 0:15:28.240 have different modes, all right. So they're excited and so 0:15:28.280 --> 0:15:30.760 they they're giving off energy and then they relax. Because 0:15:30.800 --> 0:15:32.600 things in the universe don't like to be excited. They 0:15:32.680 --> 0:15:34.920 like to spread out their energy, and that's why things 0:15:34.920 --> 0:15:38.040 emit energy because entropy, right, energy in the universe tends 0:15:38.080 --> 0:15:41.040 to diffuse, and so if you have it concentrated in 0:15:41.080 --> 0:15:43.520 one little mode, like one little electron has jumped up 0:15:43.560 --> 0:15:46.920 three energy levels, it will decay. You'll give that energy off. 0:15:47.120 --> 0:15:49.040 And the way it does that is by shooting off 0:15:49.040 --> 0:15:51.440 a photon. And so the more you heat up something up, 0:15:51.520 --> 0:15:54.240 the more you make all the atoms more excited, the 0:15:54.280 --> 0:15:56.880 more you know photons that are going to come off 0:15:56.920 --> 0:15:59.760 of this excitement exactly, and then the higher the energy 0:15:59.880 --> 0:16:02.320 of those gaps, So an electron can get pushed up 0:16:02.400 --> 0:16:04.840 several levels up that ladder, and then it can jump 0:16:04.880 --> 0:16:08.080 down five levels, and so then the photon has more energy, 0:16:08.240 --> 0:16:12.600 which corresponds to a higher frequency. So that's how, for example, 0:16:12.800 --> 0:16:15.720 hot objects can emit in the visible spectrum instead of 0:16:15.760 --> 0:16:18.120 just at the very very low energy levels. So the 0:16:18.240 --> 0:16:20.760 light that they emit has more energy, which is what 0:16:21.040 --> 0:16:24.720 higher frequency means, which is what visible light means, or 0:16:24.760 --> 0:16:29.000 invisible light has more energy per photon than infrared light. 0:16:29.040 --> 0:16:31.440 But I think it also has to be certain kinds 0:16:31.440 --> 0:16:34.080 of materials, right, like when I boil water, it doesn't 0:16:34.120 --> 0:16:36.280 start to blow. I mean it starts to glow in 0:16:36.320 --> 0:16:38.720 the infrared, but not in the visible light spectrum. That's 0:16:38.760 --> 0:16:41.000 an awesome question. How hot would you have to make 0:16:41.120 --> 0:16:43.640 water in order to make it glow? I don't think 0:16:43.680 --> 0:16:45.880 answer to that. That's a cool question. But you're right, Yeah, 0:16:45.880 --> 0:16:48.320 everything glows at some level, but not everything can be 0:16:48.400 --> 0:16:50.800 easily made to glow in the visible because I guess 0:16:50.800 --> 0:16:54.080 it will melt or burn or boil, yeah, exactly, something 0:16:54.080 --> 0:16:56.080 else will happened to it turn into vapor. And so 0:16:56.120 --> 0:16:58.080 that that's how light bulbs work. It's that they have 0:16:58.120 --> 0:17:01.280 a little thin wire of metal that you heat up 0:17:01.280 --> 0:17:03.480 and then that gives us the light. That's right. And 0:17:03.520 --> 0:17:05.639 the way you heat it up is that you send 0:17:05.760 --> 0:17:08.359 current through it, right, You send electricity through it. And 0:17:08.440 --> 0:17:11.600 most of these metals are resistors, meaning that they are 0:17:11.640 --> 0:17:14.680 not perfect conductors. So the electrons as they're trying to 0:17:14.760 --> 0:17:17.880 go through the metal are getting bounced into atoms, right, 0:17:17.920 --> 0:17:21.080 and those atoms are stealing their energy. And this is 0:17:21.080 --> 0:17:24.040 what heats up something when electricity passes through it. Like 0:17:24.320 --> 0:17:27.280 you know that block that you used to charge your laptop. 0:17:27.320 --> 0:17:29.600 Have you've been charging it for a while, it heats up, right, 0:17:29.960 --> 0:17:34.080 that's using. That's inefficient. It's using. It's stealing the electricity 0:17:34.320 --> 0:17:37.000 from those electrons in order to heat up that block. 0:17:37.320 --> 0:17:39.639 This is how you heat up the filament of tungsten. 0:17:39.680 --> 0:17:42.600 As you pass all this electricity through it, that heats 0:17:42.600 --> 0:17:44.960 it up and that makes it glow. Yeah, that's a 0:17:44.960 --> 0:17:48.040 little wire inside of the traditional light bulb and white tungsten. 0:17:48.119 --> 0:17:49.760 Is it a special kind of metal? They can heat 0:17:49.840 --> 0:17:52.000 up a lot without melting. Yeah, tungsten just sort of 0:17:52.080 --> 0:17:54.880 lasts a long time. But these things are really very 0:17:55.000 --> 0:17:58.280 very inefficient. Like it's not a very direct way to 0:17:58.359 --> 0:18:01.679 get energy into photons. Right, You're just heating this thing 0:18:01.760 --> 0:18:03.800 up and it's glowing somewhat in the visible but not 0:18:03.880 --> 0:18:07.119 always invisible, and a lot of the energy is just lost. 0:18:07.800 --> 0:18:10.720 A lot of the energy goes into the infrared, which 0:18:11.080 --> 0:18:13.760 is useless to us. Yeah, it just goes into making 0:18:13.760 --> 0:18:16.560 this thing hot, right, and not all the heat gets 0:18:16.560 --> 0:18:20.159 turned into visible light, and so only something like five 0:18:20.800 --> 0:18:22.639 of the energy that you put into a light bulb 0:18:22.680 --> 0:18:26.760 gets turned into light. Superficient, not super efficient and also 0:18:26.960 --> 0:18:30.000 kind of fragile, like you're baking this thing every single time, 0:18:30.040 --> 0:18:31.639 So it gets hot and then it gets cold, and 0:18:31.720 --> 0:18:34.080 gets hot and then it gets cold, and you know that, 0:18:34.160 --> 0:18:36.680 like that creates a lot of mechanical stress, which is 0:18:36.720 --> 0:18:39.640 why these filaments, which are already very very thin, don't 0:18:39.720 --> 0:18:43.399 last for that long. So your typical incandescent classic light 0:18:43.440 --> 0:18:46.320 bulb only works for about a thousand hours. Well, they're 0:18:46.320 --> 0:18:48.840 making a comeback, you know, and like hip her restaurants 0:18:48.840 --> 0:18:51.679 and stuff, everyone's going for the incandescent bulbs. Yeah. Well, 0:18:51.720 --> 0:18:54.119 the positive thing about incandescent bulbs is to have a 0:18:54.200 --> 0:18:56.879 very nice glow, Like it feels like sort of a 0:18:57.000 --> 0:18:59.919 natural light. You know that the process that produces this 0:19:00.080 --> 0:19:03.080 light gives you a spread, right, not just one color. 0:19:03.320 --> 0:19:05.080 It's not like a laser beam in your eye. It's 0:19:05.080 --> 0:19:07.959 a nice spread of warm white light. And so a 0:19:07.960 --> 0:19:09.920 lot of people like that. It's sort of more similar 0:19:09.960 --> 0:19:12.360 to sunlight than some of the other technologies we're gonna 0:19:12.359 --> 0:19:13.960 talk about, saying, all right, let's get into some of 0:19:13.960 --> 0:19:17.760 these other technologies like l d s, like fluorescent light bulbs, 0:19:18.280 --> 0:19:33.520 but first let's take a quick break. All right, there, 0:19:33.720 --> 0:19:37.359 we're talking about how LEDs work and specifically how lights 0:19:37.440 --> 0:19:39.080 work in general, and so we're going down the list 0:19:39.080 --> 0:19:42.560 of technologies, and so we talked about incandescent bulbs, which 0:19:42.720 --> 0:19:45.480 I'm guessing maybe my kids will never have to know 0:19:45.560 --> 0:19:49.080 how they work technically because everything is sort of moved on. 0:19:49.160 --> 0:19:51.240 But the next one in the history of light is 0:19:51.280 --> 0:19:53.399 the fluorescent light bulb. So you were saying these were 0:19:53.440 --> 0:19:56.119 invented out around the same time as the incandescent light bulb, 0:19:56.520 --> 0:19:58.680 but they worked on a totally different physics. Yeah, the 0:19:58.680 --> 0:20:01.719 physics is different. The idea here is to use excited gas, 0:20:02.160 --> 0:20:04.040 and you know, we talked about in the late eighteen 0:20:04.119 --> 0:20:07.800 hundreds of people were making vacuum tubes and you know, 0:20:07.840 --> 0:20:10.760 passing currents through it and seeing glows, and that's actually 0:20:10.800 --> 0:20:13.119 one of the things that lead to the discovery of 0:20:13.119 --> 0:20:15.919 the electron, right J. J. Thompson discovered the electron by 0:20:15.920 --> 0:20:18.800 playing with these sort of evacuated tubes and seeing how 0:20:18.920 --> 0:20:21.640 the gas inside them glows. But then people were playing 0:20:21.680 --> 0:20:23.960