How Lasers Work

It turns out that lasers are even cooler than they look. And as far as acronyms go, they’re pretty solid in that respect too. There’s way too much cool stuff about lasers to tease here so listen to this old school SYSK episode and let lasers blow away. See omnystudio.com/listener https://omnystudio.com/listener for privacy information.

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:00Speaker 00

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• 0:04Josh Clark?

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• 1:03Speaker 00

  Welcome to Stuff You Should Know, a production of iHeart Radio.

• 1:13Josh Clark?

  Hey, and welcome to the podcast. I'm Josh and there's Chuck and Jerry's here too. And she was making too many laser noises, so we asked her to please go on mute. She did, and I assume she's still making laser noises. We just can't hear it right now.

• 1:27Speaker 02

  She had a little attitude about it, too.

• 1:29Josh Clark?

  She did. I mean, I was really mean and curt, but she didn't have to be that way back.

• 1:35Speaker 02

  Yeah, this is a one way street.

• 1:37Josh Clark?

  Right. It's my way or the highway.

• 1:42Speaker 02

  You know, it's about time we did an episode on lasers. This seems like something that we would have tackled in those first formative, in that first formative decade.

• 1:53Josh Clark?

  And I'm glad we didn't because I think it's good to still do like a traditional, you know, how X works episode.

• 2:01Speaker 02

  We should do one on how X works.

• 2:04Josh Clark?

  It depends on what kind of X you're talking about.

• 2:07Speaker 02

  Ruby used to give us an X when she was little, when she was like two years old. If she didn't like something, she would do her fingers as an X.

• 2:15Josh Clark?

  And she just keeps getting cooler and cooler.

• 2:17Speaker 02

  She forgot that she lost that one along the way. I need to tell her to bring that back.

• 2:21Josh Clark?

  Yeah, that's a good one.

• 2:22Speaker 02

  Uncle Josh likes it.

• 2:23Josh Clark?

  That's like talk to the hand, but way better.

• 2:25Speaker 02

  Yeah, exactly.

• 2:28Josh Clark?

  All right. So we're talking lasers today, not necessarily X. Maybe we will do X someday. Let's find out. And everybody knows what a laser is, right?

• 2:38Speaker 02

  Yeah, I mean, I feel like it's one of the more like one of those acronyms like SCUBA that you learn when you're like on the playground. So in this case, it stands for light amplification by stimulated emission of radiation. And now that I know what a laser is and how it works, they kind of nailed it with that acronym.

• 2:59Josh Clark?

  They did. You can totally forgive them for the by and the of because that's a world-class acronym.

• 3:05Speaker 02

  Yeah, that would be LABCior.

• 3:11Speaker 02

  If they included those, laser is so much cooler.

• 3:14Josh Clark?

  LABCior doesn't, yeah, it doesn't have that same ring to it as laser.

• 3:17Speaker 02

  Throw me the LABCior gun.

• 3:20Josh Clark?

  Someone would say, no. So lasers are everywhere, everybody. They're all around you. A lot of them are pointed at you right now. You just can't see them. But like a UPC code scanner at a supermarket checkout, they still have supermarkets, right? Oh, yeah, that's right. Everyone goes in and empties all of their bank accounts into them every week.

• 3:42Speaker 02

  Right, to get sustenance.

• 3:44Josh Clark?

  Well, when you check out, boop, boop, boop, like that, that's actually a laser being triggered. You're scanning your UPC code. So lasers are everywhere. They're at the supermarket at least. That doesn't necessarily mean you understand them. I didn't understand them until we started to research this. Did you?

• 4:02Speaker 02

  No, and it's really not that like hard to wrap your head around, actually. I was, I was kind of dreading this, but it's, Dave did a great job with this article, sort of like

• 4:11Josh Clark?

  Yeah, here, here.

• 4:11Speaker 02

  In the traditional sense, like he said.

• 4:13Josh Clark?

  Yep.

• 4:14Speaker 02

  And he does a good job initially by sort of laying the groundwork of regular light compared to a laser light. And I think that's a great way to start.

• 4:23Josh Clark?

  Well, yeah, if we're going to talk about lasers, we really, I mean, we're talking about light, we kind of need to go back a couple of steps and say, okay, there's different kinds of light, you know, like the light we think of as sunlight or a light bulb or something like that, what we would call generally white light is, as a lot of people know, all of the colors of the spectrum, the visible light spectrum together, coming together to form white light.

• 4:48Speaker 02

  That's right. Many different wavelengths, but just like, you know, elementary school science, when you get that prism and your little mind is blown, it still kind of blows my mind, you scatter that light into its different wavelengths.

• 5:01Josh Clark?

  It's so beautiful.

• 5:02Speaker 02

  And it's the colors of the rainbow there, but, and this is something that like, I don't think I even realized this, even those different wavelengths, it's not a single wavelengths, it's still a spectrum of different wavelengths, creating the red or the blue or the yellow or whatever, and that's kind of where we find ourselves, you know, departing in what a laser ends up being.

• 5:26Josh Clark?

  Yeah, because, so for example, the, the yellow band, what we see is yellow in the visible spectrum occupies the 570 nanometer to 590 nanometer range.

• 5:37Speaker 02

  You show off.

• 5:37Josh Clark?

  Below that, I think you've got what, red, orange, something like that, Roy G. Biv?

• 5:42Speaker 02

  Yeah.

• 5:42Josh Clark?

  I can't remember. Above that, you've got blue, green, Roy G., green, and those just have different wavelengths. They're all electromagnetic light, it's the same thing as a microwave, it's the same thing as a radio wave, it's the same thing as a gamma ray, it's just the different frequencies make them different kinds of energy, what we call the visible spectrum. The point is, is within all those different nanometer wavelengths, say from 570 to 590, there's different kinds of yellow, there's different, different shades of yellow in there, across that, the spectrum within the spectrum, I guess.

• 6:18Speaker 02

  Yeah, spectrum within the spectrum. Also a great album title.

• 6:23Josh Clark?

  That is a great album title.

• 6:25Speaker 02

  Jazz fusion.

• 6:25Josh Clark?

  Maybe you could have like a prism with a beam of light coming in and then a rainbow coming out the other side.

• 6:31Speaker 02

  Yeah, it is 1960s for sure.

• 6:33Josh Clark?

  Yeah, a pyramid even is a prism.

• 6:36Speaker 02

  Yeah, with Isaac Hayes's head floating above it.

• 6:41Josh Clark?

  I'm describing the Dark Side of the Moon album cover.

• 6:44Speaker 02

  I know, I was just kidding.

• 6:45Josh Clark?

  Okay, well, you were really throwing me off. You were, that was some meta joking right there.

• 6:49Speaker 02

  I have a great pressing of Dark Side of the Moon, by the way.

• 6:52Josh Clark?

  You do?

• 6:53Speaker 02

  Yeah, you know, I had a record presser, a guy who does that for a living. I was hanging out with him in New York with our friend Joey Ciara and these two guys who did that. And he said, yeah, some pressing is like it's done by a human. So you might have some records that just sound really awesome.

• 7:07Josh Clark?

  Oh, neat.

• 7:07Speaker 02

  Cause it was well done. And I was like, yeah, and they're, you know, 180 gram. He was like, that's all bunk, by the way. He's like, it just makes you feel better that it's heavier. And I was like, oh, man, that's disappointing.

• 7:18Josh Clark?

  No, I do like the heft of a 880 gram.

• 7:22Speaker 02

  Apparently they said it's, that's all just for you to make you think it is better because it's heavier.

• 7:27Josh Clark?

  It's heavier, so it's worth more.

• 7:28Speaker 02

  All right. So back to lasers. What you just described very well, by the way, was regular light, wavelength within the wavelength. If you talk about the differences of a laser light, you're talking about three main differences. And the first of which is that single wavelength. It's like truly monochromatic, that beam of light that a laser is, or I guess, you know, produces, oh, no, it's what it is, is, is just a very, it's that single wavelength, highly, highly concentrated.

• 7:58Josh Clark?

  Yeah. So rather than say a wavelength between 570 and 590 for being yellow, this is a 572 nanometer wavelength that is that specific yellow.

• 8:08Speaker 02

  That's right.

• 8:08Josh Clark?

  And it's, it's not, it's made up entirely of yellow light on that exact same wavelength. That is incredibly important. That's a huge, huge difference. Lasers don't occur naturally. We've figured out how to make them. And by we, I'm including myself in you.

• 8:26Speaker 02

  That's right. The second big difference between laser light and regular light is that it's coherent. So not only is it just a single wavelength, but the photons of the light, and we're going to talk about where they come into play here in a second, thanks to Mr. Einstein or Dr. Einstein. The photons are perfectly in phase with one another. So if you look at that wavelength, the peaks and the troughs are all perfectly in sync.

• 8:51Josh Clark?

  Yeah, and not like they're following the same plane and they're just kind of in sync like that, like they're right above each other, right below each other. They're not interfering with one another in any way whatsoever.

• 9:02Speaker 02

  That's right.

• 9:03Josh Clark?

  And then the last one is that they're collimated, meaning they're all traveling in the exact same direction.

• 9:09Speaker 02

  Yeah, I mean, that's, that's important. I mean, collimated is sort of a fancy way of saying directional, but as we'll see, they all have to be traveling that same direction to pick up their little photon buddies.

• 9:20Josh Clark?

  Yeah, so essentially what you've got is a very specific kind of the exact same kind of light, none of which are interfering with the other photons that are coming out of the laser, all of which are traveling in the same direction. So they do not get in one another's way and they can be combined very, very tightly. And that's essentially what a laser does.

• 9:40Speaker 02

  Yeah, for sure. And it all goes back to that acronym stimulated emission, the SE in laser. You can't make a laser without SE.

• 9:51Josh Clark?

  That's true.

• 9:51Speaker 02

  You can't spell laser without SE and you can't have a laser without stimulated emission. And our buddy Einstein is the guy who sort of laid the theoretical groundwork. He didn't go out and build a laser. That came later, but he laid the theoretical groundwork for all of this back in the, ridiculously in the early 1900s.

• 10:10Josh Clark?

  Yeah, so back in 1905, most people were like, light's a continuous wave and by proxy, the universe is one smooth, continuous thing. And Einstein was like, I don't think that's true. I think if you zoom in far enough, close enough into the fabric of the universe, you're going to see it's actually made of discrete little, little things.

• 10:30Speaker 02

  Yeah.

• 10:30Josh Clark?

  And call them pixels, right? And he's like, if that's true, then light can't be one continuous wave either. So I think they're actually made up of those little tiny packets that I'm going to call photons. And he turned out to be right. He had a great equation for it, too. It's, it's so elegantly simple. That's the thing about Einstein. He could come up with like, three different things and could completely change our understanding of the universe.

• 10:56Speaker 02

  Yeah, for sure. This is the Planck Einstein. Einstein, what just happened? I was concentrating so heavily on not saying plank.

• 11:05Josh Clark?

  I've heard plank. I think that's how most people say it.

• 11:07Speaker 02

  Oh, I've always heard plonk. Okay.

• 11:10Josh Clark?

  I've heard both, but most of the people I've ever heard say plank, but I mean, I run in pretty lowbrow crowds.

• 11:16Speaker 02

  I think the probably the correct is plonk, but most people do say plank. You're right.

• 11:20Josh Clark?

  I like the way that you said it the first time, the plonk Einstein.

• 11:23Speaker 02

  No one says Einstein, though. Yeah, the plonk Einstein relation, which is the energy of each photon is equal to its frequency times plonk's constant. E equals HF.

• 11:39Josh Clark?

  Yeah. And all plonk's constant is, all it is, it's the smallest possible measurement of energy that anything can have on like the quantum level, right? And so Einstein was like, hey, I want to figure out how all this stuff kind of interacts because I know that photons interact with electrons. I'm just positive of it.

• 12:00Josh Clark?

  They were figuring, that's pretty good. They were figuring out, or he was figuring out, I think other people were at the same time, that when you have subatomic particles like an electron orbiting an atom, which if you go listen to our periodic table episode, I think we did a pretty decent explanation of how that, that, you know, that symbolism or that visualization of it is not very correct. But for all intents and purposes for this, let's say that these electrons orbit in different orbits around the atom. And when a photon hits it, that orbit, that electron goes up in energy. I think for like a hundred nanoseconds typically.

• 12:39Speaker 02

  Yeah.

• 12:39Josh Clark?

  And then it says, okay, I want to get back to my resting state. It's ground state and it goes back to its previous orbital. But when it does, it poops out a photon.

• 12:47Speaker 02

  You know what's funny?

• 12:48Josh Clark?

  What?

• 12:49Speaker 02

  As earlier, when I was going over there to my head, I said, poops out a photon.

• 12:52Josh Clark?

  Sure. I mean, you and I, we share a brain when it comes to toilet humor.

• 12:57Speaker 02

  Yeah, that's true. Yeah, that's exactly right. So an atom is going to absorb that energy and it can do that in a lot of ways, but let's just say in this case, it's like some, it gets heated up. You know, like literally heated up. Those electrons are going to jump around and get excited, but once they, that makes it unstable, but it wants to be stable. So when it goes back to that state, you're right, it poops out that photon. Einstein saw this. Called it spontaneous emission.

• 13:23Josh Clark?

  Yeah.

• 13:24Speaker 02

  And this happens all the time, all over the place in, in nature. These photons are getting pooped out all over the place. But Einstein was like, well, hey, if it happens all the time naturally. He theorized, maybe we can, we can stimulate it to do this. Maybe we can make this happen and control that emission.

• 13:42Josh Clark?

  Yeah, because here's the thing, right? Like you say, you have a photon that hits an atom and knocks an electron into the higher energy state, and then that electron poops out a photon. Well, that electron has just absorbed the photon.

• 13:55Speaker 02

  Right.

• 13:55Josh Clark?

  So another way of looking at it is the photon essentially goes into the electron and comes back out the other side, kind of. But there's only one photon ever. One gets absorbed, one's produced. What Einstein figured out is with stimulated emission, you can use a photon to create another photon without losing the first photon. And if you do that a bunch of times, buddy, you can have like, like you could make a basket with your shirt and fill it with photons if you do it right.

• 14:23Speaker 02

  Yeah, I mean, he, he realized that photons like to hang out with one another. So it doesn't take a lot to get them, you know, traveling in a direction and saying, hey buddy, come with me. And it creates this sort of, sort of like a snowball, like a cascading effect. Where if you can get them in an excited state and stimulate them and have them pick up other photons and have them all travel in the same direction, you're like halfway toward laser town.

• 14:54Josh Clark?

  Pretty much. You can see the outskirts of town and the light shooting up in the sky.

• 14:58Speaker 02

  Yeah, you can.

• 15:00Josh Clark?

  So, um, yeah, so that's stimulated emission. And the, the key here is you don't have to spend a photon to get a photon, right? You can excite the atom in other ways, as long as it's already in its excited state. When the photon comes along, it's going to produce another photon. Now, for the purposes of lasers, what's really, really important here is it is going to produce an exactly identical photon as the first one that passes by.

• 15:25Speaker 02

  Going in the same direction.

• 15:27Josh Clark?

  Traveling in the same direction and it's not, it's not going to interfere with the first one. So they're cohesive and they're collimated and they're exactly the same. They're monochromatic, which as we said before, those are the things you need for a laser. So Einstein figured out back in 1917, how to make a laser. And it was like, you guys figure it out. I'm going to think about some other stuff.

• 15:49Speaker 02

  Yeah. And if you say, well, wait a minute, I thought you said 1905. Like, it even took Ein- Einstein a little while to get there, you know?

• 15:56Josh Clark?

  That's right.

• 15:57Speaker 02

  Took a little while. So should we take a break?

• 16:00Josh Clark?

  Yeah, I feel like a break is imminent.

• 16:02Speaker 02

  We'll be right back with more Blazers.

• 16:18Josh Clark?

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• 19:40Speaker 02

  All right. So when we left, Einstein did some, some great work, kind of laying the groundwork, the theoretical foundation of a laser. And then he was like, guys, I like to think of things with my brain and say them out loud and write them on chalkboards.

• 19:55Josh Clark?

  Right.

• 19:56Speaker 02

  If you want to build this thing, fine. Maybe slide me some cash. But, uh, but I don't do that kind of work. So people did, though, that followed in his footsteps. And in the 1950s, there was a physicist named Charles Towns. He worked at Bell Labs. And who, he was doing research on microwaves, microwave radiation. And he was trying to, he didn't know it yet, but he was, he was halfway to laser town because he was trying to find ways to concentrate a beam of microwaves in this case.

• 20:29Josh Clark?

  What's nuts is this guy figured it out. He just basically tinkered around and made his own version of a laser, but rather than using light, he used microwave beams, right?

• 20:38Speaker 02

  Yeah, he built like a thing.

• 20:41Josh Clark?

  Yeah, he just, he used ammonia atoms. He put them in a sealed chamber and he got them to essentially emit microwave radiation that he was able to concentrate into a beam, right? So that cascading effect happened, just like we discussed before. And essentially, the only difference is it wasn't a light, it was a microwave beam. And to test it, he aimed it at the front pocket of a passing colleague Percy Spencer, who happened to have a chocolate bar in the front pocket of his shirt.

• 21:14Speaker 02

  We talked about this, I think.

• 21:15Josh Clark?

  And melted it.

• 21:16Speaker 02

  Yeah.

• 21:16Josh Clark?

  And Percy Spencer never forgave him because that was his favorite short sleeve, button down shirt.

• 21:21Speaker 02

  I think we talked about this. Did we do one of microwaves?

• 21:24Josh Clark?

  Yeah.

• 21:24Speaker 02

  Okay. Well, that would be exactly where we talked about it then, probably.

• 21:27Josh Clark?

  Yeah. And they weren't colleagues. I just made that part up, but that was a, that was for you, buddy.

• 21:32Speaker 02

  Oh, no, wait. There was a chocolate thing though. What, right?

• 21:35Josh Clark?

  Yeah, yeah, yeah. That happened, but separately. I think Percy Spencer was in the presence of some microwave generator and his chocolate bar melted and he went on to invent microwaves. This thing was totally different. It's just, it just brought Percy Spencer to mind.

• 21:48Speaker 02

  Yeah, I like it. So he literally called this a mazer, a microwave amplified stimulated emission of radiation. He teamed up with a guy, it was a colleague named Arthur Shallow, and he said, let me see if we can do the same thing with light and we'll call it an optical mazer. And everyone was like, buddy, it's right there in front of your face. Like, come on, just get there.

• 22:15Josh Clark?

  I think it was Theodore Mymon. I like to call him my man. Who actually came up with the the laser. Uh, he built the first functional laser in 1960.

• 22:28Speaker 02

  And came up with a name?

• 22:30Josh Clark?

  I think he did.

• 22:31Speaker 02

  Okay.

• 22:32Josh Clark?

  Up to this point, um, they were, uh, they were all theoretical. And my man was the first one to actually build one. And he used a ruby crystal, which, um, at the time, I think, had already been dismissed. People were like, you can't use that to to make a laser. And he's like, let me try again. And he did some more calculations. He's like, the ruby is actually going to be great. So he used a pink ruby crystal as what's called the gain medium.

• 22:58Speaker 02

  Yeah, that's like the material, lasing material that you would use.

• 23:02Josh Clark?

  Exactly. That's where the atoms that you get excited are all stored.

• 23:05Speaker 02

  Yeah, so he surrounded that crystal, uh, with a, um, with a flash. It was a coil shaped flashbulb. So that's, that's going to be the thing that, you know, the heat or whatever, or the light that stimulates the initial reactions.

• 23:19Josh Clark?

  The pump.

• 23:20Speaker 02

  Sure. And then the two ends of that crystal were painted reflective silver. So everything is sort of, um, kind of trapped in there together, encouraging all those photons to bounce around and get a little wild and create more photons and say, hey, you know, we're, we're doing something here, guys.

• 23:37Josh Clark?

  And all, yeah, all of these photons came out at 694 nanometers, which I guess is the precise wavelength of ruby red.

• 23:43Speaker 02

  Yeah, I guess so.

• 23:45Josh Clark?

  And he showed that like there, there, here's a laser. Check it out. Um, let me see your face, basically, I think, was how he showed it off.

• 23:52Speaker 02

  Right.

• 23:52Josh Clark?

  He would just wave it in people's faces.

• 23:54Speaker 02

  That's why he's my man.

• 23:57Josh Clark?

  So, um, that was it. I mean, that was the first laser that, and it was, I, I, you want to say like, it was as easy as that.

• 24:05Speaker 02

  Right.

• 24:05Josh Clark?

  Of course, that's not easy, but the principle of it is kind of, like you said, it's simple to understand, which is great. Like, we did one on the breathalyzer. And it is so ridiculously complicated.

• 24:16Speaker 02

  Yeah.

• 24:17Josh Clark?

  It's, it's more complicated than a laser by far.

• 24:20Speaker 02

  I, I hated that one.

• 24:22Josh Clark?

  I did too.

• 24:22Speaker 02

  That was a long, long time ago.

• 24:24Josh Clark?

  I remember we picked it, we started researching. I was like, wow.

• 24:27Speaker 02

  This sucks.

• 24:27Josh Clark?

  Wait, why am I not understanding this?

• 24:29Speaker 02

  Yeah.

• 24:29Josh Clark?

  It was just so complex. Let's never talk about it again.

• 24:33Speaker 02

  I think we just wanted the explanation to be like, blow in tube, tube smells beer.

• 24:38Josh Clark?

  Exactly. And just make a bunch of like drunk jokes.

• 24:41Speaker 02

  Exactly. All right, so that was the first laser. Like you said, he used that ruby to begin with, but there are all sorts of gain mediums. There can be liquids, there can be gases. And we should probably go over the five main types of laser now. Starting with, like if you've ever been for tattoo removal, or like had a skin cancer with laser removal. They're using a solid state laser in that case. And it's called solid state because they're using a solid crystal or a glass or something like that. Mix it up with a little, with a gain medium like, um, well, it's, they're all rare earth elements, like chromium or something like that. Neodymium, is that one?

• 25:25Josh Clark?

  Yeah, there's also ibiterum. Ibiterum, man, I even looked it up. Yuterbium.

• 25:34Speaker 02

  Yuterbium, I bet is right. That's, that's, that looks funny.

• 25:37Josh Clark?

  It is, it's great though. Y T T E R B I U M. Yuterbium, I got it. And all of those, basically they dope that, say like, you could still use ruby. But you would create like a ruby crystal that's doped with these impurities that you've selected based on their, say, like reflective properties or their phosphorescent properties. These things can generate some photons really efficiently. And they're going to generate them in exactly the wavelength that you want. That's a solid state laser. It follows in the tradition of that original my man's laser from 1960.

• 26:12Speaker 02

  You know, Emily knows not much about football, doesn't care, but there's always a few players that she knows of and it's always very funny. Patrick Mahomes is one of them. And every time she hears of him or anything, she just goes, "My homes."

• 26:28Josh Clark?

  Very nice.

• 26:29Speaker 02

  Sort of like, "My man."

• 26:30Josh Clark?

  Oh, no, I'm with you. That's a great way to say it. Guys, nice.

• 26:34Speaker 02

  Uh, one thing I want to point out though about these different types of lasers is all of them are, they use different types of lasers according to whatever application they want to use it for. So it's not just like, "Hey, these are cool. Let's use, let's use this crystal with this doping agent because we just think it sounds awesome." It's all highly specific to what you want to end up using it for.

• 26:56Josh Clark?

  Yeah, like even like tattoo removal, you said, which I'm in the process of I'm getting toward the end there, buddy.

• 27:02Speaker 02

  How's it looking? Pretty, pretty gone?

• 27:04Josh Clark?

  Pretty light. Yeah, it start. Yeah, I mean, you can still see it, especially if you walk up to it, but you could also miss it if you weren't looking for it. It's getting like that. Just like, wow, that guy's got mildew on his arm.

• 27:15Speaker 02

  I took the other tack, as you have seen recently, when we were on tour. I had a probably two inch by two inch tattoo that I covered with half of an arm sleeve.

• 27:24Josh Clark?

  I didn't see it. You haven't shown it to me.

• 27:26Speaker 02

  Oh, how was, was I always in long sleeves?

• 27:28Josh Clark?

  Yeah, and I forgot to ask. I actually thought about that when we were researching this. I was like, I haven't seen Chuck's new tattoo.

• 27:34Speaker 02

  Well, I'll, I'll take my shirt off in front of you soon.

• 27:37Josh Clark?

  Okay. But even with the tattoo removal ones, they have different types of solid state lasers. The, the, the game medium is different, right? There's one called the ND

• 27:52Josh Clark?

  YAG laser.

• 27:53Speaker 02

  Yeah.

• 27:54Josh Clark?

  That's a really common one. Neodymium doped yttrium. Yeah. Aluminum garnet. That's the, that's the gain medium. And that's for, I don't remember what that one's for. I think different color, like regular color tattoos, whereas like if it's green, you have to use a different kind of gain medium.

• 28:13Speaker 02

  Yeah.

• 28:13Josh Clark?

  Yeah. So it is extremely specific.

• 28:16Speaker 02

  All right. Well, can we move on to gas lasers?

• 28:19Josh Clark?

  I think it's time, yeah.

• 28:20Speaker 02

  So obviously they're going to use gases or gain medium. Could be a carbon dioxide laser, could be argon, could be krypton, if you're really into comic books. And these are different than solid state lasers, obviously.

• 28:35Speaker 02

  In solid state, the atoms are excited by a light source. In this case, it's an electrical current that's going to get them going.

• 28:42Josh Clark?

  Yeah, it gets them excited.

• 28:45Josh Clark?

  There's all sorts of stuff you can use with gas lasers, but probably one of the, the most famous one is using a carbon dioxide as the gain medium, and those things can get those photons going. You can weld with it. That's how, that's how powerful these lasers can be. You can weld metal with that stuff. And then at the same time, if you use a different gas, you might have an excimer laser. You can actually break the bonds that hold molecules together. You can alter cells. You can destroy tissue, but it, it uses UV light, so it doesn't produce heat. So that's how you can use that on someone's skin without burning them, but still say removing like a, squamous cell or something.

• 29:27Speaker 02

  Yeah. Or if you've ever heard of something being laser cut, then it's probably going to be a gas laser doing that business.

• 29:34Josh Clark?

  Yeah. Hopefully that you didn't hear about that from a squamous cell being removed.

• 29:38Speaker 02

  Right.

• 29:39Josh Clark?

  There's also fiber lasers. These are very special lasers. I don't know how they found this out, but scientists concluded that the, um, the cloaks usually, or the textiles found with bog bodies have some sort of magical properties that if you use them as a gain medium, they make really great lasers, hence fiber lasers.

• 30:00Speaker 02

  Right. But in this case, they're used in conjunction with a fiber optic cable. So these are obviously have long been used in telecommunications and stuff like that. And because they are used in conjunction with an actual cable, they're very, very efficient. So they convert more than 50% of the electricity that's input into light. But that ND

• 30:26Speaker 02

  YAG laser has about a 3% efficiency rate.

• 30:29Josh Clark?

  Yeah, that's pretty efficient. Um, that's another way that lasers are part of your everyday life. The, if you have fiber internet, like you have a laser on one end that your ISP is using to send,

• 30:44Josh Clark?

  communications or encoded information along a fiber optic cable. And your modem is basically a laser receiver that translates it into whatever your router needs to explain it to you.

• 30:56Speaker 02

  Yeah, that man, that uh, breaks my brain like vinyl records does, you know?

• 31:01Josh Clark?

  Yeah, it's pretty cool though. And that's the thing. So it's just like it when radio, with radio waves, we figured out how to encode information in radio waves. We figured out how to do that with light. It's just lasers are way more efficient. They can travel way longer than radio waves can. And apparently they're starting to look into this to, to transmit information between the earth and the moon.

• 31:25Speaker 02

  Oh, boy.

• 31:26Josh Clark?

  So you'll just be able to, you'll have basically not even fiber optic internet. You'll have laser internet on the moon.

• 31:34Speaker 02

  Wow.

• 31:35Josh Clark?

  I think that's wild, too.

• 31:37Speaker 02

  Yeah.

• 31:37Josh Clark?

  Uh, what about liquid lasers or dye lasers? I should probably say, because you played that so straight. My explanation of what the gain medium is for fiber lasers, that's, I just made that up, everybody.

• 31:51Speaker 02

  Oh, I fall victim again.

• 31:53Josh Clark?

  Did you, you thought that they used the cloaks from bog bodies for that?

• 31:57Speaker 02

  Man, I don't, all of this stuff is so brain breaking, nothing, nothing would, you could say human feces and I'd be like, yeah, of course.

• 32:04Josh Clark?

  That'd be, man, that'd be gross, but I'll bet you could. I think you could use anything with atoms that's excitable to potentially make a laser.

• 32:12Speaker 02

  You, you've become such a good straight person that it's just hard to tell anymore.

• 32:16Josh Clark?

  It's hard to tell with you, too.

• 32:18Speaker 02

  Hey, thanks.

• 32:18Josh Clark?

  Yeah, thank you.

• 32:20Speaker 02

  Uh, liquid lasers or dye lasers, these are sort of brain breaking, too. They use organic dyes as the gain medium, which is kind of crazy to think about, but each dye like, uh, will produce a different laser light. Because they're gonna have, you know, because it's a color, like a different wavelength.

• 32:35Josh Clark?

  Right.

• 32:35Speaker 02

  And these are really cool because you can actually tune them to a very, you can manipulate them and tune them within a very specific range for specific uses.

• 32:44Josh Clark?

  Yeah, so one laser can be used for all sorts of different things, which is, I'm sure, quite cost efficient.

• 32:50Speaker 02

  Yeah.

• 32:51Josh Clark?

  I think that's one of the downsides of solid state lasers is it's like one thing you can do with one laser.

• 32:56Speaker 02

  Yeah.

• 32:57Josh Clark?

  Although it'd be cool if like, it's just a cartridge you can pop out and put in a new, a new crystal.

• 33:02Speaker 02

  Yeah.

• 33:02Josh Clark?

  That'd be sweet.

• 33:03Speaker 02

  They should work on that.

• 33:05Josh Clark?

  They have to be, you know, like the cost of lasers have come down tremendously. Uh, I'm sure we'll eventually get there.

• 33:12Speaker 02

  Yeah, just ask my cat. My cat's with an S.

• 33:16Josh Clark?

  Well, let's talk about that. We're kind of at that point. Do you play with your cats with laser, um, pointers?

• 33:21Speaker 02

  No, I have, but I, they always get lost because they're always small.

• 33:26Josh Clark?

  Oh, gotcha, gotcha. Well, that is actually a kind of laser. That's why they call them laser pointers. They're the weakest laser.

• 33:33Speaker 02

  Yeah.

• 33:34Josh Clark?

  But they use diodes, which are two different materials that when you put them together with a place where they interface, creates an electron exchange and hence a flow of electrons and that creates electricity. So that's what these things are powered by. This is the, the way that the, um, the light photons get made from the excited atoms. And they're super cheap. They're not very powerful and that means that over a fairly short distance, I think like hundreds of meters, they basically, they're not a tiny point any longer.

• 34:05Speaker 02

  Yeah.

• 34:05Josh Clark?

  And I was looking into this because when I hear laser pointers, I think of jerks like trying to shine it in the light of an airline pilot.

• 34:12Speaker 02

  Oh, sure.

• 34:13Josh Clark?

  That's a real problem, actually. I think it happens a couple thousand times a year in the US alone.

• 34:17Speaker 02

  Yeah, concerts too. People do that stuff.

• 34:19Josh Clark?

  Sure. The reason you're not supposed to do that with airline pilots is because by the time it reaches the cockpit, it is spread out so much that it's just, it's like a huge ball of light.

• 34:30Speaker 02

  Yeah.

• 34:30Josh Clark?

  That is so bright in the cockpit that they can't even see the instruments anymore.

• 34:34Speaker 02

  Yeah.

• 34:35Josh Clark?

  So it's not like you're just putting like a little dot on somebody's cheek. You are blinding everybody in the cockpit right then. So it's a huge problem that you really should not do.

• 34:44Speaker 02

  Yeah. And also what's funny about messing with someone doing a very important, dangerous job where hundreds and hundreds of lives are at stake?

• 34:52Josh Clark?

  Yeah.

• 34:53Speaker 02

  Let's mess with that person.

• 34:54Josh Clark?

  Yes. And I think everyone's parents should sit them down and say,

• 34:58Speaker 02

  Yeah.

• 34:58Josh Clark?

  "Let's talk about laser pointers because you probably aren't grasping what a problem this is."

• 35:03Speaker 02

  Agreed. Uh, well, that's, that's a weak one. Those diode lasers or semiconductor lasers. But, um, since the very beginning, uh, science has tried to make the like more powerful lasers.

• 35:14Josh Clark?

  Mm hmm.

• 35:15Speaker 02

  Uh, and they have done a pretty great job at it. We'll go over some of these, but, um, you measure in, uh, a laser by how quickly that laser is emitting the energy. So it's joules of energy emitted per second.

• 35:28Josh Clark?

  Right.

• 35:28Speaker 02

  They measure that in watts. And they figured out pretty early on that a continuous beam of light emits a constant amount of energy over time. So they were like, hey, I bet we can make these even more powerful if we cut that off very quickly, over and over and over, and admit pulses of energy, because it builds up and it just gets stronger and stronger. And they tried it out, and it really worked.

• 35:54Josh Clark?

  Yeah, pulsed lasers, right? Because like you said, a traditional laser, it's the same amount of energy the whole time the beam is on. The pulsed laser, it's kind of like stopping up the beam of light, so that it just, the energy builds up behind it, and then you open it up again. And when you release it, it's this ultra-concentrated beam of energy. And it's mind-boggling how fast this happens. So fast that your puny brain just sees it as one constant beam of light.

• 36:23Speaker 02

  Yeah.

• 36:24Josh Clark?

  We don't have the technology to slow it down enough, I don't think, to see the pulsing, because we're talking billions, trillions, quadrillions, quintillions of a second, how frequently those, the thing is pulsing.

• 36:38Speaker 02

  Yeah, it's incredible. I think they first demonstrated that in 1961 with that Ruby laser. And I think they ended up with 100 nanosecond bursts in 1961, which is pretty impressive.

• 36:50Josh Clark?

  Yeah, for sure. Because a nanosecond is a billionth of a second.

• 36:53Speaker 02

  Yeah. So in 1961, they were able to get that first laser by pulsing it up to 1,000 times more powerful than my man's device.

• 37:03Josh Clark?

  Yeah, this was a year after he built that first laser, right?

• 37:07Speaker 02

  Yeah.

• 37:08Josh Clark?

  So I think that was, what'd you say, 100 nanosecond bursts? I saw that with the tech that they're using now, nanosecond pulses are called giant pulses.

• 37:17Speaker 02

  Yeah.

• 37:18Josh Clark?

  Seriously, that's what they consider them.

• 37:20Speaker 02

  Yeah, and those are quintillions of a second, which is hard to even wrap your head around.

• 37:24Josh Clark?

  For sure, right? So these things, these pulses are just like, that's, it also, Chuck, I think goes to show you how quickly energy builds up in the chamber where that, where the beam is released from, that it's, it's like creating a thousand times, or 10,000 times, or however many times stronger beam, just from backing it up in like, one quintillionth of a second.

• 37:49Speaker 02

  Yeah.

• 37:50Josh Clark?

  Sure. You want to take a break?

• 37:53Speaker 02

  Yeah, let's take a break, and let's talk about just sort of real-world uses and what's going on out there.

• 37:57Josh Clark?

  Okay.

• 38:12Josh Clark?

  Buy smart, drive for less and trade for more. That's Toyota affordability. And it all starts with a great deal on a truck from your local Toyota dealer.

• 38:21Speaker 02

  That's right. Make a smart buy on the off-road ready Tacoma or half-ton Tundra, two of Toyota's most capable and longest-lasting trucks. Built with the strength for the tough jobs, the tech to power your next big adventure, and the rugged style for everything in between.

• 38:34Josh Clark?

  Or discover Toyota's off-road lineup, including the iconic 4Runner and Land Cruiser, designed to go beyond the everyday. And with Toyota's proven reputation for quality and reliability, plus hybrid power on many models, you can get more for every mile and drive for less along the way.

• 38:50Speaker 02

  That's right. And long after you leave the lot, your Toyota keeps delivering with great resale value. So you could trade in for more when you're ready for your next Toyota. From a great deal today to a great value tomorrow, a Toyota is right for you. Shop toyota.com for deals and details, or stop by your local Toyota dealer today. Toyota, let's go places.

• 39:14Josh Clark?

  You know, eating is a huge part of our lives. It fuels us, it brings us together, and it's one of life's great pleasures. But once a meal's over, we don't think much about what happens next, unless something starts to feel off. Because what we eat and how our bodies respond to it is complicated.

• 39:30Speaker 02

  That's right. From the very first bite, food kicks off a chain reaction, signals moving between the gut, the brain, and the immune system. The constant back and forth we can't see and often don't fully understand. So we want to introduce to you Eating Interrupted, a new podcast from iHeart Ruby Studio. It's hosted by longtime journalist and Crohn's patient Cynthia McFadden. Eating Interrupted explores everything from food allergies and intolerance, and why they seem to be on the rise, to how digestion changes as we age, and what it's really like to live with a chronic GI condition.

• 39:58Josh Clark?

  Through personal stories and expert insight, listen in to unpack what it means when your body doesn't always respond to food the way you expect, and what science is now revealing about why. Listen to Eating Interrupted on the iHeart app, Apple Podcasts, or wherever you get your podcasts.

• 40:17Speaker 03

  First thought is like, wow, how are we going to do all this?

• 40:20Josh Clark?

  Hey, this is Josh and Chuck from Stuff You Should Know.

• 40:23Speaker 02

  That's Alan Goya, planning engineer at AT&T, and he's talking about Intuit Dome, home of the Los Angeles Clippers, where every seat, screen, phone, and transaction is connected with AT&T fiber and 5G, redefining the fan's experience. And Alan's master plan made it all possible.

• 40:39Speaker 03

  It was going to rival anything that was already built. And that takes quite a bit of people and different teams to all be on the same page.

• 40:47Josh Clark?

  That includes field services manager Drexel Jones. His team made sure it all came together and held up on game day.

• 40:53Speaker 04

  Through what Alan's whole crew designed, we connected the event visitors to the world.

• 40:58Speaker 02

  And after years of hard work and collaboration, it was opening night.

• 41:02Speaker 04

  To actually see the whole stadium light up and data is flowing is a beautiful thing.

• 41:06Speaker 03

  What the fans experience is incredible. It gave me a lot of pride.

• 41:10Josh Clark?

  AT&T, connecting fans to what they love.

• 41:13Speaker 05

  Connecting changes everything. AT&T.

• 41:27Josh Clark?

  So Chuck, there's some lasers that are just super powerful that are being built right now. Of course physicists are like, let's see how powerful we can make something. There's one at the University of Michigan called ZEEUS, Zeta-Watt Equivalent Ultra Short Pulse Laser System. And then there's one in the UK that's being built called the Vulcan Laser.

• 41:48Speaker 02

  Yeah, and these, I mean, the one in the UK has a power of 500 million 40-watt light bulbs.

• 41:56Josh Clark?

  Well, 40 watt.

• 41:58Speaker 02

  Well, yeah, that's true. That's not much. And the ZEEUS can generate a pulse of light that's 25 quintillions of a second long. And so...

• 42:08Josh Clark?

  But wait, how much energy does it release?

• 42:11Speaker 02

  Three petawatts, baby, which is 100 times the total electrical output of the entire world in one quick burst.

• 42:21Josh Clark?

  So these things are, they're like, um, they're so powerful and energetic that what they're, one of the main things they're going to be used for is to study what it's like inside a black hole or a star or something like that. That's, that's like what they're able to recreate and see what happens when it bounces off of an apple or something like that. What happens when you bounce a black hole off of an apple?

• 42:44Speaker 02

  Yeah, that's, that's basically why they're trying to create these this powerful. It's not so they can blow up the death star, even though that's a good case use. Uh, it's, it's so, yeah, so they can recreate like the energy and the inside of a star and find out the mysteries of the universe, basically.

• 43:02Josh Clark?

  Exactly. There's another thing you can use really, really powerful lasers for, and that's nuclear fusion. And we did a whole episode on nuclear fusion, I think in 2019. That was one of my favorites of all time. And it's this whole thing, that's the, the promise of basically free unlimited energy that you can power anything with, with almost, like what you're getting out is way more than what you're putting in. And, um, it's essentially where you take light nuclei and fuse them together to create a heavy nuclei and a lot of energy is released. It's just, we haven't quite figured it out. Well, you need like plasma concentrations. These are plasma lasers. And apparently in 2022 at

• 43:46Josh Clark?

  the Lawrence Livermore Lab, they used 192 of these lasers to essentially create the world's first nuclear fusion reaction that produced more energy than was put in. There was a net gain.

• 44:01Speaker 02

  Yeah. Uh, they called that the, the Wright Brothers moment as far as lasers go.

• 44:06Josh Clark?

  Sure.

• 44:06Speaker 02

  Because you got a net gain for the first time. They focused those lasers at a capsule the size of a peppercorn. And that did it. And I bet that was a great day in that lab.

• 44:15Josh Clark?

  I'm sure. I mean, once we get to nuclear fusion, that's. That's gonna change absolutely everything.

• 44:22Speaker 02

  Yeah, for sure.

• 44:24Josh Clark?

  So you can use it to for nuclear fusion. You can use really great lasers to recreate different crazy exotic aspects of the universe. There's also way more pedestrian uses for lasers. Like we said, barcodes, fiber optic communication. But there's like, when you start to look around, lasers are everywhere. Essentially, anything you can bounce light off of, or that you can, that will absorb light, you can use a laser for for some application or other.

• 44:56Speaker 02

  Yeah, for sure. They're all over the medical industry for in all kinds of ways. I think pretty early on, they were like, hey, these, using a laser to cut into the human body is way better than a scalpel.

• 45:08Josh Clark?

  Sure.

• 45:09Speaker 02

  It's way more precise. There's less damage on the tissue. It self kind of self cauterizes as it goes. So it's going to be sterilizing the tissue that surrounds it. It's going to be less blood loss. You're going to heal up quicker. So that's there. I mean, scalpels are still around, but they, you know, lasers are the way to go.

• 45:26Josh Clark?

  I saw that there's a brain tumor laser procedure that uses a five millimeter hole in the skull and you get discharged the next day. That's how accurate and amazing these things are. Plus also, it's way easier to attach to a robot than to give a robot a scalpel to use.

• 45:44Speaker 02

  Yeah, I hate to bring it up again, but that was just on an episode of the pit. That exact case use that you just mentioned.

• 45:50Josh Clark?

  The laser tumor?

• 45:52Speaker 02

  Yeah, the tiny hole in the skull.

• 45:54Josh Clark?

  We started watching it. I gave it another try. You mean, I did. And it's it is pretty good and engrossing.

• 46:00Speaker 02

  Yeah, and gross.

• 46:03Josh Clark?

  It is.

• 46:04Speaker 02

  Yeah. And I figured out too, watching last night, I kind of forgot the reason why I was saying there's so much of like, of Noah Wiley, over explaining everything to all the younger doctors and residences, because it's a teaching hospital.

• 46:16Josh Clark?

  Yeah, there you go.

• 46:18Speaker 02

  Which is a great vehicle to explain whatever the heck is going on to the viewer at home, you know?

• 46:23Josh Clark?

  Yep, for sure.

• 46:24Speaker 02

  All right, so back to medicals, since we're talking about the pit. If you ever had an endoscope, that's, you know, when they put a long flexible tube down your throat a lot of times, or up your nose, or who knows what holes they can put them into these days.

• 46:39Josh Clark?

  It depends. If it's a rubber hose, you know where that goes.

• 46:42Speaker 02

  That's right, Vinnie. Essentially, you can access these tough-to-reach areas with these tiny little tubes. And in this case, you can have a laser attached to it and send it in there to shrink a tumor like you were talking about.

• 46:56Josh Clark?

  Right. And then you can also use them to do things like destroy the epidermis and then heat up the dermis underneath to get rid of like spots or something like that for all sorts of aesthetic dermatological applications.

• 47:10Speaker 02

  Yeah, cosmetic stuff?

• 47:11Josh Clark?

  Yep. Tattoo removal, that kind of thing.

• 47:14Speaker 02

  Lasik, what about Lasik?

• 47:16Josh Clark?

  Yeah, Lasik is a big one. That has become vastly improved as lasers and robots have improved. I think it was first started, first became approved in the US in 1999. And since then, it's gotten really good. I think 90% of people who get Lasik have between 2020 and 2040 vision afterward. And it's like the pool of people who are candidates for it are, is pretty wide. It's not like, yeah, if you can, if you need just like those magnifying readers that you buy at the pharmacy.

• 47:50Speaker 02

  Right.

• 47:50Josh Clark?

  You're gonna, Lasik's gonna benefit. You know, you can have like pretty bad myopia and still benefit from it.

• 47:57Speaker 02

  Yeah, in this case, they use the laser to reshape the cornea. Didn't you debate Lasik at one point?

• 48:04Josh Clark?

  Yeah, I'm, I'm still thinking about it, but my vision, we're, we're basically at an age where your vision changes fairly rapidly and you want it to stabilize or else you would get Lasik once and then you'd end up needing glasses when your vision degrades again.

• 48:20Speaker 02

  I think Emily has been debating it too, a little bit lately. I'm not sure why.

• 48:24Josh Clark?

  I looked into it and I was convinced like this is, this is pretty safe and effective and, and yeah, I would do it. I'm just not there yet.

• 48:31Speaker 02

  I feel like when I've seen you lately, you're having trouble with the contact lens.

• 48:36Josh Clark?

  It, because it's been wintertime and dry and it makes them like, it makes it easier for it to like fold over or something like that. Pop out. Sucks.

• 48:45Speaker 02

  Sorry.

• 48:46Josh Clark?

  There's also weapons. Of course, you can use lasers for weapons. Apparently, the Army, the Navy, and the Air Force are developing laser weapons to different, different levels of success. But they're definitely working on them, not to necessarily like, you know, mow down troops, but to say, blow up a drone or something like that.

• 49:07Speaker 02

  Yeah, they're called directed energy systems. Some of them attach to like a turret on a ship. Those seem to work pretty well for like you said, like taking down a drone or something like that. They have others. I think the Army has one. A 50 kilowatt that's on an armored fighting vehicle, but that hasn't done so well because, you know, for a laser weapon to be pretty effective, it has to be super tightly focused and pretty locked down. And they're like, hey, we're driving this thing around. It's not very accurate.

• 49:41Josh Clark?

  Right. And that's the Stryker armored fighting vehicle, Stryker with a Y.

• 49:46Speaker 02

  Yeah.

• 49:47Josh Clark?

  It's like they look to G.I. Joe stuff to come up with names for it.

• 49:51Speaker 02

  For sure.

• 49:52Josh Clark?

  There's also, this one's pretty sweet, too. It's laser cooling. And there's also so many different applications, like you can, you can track soil moisture from space to see how bad a drought is. You can track how badly ice is receding in the, in the polar areas. You can, you can do everything with, with lasers. They're really great. In case that hasn't gotten across so far. But this one to me is just amazingly cool.

• 50:19Speaker 02

  Yeah, no pun intended, laser cooling. What they're doing is basically kind of freezing an atom or a molecule in place. It's also called a particle trap. And it's, it's the same sort of physics of stimulated emission, but kind of in reverse.

• 50:37Josh Clark?

  Yeah, when a, when a, an atom poops out a photon, that kind of pushes it in the opposite direction that the photon's traveling. They figured out that they can use lasers to keep, to basically balance that out. So these things are still producing photons, they're still doing their thing, they're, they're in energetic states and oscillating and doing all sorts of stuff like they're supposed to, but they're just not moving around in space while they're doing it.

• 51:04Speaker 02

  Yeah.

• 51:04Josh Clark?

  So they're essentially, they're just, it's like a tractor beam, holding it where you want it.

• 51:11Speaker 02

  Yeah, it just slows it down such that it's basically stopped.

• 51:15Josh Clark?

  Yeah, but it's still doing its thing, it's just not moving around while it's doing it, right? So now that you have an atom trapped, um, you can do something like, like this is the future of atomic clocks. You can measure the oscillations, oscillations of that one specific atom so precisely that atomic clocks are about to be just ridiculously, um, more reliable than the atomic clocks today, which I think we can all agree are pretty reliable. So that's a huge groundbreaking use for that.

• 51:45Speaker 02

  Yeah, for sure. I mean, it's easier to study something that's sitting still.

• 51:49Josh Clark?

  Exactly.

• 51:50Speaker 02

  Yeah.

• 51:51Josh Clark?

  Um, yeah, now that I think about it, that basically overcomes Heisenberg's uncertainty principle, where you can't measure something and know where it is at the exact same time. Apparently Heisenberg didn't think of lasers.

• 52:03Speaker 02

  That's the nerdiest sentence you've ever said. Oh, come to think of it.

• 52:09Josh Clark?

  You got anything else?

• 52:10Speaker 02

  I got nothing else. You know, there's obviously a lot more, but I think that was a good, good old fashioned overview of lasers.

• 52:16Josh Clark?

  Agreed, man. Uh, and since Chuck said old fashioned, he just accidentally triggered listener mail.

• 52:25Speaker 02

  Uh, I'm gonna call this an answer to a question. I love it when we put out a question, we get answered. We were talking about, uh, color psychology and I wondered, because I have a African-American church around the corner from me.

• 52:37Josh Clark?

  Oh, yeah, the purple.

• 52:38Speaker 02

  Actually, yeah, purple. And we heard from a listener, "Hey, guys, I'm writing to share some insight regarding the morning colors at the nearby church. While traditions can vary between African-American churches, I hope the following information is helpful. In the 21st century African-American traditions, it is common for individuals attending a funeral to wear the deceased person's favorite color," which is what I thought might be happening.

• 52:59Josh Clark?

  Oh, neat.

• 53:00Speaker 02

  "In some cases, all in attendance are encouraged to do so, while in others, it's reserved for family members. Regarding the use of purple specifically, this color is typically associated with royalty in Jesus Christ. If you consistently see purple at the church, it may signify recognition of the deceased returning to God, or maybe just the person's favorite color. So I truly appreciate your program. It allows me to stay present and provides a welcome escape from the daily news cycle. I look forward to becoming just a tad bit smarter as I continue to be an enthusiastic listener. Corrigely, Theresa." What a lovely email.

• 53:35Josh Clark?

  That was a great email, Theresa. Thank you very much for it. And now your mystery's solved, Chuck.

• 53:41Speaker 02

  That's right.

• 53:41Josh Clark?

  We love emails that solve mysteries that we were wondering about. So if you've got a solution to one of our mysteries, we would love to hear it. You can also write in for any other reason. Just send your email to [email protected].

• 53:59Speaker 00

  Stuff You Should Know is a production of iHeartRadio. For more podcasts, iHeartRadio, visit the iHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows.

• 54:15Josh Clark?

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• 55:46Speaker 00

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