Listener Questions #42

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26:55Google is a trademark of Google LLC. Sequences shortened and simulated. Hello, hello. This is Malcolm Glabal from Smart Talks with IBM. Today we're diving into a fascinating conversation with Stefano Pallard, head of fan development for Scuderia Ferrari HP. Your pronunciation is strongly American. It's more Scuderia Ferrari. I'm still working on rolling my R's. But what I was able to learn from Stefano was the importance of engaging the Tifosi, the Ferrari superfans in the digital age. Ferrari fans and superfans want to be part of something, want to belong to something. So they want to be part of a community and ultimately they want to be part of a winning team.

27:40You've got Ferrari, which has a long history, design history. And now you're interacting in a kind of digital space. I'm curious how you balance those two traditions. When it comes to fan engagement, It's really digital technology and digital channels are being able to create a deeper connection with our fans. To learn more about how Ferrari and IBM are using technology to build deeper connections with fans, visit ibm.com slash Ferrari.

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28:44Also called atopic dermatitis that is not well controlled with prescription therapies used on the skin or topicals or who cannot use topical therapies. EBCLIS can be used with or without topical corticosteroids. Don't use if you're allergic to EBCLIS. Allergic reactions can occur that can be severe. Eye problems can occur. Tell your doctor if you have new or worsening eye problems. You should not receive a live vaccine when treated with EBCLIS. Before starting EBCLIS, tell your doctor if you have a parasitic infection. Ask your doctor about EBCLIS and visit ebglis.lily.com or call 1-800-LILY-RX or 1-800-545-5979.

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29:54All right, we are back and we are done playing games and adjudicating disputes between the Wienersmiths. We are ready to get down to some serious science. Yes, we have gotten rid of Zach and it is just you and me again. Woo! And so let's bring on Mark, a veterinarian in Daytona Beach, Florida, to hear what Mark wants to know about. Hi, Daniel and Kelly. This is Mark. I'm a veterinarian in Daytona Beach, Florida. We had a cold snap the other night, which got me thinking about temperature. As I understand it, temperature's an emergent property of the energy of a group of particles, and there's an absolute lowest temperature that can be reached.

30:33My question is, does the universe have an absolute highest temperature allowed? And if so, what is it and what are the parameters that determine it? Thanks for taking my question. Keep up the great podcast. And by the way, Kelly, remind Daniel that without biology, there would be no physicists. Daniel, without biology, there would be no physics. Oh, there would be no physicists. That's what it said. That's true. Without biology, there would be no physicists. You're welcome. That's right. I'm very grateful to biology for laying the foundation on which physics can reach towards true understanding.

31:09But thank you also to Mark for asking such deep, such tough questions. Oh, my gosh. What is temperature anyway? Such a fascinating topic. Yeah. All right. So let's let's jump in. What is temperature? So before we can understand whether there is a maximum temperature, we have to understand what are we talking about anyway? Temperature turns out to be a really complicated topic. It feels really simple until you start to think about exactly what it means. And it turns out that temperature is something that is defined in several different ways, especially in different regimes. It's not something fundamental to the universe like momentum or location.

31:49It's more like an emergent property that describes something about our experience. And as we try to extend it in different directions, we end up trying to do that in different, sometimes contradictory ways. So let's start with the easy definition of temperature. This is what we call sort of the operational definition of temperature, which is like some things feel hotter, some things feel colder. Can we measure that? So we invent stuff like a thermometer, right, where you have mercury in a column or you have a wire whose resistance changes. and we define temperature according to that. We say the temperature is whatever the thermometer reads.

32:28It's 50, it's 70, it's 42 or whatever. And it seems to scale with our intuitive experience of temperature. And so we like that. And we say, that's what temperature is. But what is it really measuring? It's just the rate at which it makes mercury expand? Or, yeah, what are we really measuring when we say we're measuring that kind of temperature? So here we're relying on some chemical property of a gas or of mercury or of a wire and how that changes as things get hotter and colder. And then it's a bit of a circular definition, right? You hear me saying hotter and colder. And then we define temperature to be like zero when the thermometer reads zero and 100 when the thermometer reads 100.

33:10And so it's just sort of an operational definition because we are linking temperature, the whole concept of it, to whatever the thermometer reads without wetting ourselves to like the underlying details of how that is happening. And you can even get like a mercury thermometer and alcohol thermometer who are both calibrated to agree at zero and 100, disagreeing in between that because they expand at different rates or they respond differently. And so you just have to like pick one and define it. and say, my mercury thermometer is what defines the temperature. It's not very satisfying, but it's actually the most intuitive and useful definition of temperature.

33:49Well, I'd argue what you really want when you're measuring temperature is to understand biology better in some way. And so that works for me. Are we done? We are not done. There's also a definition of temperature that comes from thermodynamics, right? And this essentially asks, like, what direction does heat flow? because we know that things move from hot to cold, right? You put a hot thing next to a cold thing, the cold thing is gonna get hotter and the hot thing is gonna get colder. How does that work? How can you convert that flow into energy? That's what thermodynamics is all about. And that's a new definition of temperature, right?

34:25In thermodynamics, the ratio of two temperatures equals the ratio of heat exchanged by those reservoirs. So that's what temperature means in thermodynamics. It's about the rate at which heat moves. And so it's not linked to mercury or to alcohol or to resistance. No, but you wouldn't say that you're transferring the heat from your mouth into the thermometer to make the mercury move. And so don't these definitions sort of overlap in some way? Oh, absolutely. These things definitely overlap in lots of ways. They often give similar answers, but it's a different story about what temperature is. One is saying it's just the number on the thermometer.

35:04The other is saying, no, it's the heat that's flowing. And then we have even more views. Like the physicist would be like, yeah, but what's happening underneath, right? And this is what people commonly think about, like the kinetic theory of temperature. It's like molecules and they're jiggling and they're moving. The idea that hot gases have molecules that are moving faster or hot solids have molecules that are jiggling more. It's about the microscopic motion turning into this emergent experience of temperature. I guess I had always imagined that the microscopic motion is like, what is changing the temperature of the colder thing that's near a hot thing?

35:43And then you measure it with a thermometer. And to me, these don't feel like different definitions. They just feel like you're looking at it at a different level. Like you're digging one more Y down. Because the thermometer one doesn't even seem like a definition. It's just like, it's a way you measure a thing. For the most part, these things really do agree with each other. And in everyday life, around normal temperatures, they all give similar explanations. The thing you measure on the thermometer and the kinetic theory about jiggling and the motion of heat flow, they all agree. But these things break down sometimes near the extremes.

36:21Like when you try to go to absolute zero, then kinetic theory breaks down because you can't bring particles all the way to rest. Whereas thermodynamic theory says you can get to absolute zero. So it's really at the extremes, which is, I think, the places where you really illuminate what something means that things break down. And so it's all about what theory are we using in order to extrapolate to really hot or to really cold regimes? All right. And Mark is an extreme sort of person, and that is what his question was about. Actually, there's one more view of temperature, which is a sort of statistical theory.

36:57and this is more about entropy. And it tells us that, like, for example, a cold system is one where adding energy opens up many new arrangements. And a hot system, one with high temperature, gains few new arrangements per unit of energy. So it defines temperature as this relationship between entropy and energy. And you might say, Kelly, well, that just tells us why heat flows from a hot system to a cold system. And you're right. But this is a weird definition of temperature because in some systems you can even get like negative temperatures, right? Because you get systems with really weird setups between the entropy and the energy.

37:33And so you can get negative. So thermodynamics says you can get to zero. Kinetic theory says you can't get to zero. Statistical theory says you can get even negative. So it's at the extremes that these things really disagree. Okay. And they disagree a lot. And so I'm excited because at the end of this episode, you're going to tell us which understanding of temperature is correct. And so this is exciting. We're not, actually. But we are going to try to extrapolate to the extreme that Mark wants, which is to think about the maximum heat of the universe. And so I think for this exploration, I think kinetic theory is the right way to go.

38:09Kinetic theory relies on quantum mechanics. It thinks about everything as particles in motion. You have charged particles emitting light. You have black body radiation. Everything is built together with these bonds. It ignores gravity, right, which is very, very weak. And so it thinks about an object as a bunch of microscopic particles that are jiggling and moving and how they emit energy. And from that point of view, you know, how hot can things get is a fun question. Yeah, I'm having fun already. So how hot can things get, Daniel? What's the hottest thing we know about? Yeah, so the universe is filled with hot stuff.

38:45Let's calibrate, you know, and we'll use the Celsius scale. So ice, of course, at zero C. Normal human bodies at 37. The hottest fever ever measured, here's a biology take for you, is 46.5 C, right? Not good. The hottest temperature ever recorded on Earth is 71 C. Wow. Wow. All right. So that gets pretty warm. The average daytime temperature on the moon is 100 C. So, like, yes, pretty toasty. It's not going to be fun to live on the moon. The hottest temperature survived by any living thing, a tardigrade, is 151 C. Those guys are tough. They're tough. I'm going to go ahead and be a wet blanket and say that every time I've looked into a claim about tardigrades, they can survive the extreme thing, but not like forever.

39:34Right. So it probably lived at 151 C for like, I don't know, 30 seconds before it died. But that's 30 seconds longer than I would. So way to go, tardigrades. All right. So up next is the surface of Venus at 460 C, not a place I'd go on vacation. The brakes on a Formula One racing car get to about 750 C. Oh, wow. Wow. Yeah, holy cow. A typical wood-burning fire is about 1 ,000 C. Okay. Lava that you can visit in Hawaii, though don't dip your feet into it, is 1 ,200 C. Wow, okay. The surface of the sun gets up to about 5 ,500. Wow, okay. The core of the Earth is at 6 ,000, so we're getting really, really hot here.

40:16Yeah. But even in our atmosphere, we have hotter things, like a lightning bolt is very briefly 28 ,000 Kelvin. Wow. Which is very close to 28 ,000 C. That is, like, really even more amazing that people ever survive. Holy cow. Okay. The corona of the sun is much hotter than the actual surface of the sun. It has plasma at around a million C. Wow. I wouldn't have guessed the corona was going to be harder than the surface. Yeah, really fascinating solar physics there. Now go to like the core of a nuclear bomb exploding and you have a range of like 10 to 50 million C. Wow. Gas coming out of a supernova is like 50 million C.

40:57Oh my gosh. Okay. And now here's the one that surprises a lot of folks, which is the intercluster medium, right? So like we have solar system is part of the galaxy. Galaxies come together in clusters. and there's tendrils of mass between the galaxies. Not all the atoms in the universe are in galaxies. And then there's stuff between the galaxies inside the cluster. It comes out to like 10 % of the mass of the cluster. And it's really, really hot. It's like 100 million C. I would have guessed it would be really cold out there. Well, it's weird because if I dropped you out there in space, you would freeze.

41:33But you'd be surrounded by a plasma at 100 million C. and the reason is that it's very hot right we're relying here on the kinetic theory of temperature it's really hot the particles are moving really really fast right but there's not a lot of energy there and so you go out there you would radiate away your energy you know a very very dilute gas that's very very hot you're going to cool down when you're in that gas because it's not delivering a lot of heat to you see how the energy flow versus the kinetic theory can give different answers Yeah. Wait. Okay. But my mind's been blown. Okay. But so if you freeze out there, doesn't that tell you which of the definitions is like the one that is meaningful?

42:21From a biological point of view, I suppose. That's the one that counts. But, you know, a physicist using kinetic theory would say, well, that plasma in which you froze to death is very, very hot. Wow. Okay. It's confusing, right? Yeah. But there are hotter things in the universe, the quasars, the active galactic nuclei that are emitting huge amounts of radiation, often powered by supermassive black holes. These things, the gas around them gets to 50 trillion C. What? And this is just gravitational friction. This is spaghettification. This is tidal forces from the black hole heating up gas in the accretion disk.

43:00Crazy. So the hottest thing out there in the universe is probably a newly born neutron star. But we can also make really hot stuff here on Earth that gets up to trillions of Kelvin. What? And that's in particle colliders. When we smash together atomic nuclei like lead and gold, we briefly make a state called a quark-gluon plasma, where the quarks inside the protons and neutrons have become free and slosh around in this really hot state that can get up to tens or maybe even hundreds of trillions of sea. So these extreme temperatures can be reached even here on Earth. And so this is not the reactors where we're trying to contain fusion because you're not shooting lead and gold in those.

43:43But these are like the LHC reactors. Okay, wow. Yeah, exactly. At the LHC, we mostly collide protons and protons. Okay. But for a few months of the year, we collide heavy atomic nuclei because we want to study what happens when you smash big blobs of stuff into other big blobs of stuff. And it turns out you get a big hot mess. Well, did that like burn through a part of the reactor the first time you all did it? Or did you expect it and were prepared? They expected it and they were prepared. And it's mostly contained. I mean, it makes a huge explosion and particles fly out. But that's standard stuff at the LHC.

44:15We're constantly bathed in that kind of radiation from the collisions, yeah. Well, it doesn't make it sound like a safe place to work when you put it that way. It's 100 meters underground. There's plenty of shielding. Okay. But Mark's question is not just like, what is the hottest thing? He's asking, is there an absolute highest temperature allowed, right? And here's where we really come to the edge of our knowledge. In kinetic theory, there is an absolute maximum temperature. If you heat up stuff enough, then the assumption that's at the heart of kinetic theory, that we can just think about particles defined by quantum mechanics and emitting radiation and wiggling and stuff and ignore gravity, that assumption goes away.

44:56That assumption breaks because at really, really high temperatures, gravity comes back. If there's really high energy density, then curvature is important. Remember, gravity is the weakest force, but it grows with importance as energy density increases. So really high temperatures, gravity becomes important again. And this is called the Planck temperature. So essentially, our theory, our extrapolation for what happens at a certain temperature makes this assumption that you can ignore gravity. and that assumption works up to a certain temperature, which is what we call the Planck temperature or absolute hot.

45:30And beyond that, we just don't know. We cannot predict with kinetic theory what would happen past that temperature. We need quantum gravity because we need to account for the gravitational effects. Ignoring that is sort of like extrapolating the Big Bang backwards using only general relativity and ignoring quantum mechanics or saying that the heart of a black hole is a singularity which ignores quantum mechanics. You can't just ignore one tenet of modern physics in a place where you know it's relevant. How many physicists have used absolute hot as a pickup line and have failed to get a date? That's what I need to know.

46:09All of them. Oh, no. Okay, so one of the theories has an absolute hot, but the other ones don't. Is that right? So all these different theories of temperature have different extremes and different boundary conditions because of the assumptions that go into them. Thermodynamic temperature doesn't have an intrinsic maximum. It can be extended infinitely. But again, those extensions rely on assumptions which break down at the Planck scale. So I would not reliably use thermodynamic temperature to predict what happens past the Planck scale. Statistical temperature, this is a really weird one, right?

46:48This is the one that can go negative. This is the one about how entropy flows. And it has a different maximum temperature. It's called the Hagedorn temperature, which is at just about a trillion or two Kelvin. Wow. Right around the temperature of a quark-luon plasma. And it argues that as the system's density of states grows with exponentially, that there's a maximum that you can reach there, where you can pump in more and more energy and the temperature doesn't climb anymore because of how the entropy is changing. But you told me about things that are hotter than the quark gluon plasma. So does that mean that we don't have to pay attention to that theory of temperature anymore?

47:25It's like everything. It has a range in which you should apply it, right? It's like we're saying we proved Newtonian mechanics is wrong when we flew a spaceship. Does that mean I can't use it to predict a baseball? Yes, you still can and you still should in some settings. But you should always keep in mind that none of our theories of physics are fundamental or absolute. They're all approximate. They're all emergent. And they all have regimes in which you can use them and regimes in which you should not rely on them. Got it. OK. It depends. That works in physics, too. Especially at the extremes, right?

47:59In our comfortable, cozy world of California, these definitions of temperature all agree with each other. But when you get to very, very cold or very, very hot, then they say different things about heat flow or entropy flow or what the thermometer reads or what's happening. inside these objects. Got it. All right. Well, let's see what Mark has to say about your absolute hot answer. Thank you, Daniel, for answering my question. That was great. And Kelly, thank you for asking insightful questions to clarify it as it went along. I really appreciate it. I do understand it a lot better now and keep doing what you're doing.

48:34Love the show. And thanks again. Bye.

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50:04The all-new Mazda CX-5. More to move every side of you. See it in five films at mazdausa.com slash five sides. Google is a trademark of Google LLC. Sequences shortened and simulated. Hello, hello. This is Malcolm Glebel from Smart Talks with IBM. Today we're diving into a fascinating conversation with Stefano Pallard, head of fan development for Scuderia Ferrari HP. Your pronunciation is strongly American. It's more Scuderia Ferrari. I'm still working on rolling my R's. But what I was able to learn from Stefano was the importance of engaging the Tifosi, the Ferrari superfans in the digital age.

50:45Ferrari fans and superfans want to be part of something, want to belong to something. So they want to be part of a community and ultimately they want to be part of a winning team. You've got Ferrari, which has a long history, design history. And now you're interacting in a kind of digital space. I'm curious how you balance those two traditions. When it comes to fan engagement, it's really digital technology and digital channels are being able to create a deeper connection with our fans. To learn more about how Ferrari and IBM are using technology to build deeper connections with fans, visit ibm.com slash Ferrari.

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53:11All right, and we're back, and we have a question from another Daniel. And like DKEU, Daniel, not a big fan of biology.

53:22Not why I picked this question. Not why at all. All right, all right. I picked this question because I love the nickname Glowy Dan. So let's hear Glowy Dan's question. Hey, Daniel and Kelly. This is Daniel from Fort Collins, Colorado. I've always had a love for the natural sciences, except for biology. Sorry, Kelly. But especially for geology and physics, both of which I studied a bit in college. And recently, my interest in geology and mineralogy has manifested itself as a rapidly growing collection of interesting rock and mineral specimens. I have a particular love for those that have cool and interesting reactions to the ultraviolet light spectrum, which, by the way, has earned me the nickname of Glowy Dan amongst my rock friends.

54:08This leads us into my question for you guys today. Why does ultraviolet light cause these incredible reactions in rocks, and a plethora of other things that are less cool than rocks, like scorpions? Thank you guys so much for taking my question. Have a great one. All right, Glowy Dan, I'm going to look past your poor taste in subjects and focus on the fact that this is actually a really fascinating topic that includes some biology. So I'm here for it. Let's do this. I think Glowy Dan is just engaging in the long tradition of DKUU good-natured ribbing because he clearly is curious about biology.

54:47Yes. Well, and DKUU appreciates honesty. So it is all good. You like what you like, Glowy Dan. So why do rocks glow? Super fun. There's actually two different physical processes happening here. We have sort of similar names. The first one is fluorescence and the other one is phosphorescence. So we'll talk about both of them. But first, let's remind ourselves what is light and how is stuff absorbed and emitted anyway? because this is going to be important to understand what's going on inside these glowy rocks. Enlighten me.

55:26I'm on fire today. Your jokes are brilliant. I'm at absolute hot today. I wonder if Zach would agree. So remember that light is electromagnetic radiation. We have all these fields around us. Many of them are matter fields that make us up. And one of them is the electromagnetic field. field. Photons are wiggles in this field. And from the infrared to the visible to the ultraviolet, all of light are just wiggles in the electromagnetic field. So ultraviolet light is not different from visible light. It's just out of the range that we can see because it has a higher frequency. It's a difference in degree, not in kind.

56:06And the same is true of radio waves and of infrared light. All this stuff is just electromagnetic radiation at different frequencies. Okay. Cool? Yep, we're cool. Now, atoms can absorb and emit some of these frequencies, but only specific ones because of quantum mechanics. When an atom absorbs light, what's happening is the electron that's around the nucleus absorbs that photon and it jumps up an energy level. But it can only do that for photons whose energy matches the gap in energy levels. If an electron wants to take a step up a ladder, it has to eat a photon of the energy of that step. If the photon is too much energy, it can't eat it because it would put it between steps, and the electron cannot be between steps.

56:51So it can eat a photon that takes it up one step or two steps or nine steps, but not 4.7 steps. Okay. And so if it gets hit with a photon that isn't going to bring it up the right amount, does the photon just pass right through it? That's right. That's transparency, basically. Okay. That's why some materials are opaque to visible light and other materials are transparent, right? They can pass through atoms without being absorbed or they pass through atoms and do get absorbed. And so every atom has a different set of frequencies at which it can absorb based on those electron energy levels. And this is super powerful and super fascinating.

57:26It lets us, for example, identify what's in the atmosphere of distant stars without ever going there. Just by looking at the pattern of radiation, we can say, oh, look, it's hydrogen. And oh, this helium there. Oh, this one has something weird in it. I wonder if aliens are dumping their trash into this star. We can tell a lot about distant stars just by looking at the pattern of emission. We can tell what's in the atmosphere around exoplanets by seeing how light from their stars is absorbed as it passes through the atmosphere. Incredibly powerful tool because different atoms have different signatures.

58:00It's like a fingerprint. Awesome. Now, they can absorb and they can emit at these frequencies. So an electron can jump down energy levels, and when it does so, it emits a photon. And that photon has the energy of the difference in the electron's energy levels, which has a specific frequency. So you can see this emission spectrum and absorption spectrum. For example, the sun has an atmosphere, and when light from the surface of the sun passes through it, it gets absorbed at certain frequencies. And we can tell what's in the atmosphere of the sun based on those gaps where the sun has absorbed those photons.

58:35If you have a gas in the lab and you heat it up, it will emit at those frequencies. So you can tell what's in your gas based on those emissions. And does it emit at just like a constant rate or does something have to happen to get it to emit a photon? Yeah, great question. Everything in the universe that's made of charged particles is constantly emitting photons. because those particles are in motion. And anytime things are wiggling or moving or accelerating, they are emitting photons. The frequency at which they emit is dependent on their temperature. So for example, a piece of metal that's sitting on your desk and feels cool is actually emitting light, but just below the range where you can see it.

59:16As you heat it up, it starts to glow visibly. That's because now those atoms inside it are moving faster, according to kinetic theory. And so they emit at higher frequencies. That's the black body spectrum. And that's a smooth spectrum. So that's a different way that atoms can emit. That's like looking at a block of matter on a whole, it's going to be emitting a smooth spectrum. But individual atoms emit at specific frequencies. Okay. So what's going on with fluorescence? Well, what happens here is you have a source of ultraviolet light, and that matches up very well with the atomic energy level.

59:50So the atoms inside the glowy rock can absorb those ultraviolet photons because it lines up with a step for the electrons, multiple steps actually. So the electron absorbs that ultraviolet photon. It goes up a bunch of energy levels. And now you might imagine what it would do next is jump back down and emit an ultraviolet photon, right? The same frequency that came in, but that's not what happens. What happens is that it takes a couple of steps down. So it loses some of that energy to heat. It like transfers it to other molecules to make them wiggle. It doesn't have to lose energy by emitting a photon.

1:00:26It can lose energy in other ways. Like let's say, for example, it goes up 10 energy levels and then it slides down a few energy levels, giving up that energy to neighboring molecules, making them wiggle. Then it jumps down the rest of the energy levels and gives off a photon. So it absorbs a high energy photon and it emits a lower energy photon because some of the energy is lost to heat. Now that photon is in the visible. So effectively, the rock has transformed an invisible ultraviolet high energy photon to a visible lower energy photon. Whoa, that's pretty cool. It's pretty cool. Rocks are just out there like changing photons from invisible to visible.

1:01:09Very cool. And that's fluorescence. Shine an ultraviolet light on something and it glows in the visible. And this is what happens at like black light parties, right? Or raves when they turn on the ultraviolet light. And some people who are wearing certain kinds of shirts or certain glasses or whatever that fluoresce, they absorb the ultraviolet light and they glow in the visible. It looks really, really cool. That's awesome. Yeah. I was going to make a joke about people with glasses not usually being invited to raves, but surely there are cool people with glasses who are just not me. Absolutely.

1:01:42And this happens in nature, right? So there's lots of different rocks out there that glow in the visible in different ways based on these energy levels. There's calcite that glows red, blue, white, or orange. Fluorite glows blue, violet, or green. There's willamite that glows really bright green. Opal and highlight also glow in the green. There's whole web pages where you can see glowy rocks. It's really, really cool. That is really, really cool. Now I'm dying to have a room in my house filled with these rocks where the light is always off, but the black light is always on. And lots of biological critters also have stuff inside them that can do this.

1:02:17So scorpions do this. It's not fully understood, to my knowledge, why exactly scorpions fluoresce. But you put scorpions under a black light and they will glow. It might be related to signaling somehow or to reproduction. I don't think it's well understood. I don't think it's well understood either. And so this is not a thing that you can run out of, right? Because your electrons will do this over and over and over and over again forever. Is that right? That's right. Okay. Exactly. They have this beta carboline in their cuticles, which does this, and it's not like it gets used up. You are inputting new energy every time you do it.

1:02:51But if you turn off the ultraviolet light, it will stop. The other kind of glowy is different. It's the kind which continues after the light is removed. So this is phosphorescence. What's happening here is very similar, but the photon comes in, the electron absorbs the energy. but because of a weird quirk in the quantum states of some of these guys, the electrons get trapped briefly in an intermediate state. So they don't emit immediately. It's sort of like a little battery. It stores the energy for a little while and then gradually releases it. And so it decays from this intermediate state more slowly, which means that like you can shine ultraviolet light and stuff for a while.

1:03:34It'll get a bunch of electrons higher up in energy, and then you can turn off the ultraviolet light and it'll glow. It won't glow as brightly at first, but it'll glow longer. And so for example, glow in the dark stickers or watches, that's how these work. They absorb ultraviolet light when you're out around during the day. And then when you turn off the light, they're slowly dribbling that energy back out. And that's phosphorescence. It's very similar to fluorescence, but there's this delay that happens because of the nature of the quantum states in between. Where do we see that in nature? So we've talked about glow-in-the-dark stickers and watches.

1:04:08It's more rare. There's some deep-sea, unearthly creepers that do this. There's certain species of millipedes that emit a brief whitish phosphorescent afterglow. If you zap them with ultraviolet light, some plants, if they've dried them, sunflower seeds also can emit this phosphorescence. But I think it's accidental. I don't know that there's any biological reason for this. Yeah, it seems like if it is useful, but it only lasts for a little while. Yeah, and it's different from like bioluminescence, where you are producing light, right? You're not just absorbing it, changing its frequency, and then emitting it.

1:04:47You're doing some chemistry to convert internal energy into photons. So bioluminescence is a different kind of process. We should have an episode on that. And I want to do an episode on iridescence, because I want to figure out why there are those beautiful wasps that are iridescent, even though they spend a bunch of their time in the dark. Why is that helpful? It's probably for some horrifying reason that's going to give me nightmares. I hope so. All right, well, let's send this answer back to Glowy Dan and see if we have scratched his physics itch. Hey, guys, thank you for the great answer. Of course, biology is very interesting.

1:05:21It's just not so much fun for some of us to study. I was very interested to learn that the electrons actually jump up several energy levels and then lose some of their energy to heat before re-emitting a photon. Considering that there are three main peaks in the ultraviolet spectrum that can induce a fluorescent reaction, this makes me wonder if there are other wavelengths that can produce some other visible reaction, especially in heavier elements that have higher energy electrons. It's also very interesting to me that only about 10 % of mineral species fluoresce, while some of those that do not have very similar chemical makeup and crystal structure.

1:05:58I'll have to unearth some more of that groundbreaking geology research to delve even deeper into the subject. Thanks again. Well, thank you to everyone who participated today and sent us their questions. We hope you'll send us your questions, too, at questions at danielandkelly.org. We love hearing from y 'all. We really, really do. Please write to us. It makes our day.

1:06:25Thanks, everybody, for listening. Please go and do us a favor and rate the show on whatever podcast app you're using. It really helps people find us. Daniel and Kelly's Extraordinary Universe is edited by the amazing Matt Kesselman. He really is a wizard. You can also find us online on Blue Sky, Instagram, and XDNKUniverse. Come engage with us. You can email us at questions at danielandkelly.org. We really do want to hear from you. And you can find our website, www.danielandkelly.org, where you'll also find an invitation to join our Discord, where everybody comes and talks about the amazing universe.

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