Daniel and Kelly’s Extraordinary Universe - Listener Questions #42

Episode Date: June 23, 2026

Zach joins Daniel and Kelly for a segment on art and science communication. Then Daniel and Kelly explore the concept of absolute hot, and what makes some rocks glow.See omnystudio.com/listener for privacy information.

This is an I-Hard podcast. Guaranteed Human. Can science be communicated without math but with art? Listen to these science-inspired pieces and try to tell them apart. A chilly day gave a listener a puzzling thought. Does the universe have an absolute hot or not? Why do some rocks and craters glow? Listener Glowy Dan very much wants to know.

Whatever questions keep you up at night, Daniel and Kelly's answers will make it right. Welcome to Daniel and Kelly's extraordinary universe listener questions episode 42. Emily Wienersmith, I study parasites and space and today we're bringing my husband on the show, which has been requested by listeners. So there you go, everyone. Hi, I'm Daniel. I'm a particle physicist who likes to think about aliens. And when I bring my wife onto the show, she usually outvotes me and sides with you. So what's going to happen when And Zach is here today. I hope that you side with me.

And we outvote Zach because our marriage is a competition and I have to win. All right. Well, I think we all win listening to you to argue. All right. Well, let's bring him on the show and get started. Zach Weiner Smith is a resident of Weiner Smith Manor where he can be seen sporting socks and sandals. Despite what you often see in the Red Button comics on Saturday morning breakfast cereal, is dressed at Weiner-Smith Manor more often than you might think.

And his middle school book, Sawyer Lee, and the quest to just stay home, is out now. Welcome to the show, Zach Weiner-Smith. Thank you, Dr. Kelly Ween-Smith. I'm glad to have Zach on to defend himself against Kelly's thinly-veiled swipes. What? Are they veiled? Yeah, I was going to say, I object strongly to the suggestion that I veil them at all.

I'm not afraid. Well, often when I hear a comment, I wonder like, I wonder how Zach's face changes when he hears that expression or if he's even listening to that part. Well, he is one of our biggest fans, so he listens to all of them. All right. Well, today we have Zach joining us on the show because we have a special segment for today's listener questions episode. I got an email from a listener who's also a musician and who is very interested in the overlap between science and art. And we got into a conversation about whether music could be used to communicate science. And it's great to have Zach on because we are all here as part of a community folks who like to use art to communicate science. In Zach and Kelly's case, it's often cartoons,

but there's a broader community folks who use, for example, dance to communicate science. I don't know if you guys have ever seen the Higgs boson dance performance. No. Did it win? Isn't there a Dance Your PhD contest every year? That's right. Did it win? This was actually an academic piece of work by two professors at Yale, who I know, won a dance professor and one a physicist. Wow.

Well, everybody should look it up, it sounds like. Do you feel like it conveyed the nature of the Higgs? There was a lot of arm waving around, I think, to convey, like, quantum fields in motion. Oh, I thought it was because you guys don't understand it much, so it was arm waving. This was on hand waving. A lot of shrugging, a lot of confusion. But, you know, as a member of the audience, I was wondering, like, would I get the Higgs boson from this if I didn't already know the inspiration? And so as I was writing back and forth with this listener, I thought, let's do an experiment.

Here's somebody who knows some science and has some musical skills. So I suggested that he write five pieces of music, very short, each one inspired by different scientific. concept, and then we could see if people listening to those pieces of music could infer which science concept had inspired each one. Can we actually communicate science via music? What are the five categories? So I sent him five topics that span the DQU topic universe. We have black holes, vaccines, dark matter, parasites. Now, is that dark matter poop or dark? Or dark matter for physics. Sorry, physics or biology dark matter? I did not specify. So I left that one a little intentionally ambiguous. All right. All right. So we had black holes, vaccines, dark matter,

parasites, and quantum fields. Oh, I see you did one more physics than biology. I knew you were going to take objection to that. That's why I left dark matter ambiguous. See, it's the tiebreaker. Okay. That's fair. That's fair. And we are going to do the experiment right here on the show. With you, listeners, you're going to hear the pieces. And so I want you to get a piece of paper, or if you have a great memory, you could just keep track. We're going to play the pieces. And I want you to guess which one lines up with which scientific concept.

Zach and Kelly have not heard the music before. And so we're going to score them live on the show to see if science can be communicated through music. You guys ready? We're ready. Wait, this is a competition, right? This is not. We're not just having fun. Zach and I don't do fun.

We're going to take score, Zach, how you guys decide to adjudicate that later is up to you. Okay. All right. So here is the first piece of music. So think about it. What science was in the mind of the composer when they wrote that piece? Was it black holes, dark matter, quantum fields, vacuum fields, vacuum. vaccines or parasites.

All right. Zach, are you done? Are we going to wait for you all day? Oh, my God. I get a point for being done first. That's not how the points for it. You should lose a point for rudeness. That's not how it works in our house.

Wow, tone policing. All right. Thank you. All right, I have entered a guess. All right, here is the second piece. Cover my answer. Okay. Wow.

You guys were quick this time, huh? Zach, you won the first one in. I was, yeah, I was before Kelly. Bonus points for getting it in first. You said we weren't playing that way. We're changing the rules constantly. It's just like biology. All right.

Third piece of... I'm hitting play. Third piece of music. You didn't listen to the whole thing. Yes, I did. I'm just trying to appreciate the effort this musician went to, but you do it your way. Oh, my gosh. You are constantly changing the goal post.

Did you load it before he said anything? Sure did. All right, fourth file, I'm hit and play. What's the fourth file? All right, here is the fourth piece of music. Is it black holes, dark matter, quantum fields, vaccines, or parasites? Kelly's rocking out to this one. Yeah, loving it.

Done. And I appreciated the work the artist did. All right, and here is the last piece of music. Okay. So before we score your guesses, I just want to let you know that the first person to do this experiment was my daughter, Hazel, and she scored a perfect five out of five, much to her surprise. Did she? Wow. Way to go, Hazel. But after she scored five out of five, she said, wait, what's the difference between a black hole and dark matter? Oh, oh. And then she scored zero out of zero in the Whiteson House. Exactly. So I went from proud to embarrassed.

And then she made a good point. She said, well, I don't know if I understand the science better or worse than the musician, which is a fair question also. Yeah, that's true. That's true. Well, if the musician is a listener to DKEU, I suspect they've got a pretty good understanding of the difference. You know, we should do this again with Matt Kesselman at some point. I'm sure he'd be happy to make some audio for us.

Yeah. All right. So let's hear your answer. It's the first piece of music. What did you guys say, Zach? I said vaccines because it kind of lightened up towards. the end. So it was like moving from injecting yourself with cow pus to a delightful outcome. Kelly?

I said quantum fields. Zach is correct. It is vaccines. And I had the same impression. I was like, it's a hopeful message. Thank you. It's triumphant at the end. Yeah, I thought it was obvious, to be honest. Oh, my God. But the third one also is happy and upbeat. All right, well, let's not skip ahead. The second one, would you guys think the answer was which science concept was the second one communicating.

Kelly? I was a little torn between black holes and dark matter, but I went with black holes. I too went black holes because of the drop and pitch. Black holes is correct. Zach is two for two. Kelly is one out of two so far. All right. And then the third piece, what did you guys take away from that one?

Zach? This was a tough one. I originally wrote Quantum Fields. because when I picture a quantum field, I picture a sort of wobble, and this one was a little wobbly. But then the one after was even more wobbly. So I revised it to dark matter.

And so I'm going to stick with dark matter for three. All right. And Kelly? I had vaccines because it was happy, but I want to switch to quantum fields. I think it's quantum fields. Quantum fields. Wait, wait, wait, wait, wait, wait, wait.

Hold on. Do you mean you had it? Like, and then changed it during the accepted changing period or that you want to change it now after that time. Yeah, you can't change it now. You're already put quantum fields for the first one. You've already got information about the first two. Well, if you get one wrong, then you automatically have to get too wrong. That's right. Yeah. All right. So your original answer, Kelly, was quantum fields. Was quantum fields.

It's a lie. It's a lie. You have a superposition of truth and lying. Well, you're wrong in both counts because it was dark matter. Boom! It was one. Zach is three out of five so far. So Zach might get them all right. Let's see.

Oh, my God. Without cheating. That's cool. How boring. The next one, which was quite rhythmic. Zach, did you think this one was quantum fields? I went with quantum fields, yeah. All right.

And Kelly? I just heard some erasing. Quantum fields. You said quantum fields for three out of four answers so far. No, no. I had dark matter. I had dark matter. Dark matter. Well, the answer is quantum fields.

Zach is correct again. Rudd. Gee, what happens for the last one? So by process of elimination, I hope Kelly got this one. We know that the last one is parasites. Kelly, what did you put for the last one? I put parasites.

You put parasites, yes, so we end on a high note. You did the best you could. I won the race at the beginning, and you won this thing at the end, whatever. Even if you got a point for the race, you're three points behind on the score, so it doesn't matter. I got five out of five on the race

because I beat you each time. So I think this is a fascinating experiment, and we can learn a lot about the Wintersmith Marriage from the data we got today on the show, but I was also interested more broadly, like, you know, in higher statistics sampling. So I put this out there for our listeners

and also for UCI physics majors to contribute. I got more than 100, people playing this game on a website, and I was able to collect some statistics here. And so if you're just guessing by a random chance, you would get about one out of five of these right. But over 100 data points, we had people average two answers correct, which means there's a real signal here. There's definitely some information being communicated. And the one that people most often got right was black holes, then parasites, then vaccines.

So those are the ones that most effectively communicated that concept. My hypothesis, although I got them wrong, so maybe I'm not, maybe I shouldn't be positing hypotheses, is that it had something to do with like how deep the notes were and how positively these topics are imagined. So like vaccines was like the happy one. And then I feel like as you went down, you got closer to like, as the pitch got lower, it got closer to like black holes and dark matter and. And so I feel like that was part of what was being conveyed. What do you all think? There's a correlation there between pitch and how we feel about a topic? You just got to feel the music, man.

What a non-scientific. Real left-brain answer over there. I mean, I think it's definitely information-rich, right? Music has a lot of stuff going on in there. But it's symbolic, right? How he chooses to represent these ideas in the music, we have to guess at his intentions and then reverse engineer it. So I wonder if people from a different culture would interpret it differently.

I don't even know where in the world this listener is. But there must be a lot of cultural baggage in how you represent these things. Or in what sounds sound triumphant or scary or ominous or massive, right? Gosh, there's got to be someone who's studied that across cultures to see if there's a universal feeling that like a low note is like for a scary moment or something. Actually, I know somebody who studies ethnomusicology. Great. Yeah. I mean, why are we talking to Zach?

Yeah. Because he's a winner. Instead of just speculating baselessly about how culture might shape an artist's translation of science into music or how our ears would recognize those translations, I reached out to a good friend who's an expert in this area. Professor Liliana Carrizo is an ethnomusicologist whose work focuses based. broadly on music and culture, especially migration. She has studied the music of the Middle East, Mongolia, and South America, among others. I sent her these clips and asked her to share her thoughts. Here's what she had to say.

Thanks for reaching out to your friendly neighborhood ethnomusicologist. So, fair warning, if you ask an ethnomusicologist whether music contains universal meanings, there's a decent chance. We'll spend 20 minutes explaining why that answer is, well, it's complicated. Within ethnomusicology, music is generally understood as a deeply social and cultural phenomenon. Many of us are skeptical of claims about musical universals because ideas that may seem obvious to someone, like ones conveyed by melody, rhythm, consonants, or even what counts as music in the first place, can really vary enormously across cultures and historical contexts.

So something that sounds spooky, ominous, or suspenseful to one listener might communicate something entirely different to someone else. So your interpretation isn't just about the sounds themselves, it's also shaped deeply by the cultural worlds you've inhabited and the listening habits you've developed over time. That said, ethnomusicologists aren't necessarily anti-university. What many of us find compelling is the possibility that music communicates in ways that differ from language but are still central to what it means to be human. Music can be remarkably effective at conveying affect, emotion, mood, intensity, that sort of thing, all sorts of felt experiences without necessarily being tied to a single precise meaning. A piece of music might not tell everyone exactly the

same thing informationally, but it still can create overlapping frames of understanding and interpretation among listeners who share certain cultural assumptions while still leaving plenty of room for individual interpretation. So, in other words, music may be less like a dictionary and more like a really good dinner conversation. Everyone leaves with a slightly different takeaway, but somehow we're all talking about similar themes and ideas. Well, Zach, what do you think more broadly about like communicating science, you know, not through language or through math, but through visuals or music or dance or other, you know, left brain kind of stuff? I am, Kelly knows this. I'm profoundly in favor of personal irresponsibility. I enjoy communicating science

purely because it amuses me. I don't have any broader goals. And I don't know if it works, but I'm having a nice time. Kelly probably has a more uplifting view of it. I mean, I think art can be used. The kind of art that Zach does, for example, I think we found it very useful

for conveying complicated ideas. Like, there's a lot of ideas that, for people who have trouble picturing things in their heads, sort of like I do, having Zach do the comics, helps and having a bit of comic relief or having an opportunity for your brain to just sort of like take a little break and enjoy itself for a moment

before you jump back into like the details is helpful. Yeah, I do think with comics in particular, for some reason I don't really understand if you take the same paragraph and put it across four panels with a picture of a face, humans just kind of tune in a little more. Yeah, so I think if you were trying to get someone through a difficult scientific topic and then you took some musical breaks to like sort of help you visualize what was happening

and also just sort of like take a moment to let your brain do something else, then I think that could be helpful. Well, we use music all the time in storytelling in movies, right? The background music tells you how to feel. Is somebody going to jump out of the wall? Is this a good moment? But I've never seen that done like in a science talk. No.

Should I have like a background music during my presentation? We're like, this was a really tricky bit. And then we made it work. That's not. When the guy who is wrong, you put up his picture and then you do the mean music. We're at here. Yes. My colleague who disagrees,

da, da, da, da, da, da, da, da. I'm hoping this ushers in a new era of a lot more music behind scientific presentations. That's all I've got to say. And thank you so much to Max for playing along and for coming up with these great clips for us. Yes, thank you very much. Let's send this back over to Max to hear his reaction to our reactions to his music. Hi, Daniel Kelly and Zach. This is Max or Max Maroon or my actual name is Matthew. And I'm actually up in Massachusetts where all the greatest minds and comedians of the world come from. Anyways, I do want to thank Daniel for having me be a part of this experiment. Though I have to

admit that I did mess up the file names and actually, sorry Zach, Kelly got five out of five and she was the winner. But no, I'm just kidding. So it was really cool to see the results, especially Zach's live five out of five and hearing that Hazel got the five out of five. And Daniel, I'll say that Hazel, I'm sure, is a lot younger than me and I'm sure she understands the concepts far better because the youth is where it's at. It was interesting to see the results because the ones that did best, like black holes, parasites and vaccines were the ones when I did the pieces that I was most confident with. Quantum fields and dark matter are, you know, they're kind of at the edge of human understanding. But Kelly alluded to the fact of the low tones, and with those, that's what I was kind of trying to do.

So quantum fields, I was playing like a low and a high, an E and a G, and I know I was doing some hammer-ons, like the ripples, you know, coming out of the quantum field. And dark matter, I was trying to do the low note of the 85% of matter. And having the high harmonics is like the actual matter we see and experience. So I do want to thank Daniel again for having me be a part of this. Science and math and philosophy have been main drivers of my creative writing and music and my writing lyrics and poetry and everything like that. So it was really neat to be a part of this and to see actual results and to see what people could or could not get out of it.

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Just ask your smart speaker to play IHart Pride Canada. Stream us on your phone. Listen now at iHeartRadio.ca. What did black music, food, and culture teach us about who we were becoming? 2016 was sort of that last era of monoculture, where we still consumed things in community. from Beyonce and Rihanna. Everybody wanted to be Beyonce.

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girls is bringing it all to the mic listen to therapy for black girls on the iheart radio app apple podcast or wherever you get your podcast this black music month the quest love show celebrates the artists innovators and cultural voices who continue to redefine music we're sitting down with a groundbreaking country artist mickey guy the way that the country music community accepted post malone versus biance versus shabuzzi like Those are very eye-opening things. Hip-hop visionary, Fat-Fi Freddy, genre-bending musical genius, Thundercat.

And the always-legendary revolutionary voice, Chuck D. Yeah, we changed tires, man. I had 18 jobs before this became my occupation, man. Okay. I wrote, I wrote a bum rush the show as a messenger. From unforgettable stories to deep conversations about creativity, culture, and legacy. These are the voices shaping the soundtrack of Black Music Pass, present, and future. Listen to the Questlove show on the Iheart Radio app, Apple Podcasts, or wherever you get your podcast.

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A street doctor turned influencer whose work with the unhoused community has made a huge impact online and in her community. Listen to Weeley &House on the IHard Radio app, Apple Podcasts, or wherever you get your podcast. Here's something that should not be as complicated as it is. Getting a racist statue removed. And here's something that should be a whole lot easier than it is. Getting a new one put up in its place. As long as there's a politics of race and race. America. There's going to be a politics of remembering the Civil War. To get to school, I had to go down

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that is really catching. You'll see what I mean. Listen to Rebel Spirit season two on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. All right, we are back and we are done playing games and adjudicating disputes between the Wiener's Myths. 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, temperatures, an emergent property of the energy of a group of particles, and there's an absolute lowest temperature that can be reached. My 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. But 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 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. means. And it turns out the 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. It'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. You know, we say the temperature is whatever the thermometer reads. It'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. And so it's just sort of an operational definition

because we're 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 mercury thermometer and alcohol thermometer, who are both calibrated to agree at zero and 100 disagreeing in between that because they expand to 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. Well, 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 going to get hotter and the hot thing is going to 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? in 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 like 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, right? They often give similar answers, but it's a different story about what temperature is, right? One is saying it's just the number on the thermometer. The 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? And 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 a way you measure a thing. For the most part, these things really do agree with each other. And in everyday life, you know, around normal temperatures, they all give similar explanations. The thing you measure on the thermometer and the kinetic theory of a jiggling and the motion of heat flow, they all agree. Right. But these things break down sometimes near the extremes. Like 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

like what something means that things, things break down. And so it's all about, you know, 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. So actually there's one more view of temperature, which is a sort of statistical theory, and 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 when 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 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. And 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. Kinetic 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 of that 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. Let'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 46.5C, 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. Wow. So like, yes, pretty toasty. That's not going to be fun to live on the moon. The hottest temperature survived by any living thing, a tardigrade, is 151C.

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. Right. So it probably lived at 151C 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 460C, 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, like, 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. Yeah.

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.

Oh 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. It's 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 aren't in galaxies. And then there's stuff between the galaxies inside the cluster. comes out to like 10% of the mass of the cluster, and it's really, really hot. It's like a hundred 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, but 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, so, 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? From a biological point of view, I suppose. I guess so. That's the one that counts. But, you know, a physicist using Kennedy 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 and the accretion disk. Crazy. So the hottest thing out there in the universe is probably a newly born neutron star. But we could also make really hot stuff here on Earth that gets up to trillions of Kelvin. 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. But 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 and the 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. We're constantly bathed in that kind of radiation from the collisions, yeah. Oh, 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 mass. 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. That 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 plank 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 plank temperature or absolute hot. And 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 Right. That's what I need to know.

All 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. A thermodynamic temperature doesn't have an intrinsic maximum. It can be extended infinitely. But again, those extensions rely on assumptions, which break down. down at the plank scale. So I would not reliably use thermodynamic temperature to predict what happens past the plank scale. Statistical temperature, this is a really weird one, right? This 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 Hagadorn temperature, which is at just about a trillion or two Kelvin, right around the temperature of a quark gluon plasma. And it argues that as a 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 glue on plasma. So does that mean that we don't have to pay attention to that theory of temperature anymore? It'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. Okay. It depends. That works in physics, too. Especially at the extremes, right? In 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. Keep doing what you're doing. Love the show. And thanks again. Bye. only playlist you need for your Toronto Pride celebrations. Pride is so great because it gives a whole bunch of people this visibility that they've never had before. We have a ton to celebrate Toronto. Happy Pride! Iheart Radio.

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Therapy for Black Girls is bringing together the conversation shaping Black Life right now. You will never make me feel bad for being a Black girl, for being a Black American girl, ever. Therapy for Black Girls is bringing it all to the mic. Listen to therapy for Black Girls on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast. This Black Music Month, the Questlove show celebrates the artists, innovators, and cultural voices who continue to redefine music. We're sitting down with a groundbreaking country artist Mickey Guyton. The way that the country music community accepted Post Malone versus Beyonce versus Shibuzi, like those are very, eye-op-op visionary, Fat-Fi Freddy,

genre-bending musical genius, Thundercat, and the always-legendary revolutionary voice, Chuck D. Yeah, we changed tires, man. I had 18 jobs before this became my occupation, man. Okay. I wrote, I wrote a bum rush the show as a messenger. From unforgettable stories to deep conversations about creativity, culture, and legacy. These are the voices shaping the soundtrack of Black Music Pass,

present, and future. Listen to the Questlove show on the IHeartRadio app, Apple Podcasts, or wherever you get your podcast. Here's something that should not be as complicated as it is. Getting a racist statue removed. And here's something that should be a whole lot easier than it is. Getting a new one put up in its place. As long as there's a politics of race in America, there's going to be a politics of remembering the Civil War. To get to school, I had to go down Robert Lee Boulevard.

Get to the grocery store, I had to go down Jefferson Davis Parkway. If you're an historian and you leave out half of what the history is, you're not doing your job. I'm Akila Hughes, and Rebel Spirit Season 2 goes deep on both of those things. The fights, the politics, the people who won, and my personal campaign to add something to the Kentucky State House that's actually worth the wall space. We are more than our bodies. We contain essence. We contain spirit.

How do you represent that? They are just fueling a fire that is really catching. You'll see what I mean. Listen to Rebel Spirit Season 2 on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. June is Black Music Month, and on the Drink Chams podcast, we're speaking with the hottest names in the culture, like Sway Lee. Do you realize how legendary you are? I appreciate that. I'd be seeing it, but I'm like, man, I still got like so much more to do.

Like Prince, he dropped like 30 albums. We dropped like five right now. That's the rate we got to be going. Yep, that's a good attitude. You also hear stories from industry legends and hip-hop pie. pioneers like Fab Five Freddy. I directed when Nas' early videos. Which one?

One love. Wow. I literally filmed in his apartment in Queensbridge. His moms were still up in that apartment. Nause was just beginning to take off. His pops used to live near me in Harlem. His dad introduced him to a whole lot of, you know, conscious stuff, and he made a young prodigy.

No matter the era, Drink Chance brings you the biggest names and the most unfiltered conversations. Listen to Drink Chans, from the Black Effect Podcast Network on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast. All right, and we're back, and we have a question from another Daniel. And like DKEU, Daniel,

not a big fan of biology. Not why I pick this question, not why at all. All right, all right. I pick 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,

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. This 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 you. I think Glowy Dan is just engaging in the long tradition of DQU good natured ribbing because he clearly is curious about biology. Yes.

Well, and DQEU 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. They 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. Nice. I'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. 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.

And 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. Then the electron cannot be between steps. So 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. That's why some materials are opaque

to visible light and other materials are transparent. 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. It 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. 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. It'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 electrons 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. If 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. As 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. 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 its specific frequencies. Okay. So what's going on with fluorescence? Well, what happens here is that you have a source of ultraviolet light, and that matches up very well with the atomic energy levels. So the atoms inside the glowy rock can absorb those ultraviolet photons

because it lines up with a solid violet light. 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. It 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 that 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.

Wow. Very 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. And 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 like 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. So scorpions do this. It's not fully understood, to my knowledge, why exactly scorpions flores. 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 and over again forever. Is that right? That's right. 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.

But if you turn off, the ultraviolet light, it will stop. Okay. 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 bad. 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 as stuff for a while. It'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 are 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. It's more rare. There are some like deep sea on-earthy creepers that do this. There's like certain species of millipedes. And then emit a brief whitish phosphorescent afterglow. if you zap them with ultraviolet light, some plants, like if they've dried them, like 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. you'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. It'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 in crystal structure.

I'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 Daniel and Kelly. We love hearing from y'all. We really, really do. Please write to us. It makes our day.

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