Listener Questions #42

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 https://omnystudio.com/listener for privacy information.

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

• 0:00Daniel Whiteson?

  This is an iHeart Podcast. Guaranteed Human.

• 0:05Speaker 01

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• 0:55Daniel Whiteson?

  The views expressed should not be used for medical diagnosis or treatment as a substitute for professional medical advice. Individual circumstances may vary. For prescription only. Safety info found at freestylelibre.us.

• 1:05Speaker 01

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• 1:34Daniel Whiteson?

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• 2:12Daniel Whiteson?

  Can science be communicated without math, but with art? Listen to these science-inspired pieces and try to tell them apart.

• 2:21Kelly Weinersmith?

  A chilly day gave a listener a puzzling thought. Does the universe have an absolute hot or not?

• 2:27Daniel Whiteson?

  Why do some rocks and critters glow? Listener Glowey Dan very much wants to know.

• 2:33Kelly Weinersmith?

  Whatever questions keep you up at night, Daniel and Kelly's answers will make it right.

• 2:38Daniel Whiteson?

  Welcome to Daniel and Kelly's Extraordinary Universe Listener Questions, episode 42.

• 2:57Kelly Weinersmith?

  Hello, I'm Kelly Wiener-Smith. 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.

• 3:08Daniel Whiteson?

  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 Zach is here today?

• 3:20Kelly Weinersmith?

  I hope that you side with me.

• 3:24Kelly Weinersmith?

  And we outvote Zach. Because our marriage is a competition and I have to win.

• 3:31Daniel Whiteson?

  All right, well, I think we all win listening to you two argue.

• 3:35Kelly Weinersmith?

  All right, well, let's bring him on the show and get started. Zach Wiener-Smith is a resident of Wiener-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, he is dressed at Wiener-Smith Manor more often than you might think. And his middle school book, Sawyerly: And the Quest to Just Stay Home, is out now. Welcome to the show, Zach Wiener-Smith.

• 4:01Speaker 04

  Thank you, Dr. Kelly Wiener-Smith.

• 4:05Daniel Whiteson?

  I'm glad to have Zach on to defend himself against Kelly's thinly veiled swipes.

• 4:09Kelly Weinersmith?

  What?

• 4:10Speaker 04

  Are they veiled?

• 4:11Kelly Weinersmith?

  Yeah, I was gonna say, I object strongly to the suggestion that I veil them at all. I'm not afraid.

• 4:19Daniel Whiteson?

  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.

• 4:28Kelly Weinersmith?

  Well, he is one of our biggest fans, so he listens to all of them.

• 4:35Daniel Whiteson?

  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 of 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 of folks who use, for example, dance to communicate science. I don't know if you guys have ever seen the Higgs boson dance performance?

• 5:15Kelly Weinersmith?

  No. Did it win? Isn't there a dancer PhD contest every year?

• 5:19Speaker 04

  That's right.

• 5:20Kelly Weinersmith?

  Did it win?

• 5:21Daniel Whiteson?

  This was actually an academic piece of work by two professors at Yale, who I know, one a dance professor and one a physicist.

• 5:28Kelly Weinersmith?

  Wow. Well, everybody should look it up, it sounds like. Do you feel like it conveyed the nature of the Higgs?

• 5:37Daniel Whiteson?

  There was a lot of arm waving around, I think, to convey like quantum fields in motion.

• 5:42Kelly Weinersmith?

  Oh, I thought it was because you guys don't understand it much. So it was arm waving.

• 5:48Daniel Whiteson?

  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.

• 6:14Daniel Whiteson?

  Very short, each one inspired by a 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?

• 6:30Kelly Weinersmith?

  What are the five categories?

• 6:32Daniel Whiteson?

  So I sent him five topics that span the DKU topic universe. We have black holes, vaccines, dark matter, parasites.

• 6:43Kelly Weinersmith?

  Now, is that dark matter poop or dark matter for physics? Sorry, physics or biology dark matter?

• 6:50Daniel Whiteson?

  I did not specify, so I left that one a little intentionally ambiguous.

• 6:54Kelly Weinersmith?

  All right.

• 6:55Daniel Whiteson?

  All right, so we had black holes, vaccines, dark matter, parasites, and quantum fields.

• 7:02Kelly Weinersmith?

  Oh, I see you did one more physics than biology.

• 7:07Daniel Whiteson?

  I knew you were gonna take objection to that. That's why I left dark matter ambiguous. See, it's the tiebreaker.

• 7:15Kelly Weinersmith?

  That's fair, that's fair.

• 7:17Daniel Whiteson?

  And we are gonna do the experiment right here on the show with you listeners. You're gonna 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 gonna 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 gonna score them live on the show.

• 7:37Kelly Weinersmith?

  Oh, boy.

• 7:38Daniel Whiteson?

  To see if science can be communicated through music. You guys ready?

• 7:42Kelly Weinersmith?

  We're ready, so we're.

• 7:43Speaker 04

  Wait, wait, this is a competition, right? This is not.

• 7:47Speaker 04

  We're not just having fun.

• 7:51Kelly Weinersmith?

  Zach and I don't do fun.

• 7:55Daniel Whiteson?

  We're gonna take scores. Zach, how you guys decide to adjudicate that later is up to you.

• 8:00Speaker 04

  Yeah.

• 8:02Daniel Whiteson?

  All right, so here is the first piece of music.

• 8:27Daniel Whiteson?

  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, vaccines, or parasites?

• 8:35Kelly Weinersmith?

  All right. Zach, are you done? Or are we gonna wait for you all day?

• 8:39Speaker 04

  Oh my god.

• 8:42Kelly Weinersmith?

  I get a point for being done first.

• 8:43Speaker 04

  That's not how the points work. You should lose a point for rudeness.

• 8:48Kelly Weinersmith?

  That's not how it works in our house.

• 8:49Daniel Whiteson?

  Wow, tone policing, all right.

• 8:51Speaker 04

  Thank you. All right, I have entered a guess.

• 8:55Daniel Whiteson?

  All right, here is the second piece.

• 9:16Speaker 04

  Get rid of my answer.

• 9:17Kelly Weinersmith?

  Okay.

• 9:18Daniel Whiteson?

  Wow, you guys were quick this time, huh? Zach, you won the first one in.

• 9:22Speaker 04

  I was, yeah, I was for Kelly.

• 9:25Daniel Whiteson?

  Bonus points for getting it in first.

• 9:27Speaker 04

  That's right.

• 9:27Kelly Weinersmith?

  You said we weren't playing that way.

• 9:30Daniel Whiteson?

  We're changing the rules constantly. It's just like biology. All right, third piece.

• 9:35Kelly Weinersmith?

  I'm hitting play.

• 9:37Daniel Whiteson?

  Third piece of music.

• 9:56Kelly Weinersmith?

  Done.

• 9:58Speaker 04

  Well, you didn't listen to the whole thing.

• 9:59Kelly Weinersmith?

  Yes, I did.

• 10:00Speaker 04

  I'm just trying to appreciate the effort this musician went to, but you do it your way.

• 10:04Kelly Weinersmith?

  Oh my gosh, you are constantly changing the goalpost.

• 10:08Speaker 04

  Did you load it before he said anything?

• 10:10Kelly Weinersmith?

  Sure did.

• 10:12Kelly Weinersmith?

  All right, fourth file, I'm hitting play.

• 10:15Daniel Whiteson?

  What was the fourth file? All right, here is the fourth piece of music.

• 10:37Daniel Whiteson?

  Is it black holes, dark matter, quantum fields, vaccines, or parasites? Kelly's rocking out to this one.

• 10:45Kelly Weinersmith?

  Yeah, loving it. Done. And I appreciated the work the artist did.

• 10:54Daniel Whiteson?

  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.

• 11:23Speaker 04

  Did she?

• 11:24Kelly Weinersmith?

  Wow, way to go, Hazel.

• 11:26Daniel Whiteson?

  But after she scored five out of five, she said, wait, what's the difference between a black hole and dark matter?

• 11:30Kelly Weinersmith?

  Oh, and then she scored zero out of zero in the White'son house.

• 11:36Daniel Whiteson?

  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.

• 11:48Speaker 04

  Yeah, that's true. That's true.

• 11:49Kelly Weinersmith?

  Well, if the musician is a listener to D K E U, 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.

• 11:59Daniel Whiteson?

  Yeah. All right. So let's hear your answers. The first piece of music, what did you guys say? Zach?

• 12:07Speaker 04

  I said vaccines because it kind of lightened up toward the end. So it was like moving from injecting yourself with cow pus to a delightful outcome.

• 12:18Daniel Whiteson?

  Kelly?

• 12:19Kelly Weinersmith?

  I said quantum fields.

• 12:21Daniel Whiteson?

  Oh, Zach is correct. It is vaccines. And I had the same impression. I was like, it's a hopeful message.

• 12:28Speaker 04

  Thank you.

• 12:28Daniel Whiteson?

  It's triumphant at the end.

• 12:30Speaker 04

  Yeah, I thought it was obvious, to be honest.

• 12:32Kelly Weinersmith?

  Oh my God. But the third one also is happy and upbeat.

• 12:37Daniel Whiteson?

  All right. Well, let's not skip ahead. The second one, what did you guys think the answer was? Which science concept was the second one communicating? Kelly?

• 12:45Kelly Weinersmith?

  I was a little torn between black holes and dark matter, but I went with black holes.

• 12:50Speaker 04

  I too went black holes because of the drop in pitch.

• 12:55Daniel Whiteson?

  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?

• 13:07Speaker 04

  This was a tough one. I originally wrote quantum fields, uh, 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.

• 13:22Daniel Whiteson?

  All right. And Kelly?

• 13:24Kelly Weinersmith?

  I had vaccines because it was happy, but I want to switch to quantum fields. I think it's quantum fields.

• 13:32Daniel Whiteson?

  Quantum fields.

• 13:33Speaker 04

  Wait, what do you mean you had it? Wait, wait, wait, wait, wait.

• 13:37Speaker 04

  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?

• 13:47Daniel Whiteson?

  Yeah, you can't change it now. You already put.

• 13:50Speaker 04

  You've already got information about the first two.

• 13:52Kelly Weinersmith?

  Well, if you get one wrong, then you automatically have to get two wrong.

• 13:55Daniel Whiteson?

  That's right. Yeah.

• 13:58Daniel Whiteson?

  All right. So your original answer, Kelly, was?

• 14:01Kelly Weinersmith?

  Quantum fields.

• 14:02Daniel Whiteson?

  Was quantum fields.

• 14:03Speaker 04

  It's a lie. It's a lie.

• 14:07Daniel Whiteson?

  You have a superposition of truth and lying. Well, you're wrong in both counts because it was dark matter.

• 14:14Kelly Weinersmith?

  It was one.

• 14:15Daniel Whiteson?

  Zach is three out of five so far. So Zach might get them all right. Let's see.

• 14:19Speaker 04

  Oh, my God. Without cheating. That's cool.

• 14:22Kelly Weinersmith?

  How boring.

• 14:22Daniel Whiteson?

  The next one, which was quite rhythmic. Zach, did you think this one was quantum fields?

• 14:27Speaker 04

  I went with quantum fields. Yeah.

• 14:29Daniel Whiteson?

  All right. And Kelly?

• 14:31Speaker 04

  I just heard some erasing.

• 14:33Daniel Whiteson?

  You said quantum fields for three out of four answers so far.

• 14:37Kelly Weinersmith?

  No, no, I had dark matter. I had dark matter.

• 14:40Daniel Whiteson?

  Dark matter. Well, the answer is quantum fields. Zach is correct again.

• 14:46Speaker 04

  Gee, what happened to the last one?

• 14:49Daniel Whiteson?

  So by process of elimination.

• 14:52Speaker 04

  I hope Kelly got this one.

• 14:53Daniel Whiteson?

  We know that the last one is parasites. Kelly, what did you put for the last one?

• 14:58Kelly Weinersmith?

  I put parasite.

• 14:58Daniel Whiteson?

  You've put parasites. Yeah. So we end on a high note.

• 15:02Speaker 04

  You did the best you could.

• 15:04Kelly Weinersmith?

  I, I won the race at the beginning and you, you won this thing at the end, whatever.

• 15:11Speaker 04

  Even if you got a point for the race, you're three points behind on the score. So it doesn't matter.

• 15:16Kelly Weinersmith?

  I got five out of five on the race because I beat you each time.

• 15:20Daniel Whiteson?

  So I think this is a fascinating experiment and we can learn a lot about the winner Smith 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.

• 15:36Kelly Weinersmith?

  Oh.

• 15:36Daniel Whiteson?

  To contribute. I got more than a hundred 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 a hundred data points, we had people average two answers correct.

• 15:55Kelly Weinersmith?

  Oh.

• 15:55Daniel Whiteson?

  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.

• 16:12Kelly Weinersmith?

  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?

• 16:44Speaker 04

  You just gotta feel the music, man.

• 16:48Kelly Weinersmith?

  What a non-scientific-

• 16:49Daniel Whiteson?

  Real left-brain answer over there. Yeah, 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, like, 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.

• 17:18Kelly Weinersmith?

  Yeah.

• 17:18Daniel Whiteson?

  Or in what sounds sound triumphant, or scary, or ominous, or massive, right?

• 17:23Kelly Weinersmith?

  Mm-hmm. Gosh, there's gotta 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.

• 17:35Daniel Whiteson?

  Mm-hmm. Actually, I know somebody who studies ethnomusicology.

• 17:39Kelly Weinersmith?

  Great, yeah, I mean, why are we talking to Zach?

• 17:40Daniel Whiteson?

  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 Cariso is an ethnomusicologist whose work focuses 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.

• 18:18Speaker 05

  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, consonance, 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

• 19:01Speaker 05

  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-universality. 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,

• 19:45Speaker 05

  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.

• 20:11Daniel Whiteson?

  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?

• 20:23Speaker 04

  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.

• 20:43Kelly Weinersmith?

  I mean, I think, 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 a, like, 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.

• 21:13Speaker 04

  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.

• 21:23Kelly Weinersmith?

  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.

• 21:39Daniel Whiteson?

  Well, we use music all the time in storytelling in movies, right? The background music tells you how to feel. Is somebody gonna jump out of the wall? Is this a good moment? But I've never seen that done like, in a science talk. Should I have like, a background music during my presentation, like, "This was a really tricky bit, and then we made it work."

• 21:57Speaker 04

  When the guy who was wrong, you put up his picture, and then you do the mean music?

• 22:03Daniel Whiteson?

  Wah, wah, wah.

• 22:05Kelly Weinersmith?

  Yes. My colleague who disagrees.

• 22:16Kelly Weinersmith?

  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.

• 22:29Daniel Whiteson?

  Yes, thank you very much. Let's send this back over to Max to hear his reaction to our reactions to his music.

• 22:35Speaker 05

  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

• 23:17Speaker 05

  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, uh, quantum fields, I was, um, playing like a low and a high, an E and a G. And I know I was doing some hammer ons, like the ripples, um, 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, um, having

• 24:00Speaker 05

  the high harmonics is like the actual, you know, matter we see and experience. So I do want to thank Daniel again for having me be a part of this. Uh, science and math and philosophy have been main drivers of my creative writing and music and my writing lyrics and, and poetry and everything like that. So, um, it was really neat to be a part of this and, uh, to see actual results and to see what, um, people could or could not get out of it. So thanks again, guys.

• 24:38Speaker 01

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• 25:09Daniel Whiteson?

  Hey, I'm Nile Rodgers, producer, songwriter, guitarist, and co-founder of the group Sheik. A great song has a way of defining a moment, a moment of joy, heartbreak, or anything in between.

• 25:26Daniel Whiteson?

  This fall, I'll be driving across the country, dropping in on some of the coolest, most fascinating artists working today. We'll go deep into their lives and careers and hear what it was like before the moment that made them. From hitmakers like Miguel. That last year, finishing that record was the hardest experience of my life. Regardless of how everyone else buys into this, I believe in this and I'm gonna push. To rising stars like Alex Warren. You know, a song is a story and the verse is setting the scene. And for me at least, it's allowing me to be personal and vulnerable with the audience, whether it's about my wife and I'm being vulnerable about her, or it's about, you know, my parents and I'm being vulnerable to them.

• 26:11Daniel Whiteson?

  And it's almost like a cinematic piece in a way where each song tells that beautiful story. It's gonna be one hell of a trip. Experience Before the Moment, a Lincoln original series on the iHeartRadio app, YouTube, or wherever you get your podcasts. This January, bare knuckle fighting championship takes over the ocean. The inaugural Brews Cruise sails from Miami to the Bahamas aboard the Norwegian Jewel. Three straight days with pool decked bare knuckle fights in the Caribbean. Mess of parties, beach events, DJs, cigars, tequila tastings, and nonstop action. The lineup reveals coming soon. Cabins are disappearing fast and the prices won't stay this low.

• 26:52Daniel Whiteson?

  Reserve your spot with just $200 down at B K F S E A dot com.

• 27:09Daniel Whiteson?

  All right, we are back and we are done playing games and adjudicating disputes between the Wiener Smiths. We are ready to get down to some serious science.

• 27:18Kelly Weinersmith?

  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.

• 27:30Speaker 04

  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 am. 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? And 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.

• 28:05Kelly Weinersmith?

  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.

• 28:17Daniel Whiteson?

  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.

• 28:34Kelly Weinersmith?

  Yeah. All right. So let's, let's jump in. What is temperature?

• 28:37Daniel Whiteson?

  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. 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 is what we call sort of the

• 29:20Daniel Whiteson?

  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.

• 29:53Kelly Weinersmith?

  But what is it really measuring? It's just the rate at which it makes mercury expand? Or yeah, what are, what are we really measuring when we say we're measuring that kind of temperature?

• 30:03Daniel Whiteson?

  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 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 mercury thermometer and alcohol thermometer who are both calibrated

• 30:44Daniel Whiteson?

  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 a very satisfying, but it's actually the most intuitive and useful definition of temperature.

• 31:03Kelly Weinersmith?

  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?

• 31:12Daniel Whiteson?

  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.

• 31:58Kelly Weinersmith?

  No, but so 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?

• 32:09Daniel Whiteson?

  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.

• 32:48Kelly Weinersmith?

  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. Cause the thermometer one doesn't even seem like a definition. It's just a like, it's a way you measure a thing.

• 33:17Daniel Whiteson?

  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?

• 34:01Kelly Weinersmith?

  All right. And Mark is an extreme sort of person, and that is what his question was about. So.

• 34:06Daniel Whiteson?

  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, one with high temperature, gains few new arrangements per unit of energy. So it defines temperature as this relationship between entropy and energy.

• 34:32Daniel Whiteson?

  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. 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.

• 35:00Kelly Weinersmith?

  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.

• 35:10Daniel Whiteson?

  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 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.

• 35:51Kelly Weinersmith?

  Yeah, I'm having fun already. So how hot can things get, Daniel? What's the hottest thing we know about?

• 35:57Daniel Whiteson?

  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 body is 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.

• 36:20Kelly Weinersmith?

  Wow, wow.

• 36:21Daniel Whiteson?

  All right, so that gets pretty warm. The average daytime temperature on the moon is 100 C.

• 36:26Kelly Weinersmith?

  Wow.

• 36:27Daniel Whiteson?

  So like, yes, pretty toasty.

• 36:29Kelly Weinersmith?

  It's not going to be fun to live on the moon.

• 36:31Daniel Whiteson?

  The hottest temperature survived by any living thing, a tardigrade, is 151 C. Those guys are tough.

• 36:39Kelly Weinersmith?

  They're tough. I'm gonna 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.

• 36:49Daniel Whiteson?

  Right.

• 36:49Kelly Weinersmith?

  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.

• 36:57Daniel Whiteson?

  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.

• 37:09Kelly Weinersmith?

  Oh, wow.

• 37:09Daniel Whiteson?

  Wow.

• 37:10Kelly Weinersmith?

  Yeah, holy cow.

• 37:11Daniel Whiteson?

  A typical wood burning fire is about 1,000 C.

• 37:14Kelly Weinersmith?

  Okay.

• 37:15Daniel Whiteson?

  Lava that you can like, visit in Hawaii, though don't dip your feet into it, is 1,200 C.

• 37:20Kelly Weinersmith?

  Wow, okay.

• 37:21Daniel Whiteson?

  The surface of the sun gets up to about 5,500.

• 37:25Kelly Weinersmith?

  Wow, okay.

• 37:26Daniel Whiteson?

  The core of the earth is at 6,000. So we're getting really, really hot here.

• 37:31Kelly Weinersmith?

  Yeah.

• 37:31Daniel Whiteson?

  But even in our atmosphere, we have hotter things, like a lightning bolt is very briefly 28,000 Kelvin.

• 37:38Kelly Weinersmith?

  Wow.

• 37:38Daniel Whiteson?

  Which is very close to 28,000 C.

• 37:40Kelly Weinersmith?

  That is like, really even more amazing that people ever survive. Holy cow, okay.

• 37:47Daniel Whiteson?

  The corona of the sun is much hotter than the actual surface of the sun. It has plasma at around a million C.

• 37:54Kelly Weinersmith?

  Wow, I wouldn't have guessed the corona was gonna be hotter than the surface.

• 37:58Daniel Whiteson?

  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.

• 38:08Kelly Weinersmith?

  Wow.

• 38:09Daniel Whiteson?

  Gas coming out of a supernova is like 50 million C.

• 38:12Kelly Weinersmith?

  Oh, my gosh, okay.

• 38:14Daniel Whiteson?

  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 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.

• 38:41Kelly Weinersmith?

  I would have guessed it would be really cold out there.

• 38:44Daniel Whiteson?

  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?

• 39:21Kelly Weinersmith?

  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?

• 39:36Daniel Whiteson?

  From a biological point of view, I suppose.

• 39:41Daniel Whiteson?

  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.

• 39:49Kelly Weinersmith?

  Wow, okay.

• 39:51Daniel Whiteson?

  It's confusing, right?

• 39:52Kelly Weinersmith?

  Yeah.

• 39:52Daniel Whiteson?

  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.

• 40:07Kelly Weinersmith?

  What?

• 40:08Daniel Whiteson?

  And this is just gravitational friction. This is spaghettification. This is tidal forces from the black hole heating up gas in the accretion disk.

• 40:15Kelly Weinersmith?

  Crazy.

• 40:16Daniel Whiteson?

  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 C. So these extreme temperatures can be reached even here on Earth.

• 40:52Kelly Weinersmith?

  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.

• 41:01Daniel Whiteson?

  Yeah, exactly. At the LHC, we mostly collide protons and protons.

• 41:05Kelly Weinersmith?

  Okay.

• 41:05Daniel Whiteson?

  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.

• 41:17Kelly Weinersmith?

  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?

• 41:22Daniel Whiteson?

  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.

• 41:34Kelly Weinersmith?

  Oh, that doesn't make it sound like a safe place to work when you put it that way.

• 41:39Daniel Whiteson?

  It's 100 meters underground. There's plenty of shielding.

• 41:41Kelly Weinersmith?

  Okay.

• 41:41Daniel Whiteson?

  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. 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

• 42:22Daniel Whiteson?

  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. 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 while using only general relativity and ignoring quantum mechanics, or saying that the heart of a black hole is a singularity

• 43:06Daniel Whiteson?

  which ignores quantum mechanics. You can't just ignore one tenet of modern physics when you're in a place where you know it's relevant.

• 43:13Kelly Weinersmith?

  How many physicists have used absolute hot as a pick-up line?

• 43:19Kelly Weinersmith?

  And have failed to get a date. That's what I need to know.

• 43:24Daniel Whiteson?

  All of them.

• 43:25Kelly Weinersmith?

  Oh, no.

• 43:27Kelly Weinersmith?

  Okay, so one of the theories has an absolute hot, but the other ones don't. Is that right?

• 43:34Daniel Whiteson?

  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? 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 Hagedorn temperature, which is at just about a trillion or two Kelvin.

• 44:14Kelly Weinersmith?

  Wow.

• 44:14Daniel Whiteson?

  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.

• 44:30Kelly Weinersmith?

  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?

• 44:40Daniel Whiteson?

  It's like everything, it has a range in which you should apply it, right?

• 44:44Kelly Weinersmith?

  Okay.

• 44:44Daniel Whiteson?

  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.

• 45:06Kelly Weinersmith?

  Got it. Okay, it depends. That works in physics, too.

• 45:12Daniel Whiteson?

  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.

• 45:31Kelly Weinersmith?

  Got it. All right, well, let's see what Mark has to say about your absolute hot answer.

• 45:37Daniel Whiteson?

  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. Love the show and thanks again. Bye.

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• 48:31Kelly Weinersmith?

  All right, and we're back and we have a question from another Daniel. And like D K E U, Daniel, not a big fan of biology.

• 48:43Daniel Whiteson?

  Not why I picked this question, not why at all.

• 48:46Kelly Weinersmith?

  All right, all right.

• 48:47Daniel Whiteson?

  I picked this question because I love the nickname Glowey Dan. So let's hear Glowey 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 Glowey Dan amongst my rock friends. This leads us into my question for you guys today.

• 49:32Daniel Whiteson?

  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.

• 49:45Kelly Weinersmith?

  All right, Glowey 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.

• 50:00Daniel Whiteson?

  I think Glowey Dan is disengaging in the long tradition of D K E U good natured ribbing because he clearly is curious about biology.

• 50:08Kelly Weinersmith?

  Yes, well, and D K E U appreciates honesty, so it is all good.

• 50:14Kelly Weinersmith?

  You like what you like, glowy Dan.

• 50:15Daniel Whiteson?

  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.

• 50:42Kelly Weinersmith?

  Enlighten me.

• 50:47Kelly Weinersmith?

  I'm on fire today.

• 50:48Daniel Whiteson?

  Your jokes are brilliant.

• 50:49Kelly Weinersmith?

  I'm at absolute hot today.

• 50:53Daniel Whiteson?

  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.

• 51:34Kelly Weinersmith?

  Okay.

• 51:34Daniel Whiteson?

  Cool.

• 51:34Kelly Weinersmith?

  Yep, we're cool.

• 51:35Daniel Whiteson?

  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 has too much energy, it can't eat it because it would put it between steps. And 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.

• 52:17Kelly Weinersmith?

  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?

• 52:24Daniel Whiteson?

  That's right. That's transparency, basically.

• 52:27Kelly Weinersmith?

  Okay.

• 52:27Daniel Whiteson?

  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. 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 could say, oh, look, it's hydrogen. Oh, there's 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.

• 53:08Daniel Whiteson?

  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.

• 53:21Kelly Weinersmith?

  Awesome.

• 53:22Daniel Whiteson?

  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.

• 53:55Kelly Weinersmith?

  Awesome.

• 53:55Daniel Whiteson?

  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.

• 54:04Kelly Weinersmith?

  And does it emit at just like a constant rate? Or does something have to happen to get it to emit a photon?

• 54:12Daniel Whiteson?

  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.

• 54:46Kelly Weinersmith?

  Okay.

• 54:47Daniel Whiteson?

  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 hole. It's going to be emitting a smooth spectrum, but individual atoms emitted specific frequencies.

• 55:00Kelly Weinersmith?

  Okay.

• 55:01Daniel Whiteson?

  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 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.

• 55:35Kelly Weinersmith?

  What?

• 55:35Daniel Whiteson?

  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.

• 56:03Kelly Weinersmith?

  Okay.

• 56:03Daniel Whiteson?

  So it absorbs a high-energy photon and emits a lower-energy photon. Because some of that energy is lost to heat. Now that photon is invisible. So effectively, the rock has transformed an invisible ultraviolet high-energy photon to a visible, lower-energy photon.

• 56:21Kelly Weinersmith?

  Whoa, that's pretty cool.

• 56:24Daniel Whiteson?

  It's pretty cool. Rocks are just out there like changing photons from invisible. Visible to visible.

• 56:29Kelly Weinersmith?

  Wow.

• 56:29Daniel Whiteson?

  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.

• 56:52Kelly Weinersmith?

  That's awesome.

• 56:53Daniel Whiteson?

  Yeah.

• 56:54Kelly Weinersmith?

  I was gonna make a joke about people with glasses not usually being invited to raves, but, but surely there are cool people with glasses who are just not me.

• 57:01Daniel Whiteson?

  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. Fluoride glows blue violet or green. There's willamite that glows really bright green. Opal and highlight also glow in the green. There's whole webpages where you can see like glowy rocks. It's really, really cool.

• 57:26Kelly Weinersmith?

  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.

• 57:33Daniel Whiteson?

  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 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.

• 57:52Kelly Weinersmith?

  I don't think it's well understood either. Wait, and so this is not a thing that you can run out of, right? Cause your electrons will do this over and over and over and over and over again forever. Is that right?

• 58:01Daniel Whiteson?

  That's right.

• 58:02Kelly Weinersmith?

  Okay.

• 58:02Daniel Whiteson?

  Exactly. They have this beta carbolene in their cuticles, which does this. And it's not like it gets used up, you know? You are inputting new energy every time you do it. But if you turn off the ultraviolet light, it will stop.

• 58:15Kelly Weinersmith?

  Okay.

• 58:16Daniel Whiteson?

  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 at 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.

• 59:01Daniel Whiteson?

  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.

• 59:24Kelly Weinersmith?

  Where do we see that in nature? So we've talked about glow in the dark stickers and watches.

• 59:29Daniel Whiteson?

  It's more rare. There are some like deep sea unearthly 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 who 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 like biological reason for this.

• 59:54Kelly Weinersmith?

  Yeah, it seems like if it is useful, but it only lasts for a little while.

• 59:59Daniel Whiteson?

  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.

• 1:00:13Kelly Weinersmith?

  We should have an episode on that. And I want to do an episode on iridescence. Cause 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?

• 1:00:25Daniel Whiteson?

  It's probably for some horrifying reason. It's going to give me nightmares.

• 1:00:28Kelly Weinersmith?

  I hope so.

• 1:00:31Daniel Whiteson?

  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

• 1:01:13Daniel Whiteson?

  fluoresce, while some of those that do not have very similar chemical makeup and crystal structure. I'll have to unearth some more of that groundbreaking geology research to delve even deeper into the subject. Thanks again.

• 1:01:26Kelly Weinersmith?

  Well, thank you to everyone who participated today and sent us their questions. We hope you'll send us your questions too at [email protected]. We love hearing from y'all.

• 1:01:36Daniel Whiteson?

  We really, really do. Please write to us. It makes our day.

• 1:01:46Daniel Whiteson?

  Thanks, 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.

• 1:01:54Kelly Weinersmith?

  Daniel and Kelly's Extraordinary Universe is edited by the amazing Matt Kesselman.

• 1:01:58Daniel Whiteson?

  He really is a wizard. You can also find us online on Blue Sky, Instagram, and X, D and K Universe. Come engage with us.

• 1:02:08Kelly Weinersmith?

  You can email us at [email protected]. We really do want to hear from you.

• 1:02:14Daniel Whiteson?

  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.

• 1:02:25Kelly Weinersmith?

  And we also have the most amazing moderators. This is an iHeart Podcast. Thanks for joining us.

• 1:02:34Daniel Whiteson?

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