WEBVTT - What is negative temperature? 0:00:08.560 --> 0:00:11.840 Hey, Jorge, do you have any concerns about raising your 0:00:11.920 --> 0:00:15.880 kids in southern California? I don't. It's pretty great out here, 0:00:16.239 --> 0:00:18.280 although I do feel like they miss out on some 0:00:18.320 --> 0:00:21.720 things they do. What's missing in southern California? Well, definitely 0:00:21.720 --> 0:00:25.720 not plastic surgery, we got that covered for sure. But 0:00:25.800 --> 0:00:27.800 you know, there are experiences kids growing up here that 0:00:27.840 --> 0:00:29.960 they don't get that other kids do. Yeah, like what 0:00:30.080 --> 0:00:33.600 you know, like experiencing winter, snowfall. I mean, I guess 0:00:33.640 --> 0:00:36.240 I miss winter, but I wouldn't say I'm missing winter. 0:00:36.400 --> 0:00:39.320 Would you say, you know, misshoveling snow, putting on multiple 0:00:39.360 --> 0:00:42.159 layers of clothes, multiple layers of clothes. What does that 0:00:42.200 --> 0:00:45.360 even mean? Man? If you're like layers of clothes, what 0:00:45.400 --> 0:00:48.120 does that even mean? I'm recording this naked. You don't 0:00:48.120 --> 0:00:51.240 think kids should know about winter? No, I'm definitely anti winter. 0:00:51.400 --> 0:00:53.880 That's when I'm teaching my kids about winter avoided at 0:00:53.920 --> 0:00:56.600 all costs. But what if they don't? What if they 0:00:56.680 --> 0:00:58.600 end up living there and then are you going to 0:00:58.640 --> 0:01:01.120 go visit them? Depends how cute grandkids are. I guess 0:01:01.280 --> 0:01:19.200 that's pretty coold. Daniela, Hi, I'm or handmade cartoonists and 0:01:19.240 --> 0:01:22.520 the co author of Frequently Asked Questions about the Universe. Hi, 0:01:22.640 --> 0:01:25.399 I'm Daniel. I'm a physics professor at u C Irvine 0:01:25.480 --> 0:01:29.360 and a high energy physicist, and I definitely prefer high 0:01:29.480 --> 0:01:34.440 energy air molecules. You don't like low energy air? No? 0:01:34.680 --> 0:01:37.000 I like it hot outside. You know, when I moved 0:01:37.040 --> 0:01:40.480 to California, I discovered that sunshine makes me happy. Do 0:01:40.560 --> 0:01:42.720 you think maybe that's your upbringing? You grew up in 0:01:42.760 --> 0:01:45.840 New Mexico, right, and then you went to school in Texas. 0:01:46.200 --> 0:01:48.200 I did. I'm a desert person, but you know, New 0:01:48.240 --> 0:01:51.440 Mexico was pretty cold. Los Almos is seven thousand feet 0:01:51.480 --> 0:01:53.880 in elevation, and so we got a lot of snow. 0:01:54.240 --> 0:01:58.240 I remember one year we got fifty five inches overnight. 0:01:58.720 --> 0:02:01.600 I was not a happy camp Well, so you'm are 0:02:01.640 --> 0:02:05.400 of a desert person or a dessert person? Dessert in 0:02:05.440 --> 0:02:07.840 the desert, and do you like your desserts hot or cold? 0:02:08.160 --> 0:02:10.960 I like them both. I'm not picky. But anyways, welcome 0:02:11.000 --> 0:02:13.480 to our podcast, Daniel and Jorge Explained the Universe, a 0:02:13.520 --> 0:02:16.000 production of My Heart Radio in which we are hot 0:02:16.000 --> 0:02:18.240 on the mysteries of the universe and we think that 0:02:18.320 --> 0:02:21.480 everything about it is pretty cool. We want to understand 0:02:21.560 --> 0:02:24.600 how the universe works, what the rules are that govern 0:02:24.720 --> 0:02:28.600 how it operates, and whether or not we can understand them. 0:02:28.720 --> 0:02:31.480 We think one of the most fundamental questions about being alive, 0:02:31.560 --> 0:02:34.840 about being human, is why are things the way that 0:02:34.880 --> 0:02:38.600 they are? And what else could happen in this universe? 0:02:38.880 --> 0:02:40.880 That's right. We don't give a cold shoulder to the 0:02:40.960 --> 0:02:43.760 big questions out there because it is a wonderful universe 0:02:43.800 --> 0:02:46.120 full of amazing things, and sometimes we wish we could 0:02:46.240 --> 0:02:48.560 freeze it all so we can study it a little 0:02:48.560 --> 0:02:51.520 bit better. That's right. These are hot topics for us 0:02:51.560 --> 0:02:54.800 to understand, and as we look out around us in 0:02:54.840 --> 0:02:57.560 the universe, we want to understand why some things are 0:02:57.600 --> 0:02:59.600 the way they are, Why some things are hot, why 0:02:59.680 --> 0:03:02.440 somethings are cold, Why hot things tend to heat up 0:03:02.480 --> 0:03:06.399 cold things, Why cold things tend to cool down hot things. Yeah, 0:03:06.400 --> 0:03:09.160 because we want people to warm up to the extremes 0:03:09.160 --> 0:03:11.120 of the universe and all of the amazing things that 0:03:11.160 --> 0:03:14.000 can happen and many different temperatures out there. The universe 0:03:14.040 --> 0:03:17.959 has a pretty wide range from super hot explosive supernovas 0:03:18.000 --> 0:03:21.760 and hearts of neutron stars really vast voids of empty 0:03:21.800 --> 0:03:25.560 space exactly. And one of the best ways to understand 0:03:25.680 --> 0:03:28.560 how the universe works, to make it reveal it is 0:03:28.760 --> 0:03:32.160 underlying truth, the rules that governed it, is to look 0:03:32.200 --> 0:03:35.120 at the extremes to find out what is the most 0:03:35.240 --> 0:03:38.320 of something that can happen. How bright can things get, 0:03:38.400 --> 0:03:41.680 how fast can this spen, how empty can space be, 0:03:41.840 --> 0:03:45.200 how dense can matter be? So on this podcast, we'd 0:03:45.200 --> 0:03:48.160 like to explore those extremes because we think those are 0:03:48.160 --> 0:03:51.200 the places that the universe is cornered, is forced to 0:03:51.240 --> 0:03:54.360 tell us something about how the rules work. These are 0:03:54.400 --> 0:03:57.120 the edge cases, the ones where we hope the truth 0:03:57.160 --> 0:03:59.360 will reveal itself. Yeah, we have a whole series of 0:03:59.400 --> 0:04:03.000 episodes where talk about extreme things in the universe, the coldest, 0:04:03.000 --> 0:04:05.200 the brightest, the biggest. Daniel have we done the most 0:04:05.240 --> 0:04:07.400 delicious thing in the universe yet? That's just been a 0:04:07.440 --> 0:04:11.080 side research project of mine for a long time. You're 0:04:11.120 --> 0:04:14.640 just gathering data more and more every year. Yeah, you know, 0:04:14.760 --> 0:04:18.160 I'm not trying to mind my personal experience for podcast episodes, 0:04:18.360 --> 0:04:20.839 but that's a good idea. Or maybe the most delicious 0:04:20.880 --> 0:04:23.799 thing in the universe is the universe. It's a pretty 0:04:23.839 --> 0:04:26.360 tasty place. Well, the universe is the only thing in 0:04:26.400 --> 0:04:29.200 the universe, right, so it's both the most delicious and 0:04:29.240 --> 0:04:32.159 the most disgusting thing to eat in the universe. Also 0:04:32.200 --> 0:04:35.279 the most filling, I guess. But we have done a 0:04:35.279 --> 0:04:38.320 whole series of episodes on extremes and we encourage you 0:04:38.360 --> 0:04:40.159 to go back through the archive and check them out. 0:04:40.200 --> 0:04:41.839 But we did do those sort of the hottest and 0:04:41.920 --> 0:04:44.359 coldest things in the universe. Those are two episodes you 0:04:44.400 --> 0:04:47.760 can download, right, Yeah, that's right. And we recently organized 0:04:47.800 --> 0:04:51.000 a curated list of all of our episodes on our website. 0:04:51.080 --> 0:04:54.080 Listeners have been asking for us to sort the episodes 0:04:54.240 --> 0:04:56.800 by topic, and so now we have them grouped by 0:04:56.920 --> 0:05:01.400 cosmology or particle physics, or science fiction or extreme universe. 0:05:01.800 --> 0:05:05.000 So go to our website Daniel and Jorge dot com 0:05:05.200 --> 0:05:08.039 and look at the list of episodes by topic. Yeah, 0:05:08.040 --> 0:05:09.560 so it's kind of like a menu. So if you're 0:05:09.600 --> 0:05:11.039 feeling like, hey, you know, I could use a little 0:05:11.080 --> 0:05:13.640 cosmology today, or I could use a little you know, 0:05:13.839 --> 0:05:16.960 fundamental particles with my meal, you can go and help yourself. 0:05:17.240 --> 0:05:19.640 That's right, Order up a side dish of black holes. 0:05:19.920 --> 0:05:22.520 So we have talked about temperature a lot in this podcast, 0:05:22.600 --> 0:05:25.320 But recently you've got in a few questions about a 0:05:25.400 --> 0:05:28.160 new and interesting topic that's kind of floating out there, 0:05:28.240 --> 0:05:31.560 right exactly, Folks are interested in the extremes of temperature, 0:05:31.640 --> 0:05:34.240 all the way down to absolute zero, or all the 0:05:34.240 --> 0:05:37.560 way up to absolute hot, the hottest that things can 0:05:37.600 --> 0:05:41.159 get in the universe before temperature doesn't even make any sense. 0:05:41.240 --> 0:05:42.800 But over the last year so I've gotten a few 0:05:42.839 --> 0:05:45.320 emails asking me to talk about something that sounds like 0:05:45.360 --> 0:05:48.200 it makes no sense at all, something that has been 0:05:48.200 --> 0:05:51.200 bouncing around on the internet and inspire the curiosity of 0:05:51.240 --> 0:05:53.919 several listeners whether or not it's possible to go even 0:05:54.040 --> 0:05:57.919 below absolute zero. So today on the podcast, we'll be 0:05:57.960 --> 0:06:09.360 asking the question, what is negative temperature? Negative temperature? What now, Daniel, 0:06:09.400 --> 0:06:12.320 is this temperature that is not an optimist or what 0:06:13.120 --> 0:06:15.400 always looks on the dark side of things? Yeah, this 0:06:15.480 --> 0:06:19.279 is grumpy temperature exactly, whatever makes you feel bad. It's 0:06:19.320 --> 0:06:23.360 not how positivemperature. Yeah, this is a weird concept. I guess, well, 0:06:23.400 --> 0:06:25.760 I guess people are familiar with negative temperature, right, Like 0:06:25.839 --> 0:06:28.400 in some places it gets so cold it's like minus 0:06:28.440 --> 0:06:31.760 fifteen degrees, right, yeah, And like negative forty is where 0:06:31.800 --> 0:06:36.000 celsius and fahrenheit meat so on some scales, negative temperature 0:06:36.120 --> 0:06:38.520 is a pretty common experience. But I think people are 0:06:38.560 --> 0:06:43.039 probably thinking about Kelvin. You mean this physical concept is 0:06:43.040 --> 0:06:45.960 more about absolute temperature and whether or not it can 0:06:46.000 --> 0:06:49.120 be negative. Yeah. The Kelvin scale goes from zero, which 0:06:49.160 --> 0:06:51.880 is supposed to be this scenario where nothing is moving 0:06:51.920 --> 0:06:54.880 and everything is basically frozen up to very high values 0:06:54.880 --> 0:06:57.920 when things are wriggling around. So from that perspective, you know, like, 0:06:58.000 --> 0:07:00.800 what does it mean to have negative of temperature? Can 0:07:00.800 --> 0:07:03.919 you move less than not moving at all? Right? That 0:07:04.080 --> 0:07:06.760 is pretty weird. But is that maybe just the scaler thing, 0:07:06.800 --> 0:07:08.960 like we use the wrong scale. But no, because it's 0:07:09.000 --> 0:07:11.760 absolute temperature, right, there are like hard limits or at 0:07:11.840 --> 0:07:14.160 least I thought there were hard limits to absolute temperature 0:07:14.320 --> 0:07:17.360 or the Kelvin scale right zero to infinity kind of 0:07:18.560 --> 0:07:22.040 zero to the plank temperature. Actually, there is this maximum 0:07:22.120 --> 0:07:25.160 temperature beyond which we think that gravity will take over 0:07:25.240 --> 0:07:27.960 in quantum gravity effects will be important And we don't 0:07:27.960 --> 0:07:31.560 even know what temperature means there. Wait, what it's called 0:07:31.640 --> 0:07:38.760 absolute hot? Absolute hot or absolutely hot? Absolute hot is 0:07:38.840 --> 0:07:42.160 absolutely hot? For sure? It sounds like a new vodka brand, 0:07:42.360 --> 0:07:44.760 but it touches on these interesting questions of like what 0:07:45.000 --> 0:07:47.760 is temperature anyway? You know, as human as, we have 0:07:47.880 --> 0:07:51.600 experiences in the world, and then we try to build models, 0:07:51.680 --> 0:07:54.280 physical ideas that describe those things. And then we have 0:07:54.320 --> 0:07:57.119 to find a way to like mathematically express some things 0:07:57.160 --> 0:08:00.560 that we experience temperature or something that's like very tuitive 0:08:00.600 --> 0:08:02.880 to us. But in our physical models we need like 0:08:02.960 --> 0:08:06.480 equations and numbers to describe these things. And sometimes that's 0:08:06.520 --> 0:08:09.840 easy to do, like velocity or location, and sometimes it's 0:08:09.880 --> 0:08:12.000 a little bit fuzzy, and so we're gonna get into 0:08:12.040 --> 0:08:15.960 like what does temperature really mean anyway? Man? Yeah, So 0:08:16.000 --> 0:08:19.080 we have this temperature in the absolute temperature within the 0:08:19.160 --> 0:08:21.760 Kelvin scale, and so for example, like what is room 0:08:21.800 --> 0:08:25.080 temperature in kelvin zero and celsius corresponds to two hundred 0:08:25.160 --> 0:08:29.920 and seventy three in kelvin, So comfortable temperature in celsius 0:08:30.000 --> 0:08:33.600 is like twenty five, which would be like two hundred 0:08:33.760 --> 0:08:37.160 nineties something in kelvin. Okay, so room temperature is two 0:08:37.240 --> 0:08:40.880 hundred ninety eight, let's say in kelvin, and then freezing 0:08:41.120 --> 0:08:44.600 is two d seventy three, And I guess what temperature 0:08:44.640 --> 0:08:48.080 does water boil, so it would be three three, three 0:08:48.120 --> 0:08:50.839 seventy three or a hundred celsius. Okay. So then as 0:08:50.840 --> 0:08:53.120 you start to cool things and make things colder, the 0:08:53.200 --> 0:08:55.200 kelvin goes down and down and down and down. And 0:08:55.240 --> 0:08:57.240 I think we talked about what is the coldest thing? 0:08:57.280 --> 0:08:59.800 We've gotten something here on Earth? Right, Yeah, we have 0:09:00.040 --> 0:09:02.840 on the coldest thing in the universe and the coldest 0:09:02.880 --> 0:09:07.319 thing on Earth. And physicists regularly do experiments with super 0:09:07.400 --> 0:09:11.720 duper cold objects, things that like the micro kelvin temperature 0:09:11.800 --> 0:09:14.440 just about what we thought was the absolute minimum temperature, 0:09:14.480 --> 0:09:17.920 which is actually a tiny little bit above absolute zero, 0:09:18.120 --> 0:09:20.400 that's right. We talked about how the maybe the coldest 0:09:20.400 --> 0:09:22.839 thing in the universe is something you're on Earth that 0:09:22.960 --> 0:09:25.560 scientists have been able to cool down to almost zero 0:09:25.640 --> 0:09:29.920 kelvin zero point zero zero zero zero zero zero one kelvin. 0:09:30.240 --> 0:09:33.079 And so the question is can you actually go below? Right? 0:09:33.160 --> 0:09:36.079 Is there such a thing as negative absolute temperature exactly? 0:09:36.120 --> 0:09:38.760 That is the question today? Or is it even possible? 0:09:38.840 --> 0:09:41.439 I guess? And what are physicists thinking? So as usually 0:09:41.440 --> 0:09:43.559 were wondering how many people out there had thought about 0:09:43.559 --> 0:09:46.960 this question or wondered whether temperature can go negative? And 0:09:47.040 --> 0:09:50.400 so Daniel went out there into the internet or your campus. 0:09:50.640 --> 0:09:54.439 These are Internet answers and thanks again everybody who volunteers 0:09:54.480 --> 0:09:57.040 to answer these weird email the questions. If you'd like 0:09:57.080 --> 0:10:00.600 to receive some strange questions for future podcast as episodes 0:10:00.640 --> 0:10:03.000 in your inbox, please don't be shy or right to 0:10:03.080 --> 0:10:06.360 us two questions at Daniel and Jorge dot com. That's right, 0:10:06.360 --> 0:10:08.400 and you can be as positive or as negative as 0:10:08.400 --> 0:10:10.839 you want in your answers. But think about it for 0:10:10.880 --> 0:10:13.559 a second, right now, do you think absolute temperature can 0:10:13.640 --> 0:10:15.920 be negative? Here's what people had to say. This is 0:10:15.960 --> 0:10:19.400 a loaded question. Um, but if my bank account can 0:10:19.400 --> 0:10:22.120 have a negative balance, so too can a cemometer unless 0:10:22.160 --> 0:10:25.720 it's measuring in kelvin. He never goes Belusira. Well, because 0:10:25.760 --> 0:10:27.880 you're asking this, I'm going to assume that that's what 0:10:27.960 --> 0:10:31.840 the topic is. But right, persons think would be you 0:10:31.880 --> 0:10:35.360 can't you can't have a negative temperature because I'm thinking 0:10:35.400 --> 0:10:37.280 like kelvin, right, I mean, obviously you can have like 0:10:37.280 --> 0:10:39.840 a negative celsius or something, but like you can't have 0:10:39.920 --> 0:10:42.839 like a negative like kelvin amount of temperature. So no, 0:10:43.160 --> 0:10:47.040 I don't think you can. I think it zero Kelvin 0:10:47.559 --> 0:10:52.040 the molecules actually stopped moving. Not molecules, I mean particles 0:10:52.080 --> 0:10:55.240 actually stopped moving as far as I know, probably wrong, 0:10:55.320 --> 0:10:59.280 but that's my understanding. Well, on the Celsius and Fahrenheit scales, 0:10:59.400 --> 0:11:02.080 you can have a nick it of value for your temperature, 0:11:02.240 --> 0:11:07.960 but on the Kelvin or ranking scales, with positive temperature 0:11:08.000 --> 0:11:12.080 being amount of energy and zero absolute zero being um 0:11:12.880 --> 0:11:16.840 no heat energy. In that case, for a negative temperature, 0:11:17.480 --> 0:11:20.400 you would have to have this um. You'd be like 0:11:20.440 --> 0:11:24.760 a black hole of energy, or just the potential to 0:11:24.840 --> 0:11:28.800 absorb energy from somewhere else. But maybe you don't actually 0:11:28.840 --> 0:11:33.280 exist and you're just something mathematicians use. Like I my 0:11:33.440 --> 0:11:37.360 first impression would be no, I don't think you can, 0:11:37.880 --> 0:11:42.000 since if your particles are studic, then your temperature would 0:11:42.000 --> 0:11:46.440 be absolute zero. I don't I don't know. Maybe unless 0:11:46.760 --> 0:11:50.880 the particles are moving back in time some way, then 0:11:51.160 --> 0:11:54.760 you could have negative temperature. I really don't know. I'm 0:11:54.760 --> 0:11:58.959 making this up as I go, Daniel, I think you 0:11:59.080 --> 0:12:02.320 forgot about you how you moved in California, and you 0:12:02.400 --> 0:12:07.240 forgot that you can go negative during the year. I 0:12:07.320 --> 0:12:10.120 do not believe it's possible to have a negative temperature. 0:12:10.160 --> 0:12:13.360 There is a reason why absolute zero is called. Absolute 0:12:14.240 --> 0:12:16.520 temperature is the sum of the kinetic energy of the 0:12:16.600 --> 0:12:19.640 particles of the objects being measured. And I don't believe 0:12:19.679 --> 0:12:24.320 something can have negative motion unless there is some oddity 0:12:24.360 --> 0:12:27.920 and the fact that measuring motion requires the existence of 0:12:27.960 --> 0:12:31.319 a reference point, and with a boundless, infinite universe, where 0:12:31.480 --> 0:12:35.600 is that absolute reference point? But otherwise there is no 0:12:35.640 --> 0:12:38.720 possibility for negative temperature. I'm going to go with no. 0:12:39.240 --> 0:12:42.160 And also it depends on what context we're talking about 0:12:42.240 --> 0:12:45.280 this in. For example, if you're dead, I think your 0:12:45.320 --> 0:12:48.240 temperature can be negative because you'd be frozen in a 0:12:48.280 --> 0:12:52.760 refrigerator or something. But as a living human being, having 0:12:52.760 --> 0:12:55.440 a negative temperature I think would be impossible because we 0:12:55.520 --> 0:12:59.439 are made up of water and that water would freeze 0:13:00.320 --> 0:13:03.000 if it was a negative temperature, meaning we wouldn't be 0:13:03.000 --> 0:13:05.760 able to be alive. Um, blood would not be able 0:13:05.800 --> 0:13:09.440 to move, our heart couldn't beat, and things like that. Mmm. Okay, 0:13:09.720 --> 0:13:14.160 a lot of negative responses, not a lot of positive yeses. No, 0:13:14.360 --> 0:13:16.760 not a lot of believers in negative temperature, but some 0:13:16.880 --> 0:13:19.840 good creative answers you think they should have been more positive, 0:13:19.920 --> 0:13:23.040 like yes, maybe it can. I believe in your universe. 0:13:23.400 --> 0:13:26.400 You're beautiful. I think that they should have had more 0:13:26.480 --> 0:13:29.640 faith in physicists to break the rules and think outside 0:13:29.679 --> 0:13:32.520 the bounds of what is normally possible. It should have 0:13:32.520 --> 0:13:35.480 been more temperature positive that it can be negative exactly 0:13:35.520 --> 0:13:37.360 because you know, the history of physics is littered with 0:13:37.440 --> 0:13:40.600 examples of doing things that we thought were once impossible, 0:13:40.679 --> 0:13:43.079 of discovering the universe works in a way different from 0:13:43.120 --> 0:13:46.200 the way that we had imagined, of breaking the rules 0:13:46.240 --> 0:13:49.000 that we once thought were iron clad. Are you saying 0:13:49.040 --> 0:13:52.000 physicists just basically do things and they're like, you have 0:13:52.080 --> 0:13:54.160 some kind of chip on your shoulder, Hey, Daniel, I 0:13:54.240 --> 0:13:57.160 dare you to understand the universe. I think it's exciting 0:13:57.200 --> 0:14:01.600 to imagine what's impossible might be possible, to think about it. 0:14:01.600 --> 0:14:04.160 You know, that's the job of science fiction authors to think, 0:14:04.520 --> 0:14:07.160 could we get to a nearby star faster than the 0:14:07.160 --> 0:14:09.720 speed of light? How might that be possible. It's also 0:14:09.760 --> 0:14:12.040 the job of physicists to think, like, what are the 0:14:12.120 --> 0:14:14.800 actual rules of the universe? Which ones can be broken, 0:14:14.840 --> 0:14:17.360 which ones can be bent, which ones seem like rules 0:14:17.600 --> 0:14:21.280 but only in certain circumstances, and actually aren't fundamentally rules 0:14:21.320 --> 0:14:23.200 at all, although I guess you have to be careful, right, 0:14:23.360 --> 0:14:25.840 Like you don't want to dare a physicist to find 0:14:25.840 --> 0:14:27.880 a way to blow up the world or create a 0:14:27.920 --> 0:14:31.240 black hole in the center of the of our planet. Yeah, 0:14:31.280 --> 0:14:35.320 I think we've tried that already. Actually, I see you 0:14:35.400 --> 0:14:38.160 were there and that what. I guess you gave up? 0:14:38.640 --> 0:14:41.200 You I hope, well, I hope or failed. No, we 0:14:41.240 --> 0:14:43.240 are still trying to create black holes. It's a large 0:14:43.240 --> 0:14:45.800 hager on collider. In fact, we recently turned the collider 0:14:45.880 --> 0:14:48.320 back on a few weeks ago. Oh man, you're not 0:14:48.360 --> 0:14:51.120 gonna give up, are you? You know, just after we 0:14:51.200 --> 0:14:54.080 turned on the collider, the government of the UK collapsed 0:14:54.080 --> 0:14:57.440 and Boris Johnson was forced to resign as Prime minister. Really, 0:14:57.440 --> 0:15:00.440 do you think there's a correlation there. There's definitely a correlation. 0:15:00.440 --> 0:15:02.400 I don't know about causation. We'll have to turn the 0:15:02.400 --> 0:15:04.000 thing on and off a few times and see what 0:15:04.080 --> 0:15:06.400 other governments fall. I think there are other things going 0:15:06.440 --> 0:15:09.040 on besides you switching on the collider, just you know, 0:15:09.400 --> 0:15:12.080 a few things here and on on our world stage. 0:15:12.200 --> 0:15:13.960 I don't know. I don't keep up with politics, man, 0:15:14.080 --> 0:15:17.200 So I see you just flip on the switch. All right, Well, 0:15:17.240 --> 0:15:21.440 this is a fascinating question. Can absolutely temperature go negative? 0:15:21.600 --> 0:15:25.320 Can it be minus something degrees absolute? And so Daniel, 0:15:25.680 --> 0:15:28.280 that is a weird phrase, negative temperature. What does it mean? 0:15:28.400 --> 0:15:31.040 It all comes down to what we mean by temperature. 0:15:31.160 --> 0:15:33.920 And normally when we talk about temperature, we're talking about 0:15:33.920 --> 0:15:36.400 how hot something feels. You know, you touch something it 0:15:36.440 --> 0:15:39.120 feels hot, you touch something it feels cold. You have 0:15:39.160 --> 0:15:42.120 a sense for whether it's hot or cold outside. That's 0:15:42.160 --> 0:15:45.800 about like the energy flow between you and some other object. 0:15:45.920 --> 0:15:48.080 But we also have a concept for like what's going 0:15:48.120 --> 0:15:52.840 on inside, like micro physical picture of why some things 0:15:52.880 --> 0:15:55.200 are hot and some things are cold. What's going on 0:15:55.320 --> 0:15:58.400 inside something that's hot that makes it different from something 0:15:58.640 --> 0:16:01.680 that's cold. And this eco physical picture mostly is about 0:16:01.720 --> 0:16:05.320 like how much the atoms inside are moving, Like if 0:16:05.320 --> 0:16:07.560 they're zooming around a lot and jiggling a lot, if 0:16:07.600 --> 0:16:09.480 they have a lot of energy, then the thing they 0:16:09.520 --> 0:16:12.600 make up feels hot. If they're mostly not moving, they're 0:16:12.600 --> 0:16:15.360 not jiggling or whizzing around, then the thing they make 0:16:15.440 --> 0:16:19.360 up feels cold. Right, And we have ways to measure that, right, 0:16:19.440 --> 0:16:23.040 like we have devices that called thermometer, as you probably 0:16:23.040 --> 0:16:26.320 know that. Can I tell you a little bit about 0:16:26.360 --> 0:16:29.400 that kind of internal moving around of things. Yeah, And 0:16:29.400 --> 0:16:32.120 what's interesting is that thermometer is measure things that are 0:16:32.160 --> 0:16:37.720 related to temperature. None of them actually directly measure temperature itself. Wait, 0:16:37.760 --> 0:16:41.800 what a thermometer does not meter metter temperature? I know 0:16:41.880 --> 0:16:45.160 it's called a thermometer, but it doesn't actually meter thermo. 0:16:45.200 --> 0:16:47.920 I mean, take, for example, the classic bulb thermometer. What 0:16:48.080 --> 0:16:50.000 is it. It's a little pot of liquid with a 0:16:50.080 --> 0:16:52.600 tube above it. And what it's really measuring is the 0:16:52.680 --> 0:16:55.560 volume of the liquid because there's a relationship. As the 0:16:55.640 --> 0:16:59.680 liquid gets hotter, its volume increases and so it climbs 0:16:59.760 --> 0:17:03.400 up that cylinder and so you're not directly measuring temperature. 0:17:03.440 --> 0:17:06.199 You're measuring the volume, which is you think related to 0:17:06.359 --> 0:17:09.280 the temperature. Right. It's like those glass tubes with the 0:17:09.320 --> 0:17:12.080 little red line. What's actually happening is that when you 0:17:12.320 --> 0:17:15.000 stick it into like let's say, boiling water, it heats 0:17:15.040 --> 0:17:17.119 up the little red liquid and it expands. And then 0:17:17.240 --> 0:17:20.000 the more it expands, I guess, the hotter the water was. 0:17:20.080 --> 0:17:22.399 But you're saying it's not actually measuring the temperature of 0:17:22.440 --> 0:17:25.480 the water. No, it's measuring the volume of that little 0:17:25.480 --> 0:17:28.600 red liquid inside the thermometer, which of course is related 0:17:28.640 --> 0:17:31.560 to temperature, but it's indirect, right. There are other ways 0:17:31.600 --> 0:17:34.199 that are also indirect that you can measure temperature, like 0:17:34.280 --> 0:17:36.400 the thermostat in your house, the one that decides whether 0:17:36.440 --> 0:17:38.840 or not to turn on the air conditioning, that doesn't 0:17:38.880 --> 0:17:41.160 have a little ball of liquid in it. It has 0:17:41.320 --> 0:17:45.119 something called a bimetallic strip. It has two kinds of 0:17:45.160 --> 0:17:48.199 metal bonded together, and the two kinds of metal have 0:17:48.320 --> 0:17:51.920 different properties. One of them expands faster when the heat 0:17:52.000 --> 0:17:54.680 up than the other one. So if the metallic strip 0:17:54.760 --> 0:17:57.080 heats up, then it tends to bend in one direction 0:17:57.119 --> 0:17:59.560 because half of it is expanding faster than the other one, 0:17:59.680 --> 0:18:02.160 and then like closes some circuit and decides to turn 0:18:02.200 --> 0:18:04.960 on your air conditioning. So that's measuring the bending of 0:18:05.000 --> 0:18:07.720 this piece of metal, which again is related to the temperature, 0:18:07.800 --> 0:18:11.080 but it's one step indirect, right. Well, I mean, maybe 0:18:11.080 --> 0:18:12.800 it depends on what you mean by measure, but it 0:18:13.359 --> 0:18:17.200 does sort of measure the temperature of the metallic strip, right, 0:18:17.359 --> 0:18:20.399 which is I guess related to the temperature of the 0:18:20.440 --> 0:18:22.840 air around it. Yeah, I mean it's measuring the bending 0:18:22.840 --> 0:18:26.479 of the metallic strip, which is related to the temperature. Right, Like, 0:18:26.680 --> 0:18:29.720 how would you actually measure the temperature directly? You'd have 0:18:29.760 --> 0:18:33.720 to go, like measure the velocity of those particles themselves 0:18:34.080 --> 0:18:36.800 inside the object, how much they're wiggling, and that would 0:18:36.800 --> 0:18:39.959 tell you the temperature. Instead, you're measuring something which is 0:18:40.040 --> 0:18:44.280 determined by that property. So, I mean, I'm not criticizing thermometers. 0:18:44.320 --> 0:18:46.240 I'm not saying the whole thing is a hoax. Right, 0:18:46.280 --> 0:18:51.439 it's not a scam. Are you anti thermometer? I'm grow thermometer. 0:18:51.800 --> 0:18:54.399 You're saying it's all a big pharma conspiracy. No, But 0:18:54.440 --> 0:18:57.000 if we're going to think carefully about what temperature means, 0:18:57.080 --> 0:19:00.080 and let's think about what our devices are actually measuring, 0:19:00.359 --> 0:19:03.680 what they're really probing, and not just what numbers they're 0:19:03.680 --> 0:19:05.960 reading out, maybe we should have a disclaimer. You know, 0:19:06.280 --> 0:19:08.280 you should trust your thermometer. If it says you have 0:19:08.280 --> 0:19:11.360 a hundred and six degray fever, maybe you should call 0:19:11.400 --> 0:19:14.520 a doctor. Yeah, I'm not a thermometer denier or anything 0:19:14.560 --> 0:19:19.639 like that. You're a temperature denier. No, I'm not like 0:19:19.680 --> 0:19:22.360 that guy who says birds aren't real. All right, Well, 0:19:22.400 --> 0:19:25.520 that that so what you're saying. Usually we measure things 0:19:25.800 --> 0:19:28.440 like the effects of temperature and not maybe what we 0:19:28.560 --> 0:19:31.320 define temperature to be exactly. Yeah, that's right, But we 0:19:31.359 --> 0:19:33.480 do have a model again for what temperature is. We 0:19:33.520 --> 0:19:36.479 imagine that what's going on inside that liquid or inside 0:19:36.520 --> 0:19:38.440 the metal is that they're made of atoms, and those 0:19:38.440 --> 0:19:41.520 atoms wiggle and move or they fly around or they 0:19:41.560 --> 0:19:44.399 flow around, and the degree of that motion is we 0:19:44.480 --> 0:19:46.960 usually what we talk about for temperature, but this is 0:19:47.000 --> 0:19:50.280 a model of temperature. We call this the kinetic model 0:19:50.400 --> 0:19:53.480 of temperature. Is this idea that something is hot when 0:19:53.480 --> 0:19:56.280 the atoms inside of it have more kinetic energy, and 0:19:56.320 --> 0:19:58.480 something is cold when the atoms inside of it have 0:19:58.720 --> 0:20:01.440 less kinetic energy. And it's not just motion, like, it's 0:20:01.440 --> 0:20:04.600 not just velocity. You can also have spinning and vibrating 0:20:04.640 --> 0:20:06.840 and all this kind of stuff, And so it's related 0:20:06.880 --> 0:20:09.960 to this idea of kinetic energy, right, how fast things 0:20:09.960 --> 0:20:12.959 are moving. So from that perspective, you might imagine like 0:20:13.280 --> 0:20:16.800 if temperature is related to kinetic energy, or kinetic energy 0:20:17.119 --> 0:20:20.480 is either zero or more than zero, so how could 0:20:20.480 --> 0:20:23.320 you possibly have negative temperature? Right? It seems like that 0:20:23.359 --> 0:20:27.360 should tell you that temperature is zero or above zero, right, 0:20:27.400 --> 0:20:29.560 because you're saying it's sort of a measure of the 0:20:29.680 --> 0:20:32.920 I guess the average kinetic energy of of something, And 0:20:33.080 --> 0:20:35.679 I guess if it's air, you're measuring the kinetic energy 0:20:35.880 --> 0:20:39.480 of the air particles flying around. Those have kinetic energy. 0:20:39.520 --> 0:20:41.320 But if it's like a block of wood or a 0:20:41.359 --> 0:20:44.240 block of metal, then I guess the atoms aren't moving around, 0:20:44.240 --> 0:20:46.960 but they're still vibrating and bumping against each other. Right, 0:20:47.040 --> 0:20:48.879 And so you if you kind of were to measure 0:20:48.880 --> 0:20:52.280 all of those particles and take the average velocity and 0:20:52.359 --> 0:20:54.840 I guess squared it and all that, then you would 0:20:55.400 --> 0:20:58.080 get the temperature. Yeah, And there's some mathematics you can 0:20:58.080 --> 0:21:00.880 look up about exactly how tempered sure is defined based 0:21:00.880 --> 0:21:03.040 on the number of degrees of freedom, the number of 0:21:03.040 --> 0:21:05.440 ways you can move or wiggle and all this kind 0:21:05.440 --> 0:21:07.920 of stuff. But that's the basic idea for your classic 0:21:07.960 --> 0:21:11.600 definition of temperature. Right, average energy, and in fact, kinetic 0:21:11.680 --> 0:21:15.840