1 00:00:08,560 --> 00:00:11,840 Speaker 1: Hey, Jorge, do you have any concerns about raising your 2 00:00:11,920 --> 00:00:15,880 Speaker 1: kids in southern California? I don't. It's pretty great out here, 3 00:00:16,239 --> 00:00:18,280 Speaker 1: although I do feel like they miss out on some 4 00:00:18,320 --> 00:00:21,720 Speaker 1: things they do. What's missing in southern California? Well, definitely 5 00:00:21,720 --> 00:00:25,720 Speaker 1: not plastic surgery, we got that covered for sure. But 6 00:00:25,800 --> 00:00:27,800 Speaker 1: you know, there are experiences kids growing up here that 7 00:00:27,840 --> 00:00:29,960 Speaker 1: they don't get that other kids do. Yeah, like what 8 00:00:30,080 --> 00:00:33,600 Speaker 1: you know, like experiencing winter, snowfall. I mean, I guess 9 00:00:33,640 --> 00:00:36,240 Speaker 1: I miss winter, but I wouldn't say I'm missing winter. 10 00:00:36,400 --> 00:00:39,320 Speaker 1: Would you say, you know, misshoveling snow, putting on multiple 11 00:00:39,360 --> 00:00:42,159 Speaker 1: layers of clothes, multiple layers of clothes. What does that 12 00:00:42,200 --> 00:00:45,360 Speaker 1: even mean? Man? If you're like layers of clothes, what 13 00:00:45,400 --> 00:00:48,120 Speaker 1: does that even mean? I'm recording this naked. You don't 14 00:00:48,120 --> 00:00:51,240 Speaker 1: think kids should know about winter? No, I'm definitely anti winter. 15 00:00:51,400 --> 00:00:53,880 Speaker 1: That's when I'm teaching my kids about winter avoided at 16 00:00:53,920 --> 00:00:56,600 Speaker 1: all costs. But what if they don't? What if they 17 00:00:56,680 --> 00:00:58,600 Speaker 1: end up living there and then are you going to 18 00:00:58,640 --> 00:01:01,120 Speaker 1: go visit them? Depends how cute grandkids are. I guess 19 00:01:01,280 --> 00:01:19,200 Speaker 1: that's pretty coold. Daniela, Hi, I'm or handmade cartoonists and 20 00:01:19,240 --> 00:01:22,520 Speaker 1: the co author of Frequently Asked Questions about the Universe. Hi, 21 00:01:22,640 --> 00:01:25,399 Speaker 1: I'm Daniel. I'm a physics professor at u C Irvine 22 00:01:25,480 --> 00:01:29,360 Speaker 1: and a high energy physicist, and I definitely prefer high 23 00:01:29,480 --> 00:01:34,440 Speaker 1: energy air molecules. You don't like low energy air? No? 24 00:01:34,680 --> 00:01:37,000 Speaker 1: I like it hot outside. You know, when I moved 25 00:01:37,040 --> 00:01:40,480 Speaker 1: to California, I discovered that sunshine makes me happy. Do 26 00:01:40,560 --> 00:01:42,720 Speaker 1: you think maybe that's your upbringing? You grew up in 27 00:01:42,760 --> 00:01:45,840 Speaker 1: New Mexico, right, and then you went to school in Texas. 28 00:01:46,200 --> 00:01:48,200 Speaker 1: I did. I'm a desert person, but you know, New 29 00:01:48,240 --> 00:01:51,440 Speaker 1: Mexico was pretty cold. Los Almos is seven thousand feet 30 00:01:51,480 --> 00:01:53,880 Speaker 1: in elevation, and so we got a lot of snow. 31 00:01:54,240 --> 00:01:58,240 Speaker 1: I remember one year we got fifty five inches overnight. 32 00:01:58,720 --> 00:02:01,600 Speaker 1: I was not a happy camp Well, so you'm are 33 00:02:01,640 --> 00:02:05,400 Speaker 1: of a desert person or a dessert person? Dessert in 34 00:02:05,440 --> 00:02:07,840 Speaker 1: the desert, and do you like your desserts hot or cold? 35 00:02:08,160 --> 00:02:10,960 Speaker 1: I like them both. I'm not picky. But anyways, welcome 36 00:02:11,000 --> 00:02:13,480 Speaker 1: to our podcast, Daniel and Jorge Explained the Universe, a 37 00:02:13,520 --> 00:02:16,000 Speaker 1: production of My Heart Radio in which we are hot 38 00:02:16,000 --> 00:02:18,240 Speaker 1: on the mysteries of the universe and we think that 39 00:02:18,320 --> 00:02:21,480 Speaker 1: everything about it is pretty cool. We want to understand 40 00:02:21,560 --> 00:02:24,600 Speaker 1: how the universe works, what the rules are that govern 41 00:02:24,720 --> 00:02:28,600 Speaker 1: how it operates, and whether or not we can understand them. 42 00:02:28,720 --> 00:02:31,480 Speaker 1: We think one of the most fundamental questions about being alive, 43 00:02:31,560 --> 00:02:34,840 Speaker 1: about being human, is why are things the way that 44 00:02:34,880 --> 00:02:38,600 Speaker 1: they are? And what else could happen in this universe? 45 00:02:38,880 --> 00:02:40,880 Speaker 1: That's right. We don't give a cold shoulder to the 46 00:02:40,960 --> 00:02:43,760 Speaker 1: big questions out there because it is a wonderful universe 47 00:02:43,800 --> 00:02:46,120 Speaker 1: full of amazing things, and sometimes we wish we could 48 00:02:46,240 --> 00:02:48,560 Speaker 1: freeze it all so we can study it a little 49 00:02:48,560 --> 00:02:51,520 Speaker 1: bit better. That's right. These are hot topics for us 50 00:02:51,560 --> 00:02:54,800 Speaker 1: to understand, and as we look out around us in 51 00:02:54,840 --> 00:02:57,560 Speaker 1: the universe, we want to understand why some things are 52 00:02:57,600 --> 00:02:59,600 Speaker 1: the way they are, Why some things are hot, why 53 00:02:59,680 --> 00:03:02,440 Speaker 1: somethings are cold, Why hot things tend to heat up 54 00:03:02,480 --> 00:03:06,399 Speaker 1: cold things, Why cold things tend to cool down hot things. Yeah, 55 00:03:06,400 --> 00:03:09,160 Speaker 1: because we want people to warm up to the extremes 56 00:03:09,160 --> 00:03:11,120 Speaker 1: of the universe and all of the amazing things that 57 00:03:11,160 --> 00:03:14,000 Speaker 1: can happen and many different temperatures out there. The universe 58 00:03:14,040 --> 00:03:17,959 Speaker 1: has a pretty wide range from super hot explosive supernovas 59 00:03:18,000 --> 00:03:21,760 Speaker 1: and hearts of neutron stars really vast voids of empty 60 00:03:21,800 --> 00:03:25,560 Speaker 1: space exactly. And one of the best ways to understand 61 00:03:25,680 --> 00:03:28,560 Speaker 1: how the universe works, to make it reveal it is 62 00:03:28,760 --> 00:03:32,160 Speaker 1: underlying truth, the rules that governed it, is to look 63 00:03:32,200 --> 00:03:35,120 Speaker 1: at the extremes to find out what is the most 64 00:03:35,240 --> 00:03:38,320 Speaker 1: of something that can happen. How bright can things get, 65 00:03:38,400 --> 00:03:41,680 Speaker 1: how fast can this spen, how empty can space be, 66 00:03:41,840 --> 00:03:45,200 Speaker 1: how dense can matter be? So on this podcast, we'd 67 00:03:45,200 --> 00:03:48,160 Speaker 1: like to explore those extremes because we think those are 68 00:03:48,160 --> 00:03:51,200 Speaker 1: the places that the universe is cornered, is forced to 69 00:03:51,240 --> 00:03:54,360 Speaker 1: tell us something about how the rules work. These are 70 00:03:54,400 --> 00:03:57,120 Speaker 1: the edge cases, the ones where we hope the truth 71 00:03:57,160 --> 00:03:59,360 Speaker 1: will reveal itself. Yeah, we have a whole series of 72 00:03:59,400 --> 00:04:03,000 Speaker 1: episodes where talk about extreme things in the universe, the coldest, 73 00:04:03,000 --> 00:04:05,200 Speaker 1: the brightest, the biggest. Daniel have we done the most 74 00:04:05,240 --> 00:04:07,400 Speaker 1: delicious thing in the universe yet? That's just been a 75 00:04:07,440 --> 00:04:11,080 Speaker 1: side research project of mine for a long time. You're 76 00:04:11,120 --> 00:04:14,640 Speaker 1: just gathering data more and more every year. Yeah, you know, 77 00:04:14,760 --> 00:04:18,160 Speaker 1: I'm not trying to mind my personal experience for podcast episodes, 78 00:04:18,360 --> 00:04:20,839 Speaker 1: but that's a good idea. Or maybe the most delicious 79 00:04:20,880 --> 00:04:23,799 Speaker 1: thing in the universe is the universe. It's a pretty 80 00:04:23,839 --> 00:04:26,360 Speaker 1: tasty place. Well, the universe is the only thing in 81 00:04:26,400 --> 00:04:29,200 Speaker 1: the universe, right, so it's both the most delicious and 82 00:04:29,240 --> 00:04:32,159 Speaker 1: the most disgusting thing to eat in the universe. Also 83 00:04:32,200 --> 00:04:35,279 Speaker 1: the most filling, I guess. But we have done a 84 00:04:35,279 --> 00:04:38,320 Speaker 1: whole series of episodes on extremes and we encourage you 85 00:04:38,360 --> 00:04:40,159 Speaker 1: to go back through the archive and check them out. 86 00:04:40,200 --> 00:04:41,839 Speaker 1: But we did do those sort of the hottest and 87 00:04:41,920 --> 00:04:44,359 Speaker 1: coldest things in the universe. Those are two episodes you 88 00:04:44,400 --> 00:04:47,760 Speaker 1: can download, right, Yeah, that's right. And we recently organized 89 00:04:47,800 --> 00:04:51,000 Speaker 1: a curated list of all of our episodes on our website. 90 00:04:51,080 --> 00:04:54,080 Speaker 1: Listeners have been asking for us to sort the episodes 91 00:04:54,240 --> 00:04:56,800 Speaker 1: by topic, and so now we have them grouped by 92 00:04:56,920 --> 00:05:01,400 Speaker 1: cosmology or particle physics, or science fiction or extreme universe. 93 00:05:01,800 --> 00:05:05,000 Speaker 1: So go to our website Daniel and Jorge dot com 94 00:05:05,200 --> 00:05:08,039 Speaker 1: and look at the list of episodes by topic. Yeah, 95 00:05:08,040 --> 00:05:09,560 Speaker 1: so it's kind of like a menu. So if you're 96 00:05:09,600 --> 00:05:11,039 Speaker 1: feeling like, hey, you know, I could use a little 97 00:05:11,080 --> 00:05:13,640 Speaker 1: cosmology today, or I could use a little you know, 98 00:05:13,839 --> 00:05:16,960 Speaker 1: fundamental particles with my meal, you can go and help yourself. 99 00:05:17,240 --> 00:05:19,640 Speaker 1: That's right, Order up a side dish of black holes. 100 00:05:19,920 --> 00:05:22,520 Speaker 1: So we have talked about temperature a lot in this podcast, 101 00:05:22,600 --> 00:05:25,320 Speaker 1: But recently you've got in a few questions about a 102 00:05:25,400 --> 00:05:28,160 Speaker 1: new and interesting topic that's kind of floating out there, 103 00:05:28,240 --> 00:05:31,560 Speaker 1: right exactly, Folks are interested in the extremes of temperature, 104 00:05:31,640 --> 00:05:34,240 Speaker 1: all the way down to absolute zero, or all the 105 00:05:34,240 --> 00:05:37,560 Speaker 1: way up to absolute hot, the hottest that things can 106 00:05:37,600 --> 00:05:41,159 Speaker 1: get in the universe before temperature doesn't even make any sense. 107 00:05:41,240 --> 00:05:42,800 Speaker 1: But over the last year so I've gotten a few 108 00:05:42,839 --> 00:05:45,320 Speaker 1: emails asking me to talk about something that sounds like 109 00:05:45,360 --> 00:05:48,200 Speaker 1: it makes no sense at all, something that has been 110 00:05:48,200 --> 00:05:51,200 Speaker 1: bouncing around on the internet and inspire the curiosity of 111 00:05:51,240 --> 00:05:53,919 Speaker 1: several listeners whether or not it's possible to go even 112 00:05:54,040 --> 00:05:57,919 Speaker 1: below absolute zero. So today on the podcast, we'll be 113 00:05:57,960 --> 00:06:09,360 Speaker 1: asking the question, what is negative temperature? Negative temperature? What now, Daniel, 114 00:06:09,400 --> 00:06:12,320 Speaker 1: is this temperature that is not an optimist or what 115 00:06:13,120 --> 00:06:15,400 Speaker 1: always looks on the dark side of things? Yeah, this 116 00:06:15,480 --> 00:06:19,279 Speaker 1: is grumpy temperature exactly, whatever makes you feel bad. It's 117 00:06:19,320 --> 00:06:23,360 Speaker 1: not how positivemperature. Yeah, this is a weird concept. I guess, well, 118 00:06:23,400 --> 00:06:25,760 Speaker 1: I guess people are familiar with negative temperature, right, Like 119 00:06:25,839 --> 00:06:28,400 Speaker 1: in some places it gets so cold it's like minus 120 00:06:28,440 --> 00:06:31,760 Speaker 1: fifteen degrees, right, yeah, And like negative forty is where 121 00:06:31,800 --> 00:06:36,000 Speaker 1: celsius and fahrenheit meat so on some scales, negative temperature 122 00:06:36,120 --> 00:06:38,520 Speaker 1: is a pretty common experience. But I think people are 123 00:06:38,560 --> 00:06:43,039 Speaker 1: probably thinking about Kelvin. You mean this physical concept is 124 00:06:43,040 --> 00:06:45,960 Speaker 1: more about absolute temperature and whether or not it can 125 00:06:46,000 --> 00:06:49,120 Speaker 1: be negative. Yeah. The Kelvin scale goes from zero, which 126 00:06:49,160 --> 00:06:51,880 Speaker 1: is supposed to be this scenario where nothing is moving 127 00:06:51,920 --> 00:06:54,880 Speaker 1: and everything is basically frozen up to very high values 128 00:06:54,880 --> 00:06:57,920 Speaker 1: when things are wriggling around. So from that perspective, you know, like, 129 00:06:58,000 --> 00:07:00,800 Speaker 1: what does it mean to have negative of temperature? Can 130 00:07:00,800 --> 00:07:03,919 Speaker 1: you move less than not moving at all? Right? That 131 00:07:04,080 --> 00:07:06,760 Speaker 1: is pretty weird. But is that maybe just the scaler thing, 132 00:07:06,800 --> 00:07:08,960 Speaker 1: like we use the wrong scale. But no, because it's 133 00:07:09,000 --> 00:07:11,760 Speaker 1: absolute temperature, right, there are like hard limits or at 134 00:07:11,840 --> 00:07:14,160 Speaker 1: least I thought there were hard limits to absolute temperature 135 00:07:14,320 --> 00:07:17,360 Speaker 1: or the Kelvin scale right zero to infinity kind of 136 00:07:18,560 --> 00:07:22,040 Speaker 1: zero to the plank temperature. Actually, there is this maximum 137 00:07:22,120 --> 00:07:25,160 Speaker 1: temperature beyond which we think that gravity will take over 138 00:07:25,240 --> 00:07:27,960 Speaker 1: in quantum gravity effects will be important And we don't 139 00:07:27,960 --> 00:07:31,560 Speaker 1: even know what temperature means there. Wait, what it's called 140 00:07:31,640 --> 00:07:38,760 Speaker 1: absolute hot? Absolute hot or absolutely hot? Absolute hot is 141 00:07:38,840 --> 00:07:42,160 Speaker 1: absolutely hot? For sure? It sounds like a new vodka brand, 142 00:07:42,360 --> 00:07:44,760 Speaker 1: but it touches on these interesting questions of like what 143 00:07:45,000 --> 00:07:47,760 Speaker 1: is temperature anyway? You know, as human as, we have 144 00:07:47,880 --> 00:07:51,600 Speaker 1: experiences in the world, and then we try to build models, 145 00:07:51,680 --> 00:07:54,280 Speaker 1: physical ideas that describe those things. And then we have 146 00:07:54,320 --> 00:07:57,119 Speaker 1: to find a way to like mathematically express some things 147 00:07:57,160 --> 00:08:00,560 Speaker 1: that we experience temperature or something that's like very tuitive 148 00:08:00,600 --> 00:08:02,880 Speaker 1: to us. But in our physical models we need like 149 00:08:02,960 --> 00:08:06,480 Speaker 1: equations and numbers to describe these things. And sometimes that's 150 00:08:06,520 --> 00:08:09,840 Speaker 1: easy to do, like velocity or location, and sometimes it's 151 00:08:09,880 --> 00:08:12,000 Speaker 1: a little bit fuzzy, and so we're gonna get into 152 00:08:12,040 --> 00:08:15,960 Speaker 1: like what does temperature really mean anyway? Man? Yeah, So 153 00:08:16,000 --> 00:08:19,080 Speaker 1: we have this temperature in the absolute temperature within the 154 00:08:19,160 --> 00:08:21,760 Speaker 1: Kelvin scale, and so for example, like what is room 155 00:08:21,800 --> 00:08:25,080 Speaker 1: temperature in kelvin zero and celsius corresponds to two hundred 156 00:08:25,160 --> 00:08:29,920 Speaker 1: and seventy three in kelvin, So comfortable temperature in celsius 157 00:08:30,000 --> 00:08:33,600 Speaker 1: is like twenty five, which would be like two hundred 158 00:08:33,760 --> 00:08:37,160 Speaker 1: nineties something in kelvin. Okay, so room temperature is two 159 00:08:37,240 --> 00:08:40,880 Speaker 1: hundred ninety eight, let's say in kelvin, and then freezing 160 00:08:41,120 --> 00:08:44,600 Speaker 1: is two d seventy three, And I guess what temperature 161 00:08:44,640 --> 00:08:48,080 Speaker 1: does water boil, so it would be three three, three 162 00:08:48,120 --> 00:08:50,839 Speaker 1: seventy three or a hundred celsius. Okay. So then as 163 00:08:50,840 --> 00:08:53,120 Speaker 1: you start to cool things and make things colder, the 164 00:08:53,200 --> 00:08:55,200 Speaker 1: kelvin goes down and down and down and down. And 165 00:08:55,240 --> 00:08:57,240 Speaker 1: I think we talked about what is the coldest thing? 166 00:08:57,280 --> 00:08:59,800 Speaker 1: We've gotten something here on Earth? Right, Yeah, we have 167 00:09:00,040 --> 00:09:02,840 Speaker 1: on the coldest thing in the universe and the coldest 168 00:09:02,880 --> 00:09:07,319 Speaker 1: thing on Earth. And physicists regularly do experiments with super 169 00:09:07,400 --> 00:09:11,720 Speaker 1: duper cold objects, things that like the micro kelvin temperature 170 00:09:11,800 --> 00:09:14,440 Speaker 1: just about what we thought was the absolute minimum temperature, 171 00:09:14,480 --> 00:09:17,920 Speaker 1: which is actually a tiny little bit above absolute zero, 172 00:09:18,120 --> 00:09:20,400 Speaker 1: that's right. We talked about how the maybe the coldest 173 00:09:20,400 --> 00:09:22,839 Speaker 1: thing in the universe is something you're on Earth that 174 00:09:22,960 --> 00:09:25,560 Speaker 1: scientists have been able to cool down to almost zero 175 00:09:25,640 --> 00:09:29,920 Speaker 1: kelvin zero point zero zero zero zero zero zero one kelvin. 176 00:09:30,240 --> 00:09:33,079 Speaker 1: And so the question is can you actually go below? Right? 177 00:09:33,160 --> 00:09:36,079 Speaker 1: Is there such a thing as negative absolute temperature exactly? 178 00:09:36,120 --> 00:09:38,760 Speaker 1: That is the question today? Or is it even possible? 179 00:09:38,840 --> 00:09:41,439 Speaker 1: I guess? And what are physicists thinking? So as usually 180 00:09:41,440 --> 00:09:43,559 Speaker 1: were wondering how many people out there had thought about 181 00:09:43,559 --> 00:09:46,960 Speaker 1: this question or wondered whether temperature can go negative? And 182 00:09:47,040 --> 00:09:50,400 Speaker 1: so Daniel went out there into the internet or your campus. 183 00:09:50,640 --> 00:09:54,439 Speaker 1: These are Internet answers and thanks again everybody who volunteers 184 00:09:54,480 --> 00:09:57,040 Speaker 1: to answer these weird email the questions. If you'd like 185 00:09:57,080 --> 00:10:00,600 Speaker 1: to receive some strange questions for future podcast as episodes 186 00:10:00,640 --> 00:10:03,000 Speaker 1: in your inbox, please don't be shy or right to 187 00:10:03,080 --> 00:10:06,360 Speaker 1: us two questions at Daniel and Jorge dot com. That's right, 188 00:10:06,360 --> 00:10:08,400 Speaker 1: and you can be as positive or as negative as 189 00:10:08,400 --> 00:10:10,839 Speaker 1: you want in your answers. But think about it for 190 00:10:10,880 --> 00:10:13,559 Speaker 1: a second, right now, do you think absolute temperature can 191 00:10:13,640 --> 00:10:15,920 Speaker 1: be negative? Here's what people had to say. This is 192 00:10:15,960 --> 00:10:19,400 Speaker 1: a loaded question. Um, but if my bank account can 193 00:10:19,400 --> 00:10:22,120 Speaker 1: have a negative balance, so too can a cemometer unless 194 00:10:22,160 --> 00:10:25,720 Speaker 1: it's measuring in kelvin. He never goes Belusira. Well, because 195 00:10:25,760 --> 00:10:27,880 Speaker 1: you're asking this, I'm going to assume that that's what 196 00:10:27,960 --> 00:10:31,840 Speaker 1: the topic is. But right, persons think would be you 197 00:10:31,880 --> 00:10:35,360 Speaker 1: can't you can't have a negative temperature because I'm thinking 198 00:10:35,400 --> 00:10:37,280 Speaker 1: like kelvin, right, I mean, obviously you can have like 199 00:10:37,280 --> 00:10:39,840 Speaker 1: a negative celsius or something, but like you can't have 200 00:10:39,920 --> 00:10:42,839 Speaker 1: like a negative like kelvin amount of temperature. So no, 201 00:10:43,160 --> 00:10:47,040 Speaker 1: I don't think you can. I think it zero Kelvin 202 00:10:47,559 --> 00:10:52,040 Speaker 1: the molecules actually stopped moving. Not molecules, I mean particles 203 00:10:52,080 --> 00:10:55,240 Speaker 1: actually stopped moving as far as I know, probably wrong, 204 00:10:55,320 --> 00:10:59,280 Speaker 1: but that's my understanding. Well, on the Celsius and Fahrenheit scales, 205 00:10:59,400 --> 00:11:02,080 Speaker 1: you can have a nick it of value for your temperature, 206 00:11:02,240 --> 00:11:07,960 Speaker 1: but on the Kelvin or ranking scales, with positive temperature 207 00:11:08,000 --> 00:11:12,080 Speaker 1: being amount of energy and zero absolute zero being um 208 00:11:12,880 --> 00:11:16,840 Speaker 1: no heat energy. In that case, for a negative temperature, 209 00:11:17,480 --> 00:11:20,400 Speaker 1: you would have to have this um. You'd be like 210 00:11:20,440 --> 00:11:24,760 Speaker 1: a black hole of energy, or just the potential to 211 00:11:24,840 --> 00:11:28,800 Speaker 1: absorb energy from somewhere else. But maybe you don't actually 212 00:11:28,840 --> 00:11:33,280 Speaker 1: exist and you're just something mathematicians use. Like I my 213 00:11:33,440 --> 00:11:37,360 Speaker 1: first impression would be no, I don't think you can, 214 00:11:37,880 --> 00:11:42,000 Speaker 1: since if your particles are studic, then your temperature would 215 00:11:42,000 --> 00:11:46,440 Speaker 1: be absolute zero. I don't I don't know. Maybe unless 216 00:11:46,760 --> 00:11:50,880 Speaker 1: the particles are moving back in time some way, then 217 00:11:51,160 --> 00:11:54,760 Speaker 1: you could have negative temperature. I really don't know. I'm 218 00:11:54,760 --> 00:11:58,959 Speaker 1: making this up as I go, Daniel, I think you 219 00:11:59,080 --> 00:12:02,320 Speaker 1: forgot about you how you moved in California, and you 220 00:12:02,400 --> 00:12:07,240 Speaker 1: forgot that you can go negative during the year. I 221 00:12:07,320 --> 00:12:10,120 Speaker 1: do not believe it's possible to have a negative temperature. 222 00:12:10,160 --> 00:12:13,360 Speaker 1: There is a reason why absolute zero is called. Absolute 223 00:12:14,240 --> 00:12:16,520 Speaker 1: temperature is the sum of the kinetic energy of the 224 00:12:16,600 --> 00:12:19,640 Speaker 1: particles of the objects being measured. And I don't believe 225 00:12:19,679 --> 00:12:24,320 Speaker 1: something can have negative motion unless there is some oddity 226 00:12:24,360 --> 00:12:27,920 Speaker 1: and the fact that measuring motion requires the existence of 227 00:12:27,960 --> 00:12:31,319 Speaker 1: a reference point, and with a boundless, infinite universe, where 228 00:12:31,480 --> 00:12:35,600 Speaker 1: is that absolute reference point? But otherwise there is no 229 00:12:35,640 --> 00:12:38,720 Speaker 1: possibility for negative temperature. I'm going to go with no. 230 00:12:39,240 --> 00:12:42,160 Speaker 1: And also it depends on what context we're talking about 231 00:12:42,240 --> 00:12:45,280 Speaker 1: this in. For example, if you're dead, I think your 232 00:12:45,320 --> 00:12:48,240 Speaker 1: temperature can be negative because you'd be frozen in a 233 00:12:48,280 --> 00:12:52,760 Speaker 1: refrigerator or something. But as a living human being, having 234 00:12:52,760 --> 00:12:55,440 Speaker 1: a negative temperature I think would be impossible because we 235 00:12:55,520 --> 00:12:59,439 Speaker 1: are made up of water and that water would freeze 236 00:13:00,320 --> 00:13:03,000 Speaker 1: if it was a negative temperature, meaning we wouldn't be 237 00:13:03,000 --> 00:13:05,760 Speaker 1: able to be alive. Um, blood would not be able 238 00:13:05,800 --> 00:13:09,440 Speaker 1: to move, our heart couldn't beat, and things like that. Mmm. Okay, 239 00:13:09,720 --> 00:13:14,160 Speaker 1: a lot of negative responses, not a lot of positive yeses. No, 240 00:13:14,360 --> 00:13:16,760 Speaker 1: not a lot of believers in negative temperature, but some 241 00:13:16,880 --> 00:13:19,840 Speaker 1: good creative answers you think they should have been more positive, 242 00:13:19,920 --> 00:13:23,040 Speaker 1: like yes, maybe it can. I believe in your universe. 243 00:13:23,400 --> 00:13:26,400 Speaker 1: You're beautiful. I think that they should have had more 244 00:13:26,480 --> 00:13:29,640 Speaker 1: faith in physicists to break the rules and think outside 245 00:13:29,679 --> 00:13:32,520 Speaker 1: the bounds of what is normally possible. It should have 246 00:13:32,520 --> 00:13:35,480 Speaker 1: been more temperature positive that it can be negative exactly 247 00:13:35,520 --> 00:13:37,360 Speaker 1: because you know, the history of physics is littered with 248 00:13:37,440 --> 00:13:40,600 Speaker 1: examples of doing things that we thought were once impossible, 249 00:13:40,679 --> 00:13:43,079 Speaker 1: of discovering the universe works in a way different from 250 00:13:43,120 --> 00:13:46,200 Speaker 1: the way that we had imagined, of breaking the rules 251 00:13:46,240 --> 00:13:49,000 Speaker 1: that we once thought were iron clad. Are you saying 252 00:13:49,040 --> 00:13:52,000 Speaker 1: physicists just basically do things and they're like, you have 253 00:13:52,080 --> 00:13:54,160 Speaker 1: some kind of chip on your shoulder, Hey, Daniel, I 254 00:13:54,240 --> 00:13:57,160 Speaker 1: dare you to understand the universe. I think it's exciting 255 00:13:57,200 --> 00:14:01,600 Speaker 1: to imagine what's impossible might be possible, to think about it. 256 00:14:01,600 --> 00:14:04,160 Speaker 1: You know, that's the job of science fiction authors to think, 257 00:14:04,520 --> 00:14:07,160 Speaker 1: could we get to a nearby star faster than the 258 00:14:07,160 --> 00:14:09,720 Speaker 1: speed of light? How might that be possible. It's also 259 00:14:09,760 --> 00:14:12,040 Speaker 1: the job of physicists to think, like, what are the 260 00:14:12,120 --> 00:14:14,800 Speaker 1: actual rules of the universe? Which ones can be broken, 261 00:14:14,840 --> 00:14:17,360 Speaker 1: which ones can be bent, which ones seem like rules 262 00:14:17,600 --> 00:14:21,280 Speaker 1: but only in certain circumstances, and actually aren't fundamentally rules 263 00:14:21,320 --> 00:14:23,200 Speaker 1: at all, although I guess you have to be careful, right, 264 00:14:23,360 --> 00:14:25,840 Speaker 1: Like you don't want to dare a physicist to find 265 00:14:25,840 --> 00:14:27,880 Speaker 1: a way to blow up the world or create a 266 00:14:27,920 --> 00:14:31,240 Speaker 1: black hole in the center of the of our planet. Yeah, 267 00:14:31,280 --> 00:14:35,320 Speaker 1: I think we've tried that already. Actually, I see you 268 00:14:35,400 --> 00:14:38,160 Speaker 1: were there and that what. I guess you gave up? 269 00:14:38,640 --> 00:14:41,200 Speaker 1: You I hope, well, I hope or failed. No, we 270 00:14:41,240 --> 00:14:43,240 Speaker 1: are still trying to create black holes. It's a large 271 00:14:43,240 --> 00:14:45,800 Speaker 1: hager on collider. In fact, we recently turned the collider 272 00:14:45,880 --> 00:14:48,320 Speaker 1: back on a few weeks ago. Oh man, you're not 273 00:14:48,360 --> 00:14:51,120 Speaker 1: gonna give up, are you? You know, just after we 274 00:14:51,200 --> 00:14:54,080 Speaker 1: turned on the collider, the government of the UK collapsed 275 00:14:54,080 --> 00:14:57,440 Speaker 1: and Boris Johnson was forced to resign as Prime minister. Really, 276 00:14:57,440 --> 00:15:00,440 Speaker 1: do you think there's a correlation there. There's definitely a correlation. 277 00:15:00,440 --> 00:15:02,400 Speaker 1: I don't know about causation. We'll have to turn the 278 00:15:02,400 --> 00:15:04,000 Speaker 1: thing on and off a few times and see what 279 00:15:04,080 --> 00:15:06,400 Speaker 1: other governments fall. I think there are other things going 280 00:15:06,440 --> 00:15:09,040 Speaker 1: on besides you switching on the collider, just you know, 281 00:15:09,400 --> 00:15:12,080 Speaker 1: a few things here and on on our world stage. 282 00:15:12,200 --> 00:15:13,960 Speaker 1: I don't know. I don't keep up with politics, man, 283 00:15:14,080 --> 00:15:17,200 Speaker 1: So I see you just flip on the switch. All right, Well, 284 00:15:17,240 --> 00:15:21,440 Speaker 1: this is a fascinating question. Can absolutely temperature go negative? 285 00:15:21,600 --> 00:15:25,320 Speaker 1: Can it be minus something degrees absolute? And so Daniel, 286 00:15:25,680 --> 00:15:28,280 Speaker 1: that is a weird phrase, negative temperature. What does it mean? 287 00:15:28,400 --> 00:15:31,040 Speaker 1: It all comes down to what we mean by temperature. 288 00:15:31,160 --> 00:15:33,920 Speaker 1: And normally when we talk about temperature, we're talking about 289 00:15:33,920 --> 00:15:36,400 Speaker 1: how hot something feels. You know, you touch something it 290 00:15:36,440 --> 00:15:39,120 Speaker 1: feels hot, you touch something it feels cold. You have 291 00:15:39,160 --> 00:15:42,120 Speaker 1: a sense for whether it's hot or cold outside. That's 292 00:15:42,160 --> 00:15:45,800 Speaker 1: about like the energy flow between you and some other object. 293 00:15:45,920 --> 00:15:48,080 Speaker 1: But we also have a concept for like what's going 294 00:15:48,120 --> 00:15:52,840 Speaker 1: on inside, like micro physical picture of why some things 295 00:15:52,880 --> 00:15:55,200 Speaker 1: are hot and some things are cold. What's going on 296 00:15:55,320 --> 00:15:58,400 Speaker 1: inside something that's hot that makes it different from something 297 00:15:58,640 --> 00:16:01,680 Speaker 1: that's cold. And this eco physical picture mostly is about 298 00:16:01,720 --> 00:16:05,320 Speaker 1: like how much the atoms inside are moving, Like if 299 00:16:05,320 --> 00:16:07,560 Speaker 1: they're zooming around a lot and jiggling a lot, if 300 00:16:07,600 --> 00:16:09,480 Speaker 1: they have a lot of energy, then the thing they 301 00:16:09,520 --> 00:16:12,600 Speaker 1: make up feels hot. If they're mostly not moving, they're 302 00:16:12,600 --> 00:16:15,360 Speaker 1: not jiggling or whizzing around, then the thing they make 303 00:16:15,440 --> 00:16:19,360 Speaker 1: up feels cold. Right, And we have ways to measure that, right, 304 00:16:19,440 --> 00:16:23,040 Speaker 1: like we have devices that called thermometer, as you probably 305 00:16:23,040 --> 00:16:26,320 Speaker 1: know that. Can I tell you a little bit about 306 00:16:26,360 --> 00:16:29,400 Speaker 1: that kind of internal moving around of things. Yeah, And 307 00:16:29,400 --> 00:16:32,120 Speaker 1: what's interesting is that thermometer is measure things that are 308 00:16:32,160 --> 00:16:37,720 Speaker 1: related to temperature. None of them actually directly measure temperature itself. Wait, 309 00:16:37,760 --> 00:16:41,800 Speaker 1: what a thermometer does not meter metter temperature? I know 310 00:16:41,880 --> 00:16:45,160 Speaker 1: it's called a thermometer, but it doesn't actually meter thermo. 311 00:16:45,200 --> 00:16:47,920 Speaker 1: I mean, take, for example, the classic bulb thermometer. What 312 00:16:48,080 --> 00:16:50,000 Speaker 1: is it. It's a little pot of liquid with a 313 00:16:50,080 --> 00:16:52,600 Speaker 1: tube above it. And what it's really measuring is the 314 00:16:52,680 --> 00:16:55,560 Speaker 1: volume of the liquid because there's a relationship. As the 315 00:16:55,640 --> 00:16:59,680 Speaker 1: liquid gets hotter, its volume increases and so it climbs 316 00:16:59,760 --> 00:17:03,400 Speaker 1: up that cylinder and so you're not directly measuring temperature. 317 00:17:03,440 --> 00:17:06,199 Speaker 1: You're measuring the volume, which is you think related to 318 00:17:06,359 --> 00:17:09,280 Speaker 1: the temperature. Right. It's like those glass tubes with the 319 00:17:09,320 --> 00:17:12,080 Speaker 1: little red line. What's actually happening is that when you 320 00:17:12,320 --> 00:17:15,000 Speaker 1: stick it into like let's say, boiling water, it heats 321 00:17:15,040 --> 00:17:17,119 Speaker 1: up the little red liquid and it expands. And then 322 00:17:17,240 --> 00:17:20,000 Speaker 1: the more it expands, I guess, the hotter the water was. 323 00:17:20,080 --> 00:17:22,399 Speaker 1: But you're saying it's not actually measuring the temperature of 324 00:17:22,440 --> 00:17:25,480 Speaker 1: the water. No, it's measuring the volume of that little 325 00:17:25,480 --> 00:17:28,600 Speaker 1: red liquid inside the thermometer, which of course is related 326 00:17:28,640 --> 00:17:31,560 Speaker 1: to temperature, but it's indirect, right. There are other ways 327 00:17:31,600 --> 00:17:34,199 Speaker 1: that are also indirect that you can measure temperature, like 328 00:17:34,280 --> 00:17:36,400 Speaker 1: the thermostat in your house, the one that decides whether 329 00:17:36,440 --> 00:17:38,840 Speaker 1: or not to turn on the air conditioning, that doesn't 330 00:17:38,880 --> 00:17:41,160 Speaker 1: have a little ball of liquid in it. It has 331 00:17:41,320 --> 00:17:45,119 Speaker 1: something called a bimetallic strip. It has two kinds of 332 00:17:45,160 --> 00:17:48,199 Speaker 1: metal bonded together, and the two kinds of metal have 333 00:17:48,320 --> 00:17:51,920 Speaker 1: different properties. One of them expands faster when the heat 334 00:17:52,000 --> 00:17:54,680 Speaker 1: up than the other one. So if the metallic strip 335 00:17:54,760 --> 00:17:57,080 Speaker 1: heats up, then it tends to bend in one direction 336 00:17:57,119 --> 00:17:59,560 Speaker 1: because half of it is expanding faster than the other one, 337 00:17:59,680 --> 00:18:02,160 Speaker 1: and then like closes some circuit and decides to turn 338 00:18:02,200 --> 00:18:04,960 Speaker 1: on your air conditioning. So that's measuring the bending of 339 00:18:05,000 --> 00:18:07,720 Speaker 1: this piece of metal, which again is related to the temperature, 340 00:18:07,800 --> 00:18:11,080 Speaker 1: but it's one step indirect, right. Well, I mean, maybe 341 00:18:11,080 --> 00:18:12,800 Speaker 1: it depends on what you mean by measure, but it 342 00:18:13,359 --> 00:18:17,200 Speaker 1: does sort of measure the temperature of the metallic strip, right, 343 00:18:17,359 --> 00:18:20,399 Speaker 1: which is I guess related to the temperature of the 344 00:18:20,440 --> 00:18:22,840 Speaker 1: air around it. Yeah, I mean it's measuring the bending 345 00:18:22,840 --> 00:18:26,479 Speaker 1: of the metallic strip, which is related to the temperature. Right, Like, 346 00:18:26,680 --> 00:18:29,720 Speaker 1: how would you actually measure the temperature directly? You'd have 347 00:18:29,760 --> 00:18:33,720 Speaker 1: to go, like measure the velocity of those particles themselves 348 00:18:34,080 --> 00:18:36,800 Speaker 1: inside the object, how much they're wiggling, and that would 349 00:18:36,800 --> 00:18:39,959 Speaker 1: tell you the temperature. Instead, you're measuring something which is 350 00:18:40,040 --> 00:18:44,280 Speaker 1: determined by that property. So, I mean, I'm not criticizing thermometers. 351 00:18:44,320 --> 00:18:46,240 Speaker 1: I'm not saying the whole thing is a hoax. Right, 352 00:18:46,280 --> 00:18:51,439 Speaker 1: it's not a scam. Are you anti thermometer? I'm grow thermometer. 353 00:18:51,800 --> 00:18:54,399 Speaker 1: You're saying it's all a big pharma conspiracy. No, But 354 00:18:54,440 --> 00:18:57,000 Speaker 1: if we're going to think carefully about what temperature means, 355 00:18:57,080 --> 00:19:00,080 Speaker 1: and let's think about what our devices are actually measuring, 356 00:19:00,359 --> 00:19:03,680 Speaker 1: what they're really probing, and not just what numbers they're 357 00:19:03,680 --> 00:19:05,960 Speaker 1: reading out, maybe we should have a disclaimer. You know, 358 00:19:06,280 --> 00:19:08,280 Speaker 1: you should trust your thermometer. If it says you have 359 00:19:08,280 --> 00:19:11,360 Speaker 1: a hundred and six degray fever, maybe you should call 360 00:19:11,400 --> 00:19:14,520 Speaker 1: a doctor. Yeah, I'm not a thermometer denier or anything 361 00:19:14,560 --> 00:19:19,639 Speaker 1: like that. You're a temperature denier. No, I'm not like 362 00:19:19,680 --> 00:19:22,360 Speaker 1: that guy who says birds aren't real. All right, Well, 363 00:19:22,400 --> 00:19:25,520 Speaker 1: that that so what you're saying. Usually we measure things 364 00:19:25,800 --> 00:19:28,440 Speaker 1: like the effects of temperature and not maybe what we 365 00:19:28,560 --> 00:19:31,320 Speaker 1: define temperature to be exactly. Yeah, that's right, But we 366 00:19:31,359 --> 00:19:33,480 Speaker 1: do have a model again for what temperature is. We 367 00:19:33,520 --> 00:19:36,479 Speaker 1: imagine that what's going on inside that liquid or inside 368 00:19:36,520 --> 00:19:38,440 Speaker 1: the metal is that they're made of atoms, and those 369 00:19:38,440 --> 00:19:41,520 Speaker 1: atoms wiggle and move or they fly around or they 370 00:19:41,560 --> 00:19:44,399 Speaker 1: flow around, and the degree of that motion is we 371 00:19:44,480 --> 00:19:46,960 Speaker 1: usually what we talk about for temperature, but this is 372 00:19:47,000 --> 00:19:50,280 Speaker 1: a model of temperature. We call this the kinetic model 373 00:19:50,400 --> 00:19:53,480 Speaker 1: of temperature. Is this idea that something is hot when 374 00:19:53,480 --> 00:19:56,280 Speaker 1: the atoms inside of it have more kinetic energy, and 375 00:19:56,320 --> 00:19:58,480 Speaker 1: something is cold when the atoms inside of it have 376 00:19:58,720 --> 00:20:01,440 Speaker 1: less kinetic energy. And it's not just motion, like, it's 377 00:20:01,440 --> 00:20:04,600 Speaker 1: not just velocity. You can also have spinning and vibrating 378 00:20:04,640 --> 00:20:06,840 Speaker 1: and all this kind of stuff, And so it's related 379 00:20:06,880 --> 00:20:09,960 Speaker 1: to this idea of kinetic energy, right, how fast things 380 00:20:09,960 --> 00:20:12,959 Speaker 1: are moving. So from that perspective, you might imagine like 381 00:20:13,280 --> 00:20:16,800 Speaker 1: if temperature is related to kinetic energy, or kinetic energy 382 00:20:17,119 --> 00:20:20,480 Speaker 1: is either zero or more than zero, so how could 383 00:20:20,480 --> 00:20:23,320 Speaker 1: you possibly have negative temperature? Right? It seems like that 384 00:20:23,359 --> 00:20:27,360 Speaker 1: should tell you that temperature is zero or above zero, right, 385 00:20:27,400 --> 00:20:29,560 Speaker 1: because you're saying it's sort of a measure of the 386 00:20:29,680 --> 00:20:32,920 Speaker 1: I guess the average kinetic energy of of something, And 387 00:20:33,080 --> 00:20:35,679 Speaker 1: I guess if it's air, you're measuring the kinetic energy 388 00:20:35,880 --> 00:20:39,480 Speaker 1: of the air particles flying around. Those have kinetic energy. 389 00:20:39,520 --> 00:20:41,320 Speaker 1: But if it's like a block of wood or a 390 00:20:41,359 --> 00:20:44,240 Speaker 1: block of metal, then I guess the atoms aren't moving around, 391 00:20:44,240 --> 00:20:46,960 Speaker 1: but they're still vibrating and bumping against each other. Right, 392 00:20:47,040 --> 00:20:48,879 Speaker 1: And so you if you kind of were to measure 393 00:20:48,880 --> 00:20:52,280 Speaker 1: all of those particles and take the average velocity and 394 00:20:52,359 --> 00:20:54,840 Speaker 1: I guess squared it and all that, then you would 395 00:20:55,400 --> 00:20:58,080 Speaker 1: get the temperature. Yeah, And there's some mathematics you can 396 00:20:58,080 --> 00:21:00,880 Speaker 1: look up about exactly how tempered sure is defined based 397 00:21:00,880 --> 00:21:03,040 Speaker 1: on the number of degrees of freedom, the number of 398 00:21:03,040 --> 00:21:05,440 Speaker 1: ways you can move or wiggle and all this kind 399 00:21:05,440 --> 00:21:07,920 Speaker 1: of stuff. But that's the basic idea for your classic 400 00:21:07,960 --> 00:21:11,600 Speaker 1: definition of temperature. Right, average energy, and in fact, kinetic 401 00:21:11,680 --> 00:21:15,840 Speaker 1: energy you calculated by squaring the velocity of something, right, 402 00:21:16,320 --> 00:21:19,199 Speaker 1: which means that it should always be positive. Yeah, kinetic 403 00:21:19,320 --> 00:21:22,080 Speaker 1: energy is always positive, right, unless I guess you have 404 00:21:22,359 --> 00:21:28,199 Speaker 1: imaginary energy. Unless I imaginary velocity like I imagined I 405 00:21:28,200 --> 00:21:30,960 Speaker 1: went to the post office today, but I didn't because 406 00:21:31,000 --> 00:21:33,280 Speaker 1: he had negative energy because I didn't eat enough dessert 407 00:21:33,320 --> 00:21:35,359 Speaker 1: in the desert to fuel my trip. There you go, 408 00:21:35,680 --> 00:21:39,199 Speaker 1: easy solution. All right, Well, let's get into what exactly 409 00:21:39,359 --> 00:21:42,800 Speaker 1: is temperature, whether that definition of temperature as kinect energy 410 00:21:43,080 --> 00:21:46,360 Speaker 1: makes sense, and whether or not it's possible for it 411 00:21:46,440 --> 00:21:59,280 Speaker 1: to be negative. But first, let's take a quick break 412 00:22:01,560 --> 00:22:04,320 Speaker 1: or I we're asking a pretty trippy question, which is 413 00:22:04,560 --> 00:22:08,919 Speaker 1: can you have negative absolute temperature? Which is sort of 414 00:22:09,160 --> 00:22:12,639 Speaker 1: an oxymoron, right, negative absolute because absolute usually means it 415 00:22:12,680 --> 00:22:15,719 Speaker 1: can only be positive. Mm. Yeah, it's a pretty psycho 416 00:22:15,840 --> 00:22:19,159 Speaker 1: kind of idea negative temperature, and it really gets at 417 00:22:19,160 --> 00:22:22,359 Speaker 1: the heart of this question, like what is temperature anyway? 418 00:22:22,880 --> 00:22:25,360 Speaker 1: You know, which we talked about several times on the podcast, 419 00:22:25,480 --> 00:22:28,040 Speaker 1: because it's kind of a slippery idea. Yeah, and I 420 00:22:28,040 --> 00:22:30,200 Speaker 1: know you sort of hate talking about it, right, you 421 00:22:30,280 --> 00:22:32,720 Speaker 1: know you're not a fan of thermodynamics. Wait, is it 422 00:22:32,760 --> 00:22:36,040 Speaker 1: because you're a thermodenier? Is it? It's all making sense now, 423 00:22:37,400 --> 00:22:41,639 Speaker 1: it's because it's complicated, and thermodynamics involves like thousands and 424 00:22:41,720 --> 00:22:45,000 Speaker 1: thousands or millions or billions of particles. I like thinking 425 00:22:45,040 --> 00:22:48,280 Speaker 1: about individual particles bouncing off each other, really reducing the 426 00:22:48,359 --> 00:22:51,119 Speaker 1: universe down to the simplest little bits and their rules. 427 00:22:51,160 --> 00:22:54,400 Speaker 1: It's hard to think about swarms, you know, Right, does 428 00:22:54,400 --> 00:22:59,640 Speaker 1: that mean you're antidemocracy, Daniel, I don't pay attention to politics, 429 00:22:59,720 --> 00:23:02,560 Speaker 1: right the official line. Oh, that's right, we forgot form. 430 00:23:03,080 --> 00:23:06,200 Speaker 1: We established that earlier. Yeah, it kind of gets into 431 00:23:06,200 --> 00:23:08,639 Speaker 1: the question of what is temperature anyway, Like is it 432 00:23:08,720 --> 00:23:11,399 Speaker 1: really the kinetic energy of the particles inside of it? 433 00:23:11,440 --> 00:23:13,480 Speaker 1: And what does that even mean? It is really interesting 434 00:23:13,560 --> 00:23:15,800 Speaker 1: question and we talked about it several times. Even in 435 00:23:15,840 --> 00:23:19,080 Speaker 1: this idea of temperature as like the kinetic energy of particles, 436 00:23:19,400 --> 00:23:22,639 Speaker 1: you can ask weird questions like what's the kinetic energy 437 00:23:22,680 --> 00:23:26,399 Speaker 1: of one particle? Can a single particle have kinetic energy? Well, 438 00:23:26,440 --> 00:23:28,960 Speaker 1: a single particle can, right, You're wondering if it can 439 00:23:29,000 --> 00:23:32,200 Speaker 1: have temperature? Yes, can a single particle have temperature because 440 00:23:32,200 --> 00:23:34,720 Speaker 1: it can have kinetic energy. And that sort of shows 441 00:23:34,760 --> 00:23:37,840 Speaker 1: you something about the limits of this idea of temperature 442 00:23:37,880 --> 00:23:41,600 Speaker 1: as kinetic energy, because we mean more by temperature than 443 00:23:41,720 --> 00:23:44,440 Speaker 1: just like how much energy is in something. We also 444 00:23:44,520 --> 00:23:47,359 Speaker 1: mean something about how heat flows. Right, we have this 445 00:23:47,480 --> 00:23:50,600 Speaker 1: intuitive experience that we want to somehow describe as if 446 00:23:50,600 --> 00:23:53,120 Speaker 1: you put like a block of ice in your coffee, 447 00:23:53,480 --> 00:23:55,720 Speaker 1: then the ice will melt, right because the heat will 448 00:23:55,760 --> 00:23:58,919 Speaker 1: flow from the coffee to the ice cube. So temperature 449 00:23:58,960 --> 00:24:01,480 Speaker 1: is also about how how heat flows. He tends to 450 00:24:01,480 --> 00:24:04,280 Speaker 1: flow from hot things too cold things, So when we 451 00:24:04,320 --> 00:24:07,600 Speaker 1: define temperature, we also want this idea of heat flow. 452 00:24:07,880 --> 00:24:09,600 Speaker 1: But I guess you're saying there's some sort of tension 453 00:24:09,640 --> 00:24:13,600 Speaker 1: between our intuitive understanding of temperature and maybe the official 454 00:24:13,680 --> 00:24:16,040 Speaker 1: physics definition of it, because I guess you know, we 455 00:24:16,119 --> 00:24:18,080 Speaker 1: talked about the hottest things in the universe, and one 456 00:24:18,080 --> 00:24:19,919 Speaker 1: of the hottest things in the universe is is kind 457 00:24:19,960 --> 00:24:23,159 Speaker 1: of empty space, right, or at least mostly empty space, 458 00:24:23,200 --> 00:24:25,840 Speaker 1: because it's mostly empty, there's not much in it, but 459 00:24:25,880 --> 00:24:28,560 Speaker 1: there are particles in it that are moving really fast, 460 00:24:28,600 --> 00:24:32,040 Speaker 1: and so it does technically have a high temperature empty space. 461 00:24:32,040 --> 00:24:34,400 Speaker 1: But if you were there, you would freeze, And so 462 00:24:34,560 --> 00:24:36,240 Speaker 1: that I think that's what you're saying, is that, like, well, 463 00:24:36,280 --> 00:24:38,160 Speaker 1: that's kind of kind of intuitive. How can I freeze 464 00:24:38,200 --> 00:24:39,800 Speaker 1: if it's one of the hottest things in the universe, 465 00:24:39,840 --> 00:24:41,440 Speaker 1: And so it kind of makes your brain pop a 466 00:24:41,520 --> 00:24:43,520 Speaker 1: little bit. Yeah, out in the middle of empty space. 467 00:24:43,560 --> 00:24:46,320 Speaker 1: There are very fast moving particles, but not very many 468 00:24:46,440 --> 00:24:49,080 Speaker 1: of them. So if you went into empty space, those 469 00:24:49,080 --> 00:24:52,040 Speaker 1: particles would give you energy, but you'd be losing energy 470 00:24:52,119 --> 00:24:54,840 Speaker 1: more quickly than you beginning energy because you'd be readiating 471 00:24:54,880 --> 00:24:58,120 Speaker 1: it out into spaces. You would freeze. That's counterintuitive. There's 472 00:24:58,119 --> 00:25:00,840 Speaker 1: another idea here, though, which is the idea of equilibrium. 473 00:25:00,920 --> 00:25:03,840 Speaker 1: We talk about temperature in terms of many particles rather 474 00:25:03,840 --> 00:25:07,040 Speaker 1: than a single particle, because temperature really is about like 475 00:25:07,320 --> 00:25:10,600 Speaker 1: an object in equilibrium, it's like settled. It's a statement 476 00:25:10,640 --> 00:25:14,159 Speaker 1: about many many things. It's an emergent property, not the 477 00:25:14,240 --> 00:25:16,960 Speaker 1: property of an individual object. The way, for example, like 478 00:25:17,240 --> 00:25:19,879 Speaker 1: um the cost of something, the value of something is 479 00:25:19,920 --> 00:25:22,679 Speaker 1: an emergent property of the market. You can say I'm 480 00:25:22,680 --> 00:25:25,480 Speaker 1: gonna make some piece of art and I'm gonna claim 481 00:25:25,640 --> 00:25:27,920 Speaker 1: it's worth a billion dollars. Well, if you can only 482 00:25:27,920 --> 00:25:30,520 Speaker 1: sell it for seventy four dollars, then what is its value. 483 00:25:30,520 --> 00:25:34,080 Speaker 1: It's value really is seventy four dollars. So the value 484 00:25:34,119 --> 00:25:36,199 Speaker 1: of your art is really determined sort of by like 485 00:25:36,359 --> 00:25:38,520 Speaker 1: the market price for what is willing to bear. In 486 00:25:38,520 --> 00:25:41,040 Speaker 1: the same way, temperature isn't really the property of a particle. 487 00:25:41,160 --> 00:25:43,960 Speaker 1: It's like the property of a system of objects. It's 488 00:25:44,000 --> 00:25:47,280 Speaker 1: an average emergent quantity. Well, are you saying that that's 489 00:25:47,359 --> 00:25:50,200 Speaker 1: one way to measure temperature, because right before you said 490 00:25:50,200 --> 00:25:52,840 Speaker 1: that you can calculate it as the average kinetic energy 491 00:25:52,920 --> 00:25:55,359 Speaker 1: of the particles inside of something. Yeah, but you can't 492 00:25:55,359 --> 00:25:57,920 Speaker 1: define a temperature for a single particle. Even for this 493 00:25:58,000 --> 00:26:00,560 Speaker 1: kinetic theory of temperature, you can't define temperature for a 494 00:26:00,560 --> 00:26:03,919 Speaker 1: single particle. It has to do more with equilibrium sets 495 00:26:03,920 --> 00:26:06,960 Speaker 1: of particles. But what if I have empty space and 496 00:26:06,960 --> 00:26:09,760 Speaker 1: there's only one particle in it, within the kinetic energy 497 00:26:09,800 --> 00:26:13,280 Speaker 1: of that particle basically define the temperature of that empty space. Well, 498 00:26:13,320 --> 00:26:14,919 Speaker 1: in the same way that like if you are the 499 00:26:14,960 --> 00:26:17,200 Speaker 1: only person in the world and you create some art 500 00:26:17,240 --> 00:26:19,640 Speaker 1: and you say it's worth a billion dollars, you're defining 501 00:26:19,680 --> 00:26:21,439 Speaker 1: the value of that. You can't really sell it for 502 00:26:21,480 --> 00:26:24,800 Speaker 1: a billion dollars. Is nobody else in that universe. So 503 00:26:24,880 --> 00:26:27,359 Speaker 1: in that same way, like a single particle doesn't really 504 00:26:27,400 --> 00:26:29,960 Speaker 1: have a temperature. I guess I'm not sure what you're 505 00:26:29,960 --> 00:26:33,440 Speaker 1: saying that our definition of particle temperature doesn't make sense. 506 00:26:33,480 --> 00:26:35,400 Speaker 1: Is that what you're saying or that it breaks down. Yeah, 507 00:26:35,400 --> 00:26:38,359 Speaker 1: it breaks down. It breaks down intuitively or an actual 508 00:26:38,400 --> 00:26:41,080 Speaker 1: like math. I guess it breaks down intuitively, not an 509 00:26:41,080 --> 00:26:43,800 Speaker 1: actual math. I mean an individual particle can hit an 510 00:26:43,840 --> 00:26:47,120 Speaker 1: object and deposit its energy, right, that can happen. There's 511 00:26:47,119 --> 00:26:50,359 Speaker 1: no problem there. We can calculate how that happens. But 512 00:26:50,359 --> 00:26:52,240 Speaker 1: that doesn't mean that we can talk about the temperature 513 00:26:52,320 --> 00:26:55,959 Speaker 1: of this object. Temperature, in the end is a macroscopic quantities, 514 00:26:56,040 --> 00:27:00,240 Speaker 1: not a microscopic quantity. It emerges the way like consciousness does. 515 00:27:00,320 --> 00:27:03,120 Speaker 1: Like can you say that an individual neuron in your 516 00:27:03,119 --> 00:27:06,760 Speaker 1: brain is conscious? No, but somehow they come together to 517 00:27:06,840 --> 00:27:09,960 Speaker 1: make your brain self aware. Not a process we understand, 518 00:27:10,000 --> 00:27:13,399 Speaker 1: but individual neurons we don't think are self aware in 519 00:27:13,440 --> 00:27:16,040 Speaker 1: the same way, like a particle doesn't have a temperature, 520 00:27:16,080 --> 00:27:18,440 Speaker 1: and so it's a little bit slippery because temperature is 521 00:27:18,440 --> 00:27:20,840 Speaker 1: is like intuitive thing we want to describe and not 522 00:27:21,040 --> 00:27:24,679 Speaker 1: something hard and fixed about individual particles. Oh okay, So 523 00:27:24,720 --> 00:27:27,040 Speaker 1: I think what you're saying is that our intuitive sense 524 00:27:27,040 --> 00:27:29,800 Speaker 1: of what temperature is and the official physics definition of 525 00:27:29,840 --> 00:27:32,639 Speaker 1: what temperature is kind of matches up or makes sense. 526 00:27:32,720 --> 00:27:34,920 Speaker 1: If you have a lot of particles in something or 527 00:27:35,080 --> 00:27:38,320 Speaker 1: something is dense. But in some of these extreme cases, 528 00:27:38,359 --> 00:27:41,040 Speaker 1: like if you're down to one particle in empty space, 529 00:27:41,119 --> 00:27:44,439 Speaker 1: then our intuitive definition and the official definition sort of 530 00:27:44,480 --> 00:27:48,800 Speaker 1: like start to diverge or don't start to match well together. Yeah, 531 00:27:48,880 --> 00:27:51,320 Speaker 1: that's right. And to make it even more confusing, we 532 00:27:51,400 --> 00:27:55,359 Speaker 1: have more than one official definition of temperature. Like we 533 00:27:55,400 --> 00:27:57,440 Speaker 1: have one definition of temperature, which is what we talked 534 00:27:57,440 --> 00:28:01,480 Speaker 1: about earlier, related to the average kinetic energy of the particles, 535 00:28:01,480 --> 00:28:05,200 Speaker 1: But we have another completely separate definition of temperature. Wait, 536 00:28:05,280 --> 00:28:08,320 Speaker 1: what we have a second definition of temperature? We do. 537 00:28:08,359 --> 00:28:12,159 Speaker 1: We have a thermodynamic definition of temperature. So one earlier 538 00:28:12,200 --> 00:28:15,199 Speaker 1: we call that the kinetic theory of temperature relates to 539 00:28:15,200 --> 00:28:17,680 Speaker 1: the motion of the particles. Now we have another one 540 00:28:17,960 --> 00:28:21,840 Speaker 1: thermodynamic definition, which is about how heat flows. This one 541 00:28:21,880 --> 00:28:24,520 Speaker 1: comes from the observation that heat flows from hot things 542 00:28:24,560 --> 00:28:27,120 Speaker 1: too cold things, and so this one tries to build 543 00:28:27,119 --> 00:28:30,040 Speaker 1: a definition of temperature that says if two things are 544 00:28:30,080 --> 00:28:33,159 Speaker 1: at the same temperature, no heat flows between them. And 545 00:28:33,200 --> 00:28:34,959 Speaker 1: if one thing is a higher temperature and the other 546 00:28:34,960 --> 00:28:36,879 Speaker 1: one has a lower temperature, he will flow from the 547 00:28:36,920 --> 00:28:39,600 Speaker 1: higher temperature thing to the lower temperature thing. So trust 548 00:28:39,640 --> 00:28:43,080 Speaker 1: to build a theory of temperature that matches that experience. 549 00:28:43,800 --> 00:28:45,480 Speaker 1: And I see you're saying, like it's a different way 550 00:28:45,480 --> 00:28:48,840 Speaker 1: to basically think about temperature, Like temperature is not. Maybe 551 00:28:48,840 --> 00:28:51,280 Speaker 1: the kinetic energy of the particles is just kind of 552 00:28:51,280 --> 00:28:54,760 Speaker 1: like a relative property or relative quantity, Like you know, 553 00:28:54,840 --> 00:28:57,680 Speaker 1: something has more temperature than something else. If the heat 554 00:28:57,720 --> 00:28:59,560 Speaker 1: flows from the first thing to the second thing. That's 555 00:28:59,560 --> 00:29:02,280 Speaker 1: gonna saying, I guess zero would be if heat can't 556 00:29:02,360 --> 00:29:05,440 Speaker 1: flow from this thing to anything, then it must be 557 00:29:05,440 --> 00:29:07,440 Speaker 1: at zero. That's kind of what you're saying, like, let's 558 00:29:07,480 --> 00:29:09,840 Speaker 1: measure zero to be that exactly, And so then you 559 00:29:09,880 --> 00:29:13,320 Speaker 1: can come up with a new mathematical expression or how 560 00:29:13,360 --> 00:29:16,960 Speaker 1: to measure this other idea of temperature, thermodynamic temperature in 561 00:29:17,000 --> 00:29:19,240 Speaker 1: the same way that for the kinetic theory. You can say, oh, 562 00:29:19,280 --> 00:29:21,280 Speaker 1: it's about the motion of the particles, and then you 563 00:29:21,320 --> 00:29:22,800 Speaker 1: can go and write the math and say, here's the 564 00:29:22,840 --> 00:29:25,480 Speaker 1: kinetic energy and vibrational energy, and I can actually calculate 565 00:29:25,520 --> 00:29:27,720 Speaker 1: and constructed. In that same way, you can write down 566 00:29:27,760 --> 00:29:32,959 Speaker 1: mathematical expressions for thermodynamic temperature, and they relate to entropy 567 00:29:33,120 --> 00:29:36,600 Speaker 1: into energy and they help you understand like why heat 568 00:29:36,680 --> 00:29:39,280 Speaker 1: flows from hot things to cold things. So it gives 569 00:29:39,280 --> 00:29:43,200 Speaker 1: you a really interesting thermodynamic insight into like why these 570 00:29:43,200 --> 00:29:45,840 Speaker 1: things happen. But is that really sort of different in 571 00:29:45,920 --> 00:29:49,240 Speaker 1: the kinetic I guess view of things, because I imagine 572 00:29:49,280 --> 00:29:51,440 Speaker 1: if you have something where all the particles are moving 573 00:29:51,480 --> 00:29:54,160 Speaker 1: a lot that would be hot, and something that's not 574 00:29:54,240 --> 00:29:56,440 Speaker 1: moving a lot that would be cold, and you put 575 00:29:56,440 --> 00:29:58,680 Speaker 1: it together, the moving things would you know, bump up 576 00:29:58,680 --> 00:30:00,960 Speaker 1: against the other things. And that's why that's what kind 577 00:30:00,960 --> 00:30:03,040 Speaker 1: of what heat flow is. It's like the energy of 578 00:30:03,520 --> 00:30:05,040 Speaker 1: one thing going to the other. Most of the time, 579 00:30:05,080 --> 00:30:07,960 Speaker 1: these two definitions agree about what temperature is and also 580 00:30:08,160 --> 00:30:11,800 Speaker 1: how energy flows from hot things too cold things. So 581 00:30:11,880 --> 00:30:15,360 Speaker 1: in many scenarios you could use either one. But as 582 00:30:15,400 --> 00:30:19,280 Speaker 1: we'll see, thermodynamic temperature has some weird behaviors in strange 583 00:30:19,320 --> 00:30:24,480 Speaker 1: systems at extremes that might allow the existence of negative temperatures. 584 00:30:24,520 --> 00:30:26,760 Speaker 1: So I guess if you go keep going and keep 585 00:30:26,800 --> 00:30:30,480 Speaker 1: defining temperature in terms of heat flow, then that's when 586 00:30:30,480 --> 00:30:33,400 Speaker 1: you might get into trouble. Yeah, into trouble, or into 587 00:30:33,400 --> 00:30:37,680 Speaker 1: this weird territory where temperature can have non zero negative 588 00:30:37,760 --> 00:30:40,080 Speaker 1: values and like what does that mean? And in the end, 589 00:30:40,120 --> 00:30:42,960 Speaker 1: it reflects something about you know, what temperature means? What 590 00:30:43,080 --> 00:30:46,600 Speaker 1: question are you asking about the universe when you calculate 591 00:30:46,680 --> 00:30:49,640 Speaker 1: this number. So then you're saying this different definition of 592 00:30:49,680 --> 00:30:54,240 Speaker 1: temperature is the thermodynamic version. Uh, and it's related to entropy. 593 00:30:54,240 --> 00:30:56,800 Speaker 1: What does that mean? So thermodynamic temperature tries to give 594 00:30:56,880 --> 00:30:58,600 Speaker 1: us a sense for like why things flow from one 595 00:30:58,600 --> 00:31:00,080 Speaker 1: thing to the other. You know why when you with 596 00:31:00,200 --> 00:31:02,280 Speaker 1: that ice cube in your cup of coffee and you 597 00:31:02,360 --> 00:31:05,920 Speaker 1: come back in an hour, everything is about an even temperature, right, 598 00:31:05,960 --> 00:31:08,000 Speaker 1: why do things like to even out? And the answer 599 00:31:08,160 --> 00:31:11,120 Speaker 1: is entropy. The second law of thermodynamics says that entropy 600 00:31:11,200 --> 00:31:14,719 Speaker 1: always increases. And people sometimes think about entropy is like 601 00:31:14,840 --> 00:31:18,320 Speaker 1: the amount of disorganization in the universe, the messiness in 602 00:31:18,360 --> 00:31:20,160 Speaker 1: the universe, and that you know that works in some 603 00:31:20,240 --> 00:31:24,120 Speaker 1: certain circumstances. But that more accurate description of entropy is 604 00:31:24,200 --> 00:31:27,160 Speaker 1: like how many ways can you arrange something? How many 605 00:31:27,280 --> 00:31:30,600 Speaker 1: different configurations of an object and you have like in 606 00:31:30,600 --> 00:31:33,920 Speaker 1: the different microscopic particles that match, you know, the things 607 00:31:33,920 --> 00:31:36,400 Speaker 1: that you're measuring about it. And a basic concept in 608 00:31:36,440 --> 00:31:40,760 Speaker 1: thermodynamics is that every configuration is equally likely, and so 609 00:31:40,800 --> 00:31:43,920 Speaker 1: if you have some state, some condition that has lots 610 00:31:43,920 --> 00:31:47,320 Speaker 1: of possible ways to achieve it, many possible internal configurations. 611 00:31:47,560 --> 00:31:50,560 Speaker 1: You just more likely to end up in that state. Say, 612 00:31:50,600 --> 00:31:53,120 Speaker 1: for example, you have a bunch of coins and you 613 00:31:53,200 --> 00:31:55,560 Speaker 1: throw them all on the floor, right, how many ways 614 00:31:55,600 --> 00:31:58,040 Speaker 1: are there to get all heads up? There's only one way. 615 00:31:58,320 --> 00:32:00,240 Speaker 1: How many ways are there to get all heads down? 616 00:32:00,320 --> 00:32:02,400 Speaker 1: There's only one way. There's lots of ways to get 617 00:32:02,400 --> 00:32:05,160 Speaker 1: fifty heads up and fifty heads down. So if you 618 00:32:05,200 --> 00:32:06,960 Speaker 1: throw a bunch of coins on the floor, you're much 619 00:32:06,960 --> 00:32:09,560 Speaker 1: more likely to end up in that state. Those states 620 00:32:09,560 --> 00:32:14,040 Speaker 1: have higher entropy, So the universe tend towards these arrangements 621 00:32:14,040 --> 00:32:16,760 Speaker 1: with there's lots of ways, lots of configurations to get 622 00:32:16,800 --> 00:32:19,640 Speaker 1: the same value. So that's what entropy is, right, I 623 00:32:19,680 --> 00:32:21,600 Speaker 1: guess in terms of that, that coffee cup and the 624 00:32:21,640 --> 00:32:23,800 Speaker 1: ice cube, it's almost like you're saying, like, if I 625 00:32:23,880 --> 00:32:26,640 Speaker 1: take some water and I take some coffee, and I 626 00:32:26,640 --> 00:32:29,320 Speaker 1: imagine water and coffee in a cup, it's much more 627 00:32:29,360 --> 00:32:32,000 Speaker 1: likely for it to be all mixed up together in 628 00:32:32,080 --> 00:32:35,480 Speaker 1: the in the tepid temperature, right, then it would be 629 00:32:35,680 --> 00:32:39,040 Speaker 1: likely for all the water to be congregated in one place, 630 00:32:39,120 --> 00:32:41,640 Speaker 1: locked together into an ice cube and then all of 631 00:32:41,680 --> 00:32:45,239 Speaker 1: the coffee to be hot surrounding that blog. That's kind 632 00:32:45,240 --> 00:32:46,920 Speaker 1: of what you're saying. And I think you're saying that 633 00:32:46,920 --> 00:32:50,920 Speaker 1: the melted ice cube, tepid coffee, watery coffee is more 634 00:32:51,000 --> 00:32:54,120 Speaker 1: likely to happen, and therefore it's a state of higher entropy. 635 00:32:54,320 --> 00:32:57,960 Speaker 1: Exactly if you let the energy flow from the hot 636 00:32:58,000 --> 00:33:01,920 Speaker 1: coffee into the ice cube, then opens up more configurations, right, 637 00:33:01,920 --> 00:33:04,360 Speaker 1: You can arrange that in many, many more ways. Now, 638 00:33:04,520 --> 00:33:07,480 Speaker 1: that's why energy flows from hot things too cold things, 639 00:33:07,600 --> 00:33:10,200 Speaker 1: because when it does so, it increases the entropy. It 640 00:33:10,280 --> 00:33:12,960 Speaker 1: opens up the number of ways you can arrange the 641 00:33:13,080 --> 00:33:16,080 Speaker 1: little internal bits, right, But that's not why it does 642 00:33:16,120 --> 00:33:17,880 Speaker 1: it right. I think what you're saying is that's how 643 00:33:17,920 --> 00:33:20,880 Speaker 1: thermodynamic says it. Why does it right? Like, if you 644 00:33:20,920 --> 00:33:23,000 Speaker 1: were to look at it from a totally different perspective, 645 00:33:23,040 --> 00:33:24,960 Speaker 1: you would see the molecules of the eyes and the 646 00:33:25,000 --> 00:33:27,840 Speaker 1: coffee interacting and bumping against against each other, and that's 647 00:33:27,880 --> 00:33:30,320 Speaker 1: why you would say that the heat, the energy goes 648 00:33:30,360 --> 00:33:32,120 Speaker 1: from one place to the other. But if you were 649 00:33:32,160 --> 00:33:34,479 Speaker 1: to put on your thermoid dynamic glasses, you would kind 650 00:33:34,520 --> 00:33:37,280 Speaker 1: of ignore all those interactions. And just say, oh, yeah, 651 00:33:37,280 --> 00:33:39,600 Speaker 1: of course it's because of the entropy that it's going 652 00:33:39,680 --> 00:33:42,440 Speaker 1: up exactly. Yeah. So it's another way to explain it. 653 00:33:42,440 --> 00:33:45,760 Speaker 1: It's like a completely different approach, a different set of ideas, 654 00:33:46,080 --> 00:33:47,960 Speaker 1: and most of the time they predict the same thing. 655 00:33:48,560 --> 00:33:51,680 Speaker 1: And so in this thermodynamic context where you're thinking about 656 00:33:51,720 --> 00:33:54,840 Speaker 1: the energy flow and the entropy, then it's this relationship 657 00:33:54,880 --> 00:33:58,719 Speaker 1: between energy and entropy that tells us what temperature is. 658 00:33:58,880 --> 00:34:01,240 Speaker 1: If two things have this same temperature, then we don't 659 00:34:01,240 --> 00:34:03,440 Speaker 1: want any energy to flow between them. So what we 660 00:34:03,520 --> 00:34:06,560 Speaker 1: want is if two things have the same relationship between 661 00:34:06,760 --> 00:34:10,600 Speaker 1: energy and entropy, then we shouldn't have any more energy flow. 662 00:34:10,760 --> 00:34:14,080 Speaker 1: Like for example, if moving some energy from the ice 663 00:34:14,120 --> 00:34:17,320 Speaker 1: cube to the coffee cup doesn't increase the entropy anymore, 664 00:34:17,719 --> 00:34:21,080 Speaker 1: then energy won't flow. So the definition of temperature for 665 00:34:21,239 --> 00:34:24,440 Speaker 1: thermodynamics doesn't have to do with the kinetic energy objects. 666 00:34:24,520 --> 00:34:26,879 Speaker 1: It has to do with the derivative of energy with 667 00:34:26,960 --> 00:34:30,520 Speaker 1: respect to entropy. How the energy and entropy are related 668 00:34:30,560 --> 00:34:32,799 Speaker 1: to each other. I feel like you're saying that maybe 669 00:34:32,880 --> 00:34:35,440 Speaker 1: temperature is relative if you look at it from a 670 00:34:35,480 --> 00:34:37,839 Speaker 1: thermodynamic point of view. And so let's get dig into 671 00:34:37,880 --> 00:34:42,120 Speaker 1: this connection between energy, heat and temperature and entropy. But first, 672 00:34:42,160 --> 00:34:57,480 Speaker 1: let's take another quick break. All right, we are getting 673 00:34:57,560 --> 00:35:02,000 Speaker 1: hot and heavy here talking about possibly negative temperature. Can 674 00:35:02,040 --> 00:35:06,000 Speaker 1: you have negative absolute temperature? And it may be possible 675 00:35:06,080 --> 00:35:08,600 Speaker 1: depends on how you define temperature. I guess most people 676 00:35:08,640 --> 00:35:10,719 Speaker 1: know that, right, Like, if you define temperature in terms 677 00:35:10,719 --> 00:35:13,239 Speaker 1: of fahrenheit, then yeah, you can have negative temperature or 678 00:35:13,239 --> 00:35:15,600 Speaker 1: itself as you think, yeah, you can have negative temperature, 679 00:35:15,600 --> 00:35:19,040 Speaker 1: but you're saying this is something more fundamental, like maybe, um, 680 00:35:19,080 --> 00:35:22,680 Speaker 1: the universe can allow negative absolute temperature. Yeah, and it 681 00:35:22,719 --> 00:35:24,360 Speaker 1: goes to the heart of this question, or like what 682 00:35:24,400 --> 00:35:27,120 Speaker 1: do we mean by temperature anyway? And you know, we 683 00:35:27,200 --> 00:35:29,680 Speaker 1: define these things to describe our experience and then we 684 00:35:29,719 --> 00:35:32,319 Speaker 1: explore their extreme to say where does this break down? 685 00:35:32,360 --> 00:35:35,400 Speaker 1: Does this really make sense? This is something that's universal 686 00:35:35,640 --> 00:35:38,840 Speaker 1: or only something that's useful in certain contexts. So we 687 00:35:38,880 --> 00:35:42,520 Speaker 1: came up with this idea of thermodynamic temperature that basically 688 00:35:42,520 --> 00:35:46,320 Speaker 1: tells you how energy flows around to maximize entropy. The 689 00:35:46,400 --> 00:35:49,400 Speaker 1: two things have the same temperature, then we don't expect 690 00:35:49,480 --> 00:35:51,440 Speaker 1: energy to flow between them. And you know, you can 691 00:35:51,480 --> 00:35:53,480 Speaker 1: have two things that are very different. One thing could 692 00:35:53,520 --> 00:35:56,600 Speaker 1: have a lot more capacity for different configurations than the 693 00:35:56,640 --> 00:35:59,160 Speaker 1: other one, and whether energy flows from one object to 694 00:35:59,200 --> 00:36:01,719 Speaker 1: another depend on like are you going to increase the 695 00:36:01,840 --> 00:36:05,120 Speaker 1: entropy by moving that energy along? And so it is 696 00:36:05,160 --> 00:36:08,960 Speaker 1: this relationship between energy and entropy that is the thermodynamic 697 00:36:09,000 --> 00:36:12,839 Speaker 1: definition of temperature. Technically, it's the derivative of energy with 698 00:36:12,920 --> 00:36:16,680 Speaker 1: respect to entropy. So do you increase the energy as 699 00:36:16,840 --> 00:36:20,280 Speaker 1: entropy increases? That's the temperature I see, And I guess 700 00:36:20,280 --> 00:36:23,960 Speaker 1: maybe my question is why would you do that? Why 701 00:36:23,960 --> 00:36:26,080 Speaker 1: would you define it this way? Is it because it 702 00:36:26,160 --> 00:36:29,759 Speaker 1: matches usually with our other definition of temperature, or like 703 00:36:29,800 --> 00:36:32,439 Speaker 1: why would you call this temperature? Also, it's a totally 704 00:36:32,480 --> 00:36:34,880 Speaker 1: different approach, and it's the macroscopic approach, and it has 705 00:36:34,920 --> 00:36:39,600 Speaker 1: some advantages. You know. The microscopic one is weirdly time invariant. 706 00:36:39,719 --> 00:36:42,520 Speaker 1: The laws of physics governing how things bounce against each other, 707 00:36:42,600 --> 00:36:45,960 Speaker 1: those look the same forward and backwards, and so it's 708 00:36:45,960 --> 00:36:48,960 Speaker 1: hard to go from like a microscopic picture of atoms 709 00:36:49,000 --> 00:36:51,680 Speaker 1: as like little balls, to an understanding of how a 710 00:36:51,760 --> 00:36:55,840 Speaker 1: state evolves forward in time with entropy. It's complicated to 711 00:36:55,880 --> 00:36:58,000 Speaker 1: go from one to the other. This is a picture 712 00:36:58,000 --> 00:37:02,200 Speaker 1: of thermodynamics that deals directly with macroscopic quantities. It says, look, 713 00:37:02,320 --> 00:37:04,760 Speaker 1: these are the things we can measure, the entropy, the energy, 714 00:37:04,840 --> 00:37:07,200 Speaker 1: these are things we're interested in. Not all of science 715 00:37:07,239 --> 00:37:09,560 Speaker 1: has to be reductionists. There are other ways to gain 716 00:37:09,760 --> 00:37:13,120 Speaker 1: understanding and explanation than just to tear things apart into 717 00:37:13,160 --> 00:37:15,399 Speaker 1: their tiny bits. Sometimes you do that and you don't 718 00:37:15,480 --> 00:37:17,719 Speaker 1: get any understanding. Like when you look at the brain, 719 00:37:17,840 --> 00:37:21,680 Speaker 1: psychology is valuable even if neuroscience can't yet explain it. 720 00:37:21,920 --> 00:37:24,000 Speaker 1: Right right, Well, let's dig into this a little bit 721 00:37:24,000 --> 00:37:26,160 Speaker 1: because I am a little bit confused. So you're saying, 722 00:37:26,440 --> 00:37:30,040 Speaker 1: the thermodynamic definition of temperature is the derivative of say 723 00:37:30,080 --> 00:37:33,120 Speaker 1: it again, energy flow divided by entropy. Yeah, it's the 724 00:37:33,120 --> 00:37:37,640 Speaker 1: derivative of energy with respect to entropy. So energies E 725 00:37:37,760 --> 00:37:40,640 Speaker 1: and entropy is S. So temperature in this sense is 726 00:37:40,800 --> 00:37:45,680 Speaker 1: d E D S. Apologize for introducing math to the body. Yeah, 727 00:37:45,920 --> 00:37:49,440 Speaker 1: what are you doing to me here? Okay? So it's uh, 728 00:37:49,480 --> 00:37:52,960 Speaker 1: it's kind of like saying how energy changes if you 729 00:37:53,040 --> 00:37:56,520 Speaker 1: change entropy exactly, because the key idea again is that 730 00:37:56,800 --> 00:37:59,360 Speaker 1: entropy is always going to be maximized, and so what 731 00:37:59,680 --> 00:38:02,520 Speaker 1: array angagement of the stuff? What arrangement of the energy 732 00:38:02,760 --> 00:38:05,400 Speaker 1: is going to give you the most entropy, And so 733 00:38:05,480 --> 00:38:07,440 Speaker 1: to know whether something is going to flow from one 734 00:38:07,480 --> 00:38:09,640 Speaker 1: object to another, you have to know, like how much 735 00:38:09,719 --> 00:38:12,560 Speaker 1: energy does some entropy cost? If I want to increase 736 00:38:12,560 --> 00:38:15,000 Speaker 1: the entropy over here, how much energy does it cost me? 737 00:38:15,080 --> 00:38:17,160 Speaker 1: If I'm gonna gain more entropy by moving the energy 738 00:38:17,200 --> 00:38:20,160 Speaker 1: over than I lose where the energy came from, then 739 00:38:20,280 --> 00:38:22,520 Speaker 1: let's do it. So you have to understand, like how 740 00:38:22,600 --> 00:38:25,760 Speaker 1: much entropy do you get per energy? And that's basically 741 00:38:25,760 --> 00:38:28,120 Speaker 1: what temperature is, right, But then what are you trying 742 00:38:28,160 --> 00:38:31,200 Speaker 1: to measure the temperature of like one thing or two things? 743 00:38:31,400 --> 00:38:32,600 Speaker 1: You know what I mean? Like if I told you 744 00:38:32,600 --> 00:38:36,000 Speaker 1: what's the thermodynamic temperature of an ice cube, how would 745 00:38:36,040 --> 00:38:39,239 Speaker 1: you calculate it? Well, I would measure how quickly it 746 00:38:39,320 --> 00:38:43,799 Speaker 1: gains new possible configurations as I increase its energy as 747 00:38:43,800 --> 00:38:45,800 Speaker 1: you put it in coffee. I can measure the energy 748 00:38:45,880 --> 00:38:48,480 Speaker 1: of the atoms in the ice cube or in some 749 00:38:48,600 --> 00:38:50,600 Speaker 1: other way. Yeah, I guess the question is just like 750 00:38:50,640 --> 00:38:52,239 Speaker 1: if I give you an ice cube, how would you 751 00:38:52,280 --> 00:38:55,560 Speaker 1: measure the thermodynamic temperature of it? I would measure how 752 00:38:55,600 --> 00:38:58,560 Speaker 1: it's entropy changes as I change its energy, right, So 753 00:38:58,640 --> 00:39:01,680 Speaker 1: the temperature there is the relate ationship between the energy 754 00:39:02,000 --> 00:39:04,440 Speaker 1: and the entropy. So you change one and you measure 755 00:39:04,520 --> 00:39:06,920 Speaker 1: the other. Right, But how would you measure its entropy? Well, 756 00:39:06,920 --> 00:39:10,000 Speaker 1: you know, you can measure entropy by measuring temperature and energy, 757 00:39:10,120 --> 00:39:12,600 Speaker 1: because it's a relationship between the three. And that's the 758 00:39:12,640 --> 00:39:15,279 Speaker 1: thing I always hated about thermodynamics is that you feel 759 00:39:15,320 --> 00:39:18,160 Speaker 1: like you're just going in circles. Sometimes. Well, it's good, 760 00:39:18,160 --> 00:39:21,359 Speaker 1: we're spending an hour here discussing something you hate. I'm 761 00:39:21,360 --> 00:39:26,160 Speaker 1: sure people are following along, right right along. All right, Well, 762 00:39:26,200 --> 00:39:28,000 Speaker 1: let's maybe take a step. But I think what you're 763 00:39:28,000 --> 00:39:30,759 Speaker 1: saying is that temperature is kind of this weird thing, 764 00:39:31,040 --> 00:39:33,000 Speaker 1: and if you look at it from a thermodynamic point 765 00:39:33,040 --> 00:39:34,719 Speaker 1: of view, you can look at it in terms of 766 00:39:34,719 --> 00:39:37,759 Speaker 1: how it changes with respect to entropy. Like if it 767 00:39:38,000 --> 00:39:40,920 Speaker 1: something has a lot of temperature, something is hot in 768 00:39:40,920 --> 00:39:44,359 Speaker 1: the thermodynamic sense, that means what it takes a lot 769 00:39:44,400 --> 00:39:46,760 Speaker 1: of entropy, or it doesn't take a lot of entropy. 770 00:39:47,120 --> 00:39:50,000 Speaker 1: Something is hot in a thermodynamic sense, it means that 771 00:39:50,040 --> 00:39:52,920 Speaker 1: it costs a lot of energy to change its entropy. 772 00:39:53,160 --> 00:39:55,080 Speaker 1: And so if you want to take some of that 773 00:39:55,200 --> 00:39:58,600 Speaker 1: energy away, it doesn't reduce its entropy very very much. 774 00:39:58,760 --> 00:40:00,520 Speaker 1: So if you have a really hot link it surrounding 775 00:40:00,560 --> 00:40:02,720 Speaker 1: your ice cube, you can take some of that energy 776 00:40:02,880 --> 00:40:05,080 Speaker 1: out of the liquid and put it into the ice cube, 777 00:40:05,120 --> 00:40:06,759 Speaker 1: and you're not going to lose a whole lot of 778 00:40:06,840 --> 00:40:10,000 Speaker 1: entropy from the liquid. Right, high temperature means high D 779 00:40:10,200 --> 00:40:12,600 Speaker 1: E D s, so you can take energy away without 780 00:40:12,600 --> 00:40:14,680 Speaker 1: losing a whole lot of entropy. And because the ice 781 00:40:14,680 --> 00:40:18,000 Speaker 1: cube is cold, right, has low D E D s 782 00:40:18,080 --> 00:40:20,000 Speaker 1: and as you add energy to it, you get a 783 00:40:20,040 --> 00:40:22,200 Speaker 1: lot more entropy. So you lose a little bit of 784 00:40:22,280 --> 00:40:24,520 Speaker 1: entropy from the hot liquid and you gain a lot 785 00:40:24,600 --> 00:40:27,600 Speaker 1: of entropy into the cold ice cube for the same 786 00:40:27,640 --> 00:40:30,640 Speaker 1: amount of energy. I see. It's almost like the cost 787 00:40:30,960 --> 00:40:34,239 Speaker 1: of entropy for something exactly. It's like exchange rates. Yeah, 788 00:40:34,280 --> 00:40:37,160 Speaker 1: it's like how much bang for your buck does energy 789 00:40:37,200 --> 00:40:40,839 Speaker 1: give you in in the entropy of something Like if 790 00:40:40,880 --> 00:40:43,880 Speaker 1: something an ice cube which is cold, you get a 791 00:40:43,880 --> 00:40:46,960 Speaker 1: lot of entropy just by you know, breathing on it 792 00:40:47,040 --> 00:40:51,000 Speaker 1: with your warm breath, but a cold cup of coffee 793 00:40:51,200 --> 00:40:54,640 Speaker 1: you need a lot of energy to reduce its entropy. Yes, 794 00:40:54,680 --> 00:40:57,919 Speaker 1: So now we have Jorges economic theory of temperature. Yes, 795 00:40:58,080 --> 00:41:01,720 Speaker 1: my My coffee theory is you can buy entropy cheap 796 00:41:01,840 --> 00:41:03,839 Speaker 1: from a hot liquid, and you can sell it at 797 00:41:03,840 --> 00:41:07,440 Speaker 1: a high price in your cold ice cube exactly. Okay, 798 00:41:07,440 --> 00:41:10,400 Speaker 1: So that's the thermo dynamic definition, and it matches up 799 00:41:10,400 --> 00:41:12,600 Speaker 1: with the regular definition because I guess if something is 800 00:41:12,719 --> 00:41:15,399 Speaker 1: zero kelvin, entropy is cheap for something like that, right, 801 00:41:15,440 --> 00:41:16,719 Speaker 1: Like I just got to put in a little bit 802 00:41:16,719 --> 00:41:19,239 Speaker 1: of energy and I get a whole bunch of entropy. 803 00:41:19,280 --> 00:41:22,080 Speaker 1: But if something is like a million degrees kelvin, you 804 00:41:22,120 --> 00:41:23,920 Speaker 1: know it's gonna take me a lot of energy to 805 00:41:24,160 --> 00:41:27,279 Speaker 1: increase the entropy or something that's already super entropic. And 806 00:41:27,280 --> 00:41:29,440 Speaker 1: it's also about the relationship. Like this makes a lot 807 00:41:29,480 --> 00:41:32,520 Speaker 1: of sense for most things because for most things, as 808 00:41:32,560 --> 00:41:35,200 Speaker 1: you add energy, you get more entropy. As you add 809 00:41:35,239 --> 00:41:38,040 Speaker 1: energy to a liquid, you free the particles and then 810 00:41:38,000 --> 00:41:39,919 Speaker 1: they become gas and they can move in new ways 811 00:41:39,960 --> 00:41:42,879 Speaker 1: and find new arrangements, and as you cool things down, 812 00:41:42,920 --> 00:41:46,760 Speaker 1: they get less entropy. So if entropy is always increasing 813 00:41:46,760 --> 00:41:49,040 Speaker 1: with energy, then this makes perfect sense. And that's what 814 00:41:49,120 --> 00:41:51,320 Speaker 1: it does for the ideal gas. And you're like kinetic 815 00:41:51,360 --> 00:41:54,359 Speaker 1: theory of temperature and they line up as you say, 816 00:41:54,480 --> 00:41:57,640 Speaker 1: you mean like you always get something for your money, exactly. 817 00:41:57,800 --> 00:42:01,279 Speaker 1: But condensed matter physicists can imagine in some kinds of 818 00:42:01,320 --> 00:42:05,439 Speaker 1: weird materials where this isn't true, some kind of weird 819 00:42:05,480 --> 00:42:09,440 Speaker 1: materials whereas you add more energy, you actually get fewer 820 00:42:09,960 --> 00:42:13,120 Speaker 1: micro states. Do you have decreasing entropy, So as the 821 00:42:13,160 --> 00:42:16,040 Speaker 1: thing has more and more energy, there might be fewer 822 00:42:16,080 --> 00:42:19,880 Speaker 1: ways to arrange it, and that would lead to negative temperature. 823 00:42:20,200 --> 00:42:23,279 Speaker 1: M All right, now we're getting to the question of 824 00:42:23,320 --> 00:42:26,120 Speaker 1: the episode, which is you're saying that if you define 825 00:42:26,400 --> 00:42:31,560 Speaker 1: temperature in the thermoidyanatic way, um, there are things potentially 826 00:42:31,640 --> 00:42:35,200 Speaker 1: or theoretically I guess that could have negative temperature because 827 00:42:35,400 --> 00:42:37,920 Speaker 1: when you put energy into them, they actually sort of 828 00:42:37,960 --> 00:42:41,920 Speaker 1: get neater, right or colder exactly, they get neater, they 829 00:42:41,920 --> 00:42:45,880 Speaker 1: have fewer ways to arrange themselves. And here's an example. 830 00:42:46,239 --> 00:42:49,520 Speaker 1: Imagine a bunch of particles in a line, and these 831 00:42:49,560 --> 00:42:51,879 Speaker 1: particles are fixed on the line. They can't move at all. 832 00:42:51,920 --> 00:42:53,640 Speaker 1: The only thing they can do is be spin up 833 00:42:53,840 --> 00:42:56,200 Speaker 1: or spin down. Put these particles in a magnetic field, 834 00:42:56,200 --> 00:42:58,919 Speaker 1: so that like spin up has more energy than spin 835 00:42:59,000 --> 00:43:01,640 Speaker 1: down for example, meaning more energy meaning like it that 836 00:43:01,880 --> 00:43:05,040 Speaker 1: just want to spin down, Yeah exactly. Costs more energy 837 00:43:05,040 --> 00:43:07,239 Speaker 1: to spin up than to spin down, like trying to 838 00:43:07,239 --> 00:43:09,759 Speaker 1: stand up a stick. Yeah exactly. So now imagine all 839 00:43:09,800 --> 00:43:13,719 Speaker 1: these particles spin down right minimum energy, there'd be no 840 00:43:13,960 --> 00:43:16,680 Speaker 1: entropy because there's only one way to arrange all of 841 00:43:16,719 --> 00:43:19,480 Speaker 1: these things. It's just like getting all heads when you 842 00:43:19,520 --> 00:43:22,200 Speaker 1: flip a bunch of coins, or getting all tails. Right, 843 00:43:22,239 --> 00:43:24,480 Speaker 1: there's only one way to arrange them, so they're all 844 00:43:24,520 --> 00:43:28,400 Speaker 1: spin down, so there's zero entropy. It's minimum entropy, like 845 00:43:28,400 --> 00:43:30,960 Speaker 1: the block of ice. Right, everything is like neatly ordered 846 00:43:31,000 --> 00:43:34,359 Speaker 1: in a state that um it wants to be in exactly. Now, 847 00:43:34,400 --> 00:43:37,279 Speaker 1: as you add energy, some atoms start to flip right, 848 00:43:37,640 --> 00:43:41,000 Speaker 1: and you quickly add entropy. There's lots of ways to 849 00:43:41,280 --> 00:43:43,080 Speaker 1: arrange it. Now, if you say, well, I have enough 850 00:43:43,160 --> 00:43:45,520 Speaker 1: energy to flip one atom, well, there's a bunch of 851 00:43:45,520 --> 00:43:47,160 Speaker 1: different ways to do that. You can flip any of 852 00:43:47,160 --> 00:43:49,160 Speaker 1: the atoms. If you want to flip five atoms, you 853 00:43:49,160 --> 00:43:51,439 Speaker 1: have enough energy to flip five atoms, right, then there's 854 00:43:51,520 --> 00:43:53,760 Speaker 1: lots and lots of ways, and so as you add energy, 855 00:43:53,880 --> 00:43:57,320 Speaker 1: the entropy increases. Totally normal so far, but what happens 856 00:43:57,360 --> 00:44:01,320 Speaker 1: once you pass the halfway point, once more than half 857 00:44:01,320 --> 00:44:03,520 Speaker 1: of the atoms are flipped up, and as you keep 858 00:44:03,560 --> 00:44:06,920 Speaker 1: adding energy, you're reducing the number of ways you can 859 00:44:07,000 --> 00:44:09,160 Speaker 1: arrange the system until all the way up to the 860 00:44:09,200 --> 00:44:12,520 Speaker 1: maximum energy, when everything is flipped up, there's only one 861 00:44:12,640 --> 00:44:16,000 Speaker 1: way to arrange the system at the maximum energy. So 862 00:44:16,040 --> 00:44:19,160 Speaker 1: in the second half there after you pass the halfway point, 863 00:44:19,480 --> 00:44:23,319 Speaker 1: as you're adding energy, you're losing entropy, so you have 864 00:44:23,360 --> 00:44:27,400 Speaker 1: the opposite relationship between energy and entropy. WHOA, Okay, So 865 00:44:27,440 --> 00:44:29,880 Speaker 1: it's kind of like the coins that like you're saying right, like, 866 00:44:30,000 --> 00:44:35,959 Speaker 1: if all the coins are heads up, that's minimum entropy. Yeah, 867 00:44:36,120 --> 00:44:39,000 Speaker 1: that's zero entropy, and half of them heads up heads 868 00:44:39,040 --> 00:44:41,600 Speaker 1: down is maximum entropy. But then if you go all 869 00:44:41,640 --> 00:44:43,879 Speaker 1: the way I even keep going, and somehow you're able 870 00:44:43,920 --> 00:44:46,879 Speaker 1: to flip all of the coins tails up, then that's 871 00:44:46,920 --> 00:44:51,719 Speaker 1: also zero entropy. Yeah exactly. And so you have maximum 872 00:44:51,840 --> 00:44:54,919 Speaker 1: energy and zero entropy. And this is a really weird 873 00:44:54,960 --> 00:44:57,600 Speaker 1: system and not something we actually see in nature, but 874 00:44:57,680 --> 00:45:01,680 Speaker 1: in principle. Because you are adding energy but reducing entropy, 875 00:45:01,760 --> 00:45:06,400 Speaker 1: that's technically negative temperature. So everything above the halfway point 876 00:45:06,440 --> 00:45:10,400 Speaker 1: there has negative temperature. It has d E D S 877 00:45:10,480 --> 00:45:14,200 Speaker 1: is a negative value. I see in this weird situation, 878 00:45:14,480 --> 00:45:19,000 Speaker 1: after all the coins are heads and tails up, you're saying, 879 00:45:19,040 --> 00:45:22,359 Speaker 1: it actually starts to have a negative temperature again because 880 00:45:22,360 --> 00:45:24,480 Speaker 1: the entropy is going down again as I put more 881 00:45:24,560 --> 00:45:26,919 Speaker 1: energy into it, exactly, And so the system would prefer 882 00:45:27,000 --> 00:45:30,919 Speaker 1: less energy would flow towards a higher entropy situation, which 883 00:45:30,960 --> 00:45:32,840 Speaker 1: is more of a mix, right, Like you try to 884 00:45:32,840 --> 00:45:35,880 Speaker 1: buy more entropy with your energy, but you actually lose entropy. 885 00:45:36,160 --> 00:45:40,480 Speaker 1: That's what it means to be cold in this definition 886 00:45:40,480 --> 00:45:44,160 Speaker 1: of temperature. And this gets really weird. Like let's say 887 00:45:44,160 --> 00:45:45,879 Speaker 1: you have two of these things. Now you have two 888 00:45:45,880 --> 00:45:48,080 Speaker 1: of these lines of atoms, and you put them in 889 00:45:48,120 --> 00:45:50,640 Speaker 1: touch so they can share energy. Right, where is the 890 00:45:50,760 --> 00:45:53,560 Speaker 1: energy going to go? Say one of them has a 891 00:45:53,640 --> 00:45:56,560 Speaker 1: higher value of temperature than the other one. Well, in 892 00:45:56,600 --> 00:46:01,239 Speaker 1: this case, something with negative temperature actually has more energy 893 00:46:01,360 --> 00:46:04,560 Speaker 1: then the thing with positive temperature, right, because they get 894 00:46:04,680 --> 00:46:08,040 Speaker 1: to negative temperature you have to go above the halfway point, 895 00:46:08,080 --> 00:46:10,960 Speaker 1: so half of them are flipped up. So in this case, 896 00:46:11,040 --> 00:46:15,920 Speaker 1: the heat actually flows from the higher energy negative temperature 897 00:46:15,960 --> 00:46:19,279 Speaker 1: system to the positive temperature system, which sounds kind of 898 00:46:19,280 --> 00:46:23,160 Speaker 1: bonkers and backwards well, yeah, yeah, it does sound bankers. 899 00:46:23,239 --> 00:46:25,160 Speaker 1: But I feel like you're trying to maybe trying to 900 00:46:25,200 --> 00:46:28,080 Speaker 1: fudge some of these definitions, right, because like these things, 901 00:46:28,160 --> 00:46:30,799 Speaker 1: these coins only have this weird property because you kind 902 00:46:30,800 --> 00:46:33,400 Speaker 1: of introducing this bias with the magnet. Right, it's not 903 00:46:33,440 --> 00:46:36,600 Speaker 1: actually heat or energy, right, it's sort of something different 904 00:46:36,680 --> 00:46:38,920 Speaker 1: that's going from one to the other. It is energy, right. 905 00:46:38,960 --> 00:46:42,240 Speaker 1: It takes energy to be like misaligned with the magnet, 906 00:46:42,360 --> 00:46:45,240 Speaker 1: for example, and so it really is energy. The question 907 00:46:45,280 --> 00:46:47,440 Speaker 1: really is like what does this mean by temperature? We 908 00:46:47,480 --> 00:46:51,560 Speaker 1: introduce this definition of thermodynamic temperature so that we could 909 00:46:51,560 --> 00:46:53,920 Speaker 1: describe the kind of things we see in the world, right, 910 00:46:54,000 --> 00:46:57,840 Speaker 1: heat flowing from high temperature objects to low temperature objects. 911 00:46:57,840 --> 00:46:59,920 Speaker 1: And this is just an example of this definition pushed 912 00:47:00,000 --> 00:47:03,000 Speaker 1: to the extreme where it really doesn't make any sense anymore. 913 00:47:03,120 --> 00:47:05,640 Speaker 1: The same way we push the definition of kinetic temperature 914 00:47:05,680 --> 00:47:08,080 Speaker 1: to the extreme by asking what is the temperature of 915 00:47:08,120 --> 00:47:10,759 Speaker 1: one particle? In this case, while you can get technically 916 00:47:10,840 --> 00:47:14,400 Speaker 1: negative temperature, it really shows the breakdown of this idea 917 00:47:14,480 --> 00:47:18,759 Speaker 1: of thermodynamic temperature more than like actually being negative in 918 00:47:18,760 --> 00:47:21,920 Speaker 1: any meaningful way. M I see you're saying it like 919 00:47:21,960 --> 00:47:25,279 Speaker 1: if I define temperature as the cost of entropy per 920 00:47:25,480 --> 00:47:29,000 Speaker 1: bank per bug for energy. Um, that doesn't work if 921 00:47:29,000 --> 00:47:30,960 Speaker 1: you have a situation where it actually like if you 922 00:47:31,000 --> 00:47:34,040 Speaker 1: put in more energy, it actually lose this entropy exactly. Yeah, 923 00:47:34,239 --> 00:47:36,319 Speaker 1: it just doesn't really work. And you can see that 924 00:47:36,400 --> 00:47:40,440 Speaker 1: because it predicts that things flow from negative temperature to 925 00:47:40,520 --> 00:47:43,040 Speaker 1: positive temperature. What's the point of temperature then? If it 926 00:47:43,080 --> 00:47:46,000 Speaker 1: doesn't even align with our ideas and our experience? All right, Well, 927 00:47:46,040 --> 00:47:48,239 Speaker 1: I mean it's sort of like kind of I feel 928 00:47:48,280 --> 00:47:51,560 Speaker 1: like it's almost kind of like going to celsius or fahrenheit, right, 929 00:47:51,680 --> 00:47:54,840 Speaker 1: you're sort of changing the scale of things maybe, and 930 00:47:54,960 --> 00:47:57,719 Speaker 1: so then therefore you can have negative temperatures if you 931 00:47:58,239 --> 00:48:00,800 Speaker 1: define things this way. Yeah, it's true. You could always 932 00:48:00,800 --> 00:48:03,960 Speaker 1: define temperatures to be negative as well. I think this 933 00:48:04,000 --> 00:48:07,200 Speaker 1: one is interesting because it shows you, not like that 934 00:48:07,280 --> 00:48:09,840 Speaker 1: the universe breaks the rules or anything, but it shows 935 00:48:09,840 --> 00:48:12,000 Speaker 1: you that these ideas that we invent to try to 936 00:48:12,040 --> 00:48:15,279 Speaker 1: describe our experience, they have limits, and those limits aren't 937 00:48:15,320 --> 00:48:19,000 Speaker 1: physical limits, they're like conceptual limits. Like this idea doesn't 938 00:48:19,040 --> 00:48:21,920 Speaker 1: really work in that circumstance. The whole concept of temperature 939 00:48:22,040 --> 00:48:25,120 Speaker 1: doesn't really make sense for this weird invented system right, 940 00:48:25,120 --> 00:48:27,759 Speaker 1: Like it's like, maybe we have a way of describing 941 00:48:27,880 --> 00:48:30,480 Speaker 1: and calling things in the universe and calculating things, but 942 00:48:30,560 --> 00:48:33,080 Speaker 1: maybe that's not really how the universe works. Like, maybe 943 00:48:33,080 --> 00:48:35,080 Speaker 1: the universe has its own way of doing things that 944 00:48:35,120 --> 00:48:38,560 Speaker 1: are beyond what we're able to describe, kind of or define. 945 00:48:38,640 --> 00:48:40,080 Speaker 1: Is that what you're saying. Yeah, it's like the way 946 00:48:40,080 --> 00:48:42,200 Speaker 1: you can talk about feelings for a person, but can 947 00:48:42,239 --> 00:48:44,960 Speaker 1: you talk about feelings for like a rock or a river. 948 00:48:45,400 --> 00:48:48,040 Speaker 1: You know, it's an idea but doesn't really make sense 949 00:48:48,320 --> 00:48:50,719 Speaker 1: in the same way that like temperature makes sense in 950 00:48:50,880 --> 00:48:54,880 Speaker 1: certain contexts or certain behaviors emerge and have relationships, but 951 00:48:55,000 --> 00:48:57,440 Speaker 1: not in all context You can't ask what is the 952 00:48:57,440 --> 00:49:01,280 Speaker 1: temperature of every arbitrary system that you event doesn't always 953 00:49:01,280 --> 00:49:05,439 Speaker 1: make sense? I see, But what if I an imaginary friend, Rob, 954 00:49:06,120 --> 00:49:09,040 Speaker 1: can I still assign thermodynamic happiness to it? Depends how 955 00:49:09,080 --> 00:49:11,840 Speaker 1: much it's willing to spend to get more entropy? Yeah, 956 00:49:12,440 --> 00:49:14,440 Speaker 1: be flippid and it lands heads up? But what does 957 00:49:14,440 --> 00:49:18,359 Speaker 1: that mean? It means it's time for dessert, all right? 958 00:49:18,440 --> 00:49:20,360 Speaker 1: So then, um, that's kind of where this idea of 959 00:49:20,360 --> 00:49:22,640 Speaker 1: negative temperature is. I think what you're saying is that 960 00:49:22,719 --> 00:49:26,160 Speaker 1: some physicists, if they go by this definition, are allowed 961 00:49:26,200 --> 00:49:29,560 Speaker 1: to call things as having negative temperature. Right, So maybe, 962 00:49:29,600 --> 00:49:32,160 Speaker 1: like most people were saying, no, that's impossible, you can 963 00:49:32,160 --> 00:49:34,319 Speaker 1: have negative temperature, you would say, well, it depends on 964 00:49:34,320 --> 00:49:37,400 Speaker 1: who you talk to and what you mean by temperature. Yeah, exactly, 965 00:49:37,480 --> 00:49:39,400 Speaker 1: and whether you think it even makes sense to apply 966 00:49:39,520 --> 00:49:43,279 Speaker 1: temperature to these crazy, bonkers, weird situations that will never 967 00:49:43,320 --> 00:49:45,839 Speaker 1: arise in our universe. So does that mean I can 968 00:49:45,840 --> 00:49:49,760 Speaker 1: be a thermoid dynamic temperature denier but still a regular 969 00:49:49,800 --> 00:49:54,640 Speaker 1: temperature positivist. You can be whatever you want, man. So 970 00:49:54,680 --> 00:49:56,520 Speaker 1: thanks to everybody who wrote in to ask us to 971 00:49:56,560 --> 00:49:59,680 Speaker 1: talk about that tricky concept. I hope that was useful. 972 00:50:00,120 --> 00:50:01,839 Speaker 1: We hope you enjoy that and maybe made you think 973 00:50:01,880 --> 00:50:04,000 Speaker 1: about what it actually means for something to be hot 974 00:50:04,040 --> 00:50:06,680 Speaker 1: and cold. Like, maybe what we experience in our everyday 975 00:50:06,680 --> 00:50:09,600 Speaker 1: lives is just what we experience in our everyday lives. 976 00:50:09,640 --> 00:50:12,400 Speaker 1: Maybe it doesn't always apply to everything in the universe. 977 00:50:12,640 --> 00:50:23,440 Speaker 1: Thanks for joining us, see you next time. Thanks for listening, 978 00:50:23,440 --> 00:50:26,160 Speaker 1: and remember that. Daniel and Jorge Explain the Universe is 979 00:50:26,200 --> 00:50:29,719 Speaker 1: a production of I Heart Radio For More podcast from 980 00:50:29,719 --> 00:50:33,480 Speaker 1: my heart Radio, visit the i heart Radio app, Apple podcasts, 981 00:50:33,600 --> 00:50:41,719 Speaker 1: or wherever you listen to your favorite shows. Yeah.