1 00:00:08,600 --> 00:00:12,079 Speaker 1: Hey, Daniel, I noticed something about physicists. I'm afraid to 2 00:00:12,119 --> 00:00:13,800 Speaker 1: hear this. I feel like all of you like to 3 00:00:13,880 --> 00:00:16,119 Speaker 1: blow things up. We do. Actually, that's what makes us 4 00:00:16,160 --> 00:00:18,760 Speaker 1: so much fun at parties. I guess. I mean you'd 5 00:00:18,760 --> 00:00:21,599 Speaker 1: like to blow up ideas. You know, you like to 6 00:00:21,640 --> 00:00:24,480 Speaker 1: think things that people think are true and then prove 7 00:00:24,560 --> 00:00:27,560 Speaker 1: that they're actually false. That's true. Actually you mean like 8 00:00:27,920 --> 00:00:30,200 Speaker 1: the Earth being the center of the universe. Yeah, I 9 00:00:30,240 --> 00:00:32,159 Speaker 1: like that. I like that idea, but it turns out 10 00:00:32,440 --> 00:00:34,479 Speaker 1: it's false. Or you know that people thought that the 11 00:00:34,479 --> 00:00:37,240 Speaker 1: world was nice and smooth, but actually it's quantized into 12 00:00:37,360 --> 00:00:40,320 Speaker 1: little pixels called quantum physics. Al Right, So what do 13 00:00:40,320 --> 00:00:42,640 Speaker 1: you think that means about physicists. I think it probably 14 00:00:42,680 --> 00:00:45,320 Speaker 1: means that you like to disagree with the stabich ideas. 15 00:00:45,400 --> 00:00:48,960 Speaker 1: You're basically just contrarians. No, we're not. See do you 16 00:00:49,040 --> 00:01:07,039 Speaker 1: know fun at parties? Hi am or handmade cartoonists and 17 00:01:07,040 --> 00:01:10,040 Speaker 1: the creator of PhD Comics. Hi. I'm Daniel. I'm a 18 00:01:10,080 --> 00:01:13,920 Speaker 1: particle physicist, and I'm very positive about new ideas. Welcome 19 00:01:13,959 --> 00:01:16,480 Speaker 1: to our podcast Daniel and Jorge Explain the Universe, a 20 00:01:16,560 --> 00:01:19,120 Speaker 1: production of Our Heart Radio in which we consider all 21 00:01:19,160 --> 00:01:22,320 Speaker 1: the crazy new ideas out there and all the old ideas. 22 00:01:22,520 --> 00:01:24,800 Speaker 1: Which ones are real, which ones are made up, which 23 00:01:24,880 --> 00:01:27,480 Speaker 1: ones are we still clueless about. We take you on 24 00:01:27,480 --> 00:01:30,240 Speaker 1: a tour of all of them and explain them to you. Yeah, 25 00:01:30,280 --> 00:01:33,280 Speaker 1: we like to explore the universe and talk about all 26 00:01:33,319 --> 00:01:35,360 Speaker 1: of the things that are out there and this beautiful 27 00:01:35,400 --> 00:01:38,520 Speaker 1: cosmos of ours, all the things that are true, and 28 00:01:38,640 --> 00:01:40,959 Speaker 1: all the things that might be true. And part of 29 00:01:41,000 --> 00:01:44,920 Speaker 1: the journey of physics and science in general is understanding 30 00:01:44,920 --> 00:01:48,320 Speaker 1: the universe and questioning the things we thought were true, 31 00:01:48,640 --> 00:01:51,680 Speaker 1: getting a deeper, more fundamental view of the way things 32 00:01:51,840 --> 00:01:55,600 Speaker 1: actually work, which sometimes is really in contrast with the 33 00:01:55,640 --> 00:01:57,920 Speaker 1: way we thought things work. Because there are a lot 34 00:01:57,960 --> 00:02:01,120 Speaker 1: of ideas out there, right, Daniel. I mean they're ideas 35 00:02:01,160 --> 00:02:03,440 Speaker 1: about how the world works, about why things are the 36 00:02:03,440 --> 00:02:06,680 Speaker 1: way they are, and how people think that it all 37 00:02:06,720 --> 00:02:09,320 Speaker 1: comes together. Yeah, And sometimes the first idea you have 38 00:02:09,440 --> 00:02:12,840 Speaker 1: seems reasonable and sticks around for a long time, and 39 00:02:12,880 --> 00:02:16,000 Speaker 1: then you notice small little problems with it, and when 40 00:02:16,040 --> 00:02:19,120 Speaker 1: you pull on that thread, you reveal something really fascinating 41 00:02:19,360 --> 00:02:22,320 Speaker 1: about the whole universe. Like people used to think, hey, there, 42 00:02:22,360 --> 00:02:25,480 Speaker 1: Earth is flat. It certainly looks flat from here. But 43 00:02:25,520 --> 00:02:28,760 Speaker 1: then it's sort of a mind exploding discovery to realize, Wow, 44 00:02:28,800 --> 00:02:32,400 Speaker 1: we're actually living on the surface of a huge sphere. Yeah. 45 00:02:32,440 --> 00:02:34,560 Speaker 1: So there are a lot of ideas out there, and 46 00:02:34,760 --> 00:02:37,120 Speaker 1: I feel like you physicists like to reserve the right 47 00:02:37,200 --> 00:02:40,840 Speaker 1: to change your mind. That's an important part of science, right, 48 00:02:41,120 --> 00:02:43,960 Speaker 1: challenging the orthodoxy. It's one of the best things about 49 00:02:44,000 --> 00:02:47,480 Speaker 1: science that sometimes we look at the very foundations of 50 00:02:47,480 --> 00:02:49,720 Speaker 1: the ideas and we say, wait a second, is that 51 00:02:49,840 --> 00:02:52,360 Speaker 1: really true? How do we actually know that? We've been 52 00:02:52,400 --> 00:02:55,720 Speaker 1: thinking that for a long time, but is it possible 53 00:02:56,080 --> 00:02:58,160 Speaker 1: that we were wrong. I think it's one of the 54 00:02:58,200 --> 00:03:00,720 Speaker 1: deepest virtues of science. Yeah. And if like that's maybe 55 00:03:00,720 --> 00:03:04,560 Speaker 1: your favorite part of science is proving your appears wrong 56 00:03:05,720 --> 00:03:08,639 Speaker 1: on a personal level, yes, And for me it's actually 57 00:03:08,639 --> 00:03:11,560 Speaker 1: the reason I got into science, because I'm really excited 58 00:03:11,600 --> 00:03:16,119 Speaker 1: about those moments of intellectual revolution. I feel like, when 59 00:03:16,160 --> 00:03:18,480 Speaker 1: you discover that the world is really different from the 60 00:03:18,520 --> 00:03:21,240 Speaker 1: way we thought it was, we've pulled the wolf from 61 00:03:21,240 --> 00:03:24,079 Speaker 1: our eyes. We've like peeled back a layer of reality. 62 00:03:24,120 --> 00:03:27,040 Speaker 1: We've discovered some truth that was hidden to us. And 63 00:03:27,120 --> 00:03:30,640 Speaker 1: what's more exciting in science than to have a moment 64 00:03:30,720 --> 00:03:33,560 Speaker 1: of discovery like that a deep revelation, you know, not 65 00:03:33,639 --> 00:03:37,720 Speaker 1: like slowly iterately building up increments of knowledge until you 66 00:03:37,720 --> 00:03:40,960 Speaker 1: get there, like almost like a moment of revelation where 67 00:03:40,960 --> 00:03:43,760 Speaker 1: you understand the universe differently somehow and you can never 68 00:03:43,840 --> 00:03:46,400 Speaker 1: go back to seeing it the old way. Some people 69 00:03:46,440 --> 00:03:48,440 Speaker 1: go for the Eureka moment. You like to go for 70 00:03:48,520 --> 00:03:52,840 Speaker 1: the moment. That's what I'm in for. I'm in it 71 00:03:52,960 --> 00:03:55,760 Speaker 1: for the scientific revolutions, for the Hans. You're in for 72 00:03:55,800 --> 00:03:58,280 Speaker 1: the Hans I am. And there have been lots of 73 00:03:58,320 --> 00:04:00,840 Speaker 1: moments in history where people have made to discoveries like this. 74 00:04:01,080 --> 00:04:03,680 Speaker 1: They've pulled on one little string and then they've unraveled 75 00:04:03,840 --> 00:04:07,120 Speaker 1: that very foundations of science, and so it's exciting to 76 00:04:07,160 --> 00:04:09,040 Speaker 1: think that there might be more of those ahead of us. 77 00:04:09,320 --> 00:04:11,240 Speaker 1: So it's exciting when a bunch of smart people's go, 78 00:04:11,760 --> 00:04:14,880 Speaker 1: never mind, I thought there was flat, but actually it's 79 00:04:15,120 --> 00:04:18,400 Speaker 1: a giant ball. Yeah, because it changes sometimes your whole 80 00:04:18,440 --> 00:04:21,560 Speaker 1: relationship with the universe, you know, thinking that we live 81 00:04:21,600 --> 00:04:23,920 Speaker 1: at the center of the universe everything revolves around us, 82 00:04:24,320 --> 00:04:27,599 Speaker 1: to thinking we're just a tiny little speck of dust 83 00:04:27,640 --> 00:04:31,200 Speaker 1: in an insignificant corner of the universe that really changes 84 00:04:31,240 --> 00:04:33,679 Speaker 1: the way you feel about the universe and life itself 85 00:04:33,720 --> 00:04:36,360 Speaker 1: and how you should live it. So, hey, this stuff 86 00:04:36,440 --> 00:04:39,240 Speaker 1: is actually irrelevant for how people feel about themselves and 87 00:04:39,279 --> 00:04:42,640 Speaker 1: their lives. Yeah. So science is all about challenging ideas, 88 00:04:42,680 --> 00:04:45,360 Speaker 1: and so today on the program will be challenging a 89 00:04:45,480 --> 00:04:48,359 Speaker 1: very core and fundamental idea and physics. I feel like 90 00:04:48,400 --> 00:04:50,760 Speaker 1: this is a very important idea that a lot of 91 00:04:50,760 --> 00:04:53,440 Speaker 1: people have kind of internalized about the universe, but that 92 00:04:53,680 --> 00:04:57,039 Speaker 1: actually might not be so true. That's right. This is 93 00:04:57,080 --> 00:04:59,640 Speaker 1: something pretty basic that if you ask folks on the street, 94 00:05:00,000 --> 00:05:02,520 Speaker 1: it would be pretty confident was true. But it turns 95 00:05:02,520 --> 00:05:04,279 Speaker 1: out we've learned a lot about the nature of the 96 00:05:04,360 --> 00:05:07,600 Speaker 1: universe and it might actually not be quite so fundamental. 97 00:05:07,680 --> 00:05:15,039 Speaker 1: So on the program will be asking the question is 98 00:05:15,200 --> 00:05:22,000 Speaker 1: energy actually conserved? Now, Daniel, this sort of blew my mind. 99 00:05:22,080 --> 00:05:24,160 Speaker 1: How can we even ask this question? What do you mean? 100 00:05:24,200 --> 00:05:27,960 Speaker 1: Is energy always actually conserved? Yeah? That's why it's such 101 00:05:27,960 --> 00:05:30,840 Speaker 1: a wonderful question because it makes you think, like, well, 102 00:05:31,120 --> 00:05:33,600 Speaker 1: why would it be conserved? How do we actually know 103 00:05:33,720 --> 00:05:36,039 Speaker 1: it's conserved? What would it be like to live in 104 00:05:36,080 --> 00:05:39,440 Speaker 1: a universe where it's not conserved? That solve all of 105 00:05:39,440 --> 00:05:41,479 Speaker 1: our energy problems. I feel like you just told me 106 00:05:41,520 --> 00:05:43,560 Speaker 1: the world is not actually a ball. It's like a 107 00:05:43,600 --> 00:05:46,920 Speaker 1: cube or something. We live on a donut and it's 108 00:05:47,000 --> 00:05:51,400 Speaker 1: filled with energy. It's filled with sugar, energy and sprinkles. 109 00:05:51,800 --> 00:05:54,720 Speaker 1: That's right. Just eat the glaze, man, eat the glaze. 110 00:05:55,839 --> 00:05:59,120 Speaker 1: Then then my energy will not be conserved, just an 111 00:05:59,120 --> 00:06:02,120 Speaker 1: increase or be turned into mass. Probably. I know. It's 112 00:06:02,160 --> 00:06:04,480 Speaker 1: a bit mind blowing, and that's why I was especially 113 00:06:04,520 --> 00:06:06,840 Speaker 1: eager to hear what folks on the internet had to 114 00:06:06,880 --> 00:06:09,160 Speaker 1: say about this question. Yes, so it's usual Daniel went 115 00:06:09,200 --> 00:06:11,840 Speaker 1: out there into the wilds of the web and ask 116 00:06:11,880 --> 00:06:16,240 Speaker 1: people the question is energy always conserved? So thank you 117 00:06:16,279 --> 00:06:18,840 Speaker 1: to these folks in advance who participated. And if you 118 00:06:18,880 --> 00:06:22,400 Speaker 1: would like to answer tough physics questions with no preparation 119 00:06:22,520 --> 00:06:26,120 Speaker 1: and have your answers broadcast thousands of people, please write 120 00:06:26,160 --> 00:06:28,800 Speaker 1: to us two questions at Daniel and Jorge dot com. 121 00:06:28,960 --> 00:06:30,800 Speaker 1: Think about it for a second. If someone ask you 122 00:06:31,040 --> 00:06:35,120 Speaker 1: if energy is actually always conserved, what would you answer. 123 00:06:35,880 --> 00:06:37,919 Speaker 1: Here's what people had to say. I always thought that 124 00:06:38,080 --> 00:06:41,679 Speaker 1: was one of the fundamental laws, that energy and matter 125 00:06:41,839 --> 00:06:44,279 Speaker 1: can't be created or destroyed, But the fact that you're 126 00:06:44,320 --> 00:06:47,919 Speaker 1: asking me this question makes me think I'm wrong. Yes, 127 00:06:48,320 --> 00:06:51,119 Speaker 1: I don't know about the energy that goes in into 128 00:06:51,160 --> 00:06:56,520 Speaker 1: a black hole, but it's somewhere there. Yes, is one 129 00:06:56,560 --> 00:07:00,800 Speaker 1: of the fundamental principles of the universe that energy is conserved. 130 00:07:01,480 --> 00:07:03,840 Speaker 1: I know that it gets a little dicey when you're 131 00:07:03,839 --> 00:07:06,320 Speaker 1: talking about black holes. Yes, it is, but I don't 132 00:07:06,480 --> 00:07:09,159 Speaker 1: know if there's any special cases where it's not. Yes, 133 00:07:09,360 --> 00:07:13,360 Speaker 1: energy always is conserved in some form, right, I think 134 00:07:13,520 --> 00:07:18,520 Speaker 1: ultimately everything becomes heat. But if energy does not get conserved, 135 00:07:19,080 --> 00:07:21,440 Speaker 1: where does it go? All right, not a lot of 136 00:07:21,480 --> 00:07:26,120 Speaker 1: doubters here. Everyone just said yes, no confusion. I feel 137 00:07:26,160 --> 00:07:29,000 Speaker 1: like nobody was confused about this. No, nobody was confused. 138 00:07:29,080 --> 00:07:31,400 Speaker 1: I love the person who said the fact you're asking 139 00:07:31,440 --> 00:07:37,120 Speaker 1: me this question makes me think I'm wrong, which is wonderful. Man, 140 00:07:37,240 --> 00:07:41,160 Speaker 1: you totally make that person. You need a doubt because 141 00:07:41,200 --> 00:07:44,119 Speaker 1: that's the process of science. We're like, we're sure that's true. 142 00:07:44,280 --> 00:07:47,280 Speaker 1: Hold on a second, how are we sure? All of 143 00:07:47,320 --> 00:07:50,000 Speaker 1: a sudden, I'm wondering, And then you've got to explore 144 00:07:50,040 --> 00:07:53,040 Speaker 1: your own intellectual framework and wonder like, do you really 145 00:07:53,080 --> 00:07:56,480 Speaker 1: know this or is it just something you've been assuming yeah. 146 00:07:56,600 --> 00:07:59,200 Speaker 1: Especially I guess if a physicist approaches you on the 147 00:07:59,240 --> 00:08:01,640 Speaker 1: street with my acrophone and says, do you think energy 148 00:08:01,720 --> 00:08:04,040 Speaker 1: is always conserved? I feel like, you know that automatically 149 00:08:04,160 --> 00:08:06,840 Speaker 1: makes you a little suspicious. Yeah. Actually, default answer to 150 00:08:06,880 --> 00:08:10,000 Speaker 1: a random physicist asking you a question should be no, 151 00:08:10,120 --> 00:08:12,520 Speaker 1: it should be I don't know, what do you think? 152 00:08:12,920 --> 00:08:15,120 Speaker 1: And then you flipped do you want to participate in 153 00:08:15,120 --> 00:08:18,840 Speaker 1: my experiment? Uh? No? Do you want to know the 154 00:08:18,840 --> 00:08:22,800 Speaker 1: deep secrets of the universe? Not? Really? So this is 155 00:08:22,920 --> 00:08:24,760 Speaker 1: I feel like this is a pretty mind blown question, 156 00:08:24,840 --> 00:08:26,960 Speaker 1: just the idea of asking this question. I feel like 157 00:08:26,960 --> 00:08:30,960 Speaker 1: the idea that energy is always conserved seems very basic 158 00:08:31,040 --> 00:08:34,800 Speaker 1: to physics, and it seems pretty internalized by most of 159 00:08:34,840 --> 00:08:36,600 Speaker 1: the public. Like I feel like, you know, it's like 160 00:08:36,679 --> 00:08:40,080 Speaker 1: asking which way does gravity point? Or you know, it's 161 00:08:40,080 --> 00:08:42,840 Speaker 1: space big people say yes. But there's a bit of 162 00:08:42,840 --> 00:08:45,280 Speaker 1: a history here, right. It used to be that we 163 00:08:45,360 --> 00:08:48,880 Speaker 1: thought energy was conserved and that mass was conserved. We 164 00:08:48,920 --> 00:08:51,720 Speaker 1: would watch chemical reactions and we would notice that it 165 00:08:51,800 --> 00:08:55,240 Speaker 1: was mostly a rearrangement of the atoms, like puzzle pieces 166 00:08:55,240 --> 00:08:58,400 Speaker 1: moving from one place to another, and that no actual 167 00:08:58,480 --> 00:09:01,960 Speaker 1: matter was destroyed or created, and so we had two principles, 168 00:09:02,000 --> 00:09:06,040 Speaker 1: conservation of energy and conservation of mass. But then we 169 00:09:06,120 --> 00:09:09,840 Speaker 1: learned conservation of mass not actually a thing, right, You 170 00:09:09,880 --> 00:09:13,120 Speaker 1: can turn mass into other kinds of energy, and energy 171 00:09:13,160 --> 00:09:16,439 Speaker 1: into mass. So then we generalized into a larger principle, 172 00:09:16,760 --> 00:09:20,160 Speaker 1: conservation of energy, which includes mass as one of its forms. 173 00:09:20,360 --> 00:09:22,360 Speaker 1: But that's a hint, right, that's a hint. That's something 174 00:09:22,360 --> 00:09:26,360 Speaker 1: which seems fundamental, like the existence of matter doesn't necessarily 175 00:09:26,400 --> 00:09:29,160 Speaker 1: have to be concerned. Now, this isn't just a sort 176 00:09:29,200 --> 00:09:31,600 Speaker 1: of like a semantic thing, right, Like we're not saying 177 00:09:31,640 --> 00:09:35,480 Speaker 1: that energy just transforms into mass and so it's not concerned. 178 00:09:35,480 --> 00:09:38,040 Speaker 1: We're asking kind of the bigger question, like is mass 179 00:09:38,080 --> 00:09:40,800 Speaker 1: and energy conserved? That's right now, we're asking the deep 180 00:09:40,840 --> 00:09:45,559 Speaker 1: fundamental question. Is total energy concerned? When you include all forms, 181 00:09:45,600 --> 00:09:47,960 Speaker 1: not just does it slip away into some other kind 182 00:09:47,960 --> 00:09:51,560 Speaker 1: of energy, but energy itself summed up over everything, is 183 00:09:51,559 --> 00:09:55,560 Speaker 1: it actually conserved? Yeah? And it turns out that the 184 00:09:55,640 --> 00:10:01,320 Speaker 1: answer is no. How can it be? No, Daniel, The 185 00:10:01,400 --> 00:10:04,840 Speaker 1: answer is no. He's just during my world, I feel 186 00:10:04,840 --> 00:10:09,000 Speaker 1: like democracy died last night. And now physics, well, that's 187 00:10:09,000 --> 00:10:11,160 Speaker 1: what we're here for. We are here to blow people's 188 00:10:11,200 --> 00:10:14,160 Speaker 1: minds and pull back the veil and help them understand 189 00:10:14,240 --> 00:10:17,199 Speaker 1: the way the world actually works. And so this is 190 00:10:17,280 --> 00:10:19,880 Speaker 1: kind of mind boggling. But the lesson we're gonna learn 191 00:10:20,080 --> 00:10:23,880 Speaker 1: is what's actually important about the universe, what's really fundamental? 192 00:10:23,960 --> 00:10:26,600 Speaker 1: What do we actually know? What really should we be 193 00:10:26,679 --> 00:10:30,320 Speaker 1: paying attention to? All Right, so I guess the short 194 00:10:30,360 --> 00:10:33,400 Speaker 1: answer is no. Energy is not always conserved. That's right, 195 00:10:33,440 --> 00:10:36,160 Speaker 1: And that's even in a closed system. Right, we talked 196 00:10:36,160 --> 00:10:39,080 Speaker 1: about energy conservation. We're usually referring to a closed system 197 00:10:39,120 --> 00:10:41,560 Speaker 1: because you know, if you have a single thing inside 198 00:10:41,559 --> 00:10:44,160 Speaker 1: a larger system, sure it doesn't have to conserve energy, 199 00:10:44,240 --> 00:10:48,200 Speaker 1: Like a battery inside your toy is losing energy, but 200 00:10:48,280 --> 00:10:50,080 Speaker 1: you know that energy is going to other parts of 201 00:10:50,080 --> 00:10:52,599 Speaker 1: the system. But we're talking about a closed system, or 202 00:10:52,679 --> 00:10:55,559 Speaker 1: energy doesn't escape or doesn't enter, we're talking about the 203 00:10:55,559 --> 00:10:59,200 Speaker 1: whole universe. Is energy conserved for the whole universe? And 204 00:10:59,320 --> 00:11:03,400 Speaker 1: even for that, the answer, it turns out is no, Man, Daniel, 205 00:11:03,920 --> 00:11:06,240 Speaker 1: not even for a closed system. I feel like one 206 00:11:06,240 --> 00:11:09,040 Speaker 1: of those celebrities. I'm ready to throw down my microphone 207 00:11:09,080 --> 00:11:12,400 Speaker 1: and walk away. Don't mic drop just yet. There are 208 00:11:12,480 --> 00:11:16,000 Speaker 1: bigger revelations to come, I see their twists. All right, 209 00:11:16,040 --> 00:11:18,400 Speaker 1: we'll step us through first, why do we think that 210 00:11:18,559 --> 00:11:21,480 Speaker 1: energy was conserved? And then maybe we'll get into why 211 00:11:21,480 --> 00:11:24,120 Speaker 1: it wasn't it's not conserved. Yeah, that's a great question. 212 00:11:24,160 --> 00:11:27,560 Speaker 1: And essentially we thought that energy was conserved because mostly 213 00:11:27,640 --> 00:11:30,800 Speaker 1: it is, and so we never noticed we never saw 214 00:11:30,840 --> 00:11:33,960 Speaker 1: a counter example. And a lot of physics works this way. 215 00:11:34,000 --> 00:11:36,320 Speaker 1: We see things happening in the world and we see 216 00:11:36,360 --> 00:11:39,000 Speaker 1: them seeming to follow a rule, and so we just 217 00:11:39,040 --> 00:11:41,559 Speaker 1: sort of like we positive, well, maybe this rule is true. 218 00:11:41,640 --> 00:11:45,600 Speaker 1: Maybe this is fundamental. You know, electric charge is conserved, 219 00:11:45,720 --> 00:11:48,360 Speaker 1: or you know F equals m A. We don't always 220 00:11:48,440 --> 00:11:50,800 Speaker 1: have a reason for it. We don't always have like 221 00:11:50,840 --> 00:11:54,280 Speaker 1: a first principles derivation for it, which is something we observe, 222 00:11:54,840 --> 00:11:58,240 Speaker 1: we categorize, and then we elevate it to a status 223 00:11:58,320 --> 00:12:00,600 Speaker 1: and if nobody ever sees it broken, we think, well 224 00:12:00,840 --> 00:12:03,200 Speaker 1: that must be true. For some reason. We elevated to 225 00:12:03,240 --> 00:12:05,199 Speaker 1: that like a law status. We think it's a law 226 00:12:05,240 --> 00:12:07,960 Speaker 1: of the universe. Yeah, And this is the way science works, 227 00:12:08,040 --> 00:12:10,000 Speaker 1: is that we come up with a rule, we test it, 228 00:12:10,040 --> 00:12:12,880 Speaker 1: we check it, we explore it and lots of different ways, 229 00:12:12,920 --> 00:12:16,160 Speaker 1: and if it survives experimental tests over and over and 230 00:12:16,200 --> 00:12:18,240 Speaker 1: over again. We think, oh, it's probably true, and then 231 00:12:18,280 --> 00:12:21,880 Speaker 1: we can sometimes dig deeper and figure out the reason why. 232 00:12:22,080 --> 00:12:26,760 Speaker 1: We can sometimes later derive that law from deeper truths. 233 00:12:26,800 --> 00:12:29,480 Speaker 1: But sometimes we can reveal that it was only ever 234 00:12:29,559 --> 00:12:34,679 Speaker 1: approximately true. We haven't checked every possible scenario. That's impossible, right, 235 00:12:35,000 --> 00:12:37,559 Speaker 1: and so people will find a place where, look, it 236 00:12:37,640 --> 00:12:40,640 Speaker 1: turns out it's broken over here, it doesn't quite work 237 00:12:40,679 --> 00:12:43,760 Speaker 1: over there. It was the same story with conservation of mass. 238 00:12:43,840 --> 00:12:47,040 Speaker 1: If you're just doing basic chemistry, mass is mostly conserved. 239 00:12:47,320 --> 00:12:49,319 Speaker 1: It's only when you get to like higher energies where 240 00:12:49,360 --> 00:12:53,640 Speaker 1: you're destroying particles or colliding particles that you notice that 241 00:12:53,720 --> 00:12:57,120 Speaker 1: it's broken. So a lot of these conservation rules are 242 00:12:57,240 --> 00:13:01,319 Speaker 1: not exact. They're not like really true. They're almost true, 243 00:13:01,400 --> 00:13:04,080 Speaker 1: or they're true and lots of circumstances and so we 244 00:13:04,160 --> 00:13:06,559 Speaker 1: never notice. It's kind of like F equals m A. 245 00:13:06,679 --> 00:13:10,360 Speaker 1: I feel like that feels really fundamental and intuitive because 246 00:13:10,360 --> 00:13:13,959 Speaker 1: that's what dominates our everyday experience. But like if you 247 00:13:14,040 --> 00:13:17,520 Speaker 1: push the physics of it to extreme situations, it doesn't work. 248 00:13:17,559 --> 00:13:20,200 Speaker 1: It breaks, yeah, exactly. And the same is true for 249 00:13:20,280 --> 00:13:23,319 Speaker 1: things about like time. You know, we've learned that not 250 00:13:23,440 --> 00:13:26,240 Speaker 1: everybody has to agree on the order of events. We 251 00:13:26,240 --> 00:13:28,480 Speaker 1: had a whole podcast about what happens when people are 252 00:13:28,559 --> 00:13:30,960 Speaker 1: running a race and you look at it from different speeds, 253 00:13:31,360 --> 00:13:32,880 Speaker 1: and these are the kind of things you don't notice 254 00:13:32,880 --> 00:13:35,680 Speaker 1: in your everyday life. You don't approach the speed of light. 255 00:13:36,000 --> 00:13:38,320 Speaker 1: And so we never tested things in those sort of 256 00:13:38,400 --> 00:13:41,880 Speaker 1: high speed extremes until recently, and we noticed, whoops. Those 257 00:13:42,040 --> 00:13:44,640 Speaker 1: rules we thought were deep and fundamental and true turned 258 00:13:44,640 --> 00:13:46,880 Speaker 1: out to be a special case that are only valided 259 00:13:46,960 --> 00:13:51,240 Speaker 1: certain situations, not fundamental truths about the universe. And physics 260 00:13:51,280 --> 00:13:54,760 Speaker 1: is all about uncovering the fundamental truths about the universe, 261 00:13:55,200 --> 00:13:58,200 Speaker 1: not just the special cases. And so that's why we 262 00:13:58,240 --> 00:14:01,360 Speaker 1: thought energy was conserved because we've always seen it conserved 263 00:14:01,400 --> 00:14:04,680 Speaker 1: and sort of made sense. Yeah, it's conserved in most 264 00:14:04,720 --> 00:14:07,280 Speaker 1: situations that we're familiar with, right, Like, if you have 265 00:14:07,320 --> 00:14:10,400 Speaker 1: a canister of gas or something, the energy in it 266 00:14:10,440 --> 00:14:14,480 Speaker 1: is going to be mostly conserved, mostly conserved, are totally conserved, 267 00:14:14,480 --> 00:14:17,679 Speaker 1: the energy is going to be almost exactly conserved. And 268 00:14:17,800 --> 00:14:20,720 Speaker 1: thinking about when it's conserved and noticing when those rules 269 00:14:20,720 --> 00:14:23,440 Speaker 1: are broken, it's going to teach us really something fundamental 270 00:14:23,480 --> 00:14:27,000 Speaker 1: about the nature of space and symmetries and conservation laws 271 00:14:27,040 --> 00:14:31,600 Speaker 1: in general. But fuel, for example, is mostly conserved. All right, 272 00:14:31,680 --> 00:14:35,560 Speaker 1: let's get into some examples of when energy is not conserved, 273 00:14:35,720 --> 00:14:39,280 Speaker 1: and let's get into why it's not being the good 274 00:14:39,280 --> 00:14:42,280 Speaker 1: conservative we thought it was. But first let's take a 275 00:14:42,360 --> 00:14:57,600 Speaker 1: quick break. All right, Daniel, we are blowing up people's 276 00:14:57,640 --> 00:15:01,720 Speaker 1: brains here. Apparently energy is not concerned in this universe. 277 00:15:01,960 --> 00:15:04,160 Speaker 1: That's right. It's not always the same, that's right. It's 278 00:15:04,200 --> 00:15:06,640 Speaker 1: not always the same. The amount of energy in the 279 00:15:06,720 --> 00:15:09,680 Speaker 1: universe can change. And this is the kind of thing 280 00:15:09,720 --> 00:15:12,600 Speaker 1: I get email questions from listeners about all the time, 281 00:15:12,680 --> 00:15:14,880 Speaker 1: because people who have been thinking to themselves about dark 282 00:15:15,000 --> 00:15:17,600 Speaker 1: energy have come in their minds to what seems like 283 00:15:17,640 --> 00:15:22,160 Speaker 1: a contradiction. Remember, dark energy is the expansion of the universe. 284 00:15:22,200 --> 00:15:25,080 Speaker 1: It's not something we understand. It's not a law physics. 285 00:15:25,120 --> 00:15:27,840 Speaker 1: It's just sort of the observation that the expansion of 286 00:15:27,880 --> 00:15:31,560 Speaker 1: the universe is continuing and that it's speeding up, and 287 00:15:31,600 --> 00:15:33,880 Speaker 1: we don't understand the mechanism of it. But there is 288 00:15:33,920 --> 00:15:36,720 Speaker 1: something about dark energy that we do know, which is 289 00:15:36,760 --> 00:15:40,360 Speaker 1: that it's constant in space. So it makes more space, 290 00:15:40,440 --> 00:15:43,760 Speaker 1: and then that space has new dark energy. So every 291 00:15:43,840 --> 00:15:47,280 Speaker 1: cubic meter of space, for example, has its own dark energy. 292 00:15:47,440 --> 00:15:50,160 Speaker 1: And as the universe expands, you get more universe, you 293 00:15:50,240 --> 00:15:53,080 Speaker 1: get more dark energy. So these listeners right in and 294 00:15:53,120 --> 00:15:55,720 Speaker 1: they say, hold on a second, where does that energy 295 00:15:55,880 --> 00:15:59,960 Speaker 1: come from? Does that mean that dark energy doesn't concern 296 00:16:00,040 --> 00:16:02,560 Speaker 1: of energy? Right? Yeah, it's it's kind of very puzzling, 297 00:16:02,640 --> 00:16:04,960 Speaker 1: right because you're telling me that the universe is expanding 298 00:16:05,080 --> 00:16:08,440 Speaker 1: with more energy and acceleration, so it has to you know, 299 00:16:08,560 --> 00:16:12,040 Speaker 1: be drawing energy from somewhere, but it's sort of coming 300 00:16:12,040 --> 00:16:14,880 Speaker 1: out of nothingness, this dark energy. And so the answer 301 00:16:14,960 --> 00:16:17,560 Speaker 1: to those listeners is that no, it doesn't have to 302 00:16:17,640 --> 00:16:21,880 Speaker 1: come from somewhere. It violates the conservation of energy. As 303 00:16:21,920 --> 00:16:24,960 Speaker 1: the universe expands, you get more space, and that space 304 00:16:25,040 --> 00:16:29,040 Speaker 1: has new energy, and the energy in the universe increases. 305 00:16:29,480 --> 00:16:33,960 Speaker 1: So as spacetime expands, the energy can go up. And 306 00:16:34,120 --> 00:16:36,560 Speaker 1: where does that energy come from? It doesn't have to 307 00:16:36,680 --> 00:16:39,960 Speaker 1: come from anywhere, because energy conservation is not actually a 308 00:16:40,000 --> 00:16:43,680 Speaker 1: fundamental law of the universe. It's just something we never 309 00:16:43,720 --> 00:16:47,920 Speaker 1: saw broken before. I feel like that throws everything to question. Now, Daniel, 310 00:16:47,960 --> 00:16:51,720 Speaker 1: what do you mean, yes, right, Welcome to physics, questioning everything, 311 00:16:52,440 --> 00:16:54,320 Speaker 1: even even the idea of asking questions. Why are you 312 00:16:54,320 --> 00:16:59,240 Speaker 1: asking questions, Daniel, don't ask questions about that. That's a 313 00:16:59,360 --> 00:17:02,680 Speaker 1: zone of a wild So is that the primary example 314 00:17:02,720 --> 00:17:05,840 Speaker 1: of energy not being conserved is in space and in 315 00:17:05,880 --> 00:17:08,760 Speaker 1: this idea of the universe expanding or is it more 316 00:17:09,600 --> 00:17:13,720 Speaker 1: you know, kind of seeped into our everyday physics. It's 317 00:17:13,760 --> 00:17:16,920 Speaker 1: not really steeped into our everyday physics. And the cases 318 00:17:16,960 --> 00:17:19,640 Speaker 1: where energy is not conserved are really going to give 319 00:17:19,680 --> 00:17:22,520 Speaker 1: us a clue as to why it's not conserved. And 320 00:17:22,600 --> 00:17:25,439 Speaker 1: I can give you another example, which is also related 321 00:17:25,480 --> 00:17:29,680 Speaker 1: to the expansion of space. As space expands, it turns 322 00:17:29,680 --> 00:17:32,560 Speaker 1: out there's a way to lose energy. For example, a 323 00:17:32,560 --> 00:17:35,560 Speaker 1: photon photon is flying through space, and we know that 324 00:17:35,600 --> 00:17:38,199 Speaker 1: if a photon comes to you from far away, but 325 00:17:38,280 --> 00:17:41,080 Speaker 1: that the space between you and the source expands in 326 00:17:41,119 --> 00:17:45,760 Speaker 1: the meantime, that photon red shifts are red shifts associated 327 00:17:45,800 --> 00:17:48,840 Speaker 1: with that source having a velocity. Like a police siren 328 00:17:48,880 --> 00:17:52,440 Speaker 1: that's moving away from you, the wavelength of the sound 329 00:17:52,520 --> 00:17:55,080 Speaker 1: is stretched, and the same is true for light from 330 00:17:55,200 --> 00:17:57,959 Speaker 1: stars that are moving away from us. But there's another 331 00:17:58,080 --> 00:18:00,359 Speaker 1: kind of red shift, which is just the expand engine 332 00:18:00,440 --> 00:18:03,120 Speaker 1: of space between you and that light source. It will 333 00:18:03,200 --> 00:18:06,560 Speaker 1: also stretch the photon and make it redder. Won't slow 334 00:18:06,560 --> 00:18:09,879 Speaker 1: it down, it'll just shift its frequency. That will stretch it. 335 00:18:09,960 --> 00:18:12,639 Speaker 1: That's right. Photons always move with the same speed, the 336 00:18:12,640 --> 00:18:15,000 Speaker 1: speed of light, but they have different levels of energy 337 00:18:15,320 --> 00:18:18,240 Speaker 1: which correspond to their wavelength, which is equivalent to their 338 00:18:18,280 --> 00:18:20,959 Speaker 1: color or their frequency. It's all the same thing. And 339 00:18:21,040 --> 00:18:24,679 Speaker 1: so when you make a photon redder, effectively you're taking 340 00:18:24,680 --> 00:18:27,800 Speaker 1: away its energy. It's losing energy. So in that case, 341 00:18:27,920 --> 00:18:33,119 Speaker 1: the expansion of space disappears energy from a photon. What 342 00:18:33,720 --> 00:18:35,880 Speaker 1: could it all be the same energy, Daniel? Could dark 343 00:18:35,960 --> 00:18:40,080 Speaker 1: energy be the energy of photons getting redder. That wouldn't 344 00:18:40,080 --> 00:18:41,760 Speaker 1: add up to like a factor of tend to one. 345 00:18:42,400 --> 00:18:45,560 Speaker 1: There's so much more dark energy than the energy that's 346 00:18:45,600 --> 00:18:48,959 Speaker 1: being lost by photons being red shifted. But we see this. 347 00:18:49,000 --> 00:18:50,639 Speaker 1: It's a real thing. It's just kind of like a 348 00:18:50,720 --> 00:18:55,359 Speaker 1: dark red energy. I like that phrase, dark red energy. 349 00:18:55,400 --> 00:18:57,399 Speaker 1: That should be a thing. There should be a physics. 350 00:18:57,440 --> 00:19:00,600 Speaker 1: Should be the title your other sci fi novel, dark 351 00:19:00,720 --> 00:19:03,560 Speaker 1: red energy. All right, I'll do it just starting from 352 00:19:03,560 --> 00:19:05,280 Speaker 1: the title. I can just write the novel from there. 353 00:19:05,840 --> 00:19:09,280 Speaker 1: But yeah, So here are two examples, space expanding meaning 354 00:19:09,520 --> 00:19:14,240 Speaker 1: extra energy is created, or space expanding meaning energy is 355 00:19:14,280 --> 00:19:17,280 Speaker 1: lost by photons. And the thing that those two examples 356 00:19:17,280 --> 00:19:20,680 Speaker 1: have in common, of course, is that space is not static. 357 00:19:20,720 --> 00:19:24,280 Speaker 1: In those cases, space is expanding its dynamic and that's 358 00:19:24,320 --> 00:19:26,720 Speaker 1: the clue. I see. Yeah, that's kind of um, it's 359 00:19:26,760 --> 00:19:29,720 Speaker 1: like breaking a law by breaking another law, kind of 360 00:19:29,960 --> 00:19:32,359 Speaker 1: because I feel like, you know, we thought space didn't 361 00:19:32,440 --> 00:19:35,399 Speaker 1: expand we thought space was fixed before, but then we 362 00:19:35,480 --> 00:19:38,720 Speaker 1: learned that space is like malleble and bends and stretches. Yeah, 363 00:19:38,800 --> 00:19:42,600 Speaker 1: and just like thinking that Galilean transformations Newtonian physics always 364 00:19:42,600 --> 00:19:44,920 Speaker 1: worked because we had always seen it work because we'd 365 00:19:44,920 --> 00:19:48,000 Speaker 1: only ever checked low speeds and then discovering that they 366 00:19:48,040 --> 00:19:50,360 Speaker 1: break when you get too high speeds. This is an 367 00:19:50,359 --> 00:19:53,880 Speaker 1: example of something we never thought was possible, expanding space, 368 00:19:54,400 --> 00:19:57,800 Speaker 1: and when it happens, it challenges some pretty basic stuff 369 00:19:57,840 --> 00:20:00,560 Speaker 1: that we thought was true, but turns out only have 370 00:20:00,680 --> 00:20:04,000 Speaker 1: been true in the special scenario we ever tested it in, 371 00:20:04,320 --> 00:20:07,439 Speaker 1: which is fundamentally static space. Right, Well, then step us 372 00:20:07,480 --> 00:20:12,439 Speaker 1: three here, Daniel, why is an energy conserved when space expands? Well, 373 00:20:12,480 --> 00:20:13,919 Speaker 1: I think the best way to tackle that is to 374 00:20:13,920 --> 00:20:17,040 Speaker 1: think about, like, well, why should we expect it to 375 00:20:17,080 --> 00:20:19,600 Speaker 1: be conserved? Did we have a reason to think it 376 00:20:19,600 --> 00:20:23,399 Speaker 1: should be conserved. Is there some fundamental theoretical idea that 377 00:20:23,440 --> 00:20:25,639 Speaker 1: tells us it should be conserved, or is it just 378 00:20:25,720 --> 00:20:28,960 Speaker 1: something we observed and thought was true. And for that, 379 00:20:29,040 --> 00:20:30,679 Speaker 1: I think it's good to think about, like, what do 380 00:20:30,720 --> 00:20:34,280 Speaker 1: we mean exactly about conserved? Right to be kind of 381 00:20:34,280 --> 00:20:37,600 Speaker 1: specific about it, And by that we mean like, here's 382 00:20:37,640 --> 00:20:40,520 Speaker 1: something we calculate, Like you can measure the amount of 383 00:20:40,600 --> 00:20:42,879 Speaker 1: energy and something and then you can let it do 384 00:20:42,960 --> 00:20:45,080 Speaker 1: its thing. You know, maybe you turn on the engine 385 00:20:45,080 --> 00:20:47,800 Speaker 1: of your car or whatever, and then you calculate it again, 386 00:20:48,080 --> 00:20:50,199 Speaker 1: and you notice you get the same answer. So as 387 00:20:50,200 --> 00:20:53,080 Speaker 1: you said before, like you burn the fuel in your car, 388 00:20:53,400 --> 00:20:55,800 Speaker 1: but now you've added speed to your car, so energy 389 00:20:55,880 --> 00:20:58,159 Speaker 1: is moved from one part of the system to another. 390 00:20:58,520 --> 00:21:00,840 Speaker 1: And we've noticed so far that if you add up 391 00:21:00,840 --> 00:21:03,000 Speaker 1: all the energy before and you add of the energy after, 392 00:21:03,280 --> 00:21:06,359 Speaker 1: you get the same thing. And so we call that conserved, 393 00:21:06,480 --> 00:21:09,080 Speaker 1: right that there's a symmetry there that says it hasn't 394 00:21:09,160 --> 00:21:11,920 Speaker 1: changed the accounty. You can account for every cent of 395 00:21:11,960 --> 00:21:14,760 Speaker 1: that energy. That's right, And so people have long wondered, like, 396 00:21:15,040 --> 00:21:18,040 Speaker 1: why are things conserved at all? What does it mean 397 00:21:18,119 --> 00:21:20,359 Speaker 1: about the universe? Because it's the kind of thing that 398 00:21:20,400 --> 00:21:23,680 Speaker 1: makes a physicist scratch his or her head. It's like, well, 399 00:21:23,720 --> 00:21:25,920 Speaker 1: if this thing is concerned, does that mean that it's 400 00:21:25,960 --> 00:21:28,640 Speaker 1: a deep truth in the universe, that it's an important quantity. 401 00:21:28,680 --> 00:21:32,000 Speaker 1: It's like a clue about how the universe works. If 402 00:21:32,040 --> 00:21:34,960 Speaker 1: this thing doesn't change, right, it's like a constraint or 403 00:21:35,000 --> 00:21:37,479 Speaker 1: a law. And if you're on the hunt for figuring 404 00:21:37,480 --> 00:21:39,800 Speaker 1: out the fundamental rules of the universe, that seems like 405 00:21:39,840 --> 00:21:42,400 Speaker 1: an important clue, right, Yeah, well, I guess maybe it's 406 00:21:42,520 --> 00:21:46,040 Speaker 1: it's it feels fundamental because it's kind of it feels 407 00:21:46,280 --> 00:21:48,480 Speaker 1: logical for it to be conserved. I know we're trying 408 00:21:48,480 --> 00:21:50,520 Speaker 1: to question it here, but it's like, you know, if 409 00:21:50,520 --> 00:21:52,560 Speaker 1: you have some money, it has to go somewhere. Can't 410 00:21:52,600 --> 00:21:55,560 Speaker 1: just like disappear, and it can't just pop out of 411 00:21:55,560 --> 00:21:57,959 Speaker 1: the nothingness. I think that's just your intuition. You're just 412 00:21:58,080 --> 00:22:00,639 Speaker 1: used to having a conserved and actually money is a 413 00:22:00,640 --> 00:22:04,080 Speaker 1: great example because money is also not conserved. You know, 414 00:22:04,200 --> 00:22:07,399 Speaker 1: if I take a painting by Picasso and I just 415 00:22:07,440 --> 00:22:10,000 Speaker 1: set it on fire. Where does the value of that 416 00:22:10,040 --> 00:22:13,480 Speaker 1: painting go nowhere? Or if I am Picasso, when I 417 00:22:13,560 --> 00:22:16,720 Speaker 1: make a new painting, right I've created a hundred million dollars, 418 00:22:17,000 --> 00:22:20,000 Speaker 1: Where does that come from? Right? I wasn't worth a 419 00:22:20,080 --> 00:22:22,800 Speaker 1: hundred million dollars. It didn't seep out of me. Or 420 00:22:22,960 --> 00:22:26,399 Speaker 1: one day people decide that some kind of rock is 421 00:22:26,440 --> 00:22:28,520 Speaker 1: now the most valuable thing in the world, and we 422 00:22:28,560 --> 00:22:31,280 Speaker 1: will all pay five d dollars an ounce for this 423 00:22:31,400 --> 00:22:35,399 Speaker 1: kind of rock. Then we've created value. So money is 424 00:22:35,400 --> 00:22:37,560 Speaker 1: not conserved at all. It's a great example, right, But 425 00:22:37,680 --> 00:22:39,159 Speaker 1: I feel like money is kind of it's like a 426 00:22:39,200 --> 00:22:45,399 Speaker 1: psychological concept, money and value. But we're talking about like physics, right, yeah, exactly, 427 00:22:45,600 --> 00:22:47,399 Speaker 1: Like you know, if if I have something here, it 428 00:22:47,440 --> 00:22:51,080 Speaker 1: can't just disappear, or I can't just suddenly appear another 429 00:22:51,240 --> 00:22:54,320 Speaker 1: whore in front of me, although it would be cool 430 00:22:54,359 --> 00:22:58,959 Speaker 1: because then I could go to sleep. Well, there are 431 00:22:59,000 --> 00:23:02,960 Speaker 1: actually really interesting fundamental insights about why some things are 432 00:23:02,960 --> 00:23:06,439 Speaker 1: conserved and some things are not conserved. And this comes 433 00:23:06,480 --> 00:23:09,199 Speaker 1: from a law from a real genius of physics who 434 00:23:09,240 --> 00:23:12,600 Speaker 1: have been long overlooked and only recently been appreciated a 435 00:23:12,640 --> 00:23:15,560 Speaker 1: mathematical physicist from the early part of this century, I 436 00:23:15,720 --> 00:23:18,880 Speaker 1: mean Utah, and she wrote down a really interesting law, 437 00:23:18,920 --> 00:23:22,520 Speaker 1: and she says that there's a conservation. There's something that's conserved, 438 00:23:22,600 --> 00:23:27,280 Speaker 1: like energy or momentum, every time the universe has a symmetry. 439 00:23:27,359 --> 00:23:30,520 Speaker 1: But there's this deep connection between something being conserved and 440 00:23:30,560 --> 00:23:34,359 Speaker 1: the universe having some sort of balance or symmetry to it. 441 00:23:34,840 --> 00:23:36,600 Speaker 1: From a language point of view, that makes sense. If 442 00:23:36,600 --> 00:23:39,560 Speaker 1: there's a symmetry means there's like an equation, which means 443 00:23:39,600 --> 00:23:42,719 Speaker 1: things are balanced and conserved. But I'm guessing you mean 444 00:23:42,800 --> 00:23:45,880 Speaker 1: more like the mathematical idea of symmetry. And there's lots 445 00:23:45,880 --> 00:23:48,920 Speaker 1: of really fascinating examples before we get to energy. And 446 00:23:48,960 --> 00:23:52,080 Speaker 1: one of my favorites is momentum. So why is momentum 447 00:23:52,080 --> 00:23:54,440 Speaker 1: conservad at all? You might ask that, Well, it turns 448 00:23:54,440 --> 00:23:58,240 Speaker 1: out that momentum is conserved because the universe has no 449 00:23:58,400 --> 00:24:03,160 Speaker 1: preferred location called this translation symmetry, Like something that happens 450 00:24:03,400 --> 00:24:06,600 Speaker 1: here in space could equally well happen ten ms to 451 00:24:06,640 --> 00:24:10,000 Speaker 1: the right or a hundred up or whatever. The laws 452 00:24:10,000 --> 00:24:12,359 Speaker 1: of physics don't change based on where you are in 453 00:24:12,359 --> 00:24:16,000 Speaker 1: the universe. That's we call a translation symmetry, and that 454 00:24:16,080 --> 00:24:20,960 Speaker 1: translation symmetry directly implies conservation of momentum. Like if you 455 00:24:21,000 --> 00:24:24,879 Speaker 1: didn't know momentum was conserved, but you knew that, you 456 00:24:24,960 --> 00:24:27,160 Speaker 1: didn't matter where you were in the universe, you could 457 00:24:27,200 --> 00:24:31,359 Speaker 1: derive conservation of momentum mathematically, How would you, I guess, 458 00:24:31,359 --> 00:24:33,600 Speaker 1: derive it? Can you give us like an in twitter sense, 459 00:24:33,680 --> 00:24:37,280 Speaker 1: like you know, the equations can be reduced to like 460 00:24:37,440 --> 00:24:40,639 Speaker 1: you know, momentum and equals momentum out. Yeah, there actually 461 00:24:40,680 --> 00:24:44,159 Speaker 1: is a mathematical procedure. That's what Newtis theorem does. It 462 00:24:44,240 --> 00:24:48,920 Speaker 1: tells you what conservation law comes out of a specific symmetry. 463 00:24:49,320 --> 00:24:53,040 Speaker 1: If the universe is symmetric to changes in some quantity X, 464 00:24:53,400 --> 00:24:56,879 Speaker 1: then you can derive the quantity why that is conserved. 465 00:24:57,359 --> 00:24:59,679 Speaker 1: For those listeners who want a little bit more gory 466 00:24:59,720 --> 00:25:03,120 Speaker 1: Dta hills, you take the quantity that's conserved, and then 467 00:25:03,160 --> 00:25:06,480 Speaker 1: you have to take the derivative of the lagrange in 468 00:25:06,640 --> 00:25:09,520 Speaker 1: of the universe with respect to the derivative of that 469 00:25:09,560 --> 00:25:11,920 Speaker 1: thing that's conserved, and so it gets a little bit 470 00:25:11,960 --> 00:25:15,520 Speaker 1: hairy mathematically, but there is a relationship between the quantity 471 00:25:15,560 --> 00:25:18,800 Speaker 1: that has symmetry. In this case, position in space and 472 00:25:18,840 --> 00:25:22,040 Speaker 1: the thing that's being conserved in this case mass times 473 00:25:22,200 --> 00:25:25,320 Speaker 1: the velocity, which is the derivative of your position in space. 474 00:25:25,840 --> 00:25:28,240 Speaker 1: And so that's the nuts and bolts of the mathematical 475 00:25:28,320 --> 00:25:31,840 Speaker 1: genius of Emily Nuther. But the idea is that there's 476 00:25:31,840 --> 00:25:34,560 Speaker 1: a symmetry here, and I think you can understand it intuitively. Like, 477 00:25:35,080 --> 00:25:38,439 Speaker 1: think about, for example, just a single rock floating in space, 478 00:25:38,920 --> 00:25:42,120 Speaker 1: and that could be anywhere. Right, you push on that rock, 479 00:25:42,520 --> 00:25:45,400 Speaker 1: you've given it momentum. It flies off with a certain momentum. 480 00:25:45,440 --> 00:25:48,200 Speaker 1: It makes sense for momentum to be conserved, your momentum 481 00:25:48,320 --> 00:25:51,080 Speaker 1: flowing to the momentum of the rock. If nothing pushes 482 00:25:51,200 --> 00:25:54,440 Speaker 1: on you, you're going to keep coasting at the same speed. Yeah, exactly. 483 00:25:54,920 --> 00:25:57,640 Speaker 1: And that's true here, or it's true to the left, 484 00:25:57,680 --> 00:25:59,600 Speaker 1: or it's true to the right, or it's true somewhere else. 485 00:25:59,640 --> 00:26:02,359 Speaker 1: As law is, space is the same everywhere, The same 486 00:26:02,400 --> 00:26:05,159 Speaker 1: results come from the same experiment. But what is space 487 00:26:05,359 --> 00:26:08,080 Speaker 1: isn't the same everywhere? What if, like, you're near a 488 00:26:08,200 --> 00:26:12,040 Speaker 1: really massive planet and so space is curved, for example, 489 00:26:12,240 --> 00:26:14,800 Speaker 1: and so it kind of does matter how close you 490 00:26:14,840 --> 00:26:17,240 Speaker 1: are to that planet, because if you get a push 491 00:26:17,280 --> 00:26:18,840 Speaker 1: when you're close to the planet, or you get a 492 00:26:18,880 --> 00:26:20,920 Speaker 1: push when you're far from the planet, you get very 493 00:26:20,920 --> 00:26:25,720 Speaker 1: different outcomes, right, And so in that scenario, the momentum 494 00:26:25,760 --> 00:26:29,119 Speaker 1: of the rock is not conserved because space is not 495 00:26:29,200 --> 00:26:31,879 Speaker 1: the same everywhere. The answer you get depends on where 496 00:26:31,880 --> 00:26:34,840 Speaker 1: you are in space. But in that case, now you're 497 00:26:34,880 --> 00:26:36,920 Speaker 1: sort of expanding your system. Now your system is the 498 00:26:37,000 --> 00:26:39,719 Speaker 1: rock and the planet, and momentum is conserved between them, 499 00:26:39,760 --> 00:26:43,240 Speaker 1: isn't it exactly? If you include the planet in the system, 500 00:26:43,359 --> 00:26:46,000 Speaker 1: then momentum is conserved anywhere because you can move the 501 00:26:46,080 --> 00:26:49,399 Speaker 1: rock plus planet system to anywhere in space. And the 502 00:26:49,440 --> 00:26:52,199 Speaker 1: reason momentum is conserved is that now the whole system 503 00:26:52,240 --> 00:26:55,320 Speaker 1: can be shifted anywhere in space, and it as an ensemble, 504 00:26:55,440 --> 00:26:58,479 Speaker 1: does the same thing. And so the key is that 505 00:26:58,520 --> 00:27:01,080 Speaker 1: your system can be translated anywhere in space, and then 506 00:27:01,160 --> 00:27:04,280 Speaker 1: momentum is conserved if it matters where in space your 507 00:27:04,320 --> 00:27:06,720 Speaker 1: system is. If your system is just the rock, then 508 00:27:06,800 --> 00:27:09,679 Speaker 1: momentum is no longer conserved. All right. It's something to 509 00:27:09,720 --> 00:27:13,560 Speaker 1: do with this idea of symmetry and the equations of 510 00:27:13,600 --> 00:27:17,679 Speaker 1: physics and symmetry. I feel it's a tricky concept because 511 00:27:18,640 --> 00:27:20,160 Speaker 1: you know, I think we're all familiar with the idea 512 00:27:20,200 --> 00:27:22,560 Speaker 1: of symmetry, like if something looks the same in front 513 00:27:22,560 --> 00:27:24,720 Speaker 1: of a mirror, or you know, if I take a 514 00:27:24,760 --> 00:27:26,840 Speaker 1: piece of paper and folded the ink kind of like 515 00:27:27,080 --> 00:27:29,800 Speaker 1: copies from on both sides of the paper, and it 516 00:27:29,840 --> 00:27:32,640 Speaker 1: looks symmetric. But in the equations, it's it's a little 517 00:27:32,680 --> 00:27:34,919 Speaker 1: bit different, right. It sort of means kind of what 518 00:27:34,960 --> 00:27:36,920 Speaker 1: you said in me is, which means it's more about 519 00:27:36,920 --> 00:27:42,160 Speaker 1: conserving or having the laws be the same in different situations. Yeah, 520 00:27:42,240 --> 00:27:45,240 Speaker 1: exactly if you made a change, would you get the 521 00:27:45,280 --> 00:27:49,440 Speaker 1: same outcomes? Right? Do the same laws apply here and there? 522 00:27:50,080 --> 00:27:52,560 Speaker 1: And so for the example of the rock in space, 523 00:27:52,640 --> 00:27:56,000 Speaker 1: you know, the rules of the universe shouldn't depend on 524 00:27:56,160 --> 00:27:58,840 Speaker 1: where you are, right, So then it kind of seems 525 00:27:58,880 --> 00:28:01,119 Speaker 1: to sort of make sense that if you have a symmetry, 526 00:28:01,600 --> 00:28:05,080 Speaker 1: then that thing is conserved, right, Like that sort of 527 00:28:05,240 --> 00:28:07,840 Speaker 1: makes intuitive sense. That's kind of interesting. Yeah, there's a 528 00:28:07,840 --> 00:28:10,840 Speaker 1: connection between the symmetry and the thing that's conserved. In 529 00:28:10,880 --> 00:28:14,760 Speaker 1: this case, space is the symmetry, and momentum motion through 530 00:28:14,840 --> 00:28:18,720 Speaker 1: space is a thing that's conserved, right, So momentum is conserved, 531 00:28:18,760 --> 00:28:21,520 Speaker 1: but then for energy it's different. It has a different symmetry. 532 00:28:21,600 --> 00:28:24,560 Speaker 1: That's right. The idea of the conservation of energy comes 533 00:28:24,600 --> 00:28:28,359 Speaker 1: from symmetry in time. If the universe is the same 534 00:28:28,440 --> 00:28:32,800 Speaker 1: going forwards and backwards, if there's a symmetry in time, 535 00:28:33,119 --> 00:28:37,399 Speaker 1: then you get conservation of energy. And here's a little 536 00:28:37,400 --> 00:28:40,600 Speaker 1: bit trickier to understand the connection between energy and time, 537 00:28:41,040 --> 00:28:43,880 Speaker 1: but it's there, and quantum mechanically, I think it's actually 538 00:28:43,920 --> 00:28:47,000 Speaker 1: the clearest. We have the Shorting Air equation, which is 539 00:28:47,240 --> 00:28:50,600 Speaker 1: what tells us how like a quantum mechanical system changes. 540 00:28:50,880 --> 00:28:53,800 Speaker 1: It says, if you have this quantum wave function, now 541 00:28:54,160 --> 00:28:56,400 Speaker 1: what quantum wave function will you have in the future. 542 00:28:56,760 --> 00:29:00,000 Speaker 1: That's the Shorting Air equation and solutions to the Shorting 543 00:29:00,080 --> 00:29:03,280 Speaker 1: equation are things that work in the universe, but it 544 00:29:03,320 --> 00:29:06,560 Speaker 1: tells us how things move forwards in time. Well, turns 545 00:29:06,560 --> 00:29:08,840 Speaker 1: out the Shorting Your equation is just an expression for 546 00:29:08,880 --> 00:29:11,240 Speaker 1: the energy of the system. Like if you actually look 547 00:29:11,280 --> 00:29:15,400 Speaker 1: at the mathematics of it, it's kinetic energy plus potential energy. 548 00:29:15,560 --> 00:29:18,200 Speaker 1: That's just a total energy of the system. And so 549 00:29:18,560 --> 00:29:21,320 Speaker 1: if the universe is symmetric in time, then energy is 550 00:29:21,360 --> 00:29:25,280 Speaker 1: conserved in your system for served in time. Kind of 551 00:29:25,320 --> 00:29:27,400 Speaker 1: like I feel like you're telling me that there's a 552 00:29:27,400 --> 00:29:30,680 Speaker 1: symmetry in time means that what I have now she's 553 00:29:30,680 --> 00:29:32,480 Speaker 1: gonna be equal to the things that I have later. 554 00:29:33,400 --> 00:29:35,920 Speaker 1: So in a way, that sort of translates into you 555 00:29:35,920 --> 00:29:38,280 Speaker 1: don't lose or gain energy. It has to kind of 556 00:29:38,280 --> 00:29:41,360 Speaker 1: be the same here and after. Yeah, exactly. This is 557 00:29:41,400 --> 00:29:44,400 Speaker 1: sort of a conservation there, this conservation of probability. Also 558 00:29:44,680 --> 00:29:47,600 Speaker 1: in quantum mechanics, it says that things are transformed and 559 00:29:47,640 --> 00:29:51,640 Speaker 1: they slash around, but they don't disappear. And what is 560 00:29:51,680 --> 00:29:54,160 Speaker 1: the thing that doesn't disappear. Well, it's the solution to 561 00:29:54,160 --> 00:29:56,760 Speaker 1: the Shortinger equation, which is really just the sum of 562 00:29:56,760 --> 00:30:00,280 Speaker 1: all the energies in the system. And so in some sense, 563 00:30:00,360 --> 00:30:03,760 Speaker 1: it's sort of like asking what is energy. Well, energy 564 00:30:03,960 --> 00:30:07,680 Speaker 1: is the thing that's conserved if you have time symmetry 565 00:30:07,800 --> 00:30:11,520 Speaker 1: in your system. And it's something we just sort of noticed. 566 00:30:11,560 --> 00:30:14,120 Speaker 1: We're like, well, you add all these things up kinetic 567 00:30:14,200 --> 00:30:16,320 Speaker 1: energy and potential energy here, and you add it up later, 568 00:30:16,600 --> 00:30:19,400 Speaker 1: we notice we get the same answer. And that's something 569 00:30:19,440 --> 00:30:22,680 Speaker 1: we've noticed because we've mostly been doing experiments in systems 570 00:30:22,680 --> 00:30:25,480 Speaker 1: where time doesn't matter. Where if you do the experiment 571 00:30:25,520 --> 00:30:27,960 Speaker 1: now or a hundred days or in a thousand years, 572 00:30:28,200 --> 00:30:31,240 Speaker 1: you get the same answer. So whenever time is symmetric, 573 00:30:31,280 --> 00:30:34,320 Speaker 1: and it has basically always been for our experiments, then 574 00:30:34,520 --> 00:30:37,520 Speaker 1: energy is conserved. So I feel like you're saying that 575 00:30:37,680 --> 00:30:40,160 Speaker 1: energy is just an illusion of times, and yes, exactly, 576 00:30:40,160 --> 00:30:43,680 Speaker 1: that's the message, is that energy is connected to time. 577 00:30:43,720 --> 00:30:46,160 Speaker 1: And we know that already from quantum mechanics. Right. We 578 00:30:46,240 --> 00:30:48,720 Speaker 1: know quantum mechanics tells us you can't measure the position 579 00:30:48,760 --> 00:30:51,320 Speaker 1: and momentum of a particle at the same time. Those 580 00:30:51,320 --> 00:30:55,280 Speaker 1: two concepts are connected, right, And it also connects energy 581 00:30:55,360 --> 00:30:58,280 Speaker 1: and time, and it's for the same fundamental reason that 582 00:30:58,320 --> 00:31:01,720 Speaker 1: there's a connection between those two basic quantities. They're really 583 00:31:01,960 --> 00:31:05,120 Speaker 1: two sides of the same thing. One symmetry leads to 584 00:31:05,160 --> 00:31:07,280 Speaker 1: a conservation law. All right, I feel like we're set 585 00:31:07,320 --> 00:31:10,800 Speaker 1: up now to break the conservation of energy and talk 586 00:31:10,880 --> 00:31:14,040 Speaker 1: about why that's really true and what it means. But 587 00:31:14,080 --> 00:31:16,560 Speaker 1: now it's time for us to take another quick break. 588 00:31:29,200 --> 00:31:31,760 Speaker 1: All right, Dan, we're talking about the conservation of energy, 589 00:31:31,880 --> 00:31:34,360 Speaker 1: and it turns out that energy is not always conserved, 590 00:31:34,480 --> 00:31:37,480 Speaker 1: which blows my mind. You're telling me it has something 591 00:31:37,520 --> 00:31:40,400 Speaker 1: to do with the symmetry of times. If time is symmetric, 592 00:31:40,560 --> 00:31:43,920 Speaker 1: then energy is conserved. And so I'm guessing what you're 593 00:31:43,960 --> 00:31:46,400 Speaker 1: gonna say now is that time is not always symmetric, 594 00:31:46,720 --> 00:31:49,720 Speaker 1: and it's actually a little bit larger than that. It's spacetime. 595 00:31:50,320 --> 00:31:53,400 Speaker 1: If the universe in which you're doing your experiment is fixed, 596 00:31:53,440 --> 00:31:56,760 Speaker 1: if spacetime is fixed, it's not changing, then yes, energy 597 00:31:56,840 --> 00:31:59,600 Speaker 1: is conserved. And so if spacetime is flat and it's 598 00:31:59,600 --> 00:32:01,840 Speaker 1: not changed, you can do your experiments. You can fuel 599 00:32:01,840 --> 00:32:04,760 Speaker 1: your car, you can drain your battery, you can collide particles, 600 00:32:04,800 --> 00:32:07,880 Speaker 1: you can do chemistry, and energy will be conserved. But 601 00:32:08,760 --> 00:32:11,920 Speaker 1: as soon as you break the symmetry of spacetime, as 602 00:32:11,920 --> 00:32:15,880 Speaker 1: soon as spacetime is changing, right, the shape of space 603 00:32:15,920 --> 00:32:17,520 Speaker 1: and the shape of the universe. As soon as that 604 00:32:17,640 --> 00:32:20,880 Speaker 1: is changing, energy is no longer guaranteed to be conserved 605 00:32:20,960 --> 00:32:24,680 Speaker 1: because it only was conserved because space time was not changing. 606 00:32:24,840 --> 00:32:28,040 Speaker 1: Oh I see, So maybe to match up our intuitions 607 00:32:28,120 --> 00:32:31,040 Speaker 1: to this new idea, we have to maybe expand our 608 00:32:31,520 --> 00:32:33,600 Speaker 1: idea of conservation of energy. Like maybe it's not a 609 00:32:33,640 --> 00:32:36,560 Speaker 1: conservation of energy for a closed system. It's like we 610 00:32:36,600 --> 00:32:40,320 Speaker 1: have to think about conservation of energy being true for 611 00:32:40,520 --> 00:32:44,560 Speaker 1: like the same spacetime or a static spacetime. But if 612 00:32:44,560 --> 00:32:48,040 Speaker 1: you change that, if you change spacetime, then you can't 613 00:32:48,080 --> 00:32:50,560 Speaker 1: say that energy is conserved anymore. Exactly. We have to 614 00:32:50,600 --> 00:32:54,560 Speaker 1: add a qualifier. We say energy is only conserved when 615 00:32:54,840 --> 00:32:58,320 Speaker 1: time symmetry is respected, which happens when space time is 616 00:32:58,360 --> 00:33:01,360 Speaker 1: not changing. But you know, we live in a universe 617 00:33:01,360 --> 00:33:04,960 Speaker 1: where spacetime is changing. The expansion of the universe is 618 00:33:05,000 --> 00:33:08,640 Speaker 1: not just things moving through space. It's the stretching of 619 00:33:08,680 --> 00:33:12,520 Speaker 1: space itself. It's the creation of new space. So we 620 00:33:12,560 --> 00:33:16,480 Speaker 1: live in dynamic space time, which means energy fundamentally is 621 00:33:16,520 --> 00:33:19,560 Speaker 1: not conserved. It means that energy is not the deep, 622 00:33:19,680 --> 00:33:22,080 Speaker 1: true quantity that we thought it was. It means it's 623 00:33:22,080 --> 00:33:25,680 Speaker 1: not the important thing to be thinking about. So it's 624 00:33:25,840 --> 00:33:28,960 Speaker 1: expansion of space that destroys the conservation of energy. Or 625 00:33:29,040 --> 00:33:31,000 Speaker 1: is it the expansion of space time? Are you do? 626 00:33:31,040 --> 00:33:32,880 Speaker 1: You use it as the same shorthand? Yeah, Well we're 627 00:33:32,880 --> 00:33:36,040 Speaker 1: talking about the expansion of space time, right, or the 628 00:33:36,040 --> 00:33:38,600 Speaker 1: expansion of space through time. You can think about it 629 00:33:38,640 --> 00:33:42,160 Speaker 1: like that because the space in which we're doing our 630 00:33:42,200 --> 00:33:44,960 Speaker 1: experiments is changing as a function of time. And remember, 631 00:33:45,160 --> 00:33:48,240 Speaker 1: to have conservation of energy, you need to have symmetry 632 00:33:48,280 --> 00:33:50,600 Speaker 1: and time. But the universe is not the same today 633 00:33:50,880 --> 00:33:53,000 Speaker 1: as it was a thousand or a billion years ago. 634 00:33:53,120 --> 00:33:56,360 Speaker 1: It's a different universe. It's expanded. The space in which 635 00:33:56,360 --> 00:33:59,920 Speaker 1: we're doing our experiments is different, and so it changes 636 00:34:00,120 --> 00:34:03,080 Speaker 1: the results of the experiments. And it means energy is 637 00:34:03,120 --> 00:34:06,200 Speaker 1: not conserved from one moment of space to another moment 638 00:34:06,240 --> 00:34:09,279 Speaker 1: of space. And that would also work here at the 639 00:34:09,320 --> 00:34:12,200 Speaker 1: local level too, right Like, if I had a canister 640 00:34:12,360 --> 00:34:16,799 Speaker 1: of gas and I expanded the space time it was in, 641 00:34:17,360 --> 00:34:20,239 Speaker 1: I would see energy not conserved. That's true. You would 642 00:34:20,280 --> 00:34:24,200 Speaker 1: create more dark energy because you've expanded space and every 643 00:34:24,239 --> 00:34:27,040 Speaker 1: new unit of space has dark energy in it. So yeah, 644 00:34:27,080 --> 00:34:29,719 Speaker 1: you would have created more energy whether or not there 645 00:34:29,760 --> 00:34:31,960 Speaker 1: was a canister of gas there. And the thing for 646 00:34:32,000 --> 00:34:34,880 Speaker 1: people to understand is remember the expansion of the universe 647 00:34:35,000 --> 00:34:38,240 Speaker 1: seems dramatic. The universe is big, it's expanding super fast, 648 00:34:38,680 --> 00:34:41,759 Speaker 1: but locally it's not very quick, Like the expansion of 649 00:34:41,800 --> 00:34:44,400 Speaker 1: space is not something you notice day to day, and 650 00:34:44,440 --> 00:34:48,080 Speaker 1: it's actually pretty weak. It's pretty small quantity in a 651 00:34:48,160 --> 00:34:50,799 Speaker 1: small piece of space. It only adds up to be 652 00:34:50,920 --> 00:34:53,440 Speaker 1: most of the universe because the universe is already so big. 653 00:34:53,600 --> 00:34:55,920 Speaker 1: There's so much empty space out there that if you 654 00:34:55,920 --> 00:34:58,320 Speaker 1: add up all the dark energy becomes a huge number. 655 00:34:58,680 --> 00:35:02,040 Speaker 1: So this violation of energy something that's very, very small. 656 00:35:02,360 --> 00:35:05,440 Speaker 1: It's very hard to notice because the expansion of space 657 00:35:05,520 --> 00:35:09,680 Speaker 1: is a very gradual, tiny effect. I see, it's conserved mostly, 658 00:35:09,800 --> 00:35:12,160 Speaker 1: but if you think about the whole universe, it's not 659 00:35:12,239 --> 00:35:16,000 Speaker 1: actually insignificant. Yeah, exactly, it's a small violation, and an 660 00:35:16,040 --> 00:35:19,080 Speaker 1: individual unit of space added up over the whole universe 661 00:35:19,080 --> 00:35:21,480 Speaker 1: becomes kind of a big deal. But for me, it's 662 00:35:21,680 --> 00:35:24,040 Speaker 1: not as much about like the size and the number 663 00:35:24,200 --> 00:35:26,880 Speaker 1: as the fact of it, Like, whoa this thing we 664 00:35:26,920 --> 00:35:29,279 Speaker 1: thought was a deep truth in the universe turns out 665 00:35:29,360 --> 00:35:31,800 Speaker 1: to be a coincidence or just a product of where 666 00:35:31,800 --> 00:35:34,239 Speaker 1: we happen to be. You know. It's like if you 667 00:35:34,280 --> 00:35:36,600 Speaker 1: grow up eating toast for breakfast and they butter it 668 00:35:36,640 --> 00:35:38,799 Speaker 1: on the top side, you think, well, toast has to 669 00:35:38,800 --> 00:35:40,319 Speaker 1: be buttered on the top side, and then you go 670 00:35:40,400 --> 00:35:42,920 Speaker 1: visit your friend you discover what they eat butter on 671 00:35:42,920 --> 00:35:45,719 Speaker 1: the bottom side of their toast. That's even possible. It 672 00:35:45,840 --> 00:35:48,040 Speaker 1: opens your mind a whole new way of thinking about 673 00:35:48,080 --> 00:35:50,560 Speaker 1: the universe. And that's what this does. It says energy 674 00:35:50,640 --> 00:35:53,680 Speaker 1: is not the important thing. Right. Energy is something we 675 00:35:53,719 --> 00:35:56,520 Speaker 1: thought was deep and fundamental, but it's actually important to 676 00:35:56,640 --> 00:36:00,600 Speaker 1: cosmologists are things like curvature and expansion. Those are the 677 00:36:00,640 --> 00:36:04,880 Speaker 1: fundamentally interesting things about the universe, not the energy. I 678 00:36:04,880 --> 00:36:07,760 Speaker 1: guess maybe what would trip people up is thinking about 679 00:36:07,760 --> 00:36:10,359 Speaker 1: where that energy comes from, right, I mean that's sort 680 00:36:10,360 --> 00:36:12,520 Speaker 1: of the origin of the original question. If the universe 681 00:36:12,600 --> 00:36:16,319 Speaker 1: is expanding and there's more energy being created, where does 682 00:36:16,360 --> 00:36:19,000 Speaker 1: it come from? Are you saying that energy can just 683 00:36:19,040 --> 00:36:22,319 Speaker 1: be created out of the blue. Yes, that's exactly what 684 00:36:22,320 --> 00:36:24,239 Speaker 1: we're saying, is that we've discovered that it doesn't have 685 00:36:24,320 --> 00:36:27,240 Speaker 1: to come from anywhere. That's sort of the wrong question. 686 00:36:27,560 --> 00:36:30,480 Speaker 1: It's like asking where does the value come from when 687 00:36:30,480 --> 00:36:33,520 Speaker 1: Picasso paints a new painting, Right, it didn't come from anywhere. 688 00:36:33,680 --> 00:36:36,480 Speaker 1: It wasn't and now it is. It only has to 689 00:36:36,560 --> 00:36:40,160 Speaker 1: come from somewhere if it's conserved, and there are things 690 00:36:40,200 --> 00:36:43,520 Speaker 1: that are universe that are conserved, like electric charge. Right, 691 00:36:43,560 --> 00:36:47,120 Speaker 1: you can't just create an electron because it's charged, has 692 00:36:47,200 --> 00:36:51,040 Speaker 1: to come from somewhere, has to come from previously charged particles. 693 00:36:51,600 --> 00:36:53,680 Speaker 1: Or you can start with a photon and create an 694 00:36:53,680 --> 00:36:56,760 Speaker 1: electron but then you have to create an anti electron also, 695 00:36:57,160 --> 00:36:59,640 Speaker 1: so you have balance of charge. There are things that 696 00:36:59,719 --> 00:37:01,799 Speaker 1: are fundamental that have to be conserved to have to 697 00:37:01,840 --> 00:37:04,879 Speaker 1: come from somewhere, but energy is not one of them. 698 00:37:04,920 --> 00:37:07,520 Speaker 1: It should be like demoted from that list of like 699 00:37:07,600 --> 00:37:11,120 Speaker 1: super important fundamental conserved quantities because it's just sort of 700 00:37:11,160 --> 00:37:13,560 Speaker 1: like an accident of where we live that we never 701 00:37:13,640 --> 00:37:17,840 Speaker 1: noticed that's not actually conserved. Man, first you demote pluto, 702 00:37:17,960 --> 00:37:22,719 Speaker 1: and now you're demoting energy. Who's the next matter? That's right, 703 00:37:22,880 --> 00:37:25,000 Speaker 1: We are pulling back the veil. Man. We are discovering 704 00:37:25,239 --> 00:37:27,520 Speaker 1: new deep truths. Matter that was like a hundred years 705 00:37:27,560 --> 00:37:30,279 Speaker 1: ago demoted matter the same matter doesn't matter. Matter, it 706 00:37:30,360 --> 00:37:32,799 Speaker 1: doesn't matter. And you know, I think it must have 707 00:37:32,840 --> 00:37:35,680 Speaker 1: been equally bewildering a hundred years ago to think what 708 00:37:35,760 --> 00:37:38,319 Speaker 1: you can create matter? Do you think you're some sort 709 00:37:38,360 --> 00:37:41,160 Speaker 1: of divine being? Right? Matter is you can't where did 710 00:37:41,160 --> 00:37:43,759 Speaker 1: it come from? When you make new matter, and it 711 00:37:43,800 --> 00:37:46,960 Speaker 1: doesn't have to come from anywhere. It's transformed from energy. 712 00:37:47,000 --> 00:37:50,400 Speaker 1: But the matter itself didn't exist, and matter can disappear, 713 00:37:50,400 --> 00:37:52,960 Speaker 1: It can exist and then just not exist anymore. It 714 00:37:53,000 --> 00:37:56,399 Speaker 1: doesn't have to be conserved all right, Well, it sort 715 00:37:56,440 --> 00:37:58,200 Speaker 1: of blows my mind. But it turns out that this 716 00:37:58,280 --> 00:38:00,880 Speaker 1: is actually a little bit controversial in physics, Like not 717 00:38:00,960 --> 00:38:05,560 Speaker 1: everyone agrees with this conclusion that energy is not conserved. 718 00:38:05,640 --> 00:38:07,640 Speaker 1: Is that right? Yeah, that's right. There are some folks 719 00:38:07,680 --> 00:38:10,640 Speaker 1: who find this very uncomfortable and they don't like this idea, 720 00:38:10,960 --> 00:38:13,200 Speaker 1: so they try to patch up energy and say, well, 721 00:38:13,280 --> 00:38:16,080 Speaker 1: let's think about energy in a slightly different way so 722 00:38:16,120 --> 00:38:19,239 Speaker 1: that it is concerned, and that's totally valid. It's like, well, 723 00:38:19,320 --> 00:38:22,239 Speaker 1: let's find a different symmetry or a different thing, you know, 724 00:38:22,360 --> 00:38:25,239 Speaker 1: energy prime or energy two point oh, so that it 725 00:38:25,320 --> 00:38:27,480 Speaker 1: actually is conserved, because maybe that will give you some 726 00:38:27,600 --> 00:38:30,480 Speaker 1: deep insight into the universe. And the way they do 727 00:38:30,560 --> 00:38:32,840 Speaker 1: this is a little bit controversial. I would say like 728 00:38:32,920 --> 00:38:35,759 Speaker 1: three out of four cosmologists and dentists I asked would 729 00:38:35,760 --> 00:38:38,680 Speaker 1: say that energy is not conserved. But there's some people 730 00:38:38,680 --> 00:38:41,080 Speaker 1: out there that try to patch it up by folding 731 00:38:41,080 --> 00:38:44,880 Speaker 1: this energy back into the gravitational field. Meaning like maybe 732 00:38:44,960 --> 00:38:47,160 Speaker 1: they think that maybe you're just doing the accounting wrong. 733 00:38:47,560 --> 00:38:51,040 Speaker 1: They might say that a costs of paintings are conserved 734 00:38:51,040 --> 00:38:54,600 Speaker 1: in value, is just that you know, you're accounting for 735 00:38:54,719 --> 00:38:58,319 Speaker 1: people's happiness when they purchase a costs or something like that, 736 00:38:58,440 --> 00:39:03,040 Speaker 1: right exactly. And they say, there's another category of energy 737 00:39:03,040 --> 00:39:05,680 Speaker 1: that we're not accounting for, and that's the gravitational energy, 738 00:39:06,160 --> 00:39:08,799 Speaker 1: and that as the universe expands, it actually gets more 739 00:39:08,840 --> 00:39:12,640 Speaker 1: and more negative gravitational energy. That the expansion of the 740 00:39:12,680 --> 00:39:17,000 Speaker 1: universe creates negative energy in the gravitational field that offsets 741 00:39:17,280 --> 00:39:20,680 Speaker 1: the positive energy from dark matter. And they do some 742 00:39:20,760 --> 00:39:23,640 Speaker 1: calculations and show that boom, it all adds up to zero, 743 00:39:23,719 --> 00:39:27,120 Speaker 1: and so energy is actually conserved. According to these folks, 744 00:39:27,200 --> 00:39:29,919 Speaker 1: is it kind of like the photon that loses energy 745 00:39:30,000 --> 00:39:33,879 Speaker 1: Like when you grow space you're pulling things apart, which 746 00:39:33,920 --> 00:39:37,239 Speaker 1: means you're losing gravitational energy, right, or you're gaining you're 747 00:39:37,239 --> 00:39:41,040 Speaker 1: losing you're gaining when when you're pulling things apart, it 748 00:39:41,080 --> 00:39:44,840 Speaker 1: takes energy to separate objects, right, So that's negative work 749 00:39:45,320 --> 00:39:48,880 Speaker 1: and so you're losing energy. You're creating a negative energy 750 00:39:48,960 --> 00:39:52,879 Speaker 1: situation in the gravitational field. But there's a problem with 751 00:39:52,960 --> 00:39:55,319 Speaker 1: this and the other folks on the other side of 752 00:39:55,320 --> 00:39:57,799 Speaker 1: the divide that say the energy is not conserved, they 753 00:39:57,880 --> 00:40:00,359 Speaker 1: quibble with the way this calculation is done, and they 754 00:40:00,360 --> 00:40:03,400 Speaker 1: think it's not actually technically correct that you can't actually 755 00:40:03,440 --> 00:40:07,280 Speaker 1: just measure the energy of a gravitational field, because gravity 756 00:40:07,360 --> 00:40:10,000 Speaker 1: is a really complicated thing. It's not just like, here's 757 00:40:10,000 --> 00:40:13,400 Speaker 1: a fixed gravitational potential and you can measure the energy. Remember, 758 00:40:13,440 --> 00:40:18,120 Speaker 1: gravity is dynamical, it's responding to space, it's shifting, it's changing. 759 00:40:18,560 --> 00:40:20,000 Speaker 1: And so, for reasons that I think are a little 760 00:40:20,000 --> 00:40:22,800 Speaker 1: too technical to dive into, there's not really a good, 761 00:40:22,960 --> 00:40:26,120 Speaker 1: well defined way to calculate the gravitational energy of the 762 00:40:26,120 --> 00:40:29,880 Speaker 1: whole universe, or even the gravitational energy more importantly of 763 00:40:29,920 --> 00:40:33,040 Speaker 1: a part of the universe, the gravitational density. So they 764 00:40:33,040 --> 00:40:35,480 Speaker 1: say that doesn't really count. You can't include it in 765 00:40:35,520 --> 00:40:39,560 Speaker 1: the calculation. Energy is not concerned. So it's still in progress. 766 00:40:39,560 --> 00:40:41,720 Speaker 1: People are still talking about it. People are still talking 767 00:40:41,719 --> 00:40:44,200 Speaker 1: about it, but I think the consensus is energy is 768 00:40:44,239 --> 00:40:47,080 Speaker 1: not conserved, despite these efforts to try to patch it 769 00:40:47,200 --> 00:40:49,120 Speaker 1: up and fix it and to say that there's a 770 00:40:49,160 --> 00:40:51,640 Speaker 1: way to look at energy such that it is concerned. 771 00:40:52,280 --> 00:40:54,080 Speaker 1: And then what do the dentist thing that if you 772 00:40:54,160 --> 00:40:56,640 Speaker 1: maybe do a root canal, you consider bypass s base. 773 00:40:58,960 --> 00:41:01,480 Speaker 1: They think we shouldn't eating fruit loops late at night 774 00:41:01,760 --> 00:41:05,040 Speaker 1: you should be flossing more often. You'd be flossing your 775 00:41:05,040 --> 00:41:07,279 Speaker 1: theory is more often because you know you can get 776 00:41:07,320 --> 00:41:10,319 Speaker 1: gun accumulating. But to me, I think it's fascinating. It's 777 00:41:10,360 --> 00:41:13,800 Speaker 1: a great investigation into like what's real about the universe, 778 00:41:13,840 --> 00:41:16,840 Speaker 1: what's deep, what's true. The reason that we try to 779 00:41:16,920 --> 00:41:19,840 Speaker 1: identify conservation laws is not just because we need a 780 00:41:19,880 --> 00:41:22,600 Speaker 1: better energy policy, but because we're trying to understand the 781 00:41:22,600 --> 00:41:25,200 Speaker 1: way the universe works, and finding these things that are 782 00:41:25,200 --> 00:41:28,439 Speaker 1: conserved or turns out to be not conserved are ways 783 00:41:28,440 --> 00:41:30,400 Speaker 1: that we get clues as to the way the whole 784 00:41:30,440 --> 00:41:33,520 Speaker 1: machinery works deep down. Yeah, I think what I'm getting 785 00:41:33,560 --> 00:41:36,879 Speaker 1: is that physics is maybe as fickle and sensical as 786 00:41:36,960 --> 00:41:40,600 Speaker 1: the art world. I think is what you're saying, and dentistry. 787 00:41:40,960 --> 00:41:43,560 Speaker 1: Your theory is genius, it's fundamental. Actually, no, it turns 788 00:41:43,560 --> 00:41:47,960 Speaker 1: out it's worth nothing. It's like cubism itself, makes no sense. 789 00:41:49,880 --> 00:41:53,080 Speaker 1: That's right, But there's a real beauty here to this inside, 790 00:41:53,120 --> 00:41:57,239 Speaker 1: this connection between symmetries and conservation laws, and it tells 791 00:41:57,239 --> 00:42:00,400 Speaker 1: you that every time you find something symmetric about the universe, 792 00:42:00,719 --> 00:42:04,120 Speaker 1: there's something out there being conserved. And that's really cool 793 00:42:04,160 --> 00:42:07,080 Speaker 1: and beautiful to me. Well, I think the takeaway is 794 00:42:07,120 --> 00:42:09,960 Speaker 1: that we can say that energy is conserved in space time, 795 00:42:10,440 --> 00:42:13,799 Speaker 1: but that spacetime itself is not always conserved. Yeah, if 796 00:42:13,800 --> 00:42:17,239 Speaker 1: spacetime is fixed, then energy is definitely conserved. In a 797 00:42:17,320 --> 00:42:20,960 Speaker 1: situation any universe like ours, where spacetime is expanding, then 798 00:42:20,960 --> 00:42:25,239 Speaker 1: there's no guarantee of energy conservation. Energy actually increases as 799 00:42:25,280 --> 00:42:28,840 Speaker 1: space time increases, and it doesn't come from anywhere, which 800 00:42:28,880 --> 00:42:31,120 Speaker 1: is hard to grapple with, but it is our reality. 801 00:42:31,120 --> 00:42:33,960 Speaker 1: And that's the job of physics is confronting us with 802 00:42:34,239 --> 00:42:37,719 Speaker 1: hard to understand truths, things that don't make sense to 803 00:42:37,719 --> 00:42:40,480 Speaker 1: our intuition, but that we figured out through science. Right, 804 00:42:40,520 --> 00:42:43,040 Speaker 1: that's why we have science and not just intuition, to 805 00:42:43,200 --> 00:42:46,640 Speaker 1: confront us with these things which are in conflict with 806 00:42:46,680 --> 00:42:48,920 Speaker 1: what we thought but turned out to be actually true. 807 00:42:49,800 --> 00:42:51,840 Speaker 1: All right, done, I won't walk away from the interview. 808 00:42:52,400 --> 00:42:54,399 Speaker 1: I'm staying. I'm staying for the rest of it, which 809 00:42:54,480 --> 00:42:58,960 Speaker 1: is about ten seconds. All right, Well, I conserved some 810 00:42:59,120 --> 00:43:01,600 Speaker 1: energy for this last bit. Well, we hope everyone enjoyed. Dad, 811 00:43:01,680 --> 00:43:03,960 Speaker 1: Thanks for joining us, and think a little bit more 812 00:43:04,000 --> 00:43:06,880 Speaker 1: about what do you think is true about the universe 813 00:43:06,920 --> 00:43:10,160 Speaker 1: and what might be an idea that Daniel and his 814 00:43:10,239 --> 00:43:14,640 Speaker 1: dentists wrong in the future, hopefully everything. Thanks for joining us, 815 00:43:14,840 --> 00:43:24,880 Speaker 1: see you next time. Thanks for listening, and remember that 816 00:43:25,000 --> 00:43:27,719 Speaker 1: Daniel and Jorge explain the universe is a production of 817 00:43:27,880 --> 00:43:31,240 Speaker 1: I Heart Radio. Or more podcast from my heart Radio 818 00:43:31,360 --> 00:43:34,960 Speaker 1: visit the I heart Radio app, Apple Podcasts, or wherever 819 00:43:35,040 --> 00:43:36,720 Speaker 1: you listen to your favorite shows.