1 00:00:08,600 --> 00:00:11,800 Speaker 1: Hey, Danny, does the universe just blow your mind? Oh? 2 00:00:11,840 --> 00:00:14,600 Speaker 1: My god. Constantly I feel like I can't crame enough 3 00:00:14,680 --> 00:00:17,440 Speaker 1: universe into my brain. Is just excluding what's the most 4 00:00:17,800 --> 00:00:20,360 Speaker 1: mind blowing thing about the universe in your opinion? I 5 00:00:20,360 --> 00:00:22,680 Speaker 1: think the thing that drives me the craziest is that 6 00:00:22,800 --> 00:00:26,360 Speaker 1: the universe itself seems to be blowing up. The universe 7 00:00:26,360 --> 00:00:29,680 Speaker 1: is blowing up. You mean like it's going viral on 8 00:00:29,760 --> 00:00:34,560 Speaker 1: social media? Probably hashtag universe, hashtag everything in the universe 9 00:00:34,560 --> 00:00:38,040 Speaker 1: Twitter account is lit. No, I mean that it's getting bigger, 10 00:00:38,400 --> 00:00:40,920 Speaker 1: and the speed at which the universe is getting bigger 11 00:00:41,120 --> 00:01:00,600 Speaker 1: is also getting bigger. Hi am pre hammack Tunis and 12 00:01:00,680 --> 00:01:04,160 Speaker 1: the creator of PhD Comics. Hi, I'm Daniel Whitson. I'm 13 00:01:04,240 --> 00:01:07,800 Speaker 1: a particle physicist, but my brain is filled with crazy 14 00:01:07,880 --> 00:01:11,360 Speaker 1: ideas about space, time and particles. So welcome to our 15 00:01:11,400 --> 00:01:16,600 Speaker 1: podcast Daniel and Jorge explain The Exploding Universe, a production 16 00:01:16,680 --> 00:01:19,040 Speaker 1: of My Heart Radio, in which we try to take 17 00:01:19,040 --> 00:01:23,240 Speaker 1: the entire universe, everything in it, and squeeze it down 18 00:01:23,360 --> 00:01:27,080 Speaker 1: into this audio connection to you, downloading it into your 19 00:01:27,120 --> 00:01:29,800 Speaker 1: brain so that it blows up your gray matter. And 20 00:01:29,880 --> 00:01:32,280 Speaker 1: so are we here to try to blow your mind 21 00:01:32,959 --> 00:01:35,080 Speaker 1: a little bit of physics at a time, you know, 22 00:01:35,240 --> 00:01:37,720 Speaker 1: just a little bit of physics each week, twice a week, 23 00:01:37,800 --> 00:01:40,600 Speaker 1: and hopefully your mind is getting maybe bigger, may be 24 00:01:40,720 --> 00:01:43,880 Speaker 1: more connected to this giant universe we have out there. 25 00:01:44,440 --> 00:01:46,280 Speaker 1: That's right, The universe is out there, and we think 26 00:01:46,319 --> 00:01:49,720 Speaker 1: it's for everybody understanding. This incredible place we live in 27 00:01:49,760 --> 00:01:52,640 Speaker 1: shouldn't just be the province of cutting edge scientists. It 28 00:01:52,720 --> 00:01:55,880 Speaker 1: belongs to everybody, and that wonderment, that amazement should be 29 00:01:55,920 --> 00:01:59,520 Speaker 1: accessible to everybody out there. And so our goal is 30 00:01:59,560 --> 00:02:01,680 Speaker 1: to make sure that you actually understand the way the 31 00:02:01,760 --> 00:02:04,880 Speaker 1: universe works and what science does and does not know. 32 00:02:05,120 --> 00:02:07,520 Speaker 1: Is the universe for everybody? Daniel, I don't know about that. 33 00:02:07,800 --> 00:02:13,120 Speaker 1: I mean, all solar systems matter, man, All solar systems 34 00:02:13,200 --> 00:02:15,800 Speaker 1: are made of matter. Yeah, that matter matters, no, But 35 00:02:15,840 --> 00:02:17,680 Speaker 1: I think that the universe is for everybody. You know, 36 00:02:17,720 --> 00:02:19,760 Speaker 1: you don't have to be a scientist to look up 37 00:02:19,760 --> 00:02:22,120 Speaker 1: at the stars and wonder how does this whole crazy 38 00:02:22,200 --> 00:02:24,520 Speaker 1: universe work? Or to look down at your feet and 39 00:02:24,520 --> 00:02:26,960 Speaker 1: wonder about the particles that you're made out of. And 40 00:02:27,000 --> 00:02:30,160 Speaker 1: everybody deserves an explanation. And you know, science is mostly 41 00:02:30,200 --> 00:02:33,480 Speaker 1: something that's publicly funded, it's put on by governments, it's 42 00:02:33,600 --> 00:02:35,560 Speaker 1: of the people, by the people, and for the people. 43 00:02:35,639 --> 00:02:38,040 Speaker 1: And so this is the for the people part where 44 00:02:38,040 --> 00:02:40,840 Speaker 1: we try to disseminate what science has learned to everybody 45 00:02:40,880 --> 00:02:43,640 Speaker 1: out there. Yeah, for sure, I think definitely the universe 46 00:02:43,680 --> 00:02:47,000 Speaker 1: itself is definitely of people and with people in it, 47 00:02:47,120 --> 00:02:50,560 Speaker 1: and for the people. Yeah, there's a lot of prepositions 48 00:02:50,600 --> 00:02:51,960 Speaker 1: you can go for there. I just hope it's not 49 00:02:52,040 --> 00:02:54,560 Speaker 1: through people. You know, we don't don't want to go 50 00:02:54,639 --> 00:02:57,200 Speaker 1: around people are over people, what do you mean? I 51 00:02:57,280 --> 00:03:00,760 Speaker 1: think the universe is all those things, the universe going 52 00:03:00,800 --> 00:03:02,959 Speaker 1: through me right now. Well, the goal of this podcast 53 00:03:03,000 --> 00:03:05,440 Speaker 1: is to get the universe into people. Well, we're trying 54 00:03:05,480 --> 00:03:07,799 Speaker 1: to um talk about the universe and just kind of 55 00:03:07,880 --> 00:03:12,240 Speaker 1: help everyone wrapped their heads around this incredible and complex 56 00:03:12,240 --> 00:03:16,440 Speaker 1: and really big universe, right and possibly getting bigger. Yeah, 57 00:03:16,520 --> 00:03:18,960 Speaker 1: And this whole idea of the size of the universe 58 00:03:19,040 --> 00:03:21,840 Speaker 1: is something which is very very modern and people have 59 00:03:21,880 --> 00:03:23,600 Speaker 1: been looking at the stars for a long time. People 60 00:03:23,639 --> 00:03:26,040 Speaker 1: have known about other planets, people had the idea that 61 00:03:26,040 --> 00:03:28,080 Speaker 1: there are other stars out there, But it's only been 62 00:03:28,080 --> 00:03:30,720 Speaker 1: a hundred years that we've known that there are other galaxies, 63 00:03:31,160 --> 00:03:33,480 Speaker 1: and that those galaxies are moving away from us, and 64 00:03:33,520 --> 00:03:36,800 Speaker 1: that the size of the universe itself might be expanding. 65 00:03:37,200 --> 00:03:39,280 Speaker 1: So it's very recent in human history that we really 66 00:03:39,280 --> 00:03:42,760 Speaker 1: have any understanding at all of the entire context of 67 00:03:42,760 --> 00:03:45,600 Speaker 1: our lives. Yeah, that's wild, Like a hundred only a 68 00:03:45,640 --> 00:03:48,880 Speaker 1: hundred years ago, we thought it was just us right, 69 00:03:49,080 --> 00:03:51,880 Speaker 1: like us and the stars around us, and maybe that's it. Yeah, 70 00:03:52,040 --> 00:03:53,840 Speaker 1: hundred years ago, people thought it was a bunch of 71 00:03:53,880 --> 00:03:55,840 Speaker 1: stars hanging in space, and it's just sort of been 72 00:03:55,920 --> 00:03:59,600 Speaker 1: like that forever. So most humans who ever lived had 73 00:03:59,600 --> 00:04:03,080 Speaker 1: the raw long understanding of the entire universe. Only the 74 00:04:03,240 --> 00:04:06,000 Speaker 1: people who were awake, alive and listening to this podcast 75 00:04:06,360 --> 00:04:09,760 Speaker 1: have any sense for the actual context of their lives. Yeah, 76 00:04:09,880 --> 00:04:12,840 Speaker 1: it's just a small error, you know, just a few 77 00:04:12,920 --> 00:04:16,800 Speaker 1: Brazilian whatever. And the thing I love about that is 78 00:04:16,839 --> 00:04:20,480 Speaker 1: it suggests that there might be other enormous contextual errors 79 00:04:20,480 --> 00:04:23,679 Speaker 1: that we're making, you know, basic assumptions we have about 80 00:04:23,680 --> 00:04:25,960 Speaker 1: the way the universe works that are just wrong. That 81 00:04:26,040 --> 00:04:28,920 Speaker 1: in a hundred years some future podcast will be smirking 82 00:04:28,960 --> 00:04:32,800 Speaker 1: at and twortling at our ignorance, being sarcastic about while 83 00:04:32,800 --> 00:04:36,200 Speaker 1: eating bananas precisely. Do you think people back then a 84 00:04:36,279 --> 00:04:39,760 Speaker 1: hundred years ago I thought the universe was a finite size, 85 00:04:39,800 --> 00:04:41,520 Speaker 1: or did they think it was infinite, or did they 86 00:04:41,560 --> 00:04:43,479 Speaker 1: think it had a size but just not as big 87 00:04:43,520 --> 00:04:45,799 Speaker 1: as we know to be right now. I think about 88 00:04:45,800 --> 00:04:48,520 Speaker 1: a hundred years ago, before Hubble, for example, people thought 89 00:04:48,520 --> 00:04:50,839 Speaker 1: it was just a bunch of stars and it was finite, 90 00:04:51,080 --> 00:04:52,839 Speaker 1: and it just sort of a bunch of stars hanging 91 00:04:52,880 --> 00:04:56,160 Speaker 1: in space. You know, imagine like a single galaxy, whether 92 00:04:56,240 --> 00:04:58,080 Speaker 1: or not space itself went on beyond the edge of 93 00:04:58,080 --> 00:05:00,320 Speaker 1: that galaxy. I think there was a lot of debate there, 94 00:05:00,560 --> 00:05:02,599 Speaker 1: but I don't think people ever imagine that there could 95 00:05:02,600 --> 00:05:05,360 Speaker 1: be like an infinite number of stars. Well, and so 96 00:05:05,440 --> 00:05:08,080 Speaker 1: that's the topic for today's podcast is it's about the 97 00:05:08,120 --> 00:05:11,880 Speaker 1: size of the universe and more specifically, how that size 98 00:05:11,920 --> 00:05:16,120 Speaker 1: is changing, because the size of the universe is changing, right, 99 00:05:16,200 --> 00:05:18,560 Speaker 1: that's right, And this is something that Hubble himself began. 100 00:05:18,839 --> 00:05:21,840 Speaker 1: Hubble is famous not because of the Hubble space telescope, 101 00:05:21,839 --> 00:05:24,680 Speaker 1: which was named after him, but because he's the guy 102 00:05:24,680 --> 00:05:26,960 Speaker 1: who discovered that the universe is expanding. The things that 103 00:05:27,000 --> 00:05:29,240 Speaker 1: are far away from us are moving away from us. 104 00:05:29,360 --> 00:05:33,000 Speaker 1: Really quickly, where like one raise in an expanding loof 105 00:05:33,200 --> 00:05:36,240 Speaker 1: of raisin bread. And the thing that's amazing is that 106 00:05:36,279 --> 00:05:39,360 Speaker 1: we're still learning about that. We're still learning about how 107 00:05:39,480 --> 00:05:42,800 Speaker 1: fast the universe is expanding, and we're still not sure 108 00:05:42,800 --> 00:05:45,120 Speaker 1: of it. We still don't really know the answer. Really. 109 00:05:45,160 --> 00:05:48,840 Speaker 1: We think it's expanding faster and faster, but we are 110 00:05:48,920 --> 00:05:52,320 Speaker 1: not quite sure how fast it's it's it's growing, or 111 00:05:52,640 --> 00:05:55,240 Speaker 1: kind of what's causing it. Right, that's exactly right. And 112 00:05:55,320 --> 00:05:57,520 Speaker 1: people measure this stuff and there's lots of different ways 113 00:05:57,520 --> 00:06:00,640 Speaker 1: to do it, and those measurements they make don't quite agree. 114 00:06:00,839 --> 00:06:02,640 Speaker 1: And so that's what we're gonna be talking about in 115 00:06:02,680 --> 00:06:05,919 Speaker 1: today's podcast. Yeah, So today on the podcast, we'll be 116 00:06:05,960 --> 00:06:16,160 Speaker 1: tackling the question how fast is the universe blowing up? Yeah? 117 00:06:16,240 --> 00:06:18,160 Speaker 1: And this is a really fun question and what I've 118 00:06:18,200 --> 00:06:20,800 Speaker 1: been tracking for a while because different teams of scientists 119 00:06:20,839 --> 00:06:23,240 Speaker 1: are trying to measure this expansion of the universe in 120 00:06:23,279 --> 00:06:25,760 Speaker 1: totally different ways, and for a while they sort of 121 00:06:25,800 --> 00:06:29,400 Speaker 1: agreed until recently their measurements be getting more and more precise, 122 00:06:29,440 --> 00:06:32,280 Speaker 1: and now they're not agreeing that well, And then I 123 00:06:32,320 --> 00:06:34,920 Speaker 1: got a question from a listener somebody who wrote in 124 00:06:34,960 --> 00:06:36,599 Speaker 1: to ask about it, and I thought, all right, it's 125 00:06:36,600 --> 00:06:39,040 Speaker 1: time to do a podcast on it. So here's a 126 00:06:39,120 --> 00:06:42,160 Speaker 1: question from Mike and Madison who wanted to know. Hi, 127 00:06:42,279 --> 00:06:44,680 Speaker 1: Daniel and Jorge. My name is Mike. I'm an engineer 128 00:06:44,720 --> 00:06:48,200 Speaker 1: from Madison, Wisconsin. Could you guys please explain what we're 129 00:06:48,240 --> 00:06:52,640 Speaker 1: doing to try and solve the unmatching hubble constant mystery? Also, 130 00:06:52,640 --> 00:06:54,920 Speaker 1: why does it have to be a single constant? Couldn't 131 00:06:54,920 --> 00:06:58,720 Speaker 1: the universe be expanding asymmetrically or at changing or different 132 00:06:58,800 --> 00:07:01,599 Speaker 1: rates depending on where you are in the universe. Also, 133 00:07:01,640 --> 00:07:03,440 Speaker 1: I'd like to give a shout out to my uncle 134 00:07:03,520 --> 00:07:07,200 Speaker 1: Jim McClain for introducing me to this amazing podcast. All right, 135 00:07:07,240 --> 00:07:09,760 Speaker 1: thank you Mike and Madison in medisine. I like how 136 00:07:09,760 --> 00:07:14,360 Speaker 1: it's alliterative. Yeah, and in a moment we will dig 137 00:07:14,400 --> 00:07:16,800 Speaker 1: into what the hubble constant is and how it's connected 138 00:07:16,840 --> 00:07:19,600 Speaker 1: to the expansion the universe and is it a constant 139 00:07:19,600 --> 00:07:22,160 Speaker 1: after all and all that kind of stuff. Yeah, because 140 00:07:22,160 --> 00:07:24,560 Speaker 1: it's kind of a very technical question. Like at first 141 00:07:24,600 --> 00:07:27,720 Speaker 1: I heard this question, but I didn't really even know 142 00:07:27,720 --> 00:07:29,360 Speaker 1: what he was asking about. Yeah, And the best way 143 00:07:29,400 --> 00:07:30,960 Speaker 1: to think about it is that the Hubble constant is 144 00:07:31,000 --> 00:07:34,920 Speaker 1: just one way to understand how fast the universe is accelerating. 145 00:07:35,320 --> 00:07:37,600 Speaker 1: It sort of helps determine it. But of course it's 146 00:07:37,600 --> 00:07:40,720 Speaker 1: confusing because it turns out the Hubble constant not actually 147 00:07:40,760 --> 00:07:46,280 Speaker 1: a constant, so it's an un constant constant. We are 148 00:07:46,440 --> 00:07:49,400 Speaker 1: constantly messing up the names of things in physics. We 149 00:07:49,560 --> 00:07:54,080 Speaker 1: are constantly throwing out the dictionary, it seems. You know, 150 00:07:54,120 --> 00:07:56,440 Speaker 1: if we just redefine the meaning of the word constant, 151 00:07:56,440 --> 00:07:58,880 Speaker 1: then it's a constant, right, and then we'll redefine the 152 00:07:58,880 --> 00:08:02,400 Speaker 1: meaning of the word redefine, in which case we'll be 153 00:08:02,880 --> 00:08:05,600 Speaker 1: do this all the time in physics right where we 154 00:08:05,760 --> 00:08:08,600 Speaker 1: have particles that spin but it's not really spin, you know, 155 00:08:08,640 --> 00:08:10,920 Speaker 1: we have particles with flavor, but they don't really taste 156 00:08:10,920 --> 00:08:13,240 Speaker 1: like anything. And now we have constants that are not 157 00:08:13,320 --> 00:08:16,640 Speaker 1: really constant. It's like a whole new language. It's like, 158 00:08:16,800 --> 00:08:18,800 Speaker 1: I feel like you're doing on a purpose, Daniel, just 159 00:08:18,920 --> 00:08:24,200 Speaker 1: to confuse us, and um makes us, UM makes us 160 00:08:24,440 --> 00:08:27,000 Speaker 1: wonder about this crazy No, no no, no, we I'm going 161 00:08:27,040 --> 00:08:29,840 Speaker 1: to use the Donald Trump defense. It's out of pure incompetence. 162 00:08:30,000 --> 00:08:32,640 Speaker 1: We're not trying to confuse anybody. We're just not capable 163 00:08:32,679 --> 00:08:34,800 Speaker 1: of doing any better. I see that's a defense name 164 00:08:34,840 --> 00:08:39,160 Speaker 1: after him, but not necessarily something he does. That's right, 165 00:08:39,360 --> 00:08:41,439 Speaker 1: But I was wondering are people paying attention to this? 166 00:08:41,559 --> 00:08:44,040 Speaker 1: Does everybody know what the Hubble constant? Is? Are they 167 00:08:44,040 --> 00:08:46,719 Speaker 1: aware this tempest and a teapot about how fast the 168 00:08:46,800 --> 00:08:50,160 Speaker 1: universe is expanding? Or is that something just scientists are 169 00:08:50,200 --> 00:08:52,679 Speaker 1: thinking about? Yeah, how many people out there even know 170 00:08:53,000 --> 00:08:56,559 Speaker 1: what the Hubble constant is? So, as usual, Daniel went 171 00:08:56,559 --> 00:09:00,120 Speaker 1: out there into the streets and as random strangers if 172 00:09:00,160 --> 00:09:02,880 Speaker 1: they knew what the Hubble constant is, think about it 173 00:09:02,880 --> 00:09:05,400 Speaker 1: for a second. Do you know what the Hubble constant is? 174 00:09:05,600 --> 00:09:07,920 Speaker 1: And if somebody asked you on the street to define it, 175 00:09:08,040 --> 00:09:09,880 Speaker 1: would you be able to give an answer? Here's what 176 00:09:09,920 --> 00:09:12,200 Speaker 1: people had to say. Something to do with the way 177 00:09:13,000 --> 00:09:15,840 Speaker 1: things around its space. I guess I don't know. Something 178 00:09:15,920 --> 00:09:18,120 Speaker 1: do the Hubble telescope? I don't know. It's the only 179 00:09:18,160 --> 00:09:21,440 Speaker 1: thing that I know that is Hubble esque, like a 180 00:09:21,480 --> 00:09:25,240 Speaker 1: mathematical equation or something. I feel like, something about how 181 00:09:25,679 --> 00:09:30,160 Speaker 1: the stretching of the universe that's do with gravity or something. 182 00:09:30,400 --> 00:09:31,920 Speaker 1: I mean, does it have to do with that one 183 00:09:31,960 --> 00:09:34,839 Speaker 1: Hubble and like a red blue shift or anything or not. 184 00:09:36,760 --> 00:09:39,079 Speaker 1: That's that w the extent that I would know, no idea. 185 00:09:40,120 --> 00:09:42,840 Speaker 1: Have you heard of Hubble? No? I guess it has 186 00:09:42,920 --> 00:09:47,920 Speaker 1: something to do with lights and the stars and space. 187 00:09:48,800 --> 00:09:52,599 Speaker 1: The scale you're getting there. Yeah, it's a scale constant 188 00:09:53,320 --> 00:09:59,600 Speaker 1: of lights through three dimensional space, and it's like a 189 00:09:59,600 --> 00:10:02,520 Speaker 1: cost bar jegal constant um. Doesn't have to do with 190 00:10:02,720 --> 00:10:06,320 Speaker 1: the size of the universe. I think that's all I 191 00:10:06,320 --> 00:10:10,040 Speaker 1: can get from my memory right now. I've heard of Hubble. 192 00:10:10,160 --> 00:10:13,840 Speaker 1: It's like the telescope, right, And I'm not sure what 193 00:10:13,880 --> 00:10:17,679 Speaker 1: the Hubble constant is, all right. I feel like some 194 00:10:17,720 --> 00:10:19,760 Speaker 1: people knew a lot about it, but a lot of 195 00:10:19,800 --> 00:10:22,880 Speaker 1: people didn't know anything about it or had heard of it. Yeah, 196 00:10:22,920 --> 00:10:25,360 Speaker 1: and some people were totally wrong. But I love these answers. 197 00:10:25,400 --> 00:10:27,280 Speaker 1: You know, some people think it has to do with 198 00:10:27,280 --> 00:10:30,480 Speaker 1: the Hubble space Telescope, which I guess indirectly it does, 199 00:10:30,640 --> 00:10:33,480 Speaker 1: because you know, the space telescope was named for Hubble, 200 00:10:33,520 --> 00:10:38,120 Speaker 1: who discovered this thing and and quantified. They've done a 201 00:10:38,160 --> 00:10:40,640 Speaker 1: lot of really good branding on the Hubble telescope, you know, 202 00:10:40,679 --> 00:10:43,240 Speaker 1: like it's a thing. People know what it is, and 203 00:10:43,600 --> 00:10:46,680 Speaker 1: because when most people associated with the name Hubble. Yeah, 204 00:10:46,720 --> 00:10:48,719 Speaker 1: the Hubble pr team has done a good job. Hey, 205 00:10:48,720 --> 00:10:52,200 Speaker 1: you know they produced these Instagram ready images all the time. 206 00:10:52,280 --> 00:10:54,679 Speaker 1: They're beautiful. You know, you just google Hubble and you've 207 00:10:54,720 --> 00:10:56,600 Speaker 1: got a lot of really gorgeous stuff to look at. 208 00:10:56,800 --> 00:10:59,760 Speaker 1: Let a Hubble bubble up. Yeah, you know, particle physics 209 00:10:59,760 --> 00:11:02,920 Speaker 1: service Umble doesn't produce as much like pretty pictures that 210 00:11:02,960 --> 00:11:05,120 Speaker 1: you can look at and say, oh wow, look at 211 00:11:05,120 --> 00:11:07,679 Speaker 1: that amazing thing out there in the universe, because it's 212 00:11:07,720 --> 00:11:10,640 Speaker 1: harder to visualize tiny particles. So from that point of view, 213 00:11:10,640 --> 00:11:13,959 Speaker 1: astronomy definitely has the lead over particle physics. Well, I 214 00:11:13,960 --> 00:11:17,439 Speaker 1: I am definitely in league with all of these people 215 00:11:17,480 --> 00:11:19,880 Speaker 1: on the street. I don't really know or have a 216 00:11:19,960 --> 00:11:22,520 Speaker 1: good idea of what the Hubble constant. Maybe. Up until 217 00:11:22,520 --> 00:11:24,520 Speaker 1: a few years ago, I never even heard it. I 218 00:11:24,520 --> 00:11:28,160 Speaker 1: mean I heard of the Hubble telescope, not the Hubble constant. Really, 219 00:11:28,200 --> 00:11:30,920 Speaker 1: do you remember the moment you learned about the Hubble constant, 220 00:11:31,000 --> 00:11:34,960 Speaker 1: probably like five minutes after meeting you. Then I do 221 00:11:35,080 --> 00:11:39,240 Speaker 1: bring it up pretty quickly in conversation. Hi, how's it going, 222 00:11:39,360 --> 00:11:43,800 Speaker 1: how's the weather. Let's talk about the Hubble constant. So 223 00:11:43,880 --> 00:11:47,360 Speaker 1: it's it's not related to the telescope. This telescope was 224 00:11:47,440 --> 00:11:51,600 Speaker 1: named after Edwin Hubble Um. But Hubble in his time 225 00:11:51,760 --> 00:11:54,920 Speaker 1: did a lot of amazing discoveries, and one of them 226 00:11:55,000 --> 00:11:58,200 Speaker 1: was this idea of a constant in the universe. Yeah, precisely. 227 00:11:58,200 --> 00:12:00,640 Speaker 1: The Hubble constant is related to the Hubble telescope, and 228 00:12:00,679 --> 00:12:03,280 Speaker 1: we actually do use the Hubble telescope now to help 229 00:12:03,360 --> 00:12:05,760 Speaker 1: nail down the Hubble constant, which is sort of a 230 00:12:05,800 --> 00:12:08,160 Speaker 1: fun little loop there. Yeah. Of course Hubble died well 231 00:12:08,200 --> 00:12:10,480 Speaker 1: before the space telescope launched, But you're right, he was 232 00:12:10,520 --> 00:12:13,800 Speaker 1: the one who figured out that the universe is expanding. Right. 233 00:12:13,840 --> 00:12:16,200 Speaker 1: Do you think he named the constant after himself or 234 00:12:16,400 --> 00:12:19,480 Speaker 1: was it named for him? Oh that's a great question. Um, 235 00:12:19,520 --> 00:12:21,000 Speaker 1: I have to go back and look at the paper. 236 00:12:21,559 --> 00:12:24,120 Speaker 1: Now we refer to it as H zero, you know, 237 00:12:24,360 --> 00:12:27,320 Speaker 1: H for Hubble and zero for constant. But I don't 238 00:12:27,320 --> 00:12:31,880 Speaker 1: know how the Santa Claus constant is. What if you 239 00:12:31,880 --> 00:12:36,160 Speaker 1: should have called it? Um No, But I don't know 240 00:12:36,200 --> 00:12:38,160 Speaker 1: if he called it H in his paper or if 241 00:12:38,160 --> 00:12:41,400 Speaker 1: he just observed this. The breakthrough the heat provided is 242 00:12:41,400 --> 00:12:43,720 Speaker 1: that he figured out a way to measure the distance 243 00:12:43,760 --> 00:12:46,920 Speaker 1: to really far away objects. You remember, we had a 244 00:12:46,920 --> 00:12:49,880 Speaker 1: whole podcast about how we measured the distance to stars. 245 00:12:50,000 --> 00:12:52,280 Speaker 1: It's tricky because you don't know when you look at 246 00:12:52,280 --> 00:12:55,640 Speaker 1: a star if it's really bright and far away or 247 00:12:55,760 --> 00:12:58,080 Speaker 1: really close and kind of dim. So you have to 248 00:12:58,200 --> 00:13:00,959 Speaker 1: know the distance um in other way. And he was 249 00:13:01,000 --> 00:13:02,800 Speaker 1: the first one to figure out a way to measure 250 00:13:02,800 --> 00:13:06,040 Speaker 1: the distance to far away stars because, as we talked 251 00:13:06,040 --> 00:13:08,840 Speaker 1: about in that podcast, it's really hard to tell that distance. 252 00:13:08,960 --> 00:13:11,600 Speaker 1: I mean from here from Earth, things just look like 253 00:13:11,640 --> 00:13:14,920 Speaker 1: little pinpoints of light and they can be really far, 254 00:13:15,080 --> 00:13:17,199 Speaker 1: they can be really closed. You don't really know, right, 255 00:13:17,679 --> 00:13:21,680 Speaker 1: So Hobbi used these really cool stars called Cepid's now 256 00:13:21,760 --> 00:13:25,359 Speaker 1: another astronomer. Hen we had a Levitt had earlier discovered 257 00:13:25,400 --> 00:13:28,880 Speaker 1: that there's a way to relate how fast these stars 258 00:13:28,920 --> 00:13:31,720 Speaker 1: pulsate to how bright they are. And we want to 259 00:13:31,720 --> 00:13:34,880 Speaker 1: say thank you very much to Marcus Pustle for raising 260 00:13:34,920 --> 00:13:38,360 Speaker 1: this issue and reminding us of Henrietta Levitt's work. Apologies 261 00:13:38,360 --> 00:13:42,000 Speaker 1: that we neglected to mention her contributions in an earlier version. 262 00:13:42,360 --> 00:13:45,640 Speaker 1: So if you know how bright these stars are supposed 263 00:13:45,679 --> 00:13:48,079 Speaker 1: to be because you can tell how fast they're pulsating, 264 00:13:48,520 --> 00:13:51,120 Speaker 1: then you know how far away they actually are by 265 00:13:51,120 --> 00:13:55,800 Speaker 1: measuring their brightness here on Earth. So building on Levitt's discovery, 266 00:13:56,200 --> 00:13:59,200 Speaker 1: this gave Hubble a way to estimate the distance to 267 00:13:59,400 --> 00:14:02,640 Speaker 1: those ours. And then that's a moment he made an 268 00:14:02,679 --> 00:14:05,679 Speaker 1: incredible discovery that some of these things were super duper 269 00:14:05,720 --> 00:14:08,000 Speaker 1: far away. He's like, Okay, now I have a way 270 00:14:08,000 --> 00:14:10,160 Speaker 1: to measure the distance to these stars. What are the numbers? 271 00:14:11,800 --> 00:14:15,320 Speaker 1: The calculation? That's what it sounded like. And they had 272 00:14:15,360 --> 00:14:19,280 Speaker 1: calculators back there were mechanically and it's probably turned cranker. 273 00:14:19,360 --> 00:14:22,000 Speaker 1: Maybe somebody was shoveling coal in the side of his calculator. 274 00:14:22,600 --> 00:14:24,400 Speaker 1: Um no, I guess I probably had a room full 275 00:14:24,440 --> 00:14:28,720 Speaker 1: of people doing math paper. Here's the sound of it. 276 00:14:30,760 --> 00:14:33,280 Speaker 1: There's my dramatic recreation of his calculation. But he had 277 00:14:33,360 --> 00:14:36,400 Speaker 1: this moment of discovery, developed this new tool, a way 278 00:14:36,400 --> 00:14:38,920 Speaker 1: to understand how far away things are. And the numbers 279 00:14:38,920 --> 00:14:41,560 Speaker 1: he got were crazy, Like the numbers he got were 280 00:14:41,600 --> 00:14:44,600 Speaker 1: like these can't even meet inside the galaxy. And that's 281 00:14:44,600 --> 00:14:46,880 Speaker 1: what made him realize that some of the little dust 282 00:14:47,000 --> 00:14:49,200 Speaker 1: he was seeing the guy weren't in our galaxy. There 283 00:14:49,240 --> 00:14:52,360 Speaker 1: were other galaxies far away. So he gave us this 284 00:14:52,400 --> 00:14:55,200 Speaker 1: ability to understand how far away things were and gave 285 00:14:55,280 --> 00:14:58,280 Speaker 1: us the first view outside of our galaxy into deep 286 00:14:58,320 --> 00:15:01,840 Speaker 1: deep space. That's the first he did, was he expanded 287 00:15:02,000 --> 00:15:05,480 Speaker 1: our idea of how big the universe was and how 288 00:15:05,520 --> 00:15:08,600 Speaker 1: far away things were. But at that time, I think 289 00:15:09,360 --> 00:15:11,520 Speaker 1: a lot of people, most people thought that the universe 290 00:15:11,840 --> 00:15:14,200 Speaker 1: was kind of fixed, right, like it wasn't. Maybe he 291 00:15:14,640 --> 00:15:16,720 Speaker 1: figured out how big it was, but at the time, 292 00:15:16,760 --> 00:15:19,600 Speaker 1: most people, I think thought the universe wasn't changing, like 293 00:15:19,640 --> 00:15:22,160 Speaker 1: it was fixed. Yeah, precisely. Once he was able to 294 00:15:22,200 --> 00:15:24,840 Speaker 1: know how far away stuff was, he could also measure 295 00:15:25,000 --> 00:15:27,560 Speaker 1: how fast it was moving away from us, and then 296 00:15:27,600 --> 00:15:29,600 Speaker 1: he made this plot. He's like, only maybe just plot 297 00:15:29,640 --> 00:15:32,800 Speaker 1: everything in terms of how far away it is versus 298 00:15:32,800 --> 00:15:34,880 Speaker 1: how fast it's moving away from us, And it just 299 00:15:34,880 --> 00:15:37,480 Speaker 1: sort of fell in a line. So the farther away 300 00:15:37,520 --> 00:15:40,560 Speaker 1: something is the faster it's moving away from us, and 301 00:15:40,640 --> 00:15:43,680 Speaker 1: that the slope of that line is the hubble constants 302 00:15:43,720 --> 00:15:46,840 Speaker 1: the ratio between how far something is from us and 303 00:15:46,880 --> 00:15:49,240 Speaker 1: how fast it's moving away from us. Because that's a 304 00:15:49,280 --> 00:15:52,360 Speaker 1: weird concept. I think. I think that can you imagine 305 00:15:52,400 --> 00:15:57,520 Speaker 1: a universe getting bigger? It's kind of not intuitive to 306 00:15:57,560 --> 00:16:00,360 Speaker 1: think that how fast things are moving and way from 307 00:16:00,440 --> 00:16:03,200 Speaker 1: us would change. Right, Like if you think of when 308 00:16:03,240 --> 00:16:06,320 Speaker 1: a grenade explodes out in space, you know, all the 309 00:16:06,360 --> 00:16:08,560 Speaker 1: bits are moving away from each other, but they're sort 310 00:16:08,560 --> 00:16:11,240 Speaker 1: of moving at the same rate. They're not moving faster 311 00:16:11,320 --> 00:16:14,040 Speaker 1: and faster the further out you go in the explosion, 312 00:16:14,120 --> 00:16:16,640 Speaker 1: right precisely. And the reason you shouldn't think of the 313 00:16:16,720 --> 00:16:20,080 Speaker 1: universe as a grenade is because of grenade, the explosion 314 00:16:20,120 --> 00:16:22,560 Speaker 1: comes just from the center. Is that one explosion, and 315 00:16:22,600 --> 00:16:24,880 Speaker 1: then everything is just getting pushed from there. But the 316 00:16:24,960 --> 00:16:28,120 Speaker 1: universe's expansion is totally different. It's much more like raisin 317 00:16:28,120 --> 00:16:30,960 Speaker 1: bread than like a grenade. When you cook a loaf 318 00:16:31,000 --> 00:16:33,160 Speaker 1: of raisin bread, it doesn't just expand from the center. 319 00:16:33,480 --> 00:16:35,800 Speaker 1: Every part of the bread is expanding, So all the 320 00:16:35,880 --> 00:16:38,960 Speaker 1: raisins are moving away from each other. Everything is stretching 321 00:16:39,120 --> 00:16:41,840 Speaker 1: at the same time. Even the stuff that's way out 322 00:16:41,840 --> 00:16:44,520 Speaker 1: there is also stretching. Yeah, if you wanted to mix 323 00:16:44,520 --> 00:16:46,800 Speaker 1: the metaphors, you'd have to, like have a grenade bread 324 00:16:47,040 --> 00:16:49,520 Speaker 1: loaf of bread that's grenades, you know, that's expanding all 325 00:16:49,560 --> 00:16:51,960 Speaker 1: the time, A bunch of tiny little grenades. I guess 326 00:16:52,080 --> 00:16:54,040 Speaker 1: in the end bread is expanding because of all the east. 327 00:16:54,160 --> 00:16:56,600 Speaker 1: You can think of the east is like microbial grenades. 328 00:16:56,800 --> 00:17:01,400 Speaker 1: It's like it's always exploding everywhere, and oh, the stuff 329 00:17:01,440 --> 00:17:05,120 Speaker 1: that's really far away has a lot of yeast between 330 00:17:05,240 --> 00:17:08,040 Speaker 1: here and there. And so it's the stretching and the 331 00:17:08,160 --> 00:17:11,240 Speaker 1: expanding compounds, you know, like it's it's getting bigger and 332 00:17:11,280 --> 00:17:13,920 Speaker 1: bigger and bigger, bigger and bigger and faster and faster. 333 00:17:14,119 --> 00:17:17,800 Speaker 1: The further away from you you go, precisely between us 334 00:17:17,800 --> 00:17:19,720 Speaker 1: and things that are far away, there's more space, and 335 00:17:19,760 --> 00:17:22,119 Speaker 1: so there's more space to be expanding, and so the 336 00:17:22,160 --> 00:17:25,200 Speaker 1: velocities are larger. And then you're saying that the Hubble constant, 337 00:17:25,680 --> 00:17:29,520 Speaker 1: it's is what tells us just how fast that's happening, Like, 338 00:17:30,359 --> 00:17:33,679 Speaker 1: is the raising bread crazy with it's some kind of 339 00:17:33,680 --> 00:17:36,399 Speaker 1: crazy yeast or was this some kind of you know, dull, old, 340 00:17:37,119 --> 00:17:40,760 Speaker 1: kind of mild, timid east which is expanding our raising 341 00:17:40,880 --> 00:17:43,760 Speaker 1: universe a little bit slower. Yeah, And so the Hubble 342 00:17:43,800 --> 00:17:47,439 Speaker 1: constant is expressed in terms of velocity per distance. For 343 00:17:47,520 --> 00:17:50,520 Speaker 1: every light year you go, how much faster are things 344 00:17:50,800 --> 00:17:53,080 Speaker 1: accelerating away from us? All right, let's get into the 345 00:17:53,119 --> 00:17:56,840 Speaker 1: details of this constant, and let's get into um these 346 00:17:56,840 --> 00:18:02,440 Speaker 1: apparent controversy about what that constant actually is and how 347 00:18:02,440 --> 00:18:05,200 Speaker 1: it's changing and why it's changing. But first let's take 348 00:18:05,200 --> 00:18:20,879 Speaker 1: a quick break, al right, Daniel. So the universe is 349 00:18:20,920 --> 00:18:24,119 Speaker 1: getting bigger, and the rate at which it is getting 350 00:18:24,119 --> 00:18:27,600 Speaker 1: bigger is getting bigger itself. And so this idea of 351 00:18:27,600 --> 00:18:30,320 Speaker 1: the Hubble constant, it's something that tells us how fast 352 00:18:30,359 --> 00:18:32,600 Speaker 1: it's happening. And the thing that would have blown Hubble's 353 00:18:32,640 --> 00:18:36,959 Speaker 1: mind is that this expansion is not constant. You know, Hubble, imagine, oh, 354 00:18:37,000 --> 00:18:38,920 Speaker 1: things are moving away from us at a certain rate, 355 00:18:38,960 --> 00:18:41,879 Speaker 1: and if you want more expansion, you just need a 356 00:18:41,960 --> 00:18:44,760 Speaker 1: larger space. And that's cool. But it's only twenty years 357 00:18:44,760 --> 00:18:47,520 Speaker 1: ago we realized that something else was happening as well, 358 00:18:48,000 --> 00:18:51,640 Speaker 1: that this expansion wasn't just continuing, but it was actually accelerating. 359 00:18:51,840 --> 00:18:55,080 Speaker 1: So the Hubble constant is not constant. In time. As 360 00:18:55,119 --> 00:18:57,919 Speaker 1: the universe is getting older and older, this expansion is 361 00:18:57,920 --> 00:19:00,399 Speaker 1: sort of picking up speed. Yeah, It's like Yeese is 362 00:19:00,400 --> 00:19:03,160 Speaker 1: going into overdrive. Yeah. And so that's why the Hubble 363 00:19:03,240 --> 00:19:05,480 Speaker 1: constant turns out to not be a constant. He thought 364 00:19:05,480 --> 00:19:08,520 Speaker 1: of a constant. He was just measuring it in one snapshot, 365 00:19:08,560 --> 00:19:11,359 Speaker 1: but it turns out that it's actually changing. Do you 366 00:19:11,359 --> 00:19:14,200 Speaker 1: think at some point maybe you'll consider changing the name 367 00:19:14,280 --> 00:19:18,000 Speaker 1: of it so that you don't have to caveat it 368 00:19:18,119 --> 00:19:20,520 Speaker 1: is the constant that's not a constant. There's a movement 369 00:19:20,520 --> 00:19:22,840 Speaker 1: now to call it the Hubble parameter, and I think 370 00:19:22,960 --> 00:19:25,800 Speaker 1: in most of general relativity they call it the Hubble parameter. 371 00:19:26,040 --> 00:19:28,359 Speaker 1: But there's also this, there's a Hubble constant which has 372 00:19:28,440 --> 00:19:31,480 Speaker 1: historical value to it. And so it's going to take 373 00:19:31,480 --> 00:19:33,199 Speaker 1: a while. You know, we're a hundred years in. Give 374 00:19:33,280 --> 00:19:35,840 Speaker 1: us another hundred years. Maybe you'll find the right name 375 00:19:35,880 --> 00:19:38,840 Speaker 1: for you. But it's maybe it's it's more like the 376 00:19:39,000 --> 00:19:41,439 Speaker 1: Hubble rate. Maybe would that be a better name, like 377 00:19:41,480 --> 00:19:44,640 Speaker 1: the Hubble rate of expansion of the universe. Yeah. Well, 378 00:19:44,640 --> 00:19:46,880 Speaker 1: in the end, really I think it's best to connect 379 00:19:46,920 --> 00:19:50,359 Speaker 1: it to the dark energy fraction of the universe because 380 00:19:50,359 --> 00:19:54,040 Speaker 1: the thing that's causing the expansion is this thing that's 381 00:19:54,119 --> 00:19:56,960 Speaker 1: dark energy. Right, it's only twenty years ago we discovered 382 00:19:57,240 --> 00:20:00,320 Speaker 1: that the universe is not expanding constantly. It's a spending 383 00:20:00,359 --> 00:20:02,920 Speaker 1: at an accelerating rate, which means that every year it's 384 00:20:02,920 --> 00:20:05,720 Speaker 1: getting bigger. Faster and faster. And we did this by 385 00:20:05,720 --> 00:20:09,240 Speaker 1: making another breakthrough by looking even further into the past 386 00:20:09,320 --> 00:20:11,840 Speaker 1: and into the far universe, by finding these supernove but 387 00:20:11,920 --> 00:20:13,520 Speaker 1: that we could use sort of in the same way 388 00:20:13,560 --> 00:20:16,600 Speaker 1: that Hubbo use those sthords to extend our distance ladder 389 00:20:16,600 --> 00:20:20,000 Speaker 1: even farther. And that told us that this acceleration of 390 00:20:20,040 --> 00:20:23,080 Speaker 1: the universe started about five billion years ago. And that's 391 00:20:23,080 --> 00:20:25,600 Speaker 1: what we call dark energy. We say dark energy is 392 00:20:25,640 --> 00:20:29,400 Speaker 1: some weird, mysterious thing which started dominating about five million 393 00:20:29,480 --> 00:20:32,320 Speaker 1: years ago, and it's causing the universe's expansion to accelerate. 394 00:20:32,440 --> 00:20:35,879 Speaker 1: You're saying that, um, the Hubble constant is not a 395 00:20:35,920 --> 00:20:38,040 Speaker 1: good name for it, and so the solution is not 396 00:20:38,119 --> 00:20:41,840 Speaker 1: to change the name, but to call it something else mysterious. Well, 397 00:20:41,880 --> 00:20:43,679 Speaker 1: I think it's to dig into the source of it 398 00:20:43,720 --> 00:20:48,200 Speaker 1: to understand why is the universe expanding? And I see, 399 00:20:48,280 --> 00:20:51,600 Speaker 1: let's not worry about the name. Let's focus on what's 400 00:20:51,640 --> 00:20:54,679 Speaker 1: making the universe get bigger and substance over style, right, 401 00:20:55,080 --> 00:20:57,840 Speaker 1: that's my motto, because I certainly don't have much style, 402 00:20:58,359 --> 00:21:00,720 Speaker 1: so I gotta go over a substance. There's I think 403 00:21:00,720 --> 00:21:04,119 Speaker 1: there's a physics style like it's a thing, isn't it. 404 00:21:05,359 --> 00:21:07,560 Speaker 1: You're either digging for compliments or you're baiting me into 405 00:21:07,600 --> 00:21:11,440 Speaker 1: a trap here. I can't tell which one maybe, But 406 00:21:13,560 --> 00:21:16,120 Speaker 1: the hubble constant, I think it's it's interesting to dig 407 00:21:16,160 --> 00:21:19,800 Speaker 1: into the units it has, because you were saying earlier 408 00:21:19,880 --> 00:21:23,119 Speaker 1: the hubble constant, which is not a constant, but I 409 00:21:23,119 --> 00:21:25,480 Speaker 1: guess that's it has a value right now, which is, 410 00:21:26,200 --> 00:21:31,080 Speaker 1: you know, kind of around seventy kilometers per second per 411 00:21:31,720 --> 00:21:36,440 Speaker 1: million light years, seventy kilometers per second per mega parsek 412 00:21:36,760 --> 00:21:40,280 Speaker 1: mega parsic, which is sort of like a distance, right, Yeah, 413 00:21:40,320 --> 00:21:42,800 Speaker 1: parsek is a distance, even though in Star Wars they 414 00:21:42,840 --> 00:21:45,280 Speaker 1: use it as a time like didn't Han Solo do 415 00:21:45,320 --> 00:21:47,920 Speaker 1: the kettle run in eleven parsecs or something, which makes 416 00:21:47,920 --> 00:21:51,800 Speaker 1: absolutely no sense. He ran tens and ten or something 417 00:21:51,880 --> 00:21:54,640 Speaker 1: like that. UM, and those units are sort of hard 418 00:21:54,640 --> 00:21:56,919 Speaker 1: to understand, so I transformed it to another set of 419 00:21:56,960 --> 00:21:59,639 Speaker 1: units that makes more sense to me. It's forty six 420 00:21:59,720 --> 00:22:04,080 Speaker 1: thou thousand miles per hour for every million light years, 421 00:22:04,160 --> 00:22:07,199 Speaker 1: so stuff around us is moving away from us at 422 00:22:07,240 --> 00:22:10,360 Speaker 1: forty six thousand miles per hour. For example, UM, if 423 00:22:10,400 --> 00:22:13,280 Speaker 1: you move a million light years away, things are moving 424 00:22:13,280 --> 00:22:16,440 Speaker 1: away from us another forty six thousand miles per hour. 425 00:22:16,600 --> 00:22:18,880 Speaker 1: Things around this are moving away from us at forty 426 00:22:18,920 --> 00:22:21,600 Speaker 1: six thousand miles per hour, but things a million light 427 00:22:21,680 --> 00:22:24,840 Speaker 1: years from here are moving at what is it, ninety 428 00:22:24,920 --> 00:22:27,480 Speaker 1: two thousand miles per hour, And if you go another 429 00:22:27,520 --> 00:22:31,000 Speaker 1: million years further out, you add another forty six thousand 430 00:22:31,040 --> 00:22:34,760 Speaker 1: miles per hour that it's moving away from us exactly. 431 00:22:34,840 --> 00:22:37,960 Speaker 1: And this is changing because as the universe expands, matter 432 00:22:38,080 --> 00:22:40,720 Speaker 1: and radiation and all that stuff gets diluted, right, it 433 00:22:40,720 --> 00:22:44,560 Speaker 1: gets thinned out. It's like fewer stars per cubic light year. 434 00:22:44,880 --> 00:22:47,639 Speaker 1: But dark energy, dark energy does and dark energy is 435 00:22:47,640 --> 00:22:50,720 Speaker 1: like a property of space. Every new chunk of space 436 00:22:50,760 --> 00:22:53,800 Speaker 1: that's made has its own dark energy. So dark energy, 437 00:22:53,880 --> 00:22:56,920 Speaker 1: we think, is probably constant in time while everything else 438 00:22:57,000 --> 00:22:59,840 Speaker 1: is getting diluted. And that's why the universe started excel 439 00:23:00,040 --> 00:23:02,560 Speaker 1: rating about five billion years ago, because it's about five 440 00:23:02,640 --> 00:23:05,480 Speaker 1: billion years ago that dark energy became the dominant thing. 441 00:23:05,480 --> 00:23:09,560 Speaker 1: It became of the energy density of any chunk of space. 442 00:23:09,800 --> 00:23:12,960 Speaker 1: The emptier space is, the I guess, the easier it 443 00:23:13,040 --> 00:23:15,959 Speaker 1: is for dark energy to expand. It is that kind 444 00:23:16,000 --> 00:23:18,080 Speaker 1: of what you're saying, that like, as it gets emptier 445 00:23:18,080 --> 00:23:20,159 Speaker 1: and emptier, it's easier for its expand and so it 446 00:23:20,280 --> 00:23:23,840 Speaker 1: expands fast. Precisely, there's some complicated general relativity there. The 447 00:23:23,880 --> 00:23:26,240 Speaker 1: expansion of the universe is controlled by how much matter 448 00:23:26,280 --> 00:23:28,440 Speaker 1: there is and how much radiation there is, which tends 449 00:23:28,480 --> 00:23:30,680 Speaker 1: to pull it together, and then also how much dark 450 00:23:30,800 --> 00:23:33,480 Speaker 1: energy there is, which tends to push it apart. And 451 00:23:33,560 --> 00:23:36,440 Speaker 1: so as matter and radiation get diluted away, dark energy 452 00:23:36,480 --> 00:23:40,159 Speaker 1: takes over. And and that's assuming that dark energy is constant. 453 00:23:40,160 --> 00:23:42,840 Speaker 1: That when you create new space, you get more dark energy, 454 00:23:43,320 --> 00:23:47,440 Speaker 1: and so that's what's causing this acceleration. There's less gravity, 455 00:23:47,440 --> 00:23:51,560 Speaker 1: I guess right, precisely. And so really what we're doing, 456 00:23:51,560 --> 00:23:53,720 Speaker 1: we're measuring the Hubble constants. We're trying to get a 457 00:23:53,760 --> 00:23:56,280 Speaker 1: handle on the dark energy. Like what fraction in the 458 00:23:56,359 --> 00:23:59,160 Speaker 1: universe is dark energy? We'd like to know about that now. 459 00:23:59,480 --> 00:24:01,280 Speaker 1: We'd also like you know about that in the future, 460 00:24:01,400 --> 00:24:03,960 Speaker 1: like is dark energy going to tear our universe apart? 461 00:24:04,160 --> 00:24:06,040 Speaker 1: And we're curious about it in the past, like the 462 00:24:06,200 --> 00:24:09,760 Speaker 1: very early universe, what fraction of the universe was dark energy? 463 00:24:09,880 --> 00:24:12,000 Speaker 1: How do these things all work? Because we just don't 464 00:24:12,040 --> 00:24:14,560 Speaker 1: understand dark energy like at all and so we know 465 00:24:14,640 --> 00:24:18,080 Speaker 1: that the Hubble constant or this kind of proportion of 466 00:24:18,160 --> 00:24:22,359 Speaker 1: dark energy is getting bigger, which means the universe is 467 00:24:22,400 --> 00:24:26,879 Speaker 1: getting bigger at a faster rate every second right now, 468 00:24:26,920 --> 00:24:29,720 Speaker 1: which is a little alarming. But I think what you 469 00:24:29,800 --> 00:24:31,679 Speaker 1: were you were saying is that there's some kind of 470 00:24:31,720 --> 00:24:34,840 Speaker 1: controversy about just how much dark energy there is because 471 00:24:34,840 --> 00:24:38,240 Speaker 1: we measure different ways, but they don't come out the 472 00:24:38,280 --> 00:24:40,639 Speaker 1: same number. That's kind of what Mike was asking about, right. 473 00:24:41,040 --> 00:24:44,520 Speaker 1: These two physical quantities, the amount of dark energy and 474 00:24:44,600 --> 00:24:47,600 Speaker 1: the Hubble parameter, they're connected, and so we measure them 475 00:24:47,600 --> 00:24:50,320 Speaker 1: together and lost to different ways. And when we do that, 476 00:24:50,400 --> 00:24:54,000 Speaker 1: we measure these using different techniques, we get different answers 477 00:24:54,080 --> 00:24:56,240 Speaker 1: for the Hubble constant. So that's what he calls the 478 00:24:57,080 --> 00:25:01,399 Speaker 1: unmatching Hubble constant mystery, precisely precisely, And we do this 479 00:25:01,480 --> 00:25:03,720 Speaker 1: a lot in science. We say, here's something we think 480 00:25:03,760 --> 00:25:06,440 Speaker 1: we understand. Let's measure it three different ways and see 481 00:25:06,480 --> 00:25:09,159 Speaker 1: if it agrees. If it doesn't agree, then that we 482 00:25:09,200 --> 00:25:11,400 Speaker 1: have to go back and question one of our assumptions. 483 00:25:11,720 --> 00:25:14,199 Speaker 1: It's like a clue that's something new is going on. 484 00:25:14,280 --> 00:25:16,399 Speaker 1: So it's a really valuable way to do things to 485 00:25:16,480 --> 00:25:19,119 Speaker 1: measure something in independent ways and look for a mistake, 486 00:25:19,520 --> 00:25:22,920 Speaker 1: because one of those ways could be like flawed, right, 487 00:25:23,000 --> 00:25:25,480 Speaker 1: And so you want to make sure that if you 488 00:25:25,480 --> 00:25:27,600 Speaker 1: look at it from different angles, it all looks the same. Yeah, 489 00:25:27,640 --> 00:25:29,639 Speaker 1: one of the techniques could have a problem with it, right, 490 00:25:29,680 --> 00:25:31,600 Speaker 1: and you don't want that bias to change the way 491 00:25:31,640 --> 00:25:34,840 Speaker 1: you look at the universe. But also your assumptions that 492 00:25:34,880 --> 00:25:37,080 Speaker 1: you make when you say, like, these two different techniques 493 00:25:37,119 --> 00:25:39,800 Speaker 1: should give the same answer, maybe one of those assumptions 494 00:25:39,840 --> 00:25:43,120 Speaker 1: is wrong. If you're watching a thunderstorm and you say, hey, well, 495 00:25:43,440 --> 00:25:45,719 Speaker 1: you know how far away was that flash? I'm going 496 00:25:45,760 --> 00:25:47,840 Speaker 1: to make an assumption about how far away it is 497 00:25:47,880 --> 00:25:50,760 Speaker 1: based on how long the difference between when the light 498 00:25:50,800 --> 00:25:53,399 Speaker 1: comes here and the sound comes here. You know, and 499 00:25:53,480 --> 00:25:56,439 Speaker 1: somebody else makes the same measurement somewhere else, do they 500 00:25:56,480 --> 00:25:58,520 Speaker 1: get the same answer? If not, that, you know, there's 501 00:25:58,520 --> 00:26:01,600 Speaker 1: something wrong with your base assumptions. And so you want 502 00:26:01,600 --> 00:26:04,880 Speaker 1: to make multiple measurements and that helps you check those 503 00:26:04,920 --> 00:26:07,040 Speaker 1: basic assumptions. You kind of want to double check if 504 00:26:07,080 --> 00:26:10,480 Speaker 1: you're going to make claims about the universe and the 505 00:26:10,640 --> 00:26:12,840 Speaker 1: future and how big it is. Yeah, I mean these 506 00:26:12,880 --> 00:26:16,200 Speaker 1: are grandios results. Yeah, absolutely, you definitely want to get 507 00:26:16,240 --> 00:26:18,719 Speaker 1: this stuff right. Okay, So there's two ways to measure 508 00:26:18,960 --> 00:26:22,200 Speaker 1: the Hubble constant or I guess the amount of dark 509 00:26:22,320 --> 00:26:25,520 Speaker 1: energy in the universe, and they don't agree. So so 510 00:26:25,560 --> 00:26:28,239 Speaker 1: what are these two ways? Well, the first one is 511 00:26:28,280 --> 00:26:30,639 Speaker 1: just looking at the distance sladders, like how far away 512 00:26:30,720 --> 00:26:33,760 Speaker 1: is stuff and what is its velocity? And we can 513 00:26:33,760 --> 00:26:36,359 Speaker 1: measure the velocity by looking at how much the light 514 00:26:36,520 --> 00:26:39,919 Speaker 1: from it is red shifted, meaning that if something is 515 00:26:39,960 --> 00:26:42,200 Speaker 1: moving away from you at a certain speed, it changes 516 00:26:42,240 --> 00:26:45,960 Speaker 1: the frequency of the light, like stretches the wavelength. And 517 00:26:46,040 --> 00:26:48,520 Speaker 1: so we can tell how fast something is moving away 518 00:26:48,520 --> 00:26:51,359 Speaker 1: from us by measuring its velocity directly, and we know 519 00:26:51,400 --> 00:26:54,000 Speaker 1: how far stuff away is. So this is a natural 520 00:26:54,000 --> 00:26:56,239 Speaker 1: extension of what Hubble did, and so we can use 521 00:26:56,240 --> 00:26:59,000 Speaker 1: that basically just to measure directly how fast is stuff 522 00:26:59,040 --> 00:27:01,199 Speaker 1: moving away from us? And that's I guess this is 523 00:27:01,200 --> 00:27:04,280 Speaker 1: the most straightforward. I mean, I know it's not simple, 524 00:27:04,320 --> 00:27:06,119 Speaker 1: but it's it's kind of the most direct way to 525 00:27:06,160 --> 00:27:08,800 Speaker 1: measure the expansion of the universe. Is you just look 526 00:27:08,840 --> 00:27:11,520 Speaker 1: at something really far away and you see how fast 527 00:27:11,560 --> 00:27:13,560 Speaker 1: it's moving, and you look at something really close by 528 00:27:13,640 --> 00:27:16,000 Speaker 1: and you measure how fast that move that's moving, and 529 00:27:16,040 --> 00:27:18,480 Speaker 1: so that gives you the whole picture of how the 530 00:27:18,480 --> 00:27:21,440 Speaker 1: the raising bread is expanded precisely. And the wrinkle there. 531 00:27:21,480 --> 00:27:23,800 Speaker 1: The thing that makes it not trivial is that the 532 00:27:23,840 --> 00:27:26,400 Speaker 1: stuff that's far away, we don't see what it's doing 533 00:27:26,520 --> 00:27:28,960 Speaker 1: right now. We see what it was doing a billion 534 00:27:29,040 --> 00:27:31,440 Speaker 1: years ago, for example, So we have to do some 535 00:27:31,560 --> 00:27:33,520 Speaker 1: back calculation to account for the fact that some of 536 00:27:33,520 --> 00:27:36,240 Speaker 1: the information we're getting is old. On the other hand, 537 00:27:36,600 --> 00:27:39,320 Speaker 1: that's also a cool clue because it tells you how 538 00:27:39,359 --> 00:27:42,320 Speaker 1: the expansion is changing over time. That's how we discovered 539 00:27:42,520 --> 00:27:45,760 Speaker 1: that it was accelerating. We saw stuff really far away 540 00:27:46,119 --> 00:27:48,400 Speaker 1: moving at a different speed than we expected. But isn't 541 00:27:48,400 --> 00:27:50,920 Speaker 1: it easy to confuse the two, Like, if something far 542 00:27:50,960 --> 00:27:54,480 Speaker 1: away is moving really fast, how do you know that 543 00:27:54,600 --> 00:27:57,040 Speaker 1: it's a factor of the time that's passed in between 544 00:27:57,160 --> 00:28:00,880 Speaker 1: or the factor of the distance it's from you. Well, 545 00:28:00,920 --> 00:28:03,080 Speaker 1: we measure those two things separately, right, We measured the 546 00:28:03,119 --> 00:28:06,119 Speaker 1: distance and the velocity totally separately. And once you know 547 00:28:06,200 --> 00:28:08,800 Speaker 1: the distance, then you can calculate how long the information 548 00:28:08,840 --> 00:28:10,919 Speaker 1: took to get here, and so we can sort of 549 00:28:10,920 --> 00:28:13,440 Speaker 1: triangulate all that stuff. I mean, the best thing would 550 00:28:13,440 --> 00:28:15,280 Speaker 1: be if we could get a complete snapshot of the 551 00:28:15,359 --> 00:28:18,000 Speaker 1: universe at every time, then we could get all this 552 00:28:18,160 --> 00:28:21,040 Speaker 1: crazy information and really triangulates stuff. You don't just get 553 00:28:21,080 --> 00:28:22,879 Speaker 1: to wish for the data you want, You work with 554 00:28:22,920 --> 00:28:25,160 Speaker 1: the data you have. I think the real triumph hear 555 00:28:25,200 --> 00:28:28,560 Speaker 1: of physics here is is the acronym for this project. 556 00:28:29,000 --> 00:28:31,920 Speaker 1: That's like such a great acronym. Yeah, this is called 557 00:28:31,960 --> 00:28:37,679 Speaker 1: the Shoes Experiment Supernova each zero for equations of state. 558 00:28:38,120 --> 00:28:39,800 Speaker 1: And I wish I'd been in that meeting where they 559 00:28:39,800 --> 00:28:41,880 Speaker 1: were like coming up with acronyms of the white board 560 00:28:42,200 --> 00:28:46,560 Speaker 1: to to explain this thing. I always wonder about that. 561 00:28:46,560 --> 00:28:51,280 Speaker 1: They're like did It's like do they try really hard? 562 00:28:51,440 --> 00:28:53,920 Speaker 1: Do they? You know what sacrifices must you make the 563 00:28:53,960 --> 00:28:57,760 Speaker 1: science to get the perfect acronym? I don't know what 564 00:28:57,840 --> 00:29:01,040 Speaker 1: kind of grammatical sacrifices must you mean? That's not even 565 00:29:01,040 --> 00:29:03,640 Speaker 1: the best slash worst acronym we're gonna talk about today. 566 00:29:03,840 --> 00:29:07,040 Speaker 1: Hang on for later on we'll be talking about all right. 567 00:29:07,080 --> 00:29:09,160 Speaker 1: So that's one way to measure the universe. It's just 568 00:29:09,200 --> 00:29:12,120 Speaker 1: measure things and how fast they're moving and how far 569 00:29:12,160 --> 00:29:15,520 Speaker 1: our way they are but we can also um do 570 00:29:15,600 --> 00:29:18,800 Speaker 1: something more interesting, right, Yeah, we can look back at 571 00:29:18,800 --> 00:29:21,200 Speaker 1: the very early universe. And we've talked about this on 572 00:29:21,240 --> 00:29:25,200 Speaker 1: the podcast about the surface of last scattering, the moment 573 00:29:25,280 --> 00:29:28,840 Speaker 1: that the universe went from a hot, opaque plasma and 574 00:29:28,880 --> 00:29:31,880 Speaker 1: cooled down and ionized and formed atoms that light could 575 00:29:31,880 --> 00:29:34,720 Speaker 1: fly through, and the light from that plasma, it's called 576 00:29:34,760 --> 00:29:38,120 Speaker 1: the cosmic microwave background, still flying around through the universe 577 00:29:38,160 --> 00:29:41,840 Speaker 1: because after that moment, the universe became transparent. And so 578 00:29:41,880 --> 00:29:44,720 Speaker 1: we get this light from the cosmic microwave background, and 579 00:29:44,760 --> 00:29:45,920 Speaker 1: we look at it and we look at all the 580 00:29:45,920 --> 00:29:48,719 Speaker 1: wiggles in it, and we can extract an incredible amount 581 00:29:48,720 --> 00:29:52,080 Speaker 1: of information from these wiggles, and the most important thing 582 00:29:52,120 --> 00:29:53,960 Speaker 1: that we pull out of that is we get the 583 00:29:54,040 --> 00:29:56,840 Speaker 1: fraction of the universe that is matter and the fraction 584 00:29:56,880 --> 00:29:59,400 Speaker 1: of that universe that was dark energy. But that's really 585 00:29:59,400 --> 00:30:01,520 Speaker 1: far back in time, at the time of the Big 586 00:30:01,560 --> 00:30:05,600 Speaker 1: Bank basically, right, Yeah, relatively speaking, it's three hundred thousand 587 00:30:05,720 --> 00:30:08,560 Speaker 1: years after the Big Bang, and we're getting a sense 588 00:30:08,560 --> 00:30:11,160 Speaker 1: for what was going on back then. And if you 589 00:30:11,200 --> 00:30:14,280 Speaker 1: look at it online, look for the cosmic microwave background, 590 00:30:14,440 --> 00:30:16,760 Speaker 1: it looks just like a massive it looks like a 591 00:30:16,840 --> 00:30:20,760 Speaker 1: giant soup, and and so and so. But you're saying, 592 00:30:20,880 --> 00:30:24,680 Speaker 1: you guys, have you know, special formulas that really look 593 00:30:24,720 --> 00:30:28,720 Speaker 1: into the what the soup looks like. And you can 594 00:30:28,800 --> 00:30:30,680 Speaker 1: firm that you can tell a lot of things like 595 00:30:30,760 --> 00:30:33,720 Speaker 1: how much dark energy that there was at the big 596 00:30:33,720 --> 00:30:35,280 Speaker 1: after the Big band, But how do you how did 597 00:30:35,280 --> 00:30:38,000 Speaker 1: you extrapolate that to now? Because didn't you tell me 598 00:30:38,040 --> 00:30:40,960 Speaker 1: that it's changing. Yeah, so we look at this bubbling 599 00:30:40,960 --> 00:30:43,920 Speaker 1: soup and precisely the arrangement of bubbles and the size 600 00:30:43,920 --> 00:30:46,080 Speaker 1: of the bubbles tells you a lot about the competing 601 00:30:46,120 --> 00:30:48,720 Speaker 1: forces on the soup. And some of those forces aren't matter. 602 00:30:48,720 --> 00:30:51,120 Speaker 1: They're pulling it together, and some of its dark energy 603 00:30:51,120 --> 00:30:53,640 Speaker 1: that's pushing it apart. And the important thing to understand 604 00:30:53,640 --> 00:30:56,560 Speaker 1: is we're not measuring the hubble constant itself back then 605 00:30:56,600 --> 00:30:59,280 Speaker 1: there weren't even stars back then. Or measuring is how 606 00:30:59,320 --> 00:31:01,880 Speaker 1: much dark energy there was. And you're right, we measured 607 00:31:01,920 --> 00:31:04,600 Speaker 1: dark energy how much there was back then. And then 608 00:31:04,640 --> 00:31:06,800 Speaker 1: what we do is we just assume that dark energy 609 00:31:06,880 --> 00:31:10,440 Speaker 1: hasn't changed. The dark energy is constant, that that every 610 00:31:10,520 --> 00:31:12,520 Speaker 1: unit of space has the same amount of dark energy 611 00:31:12,560 --> 00:31:14,920 Speaker 1: now as it did back then. Wasn't there less space 612 00:31:14,960 --> 00:31:18,040 Speaker 1: back there? So that means there's more dark energy now, 613 00:31:18,080 --> 00:31:21,000 Speaker 1: there's more dark energy now. Um, it's a bigger fraction 614 00:31:21,040 --> 00:31:23,600 Speaker 1: in the universe. Right now dark energy dominates the universe. 615 00:31:23,640 --> 00:31:25,920 Speaker 1: But in the early days it was a tiny irrelevant 616 00:31:25,920 --> 00:31:28,720 Speaker 1: bit player because most of the energy density was in 617 00:31:28,720 --> 00:31:31,320 Speaker 1: the form of matter and radiation. But then as the 618 00:31:31,400 --> 00:31:34,920 Speaker 1: universe expands, that dilutes and now matters like really spread thin. 619 00:31:35,360 --> 00:31:38,160 Speaker 1: Oh wait, you're saying that, like a cube of like 620 00:31:38,200 --> 00:31:41,200 Speaker 1: a cubic meter of space always has the same amount 621 00:31:41,200 --> 00:31:46,000 Speaker 1: of dark energy, no matter if it was now or 622 00:31:46,160 --> 00:31:48,920 Speaker 1: before when the universe was smaller. That is the key assumption. 623 00:31:49,080 --> 00:31:51,320 Speaker 1: We are assuming that we think that might be the case. 624 00:31:51,360 --> 00:31:53,960 Speaker 1: That's sort of the simplest idea. And what we're doing 625 00:31:54,000 --> 00:31:56,600 Speaker 1: by measuring the Hubble constant or the expansion of the 626 00:31:56,640 --> 00:31:59,080 Speaker 1: universe at different times, is trying to probe whether that 627 00:31:59,200 --> 00:32:03,640 Speaker 1: idea is wrecked. And so, assuming that dark energy is constant, 628 00:32:03,680 --> 00:32:05,560 Speaker 1: you measure what it was back in the time of 629 00:32:05,600 --> 00:32:08,920 Speaker 1: the Big Bang, you propagate that forward. You can get 630 00:32:08,920 --> 00:32:11,920 Speaker 1: a number for the Hubble constant, assuming of course, that 631 00:32:12,000 --> 00:32:15,080 Speaker 1: dark energy is constant and that radiation and matter have 632 00:32:15,200 --> 00:32:17,920 Speaker 1: just diluted. We don't know that dark energy is constant. 633 00:32:17,960 --> 00:32:20,120 Speaker 1: We're assuming that. And if you assume that, then you 634 00:32:20,160 --> 00:32:23,000 Speaker 1: get a number. And this number is different than the 635 00:32:23,080 --> 00:32:27,120 Speaker 1: number you get when you measure the velocity of the stars. Yeah, 636 00:32:27,120 --> 00:32:28,720 Speaker 1: if you look at the velocity of stars, you get 637 00:32:28,720 --> 00:32:31,200 Speaker 1: a number like seventy four with an uncertainty like one 638 00:32:31,200 --> 00:32:35,200 Speaker 1: and a half units of kilometers per second per megaparsic. 639 00:32:35,680 --> 00:32:38,040 Speaker 1: But if you look at the early universe, you get 640 00:32:38,040 --> 00:32:41,200 Speaker 1: a number like sixty seven point three with a smaller 641 00:32:41,240 --> 00:32:43,920 Speaker 1: uncertainty like half. And so those two numbers, you know, 642 00:32:44,000 --> 00:32:47,560 Speaker 1: they're different by you know, seven, and the uncertainty item 643 00:32:47,680 --> 00:32:50,280 Speaker 1: is pretty small. And both of those teams have been 644 00:32:50,320 --> 00:32:53,360 Speaker 1: working really hard to make their measurements more and more precise. 645 00:32:53,800 --> 00:32:55,840 Speaker 1: And as the measurements get more and more precise, the 646 00:32:55,920 --> 00:32:58,520 Speaker 1: numbers have not been getting close together. The errors have 647 00:32:58,560 --> 00:33:00,720 Speaker 1: been getting smaller, but the numbers have not been changing 648 00:33:00,720 --> 00:33:03,480 Speaker 1: because you know, as a as someone who's not a physicist, 649 00:33:03,640 --> 00:33:05,480 Speaker 1: I would look at these numbers and think, oh, that's 650 00:33:05,480 --> 00:33:09,400 Speaker 1: pretty good. Seventy four sixty seven, what's ten percent different? 651 00:33:09,880 --> 00:33:13,960 Speaker 1: Government work, you're not good enough to make for engineering. 652 00:33:14,080 --> 00:33:17,040 Speaker 1: But the key thing here is understanding your uncertainties, like 653 00:33:17,080 --> 00:33:19,360 Speaker 1: how well do you know these things? And people spend 654 00:33:19,360 --> 00:33:22,640 Speaker 1: a lot of time, like many many peach DTCs, understanding 655 00:33:22,880 --> 00:33:26,560 Speaker 1: what are the uncertainties on our distance measurements to supernova 656 00:33:26,960 --> 00:33:29,400 Speaker 1: or coming up with other ways to make these distance 657 00:33:29,440 --> 00:33:32,520 Speaker 1: measurements to cross check, or understanding the uncertainties in the 658 00:33:32,520 --> 00:33:35,680 Speaker 1: cosmic microwave background. And you've got to know those uncertainties 659 00:33:35,680 --> 00:33:37,160 Speaker 1: so you know how well do I know this thing? 660 00:33:37,320 --> 00:33:38,760 Speaker 1: Because if you don't know how well you know it, 661 00:33:38,920 --> 00:33:41,640 Speaker 1: you can't answer the question are these two numbers in 662 00:33:41,680 --> 00:33:44,120 Speaker 1: agreement or not? So a lot of the work goes 663 00:33:44,160 --> 00:33:47,280 Speaker 1: into nailing down the size of these uncertainties to knowing 664 00:33:47,320 --> 00:33:49,920 Speaker 1: how well you know something. So that's the mystery, then, 665 00:33:50,200 --> 00:33:52,880 Speaker 1: is that we're trying to measure how much dark energy 666 00:33:52,960 --> 00:33:55,720 Speaker 1: there is in the universe, which is making it grow bigger. 667 00:33:56,160 --> 00:33:58,320 Speaker 1: And if we measure look at it one way, it's 668 00:33:58,360 --> 00:34:01,080 Speaker 1: it says there should be seventy four of this dark energy. 669 00:34:01,120 --> 00:34:02,560 Speaker 1: If you look at it another way, it says it 670 00:34:02,600 --> 00:34:06,400 Speaker 1: should be sixty seven. And that's that bothers a lot. 671 00:34:06,480 --> 00:34:10,160 Speaker 1: It bothers them because it seems really unlikely to be 672 00:34:10,200 --> 00:34:12,880 Speaker 1: an accident. Like, if there really is one Hubble constant 673 00:34:13,040 --> 00:34:15,240 Speaker 1: and both of these things are measuring the same number, 674 00:34:15,640 --> 00:34:18,640 Speaker 1: then what are the chances of getting two numbers that 675 00:34:18,719 --> 00:34:21,640 Speaker 1: are this far apart. It's like we've done into calculation, 676 00:34:21,680 --> 00:34:24,560 Speaker 1: we do the statistics, and it's like one in ten thousand. 677 00:34:24,840 --> 00:34:27,440 Speaker 1: So it seems really unlikely. A much more likely explanation 678 00:34:27,880 --> 00:34:30,359 Speaker 1: is that there's something wrong, either something wrong with our 679 00:34:30,360 --> 00:34:33,799 Speaker 1: assumptions or something wrong with one of these measurements. All right, well, 680 00:34:33,880 --> 00:34:37,520 Speaker 1: let's dig into what could explain this mystery and what 681 00:34:37,600 --> 00:34:40,440 Speaker 1: it means for the future of the universe and for 682 00:34:40,520 --> 00:34:44,040 Speaker 1: you and for me, and but and for the people 683 00:34:44,239 --> 00:34:46,880 Speaker 1: for whom the universe is for, but not the people 684 00:34:46,920 --> 00:34:51,040 Speaker 1: for for whom the universe is not for. But first, 685 00:34:51,120 --> 00:35:06,120 Speaker 1: let's take a quick break. All right, we have a 686 00:35:06,200 --> 00:35:09,759 Speaker 1: disagreement in physics in the measurement of how much dark 687 00:35:09,840 --> 00:35:12,520 Speaker 1: energy there is in the universe. And so how do 688 00:35:12,520 --> 00:35:13,960 Speaker 1: you guys decide? Do you just fight it out? Do 689 00:35:14,000 --> 00:35:18,040 Speaker 1: you get into a boxing ring or cage or something 690 00:35:18,160 --> 00:35:20,719 Speaker 1: and you throw a couple of pencils in and see 691 00:35:20,719 --> 00:35:24,600 Speaker 1: what happens? Are Yeah, it's too physicist grappling with whiteboard 692 00:35:24,600 --> 00:35:28,080 Speaker 1: markers and calling each other's faces and stuff. Um, well, 693 00:35:28,080 --> 00:35:30,400 Speaker 1: maybe one side as a chalk on the other side 694 00:35:30,400 --> 00:35:35,480 Speaker 1: as a marker. Now, it's all actually very friendly, incongenial, 695 00:35:35,719 --> 00:35:38,279 Speaker 1: and everybody wants to understand it, and it's sort of 696 00:35:38,320 --> 00:35:40,719 Speaker 1: a good situation. You know, when you make one of 697 00:35:40,760 --> 00:35:43,879 Speaker 1: these discoveries that two measurements you make of the same 698 00:35:43,920 --> 00:35:46,400 Speaker 1: thing don't agree, it's a clue, it's a sign. And 699 00:35:46,440 --> 00:35:49,160 Speaker 1: that's what we're looking for. We are trying to understand 700 00:35:49,200 --> 00:35:52,080 Speaker 1: the universe, not just confirm what we thought. And so 701 00:35:52,520 --> 00:35:54,760 Speaker 1: when the universe tells you that you're understanding is wrong, 702 00:35:55,200 --> 00:35:59,120 Speaker 1: that's it's the first clue to getting new understanding. And 703 00:35:59,200 --> 00:36:01,239 Speaker 1: so they're getting room and they try to think, like, well, 704 00:36:01,280 --> 00:36:03,480 Speaker 1: what could explain this? Is one of us doing it 705 00:36:03,520 --> 00:36:06,960 Speaker 1: wrong or is one of our assumptions wrong, And that's 706 00:36:07,000 --> 00:36:09,320 Speaker 1: I think is the most exciting explanation. Right. Well, I 707 00:36:09,600 --> 00:36:12,319 Speaker 1: have a favorite, Daniel, I don't know if you have 708 00:36:12,400 --> 00:36:17,480 Speaker 1: a favorite. I like seventy four more than I like. 709 00:36:19,000 --> 00:36:21,920 Speaker 1: I mean, like one of one of these measurements seems 710 00:36:21,960 --> 00:36:25,040 Speaker 1: more direct to me, Like if you're measuring the speed 711 00:36:25,040 --> 00:36:28,800 Speaker 1: of the stars directly through my telescopes. That seems a 712 00:36:28,840 --> 00:36:30,920 Speaker 1: lot more direct than like looking at a picture of 713 00:36:30,920 --> 00:36:34,640 Speaker 1: the universe fourteen billion years ago, and then it's replating it. Like, 714 00:36:35,080 --> 00:36:37,200 Speaker 1: do you guys have a favorite? Do you think one 715 00:36:37,239 --> 00:36:41,040 Speaker 1: of them in particular is probably wrong? Or what's the 716 00:36:41,080 --> 00:36:44,680 Speaker 1: general feeling? Well, I like the one from the early 717 00:36:44,800 --> 00:36:47,719 Speaker 1: universe because it's just so clean and precise, Like you 718 00:36:47,719 --> 00:36:49,839 Speaker 1: don't need to know how far away anything is, or 719 00:36:50,000 --> 00:36:52,279 Speaker 1: make some extrapolation from this kind of star and the 720 00:36:52,320 --> 00:36:54,520 Speaker 1: other kind of star and sort of walk up the ladder. 721 00:36:54,840 --> 00:36:57,920 Speaker 1: There's a lot of assumptions involved in those distance measurements. 722 00:36:57,960 --> 00:37:02,000 Speaker 1: Whereas the cosmic microwave background so pure and clean and 723 00:37:02,080 --> 00:37:05,640 Speaker 1: so much about it works. It's predicted and been confirmed 724 00:37:05,680 --> 00:37:08,160 Speaker 1: in so many other ways that we have this model 725 00:37:08,200 --> 00:37:10,759 Speaker 1: of the universe that just really holds together. It's hard 726 00:37:10,800 --> 00:37:13,880 Speaker 1: to imagine how that is wrong. And so I like 727 00:37:13,960 --> 00:37:16,279 Speaker 1: that measurement. I'm not sure why. It's maybe just an 728 00:37:16,280 --> 00:37:18,319 Speaker 1: aesthetic thing. You do have a favorite. I do have 729 00:37:18,360 --> 00:37:23,920 Speaker 1: a favor. I've just admitted on areas well. So there's 730 00:37:24,400 --> 00:37:27,959 Speaker 1: some possible explanations that for what could be wrong, right, 731 00:37:28,040 --> 00:37:30,319 Speaker 1: that's because something must be wrong if these measurements are 732 00:37:30,320 --> 00:37:34,319 Speaker 1: not matching up. So what's what's a possible explanation. I 733 00:37:34,320 --> 00:37:37,520 Speaker 1: think one of the favorite explanations of cosmologists is this 734 00:37:37,560 --> 00:37:41,280 Speaker 1: thing called dynamical dark energy, the idea that dark energy 735 00:37:41,360 --> 00:37:44,440 Speaker 1: isn't maybe just like a property of space and constant 736 00:37:44,680 --> 00:37:47,560 Speaker 1: that for every cubic meter is basically the same dark energy, 737 00:37:47,680 --> 00:37:49,960 Speaker 1: but maybe it's changing in time as the age of 738 00:37:50,000 --> 00:37:53,040 Speaker 1: the universe. I have to say, holy cow, that's amazing, 739 00:37:53,840 --> 00:37:56,200 Speaker 1: and that would help resolve because remember, we have this 740 00:37:56,200 --> 00:37:59,800 Speaker 1: measurement from the early universe that's measuring one dark energy 741 00:37:59,800 --> 00:38:02,200 Speaker 1: for action that gives you a Hubble constant, and these 742 00:38:02,360 --> 00:38:06,080 Speaker 1: more recent measurements from nearby stars and supernovas that give 743 00:38:06,160 --> 00:38:08,600 Speaker 1: you a more recent measurement. So one way to make 744 00:38:08,640 --> 00:38:11,280 Speaker 1: those two things agrees to say you're not actually measuring 745 00:38:11,280 --> 00:38:14,640 Speaker 1: the same thing. The thing you're measuring, it's is itself changing. 746 00:38:14,800 --> 00:38:17,920 Speaker 1: So you're saying, um, one possible explanation is that the 747 00:38:18,000 --> 00:38:21,880 Speaker 1: Hubble constant, which is not a constant, is actually measuring 748 00:38:21,960 --> 00:38:25,600 Speaker 1: something that is not a constant. You constantly amaze with 749 00:38:25,680 --> 00:38:29,560 Speaker 1: your understanding. That's kind of what you say. I feel 750 00:38:29,560 --> 00:38:31,239 Speaker 1: like that's kind of what you're saying it's not only 751 00:38:31,280 --> 00:38:33,560 Speaker 1: not a constant, but what you're it's measuring is not 752 00:38:33,600 --> 00:38:36,440 Speaker 1: a constant. That's right. And to shroud our previous mistakes, 753 00:38:36,440 --> 00:38:40,040 Speaker 1: we slap a cool label on it and call it dynamical, right, yeah, 754 00:38:40,200 --> 00:38:42,799 Speaker 1: d D. And then, of course, you know another thing 755 00:38:42,800 --> 00:38:45,520 Speaker 1: we do is to try to like get an unbiased 756 00:38:45,520 --> 00:38:47,879 Speaker 1: third estimate, Like, let's come up with a third way 757 00:38:47,880 --> 00:38:50,000 Speaker 1: to measure this and see if it agrees with one 758 00:38:50,080 --> 00:38:53,120 Speaker 1: or the other two. Let's do this democratically, let's take 759 00:38:53,120 --> 00:38:56,000 Speaker 1: a vote. You're saying, there's a third way now to 760 00:38:56,040 --> 00:38:59,719 Speaker 1: measure this dark energy in the universe, and I think 761 00:38:59,760 --> 00:39:04,400 Speaker 1: it deserves a Nobel prize right away, just in its 762 00:39:04,440 --> 00:39:08,640 Speaker 1: awesome acronym. Well, it's an acronym that contains acronyms. So 763 00:39:08,760 --> 00:39:13,440 Speaker 1: they call it the Holy Cow experiment, uh aged zero 764 00:39:13,600 --> 00:39:18,280 Speaker 1: lenses in Cosmo Girl well spring, right, and so Cosmo 765 00:39:18,360 --> 00:39:21,080 Speaker 1: Girl is the name of another experiment that stands for 766 00:39:21,160 --> 00:39:24,680 Speaker 1: something else. And so these guys have used data from 767 00:39:24,680 --> 00:39:28,400 Speaker 1: the Cosmo Girl experiment to try to measure the expansion 768 00:39:28,480 --> 00:39:32,040 Speaker 1: rid of the universe totally independently. Wow, I mean that's 769 00:39:32,080 --> 00:39:36,000 Speaker 1: just genius in acronym. It's like not only are you 770 00:39:36,200 --> 00:39:39,759 Speaker 1: betting an acronym in an acronym, that you're betting a 771 00:39:39,800 --> 00:39:43,400 Speaker 1: whole different project in this project acronym. And then if 772 00:39:43,440 --> 00:39:45,840 Speaker 1: they discover something awesome, they get to shout, holy cow, 773 00:39:45,960 --> 00:39:51,120 Speaker 1: we discovered it, Holy cow, holy cow did it. And 774 00:39:51,400 --> 00:39:54,719 Speaker 1: this is another way essentially to measure how far things 775 00:39:54,760 --> 00:39:58,520 Speaker 1: are away, and it uses gravitational lenses and says, let's 776 00:39:58,520 --> 00:40:00,319 Speaker 1: say you have a really bright source of light, like 777 00:40:00,360 --> 00:40:03,120 Speaker 1: a quasar, and then between you and that source of 778 00:40:03,200 --> 00:40:05,680 Speaker 1: light is a is a big lens, like a big galaxy. 779 00:40:05,920 --> 00:40:08,400 Speaker 1: Because remember, galaxies have a lot of gravity, and gravity 780 00:40:08,480 --> 00:40:11,400 Speaker 1: bend space, so it can act like a lens. And 781 00:40:11,480 --> 00:40:14,279 Speaker 1: what happens is then that quasar gets distorted and you 782 00:40:14,320 --> 00:40:17,560 Speaker 1: get multiple versions of it arriving here at Earth because 783 00:40:17,560 --> 00:40:20,160 Speaker 1: the galaxy between you and the quasar has lensed it. 784 00:40:20,239 --> 00:40:23,120 Speaker 1: You know, sometimes you get like weird and duplication effects 785 00:40:23,160 --> 00:40:26,120 Speaker 1: and a lens and so somehow that tells you something 786 00:40:26,120 --> 00:40:29,680 Speaker 1: about how it's expanding. The university expanding, Yeah, because the 787 00:40:29,760 --> 00:40:32,799 Speaker 1: different images take different amounts of time to get here, 788 00:40:32,880 --> 00:40:36,400 Speaker 1: and these quasars flicker as you can watch these different 789 00:40:36,440 --> 00:40:39,840 Speaker 1: images flicker, and by how much time there is between 790 00:40:39,880 --> 00:40:42,319 Speaker 1: the flickering in one image and the other image, you 791 00:40:42,320 --> 00:40:45,520 Speaker 1: can tell essentially how much space it's gone through. And 792 00:40:45,600 --> 00:40:48,880 Speaker 1: so the delay between the two different images gives you 793 00:40:48,920 --> 00:40:51,640 Speaker 1: a sense for how far away the original quasar was. 794 00:40:51,920 --> 00:40:54,759 Speaker 1: Is it kind of like lightning and thunder like precisely 795 00:40:55,000 --> 00:40:56,680 Speaker 1: you see it and you hear it, and you use 796 00:40:56,719 --> 00:40:59,640 Speaker 1: those two things to figure out how far away the 797 00:40:59,719 --> 00:41:02,200 Speaker 1: lightning was and how bright it was. Precisely, that's exactly 798 00:41:02,280 --> 00:41:03,759 Speaker 1: the way we do it. And so this is a 799 00:41:03,760 --> 00:41:06,239 Speaker 1: totally different way because it doesn't rely on supernova, doesn't 800 00:41:06,239 --> 00:41:08,919 Speaker 1: rely on sephids or the other stuff. It's another way 801 00:41:08,920 --> 00:41:12,480 Speaker 1: to make the distance measurement. And their measurement agrees with 802 00:41:12,560 --> 00:41:17,160 Speaker 1: the supernova measurement, really with my favorite measurement, not you. 803 00:41:17,400 --> 00:41:19,880 Speaker 1: I should have said it agrees with you. That was 804 00:41:19,920 --> 00:41:25,800 Speaker 1: their announcement. Actually, holy cow agrees with cartoon. Holy Cow 805 00:41:26,840 --> 00:41:30,239 Speaker 1: cartoon is nailed it. The only person surprised was the cartoonist. 806 00:41:34,600 --> 00:41:37,160 Speaker 1: So so it's agreeing with one of the measurements, which 807 00:41:37,239 --> 00:41:40,960 Speaker 1: is measuring measuring the stars themselves. And so then, um, 808 00:41:41,120 --> 00:41:43,960 Speaker 1: doesn't that close the argument doesn't that you know, and 809 00:41:44,120 --> 00:41:46,880 Speaker 1: the mystery it doesn't because remember they're measuring things at 810 00:41:46,880 --> 00:41:49,920 Speaker 1: different times in the universe, and so this would have 811 00:41:49,920 --> 00:41:52,920 Speaker 1: been problematic for the supernova measurement if it had disagreed, 812 00:41:52,960 --> 00:41:54,920 Speaker 1: because they're measuring the same thing and sort of the 813 00:41:54,920 --> 00:41:57,840 Speaker 1: same epic of the universe, and they really should This 814 00:41:57,920 --> 00:42:01,320 Speaker 1: is like confirmation of the supernova measument. And but the 815 00:42:01,400 --> 00:42:04,320 Speaker 1: early universe one from the cosmic microwave background is measuring 816 00:42:04,360 --> 00:42:07,439 Speaker 1: something older, and so it could still be that they're 817 00:42:07,480 --> 00:42:11,000 Speaker 1: both right. And the explanation is that dark energy is changing. Oh, 818 00:42:11,120 --> 00:42:13,640 Speaker 1: I see, it's it's like there you could say that 819 00:42:13,719 --> 00:42:16,640 Speaker 1: it's not wrong. It's just that a change between when 820 00:42:16,640 --> 00:42:19,239 Speaker 1: I measured it and now. Yeah, it's like I didn't 821 00:42:19,239 --> 00:42:20,840 Speaker 1: get the answer wrong on the test. I was just 822 00:42:20,880 --> 00:42:23,839 Speaker 1: answering a different question. Maybe this tells us that this 823 00:42:24,000 --> 00:42:27,200 Speaker 1: dark energy constant is changing or has changed since the 824 00:42:27,239 --> 00:42:30,040 Speaker 1: beginning of time. Yeah, it could be. Um, there's a 825 00:42:30,080 --> 00:42:31,720 Speaker 1: lot of things we can do to check the cosmic 826 00:42:31,760 --> 00:42:34,880 Speaker 1: microwave background radiation measurement, and they've done all those checks 827 00:42:34,920 --> 00:42:37,560 Speaker 1: and it all works out and it really seems very convincing. 828 00:42:37,560 --> 00:42:40,320 Speaker 1: It's hard to imagine how they would get that number wrong. 829 00:42:40,840 --> 00:42:43,719 Speaker 1: On the other hand, the supernova measurement now has independent 830 00:42:43,800 --> 00:42:47,040 Speaker 1: verification from a completely different way to measure these distances. 831 00:42:47,040 --> 00:42:49,200 Speaker 1: So it's hard to understand how that one could be wrong. 832 00:42:49,800 --> 00:42:51,799 Speaker 1: So I think we're going to have to rethink our 833 00:42:52,080 --> 00:42:56,080 Speaker 1: fundamental understanding of what's going on with dark energy. Right, 834 00:42:56,200 --> 00:43:00,359 Speaker 1: Maybe dark energy not a constant after all. Maybe it's cool. 835 00:43:00,560 --> 00:43:02,759 Speaker 1: Maybe we should never be assuming things are constant. You know, 836 00:43:02,800 --> 00:43:06,480 Speaker 1: that's just sort of like the physics things like, don't 837 00:43:06,520 --> 00:43:11,160 Speaker 1: call constants constance. We're constantly making that mistake. Well, um, 838 00:43:11,200 --> 00:43:14,560 Speaker 1: it sounds then, though, that this mystery is getting resolved 839 00:43:15,080 --> 00:43:19,160 Speaker 1: as we speak right now, So Mike and Madison stay tuned. 840 00:43:19,280 --> 00:43:23,839 Speaker 1: It sounds like, as we speak, we're resolving this mystery. Yeah, 841 00:43:23,880 --> 00:43:25,840 Speaker 1: and other stuff is gonna come online to sort of 842 00:43:25,840 --> 00:43:28,239 Speaker 1: give us more pictures of this. We can use things 843 00:43:28,280 --> 00:43:32,120 Speaker 1: like gravitational waves from neutron stars collisions to try to 844 00:43:32,160 --> 00:43:34,239 Speaker 1: measure the distance to things. So that's gonna give us 845 00:43:34,320 --> 00:43:37,319 Speaker 1: another measurement and hopefully that can peer further back in 846 00:43:37,480 --> 00:43:40,959 Speaker 1: time than the quasars are. The supernova so we really 847 00:43:41,000 --> 00:43:43,120 Speaker 1: need to do is get another measurement of dark energy 848 00:43:43,120 --> 00:43:46,240 Speaker 1: in the very early universe. And so people have ideas 849 00:43:46,239 --> 00:43:48,799 Speaker 1: for how we might do that, and gravitational waves might help, 850 00:43:49,160 --> 00:43:53,160 Speaker 1: and so stay tuned. This cosmic mystery might eventually get resolved, 851 00:43:53,200 --> 00:43:55,120 Speaker 1: and it might get resolved in a way that totally 852 00:43:55,239 --> 00:43:58,560 Speaker 1: up ends our understanding of the entire universe. But I 853 00:43:58,560 --> 00:44:01,759 Speaker 1: think one thing is here, which is the mind blowing part, 854 00:44:01,880 --> 00:44:04,720 Speaker 1: which is that it's pretty clear. And now I guess 855 00:44:04,760 --> 00:44:08,680 Speaker 1: three measurements that the universe is expanding, and it's expanding 856 00:44:08,760 --> 00:44:11,120 Speaker 1: faster and faster, like this is not a theory anymore. No, 857 00:44:11,280 --> 00:44:14,520 Speaker 1: that's for sure. Nobody, no reasonable scientists disagrees with that. 858 00:44:15,080 --> 00:44:20,080 Speaker 1: It's even more well understood than climate change. Of scientists, 859 00:44:20,239 --> 00:44:22,600 Speaker 1: that's right. All the scientists except the ones that go 860 00:44:22,640 --> 00:44:25,200 Speaker 1: on Fox News, believe the universe is expanding and that 861 00:44:25,280 --> 00:44:28,799 Speaker 1: expansion is accelerating. So I guess, yeah, the next time 862 00:44:28,840 --> 00:44:30,439 Speaker 1: you can go out there and look at the night sky, 863 00:44:30,680 --> 00:44:34,760 Speaker 1: just think about maybe the future. You know, in the future, 864 00:44:34,880 --> 00:44:37,800 Speaker 1: things are going to be even bigger. The future is big. 865 00:44:37,840 --> 00:44:40,560 Speaker 1: It's looking big, and it's also uncertain because if dark 866 00:44:40,640 --> 00:44:43,600 Speaker 1: energy is changing, we don't know what's changing it, why 867 00:44:43,640 --> 00:44:46,520 Speaker 1: it's changing, and how it's planning to change in the future. 868 00:44:47,120 --> 00:44:49,200 Speaker 1: Is dark energy gonna get stronger and stronger. Is it 869 00:44:49,320 --> 00:44:52,400 Speaker 1: gonna stop dissipate? Turn around, go the other direction. We 870 00:44:52,480 --> 00:44:55,319 Speaker 1: really just can't predict the future because we have no 871 00:44:55,440 --> 00:44:59,160 Speaker 1: understanding of this dominant source of energy in the universe. Alright, 872 00:44:59,200 --> 00:45:02,880 Speaker 1: so stay two and thank you Mike for sending us 873 00:45:02,960 --> 00:45:06,120 Speaker 1: this question. If you have a question about the universe 874 00:45:06,200 --> 00:45:11,000 Speaker 1: or about something that you've always wondered about or read about, 875 00:45:11,400 --> 00:45:13,680 Speaker 1: send it to us and we will try to answer it. 876 00:45:13,800 --> 00:45:16,880 Speaker 1: Thanks to everybody who sends in their questions. Remember questions 877 00:45:16,920 --> 00:45:19,839 Speaker 1: at Daniel and Jorge dot com is your fastest route 878 00:45:19,880 --> 00:45:22,320 Speaker 1: to an answer about the universe. I hope you enjoyed that. 879 00:45:22,480 --> 00:45:32,239 Speaker 1: Thanks for joining us. See you next time. Before you 880 00:45:32,320 --> 00:45:35,200 Speaker 1: still have a question after listening to all these explanations, 881 00:45:35,239 --> 00:45:38,200 Speaker 1: please drop us a line. We'd love to hear from you. 882 00:45:38,200 --> 00:45:41,040 Speaker 1: You can find us at Facebook, Twitter, and Instagram at 883 00:45:41,360 --> 00:45:44,440 Speaker 1: Daniel and Jorge that's one word, or email us at 884 00:45:44,760 --> 00:45:48,480 Speaker 1: Feedback at Daniel and Jorge dot com. Thanks for listening, 885 00:45:48,480 --> 00:45:51,200 Speaker 1: and remember that Daniel and Jorge explained the Universe is 886 00:45:51,239 --> 00:45:54,759 Speaker 1: a production of I Heart Radio. For more podcast from 887 00:45:54,760 --> 00:45:57,840 Speaker 1: my Heart Radio, visit the i Heart Radio app, Apple 888 00:45:57,880 --> 00:46:02,160 Speaker 1: Podcasts or wherever you listen to your favorite chips m