1 00:00:08,440 --> 00:00:11,080 Speaker 1: Hey, or Hey, I have a question for you about 2 00:00:11,240 --> 00:00:15,440 Speaker 1: drawing cartoons. Hey, finally something that I'm an expert in. 3 00:00:15,720 --> 00:00:18,680 Speaker 1: What's the question, Well, it's more about the backgrounds. Actually. 4 00:00:18,880 --> 00:00:21,920 Speaker 1: How do you decide whether to leave the cartoon background 5 00:00:21,920 --> 00:00:24,200 Speaker 1: blank or fill it in with a color, or like 6 00:00:24,280 --> 00:00:27,440 Speaker 1: draw a full scene in the background. M Well, I 7 00:00:27,480 --> 00:00:29,960 Speaker 1: guess it can be whatever you want the background. I mean, 8 00:00:30,440 --> 00:00:32,640 Speaker 1: you just don't want to take away attention from what's 9 00:00:32,680 --> 00:00:35,199 Speaker 1: happening in the panel. So the background is just like 10 00:00:35,320 --> 00:00:37,920 Speaker 1: filler to be ignored. Oh, you know, it's all hard. 11 00:00:38,320 --> 00:00:41,320 Speaker 1: You know. Sometimes that's where the treasures are hidden in 12 00:00:41,400 --> 00:00:45,320 Speaker 1: the background. Oh, sometimes that's true in physics as well. Really, 13 00:00:45,400 --> 00:00:50,080 Speaker 1: you find Waldo sometimes in the background, the cosmic Waldo background. 14 00:01:05,480 --> 00:01:08,959 Speaker 1: Hi am Orhammed, cartoonists and the creator of PhD comics. Hi. 15 00:01:09,160 --> 00:01:12,200 Speaker 1: I'm Daniel. I'm a particle physicist, and I have never 16 00:01:12,440 --> 00:01:15,800 Speaker 1: found Waldo in one of those books. Never. I think 17 00:01:15,800 --> 00:01:17,920 Speaker 1: maybe you just haven't tried, Daniel. I think that's it. 18 00:01:18,160 --> 00:01:20,240 Speaker 1: I get bored after like two seconds, I'm like, why 19 00:01:20,280 --> 00:01:23,320 Speaker 1: do I care about finding this guy? And yet finding 20 00:01:23,360 --> 00:01:26,080 Speaker 1: the Higgs boson in a bunch of noisy data. That's 21 00:01:26,120 --> 00:01:28,679 Speaker 1: somehow more interesting. Yeah, I can write a computer program 22 00:01:28,680 --> 00:01:30,720 Speaker 1: that scans it for me automatically. That could write a 23 00:01:30,760 --> 00:01:33,000 Speaker 1: computer program that looked for Waldo. That would be more 24 00:01:33,000 --> 00:01:35,720 Speaker 1: fun do it? Yeah, I mean, what else are you doing? 25 00:01:36,319 --> 00:01:38,600 Speaker 1: What else could you be doing? It's more productive than that. 26 00:01:39,240 --> 00:01:42,080 Speaker 1: Welcome to our podcast Daniel and Jorge Explain the Universe, 27 00:01:42,120 --> 00:01:44,679 Speaker 1: a production of I Heart Radio, in which we don't 28 00:01:44,720 --> 00:01:47,520 Speaker 1: look for Waldo, but we do look for answers to 29 00:01:47,600 --> 00:01:52,200 Speaker 1: the deepest questions humans have ever asked. Questions like why 30 00:01:52,480 --> 00:01:54,440 Speaker 1: is the universe the way that it is? Could it 31 00:01:54,560 --> 00:01:58,000 Speaker 1: have been another way? How big is it anyway? How 32 00:01:58,040 --> 00:02:00,440 Speaker 1: did it start, how will it end? And what is 33 00:02:00,480 --> 00:02:02,640 Speaker 1: it made out of. We don't shy away from any 34 00:02:02,680 --> 00:02:06,640 Speaker 1: of these incredible questions, which inform the entire context of 35 00:02:06,680 --> 00:02:10,200 Speaker 1: the human existence, and we admit ignorance. We don't pretend 36 00:02:10,240 --> 00:02:11,720 Speaker 1: to know all of the answers, but we try to 37 00:02:11,760 --> 00:02:15,200 Speaker 1: explain to you what science does and does not know. Yeah, 38 00:02:15,240 --> 00:02:17,440 Speaker 1: we like to talk about all of those big questions 39 00:02:17,600 --> 00:02:20,720 Speaker 1: that are at the forefront of science and the exploration 40 00:02:20,919 --> 00:02:24,200 Speaker 1: being done by physicists and other scientists. We also like 41 00:02:24,240 --> 00:02:25,880 Speaker 1: to talk about what sort of in the background of 42 00:02:25,919 --> 00:02:28,840 Speaker 1: science as well. That's right. There are wonderful surprises out 43 00:02:28,840 --> 00:02:31,200 Speaker 1: there in the universe. Sometimes you know what you're looking for. 44 00:02:31,440 --> 00:02:34,800 Speaker 1: Sometimes you stumble across something accidentally when you were looking 45 00:02:34,840 --> 00:02:37,720 Speaker 1: for something else. Sometimes you see an exciting discovery that 46 00:02:37,800 --> 00:02:40,639 Speaker 1: jumps right out at you. Sometimes it's treasures hidden in 47 00:02:40,680 --> 00:02:43,560 Speaker 1: the background. Yeah. And the crazy thing is that it's 48 00:02:43,600 --> 00:02:46,000 Speaker 1: all there right like literally, when you look at the 49 00:02:46,000 --> 00:02:47,960 Speaker 1: background of any picture that you take, and you look 50 00:02:47,960 --> 00:02:50,280 Speaker 1: at the sky behind you or behind the person that 51 00:02:50,360 --> 00:02:54,120 Speaker 1: you're taking the picture of, there's information there about the universe. 52 00:02:54,120 --> 00:02:57,720 Speaker 1: There might be hidden secrets and interesting things to discover 53 00:02:57,960 --> 00:03:01,120 Speaker 1: right there where you least expected. That's true. Even the 54 00:03:01,200 --> 00:03:04,480 Speaker 1: darkest spots in the night sky have some photons coming 55 00:03:04,480 --> 00:03:08,000 Speaker 1: to us from very very distant locations. If you pointed 56 00:03:08,040 --> 00:03:10,480 Speaker 1: the hubble instead of your iPhone at some point in 57 00:03:10,480 --> 00:03:14,080 Speaker 1: the sky, you would see millions and billions of galaxies 58 00:03:14,280 --> 00:03:16,960 Speaker 1: so fat and so distant that their photons arrived like 59 00:03:17,080 --> 00:03:19,880 Speaker 1: every few seconds or every few minutes, rather than all 60 00:03:19,880 --> 00:03:22,960 Speaker 1: the time like the sun. But there is information in 61 00:03:23,160 --> 00:03:25,840 Speaker 1: every little tiny patch of the sky about the nature 62 00:03:25,880 --> 00:03:28,320 Speaker 1: of the universe and what's going on out there. Yeah. 63 00:03:28,360 --> 00:03:32,000 Speaker 1: Can you detect wal dogs. Maybe in those signals standards, 64 00:03:32,080 --> 00:03:35,040 Speaker 1: you know, the bosons to their waldenos, they're hard to find. 65 00:03:35,080 --> 00:03:38,080 Speaker 1: I guess, yeah, if I discover particle, can I called 66 00:03:38,120 --> 00:03:40,400 Speaker 1: the waldo? Like if it's in the background of the 67 00:03:40,760 --> 00:03:43,080 Speaker 1: you know, the universe. I think that would disqualify you 68 00:03:43,120 --> 00:03:46,080 Speaker 1: from participating in any experiment because they would not want 69 00:03:46,120 --> 00:03:49,240 Speaker 1: you to give it that name. I see a pre 70 00:03:49,400 --> 00:03:52,400 Speaker 1: screen for a name giving. We don't, but we should 71 00:03:52,520 --> 00:03:56,320 Speaker 1: because there's been some bad choices in the past. But yeah, 72 00:03:56,320 --> 00:03:57,960 Speaker 1: we like to ask all of the big questions that 73 00:03:58,000 --> 00:04:00,200 Speaker 1: are out there that scientists are wondering about and that 74 00:04:00,240 --> 00:04:04,600 Speaker 1: scientists are speculating about. There are interesting things that scientists 75 00:04:04,640 --> 00:04:07,640 Speaker 1: think might exist and things that we have not yet detected. 76 00:04:07,800 --> 00:04:10,080 Speaker 1: That's right. Every time we open up a new kind 77 00:04:10,080 --> 00:04:12,080 Speaker 1: of eyeball and look out there in the universe in 78 00:04:12,120 --> 00:04:15,280 Speaker 1: a new way, we find all sorts of crazy, exciting stuff, 79 00:04:15,360 --> 00:04:17,920 Speaker 1: and sometimes we know what we're looking for. We think 80 00:04:18,000 --> 00:04:20,440 Speaker 1: that there might be a hint a message out there 81 00:04:20,440 --> 00:04:22,880 Speaker 1: in the universe we haven't detected yet that could give 82 00:04:22,960 --> 00:04:26,320 Speaker 1: us fantastic clues as to the nature of the Big Bang, 83 00:04:26,400 --> 00:04:28,680 Speaker 1: What happened in the first moment of the universe, or 84 00:04:28,720 --> 00:04:32,560 Speaker 1: what's going on with black holes dying all across the galaxy? Yeah, 85 00:04:32,600 --> 00:04:34,960 Speaker 1: because you never know where the next big answer is 86 00:04:35,000 --> 00:04:37,080 Speaker 1: going to come from, or where the next big question 87 00:04:37,160 --> 00:04:39,520 Speaker 1: might come from. For example, we have this great question 88 00:04:39,680 --> 00:04:42,240 Speaker 1: from j J, who's five years old, who sent us 89 00:04:42,400 --> 00:04:45,560 Speaker 1: a listener question through the internet. That's right, here's a 90 00:04:45,680 --> 00:04:48,640 Speaker 1: question that JJ's father sent to us because he couldn't 91 00:04:48,680 --> 00:04:54,960 Speaker 1: answer it himself. Here's j J as the son by 92 00:04:55,320 --> 00:05:00,280 Speaker 1: that in the middle of our galaxy? Oh so ute, 93 00:05:00,920 --> 00:05:03,080 Speaker 1: Wait was it a question or a statement? Is he 94 00:05:03,200 --> 00:05:05,920 Speaker 1: saying he's going to make a star goes supernova? This 95 00:05:06,000 --> 00:05:08,960 Speaker 1: is not the youngest supervillain listener that we have. He's 96 00:05:09,040 --> 00:05:13,640 Speaker 1: asking what would happen if our star win supernova next 97 00:05:13,680 --> 00:05:17,719 Speaker 1: to the supermassive black hole in the center of our galaxy. Wow, 98 00:05:17,800 --> 00:05:20,119 Speaker 1: it's amazing that a five year old knows the word 99 00:05:20,160 --> 00:05:23,800 Speaker 1: supernova and kind of what it means. Yeah, so thank 100 00:05:23,839 --> 00:05:27,320 Speaker 1: you Lowell for encouraging the scientific curiosity in your children 101 00:05:27,320 --> 00:05:31,040 Speaker 1: in the next generation. You are fueling human progress. So 102 00:05:31,080 --> 00:05:34,400 Speaker 1: that's a complex question. Here, JJ is asking what if 103 00:05:34,480 --> 00:05:37,560 Speaker 1: our son was somehow next to the black hole in 104 00:05:37,560 --> 00:05:39,960 Speaker 1: the middle of our galaxy, and then what if it 105 00:05:40,040 --> 00:05:43,159 Speaker 1: suddenly went supernova? Right, that's right, and j J doesn't 106 00:05:43,160 --> 00:05:46,160 Speaker 1: have to worry. Our son is not going to go supernova. 107 00:05:46,400 --> 00:05:49,400 Speaker 1: Supernova is one of the end stages of a star, 108 00:05:49,720 --> 00:05:53,400 Speaker 1: when it gets so massive that it collapses gravitationally. But 109 00:05:53,560 --> 00:05:55,200 Speaker 1: in order for that to happen, you have to have 110 00:05:55,240 --> 00:05:57,640 Speaker 1: a lot more mass than our son does. You need 111 00:05:57,720 --> 00:06:00,640 Speaker 1: like eight times the mass of our son the minimum 112 00:06:00,680 --> 00:06:03,840 Speaker 1: threshold for a start to end up as a supernova. Right, 113 00:06:03,880 --> 00:06:06,120 Speaker 1: But so it can go supernova on its own, but 114 00:06:06,160 --> 00:06:08,440 Speaker 1: it might eat something else and then get bigger, right, 115 00:06:08,480 --> 00:06:11,560 Speaker 1: and then go supernova. That's right. There is one possibility 116 00:06:11,600 --> 00:06:14,679 Speaker 1: our sun will probably end its life as a white dwarf. 117 00:06:15,120 --> 00:06:17,039 Speaker 1: So there will be a phase which becomes a red 118 00:06:17,080 --> 00:06:19,200 Speaker 1: giant and blows out a lot of stuff, and then 119 00:06:19,200 --> 00:06:21,839 Speaker 1: it collapses again, and then it blows out more stuff, 120 00:06:21,839 --> 00:06:23,680 Speaker 1: and at the core would be left a very very 121 00:06:23,720 --> 00:06:26,760 Speaker 1: dense blob, a white dwarf, which essentially just a hot 122 00:06:26,880 --> 00:06:29,279 Speaker 1: rock and it's white not because this fusion going on 123 00:06:29,320 --> 00:06:31,760 Speaker 1: inside it, but because it's glowing white hot. And these 124 00:06:31,760 --> 00:06:34,480 Speaker 1: white dwarves usually just sit around for trillions of years 125 00:06:34,520 --> 00:06:37,800 Speaker 1: and cool off but sometimes if there's another star that 126 00:06:37,839 --> 00:06:41,120 Speaker 1: comes nearby, they're so dense they can eat those stars, 127 00:06:41,360 --> 00:06:43,560 Speaker 1: and if they eat enough of them, that can trigger 128 00:06:43,640 --> 00:06:46,680 Speaker 1: a supernova. Wow. Yeah, I sometimes feel like that. And Thanksgiving, 129 00:06:47,760 --> 00:06:51,719 Speaker 1: don't bring around another pie. I'm gonna blow No more turkey, please, 130 00:06:52,040 --> 00:06:55,080 Speaker 1: I'm gonna supernova. Do you gravitationally attract dessert if you 131 00:06:55,120 --> 00:06:59,520 Speaker 1: eat enough turkey? No, I'm just easy electromagnetic corps for that. Nice. 132 00:07:00,360 --> 00:07:02,560 Speaker 1: But I guess the question is what happens if a star, 133 00:07:02,760 --> 00:07:04,760 Speaker 1: or I guess any star blows up next to a 134 00:07:04,800 --> 00:07:07,080 Speaker 1: black hole? Like, does it blow away the black hole? 135 00:07:07,360 --> 00:07:10,120 Speaker 1: Does it like evaporated? Does it do nothing? If you 136 00:07:10,320 --> 00:07:12,360 Speaker 1: explode it next to a black hole? What happens? Well, 137 00:07:12,400 --> 00:07:14,880 Speaker 1: first of all, you cannot explode a black hole, like 138 00:07:14,960 --> 00:07:17,800 Speaker 1: there's nothing you can do that will destroy a black hole, 139 00:07:17,840 --> 00:07:20,080 Speaker 1: because remember, a black hole is a dense blob of 140 00:07:20,160 --> 00:07:23,640 Speaker 1: matter that will eat everything else, and that includes other 141 00:07:23,720 --> 00:07:25,920 Speaker 1: forms of energy. So you shoot a particle beam, you 142 00:07:25,920 --> 00:07:28,320 Speaker 1: shoot antimatter, you shoot dark matter into a black hole. 143 00:07:28,600 --> 00:07:31,520 Speaker 1: It eats everything. It's like Jorge at Thanksgiving dinner, right, 144 00:07:31,840 --> 00:07:35,000 Speaker 1: It's happy to take anything. And so anything you blow 145 00:07:35,040 --> 00:07:38,400 Speaker 1: in there, including the remnants of a supernova will just 146 00:07:38,560 --> 00:07:41,000 Speaker 1: make it bigger and stronger. Oh, I see, So it's 147 00:07:41,040 --> 00:07:43,480 Speaker 1: not possible to like blow it away or move it, 148 00:07:43,600 --> 00:07:45,400 Speaker 1: or at least maybe like push it a little bit. 149 00:07:45,480 --> 00:07:47,160 Speaker 1: Is it possible to push a black hole? It is 150 00:07:47,200 --> 00:07:49,480 Speaker 1: possible to push a black hole to accelerate. It is 151 00:07:49,520 --> 00:07:51,760 Speaker 1: a mass, and so you can tug on it. For example, 152 00:07:51,800 --> 00:07:54,160 Speaker 1: if you bring another black hole near it, those two 153 00:07:54,160 --> 00:07:57,400 Speaker 1: black holes will accelerate towards each other, swirling around and 154 00:07:57,440 --> 00:08:00,680 Speaker 1: creating all sorts of like gravitational radiation. And it is 155 00:08:00,720 --> 00:08:03,160 Speaker 1: interesting because the supernova near a black hole, like that 156 00:08:03,240 --> 00:08:06,920 Speaker 1: supernova will eject the material really really violently. It's a 157 00:08:07,000 --> 00:08:10,240 Speaker 1: huge explosion. The stuff comes out like a significant fraction 158 00:08:10,280 --> 00:08:12,160 Speaker 1: of the speed of light. But it won't necessarily just 159 00:08:12,200 --> 00:08:14,760 Speaker 1: like get all immediately eaten by the black hole because 160 00:08:14,760 --> 00:08:17,880 Speaker 1: it's moving at such high speed unless it pointed exactly 161 00:08:17,920 --> 00:08:20,360 Speaker 1: at the black hole. They'll probably like miss a little 162 00:08:20,360 --> 00:08:23,119 Speaker 1: bit and then swirl around the black hole and become 163 00:08:23,160 --> 00:08:25,640 Speaker 1: part of the accretion disc. That's like stuff around the 164 00:08:25,680 --> 00:08:29,160 Speaker 1: black hole that's hot and glowing. Interesting, But the explosion 165 00:08:29,200 --> 00:08:32,000 Speaker 1: itself I won't impart any like momentum on the black 166 00:08:32,080 --> 00:08:34,080 Speaker 1: hole to push it a little bit, even no, it 167 00:08:34,080 --> 00:08:36,320 Speaker 1: will impart some momentum on the black hole. But you know, 168 00:08:36,440 --> 00:08:39,280 Speaker 1: supermassive black hole like we're talking about as a mass 169 00:08:39,280 --> 00:08:42,199 Speaker 1: that's millions of times the mass of the Sun, and 170 00:08:42,240 --> 00:08:44,040 Speaker 1: the kind of supernover we're talking about comes from a 171 00:08:44,040 --> 00:08:46,000 Speaker 1: white dwarf, which is like less than the mass of 172 00:08:46,000 --> 00:08:48,200 Speaker 1: our Sun. So the energy from it is just going 173 00:08:48,240 --> 00:08:50,000 Speaker 1: to be like a pin prick. It's like if a 174 00:08:50,040 --> 00:08:52,760 Speaker 1: mosquito lands on you, does it knock you over? What 175 00:08:52,880 --> 00:08:55,920 Speaker 1: depends on the mosquito, you know, it depends on what 176 00:08:56,080 --> 00:08:59,160 Speaker 1: it's carrying. I mean, I've never been to Panama. I 177 00:08:59,160 --> 00:09:01,600 Speaker 1: don't know how big those skeetos they get big. Yeah, 178 00:09:01,679 --> 00:09:04,000 Speaker 1: not as big as the Australian ones. Everything is bigger 179 00:09:04,000 --> 00:09:06,600 Speaker 1: in Australia. Well up here in the States. I've never 180 00:09:06,640 --> 00:09:09,120 Speaker 1: been knocked over by a mosquito. But you know, not yet. 181 00:09:10,000 --> 00:09:12,040 Speaker 1: I'm getting older and they're getting bigger. Well that's the 182 00:09:12,080 --> 00:09:14,480 Speaker 1: answer for j J. Thanks for sending in the question. 183 00:09:15,160 --> 00:09:17,920 Speaker 1: And so today we'll be talking about sort of what's 184 00:09:17,960 --> 00:09:21,000 Speaker 1: happening in the background of the universe. We know that 185 00:09:21,040 --> 00:09:25,839 Speaker 1: there's the cosmic microwave background radiation. That's light, that's electromagnetic 186 00:09:25,960 --> 00:09:28,559 Speaker 1: energy that's out there hanging out from the Big Bang. 187 00:09:29,000 --> 00:09:31,840 Speaker 1: But there might be other things in the background that 188 00:09:32,400 --> 00:09:34,320 Speaker 1: may or may not be there that we might have 189 00:09:34,440 --> 00:09:37,160 Speaker 1: information also about the universe. Right, that's right. The cosmic 190 00:09:37,280 --> 00:09:40,719 Speaker 1: microwave background is a really really rich source of information 191 00:09:40,760 --> 00:09:43,040 Speaker 1: about what happened in the very early universe and what's 192 00:09:43,040 --> 00:09:46,040 Speaker 1: going on now. But it's just another form of light. Right, 193 00:09:46,120 --> 00:09:50,480 Speaker 1: Microwaves are electromagnetic radiation. But recently we figured out other 194 00:09:50,520 --> 00:09:52,800 Speaker 1: ways to look at the universe, Like we were just 195 00:09:52,840 --> 00:09:56,800 Speaker 1: talking about black holes generate gravitational radiation, which is a 196 00:09:56,800 --> 00:09:59,719 Speaker 1: completely different form of radiation and another way to look 197 00:09:59,720 --> 00:10:02,400 Speaker 1: at the universe. And so now we're wondering about whether 198 00:10:02,440 --> 00:10:06,320 Speaker 1: we can see a background to the gravitational radiation in 199 00:10:06,360 --> 00:10:09,000 Speaker 1: the universe. So today on the program, we'll be asking 200 00:10:09,040 --> 00:10:19,160 Speaker 1: the question what is the cosmic gravitational background and who 201 00:10:19,200 --> 00:10:21,920 Speaker 1: will win the Nobel Prize for finding it? Interesting. So, 202 00:10:21,920 --> 00:10:24,160 Speaker 1: it's something that we haven't found yet. It is not 203 00:10:24,400 --> 00:10:27,000 Speaker 1: something that we have seen exactly. There are some hints, 204 00:10:27,080 --> 00:10:28,520 Speaker 1: and we'll talk a little bit about some of the 205 00:10:28,520 --> 00:10:31,400 Speaker 1: experiments that claim to maybe see it and have claimed 206 00:10:31,400 --> 00:10:33,959 Speaker 1: to see it and been debunked. But so far it's 207 00:10:34,040 --> 00:10:36,800 Speaker 1: not an established thing. It's like potentially a discovery in 208 00:10:36,840 --> 00:10:39,640 Speaker 1: our future. It's like a treasure chest we haven't dug 209 00:10:39,720 --> 00:10:41,800 Speaker 1: up yet. And it has a very similar name to 210 00:10:41,840 --> 00:10:46,440 Speaker 1: the cosmic microwave background. This was the cosmic gravitational background. Now, 211 00:10:46,440 --> 00:10:50,000 Speaker 1: couldn't you use a different name, like the universal Gravitational background, 212 00:10:50,080 --> 00:10:52,280 Speaker 1: just to like set it apart a little bit. No, 213 00:10:52,400 --> 00:10:54,960 Speaker 1: we want to use the same name to show the similarities. Like, 214 00:10:55,000 --> 00:10:57,800 Speaker 1: it really is very similar in concept to the CMB, 215 00:10:58,120 --> 00:10:59,720 Speaker 1: so we wanted to use a name that, you know, 216 00:11:00,000 --> 00:11:02,840 Speaker 1: invade the parallelism there. That was a little bit more awkward. 217 00:11:02,880 --> 00:11:05,199 Speaker 1: The CGB is harder to say than the c m B. 218 00:11:05,559 --> 00:11:08,000 Speaker 1: The cg B. That sounds like a rap group maybe, 219 00:11:08,360 --> 00:11:10,480 Speaker 1: or it sounds like a type of monitor. Do you 220 00:11:10,480 --> 00:11:12,640 Speaker 1: have an l E ED or a c GB or 221 00:11:12,679 --> 00:11:17,360 Speaker 1: maybe a Supreme Court justice? Maybe the r g B. Yeah, 222 00:11:17,360 --> 00:11:20,720 Speaker 1: I'm done with c g BRBG right. Yeah. Anyways, it 223 00:11:20,760 --> 00:11:23,480 Speaker 1: sounds cosmic, and we were wondering how many people out 224 00:11:23,480 --> 00:11:26,679 Speaker 1: there knew what it was or had even heard of 225 00:11:26,720 --> 00:11:29,600 Speaker 1: the cosmic gravitational background. So, as usual Daniel went out 226 00:11:29,600 --> 00:11:31,600 Speaker 1: there into the wilds of the Internet to ask people 227 00:11:32,080 --> 00:11:35,480 Speaker 1: what is the cosmic gravitational background? So thank you to 228 00:11:35,520 --> 00:11:37,640 Speaker 1: all of our listeners who do live in the wilds 229 00:11:37,679 --> 00:11:40,520 Speaker 1: of the Internet and allow me to visit. If you'd 230 00:11:40,520 --> 00:11:44,160 Speaker 1: like to participate and send your speculation to Crazy Physics 231 00:11:44,200 --> 00:11:46,880 Speaker 1: topics in the future, please don't be shy. Send me 232 00:11:46,920 --> 00:11:49,920 Speaker 1: a message to questions at Daniel and Jorge dot com 233 00:11:50,040 --> 00:11:51,880 Speaker 1: and you can show off to all your friends hearing 234 00:11:51,920 --> 00:11:54,120 Speaker 1: your voice on the podcast. So think about it for 235 00:11:54,160 --> 00:11:57,080 Speaker 1: a second. What do you think it might be. Here's 236 00:11:57,080 --> 00:11:59,960 Speaker 1: what people had to say heard of the Cosmic Gravitation 237 00:12:00,000 --> 00:12:03,920 Speaker 1: show background. Um, I'm going to guess that it has 238 00:12:03,960 --> 00:12:08,280 Speaker 1: to do with the overall mass of the universe or 239 00:12:08,360 --> 00:12:12,559 Speaker 1: density I guess of mass in the universe. It makes 240 00:12:12,600 --> 00:12:16,960 Speaker 1: me think of cotton candy and when you're making it, 241 00:12:17,040 --> 00:12:19,440 Speaker 1: you know, you get the big glob of cotton candy 242 00:12:19,480 --> 00:12:23,880 Speaker 1: on the paper cone, but after that there's still fragments 243 00:12:23,880 --> 00:12:27,160 Speaker 1: and strings of it blowing around in the machine. And 244 00:12:27,240 --> 00:12:31,680 Speaker 1: that's how I picture cosmic gravitational background, just a little 245 00:12:32,160 --> 00:12:36,680 Speaker 1: snippets that are left after the planets and the stars congealed. 246 00:12:38,480 --> 00:12:44,400 Speaker 1: Shure that the cosmic gravitational background is an option on Zoom. Well, 247 00:12:44,920 --> 00:12:51,679 Speaker 1: this is something recent. Um, it might work like a 248 00:12:51,880 --> 00:12:58,360 Speaker 1: cosmic microwave background. I think so. Never heard of the 249 00:12:58,400 --> 00:13:02,640 Speaker 1: cosmic gravitational background. I guess it might be some low 250 00:13:02,800 --> 00:13:10,280 Speaker 1: level gravitational way of background, or some general gravitational pool 251 00:13:11,080 --> 00:13:16,479 Speaker 1: of the universe to words a specific point or from 252 00:13:16,600 --> 00:13:20,959 Speaker 1: the Big Bang. I have not heard of the cosmic 253 00:13:21,000 --> 00:13:24,800 Speaker 1: gravitational background, but since it has a pretty similar name 254 00:13:24,840 --> 00:13:28,839 Speaker 1: to the cosmic background radiation, I'll guess it's some sort 255 00:13:28,880 --> 00:13:34,240 Speaker 1: of map of the very early universe and how gravity 256 00:13:34,760 --> 00:13:41,880 Speaker 1: like began to clump mass after the initial quantum fluctuations 257 00:13:41,920 --> 00:13:48,040 Speaker 1: that caused the clumping, just how gravity was distributed in 258 00:13:48,080 --> 00:13:51,240 Speaker 1: the very early universe right after the Big Bang and 259 00:13:51,280 --> 00:13:55,160 Speaker 1: all that stuff. I have never even heard this term before, 260 00:13:55,960 --> 00:13:59,920 Speaker 1: so this is a wild guess. I'm assuming it has 261 00:14:00,040 --> 00:14:05,400 Speaker 1: something to do with the gravitational field of the entire cosmos. 262 00:14:06,880 --> 00:14:09,680 Speaker 1: I don't know how you would measure it, but that 263 00:14:09,720 --> 00:14:12,480 Speaker 1: would be my guest, all right. I like the person 264 00:14:12,520 --> 00:14:14,720 Speaker 1: who say it's an option on zoom to set your 265 00:14:14,760 --> 00:14:22,280 Speaker 1: background to the cosmic gravitational background. Technically that is true, maybe, right, everything. 266 00:14:22,320 --> 00:14:25,200 Speaker 1: I guess everything in the background does have gravity, so 267 00:14:25,760 --> 00:14:28,560 Speaker 1: and it's part of the cosmos. So really all Zoom 268 00:14:28,560 --> 00:14:32,920 Speaker 1: backgrounds are cosmic gravitational backgrounds. Yeah, I wonder if astronomers 269 00:14:32,960 --> 00:14:35,080 Speaker 1: even thought to look on Zoom to find the c GB. 270 00:14:35,240 --> 00:14:37,320 Speaker 1: I mean, maybe it's just that easy, right, just an 271 00:14:37,320 --> 00:14:40,600 Speaker 1: option on Zoom win Nobel, at least in some other 272 00:14:40,800 --> 00:14:43,360 Speaker 1: noble category. Maybe. Well, there's so many options on Zoom. 273 00:14:43,360 --> 00:14:46,000 Speaker 1: Who knows what's buried in some of those sub sub menus, right, 274 00:14:46,240 --> 00:14:51,920 Speaker 1: there's a Waldo option? No, please no, because we know 275 00:14:52,080 --> 00:14:54,520 Speaker 1: it sometimes means are not that exciting. It'd be nice 276 00:14:54,560 --> 00:14:56,600 Speaker 1: to have a little a bit of a puzzle there. 277 00:14:56,680 --> 00:14:59,520 Speaker 1: Find Waldo in the background of your Zoom speaker. Yeah, 278 00:14:59,600 --> 00:15:04,720 Speaker 1: there you that's actually a pretty good idea to build 279 00:15:04,800 --> 00:15:07,400 Speaker 1: games in a Zoom to keep people entertained. So this 280 00:15:07,480 --> 00:15:10,200 Speaker 1: is pretty interesting, Daniel, I didn't even know there was 281 00:15:10,240 --> 00:15:13,480 Speaker 1: a cosmic gravitational background, like most of our listeners and 282 00:15:13,720 --> 00:15:16,480 Speaker 1: people who responded so step us three. I'm guessing it 283 00:15:16,480 --> 00:15:19,040 Speaker 1: has something to do with gravitational waves and maybe the 284 00:15:19,160 --> 00:15:22,000 Speaker 1: Lego experiment that we have to detect them exactly it 285 00:15:22,040 --> 00:15:26,040 Speaker 1: does to understand what the cosmic gravitational background is, we 286 00:15:26,080 --> 00:15:29,680 Speaker 1: first have to understand what gravitational messages are and with 287 00:15:29,720 --> 00:15:32,880 Speaker 1: the gravitational foreground is. So let's start off with what 288 00:15:33,160 --> 00:15:36,240 Speaker 1: gravitational wave is. For those of you who don't recall, 289 00:15:36,600 --> 00:15:40,680 Speaker 1: space itself can ripple because mass changes the shape of space, 290 00:15:41,040 --> 00:15:42,920 Speaker 1: like if you have a black hole or a heavy 291 00:15:42,960 --> 00:15:46,800 Speaker 1: object or something that bends space. We know now that 292 00:15:46,880 --> 00:15:49,760 Speaker 1: gravity is not just a force between two objects. It's 293 00:15:49,800 --> 00:15:54,640 Speaker 1: actually space curving around masses and changing the way things move. 294 00:15:54,920 --> 00:15:58,280 Speaker 1: So gravity is this like apparent force. That's just because 295 00:15:58,280 --> 00:16:01,320 Speaker 1: we can't see the shape of space, the bending of space. 296 00:16:01,520 --> 00:16:03,840 Speaker 1: So we know that mass can bend space. Well, what 297 00:16:03,960 --> 00:16:07,560 Speaker 1: happens when mass moves or mass changes, Well, that causes 298 00:16:07,640 --> 00:16:11,200 Speaker 1: ripples because if a mass moves, then it's gravitational field 299 00:16:11,280 --> 00:16:14,040 Speaker 1: is going to move. So that's what causes ripples in 300 00:16:14,160 --> 00:16:17,120 Speaker 1: space time, and that's what we call a gravitational wave. 301 00:16:17,480 --> 00:16:21,440 Speaker 1: Right Like, gravitational signals like the effects of gravity take 302 00:16:21,520 --> 00:16:24,360 Speaker 1: time and space to move. Right Like if our son 303 00:16:24,560 --> 00:16:28,200 Speaker 1: suddenly disappeared or started moving or jiggling, it would take 304 00:16:28,240 --> 00:16:30,560 Speaker 1: like eight minutes for us to feel those changes in 305 00:16:30,560 --> 00:16:34,040 Speaker 1: its gravity. Exactly because information takes time to propagate. The 306 00:16:34,080 --> 00:16:37,720 Speaker 1: gravitational fields don't change immediately. There's a ripple. There's like 307 00:16:37,760 --> 00:16:41,200 Speaker 1: a wave that passes through the gravitational field, sort of 308 00:16:41,400 --> 00:16:44,600 Speaker 1: updating everything, and that wave moves at the speed of light. 309 00:16:45,000 --> 00:16:47,320 Speaker 1: And this is not unique to gravity, right, happens to 310 00:16:47,440 --> 00:16:50,240 Speaker 1: lots of things anything in fact, where information takes time 311 00:16:50,280 --> 00:16:52,960 Speaker 1: to propagate. Like think about a simple string. Maybe you're 312 00:16:52,960 --> 00:16:55,400 Speaker 1: playing jump rope with your friend. You pull the string up, 313 00:16:55,640 --> 00:16:58,400 Speaker 1: the whole string doesn't move at once. Right. You see, 314 00:16:58,640 --> 00:17:00,520 Speaker 1: first the first bit of the string moves up, and 315 00:17:00,560 --> 00:17:02,880 Speaker 1: then that pulls the next bit of the string, which 316 00:17:02,880 --> 00:17:04,560 Speaker 1: pulls the next bit of the string, and which you 317 00:17:04,600 --> 00:17:07,960 Speaker 1: get is a wave moving through your jump rope. Right. So, 318 00:17:08,080 --> 00:17:11,040 Speaker 1: anytime you have a material where information takes time to propagate, 319 00:17:11,080 --> 00:17:14,320 Speaker 1: where it's not just like instantaneous transfer, that's because everything 320 00:17:14,400 --> 00:17:16,720 Speaker 1: is local, then you get a wave. And so that's 321 00:17:16,760 --> 00:17:21,080 Speaker 1: true for a jump rope, and it's also true for electromagnetism. Right. 322 00:17:21,119 --> 00:17:25,399 Speaker 1: We can think about photons as electromagnetic waves because if 323 00:17:25,440 --> 00:17:28,800 Speaker 1: you take an electron, for example, it has an electric field. 324 00:17:29,080 --> 00:17:32,760 Speaker 1: If you shake that electron, then the electric field moves 325 00:17:32,840 --> 00:17:36,280 Speaker 1: with it. But again not instantaneously. It goes back and 326 00:17:36,320 --> 00:17:39,399 Speaker 1: forth with the electron. And that's what a photon is. 327 00:17:39,400 --> 00:17:42,320 Speaker 1: It's just an update in the electromagnetic field. Yeah, it's 328 00:17:42,359 --> 00:17:45,600 Speaker 1: like a wave. It's like electromagnetic what a ripple, right, 329 00:17:45,800 --> 00:17:47,520 Speaker 1: is what a photon is. Yeah, And that's how you 330 00:17:47,560 --> 00:17:50,359 Speaker 1: generate photons. You have an antenna and you wiggle the 331 00:17:50,400 --> 00:17:54,400 Speaker 1: electrons up and down inside the antenna changing the electromagnetic 332 00:17:54,440 --> 00:17:57,199 Speaker 1: fields around the antenna in a regular pattern, and that 333 00:17:57,400 --> 00:18:00,639 Speaker 1: causes waves in those fields, which are photo That's what 334 00:18:00,800 --> 00:18:04,520 Speaker 1: light is. That's what light is, yes, exactly. And a 335 00:18:04,600 --> 00:18:08,240 Speaker 1: gravitational wave is the same concept, except instead of wiggling 336 00:18:08,240 --> 00:18:13,120 Speaker 1: a string or wiggling the electromagnetic fields, you're wiggling space itself, 337 00:18:13,240 --> 00:18:16,400 Speaker 1: which is bonkers and super fun to say. Yeah, and 338 00:18:16,480 --> 00:18:19,879 Speaker 1: it's a true thing, right, Like we have measurements of 339 00:18:19,960 --> 00:18:22,920 Speaker 1: the house space wiggles out there in space out there 340 00:18:22,920 --> 00:18:25,720 Speaker 1: in the cosmos, right, Like we've detected gravitation ways from 341 00:18:25,880 --> 00:18:29,680 Speaker 1: black holes swirling around each other and things kind of exploding. Right, Yes, 342 00:18:29,760 --> 00:18:32,480 Speaker 1: we have seen it, which is amazing. This is an 343 00:18:32,480 --> 00:18:36,359 Speaker 1: idea that's a hundred years old. When Einstein developed general relativity, 344 00:18:36,400 --> 00:18:39,119 Speaker 1: one of the big steps forward, there was this concept 345 00:18:39,359 --> 00:18:44,119 Speaker 1: that information doesn't propagate instantaneously. Right in Newton's gravity, information 346 00:18:44,240 --> 00:18:47,360 Speaker 1: was instantaneous, so the Sun disappeared, then gravity and Earth 347 00:18:47,440 --> 00:18:51,119 Speaker 1: changed instantaneously. So when Einstein introduced this concept of the 348 00:18:51,359 --> 00:18:53,919 Speaker 1: limited speed of information, which of course came from his 349 00:18:53,960 --> 00:18:57,000 Speaker 1: special relativity, this was one of the big predictions that 350 00:18:57,040 --> 00:19:00,639 Speaker 1: if general relativity was true, we should see gravitational waves. 351 00:19:00,840 --> 00:19:03,560 Speaker 1: But everybody thought these things are tiny either gonna be 352 00:19:03,600 --> 00:19:06,959 Speaker 1: really really hard to see because gravity is so weak. 353 00:19:07,640 --> 00:19:10,360 Speaker 1: And then in the seventies people saw some clues about 354 00:19:10,400 --> 00:19:14,400 Speaker 1: gravitational waves because they saw pulsars, and those pulsars were 355 00:19:14,480 --> 00:19:17,399 Speaker 1: orbiting each other and slowly falling into each other, and 356 00:19:17,440 --> 00:19:19,639 Speaker 1: the only way that happens is if they're losing energy 357 00:19:19,760 --> 00:19:24,320 Speaker 1: somehow radiating gravitational waves. We didn't see the waves themselves yet, 358 00:19:24,480 --> 00:19:27,720 Speaker 1: but we saw the things were radiating some kind of energy, 359 00:19:27,760 --> 00:19:30,520 Speaker 1: so it must have been gravitational That won a Nobel prize. 360 00:19:31,000 --> 00:19:34,200 Speaker 1: And then decades later people built machines that actually were 361 00:19:34,240 --> 00:19:37,639 Speaker 1: able to measure the gravitational waves directly, like to see 362 00:19:37,680 --> 00:19:41,200 Speaker 1: the waves themselves, operate on machines here on Earth to 363 00:19:41,280 --> 00:19:45,240 Speaker 1: see the physical effects of these ripples of space and time. Yeah, 364 00:19:45,359 --> 00:19:48,080 Speaker 1: that's the big Lego experiment a few years ago that 365 00:19:48,160 --> 00:19:50,680 Speaker 1: made a big splash in the science community. And now 366 00:19:50,720 --> 00:19:54,760 Speaker 1: we have other observatories to listen for these gravitational waves. Right, yeah, 367 00:19:54,800 --> 00:19:57,080 Speaker 1: this is one of the Nobel Prizes I didn't win. 368 00:19:58,440 --> 00:20:00,119 Speaker 1: Do you keep track of all the Nobel Prize if 369 00:20:00,119 --> 00:20:02,359 Speaker 1: you don't win. I mean there's a lot more Noble prices. 370 00:20:02,400 --> 00:20:05,480 Speaker 1: I haven't one than I have one, so it's more 371 00:20:05,480 --> 00:20:08,040 Speaker 1: work to keep track of. But I interviewed at cal 372 00:20:08,160 --> 00:20:10,160 Speaker 1: Tech and was thinking about going to grad school there 373 00:20:10,200 --> 00:20:12,320 Speaker 1: to work on this project. But I remember thinking to myself, 374 00:20:12,600 --> 00:20:14,720 Speaker 1: they're never going to see these things. Oh my gosh, 375 00:20:14,720 --> 00:20:16,919 Speaker 1: this seems too hard, and I decided to go to 376 00:20:16,960 --> 00:20:20,439 Speaker 1: particle physics instead. And you know, they won the Nobel Prize. 377 00:20:20,480 --> 00:20:22,920 Speaker 1: Congrats to them. They proved me wrong. So one more 378 00:20:22,960 --> 00:20:25,760 Speaker 1: mistake I've made in my career. Well, you were involved 379 00:20:25,760 --> 00:20:29,000 Speaker 1: in the discovering the Higgs boson that won a Noble Prize, right, Yeah, 380 00:20:29,080 --> 00:20:30,760 Speaker 1: I didn't win a Nobel Prize for that, but that 381 00:20:30,880 --> 00:20:33,440 Speaker 1: went to the theorist. But yeah, I was involved there. Anyway, 382 00:20:33,440 --> 00:20:36,640 Speaker 1: we have the Lego and the Virgo experiments. These are 383 00:20:36,720 --> 00:20:41,240 Speaker 1: observatories around the world that use interferometers to see these wiggles. 384 00:20:41,359 --> 00:20:44,840 Speaker 1: And these wiggles come from really big events, dramatic events 385 00:20:44,840 --> 00:20:47,800 Speaker 1: out there in the universe that generate gravitational waves. Like 386 00:20:47,880 --> 00:20:51,280 Speaker 1: any time any object with mass accelerates, it generates a 387 00:20:51,280 --> 00:20:54,240 Speaker 1: little gravitational wave. But you know, gravity is so weak 388 00:20:54,280 --> 00:20:56,399 Speaker 1: that in order to see these things you need a 389 00:20:56,440 --> 00:21:01,160 Speaker 1: big gravitational wave. Things like two black holes swirling around 390 00:21:01,200 --> 00:21:04,400 Speaker 1: each other and then merging and eating each other generates 391 00:21:04,440 --> 00:21:07,600 Speaker 1: a lot of gravitational wave energy. That's the kind of 392 00:21:07,640 --> 00:21:09,640 Speaker 1: thing that we can see here on Earth. But even 393 00:21:09,680 --> 00:21:11,800 Speaker 1: if it's that big, even if it's a huge, dramatic 394 00:21:11,920 --> 00:21:14,600 Speaker 1: cataclysmic event, we can just barely see it here on 395 00:21:14,680 --> 00:21:17,040 Speaker 1: Earth because the ripples in space and time are very 396 00:21:17,160 --> 00:21:19,880 Speaker 1: very small. For example, if you took a rod, then 397 00:21:19,960 --> 00:21:22,960 Speaker 1: when a gravitation wave passed, it would get shorter by 398 00:21:23,040 --> 00:21:25,960 Speaker 1: one part in ten to the twenty and then we 399 00:21:26,040 --> 00:21:28,760 Speaker 1: get longer as the wave passed by one part in 400 00:21:28,800 --> 00:21:30,600 Speaker 1: tens of the twenties. So to see these things you 401 00:21:30,600 --> 00:21:34,080 Speaker 1: need really really accurate measurements of distance. Yeah, it's a 402 00:21:34,240 --> 00:21:37,760 Speaker 1: crazy amount of engineering to be able to measure things 403 00:21:37,800 --> 00:21:41,400 Speaker 1: so small and it works. And they've seen a lot 404 00:21:41,440 --> 00:21:44,680 Speaker 1: of these crazy events like black holes colliding with each 405 00:21:44,680 --> 00:21:47,560 Speaker 1: other or black holes with neutron stars, and we've seen 406 00:21:47,640 --> 00:21:50,280 Speaker 1: like maybe a dozen of them, and so they're common 407 00:21:50,760 --> 00:21:53,640 Speaker 1: and they sort of form, as you say, the foreground 408 00:21:53,760 --> 00:21:58,520 Speaker 1: of the gravitational universe, right, the gravitational field in the universe. 409 00:21:58,720 --> 00:22:00,960 Speaker 1: And so there's the question of whether or not there's 410 00:22:01,040 --> 00:22:04,640 Speaker 1: also kind of a background in gravitational waves, and whether 411 00:22:04,720 --> 00:22:07,440 Speaker 1: or not that has some interesting signals that might tell 412 00:22:07,480 --> 00:22:10,160 Speaker 1: us about the origins of the universe. So let's get 413 00:22:10,200 --> 00:22:25,199 Speaker 1: into that. But first let's take a quick break. All right, 414 00:22:25,200 --> 00:22:28,600 Speaker 1: we're talking about the cosmic gravitational background now, Daniel, we 415 00:22:28,600 --> 00:22:31,720 Speaker 1: talked about gravitational waves. That's when like big things like 416 00:22:31,800 --> 00:22:35,120 Speaker 1: black holes and neutron stars swirl around each other and collide. 417 00:22:35,160 --> 00:22:38,000 Speaker 1: They generate these ripples in space that we can detect here. 418 00:22:38,160 --> 00:22:42,679 Speaker 1: That's what you call the foreground of the gravitational universe, right, 419 00:22:42,800 --> 00:22:46,160 Speaker 1: that's right. Those are like big shouts in the gravitational spectrum, 420 00:22:46,280 --> 00:22:50,159 Speaker 1: huge events that we're listening for specifically in their short 421 00:22:50,359 --> 00:22:53,480 Speaker 1: their localizes, they come from one direction, right, then they're 422 00:22:53,520 --> 00:22:55,959 Speaker 1: big events were like things happening, but there might be 423 00:22:56,080 --> 00:22:58,520 Speaker 1: things happening in the background as well, that's right. Just 424 00:22:58,640 --> 00:23:00,840 Speaker 1: like when you look up at the sky you see 425 00:23:00,880 --> 00:23:04,439 Speaker 1: photons from stars. Those are like little localized events. You 426 00:23:04,440 --> 00:23:06,600 Speaker 1: can see them. But then in between all the stars 427 00:23:06,800 --> 00:23:09,040 Speaker 1: is the background, right, is the thing that you're not 428 00:23:09,160 --> 00:23:12,280 Speaker 1: looking for usually, And what we're interested in here is like, 429 00:23:12,480 --> 00:23:16,520 Speaker 1: is there a background to gravitational radiation? Are there things 430 00:23:16,600 --> 00:23:20,439 Speaker 1: between these big events, these big gravitational shouts that we 431 00:23:20,480 --> 00:23:24,000 Speaker 1: can listen to and we can hear and maybe learn something. 432 00:23:24,119 --> 00:23:26,320 Speaker 1: The concept of a background is something everybody should be 433 00:23:26,359 --> 00:23:28,479 Speaker 1: familiar with. Like if you're at a party and you're 434 00:23:28,480 --> 00:23:30,800 Speaker 1: trying to talk to your friend, there's sometimes a lot 435 00:23:30,840 --> 00:23:32,920 Speaker 1: of background noise, or at a restaurant or a bar, 436 00:23:33,000 --> 00:23:35,199 Speaker 1: there can be a lot of background noise, which you know, 437 00:23:35,320 --> 00:23:37,640 Speaker 1: isn't the information you're looking for. You're trying to listen 438 00:23:37,640 --> 00:23:39,800 Speaker 1: to your friends story, trying to seem interested in it, 439 00:23:39,840 --> 00:23:42,200 Speaker 1: but there's always other noise around you, which sometimes makes 440 00:23:42,200 --> 00:23:44,960 Speaker 1: it hard to listen to it. Right, that's the background. Yeah, 441 00:23:45,000 --> 00:23:47,439 Speaker 1: there's might be stuff that you don't maybe want to 442 00:23:47,440 --> 00:23:49,960 Speaker 1: pay attention to, but maybe you do. Maybe there's some 443 00:23:50,040 --> 00:23:52,800 Speaker 1: interesting conversations behind your friends. Yeah, that's right. I like 444 00:23:52,840 --> 00:23:56,120 Speaker 1: eavesdropping in bars, listen to other people's conversations. In this case, 445 00:23:56,200 --> 00:24:00,160 Speaker 1: it's interesting because we only recently became able to serve 446 00:24:00,200 --> 00:24:03,560 Speaker 1: the cosmic gravitational four ground. Right, we were listening for 447 00:24:03,600 --> 00:24:07,280 Speaker 1: gravitational radiation and didn't hear anything for years and years 448 00:24:07,320 --> 00:24:09,720 Speaker 1: and years because we were making our instruments more and 449 00:24:09,760 --> 00:24:12,200 Speaker 1: more sensitive. It's only recently we've been able to hear 450 00:24:12,240 --> 00:24:14,760 Speaker 1: the loud shouts. Right, Only recently we've been able to 451 00:24:14,760 --> 00:24:18,040 Speaker 1: hear your friend at the bar talking in gravitational radiation. 452 00:24:18,240 --> 00:24:20,880 Speaker 1: Now we're getting ambitious. We're like, can we hear what's 453 00:24:20,880 --> 00:24:23,840 Speaker 1: going on between the shouts? Is there anything there? Also? 454 00:24:23,960 --> 00:24:27,320 Speaker 1: And it's interesting that you call it gravitational radiation? Can 455 00:24:27,359 --> 00:24:31,159 Speaker 1: I use it? Is it a technical term? Gravitational radiation? Yeah? Absolutely, 456 00:24:31,400 --> 00:24:34,840 Speaker 1: it's radiation. It's transmission of energy. And when two black 457 00:24:34,840 --> 00:24:37,240 Speaker 1: holes collide, the new black hole that's formed has less 458 00:24:37,280 --> 00:24:40,119 Speaker 1: mass than the masses of the two black holes that 459 00:24:40,200 --> 00:24:42,600 Speaker 1: formed it combined. And the reason is a lot of 460 00:24:42,640 --> 00:24:45,120 Speaker 1: the energy is lost. And it's not lost to light, 461 00:24:45,440 --> 00:24:49,040 Speaker 1: it's not lost the particles. It's lost through gravitational waves. 462 00:24:49,480 --> 00:24:52,399 Speaker 1: And sometimes it's like, you know, five times the mass 463 00:24:52,440 --> 00:24:55,760 Speaker 1: of the Sun is lost in gravitational radiation. So yes, 464 00:24:55,800 --> 00:25:00,240 Speaker 1: it's absolutely the radiation of huge amounts of energy. Interesting. Yeah, 465 00:25:00,320 --> 00:25:03,720 Speaker 1: like it's quantifiable, like it carries energy. It's not just information. 466 00:25:03,920 --> 00:25:06,560 Speaker 1: It has some sort of substance to it, It has 467 00:25:06,560 --> 00:25:08,760 Speaker 1: some energy to it. For example, you could take a 468 00:25:08,880 --> 00:25:12,119 Speaker 1: seventy solar mass black hole, combine it with a thirty 469 00:25:12,119 --> 00:25:14,639 Speaker 1: solar mass black hole, and end up with a ninety 470 00:25:14,720 --> 00:25:18,119 Speaker 1: solar mass black hole, which means that ten masses of 471 00:25:18,119 --> 00:25:21,359 Speaker 1: the Sun's worth of energy was dumped out into the 472 00:25:21,480 --> 00:25:24,840 Speaker 1: universe in gravitational radiation. Now, don't be confused, we're talking 473 00:25:24,840 --> 00:25:30,879 Speaker 1: about gravitational waves, not gravitons. Right. Gravitons are not a 474 00:25:30,960 --> 00:25:34,720 Speaker 1: thing we know exists. It's the theoretical quantization of the 475 00:25:34,760 --> 00:25:39,320 Speaker 1: gravitational field. So we know the gravitational waves exist. Those 476 00:25:39,320 --> 00:25:42,240 Speaker 1: are waves in the gravitational field, but we don't know 477 00:25:42,280 --> 00:25:45,440 Speaker 1: if that field is quantized into like the smallest piece, 478 00:25:45,440 --> 00:25:49,040 Speaker 1: which would be gravitons. So gravitational waves exist, we don't 479 00:25:49,119 --> 00:25:51,919 Speaker 1: know yet if they're made of gravitons. Interesting, So then 480 00:25:51,960 --> 00:25:55,480 Speaker 1: how would you define as the cosmic gravitational background. Is 481 00:25:55,520 --> 00:25:58,879 Speaker 1: it like fainter signals or is it like a hum or? 482 00:25:59,000 --> 00:26:02,200 Speaker 1: Is it like actually always in the gravity of the universe. Yeah, 483 00:26:02,200 --> 00:26:04,840 Speaker 1: it's all of those things. It wouldn't be localized in 484 00:26:04,880 --> 00:26:07,840 Speaker 1: any particular direction. It's not something that comes from one 485 00:26:07,920 --> 00:26:11,800 Speaker 1: particular event, like one of these cataclysmic mergers, and it 486 00:26:11,840 --> 00:26:14,439 Speaker 1: should be an overall hum And I think it's useful 487 00:26:14,640 --> 00:26:18,200 Speaker 1: to go back to the cosmic microwave background radiation as 488 00:26:18,200 --> 00:26:21,200 Speaker 1: a sort of comparison because it's very similar in concept. 489 00:26:21,400 --> 00:26:22,760 Speaker 1: Like when you look at in the night sky you 490 00:26:22,800 --> 00:26:26,320 Speaker 1: see stars and galaxies, but also between those stars and galaxies, 491 00:26:26,359 --> 00:26:29,200 Speaker 1: we are getting light from the very early universe. That's 492 00:26:29,240 --> 00:26:32,520 Speaker 1: the cosmic microwave background radiation, and it's in every direction, 493 00:26:32,520 --> 00:26:35,120 Speaker 1: no matter where you look. And it first appeared as 494 00:26:35,160 --> 00:26:37,680 Speaker 1: a hiss in a radio telescope. We had a whole 495 00:26:37,680 --> 00:26:40,359 Speaker 1: fun episode about how that was discovered. And it's left 496 00:26:40,440 --> 00:26:43,439 Speaker 1: over light from the very early universe from four hundred 497 00:26:43,440 --> 00:26:46,080 Speaker 1: thousand years after the Big Bang. The reason we call 498 00:26:46,160 --> 00:26:48,359 Speaker 1: that the background radiation is again because it's sort of 499 00:26:48,400 --> 00:26:51,960 Speaker 1: everywhere the universe was filled with this plasma and admitted 500 00:26:52,040 --> 00:26:54,439 Speaker 1: this light which was going in all direction. It's like 501 00:26:54,480 --> 00:26:57,680 Speaker 1: it's not coming from a particular thing like a sun 502 00:26:57,960 --> 00:27:00,160 Speaker 1: or a pulsar or something like that. It's like it's 503 00:27:00,200 --> 00:27:03,200 Speaker 1: coming from everywhere, like you hear this his his in 504 00:27:03,359 --> 00:27:06,239 Speaker 1: the signal of the universe everywhere you look. Yeah, and 505 00:27:06,359 --> 00:27:08,480 Speaker 1: it's sort of a funny naming thing because it's called 506 00:27:08,520 --> 00:27:11,000 Speaker 1: the background radiation for that reason that it doesn't come 507 00:27:11,040 --> 00:27:13,440 Speaker 1: from any particular direction. But you know, now we have 508 00:27:13,560 --> 00:27:17,320 Speaker 1: experiments dedicated to just looking for this. So it's like 509 00:27:17,359 --> 00:27:20,000 Speaker 1: you're looking for the background. Is it really still the background? 510 00:27:20,000 --> 00:27:22,280 Speaker 1: It's sort of like your target, it's your signal, right, 511 00:27:22,400 --> 00:27:25,240 Speaker 1: no longer the background. Right, if the background becomes a foreground, 512 00:27:25,359 --> 00:27:28,520 Speaker 1: then what's in the background the background background. We have 513 00:27:28,600 --> 00:27:33,320 Speaker 1: multiple Nobel Prizes awarded, specifically four experiments measuring and analyzing 514 00:27:33,600 --> 00:27:36,960 Speaker 1: ripples and wiggles in the cosmic microwave background. So it's 515 00:27:37,000 --> 00:27:40,400 Speaker 1: definitely you know, worth calling it a foreground something. But anyway, 516 00:27:40,480 --> 00:27:43,879 Speaker 1: you have to call it a background Nobel Prize, like 517 00:27:43,960 --> 00:27:47,200 Speaker 1: a noisy you know, static qui Nobel Prize. Maybe it's 518 00:27:47,200 --> 00:27:49,200 Speaker 1: like an off the record Nobel Prize, you know, like 519 00:27:49,280 --> 00:27:53,359 Speaker 1: this is on background only. Yeah, there you go unofficial. 520 00:27:53,680 --> 00:27:56,199 Speaker 1: The universe doesn't want to speak up about its secrets. 521 00:27:56,200 --> 00:27:58,760 Speaker 1: It just wants to like slip it to us on background. 522 00:27:58,840 --> 00:28:00,960 Speaker 1: I think that would conveniently reduce the number of noble 523 00:28:00,960 --> 00:28:03,200 Speaker 1: prices you haven't want, Daniel. That would be difficult. I 524 00:28:03,240 --> 00:28:05,280 Speaker 1: could be like, look, I have this secret about the universe, 525 00:28:05,400 --> 00:28:07,120 Speaker 1: but I can't tell you how I know it because 526 00:28:07,119 --> 00:28:09,800 Speaker 1: I got it on background from a source. I would 527 00:28:09,800 --> 00:28:12,760 Speaker 1: be pretty disappointing. And of course you gotta protect your sources, 528 00:28:12,840 --> 00:28:16,720 Speaker 1: right absolutely, even if it's the universe. Yeah, So then 529 00:28:16,960 --> 00:28:19,960 Speaker 1: the cosmic microwave background is this sort of leftover light 530 00:28:20,000 --> 00:28:24,280 Speaker 1: from the early universe. What would be the cosmic gravitational background. 531 00:28:24,440 --> 00:28:27,000 Speaker 1: So we don't know exactly because we haven't seen it. 532 00:28:27,200 --> 00:28:30,679 Speaker 1: We only have theoretical ideas for what could be creating it, 533 00:28:31,000 --> 00:28:33,840 Speaker 1: what it might look like, but we're excited to see 534 00:28:33,840 --> 00:28:36,560 Speaker 1: if it's there. The limitation on seeing this thing is 535 00:28:36,600 --> 00:28:40,200 Speaker 1: making our experiments sensitive enough to listen to these very 536 00:28:40,320 --> 00:28:43,960 Speaker 1: very quiet signals, And the challenge there is making your 537 00:28:44,000 --> 00:28:48,800 Speaker 1: experiment insensitive to other things that look like gravitational waves, right, 538 00:28:48,840 --> 00:28:51,400 Speaker 1: that look like this hum or, this hiss. Because the 539 00:28:51,440 --> 00:28:54,040 Speaker 1: way these experiments work. For examples, you have like two 540 00:28:54,120 --> 00:28:59,040 Speaker 1: mirrors hanging miles apart in a tunnel underground, shooting lasers 541 00:28:59,040 --> 00:29:01,400 Speaker 1: back and forth to me sure the distance between them, 542 00:29:01,440 --> 00:29:04,560 Speaker 1: and it's very easy to get wiggles in that distance. 543 00:29:04,600 --> 00:29:06,360 Speaker 1: It's like the mirrors shake a little bit for a 544 00:29:06,480 --> 00:29:09,520 Speaker 1: breeze flows through and moves the mirror. You know, the 545 00:29:09,520 --> 00:29:12,960 Speaker 1: size of a gravitational signal is a tiny, tiny fraction, 546 00:29:13,280 --> 00:29:16,000 Speaker 1: much smaller than the width of a human hair, and 547 00:29:16,080 --> 00:29:18,120 Speaker 1: so it's very hard to isolate these things and just 548 00:29:18,120 --> 00:29:21,040 Speaker 1: sort of like experimentally to make these systems work so 549 00:29:21,120 --> 00:29:23,400 Speaker 1: you can see these signals, and so the challenge is 550 00:29:23,480 --> 00:29:26,680 Speaker 1: making them work even better, making them even more sensitive. 551 00:29:26,840 --> 00:29:29,200 Speaker 1: So now we could pick up like a low level 552 00:29:29,480 --> 00:29:33,240 Speaker 1: omnidirectional hum if it exists, right, And I guess the 553 00:29:33,240 --> 00:29:35,560 Speaker 1: tricky thing is that you know, you have your instrument, 554 00:29:35,640 --> 00:29:38,440 Speaker 1: it's listening to the universe, and it's picking up noise 555 00:29:38,680 --> 00:29:42,240 Speaker 1: from its environment, from the Earth, from the circuits in 556 00:29:42,280 --> 00:29:45,600 Speaker 1: your instruments, but it's also maybe picking up noise from 557 00:29:45,600 --> 00:29:49,440 Speaker 1: the universe itself in gravity right in the gravitational spectrum 558 00:29:49,440 --> 00:29:51,280 Speaker 1: of the universe. And so you want to be able 559 00:29:51,320 --> 00:29:55,080 Speaker 1: to say like Okay, this crazy random noise here that's 560 00:29:55,240 --> 00:29:58,400 Speaker 1: from my experiment, and this crazy random noise here is 561 00:29:58,440 --> 00:30:01,280 Speaker 1: actually from the universe. Is gravity exactly. It will be 562 00:30:01,280 --> 00:30:05,120 Speaker 1: a much more difficult thing to demonstrate we've seen than 563 00:30:05,160 --> 00:30:08,040 Speaker 1: the gravitational waves we've seen so far, because it's easier 564 00:30:08,080 --> 00:30:11,200 Speaker 1: to see things that are like individual cate exclismic events. 565 00:30:11,600 --> 00:30:13,960 Speaker 1: First of all, they're isolated, so you can say it 566 00:30:14,080 --> 00:30:17,000 Speaker 1: happened and then it stopped, whereas the gravitational background is 567 00:30:17,040 --> 00:30:19,520 Speaker 1: going to be like all the time, so you can't 568 00:30:19,520 --> 00:30:21,560 Speaker 1: say like, oh, we turned it on and off. And 569 00:30:21,600 --> 00:30:24,160 Speaker 1: here's the difference. And also, the gravitational waves that we 570 00:30:24,200 --> 00:30:27,640 Speaker 1: have seen have a very particular signature, like when black 571 00:30:27,640 --> 00:30:31,080 Speaker 1: holes swish around each other and create these gravitational waves, 572 00:30:31,200 --> 00:30:33,640 Speaker 1: it's not just like a big screen. We know exactly 573 00:30:33,680 --> 00:30:35,920 Speaker 1: what it should look like. You should start small, and 574 00:30:35,920 --> 00:30:38,160 Speaker 1: should get bigger and bigger and faster and faster as 575 00:30:38,160 --> 00:30:40,720 Speaker 1: they swore a closer and closer. So the gravitational waves 576 00:30:40,760 --> 00:30:43,320 Speaker 1: we're looking for in the foreground have a very particular 577 00:30:43,360 --> 00:30:46,280 Speaker 1: pattern when we first saw them. That's what convinced us 578 00:30:46,320 --> 00:30:48,320 Speaker 1: that we had actually seen them right, that they look 579 00:30:48,440 --> 00:30:51,080 Speaker 1: just like what we expected. If you do these numerical 580 00:30:51,160 --> 00:30:55,080 Speaker 1: relativity calculations that predict the signature of the fingerprint of 581 00:30:55,120 --> 00:30:57,960 Speaker 1: these gravitational waves, that makes it much easier to see 582 00:30:58,000 --> 00:31:00,640 Speaker 1: they come from particular direction, they're very where it lived, 583 00:31:01,080 --> 00:31:03,720 Speaker 1: and they look different from everything else. But as you say, 584 00:31:04,120 --> 00:31:06,480 Speaker 1: we're just looking for a hiss, it's much harder to 585 00:31:06,520 --> 00:31:09,720 Speaker 1: know if that his is coming from gravitational waves or 586 00:31:09,800 --> 00:31:13,360 Speaker 1: from wiggles in your detector. So experimentally it's much much 587 00:31:13,360 --> 00:31:15,440 Speaker 1: more challenging. And I think the idea is that this 588 00:31:15,680 --> 00:31:18,360 Speaker 1: noise in the gravity of the universe and the gravitational 589 00:31:18,480 --> 00:31:21,120 Speaker 1: spectrum of the universe, again, it's not coming from anywhere 590 00:31:21,120 --> 00:31:25,560 Speaker 1: in particular, It's coming from everywhere, and it's maybe made 591 00:31:25,680 --> 00:31:27,880 Speaker 1: up of you know, what would it be made out of. 592 00:31:28,000 --> 00:31:30,920 Speaker 1: Is it made out of like big explosions somewhere else 593 00:31:31,000 --> 00:31:34,040 Speaker 1: that have sort of propagated and diffused throughout the universe? 594 00:31:34,120 --> 00:31:35,840 Speaker 1: Is there any idea? We don't know exactly what it 595 00:31:35,920 --> 00:31:37,840 Speaker 1: might look like, and we can dig in a minute 596 00:31:38,000 --> 00:31:40,920 Speaker 1: about the possibilities what could be generating it and what 597 00:31:40,960 --> 00:31:43,040 Speaker 1: it would look like. But you know, one possibility is 598 00:31:43,080 --> 00:31:45,920 Speaker 1: that it looks sort of like a hiss. Another possibility 599 00:31:46,040 --> 00:31:49,000 Speaker 1: is that it's like very slowly changing, you know, like 600 00:31:49,040 --> 00:31:52,440 Speaker 1: instead of having a wave that changes over seconds the 601 00:31:52,440 --> 00:31:55,080 Speaker 1: way gravitational waves from black holes do, it might be 602 00:31:55,120 --> 00:31:58,440 Speaker 1: like a very gradually changing tide, like we're seeing a 603 00:31:58,440 --> 00:32:04,280 Speaker 1: gravitational wave that slates over like years or decades or centuries. 604 00:32:04,680 --> 00:32:06,560 Speaker 1: And that again, it would be much harder to see 605 00:32:06,600 --> 00:32:08,440 Speaker 1: because we like to look for the pattern that tells 606 00:32:08,520 --> 00:32:10,880 Speaker 1: us that there was actually something there. But again I 607 00:32:10,920 --> 00:32:12,720 Speaker 1: think it is that you would be looking for like 608 00:32:12,760 --> 00:32:17,880 Speaker 1: a hum in the distortion of gravity in the universe, right. 609 00:32:18,120 --> 00:32:20,120 Speaker 1: We have to make sure that you know you're measuring 610 00:32:20,400 --> 00:32:24,040 Speaker 1: the wiggles in gravity really well, and then you'd be 611 00:32:24,040 --> 00:32:26,880 Speaker 1: looking for some sort of activity there that wasn't like coherent. 612 00:32:26,920 --> 00:32:30,360 Speaker 1: There wasn't like a spike or a particular shape. You 613 00:32:30,360 --> 00:32:32,840 Speaker 1: need to establish that you're seeing a signal that is 614 00:32:32,920 --> 00:32:35,960 Speaker 1: louder than the noise in your device, that your device 615 00:32:36,080 --> 00:32:38,800 Speaker 1: is less noise than the signal you are seeing, which 616 00:32:38,840 --> 00:32:40,840 Speaker 1: is tricky. And then what it would look like is, 617 00:32:40,880 --> 00:32:42,760 Speaker 1: as you say, it would be like sort of random 618 00:32:42,840 --> 00:32:45,200 Speaker 1: ripples in space and time, the way the cosmic microwave 619 00:32:45,200 --> 00:32:47,880 Speaker 1: background radiation sort of has like little ripples in it. 620 00:32:48,120 --> 00:32:50,080 Speaker 1: You get like a little distortion this direction, a little 621 00:32:50,080 --> 00:32:52,600 Speaker 1: distortion not direction, a little distortion the other direction. And 622 00:32:52,680 --> 00:32:55,040 Speaker 1: all these distortions would be much much smaller than the 623 00:32:55,080 --> 00:32:58,160 Speaker 1: signals we've already seen. It would be even fainter. Right. 624 00:32:58,320 --> 00:33:00,400 Speaker 1: And what's cool is that with our instrument snow like 625 00:33:00,520 --> 00:33:05,280 Speaker 1: Lego and Virgo, we can tell which way gravitational waves 626 00:33:05,280 --> 00:33:08,239 Speaker 1: are coming from. Right, so this would also tell you 627 00:33:08,280 --> 00:33:11,280 Speaker 1: that they're coming from everywhere, not just in a particular direction. 628 00:33:11,320 --> 00:33:13,920 Speaker 1: That's right. We can tell the direction of gravitational waves 629 00:33:14,200 --> 00:33:16,880 Speaker 1: mostly because they take time to propagate, and so we 630 00:33:16,920 --> 00:33:20,000 Speaker 1: can see them in different observatories around the world. There's 631 00:33:20,040 --> 00:33:23,160 Speaker 1: one in Louisiana, one in Washington State, and one in 632 00:33:23,240 --> 00:33:26,200 Speaker 1: Italy does Virgo, and as the gravitational waves sort of 633 00:33:26,240 --> 00:33:29,560 Speaker 1: washes over the Earth, it arrives at one place before 634 00:33:29,600 --> 00:33:32,560 Speaker 1: another place, and that timing information allows us to figure 635 00:33:32,560 --> 00:33:34,880 Speaker 1: out so where in the sky it might have been 636 00:33:34,920 --> 00:33:37,840 Speaker 1: coming from. But as you say, is cosmic gravitational background 637 00:33:37,920 --> 00:33:40,880 Speaker 1: would be coming from all directions. Cool. Well, let's get 638 00:33:40,880 --> 00:33:44,440 Speaker 1: into now whether or not this gravitational background really does 639 00:33:44,480 --> 00:33:47,040 Speaker 1: exist and what could be making it and what he 640 00:33:47,080 --> 00:33:49,200 Speaker 1: can tell us about the universe. But first, let's take 641 00:33:49,240 --> 00:34:05,640 Speaker 1: another quick break. All right, we're talking about finding wads 642 00:34:06,000 --> 00:34:09,880 Speaker 1: in the cosmic gravitational background of the universe. Then you know, like, 643 00:34:10,600 --> 00:34:14,880 Speaker 1: is there something interesting in the background noise of gravity 644 00:34:14,920 --> 00:34:17,560 Speaker 1: in the universe. Yeah, we don't know yet whether it's 645 00:34:17,600 --> 00:34:20,120 Speaker 1: out there, right, This is like an idea people have had. 646 00:34:20,320 --> 00:34:22,960 Speaker 1: There are theories that suggest it might be out there 647 00:34:23,000 --> 00:34:25,800 Speaker 1: and could contain like treasures of the universe, and people 648 00:34:25,840 --> 00:34:28,200 Speaker 1: have looked for it, but we don't really have a 649 00:34:28,200 --> 00:34:31,960 Speaker 1: conclusive evidence for it so far. Like Lego and Virgo 650 00:34:32,239 --> 00:34:35,680 Speaker 1: are best gravitational wave detectors have looked for us very specifically. 651 00:34:36,000 --> 00:34:38,480 Speaker 1: But what they see sort of in between the loud 652 00:34:38,520 --> 00:34:41,760 Speaker 1: shouts from black holes, looks to them just like noise 653 00:34:41,840 --> 00:34:44,680 Speaker 1: in their detector. Like they can estimate how much noise 654 00:34:44,719 --> 00:34:46,680 Speaker 1: they expect to have in their detector, and that's what 655 00:34:46,760 --> 00:34:49,640 Speaker 1: they see, and their estimate for their noise is above 656 00:34:50,040 --> 00:34:53,879 Speaker 1: anything that anybody predicts for cosmic gravitational background. So sort 657 00:34:53,880 --> 00:34:55,920 Speaker 1: of like you go into a library and you're listening 658 00:34:55,960 --> 00:34:58,919 Speaker 1: for whispers, but you know you can't hear the whispers yet. 659 00:34:58,960 --> 00:35:01,480 Speaker 1: All you can hear is like electronic noise in your device, 660 00:35:01,560 --> 00:35:03,640 Speaker 1: and that's what you hear, so you don't see anything. 661 00:35:03,680 --> 00:35:06,160 Speaker 1: We also haven't really learned anything yet. You just learned 662 00:35:06,160 --> 00:35:08,560 Speaker 1: that you need a better listening device. Oh, I see. 663 00:35:08,600 --> 00:35:11,719 Speaker 1: It's like, we know we have kind of a crappy microphone, 664 00:35:11,920 --> 00:35:14,680 Speaker 1: so we know that with our current set up, we 665 00:35:14,719 --> 00:35:17,359 Speaker 1: can't listen to this background radiation, which means that we 666 00:35:17,440 --> 00:35:20,040 Speaker 1: maybe don't know if it exists or not. Like this 667 00:35:20,160 --> 00:35:24,040 Speaker 1: is a theoretical concept, then this cosmic gravitational background or 668 00:35:24,400 --> 00:35:26,680 Speaker 1: does the theory pretty much predict that it exists, we 669 00:35:26,840 --> 00:35:29,120 Speaker 1: just can't measure it. Yeah, but first I gotta stand 670 00:35:29,160 --> 00:35:30,839 Speaker 1: up for Lego and Virgo, because you just called them 671 00:35:30,840 --> 00:35:35,719 Speaker 1: crappy microphones are like the world's most amazing supersensitive microphones, 672 00:35:35,840 --> 00:35:39,480 Speaker 1: just not quite supersensitive enough to listen to this incredibly 673 00:35:39,520 --> 00:35:42,360 Speaker 1: faint signal. But you're you're absolutely right. So this is 674 00:35:42,400 --> 00:35:45,120 Speaker 1: something people have theorized, and you know, there were moments 675 00:35:45,200 --> 00:35:47,680 Speaker 1: when people thought they might have seen it. Lego hasn't 676 00:35:47,680 --> 00:35:49,960 Speaker 1: seen it yet, but there was a moment people might 677 00:35:49,960 --> 00:35:53,520 Speaker 1: remember this experiment BICEP two something on the South Pole, 678 00:35:53,760 --> 00:35:57,560 Speaker 1: which thought they saw the effect of this radiation on 679 00:35:57,680 --> 00:36:01,319 Speaker 1: the cosmic microwave background radiation they can measure, and they 680 00:36:01,360 --> 00:36:03,520 Speaker 1: had this whole claim that they had discovered it and 681 00:36:03,560 --> 00:36:06,840 Speaker 1: it was evidence that there was cosmic gravitational background radiation 682 00:36:06,880 --> 00:36:10,319 Speaker 1: which was tweaking the cosmic microwave background radiation. But it 683 00:36:10,360 --> 00:36:12,319 Speaker 1: turns out it was wrong. It was just that they 684 00:36:12,360 --> 00:36:14,800 Speaker 1: didn't understand how much dust there was in the university 685 00:36:14,960 --> 00:36:17,440 Speaker 1: caused a fake signal. So there was a real excitement 686 00:36:17,480 --> 00:36:19,799 Speaker 1: there for a while, and then that faded. And now 687 00:36:19,920 --> 00:36:23,400 Speaker 1: recently there's another experiment which is super cool, which it 688 00:36:23,480 --> 00:36:27,439 Speaker 1: uses a galaxy size measuring device and they think they've 689 00:36:27,480 --> 00:36:30,960 Speaker 1: seen evidence for this cosmic gravitational background. Why you mean 690 00:36:30,960 --> 00:36:33,080 Speaker 1: we have something that big that we can use to 691 00:36:33,160 --> 00:36:36,080 Speaker 1: measure the gravitational ways of the universe. We have something 692 00:36:36,200 --> 00:36:38,480 Speaker 1: the size of a galaxy. Yeah, well, we have our 693 00:36:38,560 --> 00:36:40,920 Speaker 1: galaxy and people have figured out how to use the 694 00:36:41,000 --> 00:36:44,680 Speaker 1: galaxy as a gravitational way of observatory. We're gonna do 695 00:36:44,719 --> 00:36:47,120 Speaker 1: a whole episode on this because it's super awesome. But 696 00:36:47,440 --> 00:36:50,120 Speaker 1: very briefly, if you look at pulsars out there in 697 00:36:50,160 --> 00:36:53,520 Speaker 1: the universe, these are fast rotating neutron stars that send 698 00:36:53,600 --> 00:36:56,719 Speaker 1: us super super regular pulses of light, and you can 699 00:36:56,760 --> 00:36:58,920 Speaker 1: tell if those things get pushed away from us or 700 00:36:58,960 --> 00:37:02,239 Speaker 1: pulled towards us when a gravitational wave passes, because it 701 00:37:02,320 --> 00:37:05,440 Speaker 1: changes when those light pulses arrive. And there's an experiment 702 00:37:05,640 --> 00:37:07,759 Speaker 1: that's looked at some of these very regular pulses. It's 703 00:37:07,800 --> 00:37:11,000 Speaker 1: called nano grab and they see a signal which looks 704 00:37:11,080 --> 00:37:14,799 Speaker 1: like cosmic gravitational background radiation. But you know, it's early 705 00:37:14,920 --> 00:37:17,840 Speaker 1: days and there have been false claims before, so nobody's 706 00:37:17,880 --> 00:37:20,080 Speaker 1: really accepted this yet. It's just sort of like an 707 00:37:20,080 --> 00:37:23,759 Speaker 1: exciting possibility, all right. So we're actively listening for this 708 00:37:23,880 --> 00:37:26,359 Speaker 1: background or trying to listen to it. And it's sort 709 00:37:26,400 --> 00:37:29,440 Speaker 1: of a funny thing, right, It's like trying to see 710 00:37:29,480 --> 00:37:31,920 Speaker 1: if you can listen to the background noise and in 711 00:37:31,960 --> 00:37:35,440 Speaker 1: a noisy bar, right or in a quiet library, it's 712 00:37:35,440 --> 00:37:37,720 Speaker 1: sort of like you're trying to get everyone to quiet 713 00:37:37,760 --> 00:37:40,200 Speaker 1: down so you can see if there is sort of 714 00:37:40,200 --> 00:37:43,239 Speaker 1: a his there or not exactly. If you're curious about 715 00:37:43,280 --> 00:37:45,759 Speaker 1: what's going on outside your house, for example, you turn 716 00:37:45,800 --> 00:37:48,239 Speaker 1: off the TV and Telbrady shut up and listen to 717 00:37:48,239 --> 00:37:51,160 Speaker 1: see if it's just crickets or something else going on. Outside. 718 00:37:51,200 --> 00:37:54,120 Speaker 1: Did you turn this into a scary movie? Like what's 719 00:37:54,160 --> 00:37:57,440 Speaker 1: out there? What's out there that we we can't hear? Yeah, 720 00:37:57,560 --> 00:37:59,439 Speaker 1: And there's a whole range of reasons why we think 721 00:37:59,480 --> 00:38:02,759 Speaker 1: the cosmic a gravitational background might exist, and there's some 722 00:38:02,840 --> 00:38:05,120 Speaker 1: like kind of boring possibilities to explain it, and then 723 00:38:05,120 --> 00:38:08,759 Speaker 1: there's some crazy, exciting, bonkers possibilities. I guess, you know, 724 00:38:08,800 --> 00:38:12,640 Speaker 1: maybe as many of our listeners might be wondering, like 725 00:38:12,719 --> 00:38:15,360 Speaker 1: does it make sense that there wouldn't be a cosmic 726 00:38:15,440 --> 00:38:20,160 Speaker 1: gravitational background? Like things are everything causes gravitational ripples, so 727 00:38:20,280 --> 00:38:22,640 Speaker 1: why wouldn't there be a background exactly? And that's the 728 00:38:22,680 --> 00:38:27,600 Speaker 1: sort of most boring explanation is everything causes gravitational waves, 729 00:38:27,640 --> 00:38:30,200 Speaker 1: Like every time you accelerate in your car, you cause 730 00:38:30,280 --> 00:38:33,160 Speaker 1: a little gravitational wave. As the Earth moves around the Sun, 731 00:38:33,280 --> 00:38:35,880 Speaker 1: it's generating gravitational waves, and there's a lot of that 732 00:38:35,920 --> 00:38:38,400 Speaker 1: stuff going on in the universe. Most of that is 733 00:38:38,440 --> 00:38:40,839 Speaker 1: really really small, but the idea is that it sort 734 00:38:40,840 --> 00:38:44,520 Speaker 1: of adds up to this like overall stochastic background, and 735 00:38:44,560 --> 00:38:47,680 Speaker 1: in particular, black holes that are too far away for 736 00:38:47,760 --> 00:38:51,120 Speaker 1: us to like make out individually should add up to 737 00:38:51,200 --> 00:38:54,440 Speaker 1: like an overall sort of noise level in the background. 738 00:38:54,600 --> 00:38:57,440 Speaker 1: There should be black holes merging and neutron stars colliding 739 00:38:57,480 --> 00:39:00,120 Speaker 1: with black holes all over the galaxy. Some of them 740 00:39:00,120 --> 00:39:02,719 Speaker 1: are too far away for us to like pick out individually, 741 00:39:02,840 --> 00:39:05,080 Speaker 1: but they should turn into like a hum, the way 742 00:39:05,120 --> 00:39:07,520 Speaker 1: like a whole crowd in a baseball stadium. You can't 743 00:39:07,520 --> 00:39:09,719 Speaker 1: make out their conversations, but you can tell the people 744 00:39:09,719 --> 00:39:12,640 Speaker 1: are talking. You hear this like overall hum. So people 745 00:39:12,680 --> 00:39:15,040 Speaker 1: expect that that can tell us something about like the 746 00:39:15,080 --> 00:39:19,919 Speaker 1: overall rate at which gravitational waves are generated by distant objects. Right, 747 00:39:20,000 --> 00:39:22,560 Speaker 1: But I guess is it possible that maybe you know, 748 00:39:22,760 --> 00:39:25,799 Speaker 1: I'm just thinking, like maybe the universe could be quantized 749 00:39:25,920 --> 00:39:29,080 Speaker 1: enough so that at some point there is no noise, 750 00:39:29,320 --> 00:39:30,719 Speaker 1: do you know what I mean? Like, maybe at some 751 00:39:30,800 --> 00:39:33,399 Speaker 1: point there's a minimum size to these irritation and ways 752 00:39:33,400 --> 00:39:35,760 Speaker 1: at which point and since everything is so faint, everything 753 00:39:35,880 --> 00:39:39,160 Speaker 1: just flattens out. Is that possible? It's possible. But you know, 754 00:39:39,280 --> 00:39:42,960 Speaker 1: take an analogy to photons coming from distant galaxies. You 755 00:39:43,000 --> 00:39:44,719 Speaker 1: look up in the night sky. You can't tell that 756 00:39:44,760 --> 00:39:47,239 Speaker 1: there are galaxies there because they're so distant, Because the 757 00:39:47,280 --> 00:39:51,120 Speaker 1: photons aren't arriving very frequently because they're quantized, right, It's 758 00:39:51,120 --> 00:39:53,439 Speaker 1: not like you can get point o one photon. Every 759 00:39:53,440 --> 00:39:55,320 Speaker 1: second you get one and then a minute later you 760 00:39:55,360 --> 00:39:58,279 Speaker 1: get another one. But they are still coming, and so 761 00:39:58,320 --> 00:40:00,680 Speaker 1: there is a non zero rate there. It's not like 762 00:40:00,680 --> 00:40:02,680 Speaker 1: it goes exactly to zero. They just get less and 763 00:40:02,760 --> 00:40:06,200 Speaker 1: less frequent. And so if gravitational waves are made of 764 00:40:06,239 --> 00:40:09,719 Speaker 1: gravitons and they're super duper distant and faint, we should 765 00:40:09,719 --> 00:40:12,160 Speaker 1: still be getting gravitons every once in a while, even 766 00:40:12,239 --> 00:40:15,799 Speaker 1: from the most distant sources of gravitational radiation. But yeah, 767 00:40:15,840 --> 00:40:18,160 Speaker 1: that would be really challenging to pick up, right. But 768 00:40:18,239 --> 00:40:21,480 Speaker 1: I guess you know, photons are sort of discretized in direction, 769 00:40:21,680 --> 00:40:25,200 Speaker 1: but gravitational waves kind of goes out in all directions, right, 770 00:40:25,280 --> 00:40:27,200 Speaker 1: like a ripple in a pond. Yeah, but you know, 771 00:40:27,239 --> 00:40:29,839 Speaker 1: a star sends out photons in all directions. It's really 772 00:40:29,840 --> 00:40:32,719 Speaker 1: equivalent when a black hole merger event happens. It sends 773 00:40:32,719 --> 00:40:35,719 Speaker 1: out gravitational waves in every direction. We just only pick 774 00:40:35,800 --> 00:40:38,040 Speaker 1: them up from one direction, and so we would be 775 00:40:38,040 --> 00:40:41,080 Speaker 1: picking up the gravitons from those events. And if these 776 00:40:41,080 --> 00:40:43,520 Speaker 1: things are happening everywhere, we should be getting gravitons and 777 00:40:43,560 --> 00:40:47,200 Speaker 1: gravitational waves in every direction from all these distant events. 778 00:40:47,239 --> 00:40:49,279 Speaker 1: And so this is, you know, what people expect at 779 00:40:49,280 --> 00:40:51,800 Speaker 1: a very bare minimum. Because we know the black holes 780 00:40:51,840 --> 00:40:55,000 Speaker 1: are generating gravitational waves, we should be able to pick 781 00:40:55,040 --> 00:40:59,360 Speaker 1: out at least the gravitational background from these distant events. Interesting, 782 00:40:59,360 --> 00:41:03,040 Speaker 1: so we think there's definitely a cosmic gravitational background from 783 00:41:03,080 --> 00:41:05,520 Speaker 1: just because we know there's things happening in the universe 784 00:41:05,520 --> 00:41:07,799 Speaker 1: that are making them. So it makes sense that we 785 00:41:07,840 --> 00:41:11,319 Speaker 1: would be sort of inundated with the faint ripples from 786 00:41:11,360 --> 00:41:13,400 Speaker 1: all of these events, even things other than you know, 787 00:41:13,480 --> 00:41:16,280 Speaker 1: black hole mergers. Even for example, when a star collapses 788 00:41:16,280 --> 00:41:18,759 Speaker 1: into a black hole, you get gravitational waves. When a 789 00:41:18,840 --> 00:41:22,200 Speaker 1: supernova goes off, you get gravitational waves. If a supernova 790 00:41:22,200 --> 00:41:24,960 Speaker 1: goes off near a black hole, like JJ was suggesting, 791 00:41:25,040 --> 00:41:27,440 Speaker 1: you get gravitational waves. So we should be able to 792 00:41:27,440 --> 00:41:29,960 Speaker 1: see all these things sort of like added up all together, right, 793 00:41:30,000 --> 00:41:31,879 Speaker 1: but it might be so faint that we can't see 794 00:41:31,920 --> 00:41:34,400 Speaker 1: them or hear them. They are definitely too faint for 795 00:41:34,440 --> 00:41:36,800 Speaker 1: us to see them now. But you know, with future 796 00:41:36,840 --> 00:41:40,360 Speaker 1: observatories and improvements in our technology, we should in principle 797 00:41:40,400 --> 00:41:42,440 Speaker 1: be able to see it if it's there, right, all right. 798 00:41:42,480 --> 00:41:46,560 Speaker 1: So that's one possible source of cosmic gravitational background. What 799 00:41:46,600 --> 00:41:48,799 Speaker 1: are some of the more bonkers sources that might be 800 00:41:48,840 --> 00:41:52,440 Speaker 1: out there? One really exciting one is a mission of gravitons. 801 00:41:52,960 --> 00:41:57,520 Speaker 1: You know, in some theories, gravitons are the quantization of gravity. 802 00:41:57,880 --> 00:42:00,560 Speaker 1: Remember that our theory of gravity general real activity is 803 00:42:00,560 --> 00:42:02,880 Speaker 1: a classical theory. It says that you can have any 804 00:42:03,120 --> 00:42:07,120 Speaker 1: arbitrarily small distance, or any arbitrarilly small amount of energy, 805 00:42:07,200 --> 00:42:10,680 Speaker 1: or any arbitrarily small slice of time. The quantum mechanics 806 00:42:10,840 --> 00:42:13,440 Speaker 1: says that's probably not true, and the theory of quantum 807 00:42:13,440 --> 00:42:16,440 Speaker 1: gravity would have gravitons in it, as we've said before, 808 00:42:16,600 --> 00:42:19,640 Speaker 1: like the basic element of gravity, and these things should 809 00:42:19,640 --> 00:42:22,799 Speaker 1: be emitted basically any time anything happens, you know, when 810 00:42:22,800 --> 00:42:26,399 Speaker 1: a particle gets accelerated, it should emit a graviton, When 811 00:42:26,440 --> 00:42:29,760 Speaker 1: an electron jumps down an energy level, it should emit 812 00:42:29,800 --> 00:42:32,960 Speaker 1: a graviton. And so in principle the universe is filled 813 00:42:33,000 --> 00:42:37,400 Speaker 1: with these gravitons, and they would be very very high frequency. 814 00:42:37,520 --> 00:42:40,200 Speaker 1: Like the gravitons we've seen so far, have an oscillation 815 00:42:40,280 --> 00:42:42,600 Speaker 1: time of like you know, a few seconds, these would 816 00:42:42,640 --> 00:42:45,719 Speaker 1: be much much higher frequency, like you know, mega hurts 817 00:42:45,719 --> 00:42:48,879 Speaker 1: sort of gravitons, and so that's exciting because it would 818 00:42:48,920 --> 00:42:51,520 Speaker 1: be like a signal of quantum gravity, right, But do 819 00:42:51,600 --> 00:42:54,560 Speaker 1: they need to be gravitons, Like when a adom relaxed 820 00:42:54,600 --> 00:42:58,279 Speaker 1: us from an excited state doesn't also generate a gravitational 821 00:42:58,480 --> 00:43:00,799 Speaker 1: wave like a regular wave. It does, But now we're 822 00:43:00,800 --> 00:43:03,680 Speaker 1: talking about a quantum particle, and a quantum particle should 823 00:43:03,680 --> 00:43:08,960 Speaker 1: emit quantized bits of radiation, right, it can't admit classical radiation, 824 00:43:09,480 --> 00:43:11,399 Speaker 1: And so this is something we don't understand. We don't 825 00:43:11,440 --> 00:43:14,480 Speaker 1: know how to do gravitational calculations for a particle, for 826 00:43:14,520 --> 00:43:17,560 Speaker 1: a quantum object that requires the theory of quantum gravity. 827 00:43:17,640 --> 00:43:20,680 Speaker 1: We just don't have, so general relativity like can't tell 828 00:43:20,719 --> 00:43:22,799 Speaker 1: you what happens to the gravity of a particle. And 829 00:43:22,800 --> 00:43:25,760 Speaker 1: we can't really do those experiments very easily because particles 830 00:43:25,760 --> 00:43:28,920 Speaker 1: have almost no detectable gravity because there's so light in 831 00:43:29,040 --> 00:43:32,120 Speaker 1: mass and gravity is so weak. So we just don't know. 832 00:43:32,560 --> 00:43:34,680 Speaker 1: But you know, maybe all those particles out there are 833 00:43:34,719 --> 00:43:37,200 Speaker 1: sort of like humming in gravity and we can pick 834 00:43:37,280 --> 00:43:39,480 Speaker 1: up like the some of them like, maybe all the 835 00:43:39,520 --> 00:43:43,239 Speaker 1: particles in the universe sending us gravitons simultaneously would be 836 00:43:43,280 --> 00:43:45,920 Speaker 1: something we might be able to detect. Interesting. I think 837 00:43:45,920 --> 00:43:48,600 Speaker 1: they're saying that, maybe, like the gravitational background of the 838 00:43:48,680 --> 00:43:52,040 Speaker 1: universe is not coming from these giant events and supernovas 839 00:43:52,080 --> 00:43:55,000 Speaker 1: and black holes gliding, and it might be being generated 840 00:43:55,040 --> 00:43:57,120 Speaker 1: by everything like you and I just sitting here. It 841 00:43:57,160 --> 00:44:01,240 Speaker 1: could be generating gravitational noise. Yeah, we should be in theory, 842 00:44:01,280 --> 00:44:02,960 Speaker 1: and we should be able to measure it. And if 843 00:44:02,960 --> 00:44:05,279 Speaker 1: we see it and we measure its frequency, we can 844 00:44:05,360 --> 00:44:08,080 Speaker 1: use that to understand how they're being generated, the same 845 00:44:08,120 --> 00:44:10,120 Speaker 1: way we look at the frequency of everything else, and 846 00:44:10,160 --> 00:44:13,400 Speaker 1: we see emission from hydrogen, for example, at a particular frequency. 847 00:44:13,680 --> 00:44:17,040 Speaker 1: We see transitions in lithium gas at a particular frequency. 848 00:44:17,160 --> 00:44:20,120 Speaker 1: So these would be like a fingerprint for what's generating 849 00:44:20,160 --> 00:44:23,799 Speaker 1: gravitational waves in the universe. Who tells something about gravity 850 00:44:23,840 --> 00:44:26,239 Speaker 1: and the composition of the universe. It would be amazing 851 00:44:26,480 --> 00:44:30,560 Speaker 1: to see gravitons emitted as the cosmic gravitational background. And 852 00:44:30,600 --> 00:44:33,279 Speaker 1: what about some of the other bonkers possibilities that are 853 00:44:33,320 --> 00:44:36,439 Speaker 1: making this cosmic gravitational background. One that gets me really 854 00:44:36,440 --> 00:44:40,400 Speaker 1: excited are gravitational waves emitted from the very very early universe. 855 00:44:40,920 --> 00:44:43,120 Speaker 1: Our theory of what happened in the very beginning of 856 00:44:43,120 --> 00:44:46,560 Speaker 1: the universe is called inflation. It suggests that space was 857 00:44:46,640 --> 00:44:49,799 Speaker 1: stretched by a ridiculous amount, by like a factor of 858 00:44:49,880 --> 00:44:52,239 Speaker 1: ten to the thirty in a short amount of time, 859 00:44:52,280 --> 00:44:54,880 Speaker 1: like tend to the minus thirty. When you do that, 860 00:44:54,960 --> 00:44:57,799 Speaker 1: you've got to generate gravitational waves because that's like the 861 00:44:57,800 --> 00:45:00,799 Speaker 1: biggest ripple in space has ever seen, right, So there 862 00:45:00,800 --> 00:45:04,440 Speaker 1: should be huge gravitational waves left over from that, because, 863 00:45:04,640 --> 00:45:07,960 Speaker 1: like the CMB, it happened everywhere all at once, so 864 00:45:08,000 --> 00:45:10,920 Speaker 1: it should be like a cacophony of gravitational waves. But 865 00:45:11,040 --> 00:45:14,200 Speaker 1: over the fourteen billion years since, they've probably gotten stretched 866 00:45:14,200 --> 00:45:17,280 Speaker 1: out and smoothed over. And so this would be exciting 867 00:45:17,280 --> 00:45:20,400 Speaker 1: to detect because it would probe the very very very 868 00:45:20,520 --> 00:45:23,640 Speaker 1: very early universe. Like people talk about how the CMB 869 00:45:23,840 --> 00:45:26,239 Speaker 1: tells us about the Big Bang, it doesn't really. It 870 00:45:26,280 --> 00:45:30,120 Speaker 1: tells us about a plasma that's formed four hundred thousand 871 00:45:30,200 --> 00:45:32,600 Speaker 1: years later. It's like reading about the birth of Jesus 872 00:45:32,600 --> 00:45:35,040 Speaker 1: from somebody who wasn't there, who wrote like hundreds of 873 00:45:35,160 --> 00:45:38,440 Speaker 1: years later. Gravitational waves from inflation would come from like 874 00:45:38,600 --> 00:45:41,440 Speaker 1: ten to the minus thirty two seconds after the beginning 875 00:45:41,480 --> 00:45:43,759 Speaker 1: of the universe. So it's like really a first hand 876 00:45:43,760 --> 00:45:46,160 Speaker 1: account of the beginning of the universe. If we could 877 00:45:46,160 --> 00:45:48,480 Speaker 1: see it, it would tell us a huge amount about 878 00:45:48,520 --> 00:45:51,680 Speaker 1: how the universe actually began. All right, Yeah, interesting, I 879 00:45:51,680 --> 00:45:55,360 Speaker 1: guess you know, anything with mass and energy affects gravity, right, 880 00:45:55,440 --> 00:45:57,960 Speaker 1: or it creates gravity or and so anytime you have 881 00:45:58,000 --> 00:46:00,560 Speaker 1: a change in the universe, or anything really happening in 882 00:46:00,560 --> 00:46:04,439 Speaker 1: the universe, it's going to generate a gravitation a ripple, right, Yeah, 883 00:46:04,480 --> 00:46:06,600 Speaker 1: even like the beginning of the universe, that must have 884 00:46:06,600 --> 00:46:10,399 Speaker 1: generated a bunch of ripples. Yeah, huge ribbles exactly. Tsunamis 885 00:46:10,440 --> 00:46:14,759 Speaker 1: of gravitational waves. You could probably serve them. Yeah, with 886 00:46:14,880 --> 00:46:17,480 Speaker 1: your friend Walda on a surfboard. Look, I know you 887 00:46:17,560 --> 00:46:21,719 Speaker 1: keep trying to include him. I just don't like the guy. Okay, 888 00:46:21,960 --> 00:46:24,400 Speaker 1: what do you have against Walda? I don't know. He 889 00:46:24,520 --> 00:46:27,600 Speaker 1: just won't let me find him. You know, he's just elusive. 890 00:46:28,560 --> 00:46:32,040 Speaker 1: He's a sneaky guy. But sneaky particles are totally cool 891 00:46:32,040 --> 00:46:34,640 Speaker 1: with sneaky particles, all right, So then what's the last 892 00:46:34,640 --> 00:46:38,600 Speaker 1: possibility here that might be causing a background in the universe. 893 00:46:38,760 --> 00:46:41,279 Speaker 1: The last possibility is the most bonkers, and these are 894 00:46:41,600 --> 00:46:44,960 Speaker 1: cosmic strings. We talked about this one in the podcast 895 00:46:45,000 --> 00:46:47,920 Speaker 1: Now a couple of years ago. They're like cracks in 896 00:46:48,000 --> 00:46:50,959 Speaker 1: space and time. We are used as spacetime being sort 897 00:46:50,960 --> 00:46:53,000 Speaker 1: of smooth. If you go from here to there, you 898 00:46:53,040 --> 00:46:55,319 Speaker 1: can sort of just like slide through space. But we 899 00:46:55,360 --> 00:46:57,880 Speaker 1: don't really understand how space was formed, and as the 900 00:46:57,960 --> 00:47:01,520 Speaker 1: universe cooled, it might have like formed differently in different regions, 901 00:47:01,600 --> 00:47:05,279 Speaker 1: leading to like weird discontinuities, like parts of space are 902 00:47:05,280 --> 00:47:07,680 Speaker 1: a little different here and a little different there, and 903 00:47:07,680 --> 00:47:10,480 Speaker 1: at the boundaries there can be these cracks where like 904 00:47:10,520 --> 00:47:13,480 Speaker 1: space changes from one state to another, And so these 905 00:47:13,480 --> 00:47:16,719 Speaker 1: would be like long filaments, maybe even you know, like 906 00:47:16,840 --> 00:47:19,960 Speaker 1: thousands of light years long, that have like cracks in 907 00:47:20,000 --> 00:47:23,240 Speaker 1: space and time, and as they wiggle, they would generate 908 00:47:23,280 --> 00:47:26,040 Speaker 1: gravitational waves. And there's some theories that like the ends 909 00:47:26,040 --> 00:47:29,399 Speaker 1: of the wiggle really fast like a whip, causing these 910 00:47:29,440 --> 00:47:33,200 Speaker 1: crazy gravitational waves. So if that's happening all over the universe, 911 00:47:33,239 --> 00:47:35,160 Speaker 1: we might be able to pick up some of those 912 00:47:35,200 --> 00:47:38,600 Speaker 1: signals and detect the existence of these cosmic strings. Whoa, 913 00:47:39,320 --> 00:47:42,080 Speaker 1: it's like the universe was a giant guitar, and like 914 00:47:42,160 --> 00:47:45,640 Speaker 1: there's giant light years long strings that are you know, 915 00:47:45,719 --> 00:47:48,480 Speaker 1: basically making no it's music, right, Yeah, we don't know 916 00:47:48,520 --> 00:47:51,080 Speaker 1: if they exist. It's a super cool theory. If we 917 00:47:51,120 --> 00:47:53,000 Speaker 1: do find them, we would tell us that we understand 918 00:47:53,080 --> 00:47:56,000 Speaker 1: something deep about how space and time sort of formed 919 00:47:56,120 --> 00:47:58,319 Speaker 1: in the early universe. You can think about them sort 920 00:47:58,360 --> 00:48:00,719 Speaker 1: of like the way ice isn't as clear. If you 921 00:48:01,040 --> 00:48:03,719 Speaker 1: take water and you cool it down, you get these 922 00:48:03,760 --> 00:48:06,880 Speaker 1: cracks sometimes because it doesn't all crystallize in exactly the 923 00:48:06,960 --> 00:48:09,319 Speaker 1: same way. And so this would really tell us something 924 00:48:09,360 --> 00:48:12,120 Speaker 1: about how space itself formed in the very early universe. 925 00:48:12,200 --> 00:48:15,200 Speaker 1: Would be super awesome. That's my new theory of the 926 00:48:15,239 --> 00:48:17,880 Speaker 1: origin of the universe. Dandium. When new religion, it's that 927 00:48:17,960 --> 00:48:21,279 Speaker 1: the universe it's she's a giant guitar played by a 928 00:48:21,320 --> 00:48:27,319 Speaker 1: giant rock star named Waldo. Waldo is um we just 929 00:48:27,360 --> 00:48:29,399 Speaker 1: found it a new religion, all right, So I guess 930 00:48:29,440 --> 00:48:32,239 Speaker 1: when one final question is, how would we know which 931 00:48:32,280 --> 00:48:34,680 Speaker 1: of these origins of the background might be, Like do 932 00:48:34,760 --> 00:48:37,560 Speaker 1: we have any hope at all of ever knowing like, oh, 933 00:48:37,640 --> 00:48:41,240 Speaker 1: this noise is coming from inflation or gravitons or cosmic strings, 934 00:48:41,320 --> 00:48:44,799 Speaker 1: they would look different, right. Gravitational waves have frequencies, just 935 00:48:44,880 --> 00:48:47,719 Speaker 1: like light does. Different frequencies of light look different. You've 936 00:48:47,719 --> 00:48:50,120 Speaker 1: got radio, you've got infrared, you've got X rays, you've 937 00:48:50,120 --> 00:48:54,160 Speaker 1: got gamma. Raised in the same way, gravitational waves have frequencies. 938 00:48:54,320 --> 00:48:56,960 Speaker 1: The ones we've seen have frequencies of about a second, 939 00:48:57,360 --> 00:48:59,840 Speaker 1: and we have sensitivities due to our detectors to a 940 00:49:00,080 --> 00:49:03,520 Speaker 1: range of frequencies. So they come at very very high frequencies, 941 00:49:03,600 --> 00:49:05,960 Speaker 1: we think they might be gravitons. If they come at 942 00:49:05,960 --> 00:49:08,600 Speaker 1: lower frequencies, they might be from inflation. If they're sort 943 00:49:08,640 --> 00:49:11,760 Speaker 1: of periodic and spastic, then they might be from cosmic strings. 944 00:49:11,800 --> 00:49:14,239 Speaker 1: So each one of these has like a different fingerprint. 945 00:49:14,520 --> 00:49:16,839 Speaker 1: If there's just nothing there except for like the low 946 00:49:16,960 --> 00:49:19,840 Speaker 1: level hum that that should be pretty flat and lots 947 00:49:19,840 --> 00:49:23,080 Speaker 1: of frequencies represented. So the sort of spectrum of the 948 00:49:23,080 --> 00:49:26,319 Speaker 1: frequencies there is a fingerprint that tells you what generated it. 949 00:49:26,400 --> 00:49:28,680 Speaker 1: We just gotta, I guess, tune up those microphones and 950 00:49:28,719 --> 00:49:31,200 Speaker 1: turn up the amplifiers and reduce the noise just to 951 00:49:31,200 --> 00:49:33,799 Speaker 1: be able to maybe listen to these signals. And be 952 00:49:33,840 --> 00:49:35,640 Speaker 1: able to tell which one is which. Yeah, and we 953 00:49:35,719 --> 00:49:39,560 Speaker 1: have some exciting plans. The Ligo Observatory is based here 954 00:49:39,600 --> 00:49:42,000 Speaker 1: on Earth, and what they'd like to do is build 955 00:49:42,040 --> 00:49:45,320 Speaker 1: a much bigger version out in space. They want to 956 00:49:45,360 --> 00:49:49,080 Speaker 1: put three satellites out there that managed to somehow keep 957 00:49:49,080 --> 00:49:51,720 Speaker 1: a very precise distance from each other and then shoot 958 00:49:51,800 --> 00:49:54,759 Speaker 1: lasers back and forth to detect the passing of gravitational 959 00:49:54,800 --> 00:49:58,800 Speaker 1: waves or the cosmic gravitational background. It's not science fiction. 960 00:49:58,880 --> 00:50:01,759 Speaker 1: There's a real experiment might really happen sometime in the 961 00:50:01,760 --> 00:50:04,040 Speaker 1: next ten or fifteen years, and it can really teach 962 00:50:04,120 --> 00:50:07,000 Speaker 1: us something deep about the universe. It's Lego in space. 963 00:50:08,040 --> 00:50:11,400 Speaker 1: It's called Lisa, all right. Well, that's what the cosmic 964 00:50:11,719 --> 00:50:14,480 Speaker 1: gravitational background is. It might be there, it might not 965 00:50:14,520 --> 00:50:16,960 Speaker 1: be there. We think it's there, but we don't know 966 00:50:17,120 --> 00:50:19,759 Speaker 1: quite what's causing it, right, and we don't know if 967 00:50:19,760 --> 00:50:22,200 Speaker 1: it's there, We don't know what's causing it. But we're 968 00:50:22,280 --> 00:50:25,399 Speaker 1: desperate to listen to these signals that might contain new 969 00:50:25,440 --> 00:50:29,360 Speaker 1: treasures about the early universe. So stay tuned once again, 970 00:50:30,040 --> 00:50:31,960 Speaker 1: and maybe think about that when you look up at 971 00:50:31,960 --> 00:50:34,759 Speaker 1: the night sky once again, and how much information is 972 00:50:34,840 --> 00:50:37,919 Speaker 1: bathing over us as we speak, and that might tell 973 00:50:38,000 --> 00:50:41,120 Speaker 1: us about the very origin of the universe. And think 974 00:50:41,120 --> 00:50:44,239 Speaker 1: about all the gravitational radiation that you are generating. Every 975 00:50:44,239 --> 00:50:46,279 Speaker 1: time you go out there and get exercise or hit 976 00:50:46,320 --> 00:50:48,960 Speaker 1: the accelerator in your car. You are contributing to the 977 00:50:49,000 --> 00:50:52,360 Speaker 1: cosmic gravitational background, some of us more than others. Like 978 00:50:52,360 --> 00:50:55,239 Speaker 1: if you're a couch potato, technically you're just creating less 979 00:50:55,239 --> 00:50:57,200 Speaker 1: noise for the universe, right, that's true, But you're getting 980 00:50:57,200 --> 00:50:59,120 Speaker 1: more and more massive, So if you ever do get 981 00:50:59,160 --> 00:51:01,879 Speaker 1: off the couch, you're gonna be pretty noisy, right, there's 982 00:51:01,880 --> 00:51:04,279 Speaker 1: a trade off there, all right. Well, thanks for joining us. 983 00:51:04,280 --> 00:51:14,439 Speaker 1: We hope you enjoyed that. See you next time. Thanks 984 00:51:14,480 --> 00:51:17,120 Speaker 1: for listening, and remember that Daniel and Jorge Explain the 985 00:51:17,200 --> 00:51:20,319 Speaker 1: Universe is a production of I Heart Radio. For More 986 00:51:20,400 --> 00:51:23,760 Speaker 1: podcast For my Heart Radio, visit the I Heart Radio app, 987 00:51:24,040 --> 00:51:33,239 Speaker 1: Apple Podcasts, or wherever you listen to your favorite shows. Yeah,