1 00:00:08,600 --> 00:00:12,639 Speaker 1: Hey, Daniel, has the Large Hadron Collider found fewer or 2 00:00:12,840 --> 00:00:15,040 Speaker 1: more particles than expected? 3 00:00:15,360 --> 00:00:18,480 Speaker 2: I guess it depends on what people expected. There were 4 00:00:18,520 --> 00:00:21,640 Speaker 2: some physicists who thought we'd find zero, and some expected 5 00:00:21,840 --> 00:00:23,160 Speaker 2: hundreds of particles. 6 00:00:23,720 --> 00:00:26,480 Speaker 1: Hundreds that seems like a lot. 7 00:00:27,760 --> 00:00:29,600 Speaker 2: Well, you know, in the sixties we had this era 8 00:00:29,720 --> 00:00:32,640 Speaker 2: called the particle Zoo. Basically every time you turned on 9 00:00:32,680 --> 00:00:36,800 Speaker 2: the collider you found something new. This time, unfortunately, we've 10 00:00:36,800 --> 00:00:38,479 Speaker 2: only found the one particle. 11 00:00:38,960 --> 00:00:42,120 Speaker 1: Why is it so hard to know how many particles 12 00:00:42,159 --> 00:00:44,559 Speaker 1: you're gonna find? Don't you guys kind of have an 13 00:00:44,600 --> 00:00:45,800 Speaker 1: idea of what you're doing? 14 00:00:46,560 --> 00:00:49,640 Speaker 2: You know, research is exploration in the universe is full 15 00:00:49,680 --> 00:00:50,400 Speaker 2: of surprises. 16 00:00:50,720 --> 00:00:54,520 Speaker 1: Maybe it should be full of physicists who are also psychics. 17 00:00:56,400 --> 00:00:58,840 Speaker 2: Maybe if we stuck physicists in the collider, they would 18 00:00:58,840 --> 00:00:59,760 Speaker 2: turn into psychics. 19 00:01:00,120 --> 00:01:03,800 Speaker 1: Have you ever tried sticking your head in the beam, Daniel? 20 00:01:03,960 --> 00:01:05,360 Speaker 1: Did you get any premonitions? 21 00:01:05,720 --> 00:01:05,800 Speaker 3: No? 22 00:01:05,920 --> 00:01:08,520 Speaker 2: But if any listeners out there want to volunteer, write 23 00:01:08,560 --> 00:01:08,760 Speaker 2: to me. 24 00:01:09,080 --> 00:01:12,119 Speaker 1: There's going to be so many volunteers, the same volunteers 25 00:01:12,160 --> 00:01:14,120 Speaker 1: who want to go set up the Mars colony. 26 00:01:14,200 --> 00:01:15,960 Speaker 2: I don't know if getting your brain fried makes you 27 00:01:16,000 --> 00:01:34,520 Speaker 2: more or less likely to volunteer to go to outer space. Hi, 28 00:01:34,600 --> 00:01:37,240 Speaker 2: I'm Daniel. I'm a particle physicist and a professor at 29 00:01:37,319 --> 00:01:40,560 Speaker 2: UC Irvine, and I definitely do not have the authorization 30 00:01:40,720 --> 00:01:42,280 Speaker 2: to put your brain in the beam. 31 00:01:42,880 --> 00:01:45,919 Speaker 1: Hi I am Katie. I am not a particle physicist. 32 00:01:46,120 --> 00:01:49,600 Speaker 1: I am more interested, well not more interested, but more 33 00:01:49,640 --> 00:01:53,920 Speaker 1: familiar with the animal sides of things. And I've put 34 00:01:53,960 --> 00:01:56,840 Speaker 1: my head in a few beams and I feel great. 35 00:01:57,280 --> 00:01:57,480 Speaker 4: Well. 36 00:01:57,520 --> 00:01:59,760 Speaker 2: I have no comment about how you turned down, perhaps 37 00:02:00,040 --> 00:02:02,320 Speaker 2: to ask your parents. But on a parent thing note, 38 00:02:02,360 --> 00:02:04,720 Speaker 2: my wife is a biologist, and I have sometimes come 39 00:02:04,800 --> 00:02:08,120 Speaker 2: home to discover that she's included our children in her experiments. 40 00:02:08,360 --> 00:02:12,280 Speaker 1: Ah, the classic sort of using your own child as 41 00:02:12,440 --> 00:02:13,120 Speaker 1: the labrat. 42 00:02:14,600 --> 00:02:16,720 Speaker 2: We had to at some point lay down very strict 43 00:02:16,720 --> 00:02:20,120 Speaker 2: guidelines about how many parents have to say yes before 44 00:02:20,120 --> 00:02:22,000 Speaker 2: we could take samples from our children. 45 00:02:24,680 --> 00:02:27,840 Speaker 1: She's doing some tongue scrapings or did she built like 46 00:02:27,880 --> 00:02:29,000 Speaker 1: a maze for them? 47 00:02:29,240 --> 00:02:31,960 Speaker 2: No, our children are not the subjects of psychological experiments. 48 00:02:32,000 --> 00:02:35,040 Speaker 2: It's more like collecting samples to get data. So it's 49 00:02:35,080 --> 00:02:38,880 Speaker 2: totally passive, and she was not really breaking any moral thresholds. 50 00:02:38,919 --> 00:02:40,720 Speaker 2: But I did feel like, hey, we should have a 51 00:02:40,760 --> 00:02:44,760 Speaker 2: conversation before you do any kind of experiments on our children, 52 00:02:45,320 --> 00:02:46,240 Speaker 2: because you never know. 53 00:02:46,800 --> 00:02:49,679 Speaker 1: Just ask permission before you do a cheek swap. That's 54 00:02:49,720 --> 00:02:50,520 Speaker 1: my philosophy. 55 00:02:50,800 --> 00:02:54,440 Speaker 2: And welcome to the podcast. Daniel and Jorge explain the universe, 56 00:02:54,520 --> 00:02:57,320 Speaker 2: in which we explore all the sorts of surprises there 57 00:02:57,360 --> 00:03:00,000 Speaker 2: are out there in the universe, the things we anticip 58 00:03:00,120 --> 00:03:03,200 Speaker 2: made and the things we do not anticipate, including coming 59 00:03:03,240 --> 00:03:07,440 Speaker 2: home to our wives experimenting on our children. My guest 60 00:03:07,560 --> 00:03:09,960 Speaker 2: and normal co host, Jorge can't be with us today, 61 00:03:09,960 --> 00:03:12,760 Speaker 2: but I'm very pleased to have with us Katie Golden. Katie, 62 00:03:12,800 --> 00:03:14,360 Speaker 2: thanks very much for joining us again. 63 00:03:14,720 --> 00:03:17,160 Speaker 1: Yeah, and I have a good idea and maybe should 64 00:03:17,200 --> 00:03:20,960 Speaker 1: start having kids so that I can experiment on them. 65 00:03:21,120 --> 00:03:25,000 Speaker 1: This is this is an interesting idea because right now 66 00:03:25,040 --> 00:03:27,600 Speaker 1: I have a dog, and the only experiments I can 67 00:03:27,639 --> 00:03:32,000 Speaker 1: do are treat based behavioral studies such as who is 68 00:03:32,040 --> 00:03:33,960 Speaker 1: a good girl? Are you the good girl? 69 00:03:34,160 --> 00:03:36,760 Speaker 2: Well, you know, to some extent, every step you make, 70 00:03:36,800 --> 00:03:39,560 Speaker 2: every decision you make as a parent, you are kind 71 00:03:39,560 --> 00:03:42,520 Speaker 2: of experimenting on your kids. You're saying, hmm, let me 72 00:03:42,600 --> 00:03:45,560 Speaker 2: try this parenting technique and see if they grow up 73 00:03:45,600 --> 00:03:47,680 Speaker 2: to be a serial killer or a Nobel Prize winner 74 00:03:47,960 --> 00:03:48,400 Speaker 2: or both. 75 00:03:48,720 --> 00:03:51,560 Speaker 1: It seems like the child is the one putting you 76 00:03:51,720 --> 00:03:54,320 Speaker 1: in the skinner box, and you are just trying to 77 00:03:54,520 --> 00:03:58,040 Speaker 1: modify your behavior such that the child is happy well. 78 00:03:58,440 --> 00:04:03,440 Speaker 2: Like parenting, research is exploration, which means there are always surprises. 79 00:04:03,800 --> 00:04:05,680 Speaker 2: You know, when we land a rover on Mars and 80 00:04:05,760 --> 00:04:08,400 Speaker 2: drive around to see what's behind those rocks, we don't 81 00:04:08,440 --> 00:04:11,560 Speaker 2: know what we're gonna find. When we train our telescopes 82 00:04:11,600 --> 00:04:15,120 Speaker 2: on distant galaxies, we always find something new. The same 83 00:04:15,200 --> 00:04:17,960 Speaker 2: is true and we turn on a particle collider trying 84 00:04:17,960 --> 00:04:21,120 Speaker 2: to smash particles to create new, higher energies than have 85 00:04:21,240 --> 00:04:26,560 Speaker 2: existed since the early moments of the universe. Research is exploration, 86 00:04:26,640 --> 00:04:29,440 Speaker 2: which means that there are no guarantees about what you're 87 00:04:29,440 --> 00:04:32,520 Speaker 2: going to learn. There's always something surprising out there to 88 00:04:32,520 --> 00:04:35,520 Speaker 2: be discovered, which is one of the joys of research 89 00:04:35,560 --> 00:04:38,799 Speaker 2: and exploration and also one of its frustrations. 90 00:04:39,080 --> 00:04:42,040 Speaker 1: I mean, it sounds like your interest in research is 91 00:04:42,040 --> 00:04:45,400 Speaker 1: maybe the same as your interest in parenting. Like new 92 00:04:45,440 --> 00:04:49,160 Speaker 1: things happen, Little surprises happen. Sometimes they're great, and sometimes 93 00:04:49,200 --> 00:04:50,400 Speaker 1: they're very frustrating. 94 00:04:51,200 --> 00:04:53,719 Speaker 2: I do sometimes feel a sort of love for a 95 00:04:53,760 --> 00:04:57,240 Speaker 2: really nice result that I spent a lot of time building, Like, 96 00:04:57,279 --> 00:04:59,280 Speaker 2: oh wow, look at this little paper go out there 97 00:04:59,320 --> 00:05:01,440 Speaker 2: into the world. I hope it doesn't get crushed. 98 00:05:03,040 --> 00:05:05,680 Speaker 1: It's just cradling Matt Lab like a little baby. 99 00:05:05,880 --> 00:05:08,520 Speaker 2: But there are a lot of other real connections between 100 00:05:08,560 --> 00:05:12,320 Speaker 2: parenting and research, such as mentoring students. Just like every 101 00:05:12,400 --> 00:05:15,480 Speaker 2: child needs a different kind of parenting, every student also 102 00:05:15,560 --> 00:05:18,080 Speaker 2: needs a different kind of guidance. Some of them need 103 00:05:18,120 --> 00:05:20,120 Speaker 2: almost no guidance and some of them need a lot 104 00:05:20,120 --> 00:05:22,800 Speaker 2: of hand holding. Fortunately I haven't had to do much 105 00:05:22,839 --> 00:05:26,279 Speaker 2: like actual disciplining when it comes to my students. But 106 00:05:26,440 --> 00:05:29,720 Speaker 2: you know, it's a relationship for each individual one you. 107 00:05:29,720 --> 00:05:32,280 Speaker 1: Have to sit in like the knotty corner if you 108 00:05:33,200 --> 00:05:35,680 Speaker 1: describe a particle as a wave or a wave as 109 00:05:35,720 --> 00:05:36,320 Speaker 1: a particle. 110 00:05:36,560 --> 00:05:38,919 Speaker 2: And so when physicists are not at home at making 111 00:05:39,040 --> 00:05:42,359 Speaker 2: parenting mistakes, we are at work trying to understand the 112 00:05:42,440 --> 00:05:44,880 Speaker 2: nature of the universe the same way that you are. 113 00:05:45,000 --> 00:05:47,520 Speaker 2: And for thousands of years, we had basically only one 114 00:05:47,600 --> 00:05:51,080 Speaker 2: way to gather knowledge about the far flung corners of 115 00:05:51,120 --> 00:05:55,800 Speaker 2: the universe. That was electromagnetic radiation. Light in all of 116 00:05:55,839 --> 00:05:59,719 Speaker 2: its different flavors and kinds, from high energy gamma rays 117 00:05:59,800 --> 00:06:02,960 Speaker 2: to long wavelength radio waves would come to the Earth 118 00:06:02,960 --> 00:06:05,800 Speaker 2: and tell us what was going on in those other galaxies, 119 00:06:05,800 --> 00:06:08,599 Speaker 2: the stars burning bright and creating those photons which would 120 00:06:08,640 --> 00:06:11,800 Speaker 2: travel across the cosmos to us. But of course there 121 00:06:11,839 --> 00:06:14,760 Speaker 2: are other ways to get information about what's happening in space. 122 00:06:15,040 --> 00:06:18,200 Speaker 2: Sometimes actual particles made of matter and will fall to 123 00:06:18,320 --> 00:06:21,200 Speaker 2: the Earth and we will gather them up cosmic rays 124 00:06:21,200 --> 00:06:23,960 Speaker 2: and neutrinos and all sorts of stuff. But a few 125 00:06:24,040 --> 00:06:27,640 Speaker 2: years ago, we pioneered a brand new way to listen 126 00:06:27,760 --> 00:06:31,440 Speaker 2: to the universe to collect information about what's happening, to 127 00:06:31,440 --> 00:06:34,080 Speaker 2: be able to see and hear kinds of things we 128 00:06:34,160 --> 00:06:36,360 Speaker 2: had never seen and heard before. 129 00:06:36,680 --> 00:06:39,839 Speaker 1: Was it a kind of form of intergalactic semaphore? 130 00:06:41,920 --> 00:06:44,440 Speaker 2: In some sense, it kind of was. A few years 131 00:06:44,440 --> 00:06:47,840 Speaker 2: ago we made the fantastical reel and develop the technology 132 00:06:47,880 --> 00:06:51,760 Speaker 2: to be able to listen to gravitational waves to detect 133 00:06:51,880 --> 00:06:55,640 Speaker 2: these tiny ripples in space itself. Today, on the episode, 134 00:06:55,720 --> 00:06:57,760 Speaker 2: I want to look back to that time and think 135 00:06:57,760 --> 00:07:00,279 Speaker 2: about what we expected to hear when we first turned 136 00:07:00,279 --> 00:07:04,800 Speaker 2: on this new kind of eyeball or earball or whatever. 137 00:07:04,839 --> 00:07:07,840 Speaker 2: Biological analogy you want to make for new technology. 138 00:07:08,160 --> 00:07:11,160 Speaker 1: I mean, I'm very interested because I've had ears for 139 00:07:11,400 --> 00:07:15,240 Speaker 1: pretty much my whole life, and I have never heard 140 00:07:15,520 --> 00:07:16,480 Speaker 1: gravity before. 141 00:07:16,880 --> 00:07:20,480 Speaker 2: So well, when the scientists finished building this apparatus, they 142 00:07:20,480 --> 00:07:23,080 Speaker 2: didn't know what they were going to hear. And so 143 00:07:23,120 --> 00:07:25,239 Speaker 2: today on the episode, we're going to answer the question 144 00:07:30,440 --> 00:07:35,560 Speaker 2: have we seen fewer or more gravitational waves than we expected? 145 00:07:35,840 --> 00:07:38,080 Speaker 1: Now, this is the thing, is that this is my 146 00:07:38,200 --> 00:07:42,160 Speaker 1: first time learning about what a gravitational wave is, so 147 00:07:43,000 --> 00:07:48,200 Speaker 1: I had no expectations how many we would see, given 148 00:07:48,240 --> 00:07:50,800 Speaker 1: that this is my first time hearing about them at all. 149 00:07:50,920 --> 00:07:53,320 Speaker 2: Well, for me, it's one of those really amazing moments 150 00:07:53,680 --> 00:07:56,840 Speaker 2: when you create a new channel between the universe and 151 00:07:56,960 --> 00:08:00,120 Speaker 2: humanity and you allow nature to speak to us when 152 00:08:00,120 --> 00:08:02,360 Speaker 2: you had to ask a question and get an answer. 153 00:08:02,840 --> 00:08:05,000 Speaker 2: There are very few moments like that when you really 154 00:08:05,000 --> 00:08:07,880 Speaker 2: are hearing something from nature and answer to a question, 155 00:08:08,240 --> 00:08:11,040 Speaker 2: especially in a new channel you've never opened up before, 156 00:08:11,080 --> 00:08:14,840 Speaker 2: because it creates the possibility for great surprises, because the 157 00:08:14,920 --> 00:08:17,600 Speaker 2: universe is often very different from the way that we 158 00:08:17,680 --> 00:08:19,840 Speaker 2: thought it was, and the only way to make those 159 00:08:19,840 --> 00:08:23,440 Speaker 2: discoveries is to explore it, is to gather this information. 160 00:08:23,800 --> 00:08:26,360 Speaker 2: So I was wondering what people thought about this sort 161 00:08:26,360 --> 00:08:29,800 Speaker 2: of history of gravitational waves. Was it a surprise that 162 00:08:29,840 --> 00:08:32,440 Speaker 2: we saw some Have we seen more than we expected? 163 00:08:32,600 --> 00:08:35,200 Speaker 2: Are the gravitational waves that we have seen the kind 164 00:08:35,280 --> 00:08:38,280 Speaker 2: that we expected? Or is there something weird about them? 165 00:08:38,679 --> 00:08:40,560 Speaker 2: So I went out there into the internet and asked 166 00:08:40,600 --> 00:08:44,720 Speaker 2: our army of volunteers to give me their uneducated opinion 167 00:08:44,840 --> 00:08:48,040 Speaker 2: on this question, which helps me understand what you listeners 168 00:08:48,280 --> 00:08:50,880 Speaker 2: might have in your heads. So thanks very much to 169 00:08:50,920 --> 00:08:53,320 Speaker 2: all the volunteers. If you'd like to participate for a 170 00:08:53,360 --> 00:08:55,880 Speaker 2: future episode, please don't be shy. Write to me to 171 00:08:56,120 --> 00:09:00,520 Speaker 2: questions at Danielandjorge dot com. So before you hear the answers, 172 00:09:00,559 --> 00:09:03,560 Speaker 2: think to yourself for a moment. Have we seen fewer 173 00:09:03,720 --> 00:09:08,040 Speaker 2: or more gravitational waves than we expected? Here's what people 174 00:09:08,040 --> 00:09:08,560 Speaker 2: had to say. 175 00:09:08,960 --> 00:09:12,480 Speaker 5: Maybe fewer because I know waves and particles, you know, 176 00:09:12,720 --> 00:09:14,920 Speaker 5: they you know, act like one another. So if there's 177 00:09:14,920 --> 00:09:17,280 Speaker 5: a gravitational wave, there have to be like a particle. 178 00:09:17,559 --> 00:09:19,400 Speaker 5: Maybe we've seen a lot of waves but not the particles. 179 00:09:19,600 --> 00:09:21,599 Speaker 5: Maybe I'm going to say as much as we expected, 180 00:09:21,920 --> 00:09:23,000 Speaker 5: but we want to see more. 181 00:09:23,120 --> 00:09:25,880 Speaker 6: I think we've seen more gravitational waves than we expected 182 00:09:26,679 --> 00:09:29,440 Speaker 6: I remember correctly. I think Ligo detected the first one 183 00:09:29,440 --> 00:09:32,280 Speaker 6: in twenty seventeen, and as far as I know, there's 184 00:09:32,320 --> 00:09:34,880 Speaker 6: also been a few detections since then, so I think 185 00:09:34,960 --> 00:09:38,440 Speaker 6: we've actually been able to discover more than we were expecting. 186 00:09:38,679 --> 00:09:41,400 Speaker 7: I know that the ligo has been able to detect 187 00:09:41,440 --> 00:09:45,440 Speaker 7: some gravitational waves, but it's a really hard task. So 188 00:09:45,800 --> 00:09:46,679 Speaker 7: if it could. 189 00:09:46,559 --> 00:09:51,040 Speaker 6: Have better detection equipment, I think we would be able 190 00:09:51,080 --> 00:09:52,880 Speaker 6: to see even more detections. 191 00:09:53,000 --> 00:09:57,480 Speaker 4: I would say that we have seen more because when 192 00:09:57,559 --> 00:10:02,880 Speaker 4: we first before we first detected gravitational waves, I don't 193 00:10:03,080 --> 00:10:06,360 Speaker 4: know if we were even expecting to see any. So 194 00:10:06,720 --> 00:10:08,960 Speaker 4: since we detected some, I would say more. 195 00:10:09,000 --> 00:10:12,520 Speaker 7: I'm not sure how many gravitational waves we expected. I 196 00:10:12,520 --> 00:10:17,120 Speaker 7: think we may have discovered more than we thought we would, 197 00:10:17,160 --> 00:10:19,600 Speaker 7: but I'm not sure if it's more than what we expected. 198 00:10:20,240 --> 00:10:24,480 Speaker 1: I have a question, Daniel. Is it pronounced lego or lego? 199 00:10:25,760 --> 00:10:29,000 Speaker 2: I think it's pronounced ligo, and this also one in 200 00:10:29,040 --> 00:10:30,360 Speaker 2: Italy called rugo. 201 00:10:30,920 --> 00:10:33,360 Speaker 1: I see, so I can't say lego, mylego. 202 00:10:34,080 --> 00:10:35,920 Speaker 2: You can say that all you like, and you can 203 00:10:35,960 --> 00:10:38,840 Speaker 2: even build your own ligo out of LEGOS, I. 204 00:10:38,760 --> 00:10:41,120 Speaker 1: Believe what does logos stand for. 205 00:10:41,720 --> 00:10:48,360 Speaker 2: LEGO stands for laser interferometer gravitational wave observatory where the 206 00:10:48,760 --> 00:10:51,120 Speaker 2: W there is sort of suppressed. Otherwise it'd be like 207 00:10:51,360 --> 00:10:51,839 Speaker 2: lig wo. 208 00:10:52,160 --> 00:10:54,880 Speaker 1: That would be a little bit too like French. I 209 00:10:54,880 --> 00:10:55,800 Speaker 1: guess sounding. 210 00:10:56,320 --> 00:11:01,280 Speaker 2: I don't know lig who bro sounds a little somethings 211 00:11:01,679 --> 00:11:05,920 Speaker 2: to me. Well, we've talked about gravitational waves a couple 212 00:11:06,000 --> 00:11:08,120 Speaker 2: of times in the podcast, but maybe not everybody is 213 00:11:08,160 --> 00:11:11,480 Speaker 2: really comfortable with this idea because frankly, it's a pretty 214 00:11:11,600 --> 00:11:15,160 Speaker 2: weird concept and it's something that Albert Einstein predicted but 215 00:11:15,240 --> 00:11:18,760 Speaker 2: also predicted we would never ever be able to detect. 216 00:11:18,880 --> 00:11:20,880 Speaker 2: So it's worth taking a minutes to remind ourselves what 217 00:11:21,000 --> 00:11:23,240 Speaker 2: are gravitational waves exactly? 218 00:11:23,600 --> 00:11:27,680 Speaker 1: Yeah, because we're talking about like leg wobro and gravitational waves. 219 00:11:27,760 --> 00:11:30,880 Speaker 1: Is this something I could surf on? Is this something 220 00:11:30,960 --> 00:11:33,800 Speaker 1: I could see? Is it something where if I jump 221 00:11:33,920 --> 00:11:37,040 Speaker 1: during a gravitational wave, I feel myself get pulled down 222 00:11:37,040 --> 00:11:39,560 Speaker 1: to Earth faster. I'm ready to learn because this is 223 00:11:39,600 --> 00:11:41,120 Speaker 1: an entirely new concept to me. 224 00:11:41,440 --> 00:11:45,080 Speaker 2: Gravitational waves are one of the amazing predictions of general 225 00:11:45,080 --> 00:11:47,800 Speaker 2: relativity and one of the coolest things about them is 226 00:11:47,840 --> 00:11:50,880 Speaker 2: that they are waves, waves like we see in other things, 227 00:11:50,920 --> 00:11:54,600 Speaker 2: meaning that they follow the same mathematical formula. It's incredible 228 00:11:54,640 --> 00:11:58,000 Speaker 2: to me that the same sort of phenomenon appears in sound, 229 00:11:58,160 --> 00:12:01,000 Speaker 2: and in water and in light, and also in the 230 00:12:01,120 --> 00:12:05,560 Speaker 2: ripples of space itself. So that's what gravitational waves are. 231 00:12:05,600 --> 00:12:10,280 Speaker 2: They're like updating information about gravity. They're wiggles in space. 232 00:12:10,520 --> 00:12:14,319 Speaker 1: That sounds like a kid's program, wiggles in space. I 233 00:12:14,360 --> 00:12:16,280 Speaker 1: guess I'm trying to wrap my head around the idea 234 00:12:16,400 --> 00:12:20,160 Speaker 1: of what is a wiggle in space? How does space wiggle? 235 00:12:20,679 --> 00:12:22,880 Speaker 2: Yeah, before we can answer how to space wiggle, we 236 00:12:22,920 --> 00:12:24,800 Speaker 2: have to understand a little bit about what it means 237 00:12:24,800 --> 00:12:27,600 Speaker 2: for space to bend at all, and they will put 238 00:12:27,640 --> 00:12:30,720 Speaker 2: that together. To understanding wiggles and space bending is the 239 00:12:30,720 --> 00:12:34,240 Speaker 2: fundamental concept of general relativity. It tells us that the 240 00:12:34,280 --> 00:12:36,960 Speaker 2: force that we feel of gravity, the reason that you 241 00:12:37,000 --> 00:12:39,080 Speaker 2: are held to the Earth and the Earth is going 242 00:12:39,120 --> 00:12:41,800 Speaker 2: around the Sun, is not actually a force at all. 243 00:12:41,880 --> 00:12:44,959 Speaker 2: It's an apparent force, something we describe as a force 244 00:12:45,040 --> 00:12:48,640 Speaker 2: because we don't really understand what's going on, and apparent 245 00:12:48,679 --> 00:12:51,440 Speaker 2: forces are not something weird or magical. We experience them 246 00:12:51,440 --> 00:12:53,040 Speaker 2: all the time. If you're in a Merry go Round 247 00:12:53,040 --> 00:12:56,040 Speaker 2: with your friends and somebody spins it, you feel this 248 00:12:56,200 --> 00:12:58,760 Speaker 2: force outwards. You feel like somebody's trying to throw you 249 00:12:58,840 --> 00:13:01,439 Speaker 2: off the merry go Round, But there is no force there. 250 00:13:01,480 --> 00:13:04,520 Speaker 2: Nobody is pushing you outwards. It's just a consequence of 251 00:13:04,520 --> 00:13:08,160 Speaker 2: the fact that you're spinning. There's this accelerated frame of reference. 252 00:13:08,320 --> 00:13:10,680 Speaker 2: You want to keep going in the direction that you 253 00:13:10,720 --> 00:13:13,640 Speaker 2: were going, and that looks to somebody on the Merry 254 00:13:13,640 --> 00:13:16,000 Speaker 2: go Round as if you're being pushed, you know. Or 255 00:13:16,040 --> 00:13:17,920 Speaker 2: if you try to throw a ball from one side 256 00:13:17,920 --> 00:13:19,640 Speaker 2: of the Merry go Round to the other, it wouldn't 257 00:13:19,679 --> 00:13:22,120 Speaker 2: move in what looks to you like a straight line 258 00:13:22,360 --> 00:13:25,400 Speaker 2: because the Merry go Round is spinning. That's the concept 259 00:13:25,440 --> 00:13:28,160 Speaker 2: of an apparent force. It's not a true force. It's 260 00:13:28,160 --> 00:13:30,440 Speaker 2: something that comes out of the properties of the system 261 00:13:30,480 --> 00:13:34,800 Speaker 2: that we're in. And so gravity is also an apparent force. 262 00:13:35,280 --> 00:13:38,920 Speaker 2: Space itself curves, it bends, and when we say space bending, 263 00:13:39,240 --> 00:13:43,120 Speaker 2: we're talking about the relative distances between two points. So 264 00:13:43,200 --> 00:13:46,240 Speaker 2: as the Earth, for example, moves through space, the space 265 00:13:46,280 --> 00:13:49,000 Speaker 2: in front of it is curved, and so it moves 266 00:13:49,040 --> 00:13:52,240 Speaker 2: through what it seems to be the natural path which 267 00:13:52,320 --> 00:13:55,520 Speaker 2: follows that curvature. But to us it looks like somebody 268 00:13:55,559 --> 00:13:58,200 Speaker 2: is bending it because we can't see that curvature of 269 00:13:58,200 --> 00:13:59,000 Speaker 2: space directly. 270 00:13:59,160 --> 00:14:02,200 Speaker 1: So I I like jump from the top of the 271 00:14:02,240 --> 00:14:06,120 Speaker 1: stairs down a few steps. It feels just like I'm falling. 272 00:14:06,200 --> 00:14:08,720 Speaker 1: It's this normal, you know, I'm falling apart am I 273 00:14:09,400 --> 00:14:14,320 Speaker 1: just traveling through sort of the path of space that 274 00:14:14,640 --> 00:14:17,320 Speaker 1: has been created by the gravity of Earth. 275 00:14:17,679 --> 00:14:21,640 Speaker 2: That's exactly right. Anytime you move according to gravity, you're 276 00:14:21,680 --> 00:14:24,720 Speaker 2: in free fall. You're just following the curves of space. 277 00:14:24,880 --> 00:14:27,000 Speaker 2: So for example, you get an airplane, you fly it 278 00:14:27,080 --> 00:14:29,600 Speaker 2: pretty high, and you throw out a tennis ball. What 279 00:14:29,680 --> 00:14:32,760 Speaker 2: happens to that tennis ball. Well, Newton would say it's 280 00:14:32,800 --> 00:14:35,600 Speaker 2: accelerated by the force of gravity towards the center of 281 00:14:35,680 --> 00:14:38,160 Speaker 2: the Earth. And Einstein would say, no, no, it's just 282 00:14:38,360 --> 00:14:42,480 Speaker 2: following the curvature of space. It's just moving with space. 283 00:14:42,720 --> 00:14:46,240 Speaker 1: It's interesting that the curvature of space often like winds 284 00:14:46,320 --> 00:14:48,840 Speaker 1: up at the pavement and then I hurt myself. But 285 00:14:50,080 --> 00:14:53,480 Speaker 1: good job, space. Why couldn't you wind up always at 286 00:14:53,520 --> 00:14:54,800 Speaker 1: a nice soft mattress. 287 00:14:55,120 --> 00:14:58,200 Speaker 2: And it's really a role reversal because Newton says, oh, 288 00:14:58,200 --> 00:15:01,600 Speaker 2: that tennis ball is being accelerat, right, it's being pulled 289 00:15:01,640 --> 00:15:04,000 Speaker 2: down towards the center of the Earth. And Einstein says, no, 290 00:15:04,080 --> 00:15:07,960 Speaker 2: it's not. It's just free falling with gravity. And in fact, 291 00:15:07,960 --> 00:15:10,520 Speaker 2: if you have an accelerometer or something which measures whether 292 00:15:10,520 --> 00:15:13,840 Speaker 2: you're getting pushed or pulled on that tennis ball, then 293 00:15:13,840 --> 00:15:16,760 Speaker 2: it won't notice any acceleration. It doesn't feel like it's 294 00:15:16,840 --> 00:15:20,880 Speaker 2: being accelerated, because it's not. The acceleration comes when you 295 00:15:20,920 --> 00:15:23,680 Speaker 2: splat on the pavement and the pavement accelerates you very 296 00:15:23,760 --> 00:15:29,240 Speaker 2: rapidly upwards. Right, that's the acceleration. So Einstein reverses that 297 00:15:29,560 --> 00:15:30,080 Speaker 2: because the. 298 00:15:30,000 --> 00:15:33,920 Speaker 1: Pavement is just in the way of the way that 299 00:15:34,240 --> 00:15:37,080 Speaker 1: space is now shaped for you, right, because you're following 300 00:15:37,120 --> 00:15:41,560 Speaker 1: this sort of path carved out for you by gravity, 301 00:15:42,120 --> 00:15:45,640 Speaker 1: and it just so happens that the pavement's right there 302 00:15:45,680 --> 00:15:46,320 Speaker 1: in your way. 303 00:15:46,520 --> 00:15:49,000 Speaker 2: Einstein says, if you jump off a building, you're not 304 00:15:49,160 --> 00:15:52,400 Speaker 2: accelerating as you fall. You only accelerate when you hit 305 00:15:52,520 --> 00:15:57,400 Speaker 2: the ground, accelerate very rapidly and destructively upwards. Newton says 306 00:15:57,760 --> 00:15:59,960 Speaker 2: that if you jump off a building, yes, you're accelerated 307 00:16:00,120 --> 00:16:02,640 Speaker 2: down towards the center of the Earth. So it's two 308 00:16:02,760 --> 00:16:06,040 Speaker 2: very different pictures about how gravity works. And Einstein's picture 309 00:16:06,080 --> 00:16:09,080 Speaker 2: is beautiful because it tells us that space itself has 310 00:16:09,120 --> 00:16:12,240 Speaker 2: this feature which was invisible to us until now. Right, 311 00:16:12,280 --> 00:16:14,960 Speaker 2: we can't see the curvature directly. It's not like a 312 00:16:15,040 --> 00:16:17,440 Speaker 2: road you're following you can see it curving ahead of you. 313 00:16:17,840 --> 00:16:20,960 Speaker 2: It's invisible to us, so it looks like there's this weird, 314 00:16:21,040 --> 00:16:24,440 Speaker 2: mysterious force acting on things and changing their paths, when 315 00:16:24,480 --> 00:16:28,280 Speaker 2: really things are just naturally following the invisible curvature of space. 316 00:16:28,880 --> 00:16:33,000 Speaker 1: So before we actually had the abilities to see something 317 00:16:33,080 --> 00:16:36,320 Speaker 1: like a gravitational wave, how did we know that Einstein 318 00:16:36,680 --> 00:16:39,800 Speaker 1: was probably right and that Newton was probably wrong. 319 00:16:39,960 --> 00:16:42,920 Speaker 2: Well, Einstein makes a very different prediction from Newton in 320 00:16:42,960 --> 00:16:45,800 Speaker 2: some cases. In many cases they're totally exactly the same. 321 00:16:46,240 --> 00:16:50,040 Speaker 2: But for example, Einstein predicts that photon, that light itself 322 00:16:50,440 --> 00:16:53,560 Speaker 2: can be bent by gravity. Newton would say, well, photons 323 00:16:53,600 --> 00:16:56,880 Speaker 2: have no mass, so there's no gravitational effect. But Einstein 324 00:16:56,880 --> 00:17:00,800 Speaker 2: would say that space is curved and photons follow the curvature, 325 00:17:01,080 --> 00:17:04,679 Speaker 2: so photons can get bent around heavy things. So he 326 00:17:04,720 --> 00:17:06,800 Speaker 2: made this prediction for what we would see in eclipse 327 00:17:06,880 --> 00:17:10,280 Speaker 2: as light got bent around those heavy objects. And he 328 00:17:10,480 --> 00:17:12,320 Speaker 2: was right and Newton was wrong. 329 00:17:12,640 --> 00:17:17,720 Speaker 1: So now I understand that space can basically bend, and 330 00:17:17,880 --> 00:17:21,720 Speaker 1: this gravity is basically this bending of space. I just 331 00:17:21,800 --> 00:17:25,280 Speaker 1: follow this path of space. So if I think about it, 332 00:17:25,280 --> 00:17:28,560 Speaker 1: it's like I'm like on a sheet and someone's angling 333 00:17:28,600 --> 00:17:31,720 Speaker 1: the sheet downwards, and I slide down the sheet. And 334 00:17:32,000 --> 00:17:34,520 Speaker 1: so if you get a gravity wave, are you just 335 00:17:34,560 --> 00:17:37,160 Speaker 1: sort of like wiggling that sheet a little bit. 336 00:17:37,280 --> 00:17:39,800 Speaker 2: It's very tempting to use the sheet analogy, but I 337 00:17:39,800 --> 00:17:43,760 Speaker 2: find the kind of problematic because the sheet is two dimensional, 338 00:17:43,840 --> 00:17:46,439 Speaker 2: and now you're sliding down, which implies some sort of 339 00:17:46,480 --> 00:17:49,760 Speaker 2: gravity in the third dimension. What's really happening is that 340 00:17:49,800 --> 00:17:53,520 Speaker 2: you're changing the relative distances between things to make one 341 00:17:53,600 --> 00:17:56,240 Speaker 2: path shorter and one path longer. But you're right that 342 00:17:56,280 --> 00:17:59,640 Speaker 2: we can put this conception together to understand wiggling, because 343 00:17:59,680 --> 00:18:02,439 Speaker 2: this the course of that bending is mass. It's not 344 00:18:02,480 --> 00:18:04,960 Speaker 2: like space is just bent willy nilly here and there. 345 00:18:05,240 --> 00:18:09,879 Speaker 2: It's bent around mass. So the Sun bends space around it. Now, 346 00:18:09,920 --> 00:18:12,040 Speaker 2: what happens if you move the Sun You so of 347 00:18:12,080 --> 00:18:14,679 Speaker 2: shift the Sun over a meter. Well, the bending of 348 00:18:14,720 --> 00:18:18,400 Speaker 2: space has to follow, right, but that doesn't happen instantaneously. 349 00:18:18,880 --> 00:18:21,520 Speaker 2: So if you shift the Sun over suddenly by one meter, 350 00:18:21,880 --> 00:18:24,600 Speaker 2: then the bending of space propagates outwards. It's like a 351 00:18:24,720 --> 00:18:27,920 Speaker 2: ripple in space. Now do the wiggles where you move 352 00:18:27,960 --> 00:18:29,560 Speaker 2: the sun one meter to the right and then one 353 00:18:29,600 --> 00:18:31,199 Speaker 2: meter to the left, and you know, then do the 354 00:18:31,240 --> 00:18:33,920 Speaker 2: hokey poke and turn it all around. If you're going 355 00:18:34,000 --> 00:18:37,200 Speaker 2: back and forth, then those ripples are constantly being generated, 356 00:18:37,240 --> 00:18:40,639 Speaker 2: and what you get are wiggles in space. That's a 357 00:18:40,680 --> 00:18:41,800 Speaker 2: gravitational wave. 358 00:18:42,240 --> 00:18:46,520 Speaker 1: So if wiggles in space are caused by the movement 359 00:18:46,920 --> 00:18:50,760 Speaker 1: of large masses, or I guess it would be caused 360 00:18:50,800 --> 00:18:53,359 Speaker 1: by any mass size, right, would you just have a 361 00:18:53,400 --> 00:18:55,360 Speaker 1: smaller wiggle for a smaller mass. 362 00:18:55,440 --> 00:18:59,159 Speaker 2: Yes. Gravity is super duper weak, and so while everything 363 00:18:59,240 --> 00:19:03,240 Speaker 2: generates grab vitational waves when it accelerates, only more massive 364 00:19:03,280 --> 00:19:06,320 Speaker 2: things can generate gravitational waves that we have any chance 365 00:19:06,400 --> 00:19:09,439 Speaker 2: of detecting, which is one reason why when we started 366 00:19:09,480 --> 00:19:13,760 Speaker 2: out we looked for gravitational waves from huge black holes 367 00:19:13,920 --> 00:19:16,399 Speaker 2: spiraling around each other super duper fast. 368 00:19:16,800 --> 00:19:22,119 Speaker 1: So given that for any kind of like gravitational wave 369 00:19:22,240 --> 00:19:24,960 Speaker 1: that we would observe, it would have to be from 370 00:19:24,960 --> 00:19:26,600 Speaker 1: something pretty big, right. 371 00:19:26,600 --> 00:19:28,800 Speaker 2: It have to be from something really big and not 372 00:19:29,000 --> 00:19:30,080 Speaker 2: too far away. 373 00:19:30,400 --> 00:19:33,679 Speaker 1: So given that, I would think that it might be 374 00:19:33,800 --> 00:19:37,280 Speaker 1: kind of rare, because I don't know how many massive, 375 00:19:37,400 --> 00:19:40,639 Speaker 1: sort of wiggly bodies are too close to Earth. But 376 00:19:41,200 --> 00:19:44,080 Speaker 1: you know, so I my guess, now that I understand 377 00:19:44,080 --> 00:19:46,040 Speaker 1: what a gravity wave is, would be that we would 378 00:19:46,040 --> 00:19:47,560 Speaker 1: only see them every so often. 379 00:19:47,640 --> 00:19:50,240 Speaker 2: Well, that was exactly the question they didn't know the 380 00:19:50,280 --> 00:19:53,520 Speaker 2: answer to. They were building this new technology which could, 381 00:19:53,600 --> 00:19:55,840 Speaker 2: for the first time listen to these things. What they 382 00:19:55,840 --> 00:19:59,280 Speaker 2: didn't know was is the universe noisy in this new spectrum? 383 00:19:59,400 --> 00:20:02,680 Speaker 2: Or is it totally quiet? Is there anything out there 384 00:20:02,760 --> 00:20:05,680 Speaker 2: to here? They didn't know the answer because we don't 385 00:20:05,800 --> 00:20:09,200 Speaker 2: understand the astrophysics of black holes. How often are they 386 00:20:09,240 --> 00:20:12,639 Speaker 2: spiraling into each other and making this sound that we 387 00:20:12,840 --> 00:20:16,280 Speaker 2: just built a new microphone for? That was the fundamental question. 388 00:20:16,680 --> 00:20:20,840 Speaker 1: Well, I'm going to say it happens once a month. 389 00:20:21,080 --> 00:20:25,919 Speaker 1: That's my production as a very very educated person. But 390 00:20:26,320 --> 00:20:28,840 Speaker 1: when we will take a quick break, I'll do a 391 00:20:28,840 --> 00:20:30,960 Speaker 1: little back of the envelope math see if I got 392 00:20:30,960 --> 00:20:34,160 Speaker 1: that right, and then maybe you can tell me how 393 00:20:34,200 --> 00:20:51,640 Speaker 1: often we've actually seen these gravity waves. So we are back. 394 00:20:51,880 --> 00:20:56,280 Speaker 1: I drew this very demonstrative tic tac toe on the 395 00:20:56,280 --> 00:20:59,360 Speaker 1: back of this envelope, and I think it will lead 396 00:20:59,440 --> 00:21:04,000 Speaker 1: you to some pretty interesting revelations about gravity wells. But 397 00:21:04,320 --> 00:21:08,080 Speaker 1: maybe I should actually ask the particle physicist how many 398 00:21:08,200 --> 00:21:10,760 Speaker 1: of these gravitational waves have we actually seen. 399 00:21:11,160 --> 00:21:13,639 Speaker 2: It's amazing to me that we've seen any You know, 400 00:21:13,800 --> 00:21:17,320 Speaker 2: Einstein predicted that these things existed, but he was very 401 00:21:17,320 --> 00:21:21,080 Speaker 2: skeptical that we could ever see them because gravitational waves 402 00:21:21,119 --> 00:21:23,840 Speaker 2: are so weak. I mean, the effect they have on 403 00:21:23,920 --> 00:21:27,359 Speaker 2: matter is really really tiny. You take a ruler, for example, 404 00:21:27,359 --> 00:21:29,840 Speaker 2: and a gravitational wave passing through it would shrink it 405 00:21:29,880 --> 00:21:32,400 Speaker 2: by one part in ten to the twenty or one 406 00:21:32,440 --> 00:21:36,280 Speaker 2: part inten to the twenty one, which seemed so impossible 407 00:21:36,400 --> 00:21:40,479 Speaker 2: to measure, and it took decades before anybody even really tried. 408 00:21:41,080 --> 00:21:43,879 Speaker 2: We know now about the success of Lego and Virgo 409 00:21:43,960 --> 00:21:47,600 Speaker 2: in twenty sixteen, but well before that people were thinking 410 00:21:47,600 --> 00:21:50,600 Speaker 2: about the possibility, and there was some pretty colorful history 411 00:21:50,640 --> 00:21:51,720 Speaker 2: about early attempts. 412 00:21:51,800 --> 00:21:54,159 Speaker 1: Yeah, I mean, I can't even wrap my head around 413 00:21:54,240 --> 00:21:56,399 Speaker 1: how you measure a gravitational wave. 414 00:21:56,560 --> 00:21:59,520 Speaker 2: So what you're trying to do is see space wiggle 415 00:21:59,520 --> 00:22:02,040 Speaker 2: back and forth. And so for example, if you have 416 00:22:02,119 --> 00:22:04,960 Speaker 2: two objects at a fixed distance and a gravitational wave 417 00:22:05,040 --> 00:22:07,440 Speaker 2: passes through it, what you'll see is those things get 418 00:22:07,480 --> 00:22:10,639 Speaker 2: slightly closer and then further, and then closer and then further. 419 00:22:11,040 --> 00:22:14,080 Speaker 2: So if you have some very precise ruler which doesn't 420 00:22:14,200 --> 00:22:17,160 Speaker 2: shift also with the gravitational waves, right, it's like rigid 421 00:22:17,400 --> 00:22:19,720 Speaker 2: where it uses laser beams, as we'll talk about later. 422 00:22:19,800 --> 00:22:23,120 Speaker 2: Then if you could measure their positions super duper precisely 423 00:22:23,560 --> 00:22:26,160 Speaker 2: and you have a way to avoid them otherwise wiggling, 424 00:22:26,520 --> 00:22:29,520 Speaker 2: then you can detect gravitational waves. That's the key. 425 00:22:29,760 --> 00:22:32,960 Speaker 1: Sounds like you need someone with incredibly steady hands. 426 00:22:33,880 --> 00:22:36,280 Speaker 2: The first person is to take this seriously. It was 427 00:22:36,320 --> 00:22:39,840 Speaker 2: a guy named Joseph Weber and in the late sixties 428 00:22:40,160 --> 00:22:43,840 Speaker 2: he built this big rod made of aluminum, these huge 429 00:22:43,880 --> 00:22:47,639 Speaker 2: aluminum cylinders that could vibrate a resonant frequency. And his 430 00:22:47,760 --> 00:22:50,520 Speaker 2: idea was that gravitational waves passing through it would cause 431 00:22:50,600 --> 00:22:54,240 Speaker 2: these things to resonate. And he attached these piezoelectric sensors 432 00:22:54,280 --> 00:22:56,800 Speaker 2: to them to make them super duper sensitive to tiny, 433 00:22:56,880 --> 00:23:00,119 Speaker 2: tiny wiggles in these cylinders, and so these are called 434 00:23:00,160 --> 00:23:03,719 Speaker 2: Weber bars, and he actually made claims of discovering I mean, 435 00:23:03,760 --> 00:23:06,160 Speaker 2: he saw wiggles in these things, and he thought, I'm 436 00:23:06,200 --> 00:23:09,800 Speaker 2: seeing gravitational waves. Now, at the time, this was not 437 00:23:09,960 --> 00:23:14,280 Speaker 2: taken very seriously because nobody thought gravitational waves were observable 438 00:23:14,400 --> 00:23:16,960 Speaker 2: at all, and so the idea that this guy had 439 00:23:17,000 --> 00:23:20,679 Speaker 2: seen them was like, very, very outlandish. Another problem was 440 00:23:20,680 --> 00:23:23,240 Speaker 2: that nobody could reproduce his results. I mean, people were 441 00:23:23,240 --> 00:23:26,119 Speaker 2: excited about it in principle, and a few other people 442 00:23:26,240 --> 00:23:29,280 Speaker 2: tried building similar devices to see if they could see 443 00:23:29,320 --> 00:23:31,600 Speaker 2: what he had seen, But nobody else ever saw the 444 00:23:31,600 --> 00:23:33,080 Speaker 2: blips that Webber had seen. 445 00:23:33,320 --> 00:23:37,000 Speaker 1: So this is kind of the equivalent of someone saying, hey, 446 00:23:37,040 --> 00:23:40,399 Speaker 1: I just held a seance and found a cure for cancer, exactly. 447 00:23:40,480 --> 00:23:43,080 Speaker 2: I had sort of a polarizing impact on the field 448 00:23:43,080 --> 00:23:46,639 Speaker 2: of gravitational wave astronomy. It made some people feel like, 449 00:23:46,840 --> 00:23:49,240 Speaker 2: oh my gosh, this feel is poisoned. It's filled with 450 00:23:49,400 --> 00:23:52,480 Speaker 2: Charlatan's And you know, there was some really colorful and 451 00:23:52,520 --> 00:23:56,960 Speaker 2: heated exchanges at conferences. You know, in June nineteen seventy four, 452 00:23:57,600 --> 00:24:01,520 Speaker 2: this physicist Garwin aggressively confronted did Weber with a claim 453 00:24:01,560 --> 00:24:04,120 Speaker 2: that they had found a mistake in his computer program 454 00:24:04,160 --> 00:24:08,600 Speaker 2: that analyzed his data and said that Weber's model was insane, quote, 455 00:24:08,720 --> 00:24:11,360 Speaker 2: because the universe would convert all of its energy into 456 00:24:11,440 --> 00:24:14,920 Speaker 2: gravitational radiation in fifty million years or so if one 457 00:24:14,960 --> 00:24:18,359 Speaker 2: were really detecting what Joe Webber was detecting. So this 458 00:24:18,440 --> 00:24:20,600 Speaker 2: got pretty hot and heavy, and there were like letters 459 00:24:20,600 --> 00:24:23,560 Speaker 2: written back and forth and physics today, this is like 460 00:24:23,600 --> 00:24:24,879 Speaker 2: a real physics feud. 461 00:24:25,359 --> 00:24:29,399 Speaker 1: I mean, it's very funny from the outside looking in 462 00:24:29,720 --> 00:24:33,800 Speaker 1: that this kind of you know, very technical thing of 463 00:24:33,920 --> 00:24:37,959 Speaker 1: detecting gravity waves would cause basically a physics riot, people 464 00:24:38,119 --> 00:24:39,200 Speaker 1: turning over cars. 465 00:24:39,440 --> 00:24:42,280 Speaker 2: Well, it was an outlandish claim, right, and so while 466 00:24:42,320 --> 00:24:45,639 Speaker 2: people are excited to believe it, also scientists are skeptical 467 00:24:46,200 --> 00:24:48,119 Speaker 2: and they got to be persuaded. And you're going to 468 00:24:48,160 --> 00:24:50,440 Speaker 2: make a claim like this, it's got to be rock solid. 469 00:24:50,640 --> 00:24:54,600 Speaker 2: And Weber continued to claim until his death that his 470 00:24:54,680 --> 00:24:58,159 Speaker 2: gravitational wave discoveries were real. And so, on one hand, 471 00:24:58,520 --> 00:25:00,960 Speaker 2: nobody believes that he saw grap vietational waves, and he 472 00:25:01,040 --> 00:25:03,480 Speaker 2: sort of gave the whole field a bad name. On 473 00:25:03,520 --> 00:25:06,439 Speaker 2: the other hand, he was kind of a pioneer. He 474 00:25:06,560 --> 00:25:09,160 Speaker 2: had the courage to try something out there, something weird, 475 00:25:09,200 --> 00:25:13,159 Speaker 2: something crazy, something nobody even thought was possible at all, 476 00:25:13,320 --> 00:25:16,240 Speaker 2: and in that sense did inspire the next generation of 477 00:25:16,280 --> 00:25:20,120 Speaker 2: gravitational wave astronomers, who in the end did figure it out. 478 00:25:20,240 --> 00:25:23,480 Speaker 2: There's a quote from a famous physicist, Wheeler whose Fineman's 479 00:25:23,520 --> 00:25:26,600 Speaker 2: grad school advisor, and he says, quote, no one else 480 00:25:26,640 --> 00:25:29,480 Speaker 2: had the courage to look for gravitational waves until Weber 481 00:25:29,600 --> 00:25:32,600 Speaker 2: showed that it was within the realm of the possible. 482 00:25:32,720 --> 00:25:34,600 Speaker 2: So you got to give Weber's some props for like 483 00:25:34,760 --> 00:25:37,679 Speaker 2: cracking this field open, even if his claims of discovery 484 00:25:37,880 --> 00:25:38,840 Speaker 2: never were born out. 485 00:25:39,080 --> 00:25:42,919 Speaker 1: It's definitely sort of a situation where nobody wants to 486 00:25:42,960 --> 00:25:46,000 Speaker 1: be the first idiot to try something, and then once 487 00:25:46,320 --> 00:25:49,400 Speaker 1: someone is the first idiot, it's like, well, at least 488 00:25:49,440 --> 00:25:51,760 Speaker 1: I won't be as much of an idiot as that guy, 489 00:25:51,960 --> 00:25:54,760 Speaker 1: so I get to try it this time. But that 490 00:25:54,800 --> 00:25:58,280 Speaker 1: first idiot is often very brave, and as long as 491 00:25:58,280 --> 00:26:01,360 Speaker 1: they don't die doing it by eating the wrong berries, 492 00:26:01,440 --> 00:26:03,480 Speaker 1: they are I think heroes. 493 00:26:03,720 --> 00:26:05,440 Speaker 2: Yeah, well, you know, just feed those berries to your 494 00:26:05,440 --> 00:26:07,520 Speaker 2: dog or your kid or whoever else you're willing to 495 00:26:07,560 --> 00:26:12,639 Speaker 2: experiment on. So this whole field is facing two big questions. 496 00:26:12,760 --> 00:26:18,280 Speaker 2: One is is it technically possible to see gravitational waves right, like, 497 00:26:18,359 --> 00:26:20,720 Speaker 2: can we build a device that can detect these things? 498 00:26:20,760 --> 00:26:24,600 Speaker 2: And the second is are there any gravitational waves at all? 499 00:26:25,160 --> 00:26:27,520 Speaker 2: And you know, now we are seeing gravitational waves from 500 00:26:27,560 --> 00:26:30,600 Speaker 2: black holes. But remember that back in the sixties and seventies, 501 00:26:30,720 --> 00:26:34,120 Speaker 2: the whole idea of black holes being real was kind 502 00:26:34,160 --> 00:26:34,639 Speaker 2: of new. 503 00:26:35,160 --> 00:26:35,359 Speaker 4: You know. 504 00:26:35,400 --> 00:26:38,520 Speaker 2: Black holes were another prediction of general relativity, which for 505 00:26:38,560 --> 00:26:41,840 Speaker 2: a long time people thought, nah, that can't actually exist 506 00:26:41,920 --> 00:26:44,760 Speaker 2: in the universe. It wasn't until we found bright radio 507 00:26:44,840 --> 00:26:47,879 Speaker 2: sources from the center of the galaxy and saw compact 508 00:26:47,920 --> 00:26:51,399 Speaker 2: objects we couldn't otherwise explain. The whole idea of black 509 00:26:51,440 --> 00:26:55,199 Speaker 2: holes went from crazy land to realistic. And so this 510 00:26:55,280 --> 00:26:58,760 Speaker 2: whole field is facing these two challenges simultaneously. But Weber 511 00:26:58,840 --> 00:27:01,640 Speaker 2: did inspire a bunch of other folks who had ideas 512 00:27:01,680 --> 00:27:05,439 Speaker 2: for how to build gravitational wave detectors using lasers. One 513 00:27:05,480 --> 00:27:07,520 Speaker 2: of the problems with Weber is that his device was 514 00:27:07,600 --> 00:27:11,080 Speaker 2: just too small. I mean, gravitational waves are super duper weak, 515 00:27:11,160 --> 00:27:13,480 Speaker 2: and so if you need to see a tiny increase 516 00:27:13,520 --> 00:27:16,320 Speaker 2: in the length of something, that's easier to do if 517 00:27:16,320 --> 00:27:19,280 Speaker 2: the something is really really big, bigger than like your 518 00:27:19,320 --> 00:27:22,320 Speaker 2: basement laboratory. You want something which is like tens of 519 00:27:22,400 --> 00:27:25,639 Speaker 2: meters or even kilometers long, so the effect of the 520 00:27:25,640 --> 00:27:27,320 Speaker 2: gravitational wave is larger. 521 00:27:27,480 --> 00:27:30,920 Speaker 1: I mean, it's sort of the blue whale model of physics, 522 00:27:30,920 --> 00:27:34,919 Speaker 1: where if your prey is very very tiny, it actually 523 00:27:35,000 --> 00:27:38,359 Speaker 1: helps to have a really really big net so that 524 00:27:38,440 --> 00:27:41,560 Speaker 1: you can catch a whole bunch of them. The bigger 525 00:27:41,600 --> 00:27:43,840 Speaker 1: the mouth, the easier it is to find the tiny 526 00:27:43,880 --> 00:27:45,000 Speaker 1: things exactly. 527 00:27:45,200 --> 00:27:47,880 Speaker 2: And so a bunch of folks at Caltech developed these 528 00:27:47,960 --> 00:27:52,680 Speaker 2: ideas for using lasers. The idea is instead of building 529 00:27:52,800 --> 00:27:56,160 Speaker 2: like a bar that's a kilometer long, just having use 530 00:27:56,200 --> 00:27:59,680 Speaker 2: an interferometer, which means you don't have an actual physical device, 531 00:27:59,720 --> 00:28:03,440 Speaker 2: you know, measuring the distance between two mirrors, for example, 532 00:28:03,760 --> 00:28:06,919 Speaker 2: by shooting a laser beam back and forth. And essentially 533 00:28:06,960 --> 00:28:09,040 Speaker 2: what you're doing is you're counting the number of times 534 00:28:09,080 --> 00:28:13,040 Speaker 2: the laser has wiggled on its journey because light has 535 00:28:13,080 --> 00:28:15,760 Speaker 2: a certain wavelength, As you actually split the beam and 536 00:28:15,800 --> 00:28:18,440 Speaker 2: send it in two different directions, and so when those 537 00:28:18,480 --> 00:28:21,840 Speaker 2: two beams come back, you interfere them and if they wiggle, 538 00:28:21,920 --> 00:28:25,199 Speaker 2: the different number of wavelengths on their journey, then it 539 00:28:25,359 --> 00:28:27,399 Speaker 2: changes the pattern of light that comes out in a 540 00:28:27,440 --> 00:28:29,159 Speaker 2: way that you're very very sensitive to. 541 00:28:29,640 --> 00:28:32,359 Speaker 1: Oh interesting, So when you split a beam right and 542 00:28:33,040 --> 00:28:37,160 Speaker 1: neither of them changes when they rejoin, would they sort 543 00:28:37,160 --> 00:28:39,920 Speaker 1: of go back to the original state that they were 544 00:28:40,320 --> 00:28:42,120 Speaker 1: in when they had split exactly? 545 00:28:42,160 --> 00:28:44,520 Speaker 2: If they both take exactly the same length journey, then 546 00:28:44,560 --> 00:28:46,840 Speaker 2: when they come back, they're the same part of their 547 00:28:46,840 --> 00:28:48,719 Speaker 2: wiggle and so they add back up to be their 548 00:28:48,720 --> 00:28:51,760 Speaker 2: original beam. If instead one of them has like gone 549 00:28:51,760 --> 00:28:55,200 Speaker 2: a half wavelength further, then now it's wiggling down when 550 00:28:55,200 --> 00:28:57,440 Speaker 2: the other one's wiggling up, and they would cancel out, 551 00:28:57,720 --> 00:29:02,200 Speaker 2: they would destructively interfere. By seeing that interference pattern, you 552 00:29:02,240 --> 00:29:05,800 Speaker 2: can tell very precisely how far that photon has traveled. 553 00:29:06,280 --> 00:29:08,720 Speaker 1: That's really clever. But you got to hold the mirrors 554 00:29:08,760 --> 00:29:10,600 Speaker 1: like really stable right. 555 00:29:10,760 --> 00:29:14,120 Speaker 2: Exactly, And that is the whole challenge is stabilizing these 556 00:29:14,160 --> 00:29:17,200 Speaker 2: mirrors against like a truck driving down the highway or 557 00:29:17,320 --> 00:29:21,400 Speaker 2: you know, a fly flying by, or seismic noise from. 558 00:29:21,240 --> 00:29:26,120 Speaker 1: The under underground. I want to go underground. 559 00:29:26,880 --> 00:29:30,160 Speaker 2: So they developed this prototypic caltech in their early eighties 560 00:29:30,520 --> 00:29:33,240 Speaker 2: with these laser arms that were like forty meters long. 561 00:29:33,320 --> 00:29:35,920 Speaker 2: Actually visited this thing when I went to Caltech to 562 00:29:35,920 --> 00:29:38,040 Speaker 2: think about going to grad school there, and I remember thinking, 563 00:29:38,520 --> 00:29:41,600 Speaker 2: this is a crazy experiment that's never going to work. 564 00:29:42,960 --> 00:29:45,160 Speaker 2: And boy was I wrong. I'm very happy to be 565 00:29:45,200 --> 00:29:47,720 Speaker 2: wrong about it. That experiment improved in principle that you 566 00:29:47,720 --> 00:29:50,600 Speaker 2: could do this laser interferometry. Though there were all sorts 567 00:29:50,600 --> 00:29:54,360 Speaker 2: of like crazy cost overruns and all sorts of shenanigans 568 00:29:54,560 --> 00:29:57,080 Speaker 2: and the sort of how they actually got hundreds of 569 00:29:57,160 --> 00:30:02,000 Speaker 2: millions of dollars to build legoineteen ninety four. NSF funded 570 00:30:02,000 --> 00:30:05,680 Speaker 2: it at two hundred and seventy million dollars, this huge, 571 00:30:05,680 --> 00:30:08,680 Speaker 2: scaled up version of the Caltech project with arms that 572 00:30:08,680 --> 00:30:12,240 Speaker 2: were kilometers long. It's an amazing story of like the 573 00:30:12,360 --> 00:30:14,680 Speaker 2: right person at the right time who happened to be 574 00:30:14,760 --> 00:30:19,440 Speaker 2: really into this despite like crazy cost overruns and mismanagement 575 00:30:19,480 --> 00:30:22,640 Speaker 2: in the original project. But somehow the NSF did it. 576 00:30:22,760 --> 00:30:25,959 Speaker 2: It was the biggest project they've ever funded in their history. 577 00:30:26,080 --> 00:30:30,120 Speaker 1: That person who wrote the grant deserves some kind of 578 00:30:30,160 --> 00:30:33,480 Speaker 1: award because writing a grant where it's like, now, we 579 00:30:33,600 --> 00:30:37,640 Speaker 1: don't know if these things exist, and it's very unlikely 580 00:30:37,680 --> 00:30:42,160 Speaker 1: we would ever be able to detect them. However, money exactly. 581 00:30:42,320 --> 00:30:45,840 Speaker 2: There's a guy the NSF, Isaacson, who said, quote, it 582 00:30:45,880 --> 00:30:48,960 Speaker 2: should never have been built. There's a couple of maniacs 583 00:30:49,080 --> 00:30:52,240 Speaker 2: running around with no signal having ever been discovered, talking 584 00:30:52,320 --> 00:30:57,560 Speaker 2: about pushing vacuum technology and laser technology and material technology 585 00:30:57,640 --> 00:31:02,080 Speaker 2: and seismic isolation and feedbacks systems orders of magnitude beyond 586 00:31:02,120 --> 00:31:05,040 Speaker 2: the current state of the art, using materials that hadn't 587 00:31:05,080 --> 00:31:06,040 Speaker 2: been invented yet. 588 00:31:06,280 --> 00:31:09,080 Speaker 1: Grant writers who get their grants like rejected for a 589 00:31:09,120 --> 00:31:13,120 Speaker 1: reasonable proposal just snapping their pencils in half in rage 590 00:31:13,200 --> 00:31:13,960 Speaker 1: right now. 591 00:31:14,080 --> 00:31:17,160 Speaker 2: Yes, exactly, and so what kudos to them? At the time, 592 00:31:17,240 --> 00:31:20,360 Speaker 2: a lot of astronomers were furious because this was a 593 00:31:20,440 --> 00:31:23,160 Speaker 2: huge chunk of money which could have gone to other projects, 594 00:31:23,240 --> 00:31:25,480 Speaker 2: and this seemed like a real boondoggle and if it 595 00:31:25,480 --> 00:31:28,360 Speaker 2: didn't see anything, it was going to kill the whole field. 596 00:31:28,680 --> 00:31:31,600 Speaker 2: So it's very controversial decision at the time. You know, now, 597 00:31:31,640 --> 00:31:33,800 Speaker 2: of course it's one Nobel prizes that were all grateful 598 00:31:33,840 --> 00:31:35,960 Speaker 2: for it, but at the time it was a really 599 00:31:36,040 --> 00:31:37,720 Speaker 2: really big risk for the NSF. 600 00:31:37,960 --> 00:31:41,160 Speaker 1: It's like the saving private Ryan of the physics world. 601 00:31:41,360 --> 00:31:43,840 Speaker 2: So the first iteration of the experiment LIGO ran from 602 00:31:43,880 --> 00:31:46,560 Speaker 2: two thousand and two to twenty ten, and they didn't 603 00:31:46,560 --> 00:31:49,120 Speaker 2: see any gravitational waves. And you know, they could have. 604 00:31:49,720 --> 00:31:52,920 Speaker 2: They were sensitive to gravitational waves, but they weren't as 605 00:31:53,000 --> 00:31:56,160 Speaker 2: good at like tamping down the noise and making everything 606 00:31:56,200 --> 00:31:59,080 Speaker 2: really crisp and clean as the next version of LOGO 607 00:31:59,240 --> 00:32:01,719 Speaker 2: was the one that actually made the discoveries. So for 608 00:32:01,760 --> 00:32:04,360 Speaker 2: them to have seen something the gravitational waves would have 609 00:32:04,440 --> 00:32:07,320 Speaker 2: to be like an elephant stampede. It was really more 610 00:32:07,360 --> 00:32:10,479 Speaker 2: about the developing the technology than actually discovering anything. 611 00:32:10,640 --> 00:32:13,760 Speaker 1: Two elephant shaped black holes crashing into each other. 612 00:32:15,360 --> 00:32:16,840 Speaker 2: So they made that work and it meant a lot 613 00:32:16,880 --> 00:32:19,200 Speaker 2: of stuff along the way, and then they shut down 614 00:32:19,320 --> 00:32:23,240 Speaker 2: to build advanced LEGO, which meant like reducing the noise 615 00:32:23,400 --> 00:32:26,200 Speaker 2: even further, because the quieter you can make the environment 616 00:32:26,240 --> 00:32:29,120 Speaker 2: for your lasers, the smaller the wiggle you can actually 617 00:32:29,120 --> 00:32:31,480 Speaker 2: detect and be confident in, which means you can hear 618 00:32:31,520 --> 00:32:34,400 Speaker 2: fainter signals, which means you can hear signals from further 619 00:32:34,520 --> 00:32:37,240 Speaker 2: out in the universe, so you're sensitive out to like 620 00:32:37,440 --> 00:32:38,680 Speaker 2: larger distances. 621 00:32:39,200 --> 00:32:43,040 Speaker 1: Now, as a podcaster, which is basically the same complexity 622 00:32:43,080 --> 00:32:46,160 Speaker 1: as being a part of Cull physicist. I always struggled 623 00:32:46,240 --> 00:32:49,240 Speaker 1: to get the sound quality good. I mean, right now 624 00:32:49,560 --> 00:32:53,400 Speaker 1: I'm traveling, so I'm actually in a closet trying to 625 00:32:53,640 --> 00:32:57,840 Speaker 1: reduce the amount of bouncing of audio waves. So how 626 00:32:57,840 --> 00:33:00,760 Speaker 1: do you do this though with something like this, because 627 00:33:01,200 --> 00:33:04,440 Speaker 1: you can't just put a bunch of foam around it. 628 00:33:04,600 --> 00:33:07,760 Speaker 1: We're stuck on earth, Well we're not, but for this 629 00:33:07,880 --> 00:33:12,320 Speaker 1: we are. And you have all this movement of the earth. 630 00:33:12,480 --> 00:33:15,520 Speaker 1: How do you and like you can't even going underground, 631 00:33:15,560 --> 00:33:19,160 Speaker 1: you still have I would assume some seismic movement underground. 632 00:33:19,200 --> 00:33:21,840 Speaker 1: So what do you do to cancel that out? 633 00:33:22,080 --> 00:33:24,120 Speaker 2: So they have a lot of different tricks they use. 634 00:33:24,400 --> 00:33:26,560 Speaker 2: One is that they put it on a pendulum. They 635 00:33:26,560 --> 00:33:29,760 Speaker 2: basically balance the whole thing on a string, which helps 636 00:33:29,800 --> 00:33:32,239 Speaker 2: decouple it from the motion of the earth. But then 637 00:33:32,240 --> 00:33:35,520 Speaker 2: they actually add another pendulum to that one, and another pendulum, 638 00:33:35,520 --> 00:33:38,560 Speaker 2: so they have like four pendulum stages, so that you 639 00:33:38,600 --> 00:33:40,880 Speaker 2: can like shove the top of this thing and the 640 00:33:40,920 --> 00:33:44,840 Speaker 2: mirror itself will hardly move. On top of that, they 641 00:33:44,840 --> 00:33:49,240 Speaker 2: have like active servos to reduce seismic noise, which is 642 00:33:49,240 --> 00:33:52,280 Speaker 2: sort of like noise canceling headphones. You know, they detect 643 00:33:52,280 --> 00:33:55,720 Speaker 2: wiggles in the earth, and then they unwiggle the mirror 644 00:33:55,720 --> 00:33:58,280 Speaker 2: and sort of to move it the opposite direction to 645 00:33:58,280 --> 00:34:00,480 Speaker 2: prevent the mirror itself from moving. 646 00:34:00,840 --> 00:34:03,360 Speaker 1: Now, have they tried plugging in a chicken brain? Because 647 00:34:03,480 --> 00:34:08,920 Speaker 1: chickens and other birds are really good at stabilizing their heads. 648 00:34:09,000 --> 00:34:11,799 Speaker 1: You can grab a chicken, buy its body and move 649 00:34:11,840 --> 00:34:15,320 Speaker 1: it around and its head stays perfectly stable. So it 650 00:34:15,400 --> 00:34:19,640 Speaker 1: sounds like servos are just basically little robotic chicken brains. 651 00:34:19,840 --> 00:34:21,719 Speaker 2: Yeah, that's actually the internal name they use in the 652 00:34:21,760 --> 00:34:24,440 Speaker 2: experiment is robotic chicken head, you know, and that's how 653 00:34:24,480 --> 00:34:27,480 Speaker 2: they referred to So they rebuilt this thing. It's much 654 00:34:27,520 --> 00:34:31,200 Speaker 2: more powerful, it's much quieter. Now they're sensitive to gravitational 655 00:34:31,239 --> 00:34:33,600 Speaker 2: waves from a much larger part of the universe, or 656 00:34:33,640 --> 00:34:36,680 Speaker 2: just quieter gravitational waves. So this is like the end 657 00:34:36,719 --> 00:34:39,839 Speaker 2: of twenty fifteen. It's in September, and they're turning this 658 00:34:39,840 --> 00:34:42,160 Speaker 2: thing on and you know, nobody knows what they're going 659 00:34:42,239 --> 00:34:46,600 Speaker 2: to hear. And incredibly, what they heard on September fourteenth, 660 00:34:46,680 --> 00:34:50,160 Speaker 2: just before eleven in the morning was a huge, perfect 661 00:34:50,400 --> 00:34:54,680 Speaker 2: gravitational wave It's basically like the first few days after 662 00:34:54,719 --> 00:34:57,760 Speaker 2: they turned this thing on, they heard a perfect one. 663 00:34:58,160 --> 00:35:01,360 Speaker 2: It was so nice that people thought they were being fooled. 664 00:35:01,520 --> 00:35:04,160 Speaker 2: And the experiment had actually done test runs where they 665 00:35:04,239 --> 00:35:07,440 Speaker 2: like injected fake gravitational waves into the data to see 666 00:35:07,480 --> 00:35:10,080 Speaker 2: if people notice them, you know, just to like figure 667 00:35:10,120 --> 00:35:12,680 Speaker 2: out if their systems were working. They keep people honest, 668 00:35:13,040 --> 00:35:15,000 Speaker 2: So everybody thought, oh, this must be one of those 669 00:35:15,040 --> 00:35:18,560 Speaker 2: test ones, ha ha ha. But it wasn't. It was real. 670 00:35:18,880 --> 00:35:22,800 Speaker 1: Wow, that's amazing. That's like stepping outside and suddenly seeing 671 00:35:22,880 --> 00:35:25,880 Speaker 1: like a new planet just like waving at you across 672 00:35:25,920 --> 00:35:26,320 Speaker 1: the sky. 673 00:35:27,280 --> 00:35:28,840 Speaker 2: Or it must have been something like you know, the 674 00:35:28,880 --> 00:35:31,560 Speaker 2: development of vision. There were like hundreds of millions of 675 00:35:31,640 --> 00:35:34,400 Speaker 2: years before anything on Earth, any kind of life, was 676 00:35:34,400 --> 00:35:37,959 Speaker 2: sensitive to photons, right, and then once we opened those 677 00:35:37,960 --> 00:35:40,840 Speaker 2: first primordial eyeballs, we're like, whoa, there's a lot to 678 00:35:40,880 --> 00:35:41,560 Speaker 2: see out here. 679 00:35:41,920 --> 00:35:45,600 Speaker 1: That little flatworm was probably wigging out, Like what is 680 00:35:45,719 --> 00:35:48,600 Speaker 1: going on? I don't even have a brain yet, and 681 00:35:48,680 --> 00:35:52,200 Speaker 1: yet my mind is blown. This sounds really incredible, Daniel. 682 00:35:52,280 --> 00:35:56,520 Speaker 1: If only we could hear from someone who's actually studied. 683 00:35:56,040 --> 00:36:02,799 Speaker 2: This, and fortunately we can. Well, I had a fun 684 00:36:02,840 --> 00:36:07,400 Speaker 2: conversation with cosmologist Angelika van Son, who told us all 685 00:36:07,440 --> 00:36:10,040 Speaker 2: about why it was the surprise to hear that first 686 00:36:10,040 --> 00:36:13,160 Speaker 2: gravitational wave, how many we have seen, and what we 687 00:36:13,239 --> 00:36:16,280 Speaker 2: have learned about how many black holes are out there. 688 00:36:16,520 --> 00:36:18,919 Speaker 1: Well, why don't we take a quick break and when 689 00:36:18,960 --> 00:36:22,200 Speaker 1: we get back, I think people would like to hear 690 00:36:22,440 --> 00:36:23,400 Speaker 1: from the expert. 691 00:36:36,040 --> 00:36:37,919 Speaker 2: Okay, we're back, and now we're going to hear from 692 00:36:37,960 --> 00:36:41,880 Speaker 2: a real expert on gravitational waves. Here's my interview with 693 00:36:42,000 --> 00:36:46,480 Speaker 2: cosmologist Angelika van Son. So it's my great pleasure to 694 00:36:46,680 --> 00:36:50,520 Speaker 2: introduce to the program Leka van Son, a cosmologist at 695 00:36:50,520 --> 00:36:54,680 Speaker 2: Harvard working on black holes and gravitational waves, and who 696 00:36:54,680 --> 00:36:57,760 Speaker 2: recently wrote a paper with the phrase monstrous black holes 697 00:36:57,840 --> 00:37:00,520 Speaker 2: in the title. Nika, welcome to the program. Thank you, 698 00:37:00,960 --> 00:37:01,239 Speaker 2: Thank you. 699 00:37:01,320 --> 00:37:03,560 Speaker 3: Daniel, very happy to be here. 700 00:37:03,640 --> 00:37:06,400 Speaker 2: So we have some basic questions about gravitational wave astronomy, 701 00:37:06,480 --> 00:37:09,680 Speaker 2: especially the first days. I remember when the first discoveries 702 00:37:09,719 --> 00:37:12,520 Speaker 2: were made, everybody seemed sort of surprised, like they just 703 00:37:12,560 --> 00:37:14,480 Speaker 2: turned this machine on and all of a sudden they 704 00:37:14,480 --> 00:37:17,560 Speaker 2: were seeing a signal. Why was it such a surprise 705 00:37:17,600 --> 00:37:18,200 Speaker 2: to everybody? 706 00:37:18,360 --> 00:37:21,160 Speaker 3: Okay, so there's multiple aspects here. So first of all, 707 00:37:21,760 --> 00:37:23,880 Speaker 3: they did just turn a machine on, but you have 708 00:37:23,960 --> 00:37:26,760 Speaker 3: to take into account that the history behind us goes 709 00:37:27,320 --> 00:37:31,239 Speaker 3: back much further, Like this was already advanced Lego that 710 00:37:31,280 --> 00:37:34,000 Speaker 3: they were running, and so they've been already trying to 711 00:37:34,000 --> 00:37:38,839 Speaker 3: detect black holes for like twenty five years. But inherently 712 00:37:39,040 --> 00:37:41,759 Speaker 3: black holes are just very rare. So about one in 713 00:37:41,880 --> 00:37:45,960 Speaker 3: every ten thousand stars forms a black hole, and that's 714 00:37:46,040 --> 00:37:48,520 Speaker 3: just forming one black hole. What we were seeing with 715 00:37:48,640 --> 00:37:52,480 Speaker 3: Lego Virgo with gravitational waves was two black holes smashing 716 00:37:52,520 --> 00:37:56,680 Speaker 3: in together, forming a newer, more massive black hole. So 717 00:37:57,200 --> 00:37:59,760 Speaker 3: this brings us actually to the second part of the problem, 718 00:37:59,760 --> 00:38:03,680 Speaker 3: which WHI is what's called in the literature the separation problem. 719 00:38:04,280 --> 00:38:08,000 Speaker 3: So dravity is actually a very weak force, and so 720 00:38:08,600 --> 00:38:12,520 Speaker 3: to merge two black holes within the age of our universe, 721 00:38:13,040 --> 00:38:15,759 Speaker 3: which within a huple time, we have to put the 722 00:38:15,800 --> 00:38:19,960 Speaker 3: black holes very close together on a very very short orbit. However, 723 00:38:20,239 --> 00:38:23,279 Speaker 3: the massive stars that come before these black holes, that 724 00:38:23,320 --> 00:38:27,160 Speaker 3: are their progenitors, they are much bigger than a small orbit. 725 00:38:27,400 --> 00:38:30,280 Speaker 3: They're like a thousand times or one hundred thousand times 726 00:38:30,360 --> 00:38:33,319 Speaker 3: is big. And so this is what we call the 727 00:38:33,440 --> 00:38:38,680 Speaker 3: separation problem. Which basically asks the question, how can we 728 00:38:38,760 --> 00:38:42,040 Speaker 3: get two stars to form two black holes and such 729 00:38:42,080 --> 00:38:46,480 Speaker 3: short orbits when they cannot have worn that bain. So 730 00:38:47,280 --> 00:38:50,480 Speaker 3: this is basically the whole field of trying to understand 731 00:38:50,680 --> 00:38:54,320 Speaker 3: how binary black hole mergers form. And this is exactly 732 00:38:54,360 --> 00:38:58,320 Speaker 3: where all the uncertainties come from. But before the first detection, 733 00:38:58,960 --> 00:39:02,439 Speaker 3: we thought this was very rare. This never happens most 734 00:39:02,480 --> 00:39:06,040 Speaker 3: of the time. Stars they don't form black holes right 735 00:39:06,120 --> 00:39:09,640 Speaker 3: at the right location to form merging black holes. 736 00:39:09,760 --> 00:39:12,040 Speaker 2: So, just to make sure I understand, you're saying that, 737 00:39:12,080 --> 00:39:13,719 Speaker 2: in order to make a black hole, a star has 738 00:39:13,719 --> 00:39:17,360 Speaker 2: to be sort of already anomalously big, and that also 739 00:39:17,480 --> 00:39:19,880 Speaker 2: to make a pair of black holes that will merge, 740 00:39:19,880 --> 00:39:22,120 Speaker 2: they have to be close together. And it's hard to 741 00:39:22,160 --> 00:39:25,560 Speaker 2: understand how you get two really big stars so close together, 742 00:39:25,640 --> 00:39:28,000 Speaker 2: so they form two black holes which can end up merging. 743 00:39:28,360 --> 00:39:31,400 Speaker 3: Almost The thing is, indeed, these two black holes have 744 00:39:31,440 --> 00:39:35,200 Speaker 3: to be really close. But the stars, throughout their life 745 00:39:35,280 --> 00:39:39,480 Speaker 3: they change in their size, so throughout their life before 746 00:39:39,520 --> 00:39:42,880 Speaker 3: they die and form a black hole at one point, 747 00:39:42,920 --> 00:39:45,960 Speaker 3: they will be really big stars. When they get older, 748 00:39:46,320 --> 00:39:49,160 Speaker 3: they swell up, just like humans tend to do when 749 00:39:49,160 --> 00:39:52,560 Speaker 3: they get older, they become much bigger, and so they 750 00:39:52,560 --> 00:39:54,640 Speaker 3: become so big that they wouldn't fit next to each 751 00:39:54,640 --> 00:39:58,520 Speaker 3: other anymore. And what would happen, what we expect would happen, 752 00:39:58,719 --> 00:40:01,160 Speaker 3: is that these stars would merge as a stellar merger. 753 00:40:01,880 --> 00:40:04,840 Speaker 3: But that didn't happen because we formed two black holes. 754 00:40:05,360 --> 00:40:09,279 Speaker 3: So in some way, these stars managed to lose some 755 00:40:09,320 --> 00:40:12,960 Speaker 3: of their weights, to exchange some of their angular momentum, 756 00:40:13,360 --> 00:40:17,160 Speaker 3: and to put the stars on different orbits than they started. 757 00:40:17,200 --> 00:40:20,239 Speaker 3: So they might have started out very wide, but then 758 00:40:20,560 --> 00:40:24,520 Speaker 3: exchanged mass between each other to finally end up at 759 00:40:24,640 --> 00:40:28,440 Speaker 3: as very much smaller orbit but much more compact, forming 760 00:40:28,440 --> 00:40:29,280 Speaker 3: two black holes. 761 00:40:29,480 --> 00:40:31,839 Speaker 2: I see. So we thought this sort of arrangement, this 762 00:40:31,880 --> 00:40:34,640 Speaker 2: particular dance was pretty rare and it would be hard 763 00:40:34,680 --> 00:40:37,960 Speaker 2: to see black hole mergers because this configuration didn't happen 764 00:40:38,080 --> 00:40:38,640 Speaker 2: very often in. 765 00:40:38,600 --> 00:40:42,480 Speaker 3: The universe exactly. And this really shows how little we 766 00:40:42,600 --> 00:40:46,560 Speaker 3: actually know about binary interactions, which is this exchange of 767 00:40:46,680 --> 00:40:50,960 Speaker 3: mass between stars and massive stars in general, because massive 768 00:40:51,000 --> 00:40:54,920 Speaker 3: stars it was not a very popular field before gravitational 769 00:40:54,960 --> 00:40:58,719 Speaker 3: waves came around. If you came to your supervisor or 770 00:40:58,760 --> 00:41:01,200 Speaker 3: advisor twenty years of going, you'd said, hey, I want 771 00:41:01,239 --> 00:41:04,920 Speaker 3: to go and study stars. They probably say, wow, stars, 772 00:41:05,040 --> 00:41:07,160 Speaker 3: that's all figured out. We know that by now, we 773 00:41:07,200 --> 00:41:09,960 Speaker 3: don't have to do anything anymore. Except then they figured 774 00:41:09,960 --> 00:41:13,720 Speaker 3: out in twenty twelve that most stars don't live alone. 775 00:41:13,800 --> 00:41:17,359 Speaker 3: They actually live in pairs in these binaries, which can 776 00:41:17,400 --> 00:41:22,480 Speaker 3: then form binary black holes. And we also found out 777 00:41:22,520 --> 00:41:26,600 Speaker 3: that massive stars are wildly different from low mass stars. 778 00:41:27,080 --> 00:41:30,320 Speaker 3: And we don't have any idea how these high mass 779 00:41:30,320 --> 00:41:32,760 Speaker 3: stars live their life and die. 780 00:41:33,120 --> 00:41:35,120 Speaker 2: What are the mysteries there? I mean, they are hotter, 781 00:41:35,440 --> 00:41:38,799 Speaker 2: they burn brighter, so they shorter lived. What are the 782 00:41:38,840 --> 00:41:40,120 Speaker 2: questions people are still asking? 783 00:41:40,520 --> 00:41:43,440 Speaker 3: This hotter and brighter part is actually what makes it 784 00:41:43,480 --> 00:41:46,840 Speaker 3: so difficult to study these stars while they're alive, because 785 00:41:47,000 --> 00:41:50,640 Speaker 3: basically they live fast and die young, and as I 786 00:41:50,719 --> 00:41:55,560 Speaker 3: mentioned before, they're intrinsically rare. Most stars that form will 787 00:41:55,600 --> 00:41:58,880 Speaker 3: form as lower mass stars, and only a few stars 788 00:41:58,880 --> 00:42:02,000 Speaker 3: will form a very small fraction of all stars will 789 00:42:02,040 --> 00:42:05,759 Speaker 3: form as high mass stars. Where with high mass I 790 00:42:05,920 --> 00:42:09,560 Speaker 3: now mean something of about twenty times as massive as 791 00:42:09,560 --> 00:42:12,840 Speaker 3: our sun, because that's what you need to form a 792 00:42:12,880 --> 00:42:16,400 Speaker 3: black hole. But because they're so intrinsically rare and so 793 00:42:16,560 --> 00:42:19,600 Speaker 3: short lived, we only have a handful of stars observed 794 00:42:20,120 --> 00:42:25,120 Speaker 3: while alive of the order of fifty to one hundred 795 00:42:25,200 --> 00:42:28,319 Speaker 3: solar masses. So that solar mass is this unit that 796 00:42:28,360 --> 00:42:32,600 Speaker 3: we use for how massive stars are. And black holes, 797 00:42:32,760 --> 00:42:37,440 Speaker 3: and even when you study them, they're often shrouded in 798 00:42:37,520 --> 00:42:42,120 Speaker 3: all these clouds of dust literal dusts that they've expelled themselves, 799 00:42:42,160 --> 00:42:45,680 Speaker 3: making it very hard to actually observe any of the 800 00:42:45,719 --> 00:42:48,840 Speaker 3: internal properties or if any of the properties of these stars. 801 00:42:49,040 --> 00:42:51,480 Speaker 3: So we don't know how big they get, we don't 802 00:42:51,560 --> 00:42:55,319 Speaker 3: know how much of their fuel they will use, we 803 00:42:55,400 --> 00:42:58,920 Speaker 3: don't know if they're spinning, we don't know how strong 804 00:42:58,960 --> 00:43:02,520 Speaker 3: their winds are. And that's just for single massive stars. 805 00:43:02,880 --> 00:43:06,640 Speaker 3: Then if you make two massive stars, it's double the trouble. 806 00:43:06,680 --> 00:43:09,719 Speaker 3: And so we don't know when they interact with each other, 807 00:43:10,160 --> 00:43:14,440 Speaker 3: when they interact, how it proceeds, like is it a 808 00:43:14,560 --> 00:43:17,640 Speaker 3: stable or an unstable interaction. So there's a lot of 809 00:43:17,760 --> 00:43:21,880 Speaker 3: question marks there, and we actually hope that gravitational waves 810 00:43:21,880 --> 00:43:24,719 Speaker 3: can help us shed some light on the life of 811 00:43:24,760 --> 00:43:29,400 Speaker 3: these stars because black holes are basically foss sales of 812 00:43:29,680 --> 00:43:33,160 Speaker 3: massive stars, and so we can use them to learn 813 00:43:33,200 --> 00:43:35,800 Speaker 3: something about stars that lived long ago. 814 00:43:36,120 --> 00:43:39,280 Speaker 2: All right, So then take us back to September twenty fifteen, 815 00:43:39,480 --> 00:43:42,160 Speaker 2: they just turned on advanced lego. Nobody ever seen a 816 00:43:42,200 --> 00:43:45,360 Speaker 2: gravitational wave with this history of like Joseph Weber and 817 00:43:45,360 --> 00:43:47,239 Speaker 2: all of his claims in the field, was sort of 818 00:43:47,800 --> 00:43:50,440 Speaker 2: not the most exciting one, maybe not the one people 819 00:43:50,480 --> 00:43:53,040 Speaker 2: thought would yield the discovery. And then they turn this 820 00:43:53,040 --> 00:43:56,040 Speaker 2: thing on and they see a signal within days or 821 00:43:56,080 --> 00:43:59,680 Speaker 2: weeks of their new telescope opening this eyeball to the universe. 822 00:43:59,920 --> 00:44:02,960 Speaker 2: Is does that mean about our understanding of these massive 823 00:44:02,960 --> 00:44:05,880 Speaker 2: stars and how often binary black holes form? Did we 824 00:44:05,960 --> 00:44:08,600 Speaker 2: totally undershoot it? Were there some people who were predicting 825 00:44:08,640 --> 00:44:10,960 Speaker 2: we would see something or was it a surprise to everybody? 826 00:44:11,280 --> 00:44:17,000 Speaker 3: Yeah, basically before that we indeed definitely undershot the expectation. 827 00:44:17,239 --> 00:44:21,879 Speaker 3: Our population models expected much lower rate of binary black 828 00:44:21,880 --> 00:44:24,440 Speaker 3: hole and black hole nutron star, etcetera. And indeed, it 829 00:44:24,520 --> 00:44:27,080 Speaker 3: was right on the first date that they turned the 830 00:44:27,120 --> 00:44:29,920 Speaker 3: detector on they got this beautiful signal that was so 831 00:44:30,000 --> 00:44:32,360 Speaker 3: beautiful that people thought they were still looking at a 832 00:44:32,400 --> 00:44:35,279 Speaker 3: test signal and someone forgotten to put the test off. 833 00:44:36,400 --> 00:44:40,680 Speaker 3: But yeah, we heavily undershot with the rates. But as 834 00:44:40,719 --> 00:44:45,080 Speaker 3: I mentioned, the theory of massive stellar evolution is still 835 00:44:45,400 --> 00:44:48,080 Speaker 3: very uncertain. There's lots of things we need to learn 836 00:44:48,120 --> 00:44:51,200 Speaker 3: about how these stars live their life, and this causes 837 00:44:51,239 --> 00:44:55,160 Speaker 3: the main uncertainty in how we predict what the rates 838 00:44:55,200 --> 00:44:59,319 Speaker 3: of these events will be. And so currently we're still 839 00:44:59,320 --> 00:45:03,160 Speaker 3: at the stage where our models have a rates prediction 840 00:45:03,320 --> 00:45:08,080 Speaker 3: that varies over multiple orders of magnitude. So the rates 841 00:45:08,120 --> 00:45:10,520 Speaker 3: of Likego virgo, the rates that we see today are 842 00:45:10,560 --> 00:45:14,640 Speaker 3: within that error. But we also can heavily overshoot or 843 00:45:14,680 --> 00:45:19,960 Speaker 3: heavily undershoot, depending on what parameters we adopt in our models. 844 00:45:20,360 --> 00:45:23,439 Speaker 3: And so piece by piece, as we are getting more 845 00:45:23,480 --> 00:45:27,680 Speaker 3: information about these gravitational waves, we can constrain parts of 846 00:45:27,719 --> 00:45:30,879 Speaker 3: our models, and then not just using the rate right, 847 00:45:30,920 --> 00:45:34,560 Speaker 3: but also using the masses, their spins, their mass ratios, 848 00:45:34,600 --> 00:45:36,560 Speaker 3: all the properties that we can get our hands on. 849 00:45:37,680 --> 00:45:42,239 Speaker 3: Using that, we can slowly understand our models better and 850 00:45:42,760 --> 00:45:43,919 Speaker 3: constrain them as well. 851 00:45:44,080 --> 00:45:46,560 Speaker 2: I see, so we've measured now a bunch of gravitational waves. 852 00:45:46,880 --> 00:45:49,239 Speaker 2: We were surprised to see them so quickly, which means 853 00:45:49,239 --> 00:45:51,560 Speaker 2: we undershot them, and now we sort of adjusted all 854 00:45:51,600 --> 00:45:55,560 Speaker 2: of our estimates up to match what we've observed. Can 855 00:45:55,600 --> 00:45:58,600 Speaker 2: we then make any predictions, or we just fitting these 856 00:45:58,680 --> 00:46:01,359 Speaker 2: rates to the data, or do we have any other 857 00:46:01,440 --> 00:46:03,560 Speaker 2: alternative way to make these predictions? Now, do we have 858 00:46:03,560 --> 00:46:06,520 Speaker 2: like a deeper understanding of the internal mechanisms of the 859 00:46:06,560 --> 00:46:08,880 Speaker 2: massive stars, any other handle on this. 860 00:46:09,239 --> 00:46:12,040 Speaker 3: Yeah, so definitely what we were trying to do is 861 00:46:12,160 --> 00:46:15,759 Speaker 3: approach us from multiple sides, right, We are trying to 862 00:46:15,920 --> 00:46:21,560 Speaker 3: make these predictions from our knowledge up right, So we 863 00:46:21,640 --> 00:46:25,000 Speaker 3: start with what we know about stars, and then we say, okay, 864 00:46:25,040 --> 00:46:28,439 Speaker 3: we expect to see this many black holes, and then 865 00:46:28,600 --> 00:46:32,000 Speaker 3: some of their models actually overshoot. Some of those models 866 00:46:32,080 --> 00:46:36,160 Speaker 3: undershoot in the rate that we observed. But to make 867 00:46:36,320 --> 00:46:39,799 Speaker 3: a full picture of massive stars and black holes and 868 00:46:39,840 --> 00:46:43,040 Speaker 3: gravitational waves, we should use all the information that we have. 869 00:46:43,640 --> 00:46:49,320 Speaker 3: So we can also tailor other transient events such as supernovae, 870 00:46:49,480 --> 00:46:53,280 Speaker 3: which happens when a star dies, so that's a step 871 00:46:53,320 --> 00:46:57,560 Speaker 3: before you form emerging black hole or any black hole. 872 00:46:59,120 --> 00:47:02,040 Speaker 3: And the supernova rate is also something that we've observed 873 00:47:02,080 --> 00:47:07,640 Speaker 3: through normal electromagnetic waves. But ideally we want to match 874 00:47:07,719 --> 00:47:10,399 Speaker 3: all these different rates at the same time, which will 875 00:47:10,400 --> 00:47:13,319 Speaker 3: give us stronger constraints on which of our models make 876 00:47:13,440 --> 00:47:16,840 Speaker 3: some sense and which of our models don't make sense interesting. 877 00:47:16,920 --> 00:47:19,480 Speaker 2: And so now we have this little sample, like you know, 878 00:47:19,560 --> 00:47:23,319 Speaker 2: roughly one hundred or so gravitational waves from these mergers. 879 00:47:23,640 --> 00:47:25,800 Speaker 2: What are their features in there? Like we can measure 880 00:47:25,800 --> 00:47:28,560 Speaker 2: the masses. Are there surprises in the masses of these 881 00:47:28,560 --> 00:47:30,640 Speaker 2: black holes that we're seeing, Are there like clumps or 882 00:47:30,680 --> 00:47:33,520 Speaker 2: gaps or things in there that we didn't expect? 883 00:47:33,760 --> 00:47:35,880 Speaker 3: This is one hundred percent the way that we're going. 884 00:47:36,640 --> 00:47:41,480 Speaker 3: The distribution of masses contains more information than just the rate, 885 00:47:41,960 --> 00:47:46,120 Speaker 3: and at this moment, we've seen two features certainly in 886 00:47:46,200 --> 00:47:50,760 Speaker 3: the mass distribution of merging binary black holes. We've seen 887 00:47:50,920 --> 00:47:55,799 Speaker 3: one feature at higher masses which has received by far 888 00:47:55,840 --> 00:47:59,520 Speaker 3: the most attention and has been really in the news 889 00:47:59,560 --> 00:48:03,160 Speaker 3: a lot, and that is because this feature has been 890 00:48:03,200 --> 00:48:06,319 Speaker 3: this kind of bump in a mass distribution has been 891 00:48:06,360 --> 00:48:11,120 Speaker 3: linked to something that we call parents stability supernova, and 892 00:48:11,200 --> 00:48:16,480 Speaker 3: that's a type of supernova that basically causes the most 893 00:48:16,480 --> 00:48:20,280 Speaker 3: massive stars that would form the most massive black holes. 894 00:48:20,800 --> 00:48:24,600 Speaker 3: Instead of forming a black hole, they will die prematurely, 895 00:48:24,840 --> 00:48:27,719 Speaker 3: so they will go into supernova prematurely. I mean they 896 00:48:27,760 --> 00:48:32,000 Speaker 3: haven't finished all their burning cycles yet, and this causes 897 00:48:32,040 --> 00:48:35,160 Speaker 3: them to explode without forming any black hole at all. 898 00:48:36,440 --> 00:48:41,280 Speaker 3: And so theory predicted that single stars or massive stars 899 00:48:41,280 --> 00:48:44,919 Speaker 3: couldn't form black holes with masses above about forty five 900 00:48:44,960 --> 00:48:47,759 Speaker 3: solar masses, and that there should be a sort of 901 00:48:47,920 --> 00:48:52,480 Speaker 3: bump in the distribution right below that gap. And so 902 00:48:52,680 --> 00:48:55,880 Speaker 3: the bump that we saw in the mass distribution at 903 00:48:55,880 --> 00:48:59,680 Speaker 3: thirty five solar masses, people were really excited because they thought, oh, 904 00:48:59,800 --> 00:49:03,320 Speaker 3: that's that bump from the parent's stability. So that means 905 00:49:03,360 --> 00:49:07,000 Speaker 3: that that is the limit where normal stars can form 906 00:49:07,040 --> 00:49:11,320 Speaker 3: black holes. But we don't see a gap above this bump. 907 00:49:11,640 --> 00:49:15,560 Speaker 3: We still see black holes. So basically these black holes 908 00:49:15,560 --> 00:49:20,719 Speaker 3: shouldn't exist, but yet they are there. And so this 909 00:49:20,880 --> 00:49:23,160 Speaker 3: intrigued a lot of people in trying to figure out 910 00:49:23,239 --> 00:49:27,040 Speaker 3: how can you form black holes above this kind of 911 00:49:27,560 --> 00:49:31,640 Speaker 3: cutoff mass from massive stars above this parent stability limits. 912 00:49:31,680 --> 00:49:34,200 Speaker 3: And so that excited a lot of people coming up 913 00:49:34,239 --> 00:49:38,320 Speaker 3: with all kinds of wild ideas going from bosone stars 914 00:49:38,400 --> 00:49:42,960 Speaker 3: to just galaxy clusters where you have second order or 915 00:49:43,560 --> 00:49:49,320 Speaker 3: second generation black holes. But more recent work actually points 916 00:49:49,320 --> 00:49:53,239 Speaker 3: towards that bump not being related to the parents stability. 917 00:49:53,680 --> 00:49:58,360 Speaker 3: So I think at this point we don't know what 918 00:49:58,480 --> 00:50:02,640 Speaker 3: the bump is caused by and the real bump, the 919 00:50:02,640 --> 00:50:06,680 Speaker 3: real parent's stability limit should be somewhere around sixty solar 920 00:50:06,760 --> 00:50:10,479 Speaker 3: masses instead of thirty solar masses where we see it now. 921 00:50:11,360 --> 00:50:13,759 Speaker 3: And so I'm quite excited for the next run to 922 00:50:13,880 --> 00:50:18,800 Speaker 3: see if we will discover an extra feature at sixty 923 00:50:18,840 --> 00:50:24,560 Speaker 3: solar masses. I see there will exactly, and I want 924 00:50:24,560 --> 00:50:26,680 Speaker 3: to understand what the bump at thirty five is doing 925 00:50:26,719 --> 00:50:30,040 Speaker 3: as well. And then there's also the low mass bump. 926 00:50:30,239 --> 00:50:33,440 Speaker 3: So that bump actually is also really interesting because at 927 00:50:33,480 --> 00:50:35,920 Speaker 3: the moment we're not really sure if it's a bump 928 00:50:36,200 --> 00:50:40,920 Speaker 3: or if it's just a continuous line. And this bump 929 00:50:41,040 --> 00:50:44,480 Speaker 3: is very much related to something that we've called the 930 00:50:44,640 --> 00:50:49,600 Speaker 3: neutron star black hole mask gap, which was actually thought 931 00:50:49,600 --> 00:50:52,440 Speaker 3: of twenty years ago. Twenty years ago, people were looking 932 00:50:52,480 --> 00:50:56,480 Speaker 3: at black holes through X ray observations, so that's you 933 00:50:56,480 --> 00:50:59,319 Speaker 3: can only see black holes through X ray observations if 934 00:50:59,360 --> 00:51:02,000 Speaker 3: they are create mass. And they were looking at these 935 00:51:02,040 --> 00:51:04,839 Speaker 3: black holes that were treating mass, and they said, hey, 936 00:51:04,960 --> 00:51:08,879 Speaker 3: all of these black holes are significantly more massive than 937 00:51:09,160 --> 00:51:13,120 Speaker 3: nutron stars. So there's a gap between the most massive 938 00:51:13,160 --> 00:51:15,680 Speaker 3: nutron star and the least massive black hole that we 939 00:51:15,760 --> 00:51:20,279 Speaker 3: can form. And since people came up with this observation 940 00:51:20,480 --> 00:51:24,360 Speaker 3: twenty years ago, it has been heavily debated over the 941 00:51:24,480 --> 00:51:29,719 Speaker 3: full twenty years. But the gravitational wave detections that are 942 00:51:29,760 --> 00:51:33,640 Speaker 3: now rolling in are providing us with a new opportunity 943 00:51:33,719 --> 00:51:37,360 Speaker 3: to measure if this gap is real. And there's a 944 00:51:37,440 --> 00:51:42,680 Speaker 3: few observations that are already contradicting this gap between neutron 945 00:51:42,719 --> 00:51:46,640 Speaker 3: stars and black holes, saying that, oh, maybe there isn't 946 00:51:46,920 --> 00:51:50,200 Speaker 3: a gap between nutron stars and black holes, which tells 947 00:51:50,280 --> 00:51:53,480 Speaker 3: us a lot about how nutron stars and black. 948 00:51:53,239 --> 00:51:56,240 Speaker 2: Holes form, So why would there be a gap. 949 00:51:55,920 --> 00:51:59,120 Speaker 3: So that's a good question. This was actually a case 950 00:51:59,239 --> 00:52:04,399 Speaker 3: where the theory came after the observation, so people came 951 00:52:04,480 --> 00:52:08,319 Speaker 3: up with theories to explain the observation and X ray 952 00:52:08,320 --> 00:52:14,239 Speaker 3: binaries saying that maybe supernova for nutron stars are just 953 00:52:14,400 --> 00:52:18,480 Speaker 3: very different than supernova for black holes. Whereas, if you 954 00:52:18,560 --> 00:52:21,360 Speaker 3: have a supernova for a nutron star that forms a 955 00:52:21,440 --> 00:52:24,560 Speaker 3: nutron star, you manage to blow all of the outer 956 00:52:24,680 --> 00:52:28,160 Speaker 3: layers away and you only keep the core nutron star 957 00:52:28,239 --> 00:52:30,719 Speaker 3: that's in the inner bit of your star, Whereas if 958 00:52:30,800 --> 00:52:34,200 Speaker 3: you become slightly more massive and you have a core 959 00:52:34,280 --> 00:52:38,520 Speaker 3: that will form a black hole. Then the explosion is 960 00:52:38,560 --> 00:52:41,400 Speaker 3: no longer strong enough to really throw away all the 961 00:52:41,440 --> 00:52:45,240 Speaker 3: outer layers of the star, and part of these outer 962 00:52:45,360 --> 00:52:51,200 Speaker 3: layers fall back onto the proto black protein compact objects. 963 00:52:51,280 --> 00:52:54,799 Speaker 3: And so these extra layers add on an extra fuel 964 00:52:54,800 --> 00:52:59,439 Speaker 3: solar masses, bumping the mass up to by a few 965 00:52:59,440 --> 00:53:04,160 Speaker 3: solar mass, thereby creating a gap in a random mass distribution. 966 00:53:04,360 --> 00:53:07,920 Speaker 2: Wow. Fascinating. So what are you looking forward to seeing 967 00:53:08,040 --> 00:53:12,320 Speaker 2: in this next run of Advanced Lego and Virgo and Carga, 968 00:53:12,600 --> 00:53:13,560 Speaker 2: the one that's just starting. 969 00:53:13,920 --> 00:53:18,320 Speaker 3: Yeah, So the most exciting observations are always the crazy outliers, 970 00:53:18,640 --> 00:53:22,880 Speaker 3: because things that are outliers are things that we don't expect. 971 00:53:23,080 --> 00:53:25,680 Speaker 3: So they mean that we have to readjust our theory 972 00:53:25,800 --> 00:53:28,880 Speaker 3: or figure out something new, which as a theorist I 973 00:53:28,960 --> 00:53:32,319 Speaker 3: love to do. I mean, something super fun would be 974 00:53:32,400 --> 00:53:35,719 Speaker 3: something that contradicts both mask gaps. So something that is 975 00:53:35,760 --> 00:53:37,840 Speaker 3: in the lower end this upper mask gap at the 976 00:53:37,840 --> 00:53:42,240 Speaker 3: same time, that's something wild. I don't expect that to happen, 977 00:53:42,280 --> 00:53:45,359 Speaker 3: which is exactly why you're so exciting, but. 978 00:53:45,360 --> 00:53:48,000 Speaker 2: It sounds like you're secretly hoping for it, exactly. 979 00:53:48,400 --> 00:53:51,719 Speaker 3: I always like when things have to be thrown over 980 00:53:51,800 --> 00:53:53,439 Speaker 3: and we can start at the drawing table. 981 00:53:53,520 --> 00:53:57,080 Speaker 2: Again. Those are the most fun moments in history, absolutely exactly. 982 00:53:57,960 --> 00:54:04,000 Speaker 3: So what I'm more realistically excited about is, as I 983 00:54:04,120 --> 00:54:06,960 Speaker 3: just mentioned, at the low masses, I would like to 984 00:54:07,040 --> 00:54:10,839 Speaker 3: know if that's really truly empty or not. Is there 985 00:54:10,880 --> 00:54:13,400 Speaker 3: a gap between neutron stars and black holes or not, 986 00:54:13,719 --> 00:54:18,240 Speaker 3: And is there another feature at about sixty solar masses 987 00:54:18,360 --> 00:54:21,759 Speaker 3: or not. These are things that we can probably hopefully 988 00:54:21,920 --> 00:54:26,480 Speaker 3: see in the next four run. But also I've been 989 00:54:26,520 --> 00:54:29,560 Speaker 3: talking a lot about the masses, but I'd be very 990 00:54:29,600 --> 00:54:35,160 Speaker 3: excited if we got a certain observation of a system 991 00:54:35,239 --> 00:54:37,880 Speaker 3: with a lot of eccentricity or with a lot of spin, 992 00:54:38,320 --> 00:54:43,160 Speaker 3: because those barometers are more difficult to measure, so we 993 00:54:43,280 --> 00:54:46,080 Speaker 3: kind of need a golden event in order to be 994 00:54:46,160 --> 00:54:49,200 Speaker 3: able to make a proper observation there. So I would 995 00:54:49,239 --> 00:54:51,680 Speaker 3: love if we have one or two golden events in 996 00:54:51,719 --> 00:54:54,279 Speaker 3: the next run so that we can say something about 997 00:54:54,320 --> 00:54:55,960 Speaker 3: these spins and eccentricities. 998 00:54:56,239 --> 00:54:58,719 Speaker 2: What makes an event golden is the orientation of the 999 00:54:58,760 --> 00:55:00,520 Speaker 2: system relative to Earth or something. 1000 00:55:00,719 --> 00:55:04,160 Speaker 3: Yeah, and it's location basically, So it's golden if it 1001 00:55:04,200 --> 00:55:07,160 Speaker 3: has a very high signals to noise ratio, and you 1002 00:55:07,200 --> 00:55:09,760 Speaker 3: can do that by being very loud and very nearby. 1003 00:55:10,400 --> 00:55:15,879 Speaker 3: So loud events are more massive events, and so you 1004 00:55:15,920 --> 00:55:19,839 Speaker 3: can also do things if they're more easily distinguished, things 1005 00:55:19,840 --> 00:55:22,279 Speaker 3: if they're quite of extreme. Right, So if you have 1006 00:55:22,320 --> 00:55:26,120 Speaker 3: a very extreme mass ratio and it's quite nearby, it's 1007 00:55:26,160 --> 00:55:28,520 Speaker 3: easier to constrain what that is. 1008 00:55:28,840 --> 00:55:31,040 Speaker 2: Extreme mass ratio means like a big black hole and 1009 00:55:31,080 --> 00:55:32,160 Speaker 2: a small black hole merging. 1010 00:55:32,440 --> 00:55:34,719 Speaker 3: Yes, so it's a very big black hole at a 1011 00:55:34,800 --> 00:55:35,680 Speaker 3: very small black hole. 1012 00:55:35,719 --> 00:55:38,360 Speaker 2: Cool. And what do you think are the prospects for 1013 00:55:38,440 --> 00:55:42,239 Speaker 2: these future facilities like the Einstein Telescope or Lisa, do 1014 00:55:42,320 --> 00:55:44,520 Speaker 2: you think we'll see those things in our lifetime or 1015 00:55:44,520 --> 00:55:45,280 Speaker 2: in your career? 1016 00:55:45,680 --> 00:55:49,640 Speaker 3: Yeah? I really really hope. So, because I'm extremely excited 1017 00:55:49,680 --> 00:55:52,600 Speaker 3: about third generator. We call all these new facilities, we 1018 00:55:52,680 --> 00:55:56,200 Speaker 3: call them third generation detectors. We're currently we're kind of 1019 00:55:56,239 --> 00:56:00,520 Speaker 3: at second generation, and they're going to be wildly exciting because, 1020 00:56:00,880 --> 00:56:03,520 Speaker 3: first of all, they're going to give us thousands of 1021 00:56:03,560 --> 00:56:06,640 Speaker 3: golden events, so we're going to be able to measure 1022 00:56:06,719 --> 00:56:12,520 Speaker 3: everything to extreme precision. Secondly, because these facilities like Cosmic 1023 00:56:12,600 --> 00:56:16,360 Speaker 3: Explorer and the Einstein telescope. They'll be much bigger, like 1024 00:56:16,520 --> 00:56:19,240 Speaker 3: ten times bigger than the experiments that we have today. 1025 00:56:19,880 --> 00:56:23,040 Speaker 3: They will allow us to see the very early universe, 1026 00:56:23,360 --> 00:56:27,360 Speaker 3: or how we would call it, the very high redshift. Especially, 1027 00:56:27,360 --> 00:56:31,360 Speaker 3: they would see black hole mergers at redshift one hundred. 1028 00:56:31,719 --> 00:56:35,320 Speaker 3: And to bubble your mind about what rechift one hundred means, 1029 00:56:36,239 --> 00:56:40,560 Speaker 3: if the universe were condensed into one year, then the 1030 00:56:40,719 --> 00:56:43,960 Speaker 3: Earth was born in August and humanity came around in 1031 00:56:44,000 --> 00:56:46,000 Speaker 3: the last I don't know, twenty minutes or so, then 1032 00:56:46,120 --> 00:56:50,960 Speaker 3: redshift one hundred would be ten am on January first, 1033 00:56:51,239 --> 00:56:54,520 Speaker 3: so that we'll be right at the beginning of the universe, 1034 00:56:55,280 --> 00:56:59,080 Speaker 3: and the first stars we expect to be born at 1035 00:56:59,160 --> 00:57:03,839 Speaker 3: January third, so later than where we could throwe the 1036 00:57:03,880 --> 00:57:08,640 Speaker 3: first merging black holes. Now, if you followed along a 1037 00:57:08,680 --> 00:57:11,279 Speaker 3: little bit, you might be thinking, wait, how are you 1038 00:57:11,440 --> 00:57:14,680 Speaker 3: forming a black hole without a star, And that'd be 1039 00:57:14,640 --> 00:57:17,400 Speaker 3: a good question. We don't know, but there is a 1040 00:57:17,480 --> 00:57:20,840 Speaker 3: theory that you can form black holes without stars, and 1041 00:57:20,880 --> 00:57:24,720 Speaker 3: we call them primordial black holes. And these are black 1042 00:57:24,760 --> 00:57:29,040 Speaker 3: holes that form out of the fluctuations of the birth 1043 00:57:29,120 --> 00:57:32,400 Speaker 3: of our universe. So it's very science fiction, kind of 1044 00:57:32,480 --> 00:57:35,520 Speaker 3: spacey but we would be able to detect these with 1045 00:57:35,680 --> 00:57:41,200 Speaker 3: next generation detectors, So there's just an endless possibility of 1046 00:57:41,200 --> 00:57:43,920 Speaker 3: things that we're going to see. Also, there's, of course, 1047 00:57:45,040 --> 00:57:46,800 Speaker 3: you have to keep in mind that we're seeing a 1048 00:57:46,840 --> 00:57:51,080 Speaker 3: whole new force of nature. Gravity is not electromagnetic lights, 1049 00:57:51,120 --> 00:57:53,360 Speaker 3: which we normally see. So there's just going to be 1050 00:57:53,440 --> 00:57:56,880 Speaker 3: a whole lot of unknown unknowns of things that we 1051 00:57:56,960 --> 00:57:59,720 Speaker 3: can't even predict that what they are, but we're probably 1052 00:57:59,760 --> 00:58:02,200 Speaker 3: going to see them. And then the third thing is 1053 00:58:02,240 --> 00:58:06,160 Speaker 3: that now all I've been talking about is earth based 1054 00:58:06,320 --> 00:58:10,160 Speaker 3: or ground based detectors, so detectors or gravitational waves that 1055 00:58:10,160 --> 00:58:13,080 Speaker 3: we put on the Earth. But if you really want 1056 00:58:13,120 --> 00:58:17,760 Speaker 3: to detect very different systems, you have to go to 1057 00:58:18,080 --> 00:58:19,840 Speaker 3: very different wavelengths, and you have. 1058 00:58:19,800 --> 00:58:20,600 Speaker 2: To go to space. 1059 00:58:20,920 --> 00:58:26,120 Speaker 3: Because gravitational waves work similar to sound. So if you 1060 00:58:26,200 --> 00:58:30,200 Speaker 3: want to see a more massive thing, you have to 1061 00:58:30,240 --> 00:58:35,240 Speaker 3: look at lower frequencies, just as if a very big 1062 00:58:35,320 --> 00:58:38,720 Speaker 3: bell will ring at lower frequencies than a very small bell. 1063 00:58:39,680 --> 00:58:42,440 Speaker 3: So big black holes low frequencies, just like big bells 1064 00:58:42,480 --> 00:58:45,880 Speaker 3: low frequencies, and the big frequencies that we want to 1065 00:58:45,920 --> 00:58:48,520 Speaker 3: go to are of the order of the size of 1066 00:58:48,520 --> 00:58:53,480 Speaker 3: the Earth. So LISA is this next generation space based 1067 00:58:53,720 --> 00:58:58,080 Speaker 3: experiment where we basically have three satellites following the Earth, 1068 00:58:58,480 --> 00:59:01,800 Speaker 3: shooting lasers at each other and working as a gravitational 1069 00:59:01,840 --> 00:59:04,400 Speaker 3: wave detector like that, and they will be able to 1070 00:59:04,440 --> 00:59:08,280 Speaker 3: see super massive black holes. So now we're seeing black 1071 00:59:08,280 --> 00:59:10,919 Speaker 3: holes with thirty times the mass of the Sun. Then 1072 00:59:10,960 --> 00:59:13,360 Speaker 3: we will see black holes but a million times the 1073 00:59:13,400 --> 00:59:14,080 Speaker 3: mass of the Sun. 1074 00:59:14,280 --> 00:59:18,280 Speaker 2: So the biggest black holes make the longest wavelengths gravitational waves, 1075 00:59:18,600 --> 00:59:20,640 Speaker 2: and to see them, we need a bigger detector to 1076 00:59:20,680 --> 00:59:22,120 Speaker 2: capture those long wavelengths. 1077 00:59:22,360 --> 00:59:22,840 Speaker 3: Exactly. 1078 00:59:23,480 --> 00:59:25,760 Speaker 2: Awesome. Well, that sounds like a lot of fun. Do 1079 00:59:25,800 --> 00:59:29,360 Speaker 2: you feel like in thirty years when graduate students have like, 1080 00:59:29,720 --> 00:59:32,600 Speaker 2: you know, thousands and thousands of golden events on their laptops, 1081 00:59:32,920 --> 00:59:34,920 Speaker 2: you're going to be like, in my day, we were 1082 00:59:34,960 --> 00:59:37,080 Speaker 2: lucky to get just one. I wrote my whole thesis 1083 00:59:37,160 --> 00:59:37,400 Speaker 2: on two. 1084 00:59:37,440 --> 00:59:42,160 Speaker 3: You remember when the first detection black holes was out there? Yeah, 1085 00:59:42,160 --> 00:59:45,720 Speaker 3: and they're going to be okay, hooomer or whatever. 1086 00:59:47,800 --> 00:59:49,920 Speaker 2: Yeah. Well I feel that way because I share with 1087 00:59:50,000 --> 00:59:53,280 Speaker 2: undergraduates these data samples from the Large Hadron Collider that 1088 00:59:53,360 --> 00:59:55,600 Speaker 2: have like tens of thousands of top quarks in them, 1089 00:59:55,600 --> 00:59:58,600 Speaker 2: and I literally wrote my PhD on four top quark events, 1090 00:59:59,080 --> 01:00:02,480 Speaker 2: so that's literally my experience. But it's wonderful. It's progress, right, 1091 01:00:02,680 --> 01:00:05,600 Speaker 2: I'm glad that everybody gets to marinate in all this 1092 01:00:05,760 --> 01:00:07,920 Speaker 2: data and hope we all find surprises in it. 1093 01:00:08,200 --> 01:00:10,760 Speaker 3: Yeah, it will be a very exciting time. I'm looking 1094 01:00:10,760 --> 01:00:13,000 Speaker 3: forward to the next thirty years so wonderful. 1095 01:00:13,040 --> 01:00:15,960 Speaker 2: Well, thanks very much for telling us about this exciting field, 1096 01:00:16,040 --> 01:00:18,080 Speaker 2: all the surprises in the past and some of the 1097 01:00:18,080 --> 01:00:19,960 Speaker 2: surprises that we can look forward to in the future. 1098 01:00:20,160 --> 01:00:21,280 Speaker 2: Really appreciate your time. 1099 01:00:21,600 --> 01:00:23,000 Speaker 3: Yeah, thank you very much for having me. 1100 01:00:23,480 --> 01:00:26,960 Speaker 1: I mean, you could have, instead of that amazing interview 1101 01:00:27,240 --> 01:00:29,600 Speaker 1: just ask me to guess a bunch of stuff. But 1102 01:00:29,960 --> 01:00:33,080 Speaker 1: you know that's fine. It's fine too to actually listen 1103 01:00:33,120 --> 01:00:34,320 Speaker 1: to someone who has studied this. 1104 01:00:34,640 --> 01:00:37,080 Speaker 2: I love how you can hear in her voice the 1105 01:00:37,280 --> 01:00:40,280 Speaker 2: joy at these discoveries, you know, hearing these discoveries from 1106 01:00:40,320 --> 01:00:44,160 Speaker 2: the universe, and also the excitement for the future. There's 1107 01:00:44,160 --> 01:00:47,320 Speaker 2: so many things we still have to learn about gravitational waves, 1108 01:00:47,520 --> 01:00:49,840 Speaker 2: the kind of things that we might learn from future 1109 01:00:49,840 --> 01:00:53,360 Speaker 2: gravitational wave experiments, These crazy plans they have to build 1110 01:00:53,440 --> 01:00:57,000 Speaker 2: future detectors that are much bigger or that are floating 1111 01:00:57,080 --> 01:01:00,320 Speaker 2: in space. It's exciting to think about all the things 1112 01:01:00,320 --> 01:01:01,080 Speaker 2: that we might learn. 1113 01:01:01,240 --> 01:01:03,640 Speaker 1: I mean, it really does sound like we have now 1114 01:01:03,680 --> 01:01:06,680 Speaker 1: discovered a new secret language of the universe. 1115 01:01:07,120 --> 01:01:10,080 Speaker 2: We are definitely building out our capacity to listen to 1116 01:01:10,120 --> 01:01:12,760 Speaker 2: the secrets of the universe, to eavesdrop on the universe 1117 01:01:13,080 --> 01:01:14,440 Speaker 2: and violate its price. 1118 01:01:15,160 --> 01:01:17,680 Speaker 1: That's a creepy way to put it, but I like it. 1119 01:01:17,920 --> 01:01:19,920 Speaker 2: Maybe we need to get the universe's consent, or at 1120 01:01:20,000 --> 01:01:24,040 Speaker 2: least the universe's parents consent before we do more experiments, before. 1121 01:01:23,760 --> 01:01:27,280 Speaker 1: We swab the universe's cheeks. We got to get consent. 1122 01:01:27,400 --> 01:01:29,000 Speaker 2: So there we go, folks. The answer is that we 1123 01:01:29,040 --> 01:01:33,440 Speaker 2: have discovered a lot more gravitational waves than anybody dared hope. 1124 01:01:33,440 --> 01:01:35,120 Speaker 2: As soon as we turned on this new kind of 1125 01:01:35,160 --> 01:01:37,840 Speaker 2: ear to the universe, we heard all sorts of stuff 1126 01:01:37,880 --> 01:01:41,400 Speaker 2: going on out there, and it hasn't quieted down ever since. 1127 01:01:41,600 --> 01:01:44,600 Speaker 2: So fortunately, the universe is a very noisy place when 1128 01:01:44,600 --> 01:01:45,520 Speaker 2: it comes to gravity. 1129 01:01:45,920 --> 01:01:51,640 Speaker 1: Like whoa dude, cow bunga serfs up on those gravitational waves. 1130 01:01:51,720 --> 01:01:54,600 Speaker 2: Bra All right, thanks very much Katie for going on 1131 01:01:54,680 --> 01:01:58,480 Speaker 2: this tour with us of the history of gravitational Wave Astronomy. 1132 01:01:58,600 --> 01:02:00,520 Speaker 1: Thanks for having me Brok. 1133 01:02:00,000 --> 01:02:10,760 Speaker 2: Thank everybody for listening. Tune in next time. Thanks for listening, 1134 01:02:10,800 --> 01:02:13,480 Speaker 2: and remember that Daniel and Jorge Explain the Universe is 1135 01:02:13,520 --> 01:02:18,120 Speaker 2: a production of iHeartRadio. For more podcasts from iHeartRadio, visit 1136 01:02:18,200 --> 01:02:22,240 Speaker 2: the iHeartRadio app, Apple Podcasts, or wherever you listen to 1137 01:02:22,320 --> 01:02:23,320 Speaker 2: your favorite shows.