WEBVTT 1 00:00:03.399 --> 00:00:07.719 Welcome to Bedtime Astronomy. Explore the wonders of the cosmos 2 00:00:07.759 --> 00:00:12.279 with our soothing Bedtime Astronomie podcast. Each episode offers a 3 00:00:12.359 --> 00:00:16.320 gentle journey through the stars, planets, and beyond, perfect for 4 00:00:16.399 --> 00:00:20.239 unwinding after a long day. Let's travel through the mysteries 5 00:00:20.239 --> 00:00:22.440 of the universe as you drift off into a peaceful 6 00:00:22.480 --> 00:00:23.800 slumber under the night sky. 7 00:00:26.960 --> 00:00:30.239 Imagine just for a second, standing at the absolute edge 8 00:00:30.280 --> 00:00:30.920 of existence. 9 00:00:31.239 --> 00:00:33.840 Well, that is a pretty terrifying place to start, right. 10 00:00:33.840 --> 00:00:37.320 But just humor me. Here you are hovering just millimeters 11 00:00:37.320 --> 00:00:40.960 away from a boundary that is so profound and you know, 12 00:00:41.240 --> 00:00:44.920 so final that right before everything goes dark forever, the 13 00:00:45.039 --> 00:00:46.479 universe itself actually. 14 00:00:46.280 --> 00:00:48.000 Rings like a bell, a cosmic bell. 15 00:00:48.079 --> 00:00:51.840 Yeah, exactly, because it's basically a fundamental law of physics 16 00:00:51.920 --> 00:00:55.439 and well a massive pop culture cliche at this point 17 00:00:55.520 --> 00:00:58.079 that in the vacuum of space, no one. 18 00:00:57.960 --> 00:01:00.719 Can hear you scream because there's no air. 19 00:01:00.520 --> 00:01:03.399 Right, there is no medium for acoustic sound to travel through. 20 00:01:03.439 --> 00:01:06.719 Space is just this silent void. But there's this massive 21 00:01:06.760 --> 00:01:10.079 paradox sitting right at the center of modern astrophysics right now. 22 00:01:10.159 --> 00:01:12.640 Oh absolutely, we actually know that there is a way 23 00:01:12.680 --> 00:01:17.799 to quote unquote here the violent cataclysmic crash of two 24 00:01:17.840 --> 00:01:19.319 black holes colliding. 25 00:01:18.920 --> 00:01:21.359 Which is such a profound contradiction when you really think 26 00:01:21.400 --> 00:01:24.040 about it. I mean, we're talking about the darkest, most 27 00:01:24.079 --> 00:01:27.200 invisible objects in the universe. Yeah, and they are creating 28 00:01:27.200 --> 00:01:31.959 the most energetic outburst of noise imaginable, but not a 29 00:01:32.000 --> 00:01:34.640 sound moving through the air of course, right right, It's 30 00:01:34.640 --> 00:01:37.879 a sound moving through the very geometry of reality. 31 00:01:37.959 --> 00:01:40.280 Okay, So let's unpack this because what we are embarking 32 00:01:40.359 --> 00:01:43.400 on today is basically a journey to decode the loudest 33 00:01:43.439 --> 00:01:46.359 gravitational wave ever recorded by human beings. 34 00:01:46.640 --> 00:01:47.920 It really is a milestone. 35 00:01:48.040 --> 00:01:51.920 It is. Our mission here is to transport you, the listener, 36 00:01:52.319 --> 00:01:54.599 right to the edge of an event horizon during a 37 00:01:54.719 --> 00:01:59.359 cosmic collision, and we're gonna explore what this totally unprecedented 38 00:01:59.400 --> 00:02:03.959 signal tell us about, well, the most impenetrable boundary in 39 00:02:04.000 --> 00:02:05.200 the entire cosmos. 40 00:02:05.400 --> 00:02:07.680 And we really should establish right away that we aren't 41 00:02:07.680 --> 00:02:10.360 just talking about a loud noise in some abstract or 42 00:02:10.680 --> 00:02:13.360 you know, theoretical sense. Right when a signal of this 43 00:02:13.479 --> 00:02:18.560 magnitude hits our detectors, we're essentially unlocking space time's deepest secrets. 44 00:02:19.039 --> 00:02:21.599 We're peeling back the layers of physics that govern how 45 00:02:21.599 --> 00:02:24.599 the universe operates at its absolute extreme limits. 46 00:02:24.319 --> 00:02:26.439 The places where things get weird. 47 00:02:26.479 --> 00:02:29.520 Exactly, the places where our standard equations actually start to 48 00:02:29.560 --> 00:02:30.120 break down. 49 00:02:30.280 --> 00:02:33.159 So to really grasp the gravity of this, and yes, 50 00:02:33.240 --> 00:02:36.680 that pun is fully intended, nice, thank you, we have 51 00:02:36.719 --> 00:02:38.639 to look at the signal that started it all. This 52 00:02:38.840 --> 00:02:42.360 was basically a cosmic alarm bell ringing across the universe. 53 00:02:42.879 --> 00:02:46.199 The event is centered around a signal designated as GW 54 00:02:46.439 --> 00:02:48.280 two five zero one one. 55 00:02:48.319 --> 00:02:51.039 Fifteen, recorded just last year, right in twenty twenty five. 56 00:02:50.960 --> 00:02:54.639 YEP twenty twenty five by the two laser interferometer Gravitational 57 00:02:54.719 --> 00:02:57.719 Wave Observatories or you know LEGO as most people know 58 00:02:57.800 --> 00:03:00.080 it here in the United States. And the major our 59 00:03:00.120 --> 00:03:03.159 headline here is that it is the loudest binary black 60 00:03:03.199 --> 00:03:04.599 hole signal observed to. 61 00:03:04.680 --> 00:03:06.719 Date, which is staggering. 62 00:03:06.879 --> 00:03:09.280 It really is. I mean, we are talking roughly three 63 00:03:09.360 --> 00:03:12.960 times louder than the very first gravitational wave ever detected 64 00:03:13.159 --> 00:03:14.159 just a decade ago. 65 00:03:14.280 --> 00:03:17.360 In the concept of loudness and gravitational wave astronomy, it 66 00:03:17.439 --> 00:03:21.120 kind of requires us to completely discard our biological experience 67 00:03:21.120 --> 00:03:23.439 of hearing. Yeah, there are no sound waves right right. 68 00:03:23.479 --> 00:03:28.960 When astrophysicists say loud, they're actually referring to amplitude. Amplitude, okay, Yeah, 69 00:03:29.159 --> 00:03:32.479 gravitational waves are physical ripples in the actual fabric of 70 00:03:32.479 --> 00:03:36.520 space time. And you always hear people compare spacetime to 71 00:03:36.560 --> 00:03:37.919 a flat trampoline, which. 72 00:03:37.800 --> 00:03:40.759 Oh, the bowling ball on the trampoline analogy, Yes. 73 00:03:41.039 --> 00:03:45.560 And it is a terrible over used analogy that completely 74 00:03:45.680 --> 00:03:48.360 fails to capture the three dimensional nature of the universe. 75 00:03:48.400 --> 00:03:49.759 So what's a better way to picture it? 76 00:03:49.960 --> 00:03:54.400 Think of space time instead as a massive solid block 77 00:03:54.520 --> 00:03:56.599 of dense, clear gelatine. 78 00:03:56.639 --> 00:03:59.159 Okay, a giant block of cosmic jello. I can work 79 00:03:59.159 --> 00:03:59.680 with that, A. 80 00:03:59.639 --> 00:04:02.719 Giant block of cosmic jell exactly. So if you take 81 00:04:02.840 --> 00:04:07.800 two dense, heavy marbles and embed them deep inside that gelatin, right, 82 00:04:08.199 --> 00:04:10.360 and then you start spinning them around each other at 83 00:04:10.360 --> 00:04:12.919 a significant fraction of the speed of light, they are 84 00:04:12.960 --> 00:04:14.599 going to violently churn that material. 85 00:04:14.719 --> 00:04:15.599 Oh, I see. 86 00:04:15.719 --> 00:04:19.639 And when they finally smash together, that massive collision sends 87 00:04:19.680 --> 00:04:23.120 these severe pressure waves rippling outward through the gelatine in 88 00:04:23.199 --> 00:04:24.439 all three dimensions at once. 89 00:04:24.600 --> 00:04:27.519 Okay, So when those ripples finally reach Earth after traveling 90 00:04:27.519 --> 00:04:30.680 outward for you know, maybe billions of years, they are 91 00:04:30.720 --> 00:04:34.519 actually physically stretching and squeezing the space that we occupy. 92 00:04:34.720 --> 00:04:36.120 That's exactly what's happening. 93 00:04:36.240 --> 00:04:38.319 So, like, think about where you are sitting right now 94 00:04:38.360 --> 00:04:41.959 listening to this, as this specific wave passed through Earth, 95 00:04:42.079 --> 00:04:44.879 the room you're in, the chair you're sitting on, and 96 00:04:45.000 --> 00:04:49.120 literally your own body were physically stretched and squeezed, like 97 00:04:49.360 --> 00:04:50.560 oscillating back and forth. 98 00:04:50.600 --> 00:04:53.319 You were. But we do need to emphasize that this 99 00:04:53.360 --> 00:04:55.279 is on a microscopic. 100 00:04:54.560 --> 00:04:56.399 Scale, right, Nobody actually felt it. 101 00:04:56.480 --> 00:04:59.319 No, No, we are talking about distortions that alter the 102 00:04:59.360 --> 00:05:02.680 distance between here in the nearest star by roughly the 103 00:05:02.680 --> 00:05:03.600 width of a human hair. 104 00:05:04.040 --> 00:05:08.040 That is, I mean, that's almost impossible to even conceptualize. 105 00:05:07.399 --> 00:05:09.560 Or to bring it locally. It's like changing the length 106 00:05:09.639 --> 00:05:13.759 of logos four kilometer long vacuum tubes by just a 107 00:05:13.959 --> 00:05:16.399 fraction of the width of a single proton. 108 00:05:16.240 --> 00:05:20.360 Which honestly makes the engineering behind LIGO sound completely impossible. 109 00:05:20.439 --> 00:05:21.959 I mean, we aren't just talking about building a really 110 00:05:22.000 --> 00:05:25.000 big telescope here, not at all. These facilities they're in 111 00:05:25.079 --> 00:05:26.519 Washington State and Louisiana. 112 00:05:26.600 --> 00:05:28.040 Right, Yes, those are the two. 113 00:05:28.279 --> 00:05:32.240 They are shooting lasers down these four kilometer long vacuum tubes, 114 00:05:32.680 --> 00:05:36.720 bouncing them off perfectly suspended mirrors and basically measuring how 115 00:05:36.759 --> 00:05:38.279 long it takes for the light to return. 116 00:05:38.680 --> 00:05:42.480 And the precision required to pull that off is just 117 00:05:42.839 --> 00:05:46.839 difficult to overstate. I mean, to measure a distortion smaller 118 00:05:46.879 --> 00:05:49.759 than a proton. You have to isolate those mirrors from 119 00:05:49.800 --> 00:05:51.959 the seismic noise of the Earth itself. 120 00:05:51.639 --> 00:05:53.600 Right, because everything vibrates. 121 00:05:53.279 --> 00:05:56.439 Everything a truck driving down a highway miles away, or 122 00:05:56.480 --> 00:06:00.000 a wave crashing on some distant shoreline, even the microscope 123 00:06:00.199 --> 00:06:03.720 thermal vibrations of the actual atoms inside the mirrors themselves. 124 00:06:03.800 --> 00:06:06.480 Wait, really, the heat of the atoms in the mirror 125 00:06:06.480 --> 00:06:07.360 can mess up the reading. 126 00:06:07.439 --> 00:06:10.160 Well absolutely all that creates background noise. Yeah, so Lego 127 00:06:10.240 --> 00:06:13.399 has to mathematically and physically cancel out the ambient vibration 128 00:06:13.519 --> 00:06:16.600 of the entire planet just to hear the universe whisper. 129 00:06:16.959 --> 00:06:19.519 That is just wild. And you know, that rapid progression 130 00:06:19.519 --> 00:06:22.240 of our technological ability over just the last ten years 131 00:06:22.360 --> 00:06:23.480 is mind blowing to me. 132 00:06:23.680 --> 00:06:25.079 It's been incredibly fast. 133 00:06:24.959 --> 00:06:27.680 Like a decade ago, just confirming that these ripples existed 134 00:06:27.720 --> 00:06:31.519 at all. Was this monumental Nobel Prize winning priumph. And 135 00:06:31.639 --> 00:06:35.000 now just ten years later, we capture a signal three 136 00:06:35.040 --> 00:06:37.759 times as powerful, and we're using it as this incredibly 137 00:06:37.839 --> 00:06:42.199 precise surgical instrument to probe the black holes themselves well. 138 00:06:42.240 --> 00:06:45.360 And the amplitude is what allows for that surgical precision 139 00:06:45.399 --> 00:06:48.120 because it's louder, Right, A louder signal means that the 140 00:06:48.199 --> 00:06:52.600 stretching and squeezing of space time was significantly more pronounced. 141 00:06:52.839 --> 00:06:56.800 It implies immense energy, and crucially, it implies proximity. 142 00:06:56.920 --> 00:07:00.279 Proximity, so GW two five zero one one teen was 143 00:07:00.319 --> 00:07:00.800 close to. 144 00:07:00.800 --> 00:07:05.040 Us relatively speaking on a cosmic scale. Yes, it happened 145 00:07:05.079 --> 00:07:06.120 relatively close to us. 146 00:07:06.160 --> 00:07:08.160 Okay, let me throw out an analogy here to see 147 00:07:08.160 --> 00:07:11.360 if I'm visualizing the impact of this amplitude correctly. Sure 148 00:07:11.680 --> 00:07:14.959 it so if the first gravitational wave we detected a 149 00:07:14.959 --> 00:07:18.759 decade ago was kind of like feeling the faint rhythmic 150 00:07:18.839 --> 00:07:22.040 rumble of a distant train through the soles of your 151 00:07:22.079 --> 00:07:24.839 shoes while you're standing, I don't know, five miles away, Okay, 152 00:07:25.519 --> 00:07:28.480 is GW two five zero one to one tour more 153 00:07:28.600 --> 00:07:30.800 like standing right next to the tracks as a massive 154 00:07:30.800 --> 00:07:33.839 freight train blasts its horn and just rattles your ribcage. 155 00:07:34.040 --> 00:07:35.680 I like that. But let's actually take that train and 156 00:07:35.680 --> 00:07:38.319 analogy a step further. Okay, when you're five miles away, 157 00:07:38.600 --> 00:07:41.319 you really only feel the lowest, deepest base frequencies of 158 00:07:41.319 --> 00:07:42.000 that rumble. 159 00:07:41.800 --> 00:07:44.319 Right, Yeah, just the heavy vibrations exactly. 160 00:07:44.639 --> 00:07:47.319 The higher, more delicate frequencies, yeah, like the middle wheels 161 00:07:47.360 --> 00:07:50.560 clacking on the rails. Those are completely lost to the 162 00:07:50.560 --> 00:07:52.000 intervening distance and the soil. 163 00:07:52.199 --> 00:07:52.839 That makes sense. 164 00:07:53.199 --> 00:07:55.800 But by standing right next to the tracks, you don't 165 00:07:55.879 --> 00:07:59.160 just feel as stronger rumble. Your ear can suddenly pick 166 00:07:59.199 --> 00:08:02.439 up the complex, subtle harmonics of the machinery itself. 167 00:08:02.839 --> 00:08:05.759 Oh. I see. So the volume doesn't just make the 168 00:08:05.800 --> 00:08:09.759 main event easier to notice. The high volume actually allows 169 00:08:09.839 --> 00:08:12.879 us to hear entirely different layers of the collision. 170 00:08:13.079 --> 00:08:15.480 It unveils the harmonics. It's like in music, you know, 171 00:08:15.879 --> 00:08:19.319 a piano key doesn't just produce one pure mathematical tone 172 00:08:19.360 --> 00:08:22.439 when you strike it. It produces a fundamental frequency, but 173 00:08:22.560 --> 00:08:28.439 alongside dozens of overtones. These are higher, quieter frequencies resonating 174 00:08:28.439 --> 00:08:29.519 simultaneously and. 175 00:08:29.399 --> 00:08:31.000 That's what makes it sound like a piano and not 176 00:08:31.040 --> 00:08:31.879 a computer beep. 177 00:08:32.039 --> 00:08:36.120 Precisely, those overtones give the instrument its character. So in 178 00:08:36.159 --> 00:08:39.840 gravitational waves, the main roar is the bulk of the collision. 179 00:08:39.480 --> 00:08:42.320 The huge smash, But a profoundly. 180 00:08:41.879 --> 00:08:46.000 Loud signal like GW two five zero one fourteen has 181 00:08:46.039 --> 00:08:49.559 such an incredibly high signal to noise ratio that the 182 00:08:49.600 --> 00:08:53.000 faint overtones of the collision finally rise above the background 183 00:08:53.039 --> 00:08:54.120 static of the universe. 184 00:08:54.279 --> 00:08:58.159 Wow, which brings just a completely new layer of data 185 00:08:58.200 --> 00:09:01.000 to the table. We aren't just hearing this anymore. We're 186 00:09:01.000 --> 00:09:04.240 actually hearing the subtle vibrations of the new black hole 187 00:09:04.360 --> 00:09:07.279 settling down, Yes, the ring down, and that shifts our 188 00:09:07.279 --> 00:09:11.279 focus directly to the true protagonist of this whole cosmic drama, 189 00:09:11.320 --> 00:09:14.679 which is the event horizon, the point of no return exactly, 190 00:09:14.919 --> 00:09:17.720 this is the universe's ultimate point of no return. We 191 00:09:17.840 --> 00:09:20.080 know the basics, right, It's the boundary around a black 192 00:09:20.120 --> 00:09:23.120 hole where absolutely nothing, not even light, can escape. But 193 00:09:23.159 --> 00:09:25.960 for anyone familiar with the basic physics of gravity, the 194 00:09:26.039 --> 00:09:29.039 mechanics of this boundary get incredibly. 195 00:09:28.440 --> 00:09:31.360 Strange, oh very strange. And the strangeness really comes from 196 00:09:31.399 --> 00:09:33.879 the absolute finality of the universal. 197 00:09:33.399 --> 00:09:34.799 Speed limit the speed of light. 198 00:09:35.080 --> 00:09:38.720 Right, we know that as mass increases, the escape velocity, 199 00:09:38.759 --> 00:09:40.879 which is the speed required to break free of an 200 00:09:40.919 --> 00:09:43.320 object's gravitational pull, that increases too. 201 00:09:43.480 --> 00:09:45.879 Like how it's harder to launch a rocket from Jupiter 202 00:09:46.000 --> 00:09:46.519 than from. 203 00:09:46.360 --> 00:09:49.559 Earth exactly, and at a certain point of mass density, 204 00:09:49.799 --> 00:09:53.159 that required escape velocity hits exactly two hundred and ninety 205 00:09:53.240 --> 00:09:56.200 nine thousand, seven hundred and ninety two kilometers per. 206 00:09:56.080 --> 00:09:58.600 Second, which is the speed of light in a vacuum. Yes, 207 00:09:58.960 --> 00:10:02.399 and since Einstein equations dictate that nothing can travel faster 208 00:10:02.519 --> 00:10:05.279 than the speed of light, anything that crosses that mathematical 209 00:10:05.279 --> 00:10:07.120 boundary is just permanently trapped. 210 00:10:07.159 --> 00:10:11.720 It is a one way door in the universe information, matter, light, 211 00:10:12.159 --> 00:10:14.480 It goes in and it never comes out. 212 00:10:14.360 --> 00:10:18.960 Which presents a pretty profound paradox for observational astronomy, doesn't 213 00:10:18.960 --> 00:10:21.440 it a huge one? Because how do you observe an 214 00:10:21.480 --> 00:10:26.480 object that, by its very definition completely forbids observation. If 215 00:10:26.519 --> 00:10:29.840 no light, no radiation, and literally no information can cross 216 00:10:29.840 --> 00:10:32.960 from the inside of the event horizon to the outside universe, 217 00:10:33.519 --> 00:10:37.120 you're essentially trying to study a shadow by like turning 218 00:10:37.120 --> 00:10:37.879 off all the lights. 219 00:10:37.960 --> 00:10:40.000 Yeah, that paradox is really what trips up a lot 220 00:10:40.000 --> 00:10:41.519 of people when they first look at the data from 221 00:10:41.600 --> 00:10:42.919 GW two five zero one one day. 222 00:10:43.080 --> 00:10:44.840 I know, it tripped me up. I was like, if 223 00:10:44.879 --> 00:10:47.360 it's the ultimate trap, how did scientists witness it? We 224 00:10:47.480 --> 00:10:49.320 literally can't see the black hole itself. 225 00:10:49.399 --> 00:10:52.039 Well, the key is that we aren't seeing what comes 226 00:10:52.080 --> 00:10:55.080 out of it, because nothing does. Instead, we are witnessing 227 00:10:55.120 --> 00:10:59.440 the severe agonizing warping of the space time directly adjacent 228 00:10:59.440 --> 00:11:02.840 to the horizon and in the exact millisecond it is forming. 229 00:11:03.039 --> 00:11:05.000 Oh so it's the space around it. 230 00:11:05.120 --> 00:11:09.919 Yes. When two black holes merge, their individual event horizons deform, 231 00:11:10.240 --> 00:11:13.000 they stretch toward each other, and they finally fuse to 232 00:11:13.080 --> 00:11:17.320 form a single, larger and highly chaotic event horizon. 233 00:11:17.440 --> 00:11:19.799 Highly chaotic. So for a fraction of a second, this 234 00:11:19.919 --> 00:11:23.000 newly born remnant black hole is not a perfect sphere. 235 00:11:23.080 --> 00:11:26.480 Far from it. It is violently asymmetrical. Really, Oh yeah, 236 00:11:26.519 --> 00:11:30.200 it is wobbling, ringing, and shedding immense amounts of energy 237 00:11:30.360 --> 00:11:33.480 in the form of gravitational waves as it desperately attempts 238 00:11:33.519 --> 00:11:36.679 to settle down into a stable spherical state. Wow, it's 239 00:11:36.720 --> 00:11:40.720 that dynamic turbulent boundary the space time actively reacting to 240 00:11:40.759 --> 00:11:42.799 the violent birth of the horizon that we are observing. 241 00:11:42.919 --> 00:11:45.600 We are essentially catching the shadow just before the door 242 00:11:45.639 --> 00:11:46.679 slam shut forever. 243 00:11:46.879 --> 00:11:49.000 That is such a cool way to freeze it. Catching 244 00:11:49.000 --> 00:11:52.080 the shadow before the door slam shut, and the method 245 00:11:52.159 --> 00:11:55.080 scientists used to actually capture that fleeting moment before the 246 00:11:55.120 --> 00:11:58.960 eternal dark is just a brilliant piece of analytical detective work. 247 00:11:59.039 --> 00:11:59.559 It really is. 248 00:12:00.000 --> 00:12:03.120 And this research was led by doctor Lingsn and PhD 249 00:12:03.360 --> 00:12:06.799 candidate Neil Lou. They're over at OSGREV and the Australian 250 00:12:06.840 --> 00:12:08.080 National University, right. 251 00:12:08.039 --> 00:12:11.519 Yes, working with an international coalition spanning Canada, at the 252 00:12:11.600 --> 00:12:12.440 US and Spain. 253 00:12:12.759 --> 00:12:16.759 Just a massive global effort, and they managed to basically 254 00:12:16.840 --> 00:12:19.480 isolate the last sound these black holes made. 255 00:12:19.559 --> 00:12:22.799 And the secret to measuring this last sound lies in 256 00:12:22.879 --> 00:12:28.440 a very specific, notoriously elusive component of this signal called 257 00:12:28.480 --> 00:12:32.480 direct waves direct waves. Okay, yeah. Prior to this analysis, 258 00:12:32.480 --> 00:12:37.000 direct waves were theoretically understood but frankly impossible to extract 259 00:12:37.000 --> 00:12:39.759 from the noise. They were just buried exactly. But Neil 260 00:12:39.840 --> 00:12:44.799 Lu's new analytical framework essentially deciphered them. It pulled completely 261 00:12:44.919 --> 00:12:47.919 unique data from incredibly close to the event horizon. 262 00:12:47.919 --> 00:12:50.519 Okay, so let's dig into the how of that extraction. 263 00:12:50.720 --> 00:12:53.679 Because they couldn't just use like a standard audio filter 264 00:12:53.759 --> 00:12:55.639 to clean up the track. I was looking into the 265 00:12:55.679 --> 00:12:59.600 computational mechanics behind this, and the process of mathematical dissection 266 00:12:59.799 --> 00:13:01.039 is just staggering. 267 00:13:01.120 --> 00:13:01.720 It's intense. 268 00:13:01.879 --> 00:13:05.200 They had to rely heavily on something called numerical relativity, right. 269 00:13:05.120 --> 00:13:09.039 They did, And numerical relativity is basically the unsung hero 270 00:13:09.480 --> 00:13:13.720 of gravitational wave astronomy. Oh so well, Einstein's equations of 271 00:13:13.840 --> 00:13:18.120 general relativity. They are nonlinear partial differential. 272 00:13:17.639 --> 00:13:20.000 Equations, which means they're a nightmare to solve. 273 00:13:20.120 --> 00:13:24.679 They are famously brutally difficult to solve for decades, physicists 274 00:13:24.679 --> 00:13:29.320 could really only solve them for highly simplified, idealized scenarios. 275 00:13:29.600 --> 00:13:32.240 You cannot just write down the exact solution for two 276 00:13:32.279 --> 00:13:33.360 black holes merging. 277 00:13:33.120 --> 00:13:34.759 On a chop breaks mean a supercomputer. 278 00:13:34.919 --> 00:13:38.679 You need massive clusters of supercomputers running for months just 279 00:13:38.720 --> 00:13:40.720 to simulate a fraction of a second of a black 280 00:13:40.720 --> 00:13:41.279 hole merger. 281 00:13:41.480 --> 00:13:43.320 Months for a fraction of a second. 282 00:13:43.440 --> 00:13:47.039 Yes, the research team had to model millions of potential 283 00:13:47.039 --> 00:13:51.080 merger scenarios. They simulate the exact masses, the spins, and 284 00:13:51.120 --> 00:13:53.559 the orbital trajectories of the two black holes, and then 285 00:13:53.559 --> 00:13:56.759 the computer's crunch Einstein's equations to predict exactly what the 286 00:13:56.799 --> 00:13:59.960 main gravitational wave that dominant roar should look like. 287 00:14:00.279 --> 00:14:03.799 Okay, so if the main crash, the bulk collision is 288 00:14:03.840 --> 00:14:07.240 a deafening orchestral symbol smash happening right in front of you, 289 00:14:07.960 --> 00:14:12.080 these direct waves are like a tiny specific vibration of 290 00:14:12.200 --> 00:14:16.480 one single violin string happening at the exact same millisecond. 291 00:14:16.720 --> 00:14:17.960 That's a great way to picture it. 292 00:14:18.279 --> 00:14:20.960 So to find the violin string, they use the supercomputer 293 00:14:21.080 --> 00:14:25.000 to map out the exact acoustic profile of the symbol smash, right, 294 00:14:25.200 --> 00:14:28.120 and then they mathematically subtract it from the raw lego data. 295 00:14:28.480 --> 00:14:32.240 That's exactly what they do, but that subtraction requires an 296 00:14:32.360 --> 00:14:36.000 unprecedented level of precision. I can imagine if your numerical 297 00:14:36.039 --> 00:14:38.519 relativity model is off by even a fraction of a percent, 298 00:14:38.600 --> 00:14:41.720 the leftover data will just be statistical garbage. 299 00:14:41.399 --> 00:14:43.399 Oh, because you didn't subtract the right thing. 300 00:14:43.559 --> 00:14:47.840 Right. But by meticulously modeling and subtracting the dominant signal, 301 00:14:48.000 --> 00:14:51.120 which is the inspiral and the immediate merger. What they 302 00:14:51.120 --> 00:14:54.600 were left with was a tiny residual vibration, the ring. 303 00:14:54.440 --> 00:14:56.440 Down phase, the violin string. 304 00:14:56.320 --> 00:14:59.000 The direct waves, and the origin of those direct waves 305 00:14:59.039 --> 00:15:00.919 is really what makes them so and valuable to us. 306 00:15:00.960 --> 00:15:02.240 Why is that? Where do they come from? 307 00:15:02.559 --> 00:15:04.879 They don't come from the distant orbiting phase of the 308 00:15:04.879 --> 00:15:07.600 black holes. They are emitted right at the throat of 309 00:15:07.639 --> 00:15:10.720 the beasts. Wow. They carry the untainted fingerprint of the 310 00:15:10.799 --> 00:15:15.000 extreme gravity immediately adjacent to the newly formed event horizon. 311 00:15:15.200 --> 00:15:17.440 It's kind of like standing at a massive party with 312 00:15:17.600 --> 00:15:22.519 one hundred conversations happening, heavy music playing, glasses clinking, and 313 00:15:22.559 --> 00:15:25.159 you're trying to hear a specific whisper from across the 314 00:15:25.240 --> 00:15:28.480 room exactly except here, the team is filtering out the 315 00:15:28.519 --> 00:15:31.840 noise of the universe itself to hear a single whisper 316 00:15:32.200 --> 00:15:34.200 from billions of light years away. 317 00:15:34.000 --> 00:15:37.080 And the effort to isolate that single voice is driven 318 00:15:37.120 --> 00:15:40.759 by the totally unique physical environment it originates. 319 00:15:40.240 --> 00:15:41.879 From the event horizon itself. 320 00:15:42.039 --> 00:15:46.720 Yes, black holes are the ultimate extreme laboratories. They sit 321 00:15:46.799 --> 00:15:50.399 precisely at the intersection of our two most successful, yet 322 00:15:50.399 --> 00:15:53.200 fundamentally incompatible frameworks of physics. 323 00:15:53.279 --> 00:15:56.519 Oh right, general relativity and quantum theory exactly. This is 324 00:15:56.559 --> 00:16:00.000 where the physics gets incredibly tense because we have these 325 00:16:00.120 --> 00:16:03.519 two rule books. Right. General relativity is the master theory 326 00:16:03.559 --> 00:16:06.679 of the massive. It explains gravity orbits and the smooth, 327 00:16:06.759 --> 00:16:08.799 continuous fabric of space and time. 328 00:16:09.360 --> 00:16:09.799 Correct. 329 00:16:10.080 --> 00:16:12.840 But then we have quantum mechanics, which is the master 330 00:16:12.960 --> 00:16:18.120 theory of the microscopic. It explains atoms, subatomic particles, and 331 00:16:18.159 --> 00:16:20.759 it treats the universe as chunky like it's made of 332 00:16:20.799 --> 00:16:22.080 discrete packets. 333 00:16:21.679 --> 00:16:24.960 Of energy and under normal circumstances in the universe, those 334 00:16:24.960 --> 00:16:27.159 two rule books never have to speak to each. 335 00:16:27.000 --> 00:16:29.519 Other, right, because things are either huge or tiny. 336 00:16:29.840 --> 00:16:33.440 Exactly. You use relativity for stars and you use quantum 337 00:16:33.440 --> 00:16:36.440 mechanics for electrons. But at the event horizon of a 338 00:16:36.440 --> 00:16:39.639 black hole, the mass is so immense and the space 339 00:16:39.679 --> 00:16:44.039 it occupies is so compact that the gravity violently warps 340 00:16:44.080 --> 00:16:47.600 space time on a microscopic quantum level. 341 00:16:47.399 --> 00:16:48.480 It forces them together. 342 00:16:48.679 --> 00:16:50.919 It is the singular place in the cosmos where the 343 00:16:51.000 --> 00:16:53.840 rules of the massive crash headlong into the rules of 344 00:16:53.879 --> 00:16:54.679 the microscopic. 345 00:16:55.159 --> 00:16:58.639 So, okay, if these two frameworks fundamentally disagree on how 346 00:16:58.639 --> 00:17:01.720 the universe works. What does it actually mean for doctor 347 00:17:01.759 --> 00:17:04.440 Son and you'll lou to use these direct waves to 348 00:17:04.480 --> 00:17:06.240 test general relativity. 349 00:17:05.799 --> 00:17:06.759 Well, it's a huge deal. 350 00:17:07.039 --> 00:17:10.319 Are we essentially using this super loud gravitational wave to 351 00:17:10.359 --> 00:17:12.920 see if Einstein's equations finally break down? Like, are we 352 00:17:12.960 --> 00:17:14.000 trying to prove him wrong? 353 00:17:14.160 --> 00:17:17.039 We'll consider the implications of a breakdown. I mean, every 354 00:17:17.079 --> 00:17:20.799 single time physicists have tested general relativity over the last century, 355 00:17:21.079 --> 00:17:23.799 from the bending of starlight around the Sun to the 356 00:17:23.880 --> 00:17:27.240 time dilation in GPS satellite, it's always right. Einstein has 357 00:17:27.279 --> 00:17:31.920 been proven flawlessly correct every time. But theorists know the 358 00:17:31.920 --> 00:17:33.680 theory is incomplete. 359 00:17:33.119 --> 00:17:36.440 Because it produces infinities right right at the very center 360 00:17:36.480 --> 00:17:37.200 of a black hole. 361 00:17:37.920 --> 00:17:43.160 The singularity relativity predicts infinite density and infinite. 362 00:17:42.720 --> 00:17:45.000 Curvature, which doesn't make sense no. 363 00:17:45.079 --> 00:17:48.640 Because nature abhors in infinity and an infinity usually just 364 00:17:48.720 --> 00:17:52.119 means your math stopped working. Yeah, So theorists suspect that 365 00:17:52.240 --> 00:17:55.400 right at the boundary, right at the event horizon, general 366 00:17:55.440 --> 00:17:59.279 relativity might begin to fray, revealing subtle quantum effects. 367 00:17:59.480 --> 00:17:59.559 Oh. 368 00:18:00.440 --> 00:18:03.400 By isolating these direct waves, these little whispers from the 369 00:18:03.440 --> 00:18:07.240 absolute edge, the team is gathering the raw data needed 370 00:18:07.240 --> 00:18:09.920 to run the ultimate stress test. They are checking if 371 00:18:10.000 --> 00:18:13.440 Einstein's rulebook actually holds up under the most extreme pressure 372 00:18:13.480 --> 00:18:14.480 the universe can generate. 373 00:18:14.759 --> 00:18:18.279 Man that is fascinating. So to run those stress tests, 374 00:18:18.519 --> 00:18:21.920 the team had to pull incredibly specific measurements from that 375 00:18:22.000 --> 00:18:25.119 leftover whisper very specific. They had to essentially take the 376 00:18:25.240 --> 00:18:28.519 vitals of the newly born black hole, and the analysis 377 00:18:28.519 --> 00:18:31.559 of GW two five zero one one four allowed them 378 00:18:31.599 --> 00:18:35.920 to measure two fundamental properties of the remnant, its rotation 379 00:18:36.000 --> 00:18:37.839 frequency and its surface gravity. 380 00:18:37.960 --> 00:18:41.279 And those two properties basically define the entire existence of 381 00:18:41.279 --> 00:18:42.119 the remnant. 382 00:18:41.839 --> 00:18:44.200 And the remnant. Just to be clear, is the single 383 00:18:44.200 --> 00:18:46.599 black hole left behind after the chaotic fusion. 384 00:18:46.720 --> 00:18:50.599 Yes, And in that fusion process, a substantial percentage of 385 00:18:50.640 --> 00:18:54.440 the two parent black holes combined mass is converted instantaneously 386 00:18:54.480 --> 00:18:55.319 into pure energy. 387 00:18:55.440 --> 00:18:59.079 Oh, and that energy is the gravitational waves ligo detected. 388 00:18:58.799 --> 00:19:02.039 Exactly e equals ms squared. In its most violent form. 389 00:19:01.960 --> 00:19:04.680 The mass just turns into a ripple in space, right. 390 00:19:04.920 --> 00:19:07.720 And what remains after that burst is a new entity. 391 00:19:08.079 --> 00:19:11.319 And when we measure its rotation frequency, we are measuring. 392 00:19:10.960 --> 00:19:12.400 Its spin, because they spin. 393 00:19:12.640 --> 00:19:16.119 Black holes are rarely static stationary objects. I mean, almost 394 00:19:16.160 --> 00:19:21.000 everything in the universe possesses angular momentum. Stars spin, galaxy spin. 395 00:19:21.279 --> 00:19:24.640 When two massive black holes orbit each other e merge, 396 00:19:25.680 --> 00:19:29.240 all that tremendous orbital energy has to go somewhere. The 397 00:19:29.359 --> 00:19:33.519 law of conservation of angular momentum dictates that the rotational 398 00:19:33.640 --> 00:19:35.319 energy is inherited by. 399 00:19:35.240 --> 00:19:38.640 The remnant, meaning the resulting black hole can be spinning 400 00:19:38.640 --> 00:19:41.279 at like a significant fraction of the speed of light. 401 00:19:41.359 --> 00:19:44.640