WEBVTT 1 00:00:03.439 --> 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 --> 00:00:23.839 slumber under the night sky. 7 00:00:26.960 --> 00:00:32.600 Imagine an explosion so violent, I mean, just so incomprehensibly 8 00:00:32.719 --> 00:00:37.399 massive that it outshines all the stars in the observable universe. 9 00:00:37.079 --> 00:00:38.640 Combined, every single one. 10 00:00:38.759 --> 00:00:42.240 Yeah, I want you to picture an event that releases 11 00:00:42.320 --> 00:00:45.159 more energy in a fraction of a second than our 12 00:00:45.200 --> 00:00:48.399 own sun will produce in its entire what ten billion 13 00:00:48.479 --> 00:00:51.600 year lifespan exactly. And yet if you were, say, floating 14 00:00:51.640 --> 00:00:53.439 in space right next to it, you wouldn't see a 15 00:00:53.520 --> 00:00:55.920 blinding flash, you wouldn't hear a deafening roar. 16 00:00:56.159 --> 00:00:59.159 Nothing. It happens in complete pitch black. 17 00:00:58.960 --> 00:01:01.200 Silence, which is just to wrap your head around. The 18 00:01:01.200 --> 00:01:03.359 only way you would even know it occurred is that 19 00:01:03.399 --> 00:01:06.599 the literal fabric of space and time around you would 20 00:01:07.040 --> 00:01:08.239 stretch and squeeze right. 21 00:01:08.239 --> 00:01:10.519 You wouldn't just feel it. The actual geometry of your 22 00:01:10.560 --> 00:01:12.239 own body would momentarily distort. 23 00:01:12.400 --> 00:01:15.799 Okay, let's unpack this. Uh huh, because yesterday July first, 24 00:01:15.799 --> 00:01:19.280 twenty twenty six, our understanding of the universe fundamentally change. 25 00:01:19.400 --> 00:01:20.079 You really did. 26 00:01:20.239 --> 00:01:23.040 We're looking at the release of the Gravitational Wave Transient 27 00:01:23.079 --> 00:01:28.000 Catalog five point zero or GWTC five, and the sheer 28 00:01:28.000 --> 00:01:30.159 scale of what we were talking about here is almost 29 00:01:30.200 --> 00:01:31.280 difficult to process. 30 00:01:31.400 --> 00:01:32.200 It's staggering. 31 00:01:32.400 --> 00:01:35.439 We are talking about one hundred and sixty one newly 32 00:01:35.480 --> 00:01:39.200 identified black hole collisions and this was detected in just 33 00:01:39.280 --> 00:01:42.599 a ten month window, right between April twenty twenty four 34 00:01:42.959 --> 00:01:44.519 and January twenty twenty five. 35 00:01:44.680 --> 00:01:47.799 Yeah, and it is a monumental threshold for astrophysics. I 36 00:01:47.840 --> 00:01:49.840 mean to put that in perspective. Those one hundred and 37 00:01:49.879 --> 00:01:53.519 sixty one new events bring our total number of known 38 00:01:53.959 --> 00:01:58.799 confirmed black hole collisions to a staggering three ninety wow, 39 00:01:59.280 --> 00:02:01.599 three ninety Right. We are no longer in the era 40 00:02:01.760 --> 00:02:05.280 of viewing black hole mergers as these incredibly rare, you know, 41 00:02:05.760 --> 00:02:08.840 one off anomalies that we might catch if we're extremely lucky. 42 00:02:08.960 --> 00:02:11.000 Right, We're not just hoping to get lucky anymore. We're 43 00:02:11.199 --> 00:02:12.960 practically taking a census. 44 00:02:12.680 --> 00:02:16.520 Exactly, we are uncovering an entire hidden population because for 45 00:02:16.560 --> 00:02:21.199 the longest time, astrophysis was fundamentally constrained by the electromagnetic. 46 00:02:20.439 --> 00:02:21.439 Spectrum meaning light. 47 00:02:21.719 --> 00:02:24.199 Yeah, light, If you think about it, everything we knew 48 00:02:24.199 --> 00:02:27.240 about the cosmos came from catching light, radio waves, X rays, 49 00:02:27.360 --> 00:02:30.919 visible light. But black holes, by definition, trap light. They 50 00:02:30.919 --> 00:02:32.759 are the ultimate cosmic ghosts. 51 00:02:33.039 --> 00:02:36.840 Because the gravity is so strong, nothing escapes, right, so we. 52 00:02:36.879 --> 00:02:40.479 Only knew they existed because of how their gravity bullied 53 00:02:40.479 --> 00:02:43.039 the matter around them. You know, stars whipping around an 54 00:02:43.080 --> 00:02:47.520 invisible center, or accretion disks of superheated gas glowing as 55 00:02:47.520 --> 00:02:48.199 they fell. 56 00:02:47.960 --> 00:02:50.319 In, like seeing the wind blowing through trees rather than 57 00:02:50.360 --> 00:02:51.400 seeing the wind itself. 58 00:02:51.479 --> 00:02:53.599 That's a great way to put it. But when two 59 00:02:53.719 --> 00:02:57.039 black holes collide in a dark, empty void, there is 60 00:02:57.199 --> 00:03:02.159 no light to catch, total silence. Well until we learn 61 00:03:02.199 --> 00:03:03.639 how to listen to gravity itself. 62 00:03:03.719 --> 00:03:05.960 And the reason you need to know about this today 63 00:03:06.159 --> 00:03:10.599 is that we are crossing from a period of discovery 64 00:03:10.639 --> 00:03:13.240 into a period of archaeology. Oh absolutely, It is like 65 00:03:13.280 --> 00:03:16.560 we just mapped the ruins of a lost cosmic civilization 66 00:03:17.080 --> 00:03:19.199 and now we actually have enough data to understand how 67 00:03:19.199 --> 00:03:21.439 they lived, how they grew and how they. 68 00:03:21.319 --> 00:03:22.960 Died, which is the most exciting part. 69 00:03:23.120 --> 00:03:25.479 But before we get into the record breaking, just mind 70 00:03:25.520 --> 00:03:28.719 bending specifics at TWTC five, we have to talk about 71 00:03:28.719 --> 00:03:31.199 the how I mean a decade ago, in twenty fifteen, 72 00:03:31.240 --> 00:03:33.960 the very first detection of gravitational waves happens. 73 00:03:33.719 --> 00:03:36.199 Right, the one that proved Einstein write a century after 74 00:03:36.240 --> 00:03:38.479 he proposed general relativity exactly. 75 00:03:38.719 --> 00:03:41.759 But going from one detection a decade ago to what 76 00:03:41.840 --> 00:03:44.240 three or four a week today? How are we doing that? 77 00:03:44.560 --> 00:03:49.520 So the engine driving this revolution is the International LVK Collaboration. Okay, 78 00:03:49.680 --> 00:03:52.439 that is LIGO in the United States, which operates to 79 00:03:52.960 --> 00:03:56.840 massive detectors in Washington State and Louisiana. Then there's Virgo 80 00:03:56.960 --> 00:03:59.960 in Italy and KARA in Japan. 81 00:04:00.280 --> 00:04:03.520 And these are those massive L shaped vacuum tubes. 82 00:04:03.280 --> 00:04:06.639 Right, yeah, kilometers long where we fire lasers back and 83 00:04:06.680 --> 00:04:09.400 forth to measure the stretching of space time. But to 84 00:04:09.479 --> 00:04:12.599 understand why we are suddenly catching multiple events a week, 85 00:04:12.840 --> 00:04:14.960 you really have to look at the unsung heroes of 86 00:04:15.000 --> 00:04:15.520 the hardware. 87 00:04:15.599 --> 00:04:16.160 Who are they? 88 00:04:16.360 --> 00:04:19.319 Specifically the researchers at the University of Glasgow. They have 89 00:04:19.399 --> 00:04:22.360 been working on gravitational wave science since the nineteen seventies. 90 00:04:22.519 --> 00:04:25.879 Wait, the seventies, long before we had any proof these 91 00:04:25.920 --> 00:04:29.480 waves could actually be detected exactly long. I imagine dedicating 92 00:04:29.519 --> 00:04:31.759 forty years of your career to building parts for a 93 00:04:31.800 --> 00:04:34.759 machine to detect something that might not even be measurable. 94 00:04:34.800 --> 00:04:36.160 It takes a lot of faith in the math. 95 00:04:36.480 --> 00:04:38.560 I want to drill down into what they actually built, 96 00:04:38.600 --> 00:04:40.279 because I know it's not just a matter of pointing 97 00:04:40.319 --> 00:04:42.879 a telescope at this guy. They had to solve an 98 00:04:42.920 --> 00:04:45.759 absolute mechanical engineering nightmare. 99 00:04:45.839 --> 00:04:49.279 Oh, a total nightmare. What's fascinating here is that the 100 00:04:49.279 --> 00:04:52.879 core of the problem is isolation. The Earth is a 101 00:04:52.920 --> 00:04:54.519 remarkably noisy planet. 102 00:04:54.759 --> 00:04:54.959 Right. 103 00:04:55.160 --> 00:04:58.879 You have trucks striving on highways miles away. You have 104 00:04:59.000 --> 00:05:04.959 ocean wavesrushing against the continental shelf. You have continuous micro seismic. 105 00:05:04.600 --> 00:05:06.920 Tremors, constant vibration. 106 00:05:06.720 --> 00:05:10.160 Always even the wind pushing against the observatory buildings creates 107 00:05:10.199 --> 00:05:14.519 ground tilt. If you just bolted a highly sensitive mirror 108 00:05:14.560 --> 00:05:16.920 to the floor, it would shake violently. 109 00:05:16.959 --> 00:05:18.720 And we were trying to measure what a change in 110 00:05:18.800 --> 00:05:22.680 distance caused by a gravitational wave that is smaller than 111 00:05:22.680 --> 00:05:24.079 a fraction of an atomic. 112 00:05:23.759 --> 00:05:26.639 Nucleus, Right, so the background noise of the Earth is 113 00:05:26.879 --> 00:05:29.800 orders of magnitude louder than the signal we want. 114 00:05:29.920 --> 00:05:32.160 It's like trying to hear a single pin drop in 115 00:05:32.199 --> 00:05:35.040 the middle of a roaring hurricane using a microphone. You've 116 00:05:35.079 --> 00:05:36.120 suspended by a thread. 117 00:05:36.319 --> 00:05:38.000 That is exactly what it's like. 118 00:05:38.160 --> 00:05:40.199 So how do you separate the mirror from the planet 119 00:05:40.199 --> 00:05:40.839 it's sitting on. 120 00:05:41.319 --> 00:05:43.839 You suspend it. But you can't just hang it with 121 00:05:43.920 --> 00:05:44.639 steel wire? 122 00:05:44.839 --> 00:05:45.240 Why not? 123 00:05:45.480 --> 00:05:49.480 Because steel has internal friction. When atoms in a metal 124 00:05:49.519 --> 00:05:53.759 wire rub against each other, they generate thermal noise, microscopic 125 00:05:53.879 --> 00:05:56.759 vibrations that would travel right down to the mirror and 126 00:05:56.839 --> 00:06:00.079 mimic a gravitational wave. Ah okay, So the Glasgow Tea 127 00:06:00.199 --> 00:06:05.279 solution was to develop ultrasensitive mirror suspensions using fused silica, 128 00:06:05.519 --> 00:06:07.600 essentially extremely pure glass. 129 00:06:07.680 --> 00:06:12.720 Wait, they are hanging forty kilogram optical mirrors with glass thread. 130 00:06:12.920 --> 00:06:16.560 Yes, they literally pull these fused silica threads so they 131 00:06:16.600 --> 00:06:19.680 are incredibly thin, and then they physically weld them to 132 00:06:19.720 --> 00:06:20.800 the sides of the mirrors. 133 00:06:20.959 --> 00:06:21.480 Wow. 134 00:06:21.759 --> 00:06:25.439 It's called a monolithic suspension because it's glass to glass. 135 00:06:25.480 --> 00:06:29.800 There are no joints, no clamps, and virtually no mechanical. 136 00:06:29.240 --> 00:06:31.319 Friction, which means no thermal noise. 137 00:06:31.519 --> 00:06:35.519 Exactly when you eliminate that friction, you eliminate a massive 138 00:06:35.560 --> 00:06:40.279 source of the noise. The mirror essentially floats, completely decoupled 139 00:06:40.279 --> 00:06:43.480 from the chaotic molecular vibrations of the Earth. That's incredibly 140 00:06:43.519 --> 00:06:46.480 it's perfectly still waiting for the fabric of the universe 141 00:06:46.519 --> 00:06:47.800 itself to ripple through it. 142 00:06:48.000 --> 00:06:49.800 I just want to pause on that image for a second. 143 00:06:50.959 --> 00:06:54.560 We have a forty kilogram mirror hanging by glass threads, 144 00:06:55.079 --> 00:06:58.720 isolated so perfectly that it doesn't feel a truck driving 145 00:06:58.720 --> 00:07:02.800 by outside, but it does feel two black holes crashing 146 00:07:02.800 --> 00:07:04.720 into each other a billion light years away. 147 00:07:04.839 --> 00:07:09.480 It's beautiful engineering, and it goes even deeper than mechanical isolation. 148 00:07:10.040 --> 00:07:12.319 We also have to fight quantum noise, right. 149 00:07:12.160 --> 00:07:14.879 Because when you get down to measurements smaller than a proton, 150 00:07:15.519 --> 00:07:18.600 the universe just stops playing by normal rules. The Heisenberg 151 00:07:18.680 --> 00:07:20.160 uncertainty principle kicks in. 152 00:07:20.360 --> 00:07:23.560 Exactly at that scale, you can't know both the phase 153 00:07:23.720 --> 00:07:26.600 and the amplitude of the laser light with perfect precision. 154 00:07:26.800 --> 00:07:30.879 Right empty space itself is boiling with quantum vacuum fluctuations, 155 00:07:31.199 --> 00:07:34.920 virtual particles popping in and out of existence, randomly kicking the. 156 00:07:34.879 --> 00:07:36.639 Mirrors, which is just wild. 157 00:07:36.800 --> 00:07:40.360 It is, so the observatories use a technique called quantum squeezing. 158 00:07:40.879 --> 00:07:43.680 They literally manipulate the quantum state of the laser light. 159 00:07:44.199 --> 00:07:46.720 They choose to accept more uncertainty in a variable they 160 00:07:46.720 --> 00:07:49.160 don't care about, like the phase, so they can squeeze 161 00:07:49.199 --> 00:07:51.399 down the uncertainty in the amplitude because. 162 00:07:51.199 --> 00:07:53.720 The amplitude is what they actually need to measure. 163 00:07:53.399 --> 00:07:54.759 The wave precisely. 164 00:07:54.839 --> 00:07:57.600 It's like squeezing a balloon. You squeeze it in the 165 00:07:57.600 --> 00:07:59.600 middle to make it narrower where you need it to be, 166 00:08:00.079 --> 00:08:03.240 but it bulges out at the ends. We are physically 167 00:08:03.279 --> 00:08:07.120 pushing the quantum fuzziness out of the way of our measurement. 168 00:08:07.199 --> 00:08:11.319 That's a perfect analogy, and it's this relentless, obsessive upgrading 169 00:08:11.360 --> 00:08:15.279 that gives us catalogs like GWTC five. What's fascinating here 170 00:08:15.399 --> 00:08:17.120 is the way the validation cycle works. 171 00:08:17.279 --> 00:08:17.439 Ah. 172 00:08:17.519 --> 00:08:20.759 So the LVK collaboration operates in cycles. They don't just 173 00:08:20.879 --> 00:08:23.720 run the machines forever. They have observing runs and then 174 00:08:23.720 --> 00:08:26.839 they completely shut down for months of commissioning right to 175 00:08:26.879 --> 00:08:30.839 install the upgrades. Exactly. They install better lasers, heavier mirrors, 176 00:08:30.920 --> 00:08:34.679 better quantum squizzers, and more advanced glass extensions, and every 177 00:08:34.759 --> 00:08:38.000 time they turn the network back on, the sensitivity volume, 178 00:08:38.080 --> 00:08:39.960 meaning the total amount of space we can listen to, 179 00:08:40.519 --> 00:08:42.679 increases by a massive cube factor. 180 00:08:42.840 --> 00:08:44.960 Okay, but here's the question that always trips me up. 181 00:08:45.080 --> 00:08:48.399 We have this hyper sensitive glass pendulum and it wiggles. 182 00:08:48.639 --> 00:08:51.799 How did the scientist actually sitting at the computers know 183 00:08:52.039 --> 00:08:54.559 for sure that the wiggle was a black hole in 184 00:08:54.600 --> 00:08:58.360 another galaxy and not just a weird microscopic thermal burp 185 00:08:58.399 --> 00:09:01.840 in the glass or a rogue quantum fluctuation that slipped 186 00:09:01.879 --> 00:09:03.039 through the squeezing well. 187 00:09:03.120 --> 00:09:06.159 That is the defining challenge of data analysis in this field. 188 00:09:06.639 --> 00:09:09.639 Finding a gravitational wave isn't just looking for a bump 189 00:09:09.679 --> 00:09:10.320 on a graph. 190 00:09:10.480 --> 00:09:11.320 What are they looking for? 191 00:09:11.519 --> 00:09:14.759 You are searching for a highly specific mathematical pattern called 192 00:09:14.799 --> 00:09:15.279 a chirp. 193 00:09:15.399 --> 00:09:15.919 A chirp. 194 00:09:16.120 --> 00:09:19.519 Yeah. As two black holes spiral closer and closer together, 195 00:09:19.679 --> 00:09:23.879 they orbit faster and faster. This causes the gravitational waves 196 00:09:23.919 --> 00:09:26.879 they emit to increase in both frequency so the pitch 197 00:09:26.960 --> 00:09:29.519 goes up and amplitude so it gets louder. 198 00:09:29.799 --> 00:09:31.399 Yeah, I can picture that it looks like a. 199 00:09:31.440 --> 00:09:35.399 Very distinct sweeping curve in the data, and to quantify 200 00:09:35.440 --> 00:09:38.559 their confidence, researchers rely on a metric called the signal 201 00:09:38.559 --> 00:09:40.519 to noise ratio or SNR. 202 00:09:40.799 --> 00:09:42.960 So, if the background noise of the instrument is the 203 00:09:43.000 --> 00:09:46.159 static on an old analog TV, the signal is the 204 00:09:46.200 --> 00:09:49.919 actual broadcast trying to punch through exactly. For anyone familiar 205 00:09:49.919 --> 00:09:52.679 with signal processing, what is the usual baseline for claiming 206 00:09:52.759 --> 00:09:53.519 a real detection? 207 00:09:54.000 --> 00:09:57.279 For a typical gravitational wave detection, an SNR of around 208 00:09:57.360 --> 00:09:59.480 eight or ten is usually the threshold where the team 209 00:09:59.480 --> 00:10:02.240 feels colm that they have a real astrophysical event. 210 00:10:02.480 --> 00:10:04.679 Okay, eight or ten means it's real, not just a 211 00:10:04.759 --> 00:10:08.600 random statistical fluctuation of the noise floor. Which sets the 212 00:10:08.639 --> 00:10:13.519 stage perfectly for the absolute bombshell of the GWTC five catalog, 213 00:10:13.960 --> 00:10:17.080 because we are moving from the general how of detection 214 00:10:17.519 --> 00:10:20.080 to a specific event that I can only describe as 215 00:10:20.120 --> 00:10:23.559 the loudest whisper in the cosmos. Oh, let's talk about 216 00:10:23.639 --> 00:10:25.240 January fourteen, twenty twenty. 217 00:10:25.120 --> 00:10:28.480 Five, event GW two five zero one one two. This 218 00:10:28.559 --> 00:10:30.519 is an event that will be heavily cited in physics 219 00:10:30.519 --> 00:10:34.480 textbooks for decades. Really, oh absolutely, The black holes involved 220 00:10:34.480 --> 00:10:37.480 were massive, roughly thirty two and thirty four times the 221 00:10:37.519 --> 00:10:40.080 mass of our sun. They collided over a billion light 222 00:10:40.159 --> 00:10:43.200 years away. But the defining characteristic wasn't just the mass, 223 00:10:43.240 --> 00:10:44.120 it was the clarity. 224 00:10:44.320 --> 00:10:46.120 Okay, you just said an SNR of eight is a 225 00:10:46.159 --> 00:10:49.039 solid detection. What did GW two five zero one one 226 00:10:49.120 --> 00:10:50.080 fourteen come in at? 227 00:10:50.159 --> 00:10:52.720 It achieved a record breaking signal to noise ratio of 228 00:10:52.759 --> 00:10:54.399 seventy six point nine seventy. 229 00:10:54.159 --> 00:10:57.480 Six point nine. I mean, mathematically, that isn't just peaking 230 00:10:57.480 --> 00:10:59.960 above the noise floor, that is standing on a map 231 00:11:00.000 --> 00:11:02.919 out with a megaphone. If an SNR of eight is 232 00:11:02.960 --> 00:11:06.559 a blurry, grainy polaroid of a black hole, an SNR 233 00:11:06.639 --> 00:11:09.120 of seventy six point nine is like a four K 234 00:11:09.519 --> 00:11:12.120 ultra high definition uncompressed video. 235 00:11:12.320 --> 00:11:15.440 That's exactly what it is. It is the clearest gravitational 236 00:11:15.440 --> 00:11:18.519 wave signal humanity has ever recorded. And when you have 237 00:11:18.559 --> 00:11:22.279 a signal that pristine, the entire nature of the science shifts. 238 00:11:22.320 --> 00:11:26.320 Howso you transition from merely cataloging the demographics of black 239 00:11:26.360 --> 00:11:29.960 holes to fundamentally stress testing the laws of physics. Doctor 240 00:11:30.039 --> 00:11:33.000 John Vache, a researcher analyzing these signals at the University 241 00:11:33.039 --> 00:11:36.519 of Glasgow, noted that this unprecedented loudness allowed them to 242 00:11:36.559 --> 00:11:39.840 perform the most precise test of general relativity today. 243 00:11:39.919 --> 00:11:42.240 Wait, what are we actually testing? Though we know general 244 00:11:42.279 --> 00:11:46.440 relativity works. I mean, GPS satellites use it. Previous gravitational 245 00:11:46.480 --> 00:11:48.960 waves confirmed it true. What does a seventy six point 246 00:11:49.039 --> 00:11:50.960 nine SNR. Let us look at that we couldn't see 247 00:11:51.000 --> 00:11:51.519 before it. 248 00:11:51.600 --> 00:11:54.480 Lets us look at the deeply worked space time immediately 249 00:11:54.519 --> 00:11:58.200 before the merger and compare it with exquisite precision to 250 00:11:58.279 --> 00:12:00.600 the warped space time after the black pot holes become 251 00:12:00.720 --> 00:12:04.399 one single object, and by doing that they provided stunning 252 00:12:04.440 --> 00:12:07.960 confirmation of Stephen Hawking's black hole area theorem. 253 00:12:08.120 --> 00:12:11.720 Oh, this is where the physics gets incredibly trippy. Let's 254 00:12:11.720 --> 00:12:15.799 break down the area theorem because it completely defies human intuition. 255 00:12:16.080 --> 00:12:16.799 It really does. 256 00:12:16.919 --> 00:12:18.960 When we talk about the area of a black hole, 257 00:12:19.159 --> 00:12:22.240 we are talking about the event horizon right, the point 258 00:12:22.240 --> 00:12:23.480 of no return right. 259 00:12:23.559 --> 00:12:26.080 And it is crucial to remember that the event horizon 260 00:12:26.240 --> 00:12:28.679 is not a solid physical. 261 00:12:28.240 --> 00:12:30.320 Surface, right. It's not like the crust of the Earth. 262 00:12:30.399 --> 00:12:32.759 For the surface of an ocean exactly. It is a 263 00:12:32.759 --> 00:12:37.120 mathematical boundary in space where the escape velocity exceeds the 264 00:12:37.120 --> 00:12:41.519 speed of light. Decades ago, Hawking theorized that in any 265 00:12:41.559 --> 00:12:45.480 physical process involving black holes, the total area of their 266 00:12:45.519 --> 00:12:47.200 event horizons can never. 267 00:12:47.080 --> 00:12:48.759 Decrease, never decrease. Right. 268 00:12:48.840 --> 00:12:52.000 If two black holes merge, the area of the new 269 00:12:52.159 --> 00:12:55.720 single event horizon must be strictly greater than the sum 270 00:12:55.759 --> 00:12:57.960 of the areas of the two original black holes. 271 00:12:58.000 --> 00:13:00.639 See. I know this sounds straightforward, but about a water 272 00:13:00.720 --> 00:13:04.200 droplet analogy. If you take two separate water droplets on 273 00:13:04.240 --> 00:13:07.720 a windshield and they merge into one larger droplet, the 274 00:13:07.799 --> 00:13:11.200 total volume of water is conserved, but the total surface 275 00:13:11.240 --> 00:13:14.960 area of that new single droplet is actually less than 276 00:13:15.000 --> 00:13:17.399 the surface area the two separate droplets. 277 00:13:16.960 --> 00:13:21.080 Combined, because that is how three dimensional geometry usually works, exactly. 278 00:13:20.759 --> 00:13:23.480 But for a black hole, the rules are inverted. The 279 00:13:23.559 --> 00:13:26.639 surface area must go up. And again, this isn't physical 280 00:13:26.679 --> 00:13:30.639 matter expanding, It's a boundary of gravity. Right and GW 281 00:13:30.720 --> 00:13:34.320 two five zero one one four proved observationally that this 282 00:13:34.519 --> 00:13:39.399 invisible boundary physically grew exactly as Hawkings math demanded. 283 00:13:39.600 --> 00:13:42.879 It is a profound confirmation, but the implications go much 284 00:13:42.919 --> 00:13:46.919 deeper than geometry. Hawking's proposal wasn't just a quirk of relativity. 285 00:13:47.000 --> 00:13:51.600 It was the bridge to thermodynamics. Hawking, alongside Jacob Beekenstein, 286 00:13:52.000 --> 00:13:53.879 realized that the area of a black hole is a 287 00:13:53.960 --> 00:13:56.600 vent horizon is mathematically analogous to entropy. 288 00:13:56.879 --> 00:14:01.200 Okay, assuming everyone listening knows the second law of thermodynamics entropy, 289 00:14:01.279 --> 00:14:04.080 the measure of disorder always increases in a closed system. 290 00:14:04.279 --> 00:14:07.080 It's the arrow of time. It's why you can't unscramble 291 00:14:07.080 --> 00:14:09.519 an egg, and why a hot cup of coffee inevitably 292 00:14:09.559 --> 00:14:12.759 cools down. But applying the rules of a scrambled egg 293 00:14:12.799 --> 00:14:15.720 to a tear in space time that just feels wrong. 294 00:14:16.000 --> 00:14:18.759 It sounds absurd until you look at the math. The 295 00:14:18.799 --> 00:14:22.279 Beckenstein Hawking formula explicitly links the entropy of a black 296 00:14:22.279 --> 00:14:25.440 hole to the surface area of its event horizon. The 297 00:14:25.480 --> 00:14:28.960 area is the entropy. So when these two massive black 298 00:14:28.960 --> 00:14:31.759 holes in GW two five zero one to one team merged, 299 00:14:32.399 --> 00:14:36.600 it wasn't a clean silent fusion. The newly formed black 300 00:14:36.600 --> 00:14:39.759 hole was violently distorted. It literally rings like a bell, 301 00:14:40.200 --> 00:14:42.799 radiating away an enormous amount of energy in the form 302 00:14:42.840 --> 00:14:46.120 of gravitational ways as it settles down into a perfect sphere. 303 00:14:46.200 --> 00:14:49.240 Okay, wait, wait, if it is radiating away massive amounts 304 00:14:49.240 --> 00:14:52.919 of energy, shouldn't it be losing mass, Yes, and therefore shrinking. 305 00:14:53.000 --> 00:14:56.279 And if it shrinks, wouldn't the area and the entropy decrease, 306 00:14:56.480 --> 00:14:59.759 which violates the second law of thermodynamics. 307 00:14:59.000 --> 00:15:02.600 That is, the exact paradox. Physicists wrestled with, oh, really, yes, 308 00:15:03.240 --> 00:15:07.279 But analyzing the exceptionally clear waves from that ringing phase 309 00:15:07.399 --> 00:15:10.799 the ring down confirmed that despite throwing off several sons 310 00:15:10.840 --> 00:15:13.799 worth of energy during the merger, the geometry of a 311 00:15:13.840 --> 00:15:17.200 black hole is such that the total area still increases. 312 00:15:17.360 --> 00:15:20.759 That is, wild, the mass lost to gravitational waves is 313 00:15:20.840 --> 00:15:24.200 more than offset by the way the remaining mass configures itself. 314 00:15:24.279 --> 00:15:24.639 Okay. 315 00:15:25.080 --> 00:15:28.799 This raises an important question, though, and proves definitively that 316 00:15:28.840 --> 00:15:32.159 the laws of thermodynamics, the exact same equations that govern 317 00:15:32.279 --> 00:15:34.720 steam engines, heat flow, and the arrow of time on 318 00:15:34.799 --> 00:15:39.559 Earth apply to invisible gravitational boundaries a billion light years away. 319 00:15:39.639 --> 00:15:42.240 Here's where it gets really interesting, though. The mechanics of 320 00:15:42.279 --> 00:15:45.720 a nineteenth century steam engine governing the event horizon of 321 00:15:45.759 --> 00:15:49.039 a black hole it's poetic. It is, But if we 322 00:15:49.080 --> 00:15:52.480 are applying thermodynamics, I have to ask about temperature because 323 00:15:52.519 --> 00:15:55.759 I know there is this severe counterintuitive quirk here regarding 324 00:15:55.759 --> 00:15:57.159 how black holes handle heat. 325 00:15:57.320 --> 00:16:00.000 Ah, you are referring to negative heat capacit. 326 00:16:00.679 --> 00:16:03.519 Yes. If you're listening to this and wondering how on 327 00:16:03.519 --> 00:16:07.240 Earth a massive black hole can be cold, you aren't alone. 328 00:16:07.480 --> 00:16:10.240 Because on Earth, if I pump energy into a system, 329 00:16:10.759 --> 00:16:12.960 like if I throw a log on a campfire, the 330 00:16:13.039 --> 00:16:15.480 fire gets hotter naturally, but a black hole does the 331 00:16:15.519 --> 00:16:16.320 exact opposite. 332 00:16:16.440 --> 00:16:22.320 It completely upends our standard thermodynamic intuition. For a normal object, 333 00:16:22.440 --> 00:16:25.159 temperature is a measure of the average kinetic energy of 334 00:16:25.159 --> 00:16:29.320 its particles, right, But black holes emit thermal radiation Hawking 335 00:16:29.440 --> 00:16:33.080 radiation due to quantum effects near the event horizon, and 336 00:16:33.120 --> 00:16:36.039 the mathematics dictate that the temperature of this radiation is 337 00:16:36.080 --> 00:16:38.519 inversely proportional to the black hole's mass. 338 00:16:38.559 --> 00:16:41.519 So as the black hole eats matter, gets heavier and 339 00:16:41.559 --> 00:16:45.480 its event horizon grows, its temperature actually drops drastically. 340 00:16:45.679 --> 00:16:47.639 A black hole with the mass of our Sun has 341 00:16:47.679 --> 00:16:50.240 a temperature of about one ten millionth of a degree 342 00:16:50.279 --> 00:16:51.519 above absolute zero. 343 00:16:51.720 --> 00:16:53.320 That is, incredibly cold. 344 00:16:53.159 --> 00:16:56.120 It is, but the newly birthed black hole from gw 345 00:16:56.159 --> 00:16:59.360 two five zero one one four, which was over sixty 346 00:16:59.399 --> 00:17:02.879 times the mass of our Sun, it is exponentially colder. 347 00:17:03.559 --> 00:17:06.200 Super Massive black holes at the center of galaxies are 348 00:17:06.200 --> 00:17:09.119 some of the coldest objects in the known universe. As 349 00:17:09.160 --> 00:17:11.720 they gain energy and mass, they cool down. 350 00:17:11.920 --> 00:17:14.119 I just love picturing this. You had this newly birthed 351 00:17:14.200 --> 00:17:18.559 Leviathan born from an explosion of gravitational energy, ringing in 352 00:17:18.599 --> 00:17:22.240 the absolute freezing dark of space, and it is fundamentally 353 00:17:22.240 --> 00:17:23.720 colder than the empty space around it. 354 00:17:23.720 --> 00:17:24.680 It's a haunting image. 355 00:17:24.720 --> 00:17:28.240 And we only get to verify these incredibly exotic, almost 356 00:17:28.279 --> 00:17:32.519 philosophical truths because a glass thread in Washington State didn't shake. 357 00:17:32.759 --> 00:17:35.559 It is the ultimate triumph of fundamental physics. But you know, 358 00:17:35.599 --> 00:17:38.200 physics is only half the story of GWTC five right. 359 00:17:38.279 --> 00:17:41.000 Allowed signal is a godsend for testing Einstein and Hawking. 360 00:17:41.480 --> 00:17:43.279 But if we want to understand the actual architecture of 361 00:17:43.279 --> 00:17:45.759 the cosmos, we need to know exactly where these signals 362 00:17:45.799 --> 00:17:48.559 are coming from exactly. A sound in the dark is fascinating, 363 00:17:48.599 --> 00:17:50.519 but to map the room, you need to find the source. 364 00:17:50.839 --> 00:17:52.960 Let's look at the next major milestone in the catalog 365 00:17:53.440 --> 00:17:55.480 event GW two four zero. 366 00:17:55.319 --> 00:17:58.359 Six one five, detected on June fifteenth, twenty twenty four. 367 00:17:58.839 --> 00:18:01.920 The black holes here roughly twenty six and thirty times 368 00:18:02.000 --> 00:18:04.920 the mass of the Sun, but the standout metric is 369 00:18:04.960 --> 00:18:06.799 the distance and the localization. 370 00:18:07.160 --> 00:18:08.279 How far away was it? 371 00:18:08.319 --> 00:18:11.799 This collision happened more than three billion light years. 372 00:18:11.599 --> 00:18:14.839 Away, three billion, which means the ripples we felt in 373 00:18:14.880 --> 00:18:17.559 twenty twenty four started their journey when life on Earth 374 00:18:17.640 --> 00:18:20.720 was barely figuring out multicellularity exactly. 375 00:18:21.599 --> 00:18:24.640 But despite traveling for three billion years, this event holds 376 00:18:24.680 --> 00:18:28.440 the record for the most accurate sky localization ever achieved 377 00:18:28.440 --> 00:18:30.000 for a gravitational wave source. 378 00:18:30.160 --> 00:18:30.599 Wow. 379 00:18:31.000 --> 00:18:33.640 The researchers managed to narrow its origin down to an 380 00:18:33.720 --> 00:18:36.480 area covering only six square degrees on the sky. 381 00:18:36.920 --> 00:18:39.200 Now, anyone who follows astronomy knows that a full moon 382 00:18:39.319 --> 00:18:42.240 covers about half a degree of the sky, so six 383 00:18:42.279 --> 00:18:45.160 square degrees is still a patch of sky holding twelve 384 00:18:45.279 --> 00:18:48.359 full moons. To an optical astronomer with a telescope, that's 385 00:18:48.400 --> 00:18:51.559 a massive glory area, But in gravitational wave. 386 00:18:51.440 --> 00:18:55.480 Astronomy it is practically a pinpoint. Historically, gravitational wave localizations 387 00:18:55.519 --> 00:18:59.519 could span hundreds, sometimes thousands, of square degrees an entire 388 00:18:59.640 --> 00:19:00.960 hemic sphere of the sky. 389 00:19:00.920 --> 00:19:03.000 Basically just saying it came from up there. 390 00:19:02.960 --> 00:19:06.160 Right, So narrowing it down to six square degrees is 391 00:19:06.200 --> 00:19:08.359 a revolutionary leap in precision. 392 00:19:08.720 --> 00:19:11.599 How did we suddenly get that precise? Was it a 393 00:19:11.640 --> 00:19:14.359 hardware upgrade to the Ligo lasers or is this a 394 00:19:14.359 --> 00:19:15.119 software trick? 395 00:19:15.640 --> 00:19:19.039 It was primarily about geometry and the vital return of 396 00:19:19.079 --> 00:19:22.480 the Virgo detector in Italy m Okay. Virgo had been 397 00:19:22.480 --> 00:19:25.559 offline for upgrades during the previous run, but its return 398 00:19:25.720 --> 00:19:30.160 allowed the LVK collaboration to use all three major detectors simultaneously. 399 00:19:30.720 --> 00:19:33.599 The two Ligo facilities in the US plus Virgo in 400 00:19:33.640 --> 00:19:36.759 Europe form a massive intercontinental triangle. 401 00:19:36.960 --> 00:19:39.720