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 --> 00:00:23.800 slumber under the night sky. 7 00:00:26.920 --> 00:00:29.519 I want you to try kind of a thought experiment 8 00:00:29.559 --> 00:00:32.079 the next time you find yourself outside on a clear night, 9 00:00:32.600 --> 00:00:35.600 like a truly dark night. Maybe you're out camping away 10 00:00:35.640 --> 00:00:36.679 from the city lights. 11 00:00:36.799 --> 00:00:39.320 Oh yeah, getting away from the light pollution is key 12 00:00:39.439 --> 00:00:39.759 for this. 13 00:00:40.000 --> 00:00:42.600 Right exactly. Yeah, So you're out there, and I want 14 00:00:42.600 --> 00:00:46.039 you to look up and just locate a patch of 15 00:00:46.079 --> 00:00:51.200 the sky that appears completely, unequivocally empty, just a black 16 00:00:51.280 --> 00:00:54.520 void sitting there between the stars of our local galaxy. 17 00:00:54.240 --> 00:00:55.600 Just absolute nothingness. 18 00:00:55.679 --> 00:00:59.119 Yeah. But here is the thing. Imagine staring into that 19 00:00:59.159 --> 00:01:02.320 absolute nothing and realizing that you are not looking at 20 00:01:02.320 --> 00:01:03.520 empty space at all. 21 00:01:03.600 --> 00:01:04.239 You're really not. 22 00:01:04.480 --> 00:01:07.680 No, you are looking directly down the barrel of a 23 00:01:07.719 --> 00:01:12.280 cosmic monster, basically, this astrophysical engine that is shining, you know, 24 00:01:12.560 --> 00:01:13.840 trillions of times brighter than. 25 00:01:13.799 --> 00:01:16.640 Our own sun trillions, which is a number that's just 26 00:01:17.120 --> 00:01:18.920 it's hard to even wrap your head around it. 27 00:01:18.879 --> 00:01:22.079 Really is, and it's just so unfathomably distant that by 28 00:01:22.120 --> 00:01:25.000 the time its light reaches your naked eye. The physical 29 00:01:25.079 --> 00:01:27.439 laws of the universe, stuff like the inverse square law 30 00:01:27.480 --> 00:01:30.840 and the actual expansion of space, have reduced this blinding, 31 00:01:31.000 --> 00:01:34.760 galaxy consuming inferno to absolute invisibility. 32 00:01:35.040 --> 00:01:38.519 It's completely invisible to us. And you know that realization 33 00:01:39.159 --> 00:01:41.799 forces a complete recalibration. 34 00:01:41.159 --> 00:01:41.959 Of your perspective. 35 00:01:42.120 --> 00:01:46.719 It totally does, Yeah, to realize that the darkest, quietest 36 00:01:46.799 --> 00:01:50.680 patches of our sky are actually harboring the most violent, 37 00:01:50.879 --> 00:01:55.280 luminous and just chaotic environments in the entire cosmos. 38 00:01:55.319 --> 00:01:58.599 It's wild. And that profound dissonance, you know, between what 39 00:01:58.680 --> 00:02:00.799 we actually see with our eye and what is truly 40 00:02:00.840 --> 00:02:03.439 out there in the dark, that is the foundation of 41 00:02:03.439 --> 00:02:04.879 our entire conversation today. 42 00:02:04.920 --> 00:02:05.560 It's a big one. 43 00:02:05.599 --> 00:02:07.840 It's massive, yeah, because we are looking at the recent 44 00:02:07.879 --> 00:02:12.840 discovery of the oldest intrinsically brightest objects ever observed in 45 00:02:12.879 --> 00:02:13.719 the universe. 46 00:02:13.439 --> 00:02:14.840 The absolute record breakers. 47 00:02:14.960 --> 00:02:18.439 Right. But the reason this is sending total shockwaves through 48 00:02:18.479 --> 00:02:21.919 astrophysics isn't just about logging, you know, a new record 49 00:02:21.919 --> 00:02:23.639 in some celestial catalogs. 50 00:02:23.199 --> 00:02:25.000 Some the Yeah, not at all. It's way bigger than that. 51 00:02:25.400 --> 00:02:28.560 Yeah. The sheer existence of these objects actively fractures our 52 00:02:28.599 --> 00:02:32.159 standard models of cosmology. Like it's a glaring paradox that 53 00:02:32.199 --> 00:02:35.280 tells us our entire timeline for how the early universe 54 00:02:35.319 --> 00:02:38.240 formed is either missing a crucial chapter or is just 55 00:02:38.280 --> 00:02:39.120 fundamentally wrong. 56 00:02:39.319 --> 00:02:45.159 Fundamentally wrong. Yeah, because the standard cosmological model we use, 57 00:02:45.759 --> 00:02:49.680 which is called Lambda CDM, it sets very very strict 58 00:02:49.719 --> 00:02:53.240 speed limits on how fast structures can grow after the Big. 59 00:02:53.039 --> 00:02:55.039 Bang, okay, speed limits on mass. 60 00:02:55.840 --> 00:02:58.639 So when you find these massive structures existing at a 61 00:02:58.680 --> 00:03:01.639 point in time when the universe honestly barely had time 62 00:03:01.680 --> 00:03:05.039 to cool down, you aren't just finding a new type 63 00:03:05.039 --> 00:03:06.800 of star or a new galaxy. 64 00:03:06.879 --> 00:03:09.000 You're finding something that shouldn't be there exactly. 65 00:03:09.280 --> 00:03:12.360 You are finding an anomaly that threatens to just pull 66 00:03:12.400 --> 00:03:15.960 the thread on our entire understanding of early structure formation. 67 00:03:16.680 --> 00:03:19.560 We are literally being forced to ask how something could 68 00:03:19.599 --> 00:03:22.560 acquire that much mass in a fraction of the time 69 00:03:22.639 --> 00:03:24.479 that physics says it requires. 70 00:03:24.319 --> 00:03:26.960 Right, which is just a massive headache for physicists. So 71 00:03:27.000 --> 00:03:29.080 to understand this paradox. I think they first need to 72 00:03:29.120 --> 00:03:32.800 dissect the engine itself, right, because we're talking about thirty 73 00:03:32.800 --> 00:03:35.000 one newly discovered quasars. 74 00:03:34.560 --> 00:03:35.199 Thirty one of them. 75 00:03:35.280 --> 00:03:38.240 Yeah, and for anyone casually following astronomy, I feel like 76 00:03:38.319 --> 00:03:41.520 the term quasar gets thrown around a lot, and you know, 77 00:03:41.520 --> 00:03:43.879 it's often used interchangeably with black holes. But they aren't 78 00:03:43.879 --> 00:03:45.120 actually the same thing, are they. 79 00:03:45.319 --> 00:03:48.520 No, they really aren't. They're related, but definitely not the same. 80 00:03:49.120 --> 00:03:53.800 So a quasar, which actually stands for quasi stellar radio source, 81 00:03:53.960 --> 00:03:57.199 just as a bit of trivia, is the intensely luminous 82 00:03:57.240 --> 00:04:00.639 region right at the center of an active early galaxy. 83 00:04:00.759 --> 00:04:03.680 Okay, so it's a region, not an object itself, right. 84 00:04:03.599 --> 00:04:07.479 And it's powered by a supermassive black hole, But it's 85 00:04:07.520 --> 00:04:11.439 the activity that actually defines it as a quasar. 86 00:04:11.360 --> 00:04:14.280 Kidving, So like what the black hole is doing right 87 00:04:14.319 --> 00:04:14.680 in that. 88 00:04:14.680 --> 00:04:20.240 Moment, precisely like a dormant super massive black hole. For example, Sagittarius, 89 00:04:20.279 --> 00:04:22.480 a star right at the center of our own milky Way, 90 00:04:22.720 --> 00:04:24.240 that is not a quasar. 91 00:04:23.839 --> 00:04:25.279 Because it's basically on a diet right now. 92 00:04:25.279 --> 00:04:28.639 It's just sitting there, Yeah, exactly, it's fasting a quasar 93 00:04:28.759 --> 00:04:33.040 requires an active, just catastrophic influx of material. It is 94 00:04:33.079 --> 00:04:37.120 a highly specific, very transient phase in galactic evolution. 95 00:04:37.240 --> 00:04:38.519 I mean, it doesn't last forever. 96 00:04:38.720 --> 00:04:41.639 Right, it's fleeting on cosmic scales. The black hole is 97 00:04:41.639 --> 00:04:46.240 gobbling up the surrounding accretion disk of gas, dust, disrupted stars. 98 00:04:46.279 --> 00:04:49.360 Just an absolute feeding frenzy, an absolute feeding frenzy. 99 00:04:49.399 --> 00:04:52.920 And the luminosity generated by this process is just staggering. 100 00:04:53.040 --> 00:04:53.879 Oh it's blinding. 101 00:04:54.120 --> 00:04:57.720 Yeah, We're talking about a localized region of space outshining 102 00:04:57.759 --> 00:05:00.959 its entire host galaxy by a th of hundreds or 103 00:05:01.000 --> 00:05:02.800 even thousands thousands of time. 104 00:05:02.879 --> 00:05:05.000 Is brighter than billions of stars. 105 00:05:04.680 --> 00:05:07.920 Combined, which is just wow. But this is the part 106 00:05:07.959 --> 00:05:12.480 where I feel like the mechanics often get glossed over 107 00:05:12.639 --> 00:05:16.720 in standard science reporting, because the defining characteristic of a 108 00:05:16.720 --> 00:05:21.439 black hole is a gravitational well so speed that beyond 109 00:05:21.480 --> 00:05:24.680 the event horizon, the escape velocity is faster than the 110 00:05:24.680 --> 00:05:25.240 speed of light. 111 00:05:25.360 --> 00:05:27.600 Right, nothing gets out, not even light exactly. 112 00:05:28.000 --> 00:05:30.360 So if the central engine's primary function is to lock 113 00:05:30.439 --> 00:05:33.480 matter and light away forever from the observable universe, the 114 00:05:33.519 --> 00:05:36.720 blinding light we see obviously isn't coming from the black hole. Itself. 115 00:05:36.879 --> 00:05:39.759 Right, The light never actually crosses the event horizon to 116 00:05:39.800 --> 00:05:41.959 come back to us. It is a product of the 117 00:05:42.000 --> 00:05:45.160 macroscopic traffic jam sitting just outside. 118 00:05:44.759 --> 00:05:46.319 Of it, a cosmic traffic jam. 119 00:05:46.399 --> 00:05:49.720 I like that, Yeah, because as massive quantities of material 120 00:05:49.800 --> 00:05:53.680 fall toward that deep gravitational well, conservation of angular momentum 121 00:05:53.759 --> 00:05:56.000 basically prevents it from just dropping straight in. 122 00:05:55.959 --> 00:05:57.639 Because everything in space is spinning, right. 123 00:05:57.519 --> 00:06:01.480 Yeah, exactly, it's all swirling, so it forms this flattened, 124 00:06:01.600 --> 00:06:04.480 rapidly spinning structure called an accretion disk. 125 00:06:04.680 --> 00:06:07.720 Okay, an accretion disc, which always makes me think of 126 00:06:08.800 --> 00:06:10.879 spacecraft re entering Earth's atmosphere. 127 00:06:10.879 --> 00:06:13.120 Oh that's a really good analogy, actually, yeah. 128 00:06:12.920 --> 00:06:15.600 Because a lot of people assume the heat of reentry 129 00:06:15.720 --> 00:06:19.120 comes from the spacecraft rubbing against the air, right, like 130 00:06:19.160 --> 00:06:22.399 rubbing your hands together to get warm, right, Just basic friction, 131 00:06:22.519 --> 00:06:25.720 But it's actually ram pressure. The spacecraft is pushing the 132 00:06:25.759 --> 00:06:28.879 atmospheric gas out of the way faster than the gas 133 00:06:28.920 --> 00:06:33.199 can physically move, which compresses it. And that intense compression 134 00:06:33.519 --> 00:06:37.399 is what generates the superheated plasma. So in an accretion disc, 135 00:06:37.800 --> 00:06:41.680 you have a somewhat similar dynamic, right, This extreme friction 136 00:06:41.800 --> 00:06:45.120 and compression just scaled up to a galactic terrifying level. 137 00:06:45.240 --> 00:06:48.680 That re entry analogy captures the thermodynamics perfectly because in 138 00:06:48.720 --> 00:06:52.160 the accretion disk orbital velocities are higher the closer you 139 00:06:52.199 --> 00:06:54.639 get to the center, so the inside lanes are moving 140 00:06:54.680 --> 00:06:58.399 way faster than the outside lanes, just like a racetrack exactly. 141 00:06:58.480 --> 00:07:01.800 So you have these concentric rings of plasma just shearing 142 00:07:01.839 --> 00:07:05.360 against one another at significant fractions of the speed of light. 143 00:07:05.560 --> 00:07:05.959 Wow. 144 00:07:06.040 --> 00:07:09.959 And this differential rotation creates immense friction. But it is 145 00:07:10.079 --> 00:07:14.120 even more complex than just physical compression. We are dealing 146 00:07:14.120 --> 00:07:16.560 with highly magnetized plasma here. 147 00:07:16.639 --> 00:07:18.000 Okay, magnetized plasma. 148 00:07:18.120 --> 00:07:21.079 Yeah, so there's this thing called the magneto rotational instability 149 00:07:21.199 --> 00:07:24.240 or MRI. Not the brain scan, huh No, definitely not 150 00:07:24.279 --> 00:07:28.399 the brain scan. This MRI creates intense turbulence within the 151 00:07:28.399 --> 00:07:32.240 plasma and it acts as the main mechanism that actually 152 00:07:32.279 --> 00:07:36.040 transfers the angular momentum outward, which is what allows the 153 00:07:36.120 --> 00:07:37.639 mass to finally fall inward. 154 00:07:37.800 --> 00:07:39.879 Okay, wait, let me make sure I've got this. So 155 00:07:39.920 --> 00:07:42.040 the magnetic fields are kind of acting like the brakes 156 00:07:42.040 --> 00:07:44.519 on a car. They transfer the spin energy out which 157 00:07:44.560 --> 00:07:46.720 slows the matter down enough so it can drop closer 158 00:07:46.720 --> 00:07:49.000 to the event horizon, and that heats it up to 159 00:07:49.399 --> 00:07:51.480 hundreds of thousands of degrees in the process. 160 00:07:51.639 --> 00:07:55.560 Yes, exactly, the gravitational potential energy of all that infalling 161 00:07:55.600 --> 00:07:58.920 matter is converted into kinetic energy, and then through that 162 00:07:59.079 --> 00:08:02.199 viscous sheer and the magnetic turbulence you mentioned, it turns 163 00:08:02.199 --> 00:08:03.639 into thermal energy. 164 00:08:03.680 --> 00:08:06.759 Heat, just mind blowing amounts of heat. 165 00:08:06.639 --> 00:08:11.639 Insane amounts. The plasma gets so unimaginably hot that it 166 00:08:11.720 --> 00:08:16.680 emits this continuous, screaming barrage of ultraviolet and X ray. 167 00:08:16.560 --> 00:08:18.680 Radiation, and that light is the quasar. 168 00:08:18.839 --> 00:08:21.879 That is the quasar. You are literally seeing the death 169 00:08:21.959 --> 00:08:25.160 knell of the matter right before it crosses the threshold 170 00:08:25.240 --> 00:08:26.240 and disappears forever. 171 00:08:26.399 --> 00:08:28.879 Okay, So it's a messy eater at a cosmic buffet, 172 00:08:29.279 --> 00:08:31.839 and the glowing crumbs around its mouth are what we 173 00:08:31.920 --> 00:08:32.559 see from Earth. 174 00:08:32.879 --> 00:08:35.919 That is exactly it. And it is a violent but 175 00:08:36.320 --> 00:08:39.000 very brief era for the galaxy. 176 00:08:39.120 --> 00:08:41.039 Brief meaning what a few million. 177 00:08:40.799 --> 00:08:44.240 Years, yeah, roughly, Because it's not a steady state. The 178 00:08:44.279 --> 00:08:47.440 black hole basically clears out its immediate neighborhood, right It's 179 00:08:47.480 --> 00:08:49.519 blasting away a lot of the remaining gas with its 180 00:08:49.559 --> 00:08:50.480 own intense. 181 00:08:50.200 --> 00:08:52.240 Radiation pressure, like blowing away the smoke. 182 00:08:52.440 --> 00:08:55.200 Yeah, And eventually the fuel just runs out, the quasar 183 00:08:55.240 --> 00:08:58.399 phase ends, the lights turn off, and it leaves a quiet, 184 00:08:58.480 --> 00:09:00.720 quiescent galaxy behind. 185 00:09:00.399 --> 00:09:02.639 Just a normal galaxy with a sleeping giant in the middle, 186 00:09:02.679 --> 00:09:03.600 like our Milky. 187 00:09:03.279 --> 00:09:06.279 Way exactly, Which is why capturing them in the act 188 00:09:06.360 --> 00:09:09.879 is essentially an exercise in cosmic archaeology. You have to 189 00:09:09.919 --> 00:09:13.320 look back to the specific epochs when galaxies were young, 190 00:09:13.879 --> 00:09:17.840 gas rich, and undergoing these violent mergers that funnel all 191 00:09:17.919 --> 00:09:20.360 that material right into their centers. 192 00:09:20.159 --> 00:09:22.320 Which brings us to the real core of this new 193 00:09:22.399 --> 00:09:26.000 data because we know what equas are is now. But 194 00:09:26.080 --> 00:09:29.559 the significance of this specific discovery by astronomer Damian Yang 195 00:09:29.600 --> 00:09:34.960 and his international team it lies entirely in when these 196 00:09:34.960 --> 00:09:36.480 thirty one quasars existed? 197 00:09:36.759 --> 00:09:38.120 The when is everything here? 198 00:09:38.440 --> 00:09:41.159 Right? Because in astrophysics, since the speed of light is 199 00:09:41.200 --> 00:09:45.360 a hard physical constant, looking across vast distances of space 200 00:09:45.799 --> 00:09:48.440 is functionally identical to looking backward in time. 201 00:09:48.639 --> 00:09:52.240 It is the ultimate non theoretical time machine. It really is, Yeah, 202 00:09:52.360 --> 00:09:57.200 because we aren't inferring the past through geological strata or fossils. 203 00:09:57.440 --> 00:10:01.000 We are directly observing the actual photons that left these 204 00:10:01.039 --> 00:10:03.320 accretion discs billions of years ago. 205 00:10:03.440 --> 00:10:06.159 Right, They've just been flying through space this whole time, exactly. 206 00:10:06.519 --> 00:10:09.159 The delay in the light's arrival provides us with a literal, 207 00:10:09.240 --> 00:10:10.799 live broadcast of the early. 208 00:10:10.679 --> 00:10:15.120 Universe, live broadcast, and these specific quasars we're talking about today, 209 00:10:15.279 --> 00:10:18.200 they are situated at the absolute extreme edge of our 210 00:10:18.279 --> 00:10:20.679 observational horizon, very edge. 211 00:10:20.799 --> 00:10:20.879 Like. 212 00:10:20.919 --> 00:10:23.279 The accepted age of the universe is thirteen point eight 213 00:10:23.639 --> 00:10:26.639 billion years, and the light from the oldest pair of 214 00:10:26.720 --> 00:10:29.840 quasars in this newly discovered group of thirty one, it 215 00:10:29.919 --> 00:10:32.600 dates back to when the universe was roughly six hundred 216 00:10:32.639 --> 00:10:34.200 and seventy million years old. 217 00:10:34.000 --> 00:10:37.000 Which is just incredibly early. We really need to contextualize 218 00:10:37.039 --> 00:10:39.320 that six hundred and seventy million years. That is roughly 219 00:10:39.360 --> 00:10:41.399 five percent of the current age of the universe. 220 00:10:41.440 --> 00:10:41.879 Hacent. 221 00:10:42.080 --> 00:10:45.360 Yeah, so for a human life span of say eighty years, 222 00:10:45.720 --> 00:10:47.480 that is the equivalent of looking at a four year 223 00:10:47.480 --> 00:10:50.120 old child. Oh wow, Okay, We are observing the cosmos 224 00:10:50.159 --> 00:10:53.639 in its absolute infancy, an era immediately following the very 225 00:10:53.679 --> 00:10:56.360 first large scale structural formations. 226 00:10:56.080 --> 00:10:59.519 A cosmic toggler, and the two absolute farthest objects in 227 00:10:59.519 --> 00:11:02.159 this data, which actually broke the previous twenty twenty one 228 00:11:02.200 --> 00:11:05.240 record by about twenty million years. They have these specific 229 00:11:05.240 --> 00:11:08.240 designations that highlight just how far back we are looking. 230 00:11:08.399 --> 00:11:09.879 Yeah, the catalog names right. 231 00:11:09.799 --> 00:11:12.360 So we have eucl J one seven two and two 232 00:11:12.440 --> 00:11:15.120 nine sou nine er two point seventy five plus sixty 233 00:11:15.120 --> 00:11:17.440 four one zero eighteen point one, which sits at a 234 00:11:17.440 --> 00:11:19.200 red shift to seven point seven seven. 235 00:11:19.360 --> 00:11:21.399 Rules right off the tongue, doesn't it. 236 00:11:21.440 --> 00:11:24.399 Just And the other one is eucl J one two 237 00:11:24.519 --> 00:11:27.240 five three zero eight point five to five plus seven 238 00:11:27.320 --> 00:11:29.679 zero five four three two point three, which sits at 239 00:11:29.720 --> 00:11:33.240 a red shift of seven point six'. Nine but for anyone, 240 00:11:33.279 --> 00:11:35.480 listening who isn't you, know spending their days looking at 241 00:11:35.519 --> 00:11:39.559 cosmological data, spreadsheets we should probably unpack why red shift 242 00:11:39.600 --> 00:11:42.600 is the metric used here rather than just saying thirteen 243 00:11:42.679 --> 00:11:44.240 point one billion light years. 244 00:11:44.240 --> 00:11:47.039 Away that's a great point because distance is actually a 245 00:11:47.120 --> 00:11:48.960 very fluid concept in an expanding. 246 00:11:49.080 --> 00:11:50.440 Universe, right space itself is. 247 00:11:50.480 --> 00:11:54.320 Stretchy exactly when that ultraviolet light was first emitted by 248 00:11:54.399 --> 00:11:57.440 the quasar's accretion disc thirteen point one billion years, ago 249 00:11:57.720 --> 00:12:01.039 the universe was physically smaller than it is, now and 250 00:12:01.080 --> 00:12:04.200 as that photon travels through space toward us over billions of, 251 00:12:04.279 --> 00:12:07.559 years the very metric of space itself is expanding underneath. 252 00:12:07.559 --> 00:12:10.960 It and this expansion literally stretches the physical wavelength of the. 253 00:12:11.000 --> 00:12:14.000 Photon so light that started out as highly energetic shirt 254 00:12:14.000 --> 00:12:17.200 wavelength ultraviolet, radiation it gets stretched out like a cosmic 255 00:12:17.240 --> 00:12:19.679 slinky as the universe expands while the light is in 256 00:12:19.720 --> 00:12:20.679 transit like a. 257 00:12:20.720 --> 00:12:24.240 Slinky, yes by the time it finally reaches our telescopes 258 00:12:24.279 --> 00:12:27.360 here in The Solar, system that ultraviolet light has been 259 00:12:27.399 --> 00:12:30.279 stretched so far that it has shifted out of the 260 00:12:30.360 --> 00:12:31.279 visible spectrum. 261 00:12:31.399 --> 00:12:33.399 Entirely, wait, really it's not even visible light. 262 00:12:33.440 --> 00:12:36.480 Anymore, nope it's shifted all the way down into the near. 263 00:12:36.519 --> 00:12:39.720 Infrared so THAT zz value the red shift number like 264 00:12:39.799 --> 00:12:43.000 seven point seven to. Seven it's a direct measurement of 265 00:12:43.080 --> 00:12:45.879 exactly how much that light has been. Stretched oh, okay 266 00:12:45.919 --> 00:12:48.519 it tells us exactly how much the universe has expanded 267 00:12:48.559 --> 00:12:51.679 since the moment that photon was, emitted which in turn 268 00:12:51.879 --> 00:12:55.279 gives us the most precise measurement possible of its age 269 00:12:55.279 --> 00:12:55.600 and its. 270 00:12:55.639 --> 00:12:58.360 Distance, Okay so a red shift of seven point seven 271 00:12:58.360 --> 00:13:01.159 to seven means the wavelength of the light has been 272 00:13:01.159 --> 00:13:04.120 stretched by a factor of eight point seventy seven compared 273 00:13:04.159 --> 00:13:06.240 to when it was first. Emitted that is just an 274 00:13:06.240 --> 00:13:10.240 incredible mathematical. Tool it's. Brilliant we are basically intercepting a 275 00:13:10.399 --> 00:13:13.799 thirteen billion year old signal that has been physically altered 276 00:13:13.919 --> 00:13:16.399 by the growth of the universe itself. Exactly and the 277 00:13:16.440 --> 00:13:19.120 reason astronomers are spending you, know millions of dollars in 278 00:13:19.240 --> 00:13:22.600 years of telescope time hunting for these specific high red 279 00:13:22.600 --> 00:13:25.679 shift objects isn't just to set records for The Guinness. 280 00:13:25.679 --> 00:13:26.399 Book definitely. 281 00:13:26.440 --> 00:13:30.919 Not, no these quasars exist during a very, specific fiercely 282 00:13:30.960 --> 00:13:35.399 debated transitional era called The epoch of. Realization, yes The 283 00:13:35.480 --> 00:13:36.039 epoch of. 284 00:13:36.120 --> 00:13:40.519 Realization this is perhaps the most, critical poorly understood phase 285 00:13:40.600 --> 00:13:41.759 in the universe's entire. 286 00:13:41.799 --> 00:13:43.240 History, okay let's set the stage for. That. 287 00:13:43.279 --> 00:13:46.039 Sure so to set the, stage about three hundred and 288 00:13:46.120 --> 00:13:49.519 eighty thousand years after The Big, bang the universe finally 289 00:13:49.519 --> 00:13:52.559 cooled down enough for protons and electrons to bind together 290 00:13:52.639 --> 00:13:55.879 and form the first neutral, atoms which was mostly. Hydrogen. 291 00:13:56.200 --> 00:13:59.799 Okay this process is universally called, recombination. 292 00:13:59.320 --> 00:14:02.480 Which is honest slightly confusing terminology because it was the 293 00:14:02.480 --> 00:14:05.360 first time they ever, combined, right not a. Recombination, yeah that. 294 00:14:05.360 --> 00:14:08.679 Is a classic quirk of astronomical naming. Conventions we're not 295 00:14:08.720 --> 00:14:11.360 great in naming, things fair, Enough but the result of 296 00:14:11.360 --> 00:14:14.519 this combination was that the entire universe became filled with 297 00:14:14.559 --> 00:14:18.960 this pervasive dark fog of neutral hydrogen. Gas there were 298 00:14:18.960 --> 00:14:21.279 no stars, yet there were no, galaxies. 299 00:14:20.879 --> 00:14:23.480 Just a giant dark cloud, exactly. 300 00:14:23.200 --> 00:14:27.039 Just an expanding cooling cloud of primordial. Gas this era 301 00:14:27.159 --> 00:14:30.360 is very aptly named the cosmic dark, ages. 302 00:14:30.360 --> 00:14:34.279 Right and because neutral hydrogen is fantastic at absorbing ultraviolet, 303 00:14:34.320 --> 00:14:36.440 light even if there was a light source in, there 304 00:14:36.480 --> 00:14:38.559 you wouldn't be able to see it from far away, anyway, Right. 305 00:14:38.399 --> 00:14:40.919 Exactly the fog was optically, thick it would block. 306 00:14:41.000 --> 00:14:44.000 Everything but obviously we don't live in a dark fog 307 00:14:44.039 --> 00:14:46.679 of neutral hydrogen. Today you can see the. Stars the 308 00:14:46.759 --> 00:14:52.120 universe today is mostly ionized. Plasma so something had to 309 00:14:52.159 --> 00:14:54.799 happen to clear that massive cosmic, fog. 310 00:14:54.679 --> 00:14:58.360 Right and that's something was. Gravity gravity slowly went to 311 00:14:58.399 --> 00:15:02.159 work on the fog very slight density fluctuations in that 312 00:15:02.240 --> 00:15:05.759 primordial gas began to clump together and collapse under their own. 313 00:15:05.600 --> 00:15:06.960 Weight forming the first. 314 00:15:07.000 --> 00:15:11.039 Star, yes it eventually ignited the very first generation of, 315 00:15:11.080 --> 00:15:14.519 stars which we call population three stars and the earliest infant. 316 00:15:14.519 --> 00:15:18.320 Galaxies and as these objects lit, up they began pumping out, 317 00:15:18.720 --> 00:15:20.639 massive massive amounts of ultraviolet. 318 00:15:20.720 --> 00:15:23.840 Radiation and this is where the actual reionization. Happens oh, 319 00:15:23.879 --> 00:15:27.080 no we got, it because that ENERGETIC uv radiation blasts, 320 00:15:27.080 --> 00:15:29.960 out hits the neutral hydrogen atoms in the surrounding, fog 321 00:15:30.399 --> 00:15:33.159 knocks the electrons away from the protons, again and turns 322 00:15:33.200 --> 00:15:34.960 the gas back into an ionized. 323 00:15:35.000 --> 00:15:40.039 Plasma, right and here's the. Key ionized gas is transparent to. 324 00:15:40.120 --> 00:15:41.399 Light, oh, so. 325 00:15:41.440 --> 00:15:45.200 These early stars and galaxies were essentially carving out these 326 00:15:45.279 --> 00:15:48.799 expanding bubbles of transparency within the dark. 327 00:15:48.559 --> 00:15:50.759 Fog like blowing bubbles in dark, water. 328 00:15:50.720 --> 00:15:55.639 Exactly until eventually those bubbles expanded so much that they, 329 00:15:55.679 --> 00:15:59.039 overlapped the fog was entirely burned, away and the universe 330 00:15:59.080 --> 00:16:00.440 became transparent on a. 331 00:16:00.720 --> 00:16:02.759 Macroscopic, scale and let there be. 332 00:16:02.840 --> 00:16:05.960 Light let there be. Light but studying how this, happened 333 00:16:06.320 --> 00:16:09.879 the exact timeline and mechanics of it is a massive 334 00:16:09.919 --> 00:16:11.679 observational challenge because. 335 00:16:11.399 --> 00:16:14.559 You're trying to see through a, fog to watch the fog. 336 00:16:14.320 --> 00:16:17.600 Clear, precisely you are trying to study a process that 337 00:16:17.720 --> 00:16:20.320 is obscured by the very fog it is trying to. 338 00:16:20.360 --> 00:16:22.759 Clear it's incredibly, difficult. 339 00:16:22.320 --> 00:16:25.039 Which is Where Daming yang's brilliant methodology really comes into, 340 00:16:25.039 --> 00:16:30.159 play because he describes using these ancient redshift seven quasars as. 341 00:16:30.399 --> 00:16:33.039 Lighthouses that's a great term for. It, Yeah because a 342 00:16:33.080 --> 00:16:36.080 quasar is so blindingly, bright its light acts like a 343 00:16:36.159 --> 00:16:39.080 high power beam cutting straight through whatever neutral fog is 344 00:16:39.080 --> 00:16:40.200 still left in its path toward. 345 00:16:40.279 --> 00:16:43.559 Us, Right, so astronomers look at the spectrum of the 346 00:16:43.639 --> 00:16:46.919 quasar's light when it finally arrives here On. Earth if 347 00:16:46.919 --> 00:16:49.320 the light passed through a patch of neutral hydrogen on 348 00:16:49.360 --> 00:16:53.639 its long, journey that hydrogen will absorb very specific wavelengths 349 00:16:53.639 --> 00:16:55.840 of the, light leaving dark gaps. 350 00:16:55.559 --> 00:16:58.200 In the, spectrum kind of like a. Barcode exactly like a. 351 00:16:58.200 --> 00:17:01.639 Barcode the most notable gap is called the Gun peterson 352 00:17:01.720 --> 00:17:04.880 prof and by reading those, gaps by reading that, barcode 353 00:17:04.920 --> 00:17:07.720 we can tell exactly where the neutral fog, was how 354 00:17:07.799 --> 00:17:10.720 thick it, was and at what specific point in time it. 355 00:17:10.799 --> 00:17:13.720 Existed, okay that is, Genius BUT i do have to 356 00:17:13.720 --> 00:17:16.039 push back a little bit on the lighthouse analogy, here 357 00:17:16.440 --> 00:17:18.519 or at least the utility of. It oh how, So, 358 00:17:18.759 --> 00:17:21.240 well if you are standing on a rocky coast in 359 00:17:21.240 --> 00:17:25.079 a really thick, fog a lighthouse beam only illuminates the 360 00:17:25.160 --> 00:17:28.359 narrow column of aera directly cuts through, right just a straight. 361 00:17:28.400 --> 00:17:31.039 Line you can see the water droplets in that specific. Beam, 362 00:17:31.119 --> 00:17:34.440 sure but you are still completely blind to the vast 363 00:17:34.519 --> 00:17:38.279 dark ocean surrounding. It so if aquasar only gives us 364 00:17:38.319 --> 00:17:43.039 a single pencil thin core sample through the intergalactic, medium 365 00:17:43.920 --> 00:17:46.440 how can one beam of light possibly tell us about 366 00:17:46.480 --> 00:17:49.599 the large scale topology of the entire early? Universe are 367 00:17:49.640 --> 00:17:51.880 the models just assuming the rest of the universe looks 368 00:17:51.920 --> 00:17:53.799 exactly like that one random core. 369 00:17:53.880 --> 00:17:56.759 Sample, No and that is a fantastic, point because that 370 00:17:56.920 --> 00:18:01.000 exact limitation is what plagued all the early real ionization. Studies, 371 00:18:01.039 --> 00:18:04.079 really so it was a, problem a massive. PROBLEM a 372 00:18:04.119 --> 00:18:07.920 single sightline is subject to huge cosmic. Variants if your 373 00:18:07.920 --> 00:18:10.599 one quasar happens to be sitting in an unusually dense 374 00:18:10.640 --> 00:18:12.759 patch of neutral, gas or maybe in an area that 375 00:18:12.799 --> 00:18:15.000 cleared out unusually early compared to everywhere. 376 00:18:15.000 --> 00:18:17.759 Else then your entire model of the universe becomes totally 377 00:18:17.839 --> 00:18:19.039 skewed by that one single. 378 00:18:19.039 --> 00:18:23.119 Anomaly, Exactly you cannot extrapolate global cosmology from a single 379 00:18:23.119 --> 00:18:24.720 skewer through the intergalactic. 380 00:18:24.799 --> 00:18:27.160 Medium, okay so how does finding thirty one of them 381 00:18:27.240 --> 00:18:29.160 solve the? Problem does it just give us more? 382 00:18:29.200 --> 00:18:33.680 Skewers it gives us a statistical. Distribution moving from just 383 00:18:33.839 --> 00:18:37.400 one or two known quasars at this extreme red shift 384 00:18:37.400 --> 00:18:41.279 to thirty one is literally the difference between a single 385 00:18:41.359 --> 00:18:45.200 flashlight beam in a dark forest and a widespread network 386 00:18:45.200 --> 00:18:48.079 of searchlights all pointing at you from different. Directions. 387 00:18:48.319 --> 00:18:50.359 Ah, okay so they cross over each. Other. 388 00:18:50.519 --> 00:18:54.799 Right with thirty one distinct sightlines distributed across completely different 389 00:18:54.799 --> 00:18:58.200 regions of the, sky astronomers can actually begin THREE d 390 00:18:58.359 --> 00:18:59.880 tomography of the early. 391 00:18:59.720 --> 00:19:01.759 Universe tomography like A ct. 392 00:19:01.880 --> 00:19:05.119 Scan exactly like A ct, scan we can start to 393 00:19:05.200 --> 00:19:07.880 map where the ionized bubbles, are how large they have 394 00:19:07.920 --> 00:19:10.720 grown in different, sectors and we can trace the timeline 395 00:19:10.759 --> 00:19:13.759 of when they finally percolate and merge. Together we move 396 00:19:13.799 --> 00:19:17.079 from an anecdotal observation to a comprehensive THREE d map 397 00:19:17.119 --> 00:19:17.759 of the cosmic. 398 00:19:17.799 --> 00:19:20.920 Fog, wow we are essentially charting the topography of the 399 00:19:21.000 --> 00:19:24.359 dawn of. Light that's just an incredible achievement for, humanity really. 400 00:19:24.440 --> 00:19:27.400 Is and here's the massive twist in the narrative for. 401 00:19:27.480 --> 00:19:31.480