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 --> 00:00:23.839 slumber under the night sky. 7 00:00:26.879 --> 00:00:29.719 Okay, let's unpack this because I want you to imagine 8 00:00:29.879 --> 00:00:33.840 trying to force a physical wave of gas and dust 9 00:00:33.880 --> 00:00:38.399 through the interstellar medium at like on two and twenty 10 00:00:38.520 --> 00:00:39.600 kilometers per second. 11 00:00:39.759 --> 00:00:42.320 Yeah, that is I mean, that's not just fast. That's 12 00:00:42.320 --> 00:00:44.399 a speed that physically breaks things. 13 00:00:44.479 --> 00:00:47.439 Right. We're not talking about a beam of light or 14 00:00:47.479 --> 00:00:51.840 a subatomic particle here. We're talking about a macroscopic shockwave 15 00:00:51.920 --> 00:00:55.600 made of baryonic matter, just regular gas and dust exactly. 16 00:00:56.079 --> 00:00:59.320 And if you actually sit down and calculate the thermodynamics 17 00:00:59.359 --> 00:01:02.039 of pushing the ceial through the vacuum of space, well 18 00:01:02.079 --> 00:01:05.480 in the near vacuum, at that velocity, the physics just 19 00:01:05.519 --> 00:01:06.680 completely falls apart. 20 00:01:06.519 --> 00:01:08.879 Because it's not empty space. Yeah right, there's friction. 21 00:01:09.200 --> 00:01:12.840 Right, there is. The kinetic energy involved would cause the 22 00:01:12.879 --> 00:01:15.680 gas to heat up to the point of turning into 23 00:01:16.040 --> 00:01:20.439 basically a superheated plasma. It would radiate immense amounts of X. 24 00:01:20.519 --> 00:01:22.480 Rays, so it would just cook itself completely. 25 00:01:22.480 --> 00:01:25.640 It would unbind the structural integrity of whatever medium it 26 00:01:25.719 --> 00:01:28.400 was traveling through. You wouldn't get a neat ordered structure 27 00:01:28.439 --> 00:01:28.959 at the end of it. 28 00:01:29.000 --> 00:01:31.000 You just violently disperse into nothing. 29 00:01:31.159 --> 00:01:34.159 Yeah, the thermal dissipation alone would tear the structure apart 30 00:01:34.319 --> 00:01:37.319 long before it ever had a chance to stabilize. At 31 00:01:37.319 --> 00:01:39.920 twelve hundred and twenty kilometers per second, you are looking 32 00:01:40.000 --> 00:01:43.920 at ram pressure forces that would strip a galaxy completely bare. 33 00:01:44.120 --> 00:01:47.359 Wow. Okay, so it's a velocity that directly violates the 34 00:01:47.359 --> 00:01:51.120 fluid dynamics we observe in space. But and here is 35 00:01:51.159 --> 00:01:55.840 the crazy part, that is exactly the mathematical corner astrophysicists 36 00:01:55.879 --> 00:01:57.439 found themselves backed into recently. 37 00:01:57.599 --> 00:02:00.799 Yes they did. We observed the structure in the cosmos that, 38 00:02:01.040 --> 00:02:04.840 according to our classical models of gravity and collisions, demanded 39 00:02:04.840 --> 00:02:07.239 that impossible speed limit to exist. 40 00:02:07.000 --> 00:02:09.759 Which brings us to the anomaly itself, the object that 41 00:02:09.840 --> 00:02:13.879 is forcing this entire revaluation of the universe. It's led 42 00:02:14.159 --> 00:02:17.360 one three, one three, four, two four but astronomers affectionately 43 00:02:17.360 --> 00:02:19.120 called it the bull's eye galaxy. 44 00:02:18.719 --> 00:02:20.719 And it is a very fitting name. When Mioon Pasha 45 00:02:20.759 --> 00:02:23.479 and his team at Yale University published their observations back 46 00:02:23.520 --> 00:02:25.479 in twenty twenty five, they didn't just find, you know, 47 00:02:25.639 --> 00:02:26.919 slightly weird galaxy. 48 00:02:27.080 --> 00:02:29.400 No, they found something that completely breaks the rules. 49 00:02:29.719 --> 00:02:32.960 Right. They found a structure that basically shouldn't exist under 50 00:02:33.000 --> 00:02:37.120 the classical paradigm of astrophysics. We are talking about a 51 00:02:37.120 --> 00:02:43.199 galaxy characterized by nine distinct, perfectly concentric rings of glowing 52 00:02:43.240 --> 00:02:46.400 material radiating outward from its center. 53 00:02:46.639 --> 00:02:49.879 Nine rings like a perfectly formed nine layer wedding cake 54 00:02:50.479 --> 00:02:54.159 just floating in the middle of a messy, chaotic kitchen. 55 00:02:54.800 --> 00:02:58.120 It just begs the question who or what baked this exactly. 56 00:02:58.280 --> 00:03:00.960 It is an extraordinary morphological profile. I mean, when we 57 00:03:01.039 --> 00:03:04.960 look at typical galactic structures, we expect spiral arms like 58 00:03:05.000 --> 00:03:06.199 our own Milky Way. 59 00:03:06.000 --> 00:03:07.960 Where things are sort of swirling and. 60 00:03:07.960 --> 00:03:11.199 Messing right, where density waves propagate through the disc creating 61 00:03:11.199 --> 00:03:15.000 these trailing arms of star formation. Or we see elliptical galaxies, 62 00:03:15.159 --> 00:03:18.360 which are essentially featureless, randomized swarms of stars. 63 00:03:18.479 --> 00:03:20.039 It's a big fuzzy blob. 64 00:03:19.840 --> 00:03:24.080 Yeah, exactly. But a concentric ring structure implies a highly localized, 65 00:03:24.159 --> 00:03:27.560 highly symmetric mechanism. Finding one ring is rare, but you 66 00:03:27.599 --> 00:03:31.680 know it's mechanically explainable. But nine, Finding nine stacked with 67 00:03:31.759 --> 00:03:35.599 that level of geometric precision, that challenges the foundational models 68 00:03:35.599 --> 00:03:36.680 of how galaxies evolve. 69 00:03:36.919 --> 00:03:39.479 So the mission for today's really pull apart the physics 70 00:03:39.520 --> 00:03:41.919 of this Bull's eye galaxy because to explain how those 71 00:03:42.000 --> 00:03:45.560 nine rings got there, we basically have to entirely discard 72 00:03:45.599 --> 00:03:47.240 the classical model of galaxies. 73 00:03:47.280 --> 00:03:49.159 We do. We have to throw out the idea of 74 00:03:49.159 --> 00:03:54.000 galaxies as giant pools of gas just responding to physical collision. 75 00:03:53.680 --> 00:03:55.879 And we have to cross over into a framework where 76 00:03:56.000 --> 00:03:58.919 quantum mechanics, which are you know, the rules governing tiny 77 00:03:59.039 --> 00:04:03.400 subatomic particles, are actively dictating the macro structure of a 78 00:04:03.439 --> 00:04:07.280 galaxy that's hundreds of thousands of light years across, which. 79 00:04:07.080 --> 00:04:10.080 Is mind boggling. We are looking at a potential bridge 80 00:04:10.159 --> 00:04:14.599 between the microscopic quantum realm and macroscopic cosmological structures. 81 00:04:14.759 --> 00:04:17.839 So the Bullseye galaxy isn't just a weird space picture. 82 00:04:17.759 --> 00:04:20.639 No, not at all. If the prevailing theory holds this 83 00:04:20.759 --> 00:04:25.279 galaxy is a galactic scale quantum laboratory. It provides observational 84 00:04:25.279 --> 00:04:28.160 evidence for stuff we previously thought we could only isolate 85 00:04:28.199 --> 00:04:30.959 in like super cooled lab environments on Earth. 86 00:04:31.040 --> 00:04:34.079 Okay, to really grasp why finding nine rings in twenty 87 00:04:34.160 --> 00:04:37.360 twenty five caused such a crisis, we need to look 88 00:04:37.399 --> 00:04:41.519 at how astronomer's historically explained ringed galaxies, like what was 89 00:04:41.519 --> 00:04:42.360 the baseline. 90 00:04:42.439 --> 00:04:45.399 Well, the baseline was established way back in nineteen forty one. 91 00:04:45.800 --> 00:04:50.199 That was the discovery of the Cartwheel galaxy by Fritzwicki Zwiki. 92 00:04:49.839 --> 00:04:52.240 Was kind of a legend for finding weird stuff in space. 93 00:04:52.519 --> 00:04:56.160 Oh absolutely, he was a pioneer in identifying structural anomalies. 94 00:04:56.680 --> 00:04:59.879 When he observed the Cartwheel galaxy, it presented as this 95 00:05:00.199 --> 00:05:04.480 dense central hub surrounded by a massive luminous ring of 96 00:05:04.600 --> 00:05:06.199 young blue stars, and. 97 00:05:06.120 --> 00:05:08.639 It had these faint spokes connecting them. Right. 98 00:05:08.959 --> 00:05:11.439 It was a radical departure from the normal sequence of 99 00:05:11.519 --> 00:05:15.480 spiral and elliptical galaxies, and for decades the cartwheel served 100 00:05:15.519 --> 00:05:19.439 as the absolute archetype for what we call collisional ring galaxies. 101 00:05:19.600 --> 00:05:21.439 And the model they came up with to explain the 102 00:05:21.480 --> 00:05:24.199 cartwheel made total sense at the time. It's the drop 103 00:05:24.279 --> 00:05:25.240 through collision theory. 104 00:05:25.399 --> 00:05:25.600 Yes. 105 00:05:26.360 --> 00:05:30.000 The idea is that a smaller, really compact companion galaxy 106 00:05:30.040 --> 00:05:33.199 plunges directly through the center of a larger disc galaxy, 107 00:05:33.519 --> 00:05:34.800 like a bullet going through an apple. 108 00:05:34.839 --> 00:05:38.079 So it's a gravitational perturbation model. The smaller mass punches 109 00:05:38.120 --> 00:05:41.800 through creates a sudden localized spike in gravity at the center. 110 00:05:41.800 --> 00:05:45.360 Exactly, and as the smaller galaxy exits the other side, 111 00:05:45.519 --> 00:05:50.240 that gravitational spike vanishes. This sudden shift triggers a massive 112 00:05:50.360 --> 00:05:51.360 density wave. 113 00:05:51.480 --> 00:05:54.680 So the material in the disc gets pulled inward first, 114 00:05:55.079 --> 00:05:58.399 and then it kind of rebounds outward as this concentrated ring. 115 00:05:58.639 --> 00:06:01.120 That's a perfect way to describe it. As that density 116 00:06:01.160 --> 00:06:04.959 wave travels outward through the interstellar medium, it compresses the 117 00:06:05.000 --> 00:06:06.720 surrounding gas and dust. 118 00:06:06.600 --> 00:06:09.360 And when you compress gas in space, you get stores right. 119 00:06:09.839 --> 00:06:12.319 It pushes the gas beyond what we call the genes 120 00:06:12.399 --> 00:06:16.279 mass limit, which triggers a localized wave of star formation. 121 00:06:16.720 --> 00:06:18.920 So you end up with this glowing ring of new 122 00:06:19.040 --> 00:06:20.560 stars expanding outward. 123 00:06:20.720 --> 00:06:23.759 It's basically the leading edge of a gravitational ripple, like 124 00:06:23.839 --> 00:06:25.040 dropping a rock in a pond. 125 00:06:25.120 --> 00:06:27.920 Yes, a very very big rock and the math for 126 00:06:27.959 --> 00:06:31.399 the drop through collision works beautifully. For the cartwheel galaxy. 127 00:06:31.079 --> 00:06:32.319 The numbers actually line up. 128 00:06:32.399 --> 00:06:35.560 They do. The velocities of the expanding gas correlate perfectly 129 00:06:35.560 --> 00:06:38.120 with the mass of the intruder galaxy and the timeframe 130 00:06:38.120 --> 00:06:38.800 of the collision. 131 00:06:38.959 --> 00:06:41.240 And over the eighty years followings wiki, we found other 132 00:06:41.360 --> 00:06:44.720 examples right like Hog's object. 133 00:06:44.720 --> 00:06:48.879 We did. Hogog's object exhibits a similar ring morphology. We'd 134 00:06:48.879 --> 00:06:51.519 occasionally find galaxies with two, maybe even three. 135 00:06:51.360 --> 00:06:54.360 Rings, which you can explain by like a secondary ribble. 136 00:06:54.519 --> 00:06:57.639 Right, it can be modeled by a complex oscillating drop 137 00:06:57.680 --> 00:07:00.600 through event a secondary density wave reflection. 138 00:07:00.759 --> 00:07:03.879 But the underlying mechanism for all of them remained collisional. 139 00:07:04.160 --> 00:07:08.160 It was kinetic brute force physics. A smaller object hits 140 00:07:08.160 --> 00:07:10.240 a bigger object, ripples move outward. 141 00:07:10.720 --> 00:07:13.240 That was the consensus from nineteen forty one all the 142 00:07:13.240 --> 00:07:16.959 way until twenty twenty five. It held because the observations 143 00:07:17.040 --> 00:07:20.199 hit the parameters, the waves had enough energy to propagate 144 00:07:20.240 --> 00:07:22.480 one or two rings before friction dampened them. 145 00:07:22.560 --> 00:07:25.680 Okay, so then a mod poscious team points their instruments 146 00:07:25.680 --> 00:07:28.959 at leadie one three one three, four two four, and 147 00:07:29.000 --> 00:07:30.839 they don't see one or two rings, they see. 148 00:07:30.720 --> 00:07:32.759 Nine, nine concentric structures. 149 00:07:32.839 --> 00:07:34.959 I want to pause here. How do they even verify that? 150 00:07:35.480 --> 00:07:37.720 Because a nine ring structure at that distance could so 151 00:07:37.759 --> 00:07:40.279 easily just be a smudge on the lens or an 152 00:07:40.319 --> 00:07:42.480 optical illusion from gravitational lensing. 153 00:07:42.600 --> 00:07:44.800 That's a great point. The Yale team didn't just look 154 00:07:44.839 --> 00:07:49.120 at a photograph. They utilized deep spectroscopic imaging to confirm 155 00:07:49.120 --> 00:07:49.759 the morphology. 156 00:07:49.839 --> 00:07:51.920 So they analyze the actual movement. 157 00:07:51.600 --> 00:07:55.079 Of the gas exactly. By measuring the red shift and 158 00:07:55.079 --> 00:07:57.959 blue shift of the molecular gas, they could track the 159 00:07:58.079 --> 00:08:01.759 rotational velocity and the race expansion of the material in 160 00:08:01.800 --> 00:08:02.399 those rings. 161 00:08:02.680 --> 00:08:05.040 Wow, so they proved it wasn't just a trick of a. 162 00:08:05.000 --> 00:08:09.120 Life, right. The data confirmed these were distinct, physically coherent 163 00:08:09.279 --> 00:08:12.839 rings embedded right within the galaxy's disc, sharing the exact 164 00:08:12.839 --> 00:08:14.800 same rotational kinematic. 165 00:08:14.360 --> 00:08:17.240 Okay, so the rings are real, and the immediate scientific 166 00:08:17.279 --> 00:08:21.199 reflex is to use the old tools. The assumption was, well, 167 00:08:21.199 --> 00:08:23.519 we have rings, therefore we must have had a collision. 168 00:08:23.600 --> 00:08:26.680 They applied the drop through model. But to generate nine 169 00:08:26.720 --> 00:08:30.759 distinct rings you need a highly specific set of initial conditions. 170 00:08:30.800 --> 00:08:34.840 You'd need a massive intruder galaxy, a perfectly perpendicular hit, 171 00:08:35.360 --> 00:08:38.120 and a very tight timeline for the waves to ripple out. 172 00:08:38.240 --> 00:08:42.720 The initial hypothesis suggested this colossal impact event happened approximately 173 00:08:42.759 --> 00:08:45.799 fifty six million years ago. The logic was that a 174 00:08:45.840 --> 00:08:49.559 single energetic collision triggered a whole series of reverberating waves. 175 00:08:49.759 --> 00:08:52.399 But that is where Pierre Sickiv and Yuxinzau at the 176 00:08:52.480 --> 00:08:55.279 University of Florida enter the picture, because they look at 177 00:08:55.279 --> 00:08:58.039 that fifty six million year timeline and they run. 178 00:08:57.840 --> 00:09:00.639 The mass and the model instantly falls apart. 179 00:09:01.080 --> 00:09:02.519 Yeah, tell us why. 180 00:09:02.919 --> 00:09:07.200 What's fascinating here is that Sikidian Zou calculated the necessary 181 00:09:07.240 --> 00:09:10.840 phase velocity of the outermost ring. If a single event 182 00:09:11.120 --> 00:09:14.639 fifty six million years ago created all nine rings, then 183 00:09:14.639 --> 00:09:17.320 that outermost ring must have traveled from the center to 184 00:09:17.399 --> 00:09:19.639 its current position in exactly. 185 00:09:19.159 --> 00:09:21.720 That timeframe, which brings us right back to that speed 186 00:09:21.720 --> 00:09:24.639 limit problem we open with. For that distance to be 187 00:09:24.679 --> 00:09:27.440 covered in that time, the math demands a speed of 188 00:09:27.480 --> 00:09:29.600 twelve hundred and twenty kilometers per second. 189 00:09:29.840 --> 00:09:33.519 And let's revisit why that fluid dynamics problem is fatal. 190 00:09:34.159 --> 00:09:39.360 The interstellar medium is a fluid. It has density, temperature pressure, So. 191 00:09:39.320 --> 00:09:41.480 A wave moving through it is essentially a. 192 00:09:41.440 --> 00:09:44.120 Sound wave exactly, And the speed at which a wave 193 00:09:44.120 --> 00:09:46.480 can travel is strictly limited by the sound speed of 194 00:09:46.519 --> 00:09:47.240 that medium. 195 00:09:47.399 --> 00:09:49.440 And in a typical galaxy, what is the speed limit. 196 00:09:49.519 --> 00:09:52.120 The sound speed of interstellar gas is maybe ten to 197 00:09:52.159 --> 00:09:55.320 thirty kilometers per second, even in highly energized regions. You 198 00:09:55.399 --> 00:09:58.120 might push it slightly higher, but you are nowhere near 199 00:09:58.159 --> 00:09:59.639 one thousand kilometers per second. 200 00:10:00.159 --> 00:10:02.080 So, going back to our rock and a pond analogy, 201 00:10:02.559 --> 00:10:05.159 you drop a boulder in a lake, you expect ripples 202 00:10:05.159 --> 00:10:07.840 to move at all leisurely pace. But if you drop 203 00:10:07.840 --> 00:10:10.360 a rock and the ripples shoot out at the speed 204 00:10:10.399 --> 00:10:11.240 of a fighter. 205 00:10:11.000 --> 00:10:13.600 Jet, you wouldn't think, Wow, that water is fast. You'd 206 00:10:13.600 --> 00:10:15.440 think is this pond actually made of water? 207 00:10:15.639 --> 00:10:20.159 Yes, you'd question the medium itself, because if you force 208 00:10:20.200 --> 00:10:24.000 a wave at that supersonic speed, you flash heat the gas. 209 00:10:23.799 --> 00:10:26.600 You do it turns into X ray emitting plasma. It 210 00:10:26.600 --> 00:10:29.679 would literally boil the interstellar medium right out of the 211 00:10:29.720 --> 00:10:33.279 galactic disc. You'd be left with a sterile, dead galaxy. 212 00:10:33.679 --> 00:10:37.320 Definitely not a beautifully structured series of glowing star rings. 213 00:10:37.879 --> 00:10:39.879 The medium just cannot support it. 214 00:10:40.120 --> 00:10:44.600 Sikhivi and Zoo prove definitively that a classical collision cannot 215 00:10:44.600 --> 00:10:49.279 physically produce those nine rings without violating thermodynamics. The wave 216 00:10:49.279 --> 00:10:51.600 would die out long before reaching the outer edges. 217 00:10:51.919 --> 00:10:55.480 So when the math so directly contradicts the observation, you 218 00:10:55.559 --> 00:10:58.799 have to question everything. If a physical shock wave moving 219 00:10:58.840 --> 00:11:02.320 through gas can't create these rings, then they aren't ripples from. 220 00:11:02.159 --> 00:11:04.720 A crash, right, there are kinetic ripples at all. 221 00:11:04.879 --> 00:11:07.600 So the structure of the galaxy must be dictated by 222 00:11:07.600 --> 00:11:10.799 something else, entirely, a different underlying force. 223 00:11:10.919 --> 00:11:13.879 And this requires a massive pivot. We have to stop 224 00:11:13.919 --> 00:11:17.279 looking at the baryonic matter, the visible stars and gas, 225 00:11:17.679 --> 00:11:20.960 and start analyzing the non buryonic mass. 226 00:11:20.799 --> 00:11:24.080 The stuff that actually dominates the gravitational environment. We have 227 00:11:24.159 --> 00:11:25.399 to talk about dark matter. 228 00:11:25.559 --> 00:11:27.559 Yes, the invisible elephant in the room. 229 00:11:27.759 --> 00:11:29.879 Now. I want to frame this carefully for you listening. 230 00:11:30.360 --> 00:11:33.240 Dark matter sometimes gets a bad rap, like it's just 231 00:11:33.279 --> 00:11:36.000 a catch all plug for whenever our gravity math doesn't work. 232 00:11:36.559 --> 00:11:39.279 But it's actually a rigorously tested concept. 233 00:11:39.440 --> 00:11:42.840 It is. The empirical foundation goes back to VERA. Rubin's 234 00:11:42.879 --> 00:11:47.240 work in the nineteen seventies. She observed galaxy rotation curves. 235 00:11:47.080 --> 00:11:49.759 Right, and based on standard Newton physics, we thought the 236 00:11:49.799 --> 00:11:52.440 stars at the edge of a galaxy should orbit slower 237 00:11:52.440 --> 00:11:53.279 than the ones near. 238 00:11:53.159 --> 00:11:55.480 The center, because the further away a planet is from 239 00:11:55.519 --> 00:11:59.000 the Sun, the slower it orbits. We assumed galaxies work 240 00:11:59.080 --> 00:12:01.279 the same way, since most of the visible mass is 241 00:12:01.320 --> 00:12:02.279 packed into the center. 242 00:12:02.360 --> 00:12:04.360 But Ruben found something totally different. 243 00:12:04.759 --> 00:12:07.759 Her data show that the rotation curves were flat. Stars 244 00:12:07.759 --> 00:12:10.360 at the very edge were orbiting at the exact same 245 00:12:10.440 --> 00:12:12.360 velocity as stars much closer to the. 246 00:12:12.320 --> 00:12:15.840 Center, which means there just isn't enough visible stuff to 247 00:12:15.960 --> 00:12:19.360 generate the gravity needed to hold onto those fast moving stars. 248 00:12:19.639 --> 00:12:24.320 Exactly without an unseen source of mass, those galaxies should 249 00:12:24.360 --> 00:12:28.440 have literally flung themselves apart through centrifugal force eons ago. 250 00:12:28.600 --> 00:12:31.399 Now, just to play Devil's advocate here, why do we 251 00:12:31.480 --> 00:12:36.080 jump straight to invisible particles? What about MAM and D 252 00:12:36.519 --> 00:12:40.159 modified Newtonian dynamics. Doesn't that say we just need to 253 00:12:40.200 --> 00:12:42.799 tweak how gravity works at the edges of galaxies. 254 00:12:43.480 --> 00:12:47.159 MMND is a really fascinating theory, and it does successfully 255 00:12:47.159 --> 00:12:51.000 model the flat rotation curves of some individual galaxies. 256 00:12:50.480 --> 00:12:51.559 But it has limits, right. 257 00:12:51.440 --> 00:12:55.440 Significant limits MND applies a universal modification to gravity. It 258 00:12:55.480 --> 00:12:58.960 smooths out the gravitational potential. It struggles to explain highly 259 00:12:59.000 --> 00:13:01.759 localized comp substructions. 260 00:13:01.159 --> 00:13:03.000 Or things like the Bullet cluster where the gravity is 261 00:13:03.000 --> 00:13:04.559 separated from the visible matter. 262 00:13:04.440 --> 00:13:08.200 Precisely because MO and D basically just says gravity is 263 00:13:08.240 --> 00:13:10.840 stronger out here, it does not provide a mechanism to 264 00:13:10.879 --> 00:13:14.279 create highly specific, concentric geometrical rings. 265 00:13:14.559 --> 00:13:17.120 You can't get sharp ridges of gravity just by tweaking 266 00:13:17.120 --> 00:13:20.919 a formula. You need actual localized mass. 267 00:13:20.600 --> 00:13:23.879 Right, You need a physical substance that can clump, structure 268 00:13:23.919 --> 00:13:28.559 itself and exert localized gravitational wells. MO and D can't 269 00:13:28.600 --> 00:13:32.759 herd visible gas into nine distinct rings. We need particulate 270 00:13:32.879 --> 00:13:33.440 dark matter. 271 00:13:33.559 --> 00:13:37.159 Okay, so we're operating under the standard model here. Ordinary 272 00:13:37.240 --> 00:13:40.960 matter everything we can see makes up maybe fifteen percent 273 00:13:41.000 --> 00:13:42.440 of the universe's mass. 274 00:13:42.120 --> 00:13:45.799 And the remaining eighty five percent is non baryonic dark matter. 275 00:13:45.960 --> 00:13:48.960 And it's not just floating around randomly. It organizes into 276 00:13:49.000 --> 00:13:50.679 these massive spherical halos. 277 00:13:51.000 --> 00:13:54.399 Yes, the dark matter halo is the primary architectural component 278 00:13:54.440 --> 00:13:57.639 of any galaxy. The visible glowing disc of stars we 279 00:13:57.720 --> 00:14:01.080 see is really just a tiny secondary structure sitting inside 280 00:14:01.120 --> 00:14:02.600 a massive invisible sphere. 281 00:14:02.759 --> 00:14:05.639 Kind of an existential thought. We are the weird rare 282 00:14:05.679 --> 00:14:08.840 stuff in the universe. The dark matter dictates the rules. 283 00:14:08.759 --> 00:14:11.600 It holds the whole system together. But as you were 284 00:14:11.639 --> 00:14:15.159 hinting at earlier, a generic smooth sphere of dark matter 285 00:14:15.320 --> 00:14:18.039 still doesn't explain our nine rings. 286 00:14:17.919 --> 00:14:21.360 Because a featureless blob just provides a uniform pull. It 287 00:14:21.360 --> 00:14:23.679 wouldn't make stept geometric rings. 288 00:14:23.440 --> 00:14:27.039 Exactly, which is why sakiw and Zou didn't just invoke 289 00:14:27.159 --> 00:14:30.960 generic dark matter. They relied on a very specific theoretical 290 00:14:31.039 --> 00:14:33.200 flavor of dark matter, the axion. 291 00:14:33.480 --> 00:14:36.879 Okay, let's really dig into the axion, because it's amazing 292 00:14:36.919 --> 00:14:38.840 to me that it wasn't even invented to solve the 293 00:14:38.919 --> 00:14:40.480 dark matter problem in the first place. 294 00:14:40.679 --> 00:14:43.840 No, it was theorized to solve a completely different crisis 295 00:14:43.879 --> 00:14:46.840 in quantum physics called the strong CP problem. 296 00:14:47.080 --> 00:14:49.360 Right, So what is the strong CP problem? 297 00:14:49.440 --> 00:14:53.080 Well, it's a discrepancy regarding the strong nuclear force. The 298 00:14:53.120 --> 00:14:56.679 math of quantum chromodynamics suggests that the strong force should 299 00:14:56.720 --> 00:14:59.240 violate a principle called charge parity symmetry. 300 00:14:59.320 --> 00:15:02.240 So basically, the interaction should look different if you swap 301 00:15:02.279 --> 00:15:05.559 particles for anti particles and reflect them in a mirror. 302 00:15:05.679 --> 00:15:08.080 That's a good way to visualize it. But the problem 303 00:15:08.240 --> 00:15:12.440 is in every single lab experiment ever done, the strong 304 00:15:12.519 --> 00:15:16.759 force preserves that symmetry perfectly. The math says it should break, 305 00:15:17.039 --> 00:15:18.559 but reality says it doesn't. 306 00:15:18.639 --> 00:15:20.720 So physicists had to fix the math right. 307 00:15:21.120 --> 00:15:24.200 In nineteen seventy seven, ROBERTA. Picchet and Helen Quinn introduced 308 00:15:24.200 --> 00:15:27.240 a new symmetry to the equations to fix it, and 309 00:15:27.279 --> 00:15:31.000 shortly after Steven Weinberg and Frank Wilcheck realized that this 310 00:15:31.080 --> 00:15:35.559 new math would create a brand new, incredibly light, electrically neutral. 311 00:15:35.200 --> 00:15:37.600 Particle, and Willcheck named it the axion. 312 00:15:37.919 --> 00:15:41.320 Yes, and while it was invented to fix the nuclear force, 313 00:15:41.639 --> 00:15:44.840 cosmologists quickly realized that if axions are real, the Big 314 00:15:44.840 --> 00:15:47.279 Bang would have produced unfathomable amounts of them. 315 00:15:47.440 --> 00:15:50.799 They're light, they barely interact with normal matter. They're stable. 316 00:15:51.120 --> 00:15:53.039 They are the perfect candidate for dark matter. 317 00:15:53.159 --> 00:15:56.519 But what makes axions fundamentally different from older dark matter 318 00:15:56.639 --> 00:16:01.480 candidates like WIMPs is their quantum classification. Axions are bosons. 319 00:16:01.600 --> 00:16:04.240 Okay, this is the heavy science, but it's the critical juncture. 320 00:16:04.480 --> 00:16:06.919 The difference between a fermion and a boson is the 321 00:16:06.960 --> 00:16:08.919 whole key to the Bullseye galaxy. 322 00:16:09.200 --> 00:16:12.519 It is all particles in the universe fall into these 323 00:16:12.559 --> 00:16:16.720 two categories based on their quantum spin. Fermions, like protons 324 00:16:16.840 --> 00:16:21.279 neutrons electrons have half integer spin. They obey the poly 325 00:16:21.440 --> 00:16:23.000 exclusion principle. 326 00:16:22.840 --> 00:16:25.799 Which means no two fermions can occupy the exact same 327 00:16:25.879 --> 00:16:27.120 quantum state at the same time. 328 00:16:27.480 --> 00:16:31.480 Right. It is literally why matter has volume. Electrons in 329 00:16:31.519 --> 00:16:34.480 an atom stack up in different shells. They refuse to 330 00:16:34.559 --> 00:16:39.320 cram into the lowest energy level together. Fermions hate sharing space. 331 00:16:39.440 --> 00:16:40.960 You are rugged individualists. 332 00:16:41.120 --> 00:16:45.039 Precisely. Bosons, on the other hand, have integer spin. Photons 333 00:16:45.039 --> 00:16:48.759 are bosons, and crucially, axions are bosons. Bosons do not 334 00:16:48.879 --> 00:16:50.759 obey the exclusion principle. 335 00:16:50.440 --> 00:16:53.240 So they are perfectly fine occupying the exact same space 336 00:16:53.279 --> 00:16:54.440 at the exact same time. 337 00:16:54.600 --> 00:16:58.240 Yes, now, under normal hot conditions, this doesn't change much. 338 00:16:58.559 --> 00:17:01.720 A warm gas of bosons bounces around like a normal gas, 339 00:17:02.039 --> 00:17:05.200 but a dark matter halo is incredibly cold. 340 00:17:04.799 --> 00:17:08.279 Because as the universe expanded after the Big Bang, everything 341 00:17:08.319 --> 00:17:10.519 cooled down. The temperature plummeted. 342 00:17:10.240 --> 00:17:12.200 And when you cool a gas of bosons to near 343 00:17:12.240 --> 00:17:16.079 absolute zero, their quantum behavior shifts dramatically. It comes down 344 00:17:16.119 --> 00:17:17.799 to their thermal to Brolly wavelength. 345 00:17:18.000 --> 00:17:22.480 Okay, let's unpack that. In quantum mechanics, particles aren't just 346 00:17:22.799 --> 00:17:25.920 solid little dots, right. They act like waves. 347 00:17:26.160 --> 00:17:29.519 Yes, And the wavelength of a particle is inversely proportional 348 00:17:29.559 --> 00:17:33.000 to its momentum. So as the axion gas cools down, 349 00:17:33.319 --> 00:17:36.000 the speed of the individual axions drops, and as. 350 00:17:35.920 --> 00:17:38.400 They slow down, their momentum drops. 351 00:17:38.079 --> 00:17:41.240 Which means their Debroley wavelength physically stretches out. 352 00:17:41.319 --> 00:17:43.680 So the wave of each particle gets bigger and bigger 353 00:17:43.680 --> 00:17:44.440 as it gets colder. 354 00:17:44.559 --> 00:17:47.799 Exactly at room temperature, the wavelength of an atom is tiny, 355 00:17:48.400 --> 00:17:50.720 but in the freezing depths of a dark matter halo, 356 00:17:51.200 --> 00:17:54.759 these axion wavelengths stretch over macroscopic. 357 00:17:54.119 --> 00:17:58.200 Distances until eventually they stretch so much that they start touching. 358 00:17:58.279 --> 00:18:01.160 They don't just touch. The overlap the distance between the 359 00:18:01.160 --> 00:18:04.559 particles becomes smaller than the waves themselves, and when that 360 00:18:04.599 --> 00:18:07.599 threshold is crossed, the axions undergo a phase transition. 361 00:18:07.759 --> 00:18:09.519 They become a Bose Einstein condensation. 362 00:18:09.680 --> 00:18:14.119 Yes, the billions of overlapping wave functions merge, the axions 363 00:18:14.160 --> 00:18:17.599 lose their individual identities completely. You no longer have a 364 00:18:17.680 --> 00:18:19.640 vast collection of distinct particles. 365 00:18:19.680 --> 00:18:22.880 They have one single giant quantum. 366 00:18:22.599 --> 00:18:26.200 Entity governed by a single wave function. The entire halo 367 00:18:26.359 --> 00:18:28.720 acts as one unified superfluid. 368 00:18:28.880 --> 00:18:31.640 It's like imagine a crowded train station. Everyone is walking 369 00:18:31.640 --> 00:18:34.519 in different directions, bumping into each other. That's a normal gas. 370 00:18:35.079 --> 00:18:37.799 But a Bose Einstein condensate is like a flash mob. 371 00:18:38.279 --> 00:18:42.039 The temperature drops, the music hits, and suddenly billions of 372 00:18:42.039 --> 00:18:44.680 people are doing the exact same synchronized dance. 373 00:18:44.920 --> 00:18:48.480 That is a brilliant analogy. They stop acting like individuals 374 00:18:48.480 --> 00:18:51.680 and become one giant entity. And we aren't talking about 375 00:18:51.680 --> 00:18:54.359 a microscopic drop in a lab. We are talking about 376 00:18:54.359 --> 00:18:57.519 a condensate spanning hundreds of thousands of light years. 377 00:18:57.640 --> 00:19:00.759 It's just wild to think about quantum Canic usually rules 378 00:19:00.799 --> 00:19:03.880 things small enough to fit on a pinhead, and here 379 00:19:03.920 --> 00:19:06.400 it is dictating the shape of an entire galaxy. 380 00:19:06.440 --> 00:19:09.240 But this specific behavior is what provides the mechanism for 381 00:19:09.279 --> 00:19:12.880 the nine rings, because this galactic scale flash mob isn't 382 00:19:12.960 --> 00:19:15.680 standing still, It is rotating. 383 00:19:15.240 --> 00:19:17.519 Right, The dark Manner halo is spinning and it has 384 00:19:17.599 --> 00:19:18.440 massive gravity. 385 00:19:18.559 --> 00:19:21.680 So how does a smooth spinning sphere of axions develop 386 00:19:21.759 --> 00:19:25.240 distinct ridges. It comes down to orbital mechanics and the 387 00:19:25.240 --> 00:19:27.000 conservation of angular momentum. 388 00:19:27.079 --> 00:19:29.799 Okay, break that down for us. How does the halo 389 00:19:29.920 --> 00:19:30.920 actually form? 390 00:19:31.119 --> 00:19:34.720 It accretes mass from the surrounding space over billions of years. 391 00:19:35.640 --> 00:19:38.640 As axions fall inward toward the center of the galaxy, 392 00:19:38.880 --> 00:19:40.920 they bring angular momentum with them. 393 00:19:41.000 --> 00:19:43.279 So as they fall deeper into the gravity, well, they 394 00:19:43.319 --> 00:19:46.039 have to spin faster, like an ice skater pulling. 395 00:19:45.839 --> 00:19:48.920 Their arms in Exactly, they fall in spinning faster, but 396 00:19:48.960 --> 00:19:51.599 they don't just collapse into a black hole. They pass 397 00:19:51.720 --> 00:19:54.920 their closest approach to the center and get flung back 398 00:19:54.960 --> 00:19:56.599 outward on elliptical orbit. 399 00:19:56.480 --> 00:19:58.119 Until they run out of energy and have to fall 400 00:19:58.119 --> 00:19:58.640 back in again. 401 00:19:58.759 --> 00:20:02.119