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 astronomi 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 --> 00:00:30.000 You know, when we usually try to picture cosmological timeframes 8 00:00:30.079 --> 00:00:33.320 or just massive structures in space, there is this built 9 00:00:33.359 --> 00:00:37.119 in assumption of i don't know, relative serenity. Like we 10 00:00:37.200 --> 00:00:40.560 look up and the visual data we get implies this 11 00:00:40.960 --> 00:00:43.520 slow sweeping choreography. 12 00:00:42.920 --> 00:00:46.399 Right the rotation of galactic discs or the quiet gravitational 13 00:00:46.479 --> 00:00:49.719 dance of local groups. It all feels very distant and 14 00:00:49.759 --> 00:00:51.479 frankly mathematically stable. 15 00:00:51.679 --> 00:00:54.880 Exactly, it feels stable. But the thing is we're looking 16 00:00:54.880 --> 00:00:55.719 at a freeze frame. 17 00:00:56.039 --> 00:00:58.920 Yeah, that perception of stability is really just a byproduct 18 00:00:58.920 --> 00:01:02.799 of our extremely zaro temporal window. I mean, human observation 19 00:01:02.880 --> 00:01:05.079 represents less than a fraction of a millisecond on the 20 00:01:05.079 --> 00:01:08.640 cosmological clock. We are literally just getting a snapshot. 21 00:01:08.159 --> 00:01:10.680 Which is what makes it profoundly jarring when we point 22 00:01:10.719 --> 00:01:13.879 our instruments at a specific coordinate. In this case, we're 23 00:01:13.879 --> 00:01:17.079 talking about right ascension zero six hours fifty eight minutes 24 00:01:17.159 --> 00:01:20.480 declination minus fifty five degrees, and we realize we aren't 25 00:01:20.519 --> 00:01:22.599 looking at a stable gravitational system. 26 00:01:22.359 --> 00:01:23.760 At all, No, not even close. 27 00:01:23.920 --> 00:01:27.079 We're looking at a multi megaparsec crime scene, just a 28 00:01:27.079 --> 00:01:31.359 catastrophic kinetic event of absolutely unimaginable proportions. 29 00:01:31.680 --> 00:01:34.959 It really is the pinnacle of astrophysical violence. We are 30 00:01:35.000 --> 00:01:39.000 analyzing the immediate aftermath of a colossal merger between two 31 00:01:39.040 --> 00:01:43.879 distinct galaxy clusters, and this specific shock front, which is 32 00:01:43.920 --> 00:01:47.719 still traveling through the intergalactic medium, was generated roughly four 33 00:01:47.840 --> 00:01:48.959 billion years ago. 34 00:01:49.159 --> 00:01:51.280 Four billion years. I just want to anchor that for you. 35 00:01:51.359 --> 00:01:54.439 Listening as the photons and X ray emissions from this 36 00:01:54.519 --> 00:01:57.280 event were just beginning their transit toward our sector of 37 00:01:57.319 --> 00:02:00.799 the Milky Way. The Earth was in it Hadian to 38 00:02:01.000 --> 00:02:02.560 early Archean. 39 00:02:02.200 --> 00:02:04.120 Eon the very beginning. 40 00:02:03.840 --> 00:02:07.040 Right, the absolute earliest precursors to single sell life were 41 00:02:07.200 --> 00:02:11.560 just barely beginning to synthesize in these primordial oceans. Meanwhile, 42 00:02:11.680 --> 00:02:15.159 across the observable universe, billions of solar masses were being 43 00:02:15.159 --> 00:02:17.280 subjected to extreme ram pressure stripping. 44 00:02:17.360 --> 00:02:19.159 It's a staggering timescale and we. 45 00:02:19.120 --> 00:02:22.039 Are only just now processing the telemetry from that wreckage. 46 00:02:22.280 --> 00:02:25.120 But the reason we are analyzing this today isn't just 47 00:02:25.159 --> 00:02:28.599 a gawk at a fascinating kinetic anomaly in space. This 48 00:02:28.759 --> 00:02:32.000 specific region cataloged as one E zero six five seven 49 00:02:32.080 --> 00:02:34.039 fifty six, but universally known as the. 50 00:02:34.039 --> 00:02:36.680 Bullet Cluster, the famous Bullet Cluster, yes, right, It. 51 00:02:36.599 --> 00:02:40.599 Has served as the ultimate empirical battleground for modern physics. 52 00:02:41.080 --> 00:02:44.599 It is essentially the primary proving ground for the dominant 53 00:02:44.639 --> 00:02:47.879 cosmological paradigm, which is the existence of dark matter. 54 00:02:48.199 --> 00:02:51.080 Yeah. For over two decades now, the Bullet Cluster has 55 00:02:51.080 --> 00:02:54.840 basically operated as the cornerstone of the standard model. It 56 00:02:54.879 --> 00:02:59.800 was essentially treated as the incontrovertible empirical proof that cold 57 00:03:00.080 --> 00:03:03.479 collisionless dark matter isn't merely a mathematical placeholder. 58 00:03:03.599 --> 00:03:05.439 It's a physical reality. 59 00:03:04.960 --> 00:03:08.520 Exactly a physical reality. It formed the absolute bedrock of 60 00:03:08.560 --> 00:03:12.080 our understanding regarding the universe's unseen mass budget. 61 00:03:12.120 --> 00:03:15.039 Okay, let's unpack this because our mission today is to 62 00:03:15.080 --> 00:03:18.639 completely reevaluate that bedrock. We are analyzing how a suite 63 00:03:18.719 --> 00:03:23.520 of radically precise multi wavelength observations of this exact celestial 64 00:03:23.560 --> 00:03:27.520 structure are currently threatening to upend the entire dark matter consensus. 65 00:03:27.560 --> 00:03:29.039 It's a major paradigm shift. 66 00:03:29.080 --> 00:03:32.080 We are looking at new spectroscopic data that essentially takes 67 00:03:32.080 --> 00:03:34.960 a sledgehammer to the standard interpretation of the Bullet cluster, 68 00:03:35.520 --> 00:03:39.639 and it potentially revives a four decade old theoretical framework 69 00:03:39.919 --> 00:03:43.479 that the mainstream physics community honestly largely abandoned a long 70 00:03:43.520 --> 00:03:43.919 time ago. 71 00:03:44.199 --> 00:03:47.560 The current developments surrounding the Bullet Cluster really offer a 72 00:03:47.599 --> 00:03:51.240 master class and how scientific epistemologies must adapt when our 73 00:03:51.280 --> 00:03:55.479 instrumental resolution increases. I mean, the physics community operates under 74 00:03:55.560 --> 00:03:59.800 heavily scrutinized paradigms, but the universe is not obligated to 75 00:04:00.120 --> 00:04:01.479 form to our preferred model. 76 00:04:01.680 --> 00:04:03.159 No, it definitely isn't. 77 00:04:03.439 --> 00:04:07.000 Right. So when observational capabilities cross a new threshold, like 78 00:04:07.039 --> 00:04:12.599 in this case, unlocking unprecedented spectroscopic clarity, the foundational pillars 79 00:04:12.599 --> 00:04:16.120 of our standard models are subjected to extreme stress testing. 80 00:04:16.360 --> 00:04:18.959 Yeah, and that stress test is happening right now. Let's 81 00:04:18.959 --> 00:04:21.160 set up the parameters of the initial collision before we 82 00:04:21.199 --> 00:04:23.000 get into the new data, just so everyone is on 83 00:04:23.040 --> 00:04:27.040 the same page. We are talking about two distinct galaxy. 84 00:04:26.560 --> 00:04:28.800 Clusters, and these are not small structures. 85 00:04:29.040 --> 00:04:31.199 Right. For those of you deeply immersed in this field, 86 00:04:31.439 --> 00:04:34.120 you already know we aren't talking about small, localized groups 87 00:04:34.160 --> 00:04:38.319 of stars. These are massive, gravitationally bound structures positioned at 88 00:04:38.319 --> 00:04:42.040 a redshift of roughly z equals point two nine to six. 89 00:04:42.399 --> 00:04:45.040 The scale is absolutely vital to keep in mind. Here 90 00:04:45.399 --> 00:04:48.759 we are dealing with a main cluster and a slightly 91 00:04:48.839 --> 00:04:53.160 smaller subcluster combined. We are analyzing a system that contains 92 00:04:53.279 --> 00:04:57.279 thousands of individual galaxies. Thousands of galaxies, not just stars, yes, 93 00:04:57.720 --> 00:05:01.839 entire galaxies, all bound within an sensive gravitational potential. Well, 94 00:05:02.639 --> 00:05:05.800 but the kinetic variables are what make this merger so unique. 95 00:05:06.399 --> 00:05:09.399 The subcluster, which we call the bullet, was on a 96 00:05:09.600 --> 00:05:13.519 highly centralized trajectory rik a direct hit, a completely direct hit. 97 00:05:13.600 --> 00:05:16.040 It passed directly through the core of the main cluster 98 00:05:16.120 --> 00:05:20.079 at extraordinarily high relative velocity. We are observing a shock 99 00:05:20.160 --> 00:05:24.160 velocity approaching four thousand, five hundred klometers per second wow, 100 00:05:24.199 --> 00:05:26.959 and the subcluster itself is moving at roughly two thousand, 101 00:05:27.000 --> 00:05:28.439 five hundred kilometers per second. 102 00:05:28.680 --> 00:05:31.240 Let's just hold on that relative velocity metric for a second, 103 00:05:31.279 --> 00:05:35.160 because that is wild two five hundred kilometers per second. 104 00:05:35.439 --> 00:05:38.959 That translates to a mock number of roughly three within 105 00:05:39.000 --> 00:05:41.759 the context of the surrounding intergalactic medium. 106 00:05:41.399 --> 00:05:44.319 Which is incredibly fast for an object of that mass. 107 00:05:44.720 --> 00:05:48.759 Right, the kinetic energy dissipation required to halt or even 108 00:05:48.879 --> 00:05:51.600 just slow down an object of that size moving at 109 00:05:51.600 --> 00:05:54.199 mock three is completely staggering. 110 00:05:54.480 --> 00:05:57.399 The energy released in this event is literally second only 111 00:05:57.480 --> 00:05:59.439 to the Big Bang itself. I mean, it is a 112 00:05:59.480 --> 00:06:03.120 thermode dynamic extreme. But to model the mechanics of the 113 00:06:03.120 --> 00:06:06.279 collision accurately, we have to look really closely at the 114 00:06:06.279 --> 00:06:08.519 mass distribution of the clusters themselves. 115 00:06:08.600 --> 00:06:10.360 Okay, break that down for us well. 116 00:06:10.399 --> 00:06:14.079 As we know the visible galaxies, the stellar populations that 117 00:06:14.120 --> 00:06:17.600 we see shining account for a surprisingly small fraction of 118 00:06:17.639 --> 00:06:21.399 a cluster's total buryonic mass. I mean the ordinary matter. 119 00:06:21.480 --> 00:06:24.160 The vast majority of the ordinary matter resides in the 120 00:06:24.160 --> 00:06:25.920 intracluster medium or the ICM. 121 00:06:26.000 --> 00:06:29.160 Right, the ICM, that's the hot diffuse plasma that fills 122 00:06:29.199 --> 00:06:32.800 the empty space between the constituent galaxies. It's so easy 123 00:06:32.800 --> 00:06:35.639 to look at optical imagery like from Hubvel and just 124 00:06:35.720 --> 00:06:38.399 assume the stars are the primary actors in these. 125 00:06:38.319 --> 00:06:40.920 Structures exactly because that's where the visible light is. 126 00:06:41.040 --> 00:06:44.199 But chemically and physically, the stars are really just trace 127 00:06:44.279 --> 00:06:48.240 elements floating inside a massive reservoir of ionized hydrogen and helium. 128 00:06:48.399 --> 00:06:51.959 Right. Yes, the mass ratio is heavily skewed. The hot 129 00:06:51.959 --> 00:06:55.959 plasma of the ICM actually outweighs the combined stellar mass 130 00:06:56.000 --> 00:06:59.040 of all the galaxies within the cluster by a factor 131 00:06:59.120 --> 00:07:00.560 of anywhere from fire five to ten. 132 00:07:00.800 --> 00:07:03.399 Five to ten times more mass in the gas than 133 00:07:03.439 --> 00:07:04.040 in the stars. 134 00:07:04.319 --> 00:07:07.879 Right, So, when we analyze the kinetic mechanics of this 135 00:07:08.000 --> 00:07:11.680 high speed merger, the primary physical interaction isn't between the 136 00:07:11.720 --> 00:07:15.360 stars at all. It's the collision of these two massive 137 00:07:15.439 --> 00:07:16.920 plasma clouds. 138 00:07:16.680 --> 00:07:20.439 Which introduces fluid dynamics into the equation. We have two 139 00:07:20.439 --> 00:07:24.519 colossal volumes of interracluster medium hurtling toward each other, and 140 00:07:24.600 --> 00:07:27.279 because plasma is a collisional fluid, the moment those two 141 00:07:27.319 --> 00:07:30.240 volumes intersect, the physics get incredibly violent. 142 00:07:30.360 --> 00:07:32.360 They do. They don't just slip past one another like 143 00:07:32.399 --> 00:07:33.480 ghost ships, right. 144 00:07:33.680 --> 00:07:37.480 They experience extreme ram pressure as the subcluster's gas plows 145 00:07:37.480 --> 00:07:40.240 into the main cluster's gas. The collisional cross section of 146 00:07:40.279 --> 00:07:42.560 the protons and electrons is incredibly high. 147 00:07:42.639 --> 00:07:45.160 They essentially slam into a wall of their own, making 148 00:07:45.680 --> 00:07:48.639 the gas clouds subject each other to immense drag forces, 149 00:07:48.639 --> 00:07:52.160 and they rapidly decelerate. All that kinetic energy from the 150 00:07:52.199 --> 00:07:56.399 two thy five hundred kilometer per second impact is violently 151 00:07:56.439 --> 00:07:58.240 converted into thermal energy. 152 00:07:58.199 --> 00:08:01.079 Heating the plasma up to insane temperatures. 153 00:08:00.879 --> 00:08:02.600 It's heating it to the point where it becomes a 154 00:08:02.639 --> 00:08:06.319 massive source of bremstrolong or what we call breaking radiation. 155 00:08:06.600 --> 00:08:09.199 Breaking radiation. Yeah, let's touch on that because it's super 156 00:08:09.199 --> 00:08:11.160 important for how we actually see this stuff. 157 00:08:11.519 --> 00:08:14.399 Right, So, the deceleration of those charged particles in the 158 00:08:14.399 --> 00:08:18.920 plasma generates intense X ray emissions. When we map the 159 00:08:18.959 --> 00:08:22.360 bullet cluster today using the Chandra X ray observatory, what 160 00:08:22.439 --> 00:08:26.240 we are actually detecting is this superheuated, shocked plasma. 161 00:08:26.319 --> 00:08:27.959 It's glowing an X rays exactly. 162 00:08:28.319 --> 00:08:32.279 It presents as two distinct, incredibly bright lobes of gas 163 00:08:32.480 --> 00:08:34.960 that have been severely slowed down and basically trapped in 164 00:08:35.000 --> 00:08:38.279 the central region of the collision zone, and the morphology 165 00:08:38.320 --> 00:08:41.639 of the smaller gas cloud literally looks like a ballistic wake, 166 00:08:41.840 --> 00:08:44.159 like a bullet, like a bullet shape, Yes, which is 167 00:08:44.200 --> 00:08:45.879 exactly what gives the cluster its name. 168 00:08:46.159 --> 00:08:50.000 But here's the critical point of divergence in this whole event. 169 00:08:50.639 --> 00:08:54.240 While the intracluster medium was slamming into this hydrodynamic wall 170 00:08:54.320 --> 00:08:57.480 and bleeding off its kinetic energy and X rays, the 171 00:08:57.519 --> 00:09:03.240 constituent galaxies themselves experience an entirely different physical reality, completely 172 00:09:03.279 --> 00:09:07.519 different the actual stellar populations. All those billions of stars 173 00:09:07.720 --> 00:09:12.519 locked inside their respective galactic structures basically ignored the collision entirely. 174 00:09:12.679 --> 00:09:16.240 Yeah, they really did, because, unlike the plasma of the ICM, 175 00:09:16.399 --> 00:09:21.960 the galaxies effectively behave as collisionless particles within the broader cluster. 176 00:09:21.799 --> 00:09:23.639 Environment, meaning they don't hit each other. 177 00:09:23.879 --> 00:09:27.320 Right, The mean free path of a galaxy moving through 178 00:09:27.320 --> 00:09:30.720 another cluster is so massive compared to its actual physical 179 00:09:30.759 --> 00:09:34.799 cross section that the probability of direct stellar interactions is 180 00:09:34.840 --> 00:09:36.320 statistically negligible. 181 00:09:36.720 --> 00:09:40.840 It's the classic disparity between collisional and collisionless matter. I 182 00:09:40.879 --> 00:09:43.320 was trying to map this conceptually for you listening, and 183 00:09:43.360 --> 00:09:46.639 it essentially mirrors firing two blasts of bird shot at 184 00:09:46.639 --> 00:09:49.600 each other through a dense, suspended water droplet. 185 00:09:49.720 --> 00:09:50.759 That's a great analogy. 186 00:09:51.080 --> 00:09:54.440 Thanks. So the lead pellets, which represent the galaxies in 187 00:09:54.480 --> 00:09:57.679 this case, have such a small cross section relative to 188 00:09:57.720 --> 00:10:00.600 the vast distance between them that they just zip right 189 00:10:00.639 --> 00:10:03.679 past each other unhindered. They carry their momentum out the 190 00:10:03.679 --> 00:10:04.159 other side. 191 00:10:04.200 --> 00:10:06.360 They don't even notice the other pellet exactly. 192 00:10:06.759 --> 00:10:13.240 But the water, which represents the dense intracluster plasma, smacks together, splatters, 193 00:10:13.519 --> 00:10:15.519 and stalls out completely in the center. 194 00:10:15.840 --> 00:10:19.559 The fluid dynamics versus n body dynamics analogy holds up 195 00:10:19.559 --> 00:10:23.120 perfectly there. The galaxies retain their initial velocities while the 196 00:10:23.159 --> 00:10:26.399 gas is stripped away via ram pressure. The result is 197 00:10:26.440 --> 00:10:28.960 a profound physical separation of the. 198 00:10:28.879 --> 00:10:31.039 Cluster's components, a total decoupling. 199 00:10:31.240 --> 00:10:33.799 Right. So, following the transit, you have the bulk of 200 00:10:33.840 --> 00:10:36.840 the baryonic mass, which is that X ray emitting plasma, 201 00:10:37.240 --> 00:10:40.960 stalled right near the center of the gravitational potential. Meanwhile, 202 00:10:41.000 --> 00:10:43.720 the two groups of galaxies have sailed straight through and 203 00:10:43.759 --> 00:10:46.600 are now positioned on the far outer flanks, millions of 204 00:10:46.679 --> 00:10:49.000 light years away from their original gas halos. 205 00:10:49.279 --> 00:10:54.480 We have a macroscale centrifuge. The collision literally physically isolated 206 00:10:54.519 --> 00:10:57.840 the galaxies on the outer edges, leaving the heavily dominant 207 00:10:57.919 --> 00:10:59.960 plasma mass segregated in the center. 208 00:11:00.159 --> 00:11:00.279 Yea. 209 00:11:00.519 --> 00:11:04.240 So we possess an incredibly clear, bifurcated map of the 210 00:11:04.279 --> 00:11:08.039 system's normal matter. So my question is why did this 211 00:11:08.120 --> 00:11:12.200 specific segregation turn into the foundational proof for dark matter. 212 00:11:12.679 --> 00:11:15.960 Well, the crux of the argument relies entirely on general relativity, 213 00:11:16.159 --> 00:11:20.120 specifically the mechanics of gravitational lensing. We know from Einstein 214 00:11:20.159 --> 00:11:23.679 that any localized concentration of energy or mass induces a 215 00:11:23.679 --> 00:11:26.000 curvature in the surrounding space time metric. 216 00:11:26.200 --> 00:11:29.720 Right, it literally bends space, and photons, even though they 217 00:11:29.759 --> 00:11:33.759 are totally massless, are constrained to follow these curved geodesics. 218 00:11:34.159 --> 00:11:37.679 So a massive foreground object acts like a giant gravitational 219 00:11:37.720 --> 00:11:38.519 lens exactly. 220 00:11:38.799 --> 00:11:41.679 It deflects the light emitted by background sources. When we 221 00:11:41.720 --> 00:11:44.519 examine the deep field optical data behind the bullet cluster, 222 00:11:44.720 --> 00:11:47.320 we observe a highly pronounced weak lensing effect. 223 00:11:47.440 --> 00:11:49.240 The background galaxies look all warped. 224 00:11:49.559 --> 00:11:53.039 Yes, they are subjected to sheer forces, distorting their apparent 225 00:11:53.080 --> 00:11:58.320 morphologies into these faint, little elliptical arcs. By statistically analyzing 226 00:11:58.360 --> 00:12:02.879 the orientation and the magnitude of these sheer deformations. Astrophysicists 227 00:12:02.960 --> 00:12:07.519 can mathematically reconstruct the exact distribution of the foreground mass 228 00:12:07.519 --> 00:12:08.759 that is causing the lensing. 229 00:12:08.960 --> 00:12:12.879 So we can basically build a high fidelity topographical map 230 00:12:13.320 --> 00:12:14.720 of the cluster's gravity. 231 00:12:14.399 --> 00:12:16.720 A map of the gravitational potential. Yes, so we have 232 00:12:16.759 --> 00:12:19.360 two distinct maps to compare. We have the X ray map, 233 00:12:19.360 --> 00:12:21.919 which shows us exactly where the baryonic mass. 234 00:12:21.679 --> 00:12:25.000 Is that huge pool of hot gas stalled in the center. 235 00:12:24.840 --> 00:12:27.200 Right, and then we have the lensing map, which shows 236 00:12:27.279 --> 00:12:30.759 us exactly where the gravity actually is. The expectation if 237 00:12:30.799 --> 00:12:34.279 we base this on purely baryonic models of the universe 238 00:12:34.679 --> 00:12:38.320 was that the deepest gravitational potential wells should perfectly overlap 239 00:12:38.360 --> 00:12:40.759 with the highest concentrations of mass. 240 00:12:40.600 --> 00:12:43.559 Because more stuff equals more gravity exactly. 241 00:12:43.879 --> 00:12:45.799 And since the X ray data proves that the vast 242 00:12:45.799 --> 00:12:48.159 majority of the normal matter is stalled in the central 243 00:12:48.200 --> 00:12:51.960 plasma clouds, the gravitational lensing should be heavily centered over 244 00:12:52.000 --> 00:12:52.799 that plasma. 245 00:12:52.840 --> 00:12:55.600 But it isn't. And that right there is the paradox 246 00:12:55.600 --> 00:12:59.639 that ignited the modern cosmological consensus. When you overlay the 247 00:12:59.720 --> 00:13:03.080 X ray mass map with the gravitational lensing map, there 248 00:13:03.120 --> 00:13:07.320 is a massive glaring spatial offset. The huge offset the 249 00:13:07.360 --> 00:13:11.039 strongest gravitational lensing isn't happening over the massive gas clouds 250 00:13:11.080 --> 00:13:14.399 in the middle. The deepest gravity wells are sitting right 251 00:13:14.480 --> 00:13:16.799 on top of the separated galaxy groups on the outer 252 00:13:16.879 --> 00:13:18.919 flanks where the stars ended up. 253 00:13:19.000 --> 00:13:21.799 Yeah, the spatial offset between the baryonic mass peaks and 254 00:13:21.840 --> 00:13:25.159 the gravitational lensing peaks was measured at roughly eight sigma 255 00:13:25.559 --> 00:13:29.679 I mean it is an undeniable, mathematically robust discrepancy. The 256 00:13:29.759 --> 00:13:33.559 system is generating immense localized gravity in regions where there 257 00:13:33.600 --> 00:13:35.279 is seemingly very little mass. 258 00:13:35.519 --> 00:13:37.519 Wait, so the light is bending the most where there's 259 00:13:37.519 --> 00:13:40.519 seemingly the least amount of stuff. How is that physically 260 00:13:40.559 --> 00:13:42.519 possible unless our math is totally broken. 261 00:13:42.799 --> 00:13:46.480 Well, if we rely strictly on the observable baryonic matter, 262 00:13:46.639 --> 00:13:49.759 the math is entirely broken. The light is being sheared 263 00:13:49.799 --> 00:13:52.960 the most by regions containing the least amount of material, unless, 264 00:13:53.000 --> 00:13:55.519 of course, we introduce a non buryonic variable into the equation. 265 00:13:55.840 --> 00:13:58.159 And here we go. This is where a cold dark 266 00:13:58.200 --> 00:14:01.840 matter or CDM, and as the savior of the standard 267 00:14:01.840 --> 00:14:03.279 cosmological model. 268 00:14:03.080 --> 00:14:06.960 It really was the savior. The LAMBA CDM framework posits 269 00:14:07.000 --> 00:14:11.240 that the universe is overwhelmingly dominated by a non buryonic 270 00:14:11.320 --> 00:14:15.720 particulate substance that interacts exclusively via gravity. 271 00:14:15.519 --> 00:14:18.720 While remaining completely decoupled from the electromagnetic force. 272 00:14:18.879 --> 00:14:22.559 Exactly, it is entirely immune to the electromagnetic spectrum. It 273 00:14:22.600 --> 00:14:26.480 doesn't emit, reflect or absorb photons in any way, making 274 00:14:26.519 --> 00:14:31.320 it fundamentally invisible. But more crucially for the bullet cluster scenario, 275 00:14:31.799 --> 00:14:36.279 its lack of electromagnetic interaction means it cannot experience friction 276 00:14:36.440 --> 00:14:37.320 or ram pressure. 277 00:14:37.519 --> 00:14:40.399 Right, the collisionless nature of dark matter is its defining 278 00:14:40.480 --> 00:14:43.759 characteristic here. So prior to the merger, both the main 279 00:14:43.879 --> 00:14:47.399 cluster and the subcluster were modeled as residing within these 280 00:14:47.879 --> 00:14:50.279 massive extended dark matter halos. 281 00:14:50.000 --> 00:14:52.600 And those halos contain the vast majority of the system's 282 00:14:52.600 --> 00:14:53.320 total mass. 283 00:14:53.360 --> 00:14:56.120 So let's run the n body simulations again, but with 284 00:14:56.159 --> 00:14:59.279 the dark matter halos included. This time, the clusters collide, 285 00:14:59.360 --> 00:15:02.440 the collisional pl plasma hits the wall, generates X rays 286 00:15:02.480 --> 00:15:06.000 and stalls out in the center. The collisionless galaxies sail 287 00:15:06.200 --> 00:15:11.399 right through, and the dark matter halos. What happens to them. 288 00:15:11.320 --> 00:15:15.919 Well, they behave exactly like the collisionless galaxies. Because dark 289 00:15:15.960 --> 00:15:18.879 matter particles cannot interact with the gas or even with 290 00:15:18.960 --> 00:15:23.840 each other, they experience absolutely zero hydrodynamic drag. The dark 291 00:15:23.840 --> 00:15:27.840 matter haloes simply pass right through each other, remaining gravitationally 292 00:15:27.879 --> 00:15:30.120 bound to the collisionless stellar populations. 293 00:15:30.159 --> 00:15:33.759 They segregated themselves completely from the plasma. Yes, so the 294 00:15:33.759 --> 00:15:36.360 reason the gravitational lensing is occurring so intensely on the 295 00:15:36.360 --> 00:15:39.480 outer flanks is because the invisible dark matter halos are 296 00:15:39.519 --> 00:15:42.440 sitting right there. They're heavily concentrated around. 297 00:15:42.200 --> 00:15:44.960 The galaxies exactly. They carried the vast majority of the 298 00:15:45.000 --> 00:15:48.720 mass outward, leaving the smaller faction of visible plasma stranded 299 00:15:48.759 --> 00:15:49.279 in the center. 300 00:15:49.639 --> 00:15:52.399 It was viewed as the ultimate elegant triumph of the 301 00:15:52.480 --> 00:15:56.960 Lambda CDM model. The bullet cluster essentially provided a macro 302 00:15:57.039 --> 00:16:01.600 scale particle accelerator, naturally separating the collisional baryonic matter from 303 00:16:01.639 --> 00:16:02.879 the collisionless dark matter. 304 00:16:03.200 --> 00:16:06.519 It was textbook. The spatial offset between the X ray 305 00:16:06.559 --> 00:16:09.919 peaks and the lensing peaks was considered impossible to explain 306 00:16:10.120 --> 00:16:13.120 using any modified theory of gravity because you're clearly seeing 307 00:16:13.159 --> 00:16:16.200 the source of the gravity physically separate itself from the 308 00:16:16.240 --> 00:16:16.919 normal matter. 309 00:16:17.600 --> 00:16:19.320 But I'm going to push back on this all against 310 00:16:19.320 --> 00:16:24.360 a little bit. Yeah, because from an epistemological standpoint, introducing 311 00:16:24.399 --> 00:16:28.320 a completely unobservable substance to fix a gaping hole in 312 00:16:28.360 --> 00:16:32.720 your gravitational math carries a distinct scent of well ad 313 00:16:32.759 --> 00:16:33.519 hoc reasoning. 314 00:16:33.639 --> 00:16:34.639 It's a common critique. 315 00:16:34.720 --> 00:16:37.960 Yes, it feels uncomfortably close to adding epicycles to the 316 00:16:38.000 --> 00:16:42.200 geocentric model. So let me get this straight. We saw 317 00:16:42.320 --> 00:16:45.120 gravity where there was no visible mass, and instead of 318 00:16:45.159 --> 00:16:48.559 rigorously questioning whether our fundamental laws of gravitation, whether Poisson's 319 00:16:48.559 --> 00:16:52.480 equation or general relativity, break down at extreme low acceleration scales, 320 00:16:52.960 --> 00:16:55.840 we just assumed there was a giant, invisible, frictionless ghost 321 00:16:55.840 --> 00:16:58.720 substance perfectly placed exactly where we needed it to be. 322 00:16:59.240 --> 00:17:02.399 This raises an shortant question, and honestly, that critique is 323 00:17:02.440 --> 00:17:07.079 the very engine of alternative cosmological theories. You are completely 324 00:17:07.119 --> 00:17:10.680 right to be skeptical. The lambda CDM model requires us 325 00:17:10.720 --> 00:17:13.599 to accept that eighty five percent of the universe's mass 326 00:17:13.960 --> 00:17:17.079 is fundamentally beyond the reach of the standard model of 327 00:17:17.119 --> 00:17:18.480 particle physics. 328 00:17:18.079 --> 00:17:20.400 Eighty five percent. That's almost everything right. 329 00:17:20.440 --> 00:17:23.920 And despite decades of direct detection experiments, you know, looking 330 00:17:24.039 --> 00:17:29.000 for weakly interacting massive particles or WIMPs using highly sensitive 331 00:17:29.079 --> 00:17:33.160 underground xenon detectors, we have found absolutely nothing, not a 332 00:17:33.200 --> 00:17:36.519 single particle. So the reliance on dark matter is heavily 333 00:17:36.519 --> 00:17:41.720 predicated on its macroscopic gravitational effects, not on direct particle verification, and. 334 00:17:41.680 --> 00:17:45.039 That reliance remained relatively unshaken. The Bullet cluster was treated 335 00:17:45.079 --> 00:17:48.799 as the close case until very recently, because the fundamental 336 00:17:48.839 --> 00:17:51.519 weakness of any empirical model is that it is only 337 00:17:51.559 --> 00:17:54.640 as robust as the instruments used to compile the data. 338 00:17:54.359 --> 00:17:57.000 And our instruments just got a massive upgrade exactly. 339 00:17:57.200 --> 00:17:59.599 The data landscape has radically shifted with the deployment of 340 00:17:59.599 --> 00:18:01.279 the James Webb Space Telescope. 341 00:18:01.400 --> 00:18:05.119 The leap from legacy observatories like Hubble or Chandra to 342 00:18:05.200 --> 00:18:10.400 the JWST is fundamentally a leap in spectroscopic resolution. The 343 00:18:10.440 --> 00:18:14.759 original Bullet cluster analyzes were primarily relying on optical lensing 344 00:18:14.839 --> 00:18:17.759 data and X ray mass derivations, which. 345 00:18:17.559 --> 00:18:18.680 Were great for their time. 346 00:18:19.000 --> 00:18:22.720 They were and while they were accurate within their design parameters, 347 00:18:22.759 --> 00:18:27.599 they completely lacked the extreme infrared sensitivity required to deeply 348 00:18:27.720 --> 00:18:31.799 analyze the chemical composition of the stellar populations locked inside 349 00:18:32.000 --> 00:18:33.599 those outer galaxy flanks. 350 00:18:33.839 --> 00:18:36.559 Right, and a recent analysis led by an international team 351 00:18:36.960 --> 00:18:40.960 including Professor Pabelkruppa and researcher Dongzhang from the University of 352 00:18:41.000 --> 00:18:45.960 Bond leveraged this new capability. They utilized the JWST's near 353 00:18:46.000 --> 00:18:50.240 infrared spectrograph and mid infrared instrument to conduct an unprecedented 354 00:18:50.319 --> 00:18:53.279 chemical assay of the constituent galaxies in the Bullet cluster. 355 00:18:53.359 --> 00:18:55.319 They weren't just counting the light sources anymore. 356 00:18:55.440 --> 00:18:57.920 No, they were measuring the specific absorption lines in the 357 00:18:57.960 --> 00:18:59.039 stellar spectra. 358 00:18:58.880 --> 00:19:03.039 Because spectroscopy allows us to determine the exact elemental abundances 359 00:19:03.079 --> 00:19:07.160 within those remote galaxies. Different elements absorb light at highly 360 00:19:07.200 --> 00:19:10.559 specific wavelengths, creating unique chemical fingerprints. 361 00:19:10.880 --> 00:19:13.119 It's like a barcode for the universe exactly. 362 00:19:13.359 --> 00:19:16.359 And the critical revelation from Krupa and Zang's analysis was 363 00:19:16.359 --> 00:19:21.359 the detection of exceptionally high metallicities. Specifically, they found profound 364 00:19:21.400 --> 00:19:27.359 concentrations of heavy elements like oxygen, magnesium, and notably iron. 365 00:19:27.480 --> 00:19:31.640 And just to clarify, within the context of astrophysics, metals 366 00:19:32.240 --> 00:19:34.880 refers to any element heavier than helium. Right. 367 00:19:35.200 --> 00:19:38.880 Yes, astronomers are lazy with chemistry. Anything heavier than helium 368 00:19:38.920 --> 00:19:39.480 is a metal. 369 00:19:39.599 --> 00:19:42.359 Right. So the presence of these heavy elements in such 370 00:19:42.480 --> 00:19:46.480 high concentrations is the loose thread that begins to unravel 371 00:19:46.559 --> 00:19:50.240 the standard dark matter narrative for this cluster. Because these 372 00:19:50.279 --> 00:19:52.920 elements cannot be synthesized in the prioridial universe. 373 00:19:53.039 --> 00:19:57.400 No primordial nucleosynthesis following the Big Bang only yielded hydrogen, helium, 374 00:19:57.440 --> 00:20:01.160 and very trace amounts of lithium. The entire heavy element 375 00:20:01.200 --> 00:20:03.839 inventory of the universe must be forged within the cores 376 00:20:03.880 --> 00:20:07.200 of stars via ongoing stellar nucleosynthesis. 377 00:20:07.279 --> 00:20:10.319 A star is functionally just a hydrostatic balancing act. You 378 00:20:10.359 --> 00:20:13.880 have immense gravitational pressure crushing inward, and that's balanced by 379 00:20:13.880 --> 00:20:17.160 the outward radiation pressure generated by the continuous nuclear fusion 380 00:20:17.160 --> 00:20:18.720 of hydrogen into helium. 381 00:20:18.799 --> 00:20:21.559 But the fusion chain doesn't stop at helium. Provided the 382 00:20:21.559 --> 00:20:25.759 star has sufficient initial mass to synthesize oxygen and iron, 383 00:20:25.880 --> 00:20:29.359 you require the extreme temperatures and core pressures found only 384 00:20:29.359 --> 00:20:33.119 in the most massive stellar classifications. We're talking about stars 385 00:20:33.160 --> 00:20:36.119 exceeding eight to ten solar masses. 386 00:20:35.960 --> 00:20:39.200 Massive stars, and this brings us to the initial mass function, 387 00:20:39.279 --> 00:20:42.480 or the IMF for those listening. That IMF is basically 388 00:20:42.559 --> 00:20:45.880 the demographic distribution of a star forming region. It tells 389 00:20:45.920 --> 00:20:49.079 us the ratio of small low mass stars to giant 390 00:20:49.240 --> 00:20:51.720 high mass stars. When it galaxy forms. 391 00:20:51.519 --> 00:20:54.559 Exactly, and generating the specific abundance of iron that was 392 00:20:54.599 --> 00:20:58.359 observed by the JWST in the bullet cluster necessitates a 393 00:20:58.440 --> 00:21:02.640 highly specific stellar hit. Because iron is the terminal point 394 00:21:02.680 --> 00:21:04.480 of stellar nucleosynthesis, you. 395 00:21:04.440 --> 00:21:06.720 Can't fuse iron and get energy out of it, right. 396 00:21:06.880 --> 00:21:09.880 The fusion of iron is an endothermic process. It drains 397 00:21:09.960 --> 00:21:12.440 energy from the core rather than releasing it. So when 398 00:21:12.480 --> 00:21:15.720 a massive star develops a critical iron core, the outward 399 00:21:15.839 --> 00:21:18.640 radiation pressure collapses almost instantaneously. 400 00:21:18.720 --> 00:21:20.759 Gravity wins the battle in a fraction of a second. 401 00:21:21.000 --> 00:21:25.359