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 --> 00:00:26.800 slumber under the night sky. 7 00:00:27.039 --> 00:00:30.280 Welcome to the deep Dive. Today, we're looking at something 8 00:00:30.320 --> 00:00:33.039 that feels like it's straight out of science fiction. We 9 00:00:33.119 --> 00:00:34.679 might be at the end of a hunt that's been 10 00:00:34.719 --> 00:00:37.719 going on for what nearly one hundred years, the search 11 00:00:37.840 --> 00:00:38.600 for dark matter. 12 00:00:38.799 --> 00:00:41.520 It's the biggest piece of the cosmic puzzle, and it's 13 00:00:41.560 --> 00:00:45.679 been missing this whole time. We're talking about the invisible structure, 14 00:00:45.799 --> 00:00:49.840 the scaffolding that holds literally everything together, and for decades 15 00:00:49.880 --> 00:00:53.520 it's just been well, a number in an equation, a 16 00:00:53.560 --> 00:00:54.679 gravitational ghost. 17 00:00:54.840 --> 00:00:56.920 That's such a good way to put it. And our 18 00:00:56.960 --> 00:00:59.960 mission today is to really get into a new fine 19 00:01:00.240 --> 00:01:04.760 that is so specific, so tantilizing that it has the 20 00:01:04.920 --> 00:01:06.799 entire physics community buzzing. 21 00:01:07.000 --> 00:01:07.760 It really does. 22 00:01:07.879 --> 00:01:10.560 We're going to be unpacking the work of Professor Tomanoy 23 00:01:10.599 --> 00:01:13.640 Totani from the University of Tokyo using data from NASA's 24 00:01:13.680 --> 00:01:16.719 Fermi gamma rayse based telescope, and the claim is huge. 25 00:01:16.760 --> 00:01:18.959 They think they may have finally seen it, or at least. 26 00:01:18.840 --> 00:01:21.680 Seen its fingerprint. It's direct signature. We're going to connect 27 00:01:21.680 --> 00:01:25.079 the dots today from the abstract theories of the nineteen 28 00:01:25.120 --> 00:01:27.879 thirties all the way to this cutting edge space telescope 29 00:01:27.959 --> 00:01:29.560 data from twenty twenty five. 30 00:01:29.760 --> 00:01:32.879 And we're using the study itself as our guide, the 31 00:01:32.879 --> 00:01:36.480 one published in the Journal of Cosmology and Astroparticle. 32 00:01:35.719 --> 00:01:39.400 Physics, exactly because this isn't just about finding something new. 33 00:01:40.200 --> 00:01:43.040 If this is right, it's the discovery of a brand 34 00:01:43.079 --> 00:01:46.840 new fundamental particle, something that would force us to rewrite 35 00:01:46.879 --> 00:01:48.680 the standard model of particle physics. 36 00:01:48.760 --> 00:01:51.120 Okay, so let's unpack that. If this really is the 37 00:01:51.159 --> 00:01:54.439 smoking gun, it means that eighty five percent of all 38 00:01:54.519 --> 00:01:57.359 the matter in the universe is made of stuff that 39 00:01:57.519 --> 00:02:01.599 is fundamentally different from anything we have ever seen or cataloged. 40 00:02:01.760 --> 00:02:03.719 Right, the implications are just staggering. 41 00:02:04.000 --> 00:02:05.560 So we have to approach this with, you know, a 42 00:02:05.560 --> 00:02:07.959 lot of critical thinking. We need to understand not just 43 00:02:08.000 --> 00:02:10.680 what they found, but why on Earth it's taken us 44 00:02:10.680 --> 00:02:12.360 this long to get even a glimpse of it. 45 00:02:12.560 --> 00:02:16.360 Precisely, to really appreciate what a massive claim this is, 46 00:02:16.400 --> 00:02:20.599 you have to understand the decades of frankly frustration and 47 00:02:20.759 --> 00:02:24.919 dead ends, and that journey starts way back at the beginning. 48 00:02:25.680 --> 00:02:28.240 Why did we even think this invisible stuff existed in 49 00:02:28.280 --> 00:02:28.960 the first place. 50 00:02:29.319 --> 00:02:32.199 Okay, so let's set the scene. We're in the nineteen thirties. 51 00:02:32.680 --> 00:02:35.520 Our understanding of the universe is still pretty new, but 52 00:02:35.599 --> 00:02:39.199 it's built on these pillars of classical mechanics. You know, 53 00:02:39.280 --> 00:02:41.319 Newtonian gravity, right, And. 54 00:02:41.319 --> 00:02:44.960 The assumption was simple. What you see is what you get. 55 00:02:45.240 --> 00:02:47.159 If you want to know the mass of a galaxy, 56 00:02:47.400 --> 00:02:49.319 you just add up all the light from the stars, 57 00:02:49.520 --> 00:02:51.919 estimate the mass of the gas and dust. 58 00:02:51.759 --> 00:02:53.759 And that's your total mass. That tells you how much 59 00:02:53.759 --> 00:02:54.919 gravity it has exactly. 60 00:02:55.319 --> 00:02:58.520 And this is where the Swiss astronomer Fritz Zwicki comes in. 61 00:02:59.120 --> 00:03:03.560 He was this brilliant though apparently very cantankerous scientists. 62 00:03:03.599 --> 00:03:04.039 I heard that. 63 00:03:04.159 --> 00:03:07.000 Yeah, he was studying a huge collection of galaxies called 64 00:03:07.000 --> 00:03:09.919 the Coma cluster, and he was trying to measure how 65 00:03:09.960 --> 00:03:12.719 fast the galaxies inside it were moving around. 66 00:03:12.639 --> 00:03:17.080 So he's basically timing the speed of this giant cosmic dance. 67 00:03:17.199 --> 00:03:19.599 A very very fast dance. As it turned out, he 68 00:03:19.639 --> 00:03:22.080 did the math based on all the light coming from 69 00:03:22.120 --> 00:03:24.960 the cluster, all the visible matter, the galaxies should have 70 00:03:24.960 --> 00:03:28.039 been moving at a certain speed, but what he actually measured. 71 00:03:27.840 --> 00:03:30.080 Was just wrong. They were moving too fast. 72 00:03:29.960 --> 00:03:33.759 Way too fast, so fast in fact, that the gravity 73 00:03:33.800 --> 00:03:37.319 from all the visible stars and gas wasn't nearly strong 74 00:03:37.400 --> 00:03:38.840 enough to keep them from flying away. 75 00:03:38.960 --> 00:03:41.919 Wait, so, based on the laws of physics, the entire 76 00:03:42.039 --> 00:03:45.319 coma cluster should have just disintegrated. 77 00:03:45.439 --> 00:03:48.360 It should have flown apart billions of years ago. The 78 00:03:48.439 --> 00:03:51.439 galaxies were moving with so much energy that the cluster's 79 00:03:51.479 --> 00:03:54.039 own gravity couldn't possibly hold them in orbit. It was 80 00:03:54.080 --> 00:03:55.400 a massive paradox. 81 00:03:55.439 --> 00:03:58.719 So Zwicki had a choice. Either Newton's laws of gravity 82 00:03:58.759 --> 00:04:02.560 are completely wrong, or there's a whole lot of mass 83 00:04:02.639 --> 00:04:04.439 in that cluster that he just can't see. 84 00:04:04.479 --> 00:04:06.879 And that's the conclusion he came to. He was confident 85 00:04:06.960 --> 00:04:09.120 in his measurements. He reasoned there had to be some 86 00:04:09.240 --> 00:04:12.400 other source of gravity, an enormous amount of unseen matter 87 00:04:12.520 --> 00:04:16.600 holding it all together. He called it dunkle material, dark matter. 88 00:04:16.720 --> 00:04:18.920 And people didn't exactly jump on board with this idea, 89 00:04:18.959 --> 00:04:19.279 did they. 90 00:04:19.399 --> 00:04:22.319 Oh, not at all. He was largely ignored, even ridiculed. 91 00:04:22.519 --> 00:04:24.800 The idea that maybe ninety percent of the universe was 92 00:04:24.800 --> 00:04:27.879 made of some invisible, unknown substance was just too radical. 93 00:04:28.079 --> 00:04:29.680 People thought, you know, it must be an error in 94 00:04:29.720 --> 00:04:32.480 his calculations, or some dust were not accounting for. 95 00:04:32.560 --> 00:04:34.439 Just a weird anomaly exactly. 96 00:04:34.480 --> 00:04:37.120 The idea was just shelved for decades. It was a 97 00:04:37.160 --> 00:04:38.879 theory way ahead of its time. 98 00:04:39.040 --> 00:04:42.319 But the evidence didn't go away. In fact, it came 99 00:04:42.360 --> 00:04:45.439 back with a vengeance in the nineteen seventies with astronomers 100 00:04:45.480 --> 00:04:47.160 like VERA. Rubin and Kent Ford. 101 00:04:47.480 --> 00:04:49.639 And that was the pivot, That was the moment this 102 00:04:49.720 --> 00:04:52.879 went from a weird idea to a fundamental problem in physics. 103 00:04:53.360 --> 00:04:56.319 Reuben and Ford weren't looking at giant clusters. They were 104 00:04:56.360 --> 00:05:01.079 looking at individual spiral galaxies like our own Milky. 105 00:05:00.439 --> 00:05:03.519 And they were measuring how fast the stars were rotating 106 00:05:03.560 --> 00:05:04.959 around the center of the galaxy. 107 00:05:05.079 --> 00:05:07.920 Right, and you'd expect something similar to our solar system. 108 00:05:08.120 --> 00:05:11.120 Mercury moves really fast, Earth is a bit slower, and 109 00:05:11.279 --> 00:05:14.000 Neptune way out of the edge is just crawling along. 110 00:05:14.240 --> 00:05:16.680 The further you get from the central mass, the slower 111 00:05:16.720 --> 00:05:17.040 you go. 112 00:05:17.240 --> 00:05:19.600 But that's not what they found in galaxies. 113 00:05:19.120 --> 00:05:21.639 Not even close. They found that the stars way out 114 00:05:21.639 --> 00:05:24.000 on the fringes of the spiral arms were moving just 115 00:05:24.040 --> 00:05:26.759 as fast as the stars near the core. The rotation 116 00:05:26.879 --> 00:05:30.279 curves were flat, which is impossible unless unless there's a 117 00:05:30.360 --> 00:05:34.399 huge invisible halo of mass surrounding the entire visible galaxy, 118 00:05:34.720 --> 00:05:38.480 extending far beyond the stars. Its gravity is what's keeping 119 00:05:38.519 --> 00:05:41.759 those outer stars in their high speed orbits, stopping them 120 00:05:41.800 --> 00:05:43.279 from flying off into space. 121 00:05:43.600 --> 00:05:46.920 So after forty years, Zwicki was vindicated. This wasn't just 122 00:05:46.959 --> 00:05:50.240 a quirk of the Coma cluster. It was everywhere. Every 123 00:05:50.279 --> 00:05:53.839 galaxy seemed to be embedded in this massive, invisible halo 124 00:05:54.000 --> 00:05:54.680 of dark matter. 125 00:05:54.920 --> 00:05:58.600 It went from being a curiosity to a cosmic necessity. 126 00:05:59.000 --> 00:06:01.879 And that raises the billion dollar question that physicists have 127 00:06:01.920 --> 00:06:04.439 been wrestling with ever since. If this stuff makes up 128 00:06:04.480 --> 00:06:07.560 eighty five percent of all matter, why can't we see it? 129 00:06:07.680 --> 00:06:09.759 Why is it so incredibly elusive? 130 00:06:10.079 --> 00:06:12.879 And the answer gets down to the fundamental forces of nature. 131 00:06:13.199 --> 00:06:14.519 It's all about what it doesn't do. 132 00:06:14.720 --> 00:06:17.600 It's all about the electromagnetic force. That's the force that 133 00:06:17.639 --> 00:06:22.319 governs light, electricity, magnetism, basically everything that makes matter visible 134 00:06:22.360 --> 00:06:26.439 and interactive particles interact with photons, which are particles of light. 135 00:06:26.560 --> 00:06:29.000 They can absorb light, reflect it, emit it. 136 00:06:29.040 --> 00:06:31.279 But dark matter particles, whatever they are, they just don't 137 00:06:31.319 --> 00:06:33.439 seem to play that game. They have no electric charts. 138 00:06:33.439 --> 00:06:35.000 They just ignore light completely. 139 00:06:35.240 --> 00:06:38.240 So a particle of dark matter could pass right through you, 140 00:06:38.519 --> 00:06:42.040 right through the Earth, without hitting a single thing. It's 141 00:06:42.079 --> 00:06:43.519 completely transparent, which. 142 00:06:43.399 --> 00:06:46.639 Makes it invisible to every telescope we've ever built. We 143 00:06:46.720 --> 00:06:49.040 only know it's there because we can feel its gravity. 144 00:06:49.360 --> 00:06:50.680 We're trying to study a ghost. 145 00:06:51.000 --> 00:06:53.160 So if you can't study it with light, you have 146 00:06:53.199 --> 00:06:55.560 to find another way. You have to hope it interacts 147 00:06:55.560 --> 00:06:58.240 with one of the other fundamental forces, even if it's 148 00:06:58.240 --> 00:06:59.439 just a tiny, tiny bit. 149 00:06:59.519 --> 00:07:02.160 And that's exactactly the strategy that led scientists to the 150 00:07:02.279 --> 00:07:04.519 leading theory, to the whimp hypothesis. 151 00:07:04.600 --> 00:07:09.480 Okay, so if dark matter ignores the electromagnetic force, scientists 152 00:07:09.519 --> 00:07:12.279 had to place a bet which of the other forces 153 00:07:12.519 --> 00:07:14.800 might give us a clue, and they landed on the 154 00:07:14.839 --> 00:07:15.879 weak nuclear force. 155 00:07:16.160 --> 00:07:20.800 That's right, And this led to the dominant candidate for 156 00:07:20.839 --> 00:07:22.800 what dark matter could be for a long long time. 157 00:07:23.360 --> 00:07:26.879 The WIMP. It stands for a weekly interacting massive particle. 158 00:07:27.079 --> 00:07:29.279 And it wasn't just a random guess, right. This idea 159 00:07:29.360 --> 00:07:31.959 came out of other bigger theories in particle physics. 160 00:07:32.279 --> 00:07:37.199 Exactly. It emerged naturally from theories like supersymmetry, which proposed 161 00:07:37.240 --> 00:07:41.000 that every known particle has a heavier super partner. The 162 00:07:41.120 --> 00:07:44.600 lightest of these super partners would be stable massive and 163 00:07:44.680 --> 00:07:47.639 would interact via the weak force. It was a perfect 164 00:07:47.759 --> 00:07:50.480 dark matter candidate just waiting to be discovered. 165 00:07:50.839 --> 00:07:54.120 So let's break down the name weekly interacting Why is 166 00:07:54.160 --> 00:07:55.560 that part so important? 167 00:07:55.800 --> 00:07:58.040 Well, the weak nuclear force is one of the four 168 00:07:58.079 --> 00:08:01.959 fundamental forces, but as its name suggests, it's incredibly feeble 169 00:08:02.040 --> 00:08:05.439 and only works over very short distances. It governs things 170 00:08:05.480 --> 00:08:06.800 like radioactive decay. 171 00:08:07.040 --> 00:08:10.480 So if dark matter particles interact through that force, it 172 00:08:10.519 --> 00:08:12.160 would explain why they're so hard. 173 00:08:11.959 --> 00:08:14.920 To detect, it would. It means they would stream through 174 00:08:15.240 --> 00:08:18.399 normal matter through us through planets almost all the time 175 00:08:18.439 --> 00:08:21.480 without ever hitting anything. An interaction would be an incredibly 176 00:08:21.560 --> 00:08:24.600 rare event. It solves the elusiveness problem perfectly. 177 00:08:24.759 --> 00:08:28.120 Okay, so that's the weekly interacting part. What about massive. 178 00:08:28.160 --> 00:08:30.759 That's crucial for a couple reasons. First, they need to 179 00:08:30.759 --> 00:08:33.519 be massive enough to clump together under gravity and form 180 00:08:33.600 --> 00:08:36.720 those giant halos around galaxies that we see the effects 181 00:08:36.720 --> 00:08:38.440 of light. Particles wouldn't do that. 182 00:08:38.679 --> 00:08:40.320 And the second reason, the second. 183 00:08:40.120 --> 00:08:43.399 Reason is key for actually finding them. If they are massive, 184 00:08:43.559 --> 00:08:46.919 say hundreds of times heavier than a proton, it gives 185 00:08:46.960 --> 00:08:49.480 us something to look for. It gives us Einstein's famous 186 00:08:49.519 --> 00:08:51.720 equation E equals mc square. 187 00:08:51.879 --> 00:08:55.919 Ah. Okay, mass can be converted into energy, and this 188 00:08:56.000 --> 00:08:58.480 brings us to the really clever part of the whole search, 189 00:08:58.919 --> 00:08:59.960 the annihilation sign. 190 00:09:00.519 --> 00:09:00.679 Right. 191 00:09:01.080 --> 00:09:03.960 If trying to catch a single wimp is nearly impossible, 192 00:09:04.399 --> 00:09:06.279 what if we could see what happens when two of 193 00:09:06.320 --> 00:09:09.519 them collide? Okay, the theory predicts that WIMPs are their 194 00:09:09.559 --> 00:09:13.320 own antiparticles. So when two WIMPs zipping around in the 195 00:09:13.320 --> 00:09:16.360 dense center of a galaxy happen to crash into each. 196 00:09:16.200 --> 00:09:18.840 Other, they annihilate. They just vanish, poof. 197 00:09:18.639 --> 00:09:21.639 They're gone. But their mass can't just disappear. It gets 198 00:09:21.720 --> 00:09:25.240 converted instantaneously into a shower of pure energy, and that. 199 00:09:25.320 --> 00:09:28.120 Energy creates other particles that we can detect exactly. 200 00:09:28.679 --> 00:09:32.519 It produces a whole cascade of familiar standard model particles. 201 00:09:33.200 --> 00:09:36.159 The heavier the original wimp, the more energy is released, 202 00:09:36.200 --> 00:09:38.679 and the heavier the particles that are created, things like 203 00:09:38.799 --> 00:09:41.159 quarks or even w and z bosons. 204 00:09:41.480 --> 00:09:45.840 Now those are heavy unstable particles. They don't stick around 205 00:09:45.879 --> 00:09:46.360 for long. 206 00:09:46.200 --> 00:09:49.639 Do they not at all. They decay almost instantly, and 207 00:09:49.759 --> 00:09:53.559 in that decay process, in that chain reaction, they produce 208 00:09:53.759 --> 00:09:57.440 the final stable thing we can actually look for. 209 00:09:57.360 --> 00:10:00.919 From Earth gamma race, high energy, high. 210 00:10:00.879 --> 00:10:04.159 Energy gamma rays. That's the smoking gun. The whims disappear, 211 00:10:04.360 --> 00:10:07.960 they create these heavy unstable particles, and those particles immediately 212 00:10:08.000 --> 00:10:10.159 fall apart and release a flash of gamma ray light. 213 00:10:10.279 --> 00:10:12.039 And the beauty of this is that the energy of 214 00:10:12.039 --> 00:10:15.399 that gamma ray is directly connected to the mass of 215 00:10:15.440 --> 00:10:17.159 the original wimp that started the whole thing. 216 00:10:17.440 --> 00:10:20.120 That's the fingerprint. It's a direct line. If you can 217 00:10:20.120 --> 00:10:22.600 measure the precise energy of the gamma ray, you can 218 00:10:22.639 --> 00:10:25.879 calculate the mass of the dark matter particle that created it. 219 00:10:25.879 --> 00:10:29.120 It's no longer a ghost. It has a specific measurable property. 220 00:10:29.279 --> 00:10:31.759 So the whole strategy for the last few decades has 221 00:10:31.759 --> 00:10:35.399 been find the place where dark matter is densest, point 222 00:10:35.399 --> 00:10:38.039 a gamma ray telescope at it and look for a 223 00:10:38.080 --> 00:10:41.480 specific spike of energy that can't be explained by anything else. 224 00:10:41.919 --> 00:10:44.519 That's the game plan in a nutshell. And there's one 225 00:10:44.519 --> 00:10:47.159 place in our neighborhood that is by far the most 226 00:10:47.159 --> 00:10:48.240 promising hunting. 227 00:10:48.000 --> 00:10:51.200 Ground, the center of our own galaxy, the Milky Way. 228 00:10:51.360 --> 00:10:54.080 All the models show that our galaxy is sitting inside 229 00:10:54.080 --> 00:10:57.679 this enormous, sort of football shaped halo of dark batter, 230 00:10:58.320 --> 00:11:00.600 and the density of that halo gets highigher and higher 231 00:11:00.600 --> 00:11:02.519 the closer you get to the galactic core. 232 00:11:02.799 --> 00:11:05.720 More density means more whimps packed into a smaller. 233 00:11:05.399 --> 00:11:07.799 Space, which means a much higher chance that two of 234 00:11:07.799 --> 00:11:11.080 them will actually collide and annihilate. It's the brightest spot 235 00:11:11.080 --> 00:11:12.200 on the dark matter map. 236 00:11:12.080 --> 00:11:17.080 But it's also an incredibly messy and violent place. Astronomically speaking, 237 00:11:17.399 --> 00:11:23.159 You've got a supermassive black hole, exploding stars, pulsars, all 238 00:11:23.200 --> 00:11:25.360 sorts of things throwing out high energy radiation. 239 00:11:25.519 --> 00:11:28.240 And that's the monumental challenge. How do you listen for 240 00:11:28.320 --> 00:11:31.799 the faint, specific whisper of dark matter annihilation amidst the 241 00:11:31.840 --> 00:11:35.320 deafening roar of a thousand other cosmic fireworks going off 242 00:11:35.360 --> 00:11:38.360 at the same time. That was the problem Professor Tatani's 243 00:11:38.399 --> 00:11:41.159 team had to solve, and solving that problem required an 244 00:11:41.240 --> 00:11:44.720 instrument built for exactly this purpose. The data that Tatani's 245 00:11:44.759 --> 00:11:48.200 team analyzed came from NASA's Fermi Gamma ray space telescope. 246 00:11:48.200 --> 00:11:51.120 It's been orbiting Earth for years, mapping the sky in 247 00:11:51.159 --> 00:11:53.159 the highest energies of light, so let's. 248 00:11:53.000 --> 00:11:55.600 Get right to it. The team sifts through all this 249 00:11:55.799 --> 00:11:59.840 data from the Galactic Center, What specific signal did they 250 00:11:59.840 --> 00:12:01.639 make managed to pull out of all that noise? 251 00:12:02.000 --> 00:12:05.759 After a very very careful analysis, they isolated a gamma 252 00:12:05.840 --> 00:12:09.840 ray signal with a remarkably specific energy. The photons they 253 00:12:09.840 --> 00:12:12.440 found were clocked at twenty gig electron vaults. 254 00:12:12.720 --> 00:12:15.799 Okay, twenty gv let's ground that number for a second. 255 00:12:16.840 --> 00:12:19.759 We hear these terms, but what does twenty billion electron 256 00:12:19.840 --> 00:12:22.399 vaults actually mean? How energetic is that? 257 00:12:23.120 --> 00:12:26.639 It's immense? For perspective, the light our eyes can see 258 00:12:26.679 --> 00:12:29.559 has an energy of maybe two or three electron vaults. 259 00:12:30.080 --> 00:12:32.000 A medical X ray might be a few thousand. We're 260 00:12:32.000 --> 00:12:35.120 talking about photons that are billions of times more energetic 261 00:12:35.120 --> 00:12:35.879 than visible light. 262 00:12:36.159 --> 00:12:37.840 So it's an extremely high energy. 263 00:12:37.639 --> 00:12:40.960 Signature, an incredibly high energy signature, And that's the first clue. 264 00:12:41.000 --> 00:12:43.159 An energy that high can really only come from a 265 00:12:43.279 --> 00:12:46.879 very energetic event, like the annihilation of a really massive particle. 266 00:12:47.240 --> 00:12:49.399 The more mass you start with, the more energy you 267 00:12:49.440 --> 00:12:49.840 get out. 268 00:12:49.879 --> 00:12:52.200 So the energy level is the first perfect match. But 269 00:12:52.279 --> 00:12:54.679 the second clue, and maybe this is even more important, 270 00:12:55.120 --> 00:12:56.480 was the signal shape and location. 271 00:12:56.919 --> 00:13:00.600 Absolutely, if this was just say a pulsar, a spinning 272 00:13:00.679 --> 00:13:03.759 neutron star, you'd expect to see a single bright point 273 00:13:03.759 --> 00:13:05.519 of light. But that's not what they saw. 274 00:13:05.639 --> 00:13:06.519 What did they see. 275 00:13:06.679 --> 00:13:10.519 Tatani described it as a distinct halo like structure. It's 276 00:13:10.559 --> 00:13:13.519 not a point. It's a diffuse glow that's brightest toward 277 00:13:13.600 --> 00:13:16.559 the galactic center but extends outward, fading gradually. 278 00:13:16.879 --> 00:13:19.240 That's the clincher, isn't it. That shape is a dead 279 00:13:19.320 --> 00:13:22.600 ringer for the theoretical models of the dark Manner halo itself. 280 00:13:22.679 --> 00:13:25.559 It's an almost perfect spatial match. You have a signal 281 00:13:25.600 --> 00:13:27.639 with the right energy showing up in the right place 282 00:13:27.679 --> 00:13:30.399 and distributed in the right shape. When you line all 283 00:13:30.440 --> 00:13:32.279 three of those up, the odds of it being some 284 00:13:32.440 --> 00:13:36.039 random astronomical objects start to drop very very quickly. 285 00:13:36.320 --> 00:13:39.440 The observational data is lining up with the theoretical profile 286 00:13:39.559 --> 00:13:42.559 of a wimpiss. So let's talk about that profile. What 287 00:13:42.600 --> 00:13:45.159 does a twenty GF gamma ray tell us about the 288 00:13:45.200 --> 00:13:45.879 wink that made it? 289 00:13:46.200 --> 00:13:48.000 Well, this is where it gets really exciting for the 290 00:13:48.039 --> 00:13:51.080 particle physicists. You can work the map backwards. A gamma 291 00:13:51.159 --> 00:13:53.600 ray with twenty gv of energy would be produced by 292 00:13:53.600 --> 00:13:56.440 the annihilation of WIMPs that each have a mass of 293 00:13:56.519 --> 00:13:58.639 roughly five hundred times the mass of a. 294 00:13:58.600 --> 00:14:04.320 Proton proton masses. Now is that significant in the grand 295 00:14:04.399 --> 00:14:07.399 scheme of all the theories out there? Where does a 296 00:14:07.480 --> 00:14:09.639 five hundred proton mass particle fit? 297 00:14:09.879 --> 00:14:13.000 It's extremely significant because it starts to narrow things down. 298 00:14:13.320 --> 00:14:15.720 For a long time, many of the most popular theories, 299 00:14:15.840 --> 00:14:20.279 especially those connected to supersymmetry, were predicting much heavier WIMPs, 300 00:14:20.320 --> 00:14:22.600 maybe thousands of times the mass of a proton. 301 00:14:23.000 --> 00:14:24.600 So this is actually on the lighter side of what 302 00:14:24.639 --> 00:14:25.519 people were expecting. 303 00:14:25.639 --> 00:14:28.360 It is. A wimp with about five hundred times of 304 00:14:28.399 --> 00:14:31.519 proton's mass is still very heavy, but it falls into 305 00:14:31.559 --> 00:14:34.639 a specific window that a lot of previous searches might 306 00:14:34.679 --> 00:14:38.000 have overlooked. It immediately forces theorists to look at a 307 00:14:38.000 --> 00:14:41.120 different set of models. Any new theory of dark matter 308 00:14:41.240 --> 00:14:43.159 now has to be able to produce a particle with 309 00:14:43.240 --> 00:14:45.799 this specific mass. It's a hard data point. 310 00:14:45.879 --> 00:14:48.159 So you had the energy peak at twenty gv, but 311 00:14:48.320 --> 00:14:51.120 not just a single spike, right, The annihilation should produce 312 00:14:51.159 --> 00:14:52.639 a whole spectrum of energies. 313 00:14:53.039 --> 00:14:55.919 Yes, and that's another crucial piece of the puzzle. The 314 00:14:56.039 --> 00:14:59.039 overall shape of the energy signal they found, not just 315 00:14:59.120 --> 00:15:02.799 the peak, also aligns incredibly well with the spectrum you'd 316 00:15:02.799 --> 00:15:07.000 expect from whimps of this mass annihilating into other particles 317 00:15:07.159 --> 00:15:08.720 like bottom quarks for example. 318 00:15:08.799 --> 00:15:12.080 It's the whole package. Yeah, the energy, the shape, the spectrum, 319 00:15:12.120 --> 00:15:12.799 it all fits. 320 00:15:13.080 --> 00:15:15.399 It's a remarkably coherent picture. 321 00:15:15.840 --> 00:15:19.720 But as we said, the galactic center is chaos. How 322 00:15:19.720 --> 00:15:22.360 did they convince themselves and how do they convince the 323 00:15:22.399 --> 00:15:24.879 rest of the world that this isn't just some other 324 00:15:24.960 --> 00:15:28.320 weird thing that also happens to produce twenty jv gamma 325 00:15:28.360 --> 00:15:29.080 rays is. 326 00:15:29.000 --> 00:15:31.200 The most difficult part of the analysis, and it's what 327 00:15:31.279 --> 00:15:33.960 makes this claim so credible. They had to systematically rule 328 00:15:34.000 --> 00:15:38.320 out everything else pulsars have the wrong energy spectrum. Cosmic rays. 329 00:15:38.320 --> 00:15:41.279 Hanging gas clouds produce gamma rays, but again the shape 330 00:15:41.279 --> 00:15:43.240 in the spectrum don't match this halo. 331 00:15:43.399 --> 00:15:45.960 And their main strategy was to look just outside the 332 00:15:46.039 --> 00:15:49.120 very center right to avoid the worst of the noise. 333 00:15:49.600 --> 00:15:53.080 Exactly, they deliberately cut out the data from the central 334 00:15:53.120 --> 00:15:56.960 galactic plane itself, because it's just saturated with radiation from 335 00:15:57.039 --> 00:16:01.440 known sources. They focused on the extended diffuse glow around 336 00:16:01.440 --> 00:16:02.399 that noisy core. 337 00:16:02.679 --> 00:16:04.679 So they looked at the subtle glow in the back range, 338 00:16:04.799 --> 00:16:07.080 not the bright fireworks in the foreground. 339 00:16:06.919 --> 00:16:10.440 Right, and by doing that, they isolated a signal that is, 340 00:16:10.559 --> 00:16:13.120 in their words, not easily explained by any of the 341 00:16:13.200 --> 00:16:17.000 usual suspects. When you've ruled out every known possibility, the 342 00:16:17.000 --> 00:16:20.279 one that remains, no matter how extraordinary, starts to look 343 00:16:20.320 --> 00:16:21.120 pretty compelling. 344 00:16:21.279 --> 00:16:23.960 And the most compelling explanation left on the table is 345 00:16:24.000 --> 00:16:28.159 the annihilation of a five hundred proton mass dark matter particle. 346 00:16:28.279 --> 00:16:30.559 It all points in that direction, the energy, the distribution, 347 00:16:30.639 --> 00:16:33.879 the frequency, it all converges on that one whim model. 348 00:16:34.399 --> 00:16:37.200 Okay, so this is the moment everything pivots. If this 349 00:16:37.279 --> 00:16:40.480 signal holds up to scrutiny. If this really is wimp annihilation, 350 00:16:41.279 --> 00:16:43.159 then we're not talking about a theory anymore. 351 00:16:43.240 --> 00:16:46.960 We're talking about a real physical particle. As Professor Totwani 352 00:16:47.080 --> 00:16:49.799 himself said, this would mark the first time humanity has 353 00:16:49.840 --> 00:16:51.080 seen dark matter. 354 00:16:50.960 --> 00:16:53.799 And that leads directly to the massive consequences for physics 355 00:16:54.039 --> 00:16:55.000 for the Standard model. 356 00:16:55.240 --> 00:16:59.080 The Standard Model of particle physics has been unbelievably successful, 357 00:17:00.000 --> 00:17:02.720 describes all the known particles, all the forces, but it 358 00:17:02.759 --> 00:17:06.119 has these two huge glaring holes in it. It can't 359 00:17:06.119 --> 00:17:08.839 explain gravity, and it has absolutely nothing to say about 360 00:17:08.920 --> 00:17:09.440 dark matter. 361 00:17:09.720 --> 00:17:13.240 So if this WIMP is real, it is by definition 362 00:17:13.599 --> 00:17:17.359 a new particle. It's something that exists outside that beautiful 363 00:17:17.759 --> 00:17:18.920 established framework. 364 00:17:19.160 --> 00:17:22.400 It's the first definitive piece of evidence that the Standard 365 00:17:22.400 --> 00:17:26.640 Model is incomplete. This wimp. It's massive, it interacts with 366 00:17:26.680 --> 00:17:29.480 the weak force, but it just doesn't fit anywhere on 367 00:17:29.480 --> 00:17:32.359 the current chart of quarks and leftones. It's like finding 368 00:17:32.359 --> 00:17:34.759 a new continent on a map you thought was finished. 369 00:17:34.799 --> 00:17:36.039 It means you have to draw a new map. 370 00:17:36.119 --> 00:17:37.960 You have to expand the theory. It means there's an 371 00:17:38.119 --> 00:17:40.880 entire dark sector of particles and forces that we've been 372 00:17:40.920 --> 00:17:44.440 totally oblivious to it fundamentally changes our definition of what 373 00:17:44.519 --> 00:17:45.400 matter even is. 374 00:17:45.799 --> 00:17:49.039 But a claim that big one that rewrites the textbooks 375 00:17:49.039 --> 00:17:52.400 requires an unbelievable amount of proof. This is where the 376 00:17:52.440 --> 00:17:58.079 scientific community goes from excitement to intense skepticism. 377 00:17:57.480 --> 00:18:00.839 And rightly so. The urgeon of proof is an enormous So. 378 00:18:00.839 --> 00:18:04.039 What does that verification process actually look like? It can't 379 00:18:04.079 --> 00:18:06.240 just be one team's analysis. 380 00:18:06.160 --> 00:18:09.519 No, absolutely not. There are two main lines of attack here. 381 00:18:10.079 --> 00:18:13.839 First is independent verification. Other teams of physicists around the 382 00:18:13.880 --> 00:18:16.880 world need to take the exact same public data from 383 00:18:16.880 --> 00:18:21.960 the Fermi telescope and run their own completely independent analysis, using. 384 00:18:21.799 --> 00:18:23.960 Their own methods, their own code, to see if they 385 00:18:24.039 --> 00:18:25.599 find the same thing exactly. 386 00:18:26.000 --> 00:18:28.440 Can they filter out the background noise in their own 387 00:18:28.480 --> 00:18:31.720 way and still pull out that same twenty gv halo. 388 00:18:31.839 --> 00:18:33.160 That's step one, and what's step two. 389 00:18:33.440 --> 00:18:36.880 Step two is finding the signal somewhere else. Finding it 390 00:18:36.960 --> 00:18:40.759 once in a very messy place is fantastic, but finding 391 00:18:40.759 --> 00:18:44.160 the exact same signal in a completely different, much cleaner 392 00:18:44.240 --> 00:18:45.960 environment that would be undeniable. 393 00:18:46.079 --> 00:18:48.240 This is the wimprerun you mentioned. Yeah, you need to 394 00:18:48.240 --> 00:18:51.160 find a cosmic clean room, a place that's packed with 395 00:18:51.279 --> 00:18:54.240 dark matter but doesn't have all the other astrophysical fireworks 396 00:18:54.279 --> 00:18:54.960 going off. 397 00:18:54.759 --> 00:18:57.200 And we know exactly what to look for. Those The 398 00:18:57.240 --> 00:19:00.759 perfect targets are the dwarf galaxies that or our own 399 00:19:00.799 --> 00:19:01.359 Milky Way. 400 00:19:01.400 --> 00:19:02.759 Why are they so perfect for this. 401 00:19:02.960 --> 00:19:06.000