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 --> 00:00:26.719 slumber under the night sky. 7 00:00:26.920 --> 00:00:30.559 Welcome back everyone. Today, we're diving into something truly immense, 8 00:00:30.600 --> 00:00:35.520 maybe the biggest emptiest structures we know of the cosmic voids. 9 00:00:35.560 --> 00:00:37.640 These are just these enormous gaps you see in the 10 00:00:38.200 --> 00:00:41.320 large scale structure of the universe, the places where gravity 11 00:00:41.320 --> 00:00:46.000 seems weakest and almost everything seems to have well cleared out. 12 00:00:46.240 --> 00:00:48.039 For a long time, people pretty much assumed they were 13 00:00:48.079 --> 00:00:51.640 just completely empty, you know, huge black nothings like holes 14 00:00:51.679 --> 00:00:55.759 punched in space. But now we actually have the tools 15 00:00:55.799 --> 00:00:58.640 the technology to map these things out see how they evolve. 16 00:00:58.920 --> 00:01:01.280 So our goal today to really dig into the latest 17 00:01:01.320 --> 00:01:04.439 findings and figure out what's actually in there. If anything, 18 00:01:04.680 --> 00:01:06.640 We've pulled together the research to give you the clearest 19 00:01:06.680 --> 00:01:10.319 possible picture of what these unbelievably vast spaces contain. Because 20 00:01:10.359 --> 00:01:13.280 the answer isn't just nothing. It's more interesting than that. 21 00:01:13.319 --> 00:01:16.120 The scale, though it's almost impossible to really get your 22 00:01:16.159 --> 00:01:17.000 head around. We'll try. 23 00:01:17.159 --> 00:01:20.319 Yeah, that nothing at all idea is the starting point, absolutely, 24 00:01:20.359 --> 00:01:24.640 and it's true. They are mostly defined by well by 25 00:01:24.640 --> 00:01:28.120 what's not there, a profound lack of matter. But the 26 00:01:28.200 --> 00:01:31.519 key thing, the really crucial insight from the material we 27 00:01:31.519 --> 00:01:34.200 looked at, is that they aren't, you know, totally one 28 00:01:34.239 --> 00:01:37.159 hundred percent empty, not across their entire colossal volume. Anyway, 29 00:01:37.560 --> 00:01:40.840 They're definitely the closest thing to a vacuum we have, sure, 30 00:01:41.400 --> 00:01:44.840 but there's still structure. There's a great analogy that helps. 31 00:01:44.879 --> 00:01:47.719 I think I mentioned deserts on Earth. Okay, like say 32 00:01:48.159 --> 00:01:51.079 the empty Quarter in Arabia. It's defined by a lack 33 00:01:51.120 --> 00:01:52.959 of water, a lack of big life forms. You wouldn't 34 00:01:52.959 --> 00:01:55.480 call it teeming, right, definitely not, but it's not lifeless. 35 00:01:55.519 --> 00:01:59.280 There's still stuff there, maybe some deeprooted plants, insects, maybe 36 00:01:59.319 --> 00:02:02.120 a tiny mammal hanging on. It's incredibly sparse. 37 00:02:01.920 --> 00:02:04.239 Right, There is life, just very little. 38 00:02:03.959 --> 00:02:08.280 Of it exactly. The cosmic voids are basically the Universe's 39 00:02:08.360 --> 00:02:11.000 version of that, the ultimate sparse environment. 40 00:02:11.199 --> 00:02:13.800 Okay, so let's really get into that sparseness, that scale, 41 00:02:13.879 --> 00:02:16.599 because I think you're right. You can't grasp how empty 42 00:02:16.680 --> 00:02:19.840 a void is until you understand how empty the average 43 00:02:19.919 --> 00:02:23.280 universe is already, which is pretty staggering in itself. We 44 00:02:23.360 --> 00:02:27.919 need that baseline. So the observable universe, right, this immense 45 00:02:28.039 --> 00:02:32.960 volume ninety something billion light years across the material we 46 00:02:33.080 --> 00:02:37.280 have lays out this fantastic thought experiment. Imagine you could 47 00:02:37.319 --> 00:02:42.360 take absolutely everything in that whole volume, every planet, star, galaxy, 48 00:02:42.479 --> 00:02:46.680 gas cloud, and crucially all the dark matter, dark energy too, 49 00:02:46.840 --> 00:02:49.120 all the stuff, all the stuff, and just spread it 50 00:02:49.159 --> 00:02:52.520 out perfectly, even like cosmic butter, across the. 51 00:02:52.639 --> 00:02:54.639 Entire universe, right, a uniform smear. 52 00:02:54.759 --> 00:02:56.000 What density do you end up with? 53 00:02:56.240 --> 00:02:59.159 And the result is, well, it's mind boggling, really defines 54 00:02:59.159 --> 00:03:00.759 the emptiness for city. And you end up with an 55 00:03:00.800 --> 00:03:05.039 average density of roughly get this, Yeah, one single hydrogen 56 00:03:05.080 --> 00:03:06.520 atom per cubica. 57 00:03:06.280 --> 00:03:08.400 The one atom in a cubic meter. Just try to 58 00:03:08.400 --> 00:03:10.599 picture that a cubic meter. That's a pretty big box, right, 59 00:03:10.639 --> 00:03:16.159 like arms outstretched, wide, high, deep, and inside that entire volume, 60 00:03:16.719 --> 00:03:22.479 just one solitary, lonely hydrogen atom floating around. That's the 61 00:03:22.520 --> 00:03:24.240 average density of everything. 62 00:03:24.360 --> 00:03:25.159 It's almost nothing. 63 00:03:25.240 --> 00:03:28.080 It's practically nothing. We only think the universe is dense 64 00:03:28.159 --> 00:03:30.960 because while most of that matter is crammed into tiny 65 00:03:31.000 --> 00:03:35.080 spots like Earth or the Sun or our galaxy. 66 00:03:34.719 --> 00:03:36.280 Exactly, gravity pulls it together. 67 00:03:36.439 --> 00:03:38.840 The air you're breathing right now, the chair you're sitting on, 68 00:03:39.240 --> 00:03:43.280 that's trillions upon trillions of times denser than that cosmic average. 69 00:03:43.280 --> 00:03:45.960 It's wild, it is wild. Ye, it's almost impossible to 70 00:03:46.039 --> 00:03:48.159 visualize that kind of vacuum. I mean, even if you 71 00:03:48.199 --> 00:03:50.360 took that cubic meter box and sucked all the air out, 72 00:03:50.680 --> 00:03:53.919 cooled it to absolute zero, it would still be way 73 00:03:53.960 --> 00:03:57.000 denser than the universe's average. The vastness is just ugh. 74 00:03:57.960 --> 00:04:01.680 Okay, so that's our baseline, one atom cubic meter on average. 75 00:04:01.800 --> 00:04:03.560 Now here's where the voids come in and just blow 76 00:04:03.599 --> 00:04:06.840 that away, because they are way emptier than that already 77 00:04:06.960 --> 00:04:08.280 incredibly sparse average. 78 00:04:08.400 --> 00:04:10.080 Right, This is where it gets really interesting. They are 79 00:04:10.120 --> 00:04:11.360 the emptiest of the empty. 80 00:04:11.439 --> 00:04:12.520 So how much emptier? 81 00:04:12.800 --> 00:04:16.720 Well, when scientists model these structures, a typical void, averaging 82 00:04:16.759 --> 00:04:19.720 its density across its whole span edge to edge, comes 83 00:04:19.759 --> 00:04:23.120 out at only about one fifth, So twenty percent of 84 00:04:23.120 --> 00:04:25.279 that average universal density twenty percent. 85 00:04:25.319 --> 00:04:27.800 Okay, at first that sounds maybe not that much nuss, 86 00:04:27.839 --> 00:04:28.360 but wait. 87 00:04:28.399 --> 00:04:31.480 Exactly, but remember what the average was. It was already 88 00:04:31.519 --> 00:04:34.920 basically zero one atom per cubic meter. 89 00:04:35.040 --> 00:04:38.759 So twenty percent of almost nothing is even closer to nothing. 90 00:04:38.800 --> 00:04:41.879 Precisely, if the average universe is one hydrogen atom per 91 00:04:41.959 --> 00:04:46.519 cubic meter, avoid averages out to only point two hydrogen atoms. 92 00:04:46.240 --> 00:04:49.000 Per cubic meter zero point two, so less than one 93 00:04:49.040 --> 00:04:51.079 atom per cubic meter on average inside Avoid. 94 00:04:51.160 --> 00:04:53.319 Yeah. To put in another way, think about that box again. 95 00:04:53.519 --> 00:04:56.079 Instead of needing one cubic meter to find on average, 96 00:04:56.079 --> 00:04:58.879 one atom inside a void, you'd need a volume five 97 00:04:58.920 --> 00:05:02.720 times bigger five cubic meters, a huge space just to 98 00:05:02.759 --> 00:05:06.160 find that single, lonely hydrogen atom on average. 99 00:05:06.199 --> 00:05:09.839 Wow. Okay, that really drives home the scale of the desolation. 100 00:05:09.959 --> 00:05:12.199 I guess it really does. It fundamentally changes how you 101 00:05:12.199 --> 00:05:16.040 think about emptiness. And importantly, that twenty percent figure, that's 102 00:05:16.199 --> 00:05:19.399 itself a bit misleading because it's an average density for 103 00:05:19.439 --> 00:05:22.120 the entire void, including its edges, its boundaries. 104 00:05:22.279 --> 00:05:25.600 Yeah, right, and the edges are presumably where they bump 105 00:05:25.680 --> 00:05:27.839 up against the denser parts of the universe exactly. 106 00:05:27.839 --> 00:05:30.120 They border the filaments and walls of the cosmic web, 107 00:05:30.120 --> 00:05:33.560 where there's more matter, So those boundary regions are naturally 108 00:05:33.920 --> 00:05:36.879 a bit denser relatively speaking, they pull the average up. 109 00:05:36.959 --> 00:05:40.199 So if you could somehow just measure the very center 110 00:05:40.399 --> 00:05:42.279 the deep interior, it would. 111 00:05:42.040 --> 00:05:45.639 Be much much lower than twenty percent of the average density, 112 00:05:46.000 --> 00:05:50.199 way sparser. The vast majority of a void's volume is 113 00:05:50.319 --> 00:05:53.519 far emptier than even that zero point two atoms per 114 00:05:53.560 --> 00:05:54.720 cubic meter suggests. 115 00:05:54.920 --> 00:05:59.040 Okay, so they're these super vacuums basically, but like you said, 116 00:05:59.199 --> 00:06:02.480 not totally easier. So what is that remaining trace amount 117 00:06:02.480 --> 00:06:05.800 of stuff? What contributes to that tiny bit of density. 118 00:06:06.000 --> 00:06:08.120 Let's move beyond just the numbers. What can we actually 119 00:06:08.160 --> 00:06:09.240 see or detect in there? 120 00:06:09.399 --> 00:06:10.279 Right? What are the contents? 121 00:06:10.399 --> 00:06:13.079 Yeah, our deep galaxy surveys, the ones looking for the 122 00:06:13.079 --> 00:06:17.199 faintest light over huge distances. They do find things. It's sparse, 123 00:06:17.399 --> 00:06:20.360 very sparse, but it's specific stuff. We see things like 124 00:06:20.879 --> 00:06:25.720 dim dwarf galaxies, these little, often kind of raggedy looking 125 00:06:25.879 --> 00:06:29.720 clumps of stars, galaxies that just didn't have enough material 126 00:06:29.800 --> 00:06:32.959 nearby to grow big and grand. Like the Milky Way. 127 00:06:33.160 --> 00:06:35.600 The runs of the galactic litter, basically pretty much. 128 00:06:35.920 --> 00:06:40.519 And we also detect these incredibly thin, tenuous threads of gas, 129 00:06:41.040 --> 00:06:44.959 mostly hydrogen, sometimes linking these dwarf galaxies. 130 00:06:44.480 --> 00:06:45.360 Whispers of matter. 131 00:06:45.519 --> 00:06:49.240 Yeah, exactly. These are structures that are unbelievably hard to spot. 132 00:06:49.279 --> 00:06:51.720 They're so dim they push our telescopes right to the limit, 133 00:06:52.360 --> 00:06:55.319 but they are there. It confirms the voids aren't perfect holes. 134 00:06:55.560 --> 00:06:59.600 They have some some sparse furniture, maybe mostly near the edges. 135 00:06:59.639 --> 00:07:03.000 That's the stuff. Yeah, the baryonic matter, as we call it, 136 00:07:03.040 --> 00:07:05.519 the normal matter, like the dust motes you might see 137 00:07:05.639 --> 00:07:08.199 floating in a sunbeam in an otherwise empty room. Okay, 138 00:07:08.399 --> 00:07:11.079 but the picture gets way more complex and honestly more 139 00:07:11.079 --> 00:07:14.639 fascinating when we factor in the invisible stuff dark matter. 140 00:07:14.800 --> 00:07:17.959 Ah right, the mysterious scaffolding of the universe. We can't 141 00:07:17.959 --> 00:07:19.839 see it, but it's what like eighty five percent of 142 00:07:19.879 --> 00:07:20.800 the matter out there. 143 00:07:20.720 --> 00:07:23.959 Something like that. Yeah. It's gravity dictates where everything else goes, 144 00:07:24.639 --> 00:07:27.000 and even though we can't observe it directly, we can 145 00:07:27.040 --> 00:07:30.759 model its behavior with incredible precision using supercomputers. 146 00:07:30.839 --> 00:07:35.199 Okay, so what do those simulations show happening inside the voids? 147 00:07:35.279 --> 00:07:38.800 Is the dark matter just not there, not at all. 148 00:07:39.279 --> 00:07:41.439 This is what's so cool. The simulations show that the 149 00:07:41.480 --> 00:07:44.439 voids aren't just smooth, empty holes in the dark matter 150 00:07:44.480 --> 00:07:49.000 distribution either. They actually contain entire mini cosmic webs made 151 00:07:49.040 --> 00:07:49.680 of dark matter. 152 00:07:49.839 --> 00:07:53.160 Mini webs inside the voids, like a ghost structure within 153 00:07:53.199 --> 00:07:54.639 the emptiness. 154 00:07:54.040 --> 00:07:58.040 Exactly a ghostly hidden scaffolding. Think of the main cosmic web, 155 00:07:58.079 --> 00:08:00.639 the big one, like this massive three D spot structure, 156 00:08:01.000 --> 00:08:03.839 or a network of connected filaments and walls. Okay, yeah, 157 00:08:03.879 --> 00:08:06.040 the voids are the huge holes in that sponge. But 158 00:08:06.079 --> 00:08:09.959 the simulations show that even within those giant holes, dark 159 00:08:10.000 --> 00:08:13.279 matter is still there, just at incredibly low densities, and 160 00:08:13.360 --> 00:08:16.399 its gravity, even though it's super wank, is still enough 161 00:08:16.439 --> 00:08:18.680 to pull it into finer, sparser structures. 162 00:08:18.720 --> 00:08:20.519 So it's like webs within webs. 163 00:08:20.560 --> 00:08:24.959 Pretty much. The source material we reviewed actually knows this complexity. 164 00:08:25.279 --> 00:08:29.600 It describes how voids seem to be divided into smaller subvoids, 165 00:08:30.360 --> 00:08:33.440 and those subvoids might be further divided into sub subvoids, 166 00:08:33.879 --> 00:08:38.480 all defined by these incredibly faint filments of dark matter. Wow, 167 00:08:38.679 --> 00:08:42.320 and this structure, this pattern repeating at smaller scales, even 168 00:08:42.360 --> 00:08:45.519 in the emptiest regions gives it what the researchers call 169 00:08:46.000 --> 00:08:48.480 a slight fractal character. 170 00:08:48.799 --> 00:08:51.519 Fractal like those repeating patterns in mathematics. 171 00:08:51.559 --> 00:08:54.519 Sort of yeah. It means the basic pattern of the 172 00:08:54.519 --> 00:08:58.879 cosmic web, filaments connecting denser nodes surrounding emptier regions, seems 173 00:08:58.879 --> 00:09:01.679 to repeat itself even down here at these incredibly low 174 00:09:01.720 --> 00:09:05.440 densities within the voids themselves. It's a remarkable hint about 175 00:09:05.440 --> 00:09:08.600 how fundamental that web structure is to the universe's architecture. 176 00:09:08.639 --> 00:09:11.320 Why is that significant, though? Does it tell something important 177 00:09:11.320 --> 00:09:14.200 that there's this faint, fractal structure even in the voids. 178 00:09:14.399 --> 00:09:17.360 I think it does. It shows that gravity dominated by 179 00:09:17.440 --> 00:09:20.559 dark matter, is always at work shaping things, even where 180 00:09:20.559 --> 00:09:21.879 there's almost nothing to shape. 181 00:09:22.000 --> 00:09:23.519 Right, It's not just chaos in there. 182 00:09:23.840 --> 00:09:28.080 No, That fractal character suggests that even the weakest gravitational 183 00:09:28.120 --> 00:09:32.639 fields operating over cosmic time still impose order and structure. 184 00:09:33.200 --> 00:09:36.840 It prevents even the voids from becoming perfectly uniform. It 185 00:09:36.879 --> 00:09:41.240 shows structure formation is still happening, just incredibly slowly and 186 00:09:41.279 --> 00:09:44.240 on a tiny scale compared to the main web. It 187 00:09:44.279 --> 00:09:47.000 tells us the void isn't just a hole. It's an 188 00:09:47.039 --> 00:09:49.840 integral structured part of the cosmic landscape. 189 00:09:50.039 --> 00:09:52.759 So the big cosmic web has these holes the voids, 190 00:09:53.320 --> 00:09:57.320 but the holes themselves have this faint ghost scaffolding inside, 191 00:09:57.600 --> 00:09:59.600 making even smaller holes within them. 192 00:10:00.000 --> 00:10:01.759 It's a good way to picture it, and we have 193 00:10:01.840 --> 00:10:04.080 to keep coming back to those boundaries, those edges we 194 00:10:04.120 --> 00:10:04.840 talked about, right. 195 00:10:04.879 --> 00:10:06.679 The reason the average density isn't even. 196 00:10:06.519 --> 00:10:10.320 Lower exactly that twenty percent average figure relies heavily on 197 00:10:10.360 --> 00:10:13.639 the material clinging near the void's perimeter. The voids don't 198 00:10:13.639 --> 00:10:16.639 just stop, they as the source puts it butt up 199 00:10:16.679 --> 00:10:19.919 against walls and clusters and filaments of the main, denser 200 00:10:19.960 --> 00:10:20.639 cosmic web. 201 00:10:20.759 --> 00:10:22.759 It's like the shallow edge of a deep lake. Right. 202 00:10:22.919 --> 00:10:25.200 The edges make the average depth seem less than it 203 00:10:25.240 --> 00:10:25.840 is in the middle. 204 00:10:26.080 --> 00:10:31.759 Perfect analogy. Those boundary regions are by definition less void like. 205 00:10:32.440 --> 00:10:35.559 They have more dwarf galaxies, more gas, more dark matter 206 00:10:35.679 --> 00:10:37.399 influence from the nearby structures, so. 207 00:10:37.360 --> 00:10:41.679 They disproportionately bump up that overall average density figure, masking 208 00:10:41.840 --> 00:10:45.759 just how profoundly empty the real core of the void is, which. 209 00:10:45.519 --> 00:10:47.639 Brings us to the next step. Yeah, if we really 210 00:10:47.679 --> 00:10:52.919 want to talk about true, unadulterated emptiness, cosmic scale loneliness. 211 00:10:54.240 --> 00:10:57.320 We have to mentally zoom past those edges, past the 212 00:10:57.399 --> 00:11:00.960 dim little galaxies, past those faint gas thres We need 213 00:11:01.000 --> 00:11:03.240 to go deep into the interior. Okay, we need to 214 00:11:03.240 --> 00:11:06.519 focus on the deepest, most isolated regions of the void's heartland. 215 00:11:06.720 --> 00:11:08.600 This is where it gets really extreme, isn't it. 216 00:11:08.679 --> 00:11:11.799 This is it. These areas millions of light years away 217 00:11:11.840 --> 00:11:15.279 from any significant structure, any major gravitational pull. This is 218 00:11:15.320 --> 00:11:18.519 where the sources talk about the truly lifeless portions. 219 00:11:18.120 --> 00:11:22.240 Existing lifeless in terms of lacking structure, lacking anything pretty much. 220 00:11:22.519 --> 00:11:25.960 The information uses some really evocative comparisons to places on Earth, 221 00:11:26.080 --> 00:11:27.559 trying to give us a sense of the desolation. 222 00:11:27.960 --> 00:11:30.799 Yeah, I saw those places like the Katara Depression and 223 00:11:30.840 --> 00:11:34.399 the Sahara or the empty Quartered desert or bad Water 224 00:11:34.440 --> 00:11:37.440 Basin in Death Valley, places known for being about as 225 00:11:37.480 --> 00:11:39.480 barren and dry as Earth gets. 226 00:11:39.279 --> 00:11:43.120 Right, trying to anchor this cosmic emptiness to something terrestrial. 227 00:11:43.440 --> 00:11:47.080 But honestly, even those analogies feel like they fall short, 228 00:11:47.600 --> 00:11:48.440 massively short. 229 00:11:48.480 --> 00:11:50.840 Oh, they absolutely do, because when we talk about these 230 00:11:50.960 --> 00:11:53.799 core void regions, we're not talking about a few hundred 231 00:11:53.879 --> 00:11:57.840 kilometers of desert. We're talking about volumes of space where 232 00:11:57.919 --> 00:12:04.000 there's essentially nothing for distances up to millions of light years, millions. 233 00:12:03.279 --> 00:12:07.320 Of light years, not meters, not kilometers light years, an 234 00:12:07.320 --> 00:12:10.759 almost unbroken vacuum stretching further than many galaxies are wide. 235 00:12:10.799 --> 00:12:14.200 It just resets your whole perspective on empty Traveling from 236 00:12:14.240 --> 00:12:17.240 one random particle, maybe a stray hydgen atam, maybe a 237 00:12:17.360 --> 00:12:19.519 dark matter particle that happens to be zipping through to 238 00:12:19.559 --> 00:12:22.519 the next particle, that journey could take longer than it 239 00:12:22.559 --> 00:12:25.279 takes light to cross entire galaxy clusters. 240 00:12:25.120 --> 00:12:28.399 Millions of years for light to cross the gap between stray. 241 00:12:28.120 --> 00:12:31.080 Particles potentially yeah, in those deepest cores. 242 00:12:31.480 --> 00:12:37.000 So if the density is effectively zero over such huge scales, 243 00:12:37.879 --> 00:12:40.559 why even call it a void with structure? Why isn't 244 00:12:40.600 --> 00:12:44.679 it just incredibly empty space? Is there anything physically stopping 245 00:12:44.679 --> 00:12:46.919 it from being a perfect absolute vacuum. 246 00:12:47.080 --> 00:12:49.919 That's a really good question. Why isn't it just nothing? 247 00:12:50.720 --> 00:12:53.559 The reason it's classified as avoid is structural, right, It's 248 00:12:53.559 --> 00:12:56.240 defined by its location between the denser filaments of the 249 00:12:56.240 --> 00:12:59.559 cosmic web. It's the space carved out by gravity pulling 250 00:12:59.559 --> 00:13:00.399 matter away from it. 251 00:13:00.440 --> 00:13:03.279 Okay, so its existence is defined by what's around. 252 00:13:03.000 --> 00:13:07.240 It largely yes, and physically, is it a perfect vacuum, No, 253 00:13:07.559 --> 00:13:11.879 because quantum fluctuations can still in principle create particle antiparticle pairs, 254 00:13:11.919 --> 00:13:15.159 though they annihilate quickly, and just random chance dictates that 255 00:13:15.200 --> 00:13:18.039 some particles will eventually pass through any given volume, even 256 00:13:18.080 --> 00:13:19.519 if incredibly and frequently. 257 00:13:19.240 --> 00:13:22.559 So not technically one hundred point zero zero percent empty, 258 00:13:22.679 --> 00:13:25.519 but practically practically. 259 00:13:25.000 --> 00:13:28.960 It's the closest thing imaginable. And crucially, the dark matter 260 00:13:29.039 --> 00:13:32.240 simulations back this up. They show this profound level of 261 00:13:32.279 --> 00:13:36.039 emptiness right in the cores of the voids. The random 262 00:13:36.080 --> 00:13:40.320 particle presence is so incredibly low. The source material really 263 00:13:40.360 --> 00:13:43.559 emphasizes this that if you were sitting in one spot 264 00:13:43.919 --> 00:13:47.039 waiting for say a hydrogen atom or a dark matter 265 00:13:47.039 --> 00:13:49.559 particle to pass by, you'd have to wait a really 266 00:13:49.600 --> 00:13:51.120 really long time before the next. 267 00:13:50.919 --> 00:13:53.879 One really really long time measured in cosmic time scales. 268 00:13:53.879 --> 00:13:57.720 Problem well, easily, it's a vacuum so profound that meaningful 269 00:13:57.840 --> 00:14:01.399 particle interactions or collisions just don't happen. It's stillness on 270 00:14:01.440 --> 00:14:02.639 an unimaginable scale. 271 00:14:02.720 --> 00:14:06.240 Okay, the sheer depth of emptiness, this near total vacuum 272 00:14:06.240 --> 00:14:09.240 in the void core. It sets up this incredible thought experiment, 273 00:14:09.320 --> 00:14:11.440 one that really stood out in the research we looked at. 274 00:14:11.840 --> 00:14:16.200 It almost bridges physics and well philosophy. 275 00:14:15.759 --> 00:14:17.759 It really does. It forces you to think about the 276 00:14:17.840 --> 00:14:20.519 link between the physical structure of the universe, where we 277 00:14:20.519 --> 00:14:22.759 happen to be located, and what that means for life, 278 00:14:22.840 --> 00:14:24.639 for knowledge, for civilization itself. 279 00:14:24.879 --> 00:14:29.559 Right, So let's unpack it. The scenario post is, what 280 00:14:29.639 --> 00:14:33.000 if what if our solar system, the Sun, Earth, all 281 00:14:33.039 --> 00:14:36.759 the planets, wasn't where it is now, inside a galaxy, 282 00:14:36.759 --> 00:14:40.639 inside a filament of the cosmic web. What if somehow 283 00:14:40.879 --> 00:14:43.679 it was transported deep into the core of one of 284 00:14:43.679 --> 00:14:46.559 these massive voids, millions of light years from. 285 00:14:46.399 --> 00:14:49.159 Anything, right plunk down in the middle of that profound emptiness. 286 00:14:49.200 --> 00:14:51.519 What would that even look like? What would the consequences be? 287 00:14:51.720 --> 00:14:55.360 Well, the immediate visual impact, according the analysis is just chilling, 288 00:14:55.559 --> 00:14:58.720 and it dictates everything else. From Earth looking up at 289 00:14:58.759 --> 00:15:02.000 the night sky, there would be no stars, no stars 290 00:15:02.120 --> 00:15:05.360 at all, none, absolutely zero. The only things you'd see 291 00:15:05.360 --> 00:15:08.440 in the sky would be the Sunday obviously, our Moon, 292 00:15:08.559 --> 00:15:10.320 and the other planets in our own solar system. 293 00:15:10.360 --> 00:15:10.679 That's it. 294 00:15:11.039 --> 00:15:15.480 Everything else will be projected against a backdrop of perfect, unending, 295 00:15:15.759 --> 00:15:16.840 unbroken blackness. 296 00:15:16.879 --> 00:15:19.320 Wow. Just imagine that, looking up at night and seeing 297 00:15:19.360 --> 00:15:22.639 nothing but pitch black. Maybe Mars or Jupiter is a 298 00:15:22.639 --> 00:15:25.919 point of light, but absolutely nothing else forever. 299 00:15:26.039 --> 00:15:28.440 We totally take the story night sky for granted, don't we. 300 00:15:28.559 --> 00:15:31.240 It's the constant wallpaper of our existence completely. 301 00:15:31.399 --> 00:15:33.360 Yeah, but we only see those stars. We only know 302 00:15:33.360 --> 00:15:35.720 we're in a galaxy because we happen to live in 303 00:15:35.759 --> 00:15:38.759 a relatively dense neighborhood, a brightly lit street. 304 00:15:38.879 --> 00:15:43.080 Cosmically speaking, exactly, being in a void changes everything for discovery. 305 00:15:43.559 --> 00:15:47.360 If you're that civilization on void Earth, the nearest external 306 00:15:47.360 --> 00:15:51.000 galaxy isn't just far away, it's millions of light years. 307 00:15:50.759 --> 00:15:53.960 Away, and without any nearby stars galaxies, how would you 308 00:15:54.000 --> 00:15:55.679 even know it was out there? How would you even 309 00:15:55.799 --> 00:15:56.759 begin to look? 310 00:15:56.960 --> 00:16:01.120 That's the challenge. Even if this hypothetical avoid civilization developed 311 00:16:01.120 --> 00:16:04.720 telescopes just as powerful as ours today. Say they built 312 00:16:04.759 --> 00:16:07.559 their own version of the James webspased telescope. Okay, that 313 00:16:07.679 --> 00:16:10.639 nearest galaxy, millions of light years distant, would appear as 314 00:16:10.879 --> 00:16:15.360 just the source describes it as a faint, dim smudge 315 00:16:15.639 --> 00:16:17.000 in the extreme distance. 316 00:16:16.720 --> 00:16:18.679 A smudge, not even a point of light, just a 317 00:16:18.679 --> 00:16:20.799 barely detectable, fuzzy patch. 318 00:16:20.559 --> 00:16:23.879 Barely detectable, fainter than the faintest star we could see 319 00:16:23.919 --> 00:16:27.840 with the naked eye. It would require immense effort, long exposures, 320 00:16:27.879 --> 00:16:30.399 complex filtering just to confirm it's even there. 321 00:16:30.600 --> 00:16:35.879 So this leads to a really profound, almost unsettling question, 322 00:16:35.919 --> 00:16:39.080 doesn't it. If you're that civilization, you look up, you 323 00:16:39.120 --> 00:16:43.080 see blackness in your local planets, would you ever even 324 00:16:43.120 --> 00:16:46.679 develop astronomy beyond just mapping your own solar system? 325 00:16:46.759 --> 00:16:47.919 Would the motivation be there? 326 00:16:48.039 --> 00:16:52.360 Right? Would you pour resources into building incredibly advanced telescopes 327 00:16:52.679 --> 00:16:55.960 just to hunt for a single, incredibly faint smudge millions 328 00:16:55.960 --> 00:16:58.519 of light years away, especially when there's no guarantee you'll 329 00:16:58.519 --> 00:16:59.279 find anything at all. 330 00:16:59.519 --> 00:17:02.200 Think about the development of astronomy here on Earth. It 331 00:17:02.240 --> 00:17:07.200 was driven by observing the patterns of nearby bright objects, stars, planets, 332 00:17:07.279 --> 00:17:10.240 the Milky Way arching across the sky, that gave us 333 00:17:10.319 --> 00:17:13.799 data questions, the drive to build better instruments. But in 334 00:17:13.839 --> 00:17:17.519 the void, in the void, astronomical observation beyond your own 335 00:17:17.559 --> 00:17:21.599 system would be incredibly tedious, expensive, and give almost no 336 00:17:21.720 --> 00:17:25.480 immediate payoff the incenting to become cosmologists to study the 337 00:17:25.559 --> 00:17:28.720 universe beyond your own backyard, it would be incredibly low. 338 00:17:28.880 --> 00:17:31.519 The implications are just huge. If you don't see other 339 00:17:31.559 --> 00:17:32.799 galaxies easily, you have. 340 00:17:32.799 --> 00:17:34.160 No visible evidence for them. 341 00:17:34.359 --> 00:17:37.319 You wouldn't see the large scale structure the cosmic web 342 00:17:37.400 --> 00:17:40.000 because the walls are too far away. You wouldn't have 343 00:17:40.200 --> 00:17:43.599 easily measurable markers for things like red shift, which is 344 00:17:43.640 --> 00:17:46.400 how we figured out distances and the expansion of the universe. 345 00:17:46.599 --> 00:17:51.440 Exactly measuring red shift relies on having lots of galaxies 346 00:17:51.839 --> 00:17:55.400 at different distances to compare if your nearest neighbor is 347 00:17:56.079 --> 00:17:58.680 millions of light years off and looks like a smudge, 348 00:17:59.599 --> 00:18:01.519 good Lucke building a Hubble diagram. 349 00:18:01.640 --> 00:18:05.960 So they might never discover the expanding universe very likely not. 350 00:18:06.160 --> 00:18:08.039 They might never conceive of the Big Bang. 351 00:18:08.200 --> 00:18:10.920 How could they? The evidence would be almost completely hidden 352 00:18:10.920 --> 00:18:11.240 from them. 353 00:18:11.319 --> 00:18:15.000 Their entire understanding of physics of reality might be limited 354 00:18:15.000 --> 00:18:18.519 to just their own star system floating alone in an eternal, 355 00:18:18.680 --> 00:18:20.359 unchanging darkness. 356 00:18:19.920 --> 00:18:24.079 Which leads to that ultimate chilling question the source material poses. 357 00:18:24.680 --> 00:18:26.880 Would they even know that the rest of the universe 358 00:18:26.960 --> 00:18:27.359 is out there? 359 00:18:27.400 --> 00:18:30.000 Would they even suspect it, or would they conclude that 360 00:18:30.000 --> 00:18:32.240 their solar system is the entire universe. 361 00:18:32.519 --> 00:18:35.440 It's a profound thought. It really makes you realize how 362 00:18:35.519 --> 00:18:40.240 much of our own scientific understanding are Cosmology. Our physics 363 00:18:40.559 --> 00:18:44.119 isn't just a result of human ingenuity. It's also heavily 364 00:18:44.160 --> 00:18:47.279 dependent on our location, our lucky vantage point. 365 00:18:47.400 --> 00:18:49.359 We're lucky to live in a busy neighborhood. 366 00:18:49.440 --> 00:18:51.640 We really are. We're lucky to be bathed in the 367 00:18:51.680 --> 00:18:54.880 light from nearby stars and galaxies, lucky to be close 368 00:18:54.960 --> 00:18:57.079 enough to the large scale structure that we can actually 369 00:18:57.160 --> 00:19:00.359 map it out. Our ability to measure things like red 370 00:19:00.359 --> 00:19:03.039 shift and the Hubble flow is only easy because we 371 00:19:03.160 --> 00:19:07.200 have thousands millions of galaxies relatively close by to study. 372 00:19:07.359 --> 00:19:10.440 If those data points were all millions of light years away. 373 00:19:10.400 --> 00:19:14.599 The task of discovering cosmology would be almost insurmountably difficult, 374 00:19:15.079 --> 00:19:16.000 maybe impossible. 375 00:19:16.200 --> 00:19:18.839 It really puts things in perspective. So let's just quickly 376 00:19:18.839 --> 00:19:21.200 recap the journey we took today. We started by trying 377 00:19:21.200 --> 00:19:23.920 to grasp the average emptiness of the universe. 378 00:19:23.519 --> 00:19:26.519 Which is already stunningly empty, about one hydrogen atom per 379 00:19:26.559 --> 00:19:28.000 cubic meter on average. 380 00:19:28.039 --> 00:19:31.079 Then we plunged into the voids, finding their average density 381 00:19:31.119 --> 00:19:33.720 is even lower, around twenty percent of that maybe point 382 00:19:33.799 --> 00:19:35.960 two hydrogen atoms per cubic meter. 383 00:19:36.119 --> 00:19:39.000 But realizing that number is skewed high by the denser 384 00:19:39.079 --> 00:19:39.960 edges of the voids. 385 00:19:40.119 --> 00:19:43.400 Right and from there we went into the true deep core, 386 00:19:43.599 --> 00:19:45.000 the heart of the void. 387 00:19:44.960 --> 00:19:50.279 Where the emptiness becomes almost absolute, essentially zero density for 388 00:19:50.599 --> 00:19:53.759 millions of light years at a stretch broken only by 389 00:19:53.759 --> 00:19:57.440 the rarest stray particle or the ghost structure of dark matter. 390 00:19:57.960 --> 00:20:00.839 The main takeaway then, is that voids aren't just holes. 391 00:20:01.200 --> 00:20:04.920 They're fundamental components of the universe's structure. They define the 392 00:20:04.920 --> 00:20:06.960 walls and filaments by their very. 393 00:20:06.799 --> 00:20:10.559 Absence exactly, and while they aren't technically perfectly empty, they 394 00:20:10.599 --> 00:20:13.640 have those dwarf galaxies, the gas threads, the dark matter 395 00:20:13.680 --> 00:20:16.720 mini webs. The level of sheer desolation in their cores 396 00:20:16.759 --> 00:20:19.319 is a type of vacuum that's genuinely hard for us 397 00:20:19.720 --> 00:20:23.440 living here in our dense galaxy to truly wrap our minds. 398 00:20:23.160 --> 00:20:25.960 Around, which loops us right back to that void civilization 399 00:20:26.039 --> 00:20:28.480 thought experiment. Because of the sources we looked at, and 400 00:20:28.599 --> 00:20:30.319 with a really provocative twist on that. 401 00:20:30.319 --> 00:20:32.559