1 00:00:01,280 --> 00:00:03,766 The night sky. 2 00:00:03,790 --> 00:00:07,260 Countless stars and the majestic sweep 3 00:00:07,320 --> 00:00:11,006 of the Milky Way, but beyond our local neighborhood, 4 00:00:11,030 --> 00:00:14,476 across the cosmos, there are over 5 00:00:14,500 --> 00:00:17,130 two trillion more galaxies. 6 00:00:17,230 --> 00:00:19,076 When we first began to observe galaxies, 7 00:00:19,100 --> 00:00:20,640 we collected them like butterflies. 8 00:00:20,700 --> 00:00:23,610 Little by little, we realized that 9 00:00:23,670 --> 00:00:25,310 they formed a web. 10 00:00:25,410 --> 00:00:29,080 The cosmic web is the infrastructure that connects 11 00:00:29,110 --> 00:00:31,050 every corner of the universe. 12 00:00:31,110 --> 00:00:33,356 You don't know anything about our universe 13 00:00:33,380 --> 00:00:35,196 if you don't understand the cosmic web. 14 00:00:35,220 --> 00:00:38,050 It feeds galaxies. It forms galaxies. 15 00:00:38,120 --> 00:00:40,960 It is made of galaxies. 16 00:00:40,990 --> 00:00:44,060 It's the architect of everything, 17 00:00:44,130 --> 00:00:47,960 and our cosmic future depends on it. 18 00:00:48,060 --> 00:00:50,970 The cosmic web is one of the most important parts 19 00:00:51,030 --> 00:00:53,276 of our universe... It plays a key role 20 00:00:53,300 --> 00:00:55,646 in the evolution of the cosmos. 21 00:00:55,670 --> 00:00:58,986 Without the cosmic web, there would be no stars, 22 00:00:59,010 --> 00:01:02,140 no planets, nowhere in the universe where 23 00:01:02,210 --> 00:01:03,980 the conditions of life could exist. 24 00:01:04,080 --> 00:01:07,320 How did the universe go from a hot soup of gas 25 00:01:07,420 --> 00:01:11,250 to a cosmic web, sprinkled with galaxies, 26 00:01:11,290 --> 00:01:13,620 planets, and us? 27 00:01:28,770 --> 00:01:31,070 The universe may appear random. 28 00:01:31,140 --> 00:01:35,710 Two trillion galaxies, spread across the cosmos. 29 00:01:38,520 --> 00:01:41,250 But in this cosmic chaos, 30 00:01:41,320 --> 00:01:45,050 scientists detect water. 31 00:01:45,120 --> 00:01:47,420 When we first saw that the universe was full 32 00:01:47,490 --> 00:01:50,230 of galaxies, it seemed like overwhelming chaos, 33 00:01:50,290 --> 00:01:53,730 but it's not... They're all connected. 34 00:01:53,830 --> 00:01:58,700 Galaxies link up in a gigantic cosmic network 35 00:01:58,800 --> 00:02:00,740 spanning the entire universe. 36 00:02:00,800 --> 00:02:05,810 How this pattern emerged may be cosmology's 37 00:02:05,910 --> 00:02:08,086 biggest puzzle. 38 00:02:08,110 --> 00:02:10,656 In some senses, you don't understand something 39 00:02:10,680 --> 00:02:13,456 unless you understand how it comes into existence 40 00:02:13,480 --> 00:02:14,950 and how it's formed. 41 00:02:15,050 --> 00:02:17,720 And galaxies are the basic building block 42 00:02:17,790 --> 00:02:19,750 of our universe. 43 00:02:19,820 --> 00:02:24,366 To solve this mystery, scientists need to go deep, 44 00:02:24,390 --> 00:02:28,006 to the very edge of the observable universe, 45 00:02:28,030 --> 00:02:31,270 and study light from the first galaxies. 46 00:02:35,040 --> 00:02:37,070 Chile, 2021. 47 00:02:37,110 --> 00:02:41,140 Scientists point the VLT, or Very Large Telescope, 48 00:02:41,240 --> 00:02:45,356 towards the Hubble Ultra Deep Field. 49 00:02:45,380 --> 00:02:48,320 It's a patch of sky famously photographed 50 00:02:48,420 --> 00:02:52,196 by the Hubble Space Telescope in 1995. 51 00:02:52,220 --> 00:02:55,260 The VLT's power allows astronomers to see 52 00:02:55,330 --> 00:02:58,360 much deeper into space. 53 00:02:58,430 --> 00:03:00,230 Imagine you take a grain of sand, 54 00:03:00,330 --> 00:03:02,230 and you put it on your fingertip, 55 00:03:02,330 --> 00:03:04,206 and you hold your arm out like this, 56 00:03:04,230 --> 00:03:07,340 and you block a part of the sky looking 57 00:03:07,400 --> 00:03:09,640 at that grain of sand... That's the size 58 00:03:09,710 --> 00:03:13,140 of the Hubble Ultra Deep Field, and yet it contains 59 00:03:13,240 --> 00:03:15,886 thousands of galaxies in it. 60 00:03:15,910 --> 00:03:20,520 The telescope stares at those galaxies 61 00:03:20,620 --> 00:03:25,620 for 155 hours and picks up the faintest of glows... 62 00:03:27,190 --> 00:03:31,730 ancient hydrogen gas concentrated along a strand 63 00:03:31,830 --> 00:03:35,676 of space 15 million lightyears long. 64 00:03:35,700 --> 00:03:39,276 The filaments are just one tiny section 65 00:03:39,300 --> 00:03:43,140 of the cosmic web, the largest known 66 00:03:43,210 --> 00:03:45,340 structure in the universe. 67 00:03:48,610 --> 00:03:50,250 The scale of the cosmic web is enormous. 68 00:03:50,350 --> 00:03:52,610 It is, by definition, the largest thing 69 00:03:52,680 --> 00:03:54,620 that we can see in our universe. 70 00:03:54,680 --> 00:04:00,050 Today, the cosmic web is a lattice of filaments, 71 00:04:00,120 --> 00:04:03,060 linked streams of hydrogen gas 72 00:04:03,160 --> 00:04:06,730 that form an intergalactic network spanning 73 00:04:06,800 --> 00:04:08,676 the entire universe. 74 00:04:08,700 --> 00:04:10,576 Inside the nodes of the cosmic web, 75 00:04:10,600 --> 00:04:14,446 you'll find galaxies and stars and black holes. 76 00:04:14,470 --> 00:04:16,546 Along the filaments, you'll find gas 77 00:04:16,570 --> 00:04:19,410 that connects these nodes, and the gas will connect 78 00:04:19,510 --> 00:04:22,840 to the other galaxies and clusters of galaxies. 79 00:04:22,950 --> 00:04:25,996 It's this beautiful superhighway of 80 00:04:26,020 --> 00:04:31,050 large cities that are connected through these filaments. 81 00:04:31,120 --> 00:04:33,066 We can see the cosmic web 82 00:04:33,090 --> 00:04:35,060 about as far back as we can look, 83 00:04:35,130 --> 00:04:37,966 and really, galaxies are forming along that web 84 00:04:37,990 --> 00:04:39,830 all the way back. 85 00:04:39,930 --> 00:04:43,230 This cosmic infrastructure dates back 86 00:04:43,330 --> 00:04:45,230 to the earliest days of the universe. 87 00:04:48,810 --> 00:04:52,240 13.8 billion years ago, 88 00:04:52,310 --> 00:04:54,840 the universe ignites in a tiny ball 89 00:04:54,980 --> 00:04:58,210 of super hot energy. 90 00:04:58,310 --> 00:05:02,950 It expands and begins to cool. 91 00:05:03,020 --> 00:05:06,150 Energy transforms into primitive, 92 00:05:06,190 --> 00:05:08,720 subatomic particles of matter. 93 00:05:08,830 --> 00:05:12,790 The heat from the Big Bang is so intense, 94 00:05:12,900 --> 00:05:15,476 gravity is effectively powerless. 95 00:05:15,500 --> 00:05:18,676 The very early universe was super hot, 96 00:05:18,700 --> 00:05:21,340 super energetic, and regular particles 97 00:05:21,400 --> 00:05:23,400 of matter were zipping around so fast 98 00:05:23,510 --> 00:05:26,610 that not even gravity could hold them together. 99 00:05:26,740 --> 00:05:28,286 But regular matter wasn't the only thing 100 00:05:28,310 --> 00:05:29,710 in the early universe. 101 00:05:29,810 --> 00:05:33,050 In the background, gravity is working 102 00:05:33,150 --> 00:05:34,756 on something else... 103 00:05:34,780 --> 00:05:38,250 Regular matter's ghostly cousin, 104 00:05:38,320 --> 00:05:41,820 the invisible substance known today as dark matter. 105 00:05:41,920 --> 00:05:45,830 It makes up about 85 percent of all the matter 106 00:05:45,960 --> 00:05:47,960 created in the early universe. 107 00:05:49,570 --> 00:05:51,830 Normal matter and dark matter both existed 108 00:05:51,970 --> 00:05:54,700 around the time of the Big Bang, but they way they played out 109 00:05:54,770 --> 00:05:55,840 was very different. 110 00:05:55,910 --> 00:05:58,886 Just ten seconds after the Big Bang, 111 00:05:58,910 --> 00:06:03,340 the infant universe is billions of degrees Fahrenheit, 112 00:06:03,410 --> 00:06:06,450 still far too hot for regular matter particles 113 00:06:06,520 --> 00:06:11,620 to clump together, but dark matter plays by different rules. 114 00:06:11,690 --> 00:06:15,060 Dark matter isn't affected by the Big Bang's intense 115 00:06:15,120 --> 00:06:18,060 radiation in the same way that regular matter is, 116 00:06:18,130 --> 00:06:20,176 and so because it's able to cool, 117 00:06:20,200 --> 00:06:24,130 it clumps together in a way that regular matter doesn't. 118 00:06:24,230 --> 00:06:27,276 As dark matter clumps grow, they exert 119 00:06:27,300 --> 00:06:32,410 a gravitational pull and begin to form shadowy structures. 120 00:06:32,510 --> 00:06:35,186 As soon as the dark matter gets a foothold, 121 00:06:35,210 --> 00:06:37,610 we have a place where there's a bit more stuff, 122 00:06:37,710 --> 00:06:40,520 then that attracts more and more dark matter. 123 00:06:40,580 --> 00:06:45,250 380,000 years after the Big Bang, 124 00:06:45,320 --> 00:06:48,620 the intense heat drops to a few thousand degrees. 125 00:06:48,690 --> 00:06:52,630 Normal particles of matter move around more slowly. 126 00:06:52,700 --> 00:06:56,676 Protons and electrons bind together and form 127 00:06:56,700 --> 00:07:00,776 atoms of hydrogen and helium gas. 128 00:07:00,800 --> 00:07:04,540 Then gravity from dark matter starts to work 129 00:07:04,570 --> 00:07:06,070 on regular matter. 130 00:07:06,140 --> 00:07:08,510 Before you know it, you have this very clumpy 131 00:07:08,580 --> 00:07:11,286 universe with these huge dark matter halos 132 00:07:11,310 --> 00:07:14,996 that can now start to draw in also ordinary matter 133 00:07:15,020 --> 00:07:16,850 in the form of gas. 134 00:07:16,990 --> 00:07:21,520 A billion-year building project begins. 135 00:07:21,590 --> 00:07:25,330 The dark matter clumps pulled in clouds of gas... 136 00:07:27,760 --> 00:07:31,676 the foundations of the cosmic web and the galaxies. 137 00:07:31,700 --> 00:07:33,600 Just as when you build a building, you know, 138 00:07:33,670 --> 00:07:35,746 there's a lot of work that happens before 139 00:07:35,770 --> 00:07:38,140 the building goes up, our universe spent 140 00:07:38,210 --> 00:07:40,140 a lot of time laying the groundwork for 141 00:07:40,210 --> 00:07:42,640 this cosmic web before it switched on the lights. 142 00:07:45,050 --> 00:07:47,056 The foundations are complete, 143 00:07:47,080 --> 00:07:49,550 but the job isn't finished. 144 00:07:49,620 --> 00:07:53,450 How did those clouds of gas transform into the greatest 145 00:07:53,520 --> 00:07:55,560 structure in the universe? 146 00:07:57,790 --> 00:08:01,360 The secretive dark matter that brought the gas together 147 00:08:01,430 --> 00:08:04,530 is also on site, managing the build. 148 00:08:04,630 --> 00:08:08,400 It was really the dark matter that called the shots 149 00:08:08,510 --> 00:08:10,946 in cosmic clustering, because it outweighed 150 00:08:10,970 --> 00:08:15,510 the ordinary stuff by a big factor. 151 00:08:15,610 --> 00:08:18,156 In essence, the cosmic web is made of dark matter. 152 00:08:18,180 --> 00:08:21,350 Tendrils of material are stretched out across the cosmos. 153 00:08:21,420 --> 00:08:25,866 As the sprawling structure builds, its gravitational 154 00:08:25,890 --> 00:08:30,320 pull strengthens, pulling in more dark matter. 155 00:08:30,390 --> 00:08:33,676 The clumps begin to collapse and shrink down 156 00:08:33,700 --> 00:08:37,276 into filaments... these meet at even more tightly 157 00:08:37,300 --> 00:08:41,646 packed clusters, creating a huge, dark scaffold 158 00:08:41,670 --> 00:08:44,610 that drags in more hydrogen gas. 159 00:08:44,670 --> 00:08:47,286 Imagine drops of dew on a spider web. 160 00:08:47,310 --> 00:08:50,340 That's like hydrogen blobs being pulled in 161 00:08:50,410 --> 00:08:53,210 to dark matter's cosmic web. 162 00:08:53,320 --> 00:08:57,266 After tens of millions of years of construction, 163 00:08:57,290 --> 00:09:00,660 strands of gas stretch across the cosmos. 164 00:09:00,690 --> 00:09:06,476 Fast forward to now... The web appears 165 00:09:06,500 --> 00:09:10,530 in all its star-spangled glory, lit up with galaxies. 166 00:09:10,600 --> 00:09:13,746 We know at some point, stars and galaxies formed. 167 00:09:13,770 --> 00:09:16,140 The big question is when... What were the first 168 00:09:16,170 --> 00:09:18,986 galaxies like? That's a big mystery. 169 00:09:19,010 --> 00:09:23,210 So how then did the lights of the cosmos switch on? 170 00:09:23,310 --> 00:09:27,210 Evidence suggests that as the universe assembled its web 171 00:09:27,280 --> 00:09:29,766 of dark matter and hydrogen gas, 172 00:09:29,790 --> 00:09:32,720 the biggest stars that have ever lived 173 00:09:32,820 --> 00:09:35,320 set the cosmos ablaze. 174 00:09:44,130 --> 00:09:47,376 2018, scientists study an ancient galaxy, 175 00:09:47,400 --> 00:09:52,910 the catchily named MACS1149-JD1. 176 00:09:55,040 --> 00:09:57,980 There, they find some of the oldest stars 177 00:09:58,080 --> 00:09:59,150 ever detected. 178 00:09:59,180 --> 00:10:03,050 This particular galaxy is exciting, because it's 179 00:10:03,120 --> 00:10:06,850 forming stars just a very short time after the Big Bang. 180 00:10:06,960 --> 00:10:10,866 Those stars could hold clues as to how 181 00:10:10,890 --> 00:10:13,560 the cosmic web that supports the universe 182 00:10:13,600 --> 00:10:16,676 first lit up, but as astronomers study 183 00:10:16,700 --> 00:10:19,070 starlight from when the universe was just 184 00:10:19,140 --> 00:10:22,840 250 million years old, they get a shock. 185 00:10:25,210 --> 00:10:27,556 The stars are not just made up of hydrogen 186 00:10:27,580 --> 00:10:30,080 and helium produced in the Big Bang. 187 00:10:30,150 --> 00:10:35,666 They also contain what astronomers call metals. 188 00:10:35,690 --> 00:10:38,850 Metals in astronomy is everything heavier 189 00:10:38,950 --> 00:10:40,420 than hydrogen and helium. 190 00:10:40,520 --> 00:10:43,320 No matter where it is on the periodic table, 191 00:10:43,390 --> 00:10:46,590 if you're not hydrogen or helium, you are a metal, 192 00:10:46,700 --> 00:10:49,060 even though that makes no sense. 193 00:10:49,100 --> 00:10:52,600 If I were king of astronomy, metals is right out. 194 00:10:52,700 --> 00:10:55,970 The Big Bang only made hydrogen and helium. 195 00:10:56,040 --> 00:10:59,640 Anything heavier than that was churned up in 196 00:10:59,710 --> 00:11:01,756 the cores of dying stars. 197 00:11:01,780 --> 00:11:05,810 The bright stars of this ancient galaxy 198 00:11:05,920 --> 00:11:09,196 dating back to just 250 million years after 199 00:11:09,220 --> 00:11:12,120 the Big Bang contain chemicals that were created 200 00:11:12,190 --> 00:11:16,520 in even earlier stars. 201 00:11:16,590 --> 00:11:18,466 Some of them seem to be nearly the age of 202 00:11:18,490 --> 00:11:21,876 the universe, extremely old, and yet they contain 203 00:11:21,900 --> 00:11:24,970 elements that guarantee they can't have been 204 00:11:25,000 --> 00:11:28,440 the first generation... As old as these stars are, 205 00:11:28,500 --> 00:11:31,310 there must have been something that came before. 206 00:11:31,410 --> 00:11:33,970 The earlier first generation of stars 207 00:11:34,040 --> 00:11:37,310 remains cloaked in mystery. 208 00:11:37,410 --> 00:11:39,796 How did the first stars ignite, 209 00:11:39,820 --> 00:11:43,420 and did they kickstart the formation 210 00:11:43,520 --> 00:11:45,666 of the first galaxies? 211 00:11:45,690 --> 00:11:50,566 It sounds like a classic creation myth, 212 00:11:50,590 --> 00:11:53,330 it's out of the darkness, out of nothing, 213 00:11:53,430 --> 00:11:56,630 structure arrived, and from that structure, 214 00:11:56,700 --> 00:12:00,300 the galaxies, the lights in the universe, turned on. 215 00:12:02,710 --> 00:12:05,286 We've never seen a first-generation star, 216 00:12:05,310 --> 00:12:08,710 but physicists have a theory of how they formed 217 00:12:08,780 --> 00:12:11,310 and what they were like. 218 00:12:12,520 --> 00:12:14,550 Let's step even further back in time, 219 00:12:14,620 --> 00:12:18,050 to around 100 million years after the Big Bang. 220 00:12:18,120 --> 00:12:21,320 The early cosmic web is dark. 221 00:12:21,420 --> 00:12:26,060 There are no stars to illuminate it. 222 00:12:26,130 --> 00:12:30,176 But the universe is ready for stellar ignition. 223 00:12:30,200 --> 00:12:35,370 Cooled down after millions of years of expansion, 224 00:12:35,440 --> 00:12:38,810 the gas clouds clinging to the dark matter scaffold 225 00:12:38,940 --> 00:12:40,610 begin to contract. 226 00:12:40,680 --> 00:12:45,450 As the hydrogen gas clumps together, 227 00:12:45,520 --> 00:12:47,950 larger clouds form super dense, 228 00:12:48,050 --> 00:12:49,996 ultra hot cores. 229 00:12:50,020 --> 00:12:53,350 If you can bring hydrogen together, 230 00:12:53,420 --> 00:12:56,166 and actually get it hot and dense enough, 231 00:12:56,190 --> 00:12:59,060 hydrogen will begin to fuse into helium. 232 00:12:59,100 --> 00:13:01,630 There will be a nuclear fusion reaction going on. 233 00:13:01,730 --> 00:13:06,430 Simulations suggest that some gas clouds are 234 00:13:06,540 --> 00:13:08,800 hundreds of times the mass of the sun. 235 00:13:11,140 --> 00:13:12,970 The stars they produce 236 00:13:13,040 --> 00:13:15,910 are unlike anything that exist today. 237 00:13:18,280 --> 00:13:21,096 So the stars around us today really top out at masses 238 00:13:21,120 --> 00:13:25,050 between let's say 70 to 100 times the mass of our sun. 239 00:13:25,120 --> 00:13:28,060 There's nothing larger than that. 240 00:13:28,120 --> 00:13:32,060 These first stars were up to 1,000 times 241 00:13:32,130 --> 00:13:34,730 more massive than the sun, so if you plopped it 242 00:13:34,800 --> 00:13:36,876 in our solar system, it would extend 243 00:13:36,900 --> 00:13:39,730 all the way past Jupiter... So think about that. 244 00:13:39,800 --> 00:13:41,700 That is incredibly big. 245 00:13:41,770 --> 00:13:44,510 That scale is mind-blowing. 246 00:13:46,280 --> 00:13:48,510 So what happened to these stellar behemoths? 247 00:13:48,610 --> 00:13:53,210 The lifetime of a star has a lot to do with its mass. 248 00:13:53,280 --> 00:13:56,120 The more massive a star is, the more gravity crushes 249 00:13:56,220 --> 00:13:58,820 the interior up to high temperatures, and it burns 250 00:13:58,890 --> 00:14:02,206 through its nuclear fuel even faster, so incredibly, 251 00:14:02,230 --> 00:14:05,060 the more mass there is, the shorter a lifetime 252 00:14:05,130 --> 00:14:07,290 you get for a star. 253 00:14:07,430 --> 00:14:09,676 The first generation of stars are sort of like 254 00:14:09,700 --> 00:14:13,970 the rappers and rock stars of the universe. 255 00:14:14,070 --> 00:14:16,070 They live fast, they die young. 256 00:14:18,910 --> 00:14:21,386 First generation stars didn't live long enough 257 00:14:21,410 --> 00:14:24,950 to form complex galaxies, but they did set 258 00:14:25,010 --> 00:14:26,980 the process in motion. 259 00:14:27,050 --> 00:14:31,266 The lives of the first stars may have been rock and roll, 260 00:14:31,290 --> 00:14:34,560 but their explosive deaths and supernovas 261 00:14:34,620 --> 00:14:38,366 pump the universe full of heavy metal. 262 00:14:38,390 --> 00:14:42,746 In the galaxy today, we see a supernova 263 00:14:42,770 --> 00:14:45,446 maybe every couple of years, close to us every 264 00:14:45,470 --> 00:14:48,400 couple of decades... this must have been a fireworks show, 265 00:14:48,500 --> 00:14:52,970 giant supernovas going off all the time, all around you. 266 00:14:53,080 --> 00:14:58,150 That act of destruction is actually an act of creation. 267 00:14:58,250 --> 00:15:01,320 What a star does in its core is it creates 268 00:15:01,380 --> 00:15:03,566 heavier elements from lighter elements. 269 00:15:03,590 --> 00:15:07,720 That first generation of stars must have been 270 00:15:07,760 --> 00:15:10,666 absolutely incredible, simply exploding 271 00:15:10,690 --> 00:15:14,176 so quickly and unloading all of this wonderful new chemistry 272 00:15:14,200 --> 00:15:16,376 into the galaxy. 273 00:15:16,400 --> 00:15:20,130 200 million years after the Big Bang, 274 00:15:20,200 --> 00:15:23,700 the remains of the first stars flood the interstellar medium 275 00:15:23,810 --> 00:15:28,256 with heavier elements, like carbon, oxygen, 276 00:15:28,280 --> 00:15:30,310 silicon, and iron, 277 00:15:30,410 --> 00:15:34,950 crucial ingredients for the next wave of stars. 278 00:15:35,020 --> 00:15:38,150 It's such a beautiful story, because suddenly the whole 279 00:15:38,190 --> 00:15:40,336 process of star formation changed, 280 00:15:40,360 --> 00:15:44,660 and it literally became easier to make a star. 281 00:15:44,730 --> 00:15:49,830 Heavy elements suck heat out of the surrounding gas. 282 00:15:49,930 --> 00:15:53,230 Cooler clouds crunch down must faster. 283 00:15:53,300 --> 00:15:57,140 The smaller, second-generation stars form rapidly 284 00:15:57,210 --> 00:16:00,210 and in much greater numbers. 285 00:16:00,340 --> 00:16:04,410 Somehow, this mess of stars transformed into a network 286 00:16:04,480 --> 00:16:07,456 of young galaxies, but it wasn't easy, 287 00:16:07,480 --> 00:16:10,050 because as these baby galaxies formed, 288 00:16:10,120 --> 00:16:12,950 a breed of matter-hungry monsters 289 00:16:13,020 --> 00:16:16,260 appeared in the young cosmic web. 290 00:16:22,600 --> 00:16:26,676 13.6 billion years ago, the dark scaffold 291 00:16:26,700 --> 00:16:29,640 that supports all the regular matter in the universe 292 00:16:29,670 --> 00:16:32,810 emerges, ablaze with stars. 293 00:16:35,410 --> 00:16:38,150 But how did this stellar array evolve into a structure 294 00:16:38,210 --> 00:16:40,980 littered with organized galaxies? 295 00:16:41,020 --> 00:16:45,620 It seems they formed under constant threat of destruction. 296 00:16:49,790 --> 00:16:51,330 October 2020. 297 00:16:51,430 --> 00:16:54,960 Astronomers discover a monster lurking 298 00:16:55,030 --> 00:16:58,330 among the cosmic web's earliest structures, 299 00:16:58,400 --> 00:17:02,386 dating to 900 million years after the Big Bang, 300 00:17:02,410 --> 00:17:05,240 a supermassive black hole. 301 00:17:05,310 --> 00:17:09,286 Six galaxies surround this cosmic giant, 302 00:17:09,310 --> 00:17:11,980 caught in its grip, seemingly linked to 303 00:17:12,050 --> 00:17:14,750 the supermassive black hole by filaments 304 00:17:14,780 --> 00:17:18,620 of the developing cosmic web. 305 00:17:18,690 --> 00:17:22,720 It's like the universe has given supermassive black holes 306 00:17:22,790 --> 00:17:24,160 an umbilical cord. 307 00:17:24,230 --> 00:17:28,476 It's like an all-you-can-eat buffet, right there. 308 00:17:28,500 --> 00:17:32,970 Supermassive black holes are hungry beasts. 309 00:17:33,070 --> 00:17:37,400 They feast on any matter that gets too close to them. 310 00:17:37,510 --> 00:17:40,340 Supermassive black holes are likely some of 311 00:17:40,410 --> 00:17:43,510 the most powerful objects in the universe. 312 00:17:43,610 --> 00:17:47,510 They can be anywhere between 100,000 to 10 billion 313 00:17:47,620 --> 00:17:49,550 times the mass of the sun. 314 00:17:49,620 --> 00:17:53,050 Supermassive black holes have been a nemesis 315 00:17:53,090 --> 00:17:56,060 for generations of scientists, not because of 316 00:17:56,130 --> 00:17:59,790 their fearsome nature, but because nobody knows 317 00:17:59,900 --> 00:18:02,630 how they grew so large, so early. 318 00:18:02,700 --> 00:18:05,970 I wish I knew where supermassive black holes 319 00:18:06,040 --> 00:18:08,076 came from... if I knew, I would have a Nobel Prize 320 00:18:08,100 --> 00:18:09,646 hanging around my neck, and I would wear it 321 00:18:09,670 --> 00:18:11,240 every single day. 322 00:18:13,110 --> 00:18:17,410 As someone who deeply loves supermassive black holes, 323 00:18:17,510 --> 00:18:20,150 whose career is based on studying supermassive 324 00:18:20,220 --> 00:18:22,966 black holes, it is very frustrating to not 325 00:18:22,990 --> 00:18:24,720 know where they come from. 326 00:18:24,820 --> 00:18:27,960 Regular stellar black holes are the collapsed 327 00:18:28,060 --> 00:18:30,966 cores of dead stars, ranging from 328 00:18:30,990 --> 00:18:34,376 three to thousands of solar masses, 329 00:18:34,400 --> 00:18:39,500 but supermassive black holes, those are a different beast. 330 00:18:39,570 --> 00:18:42,400 Thirteen billion years ago, not enough stars 331 00:18:42,510 --> 00:18:45,810 had lived and died to build something as huge 332 00:18:45,940 --> 00:18:48,210 as a supermassive black hole. 333 00:18:51,310 --> 00:18:54,656 Now, the cosmic web offers scientists clues 334 00:18:54,680 --> 00:18:56,820 about the black hole conundrum. 335 00:18:56,920 --> 00:19:01,050 We now know supermassive black holes grow 336 00:19:01,120 --> 00:19:04,466 among the lattice of the young cosmic web, 337 00:19:04,490 --> 00:19:08,630 gorging on the hydrogen gas that travels along the filaments. 338 00:19:10,130 --> 00:19:12,230 At the same time, when the cosmic web 339 00:19:12,300 --> 00:19:15,800 is lighting up, supermassive black holes 340 00:19:15,910 --> 00:19:20,140 appear to be stealing star fuel from the young universe. 341 00:19:20,210 --> 00:19:23,980 You might think that would kill a growing galaxy, 342 00:19:24,050 --> 00:19:28,820 and yet most mature galaxies have a supermassive black hole. 343 00:19:28,920 --> 00:19:31,996 They really dominate the physics of what happens 344 00:19:32,020 --> 00:19:34,660 in the centers of galaxies, and even how galaxies 345 00:19:34,720 --> 00:19:36,520 can evolve. 346 00:19:36,630 --> 00:19:39,630 We think these galactic monsters have been around 347 00:19:39,700 --> 00:19:42,830 from the start... How then did the web's 348 00:19:42,930 --> 00:19:47,676 young galaxies develop around supermassive black holes? 349 00:19:47,700 --> 00:19:51,986 The Milky Way's supermassive black hole is called 350 00:19:52,010 --> 00:19:54,240 Sagittarius A-Star. 351 00:19:54,310 --> 00:19:58,080 It's around 27 million miles wide and weighs in 352 00:19:58,150 --> 00:20:01,220 at just over 4 million solar masses. 353 00:20:03,590 --> 00:20:07,166 The environment around Sagittarius A-Star 354 00:20:07,190 --> 00:20:09,820 is very dynamic... It can actually be 355 00:20:09,930 --> 00:20:13,360 a really hellish place... There's this accretion disk 356 00:20:13,430 --> 00:20:15,176 that's full of plasma, it's heated to 357 00:20:15,200 --> 00:20:18,500 thousands of degrees, so you wouldn't necessarily 358 00:20:18,570 --> 00:20:21,370 think that that's a great place for star formation 359 00:20:21,440 --> 00:20:23,270 to happen. 360 00:20:23,340 --> 00:20:26,056 But that's exactly where astronomers 361 00:20:26,080 --> 00:20:28,540 decided to look. 362 00:20:28,580 --> 00:20:31,656 Using the Atacama Large Millimeter Array, 363 00:20:31,680 --> 00:20:34,720 or ALMA for short, scientists scan 364 00:20:34,780 --> 00:20:39,466 the heart of the Milky Way for dense cores of gas and dust, 365 00:20:39,490 --> 00:20:41,960 stellar embryos. 366 00:20:42,060 --> 00:20:46,460 They found more than 800 within just a thousand lightyears 367 00:20:46,530 --> 00:20:48,160 of Sagittarius A-Star, 368 00:20:48,200 --> 00:20:52,776 including more than 40 embryos with energetic jets 369 00:20:52,800 --> 00:20:55,970 blasting from their cores, the telltale sign 370 00:20:56,040 --> 00:20:58,070 of the birth of stars. 371 00:21:02,040 --> 00:21:03,540 It's really surprising to find 372 00:21:03,650 --> 00:21:05,750 those stars there... It's like hearing 373 00:21:05,810 --> 00:21:08,420 babies' cries from a wolf's den. 374 00:21:10,820 --> 00:21:12,950 It's not the place you would expect this to happen, 375 00:21:13,020 --> 00:21:15,566 but in fact, stars are forming there. 376 00:21:15,590 --> 00:21:17,866 Now, it's not as efficient as it is out here 377 00:21:17,890 --> 00:21:20,976 in the suburbs where things are quieter, but it works. 378 00:21:21,000 --> 00:21:25,376 Baby stars igniting and thriving around 379 00:21:25,400 --> 00:21:28,476 a supermassive black hole, the kind of 380 00:21:28,500 --> 00:21:31,340 hostile environment we know existed in the young 381 00:21:31,440 --> 00:21:35,440 cosmic web... Star birth is a key part 382 00:21:35,510 --> 00:21:38,456 of kickstarting young galaxies. 383 00:21:38,480 --> 00:21:41,420 This evidence suggests that star formation 384 00:21:41,480 --> 00:21:44,366 is more resilient than researchers thought, 385 00:21:44,390 --> 00:21:48,320 and they've developed a theory to explain it. 386 00:21:48,390 --> 00:21:51,666 Gas and dust race around the black hole 387 00:21:51,690 --> 00:21:54,360 in the accretion disk... Heated to incredible 388 00:21:54,400 --> 00:21:57,460 temperatures, plumes of gas break off 389 00:21:57,530 --> 00:21:59,330 and blast into space. 390 00:21:59,430 --> 00:22:01,700 The gas rapidly cools, collapses, 391 00:22:01,770 --> 00:22:06,310 and forms baby stars... These accretion disks 392 00:22:06,410 --> 00:22:09,710 are the most chaotic of stellar nurseries. 393 00:22:09,780 --> 00:22:12,980 You see this mechanism that you think is violently 394 00:22:13,050 --> 00:22:15,256 inhibiting star formation, and at the same time, 395 00:22:15,280 --> 00:22:17,520 it's triggering the birth of new stars. 396 00:22:17,620 --> 00:22:22,760 Matter clumps at the cosmic web's intersections, 397 00:22:22,820 --> 00:22:26,060 feeding the supermassive black holes. 398 00:22:26,160 --> 00:22:29,430 Around them, stars burst into life, 399 00:22:29,500 --> 00:22:31,730 slowly building galaxies. 400 00:22:31,770 --> 00:22:35,400 This could be how our own Milky Way formed 401 00:22:35,500 --> 00:22:39,510 among the filaments of the young cosmic web. 402 00:22:39,610 --> 00:22:44,510 But new research suggests that growth in these baby galaxies 403 00:22:44,610 --> 00:22:47,996 requires murder and mayhem, and without them, 404 00:22:48,020 --> 00:22:50,150 we wouldn't exist. 405 00:22:59,060 --> 00:23:01,830 The infant universe is a dramatic place. 406 00:23:01,930 --> 00:23:05,970 Stars ignite, and stars die, 407 00:23:06,070 --> 00:23:10,370 even in the violent surroundings of supermassive black holes. 408 00:23:10,440 --> 00:23:15,986 Baby galaxies form with the cosmic web. 409 00:23:16,010 --> 00:23:17,556 But how do they grow? 410 00:23:17,580 --> 00:23:21,420 Scientists believe the critical factor is galactic turmoil. 411 00:23:24,590 --> 00:23:26,350 The universe does need to churn things up. 412 00:23:26,420 --> 00:23:28,196 You need to break some eggs to make an omelet. 413 00:23:28,220 --> 00:23:30,520 You need to introduce some chaos into your galaxy 414 00:23:30,630 --> 00:23:34,330 to rapidly form stars or grow black holes. 415 00:23:34,400 --> 00:23:39,530 Smashing things together is how the universe came to be. 416 00:23:39,600 --> 00:23:44,070 The Hubble Space Telescope discovers many distorted 417 00:23:44,110 --> 00:23:49,380 galaxies... twisted, battered, and torn, 418 00:23:49,410 --> 00:23:53,396 victims of violent collisions on a cosmic scale. 419 00:23:53,420 --> 00:23:58,420 Galaxies are never sitting quietly, doing nothing. 420 00:23:58,520 --> 00:24:01,820 They're always undergoing change... they're constantly 421 00:24:01,890 --> 00:24:04,466 encountering and slamming into and colliding with 422 00:24:04,490 --> 00:24:06,376 and mixing with other galaxies. 423 00:24:06,400 --> 00:24:09,376 You can see images in Hubble 424 00:24:09,400 --> 00:24:11,976 of total car wrecks, of galaxies that are 425 00:24:12,000 --> 00:24:13,730 trying to merge with each other. 426 00:24:16,510 --> 00:24:19,456 We know that galaxies collide now, 427 00:24:19,480 --> 00:24:21,986 but what about in the early universe, 428 00:24:22,010 --> 00:24:25,080 when the cosmic web was beginning to take shape? 429 00:24:25,150 --> 00:24:30,326 Astronomers study a strange galaxy named Himiko, 430 00:24:30,350 --> 00:24:33,720 born just 800 million years after the Big Bang. 431 00:24:35,790 --> 00:24:40,276 Three bright light sources suggest intense star formation. 432 00:24:40,300 --> 00:24:43,746 Detailed analysis reveals not one galaxy, 433 00:24:43,770 --> 00:24:47,900 but three baby galaxies, not yet fully formed. 434 00:24:50,370 --> 00:24:55,456 Scientists call these youthful star systems protogalaxies. 435 00:24:55,480 --> 00:24:59,556 The trio that make up Himiko are in mid-collision. 436 00:24:59,580 --> 00:25:04,720 Computer simulations of the early universe suggest 437 00:25:04,820 --> 00:25:10,160 protogalaxies smashed together with frightening regularity. 438 00:25:10,190 --> 00:25:13,060 These violent shake-ups trigger star birth. 439 00:25:13,130 --> 00:25:16,976 Protogalaxies are rich in gas, 440 00:25:17,000 --> 00:25:19,330 and when they collide and merge, those gas clouds 441 00:25:19,400 --> 00:25:21,640 collide and collapse and form stars, 442 00:25:21,670 --> 00:25:24,986 sometimes, at prodigious rates, and after a billion years 443 00:25:25,010 --> 00:25:27,170 or so, all of that structure forms, and you get 444 00:25:27,240 --> 00:25:29,210 a formal galaxy. 445 00:25:30,710 --> 00:25:32,256 Picture the early universe, 446 00:25:32,280 --> 00:25:35,150 500 million years after the Big Bang. 447 00:25:35,250 --> 00:25:38,120 It's smaller and more compact than today. 448 00:25:38,220 --> 00:25:40,620 Cosmic collisions are common. 449 00:25:42,160 --> 00:25:44,460 Imagine taking a bunch of cars and just letting them 450 00:25:44,490 --> 00:25:46,066 drive around in Nevada where 451 00:25:46,090 --> 00:25:47,630 there's nothing but space, right? 452 00:25:47,700 --> 00:25:49,530 You're not gonna get too many collisions. 453 00:25:49,570 --> 00:25:52,130 Now squeeze them into a tiny little city block 454 00:25:52,270 --> 00:25:54,830 some place, and you're just gonna have accidents everywhere. 455 00:25:54,940 --> 00:25:56,740 Well, it's the same thing with the universe. 456 00:25:56,770 --> 00:25:58,986 When the universe was younger, it was smaller, 457 00:25:59,010 --> 00:26:01,140 and these protogalaxies were everywhere. 458 00:26:01,180 --> 00:26:02,416 It was crowded. 459 00:26:02,440 --> 00:26:05,550 You were bound to get collisions between them back then. 460 00:26:05,580 --> 00:26:09,096 More and more baby galaxies form at the growing 461 00:26:09,120 --> 00:26:12,320 web's gas-rich intersections. 462 00:26:12,390 --> 00:26:14,866 A collision between small protogalaxies 463 00:26:14,890 --> 00:26:18,766 might trigger modest amounts of star formation 464 00:26:18,790 --> 00:26:23,360 when regions of dense matter come together. 465 00:26:23,430 --> 00:26:25,746 But a merger involving 466 00:26:25,770 --> 00:26:29,040 protogalaxies with rich reserves of gas 467 00:26:29,100 --> 00:26:31,340 can rev up the rate of stellar ignition, 468 00:26:31,410 --> 00:26:35,456 supercharging a growing galaxy. 469 00:26:35,480 --> 00:26:38,556 Gas-rich mergers can generate starburst galaxies, 470 00:26:38,580 --> 00:26:41,950 where we see incredibly vigorous events of star formation. 471 00:26:42,020 --> 00:26:46,396 Astronomers think one such smash-up, 472 00:26:46,420 --> 00:26:49,620 around 10 billion years ago, kickstarted the growth 473 00:26:49,720 --> 00:26:51,266 of the Milky Way. 474 00:26:51,290 --> 00:26:55,076 A group of stars called the Gaia Enceladus Cluster 475 00:26:55,100 --> 00:26:57,360 in the outer reaches of the galaxy 476 00:26:57,430 --> 00:27:01,170 behaves strangely compared to other stars around it. 477 00:27:01,240 --> 00:27:04,746 The stars in the Gaia Enceladus Cluster, 478 00:27:04,770 --> 00:27:07,410 they're different, they move differently, 479 00:27:07,510 --> 00:27:09,256 they act different, they're like... they're like 480 00:27:09,280 --> 00:27:12,450 kids from the next town over showing up at your school. 481 00:27:12,510 --> 00:27:15,150 You just know that they don't belong. 482 00:27:15,220 --> 00:27:18,720 The Milky Way had already largely formed, 483 00:27:18,820 --> 00:27:22,620 and then this massive cluster comes screaming in. 484 00:27:22,720 --> 00:27:24,866 It was a violent event 485 00:27:24,890 --> 00:27:28,730 that eventually ended up absorbing the stars 486 00:27:28,830 --> 00:27:31,060 from this cluster into the body of 487 00:27:31,130 --> 00:27:33,070 the Milky Way itself. 488 00:27:33,130 --> 00:27:37,400 Galaxies are built from these kinds of collisions. 489 00:27:37,510 --> 00:27:41,610 Less than a billion years after the Big Bang, 490 00:27:41,680 --> 00:27:45,510 the dark scaffold of the cosmic web begins to glow. 491 00:27:45,580 --> 00:27:49,820 Matter channeled down the web's tendrils creates 492 00:27:49,950 --> 00:27:53,550 dense clumps of gas... Even in the turbulent 493 00:27:53,620 --> 00:27:56,760 neighborhoods of supermassive black holes, 494 00:27:56,830 --> 00:27:59,676 stars burst into life. 495 00:27:59,700 --> 00:28:03,560 Baby galaxies collide, and the young universe 496 00:28:03,630 --> 00:28:05,576 sparkles with light. 497 00:28:05,600 --> 00:28:10,086 But an important question remains. 498 00:28:10,110 --> 00:28:12,610 In the mayhem of the early universe, 499 00:28:12,710 --> 00:28:15,610 how did galaxies like our Milky Way 500 00:28:15,710 --> 00:28:17,740 survive and thrive? 501 00:28:20,380 --> 00:28:23,096 Galaxy evolution is very dynamic. 502 00:28:23,120 --> 00:28:26,466 Our understanding of galaxy evolution is very dynamic, 503 00:28:26,490 --> 00:28:29,566 and there's so much that we still don't know. 504 00:28:29,590 --> 00:28:31,420 There's a lot of different competing theories 505 00:28:31,490 --> 00:28:34,690 right now as to how galaxies grew into the galaxies 506 00:28:34,800 --> 00:28:36,100 that we see today. 507 00:28:38,200 --> 00:28:39,876 It's a huge open question, and it's something that's 508 00:28:39,900 --> 00:28:41,970 a big deal in science right now. 509 00:28:42,000 --> 00:28:45,810 New research suggests that life and death 510 00:28:45,910 --> 00:28:48,840 in the cradle of the universe lay within 511 00:28:48,940 --> 00:28:50,980 the cosmic web. 512 00:28:58,820 --> 00:29:01,120 13.6 billion years ago, 513 00:29:01,190 --> 00:29:04,006 a protogalaxy, the infant Milky Way, 514 00:29:04,030 --> 00:29:09,230 forms in the tendrils of the young cosmic web. 515 00:29:09,330 --> 00:29:11,176 Today, it bears the scars 516 00:29:11,200 --> 00:29:12,876 of many collisions. 517 00:29:12,900 --> 00:29:15,476 Each one could have torn it apart. 518 00:29:15,500 --> 00:29:19,610 So what controls if a young galaxy lives or dies? 519 00:29:21,280 --> 00:29:23,186 May 2020. 520 00:29:23,210 --> 00:29:26,980 Scientists image a graceful galaxy that existed 521 00:29:27,050 --> 00:29:30,420 just 1.4 billion years after the Big Bang. 522 00:29:30,520 --> 00:29:35,050 Analysis of its light shows this 523 00:29:35,090 --> 00:29:39,166 is a starburst galaxy, pumping out newborn stars. 524 00:29:39,190 --> 00:29:42,876 Galaxies like our Milky Way are old and rather stately, 525 00:29:42,900 --> 00:29:45,876 and they don't form stars very rapidly... 526 00:29:45,900 --> 00:29:49,276 About the equivalent of the mass of the sun every year. 527 00:29:49,300 --> 00:29:51,500 Well, starburst galaxies... Yeah, they form them 528 00:29:51,640 --> 00:29:55,656 a lot more quickly... hundreds of solar masses per year. 529 00:29:55,680 --> 00:29:59,386 But BRI 1335-0417, 530 00:29:59,410 --> 00:30:03,420 4,650 times the mass of the sun every year. 531 00:30:03,520 --> 00:30:06,020 It is blasting out stars. 532 00:30:08,290 --> 00:30:10,620 Some young galaxies in the early universe 533 00:30:10,730 --> 00:30:14,376 appear to be supercharged with star fuel. 534 00:30:14,400 --> 00:30:17,530 How can they grow at such an incredible pace? 535 00:30:20,570 --> 00:30:23,886 Scientists think the answer lies in the mysterious substance 536 00:30:23,910 --> 00:30:27,586 that's controlled the flow of gas since the beginning... 537 00:30:27,610 --> 00:30:30,440 The dark structure whose tendrils stitch 538 00:30:30,510 --> 00:30:33,110 the universe together, 539 00:30:33,220 --> 00:30:38,220 but exploring this cosmic network is no easy task. 540 00:30:38,320 --> 00:30:40,196 When it comes to dark matter, 541 00:30:40,220 --> 00:30:42,420 we're flying blind. 542 00:30:46,600 --> 00:30:48,130 May 2021. 543 00:30:48,230 --> 00:30:51,160 An international team of researchers investigates 544 00:30:51,230 --> 00:30:54,876 dark matter in the local universe by observing 545 00:30:54,900 --> 00:30:58,346 its effect on the path of light. 546 00:30:58,370 --> 00:31:00,970 Gravity affects light. 547 00:31:01,040 --> 00:31:05,080 A massive object causes light to curve 548 00:31:05,150 --> 00:31:08,550 through space, even if that object is invisible, 549 00:31:08,620 --> 00:31:09,950 like dark matter. 550 00:31:11,620 --> 00:31:13,750 We can't see the dark matter directly, but we can see 551 00:31:13,820 --> 00:31:16,320 what it's doing to the light... It's stretching it, 552 00:31:16,390 --> 00:31:18,560 it's bending it, it's creating arcs in ways 553 00:31:18,630 --> 00:31:22,130 that would never happen unless the dark matter were there. 554 00:31:22,230 --> 00:31:24,960 Using an AI program, 555 00:31:25,070 --> 00:31:28,840 the team analyzes 100 million visible galaxies, 556 00:31:28,940 --> 00:31:32,186 looking for warped galactic light. 557 00:31:32,210 --> 00:31:34,740 Because the model is artificially intelligent, 558 00:31:34,810 --> 00:31:38,750 it gets better and better at finding dark matter. 559 00:31:41,680 --> 00:31:44,996 What's very clever about this kind of algorithm 560 00:31:45,020 --> 00:31:47,466 is that it's learning as it goes. 561 00:31:47,490 --> 00:31:49,960 It uses the information that it has 562 00:31:50,020 --> 00:31:53,960 to predict the existence of new structures. 563 00:31:54,030 --> 00:31:56,800 As the model teaches itself to see 564 00:31:56,900 --> 00:31:58,970 the dark matter behind the stars, 565 00:31:59,030 --> 00:32:02,376 it maps out new, dark structures, 566 00:32:02,400 --> 00:32:06,270 never-before-seen highways between galaxies. 567 00:32:06,310 --> 00:32:08,386 There's a lot more filaments, there's a lot more 568 00:32:08,410 --> 00:32:11,840 intricacies, there's a lot more cosmic web there 569 00:32:11,950 --> 00:32:13,710 than what meets the eye. 570 00:32:13,780 --> 00:32:16,996 It's like if you look how 571 00:32:17,020 --> 00:32:20,996 Manhattan is connected to the land around it, 572 00:32:21,020 --> 00:32:23,366 you can see all the bridges, but now we're also seeing 573 00:32:23,390 --> 00:32:25,120 the underwater tunnels. 574 00:32:25,260 --> 00:32:29,060 The new layout of dark matter reveals 575 00:32:29,130 --> 00:32:32,730 the local universe is a bird's nest of hidden channels, 576 00:32:32,800 --> 00:32:35,230 feeding galaxies with gas. 577 00:32:38,040 --> 00:32:40,286 Galactic structures seem to thrive 578 00:32:40,310 --> 00:32:44,340 at the cosmic web's most densely-knotted intersections. 579 00:32:46,480 --> 00:32:48,820 Because multiple filaments are intersected 580 00:32:48,880 --> 00:32:51,320 in those locations, and that is a location 581 00:32:51,420 --> 00:32:54,866 of very enhanced gravity relative to other locations, 582 00:32:54,890 --> 00:32:57,206 the material will be drawn in, 583 00:32:57,230 --> 00:33:00,960 so these galaxy clusters are likely feeding off 584 00:33:01,030 --> 00:33:02,376 the cosmic web. 585 00:33:02,400 --> 00:33:07,276 This connectivity could be the key to the rapidly-forming 586 00:33:07,300 --> 00:33:13,240 galaxies in the early universe, but there's a catch. 587 00:33:13,310 --> 00:33:15,740 Sitting right at the densest regions of 588 00:33:15,810 --> 00:33:18,886 the cosmic web can be really good for galaxy growth. 589 00:33:18,910 --> 00:33:21,196 You have all of this gas being funneled in 590 00:33:21,220 --> 00:33:24,420 for a new star formation, but being that plugged in 591 00:33:24,520 --> 00:33:26,766 to the network isn't all good news. 592 00:33:26,790 --> 00:33:30,120 There is evidence that, though the cosmic web 593 00:33:30,220 --> 00:33:34,530 gives life, it can also take life away. 594 00:33:34,630 --> 00:33:37,530 Scientists studying some of the universe's most heavily 595 00:33:37,600 --> 00:33:40,500 connected galaxies found something unexpected... 596 00:33:40,570 --> 00:33:43,840 Plummeting rates of star birth. 597 00:33:43,940 --> 00:33:46,740 In some ways, it's a little bit counter-intuitive, right? 598 00:33:46,810 --> 00:33:49,986 If these nodes are meeting grounds for all of 599 00:33:50,010 --> 00:33:54,310 this gas, right, why aren't you forming more stars there? 600 00:33:56,180 --> 00:33:58,520 One explanation? In the all-you-can-eat buffet 601 00:33:58,590 --> 00:34:01,966 of the cosmic web's matter-rich junctions, 602 00:34:01,990 --> 00:34:04,560 a young galaxy might over-indulge. 603 00:34:04,630 --> 00:34:10,360 As the cosmic web funnels more matter towards a junction 604 00:34:10,430 --> 00:34:13,600 and its growing galaxies, the gas influx doesn't 605 00:34:13,670 --> 00:34:17,746 just boost star formation, it fattens up 606 00:34:17,770 --> 00:34:21,970 the supermassive black hole at the galaxy's core. 607 00:34:22,040 --> 00:34:24,756 For a young galaxy, that's dangerous, 608 00:34:24,780 --> 00:34:28,350 because when this monster over-eats, it produces 609 00:34:28,450 --> 00:34:31,820 high-energy jets and belches out 610 00:34:31,920 --> 00:34:33,450 super hot wind. 611 00:34:33,520 --> 00:34:37,790 These black holes radiate tremendous amounts of energy 612 00:34:37,930 --> 00:34:40,330 when they grow, and that radiation can 613 00:34:40,430 --> 00:34:42,960 slam into the material around them in the galaxy 614 00:34:43,000 --> 00:34:45,330 and blow it all out of the galaxy, launch it away 615 00:34:45,400 --> 00:34:48,170 or heat it up to super high temperatures. 616 00:34:48,200 --> 00:34:51,840 Star formation requires stuff, so if you blow that stuff 617 00:34:51,940 --> 00:34:54,040 away, how are you gonna form a star? 618 00:34:57,280 --> 00:34:59,250 And what's left behind would be what we call 619 00:34:59,280 --> 00:35:03,720 a quenched galaxy that basically can't form any new stars. 620 00:35:03,820 --> 00:35:06,666 The researchers found that although connectivity 621 00:35:06,690 --> 00:35:10,120 within the cosmic web can boost galactic growth, 622 00:35:10,220 --> 00:35:13,006 it was the super connected galaxies that died 623 00:35:13,030 --> 00:35:18,360 the quickest, choked and stunted like over-watered plants. 624 00:35:18,430 --> 00:35:22,970 Perhaps our Milky Way got lucky. 625 00:35:23,040 --> 00:35:26,346 You could say that the Milky Way Galaxy is sort of 626 00:35:26,370 --> 00:35:29,186 in this Goldilocks zone of galaxy formation. 627 00:35:29,210 --> 00:35:32,250 It's been receiving enough gas over time that it's 628 00:35:32,310 --> 00:35:34,310 been able to keep up with its star formation 629 00:35:34,380 --> 00:35:37,996 but not so much gas that its central black hole 630 00:35:38,020 --> 00:35:41,266 has been fed enough that it would clear the galaxy 631 00:35:41,290 --> 00:35:42,966 out of gas. 632 00:35:42,990 --> 00:35:47,130 The cosmic web determined if galaxies lived or died. 633 00:35:47,200 --> 00:35:51,700 Its construction project brought order to chaos. 634 00:35:51,770 --> 00:35:57,086 The cosmic web is the architect, the engineer, 635 00:35:57,110 --> 00:36:00,240 the builder, the construction worker, even the interior 636 00:36:00,310 --> 00:36:02,340 designer of the cosmos. 637 00:36:04,680 --> 00:36:07,150 But now, work has shut down. 638 00:36:07,220 --> 00:36:10,466 An invisible force threatens to tear apart the very 639 00:36:10,490 --> 00:36:14,366 fabric of the cosmic web... What does this mean 640 00:36:14,390 --> 00:36:16,890 for galaxies and for us? 641 00:36:27,100 --> 00:36:30,646 The cosmic web brought order to the early universe. 642 00:36:30,670 --> 00:36:34,256 The gravitational attraction of its dark scaffolding 643 00:36:34,280 --> 00:36:37,840 helped build galaxies and fueled their development. 644 00:36:37,980 --> 00:36:43,050 But growth tops out at the level of galaxy clusters. 645 00:36:43,120 --> 00:36:45,896 Nothing bigger will ever form. 646 00:36:45,920 --> 00:36:49,866 Something has stopped the formation of structure 647 00:36:49,890 --> 00:36:51,460 in our universe. 648 00:36:51,530 --> 00:36:54,630 To understand what's going on, 649 00:36:54,700 --> 00:36:56,630 we need to return to the Big Bang 650 00:36:56,700 --> 00:36:58,970 and the formation of the cosmic web. 651 00:37:03,100 --> 00:37:08,410 13.8 billion years ago, the universe sparks into life. 652 00:37:08,510 --> 00:37:12,510 A tiny ball of pure energy cools and expands. 653 00:37:15,120 --> 00:37:18,050 The energy transforms into regular matter 654 00:37:18,150 --> 00:37:22,466 and dark matter, but another force appears 655 00:37:22,490 --> 00:37:26,230 at the same time... dark energy. 656 00:37:29,430 --> 00:37:31,676 Dark energy, as far as we understand it, 657 00:37:31,700 --> 00:37:34,970 which is not much, has always been here. 658 00:37:35,070 --> 00:37:37,370 It's always been a part of the universe, 659 00:37:37,440 --> 00:37:40,440 but it's been silent, in the background. 660 00:37:40,510 --> 00:37:44,210 Dark energy is everywhere... It's over here, 661 00:37:44,310 --> 00:37:46,810 it's over there, it's between you and me. 662 00:37:46,910 --> 00:37:48,610 It's absolutely everywhere. 663 00:37:48,720 --> 00:37:52,220 One theory is that dark energy never formed, 664 00:37:52,320 --> 00:37:54,550 that it's just a constant in the laws of physics 665 00:37:54,590 --> 00:37:56,760 that has always been there and always will be. 666 00:37:56,820 --> 00:38:01,236 Some physicists believe that dark energy 667 00:38:01,260 --> 00:38:05,260 is simply the force of emptiness. 668 00:38:05,330 --> 00:38:09,340 People used to take for granted that space was empty, 669 00:38:09,400 --> 00:38:13,286 a vacuum, but the discovery of dark energy 670 00:38:13,310 --> 00:38:15,540 has made some people wonder if space is actually 671 00:38:15,610 --> 00:38:19,550 more of a substance, and, um, that space also 672 00:38:19,610 --> 00:38:21,310 might have pressure that causes things 673 00:38:21,420 --> 00:38:25,366 to push apart, so, you know, whatever space is, 674 00:38:25,390 --> 00:38:28,220 it might be more interesting than we thought. 675 00:38:28,320 --> 00:38:31,966 Dark matter dominates the young universe, 676 00:38:31,990 --> 00:38:36,776 but as the dark scaffold of the cosmic web grows, 677 00:38:36,800 --> 00:38:39,230 it sows the seeds of self-destruction. 678 00:38:40,670 --> 00:38:43,840 As the network of matter takes shape, 679 00:38:43,970 --> 00:38:47,556 pockets of emptiness form between the filaments... 680 00:38:47,580 --> 00:38:49,310 Cosmic voids. 681 00:38:51,810 --> 00:38:56,656 In these expanding hollow spaces, dark energy grows. 682 00:38:56,680 --> 00:38:59,850 The weirdest thing about dark energy is that 683 00:38:59,990 --> 00:39:03,820 it has constant density... Constant density means 684 00:39:03,890 --> 00:39:08,560 the more volume you have, the more dark energy you have, 685 00:39:08,630 --> 00:39:11,130 so the larger the voids get, 686 00:39:11,200 --> 00:39:14,376 the more dark energy they contain. 687 00:39:14,400 --> 00:39:18,170 Dark energy pushes against the cosmic web, 688 00:39:18,240 --> 00:39:20,556 opening up huge chasms in 689 00:39:20,580 --> 00:39:22,556 the architecture of the universe. 690 00:39:22,580 --> 00:39:25,756 Five billion years ago, dark matter's strength of 691 00:39:25,780 --> 00:39:29,750 attraction is finally overwhelmed. 692 00:39:29,820 --> 00:39:32,096 Like bridge cables in a hurricane, 693 00:39:32,120 --> 00:39:35,520 the cosmic web's filaments stretch and snap, 694 00:39:35,620 --> 00:39:40,330 and the universe's substructure fails. 695 00:39:40,430 --> 00:39:45,160 Galactic construction freezes as the universe expands, 696 00:39:45,230 --> 00:39:48,530 but darker times are ahead for the cosmic web. 697 00:39:50,100 --> 00:39:53,070 As time goes on, not only is it expanding, 698 00:39:53,110 --> 00:39:56,080 but this expansion gets faster and faster and faster. 699 00:39:58,680 --> 00:40:01,050 As the dark energy in the voids increases, 700 00:40:01,150 --> 00:40:03,250 the entire structure of the cosmic web 701 00:40:03,320 --> 00:40:06,250 begins to break up. 702 00:40:07,920 --> 00:40:11,106 The effects of dark energy will get stronger 703 00:40:11,130 --> 00:40:13,630 and stronger with time, until the very fabric 704 00:40:13,690 --> 00:40:15,676 of space time gets torn apart. 705 00:40:15,700 --> 00:40:20,500 This isn't a superhero movie... The bad guy wins. 706 00:40:20,600 --> 00:40:24,970 The future of the cosmic web is looking bleak. 707 00:40:25,010 --> 00:40:26,986 Ultimately, it's gonna be 708 00:40:27,010 --> 00:40:29,140 a cold, lonely universe. 709 00:40:29,210 --> 00:40:32,980 Our closest galaxies will accelerate away, 710 00:40:33,010 --> 00:40:36,556 until they're just tiny pinpricks of light. 711 00:40:36,580 --> 00:40:40,120 Then the universe will go dark again. 712 00:40:40,220 --> 00:40:42,960 Everything will fade out. 713 00:40:43,020 --> 00:40:45,420 So the universe started with a bang, 714 00:40:45,490 --> 00:40:48,130 but it will die with a whisper. 715 00:40:48,230 --> 00:40:52,160 The cosmic web transformed the universe 716 00:40:52,230 --> 00:40:56,170 from a hot mess to a sparkling structure. 717 00:40:56,240 --> 00:41:00,170 It gave birth to billions of galaxies and us. 718 00:41:00,240 --> 00:41:02,656 Without it, space would be 719 00:41:02,680 --> 00:41:05,140 a much less interesting place. 720 00:41:05,180 --> 00:41:08,256 This giant structure, the largest thing that we know of 721 00:41:08,280 --> 00:41:12,050 in the universe, is responsible for nourishing the galaxies, 722 00:41:12,120 --> 00:41:14,666 creating the stars, making the conditions right 723 00:41:14,690 --> 00:41:18,720 to form life... we would not be here, talking right now, 724 00:41:18,790 --> 00:41:20,730 if it were not for this cosmic web. 725 00:41:20,790 --> 00:41:24,260 Understanding the cosmic web 726 00:41:24,330 --> 00:41:28,270 is understanding dark matter, is understanding dark energy, 727 00:41:28,340 --> 00:41:32,886 is understanding our past, is understanding our future. 728 00:41:32,910 --> 00:41:35,886 Really, everything that we know about how the universe works 729 00:41:35,910 --> 00:41:39,040 is directly tied to the cosmic web. 730 00:41:39,080 --> 00:41:42,356 It's amazing to think that the overall structure of 731 00:41:42,380 --> 00:41:46,766 the universe that we witness today began in the earliest 732 00:41:46,790 --> 00:41:50,060 times of the universe and has yielded 733 00:41:50,120 --> 00:41:52,760 beings like ourselves who can now 734 00:41:52,830 --> 00:41:55,830 discover it and ponder about its existence. 735 00:41:55,960 --> 00:41:57,360 That's pretty dope.