1 00:00:09,803 --> 00:00:13,043 Our universe is a place of infinite variety. 2 00:00:14,883 --> 00:00:17,163 Two trillion galaxies... 3 00:00:21,123 --> 00:00:23,883 ..billions and billions of stars... 4 00:00:27,123 --> 00:00:32,323 ..and countless planets, worlds beyond imagination. 5 00:00:36,963 --> 00:00:42,243 The universe is so vast, so incomprehensible, so terrifying, 6 00:00:42,243 --> 00:00:45,443 that I think it's quite natural for us to choose to live out our lives 7 00:00:45,443 --> 00:00:47,323 completely oblivious to it. 8 00:00:50,843 --> 00:00:55,003 Perhaps that's why there's a sense of relief that rises with the dawn. 9 00:00:55,003 --> 00:01:00,243 The brightening sky hides the stars and the questions that they pose. 10 00:01:02,163 --> 00:01:05,363 After all, they are the biggest questions. 11 00:01:08,283 --> 00:01:10,163 How did the universe come to be? 12 00:01:11,723 --> 00:01:12,923 Why are we here? 13 00:01:14,323 --> 00:01:16,163 And how will it all end? 14 00:01:22,523 --> 00:01:25,603 We have to face those questions if we're ever to acquire 15 00:01:25,603 --> 00:01:29,283 a truly deep understanding of ourselves. 16 00:01:29,283 --> 00:01:32,203 You see, astronomy challenges us. 17 00:01:32,203 --> 00:01:35,883 From one perspective, we're just grains of sand adrift 18 00:01:35,883 --> 00:01:38,763 in an infinite and indifferent ocean. 19 00:01:38,763 --> 00:01:43,643 But from another perspective, we are nature's most magnificent creation, 20 00:01:43,643 --> 00:01:48,403 collections of atoms that can think and wonder about the universe 21 00:01:48,403 --> 00:01:50,923 and choose to explore it. 22 00:01:53,443 --> 00:01:55,923 OVERLAPPING LAUNCH COUNTDOWNS 23 00:01:57,443 --> 00:02:00,323 We have liftoff... Zero... 24 00:02:05,643 --> 00:02:10,603 In our quest for answers, we're venturing ever further from home, 25 00:02:10,603 --> 00:02:12,243 far beyond the planets... 26 00:02:15,723 --> 00:02:18,043 ..and out to the stars. 27 00:02:21,563 --> 00:02:24,003 Our spacecraft are sending back a stream 28 00:02:24,003 --> 00:02:26,123 of extraordinary revelations... 29 00:02:28,403 --> 00:02:30,643 ..visions of alien worlds... 30 00:02:33,203 --> 00:02:36,243 ..with the ingredients to create life. 31 00:02:43,523 --> 00:02:45,603 We've seen galaxies collide... 32 00:02:50,243 --> 00:02:53,443 ..black holes devouring star systems... 33 00:02:56,483 --> 00:03:00,963 ..and we may have glimpsed the origin of the cosmos itself. 34 00:03:03,923 --> 00:03:07,843 With every new observation, every new piece of knowledge, 35 00:03:07,843 --> 00:03:11,723 there is the opportunity to acquire a deeper understanding. 36 00:03:11,723 --> 00:03:16,443 And as we answer question after question, we get ever closer 37 00:03:16,443 --> 00:03:22,403 to being able to tell what is surely the greatest story ever told. 38 00:03:22,403 --> 00:03:26,443 # Take me away. # 39 00:04:08,243 --> 00:04:13,243 Nasa's Parker Solar Probe, a daring mission to shed light... 40 00:04:14,603 --> 00:04:18,163 ..on the mysteries of our closest star. 41 00:04:28,563 --> 00:04:33,763 This is a journey into never-never-land, you might say. 42 00:04:43,323 --> 00:04:49,683 Nasa's Parker Solar Probe is the first spacecraft to touch a star. 43 00:05:14,443 --> 00:05:18,043 It's designed to fly through the sun's atmosphere... 44 00:05:20,203 --> 00:05:24,163 ..braving temperatures no spacecraft has ever endured. 45 00:05:53,443 --> 00:05:57,683 The Parker Solar Probe is allowing us to know our star 46 00:05:57,683 --> 00:05:59,803 as we've never known it before. 47 00:06:04,603 --> 00:06:09,403 And it's also helping us to tell the story of all the stars. 48 00:06:19,123 --> 00:06:24,203 Our sun is from a long line of stars dating back to the dawn of time... 49 00:06:26,403 --> 00:06:28,283 ..from fierce blue giants... 50 00:06:30,123 --> 00:06:32,443 ..which first lit up the universe... 51 00:06:35,163 --> 00:06:36,843 ..to later generations... 52 00:06:39,483 --> 00:06:43,683 ..whose deaths enriched the cosmos with precious elements... 53 00:06:48,123 --> 00:06:50,763 ..the building blocks of our solar system... 54 00:06:57,963 --> 00:07:00,643 ..and allowed our sun to create the thing 55 00:07:00,643 --> 00:07:03,163 which brings meaning to the cosmos... 56 00:07:11,043 --> 00:07:16,243 ..life, you and me. 57 00:07:56,043 --> 00:07:59,203 We have a strange relationship with the stars, 58 00:07:59,203 --> 00:08:02,363 somewhere between awe and indifference. 59 00:08:04,083 --> 00:08:06,883 I think we take our star, the sun, for granted, 60 00:08:06,883 --> 00:08:09,003 partly because of its predictability. 61 00:08:09,003 --> 00:08:12,843 Every day, it rises in the east and sets in the west... 62 00:08:14,723 --> 00:08:19,003 ..without any help or reverence from us. 63 00:08:23,083 --> 00:08:27,043 But many ancient cultures deified the sun. 64 00:08:27,043 --> 00:08:29,563 They treated it as a god. 65 00:08:29,563 --> 00:08:34,523 And the sun gods were creators and destroyers of worlds. 66 00:08:34,523 --> 00:08:37,203 So which is it? 67 00:08:37,203 --> 00:08:42,643 Well, I think that the modern story of the stars, as told by science, 68 00:08:42,643 --> 00:08:45,443 which is indisputably an epic story, 69 00:08:45,443 --> 00:08:49,963 stretching back over 13 billion years to the origin of the universe, 70 00:08:49,963 --> 00:08:53,563 places them firmly in the realm of the gods. 71 00:09:05,203 --> 00:09:08,963 If we want to understand where these gods came from... 72 00:09:10,603 --> 00:09:12,163 ..we have to go back... 73 00:09:17,483 --> 00:09:20,323 ..to a time before the stars. 74 00:09:49,643 --> 00:09:53,723 In the beginning, the universe was dark. 75 00:09:59,683 --> 00:10:02,043 But it was not empty. 76 00:10:06,243 --> 00:10:09,203 Something was lurking in the void... 77 00:10:12,403 --> 00:10:14,603 ..stretching out tendrils. 78 00:10:36,883 --> 00:10:40,923 The cosmic web grew to become a vast structure... 79 00:10:45,963 --> 00:10:48,443 ..crisscrossing the entire universe. 80 00:10:53,603 --> 00:10:57,603 It was formed by interlocking filaments of dark matter. 81 00:11:03,243 --> 00:11:06,043 And it was at the places where these filaments met... 82 00:11:09,043 --> 00:11:10,523 ..the intersections... 83 00:11:17,083 --> 00:11:23,643 ..that the first stars, our sun's earliest ancestors, were born. 84 00:12:00,043 --> 00:12:04,323 The cosmic web is the scaffolding of the universe, 85 00:12:04,323 --> 00:12:08,763 the vast and intricate structure that spans the void. 86 00:12:14,323 --> 00:12:17,203 The web is made primarily out of dark matter, 87 00:12:17,203 --> 00:12:21,043 a mysterious substance that dominates the universe, 88 00:12:21,043 --> 00:12:23,683 although we don't know what it is. 89 00:12:23,683 --> 00:12:25,843 It's one of the great mysteries in modern physics. 90 00:12:25,843 --> 00:12:28,723 It's probably some kind of particle 91 00:12:28,723 --> 00:12:33,443 that interacts very weakly with itself and with light. 92 00:12:33,443 --> 00:12:35,243 It doesn't interact with light. 93 00:12:35,243 --> 00:12:38,363 You can't see it, which is why it's called dark matter. 94 00:12:39,723 --> 00:12:44,003 But it does influence the universe through its gravity. 95 00:12:48,803 --> 00:12:51,803 It was in the dark heart of the cosmic web 96 00:12:51,803 --> 00:12:55,203 that gravity began to sculpt the early universe... 97 00:12:59,203 --> 00:13:04,363 ..drawing together the two simplest elements - hydrogen and helium... 98 00:13:06,403 --> 00:13:09,963 ..the raw material for the very first stars. 99 00:13:13,523 --> 00:13:17,723 Hydrogen gas clings to the filaments of the web, 100 00:13:17,723 --> 00:13:22,763 attracted there by the gravitational pull of the dark matter. 101 00:13:22,763 --> 00:13:27,283 And where those filaments cross, the gas can become dense enough 102 00:13:27,283 --> 00:13:32,163 to collapse under its own gravity to form great clusters of galaxies, 103 00:13:32,163 --> 00:13:34,683 each filled with billions of stars. 104 00:13:51,283 --> 00:13:54,683 The universe was approaching a turning point. 105 00:13:56,243 --> 00:13:59,123 Hydrogen and helium poured into the regions 106 00:13:59,123 --> 00:14:01,163 where the filaments crossed... 107 00:14:03,523 --> 00:14:06,083 ..gathering into ever denser clouds. 108 00:14:11,083 --> 00:14:13,483 Gravity asserted its grip... 109 00:14:16,603 --> 00:14:19,523 ..and the clouds of gas began to collapse... 110 00:14:24,483 --> 00:14:27,203 ..becoming denser and denser. 111 00:14:30,483 --> 00:14:34,723 And in the densest regions, the gas became so hot... 112 00:14:37,323 --> 00:14:40,083 ..that nuclear fusion reactions began. 113 00:15:01,963 --> 00:15:03,883 And out of the maelstrom... 114 00:15:05,163 --> 00:15:07,883 ..the first gods emerged. 115 00:15:10,603 --> 00:15:12,203 And there was light. 116 00:15:59,483 --> 00:16:01,963 The stars illuminate the universe. 117 00:16:03,003 --> 00:16:06,803 But that is the least interesting thing that they do. 118 00:16:08,643 --> 00:16:10,643 The thing that makes the universe interesting, 119 00:16:10,643 --> 00:16:14,003 that brings meaning to the universe is that - 120 00:16:14,003 --> 00:16:16,683 life, you and me. 121 00:16:16,683 --> 00:16:19,643 And life is just chemistry. 122 00:16:19,643 --> 00:16:23,643 And chemistry requires complex chemical elements. 123 00:16:23,643 --> 00:16:26,883 The only thing that existed in the universe before the stars 124 00:16:26,883 --> 00:16:28,803 was hydrogen and helium. 125 00:16:28,803 --> 00:16:32,483 Life requires carbon and oxygen and iron. 126 00:16:32,483 --> 00:16:36,483 All those things were made in a process called nuclear fusion, 127 00:16:36,483 --> 00:16:40,603 in the cores of stars or even, for the heavier elements like gold, 128 00:16:40,603 --> 00:16:42,963 in the collisions of stars. 129 00:16:42,963 --> 00:16:48,003 So, without the stars, the universe would be uninteresting. 130 00:16:48,003 --> 00:16:49,763 It would be meaningless. 131 00:16:49,763 --> 00:16:53,363 It would be just an infinite box of gas. 132 00:17:06,123 --> 00:17:08,323 The first stars were monsters... 133 00:17:16,963 --> 00:17:19,923 ..hundreds of times as massive as our sun. 134 00:17:24,843 --> 00:17:29,163 They burnt with such ferocity that they shone blue... 135 00:17:32,883 --> 00:17:37,563 ..with surface temperatures in excess of 100,000 degrees. 136 00:17:41,683 --> 00:17:45,083 They were the largest stars ever to have lived... 137 00:17:46,763 --> 00:17:49,443 ..violent and volatile giants. 138 00:17:59,723 --> 00:18:02,483 A star is essentially a balancing act. 139 00:18:02,483 --> 00:18:06,243 The force of gravity is constantly trying to collapse it, 140 00:18:06,243 --> 00:18:10,843 and that pushes its ingredients - primarily hydrogen, single protons - 141 00:18:10,843 --> 00:18:13,243 closer and closer together. 142 00:18:13,243 --> 00:18:16,283 Now, when those protons get close enough together, 143 00:18:16,283 --> 00:18:20,403 another of the fundamental forces of nature, the strong nuclear force, 144 00:18:20,403 --> 00:18:23,643 takes over and it can stick the protons together. 145 00:18:23,643 --> 00:18:28,923 That releases energy, which creates a pressure which holds the star up. 146 00:18:28,923 --> 00:18:33,243 Now, the more massive the star, the stronger the inward pull of gravity, 147 00:18:33,243 --> 00:18:36,963 and the more energy has to be released to maintain the balance, 148 00:18:36,963 --> 00:18:40,283 and so the faster the ingredients are used up. 149 00:19:00,403 --> 00:19:04,083 These giant stars were in a struggle for survival... 150 00:19:05,403 --> 00:19:08,283 ..fighting the relentless pull of gravity... 151 00:19:12,883 --> 00:19:16,203 ..consuming more and more hydrogen fuel 152 00:19:16,203 --> 00:19:19,163 to maintain their precarious equilibrium. 153 00:19:36,363 --> 00:19:39,323 For most of its life, a star burns hydrogen - 154 00:19:39,323 --> 00:19:43,363 the simplest chemical element, with one proton in its nucleus - 155 00:19:43,363 --> 00:19:45,643 into helium, with two protons. 156 00:19:46,683 --> 00:19:49,203 Now, when it runs out of hydrogen in the core, 157 00:19:49,203 --> 00:19:52,123 the core starts to collapse and heat up, 158 00:19:52,123 --> 00:19:56,963 and the star responds by building ever more complex elements. 159 00:19:56,963 --> 00:19:59,123 So it makes carbon, with six protons, 160 00:19:59,123 --> 00:20:01,163 and oxygen, with eight protons, 161 00:20:01,163 --> 00:20:03,923 releasing more and more energy as it goes. 162 00:20:07,123 --> 00:20:10,923 But when the star has assembled iron in its core, 163 00:20:10,923 --> 00:20:13,203 with 26 protons in its nucleus, 164 00:20:13,203 --> 00:20:16,083 no more energy can be released. 165 00:20:16,083 --> 00:20:19,483 The star loses its battle against gravity. 166 00:20:19,483 --> 00:20:20,883 It collapses 167 00:20:20,883 --> 00:20:24,483 and in a final moment of creation, 168 00:20:24,483 --> 00:20:27,603 salvaged, if you like, from its destruction, 169 00:20:27,603 --> 00:20:31,483 it distributes those newly minted heavy chemical elements 170 00:20:31,483 --> 00:20:34,123 out into the universe. 171 00:20:48,923 --> 00:20:52,203 Imagine we could journey back in time 172 00:20:52,203 --> 00:20:57,363 and watch the first star live out its brief, luminous life. 173 00:21:18,123 --> 00:21:21,003 After only a million years, 174 00:21:21,003 --> 00:21:23,563 the star used up all of its fuel... 175 00:21:34,963 --> 00:21:36,883 ..the core collapsed... 176 00:21:52,003 --> 00:21:53,763 ..the star imploded... 177 00:22:06,483 --> 00:22:12,763 ..and then rebounded in a colossal explosion - 178 00:22:12,763 --> 00:22:15,803 a supernova. 179 00:22:36,323 --> 00:22:44,083 In death, the first stars began to transform the cosmos, 180 00:22:44,083 --> 00:22:47,843 enriching the ocean of hydrogen and helium, 181 00:22:47,843 --> 00:22:53,683 which filled the universe with heavy elements, 182 00:22:53,683 --> 00:22:58,163 to build new generations of more complex stars. 183 00:23:06,643 --> 00:23:13,843 Over time, these elements gathered together... 184 00:23:19,323 --> 00:23:23,883 ..creating rich clouds of gas and dust. 185 00:23:32,203 --> 00:23:37,243 Nurseries where new generations of stars were born. 186 00:23:43,243 --> 00:23:49,483 And not just stars, but families of stars - 187 00:23:49,483 --> 00:23:53,043 the first galaxies. 188 00:23:59,003 --> 00:24:01,283 And around this time, 189 00:24:01,283 --> 00:24:04,603 some of the early star systems formed 190 00:24:04,603 --> 00:24:08,723 in our own galaxy, the Milky Way. 191 00:24:19,083 --> 00:24:23,123 A new age of complexity was dawning in the universe. 192 00:24:25,563 --> 00:24:28,683 Now there were stars of different sizes... 193 00:24:34,363 --> 00:24:36,043 ..and different colours... 194 00:24:50,403 --> 00:24:55,283 ..and, crucially, new bodies had appeared... 195 00:25:03,483 --> 00:25:06,883 ..planets. 196 00:25:06,883 --> 00:25:10,003 Places where the rich chemical elements 197 00:25:10,003 --> 00:25:16,723 built by previous generations of stars could finally find a home. 198 00:25:32,563 --> 00:25:34,963 Countless billions of stars have come and gone 199 00:25:34,963 --> 00:25:38,683 since those first giants illuminated the darkness, 200 00:25:38,683 --> 00:25:42,363 each enriching the universe with the material 201 00:25:42,363 --> 00:25:45,003 out of which the next generation formed. 202 00:25:45,003 --> 00:25:48,363 Blue stars and white stars, single stars, 203 00:25:48,363 --> 00:25:53,403 double stars, even triple star systems orbiting around each other. 204 00:25:56,083 --> 00:26:00,923 The conditions were now right for those stars to drive the universe 205 00:26:00,923 --> 00:26:04,323 into a new and profound age of complexity. 206 00:26:34,163 --> 00:26:38,643 Our Sun was formed from the ashes of generations of ancestors. 207 00:26:53,523 --> 00:26:59,643 Just one small star in a galaxy of billions of brilliant gods. 208 00:27:08,803 --> 00:27:11,683 For the first million years of its life, 209 00:27:11,683 --> 00:27:15,923 the Sun was virtually alone, 210 00:27:15,923 --> 00:27:22,563 wreathed in clouds of gas and dust. 211 00:27:22,563 --> 00:27:26,083 The dust slowly clumped together... 212 00:27:29,723 --> 00:27:34,923 ..forming clusters, the size of pebbles, 213 00:27:34,923 --> 00:27:38,123 then boulders... 214 00:27:44,203 --> 00:27:47,003 ..and finally... 215 00:27:47,003 --> 00:27:49,803 ..planets. 216 00:27:55,243 --> 00:27:58,483 But the planets were lifeless rocks. 217 00:28:05,163 --> 00:28:10,803 Only the Sun had the power to turn them into worlds. 218 00:28:17,523 --> 00:28:21,283 Some were too far away from the Sun. 219 00:28:33,883 --> 00:28:36,763 Ice giants - 220 00:28:36,763 --> 00:28:40,803 frozen, seemingly, into infertility. 221 00:28:46,043 --> 00:28:51,083 Others formed too close to the Sun, 222 00:28:51,083 --> 00:28:54,683 seared by a relentless light. 223 00:28:57,403 --> 00:29:03,563 They became scorched desert worlds, 224 00:29:03,563 --> 00:29:08,443 but there was a planet in the Sun's family 225 00:29:08,443 --> 00:29:14,283 that quite by chance formed neither too close nor too far away. 226 00:29:20,683 --> 00:29:27,403 An arcadia, where our star could breathe life into dust. 227 00:29:51,603 --> 00:29:55,723 The planets are just the leftovers from the formation of stars. 228 00:29:55,723 --> 00:29:59,043 The sort of debris, if you like. 229 00:29:59,043 --> 00:30:05,763 It's just little specks orbiting around those magnificent flames, 230 00:30:05,763 --> 00:30:09,203 but the planets are also the places in the universe 231 00:30:09,203 --> 00:30:12,523 where gravity has concentrated the heavy elements 232 00:30:12,523 --> 00:30:15,723 built by previous generations of stars. 233 00:30:15,723 --> 00:30:17,883 And that makes the planets the canvas 234 00:30:17,883 --> 00:30:20,723 on which the stars can create. 235 00:30:22,763 --> 00:30:25,363 The canvas on which the stars can create, 236 00:30:25,363 --> 00:30:26,763 what do I mean by that? 237 00:30:26,763 --> 00:30:28,243 Well, just look around. 238 00:30:28,243 --> 00:30:31,723 Everywhere you look on Earth, there is complexity. 239 00:30:31,723 --> 00:30:33,843 Not only mountains and rivers, 240 00:30:33,843 --> 00:30:37,243 but living things, animals and plants, human beings, 241 00:30:37,243 --> 00:30:38,803 human civilisation, 242 00:30:38,803 --> 00:30:42,803 the most complex thing we know of anywhere in the universe. 243 00:30:42,803 --> 00:30:47,843 So you have to ask yourself, how can it be that such complexity 244 00:30:47,843 --> 00:30:51,643 can emerge completely naturally in the universe? 245 00:30:56,043 --> 00:31:00,683 Well, the answer, in fact, was known in the 19th century, 246 00:31:00,683 --> 00:31:04,243 and it comes from the science of thermodynamics. 247 00:31:06,643 --> 00:31:08,083 In the 19th century, 248 00:31:08,083 --> 00:31:10,963 people were interested in the efficiency of steam engines, 249 00:31:10,963 --> 00:31:14,403 and steam engines are, after all, the machines that powered 250 00:31:14,403 --> 00:31:18,683 the factories that allowed people to build increasingly complex things. 251 00:31:18,683 --> 00:31:23,363 And it turns out that the only thing that matters for a steam engine, 252 00:31:23,363 --> 00:31:25,563 the thing that determines its efficiency, 253 00:31:25,563 --> 00:31:28,923 the thing that allows it to do work and build things 254 00:31:28,923 --> 00:31:33,003 is the temperature difference between the fire, 255 00:31:33,003 --> 00:31:35,483 the furnace and the heart of the steam engine 256 00:31:35,483 --> 00:31:38,363 and the cold environment surrounding it. 257 00:31:41,003 --> 00:31:45,883 In the universe, the stars are hot spots in a cold sky. 258 00:31:45,883 --> 00:31:48,763 We are sitting, in a very real sense, 259 00:31:48,763 --> 00:31:55,243 inside a giant steam engine, powered by the furnace of the Sun. 260 00:31:55,243 --> 00:31:59,963 And it's in that sense that the stars are the creators 261 00:31:59,963 --> 00:32:02,803 of complexity in the universe. 262 00:32:06,603 --> 00:32:11,123 But creating complexity is a subtle art. 263 00:32:12,763 --> 00:32:14,443 You need an engine - 264 00:32:14,443 --> 00:32:18,883 in this case, a star that's not too wild and flashy. 265 00:32:22,763 --> 00:32:27,923 A star which is consistent enough for long enough 266 00:32:27,923 --> 00:32:30,723 to kindle the sparks of life... 267 00:32:36,363 --> 00:32:40,043 ..and allow those sparks to flicker and flourish. 268 00:32:53,403 --> 00:32:56,443 The most important property of a star, 269 00:32:56,443 --> 00:33:00,883 if it's to nurture a civilisation, 270 00:33:00,883 --> 00:33:04,043 is magnificent dependability. 271 00:33:29,123 --> 00:33:33,163 No-one knows exactly how life on Earth emerged... 272 00:33:39,683 --> 00:33:43,443 ..but what we do know is that at some point, 273 00:33:43,443 --> 00:33:49,203 primitive cells living in the ocean began using the Sun's energy 274 00:33:49,203 --> 00:33:52,843 to power life-giving chemical reactions. 275 00:33:54,923 --> 00:34:02,563 These cells formed a bridge between Earth and Sun, 276 00:34:02,563 --> 00:34:08,403 delicate engines which harness the fires of our star, 277 00:34:08,403 --> 00:34:14,163 using sunlight to turn carbon dioxide and water into food. 278 00:34:20,683 --> 00:34:24,683 This process, known as photosynthesis, 279 00:34:24,683 --> 00:34:27,323 unleashed the Sun's creative power... 280 00:34:41,843 --> 00:34:45,203 ..and drove the evolution of complexity... 281 00:34:53,803 --> 00:34:56,963 ..from primitive bacteria, 282 00:34:56,963 --> 00:34:59,523 to plants and trees... 283 00:35:11,963 --> 00:35:14,883 ..and, ultimately, 284 00:35:14,883 --> 00:35:19,563 to you and me. 285 00:35:19,563 --> 00:35:24,763 Photosynthesis is a process that's very easy to describe in words. 286 00:35:24,763 --> 00:35:27,563 The plants take energy from the Sun 287 00:35:27,563 --> 00:35:31,523 then use it to react carbon dioxide and water together 288 00:35:31,523 --> 00:35:34,923 to make sugars and a waste product, oxygen. 289 00:35:34,923 --> 00:35:36,603 Really easy to say. 290 00:35:36,603 --> 00:35:38,523 Very difficult to do. 291 00:35:38,523 --> 00:35:41,843 I mean, there's a part of that photosynthetic machinery, 292 00:35:41,843 --> 00:35:43,443 everything you see here, 293 00:35:43,443 --> 00:35:46,683 every plant on the planet's got a photosystem, too. 294 00:35:46,683 --> 00:35:52,443 It's comprised of 46,630 atoms, 295 00:35:52,443 --> 00:35:55,603 all working together in an intricate machine. 296 00:35:55,603 --> 00:35:59,963 Very efficient. It took billions of years of evolution. 297 00:35:59,963 --> 00:36:04,163 Then we eat the plants, or we eat something that's eaten the plants 298 00:36:04,163 --> 00:36:06,883 and we do the reverse reaction. 299 00:36:06,883 --> 00:36:10,963 We take those sugars and we breathe in that waste product, oxygen, 300 00:36:10,963 --> 00:36:13,843 react them together, release a bit of energy, 301 00:36:13,843 --> 00:36:16,283 a bit of the stored sunlight, if you like, 302 00:36:16,283 --> 00:36:19,483 and we use that energy to maintain our structure, 303 00:36:19,483 --> 00:36:22,443 to grow, to live. 304 00:36:29,203 --> 00:36:32,963 Trillions of stars have existed since the universe began... 305 00:36:37,963 --> 00:36:44,123 ..but ours has nurtured that most miraculous thing, 306 00:36:44,123 --> 00:36:46,963 life. 307 00:36:48,803 --> 00:36:52,963 And that makes the Sun a truly remarkable star. 308 00:37:01,883 --> 00:37:03,723 That is the only star we know of 309 00:37:03,723 --> 00:37:08,163 anywhere where there are collections of atoms in orbits around it, 310 00:37:08,163 --> 00:37:09,803 you and me, 311 00:37:09,803 --> 00:37:11,923 that have named it. 312 00:37:11,923 --> 00:37:13,843 The Sun, our Sun. 313 00:37:13,843 --> 00:37:18,003 We've worshipped it, deified it since the dawn of history. 314 00:37:18,003 --> 00:37:21,363 In fact, it's been argued that the Sun lies at the foundation 315 00:37:21,363 --> 00:37:25,803 of all religion, and there may be some truth in that. 316 00:37:25,803 --> 00:37:29,043 In fact, I think there is a deep truth in that, 317 00:37:29,043 --> 00:37:31,923 because we all owe our existence, 318 00:37:31,923 --> 00:37:34,443 this brief time we have in the universe, 319 00:37:34,443 --> 00:37:36,123 to that star. 320 00:37:36,123 --> 00:37:39,483 In fact, in a deeper sense, to all the stars. 321 00:37:39,483 --> 00:37:44,843 We don't need to invent imaginary gods to explain the universe. 322 00:37:44,843 --> 00:37:47,723 We can replace them with the real thing. 323 00:38:01,523 --> 00:38:03,723 Everyone we love... 324 00:38:09,003 --> 00:38:11,003 ..everything we value... 325 00:38:14,083 --> 00:38:18,203 ..our supreme accomplishments as a civilisation... 326 00:38:22,603 --> 00:38:25,603 ..were created and crafted... 327 00:38:29,043 --> 00:38:31,523 ..by stars. 328 00:38:50,603 --> 00:38:54,243 There are over 200 billion stars in our galaxy... 329 00:38:59,323 --> 00:39:04,163 ..and there are two trillion galaxies in the observable universe. 330 00:39:13,283 --> 00:39:15,923 We're living in the Age of Stars... 331 00:39:26,763 --> 00:39:30,283 ..an era of light and life in the cosmos. 332 00:39:36,283 --> 00:39:41,523 From our fleeting human perspective, stars seem eternal... 333 00:40:01,763 --> 00:40:05,363 ..but even gods are not immortal. 334 00:40:09,483 --> 00:40:14,163 Where there is light, 335 00:40:14,163 --> 00:40:17,923 there is darkness. 336 00:40:20,523 --> 00:40:23,123 Stars are creators... 337 00:40:28,643 --> 00:40:32,083 ..but they can be jealous guardians of their creations. 338 00:40:37,003 --> 00:40:43,563 Many smaller stars don't die in spectacular explosions, 339 00:40:43,563 --> 00:40:50,243 instead, they slowly. fade away. 340 00:40:50,243 --> 00:40:56,283 They hang on to the precious elements they made, 341 00:40:56,283 --> 00:41:02,723 becoming fossil stars... 342 00:41:02,723 --> 00:41:08,403 ..and as more fossils litter the universe, 343 00:41:08,403 --> 00:41:14,843 more life-giving elements remain locked away, 344 00:41:14,843 --> 00:41:18,523 starving the cosmos of the material needed 345 00:41:18,523 --> 00:41:21,963 to make new generations of stars. 346 00:41:38,923 --> 00:41:43,523 The Age of Stars may seem infinite, 347 00:41:43,523 --> 00:41:47,443 but it had a beginning 348 00:41:47,443 --> 00:41:49,563 and it will also have an end. 349 00:41:53,043 --> 00:41:56,723 Imagine a timeline of the universe 350 00:41:56,723 --> 00:42:00,043 and imagine that this is the origin of the universe, 351 00:42:00,043 --> 00:42:03,363 the Big Bang, 13.8 billion years ago. 352 00:42:03,363 --> 00:42:07,163 After 100 million years or so, the first stars formed. 353 00:42:07,163 --> 00:42:11,963 On this scale, one centimetre is about 20 million years. 354 00:42:11,963 --> 00:42:16,923 After four billion years, the peak rate of star formation occurred. 355 00:42:16,923 --> 00:42:20,523 The maximum number of new stars were born. 356 00:42:20,523 --> 00:42:23,363 After nine billion years, 357 00:42:23,363 --> 00:42:25,883 our Sun was born. 358 00:42:25,883 --> 00:42:27,683 And today we stand, 359 00:42:27,683 --> 00:42:30,483 13.8 billion years later, 360 00:42:30,483 --> 00:42:34,363 about halfway through the lifetime of our Sun. 361 00:42:34,363 --> 00:42:37,403 Now, in about five billion years' time, 362 00:42:37,403 --> 00:42:40,883 our Sun will die, but new stars will be born 363 00:42:40,883 --> 00:42:43,603 and many of the oldest stars in the universe, 364 00:42:43,603 --> 00:42:46,963 the smallest stars, will continue to shine. 365 00:42:46,963 --> 00:42:51,523 In fact, we think that the last star will cease to shine, 366 00:42:51,523 --> 00:42:53,363 the universe will go dark, 367 00:42:53,363 --> 00:42:56,243 in around ten trillion years. 368 00:42:57,643 --> 00:43:03,083 On this scale, that's about 5,000 metres away from the Big Bang. 369 00:43:03,083 --> 00:43:04,803 But that's not the end of the universe. 370 00:43:04,803 --> 00:43:10,683 As far as we know, the universe will continue expanding forever. 371 00:43:10,683 --> 00:43:15,763 And so the Age of Starlight is the briefest moment of time 372 00:43:15,763 --> 00:43:18,083 in the infinite history of the universe. 373 00:43:18,083 --> 00:43:23,443 The Age of Darkness will go on and on and on. 374 00:43:29,803 --> 00:43:35,643 Stars won't just disappear, of course. 375 00:43:35,643 --> 00:43:39,843 They'll be here for aeons to come. 376 00:43:41,403 --> 00:43:48,003 But over time, the universe, will grow darker, 377 00:43:48,003 --> 00:43:51,003 colder and emptier. 378 00:44:01,283 --> 00:44:03,963 There are stars around today that existed 379 00:44:03,963 --> 00:44:06,883 close to the beginning of the Age of Stars... 380 00:44:15,603 --> 00:44:19,403 ..and some of them will also witness the end. 381 00:44:23,723 --> 00:44:29,123 They're the longest lived stars in the universe, 382 00:44:29,123 --> 00:44:31,763 red dwarfs. 383 00:44:38,963 --> 00:44:41,923 TRAPPIST-1 is one of these ancients. 384 00:44:49,003 --> 00:44:53,483 It's already more than seven billion years old, 385 00:44:53,483 --> 00:44:55,963 almost twice as old as our Sun... 386 00:45:05,723 --> 00:45:08,403 ..but only around a tenth of the size... 387 00:45:14,603 --> 00:45:18,363 ..and less than 1% as bright. 388 00:45:21,363 --> 00:45:27,163 It's a cool star, slow-burning... 389 00:45:32,763 --> 00:45:36,083 ..and that is the secret of its longevity. 390 00:45:40,843 --> 00:45:43,723 Because they burn slowly, 391 00:45:43,723 --> 00:45:46,683 red dwarfs live for a very long time... 392 00:45:53,603 --> 00:45:57,683 ..far longer than any other star. 393 00:46:03,123 --> 00:46:08,683 Like the Sun, TRAPPIST-1 has its own planets - 394 00:46:08,683 --> 00:46:13,843 seven rocky worlds, 395 00:46:13,843 --> 00:46:16,083 each roughly the size of Earth. 396 00:46:20,723 --> 00:46:23,723 Some may have atmospheres 397 00:46:23,723 --> 00:46:25,963 and even oceans... 398 00:46:33,843 --> 00:46:38,043 ..but there the similarity ends... 399 00:46:48,843 --> 00:46:51,203 ..because these are strange worlds. 400 00:46:54,323 --> 00:47:00,283 Every one of these planets is locked in its orbit, 401 00:47:00,283 --> 00:47:04,763 one side facing TRAPPIST-1, 402 00:47:04,763 --> 00:47:06,443 the other side frozen, 403 00:47:06,443 --> 00:47:10,763 permanently exposed to the cold void of space. 404 00:47:23,083 --> 00:47:31,003 If you could stand on the surface of one of these ancient worlds... 405 00:47:31,003 --> 00:47:38,883 ..as the aeons passed... 406 00:47:38,883 --> 00:47:46,203 ..you could watch the future of the cosmos slowly unfold. 407 00:47:55,323 --> 00:48:02,163 And one day, five billion years from now, 408 00:48:02,163 --> 00:48:10,163 you'd see our Sun flicker and fade away forever. 409 00:48:38,563 --> 00:48:42,763 The death of our Sun will probably go unremarked. 410 00:48:44,523 --> 00:48:47,203 We had hope that we'll be around to see it. 411 00:48:47,203 --> 00:48:50,763 Maybe some alien astronomer on a world far away 412 00:48:50,763 --> 00:48:55,043 across the Milky Way will see it through the end of their telescope, 413 00:48:55,043 --> 00:48:57,203 but I don't think they'll give it a second thought. 414 00:48:57,203 --> 00:48:59,363 We've seen hundreds of stars die 415 00:48:59,363 --> 00:49:01,643 and we don't give them a second thought. 416 00:49:01,643 --> 00:49:06,683 But I think the death of our Sun will matter here locally 417 00:49:06,683 --> 00:49:09,163 in this little corner of the galaxy, 418 00:49:09,163 --> 00:49:12,443 because it will mark the end of a glorious time 419 00:49:12,443 --> 00:49:14,483 in the history of our galaxy, 420 00:49:14,483 --> 00:49:18,283 where meaning, where science and literature 421 00:49:18,283 --> 00:49:21,923 and art and poetry and music existed here. 422 00:49:21,923 --> 00:49:23,963 And that does matter. 423 00:49:26,923 --> 00:49:29,643 Why does meaning have to be eternal? 424 00:49:29,643 --> 00:49:33,643 It's the fragility of our lives that makes them valuable. 425 00:49:39,083 --> 00:49:42,403 I think the wonderful thing is that our star 426 00:49:42,403 --> 00:49:46,723 has taken the laws of nature here on this planet 427 00:49:46,723 --> 00:49:50,883 and crafted such a magnificent expression of them. 428 00:49:50,883 --> 00:49:55,763 You, me and all this. 429 00:50:23,803 --> 00:50:28,883 Stars like TRAPPIST-1 will linger on long after the death of our Sun. 430 00:50:36,763 --> 00:50:40,323 We will never know the name of the last star... 431 00:50:48,043 --> 00:50:54,443 ..but we know that the last star to shine... 432 00:50:54,443 --> 00:50:57,123 ..will be a red dwarf. 433 00:51:03,323 --> 00:51:09,323 The last star will slowly cool 434 00:51:09,323 --> 00:51:15,003 and fade away. 435 00:51:25,123 --> 00:51:29,923 With its passing, the universe will become, once again, 436 00:51:29,923 --> 00:51:36,403 a void, 437 00:51:36,403 --> 00:51:39,283 without light 438 00:51:39,283 --> 00:51:43,963 or life 439 00:51:43,963 --> 00:51:47,843 or meaning. 440 00:52:04,683 --> 00:52:06,603 The stars illuminate the universe 441 00:52:06,603 --> 00:52:13,683 and create its most intricate structures, 442 00:52:13,683 --> 00:52:16,963 and one day they will all be gone. 443 00:52:20,403 --> 00:52:24,363 The stars are gods, but they are mortal gods. 444 00:52:24,363 --> 00:52:27,723 And when that time comes when the last stars have faded 445 00:52:27,723 --> 00:52:32,123 and all possibility of life and meaning in the universe 446 00:52:32,123 --> 00:52:33,363 has faded with them, 447 00:52:33,363 --> 00:52:36,763 they will have left the most profound legacy 448 00:52:36,763 --> 00:52:40,923 because for a moment in the long history of the universe, 449 00:52:40,923 --> 00:52:44,483 the stars illuminated the dark 450 00:52:44,483 --> 00:52:47,363 and allowed us to illuminate it, too. 451 00:52:47,363 --> 00:52:50,123 MUSIC: Who Knows Where The Time Goes? by Fairport Convention 452 00:52:50,123 --> 00:52:58,083 # For who knows where the time goes? 453 00:53:00,283 --> 00:53:07,723 # Who knows where the time goes? # 454 00:53:21,403 --> 00:53:25,923 We want to study the Sun because it teaches us a lot about stars. 455 00:53:25,923 --> 00:53:29,563 It teaches us a lot about all the other millions and billions 456 00:53:29,563 --> 00:53:32,043 of stars in our galaxy and beyond. 457 00:53:39,963 --> 00:53:43,083 There was a moment when we were putting the spacecraft together 458 00:53:43,083 --> 00:53:45,723 that I just took a moment and looked at the spacecraft 459 00:53:45,723 --> 00:53:50,203 and realised this is going into a star. 460 00:53:50,203 --> 00:53:52,923 And to realise how special it was 461 00:53:52,923 --> 00:53:56,003 to be able to have worked on this 462 00:53:56,003 --> 00:54:00,483 and that humanity decided this was something we wanted to do. 463 00:54:00,483 --> 00:54:02,723 Status check. 464 00:54:02,723 --> 00:54:05,723 Go, Delta. Go, PSP. 465 00:54:05,723 --> 00:54:07,043 Minus 15. 466 00:54:07,043 --> 00:54:10,123 Launch night, I was sick to my stomach. 467 00:54:10,123 --> 00:54:12,963 Five, four, three, 468 00:54:12,963 --> 00:54:14,283 two, one, 469 00:54:14,283 --> 00:54:16,683 zero. 470 00:54:16,683 --> 00:54:20,163 Liftoff of the mighty Delta IV Heavy rocket 471 00:54:20,163 --> 00:54:22,803 with Nasa's Parker Solar Probe. 472 00:54:22,803 --> 00:54:24,683 There we go. 473 00:54:24,683 --> 00:54:27,643 The spacecraft is the first that NASA has named after a living 474 00:54:27,643 --> 00:54:31,123 person because Eugene Parker is really such, you know, 475 00:54:31,123 --> 00:54:33,643 an eminent physicist in our field. 476 00:54:35,043 --> 00:54:37,643 The Delta IV Heavy is a very slow rocket 477 00:54:37,643 --> 00:54:40,683 compared to the other launches I've seen, 478 00:54:40,683 --> 00:54:45,243 so I just saw fireballs and was very, very frightened for a while. 479 00:54:45,243 --> 00:54:47,203 25 seconds into flight. 480 00:54:49,003 --> 00:54:51,923 Temp pressures continue to look good on all three boosters. 481 00:54:51,923 --> 00:54:54,083 Then realising that this was all OK, 482 00:54:54,083 --> 00:54:57,923 as it slowly made its way up into the sky. 483 00:54:57,923 --> 00:55:00,283 Now, 50 seconds into flight. 484 00:55:06,403 --> 00:55:08,843 Parker Solar Probe is so revolutionary 485 00:55:08,843 --> 00:55:12,083 because it's the first time that we're actually going in 486 00:55:12,083 --> 00:55:14,603 to touch the Sun. 487 00:55:14,603 --> 00:55:18,363 We're going 94% of the way from the Earth to the Sun 488 00:55:18,363 --> 00:55:23,483 to actually experience the solar corona, the Sun's atmosphere. 489 00:55:23,483 --> 00:55:26,003 I think at closest approach, 490 00:55:26,003 --> 00:55:29,483 it'll be about eight solar radii from the Sun, 491 00:55:29,483 --> 00:55:32,443 which is just mind-blowingly close. 492 00:55:35,683 --> 00:55:39,483 So we were expecting things to be very hot, 493 00:55:39,483 --> 00:55:41,563 over 2,500 Fahrenheit, 494 00:55:41,563 --> 00:55:44,683 but in a soup of a million degree plasma. 495 00:55:49,163 --> 00:55:51,123 That's a real challenge for the spacecraft 496 00:55:51,123 --> 00:55:52,843 to survive that environment. 497 00:55:52,843 --> 00:55:55,403 So in order to do that, there's a very large heat shield 498 00:55:55,403 --> 00:55:57,003 on the front of the spacecraft, 499 00:55:57,003 --> 00:55:59,523 which protects the majority of the instruments 500 00:55:59,523 --> 00:56:02,123 which are sat behind on the spacecraft body. 501 00:56:04,123 --> 00:56:07,883 What makes Parker so great is the fact that it has a set 502 00:56:07,883 --> 00:56:11,763 of instruments that work together in order to look in all directions, 503 00:56:11,763 --> 00:56:15,203 in order to solve those big mysteries about the solar wind. 504 00:56:22,123 --> 00:56:26,203 The solar corona has been mysterious to us since we've known about it, 505 00:56:26,203 --> 00:56:27,843 so it's a very strange thing. 506 00:56:27,843 --> 00:56:31,403 The surface of the Sun is sort of 6,000 degrees, 507 00:56:31,403 --> 00:56:34,123 and then above that, you have this very thin atmosphere 508 00:56:34,123 --> 00:56:36,843 that's a million degrees, super hot. 509 00:56:36,843 --> 00:56:39,923 And the way that's heated, we know it has something to do 510 00:56:39,923 --> 00:56:43,523 with magnetic fields, but we don't know exactly how it works. 511 00:56:43,523 --> 00:56:45,683 That's where the solar wind is generated. 512 00:56:45,683 --> 00:56:48,283 We don't know quite exactly how that works, either. 513 00:56:49,923 --> 00:56:55,523 Other things that have come out of this are coronal mass ejections. 514 00:56:55,523 --> 00:56:57,763 When we originally did the proposal, 515 00:56:57,763 --> 00:57:00,363 we were thinking that we would see five 516 00:57:00,363 --> 00:57:05,083 in the entire seven year mission, if we were lucky. 517 00:57:05,083 --> 00:57:09,403 We ended up seeing around four to five in the first year, 518 00:57:09,403 --> 00:57:12,643 so there has been just a total switch 519 00:57:12,643 --> 00:57:16,083 in terms of how active the Sun is 520 00:57:16,083 --> 00:57:18,603 or what we classify as coronal mass ejections. 521 00:57:18,603 --> 00:57:20,523 Maybe a little bit of both. 522 00:57:26,003 --> 00:57:29,483 It is a joy to see all the data coming back. 523 00:57:29,483 --> 00:57:31,843 It's a joy to share it with others 524 00:57:31,843 --> 00:57:35,923 and to see them be as curious as I have been for the last decade. 525 00:57:39,603 --> 00:57:42,083 So Parker's just begun its mission, really, 526 00:57:42,083 --> 00:57:44,963 and it's already really started to truly transform our understanding 527 00:57:44,963 --> 00:57:46,683 for how the Sun works. 528 00:57:53,963 --> 00:57:56,043 Next time... 529 00:57:56,043 --> 00:57:58,723 ..we had deeper into the galaxy... 530 00:58:02,083 --> 00:58:06,803 ..on the hunt for alien worlds... 531 00:58:06,803 --> 00:58:11,123 ..and perhaps the first signs of life. 532 00:58:18,123 --> 00:58:20,563 Journey through the universe with the Open University 533 00:58:20,563 --> 00:58:25,363 and learn more about stars, planets and galaxies with this free poster. 534 00:58:27,163 --> 00:58:31,723 Order your poster by calling... 535 00:58:31,723 --> 00:58:35,163 Or go to... 536 00:58:35,163 --> 00:58:38,163 and follow the links to the Open University. 537 00:58:40,083 --> 00:58:43,163 MUSIC: Who Knows Where The Time Goes? by Fairport Convention 538 01:00:17,243 --> 01:00:21,283 Explore this and more with our academic experts. 539 01:00:21,283 --> 01:00:24,403 Go to bbc.co.uk/theuniverse 540 01:00:24,403 --> 01:00:28,043 and follow the links to the Open University.