1 00:00:04,613 --> 00:00:08,449 We pulled the stars from the skies... 2 00:00:10,719 --> 00:00:13,721 ...and brought them down to Earth. 3 00:00:24,399 --> 00:00:27,168 But at what cost? 4 00:00:27,202 --> 00:00:30,337 When we turned on all these lights... 5 00:00:30,372 --> 00:00:32,940 we lost something precious. 6 00:00:32,974 --> 00:00:35,376 The stars. 7 00:02:35,430 --> 00:02:39,200 A long time ago, in a world lit only by fire, 8 00:02:39,234 --> 00:02:41,035 our relationship with the stars 9 00:02:41,069 --> 00:02:43,304 was far more... 10 00:02:43,338 --> 00:02:44,805 personal. 11 00:02:44,840 --> 00:02:46,507 For thousands of generations, 12 00:02:46,541 --> 00:02:47,675 we watched the stars 13 00:02:47,709 --> 00:02:49,744 as if our lives depended on it. 14 00:02:49,778 --> 00:02:52,179 Because they did. 15 00:02:53,682 --> 00:02:56,217 We humans were not the biggest, 16 00:02:56,251 --> 00:02:57,585 the strongest, nor the fastest 17 00:02:57,619 --> 00:02:59,587 of all the animals we competed against. 18 00:02:59,621 --> 00:03:01,589 But we did have one thing going for us... 19 00:03:01,623 --> 00:03:03,357 our intelligence. 20 00:03:03,392 --> 00:03:05,726 One aspect of that was a genius 21 00:03:05,761 --> 00:03:07,194 for pattern recognition. 22 00:03:07,229 --> 00:03:09,897 Night after night, we watched the stars. 23 00:03:09,931 --> 00:03:12,867 And over time, our ancestors noticed 24 00:03:12,901 --> 00:03:16,070 that the motions of the stars across the nights of the year 25 00:03:16,104 --> 00:03:17,872 foretold changes on Earth 26 00:03:17,906 --> 00:03:20,741 that threatened or enhanced our chances for survival. 27 00:03:20,776 --> 00:03:22,410 In a time when our imaginations 28 00:03:22,444 --> 00:03:25,613 were the only stage where stories came to life, 29 00:03:25,647 --> 00:03:27,381 before there were movies or TVs 30 00:03:27,416 --> 00:03:29,884 or electronic devices of any kind, 31 00:03:29,918 --> 00:03:33,054 every human culture connected the dots 32 00:03:33,088 --> 00:03:34,956 to form their own pictures. 33 00:03:36,758 --> 00:03:39,627 These images became the illustrations of a storybook 34 00:03:39,661 --> 00:03:43,464 that, on a deeper level, was also a survival manual. 35 00:03:43,498 --> 00:03:46,567 The names and personalities of the gods, heroes, 36 00:03:46,602 --> 00:03:48,736 farm animals or familiar objects 37 00:03:48,770 --> 00:03:50,938 varied from culture to culture. 38 00:03:50,973 --> 00:03:55,376 But there was one particularly gorgeous group of stars 39 00:03:55,410 --> 00:03:59,113 known to the Ancient Greeks and to us today 40 00:03:59,147 --> 00:04:01,449 as the Pleiades, 41 00:04:01,483 --> 00:04:04,952 a star cluster formed about 100 million years ago. 42 00:04:04,987 --> 00:04:08,289 Each of them is some 40 times brighter than our Sun. 43 00:04:08,323 --> 00:04:11,292 And Alcyone, the most luminous, 44 00:04:11,326 --> 00:04:14,829 outshines our Sun 1,000 times. 45 00:04:14,863 --> 00:04:17,798 For ages, the Pleiades have been used as an eye test 46 00:04:17,833 --> 00:04:21,135 for people all over the world. 47 00:04:21,169 --> 00:04:24,005 If you could see at least six of them, 48 00:04:24,039 --> 00:04:25,840 you were considered normal. 49 00:04:25,874 --> 00:04:27,675 If you saw more than seven, 50 00:04:27,709 --> 00:04:30,811 you were an ideal candidate for a warrior or scout. 51 00:04:30,846 --> 00:04:33,981 Among the Ancient Celts and Druids of the British Isles, 52 00:04:34,016 --> 00:04:37,351 the Pleiades were believed to have a haunting significance. 53 00:04:37,386 --> 00:04:39,253 On the night of the year that they reach 54 00:04:39,288 --> 00:04:41,422 the highest point in the sky at midnight, 55 00:04:41,456 --> 00:04:45,092 the spirits of the dead were thought to wander the Earth. 56 00:04:45,127 --> 00:04:47,995 This is believed to be the origin of the holiday 57 00:04:48,030 --> 00:04:50,097 once known as Samhain, 58 00:04:50,132 --> 00:04:51,632 now called Halloween. 59 00:04:51,667 --> 00:04:53,968 All over the Earth, our ancestors told 60 00:04:54,002 --> 00:04:56,037 wonderful stories to explain 61 00:04:56,071 --> 00:04:59,440 how the Pleiades came to be in the sky. 62 00:04:59,474 --> 00:05:01,809 For the Kiowa people of North America, 63 00:05:01,843 --> 00:05:03,978 it happened something like this. 64 00:05:11,687 --> 00:05:14,455 Long, long ago, some young women 65 00:05:14,489 --> 00:05:16,557 snuck away from their campsite 66 00:05:16,592 --> 00:05:19,026 to dance freely beneath the stars. 67 00:05:52,728 --> 00:05:54,428 Rock, save us! 68 00:05:54,463 --> 00:05:58,032 Rock, take pity on us! 69 00:05:58,066 --> 00:06:02,103 The rock heard their cries and grew taller. 70 00:06:07,943 --> 00:06:12,280 Until it became what is today known as the Devil's Tower. 71 00:06:16,752 --> 00:06:21,022 The maidens were transformed into the stars of the Pleiades, 72 00:06:21,056 --> 00:06:24,659 which may be seen hanging above the tower in midwinter. 73 00:06:26,562 --> 00:06:28,863 The Ancient Greeks also saw those seven jewels 74 00:06:28,897 --> 00:06:30,965 as seven maidens, 75 00:06:30,999 --> 00:06:34,569 the seven daughters of Atlas, 76 00:06:34,603 --> 00:06:37,305 pursued not by bears, but by... 77 00:06:37,339 --> 00:06:39,307 Orion the hunter, 78 00:06:39,341 --> 00:06:42,276 who spied them when he was out walking one day. 79 00:06:51,320 --> 00:06:54,922 Orion became mad with desire. 80 00:07:01,930 --> 00:07:05,666 For seven years, he chased them relentlessly. 81 00:07:07,269 --> 00:07:09,604 - Exhausted... - Zeus, help us. 82 00:07:09,638 --> 00:07:12,106 ...they prayed to Zeus for deliverance. 83 00:07:14,276 --> 00:07:18,746 Zeus, the king of the gods, felt sorry for them, 84 00:07:18,780 --> 00:07:20,982 and transformed those seven maidens 85 00:07:21,016 --> 00:07:24,285 into the Pleiades. 86 00:07:31,827 --> 00:07:35,163 But the gods are, if anything, capricious. 87 00:07:35,197 --> 00:07:38,766 When Orion was killed by the sting of a scorpion, 88 00:07:38,801 --> 00:07:42,136 Zeus placed him in the sky where he could resume his pursuit 89 00:07:42,171 --> 00:07:44,105 of the seven gorgeous sisters. 90 00:07:44,139 --> 00:07:46,274 Our ancestors, they wove 91 00:07:46,308 --> 00:07:47,842 brilliantly imaginative stories. 92 00:07:47,876 --> 00:07:50,311 But they can bring us no closer to the stars 93 00:07:50,345 --> 00:07:51,679 than our dreams. 94 00:07:51,713 --> 00:07:54,482 It took yet another few thousand years 95 00:07:54,516 --> 00:07:56,784 until three brilliant scientists unlocked the secrets 96 00:07:56,819 --> 00:07:59,754 of the true lives of the stars. 97 00:08:09,932 --> 00:08:11,566 In 1901, 98 00:08:11,600 --> 00:08:14,536 Harvard was a man's world. 99 00:08:14,570 --> 00:08:17,305 But an astronomer named Edward Charles Pickering 100 00:08:17,339 --> 00:08:19,007 broke that rule. 101 00:08:21,911 --> 00:08:24,846 Oh, Pickering's office is just down the hallway. 102 00:08:24,880 --> 00:08:27,048 And that door over there leads to the room 103 00:08:27,082 --> 00:08:30,552 where he keeps his computers. 104 00:08:41,297 --> 00:08:44,999 We're supposed to call those women "computers," but, uh, 105 00:08:45,034 --> 00:08:47,602 I've heard more than one fellow refer to those gals 106 00:08:47,636 --> 00:08:50,538 as "Pickering's Harem." 107 00:08:50,573 --> 00:08:52,907 Pickering assembled a team of women 108 00:08:52,942 --> 00:08:55,910 to map and classify the types of stars. 109 00:08:55,945 --> 00:08:59,380 One of them provided the key to our understanding 110 00:08:59,415 --> 00:09:01,082 of the substance of the stars. 111 00:09:01,116 --> 00:09:03,918 And another devised a way for us to calculate 112 00:09:03,953 --> 00:09:06,888 the size of the universe. 113 00:09:06,922 --> 00:09:10,558 For some reason, you probably never heard of either of them. 114 00:09:10,593 --> 00:09:13,061 Wonder why. 115 00:09:14,730 --> 00:09:18,399 That's Annie Jump Cannon, the leader of the team. 116 00:09:18,434 --> 00:09:20,301 Before she was through, 117 00:09:20,336 --> 00:09:22,737 she catalogued a quarter of a million stars. 118 00:09:24,440 --> 00:09:27,909 Number 11 is a B7. 119 00:09:27,943 --> 00:09:30,879 That's Alcyone in the Pleiades. 120 00:09:30,913 --> 00:09:33,414 Cannon lost her hearing during a bout of scarlet fever 121 00:09:33,449 --> 00:09:34,649 when she was a young woman. 122 00:09:34,683 --> 00:09:38,086 Number 12 is a B6. 123 00:09:38,120 --> 00:09:40,955 That's Henrietta Swan Leavitt. She's also deaf. 124 00:09:40,990 --> 00:09:44,926 And she's the other great scientist in the room. 125 00:09:44,960 --> 00:09:48,129 Leavitt discovered the law that astronomers still use 126 00:09:48,164 --> 00:09:49,898 more than a century later 127 00:09:49,932 --> 00:09:51,766 to measure the distances to the stars 128 00:09:51,801 --> 00:09:54,369 and the size of the cosmos itself. 129 00:09:56,338 --> 00:09:59,240 Annie Jump Cannon sent out a Christmas card explaining 130 00:09:59,275 --> 00:10:02,310 what she and her sisters were actually doing. 131 00:10:02,344 --> 00:10:04,279 The light from a star is allowed 132 00:10:04,313 --> 00:10:07,782 to fall through a prism placed in the telescope, she wrote. 133 00:10:07,817 --> 00:10:11,486 Thus magnified, the starlight is split up into a band 134 00:10:11,520 --> 00:10:13,922 showing its component colors, 135 00:10:13,956 --> 00:10:18,259 the red rays going to one end and the violet to the other. 136 00:10:18,294 --> 00:10:20,628 This is the spectrum of the star. 137 00:10:20,663 --> 00:10:23,531 It shows the presence of fine, dark lines. 138 00:10:23,566 --> 00:10:25,700 By comparing them with lines given 139 00:10:25,734 --> 00:10:28,002 by glowing substances in the laboratory, 140 00:10:28,037 --> 00:10:31,639 we can determine that the same elements familiar to us 141 00:10:31,674 --> 00:10:34,976 on the Earth also exist in the outermost star. 142 00:10:45,988 --> 00:10:49,724 This is plate number 12358B. 143 00:10:55,030 --> 00:10:59,834 Number one at this plate is a B-type star. 144 00:11:01,771 --> 00:11:05,540 Make that a B2. 145 00:11:07,543 --> 00:11:09,244 It took Cannon decades 146 00:11:09,278 --> 00:11:11,146 to classify the spectral character 147 00:11:11,180 --> 00:11:13,581 of hundreds of thousands of stars 148 00:11:13,616 --> 00:11:16,151 according to the scheme that she devised. 149 00:11:16,185 --> 00:11:18,586 Cannon discovered that the stars fell 150 00:11:18,621 --> 00:11:22,690 into a continuous sequence of seven broad categories 151 00:11:22,725 --> 00:11:25,026 according to their spectral line patterns. 152 00:11:25,061 --> 00:11:27,395 Each was designated by a letter. 153 00:11:27,430 --> 00:11:31,332 But the spectral lines of two stars in the same letter class 154 00:11:31,367 --> 00:11:33,501 could differ in subtle ways, 155 00:11:33,536 --> 00:11:35,703 minute variations that Cannon learned 156 00:11:35,738 --> 00:11:37,405 to recognize from memory. 157 00:11:37,440 --> 00:11:40,075 To distinguish these spectra from one another, 158 00:11:40,109 --> 00:11:44,746 she assigned ten numerical subcategories for each class. 159 00:11:44,780 --> 00:11:47,582 Annie Jump Cannon organized the stars, 160 00:11:47,616 --> 00:11:49,918 but it would fall to another scientist to decipher 161 00:11:49,952 --> 00:11:52,220 the hidden meaning in her work. 162 00:11:54,256 --> 00:11:57,692 In the England of 1923, women were forbidden 163 00:11:57,727 --> 00:12:00,061 from pursuing advanced degrees in science. 164 00:12:00,096 --> 00:12:02,964 But Cecelia Payne had attended a lecture in London 165 00:12:02,998 --> 00:12:05,233 by the astronomer Sir Arthur Eddington, 166 00:12:05,267 --> 00:12:07,869 the first scientist to provide evidence 167 00:12:07,903 --> 00:12:09,537 that Einstein's revolutionary 168 00:12:09,572 --> 00:12:11,740 General Theory of Relativity was correct. 169 00:12:11,774 --> 00:12:13,274 From that moment on, 170 00:12:13,309 --> 00:12:14,976 she knew that nothing would deter her 171 00:12:15,010 --> 00:12:17,479 from pursing her big dreams. 172 00:12:18,981 --> 00:12:21,316 She resolved to emigrate to America, 173 00:12:21,350 --> 00:12:23,651 where women had already gained the freedom 174 00:12:23,686 --> 00:12:25,787 to study the stars. 175 00:12:25,821 --> 00:12:28,823 Her application was accepted at Harvard. 176 00:12:28,858 --> 00:12:31,259 What she would discover there would challenge 177 00:12:31,293 --> 00:12:33,461 one of the central beliefs of astronomy. 178 00:12:33,496 --> 00:12:36,097 The resulting impact 179 00:12:36,132 --> 00:12:39,467 would be the dawn of modern astrophysics. 180 00:12:44,877 --> 00:12:46,678 As the decades passed, 181 00:12:46,713 --> 00:12:49,915 Annie Jump Cannon and her team kept sifting the stars, 182 00:12:49,949 --> 00:12:51,750 checking each one's spectral signature 183 00:12:51,784 --> 00:12:54,586 with a fleeting glance and then dropping them 184 00:12:54,621 --> 00:12:56,421 into one of seven categories. 185 00:12:56,456 --> 00:12:59,257 They became hundreds of thousands of dots 186 00:12:59,292 --> 00:13:02,594 in a larger picture which no one could yet understand. 187 00:13:02,629 --> 00:13:07,499 Into this community of women came one more. 188 00:13:08,901 --> 00:13:10,602 Well, hello there. 189 00:13:10,637 --> 00:13:13,772 You must be Miss Payne. 190 00:13:13,806 --> 00:13:15,073 We've been waiting for you. 191 00:13:15,108 --> 00:13:17,276 Come on in. 192 00:13:17,310 --> 00:13:19,978 Cecilia Payne had never experienced such kindness 193 00:13:20,013 --> 00:13:22,547 in a scientific setting before. 194 00:13:22,582 --> 00:13:25,217 This sisterhood generously shared 195 00:13:25,251 --> 00:13:27,319 the fruits of their labors with her, 196 00:13:27,353 --> 00:13:29,154 and she turned their observations 197 00:13:29,188 --> 00:13:32,724 into a radical new understanding of the stars. 198 00:13:32,759 --> 00:13:35,861 The two women became great friends. 199 00:13:35,895 --> 00:13:37,596 Cannon taught Payne everything she had learned 200 00:13:37,630 --> 00:13:39,131 about stellar spectra. 201 00:13:39,165 --> 00:13:40,933 And Payne began to analyze Cannon's data 202 00:13:40,967 --> 00:13:44,670 to see if she could determine the actual chemical composition 203 00:13:44,704 --> 00:13:46,905 and physical state of the stars. 204 00:13:46,940 --> 00:13:49,241 She brought to this work her expertise 205 00:13:49,275 --> 00:13:51,109 in theoretical and atomic physics. 206 00:13:53,947 --> 00:13:56,782 The most prominent features in the spectra of stars 207 00:13:56,816 --> 00:13:58,517 showed the presence of heavy elements 208 00:13:58,551 --> 00:14:02,487 such as calcium... and iron, 209 00:14:02,522 --> 00:14:05,457 which are among the most abundant elements in the Earth. 210 00:14:05,491 --> 00:14:07,459 So astronomers naturally concluded 211 00:14:07,493 --> 00:14:09,328 that the stars were made 212 00:14:09,362 --> 00:14:11,296 of the same elements as the Earth 213 00:14:11,331 --> 00:14:13,465 and in roughly the same proportions. 214 00:14:13,499 --> 00:14:18,370 In 1924, Henry Norris Russell was the dean 215 00:14:18,404 --> 00:14:21,673 of American astronomers, having made major contributions 216 00:14:21,708 --> 00:14:24,042 to our understanding of the stars. 217 00:14:24,077 --> 00:14:26,812 40 to 45 of the chemical elements 218 00:14:26,846 --> 00:14:28,680 that we have here on Earth 219 00:14:28,715 --> 00:14:31,483 are also present in the spectrum of the Sun. 220 00:14:31,517 --> 00:14:35,020 So we can assume that the composition of the Sun 221 00:14:35,054 --> 00:14:37,890 resembles that of the Earth. 222 00:14:37,924 --> 00:14:41,393 If one were to heat the crust of the Earth to incandescence, 223 00:14:41,427 --> 00:14:44,997 its spectrum would resemble that of the Sun. 224 00:14:59,579 --> 00:15:03,515 Annie, I think I now understand what it all means. 225 00:15:03,550 --> 00:15:05,417 All your years of work. 226 00:15:05,451 --> 00:15:06,685 Tell me. 227 00:15:06,719 --> 00:15:08,320 I've calculated what the spectra 228 00:15:08,354 --> 00:15:10,389 should look like across a wide range 229 00:15:10,423 --> 00:15:12,057 of temperatures, and they match 230 00:15:12,091 --> 00:15:14,893 your system of classification perfectly. 231 00:15:14,928 --> 00:15:19,097 The spectrum of any star tells you exactly how hot it is. 232 00:15:19,132 --> 00:15:25,103 Your "O-B-A-F-G-K-M" is really a temperature scale of the stars 233 00:15:25,138 --> 00:15:27,639 from the hottest to the coldest. 234 00:15:29,809 --> 00:15:32,611 Here's the headline, Annie. Thanks to your work, 235 00:15:32,645 --> 00:15:34,680 I've discovered that the stars are made almost entirely 236 00:15:34,714 --> 00:15:36,348 of hydrogen and helium. 237 00:15:36,382 --> 00:15:39,451 There's a million times more hydrogen and helium 238 00:15:39,485 --> 00:15:41,620 than the metals in the stars. 239 00:15:41,654 --> 00:15:44,289 I know, it sounds daft. 240 00:15:44,324 --> 00:15:46,358 Are you certain? 241 00:15:46,392 --> 00:15:51,096 Has anyone else checked your calculations? 242 00:15:51,130 --> 00:15:53,699 Not yet, but it's all in my thesis, 243 00:15:53,733 --> 00:15:56,168 which is already on its way to Professor Russell. 244 00:16:07,780 --> 00:16:09,815 Poor woman. 245 00:16:09,849 --> 00:16:13,085 Russell felt sorry for Cecilia Payne. 246 00:16:13,119 --> 00:16:16,622 Her thesis appeared to him to be fundamentally flawed. 247 00:16:24,197 --> 00:16:27,633 It is clearly impossible that hydrogen should be 248 00:16:27,667 --> 00:16:30,335 a million times more abundant than the metals. 249 00:16:34,541 --> 00:16:38,310 Her carefully gathered evidence flew in the face 250 00:16:38,344 --> 00:16:40,979 of conventional scientific wisdom. 251 00:16:41,014 --> 00:16:42,948 "How could I be right," she asked, 252 00:16:42,982 --> 00:16:45,184 "if that must mean 253 00:16:45,218 --> 00:16:48,187 that such a distinguished scientist was wrong?" 254 00:16:49,889 --> 00:16:52,925 Despite her confidence in the quality of her research, 255 00:16:52,959 --> 00:16:56,028 she caved and added a sentence to her thesis 256 00:16:56,062 --> 00:16:59,031 that undermined its greatest insight. 257 00:17:04,571 --> 00:17:06,004 It would be four years 258 00:17:06,039 --> 00:17:08,774 before Russell realized that Payne was right. 259 00:17:08,808 --> 00:17:11,944 To his credit, as soon as he did, 260 00:17:11,978 --> 00:17:14,313 he acknowledged that it was her discovery. 261 00:17:17,750 --> 00:17:21,553 Payne's "Stellar Atmospheres" is widely regarded 262 00:17:21,588 --> 00:17:23,689 as the most brilliant PhD thesis 263 00:17:23,723 --> 00:17:25,524 ever written in astronomy. 264 00:17:25,558 --> 00:17:29,895 It became the standard text in its field. 265 00:17:29,929 --> 00:17:33,632 I was to blame for not having pressed my point. 266 00:17:33,666 --> 00:17:38,504 I had given in to authority when I believed I was right. 267 00:17:38,538 --> 00:17:40,572 If you are sure of your facts, 268 00:17:40,607 --> 00:17:43,041 you should defend your position. 269 00:17:44,444 --> 00:17:46,512 The words of the powerful 270 00:17:46,546 --> 00:17:49,348 may prevail in other spheres of human experience, 271 00:17:49,382 --> 00:17:53,352 but in science, the only thing that counts is the evidence 272 00:17:53,386 --> 00:17:55,854 and the logic of the argument itself. 273 00:17:55,889 --> 00:17:59,258 Cecilia Payne's interpretation of Annie Jump Cannon's sequence 274 00:17:59,292 --> 00:18:02,027 of stellar spectra made it possible for us 275 00:18:02,061 --> 00:18:04,263 to read the life stories of the stars 276 00:18:04,297 --> 00:18:08,267 and to trace the story of life itself back to its beginnings 277 00:18:08,301 --> 00:18:11,303 in their fiery deaths. 278 00:18:17,289 --> 00:18:20,057 There are many kinds of stars. 279 00:18:20,092 --> 00:18:22,626 Some are bright like the Sun. 280 00:18:22,661 --> 00:18:24,762 Some are dim. 281 00:18:24,796 --> 00:18:26,897 The greatest stars are ten million times larger 282 00:18:26,932 --> 00:18:29,133 than the smallest ones. 283 00:18:29,167 --> 00:18:31,736 Some stars are old beyond imagining, 284 00:18:31,770 --> 00:18:34,939 more than ten billion years of age. 285 00:18:34,973 --> 00:18:37,308 Others are being born right now. 286 00:18:41,046 --> 00:18:44,015 When atoms fuse in the hearts of stars, 287 00:18:44,049 --> 00:18:45,316 they make starlight. 288 00:18:45,350 --> 00:18:47,251 Stars are born in litters, 289 00:18:47,285 --> 00:18:50,921 formed from the gas and dust of interstellar clouds. 290 00:18:50,956 --> 00:18:53,858 The mass of the individual stars in a litter 291 00:18:53,892 --> 00:18:56,193 can range from the runts-- not much larger 292 00:18:56,228 --> 00:18:58,262 than the largest planets-- 293 00:18:58,296 --> 00:19:01,065 to the supergiant stars that dwarf the Sun. 294 00:19:07,239 --> 00:19:11,142 The stars in the nebula below Orion's Belt are newborns, 295 00:19:11,176 --> 00:19:12,877 around five million years old, 296 00:19:12,911 --> 00:19:16,113 and still swaddled in the gas and dust 297 00:19:16,148 --> 00:19:18,315 that gave birth to them. 298 00:19:18,350 --> 00:19:21,485 The stars in the Pleiades are already toddlers, 299 00:19:21,520 --> 00:19:23,387 about 100 million years old. 300 00:19:23,422 --> 00:19:25,523 They've shed their blankets of gas and dust, 301 00:19:25,557 --> 00:19:27,458 but they're still bound together 302 00:19:27,492 --> 00:19:29,393 by their mutual gravity. 303 00:19:29,428 --> 00:19:31,329 Another few hundred million years, 304 00:19:31,363 --> 00:19:33,965 and they'll drift apart and go their separate ways, 305 00:19:33,999 --> 00:19:36,500 never to meet again. 306 00:19:36,535 --> 00:19:40,137 Most of the stars of the Big Dipper are adolescents, 307 00:19:40,172 --> 00:19:42,707 roughly half a billion years old. 308 00:19:42,741 --> 00:19:45,309 They've already drifted apart from their birth cluster, 309 00:19:45,344 --> 00:19:48,379 although we can still trace their common ancestry. 310 00:19:48,413 --> 00:19:51,816 Eventually, they'll spread out around the Milky Way galaxy. 311 00:19:51,850 --> 00:19:54,685 But most of the familiar constellations 312 00:19:54,720 --> 00:19:58,055 are a mix of entirely unrelated stars, 313 00:19:58,090 --> 00:19:59,857 some faint and nearby, 314 00:19:59,891 --> 00:20:03,027 others bright and far away. 315 00:20:05,564 --> 00:20:07,098 Our own Sun? 316 00:20:07,132 --> 00:20:09,100 From the distance of even a few light-years, 317 00:20:09,134 --> 00:20:12,536 it's hard to find amidst the other stars. 318 00:20:12,571 --> 00:20:14,572 It's that one. 319 00:20:16,208 --> 00:20:17,708 Our Sun is middle-aged 320 00:20:17,743 --> 00:20:19,677 and a long way from where it was born. 321 00:20:19,711 --> 00:20:21,379 Its sister stars, 322 00:20:21,413 --> 00:20:23,180 hatched from the same interstellar cloud, 323 00:20:23,215 --> 00:20:26,050 are dispersed throughout the galaxy. 324 00:20:26,084 --> 00:20:28,719 Many of them have their own planets. 325 00:20:28,754 --> 00:20:30,621 Perhaps some of them nurture 326 00:20:30,656 --> 00:20:33,724 the evolution of life and intelligence. 327 00:20:33,759 --> 00:20:35,860 Most of the stars in our night sky 328 00:20:35,894 --> 00:20:39,530 actually orbit around one or more stellar companions. 329 00:20:39,564 --> 00:20:41,065 With the naked eye, 330 00:20:41,099 --> 00:20:42,633 we usually can't see the fainter members 331 00:20:42,668 --> 00:20:44,902 in such double and multiple star systems. 332 00:20:47,639 --> 00:20:49,540 On a world with three suns, 333 00:20:49,574 --> 00:20:51,475 the nights would be rare 334 00:20:51,510 --> 00:20:55,146 and the days might alternate between red and blue. 335 00:21:01,653 --> 00:21:04,388 It is the destiny of stars to collapse. 336 00:21:04,423 --> 00:21:06,390 Of the thousands of stars you see 337 00:21:06,425 --> 00:21:08,559 when you look up at the night sky, 338 00:21:08,594 --> 00:21:09,894 every one of them is living 339 00:21:09,928 --> 00:21:12,063 in an interval between two collapses... 340 00:21:12,097 --> 00:21:14,932 an initial collapse of a dark, interstellar gas cloud 341 00:21:14,967 --> 00:21:16,567 to form the star, 342 00:21:16,602 --> 00:21:19,136 and a final collapse of the luminous star 343 00:21:19,171 --> 00:21:21,906 on its way to its ultimate fate. 344 00:21:21,940 --> 00:21:23,608 Gravity makes stars contract, 345 00:21:23,642 --> 00:21:25,843 unless some other force intervenes. 346 00:21:25,877 --> 00:21:29,180 The Sun is a great, big ball of incandescent gas. 347 00:21:29,214 --> 00:21:32,149 The super hot gas in its core 348 00:21:32,184 --> 00:21:34,185 pushes the Sun to expand outward. 349 00:21:34,219 --> 00:21:37,021 At the same time, the Sun's own gravity 350 00:21:37,055 --> 00:21:39,090 pulls it inward to contract. 351 00:21:39,124 --> 00:21:41,826 And our Sun is poised between these two forces 352 00:21:41,860 --> 00:21:43,694 in a stable equilibrium 353 00:21:43,729 --> 00:21:46,864 between gravity and nuclear fire, 354 00:21:46,899 --> 00:21:48,366 a balance it will maintain 355 00:21:48,400 --> 00:21:50,701 for another four billion years. 356 00:21:50,736 --> 00:21:53,037 But as the Sun consumes hydrogen, 357 00:21:53,071 --> 00:21:56,007 its core very slowly shrinks, 358 00:21:56,041 --> 00:21:59,510 and the Sun's surface gradually expands in response. 359 00:21:59,544 --> 00:22:00,978 It happens very slowly, 360 00:22:01,013 --> 00:22:02,480 imperceptibly, 361 00:22:02,514 --> 00:22:04,215 over the course of millions of years. 362 00:22:04,249 --> 00:22:06,317 But in about a billion years, 363 00:22:06,351 --> 00:22:08,286 the Sun will be ten percent brighter 364 00:22:08,320 --> 00:22:10,488 than it is today. 365 00:22:13,158 --> 00:22:15,126 Ten percent may not sound like much, 366 00:22:15,160 --> 00:22:19,163 but that extra heat will have a big effect on Earth. 367 00:22:26,271 --> 00:22:28,906 When the Sun finally exhausts its nuclear fuel 368 00:22:28,941 --> 00:22:31,576 four or five billion years from now, 369 00:22:31,610 --> 00:22:35,213 its gas will cool and the pressure will fall. 370 00:22:35,247 --> 00:22:36,647 The Sun's interior 371 00:22:36,682 --> 00:22:38,182 can no longer support the weight 372 00:22:38,217 --> 00:22:39,850 of the outer layers, 373 00:22:39,885 --> 00:22:43,221 and the initial collapse will resume. 374 00:22:43,255 --> 00:22:45,089 Nothing lasts forever. 375 00:22:45,123 --> 00:22:47,592 Even the stars die. 376 00:22:47,626 --> 00:22:49,894 Helium, the ash 377 00:22:49,928 --> 00:22:51,862 of ten billion years of hydrogen fusion, 378 00:22:51,897 --> 00:22:54,098 has built up in the core. 379 00:22:54,132 --> 00:22:56,667 With no nuclear fire to sustain its weight, 380 00:22:56,702 --> 00:22:59,170 the core collapses until it becomes hot enough 381 00:22:59,204 --> 00:23:02,540 to start fusing helium into carbon and oxygen. 382 00:23:02,574 --> 00:23:04,175 The core of the Sun 383 00:23:04,209 --> 00:23:06,410 is now much hotter than it was before. 384 00:23:06,445 --> 00:23:09,180 Its atmosphere rapidly expands. 385 00:23:09,214 --> 00:23:12,283 Over the next billion years, it'll become bloated 386 00:23:12,317 --> 00:23:14,785 to more than 100 times its original size-- 387 00:23:14,820 --> 00:23:17,922 a red giant star. 388 00:23:20,926 --> 00:23:23,127 It will envelop and devour 389 00:23:23,161 --> 00:23:25,730 the planets Mercury... 390 00:23:28,267 --> 00:23:30,635 ...and Venus... 391 00:23:35,007 --> 00:23:37,108 ...and possibly the Earth. 392 00:23:39,111 --> 00:23:40,945 I like to think that 393 00:23:40,979 --> 00:23:43,481 tens of millions of years before that far distant future, 394 00:23:43,515 --> 00:23:46,717 if there still be life born of Earth, 395 00:23:46,752 --> 00:23:50,354 it will have found new homes among the stars. 396 00:23:52,324 --> 00:23:54,392 Once the Sun burns through its helium, 397 00:23:54,426 --> 00:23:56,594 it will become highly unstable, 398 00:23:56,628 --> 00:23:59,530 casting off its outer layers into space. 399 00:24:01,934 --> 00:24:03,668 The exposed, super hot core 400 00:24:03,702 --> 00:24:05,403 will flood its surroundings 401 00:24:05,437 --> 00:24:07,805 with high-energy ultraviolet light. 402 00:24:10,042 --> 00:24:13,878 The atoms will perform a wild, fluorescent dance. 403 00:24:20,052 --> 00:24:22,954 The Sun will collapse like a soufflé, 404 00:24:22,988 --> 00:24:26,123 shrinking a hundredfold to the size of the Earth. 405 00:24:26,158 --> 00:24:28,793 And at that point, the Sun will be so dense 406 00:24:28,827 --> 00:24:31,362 that its overcrowded electrons will push back, 407 00:24:31,396 --> 00:24:33,664 stopping any further contraction. 408 00:24:33,699 --> 00:24:35,433 The kernel of light at the center 409 00:24:35,467 --> 00:24:38,870 will be the only part of the Sun that endures, 410 00:24:38,904 --> 00:24:42,340 a white dwarf star that will go on shining dimly 411 00:24:42,374 --> 00:24:45,042 for another 100 billion years. 412 00:24:45,077 --> 00:24:47,378 Will the beings of a distant future, 413 00:24:47,412 --> 00:24:49,814 sailing past this wreck of a star, 414 00:24:49,848 --> 00:24:54,719 have any idea of the life and worlds that it once warmed? 415 00:25:14,643 --> 00:25:16,711 The psychedelic death shrouds 416 00:25:16,745 --> 00:25:19,748 of ordinary stars are fleeting, 417 00:25:19,782 --> 00:25:23,118 lasting only tens of thousands of years 418 00:25:23,152 --> 00:25:26,554 before dissipating in the interstellar gas and dust 419 00:25:26,589 --> 00:25:28,623 from which the new stars will be born. 420 00:25:33,129 --> 00:25:35,530 The stars in a binary star system 421 00:25:35,564 --> 00:25:37,632 can have a different fate. 422 00:25:37,666 --> 00:25:40,802 Sirius, the brightest star in the night sky, 423 00:25:40,836 --> 00:25:43,905 has a very faint stellar companion-- 424 00:25:43,939 --> 00:25:45,306 a white dwarf. 425 00:25:45,341 --> 00:25:47,242 It was once a Sun-like star. 426 00:25:47,276 --> 00:25:50,044 Someday, when Sirius runs out of fuel 427 00:25:50,079 --> 00:25:51,880 and becomes a red giant, 428 00:25:51,914 --> 00:25:54,716 it will shed its substance onto the white dwarf. 429 00:25:54,750 --> 00:25:57,819 The intense gravity of the companion 430 00:25:57,853 --> 00:25:59,454 will attract that gas, 431 00:25:59,488 --> 00:26:01,890 pulling it into a spiraling disk. 432 00:26:01,924 --> 00:26:04,059 When the gas from the larger star 433 00:26:04,093 --> 00:26:06,061 falls onto the surface of the white dwarf, 434 00:26:06,095 --> 00:26:08,997 it will trigger nuclear explosions. 435 00:26:12,802 --> 00:26:14,669 The greatest burst will release 436 00:26:14,703 --> 00:26:17,439 100,000 times more energy than the Sun. 437 00:26:19,208 --> 00:26:22,277 Each one of those star bursts is called a "nova," 438 00:26:22,311 --> 00:26:25,513 from the Latin for "new." 439 00:26:25,548 --> 00:26:28,450 A star about 15 times as massive as the Sun, 440 00:26:28,484 --> 00:26:31,419 one like Rigel, the blue supergiant 441 00:26:31,454 --> 00:26:33,521 that forms the right foot of Orion, 442 00:26:33,556 --> 00:26:35,356 has a different fate in store. 443 00:26:35,391 --> 00:26:38,993 Its collapse will not be stopped by the pressure of electrons. 444 00:26:41,130 --> 00:26:44,332 The star will keep falling in on itself, 445 00:26:44,367 --> 00:26:47,369 until its nuclei become so overcrowded 446 00:26:47,403 --> 00:26:49,838 that they push back. 447 00:26:52,141 --> 00:26:55,176 Rigel will shrink down about 100,000 times, 448 00:26:55,211 --> 00:26:58,513 until there's no space left between the nuclei 449 00:26:58,547 --> 00:27:00,749 and it can shrink no more. 450 00:27:05,521 --> 00:27:06,955 At that point, it ignites 451 00:27:06,989 --> 00:27:10,992 a more powerful nuclear reaction, a supernova. 452 00:27:16,365 --> 00:27:17,899 Most stellar evolution 453 00:27:17,933 --> 00:27:20,001 takes millions or billions of years. 454 00:27:20,036 --> 00:27:21,736 But the interior collapse 455 00:27:21,771 --> 00:27:24,639 that triggers a supernova explosion takes only seconds. 456 00:27:24,673 --> 00:27:28,143 What remains will be an atomic nucleus 457 00:27:28,177 --> 00:27:30,845 the size of a small city-- 458 00:27:30,880 --> 00:27:34,716 a rapidly rotating neutron star called a pulsar. 459 00:27:47,396 --> 00:27:48,863 But for a star more than 460 00:27:48,898 --> 00:27:50,865 30 times as massive as the Sun-- 461 00:27:50,900 --> 00:27:53,868 a star like Alnilam, in Orion's Belt-- 462 00:27:53,903 --> 00:27:56,838 there will be no stopping its collapse. 463 00:27:56,872 --> 00:27:58,573 In a few million years, 464 00:27:58,607 --> 00:28:00,375 when Alnilam runs out of fuel, 465 00:28:00,409 --> 00:28:02,410 it, too, will go supernova. 466 00:28:02,445 --> 00:28:05,780 The imploding core of Alnilam 467 00:28:05,815 --> 00:28:09,284 will be so massive that not even nuclear forces 468 00:28:09,318 --> 00:28:12,287 will be strong enough to hold off its collapse. 469 00:28:12,321 --> 00:28:15,190 Nothing can withstand such gravity. 470 00:28:15,224 --> 00:28:17,492 And such a star has an astonishing destiny. 471 00:28:22,298 --> 00:28:24,265 It will continues to collapse, 472 00:28:24,300 --> 00:28:26,868 crossing a boundary in space-time 473 00:28:26,902 --> 00:28:29,070 called the "event horizon," 474 00:28:29,105 --> 00:28:31,139 beyond which we cannot see. 475 00:28:31,173 --> 00:28:33,241 When it traverses that frontier, 476 00:28:33,275 --> 00:28:36,511 the star will vanish completely from sight. 477 00:28:38,414 --> 00:28:41,049 It will be inside a black hole, 478 00:28:41,083 --> 00:28:43,785 a place where gravity is so strong 479 00:28:43,819 --> 00:28:47,255 that nothing, not even light, can escape. 480 00:28:51,927 --> 00:28:53,128 But there's an even 481 00:28:53,162 --> 00:28:54,396 more dramatic fate 482 00:28:54,430 --> 00:28:56,464 that awaits a rare kind of star. 483 00:28:56,499 --> 00:28:58,633 There's one of them in our galaxy. 484 00:28:58,668 --> 00:29:01,169 It's so unstable that when it goes, 485 00:29:01,203 --> 00:29:04,639 it won't become a mere nova or supernova. 486 00:29:04,674 --> 00:29:07,175 It'll become something far more catastrophic... 487 00:29:07,209 --> 00:29:09,477 a hypernova. 488 00:29:09,512 --> 00:29:12,314 And it could happen in our lifetime. 489 00:29:23,292 --> 00:29:26,127 There are few places on Earth to get a better view 490 00:29:26,162 --> 00:29:29,197 of the night sky than the Australian Outback. 491 00:29:31,000 --> 00:29:33,335 No buildings, 492 00:29:33,369 --> 00:29:36,271 no cars, streetlights, nothing out here; 493 00:29:36,305 --> 00:29:38,139 just lots of starlight... 494 00:29:38,174 --> 00:29:40,508 and the occasional kangaroo. 495 00:29:40,543 --> 00:29:42,110 You can get a particularly good view 496 00:29:42,144 --> 00:29:44,012 of the Milky Way from down here. 497 00:29:44,046 --> 00:29:45,714 The center of our galaxy 498 00:29:45,748 --> 00:29:47,349 rises high in the sky, 499 00:29:47,383 --> 00:29:49,384 and it arches across the heavens 500 00:29:49,418 --> 00:29:52,053 like the backbone of night. 501 00:29:52,088 --> 00:29:53,822 We live in a spiral galaxy. 502 00:29:53,856 --> 00:29:55,824 And when we look at the Milky Way, 503 00:29:55,858 --> 00:29:59,794 we're seeing light from billions of stars in its spiral disk. 504 00:29:59,829 --> 00:30:02,230 And under this beautiful dark sky, 505 00:30:02,264 --> 00:30:05,867 you can see that the Milky Way isn't a uniform band of light. 506 00:30:05,901 --> 00:30:09,004 There are dark patches, breaks in the starlight. 507 00:30:09,038 --> 00:30:12,907 Those dark patches are caused by interstellar dust. 508 00:30:12,942 --> 00:30:16,544 The dust blocks the starlight, and there's lots of it. 509 00:30:18,280 --> 00:30:20,749 Most cultures looked up at the stars 510 00:30:20,783 --> 00:30:22,083 and connected the dots 511 00:30:22,118 --> 00:30:24,252 to form familiar images in the sky. 512 00:30:24,287 --> 00:30:26,388 Constellations. 513 00:30:31,560 --> 00:30:33,895 But the Aboriginal people of Australia 514 00:30:33,930 --> 00:30:36,064 saw a pattern in the darkness 515 00:30:36,098 --> 00:30:38,166 running through the Milky Way. 516 00:30:38,200 --> 00:30:40,902 They saw an emu, a large bird 517 00:30:40,937 --> 00:30:43,204 native to this continent. 518 00:30:43,239 --> 00:30:47,142 Not in the stars, but in the absence of stars. 519 00:30:50,313 --> 00:30:53,048 There are so many ways to look at the night sky. 520 00:30:53,082 --> 00:30:56,084 For a million years or more, we've watched the sky. 521 00:30:56,118 --> 00:30:57,786 And a lot's happened in that time. 522 00:30:57,820 --> 00:31:01,690 Supernova explode in our galaxy about once a century. 523 00:31:01,724 --> 00:31:04,759 If we could compress all those nights of stargazing 524 00:31:04,794 --> 00:31:06,561 into a single minute, 525 00:31:06,596 --> 00:31:09,164 this is what we would see. 526 00:31:14,170 --> 00:31:16,304 Now, if our eyes were telescopes, 527 00:31:16,339 --> 00:31:19,040 if they were light buckets as big as wagon wheels 528 00:31:19,075 --> 00:31:22,711 and our vision was not limited to just one kind of light, 529 00:31:22,745 --> 00:31:27,148 then this is the Milky Way we would see. 530 00:31:27,183 --> 00:31:29,884 A galaxy in near-infrared light 531 00:31:29,919 --> 00:31:32,053 with streaming tendrils of dust 532 00:31:32,088 --> 00:31:34,756 hurled outward by those exploding supernovas, 533 00:31:34,790 --> 00:31:36,758 silhouetted against a backdrop 534 00:31:36,792 --> 00:31:39,594 of countless stars. 535 00:31:39,629 --> 00:31:42,564 About 7,500 light-years away, 536 00:31:42,598 --> 00:31:44,799 in another part of our galaxy, 537 00:31:44,834 --> 00:31:46,968 there is a place of upheaval 538 00:31:47,003 --> 00:31:49,437 on an inconceivable scale. 539 00:31:56,238 --> 00:31:59,373 This is the Carina Nebula. 540 00:31:59,408 --> 00:32:01,809 A star-making machine. 541 00:32:05,614 --> 00:32:09,584 It takes a ray of light 50 years to cross it. 542 00:32:12,621 --> 00:32:15,957 The titanic stars born here 543 00:32:15,991 --> 00:32:18,226 sear the surrounding gas and dust 544 00:32:18,260 --> 00:32:21,262 with their fierce ultraviolet radiation. 545 00:32:21,296 --> 00:32:23,731 When a massive star dies, 546 00:32:23,765 --> 00:32:27,001 it blows itself to smithereens. 547 00:32:29,671 --> 00:32:32,373 Its substance is propelled across the vastness 548 00:32:32,407 --> 00:32:34,408 to be stirred by starlight 549 00:32:34,443 --> 00:32:36,711 and gathered up by gravity. 550 00:32:36,745 --> 00:32:38,579 Stars to dust 551 00:32:38,614 --> 00:32:41,415 and dust to stars. 552 00:32:41,450 --> 00:32:44,318 In the cosmos, nothing is wasted. 553 00:32:46,455 --> 00:32:50,358 But there's an upper limit to how massive a star can be. 554 00:32:52,694 --> 00:32:55,096 Back in the 17th century, when Edmond Halley 555 00:32:55,130 --> 00:32:57,798 crossed the equator to map the southern constellations, 556 00:32:57,833 --> 00:33:01,068 Eta Carinae seemed like just another faint star. 557 00:33:01,103 --> 00:33:03,905 But in 1843, Eta Carinae 558 00:33:03,939 --> 00:33:06,641 suddenly became the second brightest star in the sky, 559 00:33:06,675 --> 00:33:09,343 outshined only by Sirius. 560 00:33:09,378 --> 00:33:11,979 And it's been flipping out ever since. 561 00:33:14,449 --> 00:33:16,617 That dumbbell-shaped cloud 562 00:33:16,652 --> 00:33:19,854 is the expanding remnant of that event. 563 00:33:24,393 --> 00:33:27,461 At its center is one crazy star. 564 00:33:27,496 --> 00:33:29,363 Talk about unstable-- 565 00:33:29,398 --> 00:33:31,332 Eta Carinae is at least 100 times 566 00:33:31,366 --> 00:33:32,967 more massive than the Sun, 567 00:33:33,001 --> 00:33:36,270 and pouring out five million times more light. 568 00:33:36,305 --> 00:33:41,776 It's pushing the upper limit of what a star can be. 569 00:33:41,810 --> 00:33:44,612 What's more, there's evidence that Eta Carinae 570 00:33:44,646 --> 00:33:48,382 is being gravitationally tormented by an evil twin-- 571 00:33:48,417 --> 00:33:51,452 another massive star in orbit around it 572 00:33:51,486 --> 00:33:55,356 as close as Saturn is to the Sun. 573 00:33:55,390 --> 00:33:59,327 The core of a supermassive star pours out so much light 574 00:33:59,361 --> 00:34:02,864 that the outward pressure can overwhelm the star's gravity. 575 00:34:02,898 --> 00:34:05,333 If a star is too massive, 576 00:34:05,367 --> 00:34:08,002 its radiation pressure overpowers its gravity 577 00:34:08,036 --> 00:34:10,872 and blows the star apart. 578 00:34:12,674 --> 00:34:14,642 The fate of Eta Carinae was sealed 579 00:34:14,676 --> 00:34:17,078 when it was born millions of years ago. 580 00:34:17,112 --> 00:34:19,180 When it finally does blow up-- 581 00:34:19,214 --> 00:34:21,515 and who knows, maybe it already has; 582 00:34:21,550 --> 00:34:24,252 after all, we're looking at it by light that left the star 583 00:34:24,286 --> 00:34:26,754 7,500 years ago-- 584 00:34:26,788 --> 00:34:30,725 it will be a cataclysm unlike anything we've seen before. 585 00:34:30,759 --> 00:34:32,693 A hypernova. 586 00:34:44,640 --> 00:34:47,608 An explosion so powerful, it'll make a supernova 587 00:34:47,643 --> 00:34:50,511 seem like a firecracker by comparison. 588 00:34:50,546 --> 00:34:52,713 If there are nearby solar systems 589 00:34:52,748 --> 00:34:57,051 with planets harboring life, their days are numbered. 590 00:34:57,085 --> 00:35:00,388 A hypernova spews so much radiation into space-- 591 00:35:00,422 --> 00:35:03,691 not just light, but X-rays and gamma rays-- 592 00:35:03,725 --> 00:35:05,726 that planets that are dozens 593 00:35:05,761 --> 00:35:08,095 or perhaps hundreds of light-years away 594 00:35:08,130 --> 00:35:10,064 could be stripped of their atmospheres 595 00:35:10,098 --> 00:35:12,733 and bathed in deadly radiation. 596 00:35:12,768 --> 00:35:14,235 It would wreak havoc 597 00:35:14,269 --> 00:35:16,971 in thousands of nearby star systems. 598 00:35:17,005 --> 00:35:19,640 Right about now, you're probably asking yourself, 599 00:35:19,675 --> 00:35:22,076 "Are we safe?" 600 00:35:22,110 --> 00:35:24,445 If Eta Carinae blows up, 601 00:35:24,479 --> 00:35:27,114 what happens to Earth? 602 00:35:27,149 --> 00:35:30,318 Rest assured, Earth will be just fine. 603 00:35:30,352 --> 00:35:32,720 Remember, we're 7,500 light-years 604 00:35:32,754 --> 00:35:34,422 away from Eta Carinae. 605 00:35:34,456 --> 00:35:36,557 The intensity of radiation from a star, 606 00:35:36,592 --> 00:35:38,426 even an exploding star, 607 00:35:38,460 --> 00:35:40,661 falls off rapidly with distance. 608 00:35:40,696 --> 00:35:44,098 But still, Eta Carinae in its death throes 609 00:35:44,132 --> 00:35:46,100 will put on quite a show. 610 00:35:46,134 --> 00:35:48,603 It will light up the night of the southern hemisphere 611 00:35:48,637 --> 00:35:50,972 with the brightness of a second moon. 612 00:35:51,006 --> 00:35:55,276 The most dramatic swan song a star can sing. 613 00:36:00,616 --> 00:36:03,284 Our ancestors worshipped the Sun. 614 00:36:03,318 --> 00:36:06,354 And they were far from foolish. 615 00:36:06,388 --> 00:36:10,091 It makes good sense to revere the Sun and stars, 616 00:36:10,125 --> 00:36:12,493 because we are their children. 617 00:36:12,528 --> 00:36:15,963 The silicon in the rocks, the oxygen in the air, 618 00:36:15,998 --> 00:36:19,834 the carbon in our DNA, the iron in our skyscrapers, 619 00:36:19,868 --> 00:36:22,136 the silver in our jewelry 620 00:36:22,171 --> 00:36:25,973 were all made in stars billions of years ago. 621 00:36:26,008 --> 00:36:29,677 Our planet, our society and we ourselves 622 00:36:29,711 --> 00:36:32,180 are stardust. 623 00:36:33,749 --> 00:36:36,884 Well, what is it that makes the atoms dance? 624 00:36:36,919 --> 00:36:39,654 How is the energy of a star transformed 625 00:36:39,688 --> 00:36:42,690 into everything that happens in the world? 626 00:36:42,724 --> 00:36:44,959 What is energy? 627 00:36:44,993 --> 00:36:46,661 We're awash in it. 628 00:36:46,695 --> 00:36:49,463 When hydrogen atoms fuse inside the Sun, 629 00:36:49,498 --> 00:36:51,165 they make helium atoms. 630 00:36:51,200 --> 00:36:53,668 And this fusion emits a burst of energy 631 00:36:53,702 --> 00:36:56,971 that can wander inside the Sun for ten million years 632 00:36:57,005 --> 00:36:59,473 before making its way to the surface. 633 00:36:59,508 --> 00:37:02,009 And once there, it's free to fly 634 00:37:02,044 --> 00:37:04,212 straight from the Sun to the Earth 635 00:37:04,246 --> 00:37:06,881 as visible light. 636 00:37:06,915 --> 00:37:10,051 If it should strike the surface of a leaf, 637 00:37:10,085 --> 00:37:13,020 it will be stored in the plant as chemical energy. 638 00:37:13,055 --> 00:37:15,056 Sunshine... 639 00:37:15,090 --> 00:37:16,958 into moonshine. 640 00:37:36,378 --> 00:37:40,081 I can feel my brain turning the chemical energy of the wine 641 00:37:40,115 --> 00:37:42,250 into the electrical energy of my thoughts 642 00:37:42,284 --> 00:37:44,018 and directing my vocal chords 643 00:37:44,052 --> 00:37:46,787 to produce the acoustic energy of my voice. 644 00:37:46,822 --> 00:37:49,257 Such transformations of energy 645 00:37:49,291 --> 00:37:51,859 are happening everywhere all the time. 646 00:37:51,894 --> 00:37:53,528 Energy from our star 647 00:37:53,562 --> 00:37:55,563 drives the wind and the waves 648 00:37:55,597 --> 00:37:57,398 and the life around us. 649 00:37:57,432 --> 00:38:00,868 How lucky we are to have this vast source of clean energy 650 00:38:00,903 --> 00:38:04,805 falling like manna from heaven on all of us. 651 00:38:04,840 --> 00:38:06,741 To Annie Jump Cannon, 652 00:38:06,775 --> 00:38:08,409 Henrietta Swan Leavitt 653 00:38:08,443 --> 00:38:10,077 and Cecilia Payne 654 00:38:10,112 --> 00:38:13,047 for blazing the trail to modern astrophysics. 655 00:38:13,081 --> 00:38:16,984 And to all the sisters of the Sun. 656 00:38:22,925 --> 00:38:26,894 There's no refuge from change in the cosmos. 657 00:38:26,929 --> 00:38:29,764 Some ten or 20 million years from now, 658 00:38:29,798 --> 00:38:32,066 it'll seem for a cosmic moment 659 00:38:32,100 --> 00:38:35,803 as if Orion is finally about to catch the seven sisters. 660 00:38:35,838 --> 00:38:38,406 But before he has them in his clutches, 661 00:38:38,440 --> 00:38:42,109 the biggest stars of Orion will go supernova. 662 00:38:42,144 --> 00:38:45,246 Orion's pursuit of the Pleiades will finally end, 663 00:38:45,280 --> 00:38:46,747 and the seven sisters 664 00:38:46,782 --> 00:38:49,617 will glide serenely into the waiting arms 665 00:38:49,651 --> 00:38:52,019 of the Milky Way. 666 00:38:54,690 --> 00:38:57,458 We on Earth marvel-- and rightly so-- 667 00:38:57,493 --> 00:39:00,294 at the return of our solitary Sun. 668 00:39:00,329 --> 00:39:02,663 But from a planet orbiting a star 669 00:39:02,698 --> 00:39:04,665 in a distant globular cluster, 670 00:39:04,700 --> 00:39:07,802 a still more glorious dawn awaits. 671 00:39:09,071 --> 00:39:11,205 Not a sunrise... 672 00:39:11,240 --> 00:39:14,175 but a galaxy rise. 673 00:39:14,209 --> 00:39:18,279 A morning filled with 200 billion suns. 674 00:39:18,313 --> 00:39:21,282 The rising of the Milky Way. 675 00:39:21,316 --> 00:39:25,019 An enormous spiral form with collapsing gas clouds, 676 00:39:25,053 --> 00:39:28,689 condensing planetary systems, luminous supergiants, 677 00:39:28,724 --> 00:39:32,627 stable middle-aged suns, red giants, white dwarfs, 678 00:39:32,661 --> 00:39:35,062 planetary nebulas, supernovas, 679 00:39:35,097 --> 00:39:38,032 neutron stars, pulsars, black holes 680 00:39:38,066 --> 00:39:40,568 and, there is every reason to think, 681 00:39:40,602 --> 00:39:44,872 other exotic objects that we have yet to discover. 682 00:39:44,907 --> 00:39:48,743 From such a world, high above the Milky Way, 683 00:39:48,777 --> 00:39:51,412 it would be clear, as it is beginning 684 00:39:51,446 --> 00:39:53,648 to be clear on our world, 685 00:39:53,682 --> 00:39:57,985 that we are made by the atoms and the stars, 686 00:39:58,020 --> 00:40:00,054 that our matter and our form 687 00:40:00,088 --> 00:40:04,692 are forged by the great and ancient cosmos, 688 00:40:04,726 --> 00:40:07,395 of which we are a part.