All language subtitles for How.the.Universe.Works.Series.7.03of10.The.Interstellar.Mysteries.1080p.HDTV.x264.AAC.MVGroup.org.eng

af Afrikaans
ak Akan
sq Albanian
am Amharic
ar Arabic
hy Armenian
az Azerbaijani
eu Basque
be Belarusian
bem Bemba
bn Bengali
bh Bihari
bs Bosnian
br Breton
bg Bulgarian
km Cambodian
ca Catalan
chr Cherokee
ny Chichewa
zh-CN Chinese (Simplified)
zh-TW Chinese (Traditional)
co Corsican
hr Croatian
cs Czech
da Danish
nl Dutch
en English
eo Esperanto
et Estonian
ee Ewe
fo Faroese
tl Filipino
fi Finnish
fr French
fy Frisian
gaa Ga
gl Galician
ka Georgian
de German
el Greek
gn Guarani
gu Gujarati
ht Haitian Creole
ha Hausa
haw Hawaiian
iw Hebrew
hi Hindi
hu Hungarian
is Icelandic
ig Igbo
id Indonesian
ia Interlingua
ga Irish
it Italian
ja Japanese
jw Javanese
kn Kannada
kk Kazakh
rw Kinyarwanda
rn Kirundi
kg Kongo
ko Korean
kri Krio (Sierra Leone)
ku Kurdish
ckb Kurdish (Soranî)
ky Kyrgyz
lo Laothian
la Latin
lv Latvian
ln Lingala
lt Lithuanian
loz Lozi
lg Luganda
ach Luo
mk Macedonian
mg Malagasy
ms Malay
ml Malayalam
mt Maltese
mi Maori
mr Marathi
mfe Mauritian Creole
mo Moldavian
mn Mongolian
sr-ME Montenegrin
ne Nepali
pcm Nigerian Pidgin
nso Northern Sotho
no Norwegian
nn Norwegian (Nynorsk)
oc Occitan
or Oriya
om Oromo
ps Pashto
fa Persian
pl Polish
pt-BR Portuguese (Brazil)
pt-PT Portuguese (Portugal)
pa Punjabi
qu Quechua
ro Romanian Download
rm Romansh
nyn Runyakitara
ru Russian
gd Scots Gaelic
sr Serbian
sh Serbo-Croatian
st Sesotho
tn Setswana
crs Seychellois Creole
sn Shona
sd Sindhi
si Sinhalese
sk Slovak
sl Slovenian
so Somali
es Spanish
es-419 Spanish (Latin American)
su Sundanese
sw Swahili
sv Swedish
tg Tajik
ta Tamil
tt Tatar
te Telugu
th Thai
ti Tigrinya
to Tonga
lua Tshiluba
tum Tumbuka
tr Turkish
tk Turkmen
tw Twi
ug Uighur
uk Ukrainian
ur Urdu
uz Uzbek
vi Vietnamese
cy Welsh
wo Wolof
xh Xhosa
yi Yiddish
yo Yoruba
zu Zulu
Would you like to inspect the original subtitles? These are the user uploaded subtitles that are being translated: 0 00:00:00,010 --> 00:00:07,777 1 00:00:03,537 --> 00:00:07,439 Interstellar space is the space between the stars. 2 00:00:10,477 --> 00:00:14,679 Interstellar space is vast, largely unknown, 3 00:00:14,681 --> 00:00:18,149 and largely unmapped. 4 00:00:18,151 --> 00:00:23,488 Now astronomers are probing this great abyss 5 00:00:23,490 --> 00:00:26,424 and discovering something remarkable. 6 00:00:30,296 --> 00:00:32,364 Interstellar space is busy. 7 00:00:32,366 --> 00:00:34,832 It's filled with activity. 8 00:00:34,834 --> 00:00:39,304 There are rogue planets that are not attached to a star. 9 00:00:39,306 --> 00:00:43,174 There are cosmic rays, there are interstellar gas clouds. 10 00:00:43,176 --> 00:00:44,842 We've even got high-velocity stars. 11 00:00:44,844 --> 00:00:47,245 All of that is careening around out there. 12 00:00:47,247 --> 00:00:50,848 The greatest secrets in our universe... 13 00:00:50,850 --> 00:00:52,917 Interstellar space is where we came from. 14 00:00:52,919 --> 00:00:55,654 ...Could lie between the stars. 15 00:00:58,725 --> 00:01:01,526 captions paid for by discovery communications 16 00:01:15,676 --> 00:01:17,543 we live in a small solar system 17 00:01:17,545 --> 00:01:20,446 in the suburbs of the milky way galaxy ... 18 00:01:23,816 --> 00:01:31,155 8 planets and more than 180 moons all orbiting the sun. 19 00:01:31,157 --> 00:01:35,293 In our solar system, the sun is the sheriff of the town. 20 00:01:35,295 --> 00:01:39,897 We do whatever the sun wants us to do. 21 00:01:39,899 --> 00:01:43,034 The sun's influence stretches more than one light-year 22 00:01:43,036 --> 00:01:46,671 in every direction 23 00:01:46,673 --> 00:01:50,241 and defines the boundary of our solar system. 24 00:01:50,243 --> 00:01:53,778 Someplace out there is a place where the sun's influence ends 25 00:01:53,780 --> 00:01:55,915 and the other stars' begins. 26 00:01:55,917 --> 00:01:58,449 That's the entrance to interstellar space. 27 00:02:04,324 --> 00:02:06,457 Interstellar space is the region 28 00:02:06,459 --> 00:02:09,294 between star systems in our galaxy. 29 00:02:12,199 --> 00:02:16,668 Until now, we've known little about it. 30 00:02:16,670 --> 00:02:18,269 For so long, we've thought the space 31 00:02:18,271 --> 00:02:20,605 in between the stars as entirely empty, 32 00:02:20,607 --> 00:02:23,409 but this turns out not to be true at all. 33 00:02:23,411 --> 00:02:25,344 There's a lot going on out there, 34 00:02:25,346 --> 00:02:28,747 and it's the forefront of astronomy. 35 00:02:28,749 --> 00:02:31,883 One of the biggest clues about interstellar space 36 00:02:31,885 --> 00:02:34,619 came right to our doorstep. 37 00:02:41,228 --> 00:02:44,228 October 2017. 38 00:02:44,230 --> 00:02:49,367 The pan-starrs1 telescope spots something unusual. 39 00:02:49,369 --> 00:02:51,703 Pan-starrs is an observatory in Hawaii, 40 00:02:51,705 --> 00:02:54,372 and it's scanning large sections of the sky, 41 00:02:54,374 --> 00:02:56,441 looking for things that change. 42 00:02:59,713 --> 00:03:02,447 All of a sudden, there was this tiny, little visitor 43 00:03:02,449 --> 00:03:04,649 just screaming through the solar system. 44 00:03:04,651 --> 00:03:07,919 It was going about 200,000 miles an hour. 45 00:03:07,921 --> 00:03:10,188 It was a much faster object 46 00:03:10,190 --> 00:03:13,391 than what might be expected for a solar-system object. 47 00:03:13,393 --> 00:03:15,727 And also its trajectory was such 48 00:03:15,729 --> 00:03:19,663 that it seemed like its orbit was not bound to the sun. 49 00:03:19,665 --> 00:03:24,837 It was totally unlike any other path, any other trajectory, 50 00:03:24,839 --> 00:03:29,674 any other orbit in our solar system. 51 00:03:29,676 --> 00:03:33,378 Astronomers reached an extraordinary conclusion. 52 00:03:35,815 --> 00:03:37,549 It became very clear that, yeah, 53 00:03:37,551 --> 00:03:39,884 this was not some solar-system object 54 00:03:39,886 --> 00:03:41,419 falling from a long way away. 55 00:03:41,421 --> 00:03:44,889 This was something that came from another star, 56 00:03:44,891 --> 00:03:48,492 and I think everybody was pretty amazed by that. 57 00:03:53,366 --> 00:03:56,167 Our first known interstellar visitor 58 00:03:56,169 --> 00:03:59,970 on a fly-by through our solar system. 59 00:03:59,972 --> 00:04:04,109 It was the very first object that we had ever discovered 60 00:04:04,111 --> 00:04:07,045 that had originated outside the solar system. 61 00:04:07,047 --> 00:04:10,648 Everything else we've seen ... every comet, every asteroid ... 62 00:04:10,650 --> 00:04:13,918 originated within our solar system. 63 00:04:13,920 --> 00:04:16,988 A big, mega solid object 64 00:04:16,990 --> 00:04:18,789 entering in our own solar system, 65 00:04:18,791 --> 00:04:22,927 that's something that, you know, I can only dream of 66 00:04:22,929 --> 00:04:25,396 but had never thought it would actually be a reality. 67 00:04:29,402 --> 00:04:32,269 Scientists named the object 'oumuamua, 68 00:04:32,271 --> 00:04:36,741 Hawaiian for "a messenger from afar arriving first." 69 00:04:38,879 --> 00:04:40,945 This thing came from interstellar space 70 00:04:40,947 --> 00:04:42,280 into our solar system, 71 00:04:42,282 --> 00:04:45,150 and the main question is, what could it be? 72 00:04:50,290 --> 00:04:54,759 The object's shape was mystifying. 73 00:04:54,761 --> 00:04:56,694 It's almost sort of shaped like a cigar. 74 00:04:56,696 --> 00:05:00,099 It's 10 times longer than it is wide. 75 00:05:00,101 --> 00:05:01,232 And this is extraordinary. 76 00:05:01,234 --> 00:05:02,834 There's no object in our solar system 77 00:05:02,836 --> 00:05:06,138 that we've ever measured that is this elongated. 78 00:05:09,175 --> 00:05:12,310 'Oumuamua looked so unnatural, 79 00:05:12,312 --> 00:05:16,914 it sparked scientists' imaginations. 80 00:05:16,916 --> 00:05:18,584 One of the things to remember about scientists 81 00:05:18,586 --> 00:05:19,984 is that we're still human beings. 82 00:05:19,986 --> 00:05:21,386 We have read science fiction. 83 00:05:21,388 --> 00:05:23,688 We have imaginations. 84 00:05:25,458 --> 00:05:26,858 I have to admit, when I first heard about it, 85 00:05:26,860 --> 00:05:29,060 my first thought is that it was rama from 86 00:05:29,062 --> 00:05:31,396 an Arthur c. Clarke story, "rendezvous with rama." 87 00:05:31,398 --> 00:05:34,065 This is a very elongated spaceship 88 00:05:34,067 --> 00:05:36,167 that came from another star. 89 00:05:38,138 --> 00:05:40,271 It reminded me of some designs 90 00:05:40,273 --> 00:05:43,474 we had for interstellar space crafts 91 00:05:43,476 --> 00:05:46,076 that have to be much longer than they are wide 92 00:05:46,078 --> 00:05:52,484 in order to minimize friction with the interstellar gas. 93 00:05:52,486 --> 00:05:57,021 Could 'oumuamua be an alien interstellar spacecraft? 94 00:06:01,828 --> 00:06:05,029 astronomers, including professor avi loeb, 95 00:06:05,031 --> 00:06:07,698 took the idea seriously. 96 00:06:07,700 --> 00:06:10,568 We decided to follow this object 97 00:06:10,570 --> 00:06:12,570 using the best telescopes in the world 98 00:06:12,572 --> 00:06:16,007 and observe whether there is any radio transmission from it. 99 00:06:18,311 --> 00:06:23,047 Astronomers hunted for signs of alien communication. 100 00:06:26,652 --> 00:06:28,786 But after eight hours of listening 101 00:06:28,788 --> 00:06:34,058 across multiple frequencies, nothing. 102 00:06:34,060 --> 00:06:37,194 Sadly, no emissions were detected. 103 00:06:37,196 --> 00:06:39,397 It's almost certainly a natural object. 104 00:06:39,399 --> 00:06:41,599 I would bet all of my money on that. 105 00:06:41,601 --> 00:06:42,800 I was disappointed. 106 00:06:42,802 --> 00:06:44,535 I would've been much more excited 107 00:06:44,537 --> 00:06:48,306 if we had found evidence for an alien civilization. 108 00:06:51,678 --> 00:06:54,679 No little green men this time. 109 00:06:54,681 --> 00:06:58,149 'Oumuamua is a natural object. 110 00:06:58,151 --> 00:07:01,419 But what exactly is it? 111 00:07:01,421 --> 00:07:05,622 At first, observers thought it might be a comet. 112 00:07:05,624 --> 00:07:08,092 Something that's mostly ice with a little bit of rock. 113 00:07:08,094 --> 00:07:09,293 Those are the sorts of bodies 114 00:07:09,295 --> 00:07:11,095 that exist really far out from the star 115 00:07:11,097 --> 00:07:15,232 and are the easiest things to eject. 116 00:07:15,234 --> 00:07:17,902 But a comet passing this close to the sun 117 00:07:17,904 --> 00:07:20,038 would warm up, 118 00:07:20,040 --> 00:07:26,176 turning the ice into a gas, forming a vapor trail. 119 00:07:26,178 --> 00:07:31,382 On 'oumuamua, astronomers saw no sign of this happening. 120 00:07:31,384 --> 00:07:33,584 There was no fuzziness around it 121 00:07:33,586 --> 00:07:34,853 that you would expect from a comet 122 00:07:34,855 --> 00:07:37,989 as the ice was turned into a gas. 123 00:07:37,991 --> 00:07:39,256 It was really mysterious, 124 00:07:39,258 --> 00:07:41,259 and so everybody who was observing it 125 00:07:41,261 --> 00:07:43,861 thought it was an asteroid. 126 00:07:46,666 --> 00:07:51,103 As team's track 'oumuamua across the sky, 127 00:07:51,105 --> 00:07:54,872 there was an unexpected twist. 128 00:07:54,874 --> 00:07:57,475 As 'oumuamua passed through our solar system, 129 00:07:57,477 --> 00:08:00,278 basically, it was falling in toward the sun, 130 00:08:00,280 --> 00:08:02,947 speeding up immensely as it passed the sun, 131 00:08:02,949 --> 00:08:05,016 before exiting the solar system 132 00:08:05,018 --> 00:08:07,151 in almost the opposite direction. 133 00:08:07,153 --> 00:08:08,352 But then something weird happened. 134 00:08:08,354 --> 00:08:09,821 As it was moving away from the sun, 135 00:08:09,823 --> 00:08:12,289 it was slowing down as you'd expect, 136 00:08:12,291 --> 00:08:16,361 but it wasn't slowing down fast enough. 137 00:08:16,363 --> 00:08:19,631 'Oumuamua gets a boost through our solar system, 138 00:08:19,633 --> 00:08:22,567 but how? 139 00:08:22,569 --> 00:08:26,037 So we think the reason is that it's outgassing. 140 00:08:26,039 --> 00:08:28,706 In other words, it was emitting a little bit of gas, 141 00:08:28,708 --> 00:08:30,107 and that was acting as a little bit 142 00:08:30,109 --> 00:08:32,243 of a rocket-motor push on it. 143 00:08:32,245 --> 00:08:34,846 It's kind of like a little jet engine on the surface ... 144 00:08:34,848 --> 00:08:38,317 just gives it a little thrust over time. 145 00:08:38,319 --> 00:08:41,585 This tiny nudge reveals 'oumuamua's 146 00:08:41,587 --> 00:08:43,421 true identity. 147 00:08:45,191 --> 00:08:48,126 So, in that case, it is looking more like a comet. 148 00:08:48,128 --> 00:08:51,929 It's just that that emission wasn't enough to see. 149 00:08:56,470 --> 00:08:59,937 Powered by outgassing, this interstellar nomad 150 00:08:59,939 --> 00:09:02,339 might travel from star to star, 151 00:09:02,341 --> 00:09:04,274 but figuring out where in the galaxy 152 00:09:04,276 --> 00:09:09,080 it came from just got more difficult. 153 00:09:09,082 --> 00:09:11,949 Now that we know 'oumuamua has outgassed, 154 00:09:11,951 --> 00:09:15,019 which changes its velocity and changes its trajectory, 155 00:09:15,021 --> 00:09:18,556 it makes it much harder to do that. 156 00:09:18,558 --> 00:09:21,892 'Oumuamua may now be safely racing away, 157 00:09:21,894 --> 00:09:24,829 but the solar system faces bombardment 158 00:09:24,831 --> 00:09:30,301 from another interstellar source firing at earth 159 00:09:30,303 --> 00:09:32,703 at close to the speed of light. 160 00:09:32,705 --> 00:09:37,543 Cosmic rays are the bullets of the universe, 161 00:09:37,545 --> 00:09:40,912 and they are flooding interstellar space. 162 00:10:01,467 --> 00:10:04,601 'Oumuamua's surface tells the story of its journey 163 00:10:04,603 --> 00:10:08,339 through interstellar space. 164 00:10:08,341 --> 00:10:10,874 Radebaugh: The interesting thing about 'oumuamua is its color. 165 00:10:10,876 --> 00:10:12,744 It's actually red. 166 00:10:12,746 --> 00:10:15,080 I'm standing on a surface that's a nice analogue 167 00:10:15,082 --> 00:10:17,215 for the surface of 'oumuamua. 168 00:10:17,217 --> 00:10:19,016 As you look around, you see a really dark, 169 00:10:19,018 --> 00:10:21,886 kind of shiny coating to all of the rocks, 170 00:10:21,888 --> 00:10:23,421 and it extends up the valley 171 00:10:23,423 --> 00:10:25,556 and even onto the mountains behind me. 172 00:10:28,894 --> 00:10:31,695 Scientists think 'oumuamua's red sheen 173 00:10:31,697 --> 00:10:33,497 comes from tholins, 174 00:10:33,499 --> 00:10:38,836 organic molecules that are the building blocks of life. 175 00:10:38,838 --> 00:10:43,040 How cool is it that something came out from some other origin, 176 00:10:43,042 --> 00:10:44,775 passed through our neighborhood, 177 00:10:44,777 --> 00:10:46,910 and it possessed some sort of organics? 178 00:10:46,912 --> 00:10:49,881 That could be a possible gold mine for us. 179 00:10:52,385 --> 00:10:54,051 In our own solar system, 180 00:10:54,053 --> 00:10:57,455 distant objects like comets and asteroids 181 00:10:57,457 --> 00:11:01,125 also carry tholins. 182 00:11:01,127 --> 00:11:03,394 This happens because their surfaces are bombarded 183 00:11:03,396 --> 00:11:06,396 by cosmic rays and that changes the nature 184 00:11:06,398 --> 00:11:08,866 of the chemicals on the surface. 185 00:11:08,868 --> 00:11:11,335 So we think the same thing has happened to 'oumuamua. 186 00:11:11,337 --> 00:11:13,004 It's been out there in interstellar space 187 00:11:13,006 --> 00:11:16,107 and been bombarded by cosmic rays over the eons. 188 00:11:20,012 --> 00:11:23,614 Galactic cosmic rays are high-energy particles 189 00:11:23,616 --> 00:11:25,349 that tear through the universe. 190 00:11:30,156 --> 00:11:36,828 interstellar space is filled to the brim with these cosmic rays. 191 00:11:36,830 --> 00:11:39,163 Things like protons and electrons or perhaps 192 00:11:39,165 --> 00:11:41,232 some heavier, the more exotic particles 193 00:11:41,234 --> 00:11:44,636 that are literally whizzing through the universe. 194 00:11:44,638 --> 00:11:46,837 Some cosmic rays can travel as fast 195 00:11:46,839 --> 00:11:48,772 as 99% the speed of light ... 196 00:11:48,774 --> 00:11:52,176 incredibly fast, energetic things. 197 00:11:52,178 --> 00:11:55,112 It takes a lot of energy 198 00:11:55,114 --> 00:12:00,117 to accelerate anything close to the speed of light. 199 00:12:00,119 --> 00:12:03,921 Cosmic rays come from many energetic and powerful 200 00:12:03,923 --> 00:12:08,525 and violent sources in our universe. 201 00:12:08,527 --> 00:12:15,166 Everything that's big and blasting generates cosmic rays. 202 00:12:15,168 --> 00:12:19,870 One of the most powerful cosmic-ray generators 203 00:12:19,872 --> 00:12:23,408 is the death of a giant star, a supernova. 204 00:12:29,349 --> 00:12:32,950 a supernova is a really energetic explosion. 205 00:12:32,952 --> 00:12:35,587 It's so energetic that it can create all kinds 206 00:12:35,589 --> 00:12:38,689 of interesting things. 207 00:12:38,691 --> 00:12:42,760 When a star runs out of fuel, it collapses. 208 00:12:42,762 --> 00:12:45,496 The mass of the star crashes inwards, 209 00:12:45,498 --> 00:12:48,165 triggering a huge explosion. 210 00:12:53,707 --> 00:12:57,174 the shock wave slams into surrounding gas, 211 00:12:57,176 --> 00:13:00,644 amplifying magnetic fields. 212 00:13:00,646 --> 00:13:02,580 If you get a particle caught in there, 213 00:13:02,582 --> 00:13:05,116 trapped in the magnetic fields of this gas, 214 00:13:05,118 --> 00:13:08,986 it can bounce back and forth, be accelerated very rapidly. 215 00:13:08,988 --> 00:13:11,188 It goes ding, ding, ding-ding-ding-ding. 216 00:13:11,190 --> 00:13:13,190 Like that. 217 00:13:13,192 --> 00:13:15,859 Eventually, the particle moves so fast 218 00:13:15,861 --> 00:13:19,430 that the magnetic field can no longer hold it. 219 00:13:21,534 --> 00:13:24,569 And, pyew, it gets shot out at very near the speed of light. 220 00:13:28,141 --> 00:13:35,012 Cosmic rays have mass, and they wreak havoc. 221 00:13:35,014 --> 00:13:39,884 Cosmic rays are the bullets of the universe, 222 00:13:39,886 --> 00:13:42,753 and they are flooding interstellar space. 223 00:13:42,755 --> 00:13:45,022 But, thankfully, we're protected. 224 00:13:49,895 --> 00:13:53,163 Cosmic rays from interstellar space battle 225 00:13:53,165 --> 00:13:57,301 with another superpower ... 226 00:13:57,303 --> 00:14:01,306 our own bodyguard in the solar system ... the sun. 227 00:14:03,242 --> 00:14:05,509 We think of the sun as the source of energy 228 00:14:05,511 --> 00:14:07,978 and warmth for earth, the giver of life, 229 00:14:07,980 --> 00:14:09,380 but it's also protecting us in ways 230 00:14:09,382 --> 00:14:11,115 you might not be aware of. 231 00:14:13,586 --> 00:14:16,720 The sun emits a stream of charged particles 232 00:14:16,722 --> 00:14:20,391 called the solar wind. 233 00:14:20,393 --> 00:14:23,327 The particles hurtle out past the planets 234 00:14:23,329 --> 00:14:25,596 at more than a million miles an hour. 235 00:14:29,001 --> 00:14:32,937 But they do eventually run out of power. 236 00:14:32,939 --> 00:14:36,273 There's this region where the solar wind grinds to a stop. 237 00:14:36,275 --> 00:14:39,076 It's plowing into this material between the stars 238 00:14:39,078 --> 00:14:41,545 and eventually slows and stops. 239 00:14:45,284 --> 00:14:49,487 The solar wind carries the sun's magnetic field with it, 240 00:14:49,489 --> 00:14:53,824 forming a bubble around our solar system. 241 00:14:53,826 --> 00:14:56,560 We call that the heliosphere, "helio" for the sun 242 00:14:56,562 --> 00:14:59,296 and "sphere" for this giant magnetic field. 243 00:14:59,298 --> 00:15:01,098 It acts, basically, like a shield, 244 00:15:01,100 --> 00:15:03,634 protecting us from these galactic cosmic rays. 245 00:15:03,636 --> 00:15:05,436 If that weren't there, 246 00:15:05,438 --> 00:15:09,306 the radiation levels hitting the earth would actually increase. 247 00:15:09,308 --> 00:15:11,775 So, in a real way, the sun is protecting us 248 00:15:11,777 --> 00:15:14,845 from the dangerous environment of interstellar space. 249 00:15:16,849 --> 00:15:18,516 The heliosphere protects us 250 00:15:18,518 --> 00:15:21,051 from the majority of cosmic rays, 251 00:15:21,053 --> 00:15:25,990 but some still make it into the solar system. 252 00:15:25,992 --> 00:15:31,862 Fortunately for us, earth also has its own defense mechanisms. 253 00:15:31,864 --> 00:15:35,466 We have our magnetic field that can redirect 254 00:15:35,468 --> 00:15:39,737 the lowest energy cosmic rays, and we have our nice, 255 00:15:39,739 --> 00:15:42,940 thick security blanket of an atmosphere, 256 00:15:42,942 --> 00:15:46,877 which absorbs most of the high-energy cosmic rays 257 00:15:46,879 --> 00:15:50,882 before they even get a chance to reach us here on the surface. 258 00:15:56,756 --> 00:15:59,690 Cosmic rays from interstellar space 259 00:15:59,692 --> 00:16:03,160 can alter DNA and cause diseases. 260 00:16:03,162 --> 00:16:07,631 But without them, we might not be here at all. 261 00:16:07,633 --> 00:16:09,433 Even that tiny fraction of cosmic rays 262 00:16:09,435 --> 00:16:10,634 that makes it through our atmosphere 263 00:16:10,636 --> 00:16:12,102 to the surface of the earth 264 00:16:12,104 --> 00:16:16,807 can have a profound influence on the evolution of life. 265 00:16:16,809 --> 00:16:18,976 Cosmic rays can damage the DNA 266 00:16:18,978 --> 00:16:21,912 that carries the information of life. 267 00:16:23,516 --> 00:16:25,649 When those molecules are broken apart, 268 00:16:25,651 --> 00:16:28,852 the atom is altered by collisions with cosmic rays. 269 00:16:28,854 --> 00:16:30,720 The information carried is changed. 270 00:16:30,722 --> 00:16:32,055 That's a mutation. 271 00:16:32,057 --> 00:16:34,592 That's what drives natural selection. 272 00:16:34,594 --> 00:16:37,861 So life and we ourselves are deeply connected 273 00:16:37,863 --> 00:16:41,732 to interstellar space around us. 274 00:16:44,803 --> 00:16:49,740 But interstellar space is also home to much larger objects, 275 00:16:49,742 --> 00:16:54,445 objects that could wipe out life all together. 276 00:17:15,768 --> 00:17:19,103 Our solar system races around the center of the milky way 277 00:17:19,105 --> 00:17:23,440 at 143 miles per second. 278 00:17:23,442 --> 00:17:25,642 At its center, the sun, 279 00:17:25,644 --> 00:17:31,047 just 1 of around 200 billion stars in our galaxy. 280 00:17:31,049 --> 00:17:32,983 We're not living in an isolated bubble 281 00:17:32,985 --> 00:17:34,585 all on our own here in the galaxy. 282 00:17:34,587 --> 00:17:38,355 We're living in a swarm, a neighborhood of other stars. 283 00:17:41,527 --> 00:17:43,527 And the movement of all these stars 284 00:17:43,529 --> 00:17:46,564 can have far-reaching effects on our solar system. 285 00:17:50,003 --> 00:17:57,808 Beyond the planets and our heliosphere... 286 00:17:57,810 --> 00:18:01,278 Lies the oort cloud 287 00:18:01,280 --> 00:18:05,883 right on the border of true interstellar space. 288 00:18:05,885 --> 00:18:09,486 The oort cloud is the remnants of the formation 289 00:18:09,488 --> 00:18:13,356 of the solar system ... small, icy, dirty bodies, 290 00:18:13,358 --> 00:18:15,359 aka comets. 291 00:18:19,298 --> 00:18:21,565 The comets in the oort cloud 292 00:18:21,567 --> 00:18:26,303 are so far out they're only weakly bound to the sun. 293 00:18:26,305 --> 00:18:29,707 They spend most their lives perfectly happy, 294 00:18:29,709 --> 00:18:33,510 orbiting the sun lazily in their frigid depths, 295 00:18:33,512 --> 00:18:36,547 but every once in a while, they can be perturbed. 296 00:18:39,652 --> 00:18:42,986 Our sun is moving through interstellar space, 297 00:18:42,988 --> 00:18:46,390 and so are other stars. 298 00:18:46,392 --> 00:18:48,325 As our sun orbits the galaxy 299 00:18:48,327 --> 00:18:51,128 and encounters other stellar neighbors, 300 00:18:51,130 --> 00:18:52,929 inevitably, there is going to be one 301 00:18:52,931 --> 00:18:57,534 that's going to pass through or near our oort cloud. 302 00:18:57,536 --> 00:18:59,536 The gravity of a nearby star 303 00:18:59,538 --> 00:19:05,942 could disrupt the oort cloud... 304 00:19:05,944 --> 00:19:08,379 Sending showers of comets 305 00:19:08,381 --> 00:19:10,447 barreling through the solar system. 306 00:19:14,420 --> 00:19:17,621 Some of them could strike earth. 307 00:19:31,637 --> 00:19:33,771 Comets falling down into the inner solar system 308 00:19:33,773 --> 00:19:35,506 is something that we really want to pay attention to, 309 00:19:35,508 --> 00:19:38,108 that could actually be dangerous to life here on earth. 310 00:19:38,110 --> 00:19:40,778 So one of the things we do is look out into the galaxy 311 00:19:40,780 --> 00:19:43,047 and see if any stars are gonna be coming nearby 312 00:19:43,049 --> 00:19:45,083 anytime in the near future. 313 00:19:48,053 --> 00:19:51,055 With a new space observatory called Gaia, 314 00:19:51,057 --> 00:19:54,925 astronomers keep watch over millions of neighboring stars 315 00:19:54,927 --> 00:19:58,462 in our galaxy, 316 00:19:58,464 --> 00:20:02,799 tracking their movements through interstellar space. 317 00:20:02,801 --> 00:20:05,003 So what's the next star that's gonna pass the earth? 318 00:20:05,005 --> 00:20:06,803 And it turns out we may know. 319 00:20:06,805 --> 00:20:08,071 There's an orange dwarf. 320 00:20:08,073 --> 00:20:10,341 It's called gliese 710. 321 00:20:12,278 --> 00:20:15,345 In 2018, new data shows 322 00:20:15,347 --> 00:20:19,149 gliese 710 is on a collision course 323 00:20:19,151 --> 00:20:21,552 with our oort cloud. 324 00:20:21,554 --> 00:20:23,219 It's gonna kick up a lot of dirt, 325 00:20:23,221 --> 00:20:24,688 kick up a lot of dust, 326 00:20:24,690 --> 00:20:28,091 and it might be bad news for the inner solar system. 327 00:20:28,093 --> 00:20:30,827 We might get a lot of unwanted visitors. 328 00:20:36,302 --> 00:20:39,235 Luckily for us, gliese 710 won't arrive 329 00:20:39,237 --> 00:20:42,306 for another 1.3 million years. 330 00:20:44,844 --> 00:20:48,912 But there are other rogue stars out there. 331 00:20:48,914 --> 00:20:50,647 All the stars that you can see in our sky 332 00:20:50,649 --> 00:20:52,916 Are in the disc of the milky way galaxy, 333 00:20:52,918 --> 00:20:55,251 and they tend to be moving in the same direction 334 00:20:55,253 --> 00:20:57,688 at about 100 miles per second around the center. 335 00:21:00,459 --> 00:21:05,795 Gaia discovers stars that follow different rules. 336 00:21:05,797 --> 00:21:07,597 They don't seem to be moving around 337 00:21:07,599 --> 00:21:09,065 with the motion of the galaxy. 338 00:21:09,067 --> 00:21:11,735 Instead, they're actually flying through space. 339 00:21:13,740 --> 00:21:15,138 And they are screaming. 340 00:21:15,140 --> 00:21:16,607 These are cannonballs. 341 00:21:16,609 --> 00:21:18,809 They're moving, three, four, five times faster 342 00:21:18,811 --> 00:21:20,677 than the other stars in the galaxy, 343 00:21:20,679 --> 00:21:24,014 and they tend to moving away from the center. 344 00:21:26,151 --> 00:21:30,621 These cosmic cannonballs are known as hypervelocity stars. 345 00:21:34,094 --> 00:21:37,627 What could cause them to move so quickly? 346 00:21:37,629 --> 00:21:41,498 Some of these stars originated from binary star systems 347 00:21:41,500 --> 00:21:44,301 in which one of the components went supernova, 348 00:21:44,303 --> 00:21:47,504 removing that gravitational tie to the other star, 349 00:21:47,506 --> 00:21:48,839 allowing that star to escape 350 00:21:48,841 --> 00:21:51,576 and basically be ejected through the galaxy 351 00:21:51,578 --> 00:21:54,979 on its own very, you know, high-speed trajectory. 352 00:21:57,916 --> 00:22:03,454 Some hypervelocity stars have a darker past. 353 00:22:03,456 --> 00:22:06,390 They're flung from a black hole. 354 00:22:06,392 --> 00:22:11,394 There are trillions of black holes in the universe. 355 00:22:11,396 --> 00:22:14,197 There are giant black holes at the centers 356 00:22:14,199 --> 00:22:17,734 of nearly all large galaxies, including our own. 357 00:22:20,005 --> 00:22:25,208 And these monsters inflict chaos on paired stars. 358 00:22:25,210 --> 00:22:27,343 Again, you have a binary system of stars, 359 00:22:27,345 --> 00:22:28,979 and they are orbiting the back hole 360 00:22:28,981 --> 00:22:30,747 in the center of our galaxy. 361 00:22:30,749 --> 00:22:32,148 When they get too close, 362 00:22:32,150 --> 00:22:33,884 one of the stars falls into the black hole, 363 00:22:33,886 --> 00:22:36,954 and the other one is ejected away at high speed. 364 00:22:39,692 --> 00:22:42,292 These hypervelocity stars Blaze through 365 00:22:42,294 --> 00:22:45,495 interstellar space. 366 00:22:45,497 --> 00:22:51,435 Their stellar winds can bring beauty out of chaos. 367 00:22:51,437 --> 00:22:52,835 A lot of these hypervelocity stars 368 00:22:52,837 --> 00:22:54,971 that we see are very massive stars, 369 00:22:54,973 --> 00:22:58,841 much larger and hotter and more luminous than the sun. 370 00:22:58,843 --> 00:23:00,977 Well, as they're plowing through the material 371 00:23:00,979 --> 00:23:03,580 in between the stars their wind is expanding 372 00:23:03,582 --> 00:23:06,516 and slamming into the gas and the dust. 373 00:23:06,518 --> 00:23:08,652 And so what you see when you look at them 374 00:23:08,654 --> 00:23:14,591 is this beautiful arc, like the bow wave off of a ship. 375 00:23:14,593 --> 00:23:17,794 And we have images of these, and they're gorgeous. 376 00:23:17,796 --> 00:23:21,431 These are beautiful, beautiful patterns. 377 00:23:24,269 --> 00:23:26,870 Hypervelocity stars paint the canvas 378 00:23:26,872 --> 00:23:29,239 of the universe. 379 00:23:31,877 --> 00:23:34,011 It looks serene, 380 00:23:34,013 --> 00:23:39,949 but interstellar space can be anything but tranquil. 381 00:23:44,757 --> 00:23:46,957 it's no man's land. It's the wild west. 382 00:23:46,959 --> 00:23:48,291 There are no rules. 383 00:23:48,293 --> 00:23:51,160 You can do whatever you want. 384 00:23:51,162 --> 00:23:56,433 In the badlands of the galaxy, outlaws reign supreme. 385 00:24:15,454 --> 00:24:17,854 Tens of light-years from the sun, 386 00:24:17,856 --> 00:24:23,126 mysterious objects lurk in the darkness. 387 00:24:23,128 --> 00:24:25,595 We've only seen a fraction of the stuff that's out there, 388 00:24:25,597 --> 00:24:28,632 you know, so this is really the next great frontier. 389 00:24:30,736 --> 00:24:34,270 In 2016, scientists spot a tiny source 390 00:24:34,272 --> 00:24:38,475 of infrared light 95 light-years from earth. 391 00:24:44,015 --> 00:24:48,118 it's too dim to be a star and not orbiting a star either. 392 00:24:50,822 --> 00:24:54,758 It can only be a rogue planet. 393 00:24:54,760 --> 00:24:56,827 When we think of a planet, we think of an object 394 00:24:56,829 --> 00:24:58,361 that's orbiting a star. 395 00:24:58,363 --> 00:25:01,264 In fact, that's the very definition of a planet today. 396 00:25:01,266 --> 00:25:03,900 Well, what if it doesn't orbit anything? 397 00:25:03,902 --> 00:25:06,303 We call those rogue planets. 398 00:25:12,845 --> 00:25:14,311 The following year, 399 00:25:14,313 --> 00:25:18,448 astronomers take more detailed images. 400 00:25:18,450 --> 00:25:23,786 They find it's not just one world but two. 401 00:25:23,788 --> 00:25:25,254 And that's incredible, right? 402 00:25:25,256 --> 00:25:27,190 There's this object out in the middle of space. 403 00:25:27,192 --> 00:25:28,591 They're not orbiting stars. 404 00:25:28,593 --> 00:25:31,128 These are rogue planets orbiting each other. 405 00:25:33,665 --> 00:25:37,333 Planets with 4 times the mass of Jupiter 406 00:25:37,335 --> 00:25:39,536 over 300 million miles apart, 407 00:25:39,538 --> 00:25:43,473 more than 3 times the distance between the earth and the sun, 408 00:25:43,475 --> 00:25:47,944 they circle each other once a century. 409 00:25:47,946 --> 00:25:49,812 Think about not just one rogue planet 410 00:25:49,814 --> 00:25:51,548 but a binary rogue planet, 411 00:25:51,550 --> 00:25:55,419 two planets circling around each other. 412 00:25:55,421 --> 00:25:58,154 They may still be gas giants, like Jupiter, 413 00:25:58,156 --> 00:26:00,023 and if that's the case, they don't have a surface. 414 00:26:00,025 --> 00:26:01,358 But if they're really old, 415 00:26:01,360 --> 00:26:03,493 they could actually have had enough time to cool 416 00:26:03,495 --> 00:26:05,429 and maybe they do have a surface. 417 00:26:05,431 --> 00:26:08,131 We don't really know, but they would be very dark. 418 00:26:08,133 --> 00:26:11,001 There's no star nearby to light them up. 419 00:26:14,172 --> 00:26:17,307 Rogue planets drift in eternal darkness 420 00:26:17,309 --> 00:26:23,046 through the frigid expanses of interstellar space, 421 00:26:23,048 --> 00:26:28,251 untouched by light for millions of years. 422 00:26:28,253 --> 00:26:30,388 Let's say you found yourself standing on the surface 423 00:26:30,390 --> 00:26:31,654 of one of these rogue planets. 424 00:26:31,656 --> 00:26:33,656 I mean, it would be such a bizarre sight. 425 00:26:33,658 --> 00:26:35,525 There wouldn't be a sun. 426 00:26:35,527 --> 00:26:40,263 You know, it would just be the night sky all around you. 427 00:26:40,265 --> 00:26:42,066 Think about the darkest, 428 00:26:42,068 --> 00:26:44,868 moonless night you can possibly imagine here on the earth. 429 00:26:44,870 --> 00:26:46,736 That's the light level that you have out there 430 00:26:46,738 --> 00:26:48,772 in interstellar space. 431 00:26:51,076 --> 00:26:54,410 Physicists now believe there could be billions 432 00:26:54,412 --> 00:27:01,485 of rogue planets in our galaxy, one for every four stars. 433 00:27:01,487 --> 00:27:05,088 The question is, why do these rogue planets exist at all? 434 00:27:05,090 --> 00:27:06,690 Did they form freely, 435 00:27:06,692 --> 00:27:10,493 or were they somehow cast out of their solar system? 436 00:27:10,495 --> 00:27:12,629 The answer is probably both. 437 00:27:18,370 --> 00:27:21,370 Some rogue planets formed from lumps of gas 438 00:27:21,372 --> 00:27:25,242 that never quite became stars. 439 00:27:25,244 --> 00:27:27,310 Others formed like planets 440 00:27:27,312 --> 00:27:32,382 around a star in solar systems like our own. 441 00:27:32,384 --> 00:27:37,320 When solar systems are formed, they're violent places. 442 00:27:37,322 --> 00:27:39,789 Sometimes planets just crash into each other 443 00:27:39,791 --> 00:27:42,191 and become a single object. 444 00:27:42,193 --> 00:27:44,193 But sometimes there are near misses, 445 00:27:44,195 --> 00:27:49,466 and they'll scatter away from each other and be ejected. 446 00:27:49,468 --> 00:27:54,137 So these rogue planets spend almost their entire lives 447 00:27:54,139 --> 00:27:56,072 completely alone. 448 00:28:01,413 --> 00:28:03,413 Without a star to keep them warm, 449 00:28:03,415 --> 00:28:08,551 rogue planets seem to be an unlikely place for life. 450 00:28:08,553 --> 00:28:10,820 A rogue planet on its own out in space, 451 00:28:10,822 --> 00:28:12,622 probably not gonna be habitable. 452 00:28:12,624 --> 00:28:13,823 It's cold out there, right? 453 00:28:13,825 --> 00:28:15,424 So if it's the size of the earth, 454 00:28:15,426 --> 00:28:18,895 it's probably a frozen ball. 455 00:28:18,897 --> 00:28:22,766 But in 2018, astronomers announced that life 456 00:28:22,768 --> 00:28:26,536 could be possible on a moon around a rogue planet. 457 00:28:29,374 --> 00:28:32,175 There are icy moons orbiting Jupiter and saturn 458 00:28:32,177 --> 00:28:35,044 that are heated by the gravity of the planets they orbit. 459 00:28:35,046 --> 00:28:38,915 It has nothing to do with the sun. 460 00:28:38,917 --> 00:28:42,051 As these moons are warped by the planet's gravity, 461 00:28:42,053 --> 00:28:45,722 friction generates heat that keeps the water liquid. 462 00:28:48,994 --> 00:28:51,194 So it's entirely possible that if a rogue planet 463 00:28:51,196 --> 00:28:54,664 was able to keep its moons and these moons are icy, 464 00:28:54,666 --> 00:28:57,000 they could have liquid oceans under their surface. 465 00:28:57,002 --> 00:28:58,401 They don't need a star. 466 00:28:58,403 --> 00:29:00,804 They've got their planet keeping them warm. 467 00:29:06,611 --> 00:29:09,746 Interstellar space is far from empty. 468 00:29:09,748 --> 00:29:13,950 It's loaded with disconnected bodies that don't have a home. 469 00:29:16,154 --> 00:29:17,486 You can think of interstellar space 470 00:29:17,488 --> 00:29:19,755 as almost sort of a cosmic pinball machine. 471 00:29:19,757 --> 00:29:21,223 You've got high-velocity stars. 472 00:29:21,225 --> 00:29:22,825 You've got rogue planets. 473 00:29:22,827 --> 00:29:25,095 You've even moons that have been thrown out from around planets. 474 00:29:25,097 --> 00:29:28,765 All of that is careening around out there. 475 00:29:28,767 --> 00:29:32,101 Interstellar space is more active and alive 476 00:29:32,103 --> 00:29:34,238 than we ever imagined. 477 00:29:34,240 --> 00:29:38,842 As it turns out, it even has clouds that sing. 478 00:30:01,466 --> 00:30:03,399 Hundreds of light-years away, 479 00:30:03,401 --> 00:30:05,001 vast amounts of gas 480 00:30:05,003 --> 00:30:10,140 and dust drift through interstellar space. 481 00:30:10,142 --> 00:30:12,141 Think about all that space between the stars, 482 00:30:12,143 --> 00:30:13,609 full of gas, dust ... 483 00:30:13,611 --> 00:30:16,380 full of the stories about how stars and planets formed. 484 00:30:16,382 --> 00:30:19,015 We've been missing a lot. 485 00:30:19,017 --> 00:30:20,950 Scientists call the gas and dust 486 00:30:20,952 --> 00:30:24,120 between the stars the interstellar medium. 487 00:30:27,292 --> 00:30:31,094 It's the most common stuff out there in the galaxy. 488 00:30:31,096 --> 00:30:34,698 It's hydrogen atoms, a few helium atoms here and there. 489 00:30:39,104 --> 00:30:41,571 The interstellar medium isn't distributed 490 00:30:41,573 --> 00:30:44,642 evenly throughout the galaxy. 491 00:30:44,644 --> 00:30:46,309 It's patchy. It's clumpy. 492 00:30:46,311 --> 00:30:47,977 And there's some regions that have more stuff, 493 00:30:47,979 --> 00:30:51,514 and some regions that have less. 494 00:30:51,516 --> 00:30:55,485 The regions with more stuff are called interstellar clouds. 495 00:30:59,057 --> 00:31:00,657 An interstellar cloud is really just 496 00:31:00,659 --> 00:31:03,193 a slightly denser concentration of gas 497 00:31:03,195 --> 00:31:07,063 and possibly dust that we see scattered across our galaxy. 498 00:31:09,735 --> 00:31:12,669 Interstellar clouds can stretch vast distances 499 00:31:12,671 --> 00:31:16,206 across the cosmos ... 500 00:31:16,208 --> 00:31:21,477 some reaching a million times the mass of the sun. 501 00:31:21,479 --> 00:31:22,879 You know, it boggles my mind 502 00:31:22,881 --> 00:31:24,747 when I look at these interstellar clouds 503 00:31:24,749 --> 00:31:27,016 and realize that they're light-years in size. 504 00:31:31,823 --> 00:31:34,624 Interstellar clouds are more than just clumps 505 00:31:34,626 --> 00:31:37,493 of gas and dust. 506 00:31:37,495 --> 00:31:40,296 They're alive. 507 00:31:40,298 --> 00:31:44,367 Scharf: We know that these are places where stars form, 508 00:31:44,369 --> 00:31:46,369 and they're also places that are, themselves, 509 00:31:46,371 --> 00:31:48,771 formed by dying stars. 510 00:31:56,114 --> 00:32:00,983 Stars form when an interstellar cloud collapses. 511 00:32:00,985 --> 00:32:04,387 Gravity pulls matter together, igniting the core. 512 00:32:09,461 --> 00:32:11,327 but astronomers don't have a full 513 00:32:11,329 --> 00:32:13,196 understanding of the process. 514 00:32:15,300 --> 00:32:16,866 Understanding the shape and structure of a cloud 515 00:32:16,868 --> 00:32:19,668 like this is important to understanding 516 00:32:19,670 --> 00:32:21,938 the process of star formation. 517 00:32:21,940 --> 00:32:24,006 Some shapes and structures just aren't big enough, 518 00:32:24,008 --> 00:32:27,210 in some dimensions, to allow a cloud to collapse. 519 00:32:27,212 --> 00:32:29,879 Everything we can learn about this sort of thing 520 00:32:29,881 --> 00:32:31,681 really depends on its shape. 521 00:32:31,683 --> 00:32:34,651 So knowing that shape is the key to understanding it. 522 00:32:38,423 --> 00:32:40,757 But there's a problem. 523 00:32:40,759 --> 00:32:42,558 When we look out into the universe, 524 00:32:42,560 --> 00:32:45,962 we're seeing everything projected onto the sky. 525 00:32:45,964 --> 00:32:50,232 So we may look at the structure like an interstellar cloud 526 00:32:50,234 --> 00:32:54,170 and have very little information about its depth. 527 00:32:54,172 --> 00:32:56,572 That's one of the big challenges for astronomers, 528 00:32:56,574 --> 00:32:59,775 is to decode the full three-dimensional shape 529 00:32:59,777 --> 00:33:01,878 of these clouds. 530 00:33:04,515 --> 00:33:07,583 In 2018, scientists get a breakthrough 531 00:33:07,585 --> 00:33:12,856 in their efforts to understand star formation. 532 00:33:12,858 --> 00:33:15,858 Around 490 light-years from earth 533 00:33:15,860 --> 00:33:21,397 lies an interstellar cloud known as musca. 534 00:33:21,399 --> 00:33:24,133 It looks like a thin snake. 535 00:33:24,135 --> 00:33:25,935 Optically, this dark doodle, 536 00:33:25,937 --> 00:33:27,537 if you will, looks like a dark cloud. 537 00:33:27,539 --> 00:33:28,972 It looks rather two-dimensional, 538 00:33:28,974 --> 00:33:32,977 silhouetted against the background stars on the sky. 539 00:33:32,979 --> 00:33:38,948 Astronomers examine musca in infrared, 540 00:33:38,950 --> 00:33:43,353 and discover it's singing. 541 00:33:43,355 --> 00:33:46,489 It vibrates, and it sets up waves 542 00:33:46,491 --> 00:33:48,424 that move through this cloud, back and forth. 543 00:33:48,426 --> 00:33:51,628 And these are called magnetohydrodynamic waves, 544 00:33:51,630 --> 00:33:53,363 which sounds awesome. 545 00:33:56,167 --> 00:33:59,369 The team converted the waves into musical notes, 546 00:33:59,371 --> 00:34:03,172 producing musca's song. 547 00:34:15,854 --> 00:34:17,854 it turns out that, if you study this, 548 00:34:17,856 --> 00:34:19,389 you can actually determine 549 00:34:19,391 --> 00:34:21,457 the three-dimensional shape of this cloud 550 00:34:21,459 --> 00:34:23,526 by the way the waves move through it. 551 00:34:28,500 --> 00:34:31,000 It's a little bit like listening to the frequency of sound 552 00:34:31,002 --> 00:34:33,736 coming from some instrument that you don't see, 553 00:34:33,738 --> 00:34:35,537 and trying to reconstruct what kind of an instrument 554 00:34:35,539 --> 00:34:36,873 that must be. 555 00:34:43,748 --> 00:34:45,415 A low notes tells you you're listening 556 00:34:45,417 --> 00:34:51,087 to something large, like a cello, 557 00:34:51,089 --> 00:34:54,089 while a high note represents something smaller, 558 00:34:54,091 --> 00:34:57,093 like a violin. 559 00:34:57,095 --> 00:34:59,229 And just as different instruments 560 00:34:59,231 --> 00:35:02,966 make very different sounds, 561 00:35:02,968 --> 00:35:08,170 clouds with different structures will vibrate in different ways. 562 00:35:08,172 --> 00:35:12,374 They'll "sing" different songs. 563 00:35:12,376 --> 00:35:13,576 The sounds, if you will, 564 00:35:13,578 --> 00:35:15,511 the frequencies coming from that cloud, 565 00:35:15,513 --> 00:35:19,582 are a clue ultimately to its shape and structure. 566 00:35:19,584 --> 00:35:20,983 And with this musca cloud, 567 00:35:20,985 --> 00:35:22,785 even though it just looks like a line in the sky, 568 00:35:22,787 --> 00:35:25,721 astronomers were able to determine its 3-d shape. 569 00:35:25,723 --> 00:35:27,323 And it's not just a filament. 570 00:35:27,325 --> 00:35:29,125 It's actually a disc. 571 00:35:29,127 --> 00:35:31,327 It's like we're seeing a disc edge-on. 572 00:35:35,601 --> 00:35:40,536 Musca is more of a pancake than a snake. 573 00:35:40,538 --> 00:35:45,340 We've just been looking at the pancake from the side. 574 00:35:45,342 --> 00:35:46,810 That's amazing. 575 00:35:46,812 --> 00:35:49,211 It's like putting on 3-d glasses for the first time 576 00:35:49,213 --> 00:35:52,081 and finally seeing depth in the universe. 577 00:35:56,287 --> 00:35:57,887 The same technique can be used 578 00:35:57,889 --> 00:36:01,957 to study other interstellar clouds. 579 00:36:01,959 --> 00:36:04,227 It brings with it a whole new wealth of knowledge 580 00:36:04,229 --> 00:36:07,697 on the structure and processes that are going on there. 581 00:36:19,711 --> 00:36:22,245 We're discovering that the interstellar space 582 00:36:22,247 --> 00:36:26,716 in our galaxy is full of stuff, 583 00:36:26,718 --> 00:36:30,386 but something doesn't quite add up. 584 00:36:30,388 --> 00:36:33,789 It turns out that if we take all of the matter 585 00:36:33,791 --> 00:36:35,858 we see around the universe today 586 00:36:35,860 --> 00:36:38,527 and add it up, it doesn't equal the total amount 587 00:36:38,529 --> 00:36:40,130 that we know must be there. 588 00:36:43,802 --> 00:36:47,470 1/3 of the matter in the universe is missing. 589 00:36:47,472 --> 00:36:50,673 So where is it? 590 00:36:50,675 --> 00:36:55,478 To find it, we have to look beyond interstellar space 591 00:36:55,480 --> 00:37:00,749 into the dark, mysterious reaches of intergalactic space. 592 00:37:21,506 --> 00:37:24,640 The milky way is one of trillions of galaxies 593 00:37:24,642 --> 00:37:28,712 in the observable universe. 594 00:37:28,714 --> 00:37:30,779 The milky way galaxy is a disc. 595 00:37:30,781 --> 00:37:33,316 It's about 100,000 light-years across. 596 00:37:33,318 --> 00:37:38,254 It's filled with stars, lots of planets, and gas and dust. 597 00:37:38,256 --> 00:37:40,523 But where does our galaxy end 598 00:37:40,525 --> 00:37:44,059 and the other galaxies begin? 599 00:37:44,061 --> 00:37:45,962 A structure like our galaxy 600 00:37:45,964 --> 00:37:49,065 doesn't really have a hard edge to it. 601 00:37:49,067 --> 00:37:52,068 It actually becomes less and less dense, 602 00:37:52,070 --> 00:37:54,537 and it gradually Peters out as you move 603 00:37:54,539 --> 00:37:57,573 into true intergalactic space. 604 00:38:01,279 --> 00:38:05,681 Between the galaxies are huge gaps ... 605 00:38:05,683 --> 00:38:09,418 intergalactic space. 606 00:38:09,420 --> 00:38:14,089 But, like interstellar space, this region isn't empty. 607 00:38:19,163 --> 00:38:25,835 new research reveals, it holds the answer to a major mystery. 608 00:38:25,837 --> 00:38:29,638 We know how much normal matter was made in the big bang. 609 00:38:29,640 --> 00:38:31,107 And we can look around us today 610 00:38:31,109 --> 00:38:33,508 and count up all the normal matter we see, 611 00:38:33,510 --> 00:38:36,546 and the problem is, they don't equal up. 612 00:38:38,516 --> 00:38:40,516 There's something wrong with the galaxies 613 00:38:40,518 --> 00:38:46,322 in our universe ... they're not massive enough. 614 00:38:46,324 --> 00:38:51,660 About 1/3 of the normal matter in the universe is missing. 615 00:38:51,662 --> 00:38:56,866 There is more normal matter that is not bound inside of galaxies. 616 00:38:56,868 --> 00:38:59,402 So where is it? 617 00:39:01,672 --> 00:39:04,474 One idea for where this missing normal matter could be, 618 00:39:04,476 --> 00:39:08,011 is that it's actually floating outside of our galaxy 619 00:39:08,013 --> 00:39:10,446 in a hot gas. 620 00:39:13,751 --> 00:39:15,885 Scientists suspected this hot gas 621 00:39:15,887 --> 00:39:22,225 might exist in long strands between the galaxies, 622 00:39:22,227 --> 00:39:24,360 but the gas is so thin and diffuse, 623 00:39:24,362 --> 00:39:28,898 it has been hard to detect... 624 00:39:28,900 --> 00:39:30,499 Until now. 625 00:39:35,706 --> 00:39:39,909 in 2018, astronomers study a bright distant quasar 626 00:39:39,911 --> 00:39:45,581 called 1es 1553. 627 00:39:45,583 --> 00:39:49,418 A quasar is when a black hole feeds. 628 00:39:51,989 --> 00:39:53,389 It gives off light, 629 00:39:53,391 --> 00:39:56,426 and we can see it all the way across the universe. 630 00:39:59,063 --> 00:40:02,465 The quasar's light takes over 4 billion years 631 00:40:02,467 --> 00:40:05,334 to reach us, 632 00:40:05,336 --> 00:40:09,605 but observers notice something unusual. 633 00:40:09,607 --> 00:40:11,808 Something is absorbing the light 634 00:40:11,810 --> 00:40:14,076 as it passes through the universe. 635 00:40:16,146 --> 00:40:19,281 The culprit? 636 00:40:19,283 --> 00:40:21,483 Ghostly strands of gas 637 00:40:21,485 --> 00:40:27,423 suspended in the spaces between galaxies. 638 00:40:27,425 --> 00:40:31,560 These results suggest that a good fraction 639 00:40:31,562 --> 00:40:34,496 of the normal matter in our universe 640 00:40:34,498 --> 00:40:37,232 is not enclosed inside of galaxies. 641 00:40:37,234 --> 00:40:39,301 They don't live in the city limits. 642 00:40:39,303 --> 00:40:41,103 Instead, they live in long, 643 00:40:41,105 --> 00:40:45,308 thin streams that connect the galaxies together. 644 00:40:50,047 --> 00:40:53,516 Heated by shock waves to millions of degrees, 645 00:40:53,518 --> 00:40:56,051 these strands of gas could extend 646 00:40:56,053 --> 00:41:00,723 throughout the universe... 647 00:41:00,725 --> 00:41:02,191 And account for the matter 648 00:41:02,193 --> 00:41:05,194 that's been missing all this time. 649 00:41:09,734 --> 00:41:13,202 this opens up a very interesting question ... 650 00:41:13,204 --> 00:41:14,871 has this matter always been there 651 00:41:14,873 --> 00:41:19,008 and just failed to accumulate onto the galaxies, 652 00:41:19,010 --> 00:41:23,546 or was it started in galaxies and gets blown out? 653 00:41:23,548 --> 00:41:25,748 We honestly don't know. 654 00:41:30,955 --> 00:41:34,757 Interstellar space, 655 00:41:34,759 --> 00:41:37,426 and now intergalactic space, 656 00:41:37,428 --> 00:41:39,629 are more alive than we thought. 657 00:41:42,266 --> 00:41:46,234 From rogue planets 658 00:41:46,236 --> 00:41:49,839 to singing clouds of gas, 659 00:41:49,841 --> 00:41:54,176 interstellar space is stranger than fiction. 660 00:41:54,178 --> 00:41:58,180 And we've only just begun to tell its story. 661 00:42:00,517 --> 00:42:01,784 Just because there's so much we don't 662 00:42:01,786 --> 00:42:03,385 understand about interstellar space, 663 00:42:03,387 --> 00:42:05,988 it makes it that much more critical to explore 664 00:42:05,990 --> 00:42:07,989 and try to figure it out. 665 00:42:07,991 --> 00:42:09,991 There's more to find out about interstellar space 666 00:42:09,993 --> 00:42:11,393 than what we know, 667 00:42:11,395 --> 00:42:13,061 and that's the beauty of exploration 668 00:42:13,063 --> 00:42:15,064 and the beauty of knowledge, is it's ever-expanding, 669 00:42:15,066 --> 00:42:18,067 and that frontier is always there. 670 00:42:18,069 --> 00:42:19,468 Who knows what else is out there? 671 00:42:19,470 --> 00:42:21,804 What else could be lurking out in the dark, 672 00:42:21,806 --> 00:42:23,473 between the stars? 53013

Can't find what you're looking for?
Get subtitles in any language from opensubtitles.com, and translate them here.