WEBVTT 00:00:25.320 --> 00:00:27.920 In the lives of every creature on Earth… 00:00:31.360 --> 00:00:32.840 …are echoes… 00:00:35.120 --> 00:00:38.880 …of events that occurred a long, long time ago. 00:00:43.680 --> 00:00:45.600 Events of unimaginable scale… 00:00:47.920 --> 00:00:49.280 and violent beauty… 00:00:51.440 --> 00:00:54.240 that connect all living things… 00:00:56.080 --> 00:00:58.760 …their every action and decision, 00:00:59.440 --> 00:01:00.920 their every heartbeat, 00:01:02.920 --> 00:01:05.720 to the grandest story ever told. 00:01:07.760 --> 00:01:12.400 This is a tale 13.8 billion years in the making… 00:01:14.680 --> 00:01:17.160 that has seen billions of stars 00:01:18.240 --> 00:01:20.040 and billions of worlds… 00:01:22.240 --> 00:01:25.440 live and die… 00:01:27.920 --> 00:01:30.520 to create the only planet we know of 00:01:32.200 --> 00:01:34.880 that is home to life. 00:01:39.200 --> 00:01:41.160 From the stardust that built us… 00:01:43.440 --> 00:01:46.640 to the cosmic ingredients that sustain us… 00:01:52.880 --> 00:01:56.400 and the starlight that powers it all, 00:01:57.960 --> 00:02:03.360 this is the story of our universe. 00:02:39.560 --> 00:02:40.800 East Africa. 00:02:46.160 --> 00:02:50.880 It's where life's most vital connection to the universe can be found. 00:02:55.000 --> 00:02:57.280 And a very special predator… 00:03:00.400 --> 00:03:02.640 named Wa Chini. 00:03:06.000 --> 00:03:10.160 Life for a cheetah is a never-ending search for food… 00:03:12.320 --> 00:03:13.680 for vital energy. 00:03:16.120 --> 00:03:21.400 And this is one of the hardest places on Earth for a predator to obtain it. 00:03:31.000 --> 00:03:34.240 The blistering sun has driven away nearly everything 00:03:34.320 --> 00:03:36.600 from these dry, desolate plains. 00:03:42.800 --> 00:03:46.840 Any creature that remains here struggles to survive. 00:03:51.480 --> 00:03:53.600 Wa Chini's sole focus… 00:03:57.360 --> 00:03:59.400 …the only thing driving her… 00:04:03.000 --> 00:04:04.080 …is hunger. 00:04:07.800 --> 00:04:10.800 This simple, primal impulse 00:04:10.880 --> 00:04:14.560 stems from a deep connection she has to her surroundings 00:04:15.520 --> 00:04:18.680 that extends beyond the Serengeti, 00:04:19.280 --> 00:04:20.840 beyond our planet 00:04:22.000 --> 00:04:23.640 to the universe itself. 00:04:29.720 --> 00:04:31.800 Every cell in Wa Chini's body… 00:04:34.160 --> 00:04:36.800 is linked to an ancient stream of energy… 00:04:39.920 --> 00:04:41.240 …connecting her life 00:04:42.920 --> 00:04:44.440 to the heart of a star. 00:04:49.840 --> 00:04:53.640 This unbroken stream spans vast reaches of space… 00:04:58.240 --> 00:05:02.160 and stretches back 13.8 billion years. 00:05:13.200 --> 00:05:18.280 Ancient energy that existed at the origin of our universe 00:05:20.120 --> 00:05:21.360 powers everything. 00:05:23.200 --> 00:05:24.480 Every planet. 00:05:26.320 --> 00:05:27.280 Every star. 00:05:30.480 --> 00:05:31.400 Every life. 00:05:40.200 --> 00:05:42.680 Wa Chini is hunting for energy… 00:05:46.080 --> 00:05:47.640 but not just for herself. 00:05:49.440 --> 00:05:52.040 A mother of two five-month-old cubs, 00:05:53.800 --> 00:05:56.880 she's desperate to feed her hungry family. 00:06:04.400 --> 00:06:07.520 It's dry season, and food is scarce. 00:06:08.920 --> 00:06:12.000 And yet, energy is more abundant than ever. 00:06:15.920 --> 00:06:17.880 It's just hiding in plain sight. 00:06:21.280 --> 00:06:25.680 The largest, brightest, hottest object in our solar system… 00:06:28.240 --> 00:06:29.240 the sun. 00:06:41.240 --> 00:06:45.600 Huge loops of searingly hot plasma erupt from its surface. 00:06:51.960 --> 00:06:57.560 Our sun blasts out the energy of four and a half trillion atomic bombs 00:06:57.640 --> 00:06:58.960 every second… 00:07:01.560 --> 00:07:04.280 sending more power to our planet in an hour 00:07:04.880 --> 00:07:07.960 than the entire world consumes in a year. 00:07:12.520 --> 00:07:16.240 But as impressive as this gigantic fireball is… 00:07:18.680 --> 00:07:21.520 Wa Chini cannot eat sunlight. 00:07:23.760 --> 00:07:26.320 She only eats things that run… 00:07:29.280 --> 00:07:30.520 like gazelle. 00:07:38.760 --> 00:07:41.440 Her spotted coat provides camouflage, 00:07:42.480 --> 00:07:44.760 essential for stalking prey. 00:07:58.200 --> 00:08:03.640 With few places to hide, getting closer isn't an option. 00:08:15.640 --> 00:08:18.920 Luckily, Wa Chini has a trick up her sleeve. 00:08:26.280 --> 00:08:29.800 Cheetah are the fastest animals on land. 00:08:32.160 --> 00:08:35.360 From zero to a hundred in just three seconds… 00:08:37.480 --> 00:08:40.800 but gazelles are a pretty close second. 00:08:45.080 --> 00:08:47.280 Wa Chini uses up a lot of energy… 00:08:59.960 --> 00:09:01.280 but gains nothing. 00:09:05.400 --> 00:09:08.880 An adult cheetah can survive for over a week without a meal. 00:09:12.600 --> 00:09:17.120 But cubs, they can go no longer than a few days. 00:09:24.080 --> 00:09:29.360 And these two are getting very, very hungry. 00:09:37.840 --> 00:09:40.920 Hunting at such great speeds is incredibly depleting. 00:09:43.200 --> 00:09:46.480 Wa Chini's energy reserves are now dangerously low. 00:09:50.680 --> 00:09:54.200 It will be hours before she has the strength to hunt again. 00:10:00.200 --> 00:10:04.000 Wa Chini and her cubs are running on empty. 00:10:22.040 --> 00:10:25.400 Animals all over the planet fight the same ongoing battle 00:10:26.480 --> 00:10:27.760 between consuming… 00:10:31.320 --> 00:10:32.800 and using energy. 00:10:38.160 --> 00:10:40.000 No matter your strategy, 00:10:40.080 --> 00:10:41.960 be it fast or slow, 00:10:47.080 --> 00:10:50.000 your next meal is never guaranteed. 00:10:59.280 --> 00:11:03.560 Hunger is something all of us must overcome. 00:11:12.600 --> 00:11:14.920 Having recovered from her last chase, 00:11:15.920 --> 00:11:18.520 Wa Chini is looking for her next opportunity. 00:11:22.920 --> 00:11:24.400 Like all cheetah mothers, 00:11:26.040 --> 00:11:27.920 she's parenting solo. 00:11:31.680 --> 00:11:33.600 To keep her young cubs well-fed, 00:11:34.320 --> 00:11:36.560 she should make a kill every day. 00:11:38.240 --> 00:11:40.920 But it's taken her so long to recover 00:11:42.240 --> 00:11:44.080 that the sun is now setting. 00:11:53.720 --> 00:11:55.280 As the light fades, 00:11:56.480 --> 00:11:58.760 so does this family's hopes of a meal. 00:12:05.880 --> 00:12:07.360 As Earth rotates… 00:12:09.960 --> 00:12:15.200 the Serengeti turns away from the sun and into darkness. 00:12:21.520 --> 00:12:24.760 It's a powerful reminder of life's connection to the sun. 00:12:29.200 --> 00:12:32.840 Our story is the sun's story. 00:12:35.160 --> 00:12:36.520 Long, long ago… 00:12:39.760 --> 00:12:44.440 …our solar system was even colder and darker than it is today. 00:12:56.880 --> 00:13:01.960 And yet, these were the perfect conditions for the birth of a star. 00:13:05.200 --> 00:13:07.760 At temperatures close to absolute zero, 00:13:08.640 --> 00:13:11.840 the force of gravity began pulling dust and gas together… 00:13:14.240 --> 00:13:15.760 …into a massive cloud. 00:13:22.880 --> 00:13:24.720 The cloud collapsed inwards, 00:13:24.800 --> 00:13:28.240 crushing itself into a glowing hot ball of gas. 00:13:32.240 --> 00:13:33.600 A protostar. 00:13:40.880 --> 00:13:45.160 Like Wa Chini, this star in the making had a ferocious hunger… 00:13:48.000 --> 00:13:51.320 pulling in so much gas that jets of hot matter 00:13:52.360 --> 00:13:54.760 were propelled from its poles, 00:13:56.280 --> 00:13:58.960 stretching out light years into space. 00:14:02.280 --> 00:14:08.320 The infant star continued to grow for 30 million years… 00:14:19.440 --> 00:14:20.680 …until finally, 00:14:21.880 --> 00:14:26.200 it became hot enough to generate power all on its own. 00:14:29.360 --> 00:14:30.320 Our sun. 00:14:33.280 --> 00:14:37.160 Its golden rays have now shone brilliantly and steadily… 00:14:39.200 --> 00:14:41.640 for 4.6 billion years. 00:14:47.400 --> 00:14:51.960 It's just one star in a galaxy of billions. 00:14:57.360 --> 00:15:00.760 And yet, it is a most special one… 00:15:03.120 --> 00:15:06.080 because it is the one that delivers heat and light… 00:15:08.440 --> 00:15:10.640 to this incredible, vibrant planet. 00:15:23.680 --> 00:15:27.760 Every living thing in the Serengeti depends on the sun for its energy. 00:15:29.800 --> 00:15:34.080 Wa Chini's cubs are drained, beyond hungry now. 00:15:35.200 --> 00:15:37.280 They need to eat today. 00:15:39.000 --> 00:15:44.160 But all Wa Chini can provide this morning is precious TLC. 00:15:45.800 --> 00:15:47.520 In this parched land, 00:15:48.560 --> 00:15:52.440 our sun both gives and takes. 00:15:53.640 --> 00:15:57.120 Its fierce energy is what life needs. 00:15:58.320 --> 00:16:02.280 But it also has the power to destroy. 00:16:06.600 --> 00:16:12.320 It was never going to be easy living this close to a giant nuclear reactor. 00:16:21.280 --> 00:16:24.160 To understand the source of this unbearable heat, 00:16:25.360 --> 00:16:28.040 we must peer into the inferno… 00:16:37.240 --> 00:16:40.240 …beneath the outer layers of bubbling hot plasma… 00:16:45.960 --> 00:16:50.120 650 thousand kilometers down… 00:16:54.920 --> 00:16:57.120 to the core of our sun. 00:17:00.840 --> 00:17:04.840 Our star's heart would seem surprisingly calm… 00:17:07.040 --> 00:17:10.880 but on an atomic level, it's pure chaos. 00:17:14.360 --> 00:17:18.280 This is the hottest part of our solar system. 00:17:21.000 --> 00:17:24.440 Temperatures here reach 15 million degrees Celsius… 00:17:27.640 --> 00:17:32.200 creating the conditions for an event that can happen almost nowhere else. 00:17:36.600 --> 00:17:39.560 Atoms collide at high speed and fuse… 00:17:45.160 --> 00:17:47.000 …releasing pure energy. 00:17:54.760 --> 00:17:59.040 This process is called nuclear fusion 00:17:59.880 --> 00:18:02.320 and is what makes our sun shine. 00:18:06.480 --> 00:18:11.120 In fact, it's what powers all the stars in our universe. 00:18:15.200 --> 00:18:20.320 This energy released by stars can be traced back to the beginning of time… 00:18:25.480 --> 00:18:27.240 when there was no matter, 00:18:27.840 --> 00:18:32.080 and all that existed in the entire universe was energy. 00:18:35.120 --> 00:18:39.000 And every bit of it lives on in our universe today. 00:18:46.600 --> 00:18:48.440 As sunlight hits the Serengeti, 00:18:49.880 --> 00:18:53.280 energy that's been flowing for 13.8 billion years 00:18:54.880 --> 00:18:58.240 finds its way to Wa Chini and her cubs 00:18:59.040 --> 00:19:03.240 and continues its journey through their environment. 00:19:04.880 --> 00:19:08.080 It is never created or destroyed. 00:19:09.000 --> 00:19:12.840 It is simply transformed endlessly. 00:19:14.240 --> 00:19:18.840 But Wa Chini and her Cubs can only access this energy in one form… 00:19:23.560 --> 00:19:24.720 meat. 00:19:33.800 --> 00:19:36.400 And there are rival predators out here… 00:19:39.200 --> 00:19:43.480 who could snatch not just her food but her cubs as well. 00:19:58.080 --> 00:19:59.960 If they don't feed soon, 00:20:01.000 --> 00:20:02.480 they will die regardless. 00:20:23.480 --> 00:20:26.560 It's a meager snack, but after two days without food, 00:20:27.080 --> 00:20:28.480 it's a lifesaver. 00:20:32.480 --> 00:20:35.840 But more than 10% of cheetah kills are stolen. 00:20:40.280 --> 00:20:43.920 Wa Chini must defend every scrap of energy she captures… 00:20:47.840 --> 00:20:49.880 …because when energy is scarce, 00:20:50.720 --> 00:20:53.160 competition is fierce. 00:20:57.080 --> 00:21:00.920 Wa Chini's struggle to survive and sustain her family is repeated 00:21:01.400 --> 00:21:03.440 day after day… 00:21:06.040 --> 00:21:07.840 …month after month. 00:21:17.880 --> 00:21:21.520 Every meal is a fight. 00:21:27.320 --> 00:21:30.440 In the battle between using and acquiring energy… 00:21:32.560 --> 00:21:35.080 Wa Chini is only just breaking even. 00:21:40.400 --> 00:21:45.600 Dry season on the Serengeti is defined by constant hunger. 00:21:52.040 --> 00:21:53.760 But change is in the air. 00:21:55.560 --> 00:22:00.680 The sun's heat has pulled what moisture there is high into the sky. 00:22:05.080 --> 00:22:06.560 And what goes up 00:22:07.880 --> 00:22:11.120 must eventually come down. 00:22:14.680 --> 00:22:17.440 Rains sweep across the plains 00:22:18.360 --> 00:22:20.880 and bring dry season to an end. 00:22:26.640 --> 00:22:28.280 As the clouds clear, 00:22:29.960 --> 00:22:31.760 a glimmer of hope appears. 00:22:44.120 --> 00:22:47.400 A single blade of grass cannot feed Wa Chini's family… 00:22:49.920 --> 00:22:51.840 but deep within its cells 00:22:52.360 --> 00:22:54.480 lies the answer to their hunger. 00:23:06.520 --> 00:23:09.080 Here, there's a hidden world. 00:23:15.000 --> 00:23:21.600 Microscopic stacks called grana bask in the warm rays from the sun. 00:23:32.800 --> 00:23:37.600 Their surface is covered with a forest of tiny, light-harvesting proteins 00:23:38.880 --> 00:23:42.720 that capture energy from our nearest star. 00:23:47.800 --> 00:23:50.720 They're packed with the green pigment chlorophyll, 00:23:52.400 --> 00:23:55.040 which absorbs rays of light. 00:24:00.000 --> 00:24:02.240 Through the magic of photosynthesis… 00:24:12.640 --> 00:24:15.200 water combines with carbon dioxide… 00:24:18.320 --> 00:24:21.360 and sunbeams are spun into sugar. 00:24:38.440 --> 00:24:43.160 In a matter of days, the once parched plains are painted green. 00:24:51.480 --> 00:24:55.440 Billions of blades of grass now soak up the boundless sunlight. 00:25:00.480 --> 00:25:04.960 And the universe's energy becomes embedded in the landscape. 00:25:10.400 --> 00:25:11.920 There's only one problem. 00:25:14.480 --> 00:25:17.000 Cheetahs can't eat grass. 00:25:22.920 --> 00:25:25.800 But far away in the northern woodlands, 00:25:27.080 --> 00:25:28.280 there are beasts… 00:25:30.360 --> 00:25:31.440 that do. 00:25:34.080 --> 00:25:36.080 Hundreds of thousands of them. 00:25:38.880 --> 00:25:40.120 Wildebeest. 00:25:43.120 --> 00:25:48.320 They have wide mouths, flexible lips, and four stomachs 00:25:49.040 --> 00:25:51.920 that are perfectly adapted to eating grass. 00:26:01.080 --> 00:26:03.880 The massive herds are constantly on the move 00:26:05.800 --> 00:26:07.640 in search of fresh grazing. 00:26:11.000 --> 00:26:14.080 To find the grass, they follow the rain. 00:26:17.800 --> 00:26:19.120 Driven, like all of us… 00:26:21.280 --> 00:26:22.320 by hunger. 00:26:32.000 --> 00:26:34.520 But if there is one rule in the Serengeti, 00:26:36.200 --> 00:26:39.080 it's that food never comes easy. 00:26:48.000 --> 00:26:49.480 The Mara River… 00:26:52.120 --> 00:26:55.160 home to some of the largest crocodiles on Earth. 00:26:59.080 --> 00:27:00.840 It's a serious roadblock 00:27:00.920 --> 00:27:04.080 in the wildebeests' quest for vital energy. 00:27:16.160 --> 00:27:19.760 To the south, Wa Chini spends every available moment 00:27:19.840 --> 00:27:22.200 scouring the plains for something edible. 00:27:33.000 --> 00:27:36.000 After six months surviving on a meager diet, 00:27:37.680 --> 00:27:40.160 one of her cubs has managed to grow bigger… 00:27:47.720 --> 00:27:50.760 …and is even learning some hunting skills of her own. 00:27:57.000 --> 00:28:01.200 But the other cub is nowhere to be seen. 00:28:07.400 --> 00:28:10.800 Just five percent of cheetah cubs make it into adulthood. 00:28:13.680 --> 00:28:17.600 Most lose their lives to hungry lions and hyenas. 00:28:25.200 --> 00:28:28.880 This cub's future is far from guaranteed… 00:28:32.880 --> 00:28:36.000 even when energy is tantalizingly close. 00:28:42.400 --> 00:28:44.360 Amassed on the banks of the Mara, 00:28:45.240 --> 00:28:48.160 the wildebeest have nowhere to go but forward. 00:28:52.080 --> 00:28:55.160 But someone needs to be first. 00:29:34.880 --> 00:29:37.080 One and a half million wildebeest 00:29:38.040 --> 00:29:40.560 make this journey each year. 00:29:44.280 --> 00:29:48.560 And here, the battle between using and consuming energy… 00:29:50.680 --> 00:29:52.680 plays out on an epic scale. 00:30:08.120 --> 00:30:10.840 For those lucky enough to make it across, 00:30:12.400 --> 00:30:14.000 this is only the beginning. 00:30:23.200 --> 00:30:25.880 Now, they must travel hundreds of kilometers 00:30:27.800 --> 00:30:28.800 day and night 00:30:30.040 --> 00:30:31.320 for over two months… 00:30:34.200 --> 00:30:35.880 to get to the grassy plains. 00:30:48.600 --> 00:30:52.400 Wa Chini eagerly awaits the arrival of the wildebeest, 00:30:53.920 --> 00:30:58.080 but there is another migration taking place that is critical 00:30:58.160 --> 00:31:00.600 to the survival of both animals. 00:31:03.840 --> 00:31:08.360 It's the journey of unfathomable distance and time. 00:31:11.640 --> 00:31:16.920 And without it, every creature on the Serengeti would go hungry. 00:31:24.240 --> 00:31:26.200 In the core of our sun, 00:31:26.280 --> 00:31:28.560 as atoms collide and fuse, 00:31:29.360 --> 00:31:34.360 photons are released and stream outwards. 00:31:38.800 --> 00:31:44.000 These tiny packages of light energy have zero mass 00:31:44.080 --> 00:31:46.080 and travel at the speed of light. 00:31:47.800 --> 00:31:51.080 But inside the unbelievably dense core, 00:31:51.160 --> 00:31:55.080 they're restrained, absorbed, scattered. 00:31:58.200 --> 00:32:03.800 A trip that would normally take just two seconds can take a million years. 00:32:10.960 --> 00:32:15.080 It's a mind-boggling torturous struggle to escape the sun. 00:32:20.000 --> 00:32:23.400 But slowly, the photons do rise 00:32:25.200 --> 00:32:27.680 upward through the sun's layers 00:32:29.640 --> 00:32:31.880 toward its raging hot surface… 00:32:34.480 --> 00:32:37.200 where they can finally be set free. 00:32:40.680 --> 00:32:43.360 They radiate out in all directions… 00:32:45.640 --> 00:32:46.880 as starlight… 00:32:53.720 --> 00:32:59.560 traveling 150 million kilometers in just over eight minutes. 00:33:04.880 --> 00:33:06.640 Arriving just in time… 00:33:09.160 --> 00:33:12.720 to meet the wildebeest at the end of their journey. 00:33:16.400 --> 00:33:22.800 Each individual blade of grass absorbs ten quadrillion photons every second… 00:33:27.880 --> 00:33:33.480 capturing enough energy overall to feed these massive herds. 00:33:43.760 --> 00:33:44.880 From star… 00:33:47.600 --> 00:33:48.640 …to grass… 00:33:52.280 --> 00:33:53.280 to wildebeest… 00:33:59.720 --> 00:34:02.560 sunlight now provides them with power to move… 00:34:04.600 --> 00:34:05.600 to grow… 00:34:07.760 --> 00:34:08.880 to reproduce. 00:34:17.160 --> 00:34:20.200 And the longer they're out on the plains eating, 00:34:21.040 --> 00:34:24.120 the longer they're available to be eaten. 00:34:39.880 --> 00:34:45.120 Rich, delicious, plentiful energy 00:34:45.200 --> 00:34:47.600 is finally within striking distance. 00:34:55.800 --> 00:34:58.160 But with three million eyes watching… 00:35:01.800 --> 00:35:03.880 Wa Chini needs to move fast. 00:35:06.560 --> 00:35:09.320 Luckily, she's a cheetah. 00:35:59.240 --> 00:36:03.080 At last, Wa Chini gets a taste of starlight. 00:36:26.040 --> 00:36:27.480 With every bite, 00:36:27.560 --> 00:36:31.680 proteins and fats imbued with cosmic energy 00:36:31.760 --> 00:36:33.680 enter Wa Chini's bloodstream. 00:36:39.840 --> 00:36:44.360 Their final destination are her body's cellular power plants, 00:36:45.520 --> 00:36:46.720 mitochondria… 00:36:49.080 --> 00:36:52.720 where one last transformation will take place. 00:37:00.840 --> 00:37:04.640 Within each mitochondrion is a surging landscape. 00:37:08.720 --> 00:37:13.000 Canyons of membranes rippling with complex chemistry. 00:37:15.080 --> 00:37:19.360 It's here that the energy-rich food reacts with oxygen 00:37:20.160 --> 00:37:21.960 and is finally broken down… 00:37:28.680 --> 00:37:33.960 releasing our universe's energy directly into Wa Chini's cells… 00:37:38.440 --> 00:37:41.160 …powering every action and thought, 00:37:41.920 --> 00:37:43.640 every little movement. 00:37:51.160 --> 00:37:54.000 The journey from star to cell is complete. 00:37:59.000 --> 00:38:01.160 Energy that once lit up the universe 00:38:02.560 --> 00:38:05.960 now gives Wa Chini and her cub the gift of life. 00:38:18.920 --> 00:38:20.200 In green season, 00:38:21.160 --> 00:38:22.880 hunger is just a memory. 00:38:32.880 --> 00:38:36.920 Across the Serengeti, energy is continually transformed… 00:38:41.320 --> 00:38:43.960 passing from one life to another, 00:38:45.640 --> 00:38:48.480 nourishing the entire ecosystem. 00:38:51.400 --> 00:38:54.320 Our sun is the ultimate provider. 00:38:55.600 --> 00:38:58.160 Everything feeds on starlight. 00:39:03.680 --> 00:39:07.320 The trouble is, there's nothing to feed the sun. 00:39:10.920 --> 00:39:12.800 And in five billion years, 00:39:13.640 --> 00:39:15.280 it will run out of fuel. 00:39:19.840 --> 00:39:21.560 As its core collapses, 00:39:22.520 --> 00:39:24.000 the sun will expand… 00:39:26.680 --> 00:39:28.240 and become a red giant… 00:39:31.520 --> 00:39:36.560 that will devour the inner planets, Mercury and Venus. 00:39:41.800 --> 00:39:43.840 As it balloons out toward Earth, 00:39:44.720 --> 00:39:48.080 the extreme gravity will rip our moon to shreds… 00:40:02.280 --> 00:40:05.280 …leaving a ring of moon rock around Earth. 00:40:10.480 --> 00:40:13.560 The ultimate fate of our planet is unknown. 00:40:18.440 --> 00:40:21.720 But there will be one last sunrise… 00:40:25.640 --> 00:40:28.600 before our star's outer layers blow away, 00:40:30.320 --> 00:40:32.160 and it takes its final breath. 00:40:40.040 --> 00:40:43.920 All that will remain is a dying ember, 00:40:44.960 --> 00:40:46.560 a white dwarf, 00:40:46.640 --> 00:40:52.120 barely the size of our Earth, surrounded by a vast glowing cloud. 00:40:55.400 --> 00:40:57.000 A beacon to the universe. 00:40:58.120 --> 00:41:00.280 We were here. 00:41:04.360 --> 00:41:05.480 But right now, 00:41:06.360 --> 00:41:09.560 our star continues to shine down on us… 00:41:12.960 --> 00:41:16.200 …and will for billions of years to come, 00:41:17.200 --> 00:41:22.280 its energy a vital force for all life. 00:41:30.200 --> 00:41:32.240 Next in the story of our universe, 00:41:33.880 --> 00:41:35.640 whether you are a blazing star… 00:41:38.080 --> 00:41:39.760 a vast black hole, 00:41:40.920 --> 00:41:43.960 or a chimpanzee learning the ropes, 00:41:44.560 --> 00:41:46.280 everything needs time. 00:41:48.080 --> 00:41:51.920 But what do you really know about this mysterious dimension? 00:41:53.200 --> 00:41:58.720 Why does everything have a past, present, and future? 00:41:59.400 --> 00:42:00.800 And would any of us be here… 00:42:03.520 --> 00:42:04.640 without time?