WEBVTT 00:00:29.520 --> 00:00:31.480 It's morning in the forest. 00:00:32.520 --> 00:00:35.120 And for this troop of chimpanzees, 00:00:35.200 --> 00:00:37.040 it's time to get out of bed 00:00:37.120 --> 00:00:38.960 and get on with the day. 00:00:45.960 --> 00:00:49.640 But when you sleep in a nest 40 meters up in the air, 00:00:51.080 --> 00:00:53.320 it can be a bit of a challenge. 00:01:12.880 --> 00:01:17.120 This morning ritual has been playing out like clockwork 00:01:18.560 --> 00:01:20.320 for countless generations. 00:01:25.680 --> 00:01:30.240 A rhythm driven by one of the most mysterious properties of our universe. 00:01:38.160 --> 00:01:39.000 Time. 00:01:41.920 --> 00:01:45.080 And time is playing an extra important role 00:01:45.160 --> 00:01:46.800 for one female chimp. 00:01:49.320 --> 00:01:51.120 Celeste is in her mid-30s, 00:01:52.720 --> 00:01:55.040 and she has a ticking clock inside her. 00:01:59.840 --> 00:02:03.840 A clock that was set 13.8 billion years ago. 00:02:14.720 --> 00:02:16.800 From The Big Bang came atoms… 00:02:20.040 --> 00:02:21.000 …and energy… 00:02:22.440 --> 00:02:25.800 …which have journeyed across vast reaches of space. 00:02:31.280 --> 00:02:32.760 And these ingredients 00:02:34.040 --> 00:02:35.720 are now assembling… 00:02:38.520 --> 00:02:40.720 to create a new life. 00:02:44.600 --> 00:02:48.760 In Celeste's womb, a tiny chimpanzee is forming. 00:02:52.960 --> 00:02:57.320 It will be another 150 days before this baby meets the world. 00:02:59.960 --> 00:03:01.440 That's the time it takes. 00:03:04.320 --> 00:03:06.120 And without time, 00:03:06.200 --> 00:03:09.440 nothing in our universe would ever be born. 00:03:12.720 --> 00:03:14.920 From the youngest chimpanzee… 00:03:16.920 --> 00:03:18.800 to the oldest black hole. 00:03:23.680 --> 00:03:27.280 But how did time start in the first place? 00:03:29.240 --> 00:03:32.480 Does everything experience time in the same way? 00:03:35.000 --> 00:03:38.440 And will our universe's clock ever stop ticking? 00:04:09.440 --> 00:04:12.960 The day begins for a chimp much as it does for us. 00:04:16.280 --> 00:04:17.200 Breakfast. 00:04:23.680 --> 00:04:27.360 A critical meal… when you're eating for two. 00:04:35.800 --> 00:04:38.760 Celeste is already an experienced mom. 00:04:42.120 --> 00:04:46.560 Her firstborn, Apollo, is the dominant male of the troop. 00:04:48.800 --> 00:04:51.960 And he can be a bit slow to get going in the morning. 00:04:59.120 --> 00:05:01.760 Each chimp is a different age. 00:05:04.640 --> 00:05:06.960 Each has a distinct personality. 00:05:09.720 --> 00:05:13.120 But all of them are creatures of routine. 00:05:17.520 --> 00:05:21.920 Their lives governed by the passage of time. 00:05:24.520 --> 00:05:25.840 We can't see it. 00:05:26.840 --> 00:05:29.040 -Or hear it. 00:05:29.840 --> 00:05:32.720 -We can't influence it in any way. 00:05:34.240 --> 00:05:39.480 And yet, every heartbeat, every choice and action, 00:05:39.560 --> 00:05:45.800 every inaction is a consequence of time's continuous flow. 00:05:47.240 --> 00:05:50.400 It can whiz by or drag on. 00:05:51.480 --> 00:05:54.040 But time ticks ever onward. 00:05:55.320 --> 00:06:00.920 Stars and planets form, age, and die. 00:06:02.440 --> 00:06:05.400 In their wake, new stars emerge. 00:06:05.480 --> 00:06:07.720 And from a rare few, 00:06:07.800 --> 00:06:11.600 the most mysterious objects in the universe are born. 00:06:13.120 --> 00:06:14.320 Black holes. 00:06:22.040 --> 00:06:24.840 Time is the cosmic conductor. 00:06:27.600 --> 00:06:30.520 Nothing can escape its grasp. 00:06:44.680 --> 00:06:49.240 Although we have devices that can track and measure time… 00:06:54.920 --> 00:06:55.800 …chimps don't. 00:07:04.280 --> 00:07:07.800 Celeste and her family use the sun as their guide. 00:07:11.800 --> 00:07:14.760 Rising and arcing across the sky. 00:07:19.120 --> 00:07:20.040 As it moves… 00:07:23.200 --> 00:07:24.080 so do they. 00:07:31.960 --> 00:07:35.080 Chimps rarely sleep in the same nest twice. 00:07:35.960 --> 00:07:39.040 Each morning, they head off in search of fresh fruit. 00:07:41.640 --> 00:07:45.280 Journeying from one part of their territory to another. 00:07:49.120 --> 00:07:52.320 But right now, the ripest fruit… 00:07:54.840 --> 00:07:57.640 is on the other side of an open plain. 00:08:02.480 --> 00:08:06.240 Apollo and the strongest members of the troop go ahead 00:08:07.160 --> 00:08:09.480 to make sure it's safe for the others. 00:08:12.280 --> 00:08:13.440 Out in the open, 00:08:13.520 --> 00:08:17.240 they're vulnerable to predators, rival chimps, 00:08:18.160 --> 00:08:20.000 and the heat of the rising sun. 00:08:24.160 --> 00:08:25.560 They need to be quick. 00:08:26.840 --> 00:08:28.760 Time is ticking. 00:08:33.720 --> 00:08:36.920 The sun traveling across the sky 00:08:37.000 --> 00:08:39.600 forms the chimps' basic unit of time. 00:08:43.680 --> 00:08:47.440 From sunrise to sunset and back to sunrise. 00:08:49.520 --> 00:08:51.000 The 24-hour day. 00:08:54.200 --> 00:08:57.400 But a day is not actually a measure of time at all. 00:08:59.160 --> 00:09:02.200 It's a measure of motion. 00:09:08.640 --> 00:09:11.480 As our planet rotates on its axis, 00:09:11.560 --> 00:09:18.120 the forest moves through space at 1,600 kilometers per hour. 00:09:20.360 --> 00:09:25.400 It takes 24 hours for Earth to do one full turn. 00:09:28.280 --> 00:09:32.000 Giving the chimps 24 hours of movement, 00:09:33.120 --> 00:09:36.880 12 in sunshine and 12 in darkness. 00:09:38.560 --> 00:09:41.680 Again and again. 00:09:46.800 --> 00:09:52.080 It's our planet's steady spin that sets Earth's master clock. 00:09:55.040 --> 00:09:58.200 And is the chimps' trusted timekeeper. 00:10:02.480 --> 00:10:05.080 But this essential cycle we take for granted… 00:10:07.320 --> 00:10:08.840 is not universal. 00:10:15.840 --> 00:10:18.480 As soon as you leave our home planet… 00:10:20.280 --> 00:10:22.960 …the 24-hour day no longer applies. 00:10:27.960 --> 00:10:29.840 Flying closest to the sun… 00:10:32.080 --> 00:10:33.520 …is the planet Mercury. 00:10:35.160 --> 00:10:39.000 Compared to us, it rotates at a snail's pace. 00:10:44.520 --> 00:10:49.760 Our neighbor Venus spins even slower. 00:10:51.400 --> 00:10:54.200 It takes longer to rotate on its axis 00:10:55.520 --> 00:10:57.760 than it does to orbit the sun. 00:11:00.920 --> 00:11:06.040 Making Venus's day longer than its year. 00:11:09.680 --> 00:11:12.640 Each planet has its own unique day length. 00:11:32.320 --> 00:11:36.040 Including planets far beyond our solar system. 00:11:40.360 --> 00:11:42.440 Sixty-three light years away, 00:11:43.520 --> 00:11:45.280 orbiting a young star, 00:11:46.360 --> 00:11:48.640 is Beta Pictoris b. 00:11:52.520 --> 00:11:55.240 It spins so fast… 00:11:58.720 --> 00:12:01.000 …it bulges out at the sides. 00:12:04.720 --> 00:12:08.160 It is the fastest-spinning world we know of. 00:12:10.200 --> 00:12:13.120 Here, a day lasts just eight hours. 00:12:18.480 --> 00:12:23.120 Every planet in our universe spins at its own speed. 00:12:26.360 --> 00:12:27.760 Billions of worlds, 00:12:28.880 --> 00:12:30.440 each with their own clock, 00:12:31.760 --> 00:12:33.800 ticking away to different rhythms. 00:12:35.360 --> 00:12:40.880 But all moving forward on a universal cosmic timeline. 00:12:58.560 --> 00:12:59.640 Back on Earth, 00:13:00.640 --> 00:13:03.120 with the sun now almost directly overhead, 00:13:05.080 --> 00:13:07.560 the chimps know exactly what time it is. 00:13:17.160 --> 00:13:18.360 It's lunchtime. 00:13:31.160 --> 00:13:35.760 And their crossing of the savanna has been timed to perfection. 00:13:42.680 --> 00:13:44.400 They've hit the jackpot. 00:13:51.760 --> 00:13:54.680 These sweet berries of the African grape tree 00:13:56.400 --> 00:13:58.560 are only around for a few weeks. 00:14:05.080 --> 00:14:08.600 A rare seasonal gift from the forest. 00:14:12.680 --> 00:14:16.280 Where the middle of the day is a very productive time. 00:14:20.840 --> 00:14:24.640 Animals of all sizes are tending to their daily tasks. 00:14:30.000 --> 00:14:32.880 And each experiences time differently. 00:14:37.120 --> 00:14:40.800 For small creatures that live fast, short lives… 00:14:45.600 --> 00:14:48.960 …lunchtime can feel like a lifetime. 00:14:54.680 --> 00:14:57.440 For slower, longer living things, 00:14:58.120 --> 00:15:01.280 an hour can go by in the blink of an eye. 00:15:08.320 --> 00:15:11.360 But whether you're living in high speed 00:15:12.360 --> 00:15:14.120 or in slow motion, 00:15:15.960 --> 00:15:21.000 all life in the forest must adhere to the same 24-hour day. 00:15:23.720 --> 00:15:25.920 And as the world keeps spinning… 00:15:29.400 --> 00:15:31.560 …those days keep ticking by… 00:15:33.600 --> 00:15:37.720 dictating the lives of every chimpanzee. 00:15:41.440 --> 00:15:42.760 One in particular. 00:15:49.960 --> 00:15:51.920 At just 15 weeks, 00:15:52.880 --> 00:15:56.960 this baby's entire body could fit in its mother's hand. 00:16:00.560 --> 00:16:02.440 For it to fully form, 00:16:02.520 --> 00:16:05.760 a cascade of perfectly timed events must occur. 00:16:08.160 --> 00:16:10.360 For the next 130 days, 00:16:11.120 --> 00:16:15.480 every minute, every nanosecond is critical. 00:16:24.200 --> 00:16:30.160 New cells divide and grow with remarkable speed and precision. 00:16:34.200 --> 00:16:35.200 Right now, 00:16:36.160 --> 00:16:41.680 brain cells are multiplying at a rate of around 15 million per hour. 00:16:51.760 --> 00:16:54.800 All of us, from our very first moments, 00:16:55.800 --> 00:17:00.160 have a deep biological relationship with time. 00:17:17.360 --> 00:17:19.120 As the sunlight wanes, 00:17:21.760 --> 00:17:24.280 the chimps instinctively switch gears. 00:17:27.840 --> 00:17:29.080 To evening mode. 00:17:39.120 --> 00:17:41.920 Nesting calls signal to the whole troop. 00:17:44.400 --> 00:17:47.560 It's time to find a safe place to spend the night. 00:18:01.400 --> 00:18:05.560 Their bedding needs to be soft but strong. 00:18:12.200 --> 00:18:14.640 It doesn't hurt if it tastes good either. 00:18:18.880 --> 00:18:21.800 The rhythm of every day in the forest 00:18:21.880 --> 00:18:25.360 is determined by the sun's position in the sky. 00:18:34.560 --> 00:18:37.000 But the chimp's innate sense of time 00:18:38.200 --> 00:18:40.920 comes from something inside them. 00:18:49.680 --> 00:18:53.680 Deep in their brains is a biological clock. 00:18:56.560 --> 00:18:59.520 Bundles of neurons act as a pendulum… 00:19:01.840 --> 00:19:06.400 …controlled by genes that switch on and off… 00:19:08.520 --> 00:19:12.960 and a cycle that repeats every 24 hours. 00:19:16.240 --> 00:19:21.320 These clock genes create a circadian rhythm in the body 00:19:22.080 --> 00:19:28.200 that waxes and wanes in sync with our planet's rotation. 00:19:30.600 --> 00:19:32.040 Controlling hormones… 00:19:36.520 --> 00:19:37.440 …heart rates, 00:19:38.800 --> 00:19:40.640 and energy levels. 00:19:46.200 --> 00:19:50.760 And right now, the chimps' body clocks are sending the message, 00:19:52.160 --> 00:19:54.720 "It's time to get sleepy." 00:19:57.960 --> 00:19:59.560 Not everyone can though. 00:20:14.320 --> 00:20:17.240 Celeste's baby's brain is still forming. 00:20:20.640 --> 00:20:23.000 With no internal clock of its own, 00:20:23.640 --> 00:20:27.240 it relies on its mother's hormones to keep it synchronized. 00:20:29.600 --> 00:20:33.360 But baby doesn't always get the memo. 00:20:37.480 --> 00:20:39.120 Lucky for Celeste, 00:20:39.200 --> 00:20:41.560 with so much growing to do, 00:20:41.640 --> 00:20:44.520 her baby does eventually drift off. 00:20:59.600 --> 00:21:03.520 While the chimps go to sleep high in the treetops… 00:21:07.280 --> 00:21:10.680 other forest dwellers are just waking up. 00:21:22.720 --> 00:21:25.400 Body clocks tick away 00:21:25.480 --> 00:21:29.760 in the cells of plants and animals throughout the forest. 00:21:38.320 --> 00:21:43.520 Clock genes evolved two and a half billion years ago 00:21:43.600 --> 00:21:45.600 in the first living cells. 00:21:48.080 --> 00:21:52.880 Those that could anticipate the light and dark of a day had an advantage. 00:21:56.160 --> 00:21:57.920 And as life evolved, 00:21:59.240 --> 00:22:01.840 it synchronized to Earth's motion. 00:22:02.880 --> 00:22:04.680 So that today, 00:22:04.760 --> 00:22:09.400 these clocks exist in almost every creature on Earth. 00:22:13.640 --> 00:22:16.440 Although some creatures prefer day and others night… 00:22:22.320 --> 00:22:26.200 all life is dancing to the same beat. 00:22:28.720 --> 00:22:30.960 Thanks to cellular clocks 00:22:31.040 --> 00:22:36.240 that tick in time with the spin of our Earth. 00:22:53.000 --> 00:22:55.520 As yesterday becomes a memory… 00:22:58.040 --> 00:23:00.440 …another new day begins in the forest. 00:23:09.560 --> 00:23:11.000 A fresh cycle, 00:23:12.760 --> 00:23:17.160 and yet, no clock can ever truly be reset. 00:23:24.720 --> 00:23:29.240 And there are subtle clues all around the forest that reveal why. 00:23:32.440 --> 00:23:38.040 Nothing is the same today as it was yesterday. 00:23:42.200 --> 00:23:44.640 Least of all Apollo, 00:23:45.720 --> 00:23:49.160 who seems to have woken up on the wrong side of the bed. 00:23:57.600 --> 00:23:59.320 When he's in a bad mood… 00:24:03.200 --> 00:24:07.840 the rest of the group just need to keep their heads down. 00:24:26.720 --> 00:24:29.560 He soon finds a target for his rage, though. 00:24:40.680 --> 00:24:44.120 Some of the younger chimps have found honey for breakfast. 00:24:56.680 --> 00:25:00.240 And they forgot to invite Apollo to join them. 00:25:14.640 --> 00:25:19.080 You soon learn, never get on the wrong side of the dominant male. 00:25:26.880 --> 00:25:28.400 He's got a nasty bite. 00:25:32.280 --> 00:25:34.800 Thankfully, it's not too serious. 00:25:43.200 --> 00:25:46.440 With a bit of care, this wound should heal. 00:25:49.360 --> 00:25:53.040 But wounds leave behind scars, 00:25:54.160 --> 00:25:56.120 etched into the chimps' bodies. 00:25:57.400 --> 00:26:03.520 Indelible marks of the past that reveal the one universal truth about time. 00:26:07.280 --> 00:26:08.560 It has a direction. 00:26:10.640 --> 00:26:13.000 You can never go back in time… 00:26:14.640 --> 00:26:17.320 …only forward into the future. 00:26:20.800 --> 00:26:22.920 This is time's arrow, 00:26:24.200 --> 00:26:27.840 and it leaves scars on everything 00:26:28.520 --> 00:26:29.480 across Earth… 00:26:31.240 --> 00:26:32.400 …and beyond. 00:26:41.160 --> 00:26:46.520 Our moon is pockmarked with battle scars that tell stories of ancient events. 00:26:56.480 --> 00:26:57.840 So too are the planets. 00:27:01.680 --> 00:27:08.640 Their surfaces testament to a lifetime of bombardment by asteroids and comets. 00:27:15.040 --> 00:27:19.120 But perhaps the most impressive impact crater in our solar system 00:27:20.680 --> 00:27:23.080 belongs to a moon of Saturn. 00:27:24.480 --> 00:27:25.480 Mimas. 00:27:27.880 --> 00:27:32.560 The Herschel crater is 130 kilometers across. 00:27:38.280 --> 00:27:40.840 Whatever created this enormous scar… 00:27:43.000 --> 00:27:46.280 must have come close to shattering the moon to pieces. 00:28:04.000 --> 00:28:06.080 Mimas lives to tell the tale. 00:28:07.840 --> 00:28:10.400 But events like this are irreversible. 00:28:15.320 --> 00:28:19.360 And they differentiate the past from the present. 00:28:22.160 --> 00:28:24.600 Impact craters are timestamps 00:28:26.360 --> 00:28:28.840 that mark a unique moment in history. 00:28:37.400 --> 00:28:40.360 We can never revisit the moment they were created. 00:28:43.960 --> 00:28:47.640 But we can piece together traces of past events 00:28:49.080 --> 00:28:51.480 and map a course back through time. 00:28:56.640 --> 00:28:57.880 Before craters. 00:28:59.640 --> 00:29:00.920 Before planets. 00:29:01.840 --> 00:29:03.080 Before stars. 00:29:05.000 --> 00:29:07.680 Back to a time before time. 00:29:14.400 --> 00:29:17.400 Our universe had a beginning. 00:29:21.840 --> 00:29:24.960 A very big bang… 00:29:27.360 --> 00:29:29.800 that created three-dimensional space 00:29:31.280 --> 00:29:32.560 and time. 00:29:36.880 --> 00:29:40.240 But space and time are not separate. 00:29:41.800 --> 00:29:44.840 Time is woven into the fabric of the universe. 00:29:49.240 --> 00:29:54.120 Bound to space as our universe's fourth dimension. 00:29:56.480 --> 00:29:59.400 The Big Bang set the universe's clock ticking. 00:30:02.920 --> 00:30:05.280 Propelling everything into the future. 00:30:09.040 --> 00:30:13.040 It created the arrow of time. 00:30:18.640 --> 00:30:21.960 From our universe's very first moments… 00:30:32.360 --> 00:30:34.640 …it pushes us all into the future, 00:30:35.720 --> 00:30:38.200 causing everything to grow, 00:30:39.640 --> 00:30:40.480 age… 00:30:42.440 --> 00:30:43.400 …and change. 00:30:45.560 --> 00:30:47.000 From childhood… 00:30:48.000 --> 00:30:49.120 …to adulthood, 00:30:50.400 --> 00:30:54.080 we all travel through life in the same direction. 00:30:55.640 --> 00:30:58.320 Getting older day by day. 00:30:59.960 --> 00:31:02.800 And with age comes wisdom 00:31:04.200 --> 00:31:07.640 as youthful innocence is replaced by experience. 00:31:13.120 --> 00:31:17.520 Time's arrow leads us through these stages of life. 00:31:21.880 --> 00:31:23.080 It shapes us. 00:31:25.760 --> 00:31:27.440 Defines who we are. 00:31:31.000 --> 00:31:32.520 From our first moments… 00:31:34.680 --> 00:31:35.800 to our last. 00:31:41.880 --> 00:31:44.480 Chimps rarely live past the age of 40. 00:31:49.200 --> 00:31:50.840 Nothing is immortal. 00:31:58.480 --> 00:32:03.240 Everything that exists in our universe has a finite lifespan. 00:32:08.680 --> 00:32:11.960 Including, perhaps, the universe itself. 00:32:19.600 --> 00:32:23.440 Today, the galaxies are filled with stars. 00:32:27.280 --> 00:32:33.600 But 95% of stars that will ever exist have already been born. 00:32:38.800 --> 00:32:41.400 So, as our universe journeys into the future… 00:32:42.800 --> 00:32:44.080 …the stars… 00:32:44.760 --> 00:32:47.800 -…one by one, will blink out… 00:32:50.320 --> 00:32:55.200 …leaving the universe to face an ever-darkening future, 00:32:56.880 --> 00:32:58.680 stretching out for trillions, 00:32:59.400 --> 00:33:02.920 that's thousands of billions, of years. 00:33:09.400 --> 00:33:11.640 The age of starlight 00:33:11.720 --> 00:33:16.280 will be followed by a dark age of black holes. 00:33:22.920 --> 00:33:27.840 These monsters feed on the remnants of dead stars and planets. 00:33:29.560 --> 00:33:31.040 And as they do, 00:33:31.120 --> 00:33:36.320 their ever-increasing gravity scars the very fabric of the universe. 00:33:43.080 --> 00:33:46.400 Distorting both space and time. 00:33:48.760 --> 00:33:53.080 The edge of a black hole, called the event horizon, 00:33:54.240 --> 00:33:57.400 is a region where gravity has become so strong 00:33:58.240 --> 00:34:03.880 it causes time to slow down practically to a standstill. 00:34:08.960 --> 00:34:12.280 But even black holes can't escape time's arrow. 00:34:15.040 --> 00:34:16.920 In the far, far future… 00:34:21.080 --> 00:34:24.360 …when there are no stars or planets left to consume, 00:34:25.920 --> 00:34:27.600 they will begin to starve. 00:34:32.800 --> 00:34:34.000 And slowly… 00:34:36.680 --> 00:34:37.920 very slowly, 00:34:39.720 --> 00:34:40.840 they will shrink. 00:34:46.360 --> 00:34:48.000 When they die, 00:34:48.080 --> 00:34:50.400 no one truly knows what comes next. 00:34:52.920 --> 00:34:57.960 But it could be the end of our universe. 00:35:07.400 --> 00:35:11.760 Here on Earth, none of us can slow the passage of time. 00:35:16.000 --> 00:35:20.280 And one of Celeste's aunts is reaching the end of her time. 00:35:24.280 --> 00:35:28.040 Retreating from the group, she heads into the forest alone. 00:35:35.800 --> 00:35:37.840 She has lived many years. 00:35:41.200 --> 00:35:44.080 But this day will be her last. 00:36:03.760 --> 00:36:06.520 While the world continues to spin, 00:36:07.920 --> 00:36:11.040 her body lies still. 00:36:23.320 --> 00:36:26.160 But time doesn't just carry us toward endings. 00:36:30.360 --> 00:36:32.400 It also creates beginnings. 00:36:37.280 --> 00:36:40.760 As days turn into weeks and weeks into months, 00:36:42.560 --> 00:36:45.600 there are big changes for one special chimpanzee. 00:36:59.600 --> 00:37:01.480 Say hello to Cosmo. 00:37:06.040 --> 00:37:08.960 Her brain and limbs are now fully formed. 00:37:10.720 --> 00:37:13.400 And her eyes are ready to see the world. 00:37:21.880 --> 00:37:24.960 The exact timing of her birth is impossible to know. 00:37:26.560 --> 00:37:29.400 But she could be born any day now. 00:37:36.000 --> 00:37:38.760 She's been in the womb for eight months. 00:37:40.240 --> 00:37:43.480 But her journey began long, long ago. 00:37:46.000 --> 00:37:50.600 The elements that made her came from dying stars. 00:37:52.520 --> 00:37:58.320 The water that flows through her body came from distant worlds. 00:38:00.400 --> 00:38:06.920 The energy that powers her muscles came from the heart of our sun. 00:38:09.720 --> 00:38:13.040 But it's that most mysterious ingredient, 00:38:13.720 --> 00:38:18.200 the one that started ticking 13.8 billion years ago… 00:38:22.280 --> 00:38:26.800 that has led all other ingredients to this moment. 00:38:30.120 --> 00:38:31.240 In this place. 00:38:33.960 --> 00:38:35.200 On this planet. 00:38:44.720 --> 00:38:47.920 Another sunrise, another morning. 00:38:53.240 --> 00:38:57.520 And this one is extra special. 00:39:08.120 --> 00:39:10.520 Welcome to Earth, Cosmo. 00:39:15.440 --> 00:39:18.680 This precious moment will never be repeated for Celeste. 00:39:19.480 --> 00:39:22.760 But Cosmo's journey has just begun. 00:39:26.000 --> 00:39:28.280 It will take around three months 00:39:28.360 --> 00:39:32.040 for her body clock to synchronize to the rhythm of the planet, 00:39:33.840 --> 00:39:36.400 one year before she can truly communicate, 00:39:38.080 --> 00:39:42.680 and perhaps 15 years until she is fully grown. 00:39:45.760 --> 00:39:47.520 So much lies ahead. 00:39:56.320 --> 00:39:57.600 Like Cosmo, 00:39:58.320 --> 00:40:01.360 our universe is still in its infancy 00:40:02.400 --> 00:40:06.640 at the beginning of an unimaginably long lifespan. 00:40:08.680 --> 00:40:11.920 We are living in the age of starlight. 00:40:14.200 --> 00:40:19.160 A moment when time's arrow has filled the universe with beauty… 00:40:22.440 --> 00:40:23.400 …and wonder. 00:40:32.360 --> 00:40:34.520 But it's a brief window of time 00:40:35.440 --> 00:40:39.200 that will never be repeated in the history of our universe. 00:40:45.320 --> 00:40:47.720 No one can slow the passage of time, 00:40:49.080 --> 00:40:50.160 nor should we try. 00:40:55.280 --> 00:40:56.920 Because without time, 00:40:58.120 --> 00:40:59.480 there would be no now. 00:41:06.720 --> 00:41:08.160 No moment in the sun. 00:41:17.200 --> 00:41:18.920 No moments, period. 00:41:24.600 --> 00:41:25.720 Without time, 00:41:27.760 --> 00:41:29.160 there would be no life. 00:41:41.320 --> 00:41:44.120 Next in the story of our universe, 00:41:45.800 --> 00:41:47.440 Earth's seasons. 00:41:48.960 --> 00:41:51.760 Like a mother bear raising her cubs… 00:41:53.120 --> 00:41:56.680 …we all experience our planet's yearly transformations. 00:41:59.760 --> 00:42:02.280 But what created Earth's seasons? 00:42:05.760 --> 00:42:08.840 How are they connected to the formation of our moon? 00:42:09.880 --> 00:42:15.680 And why does only our planet have conditions just right for life?