1
00:00:07,723 --> 00:00:10,323
[calm music playing]

2
00:00:10,403 --> 00:00:14,003
[chimpanzees screeching]

3
00:00:22,803 --> 00:00:25,643
[chimpanzees hooting]

4
00:00:27,923 --> 00:00:28,803
[clock ticks]

5
00:00:29,563 --> 00:00:31,523
[Freeman] It's morning in the forest.

6
00:00:32,563 --> 00:00:35,163
And for this troop of chimpanzees,

7
00:00:35,243 --> 00:00:37,083
it's time to get out of bed

8
00:00:37,163 --> 00:00:39,003
and get on with the day.

9
00:00:39,523 --> 00:00:42,443
[intriguing music playing]

10
00:00:42,523 --> 00:00:44,763
[chimpanzees screeching]

11
00:00:46,003 --> 00:00:49,683
[Freeman] But when you sleep
in a nest 40 meters up in the air,

12
00:00:51,123 --> 00:00:53,363
it can be a bit of a challenge.

13
00:00:58,283 --> 00:01:00,003
[playful music playing]

14
00:01:00,083 --> 00:01:01,723
[chimpanzee howling]

15
00:01:03,123 --> 00:01:04,883
[chirping]

16
00:01:12,923 --> 00:01:17,163
[Freeman] This morning ritual
has been playing out like clockwork

17
00:01:18,603 --> 00:01:20,363
for countless generations.

18
00:01:22,243 --> 00:01:24,723
[pensive music playing]

19
00:01:25,723 --> 00:01:30,283
A rhythm driven by one of the most
mysterious properties of our universe.

20
00:01:38,203 --> 00:01:39,043
Time.

21
00:01:41,963 --> 00:01:45,123
And time is playing
an extra important role

22
00:01:45,203 --> 00:01:46,843
for one female chimp.

23
00:01:49,363 --> 00:01:51,163
Celeste is in her mid-30s,

24
00:01:52,763 --> 00:01:55,083
and she has a ticking clock inside her.

25
00:01:55,603 --> 00:01:57,443
[whooshing]

26
00:01:59,883 --> 00:02:03,883
A clock that was set
13.8 billion years ago.

27
00:02:03,963 --> 00:02:06,403
[heart thumping]

28
00:02:06,483 --> 00:02:09,043
[fizzling, whooshing]

29
00:02:14,763 --> 00:02:16,843
From The Big Bang came atoms…

30
00:02:17,643 --> 00:02:19,003
[zapping]

31
00:02:20,083 --> 00:02:21,043
…and energy…

32
00:02:21,123 --> 00:02:22,403
[rumbling]

33
00:02:22,483 --> 00:02:25,843
…which have journeyed across
vast reaches of space.

34
00:02:27,123 --> 00:02:29,643
[dramatic music playing]

35
00:02:31,323 --> 00:02:32,803
And these ingredients

36
00:02:34,083 --> 00:02:35,763
are now assembling…

37
00:02:38,563 --> 00:02:40,763
to create a new life.

38
00:02:44,643 --> 00:02:48,803
In Celeste's womb,
a tiny chimpanzee is forming.

39
00:02:48,883 --> 00:02:50,643
[heartbeat thumping softly]

40
00:02:53,003 --> 00:02:57,363
It will be another 150 days
before this baby meets the world.

41
00:03:00,003 --> 00:03:01,483
That's the time it takes.

42
00:03:04,363 --> 00:03:06,163
And without time,

43
00:03:06,243 --> 00:03:09,483
nothing in our universe
would ever be born.

44
00:03:10,323 --> 00:03:11,883
[heartbeat continues thumping]

45
00:03:12,763 --> 00:03:14,963
From the youngest chimpanzee…

46
00:03:16,963 --> 00:03:18,843
to the oldest black hole.

47
00:03:18,923 --> 00:03:21,123
[fizzling]

48
00:03:22,363 --> 00:03:23,643
[whooshing]

49
00:03:23,723 --> 00:03:27,323
But how did time start in the first place?

50
00:03:29,283 --> 00:03:32,523
Does everything experience time
in the same way?

51
00:03:35,043 --> 00:03:38,483
And will our universe's clock
ever stop ticking?

52
00:03:39,163 --> 00:03:41,603
[dramatic music playing]

53
00:03:58,843 --> 00:04:01,123
[clock ticking]

54
00:04:04,323 --> 00:04:07,043
[chimpanzees hooting]

55
00:04:09,483 --> 00:04:13,003
[Freeman] The day begins for a chimp
much as it does for us.

56
00:04:16,323 --> 00:04:17,243
Breakfast.

57
00:04:18,083 --> 00:04:20,323
[pensive music playing]

58
00:04:23,723 --> 00:04:27,403
A critical meal…
when you're eating for two.

59
00:04:35,843 --> 00:04:38,803
Celeste is already an experienced mom.

60
00:04:42,163 --> 00:04:46,603
Her firstborn, Apollo,
is the dominant male of the troop.

61
00:04:48,843 --> 00:04:52,003
And he can be a bit slow
to get going in the morning.

62
00:04:59,163 --> 00:05:01,803
Each chimp is a different age.

63
00:05:04,683 --> 00:05:07,003
Each has a distinct personality.

64
00:05:09,763 --> 00:05:13,163
But all of them are creatures of routine.

65
00:05:17,563 --> 00:05:21,963
Their lives governed
by the passage of time.

66
00:05:22,043 --> 00:05:24,483
[ethereal music playing]

67
00:05:24,563 --> 00:05:25,883
We can't see it.

68
00:05:26,883 --> 00:05:29,083
-[animals growling]
-Or hear it.

69
00:05:29,883 --> 00:05:32,763
-[chimpanzee screeches]
-We can't influence it in any way.

70
00:05:32,843 --> 00:05:34,203
[elephant growls]

71
00:05:34,283 --> 00:05:39,523
And yet, every heartbeat,
every choice and action,

72
00:05:39,603 --> 00:05:45,843
every inaction is a consequence
of time's continuous flow.

73
00:05:45,923 --> 00:05:47,203
[whooshing]

74
00:05:47,283 --> 00:05:50,443
It can whiz by or drag on.

75
00:05:51,523 --> 00:05:54,083
But time ticks ever onward.

76
00:05:55,363 --> 00:06:00,963
Stars and planets form, age, and die.

77
00:06:01,043 --> 00:06:02,403
[dramatic music playing]

78
00:06:02,483 --> 00:06:05,443
In their wake, new stars emerge.

79
00:06:05,523 --> 00:06:07,763
And from a rare few,

80
00:06:07,843 --> 00:06:11,643
the most mysterious objects
in the universe are born.

81
00:06:13,163 --> 00:06:14,363
Black holes.

82
00:06:15,123 --> 00:06:17,163
[fizzling]

83
00:06:17,243 --> 00:06:19,643
[whooshing]

84
00:06:22,083 --> 00:06:24,883
Time is the cosmic conductor.

85
00:06:24,963 --> 00:06:27,003
[clock ticking]

86
00:06:27,643 --> 00:06:30,563
Nothing can escape its grasp.

87
00:06:30,643 --> 00:06:32,283
[dramatic vocal music playing]

88
00:06:37,523 --> 00:06:38,403
[clock ticks]

89
00:06:40,243 --> 00:06:41,443
[birds chirping]

90
00:06:41,523 --> 00:06:43,323
[chimpanzee hooting]

91
00:06:44,723 --> 00:06:49,283
Although we have devices
that can track and measure time…

92
00:06:49,363 --> 00:06:52,603
[dramatic music playing]

93
00:06:54,963 --> 00:06:55,843
…chimps don't.

94
00:07:04,323 --> 00:07:07,843
Celeste and her family
use the sun as their guide.

95
00:07:11,843 --> 00:07:14,803
Rising and arcing across the sky.

96
00:07:16,123 --> 00:07:19,083
[hooting]

97
00:07:19,163 --> 00:07:20,083
As it moves…

98
00:07:23,243 --> 00:07:24,123
so do they.

99
00:07:24,203 --> 00:07:26,083
[chimpanzee screeching]

100
00:07:32,003 --> 00:07:35,123
Chimps rarely sleep
in the same nest twice.

101
00:07:36,003 --> 00:07:39,083
Each morning,
they head off in search of fresh fruit.

102
00:07:41,683 --> 00:07:45,323
Journeying from one part
of their territory to another.

103
00:07:49,163 --> 00:07:52,363
But right now, the ripest fruit…

104
00:07:54,883 --> 00:07:57,683
is on the other side of an open plain.

105
00:07:57,763 --> 00:08:00,003
[ominous music playing]

106
00:08:02,523 --> 00:08:06,283
Apollo and the strongest members
of the troop go ahead

107
00:08:07,203 --> 00:08:09,523
to make sure it's safe for the others.

108
00:08:12,323 --> 00:08:13,483
Out in the open,

109
00:08:13,563 --> 00:08:17,283
they're vulnerable
to predators, rival chimps,

110
00:08:18,203 --> 00:08:20,043
and the heat of the rising sun.

111
00:08:24,203 --> 00:08:25,603
They need to be quick.

112
00:08:26,883 --> 00:08:28,803
Time is ticking.

113
00:08:28,883 --> 00:08:30,963
[suspenseful music playing]

114
00:08:33,763 --> 00:08:36,963
The sun traveling across the sky

115
00:08:37,043 --> 00:08:39,643
forms the chimps' basic unit of time.

116
00:08:43,723 --> 00:08:47,483
From sunrise to sunset
and back to sunrise.

117
00:08:49,563 --> 00:08:51,043
The 24-hour day.

118
00:08:54,243 --> 00:08:57,443
But a day
is not actually a measure of time at all.

119
00:08:59,203 --> 00:09:02,243
It's a measure of motion.

120
00:09:08,683 --> 00:09:11,523
As our planet rotates on its axis,

121
00:09:11,603 --> 00:09:18,163
the forest moves through space
at 1,600 kilometers per hour.

122
00:09:20,403 --> 00:09:25,443
It takes 24 hours
for Earth to do one full turn.

123
00:09:28,323 --> 00:09:32,043
Giving the chimps 24 hours of movement,

124
00:09:33,163 --> 00:09:36,923
12 in sunshine and 12 in darkness.

125
00:09:37,003 --> 00:09:38,523
[dramatic music playing]

126
00:09:38,603 --> 00:09:41,723
Again and again.

127
00:09:44,443 --> 00:09:46,763
[clock ticking]

128
00:09:46,843 --> 00:09:52,123
It's our planet's steady spin
that sets Earth's master clock.

129
00:09:55,083 --> 00:09:58,243
And is the chimps' trusted timekeeper.

130
00:10:02,523 --> 00:10:05,123
But this essential cycle
we take for granted…

131
00:10:07,363 --> 00:10:08,883
is not universal.

132
00:10:10,043 --> 00:10:10,923
[clock ticks]

133
00:10:11,003 --> 00:10:12,523
[ominous music playing]

134
00:10:14,043 --> 00:10:14,923
[clock ticks]

135
00:10:15,883 --> 00:10:18,523
As soon as you leave our home planet…

136
00:10:18,603 --> 00:10:19,483
[clock ticks]

137
00:10:20,323 --> 00:10:23,003
…the 24-hour day no longer applies.

138
00:10:28,003 --> 00:10:29,883
Flying closest to the sun…

139
00:10:30,643 --> 00:10:32,043
[rumbling, whooshing]

140
00:10:32,123 --> 00:10:33,563
…is the planet Mercury.

141
00:10:35,203 --> 00:10:39,043
Compared to us,
it rotates at a snail's pace.

142
00:10:44,563 --> 00:10:49,803
Our neighbor Venus spins even slower.

143
00:10:49,883 --> 00:10:51,363
[intense music playing]

144
00:10:51,443 --> 00:10:54,243
It takes longer to rotate on its axis

145
00:10:55,563 --> 00:10:57,803
than it does to orbit the sun.

146
00:11:00,963 --> 00:11:06,083
Making Venus's day longer than its year.

147
00:11:09,723 --> 00:11:12,683
Each planet has its own unique day length.

148
00:11:14,523 --> 00:11:15,483
[whooshing]

149
00:11:15,563 --> 00:11:17,843
[intense music continues]

150
00:11:19,603 --> 00:11:21,483
[whooshing]

151
00:11:25,723 --> 00:11:27,123
[whooshing]

152
00:11:30,643 --> 00:11:31,843
[whooshing]

153
00:11:32,363 --> 00:11:36,083
Including planets
far beyond our solar system.

154
00:11:36,163 --> 00:11:38,363
[whooshing]

155
00:11:40,403 --> 00:11:42,483
Sixty-three light years away,

156
00:11:43,563 --> 00:11:45,323
orbiting a young star,

157
00:11:46,403 --> 00:11:48,683
is Beta Pictoris b.

158
00:11:52,563 --> 00:11:55,283
It spins so fast…

159
00:11:56,123 --> 00:11:57,443
[whooshing rapidly]

160
00:11:57,523 --> 00:11:58,683
[rumbling]

161
00:11:58,763 --> 00:12:01,043
…it bulges out at the sides.

162
00:12:04,763 --> 00:12:08,203
It is the fastest-spinning world
we know of.

163
00:12:09,083 --> 00:12:10,163
[intense music playing]

164
00:12:10,243 --> 00:12:13,163
Here, a day lasts just eight hours.

165
00:12:13,243 --> 00:12:14,123
[clock ticks]

166
00:12:18,523 --> 00:12:23,163
Every planet in our universe spins
at its own speed.

167
00:12:23,243 --> 00:12:25,723
[whooshing]

168
00:12:26,403 --> 00:12:27,803
Billions of worlds,

169
00:12:28,923 --> 00:12:30,483
each with their own clock,

170
00:12:31,803 --> 00:12:33,843
ticking away to different rhythms.

171
00:12:33,923 --> 00:12:35,323
[multiple clocks ticking]

172
00:12:35,403 --> 00:12:40,923
But all moving forward
on a universal cosmic timeline.

173
00:12:43,763 --> 00:12:46,323
[single clock ticking]

174
00:12:49,123 --> 00:12:51,723
[calm music playing]

175
00:12:52,363 --> 00:12:53,483
[clock ticks]

176
00:12:56,003 --> 00:12:58,523
[chimpanzees screeching]

177
00:12:58,603 --> 00:12:59,683
Back on Earth,

178
00:13:00,683 --> 00:13:03,163
with the sun now almost directly overhead,

179
00:13:05,123 --> 00:13:07,603
the chimps know exactly what time it is.

180
00:13:17,203 --> 00:13:18,403
It's lunchtime.

181
00:13:20,763 --> 00:13:22,803
[calm music continues]

182
00:13:31,203 --> 00:13:35,803
And their crossing of the savanna
has been timed to perfection.

183
00:13:36,763 --> 00:13:40,243
[howling]

184
00:13:42,723 --> 00:13:44,443
They've hit the jackpot.

185
00:13:51,803 --> 00:13:54,723
These sweet berries
of the African grape tree

186
00:13:56,443 --> 00:13:58,603
are only around for a few weeks.

187
00:14:05,123 --> 00:14:08,643
A rare seasonal gift from the forest.

188
00:14:12,723 --> 00:14:16,323
Where the middle of the day
is a very productive time.

189
00:14:18,363 --> 00:14:20,243
[dramatic music playing]

190
00:14:20,883 --> 00:14:24,683
Animals of all sizes
are tending to their daily tasks.

191
00:14:30,043 --> 00:14:32,923
And each experiences time differently.

192
00:14:37,163 --> 00:14:40,843
For small creatures
that live fast, short lives…

193
00:14:41,523 --> 00:14:44,563
[dramatic music intensifies]

194
00:14:45,643 --> 00:14:49,003
…lunchtime can feel like a lifetime.

195
00:14:53,763 --> 00:14:54,643
[elephant snorts]

196
00:14:54,723 --> 00:14:57,483
For slower, longer living things,

197
00:14:58,163 --> 00:15:01,323
an hour can go by in the blink of an eye.

198
00:15:03,323 --> 00:15:05,723
[dramatic music continues]

199
00:15:08,363 --> 00:15:11,403
But whether you're living in high speed

200
00:15:12,403 --> 00:15:14,163
or in slow motion,

201
00:15:16,003 --> 00:15:21,043
all life in the forest must adhere
to the same 24-hour day.

202
00:15:23,763 --> 00:15:25,963
And as the world keeps spinning…

203
00:15:26,843 --> 00:15:29,363
[dramatic music crescendos]

204
00:15:29,443 --> 00:15:31,603
…those days keep ticking by…

205
00:15:33,643 --> 00:15:37,763
dictating the lives of every chimpanzee.

206
00:15:41,483 --> 00:15:42,803
One in particular.

207
00:15:43,563 --> 00:15:46,323
[low rumbling]

208
00:15:50,003 --> 00:15:51,963
At just 15 weeks,

209
00:15:52,923 --> 00:15:57,003
this baby's entire body
could fit in its mother's hand.

210
00:16:00,603 --> 00:16:02,483
For it to fully form,

211
00:16:02,563 --> 00:16:05,803
a cascade
of perfectly timed events must occur.

212
00:16:08,203 --> 00:16:10,403
For the next 130 days,

213
00:16:11,163 --> 00:16:15,523
every minute,
every nanosecond is critical.

214
00:16:16,283 --> 00:16:18,723
[dramatic music playing]

215
00:16:22,243 --> 00:16:24,163
[ethereal tinkling]

216
00:16:24,243 --> 00:16:30,203
New cells divide and grow
with remarkable speed and precision.

217
00:16:34,243 --> 00:16:35,243
Right now,

218
00:16:36,203 --> 00:16:41,723
brain cells are multiplying
at a rate of around 15 million per hour.

219
00:16:51,803 --> 00:16:54,843
All of us, from our very first moments,

220
00:16:55,843 --> 00:17:00,203
have a deep biological relationship
with time.

221
00:17:00,283 --> 00:17:02,723
[dramatic music continues]

222
00:17:07,843 --> 00:17:10,443
[chimpanzees hooting]

223
00:17:13,043 --> 00:17:14,083
[clock ticks]

224
00:17:15,723 --> 00:17:17,323
[calm music playing]

225
00:17:17,403 --> 00:17:19,163
As the sunlight wanes,

226
00:17:21,803 --> 00:17:24,323
the chimps instinctively switch gears.

227
00:17:27,883 --> 00:17:29,123
To evening mode.

228
00:17:29,203 --> 00:17:30,283
[chimpanzee yawning]

229
00:17:39,163 --> 00:17:41,963
Nesting calls signal to the whole troop.

230
00:17:42,043 --> 00:17:43,563
[chimpanzees hooting]

231
00:17:44,443 --> 00:17:47,603
It's time to find a safe place
to spend the night.

232
00:17:47,683 --> 00:17:50,123
[playful music playing]

233
00:18:01,443 --> 00:18:05,603
Their bedding needs to be soft but strong.

234
00:18:12,243 --> 00:18:14,683
It doesn't hurt if it tastes good either.

235
00:18:18,923 --> 00:18:21,843
The rhythm of every day in the forest

236
00:18:21,923 --> 00:18:25,403
is determined by the sun's position
in the sky.

237
00:18:27,003 --> 00:18:30,123
[pensive music playing]

238
00:18:34,603 --> 00:18:37,043
But the chimp's innate sense of time

239
00:18:38,243 --> 00:18:40,963
comes from something inside them.

240
00:18:41,043 --> 00:18:44,043
[chimpanzees screeching]

241
00:18:45,163 --> 00:18:47,243
[whooshing]

242
00:18:49,723 --> 00:18:53,723
Deep in their brains
is a biological clock.

243
00:18:56,603 --> 00:18:59,563
Bundles of neurons act as a pendulum…

244
00:18:59,643 --> 00:19:01,803
[whooshing]

245
00:19:01,883 --> 00:19:06,443
…controlled by genes
that switch on and off…

246
00:19:08,563 --> 00:19:13,003
and a cycle that repeats every 24 hours.

247
00:19:13,523 --> 00:19:16,203
[whooshing continues]

248
00:19:16,283 --> 00:19:21,363
These clock genes create
a circadian rhythm in the body

249
00:19:22,123 --> 00:19:28,243
that waxes and wanes in sync
with our planet's rotation.

250
00:19:30,643 --> 00:19:32,083
Controlling hormones…

251
00:19:34,723 --> 00:19:36,483
[chimpanzee screeching]

252
00:19:36,563 --> 00:19:37,483
…heart rates,

253
00:19:38,843 --> 00:19:40,683
and energy levels.

254
00:19:46,243 --> 00:19:50,803
And right now, the chimps' body clocks
are sending the message,

255
00:19:52,203 --> 00:19:54,763
"It's time to get sleepy."

256
00:19:55,683 --> 00:19:56,683
[moans]

257
00:19:58,003 --> 00:19:59,603
Not everyone can though.

258
00:20:01,923 --> 00:20:04,323
[heartbeat thumping softly]

259
00:20:14,363 --> 00:20:17,283
Celeste's baby's brain is still forming.

260
00:20:20,683 --> 00:20:23,043
With no internal clock of its own,

261
00:20:23,683 --> 00:20:27,283
it relies on its mother's hormones
to keep it synchronized.

262
00:20:29,643 --> 00:20:33,403
But baby doesn't always get the memo.

263
00:20:37,523 --> 00:20:39,163
Lucky for Celeste,

264
00:20:39,243 --> 00:20:41,603
with so much growing to do,

265
00:20:41,683 --> 00:20:44,563
her baby does eventually drift off.

266
00:20:47,043 --> 00:20:48,683
[insects chirping]

267
00:20:48,763 --> 00:20:50,963
[pensive music playing]

268
00:20:59,643 --> 00:21:03,563
While the chimps go to sleep
high in the treetops…

269
00:21:07,323 --> 00:21:10,723
other forest dwellers are just waking up.

270
00:21:22,763 --> 00:21:25,443
Body clocks tick away

271
00:21:25,523 --> 00:21:29,803
in the cells of plants and animals
throughout the forest.

272
00:21:32,643 --> 00:21:34,123
[bat chittering]

273
00:21:38,363 --> 00:21:43,563
Clock genes evolved
two and a half billion years ago

274
00:21:43,643 --> 00:21:45,643
in the first living cells.

275
00:21:48,123 --> 00:21:52,923
Those that could anticipate the light
and dark of a day had an advantage.

276
00:21:56,203 --> 00:21:57,963
And as life evolved,

277
00:21:59,283 --> 00:22:01,883
it synchronized to Earth's motion.

278
00:22:02,923 --> 00:22:04,723
So that today,

279
00:22:04,803 --> 00:22:09,443
these clocks exist
in almost every creature on Earth.

280
00:22:13,683 --> 00:22:16,483
Although some creatures prefer day
and others night…

281
00:22:22,363 --> 00:22:26,243
all life is dancing to the same beat.

282
00:22:26,323 --> 00:22:28,043
[dramatic music playing]

283
00:22:28,763 --> 00:22:31,003
Thanks to cellular clocks

284
00:22:31,083 --> 00:22:36,283
that tick in time
with the spin of our Earth.

285
00:22:36,363 --> 00:22:40,643
[whooshing]

286
00:22:50,723 --> 00:22:51,643
[clock ticks]

287
00:22:53,043 --> 00:22:55,563
As yesterday becomes a memory…

288
00:22:55,643 --> 00:22:58,003
[pensive music playing]

289
00:22:58,083 --> 00:23:00,483
…another new day begins in the forest.

290
00:23:00,563 --> 00:23:02,923
[chimpanzees hooting]

291
00:23:09,603 --> 00:23:11,043
A fresh cycle,

292
00:23:12,803 --> 00:23:17,203
and yet, no clock can ever truly be reset.

293
00:23:24,763 --> 00:23:29,283
And there are subtle clues
all around the forest that reveal why.

294
00:23:32,483 --> 00:23:38,083
Nothing is the same today
as it was yesterday.

295
00:23:42,243 --> 00:23:44,683
Least of all Apollo,

296
00:23:45,763 --> 00:23:49,203
who seems to have woken up
on the wrong side of the bed.

297
00:23:51,723 --> 00:23:52,563
[grunts]

298
00:23:57,643 --> 00:23:59,363
When he's in a bad mood…

299
00:24:03,243 --> 00:24:07,883
the rest of the group
just need to keep their heads down.

300
00:24:07,963 --> 00:24:10,323
[chimpanzees hooting]

301
00:24:11,723 --> 00:24:14,123
[ominous music playing]

302
00:24:23,723 --> 00:24:25,603
[Apollo grunting]

303
00:24:26,763 --> 00:24:29,603
He soon finds a target
for his rage, though.

304
00:24:33,843 --> 00:24:36,083
[bees buzzing]

305
00:24:40,723 --> 00:24:44,163
Some of the younger chimps
have found honey for breakfast.

306
00:24:46,323 --> 00:24:48,763
[ominous music continues]

307
00:24:56,723 --> 00:25:00,283
And they forgot
to invite Apollo to join them.

308
00:25:02,323 --> 00:25:03,643
[chimpanzee hooting]

309
00:25:06,323 --> 00:25:07,923
[ominous music crescendos]

310
00:25:08,003 --> 00:25:10,123
[chimpanzees screeching]

311
00:25:14,683 --> 00:25:19,123
You soon learn, never get
on the wrong side of the dominant male.

312
00:25:19,203 --> 00:25:20,643
[hooting]

313
00:25:22,403 --> 00:25:24,923
[chimpanzees screeching]

314
00:25:25,003 --> 00:25:26,843
[solemn music playing]

315
00:25:26,923 --> 00:25:28,443
He's got a nasty bite.

316
00:25:32,323 --> 00:25:34,843
Thankfully, it's not too serious.

317
00:25:43,243 --> 00:25:46,483
With a bit of care,
this wound should heal.

318
00:25:49,403 --> 00:25:53,083
But wounds leave behind scars,

319
00:25:54,203 --> 00:25:56,163
etched into the chimps' bodies.

320
00:25:57,443 --> 00:26:03,563
Indelible marks of the past that reveal
the one universal truth about time.

321
00:26:07,323 --> 00:26:08,603
It has a direction.

322
00:26:10,683 --> 00:26:13,043
You can never go back in time…

323
00:26:13,123 --> 00:26:14,603
[sound effects playing in reverse]

324
00:26:14,683 --> 00:26:17,363
…only forward into the future.

325
00:26:17,443 --> 00:26:20,763
[clock ticking continuously]

326
00:26:20,843 --> 00:26:22,963
This is time's arrow,

327
00:26:24,243 --> 00:26:27,883
and it leaves scars on everything

328
00:26:28,563 --> 00:26:29,523
across Earth…

329
00:26:29,603 --> 00:26:31,203
[clock ticking rapidly]

330
00:26:31,283 --> 00:26:32,443
…and beyond.

331
00:26:35,083 --> 00:26:37,723
[rapid ticks morph into rhythmic music]

332
00:26:41,203 --> 00:26:46,563
Our moon is pockmarked with battle scars
that tell stories of ancient events.

333
00:26:56,523 --> 00:26:57,883
So too are the planets.

334
00:27:01,723 --> 00:27:08,683
Their surfaces testament to a lifetime
of bombardment by asteroids and comets.

335
00:27:08,763 --> 00:27:10,523
[rhythmic music continues]

336
00:27:15,083 --> 00:27:19,163
But perhaps the most impressive
impact crater in our solar system

337
00:27:20,723 --> 00:27:23,123
belongs to a moon of Saturn.

338
00:27:24,523 --> 00:27:25,523
Mimas.

339
00:27:27,923 --> 00:27:32,603
The Herschel crater
is 130 kilometers across.

340
00:27:38,323 --> 00:27:40,883
Whatever created this enormous scar…

341
00:27:43,043 --> 00:27:46,323
must have come close
to shattering the moon to pieces.

342
00:27:54,923 --> 00:27:57,523
[intense electronic music playing]

343
00:28:04,043 --> 00:28:06,123
Mimas lives to tell the tale.

344
00:28:07,883 --> 00:28:10,443
But events like this are irreversible.

345
00:28:10,963 --> 00:28:13,003
[whooshing]

346
00:28:15,363 --> 00:28:19,403
And they differentiate the past
from the present.

347
00:28:19,483 --> 00:28:20,923
[intriguing music playing]

348
00:28:22,203 --> 00:28:24,643
Impact craters are timestamps

349
00:28:26,403 --> 00:28:28,883
that mark a unique moment in history.

350
00:28:37,443 --> 00:28:40,403
We can never revisit the moment
they were created.

351
00:28:44,003 --> 00:28:47,683
But we can piece together traces
of past events

352
00:28:49,123 --> 00:28:51,523
and map a course back through time.

353
00:28:56,683 --> 00:28:57,923
Before craters.

354
00:28:58,003 --> 00:28:59,603
[sound effects playing in reverse]

355
00:28:59,683 --> 00:29:00,963
Before planets.

356
00:29:01,883 --> 00:29:03,123
Before stars.

357
00:29:05,043 --> 00:29:07,723
Back to a time before time.

358
00:29:14,443 --> 00:29:17,443
Our universe had a beginning.

359
00:29:18,123 --> 00:29:19,523
[explosion rumbles]

360
00:29:20,163 --> 00:29:21,803
[dramatic music playing]

361
00:29:21,883 --> 00:29:25,003
A very big bang…

362
00:29:27,403 --> 00:29:29,843
that created three-dimensional space

363
00:29:31,323 --> 00:29:32,603
and time.

364
00:29:36,923 --> 00:29:40,283
But space and time are not separate.

365
00:29:41,843 --> 00:29:44,883
Time is woven
into the fabric of the universe.

366
00:29:45,403 --> 00:29:46,963
[dramatic music continues]

367
00:29:49,283 --> 00:29:54,163
Bound to space
as our universe's fourth dimension.

368
00:29:56,523 --> 00:29:59,443
The Big Bang
set the universe's clock ticking.

369
00:30:02,963 --> 00:30:05,323
Propelling everything into the future.

370
00:30:05,403 --> 00:30:07,123
[zapping]

371
00:30:07,203 --> 00:30:09,003
[dramatic music crescendos]

372
00:30:09,083 --> 00:30:13,083
It created the arrow of time.

373
00:30:14,683 --> 00:30:17,243
[insects, birds chirping]

374
00:30:18,683 --> 00:30:22,003
From our universe's very first moments…

375
00:30:22,603 --> 00:30:23,483
[clock ticks]

376
00:30:25,883 --> 00:30:26,763
[clock ticks]

377
00:30:29,123 --> 00:30:30,003
[clock ticks]

378
00:30:30,083 --> 00:30:32,323
[calm music playing]

379
00:30:32,403 --> 00:30:34,683
…it pushes us all into the future,

380
00:30:35,763 --> 00:30:38,243
causing everything to grow,

381
00:30:39,683 --> 00:30:40,523
age…

382
00:30:40,603 --> 00:30:41,483
[clock ticks]

383
00:30:42,483 --> 00:30:43,443
…and change.

384
00:30:43,963 --> 00:30:44,843
[clock ticks]

385
00:30:45,603 --> 00:30:47,043
From childhood…

386
00:30:47,123 --> 00:30:47,963
[clock ticks]

387
00:30:48,043 --> 00:30:49,163
…to adulthood,

388
00:30:50,443 --> 00:30:54,123
we all travel through life
in the same direction.

389
00:30:55,683 --> 00:30:58,363
Getting older day by day.

390
00:31:00,003 --> 00:31:02,843
And with age comes wisdom

391
00:31:04,243 --> 00:31:07,683
as youthful innocence
is replaced by experience.

392
00:31:07,763 --> 00:31:09,763
[chimpanzee grunting]

393
00:31:13,163 --> 00:31:17,563
Time's arrow leads us through
these stages of life.

394
00:31:17,643 --> 00:31:19,723
[calm music continues]

395
00:31:21,923 --> 00:31:23,123
It shapes us.

396
00:31:25,803 --> 00:31:27,483
Defines who we are.

397
00:31:31,043 --> 00:31:32,563
From our first moments…

398
00:31:34,723 --> 00:31:35,843
to our last.

399
00:31:41,923 --> 00:31:44,523
Chimps rarely live past the age of 40.

400
00:31:49,243 --> 00:31:50,883
Nothing is immortal.

401
00:31:52,523 --> 00:31:54,323
[solemn music playing]

402
00:31:58,523 --> 00:32:03,283
Everything that exists in our universe
has a finite lifespan.

403
00:32:08,723 --> 00:32:12,003
Including, perhaps, the universe itself.

404
00:32:14,443 --> 00:32:18,123
[whooshing]

405
00:32:19,643 --> 00:32:23,483
Today, the galaxies are filled with stars.

406
00:32:27,323 --> 00:32:33,643
But 95% of stars that will ever exist
have already been born.

407
00:32:36,723 --> 00:32:38,763
-[solemn music continues]
-[clock ticks]

408
00:32:38,843 --> 00:32:41,443
So, as our universe
journeys into the future…

409
00:32:41,523 --> 00:32:42,763
[clock ticks]

410
00:32:42,843 --> 00:32:44,123
…the stars…

411
00:32:44,803 --> 00:32:47,843
-[clock ticks]
-…one by one, will blink out…

412
00:32:47,923 --> 00:32:48,803
[clock ticks]

413
00:32:50,363 --> 00:32:55,243
…leaving the universe
to face an ever-darkening future,

414
00:32:56,923 --> 00:32:58,723
stretching out for trillions,

415
00:32:59,443 --> 00:33:02,963
that's thousands of billions, of years.

416
00:33:05,523 --> 00:33:07,843
[solemn music continues]

417
00:33:09,443 --> 00:33:11,683
The age of starlight

418
00:33:11,763 --> 00:33:16,323
will be followed by a dark age
of black holes.

419
00:33:17,643 --> 00:33:19,843
[eerie music playing]

420
00:33:22,963 --> 00:33:27,883
These monsters feed on the remnants
of dead stars and planets.

421
00:33:29,603 --> 00:33:31,083
And as they do,

422
00:33:31,163 --> 00:33:36,363
their ever-increasing gravity scars
the very fabric of the universe.

423
00:33:36,443 --> 00:33:38,723
[zapping, whooshing]

424
00:33:43,123 --> 00:33:46,443
Distorting both space and time.

425
00:33:48,803 --> 00:33:53,123
The edge of a black hole,
called the event horizon,

426
00:33:54,283 --> 00:33:57,443
is a region where gravity
has become so strong

427
00:33:58,283 --> 00:34:03,923
it causes time
to slow down practically to a standstill.

428
00:34:04,923 --> 00:34:06,603
[eerie music crescendos]

429
00:34:09,003 --> 00:34:12,323
But even black holes
can't escape time's arrow.

430
00:34:12,403 --> 00:34:15,003
[solemn music playing]

431
00:34:15,083 --> 00:34:16,963
In the far, far future…

432
00:34:18,403 --> 00:34:21,043
[clock ticking]

433
00:34:21,123 --> 00:34:24,403
…when there are no stars
or planets left to consume,

434
00:34:25,963 --> 00:34:27,643
they will begin to starve.

435
00:34:32,843 --> 00:34:34,043
And slowly…

436
00:34:36,723 --> 00:34:37,963
very slowly,

437
00:34:39,763 --> 00:34:40,883
they will shrink.

438
00:34:42,523 --> 00:34:45,043
[suspenseful music playing]

439
00:34:46,403 --> 00:34:48,043
When they die,

440
00:34:48,123 --> 00:34:50,443
no one truly knows what comes next.

441
00:34:52,963 --> 00:34:58,003
But it could be the end of our universe.

442
00:35:03,763 --> 00:35:06,243
[insects, birds chirping]

443
00:35:07,443 --> 00:35:11,803
Here on Earth, none of us can slow
the passage of time.

444
00:35:16,043 --> 00:35:20,323
And one of Celeste's aunts
is reaching the end of her time.

445
00:35:22,403 --> 00:35:24,243
[somber music playing]

446
00:35:24,323 --> 00:35:28,083
Retreating from the group,
she heads into the forest alone.

447
00:35:35,843 --> 00:35:37,883
She has lived many years.

448
00:35:41,243 --> 00:35:44,123
But this day will be her last.

449
00:35:44,843 --> 00:35:47,523
[somber music continues]

450
00:36:03,803 --> 00:36:06,563
While the world continues to spin,

451
00:36:07,963 --> 00:36:11,083
her body lies still.

452
00:36:14,643 --> 00:36:17,323
[somber music crescendos]

453
00:36:19,603 --> 00:36:22,123
[whooshing]

454
00:36:23,363 --> 00:36:26,203
But time doesn't just carry us
toward endings.

455
00:36:30,403 --> 00:36:32,443
It also creates beginnings.

456
00:36:33,283 --> 00:36:35,843
[ethereal music playing]

457
00:36:37,323 --> 00:36:40,803
As days turn into weeks
and weeks into months,

458
00:36:42,603 --> 00:36:45,643
there are big changes
for one special chimpanzee.

459
00:36:47,523 --> 00:36:49,003
[whooshing]

460
00:36:49,083 --> 00:36:51,523
[intriguing music playing]

461
00:36:51,603 --> 00:36:55,003
[heartbeat thumping softly]

462
00:36:59,643 --> 00:37:01,523
Say hello to Cosmo.

463
00:37:06,083 --> 00:37:09,003
Her brain and limbs are now fully formed.

464
00:37:10,763 --> 00:37:13,443
And her eyes are ready to see the world.

465
00:37:13,523 --> 00:37:15,843
[intriguing music continues]

466
00:37:21,923 --> 00:37:25,003
The exact timing
of her birth is impossible to know.

467
00:37:26,603 --> 00:37:29,443
But she could be born any day now.

468
00:37:29,523 --> 00:37:31,683
[dramatic vocal music playing]

469
00:37:36,043 --> 00:37:38,803
She's been in the womb for eight months.

470
00:37:40,283 --> 00:37:43,523
But her journey began long, long ago.

471
00:37:44,643 --> 00:37:45,963
[whooshing, explosion rumbles]

472
00:37:46,043 --> 00:37:50,643
The elements that made her
came from dying stars.

473
00:37:51,283 --> 00:37:52,483
[whooshing]

474
00:37:52,563 --> 00:37:58,363
The water that flows through her body
came from distant worlds.

475
00:37:58,443 --> 00:38:00,363
[dramatic music playing]

476
00:38:00,443 --> 00:38:06,963
The energy that powers her muscles
came from the heart of our sun.

477
00:38:07,043 --> 00:38:08,643
[explosion rumbles]

478
00:38:09,763 --> 00:38:13,083
But it's that most mysterious ingredient,

479
00:38:13,763 --> 00:38:18,243
the one that started ticking
13.8 billion years ago…

480
00:38:22,323 --> 00:38:26,843
that has led all other ingredients
to this moment.

481
00:38:30,163 --> 00:38:31,283
In this place.

482
00:38:31,363 --> 00:38:33,323
[ethereal music playing]

483
00:38:34,003 --> 00:38:35,243
On this planet.

484
00:38:40,643 --> 00:38:44,683
-[birds chirping]
-[chimpanzees hooting]

485
00:38:44,763 --> 00:38:47,963
Another sunrise, another morning.

486
00:38:48,043 --> 00:38:50,443
[calm music playing]

487
00:38:53,283 --> 00:38:57,563
And this one is extra special.

488
00:39:08,163 --> 00:39:10,563
Welcome to Earth, Cosmo.

489
00:39:13,123 --> 00:39:15,403
[Cosmo grunting]

490
00:39:15,483 --> 00:39:18,723
This precious moment
will never be repeated for Celeste.

491
00:39:19,523 --> 00:39:22,803
But Cosmo's journey has just begun.

492
00:39:26,043 --> 00:39:28,323
It will take around three months

493
00:39:28,403 --> 00:39:32,083
for her body clock to synchronize
to the rhythm of the planet,

494
00:39:33,883 --> 00:39:36,443
one year before she can truly communicate,

495
00:39:38,123 --> 00:39:42,723
and perhaps 15 years
until she is fully grown.

496
00:39:45,803 --> 00:39:47,563
So much lies ahead.

497
00:39:49,763 --> 00:39:51,843
[Cosmo grunting]

498
00:39:53,043 --> 00:39:54,843
[whooshing]

499
00:39:56,363 --> 00:39:57,643
Like Cosmo,

500
00:39:58,363 --> 00:40:01,403
our universe is still in its infancy

501
00:40:02,443 --> 00:40:06,683
at the beginning
of an unimaginably long lifespan.

502
00:40:06,763 --> 00:40:08,643
[majestic music playing]

503
00:40:08,723 --> 00:40:11,963
We are living in the age of starlight.

504
00:40:14,243 --> 00:40:19,203
A moment when time's arrow
has filled the universe with beauty…

505
00:40:21,003 --> 00:40:22,403
[penguins squawking]

506
00:40:22,483 --> 00:40:23,443
…and wonder.

507
00:40:23,523 --> 00:40:25,163
[majestic music continues]

508
00:40:32,403 --> 00:40:34,563
But it's a brief window of time

509
00:40:35,483 --> 00:40:39,243
that will never be repeated
in the history of our universe.

510
00:40:45,363 --> 00:40:47,763
No one can slow the passage of time,

511
00:40:49,123 --> 00:40:50,203
nor should we try.

512
00:40:55,323 --> 00:40:56,963
Because without time,

513
00:40:58,163 --> 00:40:59,523
there would be no now.

514
00:41:06,763 --> 00:41:08,203
No moment in the sun.

515
00:41:17,243 --> 00:41:18,963
No moments, period.

516
00:41:24,643 --> 00:41:25,763
Without time,

517
00:41:27,803 --> 00:41:29,203
there would be no life.

518
00:41:40,043 --> 00:41:41,283
[whooshing]

519
00:41:41,363 --> 00:41:44,163
Next in the story of our universe,

520
00:41:45,843 --> 00:41:47,483
Earth's seasons.

521
00:41:47,563 --> 00:41:48,923
[playful music playing]

522
00:41:49,003 --> 00:41:51,803
Like a mother bear raising her cubs…

523
00:41:51,883 --> 00:41:53,083
[cub groans]

524
00:41:53,163 --> 00:41:56,723
…we all experience
our planet's yearly transformations.

525
00:41:56,803 --> 00:41:58,443
[bear roars]

526
00:41:59,803 --> 00:42:02,323
But what created Earth's seasons?

527
00:42:03,163 --> 00:42:04,723
[rumbling]

528
00:42:04,803 --> 00:42:05,723
[crashing]

529
00:42:05,803 --> 00:42:08,883
How are they connected
to the formation of our moon?

530
00:42:09,923 --> 00:42:15,723
And why does only our planet
have conditions just right for life?

531
00:42:17,923 --> 00:42:19,123
[cub whines]

532
00:42:21,323 --> 00:42:24,123
[dramatic music playing]