1
00:00:27,000 --> 00:00:29,000
<i> The far north of our planet</i>

2
00:00:30,640 --> 00:00:32,800
<i>is a land of extremes.</i>

3
00:00:37,880 --> 00:00:39,440
<i>When winter takes hold…</i>

4
00:00:43,160 --> 00:00:46,160
…<i>arctic winds cause temperatures</i>
<i>to plummet.</i>

5
00:00:49,800 --> 00:00:54,080
<i>Even the hardy Alaskan brown bear</i>
<i>must take refuge.</i>

6
00:01:02,520 --> 00:01:05,160
<i>Unable to endure</i>
<i>the freezing conditions,</i>

7
00:01:07,040 --> 00:01:10,280
<i>they are forced</i>
<i>to embark on an extraordinary journey.</i>

8
00:01:15,040 --> 00:01:18,800
<i>As the North Pole tilts</i>
<i>into the darkness and cold of winter…</i>

9
00:01:24,000 --> 00:01:25,680
<i>the bears begin climbing</i>

10
00:01:27,000 --> 00:01:28,680
<i>high into the mountains…</i>

11
00:01:32,960 --> 00:01:35,400
<i>to find shelter in caves or dens</i>

12
00:01:36,600 --> 00:01:38,480
<i>dug into the steep slopes.</i>

13
00:01:41,640 --> 00:01:43,160
<i>Hundreds of meters up.</i>

14
00:02:12,680 --> 00:02:14,880
<i>Bears living at the ends of the Earth</i>

15
00:02:16,760 --> 00:02:20,880
<i>must contend with the incredible</i>
<i>challenges each season brings.</i>

16
00:02:23,920 --> 00:02:24,800
<i>To do it,</i>

17
00:02:26,320 --> 00:02:30,240
<i>they rely on a very special connection</i>
<i>to the universe,</i>

18
00:02:31,240 --> 00:02:34,680
<i>because written into a bear's biology</i>

19
00:02:34,760 --> 00:02:36,840
<i>is every critical moment…</i>

20
00:02:38,400 --> 00:02:41,960
<i>…of Earth's</i>
<i>four-and-a-half-billion-year history.</i>

21
00:02:45,040 --> 00:02:47,520
<i>Events of unimaginable power…</i>

22
00:02:48,800 --> 00:02:50,040
<i>…and destruction</i>

23
00:02:51,480 --> 00:02:56,400
<i>that have created a world</i>
<i>like nowhere else in our universe.</i>

24
00:03:33,320 --> 00:03:36,480
<i>This is Luna,</i>
<i>a six-year-old female.</i>

25
00:03:41,480 --> 00:03:43,880
<i>Having reached the safety of her den…</i>

26
00:03:46,800 --> 00:03:50,000
<i>this will be her home</i>
<i>for the next six months.</i>

27
00:03:57,960 --> 00:03:59,120
<i>A cozy spot</i>

28
00:04:00,560 --> 00:04:04,400
<i>to see out the winter in hibernation.</i>

29
00:04:22,640 --> 00:04:24,520
<i>As the days get shorter…</i>

30
00:04:27,200 --> 00:04:29,880
<i>her body responds</i>
<i>to the rhythm of our planet.</i>

31
00:04:36,360 --> 00:04:38,480
<i>Her heart rate begins to slow…</i>

32
00:04:48,280 --> 00:04:50,280
…<i>to just eight beats per minute.</i>

33
00:05:04,880 --> 00:05:06,520
<i>As she settles down…</i>

34
00:05:08,600 --> 00:05:10,600
<i>her body temperature drops.</i>

35
00:05:30,800 --> 00:05:35,880
<i>And she falls into a deep, dreamful sleep.</i>

36
00:05:52,280 --> 00:05:56,760
<i>The powerful connection</i>
<i>between bear and universe…</i>

37
00:05:59,880 --> 00:06:03,520
<i>compels her to spend</i>
<i>the harsh winter months underground.</i>

38
00:06:07,960 --> 00:06:12,080
<i>Blissfully unaware</i>
<i>of the long journey ahead.</i>

39
00:06:17,160 --> 00:06:19,120
<i>Because outside the den…</i>

40
00:06:22,480 --> 00:06:24,240
…<i>Earth is on the move.</i>

41
00:06:34,280 --> 00:06:38,400
<i>Every day,</i>
<i>the planet spins once on its axis.</i>

42
00:06:55,320 --> 00:07:00,080
<i>Each month, the Moon completes</i>
<i>one full circuit around the Earth.</i>

43
00:07:07,040 --> 00:07:08,680
<i>And as the months pass,</i>

44
00:07:09,720 --> 00:07:13,320
<i>the Earth and the Moon orbit the Sun.</i>

45
00:07:19,200 --> 00:07:21,320
<i>During the time she'll spend asleep,</i>

46
00:07:22,320 --> 00:07:26,520
<i>Luna will travel 470 million kilometers.</i>

47
00:07:32,960 --> 00:07:34,920
<i>An epic cosmic voyage</i>

48
00:07:36,640 --> 00:07:38,640
<i>halfway around the Sun.</i>

49
00:07:47,560 --> 00:07:48,680
<i>And this year,</i>

50
00:07:49,560 --> 00:07:52,200
<i>she has some new traveling companions.</i>

51
00:07:55,560 --> 00:07:58,200
<i>While in and out of sleep…</i>

52
00:07:59,520 --> 00:08:01,640
<i>…Luna has given birth…</i>

53
00:08:04,040 --> 00:08:05,880
<i>to two little bears.</i>

54
00:08:12,320 --> 00:08:16,480
<i>The cubs will eat and sleep</i>
<i>in the den until springtime.</i>

55
00:08:19,600 --> 00:08:21,400
<i>But two more mouths to feed</i>

56
00:08:23,320 --> 00:08:26,000
<i>is taking its toll on Luna's body.</i>

57
00:08:33,120 --> 00:08:35,800
<i>Fat cells beneath her skin begin to shrink</i>

58
00:08:37,440 --> 00:08:40,800
<i>as her energy stores</i>
<i>are used up producing milk.</i>

59
00:08:48,920 --> 00:08:50,960
<i>After five months underground,</i>

60
00:08:51,840 --> 00:08:55,400
<i>Luna has already lost</i>
<i>more than a quarter of her body weight.</i>

61
00:09:01,120 --> 00:09:04,440
<i>And with outside temperatures</i>
<i>still locked below zero…</i>

62
00:09:06,560 --> 00:09:09,800
<i>Luna urgently needs spring to arrive</i>

63
00:09:10,640 --> 00:09:14,000
<i>if she is to continue feeding</i>
<i>her newborn cubs.</i>

64
00:09:22,080 --> 00:09:22,960
<i>Luckily,</i>

65
00:09:24,880 --> 00:09:26,360
<i>Earth has a happy quirk.</i>

66
00:09:29,800 --> 00:09:31,480
<i>It's tilted on its side.</i>

67
00:09:35,920 --> 00:09:38,800
<i>And so, as it moves through space,</i>

68
00:09:39,720 --> 00:09:42,240
<i>at different times of the year,</i>

69
00:09:42,320 --> 00:09:45,400
<i>different parts</i>
<i>of the planet lean toward the Sun,</i>

70
00:09:47,280 --> 00:09:49,640
<i>causing the seasons to turn.</i>

71
00:10:00,360 --> 00:10:02,000
<i>Which means, in Alaska,</i>

72
00:10:03,200 --> 00:10:05,200
<i>something remarkable is happening.</i>

73
00:10:12,880 --> 00:10:14,760
<i>With each passing day,</i>

74
00:10:14,840 --> 00:10:17,000
<i>the Sun gets higher in the sky.</i>

75
00:10:20,840 --> 00:10:23,680
<i>Its warming rays transforming</i>
<i>the landscape.</i>

76
00:10:34,080 --> 00:10:37,920
<i>Just when Luna and her cubs need it most.</i>

77
00:10:42,520 --> 00:10:46,080
<i>Nerve endings in her skin detect</i>
<i>the warmth of the Sun.</i>

78
00:10:53,880 --> 00:10:55,560
<i>And as the days get longer…</i>

79
00:11:01,120 --> 00:11:04,000
<i>…specialized cells in the back of her eye</i>

80
00:11:05,480 --> 00:11:09,000
<i>sense the tiny increases in light levels.</i>

81
00:11:14,680 --> 00:11:16,960
<i>These secret messages,</i>

82
00:11:17,040 --> 00:11:19,200
<i>direct from our nearest star…</i>

83
00:11:22,400 --> 00:11:26,280
<i>tell Luna it's time</i>
<i>to wake from hibernation.</i>

84
00:11:40,720 --> 00:11:45,160
<i>As they signal the gentle turning</i>
<i>of our planet's seasons.</i>

85
00:11:54,320 --> 00:11:56,000
<i>But out in the solar system…</i>

86
00:11:58,200 --> 00:12:00,040
<i>seasons like Earth's</i>

87
00:12:01,880 --> 00:12:03,200
<i>are far from typical.</i>

88
00:12:09,640 --> 00:12:12,160
<i>Our nearest neighbor, Venus…</i>

89
00:12:14,920 --> 00:12:16,680
<i>…is much closer to the Sun</i>

90
00:12:17,640 --> 00:12:20,360
<i>and so is much hotter than Earth.</i>

91
00:12:25,160 --> 00:12:28,120
<i>And because the planet has no tilt,</i>

92
00:12:28,960 --> 00:12:31,080
<i>it has virtually no seasons.</i>

93
00:12:35,480 --> 00:12:39,400
<i>Temperatures remain searingly hot</i>
<i>all year round.</i>

94
00:12:44,280 --> 00:12:45,560
<i>Further away,</i>

95
00:12:46,080 --> 00:12:47,480
<i>out past Earth…</i>

96
00:12:49,600 --> 00:12:50,920
<i>…is Mars,</i>

97
00:12:52,880 --> 00:12:55,680
<i>whose orbit causes its distance</i>
<i>from the Sun</i>

98
00:12:56,200 --> 00:12:58,440
<i>to vary dramatically through the year,</i>

99
00:13:00,160 --> 00:13:01,960
<i>making seasons on Mars…</i>

100
00:13:03,600 --> 00:13:06,440
…<i>far more extreme than our own.</i>

101
00:13:09,200 --> 00:13:13,880
<i>During winter, over a quarter</i>
<i>of the planet's atmosphere freezes solid.</i>

102
00:13:15,880 --> 00:13:17,040
<i>While in summer,</i>

103
00:13:18,120 --> 00:13:20,440
<i>when Mars passes closer to the Sun,</i>

104
00:13:21,240 --> 00:13:24,280
<i>the increased heat creates dust storms</i>

105
00:13:24,360 --> 00:13:29,280
<i>so severe</i>
<i>they can engulf the entire planet.</i>

106
00:13:33,360 --> 00:13:34,800
<i>But beyond Mars,</i>

107
00:13:36,480 --> 00:13:37,680
<i>past Jupiter…</i>

108
00:13:41,080 --> 00:13:42,000
<i>…and Saturn…</i>

109
00:13:48,080 --> 00:13:51,000
<i>…three billion kilometers from the Sun,</i>

110
00:13:52,600 --> 00:13:57,200
<i>Uranus has the most extreme seasons</i>
<i>in the solar system.</i>

111
00:13:59,840 --> 00:14:03,240
<i>This planet spins on its side.</i>

112
00:14:04,280 --> 00:14:06,240
<i>So as it orbits,</i>

113
00:14:06,320 --> 00:14:08,480
<i>the summer side faces the Sun…</i>

114
00:14:12,040 --> 00:14:17,080
…<i>while the winter side</i>
<i>won't see daylight for 42 years.</i>

115
00:14:29,400 --> 00:14:32,800
<i>Only Earth has seasons</i>

116
00:14:34,440 --> 00:14:37,440
<i>that, even at the extremes of our planet,</i>

117
00:14:38,200 --> 00:14:40,440
<i>allow life a fighting chance.</i>

118
00:14:54,520 --> 00:14:56,120
<i>With the arrival of spring,</i>

119
00:14:57,280 --> 00:14:59,600
<i>Luna's family emerge from the den.</i>

120
00:15:06,280 --> 00:15:11,000
<i>The cubs can now enjoy</i>
<i>their first moments in the Sun.</i>

121
00:15:35,880 --> 00:15:40,360
<i>But the turning seasons mean the cubs</i>
<i>must now set off on a daunting journey.</i>

122
00:15:48,280 --> 00:15:49,760
<i>Because to find food,</i>

123
00:15:50,840 --> 00:15:53,480
<i>Luna must lead them back to the lowlands</i>

124
00:15:54,760 --> 00:15:56,760
<i>on the other side of the mountain.</i>

125
00:16:13,720 --> 00:16:16,000
<i>It's a grueling climb for little legs.</i>

126
00:16:23,840 --> 00:16:27,320
<i>With hundreds of meters</i>
<i>of ice and rock to overcome.</i>

127
00:17:21,040 --> 00:17:25,280
<i>Once they're over the summit,</i>
<i>the hardest part of the trek is over.</i>

128
00:17:36,760 --> 00:17:39,920
<i>But survival is far from guaranteed.</i>

129
00:17:43,560 --> 00:17:45,920
<i>To make it through the rest of the year,</i>

130
00:17:47,240 --> 00:17:48,840
<i>the family will rely…</i>

131
00:17:50,000 --> 00:17:52,000
<i>…on Luna's instinctive understanding</i>

132
00:17:53,200 --> 00:17:54,640
<i>of the seasons ahead.</i>

133
00:17:58,920 --> 00:18:00,280
<i>Each one…</i>

134
00:18:02,640 --> 00:18:05,480
<i>a result of Earth's yearly journey</i>
<i>through space.</i>

135
00:18:12,440 --> 00:18:13,840
<i>A journey that began…</i>

136
00:18:15,920 --> 00:18:18,960
…<i>before the Earth even existed.</i>

137
00:18:33,640 --> 00:18:39,600
<i>A time when our solar system</i>
<i>was little more than ash.</i>

138
00:18:43,120 --> 00:18:44,120
<i>No Sun,</i>

139
00:18:44,880 --> 00:18:45,720
<i>no planets,</i>

140
00:18:46,440 --> 00:18:47,600
<i>and no moons.</i>

141
00:18:50,360 --> 00:18:53,920
<i>Just a vast cloud of gas and dust.</i>

142
00:19:07,320 --> 00:19:10,960
<i>Then, in a distant solar system…</i>

143
00:19:13,400 --> 00:19:14,920
<i>…a star explodes.</i>

144
00:19:16,920 --> 00:19:21,800
<i>A supernova that sends</i>
<i>a shock wave across the galaxy.</i>

145
00:19:41,280 --> 00:19:46,280
<i>On impact, the shockwave</i>
<i>causes the cloud to fall in on itself.</i>

146
00:19:51,680 --> 00:19:53,440
<i>And begin to rotate.</i>

147
00:20:00,440 --> 00:20:02,640
<i>As it spins faster and faster,</i>

148
00:20:04,040 --> 00:20:08,280
<i>the cloud flattens out into a disc.</i>

149
00:20:10,200 --> 00:20:13,200
<i>A maelstrom of gas and rock.</i>

150
00:20:16,600 --> 00:20:19,400
<i>In the center, under intense pressure…</i>

151
00:20:23,040 --> 00:20:24,480
<i>…the Sun is born.</i>

152
00:20:28,080 --> 00:20:31,840
<i>While further out,</i>
<i>rock collides with rock…</i>

153
00:20:34,080 --> 00:20:36,200
<i>and our planet begins to grow.</i>

154
00:20:41,080 --> 00:20:43,480
<i>Until after 20 million years,</i>

155
00:20:44,880 --> 00:20:46,760
<i>Earth is fully formed.</i>

156
00:20:49,360 --> 00:20:52,720
<i>Still circling the Sun like the cloud</i>
<i>from which it grew.</i>

157
00:20:58,920 --> 00:21:02,280
<i>Orbiting once every 365 days,</i>

158
00:21:05,520 --> 00:21:07,440
<i>which is how Earth got its year.</i>

159
00:21:14,240 --> 00:21:16,600
<i>But at this point in the planet's story,</i>

160
00:21:17,760 --> 00:21:19,520
<i>it's a year without seasons.</i>

161
00:21:24,080 --> 00:21:26,720
<i>Because the chaos that created them…</i>

162
00:21:29,200 --> 00:21:31,080
<i>is still to come.</i>

163
00:21:41,560 --> 00:21:42,680
<i>In Alaska,</i>

164
00:21:43,640 --> 00:21:45,360
<i>the vibrancy of spring</i>…

165
00:21:46,600 --> 00:21:49,280
…<i>has given way to lazy summer days.</i>

166
00:22:01,480 --> 00:22:03,880
<i>The cubs are now five months old.</i>

167
00:22:06,600 --> 00:22:08,120
<i>And still learning…</i>

168
00:22:10,400 --> 00:22:11,560
<i>how to be bears.</i>

169
00:22:25,000 --> 00:22:27,080
<i>Because they're growing so quickly,</i>

170
00:22:28,040 --> 00:22:29,960
<i>the cubs are constantly hungry.</i>

171
00:22:36,520 --> 00:22:38,800
<i>And while it might look idyllic…</i>

172
00:22:41,040 --> 00:22:44,480
<i>summer in Alaska is a time of hardship.</i>

173
00:22:54,680 --> 00:22:57,520
<i>Without a decent meal to be found</i>
<i>in the meadows,</i>

174
00:22:58,040 --> 00:23:00,200
<i>the bears must make do with grass.</i>

175
00:23:11,240 --> 00:23:16,240
<i>Which means the cubs still rely</i>
<i>on their mother's milk</i>

176
00:23:16,320 --> 00:23:17,920
<i>for the bulk of their food.</i>

177
00:23:35,520 --> 00:23:39,800
<i>But Luna hasn't eaten properly</i>
<i>since before she went into hibernation,</i>

178
00:23:41,560 --> 00:23:44,040
<i>so she's running on empty.</i>

179
00:23:53,080 --> 00:23:56,040
<i>But nearby, out in space,</i>

180
00:23:57,520 --> 00:23:59,160
<i>help is on the way.</i>

181
00:24:05,880 --> 00:24:10,400
<i>Because today,</i>
<i>our planet has a constant companion.</i>

182
00:24:13,000 --> 00:24:14,040
<i>The Moon.</i>

183
00:24:16,320 --> 00:24:18,280
<i>Locked in orbit around the Earth,</i>

184
00:24:19,720 --> 00:24:22,320
<i>it's our nearest celestial neighbor.</i>

185
00:24:23,920 --> 00:24:27,960
<i>The largest and brightest object</i>
<i>in the night sky.</i>

186
00:24:32,120 --> 00:24:35,520
<i>And because the Moon</i>
<i>is very big and very close…</i>

187
00:24:37,760 --> 00:24:40,480
<i>it exerts a powerful gravitational pull.</i>

188
00:24:47,880 --> 00:24:51,480
<i>Strong enough to influence our world.</i>

189
00:24:56,080 --> 00:24:59,160
<i>It lifts the oceans away</i>
<i>from the planet's surface…</i>

190
00:25:07,520 --> 00:25:09,680
<i>…creating Earth's tides.</i>

191
00:25:15,960 --> 00:25:18,680
<i>And on a few days</i>
<i>around the full and new Moon…</i>

192
00:25:20,800 --> 00:25:25,400
<i>the lowest summer tides reveal</i>
<i>an entirely new landscape.</i>

193
00:25:29,760 --> 00:25:32,800
<i>Mudflats extend hundreds of meters</i>
<i>from the shore.</i>

194
00:25:39,120 --> 00:25:42,800
<i>Allowing hungry bears access</i>
<i>to buried treasure.</i>

195
00:25:50,560 --> 00:25:54,480
<i>At just the right time</i>
<i>for Luna and her young family.</i>

196
00:26:02,480 --> 00:26:04,720
<i>But finding what's hidden in the mud</i>

197
00:26:05,480 --> 00:26:08,200
<i>is a job best left to the grown-ups.</i>

198
00:26:17,080 --> 00:26:21,680
<i>Luna's sense of smell</i>
<i>is 2,000 times better than our own.</i>

199
00:26:24,480 --> 00:26:26,880
<i>Perfect for detecting tasty morsels.</i>

200
00:26:31,200 --> 00:26:32,680
<i>Soft-shelled clams.</i>

201
00:26:53,680 --> 00:26:56,200
<i>She's so skilled at prizing them apart,</i>

202
00:26:57,400 --> 00:27:00,200
<i>she can get through almost one a minute.</i>

203
00:27:20,440 --> 00:27:24,000
<i>The clams are a welcome supplement</i>
<i>to her meager summer diet.</i>

204
00:27:31,720 --> 00:27:34,600
<i>Vital energy</i>
<i>she can pass along to the cubs.</i>

205
00:27:39,800 --> 00:27:43,360
<i>These gifts, delivered to her by the Moon,</i>

206
00:27:43,880 --> 00:27:46,760
<i>will help Luna sustain her family</i>
<i>through summer.</i>

207
00:27:49,880 --> 00:27:52,480
<i>But the bear's relationship with the Moon…</i>

208
00:27:55,440 --> 00:27:58,440
…<i>runs much, much deeper.</i>

209
00:28:03,240 --> 00:28:08,280
<i>Because it was during the Moon's formation</i>
<i>that Earth got its seasons.</i>

210
00:28:13,880 --> 00:28:16,040
<i>Not long after it formed,</i>

211
00:28:16,960 --> 00:28:18,760
<i>our planet gained a companion.</i>

212
00:28:31,000 --> 00:28:32,800
<i>But it wasn't the Moon.</i>

213
00:28:34,920 --> 00:28:39,080
<i>It was another planet</i>
<i>that formed in Earth's orbit.</i>

214
00:28:44,520 --> 00:28:46,880
<i>A sibling called Theia.</i>

215
00:28:48,680 --> 00:28:50,800
<i>It was roughly the size of Mars.</i>

216
00:28:52,760 --> 00:28:56,680
-<i>A vast ball of rock and lava.</i>

217
00:28:59,440 --> 00:29:01,200
<i>Throughout their childhood,</i>

218
00:29:03,040 --> 00:29:05,120
<i>Earth and Theia lived in harmony.</i>

219
00:29:11,320 --> 00:29:16,280
<i>Until gravitational disturbances</i>
<i>in the young solar system…</i>

220
00:29:19,680 --> 00:29:23,400
<i>set the two planets on a collision course.</i>

221
00:29:28,880 --> 00:29:30,040
<i>In this moment…</i>

222
00:29:32,040 --> 00:29:35,040
<i>…Earth's future hangs in the balance.</i>

223
00:29:54,000 --> 00:29:56,040
<i>Theia is obliterated…</i>

224
00:29:59,480 --> 00:30:02,400
<i>as the impact melts both worlds.</i>

225
00:30:29,120 --> 00:30:31,400
<i>For an instant in cosmic time…</i>

226
00:30:34,560 --> 00:30:36,480
<i>our planet had two moons.</i>

227
00:30:46,360 --> 00:30:53,160
<i>But then gravity dragged one of them</i>
<i>back down to be consumed by Earth.</i>

228
00:31:06,720 --> 00:31:09,880
<i>Leaving only the moon we know today.</i>

229
00:31:17,040 --> 00:31:21,160
<i>And the collision transformed</i>
<i>our planet forever.</i>

230
00:31:28,280 --> 00:31:30,600
<i>The impact knocked it over to one side</i>

231
00:31:31,600 --> 00:31:35,040
<i>so that today it spins</i>
<i>with a tilt of 23 degrees.</i>

232
00:31:40,960 --> 00:31:43,760
<i>So, as it moves around in its orbit,</i>

233
00:31:45,600 --> 00:31:47,040
<i>first one hemisphere</i>

234
00:31:47,720 --> 00:31:51,640
<i>then the other is angled toward the Sun…</i>

235
00:31:55,000 --> 00:31:57,880
<i>giving Earth its seasons.</i>

236
00:32:19,600 --> 00:32:21,920
<i>As summer draws to a close,</i>

237
00:32:22,680 --> 00:32:25,200
<i>the longer nights are a sign</i>

238
00:32:25,280 --> 00:32:28,280
<i>that the harsh Alaskan winter</i>
<i>is fast approaching.</i>

239
00:32:32,560 --> 00:32:35,200
<i>The cubs are now seven months old.</i>

240
00:32:41,120 --> 00:32:45,640
<i>And Luna knows that if they are to survive</i>
<i>their long winter sleep,</i>

241
00:32:46,360 --> 00:32:49,400
<i>the family must build up</i>
<i>their fat reserves.</i>

242
00:33:06,000 --> 00:33:08,240
<i>But the Moon is a constant reminder…</i>

243
00:33:12,920 --> 00:33:14,400
…<i>help is on the way.</i>

244
00:33:19,800 --> 00:33:22,960
<i>A thousand kilometers</i>
<i>off the coast of Alaska…</i>

245
00:33:24,960 --> 00:33:28,480
<i>another creature is tuned in</i>
<i>to Earth's seasonal rhythm.</i>

246
00:33:32,200 --> 00:33:34,200
<i>Sockeye salmon.</i>

247
00:33:36,760 --> 00:33:39,080
<i>After two years roaming the Pacific Ocean…</i>

248
00:33:42,760 --> 00:33:44,120
<i>…they've reached maturity.</i>

249
00:33:46,080 --> 00:33:48,400
<i>And now, the changing day length…</i>

250
00:33:49,600 --> 00:33:52,680
<i>…triggers hormones</i>
<i>to be released into their blood.</i>

251
00:33:55,720 --> 00:33:59,080
<i>Chemical signals</i>
<i>that alter their behavior.</i>

252
00:34:08,080 --> 00:34:09,440
<i>Calling them home</i>

253
00:34:10,920 --> 00:34:13,800
<i>to breed in the rivers</i>
<i>where they were born.</i>

254
00:34:34,280 --> 00:34:36,080
<i>Luna's exhausted and hungry,</i>

255
00:34:37,120 --> 00:34:41,600
<i>but still she leads her cubs</i>
<i>to the river's edge.</i>

256
00:34:54,080 --> 00:34:59,000
<i>Because she senses something magical</i>
<i>is about to happen.</i>

257
00:35:04,080 --> 00:35:08,960
<i>Today, the unique clockwork of the seasons</i>

258
00:35:09,040 --> 00:35:12,400
<i>will deliver a vital lifeline</i>
<i>to the bears.</i>

259
00:35:33,520 --> 00:35:37,680
<i>The Earth has reached a pivotal position</i>
<i>in its journey around the Sun.</i>

260
00:35:41,720 --> 00:35:44,240
<i>And now the Moon raises the tide.</i>

261
00:35:50,000 --> 00:35:55,280
<i>Providing the final push</i>
<i>that drives the salmon into the rivers.</i>

262
00:36:40,480 --> 00:36:45,680
<i>At long last,</i>
<i>the cubs get their first taste of salmon.</i>

263
00:36:51,160 --> 00:36:54,960
<i>And although a single fish</i>
<i>will not see the bears through winter,</i>

264
00:36:55,920 --> 00:37:01,400
<i>it's the cubs' first real meal</i>
<i>in nearly eight months of life.</i>

265
00:37:18,040 --> 00:37:21,880
<i>The arrival of the first salmon</i>
<i>is a relief to Luna.</i>

266
00:37:24,720 --> 00:37:26,600
<i>Because experience has told her</i>

267
00:37:27,720 --> 00:37:31,200
<i>there will soon be</i>
<i>much richer pickings upstream.</i>

268
00:37:50,720 --> 00:37:52,720
<i>As the days grow ever shorter,</i>

269
00:37:54,400 --> 00:37:58,280
<i>the very same hormones</i>
<i>that set the salmon off on their journey</i>

270
00:37:59,200 --> 00:38:01,400
<i>now dramatically transform them.</i>

271
00:38:08,960 --> 00:38:10,560
<i>Their heads change shape.</i>

272
00:38:13,000 --> 00:38:15,680
<i>And their bodies blush bright red.</i>

273
00:38:19,040 --> 00:38:20,960
<i>As in their millions,</i>

274
00:38:21,480 --> 00:38:25,920
<i>they surge upriver</i>
<i>into their spawning grounds.</i>

275
00:38:36,120 --> 00:38:40,400
<i>And the final piece</i>
<i>of the bears' story falls into place.</i>

276
00:38:49,120 --> 00:38:52,520
<i>A story as old as the planet itself.</i>

277
00:39:02,680 --> 00:39:04,280
<i>The formation of the Earth…</i>

278
00:39:09,760 --> 00:39:12,040
<i>the collision that created the Moon…</i>

279
00:39:15,000 --> 00:39:18,840
<i>and our planet's unique relationship</i>
<i>with its moon and star…</i>

280
00:39:25,400 --> 00:39:31,520
<i>have combined to create a world</i>
<i>like nowhere else in the universe.</i>

281
00:39:33,920 --> 00:39:35,600
<i>A Goldilocks planet.</i>

282
00:39:38,600 --> 00:39:42,680
<i>The only place we know</i>
<i>that's just right for life.</i>

283
00:40:04,320 --> 00:40:05,360
<i>And for Luna,</i>

284
00:40:06,000 --> 00:40:09,000
<i>four and a half billion years</i>
<i>of cosmic history</i>

285
00:40:10,920 --> 00:40:14,000
<i>is now distilled into this moment.</i>

286
00:40:21,760 --> 00:40:27,200
<i>The annual convergence of salmon and bear.</i>

287
00:40:38,160 --> 00:40:40,400
<i>And the precious opportunity</i>

288
00:40:42,160 --> 00:40:43,440
<i>to feed her family.</i>

289
00:40:51,120 --> 00:40:55,080
<i>Luna and her cubs now have what they need</i>
<i>to make it through winter.</i>

290
00:40:57,400 --> 00:41:01,960
<i>And while ultimately, their future</i>
<i>on our changing planet is uncertain,</i>

291
00:41:03,320 --> 00:41:06,480
<i>for this year,</i>
<i>the salmon will sustain them…</i>

292
00:41:10,400 --> 00:41:13,120
<i>as our planet continues</i>
<i>on this relentless voyage…</i>

293
00:41:15,680 --> 00:41:17,000
<i>…around the Sun.</i>

294
00:41:26,640 --> 00:41:29,720
<i>Next in the story of our universe,</i>

295
00:41:31,160 --> 00:41:34,720
<i>the ocean wanderer</i>
<i>whose life cycle reveals</i>

296
00:41:35,400 --> 00:41:39,320
<i>how everything in the universe was made.</i>

297
00:41:41,120 --> 00:41:43,400
<i>Because in every turtle's egg</i>

298
00:41:44,280 --> 00:41:46,680
<i>are atoms from The Big Bang…</i>

299
00:41:49,000 --> 00:41:52,560
<i>…forged as stars die.</i>

300
00:41:56,160 --> 00:41:59,000
<i>But how are stars and planets created?</i>

301
00:42:00,840 --> 00:42:07,080
<i>And how do the same ingredients</i>
<i>transform into living things?</i>