1
00:00:06,621 --> 00:00:08,621
[thunder crashing]

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00:00:11,741 --> 00:00:12,981
[rainfall]

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[dog barking]

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[birds calling]

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00:00:16,981 --> 00:00:18,981
[varied bird calls]

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[wings fluttering]

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[narrator] The Earth,
home to millions of species.

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00:00:30,101 --> 00:00:31,301
[man talking on radio]

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00:00:31,381 --> 00:00:33,661
[woman singing]

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00:00:34,661 --> 00:00:37,901
But what might live... beyond?

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00:00:45,181 --> 00:00:48,501
There are countless planets 
throughout the universe.

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00:00:53,941 --> 00:00:57,381
If life exists on only a fraction of them,

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00:00:58,541 --> 00:01:03,221
then the universe must be... alive.

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[cawing]

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[chattering]

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All living things have the same needs.

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00:01:19,461 --> 00:01:20,661
To feed...

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00:01:27,341 --> 00:01:28,621
reproduce...

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and evolve.

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By applying the laws of life on Earth

21
00:01:41,341 --> 00:01:43,101
to the rest of the universe...

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00:01:45,141 --> 00:01:46,941
it's possible to imagine

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what could live...

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on alien worlds.

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00:02:15,741 --> 00:02:19,061
All life forms need a planet to live on.

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00:02:20,661 --> 00:02:23,781
But how many planets 
are there in the universe?

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00:02:28,941 --> 00:02:30,501
[man] Think about our star,

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the Sun,

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with Earth, Mars, Jupiter orbiting it.

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For centuries,

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people have asked themselves,
"What about the other stars?

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Uh, do they have planets as well?"

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00:02:52,141 --> 00:02:53,781
And 24 years ago,

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I found one!

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00:03:02,901 --> 00:03:06,461
Didier Queloz
is a superstar astrophysicist.

36
00:03:09,141 --> 00:03:12,861
He has won the Nobel Prize 
for discovering the first planet

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00:03:12,941 --> 00:03:14,901
beyond our solar system.

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[Didier] I was 28 years old
when I found the planet.

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00:03:22,261 --> 00:03:24,581
I was about to finish my PhD,

40
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and my PhD adviser
gave me the key of the equipment.

41
00:03:28,701 --> 00:03:32,421
And after observing a couple of times,
the star 51 Peg,

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I realized that something was going on
on that star. 

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And frankly, I just panicked at that time.

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I thought something was really wrong
with my equipment.

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And the more I wanted to understand this,
the less it made sense.

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Until the point I got convinced
it must be a planet.

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That's likely to be a planet over there.

48
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Could be Jupiter over there.

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It's pretty cool.

50
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Distant planets are invisible 
to telescopes

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because they don't emit any light.

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But if a planet passes in front of a star,

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it casts a tiny shadow,

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00:04:27,541 --> 00:04:30,701
and there's a minuscule dimming 
of the star's brightness.

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When astronomers detect
this dip in light level,

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they have found a new planet.

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Hello, guys.

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Uh... Oh, hey.
Here is what the telescope is looking at.

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This is a picture 
of the telescope right now.

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00:04:49,261 --> 00:04:52,661
Uh, in the middle, you have the...
the target we're observing.

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So, you analyze this whole field,
you process the data,

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and, um, if you're lucky enough,
you detect this.

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There's a little bit of a decrease 
of the flux,

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and this tells me 
that there is a planet orbiting that star.

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[Didier] We know there are a huge number 
of planets in the universe.

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There must be a zillion kinds
of different life.

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Let's imagine 
that this is the Earth, here...

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Right?

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So, imagine that one meter 
is 20 light-years.

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So, I've made two meters
as 40 light-years.

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00:05:37,141 --> 00:05:42,221
This is where you have 51 Peg,
where the first planet was detected.

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Each of these tiny lights 
represents a star

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where a planet has been found.

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Over the next few years,

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planets were turning up everywhere.

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♪ Planets, planets everywhere ♪

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It looks pretty cool right now. [laughs]

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A horizon of stars and planets...

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all around. [laughs]

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Planets beyond our solar system
are called exoplanets.

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Astronomers have found 
over 4,000 of them.

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And they keep finding more.

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They now believe there's at least 
one planet for every star in the universe.

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That means over 
a million, billion, trillion exoplanets.

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More than all 
the grains of sand on Earth.

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A vast canvas for the evolution of life.

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The distances are mind-boggling.

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The nearest exoplanets 
are trillions of miles from us.

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But they're all subject to the same force
that holds the Earth in place.

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Gravity.

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Imagine a world double the size of Earth,

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with twice as much gravity.

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This is Atlas.

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How would life adapt on such a world?

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[alien bird trilling]

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Gravity pulls vegetation 
to the planet's surface.

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And yet, seeds can float in the sky.

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00:08:29,541 --> 00:08:32,621
That's because gravity here is so strong.

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Air molecules are
densely packed together...

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creating a thick, buoyant atmosphere 
for seeds to drift through.

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00:08:53,541 --> 00:08:55,101
And where there are seeds...

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there are sky grazers.

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[screeches]

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Giant herbivores with six wings

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to ride on the dense pillow of air.

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[creatures calling]

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Because of the extra gravity,

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they weigh twice as much 
as they would on Earth.

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00:09:29,541 --> 00:09:31,661
But they don't fall from the sky.

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The atmosphere is thick enough
to keep them airborne.

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Whether on Atlas or on Earth,

112
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flying is always a battle 
to overcome gravity.

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[birds calling]

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[man] You might say I have a pretty
complicated relationship with gravity.

115
00:10:04,661 --> 00:10:07,301
And you can really feel that gravity 
is a force pulling you down

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00:10:07,381 --> 00:10:08,821
as you struggle your way up.

117
00:10:11,941 --> 00:10:15,301
But ultimately, my dream 
has always been to be able to fly.

118
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Whoo-hoo-hoo! [laughs]

119
00:10:23,501 --> 00:10:27,981
The thing I love most about paragliding 
is that it's so simple and intuitive.

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It's just you and the air.

121
00:10:32,061 --> 00:10:34,661
Like the sky grazers on Atlas,

122
00:10:35,141 --> 00:10:38,421
paragliders use their wings 
to generate lift.

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00:10:42,141 --> 00:10:44,701
But the atmosphere 
is less dense on Earth...

124
00:10:46,661 --> 00:10:49,701
so it takes more effort 
to stay airborne.

125
00:10:54,141 --> 00:10:56,501
[Fiorenzo] Most people
don't see air as a substance.

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00:10:58,541 --> 00:11:00,141
But for me, when I'm flying,

127
00:11:00,221 --> 00:11:04,181
I really see it as a fluid 
that's moving up and down the valleys

128
00:11:04,261 --> 00:11:05,621
and along the ridges.

129
00:11:08,741 --> 00:11:12,061
It would be really weird 
to fly in a very dense atmosphere.

130
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You could just be gliding around 
the whole time, effortlessly.

131
00:11:20,141 --> 00:11:24,181
The best way to gain altitude 
is to find an updraft,

132
00:11:25,141 --> 00:11:26,901
known as a "thermal."

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00:11:29,141 --> 00:11:31,181
[Fiorenzo] When you hit the thermal,
it's very similar

134
00:11:31,261 --> 00:11:33,461
to when you're in an elevator
and it starts.

135
00:11:36,541 --> 00:11:38,101
You feel a push upwards.

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Yeah, there we go!

137
00:11:43,741 --> 00:11:45,901
Just the power of nature
to pull me up.

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00:11:50,061 --> 00:11:52,861
When I'm flying 
and I see a bird circling up,

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00:11:52,941 --> 00:11:54,901
it means there must be a thermal there.

140
00:11:55,701 --> 00:11:57,861
So we're always
constantly looking at them.

141
00:12:02,421 --> 00:12:06,021
You can really feel the balance
between the gravity pulling you down

142
00:12:06,101 --> 00:12:07,661
and the air lifting you up.

143
00:12:08,341 --> 00:12:11,781
You can then use your bodyweight
to gain speed,

144
00:12:11,861 --> 00:12:13,861
and use that speed 
to generate more energy

145
00:12:14,461 --> 00:12:16,261
and feel that you're moving 
through the air.

146
00:12:34,701 --> 00:12:38,341
Gravity may be weaker
on Earth than on Atlas...

147
00:12:39,141 --> 00:12:42,701
but the thinner atmosphere
means there's less buoyancy.

148
00:12:45,261 --> 00:12:48,421
So, eventually, everything falls.

149
00:13:10,741 --> 00:13:14,541
On Atlas, the sky grazers
never need to land.

150
00:13:15,101 --> 00:13:16,821
[screeching]

151
00:13:18,741 --> 00:13:22,301
Their front and back wings 
are for direction and thrust.

152
00:13:25,541 --> 00:13:28,301
Their long middle wings
are for catching thermals.

153
00:13:32,101 --> 00:13:33,741
Despite their weight,

154
00:13:34,381 --> 00:13:38,341
the air is thick enough
for them to live a life

155
00:13:38,821 --> 00:13:40,101
in the sky.

156
00:13:45,141 --> 00:13:48,101
But it's not always a peaceful life.

157
00:13:48,181 --> 00:13:49,621
[creatures chattering]

158
00:13:50,661 --> 00:13:54,781
As on Earth, grazers attract predators.

159
00:13:57,421 --> 00:14:02,021
Using hydrogen-producing bacteria
to inflate their air sacs,

160
00:14:02,461 --> 00:14:04,581
they take to the skies.

161
00:14:05,421 --> 00:14:07,421
[calling loudly]

162
00:14:15,101 --> 00:14:17,861
Alone, they're no match for their prey...

163
00:14:20,461 --> 00:14:22,341
so they hunt in a pack...

164
00:14:24,421 --> 00:14:27,821
waiting for a sky grazer 
to stray from the group.

165
00:14:38,501 --> 00:14:41,941
Target sighted, they expel their gas...

166
00:14:44,461 --> 00:14:46,261
and attack from above.

167
00:14:56,861 --> 00:14:59,101
The fastest predator on Earth

168
00:14:59,181 --> 00:15:01,341
uses the same tactic.

169
00:15:04,661 --> 00:15:06,621
[man] My interest in flying falcons is...

170
00:15:07,181 --> 00:15:11,261
their predatory instinct
coupled with the speed factor...

171
00:15:16,341 --> 00:15:18,381
and how they use that speed 
to their advantage.

172
00:15:24,061 --> 00:15:27,261
But just watching 
a top predator do its thing...

173
00:15:31,541 --> 00:15:33,301
is perfection.

174
00:15:43,741 --> 00:15:46,621
I probably have 30-some birds 
at this moment.

175
00:15:47,461 --> 00:15:49,341
Each bird is a different personality.

176
00:15:50,741 --> 00:15:52,261
What I love about falcons

177
00:15:52,341 --> 00:15:55,461
is how evolution has made
the most perfect specimen.

178
00:15:58,101 --> 00:16:00,101
[imitating bird calls]

179
00:16:00,501 --> 00:16:02,501
-[falcon squawking]
-[Vahe chirping]

180
00:16:03,221 --> 00:16:04,301
[laughs]

181
00:16:05,461 --> 00:16:07,741
I do have a relationship with these guys.

182
00:16:07,821 --> 00:16:09,861
Certainly from my end, I do. [laughs]

183
00:16:09,941 --> 00:16:11,901
I don't think the falcons 
see it that way,

184
00:16:11,981 --> 00:16:14,181
but they certainly see me 
as part of the team.

185
00:16:16,581 --> 00:16:21,981
Vahe Alaverdian trains 
captive-bred falcons how to hunt.

186
00:16:27,261 --> 00:16:29,261
[Vahe] These birds are 
genetically programmed

187
00:16:29,341 --> 00:16:31,621
to be the top-notch 
avian predators that they are.

188
00:16:34,461 --> 00:16:35,861
What we do as falconers

189
00:16:35,941 --> 00:16:38,621
is try to awaken
that predatorial nature in the bird.

190
00:16:47,261 --> 00:16:49,261
Lure training is the very first step.

191
00:16:49,341 --> 00:16:51,381
Come on, buddy! Hup, hup, hup, hup, hup!

192
00:16:54,661 --> 00:16:57,021
I want to put that lure 
in front of the bird,

193
00:16:57,581 --> 00:16:59,941
and get the falcon 
to coordinate eye to foot...

194
00:17:00,021 --> 00:17:00,861
Hup, hup!

195
00:17:00,941 --> 00:17:03,061
...and throw its feet out
as if it's gonna grab it.

196
00:17:03,941 --> 00:17:06,941
As that happens,
I try to pull that away from the falcon

197
00:17:07,421 --> 00:17:10,381
to get it to shoot up in the air 
and repeat this process again.

198
00:17:11,341 --> 00:17:14,821
I wanna see that bird drop down 
as vertical as it can.

199
00:17:18,541 --> 00:17:22,141
That's something that they later on
will apply to hunting game.

200
00:17:30,461 --> 00:17:35,021
When the falcons are ready,
Vahe introduces a prey target...

201
00:17:36,621 --> 00:17:37,861
a racing pigeon.

202
00:17:41,261 --> 00:17:44,221
The falcon can't keep up with the pigeon
in a chase,

203
00:17:45,461 --> 00:17:47,581
so its best bet is to drop on it...

204
00:17:48,501 --> 00:17:49,621
using gravity.

205
00:17:55,861 --> 00:17:58,741
[Vahe] When the bird thinks
that he's got the advantage,

206
00:17:59,581 --> 00:18:01,701
that's when the wings will get tucked in.

207
00:18:04,661 --> 00:18:07,421
They stoop into a little teardrop shape...

208
00:18:09,061 --> 00:18:10,381
coming down from the heavens.

209
00:18:12,461 --> 00:18:14,901
The kinetic energy
of a falcon hitting a pigeon

210
00:18:16,141 --> 00:18:19,581
would be as if you were hit 
by a cannonball.

211
00:18:27,461 --> 00:18:30,501
In training,
the pigeon invariably gets away,

212
00:18:31,581 --> 00:18:35,141
because the falcon is made to stoop 
from less than a thousand feet.

213
00:18:38,461 --> 00:18:39,901
When hunting for real,

214
00:18:40,541 --> 00:18:42,541
it'll drop from a greater height...

215
00:18:44,301 --> 00:18:45,621
to lethal effect.

216
00:18:55,981 --> 00:18:57,781
[creatures calling]

217
00:19:00,861 --> 00:19:02,141
[screeching]

218
00:19:06,461 --> 00:19:08,701
The predators make their move.

219
00:19:19,421 --> 00:19:20,941
[wailing]

220
00:19:23,861 --> 00:19:25,621
They deploy their wings

221
00:19:25,701 --> 00:19:27,061
to create drag...

222
00:19:28,981 --> 00:19:31,221
destabilizing the sky grazer

223
00:19:31,301 --> 00:19:33,701
to devour it on the ground.

224
00:19:39,661 --> 00:19:41,221
[moans]

225
00:19:42,741 --> 00:19:46,621
But this pack is too small to take down
such a large beast.

226
00:19:53,661 --> 00:19:55,501
Today, they'll go hungry.

227
00:19:56,261 --> 00:19:57,101
[calls]

228
00:19:57,781 --> 00:19:59,781
[creatures barking and chattering]

229
00:20:01,421 --> 00:20:03,421
[creatures howling]

230
00:20:07,941 --> 00:20:10,901
The sky grazer climbs to a safe height...

231
00:20:12,541 --> 00:20:13,701
to recuperate.

232
00:20:13,781 --> 00:20:15,341
[howling]

233
00:20:19,461 --> 00:20:21,221
But as a fertile female,

234
00:20:21,941 --> 00:20:23,261
she has company.

235
00:20:25,701 --> 00:20:29,381
Male grazers,
competing to be chosen as a mate.

236
00:20:30,261 --> 00:20:32,261
[all calling]

237
00:20:36,661 --> 00:20:39,701
Their oversized tails are a handicap,

238
00:20:40,741 --> 00:20:42,221
making it harder to fly.

239
00:20:43,661 --> 00:20:47,461
But to the female,
they're a sign of vitality.

240
00:20:48,941 --> 00:20:50,741
[howling]

241
00:20:51,621 --> 00:20:53,901
The first to reach her gets to mate

242
00:20:54,741 --> 00:20:57,021
and pass on his genes.

243
00:20:58,781 --> 00:21:00,781
[birdsong]

244
00:21:04,741 --> 00:21:07,581
The same principle applies on Earth,

245
00:21:08,781 --> 00:21:10,581
whether up in the sky

246
00:21:11,301 --> 00:21:12,821
or down in the dirt.

247
00:21:15,941 --> 00:21:18,621
Males compete for the right to mate.

248
00:21:20,621 --> 00:21:22,781
[man 1] And running, set...

249
00:21:24,181 --> 00:21:27,621
[man 2] I think when people sit at home 
watching insects on television,

250
00:21:27,701 --> 00:21:30,221
they imagine the cameraman
sitting in the jungle,

251
00:21:30,781 --> 00:21:32,501
in a river or in a hedge,

252
00:21:33,141 --> 00:21:35,901
waiting for this beetle to come across

253
00:21:35,981 --> 00:21:39,461
and reproduce or have a fight 
in front of the camera.

254
00:21:42,141 --> 00:21:43,461
It doesn't work that way.

255
00:21:48,901 --> 00:21:53,221
This is a ramshackle old shed 
which is attached to my parents' place,

256
00:21:53,341 --> 00:21:54,541
which is just there.

257
00:21:55,661 --> 00:21:58,701
Huge advantages to having a place
attached to your mum and dad's.

258
00:21:58,781 --> 00:22:02,901
You get good dinners in the evening
and, uh, teas arriving during the day.

259
00:22:03,941 --> 00:22:05,741
-Have a look and see what we're doing.
-Oh!

260
00:22:06,381 --> 00:22:07,621
Oh, gosh.

261
00:22:08,581 --> 00:22:10,261
Oh! What on Earth are they?

262
00:22:10,341 --> 00:22:12,421
[Robert] They are rhinoceros beetles.

263
00:22:13,741 --> 00:22:15,301
The male's got these big horns.

264
00:22:15,381 --> 00:22:18,621
The female doesn't. 
It's a form of sexual selection,

265
00:22:18,701 --> 00:22:22,741
because the females like males
with big horns.

266
00:22:24,341 --> 00:22:25,621
So every time they mate,

267
00:22:25,701 --> 00:22:28,981
they'll mate with a beetle 
that has a slightly bigger horn

268
00:22:29,061 --> 00:22:30,781
-than the one they've last seen before.
-Oh!

269
00:22:30,861 --> 00:22:33,621
And, therefore,
that male passes its genes on.

270
00:22:34,341 --> 00:22:37,421
So, over generations,
the horns will get bigger.

271
00:22:39,301 --> 00:22:41,501
-[man 1] Anywhere particular?
-[Robert] Um, just on the...

272
00:22:41,581 --> 00:22:43,541
on the log facing the other male.

273
00:22:44,421 --> 00:22:46,341
[man 1] Here they go.
They're going straight away.

274
00:22:49,941 --> 00:22:52,181
The horns of a male rhinoceros beetle

275
00:22:52,261 --> 00:22:54,821
are like the tail of a male sky grazer.

276
00:22:57,861 --> 00:23:00,301
They've evolved for sexual competition.

277
00:23:20,661 --> 00:23:22,861
-Ha-ha!
-That dominant one's done it again.

278
00:23:28,381 --> 00:23:30,221
[Robert] That's a good shot.
The shot we wanted.

279
00:23:30,301 --> 00:23:32,061
-[man 1] Yeah.
-[Robert] Going into her, yeah.

280
00:23:35,661 --> 00:23:36,781
One, two, three.

281
00:23:37,981 --> 00:23:39,141
-That right?
-[Robert] Yeah.

282
00:23:39,781 --> 00:23:41,141
-[man 1] Yep.
-[man 3] That's it.

283
00:23:41,221 --> 00:23:42,701
-Can I... Yes.
-You putting that in?

284
00:23:48,021 --> 00:23:51,781
Male insects don't always fight 
to snare a mate.

285
00:23:53,261 --> 00:23:57,341
Sometimes it's enough just to show off
their physical prowess.

286
00:24:00,181 --> 00:24:02,541
[man 1] Right, I'm gonna bring the male
in front of you.

287
00:24:02,621 --> 00:24:03,821
He's coming in from your right.

288
00:24:06,501 --> 00:24:08,101
Now, uh-- He's flown off.

289
00:24:09,221 --> 00:24:11,581
These are stalk-eyed flies.

290
00:24:14,781 --> 00:24:17,461
[Robert] Stalk-eyed fly
is an amazing little thing.

291
00:24:17,541 --> 00:24:21,301
It looks a little bit like an ant 
with massive eyes on the ends of stalks.

292
00:24:22,701 --> 00:24:26,621
Both the male and the female
have eyes on the end of stalks,

293
00:24:26,701 --> 00:24:29,381
but the male has much longer eye stalks
than the female.

294
00:24:32,061 --> 00:24:36,221
The males with the long stalks
will come up to one another,

295
00:24:36,301 --> 00:24:38,501
and they will, kind of, 
have a little dance.

296
00:24:44,661 --> 00:24:46,021
And they will try and judge

297
00:24:46,101 --> 00:24:48,941
which of the two of them 
has the bigger stalks.

298
00:24:51,101 --> 00:24:53,021
There they are. That's the standoff!

299
00:24:57,581 --> 00:25:01,301
The winner of that will remain where they
are and the loser will then toddle off.

300
00:25:03,301 --> 00:25:05,981
That winner then will gain access
to the female,

301
00:25:06,061 --> 00:25:08,221
and be able to reproduce with her,

302
00:25:08,301 --> 00:25:11,021
and that way can pass on 
the genetics that he has,

303
00:25:11,101 --> 00:25:14,101
which will include 
that of a longer eye stalk.

304
00:25:15,621 --> 00:25:17,621
-[Robert] Yes! Got it.
-[man 1] Are-- are you on it?

305
00:25:18,221 --> 00:25:19,421
Oh, It's fantastic.

306
00:25:25,181 --> 00:25:28,301
Normally, it's a second and they're gone.
This is fantastic.

307
00:25:34,941 --> 00:25:36,981
Why would the male stalk-eyed fly 
go to the effort

308
00:25:37,061 --> 00:25:38,901
of having these enormous eye stalks?

309
00:25:39,461 --> 00:25:43,021
Well, the idea is that you are 
conspicuously signaling to the female

310
00:25:43,101 --> 00:25:48,021
that you can have this incredible 
investment of energy into this resource

311
00:25:48,101 --> 00:25:49,541
that is completely needless.

312
00:25:51,741 --> 00:25:53,461
And if you can still survive,

313
00:25:53,541 --> 00:25:57,101
if you can carry on flying and living 
and not getting predated upon,

314
00:25:57,181 --> 00:26:01,861
and still have this... wasteful
extravagance coming out of your head,

315
00:26:01,941 --> 00:26:04,901
then you're gonna be a pretty good bet
to reproduce with.

316
00:26:09,661 --> 00:26:11,661
[creatures howling and barking]

317
00:26:19,061 --> 00:26:20,301
On Atlas,

318
00:26:20,381 --> 00:26:26,101
the long tail of the male sky grazer
shows he's an ideal choice...

319
00:26:28,221 --> 00:26:30,901
to father the next generation.

320
00:26:32,741 --> 00:26:35,101
[howling]

321
00:26:37,741 --> 00:26:41,061
But the mother can't lay her eggs 
in the sky.

322
00:26:45,101 --> 00:26:46,461
[roars]

323
00:26:46,981 --> 00:26:48,821
So she's come down to land.

324
00:26:53,141 --> 00:26:58,301
Because of the gravity, she's too heavy 
to launch herself back into the sky.

325
00:26:58,381 --> 00:26:59,861
[roars]

326
00:27:02,101 --> 00:27:03,261
[moans]

327
00:27:04,221 --> 00:27:08,101
To create new life,
she must surrender her own.

328
00:27:22,141 --> 00:27:25,781
The babies grow up close 
to where their mothers die.

329
00:27:29,341 --> 00:27:33,101
Now they need to get off the ground 
and into the air.

330
00:27:33,181 --> 00:27:34,741
[all calling]

331
00:27:40,341 --> 00:27:41,501
[crunching]

332
00:27:41,581 --> 00:27:44,181
But scavengers lie in wait.

333
00:27:45,781 --> 00:27:47,381
Boneless creatures

334
00:27:47,501 --> 00:27:50,381
with no skeleton to give them form.

335
00:27:53,741 --> 00:27:55,861
[calling]

336
00:27:55,941 --> 00:28:00,221
They kill by enveloping
and dissolving their prey.

337
00:28:10,941 --> 00:28:17,261
The sky grazers have only just hatched, 
but already they're in grave danger.

338
00:28:20,861 --> 00:28:24,021
And now, there's no going back.

339
00:28:24,101 --> 00:28:25,781
[calling and squeaking]

340
00:28:35,261 --> 00:28:36,501
[insects chirping]

341
00:28:36,581 --> 00:28:38,861
[animal howling]

342
00:28:46,061 --> 00:28:48,061
[meerkat grunting]

343
00:28:48,221 --> 00:28:49,661
Every day on Earth,

344
00:28:49,741 --> 00:28:53,021
young animals have to overcome 
terrible odds,

345
00:28:53,581 --> 00:28:55,021
if they're to survive.

346
00:28:59,221 --> 00:29:03,781
Sixty percent of meerkats don't make it 
to their first birthday.

347
00:29:06,341 --> 00:29:08,941
[woman] For a young meerkat,
in their early life,

348
00:29:09,421 --> 00:29:11,861
there's a lot of danger here.

349
00:29:12,701 --> 00:29:16,701
They're vulnerable for many months 
after they're born...

350
00:29:19,861 --> 00:29:23,661
but particularly in the first month or two
after they emerge from the burrow.

351
00:29:25,941 --> 00:29:29,541
Predators are everywhere,
and a constant danger.

352
00:29:34,941 --> 00:29:36,381
There are snakes in this area

353
00:29:37,741 --> 00:29:40,021
that will eat a young meerkat.

354
00:29:51,461 --> 00:29:52,901
-[snake hisses]
-[meerkat chatters]

355
00:29:58,381 --> 00:30:00,381
[barking and chattering]

356
00:30:03,421 --> 00:30:06,301
A young meerkat is safe within a group,

357
00:30:07,261 --> 00:30:10,421
but if it lags behind, it's vulnerable.

358
00:30:15,861 --> 00:30:18,741
Scorpions are a constant threat.

359
00:30:22,141 --> 00:30:23,621
[squeaking]

360
00:30:24,581 --> 00:30:27,421
[Kirsty] The young are really
completely incompetent,

361
00:30:27,901 --> 00:30:31,141
and totally ignorant when it comes 
to dealing with scorpions, initially.

362
00:30:34,261 --> 00:30:36,741
But they can't avoid 
this danger forever.

363
00:30:38,661 --> 00:30:42,061
They're going to eventually have to learn
how to neutralize the threat.

364
00:30:48,381 --> 00:30:49,461
[whimpers]

365
00:30:49,541 --> 00:30:52,981
The first time that a young meerkat
faces a scorpion

366
00:30:53,061 --> 00:30:54,941
and it has to deal with it itself

367
00:30:56,661 --> 00:30:59,021
is probably a terrifying encounter.

368
00:31:00,741 --> 00:31:03,461
This is a real moment of truth.

369
00:31:12,381 --> 00:31:14,381
[yelping]

370
00:31:28,141 --> 00:31:32,301
It's a real rite of passage, because once
they've managed to do that themselves,

371
00:31:33,301 --> 00:31:36,341
then they really are at a stage where
they can start to forage by themselves

372
00:31:36,421 --> 00:31:39,301
and become independent 
and be a useful group member.

373
00:31:41,061 --> 00:31:44,861
So, they've really managed to escape
the vulnerability of being a pup

374
00:31:44,941 --> 00:31:48,421
and made that transition 
into being an adult.

375
00:31:57,621 --> 00:32:00,981
It's one step on the road to adulthood,

376
00:32:01,061 --> 00:32:03,741
but it's by no means plain sailing 
after that.

377
00:32:05,181 --> 00:32:07,701
There are a lot of threats out there,

378
00:32:07,781 --> 00:32:11,101
and it will have to continue to learn 
in order to reach adulthood.

379
00:32:18,261 --> 00:32:20,261
[creatures roaring]

380
00:32:23,261 --> 00:32:25,901
If the young sky grazers are to grow up,

381
00:32:27,341 --> 00:32:28,941
they have no choice.

382
00:32:31,341 --> 00:32:33,061
It's time to fly.

383
00:32:33,141 --> 00:32:34,661
[screeching]

384
00:32:46,821 --> 00:32:48,821
[predators chattering]

385
00:33:03,461 --> 00:33:06,021
Even in the air, they're still not safe.

386
00:33:14,181 --> 00:33:18,421
On Atlas, survival is a game of chance.

387
00:33:27,061 --> 00:33:31,101
Life goes on
from one generation to the next.

388
00:33:34,661 --> 00:33:36,421
At least for now.

389
00:33:41,661 --> 00:33:46,741
The strong gravity of Atlas 
pulls asteroids onto a collision course.

390
00:33:55,141 --> 00:33:57,461
Most burn up in the atmosphere.

391
00:33:59,341 --> 00:34:02,861
But there's a constant threat 
something big will get through...

392
00:34:05,181 --> 00:34:08,341
and reset the course of life 
on the planet.

393
00:34:18,541 --> 00:34:21,781
Because gravity is weaker 
on Earth than Atlas,

394
00:34:21,861 --> 00:34:24,341
asteroid strikes are less frequent.

395
00:34:27,341 --> 00:34:31,261
But when they do occur,
they can be catastrophic.

396
00:34:32,901 --> 00:34:34,901
[birds calling]

397
00:34:36,461 --> 00:34:38,661
[man] This is the Yucatán Peninsula.

398
00:34:42,501 --> 00:34:46,221
27,000 square miles of tropical jungle.

399
00:34:49,141 --> 00:34:54,621
But hidden within the jungle 
are numerous sinkholes called cenotes.

400
00:35:08,061 --> 00:35:12,301
These are entrances
to vast underground cave systems.

401
00:35:15,061 --> 00:35:18,381
There's no surface rivers or streams
in the peninsula,

402
00:35:19,341 --> 00:35:23,061
so the only source of water
is underground in caves.

403
00:35:30,101 --> 00:35:34,021
But the really interesting thing 
is the location of these cenotes.

404
00:35:34,421 --> 00:35:39,461
Although there's probably 10,000 
or more cenotes across the peninsula,

405
00:35:39,901 --> 00:35:42,021
in the northwest corner...

406
00:35:45,381 --> 00:35:50,101
they occur in a very well-defined 
semicircle.

407
00:35:50,181 --> 00:35:54,461
If we follow that semicircle 
out into the Gulf of Mexico...

408
00:35:57,901 --> 00:36:02,821
we now have a complete circle 
that marks what one would expect

409
00:36:02,901 --> 00:36:06,021
from the edge 
of an asteroid impact crater.

410
00:36:07,821 --> 00:36:10,021
[Thomas] 65 million years ago,

411
00:36:10,101 --> 00:36:13,781
gravity pulled an asteroid 
into our solar system.

412
00:36:16,581 --> 00:36:18,541
It smashed into our planet,

413
00:36:18,861 --> 00:36:22,741
causing the extinction 
of 75 percent of life on Earth.

414
00:36:33,941 --> 00:36:37,341
The asteroid strike generated 
enough debris

415
00:36:38,221 --> 00:36:41,101
to block out sunlight for two years.

416
00:36:44,541 --> 00:36:47,501
A world plunged into darkness.

417
00:36:48,701 --> 00:36:50,021
Nothing could grow.

418
00:36:54,341 --> 00:36:56,021
This would happen on Atlas

419
00:36:56,701 --> 00:36:59,301
if a big enough asteroid 
hit the planet.

420
00:37:01,181 --> 00:37:04,501
[Thomas] Cenotes
are difficult places to survive...

421
00:37:06,341 --> 00:37:10,021
just like the Earth was
65 million years ago.

422
00:37:12,261 --> 00:37:17,021
What are the characteristics that 
a species needs to survive an extinction?

423
00:37:27,741 --> 00:37:29,101
Somebody's in here.

424
00:37:39,661 --> 00:37:42,421
So, crocodiles are very resilient animals.

425
00:37:44,741 --> 00:37:48,021
They live both in the water and on land.

426
00:37:50,341 --> 00:37:54,621
They're generalists.
They don't require a specific diet.

427
00:37:56,421 --> 00:37:58,381
They'll eat almost anything.

428
00:38:00,421 --> 00:38:02,821
Whatever is available is good enough,

429
00:38:03,461 --> 00:38:04,581
they'll take it.

430
00:38:09,741 --> 00:38:11,301
Here in this cenote,

431
00:38:12,261 --> 00:38:15,621
one's fallen in, gotten trapped,
no way out...

432
00:38:17,061 --> 00:38:18,581
Somehow, some way...

433
00:38:19,861 --> 00:38:21,181
he's succeeded.

434
00:38:22,421 --> 00:38:23,861
They're survivors.

435
00:38:26,941 --> 00:38:30,981
In a changing world,
it pays to be a generalist,

436
00:38:31,061 --> 00:38:32,421
not a specialist.

437
00:38:46,421 --> 00:38:49,101
If a big enough asteroid hits Atlas,

438
00:38:49,661 --> 00:38:52,701
the sky grazers and predators 
would be doomed.

439
00:38:53,701 --> 00:38:55,701
[screeching]

440
00:38:59,381 --> 00:39:02,661
They're too specialized 
to cope with change.

441
00:39:08,061 --> 00:39:11,621
The generalists 
are the boneless scavengers.

442
00:39:13,021 --> 00:39:16,261
Like crocodiles, they eat anything...

443
00:39:17,461 --> 00:39:19,221
and live anywhere.

444
00:39:23,661 --> 00:39:26,221
On this imagined high-gravity world,

445
00:39:26,941 --> 00:39:30,141
they could be the great survivors.

446
00:39:43,461 --> 00:39:45,181
How might life adapt

447
00:39:45,261 --> 00:39:47,061
on a different world,

448
00:39:48,341 --> 00:39:49,941
where creatures are trapped

449
00:39:50,581 --> 00:39:52,181
between a searing desert

450
00:39:53,781 --> 00:39:55,701
and a frozen shadowland?

451
00:39:57,741 --> 00:40:00,621
A world of extremes.