1
00:00:02,769 --> 00:00:07,573
We live on a volatile
planet in a violent universe...

2
00:00:07,574 --> 00:00:09,240
The universe constantly
wants to kill us.

3
00:00:09,241 --> 00:00:12,111
...where planets collide.

4
00:00:12,112 --> 00:00:14,482
The entire surface of the earth
is liquefied

5
00:00:14,581 --> 00:00:16,817
that was literally
a vision of hell.

6
00:00:18,352 --> 00:00:22,388
Black holes blast out
invisible death rays.

7
00:00:22,389 --> 00:00:25,357
It would be apocalyptic
beyond apocalyptic.

8
00:00:25,358 --> 00:00:28,694
Asteroids strike
without warning.

9
00:00:28,695 --> 00:00:30,496
It is a real possibility

10
00:00:30,497 --> 00:00:32,265
that it could happen
in the next 10 minutes.

11
00:00:32,266 --> 00:00:37,269
These cosmic killers
have struck time and time again,

12
00:00:37,270 --> 00:00:39,372
wiping out entire species,

13
00:00:39,373 --> 00:00:42,909
and pushing life on earth
to the edge of oblivion.

14
00:00:42,910 --> 00:00:45,077
It's happened before.
It's gonna happen again.

15
00:00:45,078 --> 00:00:47,745
And our species could be next.

16
00:00:47,746 --> 00:00:49,949
There will be disasters
in the future,

17
00:00:49,950 --> 00:00:52,217
and one of them will destroy us.

18
00:01:07,001 --> 00:01:10,804
Not too hot, not too cold...

19
00:01:10,805 --> 00:01:14,508
With water...

20
00:01:14,509 --> 00:01:16,476
Oxygen....

21
00:01:16,477 --> 00:01:21,780
Our peaceful, plentiful planet
nurtures and protects us...

22
00:01:21,781 --> 00:01:25,685
But this lull won't last
forever.

23
00:01:25,686 --> 00:01:29,289
There are dangers all around
and trouble ahead.

24
00:01:29,490 --> 00:01:30,858
When we look around,

25
00:01:30,859 --> 00:01:32,827
we think that the universe
is rather gentle.

26
00:01:32,828 --> 00:01:35,896
We have warm breezes
and mild seasons.

27
00:01:35,897 --> 00:01:39,868
Actually, the universe
is violent. it is chaotic.

28
00:01:41,704 --> 00:01:44,171
The universe
is not a happy, safe place.

29
00:01:44,172 --> 00:01:45,673
There are asteroid impacts,

30
00:01:45,674 --> 00:01:47,542
and solar flares,
and supernova, and black holes,

31
00:01:47,543 --> 00:01:49,010
and colliding galaxies,

32
00:01:49,011 --> 00:01:52,146
and all these really amazingly
dangerous and violent events.

33
00:01:52,147 --> 00:01:55,751
And the earth
is in the cross hairs.

34
00:02:01,423 --> 00:02:03,024
During the planet's

35
00:02:03,025 --> 00:02:05,527
4 1/2-billion-year existence,

36
00:02:05,528 --> 00:02:07,695
these violent phenomena

37
00:02:07,696 --> 00:02:10,131
have wiped out
millions of species

38
00:02:10,132 --> 00:02:13,868
in a series of catastrophic
mass extinctions.

39
00:02:14,904 --> 00:02:17,506
Mass extinctions due to impacts
and other geologic

40
00:02:17,507 --> 00:02:20,642
natural processes on the earth
have actually wiped out

41
00:02:20,643 --> 00:02:23,413
more species of plants
and animals on the planet

42
00:02:23,414 --> 00:02:26,049
than exist today.

43
00:02:26,050 --> 00:02:30,353
Mass extinctions
are what happens,

44
00:02:30,354 --> 00:02:32,254
it just happens periodically,

45
00:02:32,255 --> 00:02:34,991
and we living in the quiet time
between mass extinctions.

46
00:02:34,992 --> 00:02:38,294
It's happened before.
It's gonna happen again.

47
00:02:38,295 --> 00:02:40,931
The clock is ticking.

48
00:02:40,932 --> 00:02:43,332
With every day that passes,

49
00:02:43,333 --> 00:02:47,569
the next mass extinction gets
a step closer,

50
00:02:47,570 --> 00:02:50,439
and with every new discovery,

51
00:02:50,440 --> 00:02:53,711
the universe gets
a little bit more terrifying.

52
00:02:55,012 --> 00:02:57,915
November 2012.

53
00:02:57,916 --> 00:03:00,684
Astronomers identify
a new planet

54
00:03:00,685 --> 00:03:02,853
100 light-years from earth,

55
00:03:02,854 --> 00:03:07,023
at least four times
more massive than jupiter,

56
00:03:07,024 --> 00:03:09,560
and it's gone rogue.

57
00:03:12,231 --> 00:03:15,366
Unlike earth and all the other
objects in our solar system,

58
00:03:15,367 --> 00:03:19,104
this planet doesn't orbit
a star.

59
00:03:19,105 --> 00:03:22,974
It really is lost in space.

60
00:03:22,975 --> 00:03:25,009
When i was a kid
watching science-fiction movies,

61
00:03:25,010 --> 00:03:27,077
every now and again
there would be a rogue planet,

62
00:03:27,078 --> 00:03:29,047
just some planet wondering space
without a star.

63
00:03:29,048 --> 00:03:30,615
And i thought
that was pretty silly,

64
00:03:30,616 --> 00:03:34,618
but it turns out
that might actually happen.

65
00:03:34,619 --> 00:03:36,955
When planets are forming,

66
00:03:36,956 --> 00:03:39,190
they can interact
with each other gravitationally.

67
00:03:39,191 --> 00:03:40,658
And it's entirely possible

68
00:03:40,659 --> 00:03:42,227
that when
our solar system formed,

69
00:03:42,228 --> 00:03:45,831
planets were kicked out
into interstellar space.

70
00:03:45,832 --> 00:03:48,767
There could be as many
as 200 billion rogue planets

71
00:03:48,768 --> 00:03:50,368
in our galaxy.

72
00:03:50,369 --> 00:03:55,541
That's as many rogue planets
as there are stars in the sky.

73
00:03:55,542 --> 00:03:59,179
And one of them could be
heading our way.

74
00:04:04,450 --> 00:04:08,553
A collision with another planet
sounds farfetched.

75
00:04:08,554 --> 00:04:11,090
Could it really happen?

76
00:04:11,091 --> 00:04:14,361
As a matter of fact,
it already has.

77
00:04:17,998 --> 00:04:19,864
4 1/2 billion years ago,

78
00:04:19,865 --> 00:04:25,237
A young planet
veers into the earth's orbit.

79
00:04:25,238 --> 00:04:26,806
We have the earth sitting here,

80
00:04:26,807 --> 00:04:29,275
and another planet
about the size of mars came in

81
00:04:29,276 --> 00:04:31,111
and smacked us hard.

82
00:04:33,445 --> 00:04:36,648
The two collided
over 25,000 miles an hour,

83
00:04:36,649 --> 00:04:39,686
12 times faster than a bullet.

84
00:04:41,487 --> 00:04:44,791
The impact destroys
the smaller planet.

85
00:04:44,792 --> 00:04:47,428
The earth survives,
but only just.

86
00:04:47,829 --> 00:04:50,198
The violence of this is
hard to imagine.

87
00:04:50,199 --> 00:04:52,032
Two planets coming together

88
00:04:52,033 --> 00:04:54,434
smashing together
into one molten mass.

89
00:04:54,435 --> 00:04:56,570
After an impact of that scale,

90
00:04:56,571 --> 00:04:59,840
the entire surface of the earth
is literally liquefied.

91
00:04:59,841 --> 00:05:01,907
Imagine the floor
of an active volcano

92
00:05:01,908 --> 00:05:03,309
with islands of solid rock

93
00:05:03,310 --> 00:05:04,845
and lava spurting
right and left.

94
00:05:04,846 --> 00:05:07,981
The entire surface of the planet
would've looked like that.

95
00:05:07,982 --> 00:05:09,851
The earth itself
for a little while

96
00:05:09,852 --> 00:05:12,486
would've had
an atmosphere of molten rock.

97
00:05:12,487 --> 00:05:14,323
And it was a, you know,
vision of hell.

98
00:05:17,859 --> 00:05:21,728
Debris blasted out
at 20,000 miles an hour

99
00:05:21,729 --> 00:05:23,965
orbits the molten earth.

100
00:05:26,301 --> 00:05:28,370
Gravity brings the debris
together.

101
00:05:33,174 --> 00:05:36,412
The result -- our moon.

102
00:05:37,747 --> 00:05:40,013
Our moon emerged
from the wreckage

103
00:05:40,014 --> 00:05:43,652
of the most cataclysmic event
in our planet's history.

104
00:05:43,653 --> 00:05:47,222
From destruction comes creation,

105
00:05:47,223 --> 00:05:50,859
because without this lump
of cosmic shrapnel,

106
00:05:50,860 --> 00:05:54,395
life on earth might never have
gained a foothold.

107
00:05:54,396 --> 00:05:59,000
The moon's gravity pulls
on the infant earth's oceans,

108
00:05:59,001 --> 00:06:03,570
spreading nutrients
from the land into the water.

109
00:06:03,571 --> 00:06:05,806
And it slows the earth's spin

110
00:06:05,807 --> 00:06:09,243
from a 6 to a 24 hour day.

111
00:06:09,244 --> 00:06:12,380
In this calm,
fertile environment,

112
00:06:12,381 --> 00:06:15,416
one billion years
after the impact,

113
00:06:15,417 --> 00:06:16,986
life begins.

114
00:06:16,987 --> 00:06:19,688
If we hadn't had that planetary
collision a long time ago,

115
00:06:19,689 --> 00:06:21,558
we wouldn't have the moon
today.

116
00:06:21,559 --> 00:06:23,058
So, in fact,

117
00:06:23,059 --> 00:06:25,995
this most catastrophic event
you can possibly think of

118
00:06:25,996 --> 00:06:30,466
actually may have helped life
on earth form in the first place

119
00:06:30,467 --> 00:06:34,671
and helped us evolve over the
next couple of billion years.

120
00:06:34,672 --> 00:06:37,940
But what was
a good thing in the past

121
00:06:37,941 --> 00:06:41,978
would be a disaster
if it happened today.

122
00:06:41,979 --> 00:06:44,447
Now, you don't want
a planetary collision now

123
00:06:44,448 --> 00:06:46,449
because that would wipe out
the entire planet.

124
00:06:48,418 --> 00:06:50,787
You can't even describe it
comparing it to nuclear weapons.

125
00:06:50,788 --> 00:06:52,955
It would be billions
of nuclear weapons.

126
00:06:52,956 --> 00:06:54,624
It's enough to melt

127
00:06:54,625 --> 00:06:58,695
several miles thick crust
on the earth all the way down.

128
00:06:58,696 --> 00:07:00,097
It would wipe out
all life on earth.

129
00:07:00,098 --> 00:07:01,465
That would be it.

130
00:07:01,466 --> 00:07:04,768
It would be like a hard restart
for the planet itself.

131
00:07:04,769 --> 00:07:08,304
Could this nightmare
become a reality?

132
00:07:08,305 --> 00:07:12,208
Right now even the closest rogue
planets we've discovered

133
00:07:12,209 --> 00:07:15,177
are still trillions of miles
from earth.

134
00:07:15,178 --> 00:07:17,446
And our neighboring planets
have settled

135
00:07:17,447 --> 00:07:19,784
into calm, stable orbits.

136
00:07:19,985 --> 00:07:21,419
We're not gonna get
a planetary collision

137
00:07:21,420 --> 00:07:22,653
any time soon,

138
00:07:22,654 --> 00:07:24,521
but all the gravity
of the planets

139
00:07:24,522 --> 00:07:26,723
play with each other
and change each other's orbits.

140
00:07:26,724 --> 00:07:29,893
So clearly if you run
the clock work of time forward

141
00:07:29,894 --> 00:07:31,528
billions of years,

142
00:07:31,529 --> 00:07:33,030
yes, it's entirely possible

143
00:07:33,031 --> 00:07:35,167
that we might have
another planetary collision.

144
00:07:35,168 --> 00:07:38,137
You just don't have to worry
about it for a long, long time.

145
00:07:40,406 --> 00:07:42,006
4 billion years ago,

146
00:07:42,007 --> 00:07:46,544
A devastating collision
made life on earth possible.

147
00:07:46,545 --> 00:07:49,648
2 billion years later,

148
00:07:49,649 --> 00:07:52,752
That life threatens
to destroy itself.

149
00:08:07,868 --> 00:08:09,901
Our blue planet --

150
00:08:09,902 --> 00:08:13,907
in a hostile universe,
it sustains and nurtures life.

151
00:08:16,842 --> 00:08:19,277
2.4 billion years ago,

152
00:08:19,278 --> 00:08:21,080
Simple, single-celled organisms

153
00:08:21,081 --> 00:08:23,983
drift through
the nutrient-rich oceans.

154
00:08:25,052 --> 00:08:28,622
But their world
is about to be destroyed.

155
00:08:28,623 --> 00:08:30,524
When you talk
about mass extinctions,

156
00:08:30,525 --> 00:08:32,427
you have at least two types --

157
00:08:32,428 --> 00:08:34,593
one danger coming
from outer space,

158
00:08:34,594 --> 00:08:37,632
another from our own very
backyard on the planet earth.

159
00:08:43,171 --> 00:08:46,240
The earth circles the sun,

160
00:08:46,241 --> 00:08:48,943
but this orbit is unstable.

161
00:08:48,944 --> 00:08:51,511
Over hundreds
of thousands of years,

162
00:08:51,512 --> 00:08:53,012
it changes,

163
00:08:53,013 --> 00:08:55,647
swinging the planet
further out into space

164
00:08:55,648 --> 00:08:58,018
and pivoting on its axis.

165
00:09:00,188 --> 00:09:06,092
Tilted away from the sun,
the earth cools.

166
00:09:06,093 --> 00:09:08,228
2.4 billion years ago,

167
00:09:08,229 --> 00:09:11,231
Something turns
this natural cooling

168
00:09:11,232 --> 00:09:14,200
into a global catastrophe.

169
00:09:14,201 --> 00:09:16,703
It is one of the most
dangerous things

170
00:09:16,704 --> 00:09:19,873
in all the universe life.

171
00:09:19,875 --> 00:09:22,345
Tiny organisms
populate the oceans.

172
00:09:24,946 --> 00:09:26,781
There's no oxygen around

173
00:09:26,782 --> 00:09:28,852
and that's the way
most of them like it.

174
00:09:28,853 --> 00:09:32,921
But then a new kind
of bacteria evolves --

175
00:09:32,922 --> 00:09:34,522
cyanobacteria.

176
00:09:34,523 --> 00:09:36,262
And these guys create
a serious gas problem.

177
00:09:39,963 --> 00:09:41,865
Imagine earth
billions of years ago.

178
00:09:41,866 --> 00:09:43,897
There's no oxygen.
Everybody's happy.

179
00:09:43,898 --> 00:09:48,170
Then cyanobacteria start making
oxygen.

180
00:09:48,171 --> 00:09:50,438
It's a toxic pollutant.

181
00:09:50,439 --> 00:09:52,509
If there was a regulatory agency
at the time,

182
00:09:52,510 --> 00:09:53,809
they would've been outlawed.

183
00:09:53,810 --> 00:09:56,911
Eventually they polluted
the whole world.

184
00:09:56,912 --> 00:09:58,747
They had really precipitated

185
00:09:58,748 --> 00:10:02,182
an ecological crisis
of global proportions.

186
00:10:02,183 --> 00:10:04,518
The great oxygen crisis

187
00:10:04,519 --> 00:10:07,723
upsets the greenhouse effect
that keeps the planet warm.

188
00:10:10,927 --> 00:10:13,695
Global temperatures plummet.

189
00:10:13,696 --> 00:10:17,800
The ultimate culprit is biology.

190
00:10:17,801 --> 00:10:19,770
Biology makes a mess
of the planet,

191
00:10:19,771 --> 00:10:21,470
produces oxygen.

192
00:10:21,471 --> 00:10:24,940
The oxygen destroys
the greenhouse effect of methane

193
00:10:24,941 --> 00:10:26,542
and that freezes up the earth.

194
00:10:26,543 --> 00:10:32,749
2.4 billion years ago,
Ice creeps out from the poles.

195
00:10:37,354 --> 00:10:39,156
Instead of warming the planet,

196
00:10:39,157 --> 00:10:41,758
sunlight bounces off the ice,

197
00:10:41,759 --> 00:10:43,259
temperatures fall,

198
00:10:43,260 --> 00:10:47,763
creating more ice which bounces
more sunlight back into space,

199
00:10:47,764 --> 00:10:49,800
and so on and so on

200
00:10:49,801 --> 00:10:53,637
until the cooling becomes
unstoppable.

201
00:10:53,638 --> 00:10:56,172
The ice marches on.

202
00:10:56,173 --> 00:10:58,976
Temperatures plunge.

203
00:11:01,580 --> 00:11:04,681
The blue planet turns white.

204
00:11:04,682 --> 00:11:08,118
It's a snowball earth.

205
00:11:08,119 --> 00:11:11,422
And incredibly,
this may've happened not once

206
00:11:11,423 --> 00:11:14,993
but at least three times
over the following billion years

207
00:11:14,994 --> 00:11:19,329
as the planet
lurched around the sun.

208
00:11:19,330 --> 00:11:22,267
But throughout all of this
and against all the odds,

209
00:11:22,268 --> 00:11:25,502
a handful of species
clung to life,

210
00:11:25,503 --> 00:11:28,441
thanks to volcanoes.

211
00:11:30,942 --> 00:11:34,945
Even in an earth that was
covered almost entirely by ice,

212
00:11:34,946 --> 00:11:37,415
volcanoes would've been punching
through that.

213
00:11:37,416 --> 00:11:40,584
So you certainly have
pockets of water lying about.

214
00:11:40,585 --> 00:11:42,787
And life was able to carry on

215
00:11:42,788 --> 00:11:44,691
and get through
these cold periods.

216
00:11:51,898 --> 00:11:53,666
And the whole time,

217
00:11:53,667 --> 00:11:55,968
the volcanoes
that help sustain life

218
00:11:55,969 --> 00:11:58,970
have been pumping out
carbon dioxide.

219
00:11:58,971 --> 00:12:01,605
As this greenhouse gas
increases,

220
00:12:01,606 --> 00:12:03,175
the atmosphere warms.

221
00:12:03,176 --> 00:12:05,712
Until 640 million years ago,

222
00:12:05,713 --> 00:12:09,216
the last, great snowball earth
ends.

223
00:12:11,283 --> 00:12:14,188
And the survivors
emerge into a new world.

224
00:12:15,189 --> 00:12:19,493
After snowball earth goes away,
things get very interesting.

225
00:12:19,494 --> 00:12:22,496
A lot of opportunities
open up for life,

226
00:12:22,497 --> 00:12:24,464
water's flowing, ice is melting,

227
00:12:24,465 --> 00:12:28,598
organic material built up
that hasn't been decomposing.

228
00:12:28,599 --> 00:12:31,371
So you can imagine that there
will be a burst of development.

229
00:12:31,372 --> 00:12:34,174
In the meantime,

230
00:12:34,175 --> 00:12:38,945
cyanobacteria have been
churning out ever more oxygen.

231
00:12:38,946 --> 00:12:44,550
Other organisms will either
learn to breathe it or die.

232
00:12:44,551 --> 00:12:46,752
Many organisms decided

233
00:12:46,753 --> 00:12:49,055
that this poison
could be useful,

234
00:12:49,056 --> 00:12:50,523
it's energetic,

235
00:12:50,524 --> 00:12:52,257
and that allowed them to have
an energy source

236
00:12:52,258 --> 00:12:53,859
that was so powerful

237
00:12:53,860 --> 00:12:56,128
that they could build
huge, complex structures --

238
00:12:56,129 --> 00:12:57,564
poof, animals.

239
00:12:57,565 --> 00:13:00,568
Snowball earth
is an environmental disaster

240
00:13:00,569 --> 00:13:03,637
and an evolutionary triumph.

241
00:13:03,638 --> 00:13:07,509
Complex life flourishes.

242
00:13:14,416 --> 00:13:18,587
But most of these creatures will
never evolve beyond this point.

243
00:13:18,588 --> 00:13:21,222
Something stops them dead.

244
00:13:21,223 --> 00:13:24,724
It is the most powerful weapon
in the universe,

245
00:13:24,725 --> 00:13:27,929
and it strikes
in the blink of an eye.

246
00:13:38,340 --> 00:13:40,977
In a violent universe,

247
00:13:40,978 --> 00:13:44,112
against all the odds,
life survives.

248
00:13:44,113 --> 00:13:46,048
But consider this --

249
00:13:46,049 --> 00:13:49,284
at any moment, the universe
could pull the trigger

250
00:13:49,285 --> 00:13:52,088
on a secret,
deep-space death ray,

251
00:13:52,089 --> 00:13:54,724
obliterating all life on earth.

252
00:13:54,725 --> 00:13:59,964
And until the 1960s,
nobody even knew it existed.

253
00:14:02,733 --> 00:14:07,304
1967 --
The height of the cold war.

254
00:14:07,305 --> 00:14:09,405
The united states
and soviet union

255
00:14:09,406 --> 00:14:11,341
raced to outgun each other,

256
00:14:11,342 --> 00:14:14,710
stockpiling and testing
nuclear weapons.

257
00:14:14,711 --> 00:14:17,213
America was worried
that the soviet union

258
00:14:17,214 --> 00:14:20,216
would be able to test
nuclear weapons in space.

259
00:14:20,217 --> 00:14:22,519
So what america did is launch
the series of satellites

260
00:14:22,520 --> 00:14:24,989
to go out into space
and look for the tell-tale flash

261
00:14:24,990 --> 00:14:27,689
of gamma rays
from nuclear tests.

262
00:14:27,690 --> 00:14:29,959
On july 2, 1967,

263
00:14:29,960 --> 00:14:33,429
the satellites detect
a burst of gamma rays,

264
00:14:33,430 --> 00:14:36,031
the most energetic
and destructive form

265
00:14:36,032 --> 00:14:38,169
of electromagnetic radiation.

266
00:14:38,170 --> 00:14:40,639
Immediately there was panic
in the pentagon.

267
00:14:40,640 --> 00:14:42,506
Perhaps the russians are testing

268
00:14:42,507 --> 00:14:45,077
super-gigantic hydrogen bombs
in outer space.

269
00:14:45,078 --> 00:14:47,679
And we're just caught
flat-footed.

270
00:14:47,680 --> 00:14:48,814
But it's not bombs.

271
00:14:48,815 --> 00:14:51,348
It's something far deadlier.

272
00:14:51,349 --> 00:14:53,651
And then the realization
sunk in.

273
00:14:53,652 --> 00:14:55,487
"Oh, my god.

274
00:14:55,488 --> 00:15:00,659
these flashes are coming from"
outside the milky way galaxy.

275
00:15:00,660 --> 00:15:03,929
They must be
billions of light-years away."

276
00:15:03,930 --> 00:15:05,564
a new source of energy,

277
00:15:05,565 --> 00:15:08,900
second only to the big bang
itself had been discovered.

278
00:15:08,901 --> 00:15:11,203
When gamma ray at first
were first discovered,

279
00:15:11,204 --> 00:15:14,205
people assumed that
they must be fairly close by.

280
00:15:14,206 --> 00:15:15,674
"Of course
they have to be close by.

281
00:15:15,675 --> 00:15:18,376
they're the brightest thing
that we see in the sky."

282
00:15:18,377 --> 00:15:20,145
And now we know
that gamma ray burst,

283
00:15:20,146 --> 00:15:21,579
not only are they not nearby,

284
00:15:21,580 --> 00:15:24,083
they're not in our galaxy,
they're not in nearby galaxies,

285
00:15:24,084 --> 00:15:26,049
but they're close to the edge
of the universe.

286
00:15:26,050 --> 00:15:28,719
They're as far away as
anything else that we observe,

287
00:15:28,720 --> 00:15:30,488
and that's
completely ridiculous.

288
00:15:30,489 --> 00:15:32,891
Over distance,
light gets dimmer.

289
00:15:32,892 --> 00:15:36,895
The further light has to travel,
the dimmer the light should be.

290
00:15:36,896 --> 00:15:39,332
If light from a distant galaxy
comes to earth

291
00:15:39,333 --> 00:15:41,599
and it has gamma-ray energies,

292
00:15:41,600 --> 00:15:44,102
then that explosion must've been
incredibly powerful,

293
00:15:44,103 --> 00:15:48,073
because it turns out that
as light travels through space,

294
00:15:48,074 --> 00:15:50,275
the wave length of the light
gets stretched out.

295
00:15:50,276 --> 00:15:52,910
And this stretching caused
the light to lose energy.

296
00:15:52,911 --> 00:15:56,814
And since the light rays have
traveled a very great distance

297
00:15:56,815 --> 00:15:58,482
through the cosmos to reach us,

298
00:15:58,483 --> 00:16:00,285
and they're still gamma rays,

299
00:16:00,286 --> 00:16:02,521
they must've started out
with a great deal of energy.

300
00:16:02,522 --> 00:16:04,189
And the amount of energies
are unbelievable.

301
00:16:04,190 --> 00:16:07,193
You're talking about the entire
energy budget of the sun

302
00:16:07,194 --> 00:16:08,626
over its whole lifetime

303
00:16:08,627 --> 00:16:11,698
emitted over the course
of just a few seconds.

304
00:16:11,699 --> 00:16:15,535
These are amazingly violent,
amazingly powerful events.

305
00:16:16,238 --> 00:16:18,372
In june 2008.

306
00:16:18,373 --> 00:16:21,443
Nasa launches
the fermi space telescope.

307
00:16:23,277 --> 00:16:24,511
Its mission --

308
00:16:24,512 --> 00:16:28,381
discover the source
of these huge blasts.

309
00:16:28,382 --> 00:16:29,982
What fermi does

310
00:16:29,983 --> 00:16:32,352
is open our eyes
to the universe that's there

311
00:16:32,353 --> 00:16:34,121
but gives us
such a different view

312
00:16:34,122 --> 00:16:36,622
that we really get a deeper
and greater understanding

313
00:16:36,623 --> 00:16:37,925
of what's going on.

314
00:16:37,926 --> 00:16:39,694
If you had gamma-ray eyes,

315
00:16:39,695 --> 00:16:42,295
the milky way would be
blazingly bright

316
00:16:42,296 --> 00:16:45,399
across the center of the sky.

317
00:16:45,400 --> 00:16:47,534
Your vision would be dominated

318
00:16:47,535 --> 00:16:50,571
by these very dense,
pulsing stars

319
00:16:50,572 --> 00:16:52,040
and super-massive black holes.

320
00:16:52,041 --> 00:16:55,208
And it's black holes

321
00:16:55,209 --> 00:16:58,712
that may solve the mystery
of gamma-ray bursts.

322
00:16:58,713 --> 00:17:01,680
When a truly gigantic star dies,

323
00:17:01,681 --> 00:17:05,318
one at least 25 times
more massive than our own sun,

324
00:17:05,319 --> 00:17:08,390
it collapses to form
a black hole.

325
00:17:08,391 --> 00:17:10,358
Scientists believe black holes

326
00:17:10,359 --> 00:17:12,462
are one of the few things
in the universe

327
00:17:12,463 --> 00:17:18,432
large enough and powerful enough
to generate gamma-ray bursts.

328
00:17:18,433 --> 00:17:22,070
Gamma-ray bursts are
the birth cries of black holes.

329
00:17:22,071 --> 00:17:25,841
When a massive star explodes
and becomes a supernova,

330
00:17:25,842 --> 00:17:28,410
the core collapses
and forms a black hole.

331
00:17:28,411 --> 00:17:31,714
Material falls around it,
swirls into a huge disk,

332
00:17:31,715 --> 00:17:33,681
it gets incredibly hot.

333
00:17:33,682 --> 00:17:35,150
As it's falling
into the black hole

334
00:17:35,151 --> 00:17:38,086
it forms a tremendous
magnetic field, as well.

335
00:17:45,260 --> 00:17:47,028
The remains of the star

336
00:17:47,029 --> 00:17:50,399
spiral towards the black hole.

337
00:17:50,400 --> 00:17:53,134
Enormous electromagnetic forces

338
00:17:53,135 --> 00:17:56,705
fling some of this matter
outwards.

339
00:17:56,706 --> 00:17:59,908
Hurtling up and down

340
00:17:59,909 --> 00:18:01,477
the black hole's
huge magnetic fields,

341
00:18:01,478 --> 00:18:05,581
the matter collides with debris
from the initial explosion,

342
00:18:05,582 --> 00:18:08,350
accelerating
to close to the speed of light,

343
00:18:08,351 --> 00:18:11,653
heating to millions of degrees.

344
00:18:11,654 --> 00:18:13,689
These high-speed collisions

345
00:18:13,690 --> 00:18:17,192
unleash unimaginable amounts
of energy.

346
00:18:17,193 --> 00:18:19,862
This is the gamma-ray burst.

347
00:18:19,863 --> 00:18:23,065
Gamma-ray bursts
are fascinating.

348
00:18:23,066 --> 00:18:24,767
You can study them
throughout the universe

349
00:18:24,768 --> 00:18:26,068
because they're so bright.

350
00:18:26,069 --> 00:18:29,805
But if you move them in
really close to the earth,

351
00:18:29,806 --> 00:18:32,875
let's say within
6,000 light-years of the earth,

352
00:18:32,876 --> 00:18:35,245
they become
extremely destructive.

353
00:18:35,246 --> 00:18:38,614
The beams are so huge
that if a gamma-ray burst

354
00:18:38,615 --> 00:18:42,253
occurs, say,
100 light-years from us,

355
00:18:42,254 --> 00:18:44,790
by the time it reaches
the earth, the beam will be

356
00:18:44,791 --> 00:18:48,759
wide enough to engulf
our entire solar system.

357
00:18:48,760 --> 00:18:51,295
Basically, if you were standing
on the earth and you looked up,

358
00:18:51,296 --> 00:18:52,830
you would see a flash of light,

359
00:18:52,831 --> 00:18:55,300
and before you could even say,
what's that?

360
00:18:55,301 --> 00:18:56,700
You'd be gone.

361
00:18:56,701 --> 00:19:00,070
The amount of energy in the beam
that travels across space

362
00:19:00,071 --> 00:19:02,674
is so intense it would basically
light the earth on fire

363
00:19:02,675 --> 00:19:04,441
from that distance.

364
00:19:04,442 --> 00:19:06,276
It would strip off
the earth's atmosphere,

365
00:19:06,277 --> 00:19:09,179
it would boil the oceans,
it would melt the rock.

366
00:19:09,180 --> 00:19:12,218
It would be apocalyptic
beyond apocalyptic.

367
00:19:13,652 --> 00:19:17,288
This is the worst-case scenario.

368
00:19:17,289 --> 00:19:21,426
But what if a gamma-ray burst
hit the earth from further out?

369
00:19:21,427 --> 00:19:23,929
Would we survive?

370
00:19:23,930 --> 00:19:26,497
People ask what would happen
if there was a gamma-ray burst

371
00:19:26,498 --> 00:19:29,200
within 6,000 light-years
of the earth.

372
00:19:29,201 --> 00:19:31,070
It's actually
not the right question.

373
00:19:31,071 --> 00:19:33,973
There have been gamma-ray bursts
that close to the earth,

374
00:19:33,974 --> 00:19:37,241
and there probably have been
extinctions of life on earth

375
00:19:37,242 --> 00:19:39,311
due to gamma-ray bursts.

376
00:19:40,314 --> 00:19:43,748
200 million years
After snowball earth,

377
00:19:43,749 --> 00:19:47,385
the oceans are teeming
with complex life.

378
00:19:47,386 --> 00:19:51,024
But 440 million years ago,

379
00:19:51,025 --> 00:19:54,394
85% of all those creatures died.

380
00:19:57,164 --> 00:19:59,231
And the killer may have been

381
00:19:59,232 --> 00:20:02,869
a single devastating
gamma-ray burst.

382
00:20:02,870 --> 00:20:06,471
The blast penetrates
the oceans' upper layers,

383
00:20:06,472 --> 00:20:09,342
killing the creatures
that live near the surface.

384
00:20:09,343 --> 00:20:15,648
Creatures living further down
survive the initial onslaught,

385
00:20:15,649 --> 00:20:18,685
but not for long...

386
00:20:18,686 --> 00:20:22,921
Because the blast also damages
the earth's ozone layer,

387
00:20:22,922 --> 00:20:27,125
exposing the planet to the sun's
deadly uv radiation,

388
00:20:27,126 --> 00:20:29,362
triggering acid rain

389
00:20:29,363 --> 00:20:31,997
and lowering
global temperatures.

390
00:20:31,998 --> 00:20:34,668
Over half a million years,

391
00:20:34,669 --> 00:20:37,536
the creatures that survived
the gamma-ray burst

392
00:20:37,537 --> 00:20:40,805
get taken out
by its after effects.

393
00:20:40,806 --> 00:20:45,245
If a gamma-ray burst
has wiped out life in the past,

394
00:20:45,246 --> 00:20:47,113
it could happen in the future.

395
00:20:49,684 --> 00:20:51,817
And astronomers
think the next burst

396
00:20:51,818 --> 00:20:57,325
could come from a dangerously
unstable star, wr 104.

397
00:20:57,326 --> 00:21:00,628
Wr 104 is the nightmare.

398
00:21:00,629 --> 00:21:03,297
We now have
a potential candidate

399
00:21:03,298 --> 00:21:07,468
for what may become a gamma-ray
burster with our name on it.

400
00:21:07,469 --> 00:21:11,708
We are literally staring
down the gun barrel of wr 104.

401
00:21:14,244 --> 00:21:16,245
It's not one

402
00:21:16,246 --> 00:21:19,984
but two massive stars
orbiting each other.

403
00:21:21,684 --> 00:21:25,653
The stars will die
in a massive explosion,

404
00:21:25,654 --> 00:21:27,390
spawning a black hole,

405
00:21:27,391 --> 00:21:29,759
and blasting out gamma rays.

406
00:21:32,295 --> 00:21:34,598
The object is
about 8,000 light-years away,

407
00:21:34,599 --> 00:21:38,700
so we are within the kill radius
of this object.

408
00:21:38,701 --> 00:21:41,003
So you could be
doing your laundry tomorrow,

409
00:21:41,004 --> 00:21:43,072
look up in the sky,
and all of a sudden,

410
00:21:43,073 --> 00:21:47,477
there's this burst of radiation
raining down from the heavens.

411
00:21:47,478 --> 00:21:50,679
The radiation rips off
the earth's ozone layer,

412
00:21:50,680 --> 00:21:53,015
creating a toxic smog

413
00:21:53,016 --> 00:21:56,119
and exposing us
to the sun's deadly rays.

414
00:21:56,120 --> 00:21:59,487
Life as we know it
could cease to exist.

415
00:21:59,488 --> 00:22:01,222
Plants would be scorched,

416
00:22:01,223 --> 00:22:03,525
animals,
which depend upon plant life,

417
00:22:03,526 --> 00:22:05,127
will then begin to die.

418
00:22:05,128 --> 00:22:08,930
Human civilization would
have to go underground.

419
00:22:08,931 --> 00:22:10,499
It may sound like the death star

420
00:22:10,500 --> 00:22:12,301
destroying the earth
in "star wars,"

421
00:22:12,302 --> 00:22:15,539
but the difference is the death
star isn't gonna happen,

422
00:22:15,540 --> 00:22:17,974
a gamma-ray burst might.

423
00:22:24,047 --> 00:22:27,416
Our extinction
could happen at any time.

424
00:22:27,417 --> 00:22:32,054
And the fatal blow
doesn't have to come from space.

425
00:22:32,055 --> 00:22:35,123
It could come
from the very thing

426
00:22:35,124 --> 00:22:37,493
that makes life possible --

427
00:22:37,494 --> 00:22:40,264
the earth itself.

428
00:22:50,943 --> 00:22:55,214
Our planet conceals
a weapon of mass extinction,

429
00:22:55,215 --> 00:22:58,550
primed to detonate
at any moment,

430
00:22:58,551 --> 00:23:01,388
hidden deep beneath our feet.

431
00:23:03,457 --> 00:23:06,859
Unleashed,
the heat inside our planet

432
00:23:06,860 --> 00:23:11,064
could wipe out everything
in its path on a massive scale.

433
00:23:13,932 --> 00:23:16,767
200 million years
After a gamma-ray burst

434
00:23:16,768 --> 00:23:19,137
may have devastated life
in the oceans,

435
00:23:19,138 --> 00:23:21,607
the survivors have colonized
the land.

436
00:23:22,941 --> 00:23:27,079
Among them, a motley crew
of monster reptiles --

437
00:23:27,080 --> 00:23:30,381
scutosaurus and gorgonopsians.

438
00:23:30,382 --> 00:23:34,253
They're successful, strong,
and doomed.

439
00:23:35,055 --> 00:23:37,289
Around about
250 million years ago marks

440
00:23:37,290 --> 00:23:40,794
the biggest mass extinction
that the earth has ever seen,

441
00:23:40,795 --> 00:23:43,496
the end-permian extinction.

442
00:23:43,497 --> 00:23:45,465
Just over 90% of marine fauna

443
00:23:45,466 --> 00:23:48,334
and around about 70%
of land fauna

444
00:23:48,335 --> 00:23:51,036
disappeared from the planet.

445
00:23:51,037 --> 00:23:53,439
The killer is
a volcanic eruption --

446
00:23:53,440 --> 00:23:55,608
the biggest
and most catastrophic

447
00:23:55,609 --> 00:23:57,245
the world has ever seen.

448
00:24:01,181 --> 00:24:03,551
250 million years ago,

449
00:24:03,552 --> 00:24:05,585
In what is now siberia,

450
00:24:05,586 --> 00:24:08,656
the earth's crust ruptures,

451
00:24:08,657 --> 00:24:11,025
pushed beyond breaking point

452
00:24:11,026 --> 00:24:13,660
by a vast plume of hot magma

453
00:24:13,661 --> 00:24:16,465
surging up
from deep inside the planet.

454
00:24:20,436 --> 00:24:22,972
The earth itself can
internally generate

455
00:24:22,973 --> 00:24:25,739
some very devastating events,
millions-of-years-long events

456
00:24:25,740 --> 00:24:28,343
in the form of
major volcanic eruptions

457
00:24:28,344 --> 00:24:31,446
at the continent-scale level.

458
00:24:31,447 --> 00:24:34,114
These are
basaltic-volcanism events

459
00:24:34,115 --> 00:24:38,487
that flood entire portions
of the planet with basalt lava.

460
00:24:40,323 --> 00:24:44,892
Lava spews
for two million years.

461
00:24:44,893 --> 00:24:49,330
There's enough lava to cover
the entire united states

462
00:24:49,331 --> 00:24:52,099
beneath a thousand feet.

463
00:24:52,100 --> 00:24:55,905
And the death toll
extends around the earth...

464
00:24:58,641 --> 00:25:01,542
..and deep into the oceans.

465
00:25:01,543 --> 00:25:04,247
The question is why.

466
00:25:06,583 --> 00:25:10,219
The answer lies with the most
volcanic country on earth --

467
00:25:12,720 --> 00:25:14,022
iceland --

468
00:25:14,023 --> 00:25:19,462
with a similar, smaller eruption
just 230 years ago.

469
00:25:20,596 --> 00:25:23,166
June 1783.

470
00:25:23,167 --> 00:25:26,936
A terrible chain of events
unfold

471
00:25:26,937 --> 00:25:29,304
that will devastate iceland

472
00:25:29,305 --> 00:25:32,908
and kill up to a million people
around the world.

473
00:25:32,909 --> 00:25:35,945
Near the village of laki,

474
00:25:35,946 --> 00:25:41,449
a 17-mile-long tear
opens up in the earth's crust.

475
00:25:41,450 --> 00:25:44,454
These holes and cracks
in the ground that you can see,

476
00:25:44,455 --> 00:25:45,990
they would've had jets of magma,

477
00:25:45,991 --> 00:25:48,825
jets of lava
flying up into the sky.

478
00:25:52,796 --> 00:25:54,296
To give you an idea of scale,

479
00:25:54,297 --> 00:25:57,698
the overall the amount of
material that came out of laki

480
00:25:57,699 --> 00:26:00,303
is about 3 1/2 cubic miles
of volcanic material,

481
00:26:00,304 --> 00:26:02,439
and that's a lot material.

482
00:26:02,440 --> 00:26:05,842
And it's not just the size of
laki that makes it so special,

483
00:26:05,843 --> 00:26:09,579
it's actually what's inside this
and what came out of this

484
00:26:09,580 --> 00:26:11,080
that's the dangerous thing.

485
00:26:11,081 --> 00:26:13,251
Because it had
lots of sulfur gases

486
00:26:13,252 --> 00:26:14,517
associated with the eruption

487
00:26:14,518 --> 00:26:17,853
and also lots of fluorine,
quite poisonous gases.

488
00:26:17,854 --> 00:26:21,926
Sulfur dioxide spreads
out around the atmosphere.

489
00:26:22,427 --> 00:26:25,094
Its droplets form a giant mirror

490
00:26:25,095 --> 00:26:28,666
reflecting the sun's warmth
away from the earth.

491
00:26:28,667 --> 00:26:30,366
It's clear that even

492
00:26:30,367 --> 00:26:33,202
a relatively small eruption
like laki

493
00:26:33,203 --> 00:26:36,273
can cause big, dramatic effects
in terms of the climate.

494
00:26:36,274 --> 00:26:38,374
In the northern u.s.,

495
00:26:38,375 --> 00:26:40,244
there was one of the coldest
winters ever recorded.

496
00:26:40,245 --> 00:26:42,946
In fact, the mississippi is
recorded to have frozen.

497
00:26:42,947 --> 00:26:46,618
It's been implicated in causing
the big famine in japan.

498
00:26:46,619 --> 00:26:50,353
So, the effects,
potentially, for volcanoes

499
00:26:50,354 --> 00:26:51,988
that spew these horrible gases

500
00:26:51,989 --> 00:26:55,692
into the atmosphere can be
catastrophic on a global scale.

501
00:26:55,693 --> 00:26:59,462
Now picture
the siberian eruptions

502
00:26:59,463 --> 00:27:01,798
250 million years ago.

503
00:27:01,799 --> 00:27:05,535
They're 200,000 times larger
than laki

504
00:27:05,536 --> 00:27:08,706
and last a million times longer.

505
00:27:08,707 --> 00:27:12,275
They release massive quantities
of gas

506
00:27:12,276 --> 00:27:14,778
triggering
extreme climate change --

507
00:27:14,779 --> 00:27:17,950
first cooling,
then heating the atmosphere.

508
00:27:19,250 --> 00:27:22,487
70 % of all
Land-based creatures die,

509
00:27:22,488 --> 00:27:27,324
including the mighty
gorgonopsians and scutosaurus.

510
00:27:27,325 --> 00:27:30,061
But worse is to come.

511
00:27:30,062 --> 00:27:35,233
As the oceans warm,
they lose oxygen and stagnate.

512
00:27:35,234 --> 00:27:37,401
Toxic algae takes over,

513
00:27:37,402 --> 00:27:40,605
poisoning the oceans
with hydrogen sulfide,

514
00:27:40,606 --> 00:27:43,741
killing 96% of marine life,

515
00:27:43,742 --> 00:27:47,111
and leaving
purple sulfur bacteria

516
00:27:47,112 --> 00:27:48,180
to overrun the oceans,

517
00:27:48,181 --> 00:27:50,882
turning the water pink.

518
00:27:50,883 --> 00:27:54,253
This is the closest
the earth has ever come

519
00:27:54,254 --> 00:27:56,690
to total extinction.

520
00:27:57,857 --> 00:28:02,295
But over 200 million years,
the survivors adapt and evolve.

521
00:28:02,296 --> 00:28:05,297
A new group of animals emerge.

522
00:28:05,298 --> 00:28:08,400
They are the largest,
most successful creatures

523
00:28:08,401 --> 00:28:10,236
the earth has ever seen --

524
00:28:10,237 --> 00:28:12,571
the dinosaurs.

525
00:28:12,572 --> 00:28:17,511
But they, too, will face
annihilation.

526
00:28:24,987 --> 00:28:27,854
Cosmic killers
prowl the universe

527
00:28:27,855 --> 00:28:30,092
threatening to wipe out
life on earth.

528
00:28:32,693 --> 00:28:34,695
They've struck before,

529
00:28:34,696 --> 00:28:38,265
pushing life
to the edge of extinction.

530
00:28:38,266 --> 00:28:41,268
They will strike again,

531
00:28:41,269 --> 00:28:43,970
and it could happen before
you've finished

532
00:28:43,971 --> 00:28:45,239
watching this show.

533
00:28:48,210 --> 00:28:51,980
February 15, 2013.

534
00:28:51,981 --> 00:28:54,283
9:42 a.m.

535
00:28:54,284 --> 00:28:56,319
It's another cold winter's day

536
00:28:56,320 --> 00:28:58,954
in the siberian city
of chelyabinsk

537
00:28:58,955 --> 00:29:04,593
when literally,
out of the blue...

538
00:29:04,594 --> 00:29:09,364
A 14,000-ton, 65-foot meteor

539
00:29:09,365 --> 00:29:13,869
tears through the atmosphere
at 42,000 miles an hour.

540
00:29:13,870 --> 00:29:17,506
It explodes in the air
18 miles up,

541
00:29:17,507 --> 00:29:20,542
unleashing
a powerful blast wave,

542
00:29:20,543 --> 00:29:23,044
shattering windows,

543
00:29:23,045 --> 00:29:25,546
damaging 7,000 buildings,

544
00:29:25,547 --> 00:29:28,050
and injuring 1,500 people.

545
00:29:28,051 --> 00:29:31,586
Now imagine
what would've happened

546
00:29:31,587 --> 00:29:33,856
if the asteroid had hit
the earth in one piece.

547
00:29:33,857 --> 00:29:36,659
And we saw what happened
over russia,

548
00:29:36,660 --> 00:29:38,128
over in chelyabinsk,

549
00:29:38,129 --> 00:29:40,830
with an object
that could have hit the earth --

550
00:29:40,831 --> 00:29:42,465
could've hit the earth
with a force

551
00:29:42,466 --> 00:29:44,502
of perhaps 20 hiroshima bombs.

552
00:29:44,503 --> 00:29:48,938
If you watch those videos
of that meteor in russia

553
00:29:48,939 --> 00:29:51,841
with the incredible sonic boom,

554
00:29:51,842 --> 00:29:53,977
you could see
how even a small object --

555
00:29:53,978 --> 00:29:55,911
relatively small
in a cosmic sense --

556
00:29:55,912 --> 00:29:57,881
could produce a dramatic event
for humans.

557
00:29:57,882 --> 00:29:59,650
The way it works is

558
00:29:59,651 --> 00:30:01,583
small objects are hitting
the earth every day,

559
00:30:01,584 --> 00:30:03,987
large objects, every week,

560
00:30:03,988 --> 00:30:06,256
larger objects still,
every year.

561
00:30:06,257 --> 00:30:10,360
And an object the size
of the chelyabinsk meteor

562
00:30:10,361 --> 00:30:14,431
strikes, on average,
once every century.

563
00:30:16,500 --> 00:30:18,333
So when
the next big one strikes --

564
00:30:18,334 --> 00:30:20,004
<i>not if...</i>

565
00:30:22,006 --> 00:30:23,172
...what will happen?

566
00:30:24,741 --> 00:30:26,977
The clues lie in the past

567
00:30:26,978 --> 00:30:29,346
in the extinction
of the dinosaurs.

568
00:30:29,347 --> 00:30:31,448
About 65 million years ago,

569
00:30:31,449 --> 00:30:33,083
there was a perfect morning
on earth.

570
00:30:33,084 --> 00:30:34,618
I would've loved
to have been there

571
00:30:34,619 --> 00:30:36,987
to see the giant dinosaurs,
you know,

572
00:30:36,988 --> 00:30:39,791
the pterodactyls flying
through the air, all of that.

573
00:30:39,792 --> 00:30:41,326
And then something changed,

574
00:30:41,327 --> 00:30:43,361
and the earth
would never be the same.

575
00:30:43,362 --> 00:30:45,094
If you would've looked
into the sky,

576
00:30:45,095 --> 00:30:47,198
you would've seen
a relatively dim light at first

577
00:30:47,199 --> 00:30:49,432
coming towards you,
getting brighter and brighter,

578
00:30:49,433 --> 00:30:50,502
and hotter and hotter.

579
00:30:50,503 --> 00:30:52,937
It's a six-mile-wide rock

580
00:30:52,938 --> 00:30:54,972
the size of mount everest

581
00:30:54,973 --> 00:30:59,744
racing towards the earth
at 25,000 miles an hour.

582
00:30:59,745 --> 00:31:01,347
The first wave of destruction

583
00:31:01,348 --> 00:31:03,681
would've started
before this object even hit.

584
00:31:03,682 --> 00:31:05,984
There would've been
shock waves, heat, and winds

585
00:31:05,985 --> 00:31:07,685
going across the entire planet.

586
00:31:07,686 --> 00:31:10,156
Everywhere that was
under the path of this asteroid

587
00:31:10,157 --> 00:31:12,291
would've been seared,
set on fire.

588
00:31:12,292 --> 00:31:14,026
The oceans would've been boiling
underneath it.

589
00:31:17,263 --> 00:31:19,732
The asteroid smashes
into the ocean

590
00:31:19,733 --> 00:31:22,835
off of what is now
mexico's yucatan peninsula.

591
00:31:23,603 --> 00:31:27,139
It strikes with a force
two million times greater

592
00:31:27,140 --> 00:31:30,677
than the biggest
nuclear bomb ever detonated,

593
00:31:30,678 --> 00:31:34,612
and blasts out a crater
200 miles across.

594
00:31:34,613 --> 00:31:40,620
A super-heated shock wave roars
out at twice the speed of sound.

595
00:31:40,621 --> 00:31:47,061
500 billion tons of red-hot rock
Soar to the edge of space.

596
00:31:49,763 --> 00:31:51,697
Two hours after impact,

597
00:31:51,698 --> 00:31:54,967
a 300-foot tsunami
smashes into the coast

598
00:31:54,968 --> 00:31:57,003
of what is now the u.s.a.

599
00:31:57,004 --> 00:31:59,840
Reaching as far
as north carolina.

600
00:32:03,811 --> 00:32:05,914
Over the next few hours
and days,

601
00:32:05,915 --> 00:32:10,283
the debris rains down,
setting the planet ablaze.

602
00:32:10,284 --> 00:32:13,519
In the following weeks
and months,

603
00:32:13,520 --> 00:32:15,221
smoke from the fires

604
00:32:15,222 --> 00:32:19,459
adds to the dust
blasted into the atmosphere.

605
00:32:19,460 --> 00:32:22,128
There was
so much pulverized rock,

606
00:32:22,129 --> 00:32:24,864
all of the burning materials
up into the atmosphere,

607
00:32:24,865 --> 00:32:26,300
you wouldn't have been able
to see the surface.

608
00:32:26,301 --> 00:32:28,703
And on the surface, you wouldn't
have been able to see the sun,

609
00:32:28,704 --> 00:32:30,237
and it was like that
for a long time.

610
00:32:32,806 --> 00:32:35,875
This ancient apocalypse

611
00:32:35,876 --> 00:32:38,812
is a disaster
for the dinosaurs...

612
00:32:40,381 --> 00:32:42,750
...but without it,
We wouldn't be here.

613
00:32:42,751 --> 00:32:45,186
Back then, during the time
of the dinosaurs,

614
00:32:45,187 --> 00:32:48,957
our ancestors were
probably little, furry mammals

615
00:32:48,958 --> 00:32:51,525
that were an evening snack
for a dinosaur.

616
00:32:51,526 --> 00:32:53,326
When the dinosaurs
got wiped out,

617
00:32:53,327 --> 00:32:54,661
these small, little,
furry mammals

618
00:32:54,662 --> 00:32:56,430
began to expand in size

619
00:32:56,431 --> 00:32:59,766
to take over the niche
left over by the dinosaurs.

620
00:32:59,767 --> 00:33:03,138
So, one life-form replaces
another life-form,

621
00:33:03,139 --> 00:33:07,507
in this continual process
called survival of the fittest.

622
00:33:07,508 --> 00:33:11,112
We are here
because our ancestors

623
00:33:11,113 --> 00:33:12,481
survived the extinction event,

624
00:33:12,482 --> 00:33:14,550
and, in fact,
flourished because of it.

625
00:33:14,551 --> 00:33:17,284
From our point of view,

626
00:33:17,285 --> 00:33:20,220
that extinction event
was a good thing,

627
00:33:20,221 --> 00:33:22,691
but we're here
for a brief moment.

628
00:33:22,692 --> 00:33:25,894
And there will be disasters
in the future,

629
00:33:25,895 --> 00:33:28,195
and one of them will destroy us.

630
00:33:28,196 --> 00:33:31,231
There is a 1 in 5,000 chance

631
00:33:31,232 --> 00:33:35,202
that an asteroid, the same size
as the dinosaur killer,

632
00:33:35,203 --> 00:33:38,706
will strike
within the next 100 years,

633
00:33:38,707 --> 00:33:41,242
and it could happen at any time.

634
00:33:41,243 --> 00:33:42,811
It is a real possibility

635
00:33:42,812 --> 00:33:44,979
that it could happen
in the next 10 minutes,

636
00:33:44,980 --> 00:33:47,282
but is a tiny possibility.

637
00:33:47,283 --> 00:33:49,418
So, i always say, "you don't
need to prepare very much

638
00:33:49,419 --> 00:33:50,885
"for winning the lottery,
you know.

639
00:33:50,886 --> 00:33:52,887
you may have a similar chance"
to getting taken out

640
00:33:52,888 --> 00:33:54,524
by an asteroid
in the next 15 minutes."

641
00:33:57,194 --> 00:33:59,363
april 2014.

642
00:33:59,364 --> 00:34:01,865
Scientists make
a shocking announcement --

643
00:34:01,866 --> 00:34:04,233
since the year 2000,

644
00:34:04,234 --> 00:34:08,371
26 asteroids have exploded
in the earth's atmosphere,

645
00:34:08,372 --> 00:34:11,641
each one with the force
of a nuclear blast,

646
00:34:11,642 --> 00:34:15,010
with some up to 40 times
more powerful

647
00:34:15,011 --> 00:34:17,313
than the hiroshima bomb.

648
00:34:17,314 --> 00:34:21,050
And we didn't spot a single one
of them before they struck.

649
00:34:21,051 --> 00:34:24,054
Even if we had the technology

650
00:34:24,055 --> 00:34:26,657
to detect an asteroid
before it hit us,

651
00:34:26,658 --> 00:34:29,592
could we destroy it in time?

652
00:34:29,593 --> 00:34:31,394
The hollywood favorite,
of course, is to go out there

653
00:34:31,395 --> 00:34:33,496
and nuke it,
blow it to smithereens, right?

654
00:34:33,497 --> 00:34:35,865
That could actually work
in the case of some particular,

655
00:34:35,866 --> 00:34:37,601
you know, last-ditch effort

656
00:34:37,602 --> 00:34:39,304
for asteroids
of just the right size.

657
00:34:41,439 --> 00:34:43,141
But a nuclear bomb

658
00:34:43,142 --> 00:34:45,376
could just make a bad situation
worse.

659
00:34:49,047 --> 00:34:50,947
Transforming an asteroid

660
00:34:50,948 --> 00:34:53,751
into large radioactive chunks

661
00:34:53,752 --> 00:34:56,555
that rain down
all over the planet.

662
00:35:02,627 --> 00:35:04,028
But there are also techniques,

663
00:35:04,029 --> 00:35:06,963
like shining a laser
on the asteroid or sunlight,

664
00:35:06,964 --> 00:35:09,166
which would create
an artificial cometary jet,

665
00:35:09,167 --> 00:35:11,503
if you will, would vaporize
some of the water

666
00:35:11,504 --> 00:35:13,403
and the minerals
on the surface of that asteroid

667
00:35:13,404 --> 00:35:16,506
to gently push it off
to the side.

668
00:35:16,507 --> 00:35:19,342
Another fantastic technique,
a very robust one,

669
00:35:19,343 --> 00:35:21,713
is something we call
the gravity tractor.

670
00:35:21,714 --> 00:35:23,349
You just park a spacecraft,

671
00:35:23,350 --> 00:35:25,182
the mass
of a communication satellite,

672
00:35:25,183 --> 00:35:26,885
next to that small asteroid

673
00:35:26,886 --> 00:35:29,588
and use the thrusters
on the spacecraft

674
00:35:29,589 --> 00:35:32,990
to keep it hovering just
off the surface of the asteroid,

675
00:35:32,991 --> 00:35:36,193
and that uses then gravity
between the two as a tow line

676
00:35:36,194 --> 00:35:38,998
to move the asteroid
ever so gently off course.

677
00:35:38,999 --> 00:35:41,131
Right now

678
00:35:41,132 --> 00:35:43,702
these technologies
are still on the drawing board.

679
00:35:43,703 --> 00:35:46,436
If they do become a reality,

680
00:35:46,437 --> 00:35:49,575
we'd still need months or years
to prepare.

681
00:35:54,547 --> 00:35:57,449
Rogue planets, ice ages,

682
00:35:57,450 --> 00:35:59,485
gamma-ray bursts,

683
00:35:59,486 --> 00:36:02,287
volcanic eruptions,

684
00:36:02,288 --> 00:36:04,722
and asteroid strikes.

685
00:36:04,723 --> 00:36:08,226
We've survived the worst
the universe can throw at us,

686
00:36:08,227 --> 00:36:12,497
but our species will still face
extinction.

687
00:36:12,498 --> 00:36:16,904
It's as inevitable
as the sun rising.

688
00:36:31,319 --> 00:36:34,686
In a cosmic battle
to the death,

689
00:36:34,687 --> 00:36:36,756
we are the survivors,

690
00:36:36,757 --> 00:36:40,626
but eventually
the universe will win

691
00:36:40,627 --> 00:36:44,030
and we will face extinction...

692
00:36:44,031 --> 00:36:47,499
Threatened by the very thing
that gives us life --

693
00:36:47,500 --> 00:36:50,939
our creator, the sun.

694
00:36:54,274 --> 00:36:57,043
We orbit
a giant nuclear bomb, the sun,

695
00:36:57,044 --> 00:36:58,477
but, you know,
it's not going to explode.

696
00:36:58,478 --> 00:37:00,213
It's too small to explode,

697
00:37:00,214 --> 00:37:02,715
but what happens with the sun
is that every day,

698
00:37:02,716 --> 00:37:04,416
it's a little bigger
than it was the day before.

699
00:37:04,417 --> 00:37:07,854
Since the sun's birth,

700
00:37:07,855 --> 00:37:12,425
hydrogen has been fusing
into helium in the sun's core.

701
00:37:12,426 --> 00:37:17,063
As the helium accumulates,
the core gets denser.

702
00:37:17,064 --> 00:37:20,367
With 150 million tons of helium

703
00:37:20,368 --> 00:37:23,436
squeezing into the core
every second,

704
00:37:23,437 --> 00:37:26,606
the gas compresses and heats up.

705
00:37:26,607 --> 00:37:30,041
Right now the temperature
inside the sun's core

706
00:37:30,042 --> 00:37:33,213
is 27 million degrees,

707
00:37:33,214 --> 00:37:35,850
and its getting hotter
all the time.

708
00:37:37,518 --> 00:37:39,718
What happens
when you heat up a gas?

709
00:37:39,719 --> 00:37:42,322
It expands, and so that's
what the sun is going to do.

710
00:37:42,323 --> 00:37:47,126
As the sun swells,
it will appear brighter.

711
00:37:47,127 --> 00:37:49,229
In 2 billion years,

712
00:37:49,230 --> 00:37:51,930
the sun will be
about 15% brighter

713
00:37:51,931 --> 00:37:53,365
and that will lead

714
00:37:53,366 --> 00:37:55,302
if the earth remains
in its present orbit

715
00:37:55,303 --> 00:37:58,137
inevitably
to a runaway greenhouse effect.

716
00:37:58,138 --> 00:37:59,572
The oceans will evaporate,

717
00:37:59,573 --> 00:38:01,575
and the surface temperature
of the earth

718
00:38:01,576 --> 00:38:03,711
could easily be a 1,000 degrees.

719
00:38:03,712 --> 00:38:05,177
So, if we don't do anything,

720
00:38:05,178 --> 00:38:07,214
in 2 billion years,
we'll be toast.

721
00:38:10,084 --> 00:38:14,253
If we're still here
on earth, we'll perish.

722
00:38:14,254 --> 00:38:18,691
Other tougher species may find
a way to adapt and survive,

723
00:38:18,692 --> 00:38:21,696
but they'll be living
on borrowed time.

724
00:38:23,830 --> 00:38:25,298
It's gonna fill up the sky.

725
00:38:25,299 --> 00:38:27,233
From horizon to horizon,

726
00:38:27,234 --> 00:38:29,936
the sky will literally be
on fire.

727
00:38:29,937 --> 00:38:32,405
5 billion years from now

728
00:38:32,406 --> 00:38:34,574
The sun runs out of hydrogen

729
00:38:34,575 --> 00:38:38,244
and enters the final
apocalyptic stage of its life,

730
00:38:38,245 --> 00:38:42,081
bloating to 100 times
its current size.

731
00:38:42,082 --> 00:38:47,220
Our life-giving sun
is now an angry, red giant.

732
00:38:47,221 --> 00:38:50,255
The red giant stars are so big

733
00:38:50,256 --> 00:38:52,691
they will actually eat up
their own planets.

734
00:38:52,692 --> 00:38:54,760
We know of the examples
of red giants that go

735
00:38:54,761 --> 00:38:56,595
all the way out to where
the orbit of jupiter is

736
00:38:56,596 --> 00:38:58,097
in our solar system.

737
00:38:58,098 --> 00:38:59,766
The sun will not get
quite that big,

738
00:38:59,767 --> 00:39:01,633
but it'll probably
get about out to mars.

739
00:39:01,634 --> 00:39:04,137
And eventually, in fact,
the sun will be so large

740
00:39:04,138 --> 00:39:07,006
that the earth will be located
inside of the sun,

741
00:39:07,007 --> 00:39:09,943
which certainly won't be
a very pleasant place to be.

742
00:39:09,944 --> 00:39:13,213
The red giant's bloated body

743
00:39:13,214 --> 00:39:17,083
absorbs the earth,
incinerating our planet

744
00:39:17,084 --> 00:39:22,123
until its nothing more than gas
and dust inside a dying star.

745
00:39:27,361 --> 00:39:28,827
The death of the sun

746
00:39:28,828 --> 00:39:32,398
is the ultimate
mass-extinction event.

747
00:39:32,399 --> 00:39:36,668
There's 100% chance
it will happen.

748
00:39:36,669 --> 00:39:41,240
A 100% chance
it will destroy our planet

749
00:39:41,241 --> 00:39:43,310
and any life left on it.

750
00:39:46,513 --> 00:39:48,081
But life on earth may not be

751
00:39:48,082 --> 00:39:50,518
the only life
in the solar system.

752
00:39:52,886 --> 00:39:54,588
As the sun brightens,

753
00:39:54,589 --> 00:39:57,458
you can imagine a wave
of habitability going out.

754
00:39:57,459 --> 00:40:00,726
So right now it's on earth,
it'll go to mars,

755
00:40:00,727 --> 00:40:03,430
and it'll go to jupiter,
and its moons.

756
00:40:03,431 --> 00:40:06,233
Scientists think
jupiter's moon europa

757
00:40:06,234 --> 00:40:08,401
may already harbor alien life

758
00:40:08,402 --> 00:40:12,405
in a deep, liquid ocean
beneath its frozen crust.

759
00:40:12,406 --> 00:40:14,740
But out at jupiter,
it'll be much warmer

760
00:40:14,741 --> 00:40:18,412
but not so warm that
it would destroy everything.

761
00:40:18,413 --> 00:40:21,481
So even when the earth is gone,
if there's life on europa,

762
00:40:21,482 --> 00:40:24,450
it may be able to endure that.

763
00:40:24,451 --> 00:40:27,021
But will our species go on?

764
00:40:27,022 --> 00:40:31,057
Can we survive the loss
of our home planet?

765
00:40:31,058 --> 00:40:32,559
The universe is
like an ecosystem --

766
00:40:32,560 --> 00:40:35,128
living things
are gonna survive

767
00:40:35,129 --> 00:40:37,030
based on the law
of survival of the fittest.

768
00:40:38,665 --> 00:40:41,434
What decides if you're fit
in this universe

769
00:40:41,435 --> 00:40:43,035
is if you're able
to leave your planet

770
00:40:43,036 --> 00:40:45,037
and go out and populate
other planets.

771
00:40:45,038 --> 00:40:48,273
So the only species that
are gonna live on forever

772
00:40:48,274 --> 00:40:49,710
are the ones
that leave their planet.

773
00:40:52,879 --> 00:40:55,148
We can't control the universe,

774
00:40:55,149 --> 00:40:58,284
but we may be able
to control our fate.

775
00:40:58,285 --> 00:40:59,920
Inevitably, in the long term,

776
00:40:59,921 --> 00:41:02,088
the earth is gonna become
uninhabitable.

777
00:41:02,089 --> 00:41:03,690
It's just the way
the universe works.

778
00:41:03,691 --> 00:41:06,992
It wasn't made for us,
it doesn't care that we exist,

779
00:41:06,993 --> 00:41:09,528
and it won't care
when we go away.

780
00:41:09,529 --> 00:41:12,032
The only people
who care about that are us,

781
00:41:12,033 --> 00:41:13,800
and we might be able
to do something about it.

782
00:41:13,801 --> 00:41:17,436
In that sense,
we have a fighting chance.

783
00:41:17,437 --> 00:41:20,907
Our intelligence
is our greatest asset.

784
00:41:20,908 --> 00:41:23,411
It's the end result
of four billion years

785
00:41:23,412 --> 00:41:25,744
of extinction and evolution.

786
00:41:25,745 --> 00:41:28,280
And it may give us a chance
to do something

787
00:41:28,281 --> 00:41:31,651
that no other species
has ever done before --

788
00:41:31,652 --> 00:41:35,021
break the cycle
of creation and destruction

789
00:41:35,022 --> 00:41:37,090
and live on.

790
00:41:37,091 --> 00:41:38,659
Everything that you and i are

791
00:41:38,660 --> 00:41:40,927
is a consequence
of the way the universe works.

792
00:41:40,928 --> 00:41:43,563
The universe is violent,
the universe is dynamic,

793
00:41:43,564 --> 00:41:45,497
it's constantly
pushing us to change.

794
00:41:45,498 --> 00:41:46,699
And here we are,

795
00:41:46,700 --> 00:41:49,101
these incredibly evolved,
interesting creatures.

796
00:41:49,102 --> 00:41:51,804
We're a direct consequence
of the violence,

797
00:41:51,805 --> 00:41:53,674
which, in turn,
was our creation.

798
00:41:53,724 --> 00:41:58,274
Repair and Synchronization by
Easy Subtitles Synchronizer 1.0.0.0