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(male narrator)
The end is coming.
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00:00:07,375 --> 00:00:12,580
But which cosmic catastrophe
will deliver the death blow?
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00:00:14,782 --> 00:00:16,584
Were the Vikings right
to fear
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00:00:16,617 --> 00:00:19,753
the frozen apocalypse
of an endless winter?
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00:00:21,855 --> 00:00:24,192
Did the Buddhists
correctly predict
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00:00:24,225 --> 00:00:27,161
a fiery end
to life on Earth?
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00:00:29,597 --> 00:00:33,467
Or will the thunderous
Christian vision of Armageddon
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00:00:33,501 --> 00:00:36,537
come crashing down
from the stars?
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00:00:38,639 --> 00:00:42,610
Which ancient prophesy
do scientists believe
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00:00:42,643 --> 00:00:46,614
accurately foretells
our doom?
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00:00:46,647 --> 00:00:49,250
And how close are we...
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00:00:49,283 --> 00:00:52,786
To the end of the world?
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00:00:54,755 --> 00:01:00,628
Ancient mysteries,
shrouded in the shadows of time.
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00:01:00,661 --> 00:01:07,301
Now, can they finally be solved
by looking to the heavens?
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00:01:07,335 --> 00:01:12,706
The truth is out there,
hidden among the stars
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in a place we call...
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It's the ultimate fear
for every human being on Earth
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and across time--
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The end of the world.
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00:01:33,661 --> 00:01:37,765
A time when death
is unescapable,
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delivered by fire...
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ice...
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or terrifying forces
from beyond our planet.
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Every civilization
has its own horrific vision.
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(Markley)
Every culture knows about death.
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Every culture has seen
major disasters.
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Destruction, death,
the ending of things
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00:02:02,656 --> 00:02:04,758
really looks like
it's part of the natural order,
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00:02:04,792 --> 00:02:06,527
so it shouldn't be
a surprise to us
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that every culture has
an Armageddon scenario.
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In a lot of mythologies,
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the world ends
by either cold or by fire,
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the real extremes
of weather on the Earth.
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00:02:20,941 --> 00:02:25,846
(narrator)
But which vision of Armageddon
does modern science support?
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How exactly
will the world end?
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00:02:33,687 --> 00:02:36,224
Could it be
the frozen apocalypse,
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feared by the Vikings?
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00:02:41,862 --> 00:02:45,633
It's 535 A.D.,
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and the people
of a Norse village,
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00:02:47,601 --> 00:02:50,238
so used to harsh winters,
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have never seen
anything like this.
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Even the elders can't recall
such a brutal season.
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Spring should be here,
but the winter won't let go.
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Farmers can't plant crops.
Livestock is dying.
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What if winter never ends?
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This truly feels
like the beginning
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of the end of the world.
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It's winters like this
that probably inspired
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the Norse vision
of the apocalypse.
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00:03:26,874 --> 00:03:33,281
They called it Ragnarok,
or the Twilight of the Gods.
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00:03:33,314 --> 00:03:36,284
Even the doomed
pantheon of Norse deities
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was powerless to stop it.
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It meant the rise of monsters
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and the annihilation
of gods and men.
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It starts with Fimbulwinter,
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a killing cold worse than even
a hardened Viking could imagine.
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00:03:54,935 --> 00:03:58,005
(Markley)
The Norse believed
that the end of the world
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00:03:58,038 --> 00:04:01,309
would be heralded
by a three-year mighty winter,
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00:04:01,342 --> 00:04:05,045
following which, the heavens and
the Earth would be destroyed.
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00:04:05,078 --> 00:04:10,651
Perpetual winter--
that's the end.
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(narrator)
Could the end of everything
come in cold
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as the Norse predicted?
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00:04:19,960 --> 00:04:22,062
Looking back
at our planet's history,
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it's not hard to imagine.
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Three times in the Earth's past,
glaciers may have spread
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00:04:30,971 --> 00:04:34,575
to encase the entire planet
in ice and slush,
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like a giant snowball.
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00:04:40,381 --> 00:04:43,984
Now scientists predict
something even more extreme,
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an icy apocalypse
that will put a deep freeze
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not just on Earth,
but the entire universe.
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00:04:54,862 --> 00:04:57,798
And this frigid end
was set into motion
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at the very beginning...
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00:05:02,736 --> 00:05:05,706
with the rapid expansion
of the universe
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00:05:05,739 --> 00:05:09,910
after the Big Bang.
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00:05:09,943 --> 00:05:12,780
(Johnson)
We've known for a long time
that the universe is expanding,
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00:05:12,813 --> 00:05:15,583
and it's been cooling down
as it expands
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since the Big Bang,
13.8 billion years ago.
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00:05:19,820 --> 00:05:21,689
(narrator)
Heat is energy,
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and the universe has
only so much of it to go around.
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As the universe expands,
the energy gets diluted,
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00:05:29,863 --> 00:05:34,101
and everything starts
to cool.
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Scientists once believed that
the expansion of the universe
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would eventually slow down,
or even reverse
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00:05:41,108 --> 00:05:46,680
as cosmic gravity
tapped the brakes.
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But then...
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they discovered that
some unseen, unexplained force
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was out-dueling gravity,
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accelerating us toward
a truly chilling Armageddon.
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(Johnson)
In the late '90s,
we discovered
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that the universe is actually
accelerating the expansion.
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00:06:08,736 --> 00:06:11,739
This has put a new wrinkle
on the scenarios
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about how the universe
might end.
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(Alex Filippenko)
I was a member of both teams
that were studying
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the expansion history
of the universe,
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and when I saw the results,
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that the universe is
accelerating in its expansion,
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I was just
completely stunned.
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It was a shocking result.
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Essentially,
no one had expected this.
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(narrator)
What's out there,
stronger than gravity,
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that's pulling the universe
apart?
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Incredibly, nobody knows.
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Astronomers simply call it
dark energy.
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(Johnson)
We're still not sure
exactly what dark energy is.
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It may be an intrinsic energy
that space itself has
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that actually makes it
prefer to get larger.
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00:07:05,225 --> 00:07:07,961
This rubber band has
what we call elasticity.
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00:07:07,995 --> 00:07:09,963
If I pull on it
and make it larger,
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00:07:09,997 --> 00:07:12,866
it actually tries
to pull back
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and restore its shape
to a smaller size.
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Imagine the reverse of that,
where instead,
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you have something
that likes to increase its size.
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That's the sort of physics
that might underlie dark energy,
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where it actually is driving
the acceleration
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of the whole expansion
of the universe.
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(narrator)
One thing we do know
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about the mysterious
dark energy
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is that it makes up
around 70% of the universe.
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(Howell)
That's crazy, that we don't know
about most of the universe.
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We're the weird things
in the universe.
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00:07:49,269 --> 00:07:51,972
(narrator)
So how will dark energy drive us
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00:07:52,005 --> 00:07:55,609
toward a frigid
cosmic Armageddon?
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Little by little,
but faster and faster,
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it will move everything
away from everything else.
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00:08:03,183 --> 00:08:05,753
And as clusters of galaxies
spread,
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00:08:05,786 --> 00:08:10,924
the expanding universe
will get colder.
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00:08:10,958 --> 00:08:12,760
(Danly)
When we look
out in the universe,
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00:08:12,793 --> 00:08:16,229
we see that all galaxies appear
to be moving away from us.
129
00:08:18,131 --> 00:08:20,868
(narrator)
If we could view the universe
from a different galaxy,
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00:08:20,901 --> 00:08:23,136
we'd see the same thing.
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00:08:23,170 --> 00:08:25,706
How can all the galaxies
be moving
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00:08:25,739 --> 00:08:28,909
away from all the other
galaxies?
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00:08:28,942 --> 00:08:31,278
(Danly)
One way to think
about the expanding universe
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00:08:31,311 --> 00:08:35,082
is to think about an expanding
loaf of raisin bread.
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00:08:35,115 --> 00:08:40,220
The raisins are galaxies,
and the dough is the universe.
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00:08:40,253 --> 00:08:41,855
The raisin bread
is expanding
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00:08:41,889 --> 00:08:43,991
because the baking soda
in the bread
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is causing it to expand,
kind of like dark energy.
139
00:08:48,996 --> 00:08:51,131
(narrator)
The baking soda
is expanding the dough
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00:08:51,164 --> 00:08:52,933
and spreading the raisins,
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00:08:52,966 --> 00:08:55,736
just like dark energy
is expanding the universe
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00:08:55,769 --> 00:09:02,109
and moving all the galaxies
farther and farther apart.
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00:09:02,142 --> 00:09:06,213
As the universe expands,
its energy gets diluted.
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00:09:06,246 --> 00:09:11,118
There won't be enough to build
new stars as old ones die.
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00:09:11,151 --> 00:09:15,689
With no stars to generate heat
and no new stars being born,
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00:09:15,723 --> 00:09:20,227
the universe marches
toward a bitterly cold end,
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an ice age that affects
not just one planet,
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but the entire universe.
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00:09:27,267 --> 00:09:30,604
In a universe that's
expanding eternally,
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00:09:30,638 --> 00:09:32,906
it's getting colder and colder
with time.
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00:09:32,940 --> 00:09:36,944
It's as though you're entering
a long, extended--
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Indeed, eternal winter.
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00:09:41,782 --> 00:09:44,384
(narrator)
A Nordic nightmare,
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00:09:44,417 --> 00:09:48,088
the mighty winter
that heralds Armageddon.
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But is that truly the end?
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00:09:53,927 --> 00:09:56,029
Or does dark energy
have the power
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to do something
even more destructive?
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It's possible
that the mysterious force
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00:10:02,703 --> 00:10:05,839
could grow stronger
over time.
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00:10:05,873 --> 00:10:08,241
(Filippenko)
In that case, eventually,
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clusters of galaxies
will get ripped apart,
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00:10:10,410 --> 00:10:12,680
then galaxies
will be ripped apart,
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then planetary systems
will be ripped apart,
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planets, us, and even
the atoms of which we are made.
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00:10:22,089 --> 00:10:23,256
(narrator)
It won't stop
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until nothing's left
to tear apart.
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00:10:26,827 --> 00:10:30,430
Scientists call this
"the Big Rip."
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00:10:30,463 --> 00:10:33,100
(Filippenko)
If the Big Rip were to occur,
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it would be
the ultimate Armageddon.
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Everything ripped apart.
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Wow, doesn't get
any worse than that.
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(narrator)
The Big Rip is one vision
of Armageddon
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on a universal scale.
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00:10:47,848 --> 00:10:52,853
But even if the universe
is fated to end in bitter cold,
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is the Earth itself destined
to die much sooner,
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not in cold, but fire?
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00:11:06,066 --> 00:11:09,269
(narrator)
Ancient prophesies
foretell Armageddon,
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but few agree
how it will come to pass.
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00:11:17,044 --> 00:11:21,715
The ancient Norse predicted
the beginning of the end
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00:11:21,749 --> 00:11:24,718
in bone-cracking cold,
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00:11:24,752 --> 00:11:27,254
a prophecy
that our expanding universe
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might make happen.
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00:11:31,158 --> 00:11:37,731
The Norse weren't the only ones
to fear a wintery Armageddon.
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It's the 16th century,
in what is now Mexico.
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00:11:48,942 --> 00:11:51,879
A prisoner captured
from a recent battle
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is dragged out
and held down on a slab.
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00:11:56,349 --> 00:12:00,153
The Aztec priest
raises an obsidian knife
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00:12:00,187 --> 00:12:02,422
and slices open
the prisoner's chest...
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Aah!
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00:12:04,191 --> 00:12:06,894
(narrator)
Ripping out
the still-beating heart
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00:12:06,927 --> 00:12:11,064
and raising it triumphantly
to the sun.
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00:12:11,098 --> 00:12:16,369
He holds the fate of the planet
in his bloodstained hands.
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00:12:16,403 --> 00:12:19,139
The Aztecs believed
they had a duty
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to feed the sun
through blood sacrifice,
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00:12:22,575 --> 00:12:25,312
giving it the strength
to make its daily journey
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across the sky.
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00:12:29,449 --> 00:12:31,484
If they failed to feed it,
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00:12:31,518 --> 00:12:36,489
they believed
it would disappear.
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00:12:40,060 --> 00:12:42,529
But what would
really happen
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00:12:42,562 --> 00:12:47,334
if one dark morning,
the sun vanished?
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00:12:47,367 --> 00:12:51,204
(Filippenko)
If the sun were to suddenly
disappear from the universe,
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00:12:51,238 --> 00:12:53,340
then there'd be no gravity
pulling the Earth
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00:12:53,373 --> 00:12:55,508
toward the sun anymore,
and that means
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00:12:55,542 --> 00:12:58,478
that the Earth would go
flying off in space
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00:12:58,511 --> 00:13:00,113
in a straight line
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00:13:00,147 --> 00:13:02,515
along the direction
it was moving
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00:13:02,549 --> 00:13:06,319
at the instant
that the sun disappeared.
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00:13:06,353 --> 00:13:10,824
(narrator)
This would doom the Earth
to a frozen Armageddon
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00:13:10,858 --> 00:13:15,028
that recalls
the deadly Norse winter.
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00:13:15,062 --> 00:13:18,565
Fortunately for us,
our sun won't magically vanish,
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00:13:18,598 --> 00:13:20,533
but what it will do
is evolve.
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00:13:23,003 --> 00:13:28,141
(narrator)
Evolve...and then die.
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00:13:28,175 --> 00:13:33,246
Will this mean a cold,
dark death for the Earth,
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00:13:33,280 --> 00:13:34,581
or something more like
215
00:13:34,614 --> 00:13:38,485
the ancient Buddhists
envisioned?
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00:13:38,518 --> 00:13:40,087
In the Buddhist
apocalypse,
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00:13:40,120 --> 00:13:45,325
seven suns will blaze
across the sky.
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00:13:45,358 --> 00:13:47,394
When the sixth sun rises,
219
00:13:47,427 --> 00:13:50,563
it will bake the Earth
like pottery.
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00:13:50,597 --> 00:13:55,168
Then, according to the prophesy,
"A seventh sun appears.
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00:13:55,202 --> 00:13:57,938
"The mountains
fire and blaze,
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00:13:57,971 --> 00:14:00,941
"and of this great earth,
when consumed,
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00:14:00,974 --> 00:14:05,979
neither ashes nor soot
remains."
224
00:14:09,082 --> 00:14:12,252
Although there aren't
multiple suns in our future,
225
00:14:12,285 --> 00:14:16,990
were the Buddhists right
that Earth will die by fire?
226
00:14:17,024 --> 00:14:23,030
Will we be burned into oblivion
by our dying sun?
227
00:14:23,063 --> 00:14:27,434
At 5 billion years old,
the sun has reached middle age
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00:14:27,467 --> 00:14:30,170
and its days are numbered.
229
00:14:30,203 --> 00:14:35,108
Scientists have a clear idea
of how it will die,
230
00:14:35,142 --> 00:14:40,914
and it's all driven
by pressure.
231
00:14:40,948 --> 00:14:43,150
The heat of nuclear fusion
in the core
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00:14:43,183 --> 00:14:45,352
creates enormous
outward pressure
233
00:14:45,385 --> 00:14:47,454
that should
blow the sun apart,
234
00:14:47,487 --> 00:14:49,022
but instead,
it's countered
235
00:14:49,056 --> 00:14:53,460
by the equal force
of gravity pushing in.
236
00:14:56,463 --> 00:14:59,933
Balancing inward
and outward pressure
237
00:14:59,967 --> 00:15:04,171
is something every diver
stakes his life on.
238
00:15:04,204 --> 00:15:06,106
(Howell)
The reason we
have life on earth
239
00:15:06,139 --> 00:15:08,441
is because the sun is burning
through its nuclear fuel.
240
00:15:08,475 --> 00:15:10,443
it's an equilibrium.
241
00:15:10,477 --> 00:15:13,413
It's a balance between gravity
trying to crush it down
242
00:15:13,446 --> 00:15:16,316
and pressure holding it up.
243
00:15:16,349 --> 00:15:20,988
(narrator)
So what happens
when equilibrium is lost?
244
00:15:21,021 --> 00:15:22,455
On the surface of the Earth,
245
00:15:22,489 --> 00:15:27,160
human beings are in equilibrium,
just like the sun.
246
00:15:27,194 --> 00:15:31,364
The atmosphere presses on us
at 15 pounds per square inch,
247
00:15:31,398 --> 00:15:34,267
or one atmosphere.
248
00:15:34,301 --> 00:15:36,736
We don't feel it
because the air inside us
249
00:15:36,769 --> 00:15:40,307
is pushing out
at the same pressure.
250
00:15:43,043 --> 00:15:45,478
But take an object designed
to be in equilibrium
251
00:15:45,512 --> 00:15:49,349
on the surface,
and bring it underwater,
252
00:15:49,382 --> 00:15:51,451
and you start to see
what happens
253
00:15:51,484 --> 00:15:55,055
when equilibrium is lost.
254
00:15:55,088 --> 00:15:56,323
(Howell)
I want to demonstrate
255
00:15:56,356 --> 00:16:00,193
what a small amount
of atmospheric pressure
256
00:16:00,227 --> 00:16:04,297
can do to this metal can.
257
00:16:04,331 --> 00:16:07,267
As we're descending,
258
00:16:07,300 --> 00:16:11,238
we're already seeing
effects of this can.
259
00:16:11,271 --> 00:16:13,373
Check it out.
260
00:16:13,406 --> 00:16:20,147
The can is starting to bend,
and we're only at 15 feet.
261
00:16:20,180 --> 00:16:24,217
I'm pretty surprised
that we're starting to see
262
00:16:24,251 --> 00:16:28,455
the effects of pressure
at only 15 feet.
263
00:16:28,488 --> 00:16:31,158
I dive 15 feet all the time,
and I didn't know
264
00:16:31,191 --> 00:16:35,428
I was exerting these kinds
of forces on my body.
265
00:16:36,763 --> 00:16:40,167
Now we're finally
at 33 feet.
266
00:16:40,200 --> 00:16:43,070
That's double
atmospheric pressure.
267
00:16:43,103 --> 00:16:46,606
We totally crushed our can.
268
00:16:46,639 --> 00:16:49,142
It's pretty obvious
that when you have
269
00:16:49,176 --> 00:16:52,312
twice the amount of pressure
on the outside of the can,
270
00:16:52,345 --> 00:16:58,218
what's on the inside, our can,
just can't survive.
271
00:16:58,251 --> 00:17:02,655
(narrator)
So what will drive the sun
out of equilibrium?
272
00:17:02,689 --> 00:17:07,460
And what will this mean
for our planet?
273
00:17:07,494 --> 00:17:10,363
(Lucianne Walkowicz)
The sun's lifetime
is mostly governed
274
00:17:10,397 --> 00:17:13,066
by how much fuel
it has in its core
275
00:17:13,100 --> 00:17:16,069
versus the force of gravity
of its own matter
276
00:17:16,103 --> 00:17:17,604
pushing inward.
277
00:17:17,637 --> 00:17:19,772
Over time,
stars like our sun,
278
00:17:19,806 --> 00:17:23,210
which fuse hydrogen into helium
in their cores,
279
00:17:23,243 --> 00:17:26,146
eventually start
to run out of fuel, and enter
280
00:17:26,179 --> 00:17:29,382
a period of time where they
go through these death throes.
281
00:17:29,416 --> 00:17:31,684
(narrator)
As the sun runs out of fuel,
282
00:17:31,718 --> 00:17:35,188
gravity will keep pulling
the core tighter.
283
00:17:35,222 --> 00:17:36,623
But as the core shrinks,
284
00:17:36,656 --> 00:17:39,326
it will heat
the surrounding layers of gas,
285
00:17:39,359 --> 00:17:44,231
causing hydrogen and helium
to fuse even faster than before.
286
00:17:44,264 --> 00:17:47,200
The extra energy released
will increase the pressure
287
00:17:47,234 --> 00:17:50,203
on the outer layer
of the sun.
288
00:17:50,237 --> 00:17:54,541
(Filippenko)
That extra energy will push
on the outer layers of the sun,
289
00:17:54,574 --> 00:17:58,411
causing them to expand,
becoming big.
290
00:17:58,445 --> 00:18:00,413
We call this a red giant.
291
00:18:02,349 --> 00:18:04,217
(narrator)
The core will keep contracting
292
00:18:04,251 --> 00:18:08,488
while its outer layer
grows bigger and brighter.
293
00:18:08,521 --> 00:18:11,458
(Filippenko)
The sun will become so bright
and so big
294
00:18:11,491 --> 00:18:13,893
that the Earth might actually
find itself
295
00:18:13,926 --> 00:18:16,429
inside the sun for a while.
296
00:18:16,463 --> 00:18:18,231
That would be Armageddon.
297
00:18:19,666 --> 00:18:22,302
(narrator)
The Earth will be incinerated,
298
00:18:22,335 --> 00:18:28,641
lifeless, but still a planet
after the sun gradually cools.
299
00:18:28,675 --> 00:18:31,511
(Filippenko)
The sun will fade away,
300
00:18:31,544 --> 00:18:34,281
and then the Earth
will just keep on orbiting
301
00:18:34,314 --> 00:18:41,654
a very dim, ever dimmer lump
that remains from today's sun.
302
00:18:43,656 --> 00:18:48,595
(narrator)
The dying sun will trigger
our own infernal Armageddon,
303
00:18:48,628 --> 00:18:55,335
a blazing, Buddhist finale
before eternal Aztec winter.
304
00:18:55,368 --> 00:18:57,937
Or life on Earth
could be finished
305
00:18:57,970 --> 00:19:00,173
long before that happens,
306
00:19:00,207 --> 00:19:03,710
and much, much sooner
than we expect.
307
00:19:09,582 --> 00:19:11,651
(narrator)
Ancient visions predict
308
00:19:11,684 --> 00:19:16,656
that Armageddon is inevitable
some distant day.
309
00:19:18,991 --> 00:19:23,696
But what if
our day of reckoning...
310
00:19:23,730 --> 00:19:27,300
Is today?
311
00:19:29,269 --> 00:19:33,406
Chelyabinsk, Russia,
February, 2013.
312
00:19:36,343 --> 00:19:38,611
Residents see a fireball
313
00:19:38,645 --> 00:19:43,616
blaze across the sky,
seconds before it detonates.
314
00:19:43,650 --> 00:19:46,419
[boom]
315
00:19:46,453 --> 00:19:49,422
[glass breaking
and car alarms blaring]
316
00:19:51,691 --> 00:19:56,429
The asteroid arrives
unannounced...
317
00:19:56,463 --> 00:19:59,399
leaving no time to react
or take cover.
318
00:19:59,432 --> 00:20:01,834
[boom]
319
00:20:01,868 --> 00:20:03,836
(Howell)
It exploded in the atmosphere
320
00:20:03,870 --> 00:20:07,540
with a force
about 20 times greater
321
00:20:07,574 --> 00:20:11,778
than the atomic bomb
dropped on Hiroshima.
322
00:20:11,811 --> 00:20:14,281
Luckily, it was high enough
in the atmosphere
323
00:20:14,314 --> 00:20:16,416
that the atmosphere absorbed
most of the energy.
324
00:20:16,449 --> 00:20:18,385
[boom]
325
00:20:20,587 --> 00:20:24,524
(Filippenko)
That object was only
about 20 yards in diameter.
326
00:20:24,557 --> 00:20:26,293
That was a small rock,
327
00:20:26,326 --> 00:20:28,861
yet the explosion caused
widespread damage,
328
00:20:28,895 --> 00:20:33,633
lots of imploding glass
that actually hurt 1,500 people,
329
00:20:33,666 --> 00:20:35,602
many buildings damaged.
330
00:20:37,804 --> 00:20:41,308
(narrator)
A larger asteroid or comet
331
00:20:41,341 --> 00:20:47,580
could cause
mass extinction on Earth...
332
00:20:47,614 --> 00:20:51,951
leaving the planet intact,
but lifeless.
333
00:20:56,589 --> 00:20:59,759
The idea of an Earth
devoid of people
334
00:20:59,792 --> 00:21:02,662
is something
the ancients feared.
335
00:21:02,695 --> 00:21:04,997
(Markley)
When they talk
about Armageddon scenarios,
336
00:21:05,031 --> 00:21:07,467
it's wiping away
the living organisms
337
00:21:07,500 --> 00:21:09,869
that are here now
and starting again.
338
00:21:09,902 --> 00:21:12,339
At least that's
the usual scenario.
339
00:21:12,372 --> 00:21:16,576
So the world will still be here,
the heavens will still be there.
340
00:21:16,609 --> 00:21:20,313
We won't.
341
00:21:20,347 --> 00:21:22,549
(narrator)
But the Ancients had
different visions
342
00:21:22,582 --> 00:21:26,853
of how humanity
would be wiped out.
343
00:21:26,886 --> 00:21:30,623
Muslim writings foresaw
the end of the world,
344
00:21:30,657 --> 00:21:33,693
signaled by landslides
345
00:21:33,726 --> 00:21:37,564
and a cloud of smoke...
346
00:21:37,597 --> 00:21:42,435
engulfing the planet.
347
00:21:42,469 --> 00:21:48,375
The Romans envisioned Armageddon
by fire or flood--or both--
348
00:21:48,408 --> 00:21:52,445
when the time comes
to cleanse the Earth.
349
00:21:52,479 --> 00:21:55,982
The Roman philosopher Seneca
wrote,
350
00:21:56,015 --> 00:21:58,985
"Water and fire
bring about creation,
351
00:21:59,018 --> 00:22:01,120
"they bring about
destruction,
352
00:22:01,153 --> 00:22:03,556
"so when the world
decides to change,
353
00:22:03,590 --> 00:22:06,426
"it sends the sea
crashing down on us,
354
00:22:06,459 --> 00:22:10,530
or causes extinction
by heat and fire."
355
00:22:10,563 --> 00:22:13,366
(Markley)
This sounds a lot like
the kind of thing you would get
356
00:22:13,400 --> 00:22:15,868
when you got a meteorite
slamming into the oceans,
357
00:22:15,902 --> 00:22:19,138
a global tsunami,
nuclear winter,
358
00:22:19,171 --> 00:22:21,674
the end of the world.
359
00:22:21,708 --> 00:22:24,744
(narrator)
Perhaps the most frightening
vision of Armageddon
360
00:22:24,777 --> 00:22:28,415
comes from Christianity.
361
00:22:28,448 --> 00:22:32,452
The Book of Revelation describes
all manner of destruction
362
00:22:32,485 --> 00:22:36,122
raining down on Earth.
363
00:22:36,155 --> 00:22:39,058
"And there were voices,
and thunders, and lightnings;
364
00:22:39,091 --> 00:22:42,028
"and there was
a great earthquake,
365
00:22:42,061 --> 00:22:46,065
"not seen
since men were upon the Earth.
366
00:22:46,098 --> 00:22:49,168
"He maketh fire
come down from heaven,
367
00:22:49,201 --> 00:22:56,075
and the sun became black,
and the moon became as blood."
368
00:22:58,711 --> 00:23:00,913
It's a terrifying vision,
369
00:23:00,947 --> 00:23:07,086
but can such a global cataclysm
really happen?
370
00:23:09,188 --> 00:23:11,458
(Markley)
The Christian scenario
for the end of the world
371
00:23:11,491 --> 00:23:17,864
involves raging seas, famine,
pestilence, fire, earthquakes.
372
00:23:17,897 --> 00:23:19,599
These are all
of the kind of things
373
00:23:19,632 --> 00:23:22,201
that you could have if you were
suffering multiple impacts.
374
00:23:22,234 --> 00:23:25,672
Perhaps multiple meteorites,
a comet that's fragmented
375
00:23:25,705 --> 00:23:27,907
and slammed into the Earth.
376
00:23:27,940 --> 00:23:31,077
This kind of thing could easily
happen in real life.
377
00:23:33,680 --> 00:23:39,151
(Howell)
With an asteroid impact, there's
all kinds of other side effects.
378
00:23:39,185 --> 00:23:41,721
The Earth could get
increased vulcanism,
379
00:23:41,754 --> 00:23:46,759
increased earthquakes,
the ocean could acidify.
380
00:23:46,793 --> 00:23:49,195
(narrator)
Anything not killed immediately
381
00:23:49,228 --> 00:23:52,899
might die slowly.
382
00:23:52,932 --> 00:23:56,603
(Filippenko)
The entire food chain
would be disrupted.
383
00:23:56,636 --> 00:24:00,740
Many or most species of life
on Earth would perish--
384
00:24:00,773 --> 00:24:06,646
a global mass extinction,
a real Armageddon.
385
00:24:09,181 --> 00:24:12,719
(narrator)
The sudden meteorite explosion
in Chelyabinsk
386
00:24:12,752 --> 00:24:15,555
put the world on notice.
387
00:24:15,588 --> 00:24:18,891
(Filippenko)
There are a lot of asteroids
and other big rocks
388
00:24:18,925 --> 00:24:21,628
in the solar system
just kind of flying around,
389
00:24:21,661 --> 00:24:26,899
and most of them are between
the orbits of Mars and Jupiter,
390
00:24:26,933 --> 00:24:30,136
but some of them
cross Earth's orbit,
391
00:24:30,169 --> 00:24:35,808
and so eventually,
they can slam into the Earth.
392
00:24:35,842 --> 00:24:38,578
[huge explosion]
393
00:24:38,611 --> 00:24:43,215
(narrator)
How do we know?
394
00:24:43,249 --> 00:24:48,087
Earth's battered past is carved
into the face of the moon.
395
00:24:52,659 --> 00:24:56,529
(Howell)
Over the Earth's history,
it's been bombarded by meteors,
396
00:24:56,563 --> 00:25:00,166
and one way we can tell
is just by looking at the moon.
397
00:25:00,199 --> 00:25:03,169
There are craters everywhere,
and they aren't eroded
398
00:25:03,202 --> 00:25:06,238
by the water and the air
like they are on the Earth,
399
00:25:06,272 --> 00:25:08,675
so you can look up
and see a fossil record
400
00:25:08,708 --> 00:25:13,312
of all of the impacts
near Earth.
401
00:25:13,345 --> 00:25:16,649
(narrator)
Most scientists believe
that an asteroid or comet
402
00:25:16,683 --> 00:25:18,651
measuring 6 miles across
403
00:25:18,685 --> 00:25:23,155
killed off the dinosaurs
65 million years ago,
404
00:25:23,189 --> 00:25:27,226
but few people realize
that wasn't the biggest impact
405
00:25:27,259 --> 00:25:31,731
to ever strike the Earth.
406
00:25:34,233 --> 00:25:38,771
In what is now South Africa,
an asteroid slams into the Earth
407
00:25:38,805 --> 00:25:43,175
at around
33,000 miles per hour,
408
00:25:43,209 --> 00:25:48,581
blowing out a crater
almost the size of Connecticut.
409
00:25:48,615 --> 00:25:50,316
2 billion years later,
410
00:25:50,349 --> 00:25:55,688
the Vredefort Impact Crater
remains to tell the tale.
411
00:25:55,722 --> 00:25:58,257
Luckily, that happened
billions of years ago,
412
00:25:58,290 --> 00:26:02,629
but if one were to happen today,
it would end all life on Earth.
413
00:26:07,900 --> 00:26:11,671
(narrator)
Is there another large rock
out there,
414
00:26:11,704 --> 00:26:13,339
hurtling through space
415
00:26:13,372 --> 00:26:16,275
with Armageddon
written all over it?
416
00:26:16,308 --> 00:26:18,277
Probably.
417
00:26:18,310 --> 00:26:21,047
And if an asteroid
doesn't get us,
418
00:26:21,080 --> 00:26:23,716
we might find ourselves
in the crosshairs
419
00:26:23,750 --> 00:26:26,118
of a deep-space death beam.
420
00:26:31,724 --> 00:26:33,259
(narrator)
The Christian vision
of Armageddon
421
00:26:33,292 --> 00:26:37,697
foretells a worldwide apocalypse
delivered in thunder,
422
00:26:37,730 --> 00:26:42,835
earthquakes, fire,
and brimstone.
423
00:26:42,869 --> 00:26:45,805
And frighteningly,
modern science thinks
424
00:26:45,838 --> 00:26:47,940
this kind of global cataclysm
425
00:26:47,974 --> 00:26:51,811
could actually be
in Earth's future,
426
00:26:51,844 --> 00:26:55,682
delivered by a single event--
427
00:26:55,715 --> 00:27:00,720
the impact
of a near-earth asteroid.
428
00:27:04,724 --> 00:27:06,158
(Walkowicz)
The discovery
of near Earth asteroids
429
00:27:06,192 --> 00:27:08,728
is a major priority--
430
00:27:08,761 --> 00:27:11,864
not only for scientists,
but also for our government--
431
00:27:11,898 --> 00:27:14,767
where we'd like to know
how many are out there,
432
00:27:14,801 --> 00:27:18,705
how big they are, and how likely
they are to impact Earth.
433
00:27:21,073 --> 00:27:25,044
(narrator)
Spotting a threatening asteroid
is one thing.
434
00:27:25,077 --> 00:27:29,916
Heading off asteroid Armageddon
is another.
435
00:27:29,949 --> 00:27:33,686
(Filippenko)
Detecting an asteroid
days or hours before it hits
436
00:27:33,720 --> 00:27:38,024
doesn't give us many choices
for deflecting it.
437
00:27:38,057 --> 00:27:42,929
We need a long time scale.
We need early detection.
438
00:27:42,962 --> 00:27:46,432
That's the key.
439
00:27:46,465 --> 00:27:48,701
(narrator)
If we can intercept the asteroid
440
00:27:48,735 --> 00:27:50,236
in time,
we might be able
441
00:27:50,269 --> 00:27:54,240
to gently nudge it
out of the way with rockets,
442
00:27:54,273 --> 00:27:59,178
or, as some suggest,
sunbeams...
443
00:27:59,211 --> 00:28:03,983
and a well-aimed paintball.
444
00:28:04,016 --> 00:28:08,721
Just as dark rooftops in the sun
get hotter than light ones,
445
00:28:08,755 --> 00:28:12,124
changing an asteroid's color
can change its temperature
446
00:28:12,158 --> 00:28:14,994
and its direction.
447
00:28:15,027 --> 00:28:17,930
(Filippenko)
By painting it either with white
or silver paint
448
00:28:17,964 --> 00:28:22,735
or with a very dark black paint,
that changes the degree
449
00:28:22,769 --> 00:28:27,239
to which light from the sun
is either reflected or absorbed.
450
00:28:27,273 --> 00:28:29,809
That will
ever so slightly change
451
00:28:29,842 --> 00:28:32,745
the trajectory
of the asteroid.
452
00:28:32,779 --> 00:28:35,514
Whenever you reflect light
or absorb light,
453
00:28:35,547 --> 00:28:39,018
that changes
the motion of the object
454
00:28:39,051 --> 00:28:43,355
that's reflecting
or absorbing the light.
455
00:28:43,389 --> 00:28:45,992
(narrator)
With vigilance and technology,
456
00:28:46,025 --> 00:28:49,762
we might be able
to avert Armageddon,
457
00:28:49,796 --> 00:28:54,166
at least for a while.
458
00:28:54,200 --> 00:28:56,402
But asteroids aren't
the only threat
459
00:28:56,435 --> 00:28:59,972
that can destroy the planet
without warning.
460
00:29:03,175 --> 00:29:06,112
(narrator)
On April 27, 2013,
461
00:29:06,145 --> 00:29:09,248
scientists at observatories
around the world
462
00:29:09,281 --> 00:29:13,119
are shocked
when NASA's Swift satellite
463
00:29:13,152 --> 00:29:17,489
detects a monstrous dagger
of deadly radiation
464
00:29:17,523 --> 00:29:22,061
hurtling through space
near the speed of light.
465
00:29:22,094 --> 00:29:24,163
It's a gamma ray burst,
466
00:29:24,196 --> 00:29:27,566
a death beam
for anything in its path,
467
00:29:27,599 --> 00:29:30,102
and this one
was closer to the Earth
468
00:29:30,136 --> 00:29:34,206
than anyone had ever seen.
469
00:29:35,541 --> 00:29:38,244
All light,
whether it's lamp light,
470
00:29:38,277 --> 00:29:41,948
infrared light,
radio waves, or X-rays,
471
00:29:41,981 --> 00:29:45,284
are part
of the electromagnetic spectrum.
472
00:29:45,317 --> 00:29:48,087
Gamma rays are a kind
of high-energy light
473
00:29:48,120 --> 00:29:53,192
that's much, much stronger
than X-rays.
474
00:29:53,225 --> 00:29:56,428
(Filippenko)
Gamma ray bursts are thought
to release more energy
475
00:29:56,462 --> 00:29:59,165
than any other single events
in the universe
476
00:29:59,198 --> 00:30:01,133
other than the Big Bang,
477
00:30:01,167 --> 00:30:02,969
the birth of the universe
itself.
478
00:30:03,002 --> 00:30:08,040
They release
gargantuan amounts of energy.
479
00:30:08,074 --> 00:30:11,844
(Johnson)
It's interesting to speculate
about what must be happening
480
00:30:11,878 --> 00:30:15,047
to any habitable planets
that are in the neighborhood
481
00:30:15,081 --> 00:30:16,949
of such gamma ray bursts.
482
00:30:16,983 --> 00:30:20,619
They must be bathed in a huge
amount of gamma radiation,
483
00:30:20,652 --> 00:30:22,621
which means that probably
it would be
484
00:30:22,654 --> 00:30:26,458
somewhat cataclysmic for life
neighboring such an event.
485
00:30:33,032 --> 00:30:37,436
(narrator)
So far, it appears the Earth
has been mainly spared,
486
00:30:37,469 --> 00:30:42,141
or at least
dodged the worst of it.
487
00:30:42,174 --> 00:30:45,277
(Howell)
We see gamma ray bursts
at a rate of about one a day
488
00:30:45,311 --> 00:30:48,447
in the universe, and sometimes,
they're so powerful,
489
00:30:48,480 --> 00:30:52,151
they even affect
the Earth's atmosphere.
490
00:30:52,184 --> 00:30:53,585
(Filippenko)
They can be seen easily
491
00:30:53,619 --> 00:30:55,888
from billions of light years
away,
492
00:30:55,922 --> 00:30:59,225
and if the jet is pointing
toward Earth
493
00:30:59,258 --> 00:31:02,194
and the gamma ray burst
is sufficiently nearby,
494
00:31:02,228 --> 00:31:06,065
then that can spell doom
for much of life on Earth.
495
00:31:09,101 --> 00:31:14,206
(narrator)
What could cause
these megablasts?
496
00:31:14,240 --> 00:31:17,944
(Filippenko)
Gamma ray bursts
are thought to be
497
00:31:17,977 --> 00:31:22,481
hyper-energetic explosions
of extremely massive stars.
498
00:31:24,583 --> 00:31:28,620
(narrator)
When these massive, spinning
stars suddenly collapse,
499
00:31:28,654 --> 00:31:34,393
their last gasp
is a gamma ray burst.
500
00:31:36,628 --> 00:31:39,098
Gamma ray bursts get
their enormous energy
501
00:31:39,131 --> 00:31:40,666
ultimately from gravity.
502
00:31:40,699 --> 00:31:43,635
A gravity well like this one
can help us understand
503
00:31:43,669 --> 00:31:47,406
what's happening on the inside
of massive stars when they die.
504
00:31:47,439 --> 00:31:49,508
The shape
of this gravity well
505
00:31:49,541 --> 00:31:51,577
illustrates
the strength of gravity
506
00:31:51,610 --> 00:31:54,546
around the central mass
of a star.
507
00:31:54,580 --> 00:31:58,684
When material falls
into a collapsing, massive star,
508
00:31:58,717 --> 00:32:02,154
it spirals around
until it finally falls
509
00:32:02,188 --> 00:32:05,457
into the center,
forming a black hole.
510
00:32:05,491 --> 00:32:08,194
As it does this,
enormous jets of energy
511
00:32:08,227 --> 00:32:12,031
are released
as a gamma ray burst.
512
00:32:12,064 --> 00:32:17,436
(narrator)
Where that gamma beam points is
like a game of Russian roulette,
513
00:32:17,469 --> 00:32:23,542
and if the beam strikes Earth,
it's game over.
514
00:32:23,575 --> 00:32:28,080
It might be the most agonizing
Armageddon of them all.
515
00:32:34,586 --> 00:32:37,189
(narrator)
The ancients have foreseen
Armageddon
516
00:32:37,223 --> 00:32:41,227
in all its terrible guises--
517
00:32:41,260 --> 00:32:44,430
by fire or water,
518
00:32:44,463 --> 00:32:49,135
by ice...
or cataclysm.
519
00:32:49,168 --> 00:32:55,241
But gamma ray bursts defy
even their vivid imaginations.
520
00:32:55,274 --> 00:32:56,708
The deep space death beam
521
00:32:56,742 --> 00:33:00,746
can strike the Earth
without warning.
522
00:33:02,514 --> 00:33:07,053
When a massive star explodes
as a gamma ray burst,
523
00:33:07,086 --> 00:33:09,621
a lot of the energy
gets channeled
524
00:33:09,655 --> 00:33:13,225
along the axis of rotation
of that spinning star.
525
00:33:13,259 --> 00:33:17,029
Now, the axis can point
in any random direction,
526
00:33:17,063 --> 00:33:20,632
but if it happens to point
toward the Earth,
527
00:33:20,666 --> 00:33:23,102
then the energetic
charged particles
528
00:33:23,135 --> 00:33:25,304
and the electromagnetic
radiation
529
00:33:25,337 --> 00:33:26,505
blast into the Earth,
530
00:33:26,538 --> 00:33:29,608
causing potentially
damaging effects.
531
00:33:31,810 --> 00:33:34,413
(narrator)
Driving in our cars,
532
00:33:34,446 --> 00:33:36,815
walking in the park,
533
00:33:36,848 --> 00:33:39,485
we probably
wouldn't hear a thing
534
00:33:39,518 --> 00:33:42,388
when the gamma ray
strikes our atmosphere
535
00:33:42,421 --> 00:33:46,092
and annihilates it.
536
00:33:46,125 --> 00:33:49,528
But once the Earth's
protective ozone layer is gone,
537
00:33:49,561 --> 00:33:56,368
so are we, as death spreads
slowly over the globe.
538
00:33:56,402 --> 00:33:59,238
(Filippenko)
The side of the Earth
facing the gamma ray burst
539
00:33:59,271 --> 00:34:00,839
would have
a radiation blast
540
00:34:00,872 --> 00:34:03,409
that could kill
animals and plants,
541
00:34:03,442 --> 00:34:05,211
and over the long run,
542
00:34:05,244 --> 00:34:09,248
the loss or severe depletion
of the ozone layer could let in
543
00:34:09,281 --> 00:34:12,518
a lot of the ultraviolet
radiation from the sun,
544
00:34:12,551 --> 00:34:17,589
leading to damaging effects
and loss of life.
545
00:34:20,192 --> 00:34:23,362
(narrator)
The more scientists
search the skies,
546
00:34:23,395 --> 00:34:27,099
the more they locate hazards
that could fulfill--
547
00:34:27,133 --> 00:34:31,537
or surpass--ancient visions
of Armageddon.
548
00:34:36,308 --> 00:34:41,313
From stars that explode...
549
00:34:41,347 --> 00:34:44,350
to objects like this--
550
00:34:44,383 --> 00:34:49,888
rogue planets
careening through space.
551
00:34:49,921 --> 00:34:53,359
We used to think that
all planets circled stars,
552
00:34:53,392 --> 00:34:57,396
which kept them bound to
a particular spot in the galaxy.
553
00:34:57,429 --> 00:35:02,201
It was reassuring,
but wrong.
554
00:35:02,234 --> 00:35:06,372
Scientists have recently started
discovering rogue planets,
555
00:35:06,405 --> 00:35:08,840
wandering aimlessly
through space,
556
00:35:08,874 --> 00:35:13,445
unleashed from any star's
gravitational field.
557
00:35:13,479 --> 00:35:16,415
There are more out there
than we ever imagined,
558
00:35:16,448 --> 00:35:19,918
hiding in plain sight.
559
00:35:19,951 --> 00:35:21,653
(Walkowicz)
We know that there's
a population of planets
560
00:35:21,687 --> 00:35:25,891
out there that exist
without orbiting a parent star.
561
00:35:25,924 --> 00:35:28,260
Because there's no light
from the parent star,
562
00:35:28,294 --> 00:35:30,929
and we can't use the parent star
to indirectly detect
563
00:35:30,962 --> 00:35:36,202
these planets, that makes them
very difficult to find.
564
00:35:36,235 --> 00:35:38,770
(narrator)
Maybe we need
to look harder.
565
00:35:41,573 --> 00:35:44,510
As a rogue planet wanders
into our solar system,
566
00:35:44,543 --> 00:35:47,913
its gravitational pull
could disrupt the Earth's orbit,
567
00:35:47,946 --> 00:35:53,319
slowing it down, speeding it up,
or changing its shape.
568
00:35:53,352 --> 00:35:57,389
That could affect
the seasons and the climate,
569
00:35:57,423 --> 00:36:01,927
endangering life on Earth.
570
00:36:05,697 --> 00:36:08,667
(Filippenko)
We now think that
there could easily be
571
00:36:08,700 --> 00:36:11,870
as many rogue planets
in our Milky Way Galaxy
572
00:36:11,903 --> 00:36:13,405
as there are stars,
573
00:36:13,439 --> 00:36:17,276
and perhaps many, many more
rogue planets,
574
00:36:17,309 --> 00:36:19,578
ten or hundred
or a thousand times
575
00:36:19,611 --> 00:36:24,550
as many rogue planets
as there are stars.
576
00:36:24,583 --> 00:36:25,984
(narrator)
That's an ominous discovery
577
00:36:26,017 --> 00:36:29,888
that makes our galaxy
a bit more crowded, and maybe
578
00:36:29,921 --> 00:36:34,460
a little more dangerous
to our planet's survival.
579
00:36:34,493 --> 00:36:36,662
(Filippenko)
If there are
way more rogue planets
580
00:36:36,695 --> 00:36:39,231
than there are stars
in our galaxy,
581
00:36:39,265 --> 00:36:42,000
then the chances
that they will come
582
00:36:42,033 --> 00:36:45,271
and gravitationally interact
with our solar system
583
00:36:45,304 --> 00:36:48,374
are greater.
584
00:36:48,407 --> 00:36:49,908
(Walkowicz)
Fortunately for us,
585
00:36:49,941 --> 00:36:53,645
the galaxy is still
very, very sparsely populated.
586
00:36:53,679 --> 00:36:55,747
Everything
is very far apart,
587
00:36:55,781 --> 00:36:59,251
and so it's almost
diminishingly small chances
588
00:36:59,285 --> 00:37:01,553
that you would have
one of these dark planets
589
00:37:01,587 --> 00:37:05,557
entering
our solar system.
590
00:37:05,591 --> 00:37:10,462
(narrator)
But in 2014, just on the edge
of our solar system,
591
00:37:10,496 --> 00:37:14,600
the closest rogue planet
was found to date.
592
00:37:14,633 --> 00:37:18,904
It's out there, 80 times further
from the sun than we are,
593
00:37:18,937 --> 00:37:22,441
which isn't very far
at all.
594
00:37:22,474 --> 00:37:24,343
That's the bad news.
595
00:37:24,376 --> 00:37:27,045
The good news,
if you can think of it that way,
596
00:37:27,078 --> 00:37:30,882
is that another, much larger
and more distant rogue planet
597
00:37:30,916 --> 00:37:36,288
is holding it safely
in its gravitational grip.
598
00:37:37,989 --> 00:37:40,892
Knowing the apocalypse
probably won't be tripped
599
00:37:40,926 --> 00:37:45,631
by a rogue planet
is only slightly reassuring.
600
00:37:45,664 --> 00:37:48,867
The ancients
and modern scientists agree,
601
00:37:48,900 --> 00:37:50,736
there is no escape.
602
00:37:50,769 --> 00:37:55,073
Somehow, someday,
the end is coming,
603
00:37:55,106 --> 00:37:58,410
and the final vision
of Armageddon
604
00:37:58,444 --> 00:38:00,346
is the strangest of all.
605
00:38:06,051 --> 00:38:09,321
(narrator)
We've seen Armageddon
rain down on us
606
00:38:09,355 --> 00:38:14,426
by Nordic ice
and Buddhist fire,
607
00:38:14,460 --> 00:38:16,728
Aztec darkness,
608
00:38:16,762 --> 00:38:20,599
killer meteorites
of Biblical proportions,
609
00:38:20,632 --> 00:38:24,436
and deep space
death beams,
610
00:38:24,470 --> 00:38:27,606
but maybe there's hope.
611
00:38:27,639 --> 00:38:31,477
What if the end...isn't?
612
00:38:34,546 --> 00:38:37,115
The biggest recycling project
in the universe
613
00:38:37,148 --> 00:38:41,753
might be
the universe itself,
614
00:38:41,787 --> 00:38:44,856
and according
to Ancient Hindu philosophy,
615
00:38:44,890 --> 00:38:51,062
every Armageddon
marks a new beginning.
616
00:38:51,096 --> 00:38:54,433
(Markley)
Hindu belief for the end
of the world involves cycles.
617
00:38:54,466 --> 00:38:57,369
The end of the world was also
the beginning of the world,
618
00:38:57,403 --> 00:38:59,571
which in due course
would live out its life span,
619
00:38:59,605 --> 00:39:02,408
and it too would end
and once more be reborn,
620
00:39:02,441 --> 00:39:05,977
in constant cycles.
621
00:39:06,011 --> 00:39:11,483
(narrator)
Could this view of Armageddon
really come to pass?
622
00:39:11,517 --> 00:39:14,686
Not if dark energy continues
to expand the universe
623
00:39:14,720 --> 00:39:19,458
eternally, extinguishing it
in a Big Chill.
624
00:39:21,727 --> 00:39:26,131
But the mysteries of dark energy
leave open the possibility
625
00:39:26,164 --> 00:39:31,036
that instead of a Big Chill,
there will be a Big Crunch,
626
00:39:31,069 --> 00:39:36,742
a universe that reverses course
and collapses back in on itself.
627
00:39:40,078 --> 00:39:42,648
(Filippenko)
It's conceivable
that the dark energy
628
00:39:42,681 --> 00:39:45,484
could change sign
in the future.
629
00:39:45,517 --> 00:39:48,019
Right now, it's repulsive,
but what if someday,
630
00:39:48,053 --> 00:39:50,589
it becomes
gravitationally attractive?
631
00:39:50,622 --> 00:39:52,491
We don't know
what dark energy is,
632
00:39:52,524 --> 00:39:55,661
so it's possible.
633
00:39:55,694 --> 00:39:57,496
(narrator)
During the big crunch,
634
00:39:57,529 --> 00:39:59,865
the universe
would collapse...
635
00:39:59,898 --> 00:40:04,035
and collapse...
and collapse...
636
00:40:04,069 --> 00:40:08,907
(Filippenko)
Everything becomes so dense,
so compressed,
637
00:40:08,940 --> 00:40:13,979
that we call this a singularity,
a big crunch,
638
00:40:14,012 --> 00:40:18,617
a "gnab gib,"
which is "Big Bang" backwards.
639
00:40:18,650 --> 00:40:22,521
It's conceivable
that there will be a rebirth,
640
00:40:22,554 --> 00:40:26,124
a new expansion,
a new big bang, if you will.
641
00:40:29,060 --> 00:40:33,965
(narrator)
Scientists call that
the Big Bounce.
642
00:40:33,999 --> 00:40:35,567
It's very much like what happens
643
00:40:35,601 --> 00:40:40,038
if you take a ball
and throw it up into the air.
644
00:40:40,071 --> 00:40:43,475
You give it that initial push,
that would be like the Big Bang,
645
00:40:43,509 --> 00:40:46,144
it expands out,
it goes up into the air,
646
00:40:46,177 --> 00:40:49,014
and then the gravity
of the Earth eventually
647
00:40:49,047 --> 00:40:53,184
turns it round and brings it
back down to your hand.
648
00:40:53,218 --> 00:40:55,120
(narrator)
Toss it up again...
649
00:40:55,153 --> 00:40:58,990
and again...
and that's the Big Bounce.
650
00:40:59,024 --> 00:41:02,060
(Howell)
That's what's called
the cyclic model in cosmology.
651
00:41:02,093 --> 00:41:06,264
The universe is born, dies,
and then is reborn again,
652
00:41:06,297 --> 00:41:09,167
and this process could go
over and over.
653
00:41:09,200 --> 00:41:12,203
It's akin
to Hindu mythology.
654
00:41:14,773 --> 00:41:19,645
(narrator)
If the universe does in fact
crunch and bounce back,
655
00:41:19,678 --> 00:41:22,013
as the Ancient Hindus
believed,
656
00:41:22,047 --> 00:41:24,082
then we might have been
down this road
657
00:41:24,115 --> 00:41:27,285
many times before.
658
00:41:27,318 --> 00:41:32,624
Or maybe there isn't
just one universe after all.
659
00:41:32,658 --> 00:41:36,562
We now think that there
may well be other universes
660
00:41:36,595 --> 00:41:40,098
popping into existence
with their own big bangs
661
00:41:40,131 --> 00:41:43,168
and their own expansion
and their own stars
662
00:41:43,201 --> 00:41:46,237
and perhaps even
their own life,
663
00:41:46,271 --> 00:41:51,176
and that process can lead
to a progression of universes
664
00:41:51,209 --> 00:41:54,680
that is never-ending.
665
00:41:54,713 --> 00:42:01,286
(narrator)
That's good news for universes,
if not necessarily for us.
666
00:42:01,319 --> 00:42:05,757
If the Earth can dodge
asteroid strikes
667
00:42:05,791 --> 00:42:10,762
and gamma ray bursts
and rogue planet invasions,
668
00:42:10,796 --> 00:42:13,198
we can expect our sun
to expand
669
00:42:13,231 --> 00:42:17,002
before burning out
5 billion years from now,
670
00:42:17,035 --> 00:42:21,707
incinerating the planet
as the Buddhists envision.
671
00:42:21,740 --> 00:42:23,809
If dark energy
can be trusted,
672
00:42:23,842 --> 00:42:26,344
the universe will
continue to expand,
673
00:42:26,377 --> 00:42:28,313
freezing to death
in the process,
674
00:42:28,346 --> 00:42:30,782
as the Norse predicted.
675
00:42:30,816 --> 00:42:34,052
Or maybe another universe
will spring to life
676
00:42:34,085 --> 00:42:38,724
from the corpse of the old one,
as some Hindus suggest.
677
00:42:38,757 --> 00:42:40,325
Whether we look
to the ancient lore
678
00:42:40,358 --> 00:42:43,261
of the Aztecs,
the Norse,
679
00:42:43,294 --> 00:42:47,966
the Hindus,
the Buddhists, the Romans,
680
00:42:47,999 --> 00:42:53,238
or to modern science,
the answer is the same--
681
00:42:53,271 --> 00:42:55,974
We are doomed.
682
00:42:56,007 --> 00:42:58,209
(Markley)
Sooner or later, things fail.
683
00:42:58,243 --> 00:43:00,779
Sooner or later,
people die.
684
00:43:00,812 --> 00:43:03,849
Sooner or later,
the world ends.
55494
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