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In the beginning,
there was darkness...
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and then, bang...
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giving birth to an endless
expanding existence...
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00:00:09,551 --> 00:00:12,094
of time, space, and matter.
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Now, see further
than we've ever imagined...
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00:00:14,431 --> 00:00:16,306
beyond the limits of our existence...
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in a place we call "The Universe. "
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00:00:21,479 --> 00:00:26,025
Everything that we know,
time, space, and matter...
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are doomed.
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00:00:28,194 --> 00:00:32,531
Any life that depends on sunlight
will rapidly go extinct...
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as there are fewer sources
of life-providing energy.
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00:00:37,954 --> 00:00:41,165
Whether by the Armageddon
of an inferno...
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00:00:41,207 --> 00:00:44,293
or in the grip
of an icy executioner...
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00:00:44,335 --> 00:00:49,131
The universe itself will freeze
to death and all life with it.
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00:00:50,258 --> 00:00:55,220
Or even by an unseen force
from the depths of space.
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And literally every particle, every atom...
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every structure in the universe
would explode.
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00:01:01,936 --> 00:01:05,773
Beware, here comes
the "Cosmic Apocalypse. "
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The year is 20 billion A.D...
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and there is something
gravely wrong with the universe.
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Ever since its explosive birth,
the universe has been expanding...
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growing ceaselessly
into an infinite unknown.
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However, on this day
in the distant future...
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looking up at the sky...
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galaxies from all directions
have reversed course...
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and are speeding
towards our own Milky Way.
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The catastrophic implication is fatal.
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The universe is collapsing...
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and everything we know
will cease to be.
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Life is doomed.
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00:02:02,372 --> 00:02:03,914
When we look at other galaxies...
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we'll see them coming in
toward us on a collision course.
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All of a sudden, we see stars
coming at us from all directions.
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All the galaxies
will start colliding...
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and the stars within them
will get crunched together.
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The stars will collide,
the planets will collide.
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Planets will get
swallowed by stars.
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All of a sudden,
temperatures begin to rise.
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All of a sudden,
the oceans boil.
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All of a sudden,
the mountains will melt.
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Oh, man, it's going to be chaos.
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It's going to be pandemonium.
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And the universe itself begins
to reach blistering temperatures.
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All intelligent life must die
because we'll all be incinerated.
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The universe ends with a bang,
in a cosmic fireball.
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This is the vision
of the Apocalypse...
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according to a theory
known as the Big Crunch.
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00:03:01,806 --> 00:03:04,099
What's happening
with the Big Crunch scenario...
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is that all of the matter
in the universe...
50
00:03:06,477 --> 00:03:09,688
and all the energy, the galaxies,
the stars in them...
51
00:03:09,731 --> 00:03:11,523
are all moving back
towards each other...
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and the universe is shrinking.
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Things are getting closer
and closer together.
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Our universe right now,
on the other hand, is expanding.
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Each day, there is
more and more space...
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as galaxies get
further and further apart.
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The opposite happens
during the Big Crunch.
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The space between things
is shrinking...
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00:03:33,630 --> 00:03:37,799
and that's rather like filling up
this hallway with people...
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00:03:37,842 --> 00:03:39,176
and there are
more and more people.
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The space between them, then,
is getting smaller and smaller.
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They bump into each other...
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they're trying to dodge out
of each other's way...
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and so everything is heating up.
and getting more and more energetic...
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as more and more things
happen in this small space.
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Exactly the same thing would happen
in the Big Crunch scenario...
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where various particles
that make everything up...
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are bumping into each other
more frequently.
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The galaxies and the stars...
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00:04:07,622 --> 00:04:08,622
as they're getting closer
to each other...
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start distorting each other...
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and so the whole thing's
beginning to heat up...
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just like a crowded room
would heat up.
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The process continues...
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with the temperature of the universe
getting higher and higher...
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to the point that the atoms
themselves begin to fall apart.
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Finally, our vast universe collapses...
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into a microscopic point.
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We'll end up
with this soup of matter...
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which is made
of fundamental particles...
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which are milling around
at high energy, high temperature.
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Life as we know it
has no escape.
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However, the universe
may not ultimately ignite...
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into an all-consuming hellfire.
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There are two basic paradigms
for the end of the world.
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First, the universe
is going to end in fire.
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That's the Christian theory
of Armageddon...
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fire and brimstone
and the second coming.
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00:05:13,604 --> 00:05:15,689
But the Norse
also had their legends.
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They had the legend of Ragnarok,
Twilight of the Gods...
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where there would be
this monstrous snowstorm...
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that would engulf
the entire universe.
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There would be
this great battle in heaven...
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and even Odin and even Thor
and all the great gods...
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would slowly die one by one...
96
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and we would all die
in a great freeze...
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when even the gods themselves
are frozen.
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Whereas the Big Crunch fits
the Christian vision of the end of days...
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science also has
a different theory...
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that it may instead
all end in ice.
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Ultimately, it depends
on whether the momentum...
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of the expansion
of the universe...
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can overcome the collapsing
attraction of gravity.
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00:06:04,447 --> 00:06:08,658
Imagine that the moment
of contact between bat and ball...
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is the initial explosion
of the Big Bang.
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Everything's being thrown outward...
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and the issue is,
will it re-collapse upon itself...
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or will it continue to expand?
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00:06:21,255 --> 00:06:22,839
And those two possibilities
are very similar...
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to what happens when you
launch a ball into the air.
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If I launch it upwards,
and if gravity is strong enough...
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compared to how much energy
I put into that initial launch...
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it'll pull it back down...
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and that's like the universe
expanding out for a while...
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and then crunching back in.
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But the Big Crunch doesn't
have to be the end of everything.
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If the universe collapses...
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what might subsequently follow
is another Big Bang...
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another expansion event...
120
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and that might expand for a while
and then re-collapse.
121
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So you can imagine
the possibility...
122
00:07:01,337 --> 00:07:03,296
that actually the universe
is just cyclic...
123
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and so it expands...
124
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and then contracts.
125
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Each bounce
is another Big Bang.
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But what if there isn't enough gravity
to rein in the universe?
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I launch it upwards
with enough energy...
128
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that it completely escapes.
129
00:07:26,112 --> 00:07:28,321
There's not enough mass
in the universe...
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to make it re-collapse,
and so it continues to expand.
131
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Eventually, though this
expansion ought to slow...
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shockingly, scientific observations
reveal something completely different.
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It's getting faster.
134
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The universe seems to be
careening out of control.
135
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This expansion is accelerating.
It's kicking in once again.
136
00:07:52,180 --> 00:07:55,348
We are undergoing
an inflationary expansion.
137
00:07:55,391 --> 00:07:57,809
So the universe we now know
is expanding...
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with this extra acceleration...
139
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that is beyond
what you would have thought...
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was just due
to the initial explosion.
141
00:08:09,655 --> 00:08:11,531
Not only does the ball escape...
142
00:08:11,574 --> 00:08:15,243
but it's as though a little rocket
engine was on the ball...
143
00:08:15,286 --> 00:08:18,663
and it accelerates away
from the Earth even faster.
144
00:08:19,874 --> 00:08:23,710
This is a possibility
that was somewhat unexpected.
145
00:08:25,755 --> 00:08:27,881
The volume of space
in the universe...
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seems destined
to increase forever.
147
00:08:31,802 --> 00:08:34,346
What this means is
that distant galaxies...
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are going to go
zooming away from us...
149
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and will eventually
become invisible...
150
00:08:38,184 --> 00:08:40,227
because they'll be
too far away to see.
151
00:08:42,271 --> 00:08:45,565
And without seeing galaxies
rushing away from each other...
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00:08:46,234 --> 00:08:50,070
future civilizations
will lose all sense of history.
153
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They won't know that there
was ever a Big Bang.
154
00:08:54,492 --> 00:08:57,744
So you will think
that the only structure...
155
00:08:57,787 --> 00:09:00,747
within the universe
is the Milky Way galaxy...
156
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and that the rest
of the universe...
157
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is effectively empty,
devoid of stars.
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00:09:08,506 --> 00:09:10,715
Another scientific theory proposes...
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00:09:10,758 --> 00:09:14,344
that this expansion
will balloon even faster.
160
00:09:14,387 --> 00:09:19,432
If this does happen,
a violent end awaits our cosmos.
161
00:09:19,475 --> 00:09:21,685
Suppose the amount
of repulsive energy...
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increases with time
per unit volume.
163
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It'll eventually
grow strong enough...
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to cause clusters of galaxies
to get ripped apart...
165
00:09:31,946 --> 00:09:34,739
and then galaxies themselves
will get ripped apart.
166
00:09:34,782 --> 00:09:37,075
The stars will start
flying away from one another...
167
00:09:37,118 --> 00:09:39,160
no longer held together by gravity...
168
00:09:39,203 --> 00:09:42,205
and then planetary systems
like our solar system...
169
00:09:42,248 --> 00:09:43,957
will get ripped apart...
170
00:09:44,000 --> 00:09:46,918
and then stars and planets
will get ripped apart...
171
00:09:46,961 --> 00:09:49,045
and then humans
will get ripped apart...
172
00:09:49,088 --> 00:09:53,592
and then the very atoms of which
we are made will get ripped apart.
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That's called the Big Rip,
and it's a really scary possibility.
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But don't worry.
175
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Most of us don't think
it's going to happen.
176
00:10:03,144 --> 00:10:07,689
But even if the rate of expansion
never reaches this tipping point...
177
00:10:07,732 --> 00:10:12,235
the future of our universe
still isn't promising.
178
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Its temperature decreases.
179
00:10:14,405 --> 00:10:17,949
It's getting colder and colder
and darker and darker...
180
00:10:17,992 --> 00:10:20,785
because the feeble light
emitted by stars...
181
00:10:20,828 --> 00:10:24,122
is going into a progressively
larger volume...
182
00:10:24,165 --> 00:10:28,501
so the universe is going to get
really cold and really dark.
183
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Basically, a pretty gloomy place.
184
00:10:33,924 --> 00:10:36,635
The universe itself,
we now believe...
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will die in ice,
rather than fire.
186
00:10:40,014 --> 00:10:43,308
We think the universe
will die in a great freeze...
187
00:10:43,351 --> 00:10:46,686
just like the Norse
legends foretell...
188
00:10:46,729 --> 00:10:49,939
rather than this Armageddon
of a Big Crunch.
189
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If the universe continues
on its present course...
190
00:10:56,572 --> 00:11:02,994
we're destined for a cosmic ice age
where sunlight itself goes extinct.
191
00:11:05,873 --> 00:11:08,792
By the year 100 trillion A.D...
192
00:11:08,834 --> 00:11:11,753
the last remnants
of human civilization...
193
00:11:11,796 --> 00:11:17,801
may be forced to settle here
in this distant dark corner of our galaxy.
194
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They'll be huddled around
the last burning star in the sky...
195
00:11:22,640 --> 00:11:26,142
but, sadly, it too will soon die.
196
00:11:27,269 --> 00:11:32,357
Our Milky Way, so named for its
shimmering band of sparkling stars...
197
00:11:32,400 --> 00:11:34,442
will be unrecognizable.
198
00:11:34,485 --> 00:11:37,320
Faint glowing embers
of dark stellar husks...
199
00:11:37,363 --> 00:11:38,863
will be all that remain...
200
00:11:38,906 --> 00:11:42,450
of what was once
a brilliant night vision.
201
00:11:45,705 --> 00:11:48,039
What happened
to all of the stars?
202
00:11:48,916 --> 00:11:52,711
How did we arrive
at such a dismal scenario?
203
00:11:56,632 --> 00:12:03,054
Science decrees that as our universe
expands and ages, it will cool.
204
00:12:03,097 --> 00:12:06,933
Inevitably, the future
for life as we know it...
205
00:12:06,976 --> 00:12:10,186
will grow ever more hostile.
206
00:12:10,229 --> 00:12:11,396
We are headed for a time...
207
00:12:11,439 --> 00:12:17,444
when one day the universe itself will
freeze to death and all life with it...
208
00:12:17,486 --> 00:12:19,446
and that's a law.
209
00:12:20,614 --> 00:12:23,450
When we scientists look
at the evolution of the universe...
210
00:12:23,492 --> 00:12:25,910
some critics say, "That's crazy.
211
00:12:25,953 --> 00:12:28,037
"We can barely predict
tomorrow's headlines...
212
00:12:28,080 --> 00:12:30,790
"and here you are predicting
what's going to be happening...
213
00:12:30,833 --> 00:12:32,709
"billions and billions
of years from now.
214
00:12:32,752 --> 00:12:34,419
"How do you do it?"
215
00:12:35,337 --> 00:12:39,215
Among the tools available
to scientists pondering the future...
216
00:12:39,258 --> 00:12:42,927
are the venerable
laws of thermodynamics.
217
00:12:42,970 --> 00:12:48,141
The first law says that total
matter and energy are conserved.
218
00:12:48,184 --> 00:12:50,602
In other words, you can't
get something for nothing.
219
00:12:50,644 --> 00:12:52,312
There's no free lunch.
220
00:12:52,354 --> 00:12:57,358
So it turns out that the total amount
of matter and energy in a system...
221
00:12:57,401 --> 00:12:59,402
can be neither created
nor destroyed.
222
00:13:00,154 --> 00:13:02,614
The matter and energy
can change forms...
223
00:13:02,656 --> 00:13:04,324
and they can turn
into one another...
224
00:13:04,366 --> 00:13:06,618
but the total remains the same.
225
00:13:06,660 --> 00:13:09,120
So, for example,
in this rolled-up newspaper...
226
00:13:09,163 --> 00:13:13,291
there's a lot of energy stored
in the chemical bonds of the paper...
227
00:13:13,334 --> 00:13:15,001
but if I ignite the paper...
228
00:13:15,044 --> 00:13:20,673
I can activate those bonds,
and I can start breaking them...
229
00:13:20,716 --> 00:13:24,803
and that releases energy
in the form of light and heat...
230
00:13:24,845 --> 00:13:26,679
which you can see and feel.
231
00:13:26,722 --> 00:13:29,808
The total energy content
is still the same...
232
00:13:29,850 --> 00:13:32,185
but it's being dissipated
out into space.
233
00:13:33,145 --> 00:13:37,649
And a lot of particulate matter
goes off as well and smoke goes off...
234
00:13:37,691 --> 00:13:38,691
but if I were to add up...
235
00:13:38,734 --> 00:13:41,069
all the smoke
and the particulate matter...
236
00:13:41,111 --> 00:13:44,781
and all the energy that's given off
and everything total...
237
00:13:44,824 --> 00:13:46,825
I would get
exactly the same amount...
238
00:13:46,867 --> 00:13:50,995
of mass and energy total
as I had to begin with.
239
00:13:51,038 --> 00:13:53,540
They simply changed forms.
240
00:13:55,918 --> 00:13:59,629
If the total amount of mass
and energy remain constant...
241
00:13:59,672 --> 00:14:01,339
this seems to imply the universe...
242
00:14:01,382 --> 00:14:04,634
will always have energy
and should last forever.
243
00:14:06,554 --> 00:14:09,055
But the second law
of thermodynamics...
244
00:14:09,098 --> 00:14:11,516
crushes this notion.
245
00:14:11,559 --> 00:14:13,518
The second law
of thermodynamics...
246
00:14:13,561 --> 00:14:15,520
is the most curious of all.
247
00:14:15,563 --> 00:14:19,357
It says that total amount
of disorder or entropy...
248
00:14:19,400 --> 00:14:22,235
always increases
in the universe.
249
00:14:22,278 --> 00:14:26,990
In other words,
things rust, things decay...
250
00:14:27,032 --> 00:14:30,827
everything gets old
and eventually falls apart and rots.
251
00:14:31,912 --> 00:14:35,707
In some sense, the second law
is a death warrant...
252
00:14:35,749 --> 00:14:37,750
a death warrant
for the universe.
253
00:14:40,546 --> 00:14:43,214
The second law says
all things must pass.
254
00:14:46,135 --> 00:14:48,928
The ever-present supply
of energy in the universe...
255
00:14:48,971 --> 00:14:51,097
inevitably becomes
more dispersed...
256
00:14:51,140 --> 00:14:54,225
more chaotic,
and more unusable.
257
00:14:55,352 --> 00:14:58,104
Each star burning in the sky...
258
00:14:58,147 --> 00:15:00,648
just like each briquette
of this charcoal...
259
00:15:00,691 --> 00:15:03,443
must one day face its fate.
260
00:15:04,445 --> 00:15:06,362
This piece of charcoal is fuel.
261
00:15:06,405 --> 00:15:07,989
It has a lot of energy...
262
00:15:08,032 --> 00:15:11,534
concentrated into this
small, little packet here.
263
00:15:11,577 --> 00:15:14,579
That energy goes from being
in the chemical bonds...
264
00:15:14,622 --> 00:15:16,247
of the charcoal briquette...
265
00:15:16,290 --> 00:15:20,960
to being liberated
in the form of heat and light.
266
00:15:21,003 --> 00:15:23,254
Now, a star does a similar thing.
267
00:15:23,297 --> 00:15:25,924
It doesn't burn
in a chemical sense.
268
00:15:25,966 --> 00:15:29,677
Instead, in a star,
it's nuclear energy.
269
00:15:29,720 --> 00:15:34,724
The nuclei of atoms
are being forced together...
270
00:15:34,767 --> 00:15:37,936
fusing them,
creating new nuclei...
271
00:15:37,978 --> 00:15:42,398
and, in the process, transforming
some of that matter...
272
00:15:42,441 --> 00:15:48,196
some of that mass, into the radiated
energy that we see and we feel.
273
00:15:48,238 --> 00:15:51,115
And the same process
is going on...
274
00:15:51,158 --> 00:15:53,826
in all the active stars
in the universe.
275
00:15:54,954 --> 00:15:58,581
Now, as this charcoal is burning,
the fuel is getting used up...
276
00:15:58,624 --> 00:15:59,832
and you can actually see that.
277
00:15:59,875 --> 00:16:01,834
It's turning into a gray color.
278
00:16:01,877 --> 00:16:03,211
It's turning into ashes.
279
00:16:04,380 --> 00:16:09,050
In a similar way,
stars use up their fuel.
280
00:16:09,093 --> 00:16:12,929
They fuse hydrogen into helium,
and so, with time...
281
00:16:12,972 --> 00:16:16,015
there's less and less
hydrogen to fuse.
282
00:16:16,058 --> 00:16:19,143
And the ashes have
less energy content...
283
00:16:19,186 --> 00:16:22,689
and, thus, are either
harder to burn...
284
00:16:22,731 --> 00:16:26,985
or release less energy
during the burning process.
285
00:16:29,863 --> 00:16:32,865
This is the eventual fate
of our own Sun.
286
00:16:34,201 --> 00:16:37,787
As it ages, it bloats and heats.
287
00:16:37,830 --> 00:16:40,498
The Earth will be fried to a crisp.
288
00:16:41,417 --> 00:16:44,711
Oceans will boil away,
all plants and animals will die...
289
00:16:44,753 --> 00:16:47,338
rocks will start vaporizing...
290
00:16:47,381 --> 00:16:51,384
because the Sun will be producing
so much light, so much energy.
291
00:16:52,553 --> 00:16:57,473
That'll be a pretty gruesome death
for the Earth.
292
00:16:59,393 --> 00:17:02,895
All through the universe,
stars that are like the Sun...
293
00:17:02,938 --> 00:17:05,106
are going to be facing
the same challenges...
294
00:17:05,149 --> 00:17:06,816
that our own star will face.
295
00:17:06,859 --> 00:17:08,943
They're running out of fuel,
they're swelling up...
296
00:17:08,986 --> 00:17:13,281
and they're causing problems
for the planets that orbit them.
297
00:17:13,323 --> 00:17:16,200
So it's not hard to imagine
that there are many locations...
298
00:17:16,243 --> 00:17:19,579
where life has evolved
and flourished...
299
00:17:19,621 --> 00:17:21,122
and is now being extinguished.
300
00:17:23,625 --> 00:17:26,878
Just as each star suffers
the effects of entropy...
301
00:17:26,920 --> 00:17:30,381
so, too, will the rest
of the universe.
302
00:17:30,424 --> 00:17:34,218
But stars naturally increase
the entropy of the universe...
303
00:17:34,261 --> 00:17:36,512
by giving off light and heat...
304
00:17:36,555 --> 00:17:40,058
just like this fire
of burning charcoal...
305
00:17:40,100 --> 00:17:44,270
naturally increases
the entropy of the universe.
306
00:17:44,313 --> 00:17:47,231
Right now we're kind of
in a steady period in the universe...
307
00:17:47,274 --> 00:17:50,276
where stars are born,
live out their lives, die...
308
00:17:50,778 --> 00:17:52,779
give some of that gas back
to the next generation...
309
00:17:52,821 --> 00:17:54,906
and you have another
generation of stars.
310
00:17:54,948 --> 00:18:00,328
But that rate of star formation
is gradually decreasing with time.
311
00:18:00,370 --> 00:18:04,290
And as stars use up
their fuel and burn out...
312
00:18:04,333 --> 00:18:08,169
there aren't enough new stars
being formed to replace them.
313
00:18:08,212 --> 00:18:12,090
But the moment we run out
of gas to make new stars...
314
00:18:12,132 --> 00:18:16,052
it means for every dead star
in the rolls, in the ranks...
315
00:18:16,095 --> 00:18:17,929
there's not a star to replace it.
316
00:18:18,722 --> 00:18:20,473
And so that's a bad
situation to be in...
317
00:18:20,516 --> 00:18:21,808
the day that happens.
318
00:18:22,643 --> 00:18:26,687
So, effectively, galaxies,
giant collections of stars...
319
00:18:26,730 --> 00:18:30,650
are growing progressively
dimmer with time on average.
320
00:18:30,692 --> 00:18:32,735
And, eventually,
when the universe...
321
00:18:32,778 --> 00:18:36,239
is something like
a hundred trillion years old...
322
00:18:36,281 --> 00:18:40,326
there will be essentially
no stars still shining.
323
00:18:40,369 --> 00:18:43,788
The universe will be
cold and dark indeed.
324
00:18:44,832 --> 00:18:48,543
Any life that depends on sunlight
will rapidly go extinct...
325
00:18:48,585 --> 00:18:50,628
as the universe
continues to age...
326
00:18:50,671 --> 00:18:55,091
and as there are fewer and fewer
sources of life-providing energy...
327
00:18:55,134 --> 00:18:56,384
from a host star.
328
00:18:58,011 --> 00:19:00,054
You might think
the most massive stars...
329
00:19:00,097 --> 00:19:03,432
the ones with the most fuel,
will last the longest.
330
00:19:04,268 --> 00:19:07,478
In reality,
the more fuel a star carries...
331
00:19:07,521 --> 00:19:09,522
the faster it burns through it.
332
00:19:10,440 --> 00:19:13,234
The final rays of sunlight
left in the universe...
333
00:19:13,277 --> 00:19:15,945
will come from stars
known as red dwarfs.
334
00:19:17,239 --> 00:19:18,489
These miniature stars...
335
00:19:18,532 --> 00:19:21,826
ten times less massive
than our own sun...
336
00:19:21,869 --> 00:19:25,454
burn thousands
of degrees cooler.
337
00:19:25,497 --> 00:19:27,623
Red dwarf stars
are much more miserly...
338
00:19:27,666 --> 00:19:29,000
with their fuel consumption...
339
00:19:29,042 --> 00:19:32,170
and so, even though they have
less fuel to begin with...
340
00:19:32,212 --> 00:19:34,881
they last much, much longer
than our Sun will last.
341
00:19:37,342 --> 00:19:42,680
A typical red dwarf can live
for as long as 14 trillion years.
342
00:19:42,723 --> 00:19:47,768
That's a thousand times longer
than the current age of our universe.
343
00:19:47,811 --> 00:19:51,022
Eventually, though,
even these stingy little suns...
344
00:19:51,064 --> 00:19:52,732
will begin to die off.
345
00:19:53,775 --> 00:19:56,903
So when our Milky Way galaxy
is tens of trillions of years old...
346
00:19:57,863 --> 00:20:00,239
and there's only
a few red dwarfs remaining...
347
00:20:00,282 --> 00:20:03,409
you might imagine that
any surviving civilizations...
348
00:20:03,452 --> 00:20:05,870
will realize that the end is nigh...
349
00:20:05,913 --> 00:20:10,041
and they will start crowding around
these few sources of energy...
350
00:20:10,083 --> 00:20:12,418
trying to scrape out
an existence.
351
00:20:13,754 --> 00:20:16,464
Red dwarfs could be oases of life...
352
00:20:16,506 --> 00:20:20,218
in the vast, inhospitable
desert of the universe.
353
00:20:21,637 --> 00:20:24,805
But for a planet to receive
as much heat and energy...
354
00:20:24,848 --> 00:20:28,851
from its red dwarf host as our
Earth does from the Sun...
355
00:20:30,145 --> 00:20:32,647
it would need to orbit so closely...
356
00:20:32,689 --> 00:20:36,484
that one full year
would last just six Earth days.
357
00:20:38,445 --> 00:20:42,198
The sky would be much more
sort of whitish red...
358
00:20:42,241 --> 00:20:44,992
than our blue skies here on Earth...
359
00:20:45,035 --> 00:20:48,079
because the red dwarf
puts out so little blue light...
360
00:20:48,121 --> 00:20:50,915
you wouldn't be able to have
the kind of nice blue skies...
361
00:20:50,958 --> 00:20:53,125
that we have here now.
362
00:20:53,168 --> 00:20:58,506
However, nothing left in the universe
would be hotter or brighter.
363
00:20:59,341 --> 00:21:01,175
So, there will be
a time in our galaxy...
364
00:21:01,218 --> 00:21:06,013
when there's just
a few red dwarfs still glowing...
365
00:21:06,056 --> 00:21:11,602
and maybe just then three
and two and one as they blink out.
366
00:21:11,645 --> 00:21:15,231
And, gosh, when there's
one red dwarf left...
367
00:21:15,274 --> 00:21:17,942
and suppose
I'm on the planet circling it...
368
00:21:17,985 --> 00:21:19,527
I'll think, "Man, oh, man...
369
00:21:19,569 --> 00:21:21,487
"what a lonely place
the universe is.
370
00:21:21,530 --> 00:21:24,198
"What a depressing future it holds. "
371
00:21:26,159 --> 00:21:31,122
What happens after the last red dwarf
blinks out of existence?
372
00:21:36,003 --> 00:21:40,548
Life in the 21 st century on Earth
thrives within a universe...
373
00:21:40,590 --> 00:21:44,051
that has existed
for about 14 billion years...
374
00:21:44,094 --> 00:21:46,262
since the spark of the Big Bang.
375
00:21:49,224 --> 00:21:52,935
But that's no time at all
in the grand scheme of the cosmos.
376
00:21:53,687 --> 00:21:57,189
If the universe is comparable
to a human life span...
377
00:21:57,232 --> 00:22:01,444
we are still in the infancy
of the universe.
378
00:22:04,031 --> 00:22:07,325
Getting a grasp of the time
that has already elapsed...
379
00:22:07,367 --> 00:22:11,537
and the time span still to come
can boggle the mind.
380
00:22:11,580 --> 00:22:15,166
To gain a perspective
of the vast time scales of the universe...
381
00:22:15,208 --> 00:22:19,587
let's compress the roughly
14-billion-year history of the universe...
382
00:22:19,629 --> 00:22:23,507
into one normal calendar year.
383
00:22:23,550 --> 00:22:25,885
But we'll call this
a cosmic calendar.
384
00:22:27,637 --> 00:22:30,973
So the Big Bang occurred
on New Year's, January 1 st.
385
00:22:31,933 --> 00:22:38,647
On that scale, our Milky Way galaxy
formed near the end of January...
386
00:22:38,690 --> 00:22:42,985
and our solar system formed
around the beginning of August or so...
387
00:22:43,028 --> 00:22:46,155
about two-thirds of the way
through the year.
388
00:22:46,198 --> 00:22:49,950
Life formed sometime
a little bit later in August...
389
00:22:49,993 --> 00:22:52,870
but humans formed
less than a day ago.
390
00:22:52,913 --> 00:22:58,042
So, on December 31 st sometime,
humans finally arose.
391
00:22:59,419 --> 00:23:01,754
We can also look
into the future...
392
00:23:02,756 --> 00:23:05,674
on the same cosmic calendar
time scale.
393
00:23:06,676 --> 00:23:10,137
Near the end of January
of this coming year...
394
00:23:10,180 --> 00:23:13,265
our Earth will become
quite inhospitable.
395
00:23:13,308 --> 00:23:17,395
By around May or so,
our Sun will have died...
396
00:23:17,437 --> 00:23:20,272
but there are some other stars,
the low-mass stars...
397
00:23:20,315 --> 00:23:22,441
which will live
for much, much longer...
398
00:23:22,484 --> 00:23:26,946
up to 10,000
of these cosmic years.
399
00:23:28,949 --> 00:23:33,411
That's 10,000 times longer than
the entire history of the universe...
400
00:23:33,453 --> 00:23:38,249
before these final longest-living
red dwarf stars die off.
401
00:23:38,291 --> 00:23:39,625
But then what happens?
402
00:23:40,877 --> 00:23:43,421
When we talk about
the extremely distant future...
403
00:23:43,463 --> 00:23:47,133
we're talking about
immense spans of time...
404
00:23:47,175 --> 00:23:49,552
time measured
in quadrillions of years...
405
00:23:49,594 --> 00:23:51,262
and septillions of years...
406
00:23:51,304 --> 00:23:54,098
and it becomes so overwhelming...
407
00:23:54,141 --> 00:23:57,601
that we need to evolve
another concept to really deal with it.
408
00:23:57,644 --> 00:24:00,563
So we came up with the idea
of cosmological decades.
409
00:24:03,442 --> 00:24:06,861
A cosmological decade,
each decade is ten times longer...
410
00:24:06,903 --> 00:24:11,323
than all the time that happened
prior to the start of the decade.
411
00:24:11,366 --> 00:24:14,827
And one way to think about this
is that it's like a staircase.
412
00:24:16,079 --> 00:24:19,123
Not an ordinary staircase
like this one...
413
00:24:19,166 --> 00:24:23,085
but one in which each step
is ten times higher...
414
00:24:23,128 --> 00:24:24,753
than the step before.
415
00:24:24,796 --> 00:24:28,841
So you can imagine the staircase
going up and up and up...
416
00:24:28,884 --> 00:24:31,719
to higher and higher
cosmological decades.
417
00:24:31,761 --> 00:24:37,016
Right now, we're living in
the tenth cosmological decade.
418
00:24:39,644 --> 00:24:42,813
On this scale,
the tenth cosmological decade...
419
00:24:42,856 --> 00:24:46,734
is ten times longer than
the previous nine decades combined...
420
00:24:46,776 --> 00:24:49,111
that have passed
since the Big Bang.
421
00:24:52,365 --> 00:24:54,700
The hallmark
of the tenth cosmological decade...
422
00:24:54,743 --> 00:24:58,829
is the fact that stars
are burning brightly in the night sky...
423
00:24:58,872 --> 00:25:01,790
and also that the planets
are beginning to develop...
424
00:25:01,833 --> 00:25:05,002
life and intelligence
on their surfaces.
425
00:25:05,045 --> 00:25:10,132
Another interesting hallmark
of the tenth cosmological decade...
426
00:25:10,175 --> 00:25:13,844
is the beginning
of the acceleration...
427
00:25:13,887 --> 00:25:15,888
of the expansion
of the universe.
428
00:25:17,724 --> 00:25:20,351
As our cosmological decade
continues...
429
00:25:20,393 --> 00:25:23,437
all of the other galaxies
disappear from view...
430
00:25:23,480 --> 00:25:28,025
and stars begin to die off
without being replaced.
431
00:25:28,068 --> 00:25:32,947
During the latter part of this era,
there will always be about fifty stars...
432
00:25:32,989 --> 00:25:36,200
shining in the galaxy
at any one time.
433
00:25:36,243 --> 00:25:38,869
And that will be
the last sort of gasp...
434
00:25:38,912 --> 00:25:41,121
of the kind of world,
the kind of planets...
435
00:25:41,164 --> 00:25:43,916
the kind of environments
that are familiar to us.
436
00:25:46,044 --> 00:25:50,214
As we move through the succeeding
cosmological decades...
437
00:25:50,257 --> 00:25:56,887
and after the last star dies,
we enter a new alien age.
438
00:25:56,930 --> 00:26:02,017
So up here, we're in the cosmological
decade 20 through 30...
439
00:26:02,060 --> 00:26:05,354
and if we look out
at the night sky...
440
00:26:05,397 --> 00:26:09,358
it's absolutely, utterly,
completely black.
441
00:26:09,401 --> 00:26:11,860
But if we're able
to look in light...
442
00:26:11,903 --> 00:26:14,697
that's far too red
for the human eye to see...
443
00:26:14,739 --> 00:26:18,742
then we'd actually see that the sky
is speckled with dead stars.
444
00:26:20,662 --> 00:26:22,329
This is the Degenerate Era.
445
00:26:24,749 --> 00:26:26,083
In the Degenerate Era...
446
00:26:26,126 --> 00:26:31,297
the most massive dead stars
have collapsed into black holes.
447
00:26:31,339 --> 00:26:34,592
But punctuating
the total blackness of space...
448
00:26:34,634 --> 00:26:39,847
the leftover ashes of once bright stars
are still ebbing energy.
449
00:26:41,224 --> 00:26:44,143
These ashes are called
a white dwarf.
450
00:26:44,185 --> 00:26:45,185
Now, they're really weird...
451
00:26:45,228 --> 00:26:48,480
because you've got something
like half the mass of our Sun...
452
00:26:48,523 --> 00:26:51,942
roughly 160,000 times
the mass of our Earth...
453
00:26:51,985 --> 00:26:55,362
compressed into a volume
just the size of the Earth.
454
00:26:55,405 --> 00:26:56,780
So it's very dense stuff.
455
00:26:56,823 --> 00:26:59,241
It's weird ashes, that's for sure.
456
00:27:00,493 --> 00:27:04,246
So it'll be like
the dying ember after a fire.
457
00:27:04,289 --> 00:27:08,667
It'll be generating no new energy
of its own through nuclear fusion.
458
00:27:10,503 --> 00:27:13,964
But as the dying embers
of a white dwarf cool...
459
00:27:14,007 --> 00:27:17,217
they still emit
many megawatts of power.
460
00:27:18,136 --> 00:27:22,473
But that is vastly billions,
trillions of times less energy...
461
00:27:22,515 --> 00:27:24,850
than the Sun is producing right now.
462
00:27:26,686 --> 00:27:30,439
And so if we think
we have an energy crisis now...
463
00:27:30,482 --> 00:27:32,191
the energy crisis
in the Degenerate Era...
464
00:27:32,233 --> 00:27:35,319
will be far more severe
and far more profound.
465
00:27:37,781 --> 00:27:43,035
Even so, the energy emanating
from these ancient star remnants...
466
00:27:43,078 --> 00:27:45,537
is still greater
than that consumed today...
467
00:27:45,580 --> 00:27:48,040
by all human civilization.
468
00:27:48,875 --> 00:27:51,669
If we were to imagine that
somehow a human civilization...
469
00:27:51,711 --> 00:27:54,421
were to persist
into the Degenerate Era...
470
00:27:54,464 --> 00:28:00,135
they might be tapping the energy
that's emerging from the white dwarf.
471
00:28:00,178 --> 00:28:02,930
However, humans
wouldn't be able to establish...
472
00:28:02,972 --> 00:28:06,183
an energy-gathering
outpost on its surface...
473
00:28:06,226 --> 00:28:09,561
such as an oil rig
anchored to the ocean floor.
474
00:28:10,230 --> 00:28:12,606
Surface gravity
is incredibly strong.
475
00:28:12,649 --> 00:28:14,358
You would basically be crushed...
476
00:28:14,401 --> 00:28:16,568
if you tried to stand
on the surface of a white dwarf.
477
00:28:18,488 --> 00:28:20,989
To survive, future civilizations...
478
00:28:21,032 --> 00:28:24,827
would need to establish
an orbiting colony.
479
00:28:24,869 --> 00:28:28,205
They would probably tap that energy
that's coming from the white dwarf...
480
00:28:28,248 --> 00:28:30,374
by having some sort
of absorbing panels...
481
00:28:30,417 --> 00:28:33,043
that are also in orbit
around the white dwarf.
482
00:28:33,086 --> 00:28:35,129
So the energy that's
emanating up from below...
483
00:28:35,171 --> 00:28:38,006
would be captured
and trapped and used.
484
00:28:39,926 --> 00:28:43,053
Still, light in this
white dwarf-orbiting future...
485
00:28:43,096 --> 00:28:45,556
would have to be generated
artificially.
486
00:28:46,891 --> 00:28:48,934
There's no stars shining in the sky.
487
00:28:48,977 --> 00:28:50,144
There's no moonlight.
488
00:28:50,186 --> 00:28:51,228
There's no sunlight.
489
00:28:52,480 --> 00:28:57,192
You're simply orbiting
a gigantic, dead black mass.
490
00:28:59,904 --> 00:29:04,950
Unfortunately, dead black masses
will make up the bulk of galaxies...
491
00:29:04,993 --> 00:29:06,618
during the Degenerate Era.
492
00:29:07,954 --> 00:29:11,290
So, as we go
into the Degenerate Era...
493
00:29:11,332 --> 00:29:14,835
we'll have roughly
a hundred billion dead stars...
494
00:29:14,878 --> 00:29:20,215
orbiting each other
in a giant elliptical configuration.
495
00:29:21,217 --> 00:29:23,761
Occasionally, they'll
interact with one another...
496
00:29:23,803 --> 00:29:26,597
and one will get flung out
of the galaxy...
497
00:29:26,639 --> 00:29:28,849
causing the galaxy to lose mass.
498
00:29:28,892 --> 00:29:32,436
The galaxy, in a sense,
will evaporate slowly with time...
499
00:29:32,479 --> 00:29:33,854
as these things are flung out.
500
00:29:35,982 --> 00:29:38,776
White dwarfs
and remaining galactic material...
501
00:29:38,818 --> 00:29:40,944
fall prey to black holes.
502
00:29:42,655 --> 00:29:44,698
So gradually, with time,
what will happen...
503
00:29:44,741 --> 00:29:48,494
is the galaxy will have fewer
and fewer objects in it...
504
00:29:48,536 --> 00:29:53,165
and a greater and greater
fraction of them will be black holes.
505
00:29:54,501 --> 00:29:55,959
And whatever isn't seized...
506
00:29:56,002 --> 00:29:59,797
by the millions of black holes
roaming the universe...
507
00:29:59,839 --> 00:30:02,674
begins to decay with old age.
508
00:30:03,468 --> 00:30:06,512
And this is another example
of the general process...
509
00:30:06,554 --> 00:30:10,808
by which the total amount of
randomness increases in the universe.
510
00:30:10,850 --> 00:30:14,061
The second law of thermodynamics
is once again at work.
511
00:30:14,103 --> 00:30:18,440
And all the structures,
all the stars...
512
00:30:18,483 --> 00:30:21,610
are basically
evaporating into nothing...
513
00:30:21,653 --> 00:30:24,530
and so by about
cosmological decade forty...
514
00:30:24,572 --> 00:30:27,282
most of the stuff that's been built...
515
00:30:27,325 --> 00:30:29,993
the planets and the stars,
are all gone...
516
00:30:30,829 --> 00:30:32,329
and the Degenerate Era...
517
00:30:32,372 --> 00:30:34,957
which has stretched
for huge amounts of time...
518
00:30:34,999 --> 00:30:36,500
is coming to an end.
519
00:30:37,836 --> 00:30:40,003
With nothing left
in their way...
520
00:30:40,046 --> 00:30:43,966
black holes stand poised
to rule the universe.
521
00:30:47,929 --> 00:30:51,265
This may be the grim future
of the cosmos.
522
00:30:51,307 --> 00:30:53,851
The planets decay and dissolve...
523
00:30:55,228 --> 00:30:59,690
dark galactic remnants scatter
across a bloated universe...
524
00:30:59,732 --> 00:31:03,819
and even light is just
a faint, distant memory.
525
00:31:05,405 --> 00:31:08,824
As we continue through
the vast stretches of time...
526
00:31:08,867 --> 00:31:11,201
measured
in cosmological decades...
527
00:31:11,244 --> 00:31:16,290
massive black holes survive
as the only recognizable features...
528
00:31:16,332 --> 00:31:19,376
of our once brilliant night sky.
529
00:31:19,419 --> 00:31:23,297
We're up to about cosmological decade
sixty-something...
530
00:31:23,339 --> 00:31:26,133
and when you look out
at the night sky...
531
00:31:28,344 --> 00:31:31,555
it's incredibly cold,
it's incredibly black...
532
00:31:31,598 --> 00:31:36,643
and there's only the faintest
crackle of radio waves...
533
00:31:36,686 --> 00:31:42,399
and gravitational radiation,
echoing through the empty skies.
534
00:31:42,442 --> 00:31:44,818
This is the Black Hole Era.
535
00:31:46,821 --> 00:31:51,658
The continuous expansion
of the universe has taken its toll.
536
00:31:51,701 --> 00:31:56,496
The unimaginable cold saps energy
and constricts movement.
537
00:31:56,539 --> 00:31:59,458
Time itself seems
to lose meaning.
538
00:32:00,793 --> 00:32:04,630
In the midst of the Black Hole Era,
even the Degenerate Era...
539
00:32:04,672 --> 00:32:07,841
looks like the first sliver of time
after the Big Bang.
540
00:32:09,469 --> 00:32:12,429
Does life have a chance
in this environment?
541
00:32:13,389 --> 00:32:17,142
Humans won't exist at that time
because protons won't exist...
542
00:32:17,185 --> 00:32:21,021
but it's possible to imagine
some kind of entity...
543
00:32:21,064 --> 00:32:25,150
which is living
at an extraordinarily slow rate.
544
00:32:26,778 --> 00:32:28,612
If it lives slowly enough...
545
00:32:28,655 --> 00:32:31,615
perhaps strange life
could emerge.
546
00:32:33,409 --> 00:32:36,662
A thought would take
trillions of years.
547
00:32:36,704 --> 00:32:40,624
It may take a trillion years for you
to decide what to have for lunch...
548
00:32:40,667 --> 00:32:45,837
because everything is so slow,
everything is near absolute zero.
549
00:32:47,966 --> 00:32:51,093
The creeping time scale
of the Black Hole Era...
550
00:32:51,135 --> 00:32:53,929
can be compared
to the growth of vegetation.
551
00:32:55,223 --> 00:32:59,518
From a human perspective,
involving minutes, hours, and days...
552
00:32:59,560 --> 00:33:02,479
plant life can seem frozen in time.
553
00:33:04,857 --> 00:33:07,651
Absolutely nothing
seems to be happening.
554
00:33:07,694 --> 00:33:11,655
It appears to be completely dead,
completely static.
555
00:33:11,698 --> 00:33:16,868
But if we speed up the clock,
then we see the activity.
556
00:33:18,037 --> 00:33:19,162
The plant grows...
557
00:33:19,205 --> 00:33:23,083
the plant moves its leaves
in response to where the Sun is...
558
00:33:23,126 --> 00:33:26,920
the plant is continuously in motion,
it's continuously doing things...
559
00:33:26,963 --> 00:33:31,091
but that whole scale of existence
is on a time frame that's longer...
560
00:33:31,134 --> 00:33:34,052
than what our experience
is used to dealing with.
561
00:33:39,726 --> 00:33:42,436
The real action
in the Black Hole Era occurs...
562
00:33:42,478 --> 00:33:44,146
when two black holes meet.
563
00:33:47,066 --> 00:33:52,029
Although invisible to human eyes,
a collision between these two beasts...
564
00:33:52,071 --> 00:33:54,656
sends a shudder
through space-time.
565
00:33:55,992 --> 00:34:00,328
This event can be imagined
in a sheet of perfectly still, calm water.
566
00:34:01,414 --> 00:34:06,960
It's a bit like suddenly dropping
a gigantic rock into that calm water...
567
00:34:08,921 --> 00:34:11,757
sending out
a huge series of ripples...
568
00:34:11,799 --> 00:34:14,551
and you have a lot of action
for a little bit of time...
569
00:34:14,594 --> 00:34:17,262
but then that dissipates,
the ripples die away...
570
00:34:18,639 --> 00:34:22,017
and you're back to that smooth,
glass-like sheet of water.
571
00:34:23,811 --> 00:34:26,897
But even for these kings
of the Black Hole Era...
572
00:34:26,939 --> 00:34:28,774
time is running out.
573
00:34:30,234 --> 00:34:32,861
And you might think,
"Oh, they'll last forever"...
574
00:34:32,904 --> 00:34:35,072
but even they don't last forever...
575
00:34:35,114 --> 00:34:38,909
because they evaporate
very, very slowly with time.
576
00:34:41,079 --> 00:34:42,913
Black holes in today's universe...
577
00:34:42,955 --> 00:34:46,124
grow larger as they
gobble up surrounding matter.
578
00:34:47,376 --> 00:34:49,878
But eventually, far in the future...
579
00:34:49,921 --> 00:34:53,006
there'll be
so little material to swallow...
580
00:34:53,049 --> 00:34:55,842
that the evaporation rate
will start dominating...
581
00:34:55,885 --> 00:34:59,805
over the rate at which they swallow
material from their surroundings.
582
00:34:59,847 --> 00:35:03,934
So the evaporation rate
proceeds more quickly...
583
00:35:03,976 --> 00:35:06,186
when the universe
is very, very old.
584
00:35:08,147 --> 00:35:11,608
An evaporating black hole
does not go out with a whimper...
585
00:35:11,651 --> 00:35:14,111
like the planets do
when they die...
586
00:35:14,153 --> 00:35:16,154
but rather with a bang.
587
00:35:18,407 --> 00:35:21,326
That's because it behaves
counterintuitively...
588
00:35:21,369 --> 00:35:23,411
as it runs out of fuel.
589
00:35:24,205 --> 00:35:27,457
There's basically two
strategies that you can adopt.
590
00:35:27,500 --> 00:35:29,793
One is to sort of ease up
on the gas pedal...
591
00:35:29,836 --> 00:35:31,920
and try to conserve
your energy...
592
00:35:31,963 --> 00:35:35,382
and basically try to roll
into the next gas station on fumes.
593
00:35:36,342 --> 00:35:38,802
The other strategy
is to become impatient...
594
00:35:38,845 --> 00:35:40,637
and floor the accelerator...
595
00:35:40,680 --> 00:35:44,015
and try to drive to the gas station
as fast as you can...
596
00:35:44,058 --> 00:35:45,767
in hopes of getting
to the gas station...
597
00:35:45,810 --> 00:35:47,811
before your gas runs out.
598
00:35:47,854 --> 00:35:50,730
And the black holes are definitely
taking the second route.
599
00:35:51,774 --> 00:35:57,988
Unlike a car, when a black hole
finally runs out of fuel, it explodes.
600
00:36:01,075 --> 00:36:02,826
And in the last second
of the black hole...
601
00:36:02,869 --> 00:36:05,245
when you're releasing...
602
00:36:05,288 --> 00:36:09,416
megatons and megatons worth
of TNT equivalent...
603
00:36:10,793 --> 00:36:13,545
a huge variety of particles...
604
00:36:13,588 --> 00:36:16,423
that haven't been seen
for many cosmological decades...
605
00:36:16,465 --> 00:36:20,093
comes spewing into existence
and kind of flicker away...
606
00:36:20,136 --> 00:36:23,805
in a last fireworks-like burst
after the black hole is gone.
607
00:36:26,058 --> 00:36:28,518
So after about
a google years or so...
608
00:36:28,561 --> 00:36:31,855
and the most super-massive
black holes have evaporated away...
609
00:36:31,898 --> 00:36:34,858
what you've got left
is a vast universe...
610
00:36:34,901 --> 00:36:38,069
that is really
almost entirely empty.
611
00:36:39,864 --> 00:36:43,241
Next, the universe
enters the Dark Era.
612
00:36:45,369 --> 00:36:49,581
Now we're out beyond
cosmological decade 100.
613
00:36:49,624 --> 00:36:52,209
We're in the middle
of the Dark Era.
614
00:36:52,251 --> 00:36:55,879
In the Dark Era,
everything that we have now...
615
00:36:55,922 --> 00:36:58,131
that is familiar to us is gone.
616
00:36:58,174 --> 00:37:00,967
You know that expression,
"angels fear to tread"?
617
00:37:01,010 --> 00:37:03,386
That's the Dark Era.
618
00:37:03,429 --> 00:37:06,306
The Dark Era,
you never want to go to...
619
00:37:06,349 --> 00:37:09,184
because everything
has crumbled...
620
00:37:09,227 --> 00:37:12,395
not just the sands
and monuments to man's folly...
621
00:37:12,438 --> 00:37:16,024
but even the atoms themselves
have begun to crumble.
622
00:37:16,067 --> 00:37:19,861
Even black holes are
not possible in the dark era.
623
00:37:21,948 --> 00:37:24,908
If the universe continues
to expand forever...
624
00:37:24,951 --> 00:37:28,954
it may be that only a cosmic mush
of random particles remains...
625
00:37:30,122 --> 00:37:33,959
but a few surprises may yet
rise out of these ashes.
626
00:37:36,963 --> 00:37:41,716
If, in the distant future,
chaos does rule over order...
627
00:37:41,759 --> 00:37:45,595
our once glowing-hot
universe will descend...
628
00:37:45,638 --> 00:37:48,556
into a chilling
galactic ice age.
629
00:37:51,394 --> 00:37:54,521
But it may still harbor
some potential...
630
00:37:54,563 --> 00:37:56,773
at least according
to quantum theory...
631
00:37:56,816 --> 00:38:00,193
which examines physics
at its most primal level.
632
00:38:00,987 --> 00:38:03,613
In quantum physics,
even the vacuum of space...
633
00:38:03,656 --> 00:38:06,491
that thing that we think of
as being empty with nothing in it...
634
00:38:06,534 --> 00:38:08,410
is not actually empty.
635
00:38:08,452 --> 00:38:12,163
Quantum physics allows
for everything to happen...
636
00:38:12,206 --> 00:38:14,040
with some probability.
637
00:38:16,460 --> 00:38:21,047
In other words, the universe
is playing a risky game of chance.
638
00:38:21,090 --> 00:38:24,968
And quantum theory seeks
to explain the behavior of particles...
639
00:38:25,011 --> 00:38:27,971
in a universe
where anything is possible.
640
00:38:30,433 --> 00:38:32,934
It's as if the universe
were a card dealer...
641
00:38:32,977 --> 00:38:35,812
continuously shuffling a deck...
642
00:38:35,855 --> 00:38:39,190
containing the very
building blocks of our reality.
643
00:38:41,360 --> 00:38:44,362
So if you have a bunch of particles
in a quantum field theory...
644
00:38:44,405 --> 00:38:47,365
what happens is they're going to
just rearrange themselves...
645
00:38:47,408 --> 00:38:49,534
over and over and over again
in what looks to us...
646
00:38:49,577 --> 00:38:51,828
like a random set of fluctuations.
647
00:38:55,124 --> 00:38:58,710
Quantum theory can't predict
the result of a particle shuffle...
648
00:38:59,712 --> 00:39:03,465
but it can reveal
the probability of each outcome.
649
00:39:04,383 --> 00:39:06,509
If you have something
that happens forever...
650
00:39:06,552 --> 00:39:08,303
an infinite number of times...
651
00:39:08,346 --> 00:39:10,930
even very, very unlikely things
will eventually happen.
652
00:39:12,308 --> 00:39:15,435
Ordinarily, when shuffling
a deck of cards...
653
00:39:15,478 --> 00:39:17,479
the result is a random sequence.
654
00:39:19,148 --> 00:39:22,567
Likewise, particles,
churning on a quantum level...
655
00:39:22,610 --> 00:39:26,363
don't usually create
anything orderly.
656
00:39:26,405 --> 00:39:28,698
However, with enough time...
657
00:39:28,741 --> 00:39:32,118
any kind of quantum
fluctuation can form...
658
00:39:32,161 --> 00:39:34,954
even one
that seems impossible.
659
00:39:36,916 --> 00:39:39,084
If you're in a universe
that lasts forever...
660
00:39:39,126 --> 00:39:42,712
if you have a card dealer that is
shuffling cards forever and ever...
661
00:39:42,755 --> 00:39:45,340
even unlikely events like that
will occasionally happen.
662
00:39:49,261 --> 00:39:52,680
One of these unique and
improbable random fluctuations...
663
00:39:52,723 --> 00:39:55,809
can change the fabric
of space itself.
664
00:39:57,478 --> 00:40:01,064
Empty space
is kind of like water...
665
00:40:01,107 --> 00:40:03,566
in the sense that it can
appear in different phases.
666
00:40:04,819 --> 00:40:07,487
It could be hot and be vapor...
667
00:40:07,530 --> 00:40:10,198
it could be solid
like an ice cube...
668
00:40:10,991 --> 00:40:13,284
or it could be liquid.
669
00:40:13,327 --> 00:40:16,579
The space around us right now
is in a certain physical state...
670
00:40:16,622 --> 00:40:18,581
but a phase transition
can happen...
671
00:40:18,624 --> 00:40:20,792
where that physical state
changes into something else.
672
00:40:23,045 --> 00:40:25,797
The wrong kind
of random fluctuation...
673
00:40:25,840 --> 00:40:28,925
can induce a devastating
phase transition.
674
00:40:30,177 --> 00:40:33,096
The way that would occur
is that some region of space...
675
00:40:33,139 --> 00:40:36,099
some point, would witness
the formation of a bubble...
676
00:40:36,142 --> 00:40:39,269
and that bubble would spread
throughout the space around it...
677
00:40:39,311 --> 00:40:44,983
just like this ink would
spread through the glass.
678
00:40:45,860 --> 00:40:48,653
Just as the ink changes
the nature of the water...
679
00:40:49,697 --> 00:40:53,908
so could a phase transition
transform the nature of the cosmos.
680
00:40:56,579 --> 00:40:58,496
The laws of physics
would be different...
681
00:40:58,539 --> 00:41:00,957
in the wake
of this bubble passing.
682
00:41:01,000 --> 00:41:03,042
The masses
of different particles would change...
683
00:41:03,085 --> 00:41:05,211
the charge of different
particles would change...
684
00:41:05,254 --> 00:41:08,840
all of chemistry as we know it
would be completely different...
685
00:41:08,883 --> 00:41:10,717
after this phase
transition occurred.
686
00:41:10,759 --> 00:41:13,636
What that means is that
suddenly there are new ways...
687
00:41:13,679 --> 00:41:17,223
to arrange all the particles
that we're made of...
688
00:41:17,266 --> 00:41:19,976
and it's sort of like
everything in the universe...
689
00:41:20,019 --> 00:41:21,603
becomes an atomic bomb.
690
00:41:22,980 --> 00:41:25,773
It would just rearrange itself,
releasing energy...
691
00:41:25,816 --> 00:41:28,693
and literally every particle,
every atom...
692
00:41:28,736 --> 00:41:31,070
every structure in the universe
would explode.
693
00:41:34,742 --> 00:41:39,662
So no complicated structure can
possibly survive that sort of transition.
694
00:41:39,705 --> 00:41:41,706
What would be left
is just a mess...
695
00:41:41,749 --> 00:41:45,919
nothing but a gas of particles
bumping randomly into each other.
696
00:41:49,173 --> 00:41:54,010
But a random quantum fluctuation
can also spark a bubble of hope.
697
00:41:55,262 --> 00:41:56,930
Some theoretical physicists
suggest...
698
00:41:56,972 --> 00:41:59,682
that some of these
quantum fluctuations...
699
00:41:59,725 --> 00:42:05,980
actually can give rise to
almost detached portions of space...
700
00:42:06,023 --> 00:42:11,611
dimensions that sort of branch off
from ours into a new universe.
701
00:42:13,364 --> 00:42:16,533
Perhaps a quantum fluctuation
sparked the Big Bang...
702
00:42:16,575 --> 00:42:19,285
and gave rise
to our own universe.
703
00:42:20,913 --> 00:42:22,997
You can imagine
that a universe like ours...
704
00:42:23,040 --> 00:42:25,500
even though it's ten billion
light-years across...
705
00:42:25,543 --> 00:42:28,253
is actually a baby universe
that arose...
706
00:42:28,295 --> 00:42:30,755
by pinching off
from some much bigger universe.
707
00:42:32,925 --> 00:42:35,552
We can picture
the birth of a baby universe...
708
00:42:35,594 --> 00:42:39,889
with this bottle, representing
an old, dying, chaotic universe.
709
00:42:41,433 --> 00:42:44,435
My breath is like
quantum fluctuations...
710
00:42:44,478 --> 00:42:46,771
creating new universes
that look like bubbles.
711
00:42:50,234 --> 00:42:53,319
And each one of those bubbles
is a separate universe all of its own.
712
00:42:53,362 --> 00:42:56,573
There is the possibility that there
are other universes out there...
713
00:42:56,615 --> 00:42:59,409
perhaps butted off
from our universe...
714
00:42:59,451 --> 00:43:02,120
and they may have
their own fate...
715
00:43:02,162 --> 00:43:05,832
either eternal expansion
or ultimate re-collapse.
716
00:43:07,626 --> 00:43:11,754
If other universes exist,
then perhaps future civilizations...
717
00:43:11,797 --> 00:43:14,924
may not face an irrevocable
death sentence.
718
00:43:17,261 --> 00:43:21,306
So I would suspect that trillions,
quadrillions of years from now...
719
00:43:21,348 --> 00:43:23,600
when the universe
gets really cold...
720
00:43:23,642 --> 00:43:25,935
and the universe
is near death...
721
00:43:25,978 --> 00:43:28,855
intelligent beings
will be so powerful then...
722
00:43:28,897 --> 00:43:32,358
that they may be tempted
to assemble enough energy...
723
00:43:32,401 --> 00:43:35,612
at one point
to open up bubbles...
724
00:43:35,654 --> 00:43:39,532
little soap bubbles,
gateways to another universe...
725
00:43:39,575 --> 00:43:43,578
where it's a lot warmer
and they can start all over again.
726
00:43:45,372 --> 00:43:46,956
Whether or not
our descendants...
727
00:43:46,999 --> 00:43:50,168
muster the technology
to leave this universe...
728
00:43:50,210 --> 00:43:51,836
there's no avoiding
the fact that...
729
00:43:51,879 --> 00:43:55,173
like all things,
it will come to an end.
730
00:43:58,844 --> 00:44:03,389
While science wrestles with questions
of how the universe will die...
731
00:44:03,432 --> 00:44:07,185
humanity is left to do the same
with how it will live.
732
00:44:08,729 --> 00:44:10,647
Our lives are important.
733
00:44:10,689 --> 00:44:11,856
I'm important,
you're important...
734
00:44:11,899 --> 00:44:14,275
your loved ones are important,
your friends are important...
735
00:44:14,318 --> 00:44:16,361
and we need to make
the most of our existence...
736
00:44:16,403 --> 00:44:19,530
during the fleeting time
that we have here.
737
00:44:19,573 --> 00:44:21,407
This is your life,
this is my life.
738
00:44:21,450 --> 00:44:25,078
We make the most of it,
regardless of the fate of the universe.
63544
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