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ln the beginning,
there was darkness...
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00:00:03,212 --> 00:00:05,295
and then, bang...
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00:00:05,338 --> 00:00:08,507
giving birth to an endless
expanding existence...
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00:00:08,550 --> 00:00:11,092
of time, space, and matter.
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00:00:11,135 --> 00:00:13,386
Now, see further
than we've ever imagined...
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00:00:13,429 --> 00:00:15,303
beyond the limits of our existence...
7
00:00:15,346 --> 00:00:18,181
in a place we call "The Universe."
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00:00:20,475 --> 00:00:25,020
Everything that we know,
time, space, and matter...
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00:00:25,062 --> 00:00:26,062
are doomed.
10
00:00:27,189 --> 00:00:31,525
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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00:00:36,947 --> 00:00:40,158
Whether by the Armageddon
of an inferno...
13
00:00:40,200 --> 00:00:43,285
or in the grip
of an icy executioner...
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00:00:43,327 --> 00:00:48,122
The universe itselfwill freeze
to death and all life with it.
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00:00:49,249 --> 00:00:54,210
Or even by an unseen force
from the depths of space.
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00:00:54,253 --> 00:00:56,879
And literally every particle, every atom...
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00:00:56,921 --> 00:00:59,590
every structure in the universe
would explode.
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00:01:00,925 --> 00:01:04,761
Beware, here comes
the "CosmicApocalypse."
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The year is 20 billion A.D...
20
00:01:21,859 --> 00:01:24,860
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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00:01:42,084 --> 00:01:45,418
galaxies from all directions
have reversed course...
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00:01:45,461 --> 00:01:48,046
and are speeding
towards our own Milky Way.
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00:01:49,048 --> 00:01:52,424
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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00:02:01,349 --> 00:02:02,891
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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00:02:07,312 --> 00:02:11,189
All of a sudden, we see stars
coming at us from all directions.
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00:02:12,942 --> 00:02:14,651
All the galaxies
will start colliding...
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00:02:14,693 --> 00:02:17,694
and the stars within them
will get crunched together.
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00:02:18,363 --> 00:02:21,115
The stars will collide,
the planets will collide.
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Planets will get
swallowed by stars.
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00:02:24,201 --> 00:02:26,494
All of a sudden,
temperatures begin to rise.
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00:02:27,328 --> 00:02:29,579
All of a sudden,
the oceans boil.
40
00:02:29,622 --> 00:02:32,165
All of a sudden,
the mountains will melt.
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Oh, man, it's going to be chaos.
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lt'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.
48
00:03:00,772 --> 00:03:03,065
What's happening
with the Big Crunch scenario...
49
00:03:03,108 --> 00:03:05,400
is that all of the matter
in the universe...
50
00:03:05,442 --> 00:03:08,653
and all the energy, the galaxies,
the stars in them...
51
00:03:08,696 --> 00:03:10,487
are all moving back
towards each other...
52
00:03:10,530 --> 00:03:11,989
and the universe is shrinking.
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Things are getting closer
and closer together.
54
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Our universe right now,
on the other hand, is expanding.
55
00:03:19,997 --> 00:03:22,831
Each day, there is
more and more space...
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00:03:22,874 --> 00:03:26,709
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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00:03:32,590 --> 00:03:36,758
and that's rather like filling up
this hallwaywith people...
60
00:03:36,801 --> 00:03:38,135
and there are
more and more people.
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00:03:38,178 --> 00:03:41,512
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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00:03:45,142 --> 00:03:48,518
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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00:04:05,033 --> 00:04:06,533
The galaxies and the stars...
70
00:04:06,576 --> 00:04:07,576
as they're getting closer
to each other...
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start distorting each other...
72
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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...
76
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to the point that the atoms
themselves begin to fall apart.
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Finally, ourvast 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
offundamental 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.
85
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There are two basic paradigms
for the end ofthe world.
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First, the universe
is going to end in fire.
87
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That's the Christian theory
ofArmageddon...
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fire and brimstone
and the second coming.
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But the Norse
also had their legends.
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They had the legend of Ragnarok,
Twilight ofthe 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...
95
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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.
101
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Ultimately, it depends
on whether the momentum...
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ofthe expansion
of the universe...
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can overcome the collapsing
attraction of gravity.
104
00:06:03,379 --> 00:06:07,589
lmagine that the moment
of contact between bat and ball...
105
00:06:07,632 --> 00:06:10,842
is the initial explosion
ofthe Big Bang.
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Everything's being thrown outward...
107
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and the issue is,
will it re-collapse upon itself...
108
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orwill it continue to expand?
109
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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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lf l launch it upwards,
and if gravity is strong enough...
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compared to how much energy
l 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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lf the universe collapses...
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what might subsequently follow
is another Big Bang...
119
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another expansion event...
120
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and that might expand for a while
and then re-collapse.
121
00:06:58,256 --> 00:07:00,215
So you can imagine
the possibility...
122
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that actually the universe
isjust cyclic...
123
00:07:02,260 --> 00:07:05,386
and so it expands...
124
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and then contracts.
125
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Each bounce
is another Big Bang.
126
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But what if there isn't enough gravity
to rein in the universe?
127
00:07:20,316 --> 00:07:23,485
l launch it upwards
with enough energy...
128
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that it completely escapes.
129
00:07:25,028 --> 00:07:27,237
There's not enough mass
in the universe...
130
00:07:27,280 --> 00:07:30,615
to make it re-collapse,
and so it continues to expand.
131
00:07:32,743 --> 00:07:35,411
Eventually, though this
expansion ought to slow...
132
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shockingly, scientific observations
reveal something completely different.
133
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lt's getting faster.
134
00:07:43,919 --> 00:07:46,586
The universe seems to be
careening out of control.
135
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This expansion is accelerating.
lt's kicking in once again.
136
00:07:51,092 --> 00:07:54,259
We are undergoing
an inflationary expansion.
137
00:07:54,302 --> 00:07:56,719
So the universe we now know
is expanding...
138
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with this extra acceleration...
139
00:07:58,389 --> 00:08:00,640
that is beyond
what you would have thought...
140
00:08:00,682 --> 00:08:03,266
wasjust due
to the initial explosion.
141
00:08:08,563 --> 00:08:10,439
Not only does the ball escape...
142
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but it's as though a little rocket
engine was on the ball...
143
00:08:14,193 --> 00:08:17,570
and it accelerates away
from the Earth even faster.
144
00:08:18,780 --> 00:08:22,616
This is a possibility
that was somewhat unexpected.
145
00:08:24,660 --> 00:08:26,786
The volume of space
in the universe...
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seems destined
to increase forever.
147
00:08:30,706 --> 00:08:33,250
What this means is
that distant galaxies...
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00:08:33,292 --> 00:08:34,750
are going to go
zooming away from us...
149
00:08:34,793 --> 00:08:37,044
and will eventually
become invisible...
150
00:08:37,087 --> 00:08:39,130
because they'll be
too far away to see.
151
00:08:41,173 --> 00:08:44,467
And without seeing galaxies
rushing away from each other...
152
00:08:45,135 --> 00:08:48,971
future civilizations
will lose all sense of history.
153
00:08:49,013 --> 00:08:51,973
They won't know that there
was ever a Big Bang.
154
00:08:53,392 --> 00:08:56,643
So you will think
that the only structure...
155
00:08:56,686 --> 00:08:59,646
within the universe
is the Milky Way galaxy...
156
00:08:59,689 --> 00:09:01,272
and that the rest
of the universe...
157
00:09:01,314 --> 00:09:04,859
is effectively empty,
devoid of stars.
158
00:09:07,403 --> 00:09:09,612
Another scientific theory proposes...
159
00:09:09,655 --> 00:09:13,240
that this expansion
will balloon even faster.
160
00:09:13,283 --> 00:09:18,327
lfthis does happen,
a violent end awaits our cosmos.
161
00:09:18,370 --> 00:09:20,580
Suppose the amount
of repulsive energy...
162
00:09:20,622 --> 00:09:23,540
increases with time
per unit volume.
163
00:09:24,250 --> 00:09:26,668
lt'll eventually
grow strong enough...
164
00:09:26,711 --> 00:09:30,796
to cause clusters of galaxies
to get ripped apart...
165
00:09:30,839 --> 00:09:33,631
and then galaxies themselves
will get ripped apart.
166
00:09:33,674 --> 00:09:35,967
The stars will start
flying away from one another...
167
00:09:36,010 --> 00:09:38,051
no longer held together by gravity...
168
00:09:38,094 --> 00:09:41,096
and then planetary systems
like our solar system...
169
00:09:41,139 --> 00:09:42,848
will get ripped apart...
170
00:09:42,891 --> 00:09:45,808
and then stars and planets
will get ripped apart...
171
00:09:45,851 --> 00:09:47,935
and then humans
will get ripped apart...
172
00:09:47,978 --> 00:09:52,481
and then the very atoms ofwhich
we are made will get ripped apart.
173
00:09:52,523 --> 00:09:56,525
That's called the Big Rip,
and it's a really scary possibility.
174
00:09:56,568 --> 00:09:57,985
But don't worry.
175
00:09:58,028 --> 00:10:00,111
Most of us don't think
it's going to happen.
176
00:10:02,031 --> 00:10:06,575
But even ifthe rate of expansion
never reaches this tipping point...
177
00:10:06,618 --> 00:10:11,120
the future of our universe
still isn't promising.
178
00:10:11,163 --> 00:10:13,247
lts temperature decreases.
179
00:10:13,290 --> 00:10:16,833
lt's getting colder and colder
and darker and darker...
180
00:10:16,876 --> 00:10:19,669
because the feeble light
emitted by stars...
181
00:10:19,712 --> 00:10:23,005
is going into a progressively
larger volume...
182
00:10:23,048 --> 00:10:27,383
so the universe is going to get
really cold and really dark.
183
00:10:27,426 --> 00:10:29,427
Basically, a pretty gloomy place.
184
00:10:32,805 --> 00:10:35,516
The universe itself,
we now believe...
185
00:10:35,558 --> 00:10:38,851
will die in ice,
rather than fire.
186
00:10:38,894 --> 00:10:42,187
We think the universe
will die in a great freeze...
187
00:10:42,230 --> 00:10:45,565
just like the Norse
legends foretell...
188
00:10:45,608 --> 00:10:48,817
rather than this Armageddon
of a Big Crunch.
189
00:10:52,738 --> 00:10:55,406
lf the universe continues
on its present course...
190
00:10:55,449 --> 00:11:01,870
we're destined for a cosmic ice age
where sunlight itself goes extinct.
191
00:11:04,748 --> 00:11:07,667
By the year100 trillion A.D...
192
00:11:07,709 --> 00:11:10,627
the last remnants
of human civilization...
193
00:11:10,670 --> 00:11:16,674
may be forced to settle here
in this distant dark corner of our galaxy.
194
00:11:17,634 --> 00:11:21,469
They'll be huddled around
the last burning star in the sky...
195
00:11:21,512 --> 00:11:25,013
but, sadly, it too will soon die.
196
00:11:26,140 --> 00:11:31,227
Our Milky Way, so named for its
shimmering band of sparkling stars...
197
00:11:31,270 --> 00:11:33,312
will be unrecognizable.
198
00:11:33,355 --> 00:11:36,189
Faint glowing embers
of dark stellar husks...
199
00:11:36,232 --> 00:11:37,732
will be all that remain...
200
00:11:37,775 --> 00:11:41,318
ofwhat was once
a brilliant night vision.
201
00:11:44,573 --> 00:11:46,906
What happened
to all of the stars?
202
00:11:47,783 --> 00:11:51,577
How did we arrive
at such a dismal scenario?
203
00:11:55,498 --> 00:12:01,918
Science decrees that as our universe
expands and ages, it will cool.
204
00:12:01,961 --> 00:12:05,797
lnevitably, the future
for life as we know it...
205
00:12:05,840 --> 00:12:09,049
will grow ever more hostile.
206
00:12:09,092 --> 00:12:10,259
We are headed for a time...
207
00:12:10,302 --> 00:12:16,306
when one day the universe itself
will freeze to death and all life with
it...
208
00:12:16,348 --> 00:12:18,307
and that's a law.
209
00:12:19,475 --> 00:12:22,311
When we scientists look
at the evolution of the universe...
210
00:12:22,353 --> 00:12:24,770
some critics say, "That's crazy.
211
00:12:24,813 --> 00:12:26,897
"We can barely predict
tomorrow's headlines...
212
00:12:26,940 --> 00:12:29,649
"and here you are predicting
what's going to be happening...
213
00:12:29,692 --> 00:12:31,568
"billions and billions
ofyears from now.
214
00:12:31,611 --> 00:12:33,277
"How do you do it?"
215
00:12:34,195 --> 00:12:38,073
Among the tools available
to scientists pondering the future...
216
00:12:38,116 --> 00:12:41,784
are the venerable
laws of thermodynamics.
217
00:12:41,827 --> 00:12:46,997
The first law says that total
matter and energy are conserved.
218
00:12:47,040 --> 00:12:49,457
ln otherwords, you can't
get something for nothing.
219
00:12:49,499 --> 00:12:51,167
There's no free lunch.
220
00:12:51,209 --> 00:12:56,212
So it turns out that the total amount
of matter and energy in a system...
221
00:12:56,255 --> 00:12:58,256
can be neither created
nor destroyed.
222
00:12:59,008 --> 00:13:01,467
The matter and energy
can change forms...
223
00:13:01,509 --> 00:13:03,177
and they can turn
into one another...
224
00:13:03,219 --> 00:13:05,470
but the total remains the same.
225
00:13:05,512 --> 00:13:07,972
So, for example,
in this rolled-up newspaper...
226
00:13:08,015 --> 00:13:12,142
there's a lot of energy stored
in the chemical bonds of the paper...
227
00:13:12,185 --> 00:13:13,852
but if l ignite the paper...
228
00:13:13,895 --> 00:13:19,523
l can activate those bonds,
and l can start breaking them...
229
00:13:19,566 --> 00:13:23,652
and that releases energy
in the form of light and heat...
230
00:13:23,694 --> 00:13:25,528
which you can see and feel.
231
00:13:25,571 --> 00:13:28,656
The total energy content
is still the same...
232
00:13:28,698 --> 00:13:31,033
but it's being dissipated
out into space.
233
00:13:31,992 --> 00:13:36,496
And a lot of particulate matter
goes off as well and smoke goes off...
234
00:13:36,538 --> 00:13:37,537
but if l were to add up...
235
00:13:37,580 --> 00:13:39,915
all the smoke
and the particulate matter...
236
00:13:39,957 --> 00:13:43,626
and all the energy that's given off
and everything total...
237
00:13:43,669 --> 00:13:45,670
l would get
exactly the same amount...
238
00:13:45,712 --> 00:13:49,839
of mass and energy total
as l had to begin with.
239
00:13:49,882 --> 00:13:52,384
They simply changed forms.
240
00:13:54,761 --> 00:13:58,471
lf the total amount of mass
and energy remain constant...
241
00:13:58,514 --> 00:14:00,181
this seems to imply the universe...
242
00:14:00,224 --> 00:14:03,476
will always have energy
and should last forever.
243
00:14:05,395 --> 00:14:07,896
But the second law
of thermodynamics...
244
00:14:07,939 --> 00:14:10,356
crushes this notion.
245
00:14:10,399 --> 00:14:12,358
The second law
of thermodynamics...
246
00:14:12,401 --> 00:14:14,359
is the most curious of all.
247
00:14:14,402 --> 00:14:18,196
lt says that total amount
of disorder or entropy...
248
00:14:18,239 --> 00:14:21,073
always increases
in the universe.
249
00:14:21,116 --> 00:14:25,827
ln otherwords,
things rust, things decay...
250
00:14:25,869 --> 00:14:29,664
everything gets old
and eventually falls apart and rots.
251
00:14:30,748 --> 00:14:34,543
ln some sense, the second law
is a death warrant...
252
00:14:34,585 --> 00:14:36,585
a death warrant
for the universe.
253
00:14:39,381 --> 00:14:42,048
The second law says
all things must pass.
254
00:14:44,969 --> 00:14:47,761
The ever-present supply
of energy in the universe...
255
00:14:47,804 --> 00:14:49,930
inevitably becomes
more dispersed...
256
00:14:49,973 --> 00:14:53,057
more chaotic,
and more unusable.
257
00:14:54,184 --> 00:14:56,935
Each star burning in the sky...
258
00:14:56,978 --> 00:14:59,479
just like each briquette
of this charcoal...
259
00:14:59,522 --> 00:15:02,273
must one day face its fate.
260
00:15:03,275 --> 00:15:05,192
This piece of charcoal is fuel.
261
00:15:05,235 --> 00:15:06,819
lt has a lot of energy...
262
00:15:06,862 --> 00:15:10,363
concentrated into this
small, little packet here.
263
00:15:10,406 --> 00:15:13,407
That energy goes from being
in the chemical bonds...
264
00:15:13,450 --> 00:15:15,075
of the charcoal briquette...
265
00:15:15,118 --> 00:15:19,787
to being liberated
in the form of heat and light.
266
00:15:19,830 --> 00:15:22,081
Now, a star does a similar thing.
267
00:15:22,124 --> 00:15:24,750
lt doesn't burn
in a chemical sense.
268
00:15:24,792 --> 00:15:28,503
lnstead, in a star,
it's nuclear energy.
269
00:15:28,546 --> 00:15:33,549
The nuclei of atoms
are being forced together...
270
00:15:33,592 --> 00:15:36,760
fusing them,
creating new nuclei...
271
00:15:36,802 --> 00:15:41,221
and, in the process, transforming
some of that matter...
272
00:15:41,264 --> 00:15:47,018
some of that mass, into the radiated
energy that we see and we feel.
273
00:15:47,060 --> 00:15:49,937
And the same process
is going on...
274
00:15:49,980 --> 00:15:52,647
in all the active stars
in the universe.
275
00:15:53,775 --> 00:15:57,401
Now, as this charcoal is burning,
the fuel is getting used up...
276
00:15:57,444 --> 00:15:58,652
and you can actually see that.
277
00:15:58,695 --> 00:16:00,654
lt's turning into a gray color.
278
00:16:00,696 --> 00:16:02,030
lt's turning into ashes.
279
00:16:03,199 --> 00:16:07,868
ln a similarway,
stars use up theirfuel.
280
00:16:07,911 --> 00:16:11,746
They fuse hydrogen into helium,
and so, with time...
281
00:16:11,789 --> 00:16:14,832
there's less and less
hydrogen to fuse.
282
00:16:14,875 --> 00:16:17,959
And the ashes have
less energy content...
283
00:16:18,002 --> 00:16:21,505
and, thus, are either
harder to burn...
284
00:16:21,547 --> 00:16:25,800
or release less energy
during the burning process.
285
00:16:28,677 --> 00:16:31,679
This is the eventual fate
of our own Sun.
286
00:16:33,014 --> 00:16:36,600
As it ages, it bloats and heats.
287
00:16:36,643 --> 00:16:39,310
The Earth will be fried to a crisp.
288
00:16:40,229 --> 00:16:43,522
Oceans will boil away,
all plants and animals will die...
289
00:16:43,564 --> 00:16:46,149
rocks will start vaporizing...
290
00:16:46,192 --> 00:16:50,194
because the Sun will be producing
so much light, so much energy.
291
00:16:51,363 --> 00:16:56,282
That'll be a pretty gruesome death
for the Earth.
292
00:16:58,202 --> 00:17:01,703
All through the universe,
stars that are like the Sun...
293
00:17:01,746 --> 00:17:03,914
are going to be facing
the same challenges...
294
00:17:03,957 --> 00:17:05,623
that our own starwill face.
295
00:17:05,666 --> 00:17:07,750
They're running out offuel,
they're swelling up...
296
00:17:07,793 --> 00:17:12,087
and they're causing problems
for the planets that orbit them.
297
00:17:12,129 --> 00:17:15,006
So it's not hard to imagine
that there are many locations...
298
00:17:15,049 --> 00:17:18,384
where life has evolved
and flourished...
299
00:17:18,426 --> 00:17:19,927
and is now being extinguished.
300
00:17:22,429 --> 00:17:25,682
Just as each star suffers
the effects of entropy...
301
00:17:25,724 --> 00:17:29,184
so, too, will the rest
of the universe.
302
00:17:29,227 --> 00:17:33,020
But stars naturally increase
the entropy of the universe...
303
00:17:33,063 --> 00:17:35,314
by giving off light and heat...
304
00:17:35,357 --> 00:17:38,859
just like this fire
of burning charcoal...
305
00:17:38,901 --> 00:17:43,070
naturally increases
the entropy of the universe.
306
00:17:43,113 --> 00:17:46,031
Right nowwe're kind of
in a steady period in the universe...
307
00:17:46,074 --> 00:17:49,075
where stars are born,
live out their lives, die...
308
00:17:49,577 --> 00:17:51,578
give some of that gas back
to the next generation...
309
00:17:51,620 --> 00:17:53,704
and you have another
generation of stars.
310
00:17:53,746 --> 00:17:59,125
But that rate of star formation
is gradually decreasing with time.
311
00:17:59,167 --> 00:18:03,086
And as stars use up
theirfuel and burn out...
312
00:18:03,129 --> 00:18:06,965
there aren't enough new stars
being formed to replace them.
313
00:18:07,008 --> 00:18:10,885
But the moment we run out
of gas to make new stars...
314
00:18:10,927 --> 00:18:14,846
it means for every dead star
in the rolls, in the ranks...
315
00:18:14,889 --> 00:18:16,723
there's not a star to replace it.
316
00:18:17,516 --> 00:18:19,266
And so that's a bad
situation to be in...
317
00:18:19,309 --> 00:18:20,601
the day that happens.
318
00:18:21,436 --> 00:18:25,479
So, effectively, galaxies,
giant collections of stars...
319
00:18:25,522 --> 00:18:29,442
are growing progressively
dimmerwith time on average.
320
00:18:29,484 --> 00:18:31,526
And, eventually,
when the universe...
321
00:18:31,569 --> 00:18:35,029
is something like
a hundred trillion years old...
322
00:18:35,071 --> 00:18:39,116
there will be essentially
no stars still shining.
323
00:18:39,159 --> 00:18:42,577
The universe will be
cold and dark indeed.
324
00:18:43,621 --> 00:18:47,331
Any life that depends on sunlight
will rapidly go extinct...
325
00:18:47,373 --> 00:18:49,416
as the universe
continues to age...
326
00:18:49,459 --> 00:18:53,878
and as there are fewer and fewer
sources of life-providing energy...
327
00:18:53,921 --> 00:18:55,171
from a host star.
328
00:18:56,797 --> 00:18:58,840
You might think
the most massive stars...
329
00:18:58,883 --> 00:19:02,217
the ones with the most fuel,
will last the longest.
330
00:19:03,053 --> 00:19:06,263
ln reality,
the more fuel a star carries...
331
00:19:06,306 --> 00:19:08,306
the faster it burns through it.
332
00:19:09,224 --> 00:19:12,018
The final rays of sunlight
left in the universe...
333
00:19:12,061 --> 00:19:14,728
will come from stars
known as red dwarfs.
334
00:19:16,022 --> 00:19:17,272
These miniature stars...
335
00:19:17,315 --> 00:19:20,608
ten times less massive
than our own sun...
336
00:19:20,651 --> 00:19:24,235
burn thousands
of degrees cooler.
337
00:19:24,278 --> 00:19:26,404
Red dwarf stars
are much more miserly...
338
00:19:26,447 --> 00:19:27,781
with theirfuel consumption...
339
00:19:27,823 --> 00:19:30,950
and so, even though they have
less fuel to begin with...
340
00:19:30,992 --> 00:19:33,660
they last much, much longer
than our Sun will last.
341
00:19:36,121 --> 00:19:41,458
A typical red dwarf can live
for as long as 14 trillion years.
342
00:19:41,501 --> 00:19:46,545
That's a thousand times longer
than the current age of our universe.
343
00:19:46,588 --> 00:19:49,798
Eventually, though,
even these stingy little suns...
344
00:19:49,840 --> 00:19:51,508
will begin to die off.
345
00:19:52,551 --> 00:19:55,678
So when our Milky Way galaxy
is tens of trillions ofyears old...
346
00:19:56,638 --> 00:19:59,014
and there's only
a few red dwarfs remaining...
347
00:19:59,057 --> 00:20:02,183
you might imagine that
any surviving civilizations...
348
00:20:02,226 --> 00:20:04,644
will realize that the end is nigh...
349
00:20:04,687 --> 00:20:08,814
and they will start crowding around
these few sources of energy...
350
00:20:08,856 --> 00:20:11,190
trying to scrape out
an existence.
351
00:20:12,526 --> 00:20:15,236
Red dwarfs could be oases of life...
352
00:20:15,278 --> 00:20:18,989
in the vast, inhospitable
desert of the universe.
353
00:20:20,408 --> 00:20:23,575
But for a planet to receive
as much heat and energy...
354
00:20:23,618 --> 00:20:27,620
from its red dwarf host as our
Earth does from the Sun...
355
00:20:28,914 --> 00:20:31,416
it would need to orbit so closely...
356
00:20:31,458 --> 00:20:35,252
that one full year
would lastjust six Earth days.
357
00:20:37,213 --> 00:20:40,965
The sky would be much more
sort ofwhitish red...
358
00:20:41,008 --> 00:20:43,758
than our blue skies here on Earth...
359
00:20:43,801 --> 00:20:46,845
because the red dwarf
puts out so little blue light...
360
00:20:46,887 --> 00:20:49,680
you wouldn't be able to have
the kind of nice blue skies...
361
00:20:49,723 --> 00:20:51,890
that we have here now.
362
00:20:51,933 --> 00:20:57,270
However, nothing left in the universe
would be hotter or brighter.
363
00:20:58,105 --> 00:20:59,938
So, there will be
a time in our galaxy...
364
00:20:59,981 --> 00:21:04,775
when there'sjust
a few red dwarfs still glowing...
365
00:21:04,818 --> 00:21:10,363
and maybejust then three
and two and one as they blink out.
366
00:21:10,406 --> 00:21:13,992
And, gosh, when there's
one red dwarf left...
367
00:21:14,035 --> 00:21:16,702
and suppose
l'm on the planet circling it...
368
00:21:16,745 --> 00:21:18,287
l'll think, "Man, oh, man...
369
00:21:18,329 --> 00:21:20,246
'what a lonely place
the universe is.
370
00:21:20,289 --> 00:21:22,957
"What a depressing future it holds."
371
00:21:24,918 --> 00:21:29,880
What happens after the last red dwarf
blinks out of existence?
372
00:21:34,760 --> 00:21:39,304
Life in the 21st century on Earth
thrives within a universe...
373
00:21:39,346 --> 00:21:42,806
that has existed
for about14 billion years...
374
00:21:42,849 --> 00:21:45,017
since the spark of the Big Bang.
375
00:21:47,978 --> 00:21:51,689
But that's no time at all
in the grand scheme of the cosmos.
376
00:21:52,440 --> 00:21:55,942
lf the universe is comparable
to a human life span...
377
00:21:55,985 --> 00:22:00,196
we are still in the infancy
of the universe.
378
00:22:02,782 --> 00:22:06,076
Getting a grasp of the time
that has already elapsed...
379
00:22:06,118 --> 00:22:10,287
and the time span still to come
can boggle the mind.
380
00:22:10,330 --> 00:22:13,915
To gain a perspective
of the vast time scales of the universe...
381
00:22:13,957 --> 00:22:18,335
let's compress the roughly
14-billion-year history of the universe...
382
00:22:18,377 --> 00:22:22,255
into one normal calendaryear.
383
00:22:22,298 --> 00:22:24,632
But we'll call this
a cosmic calendar.
384
00:22:26,384 --> 00:22:29,719
So the Big Bang occurred
on NewYear's, January1st.
385
00:22:30,679 --> 00:22:37,392
On that scale, our Milky Way galaxy
formed near the end of January...
386
00:22:37,435 --> 00:22:41,729
and our solar system formed
around the beginning ofAugust or so...
387
00:22:41,772 --> 00:22:44,899
about two-thirds of the way
through the year.
388
00:22:44,941 --> 00:22:48,693
Life formed sometime
a little bit later in August...
389
00:22:48,736 --> 00:22:51,612
but humans formed
less than a day ago.
390
00:22:51,655 --> 00:22:56,783
So, on December 31st sometime,
humans finally arose.
391
00:22:58,160 --> 00:23:00,495
We can also look
into the future...
392
00:23:01,496 --> 00:23:04,414
on the same cosmic calendar
time scale.
393
00:23:05,416 --> 00:23:08,876
Near the end of January
of this coming year...
394
00:23:08,919 --> 00:23:12,003
our Earth will become
quite inhospitable.
395
00:23:12,046 --> 00:23:16,133
By around May or so,
our Sun will have died...
396
00:23:16,175 --> 00:23:19,009
but there are some other stars,
the low-mass stars...
397
00:23:19,052 --> 00:23:21,178
which will live
for much, much longer...
398
00:23:21,221 --> 00:23:25,682
up to10,000
of these cosmic years.
399
00:23:27,684 --> 00:23:32,146
That's 10,000 times longer than
the entire history of the universe...
400
00:23:32,188 --> 00:23:36,983
before these final longest-living
red dwarf stars die off.
401
00:23:37,025 --> 00:23:38,358
But then what happens?
402
00:23:39,610 --> 00:23:42,154
When we talk about
the extremely distant future...
403
00:23:42,196 --> 00:23:45,865
we're talking about
immense spans of time...
404
00:23:45,907 --> 00:23:48,284
time measured
in quadrillions ofyears...
405
00:23:48,326 --> 00:23:49,993
and septillions ofyears...
406
00:23:50,035 --> 00:23:52,829
and it becomes so overwhelming...
407
00:23:52,872 --> 00:23:56,331
that we need to evolve
another concept to really deal with it.
408
00:23:56,374 --> 00:23:59,293
So we came up with the idea
of cosmological decades.
409
00:24:02,171 --> 00:24:05,589
A cosmological decade,
each decade is ten times longer...
410
00:24:05,631 --> 00:24:10,050
than all the time that happened
prior to the start ofthe decade.
411
00:24:10,093 --> 00:24:13,554
And one way to think about this
is that it's like a staircase.
412
00:24:14,806 --> 00:24:17,849
Not an ordinary staircase
like this one...
413
00:24:17,892 --> 00:24:21,810
but one in which each step
is ten times higher...
414
00:24:21,853 --> 00:24:23,478
than the step before.
415
00:24:23,521 --> 00:24:27,565
So you can imagine the staircase
going up and up and up...
416
00:24:27,608 --> 00:24:30,443
to higher and higher
cosmological decades.
417
00:24:30,485 --> 00:24:35,739
Right now, we're living in
the tenth cosmological decade.
418
00:24:38,366 --> 00:24:41,535
On this scale,
the tenth cosmological decade...
419
00:24:41,578 --> 00:24:45,455
is ten times longer than
the previous nine decades combined...
420
00:24:45,497 --> 00:24:47,831
that have passed
since the Big Bang.
421
00:24:51,085 --> 00:24:53,419
The hallmark
of the tenth cosmological decade...
422
00:24:53,462 --> 00:24:57,548
is the fact that stars
are burning brightly in the night sky...
423
00:24:57,591 --> 00:25:00,508
and also that the planets
are beginning to develop...
424
00:25:00,551 --> 00:25:03,719
life and intelligence
on their surfaces.
425
00:25:03,762 --> 00:25:08,848
Another interesting hallmark
of the tenth cosmological decade...
426
00:25:08,891 --> 00:25:12,560
is the beginning
of the acceleration...
427
00:25:12,603 --> 00:25:14,603
of the expansion
ofthe universe.
428
00:25:16,439 --> 00:25:19,066
As our cosmological decade
continues...
429
00:25:19,108 --> 00:25:22,151
all of the other galaxies
disappearfrom view...
430
00:25:22,194 --> 00:25:26,738
and stars begin to die off
without being replaced.
431
00:25:26,781 --> 00:25:31,659
During the latter part of this era,
there will always be about fifty stars...
432
00:25:31,701 --> 00:25:34,912
shining in the galaxy
at any one time.
433
00:25:34,955 --> 00:25:37,580
And that will be
the last sort of gasp...
434
00:25:37,623 --> 00:25:39,832
of the kind ofworld,
the kind of planets...
435
00:25:39,875 --> 00:25:42,626
the kind of environments
that are familiar to us.
436
00:25:44,754 --> 00:25:48,923
As we move through the succeeding
cosmological decades...
437
00:25:48,966 --> 00:25:55,595
and after the last star dies,
we enter a new alien age.
438
00:25:55,638 --> 00:26:00,724
So up here, we're in the cosmological
decade 20 through 30...
439
00:26:00,767 --> 00:26:04,060
and ifwe look out
at the night sky...
440
00:26:04,103 --> 00:26:08,063
it's absolutely, utterly,
completely black.
441
00:26:08,106 --> 00:26:10,565
But ifwe're able
to look in light...
442
00:26:10,608 --> 00:26:13,401
that's far too red
for the human eye to see...
443
00:26:13,443 --> 00:26:17,446
then we'd actually see that the sky
is speckled with dead stars.
444
00:26:19,365 --> 00:26:21,032
This is the Degenerate Era.
445
00:26:23,451 --> 00:26:24,785
ln the Degenerate Era...
446
00:26:24,828 --> 00:26:29,998
the most massive dead stars
have collapsed into black holes.
447
00:26:30,040 --> 00:26:33,293
But punctuating
the total blackness of space...
448
00:26:33,335 --> 00:26:38,547
the leftover ashes of once bright stars
are still ebbing energy.
449
00:26:39,923 --> 00:26:42,842
These ashes are called
a white dwarf.
450
00:26:42,884 --> 00:26:43,884
Now, they're really weird...
451
00:26:43,927 --> 00:26:47,178
because you've got something
like halfthe mass of our Sun...
452
00:26:47,221 --> 00:26:50,639
roughly160,000 times
the mass of our Earth...
453
00:26:50,682 --> 00:26:54,059
compressed into a volume
just the size ofthe Earth.
454
00:26:54,102 --> 00:26:55,476
So it's very dense stuff.
455
00:26:55,519 --> 00:26:57,937
lt's weird ashes, that's for sure.
456
00:26:59,189 --> 00:27:02,941
So it'll be like
the dying ember after a fire.
457
00:27:02,984 --> 00:27:07,361
lt'll be generating no new energy
of its own through nuclearfusion.
458
00:27:09,197 --> 00:27:12,657
But as the dying embers
of a white dwarf cool...
459
00:27:12,700 --> 00:27:15,910
they still emit
many megawatts of power.
460
00:27:16,828 --> 00:27:21,165
But that is vastly billions,
trillions of times less energy...
461
00:27:21,207 --> 00:27:23,541
than the Sun is producing right now.
462
00:27:25,377 --> 00:27:29,129
And so ifwe think
we have an energy crisis now...
463
00:27:29,172 --> 00:27:30,881
the energy crisis
in the Degenerate Era...
464
00:27:30,923 --> 00:27:34,008
will be far more severe
and far more profound.
465
00:27:36,470 --> 00:27:41,723
Even so, the energy emanating
from these ancient star remnants...
466
00:27:41,766 --> 00:27:44,224
is still greater
than that consumed today...
467
00:27:44,267 --> 00:27:46,727
by all human civilization.
468
00:27:47,562 --> 00:27:50,355
lfwe were to imagine that
somehow a human civilization...
469
00:27:50,397 --> 00:27:53,107
were to persist
into the Degenerate Era...
470
00:27:53,150 --> 00:27:58,819
they might be tapping the energy
that's emerging from the white dwarf.
471
00:27:58,862 --> 00:28:01,614
However, humans
wouldn't be able to establish...
472
00:28:01,656 --> 00:28:04,866
an energy-gathering
outpost on its surface...
473
00:28:04,909 --> 00:28:08,244
such as an oil rig
anchored to the ocean floor.
474
00:28:08,913 --> 00:28:11,288
Surface gravity
is incredibly strong.
475
00:28:11,331 --> 00:28:13,040
You would basically be crushed...
476
00:28:13,083 --> 00:28:15,249
ifyou tried to stand
on the surface of a white dwarf.
477
00:28:17,169 --> 00:28:19,670
To survive, future civilizations...
478
00:28:19,713 --> 00:28:23,507
would need to establish
an orbiting colony.
479
00:28:23,549 --> 00:28:26,884
They would probably tap that energy
that's coming from the white dwarf...
480
00:28:26,927 --> 00:28:29,053
by having some sort
of absorbing panels...
481
00:28:29,096 --> 00:28:31,721
that are also in orbit
around the white dwarf.
482
00:28:31,764 --> 00:28:33,807
So the energy that's
emanating up from below...
483
00:28:33,849 --> 00:28:36,683
would be captured
and trapped and used.
484
00:28:38,603 --> 00:28:41,729
Still, light in this
white dwarf-orbiting future...
485
00:28:41,772 --> 00:28:44,232
would have to be generated
artificially.
486
00:28:45,567 --> 00:28:47,609
There's no stars shining in the sky.
487
00:28:47,652 --> 00:28:48,819
There's no moonlight.
488
00:28:48,861 --> 00:28:49,903
There's no sunlight.
489
00:28:51,155 --> 00:28:55,866
You're simply orbiting
a gigantic, dead black mass.
490
00:28:58,577 --> 00:29:03,622
Unfortunately, dead black masses
will make up the bulk of galaxies...
491
00:29:03,665 --> 00:29:05,290
during the Degenerate Era.
492
00:29:06,626 --> 00:29:09,961
So, as we go
into the Degenerate Era...
493
00:29:10,003 --> 00:29:13,505
we'll have roughly
a hundred billion dead stars...
494
00:29:13,548 --> 00:29:18,884
orbiting each other
in a giant elliptical configuration.
495
00:29:19,886 --> 00:29:22,430
Occasionally, they'll
interact with one another...
496
00:29:22,472 --> 00:29:25,265
and one will get flung out
ofthe galaxy...
497
00:29:25,307 --> 00:29:27,517
causing the galaxy to lose mass.
498
00:29:27,560 --> 00:29:31,103
The galaxy, in a sense,
will evaporate slowly with time...
499
00:29:31,146 --> 00:29:32,521
as these things are flung out.
500
00:29:34,648 --> 00:29:37,442
White dwarfs
and remaining galactic material...
501
00:29:37,484 --> 00:29:39,610
fall prey to black holes.
502
00:29:41,320 --> 00:29:43,363
So gradually, with time,
what will happen...
503
00:29:43,406 --> 00:29:47,158
is the galaxy will have fewer
and fewer objects in it...
504
00:29:47,200 --> 00:29:51,828
and a greater and greater
fraction of them will be black holes.
505
00:29:53,164 --> 00:29:54,622
And whatever isn't seized...
506
00:29:54,665 --> 00:29:58,459
by the millions of black holes
roaming the universe...
507
00:29:58,501 --> 00:30:01,335
begins to decay with old age.
508
00:30:02,129 --> 00:30:05,173
And this is another example
of the general process...
509
00:30:05,215 --> 00:30:09,468
by which the total amount of
randomness increases in the universe.
510
00:30:09,510 --> 00:30:12,720
The second law of thermodynamics
is once again at work.
511
00:30:12,762 --> 00:30:17,098
And all the structures,
all the stars...
512
00:30:17,141 --> 00:30:20,268
are basically
evaporating into nothing...
513
00:30:20,311 --> 00:30:23,187
and so by about
cosmological decade forty...
514
00:30:23,229 --> 00:30:25,939
most of the stuff that's been built...
515
00:30:25,982 --> 00:30:28,649
the planets and the stars,
are all gone...
516
00:30:29,485 --> 00:30:30,985
and the Degenerate Era...
517
00:30:31,028 --> 00:30:33,612
which has stretched
for huge amounts of time...
518
00:30:33,654 --> 00:30:35,155
is coming to an end.
519
00:30:36,491 --> 00:30:38,657
With nothing left
in theirway...
520
00:30:38,700 --> 00:30:42,620
black holes stand poised
to rule the universe.
521
00:30:46,582 --> 00:30:49,917
This may be the grim future
ofthe cosmos.
522
00:30:49,959 --> 00:30:52,503
The planets decay and dissolve...
523
00:30:53,880 --> 00:30:58,341
dark galactic remnants scatter
across a bloated universe...
524
00:30:58,383 --> 00:31:02,469
and even light isjust
a faint, distant memory.
525
00:31:04,055 --> 00:31:07,473
As we continue through
the vast stretches of time...
526
00:31:07,516 --> 00:31:09,850
measured
in cosmological decades...
527
00:31:09,893 --> 00:31:14,938
massive black holes survive
as the only recognizable features...
528
00:31:14,980 --> 00:31:18,023
of our once brilliant night sky.
529
00:31:18,066 --> 00:31:21,943
We're up to about cosmological decade
sixty-something...
530
00:31:21,985 --> 00:31:24,779
and when you look out
at the night sky...
531
00:31:26,989 --> 00:31:30,200
it's incredibly cold,
it's incredibly black...
532
00:31:30,243 --> 00:31:35,287
and there's only the faintest
crackle of radio waves...
533
00:31:35,330 --> 00:31:41,042
and gravitational radiation,
echoing through the empty skies.
534
00:31:41,085 --> 00:31:43,460
This is the Black Hole Era.
535
00:31:45,463 --> 00:31:50,299
The continuous expansion
of the universe has taken its toll.
536
00:31:50,342 --> 00:31:55,136
The unimaginable cold saps energy
and constricts movement.
537
00:31:55,179 --> 00:31:58,097
Time itself seems
to lose meaning.
538
00:31:59,432 --> 00:32:03,269
ln the midst of the Black Hole Era,
even the Degenerate Era...
539
00:32:03,311 --> 00:32:06,479
looks like the first sliver of time
after the Big Bang.
540
00:32:08,107 --> 00:32:11,066
Does life have a chance
in this environment?
541
00:32:12,026 --> 00:32:15,778
Humans won't exist at that time
because protons won't exist...
542
00:32:15,821 --> 00:32:19,656
but it's possible to imagine
some kind of entity...
543
00:32:19,699 --> 00:32:23,785
which is living
at an extraordinarily slow rate.
544
00:32:25,412 --> 00:32:27,246
lf it lives slowly enough...
545
00:32:27,289 --> 00:32:30,248
perhaps strange life
could emerge.
546
00:32:32,042 --> 00:32:35,294
A thought would take
trillions ofyears.
547
00:32:35,336 --> 00:32:39,256
lt may take a trillion years for you
to decide what to have for lunch...
548
00:32:39,299 --> 00:32:44,468
because everything is so slow,
everything is near absolute zero.
549
00:32:46,596 --> 00:32:49,723
The creeping time scale
ofthe Black Hole Era...
550
00:32:49,765 --> 00:32:52,558
can be compared
to the growth ofvegetation.
551
00:32:53,852 --> 00:32:58,146
From a human perspective,
involving minutes, hours, and days...
552
00:32:58,188 --> 00:33:01,107
plant life can seem frozen in time.
553
00:33:03,484 --> 00:33:06,278
Absolutely nothing
seems to be happening.
554
00:33:06,321 --> 00:33:10,281
lt appears to be completely dead,
completely static.
555
00:33:10,324 --> 00:33:15,493
But ifwe speed up the clock,
then we see the activity.
556
00:33:16,662 --> 00:33:17,787
The plant grows...
557
00:33:17,829 --> 00:33:21,707
the plant moves its leaves
in response to where the Sun is...
558
00:33:21,750 --> 00:33:25,543
the plant is continuously in motion,
it's continuously doing things...
559
00:33:25,586 --> 00:33:29,713
but that whole scale of existence
is on a time frame that's longer...
560
00:33:29,756 --> 00:33:32,674
than what our experience
is used to dealing with.
561
00:33:38,347 --> 00:33:41,056
The real action
in the Black Hole Era occurs...
562
00:33:41,098 --> 00:33:42,766
when two black holes meet.
563
00:33:45,685 --> 00:33:50,647
Although invisible to human eyes,
a collision between these two beasts...
564
00:33:50,689 --> 00:33:53,274
sends a shudder
through space-time.
565
00:33:54,610 --> 00:33:58,945
This event can be imagined
in a sheet of perfectly still, calm water.
566
00:34:00,031 --> 00:34:05,576
lt's a bit like suddenly dropping
a gigantic rock into that calm water...
567
00:34:07,536 --> 00:34:10,372
sending out
a huge series of ripples...
568
00:34:10,414 --> 00:34:13,165
and you have a lot of action
for a little bit oftime...
569
00:34:13,208 --> 00:34:15,876
but then that dissipates,
the ripples die away...
570
00:34:17,252 --> 00:34:20,630
and you're back to that smooth,
glass-like sheet ofwater.
571
00:34:22,423 --> 00:34:25,509
But even for these kings
of the Black Hole Era...
572
00:34:25,551 --> 00:34:27,385
time is running out.
573
00:34:28,845 --> 00:34:31,472
And you might think,
"Oh, they'll last forever"...
574
00:34:31,515 --> 00:34:33,682
but even they don't last forever...
575
00:34:33,724 --> 00:34:37,519
because they evaporate
very, very slowly with time.
576
00:34:39,688 --> 00:34:41,522
Black holes in today's universe...
577
00:34:41,564 --> 00:34:44,732
grow larger as they
gobble up surrounding matter.
578
00:34:45,984 --> 00:34:48,485
But eventually, far in the future...
579
00:34:48,528 --> 00:34:51,613
there'll be
so little material to swallow...
580
00:34:51,656 --> 00:34:54,448
that the evaporation rate
will start dominating...
581
00:34:54,491 --> 00:34:58,411
over the rate at which they swallow
material from their surroundings.
582
00:34:58,453 --> 00:35:02,539
So the evaporation rate
proceeds more quickly...
583
00:35:02,581 --> 00:35:04,790
when the universe
is very, very old.
584
00:35:06,751 --> 00:35:10,211
An evaporating black hole
does not go out with a whimper...
585
00:35:10,254 --> 00:35:12,714
like the planets do
when they die...
586
00:35:12,756 --> 00:35:14,757
but ratherwith a bang.
587
00:35:17,009 --> 00:35:19,928
That's because it behaves
counterintuitively...
588
00:35:19,971 --> 00:35:22,012
as it runs out offuel.
589
00:35:22,806 --> 00:35:26,057
There's basically two
strategies that you can adopt.
590
00:35:26,100 --> 00:35:28,393
One is to sort of ease up
on the gas pedal...
591
00:35:28,436 --> 00:35:30,520
and try to conserve
your energy...
592
00:35:30,563 --> 00:35:33,981
and basically try to roll
into the next gas station on fumes.
593
00:35:34,941 --> 00:35:37,400
The other strategy
is to become impatient...
594
00:35:37,443 --> 00:35:39,235
and floor the accelerator...
595
00:35:39,278 --> 00:35:42,612
and try to drive to the gas station
as fast as you can...
596
00:35:42,655 --> 00:35:44,364
in hopes of getting
to the gas station...
597
00:35:44,407 --> 00:35:46,408
before your gas runs out.
598
00:35:46,451 --> 00:35:49,326
And the black holes are definitely
taking the second route.
599
00:35:50,370 --> 00:35:56,583
Unlike a car, when a black hole
finally runs out offuel, it explodes.
600
00:35:59,669 --> 00:36:01,420
And in the last second
of the black hole...
601
00:36:01,463 --> 00:36:03,838
when you're releasing...
602
00:36:03,881 --> 00:36:08,008
megatons and megatons worth
of TNT equivalent...
603
00:36:09,385 --> 00:36:12,137
a huge variety of particles...
604
00:36:12,180 --> 00:36:15,014
that haven't been seen
for many cosmological decades...
605
00:36:15,056 --> 00:36:18,683
comes spewing into existence
and kind offlicker away...
606
00:36:18,726 --> 00:36:22,395
in a last fireworks-like burst
after the black hole is gone.
607
00:36:24,647 --> 00:36:27,107
So after about
a google years or so...
608
00:36:27,150 --> 00:36:30,443
and the most super-massive
black holes have evaporated away...
609
00:36:30,486 --> 00:36:33,446
what you've got left
is a vast universe...
610
00:36:33,489 --> 00:36:36,656
that is really
almost entirely empty.
611
00:36:38,451 --> 00:36:41,827
Next, the universe
enters the Dark Era.
612
00:36:43,955 --> 00:36:48,166
Nowwe're out beyond
cosmological decade 100.
613
00:36:48,209 --> 00:36:50,793
We're in the middle
of the Dark Era.
614
00:36:50,835 --> 00:36:54,463
ln the Dark Era,
everything that we have now...
615
00:36:54,506 --> 00:36:56,714
that is familiar to us is gone.
616
00:36:56,757 --> 00:36:59,550
You know that expression,
"angels fear to tread"?
617
00:36:59,593 --> 00:37:01,968
That's the Dark Era.
618
00:37:02,011 --> 00:37:04,888
The Dark Era,
you neverwant to go to...
619
00:37:04,931 --> 00:37:07,765
because everything
has crumbled...
620
00:37:07,808 --> 00:37:10,976
notjust the sands
and monuments to man's folly...
621
00:37:11,019 --> 00:37:14,604
but even the atoms themselves
have begun to crumble.
622
00:37:14,647 --> 00:37:18,440
Even black holes are
not possible in the dark era.
623
00:37:20,527 --> 00:37:23,486
lf the universe continues
to expand forever...
624
00:37:23,529 --> 00:37:27,532
it may be that only a cosmic mush
of random particles remains...
625
00:37:28,699 --> 00:37:32,536
but a few surprises may yet
rise out ofthese ashes.
626
00:37:35,539 --> 00:37:40,291
lf, in the distant future,
chaos does rule over order...
627
00:37:40,334 --> 00:37:44,169
our once glowing-hot
universe will descend...
628
00:37:44,212 --> 00:37:47,130
into a chilling
galactic ice age.
629
00:37:49,967 --> 00:37:53,094
But it may still harbor
some potential...
630
00:37:53,136 --> 00:37:55,345
at least according
to quantum theory...
631
00:37:55,388 --> 00:37:58,765
which examines physics
at its most primal level.
632
00:37:59,559 --> 00:38:02,184
ln quantum physics,
even the vacuum of space...
633
00:38:02,227 --> 00:38:05,061
that thing that we think of
as being empty with nothing in it...
634
00:38:05,104 --> 00:38:06,980
is not actually empty.
635
00:38:07,022 --> 00:38:10,732
Quantum physics allows
for everything to happen...
636
00:38:10,775 --> 00:38:12,609
with some probability.
637
00:38:15,029 --> 00:38:19,615
ln otherwords, the universe
is playing a risky game of chance.
638
00:38:19,658 --> 00:38:23,535
And quantum theory seeks
to explain the behavior of particles...
639
00:38:23,578 --> 00:38:26,537
in a universe
where anything is possible.
640
00:38:28,999 --> 00:38:31,500
lt's as if the universe
were a card dealer...
641
00:38:31,543 --> 00:38:34,377
continuously shuffling a deck...
642
00:38:34,420 --> 00:38:37,754
containing the very
building blocks of our reality.
643
00:38:39,924 --> 00:38:42,925
So ifyou have a bunch of particles
in a quantum field theory...
644
00:38:42,968 --> 00:38:45,928
what happens is they're going to
just rearrange themselves...
645
00:38:45,971 --> 00:38:48,096
over and over and over again
in what looks to us...
646
00:38:48,139 --> 00:38:50,390
like a random set offluctuations.
647
00:38:53,685 --> 00:38:57,271
Quantum theory can't predict
the result of a particle shuffle...
648
00:38:58,272 --> 00:39:02,025
but it can reveal
the probability of each outcome.
649
00:39:02,943 --> 00:39:05,068
lfyou have something
that happens forever...
650
00:39:05,111 --> 00:39:06,862
an infinite number of times...
651
00:39:06,905 --> 00:39:09,488
even very, very unlikely things
will eventually happen.
652
00:39:10,866 --> 00:39:13,993
Ordinarily, when shuffling
a deck of cards...
653
00:39:14,036 --> 00:39:16,036
the result is a random sequence.
654
00:39:17,705 --> 00:39:21,123
Likewise, particles,
churning on a quantum level...
655
00:39:21,166 --> 00:39:24,918
don't usually create
anything orderly.
656
00:39:24,960 --> 00:39:27,253
However, with enough time...
657
00:39:27,296 --> 00:39:30,672
any kind of quantum
fluctuation can form...
658
00:39:30,715 --> 00:39:33,508
even one
that seems impossible.
659
00:39:35,469 --> 00:39:37,637
lfyou're in a universe
that lasts forever...
660
00:39:37,679 --> 00:39:41,264
ifyou have a card dealer that is
shuffling cards forever and ever...
661
00:39:41,307 --> 00:39:43,892
even unlikely events like that
will occasionally happen.
662
00:39:47,812 --> 00:39:51,231
One of these unique and
improbable random fluctuations...
663
00:39:51,274 --> 00:39:54,359
can change the fabric
of space itself.
664
00:39:56,028 --> 00:39:59,613
Empty space
is kind of like water...
665
00:39:59,656 --> 00:40:02,114
in the sense that it can
appear in different phases.
666
00:40:03,367 --> 00:40:06,035
lt could be hot and be vapor...
667
00:40:06,078 --> 00:40:08,745
it could be solid
like an ice cube...
668
00:40:09,538 --> 00:40:11,831
or it could be liquid.
669
00:40:11,874 --> 00:40:15,125
The space around us right now
is in a certain physical state...
670
00:40:15,168 --> 00:40:17,127
but a phase transition
can happen...
671
00:40:17,170 --> 00:40:19,337
where that physical state
changes into something else.
672
00:40:21,590 --> 00:40:24,341
The wrong kind
of random fluctuation...
673
00:40:24,384 --> 00:40:27,469
can induce a devastating
phase transition.
674
00:40:28,720 --> 00:40:31,639
The way that would occur
is that some region of space...
675
00:40:31,682 --> 00:40:34,641
some point, would witness
the formation of a bubble...
676
00:40:34,684 --> 00:40:37,811
and that bubble would spread
throughout the space around it...
677
00:40:37,853 --> 00:40:43,524
just like this inkwould
spread through the glass.
678
00:40:44,401 --> 00:40:47,193
Just as the ink changes
the nature of the water...
679
00:40:48,237 --> 00:40:52,447
so could a phase transition
transform the nature of the cosmos.
680
00:40:55,118 --> 00:40:57,034
The laws of physics
would be different...
681
00:40:57,077 --> 00:40:59,495
in the wake
of this bubble passing.
682
00:40:59,538 --> 00:41:01,579
The masses
of different particles would change...
683
00:41:01,622 --> 00:41:03,748
the charge of different
particles would change...
684
00:41:03,791 --> 00:41:07,376
all of chemistry as we know it
would be completely different...
685
00:41:07,419 --> 00:41:09,253
after this phase
transition occurred.
686
00:41:09,295 --> 00:41:12,171
What that means is that
suddenly there are newways...
687
00:41:12,214 --> 00:41:15,758
to arrange all the particles
that we're made of...
688
00:41:15,801 --> 00:41:18,510
and it's sort of like
everything in the universe...
689
00:41:18,553 --> 00:41:20,137
becomes an atomic bomb.
690
00:41:21,514 --> 00:41:24,306
lt would just rearrange itself,
releasing energy...
691
00:41:24,349 --> 00:41:27,225
and literally every particle,
every atom...
692
00:41:27,268 --> 00:41:29,602
every structure in the universe
would explode.
693
00:41:33,273 --> 00:41:38,192
So no complicated structure can
possibly survive that sort of transition.
694
00:41:38,235 --> 00:41:40,236
What would be left
isjust a mess...
695
00:41:40,279 --> 00:41:44,448
nothing but a gas of particles
bumping randomly into each other.
696
00:41:47,702 --> 00:41:52,538
But a random quantum fluctuation
can also spark a bubble of hope.
697
00:41:53,789 --> 00:41:55,457
Some theoretical physicists
suggest...
698
00:41:55,499 --> 00:41:58,209
that some ofthese
quantum fluctuations...
699
00:41:58,252 --> 00:42:04,505
actually can give rise to
almost detached portions of space...
700
00:42:04,548 --> 00:42:10,135
dimensions that sort of branch off
from ours into a new universe.
701
00:42:11,888 --> 00:42:15,056
Perhaps a quantum fluctuation
sparked the Big Bang...
702
00:42:15,098 --> 00:42:17,808
and gave rise
to our own universe.
703
00:42:19,436 --> 00:42:21,519
You can imagine
that a universe like ours...
704
00:42:21,562 --> 00:42:24,022
even though it's ten billion
light-years across...
705
00:42:24,065 --> 00:42:26,774
is actually a baby universe
that arose...
706
00:42:26,816 --> 00:42:29,276
by pinching off
from some much bigger universe.
707
00:42:31,445 --> 00:42:34,072
We can picture
the birth of a baby universe...
708
00:42:34,114 --> 00:42:38,408
with this bottle, representing
an old, dying, chaotic universe.
709
00:42:39,952 --> 00:42:42,953
My breath is like
quantum fluctuations...
710
00:42:42,996 --> 00:42:45,289
creating new universes
that look like bubbles.
711
00:42:48,751 --> 00:42:51,836
And each one of those bubbles
is a separate universe all of its own.
712
00:42:51,879 --> 00:42:55,089
There is the possibility that there
are other universes out there...
713
00:42:55,131 --> 00:42:57,924
perhaps butted off
from our universe...
714
00:42:57,966 --> 00:43:00,635
and they may have
their own fate...
715
00:43:00,677 --> 00:43:04,346
either eternal expansion
or ultimate re-collapse.
716
00:43:06,140 --> 00:43:10,267
lf other universes exist,
then perhaps future civilizations...
717
00:43:10,310 --> 00:43:13,437
may not face an irrevocable
death sentence.
718
00:43:15,773 --> 00:43:19,817
So l would suspect that trillions,
quadrillions ofyears from now...
719
00:43:19,859 --> 00:43:22,111
when the universe
gets really cold...
720
00:43:22,153 --> 00:43:24,445
and the universe
is near death...
721
00:43:24,488 --> 00:43:27,365
intelligent beings
will be so powerful then...
722
00:43:27,407 --> 00:43:30,867
that they may be tempted
to assemble enough energy...
723
00:43:30,910 --> 00:43:34,121
at one point
to open up bubbles...
724
00:43:34,163 --> 00:43:38,040
little soap bubbles,
gateways to another universe...
725
00:43:38,083 --> 00:43:42,085
where it's a lot warmer
and they can start all over again.
726
00:43:43,879 --> 00:43:45,462
Whether or not
our descendants...
727
00:43:45,505 --> 00:43:48,674
muster the technology
to leave this universe...
728
00:43:48,716 --> 00:43:50,342
there's no avoiding
the fact that...
729
00:43:50,385 --> 00:43:53,678
like all things,
it will come to an end.
730
00:43:57,348 --> 00:44:01,892
While science wrestles with questions
of how the universe will die...
731
00:44:01,935 --> 00:44:05,688
humanity is left to do the same
with how it will live.
732
00:44:07,231 --> 00:44:09,149
Our lives are important.
733
00:44:09,191 --> 00:44:10,358
l'm important,
you're important...
734
00:44:10,401 --> 00:44:12,776
your loved ones are important,
yourfriends are important...
735
00:44:12,819 --> 00:44:14,862
and we need to make
the most of our existence...
736
00:44:14,904 --> 00:44:18,030
during the fleeting time
that we have here.
737
00:44:18,073 --> 00:44:19,907
This is your life,
this is my life.
738
00:44:19,950 --> 00:44:23,577
We make the most of it,
regardless of the fate of the universe.
9999
00:00:0,500 --> 00:00:2,00
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