Would you like to inspect the original subtitles? These are the user uploaded subtitles that are being translated:
1
00:00:01,002 --> 00:00:06,272
�
2
00:00:06,274 --> 00:00:11,077
narrator: Across the universe,
an endless war rages,
3
00:00:11,079 --> 00:00:15,014
a bitter struggle
between invisible forces.
4
00:00:15,016 --> 00:00:17,215
Tegmark: We've seen this
cosmic battle go on
5
00:00:17,217 --> 00:00:19,818
for the past 14 billion years.
6
00:00:19,820 --> 00:00:23,355
Like two navies, fighting it out
in the ocean of space time.
7
00:00:25,426 --> 00:00:27,293
Narrator:
Dark matter...
8
00:00:27,295 --> 00:00:29,494
And dark energy
9
00:00:29,496 --> 00:00:32,564
battling for control
of the universe.
10
00:00:32,566 --> 00:00:35,034
They've shaped the entire
history of the universe.
11
00:00:35,036 --> 00:00:37,637
They're not about to stop now.
12
00:00:37,639 --> 00:00:41,106
Narrator: Shadowy forces
dictating our past,
13
00:00:41,108 --> 00:00:43,976
our present, and our future.
14
00:00:43,978 --> 00:00:45,978
Thaller: The dark universe
is kind of a puppet master
15
00:00:45,980 --> 00:00:47,380
behind the scenes,
16
00:00:47,382 --> 00:00:50,249
guiding the universe
that we can see.
17
00:00:50,251 --> 00:00:53,319
Oluseyi: It's taken over
the universe and, eventually,
18
00:00:53,321 --> 00:00:55,321
it may well
destroy the universe.
19
00:01:03,731 --> 00:01:06,665
-- Captions by vitac --
www.vitac.com
20
00:01:06,667 --> 00:01:09,735
captions paid for by
discovery communications
21
00:01:09,737 --> 00:01:17,009
�
22
00:01:17,011 --> 00:01:20,479
narrator: As we look out
across the universe,
23
00:01:20,481 --> 00:01:23,616
we see nebulas,
24
00:01:23,618 --> 00:01:26,686
stars,
25
00:01:26,688 --> 00:01:28,353
and planets,
26
00:01:28,355 --> 00:01:32,624
all constructed
from visible matter.
27
00:01:32,626 --> 00:01:37,829
But what we see is just
a small part of the cosmos.
28
00:01:37,831 --> 00:01:40,099
The rest is invisible,
29
00:01:40,101 --> 00:01:43,102
unknown...
30
00:01:43,104 --> 00:01:46,638
The dark universe.
31
00:01:46,640 --> 00:01:50,976
Dark universe is a very common
phrase to describe our universe,
32
00:01:50,978 --> 00:01:56,048
because it turns out
most of our cosmos is dark.
33
00:01:56,050 --> 00:01:58,050
Dark not as in night.
34
00:01:58,052 --> 00:02:01,520
Dark as in,
doesn't interact with light,
35
00:02:01,522 --> 00:02:04,657
and dark as in, we don't
really understand it.
36
00:02:04,659 --> 00:02:07,059
All the objects
in our daily experience --
37
00:02:07,061 --> 00:02:11,397
our bodies, the air, the chair
that you're sitting in,
38
00:02:11,399 --> 00:02:13,399
the planets and stars,
39
00:02:13,401 --> 00:02:16,736
all of that only adds up
to 5 percent of the universe.
40
00:02:19,273 --> 00:02:22,608
It's the other 95 percent
that is the dark stuff,
41
00:02:22,610 --> 00:02:24,209
the dark universe.
42
00:02:24,211 --> 00:02:26,879
�
43
00:02:26,881 --> 00:02:31,417
narrator: The dark universe
is made of two forces --
44
00:02:31,419 --> 00:02:35,121
dark matter and dark energy.
45
00:02:36,424 --> 00:02:39,791
In a way, the dark matter
and dark energy
46
00:02:39,793 --> 00:02:41,026
sort of oppose each other.
47
00:02:43,698 --> 00:02:47,833
Dark matter has positive gravity
that pulls things together,
48
00:02:47,835 --> 00:02:49,902
and dark energy
has repulsive gravity
49
00:02:49,904 --> 00:02:52,838
that pushes things apart.
50
00:02:52,840 --> 00:02:54,907
Freese: To encapsulate that
in one sentence,
51
00:02:54,909 --> 00:02:59,044
dark matter is attractive,
dark energy is repulsive.
52
00:02:59,046 --> 00:03:00,780
Narrator:
Since the dawn of time,
53
00:03:00,782 --> 00:03:04,984
two forces slugging it out
for control of the universe.
54
00:03:04,986 --> 00:03:06,385
Dark matter and dark energy
55
00:03:06,387 --> 00:03:08,320
are locked
in this epic struggle.
56
00:03:08,322 --> 00:03:11,123
The dark matter is trying
to bring things together.
57
00:03:11,125 --> 00:03:14,460
The dark energy is trying
to drive everything apart.
58
00:03:14,462 --> 00:03:16,628
So it's basically a battle.
Who's going to win?
59
00:03:21,535 --> 00:03:23,335
Narrator:
It's a struggle that started
60
00:03:23,337 --> 00:03:26,538
13.8 billion years ago
61
00:03:26,540 --> 00:03:29,674
in the cosmic furnace
of the big bang.
62
00:03:29,676 --> 00:03:31,944
�
63
00:03:31,946 --> 00:03:36,682
the infant universe was a super
hot ball of intense radiation,
64
00:03:36,684 --> 00:03:37,883
but suddenly...
65
00:03:37,885 --> 00:03:41,287
...it started to transform.
66
00:03:41,289 --> 00:03:43,689
It cooled and expanded,
67
00:03:43,691 --> 00:03:47,426
triggering the birth
of the regular universe
68
00:03:47,428 --> 00:03:50,763
and the dark universe.
69
00:03:50,765 --> 00:03:55,033
Scientists believe that both
dark matter and dark energy
70
00:03:55,035 --> 00:03:58,637
formed in the first moments
of the big bang.
71
00:03:58,639 --> 00:04:02,040
It would have formed probably
just fractions of a second
72
00:04:02,042 --> 00:04:03,576
after the big bang,
73
00:04:03,578 --> 00:04:06,311
around the time
that normal matter formed,
74
00:04:06,313 --> 00:04:07,913
and the processes that created
75
00:04:07,915 --> 00:04:09,782
the normal matter
we know all about.
76
00:04:09,784 --> 00:04:13,319
Similar processes probably
created the dark matter.
77
00:04:13,321 --> 00:04:15,187
�
78
00:04:15,189 --> 00:04:16,922
narrator: During these
first microseconds,
79
00:04:16,924 --> 00:04:22,060
the universe was a hot, dense
ball of matter and energy.
80
00:04:22,062 --> 00:04:24,863
They're two sides
of the same coin.
81
00:04:24,865 --> 00:04:27,199
Matter can convert
into energy...
82
00:04:29,003 --> 00:04:32,671
...and energy can convert
directly into matter,
83
00:04:32,673 --> 00:04:36,809
visible particles of regular
matter forming atoms,
84
00:04:36,811 --> 00:04:40,479
planets, stars, and us --
85
00:04:40,481 --> 00:04:42,714
and other particles.
86
00:04:42,716 --> 00:04:44,750
They are invisible.
87
00:04:44,752 --> 00:04:47,019
They are dark matter.
88
00:04:47,021 --> 00:04:50,489
One of the big mysteries that we
as astronomers have to solve
89
00:04:50,491 --> 00:04:52,158
is what this dark matter is.
90
00:04:52,160 --> 00:04:54,827
We just don't know.
91
00:04:54,829 --> 00:04:58,297
The idea of a type of matter
that you can't see
92
00:04:58,299 --> 00:05:00,699
and that acts differently
than normal matter
93
00:05:00,701 --> 00:05:01,834
is sort of out there.
94
00:05:01,836 --> 00:05:04,770
It's sort of weird.
95
00:05:04,772 --> 00:05:08,574
Narrator: But the dark universe
does leave clues.
96
00:05:08,576 --> 00:05:10,242
It's like a crime scene.
97
00:05:10,244 --> 00:05:12,644
You know that a crime
has been committed,
98
00:05:12,646 --> 00:05:15,314
even though you don't know
the perpetrator yet.
99
00:05:15,316 --> 00:05:18,184
We see the hints.
We see the signs.
100
00:05:18,186 --> 00:05:21,587
We see the signals
that something funny
101
00:05:21,589 --> 00:05:23,288
is happening
in our universe,
102
00:05:23,290 --> 00:05:26,925
even though we don't know
exactly what's causing it.
103
00:05:26,927 --> 00:05:28,794
Narrator:
There are several contenders
104
00:05:28,796 --> 00:05:31,063
for what dark matter could be.
105
00:05:31,065 --> 00:05:34,199
It could be normal matter
that we just don't see,
106
00:05:34,201 --> 00:05:36,268
or it could be some
sort of exotic matter,
107
00:05:36,270 --> 00:05:39,271
a particle of some sort
that we haven't detected yet.
108
00:05:39,273 --> 00:05:42,808
Sutter: It could be
a species of particle,
109
00:05:42,810 --> 00:05:45,811
like an electron,
like a proton,
110
00:05:45,813 --> 00:05:48,013
like a quark,
111
00:05:48,015 --> 00:05:51,951
but a special kind that
doesn't interact with light.
112
00:05:51,953 --> 00:05:54,486
One of the favorite possible
models of dark matter
113
00:05:54,488 --> 00:05:57,356
are wimps, weakly interacting
massive particles.
114
00:05:57,358 --> 00:05:58,891
�
115
00:05:58,893 --> 00:06:00,960
narrator: Wimps may not
interact strongly
116
00:06:00,962 --> 00:06:03,495
with other matter or light,
117
00:06:03,497 --> 00:06:06,232
but they do exert
a gravitational pull.
118
00:06:08,769 --> 00:06:12,037
So they're the best candidates
for the particles of dark matter
119
00:06:12,039 --> 00:06:13,906
that formed in the big bang.
120
00:06:13,908 --> 00:06:16,976
�
121
00:06:16,978 --> 00:06:20,912
the early universe was
intensely hot and dense,
122
00:06:20,914 --> 00:06:24,249
full of new particles
of both visible matter
123
00:06:24,251 --> 00:06:27,386
and invisible dark matter.
124
00:06:27,388 --> 00:06:30,989
But another force
was present --
125
00:06:30,991 --> 00:06:34,059
dark energy.
126
00:06:34,061 --> 00:06:37,796
Dark energy has existed
since the time of the big bang.
127
00:06:37,798 --> 00:06:39,665
Freese:
Dark energy was always there.
128
00:06:39,667 --> 00:06:41,800
We don't know how much
of it there was,
129
00:06:41,802 --> 00:06:44,336
but it's possible that
the same amount of dark energy
130
00:06:44,338 --> 00:06:45,470
was always there.
131
00:06:47,942 --> 00:06:50,809
Narrator: Our understanding of
what that dark energy is
132
00:06:50,811 --> 00:06:53,278
is very limited.
133
00:06:53,280 --> 00:06:56,481
Sutter:
If you were to ask a roomful
of 10 theoretical physicists
134
00:06:56,483 --> 00:06:57,882
on the nature of dark energy,
135
00:06:57,884 --> 00:07:00,953
you'd get about
12 different answers.
136
00:07:00,955 --> 00:07:05,557
We're not sure
what dark energy is.
137
00:07:05,559 --> 00:07:08,760
Dark energy is just a fancy
name for our ignorance.
138
00:07:08,762 --> 00:07:12,431
Dark energy is nothing
more than a placeholder name
139
00:07:12,433 --> 00:07:15,167
for this enormous gap
in our understanding
140
00:07:15,169 --> 00:07:16,568
of how the cosmos works.
141
00:07:16,570 --> 00:07:19,438
But we don't understand
it at all.
142
00:07:19,440 --> 00:07:21,573
It's true.
143
00:07:21,575 --> 00:07:23,375
�
144
00:07:23,377 --> 00:07:25,978
narrator: One potential answer
to what dark energy
145
00:07:25,980 --> 00:07:31,649
actually is may be found
in so-called empty space.
146
00:07:31,651 --> 00:07:34,920
Could this be the source
of dark energy?
147
00:07:34,922 --> 00:07:38,390
Tegmark: We used to think of
space as just boring emptiness.
148
00:07:38,392 --> 00:07:41,727
But now, I think it's healthier
to think of space
149
00:07:41,729 --> 00:07:44,396
as a kind of substance.
150
00:07:44,398 --> 00:07:46,197
Narrator:
A substance that carries
151
00:07:46,199 --> 00:07:48,333
a strange type of energy.
152
00:07:48,335 --> 00:07:49,934
Every small region of space
153
00:07:49,936 --> 00:07:52,270
has a little bit
of energy in it,
154
00:07:52,272 --> 00:07:55,173
just associated
with the vacuum itself.
155
00:07:55,175 --> 00:07:59,544
Vacuum energy is the idea
that vacuum isn't empty,
156
00:07:59,546 --> 00:08:01,146
that there is something there.
157
00:08:01,148 --> 00:08:04,616
There's an energy in it
with a kind of antigravity.
158
00:08:07,020 --> 00:08:08,887
Narrator:
Perhaps this vacuum energy
159
00:08:08,889 --> 00:08:12,891
that pushes against gravity
160
00:08:12,893 --> 00:08:16,094
is the mysterious dark energy.
161
00:08:16,096 --> 00:08:19,798
We simply don't know.
162
00:08:19,800 --> 00:08:23,569
We're not sure that the dark
energy is the vacuum energy.
163
00:08:23,571 --> 00:08:27,773
It could be a new type of energy
that permeates all of space.
164
00:08:27,775 --> 00:08:31,176
This is what we're
trying to measure now.
165
00:08:31,178 --> 00:08:33,445
Narrator:
Dark energy and dark matter,
166
00:08:33,447 --> 00:08:36,915
forged in the intense heat
of the big bang,
167
00:08:36,917 --> 00:08:41,920
opposing forces,
one attractive, one repulsive.
168
00:08:41,922 --> 00:08:44,990
But together,
over 13.8 billions years,
169
00:08:44,992 --> 00:08:48,660
they will shape
the history of the universe.
170
00:09:05,612 --> 00:09:08,279
�
171
00:09:08,281 --> 00:09:10,616
narrator: The story of
the universe is dominated
172
00:09:10,618 --> 00:09:15,420
by two powerful
opposing forces --
173
00:09:15,422 --> 00:09:18,757
dark matter and dark energy.
174
00:09:18,759 --> 00:09:21,693
For 13.8 billions years,
175
00:09:21,695 --> 00:09:25,564
they've battled it out
for control of the cosmos.
176
00:09:25,566 --> 00:09:27,833
Dark matter and dark energy
are out there,
177
00:09:27,835 --> 00:09:30,235
and they've shaped the entire
history of the universe.
178
00:09:30,237 --> 00:09:33,238
Our universe is actually
the balance between dark forces.
179
00:09:33,240 --> 00:09:35,641
Dark matter is trying to draw
everything together,
180
00:09:35,643 --> 00:09:39,978
and dark energy is trying
to rip everything apart.
181
00:09:39,980 --> 00:09:44,116
Narrator: After the big bang,
the infant universe was small,
182
00:09:44,118 --> 00:09:47,452
intensely hot
and intensely dense.
183
00:09:49,523 --> 00:09:53,325
Dark matter, the force bent
on bringing things together,
184
00:09:53,327 --> 00:09:55,327
thrived.
185
00:09:55,329 --> 00:09:58,463
But in this compressed space,
dark energy,
186
00:09:58,465 --> 00:10:03,936
the force trying to drive things
apart, had no room to act.
187
00:10:03,938 --> 00:10:05,737
When things were
closer together,
188
00:10:05,739 --> 00:10:08,941
the density of matter
and radiation was bigger,
189
00:10:08,943 --> 00:10:12,544
so big that the dark energy
didn't matter.
190
00:10:12,546 --> 00:10:17,549
Narrator: The environment was
also tough for normal matter.
191
00:10:17,551 --> 00:10:19,951
It was so hot,
intense radiation
192
00:10:19,953 --> 00:10:25,557
prevented visible matter from
bunching together to form atoms.
193
00:10:25,559 --> 00:10:27,759
If any normal matter
tried to clump together
194
00:10:27,761 --> 00:10:29,494
through gravity
or some other force,
195
00:10:29,496 --> 00:10:31,763
this energy would just
basically blast it apart.
196
00:10:31,765 --> 00:10:33,431
In the very early universe,
197
00:10:33,433 --> 00:10:35,100
when our universe
was a lot smaller
198
00:10:35,102 --> 00:10:37,168
and a lot hotter
and a lot denser,
199
00:10:37,170 --> 00:10:41,239
matter, normal matter,
tried to collect together,
200
00:10:41,241 --> 00:10:43,041
wanted to join the party.
201
00:10:43,043 --> 00:10:44,976
But it was prevented
from doing so
202
00:10:44,978 --> 00:10:50,649
because there was also radiation
that would throw it out.
203
00:10:50,651 --> 00:10:52,383
Narrator:
Unable to stick together,
204
00:10:52,385 --> 00:10:54,586
normal visible matter
sped out
205
00:10:54,588 --> 00:10:58,457
across the infant cosmos
in a blizzard of particles.
206
00:11:00,327 --> 00:11:02,393
But then dark matter,
207
00:11:02,395 --> 00:11:05,931
the force that brings things
together, intervened.
208
00:11:07,601 --> 00:11:10,268
Dark matter doesn't talk
to radiation,
209
00:11:10,270 --> 00:11:11,403
doesn't talk to light.
210
00:11:11,405 --> 00:11:13,004
Can do whatever it wants.
211
00:11:13,006 --> 00:11:16,407
It starts clumping together.
212
00:11:16,409 --> 00:11:19,144
Narrator: Radiation
pushes normal matter apart,
213
00:11:19,146 --> 00:11:22,881
stopping it
from forming dense regions.
214
00:11:22,883 --> 00:11:27,152
But photons simply pass straight
through the dark matter,
215
00:11:27,154 --> 00:11:32,757
allowing it to clump and fall
into dense pockets or Wells.
216
00:11:32,759 --> 00:11:36,961
The dark matter begins to clump
together gravitationally,
217
00:11:36,963 --> 00:11:39,698
and this means that the matter
is going to fall into
218
00:11:39,700 --> 00:11:42,834
those dark matter Wells.
219
00:11:42,836 --> 00:11:45,803
Narrator: Over time,
more and more regular matter
220
00:11:45,805 --> 00:11:48,840
is pulled into
the dark matter Wells.
221
00:11:48,842 --> 00:11:50,642
The regions that have
a little bit more stuff,
222
00:11:50,644 --> 00:11:52,110
gravity makes them bigger,
223
00:11:52,112 --> 00:11:54,846
and the regions that have
less stuff, those expand more.
224
00:11:54,848 --> 00:11:58,650
So you have little pockets
of slight extra matter,
225
00:11:58,652 --> 00:12:00,919
have more and more
and more matter over time.
226
00:12:02,856 --> 00:12:05,190
Narrator: Gravity-rich pockets
of dark matter
227
00:12:05,192 --> 00:12:08,260
pull particles
of regular matter together.
228
00:12:10,130 --> 00:12:13,465
Gradually, they form
giant clouds of hydrogen
229
00:12:13,467 --> 00:12:16,868
and helium gas.
230
00:12:16,870 --> 00:12:21,539
Dark matter has laid the
foundation stones of the cosmos.
231
00:12:21,541 --> 00:12:25,744
This force may be dark,
but it's highly creative.
232
00:12:25,746 --> 00:12:29,281
�
233
00:12:29,283 --> 00:12:34,353
and now, 180 million years
after the big bang,
234
00:12:34,355 --> 00:12:35,887
everything is in place
235
00:12:35,889 --> 00:12:39,291
for the next dark matter
construction milestone --
236
00:12:39,293 --> 00:12:42,761
the creation of stars.
237
00:12:42,763 --> 00:12:44,162
We know stars,
238
00:12:44,164 --> 00:12:46,431
in the very early universe
at the edge of time,
239
00:12:46,433 --> 00:12:48,900
had to form from
the collapse of gas clouds
240
00:12:48,902 --> 00:12:50,369
under their own gravity.
241
00:12:50,371 --> 00:12:53,372
�
242
00:12:53,374 --> 00:12:54,973
narrator:
But there's a problem.
243
00:12:54,975 --> 00:13:00,579
The clouds of hydrogen in the
infant universe can't collapse,
244
00:13:00,581 --> 00:13:04,716
and no collapse
means no stars.
245
00:13:04,718 --> 00:13:07,252
Bullock: The gas in the early
universe has a lot of pressure,
246
00:13:07,254 --> 00:13:09,454
and this pressure
keeps it from collapsing.
247
00:13:09,456 --> 00:13:10,656
The dark matter
doesn't experience
248
00:13:10,658 --> 00:13:12,057
that kind of pressure.
249
00:13:12,059 --> 00:13:13,525
So the dark matter can clump up
250
00:13:13,527 --> 00:13:17,328
and make sites
for structure formation.
251
00:13:17,330 --> 00:13:19,531
Narrator: So dark matter comes
to the rescue,
252
00:13:19,533 --> 00:13:23,068
creating regions
of higher gravity,
253
00:13:23,070 --> 00:13:25,270
dragging in hydrogen gas,
254
00:13:25,272 --> 00:13:29,674
forcing the clouds to get
denser and denser,
255
00:13:29,676 --> 00:13:34,479
creating the conditions
for collapse and then creation.
256
00:13:37,551 --> 00:13:40,885
�
257
00:13:40,887 --> 00:13:44,289
so it's only when the gravity
of the dark matter
258
00:13:44,291 --> 00:13:46,692
overwhelms the pressure of gases
259
00:13:46,694 --> 00:13:50,895
that the gases can collapse
and turn into stars.
260
00:13:50,897 --> 00:13:52,364
Bullock: As soon as the gas
cools down,
261
00:13:52,366 --> 00:13:54,031
it can fall into those
potential Wells
262
00:13:54,033 --> 00:13:55,901
that the dark matter created,
263
00:13:55,903 --> 00:13:58,636
almost like little nurseries
for stars,
264
00:13:58,638 --> 00:14:00,705
and they start
forming in earnest.
265
00:14:00,707 --> 00:14:02,707
�
266
00:14:02,709 --> 00:14:05,310
narrator: Dark matter provides
a boost of gravity
267
00:14:05,312 --> 00:14:10,848
to kick-start hydrogen into
constructing the first stars,
268
00:14:10,850 --> 00:14:14,719
stars that are the seeds
of the first galaxies.
269
00:14:14,721 --> 00:14:17,456
Tremblay: So it's dark matter
that would have coalesced
270
00:14:17,458 --> 00:14:20,792
in the early universe
and grown from there,
271
00:14:20,794 --> 00:14:22,660
and then the luminous
component of the universe,
272
00:14:22,662 --> 00:14:25,063
the things that we think of
as being the universe itself,
273
00:14:25,065 --> 00:14:26,531
like stars and galaxies,
274
00:14:26,533 --> 00:14:28,933
would have just been along
for the ride.
275
00:14:28,935 --> 00:14:34,272
Without the presence of dark
matter to seed structures,
276
00:14:34,274 --> 00:14:39,077
there wasn't enough time in the
early universe to form galaxies,
277
00:14:39,079 --> 00:14:42,947
which means you and me
have to thank dark matter
278
00:14:42,949 --> 00:14:45,150
for our existence.
279
00:14:45,152 --> 00:14:47,352
Narrator:
And dark matter now begins
280
00:14:47,354 --> 00:14:51,956
a much more ambitious
architectural project --
281
00:14:51,958 --> 00:14:56,294
to shape the entire
universe itself,
282
00:14:56,296 --> 00:15:00,498
to build the biggest structure
ever constructed --
283
00:15:00,500 --> 00:15:02,033
the cosmic web.
284
00:15:02,035 --> 00:15:06,171
�
285
00:15:16,983 --> 00:15:20,452
�
286
00:15:20,454 --> 00:15:23,355
narrator: The war between
dark matter and dark energy
287
00:15:23,357 --> 00:15:25,991
has been raging
since the birth of time.
288
00:15:29,062 --> 00:15:33,865
But in the early years,
it's a one-sided contest.
289
00:15:33,867 --> 00:15:36,267
In the early universe, the only
thing that really mattered
290
00:15:36,269 --> 00:15:39,804
was the dark matter
and the normal matter.
291
00:15:39,806 --> 00:15:41,873
Narrator: Dark matter,
292
00:15:41,875 --> 00:15:45,743
the force that brings things
together,
293
00:15:45,745 --> 00:15:47,345
is in the driver's seat.
294
00:15:50,951 --> 00:15:55,086
Dark energy, the force
that pulls things apart,
295
00:15:55,088 --> 00:15:57,055
is the underdog.
296
00:15:57,057 --> 00:15:59,691
We've seen this
cosmic battle go on
297
00:15:59,693 --> 00:16:01,759
for the past 14 billion years.
298
00:16:01,761 --> 00:16:06,898
Fortunately for us, the dark
energy got off to a slow start.
299
00:16:06,900 --> 00:16:10,235
Narrator: Meanwhile, dark matter
is busy at work,
300
00:16:10,237 --> 00:16:12,904
building the universe.
301
00:16:12,906 --> 00:16:17,842
Not only does it trigger
the birth of the first stars,
302
00:16:17,844 --> 00:16:20,044
it embarks on an even
more formidable
303
00:16:20,046 --> 00:16:23,014
construction project --
304
00:16:23,016 --> 00:16:26,451
the cosmic web.
305
00:16:26,453 --> 00:16:30,588
Straughn:
There's this large-scale
structure of filaments
306
00:16:30,590 --> 00:16:32,790
that galaxies
seem to form on,
307
00:16:32,792 --> 00:16:35,527
and that's what we call
the cosmic web.
308
00:16:35,529 --> 00:16:38,530
And we can trace the formation
of this cosmic web
309
00:16:38,532 --> 00:16:41,266
all the way back
to the early universe.
310
00:16:41,268 --> 00:16:43,067
Now this is such a huge
structure,
311
00:16:43,069 --> 00:16:44,736
we don't think there's time
in the universe
312
00:16:44,738 --> 00:16:47,405
for matter's gravity alone
to do this.
313
00:16:47,407 --> 00:16:49,608
There must have been
an underlying scaffold
314
00:16:49,610 --> 00:16:51,343
of dark matter.
315
00:16:51,345 --> 00:16:53,611
Plait: The dark matter started
forming into these filaments,
316
00:16:53,613 --> 00:16:55,613
and when the universe
cooled enough,
317
00:16:55,615 --> 00:16:57,282
normal matter
could start to stream
318
00:16:57,284 --> 00:17:00,418
into this gravitational
attraction of the dark matter.
319
00:17:00,420 --> 00:17:02,020
That became the scaffolding
320
00:17:02,022 --> 00:17:05,890
on which this large-scale
structure was built.
321
00:17:05,892 --> 00:17:08,826
Narrator: The filaments of
dark matter joined together,
322
00:17:08,828 --> 00:17:12,631
drawing in more
and more hydrogen gas.
323
00:17:12,633 --> 00:17:16,834
Dense clouds of gas build up at
the junctions of the filaments,
324
00:17:16,836 --> 00:17:19,904
the point where gravity
is at its strongest.
325
00:17:19,906 --> 00:17:22,908
�
326
00:17:22,910 --> 00:17:24,909
slowly and surely,
327
00:17:24,911 --> 00:17:29,447
a familiar-looking structure
starts to take shape.
328
00:17:29,449 --> 00:17:30,781
If you've ever gone outside,
329
00:17:30,783 --> 00:17:34,519
and you can see a spider web
covered in dew,
330
00:17:34,521 --> 00:17:37,388
that's kind of like
what happened with the universe.
331
00:17:37,390 --> 00:17:38,990
In this case, the spider web
332
00:17:38,992 --> 00:17:40,792
is the structure
of the dark matter.
333
00:17:40,794 --> 00:17:43,328
It's all of these filaments,
and the moisture in the air
334
00:17:43,330 --> 00:17:44,862
is what condenses around them,
335
00:17:44,864 --> 00:17:48,733
just like the normal matter
fell into the dark matter web
336
00:17:48,735 --> 00:17:51,803
to form these gigantic
structures in the universe.
337
00:17:51,805 --> 00:17:55,406
Narrator: Dark matter,
the universe's master builder,
338
00:17:55,408 --> 00:17:59,744
succeeds in stitching
together a cosmic web.
339
00:17:59,746 --> 00:18:04,683
This will be the framework
for the entire universe.
340
00:18:04,685 --> 00:18:07,619
And so it is dark matter
that would choreograph
341
00:18:07,621 --> 00:18:10,221
and sculpt the shape
of the universe itself.
342
00:18:10,223 --> 00:18:12,156
One of the amazing things
about dark matter is,
343
00:18:12,158 --> 00:18:14,359
without it, we wouldn't be here.
344
00:18:14,361 --> 00:18:16,828
It's hard to imagine how you
could have structure
345
00:18:16,830 --> 00:18:19,831
in the universe
without dark matter.
346
00:18:19,833 --> 00:18:22,433
Narrator: Galaxies,
and then galactic clusters,
347
00:18:22,435 --> 00:18:25,236
form at the junctions
of the filaments.
348
00:18:25,238 --> 00:18:30,775
Slowly, but surely, the universe
begins to take shape.
349
00:18:30,777 --> 00:18:33,778
When we look at this structure
over a cosmic scale,
350
00:18:33,780 --> 00:18:35,913
we see that it looks
kind of like a sponge.
351
00:18:35,915 --> 00:18:39,384
You see voids with galaxies
all over the edges of them.
352
00:18:39,386 --> 00:18:41,586
That is the structure
that was formed
353
00:18:41,588 --> 00:18:45,523
by the dark matter
in the early universe.
354
00:18:45,525 --> 00:18:47,659
Dark matter is the thing
that enabled,
355
00:18:47,661 --> 00:18:49,661
that provided enough gravity
356
00:18:49,663 --> 00:18:53,397
for the initial seeds of
structure formation to coalesce,
357
00:18:53,399 --> 00:18:55,600
for galaxies themselves to form.
358
00:18:57,337 --> 00:18:59,003
And, of course,
without galaxies,
359
00:18:59,005 --> 00:19:01,006
there are no stars,
and there's no planets,
360
00:19:01,008 --> 00:19:02,940
and there's no us.
361
00:19:02,942 --> 00:19:04,542
Narrator:
For 9 billion years,
362
00:19:04,544 --> 00:19:08,079
dark matter orchestrates the
construction of the universe.
363
00:19:10,016 --> 00:19:13,084
In these, the first battles
of the cosmos,
364
00:19:13,086 --> 00:19:17,022
this constructive force
is the clear Victor.
365
00:19:17,024 --> 00:19:19,624
For the time being,
the dark matter has won.
366
00:19:19,626 --> 00:19:21,492
Galaxies continue to form.
367
00:19:21,494 --> 00:19:23,895
Clusters of galaxies
are getting bigger over time.
368
00:19:27,100 --> 00:19:30,168
Narrator:
But dark matter's success
in building up the universe
369
00:19:30,170 --> 00:19:33,505
sets in motion
its potential downfall.
370
00:19:37,911 --> 00:19:41,780
As the cosmic web evolves
into a more complex structure...
371
00:19:41,782 --> 00:19:44,449
�
372
00:19:44,451 --> 00:19:48,986
...gaps form between
the filaments, the cosmic voids.
373
00:19:48,988 --> 00:19:50,788
�
374
00:19:50,790 --> 00:19:55,526
the cosmic voids formed because
other, more dense regions
375
00:19:55,528 --> 00:20:00,465
of the universe gravitationally
stole material away from them.
376
00:20:00,467 --> 00:20:02,400
So the dense parts
of the universe
377
00:20:02,402 --> 00:20:07,138
accumulated more matter at the
expense of the less dense parts,
378
00:20:07,140 --> 00:20:10,208
which then became voids.
379
00:20:10,210 --> 00:20:14,479
Narrator: And lurking
in these voids, dark energy.
380
00:20:14,481 --> 00:20:16,080
Since the dawn of time,
381
00:20:16,082 --> 00:20:19,818
it's been waiting
for its opportunity.
382
00:20:19,820 --> 00:20:23,755
Now it's preparing an offensive
that may help it
383
00:20:23,757 --> 00:20:26,224
conquer the universe.
384
00:20:26,226 --> 00:20:27,892
In the very earliest times,
385
00:20:27,894 --> 00:20:29,561
the dark matter dominated
everything.
386
00:20:29,563 --> 00:20:32,863
It was the big brother pushing
the little brother around.
387
00:20:32,865 --> 00:20:34,298
But in the long run,
388
00:20:34,300 --> 00:20:37,034
the dark energy is going
to overpower dark matter,
389
00:20:37,036 --> 00:20:39,370
and so the relationship
is entirely flipped.
390
00:20:39,372 --> 00:20:41,071
�
391
00:20:41,073 --> 00:20:43,975
plait: We used to think
the fate of the cosmos itself
392
00:20:43,977 --> 00:20:45,309
depended on dark matter,
393
00:20:45,311 --> 00:20:47,979
and it turns out
that's not the case at all.
394
00:20:47,981 --> 00:20:51,916
The fate of the universe
depends entirely on dark energy.
395
00:20:51,918 --> 00:20:54,252
Narrator:
The long reign of dark matter
396
00:20:54,254 --> 00:20:56,254
may be coming to an end.
397
00:20:56,256 --> 00:20:58,923
Dark energy,
the great destroyer,
398
00:20:58,925 --> 00:21:01,993
is hoping to take control.
399
00:21:01,995 --> 00:21:06,331
This destructive force
has one overriding aim --
400
00:21:06,333 --> 00:21:09,534
to tear the universe apart.
401
00:21:25,151 --> 00:21:28,152
Narrator:
Our universe is at war,
402
00:21:28,154 --> 00:21:32,490
a relentless conflict
between dark forces.
403
00:21:32,492 --> 00:21:38,495
For the first 9 billion years,
dark energy is subjugated.
404
00:21:38,497 --> 00:21:42,766
Dark matter has the upper hand.
405
00:21:42,768 --> 00:21:45,036
Frenk: When the universe
emerged from the big bang,
406
00:21:45,038 --> 00:21:47,705
the dark energy played no role.
407
00:21:47,707 --> 00:21:48,840
It was insignificant.
408
00:21:50,710 --> 00:21:53,210
Narrator: But at some stage
in the 14 billion years
409
00:21:53,212 --> 00:21:58,382
since the big bang,
these roles became reversed.
410
00:21:58,384 --> 00:22:02,720
Dark energy came to be
the more powerful force.
411
00:22:02,722 --> 00:22:05,790
The question was, when?
412
00:22:05,792 --> 00:22:09,660
The answer came at the end
of the 20th century.
413
00:22:09,662 --> 00:22:12,864
So it was an amazing
breakthrough, really important.
414
00:22:12,866 --> 00:22:14,131
�
415
00:22:14,133 --> 00:22:15,733
narrator: In 1999,
416
00:22:15,735 --> 00:22:19,003
scientists measure
the expansion of the universe.
417
00:22:20,407 --> 00:22:23,407
What they find shocks them.
418
00:22:23,409 --> 00:22:28,146
They expect the speed
of expansion to be decreasing.
419
00:22:28,148 --> 00:22:31,349
In fact,
it's actually increasing
420
00:22:31,351 --> 00:22:34,818
and getting faster all the time.
421
00:22:34,820 --> 00:22:38,156
The data indicate that for about
the first 9 billion years,
422
00:22:38,158 --> 00:22:39,691
it was slowing down.
423
00:22:39,693 --> 00:22:42,093
But then,
in the past 5 billion years,
424
00:22:42,095 --> 00:22:46,297
it started accelerating
faster and faster.
425
00:22:46,299 --> 00:22:49,099
Narrator: Alex filippenko
was part of the team
426
00:22:49,101 --> 00:22:52,569
that made this
explosive discovery.
427
00:22:52,571 --> 00:22:53,971
Filippenko:
It befuddled us.
428
00:22:53,973 --> 00:22:56,975
This isn't how nature
was supposed to be behaving,
429
00:22:56,977 --> 00:22:59,109
and, in fact,
initially we thought
430
00:22:59,111 --> 00:23:00,445
that there was something wrong
431
00:23:00,447 --> 00:23:03,448
with either the observations
or the measurements.
432
00:23:03,450 --> 00:23:05,850
I didn't believe it
for the longest time.
433
00:23:05,852 --> 00:23:07,385
When the first data came out,
I'm like,
434
00:23:07,387 --> 00:23:09,520
"nah, I don't believe this,
no way."
435
00:23:09,522 --> 00:23:10,922
But it's in the data.
436
00:23:10,924 --> 00:23:12,724
It's there.
You can't escape it.
437
00:23:12,726 --> 00:23:16,461
This is as shocking as if you
held up a rock, let go of it,
438
00:23:16,463 --> 00:23:17,862
and it went up into the air.
439
00:23:17,864 --> 00:23:20,864
�
440
00:23:20,866 --> 00:23:22,533
narrator:
Five billion years ago,
441
00:23:22,535 --> 00:23:26,404
galaxies started moving apart
faster than before.
442
00:23:26,406 --> 00:23:29,540
The question is, why?
443
00:23:29,542 --> 00:23:32,810
What could be causing that?
Well, one thing is clear.
444
00:23:32,812 --> 00:23:35,579
It must be getting some
extra energy from somewhere.
445
00:23:35,581 --> 00:23:37,882
Narrator:
There is one main contender
446
00:23:37,884 --> 00:23:41,619
for what may be supplying
this extra energy,
447
00:23:41,621 --> 00:23:44,455
a force with repulsive gravity,
448
00:23:44,457 --> 00:23:47,825
a force
that pushes things apart.
449
00:23:47,827 --> 00:23:50,428
This is what astronomers
call dark energy.
450
00:23:50,430 --> 00:23:53,164
It's this mysterious
repulsive force
451
00:23:53,166 --> 00:23:55,166
that we know exists
in the universe,
452
00:23:55,168 --> 00:23:58,302
and we have no idea what it is.
453
00:23:58,304 --> 00:24:01,906
Narrator: Physicists may not
agree on what dark energy is,
454
00:24:01,908 --> 00:24:03,307
but there is a consensus
455
00:24:03,309 --> 00:24:08,379
on where this repulsive force
has the most influence --
456
00:24:08,381 --> 00:24:13,184
in the regions between galaxies
and galaxy clusters,
457
00:24:13,186 --> 00:24:15,186
the cosmic voids.
458
00:24:15,188 --> 00:24:19,791
They're actually filled
to the brim with dark energy.
459
00:24:19,793 --> 00:24:21,458
The first time dark energy
is really going to make
460
00:24:21,460 --> 00:24:24,195
its Mark in the universe
is going to be the time
461
00:24:24,197 --> 00:24:26,930
when the first cosmic voids
begin to appear.
462
00:24:28,935 --> 00:24:33,270
Sutter:
We see dark energy's effects
throughout the universe.
463
00:24:33,272 --> 00:24:36,407
But when we look into
the cosmic voids,
464
00:24:36,409 --> 00:24:39,677
which are the most empty regions
of our universe,
465
00:24:39,679 --> 00:24:42,413
this is where dark energy
is strongest.
466
00:24:42,415 --> 00:24:45,282
�
467
00:24:45,284 --> 00:24:47,551
narrator: Dark energy
is the repulsive force
468
00:24:47,553 --> 00:24:49,353
pushing things apart.
469
00:24:49,355 --> 00:24:52,690
It prefers the voids
where gravity is weak.
470
00:24:54,561 --> 00:24:57,028
Bullock: These are areas where
there's a lot less dark matter,
471
00:24:57,030 --> 00:24:59,430
and because the overall density
is low,
472
00:24:59,432 --> 00:25:01,432
that's where the dark energy
starts to peek out
473
00:25:01,434 --> 00:25:04,235
and can really drive
those voids to expand.
474
00:25:04,237 --> 00:25:07,504
So the expansion and
acceleration of the universe
475
00:25:07,506 --> 00:25:10,174
are driven by the dark energy
in those regions.
476
00:25:11,711 --> 00:25:14,912
Narrator: Dark energy
pushes thing apart,
477
00:25:14,914 --> 00:25:17,782
things that get in its way,
478
00:25:17,784 --> 00:25:21,652
things like the cosmic web.
479
00:25:21,654 --> 00:25:27,058
Dark matter and normal matter
are also in its path
480
00:25:27,060 --> 00:25:30,595
and are bulldozed out
across the cosmos.
481
00:25:30,597 --> 00:25:34,866
Slowly, but surely, the balance
between dark energy
482
00:25:34,868 --> 00:25:37,468
and dark matter is changing.
483
00:25:40,006 --> 00:25:41,672
Imagine you have
a giant swimming pool,
484
00:25:41,674 --> 00:25:44,275
and at the very bottom
there's a puddle of water
485
00:25:44,277 --> 00:25:45,542
with a splash of whiskey.
486
00:25:45,544 --> 00:25:47,344
So you have sort of a strong
whiskey drink
487
00:25:47,346 --> 00:25:49,480
down at the bottom of your pool.
488
00:25:49,482 --> 00:25:53,016
But now you start dumping water
into your pool, no more whiskey,
489
00:25:53,018 --> 00:25:55,018
and it begins to get diluted
and diluted,
490
00:25:55,020 --> 00:25:57,822
and eventually, you just have
a swimming pool full of water,
491
00:25:57,824 --> 00:25:59,757
with one shot of whiskey
mixed in.
492
00:25:59,759 --> 00:26:01,159
That's not a very strong drink.
493
00:26:01,161 --> 00:26:03,294
It's basically a water
swimming pool.
494
00:26:03,296 --> 00:26:05,563
That's pretty much happening
with the dark energy.
495
00:26:05,565 --> 00:26:07,231
At first,
it's a one-to-one mixture
496
00:26:07,233 --> 00:26:08,900
of dark matter and dark energy.
497
00:26:08,902 --> 00:26:11,368
But in the long run,
it's all dark energy
498
00:26:11,370 --> 00:26:13,437
and pretty much
no dark matter left over.
499
00:26:13,439 --> 00:26:15,506
�
500
00:26:15,508 --> 00:26:17,975
narrator:
The forces of dark energy
501
00:26:17,977 --> 00:26:20,511
are on an unstoppable march,
502
00:26:20,513 --> 00:26:22,513
picking up more and more power
503
00:26:22,515 --> 00:26:26,250
from the vast scale
of the cosmic voids.
504
00:26:26,252 --> 00:26:28,986
Dark energy is intrinsically
very weak.
505
00:26:28,988 --> 00:26:30,888
There's very little dark energy
506
00:26:30,890 --> 00:26:34,859
and this repulsive effect
in every cubic centimeter.
507
00:26:34,861 --> 00:26:36,660
But the universe is vast.
508
00:26:36,662 --> 00:26:38,863
Space is big.
509
00:26:38,865 --> 00:26:42,733
So cumulatively, all this
small amount of stuff
510
00:26:42,735 --> 00:26:45,203
adds up to a very large amount,
511
00:26:45,205 --> 00:26:48,939
and over a scale encompassing
the entire universe,
512
00:26:48,941 --> 00:26:51,542
the dark energy dominates.
513
00:26:53,413 --> 00:26:55,946
Narrator: But it's been
a very long process.
514
00:26:55,948 --> 00:26:57,615
After the big bang,
515
00:26:57,617 --> 00:27:01,419
dark matter dominates
for the first 9 billion years.
516
00:27:01,421 --> 00:27:03,620
�
517
00:27:03,622 --> 00:27:06,023
then, 5 billion years ago,
518
00:27:06,025 --> 00:27:08,960
dark energy starts
to get the upper hand.
519
00:27:08,962 --> 00:27:12,763
It causes the expansion
of the universe to accelerate
520
00:27:12,765 --> 00:27:16,500
and the space in the voids
to grow more rapidly.
521
00:27:16,502 --> 00:27:20,504
As the space expands, there's
more and more dark energy
522
00:27:20,506 --> 00:27:22,173
because you have a bigger space.
523
00:27:22,175 --> 00:27:26,777
It sort of creates itself
with the expansion of space.
524
00:27:26,779 --> 00:27:29,380
Tegmark: Dark energy has
a sneaky way of taking over
525
00:27:29,382 --> 00:27:30,981
because it causes the space
526
00:27:30,983 --> 00:27:32,650
to stretch out
and get twice as big.
527
00:27:32,652 --> 00:27:36,254
So now there's twice
as much dark energy.
528
00:27:36,256 --> 00:27:39,724
Narrator: Dark energy
just can't stop pushing,
529
00:27:39,726 --> 00:27:42,459
causing the empty space
of the voids
530
00:27:42,461 --> 00:27:44,195
to continuously expand.
531
00:27:47,133 --> 00:27:50,801
As the universe expands
because of dark energy,
532
00:27:50,803 --> 00:27:53,204
more and more dark energy
is being created.
533
00:27:53,206 --> 00:27:54,739
Dark energy is
definitely gaining
534
00:27:54,741 --> 00:27:56,540
the upper hand on dark matter.
535
00:27:56,542 --> 00:28:01,546
It was always there, but it took
over compared to other stuff.
536
00:28:01,548 --> 00:28:03,146
�
537
00:28:03,148 --> 00:28:06,550
narrator: Eventually creating
enough energy to supercharge
538
00:28:06,552 --> 00:28:08,619
the expansion of the universe.
539
00:28:08,621 --> 00:28:10,922
�
540
00:28:10,924 --> 00:28:13,024
this acceleration continues.
541
00:28:13,026 --> 00:28:15,959
The universe is getting bigger
and bigger,
542
00:28:15,961 --> 00:28:19,430
and it's all powered
by the forces of repulsion,
543
00:28:19,432 --> 00:28:20,897
dark energy.
544
00:28:20,899 --> 00:28:25,836
And for the universe,
that could be very bad news.
545
00:28:25,838 --> 00:28:30,240
If that's the case, dark energy
may destroy the universe.
546
00:28:30,242 --> 00:28:31,708
It will get stronger
and stronger
547
00:28:31,710 --> 00:28:34,979
until it literally rips apart
the fabric of space-time.
548
00:28:48,127 --> 00:28:49,793
�
549
00:28:49,795 --> 00:28:51,796
narrator:
Dark matter and dark energy
550
00:28:51,798 --> 00:28:56,467
have been battling each other
for 13.8 billion years.
551
00:28:56,469 --> 00:29:01,272
For the first 9 billion years,
dark matter dominates.
552
00:29:01,274 --> 00:29:04,875
Dark matter exerts
positive gravity,
553
00:29:04,877 --> 00:29:09,947
but pulling everything together
leads to one inevitable outcome.
554
00:29:09,949 --> 00:29:14,218
If the universe was totally
dominated by matter,
555
00:29:14,220 --> 00:29:16,887
eventually our expansion
would slow down,
556
00:29:16,889 --> 00:29:20,024
glide to a stop,
and then turn around
557
00:29:20,026 --> 00:29:24,028
and collapse into
a small, dense state
558
00:29:24,030 --> 00:29:29,100
from where it came from,
an event we call the big crunch.
559
00:29:29,102 --> 00:29:30,901
Narrator:
During the big crunch,
560
00:29:30,903 --> 00:29:34,638
gravity would play havoc
with the cosmos.
561
00:29:34,640 --> 00:29:38,442
Galaxies
would be dragged together.
562
00:29:38,444 --> 00:29:42,513
Stars and planets
would smash into each other.
563
00:29:42,515 --> 00:29:46,250
The universe would collapse
in a blazing inferno
564
00:29:46,252 --> 00:29:48,919
of superdense matter
and energy.
565
00:29:52,991 --> 00:29:56,059
Fortunately, none of this
will probably happen.
566
00:29:56,061 --> 00:29:59,129
�
567
00:29:59,131 --> 00:30:03,334
scientists have now dismissed
the possibility of a big crunch.
568
00:30:03,336 --> 00:30:06,337
�
569
00:30:06,339 --> 00:30:08,739
sutter: We don't face that,
because we have a universe
570
00:30:08,741 --> 00:30:11,208
filled with dark energy.
571
00:30:11,210 --> 00:30:14,211
Dark energy is causing the
universe to do something else,
572
00:30:14,213 --> 00:30:16,947
something it would prefer
not to do.
573
00:30:16,949 --> 00:30:20,751
It is accelerating the expansion
of the universe.
574
00:30:20,753 --> 00:30:23,287
Narrator:
As dark energy gets stronger,
575
00:30:23,289 --> 00:30:26,690
it supercharges this expansion.
576
00:30:26,692 --> 00:30:32,429
The presence of dark energy
is like a high-octane additive
577
00:30:32,431 --> 00:30:34,298
into a gas tank,
578
00:30:34,300 --> 00:30:37,835
where a car isn't
just coasting along.
579
00:30:37,837 --> 00:30:40,170
It's boosting along,
580
00:30:40,172 --> 00:30:43,039
and that's what's happening
with our universe.
581
00:30:43,041 --> 00:30:46,043
Narrator: If that's correct,
this supercharged expansion
582
00:30:46,045 --> 00:30:49,980
will continue
for the next few billion years.
583
00:30:49,982 --> 00:30:54,451
The repulsive force of dark
energy will become invincible,
584
00:30:54,453 --> 00:31:00,124
and such unbridled power
will come with a high cost.
585
00:31:00,126 --> 00:31:03,660
I know of three ultimate
doomsday weapons.
586
00:31:03,662 --> 00:31:07,464
One is galactus'
ultimate nullifier.
587
00:31:07,466 --> 00:31:11,334
Another is the infinity stones
in the hands of thanos.
588
00:31:11,336 --> 00:31:13,203
But those two are make-believe.
589
00:31:13,205 --> 00:31:15,338
The real one is dark energy.
590
00:31:15,340 --> 00:31:18,742
It's the real ultimate
universe destroyer.
591
00:31:18,744 --> 00:31:20,744
�
592
00:31:20,746 --> 00:31:23,748
narrator: The universe may pay
the ultimate price
593
00:31:23,750 --> 00:31:28,385
for this ever-increasing
expansion driven by dark energy.
594
00:31:28,387 --> 00:31:29,954
Carroll:
And if that continues forever,
595
00:31:29,956 --> 00:31:33,157
the future of the universe
is very, very simple.
596
00:31:33,159 --> 00:31:35,493
It continues to expand,
to accelerate.
597
00:31:35,495 --> 00:31:37,428
Everything moves apart
from everything else,
598
00:31:37,430 --> 00:31:40,564
and the universe
becomes empty.
599
00:31:40,566 --> 00:31:42,366
There'll be nothing left
600
00:31:42,368 --> 00:31:46,103
but cold, desolate,
empty space forever.
601
00:31:46,105 --> 00:31:47,704
�
602
00:31:47,706 --> 00:31:49,639
narrator:
Dark energy will finally win
603
00:31:49,641 --> 00:31:52,309
the long war with dark matter.
604
00:31:52,311 --> 00:31:55,245
But the result
won't be pretty.
605
00:31:55,247 --> 00:32:00,784
This future universe
will be cold, dark, and empty.
606
00:32:00,786 --> 00:32:02,519
Eventually it's going
to get so cold
607
00:32:02,521 --> 00:32:05,055
that really nothing
can happen in it.
608
00:32:05,057 --> 00:32:06,790
It's the big chill.
609
00:32:06,792 --> 00:32:10,261
It gets colder and colder
and darker and darker.
610
00:32:10,263 --> 00:32:13,531
Everything will fade out,
and though it began with a bang,
611
00:32:13,533 --> 00:32:14,999
it's going to die in a whimper.
612
00:32:15,001 --> 00:32:19,069
The universe flatlines
because of dark energy.
613
00:32:19,071 --> 00:32:22,606
Narrator: The universe dies
in a big chill.
614
00:32:22,608 --> 00:32:24,942
Galaxies are so far apart,
615
00:32:24,944 --> 00:32:29,213
they're distant islands
in a sea of darkness.
616
00:32:29,215 --> 00:32:32,349
Gradually,
the galaxies dies, too.
617
00:32:32,351 --> 00:32:36,954
Star birth stops,
and the universe fades away.
618
00:32:39,091 --> 00:32:40,758
Or maybe not.
619
00:32:40,760 --> 00:32:45,429
There's another,
far more violent scenario.
620
00:32:45,431 --> 00:32:50,768
Here, dark energy just goes
from strength to strength.
621
00:32:50,770 --> 00:32:54,771
It could be that dark energy
is so strong
622
00:32:54,773 --> 00:32:58,041
that it will multiply
upon itself
623
00:32:58,043 --> 00:33:00,377
as the universe gets bigger.
624
00:33:00,379 --> 00:33:05,049
This is a process that
we call phantom dark energy.
625
00:33:05,051 --> 00:33:09,786
Narrator: Phantom energy is
dark energy on steroids.
626
00:33:09,788 --> 00:33:13,657
It multiplies uncontrollably
in the voids,
627
00:33:13,659 --> 00:33:16,059
tearing at the fabric
of the universe
628
00:33:16,061 --> 00:33:20,664
in a process
called the big rip.
629
00:33:20,666 --> 00:33:24,935
Dark energy is weird enough,
but imagine the possibility
630
00:33:24,937 --> 00:33:28,405
that there is more and more
of it as time goes on,
631
00:33:28,407 --> 00:33:32,610
and it's called phantom energy,
and in that case,
632
00:33:32,612 --> 00:33:35,745
it would rip everything apart,
even black holes.
633
00:33:39,886 --> 00:33:42,619
It will start to rip apart
galaxies themselves...
634
00:33:45,691 --> 00:33:47,757
...rip apart solar systems...
635
00:33:51,630 --> 00:33:53,230
...rip apart people,
636
00:33:53,232 --> 00:33:56,767
rip apart atoms...
637
00:33:56,769 --> 00:33:57,968
Rip apart nuclei.
638
00:34:01,173 --> 00:34:03,774
Until finally,
space itself is pulled apart.
639
00:34:05,110 --> 00:34:06,643
Narrator:
The universe, as we know it,
640
00:34:06,645 --> 00:34:08,445
will be destroyed,
641
00:34:08,447 --> 00:34:11,782
but the big rip may not be
the end of everything.
642
00:34:11,784 --> 00:34:15,852
�
643
00:34:15,854 --> 00:34:20,724
there will be no normal matter
and no dark matter.
644
00:34:20,726 --> 00:34:22,926
And with nothing
left to conquer,
645
00:34:22,928 --> 00:34:27,530
phantom energy may use its
powers to become a creator,
646
00:34:27,532 --> 00:34:29,333
triggering a rebirth.
647
00:34:31,070 --> 00:34:35,406
Eventually, when you get to this
ultimate stage of emptiness,
648
00:34:35,408 --> 00:34:36,874
because of the phantom energy,
649
00:34:36,876 --> 00:34:38,742
we're actually able to turn
the universe around
650
00:34:38,744 --> 00:34:41,211
and get it
to collapse again,
651
00:34:41,213 --> 00:34:44,147
and then go through
a series of bounces.
652
00:34:44,149 --> 00:34:45,883
So we call it
the phantom bounce.
653
00:34:45,885 --> 00:34:47,417
�
654
00:34:47,419 --> 00:34:49,285
narrator:
With this phantom bounce,
655
00:34:49,287 --> 00:34:51,755
universal life energy left
in this dead universe
656
00:34:51,757 --> 00:34:54,358
starts to collapse.
657
00:34:54,360 --> 00:34:56,493
Freese: And eventually
it becomes hotter and hotter
658
00:34:56,495 --> 00:34:59,496
and denser and denser,
and then the fiery inferno
659
00:34:59,498 --> 00:35:02,966
eventually pushes you back out
into another big bang,
660
00:35:02,968 --> 00:35:05,535
and this just keeps
going on indefinitely.
661
00:35:05,537 --> 00:35:07,237
�
662
00:35:07,239 --> 00:35:10,574
narrator: So the destructive
and repulsive dark energy
663
00:35:10,576 --> 00:35:16,313
spawns a force that becomes
the ultimate universe recycler.
664
00:35:16,315 --> 00:35:18,648
The end state of our universe
665
00:35:18,650 --> 00:35:20,917
would lead you back
into another cycle,
666
00:35:20,919 --> 00:35:22,986
a whole new big bang
from the beginning.
667
00:35:28,127 --> 00:35:32,062
Narrator: In the end,
dark energy may kill the cosmos,
668
00:35:32,064 --> 00:35:35,199
or it may create a new one.
669
00:35:35,201 --> 00:35:36,800
Dark energy is mysterious.
670
00:35:36,802 --> 00:35:38,401
Dark energy is unknown.
671
00:35:38,403 --> 00:35:41,805
Dark energy is going to do
whatever it feels like.
672
00:35:41,807 --> 00:35:43,807
Maybe dark energy will go away.
673
00:35:43,809 --> 00:35:45,875
Maybe dark energy will decay
674
00:35:45,877 --> 00:35:49,012
and become a flood
of new matter and radiation.
675
00:35:49,014 --> 00:35:51,815
Maybe dark matter
will get stronger.
676
00:35:51,817 --> 00:35:53,016
We don't know.
677
00:35:53,018 --> 00:35:56,353
�
678
00:35:56,355 --> 00:35:58,822
narrator:
For now, we think dark energy
679
00:35:58,824 --> 00:36:02,159
will determine the fate
of the universe.
680
00:36:02,161 --> 00:36:05,962
But all of our evidence
is speculative.
681
00:36:05,964 --> 00:36:07,831
What if we have it all wrong?
682
00:36:07,833 --> 00:36:11,702
What if there is
no dark universe at all?
683
00:36:11,704 --> 00:36:16,240
�
684
00:36:26,986 --> 00:36:29,853
�
685
00:36:29,855 --> 00:36:31,989
narrator: A large part of
our understanding
686
00:36:31,991 --> 00:36:33,590
of the universe's past,
687
00:36:33,592 --> 00:36:37,327
present, and future is based
on educated guesswork
688
00:36:37,329 --> 00:36:39,829
about two invisible forces --
689
00:36:42,068 --> 00:36:45,669
...dark matter and dark energy.
690
00:36:45,671 --> 00:36:49,139
But it's pure speculation.
691
00:36:49,141 --> 00:36:53,610
Perhaps dark matter
and dark energy don't exist.
692
00:36:53,612 --> 00:36:56,346
There's not new stuff
in the universe.
693
00:36:56,348 --> 00:36:57,614
Anything is possible.
694
00:36:57,616 --> 00:36:59,015
Dark energy, in particular,
695
00:36:59,017 --> 00:37:01,752
might not be real,
so maybe there's something else
696
00:37:01,754 --> 00:37:03,419
that could be pushing
the universe apart.
697
00:37:03,421 --> 00:37:05,022
Tremblay: So we could
absolutely be wrong
698
00:37:05,024 --> 00:37:07,357
about dark energy
and dark matter.
699
00:37:07,359 --> 00:37:09,025
Maybe they don't exist.
700
00:37:09,027 --> 00:37:11,962
Maybe tomorrow we'll discover
that our understanding
701
00:37:11,964 --> 00:37:14,764
was wrong all along.
702
00:37:14,766 --> 00:37:16,834
Narrator:
That's an awful lot of maybes.
703
00:37:16,836 --> 00:37:19,036
Let's add one more.
704
00:37:19,038 --> 00:37:21,704
When it comes to finding
answers,
705
00:37:21,706 --> 00:37:24,241
maybe we're looking
in the wrong place.
706
00:37:26,445 --> 00:37:29,713
Filippenko: One possibility is
that there are other universes
707
00:37:29,715 --> 00:37:34,585
out there pulling outward,
so to speak, on our universe.
708
00:37:34,587 --> 00:37:35,919
That might be the answer.
709
00:37:35,921 --> 00:37:38,588
But most theoretical physicists
and astrophysicists
710
00:37:38,590 --> 00:37:41,658
these days think
that dark energy is real
711
00:37:41,660 --> 00:37:44,794
because that seems to be
the simplest explanation
712
00:37:44,796 --> 00:37:47,664
for a wide variety
of observations.
713
00:37:47,666 --> 00:37:49,132
�
714
00:37:49,134 --> 00:37:52,802
narrator: No one really knows
what dark energy is made of.
715
00:37:52,804 --> 00:37:56,273
Maybe the answer lies
in the past.
716
00:37:56,275 --> 00:37:58,609
The best theory for dark energy
we have right now
717
00:37:58,611 --> 00:38:00,811
is the simplest one
and the oldest one,
718
00:38:00,813 --> 00:38:03,280
and that's the idea that
it's a cosmological constant.
719
00:38:03,282 --> 00:38:05,215
�
720
00:38:05,217 --> 00:38:07,417
narrator: Albert Einstein
came up with the idea
721
00:38:07,419 --> 00:38:12,289
of a cosmological constant
in 1917.
722
00:38:12,291 --> 00:38:16,160
He suggested that space
has its own energy,
723
00:38:16,162 --> 00:38:19,429
energy that can affect
the way the universe expands.
724
00:38:19,431 --> 00:38:21,965
�
725
00:38:21,967 --> 00:38:25,035
when Edwin hubble proved
the universe is expanding,
726
00:38:25,037 --> 00:38:27,971
Einstein thought
the cosmological constant
727
00:38:27,973 --> 00:38:30,106
was his biggest blunder.
728
00:38:30,108 --> 00:38:33,977
But observations that the
expansion of the universe
729
00:38:33,979 --> 00:38:35,445
is accelerating
730
00:38:35,447 --> 00:38:39,049
reveal Einstein
was right all along.
731
00:38:39,051 --> 00:38:42,986
Filippenko: Well, here we are.
We've reintroduced the idea.
732
00:38:42,988 --> 00:38:46,790
So Einstein's biggest blunder
may have actually
733
00:38:46,792 --> 00:38:49,326
conceptually been
his greatest triumph.
734
00:38:49,328 --> 00:38:52,930
�
735
00:38:52,932 --> 00:38:56,200
narrator:
But to understand the true
nature of the dark universe,
736
00:38:56,202 --> 00:39:00,603
we may need to re-evaluate what
we think we know about gravity.
737
00:39:02,874 --> 00:39:05,542
When we're trying to understand
dark energy and dark matter,
738
00:39:05,544 --> 00:39:09,479
there's a chance that just our
fundamental theories of gravity
739
00:39:09,481 --> 00:39:13,884
are wrong, that general
relativity isn't quite right.
740
00:39:13,886 --> 00:39:16,219
Narrator: Einstein's theory
of general relativity
741
00:39:16,221 --> 00:39:18,555
explains how gravity works,
742
00:39:18,557 --> 00:39:21,224
how stars orbit in galaxies,
743
00:39:21,226 --> 00:39:23,660
and planets orbit stars.
744
00:39:23,662 --> 00:39:25,495
�
745
00:39:25,497 --> 00:39:28,431
some scientists wonder
if altering this theory
746
00:39:28,433 --> 00:39:32,702
will help us understand
the dark universe.
747
00:39:32,704 --> 00:39:34,771
Tremblay: So you need not
absolutely believe
748
00:39:34,773 --> 00:39:37,974
that there is something
actually called dark matter.
749
00:39:37,976 --> 00:39:39,910
You need to only understand
that there is something
750
00:39:39,912 --> 00:39:42,846
in the universe
which behaves like dark matter.
751
00:39:42,848 --> 00:39:45,716
For example, you could
effectively mimic the behavior
752
00:39:45,718 --> 00:39:49,987
of dark matter by modifying
our current theory of gravity.
753
00:39:49,989 --> 00:39:51,988
Narrator:
But successfully modifying
754
00:39:51,990 --> 00:39:56,593
Einstein's theories on gravity
is a big challenge.
755
00:39:56,595 --> 00:39:58,795
Einstein's equations
are very robust.
756
00:39:58,797 --> 00:40:02,399
You don't fluff around
with Einstein with impunity.
757
00:40:05,137 --> 00:40:07,404
Narrator: For decades,
theoretical physicists
758
00:40:07,406 --> 00:40:10,607
have toyed
with Einstein's equations,
759
00:40:10,609 --> 00:40:14,811
looking for ways to explain
dark matter and dark energy,
760
00:40:14,813 --> 00:40:17,280
or make them go away.
761
00:40:17,282 --> 00:40:19,683
As yet, no one has managed.
762
00:40:19,685 --> 00:40:22,218
The dark universe persists.
763
00:40:23,822 --> 00:40:26,156
I think that the best
description of the observations
764
00:40:26,158 --> 00:40:29,359
we have today
is that dark matter exists.
765
00:40:29,361 --> 00:40:31,762
It's out there,
as well as dark energy.
766
00:40:31,764 --> 00:40:33,830
I think dark energy exists.
767
00:40:33,832 --> 00:40:35,365
I think dark energy is real,
768
00:40:35,367 --> 00:40:38,435
but I must admit that sometimes,
at 3 o'clock in the morning,
769
00:40:38,437 --> 00:40:41,772
I wake up screaming,
worried that, in fact,
770
00:40:41,774 --> 00:40:44,774
we've settled
on the wrong answer,
771
00:40:44,776 --> 00:40:46,910
and that in
a couple hundred years,
772
00:40:46,912 --> 00:40:48,778
they're going to be
laughing at us.
773
00:40:48,780 --> 00:40:51,715
�
774
00:40:51,717 --> 00:40:54,918
narrator: Until then, our
observations tell us the battle
775
00:40:54,920 --> 00:40:59,523
between dark matter and dark
energy has shaped the universe.
776
00:40:59,525 --> 00:41:02,992
�
777
00:41:02,994 --> 00:41:06,330
dark matter dictated the past,
778
00:41:06,332 --> 00:41:09,733
built the galaxies,
the stars, and the planets.
779
00:41:09,735 --> 00:41:11,601
�
780
00:41:11,603 --> 00:41:14,604
dark energy will determine
its future,
781
00:41:14,606 --> 00:41:18,141
potentially tearing
the universe apart.
782
00:41:18,143 --> 00:41:21,611
Just because we can't see dark
matter and dark energy directly
783
00:41:21,613 --> 00:41:24,348
doesn't mean they have not
had a profound effect
784
00:41:24,350 --> 00:41:26,749
on the evolution
of the entire universe.
785
00:41:26,751 --> 00:41:30,086
The dark universe was there at
the beginning of the universe,
786
00:41:30,088 --> 00:41:32,489
shaping it, and actually
creating the conditions
787
00:41:32,491 --> 00:41:36,225
for us to be here, and it's
taken over the universe.
788
00:41:36,227 --> 00:41:39,629
And, eventually, it may well
destroy the universe.
789
00:41:39,631 --> 00:41:41,164
�
790
00:41:41,166 --> 00:41:43,100
narrator:
Our universe may be dominated
791
00:41:43,102 --> 00:41:47,504
by the long struggle between
dark matter and dark energy.
792
00:41:47,506 --> 00:41:51,374
But all of this conflict
has led to a creative outcome,
793
00:41:51,376 --> 00:41:55,779
an outcome for which
we should all be grateful.
794
00:41:55,781 --> 00:41:59,850
The name dark matter suggests
that it's something nefarious
795
00:41:59,852 --> 00:42:02,252
and somehow bad for us,
but actually it's turned out
796
00:42:02,254 --> 00:42:04,854
that dark matter
is very much our friend.
797
00:42:04,856 --> 00:42:07,424
Because if it weren't
for the dark matter,
798
00:42:07,426 --> 00:42:08,725
we wouldn't be here.
799
00:42:09,928 --> 00:42:11,261
Thaller:
There's a wonderful irony
800
00:42:11,263 --> 00:42:13,129
to calling it
the dark universe,
801
00:42:13,131 --> 00:42:15,064
because now we're actually
beginning to shed light
802
00:42:15,066 --> 00:42:16,600
on how the universe began,
803
00:42:16,602 --> 00:42:18,935
how the largest structures
in the universe evolved.
804
00:42:18,937 --> 00:42:20,804
We wouldn't be here
without this dark universe.
805
00:42:20,806 --> 00:42:22,338
It's not dark at all.
806
00:42:22,340 --> 00:42:24,141
It's shedding light
on our own reality.
807
00:42:24,143 --> 00:42:28,512
�
63501
Can't find what you're looking for?
Get subtitles in any language from opensubtitles.com, and translate them here.