1
00:00:02,500 --> 00:00:05,068
The universe was born to die.

2
00:00:05,069 --> 00:00:09,472
But how and when
will it all end?

3
00:00:09,473 --> 00:00:11,306
That's the reason
i became a cosmologist.

4
00:00:11,307 --> 00:00:13,043
I wanted to be the first person
that would know

5
00:00:13,044 --> 00:00:15,011
How the universe would end.

6
00:00:15,012 --> 00:00:18,782
Two cosmic heavyweights
wrestle for control.

7
00:00:18,783 --> 00:00:21,283
The winner seals our fate.

8
00:00:21,284 --> 00:00:24,087
The tug of war is gravity,

9
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Which is trying
to shrink it down,

10
00:00:25,757 --> 00:00:28,558
And the expansion of space
and time itself.

11
00:00:28,559 --> 00:00:30,893
Will gravity triumph?

12
00:00:30,894 --> 00:00:34,063
The universe will get smaller
and smaller, hotter and hotter.

13
00:00:34,064 --> 00:00:37,066
Or will expansion
get the upper hand?

14
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Even the electrons around
your atoms will be ripped apart.

15
00:00:41,039 --> 00:00:42,505
The end is coming,

16
00:00:42,506 --> 00:00:46,043
And it could be
sooner than you think.

17
00:00:59,425 --> 00:01:02,494
The universe is everything

18
00:01:02,495 --> 00:01:06,198
All space, all time, all matter.

19
00:01:08,467 --> 00:01:11,436
The earth is a speck
by comparison,

20
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A grain of rock orbiting just
one of the 200 billion stars

21
00:01:16,008 --> 00:01:19,079
In our home galaxy,
the milky way.

22
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In turn, this enormous structure
is just a drop

23
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In an ocean of galaxies
that stretch

24
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For 90 billion light years.

25
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And all of this,

26
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From the biggest galaxy
to the smallest atom,

27
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Will one day die.

28
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We don't see evidence
of anything being eternal.

29
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Eternity doesn't exist.

30
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Even space and time
will come to an end.

31
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The universe has been
expanding since its birth,

32
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Gradually burning through
the fuel that lights its stars.

33
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But what happens
when the fuel runs out?

34
00:02:02,555 --> 00:02:05,056
Will it all just fade away?

35
00:02:05,057 --> 00:02:07,460
Stars die out,
use up their nuclear fuel.

36
00:02:07,461 --> 00:02:10,063
We have an empty, cold,
desolate universe.

37
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Just dead remnants of stars --

38
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Black holes, neutron stars.

39
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Eventually, they decay away,

40
00:02:15,769 --> 00:02:18,704
And you're left with a thin haze
of very low energy light.

41
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That's it.

42
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We used to think the universe

43
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Would cruise gently
into old age.

44
00:02:24,578 --> 00:02:26,679
But over the past few decades,

45
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Astronomers have
revealed a very different

46
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And disturbing picture.

47
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The universe isn't cruising.

48
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It's fighting for its life.

49
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It may seem peaceful here
on earth on a nice, sunny day,

50
00:02:38,959 --> 00:02:40,793
But in fact, above us
and all around us,

51
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Throughout the universe,
a battle is raging,

52
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And it has raged
since the beginning of time.

53
00:02:46,835 --> 00:02:50,404
Two deadly forces
grapple for control.

54
00:02:50,405 --> 00:02:54,941
The first, expansion,
pulls galaxies apart,

55
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Cooling the universe
and threatening it

56
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With a frozen extinction.

57
00:03:01,049 --> 00:03:05,585
The second, gravity, tries to
crush everything back together,

58
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Annihilating the universe
in a dense ball of fire.

59
00:03:11,992 --> 00:03:15,596
Will gravity or expansion win?

60
00:03:15,597 --> 00:03:17,631
Or will it end in a tie?

61
00:03:17,632 --> 00:03:21,437
These two colossal forces
yield three endgames.

62
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One is the big freeze.

63
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Expansion wins, and the universe
just expands forever.

64
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The second is that there is
a delicate balance

65
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Between the expansion

66
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And the amount of gravitational
attraction,

67
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And the universe gets
to a particular size,

68
00:03:34,716 --> 00:03:36,184
And it pretty much stays there.

69
00:03:36,185 --> 00:03:37,853
And the third outcome is that

70
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The gravitational
attraction wins,

71
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And the expansion stops,

72
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And the universe
begins to get smaller

73
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Until, eventually,
it goes back to a big crunch.

74
00:03:48,431 --> 00:03:50,765
So far,
the universe seems balanced

75
00:03:50,766 --> 00:03:54,703
On a tightrope between
expansion and contraction.

76
00:03:54,704 --> 00:03:58,107
But will it keep its equilibrium
until it runs out of steam,

77
00:03:58,108 --> 00:04:00,911
Or will something
tip the balance?

78
00:04:02,946 --> 00:04:05,882
I don't think there's
any bigger question than,

79
00:04:05,883 --> 00:04:08,116
Where is the universe going?

80
00:04:08,117 --> 00:04:11,654
To predict the future,
cosmologists have always looked

81
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To the past, back to
the beginning of expansion,

82
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The beginning of gravity,
the beginning of everything.

83
00:04:23,232 --> 00:04:28,202
13.8 billion years ago,
an infinitely dense,

84
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Hot speck ignites
and suddenly expands outward --

85
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The big bang.

86
00:04:36,446 --> 00:04:40,016
All energy, all space,
and all matter...

87
00:04:41,751 --> 00:04:44,786
...the building blocks of
the universe we see today,

88
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Are created and set in motion.

89
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Think of it.

90
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Everything you see around us

91
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Concentrated into a primordial
fireball that exploded,

92
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Sending all the galaxies
into motion.

93
00:05:04,309 --> 00:05:07,977
That outward blast,
the birth of expansion,

94
00:05:07,978 --> 00:05:10,647
Is still going on today.

95
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Without it, we wouldn't have
a universe big enough

96
00:05:14,052 --> 00:05:16,854
For stars
and galaxies to exist in.

97
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Expansion is an astonishing
force of nature.

98
00:05:20,124 --> 00:05:24,427
It works by inflating
the fabric of space-Time.

99
00:05:24,428 --> 00:05:28,099
Space between galaxies expands,

100
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And it pushes
the galaxies apart.

101
00:05:30,403 --> 00:05:35,506
Space carries objects with it
like a surfer on a wave.

102
00:05:35,507 --> 00:05:37,909
It's going on
in every part of space.

103
00:05:37,910 --> 00:05:39,578
Even inside your body right now,

104
00:05:39,579 --> 00:05:41,513
There's a pressure
for space to expand.

105
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Expansion generated
the vast, moving stage

106
00:05:45,418 --> 00:05:48,052
On which today's universe
plays out.

107
00:05:48,053 --> 00:05:50,956
But left unchecked,
it could have been a force

108
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For utter annihilation.

109
00:05:53,091 --> 00:05:55,326
If the universe had
been expanding much faster,

110
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It would have emptied out
so fast,

111
00:05:57,096 --> 00:05:59,364
You wouldn't have had time
to make galaxies,

112
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Planets, people.

113
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The fact
that we're here

114
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Means that something must have
put on the brakes.

115
00:06:07,341 --> 00:06:11,943
It was, of course,
our universal glue -- Gravity.

116
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Gravity and matter
go hand in hand.

117
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The more massive the object,

118
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The more pull it exerts
on everything around it.

119
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It draws atom to atom,
particle to particle...

120
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...building stars, nebulas,

121
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Galaxies --

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The hardware of the universe
we see today.

123
00:06:39,507 --> 00:06:42,340
But gravity
is a double-Edged sword.

124
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Too much, and the early universe
would never have gotten

125
00:06:45,245 --> 00:06:47,412
Out of the starting blocks.

126
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If it had been
expanding more slowly,

127
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It would have re-Collapsed
into another singularity.

128
00:06:51,718 --> 00:06:54,486
And again, you wouldn't have had
the time to make galaxies,

129
00:06:54,487 --> 00:06:56,289
Planets, or people.

130
00:06:56,290 --> 00:06:57,924
So we live in the goldilocks
universe.

131
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We live in the universe
that lasts long enough

132
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That we can be here,
but expands gently enough

133
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That we have time to form.

134
00:07:07,267 --> 00:07:11,069
The universe has
lasted for 13.8 billion years,

135
00:07:11,070 --> 00:07:15,042
Thanks to the opposing forces
of gravity and expansion.

136
00:07:15,043 --> 00:07:19,112
But just how stable
is this balancing act?

137
00:07:19,113 --> 00:07:22,615
Does our universe have just
the right amount of stuff in it

138
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To keep it from
runaway expansion

139
00:07:24,717 --> 00:07:26,787
Or catastrophic collapse?

140
00:07:27,388 --> 00:07:30,257
In the 1920s,
scientists did the math,

141
00:07:30,258 --> 00:07:34,094
And the results were
anything but reassuring.

142
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The more matter you have,
the more gravity you have.

143
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If you have lots of matter
in a very dense universe,

144
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Perhaps the universe
begins to re-Collapse.

145
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Or, if you have
very little matter,

146
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The universe would
freeze to death.

147
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So what is the critical density,
the border between the two?

148
00:07:52,380 --> 00:07:56,916
It's approximately five hydrogen
atoms per cubic meter.

149
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So think of a cubic yard,
and put just five hydrogen atoms

150
00:08:02,323 --> 00:08:05,159
Inside,
and that is the tipping point.

151
00:08:05,160 --> 00:08:07,293
If you put more than five atoms,

152
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Then the universe will
begin to collapse.

153
00:08:09,297 --> 00:08:10,831
If you have
less than five atoms,

154
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Then the universe
just keeps on going.

155
00:08:13,435 --> 00:08:15,635
If we thought
the universe was balanced

156
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On a tightrope before,
the critical density question

157
00:08:18,807 --> 00:08:23,079
Showed us that the rope
was more like a razor blade.

158
00:08:23,446 --> 00:08:26,382
Yet, when astronomers took
additional measurements,

159
00:08:26,383 --> 00:08:28,816
They liked what they saw.

160
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The universe appeared to contain
just the right amount

161
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Of matter to stay
at the critical density.

162
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More and more,
the indirect evidence

163
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And the theoretical
arguments suggested

164
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That the universe must be
exactly at the boundary

165
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Between a universe
that would collapse

166
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And one that
would expand forever,

167
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That we were teetering
on the hairy edge of expansion.

168
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The universe seemed
so perfectly balanced

169
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That it would head quietly
into old age.

170
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Then, in the 1970s, astronomers
made an observation

171
00:09:03,419 --> 00:09:05,421
That shocked them.

172
00:09:05,422 --> 00:09:09,325
The cosmos was filled
with invisible stuff,

173
00:09:09,326 --> 00:09:14,031
And its gravity could cause
a catastrophic collapse.

174
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The universe
is balanced on a tightrope.

175
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On each side of the drop
lies an early death --

176
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A big freeze, fueled by
the runaway stretching of space,

177
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Or a big crunch, the result of
gravity overcoming expansion.

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40 years ago, scientists
believed we'd stay balanced

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Between these fates
for eternity.

180
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Now things have changed
tremendously,

181
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Because we've discovered
something we never knew about

182
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40 years ago.

183
00:09:54,773 --> 00:09:59,444
In the 1970s,
astronomers are stunned.

184
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Some unknown form of matter,
invisible to telescopes,

185
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Dwarfs what we thought was
out there,

186
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Not a fraction more,
but five times more.

187
00:10:09,622 --> 00:10:12,790
We used to think
that gravity came from stars

188
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And objects you can see --
End of story.

189
00:10:15,795 --> 00:10:19,165
Now, we realize that that naive
picture is actually wrong.

190
00:10:20,200 --> 00:10:22,501
Astronomers make
the discovery,

191
00:10:22,502 --> 00:10:25,873
Studying the clockwork
nature of our universe.

192
00:10:27,275 --> 00:10:29,942
The huge gravity of the sun
holds the earth

193
00:10:29,943 --> 00:10:34,082
And all the other planets
in a delicate circular dance.

194
00:10:37,951 --> 00:10:41,487
The sun's mass controls
the speed of these orbits.

195
00:10:41,488 --> 00:10:44,657
If it were more massive,
the planets would orbit

196
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Much more quickly.

197
00:10:46,326 --> 00:10:48,895
And if it were smaller,
it would take much longer

198
00:10:48,896 --> 00:10:51,532
For a planet to complete
an orbit.

199
00:10:53,733 --> 00:10:57,002
Galaxies run
like clockwork, too.

200
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The vast mass at the center
pulls the outer stars

201
00:11:00,273 --> 00:11:03,676
Into circular,
planet-Like orbits.

202
00:11:03,677 --> 00:11:06,179
Astronomers make
precise measurements

203
00:11:06,180 --> 00:11:09,848
Of these galactic
orbits in the 1970s.

204
00:11:09,849 --> 00:11:13,021
The results change everything.

205
00:11:13,922 --> 00:11:16,489
The galaxies
were spinning too fast.

206
00:11:16,490 --> 00:11:18,025
Way too fast.

207
00:11:21,096 --> 00:11:23,965
Even accounting for
the supermassive black holes

208
00:11:23,966 --> 00:11:28,268
At their center, nine-Tenths
of their mass was missing.

209
00:11:28,269 --> 00:11:31,105
By rights,
the galaxy should fly apart.

210
00:11:31,106 --> 00:11:33,274
By rights, the earth
should have been flung

211
00:11:33,275 --> 00:11:36,244
Into intergalactic space
billions of years ago.

212
00:11:36,245 --> 00:11:39,446
We should have no
milky way galaxy, and yet,

213
00:11:39,447 --> 00:11:41,183
Our universe is
full of galaxies.

214
00:11:45,253 --> 00:11:48,188
An immense
additional source of gravity

215
00:11:48,189 --> 00:11:51,091
Must be holding galaxies
together.

216
00:11:51,092 --> 00:11:54,327
But no matter where astronomers
point their telescopes,

217
00:11:54,328 --> 00:11:56,264
They see nothing.

218
00:11:56,265 --> 00:11:59,799
Not a glimmer, not a shadow.

219
00:11:59,800 --> 00:12:04,672
Whatever this new stuff is,
it doesn't emit light,

220
00:12:04,673 --> 00:12:08,308
Reflect light,
or even block light.

221
00:12:08,309 --> 00:12:11,213
They call it dark matter.

222
00:12:11,246 --> 00:12:14,584
What we've learned is that most
of the matter in the universe

223
00:12:14,585 --> 00:12:17,220
Is not ordinary stuff.
It's not atoms.

224
00:12:17,221 --> 00:12:20,022
It's not particles we've yet
detected in any experiment

225
00:12:20,023 --> 00:12:21,724
Done here on earth.

226
00:12:21,725 --> 00:12:24,360
It's some new kind of particle
that we call the dark matter.

227
00:12:27,496 --> 00:12:29,398
Dark matter fills the universe,

228
00:12:29,399 --> 00:12:32,502
Outstripping normal matter
by 5-To-1.

229
00:12:36,105 --> 00:12:40,609
Vast filaments spread out
throughout the cosmos,

230
00:12:40,610 --> 00:12:45,081
And bright galaxies cluster
where dark matter is thickest.

231
00:12:47,417 --> 00:12:51,753
Dark matter provides
the scaffolding that underlies

232
00:12:51,754 --> 00:12:54,623
How the matter in the universe
structures itself,

233
00:12:54,624 --> 00:12:56,527
Where it goes,
and what it does.

234
00:12:57,394 --> 00:12:59,329
So,
dark matter dictated

235
00:12:59,330 --> 00:13:02,896
How the universe unfolded.

236
00:13:02,897 --> 00:13:05,035
It seems as if
out of the hot big bang,

237
00:13:05,036 --> 00:13:08,671
Dark matter condensed first,
before atoms,

238
00:13:08,672 --> 00:13:11,641
And dark matter began
to become clumpy.

239
00:13:11,642 --> 00:13:14,844
The clumpiness then began
to attract atoms

240
00:13:14,845 --> 00:13:18,547
As they were formed later,
and that formed galaxies.

241
00:13:18,548 --> 00:13:20,584
And in some sense,
the dark matter therefore

242
00:13:20,585 --> 00:13:24,189
Provides kind of a womb that
allows the birth of our galaxy.

243
00:13:27,425 --> 00:13:30,594
Dark matter holds
the universe together,

244
00:13:30,595 --> 00:13:33,064
But it also threatens
to destroy it.

245
00:13:35,897 --> 00:13:36,598
One of the most
amazing discoveries

246
00:13:36,599 --> 00:13:39,036
Of the past few decades
is dark matter,

247
00:13:39,037 --> 00:13:41,002
The fact that there's much more
matter in the universe

248
00:13:41,003 --> 00:13:42,472
Than we were aware of.

249
00:13:42,473 --> 00:13:44,976
And all of that matter
has a lot of gravity.

250
00:13:44,977 --> 00:13:47,109
So all this new matter,
all this new gravity

251
00:13:47,110 --> 00:13:49,513
Must be slowing down
the expansion of the universe.

252
00:13:50,281 --> 00:13:53,217
Dark matter may even
tip the cosmic scales

253
00:13:53,218 --> 00:13:55,218
In favor of gravity,

254
00:13:55,219 --> 00:13:58,988
Defeating expansion
and pulling the entire universe

255
00:13:58,989 --> 00:14:01,593
Towards a death by fire.

256
00:14:01,594 --> 00:14:04,395
It's called the big crunch,

257
00:14:04,396 --> 00:14:06,765
And this is how
it would play out.

258
00:14:08,467 --> 00:14:12,803
For a fraction of a second,
the universe stalls,

259
00:14:12,804 --> 00:14:16,540
Poised between
expansion and contraction.

260
00:14:16,541 --> 00:14:20,644
Then, gravity kicks off
a cataclysm.

261
00:14:20,645 --> 00:14:23,113
When you looked out,
the very first things

262
00:14:23,114 --> 00:14:25,049
As it began to turn around
that you began to see

263
00:14:25,050 --> 00:14:27,684
Is that galaxies, instead of
moving away from us on average,

264
00:14:27,685 --> 00:14:30,189
Would begin to be moving towards
us on average.

265
00:14:31,323 --> 00:14:34,294
The whole universe would look
like it was coming to get us.

266
00:14:36,096 --> 00:14:38,697
As space
contracts further,

267
00:14:38,698 --> 00:14:42,533
The density of matter increases,
gravity gets stronger,

268
00:14:42,534 --> 00:14:47,706
Temperatures soar
as the crunch gathers momentum.

269
00:14:47,707 --> 00:14:50,042
Galaxies begin to collide,

270
00:14:50,043 --> 00:14:53,012
Gas clouds begin to collide,

271
00:14:53,013 --> 00:14:56,116
Planets slam into the earth.

272
00:14:59,885 --> 00:15:03,455
Black holes will execute a death
dance around each other.

273
00:15:03,456 --> 00:15:06,892
Temperatures, of course,
will continue to skyrocket.

274
00:15:06,893 --> 00:15:10,730
Matter, space,
and time implode

275
00:15:10,731 --> 00:15:13,664
Until everything in the universe
is compressed

276
00:15:13,665 --> 00:15:19,504
Into a tiny speck of infinite
mass, heat, and pressure.

277
00:15:19,505 --> 00:15:22,273
For the last stages
of the big crunch,

278
00:15:22,274 --> 00:15:25,476
Galaxies will collide
and form a primordial atom.

279
00:15:25,477 --> 00:15:29,849
And then, life as we know it
will be impossible.

280
00:15:29,850 --> 00:15:32,283
We're back
to where it all began,

281
00:15:32,284 --> 00:15:33,421
Back at the big bang.

282
00:15:34,222 --> 00:15:37,959
The universe that we live in
will cease to exist.

283
00:15:41,528 --> 00:15:47,266
But some believe a big crunch
could herald a new beginning.

284
00:15:47,267 --> 00:15:49,602
We don't know what the end point
of a big crunch would be,

285
00:15:49,603 --> 00:15:52,338
Because the laws of physics
break down.

286
00:15:52,339 --> 00:15:55,809
It's possible, and indeed,
philosophically very pleasant,

287
00:15:55,810 --> 00:16:00,045
To imagine that that crunch
would somehow end up evolving

288
00:16:00,046 --> 00:16:03,348
Into an expansion again, and you
could have a cyclic universe

289
00:16:03,349 --> 00:16:04,883
Which goes on forever.

290
00:16:04,884 --> 00:16:08,623
Perhaps at that point, we will
recreate another big bang.

291
00:16:12,560 --> 00:16:14,928
It's conceivable that as
everything comes together

292
00:16:14,929 --> 00:16:18,463
In the crunch, something sort of
keeps it from just continuing

293
00:16:18,464 --> 00:16:22,135
And pushes out in a hot,
dense, smooth state,

294
00:16:22,136 --> 00:16:24,838
And from the other side,
it looks like a big bang,

295
00:16:24,839 --> 00:16:26,573
And a new universe has been
created.

296
00:16:26,574 --> 00:16:29,442
Our big bang might have been
someone else's big crunch.

297
00:16:29,443 --> 00:16:31,745
But just when
scientists came to terms

298
00:16:31,746 --> 00:16:35,216
With dark matter's big crunch,
the universe threw them

299
00:16:35,217 --> 00:16:37,618
Another, even bigger curve.

300
00:16:37,619 --> 00:16:42,156
Some ghostly force seemed to be
sending us hurtling toward

301
00:16:42,157 --> 00:16:44,257
A completely different death.

302
00:16:44,258 --> 00:16:47,061
My postdoctoral
scholar showed me the results.

303
00:16:47,062 --> 00:16:48,230
I nearly fell off my chair.

304
00:16:58,374 --> 00:17:00,710
Gravity and expansion
battle for control

305
00:17:00,711 --> 00:17:04,181
Of our universe
for 14 billion years...

306
00:17:08,352 --> 00:17:12,787
...expansion
pushing it outwards,

307
00:17:12,788 --> 00:17:15,393
Gravity pulling it in.

308
00:17:16,894 --> 00:17:18,995
With dark matter in its corner,

309
00:17:18,996 --> 00:17:21,497
Gravity seems to be
the inevitable winner.

310
00:17:21,498 --> 00:17:26,068
The extra mass will drag
the universe into a big crunch,

311
00:17:26,069 --> 00:17:28,104
Until a stunning discovery

312
00:17:28,105 --> 00:17:32,610
Revolutionizes our understanding
of the universe.

313
00:17:34,944 --> 00:17:39,883
Around 1990, two teams of
researchers decided to measure

314
00:17:39,884 --> 00:17:41,950
The expansion history
of the universe

315
00:17:41,951 --> 00:17:45,054
To determine whether
it's been slowing down so much

316
00:17:45,055 --> 00:17:47,291
That it'll eventually have
a big crunch,

317
00:17:47,292 --> 00:17:49,825
Or whether it hasn't been
slowing down much

318
00:17:49,826 --> 00:17:51,795
And will eternally expand.

319
00:17:51,796 --> 00:17:56,298
Astronomer alex filippenko
was on one team.

320
00:17:56,299 --> 00:17:58,901
Saul perlmutter led the other.

321
00:17:58,902 --> 00:18:01,938
We realized that it was possible
for the first time

322
00:18:01,939 --> 00:18:05,608
To go and actually make
a direct measurement

323
00:18:05,609 --> 00:18:08,111
Of how much the universe had
been slowing down in the past.

324
00:18:08,313 --> 00:18:09,847
Both teams want
to measure

325
00:18:09,848 --> 00:18:12,148
The speed of distant galaxies.

326
00:18:12,149 --> 00:18:16,020
But because the galaxies are
too dim and too far away,

327
00:18:16,021 --> 00:18:18,057
They look for something
brighter.

328
00:18:22,961 --> 00:18:27,431
Billions of light years
from earth, a star detonates.

329
00:18:27,432 --> 00:18:30,100
This is a supernova,

330
00:18:30,101 --> 00:18:34,105
A dying star's
brilliant final gasp.

331
00:18:34,106 --> 00:18:38,041
It burns brightly, 5 billion
times brighter than the sun,

332
00:18:38,042 --> 00:18:40,712
But briefly.

333
00:18:40,713 --> 00:18:42,879
Perlmutter and filippenko
have a window

334
00:18:42,880 --> 00:18:45,448
Of just one or two weeks
to measure

335
00:18:45,449 --> 00:18:48,752
How much the galaxy it sits in
is slowing down

336
00:18:48,753 --> 00:18:51,023
As it moves away from us.

337
00:18:55,128 --> 00:18:58,364
The teams look for supernovas
for eight years.

338
00:18:58,365 --> 00:19:04,170
They measure 42, and the results
seem impossible.

339
00:19:04,171 --> 00:19:06,771
We plotted the points
on the graphs,

340
00:19:06,772 --> 00:19:09,508
And...it didn't make any sense.

341
00:19:09,509 --> 00:19:11,376
They were not slowing down
at all.

342
00:19:11,377 --> 00:19:13,313
They were actually speeding up.

343
00:19:14,480 --> 00:19:18,084
What both groups found
stunned the world.

344
00:19:18,085 --> 00:19:20,920
In the last 4 or 5 billion
years,

345
00:19:20,921 --> 00:19:25,089
The universe has actually been
speeding up in its expansion.

346
00:19:25,090 --> 00:19:26,925
An accelerating universe,

347
00:19:26,926 --> 00:19:30,896
Propelled by something
mysterious.

348
00:19:30,897 --> 00:19:33,365
For so long, we've been arguing
whether the universe would

349
00:19:33,366 --> 00:19:36,201
Expand forever or collapse
back in on itself,

350
00:19:36,202 --> 00:19:38,570
But nobody thought
the answer was going to be

351
00:19:38,571 --> 00:19:40,873
That the universe was
accelerating,

352
00:19:40,874 --> 00:19:42,675
Going faster and faster
all the time.

353
00:19:44,245 --> 00:19:47,615
The acceleration
bewilders the scientists.

354
00:19:47,616 --> 00:19:50,718
It seems to defy
the laws of physics.

355
00:19:50,719 --> 00:19:52,987
Imagine i've got a baseball

356
00:19:52,988 --> 00:19:54,654
And i throw it straight up.

357
00:19:54,655 --> 00:19:57,458
And instead of slowing down
once it leaves my hand,

358
00:19:57,459 --> 00:19:59,292
Which is what
normally it will do,

359
00:19:59,293 --> 00:20:01,161
It begins to slow down at first,

360
00:20:01,162 --> 00:20:03,064
But then it starts
speeding away.

361
00:20:03,065 --> 00:20:04,699
Somehow, it's getting energy.

362
00:20:04,700 --> 00:20:10,170
The new energy seemed
to be coming from nothing,

363
00:20:10,171 --> 00:20:12,405
The vacuum of space.

364
00:20:12,406 --> 00:20:16,176
The word "vacuum" to a scientist
means completely empty space,

365
00:20:16,177 --> 00:20:18,778
No particles there at all,
no temperature,

366
00:20:18,779 --> 00:20:20,379
No energy to speak of.

367
00:20:20,380 --> 00:20:23,683
But there's an intrinsic energy
in space and time.

368
00:20:23,684 --> 00:20:27,386
Empty space has energy,
and that energy produces

369
00:20:27,387 --> 00:20:30,523
A gravitational repulsion,
a kind of anti-Gravity.

370
00:20:30,524 --> 00:20:34,962
Without a clue what
this force is or how it works,

371
00:20:34,963 --> 00:20:40,534
All scientists can do is give it
a name -- Dark energy.

372
00:20:40,903 --> 00:20:43,304
We could have called it
we-Don't-Know energy.

373
00:20:43,305 --> 00:20:44,773
We could have called it
anything.

374
00:20:44,774 --> 00:20:47,176
But we don't know what it is,
and dark or not,

375
00:20:47,177 --> 00:20:49,311
It's the biggest mystery
in physics.

376
00:20:52,480 --> 00:20:55,516
Nasa calibrates
its finest space telescopes

377
00:20:55,517 --> 00:20:58,652
To measure how much dark energy
is out there,

378
00:20:58,653 --> 00:21:01,989
And the result is mind-Blowing.

379
00:21:01,990 --> 00:21:06,795
It dominates the mass of
the universe by nearly 3-To-1.

380
00:21:06,796 --> 00:21:08,462
And the more space expands,

381
00:21:08,463 --> 00:21:11,632
The more dark energy
there seems to be.

382
00:21:11,633 --> 00:21:14,568
Dark energy is the energy
of nothing,

383
00:21:14,569 --> 00:21:16,104
And it's repulsive.

384
00:21:16,105 --> 00:21:19,908
Therefore, as this dark energy
repels galaxies,

385
00:21:19,909 --> 00:21:21,843
There's more of it,
there's more vacuum.

386
00:21:21,844 --> 00:21:23,946
And so there's more repulsion,

387
00:21:23,947 --> 00:21:26,881
And perhaps that's the reason
why the universe is accelerating

388
00:21:26,882 --> 00:21:30,218
Right now
rather than slowing down.

389
00:21:30,219 --> 00:21:33,689
Dark energy seems to
kill the big crunch theory,

390
00:21:33,690 --> 00:21:36,757
But scientists aren't yet sure
how dark energy,

391
00:21:36,758 --> 00:21:40,295
Expansion, and space
are connected.

392
00:21:40,296 --> 00:21:43,631
If a volume of space doubles
in size,

393
00:21:43,632 --> 00:21:46,534
Does the dark energy
inside it double, too?

394
00:21:46,535 --> 00:21:48,637
Or does it increase more?

395
00:21:48,638 --> 00:21:52,173
A 1-To-1 relationship leads
to a steady expansion.

396
00:21:52,174 --> 00:21:55,310
The universe ends
in a big freeze.

397
00:21:55,311 --> 00:21:59,881
But if dark energy increases
above and beyond expansion,

398
00:21:59,882 --> 00:22:04,455
A new, even more terrifying end
awaits the universe -- A big rip.

399
00:22:05,256 --> 00:22:09,291
In a big rip scenario,
the expansion is so great

400
00:22:09,292 --> 00:22:13,496
That even the galaxies begin
to expand internally,

401
00:22:13,497 --> 00:22:14,831
Which means that literally

402
00:22:14,832 --> 00:22:16,768
Our bodies
are going to be ripped apart.

403
00:22:18,067 --> 00:22:19,568
Scientists calculate

404
00:22:19,569 --> 00:22:21,905
Just how the big rip
will play out.

405
00:22:24,240 --> 00:22:28,310
One by one, the galaxies in
the night sky will blink out

406
00:22:28,311 --> 00:22:31,279
As space pulls them away
from the earth

407
00:22:31,280 --> 00:22:33,082
Faster than the speed of light.

408
00:22:34,786 --> 00:22:39,189
60 million years before the end,
dark energy overcomes gravity

409
00:22:39,190 --> 00:22:42,124
On smaller and smaller scales.

410
00:22:42,125 --> 00:22:45,428
First galaxies start
to rip apart,

411
00:22:45,429 --> 00:22:49,298
Then insides of galaxies
will begin to rip apart,

412
00:22:49,299 --> 00:22:51,969
And then solar systems will
begin to rip apart...

413
00:22:54,239 --> 00:22:57,208
then planets...

414
00:22:57,209 --> 00:23:02,614
and then rocks, people, atoms.

415
00:23:02,615 --> 00:23:05,918
The end will
be mercifully quick.

416
00:23:07,219 --> 00:23:09,487
In the space of a few minutes,

417
00:23:09,488 --> 00:23:13,658
All the stars and planets in the
universe will be destroyed,

418
00:23:13,659 --> 00:23:18,429
Their remains pulled apart
into ever-Smaller pieces

419
00:23:18,430 --> 00:23:21,099
Until finally,
when the universe has

420
00:23:21,100 --> 00:23:22,833
Less than a second to live,

421
00:23:22,834 --> 00:23:26,304
The subatomic particles
that made all matter

422
00:23:26,305 --> 00:23:27,971
Will be destroyed,

423
00:23:27,972 --> 00:23:31,275
And all that remains will be
individual photons

424
00:23:31,276 --> 00:23:33,577
Becoming scarcer and scarcer

425
00:23:33,578 --> 00:23:36,314
As the space between them
expands.

426
00:23:36,315 --> 00:23:38,783
All you're left with is very low
energy light

427
00:23:38,784 --> 00:23:40,252
That gets stretched
and stretched

428
00:23:40,253 --> 00:23:42,354
Until it might as well
not exist at all.

429
00:23:42,355 --> 00:23:44,354
The last thing to go --

430
00:23:44,355 --> 00:23:47,859
The empty vacuum
of space itself.

431
00:23:49,396 --> 00:23:51,897
It'll be pulling on the universe
so hard,

432
00:23:51,898 --> 00:23:54,800
It could tear the fabric
of the universe apart.

433
00:23:54,801 --> 00:23:58,203
Reality could dissolve.

434
00:23:58,204 --> 00:24:01,540
Will the universe end
with a big rip,

435
00:24:01,541 --> 00:24:03,875
Or a big freeze?

436
00:24:03,876 --> 00:24:08,347
The answer is locked inside
the mystery of dark energy.

437
00:24:08,348 --> 00:24:13,119
Solve that, and the fate
of the universe becomes clear.

438
00:24:26,000 --> 00:24:28,366
The end
of the universe is coming.

439
00:24:28,367 --> 00:24:30,537
But how will it play out?

440
00:24:30,538 --> 00:24:34,406
For a time, a big crunch
was the likely answer.

441
00:24:34,407 --> 00:24:38,177
Dark matter, the invisible bulk
of the universe,

442
00:24:38,178 --> 00:24:41,482
Causes space
to fall in on itself.

443
00:24:42,750 --> 00:24:47,119
Galaxies collide.
Planet merges with planet.

444
00:24:47,120 --> 00:24:51,892
Everything becomes hotter
and hotter, denser and denser.

445
00:24:51,893 --> 00:24:54,462
The universe is like
one giant star.

446
00:24:58,232 --> 00:25:02,268
Dark energy kills
the big crunch theory.

447
00:25:02,269 --> 00:25:05,404
It acts like rocket fuel
for the expansion of space

448
00:25:05,405 --> 00:25:07,641
Between galaxies.

449
00:25:07,642 --> 00:25:10,879
They're not just coasting.
They're getting pushed outward.

450
00:25:14,213 --> 00:25:16,415
Only two possible fates
remain --

451
00:25:16,416 --> 00:25:19,118
A big rip or a big freeze.

452
00:25:19,119 --> 00:25:22,020
Both scenarios rely
on dark energy.

453
00:25:22,021 --> 00:25:24,958
For the universe to be torn
to shreds in a big rip,

454
00:25:24,959 --> 00:25:28,662
Dark energy must increase
exponentially in the future.

455
00:25:28,663 --> 00:25:31,998
But a big freeze requires
a steady increase

456
00:25:31,999 --> 00:25:33,500
In dark energy,

457
00:25:33,501 --> 00:25:35,402
Pushing galaxies away
from each other.

458
00:25:35,503 --> 00:25:38,472
We can't write the last chapter
of our universe

459
00:25:38,473 --> 00:25:41,944
Until we understand the nature
of dark energy.

460
00:25:43,545 --> 00:25:46,414
May 2009.

461
00:25:46,415 --> 00:25:50,019
The european space agency
launches the planck satellite

462
00:25:50,020 --> 00:25:53,921
To search for the birth
of dark energy.

463
00:25:53,922 --> 00:25:58,392
Its ultra-Sensitive telescope
peers through space and time

464
00:25:58,393 --> 00:26:00,928
Back through billions of years,

465
00:26:00,929 --> 00:26:05,500
Towards the beginning of
everything, to capture this.

466
00:26:05,501 --> 00:26:08,003
This is our universe
as it appeared

467
00:26:08,004 --> 00:26:10,938
Over 13 billion years ago,

468
00:26:10,939 --> 00:26:14,977
380,000 years
after the big bang.

469
00:26:16,545 --> 00:26:19,147
So what planck has done
is take a picture

470
00:26:19,148 --> 00:26:21,416
Of the early universe

471
00:26:21,417 --> 00:26:24,552
And told us about what
the early universe is like

472
00:26:24,553 --> 00:26:26,988
And given us our most detailed
and accurate picture

473
00:26:26,989 --> 00:26:28,322
Of that moment in time.

474
00:26:28,323 --> 00:26:30,757
The universe in this picture

475
00:26:30,758 --> 00:26:35,264
Is a hot soup of protons,
electrons, and photons.

476
00:26:35,265 --> 00:26:38,332
Hydrogen atoms have just started
to form,

477
00:26:38,333 --> 00:26:41,069
And it's the light from this
genesis of matter

478
00:26:41,070 --> 00:26:42,938
That we see here.

479
00:26:45,007 --> 00:26:48,244
Blue areas are colder.
Reds are warm.

480
00:26:48,378 --> 00:26:50,480
Eventually, those hot spots,

481
00:26:50,481 --> 00:26:52,682
Those red spots you see
in the map,

482
00:26:52,683 --> 00:26:55,318
Are going to form large
superclusters

483
00:26:55,319 --> 00:26:59,790
Made up of hundreds or thousands
of galaxies.

484
00:26:59,791 --> 00:27:03,927
Each one of those galaxies will
contain billions of stars.

485
00:27:05,561 --> 00:27:07,864
Gravity
and expansion alone

486
00:27:07,865 --> 00:27:12,568
Appear to drive the formation
of these embryonic galaxies.

487
00:27:12,569 --> 00:27:16,839
Dark energy doesn't seem
to have switched on yet.

488
00:27:16,840 --> 00:27:21,678
So, when did dark energy take
control of the universe?

489
00:27:28,185 --> 00:27:31,387
Astronomer brenda frye
is part of a team

490
00:27:31,388 --> 00:27:33,991
Using massive
ground-Based telescopes

491
00:27:33,992 --> 00:27:36,792
Like this one at kitt peak,
arizona.

492
00:27:36,793 --> 00:27:41,164
She peers back in time
to capture the universe

493
00:27:41,165 --> 00:27:44,069
Through its childhood
as it was growing.

494
00:27:46,104 --> 00:27:48,672
Right.
So this is an aluminum plate,

495
00:27:48,673 --> 00:27:52,875
And into this plate are
drilled 640 individual holes.

496
00:27:52,876 --> 00:27:55,945
Each one is put at a very
specific place on the mask

497
00:27:55,946 --> 00:28:00,017
Which will correspond to one
particular galaxy in the sky.

498
00:28:02,386 --> 00:28:04,119
During each observation,

499
00:28:04,120 --> 00:28:08,625
The light from 640 individual
galaxies is collected

500
00:28:08,626 --> 00:28:12,029
Using fiber optic cables.

501
00:28:12,030 --> 00:28:15,499
The speed and relative position
of each galaxy is measured

502
00:28:15,500 --> 00:28:19,371
To pinpoint exactly where it is
in space.

503
00:28:19,472 --> 00:28:22,107
So far, the team
has accurately mapped

504
00:28:22,108 --> 00:28:24,943
Around a million galaxies
in 3d,

505
00:28:24,944 --> 00:28:26,812
And this is what they look like.

506
00:28:28,046 --> 00:28:30,682
Each one of these fuzzy patches

507
00:28:30,683 --> 00:28:32,516
Is a fully grown galaxy

508
00:28:32,517 --> 00:28:36,553
Containing around
200 billion stars.

509
00:28:36,554 --> 00:28:38,223
This is a very basic
measurement,

510
00:28:38,224 --> 00:28:40,390
And we think that
this will be able to help us

511
00:28:40,391 --> 00:28:43,395
To get a grasp into the nature
of dark energy.

512
00:28:43,396 --> 00:28:47,697
Scientists compare
this adolescent universe

513
00:28:47,698 --> 00:28:49,567
To its baby pictures.

514
00:28:49,568 --> 00:28:51,802
It shows dark energy emerging

515
00:28:51,803 --> 00:28:55,008
When the universe is
half as old as it is today.

516
00:28:56,276 --> 00:28:59,011
About 8 billion years
after the big bang,

517
00:28:59,012 --> 00:29:03,248
This expansion of the universe
begins to accelerate,

518
00:29:03,249 --> 00:29:05,884
And we're in the middle
of this acceleration.

519
00:29:05,885 --> 00:29:10,589
The data also shows
that as space expands,

520
00:29:10,590 --> 00:29:15,226
Dark energy
increases in lockstep with it.

521
00:29:15,227 --> 00:29:17,562
If you had a box and you put
some dark energy in it,

522
00:29:17,563 --> 00:29:19,898
And then you went and you
weighed that box...

523
00:29:19,899 --> 00:29:21,800
now you take the box,
you make it twice as big.

524
00:29:21,801 --> 00:29:23,668
You don't open it.
You don't put anything in it.

525
00:29:23,669 --> 00:29:26,205
You weigh it again, it's gonna
weigh twice as much.

526
00:29:26,206 --> 00:29:28,541
This remarkable
observation means

527
00:29:28,542 --> 00:29:32,011
That we should be safe
from a big rip.

528
00:29:32,012 --> 00:29:35,447
Dark energy will continue
to increase gradually.

529
00:29:35,448 --> 00:29:39,016
The universe is heading
for a big freeze,

530
00:29:39,017 --> 00:29:43,054
And scientists can finally
calculate a timeline

531
00:29:43,055 --> 00:29:45,925
For the end of everything.

532
00:29:55,102 --> 00:29:56,637
It now seems
that we live

533
00:29:56,638 --> 00:29:59,272
In an almost perfect universe,

534
00:29:59,273 --> 00:30:02,842
With just enough gravity
to hold the galaxies together

535
00:30:02,843 --> 00:30:06,748
And just enough dark energy
that it will expand forever

536
00:30:06,749 --> 00:30:09,385
Without ripping itself
to shreds.

537
00:30:11,320 --> 00:30:15,992
Cosmologists can finally
envision the end of it all.

538
00:30:17,326 --> 00:30:19,894
30 years ago,
it was debatable.

539
00:30:19,895 --> 00:30:22,762
But now, it appears
that the universe most likely

540
00:30:22,763 --> 00:30:24,331
Will suffer a deep freeze.

541
00:30:24,332 --> 00:30:27,637
If you look at the data,
it stares out at you.

542
00:30:28,803 --> 00:30:30,370
In a big freeze,

543
00:30:30,371 --> 00:30:34,509
Dark energy pushes galaxies
further and further apart,

544
00:30:34,510 --> 00:30:37,380
But they remain intact.

545
00:30:37,413 --> 00:30:41,083
The stars inside them
fade away.

546
00:30:41,084 --> 00:30:43,619
Every star you see in the sky,
including our sun,

547
00:30:43,620 --> 00:30:45,722
Is burning through
its nuclear fuel.

548
00:30:45,723 --> 00:30:48,923
The gas will run out,
stars will stop being made,

549
00:30:48,924 --> 00:30:52,562
And the ones that exist are it.
Those are the last ones.

550
00:30:56,967 --> 00:30:59,267
A hundred trillion
years from now,

551
00:30:59,268 --> 00:31:03,573
The biggest stars will be
the first to go extinct.

552
00:31:03,574 --> 00:31:06,708
Big stars burn bright
and die hard.

553
00:31:06,709 --> 00:31:11,147
The star's core collapses,

554
00:31:11,148 --> 00:31:13,284
Unleashing a supernova.

555
00:31:14,584 --> 00:31:17,920
Then gravity crushes
the dead star down

556
00:31:17,921 --> 00:31:20,590
To a single dense spot.

557
00:31:20,591 --> 00:31:24,027
The bright star
is now a black hole.

558
00:31:26,397 --> 00:31:28,967
Sun-Like stars go next.

559
00:31:30,434 --> 00:31:33,035
As their supply of hydrogen
runs out,

560
00:31:33,036 --> 00:31:35,405
They swell to a bloated fireball

561
00:31:35,406 --> 00:31:38,342
Over 200 times
their current size.

562
00:31:44,215 --> 00:31:46,450
And when the core
has no more hydrogen,

563
00:31:46,451 --> 00:31:49,720
It's going to bloat up
into a red giant star.

564
00:31:49,721 --> 00:31:52,089
Now, red giant stars are so big,
they will actually

565
00:31:52,090 --> 00:31:54,090
Eat up their own planets.

566
00:31:54,091 --> 00:31:55,925
We know of examples
of red giants

567
00:31:55,926 --> 00:31:57,994
That go all the way out
to where the orbit of jupiter is

568
00:31:57,995 --> 00:31:59,929
In our solar system.

569
00:31:59,930 --> 00:32:02,899
Its fuel exhausted,

570
00:32:02,900 --> 00:32:05,602
The sun-Like star
gives in to gravity

571
00:32:05,603 --> 00:32:07,704
And shrinks to a white dwarf,

572
00:32:07,705 --> 00:32:09,473
A dense ball of matter

573
00:32:09,474 --> 00:32:12,608
Just a few thousand miles
in diameter.

574
00:32:12,609 --> 00:32:16,647
It will glow with heat
for a further 10 billion years

575
00:32:16,648 --> 00:32:19,215
Before cooling to a black dwarf,

576
00:32:19,216 --> 00:32:24,255
A ball of compressed carbon,
perhaps even diamond.

577
00:32:26,959 --> 00:32:29,293
As the biggest stars die,

578
00:32:29,294 --> 00:32:32,830
The universe
will slowly turn red.

579
00:32:32,831 --> 00:32:34,598
The blue stars
will blow up,

580
00:32:34,599 --> 00:32:36,767
And then the slightly less blue
stars will blow up,

581
00:32:36,768 --> 00:32:39,136
And then stars like the sun
will fade away and die,

582
00:32:39,137 --> 00:32:41,808
Leaving just the red stars
to exist.

583
00:32:43,376 --> 00:32:45,211
Red stars
are the smallest

584
00:32:45,212 --> 00:32:47,113
And coolest in the universe.

585
00:32:47,114 --> 00:32:49,382
They burn their fuel slowly.

586
00:32:49,383 --> 00:32:52,116
But, after another
10 trillion years,

587
00:32:52,117 --> 00:32:54,520
Even these smallest
of dwarf stars

588
00:32:54,521 --> 00:32:56,789
Will use up their fuel.

589
00:32:56,790 --> 00:33:00,358
Stars as we know them
will cease to burn energy,

590
00:33:00,359 --> 00:33:02,828
And the night sky
will turn black.

591
00:33:02,829 --> 00:33:06,699
Black holes,
the corpses of dead stars,

592
00:33:06,700 --> 00:33:11,338
And cold clouds of gas and dust
are all that remains.

593
00:33:13,140 --> 00:33:15,909
The age of stars is over.

594
00:33:15,910 --> 00:33:19,645
The age of black holes begins.

595
00:33:19,646 --> 00:33:21,848
Black holes become
the fundamental building block

596
00:33:21,849 --> 00:33:23,515
Of the universe.

597
00:33:23,516 --> 00:33:25,884
A galaxy will basically be
a supermassive black hole

598
00:33:25,885 --> 00:33:27,919
In the center, with smaller
black holes orbiting it.

599
00:33:27,920 --> 00:33:30,455
In some ways, it's kind of
a ghost universe.

600
00:33:30,456 --> 00:33:32,292
It's the corpses,
the zombie stars,

601
00:33:32,293 --> 00:33:33,993
That will take us
into the future.

602
00:33:33,994 --> 00:33:37,163
Zombie galaxies
filled with black holes

603
00:33:37,164 --> 00:33:38,964
Continue to evolve.

604
00:33:38,965 --> 00:33:42,335
They sweep up the dead remains
of stars.

605
00:33:42,336 --> 00:33:46,439
Black hole merges
with black hole.

606
00:33:46,440 --> 00:33:48,540
They'll eat each other
and they'll get bigger,

607
00:33:48,541 --> 00:33:50,375
And maybe they'll fall into
the supermassive black hole

608
00:33:50,376 --> 00:33:51,844
And it'll get bigger.

609
00:33:51,845 --> 00:33:54,846
The universe will still be
an exciting, dynamic place,

610
00:33:54,847 --> 00:33:57,149
It's just that the time scales
you're talking about

611
00:33:57,150 --> 00:33:58,718
Are now trillions of years

612
00:33:58,719 --> 00:34:01,420
Instead of thousands
or millions of years.

613
00:34:01,421 --> 00:34:05,591
Any material that
evades the pull of a black hole

614
00:34:05,592 --> 00:34:10,862
Eventually dies away
as its protons disintegrate.

615
00:34:10,863 --> 00:34:14,000
A proton, one of the fundamental
building blocks

616
00:34:14,001 --> 00:34:16,835
Of atomic matter,
of what makes us up,

617
00:34:16,836 --> 00:34:19,337
Can just spontaneously
fall apart,

618
00:34:19,338 --> 00:34:23,210
And it turns out this takes
a tremendously long time.

619
00:34:23,211 --> 00:34:25,310
But even that will go away.

620
00:34:25,311 --> 00:34:30,382
All that will be left
is a sea of black holes.

621
00:34:30,383 --> 00:34:33,652
Scientists used to think
black holes were immortal,

622
00:34:33,653 --> 00:34:35,323
But even these will one day die.

623
00:34:35,424 --> 00:34:38,125
Now we're talking about
time scales

624
00:34:38,126 --> 00:34:39,794
Of unimaginable length --

625
00:34:39,795 --> 00:34:42,331
Quadrillions of years
into the future.

626
00:34:42,432 --> 00:34:43,898
But on that time scale,

627
00:34:43,899 --> 00:34:48,001
Even the black holes
begin to evaporate.

628
00:34:48,002 --> 00:34:50,238
They'll get smaller and smaller
and smaller,

629
00:34:50,239 --> 00:34:52,173
And then, poof, they'll be gone.

630
00:34:52,174 --> 00:34:54,642
The universe will end

631
00:34:54,643 --> 00:34:57,477
When the last remaining
black hole dies.

632
00:34:57,478 --> 00:35:00,280
As it gets smaller,
the evaporation rate

633
00:35:00,281 --> 00:35:02,316
Increases exponentially.

634
00:35:02,317 --> 00:35:04,517
Before long,
it reaches a size

635
00:35:04,518 --> 00:35:09,523
A billionth of a trillionth
of a trillionth of an inch.

636
00:35:09,524 --> 00:35:12,927
At that instant,
the laws of physics break down,

637
00:35:12,928 --> 00:35:17,097
And the last black hole explodes
in a flash of gamma rays,

638
00:35:17,098 --> 00:35:19,867
Leaving nothing.

639
00:35:19,868 --> 00:35:23,470
And it will die
in a sudden burst of light,

640
00:35:23,471 --> 00:35:25,139
The last burst of light

641
00:35:25,140 --> 00:35:27,475
In the entire history
of the universe.

642
00:35:28,111 --> 00:35:30,112
The big freeze is coming.

643
00:35:30,113 --> 00:35:34,416
The universe will suffer a cold,
slow, dark death

644
00:35:34,417 --> 00:35:35,784
Which will play out

645
00:35:35,785 --> 00:35:39,521
Over trillions upon trillions
of years.

646
00:35:39,522 --> 00:35:42,925
But quantum physics leaves
the door open

647
00:35:42,926 --> 00:35:44,693
For an alternative end,

648
00:35:44,694 --> 00:35:48,130
An event so powerful,
so destructive,

649
00:35:48,131 --> 00:35:53,836
That it could destroy everything
we see in the blink of an eye.

650
00:35:53,837 --> 00:35:57,007
And it could happen tomorrow.

651
00:36:06,251 --> 00:36:08,085
The end of the universe --

652
00:36:08,086 --> 00:36:09,618
It's coming.

653
00:36:09,619 --> 00:36:13,022
Dark energy accelerates
the space between galaxies,

654
00:36:13,023 --> 00:36:16,593
Pushing everything we see
to a long, cold,

655
00:36:16,594 --> 00:36:19,330
And very slow death.

656
00:36:19,331 --> 00:36:23,199
Unless, that is, something
bizarre happens first.

657
00:36:23,200 --> 00:36:27,004
A monster called
phase transition

658
00:36:27,005 --> 00:36:28,638
Is lurking in the shadows,

659
00:36:28,639 --> 00:36:32,576
And it could annihilate
the fabric of space and time

660
00:36:32,577 --> 00:36:35,678
At any moment.

661
00:36:35,679 --> 00:36:39,449
When we cool down water,
it turns into ice.

662
00:36:39,450 --> 00:36:40,951
The properties change.

663
00:36:40,952 --> 00:36:43,154
If you lived in the water,
when it changed to ice,

664
00:36:43,155 --> 00:36:44,989
Your world
would be very different.

665
00:36:44,990 --> 00:36:50,194
Water phase changes
into ice when it loses energy.

666
00:36:50,195 --> 00:36:53,230
I once left a water
bottle in my car overnight.

667
00:36:53,231 --> 00:36:56,132
It was still liquid,
but the moment i touched it,

668
00:36:56,133 --> 00:36:57,533
The slight imperfection,

669
00:36:57,534 --> 00:36:59,402
The little bit of ice
that it formed, spread,

670
00:36:59,403 --> 00:37:01,270
Poof, and filled up
the whole bottle.

671
00:37:01,271 --> 00:37:04,474
That rapid change
to something new

672
00:37:04,475 --> 00:37:06,644
Is called a phase transition,

673
00:37:06,645 --> 00:37:12,048
And bizarrely, the same thing
could happen to empty space.

674
00:37:12,049 --> 00:37:14,753
We've really come to understand

675
00:37:14,754 --> 00:37:17,956
That we shouldn't take
for granted that...vacuum,

676
00:37:17,957 --> 00:37:20,691
What we call nothing,
is actually stable.

677
00:37:20,692 --> 00:37:23,594
It could be that the energy
stored in empty space

678
00:37:23,595 --> 00:37:26,398
Is just waiting to be released
in a phase transition.

679
00:37:26,399 --> 00:37:29,535
If it is, the laws of physics
will change.

680
00:37:31,404 --> 00:37:35,106
A spontaneous glitch
in the fabric of space-Time

681
00:37:35,107 --> 00:37:39,010
Could trigger
a phase transition of space,

682
00:37:39,011 --> 00:37:43,414
A tiny bubble of new universe
that spreads out,

683
00:37:43,415 --> 00:37:45,715
Overwriting the old.

684
00:37:45,716 --> 00:37:49,387
We know it can happen,
because it's happened before.

685
00:37:53,192 --> 00:37:55,193
At the moment of the big bang,

686
00:37:55,194 --> 00:37:57,262
The universe
that's first created

687
00:37:57,263 --> 00:38:00,632
Is completely different
to the one we see today.

688
00:38:00,633 --> 00:38:03,568
Hot and without form,

689
00:38:03,569 --> 00:38:06,170
There's no matter, no time.

690
00:38:06,171 --> 00:38:09,740
The laws of physics
are different.

691
00:38:09,741 --> 00:38:13,445
Suddenly, less than a trillionth
of a second later,

692
00:38:13,446 --> 00:38:16,514
A glitch triggers
a phase transition.

693
00:38:16,515 --> 00:38:20,152
A tiny bubble of the universe
we live in today forms,

694
00:38:20,153 --> 00:38:22,387
And it races outward,

695
00:38:22,388 --> 00:38:24,356
Destroying everything it touches

696
00:38:24,357 --> 00:38:27,525
Like ice
spreading through water.

697
00:38:27,526 --> 00:38:31,262
The energy that spills out
creates the space and time

698
00:38:31,263 --> 00:38:32,898
That we exist in,

699
00:38:32,899 --> 00:38:37,503
The building blocks of matter
and the forces that govern them.

700
00:38:37,504 --> 00:38:40,239
All that energy was released,
producing all the matter

701
00:38:40,240 --> 00:38:42,175
And radiation we observe
in the universe today.

702
00:38:42,375 --> 00:38:45,211
The old universe
gives up its energy

703
00:38:45,212 --> 00:38:46,847
To create the new.

704
00:38:46,848 --> 00:38:48,982
But it holds some back.

705
00:38:48,983 --> 00:38:53,419
The vacuum of space
still has energy bound to it.

706
00:38:53,420 --> 00:38:57,957
Perhaps this is the dark energy
we see today.

707
00:38:57,958 --> 00:39:01,261
Physicists believe
that someday in the future,

708
00:39:01,262 --> 00:39:04,763
A brand new glitch in the fabric
of space-Time

709
00:39:04,764 --> 00:39:07,300
May trigger another
phase transition,

710
00:39:07,301 --> 00:39:10,870
One that wipes us
and everything we see

711
00:39:10,871 --> 00:39:12,805
Out of existence.

712
00:39:12,806 --> 00:39:16,309
This is a way to destroy
an entire universe,

713
00:39:16,310 --> 00:39:18,077
Because within your universe

714
00:39:18,078 --> 00:39:20,579
Are the seeds
of its own destruction.

715
00:39:20,580 --> 00:39:23,550
It would spread out at the speed
of light in a death bubble,

716
00:39:23,551 --> 00:39:26,519
Ruining all the galaxies
as it passes through,

717
00:39:26,520 --> 00:39:29,822
And ultimately completely
destroying our universe.

718
00:39:29,823 --> 00:39:33,327
Nothing can survive
the expanding phase transition.

719
00:39:33,328 --> 00:39:38,132
Planets, nebulas, galaxies --
All are ripped apart

720
00:39:38,133 --> 00:39:40,434
As the boundary
of the bubble reaches them.

721
00:39:40,435 --> 00:39:43,670
Inside this bubble,
protons are unstable,

722
00:39:43,671 --> 00:39:47,507
Atoms begin to rearrange
in a new form of matter.

723
00:39:47,508 --> 00:39:49,543
As these bubbles
begin to expand,

724
00:39:49,544 --> 00:39:52,179
A new universe is being born

725
00:39:52,180 --> 00:39:54,847
In the corpse
of the old universe,

726
00:39:54,848 --> 00:39:58,186
And the beginning
of a new law of physics.

727
00:39:58,387 --> 00:40:02,022
And so, the expanding universe
we now see

728
00:40:02,023 --> 00:40:05,460
May end in a phase transition,
but we won't know what hit us,

729
00:40:05,461 --> 00:40:07,395
'Cause the laws of physics
will change,

730
00:40:07,396 --> 00:40:10,131
And we will essentially most
likely disappear

731
00:40:10,132 --> 00:40:11,899
At the instant it happens.

732
00:40:11,900 --> 00:40:15,569
This bubble will expand
at the speed of light,

733
00:40:15,570 --> 00:40:17,439
And as the bubble passes you,

734
00:40:17,440 --> 00:40:20,475
All the atoms of your body
rearrange themselves,

735
00:40:20,476 --> 00:40:22,178
And you would never know it.

736
00:40:22,179 --> 00:40:24,879
You would have no warning,
because the bubble itself

737
00:40:24,880 --> 00:40:26,448
Is expanding
at the speed of light.

738
00:40:26,449 --> 00:40:29,052
You can't predict precisely
when it could happen.

739
00:40:29,053 --> 00:40:30,684
You only have a probability.

740
00:40:30,685 --> 00:40:32,921
So what you really
are predicting is a rate.

741
00:40:32,922 --> 00:40:36,092
Does it happen once a year?
Once every 10 billion years?

742
00:40:36,093 --> 00:40:38,325
Once every googol years?
Or whatever.

743
00:40:38,326 --> 00:40:41,628
It's very possible that
these bubbles get nucleated

744
00:40:41,629 --> 00:40:45,267
And grow about once every
10 or 20 billion years.

745
00:40:45,268 --> 00:40:47,903
So it hasn't happened yet
because we got lucky.

746
00:40:47,904 --> 00:40:50,840
It's unlikely it would happen
the next year or the next day,

747
00:40:50,841 --> 00:40:52,908
But the laws of physics
absolutely allow it.

748
00:40:56,245 --> 00:41:00,516
A phase change
may happen, or it may not.

749
00:41:01,650 --> 00:41:05,790
The universe plays its cards
close to its chest.

750
00:41:09,625 --> 00:41:12,829
And, like dark energy
and dark matter,

751
00:41:12,830 --> 00:41:14,799
There may be more surprises
to come...

752
00:41:16,600 --> 00:41:21,470
...surprises that will only
add to the mystery and wonder

753
00:41:21,471 --> 00:41:24,108
Our universe holds for us.

754
00:41:27,478 --> 00:41:29,113
Whatever the universe
is up to,

755
00:41:29,114 --> 00:41:30,479
We still don't know enough.

756
00:41:30,480 --> 00:41:32,582
We're in an age of discovery
right now.

757
00:41:32,583 --> 00:41:34,483
Perhaps there is something else
out there

758
00:41:34,484 --> 00:41:35,852
That we don't know about.

759
00:41:35,853 --> 00:41:38,255
So, i'm not going to draw
any conclusions

760
00:41:38,256 --> 00:41:39,957
Until things are conclusive.

761
00:41:42,659 --> 00:41:45,160
We don't understand
the nature of dark energy.

762
00:41:45,161 --> 00:41:48,765
And without that understanding,
virtually anything is possible.

763
00:41:48,766 --> 00:41:50,800
The future is still uncertain,

764
00:41:50,801 --> 00:41:53,135
And that means
there's still a mystery.

765
00:41:53,136 --> 00:41:56,507
And for me, that's the most
exciting possibility of all.