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1
00:00:04,800 --> 00:00:06,100
Hello!
2
00:00:06,200 --> 00:00:09,500
My name is Stephen Hawking...
3
00:00:09,568 --> 00:00:11,969
Physicist, cosmologist...
4
00:00:11,970 --> 00:00:14,572
And something of a dreamer.
5
00:00:14,573 --> 00:00:16,707
Although I cannot move...
6
00:00:16,708 --> 00:00:19,644
...And I have to
speak through a computer...
7
00:00:19,645 --> 00:00:22,513
In my mind, I am free...
8
00:00:25,150 --> 00:00:28,019
...Free to tour the universe
9
00:00:28,020 --> 00:00:32,757
And tell the ultimate story...
10
00:00:32,758 --> 00:00:36,727
The story of everything
there ever was...
11
00:00:40,098 --> 00:00:44,468
...From the moment
the cosmos began...
12
00:00:44,469 --> 00:00:48,639
To the creation of our world
and everything in it...
13
00:00:48,640 --> 00:00:53,277
And beyond,
to the far, far future
14
00:00:53,278 --> 00:00:57,448
And the end
of the universe itself...
15
00:00:57,449 --> 00:01:02,019
A journey through all of space
and all of time.
16
00:01:06,024 --> 00:01:08,259
Check it out.
17
00:01:25,544 --> 00:01:28,980
I spend a lot of time
thinking about the universe,
18
00:01:28,981 --> 00:01:31,816
But I never get bored.
19
00:01:31,817 --> 00:01:37,221
After all, it's a pretty
extraordinary place.
20
00:01:37,222 --> 00:01:40,224
This is the cosmos...
21
00:01:40,225 --> 00:01:43,327
At a very large scale.
22
00:01:43,328 --> 00:01:47,798
Each tiny point of light
is an entire galaxy,
23
00:01:47,799 --> 00:01:54,605
Each a cluster of as many
as 400 billion individual stars.
24
00:01:57,376 --> 00:02:00,211
This view of the universe
is only possible
25
00:02:00,212 --> 00:02:03,247
Due to the latest
supercomputers.
26
00:02:03,248 --> 00:02:06,584
I find it
indescribably beautiful...
27
00:02:06,585 --> 00:02:11,322
Uncountable billions of galaxies
forming a vast web
28
00:02:11,323 --> 00:02:14,592
Stretching away
in all directions.
29
00:02:16,828 --> 00:02:19,864
What's more,
I never get over the fact
30
00:02:19,865 --> 00:02:22,199
That within
this massive universe
31
00:02:22,200 --> 00:02:26,037
Lies one perfectly ordinary
spiral galaxy.
32
00:02:29,775 --> 00:02:34,812
Inside that galaxy exists
a commonplace yellow star...
33
00:02:37,816 --> 00:02:40,885
...Orbited by eight planets.
34
00:02:44,823 --> 00:02:48,025
On one of those planets
lives a species
35
00:02:48,026 --> 00:02:50,094
That has only just worked out
36
00:02:50,095 --> 00:02:53,297
What a remarkable place
the universe is.
37
00:02:59,738 --> 00:03:01,839
Us.
38
00:03:08,747 --> 00:03:12,917
We've discovered more about
the cosmos in the last century
39
00:03:12,918 --> 00:03:17,321
Than in all previous
human history.
40
00:03:17,322 --> 00:03:20,591
Finally, we are solving
the basic mysteries
41
00:03:20,592 --> 00:03:22,727
That have perplexed
our ancestors
42
00:03:22,728 --> 00:03:26,731
For at least 200,000 years.
43
00:03:26,732 --> 00:03:30,434
What I like above all
is that the facts themselves
44
00:03:30,435 --> 00:03:34,905
Are both breathtakingly elegant
and surprising.
45
00:03:41,279 --> 00:03:44,181
We're living
just as it dawns on us
46
00:03:44,182 --> 00:03:47,151
That the earth
and everything around us
47
00:03:47,152 --> 00:03:50,421
Was made by the stars.
48
00:03:52,491 --> 00:03:55,693
Boiling furnaces of hydrogen gas
like our sun
49
00:03:55,694 --> 00:03:58,562
Made even the atoms
in your eyelashes.
50
00:04:00,499 --> 00:04:02,666
We've worked out
that the universe
51
00:04:02,667 --> 00:04:05,836
Is almost
unimaginably ancient...
52
00:04:05,837 --> 00:04:09,073
About 14 billion years old...
53
00:04:09,074 --> 00:04:11,108
And that it will continue
to exist
54
00:04:11,109 --> 00:04:13,310
For at least twice that long.
55
00:04:16,748 --> 00:04:21,552
But without a doubt,
the most remarkable fact of all
56
00:04:21,553 --> 00:04:25,890
Is that the entire
enormous universe,
57
00:04:25,891 --> 00:04:29,360
All the innumerable galaxies,
58
00:04:29,361 --> 00:04:34,598
Even time and space and the
forces of nature themselves
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00:04:34,599 --> 00:04:39,703
Simply materialized
out of...Nothing.
60
00:04:42,974 --> 00:04:46,977
So now is a good time
to be alive, I think.
61
00:04:46,978 --> 00:04:51,015
We may only be
an advanced breed of monkey
62
00:04:51,016 --> 00:04:53,350
Living on a small planet,
63
00:04:53,351 --> 00:04:57,121
But we are able to contemplate
the universe as a whole,
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00:04:57,122 --> 00:04:59,457
Which makes us very special.
65
00:05:01,226 --> 00:05:04,095
My goal has always
been simple...
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00:05:04,096 --> 00:05:06,564
To work out
how the universe works
67
00:05:06,565 --> 00:05:08,766
And why it exists at all.
68
00:05:08,767 --> 00:05:14,105
Luckily,
there are clues everywhere,
69
00:05:14,106 --> 00:05:18,109
And the most important one
is right above our heads.
70
00:05:20,178 --> 00:05:23,581
Examine any patch
of the night sky,
71
00:05:23,582 --> 00:05:26,984
Even one as small
as the head of a pin,
72
00:05:26,985 --> 00:05:30,788
And this is what you'll find...
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00:05:30,789 --> 00:05:34,992
A tiny part
of the vast web of galaxies.
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00:05:34,993 --> 00:05:37,528
It's less than a millionth
75
00:05:37,529 --> 00:05:41,799
Of what we can see of the cosmos
from our little planet,
76
00:05:41,800 --> 00:05:46,437
But even this tiny sample
is enough to find a clue,
77
00:05:46,438 --> 00:05:49,807
The key to the past,
the present,
78
00:05:49,808 --> 00:05:53,544
And perhaps the future, too.
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00:05:53,545 --> 00:05:55,846
The clue is that,
seen from earth,
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00:05:55,847 --> 00:06:01,318
All these distant galaxies
are slightly red in color.
81
00:06:01,319 --> 00:06:03,621
They appear almost as if
82
00:06:03,622 --> 00:06:06,891
We were looking through
rose-tinted glasses.
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00:06:08,727 --> 00:06:10,461
It's this very redness
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00:06:10,462 --> 00:06:13,898
That reveals
how the universe was born.
85
00:06:13,899 --> 00:06:15,366
And to show you why,
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00:06:15,367 --> 00:06:18,903
I need a straight road
and a noisy car.
87
00:06:28,580 --> 00:06:32,950
Listen to the sound
as it passes by.
88
00:06:34,986 --> 00:06:38,556
As the car approaches,
the pitch of its engine rises.
89
00:06:41,593 --> 00:06:45,429
As it goes away,
the pitch of its engine...
90
00:06:45,430 --> 00:06:48,732
Falls.
91
00:06:48,733 --> 00:06:53,003
This phenomenon
is called a doppler shift,
92
00:06:53,004 --> 00:06:55,806
And the exact same thing
happens with light.
93
00:06:57,909 --> 00:07:00,644
If our eyes were
more sensitive to color,
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00:07:00,645 --> 00:07:03,080
We could see that the car
95
00:07:03,081 --> 00:07:08,052
Is actually very slightly blue
as it approaches...
96
00:07:08,820 --> 00:07:13,657
...And very slightly red
as it goes away.
97
00:07:18,997 --> 00:07:23,701
The same rules apply in space.
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00:07:23,702 --> 00:07:28,706
All distant galaxies
are slightly red in color,
99
00:07:28,707 --> 00:07:32,142
So by the exact same piece
of basic physics,
100
00:07:32,143 --> 00:07:36,046
They must all
be moving away, too.
101
00:07:36,047 --> 00:07:39,817
In fact, the whole universe
is expanding...
102
00:07:39,818 --> 00:07:42,286
In all directions...
103
00:07:42,287 --> 00:07:47,258
Getting bigger and bigger,
like a balloon inflating.
104
00:07:48,693 --> 00:07:50,961
I admit this sounds strange,
105
00:07:50,962 --> 00:07:55,532
But to cosmologists,
it's like winning the lottery,
106
00:07:55,533 --> 00:07:59,236
Because, to work out
where the universe came from,
107
00:07:59,237 --> 00:08:02,806
Alwe need to do
is to stop time
108
00:08:02,807 --> 00:08:06,010
And make it run in reverse.
109
00:08:09,214 --> 00:08:11,081
Rewind far enough,
110
00:08:11,082 --> 00:08:13,684
And everything gets
closer together...
111
00:08:13,685 --> 00:08:16,654
.Lot closer together.
112
00:08:16,655 --> 00:08:18,956
All the galaxies...
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00:08:18,957 --> 00:08:24,128
In fact, every single thing
converges to a single point,
114
00:08:24,129 --> 00:08:26,463
The start of everything,
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00:08:26,464 --> 00:08:30,334
13.7 billion years ago.
116
00:08:40,645 --> 00:08:42,913
So it's quite simple, really.
117
00:08:42,914 --> 00:08:44,581
Follow the clues,
118
00:08:44,582 --> 00:08:47,651
And we can deduce
that a very long time ago,
119
00:08:47,652 --> 00:08:51,288
The universe simply burst
into existence,
120
00:08:51,289 --> 00:08:54,758
An event called the big bang.
121
00:09:03,368 --> 00:09:06,770
But I'm afraid
we have to stop a moment...
122
00:09:06,771 --> 00:09:11,108
Before we get carried away
by fire and noise.
123
00:09:11,109 --> 00:09:13,077
At the very beginning,
124
00:09:13,078 --> 00:09:17,314
The big bang actually happened
in total darkness,
125
00:09:17,315 --> 00:09:20,551
Because light didn't exist yet.
126
00:09:20,552 --> 00:09:25,723
To see it, we'd have needed some
kind of cosmic night vision.
127
00:09:31,596 --> 00:09:34,665
But even this,
a view from the outside,
128
00:09:34,666 --> 00:09:36,834
Is impossible.
129
00:09:36,835 --> 00:09:39,336
Again, it sounds strange,
130
00:09:39,337 --> 00:09:43,006
But space didn't exist then,
either.
131
00:09:43,007 --> 00:09:46,744
So there was no outside.
132
00:09:46,745 --> 00:09:50,814
The only place there was
was inside.
133
00:09:56,020 --> 00:10:00,524
This early universe was
a very strange thing, indeed.
134
00:10:00,525 --> 00:10:03,827
There's still much I'd
dearly love to know about it,
135
00:10:03,828 --> 00:10:07,998
But standard concepts of time
or space don't really apply.
136
00:10:10,135 --> 00:10:15,939
It was just a very tiny,
ultra-hot fog of energy.
137
00:10:18,877 --> 00:10:22,079
Then it expanded...
138
00:10:25,150 --> 00:10:29,386
...With a tremendous flash
of radiation...
139
00:10:29,387 --> 00:10:34,391
From smaller than an atom
to about the size of an orange
140
00:10:34,392 --> 00:10:37,494
In less than a trillionth
of a second,
141
00:10:37,495 --> 00:10:39,963
Almost no time at all.
142
00:10:44,202 --> 00:10:49,173
The universe simply inflated
into existence,
143
00:10:49,174 --> 00:10:52,876
Unfolding, unfurling,
144
00:10:52,877 --> 00:10:57,314
Getting bigger and cooler
with every passing moment.
145
00:11:01,419 --> 00:11:07,558
Within 100 seconds, it was
as big as our solar system,
146
00:11:07,559 --> 00:11:10,461
Trillions of miles across.
147
00:11:13,164 --> 00:11:14,998
While this was happening,
148
00:11:14,999 --> 00:11:20,871
The pure energy of the cosmos
began to cool and create matter
149
00:11:20,872 --> 00:11:23,474
In the form
of countless trillions
150
00:11:23,475 --> 00:11:27,544
Of subatomic particles...
151
00:11:27,545 --> 00:11:30,747
The first stuff there ever was.
152
00:11:33,551 --> 00:11:36,453
Half these particles
were made of matter,
153
00:11:36,454 --> 00:11:39,256
The same kind of stuff
which makes us.
154
00:11:39,257 --> 00:11:42,226
The rest were made
of the opposite of matter,
155
00:11:42,227 --> 00:11:45,496
Stuff called antimatter.
156
00:11:45,497 --> 00:11:50,467
When the two meet, they destroy
each other in a flash of energy.
157
00:12:01,946 --> 00:12:04,748
It seems as if
building a universe
158
00:12:04,749 --> 00:12:07,117
Is a pretty wasteful process.
159
00:12:12,090 --> 00:12:15,359
Fortunately, there was
just a bit more matter
160
00:12:15,360 --> 00:12:16,894
Than antimatter.
161
00:12:16,895 --> 00:12:21,198
Just one in a billion particles
of stuff survived...
162
00:12:26,538 --> 00:12:29,273
...Which was lucky for us,
163
00:12:29,274 --> 00:12:31,174
Because that residue
164
00:12:31,175 --> 00:12:36,647
Is what our present-day universe
is made of.
165
00:12:36,648 --> 00:12:40,918
You could say we are made
of the smoke of the big bang.
166
00:12:46,658 --> 00:12:50,160
By the time the cosmos
was 10 minutes old,
167
00:12:50,161 --> 00:12:55,566
It was already thousands
of light-years in diameter.
168
00:12:55,567 --> 00:12:57,968
After that,
everything spread out and cooled
169
00:12:57,969 --> 00:13:01,605
For about 330,000 years,
170
00:13:01,606 --> 00:13:04,441
When, finally, the fog cleared
171
00:13:04,442 --> 00:13:07,611
And the universe became visible.
172
00:13:17,922 --> 00:13:21,291
So, that's how everything
got going,
173
00:13:21,292 --> 00:13:24,528
Which I think is
a pretty fantastic story
174
00:13:24,529 --> 00:13:26,296
And probably much stranger
175
00:13:26,297 --> 00:13:28,599
Than anything our ancestors
came up with
176
00:13:28,600 --> 00:13:30,701
By way of an explanation.
177
00:13:32,403 --> 00:13:35,272
But the next thing
that happened...
178
00:13:35,273 --> 00:13:38,542
Well,
that's pretty spectacular, too.
179
00:13:53,119 --> 00:13:57,289
This is the universe
seen in extreme fast-forward,
180
00:13:57,290 --> 00:14:02,094
All 14 billion years
in less than a minute.
181
00:14:05,365 --> 00:14:09,468
It shows how the universe
changed from a cloud of gas
182
00:14:09,469 --> 00:14:13,706
Into a place filled with perhaps
100 billion galaxies,
183
00:14:13,707 --> 00:14:17,576
Swirling
in a vast chaotic dance.
184
00:14:19,713 --> 00:14:22,381
What I love to get people
thinking about
185
00:14:22,382 --> 00:14:28,120
Is that all this
had to be built atom by atom,
186
00:14:28,121 --> 00:14:32,624
Celestial engineering
on a spectacular scale.
187
00:14:34,794 --> 00:14:38,964
So, what drove
this cosmic clockwork?
188
00:14:38,965 --> 00:14:43,402
I'd say it was
the force of gravity.
189
00:14:48,441 --> 00:14:52,978
The idea of gravity was worked
out by sir isaac newton...
190
00:14:52,979 --> 00:14:57,149
...Who had the same job as me
here at cambridge university
191
00:14:57,150 --> 00:14:59,918
Back in the 17th century.
192
00:15:02,889 --> 00:15:07,960
It supposedly dawned on him
when an apple fell on his head.
193
00:15:15,902 --> 00:15:17,836
The apple helped him realize
194
00:15:17,837 --> 00:15:21,974
That all objects
attract each other.
195
00:15:21,975 --> 00:15:25,878
And the greater the mass,
the stronger the pull.
196
00:15:27,747 --> 00:15:30,682
These apples
are attracted to the earth,
197
00:15:30,683 --> 00:15:32,918
And although you can't see it,
198
00:15:32,919 --> 00:15:37,556
The earth moves very slightly
up towards the apples.
199
00:15:42,028 --> 00:15:46,565
All things come together
through the power of gravity.
200
00:15:49,869 --> 00:15:52,971
Gravity was created
in the big bang
201
00:15:52,972 --> 00:15:55,774
And has been at work
ever since.
202
00:15:59,212 --> 00:16:03,582
It's what keeps
you, me, and apples
203
00:16:03,583 --> 00:16:05,751
Stuck to the earth.
204
00:16:13,960 --> 00:16:18,597
In the early universe, gravity
had a much bigger to play.
205
00:16:25,972 --> 00:16:28,040
Right after the big bang,
206
00:16:28,041 --> 00:16:30,809
The universe was just gas,
207
00:16:30,810 --> 00:16:34,079
Almost perfectly spread out
throughout space.
208
00:16:37,083 --> 00:16:40,452
Over the next 200 million years,
209
00:16:40,453 --> 00:16:44,156
Gravity began to pull the gas
back together
210
00:16:44,157 --> 00:16:46,992
To produce
the very first structures
211
00:16:46,993 --> 00:16:49,761
From which everything else
would grow.
212
00:16:52,999 --> 00:16:56,735
But even this
very nearly didn't happen.
213
00:17:02,809 --> 00:17:05,911
If it weren't for another stroke
of cosmic luck,
214
00:17:05,912 --> 00:17:09,548
There would be no you, no me,
215
00:17:09,549 --> 00:17:13,652
No stars or planets
or anything at all.
216
00:17:16,356 --> 00:17:19,091
We know this because, in 1982,
217
00:17:19,092 --> 00:17:22,094
A group of scientists,
including myself,
218
00:17:22,095 --> 00:17:24,830
Spent three solid weeks
working it out.
219
00:17:24,831 --> 00:17:28,700
Although the calculations
were hard,
220
00:17:28,701 --> 00:17:32,871
Demonstrating what we discovered
is easy.
221
00:17:32,872 --> 00:17:35,541
First, I need a nice flat floor,
222
00:17:35,542 --> 00:17:38,577
Like this one, for example.
223
00:17:38,578 --> 00:17:42,014
This is the dining room
in my college.
224
00:17:42,015 --> 00:17:47,653
I'm going to fill the place with
lots and lots of ball bearings.
225
00:18:10,310 --> 00:18:14,413
These balls represent the matter
of the early universe,
226
00:18:14,414 --> 00:18:19,084
A thin gas spread out evenly
across the vast cosmos.
227
00:18:24,257 --> 00:18:27,125
Here's where luck comes in.
228
00:18:30,363 --> 00:18:33,966
If they're all
the same distance apart,
229
00:18:33,967 --> 00:18:39,271
Gravity pulls each ball the
same amount in all directions.
230
00:18:39,272 --> 00:18:44,910
They stay perfectly aligned,
and precisely nothing happens.
231
00:18:47,413 --> 00:18:51,283
Fortunately, one of
the basic rules of the universe
232
00:18:51,284 --> 00:18:55,287
Is that nothing's perfect.
233
00:18:55,288 --> 00:18:58,490
Perfection simply doesn't exist.
234
00:19:03,196 --> 00:19:07,466
The early universe
had a tiny unevenness
235
00:19:07,467 --> 00:19:09,801
That can be simulated
by removing
236
00:19:09,802 --> 00:19:11,903
Just five ball bearings.
237
00:19:21,314 --> 00:19:24,316
It may not look
like much has changed,
238
00:19:24,317 --> 00:19:27,452
But to gravity,
those missing balls
239
00:19:27,453 --> 00:19:31,356
Create a giant opportunity.
240
00:19:31,357 --> 00:19:34,393
Gravity now pulls more strongly
241
00:19:34,394 --> 00:19:37,062
On one side
of some of the bearings.
242
00:19:40,733 --> 00:19:45,303
The tiny irregularities
in the sea of ball bearings
243
00:19:45,304 --> 00:19:49,808
Have given gravity something
to sink its teeth into.
244
00:19:49,809 --> 00:19:52,277
And this
is exactly what happened
245
00:19:52,278 --> 00:19:55,213
Back where we left
the young universe.
246
00:19:58,685 --> 00:20:01,353
Parts of the sea of early gas
247
00:20:01,354 --> 00:20:04,756
Were ever so slightly thinner
than others.
248
00:20:04,757 --> 00:20:06,925
The less dense areas
249
00:20:06,926 --> 00:20:09,528
Were like the gaps
between the ball bearings.
250
00:20:12,231 --> 00:20:14,866
The denser parts
of the sea of gas,
251
00:20:14,867 --> 00:20:17,369
Where gravity
was having its way,
252
00:20:17,370 --> 00:20:19,905
Clumped together.
253
00:20:19,906 --> 00:20:22,340
And it was in these areas
254
00:20:22,341 --> 00:20:25,844
That all the stars and galaxies
would fall.
255
00:20:30,416 --> 00:20:33,485
The cosmos had taken
its first step
256
00:20:33,486 --> 00:20:37,489
Towards the beautiful place
it is today,
257
00:20:37,490 --> 00:20:41,693
All thanks to irregularity,
imperfection,
258
00:20:41,694 --> 00:20:44,396
And lack of order.
259
00:20:47,066 --> 00:20:51,436
So next time someone complains
that you have made a mistake...
260
00:20:51,437 --> 00:20:54,005
...Tell him,
"that may be a good thing
261
00:20:54,006 --> 00:20:56,274
"because without imperfection,
262
00:20:56,275 --> 00:20:59,811
Neither you nor I would exist."
263
00:21:09,773 --> 00:21:12,941
13.5 billion years ago,
264
00:21:12,942 --> 00:21:15,978
The universe was mostly
hydrogen gas,
265
00:21:15,979 --> 00:21:18,981
With gravity doing
what gravity does,
266
00:21:18,982 --> 00:21:22,651
Which is to slowly pull it
into vast clouds.
267
00:21:24,687 --> 00:21:28,290
Hydrogen is the simplest
of gases,
268
00:21:28,291 --> 00:21:30,626
But it has
a very special property.
269
00:21:30,627 --> 00:21:33,962
It's a tremendous
source of power.
270
00:21:35,732 --> 00:21:38,801
Heat hydrogen
to around 10 million degrees,
271
00:21:38,802 --> 00:21:40,836
And it begins to produce
the energy
272
00:21:40,837 --> 00:21:44,273
That makes the stars shine...
273
00:21:44,274 --> 00:21:49,778
And supplies the universe
with warmth and light.
274
00:21:49,779 --> 00:21:51,747
To see how this works,
275
00:21:51,748 --> 00:21:56,785
Let's imagine we can make
a small star here on earth.
276
00:21:56,786 --> 00:22:00,022
First, we need plenty
of hydrogen gas,
277
00:22:00,023 --> 00:22:03,158
About a sports stadium full
would be perfect.
278
00:22:07,530 --> 00:22:09,198
Next, we need to imagine
279
00:22:09,199 --> 00:22:11,800
Squishing
this hydrogen together,
280
00:22:11,801 --> 00:22:15,170
Just as gravity does in space.
281
00:22:20,643 --> 00:22:22,845
As the hydrogen compacts,
282
00:22:22,846 --> 00:22:27,216
The atoms of gas start
bouncing off each other,
283
00:22:27,217 --> 00:22:30,385
And the temperature
begins to rise.
284
00:22:32,355 --> 00:22:37,526
By the time it's compressed down
to the size of the soccer ball,
285
00:22:37,527 --> 00:22:42,431
The hydrogen reaches the
critical 10 million degrees...
286
00:22:45,768 --> 00:22:49,505
...And a process
called nuclear fusion begins.
287
00:22:52,275 --> 00:22:55,511
The hydrogen starts
to fuse together,
288
00:22:55,512 --> 00:22:58,614
Making a new,
heavier material...
289
00:22:58,615 --> 00:23:00,082
Helium.
290
00:23:02,385 --> 00:23:05,220
With every step
of this tiny bump and grind,
291
00:23:05,221 --> 00:23:09,925
Some matter gets converted
into pure energy.
292
00:23:19,068 --> 00:23:22,504
We have created
a miniature star.
293
00:23:33,449 --> 00:23:37,586
Of course,
if this was a real experiment,
294
00:23:37,587 --> 00:23:40,222
You wouldn't want to go
anywhere near it.
295
00:23:43,993 --> 00:23:47,863
The energy given off
even from a star this small
296
00:23:47,864 --> 00:23:50,032
Would be devastating.
297
00:24:01,678 --> 00:24:03,879
Back in the early universe,
298
00:24:03,880 --> 00:24:07,015
The same process happened
for the first time
299
00:24:07,016 --> 00:24:09,785
On a much, much bigger scale.
300
00:24:12,622 --> 00:24:15,824
Gravity compressed
the hydrogen gas clouds
301
00:24:15,825 --> 00:24:17,359
Over millions of years,
302
00:24:17,360 --> 00:24:19,561
Until, deep in the center,
303
00:24:19,562 --> 00:24:23,966
The hydrogen became hot enough
for fusion to occur.
304
00:24:36,212 --> 00:24:39,815
The first star
burst into life...
305
00:24:42,352 --> 00:24:45,721
...Pouring its energy
into the vast universe,
306
00:24:45,722 --> 00:24:48,090
A product of the laws of nature
307
00:24:48,091 --> 00:24:51,660
And the raw materials left over
from the big bang.
308
00:24:54,430 --> 00:24:58,300
It was almost 1,000 times bigger
than our own sun
309
00:24:58,301 --> 00:25:01,737
And burned a deep blue.
310
00:25:01,738 --> 00:25:05,741
What's more,
this star soon had company.
311
00:25:13,282 --> 00:25:16,752
The stars were turning on.
312
00:25:23,059 --> 00:25:26,228
This same process still happens
in our sun,
313
00:25:26,229 --> 00:25:29,431
Which is where we get
the energy we need to live.
314
00:25:33,903 --> 00:25:36,204
But there was still
a long way to go
315
00:25:36,205 --> 00:25:39,875
To get from this
to where we are today.
316
00:25:47,684 --> 00:25:49,918
You can't build
a world like ours
317
00:25:49,919 --> 00:25:54,356
From simple gases
such as hydrogen and helium.
318
00:25:54,357 --> 00:25:57,059
You need all sorts
of other elements.
319
00:25:57,060 --> 00:26:01,797
You need elements like oxygen
and carbon and iron
320
00:26:01,798 --> 00:26:04,366
And many more.
321
00:26:04,367 --> 00:26:06,968
But we got lucky yet again,
322
00:26:06,969 --> 00:26:11,273
Because the very same process
that causes the stars to shine
323
00:26:11,274 --> 00:26:13,875
Also just happens
to make materials
324
00:26:13,876 --> 00:26:18,680
Like oxygen and carbon and iron.
325
00:26:22,618 --> 00:26:28,557
Stars, simply by accident,
are giant factories.
326
00:26:32,762 --> 00:26:35,764
To see a star in action,
327
00:26:35,765 --> 00:26:38,834
Let's imagine
I can split one in half.
328
00:26:46,442 --> 00:26:48,376
Just as in the soccer-ball star,
329
00:26:48,377 --> 00:26:51,012
The hydrogen atoms
are fusing together,
330
00:26:51,013 --> 00:26:55,584
Creating helium, which produces
the star's energy.
331
00:26:57,954 --> 00:27:01,523
But helium is slightly heavier
than hydrogen,
332
00:27:01,524 --> 00:27:04,659
So it sinks
to the center of the star.
333
00:27:06,028 --> 00:27:09,731
And now the helium atoms
take center stage.
334
00:27:11,200 --> 00:27:14,936
As they fuse together,
they produce even more energy
335
00:27:14,937 --> 00:27:18,707
And form yet another
new element...
336
00:27:18,708 --> 00:27:21,810
Carbon...
337
00:27:21,811 --> 00:27:26,014
A vital building block
of every living thing.
338
00:27:28,251 --> 00:27:31,419
The process repeats itself
over and over,
339
00:27:31,420 --> 00:27:35,657
And the star becomes layered,
like an onion...
340
00:27:35,658 --> 00:27:39,594
A really big onion.
341
00:27:39,595 --> 00:27:42,998
The closer to the center,
the heavier the elements,
342
00:27:42,999 --> 00:27:48,537
Like neon, oxygen,
and last of all, iron.
343
00:27:48,538 --> 00:27:51,373
Now things change.
344
00:27:51,374 --> 00:27:54,442
Iron doesn't produce energy
when it fuses,
345
00:27:54,443 --> 00:27:58,847
So the fire begins to go out.
346
00:27:58,848 --> 00:28:02,851
More and more iron builds up
in the star's core
347
00:28:02,852 --> 00:28:06,555
Until almost all
the remaining fuel runs out.
348
00:28:10,960 --> 00:28:16,331
Now gravity takes over and
squashes the star in on itself.
349
00:28:17,867 --> 00:28:20,769
As its core gets
more and more compressed,
350
00:28:20,770 --> 00:28:23,238
Its temperature soars
351
00:28:23,239 --> 00:28:28,376
Until it's over 100 times hotter
than the core of our own sun.
352
00:28:33,516 --> 00:28:38,920
Finally, the star collapses
and explodes.
353
00:28:56,072 --> 00:28:58,907
This is a supernova...
354
00:29:02,311 --> 00:29:07,649
...The death of a star
and the birth of something new.
355
00:29:11,153 --> 00:29:14,222
In these brief microseconds,
356
00:29:14,223 --> 00:29:17,792
A massive shock wave
passes through the star.
357
00:29:17,793 --> 00:29:21,963
The blast is so powerful
that it forces some of the iron
358
00:29:21,964 --> 00:29:24,933
To fuse
into even heavier elements.
359
00:29:24,934 --> 00:29:27,869
And that's how heavy elements,
360
00:29:27,870 --> 00:29:31,640
Such as gold or platinum
or lead,
361
00:29:31,641 --> 00:29:36,912
Are made, forged in the heart
of an exploding star.
362
00:29:38,681 --> 00:29:43,518
So, if you have a gold ring,
make sure you appreciate it.
363
00:29:43,519 --> 00:29:46,955
The metal was made
in a blinding flash of light
364
00:29:46,956 --> 00:29:49,624
Billions of years ago,
365
00:29:49,625 --> 00:29:51,793
The finale of the process
366
00:29:51,794 --> 00:29:56,064
That produced the elements
all around us today.
367
00:30:00,836 --> 00:30:02,904
It never ceases to amaze me...
368
00:30:02,905 --> 00:30:05,340
...That our bodies
are constructed
369
00:30:05,341 --> 00:30:07,475
Of the stuff of stars
370
00:30:07,476 --> 00:30:10,345
And that our hearts beat
because of the energy
371
00:30:10,346 --> 00:30:13,181
Given off
as those materials are made.
372
00:30:13,182 --> 00:30:16,418
But as magical as the star is,
373
00:30:16,419 --> 00:30:19,421
There are even more fascinating
and powerful things
374
00:30:19,422 --> 00:30:21,656
In our enormous cosmos.
375
00:30:40,502 --> 00:30:44,138
Around 300 million
years after the big bang,
376
00:30:44,139 --> 00:30:47,775
The early stars
began to form galaxies,
377
00:30:47,776 --> 00:30:49,576
Which slowly took on
378
00:30:49,577 --> 00:30:53,580
A bewildering variety
of shapes and sizes.
379
00:30:55,316 --> 00:30:57,885
Our galaxy, the milky way,
380
00:30:57,886 --> 00:31:00,254
Is thought to be
one of the oldest,
381
00:31:00,255 --> 00:31:02,156
Having started
to assemble itself
382
00:31:02,157 --> 00:31:05,225
Some 13 billion years ago.
383
00:31:07,495 --> 00:31:12,533
It's roughly
6,000 billion miles in diameter
384
00:31:12,534 --> 00:31:18,605
And contains something like
200 billion individual stars.
385
00:31:18,606 --> 00:31:21,408
Nobody's quite sure
exactly how many,
386
00:31:21,409 --> 00:31:23,877
Since they can't all be seen
from earth,
387
00:31:23,878 --> 00:31:27,047
And, anyway, it would take
a long time to count them.
388
00:31:31,119 --> 00:31:34,721
Because all these stars
were built by gravity,
389
00:31:34,722 --> 00:31:38,392
You could say gravity's
the hero of the universe.
390
00:31:38,393 --> 00:31:41,695
After all, it turned
a meaningless soup of gas
391
00:31:41,696 --> 00:31:44,698
Into something of beauty
and power.
392
00:31:48,136 --> 00:31:51,071
But like all interesting heroes,
393
00:31:51,072 --> 00:31:54,074
Gravity has its dark side.
394
00:31:56,110 --> 00:31:58,912
Right in the center
of our galaxy
395
00:31:58,913 --> 00:32:03,884
Lies an example of what happens
when gravity rules unchallenged.
396
00:32:10,425 --> 00:32:12,960
A black hole.
397
00:32:17,465 --> 00:32:20,667
When I was in my 20s...
398
00:32:20,668 --> 00:32:24,338
...I did some of the basic
mathematics of black holes,
399
00:32:24,339 --> 00:32:28,775
But few people shared
my fascination.
400
00:32:28,776 --> 00:32:32,446
These days,
they are a popular subject.
401
00:32:34,449 --> 00:32:37,150
Physicists all over the world
402
00:32:37,151 --> 00:32:39,086
Are studying
black-hole behavior.
403
00:32:40,321 --> 00:32:42,823
We now know that black holes
404
00:32:42,824 --> 00:32:45,692
Are not only fascinating
in their own right,
405
00:32:45,693 --> 00:32:47,828
But that they play
a fundamental role
406
00:32:47,829 --> 00:32:50,731
In the formation of galaxies.
407
00:32:50,732 --> 00:32:55,702
They also give us a glimpse
of how the universe may end.
408
00:32:59,240 --> 00:33:02,442
A black hole forms
when a large star...
409
00:33:02,443 --> 00:33:05,412
One, say, 20 times
the mass of our sun...
410
00:33:05,413 --> 00:33:08,348
Comes to the end of its life.
411
00:33:10,451 --> 00:33:14,121
Such a star looks
nothing like our sun
412
00:33:14,122 --> 00:33:16,523
Because it's become unstable,
413
00:33:16,524 --> 00:33:20,761
Convulsing violently
as its death throes begin.
414
00:33:25,266 --> 00:33:29,536
Finally, it runs out of fuel
and begins to shrink,
415
00:33:29,537 --> 00:33:33,340
Getting denser and denser,
hotter and hotter.
416
00:33:35,910 --> 00:33:37,878
But with a star this massive,
417
00:33:37,879 --> 00:33:40,314
There is no force
in the universe
418
00:33:40,315 --> 00:33:43,383
Capable of stopping
the collapse.
419
00:33:43,384 --> 00:33:45,118
The core is so heavy
420
00:33:45,119 --> 00:33:48,689
That it just keeps on
falling in on itself.
421
00:33:50,792 --> 00:33:54,061
Gravity is running wild.
422
00:33:55,897 --> 00:33:57,931
In just 15 seconds or so,
423
00:33:57,932 --> 00:34:00,701
The unstoppable force
crushes the star
424
00:34:00,702 --> 00:34:04,671
From millions of miles
in diameter
425
00:34:04,672 --> 00:34:07,841
To as little
as 12 miles in diameter.
426
00:34:11,846 --> 00:34:15,482
All the mass that was
in the star is still there,
427
00:34:15,483 --> 00:34:17,951
But its own weight
keeps forcing it down
428
00:34:17,952 --> 00:34:20,821
Smaller and smaller still.
429
00:34:23,758 --> 00:34:28,729
The temperature of the core
sores to 100 billion degrees.
430
00:34:41,409 --> 00:34:46,913
The outer layers are blasted
away in a massive supernova,
431
00:34:46,914 --> 00:34:49,683
But deep in the center,
432
00:34:49,684 --> 00:34:55,522
The core falls down what we call
a gravitational well.
433
00:34:55,523 --> 00:34:59,926
It crushes itself
into a single point.
434
00:34:59,927 --> 00:35:03,030
A black hole is born.
435
00:35:03,031 --> 00:35:07,467
Nothing nearby can escape
its pull, not even light.
436
00:35:10,338 --> 00:35:15,409
It's hard to imagine just
how dense a black hole can be.
437
00:35:15,410 --> 00:35:17,577
But I'll try and put it
into perspective
438
00:35:17,578 --> 00:35:20,347
Using something familiar...
439
00:35:20,348 --> 00:35:22,149
The earth.
440
00:35:26,087 --> 00:35:31,458
Imagine, piece by piece,
I could compress our planet
441
00:35:31,459 --> 00:35:35,696
And crush it
until gravity took over...
442
00:35:35,697 --> 00:35:39,166
And it became a black hole.
443
00:35:40,635 --> 00:35:42,869
How small would it have to be
444
00:35:42,870 --> 00:35:46,606
To vanish down its own
gravitational well?
445
00:35:56,384 --> 00:35:59,820
From 8,000 miles in diameter,
446
00:35:59,821 --> 00:36:04,825
I'd have to crush it
to the size of a pea.
447
00:36:07,528 --> 00:36:10,230
In my years
studying black holes...
448
00:36:10,231 --> 00:36:12,899
...One of my most
unexpected discoveries
449
00:36:12,900 --> 00:36:17,971
Was that a black hole
cannot be perfectly black.
450
00:36:17,972 --> 00:36:20,107
For much the same reason...
451
00:36:20,108 --> 00:36:21,475
...As the early universe
452
00:36:21,476 --> 00:36:25,312
Could not have been
perfectly spread out.
453
00:36:25,313 --> 00:36:29,583
There is no such thing
as perfection.
454
00:36:29,584 --> 00:36:33,820
Black holes
must give off radiation.
455
00:36:33,821 --> 00:36:39,092
The smaller the black hole,
the grter the radiation.
456
00:36:39,093 --> 00:36:41,194
An even tinier black hole,
457
00:36:41,195 --> 00:36:43,597
With only the mass
of a mountain range,
458
00:36:43,598 --> 00:36:45,832
Would actually shine.
459
00:36:52,640 --> 00:36:58,044
Out in space, most black holes
are much larger.
460
00:36:58,045 --> 00:37:03,183
The smaller ones have around
four times the mass of our sun
461
00:37:03,184 --> 00:37:05,585
And are 15 miles in diameter.
462
00:37:05,586 --> 00:37:08,989
Some are much larger,
463
00:37:08,990 --> 00:37:12,859
Containing the mass
of thousands of suns.
464
00:37:12,860 --> 00:37:17,631
And then there are
the really big ones...
465
00:37:17,632 --> 00:37:20,801
Supermassive black holes...
466
00:37:20,802 --> 00:37:24,638
That exist at the centers
of galaxies like our own.
467
00:37:29,410 --> 00:37:30,944
This black hole
468
00:37:30,945 --> 00:37:35,248
Is thought to have the mass
of 4 million suns
469
00:37:35,249 --> 00:37:40,720
And a diameter
of 11 million miles.
470
00:37:40,721 --> 00:37:44,624
Black holes like these
are the heavy hubs
471
00:37:44,625 --> 00:37:49,396
Around which many galaxies,
including the milky way, rotate,
472
00:37:49,397 --> 00:37:54,467
A kind of stabilizer
that gives them form and shape.
473
00:37:56,904 --> 00:38:00,540
So, 8 billion years
after the big bang,
474
00:38:00,541 --> 00:38:04,110
After a long and remarkable run
of good luck,
475
00:38:04,111 --> 00:38:07,314
We have stars
and we have galaxies
476
00:38:07,315 --> 00:38:12,219
Slowly rotating
around giant black holes.
477
00:38:12,220 --> 00:38:15,956
Now the scene is set for
something close to our hearts...
478
00:38:15,957 --> 00:38:19,626
The formation of our sun,
the earth,
479
00:38:19,627 --> 00:38:22,896
And, ultimately, us.
480
00:38:35,011 --> 00:38:38,480
Our solar system,
the place we call home,
481
00:38:38,481 --> 00:38:42,818
Lies about 26,000 light-years
from the center of our galaxy,
482
00:38:42,819 --> 00:38:46,088
The milky way...
483
00:38:46,089 --> 00:38:50,092
Or around 2/3 of the way out.
484
00:38:50,093 --> 00:38:52,728
The story of how
these huge planets
485
00:38:52,729 --> 00:38:55,798
Came to be orbiting
an average yellow star
486
00:38:55,799 --> 00:38:58,334
Is 6 billion years long,
487
00:38:58,335 --> 00:39:00,636
And since we don't have
that much time,
488
00:39:00,637 --> 00:39:02,972
I'll speed it up a bit.
489
00:39:06,042 --> 00:39:08,877
It starts with a bang.
490
00:39:13,717 --> 00:39:17,620
Long ago,
an ancient star exploded,
491
00:39:17,621 --> 00:39:20,155
Littering space
with swirling clouds
492
00:39:20,156 --> 00:39:22,358
Of the materials
it had made while it lived
493
00:39:22,359 --> 00:39:26,061
And the heavier metals
it created as it died.
494
00:39:28,331 --> 00:39:31,800
We know this because we can see
similar fields of dust
495
00:39:31,801 --> 00:39:34,003
Out in space today.
496
00:39:34,004 --> 00:39:36,905
They are called nebulae,
497
00:39:36,906 --> 00:39:40,509
And they are very beautiful.
498
00:39:40,510 --> 00:39:42,444
Every nebula is different,
499
00:39:42,445 --> 00:39:43,946
And in our case,
500
00:39:43,947 --> 00:39:49,418
The clouds contained nitrogen
and oxygen and iron and silica
501
00:39:49,419 --> 00:39:53,022
And all the other stuff needed
to build a world like ours.
502
00:39:54,591 --> 00:39:57,192
Then the tireless force
of gravity
503
00:39:57,193 --> 00:40:00,029
Started to pull it all
back together,
504
00:40:00,030 --> 00:40:05,167
And the heavy engineering
that produces planets began.
505
00:40:12,676 --> 00:40:16,612
Vast swirls of dust
began to form,
506
00:40:16,613 --> 00:40:19,281
And at the center
of one of these,
507
00:40:19,282 --> 00:40:23,986
A rocky planet called earth
started to take shape...
508
00:40:26,056 --> 00:40:30,693
...Built of stardust
and assembled by gravity.
509
00:40:35,598 --> 00:40:38,200
Fast forward 100 million years,
510
00:40:38,201 --> 00:40:41,103
And it had grown
into a giant ball,
511
00:40:41,104 --> 00:40:44,740
Sweeping up billions of tons
of celestial debris.
512
00:40:50,814 --> 00:40:54,216
This is where
the earth came from
513
00:40:54,217 --> 00:40:58,053
And, therefore,
how you and I began.
514
00:41:02,592 --> 00:41:06,562
But our planet would have
remained a large, sterile ball
515
00:41:06,563 --> 00:41:09,832
Of rock and metals
and minerals forever
516
00:41:09,833 --> 00:41:12,167
Were it not for one more event,
517
00:41:12,168 --> 00:41:15,904
One more expression
of the forces of nature.
518
00:41:20,243 --> 00:41:22,444
93 million miles away,
519
00:41:22,445 --> 00:41:25,013
At the heart
of the giant nebula,
520
00:41:25,014 --> 00:41:28,484
The pressure and temperature
of a ball of hydrogen gas
521
00:41:28,485 --> 00:41:33,288
Had become so great that the
atoms were beginning to fuse.
522
00:41:33,289 --> 00:41:38,260
A new star, our sun,
was coming to life.
523
00:41:46,102 --> 00:41:48,070
As the sun ignited,
524
00:41:48,071 --> 00:41:53,142
It gave off a huge blast
of solar wind,
525
00:41:53,143 --> 00:41:58,080
A radioactive gust of energy.
526
00:41:58,081 --> 00:42:01,016
This blew all
the remaining dust and gas
527
00:42:01,017 --> 00:42:02,951
That was left over
from the nebula
528
00:42:02,952 --> 00:42:05,754
Out to the edge
of the solar system,
529
00:42:05,755 --> 00:42:09,391
Which is why everything
is nice and orderly today.
530
00:42:14,898 --> 00:42:17,266
In the outer reaches
of the solar system,
531
00:42:17,267 --> 00:42:19,535
We have the huge gas planets...
532
00:42:19,536 --> 00:42:22,538
Jupiter...Saturn...
533
00:42:22,539 --> 00:42:24,706
Uranus...And neptune.
534
00:42:24,707 --> 00:42:27,910
Further in are the denser,
rockier planets...
535
00:42:27,911 --> 00:42:30,679
Mercury...
536
00:42:30,680 --> 00:42:33,115
Venus...
537
00:42:33,116 --> 00:42:34,516
Mars...
538
00:42:34,517 --> 00:42:38,787
And, of course, the earth.
539
00:42:38,788 --> 00:42:44,026
Lucky for us, the sun
is 865,000 miles in diameter,
540
00:42:44,027 --> 00:42:46,895
Or just the right size
to burn consistently
541
00:42:46,896 --> 00:42:49,398
For a very long time...
542
00:42:49,399 --> 00:42:51,633
8 billion years...
543
00:42:51,634 --> 00:42:57,039
Long enough to allow the next
development to take place...
544
00:42:57,040 --> 00:42:58,874
Life.
545
00:45:38,804 --> 00:45:42,741
Life is one of
the strangest phenomena known.
546
00:45:42,742 --> 00:45:44,676
In my opinion,
547
00:45:44,677 --> 00:45:48,680
It shows that the universe
is capable of almost anything.
548
00:45:51,517 --> 00:45:54,519
Yet it amazes me
that we can know so much
549
00:45:54,520 --> 00:45:59,691
About how the universe began
many billions of years ago,
550
00:45:59,692 --> 00:46:04,329
But we have yet to discover
how life itself began.
551
00:46:06,032 --> 00:46:08,133
The most likely explanation
552
00:46:08,134 --> 00:46:11,469
Is probably
that we are an accident.
553
00:46:15,474 --> 00:46:17,042
Just by chance,
554
00:46:17,043 --> 00:46:20,145
Some molecules
bumped into each other at random
555
00:46:20,146 --> 00:46:26,651
Until, finally, one formed
that could copy itself.
556
00:46:26,652 --> 00:46:30,088
Then began the slow process
of evolution
557
00:46:30,089 --> 00:46:33,725
That led to all
the extraordinary diversity
558
00:46:33,726 --> 00:46:35,794
Of life on earth.
559
00:46:38,130 --> 00:46:40,899
Life seems to be
simply what matter does,
560
00:46:40,900 --> 00:46:44,702
Given the right conditions
and enough time.
561
00:46:44,703 --> 00:46:46,271
I think that life
562
00:46:46,272 --> 00:46:48,940
Is probably quite common
throughout the universe,
563
00:46:48,941 --> 00:46:51,576
But that's another tale
altogether.
564
00:46:54,280 --> 00:46:58,883
As life developed, it changed
the planet on which it was born,
565
00:46:58,884 --> 00:47:02,187
Altering the very fabric
of the earth.
566
00:47:11,764 --> 00:47:14,466
After 4 1/2 billion years,
567
00:47:14,467 --> 00:47:18,536
The human race
arrived on the scene.
568
00:47:21,140 --> 00:47:23,541
But one thing
often troubles people...
569
00:47:23,542 --> 00:47:26,511
...When they hear this story.
570
00:47:26,512 --> 00:47:30,248
How could such
an astounding chain of events,
571
00:47:30,249 --> 00:47:35,153
Which resulted in us,
be an accident?
572
00:47:35,154 --> 00:47:37,355
Perhaps science has revealed
573
00:47:37,356 --> 00:47:40,525
There is some higher authority
at work,
574
00:47:40,526 --> 00:47:42,560
Setting the laws of nature
575
00:47:42,561 --> 00:47:46,664
So that our universe
and we can exist.
576
00:47:53,372 --> 00:47:56,007
On the face of it,
life does seem
577
00:47:56,008 --> 00:47:59,110
To be too unlikely
to be just a coincidence.
578
00:48:01,981 --> 00:48:03,948
Think about it.
579
00:48:03,949 --> 00:48:07,852
The earth lies at exactly
the right distance from the sun
580
00:48:07,853 --> 00:48:11,723
To allow liquid water
to exist on its surface.
581
00:48:13,792 --> 00:48:16,227
And the sun just happens
to be the right size
582
00:48:16,228 --> 00:48:18,196
To burn for billions of years,
583
00:48:18,197 --> 00:48:21,132
Long enough for life
to have evolved.
584
00:48:23,369 --> 00:48:25,403
The solar system is littered
585
00:48:25,404 --> 00:48:28,806
With all the elements
needed for life.
586
00:48:28,807 --> 00:48:31,142
These elements themselves
are only possible
587
00:48:31,143 --> 00:48:34,746
Because of older stars
that have burned up.
588
00:48:36,382 --> 00:48:39,050
These older stars only existed
589
00:48:39,051 --> 00:48:45,423
Because of a tiny unevenness
in the early primordial gas...
590
00:48:45,424 --> 00:48:49,594
That was itself produced
by a one-in-a-billion imbalance
591
00:48:49,595 --> 00:48:53,865
In the sea of particles
that came from the big bang.
592
00:49:01,173 --> 00:49:04,475
So is there a grand designer
593
00:49:04,476 --> 00:49:08,112
Who lined up
all this good fortune?
594
00:49:08,113 --> 00:49:12,717
In my opinion, not necessarily.
595
00:49:12,718 --> 00:49:15,019
Look at it this way.
596
00:49:15,020 --> 00:49:17,255
What if there were
other universes,
597
00:49:17,256 --> 00:49:20,425
Ones not as lucky as ours?
598
00:49:20,426 --> 00:49:22,427
Each of these universes
599
00:49:22,428 --> 00:49:24,829
Could have come
from its own big bang,
600
00:49:24,830 --> 00:49:30,335
With different laws of physics
and different conditions.
601
00:49:30,336 --> 00:49:33,504
In some,
gravity might not exist,
602
00:49:33,505 --> 00:49:36,541
And there could be no life.
603
00:49:36,542 --> 00:49:39,844
In others,
hydrogen might not fuse,
604
00:49:39,845 --> 00:49:45,016
So there would be no stars
and, again, no life.
605
00:49:45,017 --> 00:49:46,751
And for any number of reasons,
606
00:49:46,752 --> 00:49:48,886
Universes could have
come and gone
607
00:49:48,887 --> 00:49:51,723
Without producing
ything at all.
608
00:49:55,761 --> 00:49:58,496
So perhaps we should not be
too surprised
609
00:49:58,497 --> 00:50:01,766
To find ourselves
in a perfect universe
610
00:50:01,767 --> 00:50:03,668
Orbiting a perfect sun
611
00:50:03,669 --> 00:50:05,870
On a perfect planet,
612
00:50:05,871 --> 00:50:08,473
Because such perfect places
613
00:50:08,474 --> 00:50:12,277
Are the only ones
where life like us can exist.
614
00:50:19,652 --> 00:50:23,388
We are one of the many products
of the universe,
615
00:50:23,389 --> 00:50:28,126
The result of an ancient
and elegant mechanism.
616
00:50:28,127 --> 00:50:30,762
But even this
remarkable discovery
617
00:50:30,763 --> 00:50:36,034
Is only just the beginning
of what physics can tell us.
618
00:50:36,035 --> 00:50:40,471
We can find out what human kind
will face in the distant future.
619
00:50:48,147 --> 00:50:49,947
And, ultimately,
620
00:50:49,948 --> 00:50:54,686
We might discover the fate
of the universe itself.
621
00:51:04,904 --> 00:51:07,272
One reason I love cosmology
622
00:51:07,273 --> 00:51:09,507
Is that it tells us
not only where
623
00:51:09,508 --> 00:51:13,278
The vast web of galaxies
in our universe came from,
624
00:51:13,279 --> 00:51:15,413
But also what lies in store
625
00:51:15,414 --> 00:51:20,351
For both the universe
and for us.
626
00:51:20,352 --> 00:51:22,287
I think it's pretty exciting
627
00:51:22,288 --> 00:51:24,789
To be among
the first human beings
628
00:51:24,790 --> 00:51:26,224
Able to look forward
629
00:51:26,225 --> 00:51:29,094
For hundreds
and even billions of years,
630
00:51:29,095 --> 00:51:32,831
Maybe as far
as the end of time itself.
631
00:51:36,535 --> 00:51:38,870
What I see
is not only the future
632
00:51:38,871 --> 00:51:41,005
Of the cosmos we inhabit...
633
00:51:41,006 --> 00:51:43,374
...But also
the enormous challenges
634
00:51:43,375 --> 00:51:45,844
Our species will face.
635
00:51:45,845 --> 00:51:49,814
After all,
we are puny organisms
636
00:51:49,815 --> 00:51:53,618
Compared to the mighty universe
that made us.
637
00:51:53,619 --> 00:51:58,089
The earth that gave us life
will not always be
638
00:51:58,090 --> 00:52:01,493
The blue sanctuary it is today.
639
00:52:07,366 --> 00:52:10,902
The continents
of our planet are drifting.
640
00:52:12,605 --> 00:52:15,406
Fast forward 75 million years,
641
00:52:15,407 --> 00:52:19,711
And they will be clustered
towards the south pole.
642
00:52:19,712 --> 00:52:23,481
No one knows if the earth
will still be habitable then,
643
00:52:23,482 --> 00:52:24,883
But the sad truth is
644
00:52:24,884 --> 00:52:27,719
That we may not last long enough
to find out.
645
00:52:29,955 --> 00:52:32,157
As we gaze into the future,
646
00:52:32,158 --> 00:52:37,295
It turns out that the universe
is a pretty dangerous place.
647
00:52:40,232 --> 00:52:42,800
Just look at our neighborhood.
648
00:52:42,801 --> 00:52:46,037
It's littered
with billions of asteroids,
649
00:52:46,038 --> 00:52:48,039
Ancient remnants left over
650
00:52:48,040 --> 00:52:50,608
From the process
that built the solar system.
651
00:52:53,112 --> 00:52:55,947
The possibility of one of these
wiping us out
652
00:52:55,948 --> 00:52:59,651
Isn't just the stuff
of hollywood disaster movies.
653
00:52:59,652 --> 00:53:02,787
The threat from asteroids
is real.
654
00:53:02,788 --> 00:53:05,823
We've even given
some of them names.
655
00:53:09,562 --> 00:53:12,964
This one is called apophis,
656
00:53:12,965 --> 00:53:16,067
After a mythical egyptian demon,
657
00:53:16,068 --> 00:53:20,305
A god of darkness
and destruction.
658
00:53:24,743 --> 00:53:27,278
Discovered in 2004,
659
00:53:27,279 --> 00:53:32,784
Apophis is the size
of a 100-story skyscraper.
660
00:53:32,785 --> 00:53:36,654
It weighs about 20 million tons.
661
00:53:43,963 --> 00:53:48,733
Speeding through space
at 28,000 miles an hour,
662
00:53:48,734 --> 00:53:51,269
10 times as fast as a bullet,
663
00:53:51,270 --> 00:53:53,304
It carries almost as much energy
664
00:53:53,305 --> 00:53:57,976
As all the world's
nuclear weapons combined.
665
00:53:57,977 --> 00:54:00,378
And we know roughly
where it's headed.
666
00:54:05,951 --> 00:54:09,721
The precise path
is not yet fully known.
667
00:54:12,891 --> 00:54:16,728
But on April the 13th, 2029,
668
00:54:16,729 --> 00:54:19,497
This huge rock is likely to pass
669
00:54:19,498 --> 00:54:23,501
Within 23,000 miles
of the planet's surface,
670
00:54:23,502 --> 00:54:25,336
Close enough to pass
671
00:54:25,337 --> 00:54:28,106
Beneath satellites in orbit
around the earth
672
00:54:28,107 --> 00:54:30,308
And give us all a scare.
673
00:54:36,849 --> 00:54:39,617
Luckily,
there is very little chance
674
00:54:39,618 --> 00:54:42,086
That apophis
will actually hit us,
675
00:54:42,087 --> 00:54:46,991
But the problem for humanity
is that in space...
676
00:54:46,992 --> 00:54:49,027
There's always a bigger rock.
677
00:55:00,773 --> 00:55:05,109
There thousands of really large
asteroids out here.
678
00:55:07,479 --> 00:55:10,715
Some are over 10 miles long...
679
00:55:10,716 --> 00:55:14,152
The size of manhattan.
680
00:55:14,153 --> 00:55:16,854
An asteroid this size
hits the earth
681
00:55:16,855 --> 00:55:19,691
Every 100 million years or so.
682
00:55:35,341 --> 00:55:40,278
The last one struck the earth
65 million years ago
683
00:55:40,279 --> 00:55:44,349
And probably was responsible
for wiping out the dinosaurs.
684
00:55:50,189 --> 00:55:53,291
We don't know when
the next asteroid will strike,
685
00:55:53,292 --> 00:55:57,729
But if it was big enough,
it could sterilize our planet.
686
00:55:59,098 --> 00:56:00,765
That would be the end
687
00:56:00,766 --> 00:56:05,303
Of the 5 billion-year-long story
of life on earth.
688
00:56:07,272 --> 00:56:10,942
But even if we avoid
such a natural catastrophe,
689
00:56:10,943 --> 00:56:15,380
We could all too easily end up
destroying ourselves.
690
00:56:23,689 --> 00:56:25,990
In the last 10,000 years,
691
00:56:25,991 --> 00:56:30,161
Humans have come
to dominate the planet.
692
00:56:30,162 --> 00:56:31,729
We're so successful
693
00:56:31,730 --> 00:56:36,434
That it's tempting to think
we are evolution's grand prize.
694
00:56:36,435 --> 00:56:41,205
But I believe intelligence
is probably overrated.
695
00:56:41,206 --> 00:56:46,077
It's not necessarily a good
thing for a species's survival.
696
00:56:46,078 --> 00:56:51,182
Bacteria have managed without it
for over 3 billion years.
697
00:56:53,152 --> 00:56:55,686
Intelligence,
at least in our case,
698
00:56:55,687 --> 00:56:58,856
Leads to technology.
699
00:57:00,459 --> 00:57:04,796
And there are many ways
technology could wipe us out...
700
00:57:04,797 --> 00:57:06,864
The most obvious, of course,
701
00:57:06,865 --> 00:57:11,169
The threat from nuclear weapons.
702
00:57:11,170 --> 00:57:14,639
Even if the risk of a nuclear
war happening in one year
703
00:57:14,640 --> 00:57:17,775
Is miniscule...
say only one in a million...
704
00:57:17,776 --> 00:57:21,746
If we run those odds
over 100,000 years,
705
00:57:21,747 --> 00:57:26,050
The chance of catastrophe
falls to one in 10.
706
00:57:35,494 --> 00:57:40,465
Personally, I worry that even
this might be overoptimistic.
707
00:57:40,466 --> 00:57:44,135
Although we are clever enough
to have designed such weapons,
708
00:57:44,136 --> 00:57:48,172
I'm not sure we are
clever enough not to use them.
709
00:57:50,342 --> 00:57:53,878
As time marches relentlessly
into the future,
710
00:57:53,879 --> 00:57:57,348
The universe has
other surprises in store.
711
00:57:59,818 --> 00:58:02,620
There are some powerful things
out there...
712
00:58:05,190 --> 00:58:07,525
...Some of which
could destroy the earth
713
00:58:07,526 --> 00:58:10,161
Without any help from us.
714
00:58:18,569 --> 00:58:21,171
As the universe
continues to dance
715
00:58:21,172 --> 00:58:23,206
To its ancient rhythm,
716
00:58:23,207 --> 00:58:27,110
Stars will come and go
in a relentless cycle.
717
00:58:27,111 --> 00:58:30,614
And because there are
hundreds of billions of stars,
718
00:58:30,615 --> 00:58:34,317
There's always one dying
in a supernova somewhere.
719
00:58:36,320 --> 00:58:38,288
In our galaxy, for instance,
720
00:58:38,289 --> 00:58:42,459
A star dies
every 50 years or so...
721
00:58:42,460 --> 00:58:46,463
Which is but the briefest
of moments to the universe.
722
00:58:48,099 --> 00:58:49,933
It's just about conceivable
723
00:58:49,934 --> 00:58:52,669
That a supernova
could damage the earth,
724
00:58:52,670 --> 00:58:57,274
If you consider the likelihood
over a long enough time scale.
725
00:58:59,610 --> 00:59:03,146
One kind of supernova,
discovered entirely by accident,
726
00:59:03,147 --> 00:59:06,416
Is thought to be
particularly dangerous.
727
00:59:10,488 --> 00:59:15,158
In 1967, when the cold war
was at its height,
728
00:59:15,159 --> 00:59:17,761
U.S. Military satellites
picked up a massive burst
729
00:59:17,762 --> 00:59:21,698
Of something called
gamma radiation.
730
00:59:28,172 --> 00:59:29,873
Gamma radiation
731
00:59:29,874 --> 00:59:32,642
Is the most dangerous type
of radiation known.
732
00:59:32,643 --> 00:59:37,614
It's also the telltale sign
of an atomic weapon.
733
00:59:42,587 --> 00:59:44,488
Were the gamma rays detected
734
00:59:44,489 --> 00:59:48,658
Evidence of a new
and powerful soviet bomb?
735
00:59:50,962 --> 00:59:55,198
Thankfully, the answer was no.
736
00:59:59,704 --> 01:00:02,672
After careful analysis
of the data,
737
01:00:02,673 --> 01:00:06,042
They discovered that
the sudden bursts of gamma rays
738
01:00:06,043 --> 01:00:10,614
Were actually coming from space.
739
01:00:10,615 --> 01:00:15,318
Not even the russians
had that kind of technology.
740
01:00:15,319 --> 01:00:18,188
Decades later,
we still don't have proof
741
01:00:18,189 --> 01:00:22,292
Of what causes
the bursts of radiation.
742
01:00:22,293 --> 01:00:24,661
But there's
a well-respected theory
743
01:00:24,662 --> 01:00:28,665
That they are produced
by a special kind of supernova
744
01:00:28,666 --> 01:00:32,235
Called a gamma-ray burster.
745
01:00:33,938 --> 01:00:38,441
What's more,
there might be one quite nearby.
746
01:00:41,779 --> 01:00:45,348
Hidden within this massive
spiral plume of plasma,
747
01:00:45,349 --> 01:00:48,318
8,000 light-years from earth,
748
01:00:48,319 --> 01:00:52,289
Is a star called wr 104.
749
01:00:55,092 --> 01:00:59,696
Deep inside the star itself
is a bright sphere
750
01:00:59,697 --> 01:01:04,000
Throwing off a shell of hot gas
as it nears its end.
751
01:01:13,744 --> 01:01:16,046
If this star
is what we think it is,
752
01:01:16,047 --> 01:01:17,480
Then as it dies,
753
01:01:17,481 --> 01:01:21,618
It will produce two tightly
focused beams of radiation,
754
01:01:21,619 --> 01:01:23,887
One from each pole.
755
01:01:31,062 --> 01:01:36,733
The star destroys itself
as it produces these beams,
756
01:01:36,734 --> 01:01:38,568
Which contain more energy
757
01:01:38,569 --> 01:01:42,472
Than our sun will produce
in its entire life.
758
01:01:51,382 --> 01:01:56,353
The brightest known phenomena
in the entire universe.
759
01:02:01,492 --> 01:02:07,063
No one is sure if wr 104
will do this
760
01:02:07,064 --> 01:02:09,633
Or if the beam
would strike the earth,
761
01:02:09,634 --> 01:02:15,071
But if so, we could be bathed
in high-intensity radiation...
762
01:02:18,543 --> 01:02:21,845
...With some devastating
consequences.
763
01:02:24,949 --> 01:02:28,285
The beam would cause
spectacular auroras,
764
01:02:28,286 --> 01:02:31,121
Stripping the ozone
from the atmosphere,
765
01:02:31,122 --> 01:02:35,559
Allowing deadly radiation from
the sun to strike the earth.
766
01:02:39,030 --> 01:02:42,132
It may sound like
science fiction,
767
01:02:42,133 --> 01:02:44,601
But this could be
the second time
768
01:02:44,602 --> 01:02:47,938
Skies like these have been seen
on our world.
769
01:02:49,974 --> 01:02:53,176
450 million years ago,
770
01:02:53,177 --> 01:02:55,646
Over half
of all living creatures
771
01:02:55,647 --> 01:02:59,149
Were wiped out
in a great extinction.
772
01:02:59,150 --> 01:03:02,586
One explanation
is that a gamma-ray burster
773
01:03:02,587 --> 01:03:05,222
Irradiated the planet so badly
774
01:03:05,223 --> 01:03:09,760
That earth's ecosystem
virtually collapsed.
775
01:03:09,761 --> 01:03:11,762
I don't want to worry anyone,
776
01:03:11,763 --> 01:03:14,064
But I think
it's definitely a good idea
777
01:03:14,065 --> 01:03:18,468
For the human race
to venture far beyond the earth.
778
01:03:21,472 --> 01:03:23,740
We would be wise
to keep our eggs...
779
01:03:23,741 --> 01:03:27,611
...In as many baskets
as possible.
780
01:03:27,612 --> 01:03:31,882
Thankfully, that process
has already begun.
781
01:03:39,757 --> 01:03:42,826
In my opinion,
the launch of apollo 11
782
01:03:42,827 --> 01:03:47,764
Is probably the most important
moment in human history.
783
01:04:02,580 --> 01:04:07,117
It was a turning point
for the universe, too.
784
01:04:07,118 --> 01:04:12,923
Life, in the form of us,
escaped its home planet...
785
01:04:12,924 --> 01:04:16,159
And stepped on another surface.
786
01:04:31,876 --> 01:04:36,513
The astronauts' footprints
stand preserved to this day...
787
01:04:38,249 --> 01:04:40,817
...A testament to the beginning
of what I think
788
01:04:40,818 --> 01:04:46,723
Could be the next chapter
in the story of the cosmos...
789
01:04:46,724 --> 01:04:50,994
The spread of life
to other parts of the universe.
790
01:05:01,316 --> 01:05:03,551
As the universe gets older,
791
01:05:03,552 --> 01:05:05,853
We will have to get wiser.
792
01:05:07,656 --> 01:05:11,359
I think we'll have to go
much further than the moon...
793
01:05:11,360 --> 01:05:14,929
At the very least, to mars.
794
01:05:19,434 --> 01:05:21,269
The red planet is likely to play
795
01:05:21,270 --> 01:05:24,205
An important part
in our evolution,
796
01:05:24,206 --> 01:05:28,509
And maybe even
in the story of the cosmos.
797
01:05:28,510 --> 01:05:29,911
It's the second
798
01:05:29,912 --> 01:05:32,647
And possibly the most important
stepping stone
799
01:05:32,648 --> 01:05:35,650
On humanity's journey
to the stars.
800
01:05:45,727 --> 01:05:47,862
Robot missions to mars
801
01:05:47,863 --> 01:05:51,065
Have revealed
a spectacularly beautiful
802
01:05:51,066 --> 01:05:53,734
Yet dangerous
and desolate place.
803
01:05:56,972 --> 01:05:59,841
I imagine that being
a human pioneer here
804
01:05:59,842 --> 01:06:02,310
Would be an exciting business.
805
01:06:16,191 --> 01:06:19,594
For a start, it's cold.
806
01:06:19,595 --> 01:06:23,898
It's 50 million miles further
from the sun than the earth,
807
01:06:23,899 --> 01:06:25,933
And so it receives
half as much warmth,
808
01:06:25,934 --> 01:06:30,238
And the temperatures
fluctuate wildly,
809
01:06:30,239 --> 01:06:32,740
From 80 degrees...
810
01:06:32,741 --> 01:06:37,245
To minus 200
in a matter of minutes.
811
01:06:41,016 --> 01:06:46,787
If the cold doesn't get you,
the low gravity will.
812
01:06:46,788 --> 01:06:49,991
Mars is just
half the size of the earth
813
01:06:49,992 --> 01:06:53,194
And has just 38% of its gravity.
814
01:06:53,195 --> 01:06:57,465
Over time,
explorers' bones would weaken,
815
01:06:57,466 --> 01:07:00,368
And their muscles
would waste away.
816
01:07:02,104 --> 01:07:03,971
Spend long enough on mars,
817
01:07:03,972 --> 01:07:06,207
And you could find yourself
too weak
818
01:07:06,208 --> 01:07:08,376
To safely return to earth.
819
01:07:14,316 --> 01:07:16,150
The low gravity also means
820
01:07:16,151 --> 01:07:19,987
Mars struggles to hold on
to an atmosphere.
821
01:07:19,988 --> 01:07:23,658
Here, there's nothing more than
a thin wisp of carbon dioxide
822
01:07:23,659 --> 01:07:27,728
At just 1/100 the pressure
of our air.
823
01:07:34,970 --> 01:07:40,474
Mars is also bathed in harmful
radiation from the sun.
824
01:07:40,475 --> 01:07:42,977
Even though it's further away,
825
01:07:42,978 --> 01:07:46,013
Unlike earth,
it has no magnetic field
826
01:07:46,014 --> 01:07:48,616
And no ozone layer
to protect it.
827
01:07:53,889 --> 01:07:55,990
Early explorers
would have to be careful
828
01:07:55,991 --> 01:07:58,693
To minimize their exposure.
829
01:07:58,694 --> 01:08:02,730
Perhaps they'd even
have to live underground.
830
01:08:10,238 --> 01:08:13,541
But one day,
I think it'll be possible
831
01:08:13,542 --> 01:08:17,111
To drastically alter
conditions on mars,
832
01:08:17,112 --> 01:08:19,814
Perhaps using
space-borne mirrors
833
01:08:19,815 --> 01:08:23,918
To supply warmth and power.
834
01:08:23,919 --> 01:08:27,088
With perfectly foreseeable
technology,
835
01:08:27,089 --> 01:08:29,256
Much more could become possible.
836
01:08:33,028 --> 01:08:36,998
If we could erect giant domes
made of glass and plastic
837
01:08:36,999 --> 01:08:39,100
To block out the radiation,
838
01:08:39,101 --> 01:08:42,269
Inside them,
we could enrich the atmosphere.
839
01:08:46,475 --> 01:08:48,609
500 years from now...
840
01:08:48,610 --> 01:08:51,746
Which really is
a very short time, indeed...
841
01:08:51,747 --> 01:08:54,248
I think mars will have
its own language,
842
01:08:54,249 --> 01:08:58,486
Its own currency,
it's own cuisine...
843
01:08:58,487 --> 01:08:59,854
Although I'll bet you
844
01:08:59,855 --> 01:09:02,490
You'll still be able
to get a hamburger somewhere.
845
01:09:06,828 --> 01:09:08,329
But it's clear that,
846
01:09:08,330 --> 01:09:10,765
As the universe
continues to age,
847
01:09:10,766 --> 01:09:12,800
Even advances like these
848
01:09:12,801 --> 01:09:16,303
Will not be enough to guarantee
humanity's existence
849
01:09:16,304 --> 01:09:18,305
For a very long time.
850
01:09:26,882 --> 01:09:29,850
Look further into the future,
851
01:09:29,851 --> 01:09:33,421
And ultimately our solar system
will follow the same path
852
01:09:33,422 --> 01:09:36,891
As countless billions
of solar systems before it
853
01:09:36,892 --> 01:09:39,126
And cease to exist.
854
01:09:43,165 --> 01:09:47,068
Right now, the sun is
in the middle of its life cycle.
855
01:09:47,069 --> 01:09:48,903
During this phase,
856
01:09:48,904 --> 01:09:52,606
It is getting gradually
hotter and brighter all the time
857
01:09:52,607 --> 01:09:56,277
By about 6% every billion years.
858
01:09:59,648 --> 01:10:02,283
In about 5 billion years,
859
01:10:02,284 --> 01:10:04,452
The sun's temperature
will have grown
860
01:10:04,453 --> 01:10:07,755
To nearly 200 billion degrees.
861
01:10:12,627 --> 01:10:15,362
At this point, the earth will be
862
01:10:15,363 --> 01:10:19,166
An unrecognizable ball
of molten rock,
863
01:10:19,167 --> 01:10:23,637
All life
having long since perished.
864
01:10:23,638 --> 01:10:27,308
This is our planet's
unavoidable destiny,
865
01:10:27,309 --> 01:10:30,878
But that's not all
the sun has in store.
866
01:10:33,148 --> 01:10:36,650
As it runs out of fuel,
the sun will start to expand,
867
01:10:36,651 --> 01:10:40,387
Turning into what's called
a red giant.
868
01:10:40,388 --> 01:10:44,525
It will change from being
the object that gave us life
869
01:10:44,526 --> 01:10:47,862
To the one that annihilates it.
870
01:10:50,198 --> 01:10:52,266
In about 7 billion years,
871
01:10:52,267 --> 01:10:55,369
The sun will be
200 times bigger,
872
01:10:55,370 --> 01:11:00,074
About 200 million miles across.
873
01:11:00,075 --> 01:11:03,210
So vast, it will obliterate
the inner planets
874
01:11:03,211 --> 01:11:05,913
One after the other...
875
01:11:05,914 --> 01:11:08,082
Mercury, venus,
876
01:11:08,083 --> 01:11:11,485
And most probably
the lifeless earth.
877
01:11:30,605 --> 01:11:33,741
But as the universe
continues to evolve...
878
01:11:33,742 --> 01:11:35,776
...At its own relentless pace,
879
01:11:35,777 --> 01:11:39,613
New opportunities
will present themselves to us,
880
01:11:39,614 --> 01:11:43,851
If we are able to preserve
the life that the cosmos made.
881
01:11:51,092 --> 01:11:56,363
This is gliese 581d.
882
01:11:56,364 --> 01:11:59,900
It's a large, rocky,
earth-like planet,
883
01:11:59,901 --> 01:12:02,135
The nearest known.
884
01:12:02,136 --> 01:12:06,840
It's just possible
that this world or one like it
885
01:12:06,841 --> 01:12:10,777
Could, in the future,
become home to the human race,
886
01:12:10,778 --> 01:12:15,882
A second sanctuary against the
unforgiving blackness of space.
887
01:12:21,189 --> 01:12:23,957
Discovered in 2007,
888
01:12:23,958 --> 01:12:27,060
It's seven times bigger
than earth.
889
01:12:27,061 --> 01:12:31,498
It orbits a star smaller
and redder than our own,
890
01:12:31,499 --> 01:12:35,102
But it lies at just
the right distance from its sun
891
01:12:35,103 --> 01:12:38,772
To allow water to exist
on the surface.
892
01:12:41,209 --> 01:12:45,479
But even if this is
the perfect home away from home,
893
01:12:45,480 --> 01:12:49,116
There is a fundamental problem
we will have to overcome.
894
01:12:53,588 --> 01:12:59,459
Gliese is
a very, very long way away...
895
01:13:01,362 --> 01:13:06,533
...More than 20 light-years
from earth.
896
01:13:06,534 --> 01:13:11,838
That's 120 trillion miles.
897
01:13:11,839 --> 01:13:15,075
To get some idea
of this extraordinary distance
898
01:13:15,076 --> 01:13:17,277
And the challenge it presents,
899
01:13:17,278 --> 01:13:20,480
I'm going to imagine
that we could hitch a ride
900
01:13:20,481 --> 01:13:24,718
On the fastest man-made object
in existence.
901
01:13:32,627 --> 01:13:37,230
Voyager was launched in 1977.
902
01:13:37,231 --> 01:13:39,466
Now over 30 years old,
903
01:13:39,467 --> 01:13:42,936
It's traveled
more than 13 billion miles.
904
01:13:47,074 --> 01:13:52,245
Its mission so far has taken it
to jupiter and saturn.
905
01:13:54,482 --> 01:13:58,418
By using their gravity
to boost its speed,
906
01:13:58,419 --> 01:14:02,155
The little spacecraft
has entered the record books.
907
01:14:04,759 --> 01:14:06,660
It might not look fast,
908
01:14:06,661 --> 01:14:11,765
But voyager is racing through
space at 11 miles a second.
909
01:14:14,068 --> 01:14:18,171
On earth, 11 miles a second
looks like this.
910
01:14:23,811 --> 01:14:27,614
It's 39,000 miles an hour.
911
01:14:33,421 --> 01:14:34,788
At this speed,
912
01:14:34,789 --> 01:14:40,026
We could circle e globe
1 1/2 times in an hour.
913
01:14:40,027 --> 01:14:43,563
So, how long
would it take a spaceship
914
01:14:43,564 --> 01:14:45,365
Traveling at voyager' speed
915
01:14:45,366 --> 01:14:49,469
To get to the nearest
earth-like planet, gliese?
916
01:14:52,540 --> 01:14:57,277
The answer reveals
the true scale of the cosmos...
917
01:14:59,046 --> 01:15:02,482
...For even traveling
at 11 miles a second,
918
01:15:02,483 --> 01:15:04,150
The journey to gliese
919
01:15:04,151 --> 01:15:09,089
Would still take
over 350,000 years.
920
01:15:14,929 --> 01:15:16,596
I think we have a chance
921
01:15:16,597 --> 01:15:20,200
To become a lasting part
of the ever-changing universe
922
01:15:20,201 --> 01:15:23,770
And to discover what
other wonders it might hold,
923
01:15:23,771 --> 01:15:25,605
But to do this,
924
01:15:25,606 --> 01:15:28,375
We will have to develop
new technology
925
01:15:28,376 --> 01:15:31,378
On an enormous scale.
926
01:15:31,379 --> 01:15:35,515
And that's going to take
some serious engineering.
927
01:15:45,613 --> 01:15:48,615
There are many
in the field of cosmology
928
01:15:48,616 --> 01:15:51,451
Who believe, as I do,
929
01:15:51,452 --> 01:15:54,254
That finding ways
to travel great distances
930
01:15:54,255 --> 01:15:55,889
Will be essential
931
01:15:55,890 --> 01:15:59,826
To keeping humankind alive
in the universe.
932
01:16:02,664 --> 01:16:04,665
If we could build a machine
933
01:16:04,666 --> 01:16:06,967
Capable of traveling
to other solar systems,
934
01:16:06,968 --> 01:16:10,070
We'd open up
a fascinating possibility...
935
01:16:10,071 --> 01:16:15,142
The survival of the human race
for billions of years.
936
01:16:25,553 --> 01:16:28,288
Present-day engineers
have begun thinking
937
01:16:28,289 --> 01:16:31,825
About the principals
of building such a ship.
938
01:16:31,826 --> 01:16:34,561
This is what it might look like.
939
01:16:38,433 --> 01:16:41,335
It could use atomic energy
940
01:16:41,336 --> 01:16:45,138
Or perhaps more exotic fuel,
such as antimatter,
941
01:16:45,139 --> 01:16:49,409
Supplying it
with enormous amounts of power,
942
01:16:49,410 --> 01:16:54,515
Yet I think the main challenges
won't be technical.
943
01:16:54,516 --> 01:16:56,984
The first will be financial.
944
01:17:00,522 --> 01:17:04,057
The cost of constructing
an interstellar spacecraft
945
01:17:04,058 --> 01:17:05,592
Would be huge,
946
01:17:05,593 --> 01:17:07,194
And for the society
that made it,
947
01:17:07,195 --> 01:17:10,697
There would be little payback.
948
01:17:10,698 --> 01:17:14,101
They would never see it again.
949
01:17:25,680 --> 01:17:28,015
So constructing such a machine
950
01:17:28,016 --> 01:17:31,518
Will either be the greatest act
of generosity in history,
951
01:17:31,519 --> 01:17:35,789
Or it will have to be funded
by the travelers themselves.
952
01:17:37,492 --> 01:17:40,727
And that raises
the second problem.
953
01:17:43,231 --> 01:17:46,700
Even if it could travel
mind-numbingly fast...
954
01:17:46,701 --> 01:17:49,870
Say 1,000 times faster
than voyager,
955
01:17:49,871 --> 01:17:53,640
11,000 miles a second...
956
01:17:53,641 --> 01:17:57,110
A journey
to the nearest star system
957
01:17:57,111 --> 01:18:00,847
Would still take...
958
01:18:00,848 --> 01:18:03,750
73 years.
959
01:18:13,595 --> 01:18:15,796
Such a long trip means
960
01:18:15,797 --> 01:18:18,866
That at least one whole
generation of humans
961
01:18:18,867 --> 01:18:22,469
Would have to live
their entire lives in space,
962
01:18:22,470 --> 01:18:27,341
And we couldn't exactly say they
had volunteered for the mission.
963
01:18:32,047 --> 01:18:36,116
The ethics of sending a
human cargo on such a voyage
964
01:18:36,117 --> 01:18:38,319
Would have to be
carefully considered.
965
01:18:42,190 --> 01:18:45,559
Unless we could extend
human life spans
966
01:18:45,560 --> 01:18:48,762
To long enough
to make such massive journeys.
967
01:18:52,367 --> 01:18:57,438
And that, I think, is what
we will ultimately end up doing.
968
01:19:01,710 --> 01:19:04,178
The process has already begun...
969
01:19:04,179 --> 01:19:07,281
...As I know
from personal experience.
970
01:19:09,551 --> 01:19:12,219
My muscles no longer function,
971
01:19:12,220 --> 01:19:17,224
Although my eyes and my brain
are still working pretty well.
972
01:19:17,225 --> 01:19:21,295
But technology helps me
to move and communicate.
973
01:19:21,296 --> 01:19:22,696
In the future,
974
01:19:22,697 --> 01:19:26,533
Technology will do much more
than that for all of us.
975
01:19:30,405 --> 01:19:32,973
Within the next 1,000 years,
976
01:19:32,974 --> 01:19:35,509
We will see
unprecedented changes
977
01:19:35,510 --> 01:19:37,945
In our physical capabilities.
978
01:19:41,483 --> 01:19:44,818
Genetic engineering
will give us longer life spans
979
01:19:44,819 --> 01:19:47,221
And greater intelligence.
980
01:19:49,991 --> 01:19:52,960
Modifying our genes
could give us skin
981
01:19:52,961 --> 01:19:56,230
That protects us
from radiation...
982
01:19:56,231 --> 01:20:00,801
The ability to breathe
poisonous atmospheres...
983
01:20:00,802 --> 01:20:03,404
Resistance to infection.
984
01:20:07,342 --> 01:20:09,076
We may even develop
985
01:20:09,077 --> 01:20:11,678
Sophisticated
artificial life-forms,
986
01:20:11,679 --> 01:20:14,882
Using synthetic dna,
987
01:20:14,883 --> 01:20:18,385
Custom-designed for
the challenges of space travel.
988
01:20:20,755 --> 01:20:24,558
These advances would allow us
to survive long journeys
989
01:20:24,559 --> 01:20:26,960
And inhospitable worlds.
990
01:20:29,697 --> 01:20:31,832
I imagine a time
when our descendants
991
01:20:31,833 --> 01:20:37,171
Spread to planets orbiting
other stars all over our galaxy
992
01:20:37,172 --> 01:20:40,674
And perhaps further still,
993
01:20:40,675 --> 01:20:43,076
Carrying their biological cargo
994
01:20:43,077 --> 01:20:45,846
To solar systems
we have yet to discover.
995
01:20:48,349 --> 01:20:50,651
Ships like this one
996
01:20:50,652 --> 01:20:55,255
Could be designed
to split up and spread out.
997
01:21:07,135 --> 01:21:09,937
A true diaspora of life
998
01:21:09,938 --> 01:21:13,974
That would have started
with us.
999
01:21:45,039 --> 01:21:48,475
As we journey
across interstellar space,
1000
01:21:48,476 --> 01:21:52,446
I'm sure that we will unlock
nature's deepest secrets.
1001
01:21:56,217 --> 01:21:58,986
My great hope
is that we will discover
1002
01:21:58,987 --> 01:22:00,988
How the universe will end
1003
01:22:00,989 --> 01:22:04,591
And solve
the ultimate mystery...
1004
01:22:04,592 --> 01:22:08,762
Why the universe
ever existed at all.
1005
01:22:20,333 --> 01:22:23,269
I once gave a lecture in japan,
1006
01:22:23,270 --> 01:22:26,705
Where I was asked not to mention
the end of the universe
1007
01:22:26,706 --> 01:22:31,210
In case it affected
the japanese stock market.
1008
01:22:31,211 --> 01:22:33,579
Well,
I don't know if or when...
1009
01:22:33,580 --> 01:22:35,548
...The universe will end,
1010
01:22:35,549 --> 01:22:38,984
But for those of you who are
nervous about your investments,
1011
01:22:38,985 --> 01:22:42,588
I think it's a bit early
to sell.
1012
01:22:46,860 --> 01:22:50,463
At 13.7 billion years old,
1013
01:22:50,464 --> 01:22:54,166
Our universe
is still in its youth.
1014
01:22:59,005 --> 01:23:02,274
The earliest date we
cosmologists think it could end
1015
01:23:02,275 --> 01:23:06,245
Is 30 billion years from now.
1016
01:23:06,246 --> 01:23:09,215
There's still
plenty of action to come.
1017
01:23:14,221 --> 01:23:17,389
Even long after our sun
has died,
1018
01:23:17,390 --> 01:23:19,692
New stars will be born,
1019
01:23:19,693 --> 01:23:22,495
Some of which will have
new planets around them,
1020
01:23:22,496 --> 01:23:27,399
Made of the same atoms
that make you and me.
1021
01:23:27,400 --> 01:23:32,438
Maybe we'll end up as part
of some future alien ecosystem,
1022
01:23:32,439 --> 01:23:37,276
Although that's probably
a bit of a long shot.
1023
01:23:37,277 --> 01:23:41,680
What's true is that we are only
the temporary custodians
1024
01:23:41,681 --> 01:23:44,250
Of the particles
which we are made of.
1025
01:23:44,251 --> 01:23:47,620
They will go on to lead
a future existence
1026
01:23:47,621 --> 01:23:51,190
In the enormous universe
that made them.
1027
01:23:54,995 --> 01:24:00,599
Certainly, gravity will continue
its tireless, incessant work.
1028
01:24:00,600 --> 01:24:03,669
It will go on shaping
the vast strings of galaxies
1029
01:24:03,670 --> 01:24:08,274
As it has
ever since the big bang.
1030
01:24:08,275 --> 01:24:13,212
Using supercomputers, we can
simulate how gravity, even now,
1031
01:24:13,213 --> 01:24:16,448
Causes galaxies
to be attracted to one another,
1032
01:24:16,449 --> 01:24:21,053
Resulting in vast,
slow collisions.
1033
01:24:29,062 --> 01:24:33,132
Our galaxy will merge
with its nearest neighbor,
1034
01:24:33,133 --> 01:24:35,000
The andromeda galaxy,
1035
01:24:35,001 --> 01:24:38,237
In around 3 billion years.
1036
01:24:38,238 --> 01:24:40,172
A slow-motion collision
1037
01:24:40,173 --> 01:24:44,176
That will take place
over 2 billion years.
1038
01:24:58,525 --> 01:25:02,461
The same process is happening
all over the cosmos.
1039
01:25:02,462 --> 01:25:04,863
Entire clusters of galaxies
1040
01:25:04,864 --> 01:25:07,700
Are constantly colliding
and reforming...
1041
01:25:09,336 --> 01:25:11,003
...Giant collisions
1042
01:25:11,004 --> 01:25:14,206
As trillions of stars
pull on one another,
1043
01:25:14,207 --> 01:25:19,044
Their vast masses
causing them to spin and dance.
1044
01:25:24,551 --> 01:25:27,519
Gravity is driving
the cosmic clockwork
1045
01:25:27,520 --> 01:25:30,689
As it has done
ever since the big bang.
1046
01:25:34,561 --> 01:25:37,496
This is what
the universe looks like
1047
01:25:37,497 --> 01:25:41,734
When we are released
from time on a human sle.
1048
01:25:49,743 --> 01:25:54,546
But will this cosmic whirlpool
go on forever...
1049
01:25:54,547 --> 01:25:58,784
As an endless maelstrom
of mass and energy,
1050
01:25:58,785 --> 01:26:01,086
Space and time?
1051
01:26:05,859 --> 01:26:10,462
What an extraordinary question
to even be able to ask.
1052
01:26:18,271 --> 01:26:22,775
I think the solution
lies back where we began...
1053
01:26:22,776 --> 01:26:24,576
With the big bang.
1054
01:26:30,216 --> 01:26:32,318
Ask yourself this.
1055
01:26:32,319 --> 01:26:36,155
What caused the expansion
or inflation of the universe
1056
01:26:36,156 --> 01:26:38,424
In the first place?
1057
01:26:41,094 --> 01:26:46,365
When we can answer that and
fully understand the big bang,
1058
01:26:46,366 --> 01:26:50,936
We will also learn
the fate of the universe.
1059
01:26:50,937 --> 01:26:55,774
The key to it all
is something called dark energy,
1060
01:26:55,775 --> 01:27:00,946
A mysterious form of energy
that pushes space itself apart,
1061
01:27:00,947 --> 01:27:04,817
Even as gravity
is making matter clump together.
1062
01:27:07,620 --> 01:27:09,621
It seems as if dark energy
1063
01:27:09,622 --> 01:27:13,092
Supplied the kick
that inflated the universe,
1064
01:27:13,093 --> 01:27:15,761
Although
we're not quite sure how.
1065
01:27:17,764 --> 01:27:20,532
What is certain is that
the fate of the universe
1066
01:27:20,533 --> 01:27:24,837
Depends on how
this dark energy behaves.
1067
01:27:24,838 --> 01:27:28,741
If the dark energy
slowly weakens,
1068
01:27:28,742 --> 01:27:31,677
Then gravity
could get the upper hand,
1069
01:27:31,678 --> 01:27:34,012
And in 20 billion years or so,
1070
01:27:34,013 --> 01:27:36,248
The universe
would go into reverse
1071
01:27:36,249 --> 01:27:39,485
And drive everything back
to whence it came.
1072
01:27:41,721 --> 01:27:45,257
In a strange reversal
of the big bang,
1073
01:27:45,258 --> 01:27:49,528
Space itself would contract.
1074
01:27:49,529 --> 01:27:53,565
This theory is known
as the big crunch.
1075
01:27:55,869 --> 01:27:58,704
In the end,
if the theory is right,
1076
01:27:58,705 --> 01:28:01,073
In 30 billion years from now,
1077
01:28:01,074 --> 01:28:02,941
All the matter of the universe
1078
01:28:02,942 --> 01:28:07,045
Would be swallowed
by a single black hole.
1079
01:28:13,486 --> 01:28:17,823
The entire universe would exist
as one tiny point,
1080
01:28:17,824 --> 01:28:21,994
Much as it was at the instant
of the big bang.
1081
01:28:28,835 --> 01:28:31,003
But although
that's a neat ending,
1082
01:28:31,004 --> 01:28:33,639
I think that it's more likely
that dark energy
1083
01:28:33,640 --> 01:28:38,043
Will drive the expansion
of the universe forever
1084
01:28:38,044 --> 01:28:41,280
And that, ultimately, everything
will just keep spreading out
1085
01:28:41,281 --> 01:28:45,317
Until the universe
is cold and dark.
1086
01:28:45,318 --> 01:28:48,587
Everything will become
so far apart
1087
01:28:48,588 --> 01:28:51,590
That even gravity
will be defeated.
1088
01:28:51,591 --> 01:28:55,227
I think a big chill
is what we've got in store,
1089
01:28:55,228 --> 01:28:57,229
Not a big crunch.
1090
01:28:58,898 --> 01:29:04,403
So will this be the end of us
and life as we know it?
1091
01:29:04,404 --> 01:29:07,406
Or will we have figured out
how to navigate
1092
01:29:07,407 --> 01:29:09,975
To a new universe before then?
1093
01:29:09,976 --> 01:29:13,946
I think we will only know
when we truly understand
1094
01:29:13,947 --> 01:29:16,548
Why the universe exists at all.
1095
01:29:18,251 --> 01:29:20,185
Perhaps then,
1096
01:29:20,186 --> 01:29:23,889
When we finally unravel
the whole cosmic puzzle,
1097
01:29:23,890 --> 01:29:28,861
We will become masters
not just of our universe,
1098
01:29:28,862 --> 01:29:31,530
But the universe next door.
86701
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