All language subtitles for BBC.Everything.and.Nothing.2of2.Nothing.PDTV.XviD.MP3.MVGroup.org.eng
Afrikaans
Albanian
Amharic
Arabic
Armenian
Azerbaijani
Basque
Belarusian
Bengali
Bosnian
Bulgarian
Catalan
Cebuano
Chichewa
Chinese (Simplified)
Chinese (Traditional)
Corsican
Croatian
Czech
Danish
Dutch
English
Esperanto
Estonian
Filipino
Finnish
French
Frisian
Galician
Georgian
German
Greek
Gujarati
Haitian Creole
Hausa
Hawaiian
Hebrew
Hindi
Hmong
Hungarian
Icelandic
Igbo
Indonesian
Irish
Italian
Japanese
Javanese
Kannada
Kazakh
Khmer
Korean
Kurdish (Kurmanji)
Kyrgyz
Lao
Latin
Latvian
Lithuanian
Luxembourgish
Macedonian
Malagasy
Malay
Malayalam
Maltese
Maori
Marathi
Mongolian
Myanmar (Burmese)
Nepali
Norwegian
Pashto
Persian
Polish
Portuguese
Punjabi
Romanian
Russian
Samoan
Scots Gaelic
Serbian
Sesotho
Shona
Sindhi
Sinhala
Slovak
Slovenian
Somali
Spanish
Sundanese
Swahili
Swedish
Tajik
Tamil
Telugu
Thai
Turkish
Ukrainian
Urdu
Uzbek
Vietnamese
Welsh
Xhosa
Yiddish
Yoruba
Zulu
Odia (Oriya)
Kinyarwanda
Turkmen
Tatar
Uyghur
Would you like to inspect the original subtitles? These are the user uploaded subtitles that are being translated:
1
00:00:10,560 --> 00:00:13,400
What is nothing?
2
00:00:13,400 --> 00:00:17,480
It's an extremely, extremely
difficult question to answer,
3
00:00:17,480 --> 00:00:19,440
because if you think about it,
4
00:00:19,440 --> 00:00:24,640
wherever you look around you, there
always seems to be something there.
5
00:00:32,000 --> 00:00:37,000
Things appear almost impossible
to escape from.
6
00:00:38,320 --> 00:00:41,400
Even just trying to
imagine true nothingness
7
00:00:41,400 --> 00:00:45,480
seems like an impossible task.
8
00:00:47,720 --> 00:00:50,720
But this is more than just
a philosophical question.
9
00:00:50,720 --> 00:00:53,120
I have here a box. What would happen
10
00:00:53,120 --> 00:00:57,440
if I were to remove everything
I possibly could from inside it?
11
00:00:57,440 --> 00:01:01,720
All the air, dust,
every last single atom,
12
00:01:01,720 --> 00:01:03,760
until there was no thing left.
13
00:01:05,240 --> 00:01:09,360
What, then, exists inside
the space in the box?
14
00:01:09,360 --> 00:01:12,240
Is it really nothing?
15
00:01:14,160 --> 00:01:17,000
You might wonder why this matters.
16
00:01:17,000 --> 00:01:22,960
Well, emptiness is what makes up
almost the entire universe.
17
00:01:22,960 --> 00:01:26,400
Even the atoms
that make up our bodies
18
00:01:26,400 --> 00:01:32,280
and the physical world around us
comprise mostly of empty space.
19
00:01:37,400 --> 00:01:39,640
This film tells the story
20
00:01:39,640 --> 00:01:44,800
of how we've begun to understand
what is known as the void,
21
00:01:44,800 --> 00:01:46,560
or the vacuum.
22
00:01:46,560 --> 00:01:49,640
Emptiness, or simply nothing.
23
00:01:49,640 --> 00:01:54,440
It's about reality
at the very furthest reaches
of human perception.
24
00:01:54,440 --> 00:01:59,840
A place where the deepest mysteries
of the universe may be held.
25
00:02:11,840 --> 00:02:13,880
This film reveals how,
26
00:02:13,880 --> 00:02:16,400
using ingenious technology,
27
00:02:16,400 --> 00:02:20,400
humans have transcended
their physical senses,
28
00:02:20,400 --> 00:02:25,520
and found ways to understand
and probe the universe
29
00:02:25,520 --> 00:02:27,880
at the smallest scales.
30
00:02:33,360 --> 00:02:39,400
Today, we believe the void
contains nature's deepest secrets.
31
00:02:39,400 --> 00:02:44,080
It might even explain
why we exist at all.
32
00:02:44,080 --> 00:02:47,200
And that's because,
to the best of our knowledge,
33
00:02:47,200 --> 00:02:53,040
the entire universe
appeared nearly 14 billion years ago
34
00:02:53,040 --> 00:02:55,480
out of nothing.
35
00:03:15,000 --> 00:03:16,920
For over 1,000 years,
36
00:03:16,920 --> 00:03:21,920
our understanding of empty space
was defined by one man -
37
00:03:21,920 --> 00:03:24,800
the Greek philosopher Aristotle.
38
00:03:27,600 --> 00:03:32,720
To Aristotle, the concept of
nothingness was deeply disturbing.
39
00:03:32,720 --> 00:03:37,560
It seemed to present all sorts
of problems and paradoxes.
40
00:03:39,880 --> 00:03:44,240
He came to believe that nature
would forever fight against
41
00:03:44,240 --> 00:03:46,760
the creation of true nothingness.
42
00:03:46,760 --> 00:03:50,640
As he put it,
nature abhors a vacuum.
43
00:03:54,320 --> 00:03:59,640
These words stuck for over 1,000
years, because after Aristotle,
44
00:03:59,640 --> 00:04:04,640
people who attempted to make empty
space faced an uphill struggle.
45
00:04:04,640 --> 00:04:08,680
It seemed nature was indeed
doing everything in its power
46
00:04:08,680 --> 00:04:10,720
to stop them.
47
00:04:11,680 --> 00:04:14,680
Well, the whole mystery
of nothingness
48
00:04:14,680 --> 00:04:18,400
is contained inside
this simple drinking straw.
49
00:04:18,400 --> 00:04:22,080
Let me demonstrate.
If I suck out the air
from the top of the straw...
50
00:04:23,400 --> 00:04:28,320
..more air immediately rushes in
to fill the space left behind.
51
00:04:28,320 --> 00:04:33,000
And even more weirdly,
if I block off the bottom
of the straw and suck...
52
00:04:35,400 --> 00:04:39,280
..the walls of the straw
collapse in on themselves.
53
00:04:39,280 --> 00:04:44,720
It's as though the universe
won't allow me to make nothingness.
54
00:04:44,720 --> 00:04:47,840
And it gets even weirder.
If I take a sip of my drink...
55
00:04:50,640 --> 00:04:52,400
..and pinch off the top,
56
00:04:52,400 --> 00:04:55,960
then it seems nature
is so intent on stopping me
57
00:04:55,960 --> 00:04:59,360
that even the law
of gravity is suspended.
58
00:04:59,360 --> 00:05:03,000
So it's not hard to
understand why people believed
59
00:05:03,000 --> 00:05:07,200
that it was impossible
to make truly empty space.
60
00:05:09,680 --> 00:05:12,920
But there is
a very simple explanation
61
00:05:12,920 --> 00:05:15,760
for why a straw behaves like this -
62
00:05:15,760 --> 00:05:21,680
a reason that would
come as a profound shock
to the people who worked it out.
63
00:05:21,680 --> 00:05:25,920
By the 17th century, some strange
exceptions were being found
64
00:05:25,920 --> 00:05:28,680
to nature's abhorrence
of empty space.
65
00:05:28,680 --> 00:05:30,920
And it was beginning to seem
66
00:05:30,920 --> 00:05:36,080
like there may be ways of tricking
nothingness into existence.
67
00:05:38,360 --> 00:05:43,240
The man who would finally
do what Aristotle thought impossible
68
00:05:43,240 --> 00:05:48,120
was an Italian Jesuit
called Evangelista Torricelli.
69
00:05:51,000 --> 00:05:55,040
Torricelli's experiment would,
for the first time,
70
00:05:55,040 --> 00:06:00,560
create and capture empty space for
long enough to begin to study it.
71
00:06:03,200 --> 00:06:06,560
This is how the experiment went,
with a tube filled with mercury
72
00:06:06,560 --> 00:06:09,400
and a finger really
strongly clamped over the end.
73
00:06:09,400 --> 00:06:11,720
The tube was then turned upside down
74
00:06:11,720 --> 00:06:15,920
and then placed
into the bath of mercury.
75
00:06:15,920 --> 00:06:19,040
At this point,
the mercury was released.
76
00:06:19,040 --> 00:06:21,600
You can now see it dropping down.
77
00:06:21,600 --> 00:06:25,160
And then it stops.
78
00:06:25,160 --> 00:06:28,120
So I guess
the important thing is that...
79
00:06:28,120 --> 00:06:30,720
that isn't trapped air.
80
00:06:30,720 --> 00:06:36,120
We started with a tube
filled with mercury, and all
we did was we let it drain out.
81
00:06:36,120 --> 00:06:40,360
But it doesn't drain out completely,
it reaches a level and stops.
82
00:06:41,720 --> 00:06:47,080
Torricelli's experiments had not
only created an airless space,
83
00:06:47,080 --> 00:06:51,480
it had also shown that the
atmosphere has a specific weight.
84
00:06:53,560 --> 00:06:57,280
The reason my straw crumples
when I suck the air out
85
00:06:57,280 --> 00:07:01,080
is because of the pressure of
the atmosphere that surrounds it.
86
00:07:02,280 --> 00:07:06,600
But Torricelli's apparatus
was overcoming this
87
00:07:06,600 --> 00:07:11,480
by using the extreme weight
of mercury and a rigid glass tube.
88
00:07:11,480 --> 00:07:13,960
The level of mercury in his tube
89
00:07:13,960 --> 00:07:17,960
was a measure of
the weight of the atmosphere.
90
00:07:17,960 --> 00:07:22,200
The level is, of course, determined
by the weight of the mercury
on the one hand,
91
00:07:22,200 --> 00:07:25,440
and the weight of the air
pressing down on the other.
92
00:07:25,440 --> 00:07:28,720
And so the two balance out,
like scales.
93
00:07:28,720 --> 00:07:31,960
They'd found a way
to weigh the atmosphere.
94
00:07:31,960 --> 00:07:35,200
And Torricelli wrote
this fantastic phrase.
95
00:07:35,200 --> 00:07:39,600
He said, "Noi viviamo
sommersi nel fondo d'un
pelago d'aria elementare."
96
00:07:39,600 --> 00:07:43,760
"We live at the bottom
of an ocean of air."
97
00:07:43,760 --> 00:07:47,880
Suddenly, the air really
was a substance.
98
00:07:47,880 --> 00:07:52,240
But I guess the real mystery
for me now is, what's inside here?
99
00:07:52,240 --> 00:07:55,400
Could this really be nothingness?
100
00:07:55,400 --> 00:07:56,920
Indeed.
101
00:07:59,520 --> 00:08:02,760
In revealing
that the air has a weight
102
00:08:02,760 --> 00:08:07,680
and that it's pushing down on us all
the time, filling any space it can,
103
00:08:07,680 --> 00:08:11,800
Torricelli had managed
to create an empty space,
104
00:08:11,800 --> 00:08:15,840
a type of nothingness
that could now be studied.
105
00:08:20,280 --> 00:08:24,480
Over 1,000 years of thinking
about the way nature worked
106
00:08:24,480 --> 00:08:26,400
was beginning to crumble.
107
00:08:32,000 --> 00:08:35,960
Medieval philosophy, much
influenced by Aristotle, supposed,
108
00:08:35,960 --> 00:08:39,840
reasonably enough, that there is no
such thing as empty space in nature.
109
00:08:39,840 --> 00:08:42,680
And yet here is
a pretty simple device -
110
00:08:42,680 --> 00:08:46,480
a long, thin glass tube
with some liquid in it -
111
00:08:46,480 --> 00:08:50,280
which is able to produce, says
Torricelli, an empty space,
112
00:08:50,280 --> 00:08:54,080
thus showing that Aristotle
and his disciples are wrong.
113
00:08:54,080 --> 00:08:58,760
How can you show that centuries of
philosophical tradition are wrong
114
00:08:58,760 --> 00:09:00,240
just by doing a trick?
115
00:09:00,240 --> 00:09:02,040
That didn't seem right at all.
116
00:09:05,080 --> 00:09:07,200
But Torricelli was right,
117
00:09:07,200 --> 00:09:12,240
and it would fall to philosopher
and scientist Blaise Pascal
118
00:09:12,240 --> 00:09:14,800
to develop and refine his work.
119
00:09:14,800 --> 00:09:18,560
As Pascal began investigating
Torricelli's ideas,
120
00:09:18,560 --> 00:09:22,400
he discovered even more
peculiar properties.
121
00:09:22,400 --> 00:09:28,320
In Paris, he carried a mercury
tube to the top of a huge tower
122
00:09:28,320 --> 00:09:34,120
and recorded the mercury
dropping to a lower level
than it had been on the ground.
123
00:09:34,120 --> 00:09:38,800
It seemed the pressure of the air
fell as you went higher.
124
00:09:43,880 --> 00:09:48,720
Pascal's experiments would lead
to the realisation that the Earth
125
00:09:48,720 --> 00:09:54,160
is cocooned in an atmosphere
that rapidly thins out
the higher you go...
126
00:09:56,040 --> 00:10:01,800
..eventually becoming the cold,
silent expanse of space.
127
00:10:04,680 --> 00:10:09,840
Torricelli and Pascal had begun
to unravel a profound truth -
128
00:10:09,840 --> 00:10:12,560
nothing is everywhere.
129
00:10:16,080 --> 00:10:20,360
Our Earth is merely
a tiny speck of dust,
130
00:10:20,360 --> 00:10:23,560
floating through a vast expanse
131
00:10:23,560 --> 00:10:26,960
of an utterly silent,
inhospitable void.
132
00:10:28,600 --> 00:10:31,560
Nature doesn't abhor a vacuum.
133
00:10:31,560 --> 00:10:35,440
A vacuum is nature's default state.
134
00:10:44,480 --> 00:10:48,760
So what was this vast, empty space?
135
00:10:49,720 --> 00:10:53,080
Now it was possible
to make it on Earth,
136
00:10:53,080 --> 00:10:56,120
scientists became deeply curious.
137
00:10:56,120 --> 00:11:01,600
What exactly were
the properties of nothingness?
138
00:11:01,600 --> 00:11:04,600
After Torricelli
and Pascal's experiments,
139
00:11:04,600 --> 00:11:06,680
many scientists became fascinated
140
00:11:06,680 --> 00:11:09,320
with studying
the properties of the vacuum.
141
00:11:09,320 --> 00:11:12,000
And they found some very odd things.
142
00:11:12,000 --> 00:11:15,720
For instance, placing a ringing
bell inside it became silent,
143
00:11:15,720 --> 00:11:18,040
you couldn't hear it
from the outside,
144
00:11:18,040 --> 00:11:20,760
because, having removed all the air,
145
00:11:20,760 --> 00:11:24,080
there was no medium
to carry the sound waves.
146
00:11:24,080 --> 00:11:28,160
Most intriguingly, although
you couldn't hear the bell,
147
00:11:28,160 --> 00:11:30,920
you could still see it.
148
00:11:30,920 --> 00:11:35,320
This means light must be
travelling through the vacuum.
149
00:11:35,320 --> 00:11:37,480
But how could it do this?
150
00:11:37,480 --> 00:11:41,560
For those scientists carrying out
experiments with the vacuum,
151
00:11:41,560 --> 00:11:44,000
there was just one
simple conclusion.
152
00:11:44,000 --> 00:11:47,320
The vacuum wasn't empty after all.
153
00:11:47,320 --> 00:11:49,640
The fact that
they could see inside it
154
00:11:49,640 --> 00:11:53,360
meant that there still had
to be something left in there.
155
00:11:53,360 --> 00:11:56,080
Just as air carries sound waves,
156
00:11:56,080 --> 00:12:00,680
they believed there had to be
a medium carrying the light waves.
157
00:12:00,680 --> 00:12:05,240
And whatever it was, it was proving
very difficult to get rid of.
158
00:12:09,360 --> 00:12:13,280
The nothingness that had been
glimpsed by Torricelli and Pascal
159
00:12:13,280 --> 00:12:16,240
now appeared to be a something -
160
00:12:16,240 --> 00:12:20,560
a mysterious substance
which carried waves of light.
161
00:12:20,560 --> 00:12:24,360
And if that this substance
existed in our vacuums on Earth,
162
00:12:24,360 --> 00:12:29,640
it meant that it also
existed out there.
163
00:12:29,640 --> 00:12:35,520
It appeared once again
that nothingness
could not exist in nature.
164
00:12:35,520 --> 00:12:41,440
Everything in the universe
appeared to be sitting
within an invisible medium,
165
00:12:41,440 --> 00:12:45,760
what scientists called
the luminiferous aether.
166
00:12:49,280 --> 00:12:52,440
It was clear for many reasons,
many good reasons,
167
00:12:52,440 --> 00:12:54,480
that light was a kind of wave.
168
00:12:54,480 --> 00:12:59,360
But if light is a kind of wave,
what's it a wave in?
169
00:12:59,360 --> 00:13:04,640
Sound waves are waves in air,
light waves are waves in
what came to be called,
170
00:13:04,640 --> 00:13:08,000
from the early 1800s,
the luminiferous aether,
171
00:13:08,000 --> 00:13:12,680
the light-carrying fluid
that fills all space.
172
00:13:12,680 --> 00:13:18,680
If there's a fluid that fills all
space, if light is a wave,
nowhere is empty,
173
00:13:18,680 --> 00:13:21,440
because light travels everywhere.
174
00:13:21,440 --> 00:13:26,120
So at the very moment when
it seemed absolutely plausible
175
00:13:26,120 --> 00:13:29,560
that there can be empty space,
it is obvious that there isn't.
176
00:13:29,560 --> 00:13:33,520
And that there's this stuff
called aether that carries light.
177
00:13:33,520 --> 00:13:37,040
The problem was that this aether
178
00:13:37,040 --> 00:13:41,720
appeared to be so subtle
and so intangible
179
00:13:41,720 --> 00:13:44,760
that it eluded
all attempts to measure it.
180
00:13:45,800 --> 00:13:49,720
It wouldn't be until the end of
the 19th century that an experiment
181
00:13:49,720 --> 00:13:54,160
would be built that was sensitive
enough to reveal the truth.
182
00:13:54,160 --> 00:13:58,040
The experiment would take
place in the United States,
183
00:13:58,040 --> 00:14:01,880
and Albert Michelson,
the scientist who conducted it,
184
00:14:01,880 --> 00:14:06,000
would go on to become
America's first Nobel Prize winner.
185
00:14:07,520 --> 00:14:11,040
From a young age,
Michelson had relished tackling
186
00:14:11,040 --> 00:14:14,320
the particularly difficult
practical problems in physics.
187
00:14:14,320 --> 00:14:16,120
He'd earned his reputation
188
00:14:16,120 --> 00:14:21,000
by making extremely precise
measurements of the speed of light.
189
00:14:23,320 --> 00:14:28,400
Having completed his work on light,
Michelson travelled to Europe
190
00:14:28,400 --> 00:14:32,520
to spend some time amongst some of
the best scientists in the world.
191
00:14:32,520 --> 00:14:35,840
And it was there that he became
fascinated with the topic
192
00:14:35,840 --> 00:14:41,040
that everyone was talking about -
the mysterious luminiferous aether.
193
00:14:41,040 --> 00:14:44,880
One idea in particular
captured his imagination.
194
00:14:44,880 --> 00:14:50,080
It had been proposed that
if you could measure the speed
of light accurately enough,
195
00:14:50,080 --> 00:14:52,160
it might just be possible
196
00:14:52,160 --> 00:14:56,640
to actually deduce
the properties of the aether.
197
00:14:59,800 --> 00:15:01,600
And this is how.
198
00:15:01,600 --> 00:15:06,560
If there was an aether,
then as the Earth orbited the sun,
199
00:15:06,560 --> 00:15:10,240
we should be able to detect
its presence.
200
00:15:10,240 --> 00:15:14,120
It would be like sticking your hand
out of the window of a moving car.
201
00:15:14,120 --> 00:15:18,240
You feel the rush of wind
as the car travels through the air.
202
00:15:21,600 --> 00:15:26,240
Michelson realised that if this
picture of the aether was true,
203
00:15:26,240 --> 00:15:30,480
then two light beams should travel
at different speeds on Earth,
204
00:15:30,480 --> 00:15:35,760
depending on the direction they were
moving through this aethereal wind.
205
00:15:41,840 --> 00:15:45,920
The difficulty was actually
in making such a measurement.
206
00:15:45,920 --> 00:15:48,760
It seemed like
an almost impossible task.
207
00:15:48,760 --> 00:15:50,960
The problem is this.
208
00:15:50,960 --> 00:15:56,600
The speed of light is over
186,000 miles per second.
209
00:15:56,600 --> 00:15:58,280
Now that's pretty nifty.
210
00:15:58,280 --> 00:16:02,320
In comparison, the Earth
virtually crawls around its orbit.
211
00:16:02,320 --> 00:16:07,240
So the difference in speeds
between those two light beams
would be tiny -
212
00:16:07,240 --> 00:16:10,160
something like
one part in 100 million.
213
00:16:10,160 --> 00:16:14,000
So the precision needed to get
any sort of meaningful result
214
00:16:14,000 --> 00:16:18,200
was way beyond anything
that scientists thought
was possible at the time.
215
00:16:18,200 --> 00:16:21,360
But not so the headstrong Michelson.
216
00:16:21,360 --> 00:16:24,680
He began to work
his way round the problem.
217
00:16:24,680 --> 00:16:28,960
He started to develop techniques
and precision instruments
218
00:16:28,960 --> 00:16:34,400
that he believed would be capable of
unlocking the secrets of the aether.
219
00:16:41,040 --> 00:16:45,000
From 1881, Michelson
was taking measurements,
220
00:16:45,000 --> 00:16:48,000
and tweaking
and refining his apparatus.
221
00:16:48,000 --> 00:16:50,040
But it wouldn't be until 1887
222
00:16:50,040 --> 00:16:54,200
at the Case School of Applied
Science in Cleveland, Ohio,
223
00:16:54,200 --> 00:16:58,400
that Michelson would finally
build a machine sensitive enough
224
00:16:58,400 --> 00:17:00,920
to give him some definitive answers.
225
00:17:00,920 --> 00:17:05,520
There he joined forces with
another scientist, Edward Morley,
226
00:17:05,520 --> 00:17:11,240
to conduct what was to become
one of the most notorious
experiments in physics.
227
00:17:12,680 --> 00:17:16,760
The original apparatus was set
in a solid block of sandstone,
228
00:17:16,760 --> 00:17:19,320
and then suspended
in a bath of mercury
229
00:17:19,320 --> 00:17:23,560
to remove any vibrations that
might affect the measurements.
230
00:17:23,560 --> 00:17:26,640
It was incredibly
hi-tech and very expensive.
231
00:17:26,640 --> 00:17:31,960
Think of it as an 1880s version
of the Large Hadron Collider.
232
00:17:31,960 --> 00:17:35,920
OK, so here's how it works.
Light is emitted
233
00:17:35,920 --> 00:17:37,920
from this source.
234
00:17:40,760 --> 00:17:44,520
In the middle is something
called a beam splitter,
235
00:17:44,520 --> 00:17:47,880
which divides the light
up into two parts.
236
00:17:51,560 --> 00:17:53,280
Over here are two mirrors,
237
00:17:53,280 --> 00:17:56,760
which reflect the light
back to the middle
238
00:17:56,760 --> 00:18:00,680
where they recombine
at the beam splitter.
239
00:18:00,680 --> 00:18:05,400
The light is sent down
to this detector. Now,
240
00:18:05,400 --> 00:18:08,520
Now, because of the wave-like
properties of light,
241
00:18:08,520 --> 00:18:10,800
you see
a very specific pattern here.
242
00:18:10,800 --> 00:18:15,960
Basically, if the light
has travelled at the same speed
along the two paths,
243
00:18:15,960 --> 00:18:19,680
then you see a bright spot
in the middle of the pattern.
244
00:18:22,240 --> 00:18:25,160
So here's the really clever part.
245
00:18:25,160 --> 00:18:27,280
Michelson and Morley reasoned
246
00:18:27,280 --> 00:18:31,600
that if the Earth really was moving
through a stationary aether,
247
00:18:31,600 --> 00:18:35,560
the experiment should behave
in a very different way.
248
00:18:35,560 --> 00:18:39,560
Let's look at what happens when we
simulate the effect of an aether.
249
00:18:43,720 --> 00:18:47,320
The light leaves the detector
250
00:18:47,320 --> 00:18:49,040
and gets split.
251
00:18:51,200 --> 00:18:53,160
Now here's the key.
252
00:18:53,160 --> 00:18:56,840
The light that travels against
the aether and back again
253
00:18:56,840 --> 00:19:00,040
covers this journey
in a different time
254
00:19:00,040 --> 00:19:03,400
to the light travelling
across the aether.
255
00:19:03,400 --> 00:19:07,400
This means that when
the light waves recombine,
256
00:19:07,400 --> 00:19:11,000
they now interfere with each other.
257
00:19:11,000 --> 00:19:14,360
This interference
means that the image
258
00:19:14,360 --> 00:19:17,240
will have a dark spot at its centre.
259
00:19:17,240 --> 00:19:20,880
See this, and you know that
the void must be filled
260
00:19:20,880 --> 00:19:25,320
with a stationary medium through
which the Earth is moving.
261
00:19:28,160 --> 00:19:30,160
Of course I can't be sure exactly
262
00:19:30,160 --> 00:19:33,720
what was going through the minds
of Michelson and Morley
263
00:19:33,720 --> 00:19:35,720
as they began their experiment,
264
00:19:35,720 --> 00:19:39,720
but it is a safe bet that, given
the scientific consensus at the time,
265
00:19:39,720 --> 00:19:43,040
they were convinced
that the aether really existed.
266
00:19:43,040 --> 00:19:46,240
So they would have been sure
that they would have found light
267
00:19:46,240 --> 00:19:51,400
travelling at different speeds as
it moved in different directions.
268
00:19:51,400 --> 00:19:53,040
But it didn't.
269
00:19:53,040 --> 00:19:56,880
No matter how they
rotated their apparatus,
270
00:19:56,880 --> 00:20:01,720
they always found light
travelled at the same speed.
271
00:20:06,080 --> 00:20:11,040
Michelson and Morley had gained an
extraordinary and accurate result.
272
00:20:14,320 --> 00:20:18,200
But the idea of the
luminiferous aether was so ingrained
273
00:20:18,200 --> 00:20:22,080
that they believed simply
that their experiments had failed.
274
00:20:28,320 --> 00:20:30,360
So what is going on?
275
00:20:30,360 --> 00:20:35,400
Why didn't Michelson and
Morley's experiment reveal
the result they were expecting?
276
00:20:35,400 --> 00:20:39,560
How could light always be travelling
at the same speed?
277
00:20:39,560 --> 00:20:44,200
Well, the answer is simple.
The aether doesn't exist.
278
00:20:44,200 --> 00:20:47,040
No matter what light is doing,
how it is travelling,
279
00:20:47,040 --> 00:20:52,920
it doesn't need to be carried
along by this mysterious stuff
that pervades the vacuum.
280
00:20:55,640 --> 00:21:00,880
So how does light
move through empty space?
281
00:21:00,880 --> 00:21:03,160
Well, by the end
of the 19th century,
282
00:21:03,160 --> 00:21:05,640
light was known to be in fact
283
00:21:05,640 --> 00:21:11,240
a combination of fluctuating
electric and magnetic fields.
284
00:21:11,240 --> 00:21:15,280
But it would take the genius
of Einstein in 1905
285
00:21:15,280 --> 00:21:20,160
to reveal that this picture of
light doesn't need an aether.
286
00:21:20,160 --> 00:21:23,640
He showed that
it has the weird property
287
00:21:23,640 --> 00:21:28,080
of being able to propagate
through completely empty space.
288
00:21:29,920 --> 00:21:35,080
So the message from the failure
of Michelson and Morley's
experiment is this -
289
00:21:35,080 --> 00:21:37,840
there is no aether.
290
00:21:37,840 --> 00:21:42,120
Maybe the vacuum is really empty.
291
00:21:42,120 --> 00:21:44,320
If only it were that simple.
292
00:21:47,760 --> 00:21:50,560
Almost as soon as Michelson
and Morley had revealed,
293
00:21:50,560 --> 00:21:53,680
by accident, that you
really could have nothing...
294
00:21:55,560 --> 00:22:01,080
..scientists began to discover some
very weird properties of nature.
295
00:22:03,400 --> 00:22:07,560
In the 100 years that followed
Michelson and Morley's experiments,
296
00:22:07,560 --> 00:22:11,520
physics and our understanding
of the vacuum
297
00:22:11,520 --> 00:22:14,240
has been totally transformed.
298
00:22:23,240 --> 00:22:28,720
But what drove this huge shift
was not simply scientific curiosity.
299
00:22:31,000 --> 00:22:34,400
But the fact that in
the late 19th century,
300
00:22:34,400 --> 00:22:39,760
the vacuum and its many
applications had become big business.
301
00:22:43,440 --> 00:22:46,920
Industry was finding
ever more ingenious ways
302
00:22:46,920 --> 00:22:49,760
to make money out of nothing.
303
00:22:51,680 --> 00:22:55,640
Understanding and harnessing
the vacuum turned out
304
00:22:55,640 --> 00:23:00,640
to lead to a wealth
of new technologies that
we just take for granted today.
305
00:23:00,640 --> 00:23:04,200
Everything from
the light bulb to the television
306
00:23:04,200 --> 00:23:06,080
were only made possible
307
00:23:06,080 --> 00:23:11,120
because they could contain
within them small volumes of vacuum.
308
00:23:14,800 --> 00:23:19,280
The filament inside a light bulb
can glow for long periods
309
00:23:19,280 --> 00:23:22,520
because it is contained
within a vacuum.
310
00:23:22,520 --> 00:23:26,760
Expose it to air and it would
simply burn out in seconds.
311
00:23:31,080 --> 00:23:34,680
As cities around
the world began to electrify,
312
00:23:34,680 --> 00:23:38,600
the demand for
light bulbs grew massively.
313
00:23:38,600 --> 00:23:43,840
The engineers became ever more
skilled at creating cheap,
efficient vacuums.
314
00:23:44,800 --> 00:23:49,960
This technology would give rise
to a huge range of gadgets -
315
00:23:49,960 --> 00:23:55,000
everything from the valves
in radios and early computers
316
00:23:55,000 --> 00:23:56,440
to the television.
317
00:23:58,320 --> 00:24:03,000
But all the
technological innovations
that came from harnessing the vacuum
318
00:24:03,000 --> 00:24:06,960
would pale into insignificance
when compared to what scientists
319
00:24:06,960 --> 00:24:11,520
would soon find out about
the fundamental nature of reality.
320
00:24:13,880 --> 00:24:18,480
Because vacuum technology
was getting so much cheaper,
321
00:24:18,480 --> 00:24:20,000
and more efficient,
322
00:24:20,000 --> 00:24:24,840
scientists all over the world could
use it as a tool for research.
323
00:24:24,840 --> 00:24:30,160
In empty space, nature's tiniest
constituents could now be studied
324
00:24:30,160 --> 00:24:35,320
without interference
from the contaminant-filled air
of the outside world.
325
00:24:36,840 --> 00:24:39,720
This revolutionised physics.
326
00:24:41,240 --> 00:24:46,320
Because of the vacuum,
X-rays were discovered in 1895.
327
00:24:47,520 --> 00:24:52,480
The following year, the electron
was identified for the first time.
328
00:24:52,480 --> 00:24:56,600
And in 1909, Ernest Rutherford
would use vacuums
329
00:24:56,600 --> 00:25:00,400
to help reveal
the strange structure of the atom.
330
00:25:03,600 --> 00:25:07,640
These discoveries were all feeding
into a radically new picture
331
00:25:07,640 --> 00:25:12,560
of the way nature works at its
smallest and most fundamental level.
332
00:25:14,080 --> 00:25:19,000
It was a theory that would come
to be known as quantum mechanics.
333
00:25:19,000 --> 00:25:23,600
And the submicroscopic world it
describes behaves very differently
334
00:25:23,600 --> 00:25:25,160
to the world we are used to.
335
00:25:27,320 --> 00:25:31,720
This is a world where,
against all common sense,
336
00:25:31,720 --> 00:25:36,120
it seems impossible
to ever truly have nothing.
337
00:25:45,240 --> 00:25:47,880
This is the classical world,
338
00:25:47,880 --> 00:25:50,000
action and reaction.
339
00:25:51,040 --> 00:25:53,360
Cause and effect.
340
00:25:53,360 --> 00:25:56,360
It is sensible,
certain and knowable.
341
00:25:57,440 --> 00:26:03,280
But the quantum world soon revealed
itself to be very different.
342
00:26:05,600 --> 00:26:10,160
There was one discovery
that was particularly troubling
343
00:26:10,160 --> 00:26:15,080
and it's known as
Heisenberg's Uncertainty Principle.
344
00:26:19,560 --> 00:26:25,040
In everyday life
we are used to doubt, to uncertainty.
345
00:26:25,040 --> 00:26:28,720
How can we be sure that
something is this way or that way?
346
00:26:28,720 --> 00:26:34,400
Well, it turns out that nature itself
is based on indeterminacy,
347
00:26:34,400 --> 00:26:36,640
in uncertainty.
348
00:26:36,640 --> 00:26:41,280
The world of quantum physics,
the microscopic world,
is a world of uncertainty.
349
00:26:41,280 --> 00:26:44,840
It's a world where you can never
be sure of what is going to happen.
350
00:26:44,840 --> 00:26:49,600
Not because your measurements are not
good enough, simply because,
351
00:26:49,600 --> 00:26:54,480
at a very fundamental level, nature
itself is based on uncertainty.
352
00:26:57,240 --> 00:27:02,040
OK, I would like to
get across the essence of
Heisenberg's Uncertainty Principle.
353
00:27:02,040 --> 00:27:05,280
I'm going to use
a non-mathematical analogy.
354
00:27:05,280 --> 00:27:07,160
We have to be careful here -
355
00:27:07,160 --> 00:27:10,880
it is just an analogy so
we shouldn't push it too far.
356
00:27:10,880 --> 00:27:14,480
I have here two
identical memory sticks.
357
00:27:14,480 --> 00:27:18,400
On the first one
is a high-resolution image.
358
00:27:18,400 --> 00:27:21,440
It is a picture of me
having a game of pool.
359
00:27:21,440 --> 00:27:23,040
We can see it is very detailed.
360
00:27:23,040 --> 00:27:25,400
In fact, I can zoom in...
361
00:27:27,480 --> 00:27:30,160
..even quite closely
onto the pool ball.
362
00:27:30,160 --> 00:27:32,600
And you see,
even at this magnification,
363
00:27:32,600 --> 00:27:37,640
I can still see the precise
position, I can see the edges
of the ball very detailed.
364
00:27:37,640 --> 00:27:41,880
But what I don't know is
how fast the ball is moving
365
00:27:41,880 --> 00:27:45,640
or what is going to happen next.
366
00:27:45,640 --> 00:27:50,000
Now, on the second memory
stick is another file.
It's a very different kind of file.
367
00:27:50,000 --> 00:27:52,040
It is a movie.
368
00:27:52,040 --> 00:27:56,040
The important thing to note
is that the file is the same size
369
00:27:56,040 --> 00:27:58,160
as the high-resolution image.
370
00:27:59,880 --> 00:28:02,880
Now, have a look at this.
371
00:28:02,880 --> 00:28:06,400
Now we can see the whole movie
playing out. It is the same scene,
372
00:28:06,400 --> 00:28:08,400
but you can see
all the balls moving.
373
00:28:08,400 --> 00:28:12,360
But if I zoom in on some detail...
374
00:28:14,600 --> 00:28:18,640
..very quickly the balls
become fuzzy and blurred.
375
00:28:18,640 --> 00:28:20,720
So for the same amount
of information,
376
00:28:20,720 --> 00:28:25,040
although I've gained knowledge
about how the balls are moving,
377
00:28:25,040 --> 00:28:28,680
I've lost information
about their exact positions.
378
00:28:28,680 --> 00:28:32,400
So with the more I know
about where something is,
379
00:28:32,400 --> 00:28:36,120
the less I know
about how it is moving.
380
00:28:36,120 --> 00:28:38,240
In the quantum world,
381
00:28:38,240 --> 00:28:44,000
I cannot at the same time
know both these quantities exactly.
382
00:28:44,000 --> 00:28:47,800
Unfortunately,
there is no way around this.
383
00:28:47,800 --> 00:28:50,640
Heisenberg showed in his mathematics
384
00:28:50,640 --> 00:28:55,680
that this is in an inescapable
feature of reality at this scale.
385
00:28:55,680 --> 00:29:00,240
OK, so what has all
this quantum weirdness
386
00:29:00,240 --> 00:29:02,800
got to do with nothing?
387
00:29:02,800 --> 00:29:08,800
Well, you see,
Heisenberg's Uncertainty Principle
can be expressed in a different way,
388
00:29:08,800 --> 00:29:14,160
in terms of a balance between two
other quantities - energy and time.
389
00:29:14,160 --> 00:29:16,640
Now, this is going to sound
quite complicated,
390
00:29:16,640 --> 00:29:19,600
but it's very important,
so I'm going to try and explain.
391
00:29:19,600 --> 00:29:22,000
You see, if I were to examine
392
00:29:22,000 --> 00:29:27,160
a small volume of empty space
inside this box, then I could
393
00:29:27,160 --> 00:29:32,640
in principle know how much
energy it contains very precisely.
394
00:29:33,280 --> 00:29:38,120
But, if I were able
to slow time down,
395
00:29:38,120 --> 00:29:42,640
things would start
to get very strange.
396
00:29:47,000 --> 00:29:53,080
OK, so we are now looking
at a tiny interval of time
that has been stretched out.
397
00:29:56,520 --> 00:29:58,880
Heisenberg's uncertainty principle
398
00:29:58,880 --> 00:30:02,880
tells us that because I'm looking
at a smaller interval of time,
399
00:30:02,880 --> 00:30:08,480
I've lost precise information
about the exact energy in the box.
400
00:30:11,520 --> 00:30:15,760
If I could examine
an even smaller interval of time,
401
00:30:15,760 --> 00:30:19,200
and an even smaller volume
inside the box,
402
00:30:19,200 --> 00:30:25,320
then Heisenberg's equation
suggests something
truly bizarre could happen.
403
00:30:30,640 --> 00:30:35,880
I will be so uncertain about
how much energy there is in that
part of the box,
404
00:30:35,880 --> 00:30:39,320
that there is a chance
it could contain
405
00:30:39,320 --> 00:30:45,240
enough energy to create particles
literally out of nowhere...
406
00:30:47,280 --> 00:30:51,400
..provided that somehow
they went away again very quickly.
407
00:31:00,800 --> 00:31:05,000
Heisenberg's uncertainty principle
seemed to suggest that
408
00:31:05,000 --> 00:31:12,240
in truly tiny amounts
of time and space,
something could come from nothing.
409
00:31:13,960 --> 00:31:20,360
But then what?
If particles could pop into
existence, where do they go?
410
00:31:20,360 --> 00:31:24,800
Why don't we see these
particles appearing all around us?
411
00:31:28,160 --> 00:31:33,120
The vacuum, contrary to what
one normally expects from the vacuum,
412
00:31:33,120 --> 00:31:34,520
is alive.
413
00:31:34,520 --> 00:31:37,280
It's alive with what physicists
call quantum fluctuations.
414
00:31:37,280 --> 00:31:41,680
In the vacuum, little packets
of energy appear and disappear
415
00:31:41,680 --> 00:31:43,240
very, very quickly.
416
00:31:43,240 --> 00:31:45,760
This is perfectly allowed
by the laws of physics.
417
00:31:45,760 --> 00:31:47,720
It's all allowed but it has an name,
418
00:31:47,720 --> 00:31:50,640
it is called Heisenberg's
uncertainty principle,
419
00:31:50,640 --> 00:31:52,160
which tells us that you can
420
00:31:52,160 --> 00:31:55,920
borrow energy from nothing, so long
as you pay it back quickly enough.
421
00:31:58,680 --> 00:32:02,120
The vacuum is alive.
422
00:32:02,120 --> 00:32:09,160
Bizarre though these ideas seem,
they are, I promise you,
fundamental to our universe.
423
00:32:09,160 --> 00:32:11,200
To see how this can be,
424
00:32:11,200 --> 00:32:15,560
our story of nothing
takes us to one of the most
425
00:32:15,560 --> 00:32:20,280
gifted and oddest characters
in the whole history of physics.
426
00:32:24,760 --> 00:32:29,040
Behind me is Bishop Road
Primary School in Bristol
427
00:32:29,040 --> 00:32:30,720
and almost 100 years ago,
428
00:32:30,720 --> 00:32:34,720
it was attended by two students
who were destined for greatness.
429
00:32:34,720 --> 00:32:38,800
One of them, Archibald Leach,
would go on to conquer Hollywood,
430
00:32:38,800 --> 00:32:41,240
becoming better known
as Cary Grant.
431
00:32:41,240 --> 00:32:46,440
The other was a quiet, shy
and rather intense boy two years
younger than Grant,
432
00:32:46,440 --> 00:32:51,720
who would become one of
the greatest scientists
Britain has ever produced,
433
00:32:51,720 --> 00:32:54,560
the theoretical physicist
Paul Dirac.
434
00:32:59,640 --> 00:33:01,840
Even by the standards
of theoretical physicists,
435
00:33:01,840 --> 00:33:04,440
Dirac was a very queer bird.
436
00:33:04,440 --> 00:33:08,080
He was not someone
you'd go for a beer with.
437
00:33:08,080 --> 00:33:10,480
Intensely focused,
438
00:33:10,480 --> 00:33:15,320
man of extremely few words,
very, very little empathy
439
00:33:15,320 --> 00:33:18,680
and someone of rectilinear thought.
440
00:33:21,720 --> 00:33:25,960
These personality traits were key
to Dirac's genius,
441
00:33:25,960 --> 00:33:29,920
but they often resulted
in difficult or awkward
442
00:33:29,920 --> 00:33:32,800
social situations with his peers.
443
00:33:32,800 --> 00:33:38,200
Even in casual conversation, Dirac
would never speak unnecessarily.
444
00:33:38,200 --> 00:33:42,280
He'd often leave these long
pauses in between sentences while
445
00:33:42,280 --> 00:33:47,240
he worked out the most precise and
concise way of expressing himself.
446
00:33:47,240 --> 00:33:51,680
Friends had jokingly coined
the term a Dirac, which stands for
447
00:33:51,680 --> 00:33:55,760
the smallest number of words it
is possible to speak in one hour,
448
00:33:55,760 --> 00:33:58,560
while still taking part
in a conversation.
449
00:33:58,560 --> 00:34:01,920
It is a sort of unit of shyness.
450
00:34:05,880 --> 00:34:08,840
Dirac's unusual personality
had its roots
451
00:34:08,840 --> 00:34:11,600
in a difficult
and troubled childhood.
452
00:34:11,600 --> 00:34:16,240
But from a young age, he had
found solace in the classroom.
453
00:34:16,240 --> 00:34:22,880
In particular, he excelled at both
mathematics and technical drawing.
454
00:34:22,880 --> 00:34:28,120
This was something that
cultivated his visual imagination.
455
00:34:28,120 --> 00:34:31,400
In maths classes, he was
looking at mathematical symbols.
456
00:34:31,400 --> 00:34:37,440
He was looking at similar things,
but in a geometric way in
his technical drawing class.
457
00:34:37,440 --> 00:34:42,760
It is very, very suggestive of the
way he looked at physics later on
458
00:34:42,760 --> 00:34:48,880
because he always stressed that
he was pre-eminently a visualiser.
459
00:34:48,880 --> 00:34:52,560
He was someone who had a geometric
look at physics.
460
00:34:52,560 --> 00:34:56,120
He was not interested per say
in mathematical symbols.
461
00:34:56,120 --> 00:35:00,560
Rather he wanted a visual sense of
what was going on in the mathematics.
462
00:35:03,160 --> 00:35:07,840
Dirac continued his visual training,
doing a degree in engineering
463
00:35:07,840 --> 00:35:10,880
before go to Cambridge
to study mathematics.
464
00:35:10,880 --> 00:35:16,040
It would be here that
Dirac would begin to unravel
the deepest mysteries of the vacuum
465
00:35:16,040 --> 00:35:20,680
and uncover what was
really going on in empty space.
466
00:35:22,200 --> 00:35:26,640
But his insight sprang from a
seemingly unrelated difficulty.
467
00:35:28,240 --> 00:35:32,960
By 1928, physics was
struggling with a big problem.
468
00:35:32,960 --> 00:35:35,000
The two most important theories
469
00:35:35,000 --> 00:35:39,440
that described
how the universe worked
didn't agree with each other.
470
00:35:39,440 --> 00:35:43,880
On the one hand, you had Einstein's
special theory of relativity
471
00:35:43,880 --> 00:35:47,240
encapsulated
in the famous equation E=mc2.
472
00:35:47,240 --> 00:35:50,320
It was a beautiful,
simple and elegant theory
473
00:35:50,320 --> 00:35:54,400
that describes the behaviour of
things close to the speed of light.
474
00:35:54,400 --> 00:35:58,160
On the other hand, you had
Planck's discovery of the quantum
475
00:35:58,160 --> 00:36:04,040
and the revolution that followed
describing the bizarre rules
of the very, very small.
476
00:36:06,800 --> 00:36:12,520
The problems arose
when trying to describe situations
where things were small enough
477
00:36:12,520 --> 00:36:14,600
for quantum effects to be felt,
478
00:36:14,600 --> 00:36:19,240
but travelling fast enough for
special relativity to be important.
479
00:36:21,120 --> 00:36:24,720
Specifically, there were
huge problems trying to describe
480
00:36:24,720 --> 00:36:30,320
the electron, a tiny particle
whizzing around inside an atom.
481
00:36:30,320 --> 00:36:35,120
If both of these theories were true,
then they should be able to be used
482
00:36:35,120 --> 00:36:39,640
together to give a mathematical
description of the electron.
483
00:36:43,520 --> 00:36:45,640
But what if this couldn't be done?
484
00:36:45,640 --> 00:36:49,960
What if quantum physics and special
relativity couldn't be married?
485
00:36:49,960 --> 00:36:54,920
This would mean one or other
of these two cornerstones
of physics had to be wrong.
486
00:36:54,920 --> 00:37:00,000
A way had to be found for the two
theories to be married together.
487
00:37:00,000 --> 00:37:02,920
It would be Dirac
who would achieve this.
488
00:37:06,200 --> 00:37:11,320
Dirac's unification of the
special theory and the rules of
the quantum world
489
00:37:11,320 --> 00:37:16,720
would rank as one of
the greatest mathematical
accomplishments of the 20th century.
490
00:37:16,720 --> 00:37:22,480
And it would lead inadvertently
to a radical new picture of nothing.
491
00:37:24,120 --> 00:37:28,840
To get a non mathematical sense
of what he did, and how he did it,
492
00:37:28,840 --> 00:37:35,920
I've come to the cinema to see one
of Dirac's favourite films,
2001 A Space Odyssey.
493
00:37:39,040 --> 00:37:41,440
Understanding
why it appealed to him
494
00:37:41,440 --> 00:37:46,240
helps give us an insight
into how he managed to
solve this great problem.
495
00:37:46,240 --> 00:37:52,840
If you look at 2001, it was, as
Kubrick has said, a demonstration
496
00:37:52,840 --> 00:37:57,040
that you could make a really good
movie script without words
497
00:37:57,040 --> 00:37:59,960
but with a power of
the visual imagery.
498
00:37:59,960 --> 00:38:03,880
Now, that in some ways
is very closely analogous
499
00:38:03,880 --> 00:38:06,160
to Dirac's a theoretical physics
500
00:38:06,160 --> 00:38:11,160
because, for him, what was central,
were the mathematical equations.
501
00:38:11,160 --> 00:38:15,200
And more over, he had a visual
sense of what those equations meant.
502
00:38:22,280 --> 00:38:25,880
The abstract images of 2001
appealed to Dirac
503
00:38:25,880 --> 00:38:30,640
because they captivated
his brilliant visual imagination.
504
00:38:30,640 --> 00:38:35,040
It was this highly developed
and unusual way of thinking,
505
00:38:35,040 --> 00:38:39,280
honed in his schooldays,
that would enable him in 1928
506
00:38:39,280 --> 00:38:43,480
to visualise a unique
way of describing the electron.
507
00:38:43,480 --> 00:38:48,160
It was a description that
finally managed to unite Einstein's
508
00:38:48,160 --> 00:38:53,840
special theory of relativity
and the weird world
of quantum mechanics.
509
00:39:10,240 --> 00:39:15,240
Today, it's known simply
as the Dirac equation.
510
00:39:15,240 --> 00:39:18,200
It may look like a small
collection of symbols,
511
00:39:18,200 --> 00:39:23,480
but to a mathematician this
equation is profoundly beautiful.
512
00:39:23,480 --> 00:39:31,040
A complex and symmetrical
synthesis of mathematical ideas,
expressed with stunning clarity.
513
00:39:35,240 --> 00:39:41,760
This is the commemorative
plaque at Bishop Road,
Paul Dirac's primary school.
514
00:39:41,760 --> 00:39:44,640
And on it, his famous equation.
515
00:39:44,640 --> 00:39:49,920
Within these few symbols lie
profound truths about the universe.
516
00:39:49,920 --> 00:39:53,400
But don't be deceived by
its apparent simplicity,
517
00:39:53,400 --> 00:39:59,120
think of this equation as the tip
of a giant mathematical iceberg.
518
00:39:59,120 --> 00:40:03,280
Each of these terms relate to
entire branches of mathematics
519
00:40:03,280 --> 00:40:06,240
and the particular
relationships between them.
520
00:40:06,240 --> 00:40:09,760
Beneath this equation,
are mathematical ideas that
521
00:40:09,760 --> 00:40:16,000
have been developed and honed by
many, many other great individuals.
522
00:40:16,000 --> 00:40:19,840
If you think of a poem, you can
think of it as the most supercharged
523
00:40:19,840 --> 00:40:23,960
kind of language,
the way you compress meaning
524
00:40:23,960 --> 00:40:27,440
into a very, very
brief area on the page.
525
00:40:27,440 --> 00:40:31,520
Dirac was producing equations
that had that kind of concision
526
00:40:31,520 --> 00:40:33,640
and you can then unpack them,
527
00:40:33,640 --> 00:40:38,120
just as you re-read a Shakespeare
sonnet and see more and more
in it, more and more elegance.
528
00:40:38,120 --> 00:40:42,320
Same with the Dirac equation,
you find an equation there
529
00:40:42,320 --> 00:40:47,080
you can keep finding things that
were not obvious on first reading.
530
00:40:47,080 --> 00:40:50,440
In fact, Dirac once said that the
equation was smarter than he was
531
00:40:50,440 --> 00:40:53,440
because it actually gave more stuff
out than he put into it.
532
00:40:54,960 --> 00:41:00,440
There was one particularly
odd thing the equation seemed
to be saying to Dirac.
533
00:41:00,440 --> 00:41:06,440
Something that would redefine
the concept of empty space forever.
534
00:41:06,440 --> 00:41:13,120
In his description of the electron,
Dirac had been forced to use a
collection of four equations
535
00:41:13,120 --> 00:41:15,840
represented by the symbol gamma,
536
00:41:15,840 --> 00:41:21,920
in order to make special relativity
and quantum mechanics fit together.
537
00:41:21,920 --> 00:41:27,000
But the need for
four equations seemed strange.
538
00:41:27,000 --> 00:41:33,440
To Dirac and other
physicists in the 1920s, the first
two were quite recognisable.
539
00:41:33,440 --> 00:41:39,080
They described the behaviour
of an electron as it had
been observed in the laboratory.
540
00:41:39,080 --> 00:41:42,720
But the second two
were very strange.
541
00:41:42,720 --> 00:41:48,520
They seemed to be saying
there was some other type of
electron that could exist.
542
00:41:48,520 --> 00:41:52,000
One that had
never been seen before.
543
00:41:57,320 --> 00:42:01,120
So, this is the normal
world we are familiar with.
544
00:42:01,120 --> 00:42:04,280
And here, scaled up
many, many times
545
00:42:04,280 --> 00:42:08,840
is a regular electron of the type
contained within
546
00:42:08,840 --> 00:42:12,360
the trillions of atoms
that make up this table,
547
00:42:12,360 --> 00:42:15,400
me and everything else
in the universe.
548
00:42:15,400 --> 00:42:20,360
Dirac realised that
these mysterious new elements
in his equation
549
00:42:20,360 --> 00:42:24,760
predicted the existence
of a strange new kind of particle.
550
00:42:24,760 --> 00:42:32,560
In some ways, just like the
electron, and yet at the same time
very, very different.
551
00:42:40,120 --> 00:42:45,880
Dirac gradually became convinced
that the new parts of his equation
552
00:42:45,880 --> 00:42:47,480
were describing something
553
00:42:47,480 --> 00:42:51,680
that could be thought of
as an anti-electron.
554
00:42:51,680 --> 00:42:55,200
In many ways, it was like
the mirror image of an electron,
555
00:42:55,200 --> 00:42:57,760
having opposite properties like
electric charge.
556
00:42:57,760 --> 00:43:03,400
And, in principle an anti-electron
could form part of an anti-atom,
557
00:43:03,400 --> 00:43:06,840
and many anti-atoms
could fit together
558
00:43:06,840 --> 00:43:11,040
to make an anti-matter table,
or even an anti-me.
559
00:43:13,240 --> 00:43:16,400
But the weirdness didn't end there.
560
00:43:16,400 --> 00:43:21,560
Dirac realised that if things and
anti-things ever met each other,
561
00:43:21,560 --> 00:43:24,280
they would instantly annihilate,
562
00:43:24,280 --> 00:43:27,440
turning all their mass
into energy...
563
00:43:27,440 --> 00:43:29,600
EXPLOSION
564
00:43:30,080 --> 00:43:33,240
Disappearing completely.
565
00:43:37,840 --> 00:43:43,720
Here, finally was the answer
to the riddle of empty space.
566
00:43:43,720 --> 00:43:47,960
Heisenberg's uncertainty principle
had suggested that matter could
567
00:43:47,960 --> 00:43:52,160
pop into existence for
incredibly short periods of time.
568
00:43:52,160 --> 00:43:55,480
Now, Dirac had provided
the mechanism
569
00:43:55,480 --> 00:44:00,000
by which matter could
be created out of the vacuum...
570
00:44:01,840 --> 00:44:05,400
..and just as quickly,
disappear again.
571
00:44:07,000 --> 00:44:10,320
So, let's take another look
at our box.
572
00:44:10,320 --> 00:44:14,080
Whenever a particle pops out
of empty space,
573
00:44:14,080 --> 00:44:17,720
so simultaneously
does its anti-particle.
574
00:44:17,720 --> 00:44:23,120
Although this sounds
completely ridiculous,
let me assure you it is true.
575
00:44:23,120 --> 00:44:28,400
So, whenever you try to remove
everything you can from empty space,
576
00:44:28,400 --> 00:44:33,120
it's still always awash
with all these fluctuations.
577
00:44:35,760 --> 00:44:40,880
Within nothingness, there's
a kind of fizzing, a dynamic dance
578
00:44:40,880 --> 00:44:44,360
as pairs of particles
and anti-particles
579
00:44:44,360 --> 00:44:48,280
borrow energy from the vacuum
for brief moments
580
00:44:48,280 --> 00:44:52,080
before annihilating
and paying it back again.
581
00:44:58,920 --> 00:45:03,400
Dirac's theory of the electron
and the idea of anti-matter
582
00:45:03,400 --> 00:45:07,840
gives us a completely
new picture of the vacuum.
583
00:45:07,840 --> 00:45:12,840
Before you could think about the
vacuum as empty space, so to speak.
584
00:45:12,840 --> 00:45:16,640
relativity had said,
you don't need an aether,
585
00:45:16,640 --> 00:45:20,360
so the picture was
of the vacuum being empty.
586
00:45:20,360 --> 00:45:24,920
But when you bring relativity and
quantum theory together
587
00:45:24,920 --> 00:45:31,600
then you have for certain,
this notion of electron
and anti-electron pairs
588
00:45:31,600 --> 00:45:34,560
just appearing out of the vacuum.
589
00:45:34,560 --> 00:45:39,240
So you can think of these pairs just
sprouting all over the place
in the vacuum.
590
00:45:42,200 --> 00:45:46,480
So, the vacuum goes from
being nothing
591
00:45:46,480 --> 00:45:53,120
to being a place absolutely teeming
with matter, anti-matter creation.
592
00:45:53,120 --> 00:45:58,000
Dirac's ideas about empty space
were refined and developed
593
00:45:58,000 --> 00:46:01,800
into what is known today as
quantum field theory.
594
00:46:01,800 --> 00:46:04,800
And these strange
fleeting things within nothing
595
00:46:04,800 --> 00:46:09,480
became known as
virtual particles.
596
00:46:17,960 --> 00:46:24,440
So it seems, nothingness
is in fact a seething mass
of virtual particles,
597
00:46:24,440 --> 00:46:26,440
appearing and disappearing
598
00:46:26,440 --> 00:46:29,360
trillions of times
in the blink of an eye.
599
00:46:36,280 --> 00:46:39,160
I've come to
Imperial College London
600
00:46:39,160 --> 00:46:43,280
to see the effects of
these virtual particles myself.
601
00:46:43,280 --> 00:46:48,440
Thanks to a brilliant experiment
by an American scientist
called Willis Lamb,
602
00:46:48,440 --> 00:46:51,960
we now have a way to
conclusively show
603
00:46:51,960 --> 00:46:56,560
there is activity
within apparent nothingness.
604
00:46:56,560 --> 00:46:58,480
But in order to glimpse it,
605
00:46:58,480 --> 00:47:03,240
you have to peer deep
within a single atom
606
00:47:03,240 --> 00:47:07,880
and amazingly Lamb found
an ingenious way to do this.
607
00:47:09,600 --> 00:47:12,640
So, what did Lamb do?
608
00:47:12,640 --> 00:47:17,000
Well, his experiment relies on
the quantum rules of the atom.
609
00:47:17,000 --> 00:47:21,800
Within atoms, electrons have very
specific, discreet energies
610
00:47:21,800 --> 00:47:24,880
in the way
they orbit around the nucleus.
611
00:47:24,880 --> 00:47:28,920
His experiment showed that if the
vacuum really was full
612
00:47:28,920 --> 00:47:31,080
of these hidden fluctuations,
613
00:47:31,080 --> 00:47:34,600
then these would cause
the electrons' orbit
614
00:47:34,600 --> 00:47:37,080
to wobble ever-so-slightly.
615
00:47:37,080 --> 00:47:41,240
Think of it as an analogy
as though the electron is a plane
616
00:47:41,240 --> 00:47:44,040
flying along
and hitting turbulence
617
00:47:44,040 --> 00:47:47,960
forcing it to move up
to a slightly higher altitude.
618
00:47:49,120 --> 00:47:51,680
So this is how
the experiment works.
619
00:47:51,680 --> 00:47:56,880
Contained within
this vacuum chamber
are a small number of atoms.
620
00:47:56,880 --> 00:48:01,120
While Lamb used microwaves in
his original experiments,
621
00:48:01,120 --> 00:48:06,560
in this version,
the team at Imperial are
using lasers to probe the electrons.
622
00:48:06,560 --> 00:48:11,080
Now, if you think this all
looks very complex, just remember
623
00:48:11,080 --> 00:48:14,360
how small a measurement it
is we are trying to make here.
624
00:48:14,360 --> 00:48:20,320
This apparatus has to be sensitive
enough to pick up minute changes
625
00:48:20,320 --> 00:48:25,080
in the behaviour of something
that is itself, extremely tiny.
626
00:48:25,080 --> 00:48:30,120
Imagine we could scale up
the wobble in electron
that's being measured
627
00:48:30,120 --> 00:48:32,000
to the size of this apple.
628
00:48:32,000 --> 00:48:40,160
That would mean this vacuum chamber
behind me, would scale up to
being a trillion miles in size.
629
00:48:40,160 --> 00:48:43,600
The vacuum chamber
would be something like
630
00:48:43,600 --> 00:48:47,240
100 times the size
of the entire solar system.
631
00:48:47,240 --> 00:48:54,800
It would take light about 40 days
just to travel from the top
down to the bottom.
632
00:48:54,800 --> 00:48:57,760
So, what is going on in there?
633
00:48:57,760 --> 00:49:02,480
OK, so let me first fire up the
laser in the experiment behind me.
634
00:49:02,480 --> 00:49:08,040
What this monitor will show us is
exactly what's going on
inside the vacuum chamber
635
00:49:08,040 --> 00:49:10,200
down at the minutest scales.
636
00:49:10,200 --> 00:49:13,280
Now, look at this peak
that's appeared.
637
00:49:13,280 --> 00:49:15,600
BUZZING
638
00:49:15,600 --> 00:49:17,520
It may not look very exciting,
639
00:49:17,520 --> 00:49:20,920
but it's telling us
something really remarkable.
640
00:49:20,920 --> 00:49:27,640
This is measuring the amount
the electron is being wobbled about
by the vacuum itself.
641
00:49:27,640 --> 00:49:32,280
If the vacuum were truly empty,
this peak wouldn't exist,
642
00:49:32,280 --> 00:49:34,400
we'd just get a flat line.
643
00:49:34,400 --> 00:49:38,400
What this is telling us
is that however hard we try
644
00:49:38,400 --> 00:49:44,280
to remove everything we can
from space, we can never
get it truly empty.
645
00:49:44,280 --> 00:49:49,320
Everywhere in the universe,
space is filled with this vacuum
646
00:49:49,320 --> 00:49:52,320
that has a deep,
mysterious energy.
647
00:49:56,080 --> 00:49:57,760
But it doesn't end there.
648
00:49:59,280 --> 00:50:04,160
When using the mathematics laid out
by Heisenberg, Dirac and others,
649
00:50:04,160 --> 00:50:08,320
you can calculate the amount
the electron should be affected.
650
00:50:10,320 --> 00:50:14,200
When you run the real physical
experiment, the answer you get
651
00:50:14,200 --> 00:50:19,600
matches the theory
to one part in a million.
652
00:50:19,600 --> 00:50:23,760
The theory of quantum mechanics
is the most accurate
653
00:50:23,760 --> 00:50:28,280
and powerful description of
the natural world that we have.
654
00:50:30,920 --> 00:50:33,720
But there's a much more
dramatic way
655
00:50:33,720 --> 00:50:38,720
in which we can see the effects
of these quantum fluctuations.
656
00:50:38,720 --> 00:50:42,960
And that's because
they're written into the stars.
657
00:50:49,880 --> 00:50:52,800
Today, our best theories tell us
658
00:50:52,800 --> 00:50:59,400
that as the universe
sprang from the vacuum,
it expanded very rapidly.
659
00:50:59,400 --> 00:51:03,840
And this means that the rules
of the quantum world should have
660
00:51:03,840 --> 00:51:09,600
contributed to the large-scale
structure of the entire cosmos.
661
00:51:13,240 --> 00:51:19,480
When our universe first came
into existence, it was many times
smaller than a single atom.
662
00:51:19,480 --> 00:51:23,800
And down at this size it's governed
not by the classical rules we're
663
00:51:23,800 --> 00:51:29,160
familiar with, but by the
weird rules of the quantum world.
664
00:51:29,160 --> 00:51:35,040
This is for me, one of the most
profound and beautiful ideas
in the whole of science.
665
00:51:35,040 --> 00:51:38,120
That it's quantum reality that has
666
00:51:38,120 --> 00:51:42,640
shaped the structure of the
universe we see today.
667
00:51:42,640 --> 00:51:49,720
Our universe is just the quantum
world inflated many, many times.
668
00:51:49,720 --> 00:51:54,280
Nothing really has shaped
everything.
669
00:51:54,280 --> 00:51:59,080
And what's more,
we now have a way to see this.
670
00:52:06,840 --> 00:52:14,240
This is a picture
of the first light that
was released after the Big Bang.
671
00:52:14,240 --> 00:52:19,200
Think of it
as a baby photo of everything.
672
00:52:19,200 --> 00:52:24,560
This incredible picture was taken
by a team of researchers at NASA
673
00:52:24,560 --> 00:52:27,160
led by Professor George Smoot.
674
00:52:27,160 --> 00:52:30,280
This is like taking a
675
00:52:30,280 --> 00:52:35,440
picture of an embryo that's 12 hours
after conception,
676
00:52:35,440 --> 00:52:37,160
compared to taking a picture
677
00:52:37,160 --> 00:52:39,000
of a person who is 50 years old.
678
00:52:39,000 --> 00:52:40,560
It's in the same perspective.
679
00:52:40,560 --> 00:52:47,560
And 12 hours, you may have two cells,
this is very early and yet
we are seeing what's equivalent
680
00:52:47,560 --> 00:52:51,480
of the DNA, the blueprint for how
the universe is going to develop.
681
00:52:53,040 --> 00:52:56,640
With the help of highly
sensitive satellites,
682
00:52:56,640 --> 00:53:00,760
George Smoot and his team
were able to study this image
683
00:53:00,760 --> 00:53:04,280
of the embryonic universe
in amazing detail.
684
00:53:04,280 --> 00:53:10,680
And when they did, tiny variations
in its temperature were revealed.
685
00:53:10,680 --> 00:53:15,200
It soon became apparent that the
tiny differences in temperature
686
00:53:15,200 --> 00:53:21,120
are in fact the scars left by the
quantum vacuum on our universe.
687
00:53:25,480 --> 00:53:28,160
EXPLOSION
688
00:53:28,160 --> 00:53:33,960
These irregularities
created in the first
moments of existence
689
00:53:33,960 --> 00:53:39,360
by the teeming quantum vacuum
meant the matter of the universe
690
00:53:39,360 --> 00:53:42,760
didn't spread out
completely evenly.
691
00:53:42,760 --> 00:53:44,480
EXPLOSION
692
00:53:48,200 --> 00:53:53,560
Rather, it formed vast clumps
that would evolve into
693
00:53:53,560 --> 00:53:59,000
the galaxies
and clusters of galaxies
that make up the universe today.
694
00:54:00,520 --> 00:54:03,880
The application of quantum physics
to cosmology,
695
00:54:03,880 --> 00:54:05,240
to the universe as a whole
696
00:54:05,240 --> 00:54:06,920
was revolutionary.
697
00:54:06,920 --> 00:54:09,800
It really changed
our entire perception
698
00:54:09,800 --> 00:54:12,200
of the evolution of the universe,
699
00:54:12,200 --> 00:54:16,600
because it turns out
that quantum physics provides
a natural mechanism
700
00:54:16,600 --> 00:54:18,840
through quantum fluctuations
701
00:54:18,840 --> 00:54:26,280
to see into the early universe
with small irregularities that
would later grow to make galaxies.
702
00:54:26,280 --> 00:54:30,920
The thought is really overwhelming,
the idea that an object
703
00:54:30,920 --> 00:54:36,280
with billions of stars
like the Milky Way
began life as a quantum fluctuation,
704
00:54:36,280 --> 00:54:39,720
what we call a fluctuation
of the vacuum,
705
00:54:39,720 --> 00:54:43,280
an object of sub-microscopic scales,
it really is mind boggling.
706
00:54:45,200 --> 00:54:50,960
It now appears as if the quantum
world, the place we once thought of
707
00:54:50,960 --> 00:54:57,800
as empty nothingness has actually
shaped everything we see around us.
708
00:54:59,640 --> 00:55:03,480
What happens is, something
that was a small fluctuation,
709
00:55:03,480 --> 00:55:06,760
a tiny quantum fluctuation,
becomes our galaxy.
710
00:55:06,760 --> 00:55:11,320
Or becomes a cluster of galaxies
because there are lots of
quantum fluctuations,
711
00:55:11,320 --> 00:55:13,720
so it answers one of the
questions we have -
712
00:55:13,720 --> 00:55:16,720
why are there 100 billion galaxies
in our viewpoint?
713
00:55:16,720 --> 00:55:18,080
Well, in a drop of water,
714
00:55:18,080 --> 00:55:21,360
there's many more than 100
million quantum fluctuations,
715
00:55:21,360 --> 00:55:26,640
in an atom there's that many,
the vacuum has all of this
bubbling going on all the time.
716
00:55:30,440 --> 00:55:34,920
The teeming, seething activity
of the vacuum, of nothing,
717
00:55:34,920 --> 00:55:37,960
and the quantum fluctuations
within it...
718
00:55:40,720 --> 00:55:46,960
..were the seeds, seeds which grew
into the universe we see today.
719
00:55:50,840 --> 00:55:56,080
This idea
gives rise to one final revelation.
720
00:55:56,080 --> 00:56:00,480
Today, our best theories
about the cosmos tell us
721
00:56:00,480 --> 00:56:05,160
that at the beginning of time,
the universe sprang from the vacuum.
722
00:56:07,160 --> 00:56:13,680
Creating not only vast amounts of
matter, but also the strange stuff
723
00:56:13,680 --> 00:56:16,960
that was predicted by Paul Dirac...
724
00:56:19,160 --> 00:56:21,080
..anti-matter.
725
00:56:22,680 --> 00:56:26,720
But the universe we see today
is made of matter,
726
00:56:26,720 --> 00:56:31,320
nearly all of the anti-matter
seems to have vanished.
727
00:56:34,200 --> 00:56:37,000
EXPLOSION
728
00:56:38,840 --> 00:56:42,360
According to common theory,
729
00:56:42,360 --> 00:56:46,280
the Big Bang produced equal
amounts of matter and anti-matter.
730
00:56:46,280 --> 00:56:48,560
But as the universe cooled down,
731
00:56:48,560 --> 00:56:53,600
matter and anti-matter annihilated
almost perfectly, but not quite.
732
00:56:53,600 --> 00:56:58,200
For every billion particles
of matter and anti-matter,
733
00:56:58,200 --> 00:56:59,880
one was left behind.
734
00:56:59,880 --> 00:57:03,880
The matter and anti-matter that
annihilated to produce radiation
735
00:57:03,880 --> 00:57:06,120
gave rise to the heat of
the Big Bang
736
00:57:06,120 --> 00:57:09,760
that we see today in the form of
the microwave background radiation.
737
00:57:09,760 --> 00:57:13,120
The little particle that was
left behind, for every billion
738
00:57:13,120 --> 00:57:19,480
that annihilated is what makes
galaxies, stars, planets and people.
739
00:57:23,880 --> 00:57:28,600
So, we are simply the debris
of a huge annihilation
740
00:57:28,600 --> 00:57:32,880
of matter and anti-matter
at the beginning of time.
741
00:57:32,880 --> 00:57:35,040
EXPLOSION
742
00:57:36,240 --> 00:57:40,400
The leftovers of
an unimaginable explosion.
743
00:57:51,080 --> 00:57:54,120
All these insights have arisen
744
00:57:54,120 --> 00:57:59,960
from simply trying to understand
what nothing really is.
745
00:57:59,960 --> 00:58:03,320
What we once thought of as the void
746
00:58:03,320 --> 00:58:06,120
now seems to hold within it,
747
00:58:06,120 --> 00:58:11,040
the deepest mysteries
of the entire universe.
748
00:58:17,720 --> 00:58:21,640
In the 400 years or so since
Torricelli and Pascal
749
00:58:21,640 --> 00:58:24,760
began exploring vacuums
here on Earth,
750
00:58:24,760 --> 00:58:31,960
we've begun to understand in
ever greater detail the world's at
the very limits of our perception.
751
00:58:31,960 --> 00:58:38,640
And in doing so, we've uncovered the
strange truth about reality itself.
752
00:58:38,640 --> 00:58:42,880
There's a profound connection
between the nothingness
753
00:58:42,880 --> 00:58:45,000
from which we originated
754
00:58:45,000 --> 00:58:48,760
and the infinite
in which we are engulfed.
755
00:59:05,520 --> 00:59:09,880
Subtitles by Red Bee Media Ltd
756
00:59:09,880 --> 00:59:14,480
E-mail subtitling@bbc.co.uk
69094
Can't find what you're looking for?
Get subtitles in any language from opensubtitles.com, and translate them here.