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What is nothing? | 0:00:10 | 0:00:13 | |
It's an extremely, extremely difficult question to answer, | 0:00:13 | 0:00:17 | |
because if you think about it, | 0:00:17 | 0:00:19 | |
wherever you look around you, there always seems to be something there. | 0:00:19 | 0:00:24 | |
Things appear almost impossible to escape from. | 0:00:32 | 0:00:37 | |
Even just trying to imagine true nothingness | 0:00:38 | 0:00:41 | |
seems like an impossible task. | 0:00:41 | 0:00:45 | |
But this is more than just a philosophical question. | 0:00:47 | 0:00:50 | |
I have here a box. What would happen | 0:00:50 | 0:00:53 | |
if I were to remove everything I possibly could from inside it? | 0:00:53 | 0:00:57 | |
All the air, dust, every last single atom, | 0:00:57 | 0:01:01 | |
until there was no thing left. | 0:01:01 | 0:01:03 | |
What, then, exists inside the space in the box? | 0:01:05 | 0:01:09 | |
Is it really nothing? | 0:01:09 | 0:01:12 | |
You might wonder why this matters. | 0:01:14 | 0:01:17 | |
Well, emptiness is what makes up almost the entire universe. | 0:01:17 | 0:01:22 | |
Even the atoms that make up our bodies | 0:01:22 | 0:01:26 | |
and the physical world around us comprise mostly of empty space. | 0:01:26 | 0:01:32 | |
This film tells the story | 0:01:37 | 0:01:39 | |
of how we've begun to understand what is known as the void, | 0:01:39 | 0:01:44 | |
or the vacuum. | 0:01:44 | 0:01:46 | |
Emptiness, or simply nothing. | 0:01:46 | 0:01:49 | |
It's about reality at the very furthest reaches of human perception. | 0:01:49 | 0:01:54 | |
A place where the deepest mysteries of the universe may be held. | 0:01:54 | 0:01:59 | |
This film reveals how, | 0:02:11 | 0:02:13 | |
using ingenious technology, | 0:02:13 | 0:02:16 | |
humans have transcended their physical senses, | 0:02:16 | 0:02:20 | |
and found ways to understand and probe the universe | 0:02:20 | 0:02:25 | |
at the smallest scales. | 0:02:25 | 0:02:27 | |
Today, we believe the void contains nature's deepest secrets. | 0:02:33 | 0:02:39 | |
It might even explain why we exist at all. | 0:02:39 | 0:02:44 | |
And that's because, to the best of our knowledge, | 0:02:44 | 0:02:47 | |
the entire universe appeared nearly 14 billion years ago | 0:02:47 | 0:02:53 | |
out of nothing. | 0:02:53 | 0:02:55 | |
For over 1,000 years, | 0:03:15 | 0:03:16 | |
our understanding of empty space was defined by one man - | 0:03:16 | 0:03:21 | |
the Greek philosopher Aristotle. | 0:03:21 | 0:03:24 | |
To Aristotle, the concept of nothingness was deeply disturbing. | 0:03:27 | 0:03:32 | |
It seemed to present all sorts of problems and paradoxes. | 0:03:32 | 0:03:37 | |
He came to believe that nature would forever fight against | 0:03:39 | 0:03:44 | |
the creation of true nothingness. | 0:03:44 | 0:03:46 | |
As he put it, nature abhors a vacuum. | 0:03:46 | 0:03:50 | |
These words stuck for over 1,000 years, because after Aristotle, | 0:03:54 | 0:03:59 | |
people who attempted to make empty space faced an uphill struggle. | 0:03:59 | 0:04:04 | |
It seemed nature was indeed doing everything in its power | 0:04:04 | 0:04:08 | |
to stop them. | 0:04:08 | 0:04:10 | |
Well, the whole mystery of nothingness | 0:04:11 | 0:04:14 | |
is contained inside this simple drinking straw. | 0:04:14 | 0:04:18 | |
Let me demonstrate. If I suck out the air from the top of the straw... | 0:04:18 | 0:04:22 | |
..more air immediately rushes in to fill the space left behind. | 0:04:23 | 0:04:28 | |
And even more weirdly, if I block off the bottom of the straw and suck... | 0:04:28 | 0:04:33 | |
..the walls of the straw collapse in on themselves. | 0:04:35 | 0:04:39 | |
It's as though the universe won't allow me to make nothingness. | 0:04:39 | 0:04:44 | |
And it gets even weirder. If I take a sip of my drink... | 0:04:44 | 0:04:47 | |
..and pinch off the top, | 0:04:50 | 0:04:52 | |
then it seems nature is so intent on stopping me | 0:04:52 | 0:04:55 | |
that even the law of gravity is suspended. | 0:04:55 | 0:04:59 | |
So it's not hard to understand why people believed | 0:04:59 | 0:05:03 | |
that it was impossible to make truly empty space. | 0:05:03 | 0:05:07 | |
But there is a very simple explanation | 0:05:09 | 0:05:12 | |
for why a straw behaves like this - | 0:05:12 | 0:05:15 | |
a reason that would come as a profound shock to the people who worked it out. | 0:05:15 | 0:05:21 | |
By the 17th century, some strange exceptions were being found | 0:05:21 | 0:05:25 | |
to nature's abhorrence of empty space. | 0:05:25 | 0:05:28 | |
And it was beginning to seem | 0:05:28 | 0:05:30 | |
like there may be ways of tricking nothingness into existence. | 0:05:30 | 0:05:36 | |
The man who would finally do what Aristotle thought impossible | 0:05:38 | 0:05:43 | |
was an Italian Jesuit called Evangelista Torricelli. | 0:05:43 | 0:05:48 | |
Torricelli's experiment would, for the first time, | 0:05:51 | 0:05:55 | |
create and capture empty space for long enough to begin to study it. | 0:05:55 | 0:06:00 | |
This is how the experiment went, with a tube filled with mercury | 0:06:03 | 0:06:06 | |
and a finger really strongly clamped over the end. | 0:06:06 | 0:06:09 | |
The tube was then turned upside down | 0:06:09 | 0:06:11 | |
and then placed into the bath of mercury. | 0:06:11 | 0:06:15 | |
At this point, the mercury was released. | 0:06:15 | 0:06:19 | |
You can now see it dropping down. | 0:06:19 | 0:06:21 | |
And then it stops. | 0:06:21 | 0:06:25 | |
So I guess the important thing is that... | 0:06:25 | 0:06:28 | |
that isn't trapped air. | 0:06:28 | 0:06:30 | |
We started with a tube filled with mercury, and all we did was we let it drain out. | 0:06:30 | 0:06:36 | |
But it doesn't drain out completely, it reaches a level and stops. | 0:06:36 | 0:06:40 | |
Torricelli's experiments had not only created an airless space, | 0:06:41 | 0:06:47 | |
it had also shown that the atmosphere has a specific weight. | 0:06:47 | 0:06:51 | |
The reason my straw crumples when I suck the air out | 0:06:53 | 0:06:57 | |
is because of the pressure of the atmosphere that surrounds it. | 0:06:57 | 0:07:01 | |
But Torricelli's apparatus was overcoming this | 0:07:02 | 0:07:06 | |
by using the extreme weight of mercury and a rigid glass tube. | 0:07:06 | 0:07:11 | |
The level of mercury in his tube | 0:07:11 | 0:07:13 | |
was a measure of the weight of the atmosphere. | 0:07:13 | 0:07:17 | |
The level is, of course, determined by the weight of the mercury on the one hand, | 0:07:17 | 0:07:22 | |
and the weight of the air pressing down on the other. | 0:07:22 | 0:07:25 | |
And so the two balance out, like scales. | 0:07:25 | 0:07:28 | |
They'd found a way to weigh the atmosphere. | 0:07:28 | 0:07:31 | |
And Torricelli wrote this fantastic phrase. | 0:07:31 | 0:07:35 | |
He said, "Noi viviamo sommersi nel fondo d'un pelago d'aria elementare." | 0:07:35 | 0:07:39 | |
"We live at the bottom of an ocean of air." | 0:07:39 | 0:07:43 | |
Suddenly, the air really was a substance. | 0:07:43 | 0:07:47 | |
But I guess the real mystery for me now is, what's inside here? | 0:07:47 | 0:07:52 | |
Could this really be nothingness? | 0:07:52 | 0:07:55 | |
Indeed. | 0:07:55 | 0:07:56 | |
In revealing that the air has a weight | 0:07:59 | 0:08:02 | |
and that it's pushing down on us all the time, filling any space it can, | 0:08:02 | 0:08:07 | |
Torricelli had managed to create an empty space, | 0:08:07 | 0:08:11 | |
a type of nothingness that could now be studied. | 0:08:11 | 0:08:15 | |
Over 1,000 years of thinking about the way nature worked | 0:08:20 | 0:08:24 | |
was beginning to crumble. | 0:08:24 | 0:08:26 | |
Medieval philosophy, much influenced by Aristotle, supposed, | 0:08:32 | 0:08:35 | |
reasonably enough, that there is no such thing as empty space in nature. | 0:08:35 | 0:08:39 | |
And yet here is a pretty simple device - | 0:08:39 | 0:08:42 | |
a long, thin glass tube with some liquid in it - | 0:08:42 | 0:08:46 | |
which is able to produce, says Torricelli, an empty space, | 0:08:46 | 0:08:50 | |
thus showing that Aristotle and his disciples are wrong. | 0:08:50 | 0:08:54 | |
How can you show that centuries of philosophical tradition are wrong | 0:08:54 | 0:08:58 | |
just by doing a trick? | 0:08:58 | 0:09:00 | |
That didn't seem right at all. | 0:09:00 | 0:09:02 | |
But Torricelli was right, | 0:09:05 | 0:09:07 | |
and it would fall to philosopher and scientist Blaise Pascal | 0:09:07 | 0:09:12 | |
to develop and refine his work. | 0:09:12 | 0:09:14 | |
As Pascal began investigating Torricelli's ideas, | 0:09:14 | 0:09:18 | |
he discovered even more peculiar properties. | 0:09:18 | 0:09:22 | |
In Paris, he carried a mercury tube to the top of a huge tower | 0:09:22 | 0:09:28 | |
and recorded the mercury dropping to a lower level than it had been on the ground. | 0:09:28 | 0:09:34 | |
It seemed the pressure of the air fell as you went higher. | 0:09:34 | 0:09:38 | |
Pascal's experiments would lead to the realisation that the Earth | 0:09:43 | 0:09:48 | |
is cocooned in an atmosphere that rapidly thins out the higher you go... | 0:09:48 | 0:09:54 | |
..eventually becoming the cold, silent expanse of space. | 0:09:56 | 0:10:01 | |
Torricelli and Pascal had begun to unravel a profound truth - | 0:10:04 | 0:10:09 | |
nothing is everywhere. | 0:10:09 | 0:10:12 | |
Our Earth is merely a tiny speck of dust, | 0:10:16 | 0:10:20 | |
floating through a vast expanse | 0:10:20 | 0:10:23 | |
of an utterly silent, inhospitable void. | 0:10:23 | 0:10:26 | |
Nature doesn't abhor a vacuum. | 0:10:28 | 0:10:31 | |
A vacuum is nature's default state. | 0:10:31 | 0:10:35 | |
So what was this vast, empty space? | 0:10:44 | 0:10:48 | |
Now it was possible to make it on Earth, | 0:10:49 | 0:10:53 | |
scientists became deeply curious. | 0:10:53 | 0:10:56 | |
What exactly were the properties of nothingness? | 0:10:56 | 0:11:01 | |
After Torricelli and Pascal's experiments, | 0:11:01 | 0:11:04 | |
many scientists became fascinated | 0:11:04 | 0:11:06 | |
with studying the properties of the vacuum. | 0:11:06 | 0:11:09 | |
And they found some very odd things. | 0:11:09 | 0:11:12 | |
For instance, placing a ringing bell inside it became silent, | 0:11:12 | 0:11:15 | |
you couldn't hear it from the outside, | 0:11:15 | 0:11:18 | |
because, having removed all the air, | 0:11:18 | 0:11:20 | |
there was no medium to carry the sound waves. | 0:11:20 | 0:11:24 | |
Most intriguingly, although you couldn't hear the bell, | 0:11:24 | 0:11:28 | |
you could still see it. | 0:11:28 | 0:11:30 | |
This means light must be travelling through the vacuum. | 0:11:30 | 0:11:35 | |
But how could it do this? | 0:11:35 | 0:11:37 | |
For those scientists carrying out experiments with the vacuum, | 0:11:37 | 0:11:41 | |
there was just one simple conclusion. | 0:11:41 | 0:11:44 | |
The vacuum wasn't empty after all. | 0:11:44 | 0:11:47 | |
The fact that they could see inside it | 0:11:47 | 0:11:49 | |
meant that there still had to be something left in there. | 0:11:49 | 0:11:53 | |
Just as air carries sound waves, | 0:11:53 | 0:11:56 | |
they believed there had to be a medium carrying the light waves. | 0:11:56 | 0:12:00 | |
And whatever it was, it was proving very difficult to get rid of. | 0:12:00 | 0:12:05 | |
The nothingness that had been glimpsed by Torricelli and Pascal | 0:12:09 | 0:12:13 | |
now appeared to be a something - | 0:12:13 | 0:12:16 | |
a mysterious substance which carried waves of light. | 0:12:16 | 0:12:20 | |
And if that this substance existed in our vacuums on Earth, | 0:12:20 | 0:12:24 | |
it meant that it also existed out there. | 0:12:24 | 0:12:29 | |
It appeared once again that nothingness could not exist in nature. | 0:12:29 | 0:12:35 | |
Everything in the universe appeared to be sitting within an invisible medium, | 0:12:35 | 0:12:41 | |
what scientists called the luminiferous aether. | 0:12:41 | 0:12:45 | |
It was clear for many reasons, many good reasons, | 0:12:49 | 0:12:52 | |
that light was a kind of wave. | 0:12:52 | 0:12:54 | |
But if light is a kind of wave, what's it a wave in? | 0:12:54 | 0:12:59 | |
Sound waves are waves in air, light waves are waves in what came to be called, | 0:12:59 | 0:13:04 | |
from the early 1800s, the luminiferous aether, | 0:13:04 | 0:13:08 | |
the light-carrying fluid that fills all space. | 0:13:08 | 0:13:12 | |
If there's a fluid that fills all space, if light is a wave, nowhere is empty, | 0:13:12 | 0:13:18 | |
because light travels everywhere. | 0:13:18 | 0:13:21 | |
So at the very moment when it seemed absolutely plausible | 0:13:21 | 0:13:26 | |
that there can be empty space, it is obvious that there isn't. | 0:13:26 | 0:13:29 | |
And that there's this stuff called aether that carries light. | 0:13:29 | 0:13:33 | |
The problem was that this aether | 0:13:33 | 0:13:37 | |
appeared to be so subtle and so intangible | 0:13:37 | 0:13:41 | |
that it eluded all attempts to measure it. | 0:13:41 | 0:13:44 | |
It wouldn't be until the end of the 19th century that an experiment | 0:13:45 | 0:13:49 | |
would be built that was sensitive enough to reveal the truth. | 0:13:49 | 0:13:54 | |
The experiment would take place in the United States, | 0:13:54 | 0:13:58 | |
and Albert Michelson, the scientist who conducted it, | 0:13:58 | 0:14:01 | |
would go on to become America's first Nobel Prize winner. | 0:14:01 | 0:14:06 | |
From a young age, Michelson had relished tackling | 0:14:07 | 0:14:11 | |
the particularly difficult practical problems in physics. | 0:14:11 | 0:14:14 | |
He'd earned his reputation | 0:14:14 | 0:14:16 | |
by making extremely precise measurements of the speed of light. | 0:14:16 | 0:14:21 | |
Having completed his work on light, Michelson travelled to Europe | 0:14:23 | 0:14:28 | |
to spend some time amongst some of the best scientists in the world. | 0:14:28 | 0:14:32 | |
And it was there that he became fascinated with the topic | 0:14:32 | 0:14:35 | |
that everyone was talking about - the mysterious luminiferous aether. | 0:14:35 | 0:14:41 | |
One idea in particular captured his imagination. | 0:14:41 | 0:14:44 | |
It had been proposed that if you could measure the speed of light accurately enough, | 0:14:44 | 0:14:50 | |
it might just be possible | 0:14:50 | 0:14:52 | |
to actually deduce the properties of the aether. | 0:14:52 | 0:14:56 | |
And this is how. | 0:14:59 | 0:15:01 | |
If there was an aether, then as the Earth orbited the sun, | 0:15:01 | 0:15:06 | |
we should be able to detect its presence. | 0:15:06 | 0:15:10 | |
It would be like sticking your hand out of the window of a moving car. | 0:15:10 | 0:15:14 | |
You feel the rush of wind as the car travels through the air. | 0:15:14 | 0:15:18 | |
Michelson realised that if this picture of the aether was true, | 0:15:21 | 0:15:26 | |
then two light beams should travel at different speeds on Earth, | 0:15:26 | 0:15:30 | |
depending on the direction they were moving through this aethereal wind. | 0:15:30 | 0:15:35 | |
The difficulty was actually in making such a measurement. | 0:15:41 | 0:15:45 | |
It seemed like an almost impossible task. | 0:15:45 | 0:15:48 | |
The problem is this. | 0:15:48 | 0:15:50 | |
The speed of light is over 186,000 miles per second. | 0:15:50 | 0:15:56 | |
Now that's pretty nifty. | 0:15:56 | 0:15:58 | |
In comparison, the Earth virtually crawls around its orbit. | 0:15:58 | 0:16:02 | |
So the difference in speeds between those two light beams would be tiny - | 0:16:02 | 0:16:07 | |
something like one part in 100 million. | 0:16:07 | 0:16:10 | |
So the precision needed to get any sort of meaningful result | 0:16:10 | 0:16:14 | |
was way beyond anything that scientists thought was possible at the time. | 0:16:14 | 0:16:18 | |
But not so the headstrong Michelson. | 0:16:18 | 0:16:21 | |
He began to work his way round the problem. | 0:16:21 | 0:16:24 | |
He started to develop techniques and precision instruments | 0:16:24 | 0:16:28 | |
that he believed would be capable of unlocking the secrets of the aether. | 0:16:28 | 0:16:34 | |
From 1881, Michelson was taking measurements, | 0:16:41 | 0:16:45 | |
and tweaking and refining his apparatus. | 0:16:45 | 0:16:48 | |
But it wouldn't be until 1887 | 0:16:48 | 0:16:50 | |
at the Case School of Applied Science in Cleveland, Ohio, | 0:16:50 | 0:16:54 | |
that Michelson would finally build a machine sensitive enough | 0:16:54 | 0:16:58 | |
to give him some definitive answers. | 0:16:58 | 0:17:00 | |
There he joined forces with another scientist, Edward Morley, | 0:17:00 | 0:17:05 | |
to conduct what was to become one of the most notorious experiments in physics. | 0:17:05 | 0:17:11 | |
The original apparatus was set in a solid block of sandstone, | 0:17:12 | 0:17:16 | |
and then suspended in a bath of mercury | 0:17:16 | 0:17:19 | |
to remove any vibrations that might affect the measurements. | 0:17:19 | 0:17:23 | |
It was incredibly hi-tech and very expensive. | 0:17:23 | 0:17:26 | |
Think of it as an 1880s version of the Large Hadron Collider. | 0:17:26 | 0:17:31 | |
OK, so here's how it works. Light is emitted | 0:17:31 | 0:17:35 | |
from this source. | 0:17:35 | 0:17:37 | |
In the middle is something called a beam splitter, | 0:17:40 | 0:17:44 | |
which divides the light up into two parts. | 0:17:44 | 0:17:47 | |
Over here are two mirrors, | 0:17:51 | 0:17:53 | |
which reflect the light back to the middle | 0:17:53 | 0:17:56 | |
where they recombine at the beam splitter. | 0:17:56 | 0:18:00 | |
The light is sent down to this detector. Now, | 0:18:00 | 0:18:05 | |
Now, because of the wave-like properties of light, | 0:18:05 | 0:18:08 | |
you see a very specific pattern here. | 0:18:08 | 0:18:10 | |
Basically, if the light has travelled at the same speed along the two paths, | 0:18:10 | 0:18:15 | |
then you see a bright spot in the middle of the pattern. | 0:18:15 | 0:18:19 | |
So here's the really clever part. | 0:18:22 | 0:18:25 | |
Michelson and Morley reasoned | 0:18:25 | 0:18:27 | |
that if the Earth really was moving through a stationary aether, | 0:18:27 | 0:18:31 | |
the experiment should behave in a very different way. | 0:18:31 | 0:18:35 | |
Let's look at what happens when we simulate the effect of an aether. | 0:18:35 | 0:18:39 | |
The light leaves the detector | 0:18:43 | 0:18:47 | |
and gets split. | 0:18:47 | 0:18:49 | |
Now here's the key. | 0:18:51 | 0:18:53 | |
The light that travels against the aether and back again | 0:18:53 | 0:18:56 | |
covers this journey in a different time | 0:18:56 | 0:19:00 | |
to the light travelling across the aether. | 0:19:00 | 0:19:03 | |
This means that when the light waves recombine, | 0:19:03 | 0:19:07 | |
they now interfere with each other. | 0:19:07 | 0:19:11 | |
This interference means that the image | 0:19:11 | 0:19:14 | |
will have a dark spot at its centre. | 0:19:14 | 0:19:17 | |
See this, and you know that the void must be filled | 0:19:17 | 0:19:20 | |
with a stationary medium through which the Earth is moving. | 0:19:20 | 0:19:25 | |
Of course I can't be sure exactly | 0:19:28 | 0:19:30 | |
what was going through the minds of Michelson and Morley | 0:19:30 | 0:19:33 | |
as they began their experiment, | 0:19:33 | 0:19:35 | |
but it is a safe bet that, given the scientific consensus at the time, | 0:19:35 | 0:19:39 | |
they were convinced that the aether really existed. | 0:19:39 | 0:19:43 | |
So they would have been sure that they would have found light | 0:19:43 | 0:19:46 | |
travelling at different speeds as it moved in different directions. | 0:19:46 | 0:19:51 | |
But it didn't. | 0:19:51 | 0:19:53 | |
No matter how they rotated their apparatus, | 0:19:53 | 0:19:56 | |
they always found light travelled at the same speed. | 0:19:56 | 0:20:01 | |
Michelson and Morley had gained an extraordinary and accurate result. | 0:20:06 | 0:20:11 | |
But the idea of the luminiferous aether was so ingrained | 0:20:14 | 0:20:18 | |
that they believed simply that their experiments had failed. | 0:20:18 | 0:20:22 | |
So what is going on? | 0:20:28 | 0:20:30 | |
Why didn't Michelson and Morley's experiment reveal the result they were expecting? | 0:20:30 | 0:20:35 | |
How could light always be travelling at the same speed? | 0:20:35 | 0:20:39 | |
Well, the answer is simple. The aether doesn't exist. | 0:20:39 | 0:20:44 | |
No matter what light is doing, how it is travelling, | 0:20:44 | 0:20:47 | |
it doesn't need to be carried along by this mysterious stuff that pervades the vacuum. | 0:20:47 | 0:20:52 | |
So how does light move through empty space? | 0:20:55 | 0:21:00 | |
Well, by the end of the 19th century, | 0:21:00 | 0:21:03 | |
light was known to be in fact | 0:21:03 | 0:21:05 | |
a combination of fluctuating electric and magnetic fields. | 0:21:05 | 0:21:11 | |
But it would take the genius of Einstein in 1905 | 0:21:11 | 0:21:15 | |
to reveal that this picture of light doesn't need an aether. | 0:21:15 | 0:21:20 | |
He showed that it has the weird property | 0:21:20 | 0:21:23 | |
of being able to propagate through completely empty space. | 0:21:23 | 0:21:28 | |
So the message from the failure of Michelson and Morley's experiment is this - | 0:21:29 | 0:21:35 | |
there is no aether. | 0:21:35 | 0:21:37 | |
Maybe the vacuum is really empty. | 0:21:37 | 0:21:42 | |
If only it were that simple. | 0:21:42 | 0:21:44 | |
Almost as soon as Michelson and Morley had revealed, | 0:21:47 | 0:21:50 | |
by accident, that you really could have nothing... | 0:21:50 | 0:21:53 | |
..scientists began to discover some very weird properties of nature. | 0:21:55 | 0:22:01 | |
In the 100 years that followed Michelson and Morley's experiments, | 0:22:03 | 0:22:07 | |
physics and our understanding of the vacuum | 0:22:07 | 0:22:11 | |
has been totally transformed. | 0:22:11 | 0:22:14 | |
But what drove this huge shift was not simply scientific curiosity. | 0:22:23 | 0:22:28 | |
But the fact that in the late 19th century, | 0:22:31 | 0:22:34 | |
the vacuum and its many applications had become big business. | 0:22:34 | 0:22:39 | |
Industry was finding ever more ingenious ways | 0:22:43 | 0:22:46 | |
to make money out of nothing. | 0:22:46 | 0:22:49 | |
Understanding and harnessing the vacuum turned out | 0:22:51 | 0:22:55 | |
to lead to a wealth of new technologies that we just take for granted today. | 0:22:55 | 0:23:00 | |
Everything from the light bulb to the television | 0:23:00 | 0:23:04 | |
were only made possible | 0:23:04 | 0:23:06 | |
because they could contain within them small volumes of vacuum. | 0:23:06 | 0:23:11 | |
The filament inside a light bulb can glow for long periods | 0:23:14 | 0:23:19 | |
because it is contained within a vacuum. | 0:23:19 | 0:23:22 | |
Expose it to air and it would simply burn out in seconds. | 0:23:22 | 0:23:26 | |
As cities around the world began to electrify, | 0:23:31 | 0:23:34 | |
the demand for light bulbs grew massively. | 0:23:34 | 0:23:38 | |
The engineers became ever more skilled at creating cheap, efficient vacuums. | 0:23:38 | 0:23:43 | |
This technology would give rise to a huge range of gadgets - | 0:23:44 | 0:23:49 | |
everything from the valves in radios and early computers | 0:23:49 | 0:23:55 | |
to the television. | 0:23:55 | 0:23:56 | |
But all the technological innovations that came from harnessing the vacuum | 0:23:58 | 0:24:03 | |
would pale into insignificance when compared to what scientists | 0:24:03 | 0:24:06 | |
would soon find out about the fundamental nature of reality. | 0:24:06 | 0:24:11 | |
Because vacuum technology was getting so much cheaper, | 0:24:13 | 0:24:18 | |
and more efficient, | 0:24:18 | 0:24:20 | |
scientists all over the world could use it as a tool for research. | 0:24:20 | 0:24:24 | |
In empty space, nature's tiniest constituents could now be studied | 0:24:24 | 0:24:30 | |
without interference from the contaminant-filled air of the outside world. | 0:24:30 | 0:24:35 | |
This revolutionised physics. | 0:24:36 | 0:24:39 | |
Because of the vacuum, X-rays were discovered in 1895. | 0:24:41 | 0:24:46 | |
The following year, the electron was identified for the first time. | 0:24:47 | 0:24:52 | |
And in 1909, Ernest Rutherford would use vacuums | 0:24:52 | 0:24:56 | |
to help reveal the strange structure of the atom. | 0:24:56 | 0:25:00 | |
These discoveries were all feeding into a radically new picture | 0:25:03 | 0:25:07 | |
of the way nature works at its smallest and most fundamental level. | 0:25:07 | 0:25:12 | |
It was a theory that would come to be known as quantum mechanics. | 0:25:14 | 0:25:19 | |
And the submicroscopic world it describes behaves very differently | 0:25:19 | 0:25:23 | |
to the world we are used to. | 0:25:23 | 0:25:25 | |
This is a world where, against all common sense, | 0:25:27 | 0:25:31 | |
it seems impossible to ever truly have nothing. | 0:25:31 | 0:25:36 | |
This is the classical world, | 0:25:45 | 0:25:47 | |
action and reaction. | 0:25:47 | 0:25:50 | |
Cause and effect. | 0:25:51 | 0:25:53 | |
It is sensible, certain and knowable. | 0:25:53 | 0:25:56 | |
But the quantum world soon revealed itself to be very different. | 0:25:57 | 0:26:03 | |
There was one discovery that was particularly troubling | 0:26:05 | 0:26:10 | |
and it's known as Heisenberg's Uncertainty Principle. | 0:26:10 | 0:26:15 | |
In everyday life we are used to doubt, to uncertainty. | 0:26:19 | 0:26:25 | |
How can we be sure that something is this way or that way? | 0:26:25 | 0:26:28 | |
Well, it turns out that nature itself is based on indeterminacy, | 0:26:28 | 0:26:34 | |
in uncertainty. | 0:26:34 | 0:26:36 | |
The world of quantum physics, the microscopic world, is a world of uncertainty. | 0:26:36 | 0:26:41 | |
It's a world where you can never be sure of what is going to happen. | 0:26:41 | 0:26:44 | |
Not because your measurements are not good enough, simply because, | 0:26:44 | 0:26:49 | |
at a very fundamental level, nature itself is based on uncertainty. | 0:26:49 | 0:26:54 | |
OK, I would like to get across the essence of Heisenberg's Uncertainty Principle. | 0:26:57 | 0:27:02 | |
I'm going to use a non-mathematical analogy. | 0:27:02 | 0:27:05 | |
We have to be careful here - | 0:27:05 | 0:27:07 | |
it is just an analogy so we shouldn't push it too far. | 0:27:07 | 0:27:10 | |
I have here two identical memory sticks. | 0:27:10 | 0:27:14 | |
On the first one is a high-resolution image. | 0:27:14 | 0:27:18 | |
It is a picture of me having a game of pool. | 0:27:18 | 0:27:21 | |
We can see it is very detailed. | 0:27:21 | 0:27:23 | |
In fact, I can zoom in... | 0:27:23 | 0:27:25 | |
..even quite closely onto the pool ball. | 0:27:27 | 0:27:30 | |
And you see, even at this magnification, | 0:27:30 | 0:27:32 | |
I can still see the precise position, I can see the edges of the ball very detailed. | 0:27:32 | 0:27:37 | |
But what I don't know is how fast the ball is moving | 0:27:37 | 0:27:41 | |
or what is going to happen next. | 0:27:41 | 0:27:45 | |
Now, on the second memory stick is another file. It's a very different kind of file. | 0:27:45 | 0:27:50 | |
It is a movie. | 0:27:50 | 0:27:52 | |
The important thing to note is that the file is the same size | 0:27:52 | 0:27:56 | |
as the high-resolution image. | 0:27:56 | 0:27:58 | |
Now, have a look at this. | 0:27:59 | 0:28:02 | |
Now we can see the whole movie playing out. It is the same scene, | 0:28:02 | 0:28:06 | |
but you can see all the balls moving. | 0:28:06 | 0:28:08 | |
But if I zoom in on some detail... | 0:28:08 | 0:28:12 | |
..very quickly the balls become fuzzy and blurred. | 0:28:14 | 0:28:18 | |
So for the same amount of information, | 0:28:18 | 0:28:20 | |
although I've gained knowledge about how the balls are moving, | 0:28:20 | 0:28:25 | |
I've lost information about their exact positions. | 0:28:25 | 0:28:28 | |
So with the more I know about where something is, | 0:28:28 | 0:28:32 | |
the less I know about how it is moving. | 0:28:32 | 0:28:36 | |
In the quantum world, | 0:28:36 | 0:28:38 | |
I cannot at the same time know both these quantities exactly. | 0:28:38 | 0:28:44 | |
Unfortunately, there is no way around this. | 0:28:44 | 0:28:47 | |
Heisenberg showed in his mathematics | 0:28:47 | 0:28:50 | |
that this is in an inescapable feature of reality at this scale. | 0:28:50 | 0:28:55 | |
OK, so what has all this quantum weirdness | 0:28:55 | 0:29:00 | |
got to do with nothing? | 0:29:00 | 0:29:02 | |
Well, you see, Heisenberg's Uncertainty Principle can be expressed in a different way, | 0:29:02 | 0:29:08 | |
in terms of a balance between two other quantities - energy and time. | 0:29:08 | 0:29:14 | |
Now, this is going to sound quite complicated, | 0:29:14 | 0:29:16 | |
but it's very important, so I'm going to try and explain. | 0:29:16 | 0:29:19 | |
You see, if I were to examine | 0:29:19 | 0:29:22 | |
a small volume of empty space inside this box, then I could | 0:29:22 | 0:29:27 | |
in principle know how much energy it contains very precisely. | 0:29:27 | 0:29:32 | |
But, if I were able to slow time down, | 0:29:33 | 0:29:38 | |
things would start to get very strange. | 0:29:38 | 0:29:42 | |
OK, so we are now looking at a tiny interval of time that has been stretched out. | 0:29:47 | 0:29:53 | |
Heisenberg's uncertainty principle | 0:29:56 | 0:29:58 | |
tells us that because I'm looking at a smaller interval of time, | 0:29:58 | 0:30:02 | |
I've lost precise information about the exact energy in the box. | 0:30:02 | 0:30:08 | |
If I could examine an even smaller interval of time, | 0:30:11 | 0:30:15 | |
and an even smaller volume inside the box, | 0:30:15 | 0:30:19 | |
then Heisenberg's equation suggests something truly bizarre could happen. | 0:30:19 | 0:30:25 | |
I will be so uncertain about how much energy there is in that part of the box, | 0:30:30 | 0:30:35 | |
that there is a chance it could contain | 0:30:35 | 0:30:39 | |
enough energy to create particles literally out of nowhere... | 0:30:39 | 0:30:45 | |
..provided that somehow they went away again very quickly. | 0:30:47 | 0:30:51 | |
Heisenberg's uncertainty principle seemed to suggest that | 0:31:00 | 0:31:05 | |
in truly tiny amounts of time and space, something could come from nothing. | 0:31:05 | 0:31:12 | |
But then what? If particles could pop into existence, where do they go? | 0:31:13 | 0:31:20 | |
Why don't we see these particles appearing all around us? | 0:31:20 | 0:31:24 | |
The vacuum, contrary to what one normally expects from the vacuum, | 0:31:28 | 0:31:33 | |
is alive. | 0:31:33 | 0:31:34 | |
It's alive with what physicists call quantum fluctuations. | 0:31:34 | 0:31:37 | |
In the vacuum, little packets of energy appear and disappear | 0:31:37 | 0:31:41 | |
very, very quickly. | 0:31:41 | 0:31:43 | |
This is perfectly allowed by the laws of physics. | 0:31:43 | 0:31:45 | |
It's all allowed but it has an name, | 0:31:45 | 0:31:47 | |
it is called Heisenberg's uncertainty principle, | 0:31:47 | 0:31:50 | |
which tells us that you can | 0:31:50 | 0:31:52 | |
borrow energy from nothing, so long as you pay it back quickly enough. | 0:31:52 | 0:31:55 | |
The vacuum is alive. | 0:31:58 | 0:32:02 | |
Bizarre though these ideas seem, they are, I promise you, fundamental to our universe. | 0:32:02 | 0:32:09 | |
To see how this can be, | 0:32:09 | 0:32:11 | |
our story of nothing takes us to one of the most | 0:32:11 | 0:32:15 | |
gifted and oddest characters in the whole history of physics. | 0:32:15 | 0:32:20 | |
Behind me is Bishop Road Primary School in Bristol | 0:32:24 | 0:32:29 | |
and almost 100 years ago, | 0:32:29 | 0:32:30 | |
it was attended by two students who were destined for greatness. | 0:32:30 | 0:32:34 | |
One of them, Archibald Leach, would go on to conquer Hollywood, | 0:32:34 | 0:32:38 | |
becoming better known as Cary Grant. | 0:32:38 | 0:32:41 | |
The other was a quiet, shy and rather intense boy two years younger than Grant, | 0:32:41 | 0:32:46 | |
who would become one of the greatest scientists Britain has ever produced, | 0:32:46 | 0:32:51 | |
the theoretical physicist Paul Dirac. | 0:32:51 | 0:32:54 | |
Even by the standards of theoretical physicists, | 0:32:59 | 0:33:01 | |
Dirac was a very queer bird. | 0:33:01 | 0:33:04 | |
He was not someone you'd go for a beer with. | 0:33:04 | 0:33:08 | |
Intensely focused, | 0:33:08 | 0:33:10 | |
man of extremely few words, very, very little empathy | 0:33:10 | 0:33:15 | |
and someone of rectilinear thought. | 0:33:15 | 0:33:18 | |
These personality traits were key to Dirac's genius, | 0:33:21 | 0:33:25 | |
but they often resulted in difficult or awkward | 0:33:25 | 0:33:29 | |
social situations with his peers. | 0:33:29 | 0:33:32 | |
Even in casual conversation, Dirac would never speak unnecessarily. | 0:33:32 | 0:33:38 | |
He'd often leave these long pauses in between sentences while | 0:33:38 | 0:33:42 | |
he worked out the most precise and concise way of expressing himself. | 0:33:42 | 0:33:47 | |
Friends had jokingly coined the term a Dirac, which stands for | 0:33:47 | 0:33:51 | |
the smallest number of words it is possible to speak in one hour, | 0:33:51 | 0:33:55 | |
while still taking part in a conversation. | 0:33:55 | 0:33:58 | |
It is a sort of unit of shyness. | 0:33:58 | 0:34:01 | |
Dirac's unusual personality had its roots | 0:34:05 | 0:34:08 | |
in a difficult and troubled childhood. | 0:34:08 | 0:34:11 | |
But from a young age, he had found solace in the classroom. | 0:34:11 | 0:34:16 | |
In particular, he excelled at both mathematics and technical drawing. | 0:34:16 | 0:34:22 | |
This was something that cultivated his visual imagination. | 0:34:22 | 0:34:28 | |
In maths classes, he was looking at mathematical symbols. | 0:34:28 | 0:34:31 | |
He was looking at similar things, but in a geometric way in his technical drawing class. | 0:34:31 | 0:34:37 | |
It is very, very suggestive of the way he looked at physics later on | 0:34:37 | 0:34:42 | |
because he always stressed that he was pre-eminently a visualiser. | 0:34:42 | 0:34:48 | |
He was someone who had a geometric look at physics. | 0:34:48 | 0:34:52 | |
He was not interested per say in mathematical symbols. | 0:34:52 | 0:34:56 | |
Rather he wanted a visual sense of what was going on in the mathematics. | 0:34:56 | 0:35:00 | |
Dirac continued his visual training, doing a degree in engineering | 0:35:03 | 0:35:07 | |
before go to Cambridge to study mathematics. | 0:35:07 | 0:35:10 | |
It would be here that Dirac would begin to unravel the deepest mysteries of the vacuum | 0:35:10 | 0:35:16 | |
and uncover what was really going on in empty space. | 0:35:16 | 0:35:20 | |
But his insight sprang from a seemingly unrelated difficulty. | 0:35:22 | 0:35:26 | |
By 1928, physics was struggling with a big problem. | 0:35:28 | 0:35:32 | |
The two most important theories | 0:35:32 | 0:35:35 | |
that described how the universe worked didn't agree with each other. | 0:35:35 | 0:35:39 | |
On the one hand, you had Einstein's special theory of relativity | 0:35:39 | 0:35:43 | |
encapsulated in the famous equation E=mc2. | 0:35:43 | 0:35:47 | |
It was a beautiful, simple and elegant theory | 0:35:47 | 0:35:50 | |
that describes the behaviour of things close to the speed of light. | 0:35:50 | 0:35:54 | |
On the other hand, you had Planck's discovery of the quantum | 0:35:54 | 0:35:58 | |
and the revolution that followed describing the bizarre rules of the very, very small. | 0:35:58 | 0:36:04 | |
The problems arose when trying to describe situations where things were small enough | 0:36:06 | 0:36:12 | |
for quantum effects to be felt, | 0:36:12 | 0:36:14 | |
but travelling fast enough for special relativity to be important. | 0:36:14 | 0:36:19 | |
Specifically, there were huge problems trying to describe | 0:36:21 | 0:36:24 | |
the electron, a tiny particle whizzing around inside an atom. | 0:36:24 | 0:36:30 | |
If both of these theories were true, then they should be able to be used | 0:36:30 | 0:36:35 | |
together to give a mathematical description of the electron. | 0:36:35 | 0:36:39 | |
But what if this couldn't be done? | 0:36:43 | 0:36:45 | |
What if quantum physics and special relativity couldn't be married? | 0:36:45 | 0:36:49 | |
This would mean one or other of these two cornerstones of physics had to be wrong. | 0:36:49 | 0:36:54 | |
A way had to be found for the two theories to be married together. | 0:36:54 | 0:37:00 | |
It would be Dirac who would achieve this. | 0:37:00 | 0:37:02 | |
Dirac's unification of the special theory and the rules of the quantum world | 0:37:06 | 0:37:11 | |
would rank as one of the greatest mathematical accomplishments of the 20th century. | 0:37:11 | 0:37:16 | |
And it would lead inadvertently to a radical new picture of nothing. | 0:37:16 | 0:37:22 | |
To get a non mathematical sense of what he did, and how he did it, | 0:37:24 | 0:37:28 | |
I've come to the cinema to see one of Dirac's favourite films, 2001 A Space Odyssey. | 0:37:28 | 0:37:35 | |
Understanding why it appealed to him | 0:37:39 | 0:37:41 | |
helps give us an insight into how he managed to solve this great problem. | 0:37:41 | 0:37:46 | |
If you look at 2001, it was, as Kubrick has said, a demonstration | 0:37:46 | 0:37:52 | |
that you could make a really good movie script without words | 0:37:52 | 0:37:57 | |
but with a power of the visual imagery. | 0:37:57 | 0:37:59 | |
Now, that in some ways is very closely analogous | 0:37:59 | 0:38:03 | |
to Dirac's a theoretical physics | 0:38:03 | 0:38:06 | |
because, for him, what was central, were the mathematical equations. | 0:38:06 | 0:38:11 | |
And more over, he had a visual sense of what those equations meant. | 0:38:11 | 0:38:15 | |
The abstract images of 2001 appealed to Dirac | 0:38:22 | 0:38:25 | |
because they captivated his brilliant visual imagination. | 0:38:25 | 0:38:30 | |
It was this highly developed and unusual way of thinking, | 0:38:30 | 0:38:35 | |
honed in his schooldays, that would enable him in 1928 | 0:38:35 | 0:38:39 | |
to visualise a unique way of describing the electron. | 0:38:39 | 0:38:43 | |
It was a description that finally managed to unite Einstein's | 0:38:43 | 0:38:48 | |
special theory of relativity and the weird world of quantum mechanics. | 0:38:48 | 0:38:53 | |
Today, it's known simply as the Dirac equation. | 0:39:10 | 0:39:15 | |
It may look like a small collection of symbols, | 0:39:15 | 0:39:18 | |
but to a mathematician this equation is profoundly beautiful. | 0:39:18 | 0:39:23 | |
A complex and symmetrical synthesis of mathematical ideas, expressed with stunning clarity. | 0:39:23 | 0:39:31 | |
This is the commemorative plaque at Bishop Road, Paul Dirac's primary school. | 0:39:35 | 0:39:41 | |
And on it, his famous equation. | 0:39:41 | 0:39:44 | |
Within these few symbols lie profound truths about the universe. | 0:39:44 | 0:39:49 | |
But don't be deceived by its apparent simplicity, | 0:39:49 | 0:39:53 | |
think of this equation as the tip of a giant mathematical iceberg. | 0:39:53 | 0:39:59 | |
Each of these terms relate to entire branches of mathematics | 0:39:59 | 0:40:03 | |
and the particular relationships between them. | 0:40:03 | 0:40:06 | |
Beneath this equation, are mathematical ideas that | 0:40:06 | 0:40:09 | |
have been developed and honed by many, many other great individuals. | 0:40:09 | 0:40:16 | |
If you think of a poem, you can think of it as the most supercharged | 0:40:16 | 0:40:19 | |
kind of language, the way you compress meaning | 0:40:19 | 0:40:23 | |
into a very, very brief area on the page. | 0:40:23 | 0:40:27 | |
Dirac was producing equations that had that kind of concision | 0:40:27 | 0:40:31 | |
and you can then unpack them, | 0:40:31 | 0:40:33 | |
just as you re-read a Shakespeare sonnet and see more and more in it, more and more elegance. | 0:40:33 | 0:40:38 | |
Same with the Dirac equation, you find an equation there | 0:40:38 | 0:40:42 | |
you can keep finding things that were not obvious on first reading. | 0:40:42 | 0:40:47 | |
In fact, Dirac once said that the equation was smarter than he was | 0:40:47 | 0:40:50 | |
because it actually gave more stuff out than he put into it. | 0:40:50 | 0:40:53 | |
There was one particularly odd thing the equation seemed to be saying to Dirac. | 0:40:54 | 0:41:00 | |
Something that would redefine the concept of empty space forever. | 0:41:00 | 0:41:06 | |
In his description of the electron, Dirac had been forced to use a collection of four equations | 0:41:06 | 0:41:13 | |
represented by the symbol gamma, | 0:41:13 | 0:41:15 | |
in order to make special relativity and quantum mechanics fit together. | 0:41:15 | 0:41:21 | |
But the need for four equations seemed strange. | 0:41:21 | 0:41:27 | |
To Dirac and other physicists in the 1920s, the first two were quite recognisable. | 0:41:27 | 0:41:33 | |
They described the behaviour of an electron as it had been observed in the laboratory. | 0:41:33 | 0:41:39 | |
But the second two were very strange. | 0:41:39 | 0:41:42 | |
They seemed to be saying there was some other type of electron that could exist. | 0:41:42 | 0:41:48 | |
One that had never been seen before. | 0:41:48 | 0:41:52 | |
So, this is the normal world we are familiar with. | 0:41:57 | 0:42:01 | |
And here, scaled up many, many times | 0:42:01 | 0:42:04 | |
is a regular electron of the type contained within | 0:42:04 | 0:42:08 | |
the trillions of atoms that make up this table, | 0:42:08 | 0:42:12 | |
me and everything else in the universe. | 0:42:12 | 0:42:15 | |
Dirac realised that these mysterious new elements in his equation | 0:42:15 | 0:42:20 | |
predicted the existence of a strange new kind of particle. | 0:42:20 | 0:42:24 | |
In some ways, just like the electron, and yet at the same time very, very different. | 0:42:24 | 0:42:32 | |
Dirac gradually became convinced that the new parts of his equation | 0:42:40 | 0:42:45 | |
were describing something | 0:42:45 | 0:42:47 | |
that could be thought of as an anti-electron. | 0:42:47 | 0:42:51 | |
In many ways, it was like the mirror image of an electron, | 0:42:51 | 0:42:55 | |
having opposite properties like electric charge. | 0:42:55 | 0:42:57 | |
And, in principle an anti-electron could form part of an anti-atom, | 0:42:57 | 0:43:03 | |
and many anti-atoms could fit together | 0:43:03 | 0:43:06 | |
to make an anti-matter table, or even an anti-me. | 0:43:06 | 0:43:11 | |
But the weirdness didn't end there. | 0:43:13 | 0:43:16 | |
Dirac realised that if things and anti-things ever met each other, | 0:43:16 | 0:43:21 | |
they would instantly annihilate, | 0:43:21 | 0:43:24 | |
turning all their mass into energy... | 0:43:24 | 0:43:27 | |
EXPLOSION | 0:43:27 | 0:43:29 | |
Disappearing completely. | 0:43:30 | 0:43:33 | |
Here, finally was the answer to the riddle of empty space. | 0:43:37 | 0:43:43 | |
Heisenberg's uncertainty principle had suggested that matter could | 0:43:43 | 0:43:47 | |
pop into existence for incredibly short periods of time. | 0:43:47 | 0:43:52 | |
Now, Dirac had provided the mechanism | 0:43:52 | 0:43:55 | |
by which matter could be created out of the vacuum... | 0:43:55 | 0:44:00 | |
..and just as quickly, disappear again. | 0:44:01 | 0:44:05 | |
So, let's take another look at our box. | 0:44:07 | 0:44:10 | |
Whenever a particle pops out of empty space, | 0:44:10 | 0:44:14 | |
so simultaneously does its anti-particle. | 0:44:14 | 0:44:17 | |
Although this sounds completely ridiculous, let me assure you it is true. | 0:44:17 | 0:44:23 | |
So, whenever you try to remove everything you can from empty space, | 0:44:23 | 0:44:28 | |
it's still always awash with all these fluctuations. | 0:44:28 | 0:44:33 | |
Within nothingness, there's a kind of fizzing, a dynamic dance | 0:44:35 | 0:44:40 | |
as pairs of particles and anti-particles | 0:44:40 | 0:44:44 | |
borrow energy from the vacuum for brief moments | 0:44:44 | 0:44:48 | |
before annihilating and paying it back again. | 0:44:48 | 0:44:52 | |
Dirac's theory of the electron and the idea of anti-matter | 0:44:58 | 0:45:03 | |
gives us a completely new picture of the vacuum. | 0:45:03 | 0:45:07 | |
Before you could think about the vacuum as empty space, so to speak. | 0:45:07 | 0:45:12 | |
relativity had said, you don't need an aether, | 0:45:12 | 0:45:16 | |
so the picture was of the vacuum being empty. | 0:45:16 | 0:45:20 | |
But when you bring relativity and quantum theory together | 0:45:20 | 0:45:24 | |
then you have for certain, this notion of electron and anti-electron pairs | 0:45:24 | 0:45:31 | |
just appearing out of the vacuum. | 0:45:31 | 0:45:34 | |
So you can think of these pairs just sprouting all over the place in the vacuum. | 0:45:34 | 0:45:39 | |
So, the vacuum goes from being nothing | 0:45:42 | 0:45:46 | |
to being a place absolutely teeming with matter, anti-matter creation. | 0:45:46 | 0:45:53 | |
Dirac's ideas about empty space were refined and developed | 0:45:53 | 0:45:58 | |
into what is known today as quantum field theory. | 0:45:58 | 0:46:01 | |
And these strange fleeting things within nothing | 0:46:01 | 0:46:04 | |
became known as virtual particles. | 0:46:04 | 0:46:09 | |
So it seems, nothingness is in fact a seething mass of virtual particles, | 0:46:17 | 0:46:24 | |
appearing and disappearing | 0:46:24 | 0:46:26 | |
trillions of times in the blink of an eye. | 0:46:26 | 0:46:29 | |
I've come to Imperial College London | 0:46:36 | 0:46:39 | |
to see the effects of these virtual particles myself. | 0:46:39 | 0:46:43 | |
Thanks to a brilliant experiment by an American scientist called Willis Lamb, | 0:46:43 | 0:46:48 | |
we now have a way to conclusively show | 0:46:48 | 0:46:51 | |
there is activity within apparent nothingness. | 0:46:51 | 0:46:56 | |
But in order to glimpse it, | 0:46:56 | 0:46:58 | |
you have to peer deep within a single atom | 0:46:58 | 0:47:03 | |
and amazingly Lamb found an ingenious way to do this. | 0:47:03 | 0:47:07 | |
So, what did Lamb do? | 0:47:09 | 0:47:12 | |
Well, his experiment relies on the quantum rules of the atom. | 0:47:12 | 0:47:17 | |
Within atoms, electrons have very specific, discreet energies | 0:47:17 | 0:47:21 | |
in the way they orbit around the nucleus. | 0:47:21 | 0:47:24 | |
His experiment showed that if the vacuum really was full | 0:47:24 | 0:47:28 | |
of these hidden fluctuations, | 0:47:28 | 0:47:31 | |
then these would cause the electrons' orbit | 0:47:31 | 0:47:34 | |
to wobble ever-so-slightly. | 0:47:34 | 0:47:37 | |
Think of it as an analogy as though the electron is a plane | 0:47:37 | 0:47:41 | |
flying along and hitting turbulence | 0:47:41 | 0:47:44 | |
forcing it to move up to a slightly higher altitude. | 0:47:44 | 0:47:47 | |
So this is how the experiment works. | 0:47:49 | 0:47:51 | |
Contained within this vacuum chamber are a small number of atoms. | 0:47:51 | 0:47:56 | |
While Lamb used microwaves in his original experiments, | 0:47:56 | 0:48:01 | |
in this version, the team at Imperial are using lasers to probe the electrons. | 0:48:01 | 0:48:06 | |
Now, if you think this all looks very complex, just remember | 0:48:06 | 0:48:11 | |
how small a measurement it is we are trying to make here. | 0:48:11 | 0:48:14 | |
This apparatus has to be sensitive enough to pick up minute changes | 0:48:14 | 0:48:20 | |
in the behaviour of something that is itself, extremely tiny. | 0:48:20 | 0:48:25 | |
Imagine we could scale up the wobble in electron that's being measured | 0:48:25 | 0:48:30 | |
to the size of this apple. | 0:48:30 | 0:48:32 | |
That would mean this vacuum chamber behind me, would scale up to being a trillion miles in size. | 0:48:32 | 0:48:40 | |
The vacuum chamber would be something like | 0:48:40 | 0:48:43 | |
100 times the size of the entire solar system. | 0:48:43 | 0:48:47 | |
It would take light about 40 days just to travel from the top down to the bottom. | 0:48:47 | 0:48:54 | |
So, what is going on in there? | 0:48:54 | 0:48:57 | |
OK, so let me first fire up the laser in the experiment behind me. | 0:48:57 | 0:49:02 | |
What this monitor will show us is exactly what's going on inside the vacuum chamber | 0:49:02 | 0:49:08 | |
down at the minutest scales. | 0:49:08 | 0:49:10 | |
Now, look at this peak that's appeared. | 0:49:10 | 0:49:13 | |
BUZZING | 0:49:13 | 0:49:15 | |
It may not look very exciting, | 0:49:15 | 0:49:17 | |
but it's telling us something really remarkable. | 0:49:17 | 0:49:20 | |
This is measuring the amount the electron is being wobbled about by the vacuum itself. | 0:49:20 | 0:49:27 | |
If the vacuum were truly empty, this peak wouldn't exist, | 0:49:27 | 0:49:32 | |
we'd just get a flat line. | 0:49:32 | 0:49:34 | |
What this is telling us is that however hard we try | 0:49:34 | 0:49:38 | |
to remove everything we can from space, we can never get it truly empty. | 0:49:38 | 0:49:44 | |
Everywhere in the universe, space is filled with this vacuum | 0:49:44 | 0:49:49 | |
that has a deep, mysterious energy. | 0:49:49 | 0:49:52 | |
But it doesn't end there. | 0:49:56 | 0:49:57 | |
When using the mathematics laid out by Heisenberg, Dirac and others, | 0:49:59 | 0:50:04 | |
you can calculate the amount the electron should be affected. | 0:50:04 | 0:50:08 | |
When you run the real physical experiment, the answer you get | 0:50:10 | 0:50:14 | |
matches the theory to one part in a million. | 0:50:14 | 0:50:19 | |
The theory of quantum mechanics is the most accurate | 0:50:19 | 0:50:23 | |
and powerful description of the natural world that we have. | 0:50:23 | 0:50:28 | |
But there's a much more dramatic way | 0:50:30 | 0:50:33 | |
in which we can see the effects of these quantum fluctuations. | 0:50:33 | 0:50:38 | |
And that's because they're written into the stars. | 0:50:38 | 0:50:42 | |
Today, our best theories tell us | 0:50:49 | 0:50:52 | |
that as the universe sprang from the vacuum, it expanded very rapidly. | 0:50:52 | 0:50:59 | |
And this means that the rules of the quantum world should have | 0:50:59 | 0:51:03 | |
contributed to the large-scale structure of the entire cosmos. | 0:51:03 | 0:51:09 | |
When our universe first came into existence, it was many times smaller than a single atom. | 0:51:13 | 0:51:19 | |
And down at this size it's governed not by the classical rules we're | 0:51:19 | 0:51:23 | |
familiar with, but by the weird rules of the quantum world. | 0:51:23 | 0:51:29 | |
This is for me, one of the most profound and beautiful ideas in the whole of science. | 0:51:29 | 0:51:35 | |
That it's quantum reality that has | 0:51:35 | 0:51:38 | |
shaped the structure of the universe we see today. | 0:51:38 | 0:51:42 | |
Our universe is just the quantum world inflated many, many times. | 0:51:42 | 0:51:49 | |
Nothing really has shaped everything. | 0:51:49 | 0:51:54 | |
And what's more, we now have a way to see this. | 0:51:54 | 0:51:59 | |
This is a picture of the first light that was released after the Big Bang. | 0:52:06 | 0:52:14 | |
Think of it as a baby photo of everything. | 0:52:14 | 0:52:19 | |
This incredible picture was taken by a team of researchers at NASA | 0:52:19 | 0:52:24 | |
led by Professor George Smoot. | 0:52:24 | 0:52:27 | |
This is like taking a | 0:52:27 | 0:52:30 | |
picture of an embryo that's 12 hours after conception, | 0:52:30 | 0:52:35 | |
compared to taking a picture | 0:52:35 | 0:52:37 | |
of a person who is 50 years old. | 0:52:37 | 0:52:39 | |
It's in the same perspective. | 0:52:39 | 0:52:40 | |
And 12 hours, you may have two cells, this is very early and yet we are seeing what's equivalent | 0:52:40 | 0:52:47 | |
of the DNA, the blueprint for how the universe is going to develop. | 0:52:47 | 0:52:51 | |
With the help of highly sensitive satellites, | 0:52:53 | 0:52:56 | |
George Smoot and his team were able to study this image | 0:52:56 | 0:53:00 | |
of the embryonic universe in amazing detail. | 0:53:00 | 0:53:04 | |
And when they did, tiny variations in its temperature were revealed. | 0:53:04 | 0:53:10 | |
It soon became apparent that the tiny differences in temperature | 0:53:10 | 0:53:15 | |
are in fact the scars left by the quantum vacuum on our universe. | 0:53:15 | 0:53:21 | |
EXPLOSION | 0:53:25 | 0:53:28 | |
These irregularities created in the first moments of existence | 0:53:28 | 0:53:33 | |
by the teeming quantum vacuum meant the matter of the universe | 0:53:33 | 0:53:39 | |
didn't spread out completely evenly. | 0:53:39 | 0:53:42 | |
EXPLOSION | 0:53:42 | 0:53:44 | |
Rather, it formed vast clumps that would evolve into | 0:53:48 | 0:53:53 | |
the galaxies and clusters of galaxies that make up the universe today. | 0:53:53 | 0:53:59 | |
The application of quantum physics to cosmology, | 0:54:00 | 0:54:03 | |
to the universe as a whole | 0:54:03 | 0:54:05 | |
was revolutionary. | 0:54:05 | 0:54:06 | |
It really changed our entire perception | 0:54:06 | 0:54:09 | |
of the evolution of the universe, | 0:54:09 | 0:54:12 | |
because it turns out that quantum physics provides a natural mechanism | 0:54:12 | 0:54:16 | |
through quantum fluctuations | 0:54:16 | 0:54:18 | |
to see into the early universe with small irregularities that would later grow to make galaxies. | 0:54:18 | 0:54:26 | |
The thought is really overwhelming, the idea that an object | 0:54:26 | 0:54:30 | |
with billions of stars like the Milky Way began life as a quantum fluctuation, | 0:54:30 | 0:54:36 | |
what we call a fluctuation of the vacuum, | 0:54:36 | 0:54:39 | |
an object of sub-microscopic scales, it really is mind boggling. | 0:54:39 | 0:54:43 | |
It now appears as if the quantum world, the place we once thought of | 0:54:45 | 0:54:50 | |
as empty nothingness has actually shaped everything we see around us. | 0:54:50 | 0:54:57 | |
What happens is, something that was a small fluctuation, | 0:54:59 | 0:55:03 | |
a tiny quantum fluctuation, becomes our galaxy. | 0:55:03 | 0:55:06 | |
Or becomes a cluster of galaxies because there are lots of quantum fluctuations, | 0:55:06 | 0:55:11 | |
so it answers one of the questions we have - | 0:55:11 | 0:55:13 | |
why are there 100 billion galaxies in our viewpoint? | 0:55:13 | 0:55:16 | |
Well, in a drop of water, | 0:55:16 | 0:55:18 | |
there's many more than 100 million quantum fluctuations, | 0:55:18 | 0:55:21 | |
in an atom there's that many, the vacuum has all of this bubbling going on all the time. | 0:55:21 | 0:55:26 | |
The teeming, seething activity of the vacuum, of nothing, | 0:55:30 | 0:55:34 | |
and the quantum fluctuations within it... | 0:55:34 | 0:55:37 | |
..were the seeds, seeds which grew into the universe we see today. | 0:55:40 | 0:55:46 | |
This idea gives rise to one final revelation. | 0:55:50 | 0:55:56 | |
Today, our best theories about the cosmos tell us | 0:55:56 | 0:56:00 | |
that at the beginning of time, the universe sprang from the vacuum. | 0:56:00 | 0:56:05 | |
Creating not only vast amounts of matter, but also the strange stuff | 0:56:07 | 0:56:13 | |
that was predicted by Paul Dirac... | 0:56:13 | 0:56:16 | |
..anti-matter. | 0:56:19 | 0:56:21 | |
But the universe we see today is made of matter, | 0:56:22 | 0:56:26 | |
nearly all of the anti-matter seems to have vanished. | 0:56:26 | 0:56:31 | |
EXPLOSION | 0:56:34 | 0:56:37 | |
According to common theory, | 0:56:38 | 0:56:42 | |
the Big Bang produced equal amounts of matter and anti-matter. | 0:56:42 | 0:56:46 | |
But as the universe cooled down, | 0:56:46 | 0:56:48 | |
matter and anti-matter annihilated almost perfectly, but not quite. | 0:56:48 | 0:56:53 | |
For every billion particles of matter and anti-matter, | 0:56:53 | 0:56:58 | |
one was left behind. | 0:56:58 | 0:56:59 | |
The matter and anti-matter that annihilated to produce radiation | 0:56:59 | 0:57:03 | |
gave rise to the heat of the Big Bang | 0:57:03 | 0:57:06 | |
that we see today in the form of the microwave background radiation. | 0:57:06 | 0:57:09 | |
The little particle that was left behind, for every billion | 0:57:09 | 0:57:13 | |
that annihilated is what makes galaxies, stars, planets and people. | 0:57:13 | 0:57:19 | |
So, we are simply the debris of a huge annihilation | 0:57:23 | 0:57:28 | |
of matter and anti-matter at the beginning of time. | 0:57:28 | 0:57:32 | |
EXPLOSION | 0:57:32 | 0:57:35 | |
The leftovers of an unimaginable explosion. | 0:57:36 | 0:57:40 | |
All these insights have arisen | 0:57:51 | 0:57:54 | |
from simply trying to understand what nothing really is. | 0:57:54 | 0:57:59 | |
What we once thought of as the void | 0:57:59 | 0:58:03 | |
now seems to hold within it, | 0:58:03 | 0:58:06 | |
the deepest mysteries of the entire universe. | 0:58:06 | 0:58:11 | |
In the 400 years or so since Torricelli and Pascal | 0:58:17 | 0:58:21 | |
began exploring vacuums here on Earth, | 0:58:21 | 0:58:24 | |
we've begun to understand in ever greater detail the world's at the very limits of our perception. | 0:58:24 | 0:58:31 | |
And in doing so, we've uncovered the strange truth about reality itself. | 0:58:31 | 0:58:38 | |
There's a profound connection between the nothingness | 0:58:38 | 0:58:42 | |
from which we originated | 0:58:42 | 0:58:45 | |
and the infinite in which we are engulfed. | 0:58:45 | 0:58:48 | |
Subtitles by Red Bee Media Ltd | 0:59:05 | 0:59:09 | |
E-mail [email protected] | 0:59:09 | 0:59:14 |