0:00:10 > 0:00:13What is nothing?
0:00:13 > 0:00:17It's an extremely, extremely difficult question to answer,
0:00:17 > 0:00:19because if you think about it,
0:00:19 > 0:00:24wherever you look around you, there always seems to be something there.
0:00:32 > 0:00:37Things appear almost impossible to escape from.
0:00:38 > 0:00:41Even just trying to imagine true nothingness
0:00:41 > 0:00:45seems like an impossible task.
0:00:47 > 0:00:50But this is more than just a philosophical question.
0:00:50 > 0:00:53I have here a box. What would happen
0:00:53 > 0:00:57if I were to remove everything I possibly could from inside it?
0:00:57 > 0:01:01All the air, dust, every last single atom,
0:01:01 > 0:01:03until there was no thing left.
0:01:05 > 0:01:09What, then, exists inside the space in the box?
0:01:09 > 0:01:12Is it really nothing?
0:01:14 > 0:01:17You might wonder why this matters.
0:01:17 > 0:01:22Well, emptiness is what makes up almost the entire universe.
0:01:22 > 0:01:26Even the atoms that make up our bodies
0:01:26 > 0:01:32and the physical world around us comprise mostly of empty space.
0:01:37 > 0:01:39This film tells the story
0:01:39 > 0:01:44of how we've begun to understand what is known as the void,
0:01:44 > 0:01:46or the vacuum.
0:01:46 > 0:01:49Emptiness, or simply nothing.
0:01:49 > 0:01:54It's about reality at the very furthest reaches of human perception.
0:01:54 > 0:01:59A place where the deepest mysteries of the universe may be held.
0:02:11 > 0:02:13This film reveals how,
0:02:13 > 0:02:16using ingenious technology,
0:02:16 > 0:02:20humans have transcended their physical senses,
0:02:20 > 0:02:25and found ways to understand and probe the universe
0:02:25 > 0:02:27at the smallest scales.
0:02:33 > 0:02:39Today, we believe the void contains nature's deepest secrets.
0:02:39 > 0:02:44It might even explain why we exist at all.
0:02:44 > 0:02:47And that's because, to the best of our knowledge,
0:02:47 > 0:02:53the entire universe appeared nearly 14 billion years ago
0:02:53 > 0:02:55out of nothing.
0:03:15 > 0:03:16For over 1,000 years,
0:03:16 > 0:03:21our understanding of empty space was defined by one man -
0:03:21 > 0:03:24the Greek philosopher Aristotle.
0:03:27 > 0:03:32To Aristotle, the concept of nothingness was deeply disturbing.
0:03:32 > 0:03:37It seemed to present all sorts of problems and paradoxes.
0:03:39 > 0:03:44He came to believe that nature would forever fight against
0:03:44 > 0:03:46the creation of true nothingness.
0:03:46 > 0:03:50As he put it, nature abhors a vacuum.
0:03:54 > 0:03:59These words stuck for over 1,000 years, because after Aristotle,
0:03:59 > 0:04:04people who attempted to make empty space faced an uphill struggle.
0:04:04 > 0:04:08It seemed nature was indeed doing everything in its power
0:04:08 > 0:04:10to stop them.
0:04:11 > 0:04:14Well, the whole mystery of nothingness
0:04:14 > 0:04:18is contained inside this simple drinking straw.
0:04:18 > 0:04:22Let me demonstrate. If I suck out the air from the top of the straw...
0:04:23 > 0:04:28..more air immediately rushes in to fill the space left behind.
0:04:28 > 0:04:33And even more weirdly, if I block off the bottom of the straw and suck...
0:04:35 > 0:04:39..the walls of the straw collapse in on themselves.
0:04:39 > 0:04:44It's as though the universe won't allow me to make nothingness.
0:04:44 > 0:04:47And it gets even weirder. If I take a sip of my drink...
0:04:50 > 0:04:52..and pinch off the top,
0:04:52 > 0:04:55then it seems nature is so intent on stopping me
0:04:55 > 0:04:59that even the law of gravity is suspended.
0:04:59 > 0:05:03So it's not hard to understand why people believed
0:05:03 > 0:05:07that it was impossible to make truly empty space.
0:05:09 > 0:05:12But there is a very simple explanation
0:05:12 > 0:05:15for why a straw behaves like this -
0:05:15 > 0:05:21a reason that would come as a profound shock to the people who worked it out.
0:05:21 > 0:05:25By the 17th century, some strange exceptions were being found
0:05:25 > 0:05:28to nature's abhorrence of empty space.
0:05:28 > 0:05:30And it was beginning to seem
0:05:30 > 0:05:36like there may be ways of tricking nothingness into existence.
0:05:38 > 0:05:43The man who would finally do what Aristotle thought impossible
0:05:43 > 0:05:48was an Italian Jesuit called Evangelista Torricelli.
0:05:51 > 0:05:55Torricelli's experiment would, for the first time,
0:05:55 > 0:06:00create and capture empty space for long enough to begin to study it.
0:06:03 > 0:06:06This is how the experiment went, with a tube filled with mercury
0:06:06 > 0:06:09and a finger really strongly clamped over the end.
0:06:09 > 0:06:11The tube was then turned upside down
0:06:11 > 0:06:15and then placed into the bath of mercury.
0:06:15 > 0:06:19At this point, the mercury was released.
0:06:19 > 0:06:21You can now see it dropping down.
0:06:21 > 0:06:25And then it stops.
0:06:25 > 0:06:28So I guess the important thing is that...
0:06:28 > 0:06:30that isn't trapped air.
0:06:30 > 0:06:36We started with a tube filled with mercury, and all we did was we let it drain out.
0:06:36 > 0:06:40But it doesn't drain out completely, it reaches a level and stops.
0:06:41 > 0:06:47Torricelli's experiments had not only created an airless space,
0:06:47 > 0:06:51it had also shown that the atmosphere has a specific weight.
0:06:53 > 0:06:57The reason my straw crumples when I suck the air out
0:06:57 > 0:07:01is because of the pressure of the atmosphere that surrounds it.
0:07:02 > 0:07:06But Torricelli's apparatus was overcoming this
0:07:06 > 0:07:11by using the extreme weight of mercury and a rigid glass tube.
0:07:11 > 0:07:13The level of mercury in his tube
0:07:13 > 0:07:17was a measure of the weight of the atmosphere.
0:07:17 > 0:07:22The level is, of course, determined by the weight of the mercury on the one hand,
0:07:22 > 0:07:25and the weight of the air pressing down on the other.
0:07:25 > 0:07:28And so the two balance out, like scales.
0:07:28 > 0:07:31They'd found a way to weigh the atmosphere.
0:07:31 > 0:07:35And Torricelli wrote this fantastic phrase.
0:07:35 > 0:07:39He said, "Noi viviamo sommersi nel fondo d'un pelago d'aria elementare."
0:07:39 > 0:07:43"We live at the bottom of an ocean of air."
0:07:43 > 0:07:47Suddenly, the air really was a substance.
0:07:47 > 0:07:52But I guess the real mystery for me now is, what's inside here?
0:07:52 > 0:07:55Could this really be nothingness?
0:07:55 > 0:07:56Indeed.
0:07:59 > 0:08:02In revealing that the air has a weight
0:08:02 > 0:08:07and that it's pushing down on us all the time, filling any space it can,
0:08:07 > 0:08:11Torricelli had managed to create an empty space,
0:08:11 > 0:08:15a type of nothingness that could now be studied.
0:08:20 > 0:08:24Over 1,000 years of thinking about the way nature worked
0:08:24 > 0:08:26was beginning to crumble.
0:08:32 > 0:08:35Medieval philosophy, much influenced by Aristotle, supposed,
0:08:35 > 0:08:39reasonably enough, that there is no such thing as empty space in nature.
0:08:39 > 0:08:42And yet here is a pretty simple device -
0:08:42 > 0:08:46a long, thin glass tube with some liquid in it -
0:08:46 > 0:08:50which is able to produce, says Torricelli, an empty space,
0:08:50 > 0:08:54thus showing that Aristotle and his disciples are wrong.
0:08:54 > 0:08:58How can you show that centuries of philosophical tradition are wrong
0:08:58 > 0:09:00just by doing a trick?
0:09:00 > 0:09:02That didn't seem right at all.
0:09:05 > 0:09:07But Torricelli was right,
0:09:07 > 0:09:12and it would fall to philosopher and scientist Blaise Pascal
0:09:12 > 0:09:14to develop and refine his work.
0:09:14 > 0:09:18As Pascal began investigating Torricelli's ideas,
0:09:18 > 0:09:22he discovered even more peculiar properties.
0:09:22 > 0:09:28In Paris, he carried a mercury tube to the top of a huge tower
0:09:28 > 0:09:34and recorded the mercury dropping to a lower level than it had been on the ground.
0:09:34 > 0:09:38It seemed the pressure of the air fell as you went higher.
0:09:43 > 0:09:48Pascal's experiments would lead to the realisation that the Earth
0:09:48 > 0:09:54is cocooned in an atmosphere that rapidly thins out the higher you go...
0:09:56 > 0:10:01..eventually becoming the cold, silent expanse of space.
0:10:04 > 0:10:09Torricelli and Pascal had begun to unravel a profound truth -
0:10:09 > 0:10:12nothing is everywhere.
0:10:16 > 0:10:20Our Earth is merely a tiny speck of dust,
0:10:20 > 0:10:23floating through a vast expanse
0:10:23 > 0:10:26of an utterly silent, inhospitable void.
0:10:28 > 0:10:31Nature doesn't abhor a vacuum.
0:10:31 > 0:10:35A vacuum is nature's default state.
0:10:44 > 0:10:48So what was this vast, empty space?
0:10:49 > 0:10:53Now it was possible to make it on Earth,
0:10:53 > 0:10:56scientists became deeply curious.
0:10:56 > 0:11:01What exactly were the properties of nothingness?
0:11:01 > 0:11:04After Torricelli and Pascal's experiments,
0:11:04 > 0:11:06many scientists became fascinated
0:11:06 > 0:11:09with studying the properties of the vacuum.
0:11:09 > 0:11:12And they found some very odd things.
0:11:12 > 0:11:15For instance, placing a ringing bell inside it became silent,
0:11:15 > 0:11:18you couldn't hear it from the outside,
0:11:18 > 0:11:20because, having removed all the air,
0:11:20 > 0:11:24there was no medium to carry the sound waves.
0:11:24 > 0:11:28Most intriguingly, although you couldn't hear the bell,
0:11:28 > 0:11:30you could still see it.
0:11:30 > 0:11:35This means light must be travelling through the vacuum.
0:11:35 > 0:11:37But how could it do this?
0:11:37 > 0:11:41For those scientists carrying out experiments with the vacuum,
0:11:41 > 0:11:44there was just one simple conclusion.
0:11:44 > 0:11:47The vacuum wasn't empty after all.
0:11:47 > 0:11:49The fact that they could see inside it
0:11:49 > 0:11:53meant that there still had to be something left in there.
0:11:53 > 0:11:56Just as air carries sound waves,
0:11:56 > 0:12:00they believed there had to be a medium carrying the light waves.
0:12:00 > 0:12:05And whatever it was, it was proving very difficult to get rid of.
0:12:09 > 0:12:13The nothingness that had been glimpsed by Torricelli and Pascal
0:12:13 > 0:12:16now appeared to be a something -
0:12:16 > 0:12:20a mysterious substance which carried waves of light.
0:12:20 > 0:12:24And if that this substance existed in our vacuums on Earth,
0:12:24 > 0:12:29it meant that it also existed out there.
0:12:29 > 0:12:35It appeared once again that nothingness could not exist in nature.
0:12:35 > 0:12:41Everything in the universe appeared to be sitting within an invisible medium,
0:12:41 > 0:12:45what scientists called the luminiferous aether.
0:12:49 > 0:12:52It was clear for many reasons, many good reasons,
0:12:52 > 0:12:54that light was a kind of wave.
0:12:54 > 0:12:59But if light is a kind of wave, what's it a wave in?
0:12:59 > 0:13:04Sound waves are waves in air, light waves are waves in what came to be called,
0:13:04 > 0:13:08from the early 1800s, the luminiferous aether,
0:13:08 > 0:13:12the light-carrying fluid that fills all space.
0:13:12 > 0:13:18If there's a fluid that fills all space, if light is a wave, nowhere is empty,
0:13:18 > 0:13:21because light travels everywhere.
0:13:21 > 0:13:26So at the very moment when it seemed absolutely plausible
0:13:26 > 0:13:29that there can be empty space, it is obvious that there isn't.
0:13:29 > 0:13:33And that there's this stuff called aether that carries light.
0:13:33 > 0:13:37The problem was that this aether
0:13:37 > 0:13:41appeared to be so subtle and so intangible
0:13:41 > 0:13:44that it eluded all attempts to measure it.
0:13:45 > 0:13:49It wouldn't be until the end of the 19th century that an experiment
0:13:49 > 0:13:54would be built that was sensitive enough to reveal the truth.
0:13:54 > 0:13:58The experiment would take place in the United States,
0:13:58 > 0:14:01and Albert Michelson, the scientist who conducted it,
0:14:01 > 0:14:06would go on to become America's first Nobel Prize winner.
0:14:07 > 0:14:11From a young age, Michelson had relished tackling
0:14:11 > 0:14:14the particularly difficult practical problems in physics.
0:14:14 > 0:14:16He'd earned his reputation
0:14:16 > 0:14:21by making extremely precise measurements of the speed of light.
0:14:23 > 0:14:28Having completed his work on light, Michelson travelled to Europe
0:14:28 > 0:14:32to spend some time amongst some of the best scientists in the world.
0:14:32 > 0:14:35And it was there that he became fascinated with the topic
0:14:35 > 0:14:41that everyone was talking about - the mysterious luminiferous aether.
0:14:41 > 0:14:44One idea in particular captured his imagination.
0:14:44 > 0:14:50It had been proposed that if you could measure the speed of light accurately enough,
0:14:50 > 0:14:52it might just be possible
0:14:52 > 0:14:56to actually deduce the properties of the aether.
0:14:59 > 0:15:01And this is how.
0:15:01 > 0:15:06If there was an aether, then as the Earth orbited the sun,
0:15:06 > 0:15:10we should be able to detect its presence.
0:15:10 > 0:15:14It would be like sticking your hand out of the window of a moving car.
0:15:14 > 0:15:18You feel the rush of wind as the car travels through the air.
0:15:21 > 0:15:26Michelson realised that if this picture of the aether was true,
0:15:26 > 0:15:30then two light beams should travel at different speeds on Earth,
0:15:30 > 0:15:35depending on the direction they were moving through this aethereal wind.
0:15:41 > 0:15:45The difficulty was actually in making such a measurement.
0:15:45 > 0:15:48It seemed like an almost impossible task.
0:15:48 > 0:15:50The problem is this.
0:15:50 > 0:15:56The speed of light is over 186,000 miles per second.
0:15:56 > 0:15:58Now that's pretty nifty.
0:15:58 > 0:16:02In comparison, the Earth virtually crawls around its orbit.
0:16:02 > 0:16:07So the difference in speeds between those two light beams would be tiny -
0:16:07 > 0:16:10something like one part in 100 million.
0:16:10 > 0:16:14So the precision needed to get any sort of meaningful result
0:16:14 > 0:16:18was way beyond anything that scientists thought was possible at the time.
0:16:18 > 0:16:21But not so the headstrong Michelson.
0:16:21 > 0:16:24He began to work his way round the problem.
0:16:24 > 0:16:28He started to develop techniques and precision instruments
0:16:28 > 0:16:34that he believed would be capable of unlocking the secrets of the aether.
0:16:41 > 0:16:45From 1881, Michelson was taking measurements,
0:16:45 > 0:16:48and tweaking and refining his apparatus.
0:16:48 > 0:16:50But it wouldn't be until 1887
0:16:50 > 0:16:54at the Case School of Applied Science in Cleveland, Ohio,
0:16:54 > 0:16:58that Michelson would finally build a machine sensitive enough
0:16:58 > 0:17:00to give him some definitive answers.
0:17:00 > 0:17:05There he joined forces with another scientist, Edward Morley,
0:17:05 > 0:17:11to conduct what was to become one of the most notorious experiments in physics.
0:17:12 > 0:17:16The original apparatus was set in a solid block of sandstone,
0:17:16 > 0:17:19and then suspended in a bath of mercury
0:17:19 > 0:17:23to remove any vibrations that might affect the measurements.
0:17:23 > 0:17:26It was incredibly hi-tech and very expensive.
0:17:26 > 0:17:31Think of it as an 1880s version of the Large Hadron Collider.
0:17:31 > 0:17:35OK, so here's how it works. Light is emitted
0:17:35 > 0:17:37from this source.
0:17:40 > 0:17:44In the middle is something called a beam splitter,
0:17:44 > 0:17:47which divides the light up into two parts.
0:17:51 > 0:17:53Over here are two mirrors,
0:17:53 > 0:17:56which reflect the light back to the middle
0:17:56 > 0:18:00where they recombine at the beam splitter.
0:18:00 > 0:18:05The light is sent down to this detector. Now,
0:18:05 > 0:18:08Now, because of the wave-like properties of light,
0:18:08 > 0:18:10you see a very specific pattern here.
0:18:10 > 0:18:15Basically, if the light has travelled at the same speed along the two paths,
0:18:15 > 0:18:19then you see a bright spot in the middle of the pattern.
0:18:22 > 0:18:25So here's the really clever part.
0:18:25 > 0:18:27Michelson and Morley reasoned
0:18:27 > 0:18:31that if the Earth really was moving through a stationary aether,
0:18:31 > 0:18:35the experiment should behave in a very different way.
0:18:35 > 0:18:39Let's look at what happens when we simulate the effect of an aether.
0:18:43 > 0:18:47The light leaves the detector
0:18:47 > 0:18:49and gets split.
0:18:51 > 0:18:53Now here's the key.
0:18:53 > 0:18:56The light that travels against the aether and back again
0:18:56 > 0:19:00covers this journey in a different time
0:19:00 > 0:19:03to the light travelling across the aether.
0:19:03 > 0:19:07This means that when the light waves recombine,
0:19:07 > 0:19:11they now interfere with each other.
0:19:11 > 0:19:14This interference means that the image
0:19:14 > 0:19:17will have a dark spot at its centre.
0:19:17 > 0:19:20See this, and you know that the void must be filled
0:19:20 > 0:19:25with a stationary medium through which the Earth is moving.
0:19:28 > 0:19:30Of course I can't be sure exactly
0:19:30 > 0:19:33what was going through the minds of Michelson and Morley
0:19:33 > 0:19:35as they began their experiment,
0:19:35 > 0:19:39but it is a safe bet that, given the scientific consensus at the time,
0:19:39 > 0:19:43they were convinced that the aether really existed.
0:19:43 > 0:19:46So they would have been sure that they would have found light
0:19:46 > 0:19:51travelling at different speeds as it moved in different directions.
0:19:51 > 0:19:53But it didn't.
0:19:53 > 0:19:56No matter how they rotated their apparatus,
0:19:56 > 0:20:01they always found light travelled at the same speed.
0:20:06 > 0:20:11Michelson and Morley had gained an extraordinary and accurate result.
0:20:14 > 0:20:18But the idea of the luminiferous aether was so ingrained
0:20:18 > 0:20:22that they believed simply that their experiments had failed.
0:20:28 > 0:20:30So what is going on?
0:20:30 > 0:20:35Why didn't Michelson and Morley's experiment reveal the result they were expecting?
0:20:35 > 0:20:39How could light always be travelling at the same speed?
0:20:39 > 0:20:44Well, the answer is simple. The aether doesn't exist.
0:20:44 > 0:20:47No matter what light is doing, how it is travelling,
0:20:47 > 0:20:52it doesn't need to be carried along by this mysterious stuff that pervades the vacuum.
0:20:55 > 0:21:00So how does light move through empty space?
0:21:00 > 0:21:03Well, by the end of the 19th century,
0:21:03 > 0:21:05light was known to be in fact
0:21:05 > 0:21:11a combination of fluctuating electric and magnetic fields.
0:21:11 > 0:21:15But it would take the genius of Einstein in 1905
0:21:15 > 0:21:20to reveal that this picture of light doesn't need an aether.
0:21:20 > 0:21:23He showed that it has the weird property
0:21:23 > 0:21:28of being able to propagate through completely empty space.
0:21:29 > 0:21:35So the message from the failure of Michelson and Morley's experiment is this -
0:21:35 > 0:21:37there is no aether.
0:21:37 > 0:21:42Maybe the vacuum is really empty.
0:21:42 > 0:21:44If only it were that simple.
0:21:47 > 0:21:50Almost as soon as Michelson and Morley had revealed,
0:21:50 > 0:21:53by accident, that you really could have nothing...
0:21:55 > 0:22:01..scientists began to discover some very weird properties of nature.
0:22:03 > 0:22:07In the 100 years that followed Michelson and Morley's experiments,
0:22:07 > 0:22:11physics and our understanding of the vacuum
0:22:11 > 0:22:14has been totally transformed.
0:22:23 > 0:22:28But what drove this huge shift was not simply scientific curiosity.
0:22:31 > 0:22:34But the fact that in the late 19th century,
0:22:34 > 0:22:39the vacuum and its many applications had become big business.
0:22:43 > 0:22:46Industry was finding ever more ingenious ways
0:22:46 > 0:22:49to make money out of nothing.
0:22:51 > 0:22:55Understanding and harnessing the vacuum turned out
0:22:55 > 0:23:00to lead to a wealth of new technologies that we just take for granted today.
0:23:00 > 0:23:04Everything from the light bulb to the television
0:23:04 > 0:23:06were only made possible
0:23:06 > 0:23:11because they could contain within them small volumes of vacuum.
0:23:14 > 0:23:19The filament inside a light bulb can glow for long periods
0:23:19 > 0:23:22because it is contained within a vacuum.
0:23:22 > 0:23:26Expose it to air and it would simply burn out in seconds.
0:23:31 > 0:23:34As cities around the world began to electrify,
0:23:34 > 0:23:38the demand for light bulbs grew massively.
0:23:38 > 0:23:43The engineers became ever more skilled at creating cheap, efficient vacuums.
0:23:44 > 0:23:49This technology would give rise to a huge range of gadgets -
0:23:49 > 0:23:55everything from the valves in radios and early computers
0:23:55 > 0:23:56to the television.
0:23:58 > 0:24:03But all the technological innovations that came from harnessing the vacuum
0:24:03 > 0:24:06would pale into insignificance when compared to what scientists
0:24:06 > 0:24:11would soon find out about the fundamental nature of reality.
0:24:13 > 0:24:18Because vacuum technology was getting so much cheaper,
0:24:18 > 0:24:20and more efficient,
0:24:20 > 0:24:24scientists all over the world could use it as a tool for research.
0:24:24 > 0:24:30In empty space, nature's tiniest constituents could now be studied
0:24:30 > 0:24:35without interference from the contaminant-filled air of the outside world.
0:24:36 > 0:24:39This revolutionised physics.
0:24:41 > 0:24:46Because of the vacuum, X-rays were discovered in 1895.
0:24:47 > 0:24:52The following year, the electron was identified for the first time.
0:24:52 > 0:24:56And in 1909, Ernest Rutherford would use vacuums
0:24:56 > 0:25:00to help reveal the strange structure of the atom.
0:25:03 > 0:25:07These discoveries were all feeding into a radically new picture
0:25:07 > 0:25:12of the way nature works at its smallest and most fundamental level.
0:25:14 > 0:25:19It was a theory that would come to be known as quantum mechanics.
0:25:19 > 0:25:23And the submicroscopic world it describes behaves very differently
0:25:23 > 0:25:25to the world we are used to.
0:25:27 > 0:25:31This is a world where, against all common sense,
0:25:31 > 0:25:36it seems impossible to ever truly have nothing.
0:25:45 > 0:25:47This is the classical world,
0:25:47 > 0:25:50action and reaction.
0:25:51 > 0:25:53Cause and effect.
0:25:53 > 0:25:56It is sensible, certain and knowable.
0:25:57 > 0:26:03But the quantum world soon revealed itself to be very different.
0:26:05 > 0:26:10There was one discovery that was particularly troubling
0:26:10 > 0:26:15and it's known as Heisenberg's Uncertainty Principle.
0:26:19 > 0:26:25In everyday life we are used to doubt, to uncertainty.
0:26:25 > 0:26:28How can we be sure that something is this way or that way?
0:26:28 > 0:26:34Well, it turns out that nature itself is based on indeterminacy,
0:26:34 > 0:26:36in uncertainty.
0:26:36 > 0:26:41The world of quantum physics, the microscopic world, is a world of uncertainty.
0:26:41 > 0:26:44It's a world where you can never be sure of what is going to happen.
0:26:44 > 0:26:49Not because your measurements are not good enough, simply because,
0:26:49 > 0:26:54at a very fundamental level, nature itself is based on uncertainty.
0:26:57 > 0:27:02OK, I would like to get across the essence of Heisenberg's Uncertainty Principle.
0:27:02 > 0:27:05I'm going to use a non-mathematical analogy.
0:27:05 > 0:27:07We have to be careful here -
0:27:07 > 0:27:10it is just an analogy so we shouldn't push it too far.
0:27:10 > 0:27:14I have here two identical memory sticks.
0:27:14 > 0:27:18On the first one is a high-resolution image.
0:27:18 > 0:27:21It is a picture of me having a game of pool.
0:27:21 > 0:27:23We can see it is very detailed.
0:27:23 > 0:27:25In fact, I can zoom in...
0:27:27 > 0:27:30..even quite closely onto the pool ball.
0:27:30 > 0:27:32And you see, even at this magnification,
0:27:32 > 0:27:37I can still see the precise position, I can see the edges of the ball very detailed.
0:27:37 > 0:27:41But what I don't know is how fast the ball is moving
0:27:41 > 0:27:45or what is going to happen next.
0:27:45 > 0:27:50Now, on the second memory stick is another file. It's a very different kind of file.
0:27:50 > 0:27:52It is a movie.
0:27:52 > 0:27:56The important thing to note is that the file is the same size
0:27:56 > 0:27:58as the high-resolution image.
0:27:59 > 0:28:02Now, have a look at this.
0:28:02 > 0:28:06Now we can see the whole movie playing out. It is the same scene,
0:28:06 > 0:28:08but you can see all the balls moving.
0:28:08 > 0:28:12But if I zoom in on some detail...
0:28:14 > 0:28:18..very quickly the balls become fuzzy and blurred.
0:28:18 > 0:28:20So for the same amount of information,
0:28:20 > 0:28:25although I've gained knowledge about how the balls are moving,
0:28:25 > 0:28:28I've lost information about their exact positions.
0:28:28 > 0:28:32So with the more I know about where something is,
0:28:32 > 0:28:36the less I know about how it is moving.
0:28:36 > 0:28:38In the quantum world,
0:28:38 > 0:28:44I cannot at the same time know both these quantities exactly.
0:28:44 > 0:28:47Unfortunately, there is no way around this.
0:28:47 > 0:28:50Heisenberg showed in his mathematics
0:28:50 > 0:28:55that this is in an inescapable feature of reality at this scale.
0:28:55 > 0:29:00OK, so what has all this quantum weirdness
0:29:00 > 0:29:02got to do with nothing?
0:29:02 > 0:29:08Well, you see, Heisenberg's Uncertainty Principle can be expressed in a different way,
0:29:08 > 0:29:14in terms of a balance between two other quantities - energy and time.
0:29:14 > 0:29:16Now, this is going to sound quite complicated,
0:29:16 > 0:29:19but it's very important, so I'm going to try and explain.
0:29:19 > 0:29:22You see, if I were to examine
0:29:22 > 0:29:27a small volume of empty space inside this box, then I could
0:29:27 > 0:29:32in principle know how much energy it contains very precisely.
0:29:33 > 0:29:38But, if I were able to slow time down,
0:29:38 > 0:29:42things would start to get very strange.
0:29:47 > 0:29:53OK, so we are now looking at a tiny interval of time that has been stretched out.
0:29:56 > 0:29:58Heisenberg's uncertainty principle
0:29:58 > 0:30:02tells us that because I'm looking at a smaller interval of time,
0:30:02 > 0:30:08I've lost precise information about the exact energy in the box.
0:30:11 > 0:30:15If I could examine an even smaller interval of time,
0:30:15 > 0:30:19and an even smaller volume inside the box,
0:30:19 > 0:30:25then Heisenberg's equation suggests something truly bizarre could happen.
0:30:30 > 0:30:35I will be so uncertain about how much energy there is in that part of the box,
0:30:35 > 0:30:39that there is a chance it could contain
0:30:39 > 0:30:45enough energy to create particles literally out of nowhere...
0:30:47 > 0:30:51..provided that somehow they went away again very quickly.
0:31:00 > 0:31:05Heisenberg's uncertainty principle seemed to suggest that
0:31:05 > 0:31:12in truly tiny amounts of time and space, something could come from nothing.
0:31:13 > 0:31:20But then what? If particles could pop into existence, where do they go?
0:31:20 > 0:31:24Why don't we see these particles appearing all around us?
0:31:28 > 0:31:33The vacuum, contrary to what one normally expects from the vacuum,
0:31:33 > 0:31:34is alive.
0:31:34 > 0:31:37It's alive with what physicists call quantum fluctuations.
0:31:37 > 0:31:41In the vacuum, little packets of energy appear and disappear
0:31:41 > 0:31:43very, very quickly.
0:31:43 > 0:31:45This is perfectly allowed by the laws of physics.
0:31:45 > 0:31:47It's all allowed but it has an name,
0:31:47 > 0:31:50it is called Heisenberg's uncertainty principle,
0:31:50 > 0:31:52which tells us that you can
0:31:52 > 0:31:55borrow energy from nothing, so long as you pay it back quickly enough.
0:31:58 > 0:32:02The vacuum is alive.
0:32:02 > 0:32:09Bizarre though these ideas seem, they are, I promise you, fundamental to our universe.
0:32:09 > 0:32:11To see how this can be,
0:32:11 > 0:32:15our story of nothing takes us to one of the most
0:32:15 > 0:32:20gifted and oddest characters in the whole history of physics.
0:32:24 > 0:32:29Behind me is Bishop Road Primary School in Bristol
0:32:29 > 0:32:30and almost 100 years ago,
0:32:30 > 0:32:34it was attended by two students who were destined for greatness.
0:32:34 > 0:32:38One of them, Archibald Leach, would go on to conquer Hollywood,
0:32:38 > 0:32:41becoming better known as Cary Grant.
0:32:41 > 0:32:46The other was a quiet, shy and rather intense boy two years younger than Grant,
0:32:46 > 0:32:51who would become one of the greatest scientists Britain has ever produced,
0:32:51 > 0:32:54the theoretical physicist Paul Dirac.
0:32:59 > 0:33:01Even by the standards of theoretical physicists,
0:33:01 > 0:33:04Dirac was a very queer bird.
0:33:04 > 0:33:08He was not someone you'd go for a beer with.
0:33:08 > 0:33:10Intensely focused,
0:33:10 > 0:33:15man of extremely few words, very, very little empathy
0:33:15 > 0:33:18and someone of rectilinear thought.
0:33:21 > 0:33:25These personality traits were key to Dirac's genius,
0:33:25 > 0:33:29but they often resulted in difficult or awkward
0:33:29 > 0:33:32social situations with his peers.
0:33:32 > 0:33:38Even in casual conversation, Dirac would never speak unnecessarily.
0:33:38 > 0:33:42He'd often leave these long pauses in between sentences while
0:33:42 > 0:33:47he worked out the most precise and concise way of expressing himself.
0:33:47 > 0:33:51Friends had jokingly coined the term a Dirac, which stands for
0:33:51 > 0:33:55the smallest number of words it is possible to speak in one hour,
0:33:55 > 0:33:58while still taking part in a conversation.
0:33:58 > 0:34:01It is a sort of unit of shyness.
0:34:05 > 0:34:08Dirac's unusual personality had its roots
0:34:08 > 0:34:11in a difficult and troubled childhood.
0:34:11 > 0:34:16But from a young age, he had found solace in the classroom.
0:34:16 > 0:34:22In particular, he excelled at both mathematics and technical drawing.
0:34:22 > 0:34:28This was something that cultivated his visual imagination.
0:34:28 > 0:34:31In maths classes, he was looking at mathematical symbols.
0:34:31 > 0:34:37He was looking at similar things, but in a geometric way in his technical drawing class.
0:34:37 > 0:34:42It is very, very suggestive of the way he looked at physics later on
0:34:42 > 0:34:48because he always stressed that he was pre-eminently a visualiser.
0:34:48 > 0:34:52He was someone who had a geometric look at physics.
0:34:52 > 0:34:56He was not interested per say in mathematical symbols.
0:34:56 > 0:35:00Rather he wanted a visual sense of what was going on in the mathematics.
0:35:03 > 0:35:07Dirac continued his visual training, doing a degree in engineering
0:35:07 > 0:35:10before go to Cambridge to study mathematics.
0:35:10 > 0:35:16It would be here that Dirac would begin to unravel the deepest mysteries of the vacuum
0:35:16 > 0:35:20and uncover what was really going on in empty space.
0:35:22 > 0:35:26But his insight sprang from a seemingly unrelated difficulty.
0:35:28 > 0:35:32By 1928, physics was struggling with a big problem.
0:35:32 > 0:35:35The two most important theories
0:35:35 > 0:35:39that described how the universe worked didn't agree with each other.
0:35:39 > 0:35:43On the one hand, you had Einstein's special theory of relativity
0:35:43 > 0:35:47encapsulated in the famous equation E=mc2.
0:35:47 > 0:35:50It was a beautiful, simple and elegant theory
0:35:50 > 0:35:54that describes the behaviour of things close to the speed of light.
0:35:54 > 0:35:58On the other hand, you had Planck's discovery of the quantum
0:35:58 > 0:36:04and the revolution that followed describing the bizarre rules of the very, very small.
0:36:06 > 0:36:12The problems arose when trying to describe situations where things were small enough
0:36:12 > 0:36:14for quantum effects to be felt,
0:36:14 > 0:36:19but travelling fast enough for special relativity to be important.
0:36:21 > 0:36:24Specifically, there were huge problems trying to describe
0:36:24 > 0:36:30the electron, a tiny particle whizzing around inside an atom.
0:36:30 > 0:36:35If both of these theories were true, then they should be able to be used
0:36:35 > 0:36:39together to give a mathematical description of the electron.
0:36:43 > 0:36:45But what if this couldn't be done?
0:36:45 > 0:36:49What if quantum physics and special relativity couldn't be married?
0:36:49 > 0:36:54This would mean one or other of these two cornerstones of physics had to be wrong.
0:36:54 > 0:37:00A way had to be found for the two theories to be married together.
0:37:00 > 0:37:02It would be Dirac who would achieve this.
0:37:06 > 0:37:11Dirac's unification of the special theory and the rules of the quantum world
0:37:11 > 0:37:16would rank as one of the greatest mathematical accomplishments of the 20th century.
0:37:16 > 0:37:22And it would lead inadvertently to a radical new picture of nothing.
0:37:24 > 0:37:28To get a non mathematical sense of what he did, and how he did it,
0:37:28 > 0:37:35I've come to the cinema to see one of Dirac's favourite films, 2001 A Space Odyssey.
0:37:39 > 0:37:41Understanding why it appealed to him
0:37:41 > 0:37:46helps give us an insight into how he managed to solve this great problem.
0:37:46 > 0:37:52If you look at 2001, it was, as Kubrick has said, a demonstration
0:37:52 > 0:37:57that you could make a really good movie script without words
0:37:57 > 0:37:59but with a power of the visual imagery.
0:37:59 > 0:38:03Now, that in some ways is very closely analogous
0:38:03 > 0:38:06to Dirac's a theoretical physics
0:38:06 > 0:38:11because, for him, what was central, were the mathematical equations.
0:38:11 > 0:38:15And more over, he had a visual sense of what those equations meant.
0:38:22 > 0:38:25The abstract images of 2001 appealed to Dirac
0:38:25 > 0:38:30because they captivated his brilliant visual imagination.
0:38:30 > 0:38:35It was this highly developed and unusual way of thinking,
0:38:35 > 0:38:39honed in his schooldays, that would enable him in 1928
0:38:39 > 0:38:43to visualise a unique way of describing the electron.
0:38:43 > 0:38:48It was a description that finally managed to unite Einstein's
0:38:48 > 0:38:53special theory of relativity and the weird world of quantum mechanics.
0:39:10 > 0:39:15Today, it's known simply as the Dirac equation.
0:39:15 > 0:39:18It may look like a small collection of symbols,
0:39:18 > 0:39:23but to a mathematician this equation is profoundly beautiful.
0:39:23 > 0:39:31A complex and symmetrical synthesis of mathematical ideas, expressed with stunning clarity.
0:39:35 > 0:39:41This is the commemorative plaque at Bishop Road, Paul Dirac's primary school.
0:39:41 > 0:39:44And on it, his famous equation.
0:39:44 > 0:39:49Within these few symbols lie profound truths about the universe.
0:39:49 > 0:39:53But don't be deceived by its apparent simplicity,
0:39:53 > 0:39:59think of this equation as the tip of a giant mathematical iceberg.
0:39:59 > 0:40:03Each of these terms relate to entire branches of mathematics
0:40:03 > 0:40:06and the particular relationships between them.
0:40:06 > 0:40:09Beneath this equation, are mathematical ideas that
0:40:09 > 0:40:16have been developed and honed by many, many other great individuals.
0:40:16 > 0:40:19If you think of a poem, you can think of it as the most supercharged
0:40:19 > 0:40:23kind of language, the way you compress meaning
0:40:23 > 0:40:27into a very, very brief area on the page.
0:40:27 > 0:40:31Dirac was producing equations that had that kind of concision
0:40:31 > 0:40:33and you can then unpack them,
0:40:33 > 0:40:38just as you re-read a Shakespeare sonnet and see more and more in it, more and more elegance.
0:40:38 > 0:40:42Same with the Dirac equation, you find an equation there
0:40:42 > 0:40:47you can keep finding things that were not obvious on first reading.
0:40:47 > 0:40:50In fact, Dirac once said that the equation was smarter than he was
0:40:50 > 0:40:53because it actually gave more stuff out than he put into it.
0:40:54 > 0:41:00There was one particularly odd thing the equation seemed to be saying to Dirac.
0:41:00 > 0:41:06Something that would redefine the concept of empty space forever.
0:41:06 > 0:41:13In his description of the electron, Dirac had been forced to use a collection of four equations
0:41:13 > 0:41:15represented by the symbol gamma,
0:41:15 > 0:41:21in order to make special relativity and quantum mechanics fit together.
0:41:21 > 0:41:27But the need for four equations seemed strange.
0:41:27 > 0:41:33To Dirac and other physicists in the 1920s, the first two were quite recognisable.
0:41:33 > 0:41:39They described the behaviour of an electron as it had been observed in the laboratory.
0:41:39 > 0:41:42But the second two were very strange.
0:41:42 > 0:41:48They seemed to be saying there was some other type of electron that could exist.
0:41:48 > 0:41:52One that had never been seen before.
0:41:57 > 0:42:01So, this is the normal world we are familiar with.
0:42:01 > 0:42:04And here, scaled up many, many times
0:42:04 > 0:42:08is a regular electron of the type contained within
0:42:08 > 0:42:12the trillions of atoms that make up this table,
0:42:12 > 0:42:15me and everything else in the universe.
0:42:15 > 0:42:20Dirac realised that these mysterious new elements in his equation
0:42:20 > 0:42:24predicted the existence of a strange new kind of particle.
0:42:24 > 0:42:32In some ways, just like the electron, and yet at the same time very, very different.
0:42:40 > 0:42:45Dirac gradually became convinced that the new parts of his equation
0:42:45 > 0:42:47were describing something
0:42:47 > 0:42:51that could be thought of as an anti-electron.
0:42:51 > 0:42:55In many ways, it was like the mirror image of an electron,
0:42:55 > 0:42:57having opposite properties like electric charge.
0:42:57 > 0:43:03And, in principle an anti-electron could form part of an anti-atom,
0:43:03 > 0:43:06and many anti-atoms could fit together
0:43:06 > 0:43:11to make an anti-matter table, or even an anti-me.
0:43:13 > 0:43:16But the weirdness didn't end there.
0:43:16 > 0:43:21Dirac realised that if things and anti-things ever met each other,
0:43:21 > 0:43:24they would instantly annihilate,
0:43:24 > 0:43:27turning all their mass into energy...
0:43:27 > 0:43:29EXPLOSION
0:43:30 > 0:43:33Disappearing completely.
0:43:37 > 0:43:43Here, finally was the answer to the riddle of empty space.
0:43:43 > 0:43:47Heisenberg's uncertainty principle had suggested that matter could
0:43:47 > 0:43:52pop into existence for incredibly short periods of time.
0:43:52 > 0:43:55Now, Dirac had provided the mechanism
0:43:55 > 0:44:00by which matter could be created out of the vacuum...
0:44:01 > 0:44:05..and just as quickly, disappear again.
0:44:07 > 0:44:10So, let's take another look at our box.
0:44:10 > 0:44:14Whenever a particle pops out of empty space,
0:44:14 > 0:44:17so simultaneously does its anti-particle.
0:44:17 > 0:44:23Although this sounds completely ridiculous, let me assure you it is true.
0:44:23 > 0:44:28So, whenever you try to remove everything you can from empty space,
0:44:28 > 0:44:33it's still always awash with all these fluctuations.
0:44:35 > 0:44:40Within nothingness, there's a kind of fizzing, a dynamic dance
0:44:40 > 0:44:44as pairs of particles and anti-particles
0:44:44 > 0:44:48borrow energy from the vacuum for brief moments
0:44:48 > 0:44:52before annihilating and paying it back again.
0:44:58 > 0:45:03Dirac's theory of the electron and the idea of anti-matter
0:45:03 > 0:45:07gives us a completely new picture of the vacuum.
0:45:07 > 0:45:12Before you could think about the vacuum as empty space, so to speak.
0:45:12 > 0:45:16relativity had said, you don't need an aether,
0:45:16 > 0:45:20so the picture was of the vacuum being empty.
0:45:20 > 0:45:24But when you bring relativity and quantum theory together
0:45:24 > 0:45:31then you have for certain, this notion of electron and anti-electron pairs
0:45:31 > 0:45:34just appearing out of the vacuum.
0:45:34 > 0:45:39So you can think of these pairs just sprouting all over the place in the vacuum.
0:45:42 > 0:45:46So, the vacuum goes from being nothing
0:45:46 > 0:45:53to being a place absolutely teeming with matter, anti-matter creation.
0:45:53 > 0:45:58Dirac's ideas about empty space were refined and developed
0:45:58 > 0:46:01into what is known today as quantum field theory.
0:46:01 > 0:46:04And these strange fleeting things within nothing
0:46:04 > 0:46:09became known as virtual particles.
0:46:17 > 0:46:24So it seems, nothingness is in fact a seething mass of virtual particles,
0:46:24 > 0:46:26appearing and disappearing
0:46:26 > 0:46:29trillions of times in the blink of an eye.
0:46:36 > 0:46:39I've come to Imperial College London
0:46:39 > 0:46:43to see the effects of these virtual particles myself.
0:46:43 > 0:46:48Thanks to a brilliant experiment by an American scientist called Willis Lamb,
0:46:48 > 0:46:51we now have a way to conclusively show
0:46:51 > 0:46:56there is activity within apparent nothingness.
0:46:56 > 0:46:58But in order to glimpse it,
0:46:58 > 0:47:03you have to peer deep within a single atom
0:47:03 > 0:47:07and amazingly Lamb found an ingenious way to do this.
0:47:09 > 0:47:12So, what did Lamb do?
0:47:12 > 0:47:17Well, his experiment relies on the quantum rules of the atom.
0:47:17 > 0:47:21Within atoms, electrons have very specific, discreet energies
0:47:21 > 0:47:24in the way they orbit around the nucleus.
0:47:24 > 0:47:28His experiment showed that if the vacuum really was full
0:47:28 > 0:47:31of these hidden fluctuations,
0:47:31 > 0:47:34then these would cause the electrons' orbit
0:47:34 > 0:47:37to wobble ever-so-slightly.
0:47:37 > 0:47:41Think of it as an analogy as though the electron is a plane
0:47:41 > 0:47:44flying along and hitting turbulence
0:47:44 > 0:47:47forcing it to move up to a slightly higher altitude.
0:47:49 > 0:47:51So this is how the experiment works.
0:47:51 > 0:47:56Contained within this vacuum chamber are a small number of atoms.
0:47:56 > 0:48:01While Lamb used microwaves in his original experiments,
0:48:01 > 0:48:06in this version, the team at Imperial are using lasers to probe the electrons.
0:48:06 > 0:48:11Now, if you think this all looks very complex, just remember
0:48:11 > 0:48:14how small a measurement it is we are trying to make here.
0:48:14 > 0:48:20This apparatus has to be sensitive enough to pick up minute changes
0:48:20 > 0:48:25in the behaviour of something that is itself, extremely tiny.
0:48:25 > 0:48:30Imagine we could scale up the wobble in electron that's being measured
0:48:30 > 0:48:32to the size of this apple.
0:48:32 > 0:48:40That would mean this vacuum chamber behind me, would scale up to being a trillion miles in size.
0:48:40 > 0:48:43The vacuum chamber would be something like
0:48:43 > 0:48:47100 times the size of the entire solar system.
0:48:47 > 0:48:54It would take light about 40 days just to travel from the top down to the bottom.
0:48:54 > 0:48:57So, what is going on in there?
0:48:57 > 0:49:02OK, so let me first fire up the laser in the experiment behind me.
0:49:02 > 0:49:08What this monitor will show us is exactly what's going on inside the vacuum chamber
0:49:08 > 0:49:10down at the minutest scales.
0:49:10 > 0:49:13Now, look at this peak that's appeared.
0:49:13 > 0:49:15BUZZING
0:49:15 > 0:49:17It may not look very exciting,
0:49:17 > 0:49:20but it's telling us something really remarkable.
0:49:20 > 0:49:27This is measuring the amount the electron is being wobbled about by the vacuum itself.
0:49:27 > 0:49:32If the vacuum were truly empty, this peak wouldn't exist,
0:49:32 > 0:49:34we'd just get a flat line.
0:49:34 > 0:49:38What this is telling us is that however hard we try
0:49:38 > 0:49:44to remove everything we can from space, we can never get it truly empty.
0:49:44 > 0:49:49Everywhere in the universe, space is filled with this vacuum
0:49:49 > 0:49:52that has a deep, mysterious energy.
0:49:56 > 0:49:57But it doesn't end there.
0:49:59 > 0:50:04When using the mathematics laid out by Heisenberg, Dirac and others,
0:50:04 > 0:50:08you can calculate the amount the electron should be affected.
0:50:10 > 0:50:14When you run the real physical experiment, the answer you get
0:50:14 > 0:50:19matches the theory to one part in a million.
0:50:19 > 0:50:23The theory of quantum mechanics is the most accurate
0:50:23 > 0:50:28and powerful description of the natural world that we have.
0:50:30 > 0:50:33But there's a much more dramatic way
0:50:33 > 0:50:38in which we can see the effects of these quantum fluctuations.
0:50:38 > 0:50:42And that's because they're written into the stars.
0:50:49 > 0:50:52Today, our best theories tell us
0:50:52 > 0:50:59that as the universe sprang from the vacuum, it expanded very rapidly.
0:50:59 > 0:51:03And this means that the rules of the quantum world should have
0:51:03 > 0:51:09contributed to the large-scale structure of the entire cosmos.
0:51:13 > 0:51:19When our universe first came into existence, it was many times smaller than a single atom.
0:51:19 > 0:51:23And down at this size it's governed not by the classical rules we're
0:51:23 > 0:51:29familiar with, but by the weird rules of the quantum world.
0:51:29 > 0:51:35This is for me, one of the most profound and beautiful ideas in the whole of science.
0:51:35 > 0:51:38That it's quantum reality that has
0:51:38 > 0:51:42shaped the structure of the universe we see today.
0:51:42 > 0:51:49Our universe is just the quantum world inflated many, many times.
0:51:49 > 0:51:54Nothing really has shaped everything.
0:51:54 > 0:51:59And what's more, we now have a way to see this.
0:52:06 > 0:52:14This is a picture of the first light that was released after the Big Bang.
0:52:14 > 0:52:19Think of it as a baby photo of everything.
0:52:19 > 0:52:24This incredible picture was taken by a team of researchers at NASA
0:52:24 > 0:52:27led by Professor George Smoot.
0:52:27 > 0:52:30This is like taking a
0:52:30 > 0:52:35picture of an embryo that's 12 hours after conception,
0:52:35 > 0:52:37compared to taking a picture
0:52:37 > 0:52:39of a person who is 50 years old.
0:52:39 > 0:52:40It's in the same perspective.
0:52:40 > 0:52:47And 12 hours, you may have two cells, this is very early and yet we are seeing what's equivalent
0:52:47 > 0:52:51of the DNA, the blueprint for how the universe is going to develop.
0:52:53 > 0:52:56With the help of highly sensitive satellites,
0:52:56 > 0:53:00George Smoot and his team were able to study this image
0:53:00 > 0:53:04of the embryonic universe in amazing detail.
0:53:04 > 0:53:10And when they did, tiny variations in its temperature were revealed.
0:53:10 > 0:53:15It soon became apparent that the tiny differences in temperature
0:53:15 > 0:53:21are in fact the scars left by the quantum vacuum on our universe.
0:53:25 > 0:53:28EXPLOSION
0:53:28 > 0:53:33These irregularities created in the first moments of existence
0:53:33 > 0:53:39by the teeming quantum vacuum meant the matter of the universe
0:53:39 > 0:53:42didn't spread out completely evenly.
0:53:42 > 0:53:44EXPLOSION
0:53:48 > 0:53:53Rather, it formed vast clumps that would evolve into
0:53:53 > 0:53:59the galaxies and clusters of galaxies that make up the universe today.
0:54:00 > 0:54:03The application of quantum physics to cosmology,
0:54:03 > 0:54:05to the universe as a whole
0:54:05 > 0:54:06was revolutionary.
0:54:06 > 0:54:09It really changed our entire perception
0:54:09 > 0:54:12of the evolution of the universe,
0:54:12 > 0:54:16because it turns out that quantum physics provides a natural mechanism
0:54:16 > 0:54:18through quantum fluctuations
0:54:18 > 0:54:26to see into the early universe with small irregularities that would later grow to make galaxies.
0:54:26 > 0:54:30The thought is really overwhelming, the idea that an object
0:54:30 > 0:54:36with billions of stars like the Milky Way began life as a quantum fluctuation,
0:54:36 > 0:54:39what we call a fluctuation of the vacuum,
0:54:39 > 0:54:43an object of sub-microscopic scales, it really is mind boggling.
0:54:45 > 0:54:50It now appears as if the quantum world, the place we once thought of
0:54:50 > 0:54:57as empty nothingness has actually shaped everything we see around us.
0:54:59 > 0:55:03What happens is, something that was a small fluctuation,
0:55:03 > 0:55:06a tiny quantum fluctuation, becomes our galaxy.
0:55:06 > 0:55:11Or becomes a cluster of galaxies because there are lots of quantum fluctuations,
0:55:11 > 0:55:13so it answers one of the questions we have -
0:55:13 > 0:55:16why are there 100 billion galaxies in our viewpoint?
0:55:16 > 0:55:18Well, in a drop of water,
0:55:18 > 0:55:21there's many more than 100 million quantum fluctuations,
0:55:21 > 0:55:26in an atom there's that many, the vacuum has all of this bubbling going on all the time.
0:55:30 > 0:55:34The teeming, seething activity of the vacuum, of nothing,
0:55:34 > 0:55:37and the quantum fluctuations within it...
0:55:40 > 0:55:46..were the seeds, seeds which grew into the universe we see today.
0:55:50 > 0:55:56This idea gives rise to one final revelation.
0:55:56 > 0:56:00Today, our best theories about the cosmos tell us
0:56:00 > 0:56:05that at the beginning of time, the universe sprang from the vacuum.
0:56:07 > 0:56:13Creating not only vast amounts of matter, but also the strange stuff
0:56:13 > 0:56:16that was predicted by Paul Dirac...
0:56:19 > 0:56:21..anti-matter.
0:56:22 > 0:56:26But the universe we see today is made of matter,
0:56:26 > 0:56:31nearly all of the anti-matter seems to have vanished.
0:56:34 > 0:56:37EXPLOSION
0:56:38 > 0:56:42According to common theory,
0:56:42 > 0:56:46the Big Bang produced equal amounts of matter and anti-matter.
0:56:46 > 0:56:48But as the universe cooled down,
0:56:48 > 0:56:53matter and anti-matter annihilated almost perfectly, but not quite.
0:56:53 > 0:56:58For every billion particles of matter and anti-matter,
0:56:58 > 0:56:59one was left behind.
0:56:59 > 0:57:03The matter and anti-matter that annihilated to produce radiation
0:57:03 > 0:57:06gave rise to the heat of the Big Bang
0:57:06 > 0:57:09that we see today in the form of the microwave background radiation.
0:57:09 > 0:57:13The little particle that was left behind, for every billion
0:57:13 > 0:57:19that annihilated is what makes galaxies, stars, planets and people.
0:57:23 > 0:57:28So, we are simply the debris of a huge annihilation
0:57:28 > 0:57:32of matter and anti-matter at the beginning of time.
0:57:32 > 0:57:35EXPLOSION
0:57:36 > 0:57:40The leftovers of an unimaginable explosion.
0:57:51 > 0:57:54All these insights have arisen
0:57:54 > 0:57:59from simply trying to understand what nothing really is.
0:57:59 > 0:58:03What we once thought of as the void
0:58:03 > 0:58:06now seems to hold within it,
0:58:06 > 0:58:11the deepest mysteries of the entire universe.
0:58:17 > 0:58:21In the 400 years or so since Torricelli and Pascal
0:58:21 > 0:58:24began exploring vacuums here on Earth,
0:58:24 > 0:58:31we've begun to understand in ever greater detail the world's at the very limits of our perception.
0:58:31 > 0:58:38And in doing so, we've uncovered the strange truth about reality itself.
0:58:38 > 0:58:42There's a profound connection between the nothingness
0:58:42 > 0:58:45from which we originated
0:58:45 > 0:58:48and the infinite in which we are engulfed.
0:59:05 > 0:59:09Subtitles by Red Bee Media Ltd
0:59:09 > 0:59:14E-mail subtitling@bbc.co.uk