0:00:12 > 0:00:13Why are we here?
0:00:13 > 0:00:15Where do we come from?
0:00:15 > 0:00:19These are the most enduring of questions
0:00:19 > 0:00:21and it's an essential part of human nature
0:00:21 > 0:00:23to want to find the answers.
0:00:28 > 0:00:31And we can trace our ancestry back hundreds of thousands of years,
0:00:31 > 0:00:33to the dawn of humankind,
0:00:33 > 0:00:39but, in reality, our story extends far further back in time.
0:00:39 > 0:00:42Our story starts with the beginning of the universe.
0:00:47 > 0:00:51It began 13.7 billion years ago.
0:00:54 > 0:00:57And today, it's filled with over 100 billion galaxies,
0:00:57 > 0:01:02each containing hundreds of billions of stars.
0:01:03 > 0:01:07In this series, I want to tell that story,
0:01:07 > 0:01:10because, ultimately, we are part of the universe,
0:01:10 > 0:01:14so its story is our story.
0:01:17 > 0:01:22This film is about the stuff that makes us and where it all came from,
0:01:22 > 0:01:28because understanding our own origins means understanding the lives of stars.
0:01:31 > 0:01:37And how their catastrophic deaths bring new life to the universe.
0:01:37 > 0:01:39Because every mountain,
0:01:39 > 0:01:43every rock on this planet, every living thing,
0:01:43 > 0:01:49every piece of you and me was forged in the furnaces of space.
0:02:40 > 0:02:41This is Pashupatinath,
0:02:41 > 0:02:43in the Nepalese capital city of Kathmandu
0:02:43 > 0:02:47and Hindus come here from all over India and Nepal
0:02:47 > 0:02:51to worship the god Shiva. That is Shiva's temple.
0:02:51 > 0:02:56Now, Shiva is the god of destruction.
0:02:56 > 0:02:59In the Hindu faith, everything has to be destroyed,
0:02:59 > 0:03:02so that new things can be created
0:03:02 > 0:03:06and that's why pilgrims come here to the banks of the Bagmati River,
0:03:06 > 0:03:09at the foot of Shiva's temple.
0:03:15 > 0:03:18The belief in this cycle of creation and destruction
0:03:18 > 0:03:21lends Pashupatinath an added significance.
0:03:26 > 0:03:30Many of these pilgrims will have come here at the end of their lives,
0:03:30 > 0:03:33to die here and be cremated.
0:03:36 > 0:03:38Hindus believe in reincarnation,
0:03:38 > 0:03:41an eternal sequence of death and rebirth.
0:03:46 > 0:03:51Cremation helps free the soul, so it's ready for the next life.
0:03:54 > 0:03:58'They also believe that the physical elements of the body are released'
0:03:58 > 0:04:02back to the world, so they can be recycled in the next stage of creation.
0:04:09 > 0:04:16'It's an ancient belief that touches on a deeper truth about how the universe works.'
0:04:20 > 0:04:22Every civilisation,
0:04:22 > 0:04:26every religion across the world, has a creation story.
0:04:26 > 0:04:32It tells of where we came from of how we came to be here and of what will happen when we die.
0:04:38 > 0:04:44Well, I have a different creation story to tell and it's based entirely on physics and cosmology.
0:04:44 > 0:04:47It can tell us what we're made of and where we came from.
0:04:47 > 0:04:52In fact, it can tell us what everything in the world is made of and where it came from.
0:04:52 > 0:04:56It also answers that most basic of human needs, to feel part of
0:04:56 > 0:04:59something much bigger, because to tell this story
0:04:59 > 0:05:03you have to understand the history of the universe.
0:05:03 > 0:05:06And it teaches us that the path to enlightenment
0:05:06 > 0:05:10is not an understanding of our own lives and deaths,
0:05:10 > 0:05:13but the lives and deaths of the stars.
0:05:24 > 0:05:30My creation story is the story of how we were made by the universe.
0:05:31 > 0:05:36It explains how every atom in our bodies was formed, not on Earth,
0:05:36 > 0:05:39but was created in the depths of space,
0:05:39 > 0:05:42through the epic lifecycle of the stars.
0:05:44 > 0:05:50And to understand that story, we will journey to the stars in all their stages of life.
0:05:54 > 0:05:59This is where stars are born, a nebula -
0:05:59 > 0:06:03a stellar nursery, where new stars burst into life.
0:06:06 > 0:06:10Those stars will burn for billions of years,
0:06:10 > 0:06:12until their voracious hunger for fuel
0:06:12 > 0:06:15forces them to blow up, to become giants...
0:06:19 > 0:06:21..hundreds of times the size of our sun.
0:06:24 > 0:06:30And when they die, stars go out with the biggest bang in the universe.
0:06:39 > 0:06:43But to understand how we came from the stars,
0:06:43 > 0:06:46we must begin our journey much closer to home.
0:07:15 > 0:07:18Well, this is sunrise over Nepal
0:07:18 > 0:07:21and those are the tallest mountains in the world, the Himalayas.
0:07:21 > 0:07:26Every one of those peaks is over 6,500 metres.
0:07:27 > 0:07:29What a spectacular sight.
0:07:31 > 0:07:33But it's incredible to think that,
0:07:33 > 0:07:35just a few tens of millions of years ago,
0:07:35 > 0:07:38those mountains were something very different.
0:07:43 > 0:07:47'The Himalayas haven't always been mountains.'
0:07:50 > 0:07:53We can find clues to their true origin
0:07:53 > 0:07:55by looking at them more closely.
0:07:58 > 0:08:01This is Himalayan limestone,
0:08:01 > 0:08:06the rock out of which much of this magnificent mountain range is made.
0:08:06 > 0:08:11If you look closely, you can see a kind of chalky granular structure,
0:08:11 > 0:08:15because limestone is made primarily out of the bodies, the shells,
0:08:15 > 0:08:20of dead sea creatures - coral and polyps - and when they die,
0:08:20 > 0:08:23they are put under immense pressures and squashed
0:08:23 > 0:08:25and eventually form limestone.
0:08:25 > 0:08:30So the Himalayas were once living creatures.
0:08:31 > 0:08:37Much of the rock in the Himalayas was formed at the bottom of an ocean and then, over millions of years,
0:08:37 > 0:08:41it was raised up, to become these vast peaks.
0:08:42 > 0:08:45We've even found fossils at the top of Mount Everest.
0:08:45 > 0:08:50It's a beautiful example of the endless recycling of the earth's resources
0:08:50 > 0:08:53that has been going on since the dawn of time -
0:08:53 > 0:08:56and we are part of that system.
0:08:57 > 0:09:02Every atom in my body was once part of something else,
0:09:02 > 0:09:08so an ancient tree or a dinosaur or a rock, in fact,
0:09:08 > 0:09:12definitely, a rock. And the reason that the rocks of the Earth
0:09:12 > 0:09:16can become living things and then living things will return
0:09:16 > 0:09:20to the rocks of the Earth is because everything
0:09:20 > 0:09:23is made of the same basic ingredients.
0:09:26 > 0:09:29Those ingredients are the chemical elements,
0:09:29 > 0:09:32the building blocks of everything on Earth.
0:09:36 > 0:09:41Elements like hydrogen, helium, lithium,
0:09:41 > 0:09:45beryllium, borum, carbon, nitrogen,
0:09:45 > 0:09:50oxygen, fluorine, neon, sodium, magnesium...
0:09:55 > 0:09:58Everything in the world is made up of the same basic sets
0:09:58 > 0:10:01of chemical elements, just assembled in different ways.
0:10:01 > 0:10:08So these mountains, the Himalayas, are made of limestone - and that's calcium carbonate.
0:10:08 > 0:10:13Now, calcium, carbon and oxygen are three of the elements that are vital for life,
0:10:13 > 0:10:18so calcium in my teeth and bones, oxygen in the air that I breathe
0:10:18 > 0:10:22and carbon in every organic molecule in my body.
0:10:22 > 0:10:27Now, you're probably pretty familiar with those elements in their combined forms,
0:10:27 > 0:10:31but you very rarely see the elements on their own.
0:10:33 > 0:10:36There's a good reason why many of the elements are not found
0:10:36 > 0:10:41in their raw forms in nature. They're extremely reactive.
0:10:42 > 0:10:43This is sodium.
0:10:43 > 0:10:49As you can see, it's a silvery metal and it's also quite reactive.
0:10:49 > 0:10:52In fact, it's so reactive that when you drop it into water...
0:10:53 > 0:10:55..you get a violent,
0:10:55 > 0:10:59almost explosive, reaction,
0:10:59 > 0:11:01which is all the more surprising when you think that,
0:11:01 > 0:11:04when combined with chlorine, this forms sodium chloride...
0:11:04 > 0:11:05EXPLOSION
0:11:05 > 0:11:09..salt, which is vital for life.
0:11:10 > 0:11:14Excellent! Ha-ha!
0:11:14 > 0:11:15And that's why I love chemistry
0:11:15 > 0:11:17almost as much as physics!
0:11:19 > 0:11:25It's this reactivity that enables the elements to combine with one another to make new substances.
0:11:27 > 0:11:30CAMERA MAN: Where's it gone? Where the hell's it gone?!
0:11:30 > 0:11:31BRIAN LAUGHS
0:11:33 > 0:11:38That, in turn, has allowed the Earth to develop its endless variety.
0:11:41 > 0:11:45And that variety includes us.
0:11:48 > 0:11:52So, to explain where we come from,
0:11:52 > 0:11:55we must also explain where the elements come from.
0:12:01 > 0:12:05We now know that the Earth is made of 92 chemical elements
0:12:05 > 0:12:11and that's pretty amazing, if you think of the complexity that we see around us.
0:12:11 > 0:12:15We also know that everything beyond Earth, everything we can see in the universe,
0:12:15 > 0:12:17is made of those same 92 elements.
0:12:17 > 0:12:21And notice that I didn't say, "We think" that that's what they're made of.
0:12:21 > 0:12:27I said, "We know" that's what they're made of, because we can prove it.
0:12:32 > 0:12:37The chemistry set we have on Earth extends far beyond the planet.
0:12:40 > 0:12:47We have set foot on the moon and know that it's rich in helium, silver and water.
0:12:49 > 0:12:55We have sent robot landers to our neighbouring planets and discovered that Mars
0:12:55 > 0:13:01is rich in iron, which has combined with oxygen to form its familiar rusty-red colour.
0:13:04 > 0:13:08And we know that Venus's thick atmosphere is full of sulphur.
0:13:11 > 0:13:15We've sent spacecraft to the edge of the solar system
0:13:15 > 0:13:20to discover that Neptune is rich in organic molecules, like methane.
0:13:22 > 0:13:25But what of the rest of the universe?
0:13:28 > 0:13:32It seems impossible that we could discover what the stars are made of,
0:13:32 > 0:13:34because they're so far away.
0:13:39 > 0:13:42Even the nearest star, Proxima Centauri,
0:13:42 > 0:13:46is ten thousand times more distant than Neptune,
0:13:46 > 0:13:494.2 light years from Earth.
0:13:56 > 0:13:59And the nearest galaxy, Andromeda,
0:13:59 > 0:14:02is another 2.5m light years away.
0:14:05 > 0:14:10Yet despite these vast distances, these alien worlds are constantly
0:14:10 > 0:14:15sending us signals, telling us exactly what they're made of.
0:14:15 > 0:14:20Our only contact with the distant stars is their light,
0:14:20 > 0:14:23that has journeyed across the universe to reach us,
0:14:23 > 0:14:28and encoded in that light is the key to understanding what the universe is made of.
0:14:28 > 0:14:32And it's all down to a particular property of the chemical elements.
0:14:32 > 0:14:36You see, when you heat the elements, when you burn them, then they give
0:14:36 > 0:14:41off light and each element gives off its own unique set of colours.
0:14:41 > 0:14:45This is strontium and it burns...
0:14:47 > 0:14:49..with a beautiful red colour.
0:14:54 > 0:14:56Sodium is yellow.
0:14:59 > 0:15:01Potassium is lilac.
0:15:02 > 0:15:04And copper is blue.
0:15:07 > 0:15:12Each element has its own characteristic colour.
0:15:15 > 0:15:20It's this property that tells us what the stars are made of.
0:15:22 > 0:15:28But it's a little more complicated than simply looking at the colour of the light that each star emits.
0:15:30 > 0:15:35You can see why, by looking at the light from our nearest star, the sun.
0:15:39 > 0:15:43This is a spectrum of the light taken from our sun
0:15:43 > 0:15:46and, you know, at first glance, it looks very familiar.
0:15:46 > 0:15:48It looks like a stretched-out rainbow,
0:15:48 > 0:15:51because that's exactly what a rainbow is.
0:15:51 > 0:15:55It's the spectrum of the light from the sun in the sky.
0:15:55 > 0:16:00But if you look a bit more closely, then you see that this spectrum is covered in black lines.
0:16:00 > 0:16:03These are called absorption lines.
0:16:04 > 0:16:09Each element within our sun not only emits light of a certain colour,
0:16:09 > 0:16:12it also absorbs light of the same colour.
0:16:12 > 0:16:18By looking for these black lines in the sun's light, we can simply read off a list
0:16:18 > 0:16:21of its constituent elements, like a bar code.
0:16:21 > 0:16:27For example, these two black lines in the yellow bit of the spectrum are sodium.
0:16:27 > 0:16:30You can see iron.
0:16:30 > 0:16:33Right down here you can see hydrogen.
0:16:33 > 0:16:40So, by looking at these lines in precise detail, you can work out exactly what elements are present
0:16:40 > 0:16:47in the sun and it turns out that that's about 70% hydrogen, 28% helium and 2% the rest.
0:16:47 > 0:16:52And you can do this, not only for the sun, but for any of the stars
0:16:52 > 0:16:58you can see in the sky and you can measure exactly what they're made of.
0:17:03 > 0:17:06That star there is Polaris, the Pole Star,
0:17:06 > 0:17:12and you can see that because all the other stars in the night sky appear to rotate around it.
0:17:12 > 0:17:16Now it's 430 light years away.
0:17:18 > 0:17:26But we know just by looking at the light that it has about the same heavy element abundance as our sun,
0:17:27 > 0:17:32but it's got markedly less carbon and a lot more nitrogen.
0:17:37 > 0:17:40And the same applies for other stars.
0:17:41 > 0:17:45Vega, the second brightest star in the northern sky,
0:17:45 > 0:17:48has only about a third of the metal content of our sun.
0:17:51 > 0:17:53Whereas, other stars are metal-heavy.
0:17:58 > 0:18:03Sirius, the dog star, contains three times as much iron as the sun.
0:18:05 > 0:18:09And Proxima Centauri is rich in magnesium.
0:18:13 > 0:18:16But although the quantities of the elements may vary,
0:18:16 > 0:18:23wherever we look across space, we only ever find the same 92 elements that we find on Earth.
0:18:27 > 0:18:33We are made of the same stuff as the stars and the galaxies.
0:18:40 > 0:18:43But where did all this matter come from?
0:18:45 > 0:18:49And how did it become the complex universe we see today?
0:19:12 > 0:19:17In order to understand where we came from, we have to understand events
0:19:17 > 0:19:22that happened in the first few seconds of the life of the universe.
0:19:22 > 0:19:27So when the universe began, it was unimaginably hot and dense.
0:19:27 > 0:19:31We, literally, don't have the scientific language to describe it,
0:19:31 > 0:19:35but it was, in a very real sense, beautiful.
0:19:35 > 0:19:40There was no structure, there was certainly no matter.
0:19:40 > 0:19:45It was exactly the same whichever way you look at it.
0:19:50 > 0:19:53We can get some idea of how the universe developed
0:19:53 > 0:19:58from this state of pure symmetry by looking at the behaviour of water
0:19:58 > 0:20:01in this remarkable landscape.
0:20:03 > 0:20:08These are the El Tatio geysers, high in the Chilean Andes.
0:20:10 > 0:20:13As the boiling water bubbles up through the ground to meet
0:20:13 > 0:20:15the freezing mountain air,
0:20:15 > 0:20:20water can be found in all three of its natural phases -
0:20:20 > 0:20:22vapour, liquid and ice.
0:20:26 > 0:20:29In its hottest state, water is,
0:20:29 > 0:20:33like the early universe, an undifferentiated cloud.
0:20:35 > 0:20:39But as it cools, it suddenly behaves very differently.
0:20:41 > 0:20:48You see, if you look at a cloud of steam, it looks the same from every direction,
0:20:48 > 0:20:55but as it cools down, as it lands on this plate of freezing cold glass,
0:20:55 > 0:20:57then it immediately crystallises out.
0:20:57 > 0:21:00It turns into solid water - ice.
0:21:04 > 0:21:07As the ice crystals form, the symmetry of the water vapour
0:21:07 > 0:21:13disappears from view and complex, beautiful structure emerges.
0:21:16 > 0:21:21In the same way, we think that the universe, as it cooled,
0:21:21 > 0:21:25went through a series of these events, where structure emerged.
0:21:25 > 0:21:30One of the most important was about a billionth of a second after the Big Bang.
0:21:32 > 0:21:38In that moment, an important part of the symmetry of the universe was broken.
0:21:41 > 0:21:46Known as electroweak symmetry breaking, this was the moment when
0:21:46 > 0:21:52subatomic particles acquired mass - substance - for the first time.
0:21:52 > 0:21:55Amongst them, were the quarks.
0:21:57 > 0:22:02As the universe continued to cool, those quarks joined together
0:22:02 > 0:22:07to form larger, more complex structures, called protons and neutrons.
0:22:07 > 0:22:11Way before the universe was a minute old,
0:22:11 > 0:22:17the quarks had been locked away inside the protons and the neutrons
0:22:17 > 0:22:21and they were the building blocks of all atomic nuclei,
0:22:21 > 0:22:23the building blocks of the elements.
0:22:29 > 0:22:33These same protons and neutrons are with us to this day.
0:22:33 > 0:22:37They form the hearts, the nuclei, of all atoms.
0:22:50 > 0:22:53Just a few seconds after the beginning of the universe,
0:22:53 > 0:22:58the fundamental building blocks of everything had been created.
0:23:03 > 0:23:06It sounds ridiculous, the fact that everything you need
0:23:06 > 0:23:11to make up me and everything on planet Earth and,
0:23:11 > 0:23:16in fact, every star and every galaxy in the sky was there,
0:23:16 > 0:23:19after the first minutes in the life of the universe.
0:23:19 > 0:23:23It's almost unbelievable, but we have extremely strong
0:23:23 > 0:23:28experimental evidence to suggest that that is the way that it is.
0:23:28 > 0:23:32But from that point on, it was just, in a sense,
0:23:32 > 0:23:40a process of assembling those bits into more and more complex things.
0:23:41 > 0:23:44That is an incredibly fascinating story in itself.
0:24:06 > 0:24:14To tell that story, we must look deep inside the atom, to the nucleus at its centre.
0:24:15 > 0:24:19Here, we can see how protons and neutrons are assembled,
0:24:19 > 0:24:21to build up the 92 different elements.
0:24:23 > 0:24:30Now, the wonderful thing about the construction of the chemical elements is that it's so simple.
0:24:30 > 0:24:33I suppose you could call it "child's play".
0:24:41 > 0:24:45So imagine these bubbles are my universal chemistry set...
0:24:47 > 0:24:51..and the single bubbles could just be single protons.
0:24:51 > 0:24:54That's the nucleus of the simplest chemical element.
0:24:57 > 0:25:01The element with a single proton in its nucleus is hydrogen
0:25:01 > 0:25:05and, from hydrogen, you can make all the other elements.
0:25:08 > 0:25:12The first stage is to stick two protons together.
0:25:14 > 0:25:16Ha-ha! Look at that!
0:25:16 > 0:25:19That was two bubbles stuck together.
0:25:19 > 0:25:24Now what happens when you stick two protons together is one of the protons turns into a neutron.
0:25:24 > 0:25:27Now, that is called deuterium.
0:25:29 > 0:25:32Deuterium is still a form of hydrogen,
0:25:32 > 0:25:39because it has only one proton in its nucleus, and it's the number of protons that defines the element.
0:25:39 > 0:25:46It's only when two deuterium nuclei are combined that a new element is created.
0:25:46 > 0:25:53Take two deuteriums and fuse them together and you get a nucleus for two protons and two neutrons.
0:25:54 > 0:25:58That's helium, the second simplest element.
0:26:00 > 0:26:05Then, it's just a question of adding more and more protons and neutrons.
0:26:06 > 0:26:09Well, there is an incredibly complicated nucleus.
0:26:09 > 0:26:13That's about 12 things stuck together, so that would be probably
0:26:13 > 0:26:16carbon 12, which is six protons and six neutrons.
0:26:18 > 0:26:22And you can carry on building more and more complex elements...
0:26:24 > 0:26:29..all the way up to the heaviest elements in the universe,
0:26:29 > 0:26:31to uranium and beyond.
0:26:31 > 0:26:35Simple, and beautiful, physics.
0:26:43 > 0:26:48This process of building the elements is called nuclear fusion.
0:26:48 > 0:26:54It allows the simplest of ingredients to create the infinite variety of the universe.
0:26:56 > 0:27:02But although this bubble metaphor makes creating new elements seem simple, it is,
0:27:02 > 0:27:05in reality, incredibly difficult to achieve.
0:27:10 > 0:27:15So difficult that there's only one place in nature that it happens.
0:27:28 > 0:27:33It's in stars like our sun that the elements are assembled.
0:27:33 > 0:27:40They're the only places in the universe hot enough and dense enough to fuse atoms together.
0:27:40 > 0:27:47Even then, only a fraction of the star reaches the extreme temperatures necessary.
0:27:47 > 0:27:54The sun is 6,000 Celsius at its surface, not nearly hot enough to power fusion.
0:27:59 > 0:28:05But deep below, where the temperature reaches 15m degrees,
0:28:05 > 0:28:10the sun fuses hydrogen into helium at a furious rate.
0:28:10 > 0:28:16Every second, it burns 600m tons of hydrogen.
0:28:20 > 0:28:28As it does so, it releases the huge amounts of heat and light that brings our planet to life.
0:28:34 > 0:28:41It is this process of converting one element into another that allows us to exist.
0:28:44 > 0:28:48For all its power, the sun only converts hydrogen,
0:28:48 > 0:28:52the simplest element, into helium, the next simplest.
0:28:52 > 0:28:57But there are over 90 other elements present in our universe, so where did they all come from?
0:28:59 > 0:29:05If the heavier elements are not being made in stars like the sun, then there must be somewhere else
0:29:05 > 0:29:08in the universe where they are assembled.
0:29:08 > 0:29:09It's important to know
0:29:09 > 0:29:14because it's the elements beyond helium that give our world its complexity,
0:29:14 > 0:29:17and when it comes to planet Earth and human beings,
0:29:17 > 0:29:22there's one element that is particularly important - carbon.
0:29:23 > 0:29:27Life is completely dependent on carbon.
0:29:27 > 0:29:33I mean, I'm made of about a billion billion billion carbon atoms, as is
0:29:33 > 0:29:38every human being out there, every living thing on the planet.
0:29:38 > 0:29:41Imagine how many carbon atoms that is.
0:29:41 > 0:29:43So where does all that carbon come from?
0:29:43 > 0:29:50Well, it comes from the only place in the universe where elements are made - stars.
0:29:50 > 0:29:55But in order for us to live, a star must die.
0:29:57 > 0:30:03Stars in the prime of their lives, like our sun, are only hot enough to make helium.
0:30:05 > 0:30:10Forming the heavier elements requires much higher temperatures.
0:30:11 > 0:30:16Temperatures that can only be reached at the end of a star's life.
0:30:21 > 0:30:22Looking out into space,
0:30:22 > 0:30:27you might think that the cosmos is a constant, unchanging place.
0:30:27 > 0:30:30That the stars will always be there.
0:30:30 > 0:30:35But in fact, the stars are only a temporary feature in the sky,
0:30:35 > 0:30:37and though they may burn brightly
0:30:37 > 0:30:41for many millions or billions of years,
0:30:41 > 0:30:44they can only live for as long as they have a supply of hydrogen to burn.
0:30:47 > 0:30:51When a star runs out of hydrogen, it begins to die,
0:30:51 > 0:30:53but it doesn't go quietly.
0:30:57 > 0:30:58Rather than cooling,
0:30:58 > 0:31:02the star becomes much hotter, until there's a sudden flash.
0:31:04 > 0:31:07Then the star starts to expand.
0:31:10 > 0:31:12Over tens of thousands of years,
0:31:12 > 0:31:17it balloons to many hundreds of times its previous size.
0:31:18 > 0:31:20But in this bloated state,
0:31:20 > 0:31:24the star is unable to maintain its surface temperature.
0:31:26 > 0:31:33As it cools, it takes on the characteristic colour of a dying star.
0:31:33 > 0:31:36It has become a red giant.
0:31:43 > 0:31:48These are pictures of a red giant star in our galaxy, a star called Betelgeuse.
0:31:48 > 0:31:51Now, it's one of our nearest neighbours in cosmic terms.
0:31:51 > 0:31:57It's only about 600 light years away, but it's the size that's astonishing.
0:31:57 > 0:32:02If you were to put the sun there, then Venus would be about there
0:32:02 > 0:32:06and the Earth about there, and Mars here, and in fact you could
0:32:06 > 0:32:10fit everything in the solar system all the way out to Jupiter
0:32:10 > 0:32:12inside the star.
0:32:12 > 0:32:17Now, because it's so big, even though it is 600 light years away,
0:32:17 > 0:32:20you can see detail on its surface,
0:32:20 > 0:32:24so these, these are sunspots on the surface of Betelgeuse.
0:32:24 > 0:32:29But it's not what's going on on the surface that's really interesting.
0:32:29 > 0:32:33To understand where carbon comes from in the universe, we have to
0:32:33 > 0:32:37understand what's going on deep in the heart of the star.
0:33:01 > 0:33:06Imagine this old prison in Rio is a dying star like Betelgeuse.
0:33:06 > 0:33:12Out there is the bright surface, shining off into space.
0:33:12 > 0:33:16As I descend deeper and deeper into the prison,
0:33:16 > 0:33:21the conditions would become hotter and hotter and denser and denser,
0:33:21 > 0:33:27until down there in the heart in the star is the core,
0:33:27 > 0:33:33and it's in there that all the ingredients of life are made.
0:33:35 > 0:33:41Deep in its core, the star is fighting a futile battle against its own gravity.
0:33:43 > 0:33:47As it desperately tries to stop itself collapsing under its own
0:33:47 > 0:33:51weight, new elements are made in a sequence of separate stages.
0:33:56 > 0:34:02Stage one is while there is still a supply of hydrogen to burn.
0:34:08 > 0:34:13Whilst the star is burning hydrogen to helium in the core, vast amounts
0:34:13 > 0:34:18of energy are released and that energy escapes, literally creating
0:34:18 > 0:34:23an outward pressure which bounces the force of gravity and,
0:34:23 > 0:34:26well, it holds the star up and keeps it stable.
0:34:26 > 0:34:30But eventually, the hydrogen in the core will run out
0:34:30 > 0:34:34and at that point the fusion reactions will stop,
0:34:34 > 0:34:36no more energy will be released
0:34:36 > 0:34:39and that outward pressure will disappear.
0:34:39 > 0:34:44Now, at that point, the core will start to collapse very rapidly,
0:34:44 > 0:34:46leaving a shell...
0:34:49 > 0:34:53..of hydrogen and helium behind.
0:34:56 > 0:35:00Beneath this shell, as the core collapses,
0:35:00 > 0:35:03the temperature rises again
0:35:03 > 0:35:06until, at 100 million degrees,
0:35:06 > 0:35:12stage two starts and helium nuclei begin to fuse together.
0:35:20 > 0:35:23A helium fusion does two things.
0:35:23 > 0:35:28Firstly, more energy is released and so the collapse is halted.
0:35:28 > 0:35:33But secondly, two more elements are produced in that process...
0:35:35 > 0:35:37..carbon.
0:35:40 > 0:35:44Oxygen. Two elements vital for life.
0:35:44 > 0:35:49So this is where all the carbon in the universe comes from.
0:35:49 > 0:35:52Every atom of carbon in my hand,
0:35:52 > 0:35:56every atom of carbon in every living thing on the planet
0:35:56 > 0:36:02was produced in the heart of a dying star.
0:36:03 > 0:36:10But compared to the lifetime of the star, the creation process of carbon and oxygen is over
0:36:10 > 0:36:14in a blink of an eye, because, in only about a million years,
0:36:14 > 0:36:18the supply of helium in the core is used up
0:36:18 > 0:36:20and for stars as massive as the sun,
0:36:20 > 0:36:24that's where fusion stops, because there isn't enough
0:36:24 > 0:36:29gravitational energy to compress the core any further and restart fusion.
0:36:29 > 0:36:33But for massive stars like Betelgeuse,
0:36:33 > 0:36:37the fusion process can continue.
0:36:41 > 0:36:43When the helium runs out,
0:36:43 > 0:36:48gravity takes over again and the collapse continues.
0:36:50 > 0:36:54The temperature rises once more, launching stage three,
0:36:54 > 0:36:59in which carbon fuses into magnesium, neon,
0:36:59 > 0:37:01sodium, and aluminium.
0:37:01 > 0:37:03And so it goes on.
0:37:03 > 0:37:07Core collapse, followed by the next stage of fusion
0:37:07 > 0:37:14to create more elements, each stage hotter and shorter than the last.
0:37:16 > 0:37:21And, eventually, in a final stage that lasts only a couple of days,
0:37:21 > 0:37:27the heart of the star is transformed into almost pure...
0:37:27 > 0:37:32iron, whose chemical symbol is Fe,
0:37:32 > 0:37:36and this is where the fusion process stops.
0:37:36 > 0:37:39In its millions of years of life,
0:37:39 > 0:37:44the star has made all the common elements,
0:37:44 > 0:37:49the stuff that makes up 99% of the Earth.
0:37:49 > 0:37:57The core is now a solid ball of those elements stacked on top of each other in layers.
0:37:57 > 0:38:01On the outside, there's a shell of hydrogen.
0:38:01 > 0:38:04Beneath it, a layer of helium.
0:38:04 > 0:38:09Then carbon and oxygen, and all the other elements, all the way
0:38:09 > 0:38:12down to the very heart of the star.
0:38:12 > 0:38:19And once that has fused into solid iron, the star has only seconds left to live.
0:38:20 > 0:38:24When a star runs out of fuel, then it can no longer release
0:38:24 > 0:38:27energy through fusion reactions,
0:38:27 > 0:38:30and then there's only one thing that can happen.
0:38:46 > 0:38:51In about the same amount of time it takes this prison block to crumble,
0:38:51 > 0:38:53the entire star falls in on itself.
0:39:01 > 0:39:06This is the destiny that awaits most of the stars in the universe.
0:39:10 > 0:39:16Yet even the implosion of the star only forges the first 26 elements.
0:39:18 > 0:39:20What of the remaining elements,
0:39:20 > 0:39:25some of which are vital for life and many of which we hold most precious?
0:39:44 > 0:39:47These are the remote forests of northern California.
0:39:49 > 0:39:56100 years ago, this whole area was teeming with people, all in search of one element.
0:40:03 > 0:40:08And the reason they were here can still be found in the original Sixteen To One Mine.
0:40:12 > 0:40:17This once stood at the centre of the California gold rush
0:40:17 > 0:40:25and, thanks to a quirk of geology, it continues to yield its precious bounty over 100 years later.
0:40:25 > 0:40:30You know, the unique thing about this place is that it sits right on the divide
0:40:30 > 0:40:35between the North American plate and the Pacific plate.
0:40:35 > 0:40:39You see a divide there between the rock and quartz,
0:40:39 > 0:40:43then right up there you can see the top of it.
0:40:43 > 0:40:47Now, in between the faults, this rock, the quartz, formed.
0:40:47 > 0:40:52Then, 140 million years ago, in the Jurassic period, when the dinosaurs
0:40:52 > 0:40:55were running around above our heads,
0:40:55 > 0:41:01hot water welled up and flowed, and that water deposited the gold
0:41:01 > 0:41:07through the seams of quartz, and so all the miners have to do...
0:41:07 > 0:41:08and ALL they have to do...
0:41:08 > 0:41:12is follow the seams of quartz, and over hundreds of years they've
0:41:12 > 0:41:16found vast amounts of gold deposited there.
0:41:31 > 0:41:33This is what all the fuss is about.
0:41:33 > 0:41:37This is the gold as it comes out of the ground,
0:41:37 > 0:41:40and it's unusually pure as gold goes.
0:41:40 > 0:41:46This is about 85% pure gold, but it could also be found like this,
0:41:46 > 0:41:49and this is a gold nugget that was found in a river,
0:41:49 > 0:41:53on a river bed, and it's a heavy piece of gold.
0:41:53 > 0:41:56It's between about one and one and a half ounces,
0:41:56 > 0:42:00which means that at today's prices it's worth about 2,000,
0:42:00 > 0:42:07and it's that inherent value that makes mines like this worth operating.
0:42:08 > 0:42:13But there's something a bit odd about the value we attach to gold.
0:42:13 > 0:42:18Throughout history, people have gone to extraordinary lengths to get their hands
0:42:18 > 0:42:22on this most precious substance, which is strange,
0:42:22 > 0:42:26because it isn't particularly useful for anything.
0:42:26 > 0:42:29Most of the gold that's been extracted throughout human history
0:42:29 > 0:42:34has ended up as jewellery, but it has got one thing going for it
0:42:34 > 0:42:38and that's that it is incredibly rare.
0:42:38 > 0:42:42All the gold mined from the earth in all of human history
0:42:42 > 0:42:46would only just fill three Olympic-size swimming pools.
0:42:48 > 0:42:53And it's that scarcity that makes gold valuable,
0:42:53 > 0:42:56but gold is just one of many rare elements.
0:42:59 > 0:43:02There are over 60 elements heavier than iron in the universe
0:43:02 > 0:43:07and some are valuable, like gold, silver, platinum.
0:43:07 > 0:43:11Some are vital for life, like copper and zinc,
0:43:11 > 0:43:16and some are just useful, like uranium, tin and lead.
0:43:16 > 0:43:18But across the universe,
0:43:18 > 0:43:22there are vanishingly small amounts of those heavy elements.
0:43:23 > 0:43:25The reason for that scarcity
0:43:25 > 0:43:30is that creating substantial amounts of the heaviest elements requires
0:43:30 > 0:43:33some of the rarest conditions in the universe,
0:43:33 > 0:43:37and we need to look far into space to find them.
0:43:39 > 0:43:44In a galaxy of 100 billion stars, these conditions will exist
0:43:44 > 0:43:48on average for less than a minute in every century.
0:43:54 > 0:43:59That's because they're only created in the final death throes
0:43:59 > 0:44:01of the very largest stars...
0:44:04 > 0:44:07..stars of at least nine times the mass of our sun.
0:44:09 > 0:44:12Only they can reach the extreme temperatures needed
0:44:12 > 0:44:16to create large amounts of the heavy elements.
0:44:21 > 0:44:24Deep in the heart of the star,
0:44:24 > 0:44:27the core finally succumbs to gravity.
0:44:33 > 0:44:37It falls in on itself with enormous speed...
0:44:44 > 0:44:48..and rebounds with colossal force.
0:44:55 > 0:44:59As the blast wave collides with the outer layers of the star,
0:44:59 > 0:45:06it generates the highest temperatures in the universe, 100 billion degrees.
0:45:07 > 0:45:12These conditions last for just 15 seconds, but it's enough
0:45:12 > 0:45:15to form the heaviest elements like gold.
0:45:21 > 0:45:23It's called a supernova...
0:45:25 > 0:45:29..the most powerful explosion in the universe.
0:45:36 > 0:45:43It's quite a thought that something as precious to us as the gold in a wedding ring was
0:45:43 > 0:45:46actually forged in the death of a distant star,
0:45:46 > 0:45:51millions of light years away, billions of years ago.
0:45:54 > 0:45:57Despite the rarity of supernovae,
0:45:57 > 0:46:03when they do happen, they're the most dramatic events in the sky.
0:46:03 > 0:46:08This is a picture of the Tarantula Nebula, which is a cloud of gas and dust in
0:46:08 > 0:46:13the Large Magellanic Cloud, which is a satellite galaxy of the Milky Way,
0:46:13 > 0:46:19and this is what it looks like on any clear starry night of the year.
0:46:19 > 0:46:25But on one night in 1987, the Tarantula Nebula looked like that.
0:46:25 > 0:46:29You can see that a new bright star has appeared in the sky.
0:46:29 > 0:46:35This is a supernova explosion, the explosive death of a massive star,
0:46:35 > 0:46:41and they're incredibly violent cosmic events, as this picture beautifully shows.
0:46:41 > 0:46:47This is a galaxy about 55 million light years away from Earth,
0:46:47 > 0:46:51but this is a supernova explosion in that galaxy.
0:46:51 > 0:46:55You can see that it's shining as brightly as the galactic core.
0:46:55 > 0:46:59There may be a billion suns in that core,
0:46:59 > 0:47:03and one supernova can shine as brightly as that.
0:47:05 > 0:47:10Yet to really appreciate the scale of these explosions, we would need
0:47:10 > 0:47:15to see one up close, to see a star die in our own galaxy,
0:47:15 > 0:47:18the Milky Way.
0:47:18 > 0:47:20Although on average there's one big supernova
0:47:20 > 0:47:23in each galaxy every century,
0:47:23 > 0:47:28there hasn't been one in the Milky Way since the birth of modern science.
0:47:28 > 0:47:32The last was in 1604, so we're long overdue.
0:47:32 > 0:47:39Astronomers are now searching the skies for the star that is most likely to go supernova.
0:47:39 > 0:47:43And amongst the leading candidates there's a familiar name.
0:47:43 > 0:47:49This is the constellation of Orion and this is Betelgeuse,
0:47:49 > 0:47:53and we know it's extremely unstable
0:47:53 > 0:47:59because it's dimmed by about 15% in the last ten years.
0:47:59 > 0:48:04Now, astronomers think that this star could go supernova at any moment.
0:48:07 > 0:48:15That could mean any time in the next million years but equally it could explode tomorrow,
0:48:15 > 0:48:19and Betelgeuse is only 600 light years away.
0:48:21 > 0:48:26Now, when it goes, Betelgeuse will be incredibly bright.
0:48:26 > 0:48:31It'll be by far the brightest star in the sky.
0:48:31 > 0:48:34It may shine as brightly as a full moon.
0:48:34 > 0:48:39It will be almost a second sun in the daylight.
0:48:59 > 0:49:04In this single instant, Betelgeuse will release more energy
0:49:04 > 0:49:08than our sun will produce in its entire lifetime.
0:49:13 > 0:49:18As the star is torn apart, it will fire out into space
0:49:18 > 0:49:22all the elements that it created in its life and death.
0:49:24 > 0:49:28Those elements will spread out to become a nebula,
0:49:28 > 0:49:32a rich chemical cloud drifting through space.
0:49:32 > 0:49:38And at the heart of the nebula will be a tiny beacon of light,
0:49:38 > 0:49:42the remnant of a star once more than a billion and a half kilometres
0:49:42 > 0:49:48across that has been crushed out of all recognition by gravity.
0:49:51 > 0:49:56This is Betelgeuse, the neutron star.
0:50:00 > 0:50:04And it's how this once mighty star will end its life.
0:50:18 > 0:50:20Now, once Betelgeuse has gone,
0:50:20 > 0:50:23the constellation of Orion will look very different.
0:50:23 > 0:50:27I mean there will just be a hole in the sky
0:50:27 > 0:50:31where that brilliant bright red star once shone.
0:50:31 > 0:50:35But it's in the deaths of old stars that new stars are born
0:50:35 > 0:50:40and it's very much like the cycle of death and rebirth
0:50:40 > 0:50:44here on earth but played out on a cosmic scale, and you can see that
0:50:44 > 0:50:48happening today in the constellation of Orion
0:50:48 > 0:50:54because in the sword handle you can see this - the Orion nebula.
0:50:54 > 0:50:57Now, it's nothing more than a misty patch of light in the night sky
0:50:57 > 0:51:01to the naked eye but if you look more closely,
0:51:01 > 0:51:04you see that there is a lot more going on.
0:51:10 > 0:51:14The Orion nebula is one of the wonders of the universe.
0:51:20 > 0:51:23Hidden in its clouds are bright points of light.
0:51:26 > 0:51:33These are new stars, forming from the elements blown out by supernova explosions,
0:51:37 > 0:51:42new stars being born from the remains of dead ones.
0:51:44 > 0:51:52And it's from this universal process of death and rebirth that we emerged
0:51:52 > 0:51:58because it was in a nebula just like this, five billion years ago,
0:51:58 > 0:52:00that our sun was formed.
0:52:09 > 0:52:13Around it, a network of planets formed.
0:52:14 > 0:52:18Among them was the Earth.
0:52:18 > 0:52:24Everything we find on the Earth today also originated in that nebula.
0:52:27 > 0:52:32But that is not the end of this story of how the universe created us.
0:52:36 > 0:52:38Because when we look deep into the nebula,
0:52:38 > 0:52:41we don't just see individual elements.
0:52:41 > 0:52:46We see greater complexity, the seeds of our own existence.
0:52:46 > 0:52:51Well, this is a spectrum of the light from the Orion nebula taken
0:52:51 > 0:52:58by the Herschel space telescope, so it really is a picture of light from interstellar space.
0:52:58 > 0:53:04You know, I wouldn't normally show you a graph like this but this is fascinating because what it shows
0:53:04 > 0:53:10is that that gas cloud, the Orion nebula, is not just a cloud of elements.
0:53:10 > 0:53:16There's complex chemistry here happening in deep space because each peak on this graph
0:53:16 > 0:53:22corresponds to a different molecule and there are some molecules present that I suppose are quite obvious.
0:53:22 > 0:53:29There's water and there's sulphur dioxide. But there are also complex carbon compounds in here. So there's
0:53:29 > 0:53:34methanol, there's hydrogen cyanide, there's formaldehyde, there's dimethyl ether.
0:53:34 > 0:53:40So what we're seeing here is complex carbon chemistry happening in deep space.
0:53:45 > 0:53:51That carbon chemistry is the beginning of the chemistry of life,
0:53:51 > 0:53:54and there is surprising evidence that this chemistry
0:53:54 > 0:53:59may have had a direct impact on the evolution of life on Earth.
0:54:05 > 0:54:08That evidence comes from meteorites,
0:54:11 > 0:54:14debris left over from the formation of the
0:54:14 > 0:54:18solar system that occasionally collides with the earth.
0:54:27 > 0:54:31One of the most productive places for finding meteorites
0:54:31 > 0:54:35is the Atacama desert in the High Andes of South America.
0:54:44 > 0:54:49This is a meteorite, a piece of rock that fell to earth from somewhere
0:54:49 > 0:54:57out there in the solar system, and it is certainly older than any rock you can see here.
0:54:57 > 0:55:02It's probably older than any rock you can find anywhere on Earth
0:55:02 > 0:55:07because it formed from the primordial gas cloud, that nebula that collapsed
0:55:07 > 0:55:11to form the sun and the planets over four and a half billion years ago.
0:55:11 > 0:55:14So it's incredibly ancient.
0:55:14 > 0:55:19Now this is a slice, a crosssection through a meteorite.
0:55:19 > 0:55:22You see those little brown areas in there?
0:55:22 > 0:55:30Well, in those brown areas we found amino acids, the building blocks of proteins,
0:55:30 > 0:55:37which are the building blocks of me, the building blocks of life. Incredibly complex carbon compounds.
0:55:37 > 0:55:45So this says that the complex carbon chemistry you need to send you on the path to life
0:55:45 > 0:55:50was happening out there in space four and a half billion years ago.
0:55:57 > 0:56:05So the first amino acids on earth, the fundamental building blocks of life, may have formed in the depths
0:56:05 > 0:56:10of space and been delivered to the earth on meteorites.
0:56:18 > 0:56:23When we look out into space, we are looking into our own origins.
0:56:28 > 0:56:33Because we are truly children of the stars.
0:56:33 > 0:56:37And written into every atom and every molecule of our bodies
0:56:37 > 0:56:43is the entire history of the universe from the Big Bang to the present day.
0:56:48 > 0:56:51Our story is the story of the universe
0:56:51 > 0:56:55and every piece of everyone, of everything you love,
0:56:55 > 0:57:00of everything you hate, of the thing you hold most precious,
0:57:00 > 0:57:03was assembled by the forces of nature
0:57:03 > 0:57:06in the first few minutes of the life of the universe,
0:57:06 > 0:57:13transformed in the hearts of stars or created in their fiery deaths.
0:57:13 > 0:57:19And when you die, those pieces will be returned to the universe
0:57:19 > 0:57:23in the endless cycle of death and rebirth.
0:57:23 > 0:57:28What a wonderful thing it is to be a part of that universe!
0:57:28 > 0:57:29And what a story.
0:57:29 > 0:57:32What a majestic story.
0:58:00 > 0:58:04Subtitles by Red Bee Media Ltd
0:58:04 > 0:58:08E-mail subtitling@bbc.co.uk