Stardust Wonders of the Universe


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Why are we here?

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Where do we come from?

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These are the most enduring of questions

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and it's an essential part of human nature

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to want to find the answers.

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And we can trace our ancestry back hundreds of thousands of years,

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to the dawn of humankind,

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but, in reality, our story extends far further back in time.

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Our story starts with the beginning of the universe.

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It began 13.7 billion years ago.

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And today, it's filled with over 100 billion galaxies,

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each containing hundreds of billions of stars.

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In this series, I want to tell that story,

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because, ultimately, we are part of the universe,

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so its story is our story.

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This film is about the stuff that makes us and where it all came from,

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because understanding our own origins means understanding the lives of stars.

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And how their catastrophic deaths bring new life to the universe.

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Because every mountain,

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every rock on this planet, every living thing,

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every piece of you and me was forged in the furnaces of space.

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This is Pashupatinath,

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in the Nepalese capital city of Kathmandu

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and Hindus come here from all over India and Nepal

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to worship the god Shiva. That is Shiva's temple.

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Now, Shiva is the god of destruction.

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In the Hindu faith, everything has to be destroyed,

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so that new things can be created

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and that's why pilgrims come here to the banks of the Bagmati River,

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at the foot of Shiva's temple.

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The belief in this cycle of creation and destruction

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lends Pashupatinath an added significance.

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Many of these pilgrims will have come here at the end of their lives,

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to die here and be cremated.

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Hindus believe in reincarnation,

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an eternal sequence of death and rebirth.

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Cremation helps free the soul, so it's ready for the next life.

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'They also believe that the physical elements of the body are released'

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back to the world, so they can be recycled in the next stage of creation.

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'It's an ancient belief that touches on a deeper truth about how the universe works.'

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Every civilisation,

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every religion across the world, has a creation story.

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It tells of where we came from of how we came to be here and of what will happen when we die.

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Well, I have a different creation story to tell and it's based entirely on physics and cosmology.

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It can tell us what we're made of and where we came from.

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In fact, it can tell us what everything in the world is made of and where it came from.

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It also answers that most basic of human needs, to feel part of

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something much bigger, because to tell this story

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you have to understand the history of the universe.

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And it teaches us that the path to enlightenment

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is not an understanding of our own lives and deaths,

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but the lives and deaths of the stars.

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My creation story is the story of how we were made by the universe.

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It explains how every atom in our bodies was formed, not on Earth,

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but was created in the depths of space,

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through the epic lifecycle of the stars.

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And to understand that story, we will journey to the stars in all their stages of life.

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This is where stars are born, a nebula -

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a stellar nursery, where new stars burst into life.

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Those stars will burn for billions of years,

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until their voracious hunger for fuel

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forces them to blow up, to become giants...

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..hundreds of times the size of our sun.

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And when they die, stars go out with the biggest bang in the universe.

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But to understand how we came from the stars,

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we must begin our journey much closer to home.

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Well, this is sunrise over Nepal

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and those are the tallest mountains in the world, the Himalayas.

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Every one of those peaks is over 6,500 metres.

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What a spectacular sight.

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But it's incredible to think that,

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just a few tens of millions of years ago,

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those mountains were something very different.

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'The Himalayas haven't always been mountains.'

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We can find clues to their true origin

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by looking at them more closely.

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This is Himalayan limestone,

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the rock out of which much of this magnificent mountain range is made.

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If you look closely, you can see a kind of chalky granular structure,

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because limestone is made primarily out of the bodies, the shells,

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of dead sea creatures - coral and polyps - and when they die,

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they are put under immense pressures and squashed

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and eventually form limestone.

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So the Himalayas were once living creatures.

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Much of the rock in the Himalayas was formed at the bottom of an ocean and then, over millions of years,

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it was raised up, to become these vast peaks.

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We've even found fossils at the top of Mount Everest.

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It's a beautiful example of the endless recycling of the earth's resources

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that has been going on since the dawn of time -

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and we are part of that system.

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Every atom in my body was once part of something else,

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so an ancient tree or a dinosaur or a rock, in fact,

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definitely, a rock. And the reason that the rocks of the Earth

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can become living things and then living things will return

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to the rocks of the Earth is because everything

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is made of the same basic ingredients.

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Those ingredients are the chemical elements,

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the building blocks of everything on Earth.

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Elements like hydrogen, helium, lithium,

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beryllium, borum, carbon, nitrogen,

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oxygen, fluorine, neon, sodium, magnesium...

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Everything in the world is made up of the same basic sets

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of chemical elements, just assembled in different ways.

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So these mountains, the Himalayas, are made of limestone - and that's calcium carbonate.

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Now, calcium, carbon and oxygen are three of the elements that are vital for life,

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so calcium in my teeth and bones, oxygen in the air that I breathe

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and carbon in every organic molecule in my body.

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Now, you're probably pretty familiar with those elements in their combined forms,

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but you very rarely see the elements on their own.

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There's a good reason why many of the elements are not found

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in their raw forms in nature. They're extremely reactive.

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This is sodium.

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As you can see, it's a silvery metal and it's also quite reactive.

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In fact, it's so reactive that when you drop it into water...

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..you get a violent,

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almost explosive, reaction,

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which is all the more surprising when you think that,

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when combined with chlorine, this forms sodium chloride...

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EXPLOSION

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..salt, which is vital for life.

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Excellent! Ha-ha!

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And that's why I love chemistry

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almost as much as physics!

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It's this reactivity that enables the elements to combine with one another to make new substances.

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CAMERA MAN: Where's it gone? Where the hell's it gone?!

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BRIAN LAUGHS

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That, in turn, has allowed the Earth to develop its endless variety.

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And that variety includes us.

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So, to explain where we come from,

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we must also explain where the elements come from.

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We now know that the Earth is made of 92 chemical elements

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and that's pretty amazing, if you think of the complexity that we see around us.

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We also know that everything beyond Earth, everything we can see in the universe,

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is made of those same 92 elements.

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And notice that I didn't say, "We think" that that's what they're made of.

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I said, "We know" that's what they're made of, because we can prove it.

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The chemistry set we have on Earth extends far beyond the planet.

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We have set foot on the moon and know that it's rich in helium, silver and water.

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We have sent robot landers to our neighbouring planets and discovered that Mars

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is rich in iron, which has combined with oxygen to form its familiar rusty-red colour.

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And we know that Venus's thick atmosphere is full of sulphur.

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We've sent spacecraft to the edge of the solar system

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to discover that Neptune is rich in organic molecules, like methane.

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But what of the rest of the universe?

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It seems impossible that we could discover what the stars are made of,

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because they're so far away.

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Even the nearest star, Proxima Centauri,

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is ten thousand times more distant than Neptune,

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4.2 light years from Earth.

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And the nearest galaxy, Andromeda,

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is another 2.5m light years away.

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Yet despite these vast distances, these alien worlds are constantly

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sending us signals, telling us exactly what they're made of.

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Our only contact with the distant stars is their light,

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that has journeyed across the universe to reach us,

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and encoded in that light is the key to understanding what the universe is made of.

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And it's all down to a particular property of the chemical elements.

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You see, when you heat the elements, when you burn them, then they give

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off light and each element gives off its own unique set of colours.

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This is strontium and it burns...

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..with a beautiful red colour.

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Sodium is yellow.

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Potassium is lilac.

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And copper is blue.

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Each element has its own characteristic colour.

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It's this property that tells us what the stars are made of.

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But it's a little more complicated than simply looking at the colour of the light that each star emits.

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You can see why, by looking at the light from our nearest star, the sun.

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This is a spectrum of the light taken from our sun

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and, you know, at first glance, it looks very familiar.

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It looks like a stretched-out rainbow,

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because that's exactly what a rainbow is.

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It's the spectrum of the light from the sun in the sky.

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But if you look a bit more closely, then you see that this spectrum is covered in black lines.

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These are called absorption lines.

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Each element within our sun not only emits light of a certain colour,

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it also absorbs light of the same colour.

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By looking for these black lines in the sun's light, we can simply read off a list

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of its constituent elements, like a bar code.

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For example, these two black lines in the yellow bit of the spectrum are sodium.

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You can see iron.

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Right down here you can see hydrogen.

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So, by looking at these lines in precise detail, you can work out exactly what elements are present

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in the sun and it turns out that that's about 70% hydrogen, 28% helium and 2% the rest.

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And you can do this, not only for the sun, but for any of the stars

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you can see in the sky and you can measure exactly what they're made of.

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That star there is Polaris, the Pole Star,

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and you can see that because all the other stars in the night sky appear to rotate around it.

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Now it's 430 light years away.

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But we know just by looking at the light that it has about the same heavy element abundance as our sun,

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but it's got markedly less carbon and a lot more nitrogen.

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And the same applies for other stars.

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Vega, the second brightest star in the northern sky,

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has only about a third of the metal content of our sun.

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Whereas, other stars are metal-heavy.

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Sirius, the dog star, contains three times as much iron as the sun.

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And Proxima Centauri is rich in magnesium.

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But although the quantities of the elements may vary,

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wherever we look across space, we only ever find the same 92 elements that we find on Earth.

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We are made of the same stuff as the stars and the galaxies.

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But where did all this matter come from?

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And how did it become the complex universe we see today?

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In order to understand where we came from, we have to understand events

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that happened in the first few seconds of the life of the universe.

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So when the universe began, it was unimaginably hot and dense.

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We, literally, don't have the scientific language to describe it,

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but it was, in a very real sense, beautiful.

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There was no structure, there was certainly no matter.

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It was exactly the same whichever way you look at it.

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We can get some idea of how the universe developed

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from this state of pure symmetry by looking at the behaviour of water

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in this remarkable landscape.

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These are the El Tatio geysers, high in the Chilean Andes.

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As the boiling water bubbles up through the ground to meet

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the freezing mountain air,

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water can be found in all three of its natural phases -

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vapour, liquid and ice.

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In its hottest state, water is,

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like the early universe, an undifferentiated cloud.

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But as it cools, it suddenly behaves very differently.

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You see, if you look at a cloud of steam, it looks the same from every direction,

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but as it cools down, as it lands on this plate of freezing cold glass,

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then it immediately crystallises out.

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It turns into solid water - ice.

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As the ice crystals form, the symmetry of the water vapour

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disappears from view and complex, beautiful structure emerges.

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In the same way, we think that the universe, as it cooled,

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went through a series of these events, where structure emerged.

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One of the most important was about a billionth of a second after the Big Bang.

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In that moment, an important part of the symmetry of the universe was broken.

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Known as electroweak symmetry breaking, this was the moment when

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subatomic particles acquired mass - substance - for the first time.

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Amongst them, were the quarks.

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As the universe continued to cool, those quarks joined together

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to form larger, more complex structures, called protons and neutrons.

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Way before the universe was a minute old,

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the quarks had been locked away inside the protons and the neutrons

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and they were the building blocks of all atomic nuclei,

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the building blocks of the elements.

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These same protons and neutrons are with us to this day.

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They form the hearts, the nuclei, of all atoms.

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Just a few seconds after the beginning of the universe,

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the fundamental building blocks of everything had been created.

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It sounds ridiculous, the fact that everything you need

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to make up me and everything on planet Earth and,

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in fact, every star and every galaxy in the sky was there,

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after the first minutes in the life of the universe.

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It's almost unbelievable, but we have extremely strong

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experimental evidence to suggest that that is the way that it is.

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But from that point on, it was just, in a sense,

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a process of assembling those bits into more and more complex things.

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That is an incredibly fascinating story in itself.

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To tell that story, we must look deep inside the atom, to the nucleus at its centre.

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Here, we can see how protons and neutrons are assembled,

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to build up the 92 different elements.

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Now, the wonderful thing about the construction of the chemical elements is that it's so simple.

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I suppose you could call it "child's play".

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So imagine these bubbles are my universal chemistry set...

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..and the single bubbles could just be single protons.

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That's the nucleus of the simplest chemical element.

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The element with a single proton in its nucleus is hydrogen

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and, from hydrogen, you can make all the other elements.

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The first stage is to stick two protons together.

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Ha-ha! Look at that!

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That was two bubbles stuck together.

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Now what happens when you stick two protons together is one of the protons turns into a neutron.

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Now, that is called deuterium.

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Deuterium is still a form of hydrogen,

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because it has only one proton in its nucleus, and it's the number of protons that defines the element.

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It's only when two deuterium nuclei are combined that a new element is created.

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Take two deuteriums and fuse them together and you get a nucleus for two protons and two neutrons.

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That's helium, the second simplest element.

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Then, it's just a question of adding more and more protons and neutrons.

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Well, there is an incredibly complicated nucleus.

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That's about 12 things stuck together, so that would be probably

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carbon 12, which is six protons and six neutrons.

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And you can carry on building more and more complex elements...

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..all the way up to the heaviest elements in the universe,

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to uranium and beyond.

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Simple, and beautiful, physics.

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This process of building the elements is called nuclear fusion.

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It allows the simplest of ingredients to create the infinite variety of the universe.

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But although this bubble metaphor makes creating new elements seem simple, it is,

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in reality, incredibly difficult to achieve.

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So difficult that there's only one place in nature that it happens.

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It's in stars like our sun that the elements are assembled.

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They're the only places in the universe hot enough and dense enough to fuse atoms together.

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Even then, only a fraction of the star reaches the extreme temperatures necessary.

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The sun is 6,000 Celsius at its surface, not nearly hot enough to power fusion.

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But deep below, where the temperature reaches 15m degrees,

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the sun fuses hydrogen into helium at a furious rate.

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Every second, it burns 600m tons of hydrogen.

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As it does so, it releases the huge amounts of heat and light that brings our planet to life.

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It is this process of converting one element into another that allows us to exist.

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For all its power, the sun only converts hydrogen,

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the simplest element, into helium, the next simplest.

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But there are over 90 other elements present in our universe, so where did they all come from?

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If the heavier elements are not being made in stars like the sun, then there must be somewhere else

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in the universe where they are assembled.

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It's important to know

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because it's the elements beyond helium that give our world its complexity,

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and when it comes to planet Earth and human beings,

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there's one element that is particularly important - carbon.

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Life is completely dependent on carbon.

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I mean, I'm made of about a billion billion billion carbon atoms, as is

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every human being out there, every living thing on the planet.

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Imagine how many carbon atoms that is.

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So where does all that carbon come from?

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Well, it comes from the only place in the universe where elements are made - stars.

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But in order for us to live, a star must die.

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Stars in the prime of their lives, like our sun, are only hot enough to make helium.

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Forming the heavier elements requires much higher temperatures.

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Temperatures that can only be reached at the end of a star's life.

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Looking out into space,

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you might think that the cosmos is a constant, unchanging place.

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That the stars will always be there.

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But in fact, the stars are only a temporary feature in the sky,

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and though they may burn brightly

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for many millions or billions of years,

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they can only live for as long as they have a supply of hydrogen to burn.

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When a star runs out of hydrogen, it begins to die,

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but it doesn't go quietly.

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Rather than cooling,

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the star becomes much hotter, until there's a sudden flash.

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Then the star starts to expand.

0:31:040:31:07

Over tens of thousands of years,

0:31:100:31:12

it balloons to many hundreds of times its previous size.

0:31:120:31:17

But in this bloated state,

0:31:180:31:20

the star is unable to maintain its surface temperature.

0:31:200:31:24

As it cools, it takes on the characteristic colour of a dying star.

0:31:260:31:33

It has become a red giant.

0:31:330:31:36

These are pictures of a red giant star in our galaxy, a star called Betelgeuse.

0:31:430:31:48

Now, it's one of our nearest neighbours in cosmic terms.

0:31:480:31:51

It's only about 600 light years away, but it's the size that's astonishing.

0:31:510:31:57

If you were to put the sun there, then Venus would be about there

0:31:570:32:02

and the Earth about there, and Mars here, and in fact you could

0:32:020:32:06

fit everything in the solar system all the way out to Jupiter

0:32:060:32:10

inside the star.

0:32:100:32:12

Now, because it's so big, even though it is 600 light years away,

0:32:120:32:17

you can see detail on its surface,

0:32:170:32:20

so these, these are sunspots on the surface of Betelgeuse.

0:32:200:32:24

But it's not what's going on on the surface that's really interesting.

0:32:240:32:29

To understand where carbon comes from in the universe, we have to

0:32:290:32:33

understand what's going on deep in the heart of the star.

0:32:330:32:37

Imagine this old prison in Rio is a dying star like Betelgeuse.

0:33:010:33:06

Out there is the bright surface, shining off into space.

0:33:060:33:12

As I descend deeper and deeper into the prison,

0:33:120:33:16

the conditions would become hotter and hotter and denser and denser,

0:33:160:33:21

until down there in the heart in the star is the core,

0:33:210:33:27

and it's in there that all the ingredients of life are made.

0:33:270:33:33

Deep in its core, the star is fighting a futile battle against its own gravity.

0:33:350:33:41

As it desperately tries to stop itself collapsing under its own

0:33:430:33:47

weight, new elements are made in a sequence of separate stages.

0:33:470:33:51

Stage one is while there is still a supply of hydrogen to burn.

0:33:560:34:02

Whilst the star is burning hydrogen to helium in the core, vast amounts

0:34:080:34:13

of energy are released and that energy escapes, literally creating

0:34:130:34:18

an outward pressure which bounces the force of gravity and,

0:34:180:34:23

well, it holds the star up and keeps it stable.

0:34:230:34:26

But eventually, the hydrogen in the core will run out

0:34:260:34:30

and at that point the fusion reactions will stop,

0:34:300:34:34

no more energy will be released

0:34:340:34:36

and that outward pressure will disappear.

0:34:360:34:39

Now, at that point, the core will start to collapse very rapidly,

0:34:390:34:44

leaving a shell...

0:34:440:34:46

..of hydrogen and helium behind.

0:34:490:34:53

Beneath this shell, as the core collapses,

0:34:560:35:00

the temperature rises again

0:35:000:35:03

until, at 100 million degrees,

0:35:030:35:06

stage two starts and helium nuclei begin to fuse together.

0:35:060:35:12

A helium fusion does two things.

0:35:200:35:23

Firstly, more energy is released and so the collapse is halted.

0:35:230:35:28

But secondly, two more elements are produced in that process...

0:35:280:35:33

..carbon.

0:35:350:35:37

Oxygen. Two elements vital for life.

0:35:400:35:44

So this is where all the carbon in the universe comes from.

0:35:440:35:49

Every atom of carbon in my hand,

0:35:490:35:52

every atom of carbon in every living thing on the planet

0:35:520:35:56

was produced in the heart of a dying star.

0:35:560:36:02

But compared to the lifetime of the star, the creation process of carbon and oxygen is over

0:36:030:36:10

in a blink of an eye, because, in only about a million years,

0:36:100:36:14

the supply of helium in the core is used up

0:36:140:36:18

and for stars as massive as the sun,

0:36:180:36:20

that's where fusion stops, because there isn't enough

0:36:200:36:24

gravitational energy to compress the core any further and restart fusion.

0:36:240:36:29

But for massive stars like Betelgeuse,

0:36:290:36:33

the fusion process can continue.

0:36:330:36:37

When the helium runs out,

0:36:410:36:43

gravity takes over again and the collapse continues.

0:36:430:36:48

The temperature rises once more, launching stage three,

0:36:500:36:54

in which carbon fuses into magnesium, neon,

0:36:540:36:59

sodium, and aluminium.

0:36:590:37:01

And so it goes on.

0:37:010:37:03

Core collapse, followed by the next stage of fusion

0:37:030:37:07

to create more elements, each stage hotter and shorter than the last.

0:37:070:37:14

And, eventually, in a final stage that lasts only a couple of days,

0:37:160:37:21

the heart of the star is transformed into almost pure...

0:37:210:37:27

iron, whose chemical symbol is Fe,

0:37:270:37:32

and this is where the fusion process stops.

0:37:320:37:36

In its millions of years of life,

0:37:360:37:39

the star has made all the common elements,

0:37:390:37:44

the stuff that makes up 99% of the Earth.

0:37:440:37:49

The core is now a solid ball of those elements stacked on top of each other in layers.

0:37:490:37:57

On the outside, there's a shell of hydrogen.

0:37:570:38:01

Beneath it, a layer of helium.

0:38:010:38:04

Then carbon and oxygen, and all the other elements, all the way

0:38:040:38:09

down to the very heart of the star.

0:38:090:38:12

And once that has fused into solid iron, the star has only seconds left to live.

0:38:120:38:19

When a star runs out of fuel, then it can no longer release

0:38:200:38:24

energy through fusion reactions,

0:38:240:38:27

and then there's only one thing that can happen.

0:38:270:38:30

In about the same amount of time it takes this prison block to crumble,

0:38:460:38:51

the entire star falls in on itself.

0:38:510:38:53

This is the destiny that awaits most of the stars in the universe.

0:39:010:39:06

Yet even the implosion of the star only forges the first 26 elements.

0:39:100:39:16

What of the remaining elements,

0:39:180:39:20

some of which are vital for life and many of which we hold most precious?

0:39:200:39:25

These are the remote forests of northern California.

0:39:440:39:47

100 years ago, this whole area was teeming with people, all in search of one element.

0:39:490:39:56

And the reason they were here can still be found in the original Sixteen To One Mine.

0:40:030:40:08

This once stood at the centre of the California gold rush

0:40:120:40:17

and, thanks to a quirk of geology, it continues to yield its precious bounty over 100 years later.

0:40:170:40:25

You know, the unique thing about this place is that it sits right on the divide

0:40:250:40:30

between the North American plate and the Pacific plate.

0:40:300:40:35

You see a divide there between the rock and quartz,

0:40:350:40:39

then right up there you can see the top of it.

0:40:390:40:43

Now, in between the faults, this rock, the quartz, formed.

0:40:430:40:47

Then, 140 million years ago, in the Jurassic period, when the dinosaurs

0:40:470:40:52

were running around above our heads,

0:40:520:40:55

hot water welled up and flowed, and that water deposited the gold

0:40:550:41:01

through the seams of quartz, and so all the miners have to do...

0:41:010:41:07

and ALL they have to do...

0:41:070:41:08

is follow the seams of quartz, and over hundreds of years they've

0:41:080:41:12

found vast amounts of gold deposited there.

0:41:120:41:16

This is what all the fuss is about.

0:41:310:41:33

This is the gold as it comes out of the ground,

0:41:330:41:37

and it's unusually pure as gold goes.

0:41:370:41:40

This is about 85% pure gold, but it could also be found like this,

0:41:400:41:46

and this is a gold nugget that was found in a river,

0:41:460:41:49

on a river bed, and it's a heavy piece of gold.

0:41:490:41:53

It's between about one and one and a half ounces,

0:41:530:41:56

which means that at today's prices it's worth about 2,000,

0:41:560:42:00

and it's that inherent value that makes mines like this worth operating.

0:42:000:42:07

But there's something a bit odd about the value we attach to gold.

0:42:080:42:13

Throughout history, people have gone to extraordinary lengths to get their hands

0:42:130:42:18

on this most precious substance, which is strange,

0:42:180:42:22

because it isn't particularly useful for anything.

0:42:220:42:26

Most of the gold that's been extracted throughout human history

0:42:260:42:29

has ended up as jewellery, but it has got one thing going for it

0:42:290:42:34

and that's that it is incredibly rare.

0:42:340:42:38

All the gold mined from the earth in all of human history

0:42:380:42:42

would only just fill three Olympic-size swimming pools.

0:42:420:42:46

And it's that scarcity that makes gold valuable,

0:42:480:42:53

but gold is just one of many rare elements.

0:42:530:42:56

There are over 60 elements heavier than iron in the universe

0:42:590:43:02

and some are valuable, like gold, silver, platinum.

0:43:020:43:07

Some are vital for life, like copper and zinc,

0:43:070:43:11

and some are just useful, like uranium, tin and lead.

0:43:110:43:16

But across the universe,

0:43:160:43:18

there are vanishingly small amounts of those heavy elements.

0:43:180:43:22

The reason for that scarcity

0:43:230:43:25

is that creating substantial amounts of the heaviest elements requires

0:43:250:43:30

some of the rarest conditions in the universe,

0:43:300:43:33

and we need to look far into space to find them.

0:43:330:43:37

In a galaxy of 100 billion stars, these conditions will exist

0:43:390:43:44

on average for less than a minute in every century.

0:43:440:43:48

That's because they're only created in the final death throes

0:43:540:43:59

of the very largest stars...

0:43:590:44:01

..stars of at least nine times the mass of our sun.

0:44:040:44:07

Only they can reach the extreme temperatures needed

0:44:090:44:12

to create large amounts of the heavy elements.

0:44:120:44:16

Deep in the heart of the star,

0:44:210:44:24

the core finally succumbs to gravity.

0:44:240:44:27

It falls in on itself with enormous speed...

0:44:330:44:37

..and rebounds with colossal force.

0:44:440:44:48

As the blast wave collides with the outer layers of the star,

0:44:550:44:59

it generates the highest temperatures in the universe, 100 billion degrees.

0:44:590:45:06

These conditions last for just 15 seconds, but it's enough

0:45:070:45:12

to form the heaviest elements like gold.

0:45:120:45:15

It's called a supernova...

0:45:210:45:23

..the most powerful explosion in the universe.

0:45:250:45:29

It's quite a thought that something as precious to us as the gold in a wedding ring was

0:45:360:45:43

actually forged in the death of a distant star,

0:45:430:45:46

millions of light years away, billions of years ago.

0:45:460:45:51

Despite the rarity of supernovae,

0:45:540:45:57

when they do happen, they're the most dramatic events in the sky.

0:45:570:46:03

This is a picture of the Tarantula Nebula, which is a cloud of gas and dust in

0:46:030:46:08

the Large Magellanic Cloud, which is a satellite galaxy of the Milky Way,

0:46:080:46:13

and this is what it looks like on any clear starry night of the year.

0:46:130:46:19

But on one night in 1987, the Tarantula Nebula looked like that.

0:46:190:46:25

You can see that a new bright star has appeared in the sky.

0:46:250:46:29

This is a supernova explosion, the explosive death of a massive star,

0:46:290:46:35

and they're incredibly violent cosmic events, as this picture beautifully shows.

0:46:350:46:41

This is a galaxy about 55 million light years away from Earth,

0:46:410:46:47

but this is a supernova explosion in that galaxy.

0:46:470:46:51

You can see that it's shining as brightly as the galactic core.

0:46:510:46:55

There may be a billion suns in that core,

0:46:550:46:59

and one supernova can shine as brightly as that.

0:46:590:47:03

Yet to really appreciate the scale of these explosions, we would need

0:47:050:47:10

to see one up close, to see a star die in our own galaxy,

0:47:100:47:15

the Milky Way.

0:47:150:47:18

Although on average there's one big supernova

0:47:180:47:20

in each galaxy every century,

0:47:200:47:23

there hasn't been one in the Milky Way since the birth of modern science.

0:47:230:47:28

The last was in 1604, so we're long overdue.

0:47:280:47:32

Astronomers are now searching the skies for the star that is most likely to go supernova.

0:47:320:47:39

And amongst the leading candidates there's a familiar name.

0:47:390:47:43

This is the constellation of Orion and this is Betelgeuse,

0:47:430:47:49

and we know it's extremely unstable

0:47:490:47:53

because it's dimmed by about 15% in the last ten years.

0:47:530:47:59

Now, astronomers think that this star could go supernova at any moment.

0:47:590:48:04

That could mean any time in the next million years but equally it could explode tomorrow,

0:48:070:48:15

and Betelgeuse is only 600 light years away.

0:48:150:48:19

Now, when it goes, Betelgeuse will be incredibly bright.

0:48:210:48:26

It'll be by far the brightest star in the sky.

0:48:260:48:31

It may shine as brightly as a full moon.

0:48:310:48:34

It will be almost a second sun in the daylight.

0:48:340:48:39

In this single instant, Betelgeuse will release more energy

0:48:590:49:04

than our sun will produce in its entire lifetime.

0:49:040:49:08

As the star is torn apart, it will fire out into space

0:49:130:49:18

all the elements that it created in its life and death.

0:49:180:49:22

Those elements will spread out to become a nebula,

0:49:240:49:28

a rich chemical cloud drifting through space.

0:49:280:49:32

And at the heart of the nebula will be a tiny beacon of light,

0:49:320:49:38

the remnant of a star once more than a billion and a half kilometres

0:49:380:49:42

across that has been crushed out of all recognition by gravity.

0:49:420:49:48

This is Betelgeuse, the neutron star.

0:49:510:49:56

And it's how this once mighty star will end its life.

0:50:000:50:04

Now, once Betelgeuse has gone,

0:50:180:50:20

the constellation of Orion will look very different.

0:50:200:50:23

I mean there will just be a hole in the sky

0:50:230:50:27

where that brilliant bright red star once shone.

0:50:270:50:31

But it's in the deaths of old stars that new stars are born

0:50:310:50:35

and it's very much like the cycle of death and rebirth

0:50:350:50:40

here on earth but played out on a cosmic scale, and you can see that

0:50:400:50:44

happening today in the constellation of Orion

0:50:440:50:48

because in the sword handle you can see this - the Orion nebula.

0:50:480:50:54

Now, it's nothing more than a misty patch of light in the night sky

0:50:540:50:57

to the naked eye but if you look more closely,

0:50:570:51:01

you see that there is a lot more going on.

0:51:010:51:04

The Orion nebula is one of the wonders of the universe.

0:51:100:51:14

Hidden in its clouds are bright points of light.

0:51:200:51:23

These are new stars, forming from the elements blown out by supernova explosions,

0:51:260:51:33

new stars being born from the remains of dead ones.

0:51:370:51:42

And it's from this universal process of death and rebirth that we emerged

0:51:440:51:52

because it was in a nebula just like this, five billion years ago,

0:51:520:51:58

that our sun was formed.

0:51:580:52:00

Around it, a network of planets formed.

0:52:090:52:13

Among them was the Earth.

0:52:140:52:18

Everything we find on the Earth today also originated in that nebula.

0:52:180:52:24

But that is not the end of this story of how the universe created us.

0:52:270:52:32

Because when we look deep into the nebula,

0:52:360:52:38

we don't just see individual elements.

0:52:380:52:41

We see greater complexity, the seeds of our own existence.

0:52:410:52:46

Well, this is a spectrum of the light from the Orion nebula taken

0:52:460:52:51

by the Herschel space telescope, so it really is a picture of light from interstellar space.

0:52:510:52:58

You know, I wouldn't normally show you a graph like this but this is fascinating because what it shows

0:52:580:53:04

is that that gas cloud, the Orion nebula, is not just a cloud of elements.

0:53:040:53:10

There's complex chemistry here happening in deep space because each peak on this graph

0:53:100:53:16

corresponds to a different molecule and there are some molecules present that I suppose are quite obvious.

0:53:160:53:22

There's water and there's sulphur dioxide. But there are also complex carbon compounds in here. So there's

0:53:220:53:29

methanol, there's hydrogen cyanide, there's formaldehyde, there's dimethyl ether.

0:53:290:53:34

So what we're seeing here is complex carbon chemistry happening in deep space.

0:53:340:53:40

That carbon chemistry is the beginning of the chemistry of life,

0:53:450:53:51

and there is surprising evidence that this chemistry

0:53:510:53:54

may have had a direct impact on the evolution of life on Earth.

0:53:540:53:59

That evidence comes from meteorites,

0:54:050:54:08

debris left over from the formation of the

0:54:110:54:14

solar system that occasionally collides with the earth.

0:54:140:54:18

One of the most productive places for finding meteorites

0:54:270:54:31

is the Atacama desert in the High Andes of South America.

0:54:310:54:35

This is a meteorite, a piece of rock that fell to earth from somewhere

0:54:440:54:49

out there in the solar system, and it is certainly older than any rock you can see here.

0:54:490:54:57

It's probably older than any rock you can find anywhere on Earth

0:54:570:55:02

because it formed from the primordial gas cloud, that nebula that collapsed

0:55:020:55:07

to form the sun and the planets over four and a half billion years ago.

0:55:070:55:11

So it's incredibly ancient.

0:55:110:55:14

Now this is a slice, a crosssection through a meteorite.

0:55:140:55:19

You see those little brown areas in there?

0:55:190:55:22

Well, in those brown areas we found amino acids, the building blocks of proteins,

0:55:220:55:30

which are the building blocks of me, the building blocks of life. Incredibly complex carbon compounds.

0:55:300:55:37

So this says that the complex carbon chemistry you need to send you on the path to life

0:55:370:55:45

was happening out there in space four and a half billion years ago.

0:55:450:55:50

So the first amino acids on earth, the fundamental building blocks of life, may have formed in the depths

0:55:570:56:05

of space and been delivered to the earth on meteorites.

0:56:050:56:10

When we look out into space, we are looking into our own origins.

0:56:180:56:23

Because we are truly children of the stars.

0:56:280:56:33

And written into every atom and every molecule of our bodies

0:56:330:56:37

is the entire history of the universe from the Big Bang to the present day.

0:56:370:56:43

Our story is the story of the universe

0:56:480:56:51

and every piece of everyone, of everything you love,

0:56:510:56:55

of everything you hate, of the thing you hold most precious,

0:56:550:57:00

was assembled by the forces of nature

0:57:000:57:03

in the first few minutes of the life of the universe,

0:57:030:57:06

transformed in the hearts of stars or created in their fiery deaths.

0:57:060:57:13

And when you die, those pieces will be returned to the universe

0:57:130:57:19

in the endless cycle of death and rebirth.

0:57:190:57:23

What a wonderful thing it is to be a part of that universe!

0:57:230:57:28

And what a story.

0:57:280:57:29

What a majestic story.

0:57:290:57:32

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0:58:000:58:04

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0:58:040:58:08

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