Wonders of the Universe

Why are we here?

Where do we come from?

These are the most enduring of questions.

And it's an essential part of human nature

to want to find the answers.

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

to the dawn of humankind.

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

Our story starts with the beginning of the universe.

It began 13.7 billion years ago.

And today it's filled with over a hundred billion galaxies,

each containing hundreds of billions of stars.

In this series, I want to tell that story.

Because ultimately, we are part of the universe.

So its story is our story.

It's a story that you couldn't tell without something so fundamental

that's it's impossible to imagine the universe without it.

It's woven into the very fabric of the cosmos. Time.

The relentless flow of time has driven the evolution of the universe

and created many extraordinary wonders.

These wonders take us from the very first moments

in the life of the universe to its eventual end.

This is Chankillo on the northwestern coast of Peru.

And it's one of South America's lesser known archaeological sites,

but for me, it is surely one of the most fascinating.

Around two and a half thousand years ago,

a civilisation we know almost nothing about

built this fortified temple in the desert.

Its walls were once brilliant white and covered with painted figures.

Today, all but the smallest fragments of the decorations are gone.

The details of this culture and all traces of its language are lost.

And yet, if you stand in the right place,

you can still experience the true purpose of Chankillo

in just the same way as you could the day it was built.

But to do that, you have to be here before the sun rises.

These towers form an ancient solar calendar.

Now, at different times of year, the sunrise point

is at a different place on the horizon.

Actually, December 21st,

which here in the Southern Hemisphere is the summer solstice, the longest day,

and the sun rises just to the right of the rightmost tower.

Then as the year passes, the sun moves through the towers,

until, on June 21st, which is the winter solstice,

the shortest day, it rises just to the left

of the leftmost tower.

Actually, just in between that mountain you can see in the distance

and the leftmost tower.

So at any time of year, if you watch the sun rise,

you can measure its position and you can tell,

within an accuracy of two or three days, the date.

Today's date is September the 15th,

and so that means that the sun will rise between the fifth and the sixth towers.

Chankillo still works as a calendar,

because the sun still rises in the same place today

as it did when these stones were first laid down.

Now, that is a magnificent sight, as the sun burns through the towers.

You can almost feel the presence of the past here.

I mean, imagine what it must have been like.

Thousands of citizens stood here to greet the sun,

which was almost certainly a deity, almost certainly their god.

What a magnificent achievement.

I mean, it's probably one of our earliest attempts

to begin to measure the heavens.

Over the millennia,

that desire to measure what's going on in the sky

has led to modern astronomy

and the foundations of our modern civilisation.

I might build one in my garden.

I want one.

The 13 towers that line this ridge stand testament

to our enduring fascination with the clockwork of the heavens

and to the direct connection between our lives and the cosmos.

The rising and setting of the sun provides an epic heartbeat

that allows us to mark the passage of time.

A day on Earth is the 24 hours it takes our planet

to rotate once on its axis.

Our months are based on the 29 and a half days

it takes the moon to wax and wane in the night sky.

And a year is the 365 and a quarter days

it takes us to orbit once around the sun.

These familiar time scales mark the passing of our lives,

but the life of the universe plays out on a much grander scale.

When you look up into the night sky, you don't just see stars,

those tiny points of light are a million different clocks,

whose life spans mark out the passage of time

over billions or even trillions of years.

This film is about the greatest expanses of time.

The deep time that shapes the universe.

From its fiery beginnings

through countless generations of stars, planets and galaxies

to its eventual demise,

the fate of the universe is determined by the passage of time.

Time scales in the cosmos seem so unimaginably vast

it's almost impossible to relate to them.

Yet there are places on Earth where we can begin to encounter time

on these universal scales.

This is Ostional on the northern Pacific coast of Costa Rica,

and I've come here to witness a natural event

that's been happening long before there were any humans here to see it.

And I suppose it really is a window

into the distant past of life on our planet.

Once the sun has dipped below the horizon

and the moon conspired to make the tides just right,

this beach is visited by prehistoric creatures.

Under the cover of darkness, they emerge from the ocean.

Playa Ostional is one of the few beaches in the world

where large numbers of sea turtles make their nests.

But what makes this truly remarkable

is the sheer length of time scenes like this have been playing out.

This is part of one of the oldest life cycles on Earth.

On nights like these for the last hundred million years,

turtles like this have been hauling themselves out of the ocean

to lay their eggs.

It's an almost incomprehensible time span.

I mean, a hundred million years ago there were dinosaurs roaming the Earth

but the Earth itself looked very different.

I mean, South America was not connected to North America.

North America was somewhere over close to Europe.

Australia was connected to Antarctica.

It really is quite wonderful to be so close

to such an ancient cycle of life.

I can hear her breathing, actually.

It's a remarkable experience.

I mean, it really is beautiful to see that

on one night of many hundreds of millions of nights

stretching back into the past.

And she's gone.

To witness a moment like this

is to open up a connection to the deep past,

to experience time spans far longer than the history of our own species.

Yet even the hundred million years story of the turtles

only begins to connect us with the vast sweep of cosmic time.

Our entire solar system is travelling on an unimaginably vast orbit,

spinning around the centre of our galaxy.

It takes 250 million years

to make just one circuit of the Milky Way.

In the entire history of the human race,

we've travelled less than a tenth of one percent of that orbit.

These cycles seem eternal and unchanging,

but as the story of time unfolds,

a fundamental truth is revealed.

Nothing lasts forever.

This is the most profound property of time.

And it plays out just as vividly here on Earth

as it does in the depths of space.

This is the Perito Moreno Glacier in Patagonia in Southern Argentina,

and it's one of the hundreds of glaciers

that sweep down the continent from the southern Patagonian ice fields.

And you know, if you carry on that way,

so south, about... I don't know about 1000 kilometres

you get to the end of South America

and from then on there's nothing till the Antarctic.

And it feels like that today.

The glacier is such a massive expanse of ice,

but at first sight, just like the cycles of the heavens,

it appears fixed and unchanging.

Yet seen close-up, it's continually on the move,

as it has been for tens of thousands of years.

The whole face of the glacier is moving into the lake,

about something like that much every day.

And that means that well over a quarter of a billion tons of ice

drop off the face of the glacier into the lake every year.

It's about a million tons a day.

And you can hear it happening.

Just every now and again, you hear this tremendous cracking sound.

It really is like the place is alive.

You know, it's quite disturbing

when these enormous chunks of ice fall into the lake.

Although this thing seems stable and the movement seems glacially slow,

actually, there can be really violent collapses.

It's an incredibly dynamic place to be.

This movement of the glacier provides an insight into the nature of time.

It is simply the ordering of events into sequences, one step after another.

As time passes, snow falls, ice forms,

the glacier gradually inches down the valley

and huge chunks of ice fall into the lake below.

But even this simple sequence contains a profound idea.

Events always happen in the same order.

They're never jumbled up and they never go backwards.

Now, that is something that you would never see in reverse.

But interestingly, there's nothing about the laws of physics

that describe how all those water molecules are moving around

that prevent them from all getting together on the surface of the lake,

jumping out of the water, sticking together into a block of ice

and then gluing themselves back onto the surface of the glacier again.

But interestingly, we do understand

why the world doesn't run in reverse.

There is a reason, we have a scientific explanation,

and it's called the arrow of time.

We never see waves travelling across lakes,

coming together and bouncing chunks of ice back onto glaciers.

We are compelled to travel into the future.

And that's because the arrow of time dictates

that as each moment passes, things change.

And once these changes have happened, they are never undone.

Permanent change is a fundamental part of what it means to be human.

You know, we all age as the years pass by.

People are born, they live and they die.

I suppose it's part of the joy and tragedy of our lives.

But out there in the universe, those grand and epic cycles