Brian Cox: Life Of A Universe

Did our universe have a beginning?

Why is there a universe like this one?

If time began at the big bang, then was there a time before time?

Why are there rivers and flows and filaments of galaxies?

Is there an end of the universe? Is our universe eternal?

I'm on tour in Australia,

talking to audiences and scientists about two fundamental questions -

how did the universe begin...

Like in the big bang, it feels audacious.

...and how will it end?

Life on earth will become very problematic.

In the last decade,

we've been able to probe these ideas in unprecedented detail.

So, this IS the oldest light in the universe.

This is the story of our scientific quest

to understand the origin of the universe.

Of all the questions in science,

the question of the origin of the universe

is one that I think needs no motivation.

Every human culture has its own creation story,

and science is no different.

For the best part of 100 years, we've had the theory

that the universe began in the big bang.

But in the last decade or so,

new precision measurements of the cosmos,

coupled with theoretical developments,

have given us an unprecedented and detailed picture

of the origin of the universe.

If this were a lesser program,

we would start it in a deep voice going,

"There was a time... with no time."

"There was a place... not in space."

"THAT is the time before time"

"and place without space"

"that we call the big bang."

That's not what we're doing, though.

I think if you ask the question,

"WHY do you want to know the origins of the universe?"

I suppose the answer has to be curiosity.

It's surely something that must occur to everybody at some point -

why do we exist?

When I think of a scientist,

I think of an adult who still has the soul of curiosity of a child.

So I think it's very natural to ask, how did it all get here?

Indigenous Australians have been observing the stars

for more than 40,000 years,

and, like many ancient cultures,

have a number of creation stories based on the night sky.

It's the story of 'arang' - the emu.

The emu sacrificed his wings

and was given an eternal place in the southern skies.

Forever you will be seen running across the night sky

and marked as 'dyurra' - the stars.

I've always liked creation stories.

I like reading about them from across the world.

Why do we do it?

Why do we build telescopes to look back to the edge of time?

Why do we measure the expansion rate of the universe

and build theories to explain it?

But the answer is because that's what we've always done.

And the evidence for that is

that every culture you study across the world has a creation story.

And the most wonderful thing

about living in the 21st century, with modern science,

is that we also have a creation story.

You've probably heard it described as 'the big bang'.

But what is the big bang?

And what do we know about the origin of the universe?

With observations and mathematical theorising,

we have a good sense that about 13.8 billion years ago,

the universe was incredibly dense and it was incredibly hot.

Hot! Give me some heat! Give me some density!

Give me some violations of the laws of particle physics.

It underwent a rapid swelling that's called the big bang.

So, what's the big bang?

And the answer is I don't know what the big bang is.

I just know what came after the big bang,

where we have a universe that's expanding very quickly,

it's really hot.

These things, we do know.

It's the things that come after that we understand.

You can trace everything back and you get to a point

where the universe had to have been hot and small and dense

and something happened that made that expand, right?

And so that's this idea that became known as 'the hot big bang'.

I'm liking the big bang.

That just feels right. It feels audacious.

It's common to think of the big bang as the start of time itself.

The moment when everything came from nothing.

But there are cosmologists who think there may be more to it -

that the thing we used to call 'the big bang'

was an event in a pre-existing universe

and not the beginning at all.

But how can we be so confident?

How can we even dare to speak of things

that happened almost 14 billion years ago?

In 1927, the astronomer Edwin Hubble noticed

that the light from distant galaxies is stretched.

That means that space is expanding - our universe is expanding.

So, you run time backwards in your mind's eye,

that means that in the past,

the distances between the galaxies was smaller,

and you can imagine a time when the distances were so small

that everything is effectively on top of each other.

That implies that our universe had a beginning,

there was a day without a yesterday,

and that is what we call the big bang.

More than 30 years after Hubble made his observations,

cosmologists remained divided

about whether the big bang theory was correct.

More evidence was needed.

And it came in the 1960s,

with the discovery of a mysterious faint signal.

We call it the cosmic microwave background radiation.

It's seen as a faint glow, coming literally from everywhere in the sky,

but not being emitted from any particular star, galaxy or object.

So, this is the oldest light in the universe.

There are photons that have travelled 13.8 billion years from over there

and 13.8 billion years from over there,

and they're carrying information about the beginning of time.

One of the many remarkable things about the cosmic microwave background

is the story of its discovery,

because it was found entirely by accident.

We had this result. We couldn't find any explanation for it.

We couldn't make it go away. What were we going to do with this thing?

So, where did the cosmic microwave background come from?

And why do we consider it such strong evidence for the big bang theory?

So, the picture is this - the universe is expanding and cooling.

In the first few minutes, it's extremely hot,

and then the universe is filled by what's called a plasma -

so, it's too hot for atoms to form.

380,000 years after the big bang, it's cool enough for atoms to form,

the universe becomes almost instantly transparent,

so light can travel in straight lines,

and it will continue to travel in straight lines

for the rest of the expansion history of the universe

and it can enter our telescopes here on Earth 13.8 billion years later.

The cosmic microwave background is considered such strong evidence

in large part because

the big bang theory predicted that it should exist.

It was first observed in the mid-1960s,

and it's only then, really, just before I was born,

that the idea that the universe began at a hot, dense origin

really took hold.

It's an almost overwhelming piece of evidence,

because you're seeing the afterglow of that earliest of times.

We can take pictures of that light in great detail now.

We don't see it as a hum.

We can photograph, essentially, the universe as it was,

the whole sky looking out into the universe,

and see it as it was when that first light was released.

This remarkable baby photograph of the universe

confirmed that we had the basics right.

But its great detail presented fresh challenges.

As we often find with science,

when you answer one set of questions, new ones arise.

This idea that the universe had a beginning in the big bang

is in some ways unsatisfactory.

It raises a series of childlike questions.

Like, if the universe had a beginning,

then what happened before the beginning?

What caused it?

If time emerged at the big bang, then was there a time before time?

How can the universe appear spontaneously out of nothing at all?

Was there a before?

Well, that is a philosophical question,

unless you can come up with a theory

that predicts something that you can test against observation.

The clues which point the way to a theory

of what came before the big bang

can be found in problems with the big bang theory itself.

There are two problems with the standard big bang model.

They're called the horizon problem and the flatness problem.

You can picture the horizon problem as follows.

If you look at the universe as far as the eye can see in that direction,

which is to say the cosmic microwave background,

then it's the same temperature to one part in 100,000

as the universe as far as the eye can see in that direction,

which is the cosmic microwave background.

But those two points on the sky are separated today

by 90 billion light-years.

That means if you've got a universe that's been expanding sedately

and is only 13.8 billion years old,

those two points could never have been in contact with each other.

Which means there's no explanation

for how they could be so precisely the same.

And then there's the flatness problem.

When you look at our universe, it appears to be completely flat.

Which seems very strange,

because it could have been curved like the surface of a sphere

or curved like the surface of a saddle.

A solution can be found in a theory known as inflation,

which suggests that there was a time in the history of the universe

when the universe wasn't just expanding sedately as it is today -

it was expanding incredibly fast.

By "fast", I mean that it was doubling in size

every 10 to the -37 seconds.

That's one ten-million-million- million-million-million-millionths

of a second.

Why does that solve the horizon and flatness problems?