All language subtitles for How the Universe Works s02e08 Birth of the Earth.eng

Our world formed

through a series
of devastating cataclysms...

It could have literally
blown the Earth to bits,

and then we wouldn't even have
a planet today.

...An apocalyptic
planetary collision,

millions
of brutal cosmic strikes,

and the most powerful blast
in the Universe,

a supernova.

Our atoms would have been
scattered into outer space.

Yet, these catastrophes created
the planet we know today.

The Earth is
an incredibly special place.

It seems like everything has
worked out just perfectly.

Could other planets have formed
the same way?

If so, the Universe could be
full of earths...

and full of life.

== sync, corrected by elderman ==

Our planet is extraordinary.

It provides
everything life needs --

trillions of creatures, plants,

and us.

Well, you look down
at the Earth from space

and everything
that we know of that's life

is down there on that planet,
that beautiful planet

that you now are going around
every hour and a half,

and that's
almost overwhelming --

just the beauty of the Earth.

It's unique in our solar system,

but is it unique
in the Universe?

It's important
for us to understand

the conditions that led
to the formation of the Earth

because then we can
look for those conditions

around other stars.

And if we find
those conditions there,

then that would suggest

that other earths could be
forming

elsewhere in the Universe.

Could there be other planets
like ours among the stars?

To find out,
we must travel back in time...

...and discover
how the Earth was made.

Rewind the clock
4 1/2 billion years,

and this is what you see.

This speck of dust will
become the Earth

by combining
with countless others.

They're all part
of a giant cloud

called a stellar nursery.

The first step
of planetary formation

is about to start...

...an event that will
transform the cloud

into thousands
of infant solar systems,

including our own.

The same process
is happening today,

7,000 light-years away,
in the Eagle Nebula.

Our own solar system formed

inside clouds of gas and dust
like these.

There are
these three trunks of gas,

and they're nicknamed
the "pillars of creation,"

and they're
trillions of miles long.

These are huge structures.

The clouds look dense,

but they're
actually very sparse.

These gas clouds are
incredibly tenuous.

You'd have to compress,

basically, a mountain's volume
worth of this stuff,

squeeze it down just to make
a little, tiny rock like this.

To compress the gas and dust
into dense stars and planets

takes
a supremely powerful event --

one that can only follow
the death of a giant star.

In 2007,
the Spitzer Space Telescope

captured this image --

a ball of hot gas
behind the Eagle Nebula...

...evidence
that a huge star has exploded

and sent a vast wall of gas
racing toward the pillars.

There's a wave of hot material

approaching
the pillars of creation,

and this may be a shock wave
from a supernova,

a dying star.

Supernovas briefly
outshine entire galaxies.

Superheated plasma blasts
into space

at 70 million miles per hour.

A mighty shock wave speeds
toward the pillars of creation.

When it hits,
it will demolish them.

It will also create new worlds.

Supernova shock waves smash
into the pillars,

compressing
the thin gas and dust

into dense clumps.

Each is a new star,
a new solar system.

Molecular cloud minding
its own business

gets blasted
by a supernova explosion,

crushing the cloud
down into stars and planets.

Wind back 4 1/2 billion years,

and our solar system starts
the same way.

A supernova crushes
a massive dusty cloud

into a protoplanetary disk.

A thin nebulous cloud becomes

a dense whirlpool
of gas and dust --

a solar system in the making.

One star is destroyed.

A new star is born --

our sun and its planets.

This is the first link

in the long and unlikely
chain of events

that made our world.

For Earth to even be here,

we had to beat
astronomical odds.

A host of different factors
have to line up

to get a planet
just like the Earth.

You have to have
the right distance,

the right size,
the right kind of moon.

On Earth, all the conditions are
just right for life.

To get a world like ours,
you need a lot of aces.

Somehow, our solar system hit
the jackpot.

But the big question is
did it happen anywhere else?

One of the Universe's
most violent events

triggered
the birth of our planet.

A sparse cloud crushed
into a dense swirl of dust.

Some of this dust will become
planet Earth.

But how do tiny dust grains
create entire worlds?

A supernova explosion
triggers a chain of events

that will eventually create
the Earth...

...the formation
of our solar system.

A hot ball of gas grows
in the center.

This will become our Sun.

The dust that swirls around it
will form the planets.

But first,
the grains must stick together.

So, we have this
interesting conundrum, right?

So, this disk consists
of gas and dust particles.

They're about the size of,
let's say,

particles in smoke, all right?

We'll say cigarette smoke,
right?

So, these are small things.

And, somehow, we have to get
from those little grains

to what we see on the Earth.

Gravity is
a powerful attractive force.

It shapes
galaxies and solar systems,

but specks of dust are
far too small

to pull on each other.

Somehow, they clump together
to form planets.

So, if gravity doesn't
bind them, what does?

In Germany,
scientists are on the case.

Okay.

They can simulate
how dust behaves in space

inside a huge tower.

Here, we do
free-fall experiments.

So,
the whole experimental setup,

including our dust aggregates,
are in perfect free fall.

It is simulation of space,
but a very good one, indeed.

I think this is the closest
you can get to space on Earth.

Researchers place dust
in the container

and load it
into a launch capsule.

At the base of the tower,

they lower it
into a super-powerful catapult.

This launches
the half-ton capsule

from zero
to over 100 miles per hour

in a quarter of a second.

400 feet up,

the capsule reaches
the top of the tower,

then plunges back down.

A drum of polystyrene balls,
30 feet deep, breaks its fall.

All this gives
just 10 seconds of zero gravity,

just enough time, they hope,
for the dust to stick.

Three, two, one, and go.

Moments after
the capsule launches,

the dust inside becomes
weightless.

The grains clump together,

just like
the early solar system.

These images reveal

how dust particles came together
4 1/2 billion years ago

to form the Earth.

The force that binds
the aggregates together

is not gravity.

They are too small
for gravity to be efficient.

We think the force that binds
the aggregates together

is electrostatic force.

It's the same reason

that when you pull
your clothes out of the dryer --

you know how the clothes
sometimes stick to you?

That's the same effect
that allows

one dust particle
to stick to another.

Dust particles join
to form balls of fluff.

The little static charges
that they have

can make them stick
when they hit,

and you get something
sort of like the dust bunnies

that I have a lot of
underneath my bed.

These cosmic dust bunnies are
planets in the making.

They start out
smaller than a pinhead,

then grow.

The dust is now in clumps,

but it's still
just balls of dust.

Turning dust balls into rocks
takes a whole new process...

...a cosmic electric storm.

Space clouds build up charge
just like clouds here on Earth,

generating
huge bolts of lightning.

Balls of dust can
turn into solid rocks

by an energetic event,
like lightning.

The electric bolts
smash through the dust balls

and heat them
to 3,000 degrees Fahrenheit.

In minutes, they cool and fuse
into solid rock.

Meteorites today still carry
these ancient rock balls

inside them.

These tiny globules

were once the building blocks
of planets.

To form the Earth,

these tiny balls must collide,
stick, and grow.

Rocks begin to build up
by accidental collisions,

which can take a long time.

Eventually, the protoplanets,
as we call them --

the baby planets --

get the size of asteroids,
kilometers across.

The baby earth is now the size
of a few city blocks,

big enough for a new force
to take charge --

gravity.

At that point,

a single asteroid will
gravitationally attract

a neighboring asteroid.

And, so, those two asteroids

that would have
passed in the night

are gravitationally attracted,
and they hit each other.

Once gravity starts
to rear its head,

things really speed up

because instead of just randomly
plowing through material

and getting bigger that way,

now it's starting
to draw material in.

Gravity pulls rocks together,
then holds them there

to produce bigger and bigger
piles of rubble.

So, this formation process,
which was taking a long time

to get to the size
where gravity kicks in,

suddenly gets
kicked into overdrive,

and the planet grows
very rapidly.

But planets are more
than just overgrown rock piles.

These rocks are lumpy and inert.

How did the Earth become
round and full of life?

The early solar system is
a construction site for planets.

Dust sticks together
to form rocks.

Rocks join to form asteroids.

But most asteroids
look nothing like Earth.

And when you look at a close-up
of an asteroid,

it looks like
some kind of distorted peanut,

like a potato that's been
sort of bashed.

You can see
giant craters and oblong shapes.

The young Earth is one
of billions

of misshapen space boulders.

To become a planet,
it must first become round.

That process only starts

when it's several hundred miles
across,

when its own internal gravity
begins to change its shape.

Once you get enough material,
enough mass,

the gravitational force becomes
stronger.

Any giant mountain will be
crushed down

by the force of gravity.

The gravity is so strong

that it can
actually break rocks,

and the rocks, itself,
can act like a fluid,

making an object round.

Huge outcrops of rock
crumble and fall.

The immense self-gravity
of the early Earth

crushes it
into the most efficient shape --

a vast, round ball of rock...

...a lopsided pile of rubble

transformed
into a miniature world.

The Earth has a new shape,

but it's still
just a ball of rock.

Its structure will
also soon change.

Cosmic rocks and boulders
still rain down from space.

Each collision heats the ground.

There's a huge amount of energy

stored in an object
that's moving rapidly.

And when that hits the Earth,

all that energy is dumped
into the material,

and that heats it up
and melts it.

And the Earth became molten

and stayed that way
for a long time.

The young planet is
no longer solid rock.

It's a seething molten mass...

...just like this blast furnace

at the Severstal plant
in Detroit.

Believe it or not,

this process behind me makes
life on Earth possible.

They feed in ground-up iron ore,

a mixture of rock and metal...

...just like the early Earth.

Put iron ore in a furnace,
and the heat melts everything.

This molten iron is
at 2,700 degrees Fahrenheit.

That's about the temperature
of the surface of the Earth

4 1/2 billion years ago.

Imagine an entire planet molten.

In the distance, you would see

thundering volcanoes
spewing out lava.

It would be a scene
right out of Dante's "Inferno."

Iron is heavier than rock.

Now molten, they separate.

This is amazing.

We're witnessing a process

which created
the very crust of the Earth

billions of years ago --

the crust
that we walk on every day.

Molten rock rises to the surface
and cools to form the crust.

Molten iron sinks underneath.

Inside the Earth,

it sank all the way
to the planet's core.

The rocky surface is
where we live.

But without Earth's
molten iron core,

none of us could survive.

This process separated the iron
from the rocky minerals.

As the iron descended
to the center of the Earth,

it eventually created
a magnetic field,

and that's why we're here today.

The molten iron swirls
inside the Earth's core

and generates
a powerful magnetic field

around the planet --

a cosmic shield against
deadly radiation from space.

But the young Earth is
still small --

far smaller than the Moon today.

This newly-formed world
must grow.

It must also avoid
being blown to pieces.

Thousands of protoplanets

are hurtling
around the solar system,

and some are heading
straight for Earth.

It's 100,000 years
since our solar system formed.

The young Earth
already looks like a planet.

It's round.

It has an iron core
and a rocky surface.

Yet, our baby planet is
just a few hundred miles across.

It has a long way to go.

It must grow
4,000 times more massive,

and it has competition.

Thousands of other protoplanets
shoot through the solar system,

often colliding
at over 20,000 miles per hour.

You can find proof
of this ancient destructive era

in modern-day Arizona.

Not meteor crater itself --
that's just 50,000 years old --

but the asteroid
that gouged it out.

That was
4 1/2 billion years old.

Mark Sykes and Marvin Killgore

think the asteroid came
from a violent event

in the early solar system.

The asteroid flew through space
for billions of years,

then it hit Earth.

They aim to find
a fragment of the asteroid,

a remnant from the period
of planetary formation.

About six miles from here is
meteor crater,

and that was an impact
50,000 years or so ago,

and it spewed
a bunch of pieces out.

They're convinced

the original asteroid was
rich in iron,

so they've come prepared

with some
impressive metal detectors.

Does it work?

Oh, yeah.

That's the sound
we're listening for.

But even with a quad-drawn
metal detector,

meteorites are hard to find.

Yeah, are you pretty convinced
there's nothing there?

Yeah, I don't really --
I'm not detecting anything.

They find metal
but no meteorites.

My great discovery
of the afternoon

has been this bolt...

and this piece of wire.

It takes hours of searching
and many false alarms.

Then, with the light fading,
the detector sounds again.

How about that?
Success at last.

This meteorite is
over 90% iron and nickle.

It could only form

right in the core
of a protoplanet.

The protoplanet it came from

must have smashed apart
in a brutal collision.

Well, in the early solar system,
it was a pretty violent place,

and these protoplanetary embryos
would smash into each other.

They would shatter each other,

exposing
the interior cores like this.

It was a very tumultuous time.

Entire worlds reduced
to chunks of rock and metal

and scattered into outer space.

In the early solar system,

these vast collisions
are common.

The young Earth is in danger.

The period's name is
the "Titanomachia" --

literally
the "War of the Titans."

All rocky planets,
the Earth included,

go through
this destructive phase.

Sometimes,
they shatter completely.

Sometimes,
one consumes the other.

All the big guys are sort of
competing with one another

in a very violent way, actually,

to see who comes out on top
by eating all their neighbors.

The battle lasts
over 30 million years.

Finally, thousands
of protoplanets have combined

into a few full-size planets --

Mercury, Venus, Earth, Mars,
and a fifth planet, Thea.

It's racing toward earth --

our planet's last giant impact.

Thea is the size of Mars --
big enough to destroy the Earth.

If that thing had
hit us straight on,

it could have literally
blown the Earth to bits,

and then we wouldn't even have
a planet today.

If this Mars-like object had
a direct hit with the Earth,

perhaps there would have been
another asteroid belt

where the Earth is today.

But Earth is in luck.

Instead of a head-on crash,
Thea strikes a glancing blow.

It's the most violent event
the Earth has ever known.

The impact turns the Earth
back to a molten world,

a vast magma ocean
600 miles deep.

The Earth barely survives.

And the encounter changes
our world forever.

Material blasts
out into space --

enough rock to build
a mountain as wide as America

and 10,000 miles high.

There would have been
so much energy,

so much catastrophe.

Huge amounts of material
blasted off

and went into orbit
around the Earth.

The debris forms
a huge ring around the Earth.

This gathers together
to form two rocky bodies,

both orbiting the Earth.

Something the size of Mars
hit the Earth

about 4 billion years ago.

Lots of material would have been
thrown off.

We now think
that it may have formed

not only one moon but two.

For millions of years,

two moons dominate
the Earth's sky.

Eventually,
they drift together and collide.

Two moons merge into one --

the massive moon we see today.

There's no other planet
that we know of

that has a moon as large as ours

in comparison
to the size of the planet.

We're almost a binary planet --

two worlds going
around each other.

Without this large moon,
we might not even be here.

The moon plays a key role

in the survival of life
here on the Earth.

And the reason is that the Moon,
in its orbit,

stabilizes the Earth.

The Moon keeps the Earth
spinning at the same angle.

That steadies our climate.

The fact that the Earth's axis
stays in the same direction

as it goes around the sun
produces the seasons,

but regular seasons --

things that life can depend upon
as it evolves.

Earth is neither too hot
nor too cold for life

thanks to our distance
from the Sun

and our massive moon.

The Earth is not covered
in ice or steam

but in liquid water.

Yet, that water must come
from somewhere.

The newly formed earth is dry.

To get water, our planet must,
once again, face disaster.

It's half a billion years
since the Sun first ignited.

Four billion years from now,

the first humans will
set foot on Earth.

The Moon has just formed,
and the Earth is a desert.

One of the more amazing ideas
in astronomy

is that the Earth started out
hot and dry.

There was
no water here originally.

As the planets formed,

the Sun's intense radiation
vaporized the water

in the inner solar system.

Farther from the Sun,
temperatures were cooler.

So in the outer solar system,

ice and water collected
on comets and asteroids.

While closer to the Sun,
the young Earth was dry.

So, things changed.
What happened?

How is that now we have
this wonderful water cycle?

Well, the water probably came
from somewhere else.

Well, if you want to have

a solar system that has
a lot of water in it,

you have to bring it
from the outer parts

down into the inner parts,

and you can do that
through comets and asteroids.

Comets and icy asteroids contain
huge reserves of water,

but they're hundreds of millions
of miles from the young Earth.

Then something changes --

an event that tosses
the asteroids and comets

right across the solar system.

Jupiter, Saturn, Neptune, Uranus

take
a cosmic roller-coaster ride.

So, this is
an event that happened

when the solar system was young.

Think of it as more
of its teenage breakout years

where it just started
to party for a while.

The young planets have not yet
settled into stable orbits.

As their orbits shift,

Jupiter and Saturn fall
into an intricate dance.

Every time
Saturn orbits the Sun once,

Jupiter orbits twice,

so they always line up
at the same spot.

Each time, gravity tugs them
in the same direction.

First, they destabilize
each other

and then
the entire solar system.

The whole thing just goes
kaplooey.

The analogy I like to use is
when a bowling ball hits pins,

it just goes "bam!"
All over the place.

That's what this would have
looked like.

Planetary pandemonium.

Neptune and Uranus
switch places.

Saturn races outwards.

The giant planets scatter
billions of asteroids and comets

onto new paths.

Many head for Earth.

These asteroids and comets
would have been scattered

all over the place, right,

some of them hitting
the Earth and Moon.

Cosmic missiles
bombard the Earth.

We believe

that every square inch
of the Earth got hit

by a comet or an asteroid
during this period.

It would not have been
a fun time to be here.

The bombardment lasts
hundreds of millions of years

until, finally,
the gas planets settle

into the stable orbits
we see today,

restoring order.

But Earth itself has
fundamentally changed.

Those comets and asteroids were
not just made of rock

but of ice, frozen water.

Comets, we know,
are made out of ice.

They're dirty snowballs
in outer space,

and even asteroids can bring
water and ice to the Earth.

Our oceans are full
thanks to the cosmic hailstorm.

So next time you're drinking
a glass of water, realize

that you're probably drinking
comet and asteroid juice.

The arrival of water
is the final step

to create a habitable planet.

A sequence of catastrophes has
created a world

that's perfect for life.

But has it happened
elsewhere among the stars?

Or are we alone?

How did we get here?

Planet Earth only exists

because of a chain
of extraordinary events,

a lucky throw of cosmic dice.

Five billion years ago,

the odds would have seemed
extremely slim

that a planet like Earth

would form
in a rather unremarkable arm

in the Milky Way galaxy.

It's like
trying to throw two sixes

but with dice
that have thousands of sides.

We know it happened once,
else we wouldn't be here.

But what are the odds
it happened elsewhere?

That other planets have life?

Life like ours needs a planet

with the right temperature
and size,

a stabilizing moon,
a protective magnetic field,

and just the right amount
of water.

The conditions must be perfect.

Yet, amazingly, there may be

countless earth-like planets
out there, waiting to be found.

Thanks to the sheer scale
of the Universe,

we may find one any day now
with the Kepler Space Telescope.

Geoff Marcy is
mission co-investigator.

It has only one goal,

and that's to discover
earth-size planets

around other stars
that you see in the night sky.

Earth-size planets are
hard to spot.

Before Kepler,
astronomers took 20 years

to discover around 500 planets.

Most were gas giants

hundreds of times bigger
than Earth.

Since Kepler,
that number has exploded.

Kepler has already discovered

a couple thousand
planet candidates.

Many of them are members
of multi-planet systems --

two, three, four, five,
and even six planets

all orbiting the same star.

So, we're finding
an absolute avalanche of planets

out there among the stars.

Kepler has found one planet
only twice the size of Earth

and the right temperature
for life.

We don't know yet if this planet
has other earth-like attributes,

like liquid water.

But even if it doesn't,

there are
many more planets out there.

Kepler has found
only a tiny fraction of them

because it only looks
at a small part of the sky.

It's not even looking
at the whole sky.

It's looking
at a very tiny slice of stars

in the galaxy.

And, in fact,
if you were to look up,

you could cover it
with just your thumb.

In the whole of our galaxy,
there are 200 billion stars.

Many will have planets.

Based on our knowledge
from Kepler and other searches,

something like
half of those stars,

perhaps even more,
harbor planets.

That means
at least 100 billion planets

have formed in the Milky Way.

Earth-like worlds may be rare,

but it seems a safe bet
they're out there somewhere.

So, the odds of getting
an earth-like planet

are extremely small --

much smaller than getting
a double six at craps.

But if you have a lot of dice,
you're guaranteed to get sixes.

And if you have
a lot of planets,

you're guaranteed to get earths.

There are
so many planets in our galaxy,

even if the chances are
one in a million,

there should be
thousands of earth-like worlds.

Our Universe, at large,

has hundreds of billions
of galaxies,

each of which is
more or less like our Milky Way.

So, the number
of planets in our Universe

is virtually uncountable.

Alien earths must be everywhere.

Now, we haven't discovered
even one of them yet.

But statistically speaking,
it is a rock-solid certainty.

There are millions of billions
of planets like the Earth

out there.

And with
that many earth-like planets,

surely, some of them will have
intelligent life.

I would bet everything.

I would bet my house

that there is another Earth
out there somewhere.

There really can be no doubt
that, elsewhere in our Universe,

there are other smart critters
who are asking themselves,

"Gee, I wonder if there are
any other intelligent species

out there in the Universe?"

The story of
the birth of our planet

reveals that we cannot possibly
be alone in the Universe.

The question is not
"Are we alone?",

"it's how far away
are our neighbors?"

"And when will we meet?"

== sync, corrected by elderman ==

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