All language subtitles for How.the.Universe.Works.S10E04.Dark.History.of.Earth.1080p.WEB.h264-KOMPOST

The earth is over
4.5 billion years old.

Its history is
shaped by disaster...

after disaster.

Asteroid and comet collisions,

flares from the Sun.

Mass extinctions,

supernova explosions,

cosmic ray bombardment.

You name it, we've
experienced it.

It's kind of a miracle
we're here at all.

These violent events
could be why Earth has life

We tend to thin of
disaster as a bad thing,

but out of chaos
can come possibility.

When we destroy something,

we can also create
something new.

Earth has walked the
line between survival..

And destruction.

It's tipping that
fine balance of luck

between a good disaster
and a bad disaster.

Could catastrophe and chaos
be the essential ingredient

for life?

2021.

Scientists investigate
something mysterious

buried deep inside the earth

It's a long hidden
clue to our violent past.

Deep down

1,800 miles below
the surface of the earth,

our core is surrounded
by fluid rock,

but inside that,

600 miles high

and thousands of miles across

are two denser regions,

and they kind of cup the core
of our planet like two hands.

One of them is, you know, half the
size of Australia, for crying out loud.

So, I mean, they're
big lumps down there.

There's no reason
they should be there.

It's a mystery to us.

To solve this mystery,

scientists need to
examine the rocks

buried over 1,000 miles
beneath the surface.

We don't really know what
these two big rocks are made of,

sitting there on the core.

However, we've been
able to sample them.

How in the world
is that possible?

Well, these blobs are
actual feeding mantle plumes

that are rising up
through the mantle.

So, volcanoes in Iceland
and Samoa, for instance,

will dredge up some of these
lumps of rock from the mantle.

It's a precious chance for us to
sample some of that deep rock

that we'd normally
not get a chance to see.

These rocks are old.

Very old.

It turns out that the
samples in the lav

that we think came from
these blobs of rock in the mantle

are 4.5 billion years old.

That is as old as
the age of the earth.

So, they tell us something
about, you know,

how the internal structure of
our planet was, uh, arranged

in the earliest days of
the formation of our planet,

so getting samples from that
time is very, very important.

The age of the rocks may
be a clue to their origin.

They date back to a time of
monstrous cosmic mayhem.

4.5 billion years ago,

the solar system was
still a pretty wild place.

We're approaching the end
of the formation of planets.

Earth would still be growing.

Back then, you wouldn't
necessarily recognize the earth.

In fact, you wouldn't
recognize the earth at all.

For example, no moon.

The earth did not have a
moon when it first formed.

The young earth orbits the
S with other infant planets.

One of them is an object
scientists call Theia...

and it's on a collision
course with our home.

The Theia collision would
ha been a spectacular event.

It would've been one
of the coolest things

you could possibly witness

in the origin of
the solar system,

certainly the biggest event
in the history of the earth.

The Theia event is

something that completely
reshaped the earth.

The planet that the earth
was before the Theia event

is gone forever.

The impact melts rock

and throws out over a
billio billion tons of debris.

During this
incredible collision,

these two planets were
literally broken apart

and combined
into one big planet.

Huge chunks of
Theia stayed together

as the now molten
earth began to form anew.

Now, we can kind
of paint a picture

of where these big lumps of
rock might have come from.

They're very old.

They're, in fact, the same
age as that large impact event.

They could be pieces of Thei

The giant slabs of Theia
sink down into our planet...

and lie undiscovered
for billions of years.

Earth reforms from
the ruin of both planets.

Now, you might think that a
collision like this is just devastating,

there's no upside at all,

but there's some things
that came out of this collision

that may have led to
the possibility of life.

When these two planets combined,

parts of Theia's iron
core merged with Earth's.

So, that means that Earth
collected a much bigger core

than it might have
possessed on its own.

This is good news for us

because the core is the
source of the magnetic field

that protects us.

Liquid metal flowing
around in the outer core

generates Earth's
magnetic field...

a protective shield
from the Sun.

The Sun can actual
output billions of tons

of high-energy protons and
electrons in a single burp.

That, eventually, would hav
stripped away our atmosphere

If it weren't for
that active core

and that magnetic field,

we would look like Mars,

just sort of a bare
and barren desert.

Thanks to Theia's extra iron,

Earth's molten
outer core is large...

so it cools slowly,

staying molten,

and keeps on generating
a strong magnetic shield.

Because of that collision,

the extra iron, the extra heat,

we've stayed active.

We have a magnetic field.

We are protected,

and, in fact, that's why
we're here talking about it.

The catastrophic impact
helped life in other ways.

The Theia event
was absolutely huge,

and not an impact like a 100-mile
asteroid making a big crater in the desert,

but a planet hitting a planet,

causing a huge disk of debris
spread out from the earth,

out of which formed the Moon

After the collision,

the earth tilts on its side

and spins incredibly fast.

A day only lasts a few hours

The earth itself rotates
slightly on its side,

and, if left to its own devices,

would, in fact, experience
unpredictable, chaotic wobbling.

The fact that the Moon is there

stabilizes the earth,

stabilizes our climate.

The Moon's gravitational
pull on our oceans

creates tides and slows
down the earth's spin...

creating a world
primed for life.

We actually owe quite a
bit to the Moon and Theia,

its progenitor,

for making Earth a
hospitable planet for life.

A giant collision
4.5 billion years ago

sounds like a catastrophe,

but it was probably the best
thing to happen to the earth.

Theia, I would shake your ha

because we have
a lot to owe you.

We also owe the
science of chance

because we lucked out

with a one in a million impact.

If the impact from Theia
had been a little bit harder,

the earth may not have
recovered as well as it did,

and we may not be here
to talk about it right now.

If it had been a
little bit less forceful,

then the impact of it may
no have made the changes

that we think were needed
for us to be here now.

We got lucky.

Most planets don't get to
survive a collision like that

and get a bonus
moon out of the deal.

Earth's huge
collision with Theia

was not our planet's
first brush with danger.

An earlier explosive event

could have stopped
the solar system

from sparking into life...

and the earth from formin

Supernovas are one of the
universe's most destructive events...

releasing, in one second.

As much energy as our sun will

in its entire lifetime.

But rather than wipe us out

supernovas may have
kick-started the solar syste

4.6 billion years ago,

the solar system's not
even really the solar system.

It's the precursor
of the solar system.

So, what we ha was a cloud of
gas and dust collapsing in on itself,

forming the Sun in the cente

a big, flat disk around it

out of which all the
planets were forming.

There are all kind of vast clouds of
dust and g floating around the Galaxy.

What actually causes
them to start collapsing

and forming new stars?

Well, you have to
give that cloud a push.

Scientists think this push
could be a stellar blast...

a supernova.

Supernova are some of the most
powerfu events in the universe.

One explosion can light
up brighter than a galaxy.

So, not only do they eject
elements and material,

they also eject a lot
of light and energy.

A supernova explosion
sends a shock wave

racing out into space at
18,000 miles per second.

The shock wave from
a nearby supernova

compresses material together

until it begins to collapse
under its own gravity.

Was this how our
solar system started?

So far, it's been really
difficult to find, uh, evidence

that there was some supernova,

or point to something
that happened

that really kick-started
the solar system.

The ancient supernova blast
faded away a long time ago.

Imagine a crime scen

Now, imagine waiting
4.6 billion years

after the crime is committed,

and looking at it and going,

"There's... There's
nothing here.

What are we doing?"

Uh, that's kinda what
we're trying to do here.

Researchers from the
University of Minnesota

tried to solve this
ancient crime...

by studying asteroids that
fell to Earth as meteorites.

Asteroids are critical for
understanding the early solar system,

and this is because they have
frozen in place all the conditions

that existed in that
very early solar nebula,

right at 4.5 billion years ago.

The asteroids
contain information

about the time leading up to the
birth of the Sun and the solar system.

When a massive star
ends its life as a supernova,

it undergoes what
we call nucleogenesis.

In fact, we call it
explosive nucleogenesis.

Literally, the explosion is
generating new types of nuclei,

new elements, heavier elements.

Well, it turns out the
types of elements it makes

depends on the
star that blew up.

The Minnesota tea ran
computer simulations

to investigate
which elements form

when a star up to 12 times
the mass of the Sun explodes

Then, they compared the results

with analysis of elements
found in asteroids

dating back to the
birth of the solar system.

They match.

So, the remains of this supernova
was actual under our noses all along

in the elements that have been
in our solar system for ages.

And perhaps in
the earth as well.

The earth has lots of rocks
that's made of, uh, silicon.

That's only produced
in supernova explosions,

and the very core of our earth,

the thing that keeps us alive,

that's iron, nickel.

Again, you only get that
in supernova explosions.

In February 2021

scientists shed light on
the supernova explosions

that helped seed
our solar system

and provided the
materials to build our planet.

The research examined fragments

blasted off the giant
space rock, Vesta...

4.5 billion years ago,

and later landed on Earth.

These asteroid fragments
contain the fingerprints

of not one,

but at least two
supernova explosions.

Our solar system was seeded, was enriched, by
at least two separate supernova explosions.

That's incredibly lucky

because that is what delivers
the ingredients necessary for life.

Scientists believ that
these two supernovas

may have enriched
different parts

of the infant solar system.

One provided the materials

that helped form
the outer gas planets.

The other supernova
seeded the inner solar system

with elements that
built the rocky planets,

including the earth.

Once again, our fate
came down to pure chance.

A series of extraordinarily
violent supernova blasts

gave the solar system
the kick-start it needed

and the elements
to build the planets

without destroying
our future home.

It's a fine line between being
too close to a supernova,

which will just shred
your pre-stellar cloud...

and not too far away that you
don't get any of the good stuff.

Supernova play
both creation stories

and destruction stories.

They play both roles.

We lucked out.

This chapter of
the story ends well.

The solar system gets the
ingredients it needs to build planets.

Earth forms in a good location,

close to its star.

The future looks bright,

but then,

the biggest
bombardment in history

smashes into the earth.

From the moment
our planet formed...

we've been under fire.

2021.

A fireball streaks across
the night sky in Europe.

2018.

A 1,500-ton meteor
explodes over the Bering Sea

with 10 times the energy
of an atomic bomb.

2013.

An asteroid
explodes over Russia,

injuring over 1,000 people.

The earth is hit by quite
a few asteroids every day.

You see them as shooting stars,

meteors in the sky.

These events are
violent and destructive

but these space invaders also brought
something every living planet needs:

volatiles.

When we say volatiles,

what we mean are
elements that are really light

and easily moved around.

Often, they're gases,

so that's oxygen, and
water, and carbon dioxide,

and just all those
light elements

that are really important
building blocks for life.

These elements ar
abundant on our planet today

but were not
when it first formed.

From observing other solar systems
forming all around us in space,

we know that planets as close
to their stars as we are to the Sun,

when they form,
they're very hot and dry.

There's probably some
littl bit of water around there,

but really not very much.

So, what this means

is any volatiles will
basically be boiled away.

If you have a molten surface,

anything like water is
gonna get boiled away.

Young Earth was a dry planet,

devoid of all the precious
volatiles needed for life.

These materials must have been
delivered to Earth after its formation.

We think volatiles arrived in the
early days of the solar system...

when the giant planets,
including Jupiter,

moved around...

and stirred up the
conten of the solar system.

As Jupiter moves,

its gravity is pulling on
all the objects in there

basically speeding them up,

and there's a little bit of
chaos there in the first place,

but now, Jupiter is
basically supercharging it.

Jupiter's path sends
countless asteroids and comets

on a collision
course with the earth.

It would have
been utterly chaotic.

This is a rain of large objects

onto all of the inner planets,

but these objects that came
screaming into Earth were gigantic.

Four billion years ago,

a storm of giant
asteroids and comets

hits the earth.

Some are tens of miles wide

They bring the volatiles

that help fill the
earth's oceans

and build its atmosphere...

but cosmic deliveries
can both give

and take.

The importance of
impacts for atmosphere

could go either way.

You could have
a... A really big,

really powerful impact...

that blows away the atmosphere

of a small, fledgling planet

or you could have a bunch of
small impacts of water-rich asteroids

that are simply contributing
water, and volatiles,

and new chemicals to the surface

that might help the
atmosphe that's already there.

When you think about
an object coming to Earth,

is it gonna land on Earth,

and if it does land,

is it gonna be a...
An erosive event,

where material is
lost from the earth,

or is it gonna be
an accretion event,

where the earth gains material?

Well, the devil's
in the details.

Details like the
size of the impactor.

One study suggests

that asteroids between
60 fe and 3,300 feet wide

add more to the atmosphere
than they take away.

And speed at the point
of impact also matters.

Asteroids are orbiting the sun.

And when they fall towards
the sun, they are gaining speed,

they're gaining velocity.

Imagine dropping a coin
into one of those spiral wells.

As the coin gets closer
and closer to the middle,

it spins up faster and faste

The closer an
asteroid gets to the sun

the stronger the sun's
gravitational pull...

and the faster the
asteroid travels.

So proximity to your star

is a vital factor in how
intense any impacts will be.

It's possibl that the Earth

is the right distance
from its host star

so that when an impact happens,

the energy isn't insanely high.

It's just the right amount that it's the
right speed to make everything work.

Supernovas seed the solar system

with the elements
to build the planets.

Asteroids and comets delive volatile
chemicals to the surface of the Earth

Together they create a
habitable environment.

So we need those impacts to
happen to have life on Earth.

Disasters create a
planet primed for life.

But it appears that even
mor mayhem and chaos

are needed to
trigger life itself.

An asteroid tear
through the solar system,

hurdling through space
at 40,000 miles an hour.

It's destination,

Earth.

Will this space rock inflic
unimaginable damage...

or will it bring
the spark of life?

This idea of a spark of life,

we've all kinda seen it

in the Frankenstein
movies, right? "It's alive!"

This comes from legend,
from myth, from history

that there's some sort of
a spark that differentiates

cold inanimate
matter from living stuff.

And in some sense
it's kind of true.

On Earth, we thin this
spark may have arrived

over 4 billion years ago.

The Hadean Eon was the
time from the Earth's formation

about 4.6 billion years ago

to about 4 billion years ago.

It's named after
literally Hades.

So the conditions on
Earth were literally hellish.

It was hot and soupy, a
lot of water vapor around

high pressure atmosphere,
very intense heat.

You wouldn't survive.

The planet would
literally kill you back then.

It's shocking. And I
mean, really shocking

that the evidence of first
life that we have on Earth

dates to the Hadean Eon.

This was a terrible place,

molten and poisonous and awful.

And yet life somehow
arose in all of that mess.

June 2020,

Japanese scientists
simulat the conditions

of this hellish planet...

and then try to
recreate the spark of life.

So what the scientists were trying
to do was mimic those conditions

and see what would happen.

If you smash a meteorite
into the ocean back then,

could it produce sort
of the same chemicals

that we see life using today?

They use a mix of carbon
dioxide, nitrogen water, and iron

to replicate the
Hadean environment.

Firing a mini meteor at 2,000
miles an hour into this chemical soup

triggers a reaction between
the basic organic elements..

Creating amino acids.

We call amino acids
the building blocks of life.

Really they're the
building blocks of proteins.

And life needs
proteins to exist.

But that's why
they're so important.

Without amino acids,
there's no proteins,

without proteins,
no life as we know it.

The experiment proves

that meteorite impacts can
help build the components for life.

But for these building
block to come together

and create life,

we need more.

It's like making a cake.

You can put together the oil, and
the flour, and the butter, and the sugar,

but if you don't
put it in an oven,

you're not gonna
end up with a cake.

You're gonna end up
with something else.

We thought that the
violence of asteroid impacts

prevented life from forming

Now, we think they could
be an essential ingredient.

If the asteroid impact is
big enough and fast enoug

it can punch right
through the crust.

Then you're getting
geothermal heat,

heat the bubbles
up from the mantle.

And it is certainly possibl to
get an asteroid impact that big.

Large meteorite impacts
can create hydrothermal vent

which some scientists
believ were the cradles of life.

They provide warm,
wet environments

and bring up chemicals from
deep inside the Earth's crust...

the perfect place
for life to begin.

As bad as those
conditions seem to us,

to the molecules that are beginning
to combin and do their thing,

that was a
wonderful place to be.

That could actually
be that the conditions

that are best for early life

might actually be those
just after an impact.

So you have sort of this
petri dish environment

in which life
could really thrive.

These vents might be similar

to those we see in
the oceans today.

These hydrothermal
vents provide little window

into what the conditions on the
primordial Earth would've been like.

And the sort of chemistry

that goes on in those
hydrothermal fluids

seems to be the right kind
of chemistry for creating life.

Once again, Earth got lucky.

Impacts that could've
destroyed everything...

may have helped
spark life into existence.

I once hear this quote
from Confucious..

That creation is quiet
but destruction is loud.

Well, these impacts

were both destructive, but they
also may have been creators.

Earth leaves behi
the Hadean age.

The planet calms,
and life takes hold.

But disaster is our
constant companion

as we prepare to face a
stor of deadly cosmic bullets.

The universe is a
dangerous place for lif

There are asteroid impacts..

Black holes...

and exploding stars.

But public enemy No. 1

cosmic rays...

lethal energic particles
born in violent events.

Cosmic rays are incredibly small

but travel so fast,
near the speed of light,

but they can tear through
our DNA and damage I

Your full of DNA.

If that DNA gets broken
apart, guess what happens?

That could lead to
cancer and death.

At first glance, these cosmic
rays are the worst things for life.

They're terrible.

Despite their
frighting rap sheet,

cosmic rays may have played a
crucial roll in the evolution of life.

2020,

scientists at New York
and Stanford universities

investigate biological
molecules that have a twin...

mirror image versions
called chiral molecules.

The concept of
chirality in chemistry

is when you have two
molecules, two chemicals,

that are physically the same

They're made of
exactly the same things,

but their structure
is different.

And they're not just different,

they're reflections
of each other.

It's literally called handedness

because look
here's my right hand

with my thumb over here
and my fingers over here,

here's my left hand with my thumb
over here and my fingers over here.

I can't wear a left
glove on my right hand.

There's nothing I can do to
make these guys the same.

And it turns out this is
true not just for hands,

but also for large number of
simple organic compounds,

things like amino
acids or sugars,

which are the building
blocks of all life on Earth.

Billions of years ago,
early life may have had

both left- and
right-handed DNA and RNA.

But life chose to use
mostly right-handed molecule

The reason may
have been cosmic rays.

When cosmic rays hit
Earth's atmosphere...

they degrade into even
smaller subatomic particles

called muons.

Most muons spin
in one direction.

So we have these little
muons, which are very energetic,

and they're spinning
a certain way.

And when they hit a
molecule they interact with it.

They can disrupt it.
They can change it.

Some scientists believe
these spinning muons

interact more readily with
right-handed DNA and RNA...

triggering mutations.

Some mutations are beneficia
but they have to get a chanc

So if you have right-handed
molecules and left-handed molecules,

and they're both
being hit by muons,

the one that's hit more gets more
chances to have a beneficial mutation.

Cosmic rays may have
given right-handed life

an evolutionary advantage.

Left-handed life
could not compete.

It's like throwing dice.

If you're trying to
get double sixes,

and the left hand only
gets to throw ten times,

and the right hand
gets to throw 100 times,

more likely to get double sixes

with the right hand
than the left hand.

But the dice don't
always land in our favor.

359 million years ago,
Earth's luck ran out.

And cosmic rays may have
lived up to their reputation

as the baddest
particle on the block.

Earth's oceans were
teeming with marine lif

And by this period as well,

plants had started to colonize
onto the contents and landmasses,

attracting animal life,
insects, millipedes.

And it's in this environmen

the Earth experienced one of
the greatest mass extensions

in the history of life.

Something killed off 97%
of all vertebrae species.

We call this wipeout the
end Devonian extinction

One possible
explanation, a supernova.

When some dying stars
explod they fire out cosmic rays.

This radiation bombards the
upper atmospher of the Earth

and drives the chemistry of
nitrogen, turning into nitrogen dioxide,

a gas which itself then
reacts with the ozone layer

and destroys it.

Without the
protective ozone layer,

ultra violet radiation from
the sun bombards Earth

Radiation rains down
for thousands of years...

damaging the DNA
of plants and animals.

Many species die out.

The end Devonian mass
extinction mostly effected marine life

This is where we see the
greatest percentage of deaths.

The oceans once populated
by fish the size of school buses...

now host fish no
bigger than a sardine.

These smaller fish
reproduce quickly.

In the challenging environment,

they adapt and diversify
faster than larger species.

Mass extinction is not
only wipe the slate clean

and provide other animals and
other life forms an opportunity,

it creates a sort of chaoti
and complex environment

that drives natural
selectio and evolution.

If a supernova was to
blame for this extinction event,

scientists believe that the
culprit was 65 light years away.

Any closer and Earth's luck
would've run out completely

It seems the existence of life

is always balanced
on a knife edge.

When an exploding star goes
off a little bit too close to us...

and we are all destroyed

So there's this
wonderful balance

between just violent
enough and too violent.

And we have been lucky enough to
dance on that edge for 4.5 billion years.

This mass extinction
reset life on Earth

and paved the way for
four-legged creatures,

our distant ancestors.

Cataclysmic events
go hand in hand

with human evolution.

Some knocked us back

and others like the
event 66 million years ago

gave us a push forward.

66 million years ago

a massive asteroid
crashes into the Earth.

It triggers a huge
extinction event.

Without it humans
may have never evolved.

At this time in Earth's history,

we had these enormous
plants and gigantic insects

that actually would be incredibly
terrifying if we saw them today.

Pterosaurs sa through the air.

Huge marine reptiles
dominat the oceans.

And the T. rex is
the king of the world.

Then a glowing object
appear in the sky.

I'm sitting on the beach

what was then gonna
be the Yucatan of Mexico

enjoying a drink with a,
you know, a little umbrella,

but up there in the
sky all of sudden

approaching me at
40,000 miles an hour

is Mount Everest glowing thousands
of times more intensity than the sun...

and it's just seconds away
from dropping on my head.

A 6 mile wide asteroid...

slams into the Earth.

The impact throws trillions of
tons of rock and dust into the ai

The rocks heat up as
they fall back to Earth..

Setting the planet on fir

That beach holiday suddenly
turns into absolute nightmare.

The impact also throws up soot,

chocking the atmosphere.

Now, the skies are blotted
out by all these materials,

so the sun is no longer
shining brightly on the surface.

Plants need sunlight
to photosynthesize

Without this vital
energy source,

many species die out.

With their food source gone

plant eating dinosaurs
starv to death,

followed by their predators

It was a huge disruption
to all of life on Earth.

The dinosaurs have been around
for 160 million years at this point.

That's astronomical
amount of time.

And in one event, they're gone.

Again the dice
ro is in our favor.

Most dinosaurs become extinc

paving the way for the
evolution of mammals...

leading eventually to humans.

Without the asteroid
impact we wouldn't be here.

As a furry primate on this planet,
I kinda like the K-Pg impact, right?

I'm here because of it.

We all are.

Some plants benefited
from the asteroid strike.

To learn out plants
changed after the impact,

Smithsonian scientist examined
thousands of tropical plant fossils

from the time of the die off

This disaster opened the way
for new types of plants to develop.

It transforme the
plant kingdom...

producing a richer and more
diverse global ecosystem.

Before the asteroid strike,

conifers and ferns dominate the
tropical forests of South America.

But afterwards, falling
ash from the impact

enriched the soil.

And fast growing
flowering plants took over.

The impact was very
hard to recover fro

but it actually
opened the opportunity

for a greater
diversity of plant life,

which ultimately has
benefited us as humans

because it has allowed us
to have more food sources.

This new world order
eventually gave rise

to the modern Amazon Rainforest,

home to 10% of
all species on Earth.

It really destroyed and
rema our entire environment.

The world grew back, of
course it did, here we are,

but it changed everything.

And another age may
be just around the corne

We should absolutely expect

that at some
point in the future,

and I'm not saying you
should lose sleep over it,

but at some point there will
be another mass extinction.

Maybe that will be
the end our days.

It's intriguing question is

what might come after
humans on planet Earth?

Catastrophe may b the
universe's recipe for li

throughout the cosmos...

one that every
planet must follow.

Looking at our own history,

life thrives on catastrophes

We need these disasters
for evolution to work.

So, hopefully, and I hate
saying this, I know how it sounds,

hopefully, these other plane
have had terrible disasters as well.

Think abo the word disaster.

It means bad star.

It means that something
has gone wrong,

something that's dangerous.

We are children of disasters

There's no way you get us
without planets colliding...

without asteroids and comets
streaming through the atmosphere...

without even stars
exploding and supernovas.

You are a child
of that violence.

That's part of the environment
that we grew up in in a cosmic way.

And I think that is
tremendously beautiful.