All language subtitles for How the Universe Works s04e02 Earth Venuss Evil Twin.eng

Narrator:
Our galaxy, far in the future.

A planet shrouded
in turbulence, dense clouds.

Buried deep below,

an alien landscape,

extreme pressures,
and a scorched surface

with sky-high temperatures.

But this is not some
distant extraterrestrial world.

It's Earth's future,
maybe a billion years from now.

We know this
because Earth has a twin...

Venus.

And Venus has already
descended into hell.

Captions by vitac
www.Vitac.Com

captions paid for by
discovery communications

take a look
around the solar system...

Eight planets orbiting
a central star, the Sun.

Among them is Earth
and its neighbor, Venus.

Earth, our home,
is an oasis for life.

And Venus,
that's the stuff of nightmares.

Plait: Venus and Earth
couldn't be more different.

The Earth is
this beautiful planet,

and there's water everywhere.

It's ice at the poles.
It's water in the ocean.

It's in the atmosphere
as water vapor.

But then you look at Venus.

It is the worst place
imaginable.

It is so hot on the surface,
crushing pressures.

It couldn't be
any less supportive of life.

Thaller:
To me, the planet Venus

is sort of a classic definition
of the word hell.

If you were to transport
to Venus

and experience
the environment there,

you'd quickly want
to return back to Earth.

Narrator:
The conditions on Venus

are among the most inhospitable
in the solar system.

It's just a horrible place.

It's so hot,
and there's no water,

and the atmosphere is so thick.

And it rains sulfuric acid.

It's going to be a competition
between whether or not

you're gonna be cooked to death
or crushed to death.

Narrator: Earth and Venus may
seem like very different worlds,

but they shouldn't.

They're roughly
the same size, same mass

and made from the same stuff,
and they started out as twins.

Early Venus and early Earth
were very similar.

They were twins,

probably nearly identical twins,
at their earliest stages.

Given that Venus is
so Earth-like in so many ways,

it's really odd that it is
so different than the Earth.

And this makes it
one of the biggest mysteries

in the solar system.

Somewhere
in their two histories,

the Earth and Venus
took two very different paths.

Narrator: The result?

Two totally different worlds.

Their paths were so different,
you could hardly believe

that one would have been related
to the other.

But now, the opposite thing's
going to happen.

We're gonna catch up
with our twin.

We're gonna evolve to be a lot
more like Venus in the future.

Narrator: In the future,

the two planets' paths
will converge,

and they will become twin-like
once again.

There is going to be
hell on Earth.

The oceans will vaporize.
The land will melt.

Our hospitable blue planet
will vanish,

replaced by
a fiery, molten world.

We are actually on the Earth
at a time

when there's water and rain,

and it was so easy
for life to take hold.

But that's gonna change.

And take a look in at Venus
and have a look at our future.

Narrator: And Earth will surpass
the horrors of Venus.

A billion years from now,

Earth could be
an unimaginably terrible place.

Narrator:
How will this happen?

The roots of
our home world's destruction

are buried deep
in the past of our twin planet.

It's very much true that,
in studying the past of Venus,

we are also studying
the distant future of Earth.

Narrator: Both planets share
a violent birth,

scarred by brutal
planet formation,

giant cosmic impacts,
and rampant volcanism.

Grinspoon: We're trying
to reconstruct things

that happened
in the ancient, ancient past.

It's almost like
forensic planetary geology.

Narrator: 4.6 billion years ago,
hundreds of infant planets

begin to form
around the new sun.

Among them,
the baby Venus and Earth.

And as they hurtle
around the Sun...

Collisions are inevitable.

Planet formation
is like a demolition derby.

In a derby, the cars are racing
around a track,

going around in circles
at different speeds.

Well, it's the same thing
with planets.

The material
is orbiting the Sun.

It's going around, and they're
all going at different speeds,

at different angels,
different trajectories.

And sometimes, boom.

Narrator: In this derby,
planet hits planet.

Two become one.

Violently.

You have these large bodies
that are hitting each other

at really high velocity.

It's really a very hot,
violent mess.

Plait:
The amount of energy released

in these impacts is huge.

It completely dwarfs

all of the nuclear weapons
on Earth combined.

And yet, somehow,
on these scales,

you wind up forming gigantic
objects that we call planets.

Narrator: Earth and Venus
become voracious planet eaters.

But two spectacular collisions
will set the twins

on very different paths.

Grinspoon: That was the moment
Venus and Earth went through

this divergence
to what has now become

these really
dramatically different worlds.

Narrator:
The divergence begins

when a Mars-sized object
hits Earth.

The impact makes our planet
spin faster.

The core spins with it,
generating

a powerful magnetic field
around the planet.

[ Humming ]

The field fends off the worst
of the Sun's radiation.

Around the same time,

Venus takes a head-on hit
from another infant planet.

This impact explains something
very weird about Venus.

Oluseyi:
Venus is actually rotating

in the wrong direction.

How could that be?

Well, what if it got hit
really hard by some object?

That could do it.

Narrator: An object so huge,

Venus stops in its tracks
and begins to spin backwards.

If you think about
how much energy

and what size you need
to change a planet's spin,

that is an incredibly large hit.

Narrator:
But the backspin is slow,

243 times slower than Earth.

Without a fast spin,

Venus' core can't generate
a strong magnetic field.

It has no protection
from the deadly stream

of particles blasted
from the Sun.

Venus does not have
a strong magnetic field.

And so it has suffered
the full brunt

of this wind
blasted out from the Sun.

Narrator:
The tale of two planets

now splits radically.

Venus will roast

under a violent, suffocating
atmosphere.

Earth will give birth
to oceans,

life, and intelligence.

But ultimately,
these twins' fates

are one and the same.

Earth's future is Venus...

Pure hell.

Narrator:
Venus is a vision of hell.

And one day,
we'll meet our twin's fate.

It turns out
that what Venus went through

in its distant past is what
Earth is going to go through

in its distant future.

Narrator: So, exactly how
will our blue planet

become a superheated wasteland?

Only Venus can really tell us.

Something happened to Venus
long in its past

to make it
a completely different planet

with a completely
different personality

than the Earth
as we know it today.

Man: Two, three, four.

Narrator: We Earthlings
sent our first probe

to our sister planet in 1967.

And we've been sending them
ever since.

What they found
blew scientists' minds...

Rocks that look like granite.

What makes that interesting
is that, to make granite,

you need water.

That means that there
must have been abundant water

for it to have formed
in the first place.

Narrator: Abundant water
on a scorched Venus?

Hard to imagine.

But Dr. Lewis dartnell
thinks you can get a glimpse

of a wet Venus
here in Iceland.

There's the possibility

that, maybe,
in the early solar system,

there were not one
but two planets with oceans,

two water worlds...
Earth and Venus.

And if Venus did
once have oceans,

maybe they would've looked
a lot like this here,

with a raw, volcanic landscape

descending down into the ocean

with the waves
lapping against the coastline,

and maybe a overcast
and a misty, hazy atmosphere,

not unlike
what we are seeing here today.

Narrator: But Venus
couldn't hold on to its water.

Plait:
All of that water is gone.

It's just gone.
Where did it go?

Something happened, either
catastrophically or over time,

to basically dry out
this twin of the Earth.

Narrator:
The culprit was the young sun.

Since its birth,
it's grown stronger.

Krauss: Our sun, when we look
out at it during the day,

seems the same today
as it was yesterday.

But that's on
a human time scale.

On cosmic time scale,

the Sun has been getting
hotter and hotter.

Narrator: Every billion years,
the Sun gets 10% hotter,

slowly turning up
the temperature on Venus.

Not only that,

Venus formed 26 million miles
closer to our star.

As it turns out, that distance
to the Sun was critical.

It's just
an unfortunate circumstance

of being in the wrong place
at the wrong time.

Narrator: Earth is far enough
from the Sun

to hold on to its water.

But Venus can't take the heat.

Grinspoon: The intensity
of its sunlight got sort of

just a little bit too much.

It passed this threshold
where Venus

couldn't hold its water
on the surface anymore.

Narrator:
As temperatures rise,

the oceans start to evaporate.

Plait:
All of that water in the oceans,

all of those millions
of cubic miles of water,

would become water vapor,

basically steam clouds
covering the entire planet,

hiding the surface
from the outside.

Narrator:
Water vapor is a greenhouse gas.

The clouds covering Venus
trap the Sun's heat.

Temperatures on the surface
rise.

But the process
can't go on forever

because the clouds
of water vapor in the atmosphere

start to disappear,

ripped away by the solar wind.

Venus does not have
a strong magnetic field.

And so the full brunt
of the solar wind

has been slamming into Venus
for billions of years.

Over time, if a water molecule
was in the upper part

of Venus' atmosphere,

light from the Sun
could break it apart

into oxygen and hydrogen.

And then the solar wind
could blow that stuff away.

Plait: Over billions of years,

this torrent
of subatomic particles

blasted out from the Sun

has stripped the water
out of the atmosphere of Venus

and has desiccated it.

Narrator: Our twin,
stripped of its oceans,

is a terrifying vision
of our own future.

Lanza:
So, if Venus were, in the past,

a lot more Earth-like,

then that tells us
that having a habitable world

is something
that is actually very precious

and maybe is transient.

It's not something
that lasts forever.

Narrator:
But that is just the beginning.

Without its water vapor
to trap heat,

the temperature
stops rising temporarily.

Soon, a new force

will send surface temperatures
rocketing again.

It will become so hot,

metal snow will fall.

Narrator:
Four billion years ago,

Venus and Earth were twins
with oceans.

But soon,
the two planets' paths diverged.

Plait: It's pretty amazing
how different things

must have looked a billion years
after the solar system formed.

The Earth was covered in water,

basically on the path
towards life

and a future as we see it today.

Venus was on a path
away from life,

on a path toward becoming
the hellhole that it is now.

Narrator: The growing sun
burned off Venus' oceans,

for Earth, a terrible omen.

Thaller:
On the planet Venus,

we think there could have been
oceans, lakes, water, and rain.

But all of that came to an end.

That tells you that the Earth's
environment has to change, too.

Nothing is forever.

Plait:
A few billion years ago,

when you looked
in our solar system,

you might have seen two Earths.

Well, a few billion years
from now, in the future,

you might look at
our solar system

and see two venuses.

Narrator: So we can look to
Venus' past and see our future.

We know
that temperatures skyrocketed,

and the scarred surface
hints at why.

In Hawaii, planetary geologist
jani radebaugh

studies the islands' volcanoes.

These volcanoes are
a perfect model for early Venus.

What we're seeing out here
are lava flows

encroaching on
the town of pahoa,

come all the way down
from the pu'u 'o'o vent

which is about 15 miles away.

Oh, there's hot.
You can see that hot stuff.

You can see hot.
Quick, quick, quick, quick.

Right there.

It's really beautiful.

Narrator:
Hawaii's volcanic lava fields

look like Venus in miniature.

Both produce
the same kind of runny lava,

building flat,
shield-like volcanoes.

The big difference

is there are only
five active volcanoes on Hawaii.

Venus is covered in them.

Grinspoon: One thing that really
jumps out all around the planet

is the number and variety
of volcanoes.

I mean, Venus could almost be
nicknamed "volcano world."

Venus has tens of thousands of
volcanoes all over the planet.

Narrator:
But it's not the erupting lava

that turns up the heat.

It's what comes out with it.

Radebaugh: When you think back
to the histories of Venus,

I think we must have seen
a landscape

very similar to this one,

where you have
massive amounts of lava

flowing out of the surface,

dumping huge amounts of gases
into the atmosphere,

carbon dioxide, tons of the gas
into the atmosphere

every single day.

It would have been amazing
to see.

Narrator:
Up close on the surface,

jani can see
the origin of the gases.

Radebaugh:
If we look behind us,

we can see volcanic gases
gushing out of steam vents.

We've got carbon dioxide being
delivered to the atmosphere.

It's exactly like
what has happened on Venus.

Carbon dioxide has been
delivered out of volcanoes

over and over and over again
throughout its history

so that now we have

just a tremendously thick,
dense atmosphere.

The net result
of all of these volcanic gases

pouring out of volcanoes,
major greenhouse gases,

is that they have been
absorbing heat

for billions of years
of the history of Venus.

The temperature
has been gradually creeping up

until, today, the surface
of Venus is 900 degrees.

Plait: It's like if you go
into your kitchen

and set your oven to broil,

wait a couple of minutes
and stick your head in it,

and even that's
not quite hot enough.

It's a crazy, horrible,
hellish spot.

Narrator: It's hard to imagine
such extreme temperatures.

But probes orbiting the planet

revealed just how insanely hot
it is.

Scientists studying the images

noticed something strange
on the planet's mountains.

It looks like, on the mountains,

that there's apparently
snow-like structures.

Narrator: But this is not like

any snow found on Earth.

So, if you look at the
white-peaked mountains of Venus,

you would think
that it was snow,

but it's actually metals
that have rained down

and deposited
on the top of those mountains.

Narrator: Metals like
bismuth and lead melt.

Then they evaporate
into the atmosphere.

As they rise, they cool

until they finally fall
like snow on the mountaintops.

I'm not sure
even the imagination

of science-fiction authors
would have come up

with something
as weird as Venus.

I mean, just think about that.

You have possibly metal frost
on the top of mountains.

I mean, how weird is that?

It's pretty insane.
Raining metals.

Where would you ever think
about that existing?

On Venus.

Narrator: In the future,

metallic snow
is forecast for Earth, too.

And our scorching mountain caps

will glitter like Venus.

But Venus tells us

that things will get even worse.

The atmosphere will grow
heavy enough to crush cars.

Narrator: Earth and Venus
were born twins,

but they took different paths.

Earth slowly evolved
into a habitable world.

Venus was covered
in thick volcanic gases,

trapping the Sun's heat.

Temperatures rose
to 900 degrees.

Extreme temperatures

weren't the only problem
on Venus' surface.

The thick clouds of gas
kept on building up.

A 155-mile-deep
layer of carbon dioxide

piles up around the planet.

We don't think about gases
as weighing anything,

but they actually do.

Narrator:
Trillions and trillions of tons

of gas press downwards.

There is simply
so much air on Venus

that, on the surface,
it's pushing down

with a huge amount of force.

Well, atmospheric pressure
on Venus is a monster.

Think about it this way.

All right, car.

It's time
for you to be crushed, baby.

If you're on Venus,
you're gonna have

155 miles of atmosphere
above your head.

As a result,

atmospheric pressure
is 90 times that on Earth.

So, on Earth, there's about
14.6 pounds per square inch.

On Venus, we're talking about
1,300 pounds per square inch.

So, if you're driving your car
on Venus,

this is what might happen.

Narrator: The crusher delivers
the same force

as the weight
of Venus' atmosphere.

This is pretty serious stuff.

And this is why
it's so hard on Venus.

You get down to the surface,

you have the crushing atmosphere
to deal with.

Narrator:
The extreme pressure and heat

make Venus
nearly impossible to explore.

Only one nation has ever gotten
a probe to the planet's surface.

Truly, one of the engineering
triumphs of the human race

was the Soviet union's
venera program.

The Russians sent over a dozen
probes to the planet Venus.

And only a few of them
were able to survive long enough

to even be able to take pictures
from the surface.

Lanza: The venera missions
were incredible.

It's such a hostile environment
on the surface for electronics.

And they were able to land
on the surface and survive.

Narrator: The probe
that sent back these images

was crushed and burnt out
in 90 minutes.

Some day in the future,

there are going to be
interplanetary tour guides

taking people to every planet
in the solar system.

And you can imagine going
to saturn and seeing the rings

and Jupiter
and it's panoply of moons.

There are all
these great tourist attractions

in the solar system.

At the very bottom of that list
is Venus.

That is the last place
in the solar system

I would ever want to visit.

Narrator: The sun's heat
and volcanic gases

have transformed Venus
into a nightmarish world.

So, why hasn't Earth
followed the same path?

Our volcanoes
also spew out carbon dioxide.

And we orbit around
the same sun.

We're not being
crushed and broiled.

That's because Earth formed
farther away from the Sun,

staying cool enough
to hold on to its oceans.

Grinspoon: Oceans do
a lot of things for us on Earth

because not only, obviously,
are we water creatures,

and we depend on the water cycle
for our existence

in so many ways,

but people don't realize
the oceans also help

to regulate
the climate of Earth.

Narrator: Our oceans
are full of tiny creatures

that eat carbon dioxide.

Richard zeebe
from the university of Hawaii

is diving on
the island's coral reefs.

He's studying
how tiny marine organisms

turn carbon dioxide into rock.

Zeebe: What you see here
as this white stuff,

this is what we call
calcium carbonate.

And on top of this, where
you see these brown layers,

this is essentially
the living organism.

This is the coral itself.

It takes calcium
out of the seawater

and takes carbonate
out of the seawater,

combines them and makes
this piece of calcium carbonate.

Narrator: There's over
70 million billion tons

of carbon
locked up in carbonate rocks.

This helps regulate
carbon dioxide levels

in the atmosphere, keeping
temperatures from rising.

If all the carbon that is being
locked up in carbonate rocks

in these corals would be
put into the atmosphere as co2,

that would be
certainly bad news for us.

Narrator:
Currently, our carbon cycle

helps stabilize our climate.

But in the future,
this won't be able to save us.

Forces far greater
than the ones at work on Earth

will overpower our systems.

Like Venus,
our oceans will burn off.

Temperatures will rocket

as our live-giving sun
becomes a monster.

Narrator:
Venus' hellish landscape

is a glimpse
into Earth's future.

Thaller:
There will be no more rain.

There will be no more oceans.

This wonderful, life-friendly
environment we enjoy now

just won't be here in some
hundreds of millions of years.

Plait: Earth could be
an unimaginably terrible place.

Narrator: Right now,

we live just the right distance
from the Sun,

where it's just
the right temperature

for water to exist as a liquid.

But that's going to change,
just as it did for Venus.

Grinspoon: Venus started off,
probably, in the habitable zone.

And then the inner limit
of the habitable zone crossed

the distance of Venus' orbit.

Well, it's gonna cross the
distance of Earth's orbit, too.

There is an expiration date
to the Earth.

And that's due
to the Sun's evolution.

Narrator: Ever since its birth,
the Sun has been getting hotter.

That increased heat
devastated Venus.

And, in the future,
it will destroy Earth.

In 1.1 billion years,

the Sun is 10% hotter
than it is today.

The oceans start to evaporate
into thick clouds,

which trap
more of the Sun's heat.

Catastrophically, very rapidly
on a geological time scale,

the oceans will put so much
water vapor into the atmosphere

that we will get
a runaway greenhouse effect.

[ Thunder rumbles ]

Narrator: The clouds
forming in the atmosphere

trap more and more heat,

driving temperatures
even higher.

Spiraling temperatures
cause more evaporation,

so the clouds get thicker.

Which led to more heating,
which led to more evaporation.

And you can see
where this is going.

It's a vicious cycle.
It's a positive feedback.

Plait: All of the ocean's water
will boil away,

millions of cubic miles of it.

We have all of this water that
will go into the atmosphere,

covering the Earth and shrouding
it in, basically, steam.

Narrator: Earth has had oceans
for billions of years,

but it could lose them
in just 10,000.

Krauss: All of the water
in the Earth's oceans

will be in the atmosphere.

We'll have an incredibly dense
cloud cover system

where the temperatures on Earth

will be approaching
1,000 degrees.

Narrator:
Like Venus in the past,

Earth will get
hotter and hotter.

But unlike Venus,
which topped out at 900 degrees,

temperatures on Earth
will keep climbing.

Venus lost its water to space,
blasted away by the solar wind.

But Earth holds on to its water.

It's protected
by our magnetic shield.

But that is no longer
a good thing.

[ Humming ]

Unlike Venus, Earth has
a strong magnetic field

which protects it from
the erosion of the solar wind.

That water will stay with us.

The Earth could have a thicker,
hotter greenhouse atmosphere

than Venus does today,
much worse.

[ Thunder rumbles ]

Narrator: This huge volume
of water vapor

all pushes down on the surface,

around 4,000 pounds.

That's the weight
of the average American car

pressing down
on every square inch of Earth.

Surface pressure
goes through the roof,

reaching 270 times higher
than today.

It is ironic to think
that the water on Earth

will one day help contribute
to its demise

after all the water has been
the source of life on Earth.

But, in the far future,
it'll become our enemy.

Narrator: And with no oceans
and their microscopic creatures

to absorb the carbon dioxide,

there's no way back
for the Earth.

In 1.2 billion years,

a probe visiting Earth
would see an alien world,

a scorched, barren landscape.

The pressure is crushing.

Temperatures reach
1,200 degrees.

Molten metals
snow down on the mountaintops.

It's so hot, granite rock melts.

The surface liquefies.

At that point, the Earth
will become a molten ball

very similar to what it was
at the very beginning.

Narrator: Earth and Venus
started as twins.

Venus was destroyed
by rampant global warming.

Earth will follow the same path,
then overtake it.

It is inevitable
that the Earth will someday

not only be like Venus,
but actually put it to shame.

Narrator: In 1.3 billion years,
Earth could hit 3,600 degrees,

four times hotter than Venus.

It will be
the hottest and deadliest planet

in our solar system.

For Earth and its inhabitants,
it's the end of the road.

We could never survive
the extreme temperatures

or the crushing pressure.

Maybe we'll escape to space.

But there's one absolutely
crazy way we could stay here...

Move our planet
further away from the Sun.

Narrator: Earth of the future
will become

the most inhospitable planet
in the solar system.

Its oceans will boil off,
and its surface will melt.

A billion years from now,

Earth could be
an unimaginably terrible place.

Right now, today,
Venus is the evil twin of Earth.

But in the distance future,

Earth could be
the evil twin of Venus.

Narrator:
Earth's surface temperatures

will reach 3,600 degrees

with pressures 270 times greater
than today.

Plait:
At these kind of temperatures,

where rock on the surface
of the Earth is molten,

it's hard to imagine
any place there could be life.

Narrator: But there is hope.

Astrobiologist
Lewis dartnell thinks

that some forms of life
could survive

such terrible conditions.

We're here on top of
a volcanic outcrop in Iceland

with this howling Gale
whistling past our ears,

the stench of hydrogen sulfide,
of sulfurous fumes,

filling our nostrils.

And this is about as close
as you get can on Earth

to high up
in the venusian atmosphere.

About 30, 35 miles above
the surface of the planet Venus,

the air pressure
is about the same

as on the Earth's surface.

The temperature
is pretty similar, as well.

But the cloud droplets are full
of concentrated sulfuric acid,

many, many times more
concentrated than battery acid.

It's a hostile,
horrible environment.

But bizarrely enough,

there's good reasons
to think that there may be life,

venusian life,
high up in the clouds

that are kind of
high-altitude aerial biosphere.

Narrator: High above Venus,
there are nutrients,

solar energy,
and traces of water.

If life can live up there,
then perhaps it might survive

high up in the clouds
of future Earth.

You can easily imagine these
micro-organisms evaporating

in water particles
and being transported

to the upper atmosphere.

Even though it turned into
this toxic greenhouse planet,

life could potentially
still survive

in that upper atmosphere.

Narrator: But what about us?

We couldn't survive
the high temperatures

or pressures at the surface.

And a life in the clouds
doesn't seem likely.

What's our future?

Oluseyi:
If there was this life on Venus,

clearly,
they weren't advanced enough

to stop the changes
in their atmosphere

that led
to Venus' current state.

The question is, are we?

Narrator:
Maybe we'll leave our planet

and find a new home.

But there is
a more outlandish solution...

Stay on Earth and move it
farther from the Sun.

Moving the Earth is at least
imaginable because, in fact,

as objects exchange
gravitational energy,

they move in or out
in the solar system.

It's happened to our planet.

So I could imagine
engineering things

where we directed
large asteroids and comets

close to the Earth,
but not to hit it.

Narrator: The gravity
from these large objects

would slowly alter our orbit.

Krauss: Gravitational energy
would be exchanged,

and the Earth could slowly
move out.

Narrator:
Each gravitational jolt

would only move Earth
a short distance.

But do it thousands
or millions of times,

and we could push the Earth
away from the Sun,

in theory, at least.

Over a billion-year period,
it's possible to imagine.

It would require
incredible technology

and incredible coordination.

The technology is possible.

Whether humanity as a species
could ever coordinate it

is something I'm a little more
skeptical about.

Narrator: It's a crazy option,
but if we don't do something,

Earth and all of us will die,

and we'll become
just like Venus.

Earth and Venus
were probably born together

as identical twins,
but then their paths diverged.

But now, lifetime is gonna send
that cycle all the way back,

and they'll die
as identical twins again.

Narrator:
In the grand scheme of things,

they'll just be
two charred twins

spinning to oblivion in
a backwater of the universe.

On the cosmic scale,
life is short.

When you look at how Earth
evolved and how Venus evolved,

you can see the difference,

even though
it's two almost twin planets,

how life and habitability
could change over time.

So, habitability
isn't always a permanent thing.

Krauss: On human scales,

the universe seems the same
every single day.

But, of course,

that's because human life
and human civilization

is but a brief instant
in cosmic time.

On cosmic scales, the universe
evolves and changes,

and that makes the history
of the universe remarkable.

Narrator: Our tale of two
planets converges in the end,

a cautionary tale
about forces beyond our control.

Maybe a billion years
of learning from Venus

will ultimately save us
from the same terrible fate.

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