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Cosmos (1980): Season 1, Episode 5 - Blues for a Red Planet - full transcript

Carl Sagan looks at the search for life on Mars from the speculations of Percival Lowell and H.G. Wells to the arrival of the Viking probes.


The age and size of the cosmos

are written in light.

The nature of beauty and
the substance of the stars,

the laws of space and time...

they were there all along,

but we never saw them...

until we devised
a more powerful way of seeing.

The story of this awakening
has many beginnings

and no ending.

Its heroes come from many times
and places--

an Ancient Chinese philosopher,

a wizard who amazed the caliphs
of 11th-century Iraq,

a poor German orphan enslaved
to a harsh master.

Each one brought us
a little closer

to unlocking the secrets
hidden in light.

Most of their names
are forever lost to us,

but somewhere, long ago,
someone glanced up

to see light perform
one of its magic tricks.

Who knows?

Maybe that quirk of light

inspired the very first artist.

Where did all this come from?

How did we evolve
from small wandering bands

of hunters and gatherers living
beneath the stars

to become the builders
of a global civilization?

How did we get from there
to here?

There's no one answer.

Climate change,
the domestication of fire,

the invention of tools,
language, agriculture

all played a role.

Maybe there was
something else, too.

In China,
more than 2,000 years ago,

a philosopher named Mo Tze
is said to have observed

that light could be made
to paint a picture

inside a locked treasure room.

This was the description
of the first camera...

the camera obscura,

the prototype of all
image-forming cameras,

including the one that's
bringing you this picture.

Taking advantage of this funny
thing that light does

resulted in what could be
called the first movie.

Mo Tze, master of light, worked
against all forms of darkness.

A military genius

who only used his talents
to prevent violence,

he was legendary for traveling

among the kingdoms
of the warring states,

employing ingenious strategies

to talk kings out
of going to war.

He was one of the first
to dream of universal love

and an end to poverty
and other forms of inequality;

of government for the people...

and to argue against
blind obedience

to ritual and authority.

In his writings, you can find

early stirrings
of the scientific approach.

By Mo Tze's time, the Chinese
had already been recording

their thoughts in books
for at least a thousand years.

Still, our knowledge of him
is only fragmentary.

It consists largely
of the collection of essays

attributed to him
and his disciples.

In one of them,
entitled "Against Fate,"

a three-pronged test
for every doctrine is proposed.

Question its basis--

ask if it can be verified

by the sights and senses
of common people--

ask how it is to be applied

and if it will benefit
the greatest number.

Mo Tze was extremely popular,

but a few hundred years
after his death,

Qin Shi Huang,
the first emperor,

and unifier of China,
took power.

He took a continent
and turned it into a nation

that now bears his name... China.

Most of us know Emperor Qin
for the army of 7,000

terra cotta warriors
that guard his tomb.

In Emperor Qin's drive

to consolidate
his far-flung empire,

he took drastic measures

to standardize everything
within it.

This included mandating
a single coinage,

making uniform all weights
and measures,

the widths of carts and roads,
as well as the precise way

the Chinese language was
to be written,

including what you were
allowed to write and think.

Emperor Qin's philosophy--
the only one permitted--

was called "legalism,"

which is just what
it sounded like,

do as the law says... or else.

It's a philosophy that's
not highly conducive

to questioning authority.

...that all the books of
the hundred schools of thought

shall be be burned,

that anyone who uses history
to criticize the present

shall have his family executed.

The works of
MoTze and Confucius

and other philosophers
were destroyed

in the world's first
book burning.

Hundreds of scholars
bravely resisted

by trying to preserve
the forbidden books.

They were buried alive
in the capitol.

Science needs the light
of free expression to flourish.

It depends on the fearless
questioning of authority,

the open exchange of ideas.

Sparks of curiosity
in the writings of Mo Tze

and his disciples were
effectively stomped out.

It would be another thousand
years before the next movie.

Luckily, our Ship
of the Imagination

can take us anywhere
in space... and time.

The ancient Chinese
and Greeks observed

that light could be made

to do wonderful things--
but no one asked that question

favored by small children
and geniuses alike. Why?

Until a thousand years ago...

In the city of Basra, Iraq,

there lived
another master of light.

Ibn al-Hazen had a passionate
desire to understand nature.

He questioned everything,

especially those things that
everyone else took for granted.

"How do we see?" he asked.

Some of the great authorities
who came before him

had taught that rays come out
of our eyes and travel

to the objects we see
before returning to our eyes.

But al-Hazen reasoned that
the stars were too far distant

for something in our eyes
to travel all the way to them

and back in the blink
of an eye.

Excellent reasoning,
but al-Hazen didn't stop there.

He searched for ways to compel
nature to divulge her secrets.

His culture was open
to new ideas and questioning.

It was the golden age
of science

in the Islamic world.

One that stretched from Cordoba
in Spain

all the way to Samarkand
in Central Asia.

Christian and Jewish scholars
were honored guests

at the research institutes
of Baghdad, Cairo,

and other Islamic capitols.

Instead of burning books,
the caliphs sent emissaries

around the world
in search of books.

The caliphs lavishly funded
projects to translate, study,

and preserve them
for future generations.

Much of the light of Ancient
Greek science would have been

permanently extinguished
without their efforts.

The reawakening to science
that took place in Europe,

hundreds of years later,
was kindled by a flame

that had been long tended

by Islamic scholars
and scientists.

The Arabs also imported ideas
from India to the West,

including the so-called
Arabic numerals

that we all use today,

and the concept of zero...

which comes in handy

when you want to write
"billions and billions."

Arabic astronomy was
so influential,

that we still call most
of the bright stars

by their Arabic names.

And the "al's" in algebra,
algorithm, alchemy, and alcohol

are just some
of the traces left

from the time when Arabic
was the language of science.

In the 11th century,
Ibn al-Hazen set about trying

to test his ideas about light
and how we see.

So we devised an experiment
to determine how light moves.

We erected a tent
in full daylight

and sealed it tightly so that
only a single ray of light

could pierce its inner darkness.

With little more than his brains

and a straight
piece of wood-- a ruler--

al-Hazen had accomplished
a great leap forward

in the history of science.

He discovered that
light moves in straight lines.

But he was just getting started.

Al-Hazen figured out that
the key to forming any image--

whether you're talking about
an eye or camera obscura--

is a small opening to restrict
the light that can enter

an otherwise darkened chamber.

That aperture
excludes the chaos

of extraneous light rays
that surround us.

The smaller the aperture,

the fewer directions
that light can come from.

And that makes
the image sharper.

So instead of being blinded
by the light,

we can see everything
it has to show us.

Al-Hazen made his own
camera obscura

and dazzled the caliphs.

A camera obscura works best
in bright light.

The stars of the night sky
are way too dim for this.

We somehow need a bigger
opening to collect light,

but we also need
to maintain focus.

A telescope collects light

from any spot
in its field of view

across the entire lens
or mirror,

an opening much larger
than the camera obscura hole.

This is one
of the first telescopes...

the one that Galileo looked
through in 1609.

With it, he pulled aside
the heavy curtain of night

and began to discover
the cosmos.

The lens made it possible

for a telescope to have a much
larger light-collecting area

than our eyes have.

Big buckets catch more rain
than small ones.

Modern telescopes have larger
collecting areas,

highly sensitive detectors,

and they track the same object
for hours at a time

to accumulate as much
of its light as possible.

Space-based telescopes
such as the Hubble,

have captured light
from the most distant

and ancient galaxies,

giving us vastly clearer
pictures of the cosmos.

Al-Hazen discovered how images
are formed by light,

but that was far
from his greatest achievement.

Ibn al-Hazen was the first
person ever

to set down
the rules of science.

He created
an error-correcting mechanism,

a systematic and relentless way

to sift out misconceptions
in our thinking.

Finding truth is difficult...

and the road to it is rough.

As seekers after truth,

you will be wise to withhold
judgment and not simply put

your trust in the writings
of the ancients.

You must question and critically
examine those writings

from every side.

You must submit only
to argument and experiment

and not to the sayings
of any person.

For every human being
is vulnerable

to all kinds of imperfection.

As seekers after truth,

we must also suspect
and question

our own ideas as we perform
our investigations,

to avoid falling into prejudice
or careless thinking.

Take this course, and truth
will be revealed to you.

This is the method of science.

So powerful that it's carried
our robotic emissaries

to the edge of
the solar system and beyond.

It has doubled our lifespan,

made the lost worlds
of the past

come alive.

Science has enabled us
to predict events

in the distant future...

and to communicate with each
other at the speed of light,

as I am with you,
right at this moment.

This way of thinking
has given us powers

that al-Hazen himself
would have regarded as wizardry.

But it was he who put us
on this rough, endless road.

And now it has taken us
to a place

where even light itself
is enshrouded in darkness.

Light has properties unlike
anything else

in the realm
of human existence.

Take the speed of light.

The basic particle of light,
the photon,

is born traveling
at the speed of light

as it emerges from
an atom or a molecule.

A photon never knows
any other speed,

and we've not found another
phenomenon that accelerates

from zero to top speed
instantaneously.

Nothing else
could move as fast.

When we try to accelerate other
particles closer and closer

to the speed of light,
they resist more and more,

as though they're getting
heavier and heavier.

No experiment yet devised

has ever made a particle
move as fast as light.

What was that?

You hear something?

Where was I? Oh, yeah.

I don't know anything else
in life that behaves like light.

I cannot reconcile
its strange properties

with everything else
my senses tell me.

Our urge to trust
our senses overpowers

what our measuring devices
tell us about

the actual nature of reality.

Our senses work fine
for life-size objects

moving at mammal speeds,

but are ill-adapted for the
wonderland laws of lightspeed.

We don't even know why
there's a cosmic speed limit.

Time stands still when you're
traveling at the speed of light.

What is light, anyway?

Isaac Newton's enduring
fascination with light

began when he was a child...

in this very house.

By the time he was in his 20s,
Newton became the first person

to decipher the mystery
of the rainbow.

Newton discovered that some
light, or white light,

is a mixture of all the colors
of the rainbow.

Major discovery.

He named the displays of colors
a "spectrum"

from the Latin for "phantom"
or "apparition."

Begging your pardon,
Master Newton,

the cook frets that your dinner
will spoil, sir.

No, Isaac, don't
put the magnifying glass down!

Something even more amazing
is hidden in the light--

a code, a key to the cosmos.

Isaac Newton didn't miss much,
but that one was a beaut.

He just walked right past
the door to a hidden universe;

a door that would not swing open
again for another 150 years.

It would fall
on another scientist,

working in the year 1800,

to stumble
on a piece of evidence

for the unseen worlds
that surround us.

By night, William Herschel
scanned the heavens

with the largest telescope
of his time.

By day, Herschel performed
experiments.

From Newton's earlier work,
it was known that sunlight

is a blend of different colors.

And everyone knew,
just from being outside,

that sunlight carries heat.

William Herschel asked

whether some colors of light
carry more heat than others.

The nature of scientific genius
is to question

what the rest of us
take for granted...

and then do the experiment.

The thermometer that Herschel
placed outside the spectrum

was his control.

The control in any experiment

always lacks
the factor being tested.

That way, you know
if what you're testing is

really the thing responsible
for the observation.

In Herschel's experiment,

the relationship between

color and temperature
was being tested,

and so his control was
a thermometer

over the part
of the white sheet

that was not illuminated
by sunlight at all.

There's that sound again.

What is that?

Okay, red light is warmer
than blue light.

Interesting discovery,
but not exactly revolutionary.

No, there's nothing wrong
with your thermometer.

You've just discovered
a new kind of light.

Herschel was the first
to detect this unseen presence

lurking just below
the red end of the spectrum.

That's why it came
to be called "infrared."

"Infra" is Latin
for the word "below."

It's invisible.

Our eyes are not sensitive
to this kind of light,

but our skin is--
we feel it as heat.

Now, that's
a really big discovery.

But far greater secrets
were still hiding

deep inside the light.

At about the
same time that William Herschel

was discovering infrared light
in his parlor in England,

a young boy named
Joseph Fraunhofer

was trapped
in hopeless drudgery.

He stood over a cauldron
of toxic chemicals

and endlessly stirred.

Joseph had been orphaned
at the age of 11

and given to a harsh master
named Weichselberger,

the royal mirror-maker.

He prevented Joseph
from going to school.

Instead, Joseph labored in

the glass-making
workshop by day,

and tended to the master's
household chores by night.

Hurry up, stupid!

And remember, no reading.

Until Joseph got his big break.

Weichselberger's
house collapsed.

Maximilian, the future
king of Bavaria,

hurried to the scene
of the calamity

to see if he could help.

Maximilian was known for

taking an interest
in his subjects,

which was highly unusual
for its time.

In attracting the concern
of the future king of Bavaria,

young Joseph Fraunhofer

found an aperture into
a different universe.

And not just for himself.

Prince Maximilian
gave Joseph money

and asked his privy councilor

to provide further
help to the boy,

should it be needed.

Weichselberger continued
to exploit him

and prevent him
from attending school.

But the prince's councilor
intervened,

offering Joseph a position
at the Optical Institute.

This small gesture of kindness
really paid off.

By the time he was 27,

Joseph Fraunhofer was
the world's leading designer

of high-quality lenses,

telescopes and other
optical instruments.

His firm was housed here,
in the old Benediktbeuren Abbey.

In the early 19th century,

this was top-secret,
ultra-high technology.

The Benedictine monks
of earlier times

had taken a vow of secrecy.

This local tradition,

and the ability
to restrict access

to Fraunhofer's laboratory,

allowed him to maintain control

of trade and state secrets.

Fraunhofer was experimenting
with prisms

to find the best types of glass
for precision lenses.

How, he wondered,
could he get a better look

at the spectrum that
a prism produced?

Friedrich, bring me
the theodolite, please.

Okay, while Fraunhofer
sets up his theodolite--

it's a kind of telescope--

I want to show you something
in another part of the abbey.

Sound waves are
so beautiful to hear.

Imagine how beautiful
they'd be to see.

You ever wondered why organ
pipes have different lengths?

I press a key...

it sends compressed air

into a particular pipe,

producing sound waves.

If we could slow the sound waves
down a few hundred times,

they would look like this.

The length of the pipe

determines the length
of the sound wave

that can fit inside it.

A short pipe gives you
a short sound wave.

Short sounds waves have
high pitch, or frequency.

Let's stop the waves
for a better look.

The distance between
adjacent waves

is called the wavelength.

A long pipe gives you
a long sound wave

with a low pitch,
or low frequency.

The medieval manuscript of
this music, "Carmina Burana,"

was discovered
in this very abbey.

Sound waves can't travel
through a vacuum.

They need matter to ride on,

like molecules of air,
or water, or rock.

But light waves fly solo.

They can move
through empty space.

And fast--

a million times faster
than sound waves in air.

And the wavelengths
of the light we see

are so much shorter
than sound waves.

About 50,000 light waves

would fit right in here.

Oh, yeah.

Fraunhofer.

Just in time.

We didn't miss it.

Just as the wavelength of sound

determines the pitch
that we hear,

the wavelength of light

determines the color
that we see.

But how does a prism
spread out the colors

concealed in
a beam of sunlight?

When light travels
through air or space,

all its colors move
at the same speed.

But when it hits glass
at an angle,

the light slows down
and changes direction.

Inside the prism,

each color moves
at a different speed.

In glass, violet light,

which is carried by
the shortest waves we see,

slows down more than red light,

which has the longest waves.

These changes in speed

pry the colors apart,

sending their waves off

in slightly different
directions.

That's how a prism works.

If I seem unduly
emotional about this,

it's because Joseph Fraunhofer
is about to do

what Isaac Newton
could've done, but didn't.

And it'll have a powerful effect

on the course of my own life.

You are witnessing the marriage

of physics and astronomy,

the birth of my own
field of science,

astrophysics.

Written in the light,

in those vertical black lines...

is secret code.

Fraunhofer looked at them,
and wondered...

Why?

A code that comes to us

from an alien universe.

What is the message

written in these dark,
vertical lines?

It took a hundred years
of thinking,

questioning, searching
to decipher it.

Lovely, isn't it?

Why?

There are many layers to
the fine structure of beauty...

the chemistry of the Earth
and its atmosphere...

the evolution of life...

Many distinct threads.

Let's just examine one,
at the surface...

the colors of nature
that dazzle us.

What's really happening?

How does the red, the blue...

the astonishing palette
of nature's colors...

how do they happen?

Light waves of different lengths
from the Sun

strike the Earth.

The petals of these
particular flowers

absorb all the low-energy,

long red wavelengths of light.

But the petals reflect

the shorter, high-energy
blue wavelengths.

That interaction
between starlight and petal--

or water, or Van Gogh--

is what makes blue.

The longest waves,

the ones we see as red,

have the lowest energy.

Color is the way
our eyes perceive

how energetic light waves are.

A sunset...

a flag...

the eyes of your beloved...

that shiny new car.

The feelings they inspire

happen when something inside you

is triggered by
a particular variation

in the frequency and
energy of light waves.

And the secret message?

Those black vertical lines

in Fraunhofer's spectrum?

What makes them?

They occur when the light waves

of those particular colors
are being absorbed.

It happens on another level
of reality,

far smaller than the world
we're used to operating in.

To get there,
we'll need to become

ten billion times smaller
than we are.

We could pick
any one of these atoms.

But let's go
for the hydrogen atom.

The hydrogen atom is
the most plentiful kind

of atom in the cosmos.

And the simplest.

It has only one electron.

And only one proton.

We've entered
the quantum realm.

It doesn't correspond

to ordinary human experience.

Common sense is
no help here at all.

Take the hydrogen atom's
electron, for example.

In an atom, an electron

doesn't exist between orbitals.

It disappears from one orbital

and reappears in another.

It's as if you took an elevator
from the second floor

to the fourth floor,
but ceased to exist in between.

And another thing.

Quantum elevators only stop
at certain floors.

The sizes of the electron
orbits are strictly limited,

and different
for the atoms of every element.

That's why the elements
are different.

The chemistry
of anything is determined

by its electron orbits.

The force that holds
an electron in orbit

has nothing to do with gravity.

It's a force
of electrical attraction.

The electron dances a wavy ring

around the central nucleus
of a hydrogen atom.

And makes quantum leaps
from orbit to orbit.

Up or down.

The larger the orbit,

the greater the energy
of an electron.

An electron has

to get energy to leap
to a larger orbit.

And it has to lose energy
to jump back down.

Every upward leap
is caused by...

an atom absorbing a light wave.

But we have no idea what causes
the downward leaps.

What we do know that such leaps
always produce a light wave

whose color matches
the energy difference

between the orbitals.

The Sun's surface radiates
light waves of all colors.

If you look at sunlight
through a prism,

you'll see its spectrum.

When you magnify the spectrum
with a telescope,

as Joseph Fraunhofer did,

you raise the curtain

on the electron dance
within the atom.

When the energy
of the electron flags,

and it drops
to a lower orbital,

the light wave
it emits scatters.

Most of it doesn't reach us.

That leaves a dark gap

or black vertical line
in the spectrum.

These dark lines
are the shadows

cast by hydrogen atoms

in the atmosphere of the Sun.

Sodium atoms cast
different shadows.

Their electrons dance
to a different tune.

A grain of table salt
is composed

of sodium and chlorine atoms.

Ten million billion of them

doing their crazy dances

in a single grain of salt.

And a single iron atom
with 26 electrons

is like a great
big production number

in a Broadway musical.

When you look at a star
with a spectroscope,

you see the dark lines
from all the elements

in its atmosphere.

Show me the spectrum
of anything,

whether here on Earth
or from a distant star,

and I'll tell you
what it's made of.

Fraunhofer's lines are
the atomic signatures

of the elements writ large
across the cosmos.

As with every
other major revelation

in the history of science,
it opened the way

to newer and deeper mysteries.

And to the revelation
that there were

many more secrets
hiding in the light.

When Joseph Fraunhofer combined
a prism with a telescope

and turned it toward the skies,

he brought the stars
much closer to us.

When he was only 39,

he contracted a fatal illness.

Perhaps as a result of his
early and long-term exposure

to the toxic chemicals
of glassmaking.

You never know where
the next genius will come from.

How many of them do we leave
in the rubble?

The prince and his kingdom
were immeasurably enriched

by that act of kindness
to a poor orphan.

Fraunhofer's discoveries
transformed Bavaria

from a rural backwater
to a technological powerhouse.

As he lay dying,
the government was desperate

to preserve every shred
of his precious knowledge

about the high technology
of optical glass.

But it could only be divulged
to a person

with top security clearance--

the director of the mint.

The government kept
Fraunhofer's technology

for making perfect
optical glass

a State secret
for another hundred years.

This would prove
to be a major obstacle

for someone we'll meet later
in our journey.

But Fraunhofer would allow
no such secrecy

where his pure scientific
research was concerned.

He knew that science requires
openness to flourish;

that our understanding of nature
belongs to the world.

As soon as Fraunhofer discovered
the spectral lines,

he published everything
he knew about them.

And the reverberations
of his momentous discovery

echo still.

His spectral lines revealed
that the visible cosmos

is all made
of the same elements.

The planets...

The stars...

The galaxies...

We, ourselves,
and all of life...

The same star stuff.

He made it possible
for us to know

what's in the atmosphere
of other worlds.

And in galaxies millions
of light-years away.

Spectral lines revealed
not only the composition

of far-off objects,
but also their motion

towards or away from us.

Using them, we discovered
that our universe is expanding.

But perhaps the greatest
revelation of spectroscopy

is the discovery
of the thing it cannot see.

A hidden universe
of dark matter

six times more massive
than the familiar cosmos.

It's made
of some mysterious substance

that does not emit, reflect
or absorb any kind of light.

We only know it's there
because of its gravity,

which pulls on all the galaxies

and speeds up
the visible stars within them.

There are many more kinds of
light than our eyes can see.

Confining our perception
of nature to visible light

is like listening to music

in only one octave.

There are so many more.

They differ only in wavelength,

but over a huge range.

For instance, infrared light...

the kind that
William Herschel discovered

Or X-ray light.

Or radio light.

Or in gamma-ray light.

These are not just different
ways of seeing the same thing.

These other kinds of light

reveal different objects
and phenomena in the cosmos.

In gamma-ray light, for example,
we can see mysterious explosions

in distant galaxies

that we would otherwise miss.

And in microwave light,
we can see all the way back

to the birth of the universe.

We have only
just opened our eyes.