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Cosmos (1980): Season 1, Episode 11 - The Persistence of Memory - full transcript

Carl Sagan examines life on earth discussing genes, DNA, the brain, and human social development.


SAGAN: The surface of the Earth is
far more beautiful...

...and far more intricate
than any lifeless world.

Our planet is graced by life.

And one quality that sets life
apart is its complexity...

...slowly evolved through
4 billion years of natural selection.

You can describe in detail...

...how a rock is put together
in a single paragraph.

But to describe
the basic structure of a tree...

...or a blade of grass
or even a one-celled animal...

...you'd need many volumes.

It takes a great deal
of information to make...

...or even to characterize
a living thing.

The measuring rod,
the unit of information...

...is something called the bit.

It's an answer, either yes or no...

...to one unambiguously
phrased question.

So to specify whether
a light switch is on or off...

...requires only a single bit.

To specify something of greater
complexity requires more bits.

There's a popular game
called 20 Questions...

...which shows that a great deal
can be specified in only 20 bits.

For example...

...I have something in my hand.

What is it?

Is it alive? Yes.

One bit.

Is it an animal? Nope.

Two bits.

Is it big enough to see? Yep.

Does it grow on the land? Yes.

Is it a cultivated plant? Nope.

Well, with only five bits...

...we've made substantial progress
to figuring out what it is.

With 20 skillfully chosen questions...

...we could easily whittle
all the cosmos down...

...to a dandelion.

(BLOWS DANDELION)

In our explorations of the cosmos...

...the first step is to ask
the right questions.

Then, not with 20 questions,
but with billions...

...we slowly distill from
the complexity of the universe...

...its underlying order.

This game has a serious purpose.

Its name is science.

Out here in the great cosmic dark...

...there are countless
stars and planets...

...some far older than
our solar system.

Though we cannot be certain, the same
processes which led on Earth...

...to the origin of life
and intelligence...

...should've been operating
throughout the cosmos.

There may be a million worlds
in the Milky Way galaxy alone...

...which are at this moment...

...inhabited by other
intelligent beings.

What a wonder, what a joy
it would be...

...to know something
about non-human intelligence.

And we can.

Here is an exotic inhabited world...

...mostly covered with a liquid.

We seek the dominant intelligence...

...that lives beneath
its fluid surface.

This ocean of liquid water
kilometers deep...

...is teeming with strange
forms of life.

There are communities
of transparent beings.

There are societies of creatures
which communicate...

...by changing the patterns
on their bodies.

There are beings that give
off their own light.

There are hungry flowers
that devour passersby...

...gesticulating trees.

All manner of creatures
that seem to violate...

...the boundaries between
plants and animals.

There are beings that flutter
through the ocean like...

...waltzing orchids.

These are a few of the species...

...that inhabit the water world
called Earth.

They're packed with information.

Each one has
a rich behavioral repertoire...

...to ensure its own survival.

But the grandest creatures
on the planet...

...the intelligent and graceful
masters of the deep ocean...

...are the great whales.

They are the largest animals
ever to evolve on Earth...

...larger, by far,
than the dinosaurs.

Their ancestors were meat-eating
mammals who migrated...

...70 million years ago in slow steps
from the land into the waters.

Whales, like these humpbacks,
are still mammals.

We humans have much
in common with them.

Mothers suckle infants...

...there's a long childhood
when adults teach the young...

...and there's a lot of play.
These are mammalian characteristics.

Vital if an animal is to learn.

But the sea is murky.

The senses of sight and smell...

...which work well for
mammals on the land...

...are not much use here.

So the whales evolved
an extraordinary ability...

...to communicate by sound.

For tens of millions of years,
the whales had no natural enemies.

And then, a new and alien
and deadly creature...

...suddenly appeared on the placid
surface of the ocean.

(WHALES SINGING)

These often noisy and occasionally
deadly objects...

...first appeared in large numbers
only a few centuries ago.

They are artifacts...

...manufactured by land creatures...

...whose ancestors last lived
in the oceans...

...350 million years ago.

(BELL RINGS)

This particular one, however...

...is on a mission of understanding.

It's called the Regina Maris...

...the "Queen of the Sea."

And one of its jobs is to record
the sounds of the whales.

Some whale sounds are called songs...

...but we really don't know what
their contents are.

They range in frequency...

...over a broadband of sounds...

...down to frequencies well below...

...the lowest sounds the human ear
can make out.

A typical whale song lasts
maybe 15 minutes.

The longest, perhaps half an hour.

Occasionally, a group of whales
will leave their winter waters...

...in the middle of a song...

...and six months later they'll return
and pick the song up...

...at precisely the spot
that they left it off.

Beat for beat.

Measure for measure.

Sound for sound.

Whales are very good at remembering.

Other times they will
come back after...

...an absence of six months,
and the piece will have changed.

A different song will be
on the whale hit parade.

Very often the members of the group
will sing the same song together.

By some mutual consensus,
some collaborative songwriting...

...the piece changes slowly
and often predictably.

I'm not very good at singing
the songs of whales...

...but here's a try.

In January...

...a tiny fragment of
a long whale song...

...might sound like this.

Whoop. Ahh.

In February, something like this.

Whoop. Ahh. Ahh.

And then in March,
as maybe you'd predict...

Whoop. Ahh. Ahh. Ahh.

One additional "ahh" a month.

(WHALES SINGING)

The complex patterns in the songs
of the whales...

...are sometimes repeated precisely.

If I imagine that the songs
of the humpback whale are sung...

...in a tonal language...

...then the number of bits
of information in one song...

...is the same as
the information content...

...of the Iliad or the Odyssey.

(SPLASHING)

Is it just a romantic notion...

...that the whales and their cousins,
the dolphins...

...might have something akin
to epic poetry?

What might whales or dolphins
have to talk or sing about?

They have no manipulative organs.

They can't make great engineering
constructs as we can.

But they're social creatures.

They hunt and swim, fish...

...browse, frolic, mate, play...

...run from predators.

There might be a lot to talk about.

The great danger for the whales
is a newcomer...

...an upstart animal only
recently through technology...

...become competent in the oceans:

A creature called man.

For 99.99% of the history of whales...

...there were no humans
in the deep oceans.

During this period,
the whales evolved...

...their extraordinary
communications system.

Some whales emit extremely loud sounds
at a frequency of 20 hertz.

A hertz, which is spelled H-E-R-T-Z,
is a unit of sound frequency...

...and it represents one sound wave
entering my ear every second.

A frequency of 2000 hertz sounds...

...and looks like this.

(HIGH PITCHED TONE)

200 hertz, like this.

(MEDIUM PITCHED TONE)

And 20 hertz, like this.

Although your TV set
may not transmit...

...sounds with frequencies
as low as 20 hertz.

The American biologist Roger Payne
has calculated...

...that there's a deep sound channel
in the ocean at these frequencies...

...through which two whales
could communicate...

...anywhere in the world.

One whale might be off the
Ross Ice Shelf then in Antarctica...

...and communicate with another whale
in the Aleutians in Alaska.

For most of their history,
whales seem to have established...

...a global communications network.

What two whales might have to say
to each other...

...separated by 15,000 kilometers,
I haven't the foggiest idea.

But maybe it's a love song...

...cast into the vastness
of the deep.

Now, this calculation on the range
of whale communications...

...assumes that the oceans
are quiet.

(WOOD CREAKS)

(BELL RINGS)

But in the 19th century,
sailing ships like this one...

...began to be replaced
by steamships...

...another invention of those
strange land animals.

Commercial and military vessels
became more abundant.

The noise pollution in the sea
got much worse...

...especially at a frequency
of 20 hertz.

(ENGINE HUMS)

The crew of this vessel try
consciously to keep her quiet.

But when its engine is on...

...it gets very loud at
a frequency of 20 hertz.

Whales communicating
across the oceans...

...must've experienced greater
and greater difficulties.

The distance over which
they could communicate...

...must have steadily decreased.

Two hundred years ago...

...a typical distance that some whales
could communicate across...

...was perhaps 10,000 kilometers.

Today, on a typical day...

...the corresponding number is perhaps
a few 100 kilometers.

We have cut off the whales
from themselves.

Creatures which were
freely communicating...

...for tens of millions of years...

...have now effectively been silenced.

And we've done worse than that...

...because there persists
till this day...

...a traffic in the dead bodies
of whales.

There are humans who gratuitously
hunt and slaughter whales...

...and market the products
for dog food or lipstick.

Many nations understand why
whale murder is monstrous...

...but the traffic
continues chiefly...

...by Japan and Norway
and the Soviet Union.

We use "monster" to describe
an animal...

...somehow different from us,
somehow scary.

But who's the more monstrous...

...the whales,
who ask to be left alone...

...to sing their rich
and plaintive songs...

...or the humans, who set out
to hunt them and destroy them...

...and have brought many whale species
close to the edge of extinction?

We're interested in communication
with extraterrestrial intelligence.

Wouldn't a good beginning be...

...better communication
with terrestrial intelligence...

...with other human beings
of different cultures and languages...

...with the great apes,
with the dolphins...

...but particularly with the whales?

To survive, a whale must
know how to do things.

This knowledge is stored
in two principal ways...

...in the whale's genes
and in their very large brains.

We can think of their
genes and brains...

...as something like libraries
inside their bodies.

The information in the DNA,
the genetic information...

...includes how to nurse...

...how to convert
shrimp into blubber...

...how to hold your breath on a dive
one kilometer below the surface.

The information in the brains,
the learned information...

...involves such things as...

...who's your mother...

...or what the meaning is of
that song we're hearing just now.

The gene library
of whales and people...

...and everybody else on Earth...

...is made of DNA.

The only function
of this complex molecule...

...is to store and copy information.

We see here the set of instructions
in human DNA...

...written in a language billions
of years older than any human tongue.

Each colored cluster of atoms...

...is a letter in the genetic alphabet:
The language of life.

There are billions of letters...

...many billions of bits
of information.

If you came from somewhere
very different...

...you wouldn't be able
to specify a whale or a person...

...in a game of 20 Questions
with only 20 bits.

But a game called
10 Billion Questions...

...might just work.

Every organism on Earth...

...contains as its
inheritance and legacy...

...a portable library.

And the more bits of information
you have, the more you can do.

The simplest organism, a virus...

...needs only about 10,000 bits.

Equal to the amount of information
on one page of an average book.

These are all the instructions
it needs...

...to infect some other organism
and to reproduce itself...

...which are the only things
that viruses are any good at.

A bacterium uses roughly
a million bits of information...

...about 100 printed pages.

Bacteria have a lot more
to do than viruses.

They're not thoroughgoing parasites.
Bacteria have to make a living.

What about a free-swimming
one-celled amoeba?

These creatures are
also microscopic...

...but in the realm
of one-celled animals...

...they are giants.

The whales of the microbial world.

Each contains about 400 million bits
in its DNA...

...the equivalent of about
80 volumes of 500 pages each.

That's how much information
it takes to make an amoeba...

...a creature like a small city
wandering through a drop of water.

And what about a whale
or a human being?

Well, the answer seems to be...

...that there's 5 billion bits.

Five billion bits of information
in our encyclopedia of life...

...in the nucleus of every one
of our cells.

So if written out in,
say, ordinary English...

...those instructions,
that information...

...would fill 1000 volumes.

Think of it.

In every one of the 100 trillion
cells in your body...

...there's the contents of a complete
library of instructions...

...on how to make every part of you.
Those cells are smart.

If this were my gene library...

...it would contain everything
my body knows how to do...

...without being taught.

The ancient information...

...is written in exhaustive,
careful, redundant detail.

How to laugh, how to sneeze,
how to walk...

...how to recognize patterns,
how to reproduce...

...how to digest an apple.

If written out in
the language of chemistry...

...what would the instructions...

...for digesting the sugar
in an apple look like?

Well, let's see.

Amino acid synthesis,
polypeptide chains...

...transfer RNA, genetic code,
enzyme expression...

...enzyme phosphorylation.
We're getting warm.

Hexose monophosphate shunt,
citric acid cycle...

Here we are.
Anaerobic glycolysis.

Now, eating an apple...

...may seem like
a very simple thing...

...but it's not.

In fact, if I consciously had to
remember and direct...

...all the chemical steps required to
get energy out of food...

...Id probably starve to death.

And yet, even a bacterium
can do anaerobic glycolysis.

That's why apples rot.
It's lunchtime for the bacteria.

They and we and all
the creatures in between...

...possess similar
genetic instructions.

Our separate gene libraries...

...have many pages in common...

...which is another reminder
of the deep interconnection...

...of all living things
on our planet because of...

...a common evolutionary heritage.

Our present human technology...

...can duplicate only a tiny fraction
of the intricate biochemistry...

...which our bodies seem
to perform so effortlessly.

But we're just beginning
the study of biochemistry.

Evolution has had
billions of years of practice.

The DNA knows.

Now, what if what we had
to do was so complicated...

...that even several billion bits
of information wasn't enough?

What if, for example, the environment
were changing so fast...

...that the pre-coded
genetic encyclopedia...

...which may have served us perfectly
well in the past is now...

...not perfectly adequate?

Why, then...

...even a gene library of
1000 volumes wouldn't be enough.

That's why we have brains.

Like our other organs,
the brain has evolved...

...increasing over millions of years...

...in complexity
and information content.

Its structure reflects all the stages
through which it has passed.

The brain has evolved
from the inside out.

Deep inside is the oldest part,
the so-called brain stem.

It conducts many of the basic
biological functions...

...including the rhythms of life...

...like heartbeat and respiration.

The higher functions
of the brain have evolved...

...in three successive stages
according to a provocative insight...

...by the American biologist
Paul MacLean.

You see, capping the brain stem is
the so-called R-complex...

"R" for reptile.

It's the seat of...

...aggression, ritual,
territoriality...

...and social hierarchies.

It evolved some hundreds of millions
of years ago...

...in our reptilian ancestors.

So, deep inside our brains
is something rather like...

...the brain of a crocodile.

Surrounding the R-complex is
the limbic system...

...or mammal brain.

It evolved some tens of millions
of years ago...

...in ancestors who were
mammals all right...

...but not yet primates
like monkeys or apes.

It's a major source
of our moods and emotions...

...our concern and care
for the young.

And then, finally,
on the outside of the brain...

...living in a kind of
uneasy truce with...

...the more primitive brains beneath,
is the cerebral cortex...

...evolved millions of years ago...

...in ancestors who were primates.

This is the point of embarkation...

...for all our cosmic journeys.

The cerebral cortex...

...where matter is transformed
into consciousness.

Here, comprising more than
two-thirds of the brain mass...

...is the realm both of intuition
and of critical analysis.

It's here that we have
ideas and inspirations.

Here that we read and write.

Here that we do mathematics and music.

The cortex regulates
our conscious lives.

It is the distinction
of our species...

...the seat of our humanity.

Art and science live here.

Civilization is a product
of the cerebral cortex.

Behind the forehead...

...are the frontal lobes
of the cerebral cortex.

They may be where we
anticipate events...

...where we figure out the future.

But if we can foresee
an unpleasant future...

...we can take steps to avoid it.

Down here in the frontal lobes...

...may be the means
of ensuring human survival...

...if we have the wisdom
to pay attention.

Inside the cerebral cortex is
the microscopic structure of thought.

The language of the brain is not
the DNA language of the genes.

What we know is encoded
in cells called neurons...

...tiny switching elements...

...every connection representing
one bit of information.

How many neurons do each of us have?
Maybe 100 billion.

Comparable to the number of stars
in the Milky Way galaxy.

And there are something like
100 trillion neural connections.

This intricate and marvelous
network of neurons...

...has been called
an enchanted loom...

...where millions of
flashing shuttles...

...weave a dissolving pattern.

Even in sleep, the brain is pulsing
and throbbing and flashing...

...with the complex business
of human life:

Dreaming, remembering,
figuring things out.

Our thoughts, our visions,
our fantasies...

...have a tangible, physical reality.

What does a thought look like?

Well, it's made of hundreds
of electrochemical impulses.

Over there, for example, is...

...a spark of a memory.

Maybe...

...the smell of lilacs on a country
road in childhood.

And there goes a bit of
an anxious all points bulletin.

Perhaps, "Where did I leave my keys? "

The neurons store sounds too...

...and snatches of music.

Whole orchestras play
inside our heads.

The landscape of the human
cerebral cortex is deeply furrowed.

There's a good reason for it.

These convolutions...

...greatly increase the surface area
available for information storage...

...in a skull of limited size.

The world of thought is
divided into two hemispheres.

Over there is the right hemisphere
of the cerebral cortex.

It's mainly responsible
for pattern recognition...

...intuition, sensitivity,
creative insights.

And over here is
the left hemisphere...

...presiding over rational, analytic
and critical thinking.

These are the two sides...

...the dual strengths,
the essential opposites...

...that characterize human thinking.

Before us are the means...

...both for generating ideas
and for testing their validity.

There's a continuous dialogue between
the two hemispheres of the brain...

...channeled through this immense
bundle of nerve fibers...

...which is called
the corpus callosum.

It's a bridge between
creativity and analysis...

...both of which are necessary
if we are to understand the world.

The information content of
the human brain expressed in bits...

...is comparable to the number
of connections between...

...the neurons in the cortex...

...about 100 trillion bits...

...10 to the 14th connections.

If written out in English,
it would fill 20 million volumes...

...as many as in the
world's largest libraries.

The equivalent of 20 million volumes
worth of information...

...is inside the heads
of every one of us.

The brain is a very big place
in a very small space.

Most of the books in the brain are
up here in the cerebral cortex.

Down there, in the basement
of the brain...

...are the functions
that our ancestors...

...mainly depended on for survival:

Aggression, child rearing, sex...

...the willingness to
follow leaders blindly.

Lots of things that we can still
recognize in our lives today.

Of the higher brain functions...

...some of them, like...

...reading, writing, speaking...

...seem to be located in particular
places in the cerebral cortex.

On the other hand, each memory...

...seems to be stored in many
separate locales in the brain.

Old memories are in lots of places.

Here is one of my earliest memories.

(POURS LIQUID)

MOTHER:
That's a good boy.

Lunch is almost ready.

(CLICKS ON RADIO)

(MUSIC PLAYS)

That was a long time ago.

But its imprint has not faded...

...in the library of this brain.

But the brain does much more
than just recollect.

It inter-compares.

It synthesizes. It analyzes.

It generates abstractions.

The simplest thought,
like the concept of the number one...

...has an elaborate,
logical underpinning.

The brain has its own language...

...for testing the world's
structure and consistency.

But we never see the machinery
of logical analysis...

...only the conclusions.

There is so much more
that we must figure out...

...than the genes can know.

That's why the brain library...

...has 10,000 times
more information in it...

...than the gene library.

Our passion for learning is
the tool for our survival.

And unlike the musty bindings
of our gene library...

...in which hardly a word
changes in a century...

...the brain library is
made of loose-leaf books.

We're constantly adding
new pages and new volumes.

Emotions and ritual
behavior patterns...

...are built very deeply into us.

They're part of our humanity.

But they're not
characteristically human.

Many other animals have feelings.

What distinguishes our
species is thought.

The cerebral cortex is,
in a way, a liberation.

We need no longer be trapped...

...in the genetically inherited
behavior patterns...

...of lizards and baboons:

Territoriality and aggression...

...and dominance hierarchies.

We are, each of us...

...largely responsible for what
gets put into our brains...

...for what, as adults,
we wind up caring for...

...and knowing about.

No longer at the mercy
of the reptile brain...

...we can change ourselves.

Think of the possibilities.

The city, like the brain...

...has evolved in successive stages.

The vestiges of its past are
still retained...

...among the constructions
of the present.

A city like New York developed
from a small center...

...and slowly grew leaving many
of the old parts still functioning.

Some of the major streets
date to the 17th century.

Its commercial hub,
to the 18th century.

The water and gas works,
to the 19th.

The electrical and communications
systems, to the 20th century.

The city has evolved
much faster than the brain.

Only 10,000 years ago...

...the human brain looked exactly
as it does today...

...and we were just as smart.

But there were no cities...

...only a few scattered encampments
in the vast primordial forests.

Today, it's just the opposite.

Forests and grasslands often seem like
scattered islands in a sea of cities.

If you were an observer
from an alien world...

...you would've noticed that
something complicated...

...has been happening
over the last few thousand years.

It might take you a while
to figure out the details...

...but you would recognize
by its complexity...

...unmistakable evidence
for intelligent life.

On closer scrutiny,
you might recognize...

...individual, intelligent beings.

The evolution of the city is due
to their conscious activity.

Millions of human beings working,
more or less, together...

...to preserve the city,
to reconstruct it...

...and to change it.

It might be more efficient
if all civic systems...

...were periodically replaced
from top to bottom.

But, as in the brain...

...everything has to work
during the renovation.

So the city mostly adds new parts...

...while the old parts continue,
more or less, to function.

For example, in the 17th century...

...you traveled between
Brooklyn and Manhattan...

...across the East River by ferry.

In the 19th century, the technology
became available to construct...

...a suspension bridge
across the river.

It was built precisely at the site
of the ferry terminal...

...because major thoroughfares
were already converging there.

When it was possible to construct
a tunnel under the river...

...that, too, was built in the same
place and for the same reason.

This use and restructuring of
previous systems for new purposes...

...is very much like the pattern
of biological evolution.

Or consider Third Avenue.

In the 17th century...

...you made your way uptown
on foot or on horseback.

A little later, there were coaches...

...the horses prancing,
the coachmen cracking their whips.

And then these were replaced
by horse-drawn trolleys...

...clanging along fixed tracks
on this avenue.

Then electrical technology
developed...

...and a great elevated railway line
was constructed...

...called the Third Avenue El,
which dominated the street...

...until 1954, when it was
utterly demolished.

Anyway, the El was then replaced
by buses and taxicabs...

...which still are the main forms...

...of public transportation
on Third Avenue.

Now as gasoline becomes
a rare commodity...

...the combustion engine will be
replaced by something else.

Maybe public transport
on Third Avenue in the 21st century...

...will be by, I don't know,
pneumatic tubes or electric cars.

Every step in the evolution
of Third Avenue transport...

...has been conservative...

...following a route
first laid down...

...in the 17th century.

But the brain is still more
conservative than the city.

If this were the brain, we might have
horse-drawn trolleys...

...and the El and buses...

...all operating simultaneously...

...redundantly, competitively.

The vestiges of earlier history
clearly in evidence.

When our genes could not store...

...all the information necessary
for our survival...

...we slowly invented brains.

But then the time came, maybe
tens of thousands of years ago...

...when we needed to know more than...

...could conveniently be stored
in brains.

So we learned to stockpile
enormous quantities of information...

...outside our bodies.

We are the only species on Earth,
so far as we know...

...to have invented
a communal memory.

The warehouse of that memory
is called the library.

Libraries also have evolved.

The Assyrian library
of Ashurbanipal...

...had thousands of clay tablets.

The celebrated Library of Alexandria
in Egypt...

...consisted of almost
a million papyrus scrolls.

Great modern libraries,
like the New York Public Library...

...contain some 10 million books.

That's more than 10 to the 14th bits
of information in words.

More than 100 trillion bits,
and if we count pictures...

...it's something like 10 to the 15th
bits of information.

Now, that's more than 10,000 times...

...the total number of bits
of information in our genes.

Something like 10 times...

...the total amount of information
in our brains.

If I were to read a book a week...

...for my entire adult lifetime...

...and I lived an ordinary lifetime...

...when I was all done...

...I would've read maybe
a few thousand books.

No more.

In this library,
that's from about here...

...roughly...

...to about here.

But that's only
a 10th of a percent or so...

...of the total number of books
in the library.

The trick is to know
which books to read.

But they're all here.

What an astonishing thing a book is.

It's a flat object made from a tree...

...with flexible parts
on which are imprinted...

...lots of funny dark squiggles.

But one glance at it...

...and you're inside
the mind of another person.

Maybe somebody dead
for thousands of years.

Across the millennia...

...an author is speaking
clearly and silently...

...inside your head, directly to you.

Writing is perhaps the greatest
of human inventions.

Binding together people
who never knew each other.

Citizens of distant epochs.

Books break the shackles of time.

A book is proof that humans
are capable of working magic.

And this room is filled with magic.

Some of the earliest
authors wrote on...

...bones and stones.

Cuneiform writing is the remote
ancestor of the Western alphabet.

It was invented in the Near East
about 5000 years ago.

Its purpose?

To keep records.

Records of the purchase of grain,
the sale of land...

...the triumphs of kings,
the statutes of priests...

...the positions of the stars...

...the prayers to the gods.

This cone was made...

...around the year 2350 B.C.

4300 years ago, there were people
chipping and chiseling away...

...the message on this cone.

What is that message?

It's a prayer.

The inscription on this cylinder...

...honors a king.

Nebuchadnezzar, king of Babylon,
in the 6th century B.C.

For thousands of years, writing was
chiseled into stone...

...scratched onto wax
or bark or leather...

...painted on bamboo
or silk or paper...

...but always in editions of one copy.

One copy at a time...

...always, except for
inscriptions on monuments...

...for a tiny readership.

But then in China...

...between the 2nd
and the 6th centuries...

...paper, ink and printing
with carved wooden blocks...

...were all invented,
more or less, together...

...permitting many copies of a work
to be made and distributed.

This is Chinese magic...

...from the 12th century.

It took 1000 years for
the idea to catch on...

...in relatively remote
and backward Europe.

Just before the invention
of movable type...

...around the year 1450...

...there were only a few
tens of thousands of books in Europe.

Every one of them handwritten.

Fifty years later, there were
10 million printed books in Europe.

Learning became available to
anyone who could read.

Suddenly, books were being
printed all over the world.

Magic was everywhere.

It is 23 centuries...

...since the founding
of the Alexandrian library.

Since then, 100 generations
have lived and died.

If information were passed on
merely by word of mouth...

...how little we should know
of our own past...

...how slow would be our progress.

Everything would depend on
what we'd been told...

...on how accurate the account.

Ancient learning might be revered...

...but in successive retellings,
it would become muddled...

...and then lost.

Books permit us to
voyage through time...

...to tap the wisdom
of our ancestors.

A library connects us with
the insights and knowledge...

...of the greatest minds
and the best teachers...

...drawn from the whole planet
and from all our history...

...to instruct us without tiring...

...and to inspire us to make
our own contributions...

...to the collective knowledge
of the human species.

There's a fair number
of Gutenberg Bibles...

...and first folios of Shakespeare
in the world...

...but most of the books
you see here...

...are limited editions with
very few surviving copies.

But there also exists in the world...

...mass printings
of paperbound books...

...that I think are still
more wonderful.

For the price of a modest meal...

...you get the history of Rome.

Books are like seeds:
They can lie dormant for centuries...

...but they may also produce flowers
in the most unpromising soil.

These books are the repositories
of the knowledge of our species...

...and of our long
evolutionary journey...

...from genes to brains to books.

Libraries in ancient Egypt...

...bore these words on their walls:

"Nourishment for the soul."

And that's still a pretty fair
assessment of what libraries provide.

Even at night, the city,
like the brain...

...is busy assimilating
and distributing information.

Information keeps it alive...

...and provides the tools to
adapt to changing conditions.

The long human journey...

...from genes to brains
to books continues.

Information itself evolves...

...nurtured by open communication
and free inquiry.

The units of biological
evolution are genes.

The units of cultural
evolution are ideas.

Ideas are transported
all over the planet.

They reproduce through communication.

They are selected by
analysis and debate.

In the last few millennia, something
extraordinary has happened on Earth.

Rich information from
distant lands and peoples...

...has become routinely available.

The number of bits to which
we have access...

...has grown dramatically.

Computers can now store and process...

...enormous amounts of information
extremely rapidly.

In our time, a revolution has begun.

A revolution
perhaps as significant...

...as the evolution
of DNA and nervous systems...

...and the invention of writing.

Direct communication among
billions of human beings...

...is now made possible by
computers and satellites.

The potential for a global
intelligence is emerging.

Linking all the brains on Earth
into a planetary consciousness.

Elsewhere, there may be brains...

...even planetary brains...

...but there will be no brains
quite like ours.

Mutation and natural selection are
basically random processes.

If the Earth were started
over again...

...intelligence might
very well emerge...

...but anything closely resembling
a human being would be unlikely.

On another planet with a different
sequence of random processes...

...to make heredity diversity...

...and a different environment...

...to select particular
combinations of genes...

...the chance of finding beings
very similar to us...

...must be close to zero.

But the chance of finding another
form of intelligence...

...isn't close to zero.

Their brains may well have evolved
from the inside out as ours have.

They may well have switching elements
analogous to our neurons...

...but their neurons might
be different.

Maybe they're superconductors which
work at very low temperatures...

...in which case,
their speed of thought...

...might be 10 million times
faster than ours.

Or perhaps their neurons are not in...

...direct physical contact
with each other...

...but in radio communication.

So a single intelligent being...

...could be distributed
among many different organisms.

There may be planets in which
intelligent beings have...

...not 10 to the 11th neurons each,
as we do...

...but 10 to the 20th
or 10 to the 30th.

I wonder what they would know.

If we could make contact...

...there would be...

...much in their brains that would be
of enormous interest to ours.

And vice versa.

I think extraterrestrial
intelligence...

...even beings astonishingly
more evolved than we...

...will be curious about us,
about what we know, how we think...

...the course of our evolution,
the prospects for our future.

Within every human brain,
patterns of electrochemical impulses...

...are continuously forming
and dissipating.

They reflect our emotions,
ideas and memories.

When recorded and amplified...

...these impulses sound like this.

(RUMBLING)

But would an extraterrestrial being,
no matter how advanced...

...be able to read the mind
that made these sounds?

We ourselves are far
from being able to do so.

But in fact, we have sent
the very impulses you are hearing...

...reflecting the emotions, ideas
and memories of one human being...

...on a voyage to the stars.

In August and September 1977...

...two Voyager spacecraft
were launched...

...on an epic journey to
the outer solar system and beyond.

Their scientific mission was
to explore the giant planets...

...first Jupiter
and its satellites...

...and then Saturn
and its system of moons.

Close encounters with
these great worlds...

...accelerate the Voyager spacecraft
out of the solar system.

As an incidental consequence
of their trajectories...

...they will be carried inexorably
into the realm of the stars...

...where they will wander forever.

The ships will be slightly eroded
within the solar system...

...by micrometeorites,
planetary rings systems...

...and radiation belts.

But once past the planets...

...they will endure
for a billion years...

...in the cold vacuum
of interstellar space.

Perhaps in the distant future...

...beings of an alien civilization
will intercept these ships.

They'll examine our spacecraft...

...and understand much about
our science and technology.

But a machine alone can tell
only so much about its makers.

So each bears a golden
phonograph record...

...with not only the brain waves
of a woman from Earth...

...but also an anthology of music,
pictures and sounds of our planet...

...including greetings
in 60 human languages...

...and the salutations
of the humpback whales.

The record cover bears instructions
on how to hear the sounds...

...and see the pictures
encoded on the disk.

Including some snapshots
from the family album...

...of a distant world.

The Voyager record is
a message in a bottle...

...cast into the cosmic ocean.

It contains some of our thoughts
and our feelings...

...something of the information
we store...

...in genes and brains and books.

The recipients, if any...

...will understand the pictures
and sounds incompletely at best.

But one thing would
be clear about us:

No one sends such a message
on such a journey...

...without a positive passion
for the future.

For all the possible vagaries
of the message...

...they will be sure that
we were a species endowed...

...with hope and perseverance,
at least a little intelligence...

...and a longing to make
contact with the cosmos.